Trace amounts of the chemicals known as PFAS have been found in four more wells in Madison, bringing the total number of wells having the chemicals up to 10 out of the 19 wells tested so far.
The levels of PFAS detected in Madison wells are not considered a health threat, but Madison Water Utility water quality manager Joe Grande said it’s better to know what’s in the water than not.
“I think there’s a lot of value in the known vs. the unknown,” Grande said. “Our customers deserve that information.”
The four new wells are Well 7 on North Sherman Avenue, Well 13 on Wheeler Road, Well 26 on High Point Road and Well 29 on North Thompson Drive. Wells 7 and 29 had almost undetectable levels that could be a false positive, Grande said, while wells 13 and 26 had trace amounts.
Well 15 on East Washington Avenue and Well 9 on Spaanem Avenue have shown low levels of PFAS. Four wells — Wells 6 and 14 on University Avenue, Well 11 on Dempsey Road and Well 16 on Mineral Point Road — have shown trace amounts.
No PFAS were detected in nine wells, on South Whitney Way, Park Street and North Livingston streets, Tradewinds Parkway, Lake Mendota Drive, and Prairie, Queensbridge, Old Sauk and Moorland roads.
Four wells that are seasonal and used only during high-demand warm weather months will be tested in the summer. Those wells are on South Hancock Street, Leo Drive and Lakeland and North Randall avenues.
Grande said based on results so far, he would not be surprised to find very low levels of PFAS at one or more of the seasonal wells.
PFAS, short for per-fluoroalkyls and poly-fluoroalkyls, are chemicals found in non-stick cookware, water-resistant clothing, upholstery, carpeting, food packaging and firefighting foams.
Exposure to high levels of PFAS is linked to various health problems, including an increased risk of some types of cancer.
The Environmental Protection Agency has a lifetime health advisory level for two types of PFAS of 70 parts per trillion.
The highest readings found in Madison, 20-21 ppt, were in Well 15, the well closest to the airport.
Well 15 has been taken out of service in part because of heavy groundwater contamination, including from firefighting foam used in training at the Air National Guard’s Truax Field.
Madison Water Utility said the latest test results show traces of the compounds at some wells located in residential neighborhoods, far from airports, landfills or manufacturing sites, where PFAS would more commonly be found.
“These chemicals are not well understood at this point, in terms of where they are coming from,” Grande said.
“We are finding PFAS at the well closest to the airport where firefighting foams have been used, and that seems logical,” he said. “And now, that’s kind of been turned on its head. Airports and landfills are clearly not the only sources of PFAS in our environment.”
All city wells were tested for PFAS in 2014 and 2015 but no sign of the chemicals was found.
More advanced testing methods were implemented two years ago, capable of finding trace amounts down to less than 1 ppt, with the new testing detecting PFAS in wells near the airport and old landfills.