Sacramento City Council
September 16, 2025

City of Sacramento
City Council - 2PM Report
915 I Street Sacramento, CA 95814
www.cityofsacramento.org
File ID: 2025-01541 9/16/2025
Urban Level of Flood Protection Workshop: Overview and Status Update (LR25-006) File ID: 2025-01541
Location: Citywide
Recommendation: Adopt a Resolution acting as the land-use agency for the City of Sacramento accepting evidence in support of a ULOP Finding of 200-year flood protection for the Dry Creek North Levee.

Contact: Remi Mendoza, Long Range Planning Manager, (916) 808-5003, [email protected], Community Development Department; Neal Joyce, Supervising Engineer, (916) 808-1461, [email protected], Department of Utilities Presenter: Remi Mendoza, Long Range Planning Manager, (916) 808-5003, [email protected], Community Development Department Attachments:
1-Description/Analysis
2-Background
3-SB 639 overview
4-Resolution accepting the DCNL Engineer’s Report
5-Exhibit A - DCNL ULOP Engineer’s Report
6-Presentation
Description/Analysis
Issue Detail: The purpose of this workshop is to brief the City Council on the City’s progress toward meeting State law requirements for a 200-year Urban Level of Flood Protection (ULOP) by the December 31, 2025 deadline. Staff will provide an overview of recent progress, key milestones, the timeline for achieving compliance across all levee systems, and future implementation plans. Council action is required to accept the ULOP Engineer’s Report for the Dry Creek North Levee System, which will allow the City to make appropriate flood protection findings for this area in its land-use decisions. This is the first of six levee system reports prepared by SAFCA that will be brought to Council for adoption between now and the end of the year.

Policy Considerations: The 2040 General Plan includes the following goals and policies related to

File ID: 2025-01541 9/16/2025
flood protection:

GOAL Environmental Resources and Constraints (ERC-6) Protection of life and property from flooding hazards.

ERC-6.6 Flood Regulations. The City shall continue to regulate new development in accordance with State requirements for 200-year level of flood protection and federal requirements for 100-year level of flood protection.

ERC-6.8 Interagency Levee Management. The City shall coordinate with local, regional, State, and federal agencies to ensure new and existing levees are adequate in providing flood protection and coordinate to achieve local certification of levees for 200-year flood protection by 2025.

Economic Impacts: Not applicable.

Environmental Considerations: Policies to achieve a 200-year level of flood protection were included in the 2040 General Plan and evaluated in the certified Master Environmental Impact Report. Acceptance of the SAFCA ULOP Engineer’s Report for the Dry Creek Levee System will enable the City to use this document for future flood-related findings in compliance with state law.

Acceptance of this document constitutes an administrative action that will not result in direct or indirect physical changes in the environment, and the action is not a project that requires environmental review under the California Environmental Quality Act (CEQA). See CEQA Guidelines section 15378(b)(5); 15060(c)(3).

Sustainability: The proposed resolution will reduce flood risk by strengthening the linkage between local land use planning decisions and flood management practices. This resolution would also support the City’s efforts to promote urban infill and redevelopment.

Commission/Committee Action: Not applicable.

Rationale for Recommendation: Staff recommends that City Council adopt a resolution accepting the Engineer’s Report provided by SAFCA, thereby establishing that the Dry Creek North Levee Area currently meets the 200-year Urban Level of Flood Protection standard for purposes of evaluating future development proposals. Adoption of this resolution is necessary to provide the substantial evidence required under State law for the City to make appropriate findings when approving future development projects.

Financial Considerations: Not applicable.

Background

File ID: 2025-01541 9/16/2025
Historical Context of Flooding in Sacramento
Sacramento’s Comprehensive Floodplain Management Plan (CFMP) notes that the City has long been vulnerable to flooding due to its flat terrain and location at the confluence of two rivers. Before modern flood control systems were built, floods occurred regularly in the region that resulted in significant losses to life and property. As a result, early residents of downtown Sacramento were forced to build above the original ground elevation to avoid damage from floods.

Sacramento has experienced many major floods at varying intensities and impacts throughout its history, including significant events in 1850, 1852, 1862, 1911, 1913, 1951, 1956, 1963, 1964, 1986, 1995, 1997, 2005, and 2017.

Notable Floods Events in the Last 75 Years:
· 1951: Soon after construction began on Folsom Dam, the American River watershed was hit by the first of several record storms.
· 1956: A second record storm quickly filled the nearly completed Folsom Reservoir in just a week-much faster than engineers predicted-preventing flooding in Sacramento. · 1964: A third record storm in less than 15 years highlighted that Folsom Dam had been designed for only a 120-year storm event, rather than the larger 500-year standard. · 1986: Severe winter storms pushed flows in the American River basin to record levels. High releases from Folsom Reservoir combined with flows on the Sacramento River raised water above the design limits of the levees. A low spot in Strawberry Manor overtopped, flooding approximately 500 homes. Officials estimated that just three more hours of rainfall would have overwhelmed the system and flooded thousands more homes. · 1997: Heavy rain and snowmelt produced significantly high flows across the region. While Sacramento avoided the worst damage, widespread flooding occurred in nearby communities such as Olivehurst, Wilton, Manteca, and Modesto. Forty-eight counties were declared disaster areas, nearly $2 billion in damages were recorded, and nine lives were lost. · 2017: A series of atmospheric river storms triggered widespread regional flooding.

Sacramento’s Emergency Operations Center was activated, floodgates were raised, and the Sacramento Weir was fully opened to divert water from the Sacramento River and American River into the Yolo Bypass to reduce flood stages in the City limits. Localized flooding occurred at Garcia Bend Park and the I Street Bridge, and in areas along Natomas East Main Drainage Canal and Magpie Creek, though the worst impacts were outside the City. No major evacuations or deaths occurred.

Sacramento Area Flood Control Agency (SAFCA) Background The record flood of 1986 highlighted Sacramento’s vulnerability when severe storms exceeded Folsom Dam’s normal flood control capacity. The resulting high-water pressures placed significant strain on levees, causing them to nearly collapse in several areas and underscoring the need for

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stronger flood protection measures.

In response, the State Legislature created the Sacramento Area Flood Control Agency (SAFCA) in 1989. SAFCA was established under a Joint Powers Agreement and is governed by a board composed of representatives from the City of Sacramento, the County of Sacramento, the County of Sutter, the American River Flood Control District, and Reclamation District No. 1000.

SAFCA is responsible for planning and implementing major capital improvements to the region’s flood control system. By providing local cost-share funding for federal and state projects, SAFCA helps advance construction of key infrastructure needed to protect residents from catastrophic flooding.

Urban Level of Flood Protection
In 2007 the California legislature passed a package of six bills (SB 5, SB 17, AB 5, AB 70, AB 156, and AB 162) that mandated comprehensive planning for flood protection at the state and local level.

The Central Valley Flood Protection Act of 2008 (enacted by SB 5) requires all cities and counties within the Sacramento-San Joaquin Valley to make findings related to an urban level of flood protection (ULOP) for urban and urbanizing lands located within a flood hazard zone. ULOP is defined as the level of flood protection necessary to withstand flooding that has a 1-in-200 chance of occurring in any given year.

Since July 1, 2016, state law has required cities and counties within the Central Valley to make one of the following three findings before approving development agreements, tentative maps, discretionary permits, or ministerial permits for new residences:

1. Type I: Existing flood management facilities provide 200-year flood protection;

2. Type II: Conditions are imposed that will provide 200-year flood protection; or

3. Type III: Adequate progress is being made toward 200-year flood protection by December 31, 2025.

The Sacramento Area Flood Control Agency (SAFCA), in coordination with State, Federal, and local partners, has been implementing a comprehensive program of flood risk reduction projects for the Sacramento region. This program includes levee, weir, and Folsom Dam improvements which, once complete, will meet the state requirement that urban areas in the Central Valley achieve at least a 200-year level of flood protection (See Attachment 2-Background).

In 2016 SAFCA prepared an ULOP Plan that identified the improvements needed to achieve a 200- year level of flood protection, the funding sources, and a schedule for completion by December 31, 2025. On June 27, 2016, the City Council accepted this plan (Resolution No. 2016-0226).

Since then, the City has relied on SAFCA’s 2016 ULOP Plan and subsequent annual reports (2017 through 2024) as substantial evidence that SAFCA has been making adequate progress on the construction of a 200-year flood protection system (Type III finding).

File ID: 2025-01541 9/16/2025
As the flood improvement projects near completion in 2025, the SAFCA certification team is preparing six Engineer’s Reports (Table-1 below) to demonstrate that levee systems protecting the City meet ULOP in accordance with the State’s Urban Levee Design Criteria (2012). These reports will provide the substantial evidence required for the City to make Type I ULOP Findings when approving new development projects.

Senate Bill 639 has been introduced on behalf of the City and County (See Attachment 5 - SB 639 overview). If enacted, this legislation will extend the deadline for achieving ULOP from 2025 to 2030 for the Beach Lake North and Natomas Basin Subareas (See Attachment 6 -.SB 5 ULOP Findings). If SB 639 becomes law, SAFCA will prepare annual Adequate Progress Reports in place of the 2025 ULOP Engineer’s Reports for these two levee systems.

SAFCA’s certification team has finalized the ULOP Engineer’s Report for the Dry Creek North Levee System, included as attachment 5. Staff recommends the Council pass a Resolution accepting this report. Based on its findings, substantial evidence now exists for the City to make a Type 1 ULOP Finding in its land-use decisions, confirming that the Dry Creek North Levee system provides a 200- year Urban Level of Flood Protection.

As part of this workshop, staff will also present an overview and status update on key milestones, and the overall timeline for achieving the Urban Level of Flood Protection across the remainder of the city, and future implementation plans.

Summary of SAFCA’s ULOP Projects

File ID: 2025-01541 9/16/2025
SAFCA and the United States Army Corps of Engineers (USACE) have nearly completed major improvements to levee systems which will provide 200-year flood protection to flood-prone areas of the City by December 31, 2025. In 2016 SAFCA prepared a ULOP Plan which highlighted key levee improvements that will provide Sacramento with a 200-year level of flood protection, their costs, revenues to fund them, and a schedule to complete them by December 31, 2025. On June 27, 2016, the City Council accepted SAFCA’s ULOP plan (Resolution No. 2016-0226).

In summary, major aspects of the ULOP flood improvement projects include the following:

Natomas - SAFCA has largely completed its Natomas Levee Improvement Program (NLIP), which improved levees on the north and part of the west perimeter of the basin. The American River Watershed Common Features (ARCF) 2014 Natomas Basin Project is improving the basin’s remaining levees and pump stations.

Dry Creek North Levee System - No construction projects were required for the Dry Creek North Levee since its original construction in 1997.

Robla Arcade Levee System - Cutoff walls and relief wells along the Arcade Creek North Levee and relief wells along NEMDC East Levee were completed by SAFCA in 2018. A drained seepage berm at Arcade Creek and NEMDC was completed by SAFCA in 2025.

American River North Levee System - Cutoff walls along the Arcade Creek South Levee and NEMDC East Levee and were completed by SAFCA in 2018. Cutoff walls along American River North Levee and extending into the NEMDC East Levee were completed by USACE in 2015 including jet grouting at bridge crossings that were remaining from levee improvements constructed in 1999-2000.

American River South and Sacramento River East Levee - Cutoff walls along American River South Levee were completed by USACE in 2000 and jet grouting at bridge crossings were completed by 2015. Levee improvements along the Sacramento River East Levee are substantially complete to satisfy ULOP while additional work along localized sections of the levee is underway by USACE to address freeboard at the authorized design.

Magpie Creek Diversion Channel - Improvements to the Magpie Creek Diversion Channel as part of ARCF 2016 are known as the Magpie Creek Project. The project is being designed now and will be constructed after 2025.

South Sacramento Streams Group - Upstream of the UPRR, construction is complete on the Florin Creek channel improvements and the Florin Creek Multi-Use Basin project.

All Protected Areas - All of the SAFCA protected basins benefit from the Folsom Dam Modifications by lowering the peak flow releases during flood events. The first element of the modifications was largely completed in 2016. Since then, the completed project has been turned over to the U.S.

Bureau of Reclamation and the Water Control Manual has been formally adopted.

SAFCA’s ULOP Engineer’s Reports
As these improvements reach completion in 2025, state law requires cities in the Sacramento-San

File ID: 2025-01541 9/16/2025
Joaquin Valley to demonstrate that levee systems provide an Urban Level of Flood Protection, while meeting the Urban Levee Design Criteria (ULDC 2012) requirements. To support the City in meeting this obligation, SAFCA is preparing a package of ULOP Engineer’s Reports for six levee systems.

The Dry Creek North Levee (DCNL) Engineer’s Report has been completed and is being submitted to Council along with this staff report. Staff anticipate bringing to Council three additional Engineer’s Reports on October 21, 2025. These reports will provide the technical and substantial evidence needed to make a Type 1 ULOP Finding when considering development approvals. While the reports are scheduled for completion in 2025, pending state legislation (SB 639) may extend the deadline for two subareas, substituting annual Adequate Progress Reports in place of immediate ULOP certification.

Next Steps and Future ULOP/ULDC Implementation Plans
SAFCA’s Engineer’s Reports provide substantial evidence documenting compliance with the Urban Levee Design Criteria (ULDC). The ULDC provide engineering criteria and guidance for the design, evaluation, operation, and maintenance of levees and floodwalls that provide an urban level of flood protection (i.e., 200-year level of flood protection).

To the extent that any exceptions to the criteria are identified the City will prepare and adopt a plan that can be implemented for each of the exceptions such as Right of Way (ROW), Encroachments and Penetrations to meet the ULDC guidance. Per ULDC requirements, the City should prepare all implementation plans at least 1-year from adopting the Engineer’s Report. The purpose of the implementation plans is to show progress is being made for the effective period of the ULOP finding, at each incremental 5-year review, for a duration of 20 years or until the Finding is superseded.

Looking ahead, these implementation plans will require significant and ongoing investments of staff time and financial resources. The ultimate approach to funding and staffing responsibilities has not yet been determined, and will depend on continued coordination among the City, SAFCA, and other partners.

Attachment 3- SB 639 Overview
Proposed Legislation (SB 639)
Senate Bill 639 would extend the deadline for the Natomas Basin and Beach Lake subareas (see blue areas on the map on the next page) to achieve the required urban level of flood protection (ULOP) from 2025 to 2030. This targeted approach applies only to where additional time is needed for compliance, rather than applying citywide.

Certain areas in the counties of Sacramento, Sutter, Yuba and the City of Marysville are also included in this legislation. Two such legislative extensions have previously been adopted for the City of West Sacramento and Mossdale Tract in the City of Lathrop (San Joaquin County). However, previous deadline extensions limit the state’s liability by requiring the local agency that approves development in an area that does not have an urban level of flood protection to shoulder some liability for damages in the event of a major flood. Under SB 586, for example, the flood management agencies for Mossdale Tract and the City of West Sacramento are liable for their “fair and reasonable share of any property damage caused by a flood” that occurs between 2025 and 2040. This bill imposes similar liability on the cities of Marysville and Sacramento and the counties of Sacramento, Sutter, and Yuba.

Projects Requiring a Time Extension
SAFCA has been overseeing the efforts to improve the regional flood protection system. All the capital improvements required to handle the State-defined 200-year event have been completed except for the following:

1. A portion of the Natomas levee improvements
o Completion of the Reach A slurry cutoff wall extending from Interstate 80 to Sump 160 (approx 7,500 feet).
o U.S. Army Corps of Engineers contractor is scheduled to complete the slurry wall construction in 2025.

2. Sweeney Ranch Pump Station
o Modifications are required to meet current design requirements.

3. Sump 89 Outfall Replacement Project (City project)
o Modifications need to be made to meet current design standards.

Although it was anticipated that these projects would be completed by the end of 2025, due to construction delays it appears the current construction process may extend beyond the current deadline.

Potential Impacts Without Extension
Without a deadline extension, the City would need to impose cost-prohibitive conditions on most new development in the affected subareas, such as requiring buildings to be elevated 10 feet or more above ground level. These requirements would effectively halt or delay project approvals, creating major impacts on housing production and critical infrastructure.
 Natomas Subarea: Potential delays include a new hospital and residential projects totaling approximately 1,900 units.
 Beach Lake Subarea: Approximately 735 additional residential units could also be affected.

RESOLUTION NO. 2025-
Adopted by the Sacramento City Council
Date Adopted
ACCEPTING THE SACRAMENTO AREA FLOOD CONTROL AGENCY’S
ULOP ENGINEER’S REPORT FOR THE DRY CREEK NORTH LEVEE
SYSTEM IN SUPPORT OF A FINDING OF 200-YEAR URBAN LEVEL OF

FLOOD PROTECTION

BACKGROUND
A. The Central Valley Flood Protection Act of 2008 (the “Act”) prohibits cities and counties, beginning July 1, 2016, from entering into development agreements, approving discretionary permits or ministerial permits that would result in the construction of a new residence, or approving tentative or parcel maps for areas located within a flood hazard zone unless the city or county makes one of the findings set forth in the legislation. (See Government Code sections 65865.5, 65962, and 66474.5.)
B. On March 1, 2016, the city council adopted Ordinance No. 2016-0012, which makes various changes to the city code to conform to the Act.

C. SB 5 restricted development beyond July 2, 2016 unless a land use agency makes one of the following three types of findings: (1) there exists a 200-year Urban Level of Flood Protection (ULOP) (Type I ULOP Finding), (2) conditions are imposed on a development project to achieve 200-year protection (Type II Finding), or (3) adequate progress is being made toward 200-year protection by December 31, 2025 (Type III Finding) and these correspond with City Code Section 17.810
D. The Sacramento Flood Control Agency’s (SAFCA’s), substantial evidence of ULDC compliance for the Dry Creek North Levee Improvement Project will support a Type I ULOP Finding made by the City, when required as part of approval of discretionary or ministerial permits which corresponds with City code Section 17.810
E. The substantial evidence developed by SAFCA in support of a Type I ULOP Finding is described in a certified Engineer’s Report by SAFCA which is attached as Exhibit A

BASED ON THE FACTS SET FORTH IN THE BACKGROUND, THE CITY COUNCIL RESOLVES AS FOLLOWS:

Section 1. The city council accepts the substantial evidence provided by SAFCA in support of a Type I ULOP Finding that the facilities of the Dry Creek North Levee System provide an urban level of flood protection as defined by the State of California’s Urban Levee Design Criteria.

Table of Contents:

Exhibit A – SAFCA’s ULOP Engineer’s Report for the Dry Creek North Levee System

SACRAMENTO AREA FLOOD

CONTROL AGENCY

URBAN LEVEL OF FLOOD PROTECTION
ENGINEER’S REPORT

FOR THE

DRY CREEK LEVEE SYSTEM
FEBRUARY 2024
FINAL
(Back of title page)

CERTIFICATION
This Engineer’s Report was prepared by the Sacramento Area Flood Control Agency (SAFCA) certification team including Psomas, Kleinfelder, Mead and Hunt, and MBK Engineers (MBK). The purpose of this report is to support a finding that the Dry Creek Levee System, which was constructed and is owned by SAFCA and operated and maintained by the American River Flood Control District (ARFCD), provides an urban level of flood protection (ULOP) in accordance and consistent with the requirements, definitions, and descriptions provided by:

State of California Department of Water Resources (DWR) ULOP Criteria (November 2013), Section 2, EVD-1.

State of California DWR Urban Levee Design Criteria (ULDC) (May 2012), Section 7.0.

The supporting documentation, calculations, data, definitions, limitations, and/or other pertinent information contained or referenced in this report form the basis of this certification. This certification does not constitute a warranty or guarantee of performance, express or implied. The certification is made for the Dry Creek Levee System. Individual certification statements are provided in Appendix A for each ULDC topic, which have been endorsed by the certification team member responsible.

Water Resources Flood Control Water Rights WALTER BOUREZ, III, P.E. FOUNDERS:

DON TRIEU, P.E.

DARREN CORDOVA, P.E. ANGUS NORMAN MURRAY
NATHAN HERSHEY, P.E., P.L.S. 1913-1985
LEE G. BERGFELD, P.E. JOSEPH I. BURNS
BEN TUSTISON, P.E. 1926-2021
THOMAS ENGLER, P.E., CFM DONALD E. KIENLEN
MICHAEL MONCRIEF, P.E. 1930-2023

NICOLE ORTEGA-JEWELL, PMP
KYLE KNUTSON, P.E.

ANNE WILLIAMS, P.E.

CERTIFICATION
This certification is provided to the Sacramento Area Flood Control Agency (SAFCA) for the sole purpose of supporting an Urban Level of Flood Protection (ULOP) finding. This certification is made in accordance with the requirements, definitions, and descriptions in the State of California Department of Water Resources’ (DWR) Urban Level of Flood Protection Criteria (November 2013), Section 2, Subsection EVD-3 and Urban Levee Design Criteria (ULDC) (May 2012), Section 7.0 Urban Levee Design Criteria.

All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained or referenced in this document form the basis of this certification.

This certification does not constitute a warranty or guarantee of performance, express or implied. This certification is made with respect to the Dry Creek Levee System (Levee System), as described in the Sacramento Area Flood Control Agency, Urban Level of Flood Protection Engineer’s Report, February 2024 (Engineer’s Report) and assumes the levee will be properly maintained during the certification period.

Limits and Conditions of This Certification
This certification shall expire or become invalid at the earliest time any of the following conditions are met for any particular levee system:
 Integrity of the levee system has degraded to the point that the identified improvements will not be adequate to provide an urban level of flood protection, as determined by me, or a duly qualified designated successor.  Discovery of any substantive defect in the condition of any component of the levee system that was not known at the time this certification was made, and which materially affects the system’s ability to provide protection relative to a 1-in-200 chance of annual flood, as determined by me, or a duly qualified designated successor.
 20-years from the date of certification
Certification Statement
At the request of SAFCA, as supported by the information contained and referenced within the Engineer’s Report, this is to certify the following:
 Certification of Data and Information – The data and information presented in this report are accurate to the best of my knowledge.
 Certification of Analysis – To the best of my knowledge, the analyses conducted were performed in accordance with DWR’s ULDC and/or sound engineering practices, in a manner consistent with the degree of skill and care ordinarily exercised by members of the civil engineering profession currently practicing in the same locality under similar conditions.

I, Thomas F. Engler, PE, a professional registered civil engineer in the State of California, certify that the aforementioned levee system, as described in the Sacramento Area Flood Control Agency, Urban Level of Flood Protection Engineer’s Report, February 2024, provides an urban level of flood protection.
________________________ Date: February 21, 2024
Thomas F. Engler, P.E., CFM

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i

TABLE OF CONTENTS
Table of Contents ........................................................................................................................... i List of Figures..................................................................................................................................................... ii List of Appendices............................................................................................................................................ ii Acronyms and Abbreviations...................................................................................................... iii

1.0 Introduction....................................................................................................................... 1

2.0 Description of Dry Creek Levee System.......................................................................... 3 Physical Description ........................................................................................................................................4 Performance History .......................................................................................................................................5

3.0 Evaluation of Dry Creek Levee System............................................................................ 6 ULDC 7.1: Design Water Surface Elevation.............................................................................................6 ULDC 7.2: Minimum Top of Levee .............................................................................................................7 ULDC 7.3: Soil Sampling, Testing, and Logging ...................................................................................7 ULDC 7.4: Slope Stability For Intermittently Loaded Levees............................................................8 ULDC 7.5: Underseepage For Intermittently Loaded Levees...........................................................9 ULDC 7.6: Frequently Loaded Levees .................................................................................................... 10 ULDC 7.7: Seismic Vulnerability ............................................................................................................... 10 ULDC 7.8: Levee Geometry........................................................................................................................ 11 ULDC 7.9: Interfaces and Transitions ..................................................................................................... 12 ULDC 7.10: Erosion ....................................................................................................................................... 12 ULDC 7.11: Right-of-Way........................................................................................................................... 13 ULDC 7.12: Encroachments ....................................................................................................................... 14 ULDC 7.13: Penetrations............................................................................................................................. 15 ULDC 7.14: Floodwalls, Retaining Walls, and Closure Structures................................................ 16 ULDC 7.15: Animal Burrows....................................................................................................................... 17 ULDC 7.16: Levee Vegetation ................................................................................................................... 18 ULDC 7.17: Wind Setup and Wave Runup........................................................................................... 18 ULDC 7.18: Security ...................................................................................................................................... 19 ULDC 7.19: Sea Level Rise.......................................................................................................................... 19 ULDC 7.20: Emergency Actions and Flood Safety Plans................................................................. 20 ULDC 8.0 Operations & Maintenance................................................................................................... 20

4.0 Bibliography .................................................................................................................... 22 ii

LIST OF FIGURES
Figure 1. Dry Creek Levee System
Figure 2. Levee Stationing and Features of Dry Creek North Levee

LIST OF APPENDICES
Appendix A. Consultant Certification Statements
Appendix B. Independent Panel of Experts Report and Comment Closeout Appendix C. ULDC Water Surface Elevation Profiles – MBK Appendix D. Dry Creek ULDC Due Diligence, Geotech – Kleinfelder Appendix E. ULDC and FEMA Levee Inspection – MBK
Appendix F. O&M Right of Way Maps - Psomas
Appendix G. Dry Creek ULDC Due Diligence, Civil – Mead & Hunt Appendix H. ULDC Required Plans
iii

ACRONYMS AND ABBREVIATIONS
AEP annual exceedance probability
ARCF American River Common Features
ARFCD American River Flood Control District
cfs cubic feet per second
CPT Cone Penetration Test
CVFPB Central Valley Flood Protection Board
DCNL Dry Creek North Levee
DWR California Department of Water Resources
DWSE Design Water Surface Elevation
EC Engineering Circular
EM Engineering Manual
ETL Engineering Technical Letter
FEMA Federal Emergency Management Agency
fps feet per second
H:V horizontal-to-vertical ratio
HTOL Hydraulic Top of Levee
JFP Joint Federal Project
LF linear feet
LM Levee Mile
LMA Local Maintaining Agency
MBK MBK Engineers
MTOL Minimum Top of Levee
NALP North Area Local Project
NEMDC Natomas East Main Drainage Canal
NIMS National Incident Management System
NLD National Levee Database
O&M operation and maintenance
OMRR&R operation, maintenance, repair, rehabilitation, and replacement
pcf pounds per cubic foot
PIR Problem Identification Report
RD Reclamation District
RM River Mile
SB Senate Bill
SOP Standard Operating Procedure
SPFC State Plan of Flood Control
SPK Sacramento District (USACE)
ULDC Urban Levee Design Criteria
ULOP Urban Level of Flood Protection
UPRR Union Pacific Railroad
USACE U.S. Army Corps of Engineers
USACE RIP USACE Rehabilitation and Inspection Program
WSE water surface elevation
iv

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URBAN LEVEL OF FLOOD PROTECTION ENGINEER’S REPORT

DRY CREEK LEVEE SYSTEM
1 1.0 INTRODUCTION
In 2007, the California Legislature passed Senate Bill (SB) 5, which requires all cities and counties within the Sacramento-San Joaquin Valley to make findings related to an urban level of flood protection for urban and urbanizing lands within a flood hazard zone. The bill defined “urban level of flood protection” as the level of flood protection necessary to withstand flooding that has a 1-in-200 chance of occurring in any given year (annual exceedance probability or AEP) using criteria consistent with, or developed by, the California Department of Water Resources (DWR). The Urban Level of Flood Protection Criteria (ULOP Criteria) implementation guidance, issued by the State in November 2013, requires that these findings be based on substantial evidence in the record.

This document and its associated appendices provide substantial evidence that the levee system protecting a portion of the urban area in Sacramento County meets ULOP Criteria for a 200-year flood event (1-in-200 AEP) in accordance with the State of California’s Urban Levee Design Criteria (ULDC), issued in May 2012. The technical assessments performed as part of this effort are not an assessment of how floods may impact improvements (i.e., impacts to structures, facilities, docks, parks, etc.). Instead, the assessments considered a single flood event – the 200-year flood.

ULOP Criteria (EVD-1) requires that the substantial evidence include, at a minimum, “a report prepared by a Professional Civil Engineer registered in California to document the data and analyses for demonstrating the property, development project, or subdivision has an urban level of flood protection.” The ULOP Criteria indicates that the Engineer’s Report should include the following:
 A list of the flood management facilities, including, but not limited to, State Plan of Flood Control (SPFC) facilities;
 The location of the flood management facilities;
 The entities that operate and maintain the flood management facilities; and  A list of, and consideration of, reports, evaluations, inspections, and performance history of the flood management facilities.

This Engineer’s Report relies on several other documents, reports, analyses, and evaluations, some of which are listed in the bibliography at the end of this report. This report does not, nor is it intended to, present all the evidence in the record. Instead, this Engineer’s Report and its bibliography are limited to presenting the substantial evidence required to demonstrate that a ULOP exists. Documents that evaluate and describe the condition and performance of the facilities that are not included in the bibliography are incorporated by reference and have been provided separately. If the evaluation does not explicitly meet the criteria an exception has been written and is included in the supporting documentation provided in the Appendix.

The ULOP Criteria also requires a report by an Independent Panel of Experts (IPE Panel) on the review of this Engineer’s Report. The Panel’s report and responses to the Panel’s comments are provided separately in Appendix B.

In June 2016, the City of Sacramento (City) adopted an Adequate Progress Finding (APF) for the six levee systems protecting the Sacramento metropolitan area within their jurisdictions. This included the Dry Creek Levee System. The APF was based on a report prepared by SAFCA titled, Adequate Progress Towards URBAN LEVEL OF FLOOD PROTECTION ENGINEER’S REPORT

DRY CREEK LEVEE SYSTEM
2 an Urban Level of Flood Protection, Engineer’s Report, dated June 2016. This report presented substantial evidence that once the planned improvements identified in the report were completed, the structural flood control facilities protecting the urban areas of the City from flooding would be able to withstand flooding from a 1-in-200 AEP flood event, in accordance with the State of California’s ULDC, issued in May 2012.

Since the Dry Creek Levee System does not require structural improvements, and non-structural actions have been completed, this Engineer’s Report certifies the Dry Creek Levee System as meeting ULDC and the 1-in-200 AEP ULOP. This Engineer’s Report presents the substantial evidence needed to support this certification.

DRY CREEK LEVEE SYSTEM
3 2.0 DESCRIPTION OF DRY CREEK LEVEE SYSTEM
The Dry Creek Levee System comprises a single levee, the Dry Creek North (Right Bank) Levee (Figure 1).

SAFCA both constructed and owns the levee, which is maintained by the American River Flood Control District (ARFCD). Although the Dry Creek North Levee (DCNL) is a federally authorized levee, the levee has not been formally transferred to the State and is therefore not currently listed as a SPFC feature.

Figure 1. Dry Creek Levee System

DRY CREEK LEVEE SYSTEM
4 PHYSICAL DESCRIPTION
The Dry Creek Levee system is approximately 1.62 miles long and is located along the right bank of Dry Creek in the city and county of Sacramento, California (County). The only levee segment in the system is referred to as the Dry Creek North Levee, which was constructed in 1995 by SAFCA. The levee System ID in National Levee Database is 5205000391 and the Segment ID is 5204000391. The system is also commonly referred to as the ARFCD Unit 11, Dry Creek Right Bank.

The downstream (western) boundary of the levee is located at the fence line, or foundation boundary, of the Natomas East Main Drainage Canal (NEMDC) Stormwater Pumping Station (SWPS), DCNL Station 7000+00. From the downstream end, the alignment of the levee is generally eastward for approximately

1.3 miles, then changes direction to the north for approximately 0.3 miles until the upstream terminus of the levee at Rio Linda Boulevard, DCNL Station 7085+57. The evaluation continues an additional 325 feet upstream along Rio Linda Boulevard to fulfill freeboard requirements. However, this segment is not considered a levee. These features are shown on Figure 2.

Figure 2. Levee Stationing and Features for Dry Creek North Levee The Union Pacific Railroad (UPRR) crosses the levee through a stoplog closure structure at DCNL Station 7000+50. The NEMDC SWPS, also referred to as the Sacramento County D15 Pump Station (a line of protection pump station), provides closure across the NEMDC, between the UPRR closure structure and the Natomas Basin’s NEMDC west levee. Construction of the pumping station was completed in 1996.

During non-flood events, a bypass channel allows flow in the NEMDC to pass from north to south. During flood events, the radial gate at the bypass channel is closed in order to isolate the protected area, due to higher waterside stages from American River backwater and Dry Creek flows. Three diesel driven pumps lift local drainage flows upstream of the pumping plant downstream into the NEMDC. A ditch is present

DRY CREEK LEVEE SYSTEM
5 along the downstream 1,500 feet of the levee which flows under the UPRR to the pump station. Additional landside drainage is diverted through other ditches and culverts through the levee at multiple locations.

For the extent of the levee, there is no waterside development and most of the floodplain area is considered to be open space. Rural, suburban development is located on the landside of the levee, beyond the toe and drainage ditch.

PERFORMANCE HISTORY
Since its construction in 1995-1996, the Dry Creek North Levee has performed as intended without any significant impacts to its integrity. In 2001, a longitudinal crack near the centerline of the levee, a longitudinal crack along the waterside of the levee, and transverse cracks on the landside (located approximately between DCNL Station 7070+00 to 7075+00 [alignment parallel to 4th Street]) were observed. Field excavation was performed to investigate the extent and cause of the cracks. A specific cause of the cracking was not determined, but the cracking appeared to coincide with the presence of a line of eucalyptus trees located near the landside levee toe, which subsequently were removed (Kleinfelder, 2001). The cracked area was excavated longitudinally along the levee with an excavator. The resulting trench was backfilled with levee embankment materials in lifts, moisture conditioned, and compacted. No evidence of continued cracking has been observed to date. Other than the longitudinal cracking, there was no reported distress between 1997 to 2023, which included 11 high water events above flood stage measured at Elkhorn Boulevard since 2017.

There are 25 years of available gage records for Dry Creek at Vernon Street in Roseville, starting with water year 1997. Vernon Street is about 11 miles upstream of the start of the DCNL at Rio Linda Boulevard. The monitor stage of 119 feet was exceeded in 10 of these 25 years, with a maximum of 126.72 feet on January 22, 1997. There is a Sacramento County ALERT gage on the West Branch of Dry Creek at Elkhorn, about 0.7 miles upstream of Rio Linda Boulevard, with records starting in water year 2015. The defined flood stage at the Elkhorn Boulevard gage is 45.9 feet. Comparison of the gage records indicates that the Vernon Street monitor stage of 119 feet approximately coincides with the Elkhorn Boulevard flood stage of 45.9 feet, therefore it can be estimated that the flood stage at Elkorn Boulevard has been exceeded in 10 out of 25 years with available record going back to 1997, with a maximum not exceeding 47 feet. It is worth noting the computed ULDC 200-year design flood stage on the West Branch of Dry Creek at Elkhorn Boulevard is 49.2 feet, a little over 3 feet above the ALERT defined flood stage.

DRY CREEK LEVEE SYSTEM
6 3.0 EVALUATION OF DRY CREEK LEVEE SYSTEM
The ULDC requires analysis under the 20 categories listed below. SAFCA evaluated the Dry Creek North Levee for compliance with each of the 20 ULDC categories. The evaluations are summarized in the following report subsections, and detailed documentation of the analyses are provided as appendices to this report.

7.1 Design Water Surface Elevation 7.11 Right-of-Way

7.2 Minimum Top of Levee 7.12 Encroachments

7.3 Soil Sampling, Testing, and Logging 7.13 Penetrations

7.4 Slope Stability for Intermittently Loaded Levees 7.14 Floodwalls, Retaining Walls, and Closure Structures

7.5 Underseepage for Intermittently Loaded
Levees 7.15 Animal Burrows

7.6 Frequently Loaded Levees 7.16 Levee Vegetation

7.7 Seismic Vulnerability 7.17 Wind Setup and Wave Runup

7.8 Levee Geometry 7.18 Security

7.9 Interfaces and Transitions 7.19 Sea Level Rise

7.10 Erosion 7.20 Emergency Actions
ULDC 7.1: DESIGN WATER SURFACE ELEVATION
The ULDC Design Water Surface Elevation (DWSE) is the 1-in-200 AEP water surface elevation (WSE) used to design and evaluate levees and floodwalls for the purposes of providing an ULOP.

The ULDC offers two options for determination of the DWSE: 1) the Federal Emergency Management Agency (FEMA) approach, and 2) the United States Army Corps of Engineers (USACE) approach. The evaluation for the Dry Creek Levee System conforms to the FEMA approach. In accordance with the ULDC, debris loading on bridge piers was included in the hydraulic analysis. The ULDC also requires adjustments for sea level rise and superelevation. Sea level rise was incorporated into the modeling downstream boundary conditions and there are no locations along the Dry Creek North Levee subject to superelevation. Climate change is considered optional in the ULDC and was not adjusted for in this modeling. Hydrology and hydraulics modeling were updated in the model based on a new model provided by the Central Valley Hydrology Study (CVHS, 2015). A detailed description of the determination of the DWSE is found in Technical Memorandum, Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee (MBK, 2024b).

An additional elevation required by the ULDC is the hydraulic top of levee (HTOL), which is defined as the lower of the DWSE plus 3 feet or the median 500-year WSE.

DRY CREEK LEVEE SYSTEM
7 The computed DWSEs for the Dry Creek north levee are provided in Appendix C The Dry Creek Levee System meets ULDC 7.1 for development of the DWSE.

ULDC 7.2: MINIMUM TOP OF LEVEE
The Minimum Top of Levee (MTOL) is the required minimum elevation for the physical top of levee to provide a reasonable assurance of containing the DWSE and is defined as the higher of the DWSE plus 3 feet or the DWSE plus wind setup and wave runup. The determination of the MTOL is described in MBK, 2024b, and is provided in Appendix C. The existing levee crest exceeds the MTOL everywhere except for one location, station 7081+00, where it is 0.06 feet below the MTOL. In other words, there is a freeboard deficiency of 0.06 feet at this location. An exception for this freeboard deficiency is requested for following reasons. First, the deficiency is very small, less than 0.1 feet. Secondly, this deficient levee segment is very short – less than 20 feet long. Third, the design water surface barely reaches the levee embankment. Fourth, the depth of water at the waterside levee toe is less than 3 ½ feet for a distance of approximately 300 feet from the levee with Rio Linda Boulevard embankment being present approximately 200 feet waterward of the levee. These features are not likely to create significant wind setup and wave runup activity, and therefore, the freeboard deficiency of 0.06 feet at this location is considered acceptable.

Wind setup and wave runup were computed by Mead & Hunt (Mead & Hunt, 2023), and are discussed below in ULDC 7.17. There are no locations along the Dry Creek north levee where the combined wind setup and wave runup is greater than 3 feet; therefore, the MTOL is the DWSE plus 3 feet. Figure 8 in Technical Memorandum, Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee (MBK, 2024b) provides a profile showing the computed MTOL and actual top of levee profile.

The Dry Creek Levee System meets ULDC 7.2 for MTOL, by exception.

ULDC 7.3: SOIL SAMPLING, TESTING, AND LOGGING
ULDC 7.3 requires soil sampling, testing, and logging (as per standard procedures prescribed in guidance documents), including the USACE Sacramento District (SPK) Standard Operating Procedure 3 Geotechnical Levee Practice (SOP-3) and DWR Division of Flood Management’s Soil and Rock Logging, Classification, Description and Presentation Manual (DWR, 2009). This includes an evaluation of soil exploration quantity and location as outlined in the SPK SOP-3. Based on this document, explorations for levee evaluation should be obtained at the waterside toe, levee crown, landside toe, and landside field areas performed at a spacing of 1,000 to 2,000 feet for feasibility studies, and at a spacing of 500 to 1,000 feet for design and preconstruction engineering studies. The SPK SOP-3 also recommends a thorough evaluation of existing information, as available, including construction documents, improvements, performance history, existing subsurface information, and regional and local geomorphology. The standard also recommends the use of cone penetrometers (CPTs) and geophysics to supplement borings, where appropriate.

Dry Creek North Levee

DRY CREEK LEVEE SYSTEM
8 Soil sampling, testing, and logging were generally performed following the previously outlined guidance, with the exception that borings were not advanced at the waterside toe and in the field, landside of the levee. The explorations were reviewed for consistency with DWR 2009 Soil and Rock Logging Manual from a soil logging and laboratory testing standpoint. The exploration spacing was compared to USACE SPK Standard Operating Procedure 3 Geotechnical Levee Practice (SOP-3). This evaluation is consistent with the ULDC (DWR, 2012) and USACE EM 1110-2-1913 (2000) cited in Section 1.5 of the geotechnical report (Kleinfelder, 2024). Additionally, there is documentation of continuous geotechnical observation and testing during levee construction including excavation of an inspection trench. The soil explorations that were obtained were used in combination with geology and geomorphology, geophysical helicopter electromagnetic (HEM) surveys, past performance information, construction records, and historical records collected after construction of the levee to provide an adequate assessment of the subsurface conditions as outlined in the SPK SOP-3 for levee evaluations. Soil exploration information is contained in the data reports prepared by the DWR ULE Project and the SAFCA LAP (URS, 2009 and 2015c; Kleinfelder, 2013b), and the exception is discussed further in Kleinfelder’s Due Diligence Report provided in Appendix D (Kleinfelder, 2024).

The Dry Creek Levee System meets ULDC 7.3 for soil sampling, testing, and logging, through exception.

ULDC 7.4: SLOPE STABILITY FOR INTERMITTENTLY LOADED
LEVEES
The slope stability evaluation is documented in the following report:

Kleinfelder 2016a – Problem Identification Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), dated September 18, 2013. Revised April 29, 2016.

ULDC 7.4.1 requires a minimum factor of safety of 1.4 for landside slope stability under steady state seepage conditions, based on the DWSE, for failure surfaces that intersect the levee crown and are greater than a few feet deep in the levee slope. It also requires a minimum factor of safety of 1.2, based on the HTOL1 for failure surfaces that intersect the levee crown and are greater than a few feet deep in the levee slope. ULDC 7.4.2 requires a minimum factor of safety of 1.0 to 1.2 for waterside slope stability during rapid drawdown conditions for the DWSE, depending on how long the embankment is saturated, with the higher factor of safety used for events of a longer duration. A factor of safety of 1.0 was used for waterside rapid drawdown stability analysis for the Dry Creek north levee (Kleinfelder, 2016a). The HTOLs for the Dry Creek North Levee were calculated and documented by MBK (MBK, 2024c). DWR has determined that these levees are intermittently loaded, as described in ULDC 7.6 (URS, 2015b).

The slope stability evaluations performed for the Dry Creek north levee are documented, as indicated below. Strength parameters were interpreted from field explorations and laboratory testing. Pore water pressure values, calculated during the steady-state seepage analyses, were based on the DWSE or HTOL, respective to the analysis conducted, and in use at the time of the referenced stability analyses. The locations of the cross sections analyzed were selected based on critical locations with respect to 1 The hydraulic top of levee is defined by ULDC as the lower of the median 200-year WSE plus 3 feet or the median 500-year WSE. The HTOL was developed using the approach described in ULDC 7.1

DRY CREEK LEVEE SYSTEM
9 underseepage or stability issues within their representative reach. Reaches where the phreatic seepage surface exited on a levee slope (i.e. through seepage) that is composed of erodible material were generally considered to not meet criteria.

Dry Creek North Levee
The north levee along Dry Creek was previously evaluated for landside slope stability, as part of SAFCA’s LAP (Kleinfelder, 2016a; URS, 2015a; Kleinfelder, 2013a) which were reviewed again in 2023 is documented in Appendix D (Kleinfelder, 2024). A ULDC DWSE was provided by MBK Engineers (MBK, 2024c). The previous DWSE was compared to the current ULDC DWSE. The ULDC DWSE increased by approximately

0.0 to 0.6 feet upstream of approximate Station 7076+00 only; however, the ULDC DWSE (41.6 feet NAVD88) at the location of the critical cross-section is the same as was previously provided. Kleinfelder verified that the location of the critical cross-section, DCNL Station 7035+00, remained unchanged and the analysis for slope stability at the ULDC DWSE was applicable. An analysis at the critical cross-section was also performed and verified to meet ULDC slope stability criteria at the HTOL with a factor of safety for steady state conditions greater than 1.4.

The potential for through seepage conditions was also evaluated along the remainder of the alignment in areas where the ULDC DWSE is higher than the previous WSE. It was determined that through seepage conditions would not differ from the previously evaluated conditions. Therefore, additional slope stability analyses were not necessary.

The Dry Creek Levee System meets ULDC 7.4 for slope stability for intermittently loaded levees.

ULDC 7.5: UNDERSEEPAGE FOR INTERMITTENTLY LOADED
LEVEES
ULDC 7.5 provides levee underseepage criteria for intermittently loaded levees. Analysis locations were selected based on the critical underseepage conditions identified from subsurface explorations, laboratory testing, surface topography, and past performance observations of underseepage, if applicable. Locations with thin blanket conditions, high head differentials between the waterside head and the landside toe, and interbedded layers of high permeability material were primarily selected as the most critical locations for underseepage analysis. Other locations within any particular reach are expected to yield lower exit gradients and higher factors of safety.

Based on USACE Engineering Manual 1110-2-1913 (USACE, 2000) (as modified by ETL 1110-2-569) and the ULDC, the current guidance for acceptable exit gradients through soils with a minimum saturated unit weight of 112 pcf at the toe of the levee (average exit gradient) should be no greater than 0.5, and no greater than 0.8 at a distance of 150 feet from the levee toe for the DWSE. In addition, the minimum criteria for any location between the levee toe and 150 feet from the toe should be linearly interpolated between 0.5 and 0.8 for the DWSE. When modeling a scenario that incorporates the HTOL, the allowable exit gradient is no greater than 0.6 at the levee toe.

Additional evaluations were performed where the levee intersects other levees or mitigation, such as seepage berms and cutoff walls, for transition and interface between features. Further details regarding these analyses are presented in ULDC Section 7.9.

DRY CREEK LEVEE SYSTEM
10 Dry Creek North Levee
The north levee along Dry Creek was previously evaluated for ULDC 7.5 levee underseepage as part of SAFCA’s LAP (Kleinfelder, 2016a; URS, 2015a; Kleinfelder, 2013a), which were reviewed again in 2023 and documented in Appendix D (Kleinfelder, 2024). An ULDC DWSE was provided by MBK Engineers (MBK, 2024c). The previous DWSE was compared to the ULDC DWSE. The ULDC DWSE increased by approximately 0.0 to 0.6 feet upstream of Station 7076+00 only; however, the ULDC DWSE (41.6 feet NAVD88) at the location of the critical cross-section is the same as was previously provided. Kleinfelder verified that the location of the critical cross-section, Station 7035+00, remained unchanged, and the analysis for underseepage at the ULDC DWSE was applicable. In addition, an analysis at the critical crosssection was performed and verified to meet ULDC underseepage criteria at the HTOL with underseepage gradients less than 0.5.

The Dry Creek Levee System meets ULDC 7.5 for underseepage for intermittently loaded levees.

ULDC 7.6: FREQUENTLY LOADED LEVEES
ULDC 7.6 clarifies that frequently loaded levees are subject to more stringent requirements. Frequently loaded levees are those levees that experience a water surface elevation of 1 foot or higher above the elevation of the landside levee toe at least once a day for more than 36 days per year on average.

Dry Creek North Levee
As part of the ULE Program, DWR determined that the Dry Creek north levee is an intermittently loaded levee (URS, 2015b). The SAFCA team reviewed DWR’s conclusion and concurs. ULDC 7.6 for frequently loaded levees is not applicable.

ULDC 7.7: SEISMIC VULNERABILITY
ULDC 7.7 requires an analysis of seismic vulnerability of the levee system for the 200-year return period ground motions. ULDC 7.7.1 indicates that if seismic damage from the 200-year return period ground motion is expected, a post-earthquake remediation plan is required as part of a flood safety plan developed in coordination with pertinent local, State, and Federal agencies.

Analyses were performed to evaluate the seismic stability, and others were performed to evaluate the seismic liquefaction potential. This evaluation (performed in 2016) was reviewed in 2023, and is summarized in the 2024 Kleinfelder report included in Appendix D.

Dry Creek North Levee
The Dry Creek north levee was evaluated for seismic vulnerability and post-seismic flood protection ability by DWR, as part of the ULE Program. Kleinfelder also performed an evaluation, as part of the SAFCA LAP (Kleinfelder, 2015; Kleinfelder, 2013a), which was later reevaluated by Kleinfelder (Kleinfelder, 2024), using

DRY CREEK LEVEE SYSTEM
11 site specific groundwater data, following the ULE Guidance Document prepared by DWR (DWR, 2015b).

According to the DWR ULE Program and Kleinfelder’s revised findings, this levee has a “Low Vulnerability” due to the subsurface consisting of fine-grained, high-blow count soils, and depth to groundwater of over 30 feet. Because this levee has a low seismic vulnerability, seismic damage is not expected, and a postearthquake plan is not required.

The Dry Creek Levee System meets ULDC 7.7 for seismic vulnerability.

ULDC 7.8: LEVEE GEOMETRY
ULDC 7.8 requires that for new levees or levees with extensive reconstruction situated along major waterways, have a minimum 20-foot-wide crown width for Major Streams (mainstreams) or 12-foot crown width for Minor Streams (tributaries to mainstream) and 3:1 horizontal-to-vertical ratio (H:V) waterside and landside slopes are required. Landside slopes can remain 2H:1V for existing levees with good performance. This levee is considered to be situated along a minor stream.

ULDC 7.8.1 allows levees wider than the minimum requirement to have steeper slopes if the minimum required dimensions would fit entirely within the actual levee, and if seepage and slope stability criteria are met (for both deep and shallow failure surfaces).

ULDC 7.8.2 requires a patrol road along the crown of the levee for inspection, maintenance, and floodfighting. The patrol road must be designed, constructed, and maintained to provide “all-weather” support of maintenance and patrolling vehicles.

Dry Creek North Levee
As-built drawings for the levee indicate that the levee was constructed with landside and waterside slopes at 2 horizontal to 1 vertical (2H:1V) and 3H:1V inclinations, respectively, and a crown width varying between 12 feet and 20 feet. A 20-foot crown width was constructed along the main stem of Dry Creek, from the downstream end (DCNL Station 7000+00) to the landside ramp, located near DCNL Station 7065+00. A 12-foot crown width was constructed upstream of approximate DCNL Station 7065+00 to Rio Linda Boulevard, the upstream terminus of the levee. An all-weather patrol road is present along the crown of the levee, with appropriately spaced access ramps and turnouts.

Psomas performed a survey of the levee in 2013 and added additional spot surveys in 2023 (Psomas, 2023). Based on this survey, the cross section exceeds the MTOL (section ULDC 7.2) by approximately 2 feet to 5 feet along the major stream levee reach (DCNL Stations 7000+00 to 7065+00), and is equal to or exceeds the MTOL by approximately 2 feet along the minor stream levee reach (DCNL Stations 7065+00 to 7085+57). Applying the geometry template at the MTOL, the minimum levee template fits entirely within the physical levee embankment for Dry Creek (both major and minor streams) (MBK, 2024c). As described in the Kleinfelder ULDC due diligence report provided in Appendix D (Kleinfelder, 2024) there are some over steepened slopes (1.8H:1V) that are considered to meet ULDC requirements by exception due to the over widened embankment. Additionally, the levee meets ULDC requirements for slope stability (per ULDC 7.4) and underseepage (per ULDC 7.5).

The Dry Creek Levee System meets ULDC 7.8 for geometry by exception.

DRY CREEK LEVEE SYSTEM
12 ULDC 7.9: INTERFACES AND TRANSITIONS
ULDC 7.9 highlights the need to ensure that the levee system functions holistically, such that no levee reach is more susceptible to problems than an adjacent reach, due to gaps in features, loading/demand concentrations, or other three-dimensional effects when designing interfaces, transitions, and connections that commonly occur at the ends of seepage berms, seepage cutoff walls, and revetments.

Dry Creek North Levee
There are seven interfaces and transitions along the Dry Creek north levee: two at the NEMDC SWPS, two at the UPRR stoplog structure, two at Marysville Boulevard, and one at Rio Linda Boulevard. Kleinfelder performed a screening level geotechnical evaluation of some of the features, as described in the Kleinfelder ULDC due diligence report provided in Appendix D (Kleinfelder, 2024). In 2018, Kleinfelder completed a detailed, qualitative, geotechnical review of each structure or embankment interface, with respect to slope stability and seepage at the interface, with the levee embankment. This evaluation was reviewed and updated in the Kleinfelder ULDC due diligence report, provided in Appendix D (Kleinfelder, 2024). Kleinfelder reviewed these conclusions in 2024 (Kleinfelder, 2024) and confirmed that all seven interfaces met ULDC geotechnical requirements.

The Dry Creek Levee System meets ULDC 7.9 for interfaces and transitions.

ULDC 7.10: EROSION
Levees that pose an immediate erosional breaching hazard during either a flood or during normal flow conditions need to be repaired to meet ULDC. Similarly, levees that are likely to be significantly damaged during either a flood or normal flow condition should be protected with appropriate revetment. Erosion hazards are evaluated for the following conditions: 1) high-velocity flows coupled with erosive levee materials and/or poor hydraulic conditions; 2) large waves developed by wind over large, open bodies of water; and 3) boat wakes.

Dry Creek North Levee
In 2012 and 2023, MBK performed erosion evaluations of the Dry Creek Levee System based on site inspection and analysis of results from hydraulic modeling. These results were documented in an Erosion Report (MBK, 2024b). The velocity for the 200-year flow, along the right waterside slope of the Dry Creek north levee, is approximately less than 2 fps downstream of DCNL Station 7062+00 and up to 5.4 fps upstream of DCNL Station 7062+00. The calculated velocities are within the permissible range for clay embankment soil types and vegetated channel conditions. The low velocity, and non-existent boating activity along Dry Creek, diminish the likelihood of significant erosion occurring along the waterside slope.

Along the upper reaches of the levee, where the right branch of Dry Creek is nearest to the levee, the adjacent levee bank consists of erosion resistant materials and adequate vegetative cover which have prevented erosion from occurring during high-water events.

The maximum combined wind setup and wave runup (Section ULDC 7.17) along the Dry Creek north levee occurs at Station 7019+60, provided in Appendix G (Mead & Hunt, 2024). The final adjusted setup plus runup for the 2% exceedance wave is 2.5 feet at this location. Because the available still water freeboard

DRY CREEK LEVEE SYSTEM
13 (5.5 feet at this location) exceeds this total, the erosion potential due to wind setup and wave runup is very low at this location. The minimum still water freeboard of 2.5 feet occurs at Station 7080+90, but the potential wind setup and wave runup would be lower at this location. Therefore, the erosion potential due to wind setup and wave runup is low for the entire levee reach.

The Local Maintaining Agency (LMA) performs routine inspections and has not observed any noticeable signs of erosion along the waterside bank of Dry Creek north levee. The levee embankment has performed against erosion as intended during all high-water events since its construction in 1996.

Additionally, MBK Engineers performed a levee inspection to observe multiple topics related to Operation and Maintenance, including erosion, on October 18, 2023, which is included in Appendix E (MBK, 2024a).

The Dry Creek Levee System meets ULDC 7.10 for erosion.

ULDC 7.11: RIGHT-OF-WAY
As per ULDC, right-of-way criteria for levees and floodwalls in urban and urbanizing areas need to allow adequate room for maintenance, inspection, patrolling during high water, and flood-fighting; allow additional room to expand facilities in the future; and prohibit excavations and land modifications that would endanger the integrity of the levee or floodwall.

Specifically, the ULDC requires fee title or an easement for the entire levee prism extending to a minimum of 20 feet beyond the landside toe of the flood protection system for access and inspection. ULDC also allows for two alternatives where adjacent lands are developed: 1) rights for a minimum 10-foot-wide landside clear zone or 2) a 20-foot-wide landside visibility zone. Furthermore, waterward of the levee prism, where there is sufficient area to do so without resulting in the loss of sensitive riparian habitat, consideration should be given to acquiring a 15-foot-wide zone.

In addition to the minimums required by the ULDC for access and inspection, the ULDC recommends acquiring right-of-way that has a width equal to at least four times the levee height or 50 feet, whichever is greater, on the landside of the 20-foot clear zone for longer-term flood protection.

Lastly, the ULDC recommends that the city or county adopt restrictions on excavations within 200 to 400 feet, depending on the levee height.

Dry Creek North Levee
The entire length of Dry Creek north levee is located within lands owned by either SAFCA or the City of Sacramento. For the portion of the levee located within the City of Sacramento’s land, SAFCA has obtained a flood control easement. The most downstream end of the levee is comprised of a stoplog structure located on property owned by Union Pacific Railroad. Rights to access, operate, and maintain this facility have been provided to SAFCA by UPRR. The NEMDC SWPS is primarily located within, and accessed by, lands owned by RD 1000, although the facility is also located on lands owned by UPRR and can also be accessed from these lands. A Joint Use Agreement between SAFCA and RD 1000 was executed to provide SAFCA with the rights to access, operate, and maintain the NEMDC SWPS.

DRY CREEK LEVEE SYSTEM
14 Figures provided in Appendix F depict the lands under the levee. There are some portions of the levee where 20-foot fee title right-of-way landward of the levee was not possible, and in these areas, right-ofway is met through either a reduced landside right-of-way in fee or easement and/or the presence of a 20-foot “free and clear” zone, wherever feasible, This includes public land present on the landside of the levee, such as 4th Street and Rio Linda Boulevard. In general, the main stem levee has a minimum of 30 feet of landside right-of-way continuing upstream along 4th Street. Upstream of this point approximately 15 feet of landside right-of-way exist. Waterside right-of-way fluctuates between a minimum of 10 feet adjacent to the main stem levee and a minimum of 30 feet along 4th Street that abuts public land. In all cases the minimum “free and clear” zone is met. Portion of the levee includes right-of-way wide enough for future needs extending over 70 feet. A right-of-way plan is not needed.

The Dry Creek Levee System meets ULDC 7.11 for right-of-way.

ULDC 7.12: ENCROACHMENTS
ULDC 7.12 requires an assessment of each existing encroachment, permitted or not, to determine the encroachment’s impact on the reliability of levee performance. The evaluation of encroachments considers the following: age, type, condition, performance history, impacts on the levee structural integrity, impacts on the hydraulic effect of the channel, and impacts on the operation and maintenance (O&M) of the levee.

A summary of Encroachments is included in Appendix G (Mead & Hunt, 2024).

Dry Creek North Levee
In 2013, SAFCA performed an inventory of encroachments along Dry Creek north levee (Mead & Hunt, 2014). A hazard assessment of the encroachments was performed using criteria established in the “Encroachment White Paper” (SAFCA, 2015) and (Mead & Hunt, 2018). Previously, 41 encroachments (including penetrations, closure structures, and linear encroachments) were reported. Of the previous 41 reported, 27 were not associated with penetrations and closure structures, and were evaluated as encroachments. None of the encroachments were considered to be high-risk that would fall into categories 1A, 1B, or 2 (MBK, 2016). Category 1A is considered an imminent threat to the integrity of the levee that need immediate remediation. Category 1B is considered a lesser threat to the integrity of the levee that impeded O&M and should be fixed within three years of certification. Category 2 is considered to not meet ULDC criteria and should be fixed or removed within ten years of certification.

In 2023, encroachment data was verified and updated based on a site visit conducted in August 2023. The updated total number of encroachments is 51, which includes the change in stationing to incorporate the entire Dry Creek Levee system and incorporate the levee extension along Rio Linda Boulevard.

Additionally, the database was updated to reflect penetrations to include appurtenant features. Of the 51 total encroachments, 22 were found to not be associated with penetrations and closure structures.

Encroachment analysis was completed for modifications/changes to the database, consistent with previous evaluation methodology.

No high-risk encroachments were found, and no further engineering evaluations were required that would alter the hazard assessment findings provided in Appendix G (Mead & Hunt, 2024). In summary, there are no high-risk encroachments along the Dry Creek north levee.

DRY CREEK LEVEE SYSTEM
15 The Dry Creek Levee System meets ULDC 7.12 for encroachments.

ULDC 7.13: PENETRATIONS
ULDC 7.13 requires a hazard assessment of each existing penetration, permitted or not, to determine the penetration’s impact on the reliability of levee performance. If penetrations are considered high-hazard, additional evaluation and action are required. For other existing penetrations that are not considered to be high-hazard, but have not been permitted, the city or county is required to have a remediation plan in place, or reference such a plan, for the entire length of levee that the finding is to cover.

A summary of Penetrations is included in Appendix G (Mead & Hunt, 2024).

Dry Creek North Levee
In 2013, SAFCA performed an inventory of penetrations along Dry Creek north levee (Mead & Hunt, 2014).

There were five pipe crossings identified, all of which appear well maintained and are without performance issues. A hazard assessment of the penetrations was performed, and none of the penetrations were considered to be high-hazard (MBK, 2016b) and (Mead &Hunt, 2018). The hazard assessment considered penetration elevation, structural strength, jointing, emergency closure provisions, and pipe condition as described further in Mead & Hunt supporting due diligence report in Appendix G.

The levee was again surveyed in November 2017 in order to verify the data collected previously and identify any new penetrations. No new penetrations were found, and the presence of the five penetrations identified in 2013 was verified (Mead & Hunt, 2018). It should be noted that all of these features are considered authorized penetrations due to installation during original levee construction. However, an older penetration, not previously identified in 2013, was discovered as part of a separate effort. This sixth penetration is a permitted telecommunications line that pre-dates construction of the Dry Creek north levee.

Subsequently it was determined that the Rio Linda Boulevard extension upstream of the end of levee was required to be included in the assessment, as a non-levee flood protection feature to contain the 1 in 200 AEP flood event. This Rio Linda Boulevard extension includes a 4-inch high pressure gas main along the roadway west shoulder.

In 2023, Mead & Hunt performed a confirmation of penetrations and a field inspection with the LMA, as well as research update. The gravity drainage culvert crossings appeared well maintained and gate closure functionality was confirmed with the LMA (Mead & Hunt, 2024).

The review also found that in 2018, PG&E replaced a 2-inch gas distribution pipeline in Rio Linda Boulevard and abandoned the existing 2-inch pipe within the levee. PG&E provided October 4, 2018, asbuilt drawings for the rerouting of the 2-inch pipeline and the Mead & Hunt team reviewed the details with PG&E. The pipe section was capped and abandoned in place, and is waterward of the levee crown.

Approximately 20 feet from the levee centerline and a portion under the levee crown was removed back to the tie-in with the new 2-inch gas pipeline. The new 2-inch gas pipe replacement was routed within the Marysville Blvd ramp in the middle of the south lane, at a depth of 6.5 feet below surface. While the penetration is below the DWSE, the penetration is not considered to be a significant threat to levee performance, as described in the Mead & Hunt due diligence report in Appendix G. PG&E routinely

DRY CREEK LEVEE SYSTEM
16 performs leakage potential investigations of the gas mains in this area and provided 2018 test results that did not identify any areas of concerns.

Structural design of the penetrations was analyzed by Mead & Hunt, and is provided in Appendix G (Mead & Hunt, 2024). Additionally, Kleinfelder reviewed the identified penetrations for geotechnical considerations related to slope stability and seepage included in the Kleinfelder ULDC due diligence report provided in Appendix D (Kleinfelder, 2024). Kleinfelder’s evaluation included review of the construction as-builts, construction inspection and testing results, design WSE, and existing seepage and slope stability analysis. No geotechnical concerns were identified. None of the six penetrations on the Dry Creek north levee were deemed to be high-hazard. However, the one 4-inch gas main in the extension area along Rio Linda Boulevard is considered potentially high-hazard. The 4-inch gas main was further evaluated and found to not present a significant risk to levee integrity as it does not exit landward of the embankment, and is fully contained within the over widened roadway embankment and as described in the Mead & Hunt due diligence report in Appendix G (Mead & Hunt, 2024).

The pipe and culvert inspection requirements of ULDC 7.13.6 have not yet been fully met (Mead & Hunt, 2024). Inspection of exposed exteriors is occurring annually for all penetrations. However, inspection of the interiors of the 3 culverts has not been performed. However, ARFCD has a plan to inspect these in the near future and an exception is requested for the inspection frequency of these utilities. The PG&E gas pipeline testing for leakage potential, along with the cathodic protection system provided for the gas lines was assessed to be meet the corrosion assessment requirements and to verify the conduit integrity as described in the Mead & Hunt due diligence report in Appendix G (Mead & Hunt, 2024).

The 2-inch gas pipe abandonment in Marysville Boulevard and the 4-inch gas main in Rio Linda Boulevard, which does not pass completely through the levee as it runs parallel within the embankment, are not considered high-hazard penetrations. Additionally, the interior inspection of three gravity drainage culverts is pending, but a hazard assessment indicates that the pipes are concrete with negligible risk of corrosion and joints are not a risk of failure due to the reinforced concrete encasement (Mead & Hunt, 2024). Therefore, all penetrations are considered to meet ULDC 7.13. An exception is not needed because there are no high-hazard penetrations.

The Dry Creek Levee System meets ULDC 7.13 for penetrations.

ULDC 7.14: FLOODWALLS, RETAINING WALLS, AND CLOSURE

STRUCTURES
ULDC 7.14 presents requirements for design of special features such as floodwalls, retaining walls, and closure structures. There are no floodwalls along or embedded in the Dry Creek North Levee. Two closure structures, and their appurtenant retaining walls, are present in the levee system.

Dry Creek North Levee
A stoplog closure structure for the UPRR is located at the downstream end of the levee and includes two retaining walls. The stoplog structure was evaluated by SAFCA (Mead & Hunt, 2015c), and is in compliance with ULDC requirements. As prescribed by the operation and maintenance requirements for the closure structure, a successful trial installation was completed by the City of Sacramento, and was witnessed and evaluated by Mead & Hunt in 2015 (Mead & Hunt, 2015b). Subsequent successful trial

DRY CREEK LEVEE SYSTEM
17 installations were witnessed and by Mead & Hunt, most recently in 2022 (Mead & Hunt, 2024). The City of Sacramento performs annual staff training and inspection of structures and components for all closure structures before the flood season in order to verify all parts and equipment are present and in working order. However, the UPRR closure structure is not operated annually because of the challenges in coordinating closure with Union Pacific Railroad, and therefore an exception is needed to meet ULDC. The City of Sacramento also conducts training annually at a selected structure within their jurisdiction. The planning, inspection, and annual training have been deemed to meet the testing requirement of ULDC

7.14. Due to the lack of annual exercising of the UPRR stop log structure, an exception is requested.

The NEMDC stormwater pumping station is an extended line of protection at the downstream end of the Dry Creek north levee and prevents backwater along the NEMDC from traveling upstream. The facility was completed by SAFCA in 1996. In 2017, SAFCA’s civil engineers performed a field inspection and secondary source review of material related to NEMDC Pump Station to assess the facility condition, operation, and performance for compliance with applicable ULDC closure structure criteria. Structures checked for compliance were retaining walls (side walls of the pump station), a radial gate, and cantilevered wall section at the radial gate location. It was found that facility condition, operations, and performance of the NEMDC Pump Station functioning as a closure structure, were in compliance with ULDC (Mead & Hunt, 2017). In 2023, Mead & Hunt engineers performed a field inspection with county staff and witnessed operation of the radial gates and found no changes since the prior assessment (Mead & Hunt, 2024). The NEMDC pump station is operated at least once a year, including testing of all pumps and operation and inspection of radial gates.

Additionally, Kleinfelder reviewed the identified closure structures and retaining walls for geotechnical considerations related to slope stability and seepage (Kleinfelder, 2024). Kleinfelder’s evaluation included review of the construction as-builts and construction inspection and testing results. No geotechnical concerns were identified, as discussed in Appendix D.

The Dry Creek Levee System meets ULDC 7.14 for floodwalls, retaining walls, and closure structures, through exception for the UPRR closure structure.

ULDC 7.15: ANIMAL BURROWS
Borrowing animals can present a significant threat to levee integrity and, therefore, proactive animal control and damage repair are required as part of levee maintenance.

Dry Creek North Levee
Burrowing animals, such as the California ground squirrel, are present throughout ARFCD’s levee systems, which includes the Dry Creek Levee System. ARFCD implements a Rodent Control and Abatement Program (ARFCD, 2017) provided in Appendix H1 to manage populations of burrowing animals that are prevalent along the levees. The methods used for rodent abatement are consistent with the guidelines specified in Section 5 of the “Superintendent’s Guide to Operations & Maintenance of California’s Flood Control Projects” (DWR, 1980). Additionally, MBK Engineers performed a levee inspection to observe multiple topics related to Operation and Maintenance, including animal burrows, on October 18, 2023, which is included in Appendix E (MBK, 2024a). There were no observations of rodent burrowing activity observed during the inspection.

DRY CREEK LEVEE SYSTEM
18 The Dry Creek Levee System meets ULDC 7.15 for animal burrows.

ULDC 7.16: LEVEE VEGETATION
ULDC 7.16.1 requires an engineering inspection and evaluation to identify trees and other woody vegetation on the levee and within 15 feet of the levee toe that pose an unacceptable threat to the integrity of the levee. Those posing an unacceptable threat are to be removed; those not posing an unacceptable threat need not be removed. Non-hazardous vegetation is allowed to remain because it does not pose an unacceptable threat, but it must be trimmed and thinned for access and visibility.

Dry Creek North Levee
As per ULDC 7.16.1, SAFCA conducted an inspection of the Dry Creek Levee System in 2013, and determined that there is no woody vegetation on the Dry Creek north levee that poses an unacceptable threat (MBK, 2017b) to levee integrity or operation and maintenance, or which requires monitoring or trimming. As per ULDC 7.16.2 and 7.16.5, the LMA further confirms the absence of woody vegetation through routine inspection, and thus, neither levee integrity nor ongoing operation and maintenance activity are impacted. Additionally, on October 18, 2023, MBK Engineers performed a levee inspection to observe multiple topics related to Operation and Maintenance, including levee vegetation, and confirming conditions noted during previous inspections, which are included in Appendix E (MBK, 2024a). No woody vegetation was observed on or near the levee slopes.

The Dry Creek Levee System meets ULDC 7.16 for vegetation.

ULDC 7.17: WIND SETUP AND WAVE RUNUP
ULDC 7.17 requires a wind-wave analysis. The wind setup and wave runup distances must be computed and added to the median 200-year still WSE to determine the required elevation of the MTOL.

Additionally, wind setup and wave runup must also be considered for analysis of erosion and overtopping impacts.

The formation and magnitude of wind-generated waves against shoreline structures is controlled by the physical conditions present on and near the shore such as slope and roughness of the structure, wind speed, and distance over which wind blows (fetch length). Multiple evaluations documented the Wind Wave Analysis and determined the wind setup and the runup for the 2 percent exceedance wave (wave runup which is exceeded by 2 percent of waves on average. The analyses were performed at the location on the levees expected to generate the largest wind setup and wave runup.

Dry Creek North Levee
Wind and wave analysis for the Dry Creek north levee was completed in 2015, in accordance with the requirements of ULDC 7.17 and subsequently modified and updated in 2023 (Mead & Hunt 2023). The Automated Coastal Engineering System (ACES) model, which is based on the Shore Protection Manual, was the primary tool for calculating wind setup and wave runup. Design wind speed with a return period of 72.6 years and a duration of 2 minutes was used, in accordance with ULDC 7.17. Results (Mead & Hunt, 2023) indicate that the maximum combined wind setup and wave runup is 2.5 feet. The effects of wind

DRY CREEK LEVEE SYSTEM
19 setup and wave runup on the MTOL and erosion are found above in sections ULDC 7.2 and ULDC 7.10, respectively.

The Dry Creek Levee System meets ULDC 7.17 for wind setup and wave runup.

ULDC 7.18: SECURITY
ULDC 7.18 requires a security plan to protect urban and urbanizing area levee systems from acts of terrorism and other malicious or negligent acts. The security plan is to identify security personnel, responsibilities, resources, and measures. In developing the security plan, the agency/agencies responsible for levee maintenance must consider and prioritize vulnerabilities and employ an array of security measures from four basic categories to address vulnerabilities: networked detection (criterion 7.18.1); deterrence (criterion 7.18.2); physical security (criterion 7.18.3); and intrusion interdiction (criterion 7.18.4) during high-threat periods.

Dry Creek North Levee
ARFCD has a security plan (ARFCD, 2017b), Appendix H2, for the Dry Creek Levee System that identifies security measures from the four basic categories (listed above) that the LMA will undertake, and identifies key assets and vulnerabilities within the levee system. No changes to the 2017 plan have been made and this is considered the most current version of the Security Plan.

The Dry Creek Levee System meets ULDC 7.18 for security.

ULDC 7.19: SEA LEVEL RISE
ULDC 7.19 requires that the effects of sea level rise be estimated and addressed for the duration during which a ULOP Finding may be valid. The sea level rise projection estimated by DWR in the 2022 Central Valley Flood Protection Plan (CVFPP) Update (DWR 2022), was based on the State of California Sea-Level Rise Guidance 2018 Update (OPC, 2018).

Dry Creek North Levee
The 2022 CVFPP used a 50-year sea level rise projection of 3.68 feet at San Francisco. DWR computed the effects of this sea level rise throughout the Sacramento-San Joaquin Delta with the RMA Bay-Delta model.

Stage hydrographs computed by the RMA Bay-Delta model were used as downstream boundaries in the ULDC hydraulic analysis. The duration of the ULOP Finding is 20-years, therefore the use of a 50-year sea level rise projection is a conservative application. It is of interest to note that the hydraulic modeling shows that the assumed sea level rise has no effect on the DWSE for the Dry Creek north levee.

The Dry Creek Levee System meets ULDC 7.19.

DRY CREEK LEVEE SYSTEM
20 ULDC 7.20: EMERGENCY ACTIONS AND FLOOD SAFETY
PLANS
ULDC 7.20 includes requirements for preparing flood safety plans, as it is important that local maintaining agencies and communities understand the responsibilities of flood risk management within their jurisdictions. Specifically, the ULDC requires that each public agency with the responsibility for public safety for residents protected by levees and floodwalls to have a plan for flood events and other natural or man-made, flood-related, incidents that could result in human casualties, property destruction, and economic losses.

Dry Creek North Levee
Several agencies, including ARFCD; the City of Sacramento; and the County of Sacramento, have the responsibility for the public safety of residents protected by the Dry Creek North Levee System. ARFCD, with primary responsibility for the levee system, has a Flood Safety Plan (ARFCD, 2018), Appendix H3, that outlines their planned response to flood emergencies affecting their levee systems. This plan meets the requirements of California Water Code, Section 9650; and relies on the similar plans adopted by the city (City of Sacramento, 2018 and 2020) and county (Sacramento County, 2022). No changes to the 2018 plan have been made and this is considered the most current version of the Flood Safety Plan.

The Dry Creek Levee System’s performance during a 200-year flood event relies on the operation of flap gates and positive closure valves at drainage crossings, installation of the stoplog structure at the UPRR, and operation of the emergency isolation gates at NEMDC stormwater pumping plant, in addition to the performance of the levee. These features are identified in the O&M Manual for the levee system. The City of Sacramento and County of Sacramento are responsible for operation and maintenance of these features, which are documented in their respective Emergency Operations Plans.

The Dry Creek Levee System meets ULDC 7.20 for Emergency Actions.

ULDC 8.0 OPERATIONS & MAINTENANCE
The ULDC 8.0 includes requirements related to operations and maintenance. Specifically, ULDC requires:
 The levee system must have an operation and maintenance manual consistent with USACE requirements, including inspection requirements, except as may be appropriate to deviate from those requirements to comply with the ULDC.
 The facilities providing the ULOP be operated and maintained by a public agency with the authority and resources to do so.
 Damage and maintenance inadequacies identified from inspections should be prioritized and addressed in a timely manner, not awaiting the periodic review process.  Monitoring during high water needs to provide for a thorough visual inspection of both the waterside and landside levee slope (and landside berm toe area) at intervals of no more than 1 hour.

DRY CREEK LEVEE SYSTEM
21  Plans required under ULDC 7.18 for security, and ULDC 7.20 for a flood safety; other plans, such as a post-earthquake remediation plan, right-of- way plan, encroachment remediation plan, penetration remediation plan, or flood relief plan be in-place, as applicable.

Dry Creek North Levee
A new OMRR&R manual titled Operation, Maintenance, Repair, Rehabilitation, and Replacement (OMRR&R) Manual, Dry Creek North Levee Project, was prepared and submitted by SAFCA to USACE in spring 2023 as a requirement under an existing agreement between SAFCA and ARFCD. As previously indicated, the Dry Creek north levee is maintained by the ARFCD, and the City of Sacramento maintains and operates the UPRR stoplog closure structure, and the County of Sacramento maintains and operates the NEMDC SWPS, and drainage culverts. ARFCD performs inspections and patrols as outlined in the OMRR&R Manual and addresses damage and maintenance issues as they arise. A security plan and flood safety plan are in place as described in relevant sections.

The Dry Creek Levee System meets ULDC 8.0 for Operations and Maintenance.

DRY CREEK LEVEE SYSTEM
22 4.0 BIBLIOGRAPHY
As mentioned in Chapter 1, this Engineer’s Report relies on dozens of other documents, reports, analyses, and evaluations. Many of these are listed in the following bibliography; however, this bibliography is mostly limited to presenting the substantial evidence required to demonstrate that a ULOP exists. Items shown BOLD are included as appendices to this report.
(ARFCD, 2017a). American River Flood Control District Rodent Control & Abatement Program.

Revised October 2017.
(ARFCD, 2017b). American River Flood Control District Security Plan. October 2017. (ARFCD, 2018). American River Flood Control District Flood Safety Plan, as required by California Water Code 9650. January 2018.
(City of Sacramento, 2018). City of Sacramento Emergency Operations Plan. 2018. (City of Sacramento, 2020). City of Sacramento Department of Public Works, Maintenance Services, Emergency Response, Event Plan and Contact Information. 2019-2020. (Kleinfelder, 2001). Preliminary Evaluation of Dry Creek Levee Cracks. Correspondence [Letter to John Bassett]. Sacramento County, California. October 16, 2001. (Kleinfelder, 2013a). Problem Identification Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream Of American River, and Beach Lake Levee). Sacramento County, California. September 18, 2013. (Kleinfelder, 2013b). Geotechnical Data Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee). Sacramento County. May 31, 2013.
(Kleinfelder, 2015). Draft ULDC Geotechnical Results Summary, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee). Sacramento County, California. December 18, 2015. (Kleinfelder, 2024). ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California. February 16, 2024.
(MBK, 2014). SAFCA Levee Certification Erosion Report. Sacramento, California. 2014. (MBK, 2016a). Technical Memorandum. Overview of High Hazard Encroachments to Support Adequate Progress Towards an Urban Level of Flood Protection. Sacramento, California. April 15, 2016. (MBK, 2016b). Technical Memorandum. Overview of High Hazard Vegetation to Support Adequate Progress Towards an Urban Level of Flood Protection. Sacramento, California. April 15, 2016.

DRY CREEK LEVEE SYSTEM
23 (MBK, 2018). Dry Creek Levee System, Urban Level of Flood Protection, Dry Creek North Levee: Levee Geometry Analysis. February 2018.
(MBK, 2024a). SAFCA Dry Creek North Levee, Levee O&M Review in Support of FEMA and ULDC Certification. January 22, 2024.
(MBK, 2024b). SAFCA Levee Certification Dry Creek North Levee Erosion Report. January 2024. (MBK, 2024c). Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee. February 16, 2024. (Mead & Hunt, 2015). Sacramento Area Levee Recertification Project. 2015. (Mead & Hunt 2015b). City of Sacramento North Area Union Pacific Railroad (UPRR) Stop Log Structure Trial Installation Assessment. Technical Memorandum. September 25, 2015. (Mead & Hunt, 2017). Structural Calculations, NEMDC Pump Station: Floodwalls, Sacramento, CA.

December 8, 2017.
(Mead & Hunt, 2018). Memorandum. Summary of Inventory of encroachments and Penetrations on the Dry Creek Levee System. February 6, 2018.
(Mead & Hunt, 2023). Dry Creek North Levee Wind-Wave Analysis. November 30, 2023. (Mead & Hunt, 2024). Dry Creek North Levee Due Diligence Review for ULDC Certification.

February 2024.
(Psomas, 2023). O&M Right of Way Map, Dry Creek North Levee. October 2023. (Sacramento County, 2022). Sacramento County Office of Emergency Services, Emergency Operations Plan. May 2022.
(SAFCA, 2015). Sacramento Federal Emergency Management Agency Certification White Paper for Addressing Encroachments. August 6, 2015.
(URS, 2008). Levee Seismic Vulnerability Assessment Methodology Report. 2008. (URS, 2009). Geotechnical Levee Practice Standard Operating Procedures. [USACE Sacramento Districts].

Sacramento, California. 2009.
(URS, 2010). Modified Supplemental Geotechnical Data Report (MSGDR), Natomas East Main Drainage Canal (NEMDC) West Study, Urban Levee Geotechnical Evaluations Program Contract 4600007418 and 4600008101. [Department of Water Resources]. November 2010. (URS, 2015a). Geotechnical Evaluation Report, Volume 1, Existing Conditions, Natomas East Main Drainage Canal, West Study Area, Urban Levee Evaluations Project, Contract 4600008101. [Department of Water Resources]. January 2015.

DRY CREEK LEVEE SYSTEM
24 (URS, 2015b). Geotechnical Evaluation Report (Existing Conditions and Seismic Assessment), Natomas North Study Area, Urban Levee Evaluations Project, Contract 4600008101. [Department of Water Resources]. March 2015.
(USACE, 2023). Operation, Maintenance, Repair, Rehabilitation, and Replacement Manual, Dry Creek North Levee Project. [USACE]. 2023.

Appendix A.

Consultant Certification Statements
ENGINEER’S OPINION
ULDC 7.1: DESIGN WATER SURFACE ELEVATION
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee – Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee, prepared by MBK Engineers, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Don Trieu
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
_________________________________________________02/22/2024 Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.2: MINIMUM TOP OF LEVEE
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee, prepared by MBK Engineers, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Don Trieu
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
_______________________________________________02/22/2024__________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.3: SOIL SAMPLING, TESTING, AND LOGGING
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.  ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.4: SLOPE STABILITY FOR INTERMITTENTLY

LOADED LEVEES
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.  ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.5: UNDERSEEPAGE FOR INTERMITTENTLY

LOADED LEVEES
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.  ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.6: FREQUENTLY LOADED LEVEES
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Sacramento Area Flood Control Agency; Urban Level of Flood Protection Engineer’s Report for the Dry Creek Levee System, prepared by SAFCA, dated February 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Don Trieu
MBK Engineers
455 University Avenue, Suite 100
Sacramento, CA 95825-6579
____________________________________________ 02/22/24___ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.7: SEISMIC VULNERABILITY
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.  ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.8: LEVEE GEOMETRY (GEOTECHNICAL)
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.  ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.9: INTERFACES AND TRANSITIONS
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.  ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.10: EROSION
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  SAFCA Dry Creek North Levee; Levee O&M Review in Support of FEMA and ULDC Certification, prepared by MBK Engineers, dated January 22, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
__________________________________________________02/22/2024_______ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.11: RIGHT-OF-WAY
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  O&M Right of Way Map; Dry Creek North Levee, prepared by Psomas, dated October 26, 2023.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, Suite 100
Sacramento, CA 95825-6579
___________________________________________________02/22/2024________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.12: ENCROACHMENTS
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  SAFCA Dry Creek North Levee; Levee O&M Review in Support of FEMA and ULDC Certification, prepared by MBK Engineers, dated January 22, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
___________________________________________________02/22/2024_____ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.12: ENCROACHMENTS (CIVIL)
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee; Due Diligence Review for ULDC Certification, prepared by Mead & Hunt, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Steve Sullivan
Mead & Hunt
180 Promenade Circle, Suite 240
Sacramento, CA 95834
___________________________________________________________________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.13: PENETRATIONS
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee; Due Diligence Review for ULDC Certification, prepared by Mead & Hunt, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge;
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices;
 the structural works are designed in accordance with sound engineering practices to provide protection from the 200-year ULDC event; and
 the structural works are in place and functioning as intended for the 200-year ULDC event.

Steve Sullivan
Mead & Hunt
180 Promenade Circle, Suite 240
Sacramento, CA 95834
______________________________________________________________ Signature Date
Not Valid Unless Stamped
February 22, 2024
ENGINEER’S OPINION
ULDC 7.14: FLOODWALLS, RETAINING WALLS, AND CLOSURE STRUCTURES (GEOTECHNICAL)
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following document forms the basis of this opinion.
 ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57, 325-foot Rio Linda Boulevard Extension; ULDC Finding and FEMA Levee Certification Program; Sacramento Area Flood Control Agency Levee Systems; Sacramento and Sutter Counties, California, prepared by Kleinfelder, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge;  the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices;  the structural works are designed in accordance with sound engineering practices to provide protection from the 200-year ULDC event; and
 the structural works are in place and functioning as intended for the 200-year ULDC event.

Timothy Williams
Kleinfelder
3130 Kilgore Road, Suite 200
Rancho Cordova, CA 95670
____________________________________________ February 22, 2024_ Signature Date
ENGINEER’S OPINION
ULDC 7.14: FLOODWALLS, RETAINING WALLS, AND CLOSURE STRUCTURES (CIVIL) This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee; Due Diligence Review for ULDC Certification, prepared by Mead & Hunt, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge;
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices;
 the structural works are designed in accordance with sound engineering practices to provide protection from the 200-year ULDC event; and
 the structural works are in place and functioning as intended for the 200-year ULDC.

Steve Sullivan
Mead & Hunt
180 Promenade Circle, Suite 240
Sacramento, CA 95834
___________________________________________________________________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.15: ANIMAL BURROWS
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  SAFCA Dry Creek North Levee; Levee O&M Review in Support of FEMA and ULDC Certification, prepared by MBK Engineers, dated January 22, 2024.
 Rodent Control & Abatement Program, prepared by American River Flood Control District, dated October 2017.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
___________________________________________________02/22/2024_____ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.16: LEVEE VEGETATION
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  SAFCA Dry Creek North Levee; Levee O&M Review in Support of FEMA and ULDC Certification, prepared by MBK Engineers, dated January 22, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
___________________________________________________02/22/2024________ Signature Date
Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.17: WIND SETUP AND WAVE RUNUP
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee; Wind-Wave Analysis, prepared by Mead & Hunt, dated February 6, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Steve Sullivan
Mead & Hunt
180 Promenade Circle, Suite 240
Sacramento, CA 95834
___________________________________________________________________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.18: SECURITY
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Security Plan, prepared by American River Flood Control District, dated October 2017.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
___________________________________________________02/22/2024________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.19: SEA LEVEL RISE
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee, prepared by MBK Engineers, dated February 16, 2024.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Don Trieu
MBK Engineers
455 University Avenue, #100
Sacramento, CA 95825-6579
________________________________________________02/22/2024_________ Signature Date Not Valid Unless Stamped
ENGINEER’S OPINION
ULDC 7.20: OPERATIONS AND MAINTENANCE MANUALS
This opinion is made to assist the Sacramento Area Flood Control Agency (SAFCA) in complying with the requirements, definitions, and descriptions in the California Department of Water Resources’ (DWR) Urban Levee Design Criteria (ULDC) (May 2012) and to support SAFCA’s certification of the Urban Levee System of:

DRY CREEK NORTH LEVEE
All information, calculations, definitions, descriptions, restrictions, limitations, or other pertinent data contained in the following documents form the basis of this opinion.  Operation, Maintenance, Repair, Rehabilitation, and Replacement Manual, Dry Creek North Levee Project. USACE. 2023.

LIMITATIONS OF ENGINEER’S OPINION
Consistent with current practice, this opinion of expected flood control system performance is valid for 20 years from the date of the SAFCA certification.

This opinion by a registered professional engineer does not constitute a warranty or guarantee of performance, express or implied.

It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

The use of the term certification in this document is based on the following:

Per California Business And Professions Code, Division 3, Chapter 7, Article 3, 6735.5. The use of the word “certify” or “certification” by a registered professional engineer in the practice of professional engineering or land surveying constitutes an expression of professional opinion regarding those facts or findings which are the subject of the certification, and does not constitute a warranty or guarantee, either expressed or implied.

OPINION
This Engineer’s Opinion attests that:
 data used in the evaluations and analyses supporting this opinion are accurate to the best of my knowledge; and
 the analyses have been performed in accordance with DWR’s ULDC and/or sound engineering practices.

Tom Engler
MBK Engineers
455 University Avenue, Suite 100
Sacramento, CA 95825-6579
________________________________________________02/22/2024_________ Signature Date
Not Valid Unless Stamped
Appendix B.

Independent Panel of Experts Report
and Comment Closeout
February 22, 2024
Mr. Tom Engler, PE
MBK Engineers
455 University Ave, Suite 100
Sacramento, CA 95825
Dear Mr. Engler:

Subject: Sacramento Area Flood Control Agency (SAFCA)
Urban Level of Flood Protection Engineer’s Report for the Dry Creek Levee System
Independent Panel of Experts’ Concurrence with Engineers’ Report At your request, the Independent Panel of Experts (IPE) (Dr. David Williams, P.E., PH, CFM, BC.WRE, Mr. Michael Hughes, PE, and Mr. Darren Mack, PE, GE) has conducted an independent quality assurance review of the Sacramento Area Flood Control Agency’s (SAFCA) Urban Level of Flood Protection (ULOP) Engineers’ Report for SAFCA’s Dry Creek Levee System. The Dry Creek Levee System consists of the Dry Creek North (Right Bank) Levee (DCNL) from Natomas East Main Drain Canal to Rio Linda Boulevard and comprises 1.62 miles of earthen embankment (Station 7000+00 to 7085+57) plus a 325-foot section of roadway embankment that provides flood protection as a nonlevee feature at the upstream end of DCNL.

The report and its supporting documents are intended to provide substantial evidence that the Dry Creek Levee System meets the Department of Water Resources’ (DWR’s) ULOP Criteria for a 200- year flood event (1-in-200 annual chance of exceedance) in accordance with the DWRs’ Urban Levee Design Criteria (ULDC) issued in May 2012.

IPE Charge and Scope of Work
The IPE has been tasked to provide independent, expert opinion regarding SAFCA’s certification.

Tasks include, but are not limited to, the following:
• Review technical analyses and reports supporting a ULOP certification; • Preparation and attendance of IPE meetings;
• Review and comment on the Engineer’s Reports supporting the certifications; and • Preparation of IPE’s report documenting opinion on whether the flood system meets ULOP certification standards.

Materials provided to the IPE for review included the draft Engineers’ Report for the Dry Creek Levee System and the following supporting documents:
• Appendix C: Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee, MBK Engineers, February 5, 2024.
• Appendix D: ULDC Geotechnical Finding – Dry Creek North Levee Stations 7000+00 to 7085+57 325-Foot Rio Linda Boulevard Extension ULDC Finding and FEMA Levee Certification Program, Sacramento Area Flood Control Agency Levee Systems, Kleinfelder Inc, February 16, 2024. • Appendix E: SAFCA Dry Creek North Levee, Levee O&M Review in Support of FEMA and ULDC Certification, MBK Engineers, January 22, 2024.
• Appendix F: O&M Right of Way Maps, Psomas, October 26, 2023. • Appendix G: Draft Revised Dry Creek North Levee Due Diligence Review for ULDC Certification, Sacramento Area Levee Certification, Phase 3, Sacramento Area Flood Control Agency (SAFCA), Mead & Hunt, February 2024.
• Appendix H: ULDC Required Plans (Appendix H1 - Rodent Control & Abatement Program, American River Flood Control District, October 2017; Appendix H2 – Security Plan; and Appendix H3 – Flood Safety Plan, American River Flood Control District, January 2018) DWR Urban Level of Flood Protection Criterion EVD-1:

Section 2.0 of the ULOP provides the following criterion that is considered by DWR to be necessary for reasonable and responsible decision making.

EVD-1: Substantial evidence in the record to support a finding related to an urban level of flood protection based on flood management facilities providing the required level of flood protection shall include the following, at a minimum:
• A report prepared by a Professional Civil Engineer registered in California to document the data and analyses for demonstrating that the property, development project, or subdivision has an urban level of flood protection.
• A report by an Independent Panel of Experts on the review of the report prepared by the Professional Civil Engineer.
• A response by the Professional Civil Engineer to the comments from the Independent Panel of Experts.
• Any additional data and information that cities or counties use to make the finding.

DWR’s ULDC document presents mainly procedural criteria associated with making a finding consistent with legislative requirements. DWR considers that an urban level of flood protection could be achieved by structural and nonstructural means, or a combination of both. Therefore, DWR’s ULDC, as described below, are incorporated by reference in the ULOP Criteria.

DWR’s ULDC document provides the engineering criteria and guidance for the design, evaluation, operation, and maintenance of levees and floodwalls that provide a 200-year ULOP and outlines 20 technical areas associated with levee integrity and the evaluations needed for compliance, these being:
• Section 7.1 - Design Water Surface Elevation
• Section 7.2 - Minimum Top of Levee
• Section 7.3 - Soil Sampling, Testing, and Logging
• Section 7.4 - Slope Stability for Intermittently Loaded Levees • Section 7.5 - Underseepage for Intermittently Loaded Levees • Section 7.6 - Frequently Loaded Levees
• Section 7.7 - Seismic Vulnerability
• Section 7.8 - Levee Geometry
• Section 7.9 - Interfaces and Transitions
• Section 7.10 - Erosion
• Section 7.11 - Right-of-Way
• Section 7.12 - Encroachments
• Section 7.13 - Penetrations
• Section 7.14 - Floodwalls, Retaining Walls, and Closure Structures • Section 7.15 - Animal Burrows
• Section 7.16 - Levee Vegetation
• Section 7.17 - Wind Setup and Wave Runup
• Section 7.18 - Security
• Section 7.19 - Sea Level Rise
• Section 7.20 - Emergency Actions
The above listed sections were referenced during the IPE review to verify that the completed levee system certification meets the ULDC and standards.

Independent Panel of Experts Review and Findings
The IPE reviewed the Engineer’s Report and supporting documents, attended meetings with the certification team in person and via internet, visited the levee site, and provided two rounds of review comments and “backcheck” replies to Engineer’s team responses. A spreadsheet that documents the IPE comments, Engineer’s team responses, and comment closures is attached to this letter. Changes, clarifications, and improvements to the Engineer’s Report, and supporting documents, were made where needed.

Based on its review, the IPE provides the following findings:
• The certification team, in our opinion, had followed the standards of engineering required for certifying the levees included in the Dry Creek Levee System. • Adequate and appropriate information has been gathered and presented to the IPE to perform the analyses needed to support the certification package. • The engineering analyses performed were appropriate to accurately provide compliance with the ULDC to address the technical areas listed above.
• The references cited in the Engineer’s Report (including the Due Diligence and Engineer’s Opinions reports), provide the appropriate and adequate information to support those Opinions.
• Exceptions to ULDC criteria requested by the certification team are reasonable and adequately supported.
• In the IPE’s judgment, the evaluations, analyses, and management approaches were completed in accordance with sound engineering practices1to provide protection up to the 200-year flood event, and support ULOP and ULDC certification of the Dry Creek Levee System.

The Engineer’s Report is a requirement for SAFCA to obtain ULOP Certification for a levee system.

The ULOP Criteria, Sub-Section EVD-1, requires a report by the IPE documenting its review of the Engineer’s Report and its supporting documents. This letter and its attachment serve as documentation of the IPE’s review and concurrence that the completed levee system provides the required Urban Level of Flood Protection.

Respectfully submitted,
Sacramento Area Levee Certification Project
Independent Panel of Experts
_____________________________ ____________________________ Michael Hughes, P.E. Darren Mack, P.E., G.E.

Independent Expert Panel Member Independent Expert Panel Member _______________________________________
Dr. David T. Williams, P.E., PH, CFM, BC.WRE
Independent Expert Panel Member
1 It is assumed that “sound engineering practices” are practices that are performed in a manner consistent with the degree of skill and care ordinarily exercised by members of the profession currently practicing in the same locality under similar conditions.

No. DOCUMENT LOCATION IN DOCUMENT

IPE'S COMMENT
(12/22/2023)

ENGINEER'S RESPONSE
(1/22/24)
IPE's COMMENT
(1/30/2024)

ENGINEER'S RESPONSE
(Date)
IPE's FINAL COMMENT / CLOSURE
(02/15/2024)
1 Draft ULOP Engineers Repoort, Dry Creek
North Levee, November 2023.

General
General comment - page numbers should be added in the body of the report to match those shown on contents page
Page numbers are added to the Engineer's Report. Closed 2 Certification, Page 2 and 3, Section 1,
Introduction, Page 11, and Section 2,

Certification uses the term "Dry Creek Levee System", the Introduction uses "levee system", and Section 2.0 uses "Dry Creek Right Bank Levee System", "the Dry Creek Levee System, comprises a single levee: the Dry Creek North Levee". Suggest moving the detail explanation from Section 2.0 to the certification section and Introduction and then use whatever shortened term (e.g. Levee System or DCNL) thereafter.

Terminology was updated throughout the Engineer's Report for consistency.

Closed
3 Limits and Conditions of This
Certification
20-years from the date of certification. Certification by whom/entity? This Engineer’s report?
The comment is unclear. The conditions cover the questions requested.

No additional text was added. Bullet one identifies the certifier. The statement prior lists the report being used for Certification by name and reference.

Closed
Note: suggest "20-years from the date of this certification." 4 General
Currently levee system, DCNL and Dry Creek North Levee are used interchangeably throughout the report. Following on from comment #2, decide on whether the report will use the term "Levee System' or the acronym DCNL to identify the Dry Creek North Levee and introduce the term in Section 1, Intorduction at an appropriate point and maintain consistency thereafter throughout the report.

The report has adopted the term DCNL to refer to the Levee System and the change was made throughout.

Closed
5 Figure 2, Page 14
Northerly station on Figure 2 shows 7085+57, while text in paragraph above shows 7085+58. These numbers are used intercahngeably elsehwhere in the report. Choose one and make consistent throughout the report. Note: KLF report uses Station 7085+58 in their Nov. 6 2023 report.
7085+57 is the correct end Station. Reference is being updated throughout the documentation.

Closed
6 2.0 DESCRIPTION OF DRY CREEK LEVEE
SYSTEM, PERFORMANCE HISTORY, 1st
paragraph, 1st sentence.

What is the largest flood (flow and frequency) that has happened since 1995? Since probably no gages on Dry Creek, perhaps cite major precipitation storms and their frequencies.

This was added to the report in Section 2.0: There are 25 years of available gage records for Dry Creek at Vernon Street in Roseville, starting with water year 1997. Vernon Street is about 11 miles upstream of the start of the DCNL at Rio Linda Blvd. The monitor stage of 119 feet was exceeded in 10 of these 25 years, with a maximum of 126.72 feet on 1/22/1997. There is a Sacramento County ALERT gage on the West Branch of Dry Creek at Elkhorn, about 0.7 miles upstream of Rio Linda Blvd, with records starting in water year 2015. The defined flood stage at the Elkhorn Blvd gage is 45.9 feet. Comparison of the gage records indicates that the Vernon Street is monitor stage of 119 feet approximately coincides with the Elkhorn Blvd flood stage of 45.9 feet, therefore is can be estimated that the flood stage at Elkorn Blvd has been exceeded in 10 out of 25 years with available record going back to 1997, with a maximum not exceeding 47 feet. It is worth noting the computed ULDC 200-year design flood stage on the West Branch of Dry Creek at Elkhorn Blvd is 49.2 feet, a little over 3 feet above the ALERT defined flood stage.

Closed
7 Performance History, Page 15
Second to last sentence refers to trench being backfilled and compacted. Do we know the specified degree of compaction of the backfill and whether it met current standards? If so please state this information.

The letter prepared to review the crack and provided recommmendations included a statement that the trench should be backfilled and compacted in accordance with original specification requirements for levee embankment fill. Follow up testing results performed by Kleinfelder confirm the fill was placed and compacted to greater than 90% (ASTM D1557).

Closed
8 Performance History, Page 15
Last sentence states no reported distress between 1997 and 2023, but preceding sentences reference a longitudinal crack in 2001. Suggest adding the following to the start of the last sentence "Other than longitudinal cracking in 2001, there was no reported distress......."
Text was revised as suggested. Closed
9 Section 3.0, Evaluation fo Dry Creek
Levee System, Page 15

7.1 through 7.20 - current format takes up a lot of space. Consider changing format to present in two columns to reduce space.

Text was revised as suggested. Closed
10 ULDC 7.1: Design Water Surface
Elevation, Page 16
The end of the first sentence of the first paragraph refers to urban level of flood protection in full when the acronym of ULOP has already been introduced earlier in the report text. Please relace with ULOP. Check report as a whole for consistency.

Text was revised as suggested. Closed
11 ULDC 7.3: Soil Sampling Testing and
Logging, Page 17
Given that the actual number of explorations performed in the field was much less than the recommended minimum to meet USACE SPK SOP, I think the text should be clearer in conveying this fact. The lack of exploration data is offset by other factors such as geopmorphic mapping, continuous HEM data along the levee alignmnet, trenching of the levee foundation during construction and levee performance (no reported distress "despite 11 high water events above the flod stage measured at Elkhorn Blvd since 2017"). The report identifies the relevant sources of supporting information, but doesn't tie all the informnation together to present a strong justification to offset the significant discrepancy in the number and spacing of borings. See also comment on KLF 2023 report in the Supporting Reports tab.

The Engineer's report was revised to reference Kleinfelder's report. Closed 12 ULDC 7.3: SOIL SAMPLING, TESTING,
AND LOGGING, Dry Creek North Levee,
1st paragraph, 1st sentence
… following the guidance, outlined above …  Which guideline? Feasibility studies or design and preconstruction engineering studies?
The guidelines were design and preconstruction engineering studies. The information gathered was sufficient to meet the requirements for that type of study.

If the documents "USACE Sacramento District (SPK) Standard Operating Procedure 3 Geotechnical Levee Practice (SOP-3) and DWR Division of Flood Management’s Soil and Rock Logging, Classification, Description and Presentation Manual (DWR, 2009)." are all the guidance documents used, then this item is closed.

The explorations were reviewed for consistency with DWR 2009 Soil and Rock Logging Manual from a soil logging and laboratory testing standpoint. The exploration spacing was compared to USACE Sacramento District (SPK) Standard Operating Procedure 3 Geotechnical Levee Practice (SOP-3). The exploration evaluation is consistent with the ULDC (DWR, 2012) and USACE EM 1110-2-1913 (2000) cited in Section 1.5 of the geotech report.

Closed
13 ULDC 7.4: Slope Stability for Internally
Loaded Levees, Page 18
Seepage analysis has been run with ditch empty conditions per the standard of practice.

However, this results in the artificial drawdown of the steady state ground water table and higher factors of safety for slope stability, particulraly for the case of the HTOL. It also isn't reflective of the true staeady state seepage breakout point on the landslide slope for through seepage assessment. Was a sensitivity analysis run to see if there is an adequate factior of safety when the analysis is run with a ditch full condition? If not we recommend checking this and revising the report accordingly.

Kleinfelder ran a case with the ditch full as a parametric case for the Problem Identification Report. That model had a slope stability factor of safety of 1.67 (Water Surface Elevation of 41.1 feet, NAVD88). No changes were made to the Engineer's Report to address this comment.

Please provide the location in the PIR where the ditch was analysed with water in it so that the analysis can be reviewed and the comment closed.

Analysis was not published in the Kleinfelder 2016 North Area Streams PIR. However, the analysis was run as a sensitivity analysis. The analysis is provided with these comments for IPE review.

Closed
14 ULDC 7.5: Underseepage for
Intermittently Loaded Levees, Page 19
See comment #13 on slope stability above.

See response to Comment #13 and revisions to Due Diligence report. No changes were made to the Engineer's Report related to this comment.

Please provide the location in the PIR where the ditch was analysed with water in it so that the analysis can be reviewed and the comment closed.

Analysis was not published in the Kleinfelder 2016 North Area Streams PIR. However, the analysis was run as a sensitivity analysis. The analysis is provided with these comments for IPE review.

Closed
15 ULDC 7.5: Underseepage for
Intermittently Loaded Levees, Page 19
First sentence of first paragraph, Page 19. Remove the word 'our' in reference to subsurface investigation, laboratory testing, etc. Text was revised as suggested. Closed

REVIEW BY INDEPENDENT PANEL OF EXPERTS (IPC)
ULDC_DryCreekNorthLevee_IPE_RTC_BackCheckFinal_02152024 1 of 3 No. DOCUMENT LOCATION IN DOCUMENT

IPE'S COMMENT
(12/22/2023)

ENGINEER'S RESPONSE
(1/22/24)
IPE's COMMENT
(1/30/2024)

ENGINEER'S RESPONSE
(Date)
IPE's FINAL COMMENT / CLOSURE
(02/15/2024)
16 ULDC 7.7: Seismic Vulnerability, Page 20.

Second sentence of the second paragraph has a typo. Suggested re-wording to "This evaluation, performed in 2016, was reviewed in 2023 and is summarized…...." Text was revised as suggested. Closed 17 ULDC 7.7: Seismic Vulnerability, Page 20. First sentence, second line, third paragraph has a double space before DWR. Text was revised as suggested. Closed 18 ULDC 7.8: Levee Geometry, Page 20.

First sentence, first paragraph consider revising to "ULDC 7.8 requires that new levees or levees with extensive reconstruction situated along major waterways have a minimum 20- foot-wide crown width for Major Streams (mainstreams) or 12-foot crown width for Minor Streams (tributaries to mainstream) and 3:1 horizontal-to-vertical ratio (H:V) waterside and landside slopes."
Text was revised as suggested. Closed
19 ULDC 7.8: Levee Geometry, 1st
paragraph, last sentence
This levee is considered to be situated along a minor stream. Who decided this? The Engineer or a consultant?
This is defined in the 1957 Hydrology Design Memorandum No. 1, Sacramento River and Major and Minor Tributaries, California, prepared by USACE, 23 January 1957.

Closed
Note: recommend citing the document to suppport Dry Creek is a minor stream.
20 ULDC 7.8: Levee Geometry, Dry Creek,
2nd paragraph, 1st sentence.

Should reference PSOMAS as (Psomas, 2023) Text was revised as suggested. Closed 21 ULDC 7.9: Interfaces and Transitions,

The reference to Kleinfelder, 2018c, on the last line of second paragraph isn't covered in the Bibliography.

The Kleinfelder reference was updated to reference their current Due Diligence Report.

Closed
22 ULDC 7.9: Interfaces and Transitions,

General comment: conclusions on some interfaces is based on KLF, 2016b stability analysis. These conclusions need to be checked based on the outcome/response to comment #13 above.

Response to Comment #13 is the FOS for ditch full is acceptable; therefore, conclusions for the interfaces remain unchanged.

Please provide the location in the PIR where the ditch was analysed with water in it so that the analysis can be reviewed and the comment closed.

Analysis was not published in the Kleinfelder 2016 North Area Streams PIR. However, the analysis was run as a sensitivity analysis. The analysis is provided with these comments for IPE review.

Closed
23 ULDC 7.10: Erosion, Dry Creek, 1st
paragraph, 2nd sentence
The average channel velocity.. For the 200 year/design flood? Text was revised to clarify what the velocity is tied to and update velocities to 2023 MBK memo. Reference was also added. Closed 24 ULDC 7.10: Erosion, Dry Creek, 2nd
paragraph, 1st sentence
The maximum combined wind setup and wave runup… Should cite that this is from Mead & Hunt
Reference added to Mead & Hunt report in Appendix G. Closed 25 ULDC 7.10: Erosion, Dry Creek, 3rd
paragraph, 1st sentence
What about erosion from 1995 to 2012? Text was revised to clarify erosion was not observed since the levee was constructed in 1996.

Closed
26 ULDC 7.10: Erosion, Page 22.

Third paragraph infers construction completion in 1997 whereas elsewhere in the document infers 1995. Clarify and make consistent throughout report Reports will reference construction being complete in 1996. For reference the As-builts were provided in 1997.

Closed
27 ULDC 7.11: Right-Of-Way, Page 23. There is a typo in the first sentence of sixth paragraph where 'Appendix FG' should be 'Appendix F'.

The correct ROW reference should be Appendix G and the text was revised accordingly.

Could not find any reference to Right of Way in Appemdix G Right of Way figures are in Appendix F, the O&M letter from MBK should have been referenced to Appendix E. Clsoed
28 ULDC 7.12: Encroachments, Page 24 End of the fourth line of the fourth paragraph should state 51 and not 50 as shown. Correction made. Closed 29 ULDC 7.12: Encroachments, Page 24
Fifth paragraph - what constitues a 'high-hazard' encroachmnet? The report might benefit from a footnote on this.

Language modified in this section to reflect the proper language for encroachment categorization (category 1A, 1B, or 2).

Closed
Note: there is still reference to 'high-hazard' in the revised document.

Suggest screening the document and check to see if this should be changed to 'high-risk'.

High-hazard descriptions for encroachments were changed to high-risk.

Noted
30 ULDC 7.13: Penetrations, Page 25
General comments: recommend defining what constitues a high hazard penetration.

Text makes several references to request for information from PG&E and the need to conduct or evaluate subsequent hazard assessments. The dates of requests should be stated and a plan needs to be in place to outline the timelime and procedure for following up. Otherwsie these things will be forgotten. Recommend including the plan in the Mead and Hunt report.

Refer to Mead & Hunt supporting report, section 3.2. After intial screening, potentially high hazard penetrations were further analyzed using several factors, including:

Structural loading, Pipe strength, Buoyancy, Pipe material, design life, Elevation and emergency closure.

Clarification has been added in the Engineers Report and Mead & Hunt Due Diligence Report.

While the penetration is below the DWSE, the penetration is not considered a significant threat to levee performance as described in the Mead & Hunt due diligence report in Appendix G.

Closed
Refer to comment above regarding 'high-hazard' versus 'high-risk'.

High-hazard is the correct terminology for penetration
assessments. High risk is only used in the context of screening of encroachments.

Noted
31 ULDC 7.13: Penetrations, Dry Creek, 2nd
paragraph, last sentence
Subsequent communication with PG&E has been made to request inspection and asbuilt records. What is the status of this communication? If not received in time, please explicitly state that this information is not essential to the certification since it is nonlevee performance issue.

Asbuilts were reviewed with PG&E. Additonal discussion was included in the Engineer's report and the supporting Mead & Hunt Due Diligence Report, Appendix G.

Closed
32 ULDC 7.13: Penetrations, Page 25
Last line of the fifth paragraph states that leak testing is considered equivalent to corrosion assessment. What is this statement based on? Is there a standard or document that can be referenced? A stronger rationale needs to be provided and reference(s) listed.

Valid point, the methods are not equivalent but do comply with the ULDC inspection requirements, and the wording has been updated. The ULDC

7.13.6 indicates that the corrosion assessment inspections can be completed using nondestructive means. The leakage testing along with the knowledge that the gas mains are protected by active cathodic protection systems by regulation, limiting the risk of internal and external corrosion is assessed to meet the intent of the inspection provisions.

Text added to this paragraph has several grammar issues. Suggest cleaning up these sentences for clarity and clarifying how the utility was capped and abandoned to prevent a future flow path. Also, the 4-inch gas main in Rio Linda Blvd is not clearly described in the preceeding paragraphs. Additionally, this paragraph states the gas mains are in the freeboard section, although paragraph 5 states the 2-inch main in Marysville Blvd is 6.5 feet deep and below the DWSE. Please clarify.

The last paragraph of Sectoion 7.13 states, "inspection and abandonment documentation is incomplete and should be obtained" so it is unclear what is being used as the basis for certification for the two gas mains listed. Suggest a general review and upate of this paragraph for consistency.

Fifth paragraph text has been reviewed. Abandonment has been clarified.

The 4-inch gas main is described in the sixth paragraph. The 4- inch gas main was the one penetration in the Rio Linda Blvd extension, as clarified in the updated text.

The freeboard statement has been removed from last
paragraph, this was a remanent.

The statement on inspection and abandonment documentation has been removed, assessment was conducted based upon
available data.

The last paragraph has been reviewed and updated.

Closed
33 ULDC 7.16
The ROW maps (Appendix F) suggest woody vegetation is likely within 15 feet of the levee toe between STA 7065+00 and 7075+00 and near STA 7045+00. What criteria was used to rule classify this material was not posing an “unacceptable threat”? The ROW map aerial photo background is used to help identify geographic location, but should not be utilized to assess vegetation. The current condition does not have woody vegetation within 15 feet of the levee toe, as outlined in the O&M letter (Appendix F).

Response acceptabe. Comment closed.
34 ULDC 7.17: Wind Setup and Wave
Runup, Page 29
Add text to the first line of the third paragraph to reflect that Mead and Hunt modified the 2015 analysis in 2023.

Language added to indicate that the analysis was modified in 2023. Closed 35 ULDC 7.17: WIND SETUP AND WAVE
RUNUP, Dry Creek, 1st paragraph, 1st
sentence.

Should reference the Mead & Hunt report. Reference language added. Closed 36 ULDC 7.20
MBK prepared the draft OMRR&R manual titled "Operation, Maintenance, Repair, Rehabilitation, and Replacement (OMRR&R) Manual, Dry Creek North Levee Project", which is currently being reviewed by USACE. While the Engineer's Report concluded the OMRR&R meets ULDC criteria, it is unclear if an independent review outside of MBK has been performed. Given the manual has not been accepted by USACE, the IPE recommends an independent review be performed.

SAFCA and ARFCD previously reviewed the OMRR&R which is now at USACE for review and acceptance. The design team agrees than an appropriate review process has been performed and additional reviews are not needed.

Response is acceptable. Review by SAFCA and ARFCD, as well as eventual acceptance by USACE, meets the intent of this comment. Commnet closed.
37 ULDC 7.20: Emergency Actions and
Flood Safety Plans, Dry Creek, 2nd
paragraph, last sentence
Should the Emergency Operation Plans be cited?
The City and County Emergency Operation Plans are public documents and not a requirement for this report. Therefore, we did not list them in the bibliography.

If these documents are mentioned in this document, they should be properly cited and in the references.

References were cited in Section 7.20 and were added to the Bibliography.

Closed
ULDC_DryCreekNorthLevee_IPE_RTC_BackCheckFinal_02152024 2 of 3 No. DOCUMENT LOCATION IN DOCUMENT

IPE'S COMMENT
(12/22/2023)

ENGINEER'S RESPONSE
(1/22/24)
IPE's COMMENT
(1/30/2024)

ENGINEER'S RESPONSE
(Date)
IPE's FINAL COMMENT / CLOSURE
(02/15/2024)
38 ULDC 7.20: Emergency Actions and
Flood Safety Plans, Dry Creek, 2nd
paragraph, last sentence
OMRR&R manual. Should be in bibliography OMRR&R is added to the bibliography. Closed 39 Operations and Maintenance, Page 30 OMRR&R manual. Should be in bibliography OMRR&R is added to the bibliography. Closed 40 Operations and Maintenance, Page 31
General comment - should section title be changed to "ULDC 8.0: Operations and Maintenance"? This section title is also missing from the table of contents and from the itemized list of evaluation categories, Section 3 on page 16.

Text revised as suggested. Closed
ULDC_DryCreekNorthLevee_IPE_RTC_BackCheckFinal_02152024 3 of 3 No. DOCUMENT

LOCATION IN

DOCUMENT

IPE'S COMMENT
(12/22/2023)

ENGINEER'S RESPONSE
(1/22/2024)

IPE'S COMMENT
(1/30/2024)

ENGINEER'S RESPONSE
(Date)

IPE'S FINAL COMMENT / CLOSURE
(02/15/2024)
1 Engineer's Report, Appendix C,
Determination of the Urban Levee Design
Criteria Design Water Surface Elevation,
Minimum Top of Levee, and
Hydraulic Top of Levee

2. Study Area, 2nd
paragraph, 2nd sentence
For a distance above the NEMDC.. Instead of "above", suggest upstream Text was revised as suggested. Closed 2 3. Hydraulic model, 2nd
paragraph, 1st sentence
Should state why some areas were modeled as 1-D and others as 2-D. Why not all 2-D? The model was developed from a USACE 1-D model. 1-D elements were retained for reaches where hydraulics are primarily 1-D in nature (NEMDC and Arcade Creek). The 1-D elements for the floodplains and for Dry Creek, Robla Creek, Magpie Creek, and Don Julio Creek, where low flow channels are small and floodway are wide, i.e. 2-D in nature, were replaced with 2-D flow areas.

Text was revised to include this information.

Closed
3 3. Hydraulic model, 3rd
paragraph, 1st sentence,
4th sentence
What was the vertical and horizontal resolution of the terrain model? The USACE terrain was developed for the USACE design and impact analysis of the Magpie Creek Project. The documentation of the Magpie Creek Project analysis, which is referenced, does not include the requested information. The CVFED terrain used to supplement the USACE terrain has vertical accuracy of 0.6 ft, horizontal accuracy of 3.5 ft, and point spacing of 3.28 ft average.

The response information should be in the document The report has been modified to include the information. Closed 4 Figures 4 and 5
Should have a legend of the elevations for each major color - for both Fig 4 and 5. Are the hash marks the HEC-RAS cross section?
Legends have been added to Figures 4 and 5 for terrain elevations and model schematic. Closed
5 Figure 6 Please provide a legend for the land classifications. Figure 6 has been modified to include a legend for land classifications. Closed 6 Table 3 Please cite the reference where you got these "n" values Source reference has been added to the report. Did not see "HEC-RAS 2D User’s Manual" in references. Closed 7 3. Hydraulic model, last
sentence in section
What is the document that shows the elevations of the Dec 2005 - Jan 2006 flood? The source of the observed data is the Sacramento County ALERT system.

Appendix A has been modified to provide more source information.

Closed
Note: Please reference Appendix A in document.

Appendix A is referenced in the report, last sentence in Section 3. Noted 8 Table 4.

Should have another table that shows what each abbreviated term used in Table 4 are. For instance, Xyr_C= Z means X is flood event in years, Z = contributing area parameter.

Table 4 was modified to provide more information on the CVHS terminology. Closed 9 4. Hydrology, 3rd
paragraph, 2nd sentence
"During large flood events the gates .." Do these close manually or automatically? The pump station operation is automatic based on observed WSE at the pump station. This information has been added to report. Closed 10 5. Urban Levee Deisgn
Criteria, 1st paragraph,
4th sentence
Please explain why FEMA approach was used and not the COE method.

The design team reviewed the two modeling procedures and decided to use the FEMA approach. The FEMA approach is more straightforward and economical in application and results.

Please state the provided information in the document. The report has been modified to include the information. Closed 11 5.2 Debris Loading, 2nd
paragraph, 3rd sentence
"the hydraulic analysis included floating debris with a width equal to double the pier width, and a depth of 2 feet" Is the 2 foot depth below the DWSE? If so, please state As noted, the debris is "floating" debris, therefore it is 2 feet deep from the water surface at the given point in time of the analysis. Closed 12 5.6 Updated Hydraulic
model
"Therefore, no adjustment for updated hydraulic model has been included." Should explicitly say no significant physical changes to Dry Creek in the modeled portion were determined.

Text was modified as suggested. Closed
13 Figure 8 Seems like the MTOL is above the Top of Levee at about 7080+10. Please confirm this is not the case.

Under closer review the the computed MTOL exceeds the apparent top of levee at station 7081+00 by 0.06 ft. This report is documenting the computation of the DWSE, MTOL, etc. Compliance, or non-compliance, with ULDC is discussed in the Engineer's Report. The Engineer's Report was revised to reference this Station to just meeting the 3 feet. This slight amount is not significant enough to affect certification.

Disagree. The ULDC does not allow for a "slight amount" of exceedance.

This needs to be discussed with the IPE panel.

An exception was written in the Engineer's Report to address this condition. Closed
14 6.4 Seismic Vulnerability
Restoration Profile, But there is no seismic vulnerability according to the Engineer's report? Should state this here? This is a supporting document to the Engineers Report, and includes all of the hydraulic parameters defined in the ULDC. If any of these parameters are deemed not necessary in the Engineers Report, the reasoning should be included in the Engineers Report. For the Engineer's REport, there is a discussion of the Seismic Vulnerability Evaluation which utilizes the WSE provided in this H&H memo.

The IPE suggests that the topic of Seismic Vulnerability is in this document, a statement of if there is or is not vunerability should be in this document.

The report has been modified to include that a determination was made that the ULDC seismic vulnerability requirement does not apply to the DCNL.

Closed
15 References, USACE.
(2023).

Should say this is the HEC-RAS manual, not just the website. Text was modified as suggested. Closed 1 Appendix D, Dry Creek ULDC Due Diligence,
Geotech
Section 1.3,
Methodology, Page 2
Last line at the bottom of page 2 states "Since the existing analyses substantially met project criteria,.....".

Please explain what 'substantially' means in the context of meeting criteria.

The word 'substantially' was removed. Closed
2 Section 1.6 Water Surface
Elevations, Table 1, page
5 Table 2 - WSE for 2023 are given as a range while the KLF 2016b values appear to be specific to the location of the analysis cross section. Is it possible to include in parenthesis the 2023 elevations at the analysis cross section for comparision?
The difference in the 2023 200-year wse is 2.77 feet, whereas the difference for the 2023 HTOL is 1.65 feet. I thought the difference would be about the same. Are the numbers correct? Tables were updated to add ranges for 2016 and 2023 WSE. WSE values were checked against the report sources and are correct. The difference in the 200-yr WSE and the HTOL WSE are discussed in the MBK WSE memorandum.

Closed
3 Section 2.1, ULDC
Section 7.3 Soil
Sampling, Testing and
Logging, Page 6
This section of the report needs to be stronger to justify the exception. Reference is made to geomorph, geophysical data and inspection trench obseved during construction, but there is no discussion of the results and how this all demonstrates consistent subsurface conditions that justifies the exception. The geomorphology indicates older, denser, cemented deposits which is reflected by the higher blow counts of the explorations and the geophysical survey data shows predominantly fine-grained soils as corroborated by available exploration data. Discuss how these support the exception. Consider including even shallow borings in your boring count in Table 2. Even though shallow borings might not specifically meet recommended depth criteria, they help to show consistency of the geophysical survey data, and general site setting that doesn't appear problematic regarding underseepage.

This section was revised to include more detail for additional geotechnical explorations, geologic mapping, HEM, and construction observations.

Closed
Note: Response and updates made to Kleinfelder report are acceptable and adequately address this comment, however, minor typos were identified and should be rectified.

Noted, report text will be reviewed and revised accordingly. Noted 4 Section 2.2, ULDC
Section 7.4 Slopes
Stability for
Intermittently Loaded
Levees, Page 9.

Refer to comment #13 of the Engineers Report tab.

A parametric analysis was performed during preparation of the PIR for the ditch full condition. That analysis showed a FOS = 1.67 for the ditch full condition, which meets criteria. A note describing this has been added to the Slope Stability Comparison Summary is Section 7.4.

Please provide the location in the PIR where the ditch was analysed with water in it so that the analysis can be reviewed and the comment closed.

Analysis was not published in the Kleinfelder 2016 North Area Streams PIR. However, the analysis was run as a sensitivity analysis. The analysis is provided with these comments for IPE review.

Closed
5 Section 2.2, ULDC
Section 7.4 Slopes
Stability for
Intermittently Loaded
Levees, Page 8.

Last sentence states that wse's used for analysis for KLF 2016b are higher than the corresponding 2023 wse's, but Section 1.6, Methodology, states that the 2023 HTOL was slightly higher. Please clarify. Table 3 shows that the 2023 wse is indeed lower than the values used for 2016 analysis. Perhaps the wording of Section 1.6 needs revising?
The wording is off here and the HTOL is actually slightly lower in from 2016 to 2023.

The HTOL for the 2016 ULDC Geotechnical Results Summary is higher than the 2023 HTOL by 1.49 feet at Station 7000+00 to 0.57 foot at Station 7084+00 (the end of the 2014 WSE data). The 200-year WSE for the 2016 ULDC Geotechnical Results Summary is higher than the 2023 200-year WSE by 0.09 foot at Station 7000+00, meets the 2023 200-year WSE between Stations 7076+00 and 7077+00 and is 0.92 foot below the 2023 200-year WSE at Station 7084+00.

Closed
6 Section 2.3, ULDC
Section 7.5,
Underseepage, Page 11.

Why has an elevation of 34.3 feet been used to calculate the exit gradient at the landside toe in KLF, 2016a and KLF, 2016b geotechnical reports? The ground surface elevation at the toe is approximately at elevation +40 feet, which would indicate that there is no exit gradient at this location. This doesn't change the overall conclusion of meeting criteria, but the way the exit gradient calculation are presentated in these reports doesn't appear correct.

The gradient was measured at the bottom of the ditch. The gradient was not measured at the levee toe since the piezometric surface was below the toe of the levee. Measuring at the bottom of the ditch is conservative.

Closed
Note: Comment refers to analyses presented in the ULDC Geotechnical Results Summary Report for North Area Streams, dated April 29, 2016.

Figures G-7 and G-10 show exit gradient calculated at the landside levee toe, when there isn't a gradient.

SUPPORTING REPORTS

REVIEW BY INDEPENDENT PANEL OF EXPERTS (IPC)
ULDC_DryCreekNorthLevee_IPE_RTC_BackCheckFinal_02152024 1 of 3 No. DOCUMENT

LOCATION IN

DOCUMENT

IPE'S COMMENT
(12/22/2023)

ENGINEER'S RESPONSE
(1/22/2024)

IPE'S COMMENT
(1/30/2024)

ENGINEER'S RESPONSE
(Date)

IPE'S FINAL COMMENT / CLOSURE
(02/15/2024)
7 Section 2.6, ULDC
Section 7.9, Intefaces and
Transitions, Page 18 to

22. General comment: conclusions on some interfaces is based on KLF, 2016b stability analysis. These conclusions need to be checked based on the outcome/response to comment #13 on the Engineers Report tab.

See response to Comment #4.

Please provide the location in the PIR where the ditch was analysed with water in it so that the analysis can be reviewed and the comment closed.

Analysis was not published in the Kleinfelder 2016 North Area Streams PIR. However, the analysis was run as a sensitivity analysis. The analysis is provided with these comments for IPE review.

Closed
8 Appendix D, Dry Creek ULDC Due Diligence,
Geotech, Appendix A, Geotechnical
Evaluation 2023 100 year WSE Dry Creek
North Levee - 325-foot Upstream Extension,
Embankment and
Foundation Stability,

General comment: check to make sure that the conclusions of the qualitative assessment do not change based on the outcome/response to comment #13 on the Engineers Report tab.

See response to Comment #4.

Please provide the location in the PIR where the ditch was analysed with water in it so that the analysis can be reviewed and the comment closed.

Analysis was not published in the Kleinfelder 2016 North Area Streams PIR. However, the analysis was run as a sensitivity analysis. The analysis is provided with these comments for IPE review.

Closed
1 Appendix E1, DCNL Levee O&M Review in
Support of FEMA and ULDC Certification,
Nov. 2023

For information, one minor area of rilling/erosion was observed on the outisde bend (landslide) of the levee near the UPRR stop log structure during the IPE site visit on October 23, 2023.

I did not review the actual O&M manual, but am interested to know how details of rodent abatement activities are recorded as part of annual maintenance. Rodent activity has been linked to past levee failures in the Central Valley and it is important that abatement activities are recorded accurately to know the location, intensity, and other pertinent data (e.g. grout volumes at specific locations) of incidents to track intensity of activity and know whether there is the potential need to remove and reconstruct portions of a levee.

We checked with ARFCD and they indicated the erosion gully was repaired.

ARFCD has a Rodent Abatement Plan, which is included at Appendix H1 to the ULDC Report. This indicates their process in documentation and tracking. I have seen records of grouting and scheduling of different tasks.

Closed
2 General There should be a bibiliography section for the cited documents. A bibliography was added to the memo. Closed 3 1st paragraph "I reviewed the urban portion" Do you mean you went on a site inspection? The text was revised to reflect what was observed. We do not want to call it an "inspection", but chose the word "review" instead. Revised text is "I drove the urban…" and 2nd sentence "The purpose of the site visit was to review conditions to support..."
Closed
4 3rd paragraph
"MBK Engineers (MBK) performed an inspection of levee vegetation" Was there an official report on the site inspection? If so, please cite.

The word "inspection" was changed to "review". This is the document that provides observations. A separate document was not prepared. Closed 5 "Based on review of the OMRR&R and observations from this site visit, the Dry Creek North Levee meets both FEMA and ULDC requirements related to O&M" Is Tom saying this? If so, it should say "I have determined that …"
The text was revised as suggested. Closed
6 SPFC - should spell out The text was revised as suggested. Closed 7 Last sentence And the OMRR&R? OMRR&R is defined in Paragraph 1. Closed 8 End of document Will tom be sealing this document with his PE? Yes, Tom will provide his stamp. Closed 1 Appendix E2, USACE Periodic Inspection
Report No. 1 Januaryu 2010.

Table 3, Page 6 Should the river stage elevation of 4.20 feet at I Street Bridge on 7 January 2010, be 14.20 feet? Comment noted, this document was prepared by others. Closed 1 Appendix F, O&M ROW Maps .- See comment # 33 on the Engineers Report tab.

The ROW map aerial photo background is used to help identify geographic location, but should not be utilized to assess vegetation. The current condition does not have woody vegetation within 15 feet of the levee toe, as outlined in the O&M letter (Appendix F).

Response acceptabe. Comment closed
1 Appendix G, DCNL Due Dilligence Review
for ULDC Cedrtification, Mead and Hunt,
November 2023.

Section 2.2.4,
Encroachment
Assessment White Paper,

The first sentence of the first paragraph and first sentence of the last paragraph on page 7 references "high hazard encroachmnets", but the three bullets identifying the classification of encroachments on page 5 doesn't include high hazard. Please clarify what defines a high hazard encroachment.

The wording has been corrected to match with 2.2.4. Assessment of nonpenetration encroachments was conducted by MBK. Closed 2 Section 3.4, Updated
Results, Page 9
Third bullet, sixth sentence onwards - references that the interior of the culvert has not been inspected since construction and then states that the concrete pipe is not subject to corrosion. How was this conclusion drawn?
A target date for inspection should be noted if possible for tracking and planning purposes. Otherwise, inspection might get dealyed further. How does the O&M manual address this? The intent is that the RCP does not have a the same risk of corrosion as metallic pipe.

Interior inspection would reveal joint displacement or other damage, but as described the pipe joints are fully encased. The last sentence indicates that the interior inspection effort would not affect the determination.

The O&M manual addresses the need for inspection of the penetrations essential to the levee function in C.2, item 9. on a five year cycle. The pipe interior inspection is scheduled to occur within the next year.

Closed
Note: Revised text in Section 3.3 using the term 'high hazard' should this be 'high risk'?
High hazard is the correct term for penetrations per ULDC. Noted 3 Section 3.4, Updated
Results, Page 9
Fourth bullet, second sub-bullet - has a date been set to get this outstanding hazard assessment completed? A target date should be noted if possible for tracking and planning purposes. Otherwise assessmnet might get dealyed further. How does the O&M manual address this? The report has been updated to include the assessment findings.

The levee O&M manual is not intended to address encroachments in detail. The manual generally describes utility encroachments in 6-04.A.2 and Exhibit L. Exhibit L will be updated as needed. 3.03.B.3 outlines responsibility for approval of new encroachments, inspection for unauthorized encroachments,.

The wording of how this pipe was abandoned and capped, which segment of pipe was removed, and what the resulting trench was backfilled with is unclear. A screen clip (embedded figure) of the 2018 asbuilt drawing would likely be helpful here. Suggest providing addition detail on the abandonment, especially backfill materials and compaction used to backfill the excavations within the levee. Although the pipe does not penetrate the levee, is there a potential shortening of the seepage path that should be considered. It's unclear what the basis is for stating this does not pose a significant risk to the levee; additional detail would help clarify that.

Mead & Hunt is continuing outreach to PG&E for documentation of construction methods. However, the findings that the penetration does not present a significant risk to levee performance were made based upon available information.

See response to comment below.

Closed
4 Section 3.4, Updated
Results, Page 9
Fourth bullet, third sub-bullet - has a date been set to get this outstanding hazard assessment completed? A target date should be noted if possible for tracking and planning purposes. Otherwise assessmnet might get dealyed further. How does the O&M manual address this? Our report has been modified to include assessment findings.

The levee O&M manual is not intended to address encroachments in detail. See response above.

The justifications in this section should be clarifed, and consideration should be given to including a sketch or screen clip for clarity. I bleieve the intent is that the evaluation found the 2-inch main is entirely within the Marysville Blvd, prism, and as such, there is no outlet for leakge to progress to. unfiltered face for backwards erosion piping to progress to.

Suggest rephrasing the sentence, "The potential for backwards erosion piping along the penetration is not significant due to the placement in the roadway that confines the trench", as I think the intent is that there is no free face for BEP to initiate at. I'm not sure how confinement of the trench prevents BEP.

Justification has been clarified. PG&E gas main as-built drawings are confidential and cannot be shared. Description accurately describes that the pipe is capped under the landward edge of the levee crown.

Closed
5 Section 6.1, Purpose,

Section 6.1 states, "MBK Engineers has prepared the draft O&M manual for the DCNL operated by the ARFCD and will obtain concurrence to satisfy ULDC Compliance. No further review is required by Mead & Hunt." However, Section 6.3 states "The O&M manuals and operating procedures were found to cover all system components; the levee system, closure structures and the NEMDC Pump Station." It is unclear if Mead & Hunt has performed an independent review of the draft OMRR&R manual, currently being reviewed by USACE, for concurrence with the ULDC. The IPE suggest these sections be revised to clarify what has been reviewed, and if documents have not been reviewed, how they have been found to be in compliance.

Mead & Hunt was not tasked with a review of the levee O&M manual, which is being reviewed by the USACE. There is no separate manual for the closure structures, that are consider part of the levee system. The intent of the statement was to indicate the components are distinct and operated by three different public agencies. Mead & Hunt was tasked with reviewing manuals for the NEMDC Pump Station operation related to flood control operations, with findings covered in Section 6.3.

Based on the response to a similar question in the Engineer's Report, review was performed by SAFCA and ARFCD prior to submittal to USACE.

Final approval will be provided by USACE, likely on an unknown timetable, as the final compliance step. This section states MBK will "obtain concurrence to satisfy ULDC Compliance", how will the pending approval by USACE be tracked to ensure this outstanding compliance item will be eventually resolved?
Text was modified to reflect agreement between SAFCA and ARFCD with no tie to USACE. Closed
ULDC_DryCreekNorthLevee_IPE_RTC_BackCheckFinal_02152024 2 of 3 No. DOCUMENT

LOCATION IN

DOCUMENT

IPE'S COMMENT
(12/22/2023)

ENGINEER'S RESPONSE
(1/22/2024)

IPE'S COMMENT
(1/30/2024)

ENGINEER'S RESPONSE
(Date)

IPE'S FINAL COMMENT / CLOSURE
(02/15/2024)
6 Appendix A1
Appendix A1 notes that following testing of the UPRR stop log structure for DCLN (Structure RR-0), recommendations were made to replace or modify the tarp to allow proper sealing with sand bags, and to install anchorage hooks at all site. The report is silent on whether these modifications have been planned or completed.

This is not critical to facility operation as the City maintains a supply of Visqueen. The site specific tarps and anchorage were for ease of installation.

While it can be argued the hooks are not critical, the length of the custom tarp was identified to be too short for proper sealing and required modification. Although it could be modified with additional visqueen, will the crews know to install it with infrequent test installation (requested exemption)? In other words, a recommendation to modify the tarp was made based on the objectives of the December 2022 test installation - please clarify why these resulting recommendations are not crtical to fhe tunctioning of the closure structure. Why wasn't the recommendation to just bring more visqueen to the site?
Comment acknowledged. The City does maintain Visqueen on site during install and has historically utilized. The crews are supervised experienced personnel that know how to properly seal with plastic. Our recommendation for site specific tarps was for ease of installation.

Mead & Hunt is under contract with the DOT to continue to assist the City. The recommendation presented in the TM was to document improvements in the installation approach as reviewed in the field with City staff.

Closed
7 Appendix B
The Appendix B slip sheet is labeled "APPENDIX B. Exception Technical Memo for PG&E Gas Main Modification." However, the memo that follows is a justification of the exception to annual testing of the UPRR stop log structure. It is unclear if a gas main memo is missing or if the slip sheet is mislabeled. The TOC suggests the gas memo is missing.

Slip sheet title has been revised, and TOC updated. Response acceptable. Comment closed. 1 Appendix H1, Rodent Control and
Abatement Program, October 2017.

Completed Document
The memo states that when grouting is performed, grout is "…pumped at low pressures to avoid damaging the embankment,…". Where are the maximum permissible pressures defined, and how are they tracked in the field, to avoid hydrofracture of the levee embankment? For the grouting, ARFCD follows the State DWR procedure developed by the Sac Maintenance Yard. Documentation. A rather low pressure pump is used and the grout is delivered to the hole through a 50-75 foot hose. Based on this setup, ARFCD staff feel the pressure is pretty low and practically gravity feed by that point.

The response is generally accceptable, although better document of pressures would be preferred. However, where is it documented that the work is performed in accordance with the Sac Maintenenace Yard procedure? It does not appear to be noted in this document or the draft OMRR&R. How does ARFCD ensure that is the procedure that is followed in the future?
Comment acknowledged, recommendation to reference DWR
maintenance yard procedures in the plan moving forward. Email sent to Tim Kerr 2/5/24.

Closed
1 Appendix H2, Security plan General
The IPE reveiwed this document and found it to comply with established standards for a Security plan related to flood control projects. For it to be a part of the ULDC certification, should it officially be signed?
To date, this type of document has not been signed or stamped. It is usually a living document that continues to get updates as the system evolves over time. Closed 2 Appendix H2, Security plan General
The IPE found it strange that ARFCD does not document citizen observations (last sentence of 2nd paragrpah of section 2.1) but says it relies upon them to detect intrusions (last paragraph of section 2.2) Comment acknowledged. We understand from ARCFD staff that the volume of calls can be overwhelming at times and keeping track in a log type format is not feasible. Closed 1 Appendix H3, Flood Safety Plan General
Since the document provided is not signed (but dated 2018), has it been approved with a signed document? For it to be a part of the ULDC certification, should it officially be signed such as in the signature page of H2?
To date, this type of document has not been signed or stamped. It is usually a living document that continues to get updates as the system evolves over time. Closed 2 Appendix H3, Flood Safety Plan General
The IPE reveiwed this document and found it to comply with established standards for a Flood Safety plan related to flood control project.

Comment acknowledged. Closed
ULDC_DryCreekNorthLevee_IPE_RTC_BackCheckFinal_02152024 3 of 3 Appendix C.

ULDC Water Surface Elevation
Profiles - MBK
Water Resources  Flood Control  Water Rights

TECHNICAL MEMORANDUM
DATE: February 16, 2024
PREPARED FOR: SAFCA
PREPARED BY: Michael Archer, P.E.

REVIEWED BY: Don Trieu, P.E.

SUBJECT: Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee

1. Purpose
The Sacramento Area Flood Control Agency (SAFCA) is in the process of evaluating the levees within its jurisdictional boundaries for compliance with the State of California’s Urban Levee Design Criteria (ULDC) (DWR, 2012). This technical memorandum provides documentation of the determination of the hydraulic parameters listed in Table 1, which are necessary for the ULDC compliance evaluation of the Dry Creek north levee.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 1 Table 1. ULDC Hydraulic Parameters
Parameter ULDC Definition
Design Water Surface Elevation (DWSE) Median 200-year water surface elevation (WSE) Minimum Top of Levee (MTOL)
DWSE plus the higher of
• 3 feet, or
• wind setup and wave runup
Hydraulic Top of Levee (HTOL)
The lower of
• DWSE plus 3 feet, or
• Median 500-year WSE
Seismic Vulnerability Restoration Profile (SVRP)
10-year water surface elevation plus the higher of
• 3 feet, or
• wind setup and wave runup

2. Study Area
Dry Creek is a tributary to the Natomas East Main Drainage Canal (NEMDC). The NEMDC collects drainage from watersheds on the east side of the Natomas Basin, and discharges it into the Sacramento River near the mouth of the American River (Figure 1). The Dry Creek north levee extends from Rio Linda Boulevard, downstream to the NEMDC, a length of approximately 8,500 feet (Figure 2). The upstream end of the levee ties into natural high ground at Rio Linda Boulevard.

Robla Creek is another tributary to the NEMDC and is located immediately south of Dry Creek. For a distance of about 9,000 feet, starting at the NEMDC and going upstream, Dry Creek and Robla Creek have a shared floodplain. The U.S. Army Corps of Engineers (USACE) has a proposed project on Magpie Creek, a tributary to Robla Creek, authorized through the American River Common Features 2016 Project (USACE, 2022). As designed, the Magpie Creek project will prevent flood water from escaping Magpie Creek, resulting in increased conveyance to Robla Creek and downstream. For this reason, and because it is an authorized project, the Magpie Creek project is included in the ULDC analysis.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 2 Figure 1. Location Map
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 3 Figure 2. Site Map and Levee Stationing, Dry Creek North Levee

3. Hydraulic Model
A HEC-RAS 6.4.1 hydraulic model was developed for this analysis. HEC-RAS is software developed by the USACE Hydrologic Engineering Center for the purpose of performing one-dimensional (1-D) and twodimensional (2-D) hydraulic calculations for a full network of natural and constructed channels (USACE, 2023).

The hydraulic model, referred to as the Sacramento north area streams, or NAS, model is made up of both 1-D elements and 2-D flow areas. The model was developed from an existing 1-D model. Reaches with small low flow channels and wide floodways, such as Dry Creek, Robla Creek and Magpie Creek, were replaced with 2_D flow areas. A schematic of the model is shown in Figure 3. The streams within the model study area are summarized in Table 2. The downstream boundary of the model is the NEMDC at the American River north levee.

Table 2. Streams Within the Model Study Area
Stream Upstream Boundary Downstream Boundary Model
Element
Length
(miles)
Dry Creek Below Q Street NEMDC 2-D 3.5
Robla Creek Above 16th Street NEMDC 2-D 3.3
Magpie Creek Patrol Road Robla Creek 2-D 1.8
Don Julio Creek Patrol Road Magpie Creek 2-D 1.3
Arcade Creek Auburn Blvd. NEMDC 1-D 6.6
NEMDC D-15 Pump Station American R. north levee 1-D 4.3 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 4 Figure 3. North Area Stream HEC-RAS Model Schematic
A terrain model is required for 2-D modeling, as it is used to establish the geometric and hydraulic properties within 2-D flow areas. The primary terrain used for the NAS model was developed by USACE for use in their hydraulic analysis of the Magpie Creek project (USACE, 2021). The USACE terrain did not provide coverage of the entire NAS model study area, as shown in Figure 4. Terrain developed for the California Department of Water Resources (DWR) Central Valley Floodplain Evaluation and Delineation (CVFED) program (Wood Rodgers, 2014) was used to extend coverage to the entire NAS model study area, as shown in Figure 5. The vertical and horizontal accuracy and resolution of the USACE terrain is not provided in the referenced documentation. The CVFED terrain has a vertical accuracy of 0.6 feet, a horizontal accuracy of 3.5 feet, and an average point spacing of 3.28 feet.

Manning’s n roughness coefficient values within the 2-D flow areas were defined using land classification mapping from the National Land Cover Database, as shown in Figure 6. Manning’s n-values were initially assigned for the various land classifications based on recommendations in the HEC-RAS 2D User’s Manual, and refined as necessary through the calibration process, The land classifications and final associated n-values are listed in Table 3.

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Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 5 Figure 4. USACE Terrain Coverage Figure 5. Final Terrain Coverage Figure 6. Land Classification Map
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 6 Table 3. Land Classifications and Assigned Manning’s n-values Land Classification Manning’s
n-value Land Classification Manning’s n-value
Barren Land Rock-Sand-Clay 0.035 Emergent Herbaceous Wetlands 0.06 Cultivated Crops 0.038 Evergreen Forest 0.08
Deciduous Forest 0.08 Grassland-Herbaceous 0.035
Developed, High Intensity 0.10 Open Water 0.03
Developed, Low Intensity 0.05 Pasture-Hay 0.042
Developed, Medium Intensity 0.07 Shrub-Scrub 0.08
Developed, Open Space 0.04 Woody Wetlands 0.07
The model was calibrated to the high flow event that occurred during the end of December 2005 and the beginning of January 2006 (the “2006 flood”). Calibration results are provided and summarized in Appendix A.

4. Hydrology
Central Valley Hydrology Study (CVHS) procedures and hydrologic data were used in this analysis. The CVHS was commissioned by the California Department of Water Resources (DWR) and prepared by the USACE (USACE, 2015). For the Sacramento River and San Joaquin River basins, the CVHS defines a procedure in which a scaled flood event with a pattern based on a historical flood event is selected to represent the flood of a specific frequency at a specific location, or centering. The CVHS also developed hydrologic data for several smaller ungaged watersheds, including the Natomas-Area Stream Group, which includes Dry Creek and Arcade Creek (USACE, 2013). The hydrologic data for the Natomas-Area Stream Group was developed for discrete N-year flood frequencies with centerings defined by contributing area (C) parameters. The Natomas-Area Stream Group hydrologic data was updated by USACE in 2019. There are four CVHS defined flood centerings that influence the NAS model study area:
• Natomas-Area Stream Group: Dry Creek
• Natomas-Area Stream Group: Robla and Magpie Creeks
• Natomas-Area Stream Group: Arcade Creek
• Sacramento River Basin: American River at Fair Oaks and Latitude of Sacramento The ULDC requires the computation water surface elevations for the 10-year, 200-year, and 500-year flood events. The Sacramento River Basin scaled flood events and Natomas-Area Stream Group C parameters for flood frequencies and flood centerings are summarized in Table 4. The final computed maximum WSE is the composite maximum of the maximum WSE’s computed for the four flood centerings.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 7 Table 4. CVHS Flood Events
Flood Centering Recurrence
Interval
Watershed
North Area Streams Sacramento River
Dry Creek 10-year 10yr_C=99.5 1 1995-60% 2, 3
200-year 200yr_C=99.5 1 1995-105% 2
500-year 500yr_C=99.5 1 1995-120% 2
Robla-Magpie Creeks 10-year 10yr_C=RIOLINDA_MAGPIE 1 1995-60% 2, 3 200-year 200yr_C=RIOLINDA_MAGPIE 1 1995-105% 2
500-year 500yr_C=RIOLINDA_MAGPIE 1 1995-120% 2
Arcade Creek 10-year 10yr_C=ARC 1 1995-60% 2, 3
200-year 200yr_C=ARC 1 1995-105% 2
500-year 500yr_C=ARC 1 1995-120% 2
Fair Oaks-latitude of
Sacramento
10-year 1986-55% 2 1986-55% with 40% on
American R. 1, 2
200-year 1986-110% 2 1986-110% with 125% on
American R. 2
500-year 1986-100% 4 1986-100% with 176% on
American R. 4
1 Data ID from USACE 2019 updated hydrologic data set.
2 Event selection by USACE (USACE, 2019). 1995-60% means flood pattern based on 1995 flood with a 60% scale factor. 3 CVHS hydrologic data does not include the 1995-60% flood event. The closest available flood event data, 1995-75%, was used in the analysis. The 1995-75% data approximately represents the 20-year flood event. 4 Event selection by USACE (USACE, 2020)

The County of Sacramento’s D-15 pump station, at the upstream end of the modeled NEMDC reach, is an inline pump station with gates (County of Sacramento, 2007). During large flood events, the gates close automatically when the water surface elevation at the pump station reaches a pre-defined trigger elevation, preventing backwater due to high flows in Dry and Robla creeks from affecting flood stages north of the pump station. After the gates close, the pumps will automatically turn on to ensure positive flow from north to south. The station has three 333 cfs capacity pumps. The operation criteria specifies a firm capacity based on use of two of the three pumps, keeping one for a backup. However, all three pumps may be operated concurrently if required. For the ULDC analysis, the conservative assumption of a three-pump operation, with a total flow of 999 cfs, is used.

As noted earlier, the downstream boundary of the NAS model is located on the NEMDC at the American River north levee. The analysis used a stage hydrograph downstream boundary condition that was determined using a Sacramento River basin systemwide hydraulic model (MBK Engineers, 2019) to simulate the appropriate Sacramento River CVHS flood events.

5. Urban Levee Design Criteria (ULDC)
Section 7.1 of the ULDC allows for two options for the determination of the DWSE. The first option is the Federal Emergency Management Agency (FEMA) Approach, in which the DWSE is computed deterministically with a hydraulic model. The second option is the U.S. Army Corps of Engineers Approach, which incorporates uncertainty into the determination of the DWSE. The approach selected for this analysis was the FEMA Approach, due to its application and results being more straightforward and economical.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 8 The ULDC defines the DWSE as the “200-year stage or water level used to design a levee or floodwall”.

Section 7.1.1 of the ULDC specifies that the hydraulic modeling used to determine the DWSE must consider the following:
• Upstream, downstream, and nearby levees and floodwalls protecting urban areas are assumed to be raised to the median 200-year water surface elevation plus 3 feet and not allowed to breach, even if overtopped. Overtopping flows are assumed to leave the channel and remain in the 200- year floodplain.
• All project levees and floodwalls are to be modeled to incorporate a minimum crown elevation equal to the authorized (usually the 1955/1957) USACE design profiles – this affects nonurbanized areas for the most part – all such levees and floodwalls are to be allowed to overtop, act as weirs, and not breach for floods up to and including the median 500-year flood.

Overtopping flows are assumed to leave the channel and remain in the 200-year floodplain. • Non-project levees and floodwalls in non-urbanized areas in the region, to the extent they may affect the DWSE, are to be modeled at their existing or authorized height, whichever is higher, and to act as weirs without breaching if overtopped.
• Debris loading on bridges must be considered. Bridges with less than 3 feet of clearance above the DWSE may experience extraordinary debris loading that must be evaluated in addition to typical pier/bent debris loading. The evaluation should include historic and potential debris transport in the stream, an analysis of loading on the bridge, and analysis of backwater impacts on the DWSE in the vicinity of the bridge.

Section 7.1.3 of the ULDC requires adjustments to the DWSE for the effects of superelevation, when applicable. Superelevation is a tilting of the water surface, which may occur as water flows through a bend in the channel. Computational methods for determining superelevation adjustments are in the USACE Engineering Manual 1110-2-1601.

Section 7.1.3 of the ULDC also states that the “…the civil engineer should consider increasing the DWSE to account for the potential increases in water surface associated with climate change, updated hydrology, updated hydraulic models, and sea level rise”. This statement implies that adjustment for sea level rise is optional; however, Section 7.19 of the ULDC states, “the effects of sea level rise are to be estimated and addressed for the duration during which a Finding that the urban level of flood protection exists may be valid”. Based on the second statement, sea level rise adjustment appears to be mandatory.

Additionally, Section 7.1.3 of the ULDC states:
“[T]he civil engineer also needs to address two other situations: (1) whether upstream levee or floodwall breaches could produce overland flows that would reach the area protected by the levee system or increase the water surface elevation along the levee system, and (2) whether flooding in a nearby leveed area could fill that area and breach a nearby levee or floodwall, returning flow to the stream and increasing the DWSE for a portion of the levee system".

Neither of these conditions applies to the Study Area, and therefore they were not evaluated.

The following sections address the requirements in the ULDC and discuss the application of each requirement for the Dry Creek north levee:

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Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 9

5.1 Levees
As per the ULDC, all urban levees were assumed to have a minimum top elevation of the median 200-year water surface elevation plus 3 feet. All non-urban State-Federal Project levees were assumed to have a minimum crown elevation equal to the authorized USACE design profiles.

5.2 Debris Loading
The ULDC specifies that debris loading on bridges must be considered, and that “bridges with less than 3 feet of clearance above the DWSE may experience extraordinary debris loading that must be evaluated in addition to typical pier/bent debris loading”.

Bridge pier debris are applied in accordance with guidelines provided in a July 2014 letter, sent by USACE to the California Central Valley Flood Protection Board to clarify the level of screening and analysis that should be included on encroachment permit applications that are sent to the USACE for review. A copy of the letter is provided in Appendix C. Included in the letter was guidance for modeling debris build-up.

Based on this guidance, under the ULDC “typical” debris loading condition, the hydraulic analysis included floating debris with a width equal to double the pier width, and a depth of 2 feet below the water surface.

Under the ULDC “extraordinary” debris loading condition, floating debris with a depth of 2 feet below the water surface were modeled for the full width with the “extraordinary” condition.

Debris were not applied to bridges in the model upstream of the levee reaches, as debris on these bridges would have no effect on the water surface elevation in the levee reaches.

A summary of the bridge pier debris conditions included in the hydraulic analysis is provided in Table 5.

5.3 Superelevation
Superelevation is a tilting of the water surface that occurs on the outside of a river bend. The ULDC notes that, “on the outside of a bend, the superelevation needs to be added to the DWSE”. The superelevation adjustment, per USACE Engineer Manual 1110-2-1416, River Hydraulics, is specific to 1-D hydraulic modeling. The water surface elevation at the Dry Creek north levee is computed with 2-D hydraulic computations, therefore the superelevation adjustment is not applicable.

5.4 Climate Change
The effects of climate change on extreme precipitation events in the Central Valley are being studied, but there is no indication of what the outcome of that work will be. Therefore, the hydrology used in this analysis has not been adjusted for the effects of climate change.

5.5 Updated Hydrology
This analysis makes use of the most recent accepted hydrologic data for the Study Area, which was developed as part of the Central Valley Hydrology Study, as noted in Section 4 of this report.

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Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 10 Table 5. Bridge Pier Debris Loading
River River
Station 1 Bridge
Debris Loading
Condition (t=typical;
E=extraordinary)
200-yr 500-yr
Dry Creek West
Branch 1,340 ft Rio Linda Blvd. E E
Dry Creek East Branch 3,910 ft SNRR Bike Trail t t
640 ft Rio Linda Blvd. E E
Dry Creek (lower) 6,120 ft private bridge E E
110 ft UPRR (near mouth) E E
Robla Creek 9,680 ft SNRR Bike Trail E E
8,290 ft Rio Linda Blvd. E E
90 ft UPRR (near mouth) E E
Magpie Creek 6,120 ft Raley Blvd. E E
4,010 ft Vinci Ave. E E
1,130 ft Dry Creek Rd. E E
Arcade Creek 1.344 mi Rio Linda Blvd. E E

1.26 mi SNRR Bike Trail E E

0.722 mi Norwood Avenue E E

0.045 mi UPRR (near mouth) E E
NEMDC 6.139 mi Main Avenue t t

5.168 mi Interstate 80 t t

4.347 mi Silver Eagle Road t t

3.03 mi West El Camino Avenue mix E

2.653 mi Arden-Garden
Connector t t
1 River station in miles for 1-D reaches and in feet for 2-D flow area.

5.6 Updated Hydraulic Model
The hydraulic model used for this analysis was developed from the most current available data. Due to the calibration process, an updated hydraulic model would not be expected to have a substantial effect on the computed results unless significant physical changes have occurred in the modeled system. Since no significant physical changes have occurred since the data used for the model development was collected, no adjustment for updated hydraulic model has been included.

5.7 Sea Level Rise
The ULDC notes that, “the effects of sea level rise are to be estimated and addressed for the duration during which a Finding that the urban level of flood protection exists may be valid”. The duration of finding proposed for the subject project is 20 years.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 11 The analysis assumed a sea level rise of 3.68 feet at San Francisco. This is the 50-year sea level rise projection, determined by the California Department of Water Resources (DWR) for the 2022 update of the Central Valley Flood Protection Plan (CVFPP) (DWR, 2022). Being that the duration of the Urban Level of Protection finding is 20 years, the use of a 50-year projection is a conservative assumption. The effects of this sea level rise were applied at the downstream boundaries of the Sacramento River systemwide hydraulic model simulations, which were used to determine the downstream boundary conditions for the NAS model.

6. Computed ULDC Hydraulic Parameters
The following sections present the computed ULDC hydraulic parameters that were described in Section 1 of this technical memorandum:
• Design Water Surface Elevation (DWSE)
• Minimum Top of Levee (MTOL)
• Hydraulic Top of Levee (HTOL)
• Seismic Vulnerability Restoration Profile

6.1 Design Water Surface Elevation (DWSE)
The ULDC defines the DWSE as “[the] median 200-year water surface elevation”, with adjustments for the following factors:
• Bridge pier debris loading
• Superelevation
• Sea level rise
Debris loading and sea level rise are accounted for in the hydraulic model simulations, as described in Sections 5.2 and 5.7. As noted in Section 5.3, the superelevation adjustment is not applicable to the hydraulic computations at the Dry Creek north levee.

A profile plot of the computed DWSE for the Dry Creek north levee is provided in Figure 7. The levee crest profile is included on the profile plot. A tabulation of the DWSE is provided in Appendix C.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 12 Figure 7. ULDC DWSE Profile, Dry Creek North Levee

6.2 Minimum Top of Levee (MTOL)
The ULDC defines the MTOL as the higher of the DWSE plus 3 feet, or the DWSE plus the computed wind setup and wave runup. Wind setup and wave runup for the Dry Creek north levee has been computed by Mead & Hunt (Mead & Hunt, 2023). The maximum computed wind setup and wave runup is 2.5 feet.

Since this is less than 3 feet, the MTOL for the Dry Creek north levee is the DWSE plus 3 feet. A profile plot of the MTOL is provided in Figure 8. A tabulation of the MTOL is provided in Appendix C.

A detailed review of the results shows that the MTOL exceeds the top of levee by about 0.1 feet near station 7081+00, as shown in Figure 9. An exception could be made for this MTOL non-compliance for several reasons:
• The MTOL deficiency is very small, 0.1 feet at its maximum. • The length is the deficiency is short, less than 20 feet. • The DWSE barely exceeds the levee waterside toe elevation, as can be seen in the cross section plot provided in Figure 10.
• The levee is short at the deficiency location, just over 3 feet tall, and is topped by a paved road (4th Street).

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Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 13 Figure 8. ULDC MTOL Profile, Dry Creek North Levee
Figure 9. Detailed Profile at MTOL Non-compliance Location SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 14 Figure 10. Cross section at MTOL Non-compliance Location

6.3. Hydraulic Top of Levee (HTOL)
The ULDC defines the HTOL as the lower of the DWSE plus 3 feet, or the median 500-year WSE. A profile plot of the HTOL is provided in Figure 11. For reference, the DWSE plus 3 feet and 500-year WSE profiles are also shown. A tabulation of the HTOL is provided in Appendix C.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 15 Figure 11. ULDC HTOL Profile, Dry Creek North Levee

6.4 Seismic Vulnerability Restoration Profile (SVRP)
The ULDC specifies that if there is the potential for levee damage due to a seismic event, a plan needs to be in place to “restore grade and dimensions for at least 10-year WSE plus 3 feet of freeboard or higher for wind setup and wave runup within 8 weeks”. Kleinfelder evaluated the seismic vulnerability of the Dry Creek north levee (Kleinfelder, 2018), and determined that it met the DWR Urban Levee Evaluation (ULE) criteria for low seismic vulnerability, making the need for a seismic vulnerability restoration profile unnecessary.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 16 References
County of Sacramento. (2007). D-15 NEMDC Drainage Pump Station Summary of Operations and Procedures Manual. May 2007.

DWR. (2012). Urban Levee Design Criteria. May 2012.

DWR. (2022). 2022 CVFPP Update - Technical Analyses Summary Report, Public Draft. May 2022.

Kleinfelder. (2018). Geotechnical Evaluation Summary of Seismic Vulnerability; Applicable to ULDC Section 7.7 – Seismic Vulnerability; Dry Creek North Levee; Sacramento, California. February 7, 2018.

MBK Engineers. (2019). Technical Memorandum - Sacramento Weir Widening Project, Initial Hydraulic Impact Analysis. October 31, 2019.

Mead & Hunt. (2023). Dry Creek North Levee Wind-Wave Analysis. October 30, 2023.

USACE. (2013). Central Valley Hydrology Study: Natomas-area Stream Group - Pleasant Grove Creek, Dry Creek, and Arcade Creek Watersheds Hydrologic Analysis. March 26, 2013.

USACE. (2015). Central Valley Hydrology Study. November 29, 2015.

USACE. (2019). Memorandum for Record, Subject: CVHS Hydrograph Package for HEC-RAS Model Inputs. February 20, 2019.

USACE. (2020). Hydrology Technical Memorandum for Developing WRDA 2016 Water Surface Profiles.

April 10, 2020.

USACE. (2021). Hydraulic Model Summary Magpie Creek Canal For American River Common Features Project. USACE - Vicksburg District. April 2021.

USACE. (2022). Engineering Documentation Report, American River Common Features 2016, American River North Basin, Reach I, Modifications Through March 2022, Preconstruction Engineering and Design Phase. March 29, 2022.

USACE. (2023). HEC-RAS User's Manual. Retrieved from
https://www.hec.usace.army.mil/confluence/rasdocs/rasum/6.4 Wood Rodgers. (2014). Central Valley Floodplain Evaluation and Delineation, Lower Sacramento River Technical Memorandum. January 17, 2014.

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Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL

APPENDIX A
Hydraulic Model Calibration
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-1 Calibration flood event: December 2005-January 2006
The stream gages listed in Table A-1 provided the available observed data used for calibration of the Dry Creek and Robla Creek watershed area. All the gages are part of the Sacramento County ALERT system (https://www.sacflood.org/). The gage data was provided by Sacramento County. The gage locations are shown in Figure A-1.

Table A-1. Stream Gages with Observed Data Available for Calibration Gage Agency Sensor ID
Dry Creek West Branch at SNRR Bike Trail Sacramento County ALERT 2230 Dry Creek West Branch at Elkhorn Blvd. Sacramento County ALERT 1661 Dry Creek Bypass at Elkhorn Blvd. Sacramento County ALERT 1662 Dry Creek East Branch at Elkhorn Blvd. Sacramento County ALERT 2782 Robla Creek at SNRR Bike Trail Sacramento County ALERT 2753 D15/NEMDC Downstream Sacramento County ALERT 2772
Figure A-1. Stream Gage Location Map
A comparison of the observed and computed peak stages at the gage locations is provided in Table A-2.

Profile plots of the computed maximum water surface elevations with available observed gage peaks are provided in Figures A-2 through A-6.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-2 Table A-2. Calibration Results, Comparison of Observed and Computed Peak Stages Gage Maximum Stage (feet NAVD88) Difference
Observed Computed (feet)
Dry Creek West Branch at SNRR Bike Trail 47.62 48.06 +0.44 Dry Creek West Branch at Elkhorn Blvd. 46.06 46.17 +0.11 Dry Creek Bypass at Elkhorn Blvd. 46.95 46.58 -0.37
Dry Creek East Branch at Elkhorn Blvd. 46.88 49.33 +2.45 a Robla Creek at SNRR Bike Trail 40.59 40.78 +0.19
D15/NEMDC Downstream 36.44 36.69 +0.25
a The Sacramento County ALERT website for this gage notes that “when the east branch reaches 49.9’ +/- the stage at the west branch is approximately 46.5’ +/-“. The computed peak stage difference for these locations of 3.2’ is similar to the reported difference of 3.6’. Therefore, it can be concluded that the reported peak stage of 46.88’ at the Dry Creek East Branch at Elkhorn Blvd gage is suspect.

Figure A-2. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek West Branch SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-3 Figure A-3. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek East Branch Figure A-4. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek (lower) SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-4 Figure A-5. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek Bypass Channel Figure A-6. Calibration Analysis Maximum Water Surface Elevation Profile, Robla Creek SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Appendix B
USACE Letter with Debris Loading Guidance
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-1 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-2 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-3 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-4 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-5 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-6 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-7 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-8 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-9 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL

APPENDIX C
Tabulation of ULDC Hydraulic Parameters for the Dry Creel North Levee SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page C-1 Table C-1. Design Water Surface Elevation (DWSE) and Minimum Top of Levee (MTOL) Levee
Station
(feet)
DWSE
(feet)
MTOL 1
(feet)
HTOL 2
(feet)
Levee
Station
(feet)
DWSE
(feet)
MTOL 1
(feet)
HTOL 2
(feet)
7000+00 41.40 44.40 43.00 7045+00 41.44 44.44 43.03
7001+00 41.40 44.40 43.00 7046+00 41.45 44.45 43.04
7002+00 41.40 44.40 43.00 7047+00 41.45 44.45 43.04
7003+00 41.40 44.40 43.00 7048+00 41.46 44.46 43.04
7004+00 41.40 44.40 43.00 7049+00 41.46 44.46 43.05
7005+00 41.40 44.40 43.00 7050+00 41.46 44.46 43.05
7006+00 41.40 44.40 43.00 7051+00 41.46 44.46 43.05
7007+00 41.40 44.40 43.00 7052+00 41.47 44.47 43.06
7008+00 41.40 44.40 43.00 7053+00 41.48 44.48 43.06
7009+00 41.40 44.40 43.00 7054+00 41.49 44.49 43.07
7010+00 41.40 44.40 43.00 7055+00 41.51 44.51 43.08
7011+00 41.40 44.40 43.00 7056+00 41.51 44.51 43.09
7012+00 41.40 44.40 43.00 7057+00 41.52 44.52 43.09
7013+00 41.40 44.40 43.00 7058+00 41.52 44.52 43.10
7014+00 41.40 44.40 43.00 7059+00 41.53 44.53 43.10
7015+00 41.40 44.40 43.00 7060+00 41.55 44.55 43.11
7016+00 41.40 44.40 43.00 7061+00 41.56 44.56 43.12
7017+00 41.40 44.40 43.00 7062+00 41.58 44.58 43.14
7018+00 41.40 44.40 43.00 7063+00 41.62 44.62 43.17
7019+00 41.40 44.40 43.00 7064+00 41.69 44.69 43.21
7020+00 41.40 44.40 43.00 7065+00 41.76 44.76 43.24
7021+00 41.40 44.40 43.00 7066+00 41.84 44.84 43.29
7022+00 41.40 44.40 43.00 7067+00 41.94 44.94 43.34
7023+00 41.40 44.40 43.00 7068+00 42.00 45.00 43.38
7024+00 41.40 44.40 43.00 7069+00 42.09 45.09 43.44
7025+00 41.40 44.40 43.00 7070+00 42.14 45.14 43.48
7026+00 41.40 44.40 43.00 7071+00 42.15 45.15 43.49
7027+00 41.40 44.40 43.00 7072+00 42.17 45.17 43.51
7028+00 41.40 44.40 43.00 7073+00 42.19 45.19 43.52
7029+00 41.40 44.40 43.00 7074+00 42.23 45.23 43.55
7030+00 41.40 44.40 43.00 7075+00 42.29 45.29 43.58
7031+00 41.40 44.40 43.00 7076+00 42.35 45.35 43.62
7032+00 41.40 44.40 43.00 7077+00 42.79 45.79 43.72
7033+00 41.40 44.40 43.00 7078+00 43.03 46.03 43.82
7034+00 41.40 44.40 43.00 7079+00 43.20 46.20 43.91
7035+00 41.40 44.40 43.00 7080+00 43.47 46.47 44.06
7036+00 41.41 44.41 43.01 7081+00 43.72 46.72 44.24
7037+00 41.41 44.41 43.01 7082+00 43.97 46.97 44.46
7038+00 41.42 44.42 43.02 7083+00 43.97 46.97 44.46
7039+00 41.43 44.43 43.02 7084+00 44.00 47.00 44.49
7040+00 41.43 44.43 43.02 7085+00 44.18 47.18 44.64
7041+00 41.43 44.43 43.02 7086+00 44.18 47.18 44.65
7042+00 41.43 44.43 43.03 7087+00 44.19 47.19 44.65
7043+00 41.44 44.44 43.03 7088+00 44.19 47.19 44.66
7044+00 41.44 44.44 43.03 7089+00 44.19 47.19 44.66
1 MTOL = DWSE plus higher of: 1) 3 feet, or 2) wind setup and wave runup 2 HTOL = lower of: 1) the 500-year WSE, or 2) DWSE + 3 feet Appendix D.

Dry Creek ULDC Due Diligence,
Geotech - Kleinfelder
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ONLY THE CLIENT OR ITS DESIGNATED REPRESENTATIVES MAY USE THIS DOCUMENT AND ONLY FOR THE SPECIFIC PROJECT FOR WHICH THIS DATA REPORT WAS PREPARED.

ULDC GEOTECHNICAL FINDING –

DRY CREEK NORTH LEVEE
STATIONS 7000+00 TO 7085+57
325-FOOT RIO LINDA BOULEVARD EXTENSION

ULDC FINDING AND FEMA LEVEE CERTIFICATION PROGRAM

SACRAMENTO AREA FLOOD CONTROL AGENCY LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
KLEINFELDER PROJECT # 24001006.001A
24001006.001A/SAC23R158826 Page ii of vi February 16, 2024 © 2024 Kleinfelder
February 16, 2024
File No.: 24001006.001A
Mr. Pete Ghelfi, PE
Director of Engineering
Sacramento Area Flood Control Agency
1325 J Street, Suite 1700
Sacramento, CA 95814
SUBJECT: ULDC Geotechnical Finding –
Dry Creek North Levee
Stations 7000+00 To 7085+57
325-Foot Rio Linda Boulevard Extension
ULDC Finding and FEMA Levee Certification Program
Sacramento Area Flood Control Agency Levee Systems
Sacramento and Sutter Counties, California
Dear Mr. Ghelfi:

This report presents Kleinfelder’s geotechnical evaluation of the existing Dry Creek North Levee (DCNL) from the downstream (western) boundary of Station 7000+00 at the Union Pacific Railroad (UPRR) crossing to the upstream (eastern) boundary located at the intersection of Rio Linda Boulevard at Station 7085+57 and the 325-foot roadway embankment along the centerline of Rio Linda Boulevard that begins at Station 7085+57 in Sacramento County, California. The 325-foot roadway section provides flood protection as a non-levee feature at the end of DCNL before high ground and therefore was also evaluated.

This evaluation was performed for Sacramento Area Flood Control Agency (SAFCA) to provide a geotechnical engineering finding as to whether the DCNL study area can be certified from a geotechnical perspective to meet State of California Department of Water Resources Urban Levee Design Criteria (ULDC) (DWR, 2012). This report contains Kleinfelder’s review and an opinion regarding whether the DCNL meets the geotechnical aspects of the ULDC (DWR, 2012) (7.3 Soil Sampling, Testing, and Logging;

7.4 Slope Stability; 7.5 Underseepage; 7.7 Seismic Vulnerability; 7.8 Levee Geometry; 7.9 Interfaces and Transitions; and 7.14 Floodwalls, Retaining walls, and Closure Structures). Other sections of the ULDC are not addressed in this report and are being addressed by other consultants. 24001006.001A/SAC23R158826 Page iii of vi February 16, 2024 © 2024 Kleinfelder
If you have questions regarding this report or if we may be of further assistance, please contact the undersigned.

Sincerely,
KLEINFELDER, INC.

Meredith Beswick, PE, PG Timothy A. Williams, PE, GE
Senior Engineer Sr. Principal Geotechnical Engineer
CC: Mr. Pro Mitra, PE/MBK Engineers ([email protected]) Ms. Becky Money, PE/MBK Engineers ([email protected]) 24001006.001A/SAC23R158826 Page iv of vi February 16, 2024 © 2024 Kleinfelder

TABLE OF CONTENTS

SECTION PAGE
1 INTRODUCTION .....................................................................................................................1

1.1 PROJECT INTRODUCTION.................................................................................................... 1

1.2 BACKGROUND AND CONSTRUCTION HISTORY................................................................... 1

1.3 METHODOLOGY .................................................................................................................. 2

1.4 REFERENCED REPORTS........................................................................................................ 3

1.5 CRITERIA.............................................................................................................................. 4

1.6 WATER SURFACE ELEVATIONS............................................................................................ 5 2 ULDC GEOTECHNICAL CRITERIA REVIEW .................................................................................7

2.1 ULDC SECTION 7.3 SOIL SAMPLING, TESTING, AND LOGGING........................................... 7

2.1.1 Conclusion............................................................................................................ 10

2.2 ULDC SECTION 7.4 SLOPE STABILITY FOR INTERMITTENTLY LOADED LEVEES.................. 10

2.2.1 Conclusion............................................................................................................ 13

2.3 ULDC SECTION 7.5 UNDERSEEPAGE ................................................................................. 13

2.3.1 Conclusion............................................................................................................ 15

2.4 ULDC SECTION 7.7 SEISMIC VULNERABILITY .................................................................... 15

2.4.1 Conclusion............................................................................................................ 16

2.5 ULDC SECTION 7.8 LEVEE GEOMETRY............................................................................... 16

2.5.1 Current Levee Geometry ..................................................................................... 18

2.5.2 Conclusion............................................................................................................ 19

2.6 ULDC SECTION 7.9 INTERFACES AND TRANSITIONS ......................................................... 19

2.6.1 Interface of NEMDC Stormwater Pump Station to NEMDC west levee .............. 20

2.6.2 Interface of DCNL to NEMDC Stormwater Pump Station (Station 7000+00) ...... 20

2.6.3 Interface of Dry Creek north levee to UPRR closure structure and UPRR Embankment (Station 7000+50).......................................................................... 21

2.6.4 Interface of Twin RCP Drainage Pipe to Levee Embankment (Station 7032+33 to 7032+40).............................................................................................................. 22

2.6.5 Interface and Transition of DCNL to Marysville Boulevard (Station 7081+00).... 22

2.6.6 Transition to and Termination of DCNL at Rio Linda Boulevard (Station 7085+57) and the 325-foot Rio Linda Boulevard Extension into High Ground ................... 22

2.6.7 Conclusion............................................................................................................ 23

2.7 ULDC SECTION 7.14 FLOODWALLS, RETAINING WALLS, AND CLOSURE STRUCTURES..... 23

2.7.1 NEMDC Stormwater Pumping Station................................................................. 23

2.7.2 UPRR Closure Structure ....................................................................................... 24

2.7.3 Conclusion............................................................................................................ 25 3 DRY CREEK NORTH LEVEE STUDY AREA SUMMARY OF RESULTS ............................................26 4 LIMITATIONS .......................................................................................................................27 5 REFERENCES ........................................................................................................................29 24001006.001A/SAC23R158826 Page v of vi February 16, 2024 © 2024 Kleinfelder
TABLES

1.1 Water Surface Elevation Reference Summary

2.1 Summary of Exploration Locations and Approximate Spacing

2.2 Additional Geotechnical Exploration For DCNL

2.3 Stability Analyses Comparison Summary

2.4 Seepage Analyses Comparison Summary

2.5 Levee Crown and Landside Toe Reference Summary

3.1 Levee Reaches That Meet Geotechnical Aspects of ULDC Criteria

FIGURES
1 DCNL Site Vicinity Map
2 DCNL Site Location Map

APPENDICES
A Kleinfelder Technical Memorandum, “Geotechnical Evaluation 2023 100-Year WSE, Dry Creek North Levee – 325-foot Upstream Extension, North Area Streams, SAFCA FEMA Levee Accreditation, Sacramento County, California”. Dated February 16, 2024.

B MBK Technical Memorandum, “Dry Creek North Levee – Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee.” Dated February 16, 2024.

C 2023 MBK Levee Geometry Check Figures
D 2023 Psomas Top of Levee and Toe Survey Figures
E “Seismic Performance Summary Report North Area Streams Levee Areas, ULDC & FEMA Levee Certification Project, Sacramento Area Flood Control Agency Levee Systems, Sacramento County, California.” Dated February 12, 2024.
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REPORT ACRONYMS
______________________________________________________________________________________________ ARFCD American River Flood Control District
CFR Code of Federal Regulations
CPT Cone Penetration Tests
DCNL Dry Creek North Levee
DWSE Design Water Surface Elevation
DWR Department of Water Resources
EM Engineering Manual
FEMA Federal Emergency Management Agency
FOS Factor of Safety
HEM Helicopter-based electromagnetics
HTOL Hydraulic Top of Levee
MTOL Minimum Top of Levee
NEMDC Natomas East Main Drainage Canal
RCP Reinforced Concrete Pipe
SAFCA Sacramento Area Flood Control Agency
SOP Safe Operating Procedures
ULDC Urban Levee Design Criteria
ULE Urban Levee Evaluation
UPRR Union Pacific Railroad
USACE United States Army Corps of Engineers
WSE Water Surface Elevation
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1 INTRODUCTION
___________________________________________________________________________________

1.1 PROJECT INTRODUCTION
This report presents Kleinfelder’s geotechnical evaluation of the existing Dry Creek North Levee (DCNL) from the downstream (western) boundary at Station 7000+00 at the Union Pacific Railroad (UPRR) crossing to the upstream (eastern) boundary located at the intersection of Rio Linda Boulevard at Station 7085+57 and the 325-foot roadway embankment along the centerline of Rio Linda Boulevard that begins at Station 7085+57 in Sacramento County, California. The 325-foot section provides flood protection as a non-levee feature at the end of DCNL before high ground and therefore was also evaluated. This evaluation was performed for Sacramento Area Flood Control Agency (SAFCA) to provide a geotechnical engineering finding as to whether the DCNL meets the geotechnical criteria within the State of California Department of Water Resources Urban Levee Design Criteria (ULDC) (DWR, 2012).

This report contains Kleinfelder’s review and an opinion regarding whether the DCNL meets the geotechnical aspects of the ULDC (7.3 Soil Sampling, Testing, and Logging; 7.4 Slope Stability; 7.5 Underseepage; 7.7 Seismic Vulnerability; 7.8 Levee Geometry; 7.9 Interfaces and Transitions; and 7.14 Floodwalls, Retaining walls, and Closure Structures). Other sections of the ULDC are not addressed in this report and are being addressed by other consultants.

This report should be considered a “snapshot” of the condition of the levee system at this time.

Additional study and work may be needed due to the passage of time and if ULDC requirements change.

This report includes conclusions related to the geotechnical aspects of the levee. Conclusions are subject to the LIMITATIONS section of this report.

1.2 BACKGROUND AND CONSTRUCTION HISTORY
The DCNL study area includes the DCNL (Station 7000+00 to 7085+57), which is 8,557 feet in length, and the 325-foot Rio Linda Boulevard embankment extension for a total study area length of 1.68-miles (8,883 feet) long. The project location relative to cities, rivers, and existing roadways is shown on Figures 1 and 2. The American River Flood Control District (ARFCD) is the maintaining agency and is responsible for operations and maintenance.
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DCNL and the 325-foot Rio Linda Boulevard were constructed under a SAFCA contract between July and November 1995 (Kleinfelder, 1997a). As-built construction plans indicate an inspection trench was required to extend a minimum of 3 to 6 feet deep into the foundation. During construction Kleinfelder representatives observed construction activities (including material conformance and compaction testing) (Kleinfelder, 1997a). In some cases where permeable materials were present in the bottom of the planned inspection trench excavation depth the inspection trench was locally extended up to 13 feet below surrounding grade to penetrate into underlying fine-grained and/or cemented soils.

Construction included tying into a stormwater pump station just north of Dry Creek at the NEMDC confluence.

Part of the original construction in 1995 included rebuilding Rio Linda Boulevard for over 500 feet and raising the roadway embankment to the same elevation as the levee until high ground was reached.

Kleinfelder representatives observed construction of the Rio Linda Boulevard embankment. Current landside slopes along the Rio Linda Boulevard roadway embankment have been stable during previous elevated water events at slopes generally steeper than 3 horizontal (H):1 vertical (V), and more typically closer to 2H:1V. The roadway embankment is wider than the theoretical prism. Based on a FEMA 2020 review comment, this section starting at the DCNL end Station of 7085+57 and extending north along Rio Linda Boulevard for 325 feet is a non-levee reach. Kleinfelder performed a review of a 2021 evaluation based on the new 2023 100-year WSE provided by MBK Engineers (MBK, 2024). This extension is discussed in the 2024 Kleinfelder “Geotechnical Evaluation 2023 100-Year WSE Dry Creek North Levee – 325-foot upstream extension” memorandum included in Appendix A.

1.3 METHODOLOGY
Kleinfelder performed seepage and slope stability analyses at Station 7035+00 with results included in the Problem Identification Report and ULDC Geotechnical Results Summary reports (Kleinfelder, 2016a and 2016b). The analyses were prepared using 200-year design water surface elevation (DWSE) and Hydraulic Top of Levee (HTOL) WSEs that were in use at the time each report was prepared. MBK prepared a new 200-year DWSE and HTOL WSE (MBK, 2024) for the current ULDC evaluation, which are designated the 2023 200-year DWSE and 2023 HTOL WSE.

The cross section analyzed is considered the critical location based on stratigraphy and levee geometry.

The highest WSE previously analyzed was Elevation 44.6 feet (NAVD88 datum) and the highest 2023 HTOL WSE is 44.66 feet. Therefore, this summary was developed by comparing the previous analysis result at the highest WSE with the 2023 200-year and HTOL WSE. Since the existing analyses met project 24001006.001A/SAC23R158826 Page 3 of 31 February 16, 2024 © 2024 Kleinfelder
criteria, the new slightly lower (0.2 foot) 2023 HTOL or 200-year WSE (MBK, 2024) also is considered to meet criteria. This procedure is further described in Section 2 of this report.

1.4 REFERENCED REPORTS
This report includes results from previous studies performed by Kleinfelder for the DCNL (Station 7000+00 to 7085+57) and 325-foot Rio Linda Boulevard roadway embankment. Kleinfelder has reviewed and used existing analyses from the following reports.
• Balbi & Chang Associates, 1994. “Geotechnical Investigation Report, Natomas Areas Stormwater Pumping Station, SAFCA Natomas Area Flood Control Improvement Project, Sacramento, California.” Dated February 1994.
• Ensign & Buckley, Consulting Engineers, 1997, “Sacramento Area Flood Control Agency, Dry/ Robla Creek, North Levee – Plan and Profile, Station 92+00 to 108+00.” As Built Drawings. Dated October 24, 1997.
• Kleinfelder, 1994, “Geotechnical Evaluation of Proposed Levee Improvements Dry Creek Levees.” June 1994.
• Kleinfelder, 1997a. “Final Report, Field Compaction Test Results, Dry Creek – North Levee Sacramento, California,” Kleinfelder, dated February 6, 1997. • Kleinfelder, 1997b. “Final Report, Field Compaction Test Results, Pump Station, NEMDC – Units 2A/3C, and Robla Units 1B/1C, Sacramento, California,” Kleinfelder, dated March 3, 1997. • Kleinfelder, 2013. “Geotechnical Data Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee),” Kleinfelder, dated May 31, 2013. • Kleinfelder, 2016a. “Problem Identification Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee),” Kleinfelder, dated September 18, 2013. Revised April 29, 2016. • Kleinfelder, 2016b. “ULDC Geotechnical Results Summary, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee),” Kleinfelder, dated April 26, 2016. 24001006.001A/SAC23R158826 Page 4 of 31 February 16, 2024 © 2024 Kleinfelder
• URS, 2009. “Phase 1 Geotechnical Data Report (P1GDR), Natomas East Main Drainage Canal (NEMDC) East Study Area, Urban Levee Geotechnical Evaluations Program, Contract 4600007418,” dated March 2009.
• URS, 2011. “Supplemental Geotechnical Data Report (SGDR), Natomas East Main Drainage Canal (NEMDC) East Study Area, Urban Levee Geotechnical Evaluations Program, Contract 4600007418,” dated November 2011.
• URS, 2015a. “Geotechnical Evaluations Report, Volume 1, Existing Conditions, NEMDC East Study Area, Urban Levee Evaluations Project.” Prepared by URS for DWR. Dated March 2015. • URS, 2015b. “Geotechnical Evaluations Report, Volume 2, Remedial Alternatives, NEMDC East Study Area, Urban Levee Evaluations Project.” Prepared by URS for DWR. Dated March 2015.

In addition to the reports referenced above, Kleinfelder has reviewed the design and construction documents related to the DCNL study area. These documents are contained in the list of references, which are included in Section 5 of this report.

1.5 CRITERIA
The purpose of this study was to review existing geotechnical information available for DCNL (Station 7000+00 to 7085+57) and 325-foot Rio Linda Boulevard roadway embankment in order to perform an evaluation as to whether these levees currently meet the geotechnical requirements of ULDC. This information is contained in the reports referenced in Section 1. The information contained in these reports was compared to the criteria in the following references:
• USACE EM 1110-2-1913 “Design and Construction of Levees,” dated April 30, 2000 • USACE ETL 1110-2-569 “Design Guidance for Levee Underseepage,” dated May 1, 2005 • USACE SOP SPK EDG-03 “Standard Operating Procedure 3, Geotechnical Levee Practice,” dated May 2022
• US Title 44 Code of Federal Regulations 65.10: Mapping of Areas Protected by Levee Systems, dated October 1, 2011
• Urban Levee Design Criteria (ULDC), State of California Department of Water Resources, dated May 2012
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1.6 WATER SURFACE ELEVATIONS
Water surface elevations were provided to Kleinfelder for the reports referenced in Section 1.4 and to perform the evaluation for this report, above. The following table lists these WSEs.

Table 1.1
Water Surface Elevation Reference Summary
WSE or Topography
Feature
Elevation
Range
(NAVD88, ft)
Source Date
2016 ULDC Geotechnical Results Summary (Kleinfelder, 2016b) 200-Year
DWSE1 41.49 to 43.27
MBK Engineers, Table entitled “NAS
WSE data” transmitted to
Kleinfelder 02-18-2014 (MBK, 2014)
2016b
Hydraulic Top of
Levee (HTOL)1 44.49 to 45.23
MBK Engineers, Table entitled “NAS
WSE data” transmitted to
Kleinfelder 02-18-2014 (MBK, 2014)
2016b
ULDC Geotechnical Finding, 2024
2023 200-Year DWSE 41.40 to 44.19
MBK Engineers, 2024, “Dry Creek
North Levee – Determination of the
Urban Levee Design Criteria Design
Water Surface Elevation, Minimum
Top of Levee, and Hydraulic Top of
Levee.” Dated February 16, 2024.

February 16,
2024
2023 HTOL WSE 43.00 to 44.66
MBK Engineers, 2024, “Dry Creek
North Levee – Determination of the
Urban Levee Design Criteria Design
Water Surface Elevation, Minimum
Top of Levee, and Hydraulic Top of
Levee.” Dated February 16, 2024.

February 16,
2024

1. WSEs were used in the analysis performed in the 2016 ULDC Geotechnical Summary Reports.

The 2023 200-year DWSE and HTOL WSEs (MBK, 2024) used for the current ULDC evaluation were provided in tabular form at 100-foot intervals along DCNL (Station 7000+00 to 7085+57) and 325-foot Rio Linda Boulevard roadway embankment (Station 7089+00 in MBK, 2024) and are included in the technical memorandum provided by MBK in Appendix B.

The HTOL for the 2016 ULDC Geotechnical Results Summary is higher than the 2023 HTOL by 1.49 feet at Station 7000+00 to 0.57 foot at Station 7084+00 (the end of the 2014 WSE data). The 200-year WSE for 24001006.001A/SAC23R158826 Page 6 of 31 February 16, 2024 © 2024 Kleinfelder
the 2016 ULDC Geotechnical Results Summary is higher than the 2023 200-year WSE by 0.09 foot at Station 7000+00, meets the 2023 200-year WSE between Stations 7076+00 and 7077+00 and is 0.92 foot below the 2023 200-year WSE at Station 7084+00.
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2 ULDC GEOTECHNICAL CRITERIA REVIEW
___________________________________________________________________________________ Kleinfelder performed a review of existing reports and analyses contained in those reports referenced in Section 1, above. This review was performed to determine whether DCNL (Station 7000+00 to 7085+57) and 325-foot Rio Linda Boulevard roadway embankment meet the ULDC from a geotechnical perspective for the following sections:
• 7.3 Soil Sampling, Testing, and Logging
• 7.4 Slope Stability
• 7.5 Underseepage
• 7.7 Seismic Vulnerability
• 7.8 Levee Geometry
• 7.9 Interfaces and Transitions
• 7.14 Floodwalls, Retaining Walls, and Closure Structures This evaluation includes a review of existing information referenced in this report and has not included performance of new analyses or field investigation. Where available, construction inspection records have also been reviewed.

The following sections of this report contain a summary of our analysis.

2.1 ULDC SECTION 7.3 SOIL SAMPLING, TESTING, AND LOGGING This section contains a summary of the review of existing information for DCNL (Station 7000+00 to 7085+57) and 325-foot Rio Linda Boulevard roadway embankment with regards to ULDC Section 7.3 Soil Sampling, Testing, and Logging. The general requirements of this section are outlined below.

ULDC 7.3 requires soil sampling, testing, and logging per standard procedures prescribed in guidance documents, including the USACE Sacramento District’s Geotechnical Levee Practice Standard Operating Procedures (SPK SOP) (USACE, 2022) and DWR’s Division of Flood Management Soil and Rock Logging, Classification, Description and Presentation Manual (2009). This includes an evaluation of soil exploration quantity and location as outlined in the SPK SOP (USACE, 2022). Based on this document, explorations for a feasibility levee evaluation should be obtained at a spacing of approximately 1,000 feet along the levee crest. For preconstruction and design studies a spacing of approximately 500 feet along the waterside toe, levee crown, landside toe. Exploration depths should be a minimum of 4 times the levee height and extending to an appropriate stratum. Additional borings may be performed landward and waterward of the levee (100 to 500 ft away from the levee) to 24001006.001A/SAC23R158826 Page 8 of 31 February 16, 2024 © 2024 Kleinfelder
evaluate the distal seepage conditions. Explorations that did not meet the requirements outlined (e.g., explorations that were not drilled deep enough) above were not included.

The SPK SOP (USACE, 2022) recommends a thorough evaluation of existing information as part of a levee evaluation program. This includes a review of original construction (if available), improvements, performance history, existing subsurface information, and regional and local geomorphology. The standard also recommends the use of cone penetrometers (CPTs) and geophysics to supplement borings, where appropriate.

In addition, where available, the as-built plans, conformance laboratory tests, and in-place compaction tests for the construction and improvements of each levee were retained as part of the ULDC evaluation. This information was used to evaluate the levee geometry and material properties within the newly constructed and improved levee sections.

The total length of DCNL (Station 7000+00 to 7085+57) plus the 325-foot Rio Linda Boulevard embankment extension is 1.68-miles (8,883 feet) long. To meet the approximate number of explorations with a spacing of approximately 500 feet for levee design, 17 explorations each for waterside toe, levee crown, landside toe, and landside field (51 total explorations or 32 explorations per mile) would be needed.

DCNL has been explored by Kleinfelder for levee evaluations and improvement projects. Explorations include drilled borings and cone penetrometer soundings (CPTs). The explorations reviewed by Kleinfelder included those advanced for the SAFCA FEMA Levee Accreditation program, the DWR Urban Levee Evaluation (ULE) program, and previous studies by others. To be included in the summary, the explorations were evaluated for depth (generally a minimum of 4 times the levee height for crown explorations), sampling frequency, laboratory testing, and classification. For example, shallow borings that only assess the levee embankment were not included in the summary. Table 2.1 below summarizes the number of explorations performed for each levee location that meet the exploration requirement described in SPK SOP.

Table 2.1
Summary of Exploration Locations and Approximate Spacing Exploration
Location
Number of
Explorations
Spacing (ft)
Max Min Average
Waterside Toe 0 - - -
Levee Crown 8 1,619 0 1,090
Landside Toe 0 - - -
Landside Field 0 - - -
Total 8
Average Per Mile 5
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Sampling for the explorations presented in Table 2.1 used standard penetration testing at regular intervals of every 2 ½ feet to every 5 feet, documenting blow counts, and field soils descriptions.

Laboratory testing was performed on select samples generally consistent with DWR’s Division of Flood Management Soil and Rock Logging, Classification, Description and Presentation Manual (2009) such as sieve analysis, Atterberg limits, unit weight, water content, permeability, and strength testing. Cone penetration tests were performed near soil borings to aid in interpretation. The total number of explorations is not within the range of explorations specified in the SPK SOP for levee crown, waterside toe, landside toe, and landside field borings.

Additional exploration performed for the ACNL were reviewed and are summarized in Table 2.2.

Table 2.2
Additional Geotechnical Explorations for DCNL
Exploration
Location
Number of
Explorations Boring Description
1994 (7) and 2012
(1) ACNL Borings
4-Crown
4 Waterside Toe
1994 borings were drilled for original levee design.

Waterside borings located where levee alignment shifted landward of original alignment. Borings drilled 20 to 26 feet deep and ended in cemented hardpan soils.
2012 boring drilled to 26 feet and confirmed cemented
soils.
1994 NEMDC
Stormwater Pump
Station
2 Borings drilled to 70 feet deep for NEMDC pump station 2020 Rio Linda Blvd
Embankment 1
Hand auger into roadway embankment to obtain samples
for testing of embankment soils. See Appendix A.

These were 8 borings in completed between 1994 and 2012 by Kleinfelder that did not meet the requirements for depth in the SPK SOP due to depth being less than 4 times levee height and fewer laboratory tests. In 1994 two borings were drilled for the NEMDC Stormwater Pump Station. These borings were located to the west of Station 7000+00 and confirmed the soil conditions observed in the other borings at the site. A hand sample was obtained from the Rio Linda Boulevard embankment in 2020 to check the composition of the embankment.

As part of previous geotechnical evaluations of the DCNL area, geologic and geomorphologic mapping was performed of the area. This mapping identified the area was generally underlain by the Riverbank Formation with some shallow surficial channel deposits (Kleinfelder, 2016a). The Riverbank Formation in this area is typically consolidated and very dense; the very dense and/or consolidated layers of this 24001006.001A/SAC23R158826 Page 10 of 31 February 16, 2024 © 2024 Kleinfelder
formation locally referred to as “hardpan” (Kleinfelder, 2016a). The soils are characterized by low to very low hydraulic conductivities and are generally a low risk for seepage through the levee foundation (‘underseepage'). Geophysical HEM (helicopter-based electromagnetics) surveys were performed along the levee for the ULE project (URS, 2015a) and provided a continuous record of the subsurface conditions along the levee. These surveys generally showed a moderate to low resistivity, which is typical of fine-grained soils such as silts and clays. In the DCNL area, the dense to cemented hardpan soils of the Riverbank Formation also showed a moderate to low resistivity, which was confirmed in the subsurface explorations.

The DCNL was constructed in 1996 as part of a SAFCA flood control improvement project. Levee construction was observed and tested by Kleinfelder. Construction included excavation of a key trench to between 3 and 13 feet in depth to confirm the levee foundation rested on firm, low permeability hardpan soils. Levee embankment fill was tested to confirm that it met USACE requirements for levee construction.

2.1.1 Conclusion
Based on the above information, sufficient explorations were not obtained, and an exception is needed.

It is Kleinfelder’s opinion that additional and appropriate information including geologic and geomorphologic mapping, inspection trench observation, and continuous HEM data, was collected and reviewed to provide an adequate assessment of the subsurface conditions as outlined in the SPK SOP for levee evaluation. Therefore, it is Kleinfelder’s opinion that the DCNL geotechnical evaluation was generally performed following the guidance outlined above and meets the requirements of ULDC 7.3 for Soil Sampling, Testing, and Logging through Exception.

2.2 ULDC SECTION 7.4 SLOPE STABILITY FOR INTERMITTENTLY LOADED LEVEES This section contains a summary of the review of the existing reports and analyses performed for DCNL (Station 7000+00 to 7085+57) and the 325-foot Rio Linda Boulevard roadway embankment as it applies to ULDC Section 7.4 Slope Stability for Intermittently Loaded Levees. ULDC defines an intermittently loaded levee as:
“Intermittently loaded levee means a levee that does not experience a water surface elevation of one foot or higher above the elevation of the levee toe at least once a day for more than 36 days per year on average.”
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DCNL and the 325-foot Rio Linda Boulevard roadway embankment are generally subject to short-term flood events where the water rarely reaches the landside embankment toe. As such, DCNL is considered an Intermittently Loaded Levee.

The general requirements of ULDC Section 7.4 Slope Stability for Intermittently Loaded Levees are outlined below.

ULDC 7.4 requires slope stability analysis for the design water surface elevation (DWSE) and at the Hydraulic Top of Levee (HTOL) WSE. “Engineers should use sound engineering judgment and guidance from EM 1110-2-1902 to decide what constitutes a minor, insignificant slip surface versus a sliding surface that threatens the integrity of the levee. These determinations should be based on performance history, levee geometry, type of levee fill material, stratigraphy of the levee embankment and foundation soils, seepage conditions (including pore water pressures calculated for the seepage analysis), soil strength characteristics, and potential for erosion. Those surfaces which significantly threaten the integrity of the levee must meet minimum slope stability criteria.” Steady-state landside stability and rapid drawdown waterside stability should be evaluated using the minimum factors of safety summarized in Table 1.

Stability Analysis ULDC Minimum Factor of Safety (FOS)1 Steady-State DWSE, Landside Slope 1.4
Steady-State HTOL WSE, Landside Slope 1.2
Rapid Drawdown DWSE, Waterside Slope 1.0-1.22
End of Construction 1.33

1. Critical failure surface should intersect the levee crown and exceed a minimum of 3-foot depth into the level slope.

2. Minimum factor of safety dependent on time extent DWSE may have saturated the waterside levee slope.

3. End of Construction is performed for newly constructed levees. Since the DCNL was constructed nearly 30 years ago, this loading case was not analyzed for this current study.

For through seepage, reaches where the phreatic seepage surface exited on a levee slope (i.e., through seepage) that is composed of erodible material (sands and non-plastic silts and silty sands) were generally considered to not meet criteria.

Detailed discussions of the analyses previously performed in the 2016 ULDC Geotechnical Results Summary (Kleinfelder, 2016b) are included in the documents cited in the reference list. These analyses results were compared with the current 2023 200-year DWSE and HTOL WSEs (MBK, 2024) to estimate an analytical result for that WSE. Since the existing analyses met project criteria the current 2023 200- year DWSE and HTOL WSEs also meets slope stability criteria because the WSE is less than what was analyzed for the 2016 ULDC Geotechnical Results Summary (Kleinfelder, 2016b) and soil and geometry conditions have not changed.
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Slope stability analysis was performed at Station 7035+00 for the 2016 ULDC geotechnical summary report (Kleinfelder, 2016b). Based on review of current site conditions, this station is the critical model section for the DCNL and 325-foot Rio Linda Boulevard extension. Analysis input, material properties, and results were reviewed and compared to the current site conditions for the project extension. In the 2016 ULDC geotechnical summary report (Kleinfelder, 2016b), the landside steady-state 200-Year WSE factor of safety was 1.63, the waterside rapid drawdown factor of safety was 2.10, and the landside steady-state HTOL WSE factor of safety was 1.63. Table 2.3 contains the 2016 ULDC analysis results.

Table 2.3
Stability Analyses Comparison Summary
Station
Reference Report Summary, 2016 ULDC Geotechnical Results Summary 2023 ULDC Summary
Highest
WSE
Analyzed
2016
WSE (ft)
(NAVD881,2)
Meets/Does Not Meet 2023 WSE3
(ft)
(NAVD88)
Variance
from
Analysis
WSE
Meets/Does Not
Meet
Through
Seepage Slope Stability Criteria Through Seepage
Slope
Stability
Criteria
7035+00
Hydraulic
Top of
Levee
(HTOL)

44.6 Meets
Steady
State:

FOS 1.634,5
Meets
-- 43.00 -1.6 Meets Meets
7035+00 200-Year
WSE 41.6 Meets
Steady
State:

FOS 1.634, 5
Meets
Rapid
Drawdown:

FOS 2.106
Meets

41.40 -0.2 Meets Meets
1 – NAVD88 – North American Vertical Datum of 1988, which is used for elevations referenced in this report. 2- WSE used in the Reference Report
3- MBK, 2024
4—Due to a landside ditch, the phreatic surface did not exit at the levee toe; therefore, the FOS was the same for the HTOL and 200-year WSE 5-Stability analysis run for with the ditch near the levee toe empty since this is the standard procedure for levee analysis. A parametric analysis was performed for the PIR (Kleinfelder, 2016a) with the ditch full. The result of that steady state slope stability analysis was FOS = 1.67. 6-Rapid drawdown is not performed for the HTOL. Therefore, the 200-year WSE is used for comparison.

Based on this review the following conclusions can be made:
• The analysis of the cross section at 7035+00 for DCNL in the ULDC Geotechnical results summary (2016) met all criteria for slope stability and since the 2023 WSEs are lower than those previously analyzed, the criteria is also considered to be meet for the 2023 WSEs. This model is considered the critical cross section for the DCNL; therefore, slope stability for the DCNL is considered to meet project criteria. It should be noted that at the upper end of the project, between Stations 7077+00 and 7085+57, the 2023 200-year WSE is up to one foot above the 2016 ULDC Geotechnical Results summary 200-year WSE. This portion of the levee is mainly a 24001006.001A/SAC23R158826 Page 13 of 31 February 16, 2024 © 2024 Kleinfelder
freeboard levee with less than 2 feet of water above the landside levee toe; therefore, it is Kleinfelder’s opinion that this portion of the project will meet slope stability criteria. • Current landside slopes along the Rio Linda Boulevard roadway embankment have been stable during previous elevated water events at slopes generally steeper than 3 horizontal (H):1 vertical (V), and more typically closer to 2H:1V. The roadway embankment is wider than the theoretical prism and would be able to experience shallow slope failures without impacting the theoretical prism. Therefore, slope stability of the roadway embankment would meet analysis criteria.
• Compaction and laboratory test results from the 1995 embankment construction were reviewed and the embankment fill is generally over 30% fines and with a plasticity index greater than 8.

Therefore, the possibility of through seepage is considered low.

2.2.1 Conclusion
Based on the above review, it is Kleinfelder’s opinion DCNL (Station 7000+00 to 7085+57) and the 325- foot Rio Linda Boulevard roadway embankment meet the requirements of ULDC 7.4 Slope Stability for Intermittently Loaded Levees.

2.3 ULDC SECTION 7.5 UNDERSEEPAGE
This section contains a summary of the review of the existing reports and analyses performed for DCNL (Station 7000+00 to 7085+57) and the 325-foot Rio Linda Boulevard roadway embankment as it applies to ULDC Section 7.5 Underseepage for Intermittently Loaded Levees. As discussed in Section 2.2, the DCNL is an intermittently loaded levee. The general requirements of ULDC Section 7.5 Underseepage for Intermittently Loaded Levees are outlined below.
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ULDC 7.5 requires seepage analysis performed for the design water surface elevation (DWSE) and the hydraulic top of levee (HTOL) WSE. Exit gradients measured at the landside levee toe, seepage berm toe, ditches, canals, depressions, or areas of thin blanket. The allowable maximum exit gradient is summarized in the table below.

Seepage Analysis Location Allowable Maximum Exit
Gradient
Steady-State DWSE
Landside Levee Toe 0.51
Ditches, canals,
depressions, berms 0.5-0.82
Steady-State HTOL WSE
Landside Levee Toe 0.6
Ditches, canals,
depressions, berms 0.6-0.92

1. The allowable underseepage exit gradient through the combined seepage berm/blanket layer between the levee toe and the seepage berm toe for a water surface set at the DWSE is determined by interpolation, using 0.5 at the levee toe and 0.8 at the seepage berm toe.

2. Maximum allowable exit gradient at the landside levee toe is 0.5 and up to 0.8 at 150 feet from the levee toe, using linear interpolation for distances in between. ULDC does allow for higher exit gradients at the seepage berm toe provided sound engineer judgement, and additional analysis. For the HTOL, “In general if the berm is less than 100-ft wide, the maximum exit gradient may increase by up to 20 percent of the DWSE maximum exit gradient.“
ULDC 7.5 provides criteria for blanket layer soils with saturated unit weights of 112 pcf or less. DCNL stratigraphy blanket layers did not require this analysis because saturated unit weights were greater than the minimum specified.

Seepage analyses were performed at Station 7035+00 for the 2016 ULDC Geotechnical Results Summary Report geotechnical evaluation. Analysis input, material properties, and results were reviewed and compared to the current site conditions and for the project extension Detailed discussions of the analyses performed are included in the documents cited in the reference list. The cross section analyzed is considered the critical location based on stratigraphy and levee geometry and is considered more conservative than the Rio Linda segment and therefore representative for the 325-foot extension. The HTOL WSE previously analyzed at Station 7035+00 was Elevation 44.6 feet (NAVD88 datum) and the 2023 HTOL WSE is 43.01 feet. Since the existing analyses met project criteria, and the new 2023 HTOL WSE (MBK, 2024) is 0.59 feet lower, the model at Station 7035+00 is considered to meet underseepage criteria.

The exit gradient for the analysis on the HTOL WSE was 0.05 at the landside levee toe and 0.17 at the ditch beyond the levee toe. Table 2.4 contains the results of the 2016 ULDC analysis. 24001006.001A/SAC23R158826 Page 15 of 31 February 16, 2024 © 2024 Kleinfelder
Table 2.4
Seepage Analyses Comparison Summary
Station
Reference Report Summary, 2016 ULDC Geotechnical
Results Summary 2023 ULDC Summary
Highest
WSE
Analyzed
2016
WSE (ft)
(NAVD881,2)
Meets/Does Not Meet 2023 WSE3
(ft)
(NAVD88)
Variance
from
Analysis
WSE
Meets/Does Not
Meet
Underseepage Criteria Underseepage
Criteria
7035+00 HTOL 44.6
Gradient 0.05 at Levee toe
Gradient 0.17 at 25 feet
from Levee Toe
Meets

43.00 -1.6 Meets
7035+00 200-Year
WSE 41.6
Gradient 0.05 at Levee toe
Gradient 0.14 at 25 feet
from Levee Toe
Meets

41.40 -0.2 Meets
1 – NAVD88 – North American Vertical Datum of 1988, which is used for elevations referenced in this report. 2- WSE used in the Reference Report
3- MBK, 2024
The analysis of the cross section at 7035+00 for DCNL in the ULDC Geotechnical results summary (2016) met all criteria for underseepage and since the 2023 WSEs are lower than those previously analyzed, the criteria is also considered to be meet for the 2023 WSEs. This model is considered the critical cross section for the DCNL; therefore, underseepage for the DCNL is considered to meet project criteria. It should be noted that at the upper end of the project, between Stations 7077+00 and 7085+57, the 2023 200-year WSE is up to one foot above the 2016 ULDC Geotechnical Results summary 200-year WSE. This portion of the levee is mainly a freeboard levee with less than 2 feet of water above the landside levee toe; therefore, it is Kleinfelder’s opinion that this portion of the project will meet seepage criteria.

2.3.1 Conclusion
Based on the above review, it is Kleinfelder’s opinion DCNL (Station 7000+00 to 7085+57) and the 325- foot Rio Linda Boulevard roadway embankment meets the requirements of ULDC 7.5 Underseepage for Intermittently Loaded Levees.

2.4 ULDC SECTION 7.7 SEISMIC VULNERABILITY
This section contains a summary of the review of the existing reports and analyses performed for DCNL as it applies to ULDC Section 7.7 Seismic Vulnerability for Intermittently Loaded Levees. 24001006.001A/SAC23R158826 Page 16 of 31 February 16, 2024 © 2024 Kleinfelder
The objective of the seismic vulnerability evaluation was to develop information to characterize the potential vulnerability of levee segments during the postulated 200-year return period seismic event.

This information can then be used as a basis to classify the levees in terms of its ability to provide postseismic flood protection in accordance with ULDC. In accordance with ULDC, post-seismic flood protection requires maintaining a levee crown sufficient for protection against the 10-year flood with 3 feet of freeboard. For intermittently loaded levees (or floodwalls), the ULDC states the following requirement:
“If seismic damage from 200-year-return-period ground motions is expected after the urban level of flood protection is achieved, a post-earthquake remediation plan is required as part of a flood safety plan that is developed in coordination with pertinent local, State, and federal agencies.”
Kleinfelder has been tasked by SAFCA with evaluating the seismic vulnerability of the SAFCA Sacramento area levees located in Sacramento and Sutter Counties, California in support of ULDC levee certification.

As part of that project, Kleinfelder prepared a Seismic Performance Summary Report (Kleinfelder, 2024) that addresses the seismic vulnerability of the North Area Streams Levee area, which includes the DCNL.

This report is included in Appendix E.

2.4.1 Conclusion
Based upon the Seismic Performance Summary Report (Kleinfelder, 2024), the ULDC seismic vulnerability classification for DCNL is Low Seismic Vulnerability.

2.5 ULDC SECTION 7.8 LEVEE GEOMETRY
This section contains a summary of the existing information for DCNL (Station 7000+00 to 7085+57) and the 325-foot Rio Linda Boulevard roadway embankment with regards to ULDC Section 7.8 Levee Geometry. The ULDC Section 7.8 Levee Geometry is as follows. “Minimum levee geometry criteria have previously been specified by various USACE and State guidance documents. The guidance for various minimum levee geometry and their references are as follows in Table 7-1.
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“For new levees, or levees with extensive reconstruction, situated along major waterways, a minimum 20-foot-wide crown width and 3h:1v waterside and landside slopes (4h:1v waterside slope for bypass levees) is required. Exceptions may be allowed for reconstruction of existing levees where the authorized geometry provides for a steeper slope or narrower crown, the levee has performed well, and it meets stability and seepage criteria. These geometry requirements represent minimum requirements, and wider levee crowns and/or flatter slopes may be necessary in some areas, depending upon geologic and geotechnical considerations. At the same time, however, minimum requirements should be associated with generally uniform, levee materials and homogeneous embankments. Steeper slopes may be allowed in certain circumstances where there is limited space available, and where levees are demonstrated to meet minimum seepage and stability criteria. Steeper waterside levee slopes may be acceptable where stability criteria are met and either slope protection is provided or it is determined that wavewash erosion for a water surface at or below the DWSE could not result in breaching of the levee. For example, levees with slopes steeper than new minimum requirements may be acceptable with elements such as central clay cores, seepage cutoff walls, landside filters or drains, or soil reinforcement that substantially decrease seepage hazards and increase slope stability.

The levee prism should be considered to continue underground based on projection of the above-ground levee slopes. The projected levee slopes are useful for evaluating erosion, excavations, and encroachments near the levee.” Kleinfelder provided continuous geotechnical observation, inspection, and testing during construction of DCNL including continuous logging by a geotechnical engineer of the levee inspection trench that was locally deepened up to 13 feet to cutoff shallow sand layers. There was no reported distress from the 1997 high water event or more recent high-water events from 2002, 2004, 2005, 2006, 2017, or 2023.

The levee was constructed with landside and waterside slopes at 2H:1V and 3H:1V inclinations, respectively, and a crown width varying between 12 feet and 20 feet. The 20-foot crown width was 24001006.001A/SAC23R158826 Page 18 of 31 February 16, 2024 © 2024 Kleinfelder
constructed from the downstream end (Station 7000+00) to the landside ramp located near Station 7065+00. The 12-foot crown width was constructed upstream of approximate Station 7065+00 to the termination of the levee at high ground.

2.5.1 Current Levee Geometry
Psomas provided levee cross sections at approximately 700- to 900-foot spacing along the levee crown using 2013 survey data (Psomas 2013). Updated crest and toe elevations were provided by Psomas in 2023 (Psomas 2023) and are included in Appendix D. MBK (MBK, 2023) provided a geometry analysis of the DCNL by overlaying a geometry template for designated major stream levees downstream of approximate Station 7065+00 and a geometry template for minor stream levee upstream of approximate Station 7065+00 on existing levee profiles prepared by Psomas. The levee prism based on the Minimum Top of Levee (MTOL) was within the levee profiles. However, oversteepened levee slopes can still affect levee geometry if they are not stable. If oversteepened slopes are present, a slope stability analysis is required. The surveyed sections with the template overlay are included in Appendix C.

Crown elevations from the 2013 and 2023 surveys are summarized in Table 2.5, below.

Table 2.5
Levee Crown and Landside Toe Reference Summary
Topography Feature Elevation Range
(NAVD88, ft) Source Date
DCNL Crown 46 to 48 2016a Kleinfelder PIR April 29, 2016 DCNL Crown 45.8 to 47.8
2023 Psomas “O&M Right of Way
Map, Dry Creek North Levee (Sta.
700+00 to 784+20.3)” Dated October
3, 2023.

October 3, 2023
DCNL Landside Toe 34 to 41 2016a Kleinfelder PIR April 29, 2016 Top of 325-foot Rio
Linda Boulevard
Extension Embankment
47 to 49 MBK Engineers, Table entitled,
“Dry_Creek_profiles_050420”
Transmitted by MBK
on September 14,
2023
Landside Toe of
325-foot Rio Linda
Boulevard Extension
Embankment

39.5 to 46 MBK Engineers, Table entitled,
“Dry_Creek_profiles_050420”
Transmitted by MBK
on September 14,
2023
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Analysis Cross Section
Seepage and slope stability analysis were performed at Station 7035+00. The analysis cross section at Station 7035+00 was modeled with a landside slope of 1.8H:1V, a waterside slope of 3H:1V, and a crown width of 19 feet. The cross section analyzed was selected based upon the slightly oversteepened levee embankment slopes and/or a slightly narrowed crown width. The analyses results at Station 7035+00 were presented in the previous published ULDC Geotechnical Results Summary Report (Kleinfelder, 2016b) and indicate the levee geometry modeled met the applicable factor of safety criteria for steadystate landside and rapid drawdown waterside slope stability analysis at the DWSE and HTOL. This analyzed geometry is consistent with the topographic cross sections provided by Psomas.

Based upon the above data, Kleinfelder makes the following conclusions:
• The analysis cross sections were selected and modeled using oversteepened embankment slopes and/or a reduced crown width and the analysis results met slope stability criteria for landside steady-state seepage and waterside rapid drawdown conditions (Factors of Safety greater than 1.4 and 1.2, respectively).
• The analysis geometry represents the steepest slopes observed along DCNL and since the analysis geometry is more critical than the Rio Linda Boulevard embankment, which has a wider and lower embankment, is considered applicable to the Rio Linda Boulevard embankment. • Levee performance has been satisfactory during the 1997, 2002, 2004, 2005, 2006, 2017, and 2023 high water events.

2.5.2 Conclusion
Therefore, from a geotechnical perspective, the above information is considered applicable and appropriate to provide an adequate assessment of levee geometry for meeting the guidance outlined above for ULDC Section 7.8 Levee Geometry.

2.6 ULDC SECTION 7.9 INTERFACES AND TRANSITIONS
This section contains a summary of the review of existing information for DCNL with regards to ULDC Section 7.9 Interfaces and Transitions, which is defined as follows:
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The civil engineer must consider, evaluate, and explicitly design for interfaces and transitions between different types of levee sections and features along a levee system.

Appropriate overlaps, transitions, and connections between features must be evaluated and designed to ensure that the levee system functions holistically, such that no levee reach is more susceptible to problems than an adjacent reach due to gaps in features, loading/demand concentrations, or other three-dimensional effects. Such interfaces, transitions, and connections commonly occur at the ends of seepage berms, seepage cutoff walls, revetments, and floodwalls.

Each transition or interface along the Dry Creek is discussed below.

2.6.1 Interface of NEMDC Stormwater Pump Station to NEMDC west levee Kleinfelder visited the site and has reviewed the NEMDC stormwater pump station record drawings (Carollo, 1998), for geotechnical considerations related to slope stability and seepage at the transitions from the pump station embankment (Station 7000+00) to the tie-in with the NEMDC west levee during a flood event. The NEMDC stormwater pumping station facility extends 277 feet westward from Station 7000+00 to the NEMDC West levee. The transition at the NEMDC west levee is formed by the west edge of the pump station, which is the retaining wall for the west side of the low flow channel that was excavated into the lower portion and below the waterside toe of the NEMDC west levee. The foundation for this retaining wall and the channel slab are about 8 feet and 6 feet, respectively, below channel bottom with 5-foot-deep concrete cutoff trenches (11 feet below channel bottom) cast into the channel slab bottom. Compacted embankment fill was placed between the NEMDC west levee and the retaining wall for the low flow channel and for the pump station embankment, key trench fill, and levee embankment. Kleinfelder performed observation and testing during this construction and construction met compaction criteria (Kleinfelder, 1997b). There was no reported distress from the 1997 high water event or more recent high-water events from 2002, 2004, 2005, 2006, 2017, or 2023.

Based on review of the pump station compaction testing, the transition between NEMDC west levee and the pump station is uniform and does not present any gaps, or other three-dimensional effects.

Therefore, it is Kleinfelder’s opinion that this interface meets the geotechnical requirements of the ULDC

7.9 Interfaces and Transitions.

2.6.2 Interface of DCNL to NEMDC Stormwater Pump Station (Station 7000+00) Kleinfelder visited the site and has reviewed the NEMDC stormwater pump station record drawings (Carollo, 1998), for geotechnical considerations related to slope stability and seepage at the transitions from the DCNL to the pump station embankment (Station 7000+00) during a flood event. The transition 24001006.001A/SAC23R158826 Page 21 of 31 February 16, 2024 © 2024 Kleinfelder
to DCNL is at the east side of the pump station embankment. As-built plans show a 13-foot-wide key trench ranging from approximately 3 to 6 feet in depth beneath the pump station embankment and DCNL at this transition. Compacted embankment fill was placed between the DCNL and the retaining wall for the pump station embankment, key trench fill, and levee embankment. Kleinfelder performed observation and testing during this construction and construction met compaction criteria (Kleinfelder, 1997b). There was no reported distress from the 1997 high water event or more recent high-water events from 2002, 2004, 2005, 2006, 2017, or 2023.

Based on review of the pump station compaction testing, the transition between DCNL and the pump station is uniform and does not present any gaps, or other three-dimensional effects. Therefore, it is Kleinfelder’s opinion that this interface meets the geotechnical requirements of the ULDC 7.9 Interfaces and Transitions.

2.6.3 Interface of Dry Creek north levee to UPRR closure structure and UPRR Embankment (Station 7000+50)
Kleinfelder has visited the site and reviewed the UPRR stop log structure drawings included in the NEMDC stormwater pump station record drawings (Carollo, 1998) and an updated cross section prepared by Mead & Hunt dated March 25, 2015 (Mead & Hunt, 2015). The construction of this closure structure was evaluated for geotechnical considerations related to slope stability and seepage at the transition from the levee to the UPRR closure structure (both sides) during a flood event. As-built drawings show the requirement for previous backfill behind the retaining walls was removed from the project plans during construction. We understand compacted embankment fill was placed against the retaining walls. Kleinfelder performed observation and testing during this construction and construction met compaction criteria (Kleinfelder, 1997a, b). Kleinfelder concludes that the UPRR retaining wall structures were backfilled with compacted embankment fill. The UPRR embankment is undocumented fill; however, it is bound by DCNL fill which is documented and tested. As-built records show the DCNL fill was benched into the existing UPRR embankment. No past performance issues have been noted during periods of high water (1997, 2002, 2004, 2005, 2006, 2017, or 2023) at this location.

Based on the above, it is Kleinfelder’s opinion that this interface meets the geotechnical requirements of the ULDC 7.9 Interfaces and Transitions.
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2.6.4 Interface of Twin RCP Drainage Pipe to Levee Embankment (Station 7032+33 to 7032+40) Kleinfelder has reviewed the levee construction drawings (Ensign & Buckley, 1997) for the levee at this interface. As-builts indicate RCP was placed on compacted subgrade, encased in concrete, and covered with structure backfill. This is acceptable due to the absence of granular backfill or bedding materials.

Kleinfelder observed placement, backfill, and compaction. No past performance issues have been noted during periods of high water (1997, 2002, 2004, 2005, 2006, 2017, or 2023) at this location.

Based on the above, it is Kleinfelder’s opinion that this interface meets the geotechnical requirements of the ULDC 7.9 Interfaces and Transitions.

2.6.5 Interface and Transition of DCNL to Marysville Boulevard (Station 7081+00) Kleinfelder has reviewed the levee construction drawings (Ensign & Buckley, 1997) for the levee at Marysville Boulevard. The levee construction, 200-year DWSE (2016b), and construction reports were reviewed for geotechnical considerations related to slope stability and seepage at the transition from the levee to the Marysville Boulevard roadway embankment during a flood event. This evaluation identified appropriate construction methods utilizing a key trench and benching to tie the levee embankment to the roadway embankments. The existing seepage and slope stability analyses performed at Station 7035+00 met criteria for seepage and slope stability for a similar WSE and a similar levee geometry with a wider embankment than the theoretical prism. By inspection, with a similar WSE on the levee, this levee transition is considered to also meet criteria. There was no reported distress from the 1997 high water event or more recent high-water events from 2002, 2004, 2005, 2006, 2017, or 2023.

Based on review of the DCNL compaction testing, the transition between DCNL and Marysville Boulevard does not present any gaps, or other three-dimensional effects. Therefore, it is Kleinfelder’s opinion that the transition at Marysville Boulevard meets the geotechnical requirements of the ULDC Interfaces and Transitions.

2.6.6 Transition to and Termination of DCNL at Rio Linda Boulevard (Station 7085+57) and the 325- foot Rio Linda Boulevard Extension into High Ground
Kleinfelder has reviewed the levee construction drawings (Ensign & Buckley, 1997) for the levee at Rio Linda Boulevard. The levee construction, 200-year DWSE (2016b), and construction reports were reviewed for geotechnical considerations related to slope stability and seepage at the transition from 24001006.001A/SAC23R158826 Page 23 of 31 February 16, 2024 © 2024 Kleinfelder
the levee to the termination at high ground at the Rio Linda Boulevard embankment during a flood event. This evaluation identified appropriate construction methods utilizing a key trench and benching to tie the levee embankment to the roadway embankments. The existing seepage and slope stability analysis performed at Station 7035+00 met criteria for seepage and slope stability for a similar HTOL WSE (2016b). By inspection, this levee transition is considered to also meet criteria. There was no reported distress from the 1997 high water event or more recent high-water events from 2002, 2004, 2005, 2006, 2017, or 2023.

Based on review of the DCNL compaction testing, the transition between DCNL and Rio Linda Boulevard and Rio Linda Boulevard and high ground do not present any gaps, or other three-dimensional effects.

Therefore, it is Kleinfelder’s opinion that the transition at Rio Linda Boulevard meets the geotechnical requirements of the ULDC 7.9 Interfaces and Transitions.

2.6.7 Conclusion
Based upon the above information, it is Kleinfelder’s opinion the above-described interfaces and transitions meet the geotechnical requirements of ULDC Section 7.9 Interfaces and Transitions.

2.7 ULDC SECTION 7.14 FLOODWALLS, RETAINING WALLS, AND CLOSURE STRUCTURES There are no floodwalls located along this project alignment. Two closure structures are located along the levee with one located at the NEMDC stormwater pumping station facility that extends 277 feet west from Station 7000+00 to the NEMDC West levee and one at the UPRR closure structure near Station 7000+50.

This evaluation includes review of the construction details of specific structures in relation to the geotechnical aspects of slope stability and seepage as applicable to current ULDC criteria. The structural integrity of the structures was not evaluated by Kleinfelder. This evaluation has not included performance of new analysis or field investigation. Where available, construction inspection records have also been reviewed.

2.7.1 NEMDC Stormwater Pumping Station
Kleinfelder visited the site and reviewed the NEMDC stormwater pump station record drawings (Carollo, 1998), for geotechnical considerations related to the function of the pump station as a closure structure for levee safety and integrity during a flood event. The pump station consists of three, 72-inch diameter 24001006.001A/SAC23R158826 Page 24 of 31 February 16, 2024 © 2024 Kleinfelder
discharge pipes equipped with flap gates on the downstream (south) end and intake pumps attached to a wet well on the upstream (north) end and a low flow through channel equipped with a radial gate also on the upstream end. This equipment along with other appurtenant equipment is housed in a multistory structure. The pump station pipes are equipped with mechanical closure devices. Evaluation of the mechanical and structural properties of the pump station was performed by Mead and Hunt in 2023.

As-built plans show a 13-foot-wide key trench ranging from approximately 3 to 6 feet in depth extended from the east wall of the pump station to the tie in with the Dry Creek north levee. The pump station wet well slab and foundations were excavated to 16 to 19 feet below channel bottom and included 5- foot-deep concrete cutoff trenches (24 feet below channel bottom) cast into the wet well slab bottom.

The west edge of the pump station is a retaining wall for the west side of the low flow channel and was excavated into the lower portion and below the waterside toe of the NEMDC west levee. The foundation for this wall and the channel slab is about 8 feet and 6 feet, respectively, below channel bottom with 5 foot deep concrete cutoff trenches (11 feet below channel bottom) cast into the channel slab bottom.

Based on our review and site visit, Kleinfelder concludes that the pump station embankment fill was placed and compacted against all sides of the pump station structure. Kleinfelder performed observation and testing during construction and this testing indicated fill construction met compaction criteria (Kleinfelder, 1997b). Backfill of the pump station structures did not utilize permeable soils (Kleinfelder, 1997b). There was no reported distress from the 1997 high water event or more recent high-water events from 2002, 2004, 2005, 2006, 2017, or 2023.

Therefore, it is Kleinfelder’s opinion that backfill placed for the pump station meets the geotechnical requirements of the ULDC for seepage and slope stability.

2.7.2 UPRR Closure Structure
Kleinfelder visited the site and reviewed the UPRR stop log structure drawings included in the NEMDC stormwater pump station record drawings (Carollo, 1998) and an updated cross section prepared by Mead & Hunt dated March 25, 2015. The construction of this closure structure was evaluated for geotechnical considerations related to slope stability and seepage at the transition from the levee to the UPRR closure structure and retaining walls (both sides) during a flood event. The UPRR stop log retaining wall structures were constructed with an 8-inch-wide cutoff wall crossing beneath the tracks extending a minimum of 3-feet below the ballast between the retaining walls. The retaining walls were backfilled with compacted embankment fill (Kleinfelder, 1997a, b). Evaluation of the structural properties of the closure structure was performed by Mead and Hunt (Mead & Hunt, 2018). As built drawings show that the requirement for pervious backfill behind the retaining walls was removed from the project plans during construction. We understand compacted embankment fill was placed against 24001006.001A/SAC23R158826 Page 25 of 31 February 16, 2024 © 2024 Kleinfelder
the retaining walls. A ballast layer between the tracks and the underlying concrete slab is present to approximately a few inches thick below the railroad ties and approximately 8-inches-thick outside of the rail bed. During the 200-year DWSE event, approximately 4 to 5 feet of water will be retained by the stop log structure. We expect minor seepage to occur through the thin layer of ballast not cutoff by the concrete pad or cutoff wall that will drain back into the NEMDC. The as-builts show a drainpipe inlet on the landside of the stop log that drains into NEMDC upstream of the pumping plant. Therefore, it is Kleinfelder’s opinion that backfill placed for the retaining walls meets the geotechnical requirements of the ULDC for seepage and slope stability. Further, minor through seepage around the ballast may occur, but is not considered a threat to the levee.

2.7.3 Conclusion
Based upon the above data, Kleinfelder makes the following conclusions pertaining to ULDC 7.14 Floodwalls, Retaining Walls, and Closure Structures:
• Pump Station closure structure meets the geotechnical requirements of the ULDC for seepage and slope stability
• UPRR closure structure and retaining walls meet the geotechnical requirements of the ULDC for seepage and slope stability
It should be noted that Kleinfelder did not evaluate the structures as far as conformance with structural integrity, operations, or maintenance per ULDC. It is our understanding this evaluation will be performed by others.
24001006.001A/SAC23R158826 Page 26 of 31 February 16, 2024 © 2024 Kleinfelder
3 DRY CREEK NORTH LEVEE STUDY AREA SUMMARY OF RESULTS
___________________________________________________________________________________ Based on the review summarized in Section 2, above, Table 3.1 includes those reaches that it is Kleinfelder’s opinion meet or do not meet the geotechnical aspects of ULDC for Sections 7.3 Soil Sampling, Testing, and Logging; 7.4 Slope Stability; 7.5 Underseepage; 7.7 Seismic Vulnerability; 7.8 Levee Geometry; 7.9 Interfaces and Transitions; and 7.14 Floodwalls, Retaining Walls, and Closure Structures.

Table 3.1
Levee Reaches That Meet Geotechnical Aspects of ULDC Criteria Project
Levee
Approximate Levee
Stationing
Meets
Criteria
Does Not
Meet
Criteria
ULDC Criteria Section
DCNL 7000+00 to 7085+57 X

7.3 Soil Sampling, Testing, and
Logging

7.4 Slope Stability

7.5 Underseepage,

7.7 Seismic Vulnerability

7.8 Levee Geometry

7.9 Interfaces and Transitions

7.14 Floodwalls, Retaining Walls,
and Closure Structures
DCNL Rio Linda Boulevard 325-
foot extension X

7.3 Soil Sampling, Testing, and
Logging

7.4 Slope Stability

7.5 Underseepage,

7.7 Seismic Vulnerability

7.8 Levee Geometry

7.9 Interfaces and Transitions

7.14 Floodwalls, Retaining Walls,
and Closure Structures
It is Kleinfelder’s opinion that the subject levee DCNL outlined above meet the geotechnical aspects of the ULDC as outlined in Table 3.1, above.
24001006.001A/SAC23R158826 Page 27 of 31 February 16, 2024 © 2024 Kleinfelder
4 LIMITATIONS
___________________________________________________________________________________ This work was performed in a manner consistent with that level of care and skill ordinarily exercised by other members of Kleinfelder’s profession practicing in the same locality, under similar conditions and at the date the services are provided. The work performed was based on project information provided by client. Kleinfelder’s conclusions, opinions, and recommendations are based on a limited number of observations and data. It is possible that conditions could vary between or beyond the data evaluated.

Kleinfelder makes no other representation, guarantee, or warranty, express or implied, regarding the services, communication (oral or written), report, opinion, or instrument of service provided.

This report may be used only by the client and the registered design professional in responsible charge and only for the purposes stated for this specific engagement within a reasonable time from its issuance, but in no event later than two years from the date of the report.

Conclusions contained in this report are based on review of existing information referenced in this report and Kleinfelder’s present knowledge of the project. It is possible conditions could vary from that contained in those documents. If conditions are encountered that differ from those described herein, the client is responsible for ensuring that Kleinfelder is notified immediately so that we may reevaluate the conclusions of this report.

The scope of services was limited. It should be recognized that definition and evaluation of subsurface conditions are difficult. Judgments leading to conclusions and recommendations are generally made with incomplete knowledge of the subsurface conditions present due to the limitations of data from field studies. The conclusions of this assessment are based on the information presented herein.

Although risk can never be eliminated, more detailed and extensive studies yield more information, which may help understand and manage the level of risk.

All rivers, streams and lakes will flood eventually. This fact means that all levees will be called upon to combat floodwaters at some point. Levees reduce the risk of flooding. But no levee system can eliminate all risk of flooding. The term “certification” is not intended to provide a guarantee or warranty of the conditions of the levee or its performance and assumes the following 1) a certification by a registered professional engineer or other party does not constitute a warranty or guarantee of performance, expressed or implied; 2) certification of data is a statement that the data is accurate to the best of the certifier’s knowledge; and 3) certification of analyses is a statement that the analyses have 24001006.001A/SAC23R158826 Page 28 of 31 February 16, 2024 © 2024 Kleinfelder
been performed correctly and in accordance with sound engineering practices. A levee certification does not address or mitigate the inherent flood risk proposed to a particular community. 24001006.001A/SAC23R158826 Page 29 of 31 February 16, 2024 © 2024 Kleinfelder
5 REFERENCES
___________________________________________________________________________________ Balbi & Chang Associates, 1994. “Geotechnical Investigation Report, Natomas Areas Stormwater Pumping Station, SAFCA Natomas Area Flood Control Improvement Project, Sacramento, California.” Dated February 1994.

Carollo, 1995. “Record Drawings, Stormwater Pumping Station, Volume VI of VI, Natomas Area Flood Control Improvement Project, Sacramento, California.” June 1995 (plot date 1998).

Code of Federal Regulations, 2011. “Title 44 of the Code of Federal Regulations (44 CFR) Section 65.10.” Dated October 1, 2011.

Department of Water Resources, California, 2012, “Urban Levee Design Criteria, State of California, Department of Water Resources.” Dated May 2012.

Department of Water Resources, California, 2015. “Guidance Document for Geotechnical Analyses, Urban Levee Geotechnical Evaluations Program.” Dated April 27, 2015.

Department of Water Resources, California, DWR 2022. “SGMA Data Viewer, Groundwater Levels.” https://sgma.water.ca.gov/webgis/?appid=SGMADataViewer#gwlevels/. Accessed October 8, 2023.

Ensign & Buckley, 1997. “Sacramento Area Flood Control Agency, Dry/Robla Creek Levee Project, Volume V of V, Natomas Area Flood Control Improvements, Sacramento, California.” As-Built Drawings. Dated October 24, 1997.

Kleinfelder, 1994, “Geotechnical Evaluation of Proposed Levee Improvements Dry Creek Levees.” Dated June, 1994.

Kleinfelder, 1997a. “Final Report, Field Compaction Test Results, Dry Creek – North Levee, Sacramento, California.” Dated February 6, 1997.

Kleinfelder, 1997b. “Final Report, Field Compaction Test Results, Pump Station, NEMDC – Units 2A/3C, and Robla Units 1B/1C, Sacramento, California.” Dated March 3, 1997. 24001006.001A/SAC23R158826 Page 30 of 31 February 16, 2024 © 2024 Kleinfelder
Kleinfelder, 2013. “Geotechnical Data Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee).” Dated May 31, 2013.

Kleinfelder, 2016a. “Problem Identification Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), Sacramento County.” Dated September 18, 2013. Revised April 29, 2016.

Kleinfelder, 2016b, “ULDC Geotechnical Results Summary, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), Sacramento County.” Dated April 26, 2016.

Kleinfelder, 2024. “Geotechnical Evaluation 2023 100-Year WSE, Dry Creek North Levee – 325-foot Upstream Extension, North Area Streams, SAFCA FEMA Levee Accreditation, Sacramento County, California.” Dated February 16, 2024.

Kleinfelder, 2024. “Seismic Performance Summary Report North Area Streams Levee Areas, ULDC & FEMA Levee Certification Project, Sacramento Area Flood Control Agency Levee Systems, Sacramento County, California.” Dated February 12, 2024.

MBK Engineers, 2017. Dry Creek North levee cross sections at Stations 7010+00, 7017+00, 7026+00, 7034+00, 7043+00, 7051+00, 7060+00, 7069+00, and 7075+00 of Psomas 2013 GPS Survey – Vertical Accuracy +/- 0.2 ft. Drawing Dated November 15, 2017.

MBK Engineers, 2014. Table entitled “NAS WSE data” transmitted to Kleinfelder 02-18-2014.

MBK Engineers, 2023. “Dry Creek North Levee: Levee Geometry Analysis, Profile Sheets.” 5 Sheets.

Dated October 31, 2023.

MBK Engineers, 2024. “Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee.” Technical Memorandum. Dated February 16, 2024.

Mead & Hunt, 2014. “Sacramento Area Levee Recertification Project, Third Draft Report, Levees Covered: Dry Creek North, Robla Creek South, NEMCD North of I-80, Portions of American River North and South Levees, Certification Elements Covered: Levee Encroachments, Penetrations, Floodwalls, Closure Structures, Wind-wave action, O&M Manuals.” Dated January 2, 2014. 24001006.001A/SAC23R158826 Page 31 of 31 February 16, 2024 © 2024 Kleinfelder
Mead & Hunt, 2015. “UPRR Stop Log Foundations, Exhibit 1.0.” Drawing of Union Pacific Railroad stop log foundations at Robla and Dry Creeks. Project#1941500-120265.02. Dated March 25, 2015.

Mead & Hunt, 2018. “Summary of Inventory of Encroachments and Penetrations on the Dry Creek Levee System.” Memorandum from Mead & Hunt to MBK. Dated February 6, 2018.

Mead & Hunt, 2024. “Dry Creek North Levee, Due Diligence Review for ULDC Certification.” Prepared for SAFCA. Dated February 16, 2024.

Psomas, 2013. GPS Survey – Vertical Accuracy +/- 0.2 ft. Dry Creek North levee cross sections at Stations 7010+00, 7017+00, 7026+00, 7034+00, 7043+00, 7051+00, 7060+00, 7069+00, and 7075+00.

Psomas, 2023. “O&M Right of Way Map, Dry Creek North Levee (Sta. 700+00 to 784+20.3).” Dated October 3, 2023.

URS, 2009. “Phase 1 Geotechnical Data Report, NEMDC East Study Area, URS for DWR.” Dated 2009.

URS 2011. “Supplemental Geotechnical Data Report, NEMDC East Study Area, URS for DWR.” Dated 2011.

URS, 2015a. “Geotechnical Evaluations Report, Volume 1, Existing Conditions, NEMDC East Study Area, Urban Levee Evaluations Project.” Prepared by URS for DWR. Dated March 2015.

URS, 2015b, “Geotechnical Evaluations Report, Volume 2, Remedial Alternatives, NEMDC East Study Area, Urban Levee Evaluations Project.” Prepared by URS for DWR. Dated March 2015.

USACE, 2000. “Design and Construction of Levees,” US Army Corps of Engineers, Engineer Manual, EM 1110-2-1913. Dated April 30, 2000.

USACE, 2005. “Design Guidance for Levee Underseepage,” US Army Corps of Engineers, Technical Letter ETL 1110-2-569. Dated May 1, 2005.

USACE, 2022. “CESPK-EDG, SOP 3 Geotechnical Levee Practice, May 2022, Standard Operating Procedure 3, Geotechnical Levee Practice, US Army Corps of Engineers, Sacramento District, Geotechnical Engineering Branch.” Dated May 2022.

FIGURES
___________________________________________________________________________________

LIST OF ATTACHMENTS
Figure 1 DCNL Site Vicinity Map
Figure 2 DCNL Site Location Map
Site

DCNL SITE VICINITY MAP
PROJECT:

FILE NAME:

FIGURE
1 DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
SEP 2023
M. BESWICK
A. LEONARD
F1_SiteLocation.mxd
Explanation
Levee Alignment
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F1_SiteLocation.mxd

ULDC FINDING AND FEMA LEVEE

CERTIFICATION PROGRAM

SACRAMENTO AREA FLOOD CONTROL

AGENCY LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
Service Layer Credits: Copyright:© 2013 National Geographic Society, i-cubed; ESRI World Imagery, Maxar Vivid Advanded image dates 4/12/2022, 4/26/2022, and 5/4/2022; SACOG
Orthos image date 3/18/2022.

ALeonard 10/8/2023
0 1 2
Miles
Locations are Approximate
£
I
I
I I
I
I
I
I
I
I I
Dry Creek
Steelhead
Creek
7035+00

DCNL SITE LOCATION MAP
PROJECT:

FILE NAME:

FIGURE
2 DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
JAN 2024
M. BESWICK
A. LEONARD
F2_ReachLocation.mxd
Explanation
I
IDCNL
DCNL Critical Cross Section I
I325' Extension
I
I
All Other Levees Not a part of
DCNL Certification
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F2_ReachLocation.mxd Service Layer Credits: Esri, HERE, Garmin, (c)
OpenStreetMap contributors
Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community; ESRI World Imagery, Maxar Vivid Advanded
image dates 4/12/2022, 4/26/2022, and 5/4/2022; SACOG
Orthos image date 3/18/2022.
0 500 1,000
Feet
Locations are Approximate
£
7000+00

ULDC FINDING AND FEMA LEVEE

CERTIFICATION PROGRAM

SACRAMENTO AREA FLOOD CONTROL

AGENCY LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
7005+00
7010+00
7015+00
7020+00
7025+00
7030+00
7035+00
7040+00
7045+00
7050+00
7055+00
7060+00
7070+00
7075+00
7080+00
7085+00
7065+00

APPENDIX A
____________________________________________________________________________

LIST OF ATTACHMENTS
Kleinfelder, 2024. “Geotechnical Evaluation 2023 100-Year WSE, Dry Creek North Levee – 325-foot Upstream Extension, North Area Streams, SAFCA FEMA Levee Accreditation, Sacramento County, California.” Dated February 16, 2024.
24001006.001A/SAC24R164385 Page 1 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 February 16, 2024
File: 24001006.001A
Mr. Pro Mitra, PE
MBK Engineers
455 University Ave., Suite 100
Sacramento, CA 95825
SUBJECT: Geotechnical Evaluation 2023 100-Year WSE
Dry Creek North Levee – 325-foot upstream extension
North Area Streams
SAFCA FEMA Levee Accreditation
Sacramento County, California
Dear Mr. Mitra:

In 2021 Kleinfelder reviewed 325 feet of the Rio Linda Boulevard roadway embankment extending immediately upstream of the current end of the Dry Creek North Levee (DCNL) in Sacramento County, California. The purpose of this review was to assess if the roadway embankment can be included as a flood protection feature from a geotechnical standpoint. A new 2023 100-Year water surface elevation (WSE) developed by MBK Engineers has been established for this area. Kleinfelder has reviewed the new 2023 100-year WSE and the information within this report provides an opinion on whether the 2023 100-year WSE impacts the geotechnical findings.

This letter contains a summary of our analyses and conclusions. It should be noted that the roadway embankment was not originally constructed as a levee but since it can function to contain the 100-year WSE event from the protected area for it to be considered a levee it would need to meet requirements set forth in 44 CFR §65.10.

This letter specifically addresses geotechnical evaluation of the roadway embankment pertaining to geometry, settlement, foundation and embankment stability outlined in FEMA guidelines titled “Guidance for Flood Risk Analysis and Mapping for Levees,” dated November 2019. This letter addresses the geotechnical aspects of levee certification and does not include an assessment of encroachments, penetrations, or erosion.

BACKGROUND
Original Construction
Construction of DCNL included an approximately 500-foot tie-in with Rio Linda Boulevard (Ensign & Buckley, 1997) to raise the roadway embankment to the levee elevation until high ground was reached.

The construction was performed under a SAFCA contract between July and November 1995. As-built construction drawings document an inspection trench a minimum of 3 to 6 feet deep into the foundation (Plate 4-10 of the 2016 PIR). Kleinfelder prepared the geotechnical engineering report for the project (Kleinfelder, 1994) and Kleinfelder representatives observed construction (including material 24001006.001A/SAC24R164385 Page 2 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 conformance and compaction testing) (Kleinfelder, 1997). Kleinfelder engineers confirmed the key trench was extended to penetrate into underlying fine-grained and/or cemented soils.

FEMA Certification
The original 2021 review was based on the Kleinfelder 2016 Problem Identification Report on DCNL (referenced above) and provided geotechnical certifications for FEMA accreditation of the levee. The 2016 evaluation included review of the DCNL between the NEMDC pump station embankment at Station 7000+00 and the intersection with Rio Linda Boulevard at Station 7085+58 (Figure 1).

Project Extension and 2023 Water Surface Elevation Update Based upon a FEMA review comment received for the original 2021 review, MBK Engineers assessed the segment of Rio Linda Boulevard between the end of the DCNL at Station 7085+58 and high ground about 500 feet to the north and concluded that protection for the design WSE should be extended approximately 325 feet. The roadway embankment is approximately 30 feet wide at the top and about three to four feet in height, which is wider than the theoretical levee prism. The crest is at an elevation of 48 to 50feet and the top is paved with asphalt concrete.

MBK Engineers provided an updated 2023 100-year WSE for the DCNL 325-foot extension north along Rio Linda Boulevard beginning from DCNL Station 7085+58 (MBK, 2024). MBK Engineers also provided crest, landside, and waterside toe elevations of the of DCNL 325-foot extension embankment in an excel plot. Table 1 below summarizes the 2023 100-year WSE and the DCNL extension embankment crest, landside, and waterside toe elevations.

Table 1: DCNL Extension 2023 Extension and Embankment Elevations Data Elevation
(NAVD88, ft)
DCNL
Extension
325-ft
2023 100-year
WSE 43.81
Top of
Embankment 48 to 502
Waterside
Toe 40 to 442
Landside Toe 39 ½ to 462

1. Per Technical Memorandum, “Determination of the 1% Annual Chance Flood Base Flood Elevation for the Dry Creek North Levee,” dated February 16, 2024.

2. Elevations estimated from excel plot titled “Dry_Creek_profiles_050420.xls” provided by MBK Engineers.

CURRENT EVALUATION
Review of Documentation
Kleinfelder reviewed the following documents:
• Kleinfelder, 2016a. Problem Identification Report (PIR), North Area Streams, SAFCA FEMA Levee Accreditation (North Area Stream, American River, Sacramento River Downstream of American 24001006.001A/SAC24R164385 Page 3 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 River, and Beach Lake Levee), Sacramento County, California,” dated September 18, 2013 (Revised April 29, 2016).
• Kleinfelder, 2016b, “ULDC Geotechnical Results Summary, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), Sacramento County.” Kleinfelder, April 26, 2016. • Kleinfelder, 1994. “Geotechnical Evaluation of Proposed Levee Improvements Dry Creek Levees.” June, 1994.
• Kleinfelder, 1997. Final Report, Field Compaction Test Results, Dry Creek – North Levee, Sacramento, California, dated February 6, 1997.
• Ensign & Buckley, 1997. “Sacramento Area Flood Control Agency, Dry/Robla Creek Levee Project, Volume V of V, Natomas Area Flood Control Improvements, Sacramento, California.” As-Built Drawings. October 24, 1997.

Based upon review of the above documents, the foundation and embankment materials were constructed with appropriate soil types, under observation and testing of an engineer, and met project specifications consistent with Type I embankment fill criteria.

Site Visit and Laboratory Testing
On May 15, 2020, a geologist from Kleinfelder visited the site to observe general conditions of the Rio Linda Boulevard embankment within the vicinity of the extended project limits. A sample of the landside roadway embankment fill was obtained by hand and returned to Kleinfelder’s Sacramento laboratory for testing. Laboratory testing included Atterberg limits and gradation to confirm the material meets general levee fill criteria.

Results of the testing are summarized in Table 2.

Table 2
Summary of Laboratory Testing
Sample Depth
(feet)
Atterberg Limits Sieve Analysis USCS
Liquid Limit Plasticity Index Passing No. 200 (%) Classification 1 0.5-1.5 44 23 48.3 SC – Clayey
Sand
These laboratory test results meet the levee embankment fill parameters provided in the project documents.

GEOTECHNICAL EVALUATION
Geometry
It is understood the preferred levee geometry adopted for this study follows USACE criteria (Sacramento Geotechnical Levee Practice, USACE SPK SOP3 2022), which specifies minimum levee geometry as shown below:
24001006.001A/SAC24R164385 Page 4 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 • Minimum waterside slope of 3 horizontal (H):1 vertical (V) • Minimum landside slope of 2H:1V (if past performance has been satisfactory) • Minimum crown width of 20 feet for a major stream and 12 feet for a minor stream or tributary Mead & Hunt has performed a geometry check for the roadway embankment at the 100-year WSE. This analysis consisted of taking the elevation of the 100-year WSE plus three feet (for freeboard) as the top of the levee and applying the 3H:1V waterside slope and 2H:1V landside slope with a 12-foot crest width to evaluate if the theoretical levee prism falls within the roadway embankment. The levee centerline was used as the initial anchor point for the analysis with further refinements to fully encompass the template within the existing levee cross-section by adjusting the template towards the landside. It is understood that the theoretical levee prism fits within the existing roadway embankment.

Embankment and Foundation Stability
A qualitative review was performed to compare previous foundation and embankment conditions to the roadway embankment. According to published surficial geologic and soil survey mapping this embankment was observed to be located on similar fine-grained soils consistent with other areas of the project downstream. The foundation soils consist of silt, clay, silty sand, and clayey sand up to 20 feet thick with high recorded Standard Penetration Test blow counts consistent with cemented soils (hardpan). The soil sample test results indicate the roadway embankment was constructed of locally available clayey sand to sandy clay material similar to the levee embankment evaluated downstream.

Seepage and slope stability analyses were performed at Station 7035+00 for the Kleinfelder 2016 PIR and ULDC Geotechnical Summary reports referenced above. Analysis input, material properties, and results were reviewed and compared to the current site conditions for the project extension.

Based on this review the following conclusions can be made:
• A free seepage face is not likely to develop due to the low differential head (4 feet or less) between the 100-year WSE and the landside toe. In addition, the levee was constructed with cohesive fill with a low potential for internal erosion (backward erosion piping). Therefore, through seepage is not a concern.
• Underseepage is not a concern due to the presence of a thick fine-grained blanket/foundation layer approximately 20 feet thick and low differential head of up to approximately 4 feet.

Station 7035+00 was previously analyzed at a WSE of 44.6 feet and had exit gradients at the landside toe and landside ditch within acceptance criteria. • Slope stability of the roadway embankment would meet analysis criteria. Currently, landside slopes along the roadway embankment have been stable during previous elevated water events at slopes generally steeper than 3H:1V, and more typically closer to 2H:1V. The roadway embankment is wider than the theoretical prism crest width and would be able to experience shallow slope failures without impacting the theoretical prism. Station 7035+00 was previously analyzed at a WSE of 44.6 feet and had factor of safety within acceptance criteria. • The roadway was constructed in 1995 and no improvements since. Therefore, settlement is not a concern.
24001006.001A/SAC24R164385 Page 5 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 • The levee geometry of the cross section at 7035+00 was similar to Rio Linda Boulevard and had a landside slope of 1.8H:1V, a waterside slope of 3H:1V, and a crown width of 19 feet. The landside toe is at a similar elevation of 40 feet for the 7035+00 cross section and the Rio Linda Boulevard extension. Additional sampling was performed along the extension to confirm blanket thickness.

SUMMARY OF EVALUATION
It is Kleinfelder’s conclusion that the 325 feet of the Rio Linda Boulevard roadway embankment extending upstream of the DCNL meets geotechnical criteria for FEMA accreditation. No additional geotechnical remediation is necessary to meet these criteria.

LIMITATIONS
This work was performed in a manner consistent with that level of care and skill ordinarily exercised by other members of Kleinfelder’s profession practicing in the same locality, under similar conditions and at the date the services are provided. The work performed was based on project information provided by both the client and other parties. Kleinfelder’s conclusions, opinions, and recommendations are based on a limited number of observations and data. It is possible that conditions could vary between or beyond the data evaluated. Kleinfelder makes no other representation, guarantee, or warranty, express or implied, regarding the services, communication (oral or written), report, opinion, or instrument of service provided.

This report may be used only by the client and the registered design professional in responsible charge and only for the purposes stated for this specific engagement within a reasonable time from its issuance, but in no event later than two (2) years from the date of the report.

The information included on graphic representations in this report has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information.

These documents are not intended for use as a land survey product. The use or misuse of the information contained on these graphic representations is at the sole risk of the party using or misusing the information.

Conclusions and conceptual recommendations contained in this report are based on field observations and subsurface explorations, limited laboratory tests, and Kleinfelder’s present knowledge of the project. It is possible that soil or groundwater conditions could vary between or beyond the points explored. If soil or groundwater conditions are encountered that differ from those described herein, the client is responsible for ensuring that Kleinfelder is notified immediately in order that we may reevaluate the conclusions and conceptual recommendations of this report.

The scope of services was limited. It should be recognized that definition and evaluation of subsurface conditions are difficult. Judgments leading to conclusions and recommendations are generally made with incomplete knowledge of the subsurface conditions present due to the limitations of data from field studies. The conclusions of this assessment are based on the information presented herein.

Although risk can never be eliminated, more detailed and extensive studies yield more information, which may help understand and manage the level of risk. 24001006.001A/SAC24R164385 Page 6 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 We appreciate the opportunity of providing services for this project. If you have questions regarding this report or if we may be of further assistance, please contact us.

Respectfully submitted,
KLEINFELDER, INC.

Meredith Beswick PE, PG Timothy A. Williams, PE, GE
Senior Geological Engineer Senior Principal Geotechnical Engineer Attachments:

Figure 1: Site location Map
Figure 2: Dry Creek North Levee Extension
Dry Creek Profiles
24001006.001A/SAC24R164385 Page 7 of 7 February 16, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701

REFERENCES
___________________________________________________________________________________ The following references were reviewed and consulted during the preparation of this report:

Kleinfelder. 2013. “Geotechnical Data Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), Sacramento County, California,” dated May 31, 2013.

MBK Engineers. 2013a. “Drawdown NEMDC 100-yr 2013-07-29,” dated July 29, 2013.

MBK Engineers. 2013b. “Base Flood Elevations for SAFCA Levee Certification Reaches,” dated 2013.

MBK Engineers, 2024, “Determination of the 1% Annual Chance Flood Base Flood Elevation for the Dry Creek North Levee.” Dated February 16, 2024.

MBK Engineers “Dry_Creek_profiles_050420.xls”
US National Archives and Records Administration. 2011. Code of Federal Regulations. Title 44.

Emergency Management and Assistance.

USACE. 2000. “Design and Construction of Levees,” USACE, Engineering and Design Manual, EM 1110-2- 1913, April 30, 2000.

USACE. 2005. “Design Guidance for Levee Underseepage,” USACE, Technical Letter ETL 1110-2-569, May 1, 2005.

USACE 2022, “CESPK-EDG, SOP 3 Geotechnical Levee Practice, May 2022, Standard Operating Procedure 3, Geotechnical Levee Practice, US Army Corps of Engineers, Sacramento District, Geotechnical Engineering Branch.” May 2022.

Site

SITE LOCATION MAP
PROJECT:

FILE NAME:

FIGURE
1 DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
SEP 2023
M. BESWICK
A. LEONARD
F1_SiteLocation.mxd
Explanation
Levee Alignment
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F1_SiteLocation.mxd

ULDC & FEMA LEVEE CERTIFICATION PROGRAM

SACRAMENTO AREA FLOOD CONTROL

AGENCY LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
Service Layer Credits: Copyright:© 2013 National Geographic Society, i-cubed; ESRI World Imagery, Maxar Vivid Advanded image dates 4/12/2022, 4/26/2022, and 5/4/2022; SACOG
Orthos image date 3/18/2022.

ALeonard 9/28/2023
0 1 2
Miles
Locations are Approximate
£
I
0+00
1+00
2+00
3+00
4+00
5+00
I
I !(
40 42
40 44
40 40
40 48
42 42
42 44
42 40
40 40
42 40
44 40
40 42
46 44
46 42
48 40
40 D
C
NL-1

DRY CREEK NORTH LEVEE

EXTENSION
PROJECT:

FILE NAME:

FIGURE
2 DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
FEB 2024
M. BESWICK
A. LEONARD
F3_DryCreekExtension.mxd
Explanation
!( Approxmiate Hand Sample #1
Location I
I325' Extension I
IDry Creek North Reach
Construction Limit (1997)
Landside Toe Alignment
Waterside Toe Alignment
Proposed Upstream Point of Dry
Creek North Levee (Station 325)
Surface Elevation Contours
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F3_DryCreekExtension.mxd

ULDC & FEMA LEVEE CERTIFICATION PROGRAM

SACRAMENTO AREA FLOOD CONTROL

AGENCY LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
Service Layer Credits: Source: Esri, Maxar, Earthstar
Geographics, and the GIS User Community; ESRI World
Imagery, Maxar Vivid Advanded image dates 4/12/2022,
4/26/2022, and 5/4/2022; SACOG Orthos image date
3/18/2022.
0 40 80
Feet
Locations are Approximate
£
Intersection of Levee Centerline
with Roadway Embankment
Kleinfelder PIR Limit
For Dry Creek North Levee (2013)
7085+58
Dry_Creek_profiles_050420
station elevation station elevation station elevation station elevation station elevation station elevation 0 42.6862 0 43.8468 0 44.8468 0 48.43 0 40.55463208 0 40.12433

1.53056 42.68767 1.53056 43.84801 1.53056 44.84801 3.06112 48.54856 3.019609787 40.50628226 3.026464 40.17101

3.06112 42.68914 3.06112 43.84921 3.06112 44.84921 6.122241 48.55783 6.039219575 40.64647759 6.052928 40.12908

4.591681 42.69061 4.591681 43.8504 4.591681 44.8504 9.183361 48.61554 9.058829362 40.59441991 9.079393 40.1023

6.122241 42.69207 6.122241 43.85158 6.122241 44.85158 12.24448 48.66892 12.07843918 40.57800077 12.10586 40.07254

7.652801 42.69352 7.652801 43.85276 7.652801 44.85276 15.3056 48.55772 15.09804897 40.575418 15.13232 40.0395

9.183361 42.69497 9.183361 43.85392 9.183361 44.85392 18.36672 48.62773 18.11765874 40.634715 18.15879 39.9944

10.71392 42.69637 10.71392 43.85507 10.71392 44.85507 21.42784 48.76042 21.13726854 40.5783552 21.18525 40.03346

12.24448 42.69777 12.24448 43.8562 12.24448 44.8562 24.48896 48.7047 24.15687833 40.53918085 24.21171 40.05091

13.77504 42.69914 13.77504 43.85733 13.77504 44.85733 27.55008 48.59714 27.17648813 40.59997511 27.23818 40.21121

15.3056 42.70048 15.3056 43.85844 15.3056 44.85844 30.6112 48.72386 30.1960979 40.55829355 30.26464 40.39052

16.83616 42.7018 16.83616 43.85955 16.83616 44.85955 33.67232 48.71046 33.2157077 40.61560336 33.29111 40.73585

18.36672 42.70312 18.36672 43.86065 18.36672 44.86065 36.73344 48.71154 36.2353175 40.61279744 36.31757 40.73496

19.89728 42.70453 19.89728 43.86174 19.89728 44.86174 39.79456 48.72527 39.25492728 40.59043317 39.34403 40.50968

21.42784 42.70596 21.42784 43.86283 21.42784 44.86283 42.85568 48.72784 42.27453708 40.60572932 42.3705 40.29922

22.9584 42.70743 22.9584 43.86391 22.9584 44.86391 45.91681 48.79612 45.29414686 40.68908381 45.39696 40.0686

24.48896 42.70891 24.48896 43.86502 24.48896 44.86502 48.97793 48.78144 48.31375666 40.75930593 48.42343 39.97047

26.01952 42.71042 26.01952 43.86614 26.01952 44.86614 52.03905 48.76746 51.33336644 40.66541802 51.44989 39.87957

27.55008 42.71197 27.55008 43.86729 27.55008 44.86729 55.10017 48.70578 54.35297623 40.56383447 54.4403 39.858

29.08064 42.71354 29.08064 43.86846 29.08064 44.86846 58.16129 48.73821 57.37258604 40.59511694 57.4307 39.88096

30.6112 42.71515 30.6112 43.86965 30.6112 44.86965 61.22241 48.81716 60.3921958 40.60176686 60.42111 39.73426

32.14176 42.71678 32.14176 43.87087 32.14176 44.87087 64.28353 48.7965 63.41180561 40.53946706 63.41151 39.65492

33.67232 42.71846 33.67232 43.8721 33.67232 44.8721 67.34465 48.84921 66.4314154 40.535245 66.40192 39.57438

35.20288 42.72016 35.20288 43.87338 35.20288 44.87338 70.40577 48.8404 69.45102517 40.51782496 69.39233 39.58854

36.73344 42.72191 36.73344 43.87467 36.73344 44.87467 73.46689 48.8056 72.47063498 40.65605011 72.38273 39.54281

38.264 42.72367 38.264 43.87599 38.264 44.87599 76.52801 48.86486 75.49024475 40.58313727 75.37314 39.46695

39.79456 42.72548 39.79456 43.87733 39.79456 44.87733 79.58913 48.89309 78.50985455 40.58948738 78.36354 39.5048

41.32512 42.7273 41.32512 43.8787 41.32512 44.8787 82.65025 48.81343 81.62328284 40.55521266 81.35395 39.51071 FEMA ULDC ULDC plus 1 ft Top of Embankment WS Embankment Toe LS Embankment Toe Dry_Creek_profiles_050420
FEMA ULDC ULDC plus 1 ft Top of Embankment WS Embankment Toe LS Embankment Toe

42.85568 42.72917 42.85568 43.88008 42.85568 44.88008 85.71137 48.85183 84.73671119 40.46046317 84.34435 39.54755

44.38624 42.73104 44.38624 43.8815 44.38624 44.8815 88.75426 48.91048 87.8501395 40.40725796 87.33476 39.71509

45.91681 42.73295 45.91681 43.88291 45.91681 44.88291 91.79715 48.88447 90.96356782 40.47132864 90.32517 39.67452

47.44737 42.73486 47.44737 43.88435 47.44737 44.88435 94.84004 48.93764 94.07699613 40.45830099 93.31557 39.68231

48.97793 42.7368 48.97793 43.8858 48.97793 44.8858 97.88293 48.98452 97.19042445 40.41928054 96.30598 39.83807

50.50849 42.73875 50.50849 43.88727 50.50849 44.88727 100.9258 49.02618 100.3038528 40.35580199 99.29638 40.18932

52.03905 42.74072 52.03905 43.88875 52.03905 44.88875 103.9687 49.00114 103.4172811 40.31662046 102.2868 40.56649

53.56961 42.7427 53.56961 43.89025 53.56961 44.89025 107.0116 49.01997 106.5307094 40.30969211 105.3261 40.55609

55.10017 42.74471 55.10017 43.89176 55.10017 44.89176 110.0545 49.0692 109.5862927 40.36942716 108.3654 40.49031

56.63073 42.74672 56.63073 43.8933 56.63073 44.8933 113.0974 49.11691 112.641876 40.4002116 111.4047 40.55838

58.16129 42.74876 58.16129 43.89484 58.16129 44.89484 116.1403 49.08036 115.6974593 40.39405104 114.444 40.51052

59.69185 42.7508 59.69185 43.89642 59.69185 44.89642 119.1832 49.02044 118.7530426 40.31396929 117.4833 40.24352

61.22241 42.75288 61.22241 43.898 61.22241 44.898 122.2261 49.01674 121.808626 40.2079704 120.5226 39.92527

62.75297 42.75496 62.75297 43.89962 62.75297 44.89962 125.2689 49.06318 124.8642093 40.26074046 123.562 39.86896

64.28353 42.75706 64.28353 43.90125 64.28353 44.90125 128.134 49.04671 127.9197926 40.32184048 126.6013 39.96779

65.81409 42.75917 65.81409 43.9029 65.81409 44.9029 130.9991 48.98723 130.9753759 40.29969688 129.6406 40.26248

67.34465 42.76129 67.34465 43.90458 67.34465 44.90458 133.8641 48.99635 134.0309591 40.30412234 132.6799 40.55229

68.87521 42.76343 68.87521 43.90627 68.87521 44.90627 136.7292 49.02715 137.0865424 40.35164737 135.4964 40.7209

70.40577 42.76557 70.40577 43.90796 70.40577 44.90796 139.5943 49.03116 140.1421257 40.44341209 138.3128 40.67417

71.93633 42.76773 71.93633 43.90968 71.93633 44.90968 142.4593 49.02874 143.197709 40.47611501 141.1293 40.32447

73.46689 42.7699 73.46689 43.9114 73.46689 44.9114 145.3244 49.0148 146.2532923 40.48558085 143.9458 40.30579

74.99745 42.77207 74.99745 43.91312 74.99745 44.91312 148.1895 49.05946 149.3088756 40.42983439 146.7622 40.40324

76.52801 42.77425 76.52801 43.91484 76.52801 44.91484 151.0545 48.98253 152.3644589 40.30032793 149.5787 40.48523

78.05857 42.77644 78.05857 43.91655 78.05857 44.91655 153.9196 49.05964 155.4200422 40.46778939 152.3952 40.67983

79.58913 42.77862 79.58913 43.91824 79.58913 44.91824 156.9295 48.95131 158.3708637 40.59886816 155.2117 40.88051

81.11969 42.7808 81.11969 43.91992 81.11969 44.91992 159.9395 48.86203 161.3216851 40.60304228 158.0281 40.79277

82.65025 42.78298 82.65025 43.92157 82.65025 44.92157 162.9494 48.85624 164.2725066 40.36993817 160.8446 40.54238

84.18081 42.78512 84.18081 43.92321 84.18081 44.92321 165.9594 48.79428 167.2233281 40.35620333 163.6611 40.5289

85.71137 42.78724 85.71137 43.92482 85.71137 44.92482 168.9693 48.7377 170.1741496 40.39726283 166.5924 40.35999

87.23282 42.78945 87.23282 43.92654 87.23282 44.92654 171.9793 48.76437 173.1249711 40.45816608 169.5238 40.31805

88.75426 42.79163 88.75426 43.92822 88.75426 44.92822 174.9892 48.74166 176.0757925 40.5380875 172.4551 40.36821

90.27571 42.79372 90.27571 43.92989 90.27571 44.92989 177.9992 48.63916 179.026614 40.51768314 175.3865 40.27301

91.79715 42.79581 91.79715 43.93151 91.79715 44.93151 181.0091 48.6332 181.9774355 40.43552994 178.3178 40.47417

93.3186 42.79792 93.3186 43.93314 93.3186 44.93314 184.0191 48.6781 184.928257 40.43563383 181.2492 40.59878

94.84004 42.80004 94.84004 43.93478 94.84004 44.93478 187.029 48.63662 187.8790785 40.36840717 184.1805 40.61573

96.36149 42.80217 96.36149 43.93642 96.36149 44.93642 190.039 48.55183 190.8298999 40.28226727 187.1119 40.43091

97.88293 42.80429 97.88293 43.93809 97.88293 44.93809 193.0489 48.44764 193.7807214 40.17836254 190.0432 40.29053

99.40438 42.80642 99.40438 43.93977 99.40438 44.93977 196.0589 48.34822 196.7315429 40.14019746 192.9746 40.29782 100.9258 42.80855 100.9258 43.94147 100.9258 44.94147 199.0688 48.33407 199.6823644 40.1459068 195.9059 40.48791 102.4473 42.8107 102.4473 43.94318 102.4473 44.94318 202.0788 48.32446 202.7240015 40.21768951 198.8373 40.7396 103.9687 42.81285 103.9687 43.9449 103.9687 44.9449 205.0887 48.30669 205.7656387 40.30510614 201.7686 40.67979 105.4902 42.81501 105.4902 43.94663 105.4902 44.94663 208.0987 48.2646 208.8072759 40.33663312 204.5516 40.57769 107.0116 42.81718 107.0116 43.94838 107.0116 44.94838 211.1937 48.25259 211.8489131 40.38762904 207.3346 40.59862 108.533 42.81937 108.533 43.95013 108.533 44.95013 214.2887 48.20405 214.8905502 40.39028463 210.1177 40.71948 110.0545 42.82156 110.0545 43.95189 110.0545 44.95189 217.3837 48.20618 217.9321874 40.42393895 212.9007 40.83188 111.5759 42.82377 111.5759 43.95365 111.5759 44.95365 220.4787 48.1978 220.9738246 40.44414213 215.6837 40.91264 113.0974 42.82599 113.0974 43.95543 113.0974 44.95543 223.5738 48.15445 224.0154617 40.49825076 218.4667 41.20656 114.6188 42.82823 114.6188 43.95721 114.6188 44.95721 226.6688 48.16991 227.0570989 40.50749347 221.2497 41.16624 116.1403 42.83048 116.1403 43.959 116.1403 44.959 229.7638 48.2018 230.098736 40.52186984 224.0327 41.03785 117.6617 42.83274 117.6617 43.9608 117.6617 44.9608 232.8588 48.21513 233.1403732 40.65660923 226.8157 40.98659 119.1832 42.835 119.1832 43.96261 119.1832 44.96261 235.9538 48.22231 236.1820104 40.69895661 229.5987 41.20919 120.7046 42.83729 120.7046 43.96442 120.7046 44.96442 239.0488 48.20823 239.2236475 40.69704082 232.3817 41.40092 122.2261 42.83959 122.2261 43.96624 122.2261 44.96624 242.1438 48.23458 242.2652847 40.7813485 235.393 41.5106 123.7475 42.84191 123.7475 43.96806 123.7475 44.96806 245.2388 48.30196 245.3069218 40.92233463 238.4043 41.59635 125.2689 42.84423 125.2689 43.9699 125.2689 44.9699 248.3339 48.29609 248.3485589 41.09435179 241.4156 41.6114 128.134 42.84864 128.134 43.97338 128.134 44.97338 251.4289 48.38967 251.3901961 41.25408344 244.4269 41.68425 130.9991 42.8531 130.9991 43.97689 130.9991 44.97689 254.3322 48.3 254.4318332 41.47036213 247.4382 41.81552 133.8641 42.8576 133.8641 43.98043 133.8641 44.98043 257.2356 48.26185 257.5495195 41.66525532 250.4495 41.86229 136.7292 42.86213 136.7292 43.98399 136.7292 44.98399 260.1389 48.28381 260.6672059 41.75657316 253.4608 41.89428 139.5943 42.86669 139.5943 43.98755 139.5943 44.98755 263.0423 48.25834 263.7848921 41.92483155 256.4721 41.87039 142.4593 42.87128 142.4593 43.99114 142.4593 44.99114 265.9456 48.22017 266.9025785 42.05822769 259.4834 41.81419 145.3244 42.8759 145.3244 43.99476 145.3244 44.99476 268.849 48.19117 270.0202648 42.2276625 262.4947 41.7957 148.1895 42.88054 148.1895 43.9984 148.1895 44.9984 271.7523 48.20198 273.1379511 42.48315662 265.506 41.76168 151.0545 42.88521 151.0545 44.00205 151.0545 45.00205 274.6557 48.20859 276.2556374 42.74124749 268.5173 41.72382 153.9196 42.88991 153.9196 44.00571 153.9196 45.00571 277.559 48.17344 279.3733237 42.74679227 271.5286 41.73461 155.4246 42.89251 155.4246 44.00773 155.4246 45.00773 280.4624 48.14483 282.49101 42.73390858 274.5399 41.72648 156.9295 42.89513 156.9295 44.00975 156.9295 45.00975 283.3657 48.14165 285.6086963 42.81536171 277.5512 41.81997 158.4345 42.89775 158.4345 44.01179 158.4345 45.01179 286.2691 48.14858 288.7263826 42.99874141 280.5625 42.0255 159.9395 42.90038 159.9395 44.01382 159.9395 45.01382 289.1725 48.12056 291.8440689 43.05254018 283.5738 42.08981 161.4445 42.90302 161.4445 44.01587 161.4445 45.01587 292.0758 48.08793 294.9617552 43.21077541 286.5851 42.20926 162.9494 42.90568 162.9494 44.01792 162.9494 45.01792 295.084 48.06236 297.6569244 43.56030525 289.5964 42.26815 164.4544 42.90834 164.4544 44.01997 164.4544 45.01997 298.0922 48.01301 300.3520936 43.66975066 292.6077 42.21471 Dry_Creek_profiles_050420
FEMA ULDC ULDC plus 1 ft Top of Embankment WS Embankment Toe LS Embankment Toe 165.9594 42.911 165.9594 44.02202 165.9594 45.02202 301.1005 47.98845 303.0472628 43.56511022 295.6204 42.27329 167.4644 42.91367 167.4644 44.02408 167.4644 45.02408 304.1087 47.97553 305.742432 43.48113065 298.6332 42.30727 168.9693 42.91636 168.9693 44.02613 168.9693 45.02613 307.1169 47.91462 308.4376013 43.48650243 301.6459 42.36396 170.4743 42.91904 170.4743 44.0282 170.4743 45.0282 310.1251 47.86776 311.4883382 43.63918328 304.6587 42.14899 171.9793 42.92175 171.9793 44.03027 171.9793 45.03027 313.1334 47.86525 314.5390752 43.73233168 307.6714 41.84323 173.4843 42.92447 173.4843 44.03235 173.4843 45.03235 316.1416 47.84871 317.5898122 43.66548324 310.6842 41.84897 174.9892 42.92721 174.9892 44.03442 174.9892 45.03442 319.1498 47.81352 320.6405492 43.63104593 313.6969 41.74153 176.4942 42.92994 176.4942 44.03651 176.4942 45.03651 322.158 47.75451 323.6912861 43.78601034 316.7097 41.75441 177.9992 42.93269 177.9992 44.03859 177.9992 45.03859 325.1662 47.7173 326.7420231 43.88262314 319.7224 41.91979 179.5042 42.93544 179.5042 44.04068 179.5042 45.04068 328.1745 47.70313 329.7927601 44.05686795 322.7352 42.46094 181.0091 42.9382 181.0091 44.04277 181.0091 45.04277 331.1827 47.63688 332.843497 44.00642463 325.7479 43.51485 182.5141 42.94096 182.5141 44.04488 182.5141 45.04488 334.1909 47.56732 335.894234 43.82393951 328.7607 44.3783 184.0191 42.94374 184.0191 44.04698 184.0191 45.04698 337.1991 47.55471 338.9449709 43.89579411 331.7734 45.20347 185.5241 42.94651 185.5241 44.0491 185.5241 45.0491 340.2073 47.52245 341.9957079 43.90572163 334.7862 45.79056 187.029 42.9493 187.029 44.05121 187.029 45.05121 343.2156 47.48299 345.0464448 43.82563723 337.7989 45.96549 188.534 42.95209 188.534 44.05333 188.534 45.05333 346.2238 47.45483 348.0971818 43.91580467 340.8117 45.97959 190.039 42.95489 190.039 44.05545 190.039 45.05545 349.232 47.44226 351.1479187 44.01180912 343.8244 46.04175 191.544 42.95769 191.544 44.05758 191.544 45.05758 352.2402 47.40366 354.1986556 44.27280462 346.8372 46.06671 193.0489 42.96051 193.0489 44.0597 193.0489 45.0597 355.2484 47.37948 357.2493926 44.57429116 349.8499 46.08867 194.5539 42.96332 194.5539 44.06183 194.5539 45.06183 358.2567 47.38439 360.3001295 44.64236284 352.8627 46.00027 196.0589 42.96614 196.0589 44.06396 196.0589 45.06396 361.2649 47.41278 363.3508665 44.54186308 355.8754 45.3485 197.5639 42.96896 197.5639 44.06609 197.5639 45.06609 364.2731 47.43201 366.4016034 44.52620506 358.8882 44.36501 199.0688 42.97179 199.0688 44.06823 199.0688 45.06823 367.2813 47.43934 369.4523403 44.46454787 361.9009 43.91799 200.5738 42.97462 200.5738 44.07038 200.5738 45.07038 370.3173 47.40746 372.5030772 44.42766589 364.9137 43.8026 202.0788 42.97745 202.0788 44.07253 202.0788 45.07253 373.3533 47.37864 375.5538141 44.31989297 367.9264 43.51251 203.5838 42.98028 203.5838 44.07468 203.5838 45.07468 376.3893 47.39866 378.6045511 44.30589928 370.9392 43.37787 205.0887 42.98312 205.0887 44.07683 205.0887 45.07683 379.4253 47.34972 381.655288 44.35436651 373.9519 43.45969 206.5937 42.98595 206.5937 44.07898 206.5937 45.07898 382.4613 47.37377 384.7060249 44.51533415 376.9646 43.64698 208.0987 42.98878 208.0987 44.08113 208.0987 45.08113 385.4973 47.37755 387.7567618 44.9415117 379.998 44.06272 209.6462 42.99165 209.6462 44.08331 209.6462 45.08331 388.5333 47.37049 390.8074987 45.73210993 383.0314 44.71599 211.1937 42.99452 211.1937 44.0855 211.1937 45.0855 391.5693 47.34617 393.8582356 46.26752663 386.0647 44.75134 212.7412 42.99739 212.7412 44.08768 212.7412 45.08768 394.6053 47.37835 396.9089725 46.38841174 389.0981 44.91879 214.2887 43.00024 214.2887 44.08986 214.2887 45.08986 397.6413 47.35986 399.9597094 46.29979883 392.1315 45.63583 215.8362 43.0031 215.8362 44.09204 215.8362 45.09204 400.6773 47.32329 403.0104463 46.16290399 395.1648 45.89795 217.3837 43.00595 217.3837 44.09422 217.3837 45.09422 403.7133 47.32672 406.0611832 46.07671286 398.1982 45.88498 218.9312 43.0088 218.9312 44.0964 218.9312 45.0964 406.7493 47.3512 409.1119201 46.01793334 401.2316 45.84063 220.4787 43.01163 220.4787 44.09858 220.4787 45.09858 409.7853 47.35803 412.1626569 46.06880924 404.2649 45.86726 222.0263 43.01446 222.0263 44.10076 222.0263 45.10076 412.8213 47.35523 415.2133938 46.17170647 407.2983 45.86462 223.5738 43.01729 223.5738 44.10294 223.5738 45.10294 415.8573 47.401 418.2641307 46.23589227 410.3317 45.48322 225.1213 43.02011 225.1213 44.10511 225.1213 45.10511 418.8933 47.45174 421.3148676 46.32238369 413.365 44.65794 226.6688 43.02292 226.6688 44.10728 226.6688 45.10728 421.9293 47.4705 424.3177645 46.36852997 416.3984 44.34363 228.2163 43.02573 228.2163 44.10946 228.2163 45.10946 424.9653 47.45547 427.3206614 46.35718778 419.4318 44.31445 229.7638 43.02854 229.7638 44.11163 229.7638 45.11163 428.0013 47.40561 430.3235583 46.32742608 422.4651 44.31447 231.3113 43.03134 231.3113 44.1138 231.3113 45.1138 431.0373 47.41898 433.3264552 46.30312687 425.4985 44.22098 232.8588 43.03413 232.8588 44.11597 232.8588 45.11597 434.0733 47.47807 436.3293521 46.4049812 428.5319 44.11117 234.4063 43.03692 234.4063 44.11813 234.4063 45.11813 437.1093 47.51204 439.332249 46.44801108 431.5652 44.13247 235.9538 43.0397 235.9538 44.1203 235.9538 45.1203 440.1453 47.51203 442.3351459 45.99804096 434.5986 44.26412 237.5013 43.04248 237.5013 44.12246 237.5013 45.12246 443.1813 47.45939 445.3380428 45.39441048 437.632 44.41705 239.0488 43.04524 239.0488 44.12461 239.0488 45.12461 446.2173 47.39886 448.3409397 45.07868767 440.6653 44.58717 240.5963 43.04801 240.5963 44.12677 240.5963 45.12677 449.2533 47.4014 451.3438365 45.13792566 443.6987 44.76875 242.1438 43.05077 242.1438 44.12891 242.1438 45.12891 452.2892 47.45402 454.3467334 45.0519138 446.7321 44.98099 243.6913 43.05352 243.6913 44.13106 243.6913 45.13106 455.3252 47.47435 457.3496303 44.97731515 449.7654 45.25263 245.2388 43.05628 245.2388 44.1332 245.2388 45.1332 458.3612 47.48496 460.3525272 45.09716033 452.7988 45.57896 246.7864 43.05902 246.7864 44.13534 246.7864 45.13534 461.3972 47.48107 463.3554241 44.97508421 455.8322 45.85142 248.3339 43.06175 248.3339 44.13748 248.3339 45.13748 464.4332 47.49971 466.3583209 44.95101028 458.8655 45.67064 249.8814 43.06448 249.8814 44.13961 249.8814 45.13961 467.4692 47.4014 469.3612178 44.99048903 461.8989 45.68393 251.4289 43.06721 251.4289 44.14174 251.4289 45.14174 470.5052 47.37693 472.3641147 45.05197741 464.9323 45.69072 254.3322 43.07247 254.3322 44.14585 254.3322 45.14585 473.5627 47.39199 475.3670115 45.1466263 467.9656 45.66052 257.2356 43.07773 257.2356 44.14993 257.2356 45.14993 476.6202 47.42105 478.3699084 45.15671389 470.999 45.71426 260.1389 43.08297 260.1389 44.15399 260.1389 45.15399 479.6777 47.39363 481.3728052 45.07024706 474.0324 45.76548 263.0423 43.08822 263.0423 44.15803 263.0423 45.15803 482.7352 47.38013 484.3757021 45.19070801 477.0657 45.68135 265.9456 43.09348 265.9456 44.16206 265.9456 45.16206 485.7927 47.28637 487.378599 45.3402485 480.0991 45.5087 268.849 43.09876 268.849 44.16607 268.849 45.16607 488.8502 47.23293 490.3814958 45.25357944 483.1325 45.44559 271.7523 43.10408 271.7523 44.1701 271.7523 45.1701 491.9077 47.20999 493.3843927 45.17038535 486.1658 45.4952 274.6557 43.10945 274.6557 44.17414 274.6557 45.17414 494.9652 47.19444 496.4672123 45.22330238 489.1992 45.37174 277.559 43.11486 277.559 44.17821 277.559 45.17821 498.0227 47.17698 499.5500319 45.32042347 492.2326 45.23872 280.4624 43.12033 280.4624 44.18228 280.4624 45.18228 501.0802 47.1537 502.6328515 45.33656627 495.2659 45.19528 283.3657 43.12586 283.3657 44.18639 283.3657 45.18639 504.1377 47.168 505.7156711 45.32505599 498.2993 45.24582 286.2691 43.13145 286.2691 44.1905 286.2691 45.1905 507.1952 47.18421 508.7984907 45.42859746 501.3327 45.37067 289.1725 43.1371 289.1725 44.19462 289.1725 45.19462 510.2527 47.19836 511.8813104 45.52424193 504.366 45.37127 292.0758 43.1428 292.0758 44.19872 292.0758 45.19872 513.3102 47.14444 514.96413 45.65213053 507.3994 45.66042 293.5799 43.14589 293.5799 44.20094 293.5799 45.20094 516.3677 47.15009 518.0469496 45.75623187 510.4328 45.87096 Dry_Creek_profiles_050420
FEMA ULDC ULDC plus 1 ft Top of Embankment WS Embankment Toe LS Embankment Toe 295.084 43.14902 295.084 44.20316 295.084 45.20316 519.4252 47.17814 521.1297691 45.76755993 513.4661 46.19226 296.5881 43.15214 296.5881 44.20536 296.5881 45.20536 522.4827 47.15055 524.2125887 45.7221265 516.4995 46.19447 298.0922 43.15529 298.0922 44.20757 298.0922 45.20757 525.5402 47.13196 527.2954084 45.63451545 519.5329 45.90437 299.5964 43.15843 299.5964 44.20975 299.5964 45.20975 528.5977 47.09842 530.3782279 45.64000466 522.5662 45.71467 301.1005 43.16159 301.1005 44.21192 301.1005 45.21192 531.6552 47.10242 533.4610475 45.71986488 525.5996 45.64777 302.6046 43.16475 302.6046 44.21407 302.6046 45.21407 534.7127 47.14468 536.5438671 45.81010589 528.633 45.30076 304.1087 43.16792 304.1087 44.21622 304.1087 45.21622 537.7702 47.15483 539.6266867 45.81202201 531.6663 45.39731 305.6128 43.1711 305.6128 44.21835 305.6128 45.21835 540.8277 47.13311 542.7095062 45.86320598 534.6997 45.86245 307.1169 43.17428 307.1169 44.22048 307.1169 45.22048 543.8852 47.13085 545.7923258 45.93858557 537.7331 46.17266 308.621 43.17747 308.621 44.2226 308.621 45.2226 546.9427 47.12487 548.8751454 46.00624824 540.7664 46.20806 310.1251 43.18068 310.1251 44.22472 310.1251 45.22472 550.0002 47.10323 551.957965 46.05618679 543.7998 46.18648 311.6292 43.18389 311.6292 44.22682 311.6292 45.22682 553.0577 47.08912 555.0407845 46.05511686 546.8332 46.21556 313.1334 43.18712 313.1334 44.22893 313.1334 45.22893 556.1152 47.07804 549.8665 46.22875 314.6375 43.19035 314.6375 44.23102 314.6375 45.23102 559.1727 47.10908 552.8999 46.36196 316.1416 43.19359 316.1416 44.23311 316.1416 45.23311 562.2302 47.12084 555.9333 46.32764 317.6457 43.19683 317.6457 44.23519 317.6457 45.23519 558.9666 46.3308 319.1498 43.20007 319.1498 44.23728 319.1498 45.23728 562 46.33037 320.6539 43.20331 320.6539 44.23937 320.6539 45.23937
322.158 43.20656 322.158 44.24147 322.158 45.24147
323.6621 43.20981 323.6621 44.24361 323.6621 45.24361
325.1662 43.21308 325.1662 44.24577 325.1662 45.24577
326.6703 43.21636 326.6703 44.24798 326.6703 45.24798
328.1745 43.21967 328.1745 44.25022 328.1745 45.25022
329.6786 43.223 329.6786 44.25252 329.6786 45.25252
331.1827 43.22635 331.1827 44.25484 331.1827 45.25484
332.6868 43.22971 332.6868 44.2572 332.6868 45.2572
334.1909 43.23308 334.1909 44.25958 334.1909 45.25958
335.695 43.23646 335.695 44.26197 335.695 45.26197
337.1991 43.2398 337.1991 44.26437 337.1991 45.26437
338.7032 43.24314 338.7032 44.26675 338.7032 45.26675
340.2073 43.24641 340.2073 44.26912 340.2073 45.26912
341.7115 43.24968 341.7115 44.27148 341.7115 45.27148
343.2156 43.25286 343.2156 44.27384 343.2156 45.27384
344.7197 43.25604 344.7197 44.2762 344.7197 45.2762
346.2238 43.25915 346.2238 44.27857 346.2238 45.27857
347.7279 43.26225 347.7279 44.28098 347.7279 45.28098
349.232 43.2653 349.232 44.28341 349.232 45.28341
350.7361 43.26836 350.7361 44.28588 350.7361 45.28588
352.2402 43.27136 352.2402 44.28839 352.2402 45.28839
353.7443 43.27438 353.7443 44.29091 353.7443 45.29091
355.2484 43.27733 355.2484 44.29346 355.2484 45.29346
356.7526 43.2803 356.7526 44.29597 356.7526 45.29597
358.2567 43.28317 358.2567 44.29848 358.2567 45.29848
359.7608 43.28604 359.7608 44.30087 359.7608 45.30087
361.2649 43.28875 361.2649 44.30325 361.2649 45.30325
362.769 43.29144 362.769 44.3054 362.769 45.3054
364.2731 43.29389 364.2731 44.30751 364.2731 45.30751
365.7772 43.29631 365.7772 44.30935 365.7772 45.30935
367.2813 43.29844 367.2813 44.31113 367.2813 45.31113
368.7993 43.3004 368.7993 44.31254 368.7993 45.31254
370.3173 43.30209 370.3173 44.31391 370.3173 45.31391
371.8353 43.30374 371.8353 44.31507 371.8353 45.31507
373.3533 43.30517 373.3533 44.31619 373.3533 45.31619
374.8713 43.30656 374.8713 44.31719 374.8713 45.31719
376.3893 43.3078 376.3893 44.31816 376.3893 45.31816
377.9073 43.30902 377.9073 44.31908 377.9073 45.31908
379.4253 43.31015 379.4253 44.31998 379.4253 45.31998
380.9433 43.31126 380.9433 44.32087 380.9433 45.32087
382.4613 43.31233 382.4613 44.32175 382.4613 45.32175
383.9793 43.31338 383.9793 44.32264 383.9793 45.32264
385.4973 43.31441 385.4973 44.32352 385.4973 45.32352
387.0153 43.31543 387.0153 44.32441 387.0153 45.32441
388.5333 43.31644 388.5333 44.32529 388.5333 45.32529
390.0513 43.31744 390.0513 44.32619 390.0513 45.32619
391.5693 43.31843 391.5693 44.32708 391.5693 45.32708
393.0873 43.31942 393.0873 44.32798 393.0873 45.32798
394.6053 43.3204 394.6053 44.32888 394.6053 45.32888
396.1233 43.32138 396.1233 44.32977 396.1233 45.32977
397.6413 43.32235 397.6413 44.33065 397.6413 45.33065
399.1593 43.32332 399.1593 44.33154 399.1593 45.33154
400.6773 43.32428 400.6773 44.33243 400.6773 45.33243
402.1953 43.32524 402.1953 44.33331 402.1953 45.33331
Dry_Creek_profiles_050420
FEMA ULDC ULDC plus 1 ft Top of Embankment WS Embankment Toe LS Embankment Toe 403.7133 43.32621 403.7133 44.33419 403.7133 45.33419
405.2313 43.32717 405.2313 44.33507 405.2313 45.33507
406.7493 43.32814 406.7493 44.33596 406.7493 45.33596
408.2673 43.32911 408.2673 44.33685 408.2673 45.33685
409.7853 43.33009 409.7853 44.33775 409.7853 45.33775
411.3033 43.33108 411.3033 44.33864 411.3033 45.33864
412.8213 43.33207 412.8213 44.33954 412.8213 45.33954
414.3393 43.33308 414.3393 44.34044 414.3393 45.34044
415.8573 43.33409 415.8573 44.34134 415.8573 45.34134
417.3753 43.3351 417.3753 44.34225 417.3753 45.34225
418.8933 43.33613 418.8933 44.34316 418.8933 45.34316
420.4113 43.33717 420.4113 44.34408 420.4113 45.34408
421.9293 43.33823 421.9293 44.345 421.9293 45.345
423.4473 43.3393 423.4473 44.34593 423.4473 45.34593
424.9653 43.34038 424.9653 44.34687 424.9653 45.34687
426.4833 43.34147 426.4833 44.3478 426.4833 45.3478
428.0013 43.34258 428.0013 44.34874 428.0013 45.34874
429.5193 43.34369 429.5193 44.34967 429.5193 45.34967
431.0373 43.34481 431.0373 44.35061 431.0373 45.35061
432.5553 43.34594 432.5553 44.35154 432.5553 45.35154
434.0733 43.34707 434.0733 44.35247 434.0733 45.35247
435.5913 43.34821 435.5913 44.3534 435.5913 45.3534
437.1093 43.34935 437.1093 44.35433 437.1093 45.35433
438.6273 43.3505 438.6273 44.35526 438.6273 45.35526
440.1453 43.35166 440.1453 44.35619 440.1453 45.35619
441.6633 43.35282 441.6633 44.35711 441.6633 45.35711
443.1813 43.35399 443.1813 44.35803 443.1813 45.35803
444.6993 43.35516 444.6993 44.35895 444.6993 45.35895
446.2173 43.35634 446.2173 44.35987 446.2173 45.35987
447.7353 43.35752 447.7353 44.36078 447.7353 45.36078
449.2533 43.3587 449.2533 44.36169 449.2533 45.36169
450.7712 43.35988 450.7712 44.36261 450.7712 45.36261
452.2892 43.36107 452.2892 44.36352 452.2892 45.36352
453.8072 43.36225 453.8072 44.36442 453.8072 45.36442
455.3252 43.36344 455.3252 44.36533 455.3252 45.36533
456.8432 43.36463 456.8432 44.36624 456.8432 45.36624
458.3612 43.36583 458.3612 44.36715 458.3612 45.36715
459.8792 43.36703 459.8792 44.36806 459.8792 45.36806
461.3972 43.36823 461.3972 44.36897 461.3972 45.36897
462.9152 43.36944 462.9152 44.36989 462.9152 45.36989
464.4332 43.37065 464.4332 44.3708 464.4332 45.3708
465.9512 43.37186 465.9512 44.37172 465.9512 45.37172
467.4692 43.37307 467.4692 44.37264 467.4692 45.37264
468.9872 43.37429 468.9872 44.37356 468.9872 45.37356
470.5052 43.3755 470.5052 44.37448 470.5052 45.37448
472.034 43.3767 472.034 44.37539 472.034 45.37539
473.5627 43.3779 473.5627 44.37629 473.5627 45.37629
475.0915 43.3791 475.0915 44.3772 475.0915 45.3772
476.6202 43.3803 476.6202 44.37811 476.6202 45.37811
478.149 43.38151 478.149 44.37902 478.149 45.37902
479.6777 43.38272 479.6777 44.37994 479.6777 45.37994
481.2065 43.38393 481.2065 44.38086 481.2065 45.38086
482.7352 43.38515 482.7352 44.38178 482.7352 45.38178
484.264 43.38636 484.264 44.38271 484.264 45.38271
485.7927 43.38758 485.7927 44.38363 485.7927 45.38363
487.3215 43.3888 487.3215 44.38455 487.3215 45.38455
488.8502 43.39002 488.8502 44.38548 488.8502 45.38548
490.379 43.39124 490.379 44.38641 490.379 45.38641
491.9077 43.39246 491.9077 44.38735 491.9077 45.38735
493.4365 43.39369 493.4365 44.38829 493.4365 45.38829
494.9652 43.39491 494.9652 44.38922 494.9652 45.38922
496.494 43.39615 496.494 44.39015 496.494 45.39015
498.0227 43.39738 498.0227 44.39109 498.0227 45.39109
499.5515 43.39862 499.5515 44.39203 499.5515 45.39203
501.0802 43.39986 501.0802 44.39297 501.0802 45.39297
502.609 43.4011 502.609 44.39392 502.609 45.39392
504.1377 43.40233 504.1377 44.39487 504.1377 45.39487
505.6665 43.40356 505.6665 44.39582 505.6665 45.39582
507.1952 43.40479 507.1952 44.39677 507.1952 45.39677
508.724 43.40603 508.724 44.39772 508.724 45.39772
510.2527 43.40727 510.2527 44.39867 510.2527 45.39867
511.7815 43.40851 511.7815 44.39963 511.7815 45.39963
Dry_Creek_profiles_050420
FEMA ULDC ULDC plus 1 ft Top of Embankment WS Embankment Toe LS Embankment Toe 513.3102 43.40974 513.3102 44.40058 513.3102 45.40058
514.839 43.41098 514.839 44.40154 514.839 45.40154
516.3677 43.41222 516.3677 44.40251 516.3677 45.40251
517.8965 43.41345 517.8965 44.40347 517.8965 45.40347
519.4252 43.41469 519.4252 44.40443 519.4252 45.40443
520.954 43.41592 520.954 44.4054 520.954 45.4054
522.4827 43.41716 522.4827 44.40636 522.4827 45.40636
524.0115 43.4184 524.0115 44.40733 524.0115 45.40733
525.5402 43.41964 525.5402 44.40829 525.5402 45.40829
527.069 43.42088 527.069 44.40926 527.069 45.40926
528.5977 43.42213 528.5977 44.41022 528.5977 45.41022
530.1265 43.42337 530.1265 44.41119 530.1265 45.41119
531.6552 43.42462 531.6552 44.41215 531.6552 45.41215
533.184 43.42586 533.184 44.41312 533.184 45.41312
534.7127 43.42711 534.7127 44.41409 534.7127 45.41409
536.2415 43.42835 536.2415 44.41506 536.2415 45.41506
537.7702 43.4296 537.7702 44.41604 537.7702 45.41604
539.299 43.43085 539.299 44.41701 539.299 45.41701
540.8277 43.4321 540.8277 44.41798 540.8277 45.41798
542.3565 43.43336 542.3565 44.41896 542.3565 45.41896
543.8852 43.43461 543.8852 44.41994 543.8852 45.41994
545.414 43.43586 545.414 44.42092 545.414 45.42092
546.9427 43.43711 546.9427 44.42191 546.9427 45.42191
548.4715 43.43836 548.4715 44.42289 548.4715 45.42289
550.0002 43.43961 550.0002 44.42388 550.0002 45.42388
551.529 43.44086 551.529 44.42487 551.529 45.42487
553.0577 43.44211 553.0577 44.42586 553.0577 45.42586
554.5865 43.44337 554.5865 44.42685 554.5865 45.42685
556.1152 43.44463 556.1152 44.42784 556.1152 45.42784
557.644 43.44589 557.644 44.42883 557.644 45.42883
559.1727 43.44715 559.1727 44.42982 559.1727 45.42982
560.7015 43.44842 560.7015 44.43082 560.7015 45.43082
562.2302 43.44968 562.2302 44.43182 562.2302 45.43182
Dry_Creek_profiles_050420
36 37
38 39
40 41
42 43
44 45
46 47
48 49
50 51
52 0 100 200 300 400 500 600
Elevation (feet, NAVD)
Distance along Rio Linda Blvd Embankment from Levee Tie-in Point Rio Linda Blvd - WSE comparison
Top of Embankment
ULDC plus 1 ft
ULDC
FEMA
WS Embankment Toe
LS Embankment Toe
Additional length of Dry Creek north levee (325 ft) Limit of embankment raise

APPENDIX B
____________________________________________________________________________

LIST OF ATTACHMENTS
MBK Engineers, 2024, “Dry Creek North Levee – Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee.” Dated February 16, 2024.

Water Resources  Flood Control  Water Rights

TECHNICAL MEMORANDUM
DATE: February 16, 2024
PREPARED FOR: SAFCA
PREPARED BY: Michael Archer, P.E.

REVIEWED BY: Don Trieu, P.E.

SUBJECT: Dry Creek North Levee - Determination of the Urban Levee Design Criteria Design Water Surface Elevation, Minimum Top of Levee, and Hydraulic Top of Levee

1. Purpose
The Sacramento Area Flood Control Agency (SAFCA) is in the process of evaluating the levees within its jurisdictional boundaries for compliance with the State of California’s Urban Levee Design Criteria (ULDC) (DWR, 2012). This technical memorandum provides documentation of the determination of the hydraulic parameters listed in Table 1, which are necessary for the ULDC compliance evaluation of the Dry Creek north levee.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 1 Table 1. ULDC Hydraulic Parameters
Parameter ULDC Definition
Design Water Surface Elevation (DWSE) Median 200-year water surface elevation (WSE) Minimum Top of Levee (MTOL)
DWSE plus the higher of
• 3 feet, or
• wind setup and wave runup
Hydraulic Top of Levee (HTOL)
The lower of
• DWSE plus 3 feet, or
• Median 500-year WSE
Seismic Vulnerability Restoration Profile (SVRP)
10-year water surface elevation plus the higher of
• 3 feet, or
• wind setup and wave runup

2. Study Area
Dry Creek is a tributary to the Natomas East Main Drainage Canal (NEMDC). The NEMDC collects drainage from watersheds on the east side of the Natomas Basin, and discharges it into the Sacramento River near the mouth of the American River (Figure 1). The Dry Creek north levee extends from Rio Linda Boulevard, downstream to the NEMDC, a length of approximately 8,500 feet (Figure 2). The upstream end of the levee ties into natural high ground at Rio Linda Boulevard.

Robla Creek is another tributary to the NEMDC and is located immediately south of Dry Creek. For a distance of about 9,000 feet, starting at the NEMDC and going upstream, Dry Creek and Robla Creek have a shared floodplain. The U.S. Army Corps of Engineers (USACE) has a proposed project on Magpie Creek, a tributary to Robla Creek, authorized through the American River Common Features 2016 Project (USACE, 2022). As designed, the Magpie Creek project will prevent flood water from escaping Magpie Creek, resulting in increased conveyance to Robla Creek and downstream. For this reason, and because it is an authorized project, the Magpie Creek project is included in the ULDC analysis.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 2 Figure 1. Location Map
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 3 Figure 2. Site Map and Levee Stationing, Dry Creek North Levee

3. Hydraulic Model
A HEC-RAS 6.4.1 hydraulic model was developed for this analysis. HEC-RAS is software developed by the USACE Hydrologic Engineering Center for the purpose of performing one-dimensional (1-D) and twodimensional (2-D) hydraulic calculations for a full network of natural and constructed channels (USACE, 2023).

The hydraulic model, referred to as the Sacramento north area streams, or NAS, model is made up of both 1-D elements and 2-D flow areas. The model was developed from an existing 1-D model. Reaches with small low flow channels and wide floodways, such as Dry Creek, Robla Creek and Magpie Creek, were replaced with 2_D flow areas. A schematic of the model is shown in Figure 3. The streams within the model study area are summarized in Table 2. The downstream boundary of the model is the NEMDC at the American River north levee.

Table 2. Streams Within the Model Study Area
Stream Upstream Boundary Downstream Boundary Model
Element
Length
(miles)
Dry Creek Below Q Street NEMDC 2-D 3.5
Robla Creek Above 16th Street NEMDC 2-D 3.3
Magpie Creek Patrol Road Robla Creek 2-D 1.8
Don Julio Creek Patrol Road Magpie Creek 2-D 1.3
Arcade Creek Auburn Blvd. NEMDC 1-D 6.6
NEMDC D-15 Pump Station American R. north levee 1-D 4.3 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 4 Figure 3. North Area Stream HEC-RAS Model Schematic
A terrain model is required for 2-D modeling, as it is used to establish the geometric and hydraulic properties within 2-D flow areas. The primary terrain used for the NAS model was developed by USACE for use in their hydraulic analysis of the Magpie Creek project (USACE, 2021). The USACE terrain did not provide coverage of the entire NAS model study area, as shown in Figure 4. Terrain developed for the California Department of Water Resources (DWR) Central Valley Floodplain Evaluation and Delineation (CVFED) program (Wood Rodgers, 2014) was used to extend coverage to the entire NAS model study area, as shown in Figure 5. The vertical and horizontal accuracy and resolution of the USACE terrain is not provided in the referenced documentation. The CVFED terrain has a vertical accuracy of 0.6 feet, a horizontal accuracy of 3.5 feet, and an average point spacing of 3.28 feet.

Manning’s n roughness coefficient values within the 2-D flow areas were defined using land classification mapping from the National Land Cover Database, as shown in Figure 6. Manning’s n-values were initially assigned for the various land classifications based on recommendations in the HEC-RAS 2D User’s Manual, and refined as necessary through the calibration process, The land classifications and final associated n-values are listed in Table 3.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 5 Figure 4. USACE Terrain Coverage Figure 5. Final Terrain Coverage Figure 6. Land Classification Map
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 6 Table 3. Land Classifications and Assigned Manning’s n-values Land Classification Manning’s
n-value Land Classification Manning’s n-value
Barren Land Rock-Sand-Clay 0.035 Emergent Herbaceous Wetlands 0.06 Cultivated Crops 0.038 Evergreen Forest 0.08
Deciduous Forest 0.08 Grassland-Herbaceous 0.035
Developed, High Intensity 0.10 Open Water 0.03
Developed, Low Intensity 0.05 Pasture-Hay 0.042
Developed, Medium Intensity 0.07 Shrub-Scrub 0.08
Developed, Open Space 0.04 Woody Wetlands 0.07
The model was calibrated to the high flow event that occurred during the end of December 2005 and the beginning of January 2006 (the “2006 flood”). Calibration results are provided and summarized in Appendix A.

4. Hydrology
Central Valley Hydrology Study (CVHS) procedures and hydrologic data were used in this analysis. The CVHS was commissioned by the California Department of Water Resources (DWR) and prepared by the USACE (USACE, 2015). For the Sacramento River and San Joaquin River basins, the CVHS defines a procedure in which a scaled flood event with a pattern based on a historical flood event is selected to represent the flood of a specific frequency at a specific location, or centering. The CVHS also developed hydrologic data for several smaller ungaged watersheds, including the Natomas-Area Stream Group, which includes Dry Creek and Arcade Creek (USACE, 2013). The hydrologic data for the Natomas-Area Stream Group was developed for discrete N-year flood frequencies with centerings defined by contributing area (C) parameters. The Natomas-Area Stream Group hydrologic data was updated by USACE in 2019. There are four CVHS defined flood centerings that influence the NAS model study area:
• Natomas-Area Stream Group: Dry Creek
• Natomas-Area Stream Group: Robla and Magpie Creeks
• Natomas-Area Stream Group: Arcade Creek
• Sacramento River Basin: American River at Fair Oaks and Latitude of Sacramento The ULDC requires the computation water surface elevations for the 10-year, 200-year, and 500-year flood events. The Sacramento River Basin scaled flood events and Natomas-Area Stream Group C parameters for flood frequencies and flood centerings are summarized in Table 4. The final computed maximum WSE is the composite maximum of the maximum WSE’s computed for the four flood centerings.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 7 Table 4. CVHS Flood Events
Flood Centering Recurrence
Interval
Watershed
North Area Streams Sacramento River
Dry Creek 10-year 10yr_C=99.5 1 1995-60% 2, 3
200-year 200yr_C=99.5 1 1995-105% 2
500-year 500yr_C=99.5 1 1995-120% 2
Robla-Magpie Creeks 10-year 10yr_C=RIOLINDA_MAGPIE 1 1995-60% 2, 3 200-year 200yr_C=RIOLINDA_MAGPIE 1 1995-105% 2
500-year 500yr_C=RIOLINDA_MAGPIE 1 1995-120% 2
Arcade Creek 10-year 10yr_C=ARC 1 1995-60% 2, 3
200-year 200yr_C=ARC 1 1995-105% 2
500-year 500yr_C=ARC 1 1995-120% 2
Fair Oaks-latitude of
Sacramento
10-year 1986-55% 2 1986-55% with 40% on
American R. 1, 2
200-year 1986-110% 2 1986-110% with 125% on
American R. 2
500-year 1986-100% 4 1986-100% with 176% on
American R. 4
1 Data ID from USACE 2019 updated hydrologic data set.
2 Event selection by USACE (USACE, 2019). 1995-60% means flood pattern based on 1995 flood with a 60% scale factor. 3 CVHS hydrologic data does not include the 1995-60% flood event. The closest available flood event data, 1995-75%, was used in the analysis. The 1995-75% data approximately represents the 20-year flood event. 4 Event selection by USACE (USACE, 2020)

The County of Sacramento’s D-15 pump station, at the upstream end of the modeled NEMDC reach, is an inline pump station with gates (County of Sacramento, 2007). During large flood events, the gates close automatically when the water surface elevation at the pump station reaches a pre-defined trigger elevation, preventing backwater due to high flows in Dry and Robla creeks from affecting flood stages north of the pump station. After the gates close, the pumps will automatically turn on to ensure positive flow from north to south. The station has three 333 cfs capacity pumps. The operation criteria specifies a firm capacity based on use of two of the three pumps, keeping one for a backup. However, all three pumps may be operated concurrently if required. For the ULDC analysis, the conservative assumption of a three-pump operation, with a total flow of 999 cfs, is used.

As noted earlier, the downstream boundary of the NAS model is located on the NEMDC at the American River north levee. The analysis used a stage hydrograph downstream boundary condition that was determined using a Sacramento River basin systemwide hydraulic model (MBK Engineers, 2019) to simulate the appropriate Sacramento River CVHS flood events.

5. Urban Levee Design Criteria (ULDC)
Section 7.1 of the ULDC allows for two options for the determination of the DWSE. The first option is the Federal Emergency Management Agency (FEMA) Approach, in which the DWSE is computed deterministically with a hydraulic model. The second option is the U.S. Army Corps of Engineers Approach, which incorporates uncertainty into the determination of the DWSE. The approach selected for this analysis was the FEMA Approach, due to its application and results being more straightforward and economical.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 8 The ULDC defines the DWSE as the “200-year stage or water level used to design a levee or floodwall”.

Section 7.1.1 of the ULDC specifies that the hydraulic modeling used to determine the DWSE must consider the following:
• Upstream, downstream, and nearby levees and floodwalls protecting urban areas are assumed to be raised to the median 200-year water surface elevation plus 3 feet and not allowed to breach, even if overtopped. Overtopping flows are assumed to leave the channel and remain in the 200- year floodplain.
• All project levees and floodwalls are to be modeled to incorporate a minimum crown elevation equal to the authorized (usually the 1955/1957) USACE design profiles – this affects nonurbanized areas for the most part – all such levees and floodwalls are to be allowed to overtop, act as weirs, and not breach for floods up to and including the median 500-year flood.

Overtopping flows are assumed to leave the channel and remain in the 200-year floodplain. • Non-project levees and floodwalls in non-urbanized areas in the region, to the extent they may affect the DWSE, are to be modeled at their existing or authorized height, whichever is higher, and to act as weirs without breaching if overtopped.
• Debris loading on bridges must be considered. Bridges with less than 3 feet of clearance above the DWSE may experience extraordinary debris loading that must be evaluated in addition to typical pier/bent debris loading. The evaluation should include historic and potential debris transport in the stream, an analysis of loading on the bridge, and analysis of backwater impacts on the DWSE in the vicinity of the bridge.

Section 7.1.3 of the ULDC requires adjustments to the DWSE for the effects of superelevation, when applicable. Superelevation is a tilting of the water surface, which may occur as water flows through a bend in the channel. Computational methods for determining superelevation adjustments are in the USACE Engineering Manual 1110-2-1601.

Section 7.1.3 of the ULDC also states that the “…the civil engineer should consider increasing the DWSE to account for the potential increases in water surface associated with climate change, updated hydrology, updated hydraulic models, and sea level rise”. This statement implies that adjustment for sea level rise is optional; however, Section 7.19 of the ULDC states, “the effects of sea level rise are to be estimated and addressed for the duration during which a Finding that the urban level of flood protection exists may be valid”. Based on the second statement, sea level rise adjustment appears to be mandatory.

Additionally, Section 7.1.3 of the ULDC states:
“[T]he civil engineer also needs to address two other situations: (1) whether upstream levee or floodwall breaches could produce overland flows that would reach the area protected by the levee system or increase the water surface elevation along the levee system, and (2) whether flooding in a nearby leveed area could fill that area and breach a nearby levee or floodwall, returning flow to the stream and increasing the DWSE for a portion of the levee system".

Neither of these conditions applies to the Study Area, and therefore they were not evaluated.

The following sections address the requirements in the ULDC and discuss the application of each requirement for the Dry Creek north levee:

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 9

5.1 Levees
As per the ULDC, all urban levees were assumed to have a minimum top elevation of the median 200-year water surface elevation plus 3 feet. All non-urban State-Federal Project levees were assumed to have a minimum crown elevation equal to the authorized USACE design profiles.

5.2 Debris Loading
The ULDC specifies that debris loading on bridges must be considered, and that “bridges with less than 3 feet of clearance above the DWSE may experience extraordinary debris loading that must be evaluated in addition to typical pier/bent debris loading”.

Bridge pier debris are applied in accordance with guidelines provided in a July 2014 letter, sent by USACE to the California Central Valley Flood Protection Board to clarify the level of screening and analysis that should be included on encroachment permit applications that are sent to the USACE for review. A copy of the letter is provided in Appendix C. Included in the letter was guidance for modeling debris build-up.

Based on this guidance, under the ULDC “typical” debris loading condition, the hydraulic analysis included floating debris with a width equal to double the pier width, and a depth of 2 feet below the water surface.

Under the ULDC “extraordinary” debris loading condition, floating debris with a depth of 2 feet below the water surface were modeled for the full width with the “extraordinary” condition.

Debris were not applied to bridges in the model upstream of the levee reaches, as debris on these bridges would have no effect on the water surface elevation in the levee reaches.

A summary of the bridge pier debris conditions included in the hydraulic analysis is provided in Table 5.

5.3 Superelevation
Superelevation is a tilting of the water surface that occurs on the outside of a river bend. The ULDC notes that, “on the outside of a bend, the superelevation needs to be added to the DWSE”. The superelevation adjustment, per USACE Engineer Manual 1110-2-1416, River Hydraulics, is specific to 1-D hydraulic modeling. The water surface elevation at the Dry Creek north levee is computed with 2-D hydraulic computations, therefore the superelevation adjustment is not applicable.

5.4 Climate Change
The effects of climate change on extreme precipitation events in the Central Valley are being studied, but there is no indication of what the outcome of that work will be. Therefore, the hydrology used in this analysis has not been adjusted for the effects of climate change.

5.5 Updated Hydrology
This analysis makes use of the most recent accepted hydrologic data for the Study Area, which was developed as part of the Central Valley Hydrology Study, as noted in Section 4 of this report.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 10 Table 5. Bridge Pier Debris Loading
River River
Station 1 Bridge
Debris Loading
Condition (t=typical;
E=extraordinary)
200-yr 500-yr
Dry Creek West
Branch 1,340 ft Rio Linda Blvd. E E
Dry Creek East Branch 3,910 ft SNRR Bike Trail t t
640 ft Rio Linda Blvd. E E
Dry Creek (lower) 6,120 ft private bridge E E
110 ft UPRR (near mouth) E E
Robla Creek 9,680 ft SNRR Bike Trail E E
8,290 ft Rio Linda Blvd. E E
90 ft UPRR (near mouth) E E
Magpie Creek 6,120 ft Raley Blvd. E E
4,010 ft Vinci Ave. E E
1,130 ft Dry Creek Rd. E E
Arcade Creek 1.344 mi Rio Linda Blvd. E E

1.26 mi SNRR Bike Trail E E

0.722 mi Norwood Avenue E E

0.045 mi UPRR (near mouth) E E
NEMDC 6.139 mi Main Avenue t t

5.168 mi Interstate 80 t t

4.347 mi Silver Eagle Road t t

3.03 mi West El Camino Avenue mix E

2.653 mi Arden-Garden
Connector t t
1 River station in miles for 1-D reaches and in feet for 2-D flow area.

5.6 Updated Hydraulic Model
The hydraulic model used for this analysis was developed from the most current available data. Due to the calibration process, an updated hydraulic model would not be expected to have a substantial effect on the computed results unless significant physical changes have occurred in the modeled system. Since no significant physical changes have occurred since the data used for the model development was collected, no adjustment for updated hydraulic model has been included.

5.7 Sea Level Rise
The ULDC notes that, “the effects of sea level rise are to be estimated and addressed for the duration during which a Finding that the urban level of flood protection exists may be valid”. The duration of finding proposed for the subject project is 20 years.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 11 The analysis assumed a sea level rise of 3.68 feet at San Francisco. This is the 50-year sea level rise projection, determined by the California Department of Water Resources (DWR) for the 2022 update of the Central Valley Flood Protection Plan (CVFPP) (DWR, 2022). Being that the duration of the Urban Level of Protection finding is 20 years, the use of a 50-year projection is a conservative assumption. The effects of this sea level rise were applied at the downstream boundaries of the Sacramento River systemwide hydraulic model simulations, which were used to determine the downstream boundary conditions for the NAS model.

6. Computed ULDC Hydraulic Parameters
The following sections present the computed ULDC hydraulic parameters that were described in Section 1 of this technical memorandum:
• Design Water Surface Elevation (DWSE)
• Minimum Top of Levee (MTOL)
• Hydraulic Top of Levee (HTOL)
• Seismic Vulnerability Restoration Profile

6.1 Design Water Surface Elevation (DWSE)
The ULDC defines the DWSE as “[the] median 200-year water surface elevation”, with adjustments for the following factors:
• Bridge pier debris loading
• Superelevation
• Sea level rise
Debris loading and sea level rise are accounted for in the hydraulic model simulations, as described in Sections 5.2 and 5.7. As noted in Section 5.3, the superelevation adjustment is not applicable to the hydraulic computations at the Dry Creek north levee.

A profile plot of the computed DWSE for the Dry Creek north levee is provided in Figure 7. The levee crest profile is included on the profile plot. A tabulation of the DWSE is provided in Appendix C.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 12 Figure 7. ULDC DWSE Profile, Dry Creek North Levee

6.2 Minimum Top of Levee (MTOL)
The ULDC defines the MTOL as the higher of the DWSE plus 3 feet, or the DWSE plus the computed wind setup and wave runup. Wind setup and wave runup for the Dry Creek north levee has been computed by Mead & Hunt (Mead & Hunt, 2023). The maximum computed wind setup and wave runup is 2.5 feet.

Since this is less than 3 feet, the MTOL for the Dry Creek north levee is the DWSE plus 3 feet. A profile plot of the MTOL is provided in Figure 8. A tabulation of the MTOL is provided in Appendix C.

A detailed review of the results shows that the MTOL exceeds the top of levee by about 0.1 feet near station 7081+00, as shown in Figure 9. An exception could be made for this MTOL non-compliance for several reasons:
• The MTOL deficiency is very small, 0.1 feet at its maximum. • The length is the deficiency is short, less than 20 feet. • The DWSE barely exceeds the levee waterside toe elevation, as can be seen in the cross section plot provided in Figure 10.
• The levee is short at the deficiency location, just over 3 feet tall, and is topped by a paved road (4th Street).

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 13 Figure 8. ULDC MTOL Profile, Dry Creek North Levee
Figure 9. Detailed Profile at MTOL Non-compliance Location SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 14 Figure 10. Cross section at MTOL Non-compliance Location

6.3. Hydraulic Top of Levee (HTOL)
The ULDC defines the HTOL as the lower of the DWSE plus 3 feet, or the median 500-year WSE. A profile plot of the HTOL is provided in Figure 11. For reference, the DWSE plus 3 feet and 500-year WSE profiles are also shown. A tabulation of the HTOL is provided in Appendix C.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 15 Figure 11. ULDC HTOL Profile, Dry Creek North Levee

6.4 Seismic Vulnerability Restoration Profile (SVRP)
The ULDC specifies that if there is the potential for levee damage due to a seismic event, a plan needs to be in place to “restore grade and dimensions for at least 10-year WSE plus 3 feet of freeboard or higher for wind setup and wave runup within 8 weeks”. Kleinfelder evaluated the seismic vulnerability of the Dry Creek north levee (Kleinfelder, 2018), and determined that it met the DWR Urban Levee Evaluation (ULE) criteria for low seismic vulnerability, making the need for a seismic vulnerability restoration profile unnecessary.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page 16 References
County of Sacramento. (2007). D-15 NEMDC Drainage Pump Station Summary of Operations and Procedures Manual. May 2007.

DWR. (2012). Urban Levee Design Criteria. May 2012.

DWR. (2022). 2022 CVFPP Update - Technical Analyses Summary Report, Public Draft. May 2022.

Kleinfelder. (2018). Geotechnical Evaluation Summary of Seismic Vulnerability; Applicable to ULDC Section 7.7 – Seismic Vulnerability; Dry Creek North Levee; Sacramento, California. February 7, 2018.

MBK Engineers. (2019). Technical Memorandum - Sacramento Weir Widening Project, Initial Hydraulic Impact Analysis. October 31, 2019.

Mead & Hunt. (2023). Dry Creek North Levee Wind-Wave Analysis. October 30, 2023.

USACE. (2013). Central Valley Hydrology Study: Natomas-area Stream Group - Pleasant Grove Creek, Dry Creek, and Arcade Creek Watersheds Hydrologic Analysis. March 26, 2013.

USACE. (2015). Central Valley Hydrology Study. November 29, 2015.

USACE. (2019). Memorandum for Record, Subject: CVHS Hydrograph Package for HEC-RAS Model Inputs. February 20, 2019.

USACE. (2020). Hydrology Technical Memorandum for Developing WRDA 2016 Water Surface Profiles.

April 10, 2020.

USACE. (2021). Hydraulic Model Summary Magpie Creek Canal For American River Common Features Project. USACE - Vicksburg District. April 2021.

USACE. (2022). Engineering Documentation Report, American River Common Features 2016, American River North Basin, Reach I, Modifications Through March 2022, Preconstruction Engineering and Design Phase. March 29, 2022.

USACE. (2023). HEC-RAS User's Manual. Retrieved from
https://www.hec.usace.army.mil/confluence/rasdocs/rasum/6.4 Wood Rodgers. (2014). Central Valley Floodplain Evaluation and Delineation, Lower Sacramento River Technical Memorandum. January 17, 2014.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL

APPENDIX A
Hydraulic Model Calibration
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-1 Calibration flood event: December 2005-January 2006
The stream gages listed in Table A-1 provided the available observed data used for calibration of the Dry Creek and Robla Creek watershed area. All the gages are part of the Sacramento County ALERT system (https://www.sacflood.org/). The gage data was provided by Sacramento County. The gage locations are shown in Figure A-1.

Table A-1. Stream Gages with Observed Data Available for Calibration Gage Agency Sensor ID
Dry Creek West Branch at SNRR Bike Trail Sacramento County ALERT 2230 Dry Creek West Branch at Elkhorn Blvd. Sacramento County ALERT 1661 Dry Creek Bypass at Elkhorn Blvd. Sacramento County ALERT 1662 Dry Creek East Branch at Elkhorn Blvd. Sacramento County ALERT 2782 Robla Creek at SNRR Bike Trail Sacramento County ALERT 2753 D15/NEMDC Downstream Sacramento County ALERT 2772
Figure A-1. Stream Gage Location Map
A comparison of the observed and computed peak stages at the gage locations is provided in Table A-2.

Profile plots of the computed maximum water surface elevations with available observed gage peaks are provided in Figures A-2 through A-6.

SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-2 Table A-2. Calibration Results, Comparison of Observed and Computed Peak Stages Gage Maximum Stage (feet NAVD88) Difference
Observed Computed (feet)
Dry Creek West Branch at SNRR Bike Trail 47.62 48.06 +0.44 Dry Creek West Branch at Elkhorn Blvd. 46.06 46.17 +0.11 Dry Creek Bypass at Elkhorn Blvd. 46.95 46.58 -0.37
Dry Creek East Branch at Elkhorn Blvd. 46.88 49.33 +2.45 a Robla Creek at SNRR Bike Trail 40.59 40.78 +0.19
D15/NEMDC Downstream 36.44 36.69 +0.25
a The Sacramento County ALERT website for this gage notes that “when the east branch reaches 49.9’ +/- the stage at the west branch is approximately 46.5’ +/-“. The computed peak stage difference for these locations of 3.2’ is similar to the reported difference of 3.6’. Therefore, it can be concluded that the reported peak stage of 46.88’ at the Dry Creek East Branch at Elkhorn Blvd gage is suspect.

Figure A-2. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek West Branch SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-3 Figure A-3. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek East Branch Figure A-4. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek (lower) SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page A-4 Figure A-5. Calibration Analysis Maximum Water Surface Elevation Profile, Dry Creek Bypass Channel Figure A-6. Calibration Analysis Maximum Water Surface Elevation Profile, Robla Creek SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Appendix B
USACE Letter with Debris Loading Guidance
SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-1 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-2 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-3 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-4 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-5 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-6 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-7 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-8 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page B-9 SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL

APPENDIX C
Tabulation of ULDC Hydraulic Parameters for the Dry Creel North Levee SAFCA February 16, 2024
Dry Creek North Levee - Determination of the UDLC DWSE, MTOL, and HTOL Page C-1 Table C-1. Design Water Surface Elevation (DWSE) and Minimum Top of Levee (MTOL) Levee
Station
(feet)
DWSE
(feet)
MTOL 1
(feet)
HTOL 2
(feet)
Levee
Station
(feet)
DWSE
(feet)
MTOL 1
(feet)
HTOL 2
(feet)
7000+00 41.40 44.40 43.00 7045+00 41.44 44.44 43.03
7001+00 41.40 44.40 43.00 7046+00 41.45 44.45 43.04
7002+00 41.40 44.40 43.00 7047+00 41.45 44.45 43.04
7003+00 41.40 44.40 43.00 7048+00 41.46 44.46 43.04
7004+00 41.40 44.40 43.00 7049+00 41.46 44.46 43.05
7005+00 41.40 44.40 43.00 7050+00 41.46 44.46 43.05
7006+00 41.40 44.40 43.00 7051+00 41.46 44.46 43.05
7007+00 41.40 44.40 43.00 7052+00 41.47 44.47 43.06
7008+00 41.40 44.40 43.00 7053+00 41.48 44.48 43.06
7009+00 41.40 44.40 43.00 7054+00 41.49 44.49 43.07
7010+00 41.40 44.40 43.00 7055+00 41.51 44.51 43.08
7011+00 41.40 44.40 43.00 7056+00 41.51 44.51 43.09
7012+00 41.40 44.40 43.00 7057+00 41.52 44.52 43.09
7013+00 41.40 44.40 43.00 7058+00 41.52 44.52 43.10
7014+00 41.40 44.40 43.00 7059+00 41.53 44.53 43.10
7015+00 41.40 44.40 43.00 7060+00 41.55 44.55 43.11
7016+00 41.40 44.40 43.00 7061+00 41.56 44.56 43.12
7017+00 41.40 44.40 43.00 7062+00 41.58 44.58 43.14
7018+00 41.40 44.40 43.00 7063+00 41.62 44.62 43.17
7019+00 41.40 44.40 43.00 7064+00 41.69 44.69 43.21
7020+00 41.40 44.40 43.00 7065+00 41.76 44.76 43.24
7021+00 41.40 44.40 43.00 7066+00 41.84 44.84 43.29
7022+00 41.40 44.40 43.00 7067+00 41.94 44.94 43.34
7023+00 41.40 44.40 43.00 7068+00 42.00 45.00 43.38
7024+00 41.40 44.40 43.00 7069+00 42.09 45.09 43.44
7025+00 41.40 44.40 43.00 7070+00 42.14 45.14 43.48
7026+00 41.40 44.40 43.00 7071+00 42.15 45.15 43.49
7027+00 41.40 44.40 43.00 7072+00 42.17 45.17 43.51
7028+00 41.40 44.40 43.00 7073+00 42.19 45.19 43.52
7029+00 41.40 44.40 43.00 7074+00 42.23 45.23 43.55
7030+00 41.40 44.40 43.00 7075+00 42.29 45.29 43.58
7031+00 41.40 44.40 43.00 7076+00 42.35 45.35 43.62
7032+00 41.40 44.40 43.00 7077+00 42.79 45.79 43.72
7033+00 41.40 44.40 43.00 7078+00 43.03 46.03 43.82
7034+00 41.40 44.40 43.00 7079+00 43.20 46.20 43.91
7035+00 41.40 44.40 43.00 7080+00 43.47 46.47 44.06
7036+00 41.41 44.41 43.01 7081+00 43.72 46.72 44.24
7037+00 41.41 44.41 43.01 7082+00 43.97 46.97 44.46
7038+00 41.42 44.42 43.02 7083+00 43.97 46.97 44.46
7039+00 41.43 44.43 43.02 7084+00 44.00 47.00 44.49
7040+00 41.43 44.43 43.02 7085+00 44.18 47.18 44.64
7041+00 41.43 44.43 43.02 7086+00 44.18 47.18 44.65
7042+00 41.43 44.43 43.03 7087+00 44.19 47.19 44.65
7043+00 41.44 44.44 43.03 7088+00 44.19 47.19 44.66
7044+00 41.44 44.44 43.03 7089+00 44.19 47.19 44.66
1 MTOL = DWSE plus higher of: 1) 3 feet, or 2) wind setup and wave runup 2 HTOL = lower of: 1) the 500-year WSE, or 2) DWSE + 3 feet

APPENDIX C
____________________________________________________________________________

LIST OF ATTACHMENTS
2023 MBK Levee Geometry Check Figures

APPENDIX D
____________________________________________________________________________

LIST OF ATTACHMENTS
2023 Psomas Top of Levee and Toe Survey Figures

47.2 47.3 47.1 47.1 47.0 47.1 47.1 47.1 47.2 47.1 47.1 47.0 47.1 47.1 47.0 47.0 47.1 47.1 46.9 47.0 47.0 47.0 47.0 46.9 46.9 46.9 46.8 46.9 46.9 46.8 46.8 46.946.8 47.0 47.1 47.4 47.3 46.7 45.8 4th St RIO LINDA BLVD.

CITY OF SACRAMENTO
COUNTY OF SACRAMENTO W. ASCOT AVE ASCOT AVE SHEET 1 SHEET 2 SHEET 3 40.0

47.3 47.5 47.3 47.3 47.3 47.1 47.5 47.4 47.1 47.2 47.2 47.4 47.4 47.6 47.0 47.0 47.2 47.3 47.1 47.1 47.0 47.0 47.1 47.1 47.0 46.8 47.2 47.0 46.9 47.1 47.2 47.1 47.1 47.1 47.2 47.3 47.1 W. 2nd St
4th St
2nd St ASCOT AVE W. ASCOT AVE COUNTY OF SACRAMENTO CITY OF SACRAMENTO 4th St RIO LINDA BLVD.

CITY OF SACRAMENTO
COUNTY OF SACRAMENTO W. ASCOT AVE ASCOT AVE SHEET 1 SHEET 2 SHEET 3 40.0

47.8 47.7 47.9 47.1 46.5 46.8 47.3 47.5 47.9 47.1 47.0 47.2 47.6 47.4 47.5 47.3 4th St 4th ST. RIO LINDA BLVD.

MARYSVILLE BLVD. RIO LINDA BLVD.

E ST.
4th St RIO LINDA BLVD.

CITY OF SACRAMENTO
COUNTY OF SACRAMENTO W. ASCOT AVE ASCOT AVE SHEET 1 SHEET 2 SHEET 3 40.0
11' 13' 87' 85' 86' 77' 80' 16' 48' 16' 19' 57' 15'15' ASCOT AVE W. ASCOT AVE 4th St RIO LINDA BLVD.

CITY OF SACRAMENTO
COUNTY OF SACRAMENTO SHEET 1 SHEET 2
SHEET 3
19' 57' 50' 14' 13' 40' 14' 38' 10' 37' 10' 13' 42' 72' 47' 30' 33' 60' R/W W. 2nd St
2nd St

COUNTY OF SACRAMENTO
CITY OF SACRAMENTO W. ASCOT AVE ASCOT AVE
4th St ASCOT AVE W. ASCOT AVE
4th St RIO LINDA BLVD.

CITY OF SACRAMENTO
COUNTY OF SACRAMENTO SHEET 1 SHEET 2
SHEET 3
33'
8'
7'
48'
30'
60' R/W
MARYSVILLE BLVD. RIO LINDA BLVD.

E ST. 4th ST. RIO LINDA BLVD. ASCOT AVE W. ASCOT AVE
4th St RIO LINDA BLVD.

CITY OF SACRAMENTO
COUNTY OF SACRAMENTO SHEET 1 SHEET 2
SHEET 3

APPENDIX E
____________________________________________________________________________

LIST OF ATTACHMENTS
“Seismic Performance Summary Report North Area Streams Levee Areas, ULDC & FEMA Levee Certification Project, Sacramento Area Flood Control Agency Levee Systems, Sacramento County, California.” Dated February 12, 2024.
24001006.001A/SAC24R164096 Page i of vi February 12, 2024 © 2024 Kleinfelder

SEISMIC PERFORMANCE SUMMARY REPORT

NORTH AREA STREAMS LEVEE AREAS

ULDC & FEMA LEVEE CERTIFICATION PROJECT

SACRAMENTO AREA FLOOD CONTROL AGENCY LEVEE SYSTEMS

SACRAMENTO COUNTY, CALIFORNIA
FEBRUARY 12, 2024
Copyright 2024 Kleinfelder
All Rights Reserved
24001006.001A/SAC24R164096 Page ii of vi February 12, 2024 © 2024 Kleinfelder
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 February 12, 2024
File No.: 24001006.001A
Mr. Pete Ghelfi, PE
Director of Engineering
Sacramento Area Flood Control Agency
1325 J Street, Suite 1700
Sacramento, CA 95814
Subject: Seismic Performance Summary Report
North Area Streams Levee Areas
ULDC & FEMA Levee Certification Project
Sacramento Area Flood Control Agency Levee Systems
Sacramento County, California
Kleinfelder Project # 24001006.001A
Dear Mr. Ghelfi:

Kleinfelder has been tasked by the Sacramento Area Flood Control Agency (SAFCA) with evaluating the seismic vulnerability of the Sacramento area levees located in Sacramento and Sutter Counties, California in support of the Urban Levee Design Criteria (ULDC) (DWR, 2012) level certification. For the evaluation, the Sacramento area levees have been divided into three areas - Natomas Basin, American River/South Sacramento Basin, and North Area Streams (NAS). A separate Seismic Performance Summary Report (SPSR) will be prepared for each of the three areas.

The purpose of this SPSR is to document Kleinfelder’s findings, present evaluation results, and present anticipated seismic segment performance for the NAS area levees. This document provides the analysis to support the development of a forthcoming Post-Earthquake Response Plan (PERP).

NAS area includes Dry Creek North (DCNL) and South Levees (DCSL), Arcade Creek North (ACNL) and Arcade Creek South Levees (ACSL), Natomas East Main Drainage Canal East Levee (NEMDCEL), and American River North Levee (ARNL) located within Sacramento County California as shown on Figure 1-

1. 24001006.001A/SAC24R164096 Page iii of vi February 12, 2024 © 2024 Kleinfelder
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 This report has been prepared consistent with the requirements of the approved scope of work for the subject project outlined in Kleinfelder’s proposal dated May 5, 2023.

Sincerely,
KLEINFELDER, INC.

Meredith Beswick PE, PG Zia Zafir PE, GE
Senior Geologist Sr. Principal Geotechnical Engineer
Reviewed By:

Timothy A. Williams, PE, GE
Sr. Principal Geotechnical Engineer
CC: Mr. Pro Mitra, PE/MBK Engineers ([email protected]) Ms. Becky Money, PE/MBK Engineers ([email protected]) 24001006.001A/SAC24R164096 Page iv of vi February 12, 2024 © 2024 Kleinfelder

TABLE OF CONTENTS

SECTION PAGE
1 INTRODUCTION .........................................................................................................................1

1.1 PURPOSE AND SCOPE ......................................................................................................... 1

1.2 BACKGROUND..................................................................................................................... 1

1.3 REFERENCED REPORTS........................................................................................................ 2

1.4 SEISMIC VULNERABILITY EVALUATION METHODOLOGY.................................................... 2

1.4.1 Preliminary Work ................................................................................................... 3

1.4.2 Phase 1: Screening Review of Existing Analysis..................................................... 3

1.4.3 Phase 2: Targeted Evaluation ................................................................................ 4

1.4.4 Seismic Vulnerability.............................................................................................. 4 2 GEOLOGY AND GEOMORPHOLOGY.............................................................................................8

2.1 REGIONAL GEOLOGIC SETTING........................................................................................... 8

2.2 LOCAL GEOLOGY ................................................................................................................. 9

2.2.1 Surficial Geology .................................................................................................... 9

2.2.2 Generalized Near Surface Stratigraphy ............................................................... 11

2.3 SEISMOTECTONIC SETTING............................................................................................... 12 3 GROUND MOTION HAZARD ANALYSIS ......................................................................................14

3.1 SEISMIC HAZARD ANALYSIS .............................................................................................. 14

3.1.1 Seismic Analysis Results....................................................................................... 15 4 PREVIOUS EVALUATION...........................................................................................................16

4.1 SUMMARY......................................................................................................................... 16

4.1.1 General................................................................................................................. 16

4.2 SEISMIC ANALYSIS WATER SURFACE ELEVATIONS ........................................................... 17 5 CURRENT EVALUATION ............................................................................................................18

5.1 SEISMIC EVALUATION SEGMENT SELECTION ................................................................... 18

5.1.1 Liquefaction Analysis of ULDC Segments............................................................. 18

5.2 VULNERABILITY CLASSIFICATIONS FOR TARGETED SEGMENTS........................................ 20

5.2.1 Segment AR-12 .................................................................................................... 20

5.2.2 Segment AR-14 .................................................................................................... 21

5.2.3 Segment NMDE-3 ................................................................................................ 23 6 SEISMIC PERFORMANCE...........................................................................................................24

6.1 SUMMARY......................................................................................................................... 24 7 LIMITATIONS ...........................................................................................................................25 8 REFERENCES ............................................................................................................................26 24001006.001A/SAC24R164096 Page v of vi February 12, 2024 © 2024 Kleinfelder
TABLES

3.1 Seismic Hazard Analysis Site Parameters

3.2 Probabilistic Peak Horizontal Acceleration and Controlling Earthquake Magnitude

4.1 Phase 1 - Seismic Vulnerability Results Screening

5.1.1 Liquefaction Layer Changes for Targeted Segments

5.1.2 Liquefaction Factor of Safety Changes for Targeted Segments

5.2.1 2015 URS Post-Seismic Stability Analysis Factors of Safety for Targeted Segments

5.2.2 Material Properties for Segment AR-14 Post-Seismic Stability Analysis

5.2.3 Segment AR-14 Post-Seismic Slope Stability Factors of Safety

5.2.4 2015 URS Post-Seismic Stability Analysis Factors of Safety for Segment NMDE-2

6.1 Seismic Vulnerability Classifications for North Area Streams Levees

FIGURES
1-1 Site Map
1-2 Table 6-1 from DWR Guidance Document, Section 6.4
1-3 Flow Chart
2-1 Regional Geology
2-2 North Area Streams Levees Geologic Map
2-3 American River North Levee Geologic Map

APPENDIX
A Seismic Technical Approach Memo
B Ground Motion Parameter Selection Memo
C Section 6, Seismic Analysis, Guidance Document for Geotechnical Analyses, Urban Levee Evaluations Project
D Updated SPT-Based Liquefaction Calculations for Targeted Segments E Post-Seismic Slope Stability Analysis for Segment AR-14 24001006.001A/SAC24R164096 Page vi of vi February 12, 2024 © 2024 Kleinfelder

REPORT ACRONYMS
______________________________________________________________________________________________ 200-year 200-year median (i.e., flood recurrence period) ACNL Arcade Creek North Levee
ACSL Arcade Creek South Levee
ARCF American River Common Features
ARNL American River North Levee
DCNL Dry Creek North Levee
DCSL Dry Creek South Levee
DRMS Delta Risk Management Strategy
DWR California Department of Water Resources
FEMA Federal Emergency Management Agency
FOS Factor of Safety
FWLA Fugro William Lettis & Associates, Inc.

GER Geotechnical Evaluation Report
GMHA Ground Motion Hazard Analysis
KLF Kleinfelder
km Kilometer
Mw Earthquake Magnitude
NASL North Area Streams Levees
NEMDC Natomas East Main Drainage Canal
NEMDCEL Natomas East Main Drainage Canal – East Levee
PHA Peak Horizontal Acceleration
SAFCA Sacramento Area Flood Control Agency
SETAM Seismic Evaluation Technical Analysis Memorandum
SNGV Sierra Nevada-Great Valley block
SPSR Seismic Performance Summary Report
SPT Standard Penetration Test
ULDC Urban Levee Design Criteria
ULE Urban Levee Evaluation
URS URS Corporation
USACE United States Army Corps of Engineers
WUS Western United States
24001006.001A/SAC24R164096 Page 1 of 29 February 12, 2024 © 2024 Kleinfelder
1 INTRODUCTION
___________________________________________________________________________________

1.1 PURPOSE AND SCOPE
Kleinfelder has been tasked by the Sacramento Area Flood Control Agency (SAFCA) with evaluating the seismic vulnerability of the Sacramento area levees located in Sacramento and Sutter Counties, California in support of the Urban Levee Design Criteria (ULDC) (DWR, 2012) level certification. For the evaluation, the Sacramento area levees have been divided into three areas - Natomas Basin, American River/South Sacramento Basin, and North Area Streams (NAS). A separate Seismic Performance Summary Report (SPSR) will be prepared for each of the three areas.

The purpose of this SPSR is to document Kleinfelder’s findings, present evaluation results, and present anticipated seismic segment performance for the NAS area levees. This document provides the analysis to support the development of a forthcoming Post-Earthquake Response Plan (PERP).

NAS area includes Dry Creek North (DCNL) and South Levees (DCSL), Arcade Creek North (ACNL) and Arcade Creek South Levees (ACSL), Natomas East Main Drainage Canal East Levee (NEMDCEL), and American River North Levee (ARNL) located within Sacramento County California as shown on Figure 1-

1. This report has been prepared consistent with the requirements of the approved scope of work for the subject project outlined in Kleinfelder’s proposal dated May 5, 2023.

1.2 BACKGROUND
NAS levees in the greater Sacramento area were constructed over a period of years, with original construction of many reaches started around the turn of the last century. Since that time many changes have been made to the system to improve the system to meet modern flood control standards, to accommodate changes in land use, and to make the system more resilient to impacts from climate change and other factors.

Recently as part of modernization efforts, The American River Common Features (ARCF) Project improvements were authorized by the Federal Government for construction by Section 1401(2)(7) of the Water Infrastructure Improvements for the Nation Act of 2016 (Pub. L. No. 114-322, § 1401(2)(7), 130 24001006.001A/SAC24R164096 Page 2 of 29 February 12, 2024 © 2024 Kleinfelder
Stat. 1708, 1710 (2016)). The ARCF authorized work is nearing completion under the oversight of the U.S. Army Corps of Engineers (USACE) in cooperation with SAFCA and the California Department of Water Resources. Other locally sponsored modernization efforts and repair work are also or will soon be completed. As such, it is expected that by or about 2026, SAFCA will be working to apply for FEMA certification and will as part of that effort show compliance with ULDC requirements.

To better understand the potential flood risk to urban areas of California posed by levees, the California Department of Water Resources (DWR) conducted the Urban Levee Evaluations (ULE) project. As part of this effort, URS classified the seismic vulnerability of the NAS levees in the Geotechnical Evaluation Reports for the American River Study Area (URS, 2015a) and the NEMDC East Study Area (URS, 2015c).

1.3 REFERENCED REPORTS
The following reports were reviewed in support of this NAS SPSR:
• “ULE Geotechnical Evaluation Report (GER) Volume 1 and 2, American River Study Area, Urban Levee Evaluations Project, Contract 4600008101,” dated January 2015 (Issue date: 01-2015), URS (2015a).
• “ULE Geotechnical Evaluation Report Volume 2, Remedial Alternatives, NEMDC East Study Area, Urban Levee Evaluations Project, Contract 4600008101,” dated April 2015 (Issue date: 04-2015), URS (2015c).

1.4 SEISMIC VULNERABILITY EVALUATION METHODOLOGY
The seismic vulnerability evaluation was performed in accordance with Kleinfelder’s Seismic Evaluation Technical Approach Memorandum (Kleinfelder, 2023a) (SETAM) contained in Appendix A, which is generally consistent with the Urban Levee Evaluations Project Guidance Document for Geotechnical Analysis (URS, 2015b) (Guidance Document) Section 6, Seismic Analysis for intermittently loaded levees1. High, Moderate, and Low Vulnerability classifications from the Guidance Document (URS, 1 The ULDC requires classifying the levee as frequently loaded or intermittently loaded. A frequently loaded levee is defined in the ULDC as a levee with water at least one foot above the landside levee toe for more than 36 days in a year. As stated in the ULDC Geotechnical Results Summary North Area Streams (Kleinfelder, 2016) and in the ULE Geotechnical Evaluation Report Volume 1 and 2 American River Study Area (URS, 2015b), the study area levees generally do not contain water above the landside toe for this time interval. Therefore, the levees within the study area are considered intermittently loaded for this study.
24001006.001A/SAC24R164096 Page 3 of 29 February 12, 2024 © 2024 Kleinfelder
2015b) will be based on the seismic deformation estimates, see Figure 1-2 in Section 1.4.4, below. The steps for evaluating and classifying the levee are outlined in the SETAM and are described briefly below.

Figure 1-3 presents a flow chart describing the evaluation criteria.

1.4.1 Preliminary Work
Kleinfelder performed a review of the existing geotechnical analysis and subsurface data. During this process, seismic segment data gaps were identified and updated peak horizontal acceleration (PHA) and magnitude was developed.

Previous development of ground motion parameters in the area was performed by URS in 2007 as part of the Delta Risk Management Strategy (DRMS), which was updated and expanded on in 2012 by URS as part of the DWR ULE project. Updated ground motion parameters were developed following assumptions of this previous work, and detailed methodology is presented in our Seismic Evaluation Ground Motion Parameter Selection Memorandum (Kleinfelder, 2023b) (GMPSM), which is included in Appendix B. A probabilistic seismic hazard analysis was performed to determine PHA and earthquake magnitude as discussed in the GMPSM and Section 3, Ground Motion Hazard Analysis, of this report.

1.4.2 Phase 1: Screening Review of Existing Analysis
The levees are organized by selection of “segments” instead of reaches due to the variable nature of subsurface conditions under levees. Segments may overlap multiple reaches or reaches may be subdivided into multiple segments. Levee segments, which were based on portions of the levees with similar soil types and liquefaction results, and analysis sections for each segment for seismic evaluation were developed for the 2015 ULE evaluations and were adopted for this study. Levee segments are shown on Figure 1-1.

The screening process was performed to identify analysis sections where original analyses are determined to be deficient, and analysis sections where updated analyses indicate potential deformation where original analyses did not. Analysis sections determined to be non-critical for seismic performance were not used in the current analyses and are not presented in report.

Kleinfelder performed probabilistic seismic hazard analyses at select control points in the NASL area, as discussed in the GMPSM (Kleinfelder, 2023b). Newly developed PHAs and earthquake magnitudes from these analyses for critical sections were compared to ground motion parameters from previous reports.

No further analysis was required for analysis sections where any of the below conditions are true:
24001006.001A/SAC24R164096 Page 4 of 29 February 12, 2024 © 2024 Kleinfelder

1. The new PHA is lower than the original PHA and the original analysis is determined to be adequate.

2. The original analysis determined the section is not susceptible to deformation and the new PHA is not higher than the original analysis PHA.

3. The analysis section is found to have High Vulnerability or Flow Failure based on the original PHA.

1.4.3 Phase 2: Targeted Evaluation
A targeted evaluation was required for critical sections under two conditions, as follows:

1. The new PHA is less than or equal than the original PHA, the original analysis is determined to be inadequate, and the Flow Failure Factor of Safety (FOS) with original PHA is greater or equal to

1. 2. The new PHA is greater than the original PHA, the original analysis or conditions classify the section as low or moderate vulnerability, and the Flow Failure FOS with original PHA is greater than 1.

High, Moderate, and Low Vulnerability classifications were based on the seismic deformation estimates from the Guidance Document (URS, 2015a). As explained in Section 1.4.2, all segments classified as High Vulnerability in the Phase 1 screening process were not analyzed and the High Vulnerability classification was used for this study.

1.4.4 Seismic Vulnerability
The following steps were involved in assessing seismic vulnerability, Step numbers are associated with Key Steps described in Figure 6-1 of the Guidance Document (URS, 2015b); see Appendix C. These steps were performed for the ULE American River Study Area GER (URS, 2015a) and the NEMDC East Study Area (URS, 2015c) and were reviewed by Kleinfelder for this study. Liquefaction analysis spreadsheets prepared for the ULE GER were provided to Kleinfelder by DWR for review. 24001006.001A/SAC24R164096 Page 5 of 29 February 12, 2024 © 2024 Kleinfelder
Step 1. Kleinfelder performed a liquefaction analysis using revised PHA and earthquake magnitude values. The URS SPT-based liquefaction spreadsheets were used to delineate zones of liquefaction.

Based on the results of liquefaction, any additional cross sections were identified for analysis.

The analysis cross sections developed for the 2015 ULE project were used for this study where relevant.

Step 2. For selected cross sections, FOS against flow failure were estimated using residual strength for liquefiable materials and static slope stability analysis. If FOS was less than 1, the section was classified as “High Vulnerability” and no further analysis was needed.

If FOS against flow failure was greater than 1.3, the analysis section was classified as “Low Vulnerability”, unless analysis for volumetric strain resulted in a higher vulnerability class.

Kleinfelder and others have previously performed extensive slope failure modeling along the levee alignments using SLOPE/W, a two-dimensional finite element computer modeling, a package included in the GEOSTUDIO software package, which was developed by Bentley Systems, Inc. Where necessary, these models were updated to the current version of GEOSTUDIO (2023.1.2) and utilized for Targeted Flow Failure analyses. Idealized soil properties were based on previous investigations and generalized parameters from the Guidance Document (URS, 2015a). Water surface elevations for seismic flow failure analyses were the higher of either average summer or average winter water surfaces, in accordance with the Guidance Document (URS, 2015a).

Slope failure analyses considered all potential failure modes, including:
• Waterside and landside
• Deep and shallow
• Circular and wedge-shaped
Step 3. If FOS against flow failure was between 1.0 and 1.3, a simplified seismic deformation analysis was performed on the section. This involved computing a maximum horizontal seismic coefficient (Kmax) and performing a pseudo-static stability analysis using a horizontal seismic coefficient of 50% of the maximum value. This analysis was performed using the same updated SLOPE/W models used in Step 2. If the resulting FOS greater than 1.0, the section was classified as “Low Vulnerability”.
24001006.001A/SAC24R164096 Page 6 of 29 February 12, 2024 © 2024 Kleinfelder
Yield acceleration (Ky) values were then estimated using pseudo-static analyses using the same SLOPE/W models used in Step 2. Yield acceleration was defined as the minimum horizontal acceleration resulting in a just-stable slope condition, i.e. FOS = 1.0. Yield acceleration was developed for each potential failure mode.

A vertical Newmark-type deformation analysis was performed based on the Kmax and Ky values determined above. The calculated Newmark displacement was reduced by 30% for estimation of freeboard loss.

Volumetric settlement was considered for sections with potentially liquefiable soils thicker than 20 feet. Previous work performed by URS on ULE considered (N1)60-cs blow counts less than 15 as liquefiable and subject to volumetric settlement. This blow count criteria was evaluated against new research and revised, if warranted.

Seismic vulnerability classification was determined by calculating freeboard loss as the sum of Newmark-type vertical deformation and volumetric settlement (if applicable). Freeboard loss was evaluated as a percentage of levee height (as measured from hinge point on the landside toe). Engineering judgment was used to determine damage to internal levee structures, and the seismic vulnerability class was evaluated based on Table 6-1 from the Guidance Document (URS, 2015b) shown below in Figure 1-2.

Figure 1-2: Table 6-1 from DWR Guidance Document, Section 6.41 24001006.001A/SAC24R164096 Page 7 of 29 February 12, 2024 © 2024 Kleinfelder
Step 4. Advanced seismic deformation analyses as described in Appendix C only apply to frequently loaded levees and were not applicable to this study.

The stages of our evaluation were described in detail in our SETAM (KLF, 2023a) as well as Section 6 of the Guidance Document (DWR, 2015b).
24001006.001A/SAC24R164096 Page 8 of 29 February 12, 2024 © 2024 Kleinfelder
2 GEOLOGY AND GEOMORPHOLOGY
___________________________________________________________________________________

2.1 REGIONAL GEOLOGIC SETTING
The study area is located within the southern portion of the Sacramento Valley, within the Great Valley geomorphic province. The Great Valley province is a north-south trending 400-mile by 50-mile long alluvial plain in central California comprised of the Sacramento Valley in the north and the San Joaquin Valley in the south. The Sacramento Valley contains thousands of feet of accumulated fluvial, overbank, and alluvial fan deposits derived from erosion of the adjacent Sierra Nevada mountains to the east, northern Coast Range mountains to the west, and Klamath and Cascade mountains to the north. These deposits are primarily comprised of Quaternary and Tertiary age (present day to 56 million years ago) alluvial deposits and include clays, silts, sands, and gravels. The alluvial deposits thin out at the margins of the Great Valley province, exposing the underlying bedrock units. The Foothills Metamorphic Belt and the basement complex of the Sierra Nevada Batholith to the east are exposed along the eastern boundary of the valley. Sedimentary and mélange bedrock of the northern Coast Range mountains are exposed to the west. Meta-sedimentary, mélange, igneous, and volcanic bedrock of the Klamath and Cascade mountains are exposed to the north.

Geologic maps covering the study area on a regional scale were reviewed as a part of this study.

Published maps include:
• Wagner et al. “Geologic Map of the Sacramento Quadrangle, California. 1:250,000. Dated 1981. • Helley and Harwood. “Geologic Map of the late Cenozoic Deposits of the Sacramento Valley and Northern Sierran Foothills, California.” Sheet 1 of 5. 1:62,500. Dated 1985. • Gutierrez, C.I. “Preliminary Geologic Map of the Sacramento 30’ X 60’ Quadrangle, California,” Scale 1:100,000. Dated 2011.

Wagner et al. provides a generalized regional context of the geologic units within and surrounding the study area. Guitierrez provides an updated version of the Helley and Hardwood map with more detail of the alluvial deposits within and surrounding the study area than Wagner et al. In general, the three maps present the geologic units consistently in the vicinity of the study area. Figure 2-1 shows the study area on the Wagner et al. geologic map.
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2.2 LOCAL GEOLOGY
A review of the local geology was performed using larger scale geologic maps covering the study area and comparing to the previously discussed regional geologic maps and existing subsurface data. Based on this review the local geology at depth is summarized in the sections below.

Surficial geology maps were previously prepared by Fugro William Lettis Associates (FWLA) of the study area on two separate maps.
• “Surficial Geologic Map of the American River Study Area.” Scale 1:20,000. Dated 2008. (FWLA, 2008)
• “Surficial Geologic Map of the NEMDC East Study Area.” Scale 1:20,000. Dated 2011. (FWLA, 2011)
The maps were prepared by reviewing existing geologic maps of the area, topography, and aerial photographs from 1937. The FWLA maps provide more detail geologic mapping within the study area.

Figure 2-2 shows Dry Creek, Arcade Creek, and NEMDC study are levee alignments plotted on the FWLA 2008 geology Map. Figure 2-3 presents the 2011 FWLA geology map for American River.

2.2.1 Surficial Geology
The major surficial geologic deposits within the FWLA are summarized below with the geologic unit symbols used by FWLA (2008 and 2011).
• Cultural Deposits (L, RR, ML): Historical Levee (L), Railroad Embankment (RR), Road Embankment (R), and Made Land (ML); made of artificial fill (Circa 1937 except Made Land); The Made Land is described as fill material of local and exotic sources, sand, silt, organics, garbage, etc. Historical levee deposits are generally mapped along Dry Creek, Arcade Creek, NEMDCEL, and American River. Railroad are mapped along the Union Pacific Railroad tracks that cross American River and parallel NEMDCEL. Made land is mapped sporadically along and within the American River.
• Borrow Pit (BP): area mapped where the existing fill was removed as noted from the 1937 aerial photographs. The material was likely used in levee fill construction. Borrow pits are mapped along NEMDC channel from the confluence with American River to north of the intersection with Arcade Creek. Borrow pit is also mapped along the waterside toe of ARNL. 24001006.001A/SAC24R164096 Page 10 of 29 February 12, 2024 © 2024 Kleinfelder
• Vernal Pool (Vp): seasonally submerged or saturated depression usually indicative of underlying hardpan. Mapped along much of DCSL and ACNL.
• Historical Overbank Deposits (Rob): sand, silt, and clay; deposited during high-stage water flow, overtopping channel banks. Mapped along ARNL.
• Historical Channel Deposits (Rch): well-sorted sands and fine gravels. Predominantly mapped along DCNL, Dry Creek floodway, ACNL, and ARNL.
o Historical Channel Bar Deposits (Rb): fine gravel, sand, and silt deposited at or along channel lateral margins. Mapped along portions of ARNL. o Historical Point Bar Deposits (Rpb): well-sorted sand with minor amounts of silt and clay.

Mapped along ARNL.
• Historical Cut-off Channel Deposits (Rcu): occur on insides of meander bends within the river channel. Mapped along portions of ARNL.
• Historical Distributary Channel Deposits (Rdc): sand, silt, clay and trace gravel. Mapped along ARNL.
• Historical Slough Deposits (Rsl): sand, silt, and clay, fining upward, low-energy channel deposits.

Mapped along minimal portions of ARNL.
• Holocene Alluvial Fan Deposits (Hfy): sand, silt, and clay. Mapped west of NEMDC at the intersections of Arcade Creek, Magpie Creek, Dry Creek, and American River. • Holocene Overflow Channel Deposits (Hofc): vertically stratified sand, silt, and clay in channels occupied when high-stage water overtops channel banks. Mapped north of and parallel to ARNL.
• Holocene Channel Deposits (Hch): sorted sands and silts, fining upward. Mapped along NEMDCEL, ACSL, and ARNL.
• Holocene Slough Basin Deposits (Hsb): sand, silt, and cay; fining upwards, ponded, low-energy channel deposits. Mapped along portions of ARNL.
• Holocene Slough Deposits (Hsl): Holocene slough deposits; sand, silt, and clay, fining upward, low-energy channel deposits. Mapped along portions of ARNL. 24001006.001A/SAC24R164096 Page 11 of 29 February 12, 2024 © 2024 Kleinfelder
• Holocene Basin Deposits (Hn): fine sand, silt, and clay. Mapped in the area of the historical Magpie Creek intersection with NEMDCEL and where the current Magpie Creek concrete-lined channel, I-80 bridges, and pump station intersect NEMDCEL. • Holocene Marsh Deposits (Hs): silt and clay, possibly with organic-rich beds; perennially or seasonally submerged. Mapped in the area of the historical Magpie Creek intersection with NEMDCEL and where the current Magpie Creek concrete-lined channel, I-80 bridges, and pump station intersect NEMDCEL; also mapped along minimal portion of ARNL. • Holocene Alluvial Deposits (Ha): undifferentiated; sand, silt, and minor lenses of gravel. Mapped along NEMDCEL south of Arcade Creek, along ACSL, and ARNL. • Modesto Formation (Qmu, Qml): Late Pleistocene (estimated 12,000 to 45,000 years of age) alluvium consisting of gravel, sand, silt, and clay; Upper Modesto (Qmu) typically unconsolidated and dense while the lower (Qml) typically unconsolidated to semi-consolidated and dense to very dense; very dense and/or semi-consolidated layers of the Modesto Formation may be identified as “hardpan.” Mapped along much of NEMDC, Arcade Creek, Dry Creek, and ARNL. • Riverbank Formation (Qru, Qrl): Mid-Pleistocene (estimated 130,000-450,000 years of age) alluvial fan consisting of gravel, sand, silt, and clay containing high-pedogenic silt and clay content and reddish hues reflective of its relative age; upper Riverbank Formation (Qru) typically semi-consolidated to consolidated while the lower (Qrl) typically consolidated and very dense; the very dense and/or consolidated layers of this formation locally referred to as “hardpan.” Mapped along significant portions of NEMDC, Dry Creek, and ARNL. • Turlock Lake Formation (Qtl): Early Pleistocene (estimated 450,000-600,000 years of age) alluvial fan consisting of well consolidated sand with some silt and minor gravel. Mapped along ARNL.

2.2.2 Generalized Near Surface Stratigraphy
Near surface stratigraphy (approximately upper 100 feet) was based on review and interpretation of geology publications, historical aerial photographs, current and historical topography, and existing subsurface data. The following provides a generalized stratigraphic description beginning from the bottom of the section along the study area levees.

The Early Pleistocene Turlock Lake Formation underlies the study area levees at depth. The Turlock Lake Formation is an alluvial fan deposit mapped as exposed at the surface generally to the east of Watt 24001006.001A/SAC24R164096 Page 12 of 29 February 12, 2024 © 2024 Kleinfelder
Avenue where it is topographically higher than the Riverbank Formation. The Turlock Lake Formation generally consists of weathered sands with some gravels and silts.

The Pleistocene Riverbank Formation overlies the Turlock Lake Formation. Generally, the Riverbank Formation is an alluvial fan deposit mapped as exposed at the surface generally west of Watt Avenue and laterally continuous across the study area. The Riverbank Formation was gradually incised by historical and active streams to create current day conditions. The Riverbank Formation consists of predominately stiff to indurated fine-grained soils with localized channels of sands and gravels.

The Late Pleistocene Modesto Formation overlies the Riverbank Formation and is generally local to the active and historical streams and American River within the study area. The Modesto Formation varies in thickness extending to approximately 30 feet and consists of a wide range of materials including soft to indurated fine-grained soils as well as gravels and cobbles along the American River. Additionally, this unit has been significantly eroded and is laterally discontinuous.

Holocene and Recent fluvial deposits overlay the Riverbank and Modesto Formations along the study area streams and American River. The areas are generally blanketed by fine-grained soils indicative of lower energy overbank and basin deposits. The fine-grained soils are dissected by channel and crevasse deposits generally consisting of soils with higher percentage of sand.

The study area levees were constructed on top of the native soils in the mid-1900’s generally using nonmodern-day conventional construction methods and testing. The exception is the Arcade Creek north levee, the NEMDC east levee north of Arcade Creek, and DCSL, which were constructed in the mid-1950s using USACE levee construction methods, and the DCNL, which was constructed in 1996, using modern compaction and testing methods. The levee embankments generally consist of silty and clayey sands.

SAFCA and USACE have constructed improvements to the levees to strengthen them over time.

2.3 SEISMOTECTONIC SETTING
The project is located in the Western United States (WUS) in the transform plate boundary region between the Pacific Plate (transitioning northwest) and the North American Plate. The site lies within the Sierra Nevada-Great Valley block (a.k.a., the Sierra Nevada microplate, or SNGV) which generally is thought to act as an independent block that has ‘tilted’ westward. The SNGV block is bounded on its eastern edge by a zone of faults known as the Walker Lane Belt, beyond which is the crustal extensional region of the Northern Basin and Range. Further afield in the northwestern portion of the state and extending northward to the pacific northwest, the Juan de Fuca plate is currently subducting below the 24001006.001A/SAC24R164096 Page 13 of 29 February 12, 2024 © 2024 Kleinfelder
North American plate in a region known as the Cascadia Subduction Zone (Humphreys and Coblentz, 2007; Unruh and Humphrey, 2003, 2017).

Regional stress buildup due to the northwestern movement of the Pacific Plate is primarily released through displacement along faults within the San Andreas fault system (e.g., San Andreas fault, Hayward fault, etc.) and to a lesser extent by displacements along faults within the Walker Lane Belt. Crustal extension of the Northern Basin and Range has led to the development of stress in the east-west direction and caused development of an extensive system of faults within the Northern Basin and Range (Fey and Humphreys, 2008; Field et al., 2013). These faults and other regional seismic sources are shown on Figures 3 and 4 of the GMPSM (Kleinfelder, 2023b) in Appendix B. 24001006.001A/SAC24R164096 Page 14 of 29 February 12, 2024 © 2024 Kleinfelder
3 GROUND MOTION HAZARD ANALYSIS
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3.1 SEISMIC HAZARD ANALYSIS
Kleinfelder performed a site-specific probabilistic seismic hazard analysis (PSHA) for three control points within the NAS analysis area as shown on Figure 1-1. A detailed description of the probabilistic seismic hazard analysis performed for this project is presented in the GMPSM (Kleinfelder, 2023a) in Appendix B.

To account for site effects and basin effects, the site parameters in Table 3.1 were evaluated. Because ground motions were evaluated at stiff soil condition, the Vs30 (average shear wave velocity in the upper 100 feet/30 meters) value was taken as 335 m/s. Z1.0 and Z2.5 were estimated utilizing the correlations developed for the NGA West 2 project, with justification per Peterson et al. 2019.

For the Ground Motion Models (GMMs), Kleinfelder used four of the Next Generation Attenuation (NGA) West 2 relationships including Abrahamson et al. (2014), Boore et al. (2014), Chiou and Youngs (2014), and Campbell and Bozorgnia (2014) with equal weights applied for all crustal faults (e.g. reverse, strike-slip, normal) included in the fault model. The Idriss (2014) model has not been used as it is not valid for the VS30 used in our study and also for the larger distances used in this study (e.g. more than 150 km). The far-field subduction events (e.g. from Cascadia megathrust) were modeled using the relationships of Atkinson and Macias (2009), Abrahamson et al. (2016), and Zhao et al. (2006) with equal weights applied, except that for slab events the Atkinson and Macias (2009) relationship was excluded.

Spectral acceleration values are obtained by averaging the individual hazard results. These GMMs provide ‘mean’ (RotD50) values of ground motions associated with magnitude, distance, site soil conditions, and mechanism of faulting.

Table 3.1
Seismic Hazard Analysis Site Parameters
Point ID Latitude Longitude VS30
(m/s)
Z1.0
(km)
Z2.5
(km)
Arcade Creek 38.6668 -121.4762
Confluence 38.5982 -121.5087 335 0.428 1.55
American River East 38.5921 -121.3344
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3.1.1 Seismic Analysis Results
Kleinfelder calculated the probabilistic geometric mean Peak Horizontal Acceleration (PHA) values and deaggregation results at three points around the NAS analysis area (see Figure 1-1). The PHA has a 200- year return period and is listed in Table 3.2 along with the corresponding PHA value estimated from the Seismic Hazard Map in the 2015 ULE American River and NEMDC East GERs (URS, 2015a and 2015c).

Table 3.2
Probabilistic Peak Horizontal Acceleration and Controlling Earthquake Magnitude Point ID
PHA (g) Deaggregation Results
(KLF, 2023) (URS,
2015) MW Distance (km)
Arcade Creek 0.13 0.139 6.8 72
Confluence 0.14 0.146 6.8 67
American River East 0.12 0.126 6.8 81
The new PHA values calculated for each NAS analysis control point corresponding have small differences from the 2015 ULE. However, the 2015 ULE performed liquefaction analyses used an earthquake magnitude of 6.5, and Kleinfelder’s deaggregation produced a magnitude of 6.8. Hence, Kleinfelder performed liquefaction analyses using the original PHA values and the larger 2023 KLF magnitude. The old PHA values were used in the evaluation as the new values are not significantly different from the old values and are slightly conservative.
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4 PREVIOUS EVALUATION
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4.1 SUMMARY
The 2015 URS Geotechnical Evaluation Reports for the NEMDC East and American River North study areas (URS, 2015a and 2015c) performed Seismic Vulnerability Evaluations in accordance with the requirements developed for ULE. SPT-based liquefaction analyses were performed to identify layers at risk for liquefaction and non-liquefiable layers. These results were used where applicable to perform post-seismic stability and deformation analyses and classify the seismic vulnerability of each levee segment.

4.1.1 General
Kleinfelder reviewed the 2015 URS Seismic Vulnerability Analyses for the NAS levee segments as part of the Phase 1 Screening Analysis. Segments with High Vulnerability classifications and segments noted as non-liquefiable were not required to receive further analysis. Any segments noted as having both Low or Medium Vulnerability and containing at least one liquefiable layer required further review, which is discussed in Section 5 CURRENT EVALUATION, and are shaded gray in Table 4.1.

Table 4.1
Phase 1 – Seismic Vulnerability Results Screening
Segment ID Station Start Station End 2015 URS
Vulnerability
Contains
Liquefiable Layer
Additional
Analysis Required
American River – North Bank
AR-7 3000+00 3016+00 Low No No
AR-8 3016+00 3044+48 High Yes No
AR-9 3044+48 3085+35 Low No No
AR-10 3085+35 3088+60 High Yes No
AR-11 3088+60 3102+85 Low No No
AR-12 3102+85 3167+50 Low Yes Yes
AR-13 3167+50 3306+00 High Yes No
AR-14 3306+00 3458+85 Low Yes Yes
AR-15 3458+85 3482+50 High Yes No
AR-16 3482+50 3582+79 Low No No
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Table 4.1 (cont.)
Phase 1 – Seismic Vulnerability Results Screening
Segment ID Station Start Station End 2015 URS
Vulnerability
Contains
Liquefiable Layer
Additional
Analysis Required
NEMDC East/North Area Streams
NMDE-1 2986+49 2995+91 Low No No
NMDE-2 2995+91 3011+65 Low Yes Yes
NMDE-3 3011+65 3192+23 Low Yes Yes
NMDE-4 4000+00 4110+34 Low No No
NMDE-5 5000+00 5112+43 Low No No
NMDE-6 6000+00 6106+66 Low No No
NMDE-7 6106+66 6167+62 Low No No
NMDE-8 7000+00 7085+57 Low No No

4.2 SEISMIC ANALYSIS WATER SURFACE ELEVATIONS
Per the Guidance Document (URS, 2015b), seismic vulnerability analyses were performed using the higher of the average summer or winter Water Surface Elevations (WSE) at each ULDC segment.

Kleinfelder assessed the applicability of the average WSEs used for the 2015 liquefaction calculations for the updated calculations. The California Department of Water Resources (DWR) provides a database of groundwater well measurements across the Sacramento Valley. For the updated calculations, data from wells located near a ULDC segment were evaluated for further analysis. Upon review of the available information, the mean winter and summer groundwater elevations were lower than those used for the seismic analyses in 2015. Generally, mean groundwater elevations from the past ten years were lower than those used in the liquefaction analyses in the same area by approximately 10 feet, possibly due to droughts and other seasonal factors. Therefore, it was decided to continue using the same WSEs from 2015 study because they are higher in elevation and would provide conservative results for liquefaction. 24001006.001A/SAC24R164096 Page 18 of 29 February 12, 2024 © 2024 Kleinfelder
5 CURRENT EVALUATION
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5.1 SEISMIC EVALUATION SEGMENT SELECTION
Segments AR-12, AR-14, NMDE-2, and NMDE-3 were categorized by the 2015 ULE GERs as having low seismic vulnerability and layers with the potential for liquefaction. These segments met the criteria for a targeted evaluation using the updated deaggregation results from Kleinfelder’s GMHA.

5.1.1 Liquefaction Analysis of ULDC Segments
The 2015 URS evaluations produced SPT-Based Liquefaction Analysis Excel spreadsheets for multiple borings corresponding to the ULDC segments. These analyses for the selected NASL segments were recalculated using the updated GMHA deaggregation magnitude of 6.8. The spreadsheet calculations are included in Appendix D: Updated SPT-Based Liquefaction Calculations for Targeted Segments.

The borings for the targeted evaluation segments are listed in Table 5.1.1. The Factors of Safety (FOS) of some potentially liquefiable layers decreased from above to below 1.25 (“Non-Liquefiable” to “Less Likely Liquefiable”), and some decreased from above to below 1.0 (“Less Likely Liquefiable” to “Likely Liquefiable”). Table 5.1.1 notes borings where at least one layer changed in one of these ways; Table

5.1.2 describes the affected layers and their new Factors of Safety against liquefaction.

Table 5.1.1
Liquefaction Layer Changes for Targeted Segments
Segment
ID
Station
Start
Station
End
Liquefaction Analysis Boring
(Station)
Liquefiable Layer
Classification Change
American River – North Bank
AR-12 3102+85 3167+50
2F-97-04 (3106+13) No
2F-99-04A (3151+12) Yes
2F-96-10 (3126+49) Yes
AR-14 3306+00 3458+85
2F-97-06 (3307+50) Yes
2F-97-14 (3360+71) No
2F-99-09A (3397+21) No
2F-99-11A (3449+67) Yes
WCNBAR_003B (3306+35) No
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Table 5.1.1 (cont.)
Liquefaction Layer Changes for Targeted Segments
Segment
ID
Station
Start
Station
End
Liquefaction Analysis Boring
(Station)
Liquefiable Layer
Classification Change
NEMDC East/North Area Streams
NMDE-2 2995+91 3011+65 K95_BE20 (3008+90) No
NMDE-3 3011+65 3192+23
K02-B3 (3038+75) Yes
WRARFC_002B (3051+36) No
WRARFC_045B (3080+63) No
WRARFC_031B (3167+60) No
Because the liquefiable layer classifications did not change for the boring within Segment NMDE-2, it remains classified as Low Vulnerability and additional analysis was not necessary.

Table 5.1.2
Liquefaction Factor of Safety Changes for Targeted Segments1 Segment
ID
Boring
(Station)
Elevation
(feet)
Layer
Thickness
(feet)
Liquefaction FOS
(2015, Mw = 6.5)
Liquefaction FOS
(2023, Mw = 6.8)
AR-12
2F-96-10
(3126+49)

15.2 3.5 1.36 1.23

11.7 3.5 1.32 1.19
2F-99-04A
(3151+12)

13.0 3.0 1.33 1.20
AR-14
2F-97-06
(3307+50)

19.7 5.0 1.10 0.99

14.7 5.0 1.06 0.96
2F-99-11A
(3449+67)

2.9 5.0 1.03 0.94
NMDE-3
K02-B3
(3038+75)

3.5 5.0 1.26 1.14

1. Yellow: FOS indicates layer is “Less Likely Liquefiable.” Red: FOS indicates layer is “Likely Liquefiable.”
Vertical settlement calculations are not required because the liquefiable layers do not exceed 20 feet in thickness (URS, 2015b).
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5.2 VULNERABILITY CLASSIFICATIONS FOR TARGETED SEGMENTS The American River and NEMDC East GER Reports (URS, 2015a; URS, 2015c) include post-seismic slope stability models for targeted segments AR-12 and AR-14. These FOS against stability failure using global and block type analysis methods. No post-seismic stability model was produced for Segment NMDE-3.

The 2015 URS results for stability FOS are displayed in Table 5.2.1.

Table 5.2.1
2015 URS Post-Seismic Stability Analysis Factors of Safety for Targeted Segments Segment
ID
Analysis
Station
Landside
Global FOS
Landside
Block FOS
Waterside
Global
FOS
Waterside
Block FOS
2015 Seismic
Vulnerability
AR-12 3109+57 2.61 2.56 2.65 2.58 Low
AR-14 3306+10 6.03 5.47 4.63 4.43 Low
NMDE-3 No post seismic stability analysis performed in 2015 Low

5.2.1 Segment AR-12
The post-seismic cross section for Segment AR-12, Station 3109+57 analyzed in the American River GER (URS, 2015a) features a 7-foot Less Likely Liquefiable layer between approximate elevations 16.7 feet and 9.7 feet. The three Less Likely Liquefiable layers identified in the updated liquefaction calculations are found at elevations within this range; based on the thicknesses of these layers, the Less Likely Liquefiable layer for AR-12 would be updated to approximately 10 feet thick. However, this is not expected to significantly lower the segment’s post-seismic stability FOS, which exceeds 2.5 as shown in Table 5.2.1. Because the liquefaction calculations showed no layers for the segment become Likely Liquefiable, the cross-sectional material properties did not need to be updated.

As such, Segment AR-12 remains classified as Low Vulnerability. 24001006.001A/SAC24R164096 Page 21 of 29 February 12, 2024 © 2024 Kleinfelder

5.2.2 Segment AR-14
The post-seismic cross section for Segment AR-14, Station 3306+10 analyzed in the American River GER (URS, 2015a) features an 11-foot Less Likely Liquefiable SP-SM layer between approximate elevations

21.9 feet and 10.9 feet. The stratigraphy, piezometric surface, and material properties of this cross section were selected based on the lab testing and liquefaction analysis results for Boring 2F-97-06.

The layer’s post-seismic shear strength was originally calculated by reducing the static drained strengths by 30%. However, because the updated liquefaction calculations classify the 11-foot layer as Likely Liquefiable, the post-seismic cross section’s stability calculations are outdated. Therefore, the cross section for Segment AR-14 was updated using residual undrained shear strengths for the Likely Liquefiable layer. The stability analysis is included as Appendix E.

5.2.2.1 Segment AR-14 Stability Analysis – Material Properties First, the residual undrained strength of the Likely Liquefiable layer was estimated. The updated liquefaction analysis produces (N1)60 value of 9 for the Likely Liquefiable SP-SM layer. After the fines/classification correction, the (N1)60-cs value becomes 10. Using the Seed-Harder Plot for Residual Strength and the procedure described in Section 6.8.2.1 in the ULE Guidance Document (2015), the residual undrained strength for the Likely Liquefiable layer was estimated as 235psf.

Additionally, the cross-sectional material properties were checked and updated using site-specific values. Effective friction angle and cohesion values from the 2015 URS Segment 14 Transverse Cross Section were used for the SM and GP layers. Per Section 5.8 of the Guidance Document (URS, 2015b), site-specific field and laboratory results were used to select material properties not listed in the 2015 URS slope stability analysis. The SPT-based liquefaction analysis for Boring ID 2F-97-06 was used to estimate unit weights for the soil layers. The slurry wall unit weight was selected as 100 pounds per cubic foot (pcf) from the American River GER (URS, 2015a) material properties for the Reach A existing soil-cement-bentonite wall (GER Table B1-A-1). This table was also used to select the undrained friction angle and cohesion values for the CL layers.

Material properties are listed in Table 5.2.2. Refer to Appendix E for the calculation package and sources for the stratigraphy and material properties.
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Table 5.2.2
Material Properties for Segment AR-14 Post-Seismic Stability Analysis Material Unit Weight
(pcf) Ф’ (dgs) C’ (psf)
1 – SM 125 32 0
2 – SM 120 32 0
3 – SP-SM (Liquefiable) 125 0
235 (residual undrained
strength)
4 – GP 130 35 0
5 – CL 125 7 960
6 – CL Cap 125 7 960
7 – Cutoff Wall 100 0 500

5.2.2.2 Segment AR-14 Stability Analysis – Slope Stability The cross section at Station 3306+10 was constructed in SLOPE/W (GeoStudio 2023.1.2) with the Seismic Analysis WSE located at Elevation 21.9 feet (NAVD88 Datum). The FOS against slope stability failure was calculated using entry and exit slip surfaces (circular) and block specified with optimized critical slip surfaces (wedge) for the levee landside and waterside. Results are attached in Appendix E:

Post-Seismic Slope Stability Analysis for Segment AR-14. The post-seismic slope stability Factors of Safety are summarized in Table 5.2.3.

Table 5.2.3
Segment AR-14 Post-Seismic Slope Stability Factors of Safety Segment
ID
Analysis
Station
Landside
Global FOS
Landside
Block FOS
Waterside
Global
FOS
Waterside
Block FOS FOS Required
AR-14 3306+10 3.33 2.69 2.32 2.05 > 1.3
All Factors of Safety against slope stability failure are greater than 1.3. Seismic Analysis Segment AR-14 remains classified as Low Vulnerability.
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5.2.3 Segment NMDE-3
No post-seismic cross sections or stability calculations were made for Segment NMDE-3 in the NEMDC East GER (URS, 2015c) analysis because the original analysis did not identify any liquefiable layers.

However, a post-seismic analysis was performed at Station 3009+00 for Segment NMDE-2 because it contained a 12-foot-thick Likely Liquefiable layer between approximate elevations 13.5 feet and 1.5 feet. The post-seismic stability results for Segment NMDE-2 are summarized in Table 5.2.4 below:

Table 5.2.4
2015 URS Post-Seismic Stability Analysis Factors of Safety for Segment NMDE-2 Segment
ID
Analysis
Station
Landside
Global FOS
Landside
Block FOS
Waterside
Global
FOS
Waterside
Block FOS
2015 Seismic
Vulnerability
NMDE-2 3009+00 1.53 1.35 1.50 1.34 Low
Since the minimum post-seismic FOS is above 1.3, Segment NMDE-2 is classified as having Low Vulnerability. As shown in Table 5.1.2, Segment NMDE-3 features one Less Likely Liquefiable layer of thickness 5 feet. As such, it is assumed Segment NMDE-3 is comparatively less vulnerable than NMDE-2; therefore, since Segment NMDE-2 is classified as Low Vulnerability, Segment NMDE-3 remains classified as Low Vulnerability.
24001006.001A/SAC24R164096 Page 24 of 29 February 12, 2024 © 2024 Kleinfelder
6 SEISMIC PERFORMANCE
_____________________________________________________________________

6.1 SUMMARY
Four Low Vulnerability segments in the North Area Streams levee region were selected for further analysis using the results of Kleinfelder’s GMHA. Kleinfelder performed liquefaction analyses using updated magnitude Mw = 6.8 and identified segments with additional layers that became less likely or likely liquefiable. Based on further investigation into each segment, Kleinfelder concluded that the four segments remain Low Vulnerability regarding seismic hazards.

The seismic vulnerability for the North Area Streams levees remains the same as the 2015 URS analysis.

Segments and their seismic vulnerability classifications are listed in Table 6.1.

Table 6.1
Seismic Vulnerability Classifications for North Area Streams Levees Segment ID Station Start Station End 2015 Seismic
Vulnerability
2023 Seismic
Vulnerability
American River - North Bank
AR-7 3000+00 3016+00 Low Low
AR-8 3016+00 3044+48 High High
AR-9 3044+48 3085+35 Low Low
AR-10 3085+35 3088+60 High High
AR-11 3088+60 3102+85 Low Low
AR-12 3102+85 3167+50 Low Low
AR-13 3167+50 3306+00 High High
AR-14 3306+00 3458+85 Low Low
AR-15 3458+85 3482+50 High High
AR-16 3482+50 3582+79 Low Low
NEMDC East/North Area Streams
NMDE-1 2986+49 2995+91 Low Low
NMDE-2 2995+91 3011+65 Low Low
NMDE-3 3011+65 3192+23 Low Low
NMDE-4 4000+00 4110+34 Low Low
NMDE-5 5000+00 5112+43 Low Low
NMDE-6 6000+00 6106+66 Low Low
NMDE-7 6106+66 6167+62 Low Low
NMDE-8 7000+00 7085+57 Low Low
24001006.001A/SAC24R164096 Page 25 of 29 February 12, 2024 © 2024 Kleinfelder
7 LIMITATIONS
___________________________________________________________________________________ Information contained in this data report is based on our field observations, subsurface explorations completed by Kleinfelder and others, laboratory tests completed by Kleinfelder and others, and our present knowledge of the existing levee conditions. The conclusions and opinions contained in this report are also based on the assumption that information provided by the Client and/or that is referenced in this report is accurate and correct and can be relied upon. It is possible that soil conditions, including groundwater levels, could vary between or beyond the points explored.

The information, including graphic representations attached to this report, have been compiled from a variety of sources as referenced herein and are subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of the information presented in this data report. These documents are not intended for use as land survey products, nor are they designed or intended as construction design documents. The use or misuse of the information contained on these graphic representations is at the sole risk of the party using or misusing the information.

We have prepared this data report in substantial accordance with the generally accepted geotechnical engineering practice as it exists in the site area at the time of our study. No warranty, express or implied, is provided. Land use, site conditions (both on site and off site), or other factors may change over time, and additional work may be required with the passage of time. Any party other than the client who wishes to use this report shall notify Kleinfelder of such intended use. Based on the intended use of the report, Kleinfelder may require that additional work be performed and that an updated report be issued. Non-compliance with any of these requirements by the client or anyone else will release Kleinfelder from liability resulting from the use of this report by any unauthorized party. 24001006.001A/SAC24R164096 Page 26 of 29 February 12, 2024 © 2024 Kleinfelder
8 REFERENCES
___________________________________________________________________________________ Abrahamson, N., Gregor, N., Addo, K. (2016). BC Hydro Ground Motion Prediction Equations for Subduction Earthquakes. Earthquake Spectra, Volume 32, Issue 1, pp. 23-44.

Abrahamson, N.A., Silva, W.J., and Kamai, R. (2014). “Summary of the ASK14 Ground Motion Relation for Active Crustal Regions.” Earthquake Spectra, Vol. 30, No. 3, pp. 1025-1056.

Atkinson, G.M., and Macias, M. (2009). Predicted Ground Motions for Great Interface Earthquakes in the Cascadia Subduction Zone. Bulletin of the Seismological Society of America, V. 99, No. 3, pp. 1552-1578.

Boore, D.M., Stewart, J.P., Seyhan, E., and Atkinson, G. (2014). “NGA-West2 Equations for Predicting PGA, PGV, and 5% damped PSA for Shallow Crustal Earthquakes.” Earthquake Spectra, Vol. 30, No. 3, pp. 1057-1086.

Campbell, K.W., and Bozorgnia, Y. (2014). “NGA-West2 Ground Motion Model for the Average Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra.” Earthquake Spectra, Vol. 30, No. 3, pp. 1087-1116.

Cetin et al. (2004). “Standard Penetration Test-Based Probabilistic and Deterministic Assessment of Seismic Soil Liquefaction Potential,” Journal of Geotechnical and Geoenvironmental Engineering, Volume 130, Issue 12, ASCE, dated December 2004.

Chiou, B.S., and Youngs, R.R. (2014). “Update for the Chiou and Youngs NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra.” Earthquake Spectra, Vol. 30, No. 3, pp. 1117-1154.

Fey, N., Humphreys, E., 2008, Forces Acting on the Sierra Nevada Block and Implications for the Strength of the San Andreas Fault System and the Dynamics of Continental Deformation in the Western United States. Journal of Geophysical Research, Vol. 113, B 12415.

Field, E.H., Biasi, G.P., Bird, P., Dawson, T.E., Felzer, K.R., Jackson, D.D., Johnson, K.M., Jordan, T.H., Madden, C., Michael, A.J., Milner, K.R., Page, M.T., Parsons, T., Powers, P.M., Shaw, B.E., Thatcher, W.R., Weldon, R.J., II, and Zeng, Y. (2013). The Uniform California Earthquake Rupture Forecast, Version 3 (UCERF 3), USGS Open File Report 2013-1165, CGS Special Report 228, Southern California Earthquake Center Publication 1792, http://pubs.usgs.gov/of/2013/1165/. 24001006.001A/SAC24R164096 Page 27 of 29 February 12, 2024 © 2024 Kleinfelder
Fugro William Lettis & Associates, Inc. (2011). “Technical Memorandum: Surficial Geologic Map and Geomorphic Assessment of the Natomas East Main Drainage Canal, East (NEMDC East) Study Area, Sacramento County, California,” dated February 16, 2011.

Fugro William Lettis Associates (FWLA 2008). “Surficial Geologic Map of the American River Study Area.” Scale 1:20,000. Dated 2008.

Fugro William Lettis Associates (FWLA 2011). “Surficial Geologic Map of the NEMDC East Study Area.” Scale 1:20,000. Dated 2011.

Gutierrez, C. I. (2011). “Preliminary Geologic Map of the Sacramento 30’ x 60’ Quadrangle, California,” California Geological Survey, Preliminary Geologic Maps PGM-11-06 (1:100,000 scale).

Hatanaka, M., and Uchida, A. (1996). “Empirical Correlation Between Penetration Resistance and Internal Friction Angle of Sandy Soils,” Soils and Foundations, ASCE, Vol. 36, No. 4, pp. 1-9.

Helley, E. J., and Harwood, D. S. (1985). “Geologic Map of the Late Cenozoic Deposits of the Sacramento Valley and Northern Sierran Foothills, California,” U. S. Geological Survey Miscellaneous Field Studies Map MF-1790.

Humphreys, E., and Coblentz, D., 2007, North American Dynamics and Western U.S. Tectonics. American Geophysical Union, Reviews of Geophysics, 45, RG3001.

Idriss, I.M. (2014). “An NGA-West2 Empirical Model for Estimating the Horizontal Spectral Values Generated by Shallow Crustal Earthquakes.” Earthquake Spectra, Vol. 30, No. 3, pp. 1155-1177.

Jennings, C.W., Strand, R.G., and Rogers, T.H. (1977), Geologic Map of California: California Division of Mines and Geology Geologic Data Map Series Map No. 2 (1:750,000 scale).

Kleinfelder (2016a). “Problem Identification Report, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), Sacramento County, California,” dated April 29, 2016.

Kleinfelder (2016b). “ULDC Geotechnical Results Summary, North Area Streams, SAFCA FEMA Levee Accreditation (North Area Streams, American River, Sacramento River Downstream of American River, and Beach Lake Levee), Sacramento County, California,” dated April 29, 2016. 24001006.001A/SAC24R164096 Page 28 of 29 February 12, 2024 © 2024 Kleinfelder
Kleinfelder (2023a). “Seismic Evaluation Technical Approach Memorandum, ULDC & FEMA Levee Certification Project, Sacramento Area Flood Control Agency Levee Systems, Sacramento and Sutter Counties, California,” dated September 29, 2023.

Kleinfelder (2023b). “Seismic Evaluation Ground Motion Parameter Selection Memorandum, ULDC & FEMA Levee Certification Project, Sacramento Area Flood Control Agency Levee Systems, Sacramento and Sutter Counties, California,” dated October 13, 2023.

Unruh, J., and Humphrey, J., 2017, Seismogenic Deformation Between the Sierran Microplate and Oregon Coast Block, California, USA. The Geological Society of America v. 45, no. 5, pp. 415-418.

Unruh, J., Humphrey, J., and Barron, A., 2003, Transtensional Model for the Sierra Nevada Frontal Fault System, Eastern California. Geology v. 31, no. 3, pp. 327 – 330.

URS Greiner (2000). “Plans for American River Watershed Project (Common Features), California Left (South) Bank Levee Straightening, Contract 2,” dated January 18, 2000.

URS (2009). “Phase 1 Geotechnical Data Report (P1GDR), Natomas East Main Drainage Canal (NEMDC) Study Area, Urban Levee Geotechnical Evaluations Program, Contract 4600007418,” dated March 2009 (Issue date: 04-2009).

URS (2011). “Supplemental Geotechnical Data Report (SGDR), Natomas East Main Drainage Canal (NEMDC) Study Area, Urban Levee Geotechnical Evaluations Program, Contract 4600007418,” dated November 2011 (Issue date: 11-2011).

URS (2011). “Supplemental Geotechnical Data Report (SGDR), American River Study Area, Urban Levee Geotechnical Evaluations Program, Contract 4600007418,” dated June 2010 (Issue date: 06- 2010).

URS (2015a). “ULE Geotechnical Evaluation Report (GER) Volume 1 and 2, American River Study Area, Urban Levee Evaluations Project, Contract 4600008101,” dated January 2015 (Issue date: 01- 2015).

URS (2015b). “Guidance Document for Geotechnical Analyses, Urban Levee Geotechnical Evaluations Program, Contract 4600008101,” dated April 2015.

URS (2015c). “ULE Geotechnical Evaluation Report Volume 2, Remedial Alternatives, NEMDC East Study Area, Urban Levee Evaluations Project, Contract 4600008101,” dated April 2015 (Issue date: 04- 2015).
24001006.001A/SAC24R164096 Page 29 of 29 February 12, 2024 © 2024 Kleinfelder
United States Army Corps of Engineers (USACE) (1990). “Settlement Analysis, EM 1110-1-1904,” dated 30 September 1990.

USACE (2001). “Geotechnical Investigations, EM 1110-1-1804”, dated 1 January 2001.

USACE (2015). “Geotechnical Office Report, American River Watershed Common Features Project General Reevaluation Report,” dated October 2013.

USACE (2016). ER 1110-2-1806 Earthquake Design and Evaluation for Civil Works Projects.

Wagner, D.L., Jennings, C.W., Bedrossian, T.L., and Bortugno, E.J. (1981). Geologic Map of the Sacramento Quadrangle, California, 1:250,000 scale, California Department of Conservation, Geological Survey, Regional Geologic Map Series, Map No. 1A.

Zhao et al. (2006). Attenuation Relations of Strong Ground Motion in Japan using Site Classification Based on Predominant Period. Bulletin of the Seismological Society of America, V. 96, No. 3, pp. 898-913.
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PROJECT:

FILE NAME:

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1-1
DRAWN:

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The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
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Project Location
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NORTH AREA STREAMS/

AMERICAN RIVER NORTH LEVEES

SEISMIC PERFORMANCE SUMMARY REPORT

SAFCA LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
AR-13 Seismic Segment
FIGURE
DRAWN BY:

PROJECT NO.

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Arcade Creek South
Arcade Creek North
Dry Creek South
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REGIONAL GEOLOGY
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The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
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OCT 2023
M. RYAN
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Kilometers
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NORTH AREA STREAMS/

AMERICAN RIVER NORTH LEVEES

SEISMIC PERFORMANCE SUMMARY REPORT

SAFCA LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA

NORTH AREA STREAMS LEVEES

GEOLOGY MAP
PROJECT:

FILE NAME:

FIGURE
2-2
DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
OCT 2023
M. RYAN
A.LEONARD
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NORTH AREA STREAMS/

AMERICAN RIVER NORTH LEVEES

SEISMIC PERFORMANCE SUMMARY REPORT

SAFCA LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA

AMERICAN RIVER NORTH LEVEE

GEOLOGY MAP
PROJECT:

FILE NAME:

FIGURE
2-3
DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
OCT 2023
M. RYAN
A.LEONARD
SAFECA_working.mxd
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-SeismicPerformanceSumReport\PRO\SAFECA_working\SAFECA_working.aprx ALeonard 1/5/2024

NORTH AREA STREAMS/

AMERICAN RIVER NORTH LEVEES

SEISMIC PERFORMANCE SUMMARY REPORT

SAFCA LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
24001006.001A/SAC24R164096 Page A-1 February 12, 2024
© 2024 Kleinfelder

APPENDIX A

SEISMIC TECHNICAL APPROACH MEMORANDUM
_____________________________________________________________________ 24001006.001A/SAC24M163970 Page 1 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701

SEISMIC EVALUATIONTECHNICAL APPROACH MEMORANDUM
DATE: February 8, 2024
TO: Mr. Pete Ghelfi, PE
Director of Engineering
Sacramento Area Flood Control Agency
1325 J Street, Suite 1700
Sacramento, CA 95814
FROM: Ryan Hochstatter, EIT
Zia Zafir, PhD, PE, GE
SUBJECT: Seismic Evaluation Technical Approach Memorandum ULDC & FEMA Levee Certification Project
Sacramento Area Flood Control Agency Levee Systems
Sacramento and Sutter Counties, California
___________________________________________________________________________________ 1 INTRODUCTION
Kleinfelder has been tasked by the Sacramento Area Flood Control Agency (SAFCA) with evaluating the seismic vulnerability of the Sacramento area levees located in Sacramento and Sutter Counties, California as shown on Attachment 1. This technical approach memorandum presents the methodology for the seismic evaluation consistent with the Urban Levee Design Criteria (ULDC) (DWR, May 2012) and the Urban Levee Evaluations Project Guidance Document for Geotechnical Analysis (DWR Guidance Document) (DWR and URS, 2015).

This memorandum has been prepared consistent with the requirements of the approved scope of work for the subject project outlined in Kleinfelder’s proposal dated May 5, 2023. 2 PURPOSE
SAFCA is working with a team of consultants to obtain ULDC and Federal Emergency Management Agency (FEMA) certifications for the Sacramento area levees. The purpose of this document is to establish a seismic vulnerability evaluation methodology that conforms to ULDC. Methodology will generally follow seismic vulnerability guidelines for intermittently-loaded levees as described in the DWR Guidance Document (DWR and URS, 2015). The results of the seismic vulnerability evaluation will be used to evaluate the seismic vulnerability for FEMA certification.

The levees will be organized by selection of “sections” instead of reaches due to the variable nature of subsurface conditions under levees. Sections may overlap multiple reaches or reaches may be subdivided into multiple sections. Note that for sections encompassing or divided by roadway overcrossings, the overcrossings will be simplified to their centerlines, and additional improvements to the levee for overcrossing abutments will be neglected. 24001006.001A/SAC24M163970 Page 2 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 3 PROJECT FEATURES
Attachment 1, Seismic Planning Services Responsibility Map, shows the following levee systems and their associated component levees. The levee systems are summarized in Table 1 below.

Table 1: Levee Systems and Component Levees
Levee System Reach
1 - Dry Creek Dry Creek North Levee
2 - Robla-Arcade
Dry Creek South / Robla Levee
Natomas East Main Drainage Canal (NEMDC) East Levee - Robla to Arcade Creek Arcade Creek North Levee
3 - American North
Arcade Creek South Levee
NEMDC East Levee - Arcade Creek to American River
American River North Levee
4 - American South
American River South Levee
Sacramento River East Levee (SREL) - American River to NBLL North Beach Lake Levee
5 - Natomas Basin
Natomas Cross Canal South Levee (NCC)
SREL - NCC to Powerline Road
SREL - Powerline Road to American River
American River North Levee - Sacramento River to NEMDC
NEMDC West Levee
Pleasant Grove Creek Canal (PGCC) West Levee
4 GOVERNING STANDARDS
Methodology for conducting seismic vulnerability evaluation of levees is governed by design criteria developed by the California Department of Water Resources (DWR). Relevant publications that will be the primary source for Kleinfelder’s analysis includes:
• Urban Levee Design Criteria (ULDC, 2012) “Section 7.7 – Seismic Vulnerability” • Urban Levee Evaluations Project Guidance Document for Geotechnical Analysis (ULE, 2015), DWR and URS, “Section 6.0 – Seismic Analysis” - included as Attachment 3 Additionally, ground motion parameter development for evaluations is governed by applicable US Army Corps of Engineer’s Regulations and Manuals (ER & EM). Design guidance applicable to the seismic evaluation includes:
• Engineering Manual (EM) 1110-2-1913 (April 2000, USACE) “Design and Construction of Levees” 24001006.001A/SAC24M163970 Page 3 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 • Engineer Regulation (ER) 1110-2-1806 (May 2016, USACE) “Earthquake Design and Evaluation for Civil Works Projects”
• Engineering and Design Technical Letter (ETL) 1110-2-580 (March 2013, USACE) “Guidelines for Seismic Evaluation of Levees”
5 SESIMIC VULNERABILITY EVALUATION WORKFLOW
An overview of the seismic vulnerability evaluation workflow is shown on Attachment 2. The seismic vulnerability evaluation workflow was adapted from the DWR seismic vulnerability evaluation as a part of the DWR ULDC Guidance Document included as Attachment 3. Three stages of evaluation are identified as:

1. Preliminary Work

2. Phase 1: Screening Review of Existing Analysis

3. Phase 2: Targeted Evaluation
Each stage is discussed in greater detail in the sections below.

5.1 Preliminary Work and Methodology for Developing New Peak Ground Accelerations The existing geotechnical analysis and subsurface data will be reviewed to identify the seismic segments.

During this process, any data gaps will be identified, and an updated peak ground acceleration (PGA) and earthquake magnitude will be established.

5.1.1 Existing Ground Motion Data
Previous development of ground motion parameters in the area was performed by URS in 2007 as part of the Delta Risk Management Strategy (DRMS), which was updated and expanded on in 2012 by URS as part of the Department of Water Resources’ (DWR) Urban Levee Evaluation (ULE) project. A 200-year return period seismic hazard map was developed for the ULE area, which encompasses the ULDC area.

The probabilistic seismic hazard analysis performed for the ULE area was based on the UCERF2 seismic source characterization. The ground motion parameters developed by URS consisted of peak horizontal acceleration for soil/rock condition at a depth of 300 feet below the ground surface. In addition, associated earthquake magnitude was also estimated.

For this project the source characterization by others will be reviewed, where high-quality peer reviewed seismic source models are available. This will include studies performed by the United States Geological Survey applicable to the project region (e.g. Petersen et al. 2014, 2019), statewide studies performed as part of the third Uniform California Earthquake Rupture Forecast (UCERF3 - Field et al., 2013). It is expected the UCERF3 characterization will be primarily used for this project due to its wide adoption in other work and for consistency with the deprecated UCERF2 model used in previous work by URS. Additionally, Petersen et al. (2014, 2019) models will be used for far-field seismic sources outside of California (e.g. Cascadia, etc.)
24001006.001A/SAC24M163970 Page 4 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Analysis performed by URS in 2012 for ULE identified several potential seismic sources in the area that were not included in the UCERF2 model (i.e. Northern Midland fault zone). The UCERF3 model will be evaluated for inclusion of these sources.

Following evaluation of existing design ground motion data, segments of levee with either non-existent or out-of-date seismic data will be analyzed according to procedures described below.

5.1.2 Probabilistic Seismic Hazard Analysis (PSHA)
The PSHA approach that will be used to estimate the ground motion parameters (typically peak ground and spectral ground accelerations) is generally consistent with requirements of ULDC, with some modifications in implementation based on current standards of practice for probabilistic evaluations in California (e.g. “Grand Inversion” approach). The probabilistic approach is used in place of a deterministic approach as permitted by ER 1110-2-1806 §7d.

A site-specific PSHA is a useful tool in the evaluation of the potential ground motion hazard at a site. The model generally includes a representative seismic source model (such as geometry, style of faulting, magnitude, etc.), appropriate recurrence relationships, and appropriate ground motion models (aka. attenuation relationships). Modifications to the standard approach can also incorporate site-specific evaluation of site effects such as amplification. The model can be used to quantify the potential for strong ground shaking at a site. The hazard results are typically interpreted at a given earthquake return period to provide an equal or uniform hazard spectrum (UHS) for use in design.

The PSHA uses a logic tree approach to account for epistemic uncertainty in the model, with aleatoric variability accounted for in the uncertainty associated with various models (e.g. GMM’s). The logic tree is developed to account for uncertainties in the source models, ground motion models, and other items impacting the results. Important source characteristics include slip rates and fault lengths, magnitude and recurrence intervals of potential seismic events, distance from the site to the causative source, and other parameters. The effects of site soil conditions, and other considerations such as basin effects, can be accounted for using ground motion models (GMMs).

The theory behind the probabilistic approach to seismic risk analysis has been developed over many years (Cornell, 1968, 1971; Merz and Cornell, 1973; SSHAC, 1997), and is based on the "total probability theorem". Generally, this work uses an assumption that earthquakes are events that are independent of time and space from one another (e.g. time independent models). According to this approach, the probability of exceedance PE(z) at a given level of ground motion, z, at the site within a specified time period, t, is related to the annual frequency of exceedance v(z) by:

𝑃𝐸
(𝑧) = 1 −𝑒𝑥𝑝 𝑒𝑥𝑝 (−𝑣(𝑧) ∗ 𝑡)
Different probabilities of exceedance may be selected, depending on the level of performance required.

The return period is essentially equivalent to the reciprocal of v(z).

The PSHA is conducted using three generalized steps that include the following. 24001006.001A/SAC24M163970 Page 5 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701

1. Development of an appropriate seismic source model including source characterization, development of recurrence relationships, and appropriately capturing uncertainty

2. Selection of appropriate ground motion models (and site amplification models, if appropriate)

3. Conducting the calculation and processing the results The annual frequency of exceedance of a certain ground motion level can be found by summing the rates for all sources, N, with the rate for each source determined by summing over all magnitudes and source to site distances, and so forth. The annual frequency of occurrence of earthquakes of magnitude, mi, on seismic source, n, is λ(mi). The probability of an earthquake of magnitude, mi, on source, n, occurring at a certain distance, rj, from the site is P(R = rj | mi) while the probability that the ground motion level, z, will be exceeded is given as P(Z>z | mi,rj). Thus, mathematically the basic formulation for the annual frequency of exceedance, v(z), is given by (EM 1110-2-6050):
𝑣(𝑧) = ∑
𝑁
[ ∑
𝑀
𝜆(𝑚𝑖
) ∗ ∑
𝑅
𝑃(𝑚𝑖
) ∗ 𝑃(𝑚𝑖
, 𝑟𝑗)]
Modern computers make the above calculation, while computationally expensive, easily implementable at most sites. We will use the computer program HAZ (Powers, 2017) for our probabilistic analysis, which implements the above general equation. Uncertainties are accounted for within the source model using a logic tree approach and using multiple models, where appropriate.

5.1.3 Seismic Source Model
The seismic source model for a site contains all information required to characterize potential seismic sources for use in evaluation of ground motion parameters. The source model typically includes information on the geometry (e.g. length, dip, depth, etc.), style of faulting, magnitude, and recurrence relationships for all potentially active seismic sources within a distance capable of significantly impacting a site. The source model used for this work is discussed below.

5.1.4 ‘Grand Inversion’ and Recurrence Rates
The earthquake recurrence rates used in the source model will be adopted as developed by the UCERF3 project, as implemented by Petersen et al. (2019) using the branch-averaged solutions of the ‘grand inversion’. This is a departure from the older standard of practice documented in EM 1110-2-6053 and Draft EM 1110-2-6000, which solves for the entire system of faults within California simultaneously.

The ‘grand inversion’ scheme developed by the UCERF3 project team, the results of which will be adopted in this work, ‘solved’ the on-fault and off-fault recurrence rates at a system level using a set of defined constraints including the spatial probability density of off-fault seismicity, slip rate balancing, paleoseismic even rate matching, fault smoothness constraint, regional magnitude frequency distribution constraints, and fault section specific magnitude frequency distribution constraints. In simple terms the ‘grand inversion’ solves for three things: large on-fault (supra-seismogenic) event rates; small, near-fault (subseismogenic) event rates; and truly off-fault (unassociated) event rates. The 24001006.001A/SAC24M163970 Page 6 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 supra-seismogenic ‘on-fault’ events are ultimately modeled using linear fault sources while the latter two categories (subseismogenic and off-fault) are considered ‘background seismicity’ and are modeled using spatially smoothed ‘grid’ of evenly spaced cells (a.k.a. gridded seismicity). The combined on-fault and off-fault solution set (fault system solution) used the logic tree solution framework shown in a generalized form on Attachment 4. Our model implements the branch-averaged solutions.

The on-fault seismicity considers two potential alternative fault models, equally weighted, identified as fault model 3.1 (FM 3.1) and fault model 3.2 (FM 3.2). These fault models each contain a slightly different collections of fault traces that are broken into ‘segments’ for modeling purposes, with individual segments strung together during evaluation to create hundreds of thousands of potential fault-based ruptures or multi-rupture events. In our model, fault segments are modeled with the recurrence rates constrained during the ‘grand inversion’ by the UCERF2 ‘characteristic’ inversion branch (e.g. Schwartz and Coppersmith, 1984). Fault slip rates (deformations) are constrained by a combination of a ‘pure’ geologic deformation model and three other models that consider geologic and geodetic data including the average fault block model, NewKinema model, and Zeng-Shen model. The magnitude-area relationships used along with the associated slip-length models, as well as other solution constraints applied, are shown with weights on Attachment 4 and are discussed in detail in Field et al. (2013) and associated publications.

Off-fault seismicity (e.g. background seismicity) recurrence rates are solved for simultaneously by the ‘grand inversion’. This off-fault background seismicity is intended to include all smaller earthquakes (Mw<~6.5) on major faults and earthquakes of all sizes that are not associated with known faults. The off-fault background seismicity considers spatial smoothing of a ‘grid’ of evenly spaced cells using the spatial probability density function (PDF) grids of off-fault seismicity from UCERF2 and UCERF3 (equally weighted), considering the regional constraints on the model including the total regional magnitudefrequency distribution (e.g. Gutenberg-Richter distribution), maximum off-fault magnitude, number of regional events per year greater than Magnitude 5, and other constraints as shown on the logic tree (see Attachment 4). The branch-averaged, gridded seismicity solution for each fault model, as implemented by Petersen et al. (2019), was used in the source model for this work.

We note that the catalog used in this work was not updated in 2019, as re-evaluation of the grand inversion scheme requires a supercomputer. However, the USGS reviewed the catalog used for UCERF3 and concluded that the addition of recent historical events to the catalog is not needed at this time, as the additional historical events in the last half decade typically will not significantly change the model results, with changes generally small, localized, and often near active faults, and thus already adequately modeled (Petersen et al., 2019).

5.1.5 Ground Motion Model’s (GMM’s)
This study makes use of response spectral attenuation relationships, also known as ground motion models (GMMs), in evaluations at the site as required by ER 1110-2-1806.

Site-specific ground motions can be influenced by the styles of faulting, magnitudes of the earthquakes, and local soil conditions. Other effects such as near-source or basin effects can also influence the ground motions. The GMM’s used to estimate ground motion from an earthquake source need to directly or 24001006.001A/SAC24M163970 Page 7 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 indirectly consider these effects. Many GMMs have been developed to estimate the variation of spectral acceleration with earthquake magnitude and distance from the site to the source of an earthquake.

We will use four of the Next Generation Attenuation (NGA) West 2 relationships including Abrahamson et al. (2014), Boore et al. (2014), Chiou and Youngs (2014), and Campbell and Bozorgnia (2014) with equal weights applied for all crustal faults (e.g. reverse, strike-slip, normal) included in the fault model.

The Idriss (2014) model has not been used as it is not valid at the larger distances used in this study (e.g. more than 150 km). The far-field subduction events (e.g. from Cascadia megathrust) were modeled using the relationships of Atkinson and Macias (2009), Abrahamson et al. (2016), and Zhao et al. (2006) with equal weights applied, except that for slab events the Atkinson and Macias (2009) relationship was excluded. Spectral acceleration values are obtained by averaging the individual hazard results. These GMM’s provide ‘mean’ (RotD50) values of ground motions associated with magnitude, distance, site soil conditions, and mechanism of faulting. The uncertainty in the predicted ground motion was taken into consideration by including a magnitude dependent standard error in the probabilistic analysis.

5.1.6 Control Points and Site Parameters
Evaluation of seismic hazard and model development for site specific studies is usually completed at a control point considered representative of a structure or facility. For this project, multiple control points along levee alignments will be considered for evaluation of seismic hazard for the levees associated with this project. Points along levee alignment are considered adequate as active faults are generally located at distance from the site, and thus, small differences due to control point location variation should be minimal. Spacing between control points will vary based on soil conditions and mapped accelerations, with maximum spacing of 1 km (3280 ft). The control points will be used in evaluation of distance terms (rx, rjb, rrup) required for the selected GMM’s.

The above GMMs also use a set of site parameters to account for site effects and basin effects. For the NGA West 2 relationships, these include the average shear wave velocity in the upper 100 feet (30 meters, e.g. VS30), the depth to a layer with a Vs value of 3,280 feet per second (1,000 meters per second, e.g. Z1.0), and the depth a layer with Vs value of 8,200 feet per second (2.5 km/s, e.g. Z2.5).

The value of VS30 will be evaluated based on data from previous reports. Ground motions will be evaluated at the ground surface and consider average or best estimate shear wave velocity profiles applicable to the levee under consideration, without modification to the ground motions due to soft clay and liquefied soil response. Z1.0 and Z2.5 will be developed considering various geologic factors and estimates from the NGA West 2 correlations to develop best estimate values.

5.2 PHASE 1: SCREENING REVIEW OF EXISTING ANALYSIS
The purpose of the screening process is to identify sections where original analyses are determined to be deficient, and sections where updated analyses indicate potential deformation where original analyses did not.

Sections determined to be non-critical for seismic performance will not be used in analyses or presented in report.
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KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Newly developed PGA’s for critical sections will be compared to PGA’s from previous reports. If the new PGA value and associated earthquake magnitude are lower than the original values and the original analysis is found to be adequate, no further analysis is required for that section. If the original analysis determined the section is not susceptible to deformation, no further analysis is required, unless new PGA and/or earthquake magnitude show significant liquefaction susceptibility. Additionally, if the section was found to be failing in Flow Failure or High Vulnerability based on original PGA and earthquake magnitude, no further analysis will be required.

5.3 PHASE 2: TARGETED EVALUATION
The purpose of targeted evaluation is to determine susceptibility to deformation based on updated parameters.

A targeted evaluation is required for critical sections under two conditions, as follows:

1. The new PGA and earthquake magnitude is less than or equal than the original PGA, the original analysis is determined to be inadequate, and the Flow Failure factor of safety (FOS) with original PGA is greater or equal to 1

2. The new PGA and/or earthquake magnitude is greater than the original PGA, the original analysis or conditions classify the section as low or moderate vulnerability, and the Flow Failure FOS with original PGA is greater than 1
If the targeted section meets ULDC criteria, no further analysis is required. If the section does not meet ULDC criteria, Flow Failure and deformation must be analyzed using new seismic values. Flow Failure FOS and deformation results will be presented in Kleinfelder’s report and used in the development of the Seismic Performance Summary Report and Post-Earthquake Remediation Plan. 6 METHODOLOGY FOR EVALUATING SEISMIC VULNERABILITY
Seismic vulnerability evaluation will follow the guidance provided in DWR Guidance Document (DWR and URS, 2015). High, Moderate, and Low Vulnerability classifications will be based on the seismic deformation estimates. As mentioned earlier, all sections classified as High Vulnerability in the Phase 1 and Phase 2 screening process will not be analyzed.

The following steps are involved in assessing seismic vulnerability, Step numbers are associated with Key Steps described in Figure 1, Table 6-1 of the DWR Guidance Document (DWR and URS, 2015); see Attachment 2 for the workflow chart.

1. Perform liquefaction analysis using revised PGA and earthquake magnitude values using URS spreadsheets to delineate zones of liquefaction.

Based on the results of liquefaction, identify any additional cross section for analysis. We will be using the cross sections already developed for our previous studies. 24001006.001A/SAC24M163970 Page 9 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
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2. For selected cross sections, estimate FOS against flow failure using residual strength for liquefiable materials and performing static slope stability analysis. If FOS is less than 1, the section is classified as “High Vulnerability” and no further analysis is needed.

If FOS against flow failure is greater than 1.3, section will be classified as “Low Vulnerability”, unless analysis for volumetric strain results in a higher vulnerability class.

Kleinfelder has previously performed extensive slope failure modeling along the levee alignments using SLOPE/W, a two-dimensional finite element computer modeling, a package included in the GEOSTUDIO software package, which is developed by Bentley Systems, Inc. It is anticipated that those models will be updated to the current version of GEOSTUDIO (2023.1.0) and utilized for Targeted Flow Failure analyses. New analyses may need to be developed on an as-needed basis. Idealized soil properties will be based on previous investigations and generalized parameters from DWR Guidance Document (DWR and URS, 2015). Water surface elevations for seismic flow failure analyses will be the higher of either average summer or average winter water surfaces, in accordance with DWR Guidance Document (DWR and URS 2015).

Slope failure analyses should consider all potential failure modes, including:
• Waterside and landside
• Deep and shallow
• Circular and wedge-shaped

3. If FOS against flow failure is between 1.0 and 1.3, a simplified seismic deformation analysis should be performed on the section. This involves computing a maximum horizontal seismic coefficient (Kmax) and performing a pseudo-static stability analysis using a horizontal seismic coefficient of 50% of the maximum value. This analysis will be performed using the same updated SLOPE/W models used in Step 2. If the resulting FOS is greater than 1.0, the section may be classified as “Low Vulnerability”.

Yield acceleration (Ky) values must then be estimated using pseudo-static analyses using the same SLOPE/W models used in Step 2. Yield acceleration is defined as the minimum horizontal acceleration resulting in a just-stable slope condition, i.e. FOS = 1.0. Yield acceleration should be developed for each potential failure mode.

A vertical Newmark-type deformation analysis should be performed based on the Kmax and Ky values determined above. The calculated Newmark displacement may be reduced by 30% for estimation of freeboard loss.

Volumetric settlement should be considered for sections with potentially liquefiable soils thicker than 20ft. Previous work performed by URS on ULE considered (N1)60-cs blow counts less than 15 as liquefiable and subject to volumetric settlement. This blow count criteria will be evaluated against new research and revised if necessary.
24001006.001A/SAC24M163970 Page 10 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Seismic vulnerability classification is determined by calculating freeboard loss as the sum of Newmark-type vertical deformation and volumetric settlement (if applicable). Freeboard loss is evaluated as a percentage of levee height (as measured from hinge point on the landside toe).

Engineering judgment should be used to determine damage to internal levee structures, and the seismic vulnerability class should be evaluated based on Table 6-1 from the DWR Guidance Document (URS and DWR, 2015) shown below.

Figure 1: Table 6-1 from DWR Guidance Document, Section 6.4

4. Advanced seismic deformation analyses as described in Attachment 2 are applicable only to frequently loaded levees and will not be considered for this analysis. 7 LIMITATIONS
This work was performed in a manner consistent with that level of care and skill ordinarily exercised by other members of Kleinfelder’s profession practicing in the same locality, under similar conditions and at the date the services are provided. The work performed was based on project information provided by client. Kleinfelder’s conclusions, opinions, and recommendations are based on a limited number of observations and data. It is possible that conditions could vary between or beyond the data evaluated.

Kleinfelder makes no other representation, guarantee, or warranty, express or implied, regarding the services, communication (oral or written), report, opinion, or instrument of service provided.

This report may be used only by the client and the registered design professional in responsible charge and only for the purposes stated for this specific engagement within a reasonable time from its issuance, but in no event later than two years from the date of the report.

Conclusions contained in this report are based on review of existing information referenced in this report and Kleinfelder’s present knowledge of the project. It is possible conditions could vary from that contained in those documents. If conditions are encountered that differ from those described herein, the client is responsible for ensuring that Kleinfelder is notified immediately so that we may reevaluate the conclusions of this report.
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KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 The scope of services was limited. It should be recognized that definition and evaluation of subsurface conditions are difficult. Judgments leading to conclusions and recommendations are generally made with incomplete knowledge of the subsurface conditions present due to the limitations of data from field studies. The conclusions of this assessment are based on the information presented herein.

Although risk can never be eliminated, more detailed and extensive studies yield more information, which may help understand and manage the level of risk.

All rivers, streams and lakes will flood eventually. This fact means that all levees will be called upon to combat floodwaters at some point. Levees reduce the risk of flooding. But no levee system can eliminate all risk of flooding. The term “certification” is not intended to provide a guarantee or warranty of the conditions of the levee or its performance and assumes the following 1) a certification by a registered professional engineer or other party does not constitute a warranty or guarantee of performance, expressed or implied; 2) certification of data is a statement that the data is accurate to the best of the certifier’s knowledge; and 3) certification of analyses is a statement that the analyses have been performed correctly and in accordance with sound engineering practices. A levee certification does not address or mitigate the inherent flood risk proposed to a particular community. 8 CLOSING
This seismic evaluation technical approach memorandum is for review by the subject project’s peer review panel for concurrence with the approach for the forthcoming site-specific ground motion hazard analysis. If you have questions regarding this memorandum or if we may be of further assistance, please contact the undersigned.

Sincerely,
KLEINFELDER, INC.

Ryan Hochstatter, EIT Zia Zafir, PE, GE
Staff Geotechnical Engineer Sr. Principal Geotechnical Engineer

ATTACHMENTS
Levee Systems and Component Levee Map
Seismic Workflow
Seismic Vulnerability Analysis – Key Steps (DWR Guidance Document, 2015, DWR and URS) UCERF3 Source Model Logic Tree
24001006.001A/SAC24M163970 Page 12 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
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REFERENCES
___________________________________________________________________________________ Abrahamson, N., Gregor, N., Addo, K. (2016). BC Hydro Ground Motion Prediction Equations for Subduction Earthquakes. Earthquake Spectra, Volume 32, Issue 1, pp. 23-44.

Abrahamson, N.A., Silva, W.J., and Kamai, R. (2014). “Summary of the ASK14 Ground Motion Relation for Active Crustal Regions.” Earthquake Spectra, Vol. 30, No. 3, pp. 1025-1056.

Atkinson, G.M., and Macias, M. (2009). Predicted Ground Motions for Great Interface Earthquakes in the Cascadia Subduction Zone. Bulletin of the Seismological Society of America, V. 99, No. 3, pp. 1552-1578.

Boore, D.M., Stewart, J.P., Seyhan, E., and Atkinson, G. (2014). “NGA-West2 Equations for Predicting PGA, PGV, and 5% damped PSA for Shallow Crustal Earthquakes.” Earthquake Spectra, Vol. 30, No. 3, pp. 1057-1086.

California Department of Water Resources (DWR) (2012). Urban Levee Design Criteria.

Campbell, K.W., and Bozorgnia, Y. (2014). “NGA-West2 Ground Motion Model for the Average Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra.” Earthquake Spectra, Vol. 30, No. 3, pp. 1087-1116.

Chiou, B S., and Youngs, R.R. (2014). “Update for the Chiou and Youngs NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra.” Earthquake Spectra, Vol. 30, No. 3, pp. 1117-1154.

Cornell, C.A. (1968). Engineering Seismic Risk Analysis, Bulletin of the Seismological Society of America, Vol. 58, No. 5.

Cornell, C.A. (1971). Probabilistic Analysis of Damage to Structures Under Seismic Loading, Dynamic Waves in Civil Engineering, London, Interscience.

Field, E.H., Biasi, G.P., Bird, P., Dawson, T.E., Felzer, K.R., Jackson, D.D., Johnson, K.M., Jordan, T.H., Madden, C., Michael, A.J., Milner, K.R., Page, M.T., Parsons, T., Powers, P.M., Shaw, B.E., Thatcher, W.R., Weldon, R.J., II, and Zeng, Y. (2013). The Uniform California Earthquake Rupture Forecast, Version 3 (UCERF 3), USGS Open File Report 2013-1165, CGS Special Report 228, Southern California Earthquake Center Publication 1792, http://pubs.usgs.gov/of/2013/1165/.

Idriss, I. M. (2014). “An NGA-West2 Empirical Model for Estimating the Horizontal Spectral Values Generated by Shallow Crustal Earthquakes.” Earthquake Spectra, Vol. 30, No. 3, pp. 1155-1177.

Merz, H.L. and Cornell, C.A. (1973). Seismic Risk Analysis Based on a Quadratic Magnitude-Frequency Law, Bulletin of the Seismological Society of America, Vol. 63, No. 6.

Petersen, M.D., Moschetti, M.P., Powers, P.M., Mueller, C.S., Haller, K.M., Frankel, A.D., Zeng, Yuehua, Rezaeian, Sanaz, Harmsen, S.C., Boyd, O.S., Field, Ned, Chen, Rui, Rukstales, K.S., Luco, Nico, Wheeler, R.L., Williams, R.A., and Olsen, A.H. (2014). Documentation for the 2014 Update of the United States National Seismic Hazard Maps, USGS Open-File Report 2014-1091, 243 p., https://dx.doi.org/10.3133/ofr20141091.

Petersen, M.D., Shumway, A.M., Powers, P.M., et al. (2019). The 2018 Update of the US National Seismic Hazard Model: Overview of Model and Implications, Earthquake Spectra, Volume 36, Issue 1, pp. 5-41.

Powers, P.M. (2017). National Seismic Hazard Model Project Computer Code (NSHMP-HAZ) Software, https://doi.org/10.5066/F7ZW1K31.
24001006.001A/SAC24M163970 Page 13 of 13 February 8, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Schwartz, D.P. and Coppersmith, K.J. (1984). Fault Behavior and Characteristic Earthquakes: Examples from the Wasatch and San Andreas Fault Zones, Journal of Geophysical Research, Vol. 89, pp. 5681-5698.

Senior Seismic Hazard Analysis Committee (SSHAC) (1997). Recommendations for Probabilistic Seismic Hazard Analysis: Guidance on Uncertainty and Use of Experts, U.S. Nuclear Regulatory Commission, Report No. CR-6372.

URS (2015b). “Guidance Document for Geotechnical Analyses, Urban Levee Geotechnical Evaluations Program, Contract 4600008101,” dated April 2015.

United States Army Corps of Engineers (USACE). (1999). Engineering Manual (EM) 1110-2-6050 “Response Spectra and Seismic Analysis of Concrete Hydraulic Structures.” USACE (2000). Engineering Manual (EM) 1110-2-1913 “Design and Construction of Levees.” USACE (2013). Engineering and Design Technical Letter (ETL) 1110-2-580 “Guidelines for Seismic Evaluation of Levees.”
USACE (2016). Engineer Regulation (ER) 1110-2-1806 “Earthquake Design and Evaluation for Civil Works Projects.”
Zhao et al. (2006). Attenuation Relations of Strong Ground Motion in Japan using Site Classification Based on Predominant Period. Bulletin of the Seismological Society of America, V. 96, No. 3, pp. 898-913.

Yolo
Bypass
Fremont
Weir
Sacramento
Weir
w
Natomas
Cross Canal
NEMDC
River
Natomas
Basin
American
h
Sacramento
[
Folsom
Lake
Folsom
Arcade
Creek
Roseville
Dry Creek
Mo
rris
on
Creek
Strawberry
Creek
Natomas Levees
Folsom Dam Joint Federal Project
(Auxiliary Spillway)
North Area
Streams Levees
South Sacramento
Streams Group Levees
American River
Levees
Sacramento River Levees
South of Confluence
Sacramento
River
tu50
|ÿ70
§¨¦I-80
|ÿ99
§¨¦I-5
|ÿ99
|ÿ160
§¨¦I-80
PLACER
COUNTY
SUTTER
COUNTY
:

Legend
Federal Project Leveeor StructureNon Project Levee
0 3.5 1.75
Scale in Miles
SAFCA Flood Control
System Features

KLEINFELDER SEISMIC RESPONSIBILITY REACH
North Beach Lake
Levee
ATTACHMENT B: Seismic Planning Services Responsibility Map Proposal For Geotechnical Engineer & Seismic Planning Services ULDC & FEMA Levee Certification Program
Sacramento Area Flood Control Agency Levee Systems
Sacramento and Sutter Counties, California
1 Figure
6-1
Seismic Vulnerability Analysis – Key Steps

URBAN LEVEE EVALUATIONS
Department of Water Resources
Division of Flood Management
Step 2: Perform Post-Seismic Stability Analysis
Step 3f: Calculate volumetric strain, if necessary
Step 3a: Compute Kmax using Figure 6-4
Step 3e: Estimate vertical deformation as 0.7 times total Newmark displacement
Step 3g: Assign seismic vulnerability class using Table 6-1 Step 3c: Compute Ky value for sliding mass
Step 3d: Compute Newmark displacement using Kmax, Ky, and Figure 6-5 Yes
Step 3b: Perform pseudo-static stability analysis using K=0.5 Kmax No
Classify as “Low Vulnerability” unless
Volumetric Strain (Step 3f ) results in a
higher vulnerability class
Is
FSPS < 1?
Yes
No
Perform post-seismic stability analysis
Continue to Step 3
No further analysis is needed.

Classify as “High Vulnerability”
Yes
No
Classify as “Low Vulnerability” unless
Volumetric Strain (Step 3f ) results in a
higher vulnerability class
Is
FSPS > 1.3?
Is
FS ≥1?
Step 4: If Warranted, Perform More Advanced Seismic Deformation Analysis (See Section 6.11) Step 3: Perform Simplified Seismic Deformation Analysis Evaluate and document longitudinal extent of liquefiable soils Select seismic levee segments and engineering cross-sections for seismic stability and deformation analyses
Step 1: Select Seismic Segments and Cross Sections for Seismic Vulnerability Analyses SEISMIC VULNERABILITY – KEY STEPS (INTERMITTENTLY-LOADED LEVEES) G:\DWR-7418\Project Files\TASK AREAS\General\GeotechAnalysis\GuidanceDocument\Final\Figures\Fig 6-1 Seismic Vulnerability.indd Attachment
3 24001006.001A/SAC24R164096 Page B-1 February 12, 2024 © 2024 Kleinfelder

APPENDIX B

GROUND MOTION PARAMETER SELECTION MEMORANDUM
_____________________________________________________________________ 24001006.001A/SAC23M158525_R2 Page 1 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701

GROUND MOTION PARAMETER SELECTION MEMORANDUM
DATE: February 9, 2024
TO: Mr. Pete Ghelfi, PE
Director of Engineering
Sacramento Area Flood Control Agency
1325 J Street, Suite 1700
Sacramento, CA 95814
FROM: Ryan Hochstatter, EIT
Zia Zafir, PhD, PE, GE
SUBJECT: Revised Seismic Evaluation Ground Motion Parameter Selection Memorandum ULDC & FEMA Levee Certification Project
Sacramento Area Flood Control Agency Levee Systems
Sacramento and Sutter Counties, California
____________________________________________________________________________

INTRODUCTION
This technical memorandum presents the regional ground motion hazard analysis (GMHA) approach and inputs, including the development of peak horizontal acceleration (PHA) and design response spectral values to support the seismic vulnerability evaluation of levees located in the Sacramento Area of California consistent with the requirements of the Urban Levee Design Criteria (DWR, 2012).

This memorandum has been prepared consistent with the requirements of the approved scope of work for the subject project outlined in our proposal dated May 5, 2023, as well the GMHA methodology described in our Seismic Evaluation Technical Approach Memorandum dated September 5th, 2023.

PURPOSE
Sacramento Area Flood Control Agency (SAFCA) is working with a team of consultants to obtain ULDC and Federal Emergency Management Agency (FEMA) certifications for the Sacramento area levees. The purpose of this document is to provide ground motions in terms of peak horizontal acceleration (PHA) based on the new seismic sources and ground motion models. Development of ground motions follow the methodology presented in our Technical Approach Memorandum dated September 5, 2023.

The levees will be organized by selection of “sections” instead of reaches due to the variable nature of subsurface conditions under levees. Sections may overlap multiple reaches or reaches may be subdivided into multiple sections. Note that for sections encompassing or divided by roadway overcrossings, the overcrossings will be simplified to their centerlines, and additional improvements to the levee for overcrossing abutments will be neglected. 24001006.001A/SAC23M158525_R2 Page 2 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
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PROJECT FEATURES
Figure 1 shows the following levee systems and their associated component levees. The levee systems are summarized in Table 1 below.

Table 1
Levee Systems and Component Levees
Levee System Reach
1 - Dry Creek Dry Creek North Levee
2 - Robla-Arcade
Dry Creek South / Robla Levee
Natomas East Main Drainage Canal (NEMDC) East Levee - Robla to Arcade Creek Arcade Creek North Levee
3 - American
North
Arcade Creek South Levee
NEMDC East Levee - Arcade Creek to American River
American River North Levee
4 - American
South
American River South Levee
Sacramento River East Levee (SREL) -American River to NBLL North Beach Lake Levee
5 - Natomas
Basin
Natomas Cross Canal South Levee (NCC)
SREL - NCC to Powerline Road
SREL - Powerline Road to American River
American River North Levee - Sacramento River to NEMDC
NEMDC West Levee
Pleasant Grove Creek Canal (PGCC) West Levee

GOVERNING STANDARDS
Methodology for conducting seismic vulnerability evaluation of levees is governed by design criteria developed by the California Department of Water Resources (DWR). Relevant publications that will be the primary source for Kleinfelder’s analysis includes:
• Urban Levee Design Criteria (ULDC, 2012) “Section 7.7 – Seismic Vulnerability” • Urban Levee Evaluations Project Guidance Document for Geotechnical Analysis (ULE, 2015), DWR and URS, “Section 6.0 – Seismic Analysis”
Additionally, ground motion parameter development for evaluations is governed by applicable US Army Corps of Engineer’s Regulations and Manuals (ER & EM). Design guidance applicable to the seismic evaluation includes:
• Engineering Manual (EM) 1110-2-1913 (April 2000, USACE) “Design and Construction of Levees” • Engineer Regulation (ER) 1110-2-1806 (May 2016, USACE) “Earthquake Design and Evaluation for Civil Works Projects”
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KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 • Engineering and Design Technical Letter (ETL) 1110-2-580 (March 2013, USACE) “Guidelines for Seismic Evaluation of Levees”

SEISMIC SOURCE INPUTS
General
Site characterization was completed in general accordance with ER 1110-2-1806 §8. In general, this includes characterization of the topographic, hydrologic, and geologic/stratigraphic characteristics of the site and the associated engineering properties as needed for seismic evaluations.

Regional Setting
The regional setting is used in developing seismic source models and informs the interpretation of local geology. The regional setting includes discussion of the regional geology and stratigraphy, seismotectonic setting, faulting and fault rupture, and historic seismicity. Details are discussed below.

Regional Geologic Setting
The study area is located within the southern portion of the Sacramento Valley, within the Great Valley geomorphic province. The Great Valley province is a north-south trending 400-mile by 50-mile long alluvial plain in central California comprised of the Sacramento Valley in the north and the San Joaquin Valley in the south. The Sacramento Valley contains thousands of feet of accumulated fluvial, overbank, and alluvial fan deposits derived from erosion of the adjacent Sierra Nevada mountains to the east, northern Coast Range mountains to the west, and Klamath and Cascade mountains to the north. These deposits are primarily comprised of Quaternary and Tertiary age (present day to 56 million years ago) alluvial deposits and include clays, silts, sands, and gravels. The alluvial deposits thin out at the margins of the Great Valley Province, exposing underlying bedrock units. The Foothills Metamorphic Belt and the basement complex of the Sierra Nevada Batholith to the east are exposed along the eastern boundary of the valley. Sedimentary and mélange bedrock of the northern Coast Range mountains are exposed to the west. Meta-sedimentary, mélange, igneous, and volcanic bedrock of the Klamath and Cascade mountains are exposed to the north.

The study area has been regionally mapped by a number of geologists. These include published maps by Wagner et al. (1981), Helley and Harwood (1985), Gutierrez, C.I. (2011), and Fugro William Lettis & Associates (FWLA, 2010). Wagner et al. (1981) provides the most regional context but very little detail relative to the project area. Helley and Harwood mapping (performed at a scale of 1:62,500) focuses on Quaternary geologic units based on geomorphology. Gutierrez, C.I. (2011) is the most recent map of the study area and provides more current regional geologic mapping relative to Helley and Harwood (1985).

Fugro William Lettis & Associates (FWLA, 2010) provides more detailed surficial Quaternary deposits.

The project area is shown on Wagner D. L. (1981) on Figure 1.

Subsurface Stratigraphy at Depth
The Great Valley geomorphic province is characterized as an elongated low-lying basin through central California filled with thousands of feet of sediment. The Great Valley province is situated on the remnants of the Jurassic age forearc basin of the Pacific Plate subducting under the North American Plate. The forearc basin is a regional and asymmetrical feature with the western portion being deepest 24001006.001A/SAC23M158525_R2 Page 4 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 (Harwood and Helley, 1987). The sediment within the basin is referred to collectively as the Great Valley Sequence, comprised of present day to Eocene age alluvial deposits. Underlying the Great Valley Sequence are Cretaceous age marine sedimentary rocks such as shales and sandstones. Underlying the marine sedimentary rocks is an ophiolite suite which is typically comprised of ultramafic (i.e. periodite and dunite) to mafic rocks (i.e. gabbro and basalt) overlain by shale and chert (Harden 1998).

Seismotectonic Setting
The site is located in the Western United States (WUS) in the transform plate boundary region between the Pacific Plate (transitioning northwest) and the North American Plate (see Figure 4). The site lies within the Sierra Nevada-Great Valley block (a.k.a., the Sierra Nevada microplate, or SNGV) which generally is thought to act as an independent block that has ‘tilted’ westward. The SNGV block is bounded on its eastern edge by a zone of faults known as the Walker Lane Belt, beyond which is the crustal extensional region of the Northern Basin and Range. Further afield in the northwestern portion of the state and extending northward to the pacific northwest, the Juan de Fuca plate is currently subducting below the North American plate in a region known as the Cascadia Subduction Zone (Humphreys and Coblentz, 2007; Unruh and Humphrey, 2003, 2017).

Regional stress build-up due to the northwestern movement of the Pacific Plate is primarily released through displacement along faults within the San Andreas fault system (e.g. San Andreas fault, Hayward fault, etc.) and to a lesser extent by displacements along faults within the Walker Lane Belt. Crustal extension of the Northern Basin and Range has led to the development of stress in the east-west direction and caused development of an extensive system of faults within the Northern Basin and Range (Fey and Humphreys, 2008; Field et al., 2013).

Faults and Fault Rupture
Regional faulting and potential for fault rupture directly impact the potential sources of seismicity and thus the seismic risk at a site. For this study, Quaternary age faults (considered potentially seismically active) were reviewed consistent with the recommendations of EM 1110-2-1806. Based on our review, a number of Quaternary and older faults were identified as shown on Figure 3, with select Quaternary faults within 100 km1of the site listed in Table 2. Detailed discussion of faulting and potential for fault rupture is provided below.

The closest potentially active system to the site is the Great Valley fault system which lies to the west of the site. The closest segments of the Great Valley system include the Midland fault2located roughly 30 km to the southwest of the site (DWR, 2007; Unruh and Hitchcock, 2009), and the Dunnigan Hills3thrust fault which lies to the west-northwest (Jennings and Bryant, 2010; Parrish, 2018). Other significant active faults to the west of the site include faults within the San Andreas system (San Andreas fault, Hayward fault, Calaveras fault, etc.). East of the site, the active fault systems include the Foothills fault system (Paynes Peak fault, Spenceville fault, Maidu East fault, etc.) and a series of strike-slip and normal 1 A 100 km distance was used in the table for consistency with the distance to which more detailed seismic source characterization was completed, see Section 3.3 for details.
2 The Midland fault zones northern extension consists of somewhat complex geometry in the vicinity of Rio Vista and northward. Detailed geometry not shown in this report, see Unruh and Hitchcock (2009) for details. 3 The Dunnigan Hills (aka. Zamora Fault) is mapped by some researchers along the northeastern edge of the Dunnigan Hills (Harwood and Helley, 1987; USGS and CGS, 2006). However, the active fault has more recently been mapped to the southwest by Parrish (2018) and others and is considered more appropriate for evaluation of active and potentially active portion of the fault in this study. 24001006.001A/SAC23M158525_R2 Page 5 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 faults in and around the Tahoe region, as well as faults associated with crustal extension of the Northwestern Basin and Range. Much further afield, the Cascadia subduction zone (northwest corner of the state) can generate very large magnitude events and may have the potential to impact long-period ground motions at the site.

There are a series of older faults and folds that underlie the central part of the Great Valley and include the possible southeastern extension of the Willows fault and the Stockton fault. The Willows and Stockton faults are generally accepted to be seismically inactive, with deformation along the southern end of the Willows fault (closest fault to the site) considered to be older than about 3.4 million years (Harwood and Helley, 1987). Along the western edge of the Sacramento Valley, the Thornton Arch4as well as the East and West Valley faults are, likewise, considered seismically inactive with the most recent activity generally considered pre-quaternary in age (Jennings and Bryant, 2010; Parrish, 2018). These inactive faults are not considered to be significant to hazard potential at the site and thus are not listed in Table 2 although they are shown on Figure 3 for completeness.

Table 2
Potentially Active or Active Quaternary Age or Younger Faults Within 125 Km of Site Name Name Name
Alexander fault Greenville fault Poorman Gulch fault
Antioch fault Haupt Creek fault Pope Creek fault
Ashland fault Hayward fault Putah Creek
Bad Ridge fault Highway 49 fault Putah Creek fault
Bartlett Springs fault zone Hunting Creek fault Red Road fault Bennett Valley fault Hunting fault Redwood Hill fault
Black Butte fault Ione fault Rescue fault
Bowie Flat fault Kennedy fault Resort fault
Burdell Mountain fault Kirby Hills fault Rio Vista fault Calaveras fault Konocti Bay fault Rodgers Creek fault
Carnegie fault Lagoon Valley fault San Joaquin fault
Chabot fault Lakeview fault Sherburne Hills thrust fault Chico Monocline fault Little Indian Valley fault Soda Creek fault Clayton fault Livermore fault Southampton fault
Cleveland Hill fault Los Positas fault Spenceville fault Clover Valley fault Maacama fault Swain Ravine fault
Cobb Mountain fault Maidu East fault Tolay fault
Concord fault Marsh Creek fault unnamed
Cordelia fault Maxwell Creek fault Vaca fault
Corning fault Midland fault Vernalis fault
Corral Hollow fault Midway fault Verona fault
Cross Spring fault Mill Valley fault Waters Peak fault
Deadman fault Miller Creek fault West Napa fault
4 Previous studies by the California Department of Water Resources (DWR, 2007) have considered possible activity (probability of activity of 20 percent) along the Thornton Arch. However, Jennings and Bryant (2010) and other more recent studies by the various researchers have not considered this feature to be potentially active.
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KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Name Name Name
Dewitt fault Mocho fault Wildcat fault
Dunnigan Hills fault Moraga fault Williams fault
Franklin fault Northern Calaveras fault Wilson fault
Giant Gap fault Paynes Peak fault Youngs Creek fault
Green Springs Run fault Pinole fault
Green Valley fault Pleasanton fault
Notes:

Refer to Figure 3 for relative fault distances from project.

Historic Seismicity
One of the major factors for evaluation of seismic hazard is the historic record of seismicity. Patterns of historic seismicity can be used to identify known or inferred impacts of historical seismicity on a project.

Catalogs of historic seismicity are also used to characterize seismic sources in models such as those developed by Field et al. (2013) and others. This section discusses regional historic seismicity.

Kleinfelder compiled and reviewed data from the USGS ANSS Comprehensive Earthquake Catalog, known as ComCat, which contains historical seismic data compiled by the USGS from multiple sources. A search radius of 300 km centered on the site was used and yielded a record covering the years from 1808 to 2019.

Based on review of this data, the closest seismic events to the site are a set of minor events (Mw < 4) that occurred in 2002 located about 15 to 16 km northwest of the site. Another minor event occurred in 2003 located about 16 km to the southeast of the site. These events constitute the only recorded seismicity in the near-field vicinity (e.g. within about 15km) of the site and are small enough not to be of engineering significance.

More significant historic seismicity has been observed along some of the nearby active faults (see Figure 3). Historical seismicity along the Great Valley thrust fault system includes a cluster of low magnitude events near the south end of the Dunnigan Hills section. Other events along the Great Valley system include the 1892 (~Mw6.6) Vacaville-Winters sequence near the Gordon Valley section and the 1892 (Mw5.5) event near the Midland Fault (Unruh and Moores, 1992; USGS, 2019). The foothills fault system has also historically been active, with a large number of earthquakes observed near Oroville Dam (possibly reservoir induced seismicity) and significant micro-seismicity reported between Oroville and Folsom reservoirs, particularly near the Rocklin-Penryn pluton (e.g. Cramer et al, 1978).

Far-field events include a number of significant large earthquakes including the 1868 (Mw7.0) Hayward earthquake, the 1906 (Mw7.8) “Great” San Francisco earthquake, the 2014 (Mw6.0) South Napa earthquake, the 1838 (Mw7.4) San Francisco Peninsula earthquake, the 1865 (Mw6.5) Santa Cruz Mountains earthquake, and the 1989 (Mw6.9) Loma Prieta earthquake. These events are located on faults within the San Andreas fault system (Hayward, San Andreas, etc.). Review of the historic records indicates only minor impacts or damage from these events in the Sacramento region.

Intensity values such as Modified Mercalli Intensity (MMI) tend to provide an indication of the effect of historic seismicity on people and buildings and are useful in measuring the significance of events at a site. MMI values in this study were estimated using the relationship of Atkinson et al. (2014). The majority of the historic earthquake event data used in the evaluation was obtained from the USGS 24001006.001A/SAC23M158525_R2 Page 7 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 National Seismic Hazard Map project de-clustered earthquake catalog (e.g. Petersen et al. 2014). A table of historically significant seismic events, based on MMI, is provided below in Table 3. The most significant events impacting the site from this evaluation are highlighted in bold. These include the 1892 Vacaville-Winters sequence (e.g. Great Valley fault system) and the 1906 “Great” San Francisco earthquake (e.g. San Andreas fault system).

The estimated MMI values were checked against historic data for select events. For a recent event, the MMI reported by the USGS from observations for the South Napa event was 3.5 and is consistent with the estimated MMI. Some older events have reported MMI values as high as VI to VII based on record review by the California Geological Survey (CGS, Historic Earthquake Online Database, accessed 2020).

However, it is likely that these higher MMI values are influenced by lower quality of construction generally prevalent at the time.

Table 3
Select and Significant Historic Earthquakes and
Estimated Historical Impact Potential Using MMI
Magnitude
(Mw)
Event Date Event Name/Location4
Estimated
MMI1,2

7.4 6/1/1838 San Francisco Peninsula IV

7.3 1/1/1852 Pyramid Lake IV

7.9 1/9/1857 Great Fort Tejon IV

7.0 10/21/1868 Hayward IV

6.0 5/19/1889 Near Collinsville IV

6.6 4/19/1892 Vacaville-Winters Earthquake V

6.4 3/31/1898 Mare Island IV

7.8 4/18/1906 “Great” San Francisco V

6.9 10/18/1989 Loma Prieta IV

6.0 8/24/2014 South Napa3IV
Notes:

1. Approx. Modified Mercalli Intensity (MMI) developed using procedure of Atkinson et al. (2014).

2. MMI – IV- Light Shaking; V – Moderate Shaking; VI – Strong Shaking; VII – Very Strong Shaking; VIII – Severe Shaking; IX – Violent Shaking; X – Extreme Shaking (USGS.gov accessed 2020)

3. 2014 Napa earthquakes data from USGS earthquake hazards program (https://earthquake.usgs.gov/ earthquakes/eventpage/nc72282711/executive).

4. Some events including Santa Cruz Mountains earthquake (1865), induced seismicity sequence near Oroville, and microseismicity, etc. not listed due to low impact/magnitude.

GMHA IMPLEMENTATION
To be consistent with previous work performed by URS and DWR for the Urban Levee Evaluations (ULE) project, the probabilistic seismic hazard analysis (PSHA) approach was selected to perform the GMHA for this study and estimate the ground motion parameters (typically peak ground and spectral accelerations), with some modifications in implementation based on current standards of practice for probabilistic evaluations in California (e.g., “Grand Inversion” approach). Only the probabilistic approach is used, which is consistent with requirements of ULDC, and as permitted by ER 1110-2-1806 §7d. 24001006.001A/SAC23M158525_R2 Page 8 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Existing Ground Motion Data
Previous development of ground motion parameters in the area was performed by URS in 2007 as part of the Delta Risk Management Strategy (DRMS), which was updated and expanded on in 2012 by URS as part of the Department of Water Resources’ (DWR) Urban Levee Evaluation (ULE) project. A 200-year return period seismic hazard map was developed for the ULE area, which encompasses the ULDC area.

The probabilistic seismic hazard analysis performed for the ULE area was based on the UCERF2 seismic source characterization. The ground motion parameters developed by URS consisted of peak horizontal acceleration for stiff soil condition where Vs30 was taken as 335 m/s (1100 ft/s), which typically occurs depths of 100 to 120 feet below the ground surface. In addition, associated earthquake magnitude was also estimated.

For this project the source characterization by others will be reviewed, where high-quality peer reviewed seismic source models are available. This will include studies performed by the United States Geological Survey applicable to the project region (e.g. Petersen et al. 2014, 2019), statewide studies performed as part of the third Uniform California Earthquake Rupture Forecast (UCERF3 - Field et al., 2013). It is expected the UCERF3 characterization will be primarily used for this project due to its wide adoption in other work and for consistency with the deprecated UCERF2 model used in previous work by URS. Additionally, Petersen et al. (2014, 2019) models will be used for far-field seismic sources outside of California (e.g. Cascadia, etc.)
Analysis performed by URS in 2012 for ULE identified several potential seismic sources in the area that were not included in the UCERF2 model (i.e. Northern Midland fault zone). The UCERF3 model will be evaluated for inclusion of these sources.

Following evaluation of existing design ground motion data, segments of levee with either non-existent or out-of-date seismic data will be analyzed according to procedures described below.

Probabilistic Seismic Hazard Analysis (PSHA)
The PSHA approach that will be used to estimate the ground motion parameters (typically peak ground and spectral ground accelerations) is generally consistent with requirements of ULDC, with some modifications in implementation based on current standards of practice for probabilistic evaluations in California (e.g. “Grand Inversion” approach). The probabilistic approach is used in place of a deterministic approach as permitted by ER 1110-2-1806 §7d.

A site-specific PSHA is a useful tool in the evaluation of the potential ground motion hazard at a site. The model generally includes a representative seismic source model (such as geometry, style of faulting, magnitude, etc.), appropriate recurrence relationships, and appropriate ground motion models (aka. attenuation relationships). Modifications to the standard approach can also incorporate site-specific evaluation of site effects such as amplification. The model can be used to quantify the potential for strong ground shaking at a site. The hazard results are typically interpreted at a given earthquake return period to provide an equal or uniform hazard spectrum (UHS) for use in design.

The PSHA uses a logic tree approach to account for epistemic uncertainty in the model, with aleatoric variability accounted for in the uncertainty associated with various models (e.g. GMM’s). The logic tree 24001006.001A/SAC23M158525_R2 Page 9 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 is developed to account for uncertainties in the source models, ground motion models, and other items impacting the results. Important source characteristics include slip rates and fault lengths, magnitude and recurrence intervals of potential seismic events, distance from the site to the causative source, and other parameters. The effects of site soil conditions, and other considerations such as basin effects, can be accounted for using ground motion models (GMMs).

The theory behind the probabilistic approach to seismic risk analysis has been developed over many years (Cornell, 1968, 1971; Merz and Cornell, 1973; SSHAC, 1997), and is based on the "total probability theorem". Generally, this work uses an assumption that earthquakes are events that are independent of time and space from one another (e.g. time independent models). According to this approach, the probability of exceedance PE(z) at a given level of ground motion, z, at the site within a specified time period, t, is related to the annual frequency of exceedance v(z) by:

𝑃𝐸
(𝑧) = 1 −𝑒𝑥𝑝 𝑒𝑥𝑝 (−𝑣(𝑧) ∗ 𝑡)
Different probabilities of exceedance may be selected, depending on the level of performance required.

The return period is essentially equivalent to the reciprocal of v(z).

The PSHA is conducted using three generalized steps that include the following.

1. Development of an appropriate seismic source model including source characterization, development of recurrence relationships, and appropriately capturing uncertainty

2. Selection of appropriate ground motion models (and site amplification models, if appropriate)

3. Conducting the calculation and processing the results The annual frequency of exceedance of a certain ground motion level can be found by summing the rates for all sources, N, with the rate for each source determined by summing over all magnitudes and source to site distances, and so forth. The annual frequency of occurrence of earthquakes of magnitude, mi, on seismic source, n, is λ(mi). The probability of an earthquake of magnitude, mi, on source, n, occurring at a certain distance, rj, from the site is P(R = rj | mi) while the probability that the ground motion level, z, will be exceeded is given as P(Z>z | mi,rj). Thus, mathematically the basic formulation for the annual frequency of exceedance, v(z), is given by (EM 1110-2-6050):
𝑣(𝑧) = ∑
𝑁
[ ∑
𝑀
𝜆(𝑚𝑖
) ∗ ∑
𝑅
𝑃(𝑚𝑖
) ∗ 𝑃(𝑚𝑖
, 𝑟𝑗)]
Modern computers make the above calculation, while computationally expensive, easily implementable at most sites. We will use the computer program HAZ (Powers, 2017) for our probabilistic analysis, which implements the above general equation. Uncertainties are accounted for within the source model using a logic tree approach and using multiple models, where appropriate. We note that HAZ does not currently provide the uncertainty bands (16th and 84th percentiles) and thus uncertainty bands will not be evaluated or presented.
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KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Seismic Source Model
The seismic source model for a site contains all information required to characterize potential seismic sources for use in evaluation of ground motion parameters. The source model typically includes information on the geometry (e.g. length, dip, depth, etc.), style of faulting, magnitude, and recurrence relationships for all potentially active seismic sources within a distance capable of significantly impacting a site. The source model used for this work is discussed below.

Detailed review of select nearby seismic sources was performed and included review of the Midland fault, Dunnigan Hills fault, Foothills fault system, and other nearby faults. Other faults are not discussed in detail, but discussion is available in the referenced literature:
• Midland fault - The Midland fault was not considered active by Petersen et al. (2008). However, DWR (2007) and follow on work by Unruh and Hitchcock (2009) conclusively showed ongoing activity along the Midland fault within the Sacramento-San Joaquin delta. The Midland fault was characterized by DWR (2007) using a source zone to represent the northern portion of the Midland fault zone, while other later studies (Merriam, 2012; Petersen et al. 2019, etc.) generally considered this source adequately characterized using a linear fault source, and that approach was considered appropriate for this study.
• Dunnigan Hills fault - Consideration of an alternative placement of the Dunnigan Hills fault (east of the Dunnigan Hills), as was done by Merriam (2012), was not considered justified based on available geologic data.
• Thornton Arch - The Thornton arch zone, a potential seismic source identified by DWR (2007), was not modeled as an independent source by most other studies. This study likewise does not explicitly consider this as a potentially active fault source based on the lack of significant folding of the overlying Miocene age continental rocks, leading to the conclusion that the structure is pre-Miocene (e.g. Harwood and Helley, 1987).
• Foothills system - The Foothills fault system (Swain Ravine fault, Spenceville fault, Dewitt fault, etc.) was modeled as a source zone by some studies or as a fault source in more recent work for UCERF3. The fault source approach and characterization of UCERF3 (e.g. Swain RavineSpenceville Fault) was adopted in this study. • Other minor faults: Other nearby, potentially active faults (e.g. Vernalis Fault, Rio Vista Fault, Black Butte fault, etc.) were generally not considered significant to the hazard at the site. These sources were not considered as independent seismogenic sources and were more appropriately modelled by background seismicity.

We used the above characterization to review available source models and determine if any site-specific modification to the models was required.

We reviewed source characterization and seismic models developed by others where high-quality peer reviewed models were available. Available models reviewed for this work included studies performed by the USGS applicable to the project region (e.g., Petersen et al. 2019), which generally adopted the results of the statewide study performed as part of the third Uniform California Earthquake Rupture 24001006.001A/SAC23M158525_R2 Page 11 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Forecast (UCERF 3 - Field et al. 2013), and the regional study completed by the California Department of Water Resources (DWR) for the Delta Risk Management Strategy project (California DWR, 2007).

Based on the above characterization and review of the available models, the source model developed by the USGS and published by Petersen et al. (2014, 2019) was generally found to provide adequate characterization of seismic sources and uncertainties identified for inclusion in the model. No sitespecific modification was needed for this study, and thus, the model of Petersen et al. (2014, 2019) was adopted for this work without change.

Within the Western United States (WUS) region, significant independent seismogenic sources within about 300 kilometers (km) of the site are included in the model as fault sources. Very large magnitude sources, such as the Cascadia subduction zone, are included out to 500 km. Minor, potentially active faults are generally not considered significant to the seismic hazard at the site. These sources were not considered as independent seismogenic sources and were more appropriately modelled by background seismicity. Recurrence intervals and slip rates used to develop the fault models are available in referenced literature and are based on the values developed by the UCERF 3 working group.

The adopted model uses two alternative fault models, Fault Model (FM) 3.1 and FM 3.2, from the branch-averaged UCERF 3 solution to model on-fault seismicity in California. Off-fault seismicity, also known as background seismicity, is modeled using gridded seismic sources developed for consistency with each fault model. Outside of California (e.g., Cascadia, etc.), source characterization developed by Petersen et al. (2014, 2019) was used.

The seismic source model used for this work within 325 km of the site is presented on Figure 4. An abbreviated overview of significant fault sources included in the source model within 100 km of the site is provided in Attachment A1. The attached table presents a simplification of the model used for this study and does not show how the model relaxes the assumption of segmentation and allows for multifault ruptures, with numerous possible combinations. For additional details of the characterization of individual sources and associated alternative models (e.g., FM 3.1 vs FM 3.2), the reader can refer to the documentation prepared by Petersen et al. (2014, 2019) and the associated referenced documents and reports.
‘Grand Inversion’ and Recurrence Rates
The earthquake recurrence rates used in the source model will be adopted as developed by the UCERF3 project, as implemented by Petersen et al. (2019) using the branch-averaged solutions of the ‘grand inversion’. This is a departure from the older standard of practice documented in EM 1110-2-6053 and Draft EM 1110-2-6000, which solves for the entire system of faults within California simultaneously.

The ‘grand inversion’ scheme developed by the UCERF3 project team, the results of which will be adopted in this work, ‘solved’ the on-fault and off-fault recurrence rates at a system level using a set of defined constraints including the spatial probability density of off-fault seismicity, slip rate balancing, paleoseismic even rate matching, fault smoothness constraint, regional magnitude frequency distribution constraints, and fault section specific magnitude frequency distribution constraints. In simple terms the ‘grand inversion’ solves for three things: large on-fault (supra-seismogenic) event rates; small, near-fault (subseismogenic) event rates; and truly off-fault (unassociated) event rates. The 24001006.001A/SAC23M158525_R2 Page 12 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 supra-seismogenic ‘on-fault’ events are ultimately modeled using linear fault sources while the latter two categories (subseismogenic and off-fault) are considered ‘background seismicity’ and are modeled using spatially smoothed ‘grid’ of evenly spaced cells (a.k.a. gridded seismicity). The combined on-fault and off-fault solution set (fault system solution) used the logic tree solution framework shown in a generalized form on Figure 5. Our model implements the branch-averaged solutions.

The on-fault seismicity considers two potential alternative fault models, equally weighted, identified as fault model 3.1 (FM 3.1) and fault model 3.2 (FM 3.2). These fault models each contain a slightly different collections of fault traces that are broken into ‘segments’ for modeling purposes, with individual segments strung together during evaluation to create hundreds of thousands of potential fault-based ruptures or multi-rupture events. In our model, fault segments are modeled with the recurrence rates constrained during the ‘grand inversion’ by the UCERF2 ‘characteristic’ inversion branch (e.g. Schwartz and Coppersmith, 1984). Fault slip rates (deformations) are constrained by a combination of a ‘pure’ geologic deformation model and three other models that consider geologic and geodetic data including the average fault block model, NewKinema model, and Zeng-Shen model. The magnitude-area relationships used along with the associated slip-length models, as well as other solution constraints applied, are shown with weights on Figure 5 and are discussed in detail in Field et al. (2013) and associated publications.

Off-fault seismicity (e.g. background seismicity) recurrence rates are solved for simultaneously by the ‘grand inversion’. This off-fault background seismicity is intended to include all smaller earthquakes (Mw<~6.5) on major faults and earthquakes of all sizes that are not associated with known faults. The off-fault background seismicity considers spatial smoothing of a ‘grid’ of evenly spaced cells using the spatial probability density function (PDF) grids of off-fault seismicity from UCERF2 and UCERF3 (equally weighted), considering the regional constraints on the model including the total regional magnitudefrequency distribution (e.g. Gutenberg-Richter distribution), maximum off-fault magnitude, number of regional events per year greater than Magnitude 5, and other constraints as shown on the logic tree (see Figure 5). The branch-averaged, gridded seismicity solution for each fault model, as implemented by Petersen et al. (2019), was used in the source model for this work.

We note that the catalog used in this work was not updated in 2019, as re-evaluation of the grand inversion scheme requires a supercomputer. However, the USGS reviewed the catalog used for UCERF3 and concluded that the addition of recent historical events to the catalog is not needed at this time, as the additional historical events in the last half decade typically will not significantly change the model results, with changes generally small, localized, and often near active faults, and thus already adequately modeled (Petersen et al., 2019).

Ground Motion Model’s (GMM’s)
This study makes use of response spectral attenuation relationships, also known as ground motion models (GMMs), in evaluations at the site as required by ER 1110-2-1806.

Site-specific ground motions can be influenced by the styles of faulting, magnitudes of the earthquakes, and local soil conditions. Other effects such as near-source or basin effects can also influence the ground motions. The GMM’s used to estimate ground motion from an earthquake source need to directly or 24001006.001A/SAC23M158525_R2 Page 13 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 indirectly consider these effects. Many GMMs have been developed to estimate the variation of spectral acceleration with earthquake magnitude and distance from the site to the source of an earthquake.

We will use four of the Next Generation Attenuation (NGA) West 2 relationships including Abrahamson et al. (2014), Boore et al. (2014), Chiou and Youngs (2014), and Campbell and Bozorgnia (2014) with equal weights applied for all crustal faults (e.g. reverse, strike-slip, normal) included in the fault model.

The Idriss (2014) model has not been used as it is not valid for the VS30 used in our study and also for the larger distances used in this study (e.g. more than 150 km). The far-field subduction events (e.g. from Cascadia megathrust) were modeled using the relationships of Atkinson and Macias (2009), Abrahamson et al. (2016), and Zhao et al. (2006) with equal weights applied, except that for slab events the Atkinson and Macias (2009) relationship was excluded. Spectral acceleration values are obtained by averaging the individual hazard results. These GMM’s provide ‘mean’ (RotD50) values of ground motions associated with magnitude, distance, site soil conditions, and mechanism of faulting. The uncertainty in the predicted ground motion was taken into consideration by including a magnitude dependent standard error in the probabilistic analysis.

Deep Sediment Impact on Response
The Sacramento Basin, while not typically considered a true basin for purposes of seismic evaluation, does contain deep sediments which can impact the response of the system. The Campbell and Bozorgnia (2014) and Chiou and Youngs (2014) GMMs include the depth to rock (Z) parameter to better predict ground motion in regions with deep sedimentary structure. The Campbell and Bozorgnia (2014) model uses the depth to shear wave velocity of 2.5 km/s (Z2.5) and the Chiou and Youngs (2014) model uses the depth to shear wave velocity of 1.0 km/s (Z1.0). The Z1.0 and Z2.5 values can be estimated by various sources, as discussed in next section. For Northern California locations, only the Campbell and Bozorgnia (2014) factor is applied, to account for deep sedimentary structure which is analogous to a ‘basin effect’.

Therefore, the basin effect on the response spectrum either at depth or at ground surface can be considered using the appropriate site-specific Z1.0 and Z2.5 values. Previous work on DRMS (DWR, 2007) determined that the response of the levees as more sensitive to ground potions with a period lower than 1 second, so the longer period motions where deep basin effects would be most pronounced are likely not significant to the levees of this project.

Control Points and Site Parameters
Evaluation of seismic hazard and model development for site specific studies is usually completed at a control point considered representative of a structure or facility. For this project, multiple control points across the project area are considered for evaluation of ground motions. Nine points along levee alignment are considered adequate as active faults are generally located at distance from the site, and thus, small differences due to control point location variation should be minimal. The control points will be used in evaluation of distance terms (rx, rjb, rrup) required for the selected GMM’s.

The above GMMs also use a set of site parameters to account for site effects and basin effects. For the NGA West 2 relationships, these include the average shear wave velocity in the upper 100 feet (30 meters, e.g. VS30), the depth to a layer with a Vs value of 3,280 feet per second (1,000 meters per second, e.g. Z1.0), and the depth a layer with Vs value of 8,200 feet per second (2.5 km/s, e.g. Z2.5). 24001006.001A/SAC23M158525_R2 Page 14 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 The VS30 values were evaluated at depth based on data from previous reports and mapped values. for consistency with DMRS (DWR, 2007), ground motions were evaluated as a stiff soil condition where VS30 is taken as 335 m/s. it is understood that this condition typically occurs at a depth of about 100 to 120 feet below ground surface. Z1.0 and Z2.5 were developed considering various geologic factors and estimates from the NGA West 2 correlations to develop best estimate values.

The Z1.0 and Z2.5 parameters are intended to capture the basin effects on ground motion response at a given site. The Z1.0 and Z2.5 values were estimated utilizing the correlations developed for the NGA West 2 project, with justification per Petersen et al. 2019. The Z1.0 and Z2.5 values are estimated to be about

0.428 km and 1.55 km, respectively. We propose to use these values as inputs for the GMHA.

In summary, our recommended values of VS30, Z1.0, and Z2.5 are presented in Table 4 below. Further details about the development of the site parameters are presented in Attachment A2.

Table 4
Site Parameters
Point ID Latitude Longitude VS30
(m/s)
Z1.0
(km)
Z2.5
(km)
Natomas NE 38.8262 -121.5317
335 0.428 1.55
Natomas NW 38.7810 -121.6025
Natomas West 38.6904 -121.6325
Arcade Creek 38.6668 -121.4762
Confluence 38.5982 -121.5087
American River East 38.5921 -121.3344
Little Pocket 38.5293 -121.5288
Pocket 38.4989 -121.5578
SREL South 38.4447 -121.5002
Peak Horizontal Accelerations
The probabilistic geometric mean peak horizontal acceleration is taken as the geometric mean peak horizontal acceleration with a 200-year return period. The associated controlling earthquake magnitudes and distances are based on the results of the deaggregation analysis. These values are presented in Table 5. We have also provided PHA values from the previous studies for comparison in this table. It should be noted that earthquake magnitude 6.5 was used in the previous studies for the entire study area.
24001006.001A/SAC23M158525_R2 Page 15 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Table 5
Probabilistic Peak Horizontal Acceleration and Controlling Earthquake Point ID
PHA (g) Deaggregation Results
(KLF, 2023) (DWR,
2015)
MW Distance (km)
Natomas NE 0.13 0.133 6.8 73
Natomas NW 0.14 0.144 6.8 65
Natomas West 0.15 0.160 6.7 58
Arcade Creek 0.13 0.139 6.8 72
Confluence 0.14 0.146 6.8 67
American River East 0.12 0.126 6.8 81
Little Pocket 0.14 0.152 6.7 63
Pocket 0.15 0.163 6.7 60
SREL South 0.15 0.148 6.7 62

CLOSING
This technical memorandum is for review by the subject project’s peer review panel for concurrence with the approach for the forthcoming Seismic Performance Summary Reports. This document is intended to be used as an appendix to the primary Seismic Performance Summary Report and is subject to the same limitations as in that report. If you have questions regarding this memorandum or if we may be of further assistance, please contact the undersigned.

Sincerely,
KLEINFELDER, INC.

Ryan Hochstatter, EIT Zia Zafir, PE, GE
Staff Geotechnical Engineer Sr. Principal Geotechnical Engineer

ATTACHMENTS
Figure 1 – Study Area
Figure 2 – Geologic Map
Figure 3 – Regional Faulting and Seismicity
Figure 4 – Seismic Source Model
Figure 5 – UCERF 3 Source Model Logic Tree
Attachment A1 – Significant Faults Included in Source Model Attachment A2 – Calculation Package – Shear Wave Velocity and Site Parameters 24001006.001A/SAC23M158525_R2 Page 16 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701

REFERENCES
___________________________________________________________________________________ Abrahamson, N., Gregor, N., Addo, K. (2016). BC Hydro Ground Motion Prediction Equations for Subduction Earthquakes. Earthquake Spectra, Volume 32, Issue 1, pp. 23-44.

Abrahamson, N.A., Silva, W.J., and Kamai, R. (2014). “Summary of the ASK14 Ground Motion Relation for Active Crustal Regions.” Earthquake Spectra, Vol. 30, No. 3, pp. 1025-1056.

Atkinson, G.M., and Macias, M. (2009). Predicted Ground Motions for Great Interface Earthquakes in the Cascadia Subduction Zone. Bulletin of the Seismological Society of America, V. 99, No. 3, pp. 1552-1578.

Boore, D.M., Stewart, J.P., Seyhan, E., and Atkinson, G. (2014). “NGA-West2 Equations for Predicting PGA, PGV, and 5% damped PSA for Shallow Crustal Earthquakes.” Earthquake Spectra, Vol. 30, No. 3, pp. 1057-1086.

Bozorgnia, Y. and Campbell, K. (2016). Ground Motion Model for the Vertical-to-Horizontal (V/H) Ratios of PGA, PGV, and Response Spectra. Earthquake Spectra, Volume 32, Issue 2, pp. 951-978.

Bryant, W., Sander, E., and Wills, C. (2007). Digital Database for Concord and Green Valley Faults. Final Technical Report prepared for the U.S. Geological Survey National Earthquake Hazards Reduction Program, USGS Award No. 05HQGR0029.

Building Seismic Safety Council (BSSC) (2014). United States Geological Survey (USGS) Earthquake Scenario Map, https://earthquake.usgs.gov/scenarios/catalog/, accessed July 2022.

California Department of Water Resources (2007). Technical Memorandum: Delta Risk Management Strategy (DRMS) Phase 1 Topical Area: Seismology Final. Prepared by URS Corporation and Jack R. Benjamin & Associates, Inc.

California Department of Water Resources (2012). Urban Levee Design Criteria.

Campbell, K.W., and Bozorgnia, Y. (2014). “NGA-West2 Ground Motion Model for the Average Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra.” Earthquake Spectra, Vol. 30, No. 3, pp. 1087-1116.

Chiou, B S., and Youngs, R.R. (2014). “Update for the Chiou and Youngs NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra.” Earthquake Spectra, Vol. 30, No. 3, pp. 1117-1154.

Cornell, C.A. (1968). Engineering Seismic Risk Analysis, Bulletin of the Seismological Society of America, Vol. 58, No. 5.

Cornell, C.A. (1971). Probabilistic Analysis of Damage to Structures Under Seismic Loading, Dynamic Waves in Civil Engineering, London, Interscience.

Cramer, C., Toppozada, T, and Park, D. (1978). Seismicity of the Foothills Fault System Between Folsom and Oroville, California.

Fey, N., Humphreys, E., 2008, Forces Acting on the Sierra Nevada Block and Implications for the Strength of the San Andreas Fault System and the Dynamics of Continental Deformation in the Western United States. Journal of Geophysical Research, Vol. 113, B 12415.

Field, E.H., Biasi, G.P., Bird, P., Dawson, T.E., Felzer, K.R., Jackson, D.D., Johnson, K.M., Jordan, T.H., Madden, C., Michael, A.J., Milner, K.R., Page, M.T., Parsons, T., Powers, P.M., Shaw, B.E., Thatcher, W.R., Weldon, R.J., II, and Zeng, Y. (2013). The Uniform California Earthquake Rupture 24001006.001A/SAC23M158525_R2 Page 17 of 18 February 9, 2024 © 2024 Kleinfelder www.kleinfelder.com
KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Forecast, Version 3 (UCERF 3), USGS Open File Report 2013-1165, CGS Special Report 228, Southern California Earthquake Center Publication 1792, http://pubs.usgs.gov/of/2013/1165/.

Fugro William Lettis Associates (FWLA 2010). “Surficial Geologic Map of the NEMDC East Study Area.” Scale 1:20,000. Dated 2010
Graymer, R., Jones, D., Brabb, E. (2002). "Geologic Map and Map Database of Northeastern San Francisco Bay Region, California: Most of Solano County and parts of Napa, Marin, Contra Costa, San Joaquin, Sacramento, Yolo, and Sonoma Counties". Miscellaneous Field Studies Map 2403.

Gülerce, Z. and Abrahamson, N.A. (2011). Site-Specific Design Spectra for Vertical Ground Motion, Earthquake Spectra 27(4), pages 1023-1047.

Gutenberg, B. and Richter, C.F. (1956). Earthquake Magnitude, Intensity, Energy and Acceleration, Bulletin of the Seismological Society of America, Vol. 46, No. 2.

Gutierrez, C. I. (2011). “Preliminary Geologic Map of the Sacramento 30’ x 60’ Quadrangle, California,” California Geological Survey, Preliminary Geologic Maps PGM-11-06 (1:100,000 scale).

Harden, D. R. (1998). “California Geology.” Published by Prentice Hall.

Helley, E. J., and Harwood, D. S. (1985). “Geologic Map of the Late Cenozoic Deposits of the Sacramento Valley and Northern Sierran Foothills, California,” U. S. Geological Survey Miscellaneous Field Studies Map MF-1790.

Humphreys, E., and Coblentz, D. (2007). North American Dynamics and Western U.S. Tectonics.

American Geophysical Union, Reviews of Geophysics, 45, RG3001.

Hoffman, R. (1992). Structural Geology of the Concord Area. American Association of Petroleum Geologists Pacific Section Annual Convention.

Idriss, I. M. (2014). “An NGA-West2 Empirical Model for Estimating the Horizontal Spectral Values Generated by Shallow Crustal Earthquakes.” Earthquake Spectra, Vol. 30, No. 3, pp. 1155-1177.

Jennings, C.W. and Bryant, W.A. (2010). Fault Activity Map of California. California Geologic Data Map Series Map No. 6.

Lienkaemper, J., Baldwin, J., Turner, R., Sickler, R., and Brown, J. (2013). A Record of Large Earthquakes during the Past Two Millennia on the Southern Green Valley Fault, California. Bulletin of the Seismological Society of America, Vol. 103, No. 4, pp. 2386-2403.

Merriam, M. (2012). Caltrans Fault Database V2a for ARS Online. Caltrans Fault Database V2 Report (http://dap3.dot.ca.gov/ARS_Online/technical.php)
Merz, H.L. and Cornell, C.A. (1973). Seismic Risk Analysis Based on a Quadratic Magnitude-Frequency Law, Bulletin of the Seismological Society of America, Vol. 63, No. 6.

Parrish, J. (2018). Faulting in California. California Geological Survey Map Sheet 54.

Petersen, M.D., Moschetti, M.P., Powers, P.M., Mueller, C.S., Haller, K.M., Frankel, A.D., Zeng, Yuehua, Rezaeian, Sanaz, Harmsen, S.C., Boyd, O.S., Field, Ned, Chen, Rui, Rukstales, K.S., Luco, Nico, Wheeler, R.L., Williams, R.A., and Olsen, A.H. (2014). Documentation for the 2014 Update of the United States National Seismic Hazard Maps, USGS Open-File Report 2014-1091, 243 p., https://dx.doi.org/10.3133/ofr20141091.

Petersen, M.D., Shumway, A.M., Powers, P.M., et al. (2019). The 2018 Update of the US National Seismic Hazard Model: Overview of Model and Implications, Earthquake Spectra, Volume 36, Issue 1, pp. 5-41.

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KLEINFELDER 3130 Kilgore Road, Suite 200, Rancho Cordova, CA 95670 p | 916.366-1701 Schwartz, D.P. and Coppersmith, K.J. (1984). Fault Behavior and Characteristic Earthquakes: Examples from the Wasatch and San Andreas Fault Zones, Journal of Geophysical Research, Vol. 89, pp. 5681-5698.

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Unruh, J. and Hector, S. (1999). Subsurface Characterization of the Potrero-Ryer Island Thrust System, Western Sacramento-San Joaquin Delta, Northern California.

Unruh, J. and Hitchcock, C. (2009). Characterization of Potential Seismic Sources in the Sacramento-San Joaquin Delta, California. Final Technical Report prepared for the U.S. Geological Survey National Earthquake Hazards Reduction Program. USGS Award No. 08HQGR0055.

Unruh, J., and Humphrey, J., 2017, Seismogenic Deformation Between the Sierran Microplate and Oregon Coast Block, California, USA. The Geological Society of America v. 45, no. 5, pp. 415-418 Unruh, J., Humphrey, J., and Barron, A., 2003, Transtensional Model for the Sierra Nevada Frontal Fault System, Eastern California. Geology v. 31, no. 3, pp. 327 – 330.

Wagner, D.L., Jennings, C.W., Bedrossian, T.L., and Bortugno, E.J. (1981). Geologic map of the Sacramento quadrangle, California, 1:250,000.

Zhao et al. (2006). Attenuation Relations of Strong Ground Motion in Japan using Site Classification Based on Predominant Period. Bulletin of the Seismological Society of America, V. 96, No. 3, pp. 898-913.
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STUDY AREA
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FIGURE
1 DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
SEP 2023
M. RYAN
K. HAGAN
F1_SiteMap.mxd
Explanation
!( Analysis Control Point
Levee Alignment
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F1_SiteMap.mxd KHagan 9/21/2023 0 3 6
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Locations are Approximate
£

SEISMIC EVALUATION GROUND MOTION

PARAMETER MEMORANDUM

ULDC & FEMA LEVEE CERTIFICATION PROJECT

SACRAMENTO AREA FLOOD CONTROL AGENCY

LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
Service Layer Credits: Source: Esri, Maxar, Earthstar
Geographics, and the GIS User Community; ESRI World
Imagery, Maxar Vivid Advanded image dates 4/12/2022,
4/26/2022, and 5/4/2022; SACOG Orthos image date
3/18/2022.

REGIONAL GEOLOGIC MAP
PROJECT:

FILE NAME:

FIGURE
2 DRAWN:

CHECKED BY:

The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it designed or intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

DRAWN BY:
24001006.001A
SEP 2023
M. RYAN
K. HAGAN
F2_Geology.mxd
Explanation
Levee Alignment
SACRAMENTO, CA FILE: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F2_Geology.mxd KHagan 9/21/2023 0 3 6
Kilometers
Wagner, D.L., C.W. Jennings, T.L. Bedrossian, and
E.J. Bortugno, 1981, Geologic Map of the
Sacramento Quadrangle, California, 1:250,000,
California Division of Mines and Geology Regional
Geologic Map Series, Map No. 1A.

Locations are Approximate
£

SEISMIC EVALUATION GROUND MOTION

PARAMETER MEMORANDUM

ULDC & FEMA LEVEE CERTIFICATION PROJECT

SACRAMENTO AREA FLOOD CONTROL AGENCY

LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
#
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Modesto-Riverbank Formations
Basin deposits
Levee and channel deposits
Historic displacement (< 150 years)
Mapped Fault Location
Dashed were Approximated
! ! ! ! Concealed
Holocene displacement (< 15,000 years)
Mapped Fault Location
Dashed were Approximated
! ! ! ! Concealed
Late Quaternary displacement (< 750,000 years)
Mapped Fault Location
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Quaternary & unspecified displacement
(< 1,600,000 years)
undifferentiated Quaternary Well Constrained
undifferentiated Quaternary Moderately Constrained
! ! ! ! undifferentiated Quaternary Inferred
Pre-Quaternary geologic structures (CGS, 2010)
Mapped Fault Location
Dashed were Approximated
! ! ! ! Concealed
ANSS Earthquakes
Magnitude

4.0 - 4.9

4.9 - 5.9

5.9 - 6.9

6.9 - 7.9

7.9 - 8.9
125
Kilom
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s
Project
Location
Willows fault
Thornton Arch
Stockton fault
East Valley fault
West Valley fault
Capay fault
Sweitzer fault
West Napa fault
Chabot fault
Serra fault
Lagoon Valley fault
Black Butte fault
Round Valley fault zone
Williams fault
Miller Creek fault
Antioch fault Corral Hollow fault
Hayward fault
Mohawk Valley fault
Rodgers Creek fault
Franklin fault
Dollar Point fault
Dog Valley fault
Clover Valley fault
Alexander fault
Greenville fault
Cross Spr ni g fault
Spenceville fault
Soda Creek fault
Pilarcitos fault
Wildcat fault
Cordelia fault
Crosley fault
Pinole fault
Etsel Ridge fault
Mocho fault
Maacama fault Maacama fault
Canada fault
Concord fault
Polaris fault
Calaveras fault
Rio Vista fault
Clayton fault
Mission fault
G ai nt Gap fault
Stoney Creek fault
Resort fault
Dunnigan Hills faul
H
t
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Bad Ridge fault
Pleasanton fault
Ione fault
Putah Creek
Cobb Mountain fault
Maidu East fault
Swain Ravine fault
Adobe Creek fault
Tolay fault
Green Springs Run fault
Chianti fault
Waters Peak fault
San Joaquin fault
Big Valley fault
Dewitt fault
San Jose fault
Poorman Gulch fault
San Andreas fault
Rescue fault
Seal Cove fault
Hunting fault
Bloomfield fault
Hot Springs Shear zone Vaca fault
Paynes Peak fault
Stanford fault
Youngs Creek fault
Corning fault
Vernalis fault
San Gregorio fault
Point Reyes fault
Midland fault
120°0'0"W
120°0'0"W
121°30'0"W
121°30'0"W
123°0'0"W
123°0'0"W
39°0'0"N
39°0'0"N
37°30'0"N
37°30'0"N
PROJECT NO:

CREATED:

CREATED BY:

CHECKED BY:

FILE NAME:

FIGURE
Quaternary Faults (Jennings and Bryant, 2010)
£
2/7/2024
ALeonard
F3_RegionalSeismic.mxd
Date: 2/7/2024 User: ALeonard Path: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F3_RegionalSeismic.mxd

REGIONAL FAULTING

AND SEISMICITY
MRyan 3
0 20 40 80
Kilometers
The information included on this graphic representation has been compiled from a variety of sources and is subject to change without notice. Kleinfelder makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a land survey product nor is it intended as a construction design document. The use or misuse of the information contained on this graphic representation is at the sole risk of the party using or misusing the information.

BASEMAP SOURCE:

Esri ArcGIS Online World Topography Map

SEISMIC EVALUATION GROUND MOTION

PARAMETER MEMORANDUM

ULDC & FEMA LEVEE CERTIFICATION PROJECT

SACRAMENTO AREA FLOOD CONTROL AGENCY

LEVEE SYSTEMS

SACRAMENTO AND SUTTER COUNTIES, CALIFORNIA
24001006.001A
Seismic Responsibility Reach
Faults, National Seismic Hazard Map
(NSHM), 2014
normal
strike slip
thrust
unassigned
Levee Alignment
32 5 K ilom ete r R adius
Pacific
Ocean
Project
Location
Duck F al t fault
Great Valley 12
Great Valley 02
Deep Springs
Dry
Mountain
Lost Hills
Fairview fault zone
Pittville 2011 CFM
M di d el gate fault zone
Last Chance
Round Valley
West Napa 2011 CFM
Great Valley 01
Antelope Valley 2011
Little Salmon (Offshore)
Airport Lake
Table Bluff
Greenville (No) 2011 CFM
Carson Range fault
Grass Valley fault zone
Zayante-Vergeles
West Tahoe
Hayward (So) 2011 CFM
Point Reyes 2011 CFM
Ortigalita (South)
Mohawk Valley 2011 CFM
Coaldale fault 1 Great Valley 07 (Orestimba)
Battle Creek 2011 CFM
Honey Lake 2011 CFM Ra ni bow Mounta ni fault zone Independence rev 2011 Pyramid Lake fault zone
Black Rock fault zone
Ione Valley fault
So Sierra Nevada
Hosgri
Russ 2011 CFM
Trinidad (alt1)
Rinconada 2011 CFM
Likely 2011 CFM
Buena Vista Valley fault zone Smith Valley fault
Eaton Roughs 2011 CFM
Hat Creek-McArthur-Mayfield
Owens Valley
White Mountains
Dixie Valley fault zone
Wassuk Range fault zone
San Andreas (Creeping Section) 2011 CFM
Mendocino
Reliz 2011 CFM
San Gregorio (North) 2011 CFM
San Andreas (Offshore) 2011 CFM
Bartlett Springs 2011 CFM
San Andreas (North Coast) 2011 CFM
Maacama 2011 CFM
118°30'0"W
118°30'0"W
120°0'0"W
120°0'0"W
121°30'0"W
121°30'0"W
123°0'0"W
123°0'0"W
124°30'0"W
124°30'0"W
40°30'0"N
40°30'0"N
39°0'0"N
39°0'0"N
37°30'0"N
37°30'0"N
36°0'0"N
36°0'0"N
£
Date: 9/21/2023 User: KHagan Path: \\azrgisstorp03\GIS_Projects\Client\SAFCA\24001006.001A-ULDC_groundmotion\F4_SeismicSource.mxd 0 50 100 200
Kilometers
BASEMAP SOURCE: