HomeMy WebLinkAboutTechnical Report 07 - Overview of Water Service
DEXTER WILSON ENGINEERING, INC.
WATER ● WASTEWATER ● RECYCLED WATER
CONSULTING ENGINEERS
2234 FARADAY AVENUE ● CARLSBAD, CA ● (760) 438-4422
OVERVIEW OF WATER SERVICE
FOR THE
OTAY RANCH TOWN CENTER
REDEVELOPMENT
June 22, 2023
OVERVIEW OF WATER SERVICE
FOR THE
OTAY RANCH TOWN CENTER
REDEVELOPMENT
June 22, 2023
Prepared by:
Dexter Wilson Engineering, Inc.
2234 Faraday Avenue
Carlsbad, CA 92008
(760) 438-4422
Job No. 509-127
June 22, 2023 509-127
Hunsaker & Associates San Diego, Inc.
9707 Waples Street
San Diego, CA 92121
Attention: Chuck Cater, Vice President
Subject: Overview of Water Service for the Otay Ranch Town Center Redevelopment
Introduction
This report provides an overview of water service for the Otay Ranch Town Center
Redevelopment project. The project is located east of State Route 125, north of Birch Road,
west of Eastlake Parkway, and south of Olympic Parkway in the City of Chula Vista. A
vicinity map for the project is presented on Figure 1.
The existing Otay Ranch Town Center site includes five lots (Lots 1, 2, 3, 4, and 5) on
approximately 87.25 acres and comprises commercial space. The project proposes to
redevelop the northwest portion of the existing Otay Ranch Town Center site. The
redevelopment will affect Lots 1 and 4, which make up 58.49 acres of the overall site. Within
the 58.49 acres, 16.57 acres will be redeveloped with 840 residential dwelling units; there
will be no change in commercial square footage as 37,200 square feet of existing commercial
will be removed and replaced with 37,200 square feet of new commercial. The remaining
area will consist of private streets and plaza improvements. The Tentative Map title sheet
for the Otay Ranch Town Center Redevelopment project is provided in Appendix A for
reference. The title sheet includes tabulated land use breakdowns of the affected lots and
shows the location of existing Lots 1, 2, 3, 4, and 5.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 3
Potable water service and recycled water service for the existing Otay Ranch Town Center
site is provided by the Otay Water District. Potable water service is from the Otay Water
District 980 Pressure Zone. Recycled water service is from the Otay Water District 815
Pressure Zone.
Background
The backbone potable water system for the existing Otay Ranch Town Center (previously
referred to as Freeway Commercial or FC-1) site was identified in the 2002 Subarea Master
Plan that was prepared for the project. In February 2015, a Subarea Master Plan
amendment was prepared for the 2002 Subarea Master Plan. In February 2018 a second
Subarea Master Plan amendment was prepared for the project. The Subarea Master Plans
evaluated the existing backbone system in the vicinity of the project for a 5,000 gpm fire flow,
which is the maximum fire flow supplied by the Otay Water District. The Subarea Master
Plans concluded that the existing backbone system provides adequate flow and pressure to
the Otay Ranch Town Center site under a 5,000 gpm fire flow.
Potable Water Planning Criteria
The planning criteria used to evaluate the potable water system requirements for the Otay
Ranch Town Center Redevelopment project are in accordance with the Otay Water District
2015 Water Facilities Master Plan. The 2015 Water Facilities Master Plan outlines
minimum and maximum allowable pressures and velocities in the public water system under
different operating conditions. Table 1 lists the potable water planning criteria for the
project.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 4
TABLE 1
OTAY RANCH TOWN CENTER REDEVELOPMENT
POTABLE WATER SYSTEM CRITERIA
Item Criteria
Minimum Static Pressure 65 psi
Maximum Static Pressure 200 psi
Minimum Pressure – Peak Hour Demands 40 psi
Minimum Pressure – Maximum Day Demands plus Fire 20 psi
Maximum Velocity – Maximum Day Demands plus Fire 10 fps
Maximum Velocity – Peak Hour 6 fps
Maximum Headloss per thousand feet 10 ft
Minimum Diameter 8-inch
Hazen-Williams C-factor (12-inch diameter or less) 120
Maximum Day Peak Factors W.A.S. Figure 4-1-2
Peak Hour Peak Factors W.A.S. Figure 4-1-1
These criteria were used to confirm that service from the 980 Pressure Zone will provide an
acceptable static pressure range for the project. Proposed elevations within the
redevelopment area will range from 614 feet to 626 feet, which results in a maximum static
pressure range of 153 psi to 158 psi. This is an acceptable range per the design criteria
presented in Table 1. To protect private plumbing fixtures, all connections with a static
pressure greater than 80 psi must include a pressure regulator per the 2019 California
Plumbing Code.
Potable Water Demands
Potable water demands for the Otay Ranch Town Center Redevelopment project were
estimated using water demand factors provided in the Otay Water District 2015 Water
Facilities Master Plan. Table 2 summarizes the water demand factors pertinent to this
project.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 5
TABLE 2
OTAY RANCH TOWN CENTER REDEVELOPMENT PROJECT
POTABLE WATER DEMAND FACTORS
Land Use Water Demand Factor
Commercial 1,607 gpd/acre
Residential (>10 DU/ac) 170 gpd/DU
Peaking factors for the existing site and for the proposed site after the redevelopment were
determined using the charts provided in Appendix B.
Existing Otay Ranch Town Center Demand. Table 3 summarizes the average potable
water demands for the existing Otay Ranch Town Center site based on the water demand
factor presented in the 2002 Subarea Master Plan.
TABLE 3
EXISTING OTAY RANCH TOWN CENTER
AVERAGE POTABLE WATER DEMAND
Land Use Quantity Water Demand
Factor2
Average Potable Water
Demand, gpd
Commercial1 87.25 acres 1,785 gpd/acre 155,741
TOTAL 155,741
1. Acreage reflects entire Otay Ranch Town Center site. The redevelopment will only affect 16.57 acres of Lots
1 and 4 which have a total area of 58.49 acres.
2. Based on water demand factor presented in the 2002 Subarea Master Plan.
Based on Table 3, the existing Otay Ranch Town Center site is estimated to have potable
water demands as summarized below.
Average Demand: 155,741 gpd = 108 gpm
Maximum Day Demand: 155,741 gpd x 2.96 = 460,993 gpd = 320 gpm
Peak Hour Demand: 155,741 gpd x 6.71 = 1,045,022 gpd = 726 gpm
Proposed Otay Ranch Town Center Redevelopment Demand. Table 4 summarizes
the projected average potable water demands for the proposed Otay Ranch Town Center
Redevelopment project based on current water demand factors.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 6
TABLE 4
OTAY RANCH TOWN CENTER REDEVELOPMENT
AVERAGE POTABLE WATER DEMAND
Land Use Quantity Water Demand
Factor
Average Potable Water
Demand, gpd
Existing Development to Remain
Existing Commercial1 70.68 acres 1,607 gpd/acre 113,583
Proposed Development2
Residential (>10 DU/ac) 840 DU 170 gpd/DU 142,800
Proposed Commercial 0.85 acres 1,607 gpd/acre 1,366
TOTAL 257,749
1. Acreage of existing Otay Ranch Town Center site (87.25 acres) reduced by 16.57 acres (redevelopment area).
2. Acreage excludes private street area (2.93 acres) and park/plaza area (2.73 acres) as no potable water
demands are expected.
Based on Table 4, after the redevelopment the Otay Ranch Town Center site is projected to
have potable water demands as summarized below.
Average Demand: 257,749 gpd = 179 gpm
Maximum Day Demand: 257,749 gpd x 2.82 = 726,852 gpd = 505 gpm
Peak Hour Demand: 257,749 gpd x 6.00 = 1,546,494 gpd = 1,074 gpm
In comparing the average potable water demands shown on Table 3 and Table 4, the proposed
redevelopment will increase existing average potable water demand by 102,008 gpd from
155,741 gpd to 257,749 gpd.
Fire Flow Demand Requirements. Per the Otay Water District 2015 Water Facilities
Master Plan the fire flow requirements for single family residential, multi-family residential,
and commercial areas are 1,500 gpm, 2,500 gpm, and 3,500 gpm, respectively. Thus, the fire
flow requirement estimated for the Otay Ranch Town Center Redevelopment project is 3,500
gpm. The Maximum Day plus Fire Flow requirement is estimated to be 4,005 gpm (505 gpm
+ 3,500 gpm = 4,005 gpm), which is less than the 5,000 gpm fire flow requirement that was
analyzed for the backbone potable water system in previous Subarea Master Plans for the
existing site. The actual fire flow requirement will need to be determined by the City of Chula
Vista Fire Department after building construction types and square footages are available
for the proposed project buildings.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 7
Existing Potable Water System
As previously mentioned, the Otay Ranch Town Center Redevelopment project is within the
City of Chula Vista and will receive potable water service from the Otay Water District public
water system. Potable water service to the project will be from the 980 Pressure Zone.
The existing water system in the vicinity of the project is presented on Figure 2. There are
existing 12-inch potable water lines looped through the site and connected to an existing 12-
inch line in Birch Road to the south, to an existing 20-inch line in Eastlake Parkway to the
east, and to an existing 12-inch line in Town Center Drive to the north. Figure 2 presents the
existing potable water system in the vicinity of the project.
Proposed Potable Water System
The Otay Ranch Town Center Redevelopment project will receive water service by relocating
a portion of the existing public 12-inch 980 Pressure Zone potable water loop within the site.
Figure 3 presents the proposed public water system. The pipeline relocation is required to
accommodate the proposed redevelopment and will disrupt service to an existing fire hydrant
near the northwest corner of the site that was installed near the South Bay Bus Rapid Transit
Station (see Appendix C). Water service to this fire hydrant will be maintained and
coordinated with the Chula Vista Fire Department during final engineering.
Because the estimated Maximum Day plus Fire Flow requirement for the area to be
redeveloped is 4,005 gpm and the existing backbone system has previously been evaluated
for a 5,000 gpm fire flow, which is the maximum amount supplied by Otay Water District,
the backbone water system will not require any pipe size upgrades to support site
redevelopment.
Where new development is proposed, private onsite water systems with connections to the
public system will be installed. Domestic water service connections will include a master
meter and a backflow preventer, and fire service connections will include a backflow
preventer. Both domestic water service laterals and fire service laterals will be installed in
accordance with Otay Water District standards.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 10
Overview of Recycled Water Service
The existing Otay Ranch Town Center site receives recycled water from the Otay Water
District 815 Pressure Zone system. Recycled water is used to irrigate landscaped common
areas and parkways within the Otay Ranch Town Center.
Figure 4 presents the existing public recycled water system in the vicinity of the project. As
shown in Figure 4, there are existing 12-inch recycled water lines in Birch Road and Eastlake
Parkway and there are two existing 8-inch recycled water service laterals to the site: one
lateral is connected to the existing 12-inch recycled water line in Birch Road and the other is
connected to the existing 12-inch recycled water line in Eastlake Parkway. Each 8-inch
recycled water service lateral serves two existing 2-inch irrigation service laterals and meters
(four total). The existing recycled water demand for the site is estimated as follows:
Existing Commercial Area = 87.25 acres
Percent Irrigated = 10% or 8.73 acres
Average Recycled Water Demand = 8.73 acres x 1,900 gpd/acre = 16,587 gpd
Table 5 presents the projected average recycled water demand for the Otay Ranch Town
Center after the proposed redevelopment.
TABLE 5
OTAY RANCH TOWN CENTER REDEVELOPMENT
AVERAGE RECYCLED WATER DEMAND
Land Use Quantity %
Irrigated
Irrigated
Acreage
Recycled
Water
Demand
Factor
Average
Recycled
Water
Demand, gpd
Existing Development to Remain
Existing Commercial1 70.68 acres 10 7.07 1,900 gpd/ac 13,433
Proposed Development2
Mixed-Use (Residential
and Commercial) 10.91 acres 15 1.64 1,900 gpd/ac 3,116
Park/Plaza 2.73 acres 100 2.73 1,900 gpd/ac 5,187
TOTAL 21,736
1. Acreage of existing Otay Ranch Town Center site (87.25 acres) reduced by 16.57 acres (redevelopment area).
2. Acreage excludes private street area (2.93 acres) as no recycled water demand is expected.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 12
In comparing the existing average recycled water demands to the projected average recycled
water demands after the redevelopment, the proposed redevelopment will increase recycled
water demands by approximately 5,149 gpd or 31.0 percent. This increase in demand is not
expected to change private irrigation line sizing within the project.
The existing 2-inch recycled water meters serving the site have a combined capacity of 512
gpm (four (4) 2-inch meters at 128 gpm each). The existing average recycled water demand
for the existing site is approximately 16,587 gpd (11.5 gpm) and the projected average
recycled water demand for the post-redevelopment site is 21,736 gpd (15.1 gpm). Applying a
peaking factor of 6.0 (2.0 max day peaking factor x 3.0 to account for 8 hours of irrigation
over 24 hours) results in peak hour demands of 69.0 gpm and 90.6 gpm for the existing site
condition and the post-redevelopment site condition, respectively; thus, the recycled water
demands are well within the total meter capacity available to the site and it is anticipated
that new public recycled water services will not be required for the project.
To provide recycled water service to the redevelopment area the existing private irrigation
system within the Otay Ranch Town Center site will be expanded/modified. The general
location of private irrigation lines within the redevelopment area are shown in Appendix A.
Proposed elevations within the redevelopment area range from 614 feet to 626 feet, which
results in a maximum static pressure range of 81 psi to 87 psi from the 815 Pressure Zone.
Potential recycled water use areas for the proposed modifications include common landscaped
areas and the public park/plaza. The expected working pressures in the redevelopment area
are approximately 30 psi. Meter capacities, irrigation system appurtenances, and the need
for booster pumps and submeters to serve the redevelopment area will need to be evaluated
in more detail during final engineering by the project landscape architect.
Chuck Cater
June 22, 2023
ORTC Redevelopment – Overview of Water
DEXTER WILSON ENGINEERING, INC. PAGE 13
Thank you for the opportunity to assist you with the water system planning for this project.
If you have any questions regarding the information presented in this report, please do not
hesitate to call.
Dexter Wilson Engineering, Inc.
Fernando Fregoso, P.E.
FF:ru
Attachments
APPENDIX A
TENTATIVE MAP
TITLE SHEET
F C -1
F C -2
F C -1
F C -1
F C -1
F C -1
F C -1
M U /R
M U /R
P
P S
P S
P S
P S
M U /R
M U /R
M U /R
P
M U /R
M U /R
M U /R
M U /R
P
P
L O T 1 0
L O T 1
L O T 5
L O T 7
L O T 8
L O T 6
L O T 9
L O T 2
L O T 3
L O T 4
L O T A
L O T B
L O T C
L O T D
L O T H
L O T E
L O T F
L O T G
L O T 1 0
L O T 1 0
L O T 1 0
L O T 1 0
A. PROPOSED LAND USE
LOT LAND USE AREA AC COMMERCIAL DENSITY DU/AC UNITS
MU/R LOT 1 Urban Core 1.65 -77.0 -
MU/R LOT 2 Urban Core 1.23 -77.0 -
MU/R LOT 3 Urban Core 1.88 -77.0 -
MU/R LOT 4 Urban Core 1.86 *37,200 SF 77.0 -
MU/R LOT 5 Urban Core 0.73 -77.0 -
MU/R LOT 6 Urban Core 0.73 -77.0 -
MU/R LOT 7 Urban Core 1.19 -77.0 -
MU/R LOT 8 Urban Core 1.17 -77.0 -
MU/R LOT 9 Urban Core 0.47 -77.0 -
SUBTOTAL MU/R 10.91 --840
PS LOT A Private St.1.50 ---
PS LOT B Private St.0.80 ---
PS LOT C Private St.0.26 ---
PS LOT D Private St.0.37 ---
SUBTOTAL PS 2.93 ---
P LOT E Park/Plaza 0.72 ---
P LOT F Park 0.87 ---
P LOT G Park 0.38 ---
P LOT H Park 0.76 ---
SUBTOTAL PARK 2.73 ---
SUBTOTAL REDEVELOPMENT 16.57 ---
LOT 10 Commercial Retail 41.93 ---
TOTAL 58.49 *37,200 -840
Note: Acreages rounded to the nearest hundredth of an acre
*37,200 sf of existing commercial to be replaced with 37,200 sf of new commercial
B. EXISTING LOTS
LOT LAND USE AREA AC
LOT 1 Commercial Retail 50.791
LOT 4 Commercial Retail 7.699
TOTAL 58.490
CONDOMINIUM NOTES
OTAY RANCH TOWN CENTER FC-1
TENTATIVE MAP/CVT 22-0002 FOR:
CITY OF CHULA VISTA, CALIFORNIA
8
SHEET
OF
REVISIONS DATE BYNO.PREPARED BY:
HUNSAKER& ASSOCIATES
TOWN CENTER FC-1
TENTATIVE MAP/CVT 22-0002
OTAY RANCH
City Of Chula Vista, California
CVT # 22-0002
EARTHWORK/GRADING QUANTITIES
GENERAL NOTES
SOURCE OF TOPOGRAPHY
GENERAL DESIGN NOTES
BENCHMARK:
SHEET INDEX
PUBLIC UTILITIES
LEGAL DESCRIPTION:
EASEMENT & ENCUMBRANCE NOTES
ABBREVIATIONS
LEGEND
MU/R
SHEET 1 - TITLE SHEET/TABLES
SHEET 2 - STREET SECTIONS & SITE SECTION
SHEET 7 - BOUNDARY, EASEMENTS
SHEET 5 - PROJECT DESIGN
& ENCUMBRANCES
SHEET 4 - PROJECT DESIGN
SHEET 8 - BOUNDARY, EASEMENTS & ENCUMBRANCES
KEY MAP
SHEET 3 - PROJECT DESIGN
1
LAND USE SUMMARY
L D
A O
IS A S .V IALP
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C 47945
LIVIC
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TER E D P R O F E SSI NAL
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APPLICANT/OWNER
SHEET 6 - PROPOSED LOTTING, EASEMENTS &
FC-1
5
EASEMENTS OR PORTIONS OF EASEMENTS TO BE VACATED
LOT 1
LOT A
APPENDIX B
PEAKING FACTOR CURVES
APPENDIX C
SOUTH BAY BRT
WATER LINE PLANS