How Nitrate Pollution From Farming Threatens Wisconsin's Drinking Water

Chippewa Falls, Wisconsin — A city known for its clean water heritage is now on the front lines of a growing public health crisis linked to agricultural runoff.

In 1997, city officials in Chippewa Falls detected elevated nitrate levels in one of its municipal wells. In response, the city installed filtration systems and drilled deeper wells to ensure its drinking water met federal safety standards. The effort has cost the city approximately $200,000 annually to operate. While this measure protects the city’s 16,000 residents, it has highlighted a stark disparity between urban and rural water quality in Chippewa County.

Nearly 67,000 residents outside the city rely on private wells, many of which are contaminated with nitrates in concentrations exceeding the federal limit of 10 parts per million. Matthew Boos, supervisor of Chippewa Falls’ water treatment plant, acknowledges the divide. His own home, located outside the city, is supplied by a well with nitrate levels that have doubled from 10 to 20 parts per million since he moved in. After testing, Boos installed a reverse osmosis system for his family, while his parents received state grants to drill new wells.

The contamination stems from industrial agricultural practices common across the Midwest. Billions of pounds of chemical fertilizers and millions of tons of livestock manure are applied to farm fields in Wisconsin and neighboring Corn Belt states. Nitrates, formed when nitrogen from these sources is exposed to oxygen, easily infiltrate groundwater and surface water supplies. Long-term exposure to nitrates has been linked to cancers of the blood, brain, breast, bladder, and ovaries, as well as thyroid disease and birth defects.

Despite mounting scientific evidence, federal nitrate regulations have remained unchanged since 1962. The U.S. Environmental Protection Agency (EPA) has maintained the 10 parts per million limit for decades, despite studies suggesting harm at concentrations as low as 5 parts per million. Recent attempts by the Obama and Biden administrations to review the standard were blocked by the Trump administration.

Wisconsin, one of the nation’s top agricultural producers, exemplifies the scope of the problem. Nitrates are the most pervasive contaminant in the state’s groundwater, with nearly one in 10 private wells exceeding safety standards over the past 20 years. Farmers applied five times more nitrogen fertilizer in 2019 than in 1960, and expanding dairy and hog operations have contributed to increased manure runoff.

The consequences are widespread. In Chippewa County, state testing has found nitrate levels exceeding federal limits in many private wells. As a partial solution, the county has installed four "refill stations" where residents can collect treated water for drinking and cooking. However, these stations serve a fraction of the population.

Chippewa Falls remains an outlier in the region, treating 4 million gallons of water daily to ensure safety for its residents. "I tell people I would take city water over well water here any day, especially in this region," Boos said.

The disparity between urban and rural water quality underscores the broader challenge of regulating agricultural runoff in the Corn Belt. With no comprehensive federal action in sight, communities like Chippewa Falls continue to bear the burden of protecting public health amid persistent water contamination.