Mouat Industries sits in Columbus, Montana, and earned a spot on the EPA's National Priorities List (NPL) in 1986. The site processed chromite ore from 1957 to 1962, leaving hexavalent chromium in soil and groundwater. Hexavalent chromium is a hazardous substance that poses health risks if people ingest or contact contaminated soil or water. Contamination was discovered when nearby drinking water wells exceeded chromium standards.
Cleanup work began in the early 1990s. Removal actions between 1990 and 2008 secured the site with a perimeter fence, demolished the processing facility, and addressed contaminated soils. About 14,000 cubic yards of chromium-containing soil were treated on-site and formed into concrete blocks. Another 19,400 cubic yards were hauled off-site for disposal. Treated blocks and clean fill were placed back in excavated areas, covered with two feet of soil, and then vegetated or covered with gravel. The soil portion of the site was partially deleted from the NPL in 2009 after that work was done.
For groundwater, the long-term remedy relies on monitored natural attenuation, meaning the contamination is expected to break down on its own over time while regular sampling tracks its progress. The Town of Columbus supports the cleanup through a Superfund Overlay District zoning ordinance approved in March 1995. This ordinance restricts incompatible land uses, limits well drilling, requires engineering review before development in the treated soil area, and mandates deed notices to alert future property buyers. The EPA reports that human exposure is currently under control and groundwater migration has been stabilized with no unacceptable discharge to surface water.
The most recent five-year review, completed in August 2023, found the repository cap and drainage features intact and institutional controls properly maintained. However, that same review concluded the remedy is protective in the short term but may not remain protective in the future. In response, a remedial investigation began in September 2025 to evaluate the site further. The next five-year review is estimated between August and October 2028. Despite the ongoing investigation, the site has seen active redevelopment. The town built its public works building on part of the waste repository, and as of December 2024, three businesses operate on-site.
Community members who want more information can contact the EPA Remedial Project Manager or the Montana Department of Environmental Quality (DEQ) project manager. The EPA also maintains a public information repository at its Montana Office in Helena, open Monday through Friday from 8:00 a.m. to 4:30 p.m., where site records are available for review.
