Is there PFAS in Cal-water Service Co.-chico water?
Yes. EPA's final UCMR 5 results show Cal-water Service Co.-chico averaged 16.8 ppt of PFOS at its worst sampling point, 4.2 times the EPA limit of 4 ppt.
Cal-water Service Co.-chico
Serves 114,925 people · 74 PFOA samples from 37 sampling points · Sep 2023 to Jul 2024
Average above an EPA limit
PFOA Perfluorooctanoic acid
3.4 ppt avg · max 6.8
PFOS Perfluorooctanesulfonic acid
16.8 ppt avg · max 22.5
PFHxS Perfluorohexanesulfonic acid
16.9 ppt avg · max 22.1
Hazard index GenX, PFBS, PFNA, PFHxS combined
1.7 avg · max 2.2
Also detected, no federal limit: PFBS, PFHxA, PFPeA.
Cal-water Service Co.-chico is a public water system drawing on groundwater, based in San Jose, California, serving about 114,925 people, including Chico, Hamilton City, Orland. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 74 times across 37 sampling points between Sep 2023 and Jul 2024.
Every PFAS detected
Not detected: PFDoA, PFDA, PFTrDA, PFNA, PFHpA, NMeFOSAA, PFUnA, NEtFOSAA, PFEESA, 11Cl-PF3OUdS, 8:2 FTS, PFHpS, NFDHA, PFTA, PFMBA, PFMPA, 4:2 FTS, 6:2 FTS, PFBA, HFPO-DA, ADONA, 9Cl-PF3ONS, PFPeS.
Lithium, tested in the same program: highest 11.7 ppb, detected in 3 of 74 samples. EPA's health-based screening level is 10 ppb.
What the EPA limits mean here
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.
What you can do at home
Two routes work for PFAS. For drinking and cooking water only, a reverse osmosis system certified to NSF/ANSI 58 with a PFOA/PFOS reduction claim is the cheapest proven option. To treat every tap and shower, a whole-house carbon system with enough contact time works, but check that the maker has PFAS test data, not just a marketing claim. See the best filters for PFAS and how PFAS removal works.
Other systems in California
All 707 tested systems in California
ZIP codes served
95926 95928 95951 95963 95973
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Cite this page
Well & Tap. "PFAS in Cal-water Service Co.-chico water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID CA0410002. https://wellandtap.com/pfas/california/cal-water-service-co-chico/
About this data
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID CA0410002). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
