The PFAS Project Lab

Studying Social, Scientific, and Political Factors of Per- and Polyfluoroalkyl Substances

Washington County (Cottage Grove, Woodbury, Oakdale, Lake Elmo), Minnesota

Suspected contamination source: The 3M Company’s Cottage Grove facility (MDOH, 2016)

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The 3M Company produced per- and polyfluoroalkyl substances (PFASs) at its Cottage Grove facility from the late 1940’s until 2002. Perfluorooctanoic acid (PFOA) was a prominent type of PFAS made at this site.

Waste from the production process were disposed on site in a specially prepared pit. In 2004, the MDH and the MPCA learned that 3M disposed of PFAS waste in the former Washington County Landfill during the 1960s to 1970s. The on site water treatment plant that processed waste water did not remove PFAS, so these compounds eventually entered the Mississippi River. Some sludge left over from the water treatment process also contained PFASs and was disposed on site. On the west side of the site, firefighting foams containing PFASs were used in training exercises. PFASs may also have been released into the air.

“Environmental sampling determined that PFCs in the groundwater in Lake Elmo come from both the former Washington County Landfill and the 3M-Oakdale Disposal Site.  PFCs at the site in Oakdale enter Raleigh Creek, which flows east to the city of Lake Elmo and discharges into Eagle Point Lake in the Lake Elmo Park Reserve.  As the PFCs travel in the creek, some infiltrate into the groundwater and combine with PFCs already in the groundwater from the former Washington County Landfill.  Because of their ability to move between surface water and groundwater, PFCs are found in several of the area lakes (Eagle Point Lake, Lake Elmo, Sunfish Lake, and Horseshoe Lake).  In 2007 and 2018, MDH issued fish consumption advisories for Lake Elmo due to PFOS. See the MDH Site-specific Meal Advice for Tested Lakes and Rivers for more information.” — Minnesota Department of Health

Environmental testing shows that the groundwater beneath the 3M Cottage Grove site is contaminated with PFOA, and other PFASs including perfluorooctane sulfonate (PFOS) and perfluorobutanoic acid (PFBA). In some areas, the levels of PFASs exceed the Minnesota Department of Health (MDH) drinking water criteria, which as of May 2017 is:

  • 35 ppt for PFOA
  • 27 ppt for PFOS

Groundwater beneath the site flows south and discharges to the Mississippi River. Sampling of river sediments near the site and the water within those sediments detects PFASs at levels of concern for humans and wildlife, but concentrations in the river water are much lower due to dilution.

Workers at the facility were exposed to PFASs in the course of their work and also through the facility’s water supply.

In 2008, 2010, and 2014, MDH completed biomonitoring studies of selected residents in Cottage Grove, Lake Elmo, and Oakdale who were known to have been exposed to PFOA and/or PFOS in their drinking water. The average concentration of PFASs in the participants’ samples were higher than the averages for the general U.S. population. The studies found that over time, as the participants drink treated water, the PFAS concentrations in their bodies decreased. More information about the biomonitoring studies can be found at PFC Biomonitoring: East Metro.

Additional Resources

Media Coverage:

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