Supervisors press SFPUC on safety, monitoring and outreach for groundwater blending; hearing continued

The Public Safety and Neighborhood Services Committee held an extensive hearing on May 24 on the San Francisco Groundwater Supply Project, focusing on whether adding locally pumped groundwater to the city's drinking supply is safe, how the PUC monitors contaminants, and whether outreach and transparency have been adequate. Following presentations from SFPUC and the San Francisco Department of Public Health (DPH), more than two dozen public speakers raised concerns about contaminants, cumulative exposures and the adequacy of outreach. The committee voted to continue the hearing to the call of the chair for additional data and analysis.

Supervisor Norman Yee, who called the hearing, said he had heard concerns from constituents across multiple districts and invited SFPUC Assistant General Manager for Water Steve Ritchie to summarize the project. Ritchie said the effort to diversify local water sources began as a PUC policy in 2008 and is intended to bolster reliability and resilience in the face of drought, climate change and regulatory pressures affecting the Tuolumne River supply. He described the Westside Basin aquifer (roughly from the Presidio to Lake Merced and over toward the airport) and said the PUC has 45 groundwater monitoring wells at 19 locations and a long history of sampling and study.

Project specifics cited by Ritchie included plans for six production wells built in two phases (four wells in phase 1 are nearly complete; two in Golden Gate Park would follow once recycled‑water projects are ready), roughly five miles of dedicated groundwater pipeline, and an initial testing program to bring up to 1,000,000 gallons per day into the distribution system as part of a phased approach. Ritchie described construction standards intended to protect groundwater quality (well grout seals twice the depth required by state standards; well screens to depths up to about 450 feet) and a treatment/blending program that includes chlorination and pH adjustment and has been reviewed by state drinking water regulators.

Ritchie said the PUC intentionally designed the distribution so the blended groundwater is spread widely and the percentage of groundwater in the blend is minimized for any single neighborhood. He also said that blending and treatment strategies were reviewed by an outside panel of experts and approved by the State Water Resources Control Board Division of Drinking Water; he pointed to a letter in the packet from Dr. Tomas Aragon, San Francisco Health Officer, stating that "the evidence is clear that the plan to blend groundwater with surface water supplies will not create any adverse health consequences." Ritchie added that outreach has been extensive over more than a decade, including public tasting events, focus groups, mailed bill inserts, local media coverage and an environmental impact review process that included planning‑department EIR materials and hearings.

Dozens of public commenters — including neighborhood association leaders, parents, public‑health advocates and residents — expressed distrust of the program or asked for more data. Common concerns included cumulative health effects from low‑level contaminants (for example, nitrates, manganese and hexavalent chromium), the adequacy of monitoring frequency and analytes tested (including pharmaceuticals and emerging contaminants), potential subsidence or impacts on trees from groundwater pumping, transparency of PUC communications, and whether the project is needed during a year of high reservoir levels.

In response to questions from supervisors, Dr. Aragon (Health Officer) said he and the DPH epidemiologist who reviewed the project believed that, based on current science and the PUC's monitoring plans, the blended water is safe now, while acknowledging that monitoring, continued literature review and the ability to reverse blending if needed are essential. Ritchie provided numerical context: system baseline nitrate of roughly 0.35 mg/L could increase to about 1.45 mg/L with the first 1 MGD groundwater increment, remaining far below the drinking water standard (45 mg/L as nitrate). He said the PUC will continue routine and periodic testing for a broad set of constituents and make data publicly available. Supervisors asked for a fuller panel of analytes, more frequent sampling and comparative benchmarks from other systems.

Supervisor Sheehy moved to continue the hearing to the call of the chair to allow SFPUC and DPH to provide additional data (water quality analyst participation, consumption assumptions, a fuller list of analytes and monitoring frequency, and results after initial blending at the 1 MGD increment). The motion passed without objection.

What happened next: the committee left the record open for the PUC and DPH to provide further data and analysis and signaled the likelihood of a follow‑up hearing after the initial monitoring round is completed and shared with the committee.