HomeMy WebLinkAboutAppendix 4.17-2, Water Infrastructure Technical StudyAppendix 4.17-2:
Water Infrastructure Technical Study
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TECHNICAL MEMORANDUM
Date: December 14, 2020
Subject: Water Infrastructure Technical Study
Southline Development Project
The following summarizes the water infrastructure analysis performed by BKF Engineers at the planning
level for the Southline Development Project. This has been prepared for review by California Water
Service (Cal Water) and for use in the environmental documents for the Southline Development Project.
Regulatory Setting
Cal Water owns and maintains the water infrastructure within the public rights-of-way within the City of
South San Francisco. As the retail water provider for South San Francisco, Cal Water is preparing a
Water Supply Assessment (WSA) of the Southline project, as required by the State of California. The
WSA will serve as a confirmation that Cal Water can meet the future water needs of the project under
normal anticipated water supply conditions.
Existing Conditions
The Southline project site has Cal Water distribution mains located in each of the public street
frontages. A 6” cast-iron (CI) main, installed in 1943, provides water service to the current parcels
fronting Tanforan Avenue, Dollar Avenue, and S. Linden Avenue. A 12” asbestos-cement (AC) main,
installed in 1964, provides water service to the current parcels fronting Maple Avenue. The 12” AC main
is also located within Tanforan Avenue, and supplies the 6” main, but does not provide water service to
those parcels. There is no public recycled water infrastructure, and no current plans for it to be provided
in the future.
Cal Water provided the following water pressure and flow information based on fire hydrant flow-tests
performed August 3-5, 2020:
FH No. Address Main Size Static Residual Flow Flow @ 20 PSI
SSF-699 290 S. Maple Ave. 12" AC 75 66 2491 6621
SSF-879 318 S. Maple Ave. 12" AC 70 62 2928 7876
SSF-1506 325 S. Maple Ave. 6" CI; 8" AC 68 60 1960 5158
SSF-775 50 S. Tanforan Ave. 6" CI 74 68 2106 6897
SSF-1025 80 S. Tanforan Ave. 6" CI 74 67 2307 6952
SSF-183 150 S. Linden Ave. 6" CI 76 64 942 2163
Proposed Improvements
The project proposes to install a dedicated fire service and metered domestic water service for each
proposed building in the Southline project. In addition, there will be metered irrigation service provided
to the Southline campus, as well as the public landscape areas as part of the roadway and streetscape
improvements.
Proposed water demand was modeled using Redwood City Water Demand factors, Attachment Q and
applying them to the proposed building uses and areas. The Life Science campus scenario proposes to
generate the largest demands, and, therefore, was used for this analysis. The project proposes to use
approximately 460,000 gallons per day (GPD) of potable water to serve the proposed project. It is
anticipated that irrigation demands will be approximately 18,000 GPD. (See the Table A Water Demand
summary, and Table B Amenity Building Demand).
TABLE A: PROPOSED WATER DEMANDIRRIGATION5AMENITY3R&D1(GPD)0.21 0.071 6 113 317,495 317,49566,674 66,674234 71 88,200 88,200 53,0400 53,0407 6 113 295,220 295,22061,996 61,9963 6 113 447,335 447,33593,940 93,9404 6 113 411,000 411,00086,310 86,3106 6 113 465,800 465,80097,818 97,818TOTAL:2,025,05088,2001,936,85053,040406,739459,77918,228515AFY420 AFYNotes:1Demand factors based on Redwood City values for Water Demand per SF: R&D = 0.21 GPD / SF2Building heights include 15' mechanical roof screen34Annual indoor water demand (Acre-Feet per Year) based on 365 days of use per year.5Irrigation demand = 3.5 CF / SF / Year (0.07 GPD/SF), per Redwood City demand factors.6Landscape area based on conceptual landscape plans as contemplated under Southline Specific Plan; calculated across entire project site.7Fire Flow requirement to be 3,000 GPM, 4-hour duration, per hydrant.SOUTHLINE PROJECT - WATER DEMAND11/25/2020PROPOSED DOMESTIC WATER DEMAND - LIFE SCIENCEPROPOSED BUILDINGNO. OF STORIESBUILDING HEIGHT2 (FT)TOTAL AREA (GSF)DESIGN USE (SF) DEMAND (GPD)INDOOR DEMAND (GPD)AMENITY R&DSee Table A "Amenity Building - Water Demand" for modeling of Amenity Building water uses based on Redwood City demand factors.Total Annual Indoor Demand =Total Annual Irrigation Demand =260,400LANDSCAPE AREA (SF)618,22812/14/2020BKF Engineers#180624
TABLE B: AMENITY BUILDING WATER DEMANDRestaurant 16,400 3,865 Dining (SF)2258 30 7,730 Cafeteria 9,000 200 Frontage (LF)38 900 7,200 Fitness Center 49,000 980 25 36,750 Auditorium / Other13,800 680 21,360 Total:88,200 53,040 GPDNotes:1Demand factors based on Redwood City, Attachment Q, Water Demand Demand Projection Worksheet234AMENITY BUILDING - WATER DEMAND11/19/2020Restaurant seating capacity based on designated dining area and assumed 15 SF per seat, typical industry standard.Cafeteria demand based on frontage dimensions and demand factor for each 25' of frontage.Fitness Center demand based on number of users at 50 SF per user, per 8-hour shift. Assumed 1.5 shifts (12 hours operation) per day.SeatsDemand Factor1 (GPD)Demand (GPD)Occupant / Load Factors1Seats (15SF)2Frontage (25')3Users/50 SF/Shift4Area Factors1Building Use:Building Area (SF)12/14/2020BKF Engineers#180624