State looks to limit ‘forever chemicals’ in wastewater from 3M’s Cottage Grove plant

State regulators have proposed a new pollution permit for 3M’s Cottage Grove facility that requires the removal of “forever chemicals,” or PFAS, from wastewater that ends up in the Mississippi River.

It will be the first time Minnesota has required an industry to limit PFAS, or per- and polyfluoroalkyl substances, in its wastewater. 3M’s Cottage Grove plant, the epicenter of the global PFAS problem, has been operating under a permit issued more than 20 years ago.

Carly Griffith, water program director with the nonprofit Minnesota Center for Environmental Advocacy, called the draft permit “a very important milestone and step forward” that will set a precedent statewide for other industrial and municipal wastewater permits.

In a news release earlier this month, the Minnesota Pollution Control Agency called the 400-page draft permit “one of the most rigorous in state history.” It requires the removal of certain PFAS to levels so low they can’t be detected by current technology. 3M is currently building an advanced treatment system to remove the chemicals. 

Forever chemicals “have no place in any lake or river,” said MPCA commissioner Katrina Kessler in a news release.

“This permit is an opportunity to leverage the latest science, technology and regulations on PFAS to require 3M do even more to keep PFAS out of the Mississippi River,” Kessler said.

The draft permit also requires 3M to expand its efforts to monitor contamination in groundwater, upstream and downstream waters and in fish, and make the results public.

3M has manufactured PFAS at its Cottage Grove facility since the 1950s. They were used in a variety of consumer and industrial products, including furniture, cookware, carpet and water-resistant clothing. 

Some of the compounds have been linked to human health impacts, including kidney and thyroid problems, birth defects and cancer.

3M phased out the production of the two most widely known and harmful PFAS compounds, known as PFOS and PFOS, in the early 2000s. But it continues to produce other replacement PFAS with shorter carbon chains, whose health impacts are less studied. 

In a statement, 3M spokesperson Grant Thompson said the company is investing nearly $300 million in advanced water treatment systems at Cottage Grove. Construction began in 2021.

“These state-of-the-science technologies will continue to remediate PFAS in area groundwater — even after 3M exits PFAS manufacturing by the end of 2025,” Thompson stated. 

The Cottage Grove facility treats its wastewater and stormwater before discharging it into a creek that flows into the Mississippi. Under the draft permit, it would be allowed to discharge up to 15.2 million gallons a day, although in recent years it’s released five to six million gallons a day.

Some environmental and tribal groups have raised questions about whether the draft permit goes far enough to keep PFAS out of the Mississippi, where elevated levels of the chemicals already have been found in fish tissue.

The Prairie Island Indian Community, which is downstream from the Cottage Grove plant, has “significant concerns” about the draft permit, Tribal Council President Grant Johnson said in a written statement. 

“Our members rely daily on clean waters from the Mississippi and other nearby rivers to support our food sources and way of life,” Johnson stated.

Prairie Island has concerns about plans for testing and removing contaminants, the length of time it took to complete the permit and a “continued reactive versus proactive approach” to addressing PFAS, he stated.

3M has been operating under a 2003 permit. The MPCA released a draft permit in 2011 that would have set limits on PFOS. But it was never finalized because of the state of Minnesota’s lawsuit against 3M, which settled in 2018 with 3M agreeing to pay $850 million for environmental contamination.

The draft permit sets limits for six types of PFAS, including nearly undetectable levels for the legacy compounds PFOS and PFOA. It also sets limits for three shorter-chain PFAS compounds, although not as low.

Griffith said she thinks the MPCA should use caution because of the quickly evolving scientific research about PFAS, and the increased levels of contamination in the east Twin Cities metro.

“It’s a precautionary principle based on how much our understanding of these chemicals is changing, and also based on the increased body burden of Minnesotans in this part of the state,” she said.

The six PFAS compounds the permit regulates are the same chemicals for which the federal government recently set enforceable drinking water limits. Public water utilities have five years to treat their water so it meets the new limits.

“That will be very expensive,” Griffith said. “So permits like this are our opportunity now to ensure that the polluters that bear direct responsibility for this contamination are held responsible for the burden of those costs.”

And while the east Twin Cities metro is one of the most visible and dramatic examples of the impacts of PFAS in Minnesota, the chemicals have been found throughout the state, Griffith said.

The public has until Friday, Aug. 30 to comment on the draft permit. 

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