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Naturita Mill Site
Montrose County, Colorado
| Years of Operation |
Status of Mill
or Plant Site |
Uranium Ore
Processed
(Million Short Tons) |
Production
(Million Pounds U3O8) |
| 1939-1946, 1947-1958, 1961-1963 |
Decommissioned |
0.70 |
3.18 |
Remediated
Mill/Plant Area
(Acres) |
Disposal Cell
Area
(Acres) |
Disposal Cell
Radioactive
Waste
Volume
(Million Cubic Yards) |
Disposal Cell
Total Radioactivity
(Ci, 226Ra) |
Disposal Cell
Average Tailings
Radioactivity
(pCi/g, 226Ra) |
UMTRA Project
Final Cost
(Million Dollars) |
| 53 |
10 |
0.79 |
79 |
46 |
86.33 |
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.
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UMTRA Surface Remediation: Site remediation involved two phases. Phase I (May-November 1994) included demolition of structures and removal, treatment, storage, and off-site disposal of asbestos and hazardous waste. Phase II (June 1996-September 1998) included removal and transportation of residual radioactive material (including mill-demolition debris) to the an off-site repository at the Naturita Site (known also as the Upper Burbank Disposal Cell). The areas where contaminated soil materials were excavated from the prior tailings pile and surrounding tracts were remediated by backfilling with clean soil, graded to promote drainage, and revegetated with native grasses. Overall, about 800,000 cubic yards of contaminated materials were relocated from the Naturita mill site and consolidated in the disposal cell in 1998. During the project, 52 vicinity properties were also cleaned up.
Disposal Area: Contaminated material from the Naturita mill site was trucked to the Upper Burbank disposal cell site located 13 miles northwest on land acquired in 1997 by the U.S. Department of Energy near Uravan, Colorado. The new disposal cell occupies 10-acres of the 27-acre site near the town of Uravan, Colorado. The final cell is capped with a 10-foot thick, engineered cover: a clay-layer radon barrier, 3-feet thick; a clay-layer frost barrier, 5.5-feet thick; a 6-inch bedding layer of stream gravel; and a one-foot thick erosion-protection layer of graduated riprap (stream gravel material capped by basalt and sandstone boulders).
Responsibility for Remediation: U.S. Department of Energy (DOE), 90 percent; State of Colorado, 10 percent.
Stewardship: The DOE is responsible for long-term surveillance and monitoring of vegetation and groundwater conditions at the Naturita mill site. The Upper Burbank disposal cell site is subject to Title I of the UMTRCA, and the site is being managed under the DOE’s Long-Term Surveillance and Monitoring (LTSM) Program in accordance with the approved site specific plan. DOE will be responsible in perpetuity for the safety and integrity of the Upper Burbank site.
Groundwater Program: At the Naturita mill site, no remediation of the groundwater is planned. DOE assumes that compliance with the Federal Groundwater Protection Standards will be achieved through natural flushing action. Groundwater monitoring will be continued by the DOE until 2013 or sooner, pending the natural return of groundwater contaminant levels to compliance with the standards. Surface water is monitored to determine whether groundwater contaminants are impacting the San Miguel River that flows adjacent to the site. Once compliance with the groundwater standards is achieved, the site will be released for unrestricted use to its owner. At the Upper Burbank disposal cell site, no soil or groundwater contamination exists. DOE conducts biennial inspections of the site to verify that rainwater does not infiltrate through the cell cover. The need for continued groundwater monitoring is evaluated periodically. DOE assumes that monitoring will continue indefinitely, until data demonstrate that the cell has achieved infiltration control.
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