Nitrate levels in Stoughton area’s drinking water are decreasing, even as other Madison-area suburbs’ water supplies are seeing increases over time.
In the last decade, the average level of nitrates, considered a harmful nutrient that can cause health problems, in the city’s four wells has gone down from 5.2 to 3.8 parts per million (ppm). A nonprofit agency EWG, however, showed on a state wide scale the opposite is true.
The federal Environmental Protection Agency’s legal limit of nitrate in drinking water is 10 ppm, however, EWG as a watchdog environmental group recommends no more than .14 ppm.
EWG recommendation is based on recent studies showing increased health effects at nitrate exposure levels of 5 ppm and lower, according to its website.
An EWG study released in June states that of the 303 community water systems tested in Wisconsin, 54% had nitrate levels in drinking water increase over time. The levels increased by 46% on average over 14 years, according to the study’s key findings.
Locally, the EWG study did a 14 year analysis of the nitrate levels in the Bay View Heights neighborhood in the Town of Dunn along Hwy. 51, outside of the Stoughton Utilities district. The analysis showed a decrease from 2.8 ppm to 2.3 ppm.
Wisconsin State Journal reported on June 24 that McFarland, DeForest, Lodi, Sun Prairie, Waunakee and Cross Plains were among the communities in Dane and Columbia counties that experienced an increase in nitrate levels.
Stoughton Utilities director Jill Weiss said that of the four wells in Stoughton, three have almost undetectable nitrate levels, and one well, located in the center of the city, has trace amounts.
From 2003-2017, the well with trace amounts of lead had a range of 4.1 ppm to 6.3 ppm, with an average of 4.76 ppm, Weiss said. She said the water from four wells mixes together, which accounts for the lower overall level.
Stoughton Utilities tests the well with traceable amounts on a quarterly basis to monitor the amount, rather than annually like it does the other three wells, Weiss said.