The source of a chemical pollutant first detected in Lake Calhoun fish over a decade ago reached an agreement with the Minnesota Pollution Control Agency in May to end the discharge.

Douglas Corporation agreed to capture or treat stormwater runoff at its St. Louis Park metal-plating facility to limit the release of PFOS (perfluorooctane sulfonate), a type of perfluorochemical. The agreement with MPCA also commits Douglas Corporation to monitoring groundwater contamination near its plant on Xenwood Avenue.

Douglas Corporation eliminated PFOS from its chrome-plating process in 2010, the same year MPCA traced the pollution to its facility. That was six years after University of Minnesota researchers first detected high concentrations of PFOS in Lake Calhoun’s fish.

MPCA investigators determined PFOS entered the lake through the municipal stormwater system. It accumulated near vents on Douglas Corporation’s roof and then was washed off by rain and melting snow.

The plant is located less than two miles west of Lake Calhoun. Also contaminated with PFOS was Bass Lake, a smaller body of water situated roughly halfway between Douglas Corporation and Lake Calhoun.

Since 2010, the company has replaced equipment contaminated with PFOS. It closed off vents and eventually replaced the entire roof of its building.

“As we worked with them as the years went on, we trying to figure out what was the best remedy to fix the issue,” said John Elling, supervisor of the MPCA’s hazardous waste unit, said the levels of PFOS. “Slowly the numbers started coming down, but yet they weren’t down to where we wanted them.”

John Fudala, vice president of Douglas’ plating division, said the company planned to settle on a course of action within six months. Its choices are to capture contaminated stormwater and reuse it in its manufacturing process or to treat the stormwater on site to bring the levels of PFOS within an acceptable range.

“We’ve spent a lot of money on this problem but, again, we want to do the right thing,” Fudala said. “PFOS is obviously a problem for Lake Calhoun, and we don’t want to be a source of the problem.”

The Minnesota Department of Health has issued a fish consumption advisory for Lake Calhoun related to both mercury and PFOS contamination. Its advice is to limit consumption of panfish like bluegills and crappies to one meal per week and to eat larger fish from the lake no more than once per month.

The department reports perfluorochemicals are distributed widely in the environment and can be found in low levels in lakes, streams, animals and humans. Although associated with tumors and other health effects based on lab tests with animals but the human health impacts of perfluorochemicals are uncertain.