PFAS investigation and clean up

Initially developed by 3M, PFAS are a very large family of chemicals that have been used for decades. They repel grease and water, are resistant to heat, extremely strong, and virtually indestructible.

Minnesota's investigation into PFAS contamination began in 2002 when PFAS contamination was traced to four disposal sites in the east metropolitan area of the Twin Cities.

East metropolitan investigation

The 3M chemicals that contain PFOS, PFOA and other PFAS were produced in Minnesota at the 3M Chemolite facility in Cottage Grove. In 2002, 3M notified the MPCA that PFAS was detected in a production well at its Cottage Grove manufacturing facility. At the time, little was known about PFAS, so the MPCA asked the Minnesota Department of Health to develop health guidance.

From the 1950s through the early 1970s, 3M disposed of wastes from PFAS manufacturing primarily at four locations:

  • 3M Oakdale 
  • 3M Woodbury
  • 3M Cottage Grove Chemolite site 
  • Washington County Landfill

In late 2003, the MPCA discovered PFAS in groundwater at and near some of these disposal sites.

In 2004, PFAS were found to have contaminated drinking water supplies in parts of the eastern. Further investigations identified an area of groundwater contamination covering over 150 square miles, affecting the drinking water supplies of over 140,000 Minnesotans.

In the spring of 2007 the MPCA and 3M negotiated a Consent Order bringing investigation and cleanup of the three disposal sites under the formal Superfund process. The Order was approved by the MPCA Citizens’ Board in April 2007. The MPCA provides oversight of work plans or actions related to PFAS contamination at three sites — 3M Chemolite site, 3M Woodbury site, and 3M Oakdale site. The Washington County Landfill is addressed under the state Closed Landfill Program. For more information visit the PFAS waste sites webpage. 

In 2010, Minnesota’s attorney general sued 3M alleging that the company’s production of PFAS chemicals had damaged drinking water and natural resources in the southeast Twin Cities metro area. On Feb. 20, 2018, the state of Minnesota settled its lawsuit against the 3M Company in return for a settlement of $850 million. For more information about 3M Settlement activities, visit

Sampling and pilot test for ground-water treatment at Washington County Landfill

The Closed Landfill Program (CLP) began PDF icon ground-water sampling for PFOS and PFOA at the Washington County Landfill in the spring of 2004. PFOA was found in the groundwater at low levels. The MDH laboratory expanded the PFC analysis to seven compounds in early 2005; in response sampling was expanded to residential wells near the landfill in Lake Elmo and Oakdale.

The CLP completed a pilot test on anionic resins at the Washington County Landfill for treatment of groundwater contaminated with PFOS, PFOA and PFBA, and also completed laboratory tests on activated carbon as a potential treatment method during the summer of 2007. The CLP is looking at the design and associated costs of building and operating an onsite treatment system and is evaluating a range of other potential corrective actions, including a design to dig up the landfill, create a lined site, and place the wastes back on the liner.

Water quality criteria for PFOA and PFOS

From 2006 to 2007, the MPCA, with technical assistance and reports provided by STS Consultants, developed ambient surface-water quality criteria (WQC) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS). The methods that were used to develop these criteria were published in Minnesota Rules, Chapter 7050. This effort led to site-specific WQC for Lake Calhoun (now Bde Maka Ska) and Mississippi River Pool 2.

In 2020, the MPCA has been developing site-specific WQC for PFOS, PFOA, and other PFAS based on newer human health risk assessment methods in Minn. R. ch. 7050 and newer datasets. For information on past and current WQC visit the Site-specific water quality criteria web page.

U.S. EPA activities for PFAS

The U.S. Environmental Protection Agency (EPA) received information in the late 1990s indicating that PFOS was widespread in the blood of the general population and presented concerns for persistence, bioaccumulation, and toxicity.

In January 2006, EPA invited companies responsible for PFOA and related chemicals to enter a stewardship program. EPA monitored for PFAS in drinking water from 2013-2015, and issued health advisory guidance for PFOA and PFOS in 2016. However, EPA has not regulated any PFAS compounds under the Safe Drinking Water Act, meaning that there are no federal limits for PFAS concentrations in drinking water. In February 2020, EPA announced a proposal to regulate PFOA and PFOS in drinking water, but should the proposal be finalized, it would take several years for such a regulation to go into effect.

EPA is taking action related to PFAS in several regulatory arenas other than drinking water, and has summarized their policy response in the PFAS Action Plan.