Completed remedial cleanup at the Durango, Colorado uranium mill tailings remedial action site: A case study

The uranium mill tailings site near Durango, Colorado, is one of twenty-four inactive uranium mill sites designated to be remediated by the US Department of Energy (DOE) under the Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA). Remedial activities were conducted by the DOE for the long-term stabilization and control of the radioactive materials at the inactive uranium mill site. As required by the UMTRCA, remedial action at the Durango site had to comply with the regulations established by the Environmental Protection Agency (EPA). The remedial action at the Durango Uranium Mill Tailings Remedial Action (UMTRA) site consolidated approximately 2,400,000 cubic yards of contaminated materials from the uranium mill site and vicinity properties into a single, partially below-grade, disposal cell located approximately 1.5 miles southwest of the mill site. Construction sequencing of contaminated material within the cell considered the concept of reducing radon flux below EPA's standards to levels as low as reasonable achievable. A compacted earthen radon barrier 2.0 feet thick was placed directly over the contaminated material. Additional cover components were sequentially placed above the primary earthen radon barrier to provide the required low hydraulic conductivity to reduce water infiltration and to provide long-term stability