PFAS above EPA’s limits in Wisconsin.
The short answer
18 utilities serving 184,985 people, as they report it, had a location averaging above a limit, most often PFOS (12) and PFOA (12). The largest is La Crosse Waterworks, whose highest PFOS average was 4.9 ppt, 1.2 times the limit. The furthest above is Saukville Waterworks, at 7.6 times the PFOS limit.
These are EPA’s survey results, not violations: the limits take effect April 26, 2029, and compliance will rest on each utility’s own monitoring. EPA has proposed changes to the rule; as of Oct. 13, 2026, none is final.
Utilities above a limit
Largest first. Each one’s highest location average is for the limit it is furthest above, with the single highest sample of the same PFAS; its report has every result.
| Utility | Based in | Serves | Above | Highest location average | Highest single sample |
|---|---|---|---|---|---|
| La Crosse Waterworks | La Crosse | 53,000 | PFOA, PFOS | PFOS 4.9 ppt1.2 times the limit | 5.5 ppt |
| Marshfield Utilities | Marshfield | 18,815 | PFOS | PFOS 13 ppt3.3 times the limit | 14 ppt |
| Weston Municipal Utilities | Weston | 16,000 | PFOA, PFOS | PFOS 11 ppt2.7 times the limit | 13 ppt |
| Hartford Waterworks | Hartford | 15,805 | PFOA, PFOS | PFOA 6.5 ppt1.6 times the limit | 6.8 ppt |
| Sturgeon Bay Waterworks | Sturgeon Bay | 9,700 | PFOS | PFOS 4.2 ppt1.05 times the limit | 4.2 ppt |
| Hartland Waterworks | Hartland | 9,212 | PFOA, PFOS | PFOA 4.4 ppt1.1 times the limit | 4.4 ppt |
| Pewaukee City Water and Sewer Utility | Pewaukee | 8,671 | PFOA, PFOS, PFHxS, Hazard Index | Hazard Index 3.463.5 times the limit | — |
| Rhinelander Water & Wastewater | Rhinelander | 8,234 | PFOA | PFOA 6.2 ppt1.5 times the limit | 6.8 ppt |
| Lake Geneva Utility Commission | Lake Geneva | 7,107 | PFOA | PFOA 4.5 ppt1.1 times the limit | 4.7 ppt |
| Rib Mountain Water Utility | Wausau | 6,398 | PFOA, PFOS | PFOS 8.5 ppt2.1 times the limit | 9.4 ppt |
| Waupaca Waterworks | Waupaca | 6,062 | PFOS | PFOS 4.3 ppt1.06 times the limit | 4.3 ppt |
| Prairie Du Chien Waterworks | Prairie Du Chien | 6,005 | PFOS | PFOS 25 ppt6.3 times the limit | 39 ppt |
| Kewaskum Waterworks | Kewaskum | 4,309 | PFOA | PFOA 14 ppt3.4 times the limit | 15 ppt |
| Saukville Waterworks | Saukville | 4,268 | PFOS, PFHxS, Hazard Index | PFOS 31 ppt7.6 times the limit | 31 ppt |
| Prescott Waterworks | Prescott | 4,258 | PFOA, PFHxS, Hazard Index | PFOA 9.4 ppt2.4 times the limit | 9.9 ppt |
| Tomahawk Waterworks | Tomahawk | 3,180 | PFOA | PFOA 20 ppt5 times the limit | 21 ppt |
| Schofield Waterworks | Schofield | 2,205 | PFOA | PFOA 4.3 ppt1.09 times the limit | 4.7 ppt |
| Palmyra Waterworks | Palmyra | 1,756 | PFOS | PFOS 5.2 ppt1.3 times the limit | 6.2 ppt |
2 more utilities in Wisconsin had a single sample above a limit but no location average above, so they are not listed; each report shows the sample.
Results: EPA UCMR 5 occurrence data, file of Oct. 15, 2026, samples from Jan. 3, 2023 to June 17, 2026, averaged by sampling location as EPA’s final UCMR 5 data summary does. Every state, and the full data as a CSV; how this list is made. People served is what each utility reports.
Where to go next
- La Crosse Waterworks’s reportEvery PFAS result with its dates, and the certification claim that handles each.Open the report
- Every stateThe national list, the largest utilities above a limit, and the data to download.PFAS above EPA’s limits
- Filters certified for PFASRanked by certification and what they cost over five years.Best water filters for PFAS