Washington County east of the Twin Cities has about 267,000 residents in communities including Woodbury, Cottage Grove, and Stillwater.
Washington County east of the Twin Cities has about 267,000 residents in communities including Woodbury, Cottage Grove, and Stillwater. Most residents rely on groundwater from the Prairie du Chien-Jordan aquifer system. The county became the center of Minnesota's PFAS crisis after contamination from 3M's Cottage Grove facility was discovered in 2002, triggering one of the largest PFAS cleanups in the country.
3M manufactured PFOS and PFOA at its Cottage Grove plant from the 1950s until 2002, disposing of waste at the nearby Woodbury and Lake Elmo disposal sites. According to the Minnesota Pollution Control Agency's 2024 PFAS status report, the contamination plume covers over 100 square miles across eastern Washington County. More than 100 private wells have been affected, and the state has spent over $850 million from a 2018 3M settlement on remediation, including installing municipal water connections for affected homes.
Despite extensive cleanup efforts, PFAS persists. A 2024 MPCA monitoring update found PFOS at concentrations above 30 ppt in multiple monitoring wells within the plume area. Some newer PFAS compounds not covered by the settlement continue to be detected at the Cottage Grove facility boundary.
Washington County's PFAS contamination is well-documented and actively managed, but the plume's extent means you should verify your specific situation. If you received a municipal water connection as part of the settlement, you are on treated supply. If you remain on a private well, particularly in the eastern part of the county, testing is essential.
Check your water for current data at your address. For PFAS, reverse osmosis provides the highest household removal rate. Our water filter guide covers systems with certified PFAS performance. Get your detailed report for historical trends, and visit our Minnesota page for statewide patterns.