The Climax Uranium Company processed uranium ore on the banks of the Colorado River in Grand Junction, Colorado from 1951 until 1970. As a result of its operations, the mill produced 2.2 million tons of tailings, most of which were deposited in an on-site tailings pile that covered approximately 114 acres. Approximately 300,000 tons of tailings were, however, removed from the site and used as construction and fill material throughout the Grand Junction area. The City of Grand Junction used the tailings as fill when installing sewer and water lines, and businesses and homeowners used tailings as fill during construction. These, and other sites where tailings were used for construction or deposited through erosion, are known as vicinity properties (VPs). Uranium mill tailings emit radon gas, which presents a risk to human health. Congress provided for the remediation of uranium mills and their associated tailings in the Uranium Mill Tailings Radiation Control Act (UMTRCA) of 1978. The statute provides for certain institutional controls, including Department of Energy ownership and management of tailings disposal sites and annotation of land records or similar notification to prospective purchasers of mill sites. The statute also authorizes the U.S. Environmental Protection Agency to set standards to govern the cleanup of mill sites and the associated vicinity properties. These regulations include requirements for institutional controls if natural flushing is chosen as the remedy for contaminated groundwater.