No PFAS were detected in any of the 30 samples EPA's program collected.
City of Caldwell is a public water system drawing on groundwater, based in Caldwell, Idaho, serving about 74,000 people. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 30 times across 15 sampling points between Apr 2023 and Aug 2025.
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: PFDA, 8:2 FTS, 4:2 FTS, 6:2 FTS, HFPO-DA, 9Cl-PF3ONS, 11Cl-PF3OUdS, PFMPA, PFDoA, PFNA, PFHxS, PFHpA, PFHxA, PFUnA, NMeFOSAA, NEtFOSAA, PFTrDA, PFTA, NFDHA, PFPeA, PFMBA, PFOA, PFOS, ADONA, PFHpS, PFBS, PFEESA, PFPeS, PFBA.
Lithium, tested in the same program: highest 16 ppb, detected in 11 of 17 samples. EPA's health-based screening level is 10 ppb.
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 61 tested systems in Idaho
83605 83607
As reported by the utility to EPA. Neighbouring ZIPs are often split between systems; your water bill names yours.
Well & Tap. "PFAS in City of Caldwell water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID ID3140013. https://wellandtap.com/pfas/idaho/city-of-caldwell/
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID ID3140013). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
