Gilroy City Council
April 3, 2023

RESOLUTION NO. 2023-XX

A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF

GILROY ADOPTING THE SEWER SYSTEM MASTER

PLAN FOR THE CITY OF GILROY
WHEREAS, the 2022 Sewer System Master (Plan) serves as a guide to assess the current operations and functionality of the City’s existing sewer system; and WHEREAS, the City last developed a Sewer System Master Plan in 2004, which identified capacity deficiencies in the existing sewer 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 sewer system can be upgraded within the City to best suit the sewer 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 Sewer System 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:

NOES: COUNCIL MEMBERS:

ABSTAIN: COUNCIL MEMBERS:

ABSENT: COUNCIL MEMBERS:

APPROVED:

Marie Blankley, Mayor
ATTEST:
_______________________
Thai Nam Pham, City Clerk
Agenda Item 9.1 Page 490 of 768

City of Gilroy

STAFF REPORT
Agenda Item Title: Adopt the 2022 Water Master Plan
Meeting Date: April 3, 2023
From: Jimmy Forbis, City Administrator
Department: Public Works
Submitted By: Daryl Jordan, Public Works Director
Prepared By: Michael Lewis, Management Analyst
STRATEGIC PLAN GOALS Maintain and Improve City Infrastructure

RECOMMENDATION
Adopt a resolution approving the 2022 Water System Master Plan.

BACKGROUND
Cities rely on water master plans to assess the current operations and functionality of the City’s existing water system and to help meet the future water needs of the community. 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.

The City operates and maintains a domestic water system that covers most of the area within the service area limits. Currently, the water demands are provided from groundwater wells located throughout the service area. The City’s municipal water system consists of nine (9) groundwater wells, ten (10) storage reservoirs that have a cumulative capacity of 14.1 million gallons (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 above sea level in the east to approximately 250 feet above sea level 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 most recent water master plan was completed in 2004. This Master Plan Agenda Item 9.2 Page 491 of 768
Adopt the 2022 Water Master Plan
City of Gilroy City Council Page 2 of 5 April 3, 2023 1 0 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 the horizon year of 2040 to be consistent with the recently updated 2040 General Plan, state-approved Urban Water Management Plan (UWMP) and Water Service Contingency Plan (WSCP). This 2020 WSCP document builds upon previous water shortage contingency planning efforts completed by the City and documented in the 2015 UWMP Plans. 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. There were 12 water main segments out of 73 potential projects constructed from the 2004 Master Plan at a total cost of $6,923,000.

Due to the increased demand for water, it became evident that an updated water master plan was necessary. As such, the City Council approved Akel Engineering Group, Inc. to prepare the 2022 Water Master Plan and a concurrent Sewer System Master Plan and Storm Drainage Master Plan in August 2019. These documents were coordinated for consistency with the City’s 2040 General Plan.

ANALYSIS
The 2022 Water System Master Plan (Plan) 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. The Plan 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 City Council authorized Akel Engineering Group, Inc. to perform the following tasks:

1. Summarize the City’s existing domestic water system facilities.

2. Document growth planning assumptions and known future developments.

3. Summarize the water system performance criteria.

4. Project future domestic water demands.

5. Update and validate the City’s hydraulic model based on the City’s Geographic Information System (GIS).

6. Evaluate the domestic water facilities to meet existing and projected demand requirements and fire flows.

7. Evaluate existing groundwater conditions.

8. Perform a capacity analysis for major distribution mains.

9. Recommend a Capital Improvement Program (CIP) with an opinion of probable construction costs.

10. Develop a 2022 Water System Master Plan report.

Agenda Item 9.2 Page 492 of 768
Adopt the 2022 Water Master Plan
City of Gilroy City Council Page 3 of 5 April 3, 2023 1 0 RESULTS
The 2022 Water Master Plan provided recommendations for improvements based on immediate capacity needs and expected future growth. The recommended capital improvement program (Table 8.2) is attached as Attachment 1.

The Water System Master Plan identifies the current and future water needs of the community through the 2040 General Plan build-out. While there is adequate water supply now, there is an identified deficiency of 5.1 mgd if build-out occurs without any additional supply being generated. This will be remedied by constructing three new water supply wells by 2040.

Supply vs. Demand Evaluation
Supply Balance Existing 2040 Buildout
Maximum Dry Day Demand 13.7 mgd 22.3 mgd
Standby Well 2.6 mgd 2.6 mgd
Required Capacity 16.3 mgd 24.9 mgd
Available Supply Capacity1 19.8 mgd 19.8 mgd
Capacity Surplus/Deficiency +3.5 mgd -5.1 mgd
Recommended New Wells
(at 2.2 mgd each) 0 3

1. Includes capacity from the McCarthy Well #9 project that is currently in construction (projected production of 3.6 mgd).

To address deficiencies in the water distribution system, and 2040 General Plan buildout, projects have been recommended in the Water System Capital Improvement needs. The projects identified will be added to the City’s Capital Improvement Program. In total, the plan recommends 22 pipeline improvement projects, totaling $25.6 million, three groundwater well improvement projects totaling $11.8 million and one storage reservoir improvement project totaling $225,700 (attached).

Agenda Item 9.2 Page 493 of 768
Adopt the 2022 Water Master Plan
City of Gilroy City Council Page 4 of 5 April 3, 2023 1 0 Project
Number of
Replacement
Projects
Number
of New
Projects
Cost Allocation
to Existing Users
Cost Allocation
to Future Users
Pipeline
Improvements 13 9 $13,883,000 $11,747,000
Storage
Reservoir
Improvements
0 1 $0 $225,700
Ground Well
Improvements 0 3 $0 $11,776,000
Total Cost $13,883,000 $23,738,700

ALTERNATIVES
Council may amend or reject the 2022 Water Master Plan. This is not recommended as the 2022 Master Plan is essential to planning and constructing water system projects to protect the provision of water to the community now and into the future.

FISCAL IMPACT/FUNDING SOURCE
The City has two water funds which are utilized to fund the capital improvements and the annual operations and maintenance needs. The Water Impact Fund, which collects revenues in the form of impact fees from developments that impact future growth, primarily funds infrastructure/capital costs attributable to future users for future capacity needs. The Water Operations Fund funds the current annual operational, maintenance, and capital costs to repair and maintain the existing infrastructure. The Water Impact (future users) and Water Operation (existing users) funds have a projected FY23 ending fund balance of $3.8 million and $25.0 million, respectively.

Of the total $37.6 million capital improvements identified in the 2022 Water Master Plan, approximately $13.9 million is attributable to existing users – to be funded by the Water Operations fund, and $23.7 million is attributable to future users - to be funded by the Water Impact Fund. The 2022 Water Master Plan capital improvements are in addition to the existing capital improvements identified by staff.

While the Water Operations fund has adequate fund balance to fund the $13.9 million identified in existing user costs, the Water Impact fund does not have sufficient fund balances to fund the $23.7 million identified in future user costs. A typical next step after the Master Plan is updated is to review and update the utility user fees, and the development impact fees to incorporate the identified existing and future growth capital improvements and adjust the fees accordingly to ensure capital and operational needs are adequately funded for a period. The City is undergoing a rate study for the water Agenda Item 9.2 Page 494 of 768
Adopt the 2022 Water Master Plan
City of Gilroy City Council Page 5 of 5 April 3, 2023 1 0 user fees and will consider the projects contemplated in this Master Plan and the CIP to help determine the rate proposals in the next few months. Staff will plan to review and update the water impact fee as a project in the departmental workplan in the upcoming fiscal year.

NEXT STEPS
With Council approval of the 2022 Water Master Plan, staff will incorporate the projects into the City’s CIP, and plan for delivery of the recommended projects. State approval is not required.

Attachments:

1. Water System Master Plan

2. Water System Master Plan Capital Improvement Program List

3. Water Master Plan Draft Resolution
Agenda Item 9.2 Page 495 of 768
Agenda Item 9.2 Page 496 of 768
2023

CITY OF GILROY

WATER SYSTEM

MASTER PLAN
FINAL
March 2023
Agenda Item 9.2 Page 497 of 768
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
7 4 3 3 N . F I R S T S T R E E T , S U I T E 1 0 3 • F R E S N O , C A L I F O R N I A 9 3 7 2 0 • ( 5 5 9 ) 4 3 6 - 0 6 0 0 • F A X ( 5 5 9 ) 4 3 6 - 0 6 2 2 www.akeleng.com
Agenda Item 9.2 Page 498 of 768
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
Agenda Item 9.2 Page 499 of 768
City of Gilroy
Water System Master Plan
Table of Contents Page No.

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

1.1 1.2

1.3 1.4

1.5 1.6

1.7 1.8

1.9 BACKGROUND ................................................................................................. 1-1 SCOPE OF WORK ............................................................................................ 1-1 INTEGRATED APPROACH TO MASTER PLANNING ...................................... 1-3 PREVIOUS MASTER PLANS............................................................................ 1-3 RELEVANT REPORTS...................................................................................... 1-3 REPORT ORGANIZATION................................................................................ 1-4 ACKNOWLEDGEMENTS .................................................................................. 1-5 UNIT CONVERSIONS AND ABBREVIATIONS ................................................. 1-5 GEOGRAPHIC INFORMATION SYSTEMS....................................................... 1-5 CHAPTER 2 – PLANNING AREA CHARACTERISTICS................................................... 2-1

2.1 2.2

2.3 STUDY AREA DESCRIPTION........................................................................... 2-1 WATER SERVICE AREA AND LAND USE........................................................ 2-1 HISTORICAL AND FUTURE GROWTH............................................................. 2-9 CHAPTER 3 – SYSTEM PERFORMANCE AND DESIGN CRITERIA............................... 3-1

3.1 3.2

3.3 HISTORICAL WATER USE TRENDS................................................................ 3-1 SUPPLY CRITERIA ........................................................................................... 3-1 STORAGE CRITERIA........................................................................................ 3-7

3.3.1 Typical Storage Criteria........................................................................ 3-7 PRESSURE CRITERIA...................................................................................... 3-8 UNIT FACTORS ................................................................................................ 3-9 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 TRANSMISSION AND DISTRIBUTION MAIN CRITERIA .................................. 3-13

3.4 3.5

3.6 3.7
CHAPTER 4 – EXISTING DOMESTIC WATER FACILITIES............................................. 4-1

4.1 4.2

4.3 4.4

4.5 4.6
EXISTING WATER SYSTEM OVERVIEW......................................................... 4-1 SOURCE OF SUPPLY....................................................................................... 4-1 PRESSURE ZONES.......................................................................................... 4-4 WATER DISTRIBUTION PIPELINES................................................................. 4-4 STORAGE RESERVOIRS ................................................................................. 4-4 BOOSTER STATIONS....................................................................................... 4-4 March 2023 i City of Gilroy
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4.7 PRESSURE REDUCING VALVES..................................................................... 4-11 CHAPTER 5 – WATER DEMANDS AND SUPPLY CHARACTERISTICS......................... 5-1

5.1 5.2

5.3 5.4
EXISTING DOMESTIC WATER DEMANDS ...................................................... 5-1 FUTURE DOMESTIC WATER DEMANDS ........................................................ 5-1 MAXIMUM DAY AND PEAK HOUR DEMANDS ................................................ 5-4 DIURNAL DEMAND PATTERNS....................................................................... 5-4 CHAPTER 6 – HYDRAULIC MODEL DEVELOPMENT .................................................... 6-1

6.1 6.2

6.3 OVERVIEW........................................................................................................ 6-1 MODEL SELECTION......................................................................................... 6-1 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 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

6.4 CHAPTER 7 – EVALUATION AND PROPOSED IMPROVEMENTS................................. 7-1

7.1 7.2

7.3 7.4

7.5 7.6
OVERVIEW........................................................................................................ 7-1 LOW PRESSURE ANALYSIS............................................................................ 7-1 HIGH PRESSURE ANALYSIS........................................................................... 7-1 FIRE FLOW ANALYSIS..................................................................................... 7-1 WATER SUPPLY............................................................................................... 7-5 WATER SUPPLY REQUIREMENTS ................................................................. 7-5

7.6.1 Existing Supply Requirements ............................................................. 7-5

7.6.2 Future Supply Requirements................................................................ 7-5 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 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 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

7.7 7.8

7.9 CHAPTER 8 – CAPITAL IMPROVEMENT PROGRAM..................................................... 8-1

8.1 8.2
COST ESTIMATE ACCURACY ......................................................................... 8-1 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 March 2023 ii City of Gilroy
Water System Master Plan
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8.2.4 Project Related Costs .......................................................................... 8-2 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 SUGGESTED PIPELINE REPLACEMENT BUDGET ........................................ 8-4

8.3 8.4
March 2023 iii City of Gilroy
Water System Master Plan
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Water System Master Plan
Table of Contents Page No.

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
Figure 2.1
Figure 2.2
Figure 2.3
Figure 3.1
Figure 3.2
Figure 4.1
Figure 4.2
Figure 4.3
Figure 5.1
Figure 6.1
Figure 6.2
Figure 7.1
Figure 7.2
Figure 7.3
Figure 7.4
Figure 7.5
Figure 7.6
Figure 7.7
Figure 7.8
Figure 7.9
Figure 8.1
Figure 8.2
Regional Location Map ................................................................................. 1-2 Planning Area ............................................................................................... 2-2 Existing Land Use......................................................................................... 2-3 2040 General Plan Land Use........................................................................ 2-6 Historical Population vs. Average Daily Production....................................... 3-2 Water Use Per Capita Vs. Average Daily Production .................................... 3-3 Existing System ............................................................................................ 4-2 Pipelines by Pressure Zone .......................................................................... 4-5 System Hydraulic Profile Schematic ............................................................. 4-6 Diurnal Curve................................................................................................ 5-5 Storage Calibration....................................................................................... 6-5 Pump Calibration .......................................................................................... 6-6 Minimum System Pressures (Maximum Day Demand) ................................. 7-2 Minimum System Pressures (Peak Hour) ..................................................... 7-3 Maximum System Pressures ........................................................................ 7-4 Required Fire Flow........................................................................................ 7-6 Fire Flow Analysis......................................................................................... 7-7 Available Fire Flow........................................................................................ 7-8 Well Construction Schedule.......................................................................... 7-9 Recommended System Improvements ......................................................... 7-12 Existing Pipeline Deficiencies ....................................................................... 7-22 Capital Improvement Program ...................................................................... 8-5 Pipeline Relacement Budget Alternatives ..................................................... 8-9 March 2023 iv City of Gilroy
Water System Master Plan
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Water System Master Plan
Table of Contents Page No.

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
Table 1.2
Table 2.1
Table 2.2
Table 2.3
Table 2.4
Table 3.1
Table 3.2
Table 3.3
Table 3.4
Table 3.5
Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 4.5
Table 4.6
Table 5.1
Table 5.2
Table 7.1
Table 7.2
Table 7.3
Table 7.4
Table 7.5
Table 7.6
Table 7.7
Table 8.1
Table 8.2
Unit Conversions ...........................................................................................1-6 Abbreviations and Acronyms .........................................................................1-7 General Plan Land Use .................................................................................2-4 Hecker Pass and Glen Loma Land Use Summary.........................................2-7 Downtown Specific Plan Land Use Summary................................................2-8 Historical and Projected Population ...............................................................2-10 Historical Annual Water Production and Maximum Day Peaking Factors.......3-4 Historical Monthly Water Production (2017-2019)..........................................3-5 Planning and Design Criteria Summary.........................................................3-6 Water Demand Unit Factor Analysis..............................................................3-11 Recommended Water Unit Factors................................................................3-12 Existing Groundwater Supply Capacity..........................................................4-3 Existing Modeled Pipe Inventory....................................................................4-7 Pipe Roughness Coefficients.........................................................................4-8 Existing Storage Reservoirs...........................................................................4-9 Existing Booster Pumping Stations................................................................4-10 Existing Pressure Reducing Valves ...............................................................4-12 Existing Water Demands ...............................................................................5-2 Buildout Water Demand.................................................................................5-3 Supply Capacity Evaluation...........................................................................7-10 Existing Storage Requirements .....................................................................7-13 Buildout Storage Requirements.....................................................................7-14 Storage Capacity Evaluation by Pressure Zone.............................................7-15 Existing Pump Station Capacity Evaluation ...................................................7-17 Buildout Pump Station Capacity Evaluation...................................................7-18 Schedule of Improvements............................................................................7-21 Unit Costs......................................................................................................8-3 Capital Improvement Program.......................................................................8-6 March 2023 v City of Gilroy
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Agenda Item 9.2 Page 504 of 768
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Water System Master Plan
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APPENDICES
Appendix A Calibration Curves
March 2023 vi City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 505 of 768
2023 City of Gilroy

EXECUTIVE 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-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 506 of 768
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 eastwest 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 March 2023 ES-2 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 507 of 768
Calero
Reservoir
Anderson
Reservoir
101
Morgan Hill
Coyote
Reservoir
Uvas
Reservoir
101
152 Gilroy
152
101
152
25 Watsonville
152
1 129
101
129 129
Legend
Figure .1 Cities Elevation (ft)
9 - 50
1,001 - 2,000
2,001 - 3,000
3,001 - 3,792
Regional Location Map
Water System Master Plan
City of Gilroy
Study Area
City Limits 51 - 100
Urban Growth Boundary
Highway
101 - 250
251 - 500
501 - 1,000
Waterbodies
Railroads GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
Flie Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig1-1RLMap_092120.mxd Agenda Item 9.2 Page 508 of 768
101 Coyote
Reservoir
152 152
City of Gilroy
101 152
101
25 Legend
Figure
Planning Area
Water System Master Plan
City of Gilroy
.

City Limits General Plan Area
City Limits Area Roads
Specific Plan Areas Highways
Urban Service Area Railroads
Urban Growth Boundary
Sphere of Influence Boundary
Rivers & Creeks
Waterbodies GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-1PlanningArea_092120.mxd Agenda Item 9.2 Page 509 of 768
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 March 2023 ES-5 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 510 of 768
Legend
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8 101
8"
10" - 30" Booster
Station 4 Tanks: 2C-1
2C-2 Roads
Booster
Station 3 & 2 3D-1
3D-2 Booster
Station 1
Railroads
12 Well 5-2
Tank 1A City Limits
Well 7 Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 Well 2 Well 1 24 Well 8
Well 8A
8 152
Well 3-2
Tanks: 2E-1
2E-2
Booster
Station 5
Well 4
Well 6
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
Figure .

Existing System
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
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Table ES.1 Planning and Design Criteria Summary
Water System Master Plan
City of Gilroy
Design Parameter Criteria
Supply
Supply = Maximum Day Demand + Standby Well (1,805 gpm)
Storage Total Required Storage = Operational + Fire + Emergency For Pressure Zone 1
Operational Storage
Fire Storage
25% of Maximum Day Demand
Varies
Emergency Storage
For Pressure Zones 2 and 3
Operational Storage
Fire Storage
25% of Maximum Day Demand
25% of Maximum Day Demand
Varies
Emergency Storage 50% of Maximum Day Demand
Booster Pumps
Pumping Capacity = Maximum Day Demand
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
40 psi
35 psi
40 psi
20 psi
Minimum Pressure (during Maximum Day)
Minimum Pressure (during Peak Hour)
Minimum Pressure for New Development1 (during Peak Hour) Minimum Residual Pressure (during Fires)
Demand Peaking Factors Maximum Month Demand
Maximum Day Demand
Peak Hour Demand
Residential

1.50 x Average Day Demand

2.00 x Average Day Demand

3.00 x Average Day Demand
Fire Flows 1,500 gpm for 2 hours
Commercial 2,500 gpm for 2 hours
Industrial 5,000 gpm for 3 hours
2 Time-of-Use Time-of-Use considerations account for off-peak energy rate schedule before 4 PM and after 9 PM (19-hour pumping period).

Urban Water Use Targets
2020 Urban Water Management Plan Existing Coefficient 166 gpdc 149 gpdc
133 gpdc
2015 Interim Target
2020 Target (20% Conservation)
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.

Agenda Item 9.2 Page 512 of 768
Table ES.2 Buildout Water Demands
Water System Master Plan
City of Gilroy
Total Water Demand Buildout of Service Area
Water Unit
Land Use Classification Factor Average Day
Demand Existing Unchanged Redeveloped Area New Development Total Area (gpd/acre) (acres) (acres) (acres) (acres) (gpd)
Residential
Hillside Residential
Low Density Residential
Medium Density Residential
High Density Residential
1,270
2,000
442
1,583
58 112
122
177
18 353
89 907
1,794
240
1,151,593
3,587,897
3,280 6 788,743
4,260 67 18 104 442,583
Subtotal - Residential 2,151 429 466 3,045 5,970,816
Non-Residential
Office and Commercial 1
Industrial 2
1,100
990
465 281
213
153
38 100
643
129
358
7 846
1,149
841
395
27 930,592
1,137,375
151,310
450,832
31,122
293
Public Facility / Institution
Neighborhood District
City Gateway District
180 559
1,140
1,140
Varies
1,100
Varies
Varies
990
0 0 20
Downtown Specific Plan Area 3
Mixed Use Corridor High
0 57 32 89 210,626
0 25 7 33 35,976
Hecker Pass Special Use District 4
Glen Loma Ranch 4
0 328
103
43 88 416
341
83 528,763
577,791
82,587
0 0
237
Industrial Park 40
Employment Center 1,100 0 279
1,541
251
1,893
530
4,750
583,081
Subtotal - Non-Residential 1,317 4,720,055
Other
Park and Recreation Facility 410
0 995
0 0
0 0
154
0 1,149
0 471,009
Vacant 0
Open Space 0
Rural County
0 253 1,045 1,298
0 0 28 3 30 0
Subtotal - Other 1,247 28 1,202 2,477 471,009
Total
4,714 1,997 3,561 10,272 11,161,880
4/20/2022
Notes:

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.

Agenda Item 9.2 Page 513 of 768
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-9 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 514 of 768
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.

March 2023 ES-10 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 515 of 768
Legend
Recommended Improvements
Tanks
Wells
New Pipes
Pipe Replacements
Existing System
Tanks
8 101
GW-10
GW-1 Wells 2
Booster Pumps
Existing Pipes by Diameter
4" - 6"
Booster
Station 4 Tanks: 2C-1
2C-2 Booster
Station 3 & 2 3D-1
3D-2 Booster
Station 1 8"
12 Well 5-2
Tank 1A 10" - 30"
3H-1 16
P1-5 Roads
Well 7
Railroads
152 24 16
Well 2 P1-3
152
24 24 City Limits 10
P1-6
Well 8
Well 1 Well 8A
16 P1-8 Urban Growth Boundary
Rivers & Creeks
Waterbodies
8 12
P1-7
152
Well 3-2 GW-11
Tanks: 2E-1
2E-2 (Planned Well)
Booster
Station 5
Well 4
Well 6
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
16 P1-22
Figure .

Capital Improvement
Program
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
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Table ES.3 Capital Improvement Program
Water System Master Plan
City of Gilroy

PRELIMINARY
Pipeline Information Infrastructure Costs Suggested Cost Allocation Existing
Users
Cost Sharing Baseline Constr. Estimated Const. Capital Improv.

Pressure
Zone
Construction Trigger Improv. No. Improv. Type Alignment Limits Costs Costs1 Costs2 New/Parallel/ Existing Diameter Diameter Length Unit Cost Infr. Cost Future Users Existing Users Future Users Replace (in) (in) (ft) ($) ($) ($) ($) ($)
Pipeline Improvements
P1-1
P1-2
Future Growth
Future Growth
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
FF Reliability
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Day Rd From Santa Teresa Blvd to Monterey Hwy
From approx. 620' n/o Day Rd to Cohansey Ave
From 2nd St to Ioof Ave
-
-
New
New
12 12
16 16
16 10
12 16
16 16
16 16
16 16
16 16
16 16
16 16
16 16
3,860
5,780
230
254
254
304
304
304
211
254
304
304
304
304
304
304
304
304
304
304
304
304
304
304
304
978,700
1,465,500
70,000
978,700
1,465,500
70,000
1,272,400
1,905,200
91,000
1,654,200
2,476,800
118,300
With Development
With Development
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
As Funding is Available
As Funding is Available
As Funding is Available
With Development
With Development
As Funding is Available
As Funding is Available
As Funding is Available
With Development
With Development
As Funding is Available
With Development
With Development
With Development
0%
0%
100%
100%
0%
0 0
1,654,200
Monterey Hwy / Orsetti
Rd / Hwy 101
2,476,800
P1-3 Monterey Hwy
Murray Ave
Arroyo Cir
Lewis St
12 12
12 8
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
New
100%
100%
100%
100%
100%
100%
100%
100%
100%
0%
118,300
1,131,400
36,100
82,200
137,300
154,400
889,800
1,563,300
1,080,000
0 0
P1-4 From Well 5-02 to Ioof Ave 2,200
70 669,400
21,300
669,400
21,300
870,300
27,700
1,131,400
36,100
0% 0
P1-5 From Well 7 to Ioof Ave 0% 0
P1-6 From approx. 180' e/o Forest St to Chestnut St
From Well 3 to 6th St
230 48,600 48,600 63,200 82,200 0% 0
P1-7 Forest St 10
12 12
12 12
-
320 81,200 81,200 105,600
118,700
684,400
1,202,500
830,700
640,800
1,795,700
2,563,100
1,210,300
1,079,800
716,000
1,143,100
1,831,400
261,200
1,190,600
110,800
137,300 0% 0
Gilman Rd / Camino
Arroyo
P1-8 From Well 8 to approx. 80' se/o Gilman Rd
From Camino Arroyo to Cameron Blvd
From Pacheco Pass Hwy to Venture Wy
300 91,300 91,300 154,400 0% 0
P1-9 Pacheco Pass Hwy
Camino Arroyo
Cameron Blvd
ROW
1,730
3,040
2,100
1,620
4,540
6,480
3,060
2,730
1,810
2,890
4,630
660
526,400
925,000
639,000
492,900
1,381,300
1,971,600
931,000
830,600
550,700
879,300
1,408,700
200,900
915,800
85,200
526,400
925,000
639,000
492,900
1,381,300
1,971,600
931,000
830,600
550,700
879,300
1,408,700
200,900
915,800
85,200
889,800 0% 0
P1-10
P1-11
P1-12
P1-13
P1-14
P1-15
P1-16
P1-17
P1-18
P1-19
P1-20
P1-21
P1-22
FF Reliability 1,563,300
1,080,000
833,100
0% 0
0 From Pacheco Pass Hwy to approx. 200' se/o Venture
Wy
FF Reliability 0%
Future Growth
Future Growth
FF Reliability
From Camino Arroyo to approx. 1,800' e/o Luchessa Ave 100% 100%
0%
833,100
2,334,500
0 ROW / Cameron Blvd From approx. 200' se/o Venture Wy to Southside Dr - New 2,334,500 3,332,100
1,573,400
1,403,800
930,800
0% 0
Luchessa Ave
Thomas Rd
Rossi Ln
ROW
From Thomas Rd to Rossi Ln 12
12 12
-
Replace
Replace
Replace
New
100%
100%
100%
0%
3,332,100
1,573,400
1,403,800
0 FF Reliability From Luchessa Ave to Santa Teresa Rd
From Luchessa Ave to Southside Dr
0% 0
FF Reliability 0% 0
Future Growth
Future Growth
FF Reliability
From Luchessa Ave to approx. 1,800' e/o Luchessa Ave
From approx. 1,800' e/o Luchessa Ave to Southside Dr
From Hwy 101 to Arizona Cir
100%
100%
0%
930,800
1,486,100
0 ROW - New 1,486,100
2,380,900
339,600
0% 0
Garlic Farm Wy /
Southside Dr
12 -
Replace
New
100%
0%
2,380,900
Future Growth 0
Future Growth
Future Growth
Southside Dr
Southside Dr
From Arizona Cir to approx. 660' e/o Arizona Cir
From approx. 660' e/o Arizona Cir to Camaron Blvd
100%
100%
100%
339,600
1,547,800
144,100
- New 3,010
280
1,547,800
144,100
0% 0
From approx. 160' w/o Thomas Rd to approx. 110' e/o
Thomas Rd Santa Teresa Blvd - New 0% 0
Subtotal - Pipeline Improvements 15,164,400 19,714,500 25,630,000 13,883,000 11,747,000 Proposed Storage Capacity Storage Reservoir Improvements (MG) 3H-1 Storage Capacity Zone 3 Construct an additional 0.1 MG storage reservoir at existing 3D site New 0.10 133,442 133,500 173,600 225,700 813 EDU 0% 100% 0 225,700 Subtotal - Storage Reservoir Improvements 133,500 173,600 225,700 0 225,700 Agenda Item 9.2 Page 517 of 768
Table ES.3 Capital Improvement Program
Water System Master Plan
City of Gilroy

PRELIMINARY
Pipeline Information Infrastructure Costs Suggested Cost Allocation Existing
Users
Cost Sharing Baseline Constr. Estimated Const. Capital Improv.

Pressure
Zone
Construction Trigger Improv. No. Improv. Type Alignment Limits Costs Costs1 Costs2 New/Parallel/ Existing Diameter Diameter Length Unit Cost Infr. Cost Future Users Existing Users Future Users Replace (in) (in) (ft) ($) ($) ($) ($) ($)
Proposed Pumping Capacity Groundwater Well Improvements (gpm) GW-10
GW-11
GW-12
Supply Capacity
Supply Capacity
Supply Capacity
Zone 1
Zone 1
Zone 1
Construct new well near the intersection of San Ysidro Ave and Las Animas Ave Construct new well near the intersection of Camino Arroyo and Renz Lane Construct new well near the intersection of Wren Ave and Vickery Ln New
New
New
1,500
1,500
1,500
-
-
-
-
-
-
-
-
-
3,922,000
3,922,000
3,922,000
9,500 EDU
15,550 EDU
21,600 EDU
0%
0%
0%
100%
100%
100%
0 0
0 3,922,000
3,922,000
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
173,600
0 25,630,000
225,700
13,883,000 11,747,000
Storage Reservoirs 225,700
Groundwater Wells
133,500
0 0
11,766,000 0
37,621,700
11,766,000
Total Improvement Costs 15,297,900 19,888,100 13,883,000 23,738,700 3/29/2023
Notes:

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.

Agenda Item 9.2 Page 518 of 768
Table ES.4 Unit Costs
Water System Master Plan
City of Gilroy
Pipelines
Pipe Size Cost1,2
(in) ($/lineal foot)
6 $153
8 $187
$211
$254
$304
$312
$336
$400
$500
$560
$705
10 12
16 18
20 24
30 36
42 Pump Stations
Estimated Pumping Station Project Cost = 2.1*10(0.7583*log(Q)+3.1951) where Q is in gpm
Storage Reservoirs ($/gallon)1,3
≤1.0 MG

1.1 MG-3.0 MG

3.1 MG - 5.0 MG
> 5 MG
$1.33
$2.11
$3.22
$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
Agenda Item 9.2 Page 519 of 768
2023 City of Gilroy
CHAPTER 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.

March 2023 1-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 520 of 768
Calero
Reservoir
Anderson
Reservoir
101
Morgan Hill
Coyote
Reservoir
Uvas
Reservoir
101
152 Gilroy
152
101
152
25 Watsonville
152
1 129
101
129 129
Legend
Figure 1.1 Cities Elevation (ft)
9 - 50
1,001 - 2,000
2,001 - 3,000
3,001 - 3,792
Regional Location Map
Water System Master Plan
City of Gilroy
Study Area
City Limits 51 - 100
Urban Growth Boundary
Highway
101 - 250
251 - 500
501 - 1,000
Waterbodies
Railroads GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
Flie Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig1-1RLMap_092120.mxd Agenda Item 9.2 Page 521 of 768
•
•
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 1-3 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 522 of 768
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 1-4 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 523 of 768
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.

March 2023 1-5 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 524 of 768
Table 1.1 Unit Conversions
Water System Master Plan
City of Gilroy
Volume Unit Calculations
To Convert From:
acre feet
acre feet
acre feet
cubic feet
cubic feet
cubic feet
gallons
To: Multiply by:
325,851
43,560
gallons
cubic feet
million gallons
gallons

0.3259

7.481
acre feet 2.296 x 10-5

7.481 x 10-6

0.1337
million gallons
cubic feet
gallons acre feet 3.069 x 10-6
1 x 10-6
gallons million gallons
million gallons gallons 1,000,000
million gallons
million gallons
cubic feet
acre feet
133,672

3.069
Flow Rate Calculations
To Convert From: To:
mgd
cfs
Multiply By:
ac-ft/yr
ac-ft/yr
ac-ft/yr
ac-ft/yr
cfs

8.93 x 10-4

1.381 x 10-3

0.621
gpm
gpd 892.7
mgd
gpm
ac-ft/yr
gpd

0.646
cfs 448.8
cfs 724
cfs 646300
1 x 10-6

1.547 x 10-6

6.944 x 10-4

1.12 x 10-3

1.44 x 10-3

2.228 x 10-3

1.61 gpd mgd
gpd cfs
gpd gpm
ac-ft/yr
mgd
cfs
gpd
gpm
gpm
gpm
gpm
mgd
mgd
mgd
mgd
ac-ft/yr
gpd 1,440
cfs 1.547
gpm
ac-ft/yr
gpd
694.4
1,120
1,000,000
5/4/2021
Agenda Item 9.2 Page 525 of 768
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
gpm
hp
gallons per day per capita
gallons per minute
horsepower
Association for the Advancement of Cost
Engineering
AACE International
AC
ACP
ADD
Akel
CCI
acre
Asbestos Cement Pipe
average day demand
Akel Engineering Group, Inc.

Construction Cost Index
California Department of Public Health
cubic feet per second
cast iron pipe
HGL
HWL
in
hydraulic grade line
high water level
inch
LAFCO
LF
Local Agency Formation Commission
CDPH linear feet
cfs MDD
MG
maximum day demand
CI million gallons
CIB Capital Improvement Budget
Capital Improvement Program
City of Gilroy
MGD
MMD
NFPA
PHD
PRV
psi
million gallons per day
maximum month demand
National Fire Protection Association
peak hour demand
pressure reducing valve
pounds per square inch
Right of Way
CIP
City
County
DIP
DU
Santa Clara County
Ductile Iron Pipe
dwelling unit
EDU
ENR
EPA
EPS
FRC
ft
equivalent dwelling unit
Engineering News Record
Environmental Protection Agency
Extended Period Simulation
Facility Reserve Charge
feet
ROW
SCADA
SOI
Supervisory Control and Data
Acquisition
Sphere of Influence
TBD
ULL
to be determined
Urban Limit Line
VW Valley Water
fps feet per second WSMP
WTP
Water System Master Plan
FY Fiscal Year Water Treatment Plant
GIS Geographic Information Systems
4/28/2021
Agenda Item 9.2 Page 526 of 768



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 1-8 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 527 of 768
2023 City of Gilroy
CHAPTER 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 eastwest 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, March 2023 2-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 528 of 768
101 Coyote
Reservoir
152 152
City of Gilroy
101 152
101
25 Legend
Figure 2.1
Planning Area
Water System Master Plan
City of Gilroy
City Limits General Plan Area
City Limits Area Roads
Specific Plan Areas Highways
Urban Service Area Railroads
Urban Growth Boundary
Sphere of Influence Boundary
Rivers & Creeks
Waterbodies GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-1PlanningArea_092120.mxd Agenda Item 9.2 Page 529 of 768
101 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 152
City Limits 152
Roads
Railroads
Rivers & Creeks
Waterbodies
25 101
Figure 2.2
Existing Land Use
Water System Master Plan
City of Gilroy
GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig2-2ExistLandUse_092120.mxd Agenda Item 9.2 Page 530 of 768
Table 2.1 General Plan Land Use
Water System Master Plan
City of Gilroy
Existing Development
Within City Limits
Future Development Total Development
Subtotal
Existing
Within City Limits
Subtotal
Future
Development
General Plan Land Use
Classification
Existing Land Use
Classification
Urban Growth
Boundary
Urban Growth Sphere of
Development - Boundary Influence
Existing Lands -
Redeveloping
Unchanged New Lands -
Redevelopment
New
Development Existing
(acre) (acre) (acre) (acre) (acre) (acre) (acre) (acre) (acre) Residential
Rural Residential
Hillside Residential
- 0 0 0 0 0
344
45 4
0 8
0 0 0
Hillside Residential 444 -1 442
1,583
58 112
122
177
18 464
211
183
36 907 913
Low Density Residential
Medium Density Residential
High Density Residential
Low Density Residential
Medium Density Residential
High Density Residential
Subtotal - Residential
1,704
100
-121
-42
44 2
1,794
240
4,221
248
249 -182
-346
67 15
408
3 104 111
2,496 2,151 429 58 895 3,045 5,493
Non-Residential
Visitor Serving Commercial
General Services Commercial
Visitor Serving Commercial 99
524
1 -67
-91
0 32
432
1 176
106
0 0
55 0
0 44
0 176
205
0 208
637
1 208
837
1 General Services Commercial
Professional Office
General Industrial General Industrial 320
56 12
596
94 0
-71
-12
-5
249
44 7
213
0 255
0 389
0 856
0 1,105
44 2,036
Campus Industrial 44
Educational Facility
Public/Quasi-Public Facility
Neighborhood District
City Gateway District
Educational Facility 1 0 0 1 8 22
Public/Quasi-Public Facility -44
-94
0 552
0 152
38 102
22 7
28 336
0 281
395
27 833
395
27 1,013
428
27 Neighborhood District
- 0 20
Downtown Specific Plan Area
Mixed Use Corridor High
Hecker Pass Special Use District
Glen Loma Ranch
- 0 0 0 57 32
7 0 89 89 89
- 0 0 0 25 0 33 33 33
- 0 0 0 328
103
43 88
237
40 30
876
0 416
341
83 416
341
83 416
341
83 - 0 0 0 0
Industrial Park - 0 0 0 0
Employment Center - 0 0 0 279
1,541
222
1,017
530
3,434
530
4,750
530
Subtotal - Non-Residential 1,701 -384 1,317 6,109
Other
Agriculture
Park and Recreation Facility
Vacant
-
Park and Recreation Facility
Vacant
0 0 0
995
0 0
0 0
66 0
88 0
0 154
0 0 0
1,232
2,391
1,282
0 -238
-2,391
-1,030
0 1,149
0 2,392
0 0 0
Open Space Open Space
-
253
0 0 1,041
0 4 1,045
30 1,298
30 2,897
17,726
23,015
Rural County 28
28 3
Subtotal - Other 4,905 -3,658 1,247 1,107 95 1,230 2,477 Total
Total Developed Area 9,102 -4,388 4,714 1,997 2,391 1,170 5,558 10,272 34,616 0 5/12/2021
Notes:

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.

Agenda Item 9.2 Page 531 of 768
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 nonresidential 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.

March 2023 2-5 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 532 of 768
101 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 152
Public and Quasi-Public Facility
Neighborhood District
Mixed Use
152
Rural County
Open Space
Park and Recreation Facility
Specific Plan Areas
Downtown
Glen Loma Ranch
Hecker Pass
Roads
Railroads
Rivers & Creeks
25 Waterbodies
101
Figure 2.3
2040 General Plan
Land Use
Water System Master Plan
City of Gilroy
GIS
0 0.5 1 2
Updated: December 6, 2019 Miles
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Table 2.2 Glen Loma and Hecker Pass Specific Plans, Remaining Development Water Demand Water Master Plan
City of Gilroy
Land Use Types
Residential Non-Residential Other
Specific Plan Units
Total
Total Development1
Hecker Pass
Glen Loma
Acres
Acres

46.2 0.0

16.3 112.9
129.2

99.1 70.3

2.2 58.0 0.0 95.7 51.7

0.0 46.8

95.7 416.0
341.0
757.0

26.5 28.7

0.0 26.9

26.9 8.7
Subtotal 46.2 169.5 58.0 104.3 51.7 142.5
Existing Development2
Hecker Pass
Glen Loma
Acres
Acres

11.2 0.0

7.6 89.3

70.3 0.0

0.3 0.3

36.8 0.0

0.0 95.7

3.9 16.6

0.0 0.1 257.1
154.7
411.9

33.7 41.2

24.5 24.5

22.0 Subtotal 11.2 159.6 36.8 99.6 16.6 22.1
Remaining Development3
Hecker Pass
Glen Loma
Acres
Acres

35.0 0.0

8.8 9.9

0.0 9.9

2.2 21.2

0.0 0.0

2.3 2.3

0.0 4.8

4.8 35.1

0.0 46.7

73.8 158.8
186.3
345.1

79.2 88.0

26.2 Subtotal 35.0 28.4 21.2 35.1 120.5
Existing Average Daily Demand
(1,270 (2,000 (3,280 (4,260 (1,100 (180 (410 (0 (0
gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) Hecker Pass
Glen Loma
gpd
gpd
14,199
0 15,112
67,314
82,426
292,754
230,747
523,501
20 40,450
0 0 39,221
1,604
0 0
0 0
0 0
401,756
305,472
707,228
1,390
1,410
4,417
Subtotal 14,199 40,450 4,417 40,825
Remaining Average Day Demand
(1,270 (2,000 (3,280 (4,260 (1,100 (180 (410 (0 (0
gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) gdp/acre) Hecker Pass
Glen Loma
gpd
gpd
44,505
0 17,527
158,482
176,009
32,337
0 9,333 23,306
0 0 0 0
0 0
0 0
0 127,007
272,320
399,327
111,465
120,798
418
418
1,954
Subtotal 44,505 32,337 23,306 1,954
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.

Agenda Item 9.2 Page 534 of 768
Table 2.3 Downtown Specific Plan, Redevelopment and New Development Water Demand Water Master Plan
City of Gilroy
Estimated Land Use Development and Land Use Land Use Properties1 Unit Factors Additional Water Demand for Breakdown2 Assumptions
Redevelopment and
New Development8
Total
Dwelling
Units2
Existing
Development Development Development
Re- New Total
Buildout
Residential Commercial
Land Use District Residential Commercial Residential4 Commercial5,6 Weighted7 Density3 Density2
(acres)
2 (acres)
3 (acres)
4 (acres)
5 %
6 %
7 DU DU/acre
9 FAR
10 gpd/acre
11 gpd/acre
12 gpd/acre
13 (gpd)
1 8 14
Historic 5.4
-

0.8 7.8

11.7 0.0

17.9 7.8
44%
96%
44%
29%
69%
40%
73%
56%
4%
56 320
448
760
79 3.1

41.0 9.4

2.5 2.5

2.5 2.0

1.5 1.5

0.75 594
7,792
1,776
3,877
735
2,750
2,750
2,750
2,200
1,650
1,650
825
1,801
7,614
2,321
2,686
1,019
1,052
629
22,529
59,388
34,250
77,319
280
VTA Transit-Oriented
Development 9
Expansion 33.2

8.4 5.8 9.0 47.9

37.2 20.4

17.0 54.3
202.5
56%
71%
31%
60%
27%
Cannery District
Transitional
Civic/Residential Only
Gateway

17.4 0.28

1.3 11.4

0.0 20.4

20.1 3.9

14.8 31.2
113.1

1.0 14 0.8 156 2,361

11.7 45.0

11.4 44.4
159
1,836

2.9 556 14,499
Total 210,626
5/12/2021
Notes:

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 units

5. 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.

Agenda Item 9.2 Page 535 of 768
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 nonresidential 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.

March 2023 2-9 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 536 of 768
Table 2. Historical and Projected Population
Water System Master Plan
City of Gilroy
Annual Growth Year Population1,2
(%)
Historical
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
41,464
42,436
43,144
43,866
45,026
45,782
46,446
47,047
48,353
48,627
48,821
49,622
50,716
52,475
53,325
54,233
54,849
55,811
56,030
56,635
56,704

2.3%

1.7%

1.7%

2.6%

1.7%

1.5%

1.3%

2.8%

0.6%

0.4%

1.6%

2.2%

3.5%

1.6%

1.7%

1.1%

1.8%

0.4%

1.1%

0.1%
Projected
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
57,555
58,418
59,294
60,184
61,086
62,003
62,933
63,877
64,835
65,807
66,794
67,796
68,813
69,845
70,893
71,957
73,036
74,131
75,243

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

1.5%

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.

Agenda Item 9.2 Page 537 of 768
2023 City of Gilroy
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.

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.

March 2023 3-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 538 of 768
70,000
67,000
64,000
61,000
58,000
55,000
52,000
49,000
46,000
43,000
40,000
10 9
8 7
6 5
4 3
2 1
0 8.3 8.2 8.2

7.9 7.7 7.6 7.4 7.3 7.3

7.1 7.1 7.1 7.1

6.9 7.0 7.0 7.0 6.9

6.2 6.1
54,123
48,821
45,782
41,464
2000 2005 2010 2015 2020
Year
LEGEND Figure 3.1
Population Historical Population vs.

Average Daily Production
Water System Master Plan
City of Gilroy
Average Daily Production (MGD)
September 18, 2020
Agenda Item 9.2 Page 539 of 768
250
225
200
175
150
125
100
9 8
7 6
5 4

8.3 8.2 8.2

7.9 7.7

7.6 7.4

7.3 7.3

7.1 7.1 7.1 7.1 7.0 7.0 7.0 6.9 6.9
174
171 171 6.1 168 6.2 167 165 165
161 159
155 156
152
147 146
138
125 125
121
113 113
3 2000 2005 2010 2015 2020
Year
LEGEND Figure 3.2
Water Use Per Capita (gpdc) Water Use Per Capita vs.

Average Daily Production (MGD)
Average Daily Production
Water System Master Plan
City of Gilroy
September 18, 2020
Agenda Item 9.2 Page 540 of 768
Table 3.1 Historical Water Production and Maximum Day Peaking Factors (2000-2019) Water System Master Plan
City of Gilroy
Historical Water Production
Average Daily
Water Use per
Capita
% Monthly Production Year Population1
Increase Annual Production2 % Increase
Month of Max-to- Average Maximum3,4
Occur. Avg Ratio
(AF) (MGY)
2,542
(gpm)
4,836
(MGM)
212
(MGM)
308
(gpdc)
2000 168
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
41,464
42,436
43,144
43,866
45,026
45,782
46,446
47,047
48,353
48,627
48,821
49,611
50,698
52,378
53,208
54,123
54,916
55,932
56,198
56,854
- 7,800 - August
July

1.46 1.48

1.43 1.60

1.47 1.61

1.61 1.46

1.61 1.54

1.56 1.47

1.48 1.54

1.42 1.24

1.44 1.44

1.43 1.43
2%
2%
2%
3%
2%
1%
1%
3%
1%
0%
2%
2%
3%
2%
2%
1%
2%
0%
1%
8,006
8,498
7,897
8,333
7,961
8,898
9,190
9,261
8,475
7,986
8,186
8,642
9,324
8,208
6,870
6,977
7,814
7,854
7,691
2,609
2,769
2,573
2,715
2,594
2,899
2,995
3,017
2,762
2,602
2,667
2,816
3,038
2,675
2,239
2,273
2,546
2,559
2,506
4,963
5,269
4,896
5,166
4,936
5,516
5,698
5,741
5,254
4,951
5,075
5,358
5,781
5,089
4,259
4,325
4,844
4,869
4,768
3% 217
231
214
226
216
242
250
251
230
217
222
235
253
223
187
189
212
213
209
323
330
342
332
348
389
365
404
355
337
327
348
390
316
232
273
305
305
299
168
176
161
165
155
171
174
171
156
146
147
152
159
138
113
113
125
125
121
6% July
-7%
6%
July
July
-4%
12%
3%
August
August
July
1% July
-8%
-6%
3%
June
July
August
6% July
8% June
-12% July
-16%
2%
July
July
12%
1%
July
July
-2% August
Historical Maximum Month Peaking Factors
10-Year Maximum (2010-2019)
5-Year Maximum (2015-2019)
3-Year Maximum (2017-2019)
Last Year's Maximum (2019)
9,324
7,854
7,854
7,691
3,038
2,559
2,559
2,506
5,781
4,869
4,869
4,768
12%
12%
12%
-2%
253
213
213
209
390
305
305
299

1.56 1.44

1.44 1.43
159
125
125
121
2020 Water System Master Plan Peaking Factors
Maximum Month Demand
Maximum Day Demand

1.5 x Average Day Demand

2.0 x Average Day Demand
9/21/2020
Notes:

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.

Agenda Item 9.2 Page 541 of 768
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
Monthly Monthly Monthly Month
Percent of
Annual
Month to Avg
Factor
Percent of
Annual
Month to Avg
Factor
Percent of
Annual
Month to Avg
Factor
Average Day Production Average Day Production Average Day Production (MGD) (MGM) (%) (MGD) (MGM) (%) (MGD) (MGM) (%)
January
February
March

4.29 4.19

4.74 5.37

8.10 9.31

9.85 9.74

9.17 8.16

5.60 5.00
133
117
147
161
251
279
305
302
275
253
168
155
5%
5%

0.63 0.55

0.69 0.76

1.18 1.32

1.44 1.42

1.30 1.19

0.79 0.73

4.48 5.07

4.58 5.63

7.94 9.10

9.84 9.68

8.87 7.94

6.43 4.45
139
142
142
169
246
273
305
300
266
246
193
138
5%
6%

0.65 0.67

0.67 0.79

1.15 1.28

1.43 1.41

1.25 1.15

0.91 0.65

4.26 4.14

4.29 5.83

7.13 8.70

9.61 9.65

9.23 8.13

6.83 4.45
132
116
133
175
221
261
298
299
277
252
205
138
5%
5%

0.63 0.56

0.64 0.84

1.06 1.25

1.43 1.43

1.33 1.21

0.98 0.66
6% 6% 5%
April 6% 7% 7%
May 10%
11%
12%
12%
11%
10%
7%
10%
11%
12%
12%
10%
10%
8%
9%
June 10%
12%
12%
11%
10%
8%
July
August
September
October
November
December 6% 5% 6%
Total
Average Value
Maximum Value
2,547
212
305
2,559
213
305
2,507
209
299

6.96 7.00 6.85

1.44 1.43 1.43
9/21/2020
Note:

1. Source: 2017-2019 Monthly Well Production provided by City Staff on June 5, 2020.

Agenda Item 9.2 Page 542 of 768
Table 3.3 Planning and Design Criteria Summary
Water System Master Plan
City of Gilroy
Design Parameter Criteria
Supply
Supply = Maximum Day Demand + Standby Well (1,805 gpm)
Storage Total Required Storage = Operational + Fire + Emergency For Pressure Zone 1
Operational Storage
Fire Storage
25% of Maximum Day Demand
Varies
Emergency Storage
For Pressure Zones 2 and 3
Operational Storage
Fire Storage
25% of Maximum Day Demand
25% of Maximum Day Demand
Varies
Emergency Storage 50% of Maximum Day Demand
Booster Pumps
Pumping Capacity = Maximum Day Demand
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
40 psi
35 psi
40 psi
20 psi
Minimum Pressure (during Maximum Day)
Minimum Pressure (during Peak Hour)
Minimum Pressure for New Development1 (during Peak Hour) Minimum Residual Pressure (during Fires)
Demand Peaking Factors Maximum Month Demand
Maximum Day Demand
Peak Hour Demand
Residential

1.50 x Average Day Demand

2.00 x Average Day Demand

3.00 x Average Day Demand
Fire Flows 1,500 gpm for 2 hours
Commercial 2,500 gpm for 2 hours
Industrial 5,000 gpm for 3 hours
2 Time-of-Use Time-of-Use considerations account for off-peak energy rate schedule before 4 PM and after 9 PM (19-hour pumping period).

Urban Water Use Targets
2020 Urban Water Management Plan Existing Coefficient 166 gpdc 149 gpdc
133 gpdc
2015 Interim Target
2020 Target (20% Conservation)
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.

Agenda Item 9.2 Page 543 of 768
Each new supply well should have adequate connections to power facilities, and every 4th 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 3-7 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 544 of 768
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 3-8 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 545 of 768
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 3-9 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 546 of 768
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.

March 2023 3-10 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 547 of 768
Table 3.4 Water Demand Unit Factor Analysis
Water System Master Plan
City of Gilroy
Existing Average Daily Water Demand Unit Factors
Existing
Development within
City Limits
Consumption1 Production2 Production at 100% Occupancy3,4,5 Recommended Water Unit Factor Balance Using
Existing Land Use Classification
Unadjusted Water
Unit Factors
Unadjusted Water Production (w/o
Vacancy rate)
Projected Production at 100%
Occupancy
Recommended
Factor
Annual Consumption Vacancy Rate Recommended Unit
Factor
Unit Factors
(acres) (gpd/acres) (kgal/year) (gpd) (gpd/acres) (gpd) (%) (gpd/acres) (gpd) (gpd/acres) (gpd) Residential
Hillside Residential 444
1,704
100
1,128
1,785
2,923
3,799
182,582
1,110,017
106,181
500,226
3,041,144
290,906
1,219
1,929
3,160
4,107
540,815
3,287,904
314,510

3.5%

3.5%

3.5%

3.5%
1,262
1,997
3,271
4,251
559,743
3,402,981
325,518
1,270
2,000
3,280
4,260
563,307
3,408,180
326,448
Low Density Residential
Medium Density Residential
High Density Residential
Subtotal - Residential
249 345,322 946,088 1,022,855
5,166,084
1,058,655
5,346,897
1,061,015
2,496 1,744,103 4,778,364 5,358,951
Non-Residential
Office and Commercial6 623
376
608
94 938
892
213,440
122,486
35,256
584,767
335,578
96,592
1,014
964
632,216
362,807
104,430
102,759
1,202,212

7.5%

2.0%

2.0%

3.5%
1,090
983
679,632
370,064
106,519
106,356
1,262,570
1,100
990
685,641
372,542
109,388
106,774
1,274,344
Industrial7
Public Facility / Institution8 159 172 175 180
Neighborhood District 1,015 34,692 95,047 1,097 1,136 1,140 Subtotal - Non-Residential
Other
1,701 405,875 1,111,985
Park and Recreation Facility 1,232
2,391
374
0 168,058
0 460,432
0 404
0 497,792
0 0
0 0
404
0 497,792
0 410
0 505,174
Vacant 0
Open Space 1,282 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".

Agenda Item 9.2 Page 548 of 768
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
High Density Residential
Non-Residential
3,280
4,260
Office and Commercial
Industrial
1,100
990
Public Facility / Institution
Neighborhood District
Park and Recreation Facility
180
1,140
410
4/27/2021
Agenda Item 9.2 Page 549 of 768
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 3-13 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 550 of 768
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 3-14 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 551 of 768
2023 City of Gilroy
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.

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.

March 2023 4-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 552 of 768
Legend
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8 101
8"
10" - 30" Booster
Station 4 Tanks: 2C-1
2C-2 Roads
Booster
Station 3 & 2 3D-1
3D-2 Booster
Station 1 Railroads
12 Well 5-2
Tank 1A City Limits
Well 7 Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 Well 2 Well 1 24 Well 8
Well 8A
8 152
Well 3-2
Tanks: 2E-1
2E-2
Booster
Station 5
Well 4
Well 6
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
Figure 4.1
Existing System
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: January 27, 2021 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig4-1_ExistingSystem_012721.mxd Agenda Item 9.2 Page 553 of 768
Table 4. Existing Groundwater Supply Capacity
Water System Master Plan
City of Gilroy
1 2
Specifications Pump Test Data Additional Information
Supply Well Well Location Total Dynamic
Head
Ground
Elevation
Rated Capacity Design Head Pump Test Date Flow Rate Pumping Level Horsepower (gpm)
1,200
(mgd) (ft) (gpm)
1,113
(ft) (ft)
83 (HP)
107
(ft)
Well 1
Well 2
Well 3
Well 4
Well 5
Well 6
Well 7
Well 8
Well 8A
100 Ioof Avenue
660 1st Street

1.73 1.58

3.31 1.73

2.30 2.16

2.45 3.17

0.35 235 7/23/2020
8/23/2018
7/23/2020
7/23/2020
7/23/2020
9/19/2016
7/23/2020
7/23/2020
7/23/2020
263 200
1,100
2,300
1,200
1,600
1,500
1,700
2,200
240
219
357
266
312
204
206
230
339
841
2,075
1,179
1,718
1,697
1,296
2,414
228
259
290
266
311
253
241
184
646
120
110
105
145
75 97
231
122
204
64 211
192
202
196
189
196
188
188
7325 Forrest Street
695 9th Street
8295 Rosanna Street
6552 Brem Lane
7820 Arroyo Circle
701 Gilliam Road
700 Gilliam Road
71 150
250
94 108
470
Total and Firm Supply Capacity
Total Supply Capacity 13,040
10,740

18.78 15.47
12,561
Firm Capacity (Excluding
largest Well) 10,147
5/12/2021
Notes:

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.

Agenda Item 9.2 Page 554 of 768

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.

March 2023 4-4 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 555 of 768
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
8 101
Booster
Station 4 Tanks: 2C-1
2C-2 Booster
Station 3 & 2 3D-1
3D-2 Booster
Station 112 Well 5-2
Tank 1A Railroads
Well 7 City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 Well 2 Well 1 24 Well 8
Well 8A
8 152
Well 3-2
Tanks: 2E-1
2E-2
Booster
Station 5
Well 4
Well 6
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
Figure 4.2
Pipelines by Pressure Zone
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: May 13, 2021 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\2014MP\GL_Fig4-2_PipesByPZ_070721.mxd Agenda Item 9.2 Page 556 of 768
700'
600'
500'
400'
300'
200'
100'
700'
600'
500'
400'
300'
200'
100'
3D-1 3D-2
644 644

0.41 0.41
621 MG MG 621
540'
2E-1 2E-2 2F-1 2C-1 2C-2 BS2
533.5 533.5 533.5 533.5 533.5 Mantelli Dr.
540' ZONE 3
SHGL =
644'

0.71 0.71 0.71 0.41 0.41 BS3
510.5 MG MG 510.5 MG 510.5 510.5 MG MG 510.5 Country Club Dr. 490'
430' 430'
430'
PRV 2 1G 1B 1A
374 374 PRV 3 374
ZONE 2S
SHGL =
533.5'
ZONE 2N
SHGL =
533.5'
BS6

2.00 2.00 Miller Ave. 3.00 347.5 MG MG 347.5 MG 342.5
340'
BS5 BS1
Club Dr. Rancho Hills Ct.

PRV 5 280' BS4 280' 280' 280' PRV 6
W 4
Rancho Hills Dr.
260' PRV 1
PRV 4 250'
ZONE 1
SHGL =
374'
W 1 W 2 W 3 W 5 W 6 W 7 W 8 W 8A W 9
1,200 gpm 1,100 gpm 2,300 gpm 1,200 gpm 1,600 gpm 1,500 gpm 1,700 gpm 2,200 gpm 240 gpm 700 gpm 140'
LEGEND Figure 4.3

ID HIGH
LOW
Reservoir Pressure Zone
HIGH: Highest Service Elevation (ft)
ZONE: Zone ID
SHGL: Static Hydraulic Grade Line
HWL: Lowest Service Elevation (ft)
Existing Hydraulic Profile HWL
ID: Tank ID ZONE
SHGL
ID Proposed Well
HWL: High Water Level (ft)
VOL: Reservoir Capacity (MG)
LOW: Bottom Elevation (ft)
ID: Well ID
VOL GPM: Well Production (gpm) Schematic
Water System Master Plan
City of Gilroy
LOW MG
GPM
Booster Pumping Station ID Existing Well
ID ID: Booster Station ID ID: Well ID
ELEV: Station Elevation (ft) GPM: Well Production (gpm)

ELEV GPM
ID Pressure Regulating Valve
ID: Valve ID Transmission Main
Last Updated: 11/29/2021
Agenda Item 9.2 Page 557 of 768
Table 4.2 Existing Modeled Pipe Inventory
Water System Master Plan
City of Gilroy
Pipe Length by Material
Pipe Diameter
C.I.P. D.I.P. P.V.C. C.M.P. Unknown Total
(in)
1 (ft) (ft) (ft) (ft) (ft) (ft) (miles)
0 182
0 1,009
146
0 0
0 0
1,192 0.2

1.25 2
0 0
146
1,579

0.03 887 266 0 426 0.3
3 0 174 594 0 0 768 0.1
4 5,928
64,482
82,156
15,286
31,728
0 22,174
98,096
325,392
38,486
169,851
283
8,562
10,753
15,155
2,274
12,737
0 0 2,262
15,332
25,885
1,110
16,193
0 38,926
188,776
448,588
57,155
230,509
283

7.4 6 113
0 35.8

85.0 10.8

43.7 0.1
8 10
12 15
16 24
30 Total
0 0
0 0 44,340
48,658
0 3 0 0 44,343
54,876
1,836

8.4 0 341 0 5,877
0 10.4
1,836 0 0 0.3
202.5
5/11/2021
201,416 748,523 51,840 113 67,085 1,068,976
Agenda Item 9.2 Page 558 of 768
Table 4. Pipe Roughness Coefficients
Water System Master Plan
City of Gilroy
Age (years)
Pipe Material
0 10 20 30 40 50
Cast Iron
Ductile Iron
Plastic (PVC)
120 110 100
120
140
90 85 80
130
145
125
145
115
140
110
135
105
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.

Agenda Item 9.2 Page 559 of 768
Table 4. Existing Storage Reservoirs
Water System Master Plan
City of Gilroy
Hydraulic Information
Pressure Overflow
Zone
Tank
Number
Location Bottom
Elevation Height
(ft)
SHGL Diameter
(ft)
Volume
(MG)
Height
(ft) (ft) (ft)
Zone 1 1A
1B
Welburn Ave. at Rancho Real
Santa Teresa Blvd. at Miller Ave.

Santa Teresa Blvd. at Miller Ave.

Mantelli Dr. at Periwinkle Dr.

Mantelli Dr. at Periwinkle Dr.

South end of Hoylake Court
South end of Hoylake Court
Walton Heath Court
342.5 34 32
27 27
24 24
24 24
24 24
24 374 128 3.00
347.5
347.5
510.5
510.5
510.5
510.5
510.5
621.0
621.0
29 29
25 25
25 25
25 25
25 374
374
112 2.00

5.30 0.41

0.41 0.71

0.71 0.71

0.41 0.41
1G 165 x 165
Zone 2N
Zone 2S
2C-1
2C-2
2E-1
2E-2
2F-1
3D-1
3D-2
533.5
533.5
533.5
533.5
533.5
644
54 54
70 70
70 54
54 Zone 3 South end of Periwinkle Drive
South end of Periwinkle Drive 644
Total Storage 14.1
1/26/2021
Note:

1. Source: City of Gilroy 2004 Water System Master Plan, Table 4.2 Agenda Item 9.2 Page 560 of 768
Table 4. Existing Booster Pumping Stations
Water System Master Plan
City of Gilroy
Operational Controls
(Reservoir Levels)
Source
Elevation Pressure
Zone
Destination
Pressure
Zone
Pump Station Pump Station Individual
Classification Horsepower
Operational
Capacity2
Pump Head2
Pump
Number Name Description Capacity Horsepower Pump Test Date Operational On
(ft)

20.0 Off
(ft)
Reservoir
(ft) (gpm) (mgd) (hp) (hp) (gpm)
641
(gpm)
162
Priority
Booster Station 1 Rancho Hills Court 280
540
490
250
260
340
1 (374')
2 (533.5')
2 (533.5')
1 (374')
1 (374')
1 (374')
2 (533.5')
3 (644')
1,710
870

2.5 1.3

1.3 2.5

2.5 2.5
138.6 7/23/2020
7/23/2020
7/23/2020
1 2
3 1
2 3
1 2
3 1
2 3
1 2
3 1
2 3
Lead
Lag

45.1 45.2

48.3 15
2C-1
2C-1
2C-1
3D-1
3D-1
3D-1
3D-1
3D-1
3D-1
2C-1
2C-1
2C-1
2E-1
2E-1
2E-1
2E-2
2E-2
2E-2
Lead 22.5
585
655
290
290
290
290
290
290
438
440
443
622
605
611
410
536
524
176
166
Lag 1
Lag 2
Lead
Lag 1
Lag 2
Lead
Lag 1
Lag 2
Lead
Lag 1
Lag 2
Lead
Lag 1
Lag 2
Lead
Lag 1
Lag 2

18.0 18.0

20.0 18.0

18.0 20.0

18.0 18.0

20.0 18.0

18.0 20.0

18.0 18.0

20.0 18.0

18.0 20.0

20.0 22.5

20.0 20.0

22.5 20.0

20.0 22.5

20.0 20.0

22.5 20.0

20.0 22.5

20.0 20.0
Standby
Booster Station 2 Lead
Booster Station 3
Booster Station 4
Booster Station 5
Booster Station 6
Mantelli Dr. at Periwinkle
Country Club Dr.
45 45
Lag 15
Standby
Lead
15 3 (644') 870 15
Lag 15
Standby
Lead
15 Rancho Hills Dr. 2 (533.5')
2 (533.5')
2 (533.5')
1,710
1,710
1,710
150
150
150
7/23/2020
7/23/2020
7/23/2020
7/23/2020
7/23/2020
7/23/2020
7/23/2020
7/23/2020
7/23/2020

48.1 46.9

42.3 41.9

40.8 41
203
203
203
180
178
178
199
194
171
Lag
Standby
Club Dr. Lead
Lag
Standby
Miller Ave. at Santa Teresa Blvd Lead 30.6

36.4 35.8
Lag
Standby
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.

Agenda Item 9.2 Page 561 of 768

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.

March 2023 4-11 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 562 of 768
Table 4.6 Existing Pressure Reducing Valves
Water System Master Plan
City of Gilroy
Pressure Zone Downstream
Setpoint
Size
Location PRV ID
Upstream Downstream
(in) (psi)
Rancho Hills Court Valve_BS1
Valve_BS2
Valve_BS3
Valve_BS4
10" 2N
3 1
2N
2N
1 15.0
Mantelli Dr. at Periwinkle
Country Club Dr.
8" 5.0
10"
12"
3 10.0
Rancho Hills Dr. 2N 20.0
Club Dr. Valve_BS5
Valve_BS6
8" 2S
2S
1 1

20.0 Miller Ave. at Santa Teresa Blvd 16" 1.0
1/26/2021
Agenda Item 9.2 Page 563 of 768
2023 City of Gilroy
CHAPTER 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.

March 2023 5-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 564 of 768
Table 5.1 Existing Water Demands
Water System Master Plan
City of Gilroy
Existing Water Demands
SCADA Based Peaking Factors Design Criteria Peaking Factors Average Day Pressure Zone 1 Demand
Maximum Day Peak Hour Maximum Day Peak Hour
2 3 4 5
Demand Demand Demand Demand
(gpm)
4,200
(gpm)
6,702
(gpm) (gpm)
8,400
(gpm)
Zone 1
Zone 2N
Zone 2S
Zone 3
Total
10,215 12,600
170
307
271
490
413
747
339
615
509
922
91 145 222 182 273
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
Agenda Item 9.2 Page 565 of 768
Table 5.2 Buildout Water Demands
Water System Master Plan
City of Gilroy
Total Water Demand Buildout of Service Area
Water Unit
Land Use Classification Factor Average Day
Demand Existing Unchanged Redeveloped Area New Development Total Area (gpd/acre) (acres) (acres) (acres) (acres) (gpd)
Residential
Hillside Residential
Low Density Residential
Medium Density Residential
High Density Residential
1,270
2,000
442
1,583
58 112
122
177
18 353
89 907
1,794
240
1,151,593
3,587,897
3,280 6 788,743
4,260 67 18 104 442,583
Subtotal - Residential 2,151 429 466 3,045 5,970,816
Non-Residential
Office and Commercial 1
Industrial 2
1,100
990
465 281
213
153
38 100
643
129
358
7 846
1,149
841
395
27 930,592
1,137,375
151,310
450,832
31,122
293
Public Facility / Institution
Neighborhood District
City Gateway District
180 559
1,140
1,140
Varies
1,100
Varies
Varies
990
0 0 20
Downtown Specific Plan Area 3
Mixed Use Corridor High
0 57 32 89 210,626
0 25 7 33 35,976
Hecker Pass Special Use District 4
Glen Loma Ranch 4
0 328
103
43 88 416
341
83 528,763
577,791
82,587
0 0
237
Industrial Park 40
Employment Center 1,100 0 279
1,541
251
1,893
530
4,750
583,081
Subtotal - Non-Residential 1,317 4,720,055
Other
Park and Recreation Facility 410
0 995
0 0
0 0
154
0 1,149
0 471,009
Vacant 0
Open Space 0
Rural County
0 253 1,045 1,298
0 0 28 3 30 0
Subtotal - Other 1,247 28 1,202 2,477 471,009
Total
4,714 1,997 3,561 10,272 11,161,880
4/20/2022
Notes:

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.

Agenda Item 9.2 Page 566 of 768

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.

March 2023 5-4 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 567 of 768
EPS 2020 Demand Diurnal
2 1.8

1.6 1.4

1.2 1

0.8 0.6

0.4 0.2
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours)
LEGEND
Notes:

Figure 5.1
Diurnal Curve
Water System Master Plan
City of Gilroy
Water Demand

1. Diurnal curve was developed based on SCADA data observed June 2020 through August 2020.

May 12, 2021
Agenda Item 9.2 Page 568 of 768
2023 City of Gilroy
CHAPTER 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 6-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 569 of 768

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 6-2 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 570 of 768
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 6-3 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 571 of 768

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.

March 2023 6-4 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 572 of 768
Avg. % Difference = 4% Avg. % Difference = 3% Tank 1A Tank 1B Pressure Zone 1 Pressure Zone 1
25 20
15 10
5 20
15 10
5 0
0 0
6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
Avg. % Difference = 11% Avg. % Difference = 3% Tank 1G 1 Pressure Zone 1
Tank 1G 2
Pressure Zone 1
25 20
15 10
5 20
15 10
5 0
0 0
6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure 6.1
Storage Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 573 of 768
Avg. % Difference = 0% Avg. % Difference = 3%
Well 3 Flow
Pressure Zone 1
Well 3 Outlet Pressure
Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12
Time (hours)
18 24
Time (hours)
Avg. % Difference = 1% Avg. % Difference = 3%
Well 4 Flow Well 4 Outlet Pressure
Pressure Zone 1 Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure 6.2
Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 574 of 768
2023 City of Gilroy
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.

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.

March 2023 7-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 575 of 768
Legend
Node Pressures < 40 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8 101
8"
10" - 30"
Roads
Railroads
City Limits
12 Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 24
8 152
Figure 7.1
Minimum System Pressures
(Maximum Day Demand)
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: April 28, 2021 Mile
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Legend
Node Pressures < 35 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8 101
8"
10" - 30"
Roads
Railroads
City Limits
12 Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 24
8 152
Figure 7.

Minimum System Pressures
(Peak Hour)
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: April 28, 2021 Mile
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Legend
Node Pressures > 80 psi
Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8 101
8"
10" - 30"
Roads
Railroads
City Limits
12 Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 24
8 152
Figure 7.

Maximum System Pressures
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: April 23, 2021 Mile
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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 March 2023 7-5 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 579 of 768
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
8 Existing System
Tanks
Wells
101
Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
12 10" - 30"
Roads
Railroads
152 24 152
24 24 City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbod
8 152
Figure 7.

Required Fire Flow
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: April 29, 2021 Mile
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Legend
Residual Pressure < 20 psi
Residual Pressure = 0 psi
Existing System
Tanks
Wells
8 Booster Pumps
Existing Pipes by Diameter
4" - 6"
101
8"
10" - 30"
Roads
Railroads
12 City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 24
8 152
Figure 7.

Fire Flow Analysis
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: July 7, 2021 Mile
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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
8 Less than 500 gpm
101 Existing System
Tanks
Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
12 8"
10" - 30"
Roads
152 24 152
24 24 Railroads
City Limits
8 Urban Growth Boundary
Rivers & Creeks
Waterbodies
152
Note:

It should be noted that available
fire flow values shown are based
on a residual pressure of 20 psi.

Figure 7.

Available Fire Flow
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: April 23, 2021 Mile
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Well Construction Schedule
100,000
90,000
80,000
70,000
60,000
50 45
40 35
30 25
20 15
10 5
88,633
82,274
76,372
70,893 Construct New Well
65,807 (2.2 mgd) by 2048 Construct New Well
(2.2 mgd) by 2041 61,086 Construct New Well
(2.2 mgd) by 2033 56,704
50,000
40,000
30,000
20,000
10,000
0 Existing Supply Capacity = 19.8 MGD
0 2020 2025 2030 2035
Year
2040 2045 2050
LEGEND Figure 7.7
Well Construction
Schedule
Water System Master Plan
City of Gilroy
Assumptions: Population
Required Supply Capacity
Available Supply Capacity

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).

April 22, 2022
Agenda Item 9.2 Page 583 of 768
Table 7.1 Supply Capacity Evaluation
Water System Master Plan
City of Gilroy
Well No. Rated Supply Capacity
Supply Capacity Criteria
Firm supply capacity to equal Maximum Day Demand +
Standby Well (2.6 mgd)
Groundwater Supply Capacity
No. 1
No. 2
No. 3
No. 4
No. 5
No. 6
No. 7
No. 8
No. 8A
1,200 gpm
1,100 gpm
2,300 gpm
1,200 gpm
1,600 gpm
1,500 gpm
1,700 gpm
2,200 gpm
240 gpm
1 No. 9 700 gpm
Supply vs. Demand Evaluation
Supply Balance Existing Buildout
Maximum Day Demand
(mgd) 13.7

2.6 22.3

2.6 Standby Well
(mgd)
Required Capacity
(mgd)

16.3 19.8

3.5 24.9

19.8 -5.1
Available Supply Capacity
(mgd)
Capacity Surplus/Deficiency
(mgd)
Recommended New Wells
(at 2.2 mgd each 2)
0 3.0
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.

Agenda Item 9.2 Page 584 of 768
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.

March 2023 7-11 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 585 of 768
Legend
Recommended Improvements
Tanks
Wells
New Pipes
Pipe Replacements
Existing System
Tanks
8 101
GW-10
GW-12 Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
Booster
Station 4 Tanks: 2C-1
2C-2 Booster
Station 3 & 2 3D-1
3D-2 Booster
Station 1 8"
12 Well 5-2
Tank 1A 10" - 30"
3H-1 16 Roads
Well 7
Railroads
152 24 152
24 Well 2 Well 1 24 Well 8 City Limits
Well 8A
Urban Growth Boundary
Rivers & Creeks
Waterbodies
8 152
Well 3-2 GW-11
Tanks: 2E-1
2E-2 (Planned Well)
Booster
Station 5
Well 4
Well 6
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2 16
Figure 7.8
Recommended System
Improvements
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: September 14, 2021 Mile
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Table 7.2 Existing Storage Requirements
Water System Master Plan
City of Gilroy
1 Existing Water Demands Existing Water Storage Requirements Pressure Zone
Average Day
Demand
Maximum Day Fire
Protection 3
Total, By
Pressure Zone
Operational Emergency Demand 2
(MGD) (MGD) (MG) (MG) (MG) (MG)
Zone 1
Zone 2N
Zone 2S

6.05 12.10 3.02 3.02 0.90 6.95

0.24 0.44

0.49 0.88

0.12 0.22

0.24 0.44

0.18 0.30

0.55 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.

Agenda Item 9.2 Page 587 of 768
Table 7.3 Buildout Storage
Requirements Water System Master Plan
City of Gilroy
1 Buildout Water Storage
Requirements
Buildout Water Demands
Pressure Zone Average Day
Demand
Maximum Day Fire
Protection 3
Total, By
Pressure Zone Operational Emergency Demand 2
(MGD) (MGD) (MG) (MG) (MG) (MG)
Zone 1
Zone 2N
Zone 2S

9.16 18.31 4.58 4.58 0.90 10.06

0.28 1.23

0.56 2.45

0.14 0.61

0.28 1.23

0.18 0.30

0.60 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.

Agenda Item 9.2 Page 588 of 768
Table 7.4 Storage Capacity Evaluation by Pressure Zone
Water System Master Plan
City of Gilroy
Proposed New Storage
Reservoirs
Existing Water Storage Existing Water Storage
Requirements Existing Storage Reservoirs Buildout Water StorageRequirements Buildout Water Storage
Requirements Requirements
Pressure Zone
(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 1
Zone 2N
Zone 2S
Zone 3
Total

6.0 12.1 6.0

0.4 0.7

0.2 7.3

0.9 6.9

0.5 1.0

0.4 8.8

3.0 2.0 5.3 10.3 3.4 9.2 18.3 9.2 0.9 10.1 0.0 10.3 0.24

0.2 0.4

0.1 6.9

0.5 0.9

0.2 0.3

0.2 1.6

0.4 0.4 0.8

2.1 0.3

1.2 0.4

5.2 0.3

1.2 0.6

2.4 0.4

1.8 0.2

0.3 0.2

0.6 2.1

0.9 0.0

0.0 0.8

2.1 0.9

0.22 0.00

0.00 0.7 0.7 0.7

0.3 0.4 0.4 0.8 0.5 1.0 0.7 0.1 0.1

13.7 14.1 11.2 22.3 12.2 1.6 13.7 0.10 14.17 0.46
5/13/2021
Agenda Item 9.2 Page 589 of 768
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.

March 2023 7-16 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 590 of 768
Table 7.5 Existing Pump Station Capacity Evaluation
Water System Master Plan
City of Gilroy
Pressure Zone Pump Station Capacity Analysis
2 Required Existing Capacity
Total
Capacity
Firm
Capacity
Surplus/
Deficiency
Supply
Dependent
Zones
Pump Station Supply
Dependent
Zones
Destination
Zone Source Zone 1
Destination Zone Total
(gpm) (gpm) (gpm) (gpm) (gpm) (gpm)
Pressure Zone 2N
Booster Station 1 1
1 2N
2N
3 3
1,881
1,321
3,202
1,226
Booster Station 4 878
Total 2,104 339
615
182
182 522
615
182
1,582
Pressure Zone 2S
Booster Station 5 1
1 2S
2S
1,838
1,470
3,308
1,216
Booster Station 6 934
Total 2,150 0 1,535
Pressure Zone 3
Booster Station 2 2N
2N
3 3
870
870
580
Booster Station 3 580
Total 1,740 1,160 0 978
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.

Agenda Item 9.2 Page 591 of 768
Table 7.6 Buildout Pump Station Capacity
Evaluation
Water System Master Plan City of Gilroy
Pressure Zone Pump Station Capacity Analysis
2 Required Buildout Capacity
Supply
Dependent
Zones
Total
Capacity
Firm
Capacity 1
Surplus/
Deficiency Pump Station Supply
Dependent
Zones
Destination
Zone Source Zone Destination Zone Total
(gpm) (gpm) (gpm) (gpm) (gpm) (gpm)
Pressure Zone 2N
Booster Station 1 1
1 2N
2N
3 3
1,881
1,321
3,202
1,226
Booster Station 4 878
Total 2,104 389
1,705
692
692 1,081
1,705
692
1,023
Pressure Zone 2S
Booster Station 5 1
1 2S
2S
-
-
1,838
1,470
3,308
1,216
Booster Station 6 934
Total 2,150 0 445
Pressure Zone 3
Booster Station 2 2N
2N
3 3
-
-
870
870
580
Booster Station 3 580
Total 1,740 1,160 0 468
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.

Agenda Item 9.2 Page 592 of 768

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 7-19 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 593 of 768
 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.

March 2023 7-20 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 594 of 768
Table 7.7 Schedule of Improvements
Water System Master Plan
City of Gilroy
Pipeline Improvements
Existing
Improv. No. Improv. Type Pressure Zone
Pipeline Improvements
Alignment Limits Diameter New/Parallel/
Diam. Length Replace
(in) (in) (ft)
P1-1
P1-2
Future Growth
Future Growth
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
FF Reliability
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Day Rd From Santa Teresa Blvd to Monterey Hwy
From approx. 620' n/o Day Rd to Cohansey Ave
From 2nd St to Ioof Ave
-
-
New
New
12 12
16 16
16 10
12 16
16 16
16 16
16 16
16 16
16 16
16 16
16 16
3,860
5,780
230
Monterey Hwy / Orsetti
Rd / Hwy 101
P1-3 Monterey Hwy
Murray Ave
Arroyo Cir
Lewis St
12 12
12 8
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
New
P1-4 From Well 5-02 to Ioof Ave 2,200
P1-5 From Well 7 to Ioof Ave 70
P1-6 From approx. 180' e/o Forest St to Chestnut St
From Well 3 to 6th St
230
P1-7 Forest St 10
12 12
12 12
-
320
Gilman Rd / Camino
Arroyo
P1-8 From Well 8 to approx. 80' se/o Gilman Rd
From Camino Arroyo to Cameron Blvd
From Pacheco Pass Hwy to Venture Wy
300
P1-9 Pacheco Pass Hwy
Camino Arroyo
Cameron Blvd
ROW
1,730
3,040
2,100
1,620
4,540
6,480
3,060
2,730
1,810
2,890
4,630
660
P1-10
P1-11
P1-12
P1-13
P1-14
P1-15
P1-16
P1-17
P1-18
P1-19
P1-20
P1-21
P1-22
FF Reliability
From Pacheco Pass Hwy to approx. 200' se/o Venture
Wy
FF Reliability
From Camino Arroyo to approx. 1,800' e/o Luchessa
Ave
Future Growth
Future Growth
FF Reliability
ROW / Cameron Blvd From approx. 200' se/o Venture Wy to Southside Dr - New Luchessa Ave
Thomas Rd
Rossi Ln
ROW
From Thomas Rd to Rossi Ln 12
12 12
-
Replace
Replace
Replace
New
FF Reliability From Luchessa Ave to Santa Teresa Rd
FF Reliability From Luchessa Ave to Southside Dr
From Luchessa Ave to approx. 1,800' e/o Luchessa
Ave
Future Growth
Future Growth
FF Reliability
From approx. 1,800' e/o Luchessa Ave to Southside
Dr
ROW - New
Garlic Farm Wy /
Southside Dr From Hwy 101 to Arizona Cir 12
-
Replace
Future Growth New
Future Growth
Future Growth
Southside Dr
Southside Dr
From Arizona Cir to approx. 660' e/o Arizona Cir
From approx. 660' e/o Arizona Cir to Camaron Blvd - New 3,010 280 From approx. 160' w/o Thomas Rd to approx. 110'
e/o Thomas Rd Santa Teresa Blvd - New
Proposed Storage Capacity Storage Reservoir Improvements (MG)
3H-1 Storage Capacity Zone 3 Construct an additional 0.2 MG storage reservoir at existing 3D site New 0.10 Proposed Pumping Capacity Groundwater Well Improvements (gpm)
GW-10
GW-11
GW-12
Supply Capacity
Supply Capacity
Supply Capacity
Zone 1
Zone 1
Zone 1
Construct new well near the intersection of San Ysidro Ave and Las Animas Ave Construct new well near the intersection of Camino Arroyo and Renz Lane Construct new well near the intersection of Wren Ave and Vickery Ln New
New
New
1,500
1,500
1,500
7/1/2021
Agenda Item 9.2 Page 595 of 768
Legend
Existing Pipeline Deficiencies
Headloss is Greater than 10 ft/kft
Velocity is Greater than 8 fps
Existing System
Tanks
8 Wells
101 Booster Pumps
Existing Pipes by Diameter
4" - 6"
8"
10" - 30"
Roads
12 Railroads
City Limits
Urban Growth Boundary
Rivers & Creeks
Waterbodies
152 24 152
24 24
8 152
Figure 7.

Existing Pipeline Deficiencies
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: April 23, 2021 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig7-6_ExistDeficiencies_042321.mxd Agenda Item 9.2 Page 596 of 768
2023City of Gilroy
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.

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 8-1 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 597 of 768

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 March 2023 8-2 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 598 of 768
Table 8.1 Unit Costs
Water System Master Plan
City of Gilroy
Pipelines
Pipe Size Cost1,2
(in) ($/lineal foot)
6 $153
8 $187
$211
$254
$304
$312
$336
$400
$500
$560
$705
10 12
16 18
20 24
30 36
42 Pump Stations
Estimated Pumping Station Project Cost = 2.1*10(0.7583*log(Q)+3.1951) where Q is in gpm
Storage Reservoirs ($/gallon)1,3
≤1.0 MG

1.1 MG-3.0 MG

3.1 MG - 5.0 MG
> 5 MG
$1.33
$2.11
$3.22
$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
Agenda Item 9.2 Page 599 of 768
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.

March 2023 8-4 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 600 of 768
Legend
Recommended Improvements
Tanks
Wells
New Pipes
Pipe Replacements
Existing System
Tanks
8 101
GW-10
GW-12 Wells
Booster Pumps
Existing Pipes by Diameter
4" - 6"
Booster
Station 4 Tanks: 2C-1
2C-2 Booster
Station 3 & 2 3D-1
3D-2 Booster
Station 1 8"
12 Well 5-2
Tank 1A 10" - 30"
3H-1 16
P1-5 Roads
Well 7
Railroads
152 24 16
Well 2 P1-3
152
24 24 City Limits 10
P1-6
Well 8
Well 1 Well 8A
16 P1-8 Urban Growth Boundary
Rivers & Creeks
Waterbodies
8 12
P1-7
152
Well 3-2 GW-11
Tanks: 2E-1
2E-2 (Planned Well)
Booster
Station 5
Well 4
Well 6
Booster
Station 6
Tanks: 1B
2F-1
1G-1
1G-2
16 P1-22
Figure 8.1
Capital Improvement
Program
Water System Master Plan
101 City of Gilroy
GIS
0 0.25 0.5 1
Updated: September 14, 2021 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Water\200625-MP\GL_Fig8-1_CIP_091421.mxd Agenda Item 9.2 Page 601 of 768
Table 8.2 Capital Improvement Program
Water System Master Plan
City of Gilroy

PRELIMINARY
Pipeline Information Infrastructure Costs Suggested Cost Allocation Existing
Users
Cost Sharing Baseline Constr. Estimated Const. Capital Improv.

Pressure
Zone
Construction Trigger Improv. No. Improv. Type Alignment Limits Costs Costs1 Costs2 New/Parallel/ Existing Diameter Diameter Length Unit Cost Infr. Cost Future Users Existing Users Future Users Replace (in) (in) (ft) ($) ($) ($) ($) ($)
Pipeline Improvements
P1-1
P1-2
Future Growth
Future Growth
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
FF Reliability
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Zone 1
Day Rd From Santa Teresa Blvd to Monterey Hwy
From approx. 620' n/o Day Rd to Cohansey Ave
From 2nd St to Ioof Ave
-
-
New
New
12 12
16 16
16 10
12 16
16 16
16 16
16 16
16 16
16 16
16 16
16 16
3,860
5,780
230
254
254
304
304
304
211
254
304
304
304
304
304
304
304
304
304
304
304
304
304
304
304
978,700
1,465,500
70,000
978,700
1,465,500
70,000
1,272,400
1,905,200
91,000
1,654,200
2,476,800
118,300
With Development
With Development
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
Existing Deficiency
As Funding is Available
As Funding is Available
As Funding is Available
With Development
With Development
As Funding is Available
As Funding is Available
As Funding is Available
With Development
With Development
As Funding is Available
With Development
With Development
With Development
0%
0%
100%
100%
0%
0 0
1,654,200
Monterey Hwy / Orsetti
Rd / Hwy 101
2,476,800
P1-3 Monterey Hwy
Murray Ave
Arroyo Cir
Lewis St
12 12
12 8
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
New
100%
100%
100%
100%
100%
100%
100%
100%
100%
0%
118,300
1,131,400
36,100
82,200
137,300
154,400
889,800
1,563,300
1,080,000
0 0
P1-4 From Well 5-02 to Ioof Ave 2,200
70 669,400
21,300
669,400
21,300
870,300
27,700
1,131,400
36,100
0% 0
P1-5 From Well 7 to Ioof Ave 0% 0
P1-6 From approx. 180' e/o Forest St to Chestnut St
From Well 3 to 6th St
230 48,600 48,600 63,200 82,200 0% 0
P1-7 Forest St 10
12 12
12 12
-
320 81,200 81,200 105,600
118,700
684,400
1,202,500
830,700
640,800
1,795,700
2,563,100
1,210,300
1,079,800
716,000
1,143,100
1,831,400
261,200
1,190,600
110,800
137,300 0% 0
Gilman Rd / Camino
Arroyo
P1-8 From Well 8 to approx. 80' se/o Gilman Rd
From Camino Arroyo to Cameron Blvd
From Pacheco Pass Hwy to Venture Wy
300 91,300 91,300 154,400 0% 0
P1-9 Pacheco Pass Hwy
Camino Arroyo
Cameron Blvd
ROW
1,730
3,040
2,100
1,620
4,540
6,480
3,060
2,730
1,810
2,890
4,630
660
526,400
925,000
639,000
492,900
1,381,300
1,971,600
931,000
830,600
550,700
879,300
1,408,700
200,900
915,800
85,200
526,400
925,000
639,000
492,900
1,381,300
1,971,600
931,000
830,600
550,700
879,300
1,408,700
200,900
915,800
85,200
889,800 0% 0
P1-10
P1-11
P1-12
P1-13
P1-14
P1-15
P1-16
P1-17
P1-18
P1-19
P1-20
P1-21
P1-22
FF Reliability 1,563,300
1,080,000
833,100
0% 0
0 From Pacheco Pass Hwy to approx. 200' se/o Venture
Wy
FF Reliability 0%
Future Growth
Future Growth
FF Reliability
From Camino Arroyo to approx. 1,800' e/o Luchessa Ave 100% 100%
0%
833,100
2,334,500
0 ROW / Cameron Blvd From approx. 200' se/o Venture Wy to Southside Dr - New 2,334,500 3,332,100
1,573,400
1,403,800
930,800
0% 0
Luchessa Ave
Thomas Rd
Rossi Ln
ROW
From Thomas Rd to Rossi Ln 12
12 12
-
Replace
Replace
Replace
New
100%
100%
100%
0%
3,332,100
1,573,400
1,403,800
0 FF Reliability From Luchessa Ave to Santa Teresa Rd
From Luchessa Ave to Southside Dr
0% 0
FF Reliability 0% 0
Future Growth
Future Growth
FF Reliability
From Luchessa Ave to approx. 1,800' e/o Luchessa Ave
From approx. 1,800' e/o Luchessa Ave to Southside Dr
From Hwy 101 to Arizona Cir
100%
100%
0%
930,800
1,486,100
0 ROW - New 1,486,100
2,380,900
339,600
0% 0
Garlic Farm Wy /
Southside Dr
12 -
Replace
New
100%
0%
2,380,900
Future Growth 0
Future Growth
Future Growth
Southside Dr
Southside Dr
From Arizona Cir to approx. 660' e/o Arizona Cir
From approx. 660' e/o Arizona Cir to Camaron Blvd
100%
100%
100%
339,600
1,547,800
144,100
- New 3,010
280
1,547,800
144,100
0% 0
From approx. 160' w/o Thomas Rd to approx. 110' e/o
Thomas Rd Santa Teresa Blvd - New 0% 0
Subtotal - Pipeline Improvements 15,164,400 19,714,500 25,630,000 13,883,000 11,747,000 Proposed Storage Capacity Storage Reservoir Improvements (MG) 3H-1 Storage Capacity Zone 3 Construct an additional 0.1 MG storage reservoir at existing 3D site New 0.10 133,442 133,500 173,600 225,700 813 EDU 0% 100% 0 225,700 Subtotal - Storage Reservoir Improvements 133,500 173,600 225,700 0 225,700 Agenda Item 9.2 Page 602 of 768
Table 8.2 Capital Improvement Program
Water System Master Plan
City of Gilroy

PRELIMINARY
Pipeline Information Infrastructure Costs Suggested Cost Allocation Existing
Users
Cost Sharing Baseline Constr. Estimated Const. Capital Improv.

Pressure
Zone
Construction Trigger Improv. No. Improv. Type Alignment Limits Costs Costs1 Costs2 New/Parallel/ Existing Diameter Diameter Length Unit Cost Infr. Cost Future Users Existing Users Future Users Replace (in) (in) (ft) ($) ($) ($) ($) ($)
Proposed Pumping Capacity Groundwater Well Improvements (gpm) GW-10
GW-11
GW-12
Supply Capacity
Supply Capacity
Supply Capacity
Zone 1
Zone 1
Zone 1
Construct new well near the intersection of San Ysidro Ave and Las Animas Ave Construct new well near the intersection of Camino Arroyo and Renz Lane Construct new well near the intersection of Wren Ave and Vickery Ln New
New
New
1,500
1,500
1,500
-
-
-
-
-
-
-
-
-
3,922,000
3,922,000
3,922,000
9,500 EDU
15,550 EDU
21,600 EDU
0%
0%
0%
100%
100%
100%
0 0
0 3,922,000
3,922,000
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
173,600
0 25,630,000
225,700
13,883,000 11,747,000
Storage Reservoirs 225,700
Groundwater Wells
133,500
0 0
11,766,000 0
37,621,700
11,766,000
Total Improvement Costs 15,297,900 19,888,100 13,883,000 23,738,700 3/29/2023
Notes:

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.

Agenda Item 9.2 Page 603 of 768
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.

March 2023 8-8 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 604 of 768
R&R Budget Alternatives
$5,000,000
$4,000,000
$3,000,000
$2,000,000
$1,000,000
$0
Industry Average
Pipe R&R Budgets
Industry Goal is at 1.0% per year for
100-year Pipe Replacement Cycle
2020 2025 2030 2035
Year
2040 2045 2050 2055
LEGEND
Industry Standard Replacement Schedule
Figure 8.

Pipeline Replacement
Budget Alternatives
Water System Master Plan
City of Gilroy
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
August 6, 2021
Agenda Item 9.2 Page 605 of 768
City of Gilroy

APPENDICES
March 2023 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 606 of 768
City of Gilroy

APPENDIX A
Calibration Curves
March 2023 City of Gilroy
Water System Master Plan
Agenda Item 9.2 Page 607 of 768
Avg. % Difference = 4% Avg. % Difference = 3% Tank 1A Tank 1B Pressure Zone 1 Pressure Zone 1
25 20
15 10
5 20
15 10
5 0
0 0
6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
Avg. % Difference = 11% Avg. % Difference = 3% Tank 1G 1 Pressure Zone 1
Tank 1G 2
Pressure Zone 1
25 20
15 10
5 20
15 10
5 0
0 0
6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure .1
Storage Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 608 of 768
Avg. % Difference = 5% Avg. % Difference = 6% Tank 2C 1 Tank 2C 2 Pressure Zone 2N Pressure Zone 2N
30 25
20 15
10 5
30 25
20 15
10 5
0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
Avg. % Difference = 2% Avg. % Difference = 1% Tank 2E 1 Pressure Zone 2S
Tank 2E 2
Pressure Zone 2S
30 25
20 15
10 5
30 25
20 15
10 5
0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure .

Storage Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 609 of 768
Avg. % Difference = 4% Avg. % Difference = 4% Tank 2F 1 Tank 3D 1 Pressure Zone 2S Pressure Zone 3
30 25
20 15
10 5
30 25
20 15
10 5
0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
Avg. % Difference = 5% Tank 3D 2
Pressure Zone 3
30 25
20 15
10 5
0 0 6 12 18 24
Time (hours)
LEGEND Figure .

Storage Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 610 of 768
Avg. % Difference = 1% Avg. % Difference = 1%
Well 1 Flow
Pressure Zone 1
Well 1 Outlet Pressure
Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12
Time (hours)
18 24
Time (hours)
Avg. % Difference = 0% Avg. % Difference = 149%
Well 2 Flow Well 2 Outlet Pressure
Pressure Zone 1 Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure .

Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 611 of 768
Avg. % Difference = 0% Avg. % Difference = 3%
Well 3 Flow
Pressure Zone 1
Well 3 Outlet Pressure
Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12
Time (hours)
18 24
Time (hours)
Avg. % Difference = 1% Avg. % Difference = 3%
Well 4 Flow Well 4 Outlet Pressure
Pressure Zone 1 Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure .

Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 612 of 768
Avg. % Difference = 0% Avg. % Difference = 8%
Well 5 Flow
Pressure Zone 1
Well 5 Outlet Pressure
Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12
Time (hours)
18 24
Time (hours)
Avg. % Difference = 4% Avg. % Difference = 2%
Well 6 Flow Well 6 Outlet Pressure
Pressure Zone 1 Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure .

Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 613 of 768
Avg. % Difference = 1% Avg. % Difference = 10%
Well 7 Flow
Pressure Zone 1
Well 7 Outlet Pressure
Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12
Time (hours)
18 24
Time (hours)
Avg. % Difference = 2% Avg. % Difference = 13%
Well 8 Flow Well 8 Outlet Pressure
Pressure Zone 1 Pressure Zone 1
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure
Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 614 of 768
Avg. % Difference = 15% Avg. % Difference = 64%
Well 8A Flow BS1 Flow
Pressure Zone 1 Pressure Zone 2N
3,000
2,500
2,000
1,500
1,000
500
3,000
2,500
2,000
1,500
1,000
500
0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
Avg. % Difference = 6% Avg. % Difference = 41%
BS1 Outlet Pressure BS2 Flow
Pressure Zone 2N Pressure Zone 3
150
120
90 60
30 0
3,000
2,500
2,000
1,500
1,000
500
0 0 6 12 18 24 0 6 12
Time (hours)
18 24
Time (hours)
LEGEND Figure
Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 615 of 768
Avg. % Difference = 25% Avg. % Difference = 38%
BS2 Outlet Pressure BS3 Flow
Pressure Zone 3 Pressure Zone 3
150
120
90 60
30 0
3,000
2,500
2,000
1,500
1,000
500
0 0 6 12 0
Time (hours)
18 24 6 12
Time (hours)
18 24
Avg. % Difference = 11% Avg. % Difference = 63%
BS3 Outlet Pressure BS4 Flow
Pressure Zone 3 Pressure Zone 2N
150
120
90 60
30 0
3,000
2,500
2,000
1,500
1,000
500
0 0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure
Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 616 of 768
Avg. % Difference = 17% Avg. % Difference = 2%
BS4 Inlet Pressure BS4 Outlet Pressure
Pressure Zone 2N Pressure Zone 2N
150
120
90 150
120
90 60 60
30 30
0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
Avg. % Difference = 92% Avg. % Difference = 1%
BS5 Flow BS5 Inlet Pressure
Pressure Zone 2S Pressure Zone 2S
3,000
2,500
2,000
1,500
1,000
500
150
120
90 60
30 0
0 0
6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure
Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 617 of 768
Avg. % Difference = 0% Avg. % Difference = 35%
BS5 Outlet Pressure BS6 Flow
Pressure Zone 2S Pressure Zone 2S
150
120
90 60
30 0
3,000
2,500
2,000
1,500
1,000
500
0 0 6 12 0
Time (hours)
18 24 6 12 18 24
Time (hours)
Avg. % Difference = 48% Avg. % Difference = 3%
BS6 Inlet Pressure BS6 Outlet Pressure
Pressure Zone 2S Pressure Zone 2S
150
120
90 150
120
90 60 60
30 30
0 0
0 6 12 18 24 0 6 12 18 24
Time (hours) Time (hours)
LEGEND Figure
Pump Calibration
Water System Master Plan
City of Gilroy
Telemetry Data
Model Data
April 20, 2021
Agenda Item 9.2 Page 618 of 768
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 Trigger Baseline Constr.

Improv. Type Costs Pressure
Zone Alignment Limits
Agenda Item 9.2 Page 619 of 768
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.

Costs1 Improv. No.

Pipeline Information Capital Improv.

Costs2 Construction Trigger Baseline Constr.

Improv. Type Costs 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
Agenda Item 9.2 Page 620 of 768
RESOLUTION NO. 2023-XX

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:

NOES: COUNCIL MEMBERS:

ABSTAIN: COUNCIL MEMBERS:

ABSENT: COUNCIL MEMBERS:

APPROVED:

ATTEST: __________________________
Marie Blankley, Mayor
__________________________
Thai Nam Pham, City Clerk
Agenda Item 9.2 Page 621 of 768

City of Gilroy

STAFF REPORT
Agenda Item Title: Adopt the 2022 Storm Drainage System Master Plan Meeting Date: April 3, 2023
From: Jimmy Forbis, City Administrator
Department: Public Works
Submitted By: Daryl Jordan, Public Works Director
Prepared By: Michael Lewis, Management Analyst
STRATEGIC PLAN GOALS Maintain and Improve City Infrastructure

RECOMMENDATION
Approve a resolution to adopt the 2022 Storm Drainage System Master Plan.

BACKGROUND
The City’s most recent storm drainage master plan was completed in 2004. This 2004 Master Plan included evaluation of the existing system and identifying storm drainage improvements required to serve future growth. Additionally, the 2004 Master Plan included the development of the hydrologic and hydraulic models, which were used for evaluating the storm drainage system. Improvements were recommended for servicing existing and future growth areas, and a corresponding Capital Improvement Program was developed to quantify the costs associated with each improvement. With the recent update to the 2040 General Plan, there was a need to update the 2004 Master Plan to accommodate the expected growth and land use changes identified in the updated plan.

Currently, stormwater runoff discharges to the Uvas Creek, Ronan Channel, Miller Slough Channel, Princevalle Channel, and Lower Miller Slough Channel. The City maintains a rich diversity of land use types, contributing to varying stormwater runoff containment needs. Several creeks, a vast array of agricultural lands, and small pockets of development, and the city comprises a wide array of runoff generation and conveyance within the planning area.

Agenda Item 9.3 Page 622 of 768
Adopt the 2022 Storm Drainage System Master Plan
City of Gilroy City Council Page 2 of 4 April 3, 2023 9 2 The city has multiple major watersheds within the Urban Growth Boundary that collect and convey stormwater runoff, and are as follows: Uvas Creek, Llagas Creek, and Pajaro River. The portion of the Uvas Creek Watershed within the City Limits is generally defined as the area bounded by Rancho Vista Drive to the west and Santa Teresa Boulevard to the east, with the northern and southern boundaries approximately represented by Uvas Creek and Santa Cruz Mountains, respectively.

The portion of the Lower Coyote Creek Watershed within the City Limits is generally bounded by Olea Court to the west and Llagas Creek to the east, with the northern and southern boundaries approximately represented by Fitzgerald Avenue and Luchessa Avenue, respectively.

The Pajaro River Watershed within the City Limits is generally defined as the area bounded by Uvas Creek to the west and Llagas Creek to the east, with the northern and southern boundaries approximately represented by Luchessa Avenue and Southside Drive, respectively.

To improve existing deficiencies and provide infrastructure to support future growth, it became apparent that an updated Storm Drainage Master Plan was necessary. As such, the City Council approved Akel Engineering Group, Inc. to prepare the 2022 Master Plan and a concurrent Sewer System Master Plan and Water Master Plan in August 2019. These documents were coordinated for consistency with the City’s 2040 General Plan.

ANALYSIS
The 2022 Master Plan updates elements of the 2004 Master Plan to reflect current land use conditions and 2040 General Plan updates.

The City Council authorized Akel Engineering Group, Inc. to perform the following tasks:

1. Summarize the City’s existing stormwater system facilities.

2. Document growth planning assumptions and known future developments.

3. Update the stormwater system performance criteria and design storm events.

4. Develop new hydrologic and hydraulic models.

5. Evaluate the storm drainage facilities to address hydraulic capacity requirements from existing and projected developments.

6. Recommend a capital improvement program (CIP) with an opinion of probable construction costs.

7. Perform a cost allocation analysis for cost-sharing purposes.

8. Develop a 2022 Storm Drainage System Master Plan Report.

Agenda Item 9.3 Page 623 of 768
Adopt the 2022 Storm Drainage System Master Plan
City of Gilroy City Council Page 3 of 4 April 3, 2023 9 2 RESULTS
The 2022 Master Plan provides recommendations for improvements needed to mitigate existing deficiencies and improvements needed to expand the system to service future growth identified in the 2040 General Plan. The recommended capital improvement program (Table 6.2) is attached as Attachment 1.

The Master Plan indicates that overall that the City’s storm system is in fair condition but in need of improvements to mitigate some specific deficiencies and that future capacity projects will be development driven. In total, the plan recommends 43 pipeline improvement and replacement projects in six (6) drainage areas. Seven out of forty-two projects worth $2,300,000 were completed from the last master plan. The current list includes projects carried over from the 2004 Master Plan that was not completed and new projects needed to accommodate future growth based on the updated Storm Drainage System modeling. The projects identified will be added to the City’s Capital Improvement Program and budget.

Drainage
Basin
Number of
Improvements
Needed for
Capacity
Cost of
Needed
Capacity
Improvements
Number of
Improvements
to Support
Future Growth
Cost of Future
Improvements
Ronan
Channel 4 $5,061,676 5 $5,228,524
Miller Slough 6 $2,543,000 0 $0
North Uvas 4 $7,580,300 4 $2,808,900
South Uvas 1 $217,700 0 $0
Princevalle 12 $8,391,047 1 $79,253
Lower Miller
Slough 6 $2,926,500 0 $0
Total Cost $26,720,424 $8,116,676

ALTERNATIVES
Council may modify or reject the 2022 Storm Drainage System Master Plan. This is not recommended due to the fact that this would restrict opportunities to update and maintain the citywide storm drains system.

FISCAL IMPACT/FUNDING SOURCE
The City currently has one Storm Drain Impact Fee Fund which is utilized to fund the capital improvements. The Fund, which collects revenues from impact fees from developments that impact future growth, primarily funds infrastructure/capital costs attributable to future users for future capacity needs. The Fund has a projected FY23 ending fund balance of $1.2 million. There is no current revenue source, other than Agenda Item 9.3 Page 624 of 768
Adopt the 2022 Storm Drainage System Master Plan
City of Gilroy City Council Page 4 of 4 April 3, 2023 9 2 General Fund, to fund the annual operational, maintenance, and capital costs to repair and maintain existing infrastructure.

Of the total $34.8 million in capital improvements identified in the Master Plan, approximately $8.1 million is attributable to existing users, and $26.7 million is attributable to future users - to be funded by Storm Drain Impact Fee Fund. The Master Plan capital improvements are in addition to the existing capital improvements identified by staff.

The Storm Drain Impact Fee Fund does not have sufficient fund balances to fund the $8.1 million identified in future user costs. A typical next step after the Master Plans are updated is to review and update the development impact fees to incorporate the identified future growth capital improvements and adjust the fees accordingly to ensure capital needs are adequately funded for a period of time. Staff will plan to review and update the storm drain impact fee as a departmental work plan in the upcoming fiscal year.

There is also a need to develop another revenue stream to pay for stormwater improvements, as well as operations and maintenance. Additional funding mechanisms are required since Storm Drainage is not an Enterprise Fund, like Sewer and Water, funded by user fees. Because of this, storm drain maintenance and capital projects must be paid out of the General Fund if it does not qualify for the use of storm drain impact fees. This will be studied over the next year.

NEXT STEPS
With Council adoption of the 2022 Storm Drainage System Master Plan, staff will incorporate the projects into the City’s Capital Improvement Program and plan for the delivery of these projects.

Attachments:

1. Storm Drainage System Master Plan Attachment 1

2. Storm Drainage System Master Plan Capital Improvement Program List

3. Storm Drainage System Master Plan Resolution
Agenda Item 9.3 Page 625 of 768
Agenda Item 9.3 Page 626 of 768

CITY OF GILROY
2023

STORM DRAINAGE
SYSTEM

MASTER PLAN
Final
March 2023
Agenda Item 9.3 Page 627 of 768
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 Storm Drainage System Master Plan – Final Report Dear Gary:

We are pleased to submit the draft report for the City of Gilroy Storm Drainage 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 system facilities, acceptable hydrologic and hydraulic performance criteria, and projected stormwater runoff consistent with the Urban Planning Area •
•
Development of the City’s GIS-based hydrologic and hydraulic stormwater models.

Capacity evaluation of the existing 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, 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., D. WRE
President
Enclosure: Report
7 4 3 3 N . F I R S T S T R E E T , S U I T E 1 0 3 • F R E S N O , C A L I F O R N I A 9 3 7 2 0 • ( 5 5 9 ) 4 3 6 - 0 6 0 0 • F A X ( 5 5 9 ) 4 3 6 - 0 6 2 2 www.akeleng.com
Agenda Item 9.3 Page 628 of 768
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
Agenda Item 9.3 Page 629 of 768
City of Gilroy
Storm Drainage System Master Plan
TABLE OF CONTENTS PAGE NO.

EXECUTIVE SUMMARY .................................................................................................ES-1 ES.1 STUDY OBJECTIVES .....................................................................................ES-1 ES.2 INTEGRATED APPROACH TO MASTER PLANNING ....................................ES-1 ES.3 STUDY AREA DESCRIPTION.........................................................................ES-2 ES.4 SYSTEM PERFORMANCE AND DESIGN CRITERIA.....................................ES-2 ES.5 HYDROLOGIC AND HYDRAULIC MODEL DEVELOPMENT..........................ES-6 ES.6 CAPACITY EVALUATION ...............................................................................ES-6 ES.7 CAPITAL IMPROVEMENT PROGRAM...........................................................ES-9 CHAPTER 1 - INTRODUCTION ......................................................................................1-1

1.1 1.2

1.3 1.4

1.5 1.6

1.7 1.8

1.9 BACKGROUND...............................................................................................1-1 SCOPE OF WORK..........................................................................................1-1 INTEGRATED APPROACH TO MASTER PLANNING ....................................1-3 PREVIOUS MASTER PLANS..........................................................................1-3 RELEVANT REPORTS ...................................................................................1-3 REPORT ORGANIZATION..............................................................................1-4 ACKNOWLEDGEMENTS................................................................................1-4 UNIT CONVERSIONS AND ABBREVIATIONS...............................................1-5 GEOGRAPHIC INFORMATION SYSTEMS.....................................................1-5 CHAPTER 2 – PLANNING AREA CHARACTERISTICS ................................................2-1

2.1 2.2
STUDY AREA DESCRIPTION.........................................................................2-1 WATERSHEDS AND DRAINAGE AREAS ......................................................2-1

2.2.1 Watersheds .......................................................................................2-3

2.2.2 Drainage Areas..................................................................................2-3 FLOODPLAINS ...............................................................................................2-3 EXISTING SERVICE AREAS AND LAND USE ...............................................2-6 HISTORICAL AND PROJECTED POPULATION.............................................2-6

2.3 2.4

2.5 CHAPTER 3 – SYSTEM PERFORMANCE AND DESIGN CRITERIA.............................3-1

3.1 HYDROLOGIC CRITERIA...............................................................................3-1

3.1.1 Precipitation Characteristics ..............................................................3-1

3.1.2 Design Storms...................................................................................3-1

3.1.3 Design Storm Events.........................................................................3-4

3.1.4 Soil Imperviousness...........................................................................3-4 HYDRAULIC CRITERIA ..................................................................................3-8

3.2.1 Gravity Conveyance Facilities............................................................3-8

3.2 CHAPTER 4 – EXISTING FACILITIES AND MODEL DEVELOPMENT..........................4-1

4.1 HYDROLOGIC SYSTEM OVERVIEW.............................................................4-1

4.1.1 Watersheds .......................................................................................4-1

4.1.2 Drainage Areas..................................................................................4-1

4.1.3 Drainage Sub-catchment...................................................................4-3 HYDRAULIC SYSTEM OVERVIEW ................................................................4-4

4.2.1 Conveyance System..........................................................................4-4

4.2.2 Outfalls..............................................................................................4-4 MODEL DEVELOPMENT................................................................................4-8

4.3.1 Modeling Software.............................................................................4-8

4.2 4.3
March 2023 i City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 630 of 768
City of Gilroy
Storm Drainage System Master Plan
TABLE OF CONTENTS PAGE NO.

4.3.2 Land Use and Routing Methodology..................................................4-8

4.3.3 Hydrological Soil Classification..........................................................4-9

4.3.4 Typical Channel Cross-Section..........................................................4-9

4.3.5 Physical Hydraulic Model Elements...................................................4-9 CHAPTER 5 – EVALUATION AND PROPOSED IMPROVEMENTS ..............................5-1

5.1 5.2

5.3 5.4
OVERVIEW .....................................................................................................5-1 KNOWN AREAS OF CONCERN.....................................................................5-1 PIPELINE CONVEYANCE CAPACITY EVALUATION.....................................5-1 CAPACITY EVALUATION ANALYSIS.............................................................5-1

5.4.1 Alternative 1 - 8th Street 36-inch Pipeline Improvements....................5-4

5.4.2 Alternative 2 – Diverting Stormwater Runoff to Princevalle Channel..5-4

5.4.3 Ronan Channel Drainage Area..........................................................5-9

5.4.4 Miller Slough Drainage Area..............................................................5-9

5.4.5 North Uvas Drainage Area.................................................................5-10

5.4.6 South Uvas Drainage Area................................................................5-10

5.4.7 Princevalle Drainage Area.................................................................5-11

5.4.8 Lower Miller Slough Drainage Area ...................................................5-12

5.5 OUTFALLS......................................................................................................5-12 CHAPTER 6 - CAPITAL IMPROVEMENT PROGRAM ...................................................6-1

6.1 6.2
COST ESTIMATE ACCURACY.......................................................................6-1 COST ESTIMATE METHODOLOGY...............................................................6-2

6.2.1 Unit Costs..........................................................................................6-2

6.2.2 Construction Cost Index ....................................................................6-2

6.2.3 Construction Contingency Allowance.................................................6-2

6.2.4 Project Related Costs........................................................................6-2 CAPITAL IMPROVEMENT PROGRAM...........................................................6-4

6.3.1 Capital Improvement Costs................................................................6-4

6.3.2 Pipelines............................................................................................6-4

6.3.3 Recommended Cost Allocation Analysis............................................6-9

6.3 March 2023 ii City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 631 of 768
City of Gilroy
Storm Drainage System Master Plan
TABLE OF CONTENTS PAGE NO.

FIGURES
Figure ES.1
Figure ES.2
Figure ES.3
Figure ES.4
Figure 1.1
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 2.5
Figure 3.1
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 5.1
Figure 5.2
Figure 5.3
Figure 6.1
Regional Location Map......................................................................ES-3 Planning Area....................................................................................ES-4 Existing Storm Drainage System .......................................................ES-7 Capital Improvement Program...........................................................ES-8 Regional Location Map....................................................................................1-2 Planning Area..................................................................................................2-2 Waterways and Watersheds............................................................................2-4 FEMA 100 Year Flood Zones ..........................................................................2-5 Existing Land Use ...........................................................................................2-7 2040 General Plan Land Use ..........................................................................2-8 10-Year/24-Hour Unit Hyetograph ...................................................................3-5 Storm Drainage Areas.....................................................................................4-2 Existing Modeled Storm Drainage Systems.....................................................4-5 Hydrological Soil Classification........................................................................4-10 Typical Channel Cross-Section .......................................................................4-11 Existing System Analysis 10-Year Design Storm.............................................5-2 Proposed Improvements Alternative 1.............................................................5-5 Proposed Improvements Alternative 2.............................................................5-6 Capital Improvement Program.........................................................................6-5 TABLES
Table ES.1 Hydrologic and Hydraulic Design Criteria ........................................................ ES-5 Table ES.2 Unit Costs ....................................................................................................... ES-10 Table ES.3 Capital Improvement Program......................................................................... ES-11 Table 1.1
Table 1.2
Table 2.1
Table 2.2
Table 3.1
Table 3.2
Table 3.3
Table 3.4
Table 3.5
Table 4.1
Table 4.2
Table 5.1
Table 5.2
Table 6.1
Table 6.2
Unit Conversions............................................................................................. 1-6 Abbreviations and Acronyms........................................................................... 1-7 Existing and Future Land Use ......................................................................... 2-9 Historical and Projected Population................................................................. 2-10 Precipitation Depth-Duration-Frequency Data................................................. 3-2 Precipitation Depth-Duration-Frequency Comparison...................................... 3-3 Relevant Design Storms.................................................................................. 3-6 Soil Imperviousness and SCS Curve Numbers ............................................... 3-7 Hydrologic and Hydraulic Design Criteria ........................................................ 3-9 Existing GIS Storm Pipe Inventory .................................................................. 4-6 Existing Modeled Storm Pipe Inventory........................................................... 4-7 Storm Drainage System Problem Areas.......................................................... 5-3 Proposed Improvements ................................................................................. 5-7 Unit Costs ....................................................................................................... 6-3 Capital Improvement Program......................................................................... 6-6 March 2023 iii City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 632 of 768
City of Gilroy
Storm Drainage System Master Plan

TABLE OF CONTENTS

APPENDICES
Appendix A Hydrology Review
Appendix B Storm Drainage Area Hydrologic Routing
March 2023 iv City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 633 of 768
2023 City of Gilroy

EXECUTIVE SUMMARY
This executive summary presents a brief background of the City of Gilroy’s (City) storm drainage system, the planning area characteristics, the hydrology and hydraulic criteria, and the hydrology and hydraulic model developments.

These hydrology and hydraulic models were used to evaluate the capacity adequacy of the existing stormwater drainage system, for recommending improvements to mitigate existing deficiencies and for servicing future growth. The prioritized capital improvement program accounts for growth through the Gilroy Planning Area.

ES.1 STUDY OBJECTIVES
Recognizing the importance of planning, developing, and financing system facilities to provide reliable stormwater system service to existing customers and for servicing anticipated growth within the sphere of influence, the City initiated the 2022 Storm Drainage System Master Plan.

The City of Gilroy authorized Akel Engineering Group Inc. to complete the following tasks:
•
•
•
•
•
Summarize the City’s existing stormwater system facilities.

Document growth planning assumptions and known future developments.

Update the stormwater system performance criteria and design storm event.

Develop new hydrologic and hydraulic models.

Evaluate the storm drainage facilities to address hydraulic capacity requirements from existing and projected developments.
• Recommend a capital improvement program (CIP) with an opinion of probable construction costs.
•
•
Perform a cost allocation analysis for cost sharing purposes.

Develop a 2023 Storm Drainage System Master Plan Report.

ES.2 INTEGRATED APPROACH TO MASTER PLANNING
The City implemented an integrated master planning approach and contracted the services of Akel Engineering Group Inc. to prepare the following documents:
•
•
•
2023 Water System Master Plan
2023 Sewer System Master Plan
2023 Storm Drainage System Master Plan
March 2023 ES-1 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 634 of 768
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.

ES.3 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 56,599 residents, according to Department of Finance as of January 2021. Figure ES.1 displays the City’s location.

The City’s service area 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. U.S. Route 101 divides the City in a southeast to northwest direction and the California State Route 152 (Hecker Pass Hwy) runs eastwest direction in the northern half of the City. The topography is generally 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 (UGB) of the City and Planning Area / Sphere of Influence (SOI).

The City operates and maintains a storm drainage system that covers the area within the City Limits. Currently, stormwater runoff discharges to the Uvas Creek, Ronan Channel, Miller Slough Channel, Princevalle Channel and Lower Miller Slough Channel.

ES.4 SYSTEM PERFORMANCE AND DESIGN CRITERIA
This report documents the City’s performance and design criteria that were used for evaluating hydrologic and hydraulic systems within the City’s drainage watershed (Table ES.1). Hydrologic criteria are developed to characterize the flood routing of rainfall runoff in a defined drainage system. Akel Engineering Group Inc. obtained the services of Kasraie Consulting to review the hydrologic modeling approach, applied rainfall depths and distributions, sub-catchment delineations, model runoff, and outflow hydrographs of this project. The hydraulic criteria for the storm drainage system were used to evaluate the capacity requirements of conveyance facilities.

Two design storms were used for the evaluation of the City’s existing storm drainage system, and for the future drainage conveyance facilities. The 10-year 24-hour design storm was used for evaluating the pipeline conveyance facilities as well as to size future pipeline while the 100-year 24-hour design storm was used to determine if street flooding exceeds one foot in depth.

March 2023 ES-2 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 635 of 768
Calero
Reservoir
Anderson
Reservoir
£¤
101
Morgan Hill
!(
Coyote
Reservoir
Uvas
Reservoir £¤
101
UV152 Gilroy
UV152 £¤
101
UV152
UV25
Watsonville
UV !(
UV
152
UV 129
1 £¤ UV UV 101 129 129
Legend
Figure ES.1
Regional Location Map
!( Cities
Study Area
Elevation (ft)
9 - 50
1,001 - 2,000
2,001 - 3,000
3,001 - 3,792 Storm Drainage System Master Plan
City of Gilroy
City Limits 51 - 100
Urban Growth Boundary
Highway
101 - 250
251 - 500
501 - 1,000
Waterbodies
Railroads 5GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
Flie Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig1-1RLMap_092120.mxd Agenda Item 9.3 Page 636 of 768
¤
101
Coyote
Reservoir
UV152 UV152
City of Gilroy
£¤
101
UV152
£¤
101
V25
Legend
Figure ES.2
Planning Area
City Limits General Plan Area
City Limits Area Roads
Storm Drainage System Master Plan
City of Gilroy
Specific Plan Areas
Urban Service Area
Urban Growth Boundary
Sphere of Influence Boundary
Highways
Railroads
5 Rivers & Creeks
Waterbodies GIS
0 0.5 1 2
Updated: April 15, 2022 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig2-1PlanningArea_041522.mxd Agenda Item 9.3 Page 637 of 768
Table ES.1 Hydrologic and Hydraulic Design Criteria
Storm Drainage System Master Plan
City of Gilroy
Hydrology and Hydraulics Design Criteria
Conveyance Facilities
10-Year 24-Hour design storm to determine if storm water Pipelines
Streets
have a minimum of one foot of freeboard between the top of curb and the Hydraulic Grade Line.
100-Year 24-Hour design storm to determine if flooding
exceeds one foot in depth and can flood buildings or create safety hazards.

FEMA 100-year water surface elevations used for
downstream control for facilities where 100-year flood maps are available.

Receiving Waters
(Streams, Creeks, Channels)
9/16/2020
Agenda Item 9.3 Page 638 of 768
ES.5 HYDROLOGIC AND HYDRAULIC MODEL DEVELOPMENT
Factors critical to the hydrologic model development include watersheds, drainage areas within each watershed, overland flow routing within drainage sub-catchments, and conveyance that makes full use of pipes as well as streets for routing 100-year design storm events. The hydraulic model was developed to evaluate the capacity adequacy of the City’s storm drainage system. The model was used to identify capacity deficiencies and to recommend improvements to mitigate those deficiencies.

The hydrologic and hydraulic modeling software used for evaluating the capacity adequacy of the City’s storm drainage system, InfoSWMM by Innovyze Inc. The software uses the fully dynamic St. Venant’s Equation, which has a more accurate engine for simulating backwater and surcharge conditions. The software also incorporates the use of the Manning Equation in other calculations including upstream pipe flow conditions.

The physical hydraulic model was thus developed, as shown on Figure ES.3. The model was populated to include rim elevations at manholes, invert elevations of pipelines, pipe sizes, pipe slopes, pipe lengths, and outfall elevations. Tributary catchments contributing runoff to the City’s drainage system were delineated based on 1 feet contours. The hydrologic model developed in InfoSWMM was used to generate runoff from these tributary catchments. Inflow hydrographs from the hydrologic model were then imported to the hydraulic model to simulate runoff entering the piped system.

ES.6 CAPACITY EVALUATION
The City’s hydrology and hydraulic models were used to evaluate the capacity adequacy of the existing system and for sizing future improvements.

Using the criteria described in the System Performance and Design Criteria chapter, the hydrology and hydraulic models were used to recommend capacity improvements. The recommended pipe improvements to mitigate existing system deficiencies and to serve future growth are shown on Figure ES.4.

March 2023 ES-6 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 639 of 768
¤101 Legend
Existing Modeled System
!C Outfalls
Pipes by Diameter
18" or Less
Y R
DA
D
PUEBLO ST 21" - 36"
42" or Greater
!C Channels !C
!C
!C Non-Modeled System
Pipes
Uvas Creek !C !C !C !C !C
!C
!C
!C !C
!C
!C
18 !C !C !C
!C
!C
!C Channels !C!C
18!C
!C
Roads
!C
!C !C !C Railroads
!C
City Limits V
!C
152 V152
Urban Growth Boundary
Rivers & Creeks
Waterbodies
!C
!C !C
!C
!C !C !C !C V152 !C !C
!C !C
!C !C
!C !C
!C !C
!C
!C !C
!C
!C !C
¤101
Princevalle
!C !C !C !C !C !C
!C
!C
!C
!C
!C
!C
Figure ES.3
Existing Modeled Storm !C !C
Drainage System
Storm Drainage System Master Plan
City of Gilroy 5GIS
0 0.25 0.5 1
Updated: April 14, 2022 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig4-1_ExistingSys_041422.mxd Agenda Item 9.3 Page 640 of 768
¤101 Legend
Proposed Improvements
!C Outfall
Pipes
Existing Modeled System Y R
DA
D
PUEBLO ST !C Outfalls
Pipes by Diameter
!C 18" or Less !C
!C
Uvas Creek !C !C !C !C !C !C 21" - 36"
!C
!C
!C 42" or Greater
Channels
!C
!C
!C
18 !C !C !C
!C
!C
!C !C!C
18!C
!C
Non-Modeled System
Pipes !C
!C !C !C
MS-5 !C
Channels
V NU-2
!C
152 V 24
MS-2
152
Roads !C
PR-3 Railroads !C !C
42 PR-2
!C
!C !C !C !C V152 City Limits !C !C
!C !C
!C !C LM-3 Urban Growth Boundary
Rivers & Creeks
Waterbodies
!C !C
!C PR-6 !C
!C
!C !C
!C
!C !C
¤101
Princevalle
!C !C !C !C !C !C
!C
!C
!C
!C
!C
90 NU-8
!C
!C
Figure ES.4
Capital Improvement !C !C
Program
Storm Drainage System Master Plan
City of Gilroy 5GIS
0 0.25 0.5 1
Updated: April 15, 2022 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig6-1_CIP_Scen2_041522.mxd Agenda Item 9.3 Page 641 of 768
ES.7 CAPITAL IMPROVEMENT PROGRAM
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 ES.3, and are graphically represented on Figure ES.4. Each improvement was assigned a uniquely coded identifier corresponding to its respective hydrologic drainage area. The baseline costs for pipelines are shown in Table ES.2.

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 Storm Drainage System Master Plan were benchmarked using a 20-City national average ENR CCI of 12,647, reflecting a date of November 2021. In total, the CIP project cost totals approximately $34.8 million dollars.

March 2023 ES-9 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 642 of 768
Table ES.2 Unit Costs
Storm Drainage System Master Plan
City of Gilroy
Pipelines
(in) ($/Lineal Foot)
24 245
27 30
36 42
48 54
60 66
72 84
90 283
302
358
414
489
545
564
622
678
866
928
Pipeline Casings
$22 per inch diameter per liner foot
3/29/2023
Note :

1. Unit costs are based on an ENR CCI Index Value
of 13,176 (March 2023).

Agenda Item 9.3 Page 643 of 768
Table ES.3 Capital Improvement Program
Storm Drainage System Master Plan
City of Gilroy
Suggested Cost
Allocation Pipeline Improvements Infrastructure Costs Cost Sharing Improv.

No.

Alignment Limits Baseline
Constr. Costs Constr. Costs
Estimated Capital Improv.

Costs Existing
Diameter
(in)
New/Parallel/
Replace
Existing Future
Users
(%)
Diameter Length Unit Cost Infr. Cost Existing Users Future users Users (in) (ft) ($/lf) ($) ($) ($) ($) (%) ($) ($)
Ronan Channel Drainage Area
RC-1
RC-2
RC-3
RC-4
RC-5
RC-6
RC-7
RC-8
RC-9
Sunrise Dr
Mantelli Dr
Zamzow Ct
Cohansey Ave
Murray Ave
Murray Ave
From Dream Catcher Way to Golden Sky Way
From Muir Drive to Delta Dr
18 18
-
Replacement
Replacement
New
30 24
48 48
48 48
36 48
42 400
1,250
1,200
1,450
2,800
600
302
245
489
489
489
489
358
489
414
120,601
306,506
586,990
709,280
1,369,643
293,495
1,216,516
1,675,367
62,114
121,000
307,000
587,000
710,000
1,370,000
294,000
1,217,000
1,676,000
63,000
158,000
400,000
764,000
923,000
1,781,000
383,000
1,583,000
2,179,000
82,000
206,000
520,000
100%
100%
8%
0%
0%
206,000
520,000
74,621
0 0
0 From approx. 1,250' n/o Cohansey Ave to
Cohansey Ave
From approx. 350' e/o Monterey Rd to Murray
Ave
994,000 92%
100%
91%
87%
9%
919,379
1,200,000
2,096,660
430,822
182,080
605,415
14,341
- New 1,200,000
2,316,000
498,000
0%
From Cohansey Ave to Tomkins Ct
From Tomkins Ct to Ronan Channel
- New 9% 219,340
67,178
1,875,920
2,227,585
92,659
24 -
Replacement
New
13%
91%
79%
87%
No Name Uno/Las Animas From approx. 1,500' s/o Buena Vista Ave to San 3,400 3,425
150
2,058,000
2,833,000
107,000
Ave Ysidro Ave
From Las Animas Ave to approx. 500' n/o
Leavesley Rd
From approx. 220' e/o Forest St to approx. 360'
e/o Forest St
San Ysidro Ave - New 21%
Leavesley Rd 18 Replacement 13%
Subtotal - Ronan Channel Drainage Area 6,345,000 8,253,000 10,732,000 5,283,303 5,448,697 Miller Slough Drainage Area
MS-1
MS-2
MS-3
MS-4
MS-5
MS-6
Wren Ave
First St
From approx. 290' n/o First St to Lawrence Dr
From approx. 180' e/o Princevalle St to Sargent St
From First St to Broadway
24 18
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
30 24
24 30
30 27
2,325
525
302
245
245
302
302
283
700,991
128,732
104,212
324,114
120,601
190,847
701,000
129,000
105,000
325,000
121,000
191,000
912,000
168,000
137,000
423,000
158,000
249,000
1,186,000
219,000
179,000
550,000
206,000
324,000
100%
100%
100%
100%
100%
100%
0%
0%
0%
0%
0%
0%
1,186,000
219,000
179,000
550,000
206,000
324,000
0 0
0 0
0 0
Sargent St
Broadway
Church St
Monterey Rd
18 425
From Sargent St to Church St 18/21
21 1,075
From Broadway to approx. 100' s/o Howson St 400
From Second St to First St 18/24 675
Subtotal - Miller Slough Drainage Area 1,572,000 2,047,000 2,664,000 2,664,000 0 North Uvas Drainage Area
From approx. 3,080' w/o Santa Teresa Blvd to
approx. 360' w/o Santa Teresa Blvd
From approx. 360' w/o Santa Teresa Blvd to
Santa Teresa Blvd
From approx. 70' s/o Hecker Pass Hwy to Uvas
Creek
NU-1
NU-2
NU-3
NU-4
Hecker Pass Hwy
Hecker Pass Hwy
Santa Teresa Blvd
Westwood Dr
- New 30
30 30
24 2,825
350
302
302
302
245
851,742
105,526
776,367
104,212
852,000
106,000
777,000
105,000
1,108,000
138,000
1,441,000
180,000
0%
0%
100%
100%
100%
0%
0 1,441,000
180,000
1,315,000
0 24
24 18
Replacement
Replacement
Replacement
0 2,575 0
425
1,011,000
137,000
1,315,000
179,000
0%
From approx. 150' s/o Third St to Kentwood Ct 100% 179,000 Agenda Item 9.3 Page 644 of 768
Table ES.3 Capital Improvement Program
Storm Drainage System Master Plan
City of Gilroy
Suggested Cost
Allocation Pipeline Improvements Infrastructure Costs Cost Sharing Improv.

No.

Alignment Limits Baseline
Constr. Costs Constr. Costs
Estimated Capital Improv.

Costs Existing
Diameter
(in)
New/Parallel/
Replace
Existing Future
Users
(%)
Diameter Length Unit Cost Infr. Cost Existing Users Future users Users (in) (ft) ($/lf) ($) ($) ($) ($) (%) ($) ($)
NU-5
NU-6
NU-7
NU-8
Monterey Rd
Monterey Rd
ROW
From Princevalle Channel to Victoria Dr -
42 -
New
Replacement
New
90 90
90 90
775
2,175
975
928
928
928
928
718,859
2,017,443
904,371
927,560
719,000 935,000 1,216,000 100%
100%
100%
100%
0%
0%
0%
0%
1,216,000 0
From Victoria Dr to approx. 950' n/o Farman Ln 2,018,000 905,000
928,000
2,624,000
1,177,000
1,207,000
3,412,000
1,531,000
1,570,000
3,412,000
1,531,000
1,570,000
0 0
0 From Monterey Rd to approx. 970' n/o Uvas
Creek
ROW From approx. 970' n/o Uvas Creek to Uvas Creek - New 1,000 Subtotal - North Uvas Drainage Area 6,410,000 8,337,000 10,844,000 7,908,000 2,936,000 South Uvas Drainage Area
From Carnoustie Ct to approx. 380' nw/o
Carnoustie Ct SU-1 St Andrews Cir 18 Replacement 36 375 358 134,175 135,000 176,000 229,000 100% 0% 229,000 0 Subtotal - South Uvas Drainage Area 135,000 176,000 229,000 229,000 0 Princevalle Drainage Area
PR-1
PR-2
PR-3
PR-4
PR-5
PR-6
PR-7
PR-8
PR-9
PR-10
PR-11
PR-12
PR-13
Third St
Third St
From Santa Paula Dr to Wren Ave 27
27 Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
New
30 42
48 48
48 48
48 30
54 24
24 48
48 825
675
302
414
489
489
489
489
489
302
545
245
245
489
489
248,739
279,515
97,832
249,000
280,000
98,000
324,000
364,000
128,000
605,000
431,000
255,000
796,000
491,000
870,000
264,000
201,000
1,575,000
494,000
422,000
474,000
167,000
787,000
561,000
332,000
1,035,000
639,000
1,131,000
344,000
262,000
2,048,000
643,000
100%
100%
100%
100%
100%
100%
100%
100%
100%
84%
0%
0%
0%
0%
0%
0%
0%
0%
0%
16%
11%
0%
0%
422,000
474,000
167,000
787,000
561,000
332,000
1,035,000
639,000
1,131,000
288,575
234,103
2,048,000
643,000
0 From Wren Ave to approx. 170' e/o Santa
Theresa Dr
From approx. 170' e/o Santa Theresa Dr to Santa
Theresa Dr
0 Third St 27 200 0
Santa Theresa Dr
ROW
From Third St to approx. 300' s/o Fourth St
From Santa Theresa Dr to Miller Ave
From approx. 300' s/o Fourth St to Fifth St
From Miller Ave to Princevalle St
From Third St to Fifth St
27/30
30 950 464,700
330,182
195,663
611,448
376,877
668,183
202,294
153,253
1,210,667
379,098
465,000
331,000
196,000
612,000
377,000
669,000
203,000
154,000
1,211,000
380,000
0 675 0
Miller Ave
Fifth St
30 400 0
30 1,250
1,250
1,225
825
0 Princevalle St
Princevalle St
Alexander St
Banes Ln
18 0
From Fifth St to Seventh St 42 0
55,425
27,897
0 From Tenth St to Banes Ln 18
From Alexander St to Automall Pkwy
From approx. 380' n/o 8th St to Angra Way
From Angra Way to Princevalle Channel
18 625 89%
Monterey Rd
Monterey Rd
- 2,475
775
100%
42 Replacement 100% 0
Subtotal - Princevalle Drainage Area 5,225,000 6,798,000 8,845,000 8,761,678 83,322 Agenda Item 9.3 Page 645 of 768
Table ES.3 Capital Improvement Program
Storm Drainage System Master Plan
City of Gilroy
Suggested Cost
Allocation Pipeline Improvements Infrastructure Costs Cost Sharing Improv.

No.

Alignment Limits Baseline
Constr. Costs Constr. Costs
Estimated Capital Improv.

Costs Existing
Diameter
(in)
New/Parallel/
Replace
Existing Future
Users
(%)
Diameter Length Unit Cost Infr. Cost Existing Users Future users Users (in) (ft) ($/lf) ($) ($) ($) ($) (%) ($) ($)
Lower Miller Slough Drainage Area
LM-1
LM-2
LM-3
LM-4
LM-5
LM-6
Fourth St
Monterey Rd
Monterey Rd
Monterey Rd
ROW
From Eigleberry St to Monterey Rd
From Fourth St to Sixth St
18 27
27 33
18 24
Replacement
Replacement
Replacement
Replacement
Replacement
Replacement
30 36
42 42
24 36
400
1,250
425
302
358
414
414
245
358
120,601
447,248
175,991
320,924
275,855
465,138
121,000
448,000
176,000
321,000
276,000
466,000
158,000
583,000
229,000
418,000
359,000
606,000
206,000
758,000
298,000
544,000
467,000
788,000
100%
100%
100%
100%
100%
100%
0%
0%
0%
0%
0%
0%
206,000
758,000
298,000
544,000
467,000
788,000
0 0
0 0
0 0
From Sixth St to Hornlein Ct
From Hornlein Ct to approx. 240' n/o Eighth St
From Rosanna St to Monterey Rd
From Sixth St to Eighth St
775
1,125
Alexander St 1,300
Subtotal - Lower Miller Slough Drainage Area 1,808,000 2,353,000 3,061,000 3,061,000 0 Total Costs
Subtotal - Ronan Channel Drainage Area
Subtotal - Miller Slough Drainage Area
Subtotal - North Uvas Drainage Area
Subtotal - South Uvas Drainage Area
Subtotal - Princevalle Drainage Area
Subtotal - Lower Miller Slough Drainage Area
6,345,000 8,253,000 10,732,000
1,572,000 2,047,000 2,664,000
6,410,000 8,337,000 10,844,000
5,283,303
2,664,000
7,908,000
229,000
5,448,697
0 2,936,000
135,000 176,000 229,000 0
83,322
0 5,225,000 6,798,000 8,845,000
1,808,000 2,353,000 3,061,000
8,761,678
3,061,000
Total Improvement Costs 21,495,000 27,964,000 36,375,000 27,906,981 8,468,019 3/29/2023
Notes:

1. Cost estimates are based on the Engineering News Record (ENR) construction cost index (CCI) of 13,176 for March 2023

2. Baseline construction costs plus 30% to account for unforeseen events and unknown conditions.

3. Estimated construction cost plus 30% to cover other costs including: engineering design, project administration (developer and City staff), construction management and inspection, and legal costs.

Agenda Item 9.3 Page 646 of 768
2023 City of Gilroy
CHAPTER 1 - INTRODUCTION
This chapter provides a brief background of the City of Gilroy’s (City) Storm Drainage system, the need for this master plan, and the objectives of the study. 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 City of Hollister (Figure 1.1). The City provides storm drainage services to approximately 17,000 residential, commercial, industrial, and institutional establishments. The City currently owns and operates more than 132 miles of storm drainage pipelines, with up to 84-inch pipe sizes.

In 2004, the City of Gilroy developed a Storm Drainage System Master Plan that identified capacity deficiencies in the storm drainage system and recommended improvements to alleviate deficiencies and serve future developments in the Gilroy Planning Area.

Recognizing the importance of planning, developing, and financing system facilities to provide enhanced stormwater drainage system service to existing customers and for servicing anticipated growth within the Gilroy Planning Area, the City initiated updating elements of the 2004 Storm Drainage System Master Plan, to reflect current land use conditions and General Plan updates.

1.2 SCOPE OF WORK
City Council approved Akel Engineering Group Inc. to prepare this 2022 Storm Drainage System Master Plan (SDSMP) and a concurrent Water System Master Plan and Sewer System Master Plan. The 2022 SDSMP evaluates the City’s storm drainage system and recommends capacity improvements necessary to service the needs of existing users and for servicing the future growth of the City. This 2022 SDSMP is intended to serve as a tool for planning and phasing the construction of future storm drainage infrastructure for the projected buildout of the City’s service area. The planning area and horizon for this master plan is based on the City’s 2040 General Plan. Should planning conditions change, and depending on their magnitude, adjustments to the master plan recommendations might be necessary.

The master plan included the following tasks:
•
•
•
•
Summarize the City’s existing stormwater system facilities.

Document growth planning assumptions and known future developments.

Update the stormwater system performance criteria and design storm event.

Develop new hydrologic and hydraulic models.

March 2023 1-1 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 647 of 768
Calero
Reservoir
Anderson
Reservoir
£¤
101
Morgan Hill
!(
Coyote
Reservoir
Uvas
Reservoir £¤
101
UV152 Gilroy
UV152 £¤
101
UV152
UV25
Watsonville
UV !(
UV
152
UV 129
1 £¤ UV UV 101 129 129
Legend
Figure 1.1
Regional Location Map
!( Cities
Study Area
Elevation (ft)
9 - 50
1,001 - 2,000
2,001 - 3,000
3,001 - 3,792 Storm Drainage System Master Plan
City of Gilroy
City Limits 51 - 100
Urban Growth Boundary
Highway
101 - 250
251 - 500
501 - 1,000
Waterbodies
Railroads 5GIS
0 0.5 1 2
Updated: September 21, 2020 Miles
Flie Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig1-1RLMap_092120.mxd Agenda Item 9.3 Page 648 of 768
•
•
Evaluate the storm drainage facilities to address hydraulic capacity requirements from existing and projected developments.

Recommend a capital improvement program (CIP) with an opinion of probable construction costs.
•
•
Perform a cost allocation analysis for cost sharing purposes.

Develop a 2023 Storm Drainage System Master Plan Report.

1.3 INTEGRATED APPROACH TO MASTER PLANNING
This City implemented an integrated master planning approach and contracted the services of Akel Engineering Group Inc. 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 2040 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 storm drainage master plan was completed in 2004. This master plan included evaluation of servicing growth to the planning area, evaluating the existing system, and identifying storm drainage improvements required to serve future growth. Additionally, the 2004 master plan included the development of the hydrologic and hydraulic models, which were used for evaluating the storm drainage system. Improvements were recommended for servicing existing and future growth areas, and a corresponding Capital Improvement Program was developed to quantify the costs associated with each improvement.

1.5 RELEVANT REPORTS
The City has completed several special studies intended to evaluate localized growth. These reports were referenced and used during the capacity analysis. The following lists relevant reports 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.

March 2023 1-3 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 649 of 768
• City of Gilroy Storm Drainage System Master Plan, May 2004 (2004 SDSMP). This report documents the planning and performance criteria, evaluates the storm drainage system, recommends improvements, and provides an estimate of costs.

1.6 REPORT ORGANIZATION
The Storm Drainage System Master Plan report contains the following chapters:

Chapter 1 – Introduction. This chapter provides a brief background of the City’s Storm Drainage system, the need for this master plan, and the objectives of the study. Unit conversions, abbreviations, and definitions are also provided in this chapter.

Chapter 2 – Planning Area Characteristics. This chapter presents a discussion of the planning area characteristics affecting the hydrologic and hydraulic analysis of this master plan. These characteristics include soil, topography, floodplains, and land use.

Chapter 3 – System Performance and Design Criteria. This chapter presents the City’s planning and design criteria that were used for evaluating hydrologic and hydraulic systems within the City’s drainage watershed.

Chapter 4 –Existing Facilities Model Development. This chapter defines the hydrologic delineation of storm drainage areas, routing to their respective receiving facilities, and includes the hydrologic model development. Additionally, this chapter includes an overview of the storm drainage system, and the hydraulic model development.

Chapter 5 – Evaluation and Proposed Improvements. This chapter presents a summary of the storm drainage system evaluation and identifies improvements needed to mitigate existing deficiencies, as well as improvements needed to expand the system and service future growth.

Chapter 6 – Capital Improvement Program. This chapter provides a summary of the recommended storm drainage system improvements intended to mitigate existing capacity deficiencies and for accommodating anticipated future growth. This chapter also presents the cost criteria and methodologies for developing the Capital Improvement Program (CIP). Finally, a cost 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:
•
•
•
Daryl Jordan, P.E.; Director of Public Works
Gary Heap, P.E.; City Engineer
Jorge Duran, P.E.; Senior City Engineer
March 2023 1-4 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 650 of 768
• 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 storm drainage system. Where it was necessary to report values in smaller or large 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 are shown on Table 1.1.

Various abbreviations and acronyms were also used in this report to represent relevant storm drainage 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:
•
•
•
Developing the physical characteristics of the hydraulic model.

Delineating stormwater tributary areas, and outlining watershed areas.

Extracting ground elevations along the storm drainage system from available contour maps and digital elevation models.
• Generating maps and exhibits used in this master plan.

March 2023 1-5 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 651 of 768
Table 1.1 Unit Conversions
Storm Drainage System Master Plan
City of Gilroy
Volume Unit Calculations
To Convert From: To:
gallons
cubic feet
million gallons
gallons
Multiply by:
325,857
43,560

0.3259

7.481

2.296 x 10-5
acre feet
acre feet
acre feet
cubic feet
cubic feet acre feet

7.481 x 10-6

0.1337
cubic feet
gallons
million gallons
cubic feet

3.069 x 10-6 gallons acre feet
1 x 10-6
1,000,000
133,672

3.069
gallons million gallons
gallons
cubic feet
acre feet
million gallons
million gallons
million gallons
Flow Rate Calculations
To Convert From: To: Multiply By:

8.93 x 10-4 ac-ft/yr mgd

1.381 x 10-3

0.621
ac-ft/yr
ac-ft/yr
ac-ft/yr
cfs
cfs
cfs
cfs
gpm
gpd
mgd
gpm
ac-ft/yr
gpd
892.7

0.646
448.8
724
cfs 646300
1 x 10-6 gpd mgd

1.547 x 10-6

6.944 x 10-4

1.12 x 10-3

1.44 x 10-3
gpd
gpd
gpd
gpm
cfs
gpm
ac-ft/yr
mgd

2.228 x 10-3

1.61 gpm
gpm
gpm
mgd
mgd
mgd
mgd
cfs
ac-ft/yr
gpd
cfs
gpm
1,440

1.547
694.4
ac-ft/yr 1,120
gpd 1,000,000
9/16/2020
Agenda Item 9.3 Page 652 of 768
Table 1.2 Abbreviations and Acronyms
Storm Drainage System Master Plan
City of Gilroy
Abbreviation Expansion Abbreviation Expansion
2016 Storm Drainage System
Master Plan 2016 SDSMP
10Yr-24Hr
100Yr-24Hr
AC
ft
fps
Feet
10-Year 24-Hour
100-Year 24-Hour
Acre
Feet per Second
Geographic Information Systems
High Density Polyethylene Pipe
Inch
GIS
HDPE
ACP Asbestos Cement Pipe in
Akel Akel Engineering Group, Inc. in/hr
LF
Inch per Hour
California Department of
Transportation
Caltrans
City
Linear Feet
City of Gilroy mi Miles
National Resource Conservation
Service
National Oceanic and Atmospheric
Administration
CCI Construction Cost Index
Cubic Feet per Second
Cast Iron Pipe
NRCS
NOAA
PVC
cfs
CI Polyvinyl Chloride Pipe
CIP Capital Improvement Program
County of Santa Clara
Corrugated Metal Pipe
Ductile Iron Pipe
RCP Reinforced Concrete Pipe
County Right of Way
CMP
ROW
SCS Soil Conservation Service
DIP SOI Sphere of Influence
DDF Depth Duration Frequency
Engineering News Record
Environmental Protection Agency
Department of Finance
SSURGO
SWMM
UGB
UWMP
VCP
Soil Survey Geographic database
Stormwater Management Model
Urban Growth Boundary
Urban Water Management Plan
ENR
EPA
DOF
Federal Emergency Management
Agency
FEMA Verified Clay Pipe
9/16/2020
Agenda Item 9.3 Page 653 of 768
2023 City of Gilroy
CHAPTER 2 – PLANNING AREA CHARACTERISTICS
This chapter presents a discussion of the planning area characteristics affecting the hydrologic and hydraulic analysis of this master plan. These characteristics include soil, topography, floodplains, and land use.

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 57,000 residents, according to Department of Finance as of January 2021. Figure 1.1 displays the City’s location.

The City’s service area 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. U.S. Route 101 divides the City in a southeast to northwest direction and the California State Route 152 (Hecker Pass Hwy) runs eastwest direction in the northern half of the City. The topography is generally 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 (UGB) of the City and Planning Area / Sphere of Influence (SOI).

The City operates and maintains a storm drainage system that covers the area within the City Limits. Currently, stormwater runoff discharges to the Uvas Creek, Ronan Channel, Miller Slough Channel, Princevalle Channel and Lower Miller Slough Channel, as describe in the following section.

2.2 WATERSHEDS AND DRAINAGE AREAS
The City of Gilroy maintains a rich diversity of land use types, which contribute to a varying degree of stormwater runoff containment needs. Several creeks, a vast array of agricultural lands, small pockets of development, and the City itself comprises the wide array of runoff generation and conveyance within the planning area.

March 2023 2-1 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 654 of 768
¤
101
Coyote
Reservoir
UV152 UV152
City of Gilroy
£¤
101
UV152
£¤
101
V25
Legend
Figure 2.1
Planning Area
City Limits General Plan Area
City Limits Area Roads
Storm Drainage System Master Plan
City of Gilroy
Specific Plan Areas
Urban Service Area
Urban Growth Boundary
Sphere of Influence Boundary
Highways
Railroads
5 Rivers & Creeks
Waterbodies GIS
0 0.5 1 2
Updated: April 15, 2022 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig2-1PlanningArea_041522.mxd Agenda Item 9.3 Page 655 of 768

2.2.1 Watersheds
The City has multiple major watersheds within the Urban Growth Boundary that collect and convey stormwater runoff, and are as follows: Uvas Creek, Llagas Creek, and Pajaro River (Figure 2.2). The following are brief descriptions of the three watersheds:
• Uvas Creek Watershed – The portion of the Uvas Creek Watershed within the City limits is generally defined as the area bounded by Rancho Vista Drive to the west and Santa Teresa Boulevard to the east, with the northern and southern boundaries approximately represented by Uvas Creek and Santa Cruz Mountain respectively. • Llagas Creek Watershed – The portion of the Lower Coyote Creek Watershed within the City limits is generally bounded by Olea Court to the west and Llagas Creek to the east, with the northern and southern boundaries approximately represented by Fitzgerald Avenue and Luchessa Avenue respectively.
• Pajaro River Watershed – The Pajaro River Watershed within the City limits is generally defined as the area bounded by Uvas Creek to the west and Llagas Creek to the east, with the northern and southern boundaries approximately represented by Luchessa Avenue and Southside Drive respectively.

2.2.2 Drainage Areas
Watersheds are typically comprised of smaller drainage areas defined by topographical features.

Additionally, these drainage areas may comprise multiple soil types as defined by Natural Resources Conservation Service (NRCS). The City’s storm drainage system consists of a series of conveyance networks. These networks have different means of disposing of stormwater runoff, which include outfall points to Uvas Creek or Llagas Creek, or being conveyed to the canals and sloughs throughout the City.

2.3 FLOODPLAINS
Floodplains are important for delineating the extent of water-level rise during major floods.

Typically, floodplains are estimated for the historic 100-Year and 500-Year flood. Most of the floodplains for the City are located southeast boundary of the City limits, as shown on Figure 2.3.

The Federal Emergency Management Agency (FEMA) produces Flood Insurance Rate Maps that show areas subject to flooding during major storm events. The flood risk information shown on these maps is based on historical data, including meteorological, hydrological, and hydraulic data for the specified area. The map creation is a result of the 1968 National Flood Insurance Program, aimed at reducing or preventing property owner losses due to flooding by allowing premiums to be paid for those in need of protection.

March 2023 2-3 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 656 of 768
£¤101 Legend
Existing Modeled System
Llagas Creek
Watershed
!C Outfalls
Pipes by Diameter
18" or Less
Y R
DA
D
PUEBLO ST 21" - 36"
Uvas Creek
Watershed
42" or Greater
!C Channels !C
!C
!C !C !C Non-Modeled System
Pipes
Uvas Creek !C !C !C !C !C
!C Pajaro River
Watershed
!C
18 !C
!C
!C
!C !C !C
!C !C Channels !C!C
18!C
!C
Watershed Boundaries
Llagas Creek
Pajaro River
Uvas Creek
!C
!C !C !C
!C
!C
UV
!C
152 UV152
!C
Roads !C !C
!C
!C !C !C !C UV152 Railroads !C !C
!C !C
!C !C !C !C City Limits
!C !C
!C
!C !C
!C Urban Growth Boundary
Rivers & Creeks
Waterbodies
!C !C
£¤101
Princevalle
!C !C !C !C !C !C
!C
!C
!C
!C
!C
!C
Figure 2.2
Waterways !C !C
and Watersheds
Storm Drainage System Master Plan
City of Gilroy 5GIS
0 0.25 0.5 1
Updated: April 14, 2022 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig2-2_Watersheds_041522.mxd Agenda Item 9.3 Page 657 of 768
¤101 Legend
FEMA 100 Year Flood Zones

0.2% Annual Chance Flood Hazard
1% Annual Chance Flood Hazard
Regulatory Floodway
Area of Minimal Flood Hazard
Area with Reduced Risk Due to Levee
Area of undetermined Flood Hazard
Existing Modeled System
Y R
DA
D

PUEBLO ST
!C
!C
!C
!C Outfalls
!C
!C
Uvas Creek !C !C !C !C !C Pipes by Diameter
18" or Less
21" - 36"
!C
!C !C
!C
!C
18 !C
!C
!C !C !C
!C !C!C
18!C
42" or Greater
Channels
!C
!C
!C Non-Modeled System
Pipes
!C !C
!C
V
!C
152 UV152 Channels
!C Roads
!C !C
!C Railroads
!C !C
!C
!C !C UV152
!C City Limits
!C!C !C !C
!C !C Urban Growth Boundary
!C !C
!C
Rivers & Creeks
Waterbodies
!C !C
!C
!C !C
£¤101
Princevalle
!C !C !C !C !C !C
!C
!C
!C
!C
!C
!C
Figure 2.3
FEMA 100 Year !C !C
Flood Zones
Storm Drainage System Master Plan
City of Gilroy 5GIS
0 0.25 0.5 1
Updated: April 14, 2022 Mile
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig2-3_FEMA_Flood_041522.mxd Agenda Item 9.3 Page 658 of 768

2.4 EXISTING SERVICE AREAS AND LAND USE
The City’s storm drainage system services residential and non-residential lands within the City limits, as summarized on Table 2.1, and shown graphically on Figure 2.4. Areas within the City limit include 4,197 acres of developed lands and 4,905 acres of undeveloped lands.

At ultimate development of the General Plan, the City’s storm drainage system is anticipated to service approximately 3,045 acres of residential land use, 4,750 acres of non-residential land use, and 2,477 acres of open space land use, for a total of 10,272 acres inside the City’s Urban Growth Boundary (Table 2.1). The land use designations utilized in this master plan are consistent with the Land Use Element of the City’s 2040 General Plan received from the City’s planning division, and shown on Figure 2.5.

2.5 HISTORICAL AND PROJECTED POPULATION
According to California Department of Finance (DOF) population estimates, the 2021 City population is approximately 57,000 people. From 2015 to present, the City’s service area has observed an average annual growth rate of approximately 0.7%. This 2022 SDSMP 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 2.2.

March 2023 2-6 City of Gilroy
Storm Drainage System Master Plan
Agenda Item 9.3 Page 659 of 768
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101
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
V Vacant 152
UV City Limits 152
Roads
Railroads
Rivers & Creeks
Waterbodies
UV25
£¤
101
Figure 2.4
Existing Land Use
Storm Drainage System Master Plan
City of Gilroy 5GIS
0 0.5 1 2
Updated: April 15, 2022 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig2-4_ExistLandUse_041522.mxd Agenda Item 9.3 Page 660 of 768
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101
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
V Industrial Park 152
UV Public and Quasi-Public Facility
Neighborhood District
Mixed Use
152
Rural County
Open Space
Park and Recreation Facility
Specific Plan Areas
Downtown
Glen Loma Ranch
Hecker Pass
Roads
Railroads
Rivers & Creeks
UV25 Waterbodies £¤
101
Figure 2.5
2040 General Plan
Land Use
Storm Drainage System Master Plan
City of Gilroy 5GIS
0 0.5 1 2
Updated: April 15, 2022 Miles
File Path: P:\xGIS\GIS_Projects\Gilroy\Storm\200626-MP\GL_Fig2-5_GeneralPlanLU_041522.mxd Agenda Item 9.3 Page 661 of 768
Table 2.1 Existing and Future Land Use
Storm Drainage System Master Plan
City of Gilroy
Existing Development
Within City Limits
Future Development
Total
Development
Subtotal
Existing
Within City Limits
Subtotal
Future
Development
General Plan Land Use
Classification
Existing Land Use
Classification
Urban Growth
Development - Boundary
Existing Lands - Unchanged
Redeveloping
New Lands - New Existing Redevelopment Development
(acre) (acre) (acre) (acre) (acre) (acre) (acre) (acre) Residential
Rural Residential
Hillside Residential
- 0 0 0 0 0
344
45 4
0 8
0 0
Hillside Residential 444 -1 442
1,583
58 112
122
177
18 464
211
183
36 907
Low Density Residential
Medium Density Residential
High Density Residential
Low Density Residential
Medium Density Residential
High Density Residential
Subtotal - Residential
1,704
100
-121
-42
44 2
1,794
240
249 -182
-346
67 15
408
3 104
2,496 2,151 429 58 895 3,045
Non-Residential
Visitor Serving Commercial
General Services Commercial
Visitor Serving Commercial 99
524
1 -67
-91
0 32
432
1 176
106
0 0
55 0
0 44
0 176
205
0 208
637
1 General Services Commercial
Professional Office
General Industrial General Industrial 320
56 12
596
94 0
-71
-12
-5
249
44 7
213
0 255
0 389
0 856
0 1,105
Campus Industrial 44
Educational Facility
Public/Quasi-Public Facility
Neighborhood District
City Gateway District
Educational Facility 1 0 0 1 8
Public/Quasi-Public Facility -44
-94
0 552
0 152
38 102
22 7
28 336
0 281
395
27 833
395
27 Neighborhood District
- 0 20
Downtown Specific Plan Area
Mixed Use Corridor High
Hecker Pass Special Use District
Glen Loma Ranch
- 0 0 0 57 32
7 0 89 89
- 0 0 0 25 0 33 33
- 0 0 0 328
103
43 88
237
40 30
876
0 416
341
83 416
341
83 - 0 0 0 0
Industrial Park - 0 0 0 0
Employment Center - 0 0 0 279
1,541
222
1,017
530
3,434
530
Subtotal - Non-Residential 1,701 -384 1,317 4,750
Other
Agriculture
Park and Recreation Facility
Vacant
-
Park and Recreation Facility
Vacant
0 0 0
995
0 0
0 0
66 0
88 0
0 154
0 0
1,232
2,391
1,282
0 -238
-2,391
-1,030
0 1,149
0 0 0
Open Space Open Space
-
253
0 0 1,041
0 4 1,045
30 1,298
Rural County 28 30
28 3
Subtotal - Other 4,905 -3,658 1,247 1,107 95 1,230 2,477 Total
Total Developed Area 9,102 -4,388 4,714 1,997 2,391 1,170 5,558 10,272 3/10/2022
Notes: