Groundwater in Washington County has contaminants above the established health risk limits in a several aquifers. The contamination is generally of three types:
- Contamination resulting from volatile organic or inorganic chemicals leaching from legal and illegal waste disposal and underground storage tanks.
- Contamination of nitrates in parts of the county resulting from certain land use practices and sensitive geologic conditions.
- Contamination from wastes containing perfluoro-alkyl substances (PFAS), also known as perfluorochemicals (PFCs), disposed of by the 3M Company at the 3M disposal sites in Oakdale, Woodbury, and Cottage Grove, and the former Washington County Landfill in Lake Elmo.
The Minnesota Pollution Control Agency (MPCA) has put together a tool to help residents learn about contamination issues, the Minnesota Groundwater Contamination Atlas. As of June 2020, the Atlas contains current and available data from active state Superfund sites. Washington County residents can search the map to view areas of concern for sites in the county with remediation programs.
Special Well and Boring Construction Area (SWCA)
The Minnesota Department of Health declared a Special Well and Boring Construction Area (SWCA), sometimes called a well advisory, for areas in which contaminants are found at a level that poses public health risks. The purpose of a SWCA is to inform the public of potential health risks in areas of groundwater contamination, provide for the construction of safe water supplies, and prevent the spread of contamination due to the improper drilling of wells or borings. The SWCA designation provides for controls on the drilling or alteration of public and private water supply wells, and the monitoring of wells in the area. Washington County has four Special Well and Boring Construction Areas:
- Lake Elmo/Oakdale
- Baytown/West Lakeland Townships
- Lakeland/Lakeland Shores
- St. Paul Park/Newport
In Washington County, Minnesota Statutes, section 103I.236, states “Before signing an agreement to sell or transfer real property in Washington County that is not served by a municipal water system, the seller must state in writing to the buyer whether, to the seller’s knowledge, the property is located within a special well and boring construction area."
See the Minnesota Department of Health Special Well and Boring Construction Areas to learn more information about each site.
Perfluoro-alkyl Substances (PFAS) in Washington County
Wastes containing perfluoro-alkyl substances (PFAS), also known as perfluorochemicals (PFCs), were disposed of by the 3M Company at the 3M disposal sites in Oakdale, Woodbury, and Cottage Grove, and the former Washington County Landfill in Lake Elmo. PFAS were released from the sites, resulting in contamination of groundwater and nearby drinking water wells.
PFAS is monitored by the state of Minnesota. Public and private wells within PFAS contamination areas are monitored regularly.
The most up -to-date information on PFAS can be found on the Minnesota Department of Health website:
If you own a well within the PFAS sampling area and it has not been sampled yet, you may request to have it sampled. The Minnesota Department of Health website has links to an interactive map to determine whether homes are within the sampling area and another link to an online form to fill out to request to have well water sampled
For questions or health related concerns, contact the Minnesota Department of Health Site Assessment and Consultation Unit at 651-201-4897 or firstname.lastname@example.org.
In February of 2018, the State of Minnesota reached a settlement agreement with 3M regarding PFAS, in a Natural Resource Damages lawsuit. See the 3M Settlement page for more information.
Volatile Organic Compounds Testing in Contamination Areas
The Department of Public Health and Environment offers private well water testing for volatile organic compounds, including trichloroethylene. See the water tests page for more information.
In response to the MDH guidance and the need to prioritize sampling being conducted by MPCA and MDH, the county has suspended PFAS testing until further notice.
Nitrates in Washington County
Nitrates have also been found in private wells at levels that exceed the established health risk level of 10 mg/L. The majority of wells affected by nitrate contamination are found in Cottage Grove and Denmark Township, though high nitrates may exist in other areas, from localized sources.