Several abandoned uranium mine sites in the Pryor Mountains of south-central Montana have been closed after federal agencies identified safety, radiation and environmental risks. The work was carried out on lands managed by the Bureau of Land Management (BLM), with the Department of Energy’s Defense Related Uranium Mine (DRUM) programme and other partners involved.The project focused on five historic mine sites where workers addressed dangerous openings and other hazards, according to the information available on BLM’s website. In September 2025, contractors completed work to close 20 mine features by backfilling mine openings, installing bat-friendly closure gates, fencing dangerous highwalls, plugging drill holes and removing solid waste.The need for the work was linked to the condition of the abandoned mines. The BLM said entering abandoned mine sites on public lands can be dangerous and, in some cases, fatal. The structures can become unstable over time because they are no longer maintained, increasing the risk of collapse and injury to visitors.Some of the uranium mines in the Pryor Mountains also presented additional risks because of elevated metals and radiation levels in underground workings. The BLM said these levels were linked to remaining mineralisation and were another important reason to prevent public entry into the sites.
Work began with detailed site assessments
The DRUM programme began assessing abandoned uranium mines in the Pryor Mountains in 2020. Contractors examined the sites for physical hazards, radiation levels and chemical contamination. The assessments helped identify safety risks and determine what reclamation and closure work was required.The sites are part of a much larger national programme. DRUM is a partnership involving the Department of Energy, federal land management agencies, and state and Tribal abandoned mine lands programmes.The mines being addressed under the programme supplied uranium ore to the US Atomic Energy Commission for defence-related activities between 1947 and 1970. The DRUM programme is responsible for helping mitigate safety hazards at these abandoned mine sites.Additional environmental surveys were carried out in 2024. Bat Conservation International (BCI) studied the sites to identify bat habitat, rare plants and cultural resources that could require protection during the closure work.
Bats and rare plants were considered
The presence of wildlife meant that the mine closures had to be planned carefully. BCI personnel worked with an interdisciplinary team of resource specialists to identify biological resources and determine how they should be protected during the project.
2025 pre-reclamation photo
One of the concerns was bat habitat inside the abandoned mine workings. The project therefore included the installation of bat-friendly closure gates at some mine openings. BCI personnel also relocated a bat before an abandoned mine adit was backfilled.Rare plants were also considered before reclamation work began. BLM Botanist Eric Puetz marked rare plant populations before the mine closure work. One of the plants identified was thick-leaved bladderpod, which the BLM said occurs only in the Pryor Mountain foothills area.The BLM also contacted mining claimants at the sites to ensure that mineral resources remained accessible. After completing the required environmental analysis, the agency issued a decision in August 2025 to proceed with abandoned mine work at multiple sites in the Pryor Mountains.
Five sites received closure work
The physical mitigation work was completed in September 2025 by Department of Energy subcontractors from Mountain States Restoration, LLC. Work was carried out at five historic abandoned uranium mine sites.The 20 mine features addressed during the project required different measures depending on the hazards present. Mine openings were backfilled, while bat-compatible gates were installed where appropriate. Dangerous highwalls were fenced, drill holes were plugged and solid waste was removed.The project also involved reclamation measures to help the affected areas recover. A later monitoring visit showed vegetation growing successfully under installed erosion matting at the Swamp Frog mine.However, the BLM said the work does not end when the physical closure is completed. Abandoned mine sites continue to change because of natural processes and human interference.
BLM says monitoring will continue
Dan Seifert, BLM Montana/Dakotas Abandoned Mine Lands and Hazmat programme lead, said continued monitoring is necessary to make sure the closures remain effective.“We need to acknowledge that we can’t just walk away from these sites after closure work – gravity and erosion continue to occur and mine grates are often vandalized and broken into,” Seifert said.The BLM’s monitoring work is therefore intended to check whether the closures continue to function and whether additional problems develop at the sites.
