The Koch Refining Co./N-Ren Corp. site is an active oil refinery covering 1,200 acres in Rosemount, Minnesota, operating since 1955. Storage tank spills beginning in the early 1970s contaminated soil and groundwater with hazardous chemicals. EPA added the site to the National Priorities List (NPL) in June 1986. EPA deleted it from the NPL in June 1995 after determining no further Superfund action was needed, and oversight shifted to the Minnesota Pollution Control Agency (MPCA) under state and federal programs.
Twenty-five contaminants of concern have been identified at the site, mostly in groundwater. They include volatile organic compounds (VOCs) such as benzene, toluene, and carbon tetrachloride, heavy metals including arsenic, cadmium, and lead, chlorinated solvents such as tetrachloroethene and dichloromethane, and polycyclic aromatic hydrocarbons (PAHs) and phenols. Total petroleum hydrocarbons are present in both groundwater and soil. Soil contamination includes VOCs such as benzene, toluene, and xylenes, as well as PAHs.
In 1985, Koch Refining signed a Consent Agreement with the MPCA for cleanup under federal Resource Conservation and Recovery Act (RCRA) authority. A remedy finalized in September 1991 called for recovering spilled materials, capturing and treating contaminated groundwater, and treating soil. Methods include extraction wells, multi-phase extraction, soil vapor extraction, off-gas treatment, and a centralized waste treatment facility. Several million gallons of petroleum-related contaminants have been removed. Physical construction of the cleanup was completed in July 2008.
EPA has determined that human exposure is currently under control, with no unacceptable exposure pathways across the site. Contaminated groundwater has been stabilized in its original area. However, the site is not yet ready for all anticipated uses because one or more cleanup criteria or land-use controls remain to be fully implemented. Institutional controls restrict residential development and other incompatible land uses to limit exposure to remaining contamination. The refinery continues to operate under state oversight, managing spill protection, waste handling, wastewater discharge, and air emissions. As of December 2024, the on-site refinery employed 1,200 people and generated approximately $1.1 billion in annual sales revenue.
Community members with questions can contact EPA's Community Involvement Coordinator or Remedial Project Manager. The MPCA also handles site-related matters. Public records related to Superfund work at this site are available for review at the MPCA office at 520 Lafayette Road North, St. Paul, Minnesota.
