Contamination Areas

Groundwater Contamination


Groundwater in Washington County has contaminants above the established health risk limits in a number of aquifers. The contamination is generally of two 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

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 where 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."

Go to the Minnesota Department of Health Special Well and Boring Construction Areas to learn more information about each site.

Perfluorochemical (PFC) Waste



Perfluorochemical (PFC) containing wastes 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. PFCs were released from the sites, resulting in contamination of groundwater and nearby drinking water wells. PFCs are also referred to as Perfluoroalkyl Substances (PFAS). 

Additional information on PFC contamination



In May 2017, MDH released updated guidance values for some PFCs, after review of data provided by the US Environmental Protection Agency (EPA). State officials have identified additional private wells in the East Metro area (mainly parts of Lake Elmo and Cottage Grove not served by city water) with water that exceeds the updated values, and they will also be testing many others. Private wells that exceed health advice will be provided an alternate water source. 

In addition, Cottage Grove, Oakdale, Woodbury, and St. Paul Park have a number of supply wells for their public drinking water systems affected by the updated values. All affected community public drinking water systems will be able to put in place interim measures that will provide drinking water at or below the new MDH health-based guidance. Cottage Grove in particular has made some temporary changes in their water supply system to ensure compliance with new health based values. 

For more information on MDH and MPCA’s response to this new guidance and the impacts, please visit the MDH website.

You can also view this interactive map to see if you may be in a priority sampling area.

For questions or health related concerns, please contact the Minnesota Department of Health

MDH HazHealth line – 651-201-4897 or health.hazard@state.mn.us

Residents of south Washington County who live in or near areas where groundwater has been contaminated with perfluorochemicals (PFCs) will have an opportunity to ask questions about PFCs and discuss this issue one-on-one with staff from the Minnesota Department of Health (MDH), the Minnesota Pollution Control Agency (MPCA) and Washington County. There will be a short presentation as well. 

June 6, 2017


6 p.m. to 8:30 p.m. - Open House
7 p.m. - Presentation
Oak-Land Junior High Cafeteria
820 Manning Ave N Lake Elmo, MN 

June 7, 2017


6 p.m. to 8:30 p.m. - Open House
7 p.m. - Presentation 
Cottage Grove City Hall
12800 Ravine Parkway South, Cottage Grove, MN


VOC Testing in Contamination Areas



The Department of Public Health and Environment offers private well water testing for volatile organic compounds, including trichloroethylene. Please go to the water tests page for more information. 

In response to the MDH guidance, for PFOS and PFOA, and the need to prioritize sampling being conducted by MPCA and MDH, the county has suspended PFC 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 you can see high nitrates in other areas, from localized sources. See the link below for results of a recent private well testing study conducted by the Minnesota Department of Agriculture, in partnership with the county and the Washington Conservation District.

MDA Washington County 2014 Summary Report