Naturita Mill

Location: The Naturita mill site is located two miles northwest of Naturita in Montrose County, Colorado, in the narrow, steep-walled canyon of the San Miguel River.

Background: Built about 1930 by the Rare Metals Company, the mill was first operated in 1939 after being purchased and rebuilt by the Vanadium Corporation of America (VCA). The mill produced a uranium-vanadium sludge (1942-1946) that was sold to the Manhattan Engineering District (MED), Army Corps of Engineers. At that time, old vanadium mill tailings from the Naturita site were also sold to MED for uranium recovery at the Government-owned Uravan, Colorado, mill. The U.S. Atomic Energy Commission’s (AEC) first uranium procurement contract was with VCA in May 1947. From 1947-1958, the mill processed ore that averaged 0.30 percent U3O8 and 1.68 percent V2O5. The ore came from small underground mines in the Uravan mineral belt area of Colorado and Utah. Ore-processing recovery rates at the mill averaged only 77 percent for uranium and 68 percent for vanadium, resulting in higher than usual residual metal values remaining in the mill tailings. The mill was shut down in1958. VCA continued to receive uranium-vanadium ores at the mill site after the shut down, and the company constructed an upgrader plant on the site in 1961 to treat that ore. The upgrader products (ore slimes and uranium and vanadium precipitates) were shipped for processing to other VCA mills, mainly the VCA mill at Durango, Colorado. When the upgrader plant was shut down in 1963, the remaining Naturita mill buildings and the upgrader were dismantled. In 1967, VCA merged with the Foote Mineral Company, which became the new mill site owner. General Electric leased a portion of the mill site in 1975 for use as an ore-buying depot. In 1976, Ranchers Exploration and Development Corporation (later acquired by Hecla Mining Company) purchased the Naturita tailings pile for its high residual metal values. In 1977-1979, Hecla moved the mill tailings to its Durita site where the tailings were reprocessed to recover the residual high uranium and vanadium values. Ranchers then covered and stabilized the relocated, reprocessed tailings according to Colorado Department of Health regulations. In 1996, the old Naturita mill site consisted of the original 53-acre mill site with residual radioactively contaminated soil and remaining mill structures plus 85 adjacent acres contaminated by wind-blown and water-borne mill-tailings materials from the mill site.