SFPUC says groundwater blending meets monitoring targets; supervisors continue hearing after extensive public comment

Assistant General Manager Steve Ritchie of the San Francisco Public Utilities Commission told the Public Safety and Neighborhood Services Committee on May 9 that the agency has been testing and incrementally adding groundwater to the city's distribution system and that blended water samples to date meet state and federal standards.

Ritchie said four phase‑1 wells in the Westside Groundwater Basin have been completed and tested, and that SFPUC pumped about 5.4 million gallons of groundwater from April through December of the prior year and roughly 30 million gallons from January through April of the current year while still in a testing phase. He reiterated the SFPUC's short‑term target of delivering an average of 1,000,000 gallons per day in the first full year of operation but emphasized the utility has not begun that operation and is proceeding slowly to validate system performance.

Ritchie explained the agency's blending and treatment strategy, permitted by the state, includes disinfection (sodium hypochlorite) at well stations, pH adjustment with sodium hydroxide for corrosion control and continuous SCADA monitoring with automatic alarms and shutoffs to prevent distribution of water that approaches health limits. He said routine monitoring shows average concentrations of hexavalent chromium, manganese and nitrate in blended water are well below the state's maximum contaminant levels (MCLs) and that SFPUC posts data twice monthly on its website.

Dr. June Weintraub, senior epidemiologist and manager of water regulatory programs at the San Francisco Department of Public Health, said bioaccumulation and other toxicology questions are complex and that regulatory limits are developed by scientific review and are periodically reassessed. She told the committee her office reviews the data and supports continued monitoring and public reporting.

Public comment was extensive and mixed. SPUR (represented by Sierra DeSalvia) argued the groundwater program is a necessary, long‑studied diversification step that will strengthen regional reliability in droughts and earthquakes and said SFPUC and public‑health staff have attested the plan will not create adverse health consequences. Multiple nonprofit and program representatives described testing programs and urged continued implementation with transparent data reporting.

Opponents raised technical and outreach concerns. George Wooding of the Coalition for San Francisco Neighborhoods said outreach had been inadequate and warned that small, intermittent pilot volumes risk masking worst‑case concentrations. Richard Frisby and others flagged the location of wells near mapped fault lines and urged more consideration of seismic risk to aquifers. Chris Bowman and other public‑health advocates cited research and urged that blending targets consider public‑health goals that are sometimes stricter than MCLs, particularly for nitrate exposures in sensitive populations.

On hexavalent chromium, Ritchie noted the State Water Resources Control Board previously proposed a 10 parts‑per‑billion level but a court decision vacated that standard (Vacaville litigation) and the state is reinitiating rulemaking; SFPUC reported blended chromium‑6 concentrations in Sunset Reservoir around 0.00017 mg/L, substantially below the informational 10 ppb figure cited in the slides.

Following presentations and public comment, the committee agreed to continue the groundwater item to the call of the chair for a follow‑up hearing when SFPUC stages further activation and provides additional, peer‑reviewable data. The continuation was entered without objection.

Next steps: supervisors asked SFPUC and the Department of Public Health to continue posting monitoring data, provide well‑specific source data on request and return to the committee for a follow‑up hearing before full activation of the first operational year.