HomeMy WebLinkAboutResolution No. 2023-18 | Water Master Plan | Adopted 04/03/2023
RESOLUTION NO. 2023-18
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF
GILROY ADOPTING THE WATER MASTER PLAN FOR
THE CITY OF GILROY
WHEREAS, the 2022 Water Master Plan (Plan) serves as a guide to assess the
current operations and functionality of the City’s existing water system; and
WHEREAS, the City last developed a Water Master Plan in 2004, which identified
capacity deficiencies in the existing water system and recommended improvements to
alleviate existing deficiencies and serve future developments in the Gilroy Planning Area;
and
WHEREAS, Akel Engineering Group, Inc. was retained by the City Council in
August 2019 to prepare the Plan; and
WHEREAS, the objective of the Plan is to review and make recommendations on
how the current water system can be upgraded within the City to best suit the water needs
of the City in the future; and
WHEREAS, the projects identified in the Plan will be added to the City’s Capital
Improvement Program; and
NOW, THEREFORE, BE IT RESOLVED that the City Council of the City of Gilroy
hereby adopts the Water Master Plan attached hereto and made a part hereof.
PASSED AND ADOPTED by the City Council of the City of Gilroy at a regular
meeting duly held on the 3rd day of April 2023 by the following roll call vote:
AYES: COUNCIL MEMBERS: ARMENDARIZ, BRACCO, CLINE,
MARQUES, TOVAR, BLANKLEY
NOES: COUNCIL MEMBERS: NONE
ABSTAIN: COUNCIL MEMBERS: NONE
ABSENT: COUNCIL MEMBERS: HILTON
APPROVED:
__________________________
Marie Blankley, Mayor
ATTEST:
__________________________
Thai Nam Pham, City Clerk
Marie Blankley (Apr 4, 2023 14:49 PDT)
Marie Blankley
2023 Water System Master Plan
City of Gilroy
DRAFT
2023
CITY OF GILROY
WATER SYSTEM
MASTER PLAN
FINAL
March 2023
74 3 3 N. F I RS T S T RE E T , S UI T E 1 0 3 • F RE S NO , CA LI F O RN I A 9 37 2 0 • ( 5 59) 43 6 -06 0 0 • F A X ( 55 9) 4 3 6 -0622
www.akeleng.com
Smart Planning Our Water Resources
March 29, 2023
City of Gilroy
7351 Rosanna Street
Gilroy, CA 95020
Attention: Gary Heap, P.E.
City Engineer
Subject: 2023 Water System Master Plan – Final Report
Dear Gary:
We are pleased to submit the draft report for the City of Gilroy Water System Master Plan. This
master plan is a standalone document, though it was prepared as part of the integrated
infrastructure master plans for the water, sewer, and storm drainage master plans. The master
plan documents the following:
•Existing distribution system facilities, acceptable hydraulic performance criteria, and
projected water demands consistent with the Urban Planning Area
•Development and calibration of the City’s GIS-based hydraulic water model.
•Capacity evaluation of the existing water system with improvements to mitigate existing
deficiencies and to accommodate future growth.
•Capital Improvement Program (CIP) with an opinion of probable construction costs and
suggestions for cost allocations to meet AB 1600.
We extend our thanks to you, Sharon Goei, Community Development Director; Daryl
Jordan, Director of Public Works; and other City staff whose courtesy and cooperation
were valuable components in completing this study.
Sincerely,
AKEL ENGINEERING GROUP, INC.
Tony Akel, P.E.
Senior Principal
Enclosure: Report
City of Gilroy
Water System Master Plan
Acknowledgements
City Council
Marie Blankley, Mayor
Dion Bracco, Mayor Pro Tempore
Rebeca Armendariz
Tom Cline
Zach Hilton
Carol Marques
Fred Tovar
Management Personnel
Jimmy Forbis, City Administrator
Daryl Jordan, P.E., Director of Public Works
Gary Heap, P.E., City Engineer
Jorge Duran, P.E., Senior City Engineer
Sharon Goei, Community Development Director
Matt Jones, Deputy Director of Public Works
Other City Engineering, Planning, and Operations Staff
City of Gilroy
Water System Master Plan
Table of Contents Page No.
March 2023 i City of Gilroy
Water System Master Plan
0.0 EXECUTIVE SUMMARY ................................................................................................... ES-1
ES.1 STUDY OBJECTIVES ........................................................................................ ES-1
ES.2 INTEGRATED APPROACH TO MASTER PLANNING ...................................... ES-2
ES.3 STUDY AREA .................................................................................................... ES-2
ES.4 SYSTEM PERFORMANCE AND DESIGN CRITERIA ....................................... ES-2
ES.5 EXISTING DOMESTIC WATER SYSTEM OVERVIEW ..................................... ES-5
ES.6 EXISTING AND FUTURE DOMESTIC WATER DEMANDS .............................. ES-5
ES.7 HYDRAULIC MODEL DEVELOPMENT ............................................................. ES-5
ES.8 FIRE FLOW ANALYSIS ..................................................................................... ES-9
ES.9 SUPPLY AND STORAGE EVALUATION ........................................................... ES-9
ES.10 CAPITAL IMPROVEMENT PROGRAM ............................................................. ES-9
1.0 CHAPTER 1 - INTRODUCTION......................................................................................... 1-1
1.1 BACKGROUND ................................................................................................. 1-1
1.2 SCOPE OF WORK ............................................................................................ 1-1
1.3 INTEGRATED APPROACH TO MASTER PLANNING ...................................... 1-3
1.4 PREVIOUS MASTER PLANS ............................................................................ 1-3
1.5 RELEVANT REPORTS ...................................................................................... 1-3
1.6 REPORT ORGANIZATION ................................................................................ 1-4
1.7 ACKNOWLEDGEMENTS .................................................................................. 1-5
1.8 UNIT CONVERSIONS AND ABBREVIATIONS ................................................. 1-5
1.9 GEOGRAPHIC INFORMATION SYSTEMS ....................................................... 1-5
2.0 CHAPTER 2 – PLANNING AREA CHARACTERISTICS ................................................... 2-1
2.1 STUDY AREA DESCRIPTION ........................................................................... 2-1
2.2 WATER SERVICE AREA AND LAND USE ........................................................ 2-1
2.3 HISTORICAL AND FUTURE GROWTH ............................................................. 2-9
3.0 CHAPTER 3 – SYSTEM PERFORMANCE AND DESIGN CRITERIA ............................... 3-1
3.1 HISTORICAL WATER USE TRENDS ................................................................ 3-1
3.2 SUPPLY CRITERIA ........................................................................................... 3-1
3.3 STORAGE CRITERIA ........................................................................................ 3-7
3.3.1 Typical Storage Criteria ........................................................................ 3-7
3.4 PRESSURE CRITERIA ...................................................................................... 3-8
3.5 UNIT FACTORS ................................................................................................ 3-9
3.6 SEASONAL DEMANDS AND PEAKING FACTORS .......................................... 3-10
3.6.1 Maximum Month Demand .................................................................... 3-10
3.6.2 Maximum Day Demand ........................................................................ 3-10
3.6.3 Peak Hour Demand ............................................................................. 3-13
3.7 TRANSMISSION AND DISTRIBUTION MAIN CRITERIA .................................. 3-13
4.0 CHAPTER 4 – EXISTING DOMESTIC WATER FACILITIES ............................................. 4-1
4.1 EXISTING WATER SYSTEM OVERVIEW ......................................................... 4-1
4.2 SOURCE OF SUPPLY ....................................................................................... 4-1
4.3 PRESSURE ZONES .......................................................................................... 4-4
4.4 WATER DISTRIBUTION PIPELINES ................................................................. 4-4
4.5 STORAGE RESERVOIRS ................................................................................. 4-4
4.6 BOOSTER STATIONS ....................................................................................... 4-4
City of Gilroy
Water System Master Plan
Table of Contents Page No.
March 2023 ii City of Gilroy
Water System Master Plan
4.7 PRESSURE REDUCING VALVES ..................................................................... 4-11
5.0 CHAPTER 5 – WATER DEMANDS AND SUPPLY CHARACTERISTICS ......................... 5-1
5.1 EXISTING DOMESTIC WATER DEMANDS ...................................................... 5-1
5.2 FUTURE DOMESTIC WATER DEMANDS ........................................................ 5-1
5.3 MAXIMUM DAY AND PEAK HOUR DEMANDS ................................................ 5-4
5.4 DIURNAL DEMAND PATTERNS ....................................................................... 5-4
6.0 CHAPTER 6 – HYDRAULIC MODEL DEVELOPMENT .................................................... 6-1
6.1 OVERVIEW........................................................................................................ 6-1
6.2 MODEL SELECTION ......................................................................................... 6-1
6.3 HYDRAULIC MODEL DEVELOPMENT ............................................................. 6-1
6.3.1 Skeletonization..................................................................................... 6-2
6.3.2 Pipes and Nodes .................................................................................. 6-2
6.3.3 Digitizing and Quality Control ............................................................... 6-2
6.3.4 Demand Allocation ............................................................................... 6-2
6.4 MODEL CALIBRATION ..................................................................................... 6-3
6.4.1 Calibration Plan and SCADA ................................................................ 6-3
6.4.2 EPS Calibration .................................................................................... 6-3
6.4.3 Use of the Calibrated Model ................................................................. 6-4
7.0 CHAPTER 7 – EVALUATION AND PROPOSED IMPROVEMENTS ................................. 7-1
7.1 OVERVIEW........................................................................................................ 7-1
7.2 LOW PRESSURE ANALYSIS ............................................................................ 7-1
7.3 HIGH PRESSURE ANALYSIS ........................................................................... 7-1
7.4 FIRE FLOW ANALYSIS ..................................................................................... 7-1
7.5 WATER SUPPLY ............................................................................................... 7-5
7.6 WATER SUPPLY REQUIREMENTS ................................................................. 7-5
7.6.1 Existing Supply Requirements ............................................................. 7-5
7.6.2 Future Supply Requirements ................................................................ 7-5
7.7 WATER STORAGE REQUIREMENT................................................................. 7-11
7.7.1 Existing Storage Requirements ............................................................ 7-11
7.7.2 Future Storage Requirements .............................................................. 7-11
7.7.3 Recommended New Storage Facilities ................................................ 7-11
7.8 PUMP STATION CAPACITY ANALYSIS ........................................................... 7-16
7.8.1 Existing Pump Station Capacity Requirements .................................... 7-16
7.8.2 Future Pump Station Capacity Requirements ...................................... 7-16
7.9 PIPELINE IMPROVEMENTS ............................................................................. 7-16
7.9.1 Pipeline Improvements to Serve Future Growth ................................... 7-19
7.9.2 Pipeline Improvement to Increase Fire Flow Reliability ........................ 7-19
7.9.3 Pipeline Improvements to Mitigate Existing System Deficiencies ......... 7-20
8.0 CHAPTER 8 – CAPITAL IMPROVEMENT PROGRAM ..................................................... 8-1
8.1 COST ESTIMATE ACCURACY ......................................................................... 8-1
8.2 COST ESTIMATE METHODOLOGY ................................................................. 8-2
8.2.1 Unit Costs ............................................................................................ 8-2
8.2.2 Construction Cost Index ....................................................................... 8-2
8.2.3 Construction Contingency Allowance ................................................... 8-2
City of Gilroy
Water System Master Plan
Table of Contents Page No.
March 2023 iii City of Gilroy
Water System Master Plan
8.2.4 Project Related Costs .......................................................................... 8-2
8.3 CAPITAL IMPROVEMENT PROGRAM ............................................................. 8-4
8.3.1 Capital Improvements Costs ................................................................ 8-4
8.3.2 Recommended Cost Allocation Analysis .............................................. 8-4
8.3.3 Construction Triggers ........................................................................... 8-4
8.4 SUGGESTED PIPELINE REPLACEMENT BUDGET ........................................ 8-4
City of Gilroy
Water System Master Plan
Table of Contents Page No.
March 2023 iv City of Gilroy
Water System Master Plan
FIGURES
Figure ES.1 Regional Location Map ................................................................................. ES-3
Figure ES.2 Planning Area ............................................................................................... ES-4
Figure ES.3 Existing System ............................................................................................ ES-6
Figure ES.4 Capital Improvement Program ...................................................................... 11
Figure 1.1 Regional Location Map ................................................................................. 1-2
Figure 2.1 Planning Area ............................................................................................... 2-2
Figure 2.2 Existing Land Use ......................................................................................... 2-3
Figure 2.3 2040 General Plan Land Use ........................................................................ 2-6
Figure 3.1 Historical Population vs. Average Daily Production ....................................... 3-2
Figure 3.2 Water Use Per Capita Vs. Average Daily Production .................................... 3-3
Figure 4.1 Existing System ............................................................................................ 4-2
Figure 4.2 Pipelines by Pressure Zone .......................................................................... 4-5
Figure 4.3 System Hydraulic Profile Schematic ............................................................. 4-6
Figure 5.1 Diurnal Curve ................................................................................................ 5-5
Figure 6.1 Storage Calibration ....................................................................................... 6-5
Figure 6.2 Pump Calibration .......................................................................................... 6-6
Figure 7.1 Minimum System Pressures (Maximum Day Demand) ................................. 7-2
Figure 7.2 Minimum System Pressures (Peak Hour) ..................................................... 7-3
Figure 7.3 Maximum System Pressures ........................................................................ 7-4
Figure 7.4 Required Fire Flow........................................................................................ 7-6
Figure 7.5 Fire Flow Analysis ......................................................................................... 7-7
Figure 7.6 Available Fire Flow........................................................................................ 7-8
Figure 7.7 Well Construction Schedule .......................................................................... 7-9
Figure 7.8 Recommended System Improvements ......................................................... 7-12
Figure 7.9 Existing Pipeline Deficiencies ....................................................................... 7-22
Figure 8.1 Capital Improvement Program ...................................................................... 8-5
Figure 8.2 Pipeline Relacement Budget Alternatives ..................................................... 8-9
City of Gilroy
Water System Master Plan
Table of Contents Page No.
March 2023 v City of Gilroy
Water System Master Plan
TABLES
Table ES.1 Planning and Design Criteria Summary ......................................................... ES-7
Table ES.2 Buildout Water Demands ............................................................................... ES-8
Table ES.3 Capital Improvement Program ....................................................................... ES-12
Table ES.4 Unit Costs ...................................................................................................... ES-14
Table 1.1 Unit Conversions ........................................................................................... 1-6
Table 1.2 Abbreviations and Acronyms ......................................................................... 1-7
Table 2.1 General Plan Land Use ................................................................................. 2-4
Table 2.2 Hecker Pass and Glen Loma Land Use Summary ......................................... 2-7
Table 2.3 Downtown Specific Plan Land Use Summary ................................................ 2-8
Table 2.4 Historical and Projected Population ............................................................... 2-10
Table 3.1 Historical Annual Water Production and Maximum Day Peaking Factors....... 3-4
Table 3.2 Historical Monthly Water Production (2017-2019) .......................................... 3-5
Table 3.3 Planning and Design Criteria Summary ......................................................... 3-6
Table 3.4 Water Demand Unit Factor Analysis .............................................................. 3-11
Table 3.5 Recommended Water Unit Factors ................................................................ 3-12
Table 4.1 Existing Groundwater Supply Capacity .......................................................... 4-3
Table 4.2 Existing Modeled Pipe Inventory .................................................................... 4-7
Table 4.3 Pipe Roughness Coefficients ......................................................................... 4-8
Table 4.4 Existing Storage Reservoirs........................................................................... 4-9
Table 4.5 Existing Booster Pumping Stations ................................................................ 4-10
Table 4.6 Existing Pressure Reducing Valves ............................................................... 4-12
Table 5.1 Existing Water Demands ............................................................................... 5-2
Table 5.2 Buildout Water Demand ................................................................................. 5-3
Table 7.1 Supply Capacity Evaluation ........................................................................... 7-10
Table 7.2 Existing Storage Requirements ..................................................................... 7-13
Table 7.3 Buildout Storage Requirements ..................................................................... 7-14
Table 7.4 Storage Capacity Evaluation by Pressure Zone ............................................. 7-15
Table 7.5 Existing Pump Station Capacity Evaluation ................................................... 7-17
Table 7.6 Buildout Pump Station Capacity Evaluation ................................................... 7-18
Table 7.7 Schedule of Improvements ............................................................................ 7-21
Table 8.1 Unit Costs ...................................................................................................... 8-3
Table 8.2 Capital Improvement Program ....................................................................... 8-6
City of Gilroy
Water System Master Plan
Table of Contents Page No.
March 2023 vi City of Gilroy
Water System Master Plan
APPENDICES
Appendix A Calibration Curves
March 2023 ES-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
0.0EXECUTIVE SUMMARY
This executive summary presents a brief background of the City of Gilroy’s (City) water
distribution system, the planning area characteristics, the system performance and design criteria,
the hydraulic model, and a capital improvement program.
The hydraulic model was used to evaluate the capacity adequacy of the existing distribution
system and for recommending improvements to mitigate existing deficiencies, as well as servicing
future growth. The prioritized capital improvement program accounts for growth throughout the
Gilroy planning area.
ES.1 STUDY OBJECTIVES
Recognizing the importance of planning, developing, and financing system facilities to provide
reliable domestic water system service to existing customers and for servicing anticipated growth
within the sphere of influence, the City initiated the 2023 Water System Master Plan.
The City of Gilroy authorized Akel Engineering Group Inc. to complete the following tasks:
• Summarizing the City’s existing domestic water system facilities.
• Documenting growth planning assumptions and known future developments.
• Summarizing the water system performance criteria.
• Projecting future domestic water demands.
• Updating and validating the City’s hydraulic model based on the City’s Geographic
Information Systems (GIS).
• Evaluating the domestic water facilities to meet existing and projected demand
requirements, and fire flows.
• Evaluating the existing groundwater conditions.
• Performing a capacity analysis for major distribution mains.
• Performing a fire flow analysis.
• Recommending a capital improvement program (CIP) with an opinion of probable
construction costs.
• Performing a capacity allocation analysis for cost sharing purposes.
• Developing a 2023 Water System Master Plan report.
March 2023 ES-2 City of Gilroy
Water System Master Plan
ES.2 INTEGRATED APPROACH TO MASTER PLANNING
The City implemented an integrated master planning approach and contracted the services of
Akel Engineering Group to prepare the following documents:
• 2023 Water System Master Plan
• 2023 Sewer System Master Plan
• 2023 Storm Drainage System Master Plan
While each of these reports is published as a standalone document, they have been coordinated
for consistency with the City’s General Plan. Additionally, each document has been cross
referenced to reflect relevant analysis results with the other documents.
ES.3 STUDY AREA
The City of Gilroy is located in Santa Clara County near the west coast of California, south of City
of San Francisco. The City of Gilroy lies within the seismically active region of San Francisco Bay.
The City of Gilroy lies in the southern portion of the Santa Clara County and is the most southern
city located within the county. The City is located approximately 32 miles southeast of the City of
San Jose, 8 miles southeast of Morgan Hill, 25 miles east of City of Santa Cruz, and 16 miles
northwest of City of Hollister. The City limits currently encompass 16.5 square miles, with an
approximate population of 56,600 residents, according to Department of Finance as of January
2021. Figure ES.1 displays the City’s location.
The City of Gilroy is generally bound to the north by Fitzgerald Avenue, to the northeast by San
Ysidro Avenue, to the southeast by Camino Arroyo, to the west by Burchell Road and Rancho
Vista Drive, and to the south by Carnadero Avenue. The U.S. Route 101 divides the City in a
southeast to northwest direction and the California State Route 152 (Hecker Pass Hwy) runs east-
west direction in the northern half of the City. The topography is relatively flat in the middle of the
service area, with increasing slopes in the east and west side of the city due to the Santa Cruz
Mountains to the west and the Diablo Range to the east. Figure ES.2 displays the planning area
showing city limits, the Urban Growth Boundary (UGC) of the City and Planning Area / Sphere of
Influence (SOI).
The City operates and maintains a domestic water system that covers the majority of the area
within the service area limits. Currently, the water demands are provided from groundwater wells
located throughout the service area.
ES.4 SYSTEM PERFORMANCE AND DESIGN CRITERIA
This report documents the City’s performance and design criteria that were used for evaluating
the domestic water system. The system performance and design criteria are used to establish
guidelines for determining future water demands, evaluating existing domestic water facilities, and
Morgan Hill
Watsonville
Gilroy
101
101
101
101
152
152
25
152
129
129 129
1
152
Calero
Reservoir
Anderson
Reservoir
Coyote
Reservoir
Uvas
Reservoir
Figure .1
Regional Location Map
Water System Master Plan
City of Gilroy
Updated: September 21, 2020
GIS
0 1 20.5 Miles
Legend
Cities
Railroads
Highway
City Limits
Urban Growth Boundary
Study Area
Elevation (ft)
51 - 100
101 - 250
251 - 500
501 - 1,000
1,001 - 2,000
2,001 - 3,0009 - 50
3,001 - 3,792
Waterbodies
Flie Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig1-1RLMap_092120.mxd
City of Gilroy
101
101
101
152
152
25
152
Coyote
Reservoir
Figure .
Planning Area
Water System Master Plan
City of Gilroy
Updated: September 21, 2020
GIS
0 1 20.5
Miles
Legend
City Limits
City Limits Area
Specific Plan Areas
Urban Service Area
Urban Growth Boundary
Sphere of Influence Boundary
General Plan Area
Roads
Highways
Railroads
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-1PlanningArea_092120.mxd
March 2023 ES-5 City of Gilroy
Water System Master Plan
for sizing future facilities. Table ES.1 documents the system performance and design criteria for
the domestic water system. This criterion was used in the capacity evaluation and for sizing
recommended improvements.
ES.5 EXISTING DOMESTIC WATER SYSTEM OVERVIEW
The City’s municipal water system consists of 9 groundwater wells, 10 storage reservoirs that
have a cumulative capacity of 14.1 MG, and over approximately 202 miles of distribution
pipelines. The City’s generally flat topography slopes up from east to west at approximately 180
feet in the east to approximately 250 feet in the west. Even with this generally flat topography, the
City utilizes three separate pressure zones due to the slopes on the west side.
The City’s existing domestic water distribution system is shown in Figure ES.3, with color coded
pipe sizes. This figure also identifies the location of existing wells and the storage reservoir.
ES.6 EXISTING AND FUTURE DOMESTIC WATER DEMANDS
The existing water demands used for this master plan were based on the City’s 2019 PWSS
consumption records, which included the monthly demands for each land use category, as well as
total annual production. These existing water demands in this analysis are adjusted to match the
annual production records and account for system losses.
The existing demand distribution, by pressure zone, was obtained from the water billing records.
Using GIS, each customer account was geocoded to its physical location within its existing
pressure zone. The accounts were then stored by pressure zone and total demand in each zone
was calculated.
The City’s existing average day domestic water demand, as extracted from water billing records,
were lower than the total demand listed in the annual production records due to system losses
that occurred between groundwater wells and customer service connections. The total domestic
water demand was increased proportionally to 4,768 gpm to reflect the total 2019 production and
account for transmission main losses. The existing domestic water demands for each pressure
zone (2019 SCADA) and design criteria peaking factors are summarized on Table ES.2.
ES.7 HYDRAULIC MODEL DEVELOPMENT
Hydraulic network analysis has become an effectively powerful tool in many aspects of water
distribution planning, design, operation, management, emergency response planning, system
reliability analysis, fire flow analysis, and water quality evaluations. The City’s hydraulic model
was used to evaluate the capacity adequacy of the existing system and to plan its expansion to
service anticipated future growth.
The City’s previous hydraulic model was developed using the Environmental Protection Agency’s
EPANET software, which allows the use of a single modeling scenario, and basic simulation
101
101
152
152
152
12
24
24
12
8
8
8
8
12
Well 8
Well 7
Well 8A
Well 5-2
Well 1
Well 3-2
Well 6
Well 4
Well 2
Booster
Station 4
Booster
Station 1
Booster
Station 3 & 2
Booster
Station 5
Tanks: 2C-1
2C-2
3D-1
3D-2
Tank 1A
Tanks: 2E-1
2E-2
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
24
Figure .
Existing System
Water System Master Plan
City of Gilroy
Updated: January 27, 2021
GIS
0 0.5 10.25
Mile
Legend
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig4-1_ExistingSystem_012721.mxd
Table ES.1 Planning and Design Criteria Summary
Water System Master Plan
City of Gilroy
Design Parameter Criteria
Supply
Storage Total Required Storage = Operational + Fire + Emergency
For Pressure Zone 1
Operational Storage 25% of Maximum Day Demand
Fire Storage Varies
Emergency Storage 25% of Maximum Day Demand
For Pressure Zones 2 and 3
Operational Storage 25% of Maximum Day Demand
Fire Storage Varies
Emergency Storage 50% of Maximum Day Demand
Booster Pumps
Distribution Mains Distribution mains should be designed to meet the greater of:
1) Peak Hour Demand, or 2) Maximum Day Demand + Fire Flow
Criteria for existing and future pipelines include:
Maximum pipe velocity of 8 feet per second
Maximum friction losses of 10 feet / 1,000 feet
Service Pressures Maximum Pressure 80 psi
Minimum Pressure (during Maximum Day)40 psi
Minimum Pressure (during Peak Hour)35 psi
Minimum Pressure for New Development1 (during Peak Hour)40 psi
Minimum Residual Pressure (during Fires)20 psi
Demand Peaking Factors Maximum Month Demand 1.50 x Average Day Demand
Maximum Day Demand 2.00 x Average Day Demand
Peak Hour Demand 3.00 x Average Day Demand
Fire Flows Residential 1,500 gpm for 2 hours
Commercial 2,500 gpm for 2 hours
Industrial 5,000 gpm for 3 hours
Time-of-Use 2
Urban Water Use Targets
2020 Urban Water Management Plan Existing Coefficient 166 gpdc
2015 Interim Target 149 gpdc
2020 Target (20% Conservation)133 gpdc
5/11/2021
Notes:
1. Unless otherwise noted, criteria is based on California Department of Public Health Title 22, Chapter 16, Article 8.
2. Source: PG&E Time-of-Use Pricing Schedule.
Pumping Capacity = Maximum Day Demand
Supply = Maximum Day Demand + Standby Well (1,805 gpm)
Time-of-Use considerations account for off-peak energy rate schedule before
4 PM and after 9 PM (19-hour pumping period).
Table ES.2 Buildout Water Demands Water System Master Plan City of GilroyExisting Unchanged Redeveloped Area New Development Total AreaAverage Day Demand(gpd/acre)(acres)(acres)(acres)(acres)(gpd)ResidentialHillside Residential 1,270 442 112 353 907 1,151,593Low Density Residential2,0001,583122891,7943,587,897Medium Density Residential3,280581776240788,743High Density Residential4,260671818104442,583Subtotal ‐ Residential 2,1514294663,0455,970,816Non‐ResidentialOffice and Commercial 11,100465281100846930,592Industrial 29902932136431,1491,137,375Public Facility / Institution180559153129841151,310Neighborhood District1,140038358395450,832City Gateway District1,14002072731,122Downtown Specific Plan Area 3Varies0573289210,626Mixed Use Corridor High1,10002573335,976Hecker Pass Special Use District 4Varies032888416528,763Glen Loma Ranch 4Varies0103237341577,791Industrial Park990043408382,587Employment Center1,1000279251530583,081Subtotal ‐ Non‐Residential 1,3171,5411,8934,7504,720,055OtherPark and Recreation Facility 410 995 0 154 1,149 471,009Vacant 000000Open Space025301,0451,2980Rural County00283300Subtotal ‐ Other 1,247281,2022,477471,009Total4,7141,9973,56110,27211,161,8804/20/2022Notes:1. Office and Commercial accounts for Visitor Serving Commercial and General Services Commercial Land Use types.2. Industrial accounts for General Industrial and Campus Industrial Land Use types.3. Downtown Specific Plan Water Unit Factors vary based on land use.4. Glen Loma and Hecker Pass water demand estimated separately, based on itemized land use plan and associated land use factors.Land Use ClassificationWater Unit FactorTotal Water Demand Buildout of Service Area
March 2023 ES-9 City of Gilroy
Water System Master Plan
options for steady-state and extended period simulations. As part of this master plan, the
hydraulic model has been updated for consistency the City’s current GIS database and
redeveloped using the InfoWater hydraulic modeling software, available from Innovyze Inc. This
software is directly integrated with ESRI’s ArcGIS (GIS) environment, providing a useful modeling
tool linked to the City’s newly developed GIS database.
ES.8 FIRE FLOW ANALYSIS
The fire flow analysis consisted of using the maximum day demand in the hydraulic model and
applying hypothetical fire flows. The magnitude and duration of each fire flow was based on the
governing land use type within proximity to the fire location. The criterion for fire flows was also
summarized in the System Performance and Design Criteria chapter. The hydraulic model
indicates that the City’s existing distribution system performed adequately during the fire flow
analysis, with the exceptions noted in the Evaluation and Proposed Improvements Chapter.
ES.9 SUPPLY AND STORAGE EVALUATION
The water supply source, in this case groundwater, must meet the maximum day demands for
both existing and future growth conditions. Additionally, the groundwater supply capacity must
include a redundancy, which assumes the largest well remains out of service due to equipment
malfunction or reduced supply capacity during droughts.
Currently, the City of Gilroy’s existing water supply requirement based on current water demands
is approximately 16.3 MGD. The water supply evaluation indicates the available capacity is
approximately 19.8 MGD, which results in a supply surplus of 3.5 MGD. Similarly, the future
supply requirement based on the buildout of the 2040 General Plan is approximately 24.9 MGD,
which results in a supply deficit of 5.1 MGD. As such, three new groundwater wells are
recommended to meet city performance and design criteria. The first new well is recommended to
be operational by year 2033, the second well by year 2041 and the third well by year 2048.
A water storage evaluation was also conducted in each pressure zone based on City’s
operational, emergency and fire storage criteria. The results of the storage analysis indicate that
the existing storage volume is sufficient under existing conditions but is unable to meet the
requirements for both existing and future customers at the buildout of the General Plan.
Therefore, a new storage reservoir with a capacity of 0.1 MG is recommended specifically in Zone
3 to mitigate future deficiency.
ES.10 CAPITAL IMPROVEMENT PROGRAM
The overall capital improvements required for mitigating existing system deficiencies and for
serving anticipated future growth throughout the City are summarized on Table ES.3, and are
graphically represented on Figure ES.4. The unit costs for pipeline improvements, reservoir
construction and groundwater well construction are also identified on Table ES.4.
March 2023 ES-10 City of Gilroy
Water System Master Plan
The estimated construction costs include the baseline costs plus 30 percent contingency
allowance to account for unforeseen events and unknown field conditions. Capital improvement
costs include the estimated construction costs plus 30 percent project-related costs (engineering
design, project administration, construction management and inspection, and legal costs).
The costs in this Water System Master Plan were benchmarked using a 20-City national average
Engineering News Record (ENR) Construction Cost Index (CCI) of 13,176, reflecting a date of
March 2023. In total, the CIP includes approximately 9.8 miles of pipeline improvements, one new
reservoir and three new groundwater wells with a total capital cost of over 37.6 million dollars.
101
101
152
152
152
12
24
24
12
8
8
8
8
12
24
12
16
16
Well 8
Well 7
Well 8A
Well 5-2
Well 1
Well 3-2
Well 6
Well 4
Well 2
Booster
Station 4
Booster
Station 1
Booster
Station 3 & 2
Booster
Station 5
Tanks: 2C-1
2C-2
3D-1
3D-2
Tank 1A
Tanks: 2E-1
2E-2
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
10
3H-1
P1-3
P1-6
P1-8
P1-7
16P1-5
P1-2216
GW-10
(Planned Well)
GW-11
Figure .
Capital Improvement
Program
Water System Master Plan
City of Gilroy
Updated: September 14, 2021
GIS
0 0.5 10.25
Mile
Legend
Recommended Improvements
Tanks
Wells
New Pipes
Pipe Replacements
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig8-1_CIP_091421.mxd
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
GW-12
Table ES.3 Capital Improvement Program
Water System Master Plan
City of Gilroy
PRELIMINARY
Infrastructure Costs Suggested Cost Allocation Cost Sharing
Existing Diameter New/Parallel/
Replace Diameter Length Unit Cost Infr. Cost Existing
Users Future Users Existing Users Future Users
(in)(in)(ft)($)($)($)($)($)
Pipeline Improvements
P1-1 Future Growth Zone 1 Day Rd From Santa Teresa Blvd to Monterey Hwy -New 12 3,860 254 978,700 978,700 1,272,400 1,654,200 With Development 0%100%0 1,654,200
P1-2 Future Growth Zone 1 Monterey Hwy / Orsetti
Rd / Hwy 101 From approx. 620' n/o Day Rd to Cohansey Ave -New 12 5,780 254 1,465,500 1,465,500 1,905,200 2,476,800 With Development 0%100%0 2,476,800
P1-3 Existing Deficiency Zone 1 Monterey Hwy From 2nd St to Ioof Ave 12 Replace 16 230 304 70,000 70,000 91,000 118,300 Existing Deficiency 100%0%118,300 0
P1-4 Existing Deficiency Zone 1 Murray Ave From Well 5-02 to Ioof Ave 12 Replace 16 2,200 304 669,400 669,400 870,300 1,131,400 Existing Deficiency 100%0%1,131,400 0
P1-5 Existing Deficiency Zone 1 Arroyo Cir From Well 7 to Ioof Ave 12 Replace 16 70 304 21,300 21,300 27,700 36,100 Existing Deficiency 100%0%36,100 0
P1-6 Existing Deficiency Zone 1 Lewis St From approx. 180' e/o Forest St to Chestnut St 8 Replace 10 230 211 48,600 48,600 63,200 82,200 Existing Deficiency 100%0%82,200 0
P1-7 Existing Deficiency Zone 1 Forest St From Well 3 to 6th St 10 Replace 12 320 254 81,200 81,200 105,600 137,300 Existing Deficiency 100%0%137,300 0
P1-8 Existing Deficiency Zone 1 Gilman Rd / Camino
Arroyo From Well 8 to approx. 80' se/o Gilman Rd 12 Replace 16 300 304 91,300 91,300 118,700 154,400 Existing Deficiency 100%0%154,400 0
P1-9 FF Reliability Zone 1 Pacheco Pass Hwy From Camino Arroyo to Cameron Blvd 12 Replace 16 1,730 304 526,400 526,400 684,400 889,800 As Funding is Available 100%0%889,800 0
P1-10 FF Reliability Zone 1 Camino Arroyo From Pacheco Pass Hwy to Venture Wy 12 Replace 16 3,040 304 925,000 925,000 1,202,500 1,563,300 As Funding is Available 100%0%1,563,300 0
P1-11 FF Reliability Zone 1 Cameron Blvd From Pacheco Pass Hwy to approx. 200' se/o Venture
Wy 12 Replace 16 2,100 304 639,000 639,000 830,700 1,080,000 As Funding is Available 100%0%1,080,000 0
P1-12 Future Growth Zone 1 ROW From Camino Arroyo to approx. 1,800' e/o Luchessa Ave -New 16 1,620 304 492,900 492,900 640,800 833,100 With Development 0%100%0 833,100
P1-13 Future Growth Zone 1 ROW / Cameron Blvd From approx. 200' se/o Venture Wy to Southside Dr -New 16 4,540 304 1,381,300 1,381,300 1,795,700 2,334,500 With Development 0%100%0 2,334,500
P1-14 FF Reliability Zone 1 Luchessa Ave From Thomas Rd to Rossi Ln 12 Replace 16 6,480 304 1,971,600 1,971,600 2,563,100 3,332,100 As Funding is Available 100%0%3,332,100 0
P1-15 FF Reliability Zone 1 Thomas Rd From Luchessa Ave to Santa Teresa Rd 12 Replace 16 3,060 304 931,000 931,000 1,210,300 1,573,400 As Funding is Available 100%0%1,573,400 0
P1-16 FF Reliability Zone 1 Rossi Ln From Luchessa Ave to Southside Dr 12 Replace 16 2,730 304 830,600 830,600 1,079,800 1,403,800 As Funding is Available 100%0%1,403,800 0
P1-17 Future Growth Zone 1 ROW From Luchessa Ave to approx. 1,800' e/o Luchessa Ave -New 16 1,810 304 550,700 550,700 716,000 930,800 With Development 0%100%0 930,800
P1-18 Future Growth Zone 1 ROW From approx. 1,800' e/o Luchessa Ave to Southside Dr -New 16 2,890 304 879,300 879,300 1,143,100 1,486,100 With Development 0%100%0 1,486,100
P1-19 FF Reliability Zone 1 Garlic Farm Wy /
Southside Dr From Hwy 101 to Arizona Cir 12 Replace 16 4,630 304 1,408,700 1,408,700 1,831,400 2,380,900 As Funding is Available 100%0%2,380,900 0
P1-20 Future Growth Zone 1 Southside Dr From Arizona Cir to approx. 660' e/o Arizona Cir -New 16 660 304 200,900 200,900 261,200 339,600 With Development 0%100%0 339,600
P1-21 Future Growth Zone 1 Southside Dr From approx. 660' e/o Arizona Cir to Camaron Blvd -New 16 3,010 304 915,800 915,800 1,190,600 1,547,800 With Development 0%100%0 1,547,800
P1-22 Future Growth Zone 1 Santa Teresa Blvd From approx. 160' w/o Thomas Rd to approx. 110' e/o
Thomas Rd -New 16 280 304 85,200 85,200 110,800 144,100 With Development 0%100%0 144,100
Subtotal - Pipeline Improvements 15,164,400 19,714,500 25,630,000 13,883,000 11,747,000
Storage Reservoir Improvements
3H-1 Storage Capacity Zone 3 Construct an additional 0.1 MG storage reservoir at existing 3D site New 133,442 133,500 173,600 225,700 813 EDU 0%100%0 225,700
Subtotal - Storage Reservoir Improvements 133,500 173,600 225,700 0 225,700
Estimated Const.
Costs1
Proposed Storage Capacity
(MG)
0.10
Improv. No.
Pipeline Information Capital Improv.
Costs2 Construction TriggerBaseline Constr.
CostsImprov. Type Pressure
Zone Alignment Limits
Table ES.3 Capital Improvement Program
Water System Master Plan
City of Gilroy
PRELIMINARY
Infrastructure Costs Suggested Cost Allocation Cost Sharing
Existing Diameter New/Parallel/
Replace Diameter Length Unit Cost Infr. Cost Existing
Users Future Users Existing Users Future Users
(in)(in)(ft)($)($)($)($)($)
Estimated Const.
Costs1Improv. No.
Pipeline Information Capital Improv.
Costs2 Construction TriggerBaseline Constr.
CostsImprov. Type Pressure
Zone Alignment Limits
Groundwater Well Improvements
GW-10 Supply Capacity Zone 1 Construct new well near the intersection of San Ysidro Ave and Las Animas Ave New ---3,922,000 9,500 EDU 0%100%0 3,922,000
GW-11 Supply Capacity Zone 1 Construct new well near the intersection of Camino Arroyo and Renz Lane New ---3,922,000 15,550 EDU 0%100%0 3,922,000
GW-12 Supply Capacity Zone 1 Construct new well near the intersection of Wren Ave and Vickery Ln New ---3,922,000 21,600 EDU 0%100%0 3,922,000
Subtotal - Groundwater Well Improvements 0 0 11,766,000 0 11,766,000
Total Improvement Cost
Pipeline Improvements 15,164,400 19,714,500 25,630,000 13,883,000 11,747,000
Storage Reservoirs 133,500 173,600 225,700 0 225,700
Groundwater Wells 0 0 11,766,000 0 11,766,000
Total Improvement Costs 15,297,900 19,888,100 37,621,700 13,883,000 23,738,700
Notes: 3/29/2023
1. Baseline construction costs plus 30% to account for unforeseen events and unknown conditions.
2. Estimated construction costs plus 30% to cover other costs including: engineering design, project administration (developer and City staff), construction management and inspection, and legal costs.
3. Cost estimates are based on the Engineering News Record (ENR) construction cost index (CCI) of 13,176 for March 2023.
1,500
Proposed Pumping Capacity
(gpm)
1,500
1,500
Table ES.4 Unit Costs
Water System Master Plan
City of Gilroy
Pipelines
Pipe Size Cost1,2
(in)($/lineal foot)
6 $153
8 $187
10 $211
12 $254
16 $304
18 $312
20 $336
24 $400
30 $500
36 $560
42 $705
Storage Reservoirs ($/gallon)1,3
≤1.0 MG $1.33
1.1 MG-3.0 MG $2.11
3.1 MG - 5.0 MG $3.22
> 5 MG $4.89
Groundwater Wells1,4,5
1,500 gpm Capacity $3,922,000
3/28/2023
Notes:
1. Construction costs estimated using March 2023 ENR CCI of 13,176.
2. Pipeline cossts include utilities, construction staging, traffic control, and
lighting and signing
3. Source: City of Gilroy 2004 Water System Master Plan
4. Source: City of Gilroy 2021-2025 Capital Improvement Program
5. One new 1,500 gpm well costs $3,626,645, per City of Gilroy 2021-2025
Capital Improvement Program. The cost accounts for Design, CEQA,
Construction, Con. Support, and Land Acquisition
Pump Stations
Estimated Pumping Station Project Cost = 2.1*10(0.7583*log(Q)+3.1951)
where Q is in gpm
March 2023 1-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
1.0CHAPTER 1 - INTRODUCTION
This chapter provides a brief background of the City of Gilroy’s (City) domestic water system, the
need for this master plan, and the objectives of the study. Unit conversions, abbreviations, and
definitions are also provided in this chapter.
1.1 BACKGROUND
The City of Gilroy is located approximately 32 miles southeast of the City of San Jose, 8 miles
southeast of Morgan Hill, 25 miles east of the City of Santa Cruz, and 16 miles northwest of the
City of Hollister. (Figure 1.1). The City provides potable water service to approximately 56,700
residents, as well as a myriad of commercial, industrial, and institutional establishments. The City
operates a domestic water distribution system that consists of 9 groundwater wells, 10 storage
reservoirs providing 14.1 MG total storage, and approximately 202 miles of distribution pipelines.
In 2004, the City developed a Water System Master Plan that identified capacity deficiencies in
the existing water system and recommended improvements to alleviate existing deficiencies and
service anticipated developments in the Gilroy Urban Growth Boundary.
Recognizing the importance of planning, developing, and financing system facilities to provide
reliable water service to existing customers and for servicing anticipated growth within the Gilroy
Urban Growth Boundary, the City initiated updating elements of the 2004 Water System Master
Plan, to reflect current land use conditions.
1.2 SCOPE OF WORK
City Council approved Akel Engineering Group Inc. to prepare this 2022 Water System Master
Plan (WSMP) and a concurrent Sewer System Master Plan and Storm Drainage System Master
Plan in August 2019. The 2022 WSMP evaluates the City’s domestic water system and
recommends capacity improvements necessary to service the needs of existing users and for
servicing the future growth of the City. This 2022 WSMP is intended to serve as a tool for planning
and phasing the construction of future domestic water system infrastructure for the projected
buildout of the City’s service area. The area and horizon for this master plan is based on the City’s
General Plan. Should planning conditions change, and depending on their magnitude,
adjustments to the master plan recommendations might be necessary.
This master plan included the following tasks:
Summarizing the City’s existing domestic water system facilities.
Documenting growth planning assumptions and known future developments.
Summarizing the water system performance criteria.
Morgan Hill
Watsonville
Gilroy
101
101
101
101
152
152
25
152
129
129 129
1
152
Calero
Reservoir
Anderson
Reservoir
Coyote
Reservoir
Uvas
Reservoir
Figure 1.1
Regional Location Map
Water System Master Plan
City of Gilroy
Updated: September 21, 2020
GIS
0 1 20.5 Miles
Legend
Cities
Railroads
Highway
City Limits
Urban Growth Boundary
Study Area
Elevation (ft)
51 - 100
101 - 250
251 - 500
501 - 1,000
1,001 - 2,000
2,001 - 3,0009 - 50
3,001 - 3,792
Waterbodies
Flie Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig1-1RLMap_092120.mxd
March 2023 1-3 City of Gilroy
Water System Master Plan
•Projecting future domestic water demands.
•Updating and validating the City’s hydraulic model based on the City’s Geographic
Information Systems (GIS).
•Evaluating the domestic water facilities to meet existing and projected demand
requirements and fire flows.
•Evaluating the existing groundwater conditions.
•Performing a capacity analysis for major distribution mains.
•Performing a fire flow analysis.
•Recommending a capital improvement program (CIP) with an estimation of probable costs.
•Performing a capacity allocation analysis for cost sharing purposes.
•Developing a 2023 Water System Master Plan report.
1.3 INTEGRATED APPROACH TO MASTER PLANNING
The City implemented an integrated master planning approach and contracted the services of
Akel Engineering Group to prepare the following documents:
•2023 Water System Master Plan
•2023 Sewer System Master Plan
•2023 Storm Drainage System Master Plan
While each of these reports is published as a standalone document, it has been coordinated for
consistency with the City’s General Plan. Additionally, each document has been cross referenced
to reflect relevant analysis results with the other documents.
1.4 PREVIOUS MASTER PLANS
The City’s most recent water master plan was completed in 2004. This master plan included an
evaluation of servicing growth to the planning area, evaluated existing demands and projected
future demands, evaluated groundwater conditions and management, and recommended phased
improvements to the water system for a horizon year of 2040. Additionally, the 2004 master plan
included the development of the original hydraulic model, which was then used for evaluating the
water system. Improvements were recommended for servicing existing and future growth areas,
and a corresponding Capital Improvement Program was developed to quantify construction costs.
1.5 RELEVANT REPORTS
The City has completed several special studies intended to evaluate localized growth. These
reports were referenced and used during this capacity analysis. The following lists relevant reports
March 2023 1-4 City of Gilroy
Water System Master Plan
that were used in the completion of this master plan, as well as a brief description of each
document:
City of Gilroy 2040 General Plan, November 2020 (2040 GP). The City’s 2040 General
Plan provides future land use planning, and growth assumptions for the Planning Area,
Additionally, this report establishes the planning horizon for improvements in this master
plan.
City of Gilroy Water System Master Plan, February 2004 (2004 SSMP). This report
documents the planning and performance criteria, evaluates the water system,
recommends improvements, and provides an estimate of costs.
1.6 REPORT ORGANIZATION
The water system master plan report contains the following chapters:
Chapter 1 - Introduction. This chapter provides a brief background of the City’s domestic water
system, the need for this master plan, and the objectives of the study. Abbreviations and
definitions are also provided in this chapter.
Chapter 2 - Planning Areas Characteristics. This chapter presents a discussion of the planning
area characteristics for this master plan and defines the land use classifications. The planning
area is divided into several planning sub-areas, as established by the City’s Planning Division.
Chapter 3 – System Performance and Design Criteria. This chapter presents the City’s
performance and design criteria, which was used in this analysis for identifying current system
capacity deficiencies and for sizing proposed distribution mains, storage reservoirs, and wells.
Chapter 4 – Existing Domestic Water Facilities. This chapter provides a description of the
City’s existing domestic water system facilities including the existing wells, distribution mains,
storage reservoirs, and booster station pumps.
Chapter 5 - Water Demands and Supply Characteristics. This chapter summarizes
groundwater quality, existing domestic water demands, identifies the recycled water demands,
and projects the future domestic water demands.
Chapter 6 - Hydraulic Model Development. This chapter describes the development and
calibration of the City’s domestic water distribution system hydraulic model. This hydraulic model
was used to evaluate the capacity adequacy of the existing system and to plan its expansion to
service anticipated future growth.
Chapter 7 - Evaluation and Proposed Improvements. This chapter presents a summary of the
domestic water system evaluation and identifies improvements needed to mitigate existing
deficiencies, as well as improvements needed to expand the system and service growth.
March 2023 1-5 City of Gilroy
Water System Master Plan
Chapter 8- Capital Improvement Program. This chapter provides a summary of the
recommended domestic water system improvements to mitigate existing capacity deficiencies and
to accommodate anticipated future growth. The chapter also presents the cost criteria and
methodologies for developing the capital improvement program. Finally, a capacity allocation
analysis, usually used for cost sharing purposes, is also included.
1.7 ACKNOWLEDGEMENTS
Obtaining the necessary information to successfully complete the analysis presented in this
report, and developing the long term strategy for mitigating the existing system deficiencies and
for accommodating future growth, was accomplished with the strong commitment and very active
input from dedicated team members including:
Karen L. Garner; Community Development Director
Gary Heap, P.E.; City Engineer
Jorge Duran, P.E.; Senior City Engineer
Daryl Jordan, P.E.; Director of Public Works
Matt Jones, Deputy Public Works Director
1.8 UNIT CONVERSIONS AND ABBREVIATIONS
Engineering units were used in reporting flow rates and volumes pertaining to the design and
operation of various components of the domestic water system. Where it was necessary to report
values in smaller or larger quantities, different sets of units were used to describe the same
parameter. Values reported in one set of units can be converted to another set of units by
applying a multiplication factor. A list of multiplication factors for units used in this report is shown
on Table 1.1.
Various abbreviations and acronyms were also used in this report to represent relevant water
system terminologies and engineering units. A list of abbreviations and acronyms is included in
Table 1.2.
1.9 GEOGRAPHIC INFORMATION SYSTEMS
This master planning effort made extensive use of Geographic Information Systems (GIS)
technology, for completing the following tasks:
Develop the physical characteristics of the hydraulic model (pipes and junctions, wells, and
storage reservoirs).
Allocate existing water demands, as extracted from the water billing records, and based on
each user’s physical address.
Table 1.1 Unit Conversions
Water System Master Plan
City of Gilroy
Volume Unit Calculations
To Convert From:To:Multiply by:
acre feet gallons 325,851
acre feet cubic feet 43,560
acre feet million gallons 0.3259
cubic feet gallons 7.481
cubic feet acre feet 2.296 x 10-5
cubic feet million gallons 7.481 x 10-6
gallons cubic feet 0.1337
gallons acre feet 3.069 x 10-6
gallons million gallons 1 x 10-6
million gallons gallons 1,000,000
million gallons cubic feet 133,672
million gallons acre feet 3.069
Flow Rate Calculations
To Convert From:To:Multiply By:
ac-ft/yr mgd 8.93 x 10-4
ac-ft/yr cfs 1.381 x 10-3
ac-ft/yr gpm 0.621
ac-ft/yr gpd 892.7
cfs mgd 0.646
cfs gpm 448.8
cfs ac-ft/yr 724
cfs gpd 646300
gpd mgd 1 x 10-6
gpd cfs 1.547 x 10-6
gpd gpm 6.944 x 10-4
gpd ac-ft/yr 1.12 x 10-3
gpm mgd 1.44 x 10-3
gpm cfs 2.228 x 10-3
gpm ac-ft/yr 1.61
gpm gpd 1,440
mgd cfs 1.547
mgd gpm 694.4
mgd ac-ft/yr 1,120
mgd gpd 1,000,000
5/4/2021
Table 1.2 Abbreviations and Acronyms
Water System Master Plan
City of Gilroy
Abbreviation Expansion Abbreviation Expansion
2004 WSMP 2004 Water System Master Plan gpd gallons per day
2021 WSMP 2021 Water System Master Plan gpdc gallons per day per capita
AACE International Association for the Advancement of Cost
Engineering gpm gallons per minute
AC acre hp horsepower
ACP Asbestos Cement Pipe HGL hydraulic grade line
ADD average day demand HWL high water level
Akel Akel Engineering Group, Inc.in inch
CCI Construction Cost Index LAFCO Local Agency Formation Commission
CDPH California Department of Public Health LF linear feet
cfs cubic feet per second MDD maximum day demand
CI cast iron pipe MG million gallons
CIB Capital Improvement Budget MGD million gallons per day
CIP Capital Improvement Program MMD maximum month demand
City City of Gilroy NFPA National Fire Protection Association
County Santa Clara County PHD peak hour demand
DIP Ductile Iron Pipe PRV pressure reducing valve
DU dwelling unit psi pounds per square inch
EDU equivalent dwelling unit ROW Right of Way
ENR Engineering News Record SCADA Supervisory Control and Data
Acquisition
EPA Environmental Protection Agency SOI Sphere of Influence
EPS Extended Period Simulation TBD to be determined
FRC Facility Reserve Charge ULL Urban Limit Line
ft feet VW Valley Water
fps feet per second WSMP Water System Master Plan
FY Fiscal Year WTP Water Treatment Plant
GIS Geographic Information Systems
4/28/2021
March 2023 1-8 City of Gilroy
Water System Master Plan
Calculate and allocate future water demands, based on future developments’ water use.
Extract ground elevations along the distribution mains from available contour maps.
Generate maps and exhibits used in this master plan.
March 2023 2-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
2.0CHAPTER 2 – PLANNING AREA CHARACTERISTICS
This chapter presents a discussion of the planning area characteristics for this master plan and
defines the land use classifications. The planning area is divided into several planning sub-areas,
as established by the City’s Planning Division.
2.1 STUDY AREA DESCRIPTION
The City of Gilroy is located in Santa Clara County near the west coast of California, south of City
of San Francisco. The City of Gilroy lies within the seismically active region of San Francisco Bay.
The City of Gilroy lies in the southern portion of the Santa Clara County and is the most southern
city located within the county. The City is located approximately 32 miles southeast of the City of
San Jose, 8 miles southeast of Morgan Hill, 25 miles east of City of Santa Cruz, and 16 miles
northwest of City of Hollister. The City limits currently encompass 16.5 square miles, with an
approximate population of 56,600 residents, according to the Department of Finance as of
January 2021. Figure 1.1 displays the City’s location.
The City of Gilroy is generally bound to the north by Fitzgerald Ave, to the northeast by San
Ysidro Avenue, to the southeast by Camino Arroyo, to the west by Burchell Road and Rancho
Vista Drive, and to the south by Carnadero Avenue. The U.S. Route 101 divides the City in a
southeast to northwest direction and the California State Route 152 (Hecker Pass Hwy) runs east-
west direction in the northern half of the City. The topography is relatively flat in the middle of the
service area, with increasing slopes in the east and west side of the city due to the Santa Cruz
Mountains to the west and the Diablo Range to the east. Figure 2.1 displays the planning area
showing city limits, the Urban Growth Boundary (UGC) of the City and Planning Area / Sphere of
Influence (SOI).
The City operates and maintains a domestic water system that covers the majority of the area
within the service area limits. Currently, the water demands are provided from groundwater wells
located throughout the service area.
2.2 WATER SERVICE AREA AND LAND USE
The City’s domestic water system services residential and non-residential lands within the City
limits, as summarized on Table 2.1 and shown graphically on Figure 2.2. Areas within the City’s
existing service area include:
5,429 acres of developed lands inside the City limits
3,673 acres of undeveloped lands inside the City limits.
At ultimate development of the General Plan, the City’s domestic water system is anticipated to
serve approximately 3,045 acres of residential land use, 4,750 acres of non-residential land use,
City of Gilroy
101
101
101
152
152
25
152
Coyote
Reservoir
Figure 2.1
Planning Area
Water System Master Plan
City of Gilroy
Updated: September 21, 2020
GIS
0 1 20.5
Miles
Legend
City Limits
City Limits Area
Specific Plan Areas
Urban Service Area
Urban Growth Boundary
Sphere of Influence Boundary
General Plan Area
Roads
Highways
Railroads
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-1PlanningArea_092120.mxd
101
101
152
152
25
Hecker Pass Rd
Figure 2.2
Existing Land Use
Water System Master Plan
City of Gilroy
Legend
Existing Land Use
Low Density Residentia
Medium Density Residential
High Density Residential
Neighborhood District
Public/Quasi-Public Facility
Educational Facility
Professional Office
General Services Commercial
Visitor-Serving Commercial
Industrial
Open Space
Park and Recreation Facility
Vacant
City Limits
Roads
Railroads
Rivers & Creeks
Waterbodies
Updated: September 21, 2020
0 1 20.5
Miles
GIS
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-2ExistLandUse_092120.mxd
Table 2.1 General Plan Land Use Water System Master Plan City of GilroyExistingExisting Lands ‐ RedevelopingNew Lands ‐ RedevelopmentNew Development(acre)(acre)(acre)(acre)(acre)(acre)(acre)(acre)(acre)ResidentialRural Residential‐0 0 00000 0 0Hillside Residential Hillside Residential 444‐1 442 112 344 8 464 907 913Low Density Residential Low Density Residential 1,704‐121 1,583 122 45 44 211 1,794 4,221Medium Density Residential Medium Density Residential 100‐42 58 177 4 2 183 240 248High Density Residential High Density Residential 249‐182 67 18 15 3 36 104 111Subtotal ‐ Residential 2,496‐346 2,151 429 408 58 895 3,045 5,493Non‐ResidentialVisitor Serving Commercial Visitor Serving Commercial 99‐67 32 176 0 0 176 208 208General Services Commercial General Services Commercial 524‐91 432 106 55 44 205 637 837Professional Office 1 0 1 0 0 0 0 1 1General Industrial General Industrial 320‐71 249 213 255 389 856 1,105 2,036Campus Industrial 56‐12 44 0 0 0 0 44 44Educational Facility Educational Facility 12‐571001 8 22Public/Quasi‐Public Facility Public/Quasi‐Public Facility 596‐44 552 152 102 28 281 833 1,013Neighborhood District Neighborhood District 94‐94 0 38 22 336 395 395 428City Gateway District‐0 0 0207 02727 27Downtown Specific Plan Area‐0 0 0573208989 89Mixed Use Corridor High‐0 0 0257 03333 33Hecker Pass Special Use District‐000328880416416416Glen Loma Ranch‐0001032370341341341Industrial Park‐0 0 0434008383 83Employment Center‐00027930222530530530Subtotal ‐ Non‐Residential 1,701‐3841,3171,5418761,0173,4344,7506,109OtherAgriculture‐0 0 00000 0 0Park and Recreation FacilityPark and Recreation Facility1,232‐238995066881541,1492,392VacantVacant2,391‐2,3910000000Open SpaceOpen Space1,282‐1,03025301,04141,0451,2982,897Rural County‐0 0 0280 3303017,726Subtotal ‐ Other 4,905‐3,6581,247281,107951,2302,47723,015TotalTotal Developed Area 9,102‐4,388 4,714 1,997 2,391 1,170 5,558 10,272 34,61605/12/2021Notes:1.Source: City of Gilroy General Plan Alternatives Report, Public Review Draft July 2019.2.Specific Plan land use types (Downtown, Hecker Pass, Glen Loma) are comprised of multiple land use types. As such, existing land use acreages reflect existing Specific Plan development under current existing land use designations.Sphere of InfluenceGeneral Plan Land Use ClassificationExisting Land Use ClassificationTotal DevelopmentFuture DevelopmentUrban Growth BoundaryWithin City LimitsExisting DevelopmentSubtotal Existing Development ‐UnchangedWithin City LimitsUrban Growth BoundarySubtotal Future Development
March 2023 2-5 City of Gilroy
Water System Master Plan
and 2,477 acres of other (open space and parks) land use, for a total of 10,272 acres inside the
City’s Urban Growth Boundary (Table 2.1). The land use designations used in this master plan
are consistent with the City’s 2040 General Plan. The Land Use Element received from the City’s
Planning Division is shown on Figure 2.3.
In addition to the General Plan Land Use documented on Figure 2.3, there are multiple areas of
known development, which are defined by Specific Plans or other development planning
information. These known development areas provide a more refined definition of planned land
uses, which is critical for estimating future demands. The known development areas are
summarized on Figure 2.3, with the land use information shown on Table 2.1. Based on a review
of aerial imagery and existing land use information, some known development areas are partially
developed or completely developed. The known development areas are summarized in the
following sections.
Hecker Pass Specific Plan: This development area includes approximately 416 acres,
which includes 164 acres of residential, 154 acres of non-residential, and 98 acres of other
land use as documented in Table 2.2.
Glen Loma Specific Plan: This development area includes approximately 341 acres,
which includes 210 acres of residential, 35 acres of non-residential, and 96 acres of other
land use as documented in Table 2.2.
Downtown Specific Plan: This development area includes approximately 202 acres,
which includes 108 acres of residential and 94 acres of non-residential land use as
documented in Table 2.3. This development area is comprised of multiple land use
districts as summarized in the following sections.
o Historic Land Use District: This development area includes approximately 18
acres, which includes 8 acres of residential and 10 acres of non-residential land
use.
o VTA Transit-Oriented Development: This development area includes
approximately 8 acres, which is mostly residential (7.5 acres) with very limited non-
residential land use (0.3 acres).
o Expansion Land Use District: This development area includes approximately 48
acres, which includes 21 acres of residential and 27 acres of non-residential land
use.
o Cannery Land Use District: This development area includes approximately 37
acres, which includes 11 acres of residential and 26 acres of non-residential land
use.
101
101
152
152
25
Hecker Pass Rd
Figure 2.3
2040 General Plan
Land Use
Water System Master Plan
City of Gilroy
Legend
Planning Area/Sphere of Influence
Urban Growth Boundary
City Limits
General Plan Land Use
Hillside Residential
Low Density Residential
Medium Density Residential
High Density Residential
General Services Commercial
City Gateway District
Visitor Serving Commercial
General Industrial
Employment Center
Industrial Park
Public and Quasi-Public Facility
Neighborhood District
Mixed Use
Rural County
Open Space
Park and Recreation Facility
Specific Plan Areas
Downtown
Glen Loma Ranch
Hecker Pass
Roads
Railroads
Rivers & Creeks
Waterbodies
Updated: December 6, 2019
0 1 20.5
Miles
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File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-3GeneralPlanLU_121019.mxd
Table 2.2 Glen Loma and Hecker Pass Specific Plans, Remaining Development Water Demand
Water Master Plan
City of Gilroy
Residential Non‐Residential Other
HillsideLow DensityMedium DensityHigh DensityOffice and CommercialPublic Facility / InstitutionPark and Recreation FacilityAgricultureOpen SpaceTotal Development1
Hecker Pass Acres 46.2 16.3 99.1 2.2 58.0 0.0 95.7 51.7 46.8 416.0
Glen Loma Acres 0.0 112.9 70.3 26.5 0.0 26.9 8.7 0.0 95.7 341.0
Subtotal 46.2 129.2 169.5 28.7 58.0 26.9 104.3 51.7 142.5 757.0
Existing Development2
Hecker Pass Acres 11.2 7.6 89.3 0.0 36.8 0.0 95.7 16.6 0.1 257.1
Glen Loma Acres 0.0 33.7 70.3 0.3 0.0 24.5 3.9 0.0 22.0 154.7
Subtotal 11.2 41.2 159.6 0.3 36.8 24.5 99.6 16.6 22.1 411.9
Remaining Development3
Hecker Pass Acres 35.0 8.8 9.9 2.2 21.2 0.0 0.0 35.1 46.7 158.8
Glen Loma Acres 0.0 79.2 0.0 26.2 0.0 2.3 4.8 0.0 73.8 186.3
Subtotal 35.0 88.0 9.9 28.4 21.2 2.3 4.8 35.1 120.5 345.1
Existing Average Daily Demand
(1,270
gdp/acre)
(2,000
gdp/acre)
(3,280
gdp/acre)
(4,260
gdp/acre)
(1,100
gdp/acre)
(180
gdp/acre)
(410
gdp/acre)
(0
gdp/acre)
(0
gdp/acre)
Hecker Pass gpd 14,199 15,112 292,754 20 40,450 0 39,221 0 0 401,756
Glen Loma gpd 0 67,314 230,747 1,390 0 4,417 1,604 0 0 305,472
Subtotal 14,199 82,426 523,501 1,410 40,450 4,417 40,825 0 0 707,228
Remaining Average Day Demand
(1,270
gdp/acre)
(2,000
gdp/acre)
(3,280
gdp/acre)
(4,260
gdp/acre)
(1,100
gdp/acre)
(180
gdp/acre)
(410
gdp/acre)
(0
gdp/acre)
(0
gdp/acre)
Hecker Pass gpd 44,50517,52732,3379,33323,3060000127,007
Glen Loma gpd 0 158,482 0 111,465 0 418 1,954 0 0 272,320
Subtotal 44,505 176,009 32,337 120,798 23,306 418 1,954 0 0 399,327
2/25/2022
Notes:
1. Unless noted otherwise, development information shown based on Final Hecker Pass Specific Plan (May 2015) and Glen Loma Ranch Specific Plan (May 2014).
2. Existing development area based on a combination of City of Gilroy General Plan Land Use and aerial imagery review.
3. Remaining development area based on a combination of City of Gilroy General Plan Land Use and aerial imagery review.
Specific Plan Units
Land Use Types
Total
Table 2.3 Downtown Specific Plan, Redevelopment and New Development Water Demand Water Master Plan City of GilroyLand Use DistrictExisting DevelopmentRe‐DevelopmentNew DevelopmentTotal BuildoutResidential CommercialTotal Dwelling Units2Residential Density3Commercial Density2Residential4Commercial5,6Weighted7(acres) (acres) (acres) (acres) %%DU DU/acre FAR gpd/acre gpd/acre gpd/acre(gpd)1 2 3 4 567891011 12 13 14Historic5.4 0.8 11.7 17.9 44% 56% 56 3.1 2.5 594 2,750 1,801 22,529VTA Transit‐Oriented Development 9‐7.8 0.0 7.8 96% 4% 320 41.0 2.5 7,792 2,750 7,614 59,388Expansion33.25.89.0 47.9 44% 56% 448 9.4 2.5 1,7762,7502,32134,250Cannery District8.417.4 11.4 37.2 29% 71% 760 20.4 2.0 3,8772,2002,68677,319Transitional20.1 0.280.0 20.4 69% 31% 79 3.9 1.57351,6501,019280Civic/Residential Only14.81.31.0 17.0 40% 60% 14 0.8 1.51561,6501,0522,361Gateway31.2 11.7 11.4 54.3 73% 27% 159 2.9 0.7555682562914,499Total113.1 45.0 44.4 202.51,836210,6265/12/2021Notes:1. Development area based on a combination of City of Gilroy General Plan Land Use, Downtown Gilroy Specific Plan, and aerial imagery review.2. Source: Downtown Gilroy Specific Plan.3. Residential Density calculated based on Total Dwelling Units and Total Buildout Acres.4. Residential Unit Factor based on assumed residential density and a per dwelling unit consumption of 190 gpd/DU, which is estimated based on total High Density Residential consumption and number of dwelling units5. Factors adjusted to account for increase in FAR.6. WSMP Commercial Unit Factor of 1,100 gpd/acre assumes a FAR of 1.0.7. Weighted unit factor based on Estimated Land Use Breakdown and Master Plan Unit Factors.8. Additional water demand for new development and redevelopment estimated using weighted water unit factor.Land Use Properties1Estimated Land Use Breakdown2Development and Land Use AssumptionsUnit FactorsAdditional Water Demand for Redevelopment and New Development8
March 2023 2-9 City of Gilroy
Water System Master Plan
o Transitional Land Use District: This development area includes approximately 20
acres, which includes 14 acres of residential and 6 acres of non-residential land
use.
o Civic/Residential Only Land Use District: This development area includes
approximately 17 acres, which includes 7 acres of residential and 10 acres of non-
residential land use.
o Gateway Land Use District: This development area includes approximately 54
acres, which includes 40 acres of residential and 14 acres of non-residential land
use.
2.3 HISTORICAL AND FUTURE GROWTH
According to the California Department of Finance (DOF) population estimates, the 2021 City
population is approximately 56,559 people. From 2015 to present, the City’s service area has
observed an average annual growth rate of approximately 0.7%. This 2022 WSMP is consistent
with the City’s 2020 Urban Water Management Plans (UWMP’s) annual growth rate factor of
1.5%. The current and projected service area population is summarized in Table 2.4.
Estimates of future water demands were not based on population, but rather on gross acreage for
residential and non-residential land uses. Future population was used as a means for estimating
the planning horizon of the domestic water system.
Table 2.Historical and Projected Population
Water System Master Plan
City of Gilroy
Annual Growth
(%)
Historical
2000 41,464
2001 42,436 2.3%
2002 43,144 1.7%
2003 43,866 1.7%
2004 45,026 2.6%
2005 45,782 1.7%
2006 46,446 1.5%
2007 47,047 1.3%
2008 48,353 2.8%
2009 48,627 0.6%
2010 48,821 0.4%
2011 49,622 1.6%
2012 50,716 2.2%
2013 52,475 3.5%
2014 53,325 1.6%
2015 54,233 1.7%
2016 54,849 1.1%
2017 55,811 1.8%
2018 56,030 0.4%
2019 56,635 1.1%
2020 56,704 0.1%
Projected
2021 57,555 1.5%
2022 58,418 1.5%
2023 59,294 1.5%
2024 60,184 1.5%
2025 61,086 1.5%
2026 62,003 1.5%
2027 62,933 1.5%
2028 63,877 1.5%
2029 64,835 1.5%
2030 65,807 1.5%
2031 66,794 1.5%
2032 67,796 1.5%
2033 68,813 1.5%
2034 69,845 1.5%
2035 70,893 1.5%
2036 71,957 1.5%
2037 73,036 1.5%
2038 74,131 1.5%
2039 75,243 1.5%
2040 76,372 1.5%
8/31/2021
Notes:
1. Historical populations extracted from California Department of Finance, Population Estimates E 4.
2. Projected population assuming medium annual growth rate of 1.5% per the City of Gilroy 2020 Urban Water Management Plan.
Year Population1,2
March 2023 3-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
3.0CHAPTER 3 – SYSTEM PERFORMANCE AND DESIGN CRITERIA
This chapter presents the City’s performance and design criteria, which was used in this analysis
for identifying current system capacity deficiencies and for sizing proposed distribution mains,
storage reservoirs, and wells.
3.1 HISTORICAL WATER USE TRENDS
The historical domestic water consumption per capita was calculated to determine the average
water use per capita per day. This was accomplished by dividing the City’s historical water
production by the historical population for the respective year.
The City’s historical per capita consumption factors, for the period 2000-2019, are listed in Table
3.1. The City’s per capita consumption has generally decreased since 2008 by approximately
16%. This trend is largely attributed to the City’s effort of implementing water conservation
measures. Table 3.2 lists the last three years of monthly water production in the City from 2017 to
2019.
The ultimate demand forecasts included in this master plan for residential and non-residential land
uses is based on net acreages. However, to generalize trends in the City’s water use, per capita
water use was documented. Figure 3.1 displays the historical population in relation to average
daily water production. Figure 3.2 displays a comparison in the per capita water use and average
daily water production. The remainder of the City’s criteria are summarized in the following
sections and on Table 3.3.
3.2 SUPPLY CRITERIA
In determining the adequacy of the domestic water supply facilities, the source must be large
enough to meet the varying water demand conditions, as well as provide sufficient water during
potential emergencies such as power outages and natural or created disasters.
Ideally, a water distribution system should be operated at a constant water supply rate with
consistent supply from the water source. On the day of maximum demand, it is desirable to
maintain a water supply rate equal to the maximum day rate. Water required for peak hour
demands or for fire flows would come from storage.
As the City is currently using groundwater wells as a sole source of supply, groundwater should
be viewed as a sustainable resource. With little available existing storage in the system to supply
during peak period usage, supply wells should be capable of meeting maximum day demand,
including a 1,805 gallon per minute (gpm) standby capacity. The design criteria for water supply
are documented on Table 3.3.
41,464
45,782
48,821
54,123
6.9 7.1 7.1 7.0
7.4
7.1
7.9 8.2 8.2
7.6
7.1 7.3
7.7
8.3
7.3
6.1 6.2
7.0 7.0 6.9
0
1
2
3
4
5
6
7
8
9
10
40,000
43,000
46,000
49,000
52,000
55,000
58,000
61,000
64,000
67,000
70,000
2000 2005 2010 2015 2020 Average Daily Production (MGD)PopulationYear
Population
Average Daily Production (MGD)
September 18, 2020
Figure 3.1
Historical Population vs.
Average Daily Production
Water System Master Plan
City of Gilroy
LEGEND
167 168 165 161 165
155
171 174 171
156
146 147
152
159
138
113 113
125 125 121
6.9
7.1 7.1 7.0
7.4
7.1
7.9
8.2 8.2
7.6
7.1
7.3
7.7
8.3
7.3
6.1 6.2
7.0 7.0 6.9
3
4
5
6
7
8
9
100
125
150
175
200
225
250
2000 2005 2010 2015 2020 Average Daily Production (MGD)Water Use Per Capita (gpdc)Year
Water Use Per Capita (gpdc)
Average Daily Production (MGD)
Figure 3.2
Water Use Per Capita vs.
Average Daily Production
Water System Master Plan
City of Gilroy
LEGEND
September 18, 2020
Table 3.1 Historical Water Production and Maximum Day Peaking Factors (2000-2019)
Water System Master Plan
City of Gilroy
Average Maximum3,4 Month of
Occur.
Max-to-
Avg Ratio
(AF) (MGY) (gpm)(MGM) (MGM)(gpdc)
2000 41,464 -7,800 2,542 4,836 - 212 308 August 1.46 168
2001 42,436 2% 8,006 2,609 4,963 3% 217 323 July 1.48 168
2002 43,144 2% 8,498 2,769 5,269 6% 231 330 July 1.43 176
2003 43,866 2% 7,897 2,573 4,896 -7% 214 342 July 1.60 161
2004 45,026 3% 8,333 2,715 5,166 6% 226 332 July 1.47 165
2005 45,782 2%7,961 2,594 4,936 -4% 216 348 August 1.61 155
2006 46,446 1% 8,898 2,899 5,516 12% 242 389 August 1.61 171
2007 47,047 1% 9,190 2,995 5,698 3% 250 365 July 1.46 174
2008 48,353 3% 9,261 3,017 5,741 1% 251 404 July 1.61 171
2009 48,627 1% 8,475 2,762 5,254 -8% 230 355 June 1.54 156
2010 48,821 0%7,986 2,602 4,951 -6% 217 337 July 1.56 146
2011 49,611 2% 8,186 2,667 5,075 3% 222 327 August 1.47 147
2012 50,698 2% 8,642 2,816 5,358 6% 235 348 July 1.48 152
2013 52,378 3% 9,324 3,038 5,781 8% 253 390 June 1.54 159
2014 53,208 2% 8,208 2,675 5,089 -12% 223 316 July 1.42 138
2015 54,123 2%6,870 2,239 4,259 -16% 187 232 July 1.24 113
2016 54,916 1% 6,977 2,273 4,325 2% 189 273 July 1.44 113
2017 55,932 2% 7,814 2,546 4,844 12% 212 305 July 1.44 125
2018 56,198 0% 7,854 2,559 4,869 1% 213 305 July 1.43 125
2019 56,854 1% 7,691 2,506 4,768 -2% 209 299 August 1.43 121
Historical Maximum Month Peaking Factors
10-Year Maximum (2010-2019)9,324 3,038 5,781 12% 253 390 1.56 159
5-Year Maximum (2015-2019)7,854 2,559 4,869 12% 213 305 1.44 125
3-Year Maximum (2017-2019)7,854 2,559 4,869 12% 213 305 1.44 125
Last Year's Maximum (2019)7,691 2,506 4,768 -2% 209 299 1.43 121
2020 Water System Master Plan Peaking Factors
Maximum Month Demand 1.5 x Average Day Demand
Maximum Day Demand 2.0 x Average Day Demand
Notes:
9/21/2020
1. Source: Historical populations extracted from California Department of Finance, Population Estimates E-4.
2. Source: Years 2000-2010, 2010 Urban Water Management Plan. Years 2011-2019, Monthly Well Production Data received from City staff.
Year Population1 %
Increase
Historical Water Production
Average Daily
Water Use per
Capita Annual Production2 % Increase
Monthly Production
Table 3.2 Historical Monthly Water Production (2017-2019)
Water System Master Plan
City of Gilroy
2017 2018 2019
Daily
Production
Peaking
Factor
Daily
Production
Peaking
Factor
Daily
Production
Peaking
Factor
Average Day Production Percent of
Annual
Month to Avg
Factor Average Day Production Percent of
Annual
Month to Avg
Factor Average Day Production Percent of
Annual
Month to Avg
Factor
(MGD)(MGM)(%)(MGD)(MGM)(%)(MGD)(MGM)(%)
January 4.29 133 5% 0.63 4.48 139 5% 0.65 4.26 132 5% 0.63
February 4.19 117 5% 0.55 5.07 142 6% 0.67 4.14 116 5% 0.56
March 4.74 147 6% 0.69 4.58 142 6% 0.67 4.29 133 5% 0.64
April 5.37 161 6% 0.76 5.63 169 7% 0.79 5.83 175 7% 0.84
May 8.10 251 10% 1.18 7.94 246 10% 1.15 7.13 221 9% 1.06
June 9.31 279 11% 1.32 9.10 273 11% 1.28 8.70 261 10% 1.25
July 9.85 305 12%1.44 9.84 305 12%1.43 9.61 298 12%1.43
August 9.74 302 12% 1.42 9.68 300 12% 1.41 9.65 299 12% 1.43
September 9.17 275 11% 1.30 8.87 266 10% 1.25 9.23 277 11% 1.33
October 8.16 253 10% 1.19 7.94 246 10% 1.15 8.13 252 10% 1.21
November 5.60 168 7% 0.79 6.43 193 8% 0.91 6.83 205 8% 0.98
December 5.00 155 6% 0.73 4.45 138 5% 0.65 4.45 138 6% 0.66
Total 2,547 2,559 2,507
Average Value 6.96 212 7.00 213 6.85 209
Maximum Value 305 1.44 305 1.43 299 1.43
9/21/2020
Note:
1. Source: 2017-2019 Monthly Well Production provided by City Staff on June 5, 2020.
Month Monthly MonthlyMonthly
Table 3.3 Planning and Design Criteria Summary
Water System Master Plan
City of Gilroy
Design Parameter Criteria
Supply
Storage Total Required Storage = Operational + Fire + Emergency
For Pressure Zone 1
Operational Storage 25% of Maximum Day Demand
Fire Storage Varies
Emergency Storage 25% of Maximum Day Demand
For Pressure Zones 2 and 3
Operational Storage 25% of Maximum Day Demand
Fire Storage Varies
Emergency Storage 50% of Maximum Day Demand
Booster Pumps
Distribution Mains Distribution mains should be designed to meet the greater of:
1) Peak Hour Demand, or 2) Maximum Day Demand + Fire Flow
Criteria for existing and future pipelines include:
Maximum pipe velocity of 8 feet per second
Maximum friction losses of 10 feet / 1,000 feet
Service Pressures Maximum Pressure 80 psi
Minimum Pressure (during Maximum Day)40 psi
Minimum Pressure (during Peak Hour)35 psi
Minimum Pressure for New Development1 (during Peak Hour)40 psi
Minimum Residual Pressure (during Fires)20 psi
Demand Peaking Factors Maximum Month Demand 1.50 x Average Day Demand
Maximum Day Demand 2.00 x Average Day Demand
Peak Hour Demand 3.00 x Average Day Demand
Fire Flows Residential 1,500 gpm for 2 hours
Commercial 2,500 gpm for 2 hours
Industrial 5,000 gpm for 3 hours
Time-of-Use 2
Urban Water Use Targets
2020 Urban Water Management Plan Existing Coefficient 166 gpdc
2015 Interim Target 149 gpdc
2020 Target (20% Conservation)133 gpdc
5/11/2021
Notes:
1. Unless otherwise noted, criteria is based on California Department of Public Health Title 22, Chapter 16, Article 8.
2. Source: PG&E Time-of-Use Pricing Schedule.
Pumping Capacity = Maximum Day Demand
Supply = Maximum Day Demand + Standby Well (1,805 gpm)
Time-of-Use considerations account for off-peak energy rate schedule before
4 PM and after 9 PM (19-hour pumping period).
March 2023 3-7 City of Gilroy
Water System Master Plan
Each new supply well should have adequate connections to power facilities, and every 4 th well
should have provisions for a backup power generator. For the purposes of this master plan, every
10th well was assumed to have provisions for water quality treatment.
3.3 STORAGE CRITERIA
The intent of domestic water storage is to provide adequate supply for operation equalization,
emergency conditions and fire protection. Operational or equalization storage provides the
difference in quantity between the customer’s peak hour demands and the system’s available
reliable supply. Emergency storage allows the system to maintain service pressures in the event
of emergency, such as system failure or power outages. Fire protection storage provides
adequate supply to mitigate potential fire hazards while maintaining adequate service pressure.
3.3.1 Typical Storage Criteria
City of Gilroy’s storage criteria consists of three main elements: operational, emergency, and fire
storage. These elements can typically vary for each pressure zone depending on key factors
including service population and demands. The storage criteria used for this master plan is
described below and documented in Table 3.3.
Operational Storage
Operational or equalization storage capacity is necessary to reduce the variations imposed on the
supply system by daily demand fluctuations. Peak hour demands may require up to 1.5 times the
amount of maximum day supply capacity. With storage in place, this increase in demand can be
met by the operational storage rather than by increasing production from the supply sources.
Equalization storage also stabilizes system pressures for enhancing the service. Equalization
storage requirements typically range from 25 percent to 50 percent of maximum day demand. For
all three pressure zones, the City criterion requires that 25 percent of the maximum day demand
be reserved for operational storage.
Emergency Storage
Emergency storage is the volume of water stored to meet demand during emergency situations
such as pipe failures, distribution main failures, pump failures, power outages, natural disasters,
or other cases in which the supply sources are not able to meet the demand condition.
The amount of water reserved for emergencies is determined by policies adopted by the City and
is based on an assessment of the costs and benefits including the desired degree of system
reliability, risk during an emergency situation, economic considerations, and water quality
concerns.
In California, the amount of emergency storage reserve in municipal water systems is usually
between 25 percent and 100 percent of the maximum day demand. The City criterion requires that
March 2023 3-8 City of Gilroy
Water System Master Plan
25 percent of the maximum day demand for Pressure Zone 1 be reserved for emergency storage.
Additionally, the City criterion requires that 50 percent of the maximum day demand for Pressure
Zone 2 and Zone 3 be reserved for emergency storage.
Fire Storage Requirement
Fire storage is also needed to maintain acceptable service pressures within a service zone, in the
event of a fire flow, which may occur during the maximum day demand. The recommended fire
storage capacity varies by land use type, and is usually higher for commercial and industrial
areas. Fire flow provisions were calculated based on the governing (highest) land use type within
the reservoir service area as follows:
Residential: 1,500 gpm for 2 hours = 0.18 MG
Commercial/Public Facility: 2,500 gpm for 2 hours = 0.30 MG
Industrial: 5,000 gpm for 3 hours = 0.90 MG
Total Storage Requirement
For pressure zone 1, the total storage is the summation of operational (equalization), fire, and
emergency storage requirements as follows:
Qs = 25% MDD (equalization) + fire flow (varies) + 25% MDD (emergency)
For pressure zones 2 and 3, the total storage is the summation of operational (equalization), fire,
and emergency storage requirements as follows:
Qs = 25% MDD (equalization) + fire flow (varies) + 50% MDD (emergency)
where:
Qs is the Total Required Storage, in gallons
MDD is the Maximum Day Demand, in gallons
3.4 PRESSURE CRITERIA
Acceptable service pressures within distribution systems vary depending on City criteria and
pressure zone topography. It is essential that the water pressure in a consumer’s residence or
place of business be maintained within an acceptable range. Low pressures below 30 psi can
cause undesirable flow reductions when multiple faucets or water using appliances are used at
once.
Excessively high pressures can cause faucets to leak and valve seats to wear out prematurely.
Additionally, high service pressures can cause unnecessarily high flow rates, which can result in
March 2023 3-9 City of Gilroy
Water System Master Plan
wasted water and high utility bills. The criteria for pressures in the domestic water system include
the following:
Maximum pressure, usually experienced during low demands and winter months
Minimum pressure, usually experienced during peak hour demands and summer months
Minimum pressure during fire flows and during the maximum day demand
The American Water Works Association Manual on Computer Modeling and Water Distribution
System (AWWA M-32) indicates that maximum pressures are usually in the range of 90-110
pounds per square inch (psi). In some communities, the maximum pressure may be limited to 80
psi to mitigate the impact on internal plumbing. In this case, the distribution system is usually
sized for the higher pressures, and individual pressure-reducing valves are installed on service
lines where the pressure may be exceeded.
The minimum acceptable pressure is usually in the range of 40-50 psi, which generally provides
for sufficient pressures for second story fixtures. When backflow preventers are required, they
may reduce the pressures by approximately 5-15 psi. The recommended minimum pressure
during fire flows is 20 psi, as established by the National Fire Protection Association (NFPA).
The City’s pressure criteria are summarized as follows:
Maximum pressure: 80 psi
Minimum pressure: 40 psi during maximum day and 35 psi during peak hour demands,
and 40 psi for new developments during peak hour demands
Minimum pressure during fire flows: 20 psi
3.5 UNIT FACTORS
Domestic water demand unit factors are coefficients commonly used in planning level analysis to
estimate future average daily demands for areas with predetermined land uses. The unit factors
are multiplied by the number of dwelling units or gross acreages for residential categories, and by
the gross acreages for non-residential categories, to yield the average daily demand projections.
There are several methods for developing the unit factors. This analysis relied on the City’s 2019
Public Water System Statistics (PWSS) report, which lists the monthly water consumption by land
use type in the City, to estimate the unit factors within the City service area.
The total domestic water demand was calculated from the consumption data. The demand was
adjusted to balance with current production records, and to account for transmission main losses
and vacancies in existing land uses. The demand unit factor was then calculated using the total
water production and total number of residential and non-residential land use acreages.
March 2023 3-10 City of Gilroy
Water System Master Plan
The analysis generally indicates that existing single family residential, multiple family residential,
public and park land uses have higher consumptive use factors than that of other land uses. The
existing unit factor analysis is shown on Table 3.4. The recommended water unit factors for the
City’s General Plan land use designations are summarized in Table 3.5.
3.6 SEASONAL DEMANDS AND PEAKING FACTORS
Domestic water demands within municipal water systems vary with the time of day and month of
the year. It is necessary to quantify this variability in demand so that the water distribution system
can be evaluated and designed to provide reliable water service under these variable demand
conditions.
Water use conditions that are of particular importance to water distribution systems include the
average day demand (ADD), the maximum month demand (MMD), the maximum day demand
(MDD), the peak hour demand (PHD), and the minimum month demand (MinMD).
The average day demand represents the annual water demand, divided by 365 days, since it is
expressed in daily units. The minimum month demand typically represents the low month water
demands (winter) and is used for simulating water quality analysis.
3.6.1 Maximum Month Demand
The maximum month demand (MMD) is the highest demand that occurs within a calendar month
during a year. The City’s MMD usually occurs in the summer months in either July or August. The
MMD is used primarily in the evaluation of supply capabilities.
Historical monthly water production records, obtained for the period between 2000 and 2019
(Table 3.1), indicate the maximum month to average month ratio ranging between 1.2 and 1.6.
Over the reviewed period, this ratio neither showed significant increasing or decreasing trends.
Therefore, an MMD factor of 1.5 was deemed representative of trends in the City of Gilroy. This is
a slight decrease in the peaking factor of 1.6 used in the 2004 master plan. The following equation
is recommended for estimating the maximum month demand, given the average day demand:
Maximum Month Demand = 1.5 x Average Day Demand
3.6.2 Maximum Day Demand
The maximum day demand (MDD) is the highest demand that occurs within a 24 hour day during
a year. The City’s MDD, which usually occurs during the summer months, is typically used for the
evaluation and design of storage facilities, distribution mains, pump stations, and pressure
reducing valves. The MDD, when combined with fire flows, is one of the highest demands that
these facilities should be able to service while maintaining acceptable pressures within the
system.
Table 3.4 Water Demand Unit Factor Analysis
Water System Master Plan
City of Gilroy
Unadjusted Water
Unit Factors
Unadjusted Water
Unit Factors
Production (w/o
Vacancy rate)Vacancy Rate Recommended
Factor
Balance Using
Recommended Unit
Factor
(acres)(gpd/acres) (kgal/year) (gpd)(gpd/acres)(gpd)(%)(gpd/acres)(gpd)(gpd/acres)(gpd)
Residential
Hillside Residential 444 1,128 182,582 500,226 1,219 540,815 3.5%1,262 559,743 1,270 563,307
Low Density Residential 1,704 1,785 1,110,017 3,041,144 1,929 3,287,904 3.5%1,997 3,402,981 2,000 3,408,180
Medium Density Residential 100 2,923 106,181 290,906 3,160 314,510 3.5%3,271 325,518 3,280 326,448
High Density Residential 249 3,799 345,322 946,088 4,107 1,022,855 3.5%4,251 1,058,655 4,260 1,061,015
Subtotal - Residential 2,496 1,744,103 4,778,364 5,166,084 5,346,897 5,358,951
Non-Residential
Office and Commercial6 623 938 213,440 584,767 1,014 632,216 7.5%1,090 679,632 1,100 685,641
Industrial7 376 892 122,486 335,578 964 362,807 2.0%983 370,064 990 372,542
Public Facility / Institution8 608 159 35,256 96,592 172 104,430 2.0%175 106,519 180 109,388
Neighborhood District 94 1,015 34,692 95,047 1,097 102,759 3.5%1,136 106,356 1,140 106,774
Subtotal - Non-Residential 1,701 405,875 1,111,985 1,202,212 1,262,570 1,274,344
Other
Park and Recreation Facility 1,232 374 168,058 460,432 404 497,792 0 404 497,792 410 505,174
Vacant 2,391 0 0 0 0 0 0 0 0 0 0
Open Space 1,282 0 0 0 0 0 0 0 0 0 0
Subtotal - Other 4,905 168,058 460,432 497,792 497,792 505,174
Total Developed Area 9,102 2,318,035 6,350,781 6,866,088 7,107,258 7,138,469
4/27/2021
Notes:
1. 2019 Water Consumption provided by City staff on August 12, 2020.
2. In order to account for water system losses and other unmetered consumption, production was assumed to be equal to consumption increased by 8% based on Akel Engineering Group experience.
3. Residential vacancy rate extracted from California Department of Finance Sheet E-5 published 2020.
4. Office and Commercial vacancy rate extracted from Cushman & Wakefield Silicon Valley Retail MarketBeat report published Q2 2020.
5. Industrial vacancy rate extracted from Cushman & Wakefield Silicon Valley Industrial MarketBeat report published Q2 2020.
6. "Office and Commercial" contains development and consumption for "Visitor Serving Commercial", "General Services Commercial", and "Professional Office".
7. "Industrial" contains development and consumption for "General Industrial" and "Campus Industrial".
8. "Public Facility / Institution" contains development and consumption for "Public/Quasi-Public Facility" and "Educational Facility".
Existing Land Use Classification
Existing
Development within
City Limits
Existing Average Daily Water Demand Unit Factors
Consumption1 Production2 Production at 100% Occupancy3,4,5 Recommended Water Unit Factor
Annual Consumption Projected Production at 100%
Occupancy
Table 3.5 Recommended Water Unit Factors
Water System Master Plan
City of Gilroy
Land Use
Classification
Recommended
Factor
(gpd/net acre)
Residential
Hillside Residential 1,270
Low Density Residential 2,000
Medium Density Residential 3,280
High Density Residential 4,260
Non-Residential
Office and Commercial 1,100
Industrial 990
Public Facility / Institution 180
Neighborhood District 1,140
Park and Recreation Facility 410
4/27/2021
March 2023 3-13 City of Gilroy
Water System Master Plan
Daily production records were not available for the period between 2000 to 2019. Due to the
limited daily production data, it was determined that a ratio of 2.0 (as recommended by California
Water Board standards) would be used in this master plan. The following equation is then used to
estimate the maximum day demand, given the average day demand:
Maximum Day Demand = 2.0 x Average Day Demand
3.6.3 Peak Hour Demand
The peak hour demand (PHD) is another high demand condition that is used in the evaluation and
design of water distribution systems. The peak hour demand is the highest demand that occurs
within a one hour period during a year. The peak hour demand is considered to be the largest
single measure of the maximum demand placed on the distribution system. The PHD is often
compared to the MDD plus fire flow to determine the largest demand imposed on the system for
the purpose of evaluating distribution mains.
In general, the PHD ranges between 2.5 and 3.5 times greater than the average annual demand.
In the absence of City metering records to assess the City's peak hour factor, and in accordance
with direction from City staff this study recommends a peaking factor of 3.0. This is slightly lower
than the peak use factor of 3.5 used in the previous master plan. The peak hour demand can then
be calculated using the average day demand and the following equation:
Peak Hour Demand = 3.0 x Average Day Demand
3.7 TRANSMISSION AND DISTRIBUTION MAIN CRITERIA
Transmission and distribution mains are usually designed to convey the maximum expected flow
condition. In municipal water systems, this condition is usually the greater of either the peak hour
demand or the maximum day demand plus fire flow. The hydrodynamics of pipe flow create two
additional parameters that are taken into consideration when evaluating or sizing water mains:
head loss and velocity.
Head loss is a loss of energy within pipes that is caused by the frictional effects of the inside
surface of the pipe and friction within the moving fluid itself. Head loss creates a loss in pressure
which is undesirable in water distribution systems. Head loss, by itself, is not an important factor
as long as the pressure criterion has not been violated. However, high head loss may be an
indicator that the pipe is nearing the limit of its carrying capacity and may not have sufficient
capacity to perform under stringent conditions. The City’s criterion for maximum pipeline head loss
is summarized as follow:
Greater of PHD or MDD + Fire Flow: 10 feet per 1,000 feet of pipe.
Since high flow velocities can cause damage to pipes and lead to high head loss, it is desirable to
keep the velocity below a predetermined limit. The City’s criterion for maximum pipeline velocity
used in this master plan is 8 feet per second. This criterion also ensures that the head loss is kept
March 2023 3-14 City of Gilroy
Water System Master Plan
below an acceptable limit, as the head loss in a pipe is a function of the flow velocity. The City’s
criterion. The City’s criteria for maximum pipeline velocity is summarized as follow:
Greater of PHD or MDD + Fire Flow: 8 feet per second.
A summary of the criteria pertaining to transmission and distribution mains is included in Table
3.3. It should be noted that the head loss criteria in transmission mains may be relaxed, where
feasible, to account for transmission main redundancy and reliability. Relaxing of the criteria
requires the review and approval of the City Engineer.
March 2023 4-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
4.0CHAPTER 4 – EXISTING DOMESTIC WATER FACILITIES
This chapter provides a description of the City’s existing domestic water system facilities including
the existing wells, distribution mains, storage reservoirs, and booster station pumps.
4.1 EXISTING WATER SYSTEM OVERVIEW
The City’s municipal water system consists of 9 groundwater wells, 10 storage reservoirs that
have a cumulative capacity of 14.1 MG, and over approximately 202 miles of distribution
pipelines. The City’s generally flat topography slopes up from east to west at approximately 180
feet in the east to approximately 250 feet in the west. Even with this generally flat topography, the
City utilizes three separate pressure zones due to the slopes on the west side.
The City’s existing domestic water distribution system is shown in Figure 4.1, which displays the
existing system by pipe size. This figure provides a general color coding for the distribution mains,
as well as labeling the existing wells and the storage reservoir.
4.2 SOURCE OF SUPPLY
The City currently uses groundwater as the sole source of supply. There are 9 existing
groundwater wells in the City that have been used for supply (Figure 4.1). The rated capacities for
the existing groundwater wells were extracted from the City’s 2004 Water System Master Plan as
well as information provided by City staff. During the summer months, which are typically the peak
for domestic water use, the City operates most available existing wells in some capacity. During
the winter months, which are typically the minimum system demand, all of the wells operate.
During the preparation of this master plan, City operations staff provided well capacity ratings. It
should be noted that, over time, well efficiencies may vary based on equipment conditions and
groundwater levels. In periods of prolonged drought, well efficiency ratings may decrease due to a
decline in groundwater levels. The opposite may occur in wet periods, as well efficiencies may
increase as the groundwater levels recover. As such, the City should monitor the well efficiencies
on a frequent basis to adequately manage the groundwater supply. If periods of prolonged
drought persist, it may be necessary to construct additional wells to maintain adequate supply
capacity.
Table 4.1 lists the City’s current total rated supply at approximately 18.8 million gallons per day
(MGD). Consistent with the system performance and design criteria, the firm capacity was
calculated as the capacity with the largest well out of service. Well No. 3 is the highest typical
yield well with at a capacity of 2,300 gallons per minute (gpm). The firm capacity of the well supply
is estimated at 15.5 MGD.
101
101
152
152
152
12
24
24
12
8
8
8
8
12
Well 8
Well 7
Well 8A
Well 5-2
Well 1
Well 3-2
Well 6
Well 4
Well 2
Booster
Station 4
Booster
Station 1
Booster
Station 3 & 2
Booster
Station 5
Tanks: 2C-1
2C-2
3D-1
3D-2
Tank 1A
Tanks: 2E-1
2E-2
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
24
Figure 4.1
Existing System
Water System Master Plan
City of Gilroy
Updated: January 27, 2021
GIS
0 0.5 10.25
Mile
Legend
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig4-1_ExistingSystem_012721.mxd
Table 4.Existing Groundwater Supply Capacity
Water System Master Plan
City of Gilroy
Design Head Pump Test Date Flow Rate
Total Dynamic
Head Pumping Level Horsepower
Ground
Elevation
(gpm) (mgd)(ft)(gpm)(ft)(ft)(HP)(ft)
Well 1 100 Ioof Avenue 1,200 1.73 235 7/23/2020 1,113 263 83 107 200
Well 2
660 1st Street 1,100 1.58 219 8/23/2018 841 259 120 97 211
Well 3 7325 Forrest Street 2,300 3.31 357 7/23/2020 2,075 290 110 231 192
Well 4
695 9th Street 1,200 1.73 266 7/23/2020 1,179 266 105 122 202
Well 5 8295 Rosanna Street 1,600 2.30 312 7/23/2020 1,718 311 145 204 196
Well 6 6552 Brem Lane 1,500 2.16 204 9/19/2016 1,697 253 75 64 189
Well 7 7820 Arroyo Circle 1,700 2.45 206 7/23/2020 1,296 241 71 150 196
Well 8
701 Gilliam Road 2,200 3.17 230 7/23/2020 2,414 184 108 250 188
Well 8A 700 Gilliam Road 240 0.35 339 7/23/2020 228 646 470 94 188
Total and Firm Supply Capacity
Total Supply Capacity 13,040 18.78 12,561
Firm Capacity (Excluding
largest Well)
10,740 15.47 10,147
Notes:
5/12/2021
1. Unless noted otherwise, information extracted from City of Gilroy 2004 Water System Master Plan, Table 4.1
2. Pump test data extracted from pump efficiency test received from City staff August 20, 2020.
Supply Well Well Location
Specifications 1 Pump Test Data
2 Additional Information
Rated Capacity
March 2023 4-4 City of Gilroy
Water System Master Plan
4.3 PRESSURE ZONES
The City’s current water system serves communities located between an elevation of 180 feet
above sea level to more than 600 feet. To adequately provide water in the City’s service area, the
water distribution system is divided into multiple pressure zones that operate with varying
pressures between 45 and greater than 100 psi. Figure 4.2 shows the water distribution system
and names for these pressure zones.
4.4 WATER DISTRIBUTION PIPELINES
Groundwater is pumped directly into the City’s distribution system via more than 200 miles of
pipeline with diameters ranging from pipelines 1.0-inches to 30-inches in diameter. The existing
system pipelines are documented on Figure 4.1, and color coded by pipe size. Similarly, Figure
4.2 documents the existing system and color coded by pressure zone serviced
The City’s domestic water system consists mainly of looped network connections. Looped
connections provide an increased capacity and reliability of the distribution system. These
connections allow peak demands and fire flows to be serviced from multiple directions, which
typically relieves the need for large mains.
An inventory of existing pipes, extracted from the GIS-based hydraulic model and used in this
analysis, is included in Table 4.2. For each pipe diameter, the inventory lists the length in feet, as
well as the total length in units of miles. Additionally, standard Hazen-Williams pipe roughness
coefficients used for various materials are included for reference on Table 4.3.
4.5 STORAGE RESERVOIRS
Storage reservoirs are typically incorporated in the water system to provide water supply for
operation during periods of high demand, for meeting fire flow requirements, and for other
emergencies, as defined in the City’s planning criteria.
The City’s existing storage reservoirs are summarized in Table 4.4, along with their volumes,
height, diameter, bottom elevations, SHGL, overflow height and locations. The reservoirs are also
shown on the hydraulic profile schematic (Figure 4.3), with the high-water level and bottom tank
elevation. The City maintains a robust system storage capacity, in excess of 14 million gallons.
4.6 BOOSTER STATIONS
Water is conveyed from the lower supply pressure zones to the higher pressure zones via a series
of booster pump stations. There are a total of 6 booster stations located in the City and listed in
Table 4.5. This table also indicates booster station ground elevation, source and destination
pressure zone, total pump capacity and additional information.
101
101
152
152
152
12
24
24
12
8
8
8
8
12
Well 8
Well 7
Well 8A
Well 5-2
Well 1
Well 3-2
Well 6
Well 4
Well 2
Booster
Station 4
Booster
Station 1
Booster
Station 3 & 2
Booster
Station 5
Tanks: 2C-1
2C-2
3D-1
3D-2
Tank 1A
Tanks: 2E-1
2E-2
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
24
Figure 4.2
Pipelines by Pressure Zone
Water System Master Plan
City of Gilroy
Updated: May 13, 2021
GIS
0 0.5 10.25
Mile
Legend
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Pressure Zone
Pressure Zone 1
Pressure Zone 2N
Pressure Zone 2S
Pressure Zone 3
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\2014MP\GL_Fig4-2_PipesByPZ_070721.mxd
700'600'500'400'300'200'100'700'600'500'400'300'200'100'ZONE 2SSHGL =533.5'ZONE 1SHGL =374'BS5Club Dr.BS6Miller Ave.260'BS1Rancho Hills Ct.340'280'BS4Rancho Hills Dr.250'ZONE 2NSHGL =533.5'ZONE 3SHGL =644'BS2Mantelli Dr.540'BS3Country Club Dr.490'PRV 6PRV 5PRV 4PRV 1PRV 2PRV 3W 5W 4W 3W 2W 11,200 gpm 1,100 gpm 2,300 gpm 1,200 gpm 1,600 gpmW 8AW 8W 7W 61,500 gpm 1,700 gpm 2,200 gpm 240 gpm 700 gpmIDELEVIDZONESHGL140'280'280'430'280'430'430'540'ReservoirID: Tank IDHWL: High Water Level (ft)VOL: Reservoir Capacity (MG)LOW: Bottom Elevation (ft)Booster Pumping StationID: Booster Station IDELEV: Station Elevation (ft)Pressure Regulating ValveID: Valve IDLOWHIGHPressure ZoneHIGH: Highest Service Elevation (ft)ZONE: Zone IDSHGL: Static Hydraulic Grade LineHWL: Lowest Service Elevation (ft)Transmission MainIDGPMIDGPMExisting WellID: Well IDGPM: Well Production (gpm)Proposed WellID: Well IDGPM: Well Production (gpm)Last Updated:11/29/2021City of GilroyWater System Master PlanExisting Hydraulic ProfileSchematicFigure 4.32E-20.71510.5533.5MG1B2.00347.5374MG1A3.00342.5374MG2C-20.41510.5533.5MG3D-20.41621644MGW 9MGIDVOLLOWHWLMG2E-10.71510.5533.5MG1G2.00347.5374MG2C-10.41510.5533.5MG3D-10.416216442F-10.71510.5533.5MGLEGEND
Table 4.2 Existing Modeled Pipe Inventory
Water System Master Plan
City of Gilroy
Pipe Length by Material
C.I.P.D.I.P. P.V.C.C.M.P. Unknown Total
(in)(ft) (ft) (ft) (ft) (ft)(ft) (miles)
1 0 182 1,009 0 0 1,192 0.2
1.25 0 0 146 0 0 146 0.03
2 0 887 266 0 426 1,579 0.3
3 0 174 594 0 0 768 0.1
4 5,928 22,174 8,562 0 2,262 38,926 7.4
6 64,482 98,096 10,753 113 15,332 188,776 35.8
8 82,156 325,392 15,155 0 25,885 448,588 85.0
10 15,286 38,486 2,274 0 1,110 57,155 10.8
12 31,728 169,851 12,737 0 16,193 230,509 43.7
15 0 283 0 0 0 283 0.1
16 0 44,340 3 0 0 44,343 8.4
24 0 48,658 341 0 5,877 54,876 10.4
30 1,836 0 0 0 0 1,836 0.3
Total 201,416 748,523 51,840 113 67,085 1,068,976 202.5
5/11/2021
Pipe Diameter
Table 4.Pipe Roughness Coefficients
Water System Master Plan
City of Gilroy
Age (years)
0 10 20 30 40 50
Cast Iron 120 110 100 90 85 80
Ductile Iron 130 125 120 115 110 105
Plastic (PVC)145 145 140 140 135 135
5/12/2021
Note:
1. At an age of zero, the roughness coefficients are commonly used values for new pipes. Roughness coefficients decrease with age at a rate that depends on
pipe material. For planning purposes, the hydraulic analysis assumed an average pipe age of 15 20 years for both existing and future scenarios.
2. Pipes with an unknown material or age were assigned a roughness coefficient of 111 or 121.
Pipe Material
Table 4. Existing Storage Reservoirs
Water System Master Plan
City of Gilroy
(ft)(ft)(ft)(ft)(ft) (MG)
Zone 1 1A Welburn Ave. at Rancho Real 342.5 34 32 374 128 3.00
1B Santa Teresa Blvd. at Miller Ave.347.5 29 27 374 112 2.00
1G Santa Teresa Blvd. at Miller Ave.347.5 29 27 374 165 x 165 5.30
Zone 2N 2C-1 Mantelli Dr. at Periwinkle Dr. 510.5 25 24 533.5 54 0.41
2C-2 Mantelli Dr. at Periwinkle Dr. 510.5 25 24 533.5 54 0.41
Zone 2S 2E-1 South end of Hoylake Court 510.5 25 24 533.5 70 0.71
2E-2 South end of Hoylake Court 510.5 25 24 533.5 70 0.71
2F-1 Walton Heath Court 510.5 25 24 533.5 70 0.71
Zone 3 3D-1 South end of Periwinkle Drive 621.0 25 24 644 54 0.41
3D-2 South end of Periwinkle Drive 621.0 25 24 644 54 0.41
Total Storage 14.1
1/26/2021
Note:
1. Source: City of Gilroy 2004 Water System Master Plan, Table 4.2
Pressure
Zone
Tank
Number
Location
Hydraulic Information
Bottom
Elevation Height Overflow
Height SHGL Diameter Volume
Table 4. Existing Booster Pumping Stations
Water System Master Plan
City of Gilroy
Operational Controls
(Reservoir Levels)
Operational On Off
(ft)(gpm) (mgd) (hp)(hp) (gpm) (gpm)Priority (ft) (ft)
Booster Station 1 Rancho Hills Court 280 1 (374') 2 (533.5') 1,710 2.5 138.6 7/23/2020 1 Lead 45.1 641 162 2C-1 Lead 20.0 22.5
7/23/2020 2 Lag 45.2 585 176 2C-1 Lag 1 18.0 20.0
7/23/2020 3 Standby 48.3 655 166 2C-1 Lag 2 18.0 20.0
Booster Station 2 Mantelli Dr. at Periwinkle 540 2 (533.5') 3 (644') 870 1.3 45 1 Lead 15 290 3D-1 Lead 20.0 22.5
2 Lag 15 290 3D-1 Lag 1 18.0 20.0
3 Standby 15 290 3D-1 Lag 2 18.0 20.0
Booster Station 3 Country Club Dr.490 2 (533.5') 3 (644') 870 1.3 45 1 Lead 15 290 3D-1 Lead 20.0 22.5
2 Lag 15 290 3D-1 Lag 1 18.0 20.0
3 Standby 15 290 3D-1 Lag 2 18.0 20.0
Booster Station 4 Rancho Hills Dr.250 1 (374') 2 (533.5') 1,710 2.5 150 7/23/2020 1 Lead 48.1 438 203 2C-1 Lead 20.0 22.5
7/23/2020 2 Lag 46.9 440 203 2C-1 Lag 1 18.0 20.0
7/23/2020 3 Standby 42.3 443 203 2C-1 Lag 2 18.0 20.0
Booster Station 5 Club Dr.260 1 (374') 2 (533.5') 1,710 2.5 150 7/23/2020 1 Lead 41.9 622 180 2E-1 Lead 20.0 22.5
7/23/2020 2 Lag 40.8 605 178 2E-1 Lag 1 18.0 20.0
7/23/2020 3 Standby 41 611 178 2E-1 Lag 2 18.0 20.0
Booster Station 6 Miller Ave. at Santa Teresa Blvd 340 1 (374') 2 (533.5') 1,710 2.5 150 7/23/2020 1 Lead 30.6 410 199 2E-2 Lead 20.0 22.5
7/23/2020 2 Lag 36.4 536 194 2E-2 Lag 1 18.0 20.0
7/23/2020 3 Standby 35.8 524 171 2E-2 Lag 2 18.0 20.0
1/26/2021
Notes:
1. Unless noted otherwise, data extracted from City of Gilroy 2004 Water System Master Plan, Table 4.3
2. Operational capacity for booster stations 1, 4, 5, 6 extracted from 2020 Pump efficiency tests, received from City staff August 20, 2020.
3. Booster station information based on location provided in updated City of Gilroy Water System GIS, provided August 20, 2020.
Pump Head2
Reservoir
Pump Station
Horsepower Pump Test Date Pump
Number Classification
Individual
Horsepower
Operational
Capacity2
Pump Station
CapacityNameDescriptionElevation
Source
Pressure
Zone
Destination
Pressure
Zone
March 2023 4-11 City of Gilroy
Water System Master Plan
4.7 PRESSURE REDUCING VALVES
Some pressure zones are served from higher pressure zones through pressure reducing valves
(PRVs), which are summarized on Table 4.6. PRVs constructed at pressure zone intersections,
allow the conveyance of water from higher pressure zones to the lower pressure zones in the City.
Additionally, some PRVs provide a source of emergency supply to reduce service pressures in the
case of booster station failure or other operational issues. The City currently operates 6 pressure
reducing valves throughout its water system.
Table 4.6 Existing Pressure Reducing Valves
Water System Master Plan
City of Gilroy
Pressure Zone
(in)(psi)
Rancho Hills Court Valve_BS1 10" 2N 1 15.0
Mantelli Dr. at Periwinkle Valve_BS2 8" 3 2N 5.0
Country Club Dr. Valve_BS3 10" 3 2N 10.0
Rancho Hills Dr. Valve_BS4 12" 2N 1 20.0
Club Dr. Valve_BS5 8" 2S 1 20.0
Miller Ave. at Santa Teresa Blvd Valve_BS6 16" 2S 1 1.0
1/26/2021
Location PRV ID Size Downstream
Setpoint
Upstream Downstream
March 2023 5-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
5.0CHAPTER 5 – WATER DEMANDS AND SUPPLY CHARACTERISTICS
This chapter summarizes exiting domestic water demands and projects the future domestic water
demands.
5.1 EXISTING DOMESTIC WATER DEMANDS
The existing water demands used for this master plan were based on the City’s 2019 PWSS
consumption records, which included the monthly demands for each land use category, as well as
total annual production. These existing water demands in this analysis are adjusted to match the
annual production records and account for system losses.
The existing demand distribution, by pressure zone, was obtained from the water billing records.
Using GIS, each customer account was geocoded to its physical location within its existing
pressure zone. The accounts were then stored by pressure zone and total demand in each zone
was calculated.
The City’s existing average day domestic water demand, as extracted from water billing records,
were lower than total demand listed in the annual production records due to system losses that
occurred between groundwater wells and customer service connections. The total domestic water
demand was increased proportionally to 4,768 gpm to reflect the total 2019 production and
account for transmission main losses. The existing domestic water demands, for each pressure
zone for 2019 SCADA and designed criteria peaking factors, are summarized on Table 5.1.
5.2 FUTURE DOMESTIC WATER DEMANDS
Future demands were projected using the unit factors for residential and non-residential land uses
and included the anticipated developments within the City’s service area. Table 5.2 organizes the
future land use categories and their corresponding domestic water demands. It should be noted
that the existing domestic water demands in Table 5.2 were calculated using the recommended
water unit factors, which account for future water conservation practices, and are intended to
represent the water use of existing users at buildout of the master plan horizon (2040). The
average day domestic water demands from existing and future developments is calculated at 11.2
MGD.
These demands were used in sizing the future facilities, including distribution mains, storage
reservoirs, and booster stations. Demands were also used for allocating and reserving capacities
in the existing or proposed facilities.
Table 5.1 Existing Water Demands
Water System Master Plan
City of Gilroy
Existing Water Demands
Maximum Day
Demand 2
Peak Hour
Demand 3
Maximum Day
Demand 4
Peak Hour
Demand 5
(gpm)(gpm)(gpm)(gpm)(gpm)
Zone 1 4,200 6,702 10,215 8,400 12,600
Zone 2N 170 271 413 339 509
Zone 2S 307 490 747 615 922
Zone 3 91 145 222 182 273
Total 4,768 7,609 11,597 9,536 14,304
5/12/2021
Note:
1. Total demand was adjusted to reflect the total production for 2019, from Groundwater well production records. The distribution is based on 2019 water billing reco
2. Maximum Day Demand = 1.6 x Average Day Demand, as based on 2019 SCADA.
3. Peak Hour Demand = 2.4 x Average Day Demand, as based on 2019 SCADA .
4. Maximum Day Demand = 2.0 x Average Day Demand
5. Peak Hour Demand = 3.0 x Average Day Demand
Pressure Zone
Average Day
Demand 1
SCADA Based Peaking Factors Design Criteria Peaking Factors
Table 5.2 Buildout Water Demands Water System Master Plan City of GilroyExisting Unchanged Redeveloped Area New Development Total AreaAverage Day Demand(gpd/acre)(acres)(acres)(acres)(acres)(gpd)ResidentialHillside Residential 1,270 442 112 353 907 1,151,593Low Density Residential2,0001,583122891,7943,587,897Medium Density Residential3,280581776240788,743High Density Residential4,260671818104442,583Subtotal ‐ Residential 2,1514294663,0455,970,816Non‐ResidentialOffice and Commercial 11,100465281100846930,592Industrial 29902932136431,1491,137,375Public Facility / Institution180559153129841151,310Neighborhood District1,140038358395450,832City Gateway District1,14002072731,122Downtown Specific Plan Area 3Varies0573289210,626Mixed Use Corridor High1,10002573335,976Hecker Pass Special Use District 4Varies032888416528,763Glen Loma Ranch 4Varies0103237341577,791Industrial Park990043408382,587Employment Center1,1000279251530583,081Subtotal ‐ Non‐Residential 1,3171,5411,8934,7504,720,055OtherPark and Recreation Facility 410 995 0 154 1,149 471,009Vacant 000000Open Space025301,0451,2980Rural County00283300Subtotal ‐ Other 1,247281,2022,477471,009Total4,7141,9973,56110,27211,161,8804/20/2022Notes:1. Office and Commercial accounts for Visitor Serving Commercial and General Services Commercial Land Use types.2. Industrial accounts for General Industrial and Campus Industrial Land Use types.3. Downtown Specific Plan Water Unit Factors vary based on land use.4. Glen Loma and Hecker Pass water demand estimated separately, based on itemized land use plan and associated land use factors.Land Use ClassificationWater Unit FactorTotal Water Demand Buildout of Service Area
March 2023 5-4 City of Gilroy
Water System Master Plan
5.3 MAXIMUM DAY AND PEAK HOUR DEMANDS
The maximum day and peak hour demands for the existing and future demands were calculated
using the average day demands and City peaking factor criteria. The maximum day to average
day ratio of 2.0, and peak hour to average day ratio of 3.0, were applied to the average day
demands to obtain estimates of the higher demand conditions. The maximum day and peak hour
demand estimates for the buildout of the Urban Growth Boundary are 22.3 mgd and 33.5 mgd,
respectively.
5.4 DIURNAL DEMAND PATTERNS
Water demands vary with the time of day and by account type according to the land use
designation. These fluctuations were accounted for in the modeling effort and evaluation of the
water distribution system. The diurnal demand patterns are a collection of unit factors that are
applied to the demand, and which reflect the variable hourly fluctuation. Due to the sufficient
SCADA data, the City was able to generate diurnal demand curve. Figure 5.1 shows the city’s
diurnal, developed based on SCADA data observed June 2020 through August 2020.
May 12,2021
Figure 5.1
Diurnal Curve
Water System Master Plan
City of Gilroy
LEGEND
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24Peaking Factor
Time (hours)
EPS 2020 Demand Diurnal
Water Demand
Notes:
1. Diurnal curve was developed based on SCADA data observed June 2020 through August
2020.
March 2023 6-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
6.0CHAPTER 6 – HYDRAULIC MODEL DEVELOPMENT
This chapter describes the development and calibration of the City’s domestic water distribution
system hydraulic model. The hydraulic model was used to evaluate the capacity adequacy of the
existing system and to plan its expansion to service anticipated future growth.
6.1 OVERVIEW
Hydraulic network analysis has become an effectively powerful tool in many aspects of water
distribution planning, design, operation, management, emergency response planning, system
reliability analysis, fire flow analysis, and water quality evaluations. The City’s hydraulic model
was used to evaluate the capacity adequacy of the existing system and to plan its expansion to
service anticipated future growth.
6.2 MODEL SELECTION
The City’s hydraulic model combines information on the physical characteristics of the water
system (pipelines, groundwater wells, and storage reservoirs) and operational characteristics
(how they operate). The hydraulic model then performs calculations and solves series of
equations to simulate flows in pipes and calculate pressures at nodes or junctions.
There are several network analysis software products that are released by different
manufacturers, which can equally perform the hydraulic analysis satisfactorily. The selection of a
particular software depends on user preferences, the distribution system’s unique requirements,
and the costs for purchasing and maintaining the software.
The City’s previous hydraulic model was developed using the Environmental Protection Agency’s
EPANET software, which allows the use of a single modeling scenario, and basic simulation
options for steady-state and extended period simulations. As part of this master plan, the
hydraulic model has been updated for consistency the City’s current GIS database and
redeveloped using the InfoWater hydraulic modeling software, available from Innovyze Inc. This
software is directly integrated with ESRI’s ArcGIS (GIS) environment, providing a useful modeling
tool linked to the City’s newly developed GIS database.
6.3 HYDRAULIC MODEL DEVELOPMENT
Developing the hydraulic model included skeletonization, digitizing and quality control, developing
pipe and node databases, and water demand allocation, as described in detail below.
March 2023 6-2 City of Gilroy
Water System Master Plan
6.3.1 Skeletonization
Skeletonizing the model refers to the process where pipes not essential to the hydraulic analysis
of the system are stripped from the model. Skeletonizing the model is useful in creating a system
that accurately reflects the hydraulics of the pipes within the system, while reducing complexities
of large systems, which will reduce the time of analysis while maintaining accuracy, but will also
comply with limitations imposed by the computer program.
In the City of Gilroy’s case, skeletonizing was kept to a minimum due to the availability of the
existing model, which has been maintained and updated since the completion of the 2004 Water
System Master Plan.
6.3.2 Pipes and Nodes
Computer modeling requires the compilation of large numerical databases that enable data input
into the model. Detailed physical aspects, such as pipe size, pipe elevation, and pipe lengths,
contribute to the accuracy of the model.
Pipes and nodes represent the physical aspect of the system within the model. A node is a
computer representation of a place where demand may be allocated into the hydraulic system,
while a pipe represents the distribution and transmission aspect of the water demand. In addition,
reservoir dimensions and capacities, and groundwater well capacity and design head, were also
included in the hydraulic model.
6.3.3 Digitizing and Quality Control
The City’s existing domestic water distribution system was digitized in GIS using several sources
of data and various levels of quality control. The data sources included the City’s existing system
as maintained by staff in GIS, as well as the previously developed hydraulic model and
subsequent updates.
After reviewing the available data sources, the hydraulic model was updated and verified by City
staff. Resolving discrepancies in data sources was accomplished by graphically identifying each
discrepancy and submitting it to engineering and public works staff for review and comments. City
comments were incorporated in the verified model.
6.3.4 Demand Allocation
Demand allocation consists of assigning water demand values to the appropriate nodes in the
model. The goal is to distribute the demands throughout the model to best represent actual
system response.
Allocating demands to nodes within the hydraulic model required multiple steps, incorporating the
efficiency and capabilities of GIS and hydraulic modeling software. Existing land use water
demand factors were used in conjunction with the existing land use map. Each demand factor was
March 2023 6-3 City of Gilroy
Water System Master Plan
applied to the appropriate land use and then multiplied by the acreage. In the absence of
complete water billing records, this methodology was considered the best approach to allocate
existing water demands.
Domestic water demands from each anticipated future development, as presented in a previous
chapter, were also allocated to the model for the purpose of sizing the required future facilities.
The demands from the greater Planning Area were allocated based on proposed land use and the
land use acreages. Since many of the areas were very large in size, demands were allocated
evenly to the demand nodes within each area. Infill areas, redevelopment areas, and vacant lands
were also included in the future demand allocation.
6.4 MODEL CALIBRATION
Calibration is intended to instill a level of confidence in the pressures and flows that are simulated.
Calibration generally consists of comparing model predictions to field measured results and
making necessary adjustments.
6.4.1 Calibration Plan and SCADA
In order to calibrate the hydraulic model, pressure SCADA data was collected for points
throughout the water distribution system, as well as water level data for the City’s storage
reservoirs. City staff provide 10-minute pressure and flow data for each groundwater well and
booster station as well as 10-minute water level data for the City’s storage reservoirs, for the
period between June and August 2020.
City staff provided hourly pressure and flow data for each well, as well as the pressure at the base
of the water tank, for the period between June and August 2020. This data was further
consolidated and compared with daily demand data to best calibrate to average day conditions.
The calibration results are shown in Figure 6.1 and Figure 6.2.
6.4.2 EPS Calibration
Calibration can be performed for steady state conditions or for extended period simulations (EPS).
In steady state calibration, the model is compared to field monitoring results consisting of a single
value, such as a single hydrant test. EPS calibration consists of comparing model predictions to
diurnal operational changes in the water system.
The calibration process was iterative and resulted with satisfactory comparisons between the field
measurements and the hydraulic model predictions at each well site and the water tank. The
calibration results were graphically summarized for each site and included in Appendix A.
Representative extracts from Appendix A are shown on Figure 6.1 and Figure 6.2 for calibration
points at the water tank 1A, 1B, 1G-1, 1G-2 and well 3, 4, respectively.
March 2023 6-4 City of Gilroy
Water System Master Plan
6.4.3 Use of the Calibrated Model
The calibrated hydraulic model was used as an established benchmark in the capacity evaluation
of the existing water distribution system. The model was also used to identify improvements
necessary for mitigating existing system deficiencies and for accommodating future growth. This
valuable investment will continue to prove its value to the City as future planning issues or other
operational conditions surface. It is recommended that the model be maintained and updated with
recent construction to preserve its integrity.
Figure 6.1
Storage Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
5
10
15
20
25
0 6 12 18 24Level (ft)
Time (hours)
Tank 1A
Pressure Zone 1
Avg. % Difference = 4%
0
5
10
15
20
0 6 12 18 24Level (ft)
Time (hours)
Tank 1B
Pressure Zone 1
Avg. % Difference = 3%
0
5
10
15
20
25
0 6 12 18 24Level (ft)
Time (hours)
Tank 1G 1
Pressure Zone 1
Avg. % Difference = 11%
0
5
10
15
20
0 6 12 18 24Level (ft)
Time (hours)
Tank 1G 2
Pressure Zone 1
Avg. % Difference = 3%
Figure 6.2
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 3 Flow
Pressure Zone 1
Avg. % Difference = 0%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 3 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 3%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 4 Flow
Pressure Zone 1
Avg. % Difference = 1%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 4 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 3%
March 2023 7-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
7.0CHAPTER 7 – EVALUATION AND PROPOSED IMPROVEMENTS
This chapter presents a summary of the domestic water system evaluation and identifies
improvements needed to mitigate existing deficiencies, as well as improvements needed to
expand the system and service growth.
7.1 OVERVIEW
The calibrated hydraulic model was used for evaluating the distribution system for capacity
deficiencies during peak hour demand and during maximum day demands in conjunction with fire
flows. Since the hydraulic model was calibrated for extended period simulations, the analysis
duration was established at 24 hours for analysis.
The criteria used for evaluating the capacity adequacy of the domestic water distribution system
facilities (transmission mains, storage reservoirs, and booster stations) was discussed and
summarized in the System Performance and Design Criteria chapter.
7.2 LOW PRESSURE ANALYSIS
The hydraulic model was also used to determine if the existing domestic water distribution system
meets the City’s System Performance and Design Criteria for the maximum day and peak hour
pressures, as discussed in a previous chapter. During maximum day demands the minimum
pressure requirement is 40 psi, while during the peak hour demand, the minimum pressure
requirement is 35 psi. The hydraulic analysis indicated the City’s existing system performed
reasonably well during under maximum day (Figure 7.1) and peak hour (Figure 7.2) operating
conditions.
7.3 HIGH PRESSURE ANALYSIS
The hydraulic model was also used to identify areas that experience high pressure under
maximum day demand conditions, as shown on Figure 7.3. Areas of high pressure may be more
susceptible to pipeline breaks and ruptures. The City’s maximum desired pressure criterion is 80
psi. The hydraulic analysis indicated the City’s system observes some periods of high pressures,
primarily in the northwest, southwest and southeast sections of the City.
7.4 FIRE FLOW ANALYSIS
The fire flow analysis consisted of using the maximum day demand in the hydraulic model and
applying hypothetical fire flows. The magnitude and duration of each fire flow was based on the
governing land use type within proximity to the fire location. The criterion for fire flows was also
summarized in the System Performance and Design Criteria chapter.
101
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Figure 7.1
Minimum System Pressures
(Maximum Day Demand)
Water System Master Plan
City of Gilroy
Updated: April 28, 2021
GIS
0 0.5 10.25
Mile
Legend
Node Pressures < 40 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-1A_MinPress_MaxDay_042821.mxd
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Figure 7.
Minimum System Pressures
(Peak Hour)
Water System Master Plan
City of Gilroy
Updated: April 28, 2021
GIS
0 0.5 10.25
Mile
Legend
Node Pressures < 35 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-1B_MinPress_Hour_042821.mxd
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Figure 7.
Maximum System Pressures
Water System Master Plan
City of Gilroy
Updated: April 23, 2021
GIS
0 0.5 10.25
Mile
Legend
Node Pressures > 80 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-2_MaxPress_042321.mxd
March 2023 7-5 City of Gilroy
Water System Master Plan
The hydraulic model indicates that the City’s existing distribution system performed adequately
during the fire flow analysis. The required fire flow, based on different types of land uses, are
presented on Figure 7.4. Areas where the City’s water system did not meet the fire flow criteria
are documented on Figure 7.5. The available fire flow at the City’s residual pressure criteria of 20
psi is shown on Figure 7.6.
7.5 WATER SUPPLY
The criteria for water supply should be capable of meeting maximum day demand, including a 2.6
million gallons per day (MGD) standby capacity.
The City’s existing water supply requirement for maximum day demands plus a 2.6 MGD standby
capacity is 16.3 MGD. The buildout water supply requirement for Planning Area demands is
projected at 25.0 MGD. Table 7.1 includes a supply analysis for the City through the buildout of
the Gilroy Planning Area.
It should be noted that the 2020 Urban Water Management Plan (UWMP) projected an average
daily supply requirement of 7.4 MGD for existing conditions and projected 21.8 MGD for future
conditions. This differs from the master plan average daily supply requirement of 6.9 MGD for
existing conditions and projected 11.2 MGD for 2040 General Plan buildout conditions. The
master plan demand projections have been reviewed and approved by City staff.
7.6 WATER SUPPLY REQUIREMENTS
The City’s existing domestic water supply capacity is identified in this section. Additionally, the
section identifies the additional supply capacity required to meet the supply requirement.
7.6.1 Existing Supply Requirements
Existing supply requirements were identified for the City and are summarized on Table 7.1. The
City’s existing water supply requirement is approximately 16.3 mgd, as based on existing land use
and recommended water demands. The existing available supply capacity is approximately 19.8
mgd, which results in a supply surplus of 3.5 mgd.
7.6.2 Future Supply Requirements
Future supply requirements were identified based on the buildout of the 2040 General Plan and
are summarized on Table 7.1. As shown on Table 7.1 the City’s existing firm supply capacity is
not sufficient to meet the City’s buildout supply requirement, and three (3) new wells are required
to be constructed. With the construction of three new wells (2.2 mgd capacity for each) in the City,
the City’s future firm supply capacity will meet the future supply requirement of 25 mgd under
buildout conditions. Figure 7.7 shows the projected population, required and available supply
capacity through year 2020 to year 2040, and identifies the time when the proposed groundwater
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Figure 7.
Required Fire Flow
Water System Master Plan
City of Gilroy
Updated: April 29, 2021
GIS
0 0.5 10.25
Mile
Legend
Required Fire Flow
Industrial: 5,000 gpm for 3 Hours
Commercial: 2,500 gpm for
2 Hours
Residential: 1,500 gpm for
2 Hours
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-3_FFReq_042921.mxd
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbod
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152
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Figure 7.
Fire Flow Analysis
Water System Master Plan
City of Gilroy
Updated: July 7, 2021
GIS
0 0.5 10.25
Mile
Legend
Residual Pressure < 20 psi
Residual Pressure = 0 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-4_FFAnalysis_070721.mxd
101
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Figure 7.
Available Fire Flow
Water System Master Plan
City of Gilroy
Updated: April 23, 2021
GIS
0 0.5 10.25
Mile
Legend
Available Fire Flow
Greater than 5,000 gpm
2,500 gpm - 5,000 gpm
1,500 gpm - 2,500 gpm
500 gpm - 1,500 gpm
Less than 500 gpm
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-5_AvailFF_042321.mxd
Note:
It should be noted that available
fire flow values shown are based
on a residual pressure of 20 psi.
Population
Required Supply Capacity
Available Supply Capacity16.917.117.417.617.818.018.318.518.719.019.219.519.720.020.220.520.821.121.321.621.922.222.522.823.123.423.724.024.324.725.025.356,704
61,086
65,807
70,893
76,372
82,274
88,633
0
5
10
15
20
25
30
35
40
45
50
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
100,000
2020 2025 2030 2035 2040 2045 2050 Supply Capacity (MGD)PopulationYear
Well Construction Schedule
Figure 7.7
Well Construction
Schedule
Water System Master Plan
City of Gilroy
April 22, 2022
LEGEND
Assumptions:
1. Water demand projections based on a demand factor of
126.35 gpcd.
2. Projected water demand based on Maximum Day
Demand + Standby Well Requirement (2.6 MGD).
Construct New Well
(2.2 mgd) by 2033
Existing Supply Capacity = 19.8 MGD
Construct New Well
(2.2 mgd) by 2041
Construct New Well
(2.2 mgd) by 2048
Table 7.1 Supply Capacity Evaluation
Water System Master Plan
City of Gilroy
Well No.
Supply Capacity Criteria
Groundwater Supply Capacity
No. 1 1,200 gpm
No. 2 1,100 gpm
No. 3 2,300 gpm
No. 4 1,200 gpm
No. 5 1,600 gpm
No. 6 1,500 gpm
No. 7 1,700 gpm
No. 8 2,200 gpm
No. 8A 240 gpm
No. 9 1 700 gpm
Supply vs. Demand Evaluation
Supply Balance Existing Buildout
Maximum Day Demand
(mgd)13.7 22.3
Standby Well
(mgd)2.6 2.6
Required Capacity
(mgd)16.3 24.9
Available Supply Capacity
(mgd)19.8 19.8
Capacity Surplus/Deficiency
(mgd)3.5 ‐5.1
Recommended New Wells
(at 2.2 mgd each 2)03.0
7/6/2021
Note:
1.Project is currently under way to construct Well No. 9.
2.Recommended new well capacity of 2.2 mgd is
consistent with the 2004 WSMP.
Firm supply capacity to equal Maximum Day Demand +
Standby Well (2.6 mgd)
Rated Supply Capacity
March 2023 7-11 City of Gilroy
Water System Master Plan
wells need to be constructed. The proposed groundwater well sites are shown graphically in
Figure 7.8 and described as follows:
GW-10: Construct a new 1,500 gpm groundwater well near the intersection of San Ysildro
Avenue and Las Animas Avenue (Anticipated Construction Year: 2033).
GW-11: Construct a new 1,500 gpm groundwater well near the intersection of Camino
Arroyo and Renz Lane (Anticipated Construction Year: 2041).
GW-12: Construct a new 1,500 gpm groundwater well near the intersection of Wren
Avenue and Vickery Lane (Anticipated Construction Year: 2048).
Akel recommends a feasibility study of each proposed site to confirm site-specific constraints such
as subsurface conditions, aquifer depth, water quality treatment requirements and overall
constructability.
7.7 WATER STORAGE REQUIREMENT
The City’s existing domestic water system storage capacity is identified in this section.
Additionally, this section identifies the existing and future storage requirements to meet the
storage capacity and compares it with the existing storage facilities in each zone and makes
recommendation for new storage facilities.
7.7.1 Existing Storage Requirements
Existing storage requirements were identified for each pressure zone and are summarized in
Table 7.2. The table lists the existing domestic water demands and identifies the operational,
emergency and fire storage for each pressure zone. The table also lists the total required storage
for existing domestic water demands at 8.8 MG.
7.7.2 Future Storage Requirements
Future storage requirements were identified based on the buildout of the 2040 General Plan and
summarized by pressure zone on Table 7.3. The table lists the future domestic water demands
and identifies the operational, emergency and fire storage for each pressure zones. The table also
lists the total required storage for future domestic water demands at 13.7 MG.
7.7.3 Recommended New Storage Facilities
The existing and future storage requirements, shown on Table 7.2 and Table 7.3, were compared
with existing City storage facilities in each pressure zone and requirement storage facility
improvements that were identified and listed on Table 7.4. The table lists existing storage facilities
for each pressure zone, identifies existing storage capacity deficiencies, and identifies future
storage capacity requirements to meet the needs from future growth.
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8
12
24
16
GW-11
GW-10
(Planned Well)
Well 8
Well 7
Well 8A
Well 5-2
Well 1
Well 3-2
Well 6
Well 4
Well 2
Booster
Station 4
Booster
Station 1
Booster
Station 3 & 2
Booster
Station 5
Tanks: 2C-1
2C-2
3D-1
3D-2
Tank 1A
Tanks: 2E-1
2E-2
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
3H-1
16
Figure 7.8
Recommended System
Improvements
Water System Master Plan
City of Gilroy
Updated: September 14, 2021
GIS
0 0.5 10.25
Mile
Legend
Recommended Improvements
Tanks
Wells
New Pipes
Pipe Replacements
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-8_RecImp_091421.mxd
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
GW-12
Table 7.2 Existing Storage Requirements
Water System Master Plan
City of Gilroy
Existing Water Demands
1 Existing Water Storage Requirements
Average Day
Demand
Maximum Day
Demand 2 Operational Emergency
Fire
Protection 3
Total, By
Pressure Zone
(MGD)(MGD)(MG) (MG) (MG)(MG)
Zone 1 6.05 12.10 3.02 3.02 0.90 6.95
Zone 2N 0.24 0.49 0.12 0.24 0.18 0.55
Zone 2S 0.44 0.88 0.22 0.44 0.30 0.96
Zone 3 0.13 0.26 0.07 0.13 0.18 0.38
Total 6.87 13.73 3.43 3.84 1.56 8.83
5/11/2021
Notes:
1. Total demands reflect the average day production and escalated using the peaking factor. The distribution is based on 2019 water billing records.
2. Maximum Day Demand = 2.0 x Average Day Demand
3. Fire Protection requirement represents largest fire requirement for each zone, based on existing land use types.
Pressure Zone
Table 7.3 Buildout Storage Requirements
Water System Master Plan
City of Gilroy
Buildout Water Demands 1 Buildout Water Storage Requirements
Average Day
Demand
Maximum Day
Demand 2 Operational Emergency Fire
Protection 3
Total, By
Pressure Zone
(MGD)(MGD)(MG)(MG)(MG)(MG)
Zone 1 9.16 18.31 4.58 4.58 0.90 10.06
Zone 2N 0.28 0.56 0.14 0.28 0.18 0.60
Zone 2S 1.23 2.45 0.61 1.23 0.30 2.14
Zone 3 0.50 1.00 0.25 0.50 0.18 0.93
Total 11.16 22.32 5.58 6.58 1.56 13.72
5/17/2022
Notes:
1. Buildout water demands include existing and future demands.
2. Maximum Day Demand = 2.0 x Average Day Demand
3. Fire Protection requirement represents largest fire requirement for each zone, based on existing land use types.
Pressure Zone
Table 7.4 Storage Capacity Evaluation by Pressure Zone Water System Master Plan City of GilroyExisting Water Storage RequirementsExisting Water Storage RequirementsExisting Storage Reservoirs Buildout Water Storage RequirementsBuildout Water Storage RequirementsProposed New Storage ReservoirsExisting Average Day DemandExisting Maximum Day DemandOperational + EmergencyFire ProtectionTotal1A1B1G2C‐12C‐22E‐12E‐22F‐13D‐13D‐2TotalBuildout Average Day DemandBuildout Maximum Day DemandOperational + EmergencyFire ProtectionTotalZone 1Zone 2NZone 2SZone 3Total(MGD) (MGD) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG)(MG)(MGD) (MGD) (MG) (MG) (MG) (MG) (MG) (MG) (MG) (MG)(MG) (MG)Zone 16.0 12.1 6.0 0.9 6.93.0 2.0 5.310.3 3.4 9.2 18.3 9.2 0.9 10.10.010.3 0.24Zone 2N 0.2 0.5 0.4 0.2 0.50.4 0.40.8 0.3 0.3 0.6 0.4 0.2 0.60.00.8 0.22Zone 2S 0.4 0.9 0.7 0.3 1.00.7 0.7 0.72.1 1.2 1.2 2.4 1.8 0.3 2.10.02.1 0.00Zone 30.1 0.3 0.2 0.2 0.40.4 0.40.8 0.4 0.5 1.0 0.7 0.2 0.90.10.10.9 0.00Total6.9 13.7 7.3 1.6 8.814.1 5.2 11.2 22.3 12.2 1.6 13.70.10 14.17 0.465/13/2021Pressure ZoneStorage Balance for Existing DemandsTotal StorageExisting and Buildout Storage Balance
March 2023 7-16 City of Gilroy
Water System Master Plan
The results of the storage analysis indicate that the existing storage volume is sufficient under
existing conditions but is unable to meet the requirements for both existing and future customers
at the buildout of the General Plan. Therefore, a new storage reservoir is recommended
specifically in Zone 3 to mitigate the storage deficiency.
The proposed storage reservoir is summarized on Table 7.4 and graphically shown on Figure
7.8. This reservoir is described as follows, with a preliminary capacity of 0.1 MG:
R 3H-1: Construct a new 0.1 MG storage reservoir at existing Zone 3 Tank site,
located on Periwinkle Drive, to provide additional storage for future demand.
It should be noted that a minimum storage capacity of 0.1 MG was required in pressure zone 3 to
meet the buildout requirements. Potential for additional capacity should be investigated during
subsequent design phases to provide resiliency, if feasible.
7.8 PUMP STATION CAPACITY ANALYSIS
The City’s existing station capacity is identified in this section. Additionally, this section identified
the existing and future pump station capacity requirements and compares it with the existing
pump station facilities in each zone and makes recommendations for new pump station facilities.
7.8.1 Existing Pump Station Capacity Requirements
Existing pump station capacities and requirements established from the City criteria are
summarized on Table 7.5. This table indicates the City’s existing pump stations have adequate
capacity to meet existing requirements.
7.8.2 Future Pump Station Capacity Requirements
Existing pump station capacities and future requirements established from the City criteria are
summarized on Table 7.6. This table indicates the City’s existing pump stations have sufficient
capacity to meet projected water demands under buildout conditions.
7.9 PIPELINE IMPROVEMENTS
The buildout of the 2040 General Plan includes development outside of the extents of the existing
domestic water distribution system. Distribution pipelines are recommended to serve future growth
as well as increase the hydraulic reliability of the domestic water distribution system. Each
pipeline improvement is assigned a uniquely coded identifier, which is intended to aid in defining
the location of the improvement for mapping purposes. These identifiers reflect the pressure zone,
improvement type, and sequence in the improvement schedule. The pipeline improvements are
summarized on Table 7.7 and described in detail on the following pages.
Table 7.5 Existing Pump Station Capacity Evaluation
Water System Master Plan
City of Gilroy
Pump Station Capacity Analysis
Destination Zone
Supply
Dependent
Zones
Total
(gpm)(gpm)(gpm)(gpm)(gpm)(gpm)
Pressure Zone 2N
Booster Station 1 1 2N 3 1,881 1,226
Booster Station 4 1 2N 3 1,321 878
Total 3,202 2,104 339 182 522 1,582
Pressure Zone 2S
Booster Station 5 1 2S 1,838 1,216
Booster Station 6 1 2S 1,470 934
Total 3,308 2,150 615 0 615 1,535
Pressure Zone 3
Booster Station 2 2N 3 870 580
Booster Station 3 2N 3 870 580
Total 1,740 1,160 182 0 182 978
5/7/2021
Notes:
1. Firm capacity for each pressure zone is defined as the sum of the total capacity of each pump station pumping into the pressure zone, with each pump station operating without their largest unit.
2. Pump stations to supply MDD of destination zone and all other supply dependent zones.
Firm
Capacity 1
Required Existing Capacity
2
Surplus/
DeficiencyPump Station
Pressure Zone
Source Zone
Destination
Zone
Supply
Dependent
Zones
Total
Capacity
Table 7.6 Buildout Pump Station Capacity Evaluation
Water System Master Plan
City of Gilroy
Pump Station Capacity Analysis
Destination Zone
Supply
Dependent
Zones
Total
(gpm)(gpm)(gpm)(gpm)(gpm)(gpm)
Pressure Zone 2N
Booster Station 1 1 2N 3 1,881 1,226
Booster Station 4 1 2N 3 1,321 878
Total 3,202 2,104 389 692 1,081 1,023
Pressure Zone 2S
Booster Station 5 1 2S -1,838 1,216
Booster Station 6 1 2S -1,470 934
Total 3,308 2,150 1,705 0 1,705 445
Pressure Zone 3
Booster Station 2 2N 3 -870 580
Booster Station 3 2N 3 -870 580
Total 1,740 1,160 692 0 692 468
5/17/2022
Notes:
1. Firm capacity for each pressure zone is defined as the sum of the total capacity of each pump station pumping into the pressure zone, with each pump station operating without their largest unit.
2. Pump stations to supply MDD of destination zone and all other supply dependent zones.
Required Buildout Capacity 2
Surplus/
Deficiency
Pressure Zone
Source ZonePump Station Destination
Zone
Supply
Dependent
Zones
Total
Capacity
Firm
Capacity 1
March 2023 7-19 City of Gilroy
Water System Master Plan
7.9.1 Pipeline Improvements to Serve Future Growth
This section documents pipeline improvements within the Pressure Zone 1.
P1-1. Construct approximately 3,860 feet of a new 12-inch pipeline in Day Road from
Santa Teresa Boulevard to Monterey Highway.
P1-2. Construct approximately 5,780 feet of a new 12-inch pipeline in Monterey Highway /
Orsetti Road / Highway 101 from 620 feet north of Day Road to Cohansey Avenue.
P1-12. Construct approximately 1,620 feet of a new 16-inch pipeline in ROW from Camino
Arroyo to approximately 1,800 feet east of Luchessa Avenue.
P1-13. Construct approximately 4,540 feet of a new 16-inch pipeline in ROW / Cameron
Boulevard from approximately 200 feet southeast of Venture Way to Southside Drive.
P1-17. Construct approximately 1,810 feet of a new 16-inch pipeline in ROW from
Luchessa Avenue to approximately 1,800 feet east of Luchessa Avenue.
P1-18. Construct approximately 2,890 feet of a new 16-inch pipeline in ROW from
approximately 1,800 feet east of Luchessa Avenue to Southside Drive.
P1-20. Construct approximately 660 feet of a new 16-inch pipeline in Southside Drive from
Arizona Circle to approximately 660 feet of Arizona Circle.
P1-21. Construct approximately 3,010 feet of a new 16-inch pipeline in Southside Drive
from approximately 660 feet east of Arizona Circle to Camaron Boulevard.
P1-22. Construct approximately 280 feet of a new 16-inch pipeline in Santa Teresa
Boulevard from approximately 160 feet west of Thomas Road to approximately 110 feet
east of Thomas Road.
7.9.2 Pipeline Improvement to Increase Fire Flow Reliability
Improvements to mitigate specific fire flow deficiencies are discussed below with the
corresponding coded identifier, which is also consistent with the capital improvements chapter:
P1-9. Replace approximately 1,730 feet of 12-inch pipeline from Camino Arroyo to
Cameron Boulevard along Pacheco Pass Highway with 16-inch pipeline.
P1-10. Replace approximately 3,040 feet of 12-inch pipeline from Pacheco Pass Highway
to Venture Way along Camino Arroyo with 16-inch pipeline.
P1-11. Replace approximately 2,100 feet of 12-inch pipeline from Pacheco Pass Highway
to 200 feet southeast of Venture Way along Cameron Boulevard with 16-inch pipeline.
March 2023 7-20 City of Gilroy
Water System Master Plan
P1-14. Replace approximately 6,480 feet of 12-inch pipeline from Thomas Road to Rossi
Lane along Luchessa Avenue with 16-inch pipeline.
P1-15. Replace approximately 3,060 feet of 12-inch pipeline from Luchessa Avenue to
Santa Teresa Road along Thomas Road with 16-inch pipeline.
P1-16. Replace approximately 2,730 feet of 12-inch pipeline from Luchessa Avenue to
Southside Drive along Rossi Lane with 16-inch pipeline.
P1-19. Replace approximately 4,630 feet of 12-inch pipeline from Highway 101 to Arizona
Circle along Garlic Farm Way / Southside Drive with 16-inch pipeline.
7.9.3 Pipeline Improvements to Mitigate Existing System Deficiencies
The hydraulic model was also used to identify areas that experience high headloss or high
velocity under maximum day demand conditions. The areas of existing pipeline deficiencies are
shown graphically on Figure 7.9. Areas of high velocity or high headloss may be more susceptible
to pipeline breaks and ruptures. The City’s maximum desired velocity criterion is 8 feet per second
and maximum desired headloss is 10 ft per thousand feet. Improvements to mitigate existing
pipeline deficiencies are discussed below with the corresponding coded identifier, which is also
consistent with the capital improvements chapter:
P1-3. Replace approximately 230 feet of 12-inch pipeline from Second Street to Loof
Avenue along Monterey Highway with 16-inch pipeline.
P1-4. Replace approximately 2,200 feet of 12-inch pipeline from Well 5-02 to Loof Avenue
along Murray Avenue with 16-inch pipeline.
P1-5. Replace approximately 70 feet of 12-inch pipeline from Well 7 to Loof Avenue along
Arroyo Circle with 16-inch pipeline.
P1-6. Replace approximately 230 feet of 8-inch pipeline from approximately 180 east of
Forest Street to Chestnut Street along Lewis Street with 10-inch pipeline.
P1-7. Replace approximately 320 feet of 10-inch pipeline from Well 3 to Sixth Street along
Forest Street with 12-inch pipeline.
P1-8. Replace approximately 300 feet of 12-inch pipeline from Well 8 to approximately 80
feet southeast of Gilman Road along Gilman Road / Camino Arroyo with 16-inch pipeline.
Table 7.7 Schedule of Improvements
Water System Master Plan
City of Gilroy
Pipeline Improvements
New/Parallel/
Replace Diam. Length
(in)(in)(ft)
Pipeline Improvements
P1‐1 Future Growth Zone 1Day Rd From Santa Teresa Blvd to Monterey Hwy ‐New 12 3,860
P1‐2 Future Growth Zone 1 Monterey Hwy / Orsetti
Rd / Hwy 101 From approx. 620' n/o Day Rd to Cohansey Ave ‐New 12 5,780
P1‐3 Existing Deficiency Zone 1Monterey Hwy From 2nd St to Ioof Ave 12 Replace 16 230
P1‐4 Existing Deficiency Zone 1 Murray Ave From Well 5‐02 to Ioof Ave 12 Replace 16 2,200
P1‐5 Existing Deficiency Zone 1 Arroyo Cir From Well 7 to Ioof Ave 12 Replace 16 70
P1‐6 Existing Deficiency Zone 1Lewis St From approx. 180' e/o Forest St to Chestnut St 8 Replace 10 230
P1‐7 Existing Deficiency Zone 1Forest St From Well 3 to 6th St 10 Replace 12 320
P1‐8 Existing Deficiency Zone 1 Gilman Rd / Camino
Arroyo From Well 8 to approx. 80' se/o Gilman Rd 12 Replace 16 300
P1‐9 FF Reliability Zone 1Pacheco Pass Hwy From Camino Arroyo to Cameron Blvd 12 Replace 16 1,730
P1‐10 FF Reliability Zone 1Camino Arroyo From Pacheco Pass Hwy to Venture Wy 12 Replace 16 3,040
P1‐11 FF Reliability Zone 1Cameron Blvd From Pacheco Pass Hwy to approx. 200' se/o Venture
Wy 12 Replace 16 2,100
P1‐12 Future Growth Zone 1ROWFrom Camino Arroyo to approx. 1,800' e/o Luchessa
Ave ‐New 16 1,620
P1‐13 Future Growth Zone 1ROW / Cameron Blvd From approx. 200' se/o Venture Wy to Southside Dr ‐New 16 4,540
P1‐14 FF Reliability Zone 1 Luchessa Ave From Thomas Rd to Rossi Ln 12 Replace 16 6,480
P1‐15 FF Reliability Zone 1Thomas Rd From Luchessa Ave to Santa Teresa Rd 12 Replace 16 3,060
P1‐16 FF Reliability Zone 1 Rossi Ln From Luchessa Ave to Southside Dr 12 Replace 16 2,730
P1‐17 Future Growth Zone 1ROWFrom Luchessa Ave to approx. 1,800' e/o Luchessa
Ave ‐New 16 1,810
P1‐18 Future Growth Zone 1ROWFrom approx. 1,800' e/o Luchessa Ave to Southside
Dr ‐New 16 2,890
P1‐19 FF Reliability Zone 1 Garlic Farm Wy /
Southside Dr From Hwy 101 to Arizona Cir 12 Replace 16 4,630
P1‐20 Future Growth Zone 1Southside Dr From Arizona Cir to approx. 660' e/o Arizona Cir ‐New 16 660
P1‐21 Future Growth Zone 1Southside Dr From approx. 660' e/o Arizona Cir to Camaron Blvd ‐New 16 3,010
P1‐22 Future Growth Zone 1Santa Teresa Blvd From approx. 160' w/o Thomas Rd to approx. 110'
e/o Thomas Rd ‐New 16 280
Storage Reservoir Improvements Proposed Storage Capacity
(MG)
3H‐1 Storage Capacity Zone 3Construct an additional 0.2 MG storage reservoir at existing 3D site New 0.10
Groundwater Well Improvements Proposed Pumping Capacity
(gpm)
GW‐10 Supply Capacity Zone 1Construct new well near the intersection of San Ysidro Ave and Las Animas Ave New 1,500
GW‐11 Supply Capacity Zone 1Construct new well near the intersection of Camino Arroyo and Renz Lane New 1,500
GW‐12 Supply Capacity Zone 1Construct new well near the intersection of Wren Ave and Vickery Ln New 1,500
7/1/2021
Existing
DiameterImprov. No. Improv. Type Pressure Zone Alignment Limits
101
101
152
152
152
12
24
24
12
8
8
8
8
12
24
Figure 7.
Existing Pipeline Deficiencies
Water System Master Plan
City of Gilroy
Updated: April 23, 2021
GIS
0 0.5 10.25
Mile
Legend
Existing Pipeline Deficiencies
Headloss is Greater than 10 ft/kft
Velocity is Greater than 8 fps
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-6_ExistDeficiencies_042321.mxd
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
March 2023 8-1 City of Gilroy
Water System Master Plan
2023 City of Gilroy
8.0CHAPTER 8 – CAPITAL IMPROVEMENT PROGRAM
This chapter provides a summary of the recommended domestic water system improvements to
mitigate existing capacity deficiencies and to accommodate anticipated future growth. The chapter
also presents the cost criteria and methodologies for developing the capital improvement
program. Finally, a capacity allocation analysis, usually used for cost sharing purposes, is also
included.
8.1 COST ESTIMATE ACCURACY
Cost estimates presented in the CIP were prepared for general master planning purposes and,
where relevant, for further project evaluation. Final costs of a project will depend on several
factors including the final project scope, costs of labor and material, and market conditions during
construction.
The Association for the Advancement of Cost Engineering (AACE International), formerly known
as the American Association of Cost Engineers has defined three classifications of assessing
project costs. These classifications are presented in order of increasing accuracy: Order of
Magnitude, Budget, and Definitive.
Order of Magnitude Estimate. This classification is also known as an “original estimate”,
“study estimate”, or “preliminary estimate”, and is generally intended for master plans and
studies.
This estimate is not supported with detailed engineering data about the specific project,
and its accuracy is dependent on historical data and cost indexes. It is generally expected
that this estimate would be accurate within -30 percent to +50 percent.
Budget Estimate. This classification is also known as an “official estimate” and generally
intended for predesign studies. This estimate is prepared to include flow sheets and
equipment layouts and details. It is generally expected that this estimate would be
accurate within -15 percent to +30 percent.
Definitive Estimate. This classification is also known as a “final estimate” and prepared
during the time of contract bidding. The data includes complete plot plans and elevations,
equipment data sheets, and complete specifications. It is generally expected that this
estimate would be accurate within -5 percent to + 15 percent.
Costs developed in this study should be considered “Order of Magnitude” and have an expected
accuracy range of -30 percent and +50 percent.
March 2023 8-2 City of Gilroy
Water System Master Plan
8.2 COST ESTIMATE METHODOLOGY
Cost estimates presented in this chapter are opinions of probable construction and other relevant
costs developed from several sources including cost curves, Akel experience on other master
planning projects, and input from City staff on the development of public and private cost sharing.
Where appropriate, costs were escalated to reflect the more current Engineering News Records
(ENR) Construction Cost Index (CCI).
This section documents the unit costs used in developing the opinion of probable construction
costs, the Construction Cost Index, the land acquisition costs, and markups to account for
construction contingency and other project related costs.
8.2.1 Unit Costs
The unit cost estimates used in developing the Capital Improvement Program are summarized on
Table 8.1. Domestic water pipeline unit costs are based on length of pipes, in feet. Storage
reservoir unit costs are based on capacity, per million gallons (MG). Pump Station costs are
based on an equation that replaces the pump curve.
The unit costs are intended for developing the Order of Magnitude estimate and do not account
for site-specific conditions, labor and material costs during the time of construction, final project
scope, implementation schedule, detailed utility and topography surveys for reservoir sites,
investigation of alternative routings for pipes, and other various factors. The capital improvement
program included in this report accounts for construction and project-related contingencies as
described in this chapter.
8.2.2 Construction Cost Index
Costs estimated in this study are adjusted utilizing the Engineering News Record (ENR)
Construction Cost Index (CCI), which is widely used in the engineering and construction
industries.
The costs in this Water System Master Plan were benchmarked using a 20-City national average
ENR CCI of 13,176, reflecting a date of March 2023.
8.2.3 Construction Contingency Allowance
Knowledge about site-specific conditions for each proposed project is limited at the master
planning stage; therefore, construction contingencies were used. The estimated construction
costs in this master plan include a 30 percent contingency allowance to account for unforeseen
events and unknown field conditions, as well as market uncertainty and unpredictable inflation.
8.2.4 Project Related Costs
The capital improvement costs also account for project-related costs, comprising of engineering
design, project administration (developer and City staff), construction management and
Table 8.1 Unit Costs
Water System Master Plan
City of Gilroy
Pipelines
Pipe Size Cost1,2
(in)($/lineal foot)
6 $153
8 $187
10 $211
12 $254
16 $304
18 $312
20 $336
24 $400
30 $500
36 $560
42 $705
Storage Reservoirs ($/gallon)1,3
≤1.0 MG $1.33
1.1 MG-3.0 MG $2.11
3.1 MG - 5.0 MG $3.22
> 5 MG $4.89
Groundwater Wells1,4,5
1,500 gpm Capacity $3,922,000
3/28/2023
Notes:
1. Construction costs estimated using March 2023 ENR CCI of 13,176.
2. Pipeline cossts include utilities, construction staging, traffic control, and
lighting and signing
3. Source: City of Gilroy 2004 Water System Master Plan
4. Source: City of Gilroy 2021-2025 Capital Improvement Program
5. One new 1,500 gpm well costs $3,626,645, per City of Gilroy 2021-2025
Capital Improvement Program. The cost accounts for Design, CEQA,
Construction, Con. Support, and Land Acquisition
Pump Stations
Estimated Pumping Station Project Cost = 2.1*10(0.7583*log(Q)+3.1951)
where Q is in gpm
March 2023 8-4 City of Gilroy
Water System Master Plan
inspection, and legal costs. The project related costs in this master plan were estimated by
applying an additional 30 percent to the estimated construction costs.
8.3 CAPITAL IMPROVEMENT PROGRAM
This section documents the capital improvement program, contingencies included in the costs,
and the allocation of costs to meet the requirements of AB1600.
8.3.1 Capital Improvements Costs
The Capital Improvement Program costs for the projects identified in this master plan for
mitigating existing system deficiencies and for serving anticipated future growth throughout the
City are summarized on Table 8.2.
Each improvement was assigned a unique coded identifier associated with the improvement type,
and is summarized graphically on Figure 8.1. The estimated construction costs include the
baseline costs plus 30 percent contingency allowance to account for unforeseen events and
unknown field conditions, as described in a previous section. Capital improvement costs include
the estimated construction costs plus 30 percent project-related costs (engineering design,
project administration, construction management and inspection, and legal costs).
8.3.2 Recommended Cost Allocation Analysis
Cost allocation analysis is needed to identify improvement funding sources, and to establish a
nexus between development impact fees and improvements needed to service growth. In
compliance with the provisions of Assembly Bill AB1600, the analysis differentiates between the
project needs of servicing existing users and for those required to service anticipated future
developments. The cost responsibility is based on model parameters for existing and future land
use, and may change depending on the nature of development. Table 8.2 lists each improvement,
and separates the cost by responsibility between existing and future users.
8.3.3 Construction Triggers
As a part of this master planning process, construction triggers were developed in an effort to plan
the expansion of the water system in an orderly manner. The construction triggers for multiple
improvements are based on mitigating an existing system deficiency, increasing hydraulic
reliability, or continuing improvements currently planned by the City. Other improvements replace
existing infrastructure that is not currently deficient, but will violate master plan criteria with future
development. The construction triggers quantify the amount of additional development that may
occur before the improvement becomes necessary.
8.4 SUGGESTED PIPELINE REPLACEMENT BUDGET
The suggested pipeline replacement budget alternatives are shown on Figure 8.2, and includes
the estimated costs for replacing pipelines phased by 5-year fiscal periods through the year 2055.
101
101
152
152
152
12
24
24
12
8
8
8
8
12
24
12
16
16
Well 8
Well 7
Well 8A
Well 5-2
Well 1
Well 3-2
Well 6
Well 4
Well 2
Booster
Station 4
Booster
Station 1
Booster
Station 3 & 2
Booster
Station 5
Tanks: 2C-1
2C-2
3D-1
3D-2
Tank 1A
Tanks: 2E-1
2E-2
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
10
3H-1
P1-3
P1-6
P1-8
P1-7
16P1-5
P1-2216
GW-10
(Planned Well)
GW-11
Figure 8.1
Capital Improvement
Program
Water System Master Plan
City of Gilroy
Updated: September 14, 2021
GIS
0 0.5 10.25
Mile
Legend
Recommended Improvements
Tanks
Wells
New Pipes
Pipe Replacements
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig8-1_CIP_091421.mxd
4" - 6"
8"
10" - 30"
Roads
Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
GW-12
Table 8.2 Capital Improvement Program
Water System Master Plan
City of Gilroy
PRELIMINARY
Infrastructure Costs Suggested Cost Allocation Cost Sharing
Existing Diameter New/Parallel/
Replace Diameter Length Unit Cost Infr. Cost Existing
Users Future Users Existing Users Future Users
(in)(in)(ft)($)($)($)($)($)
Pipeline Improvements
P1-1 Future Growth Zone 1 Day Rd From Santa Teresa Blvd to Monterey Hwy -New 12 3,860 254 978,700 978,700 1,272,400 1,654,200 With Development 0%100%0 1,654,200
P1-2 Future Growth Zone 1 Monterey Hwy / Orsetti
Rd / Hwy 101 From approx. 620' n/o Day Rd to Cohansey Ave -New 12 5,780 254 1,465,500 1,465,500 1,905,200 2,476,800 With Development 0%100%0 2,476,800
P1-3 Existing Deficiency Zone 1 Monterey Hwy From 2nd St to Ioof Ave 12 Replace 16 230 304 70,000 70,000 91,000 118,300 Existing Deficiency 100%0%118,300 0
P1-4 Existing Deficiency Zone 1 Murray Ave From Well 5-02 to Ioof Ave 12 Replace 16 2,200 304 669,400 669,400 870,300 1,131,400 Existing Deficiency 100%0%1,131,400 0
P1-5 Existing Deficiency Zone 1 Arroyo Cir From Well 7 to Ioof Ave 12 Replace 16 70 304 21,300 21,300 27,700 36,100 Existing Deficiency 100%0%36,100 0
P1-6 Existing Deficiency Zone 1 Lewis St From approx. 180' e/o Forest St to Chestnut St 8 Replace 10 230 211 48,600 48,600 63,200 82,200 Existing Deficiency 100%0%82,200 0
P1-7 Existing Deficiency Zone 1 Forest St From Well 3 to 6th St 10 Replace 12 320 254 81,200 81,200 105,600 137,300 Existing Deficiency 100%0%137,300 0
P1-8 Existing Deficiency Zone 1 Gilman Rd / Camino
Arroyo From Well 8 to approx. 80' se/o Gilman Rd 12 Replace 16 300 304 91,300 91,300 118,700 154,400 Existing Deficiency 100%0%154,400 0
P1-9 FF Reliability Zone 1 Pacheco Pass Hwy From Camino Arroyo to Cameron Blvd 12 Replace 16 1,730 304 526,400 526,400 684,400 889,800 As Funding is Available 100%0%889,800 0
P1-10 FF Reliability Zone 1 Camino Arroyo From Pacheco Pass Hwy to Venture Wy 12 Replace 16 3,040 304 925,000 925,000 1,202,500 1,563,300 As Funding is Available 100%0%1,563,300 0
P1-11 FF Reliability Zone 1 Cameron Blvd From Pacheco Pass Hwy to approx. 200' se/o Venture
Wy 12 Replace 16 2,100 304 639,000 639,000 830,700 1,080,000 As Funding is Available 100%0%1,080,000 0
P1-12 Future Growth Zone 1 ROW From Camino Arroyo to approx. 1,800' e/o Luchessa Ave -New 16 1,620 304 492,900 492,900 640,800 833,100 With Development 0%100%0 833,100
P1-13 Future Growth Zone 1 ROW / Cameron Blvd From approx. 200' se/o Venture Wy to Southside Dr -New 16 4,540 304 1,381,300 1,381,300 1,795,700 2,334,500 With Development 0%100%0 2,334,500
P1-14 FF Reliability Zone 1 Luchessa Ave From Thomas Rd to Rossi Ln 12 Replace 16 6,480 304 1,971,600 1,971,600 2,563,100 3,332,100 As Funding is Available 100%0%3,332,100 0
P1-15 FF Reliability Zone 1 Thomas Rd From Luchessa Ave to Santa Teresa Rd 12 Replace 16 3,060 304 931,000 931,000 1,210,300 1,573,400 As Funding is Available 100%0%1,573,400 0
P1-16 FF Reliability Zone 1 Rossi Ln From Luchessa Ave to Southside Dr 12 Replace 16 2,730 304 830,600 830,600 1,079,800 1,403,800 As Funding is Available 100%0%1,403,800 0
P1-17 Future Growth Zone 1 ROW From Luchessa Ave to approx. 1,800' e/o Luchessa Ave -New 16 1,810 304 550,700 550,700 716,000 930,800 With Development 0%100%0 930,800
P1-18 Future Growth Zone 1 ROW From approx. 1,800' e/o Luchessa Ave to Southside Dr -New 16 2,890 304 879,300 879,300 1,143,100 1,486,100 With Development 0%100%0 1,486,100
P1-19 FF Reliability Zone 1 Garlic Farm Wy /
Southside Dr From Hwy 101 to Arizona Cir 12 Replace 16 4,630 304 1,408,700 1,408,700 1,831,400 2,380,900 As Funding is Available 100%0%2,380,900 0
P1-20 Future Growth Zone 1 Southside Dr From Arizona Cir to approx. 660' e/o Arizona Cir -New 16 660 304 200,900 200,900 261,200 339,600 With Development 0%100%0 339,600
P1-21 Future Growth Zone 1 Southside Dr From approx. 660' e/o Arizona Cir to Camaron Blvd -New 16 3,010 304 915,800 915,800 1,190,600 1,547,800 With Development 0%100%0 1,547,800
P1-22 Future Growth Zone 1 Santa Teresa Blvd From approx. 160' w/o Thomas Rd to approx. 110' e/o
Thomas Rd -New 16 280 304 85,200 85,200 110,800 144,100 With Development 0%100%0 144,100
Subtotal - Pipeline Improvements 15,164,400 19,714,500 25,630,000 13,883,000 11,747,000
Storage Reservoir Improvements
3H-1 Storage Capacity Zone 3 Construct an additional 0.1 MG storage reservoir at existing 3D site New 133,442 133,500 173,600 225,700 813 EDU 0%100%0 225,700
Subtotal - Storage Reservoir Improvements 133,500 173,600 225,700 0 225,700
Estimated Const.
Costs1
Proposed Storage Capacity
(MG)
0.10
Improv. No.
Pipeline Information Capital Improv.
Costs2 Construction TriggerBaseline Constr.
CostsImprov. Type Pressure
Zone Alignment Limits
Table 8.2 Capital Improvement Program
Water System Master Plan
City of Gilroy
PRELIMINARY
Infrastructure Costs Suggested Cost Allocation Cost Sharing
Existing Diameter New/Parallel/
Replace Diameter Length Unit Cost Infr. Cost Existing
Users Future Users Existing Users Future Users
(in)(in)(ft)($)($)($)($)($)
Estimated Const.
Costs1Improv. No.
Pipeline Information Capital Improv.
Costs2 Construction TriggerBaseline Constr.
CostsImprov. Type Pressure
Zone Alignment Limits
Groundwater Well Improvements
GW-10 Supply Capacity Zone 1 Construct new well near the intersection of San Ysidro Ave and Las Animas Ave New ---3,922,000 9,500 EDU 0%100%0 3,922,000
GW-11 Supply Capacity Zone 1 Construct new well near the intersection of Camino Arroyo and Renz Lane New ---3,922,000 15,550 EDU 0%100%0 3,922,000
GW-12 Supply Capacity Zone 1 Construct new well near the intersection of Wren Ave and Vickery Ln New ---3,922,000 21,600 EDU 0%100%0 3,922,000
Subtotal - Groundwater Well Improvements 0 0 11,766,000 0 11,766,000
Total Improvement Cost
Pipeline Improvements 15,164,400 19,714,500 25,630,000 13,883,000 11,747,000
Storage Reservoirs 133,500 173,600 225,700 0 225,700
Groundwater Wells 0 0 11,766,000 0 11,766,000
Total Improvement Costs 15,297,900 19,888,100 37,621,700 13,883,000 23,738,700
Notes: 3/29/2023
1. Baseline construction costs plus 30% to account for unforeseen events and unknown conditions.
2. Estimated construction costs plus 30% to cover other costs including: engineering design, project administration (developer and City staff), construction management and inspection, and legal costs.
3. Cost estimates are based on the Engineering News Record (ENR) construction cost index (CCI) of 13,176 for March 2023.
1,500
Proposed Pumping Capacity
(gpm)
1,500
1,500
March 2023 8-8 City of Gilroy
Water System Master Plan
Costs are estimated based on the industry average goal of pipe R&R budgets, which is at 1.0%
per year for 100-year pipe replacement cycle. The estimated costs are starting from a base rate of
3.5 million dollars per year, with a pipe replacement rate of 1% of system length per year, which is
2.8 miles of new construction per year for the City. The future costs in 2055 are expected to be
approximately 4.2 million dollars per year.
Industry Standard Replacement Schedule
$0
$1,000,000
$2,000,000
$3,000,000
$4,000,000
$5,000,000
2020 2025 2030 2035 2040 2045 2050 2055Dollars per year ($)Year
R&R Budget Alternatives
Figure 8.
Pipeline Replacement
Budget Alternatives
Water System Master Plan
City of Gilroy
August 6, 2021
LEGEND Assumptions:
1. System Growth: 2.8 miles of new construction per year (based
on historical construction)
2. All costs in 2021 dollars
3. Weighted average pipeline unit cost = $329/foot
4. 30% contengency added for estimated construction cost
5. 30% contengency added for capital improvement cost
Industry Average
Pipe R&R Budgets
Industry Goal is at 1.0% per year for
100-year Pipe Replacement Cycle
March 2023 City of Gilroy
Water System Master Plan
City of Gilroy
APPENDICES
March 2023 City of Gilroy
Water System Master Plan
City of Gilroy
APPENDIX A
Calibration Curves
Figure .1
Storage Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
5
10
15
20
25
0 6 12 18 24Level (ft)
Time (hours)
Tank 1A
Pressure Zone 1
Avg. % Difference = 4%
0
5
10
15
20
0 6 12 18 24Level (ft)
Time (hours)
Tank 1B
Pressure Zone 1
Avg. % Difference = 3%
0
5
10
15
20
25
0 6 12 18 24Level (ft)
Time (hours)
Tank 1G 1
Pressure Zone 1
Avg. % Difference = 11%
0
5
10
15
20
0 6 12 18 24Level (ft)
Time (hours)
Tank 1G 2
Pressure Zone 1
Avg. % Difference = 3%
Figure .
Storage Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 2C 1
Pressure Zone 2N
Avg. % Difference = 5%
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 2C 2
Pressure Zone 2N
Avg. % Difference = 6%
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 2E 1
Pressure Zone 2S
Avg. % Difference = 2%
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 2E 2
Pressure Zone 2S
Avg. % Difference = 1%
Figure .
Storage Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 2F 1
Pressure Zone 2S
Avg. % Difference = 4%
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 3D 1
Pressure Zone 3
Avg. % Difference = 4%
0
5
10
15
20
25
30
0 6 12 18 24Level (ft)
Time (hours)
Tank 3D 2
Pressure Zone 3
Avg. % Difference = 5%
Figure .
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 1 Flow
Pressure Zone 1
Avg. % Difference = 1%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 1 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 1%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 2 Flow
Pressure Zone 1
Avg. % Difference = 0%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 2 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 149%
Figure .
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 3 Flow
Pressure Zone 1
Avg. % Difference = 0%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 3 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 3%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 4 Flow
Pressure Zone 1
Avg. % Difference = 1%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 4 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 3%
Figure .
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 5 Flow
Pressure Zone 1
Avg. % Difference = 0%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 5 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 8%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 6 Flow
Pressure Zone 1
Avg. % Difference = 4%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 6 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 2%
Figure
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 7 Flow
Pressure Zone 1
Avg. % Difference = 1%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 7 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 10%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 8 Flow
Pressure Zone 1
Avg. % Difference = 2%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
Well 8 Outlet Pressure
Pressure Zone 1
Avg. % Difference = 13%
Figure
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
Well 8A Flow
Pressure Zone 1
Avg. % Difference = 15%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
BS1 Flow
Pressure Zone 2N
Avg. % Difference = 64%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS1 Outlet Pressure
Pressure Zone 2N
Avg. % Difference = 6%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
BS2 Flow
Pressure Zone 3
Avg. % Difference = 41%
Figure
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
BS3 Flow
Pressure Zone 3
Avg. % Difference = 38%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS2 Outlet Pressure
Pressure Zone 3
Avg. % Difference = 25%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
BS4 Flow
Pressure Zone 2N
Avg. % Difference = 63%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS3 Outlet Pressure
Pressure Zone 3
Avg. % Difference = 11%
Figure
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS4 Inlet Pressure
Pressure Zone 2N
Avg. % Difference = 17%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
BS5 Flow
Pressure Zone 2S
Avg. % Difference = 92%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS4 Outlet Pressure
Pressure Zone 2N
Avg. % Difference = 2%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS5 Inlet Pressure
Pressure Zone 2S
Avg. % Difference = 1%
Figure
Pump Calibration
Water System Master Plan
City of Gilroy
LEGEND
April 20, 2021
Telemetry Data
Model Data
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS5 Outlet Pressure
Pressure Zone 2S
Avg. % Difference = 0%
0
500
1,000
1,500
2,000
2,500
3,000
0 6 12 18 24Flow (gpm)
Time (hours)
BS6 Flow
Pressure Zone 2S
Avg. % Difference = 35%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS6 Inlet Pressure
Pressure Zone 2S
Avg. % Difference = 48%
0
30
60
90
120
150
0 6 12 18 24Pressure (psi)
Time (hours)
BS6 Outlet Pressure
Pressure Zone 2S
Avg. % Difference = 3%
CERTIFICATE OF THE CLERK
I, THAI NAM PHAM, City Clerk of the City of Gilroy, do hereby certify that the
attached Resolution No. 2023-18 is an original resolution, or true and correct copy of a
city Resolution, duly adopted by the Council of the City of Gilroy at a Regular Meeting of
said held on Council held Monday, April 3, 2023, at which meeting a quorum was
present.
IN WITNESS WHEREOF, I have hereunto set my hand and affixed the Official
Seal of the City of Gilroy this Monday, April 3, 2023.
____________________________________
Thai Nam Pham, CMC, CPMC
City Clerk of the City of Gilroy
(Seal)