Oak Grove Sanitary Landfill operated from 1967 to 1984 in Oak Grove Township, Minnesota, accepting commercial, municipal, and industrial solid waste across 52 acres. EPA added it to the National Priorities List as a Superfund site in 1984. It was deleted from that list in October 1996, and in January 2010 it achieved sitewide ready for anticipated reuse status, meaning all cleanup goals for current and expected future land uses have been met.
The site contaminated groundwater, surface water, soil, and leachate with dozens of chemicals. Groundwater contaminants include benzene, vinyl chloride, 1,2-dichloroethane, arsenic, nickel, toluene, and xylene, among others. Surface water, soil, and leachate contain additional chemicals such as acetone, dichloromethane, chromium, mercury, and zinc. In all, EPA identified 42 contaminants of concern across the site.
Cleanup was organized into two operable units. The first focused on source control, which led to a new landfill cap installed in 1992 and 1993, along with drainage controls and landfill gas collection. A gas extraction system with an enclosed flare was added in 2003. The second operable unit addressed groundwater migration through monitored natural attenuation, a process where environmental conditions naturally reduce contaminant levels over time, backed by institutional controls that restrict property use and prevent drinking water exposure. The Minnesota Pollution Control Agency (MPCA) took over site management in 1994 and has handled operation and maintenance since March 1996 through its Closed Landfill Program. MPCA regularly monitors methane gas at the landfill edges and samples groundwater and surface water near the site.
Human exposure at the site is now under control. However, EPA's July 2022 five-year review noted that the status of groundwater migration control remains uncertain due to insufficient data on whether contaminated groundwater has stabilized. The review recommended that MPCA finalize a long-term stewardship plan, determine the full extent of the groundwater plume downgradient from the site, investigate per- and polyfluoroalkyl substances (PFAS) at nearby residences, and install filtration systems at homes where needed. The next five-year review is estimated between July and September 2027.
Community members with questions can contact EPA's Community Involvement Coordinator or Remedial Project Manager. Questions about MPCA's ongoing oversight can be directed to the agency. Public records about the site are available at the MPCA office at 520 Lafayette Road North, St. Paul, Minnesota 55155.
