No PFAS were detected in any of the 9 samples EPA's program collected.
Marin Municipal Water District is a public water system drawing on surface water, based in Corte Madera, California, serving about 186,895 people, including San Rafael, Greenbrae, Belvedere Tiburon, Corte Madera, Rohnert Park, Fairfax. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 9 times across 3 sampling points between Jul 2023 and Jul 2024.
None of the 29 PFAS were found at or above EPA's minimum reporting levels (2 to 20 ppt depending on the compound).
Not detected: PFHpA, 11Cl-PF3OUdS, PFUnA, PFHxA, 9Cl-PF3ONS, PFDA, PFOS, PFNA, PFTA, PFTrDA, NMeFOSAA, PFDoA, PFBS, PFHxS, NEtFOSAA, PFMBA, PFOA, PFPeS, ADONA, PFEESA, PFHpS, PFPeA, PFMPA, 8:2 FTS, 4:2 FTS, 6:2 FTS, PFBA, HFPO-DA, NFDHA.
Lithium, tested in the same program: not detected.
In April 2024 EPA set enforceable limits of 4 ppt for PFOA and PFOS, 10 ppt each for PFHxS, PFNA and GenX, and a hazard index of 1 for mixtures. Utilities were given until 2029 to comply. In May 2026 EPA proposed keeping only the PFOA and PFOS limits and moving that deadline to 2031. Until that proposal is final, the 2024 limits stand.
Compliance is judged on a running annual average at each entry point, so we show the average at this system's worst sampling point next to its single highest result. UCMR 5 results do not by themselves put a utility in or out of compliance.
No PFAS action is needed on these results. If your water tastes or smells of chlorine, a whole-house city water filter is the usual fix.
All 707 tested systems in California
94901 94903 94904 94912 94920 94925 94928 94930 94933 94937 94938 94939 94941 94942 94946 94947 94949 94957 94960 94963 94964 94965 94966 94973 95925
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Well & Tap. "PFAS in Marin Municipal Water District water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID CA2110002. https://wellandtap.com/pfas/california/marin-municipal-water-district/
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID CA2110002). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
