Recycled Water StudySchaaf GPWheeler
CONSULTING CIVIL ENGINEERS
MEMORANDUM
1171 Homestead Rd., Suite 255
Santa Clara, CA 95050-5485
t. 408-246-4848
f. 408-246-5624
s&w@swsv.com
TO: Kristy Weis (David J. Powers & Associates) DATE: May 18, 2018
FROM: Leif Coponen, PE (C70139) JOB#: DPOW 101.18.001
Melissa Reardon
SUBJECT: Vallco Area Specific Plan Recycled Water Study (DRAFT)
Schaaf & Wheeler has been retained by David J. Powers & Associates to prepare a feasibility report for
the extension of recycled water to the Vallco Area Specific Plan (Project) area. The Project proposes the
redevelopment of approximately 70 acres within the City of Cupertino with a combination of commercial,
office, hotel, and residential land uses.
The proposed project consists of 600,000 square feet (sf) of commercial, 2,000,000 sf of office, 339 hotel
rooms, and 800 residential dwelling units. The Specific Plan could also include a 30 -acre green roof and
65,000 square feet of civic space. The City of Cupertino has also identified three alternatives to the
proposed project: General Plan Buildout with Maximum Residential, Retail and Residential, and
Occupied/Re-tenanted Mall. A summary of the development proposed under the project and project
alternatives is provided in the table below.
Table 1. Summary of Project and
ment
Proposed Specific
Plan
General Plan Buildout
with Maximum
Residential
Alternative
Retail and Residential
_ Alternative
Occupied/Re-
tenanted Mall
Alternative
600,000 2,000,000 339 800 30
Project Alternatives
600,000 1,000,000 339 2,640 30
600,000 0 339 4,000 0
65,000 (10,000 of
which would be for
STEM lab use)
65,000 (10,000 of
which would be for
STEM lab use)
17
1,207,774 0 148 0 0 0
Weis (David J. Powers & Associates) May 18, 2018
All alternatives include irrigated landscape. The extension of the recycled water infrastructure is proposed
for landscaping irrigation purposes for the proposed project, General Plan Buildout with Maximum
Residential Alternative, and Retail and Residential Alternative.
The Occupied/Re-tenanted Mall Alternative would not result in redevelopment of the site. The existing
landscaping and irrigation would remain as it is currently under the Occupied/Re-tenanted Mall
Alternative. Use of recycled water or the extension of the recycled water infrastructure is not proposed as
part of the Occupied/Re-tenanted Mall Alternative. For these reasons, the Occupied/Re-tenanted Mall
Alternative is not evaluated in this memo.
This study focuses on the proposed project, General Plan Buildout with Maximum Residential Alternative,
and Retail and Residential Alternative and assumes the irrigated landscape area is the same for all three
of the alternatives under consideration.
Project Recycled Water Demand
Two recycled water demand scenarios are evaluated for this study: landscape irrigation (Baseline) and
landscape irrigation with green roof (Green Roof).
Baseline Demand Scenario: Landscape Irrigation Only
Recycled water demand in this scenario includes landscape irrigation demand only. Based on information
provided by the City, there will be between 2.8 and 5.6 acres of irrigated landscape. An irrigation demand
of 2 acre-feet per year (AFY) per acre is assumed for the irrigated landscape, which is consistent with the
Water Supply Assessment being prepared for the Project. Thus, the recycled water demand for the
Baseline demand scenario is between 4,999 and 9,999 gallons per day (gpd) of Average Day Demand
(ADD).
A peaking factor of 6.40 from the City of Sunnyvale Feasibility Study for Recycled Water Expansion
Report(Hydroscience, 2013) was applied to the Baseline ADD to determine Baseline Peak Hour Demand
(PHD). The Baseline PHD is between approximately 32,000 and 64,000 gpd. A summary of ADD and PHD
for the Baseline demand scenario is provided in Table 2.
Table 2. Baseline ADD and PHD
Average Day Demand 6-11 4,999 — 9,999 4-7
Peak Hour Demand 36-72 31,994 — 63,994 22-45
Green Roof Demand Scenario: Landscape Irrigation with Green Roof
Recycled water demand in the Green Roof demand scenario includes landscape irrigation demand, as
described above, in addition to irrigation demand for a 30 -acre green roof. The recycled water demand
for the irrigated landscape is between 4,999 and 9,999 gpd of ADD. The green roof is assumed to have a
demand of 90 AFY, or 80,436 gpd. The total recycled water demand for the Green Roof demand scenario
is between approximately 85,000 and 90,000 gpd of ADD.
A peaking factor of 6.40 from the City of Sunnyvale Feasibility Study for Recycled Water Expansion
Report(Hydroscience, 2013) was applied to the Green Roof ADD to determine Green Roof PHD. The
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Weis (David J. Powers & Associates)
18, 2018
Green Roof PHD is between approximately 547,000 and 579,000 gpd. A summary of ADD and PHD for
the Green Roof demand scenario is provided in Table 3.
Table 3. Green Roof ADD and PHD
Average Day Demand 96-101 85,367 - 90,365 59-63
Peak Hour Demand 612-648 546,784 - 578,784 371-402
Recycled Water System Supply
Recycled water for the existing distribution system is supplied by the City of Sunnyvale's Water Pollution
Control Plant (WPCP). Currently, the WPCP treats wastewater to recycled water standards (Title 22,
Chapter 3 of the California Code of Regulations: Water Recycling Criteria) in batches, rather than
continuously, due to plant configuration limitations. As a result, potable water has historically been
blended with recycled water to meet peak demands in the recycled water system.
In 2014, the City of Sunnyvale received grant funding to make improvements to the WPCP to provide
recycled water continuously. These improvements are expected to be complete in Summer of 2019.
According to the grant application (Association of Bay Area Governments, 2014), the WPCP
improvements will allow for the production of, at a minimum, 1,680 AFY to meet 1,120 AFY of existing
demand within Sunnyvale and 560 AFY of demand along the Wolfe Road Pipeline in Sunnyvale and
Cupertino.
The 560 AFY of demand for the Wolfe Road Pipeline includes demands for the Apple Campus 2, 11 sites
along the pipeline, and eight sites extending from the pipeline previously identified in the City of
Sunnyvale Feasibility Study for Recycled Water Expansion Report (Hydroscience, 2013). The demand for
these projects, however, is estimated as 495 AFY in the Hydroscience (2013) report. Based on the
Baseline maximum ADD of 11 AFY, there should be adequate supply available for the Project from the
WPCP with the upgrades to be completed in Summer of 2019 under the Baseline demand scenario.
Currently, demand for recycled water consists of the existing Sunnyvale demand and the Apple Campus 2
demand. The Apple Campus 2 is estimated to have a demand of 235 AFY in the Hydroscience (2013)
report. Based on the minimum planned capacity of the WPCP with improvements of 1,680 AFY and
current demand of 1,355 AFY, there should be adequate supply for the Project with the Green Roof
maximum ADD of 101 AFY. However, as stated above, there are about 20 sites that were previously
identified in the Hydroscience (2013) report as potential recycled water customers from the Wolfe Road
Pipeline. If these projects connect to the recycled water system before the Project with the demands
estimated in the Hydroscience (2013) report, there may not be sufficient supply from the WPCP for the
Project with the Green Roof demand. As the Project moves forward, any potential service constraints will
have to be discussed with the City of Sunnyvale as the recycled water supplier and the Santa Clara Valley
Water District (SCVWD) as the wholesaler.
Recycled Water Distribution System
The existing recycled water distribution system delivers recycled water from the City of Sunnyvale WPCP
to customers in Sunnyvale and to the Apple Campus 2 in Cupertino via the recently constructed Wolfe
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Weis (David J. Powers & Associates)
18, 2018
Road Pipeline. Recycled water is pumped from the WPCP to the San Lucar site, which has an existing 2.0
MG tank and pump station that serves Sunnyvale customers primarily located in northern Sunnyvale.
The recently constructed Wolfe Road Pipeline Project extends the recycled water system from the existing
San Lucar site south to the intersection of Wolfe and Homestead Roads in the City of Cupertino. The
pipeline project also included the construction of a booster pump station at the San Lucar site, which has
a current maximum capacity of 250 gallons per minute (gpm) but can be expanded in the future to a
maximum of 7,000 gpm based on drawings from the SCVWD. The SCVWD owns the Wolfe Road Pipeline
and booster pump station and is the wholesaler of recycled water from the pipeline.
In the future, the SCVWD plans to expand the recycled water system within the District through a
number of possible projects. The Wolfe Road Pipeline, for example, has the potential to deliver 10,100
AFY of advanced purified water to SCVWD groundwater injection wells. The SCVWD may also extend the
recycled water piping system south and east of the Project area from the terminus of the Wolfe Road
Pipeline (Figure 1).
Figure 1. SCVWD Recycled Water System Expansion
Source: SCVWD P-3 Purified Water Program, 2017
Schaaf &' Wheeler Page 4
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Source: SCVWD P-3 Purified Water Program, 2017
Schaaf &' Wheeler Page 4
Weis (David J. Powers & Associates) May 18, 2018
Based on discussions with the SCVWD, there may be adequate capacity with the existing booster pumps
at the Wolfe Road Pipeline booster pump station to serve the Project under the Baseline demand
scenario. The current booster pumps are designed to only serve the Apple Campus 2 demand, which is
estimated as 235 AFY in the City of Sunnyvale Feasibility Study for Recycled Water Expansion Report
(Hydroscience, 2013). Further analysis is required to determine the 24-hour demand cycles at the Project
and to compare these to existing demand cycles, especially for summer time use. If adequate capacity is
not available at the Project with the existing pumps, one additional pump would need to be added at the
Wolfe Road Pipeline booster pump station.
Under the Green Roof demand scenario, there likely will not be adequate capacity with the existing
booster pumps. Because the Green Roof maximum ADD is approximately half of the Apple Campus 2
demand, one or more additional pumps would need to be added to the Wolfe Road booster pump station.
Potential Project Connections
There are two potential connections to the recycled water system for the Project considered in this study,
as shown in Figure 2. For both connections, the SCVWD is the recycled water wholesaler and California
Water Service Company (Cal Water) is the recycled water retailer within the Project area. In Connection
Option 1, a new pipe would be constructed from the terminus of the Wolfe Road Pipeline south along
Wolfe Road to the Project area. In Connection Option 2, the Project would connect to the future SCVWD
recycled water pipeline at Tantau Avenue and Stevens Creek Boulevard with a pipe extending west along
Stevens Creek Boulevard to the Project area.
It is assumed that a pipeline would be extended from the recycled water mains to the Project area in this
study. However, the SCVWD has expressed that it may instead want the Project to build a new 24 -inch
recycled water main along Wolfe Road to the Project area with a turnout for the Project at the terminus
of the new main. This would allow the SCVWD recycled water system to extend further south and reach
other potential customers. While this option is not analyzed in this study, constructing this new 24 -inch
main would require certain agreements with the SCVWD, as discussed at the end of this study.
Schaaf 6- Wheeler Page 5
Weis (David J. Powers & Associates)
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Figure 2. Potential Connections to the Project
Recycled Water Pipe Sizing and Hydraulics
In sizing the connection between the Project and the recycled water system, flow in the pipe is
conservatively assumed to be the maximum PHD for each demand scenario. Velocity is constrained to 5
feet per second for both demand scenarios to determine a minimum pipe diameter. However, the
ultimate goal of the hydraulic analysis is to minimize the head loss in the pipe within reason. Head loss is
calculated using the Hazen Williams equation with a roughness value of 130. Both connection options are
considered for each demand scenario. In total, four demand scenario -connection option combinations are
analyzed.
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Figure 2. Potential Connections to the Project
Recycled Water Pipe Sizing and Hydraulics
In sizing the connection between the Project and the recycled water system, flow in the pipe is
conservatively assumed to be the maximum PHD for each demand scenario. Velocity is constrained to 5
feet per second for both demand scenarios to determine a minimum pipe diameter. However, the
ultimate goal of the hydraulic analysis is to minimize the head loss in the pipe within reason. Head loss is
calculated using the Hazen Williams equation with a roughness value of 130. Both connection options are
considered for each demand scenario. In total, four demand scenario -connection option combinations are
analyzed.
Schaaf (P Wheeler Page 6
Weis (David J. Powers & Associates) May 18, 2018
Baseline Demand Scenario
With a velocity constraint of 5 feet per second in the pipe and the Baseline maximum PHD of 45 gpm, the
pipe could have a 2- to 4 -inch diameter. A four -inch diameter pipe would allow for higher demands in
the future should Project demands increase; the two-inch diameter pipe would limit demand to the 45
gpm estimated in this study given the velocity constraint of 5 feet per second.
Currently the booster pump station for the Wolfe Road Pipeline maintains a pressure of 55 psi at the
terminus of the pipeline, based on discussions with the SCVWD. The anticipated static pressure at the
Project is approximately 46 psi based on the difference in elevation between the terminus of the Wolfe
Road Pipeline and the Project Area. Assumptions made in the head loss calculations for both connection
options are given in Table 4.
Connection Option I; Wolfe Road Connection
For Connection Option 1, approximately 3,000 feet of new pipe would be extended from the intersection
of Wolfe and Homestead Roads to the northern edge of the Project along Wolfe Road. Head loss in the
pipe is anticipated to be 2.3 pounds per square inch (psi). The anticipated pressure at the Project area
with Baseline demand is therefore approximately 43.7 psi.
Connection Option 2; Tantau Avenue Connection
In this connection option, approximately 2,300 feet of new pipe would be laid from the intersection of
Tantau Avenue and Stevens Creek Boulevard to the southern edge of the Project at the intersection of
Wolfe Road and Stevens Creek Boulevard. Head loss in the pipe is anticipated to be 1.7 psi with the
Baseline demand so pressure at the Project area is anticipated to be approximately 44.3 psi.
Table 4. Baseline Demand Scenario Hydraulics
Pipe Diameter (in)
Pipe Length (ft) �
Hazen Williams Roughness Value, C
`_ 4
3,000
I 130
1 4
_
2,300
I 130
45
Flow Rate (gpm)
45
Total Head Loss (psi)
I 2.3
I 1.7
Pressure at Project site (psi)
I 43.7
I 44.3
Green Roof Demand Scenario
With a velocity constraint of 5 feet per second in the pipe and the Green Roof maximum PHD of 402
gpm, the pipe could have a 6 -inch diameter at a minimum. However, because head loss could be
considerable, this analysis considers both 6 -inch diameter pipe and 8 -inch diameter pipe for each
connection option.
As described previously, the anticipated static pressure at the Project site with the current booster pump
station for the Wolfe Road Pipeline is 46 psi. It is conservatively assumed that the additional pump or
pumps required for the Green Roof demand scenario do not result in higher static pressure. Assumptions
made in the head loss calculations for both pipe diameters and both connection options are given in
Table 5.
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Weis (David J. Powers & Associates)
Connection Option Z; Wolfe Road Connection
18, 2018
For this connection option, approximately 3,000 feet of new pipe would be laid to connect to the Project
area. Head loss in the pipe is anticipated to be 18.2 psi with 6 -inch diameter pipe and 4.5 psi for 8 -inch
diameter pipe, respectively. Because the 8 -inch diameter pipe results in a considerably lower head loss,
the recommended pipe for this connection option is 8 -inch diameter. The anticipated pressure at the
Project area with Project demand is therefore approximately 41.5 psi with the recommended pipe.
Connection Option 2; Tantau Avenue Connection
Assuming 2,300 feet of new pipe is laid for this connection option, head loss is anticipated to 13.9 psi
with the 6 -inch diameter pipe and 3.4 psi with the 8 -inch diameter, respectively. Because the 8 -inch
diameter pipe results in a considerably lower head loss, the recommended pipe for this connection option
is 8 -inch diameter. Pressure at the Project area with Green Roof demand is anticipated to be
approximately 42.6 psi with the recommended pipe.
Table S. Green Roof Demand Scenario Hydraulics
Pipe Diameter (in) 1
6
8
6
8
Pipe Length (ft)
3,000
3,000
2,300
2,30(
Hazen Williams Roughness Value, C
130
130
130
130
Flow Rate (gpm)
403
403
403
403
Total Head Loss (psi)
18.2
_4.5
13.9
3.4
Pressure at Project site (psi)
27.8
41.5
32.1
42.6
Additional Required Infrastructure
Irrigation systems can require pressures higher than what is anticipated for the Project. For example,
spray irrigation systems typically operate at higher pressures. An on-site irrigation booster pump may be
required for the irrigated landscape and green roof considered in this study.
Required Agreements and Additional Considerations
Further discussions may be required with the SCVWD, Cal Water, and other entities should the Project
choose to go forward with recycled water use. Regardless of the demand scenario or connection option, a
series of agreements between the City of Sunnyvale, SCVWD, Cal Water, and the Project would need to
be made to provide a specified amount of recycled water to the Project. The SCVWD, as the wholesaler,
would coordinate with the City of Sunnyvale, as the recycled water supplier, to execute new agreements
or amend existing agreements, as appropriate, to secure recycled water for the Project. The SCVWD and
the City of Sunnyvale would ultimately determine if there is sufficient supply for the Project. The SCVWD,
as the wholesaler, then would execute new agreements or amend existing agreements, as appropriate,
with Cal Water, as the water retailer, to provide water to the Project. Finally, the service agreement
between Cal Water, as the retailer, and the Project, as the customer, would specify how much water will
be available for purchase.
Additional agreements would need to be made with the SCVWD depending on the ultimate demand
scenario and connection option for the Project. If one or more additional pumps are required to provide
recycled water to the Project, the Project would need to discuss cost-sharing for the addition of the new
pump or pumps with the SCVWD, as the SCVWD owns, maintains, and operates the Wolfe Road Pipeline
and booster pump station. Further agreements would need to be made if the Project chose to build a
Schaaf 6- Wheeler Page 8
Weis (David J. Powers & Associates) May 18, 2018
new 24 -inch main down Wolfe Road as discussed earlier in this study. Based on conversations with the
SCVWD, a funding agreement between the SCVWD and the Project would likely need to be prepared
whereby the Project pays for the construction of the 24 -inch recycled water main and the District accepts
ownership of the pipeline and responsibility for operations and maintenance. There would also likely be a
provision whereby the District provides the operations and maintenance itself or can contract with
another entity to provide the operations maintenance.
The Project may also need to have discussions with Cal Water as the recycled water retailer for the
Project area. In the agreement between the SCVWD and Cal Water for the Wolfe Road Pipeline and
booster pump station, Cal Water was responsible for the construction and maintenance of service lines,
turnouts, and meters as the recycled water retailer to the Apple Campus 2. Because Cal Water is also the
recycled water retailer for the Project area, discussions with Cal Water may include pipeline construction
cost-sharing as well as ownership, operations, and maintenance of the pipeline from the recycled water
system to the Project. The Project would also need to secure a service agreement with Cal Water to
purchased recycled water.
Additionally, encroachment permits from Caltrans will be required for construction of the pipeline to the
Project area. For Connection Option 1 in particular, an encroachment permit from Caltrans would be
required as the pipeline would cross Interstate 280 to reach the Project area from the intersection of
Wolfe and Homestead Roads.
References
Association of Bay Area Governments. Proposition 84 Integrated Regional Water Management 2014
Drought Grant Application Attachment 3: Project Justification. September 2014.
Hydroscience. City of Sunnyvale Feasibility Study for Recycled Water Expansion Report. June 2013.
Santa Clara Valley Water District. Board Agenda Memo: Agreements with City of Sunnyvale, California
Water Service Company, and Apple Inc., for Expansion of Recycled Water. September 2014.
Santa Clara Valley Water District. P-3 Purified Water Program.
https://www.vaIIeywater.org/contractors/doing-businesses-with-the-district/p3-purified-water-program.
Schaaf 6- Wheeler Page 9