Cupetino Sanitary District Sewer AnalysisDISTRICT MANAGER -ENGINEER
MARK THOMAS & COMPANY, INC.
RICHARD K. TANAKA
DISTRICT COUNSEL
ATKINSON • FARASYN, LLP.
MARC HYNES
April 23, 2018
Mr. Chad Mosley, P.E.
City Engineer
Public Works Department
City of Cupertino
10300 Torres Avenue
Cupertino, CA 95014
sANIrARro's
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20863 STEVENS CREEK BOULEVARD, SUITE 100
CUPERTINO, CALIFORNIA 95014-2154
PHONE (408) 253-7071 • Fax (408) 253.5173
RE: Vallco Development Alternatives
Dear Chad:
BOARD OF DIRECTORS
JOHN M. GATTO
WILLIAM A. BOSWORTH
PATRICK S. KWOK
ANGELA S. CHEN
TAG HI S. SAADATI
We have reviewed the information you provided for potential redevelopment of the
Vallco Shopping Mall. The information you provided included four alternatives, one of
which is getting new tenants to occupy the mall. The details of the alternatives are
provided in Table 1.
Table 1— Vallco Proiect Alternatives
SUPPLYING SANITARY SEWERAGE SERVICES FOR: CITY OF CUPERTINO, PORTIONS OF THE CITIES OF SARATOGA, SUNNYVALE, LOS ALTOS AND
SURROUNDING UNINCORPORATED AREAS
Commercial (SF)
Office (SF)
Hotel (rooms)
Residential
Hyatt
Civic
EIR Project
House
Space
AlternativesBuild
Buildo
Existing
Buildout
Existing
Buildout
Existing
Buildout
Existing
out
ut
1.0ccupied/
Re -tenanted
Mall (No
1,207,774
0
148
0
0
Project
Alternative)
2. General
65,000
Plan Buildout
(10,00
with
0 SF
Residential
600,000
2,000,000
339
800
for
Allocation
Stem
(Proposed
1,207,774
0
148
0
Hotel
Lab)
Project)
3. General
65,000
(10,00
Plan Buildout
w/ Maximum
600,000
1,000,000
339
2,640
0 SF
for
Residential
Alternative
Stem
Lab)
4.Retail and
Residential
600,000
0
339
4,000
0
Alter
SUPPLYING SANITARY SEWERAGE SERVICES FOR: CITY OF CUPERTINO, PORTIONS OF THE CITIES OF SARATOGA, SUNNYVALE, LOS ALTOS AND
SURROUNDING UNINCORPORATED AREAS
DISTRICT MANAGER -ENGINEER
MARK THOMAS & COMPANY, INC.
RICHARD K. TANAKA
DISTRICT COUNSEL
ATKINSON • FARASYN, LLP.
MARC HYNES
Page 2
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20863 STEVENS CREEK BOULEVARD, SUITE 100
CUPERTINO, CALIFORNIA 95014-2154
PHONE (408) 253-7071 • Fax (408) 253.5173
BOARD OF DIRECTORS
JOHN M. GATTO
WILLIAM A. BOSWORTH
PATRICK S. KWOK
ANGELA S. CHEN
TAG HI S. SAADATI
The Vallco shopping mall facility is connected via its laterals to 12", 15" and 27" sewer
mains running north on Wolfe Road to Homestead road and subsequently to CuSD's
Flume station, where CuSD's flow enters the City of Santa Clara system to the San
Jose -Santa Clara Regional Wastewater Facility for treatment.
We have estimated the average daily sewage generation rates for each of the
alternatives at the Vallco site, using CuSD's standard generation rates and applying
them to the use types provided. The increase in average daily flow from the three
development alternatives, as compared to the design flow for the current mall, ranges
from 0.72 MGD to 1.04 MGD. The design average daily flow summary is provided in
Table 2.
Table 2. Average Daily Flow Summary
Alternative
Average Daily
Flow (MGD)
Flow greater than
Alternative 1 (MGD)
1
0.28
-
2
1.00
0.72
3
1.21
0.94
4
1.32
1.04
Based on our analysis, the impact of additional flows from the Vallco alternatives will
have a substantial impact on CuSD's collection system. The following collection system
characteristics were considered in our evaluation:
1. District Collection System -Capacity in 12", 15", and 27" sewer mains
2. Permitted peak flow through Santa Clara system (13.8 MGD)
3. CuSD allocated capacity at the San Jose -Santa Clara Regional Wastewater
Facility (7.85 MGD)
1. District Collection System -Capacity in 12", 15', and 27" Sewers
The 12" and 15" sewers that currently serve Vallco and downstream connections are
already near their design capacities without further development at the Vallco site. The
depth of flow divided by pipe diameter (d/D) modeling results for peak dry weather flow
(PDWF) and peak wet weather flow (PWWF) are provided in Table 3. The d/D values
are given as a range because they vary throughout the length of the pipe segment.
SUPPLYING SANITARY SEWERAGE SERVICES FOR: CITY OF CUPERTINO, PORTIONS OF THE CITIES OF SARATOGA, SUNNYVALE, LOS ALTOS AND
SURROUNDING UNINCORPORATED AREAS
DISTRICT MANAGER -ENGINEER
MARK THOMAS & COMPANY, INC.
RICHARD K. TANAKA
DISTRICT COUNSEL
ATKINSON • FARASYN, LLP.
MARC HYNES
Page 3
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20863 STEVENS CREEK BOULEVARD, SUITE 100
CUPERTINO, CALIFORNIA 95014-2154
PHONE (408) 253-7071 • Fax (408) 253.5173
BOARD OF DIRECTORS
JOHN M. GATTO
WILLIAM A. BOSWORTH
PATRICK S. KWOK
ANGELA S. CHEN
TAG HI S. SAADATI
Table 3 -Comparison of existing 12" and 15" sewer main to future conditions
Other than Alternative 1, development alternatives 2, 3, and 4 will require upsizing both
the 12" and 15" sewers. Either a parallel pipe, ranging in sizes from 18" to 21" or a new
pipe would need to be installed to upsize the existing 12" and 15" sewers.
The flow modeling results for the 27" sewer under buildout conditions are provided in
Table 4. The modeling results indicate that the 27" sewer would be operating beyond
design capacity (d/D=2/3) during peak dry -weather and peak wet -weather conditions.
The impact of this has not yet been determined, i.e. the impact to the Apple Campus
and the potential for SSOs.
Table 4. 27" Sanitary Sewer Main under Buildout with Vallco's Alternatives
PDWF d/D
PWWF d/D
PWWF
12" Segment
15" Segment
12" Segment
15" Segment
Alternative 1
0.65
0.58-0.9
0.8
0.65-1.4
Alternative 2
5-6
1-4
6-10
1-8
Alternative 3
9-10
1-7
9-10
6-7
Alternative 4
6-10
2-6
8-11
6-8
Other than Alternative 1, development alternatives 2, 3, and 4 will require upsizing both
the 12" and 15" sewers. Either a parallel pipe, ranging in sizes from 18" to 21" or a new
pipe would need to be installed to upsize the existing 12" and 15" sewers.
The flow modeling results for the 27" sewer under buildout conditions are provided in
Table 4. The modeling results indicate that the 27" sewer would be operating beyond
design capacity (d/D=2/3) during peak dry -weather and peak wet -weather conditions.
The impact of this has not yet been determined, i.e. the impact to the Apple Campus
and the potential for SSOs.
Table 4. 27" Sanitary Sewer Main under Buildout with Vallco's Alternatives
2. Permitted peak flow through Santa Clara system (13.8 MGD)
The modeling results provided in Table 4 above indicate that CuSD would exceed the
peak flow of 13.8 MGD through the City of Santa Clara. If the City of Santa Clara
requires the District to upsize the Santa Clara's system to accommodate these flows,
the District would expect the developer to provide these improvements within the City of
Santa Clara. The District would consider an Installers' Agreement with future
reimbursements.
SUPPLYING SANITARY SEWERAGE SERVICES FOR: CITY OF CUPERTINO, PORTIONS OF THE CITIES OF SARATOGA, SUNNYVALE, LOS ALTOS AND
SURROUNDING UNINCORPORATED AREAS
ADWF
(MGD)
PDWF
PWWF
mgd
d/D
mgd
d/D
Alt.2
5.370
9.95
0.54-0.69
14.04
0.68-0.88
Alt.3
5.597
10.6
0.56-0.69
14.06
0.74-0.9
Alt.4
5.71
10.95
0.61-0.73
14.51
0.73-0.91
2. Permitted peak flow through Santa Clara system (13.8 MGD)
The modeling results provided in Table 4 above indicate that CuSD would exceed the
peak flow of 13.8 MGD through the City of Santa Clara. If the City of Santa Clara
requires the District to upsize the Santa Clara's system to accommodate these flows,
the District would expect the developer to provide these improvements within the City of
Santa Clara. The District would consider an Installers' Agreement with future
reimbursements.
SUPPLYING SANITARY SEWERAGE SERVICES FOR: CITY OF CUPERTINO, PORTIONS OF THE CITIES OF SARATOGA, SUNNYVALE, LOS ALTOS AND
SURROUNDING UNINCORPORATED AREAS
DISTRICT MANAGER -ENGINEER
MARK THOMAS & COMPANY, INC.
RICHARD K. TANAKA
DISTRICT COUNSEL
ATKINSON • FARASYN, LLP.
MARC HYNES
Page 4
sANirARro's
9
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20863 STEVENS CREEK BOULEVARD, SUITE 100
CUPERTINO, CALIFORNIA 95014-2154
PHONE (408) 253-7071 • Fax (408) 253.5173
BOARD OF DIRECTORS
JOHN M. GATTO
WILLIAM A. BOSWORTH
PATRICK S. KWOK
ANGELA S. CHEN
TAG HI S. SAADATI
3. CuSD allocated capacity at the San Jose -Santa Clara Regional Wastewater Facility
(7.85 MGD)
The CuSD allocation at the San Jose -Santa Clara Regional Wastewater Facility is
based on average daily flow capacity of 7.85 MGD. Vallco developments will be within
the allocated capacity for the treatment of the wastewater.
Project proposed under SB 35 would have similar impacts as above.
Prior to commencement of final design, Developer will be required to enter into an
Installers' Agreement with the District, covering the installation of the parallel pipes,
requirements of the downstream pipe capacity through City of Santa Clara and paying
change in use fee, plan check engineering, inspection, and administration. in
accordance with Operations Code, Chapter VII, "Permits, Fees and Service Charges".
Our Operations Code are posted on our District Website.
If you have any questions, please feel free to contact Benjamin Porter or myself at (408)
253-7071.
Sincerely,
Richard K. Tanka, P.E.
District Manager/Engineer
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