mouat industries

ADJACENT TO AIR STRIP IN CY

The Mouat Industries site is located south of Columbus, Montana. The site lies in the flood-plain of the Yellowstone River, less than 0.6 miles north of the present river channel in the SW ¼ of the NW ¼ of Section 27, T2S, R20E. The site is approximately 4.5 acres. The land is owned by the town of Columbus and was leased to Mouat Industries from 1957 to 1962. Mouat Industries processed chromite ore mined from the Stillwater Mining Complex in south-central Montana into high-grade sodium dichromate, which was sold as a corrosion inhibitor. The process subsequently generated sodium sulfate process wastes containing sodium chromate and sodium dichromate. These hexavalent chromium-containing compounds leached from the sodium sulfate waste piles into underlying soils and eventually into the site groundwater. Additionally, normal facility operations resulted in sodium dichromate spills. The chromium processing plant was built and operated from 1957 to 1962. Chromium wastes were created during this time, but not after 1962. EPA conducted a preliminary assessment/site inspection from 1979 to 1980. Various entities also conducted multimedia sampling during the late 1970s and 1980s. These studies led EPA to send a letter to the town in 1984 stating that the analytical numbers from the sampled monitoring wells exceeded the recommended drinking water standards for chromium and recommended that the contaminated groundwater not be used for human and animal consumption. EPA proposed the facility for the National Priorities List (NPL) in Federal Register notice 29 FR 40320 of October 15, 1984. The site received a Hazard Ranking System score of 31.66. The listing was final in 51 FR 21054 of June 10, 1986.

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