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San Dieguito Water District says treated water meets regulatory standards; report highlights PFAS detections below federal limits
Summary
Staff presented the district’s 2025 public health goals report, noting detections of disinfection byproducts and PFAS below current regulatory thresholds and outlined potential treatment options and high-level cost estimates from EPA tools.
San Dieguito Water District staff told the board on June 18 that constituents in the district’s drinking water were detected above public health goals in some cases but that the district has complied with all state and federal primary drinking water standards.
Tim Bailey, director of water treatment for the R.E. Badger Filtration Plant, presented the 2025 public health goals report, explaining that public health goals are non‑regulatory reference levels set by scientific agencies and are often far lower than enforceable Maximum Contaminant Levels (MCLs). Bailey said the district’s water has complied with all National Primary Drinking Water Standards during his tenure.
The report separated detections into two categories: disinfection byproducts (including trihalomethanes and haloacetic acids) and poly‑ and perfluoroalkyl substances (PFAS). For disinfection byproducts, Bailey said measured ranges sometimes exceeded public health goals but remained below regulatory compliance thresholds (for example, the combined THM and HAA regulatory limits cited in the presentation). For PFAS, the presentation listed an EPA national primary drinking water standard of 4 parts per trillion and a public health goal far lower; the highest PFAS result cited in the presentation was 2.8 parts per trillion with an average of about 0.65 parts per trillion.
Bailey described treatment options the EPA tool identifies as most effective for lowering those constituents: enhanced coagulation with granular activated carbon (GAC) or reverse osmosis (RO). He read high‑level cost estimates produced by the EPA tool: roughly $6 million capital and $1.1 million annual operating cost for GAC, and roughly $30 million capital and $6 million annual operating cost for RO, and cautioned that those estimates are starting points and not prescriptive.
Board members asked clarifying questions about PFAS units (parts per trillion equals nanograms per liter) and how the district’s conventional filtration system at the Badger plant compares with membrane systems at other facilities. Bailey said conventional filtration is a “bulletproof” approach and that microfiltration membranes used at some other plants are effective but can foul if source water contains organics; reverse osmosis would be needed to reliably remove PFAS.
No further action was recommended in the report; staff said there were no immediate changes proposed and offered to answer questions. The public hearing was opened and no members of the public spoke; the hearing was then closed.
