Ore for the mill came from numerous small mines in the Four-Corners area of Arizona, Colorado, New Mexico, and Utah. The plant also processed the uranium concentrate product from the Monument Valley, Arizona, upgraded facility; slime concentrates from the Naturita, Colorado, plant; and vanadium liquors bought from other producers. Uranium recovery averaged 80 percent and vanadium 70 percent from the combined mill feed. From 1949-1963, AEC purchased all of the mill's U₃O₈ production and its V₂O₅ production in excess of commercial demand. At the mill site, two tailings piles and one raffinate (milling process liquids) pond covering about 25 acres remained at the site before cleanup.

UMTRA Surface Remediation:   Surface cleanup (October 1986 to May 1991) to stabilize the radioactively contamination materials involved removal of all contaminated mill tailings, building debris, and soil from the mill site and from 129 vicinity properties. The excavated areas were backfilled with clean soil, contoured to promote drainage, and re-vegetated. All radioactive waste was trucked to the Bodo Canyon disposal area located a few miles southwest of the mill site. Of the $53.5 million spent on site cleanup, the handling of mill tailings cost $11.2 million and was the largest major cost component expenditure.

Disposal Area:   The Bodo Canyon Cell was built by the Department of Energy to receive mill tailings, contaminated soil, and construction debris from the Durango mill site cleanup. The disposal cell site covers nearly 120 acres and is located on land acquired by the State of Colorado from the U.S. Bureau of Land Management. The disposal-cell structure is about 90 feet thick overall from its lowest to highest points. The cell’s cover is an engineered, 6-7 foot thick, multilayered cap: a 2-foot thick, radon barrier of compacted silty clay and clay amended with bentonite clay (7 percent) on upper side slopes encapsulates the radioactive materials; a geo-membrane layer (a bentonite layer between two geo-textile layers) restricts infiltration on the top slope; and a 6-inch sand layer provides drainage on the side and top slopes. The top slope is covered with a 1.5-foot thick riprap layer to provide bio-intrusion protection, a 2.5-foot thick clay layer protects against frost heaving, and an overlying 6 inches of rock-soil is seeded with native grass species. Outer side slopes are protected by a 1.5-foot thick layer of clay for frost protection sandwiched between two 6-inch thick bedding layers; the “sandwich” is covered by a 1-foot thick riprap layer for erosion control. A toe drain was installed at the foot of the disposal cell to handle potential seepage from the cell. The disposal cell was transferred to the Federal Government in September 1996.

Responsibility for Remediation:   U.S. Government, 90 percent, and State of Colorado, 10 percent. The Bodo Canyon disposal cell site is being managed under the U.S. Department of Energy’s Long-Term Surveillance and Monitoring Program in accordance with the approved site specific plan.

Stewardship:  The Bodo Canyon disposal cell site is being managed under the U.S. Department of Energy’s Long-Term Surveillance and Monitoring Program in accordance with the approved site specific plan.

Groundwater Program:   Durango Mill Site - DOE is responsible for conducting the long-term stewardship at this site under applicable Federal regulations and a cooperative agreement with the State of Colorado. The NRC will not license the mill site, since the residual radioactive materials, including the tailings and contaminated soils, were relocated to an offsite disposal area. Site characterization and modeling of groundwater parameters will continue through fiscal year 2002. DOE assumes that by the natural flushing action of groundwater at the mill site, the level of contaminated will be reduced and that compliance with cleanup standards will be achieved before 2070 without active remediation. Groundwater use at the mill site will be restricted until compliance with the EPA standards is achieved. Bodo Canyon Cell - Groundwater in the uppermost aquifer at the Bodo Canyon site contains a high level of total dissolved solids and is not suitable for domestic use. To assure continued protection of the natural environment, long-term surveillance and maintenance are performed at the site. Groundwater is regularly monitored to determine cell integrity and to check for leakage of wastes from the cell. Natural compaction of the waste materials encapsulated in the cell is expected to result in some seepage, which is diverted to the site holding pond. Such seepage is expected to cease by 2004. The Department of Energy manages the site under its long-term surveillance program to perform annual inspection of the site’s surface, maintenance as needed, groundwater monitoring, treatment of seepage solutions and discharge of pond water.