City Council and Authorities Concurrent
December 9, 2025

Resolution/Sanitary Sewer Master Plan Update Page 1 of 2 Rev: 7/27/2023
RESOLUTION NO. 25-9514

A RESOLUTION OF THE CITY OF SANTA CLARA, CALIFORNIA,

APPROVING THE SANITARY SEWER MASTER PLAN UPDATE
REPORT
WHEREAS, the San Francisco Regional Water Quality Control Board and the California State Water Resources Control Board have both independently mandated that all sanitary sewer system operators within the San Francisco region and within the State of California, respectively, prepare and implement Sanitary Sewer Management Plans (“SSMP”); WHEREAS, the City operates and maintains a sanitary sewer collection system within the city limits and the City Council of the City of Santa Clara is the governing body of the City’s sewer utility;
WHEREAS, the State Water Resources Control Board requires that the SSMP be updated every 6 years and adopted by the City Council at a regular or special meeting to ensure that the City Council is aware of the scope of the SSMP and its potential impacts; WHEREAS, the City Council most recently approved a 2025 Update to the SSMP on July 15, 2025 (Resolution 25-9470);
WHEREAS, a system evaluation and capacity assurance plan is a required element of a SSMP; WHEREAS, the Department of Public Works has prepared a report entitled “Sanitary Sewer Master Plan Update 2025” (the "Report") to guide the ongoing and future sanitary sewer system capacity improvements and to fulfill the SSMP requirement for a system evaluation and capacity assurance plan;
WHEREAS, the system evaluation and capacity assurance plans contained in the 2025 Update to the SSMP included the 2007 Assessment, 2016 Master Plan, and preliminary draft of the Sanitary Sewer Master Plan Update 2025 Report;
WHEREAS, the Report which is attached is on file in the Office of the City Clerk, available for public inspection, and incorporated herein by this reference; //
WHEREAS, the Report was made available for public inspection at least ten days before the public hearing by placing the data on file with the City Clerk's office on November 5, 2025 in accordance with Government Code 66016; and,
WHEREAS, the City Council now desires to approve the Report.

NOW THEREFORE, BE IT RESOLVED BY THE CITY OF SANTA CLARA AS FOLLOWS:

1. That the City Council hereby finds that the above Recitals are true and correct and by this reference makes them a part hereof.

2. 3.

That said Report, as duly revised and corrected if necessary, is hereby approved.

Effective date. This resolution shall become effective immediately.

I HEREBY CERTIFY THE FOREGOING TO BE A TRUE COPY OF A RESOLUTION PASSED

AND ADOPTED BY THE CITY OF SANTA CLARA, CALIFORNIA, AT A REGULAR MEETING THEREOF HELD ON THE grn DAY OF DECEMBER, 2025, BY THE FOLLOWING VOTE:

AYES: COUNCILORS:

NOES: COUNCILORS:

ABSENT: COUNCILORS:

ABSTAINED: COUNCILORS:

Attachments incorporated by reference:

1. Sanitary Sewer Master Plan Update - August 2025
Resolution/Sanitary Sewer Master Plan Update
Rev: 7/27/2023
Chahal, Cox, Gonzalez, Hardy, Jain, and Park, and
Mayor Gillmor
None
None
None
ATTEST: ~

NORA PIMENTEL, MMC

ASSISTANT CITY CLERK

CITY OF SANTA CLARA

Sanitary Sewer
Master Plan
Update
Final Report
0012307.00
City of Santa Clara
August 2025
woodardcurran.com
51 East Campbell Avenue | Suite 128
Campbell, California 95008
800.426.4262
DRAFT
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Master Plan Report - Final August 2025

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 Woodard
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4. SYSTEM CAPACITY ANALYSIS .......................................................................................................4-1

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 Tracy/Pomeroy/Homestead/Kiely ............................................................................................. 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 Mission College Blvd ...................................................................................................................... 4-24

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

4.5.11 GAP East Trunk ................................................................................................................................. 4-26

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

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

4.6 Infiltration and Inflow Discussion .......................................................................................................... 4-27

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 .......................................................... 4-31

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 Tracy/Pomeroy/Homestead/Kiely ................................................................................................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 Mission College Blvd .........................................................................................................................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 Woodard
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5.7.13 Lafayette Street................................................................................................................................. 5-10

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 - Final August 2025

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: Summary of Existing Information
Appendix B: Flow Monitoring Data Plots
Appendix C: Future Development Assumptions
Appendix D: Pump Station Capacity Calculations
Appendix E: Field-Collected Survey Information Data Sheets Appendix F: Calibration Results
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Master Plan Report - Final August 2025
Appendix G: Sewer Performance and Design Criteria Technical Memorandum Appendix H: Siphon Lining Assumptions
Appendix I: Sewer Capacity CIP Project Cost Estimates, Maps, and Profiles

ACKNOWLEDGEMENTS
City of Santa Clara
Craig Temple, Project Manager
Falguni Amin, Principal Engineer
Michael Liw, City Engineer / Assistant Director of Public Works Craig Mobeck, Director of Public Works
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
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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 - Final August 2025

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.

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 ES-2) 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 approximately 12 miles of sewer pipelines not owned by the City, excluding laterals) 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 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.

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Master Plan Report - Final August 2025
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.

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Master Plan Report - Final August 2025
FIGURE ES-1: SANTA CLARA SANITARY SEWER SYSTEM AND SERVICE AREA AIIK
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Figure ES-1
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Master Plan Report - Final August 2025
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 entitlements. 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 long-term future scenario included all development assumptions applied to the near-term future scenario plus development assumptions associated with the City’s General Plan and entitlements. 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 entitlements, 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.

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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 (from a predicted flow of 11.5 mgd) 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 and 1.7 miles of siphons, 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 City-owned 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 Woodard
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Master Plan Report - Final August 2025
flows and adjusting the model assumptions and parameters as needed until a reasonably good match is 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.

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Master Plan Report - Final August 2025
Figure ES-3 presents a visual representation of the wet weather calibration model results in terms of the 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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Master Plan Report - Final August 2025
FIGURE ES-2: FLOW MONITORING PROGRAM
FlowMet...-Basin 26
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10 28
11 "' 12
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Sewer Master Plan Update
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City of Santa Clara (0012307.00) ES-9 Woodard & Curran, Inc.

Master Plan Report - Final August 2025
FIGURE ES-3: RDI/I RATE BY FLOW METER BASIN
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Figure ES-3
RDl/1 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 - Final August 2025
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 Woodard
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Master Plan Report - Final August 2025
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 Woodard
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Master Plan Report - Final August 2025
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.

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Master Plan Report - Final August 2025
FIGURE ES-4: OVERVIEW OF CAPACITY DEFICIENCIES
Figure ES-4
Overview of Capacity "
Deficiencies J
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I' ---• ... "===',.'-----'~ I Modeled Sewers
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--<1 (no su,ch.arge)
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Master Plan Report - Final August 2025
FIGURE ES-5: OVERVIEW OF CAPACITY IMPROVEMENT PROJECTS
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Overview of Ca pacity
Improvement Projects
Sewer Master Plan Update
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Master Plan Report - Final August 2025
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 Tasman/GAP, 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 7-8
years $25K annually
Hydraulic Model Maintenance and Support;
Future Master Plan updates (next in
2032-2033); Technical Analyses for Model
1Designed to reflect costs derived directly from construction of the capacity improvement projects only. Verification 2Other costs associated with improvement of flow conveyance in the system.

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Master Plan Report - Final August 2025
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 (Tasman/GAP) 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
Tracy/Pomeroy/Homestead
/Kiely
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 Mission College Boulevard
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 - Final August 2025
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 entitlements would not need to be implemented until the entitled parcel(s) provide notice to the City of their intent to increase their discharge up to their entitled flow. • 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 - Final August 2025

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. The City has also implemented all projects recommended in the 2007 Master Plan, such as the Walsh Ave (West-to-East trunk), Monroe St, Machado Ave, Chromite Dr, Nobili Ave, Scott Blvd, and Park Ave improvements.

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. Multiple data sets provided by the City were used to execute the tasks to meet each of the objectives of this study. Each section provides a discussion of the available data, and a summary of the existing information provided by the City is presented in Appendix A. 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 1 City of Santa Clara, Sanitary Sewer Master Plan Update, RMC Water and Environment, April 2016.

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Master Plan Report - Final August 2025
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.

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.

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Master Plan Report - Final August 2025
FIGURE 1-1: SANTA CLARA SANITARY SEWER SYSTEM AND SERVICE AREA flcJ
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Figure 1-1
Sanitary Sewer System 1?
and Service Area ~ -.J
Sr.\'er Master Plan Update
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Master Plan Report - Final August 2025

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 a summary of data available for the project, plots of flow monitoring and rainfall data and model calibrations, future land use assumptions, and detailed project descriptions, the Sewer Performance and Design Criteria technical memorandum, cost estimates, and figures for capacity improvement projects.

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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.

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Master Plan Report - Final August 2025
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 B.

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 Woodard
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Master Plan Report - Final August 2025
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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Master Plan Report - Final August 2025
FIGURE 2-1: FLOW MONITORING PROGRAM
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Master Plan Report - Final August 2025
FIGURE 2-2: TRUNK SEWER SYSTEM SCHEMATIC
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Master Plan Report - Final August 2025

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 B.

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

3.0 4.0

5.0 6.0

7.0 8.0

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. 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 Woodard
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Master Plan Report - Final August 2025
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. ~ 0
i:i:

Rainfall
Time
(24 Hours)
(not to scale)
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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 Woodard
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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.

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FIGURE 2-5: WATER BILLING DATA
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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 C. 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 Woodard
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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 C. 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 Woodard
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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 C.

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 Woodard
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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
0 6 12 18 24
TTme(hr.)
30 slowest
36 -
42 48
....- slow
....- slower
slowest
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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 Autodesk’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 Autodesk Help Menu Documentation on Hydraulic Model Theory, available online at:
https://help.autodesk.com/view/IWICMS/2025/ENU/?guid=GUID-3AF862EF-FC9D-4632-BACD-06CC4BC0431C.

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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 Woodard
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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 D. 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 D 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 H.

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1-----------------------•-••••• •• .. • •• • ••••• ••• .. • •• .. • • :•••••• •••••• •• .. • •• • •••••• •• .. ------------------- 105.0 -
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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 E) 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 Woodard
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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.

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Master Plan Report - Final August 2025
FIGURE 3-3: CITY’S TOP WATER USERS (WATER USE GREATER THAN 50,000 GPD) ,__r
... i
I) bihg
Figure 3-3
Top Water Users
Sewet Master Plan Update
,----
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, ........

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00 OMA. NDA
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Master Plan Report - Final August 2025

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.

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 (2023)
Weekday (2016)
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
Flow
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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

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
1Same profile assumed for weekday and weekend.

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Master Plan Report - Final August 2025
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 F.

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- Woodard
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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)
Flow(MGD)

5.oo ~ -

4.ao -
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o.oo -+-----~-------<--~--~--~--~--~
12/17/2022
Flow(MGD)

8.00 6.40

1.60 12/19/2022 12/21/2022 12/23/2022
o.oo+-------~--~-----+----~----r---~
12/17/2022 12/19/2022 12/21/2022 12/23/2022
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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.

Flow(MGD)

6.00 4.80
Woodard
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o.oo+----~-~-~-~--~-~-~
12/17/2022 12/19/2022 12/21/2022 12/23/2022
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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 F. 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 Woodard
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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 F, 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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Master Plan Report - Final August 2025
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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Master Plan Report - Final August 2025
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 F.

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 F, 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
Rainfall intensity (in/ hr)
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Master Plan Report - Final August 2025
FIGURE 3-11: WET WEATHER CALIBRATION RESULTS AT FM 2
FIGURE 3-12: WET WEATHER CALIBRATION RESULTS AT FM 3
Rainfall intensity (in/hr)

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Master Plan Report - Final August 2025
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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Master Plan Report - Final August 2025
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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Master Plan Report - Final August 2025
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.

Rainfal l intensity (in/ hr)
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Master Plan Report - Final August 2025
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.

Rainfal l intensity (in/hr)
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1 t:-4- 1.00

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Master Plan Report - Final August 2025
FIGURE 3-15: WET WEATHER CALIBRATION RESULTS – RDI/I RATES BY FLOW METER BASIN S,,r, k"'
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City of Santa Clara (Project 0012307.00) 4-1 Woodard & Curran, Inc.

Master Plan Report - Final August 2025

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.

The various flow components and the development of existing, near-term future, and long-term future wastewater flows (referred to as model “loads”) are discussed in Section 2. That section also discusses the application of a design storm in conjunction with calibrated model parameters that represent rainfalldependent infiltration and inflow (RDI/I) into the sewer system to generate wet weather design flows.

The characteristics of the City’s design storm event that is used to generate wet weather design flows are presented in Section 4.1.1. That section also 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 the Sewer Performance and Design Criteria Technical Memorandum, which is attached to this report as Appendix G.

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 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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Master Plan Report - Final August 2025
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.

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

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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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 (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 Woodard
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that of the synthetic nested distribution, and significantly higher than that of the SCS Type IA 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
,-/

I ' I ' I ' I ' I
I
I ,,,'
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,
,
I
,,,~ ,
I
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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

3.35 in;

0.70 in/hr
"
t
Curt, -c oot f;
l
.,.~~ntl
~ Cl•••
High
School
10-yr, 24-hr Rainfall (typ.)
Depth = 2.77 in;
Peak Intensity = 0.61 in/hr

3.09 in;

0.68 in/hr
..

HOM(SHAO Kl~LY .... I
~~ .. MAU RIC IA KIELY

2.91 in;

0.61 in/hr
II
Santa Clara
DOW TOWN S•n•• SANTA CURA CJ.a,
Unv.r
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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 are 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
Lined 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 Tasman/GAP: 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 Mission College Boulevard: 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 H. 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
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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.

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FIGURE 4-5: RCP TRUNKS IDENTIFIED FOR FUTURE LINING (LINED MODEL NETWORK ONLY) Sunnyvale
Bay/ands
County Park
,asman Dr
G2
E Arques Ave
;fer Rd
~eed Ave
Ho
.

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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 I. 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, Tasman/GAP, Mission College Boulevard). 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)
NearTerm
Future
(NTFL)
LongTerm
Future
(LTFL)
Dry
Weather
(DWF)
Wet
Weather
(WWF)
Unlined
(UMN)
Future
Lined
(LMN)
Tracy/Pomeroy/Homestead/Kiely ✓ (E) ✓ ✓ N/A
Homestead Road ✓ ✓ ✓ N/A
Kiely Boulevard ✓ (GP) ✓ ✓ N/A
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Deficiency Name
Wastewater Flow Trigger1 Design Flow
Trigger Network Trigger
Existing
(EL)
NearTerm
Future
(NTFL)
LongTerm
Future
(LTFL)
Dry
Weather
(DWF)
Wet
Weather
(WWF)
Unlined
(UMN)
Future
Lined
(LMN)
Victoria Avenue
✓ (SD,
GP)
✓ ✓ N/A
Cabrillo Avenue ✓ ✓ ✓ N/A
CMC Basin ✓ ✓ ✓ N/A
Bowers Avenue ✓ ✓ ✓
Calabazas Trunk ✓ ✓ ✓
Agate Drive ✓ (O2) ✓ ✓ N/A
Mission College Boulevard ✓ (SD) ✓ ✓ N/A
PHD ✓ (SD) ✓ ✓ N/A
Tasman/GAP ✓ (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.

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FIGURE 4-6: CAPACITY DEFICIENCIES OVERVIEW MAP
. :

Figure 4-6
Overview of Capacity -g
Deficiencies 2'
..J
0 1-· --•.,"'==•;,;• .... ____ ,~ I
Modeled S..-weo:

Surcharge Slate
-- ~ 1 (no surcharge)
--1 (backwater surc.karge)
--2 (throttle surcha, e) fl,,d ..... "50.0..1M_ll_.....__._,.._..,,_....,. __ N!i199_1t° ..... ,._tll..,~-- ,.,.,""'---....... •NW----t.-.... ""'•---<--...

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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 D 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.

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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 Tasman/GAP 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 Mission College Boulevard 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 I 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.

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FIGURE 4-7: CAPACITY IMPROVEMENT PROJECTS OVERVIEW MAP
j MeedAYI!
1 Figure 4-7
overview of Capacity
lmprovtmtnt Projtets --- --- Woodar
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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. Tracy/Pomeroy/
Homestead/Kiely
(Section 0)
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. Mission College
Boulevard
(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
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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. Tasman/GAP6
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 Mission Point developer.

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4.5.1 Tracy/Pomeroy/Homestead/Kiely
The Tracy/Pomeroy/Homestead/Kiely 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 mgd1. 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 Tracy/Pomeroy/Homestead/Kiely 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 re1 Based on winter season billing data from 2019-2022. Annual water billing data from 2021 and 2022 suggest that the annual flow may be as high as 0.07 mgd.

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slope 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 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 Tracy/Pomeroy/Homestead/Kiely project in Section 4.5.1). The Homestead Road and Tracy/Pomeroy/Homestead/Kiely 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). Although the Homestead Road and Tracy/Pomeroy/Homestead/Kiely projects will work together to solve both deficiencies, the two deficiencies are not dependent of each other, meaning that if Agilent never discharges its entitled flow (i.e. The Tracy/Pomeroy/Homestead/Kiely deficiency does not occur), the improvements to the Homestead Road trunk are still needed.

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 Woodard
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(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.

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 I, 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 shortWoodard ~
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duration 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.

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 I 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 Mission College Boulevard
The Mission College Boulevard capacity improvement project would relieve the surcharge capacity deficiency first triggered in the model under long-term future sewer loads, during dry weather conditions, Woodard
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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 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.

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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 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 I); 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 I 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 Woodard
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Master Plan Report - Final August 2025
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.

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
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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).

FIGURE 4-9: OBSERVED FLOW MONITORING DATA AT FM 31 (S62-50, 10”) 12/16 12/18 12/20 12/22 12/24 12/26 12/28 12/30 1/1
16 14
12 i 10 Pie_e Diameter--------------------------
-5
C
C 8
£
a.
..
0 4
0 1.50 'I' 1'r -Flow 2022·23 (mgd)

1.25 1.00
,;;-
"' .S 0.75 3
£ 0.50

0.25 0.00
12/16 12/18 12/20 12/22 12/24 12/26 12/28 12/30 1/1
1/3 1/5 1n 1/9 1/11 1/13
'lf' 'f ,. " ',
1/3 1/5 1n 1/9 1/11 1/13
1/15 1/17 1/19 1/21
1/15 1/17 1/19 1/21
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0.0 0.5

1.0 1.5

2.0 i
.E 2.5 ;;
J!

3.0 ! 3.5

4.0 4.5

5.0 1/23
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Master Plan Report - Final August 2025
FIGURE 4-10: NOAA RAINFALL STATISTICS COMPARED TO OBSERVED JANUARY 2023 RAINFALL IN

SANTA CLARA, CA
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 14 - Ra,n Gaug _ 2
5 yr NOAA
- • -10-yr NOAA
12 - ~ -- 2S-yr NOAA
- • - SO yr NOAA
i
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10 !. 8
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0 i
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~ £,
4 2
0 1 hr 6-hr 1-day 2-day 4-day
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7-day 10-day
,.
20-day 30-day
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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.

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 Woodard
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Master Plan Report - Final August 2025
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.

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 0, 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 0-

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 I.

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.

The capacity deficiencies were relieved by a) increasing the capacity of deficient segments by upsizing sewers, adding additional parallel pipes, and/or re-sloping segments b) decreasing the flow through deficient pipe segments by diverting flow towards pipe segments with more capacity, or c) a combination of both a and b. All new pipes were sized according to the City’s Design Criteria (refer to Table 4-4), except when the City decided not to do so, which is stated in the project descriptions included in Section 4.5.

Each project solution was tested in the hydraulic model to confirm that it would provide system capacity relief and to determine the pipe size required for any new sewers. Finally, the proposed pipe alignment was reviewed using GIS maps and aerial imagery to identify potential constructability issues. Complicating factors such as highway crossings, railroad crossings, creek proximity and crossings, and projects on sewers with many laterals (thereby impacting flow control during construction) were noted. Although this constructability review was done at a high level for planning rather than a detailed design level, the issues identified provide a reasonable starting point for further project development during the pre-design phase.

The goal of the constructability review was to flag key areas where trenchless construction may be required.

Pipe-bursting may be feasible but was not evaluated during this Master Plan Update; detailed utility separation and geotechnical investigations would be required to fully evaluate feasibility.

5.2 Project Prioritization Methodology
Each project was prioritized from “1” (highest priority) to “7” (lowest priority) based on a combination of factors including the wastewater flow trigger (existing load or EL vs. near-term future load or NTFL vs. longterm future load or LTFL), design flow trigger (dry weather flow or DWF vs. wet weather flow or WWF), physical network trigger (future lined network or LMN vs. no future lining network or UMN), and assumed Woodard
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structural condition trigger (RCP segments present vs. not present). Projects that address existing deficiencies with future lining assumptions not in place should have the highest priority because they pose the greatest risk of a sanitary sewer overflow (SSO). Table 5-1 shows the ranking classifications used to assign priorities to each of the projects.

TABLE 5-1: PROJECT PRIORITIZATION RANKING1
Priority
Ranking
Wastewater Flow
Trigger(s)
Design Flow
Trigger(s)
Physical
Network
Trigger
Structural
Condition
Trigger
Notes
1 EL WWF UMN -
2 EL WWF LMN -
3 LTFL WWF UMN RCP trunk
Not Priority 1 or 2 but
alignment includes RCP trunk
identified for future lining.
4 LTFL WWF LMN RCP trunk
Not Priority 1 or 2 but
alignment includes RCP trunk
identified for future lining.
5 LTFL DWF UMN -
6 LTFL WWF UMN -
7 LTFL (entitlement) DWF or WWF UMN -
1Note: 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.

5.3 Project Level of Confidence
The capacity improvement projects developed to resolve the hydraulic deficiencies are primarily based on forecasted flows predicted from the calibrated model. As discussed in Section 4.1, the hydraulic model utilizes a design rainfall event along with other modeling assumptions to identify hydraulic deficiencies and resulting capacity improvement projects. Because these assumptions impact the recommended capacity improvement projects, it becomes necessary to independently validate the need for these projects by reviewing local flow monitoring data, review of reported surcharging and operational issues, and compatibility between flow meter data and the model. The project validation process, often referred to as a ‘level of confidence’ evaluation, was conducted for each recommended project with the results discussed by project in Section 5.7. The confirmation levels used in the validation process are shown in Table 5-2.

TABLE 5-2: PROJECT FLOW CONFIRMATION LEVELS
Flow
Confirmation
Level
Description
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.

For projects with a Level 1 rating, the need for the project has effectively already been confirmed by previous flow monitoring data. Level 2 projects were confirmed to have reasonably accurate model flows based on Woodard
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Master Plan Report - Final August 2025
model comparison to flow meter data but have no confirmed surcharging during the monitoring period (calibration events may have been too small to cause surcharging at these locations). Level 3 projects were confirmed to have reasonably accurate model flows based on model comparison to flow meter data. Level 4 and 5 projects have no reliable confirmation of model flows; conducting flow monitoring on these project reaches prior to design would provide a greater level of confidence in modeled flows.

It should be noted that projects triggered by projected flows from historic entitlement agreements or specific future development flow estimates were not assigned a confidence level as it relates to monitored flows.

5.4 Project Cost Estimates
Planning level cost estimates were developed for each recommended project. This level of cost estimate corresponds to the Planning-Level “Class-5” cost as defined by the American Association of Cost Engineers, International (AACE 2005). The AACE provides guidelines on accuracy ranges defined as percentages +/- of the expected average bid cost of the work. The Planning Level cost is expected to range from a high of:
+30% to+100% and from a low of: -20% to -50% of the eventual cost of the project.

The cost index used for escalation of past bid prices was the Engineering News Records Construction Cost Index (ENR 2024) for the San Francisco area as of August 2024 (CCI of 15367.24).

Cost criteria include baseline construction costs for gravity trunk sewers using open-cut construction1. Unit costs for gravity trunk sewers vary with pipe diameter and depth. Baseline costs include all standard materials, equipment, possible weir installation or adjustment, potential lateral reconnection, potential manhole modifications, and labor to construct a pipeline project, except for site-specific items (e.g., possible dewatering and shoring needs or bypass pumping). The unit cost for open-cut construction ranged from $654 per linear-foot (LF) for a shallow (pipe depth less than 16 feet), 8-inch sewer to $1,579 per LF for a deep (from 25 to 30 ft of depth), 60-inch sewer.

An allowance of 10% of baseline construction costs was provided for traffic control, or 20% for high traffic areas. Additional allowances were provided for dewatering, bypass pumping, remove and replace activities, and pavement restoration. Subtotal construction costs reflect these allowances plus the baseline construction cost. The estimated construction subtotal cost for each project also includes an allowance for mobilization/demobilization (5% of subtotal construction costs), plus an additional allowance for contingencies and unknown conditions (30% of construction cost subtotal, and an allowance for engineering and inspection costs (25% of construction cost). Costs for lining City-identified RCP trunks are not included in the Sewer Capacity CIP as these are condition-related maintenance costs.

The itemized cost estimate for each project is detailed in the individual project information sheets included in Appendix I. Note that all costs presented in this Master Plan Update report represent August 2024 costs for the San Francisco Area and are not escalated for future years.

5.5 Other Costs
The project cost estimates developed would reflect costs derived directly from construction of the projects only. However, there would be other additional costs associated with improvement of flow conveyance in the City’s sanitary sewer system. For this Master Plan Update, these costs were categorized as three-fold:
1 Pipe-bursting may be feasible but was not evaluated during this Master Plan Update. Detailed utility separation and geotechnical investigations would be required to fully evaluate feasibility.

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1) Hydraulic Model Maintenance & Support Costs, which include continuous updates to the hydraulic model to reflect improvements to the system, updates to base flow scenarios based on specific development project status or General Plan updates, and maintenance of consistent documentation in model files;
2) Future Master Plan Update Costs, which include updates to the master plan to incorporate updates to the hydraulic model, compare model results to flow monitoring data, update model calibration, perform system capacity evaluations, develop capacity improvement projects to resolve deficiencies, and produce accompanying memoranda and reports; and 3) Technical Analyses to Support System Verification and Hydraulic Model Accuracy, which includes performing I/I studies, conducting flow monitoring to verify system hydraulic conditions (in addition to flow monitoring mentioned above), analyzing water usage and sewer generation rates, performing pump station evaluations, evaluating proposed improvements for system performance, and conducting other studies and analyses.

Table 5-3 shows the additional anticipated other costs by category, which were provided by the City. Note that these costs reflect 2024 US Dollars and should be escalated for future years.

TABLE 5-3: OTHER COSTS IN ADDITION TO SEWER CAPACITY CIP PROJECT COSTS Category Frequency Cost1
Hydraulic Model Maintenance & Support Annual $75,000
Future Master Plan Updates Every 7-8 years $950,000
Technical Analyses to Support System
Verification and Hydraulic Model Accuracy Annual $25,000 1Cost is estimated in 2024 Dollars. Use an escalation factor of 3% to 5% per year for subsequent years.

5.6 Project Costs Financed by Developers
As discussed in Section 4.5, two capacity improvement projects were developed to address the modelpredicted deficiencies resulting from the PHD and Mission Point developments. These improvement projects will be paid for by the developers and not by the City. For this reason, they are not included in the Sewer Capacity CIP project list and are not addressed further in this section. Any changes to their respective design and/or elimination may impact the sizing and timing of the capacity improvement projects identified in this study, specifically those proposed downstream along the GAP and Lafayette trunks.

5.7 Summary of Recommended Capacity Improvement Projects Based on results of the capacity evaluation discussed in Section 4, there are thirteen (13) recommended capacity improvement projects with a total length of approximately 38,100 LF of new pipelines. The total estimated cost of the capacity improvement projects is approximately $100.6 million.

Table 5-4 shows a summary of the capacity improvement projects, including their priority, flow confidence level, wastewater flow trigger, design flow trigger, physical network trigger, and the estimated planninglevel cost. Figure 4-7 provides a system overview map and shows the locations of all thirteen (13) projects.

Appendix I includes a plan view figure for and a detailed description of each project as well as an associated cost estimate. The projects are listed in upstream-to-downstream order. The project descriptions on the cost estimate page follow a standard format, consisting of a summary project description, project triggers, estimated cost, priority, and any associated comments, assumptions, or project alternatives. Each cost estimate page also includes an itemized cost estimate, as well as the estimated existing and future flows and dry weather velocities. Note the comments listed on each project description page. In some cases, the Woodard
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need for additional verification is noted. A brief discussion for each project focusing on the rationale and validation justifying the project need is included in Sections 5.7.1-5.7.13.

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TABLE 5-4: CAPACITY IMPROVEMENT PROJECTS
1Projects are numbered from upstream to downstream. Table does not include Project Nos. 10 (Patrick Henry Drive) and 11 (Tasman/GAP) 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 Tracy/Pomeroy/Hom
estead/Kiely
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 Mission College Blvd 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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5.7.1 Tracy/Pomeroy/Homestead/Kiely
This project was assigned priority 7 (least priority) as it was created to accommodate mainly the historic entitlement flow from Agilent Technologies (average dry weather flow of 0.95 million gallons per day or mgd).

Because the project is driven by the projected flows from the Agilent historic entitlement agreement, it was not assigned a confidence level as it relates to monitored flows. This project should not be implemented until the City has more certainty on the parcel’s plan to discharge its entitled flow.

It should also be noted that a trenchless crossing would be required to cross under Lawrence Expressway (from manhole S11-77 to S11-80) so the cost estimate assumes that the PTGAB construction method would be used for these segments.

5.7.2 Homestead Road
This project was assigned priority 3 as it is triggered under the long-term future peak wet weather flows in the unlined model network. The deficiency in the north Homestead trunk is just upstream of FMs 19 and

20. Neither flow meter surcharged during monitored wet weather flow events. As a result, the project has a confidence Level 3 because the downstream flow meters confirmed the flow but did not surcharge during the monitored events. This project is also highly dependent on the projected future incoming peak wet weather flows (13.8 mgd) from CuSD, which were based on the current contractual agreement. Any change to the contractual agreement affecting the maximum flow would affect the resulting deficiency and project.

It should also be noted that a trenchless crossing would be required to cross under Lawrence Expressway (from manhole S20-10 to S21-43) so the cost estimate assumes that the PTGAB construction method would be used for this segment. Special considerations should be given to the construction set up upstream of this crossing as manhole S20-10 houses the Lawrence/Homestead gate structure.

5.7.3 Kiely Boulevard
This project was assigned priority 6 as it is triggered under the long-term future peak wet weather flows in the unlined model network. Although its wastewater flow, design flow, and physical network triggers are the same as those assigned to the Homestead Road project, it is much lower priority because it is not located on an alignment that includes RCP trunks identified for future lining by the City.

The Kiely Boulevard trunk flowed into FM 13, which was located on the Bowers Avenue trunk a considerable distance downstream of the deficient segment. As a result, this project has a confidence Level 4 and conducting flow monitoring on the project reach prior to design would provide a greater level of confidence.

5.7.4 Victoria Avenue
This project was assigned priority 6 as it is triggered under the long-term future peak wet weather flows in the unlined model network. Although its wastewater flow, design flow, and physical network triggers are the same as those assigned to the Homestead Road project, it is much lower priority because it is not located on an alignment that includes RCP trunks identified for future lining by the City.

The Victoria Avenue trunk flowed into FM 26 which did not surcharge during the monitored rainfall events.

FM 26 was downstream of the project (i.e., not on the Victoria Avenue trunk itself). The project therefore has confidence Level 3 as the model was confirmed to have reasonably accurate model flows based on model comparison to flow meter data, but there was no confirmed surcharging during the wet weather calibration events.

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City of Santa Clara (Project 0012307.00) 5-8 Woodard & Curran, Inc.

Master Plan Report - Final August 2025

5.7.5 Cabrillo Avenue
This project was assigned priority 1 as it is triggered under the existing peak wet weather flows in the unlined model network. As discussed in Section 4.5.5, this project consists of the installation of two weirs to divert flow to segments with more capacity, which are reflected in the costs for the Cabrillo Avenue project.

The Cabrillo Avenue trunk flowed into FM 26 which did not surcharge during the monitored rainfall events.

FM 26 was downstream of the project (i.e., not on the Cabrillo trunk itself). The project therefore has confidence Level 3 as the model was confirmed to have reasonably accurate model flows based on model comparison to flow meter data, but there was no confirmed surcharging during the wet weather calibration events.

5.7.6 CMC Basin
The segments in Santa Maria Ave and Amethyst Drive become deficient under existing loads and wet weather flow due to high rainfall-derived infiltration and inflow (RDI/I) that occur in the CMC basin. As a result, they have a priority ranking of 1.

The Amethyst Drive trunk flowed into FM 28 which surcharged during the monitored rainfall event on January 1st, 5th, and 9th, 2023. As a result, the project was assigned a high level of confidence (i.e., Level 1) because the need has been confirmed by previous flow monitoring data.

The Santa Maria Ave project flowed into FM 10. FM 10 showed a high RDI/I response during the monitored rainfall events but did not surcharge. This project was assigned a Level 2 confidence rating as the model was confirmed to have reasonably accurate model flows based on model comparison to flow meter data, but there was no confirmed surcharging during the wet weather calibration events.

The recommended capacity improvement upsizing project was developed to accommodate the flow during wet weather; however, the City also has the option to reduce the RDI/I in the basin. The cost of reducing the RDI/I would include smoke testing to identify specific sources of infiltration and additional flow monitoring in the basin. An annual allowance for these other non-construction costs is shown in Section

5.5. 5.7.7 Bowers Avenue
This project was assigned priority 4 as it is triggered under long-term future peak wet weather flows in the lined model network and is located on an alignment that includes RCP trunks identified for future lining by the City.

The Bowers Avenue deficiency was just downstream of flow meter 13 which did not surcharge during the monitored wet weather events. However, as described in Section 3.4.3.1, the 2022-2023 flow monitoring data at FM 13 showed that observed flows in the Bowers trunk at this location were significantly lower than the model-predicted flows based on the assumed system flow routing under normal conditions. Further investigation by Woodard & Curran and additional field surveys conducted by the City revealed that the system was not operating under normal conditions during the 2022-2023 flow monitoring program; the Lawrence/Homestead gate structure was routing significantly more flow to the trunk on Lawrence Expressway (80%) and only 20% to the trunk on Homestead Road, compared to the approximate 50/50 split that is observed during normal conditions. Additionally, City staff observed surcharge conditions farther downstream during dry weather, suggesting that some of the increased flows to the trunk on Lawrence Expressway were backing up through the El Sobrante overflow pipe towards FM 13 and away from FM 9A.

Because of these atypical and temporary issues, a flow balance between FMs 13 and 9A was impossible to Woodard
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Master Plan Report - Final August 2025
achieve. Model-predicted flows assuming normal system flow routing were compared to the 2014-2015 flow monitoring data and matched more closely, but due to the inconsistencies discussed above with the 2022-2023 flow monitoring data, this project was assigned a confidence Level 5 (flow meter shows significantly different flow than model). Therefore, it is recommended that additional flow monitoring be conducted prior to design to provide a greater level of confidence in modeled flows.

It should be noted that the proposed alignment would require a trenchless crossing under the Caltrain railroad tracks (between manhole S53-7 and S63-36). Additionally, the alignment between manholes S63- 36 and S63-27 has many bends and does not follow the Bowers Avenue public right-of-way (ROW). The design of the new project may want to consider realigning the sewer to be closer to Bowers Avenue.

5.7.8 Calabazas Trunk
The Calabazas Trunk project is triggered by existing wet weather flows in the lined model network and therefore was assigned a priority ranking of 2. The Calabazas Trunk Improvements assume that all deficiencies upstream have been relieved. Because this project is a higher priority than the projects upstream (i.e., Tracy/Pomeroy/Homestead/Kiely and Homestead Road), this assumption should be considered during the design phase.

The deficient segments of the Calabazas trunk flowed into FM 9A located somewhat downstream. FM 9A did not surcharge during the monitored wet weather events. However, as described in Section 3.4.3.1 and in Section 5.7.7 above, inconsistencies with the 2022-2023 flow monitoring data made it impossible to achieve a flow balance at FMs 9A and 13. Due to the atypical flow routing, the model comparison to FM 9A is inconclusive. As a result, this project has confidence Level 5 (flow meter shows significantly different flow than model), and it is recommended that additional flow monitoring be conducted prior to design to provide a greater level of confidence in modeled flows.

It should be noted that the alignment would require a trenchless crossing under the Caltrain and private railroad tracks to the north (between manhole S52-4 and S62-52).

5.7.9 Mission College Boulevard
The proposed project was assigned priority ranking 5 as it is triggered by long-term future dry weather flows as a result of the proposed Freedom Circle Focus Area development project. It is therefore highly dependent on the final loads generated by the proposed development and should be reviewed should those flows change.

This project is driven by the projected flows from the Freedom Circle Focus Area specific development. As a result, it was not assigned a confidence level as it relates to monitored flows.

5.7.10 GAP West Trunk
The proposed project was assigned priority ranking 3 as it is triggered by long-term future loads combined with wet weather flow conditions in the unlined model network and is located on an alignment that includes RCP trunks identified for future lining by the City.

The GAP West trunk had a flow meter on the deficient sewer segment (FM 2). Flow monitoring data showed the sewer did not surcharge during the monitored wet weather events although the d/D ratio reached 75%.

As a result, the project has a confidence Level 2 (flow meter on capacity deficient pipe reach confirms model flow, but did not surcharge).

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City of Santa Clara (Project 0012307.00) 5-10 Woodard & Curran, Inc.

Master Plan Report - Final August 2025
It should be noted that the alignment would require a trenchless crossing under the Valley Transportation Authority (VTA) light rail tracks on West Tasman Drive.

Because of their interconnections, the GAP West and East trunks should be evaluated together during the pre-design and design phases.

5.7.11 GAP East Trunk
The proposed project was assigned priority ranking 4 as it is triggered under long-term future peak wet weather flows in the lined model network and is located on an alignment that includes RCP trunks identified for future lining by the City.

The GAP East trunk had FM 5 just upstream of the deficient sewer segment. However, the flow meter data did not show a surcharge condition under the monitored wet weather events. As a result, this project was assigned a confidence Level 2.

Because of their interconnections, the GAP West and East trunks should be evaluated together during the pre-design and design phases.

5.7.12 Bunker Hill East Lane
This project was assigned priority 7 (least priority) because it is triggered by long-term future loads as a result of a historic entitlement flow assumption from parcels with APNs 104-55-012 and 104-55-013 (site of the current Santa Clara Convention Center) under wet weather flows. During the pre-design phase, the City should verify the inverts along the alignment and at the downstream connection with the GAP East Trunk at manhole S93-7.

This project is driven by the projected flows from the historic entitlement agreement from the two parcels identified above. As a result, it was not assigned a confidence level as it relates to monitored flows.

5.7.13 Lafayette Street
This project was assigned priority 3 as it is triggered under long-term future peak wet weather flows in the unlined model network and is located on an alignment that includes RCP trunks identified for future lining by the City. As discussed in Section 4.5.13, the project would include re-sloping of some minimally sloped (approximately 0.02%) existing pipe segments according to record information. Due to lack of data, it was not possible to confirm if there are other utilities near the deficient segment in Lafayette Street. Therefore, the project alignment was developed assuming that there are no obstacles in upsizing and re-sloping the segments to relieve the deficiency. However, this assumption should be confirmed during the pre-design phase.

The Lafayette trunk had FM 1 on one of the deficient sewer segments. Flow monitoring data showed the sewer did not surcharge during the monitored wet weather events and the d/D ratio reached a maximum of 50%. As a result, the project has a confidence Level 2 (flow meter on capacity deficient pipe reach confirms model flow, but did not surcharge).

5.8 Schedule
A preliminary Sewer Capacity CIP schedule was developed and is presented in Table 5-5. Because none of the projects have a near-term future loads wastewater flow trigger, the projects are scheduled for either implementation within the next five years (2025-2030), if triggered by existing loads, or implementation within the next 10 years (or beyond 2035), if triggered by long-term future loads. Projects triggered by Woodard
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Master Plan Report - Final August 2025
entitlement flows (i.e., Tracy/Pomeroy/Homestead/Kiely and Bunker Hill Lane East) are still listed for implementation beyond 2035; however, if the entitlement holders do not exercise their rights, then implementation of these projects would not be necessary. Preliminary design, including condition assessments (e.g., smoke testing, CCTV, etc.), final design, and permitting activities should commence two (2) to three (3) years prior to project trigger. It is worth noting that all costs are calculated in August 2024 dollars; thus, if a project is scheduled to be constructed in 2035, the cost should be scaled to 2035 using an escalation factor of 3% to 5% per year.

TABLE 5-5: CAPACITY IMPROVEMENT PROJECTS SCHEDULE
Project No. Project ID Schedule
1 Tracy/Pomeroy/Homestead/Kiely
2035
2 Homestead Road 2035
3 Kiely Boulevard 2035
4 Victoria Avenue 2035
5 Cabrillo Avenue 2025
6 CMC Basin 2025
7 Bowers Avenue 2035
8 Calabazas Trunk 2025
9 Mission College Blvd 2035
12 GAP West Trunk 2035
13 GAP East Trunk 2035
14 Bunker Hill Lane East 2035
15 Lafayette Street 2035

5.9 Implementation Recommendations
The City should begin implementation of the Sewer Capacity CIP recommended in this Master Plan Update, starting with the highest priority 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.

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City of Santa Clara (Project 0012307.00) 5-12 Woodard & Curran, Inc.

Master Plan Report - Final August 2025
• 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.

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

Master Plan Report - Final August 2025
APPENDIX A: SUMMARY OF EXISTING INFORMATION
Woodard
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List and Summary of Existing Information
No. Item Description File Type Requested for
1 2016 Sanitary Sewer Master Plan Update
Hydraulic model
Trunk model created and calibrated as a part of the 2016 Sanitary Sewer Master Plan. Updated continuously to the present
InfoWorks ICM
transportable
database
Task 3
2 Sanitary Sewer Geospatial Data
database containing all Manhole IDs and hydraulic
information of all pipes, such as diameters, materials, invert elevations, and lengths.

Shapefile Task 3
3 Sanitary Sewer Block Book (2020) File that shows a summary of all sewer pipe alignments, manholes, and other structures pdf file Task 3
4 Siphon information Location for all siphons in the City's Sanitary system Shapefile Task 3 5 Flow data from system pump stations
and lift stations SCADA data for Rabello and Northside pump stations Excel Spreadsheet Task 3 6 flow monitoring data Flow data for all meters for the 2022/2023 flow monitoring period Excel Spreadsheet Task 2
7 Citywide Parcel data Parcel information for all parcels within the limits of the City of Santa Clara Shapefile Task 3
8 County Parcel Data Parcel information for all the parcels within Santa Clara County
Shapefile Task 3
9 land use mapping Zoning information for each parcel in the City of Santa Clara Shapefile Task 3 10 Ground Elevation Data 2-ft by 2-ft hydroflattened ground model DEM of the County of Santa Clara tiff raster Task 3
11 Known proposed development plans
under discussion List of Near-term and long-term Proposed developments Excel Spreadsheet Task 3 12 Water use records to update the model
loads and unit flow criteria
Water Billing data for the City of Santa Clara by account number (with address)
Microsoft Excel CSV
file
Task 3
13 2024 Calabazas/Great America Pkwy
Lining
List of lining projects carried out by the City Spreadsheer Task 3 14 Flow data for Tributary agencies
(Cupertino Sanitary District)
Existing, near-term, and long-term dry and wet flow from Cupertino Sanitary District. 15-min intervals between
readings
Microsoft Excel CSV
file
Task 3
15 Sewer inspection records Sewer gravity main with defect scores Shapefile Task 3/4 16 Siphon inspection reports CCTV Assessment for siphons Excel Spreadsheet Task 3/4 17 Sewer System Management Plan Plan that identifies network susceptibilites, people responsible, and activities to minimize SSOs pdf file Task 3/4 18 known problem areas Summary of the locations identified by the City as "Hotspots"
pdf file Task 3/4
19 Sewer rates, fees, and expenditures Summary of the current sewer fees adopted for residential and non-residential users Website link Task 6
20 2007 Sanitary Sewer Capacity
Assessment Final Report
Report for the City of Santa Clara on the capacity
assessment of the sewer system in 2007 pdf file Task 4
21 2016 Sanitary Sewer Master Plan Update
Final report
Report for the update to the Sanitary Sewer Master Plan, carried out in 2016 pdf file Task 3/4
22 2022 addendum to the 2016 Sanitary
Sewer Master Plan Update
Report to update the capacity improvement of project E1 and address capacity deficiencies along the Calabazas Creek trunk and the Great America Pkwy West trunk
Word Document Task 4
23 2022 Citywide Data Center Discharge
Study
File that summarizes the peak summer flow into the City's sanitary sewer from several data centers Excel Spreadsheet Task 3 24 Current Municipal Fee including sewer
conveyance fee
Summary of the current conveyance fee and other municipal fees pdf file Task 6
25 Northside and Rabello Pump Station
Firm Capacity Evaluation
Memorandum/report
Technical memorandum describing the firm capacities of the Rabello and Northside pump stations and the tests
conducted to determine them.
pdf file Task 3
26 Entitlement Assumptions Excel spreadsheet provided to City for review. City provided feedback on which entitlement parcel no longer applies. Excel Spreadsheet Task 3/4 27 Field verification of flow split manholes
and structures Field survey data sheets provided by City. pdf, jpg, mov files Task 3 28 2024 Sewer Flow Monitoring and
Inflow/Infiltration Study I/I Study for the Chromite-Machado-Cabrillo (CMC) basin. pdf file Task 3 29 Record Drawings Various record drawings provided by the City. pdf file Task 3 30 2007 Santa Clara County Drainage
Manual
Drainage Manual with information on the County's rainfall statistics including design storm. pdf file Task 3
31 General Plan Parcel Data Parcel and future land use data for all parcels in the General Plan Phase 3
Shapefile Task 3
32 2023-2031 Housing Element Housing Element with information about the City's housing goals from 2023 to 2031
pdf file Task 3