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PUC to introduce groundwater blending to city water system; staff says quality meets standards
Summary
Assistant GM Steve Ritchie told the PUC the Groundwater Supply Project will bring up to 4 million gallons per day from six wells on the Westside Basin, beginning around 1 million gallons per day and ramping up; staff said constituent levels (nitrate ~1.45 mg/L) remain well under drinking‑water standards and Division of Drinking Water approval is imminent.
The San Francisco Public Utilities Commission received an update on the San Francisco Groundwater Project, which staff said will diversify the city's supplies by tapping the Westside Basin Aquifer and blending groundwater with regional supplies distributed to roughly half the city.
Key facts presented: staff said the project will ultimately access about six wells and is expected to supply up to 4,000,000 gallons per day; initial operations are planned at roughly 1,000,000 gallons per day with an annual ramp of about 1,000,000 gpd. Phase 1 includes four wells delivering up to about 2,800,000 gpd with substantial completion anticipated in May and staff expected Division of Drinking Water approval for adding the supply 'in the next few days' (as stated at the hearing).
Quality and monitoring: Steve Ritchie told commissioners that some constituent concentrations rise slightly after blending but 'all of the constituents remain well below the drinking water standards.' He noted groundwater nitrate measured in the presentation at about 1.45 mg/L compared with the nitrate standard of 45 mg/L, and committed to provide the Commission with the sampling/testing frequency as part of the Division of Drinking Water application.
Operational considerations: staff emphasized controls to manage seawater intrusion and the ability to shift pumping among wells, and that some well stations will operate with emergency power to support emergency operations (up to 6,000,000 gpd in emergency scenarios). The project includes converting two Golden Gate Park irrigation wells to municipal supply in a later phase (potentially late 2020) once recycled irrigation supply is in place.
Community outreach and transparency: staff said outreach has been ongoing since 2007, including public taste tests, focus groups, fact sheets, digital, paid and transit advertising and roadshows; staff agreed to post the presentation and an updated fact sheet online and to provide empirical water‑quality data requested by public commenters.
Ending: Commissioners asked for more detail on testing frequency and monitoring; staff agreed to provide the exact testing schedule with the Division of Drinking Water submittal and indicated new fact sheets and the presentation would be posted to the PUC website.
