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SFPUC outlines draft groundwater project: six wells, 5 miles of pipeline, up to 4 million gallons a day
Summary
SFPUC staff briefed the Planning Commission on a draft EIR for a proposed San Francisco groundwater supply project that would construct six wells, roughly five miles of pipeline and pump an average of up to 4,000,000 gallons per day (3,000,000 gpd phase 1), with emergency capacity up to 6,000,000 gpd for about 30 days; staff noted monitoring and mitigation measures for Lake Merced and Golden Gate Park.
The San Francisco Public Utilities Commission presented its draft environmental impact report for a proposed groundwater supply project to the Planning Commission on April 18. Jeff Gillman, project manager for the SFPUC, described facilities and operations, and staff explained how the project fits into the WSIP bond-funded program.
Project details: the proposal would build up to six well facilities in two phases (four in phase 1, two in phase 2), create approximately five miles of conveyance pipeline to connect wells to Sunset Reservoir for blending with regional supplies, and include small one-story well buildings (800'00 to 1,500 sq ft, 12—9.5 feet high). The SFPUC estimates average annual groundwater production of up to 4,000,000 gallons per day at full build-out (phase 1 ~3,000,000 gpd), with emergency pumping capacity of up to 6,000,000 gpd for up to 30 days. Two wells (West Sunset and North Lake) are designed for emergency power operation.
The agency described site-by-site design and construction methods: trenching and cut-and-cover for pipelines (300'600 feet per week), and trenchless auger-boring at intersections near Muni light-rail corridors to reduce disruption. SFPUC staff said monitoring has been ongoing for over a decade in the Westside Groundwater Basin, with 41 monitoring wells at 17 locations in San Francisco.
Public comment raised engineering concerns: Tim Kennedy, a certified distribution and treatment operator living near 40th Avenue, urged the commission and SFPUC to reconsider a South Sunset pipeline alignment that includes several ninety-degree turns near 40th and Wawona; Kennedy argued those bends plus lack of surge tanks could raise risk of water main breaks and recommended reviewing the Sunset Boulevard alignment alternative. Commissioners pressed staff on lake-level impacts to Lake Merced; planning staff referenced mitigation HY9 (lake-level management plan) in the DEIR, which could require supplemental water additions, use of the Vista Grande drainage canal, adjustments to pumping rates or suspension of Lake Merced pumping if monitoring shows adverse effects.
SFPUC emphasized the project's objective to diversify San Francisco's water supply portfolio and provide a local emergency source in the event of a major earthquake; the commission opened the EIR record for public comment and noted written comments will be accepted through April 29, 2013.
