Appendices J-M.pdf — City Council and Authorities Concurrent, July 15, 2025 (part 1 of 3)

Appendix J
City of Santa Clara Sewer Capacity
Assessment
Water and Environment
May 2007
City of Santa Clara
Sanitary Sewer Capacity
Assessment

FINAL REPORT
Prepared by:

Appendix J

May 31, 2007
Mr. Rajeev Batra
City Engineer
City of Santa Clara Engineering Department
1500 Warburton Avenue
Santa Clara, CA 95050
Subject: Sanitary Sewer Capacity Assessment
Dear Mr. Batra:

RMC Water and Environment is pleased to submit this Final Report on the Sanitary Sewer Capacity Assessment for the City of Santa Clara. The report reflects the collaborative efforts of the RMC team and dedicated staff of the City’s Public Works Engineering Department and Water and Sewer Utilities to prepare a comprehensive assessment of the capacity needs of the City’s trunk sewer system.

The Capacity Assessment has been based on a detailed study methodology encompassing use of sewer flow monitoring, water use, and land use planning data, coupled with stateof-the-art hydraulic modeling, to identify the future capacity requirements of the City’s sanitary sewer system and develop recommended capacity improvement projects. The study also complies with Regional and State regulatory requirements for all collection system agencies to prepare Sewer System Management Plans addressing the operation, maintenance, and management of their systems.

The Capacity Assessment report identifies nine capacity improvement projects in the trunk sewer system, totaling about $20 million in capital costs, that will enable the City to maintain its high level of service to the community and provide adequate capacity to serve proposed future development and redevelopment. The report also includes recommendations and guidelines for implementing the recommended capital improvement program and continuing to track the flows and capacity of the system. The hydraulic model of the trunk sewer system developed for this study will allow the City to update the capacity assessment as changes occur over time.

We appreciate the opportunity to have worked with the City on this very challenging project. We would like to thank you for your oversight and direction of this effort, for the guidance and dedication of the City’s Project Manager, Falguni Amin, and for the input and assistance provided by many other City staff members on this Capacity Assessment project.

Sincerely,
Gisa Ju, P.E. Tammy Qualls, P.E.

Project Manager Project Engineer

City of Santa Clara
Sanitary Sewer Capacity Assessment
Final Report
Prepared by:

Water andEnvironment
May 2007
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City of Santa Clara Sanitary Sewer Capacity Assessment Table of Contents May 2007 i
Table of Contents
Executive Summary..............................................................................................................ES-1 Chapter 1 Introduction ...........................................................................................................1-1

1.1 Background and Study Objectives ..........................................................................1-1

1.2 Wastewater Collection System ...............................................................................1-1

1.3 Scope of Study........................................................................................................1-1

1.4 Report Organization................................................................................................1-5 Chapter 2 Land Use and Flow Estimates .............................................................................2-1

2.1 Land Use Projections..............................................................................................2-1

2.1.1 Planning Scenarios .................................................................................................2-1

2.2 Flow Monitoring Program........................................................................................2-4

2.3 Wastewater Flows...................................................................................................2-7

2.3.1 Wastewater Flow Components ...............................................................................2-7

2.3.2 Methods for Estimating Base Wastewater Flows....................................................2-8

2.3.3 Diurnal Base Wastewater Flow Patterns.................................................................2-9

2.3.4 Large Users...........................................................................................................2-11

2.3.5 Infiltration/Inflow ....................................................................................................2-12

2.3.6 Design Event.........................................................................................................2-13

2.3.7 Flows from Cupertino Sanitary District..................................................................2-14

2.3.8 Wastewater Flow Estimates..................................................................................2-15 Chapter 3 Hydraulic Model Development.............................................................................3-1

3.1 Modeled System .....................................................................................................3-1

3.2 Model Network Construction and Validation ...........................................................3-1

3.3 Development of Model Loads .................................................................................3-3

3.3.1 Base Wastewater Loads .........................................................................................3-3

3.3.2 I/I Loads ..................................................................................................................3-3

3.4 Model Calibration ....................................................................................................3-6

3.4.1 Dry Weather Calibration..........................................................................................3-6

3.4.2 Wet Weather Calibration.........................................................................................3-9 Chapter 4 Capacity Analysis .................................................................................................4-1

4.1 Hydraulic Analysis and Design Criteria ...................................................................4-1

4.2 Capacity Analysis Results.......................................................................................4-2

4.2.1 Cupertino Sanitary District Flows............................................................................4-2

4.3 Preliminary Solutions to Capacity Deficiencies.......................................................4-5 Chapter 5 Capacity Improvement Projects ..........................................................................5-1

5.1 Potential Flow Diversion Alternatives......................................................................5-1

5.2 Potential Diversions to New Sewers .......................................................................5-2

5.3 Construction Considerations...................................................................................5-2

5.4 Capacity Relief Projects..........................................................................................5-3

5.4.1 Projects 1 and 2 – Bowers Ave, Mission College Blvd and Great America Pkwy...5-3

5.4.2 New West-to-East Trunk Sewer Alternative............................................................5-5

5.4.3 Projects 4A and 4B – Machado Avenue and Chromite Drive .................................5-6

5.4.4 Project 5 – Monroe Street .......................................................................................5-6

5.4.5 Project 6 – Nobili Avenue and Machado Avenue....................................................5-6

5.4.6 ECR Diversion to Calabazas Trunk Sewer .............................................................5-6 City of Santa Clara Sanitary Sewer Capacity Assessment Table of Contents May 2007 ii

5.4.7 Project 8 – El Camino Real.....................................................................................5-7

5.4.8 Project 9 – Scott Boulevard.....................................................................................5-7

5.4.9 Project 10 – Park Avenue .......................................................................................5-7 Chapter 6 Recommended Capital Improvement Program ..................................................6-1

6.1 Estimated Cost of Proposed Sewer Improvement Projects ....................................6-1

6.2 Comparison of Major Alternatives ...........................................................................6-3

6.3 Prioritization and Schedule for Proposed CIP Projects...........................................6-3

6.4 Implementation Recommendations.........................................................................6-5 List of Tables
Table ES-1 Sewer System Flow Estimates ............................................................................ES-6 Table ES-2 Recommended Capacity Improvement Projects..................................................ES-9 Table ES-3 Project Costs and Priority Groups......................................................................ES-10 Table 2-1 Planned Development/Redevelopment .....................................................................2-2 Table 2-2 Planned Development Summary ...............................................................................2-4 Table 2-3 Flow Monitoring Locations .........................................................................................2-5 Table 2-4 Rain Events during Flow Monitoring Period...............................................................2-7 Table 2-5 Base Wastewater Flow Unit Flow Factors .................................................................2-9 Table 2-6 Large Dischargers ...................................................................................................2-11 Table 2-7 Sewer System Flow Estimates ................................................................................2-15 Table 3-1 Comparison of Meter and Model Flow.......................................................................3-6 Table 3-2 GWI and RDI/I Parameters by Meter Area ..............................................................3-11 Table 4-1 Hydraulic Design Criteria ...........................................................................................4-1 Table 4-2 Capacity Deficiencies and Preliminary Solutions.......................................................4-6 Table 5-1 Recommended Capacity Improvement Projects .......................................................5-3 Table 6-1 Summary of Cost Criteria ..........................................................................................6-2 Table 6-2 Estimated Costs of Capacity Improvement Projects..................................................6-2 Table 6-3 Project Priority Groups...............................................................................................6-4 City of Santa Clara Sanitary Sewer Capacity Assessment Table of Contents May 2007 iii
List of Figures
Figure ES-1 Sewer System.....................................................................................................ES-2 Figure ES-2 Modeled System .................................................................................................ES-4 Figure ES-3 Planned Development/Redevelopment ..............................................................ES-5 Figure ES-4 Predicted Capacity Deficiencies .........................................................................ES-7 Figure ES-5 Recommended Capacity Improvement Projects ................................................ES-8 Figure ES-6 Proposed CIP Schedule ...................................................................................ES-11 Figure 1-1 Study area ................................................................................................................1-2 Figure 1-2 Sewer System ..........................................................................................................1-3 Figure 2-1 Planned Development/Redevelopment ....................................................................2-3 Figure 2-2 Flow Meter Sites.......................................................................................................2-6 Figure 2-3 Wastewater Flow Components.................................................................................2-8 Figure 2-4 Diurnal Curves........................................................................................................2-10 Figure 2-5 RDI/I Hydrograph Components ..............................................................................2-13 Figure 2-6 10-Year Design Storm for San Jose Airport ...........................................................2-14 Figure 3-1 Modeled System.......................................................................................................3-2 Figure 3-2 Subbasins and Load Manholes ................................................................................3-4 Figure 3-3 Flow Meter Areas Used for I/I Analysis ....................................................................3-5 Figure 3-4 Meter Schematic.......................................................................................................3-7 Figure 3-5 Example Dry Weather Calibration Plots ...................................................................3-8 Figure 3-6 Example Wet Weather Calibration Plots ................................................................3-10 Figure 4-1 Model Results – Future PDWF.................................................................................4-3 Figure 4-2 Model Results – Future PWWF ................................................................................4-4 Figure 4-3 Preliminary Capacity Improvements.........................................................................4-7 Figure 5-1 Recommended Capacity Improvement Projects ......................................................5-4 Figure 6-1 Proposed CIP Schedule ...........................................................................................6-5 Appendices
Appendix A - Plots of Flow Monitoring Data
Appendix B - Project Descriptions and Cost Estimates
City of Santa Clara Sanitary Sewer Capacity Assessment Table of Contents May 2007 iv
Acknowledgements
City of Santa Clara
Rajeev Batra, City Engineer
Tom Supan, Principal Engineer
Falguni Amin, Project Manager
Gustavo Gomez, Principal Engineer
Jim Parissenti, Principal Engineer
Kimchi Tran, Civil Engineer I
Robin Saunders, Director of Water and Sewer Utilities
Alan Kurotori, Assistant Director Sewer Utility
Kevin Riley, Director of Planning and Inspection
Doug Handerson, Associate Planner
RMC Water and Environment
Steve Bui, Principal-in-Charge
Gisa Ju, Project Manager
Tammy Qualls, Project Engineer
Carrie Teng
Catherine Greenman
Glenn Hermanson
E2 Consulting Engineers, Flow Monitoring
City of Santa Clara Sanitary Sewer Capacity Assessment Table of Contents May 2007 v
List of Abbreviations and Definitions
ADWF Average dry weather flow: the average flow during dry (non-rainfall) periods APN Assessor parcel number
CIP Capital Improvement Program
City City of Santa Clara
CSJ City of San Jose
CuSD Cupertino Sanitary District
d/D Ratio of flow depth to pipe diameter
DU Dwelling unit
DWF Dry weather flow: the flow during non-rainfall periods, composed of normal sanitary flow contributions from residential, commercial, institutional, and industrial users of a sewer system plus any dry season groundwater infiltration.

E2 E2 Consulting Engineers, Inc.

ECR El Camino Real
ENR-CCI Engineering News Record Construction Cost Index: an index published monthly by Engineering News Record magazine and used to reference construction costs (such as those for wastewater system facilities) to a specific date and location.

FAR Floor-area-ratio: the ratio of building floor space to total parcel area GIS Geographic Information System: a computerized system in which geographical features (e.g., sewer facilities, parcels, land use) are linked to an attribute database to facilitate analysis and presentation of information. gpad or gpd/ac Gallons per day per acre
gpcd Gallons per capita per day
gpd Gallons per day
gpm Gallons per minute
GWI Groundwater infiltration: extraneous water that infiltrates a sewer system from the ground through defective pipes and manholes. Groundwater is considered to be a relatively constant daily flow that varies seasonally and depends on location of sewers with respect to the groundwater table.

City of Santa Clara Sanitary Sewer Capacity Assessment Table of Contents May 2007 vi
IDF Intensity-duration-frequency: rainfall statistics that establish the rainfall intensity over specified durations for various recurrence frequencies I/I Infiltration/inflow: extraneous groundwater and/or storm water that enter a sanitary sewer system.

K Recession coefficient of RDI/I unit hydrograph
lf Linear feet
mgd Million gallons per day
PDWF Peak dry weather flow: the peak flow during non-rainfall periods PS Pump Station
PWWF Peak wet weather flow: the peak flow during a given storm event from dry weather flow plus infiltration and inflow.

R Ratio of RDI/I volume to rainfall volume
R&D Research and Development
RDI/I Rainfall-dependent infiltration/inflow: the infiltration and inflow into a sewer system directly related to a rainfall event. RDI/I may cause rapid, short-term peak flows in the sewer system that recede after the rainfall has ended.

RG Rain gauge
Regional Board Regional Water Quality Control Board: a division of the State Water Resources Control Board that administers wastewater discharge permits in a specific region of California. The City of Santa Clara falls under the jurisdiction of the San Francisco Bay Regional Board.

RMC RMC Water and Environment
SJ/SC WPCP San Jose/Santa Clara Water Pollution Control Plant SSMP Sewer System Management Plan
State Board State Water Resources Control Board
Surcharge The hydraulic condition in a sewer pipeline in which the elevation of the hydraulic gradeline (water level) is above the crown (top) of the pipe. Under such a condition, the water in the pipe rises into the manholes and could overflow onto the ground if the hydraulic gradeline exceeds the elevation of the manhole rims.

T Time to peak of RDI/I unit hydrograph
Executive Summary

City of Santa Clara Sanitary Sewer Capacity Assessment Executive Summary May 2007 ES-1
Executive Summary
This report summarizes the results and recommendations of the Sanitary Sewer System Capacity Assessment for the City of Santa Clara (City). The Capacity Assessment was prepared by RMC Water and Environment (RMC) in close coordination with City staff. The Capacity Assessment will be used to guide improvements to the City’s sanitary sewer system to accommodate current and future development to ensure that the City continues to maintain a high level of service to its customers.

Background and Purpose of Capacity Assessment
The City of Santa Clara is located in central Santa Clara County adjacent to the Cities of San Jose, Cupertino, and Sunnyvale. The City has a population of approximately 110,000 and is served by a wastewater collection system consisting of approximately 270 miles of sewer pipelines and six sewage pump stations. The collection system conveys wastewater flows to the San Jose/Santa Clara Water Pollution Control Plant (SJ/SC WPCP), located north of Highway 237 in San Jose. The City also receives flow from the Cupertino Sanitary District (CuSD) at Homestead Road under an agreement with the City executed in 1985. The City’s sewer system and service area are shown in Figure ES-1.

The City is experiencing significant growth and redevelopment, necessitating an evaluation of the capacity of the sanitary sewer system to handle future wastewater flows. This evaluation will help identify future capital needs for capacity improvements and associated requirements for financing those improvements through increased connection fees or other sources of funding.

Furthermore, the City is also required to complete a capacity evaluation and capacity assurance plan as part of preparing its Sewer System Management Plan (SSMP). The SSMP addresses the overall management, operation, and maintenance of the sanitary sewer system and is required for all sewer system agencies by the Regional Water Quality Control Board, as well as under the Statewide General Waste Discharge Requirements adopted in 2006 by the State Water Resources Control Board.

The overall objectives of this Capacity Assessment study are to develop wastewater flow projections for the City’s collection area using up-to-date water use and land use information; develop a hydraulic model of the trunk sewer system; use the model to identify capacity deficiencies in the existing system and future capacity requirements; and develop a phased Capital Improvement Program, including budget estimates, for implementing the required capacity improvements to the sanitary sewer system.

This Executive Summary is presented in two parts:
▪ How the Capacity Assessment was Prepared describes the scope and methodologies of the planning effort, including the key planning and technical assumptions incorporated into the sewer system capacity analysis.
▪ Recommended Capacity Improvement Program presents the recommended Capital Improvement Program (CIP), including capacity improvement projects, priorities, and estimated costs. In addition, recommendations are presented for implementing the proposed capacity improvement program.

How the Capacity Assessment Was Prepared
The City’s wastewater collection system includes sewer pipelines ranging in size from 4 to 48 inches in diameter. The larger pipes, primarily the 15-inch and larger sewers and a portion of the smaller diameter pipes, comprise the trunk sewer system, which is the primary network for conveying flows generated from the City’s service area to the SJ/SC WPCP. The trunk sewer system was the focus of the capacity assessment in this study.
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Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Parcels
Pump Stations
Sewers by Size
6" and smaller
8" - 10"
12" - 16"
18" - 24"
27" - 48"
Sewer System
Figure ES-1
Flow from
CuSD
Flow To

SJ/SC WPCP
Flow To CSJ
Interceptor in
Zanker Rd
City of Santa Clara Sanitary Sewer Capacity Assessment Executive Summary May 2007 ES-3
The project team used a systematic process that incorporated land use planning information, water use and flow monitoring data, and design criteria for estimating wastewater flows into a computer hydraulic model of the trunk sewer system. The modeled system is shown in Figure ES-2. The model was used to assess how the system would perform under various planning scenarios and identifies pipes that may not have sufficient capacity to convey the predicted flows under future conditions. Improvement projects were developed to provide the required capacity, the capital costs of the required projects were estimated, and the projects were prioritized based on the model results and anticipated timing of development.

Capacity Assessment Considers Existing and Future Planning Scenarios Two planning scenarios, defined based on planning information and discussions with the City’s Planning Department staff, were evaluated for this study. The Existing Scenario examined the current capacity of the sewer system based on existing development and flow monitoring data collected in early 2006. The Future Scenario assumed construction of all currently planned major development and redevelopment projects in the City, as well as potential increased densities in mixed use and transit-oriented mixed use and commercial/office areas consistent with the City’s 2010 General Plan and General Plan Update.

Figure ES-3 shows the location of these planned and recently constructed developments. Planned development and redevelopment represents over 10,000 new residential dwelling units and over 5 million square feet of new commercial and office space. The Future Scenario was used to examine the impact on the system of future increases in wastewater flows due to new development and redevelopment and determine the required sewer system capacity needed to serve that development.

Potential Capacity Deficiencies Were Identified for Future Flow Conditions For each of the planning scenarios examined, projected dry and wet weather flows were simulated in the hydraulic model. The model was calibrated to actual flow monitoring data to ensure that it represents an accurate depiction of system conditions. For this study, a wet weather flow monitoring program consisting of 26 temporary flow meters installed in the system for a period of two months was used to calibrate the hydraulic model and verify existing system flows.

Table ES-1 presents the estimated existing and future average dry weather flow (ADWF) and peak wet weather flow (PWWF) for a 10-year design storm for the City’s sewer system developed based on the modeling conducted for this study.

Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Modeled Pump Stations
Pump Stations Not in Model
Modeled Trunk Sewers
Sewer Mains
Parcels
Modeled System
Figure ES-2
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4767 Lafayette St. Detached Family
Home Project
BAREC Area
Train Station
Area
El Camino
Intensification
Downtown Revitalization
Kohl's Site
Taylor Woodrow/BRE
Cherry
Orchard Place
Valley Fair
Mall Expansion
Old Kaiser
Campus Site
Extreme
Networks
North SC Intensification
Future Hotel
Development
HP/ Agilent
Applied Materials
Kaiser
New Hospital
Rivermark
Hyatt Hotel Expansion &
Santa Clara Convention
Center Expansion
Citation Project
Yerba Buena/ Irvine
Santa Clara
University Classroom
Expansion
Marvell
Intel (Juliet site)
Shea Project
Sobrato Project
Intel (Freedom Site)
3600 Pruneridge
Ave. Residential
Project
Vidovich Project
(Homes and Retail)
2250 El Camino Real
Condominiums
(Sal Caruso)
Legend
City Boundary
Parcels
Planned Development/Redevelopment Projects
Commercial/Office/R&D
Residential
Commercial/Residential
Land Use Intensification
Mixed Use
Transit Oriented Mixed Use
Commercial/Office
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity Analysis
Planned
Development/Redevelopment
Figure ES-3
City of Santa Clara Sanitary Sewer Capacity Assessment Executive Summary May 2007 ES-6
Table ES-1 Sewer System Flow Estimates
Existing Flow
(mgd)
Future Flow
(mgd)
System Outfall ADWF PWWF ADWF PWWF
North (to Northside
and Rabello Pump
Stations)

17.7 40.8 21.2 43.1a
East (to San Jose
Trimble Road trunk
sewer)

6.0 13.2 6.9 14.1
Total 24 54 28 57
(a) Assumes peak flow from Cupertino Sanitary District flow does not increase above its contracted maximum capacity of 13.8 mgd.

Model results were examined to determine trunk system capacity needs, as indicated by areas where the flow in the pipes would exceed their capacity and cause surcharge conditions (water levels higher than the tops of the pipes) under peak wet weather flows. Figure ES-4 shows the existing trunk sewers that were determined by the modeling to have insufficient capacity to handle future flows.

The Proposed Improvement Projects Address the Potential Capacity Deficiencies To address the capacity deficiencies identified through the modeling effort, three primary types of capacity relief alternatives were explored:
▪ Upsizing pipes (i.e., replacing existing pipes with larger ones) ▪ Construction of parallel pipes
▪ Flow diversions to other sewers with available capacity or to new sewer pipelines Potential flow routing and capacity improvement alternatives were developed and tested, and proposed improvements were verified using the hydraulic model. Field visits were conducted to each proposed project site to identify site constraints and assess potential construction conditions, methods, and issues.

Based on these analyses, recommended capacity improvement projects were developed.

Figure ES-5 and Table ES-2 present the recommended capacity improvement projects. Note that the recommended plan reflects the construction of a new siphon crossing Calabazas Creek at El Camino Real, which is currently being designed as part of channel improvements being constructed by the Santa Clara Valley Water District (SCVWD). As part of that project, the City is coordinating with SCVWD to divert flows from the siphon outlet to the existing 24-inch Calabazas trunk sewer, thereby alleviating the predicted capacity deficiencies in El Camino Real east of Calabazas Creek and in the 8-inch sewer in the west side of Calabazas Boulevard north of El Camino Real.

The overall capacity improvement plan also shows a “West-to-East Trunk Alternative,” which is an alternative to constructing a major relief trunk sewer in Bowers Avenue and Great America Parkway (Projects 1 and 2), two of the busiest roads in the City that already contain large diameter sewer pipelines.

The West-to-East alternative would likely be easier to construct and could provide additional benefits, including greater system flexibility and potential reduction in costs for pumping flows that now are conveyed to the City’s Rabello and Northside Pump Stations. However, more detailed alignment studies and constructability evaluations would be needed to reach a final decision on whether the Bowers/Great America Parkway relief sewer or West-to-East Trunk is the most viable alternative.

Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Predicted Capacity Deficiencies
Modeled Trunk Sewers
Parcels
Predicted Capacity
Deficiencies
Figure ES-4
Monroe St.

Machado Ave.

Chromite Dr. U.P.R.R.

Central Expwy.

Walsh Ave.

Calabazas Blvd.

Scott Blvd.
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Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
5 Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr.

U.P.R.R.

Walsh Ave.

Dia. (in.)
Req'd. Dia.
(in.)b
1 Augustine Dr., Lakeside Dr., crossing of U.S.
101, Mission College Boulevard, Great
America Pkwy. from Bowers Ave. to south of
Hetch Hetchy ROW
S73-20 S93-57 7,200 33-36 21 (P)
2 Chromite Dr., Alhambra Dr., Bracher Park,
crossing of UPRR, Bowers Ave. from Bowers
Ave. to Augustine Dr.

S53-34 S73-20 6,200 27-33 21 (P)
West-toEast
Trunkc
Chromite Dr., Alhambra Dr., Bracher Park,
crossing of UPRR, Walsh Ave., Lafayette,
Lafayette St., Central Expwy. From Bowers Dr.
to UPRR
S53-41 S67-18 12,200 NA 24
4A Monroe St. and Chromite Dr. from Machado
Ave. to west of Bowers Ave. S52-80 S53-41 2,200 18 24-27 (R) 4B Machado Ave. from Calabazas Blvd. to
Monroe St. S52-103 S52-80 1,500 15 21 (R)
5 Monroe St. from Fordham Dr. to Chromite Dr. S51-22 S52-65 2,500 10 8(siphon)
12 (R)
8(siphon) (P)
6 Nobili Ave. and Machado Ave. from Flora Vista
Ave. to Calabazas Blvd. S41-53 S52-101 3,100 10-15 15-18 (R) 8 El Camino Real from Flora Vista Ave. to
Calabazas Blvd. S41-113 S32-5 2,600 10 12-15 (R)
9 Scott Blvd. from Serra Ave. to Homestead Rd. S25-37 S35-98 800 8 10 (R) 10 Park Ave. south of Bellomy St. S38-75 S38-66 250 10 12 (R) (a) Note: there are no projects 3 and 7.
(b) P = parallel sewer; R = remove and replace
(c) Alternative to Projects 1 and 2.

Recommended Capacity Improvement Program
The Capital Improvement Program (CIP) recommended in this study is designed to provide for adequate sewer system capacity for the City’s existing and anticipated future development. The total estimated capital cost of the CIP is approximately $20 million, as shown in Table ES-3. These costs include baseline construction costs for gravity trunk sewers using open-cut and trenchless (e.g., microtunneling) methods, costs for lower lateral replacement for remove-and-replace projects, costs for major sewer junction and siphon structures, and costs allowances for project mobilization/demobilization, traffic control, bypass pumping and delay factors for remove-and-replace projects, extra dewatering requirements in areas of high groundwater, and acquisition of temporary and permanent easements if needed. The total estimated capital costs also include a 30 percent allowance for contingencies for unknown conditions and an allowance of 25 to 35 percent of construction cost (depending on project size) for engineering, administration, and legal costs. The estimated costs are considered planning or conceptual level estimates and are considered to have an estimated accuracy range of -30 to +50 percent.

The recommended projects were divided into the two priority groups based on the relative magnitude of predicted capacity deficiencies, as well as the likely timing of developments that may impact the need for the projects. The priority groups are also shown in Table ES-3.

City of Santa Clara Sanitary Sewer Capacity Assessment Executive Summary May 2007 ES-10
Table ES-3 Project Costs and Priority Groups
Project No.

Estimated
Construction
Cost ($)
Estimated Capital
Cost ($)
2 5,286,000 7,324,000
4A 1,489,000 1,861,000
8 945,000 1,276,000
Subtotal 7,720,000 10,461,000
1 4,539,000 5,674,000
4B 1,060,000 1,325,000
5 1,046,000 1,308,000
6 1,139,000 1,424,000
9 256,000 346,000
10 77,000 104,000
Subtotal 8,117,000 10,181,000
Total 15,837,000 20,642,000
West-to-East Alternativea 9,752,000 12,906,000
Total w/West-to-East
Alternative 15,764,000 20,550,000
Priority Group 1
Priority Group 2
(a) Would replace Projects 1 and 2 and be included in Priority Group 1.

A preliminary schedule for completion of the recommended CIP projects over a five-year period was developed based on the project priorities. Figure ES-6 shows a preliminary schedule for the recommended five-year CIP. Two schedules are provided to reflect the two major alternatives. However, the schedules also provide for a preliminary alignment study of both the Bowers/Great America Parkway and the West-to-East trunk alternatives. Note also that the schedule could be compressed to achieve greater economy of scale and potential cost savings by combining individual projects and/or using alternative bid schedules.

Implementation Recommendations
The City should begin implementation of the Capital Improvement Program recommended in this Sanitary Sewer Capacity Assessment, starting with the highest priority projects. The following items should be considered in project scheduling and design, and in future updates of the Capacity Assessment. ▪ The alignments and sizes of all recommended projects should be verified with detailed predesign analyses, including topographic surveys, geotechnical investigations, utility research, and constructability reviews.
▪ The decision to parallel or replace existing sewers should consider the physical condition and remaining useful life of the existing pipelines; the availability of pipeline corridors for new sewer construction; and operation and maintenance concerns.
▪ The hydraulic model has been developed to assist the City in performing capacity analyses and updating the Capacity Assessment in the future. The model should be kept up-to-date with any changes to existing sewer connections, development plans, and sewer system facilities.

City of Santa Clara Sanitary Sewer Capacity Assessment Executive Summary May 2007 ES-11
Figure ES-6 Proposed CIP Schedule
With Projects 1 and 2
Alignment Study
Project 8
Project 4A
Project 2
Project 1
Project 4B
Projects 5&6
Projects 9&10
With West-to-East Trunk Alternative
Alignment Study
Project 8
Project 4A
West-to-East Trunk
Project 4B
Projects 5&6
Projects 9&10
Planning
Design
Bid and Award
Construction
Project Year 1 Year 2 Year 3 Year 4 Year 5
Project Year 1 Year 2 Year 3 Year 4 Year 5
▪ The City should periodically calibrate its permanent flow meters at the Northside and Rabello Pump Stations and on the Trimble Road trunk sewer to ensure that accurate flow information is available to track the changes in the flows in the City’s system over time. ▪ The City should conduct additional flow monitoring at key locations in the sewer system, particularly the area tributary to the Chromite/Machado trunk sewers where the 2006 flow monitoring indicated high I/I flows. Flow levels during large storm events should be compared to the peak flows simulated by the hydraulic model to verify the modeling predictions for the 10-year design storm and confirm the need for and sizing of Projects 4A, 4B, 5, and 6.
▪ The City should consider additional field investigations, including smoke testing, and manhole and pipeline television inspection, in this area to identify potential sources of I/I and possible opportunities for I/I reduction.
▪ The City should coordinate with the Cupertino Sanitary District on flow and planning assumptions to ensure that adequate capacity exists in the Santa Clara system to handle future flows from CuSD.

The City should encourage CuSD to verify the calibration of its flow meter at Homestead Road and confirm its projections of future wastewater flows entering the Santa Clara system. ▪ The City should coordinate with the City of San Jose to ensure that its flow criteria and planning assumptions are consistent with those used by San Jose in its capacity master planning. ▪ The City should assess its connection fees and evaluate financial alternatives to fund the recommended capacity assessment CIP.

This Sanitary Sewer Capacity Assessment report is intended to be a working document to be refined and updated as additional data and new planning information becomes available. The Capacity Assessment should be updated whenever there are major changes in planning assumptions or, at a minimum, every five years.

Introduction
Chapter 1

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 1 Introduction May 2007 1-1
Chapter 1 Introduction
This report presents the results and recommendations of the Sanitary Sewer Capacity Assessment for the City of Santa Clara (City). The report was prepared by RMC Water and Environment (RMC).

1.1 Background and Study Objectives
The City of Santa Clara is located in central Santa Clara County and is bounded by the City of San Jose on the north, east and south, the City of Cupertino on the southwest, and the City of Sunnyvale on the west. As shown in Figure 1-1, the capacity assessment study area compromises the area within the Santa Clara city limits.

Furthermore, the City is also required to complete a capacity evaluation and capacity assurance plan as part of preparing its Sewer System Management Plan (SSMP). The SSMP addresses the overall management, operation, and maintenance of the sanitary sewer system and is required for all sewer system agencies by the Regional Water Quality Control Board (Regional Board), as well as under the Statewide General Waste Discharge Requirements adopted in 2006 by the State Water Resources Control Board (State Board).

The overall objectives of this Capacity Assessment study are to develop wastewater flow projections for the City’s collection area using up-to-date water use and land use information; develop a hydraulic model of the trunk sewer system; use the model to identify existing capacity deficiencies and future capacity requirements; and develop a phased Capital Improvement Program, including budget estimates, for implementing the required capacity improvements to the wastewater collection system.

1.2 Wastewater Collection System
The City’s wastewater collection system includes approximately 270 miles of sewer pipelines ranging from 4 to 48 inches in diameter, and six sewage pump stations. Flow from Cupertino Sanitary District enters the City’s sewer system at Homestead Road. The collection system conveys wastewater to the San Jose/Santa Clara Water Pollution Control Plant (SJ/SC WPCP), located north of Highway 237 in San Jose. The City of Santa Clara collection system is shown in Figure 1-2.

1.3 Scope of Study
RMC was authorized by the City to provide engineering consulting services for the Sanitary Sewer Flow Monitoring Program and Sanitary Sewer Capacity Assessment under an Agreement with the City dated December 13, 2005, and amended March 21, 2006.

The scope of the Capacity Assessment, as well as a brief discussion of work conducted under each task, is described below.
Task 1 – Project Management and Quality Control. Periodic progress meetings were held with the City staff to review project status and discuss project issues, and monthly status reports were prepared to document the work completed. Quality control was carried out, including checking of data and calculations, as well as senior review of proposed criteria, recommendations, and project deliverables.
(This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd.Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr.

U.P.R.R.

Walsh Ave.

Central Expwy.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Parcels
Study Area
Figure 1-1
(This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr. U.P.R.R.

Walsh Ave.

SJ/SC WPCP
Flow To CSJ
Interceptor in
Zanker Rd
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 1 Introduction May 2007 1-4
Task 2 – Flow Monitoring Site Selection. Sanitary sewer system maps and previous reports were reviewed in order to delineate the trunk sewer network and refine major sewer basins and subbasins.

Meter and rain gauge sites were identified, investigated, and finalized. A flow monitoring plan with a listing and map of the final sites, schedule for the field work and site traffic control plans was prepared.
Task 3 – Flow Monitoring. A flow monitoring program, consisting of the 26 meters and 3 rain gauges installed in the collection system for a period of about two months during the 2005-2006 wet weather season, was conducted to obtain data to characterize flows in the system and calibrate the hydraulic model. In addition, two existing City-owned ISCO flow meters were also calibrated and utilized for the study.
Task 4 – Flow Monitoring Report. A flow monitoring report containing copies of monitor site reports, weekly plots of flow and rainfall, and summary tables of average, minimum, and maximum daily flows for each meter was submitted to the City. In addition, all data in electronic format were also submitted.
Task 5 - Compile and Review Existing Information. This task involved assembling, organizing, reviewing maps and documents, and compiling the information in a format that was useful for subsequent tasks.
Task 6 – Develop Land Use Planning Information and Parcel Loads. Meetings were held with the City Planning staff to identify and obtain pertinent land use planning data, vacant land inventory and other information required for the Capacity Assessment, and to discuss specific planning issues and potential growth or redevelopment areas in the City. The City’s 2010 General Plan and General Plan Amendment were reviewed. Water use data was compiled for existing customers. The information collected was used to develop estimates of existing and future wastewater flows. Task 7 – Develop Design Flow and Hydraulic Criteria. This task involved developing criteria used for estimating wastewater generation and wet weather flows in the sanitary sewer system. ).

Design flow criteria were developed, including base wastewater flow and infiltration/inflow factors, as well as an appropriate design storm to be used for analyzing and determining the required capacity of sewer system facilities. Hydraulic criteria were proposed for evaluating and sizing system facilities for the capacity assessment.
Task 8 – Develop Hydraulic Model. In this task, the model network files were built using the District’s mapping and sewer inventory files and additional data developed for this project. A digital sewer subbasin map was developed for the model. Flow input data for the model were compiled using the water use and land use data and design flow criteria developed under previous tasks. The model was verified for system connectivity, calibrated for dry weather conditions, and then calibrated for wet weather conditions using actual storm events from the flow monitoring program. Task 9 – Evaluate System Hydraulic Performance. Under this task, the model was used to determine collection system capacity requirements for peak dry and wet weather conditions. The model runs identified capacity deficiencies in the existing system and the required system capacity to serve future development. Preliminary solutions to capacity deficiencies were identified and tested in the model.
Task 10 – Model Training and Support. Training of City staff in use of the model was deferred until after completion of the study.
Task 11 – Develop Capital Improvement Projects. Detailed analysis was conducted to refine and further develop the proposed solutions for capacity deficiencies. This work included investigation of alternative alignments and assessment of design and constructability issues.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 1 Introduction May 2007 1-5
Task 12 – Develop Sewer System Capital Improvement Program. Unit construction costs for components of sewer construction were developed, and estimated capital costs for the recommended improvement projects were prepared. In conjunction with City staff, the recommended improvement projects were prioritized, and a phased Capital Improvement Program (CIP) was developed. Task 13 – Prepare Capacity Assessment Report. This report was prepared to summarize and present the results and recommendation of the study.

1.4 Report Organization
This report includes six sections, which are described below. Section 1, Introduction, presents the background, objectives, and scope of the Sanitary Sewer Capacity Assessment.
Section 2, Land Use and Flow Estimates, discusses the planning area land use projections, the basis for developing estimates for each component of wastewater flows, and the flow projections for the service area.
Section 3, Hydraulic Model Development, describes the modeled sewer system, development of the model network and model loads, and model calibration.
Section 4, Capacity Analysis, describes the capacity analysis and design criteria, model results, and preliminary solutions for identified capacity deficiencies. Section 5, Capacity Improvement Projects, explains the process for development of capacity improvement projects, and presents the recommended projects. Section 6, Recommended Capital Improvement Program, presents the recommended CIP, including project costs, prioritization, CIP schedule, and implementation recommendations.

The Appendices to this report include plots of the flow monitoring data and documentation for the recommended CIP, including project descriptions and cost estimates. (This page intentionally left blank)
Land Use and Flow Estimates
Chapter 2

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-1
Chapter 2 Land Use and Flow Estimates
This chapter presents the land use and design wastewater flow estimates for the City of Santa Clara. The section describes existing and projected future land uses for the City, which form the basis for generating flows in the hydraulic model. Flow monitoring was conducted to verify existing flows in major trunk sewers. Design flow estimates were developed based on criteria developed for each flow component:
base wastewater flow, groundwater infiltration, and rainfall-dependent infiltration and inflow.

2.1 Land Use Projections
Land use data form the basis for estimating wastewater flows in the sewer system. Land use data for the City of Santa Clara are based on the City’s 2010 General Plan and General Plan Amendment, and information on specific developments provided by the City’s Planning Department.

2.1.1 Planning Scenarios
The Sanitary Sewer Capacity Assessment Project includes two modeling scenarios: Existing and Future.

For the purposes of this Capacity Assessment, the Existing Scenario was defined as current development as of winter 2005-2006. Actual water use data were used to estimate wastewater flows for the existing scenario, and flow monitoring data collected during this time period were used to calibrate the hydraulic model for existing flows.

The Future Scenario assumes construction of all currently planned major development and redevelopment projects in the City, as well as potential increased densities in mixed use and transit-oriented mixed use and commercial/office areas consistent with the City’s current General Plan. The future scenario was used to examine the impact on the system of future increases in wastewater flows due to new development and redevelopment.

RMC met with the City’s Planning Department in July 2006 in order to identify planned development and redevelopment for the Future Scenario. Table 2-1 lists the planned development and redevelopment projects based on information provided by the Planning Department and compiled from the General Plan and General Plan Amendment. It includes the following categories of development/redevelopment:
• Developments under construction or recently constructed • Planned developments, approved
• Planned developments, not yet approved
• Land use intensification per General Plan and General Plan Amendment, no specific development plan available
Figure 2-1 shows the locations of these planned and recently constructed developments. Table 2-2 summarizes the quantity of residential and non-residential development represented by the planned developments listed in Table 2-1 and shown in Figure 2-1.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-2
Table 2-1 Planned Development/Redevelopment
Name Type a Planned
Development b, c
Intel (Juliet site) Commercial 100,000 SF
Intel (Freedom site) Commercial 400,000 SF
Applied Materials R&D 840,000 SF
Kaiser -New Hospital Commercial 675,000 SF
HP/ Agilent R&D 727,500 SF
Marvell Site (previously 3Com Pal) R&D 278,000 SF
Yerba Buena/ Irvine Commercial 910,000 SF
Hotel Development (previously Marriott) Hotel 225 Rooms Commercial 8,800 SF Vidovich Project Multi Family 64 DU Santa Clara University Commercial 250,000 SF
Citation Project Single Family 413 DU
Sobrato Project Apartment 306 DU
3600 Pruneridge Single Family 31 DU
Multi Family 2 DU
Shea Project Multi Family 130 DU
4767 Lafayette St Single Family 27 DU
Hyatt Regency Hotel Expansion (previously Westin) Hotel 250 Rooms 2250 El Camino Real (Sal Caruso) Condominiums 45 DU
Citation Project 2 Multi Family 59 DU
Rivermark Multi Family 964 DU
Taylor Woodrow/BRE Single Family 63 DU
Rental Condominiums 277 DU
Kohl's Site Development Condominiums 490 DU
Commercial 52,300 SF
Extreme Networks TOMU 15 Acres
Santa Clara Convention Center New Ballroom Commercial 24,000 SF Valley Fair Mall Expansion Commercial 22,000 SF
Downtown Revitalization MU 7 Acres
Train Station Area MU 17 Acres
BAREC Area Single Family 110 DU
Multi Family 165 DU
El Camino Real Intensification MU 9 Acres
North Santa Clara Intensification Higher Intensity Office 524 Acres Cherry Orchard Place Single Family 14 DU
Old Kaiser Campus Medium Density Residential 27 Acres
General Plan Developments MU 142 Acres
General Plan Developments TOMU 62 Acres
(a) R&D = Research & Development; MU = Mixed Use; TOMU = Transit-Oriented Mixed Use; Multi Family = condominiums/townhouses
(b) DU = dwelling units; SF = square feet
(c) MU and TOMU assumed to be moderate and medium density residential, respectively (added to existing commercial area)
4767 Lafayette St. Detached Family
Home Project
BAREC Area
Train Station
Area
El Camino
Intensification
Downtown Revitalization
Kohl's Site
Taylor Woodrow/BRE
Cherry
Orchard Place
Valley Fair
Mall Expansion
Old Kaiser
Campus Site
Extreme
Networks
North SC Intensification
Future Hotel
Development
HP/ Agilent
Applied Materials
Kaiser
New Hospital
Rivermark
Hyatt Hotel Expansion &
Santa Clara Convention
Center Expansion
Citation Project
Yerba Buena/ Irvine
Santa Clara
University Classroom
Expansion
Marvell
Intel (Juliet site)
Shea Project
Sobrato Project
Intel (Freedom Site)
3600 Pruneridge
Ave. Residential
Project
Vidovich Project
(Homes and Retail)
2250 El Camino Real
Condominiums
(Sal Caruso)
Legend
City Boundary
Parcels
Planned Development/Redevelopment Projects
Commercial/Office/R&D
Residential
Commercial/Residential
Land Use Intensification
Mixed Use
Transit Oriented Mixed Use
Commercial/Office
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity Analysis
Planned
Development/Redevelopment
Figure 2-1
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-4
Table 2-2 Planned Development Summary
Type of Development/Redevelopment Quantity Units
Single Family 658 DUs
Condominiums/Townhouses 2,196 DUs
Apartments 306 DUs
Hotel 475 Rooms
Commercial 2,442,100 Sq. Ft.

R&D 1,845,500 Sq. Ft.

Commercial/Office Intensification a 913,018 Sq. Ft.

Additional Mixed Use per GP b 4,444 DUs
Additional Transit-Oriented Mixed Use per GP c 2,772 DUs

Total Additional DUs 10,376
Total Additional Sq. Ft. Commercial/Office/R&D 5,200,618 (a) Assumes increase in floor-area-ratio (FAR) on 0.04. (b) Assumes residential density of 22 DU/acre.
(c) Assumes residential density of 36 DU/acre.

2.2 Flow Monitoring Program
Flow monitoring was conducted by field services staff of E2 Consulting Engineers, subcontractor to RMC, to obtain data to quantify flows in the system and enable analysis of wet weather infiltration/inflow (I/I) and calibration of a hydraulic model. The flow monitoring program consisted of 26 flow meters and three rain gauges operating for a period of approximately ten weeks.

The flow monitoring sites are listed in Table 2-3 and shown on Figure 2-2. The meters were installed from January 19 to 24, 2006, and most were removed on about April 3. Five of the meters were left in place for a few additional weeks to further verify meter calibration parameters. The meter sites utilized Sigma 910 meters with pressure depth transducers and Doppler velocity sensors. Along with the 26 meters, two existing City-owned ISCO flow meters installed on the parallel 33-inch lines at the east side of Santa Clara near Highway 101 were also calibrated per the City’s request. In addition, Cupertino Sanitary District has a flow monitor installed at Homestead Road to measure sewer flows that enter Santa Clara at the western city limits; RMC also obtained data from this meter during the flow monitoring period.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-5
Table 2-3 Flow Monitoring Locations
Flow
Monitor Location
Manhole
Number
Pipe Size
(in.)
1 Easement off of Lafayette St. north of Calle De Mundo S104-23 33 2 Lafayette St. north of Calle de Mundo S104-30 42
3 Primavera Lift Station S105-34 24
4 Lafayette St. south of Calle De Luna S104-36 36
5 Montague Expwy. east of Lafayette S86-17 18
6 Lafayette at Montague Expwy. S86-20 30
7 Mission College Blvd. north of Our Lady's Way S83-21 33 8 Mission College Blvd. north of Our Lady's Way S83-22 33 9 Calabazas Creek south of Kifer Rd. S62-40 24
10 Bowers Ave. at Chromite Dr. S53-34 30
11 Chromite Dr. at Bowers Ave. S53-41 18
12 Scott Blvd. south of Central Expwy. S65-34 24
13 Scott Blvd. south of Central Expwy. S65-33 18
14 Central Expwy. west of UPRR S67-16 27
15 De La Cruz Blvd. south of Central Expwy. S67-26 48
16 Brokaw Rd. north-east of UPRR S48-36 18
17 Benton St. west of The Alameda S38-1 12
18 Los Padres Blvd. at Bray Ave. S45-80 18
19 Los Padres Blvd. at Karen Dr. S25-1 15
20 San Tomas Expwy. at Warburton S44-57 15
21 Bowers Ave. south of Warburton S43-86 27
22 Kiely Blvd. north of Homestead S23-20 18
23 Saratoga Creek west of Kiely Blvd. S23-12 21
24 Homestead Rd. east of Bing Dr./Princeton Way S2147 18 25 Homestead Rd. east of Bing Dr./Princeton Way S21-54 15 26 Wren Ave. at Lerwick Ct. S21-23 24
During the flow monitoring period, all of the monitoring sites were visited weekly to check meter operation and site conditions, obtain field calibration measurements, and download collected data. Field calibration involves taking manual depth measurements and flow velocity measurements using a portable velocity meter. These calibration measurements were compared to and used to adjust monitor-recorded depth and velocity if needed. Calibration measurements were taken at different times of day in order to obtain calibration points for the full range of typical diurnal flows.

Three rain gauges were installed to collect representative rainfall over the service area during the monitoring period. The rain gauge locations were:

Rain Gauge 1: Santa Clara Corporation Yard
Rain Gauge 2: Primavera Pump Station
Rain Gauge 3: Santa Clara Tank Site, off of Highway 280 and Lawrence Expressway Approximately 12 storm events occurred during the flow monitoring period, totally about six inches of rainfall. Most of the events, however, were relatively small. The duration and the total rainfall for each event are summarized in Table 2-4.

(This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

Flow from
CuSD
9 8
7 6
5 3
4 2
1 26
25 24
23 22
21 20
19 18 17 16
15 14 13
12 11
10 ISCO-23
ISCO-01
3 1
2 0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Flow Meter and ID 5
Rain Gauge and ID 1
Modeled Trunk Sewers
Sewer Subbasins
Parcels
Flow Meter Sites
Figure 2-2
Machado Ave.

Monroe St. Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.

Scott Blvd.

Calabazas Blvd.

Flow To

SJ/SC WPCP
Flow To CSJ
Interceptor in
Zanker Rd
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-7
Table 2-4 Rain Events during Flow Monitoring Period
Start Duration Storm Rainfall (in.) Max. Hour (in.)
Date/Time
End
Date/Time (hours) Avg. RG1 RG2 RG3 RG1 RG2 RG3
2/17/06 12 PM 2/17/06 8 PM 8 0.23 0.20 0.19 0.31 0.09 0.08 0.15 2/26/06 11 PM 2/28/06 2 AM 27 1.16 1.14 0.99 1.34 0.17 0.16 0.19 3/2/06 12 AM 3/2/06 4 AM 4 0.27 0.25 0.30 0.27 0.10 0.14 0.10 3/3/06 1 AM 3/3/06 5 PM 16 0.26 0.42 0.03 0.32 0.19 0.02 0.13 3/5/06 3 PM 3/6/06 4 AM 13 0.68 0.56 0.66 0.81 0.12 0.13 0.13 3/10/06 6 PM 3/11/06 7 AM 13 0.23 0.28 0.26 0.15 0.08 0.12 0.06 3/13/06 11 PM 3/14/06 7 AM 8 0.38 0.34 0.39 0.42 0.10 0.14 0.12 3/16/06 9 PM 3/17/06 12 AM 3 0.39 0.39 0.37 0.40 0.26 0.26 0.24 3/20/06 10 AM 3/21/06 5 AM 19 0.74 0.71 0.92 0.58 0.22 0.24 0.18 3/24/06 5 PM 3/25/06 6 AM 13 0.61 0.53 0.65 0.66 0.13 0.13 0.19 3/29/06 3 AM 3/29/06 10 AM 7 0.20 0.18 0.13 0.28 0.06 0.05 0.10 4/2/06 4 PM 4/3/06 2 PM 22 0.71 0.74 0.66 0.74 0.11 0.12 0.10 Following the completion of flow monitoring, E2 prepared a summary report containing copies of the meter site reports and photographs; 7-day graphs of the flow and rainfall data; and summary tables of minimum, maximum, and average daily flows and rainfall. In addition, electronic files of all data were provided to the City. The final flow monitoring report has been provided to the City as a separate attachment. Summary plots of the flow and rainfall data are included in Appendix A of this report.

2.3 Wastewater Flows
The components of wastewater flows and methodology for quantifying each flow component are discussed below.

2.3.1 Wastewater Flow Components
Wastewater flows include three components: base wastewater flow (BWF), groundwater infiltration (GWI), and rainfall-dependent infiltration/inflow (RDI/I), as illustrated conceptually in Figure 2-3. BWF represents the sanitary and process flow contributions from residential, commercial, institutional, and industrial users of the system. GWI is groundwater that infiltrates into defects in sewer pipes and manholes, particularly in winter and springtime in low-lying areas. GWI is typically seasonal in nature and remains relatively constant during specific periods of the year. RDI/I is storm water inflow and infiltration that enter the system in direct response to rainfall events, typically through direct connections such as holes in manhole covers or illegally connected roof leaders or area drains, or, more commonly, through defects in sewer pipes, manholes, and service laterals. RDI/I typically results in short term peak flows that recede quickly after the rainfall ends.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-8
Figure 2-3 Wastewater Flow Components
(Not to scale)
Flow
Rainfall
Time
(24 Hours)
RDI/I
BWF
GWI

2.3.2 Methods for Estimating Base Wastewater Flows
Base wastewater flow consists of the normal sanitary flow contribution from residential, commercial, institutional, and industrial users of the sewer system. Base wastewater flows are typically calculated by applying unit BWF factors (in gpd per acre or gpd per DU) to existing and/or future land use quantities.

For residential areas, BWF factors depend primarily on residential density and the average number of persons per dwelling unit. For commercial and industrial areas, BWF factors depend primarily on the type and distribution of the commercial and industrial establishments. Since BWF factors would be expected to be similar for communities with similar types of development, BWF factors are often developed based on published values and verified by flow monitoring or analysis of water consumption data for a particular community.

For the City’s Sanitary Sewer Capacity Assessment, BWF loads were developed for both existing and future development conditions. Existing loads were developed based on actual winter water use data from the City’s customer billing records, and future loads were based on projected development and redevelopment projects anticipated by the City. The unit flow factors used to compute BWF from future development are summarized in Table 2-5. The residential factors shown in the table are consistent with the City’s standard residential design flow rate of 70 gallons per capita per day (gpcd) and residential densities for various land use classifications. The rates per square foot for commercial/office and office/research & development (R&D) development are based on typical design factors used for other similar areas.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-9
Table 2-5 Base Wastewater Flow Unit Flow Factors
Type of Development Unit Flow Factor Basis
Single Family Detached 245 gpd/DU 3.5 people/DU @ 70 gpcd Townhouses/Condominiums 175 gpd/DU 2.5 people/DU @ 70 gpcd Apartments 154 gpd/DU 2.2 people/DU @ 70 gpcd
Hotels 100 gpd/room
Commercial/Office 0.1 gpd/sq. ft.

Office/R&D 0.15 gpd/sq. ft.

Moderate Density Residential
(Mixed Use) 3,200 gpd/acre 21 DU/acre @154 gpd/DU
Medium Density Residential
(Transit-Oriented Mixed Use) 4,600 gpd/acre 30 DU/acre @ 154 gpd/DU Commercial/Office/R&D
Intensificationa + 300 gpd/acre + 0.04 FAR @ 0.15 gpd/sq. ft. (a) Applied to areas of North Santa Clara where existing development is anticipated to increase in intensity from a current average floor-area-ratio (FAR) of 0.41 to a future average of 0.45.

2.3.3 Diurnal Base Wastewater Flow Patterns
In most sewer systems, BWF exhibits typical diurnal patterns depending on the type of land use. For Santa Clara, typical diurnal curves were developed for residential, commercial, and industrial areas, for both weekend and weekday conditions. These curves are shown in Figure 2-4. Each area of the system was assigned a diurnal curve according to its predominant land use type.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-10
Figure 2-4 Diurnal Curves

0.0 0.2

0.4 0.6

0.8 1.0

1.2 1.4

1.6 1.8

2.0 0 3 6 9 12 15 18 21 24
Hour
Ratio to Average Flow
Residential Weekend Residential Weekday

0.0 0.2

0.4 0.6

0.8 1.0

1.2 1.4

1.6 1.8

2.0 0 3 6 9 12 15 18 21 24
Hour
Ratio to Average Flow
Commerical Weekday and Weekend

0.0 0.2

0.4 0.6

0.8 1.0

1.2 1.4

1.6 1.8

2.0 0 3 6 9 12 15 18 21 24
Hour
Ratio to Average Flow
Industrial Weekend Industrial Weekday
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-11

2.3.4 Large Users
For purposes of this study, a “large” discharger was defined as one discharging more than an average of 40,000 gallons per day (gpd) average flow or 50,000 gpd maximum month flow during the winter months. Based on winter 2005-2006 water and recycled water billing records provided by the City, there are eighteen large dischargers that meet the criteria outlined above. Wastewater flows for large users were based on average winter flow.

All dischargers to the sewer system are included in the City’s water billing database and are therefore accounted for in the calculation of existing BWF loads. However, some large dischargers do not exhibit typical industrial diurnal wastewater flow patterns and therefore must be accounted for separately.

Typically, these are users that discharge wastewater on a relatively constant basis, 24 hours per day and 7 days per week (24/7). These users were given separate constant diurnal profiles in the hydraulic model.

Table 2-6 lists the eighteen large dischargers in the Santa Clara system and those that are considered 24/7 users.

Table 2-6 Large Dischargers
Large Water User APN Address Average Flow a
(gpd)
Maximum
Month Flow a
(gpd)
KOLL 104-13-090 2151 Mission College Blvd 934,461 1,101,270

CONTAINER CORP OF
AMERICA b,c 230-03-100 2600 De La Cruz Blvd 381,870 413,739

NEWARK GROUP
INDUSTRIES INC b,c 230-03-090 525 Mathew St 473,003 561,917 SILICONIX INC b 104-39-023 2201 Laurelwood Rd 411,666 422,353 DVR POWER PLANT d 224-36-047 850 Duane Ave 103,354 576,000 RENAULT 216-49-019 3320 Scott Blvd 165,222 181,586

OWENS-CORNING
FIBERGLAS CORP b,c 224-07-099 960 Central Expy 19,715 21,242 ANADITE INC 104-14-047 1440 Norman Ave 142,536 148,429
INTEL CORPORATION 104-48-010 3603 Juliette Ln 118,250 120,743 INTERNATIONAL INTEL 216-46-015 3065 Bowers Ave 91,713 97,439

AGILENT
TECHNOLOGIES INC 316-17-018 5301 Stevens Creek Blvd 88,963 131,152 SCP 2001PE LLC 104-13-083 2175 Mission College Blvd 88,922 98,976

APPLIED MATERIALS
INC 216-49-024 3070 Bowers Ave 88,129 100,579
DLC ASSOCIATES II 097-31-062 3495 De La Cruz Blvd 67,262 75,719 LEON MARDIROSSIAN 224-06-170 1415 Richard Ave 64,683 66,340

NATIONAL

SEMICONDUCTOR

CORPORATION
205-39-022 2900 Semiconductor Dr 57,636 72,896
SIGMA CIRCUITS INC 230-47-112 351 Mathew St 54,302 57,047

ADVANCED

CARDIOVASCULAR

SYSTEMS INC
216-30-040 3200 Lakeside Dr 35,261 51,453
(a) For December 2005 through March 2006 period.
(b) 24/7 discharger.
(c) Derived from water use data adjusted by a factor provided by the City. (d) Based on DVR Power Plant data provided by the City.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-12

2.3.5 Infiltration/Inflow
Infiltration/inflow is extraneous groundwater and storm water that enter the sewer system through illegal connections or defects in sewer pipelines, manholes, and service laterals. The primary types of I/I are groundwater infiltration and rainfall-dependent I/I.

Groundwater Infiltration
Groundwater infiltration is generally quantified based on actual flow monitoring data, since it is difficult to predict GWI rates based on physical system data alone. In the context of design flow criteria, GWI represents the incremental groundwater infiltration that occurs during the wet weather season above the “baseline” infiltration level during the driest months of the year.

GWI can be estimated based on minimum flows during non-rainfall periods during a wet weather flow monitoring period. Minimum flows typical occur during the nighttime or early morning hours when base wastewater flows are at a low. Alternatively, GWI can be estimated as the difference between average metered flow during non-rainfall periods and computed average BWF. In either case, the resulting GWI, is expressed on a unit basis (gpd/acre or gpad) by dividing by the sewered acreage of the monitored area.

Typical GWI rates may range from 100 to over 1,000 gpad.

GWI flows were estimated through the model calibration process (described in the next chapter of this report) by comparing model-simulated BWF to actual flow measurements from the temporary flow monitoring program conducted in January through April 2006. Cases where model-predicted BWF was noticeably lower than monitored flow indicated the possible occurrence of GWI.

Rainfall-Dependent I/I
RDI/I flows result from rainfall events that produce infiltration and inflow of storm water runoff into the sewer system. RDI/I can be quantified as the difference between the total flow during and immediately following a storm event and the non-rainfall “base flow” (BWF plus GWI) that is estimated to have occurred during the storm period. The magnitude of the resulting RDI/I response is typically described by the percentage of the rainfall volume (called the “R value”) represented by the volume of the RDI/I hydrograph. The R value can vary from storm to storm, depending on such factors as the degree of soil saturation (due to antecedent rainfall) prior to the storm event.

The shape of the RDI/I hydrograph is also important in determining the peak RDI/I response. The RDI/I hydrograph shape in often defined by separating the total RDI/I hydrograph volume into components, representing different response times to rainfall (fast, medium, and slow). Each component is identified by a percentage of the total RDI/I volume and specific time to peak (T) and recession coefficient (K), illustrated in Figure 2-5. The R component percentages and T and K values can be applied to each hour of rainfall to generate a “synthetic hydrograph” that approximates the volume and shape of the hydrograph from the actual observed event. These parameters, when applied to a different rainfall pattern, can be used to estimate the RDI/I response to that particular rainfall event. This methodology is used to synthesize RDI/I hydrographs for a “design storm” for collection system modeling.

Design criteria for RDI/I include design R values and hydrograph shape parameters and the hourly rainfall for the selected design storm event. As described in the next chapter of this report, R values and hydrograph parameters are determined through the process of model calibration, in which actual observed rainfall events are simulated in the hydraulic model, and the resulting model hydrographs are compared to the measured flows at flow meters locations. The RDI/I parameters are adjusted as needed to achieve the best match of modeled to monitored flows. Once calibrated, the model RDI/I parameters can be applied to a design storm to simulate wet weather flows for a design event.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-13
Figure 2-5 RDI/I Hydrograph Components

2.3.6 Design Event
Wastewater collection systems are typically sized for a specific “design” condition, often represented by a development condition (e.g., “buildout”) under a design wet weather event, in combination with a designated system performance criterion.

Generally, the performance criterion is defined by the maximum allowable water level in the system, which may be at the ground surface (i.e., “no overflows”), a specified distance below the ground (say 5 feet below the manhole rims), or more conservatively, by a maximum allowable flow depth to pipe diameter (d/D) ratio. The maximum d/D may vary by pipe size. A maximum allowable d/D of 1.0 (i.e., “no surcharge”) is commonly used, although a smaller value (e.g., 0.75) may be used for smaller diameter sewers to account for the greater potential for reduced capacity due to obstructions in the pipes, or to add more conservatism to sizing of new pipes.

The “design event” establishes the maximum recurrence frequency under which the design performance criterion can be exceeded. Thus, if the performance criterion is “no surcharge” and the recurrence T1
T2
T2 K2
T3 T3K3
RDI/I
R1
R2
R3
R = R1+R2+R3
P
P is rainfall intensity over 1 hour
Total Rainfall Volume = P x Drainage Area
1 hour
Triangular Hydrograph 1
(fast response)
Triangular Hydrograph 2
(medium response)
Triangular Hydrograph 3
(slow response)
Total RDI/I Hydrograph
Time
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-14
frequency is 10 years, then the system must be designed such that pipes would not surcharge any more frequently than once every 10 years.

In practice, the design event is often equated to a specified recurrence frequency rainfall event, which can be developed based on historical rainfall intensity-duration-frequency (IDF) statistics. The City of San Jose has adopted a 10-year design storm for its capacity assessment program. Based on IDF data and guidelines from the County of Santa Clara Storm Design Requirements, a synthetic 10-year, 24-hour design storm was determined for the San Jose Airport (see Figure 2-6 below) and applied to other areas of the system in proportion to average annual rainfall. Applying this approach to Santa Clara, the design rainfall would be approximately 1.0 to 1.2 times the San Jose Airport rainfall (varying over the service area from north to south).

Figure 2-6 10-Year Design Storm for San Jose Airport
10-Year, 24-hour Storm

0.00 0.10

0.20 0.30

0.40 0.50

0.60 0.70
0:00
2:00
4:00
6:00
8:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
Rainfall (in)
To develop the projected RDI/I flows for the design event, the RDI/I hydrograph parameters determined from the wet weather calibration would be applied to the design storm rainfall. Note that the design event can be superimposed on an average base wastewater flow condition, based on the assumption that the peak rainfall could potentially occur at any time of the day, or it can be constructed so that the peak RDI/I roughly coincides with the peak BWF for a typical residential diurnal pattern, providing a higher level of conservatism in the design flows. The City of San Jose utilizes the more conservative assumption for sewer system planning. Therefore for Santa Clara, it was recommended that the same design event criteria be used. This is a reasonable assumption given that peak wet weather flows in the Santa Clara sewer system are relatively low.

2.3.7 Flows from Cupertino Sanitary District
Flows from Cupertino Sanitary District (CuSD) enter the City’s sewer system on Homestead Road.

CuSD maintains a flow meter at the discharge point to the City’s system. Initially, data from the District’s meter was reviewed in order to estimate CuSD flows discharging into Santa Clara; however, the data was found to be inconsistent, with unexplained changes in average daily flows over the course of the City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 2 Land Use and Flow Estimates May 2007 2-15
10-month period (January through October 2006). It is believed that this meter may have been out of calibration and was calibrated at some point during the year.

As part of a separate study conducted for CuSD, RMC estimated existing and future average dry weather flow (ADWF) from CuSD based on data on sewer connections, land use, and population density. The existing flow from the metered area of CuSD (portion tributary to Santa Clara, which represents about 89 percent of the total service area flow) was estimated to be 4.9 mgd, which matches well to the total flows at the temporary meters immediately downstream of the CuSD discharge point. Therefore, for purposes of the Santa Clara model, this value was used as the existing CuSD flow. The RMC study estimates the total future (year 2030) ADWF for CuSD at about 7.2 mgd; therefore, a preliminary estimate of future ADWF from CuSD entering the Santa Clara system at Homestead Road is 6.4 mgd (89 percent of the total future flow).

2.3.8 Wastewater Flow Estimates
The estimated existing and future average dry weather flow (ADWF), peak dry weather flow (PDWF), and design storm PWWF flows for the City’s system were developed based on modeling as described in Chapters 3 and 4 of this report. The results are summarized in Table 2-7.

Table 2-7 Sewer System Flow Estimates
Existing Flow (mgd) Future Flow (mgd) System Outfall ADWF PDWF PWWF ADWF PDWF PWWF North (to Northside and
Rabello Pump Stations) 17.7 23.6 40.8 21.2 28.7 43.1a
East (to San Jose Trimble
Road trunk sewer) 6.0 8.7 13.2 6.9 10.0 14.1
Total 24 32 54 28 38 57
Note: ADWF and PDWF represent a non-rainfall wintertime condition and include groundwater infiltration.

PWWF represents a 10-year frequency design storm.
(a) Assumes peak flow from Cupertino Sanitary District does not increase above its contracted maximum capacity of 13.8 mgd.

Hydraulic Model Development
Chapter 3

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-1
Chapter 3 Hydraulic Model Development
The City, in conjunction with RMC, selected DHI’s MIKE URBAN™ with EPA SWMM 5 as the software to be used for the Sewer System Capacity Assessment. EPA SWMM 5 is the latest version of the U.S. EPA’s public domain Storm Water Management Model, which provides a fully dynamic solution for modeling storm water and sanitary sewer systems. MIKE URBAN is an ArcGIS-based model interface that provides the user environment for building and running the model and viewing model results. RMC also utilized another modeling program, InfoWorks™, to help in model construction and validation. The process of developing the model for use in the capacity assessment is described below.

3.1 Modeled System
The hydraulic model developed for the City’s Sewer System Capacity Assessment represents the trunk sewer system, the network of larger diameter pipes that comprises the “backbone” of the system. The wastewater is conveyed from the City to the San Jose/Santa Clara Water Pollution Control Plant (SJ/SC WPCP) at two locations: at the northeast corner of the City just east of Lafayette Street, where flow is pumped via the Northside and Rabello Pump Stations and force mains to the WPCP; and on the eastern side of the City east of De La Cruz Boulevard and Highway 101, where flow discharges by gravity into a 48-inch sewer in Trimble Road that conveys the flow to the City of San Jose’s interceptor in Zanker Road. The City also receives flows from the Cupertino Sanitary District (CuSD), which discharge into the Santa Clara sewer system on Homestead Road at Swallow Drive.

The City’s wastewater collection system includes a total of approximately 270 miles of sewer pipelines, of which approximately 28 percent, or 76 miles, are included in the modeled system. The modeled network includes almost all of the 15-inch and larger pipes, about 40 percent of the 10- and 12-inch pipes, and a few 6- and 8-inch pipes. The modeled system also includes four of the system’s six wastewater pump stations: Westside, Primavera, Tasman, and De La Cruz. The Northside and Rabello Pump Stations are not explicitly modeled, as their downstream hydraulic control points are governed by the downstream force mains and hydraulic gradeline at the WPCP. Rather, the northern outlet of the model is located at the junction manhole (S114-19) just upstream of the Rabello Pump Station. The modeled network is shown in Figure 3-1.

3.2 Model Network Construction and Validation
Network data for the model were provided by the City in the form of AutoCAD mapping and Excel files with manhole and pipe attribute data (manhole coordinates and rim elevations; pipe diameters, lengths, and invert elevations). Through a multi-step process, the AutoCAD file and attribute data were imported into ArcGIS to create GIS datasets of all of the pipes and manholes in the City’s system. The pipes and manholes to be included in the modeled network, described previously, were then extracted out of those datasets. The GIS files of the modeled pipes and manholes formed the basis for model construction and validation; these files were imported into the modeling environment in InfoWorks and subsequently into MIKE URBAN.

The model construction and validation process included the following steps:
▪ The modeled network was checked for connectivity, i.e., verifying that correct upstream/downstream manholes were identified for each pipe and there were no missing links in the network. ▪ Profiles were plotted for each series of pipe segments in the modeled network to visually check for missing or suspect data. Examples of missing or suspect data included missing rim or invert elevations, negative pipe slopes, or abrupt steps up or down in pipe inverts. Where appropriate, missing or suspect data were interpolated, or verification in the form of additional survey information or as-built drawings were requested from the City.
(This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Modeled Pump Stations
Pump Stations Not in Model
Modeled Trunk Sewers
Sewer Mains
Parcels
Modeled System
Figure 3-1
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-3
▪ As-built information was used to manually input details for each of the 22 inverted siphons in the modeled network. Dummy nodes were created as needed for the siphon angle points so that the three “legs” of the siphon (downward, horizontal, and upward) could be represented explicitly. ▪ As-built information was used to manually input details on the modeled pump stations. Information required included wet well elevations and dimensions, number of pumps, pump capacities, on/off levels, and discharge curves.
▪ Flow splits (manholes with more than one outlet pipe) were identified for further verification of outlet pipe elevations and/or the existence of weir overflows or other control structures. Field verification and/or as-built drawings were requested from the City as needed. Two structures in particular, the diversion structure at manhole S20-10 and the “flume” structure at manhole S65-30 required special investigations and model configurations.

3.3 Development of Model Loads
Flows are loaded into the model at “load manholes,” each of which represents the point where flows from unmodeled sewers discharge into the modeled network. The unmodeled sewers were grouped into sewer subbasins, each with a unique load manhole in the network. Approximately 175 sewer subbasins were delineated for defining the model loads. The subbasins and load manholes are shown in Figure 3-2.

3.3.1 Base Wastewater Loads
The City’s water billing data and recycled water discharge data from December 2005 to March 2006 were used to develop existing loads to the hydraulic model. The billing data provided by the City was compiled into a database, with each billing record (account) associated with its Santa Clara County Assessor’s Parcel Number (APN). Since many of the water billing records contained incorrect APNs or no APN at all, an extensive process was used to acquire these APNs from street address cross reference tables and other information supplied by the City. Water usage for multiple water accounts associated with the same parcel were added together. The average water use by parcel was then determined by averaging the monthly use for the four winter months (December through March). Winter water use is considered a reasonable approximation of wastewater flow because outdoor water use (irrigation) during the wintertime is minimal.

The water billing records were then linked to the City’s parcel GIS file. Each of the parcels was associated with the appropriate sewer subbasin. Finally, the total average base wastewater flow per sewer subbasin was computed by adding the flows (water use) for all parcels contained with the subbasin. Each subbasin was also characterized based on its predominant land use type (residential, commercial, or industrial) in order to apply an appropriate diurnal wastewater pattern to simulate the flows in the model.

Flows from large dischargers were removed from the cumulative sewer subbasin flow and added to the model as point loads at specific locations in the modeled system. As noted in Chapter 2, model loads for large users were based on average winter flow.

3.3.2 I/I Loads
GWI and RDI/I flows were also loaded to the model by subbasin by associating each subbasin with a flow meter area. The flow meter areas are shown in Figure 3-3. For each subbasin, the total sewered area (i.e., area that potentially contributes I/I) was determined by summing the acreage of non-open space land uses in the subbasin. Non-open space land uses include residential, commercial, industrial, and institutional uses, but do not include parks, drainage channels, and large roadways such as freeways. I/I flows for each subbasin were computed in the model by applying the appropriate meter area GWI and RDI/I parameters (determined during the model calibration process described below) to the sewered area of the subbasin.

Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Modeled Trunk Sewers
Subbasin Load Manholes
Sewer Subbasins
Parcels
Subbasins and Load
Manholes
Figure 3-2
Machado Ave.

Monroe St. Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.

Scott Blvd.

Calabazas Blvd.
(This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.

M_01
M_04
M_11
M_02
M_14
M_10
M_03
M_06
M_17
M_21
M_18
M_20
M_05
M_16
M_08 M_07
M_12
M_15
M_22
M_19
M_25
M_23
M_24
M_09
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Modeled Trunk Sewers
Meter Tributary Area
Parcels
Flow Meter Areas Used for
I/I Analysis
Figure 3-3
Monroe St. Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.

Machado Ave.

Calabazas Blvd.

Scott Blvd.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-6

3.4 Model Calibration
Model calibration is the process of comparing model-computed flows to observed (monitored) flows to verify that the model is accurately simulating flows in the sewer system. The model is calibrated for both dry and wet weather conditions.

As described in Chapter 2, a temporary flow monitoring program consisting of 26 flow meters and 3 rain gauges installed in the Santa Clara system for a period of about two months (late January through early April 2006) provided data for calibration of the hydraulic model. A flow meter schematic is shown in Figure 3-4.

3.4.1 Dry Weather Calibration
The 7-day dry period from February 4 to 10, 2006, was used as the dry weather calibration period for the model. The dry weather calibration process was used to verify BWF loads and diurnal curves, and to quantify GWI (as indicated by monitored flows that were higher than estimated BWF). The model calibration resulted in a reasonably good match of modeled to metered flow at most locations, but some significant differences at others. These differences may be due to inaccuracies in the meter data, in water use loadings, or in the configuration of the system (e.g., upstream flow splits). The calibration process did result in further investigation and adjustments to several flow split locations in the model. Every effort was made to resolve as many of the calibration differences as possible. As shown in Table 3-1, the total flows in the system, as indicated by the sum of the flows at the most downstream meters (Meters 1, 2, 3, 4, 14, and 15), were within 3 percent of the modeled flows, which provides confidence that the overall flows in the model are reasonably accurate.

Table 3-1 Comparison of Meter and Model Flow
Meter Meter Avg.

Flow (mgd)
Model Avg.

Flow (mgd)
Difference
(mgd)
Percent
Difference
1 5.45 6.06 0.61 11%
2 6.17 6.66 0.49 8%
3 1.06 0.70 -0.36 -34%
4 4.25 4.20 -0.05 -1%
14 2.15 2.23 0.08 4%
15 4.06 3.90 -0.16 -4%
Total 23.13 23.74 0.61 3%
Figure 3-5 shows example plots of model vs. metered flow for two locations in the system (Meters 1 and 15).

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-7
Figure 3-4 Meter Schematic
S62-8
Outfall
Outfall
ISCO 1/2 ISCO 3
22 Flow from CuSD
25 26
24 23
21 9
10 11
8 7
1 2
3 4
5 6
12 13
20 18
19 16
17 14 15
S20-9
S20-10
gates
S20-16
S10-29
S32-68 S33-5
S22-64
S23-27
S32-101
S93-53 S93-52
S73-29
S52-5
S41-113 &
S41-104
S42-104
S53-34
S68-15
S65-30
flume
S64-32
S64-46
Legend
24 S20-16
Flow Meter
Modeled flow split and node ID
Flow path
Alternate flow path
S10-29
S62-8
Outfall
Outfall
ISCO 1/2 ISCO 3
22 Flow from CuSD
25 26
24 23
21 9
10 11
8 7
1 2
3 4
5 6
12 13
20 18
19 16
17 14 15
S20-9
S20-10
gates
S20-16
S10-29
S32-68 S33-5
S22-64
S23-27
S32-101
S93-53 S93-52
S73-29
S52-5
S41-113 &
S41-104
S42-104
S53-34
S68-15
S65-30
flume
S64-32
S64-46
Legend
24 S20-16
Flow Meter
Modeled flow split and node ID
Flow path
Alternate flow path
S10-29
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-8
Figure 3-5 Example Dry Weather Calibration Plots
Meter/Model Comparison at Meter 1
0 2
4 6
8 10
12 14
16 2/4 2/5 2/6 2/7 2/8 2/9 2/10 2/11
Date
Flow (mgd)
Model Meter
Meter/Model Comparison at Meter 15
0 1
2 3
4 5
6 7
8 9
10 2/4 2/5 2/6 2/7 2/8 2/9 2/10 2/11
Date
Flow (mgd)
Model Meter
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-9

3.4.2 Wet Weather Calibration
Two of the larger storm events from the 2006 monitoring period, February 27 and March 5-6, were used for wet weather calibration. In general, the response to rainfall in the Santa Clara system is relatively small, as evidenced by the relatively low peak flow response to the rainfall events. As described in Chapter 2, RDI/I response to rainfall events was quantified in terms of three sets of triangular unit hydrograph parameters that represent the volume percentage of rainfall that enters the system as RDI/I and the shape of the RDI/I hydrograph as a function of each hour of rainfall. Through the wet weather calibration process, RDI/I hydrograph parameters were developed for each meter area. Additionally, wet weather GWI, as evidenced by elevated flows following the rainfall events, was determined for some areas.

Figure 3-6 presents some wet weather calibration plots for the same meters as shown in Figure 3-5.

Table 3-2 lists the GWI rates that were used for the dry and wet weather calibration by flow meter area and the RDI/I “R values” (percentages of rainfall) for each area.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-10
Figure 3-6 Example Wet Weather Calibration Plots
Meter/Model Comparison at Meter 1
0 2
4 6
8 10
12 14
16 3/4 3/5 3/6 3/7 3/8 3/9 3/10 3/11
Date
Flow (mgd)

0.00 0.05

0.10 0.15

0.20 Rainfall per 15-minute Interval (in.)
Rain Gauge 1 Model Meter
Meter/Model Comparison at Meter 15
0 1
2 3
4 5
6 7
8 9
10 3/4 3/5 3/6 3/7 3/8 3/9 3/10 3/11
Date
Flow (mgd)

0.00 0.05

0.10 0.15

0.20 Rainfall per 15-min Interval (in.)
Rain Gauge 2 Model Meter
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 3 Hydraulic Model Development May 2007 3-11
Table 3-2 GWI and RDI/I Parameters by Meter Area
Meter Areaa
Dry
Weather
GWIb
(gpd/acre)
Wet
Weather
GWIc
(gpd/acre)
R1 RDI/I
Vol. (%)
(2 hrs. to
peak)
R2 RDI/I
Vol. (%)
(6 hrs. to
peak)
R3 RDI/I
Vol. (%)
(12 hrs. to
peak)
M_01 0 0 0.5 0.8 0.8
M_02 0 0 0.5 0.8 0.8
M_03 0 0 0.6 0.1 0.1
M_04 500 1,300 0.6 0.1 0.1
M_05 700 1,000 0.6 0.1 0.1
M_06 0 0 0.6 0.1 0.1
M_07 1,900 1,900 0.3 0.5 0.5
M_08 0 0 0.3 0.5 0.5
M_09 0 0 0.6 0.1 0.1
M_10 0 0 0.6 0.1 0.1
M_11 1,600 2,300 0.9 1.7 6.0
M_12 0 0 0.9 1.0 0.5
M_14 0 0 0.6 0.1 0.1
M_15 300 700 1.0 0.2 0.2
M_16 900 1,600 1.0 0.2 0.2
M_17 200 200 0.6 0.1 0.1
M_18 0 0 0.8 1.0 0.1
M_19 0 0 0.3 0.1 0.1
M_20 0 0 0.6 0.1 0.1
M_21 0 0 0.6 0.1 0.1
M_22 0 0 0.6 0.1 0.1
M_23 0 0 0.6 0.1 0.1
M_24 0 0 0.6 0.1 0.1
M_25 0 0 0.6 0.1 0.1
CuSD 0 0 0.5 0.2 0.4
(a) See Figure 3-3.
(b) Represents GWI during non-rainfall periods (e.g., early to mid-February) of the 2006 flow monitoring period.
(c) Represents GWI immediately following rainfall events. (This page intentionally left blank)
Capacity Analysis
Chapter 4

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 4 Capacity Analysis May 2007 4-1
Chapter 4 Capacity Analysis
This chapter describes the hydraulic analysis and design criteria used to evaluate system performance and size capacity relief projects, the capacity deficiencies based on the results of model runs, and preliminary solutions to identified capacity deficiencies.

4.1 Hydraulic Analysis and Design Criteria
Hydraulic analysis criteria define the conditions under which an existing component of the sewer system is considered to be deficient in capacity. As discussed in Chapter 2, these conditions are based on the design flow and performance criteria established for the system. In the case of Santa Clara, it was recommended that the trunk sewer system be evaluated with respect to its ability to convey peak flows from a 10-year design storm at service area buildout under a peak base wastewater flow condition. Based on discussions with City staff, it was also recommended that a performance criterion of no surcharge (or, more practically, minimal surcharge, e.g., no more than about one foot of surcharge if the sewer is reasonably deep) be used to identify capacity-deficient sewers.

Hydraulic analysis criteria may different from the hydraulic design criteria used to size new or relief system facilities. Hydraulic design criteria needed for sewer system capacity planning include pipe friction factor, minimum pipe diameter and depth, maximum allowable flow depth to diameter ratio (d/D), and minimum and maximum pipe slopes and velocities. Table 4-1 presents the recommended hydraulic design criteria for the Santa Clara sewer system capacity assessment. These criteria are consistent with the City’s current sanitary sewer design criteria.

Table 4-1 Hydraulic Design Criteria
Criterion Description Value
Manning’s ‘n’ Pipe friction factor 0.013
Pipe Diameter
(gravity sewers) Minimum
8 inches in residential areas, 10 inches
in commercial areas, 12 inches in
industrial areas
Pipe Depth Minimum cover over pipe 6 feet
Design Pipe Capacity Pipe capacity at peak design wet
weather flow 0.75 d/D for new or relief sewers
Minimum (pipe full or half full) 2 feet/second
Velocity
Maximum (at peak design flow) 10 feet/second
Minimum Sufficient to obtain minimum velocity
Pipe slope
Maximum Less than slope that would produce
maximum velocity
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 4 Capacity Analysis May 2007 4-2

4.2 Capacity Analysis Results
The results of model runs for future peak dry weather flow (PDWF) and design storm peak wet weather flow (PWWF) scenarios are shown in Figure 4-1 and Figure 4-2, respectively. The figures show pipes that are predicted to surcharge due to capacity deficiency or backwater from a downstream capacity deficiency. Note that the results shown reflect an “unrelieved” system, meaning that peak flows are dampened out in pipes that are under heavy surcharge due to backwater from downstream constrictions, and the true peak flows cannot be determined until the downstream capacity deficiencies are relieved.

Therefore, the data shown for percent full capacity are only approximations of system performance.

The majority of the predicted future capacity deficiencies in the system are located on the west side of the City along the 27- through 36-inch trunk sewer in Great America Parkway and Bowers Avenue and extending upstream into the smaller trunk sewers in Chromite Drive and Machado Avenue). There are also additional areas of predicted capacity deficiencies in portions of Calabazas Boulevard north of El Camino Real (ECR), ECR east and west of Calabazas Boulevard, Machado Avenue and Nobili Avenue west of Calabazas Boulevard, Monroe Street west of Chromite Drive, Scott Boulevard north of Saratoga Avenue, and Park Avenue south of Bellomy Street.

Using the model software, hydraulic profiles were generated for all areas of the system identified as being surcharged under the future design PWWF scenario. The profiles were reviewed to identify where relief capacity would be required to eliminate surcharged conditions.

It should be noted that a number of capacity deficiencies are identified in the area of the system tributary to the 18-inch trunk sewer in Chromite Drive west of Bowers Avenue (area designated as M_11 in Figure 3-3). This area is roughly bounded by Monroe Avenue and Chromite Drive on the north, ECR on the south, Bowers Avenue on the east, and the city limits on the west. The flow data from Meter 11 showed a very high volume, delayed response to rainfall, as indicated by the high values for R2 and R3 for this meter in Table 3-2. When applied to the 10-year design storm rainfall, these parameters produce a high peak response several hours after the peak of the storm. It is possible that the calibration parameters, which reasonably approximate the observed flow response to the smaller observed rainfall events in the 2006 flow monitoring period, may overestimate the response for a larger, more intense rainfall event like the 10-year design storm. Therefore, the City should consider conducting further wet weather flow monitoring in this area to verify RDI/I response prior to the design of capacity improvements.

4.2.1 Cupertino Sanitary District Flows
Based on preliminary model runs for future conditions, the projected PWWF from CuSD was estimated to be about 16 mgd. This exceeds CuSD’s contracted maximum capacity of 13.8 mgd in the Santa Clara system. Model runs were also conducted assuming no future growth in CuSD, which resulted in a peak flow of 13.9 mgd, or approximately equal to the contract capacity. Therefore, for purposes of the capacity assessment presented in this report, the maximum contract flow of 13.8 mgd was assumed for CuSD.

Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Parcels
Modeled Trunk Sewers
Percent of Full Pipe Capacity
100 - 150
> 150
Surcharged due to Backwater
Model Results
Future PDWF
Figure 4-1
Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr. U.P.R.R.

Walsh Ave.

Central Expwy.
(This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Surcharged due to Backwater
Modeled Trunk Sewers
Percent of Full Pipe Capacity
100 - 150
> 150
Parcels
Model Results
Future PWWF
Figure 4-2
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 4 Capacity Analysis May 2007 4-5

4.3 Preliminary Solutions to Capacity Deficiencies
Based on the model results and hydraulic profiles, the identified capacity-deficient locations were further reviewed to determine if they should be recommended for capacity improvement. The criterion used to make this determination was that the capacity deficiency results in at least one foot of surcharge above pipe crown, or less than five feet of freeboard under the design storm PWWF condition. This criterion allows for flexibility to eliminate the need to provide potentially expensive capacity relief projects for barely surcharged sewers.

Based on the identified capacity deficiencies, the sizes of required replacement sewers to handle the predicted future PWWF were determined. The model was then re-run with the upsized pipes to confirm that they would resolve the predicted surcharge. The development of relief solutions was an iterative process of gradually upsizing needed pipes to eliminate any significant surcharge in the system under the design peak flow condition.

The required improvements were refined by determining parallel pipe sizes that would be equivalent to pipe replacement for larger diameter sewers requiring capacity relief (the parallel pipe sizes were estimated based on model flows and existing pipe slopes). Parallel pipes were considered an alternative to replacement for trunk sewers with required diameters of 21 inches and larger. Replacement pipes were generally assumed for smaller diameter sewers. During project refinement, other factors such as constructability issues, or the need to rehabilitate or replace a pipe that may be nearing the end of its useful life, would also be taken into consideration in determining whether to parallel or replace a capacity deficient sewer.

The preliminary capacity solutions are listed in Table 4-2 and shown in Figure 4-3. Note that a capacity deficiency (identified as Project 3) was initially identified on the 24-inch Calabazas Trunk Sewer based on the initial estimate of 16 mgd future flow from CuSD. However, if CuSD flows do not exceed the

13.8 mgd contract capacity, the project would not be needed. Therefore, this project was eliminated from consideration and is not shown in Table 4-2 or Figure 4-3.

The identified projects represent preliminary solutions to the identified capacity deficiencies in the Santa Clara trunk sewer system. In the next chapter of the report, other alternatives for addressing these capacity deficiencies, including possible diversions to other trunk sewers with available capacity, or alternative relief sewer alignments that may be more cost effective to construct, are developed and evaluated in order to develop more definitive estimates for the City’s long-term Capital Improvement Program for the sanitary sewer system.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 4 Capacity Analysis May 2007 4-6
Table 4-2 Capacity Deficiencies and Preliminary Solutions Project
No. Location US MH DS MH Length (ft.)
Design
Flow
(mgd)
Exist.

Dia. (in.)
Req'd.

Dia. (in.)
Parallel
Dia. (in.)
1A
Great America Pkwy. from
Mission College Blvd. to Hetch
Hetch crossing
S83-12 S93-57 1,900 23 36 39 21
1B
Great America Pkwy. from
north side of US 101 to Mission
College Blvd.

S73-1 S83-12 1,800 22 33 39 21
2A Bowers Ave. from Kifer Rd. to
north side of US 101 S63-20 S73-1 5,000 20 30-33 39 21
2B Bowers Ave. from Chromite Dr.
to Kifer Rd. S53-34 S63-20 2,600 19 27 33 21
4A
Chromite Dr. and Monroe St.
from Machado Ave. to west of
Bowers Ave.

S52-80 S53-41 2,200 5.0-6.9 18 24-27 18-21
4B Machado Ave. from Calabazas
Blvd. to Monroe St. S52-103 S52-80 1,500 4.1 15 21 15
5 Monroe St. from Fordham Dr.
to Chromite Dr. S51-22 S52-65 2,500 0.96 10
8(siphon)
12 10(siphon) --
6 Nobili Ave. and Machado Ave.
from Flora Vista Ave. to
Calabazas Blvd.

S41-53 S52-101 3,100 2.2-3.5 10-15 15-18 --
7 Calabazas Blvd. from El
Camino Real to Cabrillo Ave. S42-106 S42-30 2,400 0.47 8 10 -- 8A El Camino Real from Pomeroy
Ave. to Bowers Ave. S42-121 S33-5 2,600 1.2 10
6(siphon)
15 8/10(siphon) --
8B El Camino Real from Flora
Vista Ave. to Pomeroy Ave. S41-113 S42-121 1,800 1.0 10 12 -- 9 Scott Blvd. from Serra Ave. to
Homestead Rd. S25-37 S35-98 800 0.56 8 10 --
10 Park Ave. south of Bellomy St. S38-75 S38-66 250 0.84 10 12 -- (This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
7 5
2A
2B
1B
8B
4A
9 4B
8A
10 6
1A
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Preliminary Capacity Improvements
Modeled Trunk Sewers
Parcels
Preliminary Capacity
Improvements
Figure 4-3
Monroe St.

Machado Ave.

Chromite Dr. U.P.R.R.

Central Expwy.

Walsh Ave.

Calabazas Blvd.

Scott Blvd.
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Capacity Improvement Projects
Chapter 5

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 5 Capacity Improvement Projects May 2007 5-1
Chapter 5 Capacity Improvement Projects
This section summarizes the improvement projects recommended for Santa Clara’s wastewater collection system. Recommended improvements were developed from the results of hydraulic modeling of the trunk sewer system for predicted future flow conditions, as described in Chapter 4. This section discusses the projects, including alternative projects, needed to address potential capacity deficiencies in the existing trunk sewer system.

5.1 Potential Flow Diversion Alternatives
The first step in developing project alternatives was to identify potential flow diversions that could possibly relieve capacity deficiencies without the need for relief sewers, or by significantly reducing the length of needed relief sewers. The following potential flow diversions were identified:
Divert a portion of the flow from the east trunk sewer to the west trunk sewer in Great America Parkway. This diversion could potentially eliminate the need for Projects 1A and/or 1B. Divert flow from the south sewer in El Camino Real (ECR) into the 24-inch trunk sewer that runs along the east side Calabazas Boulevard. This diversion would relieve the capacity deficiency in the south sewer in ECR, which causes flow to back up into the north sewer and then flow north into the 8-inch sewer located on the west side of Calabazas Boulevard. The diversion could be accomplished by diverting flow from the south sewer in ECR into the 24-inch Calabazas trunk sewer just east of Calabazas Creek. This diversion could potentially eliminate the need for Project 7 and Project 8A, and reduce the flow to Projects 4B and 4A.
Divert flow from the sewer in Machado Avenue west of Calabazas Boulevard into the 24-inch Calabazas trunk sewer. This diversion could potentially eliminate the need for or reduce the required sizes of Projects 4B and 4A.
Divert flow from the sewer in Monroe Avenue west of Calabazas Creek into the 24-inch Calabazas trunk sewer. This diversion could potentially eliminate the need for the portion of Project 5 east of Calabazas Creek, and reduce the size of Project 4A.

Modeling indicated that diversion of flow from the east to the west trunk sewer in Great America Parkway would not be effective in eliminating the need for capacity relief for that area of the system. A possible connection between manhole S83-18 on the east side of Great America Parkway and S83-17 on the west side of Great America Parkway was evaluated as a potential alternative. However, since the west pipe was higher in elevation than the east pipe a cross connection to relieve the surcharged east pipe is not feasible. The lack of available capacity in both of these pipes further downstream makes the idea of an intertie along Great America Parkway even less feasible.

Modeling of the potential flow diversions to the Calabazas trunk sewer determined that the diversion at ECR and Calabazas Creek could eliminate the need for Project 7 and the portion of Project 8B east of Calabazas Creek. However, the amount of capacity available further downstream in the Calabazas trunk sewer is limited to approximately 1 mgd based on the critical pipe segment between Kifer Road and Scott Boulevard (MHs S62-37 to S72-20). Any additional diversions (e.g., at Machado or Monroe) would result in too much flow in the Calabazas trunk sewer. Furthermore, a diversion at Machado does not appear to be hydraulically feasible because there is insufficient elevation difference between the Machado and Calabazas sewers. Therefore, only the diversion at ECR to the Calabazas trunk sewer was carried forward as a feasible alternative.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 5 Capacity Improvement Projects May 2007 5-2

5.2 Potential Diversions to New Sewers
The second step in the alternatives analysis process was to identify locations where flows could be diverted to new trunk sewers that could be less difficult or less costly to construct than paralleling or replacing capacity deficient sewers in the same alignment. The following potential diversions to new sewers were identified:
Divert flow from the Bowers Avenue trunk sewer into a new trunk sewer that would convey flow to the eastern side of the system and ultimately to the system outfall in Trimble Road. This diversion could potentially eliminate the need for Projects 1 and 2. Divert flow from the south sewer in ECR into a new sewer in Flora Vista Avenue that would convey flow to Project 6 in Nobili Avenue. This diversion and new sewer would eliminate Project 8B and the need for construction in ECR, but Project 6, 4B and 4A would likely need to be increased in size.

Examination of the model results determined that the eastern portion of the trunk sewer system has excess capacity downstream (east) of Lafayette Street, where the trunk sewer in Central Expressway increases in size to 27 inches and then to 48 inches at De La Cruz Boulevard. Therefore, constructing a new trunk sewer from Bowers Avenue to Central Expressway east of Lafayette to divert flow from the western to the eastern part of the system could potentially reduce the flow in the Bowers Avenue and Great America Parkway trunk sewers sufficiently enough to eliminate the need for capacity relief. In order to ensure adequate grade between the flow diversion point on Bowers Avenue to the connection point to the existing system at Central Expressway, flow would need to be diverted from the existing 18-inch sewer in Chromite Drive just west of Bowers Avenue, which is about 5 feet higher than the Bowers Avenue trunk.

Modeling of this alternative indicates that up to 3.5 mgd could be diverted, which would be sufficient to eliminate the need for capacity relief for the Bowers Avenue/Great America Parkway trunk sewer.

Therefore, a potential new west-to-east trunk sewer was carried forward as a feasible alternative.

The potential diversion of flow into a new sewer in Flora Vista Avenue is also feasible. However, this alignment would be longer than the project in ECR, would require extensive construction through residential neighborhoods, and would ultimately increase the flow to the sewers in Machado Avenue, Chromite Drive, and Bowers Avenue. Therefore, although this alternative reduces the amount of construction on ECR, it does not offer any significant advantage over the preliminary capacity solution (Project 8B).

5.3 Construction Considerations
To further develop the proposed capacity improvement projects, field visits were conducted to evaluate the proposed project alignments, identify feasible pipeline corridors, and assess potential constructability issues. Utility maps were also obtained to identify potential conflicts with major utilities (e.g., storm drains, large water or recycled water mains) in the proposed project corridors. Based on these investigations, the proposed project alignments and construction methods were refined, as described below. In general, for relief projects to be constructed in the same alignment as existing capacitydeficient trunk sewers, it was assumed that the existing pipeline would be replaced rather than paralleled.

This provides a more conservative estimate, appropriate for the planning phase of these projects. For those projects in which the existing sewer is recommended for replacement with a new sewer of one or two pipe diameters larger, however, pipe bursting could also be considered as an alternative to remove and replace.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 5 Capacity Improvement Projects May 2007 5-3

5.4 Capacity Relief Projects
Table 5-1 summarizes the recommended projects. The locations of the proposed projects are shown in Figure 5-1 and described in the paragraphs below.

Table 5-1 Recommended Capacity Improvement Projects
Project
No.a Location US MH DS MH Length
(ft.)
Exist.

S53-34 S73-20 6,200 27-33 21 (P)
West-toEast
Trunkc
Chromite Dr., Alhambra Dr., Bracher Park,
crossing of UPRR, Walsh Ave., Lafayette,
Lafayette St., Central Expwy. From Bowers Dr.
to UPRR
S53-41 S67-18 12,200 NA 24
4A Monroe St. and Chromite Dr. from Machado
Ave. to west of Bowers Ave. S52-80 S53-41 2,200 18 24-27 (R) 4B Machado Ave. from Calabazas Blvd. to
Monroe St. S52-103 S52-80 1,500 15 21 (R)
5 Monroe St. from Fordham Dr. to Chromite Dr. S51-22 S52-65 2,500 10 8(siphon)
12 (R)
8(siphon) (P)
6 Nobili Ave. and Machado Ave. from Flora Vista
Ave. to Calabazas Blvd. S41-53 S52-101 3,100 10-15 15-18 (R) 8 El Camino Real from Flora Vista Ave. to
Calabazas Blvd. S41-113 S32-5 2,600 10 12-15 (R)
9 Scott Blvd. from Serra Ave. to Homestead Rd. S25-37 S35-98 800 8 10 (R) 10 Park Ave. south of Bellomy St. S38-75 S38-66 250 10 12 (R) (a) P = parallel sewer; R = remove and replace
(b) Alternative to Projects 1 and 2.

5.4.1 Projects 1 and 2 – Bowers Ave, Mission College Blvd and Great America Pkwy These projects would provide capacity relief for the trunk sewer in Bowers Avenue from Chromite Drive to Highway 101 and the east trunk sewer in Great America Parkway from Highway 101 to just south of the Hetch Hetchy right-of-way. Crossing the Union Pacific Railroad (UPRR) and Highway 101 present particular challenges for this alignment, as well as dealing with the heavy traffic along the entire pipeline alignment. Furthermore, there are several large-diameter utilities in the area of Projects 1 and 2.

The proposed project would consist of a parallel 21-inch pipeline to provide capacity relief along this alignment. The majority of the pipeline could be constructed by open trench methods. Because of the need to cross the UPRR (where Bowers Avenue is depressed below grade at the railroad crossing) and Highway 101, and because portions of the existing trunk sewer are located in utility easements that contain other sewer and storm drain pipelines, the new sewer alignment could not exactly parallel the existing trunk sewer. Therefore, a new alignment was developed to facilitate the UPRR and Highway 101 crossings, as well as to keep the pipeline in the public right-of-way as much as possible. (This page intentionally left blank)
Great America
Theme Park
Mission
College
Santa Clara
University
El Camino Real
US 101
US 101
Montague Expwy.

San Tomas Expwy.

Lawrence Expwy.

Lafayette St.

De La Cruz Blvd.

Stevens Creek Blvd. Bowers Ave. Great America Pkwy. Kiely Blvd.

Homestead Rd.

Hwy 237
Trimble Rd.
5 Scott Blvd.

Machado Ave.

Monroe St.

Calabazas Blvd.

Chromite Dr.

U.P.R.R.

Walsh Ave.

Central Expwy.
6 2
1 West-to-East
Trunk Alternative
4A
8 9
4B
10 ECR
Diversion
0 0.5 1
Miles
City of Santa Clara
Sanitary Sewer Capacity
Assessment
Legend
Study Area Boundary / City Limit
Capacity Improvement Projects
Modeled Trunk Sewers
Parcels
Recommended Capacity
Improvement Projects
Figure 5-1
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 5 Capacity Improvement Projects May 2007 5-5
Starting at the intersection of Bowers Avenue and Chromite Drive (manhole S53-34), the pipeline would extend eastward along Chromite Drive to Alhambra Drive and then north to Bracher Park. From the south end of Bracher Park, the pipeline would be tunneled roughly 850 feet underneath the park and the UPRR and underneath a private parking lot, and would then be tunneled approximately 500 feet roughly parallel to the northern edge of the City’s power substation property, terminating at approximately the intersection of Bowers Avenue and Mead Avenue. Temporary and permanent easements would be required for construction in the properties adjacent to the City’s power substation.

Extending north from Mead Avenue, the pipeline could be aligned along the east side of Bowers Avenue to Central Expressway. Trenchless construction methods would be used to cross Central Expressway.

The pipeline would continue north on the west side of Bowers until turning west on Augustine Drive. At Lakeside Drive it would turn north again. Junction structures would be needed where the proposed pipeline crosses the alignment of the existing 21-inch and 30-inch sewers in Lakeside Drive. From near manhole S73-6 on Lakeside Drive, the pipeline would be tunneled approximately 500 feet across Highway 101 to Mission College Boulevard, parallel to the existing 30-inch sewer crossing.

The pipeline would extend north and then east on Mission College Boulevard to Great America Parkway.

It is assumed that an inverted siphon would be used to cross under the existing 33- and 36-inch trunk sewers and the 54-inch storm drain located in the utility easement that crosses the east-west segment of Mission College Boulevard. From Mission College Boulevard, the pipeline would follow the east side of Great America Parkway, terminating at manhole S93-57.

5.4.2 New West-to-East Trunk Sewer Alternative
As described above, a new west-to-east trunk sewer would be a possible alternative to Projects 1 and 2.

The project would involve intercepting a portion of the flow from the sewer in Chromite Drive just west of Bowers Avenue, which currently discharges to the Bowers Avenue trunk sewer, and diverting it into a new 24-inch sewer that would run in a general west-to-east direction, discharging to the existing 27-inch trunk sewer in Central Parkway east of Lafayette Street. The advantage of this alignment would be avoiding the potentially difficult construction that would be required for Projects 1 and 2 (described above), as well as reducing the flow to the Northside and Rabello Pump Stations, thereby saving in pumping costs. A new west-to-east trunk sewer would also increase the overall flexibility of the system by connecting the west and east basins.

Various alignments for a west-to-east trunk sewer were evaluated using aerial mapping as well as field investigation. The most difficult challenge of the sewer alignment would be the crossing of the UPRR right-of-way. Based on field verification, the preferred alignment would be similar to that proposed for Project 2 from the intersection of Chromite Drive and Bowers Avenue, east to Alhambra Drive, and then north to Bracher Park. As in that project, the pipeline would be tunneled under Bracher Park and across the UPRR to the parking lot behind the buildings on Walsh Avenue. The new sewer would then turn east and be tunneled through the parking lot to Walsh Avenue, then continue east along Walsh Avenue. Twin 15-inch siphons would be installed across San Tomas Aquino Creek. The pipeline would also be tunneled underneath San Tomas Expressway. An inverted siphon would also need to be installed at the Scott Boulevard crossing to avoid a 42-inch storm drain.

On Walsh Avenue between Scott and Lafayette, the existing alignment of utilities makes placing a new 24-inch sewer a challenge. Roughly 1,500 feet of an existing 8-inch water pipeline may need to be moved to provide room for the new sewer pipeline. At Lafayette, the new sewer line would turn north, with a siphon needed to cross Lafayette Street at the south side of Central Expressway to cross under an existing storm drain.

Because the existing 27-inch trunk in Central Expressway at Lafayette Street is located in the center of the road, the proposed new trunk sewer would turn east and follow the southern shoulder of Central Expressway before connecting into the 27-inch line. To alleviate a potential backwater condition due to a City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 5 Capacity Improvement Projects May 2007 5-6
very flat section of pipe that crosses under the UPRR further downstream, the proposed west-to-east trunk pipeline was extended downstream to manhole S67-18.

The west-to-east trunk sewer would increase the peak design flow in the 48-inch Trimble Road trunk sewer from 14.1 to 16.7 mgd. Note that the most downstream parallel 33-inch lines in Trimble Road between North First Street and Zanker Road, where the City’s Trimble Road trunk sewer connects into the City of San Jose’s interceptors, were not included in the hydraulic model. It is assumed that these lines would have sufficient capacity to handle the increased flows. It is also assumed that the additional flow from the Trimble Road trunk sewer would have minimal impact on the flows in the interceptors in Zanker Road.

5.4.3 Projects 4A and 4B – Machado Avenue and Chromite Drive This project would provide capacity relief on Machado Avenue, Monroe Street, and Chromite Drive from Calabazas Boulevard to just west of Bowers Avenue (manholes S52-103 to S53-41). (The existing 12- inch siphon across Calabazas Creek would not need to be upsized.) The existing 15- and 18-inch sewers would need to be replaced with 21-, 24-, and 27-inch pipes. A parallel sewer could be an option; however, there is limited room in these streets for another sewer because of other utilities. Approximately 85 lower laterals and cleanouts would also need to be replaced along this alignment, in accordance with the City’s policy of replacing lower laterals whenever the main sewer is replaced. Because it is generally considered inadvisable to connect laterals to larger diameter pipelines (e.g., larger than about 18 inches), possibly a parallel 8-inch line could be installed above or adjacent to the new pipe, to which the laterals could be connected.

5.4.4 Project 5 – Monroe Street
Along Monroe Street, from Fordham Drive to Chromite Drive, approximately 2,500 feet of 10-inch sewer would be replaced with 12-inch pipe in order to increase the capacity of this sewer from manholes S51-22 to S52-65. Additionally, a parallel siphon at Calabazas Creek would be installed to increase the capacity of the existing single 8-inch siphon. It is estimated that eight lower laterals would need to be replaced as part of this project.

The portion of the project from MHs S52-51 to S52-65 could possibly be eliminated by a diversion into the 24-inch Calabazas trunk sewer. However, the model indicates that there would be limited capacity available in this pipeline once the El Camino Real Diversion is constructed, so this alternative is not recommended at this time. The diversion, or a potential partial diversion (e.g., with an overflow weir) could be considered in the future if capacity in the Calabazas trunk sewer appears to be adequate.

5.4.5 Project 6 – Nobili Avenue and Machado Avenue
This project would replace 3,100 feet of pipeline along Nobili and Machado Avenues, extending from manholes S41-53 to S52-101. The existing 10-, 12- and 15-inch sewers would be replaced with 15- and 18-inch pipe. Approximately 52 lower laterals would also need to be replaced along this alignment.

5.4.6 ECR Diversion to Calabazas Trunk Sewer
As an alternative to preliminary projects 7 and 8A, a diversion on El Camino Real can be constructed to direct flow into the 24-inch Calabazas trunk sewer. For this diversion, a new pipe would be needed to connect the sewer just downstream of the siphon on the ECR south sewer to divert the flow into the 24- inch Calabazas trunk (at approximately manhole S32-8). This diversion is not listed as a capacity improvement project in Table 5-1 because it is assumed that the connection will be coordinated with the siphon upgrade at Calabazas Creek (replacement of the existing 6-inch siphon with an 8- and 10-inch double siphon) being constructed in conjunction with the channel work being conducted by the Santa Clara Valley Water District. Only a small segment of pipe would be needed to complete this diversion, making it a cost effective alternative to preliminary projects 7 and 8A.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 5 Capacity Improvement Projects May 2007 5-7

5.4.7 Project 8 – El Camino Real
The existing 10-inch pipeline on the south side of El Camino Real between Flora Visa Avenue and Calabazas Boulevard should be upsized to 12-inch diameter from Flora Visa Avenue to Pomeroy Avenue and to 15-inch diameter from Pomeroy Avenue to Calabazas Creek. This capacity relief project would involve replacing roughly 2,600 feet of pipeline and twelve lower laterals, from manholes S41-113 to S32-5.

5.4.8 Project 9 – Scott Boulevard
This capacity upgrade project is located on Scott Boulevard from Serra Avenue to Homestead Road. It would involve replacing 800 feet of 8-inch sewer with 10-inch pipe and 14 lower laterals, from manholes S25-37 to S35-98.

5.4.9 Project 10 – Park Avenue
The 10-inch pipe on Park Avenue, south of Bellomy Street should be replaced with a 12-inch pipe in order to provide capacity relief. This project would involve 250 feet of pipeline, from manhole S38-75 to manhole S38-66, including two lower laterals.

Recommended Capital
Improvement Program
Chapter 6

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 6 Recommended Capital Improvement Program
May 2007 6-1
Chapter 6 Recommended Capital Improvement Program
This chapter presents the recommended Capital Improvement Program (CIP) for capacity improvements to the Santa Clara wastewater collection system, along with estimated project costs and proposed schedule for construction.

6.1 Estimated Cost of Proposed Sewer Improvement Projects The estimated costs of the proposed projects were refined based on more detailed quantity takeoffs and evaluation of likely construction methods and requirements. Unit cost criteria (updated to current dollars) and cost assumptions developed for the City of San Jose’s Phase I Sanitary Sewer Master Plan Capacity Assessment were used in developing the cost estimates. These criteria include baseline construction costs for gravity trunk sewers using open-cut and trenchless (e.g., microtunneling) methods, costs for lower lateral replacement for remove-and-replace projects, costs for major sewer junction structures and siphon inlet and outlet structures, and costs allowances for project mobilization/demobilization, traffic control, bypass pumping and delay factors for remove-and-replace projects, extra dewatering requirements in areas of high groundwater, and acquisition of temporary and permanent easements if needed. A 30 percent allowance for contingencies for unknown conditions was also included, as well as an allowance of 25 to 35 percent of construction cost (depending on project size) for engineering, administration, and legal costs.

Table 6-1 summarizes the cost criteria used for preparing the project cost estimates. These cost estimates are planning or conceptual level estimates, and are considered to have an estimated accuracy range of -30 to +50 percent. This level of accuracy corresponds to an “order of magnitude” or “Class 5” cost estimate as defined by the American Association of Cost Estimators. These estimates are suitable for use for budget forecasting, CIP development, and project evaluations, with the understanding that refinements to the project details and costs would be necessary as projects proceed into the design and construction phases.

Table 6-2 presents the estimated construction and capital costs for the proposed projects and major project alternatives. More detailed breakdowns of the costs for each project are included in Appendix B.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 6 Recommended Capital Improvement Program
May 2007 6-2
Table 6-1 Summary of Cost Criteria
Item Description/ Assumptions Unit Costa
Open-Cut Gravity Trunk Sewers 10" - 27" diameter, 8' - 16' depth $160 - $240/lf 36" - 49" casing $90 - $1,200/lf
Jacking/Receiving Pits $70,000/$40,000
Lower Lateral Replacement $2,000
Special Structures Junctions, siphon inlet/outlet $6,000 - $9,000 High Groundwater (north of
Highway 101)
Dewatering plus extra sheeting
and shoring
$100/lf
Bypass Pumping/Diversion 10%
Remove/Replace Delay Factor 2%
Mobilization/Demobilization 5%
Traffic Control 10%
Contingencies 30%
Temporary Easement Easement width = 80 ft $4/sq. ft.

Permanent Easement Easement width = 30 ft $25/sq. ft.

Engineering, Administration,
and Legal Costs
% of Construction Cost Total
(varies depending on magnitude
of Estimated Construction Cost)
25% - 35%
Baseline Pipeline Construction Costs
% of Baseline Construction Cost
for remove and replace projects
Construction Cost Allowances
Easement Acquisition
Site Specific Construction Costs
% of Construction Cost Subtotal
Microtunneling
(a) Based on an Engineering News Record (ENR) Construction Cost Index for the San Francisco Bay Area of 9103 (March 2007).

Table 6-2 Estimated Costs of Capacity Improvement Projects Project No.

Estimated
Construction
Cost ($)
Estimated Capital
Cost ($)
1 4,539,000 5,674,000
2 5,286,000 7,324,000
4A 1,489,000 1,861,000
4B 1,060,000 1,325,000
5 1,046,000 1,308,000
6 1,139,000 1,424,000
8 945,000 1,276,000
9 256,000 346,000
10 77,000 104,000
Total 15,837,000 20,642,000
West-to-East Alternative 9,752,000 12,906,000
Total w/West-to-East
Alternative 15,764,000 20,550,000
City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 6 Recommended Capital Improvement Program
May 2007 6-3

6.2 Comparison of Major Alternatives
As described in Chapter 5, two major alternatives were evaluated for providing capacity relief for the major trunk sewers in Bowers Avenue and Great America Parkway: paralleling or replacement of those sewers, or diverting flow to a new West-to-East trunk sewer. As presented above, the two alternatives are virtually equal in terms of estimated capital cost. Other factors that should be considered in comparing these alternatives are:
Constructability. Bowers Avenue and Great America Parkway are two of the busiest roads in the City. Construction in those corridors would require extensive traffic control and potentially have significant impact on businesses in the area. The sewer alignment also has a number of significant other utilities (e.g., large storm drains). The West-to-East trunk sewer would likely have fewer traffic impacts, but could require the realignment of about 1,500 feet of water main along part of the corridor, siphon crossings under San Tomas Aquino Creek and several large storm drains, and some construction along the shoulder of busy Central Expressway. Permits and Easements. The Bowers/Great America Parkway project would require a permit from Caltrans for a new sewer crossing under Highway 101. Both projects would require crossing the UPRR west of Bowers, including obtaining a permanent sewer easement across properties adjacent to the City’s power substation on the north side of the UPRR. The West-to-East trunk would require coordination with Santa Clara Valley Water District for the crossing of San Tomas Aquino Creek.

Both projects would require permits from the County for work in or crossing Central Expressway and, in the case of the West-to-East project, San Tomas Expressway. Project Phasing/Flexibility. The Bowers/Great America Parkway project could be constructed and put into operation in phases, whereas the West-to-East project could not be used until the entire project was constructed. However, that project would provide greater overall system flexibility by linking the west and east basins by a major trunk.
Coordination with Development and Other City Projects: Current development activity on the west side of the City may provide opportunities for the City to coordinate with developers in construction of some capacity improvement projects. For example, proposed developments in the area of El Camino Real and Lawrence Expressway may construct or fund improvements, such as the El Camino Real relief sewer (Project 8), to allow those developments to move forward more quickly.

Other potential projects, either by City or other utilities, may also impact the desirability of one or the other of the major trunk system alternatives.
Long-term Cost Savings. Diverting flow from the west to the east basin could reduce the overall flows to the Rabello and Northside Pump Stations. The amount of such reduction would depend on the configuration of the flow diversion to the West-to-East trunk. A rough estimate of the reduction in average daily flow would indicate a potential annual cost savings of about $10,000 based on City’s estimate of $8,000 per mgd cost for power for pumping.

Because the estimated capital costs of the two major alternatives are nearly identical, it is recommended that the City pursue additional predesign level alignment and constructability evaluations of both alternatives before making a decision on which alternative to implement as part of the overall capacity improvement program.

6.3 Prioritization and Schedule for Proposed CIP Projects A preliminary schedule for completion of the recommended CIP projects over a five-year period has been developed based on assigning relative priorities to the proposed capacity improvements. Priorities have been based on the relative magnitude of the predicted capacity deficiencies, as well as the likely timing of City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 6 Recommended Capital Improvement Program
May 2007 6-4
developments that may impact the need for the projects. Based on these considerations, the projects have been divided into two priority groups, as listed in Table 6-3.

Table 6-3 Project Priority Groups
Project No.

For each project, a preliminary estimate of time required to implement the project has been developed, considering time required for design and construction, including obtaining necessary permits and easements. Based on the project schedules and priorities, Figure 6-1 shows a preliminary schedule for the recommended five-year capacity improvement CIP. The schedule is based on proceeding with the Bowers/Great America Parkway relief sewer, but provides for a preliminary alignment study of both this and the West-to-East trunk alternative, as recommended above. If the City decides to proceed with the West-to-East alternative in lieu of the Bowers/Great America Parkway relief, then the overall CIP schedule would need to be modified.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 6 Recommended Capital Improvement Program
May 2007 6-5
Figure 6-1 Proposed CIP Schedule
With Projects 1 and 2
Alignment Study
Project 8
Project 4A
Project 2
Project 1
Project 4B
Projects 5&6
Projects 9&10
With West-to-East Trunk Alternative
Alignment Study
Project 8
Project 4A
West-to-East Trunk
Project 4B
Projects 5&6
Projects 9&10
Planning
Design
Bid and Award
Construction
Project Year 1 Year 2 Year 3 Year 4 Year 5
Project Year 1 Year 2 Year 3 Year 4 Year 5

6.4 Implementation Recommendations
The City should begin implementation of the Capital Improvement Program recommended in this Sanitary Sewer Capacity Assessment, starting with the highest priority projects. The following items should be considered in project scheduling and design, and in future updates of the Capacity Assessment. ▪ The alignments and sizes of all recommended projects should be verified with detailed predesign analyses, including topographic surveys, geotechnical investigations, utility research, and constructability reviews.
▪ The decision to parallel or replace existing sewers should consider the physical condition and remaining useful life of the existing pipelines; the availability of pipeline corridors for new sewer construction; and operation and maintenance concerns.
▪ The hydraulic model has been developed to assist the City in performing capacity analyses and updating the Capacity Assessment in the future. The model should be kept up-to-date with any changes to existing sewer connections, development plans, and sewer system facilities. ▪ The City should periodically calibrate its permanent flow meters at the Northside and Rabello Pump Stations and on the Trimble Road trunk sewer to ensure that accurate flow information is available to track the changes in the flows in the City’s system over time. ▪ The City should conduct additional flow monitoring at key locations in the sewer system, particularly the area tributary to the Chromite/Machado trunk sewers (flow meter 11 area). Flow levels during large storm events should be compared to the peak flows simulated by the hydraulic model to verify the modeling predictions for the 10-year design storm and confirm the need for and sizing of Projects 4A, 4B, 5, and 6.

City of Santa Clara Sanitary Sewer Capacity Assessment Chapter 6 Recommended Capital Improvement Program
May 2007 6-6
▪ The City should consider additional field investigations, including smoke testing, and manhole and pipeline television inspection, in the flow meter 11 area to identify potential sources of I/I and possible opportunities for I/I reduction in this area.
▪ The City should coordinate with the Cupertino Sanitary District on flow and planning assumptions to ensure that adequate capacity exists in the Santa Clara system to handle future flows from CuSD.

Plots of Flow Monitoring
Data
Appendix A

Site 1 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 1
86420
201816141210
1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14 2/16 2/18 2/20 2/22 2/24 2/26 2/28 3/2 3/4 3/6 3/8 3/10 3/12 3/14 3/16 3/18 3/20 3/22 3/24 3/26 3/28 3/30 4/1 4/3 Date
Flow (mgd)
Site 2 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 2
86420
201816141210
1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 3 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 3

5.04.54.03.53.02.52.01.51.00.50.0 1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14 2/16 2/18 2/20 2/22 2/24 2/26 2/28 3/2 3/4 3/6 3/8 3/10 3/12 3/14 3/16 3/18 3/20 3/22 3/24 3/26 3/28 3/30 4/1 4/3 Date
Flow (mgd)
Site 4 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 4
9876543210
121110
1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 5 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 5
55443322110
1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 6 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 6

5.04.54.03.53.02.52.01.51.00.50.0 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 7 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 7
86420
1816141210
1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 8 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 8
9876543210
10 1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14 2/16 2/18 2/20 2/22 2/24 2/26 2/28 3/2 3/4 3/6 3/8 3/10 3/12 3/14 3/16 3/18 3/20 3/22 3/24 3/26 3/28 3/30 4/1 4/3 4/5 Date
Flow (mgd)
Site 9 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 9
9876543210
10 1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14 2/16 2/18 2/20 2/22 2/24 2/26 2/28 3/2 3/4 3/6 3/8 3/10 3/12 3/14 3/16 3/18 3/20 3/22 3/24 3/26 3/28 3/30 4/1 4/3 Date
Flow (mgd)
Site 10 061406.xls, Flow ]
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 10
86420
201816141210
1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14 2/16 2/18 2/20 2/22 2/24 2/26 2/28 3/2 3/4 3/6 3/8 3/10 3/12 3/14 3/16 3/18 3/20 3/22 3/24 3/26 3/28 3/30 4/1 4/3 Date
Flow (mgd)
Site 11 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 11
876543210
1/19 1/21 1/23 1/25 1/27 1/29 1/31 2/2 2/4 2/6 2/8 2/10 2/12 2/14 2/16 2/18 2/20 2/22 2/24 2/26 2/28 3/2 3/4 3/6 3/8 3/10 3/12 3/14 3/16 3/18 3/20 3/22 3/24 3/26 3/28 3/30 4/1 4/3 Date
Flow (mgd)
Site 12 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 12
9876543210
10 1/18 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 13 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 13

1.00.90.80.70.60.50.40.30.20.10.0 1/18 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 4/6 4/8 4/10 4/12 4/14 Date
Flow (mgd)
Site 14 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 14
9876543210
10 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 15 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 15
9876543210
10 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 16 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 16
55443322110
1/18 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 4/6 4/8 4/10 4/12 4/14 4/16 4/18 Date
Flow (mgd)
Site 17 081106.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 17

1.21.00.80.60.40.20.0 1/20 1/23 1/26 1/29 2/1 2/4 2/7 2/10 2/13 2/16 2/19 2/22 2/25 2/28 3/3 3/6 3/9 3/12 3/15 3/18 3/21 3/24 3/27 3/30 4/2 4/5 4/8 4/11 4/14 4/17 4/20 4/23 4/26 4/29 5/2 Date
Flow (mgd)
Site 18 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 18

4.03.53.02.52.01.51.00.50.0 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 19 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 19

3.02.52.01.51.00.50.0 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 20 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 20

2.01.81.61.41.21.00.80.60.40.20.0 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 4/6 4/8 4/10 4/12 4/14 4/16 4/18 Date
Flow (mgd)
Site 21 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 21
86420
201816141210
1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 22 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 22

2.01.81.61.41.21.00.80.60.40.20.0 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 23 072906.xls, Flow \
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 23
9876543210
10 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 24 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 24
9876543210
10 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Site 25 061406.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 25

1.00.80.60.40.20.0 1/20 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 4/6 4/8 4/10 4/12 4/14 4/16 4/18 Date
Flow (mgd)
Site 26 072906.xls, Flow
City of Santa Clara
Sanitary Sewer Flow Monitoring, Site 26
9876543210
10 1/22 1/24 1/26 1/28 1/30 2/1 2/3 2/5 2/7 2/9 2/11 2/13 2/15 2/17 2/19 2/21 2/23 2/25 2/27 3/1 3/3 3/5 3/7 3/9 3/11 3/13 3/15 3/17 3/19 3/21 3/23 3/25 3/27 3/29 3/31 4/2 4/4 Date
Flow (mgd)
Project Descriptions and
Cost Estimates
Appendix B

PROJECT ID:…………………………………………………………1
PROJECT LOCATION:………………………………………………
BRIEF PROJECT DESCRIPTION:……………………
SANITARY SEWER PLAT MAP(S):……………………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:…………………………..

ALTERNATIVES:……………………………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH*
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Augustine Dr, Lakeside Dr. and HWY 101 Crossing 21 8-16 2,300' 210 $/ft $483,000 HWY 101 (casing) 43 Microtunnel 700' 1,000 $/ft $700,000 Mission College Blvd. 21 8-16 2,900' 210 $/ft $609,000
Mission College Blvd. double 15" Siphon under utilties 49 Microtunnel 50' 1,200 $/ft $60,000 Carrier piping for 15-inch double siphon 15 Carrier pipe 100' 180 $/ft $18,000 Great America Parkway 21 8-16 2,000' 210 $/ft $420,000
Jacking Pits 2 pits $70,000 $140,000
Receiving Pits 2 pits $40,000 $80,000
Structures
Sewer Junction Structure: Lakeside and Augustine $6,000 $6,000 Sewer Junction Structure: Lakeside Drive near HWY 101 $6,000 $6,000 Siphon structures at Mission College Blvd 2 structures $6,000 $12,000 Sewer Junction Structure: Great America Pkwy. near
Patrick Henry $6,000 $6,000
Sewer Junction Structure: connection to S93-57 $6,000 $6,000

SITE SPECIFIC CONSTRUCTION COST
High Groundwater
Dewatering (North of HWY 101) 4,900' 50 $/ft $245,000
Sheeting/Shoring
Solid Shoring (North of HWY 101) 4,900' 50 $/ft $245,000 SUBTOTAL $3,036,000
Mobilization and Demobilization 5% $151,800
Traffic Control 10% $303,600
CONSTRUCTION COST SUBTOTAL $3,491,400
Contingencies 30% $1,047,420
CONSTRUCTION COST TOTAL $4,538,820
Engineering and Inspection Costs 25% $1,134,705
CAPITAL IMPROVEMENT COST TOTAL $5,673,525
ENR = 9103 (S.F. March 2007) rounded $5,674,000
* Pipe lengths include carrier pipe for siphons, double siphons and tunneled sewers. 63, 73, 83, 93

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Augustine Dr., Lakeside Dr., crossing of U.S. 101, Mission College Boulevard, Great America Pkwy. from Bowers Ave. to south of Hetch Hetchy ROW
Near MH S73-20 to MH S93-57
Install 7,200 feet of 21-inch pipeline.

New West-to-East pipeline extending from Bowers at Chromite to Central east of Lafayette.

Bowers Ave., Mission College Blvd., and Great America Pkwy. from Augustine Dr. to south of Hetch Hetchy ROW
Diameter of existing deficient pipes: 33"-36"
Caltrans permit required for crossing Hwy. 101. Best placement of new sewer in Lakeside Dr. is along the west side (to avoid 21" sewer, 12" water, and 24" storm drain). Best placement of new sewer in Mission College Blvd. is along west side (to avoid 18" storm drain and 30" and 33" sewers).

Assume siphon under 54" storm drain and 33" and 36" sewers in Mission College Blvd. west of Great America Pkwy. Best placement for new sewer is along east side of Great America Pkwy. (to avoid 66" to 72" storm drain on west side).

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 1 May 2007
PROJECT ID:………………………………………………………2
PROJECT LOCATION:……………………………………………
BRIEF PROJECT DESCRIPTION:……………………
SANITARY SEWER PLAT MAP(S):……………………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:…………………………..

ALTERNATIVES:……………………………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH*
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Chromite, Alhambra, Bracher Park, easement to Bowers 21 8-16 2,300' 210 $/ft $483,000 UPRR Crossing (casing) 43 Microtunnel 1,350' 1,000 $/ft $1,350,000 Central Expressway (casing) 43 Microtunnel 600' 1,000 $/ft $600,000 Bowers Ave (Mead to Augustine) 21 8-16 3,900' 210 $/ft $819,000 Jacking Pits 2 pits $70,000 $140,000
Receiving Pits** 3 pits $40,000 $120,000
Structures
Sewer Junction Structure: Bowers and Chromite $6,000 $6,000 Sewer Junction Structure: Bowers and Walsh $6,000 $6,000 Sewer Junction Structure: Bowers and Central $6,000 $6,000 Sewer Junction Structure: Bowers and Scott $6,000 $6,000 SUBTOTAL $3,536,000
Mobilization and Demobilization 5% $176,800
Traffic Control 10% $353,600
CONSTRUCTION COST SUBTOTAL $4,066,400
Contingencies 30% $1,219,920
CONSTRUCTION COST TOTAL $5,286,320
Land Acquisition - Temporary Easement Cost
(Trenchless staging) 150' wide 150' 4 $/sf $78,750
Land Acquisition - Permanent Easement Cost
(Pipeline Alignment) 30' wide 850' 25 $/sf $637,500
Engineering and Inspection Costs 25% $1,321,580
CAPITAL IMPROVEMENT COST TOTAL $7,324,150
ENR = 9103 (S.F. March 2007) rounded $7,324,000
* Pipe lengths include carrier pipe for siphons, double siphons and tunneled sewers. ** For tunneling under UPRR to Bowers, two receiving pits and one jacking pit are needed. 53, 63

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Chromite Dr., Alhambra Dr., Bracher Park, crossing of UPRR, Bowers Ave. from Bowers Ave. to Augustine Dr.

MH S53-34 to near MH S73-20
Install 6,200 feet of 21-inch pipe.

New West-to-East pipeline extending from Bowers at Chromite to Central east of Lafayette. Alternative UPRR crossing from Park through City-owned substation not selected due to utility conflicts (this alignment might be feasible, but it is not considered best alternative).

Bowers Ave. from Chromite Dr. to Augustine Dr.

Diameter of existing deficient pipes: 27"-33"
UPRR permit required for crossing. County permit required for crossing Central Expwy. Permanent easements required through properties on Walsh and Bowers north of UPRR. Best placement for new sewer is along east side of Bowers south of Central Expwy. and along west side of Bowers north of Central Expwy (to avoid 12" water and 42" storm drain). Trenchless crossing assumed under Central Expwy.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 2 May 2007
PROJECT ID:…………………………………………………………. West-to-East Alternative PROJECT LOCATION:…………………………………………………
BRIEF PROJECT DESCRIPTION:……………………
SANITARY SEWER PLAT MAP(S):…………………………… 53, 54, 55, 56, 63, 64, 66, 67 LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:…………………………..

ALTERNATIVES:……………………………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH*
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Chromite, Alhambra, Bracher Park, easement to Walsh 24 8-16 2,300' 220 $/ft $506,000 Walsh, Lafayette, and Central Expwy. 24 8-16 9,900' 220 $/ft $2,178,000 UPRR Crossing (casing)** 49 Microtunnel 1,350' 1,200 $/ft $1,620,000 San Tomas Aquino Creek Crossing Siphon (casing) 49 Microtunnel 200' 1,200 $/ft $240,000 San Tomas Expwy. Crossing (casing) 49 Microtunnel 400' 1,200 $/ft $480,000 Scott Blvd. siphon under street and strom drain (casing) 49 Microtunnel 300' 1,200 $/ft $360,000 Lafayette at Central siphon under storm drain (casing) 49 Microtunnel 50' 1,200 $/ft $60,000 Carrier piping for 15-inch double siphons 15 Carrier Pipe 1,100' 180 $/ft $198,000 Relocate existing waterline on Walsh due to utility conflicts 8 1,500' 150 $/ft $225,000 Jacking Pits 5 pits $70,000 $350,000
Receiving Pits 6 pits $40,000 $240,000
Structures
Sewer Junction Structure: Chromite $6,000 $6,000
Sewer Junction Structure: Walsh and Northwestern Pkwy. $6,000 $6,000 Siphon structures- San Tomas Aquino Creek 2 structures $6,000 $12,000 Sewer Junction Structure: Wash and San Tomas Expwy. $6,000 $6,000 Siphon structures- Scott Blvd 2 structures $6,000 $12,000 Siphon structures- Lafayette St. 2 structures $6,000 $12,000 Sewer Junction Structure: Central Expwy. at S67-15 $6,000 $6,000 Sewer Junction Structure: Central Expwy. at S67-18 $6,000 $6,000 SUBTOTAL $6,523,000
Mobilization and Demobilization 5% $326,150
Traffic Control 10% $652,300
CONSTRUCTION COST SUBTOTAL $7,501,450
Contingencies 30% $2,250,435
CONSTRUCTION COST TOTAL $9,751,885
Land Acquisition - Temporary Easement Cost
(Trenchless staging) 150' wide 150' 4 $/sf $78,750
Land Acquisition - Permanent Easement Cost
(Pipeline Alignment) 30' wide 850' 25 $/sf $637,500
Engineering and Inspection Costs 25% $2,437,971
CAPITAL IMPROVEMENT COST TOTAL $12,906,106
ENR = 9103 (S.F. March 2007) rounded $12,906,000
* Pipe lengths include carrier pipe for siphons, double siphons and tunneled sewers. ** For tunneling under UPRR to Walsh, two receiving pits and one jacking pit are needed.

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Chromite Dr., Alhambra Dr., Bracher Park, crossing of UPRR, Walsh Ave., Lafayette, Lafayette St., Central Expwy. From Bowers Dr. to UPRR MH S53-41 to MH S67-18
Install 12,200 feet of 24-inch pipe.

Projects 1 and 2.

Bowers Ave., Mission College Blvd., and Great America Pkwy. from Chromite to south of Hetch Hetchy ROW
Diameter of existing deficient pipes: 27"-36"
UPRR Permit required for crossing. Permanent easement needed for crossing into parking lot on north side of UPRR to Walsh. SCVWD permit required for crossing San Tomas Creek. County permit required for crossing San Tomas Expwy. and work in Central Expwy. Best placement for new sewer along Walsh is on north side (to avoid 15" sewer, 12" water, and 15" storm drain. On Walsh between Scott and Lafayette, reolcation of existing water line may be needed. Best placement for new sewer along Lafayette is on west side (to avoid 45" storm drain and 12" water). Siphons (assume twin 15") required to cross San Tomas Aquino Creek and storm drains at Scott and Lafayette.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project WEST-TO-EAST May 2007 PROJECT ID:…………………………………………4A
PROJECT LOCATION:………………………………
BRIEF PROJECT DESCRIPTION:…………………
SANITARY SEWER PLAT MAP(S):…………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:………………………
ALTERNATIVES:………………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Monroe St. 24 8-16 600' 220 $/ft $132,000
Chromite Dr. 27 8-16 1,600' 240 $/ft $384,000
Collector line on Monroe St 8 8-16 600' 160 $/ft $96,000 Collector line of Chromite Dr. 8 8-16 1,600' 160 $/ft $256,000 Lower Laterals plus Cleanout (Monroe St.) 8 $2,000 $16,000 Lower Laterals plus Cleanout (Chromite Dr.) 22 $2,000 $44,000 Structures
Sewer Junction Structure: Chromite and Monroe $6,000 $6,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $51,600 Remove and Replace Factor 2% of baseline pipe cost 2% $10,320 SUBTOTAL $995,920
Mobilization and Demobilization 5% $49,796
Traffic Control 10% $99,592
CONSTRUCTION COST SUBTOTAL $1,145,308
Contingencies 30% $343,592
CONSTRUCTION COST TOTAL $1,488,900
Engineering and Inspection Costs 25% $372,225
CAPITAL IMPROVEMENT COST TOTAL $1,861,126
ENR = 9103 (S.F. March 2007) rounded $1,861,000
Parallel pipe (if space available)
Same as project location
Diameter of existing deficient pipes: 18"
Assume parallel 8" collector sewer for lateral connections. 52, 53

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Monroe St. and Chromite Dr. from Machado Ave. to west of Bowers Ave.

MH S52-80 TO S53-41
Replace 600 feet of 18-inch pipe with 24-inch pipe. Replace 1,600 feet of 18- inch pipe with 27-inch pipe.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 4A May 2007
PROJECT ID:……………………………………………………… 4B
PROJECT LOCATION:……………………………………………
BRIEF PROJECT DESCRIPTION:……………………
SANITARY SEWER PLAT MAP(S):……………………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:…………………………..

ALTERNATIVES:……………………………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Machado 21 8-16 1,500' 210 $/ft $315,000
Collector line on Machado 8 8-16 1,500' 160 $/ft $240,000 Lower Laterals plus Cleanout (Machado) 55 $2,000 $110,000 Structures
Sewer Junction Structure: Machado and Monroe $6,000 $6,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $31,500 Remove and Replace Factor 2% of baseline pipe cost 2% $6,300 SUBTOTAL $708,800
Mobilization and Demobilization 5% $35,440
Traffic Control 10% $70,880
CONSTRUCTION COST SUBTOTAL $815,120
Contingencies 30% $244,536
CONSTRUCTION COST TOTAL $1,059,656
Engineering and Inspection Costs 25% $264,914
CAPITAL IMPROVEMENT COST TOTAL $1,324,570
ENR = 9103 (S.F. March 2007) rounded $1,325,000
52 TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Machado Ave. from Calabazas Blvd. to Monroe St.

MH S52-103 TO S52-80
Replace 1,500 feet of 15-inch pipe with 21-inch pipe.

Parallel pipe (if space available)
Same as project location.

Diameter of existing deficient pipes: 15"
Assume parallel 8" collector sewer for lateral connections.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 4B May 2007
PROJECT ID:…………………………………………………………5
PROJECT LOCATION:………………………………………………
BRIEF PROJECT DESCRIPTION:……………………
SANITARY SEWER PLAT MAP(S):……………………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:…………………………..

ALTERNATIVES:……………………………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Monroe 12 8-16 2,400' 170 $/ft $408,000
Siphon at Calabazas Creek (casing) 36 Microtunnel 100' 900 $/ft $90,000 Siphon pipe 8 Carrier Pipe 100' 150 $/ft $15,000
Lower Laterals plus Cleanout (Monroe) 8 $2,000 $16,000
Jacking Pits 1 pits $70,000 $70,000
Receiving Pits 1 pits $40,000 $40,000
Structures
Siphon structure- Calabazas Creek 2 structures $6,000 $12,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $40,800 Remove and Replace Factor 2% of baseline pipe cost 2% $8,160 SUBTOTAL $699,960
Mobilization and Demobilization 5% $34,998
Traffic Control 10% $69,996
CONSTRUCTION COST SUBTOTAL $804,954
Contingencies 30% $241,486
CONSTRUCTION COST TOTAL $1,046,440
Engineering and Inspection Costs 25% $261,610
CAPITAL IMPROVEMENT COST TOTAL $1,308,050
ENR = 9103 (S.F. March 2007) rounded $1,308,000
Project extents from S52-51 to S-52-65 could possibly be eliminated by diversion into 24" Calabazas trunk sewer if sufficient capacity is available.

Pipe bursting could be an alternative to remove and replace.

Same as project location
Diameter of existing deficient pipes: 10" (6" siphon)
51, 52

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Monroe St. from Fordham Dr. to Chromite Dr.

MH S51-22 TO S52-65
Replace 2,400 feet of 10-inch pipe with 12-inch pipe. Parallel 6" siphon under Calabazas Creek with 8-inch siphon.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 5 May 2007
PROJECT ID:………………………………………6
PROJECT LOCATION:……………………………
BRIEF PROJECT DESCRIPTION:………………
SANITARY SEWER PLAT MAP(S):………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:……………………
ALTERNATIVES:……………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Nobili Ave 15 8-16 700' 180 $/ft $126,000
Nobili Ave and Machado Ave 18 8-16 2,400' 190 $/ft $456,000 Lower Laterals plus Cleanout (Nobili Ave) 31 $2,000 $62,000 Lower Laterals plus Cleanout (Machado Ave) 21 $2,000 $42,000 Structures
Sewer Junction Structure: Machado and Calabazas $6,000 $6,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $58,200 Remove and Replace Factor 2% of baseline pipe cost 2% $11,640 SUBTOTAL $761,840
Mobilization and Demobilization 5% $38,092
Traffic Control 10% $76,184
CONSTRUCTION COST SUBTOTAL $876,116
Contingencies 30% $262,835
CONSTRUCTION COST TOTAL $1,138,951
Engineering and Inspection Costs 25% $284,738
CAPITAL IMPROVEMENT COST TOTAL $1,423,689
ENR = 9103 (S.F. March 2007) rounded $1,424,000
Pipe bursting could be an alternative to remove and replace.

Same as project location.

Diameter of existing deficient pipes: 10"-15"
41, 51, 52

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Nobili Ave. and Machado Ave. from Flora Vista Ave. to Calabazas Blvd.

MH S41-53 TO S52-101
Replace exisiting 10-inch, 12-inch and 15-inch pipe with 700 feet of 15-inch pipe and 2,400 feet of 18-inch pipe.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 6 May 2007
PROJECT ID:………………………………………8
PROJECT LOCATION:……………………………
BRIEF PROJECT DESCRIPTION:………………
SANITARY SEWER PLAT MAP(S):………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:……………………
ALTERNATIVES:……………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
El Camino Real, Flora Vista to Pomeroy 12 8-16 1,800' 170 $/ft $306,000 El Camino Real, Pomeroy to Calabazas 15 8-16 800' 180 $/ft $144,000 Lower Laterals plus Cleanout (El Camino Real) 12 $2,000 $24,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $45,000 Remove and Replace Factor 2% of baseline pipe cost 2% $9,000 Concrete Pavement Replacement Allowance 2,600' 40 $/ft $104,000 SUBTOTAL $632,000
Mobilization and Demobilization 5% $31,600
Traffic Control 10% $63,200
CONSTRUCTION COST SUBTOTAL $726,800
Contingencies 30% $218,040
CONSTRUCTION COST TOTAL $944,840
Engineering and Inspection Costs 35% $330,694
CAPITAL IMPROVEMENT COST TOTAL $1,275,534
ENR = 9103 (S.F. March 2007) rounded $1,276,000
31, 32, 41, 42

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
El Camino Real from Flora Vista Ave. to siphon at Calabazas Creek.

MH S41-113 TO S32-5
Replace 2,600 feet of 10-inch pipe with 12- and 15-inch pipe.

Pipe bursting could be an alternative to remove and replace. Possible alternative alignment on Flora Visa Ave, from El Camino Real to Nobili (upstream end of project 6).

Same as project location
Diameter of existing deficient pipes: 10"
Permits required from Caltrans.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 8 May 2007
PROJECT ID:………………………………………9
PROJECT LOCATION:……………………………
BRIEF PROJECT DESCRIPTION:………………
SANITARY SEWER PLAT MAP(S):………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:……………………
ALTERNATIVES:……………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Scott Blvd. 10 8-16 800' 160 $/ft $128,000
Lower Laterals plus Cleanout (Scott Blvd.) 14 $2,000 $28,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $12,800 Remove and Replace Factor 2% of baseline pipe cost 2% $2,560 SUBTOTAL $171,360
Mobilization and Demobilization 5% $8,568
Traffic Control 10% $17,136
CONSTRUCTION COST SUBTOTAL $197,064
Contingencies 30% $59,119
CONSTRUCTION COST TOTAL $256,183
Engineering and Inspection Costs 35% $89,664
CAPITAL IMPROVEMENT COST TOTAL $345,847
ENR = 9103 (S.F. March 2007) rounded $346,000
Pipe bursting could be an alternative to remove and replace.

Same as project location.

Diameter of existing deficient pipes: 8"
25, 35

TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Scott Blvd. from Serra Ave. to Homestead Rd.

MH S25-37 TO S35-98
Replace 800 feet of 8-inch pipe with 10-inch pipe.

City of Santa Clara
Sanitary Sewer Capacity Assessment Project 9 May 2007
PROJECT ID:………………………………………10
PROJECT LOCATION:……………………………
BRIEF PROJECT DESCRIPTION:………………
SANITARY SEWER PLAT MAP(S):………………
LOCATION OF CAPACITY DEFICIENCY: ……
SPECIAL CONSIDERATIONS:……………………
ALTERNATIVES:……………………………………
MAJOR ITEMS DIA. (in.) DEPTH
(feet)
LENGTH
(feet) UNIT COST COST

BASELINE CONSTRUCTION COST
Pipe Construction
Park Ave. 12 8-16 250' 170 $/ft $42,500
Lower Laterals plus Cleanout (Park Ave.) 2 $2,000 $4,000

SITE SPECIFIC CONSTRUCTION COST
Bypass Pumping / Flow Diversion Costs 10% of baseline pipe cost 10% $4,250 Remove and Replace Factor 2% of baseline pipe cost 2% $850 SUBTOTAL $51,600
Mobilization and Demobilization 5% $2,580
Traffic Control 10% $5,160
CONSTRUCTION COST SUBTOTAL $59,340
Contingencies 30% $17,802
CONSTRUCTION COST TOTAL $77,142
Engineering and Inspection Costs 35% $27,000
CAPITAL IMPROVEMENT COST TOTAL $104,142
ENR = 9103 (S.F. March 2007) rounded $104,000
38 TRUNK SEWER SYSTEM PROJECT DESCRIPTION
Park Ave. south of Bellomy St.

MH S38-75 TO S38-66
Replace 250 feet of 10-inch pipe with 12-inch pipe.

Pipe bursting could be an alternative to remove and replace.

Same as project locatin.

Diameter of existing deficient pipes: 10"
City of Santa Clara
Sanitary Sewer Capacity Assessment Project 10 May 2007

Water and Environment
2290 North First Street
Suite 212
San Jose, CA 95131
T 408.240.8160
F 408.240.8161
www.rmcwater.com
City of Santa Clara
Sanitary Sewer Master Plan Update
Final Report
Prepared by:

April 2016
City of Santa Clara
Sanitary Sewer Master Plan Update
April 2016 i
Table of Contents
Executive Summary ...................................................................................................................... 1 Background and Purpose of Master Plan ..................................................................................... 1 How the Capacity Assessment Was Prepared ............................................................................. 2 Recommended Capacity Improvement Program .......................................................................... 6 Chapter 1 Introduction ............................................................................................................. 1-1

1.1 Background and Study Objectives .......................................................................... 1-1

1.2 Scope of Study ........................................................................................................ 1-2

1.3 Report Organization ................................................................................................ 1-4 Chapter 2 Basis of Flow Estimates .......................................................................................... 2-1

2.1 Wastewater Flow Components ............................................................................... 2-1

2.2 Base Wastewater Flow ........................................................................................... 2-2

2.2.1 Existing Base Wastewater Flow .............................................................................. 2-2

2.2.2 Future Base Wastewater Flow ................................................................................ 2-2

2.2.3 Diurnal Curves ........................................................................................................ 2-5

2.3 Groundwater Infiltration ........................................................................................... 2-7

2.4 Rainfall-Dependent I/I ............................................................................................. 2-7

2.5 Flow from Cupertino Sanitary District ...................................................................... 2-8 Chapter 3 Hydraulic Model Development ................................................................................ 3-1

3.1 Modeling Terminology ............................................................................................. 3-1

3.2 Delineation of Modeled System .............................................................................. 3-1

3.3 Model Network Construction and Validation ........................................................... 3-4

3.4 Flow Monitoring Program ........................................................................................ 3-4

3.5 Model Calibration .................................................................................................... 3-9

3.5.1 Dry Weather Calibration .......................................................................................... 3-9

3.5.2 Wet Weather Calibration ....................................................................................... 3-11 Chapter 4 Capacity Analysis .................................................................................................... 4-1

4.1 Design Event Criteria .............................................................................................. 4-1

4.1.1 Design Storm Condition .......................................................................................... 4-1

4.2 Hydraulic Capacity Criteria ...................................................................................... 4-2

4.2.1 Capacity Deficiency Criteria .................................................................................... 4-3

4.2.2 Sizing Criteria for New Sewer Facilities .................................................................. 4-4

4.3 Capacity Analysis Results and Proposed Solutions ................................................ 4-5

4.3.1 Pump Station Firm Capacity Analysis ..................................................................... 4-8 Chapter 5 Recommended Capacity Improvement Program .................................................. 5-10

5.1 Development of Capacity Improvement Projects .................................................. 5-10

5.2 Implementation Recommendations ....................................................................... 5-13 Appendices
Appendix A - Plots of Flow Monitoring Data and Summary of Daily Flows Appendix B - Dry Weather Flow Calibration Graphs
Appendix C - Wet Weather Flow Calibration Graphs
Appendix D - Model Hydraulic Profiles of Capacity Deficiencies Appendix E - Rabello & Northside Pump Station Capacity and Forcemain Calibration TM Appendix F - Project Descriptions and Cost Estimates
Appendix G - General Plan Land Use and Recent (2009-2015) Developments City of Santa Clara
Sanitary Sewer Master Plan Update
April 2016 ii
List of Tables
Table ES-1: Collection System Flow Estimates ............................................................................ 6 Table ES-2: Recommended Capacity Improvement Projects ..................................................... 10 Table 2-1: Base Wastewater Flow Unit Flow Factors ................................................................ 2-4 Table 2-2: Base Wastewater Flow Estimates ............................................................................ 2-5 Table 2-3: City’s Large Water Users .......................................................................................... 2-6 Table 3-1: Sewer Collection System Model Summary ............................................................... 3-2 Table 3-2: Collection System Pump Station Summary .............................................................. 3-2 Table 3-3: Summary of Flow Monitoring Sites ........................................................................... 3-5 Table 3-4: Dry Weather Flow Calibration Results .................................................................... 3-10 Table 3-5: Wet Weather Flow Calibration Results ................................................................... 3-12 Table 4-1: Summary of Capacity Analysis Results .................................................................... 4-5 Table 4-2: Capacity Deficiencies and Proposed Solutions ........................................................ 4-6 Table 4-3: Pump Station Firm Capacity Analysis ....................................................................... 4-8 Table 4-4: Recommended Revised Set Levels for Lift Stations ................................................. 4-9 Table 5-1: Recommended Capacity Improvement Projects .................................................... 5-11 List of Figures
Figure ES-1: Sanitary Sewer Collection System Overview ........................................................... 3 Figure ES-2: Modeled Trunk System ............................................................................................ 4 Figure ES-3: Recent and Future Growth Areas ............................................................................ 5 Figure ES-4: Model Predicted System Surcharge Under Future PWWF ...................................... 8 Figure ES-5: Capacity Improvement Projects and Project for Entitlement Compliance ................ 9 Figure 1-1: Study Area ............................................................................................................... 1-3 Figure 2-1: Wastewater Flow Components ................................................................................ 2-1 Figure 2-2: Recent and Future Growth Areas ............................................................................ 2-3 Figure 2-3: Wastewater Diurnal Curves ..................................................................................... 2-5 Figure 2-4: RDI/I Hydrograph Components ............................................................................... 2-8 Figure 3-1: Modeled Trunk System ............................................................................................ 3-3 Figure 3-2: Subcatchments and Loading Manholes .................................................................. 3-6 Figure 3-3: Flow Meter and Rain Gauge Locations ................................................................... 3-7 Figure 3-4: Trunk Sewer System Schematic ............................................................................. 3-8 Figure 3-5: Example Dry Weather Calibration Graphs ............................................................ 3-11 Figure 3-6: Example Wet Weather Calibration Graphs for 2014 Storm Period........................ 3-13 Figure 4-1: Design Storm Pattern for the San Jose International Airport MAP Area ................. 4-2 Figure 4-2: PWWF Hydraulic Deficiency Criteria for Gravity Sewers ......................................... 4-4 Figure 4-3: Model Predicted System Surcharge Under Future PWWF...................................... 4-7 Figure 5-1: Capacity Improvement Projects and Project for Entitlement Compliance ............. 5-12 City of Santa Clara
Sanitary Sewer Master Plan Update
April 2016 iii
Acknowledgements
City of Santa Clara
Rajeev Batra, Director of Public Works/City Engineer
Falguni Amin, Principal Civil Engineer
Evelyn Liang, Senior Civil Engineer (Project Manager)
Kimchi Tran, Civil Engineer
Christopher de Groot, Director of Water and Sewer Utilities Shilpa Mehta, Principal Engineer
Garrett Brown, Sanitary Sewer Assistant Superintendent
Gloria Sciara, Development Review Officer
Jeff Schwilk, Associate Planner
Debby Fernandez, Project Planner
Payal Bhagat, Associated Planner
RMC Water and Environment
Gisa Ju, Principal-in-Charge/Technical Director
Steve Bui, Project Manager
Winola Cheong, Project Engineer
V&A Consulting Engineers, Flow Monitoring
Schaaf & Wheeler Consulting Civil Engineers, Pump Station Capacity Assessment City of Santa Clara
Sanitary Sewer Master Plan Update
April 2016 iv
Abbreviations and Definitions
ABAG Association of Bay Area Governments
ABWF Average base wastewater flow
ADWF Average dry weather flow
APN Assessor parcel number
Backwater A condition in which the hydraulic gradeline (see definition of HGL below) increases upstream of a location in the system due to a downstream hydraulic constriction.

BWF Base wastewater flow: sanitary and process flow contributions from residential, commercial, institutional, and industrial users.

CIP Capital Improvement Program
City City of Santa Clara
CSJ City of San Jose
CuSD Cupertino Sanitary District
d/D Ratio of flow depth to pipe diameter
Design Storm A rainfall event, defined based on statistical probability of occurrence, which determines the peak wet weather flow conditions for which the capacity of sewer system facilities are evaluated and/or designed.

Diurnal Curve Change in dry weather flow over a typical 24-hour period on an hourly basis.

DU Dwelling unit
DWF Dry weather flow: the flow during non-rainfall periods, composed of normal base wastewater flow plus any dry season groundwater infiltration.

ENR-CCI Engineering News Record Construction Cost Index; an index published monthly by Engineering News Record magazine and used to reference construction costs (such as those for wastewater system facilities) to a specific date and location.

Firm capacity The capacity of a pump station with the largest pump out of service. fps Feet per second
GIS Geographic Information System: a computerized system in which geographical features (e.g., sewer facilities, parcels, land use) are linked to an attribute database to facilitate analysis and presentation of information
gpad or gpd/ac Gallons per day per acre
gpcd Gallons per capita per day
gpd Gallons per day
GWDR General Waste Discharge Requirements for Sanitary Sewer Systems: regulations adopted by the State Water Resources Control Board in 2006 that address the operation, maintenance, and management of publicly-owned sanitary sewer systems in California

City of Santa Clara
Sanitary Sewer Master Plan Update
April 2016 v
GWI Groundwater infiltration: extraneous water that infiltrations into a sewer system from the ground through defective pipes and manholes. Groundwater infiltration is considered to be a relatively constant daily flow that varies seasonally and depends on location of sewers with respect to the groundwater table.

HGL Hydraulic Grade Line: in a gravity pipeline system, the water surface elevation in the pipes; or in a system flowing under pressure, the elevation representing the sum of pressure head plus elevation head
Hydrograph A graph of flow versus time.

IDF Intensity-duration-frequency: rainfall statistics that establish the rainfall intensity over specified durations for various recurrence frequencies I/I Infiltration/inflow (see definitions below)
Infiltration Extraneous groundwater or storm water that enters sewer pipes, manholes, and service laterals via the soil through breaks, cracks, and defective joints.

Inflow Storm water that enters the sewer system from the ground surface through direct drainage connections (e.g., directly connected catch basins, area drains, or roof drains) or through manhole or cleanout lids.

Inverted Siphon A sewer configuration (also called a “siphon”), typically consisting of a downward leg, horizontal section, and upward leg, in which the flow is forced through the pipe by the pressure head created by the elevation difference between the upstream and downstream ends of the siphon. An inverted siphon is typically used to cross under a creek, channel, or another pipeline.

Isohyetal A contour of equal precipitation (typically average annual rainfall) K Recession coefficient of RDI/I unit hydrograph (see Figure 2-4) lf Linear feet
Loading Manhole A manhole in the modeled sewer network to which flows from unmodeled sewers discharge into the modeled network (also see definition of subcatchment below).

LS Lift Station
MAP Mean annual precipitation
mgd Million gallons per day
NAICS North American Industrial Classification System
O&M Operations and maintenance
PDWF Peak dry weather flow: the peak flow during non-rainfall periods.

PS Pump Station
PWWF Peak wet weather flow: the peak flow during a given storm event from dry weather flow plus infiltration and inflow.

R Ratio of RDI/I volume to rainfall volume
RDI/I Rainfall-dependent infiltration/inflow: the infiltration and inflow into a sewer system directly related to a rainfall event. RDI/I may cause rapid, short-term peak flows in the sewer system that recede after the rainfall has ended.

RG Rain gauge
RMC RMC Water and Environment

City of Santa Clara
Sanitary Sewer Master Plan Update
April 2016 vi
sf or sq. ft. Square feet
SCVWD Santa Clara Valley Water District
SECAP System Evaluation and Capacity Assurance Plan
Siphon See Inverted Siphon
SJ/SC RWF San Jose / Santa Clara Regional Wastewater Facility SSMP Sewer System Management Plan
SSO Sanitary sewer overflow
Subcatchment A small area of the sewer system that contributes flow to the modeled sewer network, in which the unmodeled collection sewers are assumed to discharge to a common point (manhole) in the modeled network
Surcharge The hydraulic condition in a sewer pipeline in which the elevation of the hydraulic gradeline (water level) is above the crown (top) of the pipe. Under such a condition, the water in the pipe rises into the manholes and could overflow onto the ground if the hydraulic gradeline exceeds the elevation of the manhole rims.

T Time to peak of RDI/I unit hydrograph (see Figure 2-4) TM Technical Memorandum
WWF Wet weather flow: the flow during rainfall periods, composed on base wastewater flow, wet season groundwater infiltration, and rainfall-dependent I/I.

City of Santa Clara
Sanitary Sewer Master Plan Update Executive Summary
April 2016 ES-1
Executive Summary
This report summarizes the results and recommendations of the Sanitary Sewer Master Plan Update (Master Plan) for the City of Santa Clara (City). The Master Plan was prepared by RMC Water and Environment (RMC) in close coordination with City staff. The Master Plan will be used to guide improvements to the City’s sanitary sewer system to accommodate current and future development and ensure that the City continues to provide a high level of service to its customers.

Background and Purpose of Master Plan
The City of Santa Clara is located in central Santa Clara County adjacent to the Cities of San Jose, Cupertino, and Sunnyvale. The City has a population of approximately 120,000 and is served by a wastewater collection system consisting of approximately 270 miles of sewer pipelines and seven sewage pump stations. The system collects wastewater flows generated within the City limits and also flows from the major portion of the Cupertino Sanitary District (CuSD) via a connection at Homestead Road and Swallow Drive. Flow is conveyed eastward to the City of San Jose’s interceptor sewer on Zanker Road and also northward to the Northside and Rabello Pump Stations, where the flow is pumped to the San Jose/Santa Clara Regional Wastewater Facility (SJ/SC RWF) for treatment and disposal. The City’s sewer system and service area are shown in Figure ES-1.

The City’s last sanitary sewer master plan was completed in 20071 . Since that time, the City has completed
a number of sewer improvement projects and is experiencing significant growth and redevelopment in a number of areas, necessitating an evaluation of the capacity of the sanitary sewer system to handle future wastewater flows. This Master Plan will help identify future capital needs for capacity improvements and associated requirements for financing those improvements through increased connection fees or other sources of funding.

The City is also required to comply with the Statewide General Waste Discharge Requirements for Sanitary Sewer Systems (GWDR) adopted in 2006 by the State Water Resources Control Board. The GWDR, which applies to all publicly-owned sewer systems in California, includes the requirement to complete a Sewer System Management Plan (SSMP). The SSMP addresses the overall management, operation, and maintenance of the sanitary sewer system and must include a System Evaluation and Capacity Assurance Plan (SECAP). Therefore, this Master Plan is also intended to satisfy the SECAP requirements of the SSMP.

The overall objectives of this Master Plan are to develop wastewater flow projections for the City’s collection area using up-to-date water use and land use information and flow monitoring data; develop an updated hydraulic model of the trunk sewer system; use the model to identify existing capacity deficiencies and future projected capacity requirements; and develop a Capital Improvement Program (CIP), including budget estimates, for implementing the required capacity improvements to the collection system.

This Executive Summary is presented in two parts:
 How the Capacity Assessment Was Prepared describes the scope and methodologies of the planning effort, including the key planning and technical assumptions incorporated into the sewer system capacity analysis.
 Recommended Capacity Improvement Program presents the recommended CIP, including capacity improvement projects, priorities, and estimated costs. In addition, recommendations are presented for implementing the proposed capacity improvement program.

1 City of Santa Clara Sanitary Sewer Capacity Assessment, RMC Water and Environment, May 2007.

City of Santa Clara
Sanitary Sewer Master Plan Update Executive Summary
April 2016 ES-2
How the Capacity Assessment Was Prepared
The City’s wastewater collection system includes sewer pipelines ranging in size from 4 to 48 inches in diameter. The larger pipes, primarily the 10-inch and larger sewers and a portion of the smaller diameter pipes, comprise the trunk sewer system, which is the primary network for conveying flows generated from the City’s service area and CuSD to the SJ/SC RWF. The trunk sewer system, comprising about 34 percent of the total pipe footage in the system, was the focus of the capacity assessment in this study.

The project team used a systematic process that incorporated land use planning information, water use and flow monitoring data, and design criteria for estimating wastewater flows, applied in a computer hydraulic model of the trunk sewer system. The modeled system is shown in Figure ES-2. The model was used to assess how the system would perform under various planning and flow scenarios and identify pipes and/or pump stations that may not have sufficient capacity to convey the predicted flows under existing or future conditions. Improvement projects were developed to provide the required capacity, the capital costs of the required projects were estimated, and the projects were prioritized based on the model results.

Capacity Assessment Considers Existing and Future Planning Scenarios Two planning scenarios were evaluated for this study: existing (2015) and future (2035) scenarios. The existing scenario examined the current capacity of the sewer system based on existing land use, with flows defined based on winter water use data and calibrated to flow monitoring data collected in the 2014/15 winter season. The future scenario incorporated information on planned development provided by the City.

Figure ES-3 shows the location of the areas of anticipated development. Planned development within the City represents over 15,000 new residential dwelling units and over 20 million square feet of commercial and industrial building floor space. In addition, CuSD has also projected an increase in their base wastewater flow due to anticipated additional development. Together, these projections are estimated to increase current base wastewater flows by over two folds. The future scenario was used to examine the impact on the system of future increases in wastewater flows due to anticipated development and determine the required sewer system capacity needed to serve both existing and future users.

Potential Capacity Deficiencies under Existing and Future Flow Conditions For each of the planning scenarios, projected dry and wet weather flows were simulated in the hydraulic model. The model was calibrated to flow monitoring data to ensure that it represents a reasonably accurate depiction of system conditions. For this study, a flow monitoring program consisting of 25 temporary flow meters installed in the system during the 2014/15 wet weather season was conducted to provide data to calibrate the hydraulic model and verify existing system flows. The collected data was useful for confirming dry weather flows and characterizing the relative wet weather flow response in different areas of the system.

The model integrates various dry and wet weather flow parameters to determine system capacity under different flow and planning scenarios. Key flow components incorporated into the model included: base (dry weather) wastewater flow (BWF), estimated based on winter water use data; groundwater infiltration (GWI), which occurs when water seeps into pipes under the ground through cracks and pipe joints; and rainfall-dependent infiltration and inflow (RDI/I) during storm events. For this Master Plan, a 10-year return period, 24-hour duration rainfall event was selected as the “design storm” to serve as the basis for computing design peak wet weather flows in the system. A 10-year return period has become a standard design storm criterion for many Bay Area agencies. Table ES-1 presents the estimated existing and future average dry weather flow (ADWF) and peak wet weather flow (PWWF) for the selected design storm for the City’s sewer system, based on the modeling conducted for this study. 0 0.5
1 Mile µ Legend
Sew ers by Diam eter:
≤ 6"
8" - 10"
12" - 16"
18" - 24"
≥ 27"
ÉP Pum p/Lift Station
Santa Clara Force Mains
San Jose Interceptors
City Lim it
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Sanitary Sew er
Master PlanU pdate
Figure ES-1
Sanitary Sewer Collection
System Overview
0 0.5
1 Mile µ Legend
Modeled Trun k Sew ers
≤ 6"
8" - 10"
12" - 16"
18" - 24"
≥ 27"
ÉP Modeled Pum p/Lift Station
Un m odeled Sew ers
San Jose In terceptors
City Lim it
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San itary Sew er
Master Plan Update
Figure ES-2
Modeled Trunk System
0 0.5 1 Mile
Legend
Recent (2009-2015) Development Projects
General Plan Phase 3 (2035) Development
µ
ÉP Pump/Lift Station
Modeled Trunk Sewers
Unmodeled Sewers
San Jose Interceptors
City Limit
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Sanitary Sewer
Master Plan Update
Figure ES-3
Recent and
Future Growth Areas
CSJ Interceptor
(not modeled)
San Jose / Santa Clara
Regional
Wastewater Facility
SC Influent
Junction Structure
CuSD Flow
City of Santa Clara
Sanitary Sewer Master Plan Update Executive Summary
April 2016 ES-6
Table ES-1: Collection System Flow Estimates
Existing
ADWF (2)
(mgd)
Existing
PDWF (2)
(mgd)
Existing
PWWF (3)
(mgd)
Future
ADWF (2)
(mgd)
Future
PDWF (2)
(mgd)
Future
PWWF (3,4)
(mgd)
Flow Estimates by System Outfall (1)
North (to Northside and Rabello
Pump Stations) 10.2 15.2/16.0 27.9 24.6 33.5/34.4 41.0
East (to San Jose Zanker Road
Interceptor) 4.7 6.4 11.7 9.8 13.3 18.3
Total 14.9 21.6/22.4 39.6 34.4 46.8/47.7 59.4
Flow Estimates by Agency (1)
Santa Clara System 11.3 15.4/16.2 26.8 27.5 34.6/35.5 45.6 Cupertino Sanitary District 3.5 6.2 12.8 6.9 12.2 13.8
Total 14.9 21.6/22.4 39.6 34.4 46.8/47.7 59.4

1. Assuming that trunk sewer capacity deficiencies are relieved with recommended capital improvement projects presented in Table ES-2.

2. Includes groundwater infiltration for a typical wintertime period. ADWF and first value shown for PDWF includes typical non-game day flow from Levi’s Stadium; second value shown for PDWF includes a peak game day flow from Levi’s Stadium.

3. For 10-year design storm; assumes non-game day flow from Levi’s Stadium.

4. Assuming peak wet weather flow from CuSD would not increase above its contractual maximum flow of 13.8 mgd.

Model results were examined to determine trunk system capacity needs, as indicated by areas where the flow in the pipes would exceed their capacity and cause surcharge conditions (water levels higher than the tops of the pipes). Figure ES-4 shows the capacity assessment results for future PWWF conditions, indicating existing trunk sewers that were predicted by the model to be surcharged due to “throttle” conditions (peak flow exceeding full pipe capacity) or due to backwater from a downstream throttle condition, and locations of where the model predicts a surcharge condition severe enough to violate the City’s capacity criteria, defined as water level that exceeds one (1) foot above the top of pipe. Most of these locations were predicted to be capacity issues only under future PWWF. Note that the locations of criteria violations are not necessarily the locations of the actual capacity-deficient pipes, but are typically located further upstream due to backwater from downstream deficiencies.

Note that no overflows are predicted under design storm conditions. Furthermore, all of the modeled pump stations have adequate firm capacity (capacity with largest pumping unit out of service) to convey the predicted PWWF without violating freeboard criteria or resulting in sewer overflows, although for two of the stations (Westside and Tasman), noticeable backwater surcharge was predicted because the switch-on set points for the lead pumps are higher than the influent lines.

Recommended Capacity Improvement Program
The Capital Improvement Program (CIP) recommended in this study is designed to provide for adequate sewer system capacity for the City’s existing and anticipated future development. Figure ES-5 and Table ES-2 present the recommended capacity improvement projects. Projects have been assigned relative priorities based on the extent of criteria violations or surcharge. Priority 1 and 2 projects are required to address capacity deficiencies that result in criteria violations under current conditions, while Priority 3 projects are those that result in criteria violations under future conditions. In addition to these projects, there was also an additional project (Project E1) that was triggered by an entitlement requirement, discussed in more detail in Chapter 5.

City of Santa Clara
Sanitary Sewer Master Plan Update Executive Summary
April 2016 ES-7
As indicated in Table ES-2, the total estimated cost of the recommended capacity improvement program (without Project E1) is about $1.7 million. The total estimated cost, if the City implements Project P6-Alt instead of P6, would be approximately $2.8 million. Note that implementing Project P6-Alt would also increase the peak flow to the Rabello and Northside Pump Stations by about 1 mgd to each pump station, which could require further evaluation of and potential improvements to increase pump station capacity.

Implementation Recommendations
The City should begin implementation of the Capital Improvement Program recommended in this Master Plan, starting with the highest priority projects. The following items should be considered in project scheduling and design, and in future updates of the Master Plan. ▪ The alignments and sizes of projects should be verified with detailed predesign analyses, including topographic surveys, geotechnical investigations, utility research, and constructability reviews. ▪ The estimated costs assumed open cut construction, but alternative methods such as trenchless construction or construction of parallel relief pipes could be considered during design. The decision to parallel or replace existing sewers should consider the physical condition and remaining useful life of the existing pipelines; the availability of pipeline corridors for new sewer construction; and operation and maintenance concerns.
▪ The hydraulic model has been developed to assist the City in performing capacity analyses and updating the Master Plan in the future. The model should be kept up-to-date with changes to existing sewer connections, development plans, and sewer system facilities. ▪ The City should conduct additional flow monitoring at key locations in the sewer system, particularly the area tributary to the Chromite/Machado trunk sewers where both the 2006 and 2015 flow monitoring programs indicated high I/I. The City should also conduct smoke testing and television inspection to identify potential sources of I/I. Flow levels during large storm events should be compared to the peak flows simulated by the hydraulic model to verify the modeling predictions for the 10-year design storm and confirm the need for and sizing of Project P3 (Cabrillo Avenue Sewer Improvement). ▪ The City should coordinate with the CuSD on flow and planning assumptions to ensure that adequate capacity exists in the Santa Clara system to handle future flows from the District. The City should encourage CuSD to monitor the flows at the flow meter that it operates and maintains on Homestead Road at Swallow Drive on an on-going basis and periodically confirm meter calibration to verify the wastewater flows entering the Santa Clara system.
▪ The City should coordinate with the City of San Jose to ensure that its flow criteria and planning assumptions are consistent with those used by San Jose in its capacity master planning. ▪ The City should verify the need to implement project E1 (Tracy Drive Sewer Improvement). The project is triggered by the large sewer discharge assumed for parcel APN 316-17-018, which holds an entitlement agreement to discharge a potential flow of 0.95 mgd; however, it is currently discharging less than 10 percent of the entitled rate. While the City is obligated to provide capacity for entitlement holders, it is important to note that implementing this project now may result in oversized sewers where the current daily flow is not sufficient to provide the minimum cleaning velocity and thus creating potential debris and odor issues.
0 0.5
1 Mile µ Legend
Surcharge due to Backwater
Surcharge due to Throttle
Surcharge Criteria Violation
under Existing PWWF
Surcharge Criteria Violation
under Future PWWF
ÉP Modeled Pump/Lift Station
Modeled Trunk Sewers
San Jose Interceptors
City Limit
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Sanitary Sewer
Master Plan Update
Figure ES-4
Model Predicted
System Surcharge
0 0.5 1 Mile
µ Legend
Modeled Trunk Sewer
Unmodeled Sewer
Santa Clara Force Mains
San Jose Interceptors
Recommended Capital Improvement Projects
Project for Entitlement Compliance
J:\Projects\149 SANTA CLARA\149-008 Santa Clara 2015 Sanitary Sewer MP Update\G. GIS Files\_MXDs\Master Plan Report Figures\MPFigES5_CIPs_08Apr2016.mxd City of Santa Clara
Sanitary Sewer
Master Plan Update
Figure ES-5
Capacity Improvement
Projects and Project for
Entitlement Compliance
City of Santa Clara
Sanitary Sewer Master Plan Update Executive Summary
April 2016 ES-10
Table ES-2: Recommended Capacity Improvement Projects
Project
ID Priority Project Name U/S MHID D/S MHID Description Est. Capital Improvement Cost1 P12 1 Westside Lift Station Set Point Adjustment N/A N/A Adjust the set points for the pumps to a lower elevation to eliminate unnecessary backups in the influent line. -- P22 2 Tasman Lift Station Set Point Adjustment N/A N/A Adjust the set points for the pumps to a lower elevation to eliminate unnecessary backups in the influent line. -- P3 2 Cabrillo Avenue Sewer Improvement S41-13 S41-20 Upsize 1,600 feet of 8-inch line in Cabrillo Ave. between Lawrence Expressway and Nobili Ave. to a 12-inch line. $1,097,000 P4 3 Tasman Drive Sewer Improvement S93-24 S93-35 Upsize 600 feet of 12-inch line in Tasman Dr. between Old Ironsides Dr. and Great America Pkwy. to a 15-inch line. $327,000 P5 4 Sewer Diversion at Los Prades Boulevard and Saratoga Avenue S25-85 S25-85
Install a weir in manhole S25-85 located in the intersection of Padres Blvd. and Saratoga Ave. to divert flow northwest to the existing 12-in line in Los Padres Blvd. $77,000
P6 4
Sewer Diversion at Calabazas Boulevard and Machado Avenue U/S of
S52-93 S52-120
Install a new manhole upstream of S52-93 in the intersection of Calabazas Blvd. and Machado Ave., and install a new 15-inch high-level diversion line (approximately 200 feet) to divert excess flow from the existing 24-inch line in Calabazas Blvd. to the 21-inch line in Machado Ave. The diversion line should be about 6 inches higher than the invert of the 24-inch line. $166,000
P6-Alt.3 4 Calabazas Creek Sewer Improvement S62-31 S72-20 Upsize 1,800 feet of 24-inch line next to Calabazas Creek between Kifer Rd. and Scott Blvd. to a 27-inch line. $1,334,000 Estimated Total Cost for Recommended Projects P1 to P6:

Estimated Total Cost for Projects P1 to P5 and P6-Alt:
$1,667,000 $2,835,000
E14 N/A Tracy Drive Sewer Improvement S10-77 S22-51
Upsize approximately 6,600 feet of 10- to 12-inch line in Tracy Dr. and Pomeroy Ave. to a 15-inch line; install a new 15-inch line between manholes S22-55 and S22-46 in Pomeroy Ave. and Homestead Rd. (approximately 50 feet) to divert flow into Homestead Rd., and upsize approximately 1,400 feet of 18-inch line downstream to a 21-inch. $4,654,000
Estimated Total Cost (P1 to P6) including Project E1:

Estimated Total Cost (P1 to P5 and P6-Alt) including Project E1:
$6,321,000 $7,489,000

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 1
Introduction
April 2016 1-1
Chapter 1 Introduction
This report presents the results and recommendations of the Sanitary Sewer Master Plan Update (Master Plan) for the City of Santa Clara (City). The report was prepared by RMC Water and Environment (RMC).

1.1 Background and Study Objectives
The City of Santa Clara is located in central Santa Clara County adjacent to the Cities of San Jose, Cupertino, and Sunnyvale. The City has a population of approximately 120,000 and is served by a wastewater collection system consisting of approximately 270 miles of sewer pipelines and seven sewage pump stations. The system collects wastewater flows generated within the City’s service area and also wastewater flows from the major portion of the Cupertino Sanitary District (CuSD) via a connection at Homestead Road and Swallow Drive. Flow is conveyed eastward to the City of San Jose’s interceptor sewer on Zanker Road and also northward to the Northside and Rabello Pump Stations, where the flow is pumped to the San Jose/Santa Clara Regional Wastewater Facility (SJ/SC RWF) for treatment and disposal. The City’s sewer system and service area are shown in Figure 1-1.

The City’s last sanitary sewer master plan was completed in 20072 . Since that time, the City has completed
a number of sewer improvement projects and is experiencing new development in a number of areas, necessitating an evaluation of the capacity of the sanitary sewer system to handle future wastewater flows.

This evaluation will help identify future capital needs for capacity improvements and associated requirements for financing those improvements through increased connection fees or other sources of funding. This Master Plan will confirm flows in the collection system and identify capital needs for capacity improvements.

The overall objectives of this Master Plan are to develop wastewater flow projections for the City’s collection area using up-to-date water use and land use information and flow monitoring data; develop an updated hydraulic model of the trunk sewer system; use the model to identify existing capacity deficiencies and future anticipated capacity requirements; and develop a phased Capital Improvement Program (CIP), including budget estimates, for implementing the required capacity improvements to the collection system.

2 City of Santa Clara Sanitary Sewer Capacity Assessment, RMC Water and Environment, May 2007.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 1
Introduction
April 2016 1-2

1.2 Scope of Study
The scope of the Master Plan, as well as a brief discussion of work conducted under each task, is described below.
 Task 1 – Project Management and Coordination. Periodic progress meetings were held with City staff to review project status and discuss project issues, and monthly status reports were prepared to document the work completed. Quality control was carried out, including checking of data and calculations, as well as senior review of proposed criteria, recommendations, and project deliverables.  Task 2 – Data Collection and Review. Data, maps, geographic information system (GIS) files, and previous reports related to the wastewater collection system were reviewed to identify the information available for completing the Master Plan.
 Task 3 – Flow Monitoring. A flow monitoring program, consisting of the 23 meters and 4 rain gauges installed in the collection system for a period of about two months during the 2014/15 wet weather season was conducted to obtain data to characterize flows in the system and calibrate the hydraulic model. Two additional FloDar meters were also installed at the Guadalupe Chart Station on the Trimble Road trunk sewer to confirm flows recorded by the City’s existing permanent meters at that site. Four of the sites were installed early, including a meter at Levi’s Stadium to capture the 2014 Thanksgiving Day football game, and at the three most downstream meters to capture total flows to the Rabello and Northside Pump Stations.
 Task 4 – Hydraulic Model Update. An expanded hydraulic model of the City’s trunk sewer system was developed using InfoWorks™ CS modeling software. Subcatchments (small areas of unmodeled sewers that contribute flow to the modeled system) were delineated to define areas loading to the model, and flow loads to the model were compiled using water use and land use data and flow factors representing unit base wastewater flow (BWF) rates, diurnal BWF patterns, and infiltration/inflow (I/I).

The expanded model also included the Northside and Rabello Pump Stations, the two associated force mains, and a junction structure between the pump stations and the SJ/SC RWF. Meetings were held with City planning staff to identify and obtain pertinent land use data and to discuss specific planning issues and potential growth or development areas in the City. Additional meetings were also held with the City of Cupertino and the CuSD to obtain updated flow projections. The model was verified for system connectivity, calibrated for dry weather conditions, and then calibrated for wet weather conditions using actual storm events from the flow monitoring program under Task 3.  Task 5 – Evaluate System Hydraulic Performance and Develop Capital Improvement Projects.

The model was used to determine sewer system capacity requirements and identify capacity deficiencies under peak dry and wet weather flow conditions, defined based on a design storm and system performance criteria. Potential solutions to capacity deficiencies were identified and tested in the model, and capacity improvement projects and associated costs were developed based on these analyses. The model was also used to confirm the results of the City’s 2010 Pump Station Evaluation to determine if the City’s pump stations are adequate to convey future flows. The recommended capacity improvement projects were prioritized to develop a Capital Improvement Program (CIP).  Task 6 – Prepare Sanitary Sewer Master Plan (Update) Report. This report was prepared to summarize and present the results and recommendation of the study. 0 0.5
1 Mile µ Legend
Sew ers by Diam eter:
≤ 6"
8" - 10"
12" - 16"
18" - 24"
≥ 27"
ÉP Pum p/Lift Station
San ta Clara Force Main s
San Jose In terceptors
City Lim it
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San itary Sew er
Master Plan Update
Figure 1-1
Sanitary Sewer Collection
System Overview
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 1
Introduction
April 2016 1-4

1.3 Report Organization
This report includes five Chapters, which are described below.  Chapter 1, Introduction, presents the background, objectives, and scope of the Sanitary Sewer Master Plan Update.
 Chapter 2, Basis of Flow Estimates, discusses the planning area land use projections, the basis for developing estimates for each component of wastewater flows, and the base wastewater flow projections for the service area.
 Chapter 3, Hydraulic Model Development, describes the modeled sewer system, development of the model network and model loads, flow monitoring program, and model calibration.  Chapter 4, Capacity Analysis, describes the capacity analysis and design criteria, model results, and potential solutions for identified capacity deficiencies.  Chapter 5, Recommended Capacity Improvement Program, presents the recommended capacity improvement CIP, including project costs, prioritization, and implementation recommendations.

The Appendices to this report include plots of the flow monitoring data, model calibration graphs, model hydraulic profiles, and documentation for the recommended CIP, including project descriptions and cost estimates.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 2
Basis of Flow Estimates
April 2016 2-1
Chapter 2 Basis of Flow Estimates
This chapter presents the basis of wastewater flow estimates for the City’s sanitary sewer system. The section describes the wastewater flow components used in the hydraulic model and the existing and projected future land uses for the City, which form the basis for generating base wastewater flows. Design flow estimates were developed based on criteria developed for each flow component: base wastewater flow, groundwater infiltration, and rainfall-dependent infiltration and inflow, and confirmed through model calibration, as described in Chapter 3 of this report.

2.1 Wastewater Flow Components
Wastewater flows include three components: base wastewater flow (BWF), groundwater infiltration (GWI), and rainfall-dependent infiltration/inflow (RDI/I), as illustrated conceptually in Figure 2-1. BWF represents the sanitary and process flow contributions from residential, commercial, institutional, and industrial users of the system. GWI is groundwater that infiltrates into defects in sewer pipes and manholes, particularly in winter and springtime in low-lying areas. GWI is typically seasonal in nature and remains relatively constant during specific periods of the year. RDI/I is storm water inflow and infiltration that enter the system in direct response to rainfall events, typically through direct connections such as holes in manhole covers or illegally connected roof leaders or area drains or, more commonly, through defects in sewer pipes, manholes, and service laterals that may have resulted from poor initial construction, settlement of trench backfill, or deterioration due to age. RDI/I typically results in short-term peak flows that recede quickly after the rainfall ends.

Figure 2-1: Wastewater Flow Components
Flow
Rainfall
Time
(24 Hours)
RDI/I
BWF
GWI
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 2
Basis of Flow Estimates
April 2016 2-2

2.2 Base Wastewater Flow
For the City’s Master Plan Update, BWF loads were developed for both existing and future development conditions. Existing loads were developed based on average winter water use data from the City’s customer billing records, and future loads were based mainly on the General Plan Phase 3 (2035) development forecast and known development and redevelopment projects that had occurred in recent years. The loading methodology for existing conditions and for projecting future BWF are discussed in the following subsections.

2.2.1 Existing Base Wastewater Flow
Existing BWF was estimated based on actual water billing records in the City’s customer billing database.

Data were first processed to exclude non-wastewater generating accounts such as fire, construction, or irrigation accounts; data for the remaining accounts were converted to average water use (in gallons per day, gpd) using the billing dates and quantities. Each account’s BWF was estimated based on the average water use during the four winter periods between December 2010 and February 2014. Each user was also assigned one of three land use types (residential, commercial, or industrial) according to the account’s North American Industry Classification System (NAICS) designation.

The City also has customers who use domestic wells and/or recycled water. The BWF for these customers were individually estimated based on their winter well usage data and recycled water billing data.

The BWF data (both water use and land use type) were further processed in GIS by geocoding the data to their corresponding parcels using the account’s service address. The total BWF for each sewer subcatchment was then estimated by overlaying the subcatchment boundary on the parcels and summing the BWF of all parcels within each subcatchment.

The data were then imported into the hydraulic model to perform a dry weather simulation run, and the results were compared to the flow data collected during the most recent flow monitoring program, in which a total of 25 meters were installed at selected locations throughout the system and collected actual flow data between November 2014 and March 2015 (see further discussion of model calibration in Chapter 3). It was noticed that the modeled flows were consistently about 10 to 20 percent higher than the observed flows.

One possible explanation was that there was some level of irrigation activities occurring even in the winter months due to the lack of rainfall in recent years. As such, a wastewater return factor of 10 to 20 percent was applied to the estimated BWF based on the water use data to attain a more reasonable match with actual flows observed in the field. The revised estimated BWF including the wastewater return factor is 6.5 million gallons per day (mgd) for residential accounts and 4.4 mgd for commercial and industrial accounts. These estimates do not include flow from the Levi’s Stadium, which varies widely depending on the use of the venue and could potentially generate daily peak flows ranging from less than 0.1 mgd (for local events such as team practice or stadium public tours) to 1.0 mgd or higher (for major events such as the Super Bowl).

2.2.2 Future Base Wastewater Flow
The future scenario for this Master Plan Update refers to the projected flow condition in year 2035, which is the planning horizon for the City’s current General Plan. The BWF for this scenario was estimated using multiple data sources, including the original General Plan Phase 3 development forecast that was prepared in 2009 plus various additions and corrections that City staff identified in 2015, development and redevelopment projects that have occurred between 2009 and 2015, and entitlement agreements for specific parcels. These areas are shown in Figure 2-2. A more detailed map and tabulation of the recent developments are included in Appendix G.

0 0.5 1 Mile
Legend
Recent (2009-2015) Development Projects
General Plan Phase 3 (2035) Development
µ
ÉP Pump/Lift Station
Modeled Trunk Sewers
Unmodeled Sewers
San Jose Interceptors
City Limit
J:\Projects\149 SANTA CLARA\149-008 Santa Clara 2015 Sanitary Sewer MP Update\G. GIS Files\_MXDs\Master Plan Report Figures\MPFig2-2_Dvpt_05Apr2016.mxd City of Santa Clara
Sanitary Sewer
Master Plan Update
Figure 2-2
Recent and
Future Growth Areas
CSJ Interceptor
(not modeled)
San Jose / Santa Clara
Regional
Wastewater Facility
SC Influent
Junction Structure
CuSD Flow
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 2
Basis of Flow Estimates
April 2016 2-4
The original future BWF projection was developed in 2009 as part of the City’s overall General Plan Update effort, in which over one thousand parcels with development potential were identified and their developments were quantified in terms of dwelling units (for residential developments) and/or building square footage (for non-residential developments). The development quantities were multiplied by the corresponding unit flow factors depending on land use to convert the information into BWF estimates.

These unit flow factors are summarized in Table 2-1.

Table 2-1: Base Wastewater Flow Unit Flow Factors
Type of Development Unit Flow Factor (1) Basis
Single Family Detached 245 gpd/DU 3.5 people/DU, 70 gpcd Townhouse or Condominiums 175 gpd/DU 2.5 people/DU, 70 gpcd Apartments 154 gpd/DU 2.2 people/DU, 70 gpcd
Hotels 100 gpd/room n/a
Commercial Offices 0.1 gpd/sq. ft. n/a
R&D Offices 0.15 gpd/sq.ft. n/a

1. All unit flow factors are consistent with factors used in the 2007 Capacity Assessment.

Parcels that were not identified with development potential were assumed to retain the same land use through 2035 and therefore also maintain approximately the same level of wastewater generation, which was developed based on their 2005-2006 winter water billing data. This version of the future BWF projection has since then been used for various capacity evaluations, and was updated regularly when new development or redevelopment project applications were submitted to the City for capacity evaluation.

In 2015, the City identified a number of additional developments that were not accounted for in the original General Plan Phase 3 development forecast prepared in 2009. The City also identified a list of parcels with entitlement agreements that allow the owners of these parcels to discharge wastewater up to a certain flow rate without applying for permission or notifying the City. Neither set of data was accounted for in the original projection. Furthermore, the revised existing BWF estimates are noticeably lower than those developed based on the 2005-2006 winter water billing data. The decline could be mostly attributed to increased water conservation activities in response to the recent drought. This is also evidenced in the City’s potable water sales records, which shows a sharp decline in the past ten years despite continuous population growth in the City. While it is possible that water use could rebound if and when the drought is over (e.g., behavioral changes such as reverting back to longer showers), some of the reduction is likely to remain permanent as a result of installing water-efficient plumbing fixtures and greater awareness of the need to continue conserving water.

In light of the various changes in water use and development information, a focused effort was undertaken to revise the City’s future BWF projections. Parcels that were identified to have development potential in the revised General Plan Phase 3 forecast were re-processed using the updated development quantities.

Parcels that were not identified with development potential were assumed to maintain their current water use, which is the updated existing BWF described in the previous section, instead of the original BWF based on previous 2005-2006 water use data, plus a 10 percent rebound factor to account for possible increase in water use in the future. For parcels that are on the list of development/redevelopment projects that the City has received between 2009 and 2015, their BWF was estimated according to the development quantities specified in their project applications. For parcels that hold entitlement agreements, BWF was set to their entitled flow rates.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 2
Basis of Flow Estimates
April 2016 2-5
Table 2-2 summarizes the existing (circa 2015) and future (2035) BWF for residential and non-residential sectors. Based on these estimates, BWF is projected to increase by over two fold to 27.1 mgd in 2035.

Table 2-2: Base Wastewater Flow Estimates
Land Use Existing Flow
(mgd)
Future Flow
(mgd)
Residential 6.5 10.7
Non-Residential (1) 4.4 16.4
Total (2) 11.0 27.1

1. Does not include flow from the Levi’s Stadium, which varies greatly depending on the use of the venue; average flow on a peak game day is approximately 0.19 mgd based on flow monitoring conducted as part of this project.

2. Does not include flow from the Cupertino Sanitary District (CuSD), which is discussed in section 2.5.

2.2.3 Diurnal Curves
In most sewer systems, BWF typically exhibits distinctive diurnal patterns depending on the land use, usually categorized as residential, commercial, and industrial. For Santa Clara, flow monitoring data showed typical responses to commercial and industrial patterns, but also two residential patterns: the northeastern part of the City in the vicinity of Lafayette Street and Montague Expressway appeared to have a more pronounced morning peak flow and a lower evening peak, while the rest of the City had a less peaky morning peak and a somewhat higher evening peak. As such, two residential diurnal curves were created to represent these two patterns.

The diurnal curves are shown in Figure 2-3. Each subcatchment was assigned one of the residential curves according to its location (Lafayette Area vs. all other areas); and one of the non-residential curves according to the primary type of non-residential establishments (commercial or industrial).

Figure 2-3: Wastewater Diurnal Curves
Figure 5A: Typical Residential Flow Figure 5B: Lafayette Area Residential Flow

0.0 0.5

1.0 1.5

2.0 0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00
Factor
Time
Weekday
Weekend

0.0 0.5

1.0 1.5

2.0 0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00
Factor
Time
Weekday
Weekend
Flow Factor
Flow Factor
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 2
Basis of Flow Estimates
April 2016 2-6
Figure 5C: Commercial Flow Figure 5D: Industrial Flow
Some of the City’s large water users do not exhibit typical diurnal curves. To ensure their flow patterns are accurately reflected in the model, nonresidential accounts with average water use of over 50,000 gpd were identified and individually researched. A total of 18 such large users were identified, and City staff contacted each user to collect operational information regarding their sewer discharge pattern. Individual diurnal curves were created for each based on the operational hours indicated on their wastewater discharge permits or surveys. These large water users are summarized in Table 2-3.

Table 2-3: City’s Large Water Users
Account Holder APN Address Est. Average
Flow (mgd)
Graphic Packaging Intl. Inc. 230-03-100 2600 De La Cruz Blvd. 0.587 Siliconix Inc. 104-39-023 2201 Laurelwood Rd. 0.405
Streamline Circuits Corp. 224-06-170 1415 Richard Ave. 0.308 Intel Corporation 104-48-010 3600 Juliette Ln. 0.191
Intel Corporation 216-46-015 3065 Bowers Ave. 0.099
Marvell Semiconductor Inc. 104-52-024 5488 Marvell Ln. 0.081 APCT Inc. 101-15-033 3495 De La Cruz Blvd. 0.074
Perkin Elmer Optoelectronics 104-13-083 2175 Mission College Blvd. 0.071 Owens Corning Sales LLC 224-07-099 960 Central Exp. 0.069 Applied Materials 216-49-024 3070 Bowers Ave. 0.067
Reaction Technology Inc. 104-51-001 3400 Bassett St. 0.067 City of Santa Clara – Electrical Dept. 230-03-067 524 Robert Ave. 0.065 Abbott Diagnostics Div. 104-50-016 5440 Patrick Henry Dr. 0.063 Diana Fruit Co. Inc. 224-40-001 651 Mathew St. 0.061
Oracle America Inc. 097-08-114 4100 Network Cl. 0.058
Digital 3011 Lafayette LLC 224-36-052 3011 Lafayette St. 0.053 Intel Corporation 104-39-020 2200 Mission College Blvd. 0.053 Agilent Technology 316-17-018 5301 Stevens Creek Blvd. 0.051

0.0 0.5

1.0 1.5

2.0 0:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00
Factor
Time
Weekday
Weekend

0.0 0.5

1.0 1.5

2.3 Groundwater Infiltration
Groundwater infiltration is generally quantified based on actual flow monitoring data, since it is difficult to predict GWI rates based on physical system data alone. In the context of design flow criteria, GWI represents the incremental groundwater infiltration that occurs during the wet weather season above the “baseline” infiltration level during the driest months of the year.

Typical GWI rates may range from about 100 to 1,000 gpad.

GWI were estimated through the model calibration process (described in Chapter 3) by comparing modelsimulated BWF to actual flow measurements from the temporary flow monitoring programs. Cases where model-predicted BWF was noticeably lower than monitored flow indicated the possible occurrence of GWI.

2.4 Rainfall-Dependent I/I
RDI/I flows result from rainfall events that produce infiltration and inflow of storm water into the sewer system. RDI/I can be quantified as the difference between the total flow during and immediately following a storm event and the non-rainfall “base flow” (BWF plus GWI) that is estimated to have occurred during the storm period. The magnitude of the resulting RDI/I response is typically described by the percentage of the rainfall volume (called the “R value”) represented by the volume of the RDI/I hydrograph. The R value can vary from storm to storm, depending on such factors as the degree of soil saturation (due to antecedent rainfall) prior to the storm event.

The shape of the RDI/I hydrograph is also important in determining the peak RDI/I response. The RDI/I hydrograph shape is often defined by separating the total RDI/I hydrograph volume into components, representing different response times to rainfall (fast, medium, and slow). Each component is identified by a percentage of the total RDI/I volume and specific time to peak (T) and recession coefficient (K), illustrated in Figure 2-4. The R component percentages and T and K values can be applied to each hour of rainfall to generate a “synthetic hydrograph” that approximates the volume and shape of the hydrograph from the actual observed event. These parameters, when applied to a different rainfall pattern, can be used to estimate the RDI/I response to that particular rainfall event. This methodology is used to synthesize RDI/I hydrographs for a “design storm” for collection system modeling (see Chapter 3 for discussion of design storms).

Design criteria for RDI/I include design R values and hydrograph shape parameters and the hourly rainfall for the selected design storm event. As described in the next chapter, R values and hydrograph parameters are determined through the process of model calibration, in which actual observed rainfall events are simulated in the hydraulic model, and the resulting model hydrographs are compared to the measured flows at flow meters locations. The RDI/I parameters are adjusted as needed to achieve the best match of modeled to monitored flows. Once calibrated, the model RDI/I parameters can be applied to a design storm to simulate wet weather flows for a design event.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 2
Basis of Flow Estimates
April 2016 2-8
Figure 2-4: RDI/I Hydrograph Components

2.5 Flow from Cupertino Sanitary District
CuSD provides sewer collection services for the majority of City of Cupertino, portions of the City of Saratoga, and several unincorporated areas within Santa Clara County east of San Jose. Most of the flow is discharged into the Santa Clara system via a 27-inch sewer line in Homestead Road; the rest is discharged into the City of San Jose (CSJ) system at various other connection points.

CuSD maintains a permanent flow meter at its discharge point in Homestead Road. Meter data between November 2014 and March 2015 were reviewed and analyzed; the average dry weather flow (ADWF) was about 3.5 mgd. Similar to the declining trend observed for the City, CuSD’s flow has also declined over 28 percent from the 2007 estimates of 4.9 mgd to the current estimates of 3.5 mgd, most likely also due to increased water conservation activities in response to the recent drought.

Multiple meetings were held with City staff and CuSD staff to discuss development projections within the CuSD service areas in an effort to estimate the future BWF for the CuSD system. Information from sources such as the City of Cupertino’s General Plan 2020 and General Plan 2040, CuSD-SJ Joint Interceptor Cost Sharing Agreement (which indicates how much flow CuSD would be discharging into the San Jose system), ABAG projections, and CuSD meter data were discussed. Characteristics of the CuSD system, such as system age and I/I, planned sewer improvements, and known large development projects were also considered. Preliminary model simulations were conducted to understand the potential impact of the CuSD flow on the Santa Clara system under future peak design storm condition. For this Master Plan Update, City staff has directed RMC to use 6.90 mgd as CuSD’s future ADWF, and cap its future PWWF at 13.8 mgd, which is the maximum flow rate set forth in the agreement3 between the City and CuSD.
3 Agreement between the City of Santa Clara and the Cupertino Sanitary District for (a) the purchase of capacity in Cupertino’s sanitary interceptor sewer within the City of Santa Clara and (b) continued use by Cupertino Sanitary District of 13.8 MGD Peak Capacity in the City of Santa Clara’s interceptor sewer system.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 3
Hydraulic Model Development
April 2016 3-1
Chapter 3 Hydraulic Model Development
This chapter describes the process of developing and calibrating the hydraulic model for use in the capacity assessment, including the flow monitoring program that was conducted for this study.

3.1 Modeling Terminology
Network refers to the representation of the physical facilities being modeled. The primary components of the modeled network are pipes, manholes, and pump stations.

Nodes are primarily manholes, but also include pump station wet wells, outfalls (discharge points of the modeled system) and breaks (changes in slope or diameter without a structure, such as at the vertical bends in inverted siphons). The primary data associated with nodes are rim and invert elevations. In the case of wet wells, the data also includes the diameter (for a circular well) or cross-sectional area.

Pipes are connections between nodes. The primary data associated with pipes are upstream and downstream node IDs, pipe length, diameter, and upstream and downstream invert elevations. Pipes include both gravity sewers and force mains.

Pumps are represented by links connecting the wet well node(s) and the discharge manhole or upstream end of the force main. Pumps are controlled by a number of user-defined parameters, including the switchon and switch-off levels, types of pumps, and head discharge curves.

Other model components include Gates and Weirs, which are represented by links with zero length.

Primary data associated with gates are the opening width and invert; data associated with weirs are the crest width and crest elevation.

Subcatchments are areas that contribute flow to the modeled sewer network and represent the unmodeled sewers in the collection system. Data associated with subcatchments include base wastewater (sanitary) flow (computed based on population, water use, or other available data), type of land use (which defines the diurnal profile associated with the base wastewater flow), infiltration/inflow (I/I) parameters, and the node at which the flow from the subcatchment enters the modeled system.

Loads are the flows assigned to each subcatchment. Components of model loads include residential and commercial base wastewater flow (BWF), groundwater infiltration (GWI), and rainfall-dependent I/I (RDI/I). As a sum, they represent the total wastewater flow applied to the model.

Models are the combination of a modeled network, its associated subcatchments and loads, and other data files (e.g., rainfall, diurnal profiles, etc.) that comprise a specific model scenario.

3.2 Delineation of Modeled System
A hydraulic model is typically developed to represent the trunk sewer system, which is the network of larger diameter pipes that comprises the “backbone” of the entire system. The City’s original hydraulic model was developed by RMC as part of the 2007 Capacity Assessment project and included approximately 28 percent (about 76 miles) of the total sewer pipelines and four of the pump stations. The model was originally constructed using modeling software MIKE URBANTM (SWMM version) and was converted to InfoWorksTM CS in 2008. RMC has continuously maintained and updated the model as sewer improvement projects were implemented or when new network data became available.

For this Master Plan Update, the model was expanded to include approximately 34 percent (about 92 miles) of the total pipelines and all seven pump stations. The force mains downstream of the Rabello and Northside pump stations were also added. A summary of the system’s pipeline inventory is provided in Table 3-1.

The modeled network is shown in Figure 3-1.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 3
Hydraulic Model Development
April 2016 3-2
Table 3-1: Sewer Collection System Model Summary
Pipe Diameter (in) Total Length1
(ft)
Length Modeled1
(ft)
Percent
Modeled
4-6 197,400 1,800 0.9%
8 619,600 48,300 8%
10 132,300 65,200 49%
12 224,900 120,300 53%
14-16 62,800 59,400 95%
18 43,700 42,000 96%
20-21 15,300 15,300 100%
24 49,600 49,600 100%
27 15,000 15,000 100%
30 25,900 25,900 100%
>30 38,100 38,100 100%
Force Main 13,000 13,000 100%
Total (feet) 1,437,600 493,900 34%
Total (miles) 272.3 93.5 34%
Approx. No. of Manholes 5,260 1,870 36%
No. of Siphons2 53 53 100%

1. Rounded to the nearest hundred feet.

2. This refers to the total number of barrels. Some siphons have multiple barrels.

All seven pump stations in the system are included in the model. A survey was conducted to collect information on pump curves and the operational sequences, as summarized in Table 3-2 below. Pump capacity analysis was conducted for all stations and the results are summarized in Chapter 4 of this report.

Table 3-2: Collection System Pump Station Summary
No. Station Name No. of
Pumps Description Emergency Bypass
1 Westside Lift Station 2 Identical Flygt 3127 pumps. Yes 2 Tasman Lift Station 2 Identical Flygt 3127 pumps. Yes 3 De La Cruz Lift Station 2 Identical Flygt 3127 pumps. Yes 4 Primavera Lift Station 6 Identical Flygt 3127 pumps. Yes 5 Stadium Lift Station 6
New lift station completed in 2014. Two
identical low-flow pumps (Flygt 3127) and
four identical high-flow pumps (Flygt 3153).

Yes
6 Rabello Pump Station 8 Identical Flygt 3202 pumps. Four new pumps installed in 2013 and in 2014. Yes
7 Northside Pump Station 4 Four identical Flygt 3356 pumps. Yes 0 0.5
1 Mile µ Legend
Modeled Trun k Sew ers
≤ 6"
8" - 10"
12" - 16"
18" - 24"
≥ 27"
ÉP Modeled Pum p/Lift Station
Un m odeled Sew ers
San Jose In terceptors
City Lim it
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San itary Sew er
Master Plan Update
Figure 3-1
Modeled Trunk System
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 3
Hydraulic Model Development
April 2016 3-4
Flows are loaded into the model at “loading manholes,” each representing the point where flows from adjacent parcels or parcels connected to unmodeled sewers discharge to the modeled network. The parcels connected to unmodeled sewers were grouped into sewer subcatchments based on the modeled manhole to which the unmodeled sewers drain. Each subcatchment was associated with a unique load manhole in the model network. Approximately 860 sewer subcatchments and associated loading manholes were delineated for defining the model loads. The subcatchments and load manholes are shown in Figure 3-2.

3.3 Model Network Construction and Validation
Data of the expanded network were compiled from available as-built drawings, field measurements, and Excel files from previous modeling efforts. The network was also validated using the following steps:
 The entire modeled network (both the original network and the expanded portion) was checked for connectivity, i.e., verifying that correct upstream/downstream manholes were identified for each pipe and there were no missing links in the network.
 Profiles were plotted for each series of pipe segments to visually check for missing or suspect data, such as missing rim or invert elevations, negative pipe slopes, or abrupt steps up or down in pipe inverts.

Where appropriate, data were interpolated or verified through field investigation or as-built drawings.  As-built drawings and field data were used to develop details for the modeled pump stations, such as wet well elevations and dimensions, number of pumps, pump types, on/off levels, and discharge curves.  Flow splits (manholes with more than one outlet pipe) were identified, and field verification and/or asbuilt drawings were requested as needed for further verification of outlet pipe elevations and/or the existence of weirs or other flow diversion structures.

3.4 Flow Monitoring Program
Flow monitoring was conducted between November 2014 and March 2015 to measure actual flows in the system for analysis and calibration purposes. The monitoring was conducted by V&A Consulting Engineers (V&A) as subcontractor to RMC. The flow monitoring program originally consisted of 23 flow meters and four rain gauges. Most of the meters were installed and operational from December 10, 2014 to March 4, 2015 (approximately 12 weeks). Four of the meters, Meters 1 through 4, were installed earlier on November 22, 2014 to collect data during scheduled game events at the new Levi’s Stadium.

Factors that were considered in selecting the flow meter sites included:
 Location of sites used in 2006 flow monitoring program for the City’s previous sewer system capacity assessment study
 Similar sized tributary areas
 Ability to isolate areas to characterize flows for model calibration  Provides more specific information about flow splits
 Preferred hydraulic conditions (i.e., manholes on a straight line preferred over manholes on bends or with multiple incoming pipes)
 Ease of access and safety considerations
In addition to the 23 sites, the City also owns and maintains two permanent flow meters at the Guadalupe Chart Station just upstream of the connection with the City of San Jose’s Interceptors. Upon review of the data collected at these two meters, it was determined that a field calibration was necessary. V&A performed field calibration, and also installed two temporary flow meters at the same site to verify and ensure data quality of the two permanent meters.

The flow monitoring sites are listed in Table 3-3 and shown on Figure 3-3. A flow meter schematic is shown on Figure 3-4. Four rain gauges were installed to collect representative rainfall data over the service area during the monitoring period. The rain gauge locations are also shown on Figure 3-3.

City of Santa Clara
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Chapter 3
Hydraulic Model Development
April 2016 3-5
Table 3-3: Summary of Flow Monitoring Sites
Meter
ID Location Manhole ID
Pipe Size
(in)
Avg.

Flow (1)
(mgd)
Peak
Flow (2)
(mgd)
1 (3) Lafayette St. north of Calle de Mundo S104-28 36 3.91 7.95 2 (3) Golf course private road west of Lafayette St. S104-26 33 3.97 8.36 3 (3) Lafayette St. north of Calle de Mundo S104-30 42 3.05 9.24 4 (3, 4) Parking lot of the new Levis Stadium S94-35 24 0.22 0.94 5 Mission College Blvd. north of Our Lady’s Wy. S83-21 33 3.97 10.3 6 Mission College Blvd. north of Our Lady’s Wy. S83-22 30 2.60 6.37 7 Upstream of Primavera Lift Station. S105-34 24 0.89 1.81 8 Lafayette St. north of Montague Expwy. S86-12 30 1.79 4.80 9 Calabazas Creek south of Kifer Rd. S62-40 24 1.98 6.34 10 San Juan Ave. and Monroe St. S52-79 24 0.80 2.80
11 Chromite Dr. and Pilot Knob Dr. S53-40 24 1.06 4.76
12 Chromite Dr. and Alhambra S53-23 24 1.19 4.74
13 Bowers Ave. just north of Bonnie Dr. S53-54 30 3.50 7.22 14 South Dr. south of Loma Vista Ln. S54-16 15 0.53 1.12 15 Nvidia Parking lot, west off of Scott Blvd. south of Central Expwy. S65-50 18 0.45 1.44
16 Central Expwy west of UPRR S67-13 27 1.43 2.70
17 De La Cruz Blvd. north of Martin Ave. S58-9 24 0.40 1.48 18 De La Cruz Blvd. north of Martin Ave. S58-8 24 1.14
19 North of intersection of Wren Ave. at Kent Avenue S21-18 24 1.63 3.13 20 Homestead Rd. west of Cherry Orchard Place S21-47 18 1.74 4.00 21 Kiely Blvd. south of Kaiser Dr. S23-6 24 2.25 3.68
22 Los Padres Blvd. at Bray Ave. S45-80 18 0.76 4.60
23 Brokaw Rd. north-east of UPRR S48-31 18 0.58 1.81
M1 (5) Guadalupe Chart Station East Line N/A 33 (6) 3.89 5.80 M2 (5) Guadalupe Chart Station West Line N/A 33 1.07 2.64

1. Average flow during non-rainfall period in mid- to late January.

2. Peak 15-minute flow during flow monitoring period (during December 11-12, 2014 storm event for most meters)

3. Meters 1 through 4 were installed on November 22, 2014. All other meters were installed on or around December 10, 2014.

All meters were removed on or around March 4, 2015.

4. Average flow represents a typical non-game day flow; peak flow represents a game day flow.

5. Meters M1 and M2 were installed starting January 9, 2015 in addition to the two permanent meters at the Guadalupe Chart Station.

6. Field measurements and observation show this line to be a 36-inch pre-fabricated T-lock lined pipe, while design drawings show its diameter to be 33 inches. A research was done to verify the pipe diameter but did not reach a conclusive result. As such, this pipe remains a 33-inch in the model.
0 0.5
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Legend !( Loading Manholes
µ
ÉP Modeled Pump/Lift Station
Modeled Trunk Sewers
Unmodeled Sewer
San Jose Interceptors
Subcatchment
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Sanitary Sewer
Master Plan Update
Figure 3-2
Subcatchments and
Loading Manholes
0 0.5
1 Mile
Legend !( Flow Monitoring Site & ID
µ
Õ Rain Gauge Site and ID ÉP Modeled Pump/Lift Station
Modeled Trunk Sewers
Unmodeled Sewer
San Jose Interceptors
City Limit
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Sanitary Sewer
Master Plan Update
Figure 3-3: Flow Meter
and Rain Gauge Locations
20-26
21-49
10-29 11-41
15”@
126.8’
15”@
127.4
Gate 1
Gate 2
103-22 103-23
93-53
83-17
104-21
33”@-8.14
33”@-7.89
104-22
Calle PS
Westside PS
93-36
Tasman PS
33”@-2.61
93-52
33”@2.32
83-18
33”@6.89
73-7
21”@

19.76 18”@

19.98 73-30
63-20
53-34
62-6
62-8
62-10
53-105
10”
@40.9
62-5
15”@27.37
12”@31.06 21”@27.76
15”@31.01
61-17
61-16
73-29
8”@40.77+6”@43.47
52-4
32-102
ECR siphon
10”@76.16
32-101
15”@75.23 32-8
32-45
15”@75.45 33-33 33-34
15”@83.23
15”@82.83
12”@91.73
15”@91.53
32-68
15”@75.45
12”@113.06 22-55
21”@
100.23
10”@100.23
22-64
22-52
23-14
33-63
10”@131.94
23-27 24-32
10”@131.89
15”@
109.91 12”@

94.62 18”@

90.32 23-24
33-5
15-13
25-85
34-6
104-35
104-37
64-34
57-54
58-12
65-30
58-21
58-11
58-22
57-37
58-23
48-2
47-54
35-2
47-58
Trimble to
San Jose Interceptor
36-83
47-59
47-77
48-3
48-11
12”@

65.32 38-5
38-4
24”@

32.8 15”@

56.37 12”@

58.15 15”@

57.55 12”@

63.77 24”@35.52
48-48
24”@

28.91 57-57
38-14
37-48
12”@

58.89 15”@30.51
48-38
47-30
18”@37.07
58-3
68-23
18”@33.15
18”@33 18”@32.9
30”@

25.75 18”@26.75
68-20
33-4
27”@65.78
12”@72.03
64-41
25-9
64-46
64-44
64-45
105-37
104-33
105-35
105-6
21”@-11.15
21”@-11.15
105-7
105-36
18”@-2.7 15”@-2.71
104-49
104-31
105-27
24”@-9.19
12”@-9.04
22 6
4 3
2 Figure 8: City of Santa Clara Trunk Sewer System Schematic Last Updated: April 4, 2016
De La Cruz PS
1 # 2015 Flow Monitoring Sites
City’s Permanent Meters
Pump Station
Flow Split Manhole
Junction Manhole
Rabello PS
104-19
Northside PS
Santa Clara
Influent Structure 1
(San Jose)
52-65
10 41-104 10”@83.48
10”@

84.16 42-104 10”@78.98
10”@78.98
20-9
5 9
11 12 13
17 18
23 12”@

71.33 12”@

71.48 15
15”@
129.78
27”@
129.28
20-16
19 20
14 Walsh Line
M
M2
M1
97-10
Flow Diversion Structure (e.g., weir)
Stadium PS
86-20
New MH
16 21
8 7
Flow Direction
High‐Level Overflow
63-33
54-101
54-100
15”@

36.45 12”@

36.45 64-32
41-125
41-113 41-121
41-123
42-125
12”@

39.6 27”@

37.82 M
Santa Clara
Junction Structure
M
42”
42”
36”
42”
Control
Chamber
48”
36”
36”
48” FM
D
C
B
A
E
SJ Interceptors
M
24-62
13-38
13-27
13-55
12-50
23-51
23-28
26-44
35-42
26-70
35-20
35-37
35-25
35-17 35-87
36-1
47-60
47-32
47-55
City of Santa Clara
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Hydraulic Model Development
April 2016 3-9
During the flow monitoring period, all of the monitoring sites and the two permanent meter sites at the Guadalupe Chart Station were visited approximately biweekly to check meter operation and site conditions, obtain field calibration measurements, and download collected data. Field calibration involves taking manual depth measurements and flow velocity measurements using a portable velocity meter. These calibration measurements were compared to and used to adjust monitor-recorded depth and velocity if needed. Calibration measurements were taken at different times of day in order to obtain calibration points for the full range of typical diurnal flows.

Approximately four storm events occurred during the flow monitoring period. The biggest event occurred on December 11, 2014, in which over 3 inches of rainfall were recorded within a 24-hour period, with a peak hour rainfall of 0.38 inch between 9 a.m. and 10 a.m. This is the event used for wet weather flow calibration, discussed further in Chapter 3.

Plots of the flow monitoring data and a tabular summary of daily average, minimum, and maximum flows for each meter are included in Appendix A.

3.5 Model Calibration
Model calibration is the process of comparing model-computed flows to observed (monitored) flows to verify that the model is accurately simulating flows in the sewer system. As described above, temporary flow monitoring programs consisting of 25 flow meters installed in the Santa Clara system during the 2014/15 winter season as part of the study. The data collected during this flow monitoring program were used for model calibration.

3.5.1 Dry Weather Calibration
The 14-day non-rainfall period from January 17 to January 30, 2015 was used for dry weather calibration.

The dry weather calibration process was used to verify BWF loads and diurnal curves, and to quantify GWI (as indicated by monitored flows that were higher than estimated BWF). Table 3-4 compares the model vs. metered average dry weather flow (ADWF) at each of the meter locations. Figure 3-5 shows an example plot of model vs. metered flow for one of the flow monitoring locations in the system (Meter 5). Dry weather calibration graphs for all meters are included in Appendix B.

Overall, the model calibration resulted in a reasonably good match at most locations, but there were differences at some locations. These differences may be due to inaccuracies in the meter data, water use loadings, or configuration of the system (e.g., upstream flow splits, weir settings, etc.). Extensive effort was made to resolve as many of the calibration differences as possible. As shown in Table 3-4, the sum of the observed flows at the most downstream meters (Meters 1, 2, 3, M1 and M2) was within 6 percent of the modeled flows, which provides confidence that the overall flows in the model are reasonably accurate.

Note that the total model ADWF is higher than the estimated existing BWF shown in Table 2-2 because the model ADWF also accounts for the CuSD flow (observed flow data was used, which was approximately

3.57 mgd for the calibration period) and about 0.35 mgd of GWI that was added to the system during the calibration process, which was applied to the basins tributary to meters 10 and 11, at an estimated rate of 1,000 gpd/acre. As described in Chapter 2, GWI is calculated based on the difference between average flow on non-rainfall days during the flow monitoring period and estimated BWF for meters for which estimated BWF is noticeable lower than monitored flow. Other meter areas may also include some nominal dry weather GWI, which is assumed to be included in the BWF estimates.

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Table 3-4: Dry Weather Flow Calibration Results
Meter ID Meter
Avg. Flow (mgd)
Model
Avg. Flow (mgd)
Difference
(mgd)
Percent
Difference
1 3.91 3.42 -0.49 -12%
2 3.97 3.71 -0.26 -7%
3 3.05 3.27 0.21 7%
4 (1) 0.22 0.22 0.00 0%
5 3.97 3.99 0.02 0%
6 2.60 2.54 -0.06 -2%
7 0.89 0.74 -0.16 -17%
8 1.79 1.70 -0.09 -5%
9 1.98 2.25 0.27 13%
10 0.80 0.80 0.00 0%
11 1.06 1.10 0.04 4%
12 1.19 1.14 -0.05 -4%
13 3.50 3.59 0.09 3%
14 0.53 0.51 -0.02 -4%
15 (2) 0.45 0.81 0.36 79%
16 (2) 1.43 1.06 -0.37 -26%
15 & 16 (2) 1.88 1.87 -0.01 -1%
17 0.40 0.54 0.14 34%
18 1.14 0.99 -0.15 -13%
19 1.63 1.56 -0.07 -4%
20 1.74 1.51 -0.23 -13%
21 2.25 2.09 -0.15 -7%
22 0.76 0.91 0.14 19%
23 (3) 0.58 0.69 0.11 18%
M1 (Guadalupe East) 3.89 3.41 -0.48 -12%
M2 (Guadalupe West) 1.07 1.16 0.09 8%
Sum of D/S Meters (4) 15.90 14.97 -0.92 -6%

1. Meter 4 was installed immediately downstream of the Levi’s stadium with the intention to collect data to study flow patterns during major game events. The meter did capture good flow data for a number of game events, but also encountered a technical issue in late January that caused data collected between January 20 and February 18 (overlapping with the calibration period) to be unrecoverable. As such, data collected between January 11 and January 18 (a 7-day non-rainfall period when the venue was not used for any games) was used to establish the baseline flow for the stadium.

2. Meters 15 and 16 had an unexpected shift in flow distribution between late December 2014 and early January 2015, possibly caused by a temporary blockage upstream of the two meters. City staff was informed of this shift but could not provide an explanation. Although the meter flows did return to a higher level in late January 2015, they never returned to the pre-shift level. As such, their data was deemed not suitable to be used for calibration for each meter basin individually; instead, their tributary subcatchments were calibrated together as one basin using the combined data of the two meters.

3. Meter 23 was located downstream of the Santa Clara University. The dry weather calibration period coincided with the registration week of the school’s winter quarter when student population was not at its maximum. The observed flow for this meter was therefore noticeably lower than the modeled flow (which was developed based normal school period).

4. Downstream (D/S) Meters are meters 1, 2, 3, M1, and M2. See system schematic in Figure 3-4.

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Figure 3-5: Example Dry Weather Calibration Graphs

3.5.2 Wet Weather Calibration
The storm that occurred on December 11, 2014 was used for wet weather calibration. As described previously, RDI/I response to rainfall events was quantified in terms of three sets of triangular unit hydrograph parameters that represent the volume percentage of rainfall that enters the system as RDI/I and the shape of the RDI/I hydrograph as a function of each hour of rainfall. Through the wet weather calibration process, RDI/I hydrograph parameters were developed for each meter area. In general, the response to rainfall in the Santa Clara system is relatively small, as evidenced by the relatively low peak flow response to the rainfall event, with the exception of areas in the western portion of the City near Monroe Street, which showed both a high peak inflow during the rainfall event and an extended period of infiltration after the event.

Table 3-5 lists the “R values” (as percentages of rainfall) for each flow meter area. Figure 3-6 shows an example plot of model vs. metered flow for one of the flow monitoring locations in the system (Meter 5).

A complete set of wet weather calibration graphs of modeled vs. metered flow for all meter locations are included in Appendix C.

Obs.
...n Runs>DWF_1/17/2015+14D (w/GWI)>DWF
Flow (MGD)
Min

1.390

1.380
Max

6.323

6.119
Volume (US Mgal)

55.644

55.886
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Table 3-5: Wet Weather Flow Calibration Results
Meter ID R1 RDI/I Vol. (%) R2 RDI/I Vol. (%) R3 RDI/I Vol. (%) Total R (%) 1 0.3% 0.3% 0.8% 1.4%
2 0.1% 0.5% 0.8% 1.4%
3 0.1% 0.1% 0.1% 0.3%
4 1.0% 0.1% 0.1% 1.2%
5 0.1% 1.0% 1.5% 2.6%
6 0.1% 0.5% 1.5% 2.1%
7 0.2% 0.5% 0.8% 1.5%
8 0.3% 0.5% 1.2% 2.0%
9 0.5% 3.5% 8.0% 12.0%
10 1.0% 4.2% 8.0% 13.2%
11 0.1% 2.0% 15.0% 17.1%
12 0.2% 1.0% 20.0% 21.2%
13 0.1% 0.1% 0.8% 1.0%
14 0.4% 0.1% 0.5% 1.0%
15 & 16 (1) 0.1% 0.1% 0.3% 0.5%
17 0.5% 0.5% 0.5% 1.5%
18 0.5% 0.8% 1.0% 2.3%
19 0.3% 0.4% 0.5% 1.2%
20 0.1% 0.1% 0.1% 0.3%
21 0.2% 0.1% 0.1% 0.4%
22 0.1% 0.2% 0.1% 0.4%
23 0.5% 0.2% 0.1% 0.8%
CuSD 0.25% 0.35% 0.5% 1.1%

1. Meters 15 and 16 were calibrated together due to unexpected field conditions. See note 2 under Table 3-4.

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Figure 3-6: Example Wet Weather Calibration Graphs for 2014 Storm Period Rain
Obs.
...Rainfall Event (11/18-3/05)
Rainfall
Depth (in)

4.990
Peak (in/hr)

1.280
Average (in/hr)

0.019
Flow (MGD)
Min

1.319

1.515
Max

10.323

9.470
Volume (US Mgal)

53.945

52.096
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 4
Capacity Analysis
April 2016 4-1
Chapter 4 Capacity Analysis
This chapter describes the hydraulic analysis and design criteria used to evaluate system performance and size capacity relief projects, the capacity deficiencies based on the results of model runs, and preliminary solutions to identified capacity deficiencies. The chapter also summarizes the pump station capacity evaluation and analysis.

4.1 Design Event Criteria
Peak design flows for sewer systems consist of dry weather base wastewater flow (BWF), groundwater infiltration (GWI), and rainfall-dependent infiltration/inflow (RDI/I). Criteria for computing existing BWF, GWI, and RDI/I (developed as part of model calibration), and unit flow assumptions for future development were discussed in the previous chapters. However, the peak design flow criteria must also specify the set of conditions (e.g., design storm rainfall and timing with respect to seasonal GWI and diurnal BWF) that will generate the highest peak flows that the sewer system must be capable of hydraulically conveying.

The following subsections discuss design storm criteria, present data from recent storm events, and identify options and recommendations for selection of a design event for use in this Master Plan Update.

4.1.1 Design Storm Condition
The use of wet weather design events as the basis for sewer capacity evaluation is a well-accepted practice.

The approach is to first calibrate a hydraulic model of the system to match wet weather flows from observed storms, and then apply the calibrated model to a design rainfall event to identify capacity deficiencies and size improvement projects. The design event may be synthesized from rainfall statistics, or may be an actual historical rainfall event of appropriate duration and intensity.

A design storm is used to simulate a peak wet weather flow condition to identify system deficiencies and develop solutions for them. Design storms are typically classified by their return period and duration. The return period defines the probability that the design rainfall will be exceeded in any given year. For example, a storm with a 10-year return period means there is a 1 in 10 chance, or 10 percent probability, of exceeding the design rainfall in a given year. The chosen return period reflects the degree of risk an agency will tolerate of experiencing sanitary sewer overflows (SSOs) due to future storm events. However, choosing a design storm with a very high return period (reflecting a very low risk tolerance) could lead to the identification of so many system capacity deficiencies that the cost of improvements is prohibitive. Additionally, sizing a system for a very rare event could mean that the system does not function well under typical conditions during much lower flows (due to slow velocities in oversized pipes, or oversized pump stations).

A storm duration must be specified along with the return period. Most Bay Area agencies use a 24-hour storm, though shorter or longer durations may sometimes be appropriate depending on system size and how quickly or slowly the system responds to rainfall. Design storm may be actual historical rainfall events or synthetic events that are designed to represent a certain return period for a specified storm duration or durations.

The City’s 2007 Capacity Assessment used a 10-year, 24-hour storm, with one-hour and six-hour 10-year events included within the 24-hour event. This storm was based on the Santa Clara County intensityduration-frequency (IDF) curve that was current at the time, representing rainfall statistics at the San Jose International Airport. To reflect differences in rainfall characteristics across the service area, the storm was scaled for different areas based on the isohyetal map of average annual rainfall from the Consoer, Townsend & Associates Sanitary Sewer I/I Analysis, dated 1974.

Since the completion of the Capacity Assessment, Santa Clara County released a new County Drainage Manual in October 2007. The Manual includes updated mean annual precipitation isohyetal lines from Santa Clara Valley Water District (SCVWD) and updated, distinct IDF curves for each mean annual City of Santa Clara
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April 2016 4-2
precipitation area. In addition to the IDF curves, Appendix D of the 2007 manual includes a 24-hr design storm pattern. According to the manual, this storm pattern is based on an actual event that occurred in December 1955, but with some adjustments to better reflect IDF statistics for various storm durations. Like the previous design storm, the design storm used for this Master Plan Update is also a 10-year, 24-hour storm that varies across the service area, but the storm pattern and hourly rainfall intensities are based on this updated Santa Clara County Drainage Manual. Figure 4-1 shows the design storm hourly rainfall as it occurs in the vicinity of the San Jose International Airport. At this location, the total rainfall for the 1, 6-, and 24-hour durations is 0.65, 1.49, and 2.92 inches, respectively.

Figure 4-1: Design Storm Pattern for the San Jose International Airport MAP Area The design storm represents the “point precipitation” at any single location in the system. The storm is applied in the model at the subcatchment level, with the assumption that the rainfall occurs simultaneously on all subcatchments, which is a conservative assumption.

As noted previously, the timing of the design storm also affects the resulting peak wastewater flows. If the design storm is timed to cause peak RDI/I at the same time as peak base wastewater flow, the total peak wet weather flow will be higher than if the design storm occurs during minimum or average base wastewater flow. Due to variations in the diurnal flow patterns as well as variations in the calibrated I/I response throughout the system, it is not possible to time the rainfall to create a peak-on-peak response everywhere in the system. However, the design storm was timed to achieve a peak-on-peak response in most areas of the system, with the peak hour rainfall occurring at 8:00 a.m. on a weekday.

4.2 Hydraulic Capacity Criteria
The hydraulic capacity criteria determine which sewer pipes should be relieved or replaced due to inadequate capacity to convey existing or future peak flows, and how large the new sewers should be. The criteria adopted by the City should ideally be stringent enough to ensure that sewer overflows caused by capacity limitations (as distinguished from other causes such as obstructions or structural failures) are very rare occurrences, but not so conservative that they cause the City to spend capital improvement funds unnecessarily or result in pipes that are so large that cleaning velocities cannot be achieved under normal flow conditions, causing solids build up and related problems.

The capacity deficiency criteria identify the need to replace an existing facility, while design criteria determine the sizing of new facilities. These criteria are discussed in the paragraphs below. 0 0.1

0.2 0.3

0.4 0.5

0.6 0.7
0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 Rainfall Intensity (in/hr)
Hour
City of Santa Clara
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Capacity Analysis
April 2016 4-3

4.2.1 Capacity Deficiency Criteria
The capacity deficiency criteria are used to determine when the capacity of an existing sewer facility is exceeded to the extent that a relief sewer or larger replacement sewer or potential pump station capacity upgrade is required. Capacity deficiency criteria are sometimes called “trigger” criteria in that they trigger the need for a capacity relief project. These criteria often differ from criteria that are applied to determine the size of a new facility, which are typically more conservative.

It is important that the capacity deficiency criteria be coordinated with the peak design flow criteria. For example, if the peak design flow were to be based on only peak dry weather flow (PDWF), the deficiency criteria would need to be conservative (e.g., require pipes to flow less than full to allow capacity for I/I).

On the other hand, if the peak design flow includes I/I from an infrequent storm event, it may be appropriate to allow the sewers to flow surcharged to some extent, since the peak flows will be infrequent and brief in duration.

Gravity Sewers
Since the peak wet weather design flow as recommended in the previous section of this chapter includes RDI/I from a 10-year return period event and is assumed to be concurrent with peak BWF, the City should consider it acceptable to allow gravity sewers to flow surcharged to some extent before a capacity relief project is triggered. For example, significant surcharging may be acceptable in larger, deeper sewers provided the hydraulic gradeline remains a reasonable distance below the ground surface and no surcharging occurs during dry weather flow conditions. For smaller or shallow sewers, a more conservative criteria could be considered to account for the chance that capacity could also be compromised by factors such as offset joints, roots, grease, and debris (which cannot be accounted for in the hydraulic model), or that surcharge could result in flow backing up into connecting laterals.

Based on discussion of these considerations, the following criteria are proposed under which gravity sewers would be considered capacity deficient:
 PDWF: No surcharge allowed (d/D ≤ 1.0)
 PWWF:
o Gravity sewer with less than 6 feet of cover: no surcharge allowed (i.e., d/D ≤ 1.0) o Gravity sewer with 6 feet or more of cover: surcharge of up to 1 foot under PWWF (see Figure 4-2 for clarification)
 Case-by-case exceptions could be made for isolated short pipe reaches. Conversely, more stringent criteria could be applied for sewers located in areas where the consequences of an overflow would be greater (e.g., adjacent to creeks, schools, or hospitals).  Note that for evaluating the performance of existing sewers, a Manning’s “n” value of 0.013 is assumed for all pipes, regardless of material or age. Although new pipes, particularly plastic materials, would provide a lower initial roughness factor, it is assumed that over time, a “slime layer” formation on the walls of the pipes and/or other obstructions in the sewer, such as roots, debris, or structural defects, may increase pipe roughness. Therefore, an assumption of 0.013 for all pipes is considered to be appropriately conservative for master planning purposes.

Pump Stations and Force Mains
For master planning capacity assessments, the performance of pump stations and force mains are typically evaluated based on pumping capacity and peak force main velocities. Pump stations are considered to be capacity deficient if the station’s firm capacity (capacity with largest pumping unit out of service) is insufficient to convey the peak design flow. Force mains are considered to be deficient if velocity under peak design flow exceeds 10 feet per second (fps).

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Figure 4-2: PWWF Hydraulic Deficiency Criteria for Gravity Sewers Scenario A:

Shallow Pipe (cover less than 6 feet)
Criteria: d/D ≤ 1.0
Scenario B:

Deep Pipe (cover of or more than 6 feet)
Criteria: Surcharge ≤ 1.0 foot

4.2.2 Sizing Criteria for New Sewer Facilities
The following criteria are proposed for sizing new trunk gravity sewers as part of the Master Plan. They are consistent with the City’s current sanitary sewer design criteria. Note that the City may use somewhat different criteria for new developments or actual design, e.g., varying Manning’s n for different pipe materials, or a more conservative d/D for smaller diameter sewer mains. These criteria would be based on the modeled design storm peak wet weather flows in the system.  Maximum allowable flow depth-to-diameter ratio (d/D) of 0.75 under peak design flow  A Manning’s ‘n’ of 0.013
 Minimum pipe size of 8 inches diameter in residential areas; 10 inches in commercial areas; and 12 inches in industrial areas
 Minimum velocity of 2 feet per second (fps) at half-full pipe  Maximum velocity of 10 fps at peak design flow
 Downstream pipes at least as large as upstream pipes
 Minimum and maximum pipe slopes determined based on above velocity criteria to the extent feasible (it is recognized that elevation constraints in the existing system may prevent achieving desired minimum slopes for some projects, and terrain may dictate higher maximum slopes in some cases)
 Minimum pipe cover of 6 feet
Gravity Sewer

D
d

Cover (<6’)
Freeboard (≥5’)
Cover (≥6’)
Surcharge (≤1’)
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Capacity Analysis
April 2016 4-5

4.3 Capacity Analysis Results and Proposed Solutions
Based on the criteria described above, the hydraulic model was run for four sets of conditions representing combinations of existing or future development and dry weather flow or design storm wet weather flow.

Figure 4-3 shows the model results for future PWWF conditions. Pipes shown in red are predicted to be surcharged due to “throttle” (peak flow exceeding full pipe capacity), and pipes shown in blue are surcharged due to backwater from a downstream throttle condition. Locations of capacity criteria violations (surcharge of more than 1 foot due to either throttle or backwater conditions) are highlighted in yellow (pipes with criteria violations under both existing and future conditions) or orange (future conditions only).

Note that the locations of criteria violations (i.e., higher than allowable surcharge) are not necessarily the locations of the actual capacity-deficient pipes, but are typically located further upstream due to backwater from downstream throttle conditions. Appendix D includes model hydraulic profiles for each of these areas.

Potential solutions for the identified capacity deficiencies were developed in order to assess the potential extent of required capacity improvements and to estimate the resulting peak flow to the SJ/SC RWF once capacity deficiencies are relieved. Table 4-1 summarizes the predicted flow under each condition. Table 4-2 describes the solutions. The solutions model results indicate that the combined total estimated design storm future PWWF from the City’s system (including flows from CuSD) would be approximately 59 mgd.

Table 4-1: Summary of Capacity Analysis Results
Existing
ADWF (2)
(mgd)
Existing
PDWF (2)
(mgd)
Existing
PWWF (3)
(mgd)
Future
ADWF (2)
(mgd)
Future
PDWF (2)
(mgd)
Future
PWWF (3,4)
(mgd)
Flow Estimates by System Outfall (1)
North (to Northside and Rabello
Pump Stations) 10.2 15.2/16.0 27.9 24.6 33.5/34.4 41.0
East (to San Jose Zanker Road
Interceptor) 4.7 6.4 11.7 9.8 13.3 18.3
Total 14.9 21.6/22.4 39.6 34.4 46.8/47.7 59.4
Flow Estimates by Agency (1)
Santa Clara System 11.3 15.4/16.2 26.8 27.5 34.6/35.5 45.6 Cupertino Sanitary District 3.5 6.2 12.8 6.9 12.2 13.8
Total 14.9 21.6/22.4 39.6 34.4 46.8/47.7 59.4

1. Assuming that trunk sewer capacity deficiencies are relieved with recommended capital improvement projects presented in Table ES-2.

2. Includes groundwater infiltration for a typical wintertime period. ADWF and first value shown for PDWF includes typical nongame day flow from Levi’s Stadium; second value shown for PDWF includes a peak game day flow from Levi’s Stadium.

3. For 10-year design storm; assumes non-game day flow from Levi’s Stadium.

4. Assuming peak wet weather flow from CuSD would not increase above its contractual maximum flow of 13.8 mgd.

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Table 4-2: Capacity Deficiencies and Proposed Solutions Def.

ID
Deficiency
Location (1)
Trigger
Scenario Surcharge or Criteria Violation (2) Proposed Solution 1 Westside Lift Station 2015 PDWF
Current set point of the lead pump is about 5 feet above the invert of the influent line, causing backup issues upstream between MH S102-3 and S103-8 (station wet well).

Adjust the set point of the lead pump to be equal or lower than the invert of the influent gravity line. 2 Tasman Lift Station 2015 PDWF
Current set point of the lead pump is about 2 feet above the invert of the influent line, causing backup issues upstream between MH S93-24 and S93-35 (station wet well).

Adjust the set point of the lead pump to be equal or lower than the invert of the influent gravity line. 3 Cabrillo Avenue 2015 PWWF
Surcharge of up to 5 feet from MH S41-13 to S41-20 under existing PWWF scenario and potential overflow in S41-13, S41-14 and S41-15 under future PWWF scenarios.

Conduct smoke testing and television inspection in the flow tributary area to identify and address high inflow/infiltration sources. If field investigations indicate that I/I reduction is not feasible or cost-effective, then upsize the existing 8-inch line to a 12-inch between S41-13 and S41-20. 4 Tasman Drive and Old Ironsides Drive 2035 PWWF Surcharge of up to 3 feet upstream of Tasman Lift Station. Upsize 800 feet of existing 12-inch line between S93-24 and S93-35 to a 15-inch line. 5 Scott Blvd. 2035 PWWF Surcharge of up to 1 foot between S25-78 and S26- 44, and S26-57 and S25-37. Install a weir in S25-85 to divert flow northwest to Los Padres Blvd. 6 Calabazas Creek Trunk Sewer 2035 PWWF Surcharge of up to 3 feet in the existing 24-inch line along Calabazas Creek between S52-52 and S62-14. Install a new 200-ft 15-inch line between S42-12 and S52- 93 (Calabazas Blvd. and Machado Ave.) to partially divert flow from the 24-inch to the 21-inch on Machado Ave. 7 Tracy Dr., Pomeroy Ave., and Homestead Rd.
2035
PWWF
Surcharge and potential overflow between S10-77 and S22-55.

Upsize the existing 10- to 12-inch line between S10-77 and S22-55 to a 15-inch line, install a new 15-inch diversion line between S22-55 and S22-46, and upsize the existing 18-inch line between S22-46 and S22-51 to a 21-inch line.

1. Refer to Figure 4-3 for deficiency locations

2. Under PWWF conditions.
0 0.5
1 Mile µ Legend
Surcharge due to Backwater
Surcharge due to Throttle
Surcharge Criteria Violation
under Existing PWWF
Surcharge Criteria Violation
under Future PWWF
Õ Deficiency ID ÉP Modeled Pump/Lift Station
Modeled Trunk Sewers
Unmodeled Sewers
San Jose Interceptors
City Limit
J:\Projects\149 SANTA CLARA\149-008 Santa Clara 2015 Sanitary Sewer MP Update\G. GIS Files\_MXDs\Master Plan Report Figures\MPFig4-3_Deficiencies_05Apr2016.mxd City of Santa Clara
Sanitary Sewer
Master Plan Update
Figure 4-3
Model Predicted
System Surcharge
D1
D1
D2
D4
D3
D7
D5
D6
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 4
Capacity Analysis
April 2016 4-8

4.3.1 Pump Station Firm Capacity Analysis
All seven lift and pump stations in the system were evaluated to determine if each station had adequate firm capacity to handle the design peak flow. Firm capacity is defined as the capacity of a station with the largest pump out of service. Table 4-3 below provides a summary of station firm capacity compared with peak inflow for future PWWF conditions.

Table 4-3: Pump Station Firm Capacity Analysis
No. Station Name No. of
Pumps
Estimated
Peak Inflow
(mgd) (1)
Estimated
Firm
Capacity
(mgd)
Firm Capacity Status(6)
1 Westside Lift Station 2 0.6 0.6 (3) Sufficient firm capacity 2 Tasman Lift Station 2 1.5 1.5 (3) Sufficient firm capacity 3 De La Cruz Lift Station 2 1.2 1.7 (3) Sufficient firm capacity 4 Primavera Lift Station 6 2.0 5.7 (3) Sufficient firm capacity 5 Stadium Lift Station 6 1.0 6.0 (4) Sufficient firm capacity 6 Rabello Pump Station 8 20 (2) 20 (5) Sufficient firm capacity 7 Northside Pump Station 4 21 (2) 21 (5) Sufficient firm capacity

1. Peak inflow refers to the maximum flows predicted by the model under future peak wet weather scenario using the solution network. The solution network eliminates flow restrictions upstream of the pump stations.

2. Peak inflow reflects the maximum flows predicted by the solution network in which CIP Project P6 (Sewer Diversion at Calabazas Boulevard and Machado Avenue) is implemented, which would divert excess flow from the 24-inch sewer line along Calabazas Boulevard into the 21-inch sewer line in Machado Ave, ultimately flowing to the City of San Jose’s interceptor in Zanker Road. This would reduce the flow conveyed north to the Rabello and Northside Pump Stations to the values shown in the table. Conversely, implementation of Project P6-Alt. would increase the peak flow to the Rabello and Northside Pump Stations by about 1 mgd to each pump station, which could require further evaluation of and potential improvements to increase pump station capacity.

3. Source: Table 1 (Pump Station Firm Capacities and Inflows) of the City of Santa Clara Sanitary Sewer Pump Station Evaluation, Schaaf & Wheeler, December 2010. The firm capacities of Primavera, Tasman, Westside, and De La Cruz lift stations were determined by performing a drawdown test.

4. Based on results from field drawdown tests conducted on September 17, 2015.

5. Source: Rabello and Northside Pump Station Capacity and Forcemain Calibration Technical Memorandum, Schaaf & Wheeler, November 13, 2015. See Appendix E.

6. The lift and pump stations have sufficient firm capacities within the accuracy of the estimated peak flows and capacities.

Although no capacity issues were identified for the pump stations, review of pump station drawings and current on/off set points for the pumps revealed that four of the stations may experience backwater issues in the influent pipes. The current set point of the lead pump at Tasman, Westside, and De La Cruz is above the crown of the influent gravity line. Under this condition, the lead pump will not turn on until the influent line is completely submerged, causing backwater issues upstream. This can be resolved by adjusting the set points to be equal or lower than the invert of the influent line. Primavera Lift Station has a similar condition with the set point of the lag pump. Table 4-4 summarizes the review findings and presents the suggested set points for each of the four stations. Set point revisions for Westside and Tasman are needed to address capacity criteria violations (Deficiencies 1 and 2 in Table 4-2). These settings should be evaluated by the City's pump operators to determine feasibility and if there are other operational issues that should be considered.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 4
Capacity Analysis
April 2016 4-9
Table 4-4: Recommended Revised Set Levels for Lift Stations Pump Station
Maximum
Starts Per Hour
Per Pump w/
Existing Set
Levels (1)
Maximum
Starts Per Hour
Per Pump w/
Recommended
Set Levels (1)
Set points
Recommended
Revised Set
Points (ft from
Wet Well Floor) (2)
Westside Lift Station
No. of Pumps: 2 7.2 3.7
Level Alarm: High | Low 8.0 | 1.2
Lead Pump on | off 6.0 | 1.7
Lag Pump on | off 7.0 | 2.2
Tasman Lift Station
No. of Pumps: 2 4.6 6.4
Level Alarm: High | Low 7.0 | 1.2
Lead Pump on | off 6.0 | 1.7
Lag Pump on | off 6.5 | 2.2
De La Cruz Lift Station
No. of Pumps: 2 4.8 6.2
Level Alarm: High | Low 6.0 | 1.2
Lead Pump on | off 5.5 | 1.7
Lag Pump on | off 6.0 | 2.2
Primavera Lift Station
No. of Pumps: 6 1.0 2.0
Level Alarm: High | Low 6.0 | 1.2
Lead Pump on | off 5.5 | 1.7
Lag Pump 1 on | off 6.0 | 2.2
Lag Pump 2 on | off 6.0 | 1.2
Lag Pump 3 on | off 5.5 | 1.7
Lag Pump 4 on | off 6.0 | 2.2
Lag Pump 5 on | off 6.0 | 1.2

1. Based on predicted future peak wet weather flow condition.

2. Recommendations provided by Schaaf & Wheeler based on pump information provided by RMC.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 5
Recommended Capacity
Improvement Program
April 2016 5-10
Chapter 5 Recommended Capacity Improvement Program
This section summarizes the capacity improvement projects recommended for the City of Santa Clara’s sanitary sewer system. Recommended improvements were developed from the results of hydraulic modeling of the trunk sewer system for predicted flow conditions, as described in Chapter 4. This section discusses the projects needed to address potential capacity deficiencies and unnecessary backups in the existing trunk sewer system including estimated capital costs and priorities for construction.

5.1 Development of Capacity Improvement Projects
Based on the proposed solutions described above, each proposed project was reviewed to identify potential design, permitting, environmental, and constructability issues. Feasible construction methods were also identified for each project, and preliminary estimates of probable construction costs were prepared.

Estimated costs for capacity improvements were based on cost data compiled by RMC from similar projects. The costs are conceptual level estimates, considered to have an estimated accuracy range of -30 to +50 percent, suitable for use for budget forecasting, capital improvement program development, and project evaluations, with the understanding that refinements to the project details and costs would be necessary as projects proceed to design and construction. All costs are presented in 2015 dollars and include a 30 percent allowance for contingencies for unknown conditions and a 25 percent allowance for engineering, administration, and legal costs.

Figure 5-1 shows the locations of the proposed improvements, and Table 5-1 presents the recommended capacity improvement projects, including brief project descriptions and estimated capital costs. Relative priorities have been assigned to the projects based on the flow scenario in which deficiency criteria are violated. Priority 1 and Priority 2 projects are required to address deficiencies that result in criteria violations under current flow conditions. Priority 3 projects are required to address deficiencies that result in criteria violations under future (2035) flow conditions.

Note that an alternative for Project P6 is also presented. While substantially more expensive than Project P6, this alternative would maintain the current system flow configuration of conveying all flows in the Calabazas Creek trunk sewer (including flows from CuSD) to the Northside and Rabello Pump Stations and avoid increasing flows in the Machado, Chromite, and Walsh Avenue trunk sewers that may be needed in the future to handle additional new development within the City. Implementation of Project P6-Alt would also increase flow to the Rabello and Northside Pump Stations by about 1 mgd to each pump station, which could require further evaluation of and potential improvements to increase pump station capacity.

The total estimated cost of the recommended capacity improvement program is approximately $1.7 million.

The total estimated cost, if the City were to implement Project P6-Alt instead of P6, would be approximately $2.8 million. More detailed project descriptions and cost estimates and maps of the recommended capacity improvement projects are included in Appendix F.

One of the projects was triggered due to the large sewer discharge assumed for parcel APN 316-17-018, which holds an entitlement agreement to discharge a potential flow of 0.95 mgd; however, it is currently discharging less than 10 percent of the entitled rate. While the City is obligated to provide capacity for entitlement holders, it is important to note that implementing this project may result in oversized sewers where the daily flow is not sufficient to provide the minimum cleaning velocity and thus creating potential debris and odor issues. This project is included in the summary table as project E1 (Tracy Drive Sewer Improvement), and is not part of the recommended Capital Improvement Program. It is recommended that the City implement project E1 as part of its Capital Improvement Program before the parcel begins to discharge its entitled flow of 0.95 mgd.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 5
Recommended Capacity Improvement Program
April 2016 5-11
Table 5-1: Recommended Capacity Improvement Projects
Project
ID Priority Project Name U/S MHID D/S MHID Description Est. Capital Improvement Cost1 P12 1 Westside Lift Station Adjustment N/A N/A Adjust the set points for the pumps to a lower elevation to eliminate unnecessary backups in the influent line. -- P22 2 Tasman Lift Station Adjustment N/A N/A Adjust the set points for the pumps to a lower elevation to eliminate unnecessary backups in the influent line. -- P3 2 Cabrillo Avenue Sewer Improvement S41-13 S41-20 Upsize 1,600 feet of 8-inch line in Cabrillo Ave. between Lawrence Expressway and Nobili Ave. to a 12-inch line. $1,097,000 P4 3 Tasman Drive Sewer Improvement S93-24 S93-35 Upsize 600 feet of 12-inch line in Tasman Dr. between Old Ironsides Dr. and Great America Pkwy. to a 15-inch line. $327,000 P5 4 Sewer Diversion at Los Prades Boulevard and Saratoga Avenue S25-85 S25-85
Install a weir in manhole S25-85 located in the intersection of Padres Blvd. and Saratoga Ave. to divert flow northwest to the existing 12-in line in Los Padres Blvd. $77,000
P6 4
Sewer Diversion at Calabazas Boulevard and Machado Avenue U/S of
S52-93 S52-120
Install a new manhole upstream of S52-93 in the intersection of Calabazas Blvd. and Machado Ave., and install a new 15-inch high-level diversion line (approximately 200 feet) to divert excess flow from the existing 24-inch line in Calabazas Blvd. to the 21-inch line in Machado Ave. The diversion line should be about 6 inches higher than the invert of the 24-inch line. $166,000
P6-Alt.3 4 Calabazas Creek Sewer Improvement S62-31 S72-20 Upsize 1,800 feet of 24-inch line next to Calabazas Creek between Kifer Rd. and Scott Blvd. to a 27-inch line. $1,334,000 Estimated Total Cost for Recommended Projects P1 to P6:

Estimated Total Cost (P1 to P5 and P6-Alt) including Project E1:
$6,321,000 $7,489,000

1. All costs are presented in 2015 dollars and include 30 percent allowance for contingencies for unknown conditions and 25 percent for engineering, administration, and legal costs. 2. These proposed projects are operational, not capital improvements. Refer to Table 4-4 for recommended set points. 3. Project P6-Alt is presented for the purpose of identifying the solution and associated cost to maintain the current system flow configuration. Project P6 is the recommended project. 4. Project E1 addresses the potential capacity deficiency when parcel APN 316-17-018 begins to discharge its entitled flow of 0.95 mgd into the City’s system. 0 0.5 1 Mile
µ Legend
Modeled Trunk Sewer
Unmodeled Sewer
Santa Clara Force Mains
San Jose Interceptors
Recommended Capital Improvement Projects
Project for Entitlement Compliance
J:\Projects\149 SANTA CLARA\149-008 Santa Clara 2015 Sanitary Sewer MP Update\G. GIS Files\_MXDs\Master Plan Report Figures\MPFig5-1_CIPs_08Apr2016.mxd City of Santa Clara
Sanitary Sewer
Master Plan Update
Figure 5-1
Capacity Improvement
Projects and Project for
Entitlement Compliance
City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 5
Recommended Capacity
Improvement Program
April 2016 5-13

5.2 Implementation Recommendations
The City should begin implementation of the Capital Improvement Program recommended in this Master Plan, starting with the highest priority projects. The following items should be considered in project scheduling and design, and in future updates of the Master Plan. ▪ The alignments and sizes of all recommended projects should be verified with detailed predesign analyses, including topographic surveys, geotechnical investigations, utility research, and constructability reviews.
▪ The estimated costs assumed open cut construction, but alternative methods such as trenchless construction or construction of parallel relief pipes could be considered during design. The decision to parallel or replace existing sewers should consider the physical condition and remaining useful life of the existing pipelines; the availability of pipeline corridors for new sewer construction; and operation and maintenance concerns.
▪ The hydraulic model has been developed to assist the City in performing capacity analyses and updating the Master Plan in the future. The model should be kept up-to-date with any changes to existing sewer connections, development plans, and sewer system facilities. ▪ The City should conduct additional flow monitoring at key locations in the sewer system, particularly the area tributary to the Chromite/Machado trunk sewers where both the 2006 and 2015 flow monitoring programs indicated high I/I. City should also conduct smoke testing and television inspection to identify potential sources of I/I. Flow levels during large storm events should be compared to the peak flows simulated by the hydraulic model to verify the modeling predictions for the 10-year design storm and confirm the need for and sizing of Project P3 (Cabrillo Avenue Sewer Improvement). ▪ The City should coordinate with the CuSD on flow and planning assumptions to ensure that adequate capacity exists in the Santa Clara system to handle future flows from the District. The City should encourage CuSD to monitor the flows at the flow meter that it operates and maintains on Homestead Road at Swallow Drive on an on-going basis and periodically confirm meter calibration to verify the wastewater flows entering the Santa Clara system.
▪ The City should consider adjusting its set points for the four lift stations identified in Table 4-4 to address upstream backwater issues and capacity criteria violations. These settings should be evaluated by the City's pump operators to determine feasibility and if there are other operational issues that should be considered. In addition, the City should continue to conduct regular maintenance as needed to maintain adequate firm pumping capacity at all pump stations, including cleaning the force mains as needed.
▪ The City should coordinate with the City of San Jose to ensure that its flow criteria and planning assumptions are consistent with those used by San Jose in its capacity master planning. ▪ Parcel APN 316-17-018 holds an entitlement agreement to discharge up to 0.95 mgd into the City’s system; however, it is currently discharging less than 10 percent of its entitled rate. While the City is obligated to provide capacity for entitlement holders, it is important to note that implementing this project may result in oversized sewers where the daily flow is not sufficient to provide the minimum cleaning velocity and thus creating potential debris and odor issues. However, the City should implement project E1 (Tracy Drive Sewer Improvement) to address the potential capacity deficiency before the parcel begins to discharge its entitled flow of 0.95 mgd.

City of Santa Clara
Sanitary Sewer Master Plan Update
Chapter 5
Recommended Capacity
Improvement Program
April 2016 5-14
This Master Plan report is intended to be a working document to be refined and updated as additional data and new planning information becomes available. The capacity assessment should be updated whenever there are major changes in planning assumptions or, at a minimum, every ten years.

Sanitary Sewer
Master Plan
Update
Draft Report
0012307.00
City of Santa Clara
December 2024
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51 East Campbell Avenue | Suite 128
Campbell, California 95008
800.426.4262
City of Santa Clara (0012307.00) TOC-1 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

TABLE OF CONTENTS
SECTION PAGE NO.

EXECUTIVE SUMMARY...........................................................................................................................ES-1

1. INTRODUCTION..............................................................................................................................1-1

1.1 Background and Study Objectives ...........................................................................................................1-1

1.2 Sanitary Sewer System and Service Area...............................................................................................1-1

1.3 Report Organization ......................................................................................................................................1-4

2. WASTEWATER FLOW ASSUMPTIONS...........................................................................................2-1

2.1 Flow Monitoring Program ...........................................................................................................................2-1

2.1.1 Flow Monitoring and Rain Gauge Sites .....................................................................................2-1

2.1.2 Flow Monitoring Data.......................................................................................................................2-6

2.1.3 Additional Monitoring for Dry Weather Flow Verification .................................................2-7

2.2 Basis of Hydraulic Model’s Wastewater Flow Estimates ..................................................................2-7

2.2.1 Wastewater Flow Components .....................................................................................................2-7

2.2.2 Base Wastewater Flow Estimates..................................................................................................2-8

2.2.2.1 Existing BWF Loads ............................................................................................................2-9

2.2.2.2 Future BWF Loads............................................................................................................ 2-12

2.2.3 Groundwater Infiltration ............................................................................................................... 2-15

2.3 Rainfall-Dependent I/I................................................................................................................................ 2-16

3. HYDRAULIC MODEL DEVELOPMENT AND VALIDATION ............................................................3-1

3.1 Hydraulic Modeling Software and Modeling Terminology............................................................3-1

3.2 Hydraulic Model Network Development...............................................................................................3-2

3.2.1 Modeled System .................................................................................................................................3-2

3.2.2 Model Network Construction and Validation .........................................................................3-3

3.2.3 Subcatchments ....................................................................................................................................3-4

3.2.4 Special Structures and Flow Splits ...............................................................................................3-5

3.2.5 Pump Stations ......................................................................................................................................3-5

3.2.5.1 Siphons ...................................................................................................................................3-6

3.2.5.2 Flow Splits..............................................................................................................................3-7

3.3 Model Calibration Process and Results ..................................................................................................3-7

3.4 Dry Weather Flow Calibration....................................................................................................................3-7

3.4.1 Dry Weather Flow Calibration Methodology...........................................................................3-8

3.4.1.1 Review of Largest Water Users ......................................................................................3-8

3.4.1.2 Diurnal Pattern Development and Refinement.................................................... 3-12

3.4.2 Base Flow Adjustments and Addition of GWI ...................................................................... 3-13

3.4.3 Dry Weather Flow Calibration Results ..................................................................................... 3-14

3.4.3.1 Differences Between 2022-2023 & 2014-2015 Flow Monitoring Data ...... 3-19

3.5 Wet Weather Flow Calibration................................................................................................................ 3-21

3.5.1 Wet Weather Flow Calibration Methodology ...................................................................... 3-21

3.5.2 Wet Weather Flow Calibration Results.................................................................................... 3-21

3.5.2.1 RDI/I Response.................................................................................................................. 3-26

4. SYSTEM CAPACITY ANALYSIS .......................................................................................................4-1 City of Santa Clara (0012307.00) TOC-2 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

4.1 Hydraulic Assumptions Used for the Capacity Analysis ..................................................................4-1

4.1.1 Summary of Design Storm, Performance Criteria, and Design Criteria ........................4-1

4.1.2 Physical Model Network ..................................................................................................................4-9

4.1.2.1 Lined Model Network Assumptions......................................................................... 4-10

4.2 Capacity Evaluation Results ..................................................................................................................... 4-13

4.3 Gravity Sewer System Capacity Deficiencies ..................................................................................... 4-13

4.4 Pump Station and Force Main Capacity Deficiencies .................................................................... 4-16

4.5 Capacity Improvement Projects ............................................................................................................. 4-17

4.5.1 Agilent.................................................................................................................................................. 4-21

4.5.2 Homestead Road ............................................................................................................................. 4-21

4.5.3 Kiely Boulevard ................................................................................................................................. 4-22

4.5.4 Victoria Avenue ................................................................................................................................ 4-22

4.5.5 Cabrillo Avenue ................................................................................................................................ 4-23

4.5.6 CMC Basin........................................................................................................................................... 4-23

4.5.7 Bowers Avenue ................................................................................................................................. 4-24

4.5.8 Calabazas Trunk ............................................................................................................................... 4-24

4.5.9 Freedom Circle.................................................................................................................................. 4-24

4.5.10 GAP West Trunk ............................................................................................................................... 4-25

4.5.11 GAP East Trunk ................................................................................................................................. 4-25

4.5.12 Bunker Hill Lane East...................................................................................................................... 4-26

4.5.13 Lafayette Street................................................................................................................................. 4-26

4.6 Infiltration and Inflow Discussion .......................................................................................................... 4-26

4.6.1 Completed Infiltration and Inflow Investigations ............................................................... 4-27

4.6.2 I/I Source Detection and Control Methods ........................................................................... 4-29

4.6.3 I/I Investigation Recommendations for Santa Clara .......................................................... 4-30

5. RECOMMENDED SEWER CAPACITY CAPITAL IMPROVEMENT PROGRAM ...............................5-1

5.1 Project Development Process ....................................................................................................................5-1

5.2 Project Prioritization Methodology..........................................................................................................5-1

5.3 Project Level of Confidence ........................................................................................................................5-2

5.4 Project Cost Estimates...................................................................................................................................5-3

5.5 Other Costs........................................................................................................................................................5-3

5.6 Project Costs Financed by Developers ...................................................................................................5-4

5.7 Summary of Recommended Capacity Improvement Projects ......................................................5-4

5.7.1 Agilent.....................................................................................................................................................5-7

5.7.2 Homestead Road ................................................................................................................................5-7

5.7.3 Kiely Boulevard ....................................................................................................................................5-7

5.7.4 Victoria Avenue ...................................................................................................................................5-7

5.7.5 Cabrillo Avenue ...................................................................................................................................5-8

5.7.6 CMC Basin..............................................................................................................................................5-8

5.7.7 Bowers Avenue ....................................................................................................................................5-8

5.7.8 Calabazas Trunk ..................................................................................................................................5-9

5.7.9 Freedom Circle.....................................................................................................................................5-9

5.7.10 GAP West Trunk ..................................................................................................................................5-9

5.7.11 GAP East Trunk ................................................................................................................................. 5-10

5.7.12 Bunker Hill East Lane...................................................................................................................... 5-10

5.7.13 Lafayette Street................................................................................................................................. 5-10 City of Santa Clara (0012307.00) TOC-3 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

5.8 Schedule .......................................................................................................................................................... 5-10

5.9 Implementation Recommendations ..................................................................................................... 5-11 TABLES
Table ES-1: Summary of Sanitary Sewer System Infrastructure Table ES-2: Average Base Wastewater Flow Assumptions for Santa Clara1 Table ES-3: Wastewater Flow Assumptions for CuSD1
Table ES-4: Summary of Hydraulic Model Calibration Results1 Table ES-5: Summary of Design and Performance Criteria
Table ES-6: Summary of Capacity Analysis Model Scenarios Table ES-7: Summary of Recommended Sewer Capacity CIP
Table ES-8: Capacity Improvement Project Details
Table 1-1: Summary of Sanitary Sewer System Infrastructure Table 2-1: Flow Meter Sites
Table 2-2: Summary of BWF Loads for Existing, Near-Term, and Future Conditions1 Table 2-3: Land Use Classifications and Existing BWFs by Use Category Table 2-4: Unit Flow Factors Used to Estimate Future BWF Loads Table 2-5: Wastewater Flow Assumptions for CuSD1
Table 3-1: Sewer System Model Pipe Summary
Table 3-2: Sewer System Model Pump Station Summary
Table 3-3: City’s Largest Water Users (water use greater than 50,000 gpd) Table 3-4: Dry Weather Flow Calibration Results Summary1 Table 3-5: Dry Weather Flow Calibration Results vs. 2022-2023 Flow Monitoring Data1 Table 3-6: Dry Weather Flow Calibration Results vs. Select 2014-2015 Flow Monitoring Data1 Table 3-7: Dry Weather Flow Summary (Existing Conditions) Table 3-8: Rainfall Events Referenced for Wet Weather Calibration1 Table 3-9: Wet Weather Flow Calibration Results Summary1 Table 3-10: Wet Weather Flow Calibration Results vs. 2022-2023 Flow Monitoring Data1 Table 3-11: Wet Weather Flow Calibration Results vs. Select 2014-2015 Flow Monitoring Data1 Table 4-1: Rainfall Design Event Criteria Used for Santa Clara Master Plan Update Table 4-2: Characteristics of Design Storm Distributions Considered1 Table 4-3: Capacity Deficiency Criteria Used for Santa Clara Master Plan Update Table 4-4: Design Criteria Used for Santa Clara Master Plan Update Table 4-5: Future Liner Thickness Assumptions for RCP Trunks and Siphons (Lined Model Network Only)1 Table 4-6: RCP Trunks Identified for Future Lining (Lined Model Network Only) Table 4-7: Summary of Model-Predicted Gravity Sewer Capacity Deficiencies Table 4-8: Summary of Model-Predicted Pump Station and Force Main Capacity Deficiencies Table 4-9: Summary of Capacity Improvement Projects
Table 5-1: Project Prioritization Ranking1
Table 5-2: Project Flow Confirmation Levels
Table 5-3: Other Costs in Addition to Sewer Capacity CIP Project costs Table 5-4: Capacity Improvement Projects
Table 5-5: Capacity Improvement Projects Schedule
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Master Plan Report - Draft December 2024

FIGURES
Figure ES-1: Santa Clara Sanitary Sewer System and Service Area Figure ES-2: Flow Monitoring Program
Figure ES-3: RDI/I Rate by Flow Meter Basin
Figure ES-4: Overview of Capacity Deficiencies
Figure ES-5: Overview of Capacity Improvement Projects
Figure 1-1: Santa Clara Sanitary Sewer System and Service Area Figure 2-1: Flow Monitoring Program
Figure 2-2: Trunk Sewer System Schematic
Figure 2-3: Plot of Typical Flow Data for 2022-2023 Flow Monitoring Period Figure 2-4: Wastewater Flow Components
Figure 2-5: Water Billing Data
Figure 2-6: RDI/I Hydrograph Components
Figure 3-1: Sample Siphon Profile
Figure 3-2: Flume Diversion Structure to Homestead Rd. or Lawrence Expwy.

Figure 3-3: City’s Top Water Users (water use greater than 50,000 gpd) Figure 3-4: Residential Diurnal Patterns
Figure 3-5: Non-Residential Diurnal Profiles
Figure 3-6: Dry Weather Calibration Graph (FM 1)
Figure 3-7: Dry Weather Calibration Graph (FM 2)
Figure 3-8: Dry Weather Calibration Graph (FM 3)
Figure 3-9: Daily Rainfall Observed During 2022-2023 Flow Monitoring Period (in)1 Figure 3-10: Wet Weather Calibration Results at FM 1
Figure 3-11: Wet Weather Calibration Results at FM 2
Figure 3-12: Wet Weather Calibration Results at FM 3
Figure 3-13: Wet Weather Calibration Results – RDI/I Response at FM 31 Figure 3-14: Wet Weather Calibration Results – RDI/I Response at FM 27 Figure 3-15: Wet Weather Calibration Results – RDI/I Rates by Flow Meter Basin Figure 4-1: Design Storm Event for Central Santa Clara (MAP ~14.5 inches) Figure 4-2: Design Storm Event for Central Santa Clara (Weekend) Figure 4-3: Design Storm Event for Central Santa Clara (Weekday) Figure 4-4: Spatial Variation of Rainfall Throughout Santa Clara’s Service Area Figure 4-5: RCP Trunks Identified for Future Lining (Lined Model Network Only) Figure 4-6: Capacity Deficiencies Overview Map
Figure 4-7: Capacity Improvement Projects Overview Map
Figure 4-8: CMC Basin Tributary Area
Figure 4-9: Observed flow monitoring data at FM 31 (S62-50, 10”) Figure 4-10: NOAA Rainfall Statistics Compared to Observed January 2023 Rainfall in Santa Clara, CA

APPENDICES
Appendix A: Flow Monitoring Data Plots
Appendix B: Future Development Assumptions
Appendix C: Pump Station Capacity Calculations
Appendix D: Field-Collected Survey Information Data Sheets City of Santa Clara (0012307.00) TOC-5 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
Appendix E: Calibration Results
Appendix F: Siphon Lining Assumptions
Appendix G: Sewer Capacity CIP Project Cost Estimates, Maps, and Profiles

ACKNOWLEDGEMENTS
City of Santa Clara
Craig Temple, Principal Engineer (Project Manager)
Falguni Amin, Principal Engineer
Woodard & Curran
Kraig Erickson, Project Manager
Nuria Bertran-Ortiz, Technical Manager
Stephanie Estabrook, Project Engineer
Nery Barrera, Staff Engineer
Cathy Greenman, Technical Reviewer
Gisa Ju, Technical Reviewer
Subconsultants
V&A Consulting Engineers, Inc. (Flow Monitoring)

LIST OF ACRONYMS AND ABBREVIATIONS
ADWF Average Dry Weather Flow
APN Assessor Parcel Number
BWF Base Wastewater Flow
CCTV Closed-Circuit Television
CIP Capital Improvement Program or Capital Improvement Plan CIPP Cured-in-Place Pipe
City City of Santa Clara
CMC Chromite-Machado-Cabrillo
County Santa Clara County
CSJ City of San Jose
CuSD Cupertino Sanitary District
d/D Depth to Diameter Ratio
DDF Depth, Duration, Frequency
DIP Ductile Iron Pipe
DTM Digital Terrain Model
DU Dwelling Unit
DWF Dry Weather Flow
EL Existing Loads
ENR CCI Engineering News Record Construction Cost Index FAR Floor-area-ratio
FM Flow Meter
fps Feet per second
City of Santa Clara (0012307.00) TOC-6 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
GAP Great America Parkway
GIS Geographic Information System
GP General Plan
gpd Gallons per day
gpcd Gallons per capita per day
GWI Groundwater Infiltration
I/I Infiltration and Inflow
ICM InfoWorks ICM™
IDF Intensity, Duration, Frequency
LiDAR Light Detection and Ranging
LF Linear Feet
LMN Lined Model Network (Future)
LTFL Long-Term Future Loads
MAP Mean Annual Precipitation
mgd Million gallons per day
MH Sanitary Sewer Manhole
MP Master Plan
NAICS North American Industry Classification System
NAVD North American Vertical Datum of 1988
NGVD National Geodetic Vertical Datum of 1929
NOAA National Oceanic and Atmospheric Administration
NRCS Natural Resources Conservation Service
NTFL Near-Term Future Loads
PDWF Peak Dry Weather Flow
PHD Patrick Henry Drive
PS Pump Station
PVC Polyvinyl Chloride (Pipe)
PWWF Peak Wet Weather Flow
RCP Reinforced Concrete Pipe
RDI/I Rainfall-Dependent Infiltration and Inflow
SCADA Supervisory Control and Data Acquisition
SCS Soil Conservation Service
SD Specific Development
SF Square Feet
SJ/SC RWF San Jose / Santa Clara Regional Wastewater Facility SMH Sanitary Sewer Manhole
SSO Sanitary Sewer Overflow
UMN Unlined Model Network (Current)
USDA United States Department of Agriculture
V&A V&A Consulting Engineers, Inc.

VCP Vitrified Clay Pipe
VFD Variable Frequency Drive
W&C Woodard & Curran
WWF Wet Weather Flow
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Master Plan Report - Draft December 2024

EXECUTIVE SUMMARY
This report summarizes the results and recommendations of the Sanitary Sewer Master Plan Update (Master Plan Update) for the City of Santa Clara (City or Santa Clara). Woodard & Curran prepared the Master Plan Update in close coordination with City staff. The Master Plan Update will be used to guide improvements to the City’s sewer system to accommodate current and future development and to help the City continue to provide a high level of service to its customers.

The overall objectives of this Master Plan Update were to develop wastewater flow projections for the City’s sewer service area using up-to-date development and land use information and flow monitoring data; update and expand its existing hydraulic model of the sanitary sewer system; use the model to identify existing capacity deficiencies and future capacity requirements; and develop a phased Capital Improvement Program (CIP), including cost estimates, for implementing the required capacity improvements to the sewer system.

The Master Plan Update included preparation of the following four (4) key technical memoranda (TMs), which were referenced for development of this Master Plan Update report:
• TM #1 – Santa Clara Sewer Model Development and Calibration • TM #2 – Santa Clara Sewer Performance and Design Criteria • TM #3 – Santa Clara Sewer Performance Evaluation
• TM #4 – Capital Improvement Plan Report
This Executive Summary provides a concise summary of the Master Plan Update report, highlighting critical information including objectives, findings, conclusions, and recommendations. It is presented in three parts:
1) Introduction to the City’s Existing Sewer System and Service Area (Section ES-1) discusses the City of Santa Clara’s existing sewer system infrastructure and service area. 2) Description of How the Capacity Analysis was Prepared (Section 0) describes the scope and methodologies of the planning effort, including the key planning and technical assumptions incorporated into the sewer system capacity analysis.
3) Recommended Capital Improvement Program (Section ES-3) presents the recommended CIP, including capacity improvement projects, phasing, and estimated costs. In addition, recommendations are presented for implementing the proposed CIP.

ES-1 Introduction to the City’s Existing Sewer System and Service Area Santa Clara is located in central Santa Clara County adjacent to the cities of San Jose, Cupertino, and Sunnyvale and covers approximately 18 square miles. The City has a population of approximately 130,000 and is served by a wastewater system comprising approximately 288 miles of sewer pipelines generally ranging from 4 to 48 inches in diameter (including 12 miles of private sewer pipelines) and seven (7) sewage pump stations.

The City collects wastewater generated within the City’s service area from approximately 25,000 City customers (connections). Based on the City’s billing database, roughly 90% of the City’s existing customers are residential users and the remaining 10% are non-residential users, including commercial, municipal, and industrial users. In addition to collecting wastewater flows from customers within its service area, the City City of Santa Clara (0012307.00) ES-2 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
also has an agreement to convey wastewater flows from a major portion of the Cupertino Sanitary District (CuSD) via a connection at Homestead Road and Swallow Drive.

Wastewater flows collected are generally conveyed eastward and northward. A portion of the City’s flow continues eastward to the Trimble Trunk and conveyed to the City of San Jose’s interceptor sewers on Zanker Road. The remainder of the City’s flow and all the CuSD flow travels northward to the City’s Northside and Rabello Pump Stations, where the flow is pumped to the San Jose/Santa Clara Regional Wastewater Facility (SJ/SC RWF) for treatment and disposal. The City’s sewer system and service area are shown in Figure ES-1. A summary of the City’s sanitary sewer system infrastructure is presented in Table ES-1.

TABLE ES-1: SUMMARY OF SANITARY SEWER SYSTEM INFRASTRUCTURE Infrastructure Quantity Unit
Sewer Mains (Pipes) 1,456,4001/ 276 Feet / Miles
Manholes 5,500 -
Siphons 34 (59 barrels2) -
Pump Stations 7 -
1Total length is rounded to the nearest one hundred feet. 2Some siphons have multiple barrels: Three (3) siphons have three (3) barrels, 19 siphons have two (2) barrels, and the remaining 12 siphons have a single barrel.

De La Cruz LS
Primavera LS
Westside LS
Rabello PS
Northside PS
Tasman LS
Stadium LS
SC Influent
Junction
Structure
CuSD Flow
Legend
Figure ES-1
Sanitary Sewer System
and Service Area
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx City Boundary
Pump Station
Santa Clara Force Mains
San Jose Interceptors
CuSD Joint Usage Sewers
Sewers by Diameter
≤6"
8"-10"
>10"-16"
>16"-24"
≥27"
CSJ Interceptor
(Not Modeled)
San Jose/Santa Clara
Regional
Wastewater Facility
Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk. ±
0 0.25 0.5 1
Miles
City of Santa Clara (0012307.00) ES-4 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
ES-2 Description of How the Capacity Analysis was Prepared This study is intended to provide a comprehensive update of the City’s Sanitary Sewer Master Plan to reflect the most current and accurate information on wastewater flows, projected growth, and system performance.

To accomplish this, the City recognizes the need to update the hydraulic model of its sewer system, which is used to assess system performance and identify system capacity needs for both existing and projected future wastewater flows. This section describes how the capacity analysis was prepared and discusses the wastewater flow assumptions, hydraulic model development and calibration, design and performance criteria, and capacity analysis scenarios and results.

Wastewater Flow Assumptions
Wastewater flow assumptions are required to develop a hydraulic model that is an accurate representation of reality. The Santa Clara model includes both existing and future projected wastewater flow scenarios.

Existing base wastewater flow (BWF) was estimated for each parcel within the City’s service area based on recent customer water usage records obtained from the City’s water billing database.

Future BWF projections were estimated by incorporating the most current development information that was available for the City’s service area, which included development projects in review, specific plans, General Plan, and entitlement agreements. Based on the timing and type of development, the future base wastewater flows were assigned to one of two scenarios: near-term future or long-term future. The longterm future scenario included all development assumptions applied to the near-term future scenario plus development assumptions associated with the City’s General Plan and entitlement agreements. The City’s billing database records show that many entitlement holders have historically discharged less than their flow entitlements; however, considering the City is required to provide capacity to these users should they have the need to increase their discharges, the long-term future BWF scenario conservatively assumes that all entitlement holders would make use of their full discharge allowances.

Table ES-2 summarizes the average BWF assumptions applied to the hydraulic model for the City’s service area.

TABLE ES-2: AVERAGE BASE WASTEWATER FLOW ASSUMPTIONS FOR SANTA CLARA1 Land Use Residential Non-Residential Total
Flow Scenario (mgd) (mgd) (mgd)
Existing 6.72 4.50 11.22
Near-Term Future 10.11 6.09 16.20
Long-Term Future2 13.58 15.48 29.06
1Does not include sewer flows from the Cupertino Sanitary District (CuSD). Refer to Table ES-3. 2 Includes 5.09 mgd assumed for entitlement agreements, mostly for non-residential land uses.

The Santa Clara hydraulic model includes flow scenarios that represent both dry weather (non-rainfall) and wet weather (rainfall) conditions. In dry weather conditions, the base wastewater flows presented above account for the vast majority of total discharges to the sewer system. During wet weather conditions, total discharges to the sanitary sewer system increase due to the introduction of storm water inflow and infiltration, which enters the sanitary sewer system in direct response to rainfall events through holes in manhole covers, defects in sewer pipelines and service laterals, or illegally connected storm drainage infrastructure. If groundwater levels are high enough, some infiltration can also occur during dry weather conditions as it infiltrates into sewer infrastructure from below through defects. Wet weather flows are generated by simulating a design storm rainfall event in the hydraulic model.

City of Santa Clara (0012307.00) ES-5 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
Because CuSD discharges to Santa Clara’s sanitary sewer system, the existing and future projected wastewater flow scenarios in the hydraulic model also include wastewater flow assumptions for CuSD for both dry and wet weather conditions. CuSD flows were incorporated into the hydraulic model as inflow hydrographs, which define the rate of wastewater flow entering a specific point (i.e., manhole) in the network during a simulation. CuSD flows for existing dry weather conditions were based on flow monitoring data.

CuSD flows for existing wet weather conditions, near-term future dry and wet weather conditions, and longterm future dry and wet weather conditions were based on flows from CuSD’s hydraulic model, which was most recently re-calibrated in 2023 by AKEL Engineering. For these flow scenarios, Woodard & Curran created inflow hydrographs based on the results that were exported from CuSD’s re-calibrated model; the magnitude of flows was maintained but the timing was slightly shifted to match the diurnal usage pattern observed in the flow monitoring data and to align the peak wet weather response where applicable. For the long-term future wet weather flow scenario only, the peak flow was conservatively scaled up to match the contractual limit (13.8 mgd) defined in Santa Clara’s agreement with CuSD.

Table ES-3 summarizes CuSD’s average BWF assumptions applied to the hydraulic model for the City’s service area.

TABLE ES-3: WASTEWATER FLOW ASSUMPTIONS FOR CUSD1
Flow Scenario Average Dry Peak Dry Average Wet Peak Wet (mgd) (mgd) (mgd) (mgd)
Existing 3.7 5.6 4.1 10.7
Near-Term Future 4.2 6.3 4.6 11.3
Long-Term Future 4.6 6.7 5.9 13.82
1Based on CuSD’s hydraulic model results for a seven (7) day period. 2Assumed to be contractual limit defined in agreement between Santa Clara and CuSD.

Hydraulic Model Network Development
A hydraulic model of the City’s sewer system was developed for this study. The model includes all Cityowned pipes and manholes within the sanitary sewer system, excluding approximately 12 miles of privatelyowned sewer mains. Therefore, the model network consists of about 276 miles of sewers, including 2.7 miles of force mains, or roughly 96% of the total 288 miles of sewer pipeline within the City’s system. The model also includes all seven sewage pumping stations. The model is a significant expansion of the model used for the 2016 Master Plan, which was developed to represent the trunk or “backbone” of the sewer system and as such contained approximately 34% (or 94 miles) of the total length of the City’s sewers. Since 2016, Woodard & Curran has maintained and updated the City’s model as sewer improvement projects were implemented, development reviews were requested, or when new network data became available, and this Master Plan Update builds on that work by significantly expanding the model network to include all Cityowned sewer pipelines.

The model was used to assess how the system would perform under various planning and flow scenarios and to identify pipes or pump stations that may not have sufficient capacity to convey the predicted flows under existing or future conditions.

Hydraulic Model Calibration
Before the hydraulic model can be used for the capacity analysis performance evaluation, it must be calibrated to confirm that it is an accurate representation of the flows and hydraulic conditions in the City’s sanitary sewer system. Model calibration is the process of comparing model-simulated flows to observed flows and adjusting the model assumptions and parameters as needed until a reasonably good match is City of Santa Clara (0012307.00) ES-6 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
achieved. Generally, the model calibrator attempts to match flow volumes and peak flows between the model-simulated and observed data.

Model calibration is first performed for dry weather flows to achieve an accurate prediction of the base wastewater flows and baseline groundwater infiltration if present during non-rainfall conditions. Wet weather calibration is then performed to achieve an accurate prediction of the storm water inflow and infiltration that discharges to the sanitary sewer system during rainfall events.

A temporary flow monitoring program (shown in Figure ES-2) was conducted as part of this study to facilitate model calibration. The program obtained flow depth and velocity data (used to compute flow rate) at 31 strategically identified locations throughout Santa Clara’s sanitary sewer system during both dry weather and wet weather conditions and rainfall data at three distinct locations. The observed data were compared to the model-simulated flows during the calibration process to confirm actual flows and system routing and characterize infiltration and inflow into the sewers within each distinct flow meter (FM) basin.

The model calibration process also included reviewing key flow splits in the City’s sewer system to confirm flow routing, refining diurnal flow patterns to accurately represent the typical variation of flows throughout the day, and reviewing the City’s largest dischargers and their discharge locations.

Table ES-4 summarizes the final model calibration results for the overall system based on discharge location by comparing model-simulated to observed flows during both dry weather and wet weather conditions for the downstream most flow meters. It was determined that a reasonably good match was achieved for the overall system considering the observed average dry weather flows and peak wet weather flows were within 10% of the model-simulated flows at both discharge locations. The period used for the dry weather calibration was the seven (7) day dry period from December 17 through December 23, 2022. Wet weather calibration was performed for the full 2022-2023 season because the flow monitoring program captured several rainfall events. The January 13-16, 2023 rainfall event produced the largest flow response and was used as the primary basis for calibrating the model to match observed peak wet weather flows. Several storms occurred within a short amount of time during the flow monitoring period, so there were likely cumulative impacts that increased the inflow and infiltration response during the subsequent storms.

Additionally, the calibration focused on selecting parameters to conservatively match peak flows observed during the mid-January event which occurred later in the season after significant rainfall had already fallen and soils were generally saturated. As a result, the modeled and metered peak flows and volumes typically matched better for the later season rainfall events.

TABLE ES-4: SUMMARY OF HYDRAULIC MODEL CALIBRATION RESULTS1 Average Dry Weather Flows (mgd) Peak Wet Weather Flows (mgd) Discharge Location Observed Modeled Difference2 Observed Modeled Difference2 Santa Clara Northside and
Rabello Pump Stations3

10.54 10.09 -4.3% 23.03 24.22 +5.2%
Trimble Trunk 4.65 4.46 -4.1% 13.65 13.93 +2.1%
1Model results are compared to the 2022-2023 flow monitoring data. 2Difference is reported as modeled minus observed flow. 3 Includes flows from CuSD.

The infiltration and inflow response to rainfall, which is referred to as rainfall-dependent infiltration and inflow (RDI/I), was quantified within each flow meter basin through the wet weather calibration process.

Figure ES-3 presents a visual representation of the wet weather calibration model results in terms of the City of Santa Clara (0012307.00) ES-7 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
total RDI/I rate that was applied to the model for each meter basin to match model-simulated and observed flows. The total RDI/I rate (or “Total R”) is a percentage that represents the total amount of rainfall that becomes runoff and eventually enters the sanitary sewer system as RDI/I. As shown in the figure, half of the City’s flow meter basins had RDI/I rates of less than 5%. In contrast, flow meter basins concentrated within the central western portion of Santa Clara’s system displayed very high RDI/I rates of greater than 80%.

These flow meter basins are located within the Chromite-Machado-Cabrillo (CMC) tributary area and the adjacent Agate Drive tributary area. The flow monitoring data showed that the nature of the RDI/I responses to rainfall in these areas were indicative of significant infiltration, as the response was generally slower and took a long time to recede (i.e., several weeks following rainfall). Moreover, because consecutive rainfall events occurred within a short period of time during the flow monitoring period, the infiltration response did not fully recede before another rainfall event occurred. The flow monitoring results were consistent with the findings of other field investigations completed recently in the CMC basin, which concluded that rainfalldependent infiltration appeared to be the most significant contributor to the wet weather response, possibly from defects in tributary sewer laterals and mains.

During the dry weather calibration process, a total of 0.158 mgd of additional GWI flow was applied to the system uniformly throughout two (2) of the 31 flow meter areas (i.e., FM 26 and FM 31), which were located in the CMC and Agate Drive tributary areas, respectively. GWI represents a seasonal increase in wastewater flows due to infiltration into the sewers during non-rainfall conditions, typically in low-lying areas or areas close to creeks or other water bodies. The need to add GWI to these flow meter basins to calibrate for dry weather conditions further suggests that significant infiltration is occurring, likely through defects in tributary sewer laterals and mains.
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De La
Cruz LS
Westside LS Primavera LS
Rabello PS
Northside PS
Tasman LS
Stadium LS
SC Influent
Junction
Structure
Legend
Figure Exported: 12/31/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

City of Santa Clara Boundary
2022-23 Flow Meters
% 2014-2015 & 2022-2023 Flow Meter Site
% 2022-2023 Flow Meter Site
RDI/I Rate (Total R)
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5 - 10
> 10 - 20
> 20 - 40
Figure ES-3 > 80
RDI/I Rate by
Flow Meter Basin
Sewer Master Plan Update
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City of Santa Clara (0012307.00) ES-10 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
Design and Performance Criteria
The capacity analysis requires selection of design and performance criteria, which are applied so that the hydraulic model can be used to determine if sewer facilities would have adequate capacity under the flow scenarios developed or if the capacity would be exceeded, requiring system improvements. Table ES-5 presents and describes the design and performance criteria that were selected for this Master Plan Update.

TABLE ES-5: SUMMARY OF DESIGN AND PERFORMANCE CRITERIA
Criterion Purpose Selected
Design
Storm
Rainfall
Single event rainfall
assumed to produce peak
flows generated from a
rainfall event of a desired
return period to assess
system capacity during
wet weather conditions.
• Return Period: 10 years
• Duration: 24 hours
• Rainfall Depth and Temporal Distribution: Based on
Santa Clara County Drainage Manual (developed
from historical rainfall event in December 1955)
• Storm Timing: Peak-on-peak1(weekday)
• Antecedent Conditions: Wet, saturated soils
• Spatial Distribution: Lowest intensity north and
highest intensity southwest
Performance
(Capacity
Deficiency)
Used to determine if the
capacity of an existing
sewer facility is inadequate
to the extent that a
capacity improvement
project would be needed.
• Gravity Sewers: Flow depth exceeds full pipe (d/D2 >
1) during either dry weather or design storm wet
weather conditions (i.e., no surcharge is allowed).
• Pump Stations: Firm capacity3 greater than the peak
wet weather flow during the design storm.
• Force Mains: Velocity exceeds 8 feet per second (fps).

Design
Used for the purpose of
sizing new or relief
facilities based on the
City’s desired level of
service and are generally
more conservative than
the performance criteria
because new facilities
should be designed to a
higher standard.

Gravity Sewers:
• d/D < 0.75 under future peak wet weather flows
• Minimum Velocity = 2 fps for daily dry weather
• Maximum Velocity = 10 fps at peak design flow
• Minimum Pipe Diameter = 8 inches
• Minimum Cover = 6 feet (ground to pipe crown)
Pump Stations: Firm capacity greater than the peak wet
weather flow during the design storm.

Force Mains:
• Minimum/Maximum Velocity: 3 fps /8 fps
• Minimum Cover = 6 feet (ground to pipe crown)
1Peak RDI/I occurs at approximately the same time as peak BWF for most areas of the sewer system. 2d/D = Depth-to-Diameter Ratio representing the depth of flow within the pipe. 3Capacity of the pump station assuming that the largest pump is out of service.

The design and performance criteria selected for sewer master planning efforts vary by agency and are reflective of the level of risk that is acceptable to each agency. Common criteria for several agencies both inside and outside of California were reviewed during the process of selecting the City’s criteria. Ultimately, Santa Clara elected to apply relatively conservative criteria in order to identify all potential projects, recognizing that conditions may change in the future due to variable factors such as sewer condition, additional development, and climate change. However, engineering judgment was used when applying the City of Santa Clara (0012307.00) ES-11 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
performance criteria to avoid identifying capacity deficiencies where gravity sewers showed only minor criteria violations.

Capacity Analysis Scenarios and Results
The capacity analysis is performed using the calibrated hydraulic model to identify sewer facilities that may not have sufficient capacity to convey the predicted flows based on the selected performance criteria. A total of 12 model scenarios were developed to assess system performance and were a combination of the wastewater flow scenario (existing, near-term future, or long-term future), design flow (dry or wet weather), and physical network assumptions (with or without assumed lining of City-identified reinforced concrete sewers likely to be in poor condition) listed in Table ES-6.

TABLE ES-6: SUMMARY OF CAPACITY ANALYSIS MODEL SCENARIOS Wastewater Flow Design Flow Physical Network
Existing Dry Weather Unlined: Current system with no future lining assumed Near-Term Future Wet Weather Lined: Assumes future lining of City-identified RCP trunks in poor condition Long-Term Future
The capacity analysis identified a total of 16 gravity sewer deficiencies, the locations of which are shown in Figure ES-4. In the figure, pipes shown in pink are predicted to surcharge due to “throttle” conditions, indicating that the full capacity of the pipe is less than the predicted peak flow. Pipes shown in purple are predicted to surcharge due to backwater from a downstream throttle condition. A total of 15 capacity improvement projects were developed to relieve the gravity sewer capacity deficiencies identified through the capacity analysis. The project locations and extents are shown in Figure ES-5. Most projects were developed to either replace the existing, capacity-deficient pipe with a larger pipe or to re-direct a portion of flows to other existing sewers with adequate available capacity. Replacement pipes were sized based on the selected design criteria to convey flow for the most conservative model scenario (i.e., long-term future wastewater flow, wet weather design flow, and lined physical network). The number of projects developed (15) is less than the number of capacity deficiencies identified (16) because model runs showed that the Agate Drive deficiency would be relieved once the Calabazas Trunk project was implemented.

The capacity analysis did not identify any pump station or force main capacity deficiencies. The firm and total capacities of each of the City’s seven sewer pump stations were estimated based on basic information, pump settings, pump curves, and system curves provided by the City. Those theoretical capacities were then compared to the model-predicted peak wet weather flows generated from the design storm rainfall event.

Because the theoretical firm capacity of each station did not exceed the model-predicted flow into the station, it was assumed that each station had adequate capacity to convey flows during the most conservative condition evaluated based on the City’s performance criteria. Model-predicted force main velocities were also within the specified performance criteria (i.e., less than 10 fps) during the most conservative condition evaluated, and similarly, no capacity deficiencies were identified. Although the capacity analysis did not identify any pump station capacity deficiencies, the model-predicted peak design flows to the Rabello and Northside Pump Stations during long-term future wet weather conditions (44.8 mgd) are close to the combined firm capacities of these two stations (45.2 mgd). Based on discussions with the City’s Water and Sewer Department, the diversion box upstream of these two pump stations contains a wet well with weir slots that the City has the ability to adjust by dropping in weir boards to control the flow.

Under dry weather conditions and normal settings, approximately 80% of flows go to the Rabello PS and the remaining 20% go to the Northside PS. City staff had not observed flows overtopping the weir boards towards Northside PS, but suspects there may be a gap underneath the weir boards considering SCADA City of Santa Clara (0012307.00) ES-12 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
confirms that flows go to both pump stations. The City should continue to monitor influent flows to these two pump stations as future developments come online and adjust the diversion box weir settings as needed to maximize the available capacity.

Crossman Ave
E Caribbean Dr
237 G2
Sunnyvale
Baylands
County Park
E Arques Ave
Kifer Rd
Stewart Dr
Lakebird Dr
B al zingwood Dr
Tasman Dr
G2
Henderson Ave
Azalea Dr
Reed Ave
Aster Ave
Benton St
Qu
ail Ave
Teal Dr
Bryant Way
Lily Ave
Lillick Dr
Nobili
Ave
Briarwood
Dr
Vireo
Ave
Sequoia Dr
Lorne Way
d Rd
G2
Sunken
Gardens
Golf
Course
Marian A
Peterson Middle
School
Kaiser
Permanente
Santa Clara
Medical Center
Pruneridge Ave
Har vard
Ave
Calvert Dr
N Tantau Ave
allco Pkwy
Stern Ave
Judy Ave
Calvert Dr
Holger Way
N 1st St
Great America Pkwy
Tasman Dr
W Tasman Dr
Gold St
237
Ulistac Natural
Area
Santa
Clara Golf
and
Tennis
Club
Lakeside Dr
Agnew Rd
Agnew Rd
Wals h Ave
Laurelwood Rd
Oakmea
d Pk
wy
Kifer Rd
Norman Ave
Clyde
Ave
Hope Dr
Comstock St
Cheeney
St
Lake shore Dr
Torrance Ave
Tasman Dr
Great A
meri
ca Pkwy
Central Expy
Montague Expy
101
Fairwood Park
Lick Mill Park
California's
Great America
Levi's Stadium
West Valley
College Mission
Campus
Harrison St
Benton St
Pomer
oy A
ve
Pomeroy Ave
Martin Ave
Reeve St
Nobili Ave
Walsh Ave
Chromite Dr
Warburton Ave War burton Ave Scott Blvd
Anna Dr
Calabazas Blvd
Newhall St
Los
Olivos
Dr
Richard Ave
Main St
Mark Ave
Enright Ave
Macha do Ave
Francis Ave
El Sobrante St
Agate Dr
Victoria Ave
Borax Dr Bray Ave
Toledo Ave
Homestead Rd
Bellomy St
Kiely Blvd
Saratoga Ave
Bowers
A
ve
La
fayette St
Monroe St
82 Santa Clara
High School

S A N T A

C L A R A
Wood hams Rd
Northlake Dr
Fo rbes Ave
Forest Ave
Pruneridge Ave
Albany Dr
Harold
Ave
Cronin Dr
Rodonovan
Dr
McKinley Dr
Estella Dr
Rebeiro Ave
Rosita Ave
Saratoga
Ave
Stevens Creek Blvd
Kiely Blvd
N Winchester Blvd
Pruneridge
Golf Club
Coy o te Cree
Ce k
nter Rd
C
ente
r Rd
Cisco Way
Balboa St
Holger Way
E Tasman Dr
N
1st St
237
Gua
dalupe Rive r
Innovation Dr
Aldo Ave
River Oaks Pkwy
Laurelwood Rd
Laurie Av e
Ewert Rd
N 1st
St
E Trimble R
Lick Mill B
lvd
G4
101
Alviso St
Newhall St
Main St
Jackson
St
Emory St
Boxwood Dr
Brokaw Rd
Airport Blvd
Lafayette St
Market St
The Alameda
De La Cruz Blvd
82 Santa Clara
Catholic
Cemetery
PayPal Park
San José Mineta
International
Airport
Santa Clara
University
University Ave
Olive Ave Shasta A
Woodland Ave
Bradley Ave
Bailey Ave
Cherrystone Dr
Kenwood Ave
Elliott St
N Bascom
Ave
Stevens Creek Blvd
Naglee Ave
Westfield Valley
Fair ATM
Agilent
CMC Basin
GAP W
GAP E
Calabazas Trunk
Lafayette St
Bowers Ave Kiely Blvd GAP W
Agilent
GAP E
CMC Basin
Homestead
Victoria Ave
Freedom Circle
Bunker Hill Ln E
Cabrillo Ave
Agate Dr
Legend
±
Figure ES-4
Overview of Capacity
Deficiencies
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx 0 0.25 0.5 1
Miles
Modeled Sewers
Surcharge State
<1 (no surcharge)
1 (backwater surcharge)
2 (throttle surcharge)
Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

S A N T A

C L A R A
Wood hams Rd
Northlake Dr
Fo rbes Ave
Forest Ave
Pruneridge Ave
Albany Dr
Harold
Ave
Cronin Dr
Rodonovan
Dr
McKinley Dr
Estella Dr
Rebeiro Ave
Rosita Ave
Saratoga
Ave
Stevens Creek Blvd
Kiely Blvd
N Winchester Blvd
Pruneridge
Golf Club
Coy o te Cree
Ce k
nter Rd
C
ente
r Rd
Cisco Way
Balboa St
Holger Way
E Tasman Dr
N
1st St
237
Gua
dalupe Rive r
Innovation Dr
Aldo Ave
River Oaks Pkwy
Laurelwood Rd
Laurie Av e
Ewert Rd
N 1st
St
E Trimble R
Lick Mill B
lvd
G4
101
Alviso St
Newhall St
Main St
Jackson
St
Emory St
Boxwood Dr
Brokaw Rd
Airport Blvd
Lafayette St
Market St
The Alameda
De La Cruz Blvd
82 Santa Clara
Catholic
Cemetery
PayPal Park
San José Mineta
International
Airport
Santa Clara
University
University Ave
Olive Ave Shasta A
Woodland Ave
Bradley Ave
Bailey Ave
Cherrystone Dr
Kenwood Ave
Elliott St
N Bascom
Ave
Stevens Creek Blvd
Naglee Ave
Westfield Valley
Fair ATM
Agilent
CMC Basin
GAP W
GAP E
Calabazas Trunk
Lafayette St
Bowers Ave Kiely Blvd GAP W
Agilent
Agilent
CMC Basin
Homestead
Victoria Ave
Freedom Circle
Bunker Hill Ln E
Cabrillo Ave
Legend
±
Figure ES-5
Overview of Capacity
Improvement Projects
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx 0 0.25 0.5 1
Miles
Modeled Sewers
Capacity Improvement Project
Bunker Hill Ln E
Agilent
Bowers Ave
CMC Basin
Calabazas Trunk
GAP E Trunk
GAP W Trunk
Homestead Rd
Kiely Blvd
Lafayette St
Victoria Ave
Freedom Circle
Cabrillo Extent (Not Actual Project) Project #: 0012307.00 Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

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Master Plan Report - Draft December 2024
ES-3 Recommended Sewer Capacity Capital Improvement Plan The Sewer Capacity CIP recommended in this study is designed as guidance for the City to provide adequate sewer system capacity for the City’s existing and anticipated future development. Table ES-7 and Table ES-8 provide a summary and detail of the recommended capacity improvement projects, respectively. The wastewater flow, design flow, and physical network triggers listed next to each project in Table ES-8 represent the least conservative condition (i.e., lowest flow and available capacity) that first caused the deficiency to occur. Relative priorities of “1” (highest priority) to “7” (lowest priority) were assigned to each project based on a combination of factors including the wastewater flow trigger, design flow trigger, and physical network trigger, and assumed structural condition. Therefore, projects that address existing deficiencies without future lining assumptions in place were assigned the highest priority because they pose the greatest risk of a sanitary sewer overflow (SSO). Those projects were subsequently scheduled for earlier implementation, assuming a start date in 2025. The remaining projects, which would be triggered by future loading conditions, were assigned an implementation start date of 2035. Projects were also assigned a flow confidence level from “1” (highest confidence) to “5” (lowest confidence) to reflect the level of confidence in the data that were used to calibrate the hydraulic model, forecast flows, and identify deficiencies. Projects which were assigned a confidence level “4” or “5” had no reliable confirmation of model flows; thus, conducting flow monitoring on these project reaches prior to design would provide a greater level of confidence in modeled flows.

The total estimated capital cost of the Sewer Capacity CIP is approximately $100.6 million in 2024 dollars.

These costs include baseline construction costs for new sewer mains and sewer structures using open-cut methods; and cost allowances for project mobilization/demobilization, traffic control, and bypass pumping as needed. The total estimated construction costs also include a 30% allowance for contingencies for unknown conditions, and the total estimated capital cost includes an allowance of 25% of construction cost for engineering, administration, construction management, and legal costs. Costs for lining City-identified RCP trunks are not included in the Sewer Capacity CIP as these are condition-related maintenance costs.

The estimated costs are planning or conceptual level estimates to be used for budgeting purposes only and are considered to have an estimated accuracy range of -30% to +50%. Note that the Sewer Capacity CIP does not include costs for two of the specific developer-driven capacity improvement projects, Patrick Henry Drive (PHD) and Mission Point, as the developers will fund those improvements. Additionally, it is assumed that the City’s overall sewer system CIP will also include costs for condition-related improvements; however, these projects are not addressed in this Master Plan Update report.

TABLE ES-7: SUMMARY OF RECOMMENDED SEWER CAPACITY CIP
Description Quantity Notes
Number of Projects 13 3 to be implemented in 2025; 10 after 2035 Total Length of New Sewers 38,100 LF Approximately 7.2 miles Range of New Sewer Diameters 8” – 48” Standard pipe sizes only (inside diameters) Number of New Weirs 4 Used to modify flow routing
Total Estimated CIP Cost1 $100.6M Based on August 2024 dollars Total Other Costs2
$75K annually
$950K every 7 years
$25K annually
Hydraulic Model Maintenance and Support;
Future Master Plan updates (next in 2029);
Technical Analyses for Model Verification
1Designed to reflect costs derived directly from construction of the capacity improvement projects only. 2Other costs associated with improvement of flow conveyance in the system.

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Master Plan Report - Draft December 2024
TABLE ES-8: CAPACITY IMPROVEMENT PROJECT DETAILS
1Projects are numbered from upstream to downstream. Table does not include Project Nos. 10 (Patrick Henry Drive) and 11 (Mission Point) because project costs will be paid for by the developers. 2Pre-project pipe diameters include future lining assumptions. 3Projects are prioritized based on wastewater flow, design flow, and physical network triggers as well as assumed structural condition. 4Rating assigned to validate the need for the project through review of flow monitoring data and reported surcharging and operational issues, and compatibility between flow meter data and the model. Descriptions of the flow confidence levels are as follows: N/A = Not assigned because project would be triggered by entitlement flow or specific development; 1 = Flow meter on or very near to the project reach surcharged during metered storm; 2 = Flow meter on or very near to the project reach confirms flow, but did not surcharge during metered storm; 3 = Flow meter near the project reach (upstream or downstream) confirms flow; 4 = No flow meter near the project reach to confirm flow; 5 = Conflicting flow between meter and model. 5EL = Existing Loads; LTFL = Long-Term Future Loads; DWF = Dry Weather Flow; WWF = Wet Weather Flow; UMN = Unlined Model Network; LMN = Lined Model Network. 6Costs are based on August 2024 ENR CCI of 15367.24 for the San Francisco Area and are Class 5 estimates (planning level).

Project No.1 Project ID Project Location Pre-Project Pipe Diameter(s)2
Project Description Priority3
Flow Confidence
Level4
Wastewater Flow
Trigger5
Design Flow
Trigger5
Physical Network
Trigger
5 Project Cost
6 1 Agilent Tracy Dr, Pomeroy Ave, Homestead
Rd (S Trunk), Kiely Blvd 10 to 22.8-inch 12,313 LF of 15 to 27-inch diameter pipe 7 N/A LTFL (entitlement) DWF UMN $26,942,000 2 Homestead Road N Homestead Trunk from Swallow
Wy to Saratoga Creek 18 to 30-inch 6,407 LF of 24 to 33-inch diameter pipe 3 3 LTFL WWF UMN $17,156,000 3 Kiely Boulevard Orthello Wy to S of El Sobrante St 8-inch 266 LF of 10-inch diameter pipe 6 4 LTFL WWF UMN $513,000
4 Victoria Avenue Fowler Ave & Pomeroy Ave to
Nobili Ave & Victoria Ave 8-inch 764 LF of 10-inch diameter pipe 6 3 LTFL WWF UMN $1,337,000 5 Cabrillo Avenue Halford Ave & Buckley St; St.

Lawrence Dr, W of Lawrence Expwy 8-inch
Flow Diversion Weirs
only. No pipe
replacement.
1 3 EL WWF UMN $154,000
6 CMC Basin Santa Maria Ave & Francis Ave;
Amethyst Dr 8 to 12-inch 3655 LF of 12 to 15-inch diameter pipe 1 1 & 2 EL WWF UMN $7,263,000 7 Bowers Avenue Bowers Ave from Chromite Dr to
Walsh Ave 25.7-inch 2605 LF of 30-inch diameter pipe 4 5 LTFL WWF LMN $8,047,000 8 Calabazas Trunk Calabazas Creek from S of Agate Dr
to Central Expwy 22.8 to 27-inch 2791 LF of 18 to 27-inch diameter pipe 2 5 EL WWF LMN $8,731,000 9 Freedom Circle Mission College Blvd from Freedom
Cir to west of Great America Pkwy 12 to 15-inch 1886 LF of 15-inch diameter pipe 5 N/A LTFL (specific development) DWF UMN $3,830,000 12 GAP West Trunk S of West Tasman Dr to Lafayette St 28.5 to 35.7-inch 4810 LF of 36 to 42- inch diameter pipe 3 2 LTFL WWF UMN $17,781,000
13 GAP East Trunk Old Glory Ln to S of Bunker Hill Ln;
Stars and Stripes Dr 31.4-inch 231 LF of 39-inch diameter pipe 4 2 LTFL WWF LMN $1,002,000 14 Bunker Hill Lane East E of Great America Pkwy 6-inch 107 LF of 8-inch diameter pipe 7 N/A LTFL (entitlement) WWF UMN $301,000 15 Lafayette Street N of Calle del Mundo to S of Great
America Wy 34.2 to 40.3-inch 2290 LF of 42 to 48-inch diameter pipe 3 2 LTFL WWF UMN $7,515,000 TOTAL

ESTIMATED
COST
$100,572,000
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Master Plan Report - Draft December 2024
Implementation Recommendations
The City should begin implementation of the Capital Improvement Program recommended in this Master Plan Update, starting with projects needed to address existing system capacity deficiencies. The following items should be considered in project scheduling and design, and in future updates of the Master Plan:
• The City should consider conducting additional flow monitoring or observation to document flow levels during large storm events at locations in the system where the model predicts significant surcharge or where there is a significant difference between previous flow monitoring conducted and the model results. Flow levels during large storm events should be compared to the water levels simulated by the hydraulic model to verify if the modeling predictions for the design storm seem reasonable, and to confirm the need for and, if necessary, refine project sizing. • The alignments and sizes of all recommended projects should be verified with detailed pre-design analyses, including topographic surveys, geotechnical investigations, utility research, and constructability reviews. Detailed pre-design analyses should consider feasibility of trenchless construction methods including pipe-bursting and Pilot Tube Guided Auger Boring (PTGAB), especially at major roadway, railway, and creek crossings. • The decision to parallel or replace existing sewers should consider the physical condition and remaining useful life of the existing pipelines and laterals; the availability of pipeline corridors for new sewer construction; and operation and maintenance concerns. • Capacity improvement projects triggered by long-term future flow assumptions associated with entitlement agreements would not need to be implemented until the entitled parcel(s) begin to discharge their entitled flow(s).
• The hydraulic model has been developed to assist the City in performing capacity analyses and updating the Master Plan in the future. The model should be kept up to date with any changes to existing sewer connections, development plans, and sewer system facilities.

This Master Plan Update report is intended to be a working document to be refined and updated as additional data and new planning information become available. The capacity assessment should be updated whenever there are major changes in planning assumptions or, at a minimum, every five to ten years.

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Master Plan Report - Draft December 2024

1. INTRODUCTION
This introductory section identifies the background and study objectives for the Master Plan Update, briefly describes the City’s sanitary sewer system and service area and presents an overview of the report’s organization by summarizing the content discussed within each section.

1.1 Background and Study Objectives
Prior to this study, the City last conducted a comprehensive assessment of its wastewater system in its 2016 Sanitary Sewer Master Plan Update1(2016 Master Plan). Of the seven (7) capacity improvement projects recommended in the 2016 Master Plan, three (3) projects were implemented: two (2) of which were operational adjustments to the set points for the Westside and Tasman Pump Stations to eliminate unnecessary backups in the influent gravity sewers, and the third was a capital project to upsize approximately 1,800 feet of 24-inch sewers along the Calabazas Creek trunk between Kifer Road and Scott Boulevard to 27-inch sewers.

Since 2016, in addition to completing a few sewer improvement projects, the City has experienced a significant amount of new development, necessitating an update to the 2016 Master Plan that includes an evaluation of the capacity of the sanitary sewer system to handle existing and future wastewater flows.

Several development reviews have also been completed since the 2016 Master Plan. These development reviews are conducted using the City’s hydraulic model to assess if the sanitary sewer system has enough available system capacity for the individual development to connect to the system.

Thus, the purpose of this study is to build an updated, comprehensive hydraulic model of the City’s sewer system, calibrate the model to current flow monitoring data, and identify needed capacity improvements based on existing and projected future flows. This Master Plan Update summarizes the basis of the sewer flow estimates and the hydraulic model development and calibration process, presents the criteria used for the capacity analysis and the deficiencies identified, and describes the proposed projects to address identified capacity deficiencies. Due to the relatively high rates of I/I in specific areas of the system, this assessment also included identifying areas of higher I/I appropriate for further investigation.

1.2 Sanitary Sewer System and Service Area
Santa Clara is a city of approximately 130,000 people located in central Santa Clara County adjacent to the cities of San Jose, Cupertino, and Sunnyvale and covers approximately 18 square miles. The City’s wastewater system serves approximately 25,000 City customers in its service area (primarily residential users) through approximately 288 miles of sewer pipelines generally ranging from 4 to 48 inches in diameter (including 12 miles of private sewer pipelines) and seven (7) sewage pump stations. The City also has an agreement to convey wastewater flows from a major portion of the Cupertino Sanitary District (CuSD) via a connection at Homestead Road and Swallow Drive. Wastewater flows collected are generally conveyed eastward and northward. A portion of the City’s flow continues eastward to the Trimble Trunk and is conveyed to the City of San Jose’s interceptor sewers on Zanker Road. The remainder of the City’s flow and all the CuSD flow travels northward to the City’s Northside and Rabello Pump Stations, where the flow is pumped to the San Jose/Santa Clara Regional Wastewater Facility (SJ/SC RWF) for treatment and disposal.

A summary of the City’s sanitary sewer system infrastructure is presented in Table ES-1. The City’s sewer system and service area are shown in Figure ES-1.
1 City of Santa Clara, Sanitary Sewer Master Plan Update, RMC Water and Environment, April 2016.

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Master Plan Report - Draft December 2024
TABLE 1-1: SUMMARY OF SANITARY SEWER SYSTEM INFRASTRUCTURE Infrastructure Quantity Unit
Sewer Mains (Pipes) 1,456,4001/ 276 Feet / Miles
Manholes 5,500 -
Siphons 34 (59 barrels2) -
Pump Stations 7 -
1Total length is rounded to the nearest one hundred feet. 2Some siphons have multiple barrels: Three (3) siphons have three (3) barrels, 19 siphons have two (2) barrels, and the remaining 12 siphons have a single barrel.

De La Cruz LS
Primavera LS
Westside LS
Rabello PS
Northside PS
Tasman LS
Stadium LS
SC Influent
Junction
Structure
CuSD Flow
Legend
Figure 1-1
Sanitary Sewer System
and Service Area
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx City Boundary
Pump Station
Santa Clara Force Mains
San Jose Interceptors
CuSD Joint Usage Sewers
Sewers by Diameter
≤6"
8"-10"
>10"-16"
>16"-24"
≥27"
CSJ Interceptor
(Not Modeled)
San Jose/Santa Clara
Regional
Wastewater Facility
Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk. ±
0 0.25 0.5 1
Miles
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Master Plan Report - Draft December 2024

1.3 Report Organization
The contents of each of the sections and appendices of this Master Plan Update report are described below. • Section 1 – Introduction: This introductory section provides background information on the objectives and scope of the Master Plan Update, the City’s sanitary sewer system and service area, and the contents and organization of this report.
• Section 2 – Wastewater Flow Assumptions: This section describes the flow monitoring program and basis for estimating model flows for existing conditions and future conditions with projected development.
• Section 3 – Hydraulic Model Development and Validation: This section describes the modeled sanitary sewer system, development of the hydraulic model network, and the calibration of the hydraulic model for dry and wet weather flow conditions. • Section 4 – System Capacity Analysis: This section defines the basis for the capacity assessment of the system, including the selected design storm and performance criteria used to identify deficiencies, and presents the capacity deficiencies identified based on the model results. The section also identifies areas of the system with high I/I and recommends additional investigations to isolate potential direct inflow sources in those areas. • Section 5 – Recommended Capital Improvement Plan: This section presents the recommended capacity improvement projects based on the results of the system capacity analysis using the calibrated hydraulic model. Each recommended project is documented with a general description, planning level capital cost estimate, relative priority rating, and flow confidence level. • Appendices: The appendices to the report provide additional detailed information to support the findings and recommendations presented in the report sections, including plots of flow monitoring and rainfall data and model calibrations, future land use assumptions, and detailed project descriptions, cost estimates, and figures for capacity improvement projects.

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Master Plan Report - Draft December 2024

2. WASTEWATER FLOW ASSUMPTIONS
This section describes the flow monitoring program and basis for estimating model flows for existing conditions and future conditions with projected development.

2.1 Flow Monitoring Program
To support the development of the hydraulic model and Master Plan Update, a temporary flow monitoring program was conducted as part of this study. The purpose of the flow monitoring program was to obtain data to quantify actual flows and characterize infiltration and inflow (I/I) within the sewer system, and to calibrate the hydraulic model for both dry and wet weather conditions.

2.1.1 Flow Monitoring and Rain Gauge Sites
One critical purpose of a flow monitoring program is to aid in the calibration of the model, which is discussed further in Section 3.3. Considerations for flow meter (FM) placement to support model calibration generally include:
• Isolate areas to characterize flows for model calibration; • Select sites on downstream trunks for flow confirmation; • Align the location with flow meters previously used;
• Further divide tributary areas with suspected high I/I based on previous flow monitoring data to further isolate I/I;
• Prioritize preferred hydraulic conditions (i.e., manholes on a straight line preferred over manholes on bends or with multiple incoming pipes); and • Consider ease of access and safety.

Santa Clara has conducted citywide flow monitoring programs in 2006 and 2015 as part of the City’s sewer system capacity assessment study and sewer master plan, respectively. The City also conducted additional selective flow monitoring in the Chromite-Machado-Cabrillo (CMC) tributary area (an area with suspected high I/I based on previous monitoring programs) as detailed in a September 2020 report1.

The 2022-2023 flow monitoring program for this Master Plan Update included 31 temporary gravity flow meters. Prioritizing the placement of the flow meters in the same locations used for previous monitoring programs is beneficial because it allows for comparison to the previously monitored flows to identify changes over time (e.g., increase in I/I). Therefore, the 2022-2023 program included placement of flow meters in all the same locations as in 2015 except for FM2, which was moved three manholes upstream due to safety concerns, and FM9, which was moved farther downstream to be north of Scott Blvd. The 2022- 2023 program also included installation of 8 additional flow meters that were not part of the 2015 program, including a flow meter along Uranium Drive south of Mead Avenue which the City added onto the initial program. Four (4) rain gauges were also installed during the 2022-2023 program, all in the same locations as the rain gauges installed during 2015 and placed to capture spatial variability of rainfall within the City.

V&A Consulting Engineers (V&A), under sub-contract to Woodard & Curran, installed the flow meters and rain gauges and conducted the monitoring program. The flow meters and rain gauges were installed and 1 Sewer Flow Monitoring and Inflow/Infiltration Study prepared by V&A in September 2020 included flow monitoring at 20 sites conducted during two phases.

City of Santa Clara (Project 0012307.00) 2-2 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
operational from December 13, 2022 to February 13, 2023 (approximately 9 weeks). The flow meters collected flow depth and velocity data which were used to compute flow rate.

In addition to the 31 temporary flow meter sites, CuSD also maintains a permanent flow meter at the CuSD’s and City’s sewer connection point to monitor CuSD flows discharging to the City’s sewer system. CuSD provided V&A with flow data recorded by the permanent meter for the duration of the flow monitoring period.

The location of the flow monitoring sites and rain gauges are shown in Figure 2-1. The figure also shows the associated tributary area (basin) for each flow meter. Note that some meters were located downstream of other meters. In those cases, the meter tributary areas are “incremental” (areas between the flow meter and tributary basins of the upstream flow meters). Table 2-1 lists the flow meter locations and pipe diameters, and notes if the meter is incremental (i.e., has upstream flow meters). A schematic of the City’s trunk sewer system including the temporary flow meters, pump stations, flow split manholes, and diversion structures is presented as Figure 2-2. Plots of the flow monitoring data, including flow, velocity, and level, are provided as Appendix A.

During the flow monitoring period, V&A visited all the temporary flow monitoring sites approximately monthly to check meter operation and site conditions, obtain field calibration measurements, and download collected data. Field calibration involves taking manual depth measurements and flow velocity measurements using a portable velocity meter. These calibration measurements were compared to and used to adjust monitor-recorded depth and velocity, if needed. Calibration measurements were taken at different times of day to obtain calibration points for the full range of typical diurnal flows.

TABLE 2-1: FLOW METER SITES
FM
ID Site Location MH ID1 Upstream Meter ID(s) Pipe Size (in)2 1 Lafayette St. north of Calle de Mundo S104-28 4, 7-8, 10-12, 14-15, 19- 22, 26-29 36
2 Parking Lot east of Great America Pkwy and
north of Stars and Stripes Dr S104-26 6, 9, 19-20, 29-30 33 3 Lafayette St. north of Calle de Mundo S104-30 5-6, 9-13, 19-21, 24, 26- 31 42
4 Parking lot of Levis Stadium S94-35 -- 24
5 Mission College Blvd. north of Our Lady’s Wy. S83-21 10, 11, 12, 13, 20, 21, 24, 26, 27, 28, 29, 30, 31 33
6 Mission College Blvd. north of Our Lady’s Wy. S83-22 9, 19-20, 29-30 30 7 Upstream of Primavera Lift Station. S105-34 -- 24
8 Lafayette St. north of Montague Expwy. S86-12 11-15, 20-22, 26-29 30 9 Calabazas Creek north of Scott Blvd. S72-17 19, 20, 29 30 10 San Juan Ave. and Monroe St. S52-79 26-27 24
11 Chromite Dr. and Pilot Knob Dr. S53-40 10, 26-28 24
12 Chromite Dr. and Alhambra Dr. S53-23 10-11, 26-28 24 13 Bowers Ave. just north of Bonnie Dr. S53-54 20-21, 29 30 14 South Dr. south of Loma Vista Ln. S54-16 20-21, 29 15 City of Santa Clara (Project 0012307.00) 2-3 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
FM
ID Site Location MH ID1 Upstream Meter ID(s) Pipe Size (in)2 15 Nvidia Parking lot, west off of Scott Blvd.
south of Central Expwy. S65-50 22 18
16 Central Expwy west of UPRR S67-13 10-12, 14, 20-22, 26-29 27 17 De La Cruz Blvd. north of Martin Ave. (western
sewer) S58-9 22 24
18 De La Cruz Blvd. north of Martin Ave. (eastern
sewer) S58-8 22-23 24
19 North of intersection of Wren Ave. at Kent
Avenue S21-18 -- 24
20 Homestead Rd. west of Cherry Orchard Place S21-47 -- 18 21 Kiely Blvd. north of Hearth Pl. and south of
Kaiser Dr. S23-6 20, 29 24
22 Los Padres Blvd. at Bray Ave. S45-80 -- 18
23 Brokaw Rd. northeast of UPRR S48-31 -- 18
24 Bowers Ave. (southbound) north of Central
Expwy. S63-1 10-13, 20-21, 26-29, 31 33
25 West of De La Cruz Blvd. (southbound) and
east of Walsh Ave. S57-56 10-12, 26- 28 30
26 Machado Ave. east of Santa Cruz Ave. S52-87 -- 21
27 Francis Ave. north of Cabrillo Ave. S43-2 -- 10
28 Amethyst Dr. south of Chromite Dr. and north
of Kearney Ave. S53-46 -- 8
29 Homestead Rd. west of Bond Pl. and east of
Cherry Orchard Pl. S21-55 -- 15
30 Parking lot south of Scott Blvd, north of
Central Expwy., west of Oakmead Village Dr. S72-33 -- 15 31 Uranium Dr. south of Mead Ave. S65-50 -- 10
32 CuSD FM at Homestead Rd. and Swallow Dr. S20-9 -- 15 1 Flow meters were placed on the downstream end of the influent pipe. 2 GIS pipe diameter. Actual diameter as measured by V&A may be slightly different. When manholes have multiple incoming manholes, the largest pipe was monitored.
%
%
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%
%
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23 2&3
1 5
31 22
13 19&20
18 14
28 21
24 6
12 26
10 25
16 29
4 2
15 9A&31
8 9A
11 17
7 20
27 30
3 FM 1
FM 10
FM
11 FM 12
FM 13
FM 14
FM 15
FM 16
FM 17
FM 18
FM 19
FM 2
FM 20
FM 21
FM 22
FM 23
FM 24
FM 25
FM 26
FM 27
FM 28
FM 29
FM
3 FM 30
FM 4
FM 5
FM 6
FM
7 FM 8
FM 9A
FM 31
CuSD Meter
De La
Cruz LS
Westside LS Primavera LS
Rabello PS
Northside PS
Tasman LS
Stadium LS
SC Influent
Junction
Structure
Legend
Figure Exported: 12/31/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk. % 2014-2015 & 2022-2023 Flow Meter Site
% 2022-2023 Flow Meter Site
%, CuSD Flow Meter Site (FM 32)
City of Santa Clara Boundary
Pump Station
San Jose Interceptors
Trunk Mains
Gravity Main
Force Main
Small Diameter Mains
Flow Meter Basin
1 10
11 12
13 14
15 16
17 18
19&20
2 2&3
20 21
22 23
24 25
26 27
28 29
3 30
31 4
5 6
7 8
9A
9A&24
9A&30
9A&31
Figure 2-1
Flow Monitoring
Program
Sewer Master Plan Update
±
0 0.3 0.6 1.2
Miles
San Jose/Santa Clara
Regional
Wastewater Facility
20-26
21-49
10-29 11-41
103-22 103-23
93-53
83-17
104-21 33”@-7.99
104-22
Primavera PS
Westside PS
93-36
Tasman PS
93-52
83-18
73-7
73-30
63-20
53-34
62-6
62-8
62-10
53-105
61-17
61-16
73-29
32-102
ECR
siphon
32-101
32-8
32-45
33-33 33-34
32-68
22-55 22-64
22-52
23-14
33-63
23-24 23-27 24-32
33-5
15-13
25-85
34-6
104-35
104-37
64-34
57-54
58-12
65-30
58-21
58-11
58-22
57-38
58-23
48-2
47-54
35-2
47-58
Trimble to
San Jose Interceptor
36-83
47-59
47-77
48-3
48-11
38-5
38-4 48-48
57-57
38-14
37-48
48-38
47-30
58-3
68-23 68-20
33-4
54-102
25-9
64-46
64-47
56-2
105-37
104-33
105-35
105-6
105-7
105-36
104-49
104-31
105-27
22 6
4 3
2 Figure 2-2: City of Santa Clara Trunk Sewer System Schematic De La Cruz PS
1 # 2014-2015 Temporary Flow Meter Site
Permanent Flow Meter Site
Pump Station
Flow Split Manhole
Junction Manhole
Rabello PS
104-19
Northside PS
Santa Clara
Influent Structure 1
(San Jose)
52-65
10 41-104 42-100
20-9
5 11
12 13
17 18
23 20-16
19 20
14 Walsh Line
M
M2
M1
97-10
Flow Diversion Structure (e.g., weir)
Stadium PS
86-20
95-133
21 8
7 Flow Direction
High-Level Overflow
63-33
54-101
54-100
64-32
41-125
41-113
42-121
42-123 42-125
M
Santa Clara
Junction Structure
M
42”
42”
36”
42”
Control
Chamber
48”
36”
36”
48” FM
D
C
B
A
E
SJ Interceptors
M
24-62
13-38
13-27
13-55
12-50
23-51
23-28
26-44
35-42
26-70
35-20
35-37
35-25
35-17 36-87
36-1
47-60
47-32
47-55
24 25
28 53-47
29 30
9A
82-9
31 52-5
52-4
52-15
2014-2015 and 2022-2023 Temporary Flow Meter Site
52-80
53-74
26 27
# 2022-2023 Temporary Flow Meter Site
#
9 M
20-10
13-26
53-110
15 16
58-17
58-18
58-7 58-6
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2.1.2 Flow Monitoring Data
During the flow monitoring program, V&A routinely inspected the flow meters as discussed above, and temporary flow meter data was uploaded on a regular basis to an online portal (Claros). Claros generates tabular reports and graphs of recorded level and velocity, as well as scattergraphs of level versus velocity.

In addition to V&A’s internal data review and quality analysis procedures, Woodard & Curran staff periodically reviewed the preliminary flow meter data over the course of the monitoring program to inspect for changes in flow indicating potential problems with the flow meter (e.g., debris buildup on the sensor), change in system operation, or customer discharges, or response to wet weather events. V&A provided “final” (quality controlled and adjusted data) after the conclusion of the program.

Two (2) of the temporary flow meters in the Chromite Drive and Machado Avenue area (FMs 11 and 28) experienced data loss during the flow monitoring period that coincided with wet weather events. Although the data loss occurred during periods with significant rainfall, there were still data available at these sites from other rainfall events that occurred during the flow monitoring period. V&A used the available data to recreate data for the missing periods.

Figure 2-3 shows typical plots of measured flow and rainfall for one flow meter for the flow monitoring period between December 2022 and February 2023. Plots of the flow monitoring data, including flow, velocity, and level, are provided for all meters as Appendix A.

FIGURE 2-3: PLOT OF TYPICAL FLOW DATA FOR 2022-2023 FLOW MONITORING PERIOD

0.0 0.5

1.0 1.5

2.0 2.5

0.0 3.0

1.0 2.0

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9.0 10.0
12/16 12/23 12/30 1/6 1/13 1/20 1/27 2/3 2/10 2/17
Rainfall (in/hr)
Flow (mgd)
Date
FM 3 (S104-30, 42-in)
Flow 2022-23 (mgd)
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2.1.3 Additional Monitoring for Dry Weather Flow Verification In addition to the systemwide flow monitoring program conducted during the winter of 2022-2023, V&A also performed selective monitoring per direction from the City and Woodard & Curran as described below.

Review of the flow monitoring data versus model dry weather flows revealed that FM 12 was placed in the incorrect location during the initial winter 2022-2023 flow monitoring program. To remedy this, Woodard & Curran and the City requested that V&A collect one week of dry weather flow data at the correct location over the summer to enable confirmation of model dry weather flows.

Per the City’s request, additional dry weather flow monitoring was also performed by V&A at eight (8) FM sites during a 7-day dry period from December 9-15, 2023 (site map included in Appendix E). The purpose of the additional flow monitoring was to confirm if the sewer system’s routing of dry weather flows was in alignment with the City’s normal operating conditions. The City’s desire for confirmation was due to discrepancies observed during the winter 2022-2023 flow monitoring program and the previous flow monitoring program conducted during the winter of 2014-2015, which were identified during the model calibration process and are discussed further in Section 3.3.

2.2 Basis of Hydraulic Model’s Wastewater Flow Estimates This section presents the basis of wastewater flow estimates for the City’s sanitary sewer system. It describes the wastewater flow components used in the hydraulic model and the existing and projected future land uses for the City, which form the basis for generating base wastewater flows that are applied to the model.

Design flow estimates are based on criteria developed for three major flow components discussed below and confirmed through model calibration as described in Section 3.3.

2.2.1 Wastewater Flow Components
Wastewater flows include three components: base wastewater flow (BWF), groundwater infiltration (GWI), and rainfall-dependent infiltration/inflow (RDI/I), as illustrated conceptually in Figure 2-4.

Base Wastewater Flow (BWF)
BWF represents the sanitary and process flow contributions from residential, commercial, institutional, and industrial users of the system. BWF varies throughout the day, but typically follows predictable diurnal patterns depending on the type of land use. (Note: the hydraulic modeling software refers to BWF as “foul flow.”)
Groundwater Infiltration (GWI)
GWI is groundwater that infiltrates into defects in sewer pipes and manholes, particularly in winter and springtime in low-lying areas. GWI is typically seasonal in nature and remains relatively constant during specific periods of the year. However, rainfall typically has long-term impacts on GWI rates, as evidenced by measurable increases in GWI after prolonged periods of rainfall. (Note: the hydraulic modeling software refers to GWI as “baseflow.”)
Rainfall-Dependent Infiltration and Inflow (RDI/I)
RDI/I is storm water inflow and infiltration that enter the system in direct response to rainfall events, either through direct connections such as holes in manhole covers or illegally connected roof leaders or area drains, or, more commonly, through defects in sewer pipes, manholes, and service laterals. RDI/I typically result in short term peak flows that recede relatively quickly after the rainfall ends. The magnitude of RDI/I City of Santa Clara (0012307.00) 2-8 Woodard & Curran, Inc.

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flows are related to the intensity and duration of the rainfall, the relative soil moisture at the time of the rainfall event, and the condition of the sewers.

FIGURE 2-4: WASTEWATER FLOW COMPONENTS

2.2.2 Base Wastewater Flow Estimates
For the City’s Master Plan Update, BWF loads were developed for existing conditions, near-term future development conditions, and long-term future development conditions. Existing loads were developed based on average winter water use data from the City’s customer billing records, and future loads were based mainly on specific, known development and redevelopment projects combined with the City’s 2035 General Plan (GP) development forecast. The loading methodology for existing conditions and projected near-term and long-term future BWF are discussed further in the following subsections. A summary of the BWF loads associated with both existing and future land use conditions is presented in Table 2-2.

TABLE 2-2: SUMMARY OF BWF LOADS FOR EXISTING, NEAR-TERM, AND FUTURE CONDITIONS1 Existing Conditions Future Conditions
Flow Component Existing Load (mgd)2 Near-Term Load (mgd) Long-Term Load (mgd)3 Residential BWF 6.72 10.11 13.58
Non-Residential BWF 4.49 6.09 15.48
Total Average BWF 11.21 16.20 29.06
1Does not include loads from CuSD, which are discussed in subsequent subsections. 2Estimated existing BWF calculated from winter water use data. 3 Includes 5.09 mgd assumed for entitlement agreements, mostly for non-residential land uses.

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2.2.2.1 Existing BWF Loads
Existing BWF was estimated based on actual water billing records exported from the City’s customer billing database. The City’s Information Technology (IT) group used the Esri ArcGIS software (GIS) to add location identifier fields to the raw billing data, including the assessor parcel number (APN) and service address.

Raw billing data were first processed to exclude non-wastewater generating accounts, which consisted of selecting only the billing data records with field “utility_type” equal to “S” for sewer. By isolating the sewer accounts, the metered potable water and recycled water accounts that do not generate sewer discharges (e.g., meters that serve fire, construction, or irrigation uses) were removed. The City also has customers who use domestic wells and/or recycled water; however, the BWF for these customers were assumed to be included in the sewer billing data per conversations with the City’s finance department.

Each account’s BWF was estimated based on the average water use for three winter periods (December through March) between December 2019 and March 2022. Metered water use during the winter months most closely approximates wastewater generation because outdoor water use is at a minimum. Each user was also assigned one of two land use types (i.e., residential or non-residential) according to the account’s use category designation as shown in Table 2-3.

TABLE 2-3: LAND USE CLASSIFICATIONS AND EXISTING BWFS BY USE CATEGORY Assigned Land Use Use Category1 Use Category Description Existing BWF (mgd) Residential SF Single-family residential 3.20
MF Multi-family residential 3.522
Non-Residential
CI Commercial industrial 3.782
MU Municipal 0.46
MJ Major sewer users 0.25
Total 11.21
1Based on billing data field “CustomerType_Category”.
2A portion of the customers assigned to the “CI” use category in the City’s billing database were re-assigned to the “MF” use category for the purpose of estimating BWFs because they represented water use from multi-family residential buildings. Detailed land use descriptions based on the North American Industry Classification System (NAICS) were used to identify these customers.

The billing data were further processed in GIS for the purpose of associating each billing data point with its physical service location. Most water billing records were geocoded according to the APN from the City’s land parcels dataset. Where parcel APN did not match between the parcel shapefile and the water billing data, billing records were geocoded according to service address. A visual assessment of the City’s water meter locations and parcels using GIS confirmed that the data were available for most significantly developed parcels within the City. Figure 2-5 shows the geocoded water billing data by customer type.

The procedure used to determine the loading point of each parcel is discussed in Section 3.2.3.

Existing Flow from Cupertino Sanitary District (CuSD)
CuSD provides sewer services for the majority of City of Cupertino, portions of the City of Saratoga, and several unincorporated areas within Santa Clara County adjacent to San Jose. Most of the flow is discharged into the Santa Clara system via a 27-inch sewer line in Homestead Road; the rest is discharged into the City of San Jose (CSJ) system at various other connection points.

CuSD maintains a permanent flow meter at its discharge point in Homestead Road. Meter data between December 2022 and February 2023 were reviewed and analyzed; based on the raw data, monitored average City of Santa Clara (0012307.00) 2-10 Woodard & Curran, Inc.

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dry weather flow (ADWF) and peak dry weather flow (PDWF), based on the period from December 17-23, 2022, were about 3.6 and 5.7 mgd, respectively. Similar to the declining trend observed for the City, CuSD’s ADWF has also declined over 20% compared to the 2007 estimate of 4.9 mgd but increased slightly compared to the 2015 estimate of 3.5 mgd. The initial reduction can likely be explained by increased water conservation activities in response to drought and increased efficiency of water fixtures over time as new homes are built or existing homes are remodeled.

For the purposes of model calibration (discussed further in Section 3.3), the monitored flows were used as the BWF loads from CuSD in the model and were applied to the model network as inflow hydrographs.

However, the raw CuSD flow data were adjusted (i.e., reduced by approximately 5% by volume, resulting in a revised ADWF closer to 3.45 mgd) when applied to the model because it was suspected that the CuSD flow meter was recording higher than actual flows. The CuSD flow meter was not calibrated prior to or during the City’s flow monitoring period, whereas the temporary meters installed throughout the City were calibrated by V&A several times. Moreover, the summation of flow data recorded at FMs 19, 20, and 29 (downstream of CuSD) was less than the CuSD recorded flows prior to the adjustment.

Legend
Figure 2-5
Water Billing Data
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

City of Santa Clara Boundary
Billing Data
Customer Type
CI - Non-Residential
MF - Residential
MJ - Non-Residential
MU - Non Residential
SF - Residential
±
0 0.25 0.5 1
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2.2.2.2 Future BWF Loads
Future loads, for both near-term and long-term projected land use conditions, were estimated based on development information tracked by Woodard & Curran, additional development information provided by the City, and unit flow factors developed for the 2016 Master Plan. The development of future load estimates, including the assumed unit flow factors, is discussed further in the following subsections.

Unit Flow Factors for Projected Future Development
Unit flow factors, which are representative of the typical per unit wastewater usage associated with a specific land use type, were referenced for the future load calculations. All unit flow factors used for the calculation are from the 2016 Master Plan and the San José-Santa Clara Regional Wastewater Facility (RWF) sewage coefficient table and are presented in Table 2-4, which also shows the associated density and floor-arearatio (FAR) assumptions where applicable (i.e., for parcels associated with the City’s 2035 General Plan). Unit flow factors were also calculated based on the recent billing data that were used to develop existing BWF loads. The multi-family residential unit flow factors calculated using the recent billing data were around 165 gallons per day per dwelling unit (gpd/DU) on average, which is comparable to the 2016 Master Plan unit flow factor values (i.e., 154 gpd/DU for apartments and 175 gpd/DU for condos and townhomes). However, the single-family residential unit flow factor calculated using the recent billing data (i.e., approximately 175 gpd/DU) was significantly lower compared to the 2016 Master Plan unit flow factor of 245 gpd/DU. The reduction observed in per unit water use consumption for single-family dwellings is reasonable considering that outdoor water use is higher for single-family residential customers and several water use restrictions have targeted outdoor water use and irrigation in response to prolonged drought conditions in California.

However, for the purpose of this Master Plan Update effort, the City elected to use the single-family residential unit flow factor from the 2016 Master Plan, given that this is a planning exercise, and it is a more conservative assumption.

TABLE 2-4: UNIT FLOW FACTORS USED TO ESTIMATE FUTURE BWF LOADS Land Use Category Description Unit Flow Factor2 Density/FAR Assumed3
Very High Density Residential 121 gpd/DU -
Apartments 154 gpd/DU -
Corridor Mixed Use and Community Commercial (Residential) 154 gpd/DU 25 DU/acre Regional Commercial Mixed (Residential) 154 gpd/DU 40 DU/acre Condos and Townhomes 175 gpd/DU -
Corridor Residential 175 gpd/DU -
Single Family Residential 245 gpd/DU -
Office (Low Density) 0.1 gpd/SF -
Agricultural Open Space 0 gpd/SF -
Retail 0.1 gpd/SF -
Community 0.1 gpd/SF -
Amenity 0.1 gpd/SF -
Research and Development (R&D) Office and High-Density Office 0.15 gpd/SF - Daycare 0.183 gpd/SF -
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Land Use Category Description Unit Flow Factor2 Density/FAR Assumed3
Police 0.21 gpd/SF -
Swim center 0.3 gpd/SF -
Retail Mixed or High-Density Retail 0.3 gpd/SF -
Corridor Mixed Use (Non-Residential)1 0.335 gpd/SF -
Regional Commercial Mixed (Non-Residential)1 0.335 gpd/SF - Fitness 0.42 gpd/SF -
Beauty Parlor 0.47 gpd/SF -
Hotel 0.48 gpd/SF or
100 gpd/room -
Medical Office 0.51 gpd/SF -
Restaurant (Small Food Service) 0.9 gpd/SF -
Restaurant (Full Service) 1.04 gpd/SF -
Public (Educational Facilities) 15 gpd/student or

0.21/SF 0.2
Theater 5 gpd/seat -
Assisted Living Facility 77 gpd/bed -
University Residences 70 gpd/bed -
Medium Density Residential 154 gpd/DU 25 DU/acre
High Density Residential 154 gpd/DU 40 DU/acre
Low Density Residential 245 gpd/DU 25 DU/acre
Neighborhood Commercial (Residential) 154 gpd/DU 25 DU/acre Parks/Recreation 0 gpd/SF 0.2
Neighborhood Commercial (Non-Residential) 0.1 gpd/SF 0.3 Community Commercial (Non-Residential) 0.1 gpd/SF 0.4
Regional Commercial (Non-Residential) 0.1 gpd/SF 0.5
Heavy Industrial 0.15 gpd/SF 1.25
Light Industrial 0.15 gpd/SF 0.85
1 Unit Flow factor assumes 25% of full-service restaurants and 75% commercial. 2 gpd = gallons per day. DU = dwelling unit. SF = square foot. 3 Only used for the GP Phase 3 developments. For specific developments, the square footage was provided by the City or the developer.

BWF Loads for Near-Term Future Projected Development
A list of the near-term future development parcels as well as a figure depicting their locations are provided in Appendix B. Near-term future development parcels were identified based on a development tracking spreadsheet that Woodard & Curran created and updated regularly as part of the on-call hydraulic modeling services provided to the City, including near-term future load projections and several development reviews. In January 2023, the City Planning Department reviewed the spreadsheet and City of Santa Clara (0012307.00) 2-14 Woodard & Curran, Inc.

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updated the project development assumptions, including project status and timeline, number of units for projects with residential development and development square footage for projects with non-residential development, where applicable. If the City indicated that a specific development was “approved” or “under construction” as of January 2023, it was assumed to be a near-term future development. City Planning indicated a phased approach would be applied to some of the larger development projects associated with specific plans (e.g., Patrick Henry Drive), in which case a portion of the development was included in the near-term future loading scenario and the remainder was applied to the long-term future development scenario. The land use assumptions (e.g., number of units, office square footage) associated with development projects identified as near-term in the updated tracking spreadsheet were multiplied by the appropriate unit flow factors presented in Table 2-4 to calculate the BWF loads. For near-term specific developments that were also associated with development reviews, the development reviews were referenced to confirm the calculated BWF loads.

When applying the near-term future BWF loads to the model, it was assumed that the existing BWF loads associated with the parcels identified as near-term developments would be replaced.

BWF Loads for Long-Term Future Projected Development
A list of the long-term future development parcels as well as a figure depicting their locations are provided in Appendix B. Long-term future development parcels were identified based on Woodard & Curran’s development tracking spreadsheet discussed above and the City’s 2035 General Plan assumptions. Some of the specific developments in the development tracking spreadsheet were assumed to be long-term future rather than near-term future, mostly in cases where projects were associated with specific plans (e.g., Patrick Henry Drive) and City Planning indicated a phased approach would be applied as discussed in the previous section. Like the near-term BWF loads, the BWF loads associated with the long-term future specific development projects were calculated based on the specific project’s development assumptions and the corresponding unit flow factors. Parcels identified as Phase 3 developments in the City’s 2035 General Plan were also identified as long-term future developments. Some parcels were removed from the original Phase 3 General Plan development parcels dataset, including parcels that were already associated with specific developments and parcels that had been removed from the General Plan based on feedback provided by City Planning. The General Plan designation field (GPLANCRT) of the General Plan parcels shapefile (GeneralPlanParcels_Shapefile.shp) provided by the City was used to assign the appropriate unit flow factors, density, and FAR assumptions to the Phase 3 parcels based on the corresponding land use. The long-term future BWF loads for the Phase 3 parcels were then calculated by applying those assumptions to the square footage (SF) of the parcel. For example, BWF loads for a parcel associated with a GPLANCRT of “Office (High Density)” were calculated by multiplying the area of the parcel by the unit flow factor (0.15 gpd/SF per Table 2-4) and the FAR (1.25 per Table 2-4).

BWFs for the long-term future development scenario also included flow assumptions for entitlement holders that discharge to the City’s sewers. The City is obligated to provide sewer system capacity for entitlement holders up to the flows specified in the entitlement agreements. The City’s billing database records show that many entitlement holders have historically discharged less than their flow entitlements; however, considering the City is required to provide capacity to these users should they have the need to increase their discharges, the long-term future BWF scenario conservatively assumes that all entitlement holders would make use of their full discharge allowances. Flow assumptions for entitlement holders were also included in the City’s 2016 Master Plan. The City reviewed the entitlement flow assumptions that were included in the 2016 Master Plan and updated those assumptions for this Master Plan Update based on available information. The long-term future BWF scenario includes flow assumptions for entitlement holders totaling approximately 5.09 mgd, the vast majority of which is allocated to non-residential land users. In City of Santa Clara (0012307.00) 2-15 Woodard & Curran, Inc.

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limited cases where entitlement flow assumptions were applied to the same parcels with planned future development, the higher flow was applied. Therefore, where entitlement flows were assumed to be less than future flows, the more conservative future flows were used in the model for the long-term future scenario.

The entitlement flow assumptions are documented in Appendix B.

When applying the long-term future BWF loads to the model, it was assumed that the existing BWF loads associated with the parcels identified as long-term developments would be replaced.

Future Projected Flow from Cupertino Sanitary District
Future projected load assumptions for CuSD were incorporated into Santa Clara’s Master Plan Update based on the latest information available from CuSD’s hydraulic model, which was most recently re-calibrated in 2023 by AKEL Engineering. CuSD exported the results from its re-calibrated hydraulic model and provided the flow hydrographs to Woodard & Curran for both near-term and long-term future development projections during both dry weather and wet weather flow conditions. Woodard & Curran created inflow hydrographs based on the results that were exported from CuSD’s re-calibrated model; the magnitude of flows were maintained but the timing was slightly shifted to match the diurnal usage pattern observed in the flow monitoring data and to align the peak wet weather response where applicable. Table 4-6 summarizes the wastewater flow assumptions applied to Santa Clara’s hydraulic model to represent the future projected inflows from CuSD. Note that for the long-term future wet weather flow scenario only, the peak flow was conservatively scaled up to match the contractual limit defined in Santa Clara’s agreement with CuSD which is equal to 13.8 million gallons per day (mgd).

TABLE 2-5: WASTEWATER FLOW ASSUMPTIONS FOR CUSD1
Flow Scenario Average Dry Peak Dry Average Wet Peak Wet (mgd) (mgd) (mgd) (mgd)
Near-Term Future 4.2 6.3 4.6 11.3
Long-Term Future 4.6 6.7 5.9 13.82
1Based on CuSD’s hydraulic model results for a seven (7) day period. 2Assumed to be contractual limit defined in agreement between Santa Clara and CuSD.

2.2.3 Groundwater Infiltration
GWI represents a seasonal increase in wastewater flows due to infiltration into the sewers, typically in lowlying areas or areas close to creeks or other water bodies. In the context of design flow criteria, GWI represents the incremental groundwater infiltration that occurs during the wet weather season which is in addition to the “baseline” groundwater level during the driest months of the year.

GWI is applied in the model as a constant flow in addition to the BWF. The amount of GWI in any particular area of the sewer system is determined during model calibration by comparing the modeled flows to the actual observed dry weather (non-rainfall period) flows at points in the system where flow data are available (e.g., at flow meter sites). Where modeled BWF is noticeably less than monitored dry weather flow by a constant value throughout the day, the difference is assumed to represent GWI. Note that because GWI is seasonal in nature, the modeled GWI is intended to represent a typical GWI rate during the wet weather season (wintertime) rather than a dry season (summertime) GWI. Typical wintertime GWI rates may range from about 100 to 1,000 gallons per acre per day (gpad).

The GWI determined at the monitoring location is then distributed to the upstream meter tributary area on a weighted per-contributing drainage area basis. For Santa Clara, contributing areas for most parcels were set equal to the total area of those parcels. For parcels identified as open space or parks, the contributing City of Santa Clara (0012307.00) 2-16 Woodard & Curran, Inc.

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area was set equal to 0. For parcels identified as schools, the contributing area was assumed to be half of the total area to exclude grass sports fields from the contributing area calculation. All parcels with total areas greater than 5 acres were visually inspected, and the contributing area was zeroed out or reduced if it was determined that significant areas within those parcels did not contribute sewer flows.

2.3 Rainfall-Dependent I/I
RDI/I flows result from rainfall events that produce infiltration and inflow of storm water runoff into the sanitary sewer system. RDI/I can be quantified as the difference between the total flow during and immediately following a storm event and the non-rainfall “base flow” (BWF plus GWI) that is estimated to have occurred during the storm period. RDI/I varies depending on many factors including the magnitude and intensity of the storm event, area topography, type of soil and the degree of soil saturation (due to antecedent rainfall) prior to the storm event, and the condition of the sewers, manholes, and service laterals.

RDI/I is usually expressed as a volume or a percentage of the rainfall volume (termed the “R value”) entering the sewer system from subcatchment contributing areas for each of several flow components representing different response patterns to rainfall events (e.g., fast, medium, slow).

For this modeling effort, five RDI/I response components were used, with each component identified by a percentage of the total RDI/I volume and other parameters that reflect the timing of the flow response, as illustrated conceptually in Figure 2-6. The “fast” component of the hydrograph has the largest impact on the magnitude of the peak wet weather flow response, while the slower components can contribute significantly to the total volume of the RDI/I response. The slowest response component can extend out many days or weeks after the rainfall (alternately, this component could be represented as an increase in GWI). Summing all of the component hydrographs for the duration of the rainfall events results in the total RDI/I hydrograph for that area. R values and hydrograph parameters are determined through the process of wet weather model calibration, discussed in Section 3.5 of this report, in which actual observed rainfall events are simulated in the hydraulic model, and the resulting model hydrographs are compared to the measured flows at the flow meter locations. The RDI/I parameters are adjusted as needed to achieve the best match of modeled to monitored flows. The same calibrated parameters are generally applied to all subcatchments within each meter area. Once calibrated, the model RDI/I parameters can be applied to a design storm to simulate wet weather flows for a design event.

FIGURE 2-6: RDI/I HYDROGRAPH COMPONENTS
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3. HYDRAULIC MODEL DEVELOPMENT AND VALIDATION
This section provides an overview of the hydraulic modeling software and modeling terminology and describes the hydraulic model development and validation process, which includes discussion of the modeled sewer network and facilities as well as the methodology and results associated with calibration of the hydraulic model.

3.1 Hydraulic Modeling Software and Modeling Terminology The modeling software used for development of the Master Plan Update hydraulic model was InfoWorks ICM™ by Autodesk (InfoWorks or ICM), a fully dynamic hydraulic model that was used for Santa Clara’s 2016 Master Plan and the development reviews completed since as well as for many other wastewater systems in the Bay Area, including San Jose and Sunnyvale. InfoWorks uses the implicit method to solve fully dynamic equations of motion (St. Venant equations) for all pipe segments simultaneously at each time step. Detailed information regarding the model software and hydraulic theory (i.e., solution model, equation system, solver, and modeling features) can be found on Innovyze’s help webpage1. Implicit solvers tend to be more stable than explicit solvers with pumping situations and perform better than explicit solvers when dealing with short pipes and loops in the network. Woodard & Curran used its own InfoWorks licenses for this work.

Key hydraulic modeling terms are defined below.
• Network refers to the representation of the physical facilities being modeled. Modeled network components include pipes, manholes, pump stations, etc. • Nodes are primarily manholes, but also include pump station wet wells and outfalls (discharge points from the modeled system). Key data associated with nodes include manhole ground elevations and pump station wet well elevations and cross-sectional areas. • Pipes or conduits are connections between nodes and include both gravity sewers and force mains.

Key data associated with pipes are upstream and downstream node IDs, pipe length, diameter, roughness and headloss factors, and upstream and downstream invert elevations. • Pumps are modeled individually, connecting pump station wet wells with the upstream node of associated force mains. Data associated with pumps include type (e.g., fixed or variable speed), on and off levels, pump capacities, and pump discharge curves. • Subcatchments (also called sewersheds or subbasins) are areas that contribute flow to the modeled sewer network. Data associated with subcatchments include sanitary flow (computed based on population, water use, or other available data), type of diurnal sanitary flow profile (which is a function of land use), infiltration/inflow (I/I) parameters, and the node at which the flow from the subcatchment enters the modeled system.
• Model loads are the flows entering the modeled sewer system from each subcatchment. Model loads include residential and commercial sanitary or BWF, GWI, and RDI/I. As a sum, they represent the total sewer system flow applied to the model. Development of model loads is discussed in Section 2.2.
1 Innovyze Help Menu Documentation on Hydraulic Model Theory, available online at:
https://help2.innovyze.com/infoworksicm/Content/HTML/ICM_ILCM/Hydraulic_Theory.htm.

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• Models are the combination of a modeled network, its associated subcatchments and loads, and other data (e.g., rainfall, diurnal profiles, inflows from other areas, etc.) that comprise a specific model scenario.

3.2 Hydraulic Model Network Development
The hydraulic model network includes the pipes, manholes, and other physical facilities that comprise the modeled sewer system. This section describes the modeled system, including how the sewer facilities are represented in the model, the data attributes that describe the facilities, and the processes for validating those data.

3.2.1 Modeled System
The hydraulic model network developed for this Master Plan Update includes all City-owned pipes within the sanitary sewer system based on the City's GIS data layers. Approximately 12 miles of privately-owned sewer mains were excluded from the model network; therefore, the network consists of about 276 miles of sewers, including 2.7 miles of force mains, or roughly 96% of the total 288 miles of sewer pipeline within the City’s system. The hydraulic model also includes all seven sewage pumping stations. The 2016 Master Plan model was developed to represent the trunk or “backbone” of the sewer system and as such contained approximately 34% (or 94 miles) of the total length of the City’s sewers. Woodard & Curran has maintained and updated the model as sewer improvement projects were implemented, development reviews were requested, or when new network data became available, and this Master Plan Update built on that work by significantly expanding the model network to include all City-owned sewer pipelines. A summary of the pipes and other facilities included in the hydraulic model network is presented in Table 3-1.

TABLE 3-1: SEWER SYSTEM MODEL PIPE SUMMARY
Pipe Diameter (in) Total Length1(ft)
4-6 199,600
8-10 757,800
11-12 222,000
14-16 63,800
17-21 60,100
22-24 48,200
27-29 16,200
30 26,600
>30 47,700
Force Main 14,400
Total Length (feet) 1,456,400
Total Length (miles) 276
Approx. No. of Manholes 5,500
No. of Siphons 34 (59 barrels2)
1Rounded to the nearest hundred feet.
2Some siphons have multiple barrels: Three (3) siphons have three (3) barrels, 19 siphons have two (2) barrels, and the remaining 12 siphons have a single barrel.

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3.2.2 Model Network Construction and Validation
The updated and expanded model network was constructed using the City’s current GIS files of the sewer system, network data from the previous trunk model, 2020 LiDAR ground elevation data, invert data obtained during previous master planning efforts on the small diameter pipes in the system, review of selected record drawings, and limited field investigations.

The GIS shapefiles were used to spatially define the model network, as well as to initially populate asset properties of pipe diameter, pipe length, and pipe material. Invert and rim elevation data were not included in the City’s GIS data but are essential for the model. Therefore, elevation data were obtained from a combination of data sources.

For manhole rims, elevations were assigned based on LiDAR ground elevation data as obtained from the County of Santa Clara1. Elevations were adjusted from NAVD 88 to NGVD 29 by -2.69 feet based on the National Geodetic Survey Coordinate Conversion and Transformation Tool2. The same datum adjustment was used for the 2016 Master Plan and ongoing modeling studies.

For sewer pipe inverts, elevations were populated using the trunk model that was developed for previous master plan efforts (updated on an ongoing basis), small-diameter pipe invert elevations obtained during previous master planning efforts, and depth data from the City’s current GIS (invert estimated by subtracting the depth from the inferred manhole rim), in order of priority. For areas with missing data or in areas where more information was needed to construct the model, additional as-built drawings and field investigations were requested and incorporated.

For sewer pipe diameters, diameters of trunk sewer pipes were assigned based on the trunk model that was developed for previous master plan efforts (updated on an ongoing basis). In select cases where as-builts from specific pipeline lining projects were available (e.g., along the Calabazas trunk near Kifer Road), diameters for lined pipes in the trunk system were updated to reflect their internal diameters. Nominal diameters were assumed for all other pipes. Diameters of small-diameter pipes (not included in the trunk model) were populated from the City’s current GIS.

Several model construction and validation processes were applied to review the initial data that were imported into the model network. The goal of the review was to resolve potential connectivity and data entry errors associated with the GIS data. The result of the model construction and validation process was a fully connected, all-pipe model network representing the City’s physical sewer infrastructure (i.e., pipes, manholes, and special structures) and sewer system inflows from individual parcels throughout the City (i.e., subcatchments).

Model construction and network validation processes included the following:
• The model network was checked for connectivity, i.e., verifying that correct upstream/downstream manholes were identified for each pipe and that there were no missing links in the network.
• Model special structures, such as siphons, sluice gates, weirs, orifices, and pumps were added as described in Section 3.2.4. As-built drawings and field data were used to develop details for 1 Elevation data (2-foot resolution, hydro flattened digital terrain model (DTM) developed based on LiDAR) were published by the County of Santa Clara. The data are available for download here:
https://www.arcgis.com/home/item.html?id=44a391b570a14d4687591fa2e89ebb11 (last updated October 2022). 2 Tool used to determine height adjustments between vertical datums at specific locations of interest. Available online at: https://geodesy.noaa.gov/NCAT/.

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the modeled pump stations, such as wet well elevations and dimensions, number of pumps, pump types, on/off levels, and discharge curves.
• Flow splits (manholes with more than one outlet pipe) were identified, and field verification and/or as-built drawings were requested as needed for further verification of outlet pipe elevations and/or the existence of weirs or other flow diversion structures (refer to Section

3.2.4).
• Manhole and pipeline network data, including rim and invert elevations and pipeline sizes, were assigned based on the following:
▪ In select locations, record drawings for several pipelines were provided by the City and were used to refine elevation, size, and connectivity information. User text fields within the model were used to document the title of the referenced record drawing.
▪ Where invert elevation data were missing or inconsistent with nearby elevations, and not determined through as-built information, interpolated values between known values were used as appropriate or pipe slope was used to infer invert elevations at the upstream ends of the system.
▪ Elevation data in the as-builts were adjusted as needed to the NGVD 29 datum. • Based on the data provided by the sources above, SQL scripts were created and run in order to identify missing or suspect data in the modeled network. Profiles were plotted for each series of pipe segments identified by the scripts to visually check for missing rim or invert elevations, negative or reverse pipe slopes, or abrupt steps up or down in pipe inverts. Where data indicated a discrepancy, an approach to resolve the discrepancy was identified and data were either interpolated or verified through field investigations conducted by the City or as-built drawings. Profiles were also plotted for major trunk sewers and a random subset of sewers within the system to check for missing or suspect data. • The sources of model data (e.g., GIS, as-built/record drawings, survey/field investigation) were documented using “flags” in the model database.
• All gravity pipelines were modeled assuming a Manning’s n of 0.013. • Headloss coefficients for pipelines were inferred using InfoWorks ICM’s “Inference Data Editor” tool, which infers the upstream and downstream headloss coefficients for a pipe based on the planar intersection angle at manholes or other model nodes. Larger intersection angles correspond to higher headloss coefficients.
• Model subcatchments were created to represent parcels and their wastewater discharges as discussed in Section 3.2.3.

3.2.3 Subcatchments
Model subcatchments define areas tributary to the modeled pipe network. For this new all-pipe model, each subcatchment represents a single assessor parcel within the City and “loads” to a pipe or pipes in the modeled network to define where flow from that parcel enters the sewer system. The model includes approximately 23,300 subcatchments, ranging in size from less than 1 acre to 110 acres.

To assign the load pipes to subcatchments, the laterals shapefile from the City’s GIS was used. Load pipes were assigned to subcatchments based on proximity to the closest lateral and were defined as the sewer City of Santa Clara (0012307.00) 3-5 Woodard & Curran, Inc.

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pipe intersecting with the closest lateral. This process assigned a loading pipe to each of the parcels. A visual inspection complemented the process where parcels either did not have a lateral nearby or had multiple laterals. The load pipes are then refined as needed as part of the calibration process (discussed in Section

3.3). Additional discussion of model load development and allocation is provided in Section 2.2.

3.2.4 Special Structures and Flow Splits
Special structures discussed in this section include siphons, gates, weirs, and pumps. Some of these structures were not included in the GIS database of pipes and manholes and therefore were manually added to the model network based on their location. In most cases, the trunk model data were referenced when manually adding these special structures to the model network because most of the special structures were already included in the trunk model used for development reviews. The information specific to each structure that was extracted from the existing trunk network was complemented with information from asbuilt drawings and/or other information provided by the City where available. Overall, the trunk network included 26 weirs, three (3) gates (at two (2) manholes), and one (1) orifice. The all-pipe model network includes the same number of gates and orifices but two (2) additional weirs, so 28 weirs in total.

3.2.5 Pump Stations
All seven (7) of the City’s sewage pumping stations are included in the model network. Pump data summary sheets provided by the City and available record drawings for the lift stations were used to configure the pump stations in the model. Pump on/off levels (converted to elevations) were based on the on/off wet well levels indicated in the pump station summary sheets and as-builts received as part of the 2016 Master Plan and updates received since. Firm capacity (i.e., capacity with the largest pump out of service) and total capacity for each pump station were estimated based on basic information, pump settings, pump curves, and system curves provided by the City. City staff confirmed that none of the pump stations are equipped with variable frequency drives (VFDs). Table 3-2 presents a summary of modeled pump stations, including their estimated firm and total capacities; the calculations for which are provided in Appendix C. The locations of the City’s pump stations are shown in Figure 1-1.

TABLE 3-2: SEWER SYSTEM MODEL PUMP STATION SUMMARY
No. Pump Station Name No. of Pumps Firm Capacity
(mgd)1
Total Capacity
(mgd)
1 Westside 2 1.552 2.532
2 Tasman 2 1.612 2.342
3 De La Cruz 2 1.612 2.522
4 Primavera 6 5.722 6.392
5 Stadium 6 2.562 2.682
6 Rabello 8 25.43 27.94
7 Northside 4 19.83 21.34
1 Firm capacity is defined as the capacity with the largest pump out of service. 2 Theoretical firm and total capacities were estimated for Westside, Tasman, De La Cruz, Primavera, and Stadium Pump Stations based on basic information, pump settings, pump curves, and system curves provided by the City. Refer to Appendix C for detailed calculations for each pump station. 3 Theoretical firm capacities for Rabello and Northside Pump Stations were estimated by Schaaf & Wheeler Consulting Civil Engineers (S&W) as reported in a memorandum titled “Northside and Rabello Pump Station Firm Capacity Evaluation”, dated July 5, 2022.

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4 Theoretical total capacities for Rabello and Northside Pump Stations were estimated using excel spreadsheet tools developed by Schaaf & Wheeler as part of the firm capacity study (refer to footnote 3). System curves for total capacities were estimated based on inferred data because Schaaf & Wheeler did not collect test points with all pumps running.

3.2.5.1 Siphons
The model includes 59 inverted siphons ranging in diameter from 6 to 24 inches; 12 of these are singlebarrel siphons, 38 are part of double-barrel siphons (i.e., at 19 locations), and 9 are triple-barrel siphons (i.e., at 3 locations). Siphons were added to the model as pipes with lengths that reflect actual siphon geometry as obtained from record drawings (sum of downslope, horizontal, and upslope portions). A sample siphon profile is shown in Figure 3-1.

FIGURE 3-1: SAMPLE SIPHON PROFILE
Siphons include downslope, horizontal, and upslope portions, but can be modeled appropriately without the downslope and upslope segments as shown in Figure 3-1. Record drawing information incorporated into the model includes siphon size, invert elevations, segment lengths and locations of the angle points.

Where record drawings were not available, GIS data and/or other information provided by the City was referenced. The following rules were applied in the modeling of siphons:
• Siphons with two or more barrels were represented as separate pipes connecting to the same upstream and downstream nodes with diameter and elevations specified for each pipe. • The friction factor (Manning’s “n”) was set to the same value (0.013) as those specified for gravity pipes elsewhere in the modeled system.

All siphons were assumed to operate under self-cleansing conditions preventing any major sediment buildup. Therefore, no sediment was included in the model siphons.

A list of the siphons included in the hydraulic model and the corresponding assumptions is provided in Appendix F.

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3.2.5.2 Flow Splits
Flow splits, or diversions, are nodes in the system with two or more downstream pipes. The City collected survey information at key flow split locations that Woodard & Curran identified to confirm invert elevations, rim elevations, and flow conditions. The field-collected survey information (data sheets included as Appendix D) was used to update the model attribute information.

Examples of key connections, flow splits, and diversion structures include the following:
• Connection at Homestead Rd. and Swallow Dr. that sends CuSD’s sewer flows to Santa Clara’s system via a 27-inch sewer line.
• Diversion structure modeled to divert part of the flow going to Northside PS and to Rabello PS. • Flume structure modeled to split the flow to the sewer going north on Lawrence Expwy and the sewer going east on Homestead Rd. (refer to Figure 3-2).

FIGURE 3-2: FLUME DIVERSION STRUCTURE TO HOMESTEAD RD. OR LAWRENCE EXPWY.

3.3 Model Calibration Process and Results
This section discusses the model calibration methodology and results. Model calibration is the process of comparing model-simulated flows to monitored (observed) flows and adjusting model parameters until a reasonably good match is achieved. It is not expected that the calibration results in an exact match between modeled and observed flows at every meter at all times; however, modeled flows at most meters should reasonably match the flow volumes and peak flows in the observed data. Model calibration was achieved first through comparing modeled versus metered flows during a dry weather (non-rainfall) period to achieve an accurate prediction of BWF and GWI, and then during a wet weather period to estimate the RDI/I response.

3.4 Dry Weather Flow Calibration
This section discusses the methodology and procedures used to calibrate the model for dry weather flow conditions and presents the results of the dry weather calibration.

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3.4.1 Dry Weather Flow Calibration Methodology
The goal of dry weather calibration is to confirm that the modeled flows and hydraulic conditions are reasonable compared to the metered flows during non-rainfall periods. Dry weather calibration is an iterative process; if legitimate differences are found between modeled and metered flows, these differences are investigated, and adjustments would be made to the modeled flows as appropriate.

The general approach to dry weather flow calibration was as follows:
1) Confirm overall model loads match metered flows. Compare total model flows to metered flows at the most downstream flow meters (FM1, FM2, FM3). If significant discrepancies are identified, review the model loads and billing data for major issues. Investigate and resolve issues. 2) Compare modeled and metered average flows to identify major discrepancies. Starting at the upstream ends of the system and continuing downstream until the model outfall, identify any flow meters where the difference between average modeled and metered flows is greater than 30%. If discrepancies are identified at a meter, review the tributary model loads and associated billing for major issues and/or flow routing at flow splits and diversion structures. Investigate and resolve issues.
3) Compare modeled and metered average flows to identify modest discrepancies. Starting at the upstream ends of the system and continuing downstream until the model outfall, identify any flow meters where the difference between average modeled and metered flows is between 10% and 30%. If discrepancies are identified at a meter, review parcel loading assignments, major dischargers, or need to use a return factor or discharge cap for selected residential customers. Some modest discrepancies in average flows could be due to the need to add GWI, which are considered in conjunction with review of diurnal patterns. Investigate and resolve issues. 4) Compare modeled average flows to pump station SCADA. If hourly pump station SCADA are available, compare the data to modeled flows.
5) Review diurnal patterns. Balance adjustment of diurnal patterns with the need to add constant GWI. Adjust patterns as needed or as available information allows for large users (customers with average water use above 50,000 gpd), permitted industrial dischargers (particularly those with batch discharges), and event venues with highly variable use (e.g., Levi Stadium). 6) Review flow monitoring and model surcharge status. If the model predicts any surcharge during DWF, those locations should be reviewed for potential network data errors.

For meters that are downstream of multiple other meters, a flow balance was performed to confirm that the total upstream metered flow is less than or equal to the downstream metered flow (e.g., if FM 3 is downstream of FM 1 and FM 2, then FM 1 flows + FM 2 flows should be ≤ FM 3 flows).

3.4.1.1 Review of Largest Water Users
A total of 22 accounts with average winter water use of over 50,000 gpd were identified based on the billing data, which are summarized in Table 3-3 and shown in Figure 3-3. During calibration, average flows from these large users were reviewed. Only base flows from the account located at 444 Saratoga Avenue were adjusted from the initial water consumption value presented below to better match modeled and metered flows; base flows were reduced by approximately 20% because an 80% return factor was applied to the FM 22 tributary area as discussed in Section 3.4.2. This adjustment was reasonable given that it is a very large multi-family residential property with a significant amount of irrigated landscape surrounding the 468 units.

Several of these large users were assigned distinct diurnal patterns as discussed in Section 3.4.1.2.

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TABLE 3-3: CITY’S LARGEST WATER USERS (WATER USE GREATER THAN 50,000 GPD) Account Holder Account
No. Address APN Customer Type2 NAICS Class Description3 Avg Water Use (gpd)4 ELEC DEPT 72271 850 Duane Ave 224-08-153 MU Other General Government Support (Power Plant) 345,810

CALIFORNIA
PAPERBOARD 63199 525 Mathew St 230-03-090 MJ Paperboard Mills 239,508 INTEL CORPORATION 64334 3065 Bowers Ave 216-46-015 CI Semiconductor & Related Device Manufacturing 137,542

THE IRVINE
COMPANY LLC 82043 3355 Octavius Dr 216-45-058 CI Lessors of Nonresid. Build. excpt Miniwarehou 125,548

SUMMERHILL
LAWRENCE LLC1
81664 3494 Toomey Pl 216-60-025 CI New MF Housing Const Excpt Operative Builders 119,422

CORESITE

CORONADO

STENDER LLC
62292 3035 Stender Wy 216-29-084 CI Bare Printed Circuit Board Manufacturing 115,565
ELEC DEPT 64922 524 Robert Ave 230-03-067 MU Other General Government Support (Power Plant) 115,177
KAISER PERMANENTE 68692 702 Lawrence Expy 316-09-046 CI General Medical and Surgical Hospitals 109,415

SUMMERWOOD AT
SARATOGA CA INC 64126 444 Saratoga Ave 294-04-000 MF Lessors of Residential Buildings and Dwelling 101,166 APPLIED MATERIALS 64284 3300 Scott Blvd 216-49-024 CI Semiconductor & Related Device Manufacturing 100,189
INTEL CORPORATION 64352 2150 Mission College Blvd 104-48-010 CI Semiconductor & Related Device Manufacturing 89,168
3515-3585 MONROE
STREET LLC1
76100 3555 Monroe St 216-25-008 CI New MF Housing Const Excpt Operative Builders 83,570

VANTAGE DATA
CENTERS LLC 64337 2880 Northwestern Pkwy 216-28-133 CI Semiconductor & Related Device Manufacturing 83,110

STREAMLINE
CIRCUITS CORP 62970 1415 Richard Ave 224-06-170 CI Bare Printed Circuit Board Manufacturing 73,936 City of Santa Clara (Project 0012307.00) 3-10 Woodard & Curran, Inc.

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Account Holder Account
No. Address APN Customer Type2 NAICS Class Description3 Avg Water Use (gpd)4 APPLE INC 76270 3250 Scott Blvd 216-29-117 CI All Other Business Support Services 63,907

CYXTERA DATA
CENTERS INC 61293 4650 Old Ironsides Dr 104-04-077 CI Data Processing, Hosting, & Related Services 61,571

WOODSBOROUGH
HOMES ASSOC 64115 950 Kiely Blvd 290-62-000 MF Othr Orgs (HOA, TOA, Tennant Assoc&Similar) 59,979

DIGITAL REALTY
TRUST LP TOTALZ 78636 2220 De La Cruz Blvd 230-03-108 CI Data Processing, Hosting, & Related Services 59,632

SANTA CLARA
UNIVERSITY 64018 500 Lafayette St 269-38-090 CI Rooming and Boarding Houses 57,109

FUJIFILM DIAMATIX
INC 82985 2230 Martin Ave 224-10-126 CI R&D in Physical, Engineering & Life Sciences 53,903

PROMETHEUS REAL
ESTATE MS #2 61640 4101 Lick Mill Blvd 097-08-100 MF Lessors of Residential Buildings and Dwelling 53,215 APCT INC 61520 3495 De La Cruz Blvd 101-15-033 CI Radio&TV Broadcast&Wireless Comm Equip Manuf 51,944
1Recent new construction.
2MU = Municipal; MJ = Major User; CI = Commercial Industrial; MF = Multi-Family Residential. 3NAICS = North American Industry Classification System. Federal standard used to classify businesses by type. 4Estimated based on winter water use billing data (“utility_type” = sewer records from December 2021 - March 2022). May not correspond directly with the largest sewer dischargers, especially in cases where large volumes of water may be used onsite and therefore not discharge to the sewer system (e.g., data centers). Sewer flows from large users are reviewed and updated as appropriate during the dry weather calibration procedure.

APCT INC

ELEC DEPT

APPLE INC

NVIDIA CORP

KAISER PERMANENTE

APPLIED

MATERIALS

INTEL CORPORATION

CALIFORNIA PAPERBOARD

FUJIFILM DIAMATIX INC

SANTA CLARA UNIVERSITY

SUMMERHILL LAWRENCE LLC

WOODSBOROUGH HOMES ASSOC

CYXTERA DATA CENTERS INC

VANTAGE DATA CENTERS LLC

STREAMLINE CIRCUITS CORP
3515-3585 MONROE STREET LLC
PROMETHEUS REAL ESTATE MS #2

SUMMERWOOD AT SARATOGA CA INC

DIGITAL REALTY TRUST LP TOTALZ

CORESTIE CORONADO STENDER LLC

THE IRVINE COMPANY LLC
Legend
Figure Exported: 12/31/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

Largest Water Users (greater than 50,000 gpd)
City Boundary
Trunk Mains
Gravity Main
Force Main
Small Diameter Mains
Figure 3-3
Top Water Users
Sewer Master Plan Update
±
0 0.25 0.5 1
Miles
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3.4.1.2 Diurnal Pattern Development and Refinement
In most sewer systems, BWF typically exhibits distinctive diurnal patterns depending on the land use, usually categorized as residential and non-residential. BWF varies throughout the day in a typical way, generally peaking early in the morning in most predominantly residential areas. Typical hourly peaks from residential areas tend to be about twice the average flow. Higher peaks can occur on atypical days of the year (e.g., on major holidays such as Thanksgiving or at halftime on Super Bowl Sunday). For Santa Clara’s sewer model, typical diurnal patterns were developed for residential and commercial/industrial (i.e., non-residential) wastewater flows for both weekend and weekday conditions. Additional non-residential patterns were also developed for specific large users. The patterns were applied to the subcatchment BWF in the model based on the subcatchment’s land use and location.

During the dry weather calibration process, the typical residential and non-residential diurnal patterns developed were reviewed and updated accordingly based on a comparison of modeled versus metered flow data. The typical residential diurnal pattern developed for the 2016 Master Plan (shown in Figure 3-4) was adjusted to better match the more recent flow meter data, which showed a later and less peaky residential morning peak that can likely be explained by lifestyle changes associated with the COVID-19 pandemic including work-from-home trends. Diurnal patterns exhibited at specific meters that receive predominantly residential flows (e.g., FM 22) were reviewed to refine the residential diurnal curve. The residential diurnal curve that was developed for the Lafayette Area (northeastern part of the City in the vicinity of Lafayette St. and Montague Expwy.) during the 2016 Master Plan (shown in Figure 3-4) was also reviewed and compared to the flow monitoring data. Based on the comparison, it was not evident that this distinct, peakier pattern was still an appropriate representation of base flows from this area, so it was removed from the model.

FIGURE 3-4: RESIDENTIAL DIURNAL PATTERNS
Pattern 1: Typical Residential Flow Pattern 2: Lafayette Area Residential Flow (not used) Similarly, typical non-residential diurnal patterns developed for the 2016 Master Plan (shown in Figure 3-5) were reviewed based on a comparison between modeled versus metered flow data. Specifically, diurnal patterns exhibited at meters that receive predominantly non-residential flows (e.g., FM 17) were reviewed to determine if refinement of existing and/or development of alternate non-residential diurnal curves was warranted. Based on the review, it was determined that the non-residential curves used for the 2016 Master Plan were still an appropriate representation of the typical base flows, so no adjustments were made.

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FIGURE 3-5: NON-RESIDENTIAL DIURNAL PROFILES
Pattern 1: Commercial Flow1 Pattern 2: Industrial Flow
Operational information regarding sewer discharge patterns for permitted industrial dischargers within the City was obtained during the 2016 Master Plan and was used to create individual non-residential diurnal curves for specific dischargers at that time based on batch discharge information indicated on their wastewater discharge permits or surveys. Individual diurnal patterns developed during the 2016 Master Plan were applied to the following specific non-residential dischargers: Levis Stadium (assuming a 1:00 pm home game), Great America Waterpark, Agilent, Digital LLC, Oracle, City Electric Department (power plants), Applied Material, Owens Corning, APCT Inc., Marvell Semiconductor, Intel, and Streamline Circuits. Woodard & Curran attempted to obtain more recent batch discharge information for permitted industrial dischargers from the City of San Jose but was unsuccessful. However, based on review of the modeled versus metered flow data, the individual patterns obtained for the 2016 Master Plan and applied to specific non-residential dischargers in the model reasonably represented their base flows.

3.4.2 Base Flow Adjustments and Addition of GWI
To better match the modeled and metered flows, some base flow adjustments were applied during the dry weather calibration process. Existing base loads from residential customers, both single-family and multifamily, were capped at a maximum of 300 gpd/dwelling unit. Even though the loads were developed using winter water use billing data (typically the season with the lowest outdoor irrigation), it is likely that some outdoor irrigation is still occurring, so this cap on residential water use was applied to reduce the impacts of excessive outdoor irrigation. Additionally, a return factor, which represents the proportion of water used that is returned to the wastewater system, was considered for the basins where modeled base flows were significantly higher than observed flows. A return factor of 80% was applied to the base flows from upstream basins that primarily collect sewer flows from single-family residential properties (FMs 21, 22, and 23) also to try to remove outdoor irrigation from the water use data to better match modeled and metered flows. A similar return factor was applied to these upstream basins during the 2016 Master Plan effort.

After the base flows adjustments described above were applied, GWI was then added when the observed (metered) dry weather hydrographs were greater than the model-simulated hydrographs by a relatively constant value throughout the day. A total of 0.158 mgd of additional GWI flow was applied to the system uniformly throughout 2 of the 32 flow meter areas at a rate of 250 gpad for FM 26 and 1,800 gpad for FM

31. It should be noted that it may be difficult to assess the actual amount of GWI in any given area, as the relative accuracy of the flow monitoring data, water consumption data, and other model assumptions may affect the amount of flow attributed to GWI. However, this methodology is considered adequate for modeling purposes. It should be noted that this estimate is representative of early-season GWI; however, GWI typically increases throughout the wet weather season as the soil progressively becomes saturated as

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Weekend

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Time
Weekday
Weekend
Flow Factor
Flow Factor
1Same profile assumed for weekday and weekend.

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more rainfall occurs. Late-season GWI or extended rainfall-dependent infiltration is accounted for during wet weather calibration.

3.4.3 Dry Weather Flow Calibration Results
The seven (7) day dry period from December 17 through December 23, 2022 was used as the primary dry weather calibration period for comparing flow data from the 2022-2023 flow monitoring program to the model results. The primary focus of the dry weather calibration was to confirm that the calculated average BWF based on winter water consumption was consistent with the measured flows at the meter locations.

The other objectives of the dry weather calibration were to confirm the flow routing in the system, particularly in areas where flow can be diverted in more than one direction (flow splits), as well as to confirm the diurnal profiles used to represent the hourly variations in BWF. The diurnal curves shown in Figure 3-4 and Figure 3-5 were developed and/or confirmed based on the calibration.

Table 3-4 compares the model versus meter average dry weather flows at the downstream most flow meters, Table 3-5 and Table 3-6, respectively, compare the model versus 2022-2023 and 2014-2015 meter average dry weather flow at each meter location, and Figure 3-6, Figure 3-7, and Figure 3-8 show plots of model versus metered dry weather flow for the total flow at the downstream-most meters (FM 1, FM 2, and FM 3, respectively). In these graphs, the green line represents the monitored (observed) flow, and the red line represents the model-simulated flow. Dry weather calibration plots of model-predicted versus metered flows at all flow meter locations for both 2022-2023 and 2014-2015 are provided as Appendix E.

As indicated in Table 3-5, the dry weather model calibration resulted in a reasonably good match of modeled to metered flow (within 10% at the downstream most flow meters). A comparison of 10% is considered a good match due to fluctuations in flows typically observed over time, as well as potential errors inherent in metering flows in a field environment. At meters with very low flows, small differences between modeled and metered flows can result in a relatively large percent difference; therefore, at these meters (e.g., FM 30), modeled flows within 0.1 mgd of the meter data were also considered a good match.

However, it should also be noted that review of the 2022-2023 flow meter data and comparison to the 2014-2015 data collected for the 2016 Master Plan revealed significant differences that, upon further investigation, were determined to be caused by temporary system conditions that were not representative of typical operations. The initial calibration showed significant, unexpected differences between modeled and metered flows along the Calabazas and Bowers trunks downstream of the Lawrence/Homestead gate structure (pictured in Figure 3-2). Through additional review of flow data collected for the 2016 Master Plan; system data and potential flow split locations; and field investigation by City staff, it was determined that the likely cause of the differences was two-fold. First, the Lawrence/Homestead gate structure was likely clogged with rags during the flow monitoring period, causing more flow than expected to be routed to the Calabazas trunk. Second, it was surmised that some issue in the Calabazas trunk (possibly a temporary blockage) caused significant surcharging, enough to reach the level that would route flows away from the Calabazas trunk and into the Bowers trunk through a higher-level split at El Sobrante. Moreover, this second condition seemed to change over time, with significant shifts in metered flows observed at FM 9A, with corresponding shifts at FM 13. These temporary, atypical system conditions that were present during the 2022-2023 flow monitoring period are discussed further in Section 3.4.3.1.

The dry weather calibration results presented in Table 3-5 are based on a model run that attempted to replicate the first difference (clog at the Lawrence/Homestead gate structure), but the second difference (Calabazas trunk backup into Bowers trunk) could not be replicated in the model because although a blockage was suspected based on the data, it was not identified or confirmed at a specific location. Given that the dry weather calibration should be performed assuming normal operating conditions, the 2014- City of Santa Clara (Project 0012307.00) 3-15 Woodard & Curran, Inc.

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2015 flow meter data was also compared to the dry weather model calibration results (with the Lawrence/Homestead gate structure settings back to normal) for the locations affected by the two issues discussed above. Table 3-6 presents the results of that comparison.

TABLE 3-4: DRY WEATHER FLOW CALIBRATION RESULTS SUMMARY1 FM IDs
Discharge
Location
Meter ADWF
(mgd)
Model ADWF
(mgd)
Difference
(mgd)2 Difference (%)2
1+2+3
Lafayette and
GAP3 Trunks (FM
1+FM 2+FM3)

10.54 10.09 -0.45 -4.3%
16+17+18+25
Trimble Trunk
(FM16+FM17 +
FM18 + FM25)

4.65 4.46 -0.19 -4.1%
1Model results are compared to the 2022-2023 flow monitoring data. 2 Difference is reported as model flow minus meter flow. 3 GAP = Great America Parkway.

TABLE 3-5: DRY WEATHER FLOW CALIBRATION RESULTS VS. 2022-2023 FLOW MONITORING DATA1

FM ID GWI
(gpad)
Return
Factor
Applied (%)2
Meter
ADWF
(mgd)
Model
ADWF
(mgd)
Difference
(mgd)3
Difference
(%)
1 - - 2.91 2.91 <-0.01 0.1%
2 - - 4.71 4.57 -0.14 -3.0%
3 - - 2.92 2.61 -0.31 -10.6%
4 4
- - 0.03 0.04 0.01 33.3%
5 - - 2.93 3.11 0.18 6.1%
6 - - 2.75 3.69 0.94 34.2%
7 5
- - 1.10 0.83 -0.27 -25%
8 - - 1.46 1.51 0.05 3.3%
9A - - 2.24 3.52 1.28 57.1%
10 - - 0.65 0.65 <0.01 0.2%
11 - - 0.77 0.89 0.11 15%
12 - - 0.83 0.90 0.07 8.3%
13 - - 2.10 2.05 -0.05 -2.5%
14 - - 0.41 0.46 0.05 12%
15 - - 0.23 0.24 0.01 5.8%
16 - - 1.46 1.35 -0.11 -7.5%
17 - - 0.77 0.92 0.14 19%
18 - - 1.18 0.97 -0.21 -18%
19 - - 2.65 2.78 0.13 4.7%
20 - - 0.42 0.50 0.08 19%
21 - 80% 0.89 0.95 0.06 6.5%
22 - 80% 0.82 0.87 0.04 5.4%
23 - 80% 0.59 0.66 0.07 12%
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FM ID GWI
(gpad)
Return
Factor
Applied (%)2
Meter
ADWF
(mgd)
Model
ADWF
(mgd)
Difference
(mgd)3
Difference
(%)
24 - - 2.39 2.58 0.19 8.2%
25 - - 1.24 1.22 -0.02 -1.9%
26 250 - 0.55 0.55 <-0.01 0.4%
27 - - 0.02 0.02 <-0.01 -6.6%
28 - - 0.08 0.06 -0.02 -22%
29 - - 0.20 0.23 0.03 15%
30 - - 0.04 0.05 0.01 25%
31 1,800 - 0.24 0.23 -0.01 -6.3%
32 (CuSD)6- - 3.63 3.45 -0.18 -5.0%
1 Model results are compared to the 2022-2023 flow monitoring data and assume a blockage at the Lawrence/Homestead gate structure.
2 Return factors applied are based on incremental areas (i.e., do not include flows that are upstream of the tributary area).
3 Difference is reported as model flow minus meter flow. Rounded to nearest 0.01 mgd. 4 Flow data were highly variable due to impact from Levi’s Stadium events. 5 Flow data were likely impacted by backwater influence from the Primavera Pump Station. Raw data showed frequent spikes in flow.
6 Raw flow data from CuSD’s permanent flow meter were reduced by approximately 5% when applied to the model as discussed in Section 2.2.2.1.

TABLE 3-6: DRY WEATHER FLOW CALIBRATION RESULTS VS. SELECT 2014-2015 FLOW MONITORING DATA1

FM ID GWI
(gpad)
Return
Factor
Applied (%)2
Meter
ADWF
(mgd)
Model
ADWF
(mgd)
Difference
(mgd)3
Difference
(%)
2 - - 4.05 4.72 0.67 16.5%
3 - - 2.98 2.79 -0.19 6.4%
5 - - 3.94 4.13 0.19 4.8%
6 - - 2.65 3.00 0.35 13.2%
7 - - 0.88 0.82 -0.06 -6.8%
9 4
- - 2.00 2.66 -0.66 33.0%
13 - - 3.50 3.07 -0.43 -12.3%
1 Model results are compared to the 2014-2015 flow monitoring data and assume normal settings (no blockages) at the Lawrence/Homestead gate structure.
2 Model BWF values and return factors applied are based on incremental areas (i.e., do not include flows that are upstream of the tributary area).
3 Difference is reported as model flow minus meter flow. Rounded to nearest 0.01 mgd. 4 Located upstream of FM 9A but still along the Calabazas trunk and downstream of El Sobrante overflow connection.

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FIGURE 3-6: DRY WEATHER CALIBRATION GRAPH (FM 1)
FIGURE 3-7: DRY WEATHER CALIBRATION GRAPH (FM 2)
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FIGURE 3-8: DRY WEATHER CALIBRATION GRAPH (FM 3)
Table 3-7 summarizes the total estimated dry weather flow (DWF) within Santa Clara’s sewer system based on the model calibration and the existing loads described previously.

TABLE 3-7: DRY WEATHER FLOW SUMMARY (EXISTING CONDITIONS) Flow Component Flow (mgd)
City Residential BWF 5.69
City Non-Residential BWF 5.53
CuSD Total BWF1 3.45
Total Average BWF 14.67
Estimated GWI2 0.16
Total Average DWF 14.83
1Average modeled daily dry weather flow from CuSD based on dry weather calibration period from Table 3-5. 2Calculated based on difference between metered non-rainfall period flows and estimated BWF calculated from winter water use data.

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3.4.3.1 Differences Between 2022-2023 & 2014-2015 Flow Monitoring Data During the dry weather calibration and review of the flow monitoring data, Woodard & Curran identified significant differences between the 2022-2023 and 2014-2015 flow monitoring data at the following meters:
• FMs 19 & 20: Based on the 2014-2015 flow monitoring data and field inspections recorded by the City, the diversion structure located at Homestead Road and Lawrence Expressway (shown in Figure 3-2) splits flows roughly evenly, routing approximately 50% of the flow to the trunk on Homestead and the remaining 50% to the trunk on Lawrence. The model replicated this expected split based on field measurements of gate openings at that time. However, the 2022- 2023 flow monitoring data showed that approximately 80% of flow was being routed to the trunk on Lawrence and the remaining 20% was being routed to the trunk on Homestead. The City’s Water and Sewer Department staff performed a field inspection to investigate the discrepancy in August 2023 and discovered that rags had built up on the center divider and were impacting the distribution of flow. After City staff removed the rags, they reported that both gates were fully open, and flows appeared to be evenly split. Staff also confirmed that gate settings had not been changed since 2015.
• FMs 9A & 13: The 2022-2023 flow monitoring data showed that flows in the Calabazas trunk at FM 9A were significantly lower than flows recorded at FM 9 in 2014-2015, which is located upstream of FM 9A. Additionally, the 2022-2023 flows at FM 19, which is located considerably upstream of FMs 9A and 9, were higher than the flows recorded at FM 9A. These data suggested that flows were being diverted away from the Calabazas trunk somewhere between FM 19 and FM 9A, which was not evident in the 2014-2015 flow monitoring data. Further investigation by Woodard & Curran and additional field surveys conducted by the City revealed that surcharged conditions were observed in the Calabazas line at manhole S32-101 located at the Pomeroy Avenue and El Sobrante Street intersection in March 2023 during dry weather conditions. The invert of the overflow pipeline on El Sobrante is significantly higher compared to that of the Calabazas line (+2.9 ft per the survey data), so it would take a substantial increase in hydraulic grade line for flows to back up into El Sobrante (away from FM 9A and into FM 13). When the same location was surveyed in August 2023, no surcharging was discovered, and flows appeared to have returned to normal. Woodard & Curran was unable to replicate the surcharging observed in March 2023 dry weather conditions in the model. Therefore, in addition to flows in the Calabazas trunk being higher than normal due to rag build up at the Homestead/Lawrence diversion structure (discussed above), it is suspected that there was a temporary downstream blockage in the Calabazas trunk somewhere downstream of the El Sobrante connection that forced flows to backup into the overflow pipe. Flows to El Sobrante are routed to FM 13. Other downstream flow meters affected by the atypical flow routing include FMs 2, 3, 5, 6, and 24. The reported flow differences are greater at FMs 5 and 6 compared to FMs 2 and 3 because there are interconnectors between the two GAP trunks downstream of FMs 5 and 6 but upstream of FMs 2 and 3.
• FM 7: The 2022-2023 flow monitoring data were likely affected by backwater influence from the pump station. Numerous spikes were observed in the raw flow data, which were not present in the 2014-2015 flow data. As shown in Table 3-6, the modeled dry weather flows were only

6.8% lower by volume than the 2014-2015 recorded flows; moreover, V&A installed the 2022- 2023 flow meter one manhole upstream of the 2014-2015 flow meter due to the pump station backwater influence observed at the original location during the site investigations.

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Per the City’s request, additional dry weather flow monitoring was performed for a week in early December 2023 as described in Section 2.1.3 to further investigate the major discrepancies which are summarized below.

Summary of Major Discrepancies Identified
It was determined that the likely cause of the differences between the 2022-2023 and 2014-2015 flow monitoring data was two-fold:
1) Lawrence/Homestead Gate Structure Flow Split: The Lawrence/Homestead gate structure was likely clogged with rags during the initial flow monitoring period, causing more flow than expected to be routed to the Calabazas trunk.
2) Calabazas Trunk Line Temporary Blockage: It was surmised that some issue in the Calabazas trunk (possibly a temporary blockage) caused significant surcharging, enough to reach the level that would route flows away from the Calabazas trunk and into the Bowers trunk through a higher-level split at El Sobrante. Moreover, this second condition seemed to change over time, with significant shifts in metered flows observed at FM 9A (located on the Calabazas trunk), with corresponding shifts at FM 13 (located on the Bowers trunk).

Conclusions from Additional DWF Monitoring Investigations Metered ADWFs for the 7-day dry period between December 9-15, 2023 were compared to the winter 2022- 2023 and winter 2014-2015 metered ADWFs at the same locations as well as model-predicted ADWFs.

Graphs of metered versus modeled ADWFs are included in Appendix E. Based on a comparison of the results, Woodard & Curran suspects that the two major differences identified above (1.

Lawrence/Homestead Gate Structure Flow Split; 2. Calabazas Trunk Line Temporary Blockage) had been resolved as of the December 2023 flow monitoring period and that the City’s Calabazas and Bowers trunk lines were operating closer to normal and as intended. To prevent future clogs that could affect sewer flow routing, it is recommended that the City periodically inspect and clean the Lawrence/Homestead gate structure as well as other structures or locations prone to rags or blockages.

Key findings based on the flow monitoring data were as follows:
• During the December 2023 flow monitoring period, the flow split at the Lawrence/Homestead gate structure (FM 19 along Lawrence Expwy, and FM 20 along Homestead Rd) was operating much closer to the approximately 50/50 flow split that the City considers to be “normal” conditions. Based on the flow monitoring data, metered flows at the split were as follows:
o December 9-15, 2023 ADWFs: ~39% to Lawrence Expwy / Calabazas trunk line (FM 19) vs. ~61% to Homestead Rd / Bowers trunk line (FM 20). It should be noted that this split was used in the model and is reflected in the Model Flow results shown on the attached graphs. o December 17-23, 2022 ADWFs: ~86% to Lawrence Expwy / Calabazas trunk line (FM 19) vs. ~14% to Homestead Rd / Bowers trunk line (FM 20).
• The December 2023 flow monitoring results at FM 21 (along Kifer Rd downstream of FM 20) also confirmed that flows along Homestead Rd continued through to the Bowers trunk line. The December 2023 ADWFs were similar to the winter 2014-2015 metered ADWFs. • New flow meter sites (FM 33 along El Sobrante St and FM 34 along El Camino Real) were added to check if flows were leaving the Calabazas trunk line at these locations. The December 2023 flow monitoring results confirmed that during the monitoring period flows were retained within the City of Santa Clara (Project 0012307.00) 3-21 Woodard & Curran, Inc.

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Calabazas trunk line and did not discharge to the sewers along El Sobrante St or El Camino Real.

Additionally, FM 30 (east of Calabazas trunk line between E Arques Ave and Central Expwy) was repeated to confirm flows from the Calabazas trunk line were not discharging to Central Expwy. The December 2023 flow monitoring results were consistent with the 2022 data at this site, showing very low flows through FM 30.
• Shifts in ADWFs that were apparent in the winter 2022-2023 flow monitoring data at FM 9A (along the Calabazas trunk line north of E Arques Ave) and FM 13 (along Bowers Ave on the Bowers trunk line between Chromite Dr and Monroe St) were not present during the one week of December 2023 flow monitoring.
• As evident on the graphs included in Appendix E, the model overpredicts flows at both FM 9A and FM 13. In reviewing the collected data, however, no changes to the model flows were incorporated.

Total metered flows at FM 19 and FM 20 were very similar between the 2015, 2022, and 2023 flow monitoring periods. Likewise, total metered flows at the downstream meters FM 2 and FM 3 were very similar between 2015 and 2022. The model matches overall flows at these locations well.

Conversely, the total metered flows between FM 9A and FM 13 in 2023 and 2022 were 24% and 27% lower than the 2015 metered flows (at FM 9 and FM 13). However, attempting to adjust the model to replicate these lower flows would adversely affect the calibration of downstream meters.

3.5 Wet Weather Flow Calibration
This section discusses the methodology and procedures used to calibrate the model for wet weather flow conditions and presents the results of the wet weather calibration.

3.5.1 Wet Weather Flow Calibration Methodology
Wet weather calibration builds on the dry weather calibration procedure. The goal of wet weather calibration is to match modeled and metered flows during the rainfall events observed during the flow monitoring period. Specifically, the model calibrator strives to achieve a reasonably good match between the modeled and metered peak flows and volumes observed during and before and after the rainfall event. Like dry weather calibration, wet weather calibration is also an iterative process during which adjustments are made to GWI (if needed to match pre-rainfall conditions) and to model parameters governing the volume and response time of RDI/I.

To define the RDI/I parameters, actual rainfall events observed during the flow monitoring period were simulated in the hydraulic model, and the resulting model hydrographs were compared to the measured flows at the flow meter locations. The RDI/I parameters were adjusted as needed to achieve a reasonable match of modeled to monitored flows. The same calibrated parameters were applied to all subcatchments within each meter basin.

3.5.2 Wet Weather Flow Calibration Results
During wet weather calibration, the percentage volume of each of five RDI/I components representing a range of response times (pictured conceptually in Figure 2-6) were adjusted to simulate the volume and timing of RDI/I for monitored storm events in order to best match the overall wet weather hydrograph shape and magnitude of peak flows. To simulate a rainfall event in the model, the rainfall was assigned to subcatchments using observed data from the closest available rain gauge. The model-predicted wet weather response, which is based on the assigned rainfall intensity and RDI/I components, was then compared to the observed flow monitoring data.

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The flow monitoring program conducted in winter of 2022-2023 as part of this Master Plan Update (refer to Section 2.1) captured several rainfall events for the wet weather calibration effort. Rainfall for key events referenced for the wet weather calibration is summarized in Table 3-8. For comparison (based on the County Drainage Manual and an assumed MAP of 14.5 inches), the 10-year, 24-hour rainfall volume for central Santa Clara is approximately 2.92 inches with a peak hour intensity of 0.65 in/hr and the 5-year, 24- hour rainfall volume for central Santa Clara is approximately 2.45 inches with a peak hour intensity of 0.54 in/hr. Therefore, based on the statistics reported in Table 3-8, all the rainfall events observed during the flow monitoring period were individually less than a 10-year return period for the 24-hour duration and the January 4-5, 2023 storm was close to a 5-year return period. However, several of the storms occurred within a short amount of time so there were likely cumulative impacts that increased the inflow and infiltration response during subsequent storms. For example, the January 13-16, 2023 storm event was close to a 10- year storm based on NOAA statistics for the 2-day and 4-day durations. Figure 3-9 graphically depicts the daily rainfall recorded during the temporary flow monitoring period, in inches.

TABLE 3-8: RAINFALL EVENTS REFERENCED FOR WET WEATHER CALIBRATION1 Date of Event Min 24-Hour
Rainfall (in)
Max 24-Hour
Rainfall (in)
Min Peak 1-Hour
Intensity (in/hr)2
Max Peak 1-Hour
Intensity (in/hr)2
Dec 27, 2022 1.52 1.89 0.28 0.37
Dec 31, 2022 1.55 2.15 0.28 0.36
Jan 4-5, 2023 1.29 2.34 0.36 0.59
Jan 8-10, 2023 1.11 2.08 0.23 0.39
Jan 13-16, 2023 1.62 2.06 0.29 0.42
1Rainfall totals based on temporary rain gauge data from gauges 1-4. Minimum rainfall totals are generally from rain gauge 1 located in the northern portion of the City and maximum rainfall totals are generally from rain gauge 3 located in the southern portion of the City.
2 Intensity is reported as an hourly average of 15-minute rainfall data.

FIGURE 3-9: DAILY RAINFALL OBSERVED DURING 2022-2023 FLOW MONITORING PERIOD (IN)1 1Rainfall totals are from rain gauge 3 located in the southern portion of the City.

Table 3-9 compares the model versus meter peak wet weather flows discharged to the City’s GAP and Trimble trunks, Table 3-10 and Table 3-11, respectively, compare the model versus 2022-2023 and 2014- 2015 meter wet weather flows at each meter location, and Figure 3-10, Figure 3-11, and Figure 3-12, show plots of model versus metered wet weather flow at the downstream-most meters (FM 1, FM 2, and FM 3, 0 0.5
1 1.5
2 2.5
12/2512/2612/2712/2812/2912/3012/31
1/11/21/31/41/51/61/71/81/9
1/101/111/121/131/141/151/161/171/181/191/201/211/221/231/241/251/261/271/281/291/301/31 2/12/22/32/42/52/62/72/82/9
2/102/11
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respectively). In these graphs, the green line represents the monitored (observed) flow, and the red line represents the model-simulated flow. Wet weather calibration plots of model-predicted versus metered flows at all flow meter locations for both 2022-2023 and 2014-2015 are provided as Appendix E.

As indicated in Table 3-10, the wet weather model calibration resulted in a reasonably good match of modeled to metered volumes and peak flows (within 15% at most locations). However, because it was determined that temporary system conditions that were not representative of typical operations were present during the 2022-2023 flow monitoring period (discussed in Section 3.4.3.1), the 2014-2015 flow monitoring data were also compared to the model results at select, affected locations as shown in Table 3-11. As part of the wet weather calibration process, Woodard & Curran still reviewed data from both the 2014/2015 and 2022/2023 seasons to confirm that the model was at least reasonable for both conditions at all flow meter locations. The 2014/2015 wet weather season had one very large early season rainfall event, which differed from the 2022/2023 wet weather season in which several, smaller individual storms occurred in a short amount of time.

As evident in the wet weather calibration plots included in Appendix E, the modeled and metered peak flows and volumes typically matched better for the later season rainfall events. This is because the full 2022- 2023 season was reviewed as the wet weather calibration period; the volume and peak flows associated with the early-season rainfall events are typically overestimated because the same RDI/I parameters were applied across all rainfall events. The RDI/I response typically increases throughout the wet weather season as the soil progressively becomes saturated as more rainfall occurs. Therefore, the wet weather calibration was performed to conservatively match the observed volume and peak flows resulting from higher RDI/I responses during late-season wet weather events.

FIGURE 3-10: WET WEATHER CALIBRATION RESULTS AT FM 1
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FIGURE 3-11: WET WEATHER CALIBRATION RESULTS AT FM 2
FIGURE 3-12: WET WEATHER CALIBRATION RESULTS AT FM 3
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The results of the wet weather calibration are shown in Table 3-10. Wet weather peaking factors were calculated for each flow meter based on the ratio of peak flow to average flow.

TABLE 3-9: WET WEATHER FLOW CALIBRATION RESULTS SUMMARY1 FM IDs Discharge Location Meter PWWF
(mgd)
Model PWWF
(mgd)
Difference
(mgd)2
Difference
(%)2
1+2+3 Lafayette and GAP Trunks 23.03 24.22 1.19 5.2%
16+17+18+25 Trimble Trunk 13.65 13.93 0.28 2.1%
1 Model results are compared to the 2022-2023 flow monitoring data. 2 Difference is reported as model flow minus meter flow.

TABLE 3-10: WET WEATHER FLOW CALIBRATION RESULTS VS. 2022-2023 FLOW MONITORING DATA1
FM ID Meter PWWF
(mgd)2
Model PWWF
(mgd)
Difference
(mgd, %)
Avg Flow
(mgd)3
Peaking
Factor4
1 8.67 7.59 -1.07, -12.4% 2.91 3.0
2 9.97 8.75 -1.22, -12.2% 4.71 2.1
3 7.39 7.88 0.49, 6.6% 2.92 2.5
4 5 1.25 0.44 -0.81, -64.8% 0.04 31.3
5 8.96 7.78 -1.18, -13.2% 2.93 3.1
6 4.88 7.90 3.02, 61.8% 2.75 1.8
7 2.27 1.80 -0.47, -20.5% 1.10 2.1
8 3.12 2.77 -0.36, -11.5% 1.46 2.1
9 3.85 7.59 3.74, 97.1% 2.24 1.7
10 3.41 3.28 -0.13, -3.7% 0.65 5.2
11 4.94 4.57 -0.37, -7.4% 0.77 6.4
12 -
6 5.28 -6 0.83 -6
13 8.56 5.75 -2.81, -32.8% 2.10 4.1
14 1.14 1.05 -0.10, -8.5% 0.41 2.8
15 0.84 0.95 0.11, 12.6% 0.23 3.6
16 2.77 3.03 0.26, 9.2% 1.46 1.9
17 1.68 1.62 -0.06, -3.3% 0.77 2.2
18 2.53 2.81 0.28, 11.1% 1.18 2.1
19 5.98 5.94 -0.05, -0.7% 2.65 2.3
20 1.94 2.26 0.32, 16.6% 0.42 4.6
21 2.90 3.30 0.39, 13.6% 0.89 3.3
22 1.95 2.07 0.11, 5.8% 0.82 2.4
23 1.22 1.49 0.27, 2.2% 0.59 2.1
24 8.30 7.14 -1.16, -13.9% 2.39 3.5
25 6.67 6.47 -0.197, -3.0% 1.24 5.4
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FM ID Meter PWWF
(mgd)2
Model PWWF
(mgd)
Difference
(mgd, %)
Avg Flow
(mgd)3
Peaking
Factor4
26 1.70 1.70 0.004, 0.2% 0.55 3.1
27 0.47 0.46 -0.001, -0.2% 0.02 23.5
28 1.36 0.88 -0.48, -3.5% 0.08 17.0
29 1.16 1.04 -0.12, -10.4% 0.20 5.8
30 0.14 0.11 -0.02, -17.0% 0.04 3.5
31 1.23 1.28 0.06, 4.6% 0.24 5.1
327 9.51 8.95 -0.56, -5.9% 3.45 6.0
1 Model results are compared to the 2022-2023 flow monitoring data and assume a blockage at the Lawrence/ Homestead gate structure.
2 Based on meter response during January 15-16, 2023 rainfall event. 3 Average metered dry weather flow from Table 3-5.
4 Ratio of metered peak flow to metered average flow.
5 FM 4 base flows were highly variable because of sporting events held at Levi’s Stadium. FM was calibrated to match the wet weather response from rainfall on non-gamedays, resulting in an underestimation of total gameday flows. 6 Meter was not installed in the correct location during the wet weather flow monitoring period, so data are not available. 7 Permanent CuSD flow meter.

TABLE 3-11: WET WEATHER FLOW CALIBRATION RESULTS VS. SELECT 2014-2015 FLOW MONITORING DATA1
FM ID Meter PWWF
(mgd)2
Model PWWF
(mgd)
Difference
(mgd, %)
2+3 17.59 17.72 0.13, 0.7%
5+6 16.69 16.30 -0.39, -2.3%
9 3 6.34 6.43 0.09, 1.4%
13 7.22 7.65 0.43, 6.0%
1 Model results are compared to the 2014-2015 flow monitoring data and assume normal settings (no blockages) at the Lawrence/Homestead gate structure.
2 Based on meter response during December 11, 2014 rainfall event. 3 FM 9 is located along the Calabazas trunk but upstream of FM 9A (south of Central Expressway).

3.5.2.1 RDI/I Response
As discussed in Section 2.3 and shown in Figure 2-6, RDI/I is estimated in the model using five runoff components that reflect a range of response times from fast to slow. The total RDI/I hydrograph for each flow meter basin is the summation of all the component hydrographs for the duration of the rainfall events.

As expected, a very high RDI/I response was observed within the meter basins that collect flows from the CMC tributary area which is upstream of FMs 11 and 12 (discussed in Section 2.1) and at FM 31 which is a basin that is adjacent to the CMC tributary area but upstream of FM 24. Examples of the very high RDI/I responses observed at a few of these meters (FM 31 and FM 27) are presented in Figure 3-13 and Figure 3-14. In both examples, the nature of the response is indicative of significant infiltration as the response is generally slower and takes a long time to recede (i.e., several weeks after the January 15-16, 2023 storm as shown in the figures). Moreover, because several consecutive rainfall events occurred within a short period of time, the infiltration response did not fully recede before another rainfall event occurred.

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These flow monitoring results are consistent with the findings of other field investigations that were completed recently in the CMC basin. The City retained V&A to perform I/I investigations within the CMC tributary area with the objective of identifying specific areas of high I/I to a sub-basin or micro-basin level.

Investigation methods included targeted night-time I/I reconnaissance and CCTV inspections, which occurred during the 2022-2023 winter wet weather season. V&A’s report1, which details the scope and findings of these investigations, concluded that rainfall-dependent infiltration appeared to be the most severe component in the CMC basin, as opposed to the rainfall-dependent inflow. V&A observed a rapid response but also long-term, sustained rainfall-dependent infiltration, which are presumably due to increased groundwater elevations that take a long time to recede. V&A suspected that the rainfalldependent infiltration was entering the sewer system from defects in sewer laterals and mains, rather than from defects within the sewer manhole structures. City staff suspect that laterals in some areas within the CMC basin were constructed using Orangeburg pipe material, which is known to have high rates of defects and may be a significant source of RDI/I. V&A’s report recommended that the City consider smoke testing in the CMC basin, which may better identify lateral defects. Options to identify and reduce RDI/I in the CMC basin were identified and are suggested as part of the system capacity assessment (refer to Section 4.6.3).

FIGURE 3-13: WET WEATHER CALIBRATION RESULTS – RDI/I RESPONSE AT FM 31 1 Sewer Flow Monitoring and Inflow/Infiltration Study prepared by V&A for City of Santa Clara dated August 2023.

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FIGURE 3-14: WET WEATHER CALIBRATION RESULTS – RDI/I RESPONSE AT FM 27 Figure 3-15 on the next page presents a visual representation of the wet weather calibration results in terms of the total RDI/I rate that was applied to the model for each meter basin to try to match modeled and metered flows.
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Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

City of Santa Clara Boundary
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4. SYSTEM CAPACITY ANALYSIS
This section defines the basis for the capacity assessment of the system, including the selected design storm and performance criteria used to identify deficiencies, and presents the capacity deficiencies identified based on the model results. The section also identifies areas of the system with high I/I and recommends additional investigations to isolate potential direct inflow sources in those areas.

4.1 Hydraulic Assumptions Used for the Capacity Analysis This section summarizes the hydraulic assumptions used for the capacity evaluation, including the dry weather flow scenarios (i.e., existing, near-term future, long-term future), wet weather design flows, performance (or capacity deficiency) criteria, and physical model network.

Section 2 discusses the various flow components and the development of existing, near-term future, and long-term future wastewater flows (referred to as model “loads”). It also discusses the application of a design storm in conjunction with calibrated model parameters that represent rainfall-dependent infiltration and inflow (RDI/I) into the sewer system to generate wet weather design flows.

Section 4.1.1 presents the characteristics of the City’s design storm event that is used to generate wet weather design flows and summarizes the performance criteria that are applied to identify system capacity deficiencies and the design criteria that are applied to develop project solutions for the identified capacity deficiencies.

The physical model network assumptions, including development of a new “Lined Model Network” as requested by the City, is described in more detail in Section 4.1.2.

4.1.1 Summary of Design Storm, Performance Criteria, and Design Criteria Criteria used by other agencies both inside and outside of California were referenced when selecting the criteria that was used for the City’s sewer system capacity analysis. These references are further discussed in TM #2 (Santa Clara Sewer Performance and Design Criteria), which was submitted to the City.

Design Storm
Key factors needed to define a design storm event for the purpose of sewer modeling and master planning include return period, rainfall depth, storm duration, temporal and spatial distribution of rainfall, storm timing, and antecedent conditions. Characteristics of the selected design storm related to these key factors are presented in Table 4-1 and discussed further below.

The City elected to continue to use the same 10-year, 24-hour design storm event that was used for its 2016 Master Plan for this Master Plan Update. The design storm used for the 2016 Master Plan Update is a 10- year, 24-hour storm that varies across the service area. The storm pattern and hourly rainfall intensities are based on the Santa Clara County’s Drainage Manual (October 2007)1. The manual includes mean annual precipitation (MAP) isohyetal lines from Santa Clara Valley Water District (SCVWD) and distinct intensity, depth, frequency (IDF) curves for each MAP area in Appendix B. In addition to the IDF curves, Appendix D of the manual includes a 24-hour design storm pattern. According to the manual, this storm pattern is based on an actual three-day rainfall event that occurred in December 1955, but with some adjustments to better reflect IDF statistics for various storm durations.
1 Santa Clara County’s Drainage Manual is available online at:
https://stgenpln.blob.core.windows.net/document/DrainageManual_Final.pdf.

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Figure 4-1 shows the design storm hourly rainfall as it occurs in the vicinity of central Santa Clara, including the San Jose International Airport area. At this location, the total rainfall for the 1-, 6-, and 24-hour durations is 0.65, 1.49, and 2.92 inches, respectively. For this graph, the storm timing has been adjusted so that the peak intensity coincides with the weekday morning peak of the diurnal wastewater pattern.

FIGURE 4-1: DESIGN STORM EVENT FOR CENTRAL SANTA CLARA (MAP ~14.5 INCHES) Santa Clara selected its design storm event based on the key considerations presented in Table 4-1 with respect to its desired level of service to reflect the level of risk that is acceptable to the City. For future modeling efforts, the City may consider applying a more conservative design storm event with a higher return period and/or perform a sensitivity analysis to evaluate potential impacts of climate change. The analysis could either be performed prior to, or concurrent with, the next update.

TABLE 4-1: RAINFALL DESIGN EVENT CRITERIA USED FOR SANTA CLARA MASTER PLAN UPDATE Design Event Criterion Santa Clara Selection
Return Period 10 years
Rainfall Depth Based on County Drainage Manual
IDF curves
Storm Duration 24 hours
Rainfall Temporal Distribution
Based on County Drainage Manual
(developed from historical rainfall
event in December 1955)
Storm Timing Peak-on-Peak (weekday)
Spatial Rainfall Distribution Lowest intensity: North
Highest intensity: Southwest
Antecedent Conditions Wet, saturated soils
The key factors used to define Santa Clara’s selected design storm event are further described below:
• Return Period: The return period defines the probability that the design rainfall will be exceeded in any given year. For example, a storm with a 5-year return period means that there is a 1 in 5 chance, or 20 percent probability, that the design rainfall will be exceeded in any given year. For sewer modeling and master planning applications, the chosen return period reflects the degree of risk that an agency is willing to accept regarding the potential of experiencing sanitary sewer overflows

0.0 0.1

0.2 0.3

0.4 0.5

0.6 0.7

0.8 0.9

1.0 0:001:002:003:004:005:006:007:008:009:00
10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00 Rainfall Intensity (in/hr)
Hour
Peak Hour
Intensity
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(SSOs) due to future storm events. However, selecting a design storm with a very high return period (reflecting a very low risk tolerance) could lead to identification of a significant number of system capacity deficiencies that would make the cost of improvements prohibitive. Additionally, sizing a system for a very infrequent event could mean that the system does not function well under typical conditions during much lower flows (due to slow velocities in oversized pipes, or oversized pump stations).
• Rainfall Depth: Synthetic design storms are typically based on rainfall IDF or depth, duration, frequency (DDF) statistics that have been compiled for a local area. These statistics give the rainfall depths or intensities for various return periods (e.g., 2-year, 5-year, etc.) and durations of rainfall (e.g., 1-hour, 2-hour, etc.). Rainfall IDF statistics are available through the National Oceanic and Atmospheric Administration (NOAA), which provides the IDF statistics for any location in the U.S. based on latitude/longitude coordinates. IDF curves specific to Santa Clara County (one for each MAP area) for various return periods and durations are provided in Appendix B of the 2007 County Drainage Manual. These IDF curves were used to define the selected design storm event. MAP varies spatially throughout Santa Clara, with the highest average annual rainfall typically occurring in the southern portion of the City. In central Santa Clara, according to the County Drainage Manual, the MAP is approximately 14.5 inches, and the 10-year, 24-hour rainfall depth is approximately 2.92 inches (versus 2.63 inches according to NOAA Atlas 14). • Storm Duration: A storm duration must be specified for the design storm along with the return period. Most Bay Area agencies use a 24-hour storm, although shorter or longer durations may sometimes be appropriate (e.g., a shorter duration in a very small system with fast response to rainfall or in an area where storm events are typically very brief; a longer duration in a very large system or one with a very slow response to rainfall). Typically, the 24-hour duration storms are constructed such that the more intense rainfall occurs during a shorter (e.g., 4- to 6-hour) period.

Santa Clara’s selected design storm uses a 24-hour duration.

Rainfall Temporal Distribution: The temporal rainfall distribution of a design storm may be based on a synthetic storm or an actual historical event. Commonly used synthetic storm distributions include nested storms (which incorporate design rainfall intensities for a given return period for several durations within the total storm duration), or a “SCS” storm distribution, a dimensionless 24-hour rainfall distribution developed by the SCS (Soil Conservation Service), now known as the NRCS (Natural Resources Conservation Service). The SCS developed four 24-hour distributions, with each distribution representative of a specific region of the U.S., as presented in the USDA guidance document Urban Hydrology for Small Watersheds TR-55 (June 1986). The City’s service area generally falls within the area covered by the “Type I” distribution, but it is close to the boundary between the “Type I” and “Type IA” distributions. It is sometimes preferable to use historical rainfall patterns to depict the design storm temporal rainfall distribution of the design event. As described above and shown in Figure 4-3, Santa Clara County’s Drainage Manual defines a temporal rainfall distribution based on a historical event that occurred during December of 1955. The rainfall for a historical storm could be scaled to match the desired rainfall depth and return period of the design storm. Table 4-2 compares the peak hour intensity of the County Drainage Manual design storm distribution to the peak hour intensities of the synthetic distributions (SCS-I and SCS-IA, and nested) based on the County Drainage Manual IDF statistics for a 10-year, 24-hour rainfall event. As shown in the table, in central Santa Clara, peak hour rainfall intensity of the County Drainage Manual distribution is very similar to that of the synthetic SCS Type I distribution, moderately lower than that of the synthetic nested distribution, and significantly higher than that of the SCS Type IA City of Santa Clara (Project 0012307.00) 4-4 Woodard & Curran, Inc.

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distribution. The temporal distribution of Santa Clara’s selected design storm is based on an actual historical event (i.e., December 1955).

TABLE 4-2: CHARACTERISTICS OF DESIGN STORM DISTRIBUTIONS CONSIDERED1 Frequency Duration IDF Statistics
Source
Temporal
Distribution
Volume
(in)
Peak Hour
Intensity
(in/hr)
10-yr 24-hr
Historical,
County Drainage
Manual
Historical,
County Drainage
Manual

2.92 0.65
10-yr 24-hr NOAA Synthetic, Nested 2.92 0.64
10-yr 24-hr NOAA Synthetic, SCS-I 2.92 0.76
10-yr 24-hr NOAA Synthetic, SCS-IA 2.92 0.46
1Based on County Drainage Manual and assumed MAP of 14.5 inches for central Santa Clara. • Storm Timing: The selected event is based on the Santa Clara County Drainage Manual design storm with peak-on-peak BWF timing. Generally, peak-on-peak timing is achieved by adjusting the timing of the peak intensity of the rainfall event so that it occurs one to two hours prior to the peak BWF to account for the typical delay between the rainfall occurring and observation of the RDI/I response. For the 2016 Master Plan, the design storm rainfall was timed such that the peak rainfall occurred around 8 a.m., resulting in a peak RDI/I flow at approximately the same time as the typical weekend day peak BWF in most areas of the system (graphically depicted in Figure 4-2). Given that the peak BWF typically occurs earlier on a weekday compared to a weekend day, Santa Clara’s selected design storm for this Master Plan Update was evaluated assuming an earlier peak rainfall intensity (around 6 a.m.) so as to align the peak intensity with the typical weekday peak BWF (graphically depicted in Figure 4-3).

FIGURE 4-2: DESIGN STORM EVENT FOR CENTRAL SANTA CLARA (WEEKEND) 0 0.2

0.4 0.6

0.8 1

1.2 1.4

1.6 1.8

0.0 0.1

0.2 0.3

0.4 0.5

0.6 0.7

0.8 0.9

1.0 0:001:002:003:004:005:006:007:008:009:00
10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00 0:001:00
Base Wastewater Flow (Multiplier x
Average)
Rainfall Intensity (in/hr)
Hour
Design Storm (10-year,
24-hour) (varies spatially)
Residential Diurnal Pattern
Non-Residential Commercial
Diurnal Pattern
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FIGURE 4-3: DESIGN STORM EVENT FOR CENTRAL SANTA CLARA (WEEKDAY) • Spatial Rainfall Distribution: The magnitude of rainfall may vary spatially, generally based on topography and the typical movement of storms over the service area. Based on the County Drainage Manual, MAP in the City’s service area varies from about 13 to 16 inches in a north to southwest direction. While this pattern may not hold true for every storm event, it is common practice to apply the spatial variation of average annual rainfall to the design storm. As such, the IDF curves (one for each MAP) provided in Appendix B of the County Drainage Manual were referenced to obtain IDF statistics (rainfall depth, duration, and peak intensity) for subareas within the City. Figure 4-4 presents the spatial variation of rainfall depth and peak intensity throughout the City’s service area for a 10-year, 24-hour event that the selected design storm is based upon; it illustrates that the highest and most intense rainfall typically occurs within the southwest portion of the City.
• Antecedent Conditions: Based on flow monitoring data from the 2022-2023 winter season, flow response to rainfall in portions of the City’s service area (e.g., CMC tributary area) is characterized by prolonged elevated flows extending for several days and in some cases weeks after storm events.

Thus, a storm happening later in the season after several storm events have occurred may produce higher peak flows because the ground is saturated (meaning less rainfall can be “absorbed” by the soil) and flows are already elevated due to the preceding events. This “wet” antecedent condition can be modeled as a prolonged RDI/I response (when the model simulation includes multiple events) or as an elevated, antecedent GWI condition (when modeling a single event such as a design storm). Because it is not unusual for large storm events to occur after periods of preceding rainfall, it is common to define a design storm as occurring under “saturated soil” or “wet” antecedent conditions; this approach was applied when defining Santa Clara’s selected design storm. Assuming dry or moderately dry soil conditions would be a less conservative approach. 0 0.2

0.4 0.6

0.8 1

1.2 1.4

1.6 1.8

0.0 0.1

0.2 0.3

0.4 0.5

0.6 0.7

0.8 0.9

1.0 0:001:002:003:004:005:006:007:008:009:00
10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00 Base Wastewater Flow (Multiplier x
Rainfall Intensity (in/hr)
Average)
Hour
Design Storm (10-
year, 24-hour)
(varies spatially)
Residential Diurnal Pattern
Non-Residential
Commercial Diurnal Pattern
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FIGURE 4-4: SPATIAL VARIATION OF RAINFALL THROUGHOUT SANTA CLARA’S SERVICE AREA City of Santa Clara (Project 0012307.00) 4-7 Woodard & Curran, Inc.

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Capacity Deficiency Criteria
Capacity deficiency criteria are used to determine if the capacity of an existing sewer facility is exceeded to the extent that a capacity improvement project is needed. These criteria are sometimes called “trigger” criteria, in that they trigger the need for a capacity improvement project. An agency defines its capacity deficiency criteria based on its desired level of service. As such, the criteria vary by agency and are reflective of the level of risk that is acceptable to each agency.

The capacity deficiency criteria differ from the design criteria that are applied to determine the size of a new facility; the latter typically being more conservative. The difference between capacity deficiency criteria and design criteria reflect the concept that some existing facilities can continue to provide adequate, if not optimal, conveyance capacity without undue risk, but new facilities should be designed to a higher standard.

The capacity deficiency criteria utilized for the Master Plan Update to identify capacity deficiencies under both Peak Dry Weather Flow (PDWF) and Peak Wet Weather Flow (PWWF) design flow conditions are summarized in Table 4-3. The City’s selected criteria were conservative in order to identify all potential projects, recognizing that conditions may change in the future due to variable risk factors (e.g., sewer condition, additional development, climate change). Evaluating system capacity based on conservative criteria provides an “advance warning” of more vulnerable areas of the system that could require deficiencies to be corrected as these future potential risks materialize. All projects identified were prioritized based on the cause and extent of the model-predicted capacity deficiency as discussed in Section 5.

TABLE 4-3: CAPACITY DEFICIENCY CRITERIA USED FOR SANTA CLARA MASTER PLAN UPDATE Facility Design Flow Condition(s) Capacity Deficiency Criteria Gravity Sewer PDWF or PWWF No surcharge allowed (d/D1 ≤ 1.0) Force Main PDWF or PWWF Velocities less than 10 feet per second Pump Station PDWF or PWWF Flows less than firm capacity2 1 Ratio of depth (d) of water to pipe diameter (D), which represents the approximate percent full within a pipe. 2 Firm capacity is defined as the capacity of the pump station with the largest pump out of service.

For evaluating the performance of existing sewers, a Manning’s “n” value of 0.013 was assumed for all pipes, regardless of material or age. Although new pipes, particularly plastic materials, would provide a lower initial roughness factor, it was assumed that over time, a “slime layer” formation on the walls of the pipes and/or other obstructions in the sewer, such as roots, debris, or structural defects, may increase pipe roughness.

Therefore, an assumption of 0.013 for all pipes was considered appropriately conservative for master planning purposes.

Note that engineering judgment was used in conjunction with applying the capacity deficiency criteria presented above to identify model-predicted capacity deficiencies in gravity sewers. Gravity sewers that showed only minor criteria violations were not considered deficient if one or more of the following conditions applied:
• Surcharged on one end only (i.e., downstream end caused by backwater); • Isolated flat pipe segments;
• Invert differences (i.e., offsets) between adjacent pipes; • Smaller diameter sewers connected to larger diameter pipes at equal inverts; or • Sewers protected from overflows by a high-level flow diversion or parallel pipe.

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Design Criteria
The key design criteria that were applied for the Master Plan Update when developing project solutions to relieve the identified capacity deficiencies are summarized in Table 4-4. The City’s “Design Criteria” (April 2015)1, which specify criteria for hydraulic design of sanitary sewer facilities (e.g., pipe material and diameter and roughness for gravity sewers), were referenced to develop the design criteria used for this Master Plan Update.

TABLE 4-4: DESIGN CRITERIA USED FOR SANTA CLARA MASTER PLAN UPDATE Facility Component Design Criteria
Gravity Sewer d/D Ratio Less than or equal to 0.75 unless minimum velocities are a concern.

Gravity Sewer Velocity Minimum 2 fps during existing peak dry weather flow; maximum 10 fps during design peak wet weather flow.

Gravity Sewer Diameter
Minimum 8-inch, 10-inch, and 12-inch for residential, commercial, and industrial land uses, respectively; downstream pipes at least as large as upstream pipes where feasible.

Gravity Sewer Roughness Manning’s n friction coefficient of 0.013.

Gravity Sewer Inverts Match crowns at junctions of side sewers and trunk sewers.

Gravity Sewer Slope Determined based on velocity criteria to the extent feasible.

Gravity Sewer Cover 6 feet from finished grade to sewer crown if feasible.

Gravity Sewer Material1
RCP for 24-inch and larger; VCP for greater than 12- to 24-inch or PVC if approval given by Director of Public Works / City Engineer; VCP or PVC SDR 26 for 12-inch and smaller.

Gravity Sewer Alignment2
Generally, 5-foot offset from street centerline on side opposite the storm drain and 8-foot clear distance separation from all other parallel facilities.

Gravity Sewer
Manhole
Placement
and Spacing2
Located at sewer main or street intersections, at upstream terminal ends of sewer lines, at any change in pipe direction, slope, diameter, or material, and where laterals have the same diameter as the sewer main or are 8 inches or larger. Nominal and maximum manhole spacing shall be 450 and 500 feet, respectively.

Force Main Velocity Minimum 3 fps to prevent solids from settling out and maximum 8 fps to prevent excessive head losses in the force main.

Force Main Cover 6 feet from finished grade to sewer crown if feasible.

Pump Station Roughness Hazen-Williams C-value of 100 but must have proper operation at C-value of 120.
1 Note that material is tracked in the hydraulic model, but roughness values are what impact the hydraulic analysis. 2 Note that these details were considered for the hydraulic modeling analysis but are generally more applicable to project development during the pre-design stage.
1 City of Santa Clara’s Sanitary Sewer Design Criteria (Section 5) are available online at:
https://www.santaclaraca.gov/home/showpublisheddocument/61878/636766631787130000.

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4.1.2 Physical Model Network
Two physical model networks were used to evaluate the capacity of the City’s sanitary sewer system. One of these networks included future lining assumptions applied to City-identified RCP trunks and VCP siphons within the City’s sewer system based on information provided by the City (“Lined Model Network”); the other did not (“Unlined Model Network”). Section 4.1.2.1 discusses the assumptions applied to the Lined Model Network in more detail.

The following assumptions were applied to the physical model network (both the Lined Model Network and Unlined Model Network):
• A Manning’s n of 0.013 was assumed for all pipes in the model, including lined pipes. Lined pipes can initially reduce the friction factor. However, over time, with sedimentation and fouling, the friction factor may increase. Assuming a friction factor of 0.013 for lined pipes therefore represents a conservative assumption.
• The flume diversion structure located at Homestead Road and Lawrence Expressway (Lawrence/Homestead gate structure), which splits the flow to either the eastern sewer on Homestead or the northern sewer on Lawrence Expressway, was modeled assuming a 50% flow split for the capacity evaluation. Therefore, half of the influent sewer flows are sent east to the Homestead sewer and the other half are sent north to the Lawrence sewer. This even flow split assumption was applied for the capacity evaluation because it is the City’s normal and desired flow setting at that structure. It should be noted that the model calibration (described in Section 3.3) considered both normal settings and a temporary blockage condition which existed during the flow monitoring period but was investigated and cleared by City staff thereafter. • Pump stations were set up in the model using Archimedean screw pumps, meaning that all the influent sewer flows from the upstream sewer system would be pumped out through the force main at the same flow rate they reach the pump station (i.e., influent flow rate = effluent flow rate). Pump station firm capacities were estimated based on information provided by the City and compared to the model PWWF as described further in Section 4.4.
• Non-free-fall (submerged) conditions were assumed at the downstream most discharge structure where the Rabello and Northside force mains outfall to a discharge box structure. Based on information provided by the City, the water level in the structure was set to be eight (8) feet above the crown of the force mains which was the approximate water level during a City field inspection completed on June 19, 2024. At the time of the field inspection, the City noted that the high-water level within the structure appeared to be approximately 13 feet above the crown of the force mains; however, considering it is not known when or how often that condition occurs, it was not used as the design condition.
• Project solutions for the following specific development projects that were already identified and modeled during previous development reviews were included in the appropriate future loading model scenario(s) based on timing:
o Patrick Henry Drive (PHD): Included in both the near-term future and long-term future model load scenarios. The sanitary sewer improvements within the PHD plan area and the upsize of the Great America Parkway (GAP) West Trunk (from PHD to the Bay Division pipelines crossing) are both to be paid by the developers; therefore, the previously modeled improvements for PHD will not be further discussed in this Master Plan Update or included in the City’s Sewer Capacity CIP.

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o Mission Point: Included in the long-term future model load scenario only. The City is allowing either of two developer-proposed alternatives, one of which (Revised Option 2A) is included in the model. Both alternatives are assumed to be completely at the developer’s cost and therefore will not be further discussed in this Master Plan Update or included in the City’s Sewer Capacity CIP.
o Freedom Circle: Included in the long-term future model load scenario only. No separate infrastructure fee area has been established for the Freedom Circle Focus Area; therefore, the previously modeled improvements are presented in this Master Plan Update and will be included in the City’s Sewer Capacity CIP.

4.1.2.1 Lined Model Network Assumptions
The Lined Model Network assumes RCP trunks identified by the City to be in poor condition would be lined in future as shown in Table 4-6 and Figure 4-5). The Lined Model Network also assumes that select unlined siphons constructed of either vitrified clay pipe (VCP), cast iron pipe (CIP), or ductile iron pipe (DIP) material would be lined as identified in the table provided as Appendix F. The table also includes condition assessment information (i.e., structural quick rating score) from recent CCTV inspections that the City conducted on select siphons between January 2024 and May 2024. The four siphons with the highest severity grade of 4 were part of the group of siphons identified for future lining.

Future lining assumptions were only incorporated into the Lined Model Network, while sewers and siphons already lined were incorporated into both the lined and unlined networks. Gravity sewers and siphons assumed to be lined in the future were assigned a reduced diameter based on an assumed liner thickness and the “FLIN” (future lining) model flag was then applied to the diameter field.

Liner thicknesses, and the corresponding diameter reductions, were calculated based on conservative assumptions. Woodard & Curran referenced information provided by the City from recent lining projects and expertise from condition assessment experts to develop conservative lining assumptions based on the original diameter as shown in Table 4-5.

TABLE 4-5: FUTURE LINER THICKNESS ASSUMPTIONS FOR RCP TRUNKS AND SIPHONS (LINED MODEL NETWORK ONLY)1
Original Diameter
(in)
Assumed Liner
Thickness (in)
Assumed Diameter
Reduction (in)
12 0.297 0.594
18 0.446 0.892
19 0.471 0.942
20 0.496 0.992
21 0.521 1.042
24 0.596 1.192
27 0.671 1.342
30 0.745 1.49
33 0.82 1.64
36 0.895 1.79
39 0.97 1.94
42 1.046 2.092
53 1.324 2.648
City of Santa Clara (Project 0012307.00) 4-11 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
1Assumed future liner thicknesses were conservatively calculated based on key assumptions such as host pipe condition, groundwater table, soil properties, etc.

TABLE 4-6: RCP TRUNKS IDENTIFIED FOR FUTURE LINING (LINED MODEL NETWORK ONLY) Trunk Lined Section1 Original
Diameter (in)
Lined
Diameter (in)2
Capacity
Reduction3
Homestead S20-9 to S21-43 27-30 25.7-28.5 12.8%
Calabazas S52-113 to S83-17 24-33 22.8-31.4 12.8%
Bowers S22-51 to S83-18 21-33 20-31.4 12.8%
Lafayette S65-30 to S115-8 24-53 22.8-50.4 12.8%
Central Expressway S64-44 to S67-21 24-27 22.8-25.7 12.9% De La Cruz East S48-11 to S58-2 24 22.8 12.8%
De la Cuz West S48-2 to S58-14 24 22.8 12.7%
Lafayette West S114-23 to S114-18 42 39.9 12.8%
GAP E Trunk S83-18 to S104-30 33-42 31.4-39.9 12.8%
GAP W Trunk S83-17 to S104-51 30-33 28.5-31.4 12.8%
1 Upstream to downstream manhole. 2 Rounded to the nearest 0.01-in. 3 Capacity Reduction was calculated as the maximum percent difference of the full capacities of the unlined and lined scenarios.

City of Santa Clara (Project 0012307.00) 4-12 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
FIGURE 4-5: RCP TRUNKS IDENTIFIED FOR FUTURE LINING (LINED MODEL NETWORK ONLY) City of Santa Clara (Project 0012307.00) 4-13 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

4.2 Capacity Evaluation Results
The calibrated model was run for existing, near-term future, and long-term future load conditions using both the Unlined Model Network and Lined Model Network to identify areas of the system that fail to meet the specified performance criteria described in Section 4.1.1. Areas that fail to meet the specified performance criteria were identified as capacity deficiencies.

This section presents the results of the system capacity evaluation as it relates to the City’s gravity sewers (Section 4.3) and pump stations and force mains (Section 4.4).

4.3 Gravity Sewer System Capacity Deficiencies
All the capacity deficiencies identified in the model for the City’s gravity sewer pipes are summarized in Table 4-7, including the load scenario, design flow, and physical network conditions that would trigger each deficiency. An overview map showing the locations of all the model-identified capacity deficiencies is provided as Figure 4-6. In the figure, pipes shown in pink are predicted to surcharge due to “throttle” conditions, indicating that the full capacity of the pipe is less than the predicted peak flow. Pipes shown in purple are predicted to surcharge due to backwater from a downstream throttle condition. The deficiencies listed in Table 4-7 are the gravity sewer pipes that would fail to meet the City’s specified performance criteria and would therefore need some type of capacity relief, either by increasing their capacity (e.g., upsize to larger diameter) or reducing the flow (e.g., divert flow away from pipe, reducing RDI/I). Project solutions modeled to relieve the identified capacity deficiencies are discussed in Section 4.5.

Profiles of the capacity deficient sewers, both before and after project implementation, are provided in Appendix G. Profiles are not provided for the specific development projects identified in Section 4.1.2 that have been previously modeled as part of the development review process (i.e., PHD, Mission Point, Freedom Circle). Note that model-predicted surcharging or overflows (depicted in the before profiles) do not necessarily mean that pipes would be capacity deficient at that location, as flows can back up due to downstream capacity limitations and cause surcharging or potential overflows at upstream locations due to backwater. Additionally, although the profiles indicate where modeled surcharging would occur due to backwater versus due to a capacity limitation (“throttle” condition), the results reflect an “unrelieved” system, meaning that peak flows are dampened out in the pipes that are under heavy surcharge or reduced due to overflows. This means that, as upstream deficiencies are relieved through capacity projects, the peak flows reaching downstream pipes would increase, potentially causing additional surcharging or overflows and triggering additional deficiencies and projects. Therefore, it would be necessary to model the project solutions starting upstream and then proceed to review the deficiencies downstream to confirm that any additional downstream deficiencies are addressed, as the system starts to be relieved.

TABLE 4-7: SUMMARY OF MODEL-PREDICTED GRAVITY SEWER CAPACITY DEFICIENCIES Deficiency Name
Wastewater Flow Trigger1 Design Flow Trigger Network Trigger Existing
(EL)
Near-Term
Future
(NTFL)
Long-Term
Future
(LTFL)
Dry
Weather
(DWF)
Wet
Weather
(WWF)
Unlined
(UMN)
Future
Lined
(LMN)
Agilent ✓ (E) ✓ ✓ N/A
Homestead Road ✓ ✓ ✓ N/A
Kiely Boulevard ✓ (GP) ✓ ✓ N/A
Victoria Avenue ✓ (SD, GP) ✓ ✓ N/A
Cabrillo Avenue ✓ ✓ ✓ N/A
City of Santa Clara (Project 0012307.00) 4-14 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
Deficiency Name
Wastewater Flow Trigger1 Design Flow Trigger Network Trigger Existing
(EL)
Near-Term
Future
(NTFL)
Long-Term
Future
(LTFL)
Dry
Weather
(DWF)
Wet
Weather
(WWF)
Unlined
(UMN)
Future
Lined
(LMN)
CMC Basin ✓ ✓ ✓ N/A
Bowers Avenue ✓ ✓ ✓
Calabazas Trunk ✓ ✓ ✓
Agate Drive ✓ (O2) ✓ ✓ N/A
Freedom Circle ✓ (SD) ✓ ✓ N/A
PHD ✓ (SD) ✓ ✓ N/A
Mission Point ✓ (SD) ✓ ✓ N/A
GAP West Trunk ✓ ✓ ✓ N/A
GAP East Trunk ✓ ✓ ✓
Bunker Hill Lane East ✓ (E) ✓ ✓ N/A
Lafayette Street ✓ ✓ ✓ N/A
1 Deficiency cause: SD = Specific Development Project; GP = General Plan; E = Entitlement Flow. O = Other (see notes).

If no specific cause is listed, deficiency would be caused by future lining assumption and/or cumulative impacts from upstream due to development and/or relieving upstream capacity constraints. 2 During wet weather design flows only, Agate Drive deficiency would be triggered because the Calabazas Trunk has insufficient capacity. Flows from Calabazas would backup and overflow to the Agate Drive sewers in the model through manhole S52-4, which is located just upstream of the Agate Drive siphon crossing. However, once the Calabazas Trunk deficiency is relieved, the model runs show that the Agate Drive deficiency would go away. Therefore, Section 4.5 does not include a capacity improvement project specific to Agate Drive, but Section 4.6 discusses this area in more detail due to the prolonged RDI/I observed during the flow monitoring program.

S A N T A

C L A R A
Wood hams Rd
Northlake Dr
Fo rbes Ave
Forest Ave
Pruneridge Ave
Albany Dr
Harold
Ave
Cronin Dr
Rodonovan
Dr
McKinley Dr
Estella Dr
Rebeiro Ave
Rosita Ave
Saratoga
Ave
Stevens Creek Blvd
Kiely Blvd
N Winchester Blvd
Pruneridge
Golf Club
Coy o te Cree
Ce k
nter Rd
C
ente
r Rd
Cisco Way
Balboa St
Holger Way
E Tasman Dr
N
1st St
237
Gua
dalupe Rive r
Innovation Dr
Aldo Ave
River Oaks Pkwy
Laurelwood Rd
Laurie Av e
Ewert Rd
N 1st
St
E Trimble R
Lick Mill B
lvd
G4
101
Alviso St
Newhall St
Main St
Jackson
St
Emory St
Boxwood Dr
Brokaw Rd
Airport Blvd
Lafayette St
Market St
The Alameda
De La Cruz Blvd
82 Santa Clara
Catholic
Cemetery
PayPal Park
San José Mineta
International
Airport
Santa Clara
University
University Ave
Olive Ave Shasta A
Woodland Ave
Bradley Ave
Bailey Ave
Cherrystone Dr
Kenwood Ave
Elliott St
N Bascom
Ave
Stevens Creek Blvd
Naglee Ave
Westfield Valley
Fair ATM
Agilent
CMC Basin
GAP W
GAP E
Calabazas Trunk
Lafayette St
Bowers Ave Kiely Blvd GAP W
Agilent
GAP E
CMC Basin
Homestead
Victoria Ave
Freedom Circle
Bunker Hill Ln E
Cabrillo Ave
Agate Dr
Legend
±
Figure 4-6
Overview of Capacity
Deficiencies
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx 0 0.25 0.5 1
Miles
Modeled Sewers
Surcharge State
<1 (no surcharge)
1 (backwater surcharge)
2 (throttle surcharge)
Project #: 0012307.00
Map Created: December 2024
Third Party GIS Disclaimer: This map is for reference and graphical purposes only and should not be relied upon by third parties for any legal decisions.

Any reliance upon the map or data contained herein shall be at the users’ sole risk.

City of Santa Clara (Project 0012307.00) 4-16 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

4.4 Pump Station and Force Main Capacity Deficiencies
Table 4-8 compares the estimated (theoretical) firm and total capacity of each modeled pump station to the modeled flows under buildout PWWF conditions. The table indicates that all pump stations would have sufficient capacity to convey model-predicted buildout PWWF. The table also indicates that modelpredicted force main velocities under buildout PWWF for Westside, Tasman, De La Cruz, Primavera, and Stadium Pump Stations would all be less than the capacity deficiency criteria threshold of 10 fps. Velocities are not reported for the Rabello and Northside Pump Station force mains because sufficient information was not available to reasonably represent the operation of these pump stations and force mains in the model (i.e., City could not confirm settings at the flow split gate structure upstream of the pump stations located at S114-19; City reported that the force main discharge pipes are normally submerged but could not provide monitored level data; actual typical pump operations / pump sequencing is unknown).

It should be noted that the model-predicted PWWFs and force main velocities presented may be slightly underpredicted compared to actual measured flows because of the way that the pumps are modeled; all pump stations are represented in the model network using Archimedean screw pumps, meaning that all the influent sewer flows from the upstream sewer system would be pumped through the force main at the same flow rate they reach the pump station (i.e., influent flow rate = effluent flow rate). Therefore, modeled Archimedean screw pumps mimic the smoother trunk flows coming into the pump station rather than the “peakier” downstream flows created by nature of the pumps turning on and off. However, considering SCADA flow data were not available to compare observed flows to model-predicted flows, this approach was considered to be a reasonable representation of flows and velocities.

TABLE 4-8: SUMMARY OF MODEL-PREDICTED PUMP STATION AND FORCE MAIN CAPACITY

DEFICIENCIES
Pump Station
(Number of
Pumps)
Model-Predicted
Buildout PWWF
(mgd)1
Firm
Capacity
(mgd)
Total
Capacity
(mgd)
Force Main Velocity
at Buildout PWWF
(mgd)1
Capacity
Deficiency4
Westside (2) 0.99 1.552 2.532 4.41 No
Tasman (2) 0.52 1.612 2.342 3.20 No
De La Cruz (2) 0.64 1.612 2.522 2.92 No
Primavera (6) 2.65 5.722 6.392 7.9 No
Stadium (6) 0.66 2.562 2.682 4.78 No
Rabello (8)

44.8 25.43 27.95- No
Northside (4) 19.83 21.35- No
1 Model Buildout PWWF values and force main velocities reported are from the long-term future load scenario using the Lined Model Network and the relieved system (assuming project solutions have been implemented). mgd = million gallons per day.
2 Theoretical firm and total capacities were estimated for Westside, Tasman, De La Cruz, Primavera, and Stadium Pump Stations based on basic information, pump settings, pump curves, and system curves provided by the City. Refer to Appendix C for detailed calculations for each pump station. 3 Theoretical firm capacities for Rabello and Northside Pump Stations were estimated by Schaaf & Wheeler Consulting Civil Engineers (S&W) as reported in a memorandum titled “Northside and Rabello Pump Station Firm Capacity Evaluation”, dated July 5, 2022.
4A capacity deficiency would be identified for cases where model-predicted PWWF exceeds the theoretical firm capacity or where force main velocity during PWWF exceeds 10 fps (refer to Table 4-3 for the capacity deficiency criteria). 5 Theoretical total capacities for Rabello and Northside Pump Stations were estimated using excel spreadsheet tools developed by Schaaf & Wheeler as part of the firm capacity study (refer to footnote 3). System curves for total capacities were estimated based on inferred data because Schaaf & Wheeler did not collect test points with all pumps running.

City of Santa Clara (Project 0012307.00) 4-17 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

4.5 Capacity Improvement Projects
This section presents the capacity improvement projects that were identified for the City’s sanitary sewer system based on the results of the performance evaluation described in Sections 4.3 and 4.4. An overview map showing the locations of all the model-identified capacity improvement projects is provided as Figure 4-7.

For most of the gravity sewer capacity deficiencies identified in Table 4-7, a project was developed to either replace the existing pipe with a larger pipe or redirect flows to other existing sewers with adequate available capacity. The PHD and Mission Point projects were already modeled during the development review process and will be paid for by the developers (as discussed in Sections 4.1.2 and 5.6); these projects will not be included in the Master Plan Update’s Sewer Capacity CIP but are still included in Table 4-9 for reference.

The Freedom Circle project is also included in Table 4-9 and discussed below; no separate infrastructure fee area has been established for the Freedom Circle Focus Area, so the previously modeled improvements are included in the City’s Sewer Capacity CIP. Additionally, a specific project was not identified to address the Agate Drive deficiency because model runs showed that this deficiency would be relieved once the Calabazas Trunk project was implemented to relieve existing capacity constraints within the Calabazas Trunk. The assumptions used to define the capacity improvement projects, including the design criteria applied (refer to Section 4.1.1 for more detail), are discussed briefly below.

Replacement pipes were sized to convey the buildout PWWF using the Lined Model Network with a maximum d/D ratio of 0.75; some exceptions were made to allow a slightly higher d/D ratio (always less than 1) to avoid oversizing isolated, flat segments just to meet this criterion. Existing pipe slopes and depths were preserved when upsizing sewers in-place. Projects that included re-sloping (i.e., replacing the existing pipe at a different slope) are identified as such in the project descriptions. Diameters were increased as minimally as possible to prevent oversizing and subsequent low velocities during dry weather conditions, while also considering standard pipe sizes.

Iterative model runs with all capacity improvement projects in place were performed to verify that no additional sewer system capacity deficiencies would occur after upstream capacity improvements were implemented and to review the flow and capacity of the pump stations in the sewer system. These model runs assessed the cumulative impact of increased capacity from upstream projects on peak flows in pipes downstream. Therefore, project solutions for the GAP West and GAP East Trunks were modeled last.

The recommended capacity improvement projects are all listed in Table 4-9 and discussed in more detail in the following subsections. In total, the table presents fifteen (15) capacity improvement projects which were identified as part of this Master Plan Update. Each project is documented in further detail in Appendix G with an individual plan view map and profile views of the impacted sewers before and after project implementation. Project prioritization and planning-level capital cost estimates were prepared for each of the thirteen (13) recommended projects to be funded by the City and included in its Sewer Capacity CIP; these are presented in Section 5 of this report.

S A N T A

C L A R A
Wood hams Rd
Northlake Dr
Fo rbes Ave
Forest Ave
Pruneridge Ave
Albany Dr
Harold
Ave
Cronin Dr
Rodonovan
Dr
McKinley Dr
Estella Dr
Rebeiro Ave
Rosita Ave
Saratoga
Ave
Stevens Creek Blvd
Kiely Blvd
N Winchester Blvd
Pruneridge
Golf Club
Coy o te Cree
Ce k
nter Rd
C
ente
r Rd
Cisco Way
Balboa St
Holger Way
E Tasman Dr
N
1st St
237
Gua
dalupe Rive r
Innovation Dr
Aldo Ave
River Oaks Pkwy
Laurelwood Rd
Laurie Av e
Ewert Rd
N 1st
St
E Trimble R
Lick Mill B
lvd
G4
101
Alviso St
Newhall St
Main St
Jackson
St
Emory St
Boxwood Dr
Brokaw Rd
Airport Blvd
Lafayette St
Market St
The Alameda
De La Cruz Blvd
82 Santa Clara
Catholic
Cemetery
PayPal Park
San José Mineta
International
Airport
Santa Clara
University
University Ave
Olive Ave Shasta A
Woodland Ave
Bradley Ave
Bailey Ave
Cherrystone Dr
Kenwood Ave
Elliott St
N Bascom
Ave
Stevens Creek Blvd
Naglee Ave
Westfield Valley
Fair ATM
Agilent
CMC Basin
GAP W
GAP E
Calabazas Trunk
Lafayette St
Bowers Ave Kiely Blvd GAP W
Agilent
Agilent
CMC Basin
Homestead
Victoria Ave
Freedom Circle
Bunker Hill Ln E
Cabrillo Ave
Legend
±
Figure 4-7
Overview of Capacity
Improvement Projects
Sewer Master Plan Update
Figure Exported: 12/27/2024 By: SEstabrook Using: \\woodardcurran.net\shared\Projects\0012307.00 Santa Clara CA Sewer Master Plan Update\wip\C. GIS\3. ArcGIS Pro\SantaClaraSewerMasterPlan2024_Report.aprx 0 0.25 0.5 1
Miles
Modeled Sewers
Capacity Improvement Project
Bunker Hill Ln E
Agilent
Bowers Ave
CMC Basin
Calabazas Trunk
GAP E Trunk
GAP W Trunk
Homestead Rd
Kiely Blvd
Lafayette St
Victoria Ave
Freedom Circle
Cabrillo Extent (Not Actual Project)
City of Santa Clara (Project 0012307.00) 4-19 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
TABLE 4-9: SUMMARY OF CAPACITY IMPROVEMENT PROJECTS
Project Triggers1
Project Details
MH IDs
(US - DS)
Length
(LF)2
Pre-Project
Diameters
(in)3
Post-Project
Diameters
(in)3
New
Weirs Location & Description

1. Agilent
(Section 4.5.1)
LTFL
DWF
UMN
S10-77 - S33-33 12,313 10, 21, 24 15, 24, 27 S22-55
Tracy Dr, Pomeroy Ave,
Homestead Rd (S Trunk), Kiely
Blvd

2. Homestead Road
(Section 4.5.2)
LTFL
WWF
UMN
S20-9 - S23-18
(excluding siphon) 6,407 18, 27, 30 24, 30, 33 S20-16
N Homestead Trunk from
Swallow Wy to Saratoga
Creek

3. Kiely Boulevard
(Section 4.5.3)
LTFL
WWF
UMN
S33-42 - S33-35 270 8 10 -
Orthello Wy to S of El
Sobrante St

4. Victoria Avenue
(Section 4.5.4)
LTFL
WWF
UMN
S42-113 - S42-36 765 8 10 -
Fowler Ave & Pomeroy Ave to
Nobili Ave & Victoria Ave

5. Cabrillo Avenue
(Section 4.5.5)
EL
WWF
UMN
- - - -
S40-16,
S41-38
Halford Ave & Buckley St; St.

Lawrence Dr, W of Lawrence
Expwy

6. CMC Basin
(Section 4.5.6)
EL
WWF
UMN
S52-104 - S52-80
S43-14 - S53-103 3,655 8 12, 15 -
Santa Maria Ave & Francis
Ave; Amethyst Dr

7. Bowers Avenue
(Section 4.5.7)
LTFL
WWF
LMN
S53-34 - S63-20 2,605 25.7 30 - Chromite Dr to Walsh Ave

8. Calabazas Trunk
(Section 4.5.8)
EL
WWF
LMN
S52-4 - S62-31
S62-31 - S62-10
S62-37 - S62-38
2,7604 22.8, 24, 27 18, 27 -
Calabazas Creek from S of
Agate Dr to Central Expwy

9. Freedom Circle
(Section 4.5.9)
LTFL
DWF
UMN
S84-12 - S83-18 1,8855 12 15 -
Mission College Blvd from
Freedom Cir to west of Great
America Pkwy
City of Santa Clara (Project 0012307.00) 4-20 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
Project Triggers1
Project Details
MH IDs
(US - DS)
Length
(LF)2
Pre-Project
Diameters
(in)3
Post-Project
Diameters
(in)3
New
Weirs Location & Description

10. Patrick Henry Drive
(PHD)6
LTFL
DWF
UMN
S92-16 – S93-50 6,185 - 6-39 -
Patrick Henry Drive and Great
America Parkway.

11. Mission Point6
LTFL
DWF
UMN
S92-15 – PHD-11 6,560 - 12-15 -
West Tasman Drive and Great
America Parkway.

12. GAP West Trunk
(Section 4.5.10)
LTFL
WWF
UMN
S93-42 - S104-19
(excluding siphon) 4,810 28.5-35.7 36, 42 -
S of West Tasman Dr to
Lafayette St

13. GAP East Trunk
(Section 4.5.11)
LTFL
WWF
LMN
S83-20 to S83-18 231 31.4 39 -
Old Glory Ln to S of Bunker
Hill Ln; Stars and Stripes Dr

14. Bunker Hill Lane
East (Section 4.5.12)
LTFL
WWF
UMN
S93-10 - S93-7 110 6 8 - E of Great America Pkwy

15. Lafayette Street
(Section 4.5.13)
LTFL
WWF
UMN
S104-29 - S104-8 2,2905 34.2, 40.3, 42 42, 48 -
N of Calle del Mundo to S of
Great America Wy
1 Triggers include: EL = Existing Loads; NTFL = Near-Term Future Loads; LTFL = Long-Term Future Loads; DWF = Dry Weather Flows; WWF = Wet Weather Flows; UMN = Unlined Model Network; LMN = Lined Model Network.
2 Length of sewers included in upsizing project, rounded up to the nearest 5 linear feet (LF). 3 Range of pipe diameters included in the project. If the project sewers were identified for future lining, the pre-project diameters represent the future lined diameter assumption that was applied to the Lined Model Network which may be different from the existing diameters that exist in the field. 4 Includes length of sewers to be re-sloped and new parallel sewer segment. 5Includes length of sewers to be re-sloped. 6 Proposed project to be paid for by the developer.

City of Santa Clara (Project 0012307.00) 4-21 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024

4.5.1 Agilent
The Agilent capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during dry weather conditions, in the Unlined Model Network (as indicated in Table 4-7).

The recommended project includes replacement of 12,557 LF of 10-, 21-, and 24-inch pipe with 15-, 24-, and 27-inch pipe along Tracy Drive, Pruneridge Avenue, Pomeroy Avenue, Homestead Road (South Homestead Trunk), Saratoga Creek, and Kiely Boulevard (from manhole S10-79 to S33-33). The recommended project also includes installation of a weir at manhole S22-55 to divert the influent flows from Homestead Road South Trunk and Pomeroy Avenue sewers to the Homestead Road South Trunk, which would be upsized as part of the project. The recommended project would maximize capacity in the Homestead Road South Trunk and send as much flow as possible to an upsized Bowers Avenue Trunk.

An alternative involving diverting flows to the larger diameter Homestead Road North Trunk instead of the South Trunk was also preliminarily considered and investigated. However, pipe condition data provided by the City showed that the Homestead Road South Trunk was known to be in worse condition; this pipe had defect scores of 4 or 5 (assigned based on the severity of the worst defect detected) along the stretch of pipe that would be upsized. Therefore, the recommended alternative includes upsizing of the Homestead Road South Trunk. Moreover, it should be noted that a capacity improvement project was also identified for the Homestead Road North Trunk and is discussed in Section 4.5.2.

The primary reason for this capacity deficiency is a historic entitlement flow of 0.95 mgd associated with Parcel APN 316-17-018 located at 5301 Stevens Creek Boulevard (current owner Agilent Technologies). This entitlement flow is significantly greater than the company’s recent historical water usage of approximately

0.02 mgd (based on winter season water billing data from 2019-2022). Implementing this project in the near term would result in oversized sewers where the daily flow is not sufficient to provide the minimum cleaning velocity and thus could create potential debris and odor issues. However, the City should implement the Agilent capacity improvement project to address the potential capacity deficiency before the parcel begins to discharge its entitled flow of 0.95 mgd. Based on model runs, the maximum flow that Agilent could discharge before the capacity project would be needed is approximately 0.23 mgd; the deficiency would first occur in the sewers along Pomeroy Avenue, south of Homestead Road.

4.5.2 Homestead Road
The Homestead Road capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Unlined Model Network. The long-term future loads scenario assumes that the Cupertino Sanitary District (CuSD) discharges a future flow to the City’s sanitary sewer system up to its current contractual limit (13.8 mgd), which contributes to the deficiency identified in the Homestead Road sewers.

The recommended project includes replacement of 6,565 LF of 18-inch, 27-inch, and 30-inch pipe with 24- inch, 30-inch, and 33-inch pipe along Homestead Road from Swallow Way to Saratoga Creek (from manhole S20-9 to S23-18). The proposed upsizing project that was modeled maintains the existing pipe slopes; however, if feasible, the City may wish to evaluate alternatives during preliminary design that would reslope and steepen the flatter pipe segments (i.e., proposed 33-inch pipes between manholes S20-18 and S21-43). It should be noted that the proposed project does not include improvements to the siphon between manhole S20-26 and S20-18 because the siphon would not be capacity deficient. Per the City’s records, that siphon is not currently lined and is made of polyethylene with an internal diameter of 20.2 City of Santa Clara (Project 0012307.00) 4-22 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
inches; therefore, it was not assumed for future lining in the Lined Model Network based on the material classification.

The recommended project also includes installation of a weir at manhole S20-16 to divert as much flow as possible to maximize the available capacity within the upsized Homestead Road South Trunk (refer to description of the Agilent project in Section 4.5.1). The Homestead Road and Agilent capacity improvement projects would work together to maximize capacity within both trunks along Homestead Road to send as much flow as possible to an upsized Bowers Avenue Trunk. This approach targets replacement efforts to older pipelines assumed to be in worse condition and diverts flow away from the Calabazas Trunk, which is relatively shallow in some locations (i.e., at higher risk of sewer overflows) and also had capacity issues during wet weather flows which were first identified under existing loading conditions using the Lined Model Network and under near-term loading conditions in the Unlined Model Network (refer to Section

4.5.8 for discussion of the Calabazas Trunk project).

4.5.3 Kiely Boulevard
The Kiely Boulevard capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Unlined Model Network. Simulation results show that the capacity deficiency is caused by cumulative impacts of increased discharges from General Plan parcels (discussed in Section 2.2.2.2), specifically parcels draining to the Homestead Road North Trunk and the sewer along Brookdale Drive.

The recommended project includes upsizing of one 270 LF segment of 8-inch pipe to 10-inch pipe on Kiely Boulevard from Orthello Way to south of El Sobrante Street (from manhole S32-42 to S33-35).

4.5.4 Victoria Avenue
The Victoria Avenue capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Unlined Model Network. According to the simulation results, the capacity deficiency is caused by cumulative impacts of increased discharges from the El Camino Real Specific Plan and General Plan parcels, specifically parcels draining to the sewers on the north side of El Camino Real and along Warburton Avenue.

The recommended project includes upsizing and re-sloping of 515 LF of 8-inch pipe to 10-inch pipe on Fowler Avenue from Pomeroy Avenue to Nobili Avenue and installation of 250 LF of new 10-inch pipe on Nobili Avenue from Fowler Avenue to Victoria Avenue (from manhole S42-113 to S42-36). The project also would include abandoning 255 LF of existing 8-inch sewer between Fowler Avenue and Victoria Avenue (from manhole S42-48 to S42-36), which crosses through an easement underneath single-family residential parcels.

The recommended project is an alternative solution to the project that was preliminarily modeled, which included upsizing of only two pipe segments along Victoria Avenue from Pomeroy Avenue to Nobili Avenue (from manhole S42-36 to S42-113). However, upon further review and based on discussions with the City, the alternative was expanded so that the pipe located within the existing easement could be abandoned.

This project solution does not include two pipe segments between manholes S42-113 and S41-53, because they would have adequate capacity based on the City’s capacity criteria (no surcharge), thus they were not included in the proposed project. However, considering these pipe segments are located between the Victoria Avenue proposed project and the recently upsized section downstream of manhole S41-53, the City may wish to consider expanding the project to include these pipes during preliminary design.

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4.5.5 Cabrillo Avenue
The Cabrillo Avenue capacity improvement project would relieve the surcharge capacity deficiency first triggered in the Unlined Model Network under existing sewer loads during wet weather conditions. Note that the capacity deficiency is also triggered during dry weather conditions but only under long-term future loads.

The recommended project includes installation of two weirs (at manhole S40-16 and S41-38) to divert as much flow as possible away from the capacity deficient sewers along Cabrillo Avenue and maximize use of available capacity within adjacent existing sewers. The first weir would be installed in manhole S40-16 at the intersection of Halford Avenue and Buckley Street and would divert flow east through the sewers along Buckley Street and away from the sewers to the north along Halford Avenue that eventually drain to Cabrillo Avenue. The second weir, which would be located downstream of the first weir, would be installed in manhole S41-38 at the intersection of Lawrence Expressway and Saint Lawrence Drive and would continue to divert flow east through the sewers along Saint Lawrence Drive and away from the sewers to the north that eventually drain to Cabrillo Avenue. Model simulation results suggest a maximum change in d/D of 28% (from 37% to 65% full) in the sections downstream of the weirs. However, with flows diverted away from Cabrillo Avenue through these two new weirs, the capacity deficiency along Cabrillo Avenue would be eliminated.

An alternative solution was preliminarily modeled to upsize existing 8-inch pipes to 12-inch along Cabrillo Avenue (from manhole S41-13 to S41-20) and one pipe segment on Lawrence Expressway from 8-inch to 10-inch; however, the City preferred the recommended solution which avoids the need for pipe replacement. Additionally, any pipe replacement along Lawrence Expressway would require obtaining a permit from Santa Clara County, which would add cost and complexity to the project.

4.5.6 CMC Basin
The CMC Basin capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under existing sewer loads, during wet weather conditions, in the Unlined Model Network.

The recommended upsizing project includes replacement of approximately 3,655 LF of 8-inch pipe with 12- inch pipe along Amethyst Drive (from manhole S43-14 to S53-103) and 15-inch pipe along Santa Maria Avenue and Francis Avenue (from manhole S52-104 to S52-80).

Although the model runs show that the recommended upsizing project would meet the City’s d/D design criteria under PWWF as shown in the project solution profile presented in Appendix G, it would not meet the City’s velocity design criteria under PDWF (i.e., minimum of 2 fps) within the upsized 12-inch pipe segments between S43-14 and S53-103 on Amethyst Drive and the upsized 15-inch pipe segments between S52-104 and S53-74 on Santa Maria Avenue. These criteria often come into conflict with one another because increasing the size of the pipe to meet the required maximum d/D criterion under a relatively shortduration PWWF condition means that the pipe will experience lower velocities during normal dry weather conditions which occur much more often.

Flow meters within the CMC Basin tributary area exhibited a very high RDI/I response during the monitoring program. Therefore, it is recommended that the City conduct I/I investigations prior to project implementation to attempt to pinpoint and eliminate significant sources of excessive I/I within the CMC Basin, if possible. However, model runs show that the RDI/I would need to be reduced by at least 50% to 60% to eliminate the capacity deficiency. Refer to Section 4.6 for a more detailed discussion on I/I, including source detection and control methods and previous investigations and recommendations for Santa Clara.

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4.5.7 Bowers Avenue
The Bowers Avenue capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Lined Model Network only. The capacity deficiency would be caused by the assumed future lining of the Bowers Trunk, which the City identified as a RCP sewer.

The recommended upsizing project includes replacement of approximately 2,605 LF of existing 27-inch pipe (25.7-inch with assumed future lining) with 30-inch pipe along Bowers Avenue (from manhole S53-34 to S63-20) from Chromite Drive to Walsh Avenue. The project profile in Appendix G shows that the downstream end of the downstream-most pipe segment included in the proposed project (from manhole S63-26 to S63-20) would exceed the City’s 0.75 maximum d/D design criterion under PWWF; however, the pipe was not upsized because the resulting d/D ratio was still less than 1 and the City preferred to keep diameters consistent rather than upsize one isolated pipe segment just to meet the d/D design criterion.

4.5.8 Calabazas Trunk
The Calabazas Trunk capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under existing sewer loads, during wet weather conditions, in the Lined Model Network. The capacity deficiency also appears in the Unlined Model Network under near-term and longterm future loads during wet weather flow conditions.

The recommended project includes upsizing of approximately 2,000 LF of existing 22.8 – 27-inch pipes along Calabazas Creek (from manhole S52-4 to S62-10) from south of Agate Drive to Central Expressway.

It should be noted that the recommended project includes pipe segments that are already lined between manhole S62-51 and S62-32. The Lined Model Network assumes existing, unlined 27-inch RCP pipes would be lined resulting in a diameter of 25.7-inch. Roughly 750 LF of pipe between manhole S62-31 and S62-10 of the 2,000 LF that would be upsized to 27-inch would also be re-sloped. In addition to upsizing and resloping, the project includes installation of a new 18-inch pipe between manhole S62-37 and S62-38 that runs parallel to the existing sewer to relieve the capacity restriction at that location due to a storm drain crossing north of Kifer Road.

The model runs show that the Calabazas Trunk project would eliminate the overflow diversion from the Calabazas Trunk into the Agate Drive sewers at manhole S52-4, which is located just upstream of the Agate Drive siphon crossing. Therefore, the Calabazas Trunk project solution would eliminate the Agate Drive capacity deficiency so that no additional project would be required for Agate Drive.

4.5.9 Freedom Circle
The Freedom Circle capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during dry weather conditions, in the Unlined Model Network. The capacity deficiency would be caused by increased flows from the Freedom Circle Focus Area specific development project that would discharge into the City’s sewers along Freedom Circle Drive and Mission College Boulevard. This project was previously modeled during the development review process but is still identified as a Master Plan Update project to be included in the City’s Sewer Capacity CIP. The recommended project is a slight modification of the project identified during the development review and includes re-sloping to meet the City’s design criteria d/D (maximum of 0.75 during PWWF).

The recommended upsizing project includes replacement and re-sloping of 1,885 LF of 12-inch pipe and 15-inch pipe with 15-inch pipe along Mission College Boulevard (from manhole S84-12 - S83-18) from Freedom Circle Drive to west of Great America Parkway. The downstream most segment of the project (from City of Santa Clara (Project 0012307.00) 4-25 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
manhole S83-13 to S83-18) was assumed to connect to the GAP East trunk at equal crown elevations to minimize impacts from the GAP East trunk hydraulics.

4.5.10 GAP West Trunk
The GAP West Trunk capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Unlined Model Network. The GAP West Trunk sits lower than the GAP East Trunk, to which it is interconnected, and therefore reaches capacity first. However, a capacity deficiency project was also identified for the GAP East Trunk (triggered by the Lined Model Network only) and is discussed further in Section 4.5.11. Considering that the capacity deficient sewers are located towards the downstream end of the City’s sewer system, the capacity deficiency would likely be caused by the cumulative impacts of long-term future loads on the system combined with wet weather conditions. The deficiency would be slightly exacerbated with assumed future lining of the GAP West Trunk, which the City identified as a RCP sewer.

The recommended upsizing project includes replacement of approximately 4,810 LF of existing 28.8-31.7- inch pipe (already lined), 30-inch pipe, and 33-inch pipe with 36-inch and 42-inch pipe along Great America and the easement north of Stars and Stripes Drive (from manhole S93-42 to S104-19) from south of West Tasman Drive to Lafayette Street. The recommended project does not include improvements to the existing siphon between manhole S103-19 and S103-16, because the simulation results do not predict this siphon to be deficient. It should be noted that this siphon was assumed to be lined in the future as part of the Lined Model Network, but it is not currently lined. Even with the reduced diameter assumed based on future lining, the siphon would not be capacity deficient. However, the City may wish to consider evaluating alternatives during preliminary design that would replace or remove this siphon that crosses under the San Tomas Aquino Creek, if feasible.

It should also be noted that the project does not include the GAP West Trunk improvements associated with the PHD development. The cost to upsize the GAP West Trunk from the PHD specific development project’s discharge point to the Bay Division pipelines crossing (from manhole S83-5 to S93-53) is to be paid by the developers as discussed in Section 4.1.2; therefore, this portion of the project is not included in the Master Plan Update and will not be reflected in the City’s Sewer Capacity CIP. The Master Plan Update and Sewer Capacity CIP will only include the GAP West Trunk capacity improvements located downstream (north of Old Glory Lane) and which are not part of the PHD agreement. There are, however, two pipe segments between manholes S93-48 and S93-42 that are downstream of the PHD project and the GAP West project that would still have capacity based on the City’s capacity criteria of no surcharge. They are not included in the proposed project, but the City may wish to consider expanding the project to include them during preliminary design.

4.5.11 GAP East Trunk
The GAP East Trunk capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Lined Model Network only because the City identified the GAP East Trunk as a RCP sewer. Therefore, the capacity deficiency would not be triggered in the Unlined Model Network. Considering the capacity deficient sewers are located at the downstream end of the City’s sewer system, the deficiency is due to the combined effects of the assumed future lining plus long-term future loads plus wet weather conditions.

The recommended upsizing project includes replacement of approximately 230 LF of existing 33-inch (assumed lined inside diameter of 31.4-inches) to 39-inch pipe from manhole S83-20 to S83-18 (at the manhole connecting the Freedom Circle trunk with the GAP East Trunk). The scope of the recommended City of Santa Clara (Project 0012307.00) 4-26 Woodard & Curran, Inc.

Master Plan Report - Draft December 2024
improvement project is minimal because simulation results show that the recommended improvements to the GAP West Trunk (discussed in Section 4.5.10) would relieve most of the deficiencies in the GAP East Trunk.

4.5.12 Bunker Hill Lane East
The Bunker Hill Lane East capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Unlined Model Network. The primary cause of the capacity deficiency is due to historic entitlements held by parcel APNs 104-55-012 and 104-55-013 (located near Bunker Hill Lane and east of Great America Parkway by the Santa Clara Convention Center). Combined, these two parcels are entitled to discharge up to 0.27 mgd into the City’s sewer system.

Assuming that the entitlement flow would be loaded to the City’s sewer system, the existing 6-inch sewers between manhole S93-13 and S93-7 would be surcharged during PWWF conditions (as shown in the profile provided in Appendix G); specifically, the sewer between manhole S93-10 and S93-7 would be capacity deficient and would need to be upsized to convey the flow. Therefore, the recommended project includes replacement of the existing 6-inch pipe that would experience the throttle surcharge (between manhole S93-10 and S93-7) with approximately 110 LF of 8-inch pipe. The project solution profile in Appendix G shows that the pipe segment immediately downstream of the pipe to be upsized would still be surcharged at the downstream end. However, this model-predicted surcharge is a backwater surcharge on one end only that is caused by the hydraulic grade line from the connection to the larger diameter GAP East Trunk. Prior to project implementation, the City should verify the inverts of sewers along the project alignment and at the downstream connection to the GAP East trunk sewer.

This project should not be implemented until these parcels begin to discharge their entitled flow.

4.5.13 Lafayette Street
The Lafayette Street capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during wet weather conditions, in the Unlined Model Network. Considering the capacity deficient sewers are located towards the downstream end of the City’s sewer system, the capacity deficiency would likely be caused by the cumulative impacts of long-term future loads on the system combined with wet weather conditions. The deficiency would be slightly exacerbated with assumed future lining of the Lafayette Trunk, which the City identified as a RCP sewer.

The recommended upsizing project includes replacement of approximately 2,290 LF of existing 36-inch (34.2-inch with assumed future lining), 40.3-inch pipe (already lined), and 42-inch pipe with 42-inch and 48- inch pipe along Lafayette Street (from manhole S104-29 to S104-8) from north of Calle del Mundo to south of Great America Way. The project also includes some re-sloping of the existing pipe segments from manhole S104-22 to S104-14; per record information, the existing slope is minimal at approximately 0.02%.

4.6 Infiltration and Inflow Discussion
There are various methods for characterizing the relative contributions of RDI/I from different areas of the sewer system. Because the critical issue with respect to RDI/I is the impact that peak flows have on the system, the focus is on characterizing peak RDI/I in particular. Potential approaches to quantify peak RDI/I include: the ratio of PWWF to average dry weather flow (ADWF), referred to as the wet weather peaking factor; peak RDI/I per acre of contributing area; and peak RDI/I per foot of pipe; where PWWF and peak RDI/I are based on design storm flows. The RDI/I response can be characterized for each metered basin based on these parameters.

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4.6.1 Completed Infiltration and Inflow Investigations
Based on the flow monitoring data collected during the winter 2022-2023 season and as discussed in Sections 2.1 and 3.5.2.1, a very high RDI/I response was observed within the flow meter (FM) basins in the CMC tributary area, the extent of which is shown in Figure 4-8.

FIGURE 4-8: CMC BASIN TRIBUTARY AREA
During the flow monitoring period, wet weather peaking factors of 23.5 and 17.0 were observed in the FM 27 and FM 28 basins, respectively; these peaking factors (presented in Section 3.5.2) were much higher than the peaking factors observed in other FM basins throughout the City which, when averaged together not including FM 27, FM 28, and FM 4 (Levis stadium flows), were approximately 3.4. The adjacent Agate Drive tributary area (FM 31) also showed a significant and sustained response to rainfall. The nature of the responses at FM 27 and FM 31 were indicative of significant infiltration, as the response was generally slower and took a long time to recede (i.e., several weeks following rainfall). Moreover, because several consecutive rainfall events occurred within a short period of time during the flow monitoring period, the infiltration response did not fully recede before another rainfall event occurred. For example, the FM 31 data indicate that depth of flow did not return to baseline levels in between rainfall events from December 27, 2023, and January 19, 2024, as shown in Figure 4-9. Based on NOAA rainfall statistics (refer to Figure 4-10), actual rainfall observed during the wet weather monitoring season was greater than a 10-yr event for longer durations (10+ days).

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FIGURE 4-9: OBSERVED FLOW MONITORING DATA AT FM 31 (S62-50, 10”) FIGURE 4-10: NOAA RAINFALL STATISTICS COMPARED TO OBSERVED JANUARY 2023 RAINFALL IN

SANTA CLARA, CA
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The flow monitoring results are consistent with the findings of other field investigations that V&A recently completed in the CMC basin as discussed in Section 3.5.2.1. V&A’s associated report recommended that the City consider smoke testing in the CMC basin, which may better identify lateral defects.

4.6.2 I/I Source Detection and Control Methods
A necessary step in identifying potential I/I control measures is a realistic assessment of the actual sources of I/I in the sewer system. Based on the pattern and magnitude of flows in the City’s sewer system, the likely sources of RDI/I flows are defects in sewers and service laterals, and possibly some direct connections (e.g., illegally connected roof and area drains, direct connections from the storm drain system, etc.). Appropriate I/I control methods depend on the type and sources of I/I. Control methods must include detection as well as correction.

Direct Inflow Sources
Direct inflow sources can contribute significantly to both volume and peak rates of I/I and have the greatest probability of being cost effective to eliminate. The main methods used to detect and locate direct inflow sources are smoke and dye testing (dye testing is used primarily as a confirmatory test). Smoke testing is considered to be a relatively easy and inexpensive method (cost is approximately $1.00 to $1.25 per foot if a substantial length of pipe is tested), and discovery of just a few direct storm drain cross-connections, for example, can make the effort worthwhile. However, unless there is some indication or knowledge of the existence of direct connections in the system, finding them may require an extensive smoke testing program, which requires public notification measures and access to private property to document the smoke returns. For this reason, smoke testing is generally targeted at specific areas with high peak RDI/I rates.

Generally, the most numerous types of sources found during smoke testing are not direct inflow connections but defects in shallow pipes, primarily laterals. Rehabilitation of laterals may be a challenging institutional issue (see discussion below on correction of private property I/I sources).

Manholes subject to ponding or located in drainage courses may also be sources of direct inflow. The amount of I/I depends on the manhole location, type of manhole cover (number and size of holes), and the condition of the cover and frame. Physical inspection of manholes is the most effective way to identify such conditions, and correction is relatively straightforward (replace cover, realign frame, raise manhole to grade, remove or relocate manhole in watercourse, etc.). Physical inspection can be conducted in conjunction with sewer inspection or routine cleaning work, or as a separate activity.

Elimination of direct inflow connections requires disconnection of the source and re-direction of the drainage to an appropriate location. This may simply be to the ground surface (as in the case of roof drains), or connection to a nearby storm drain or street gutter. In general, each identified source needs to be evaluated on a case-by-case basis to identify the appropriate corrective measure.

Infiltration Sources in Sewer Mains and Manholes
Infiltration sources are defects in sewer pipes or manholes caused by defective materials or construction, general deterioration, or damage caused by physical conditions such as ground movement or settlement, traffic loads, or root intrusion. Infiltration sources (defects) are detected by inspection: visual inspection in the case of manholes and CCTV inspection for sewer mains. However, visual observation of active I/I is generally not feasible because the RDI/I generally occurs for only short periods during rainfall events, and the pipes may fill up during those periods, making CCTV inspection difficult or impossible.

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Infiltration correction methods involve rehabilitation or replacement of entire pipe segments or manholes or spot repair of localized defects. There are numerous materials and methods used for this type of rehabilitation. In general, however, the cost per unit amount of I/I removed is relatively high, because the defects individually contribute relatively small amounts of flow. It is recognized that infiltration in the sewer system will “migrate” to other nearby defects that are left un-repaired. Therefore, a fairly extensive area of the system may need to be included in the rehabilitation effort in order to achieve substantial flow reduction. Furthermore, reductions greater than about 30% can rarely be achieved without also addressing the infiltration from private laterals. Generally, rehabilitation to reduce infiltration is cost effective only if a significant amount of infiltration can be isolated to a relatively small area, or there are extremely costly improvements required downstream to convey, treat, and dispose of the excess flow.

I/I Sources on Private Property
I/I sources on private property are primarily defective laterals, but may also include broken cleanouts or cleanout caps, or directly connected roof and area drains. Smoke testing is the primary method for detecting private property I/I sources.

It should be noted that low lying areas and any buildings with basements are likely to have sump pumps. It is possible that some sump pumps may be directly connected to the sewer system, rather than the storm system, or may be discharging to the street, in which case those flows would likely enter the storm system but could also enter the sewer system through manhole cover openings. Connected sump pumps would not be identified by any of the source detection methods described here, but building inspectors may have more information about whether these types of connections exist in the area. Therefore, for more aggressive programs, building or property inspections can be conducted, and/or laterals can be CCTV inspected or tested for leaks using air or water pressure tests. These types of inspections and tests generally require that the lateral have cleanout access, ideally at both the connection to the building plumbing and at or near the property line. However, new technologies are now available, such as cameras that can be “launched” up the lateral during CCTV inspection of the mainline, that make it easier to inspect private laterals.

4.6.3 I/I Investigation Recommendations for Santa Clara Reducing I/I through locating defects and sewer main replacement programs could be an effective alternative to capacity improvement projects; specifically, the capacity improvement project recommended for the CMC Basin. However, it can be difficult to predict the extent of I/I reduction that could be achieved through any individual I/I reduction project. In the CMC Basin tributary area, for example, model runs show that RDI/I would need to be reduced by at least 50% to 60% to eliminate the CMC Basin capacity deficiency (i.e., surcharge along Amethyst Drive and Santa Maria Avenue and Francis Avenue) and the need for a capacity improvement project that includes upsizing the existing sewers.

Even if the required I/I reduction is achievable, the cost of the significant sewer main (and sewer lateral) replacement needed to achieve meaningful reductions of I/I is often more expensive than adding additional conveyance capacity. Moreover, the time needed to implement I/I reduction projects and assess their impacts on system through pre-and-post-implementation flow monitoring programs could be significant.

Therefore, I/I reduction may not be a cost-effective approach.

Still, it is recommended that the City’s Sewer Capacity CIP include some budget for I/I source detection methods to attempt to further characterize and pinpoint significant sources of I/I to the sanitary sewer system. The V&A report (discussed in Section 4.6.1) recommended CIPP lining of pipe segments that were investigated via CCTV during the study because all showed condition defects; however, it is recommended that further basin wide investigations be completed prior to implementing targeted rehabilitation projects.

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At minimum, smoke testing and CCTV investigations should be conducted within the CMC Basin prior to implementation of the capacity improvement project discussed in Section 4.5.1, which consists of upsizing the capacity deficient sewers. Additionally, the City should consider conducting smoke testing and CCTV investigations within the FM 31 basin area that is tributary to the Agate Drive sewers. An allowance for these recommended I/I investigations is included in the Sewer Capacity CIP in the form of other additional costs (refer to Section 5.5).

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5. RECOMMENDED SEWER CAPACITY CAPITAL IMPROVEMENT PROGRAM This section presents the specific sewer projects that are recommended for inclusion in the City’s Sewer Capacity CIP based on the findings of the sewer system capacity analysis discussed in Section 4.

The sections below give an overview of the process, information and assumptions used, specifically:
• Project development process
• The methodology used to prioritize projects and estimate their costs • Indirect cost resulting from implementing the capacity improvement projects • Level of confidence in the projects
• Projects that will not be financed by the City
• An overall summary of all recommended projects, along with a brief discussion for each project focusing on the rationale and validation to justify the need for the project (refer to Sections 4.5.1-

4.5.13 for more detailed descriptions of the model-predicted capacity deficiencies and the solutions modeled)
• Project schedule
Details for each project are included in Appendix G.

5.1 Project Development Process
Capital improvement projects were developed to address potential deficiencies identified in the capacity analysis. One project was developed from up to three alternatives analyzed for each of the capacity deficiencies presented in Section 4.

City Council and Authorities ConcurrentJuly 15, 2025

City Council and Authorities Concurrent
July 15, 2025