DNR orders Mitchell Airport to cleanup 'forever' chemicals detected in Lake Michigan tributaries

High levels of a family of toxic chemicals have been detected in stormwater flowing to Wilson Park Creek and Oak Creek from sites at Milwaukee Mitchell International Airport.

The findings made public Friday by state officials suggest the compounds, known generically as PFAS, are making their way to Lake Michigan, the source of drinking water for nearly 900,000 residents in metropolitan Milwaukee.

PFAS compounds were detected on airport property in three stormwater points that empty into the two creeks — sometimes at levels that far exceeded minimum thresholds the administration of Gov. Tony Evers is proposing for groundwater. 

Wilson Park Creek drains into the Kinnickinnic River and eventually Lake Michigan. Oak Creek flows directly to Lake Michigan.

The state Department of Natural Resources has ordered the airport to determine the source and extent of the contamination, prevent future discharges and develop a cleanup plan. 

“We don’t want to see chemicals at these levels being discharged into the environment,” said Darsi Foss, the DNR's administrator of the division of environmental management.

In August, the Journal Sentinel reported sampling in 2017 and 2018 showed PFAS chemicals turned up for the first time in raw lake water and after it was treated by Milwaukee Water Works, which serves about 865,000 people in Milwaukee and 16 other communities.

The DNR said that the levels were not a public health concern but something for the water utility to monitor.

PFAS chemicals are believed to be widespread and have been used for decades in industry and consumer products, ranging from fire retardants to nonstick pans.

Epidemiology studies have suggested that they can lead to increased risk of pregnancy-induced hypertension, liver damage, thyroid disease, asthma, decreased fertility, some cancers and a decline in response to vaccines. 

The DNR had directed airport officials to test stormwater on the property because of past discoveries of the chemicals in soil and groundwater at the Air National Guard 128th Air Refueling Wing and the 440th Airlift Wing of the Air Force Reserve. The 440th moved to a base in North Carolina in 2007.

Airports and military sites are suspected problem areas for the chemicals because they use fire retardants containing PFAS compounds. 

Known as “forever chemicals” because of their difficulty in breaking down in the environment, PFAS compounds are coming under growing scrutiny across the country.

Mitchell spokesman Harold Mester said in an email that the chemicals were used in firefighting but were discontinued in 2012 when the airport switched to a more environmentally friendly firefighting foam. 

Mester said airport officials believe the source of the chemicals appears to come from land used by others, including the 128th and the 440th.

“Clearly, we need to be doing more testing for these chemicals,” said Cheryl Nenn of Milwaukee Riverkeeper, who said her group wants to see Mitchell move quickly to screen the contaminants from stormwater. 

Test results in April, May and June turned up about a half dozen compounds, including PFOA and PFOS, which have also been detected in other locations in the state.

The highest concentration involved a compound, PFHxS, of nearly 80,000 parts per trillion, a figure that airport officials said could be misleading because of low water flow at the time of the test that can magnify readings.

Still, other results from Mitchell showed concentrations far higher than those reported at Madison’s airport during the same period. 

Wisconsin has no health standards for PFAS, but is in the early stages of setting limits in groundwater and intends to do the same for drinking water and surface water. 

In June, the state Department of Health Services recommended a combined limit in PFOA and PFOS of 20 parts per trillion in groundwater.

On a separate front, a coalition representing water and wastewater utilities said it is recommending members not start sampling wastewater for the chemicals as requested by the Evers administration.  

The Municipal Water Coalition said members are not the source but “receivers” of such chemicals.

The group said it is developing ways to screen for the chemicals and work with dischargers to reduce their use of the chemicals.