EAU CLAIRE — The city shut down a quarter of its wells last week after learning water in them had elevated levels of chemicals that are believed to pose human health risks.

On Monday the city announced that it had shut down four out of the 16 wells that provide Eau Claire’s drinking water supply when it received test results showing levels of PFAS exceeding state standards.

“We have taken swift action to protect the public’s health and safety by immediately shutting down wells that had PFAS levels above newly recommended standards,” Interim City Manager Dave Solberg said. “Because the wells were immediately shut down, Eau Claire residents do not need to stop drinking or using water from the city’s water supply.”

Known as “forever chemicals” because they don’t break down in the environment, PFAS are a group of human-made chemicals used in a variety of products since the 1950s. They are found in non-stick cookware, fast food wrappers, stain-resistant sprays and firefighting foam.

Scientists are still studying health effects of various PFAS on humans, the state Department of Health Services states on its website. Not all PFAS have the same health effects, but research suggests that high levels of certain chemicals may raise cholesterol levels, decrease how well bodies respond to vaccines, increase risk of thyroid disease, lower fertility in women, increase risk of conditions including high blood pressure in pregnant women, and result in slightly lower infant birth weights.

Water samples the city took in June 2020 and April 2021 were both within PFAS standards set by the state, according to city officials. However, in June the state Department of Health Services issued revised guidance on the the amount of PFAS compounds that can be found in water supplies. Based on those changing rules, Eau Claire’s previous water samples now caused concern for elevated health risks. New samples were taken on July 6 from all the city’s wells and results arrived on Thursday.

“Those results indicated we had four wells with slightly elevated levels of PFAS so we immediately shut those wells off,” said Lane Berg, city utilities manager.

For a group of PFAS chemicals, the state recommends concentrations of no more than 20 nanograms per liter of water. In the wells that were shut down, they had between 21.3 and 70 nanograms per liter.

Three of those wells are in close proximity to each other, while another is in a different part of the city’s wellfield, Berg said. Why those wells showed higher PFAS levels while others didn’t is part of an examination being done in hopes of tracking down the reason for the contamination and preventing it from happening again.

“That’s something we are going to continue to investigate,” Berg said.

PFAS contamination typically occurs after chemicals spill on the surface and gradually get washed down by rain into the groundwater, he noted.

With four wells out of service due to the PFAS levels and another down for repairs, that leaves 11 wells still providing water for the city.

Based on that, the city’s water treatment plant can provide about 16 million gallons of water a day, Berg said. In recent days, residents have been using 12 million gallons of water per day.

“Unless things get really dry we should be able to maintain our water supply,” Berg said.

So far this summer Eau Claire hasn’t imposed any water restrictions, such as limiting how often residents can water their lawns, while some neighboring municipalities have implemented those to maintain their water supply.

The city is evaluating its treatment options for the four wells with elevated PFAS levels to get them back in service when samples from them meet state standards.

Since the elevated PFAS levels were discovered in those four wells, those near them will be tested regularly every two weeks.

A sampling of the city’s water supply was taken Monday and results are expected Wednesday.

Contact: 715-833-9204, andrew.dowd@ecpc.com, @ADowd_LT on Twitter