The City of Pewaukee has issued a Tier 2 public notice after a routine test showed elevated levels of per- and polyfluoroalkyl substances (PFAS) in a municipal well. A sample collected on July 7 from City Well #8 detected PFHxS at 47.0 parts per trillion (ppt), and PFOA and PFOS above the state drinking water standard of 4.0 ppt.
According to the City, the Wisconsin Department of Natural Resources (DNR) requires a Tier 2 notice when sample results exceed applicable limits. The notice states that PFAS chemicals have been found in the drinking water supplied by the utility at concentrations exceeding maximum contaminant levels when evaluated under the running annual average framework. While the current results do not constitute an immediate maximum contaminant level violation, the utility is advising residents to consider alternate drinking water sources that have been tested and meet recommended standards.
The City also outlined point-of-use treatment options for households that choose to continue using tap water for drinking. Recommended products include granular activated carbon (GAC) filters certified to ANSI/NSF Standard 53, or reverse osmosis (RO) units that incorporate a GAC component, both of which can reduce PFAS concentrations.
To address the exceedances at the system level, Pewaukee plans to begin work in 2027 on an anion exchange water treatment facility designed to remove PFAS from Well #8. Anion exchange is among the treatment technologies utilities deploy to target these compounds and is expected to provide a long-term solution for the affected source.
PFAS are a group of synthetic chemicals used in a wide range of commercial and consumer applications since at least the 1940s. They are persistent in the environment and have been detected in groundwater in several Wisconsin communities. Groundwater supplies drinking water for the vast majority of the state’s public systems via wells—11,149 of 11,209 total public water systems, according to the DNR. PFAS exposure has been linked to certain cancers and other adverse health and reproductive effects.
At the state level, funding and standards have recently shifted to support PFAS response. In April 2026, legislation released $133 million to address contamination across Wisconsin. Separately, new rules aligning Wisconsin’s drinking water standards with federal limits took effect July 1, setting the acceptable level for PFOA and PFOS at 4.0 ppt, a reduction from the prior 70 ppt threshold.
