Kewaunee County, Wisconsin: drinking water report. Kewaunee County on Wisconsin's Lake Michigan shore has about 20,000 residents in a deeply rural,…
Kewaunee County on Wisconsin's Lake Michigan shore has about 20,000 residents in a deeply rural, dairy-dependent community. Nearly all residents rely on private wells tapping the Silurian dolomite aquifer. The county has become a focal point in the national debate over concentrated dairy farming and groundwater contamination – with good reason.
Kewaunee County's groundwater crisis is among the most severe of any rural county in the Midwest. According to the Wisconsin DNR's 2024 well water testing summary, 34% of tested private wells exceeded the nitrate MCL and 28% tested positive for coliform bacteria. The county's shallow fractured dolomite bedrock, overlain by thin glacial soil, provides essentially no natural filtration between the surface and the aquifer.
Concentrated animal feeding operations (CAFOs) in the county spread millions of gallons of liquid manure annually on fields overlying this fractured bedrock. A 2024 USGS study traced nitrate isotopes in Kewaunee County wells directly to animal manure rather than synthetic fertilizer, confirming the dairy operation pathway. Some wells have shown nitrate concentrations above 40 mg/L – four times the MCL.
Kewaunee County's groundwater situation is among the most documented in the country, and the data is clear – private wells in fractured dolomite areas face a high probability of contamination. If you have not tested your well recently, the risk of exceeding safe limits is roughly one in three.
Check your water for any available data on your area. For nitrate at the levels found in this county, reverse osmosis is the recommended household treatment. For bacteria, add UV disinfection. Our water filter guide covers systems for high-contamination well water. Get your detailed report for context, and visit our Wisconsin page for statewide patterns.