The 300-acre Monticello Mill Tailings site is comprised of a 7S-acre inactive uranium and vanadium milling operation and affected peripheral properties in Monticello, San Juan County, Utah. Surrounding land use is rural residential and agricultural. The site overlies a shallow alluvial aquifer, and part of the site lies within the floodplain of Montezuma Creek. Approximately IS-acres of wetlands adjacent to Montezuma Creek also have been contaminated by tailings. In 1940, the site was operated as a vanadium ore-buying station. Milling of ore began in 1942, and a vanadium/uranium sludge product was produced onsite from 1943 to 1944. Onsite uranium milling processes began in the mid-forties and continued until 1959. Mill tailings from these operations were disposed of in four onsite tailings piles that are within the floodplain of the Montezuma Creek. The mill was permanently closed in 1960, and the tailings piles were covered and vegetated. From 1964 to 1965, the entire plant was dismantled and foundations were partially buried onsite along with contaminated material. Onsite and offsite soil contamination is the result of wind and surface water erosion of the contaminated tailings piles with subsequent deposition elsewhere. In 1972, 15,000 cubic yards of contaminated soil were excavated and disposed of on the onsite tailings piles.
U.S. Environmental Protection Agency and Office of Emergency and Remedial Response, "Superfund Record of Decision: Monticello Mill Tailings (DOE), UT First Remedial Action" (1990). All U.S. Government Documents (Utah Regional Depository). Paper 504.