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Midwest Photo: The House of Photography, Manhattan Engineer District, Grand Junction, ca. 1950-1959, Colorado Mining Association Collection, Colorado School of Mines


Manhattan Engineer District - Grand Junction Pilot Plant

The U.S. War Department acquired the 55-acre property in 1943 for use by the U.S. Army Corps of Engineers Manhattan Engineer District, which operated a refinery onsite from 1943 to 1946 to concentrate uranium oxide. Located in west-central Colorado near the city of Grand Junction, the site was acquired because of its proximity to the Gunnison River, easy railroad access, and relative isolation. The refinery produced an estimated 2.6 million pounds of uranium oxide from Colorado Plateau vanadium mill tailings (including that of Naturita, Rifle, Slick Rock, Durango, and Uravan, among other Colorado and Utah mills), which were later transported and processed offsite. The refinery operated as the only domestic uranium procurement site during that time period.

After the end of the Second World War, the site was repurposed under the Atomic Energy Commission (AEC) and proceeded to facilitate private and public uranium exploration, experimentation, mining, and milling projects. In 1947, the AEC established the Colorado Raw Materials Office at Grand Junction, which became the primary office for uranium research during the Cold War. Pilot mills and experimental ore milling techniques processed approximately 30,000 tons of ore before milling ceased in 1958. The AEC  ran an assay laboratory and uranium concentrate sampling plant on the property until 1974.

Milling operations resulted in contamination of soil and groundwater at the site. Surplus uranium ore, uranium mill tailings, contaminated equipment, and other waste from the pilot mills and sampling plant were disposed of on-site. Contaminants in the stockpile and buried tailings leached into the shallow alluvial groundwater, which is in direct hydraulic contact with the two on-site ponds and wetlands as well as the Gunnison River. From 1986 to 2001, the Department of Energy (DOE)—successor to the AEC—was in charge of the cleanup of radioactive material. An estimated 100,000 cubic yards of mill tailings and contaminated soils were stabilized on-site, and another 300 cubic yards of contaminated process equipment were buried at the site. While mill tailings removal was generally completed by 1994, remedial action continued onsite until as late as 2014.

The government sold the property to the private Riverview Technology Corporation (RTC) in 2001, and the site is currently occupied by a small business incubator, a technology company, and an army reserve. In 2016, the DOE submitted a proposal to add the Grand Junction Office to the National Register of Historic Places, subsequently transforming the log cabin office into a learning center about Grand Junction’s nuclear history.

Note: Climax Uranium operated a different uranium mill from 1950-1970 along the Colorado River near Grand Junction. The company demolished most of the site and eventually moved the contaminated remains to a disposal site about 18 miles away.


Atomic Heritage Foundation. "Grand Junction, CO." Accessed July 31, 2020.

Chenowith, William. "Grand Junction and the Manhattan Project." Presentation at the American Association of Petroleum Geologists Rocky Mountain Section Meeting, Grand Junction, CO. September 9-12, 2012. Accessed July 31, 2020.

U.S. Department of Energy, Office of Legacy Management. "Grand Junction, Colorado" Fact Sheet. May 2020. Accessed July 31, 2020.

U.S. Department of Interior, National Park Service. "National Register of Historic Places Registration Form." 2016. Accessed June 11, 2021.

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