The Olmsted County Sanitary Landfill sits on about 52 acres of a 304-acre property in Oronoco, Minnesota. It accepted municipal solid waste along with commercial and industrial waste, including electroplating sludge, asbestos, transformers, paint, and solvents. The landfill operated from the early 1970s through the mid-1980s before shifting to demolition debris and ash. EPA placed it on the National Priorities List (NPL) in 1986 after seeps from the landfill contaminated groundwater with volatile organic compounds (VOCs) and heavy metals. An intermittent stream also carried contaminants during heavy rains.
A combined remedial investigation and feasibility study ran from December 1989 through September 1993 under state oversight. The county then capped the landfill and installed a leachate collection system in 1994. Leachate is liquid that drains through waste and can carry contaminants into the ground. EPA issued its Record of Decision on June 21, 1994, and determined that no cleanup beyond what the state required was necessary. The site was deleted from the NPL on February 15, 1995.
Today the Minnesota Pollution Control Agency (MPCA) oversees the site through its Closed Landfill Program. The MPCA handles regular monitoring and maintenance of the cap and leachate collection system. EPA has determined that human exposure is currently under control across the entire site, with no unacceptable exposure pathways identified. Groundwater migration is also stabilized, and no unacceptable discharge to surface water is expected. EPA continues monitoring to confirm that affected groundwater stays within its original contamination area.
The site achieved sitewide ready for anticipated use status on September 29, 2011, meaning all cleanup goals for current and expected future uses have been met. Olmsted County adopted a "Closed Landfill Restricted" zoning designation in 2011 to block incompatible uses like residential development. Institutional controls remain in place to reduce exposure to remaining contamination. Portions of the property have already been put to compatible use, including a radio-controlled model airplane flying facility operated by the Rochester Aero Model Society since 2008.
Community members with questions can contact EPA's Remedial Project Manager Andrew Kleist or reach the MPCA's Shawn Ruotsinoja for questions about ongoing state oversight. Public records related to the site are available through EPA's Superfund records system and can be reviewed at the MPCA office at 520 Lafayette Road North in Saint Paul, Minnesota.
