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SFPUC to review groundwater blending after commissioners and public raise water-quality concerns
Summary
Commissioner Kane and multiple public commenters urged the San Francisco Public Utilities Commission to examine why groundwater is being blended into the city’s drinking supply, citing odors and possible nitrates; staff agreed to schedule a hearing for the July 11 meeting to present data and options.
Commissioner Kane asked the San Francisco Public Utilities Commission on June 13 why the agency is blending groundwater into the municipal supply when surface-water supplies appear abundant, saying he worried the practice could add unnecessary nitrates to tap water and asking for a formal presentation and hearing.
"I want to learn more about this and why we're doing it," Commissioner Kane said, noting Hetch Hetchy conditions he observed and asking staff to bring the item back to the commission. Staff and commissioners agreed a fuller presentation would be useful and scheduled the topic for the July 11 meeting to allow time for preparation.
Public commenters amplified the concern. Mr. DeCosta said a prior hearing had drawn dozens of residents who reported smelling or tasting issues after blending, and urged the commission to treat the matter as a PUC hearing item. "Even today in the morning, the water was smelling," DeCosta said, calling for the commission to "do something about it."
SFPUC staff told the commission that the proportion of groundwater blended into the system varies and that there have been periods when no blending occurred; staff recommended presenting monitoring data, wholesale-customer implications and options for using blended water for nonpotable purposes. A staff member also noted that some state actions could affect system yield and that context would be part of the scheduled review.
The commission directed staff to prepare materials that address the volume and purpose of blending, water-quality monitoring (including any nitrate data), how blended water is allocated across retail and wholesale customers, and options for using groundwater for nonpotable supply if appropriate. Staff indicated the July 11 meeting would include a presentation covering those points.
