ASSESSMENT OF LOCATION, IMPACTS, POTENTIAL RISKS, AND CLEANUP COSTS OF DEFENSE-RELATED URANIUM MINES IN THE UNITED STATES

A 2014 Report to Congress identified mines in the United States that provided uranium ore to the U.S. Atomic Energy Commission (AEC) between 1947 and 1970. The report identified their locations, reclamation/remediation status, radiological risks and other hazards, costs for reclamation and remediation, and prioritization for mine cleanup. For developing reclamation and remediation cleanup cost estimates and assessing risks, mines were grouped into six categories by tons of ore produced, ranging from Small (<100) to Very Large (>500,000). Radiological risk was calculated using RESRAD computer code for five exposure scenarios: offsite and onsite residents, occasional visitor, recreational visitor, and mine reclamation worker.

Results indicate that 69% of the mines are in Colorado and Utah, 23% are in Arizona, Wyoming, and New Mexico; 68% of mines produced <1000 tons of uranium ore. Although having fewer mines (247) than the other states in the Colorado Plateau region, New Mexico mines produced 45% of the 79.5 million tons of AEC uranium ore, primarily from the Grants Mineral Belt. About 50% of the mines are on public land managed by the Bureau of Land Management; 435 mines are on the Navajo Nation. Risk estimates for the onsite resident scenario (plausible on tribal and non-federal land) could result in incremental cancer risk greater than 10^‑4 . Radon inhalation was the dominant contributor to radiological risk for the five exposure scenarios evaluated. Different state and federal agencies are conducting cleanup of some mines under various remedial authorities. Activities constituting mine “reclamation” may reduce radiological risks to humans to acceptable levels for many mines on federal public lands if occasional visitor and recreational scenarios are assumed. Addressing physical hazards (e.g., open shafts) at mines where conditions can cause serious injuries typically is a priority of public land management agencies.

Where mine-related groundwater contamination occurs, it is a significant contributor to cleanup costs. However, most Small and Small/Medium mines were likely developed above the water table, and many “wet” mines are in areas where naturally occurring elements (including radioactive elements) that are typically associated with uranium mines also occur in naturally high concentrations.