Is there PFAS in Rapid City water?
Yes, at low levels. 1 PFAS was detected, all below EPA's 2024 limits.
Rapid City
Serves 72,009 people · 20 PFOA samples from 8 sampling points · Aug 2024 to Sep 2025
PFAS found, below EPA limits
PFOA Perfluorooctanoic acid
not detected
PFOS Perfluorooctanesulfonic acid
not detected
PFHxS Perfluorohexanesulfonic acid
4.8 ppt avg · max 5.6
Hazard index GenX, PFBS, PFNA, PFHxS combined
0.5 avg · max 0.6
Rapid City is a public water system drawing on surface water, based in Rapid City, South Dakota, serving about 72,009 people. Under EPA's Fifth Unregulated Contaminant Monitoring Rule it was tested for 29 PFAS and lithium 20 times across 8 sampling points between Aug 2024 and Sep 2025.
Every PFAS detected
Not detected: PFMPA, PFHpS, PFTA, NFDHA, PFPeS, PFEESA, PFPeA, 8:2 FTS, PFTrDA, PFBA, PFMBA, NEtFOSAA, NMeFOSAA, PFOA, PFDA, PFDoA, PFHxA, PFUnA, 11Cl-PF3OUdS, 9Cl-PF3ONS, 4:2 FTS, HFPO-DA, 6:2 FTS, PFOS, ADONA, PFNA, PFBS, PFHpA.
Lithium, tested in the same program: not detected.
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
Levels here are under EPA's limits, so no treatment is required. If you want them lower anyway, a certified reverse osmosis system under the sink handles drinking water, and a whole-house carbon filter also takes out the chlorine or chloramine your utility adds.
Other systems in South Dakota
All 49 tested systems in South Dakota
ZIP codes served
57702
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 Rapid City water: EPA UCMR 5 results." Data: U.S. EPA Fifth Unregulated Contaminant Monitoring Rule, final release August 2026, PWSID SD4600406. https://wellandtap.com/pfas/south-dakota/rapid-city/
About this data
Source: U.S. EPA, UCMR 5 occurrence data, final release August 2026 (PWSID SD4600406). Population: EPA SDWIS. Averages count results below the reporting level as zero, the same convention EPA uses for running annual averages. Full method.
