La Crosse County, Wisconsin: drinking water report. La Crosse County in western Wisconsin has about 120,000 residents, with the City of La Crosse situated
La Crosse County in western Wisconsin has about 120,000 residents, with the City of La Crosse situated at the confluence of the Mississippi, Black, and La Crosse Rivers. The city draws drinking water from deep wells tapping the Jordan Sandstone aquifer – a confined aquifer system that has provided reliable, high-quality water for generations. The Mississippi River's proximity, however, creates a complex surface-groundwater interaction zone.
La Crosse's deep wells have historically produced excellent water, but the aquifer system faces emerging pressures. According to the Wisconsin DNR's 2024 groundwater assessment, nitrate concentrations in the shallow aquifer overlying the confined Jordan Sandstone have been increasing steadily, driven by agricultural activity in the county's eastern townships. Some shallow wells in the town of Onalaska have exceeded the 10 mg/L MCL.
The La Crosse Regional Airport has confirmed AFFF firefighting foam use. Wisconsin DNR's 2024 PFAS investigation found combined PFAS at 16 ppt in monitoring wells near the airport – within range of the proposed state standard of 20 ppt. The Fort McCoy military installation, 30 miles northeast, has documented PFAS contamination that may affect regional groundwater flow patterns.
La Crosse's deep well supply is among the better-protected water sources in Wisconsin, but the shallow aquifer that feeds private wells in the surrounding area tells a different story. If you are on a private well, testing for nitrate is essential.
Check your water for data at your location. For most La Crosse municipal users, a carbon filter addresses taste and disinfection byproducts. Well owners should consider reverse osmosis for nitrate and PFAS protection. Our water filter guide covers both scenarios. Get your detailed report for trends, and visit our Wisconsin page for statewide patterns.