In the 1950s and 1960s, uranium mill tailings from the Climax mill had been made available to the public. An estimated 300,000 tons of tailings were ultimately used in construction as a sand substitute or for backfill material at various sites throughout the Grand Junction and Mesa County area. These sites later became known as "vicinity properties." In 1972, Congress passed Public Law 92-314 (amended by P.L. 95-238) to provide funding and authority for a Federal/State program to perform remedial action on Grand Junction sites where uranium mill tailings were used, including private residences, schools, churches, and commercial locations. Relocation of tailings under the Federal program began in 1973, and the excavated materials were temporarily stored on the 40-acre State-held tract pending final burial. Under this cooperative program with the State of Colorado, the Government was responsible for 75 percent and the State 25 percent of the remediation cost.

UMTRA Surface Remediation:   Under the UMTRA Title I remediation project, all low level radioactive tailings were removed from the Climax mill site (known also as the Grand Junction Mill ) and placed in the Cheney disposal cell by the spring of 1994. Mill site remediation was performed in two phases. In Phase I, begun December 1988, mill buildings remaining on the site were demolished and decontamination facilities were prepared. Phase II, begun December 1989, involved constructing the Cheney disposal cell and transportation of the radioactive materials in a staged-movement plan; hauling by trucking to the Grand Junction rail spur, by railcar to the disposal-site spur, and then by truck to the disposal cell. The mill site was restored to a suitable grade with clean backfill, contoured for proper drainage, seeded, and wetlands established by August 1994. In March 1997, NRC certified the Climax mill site as clean. About 4.4 million cubic yards of contaminated materials were transported to the disposal cell.

Disposal Area:   The Cheney disposal cell, operated by the DOE, was constructed to consolidate and stabilize relocated uranium mill tailings and contaminated building materials from the Climax Uranium mill and Grand Junction Mill 2 (Grand Junction Offices site). Contaminated tailings materials from 4,266 remediated vicinity properties also was relocated to the cell. The 360-acre Cheney site, which contains the 98-acre disposal cell, is located about 18 miles southeast of Grand Junction. The cell is about 80 feet deep from lowest to highest points and is capped with an engineered, 7-foot thick multi-component cover. Materials that comprise the cover are: a 1.5-foot thick transition layer placed directly on the radioactive materials; a 2-foot thick clay layer serves as the radon barrier and minimizes water infiltration; a 2-foot thick layer of clay above the radon/infiltration barrier minimizes freeze-thaw damage; a 6-inch thick coarse-grained bedding layer covers the freeze-thaw barrier to minimize capillary movement of fluids and provide surface drainage; a 12-inch thick riprap erosion protection layer. The stabilized radioactive materials in the cell in 1994 were covered, and that part of the cell was closed. Under the Long-Term Radon Management Project, a 20-acre area on top of the cell will remain open and continue to accept contaminated materials for short durations each year until 2023, or until the design capacity is reached. The NRC has conditionally approved the closed portion of the disposal cell. A full NRC license will be granted after the whole cell is closed.

Responsibility for Remediation:   UMTRA mill site remediation; U.S. Government 90 percent and State of Colorado 10 percent. The Cheney Reservoir disposal cell site is owned by the Federal Government.

Stewardship:  The closed portion of the cell 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:   Groundwater contamination is present in the Climax mill site area in the alluvial sand and gravel (uppermost aquifer) associated with the Colorado River. Contamination extends at least 3,300 feet down gradient from the site, but the total extent of contamination is not known. Because water from within this area is not known to be used domestically, the risk to human health and the environment is believed to be limited. Supplemental standards, as defined in Title 40 of the CFR Part 192.22, for site groundwater were proposed by DOE based on ambient poor water quality in the aquifer caused by the naturally high sulfate concentrations. A strategy of natural groundwater flushing can be relied upon to reduce the concentration of contaminations to maximum background levels within 100 years, as established in the EPA standards. Groundwater monitoring will be conducted annually pending approval by the NRC of the site’s proposed groundwater compliance plan. As currently planned by the DOE, annual monitoring of the groundwater will continue until 2070. The annual monitoring could end in 2010, if the supplemental standards (see above) are accepted. During the period of natural flushing, the City of Grand Junction will impose deed restrictions that prohibit domestic use of groundwater within the Climax mill site boundaries. Water in the adjacent Colorado River has not been affected by the groundwater contamination at the Climax mill site, and no groundwater remediation will be conducted.