Madison Water Utility announced Tuesday that four city wells were found to contain trace amounts of a contaminant, though they did not advise closing them.
Last month, Madison Water Utility tested 14 of the city’s 23 municipal wells for perfluorinated compounds, or PFAS compounds. PFAS are a group of chemicals used in non-stick cookware, water-resistant clothing, food packaging and firefighting foams. High concentrations of PFAS could have potential health effects on humans.
Madison wells were tested in 2015 for PFAS, but none were detected. In 2017, Madison Water Utility began re-testing the wells using more sensitive methods, finding two contaminated wells. The results of last month’s tests now bring the total number of wells containing traces of PFAS to six. The remaining wells will be tested within the next couple of months.
City officials pinpoint nearby Traux Air Field’s use of fire fighting foams as the likely cause of contamination at one well on Madison’s east side. However, the source of PFAS for the other wells remain unknown.
The highest level found at any Madison well was one-seventh of the Environmental Protection Agency’s Lifetime Health Advisory Level for PFAS. Public Health Madison and Dane County do not consider the water to be a threat to public health, nor recommend investing in filters or bottled water.
“We’re talking about really trace level detections, anywhere from less than one part per trillion to around five parts per trillion,” Madison Water Utility water quality manager Joe Grande said. “Those are the typical concentrations we’re finding.”
A complete data set with PFAS testing results for all Madison wells will likely be completed by the end of this fall.
“This is the first time that people are hearing or knowing about this, and it can sound scary,” Grande said. “We don’t want to frighten people, but we have an obligation to let them know what we’re finding, even if the levels are very, very low.”
