Waukesha County, Wisconsin: drinking water report. Waukesha County lies just west of Milwaukee with a population of about 410,000.
Waukesha County lies just west of Milwaukee with a population of about 410,000. For decades, the county relied on deep wells drawing from a confined sandstone aquifer. But overpumping dropped water levels by hundreds of feet and caused naturally occurring radium to concentrate in the remaining water. In 2023, after years of legal and political battles, the City of Waukesha completed a $286 million pipeline to Lake Michigan – the first community outside the Great Lakes basin approved to divert lake water under the Great Lakes Compact.
Radium contamination drove the switch to Lake Michigan water. According to the Wisconsin DNR's historical monitoring data, Waukesha's deep wells consistently exceeded the EPA's MCL of 5 pCi/L for combined radium-226 and radium-228, with some wells testing above 10 pCi/L. The Lake Michigan supply has eliminated radium as a concern for the city, but suburban communities in the county that still use deep wells continue to face elevated radium levels.
The EPA's UCMR5 data shows PFAS detections at low levels in several county systems. The Waukesha County Airport and General Mitchell International Airport in neighboring Milwaukee County are potential PFAS sources. A 2024 Wisconsin DHS report found two public water systems in the county with PFAS above the state's recommended groundwater standard of 20 ppt.
If you are in the City of Waukesha on the new Lake Michigan supply, your radium concern is resolved. But if you are in a suburban community still on deep wells, radium may still be present and is not detectable by taste, smell, or appearance.
Check your water to see which system serves you and what contaminants have been detected. For radium, reverse osmosis or ion exchange treatment is effective. For PFAS, RO handles both. Our water filter guide covers well-water-specific options. Pull your detailed report for historical data, and visit our Wisconsin page for statewide context.