A Cold War-era uranium mine in the Stanislaus National Forest that provided ore for nuclear power and nuclear weapons in the 1950s and 1960s is now described by its federal custodians as a uranium mine waste landfill, and it needs maintenance and repairs.
Work at the Juniper Uranium Mine site east of Eagle Meadow is scheduled for Monday through Oct. 30, according to Stanislaus National Forest staff. Contractor HelioTech is expected to work on a storm water management system and import riprap rock materials and construction equipment to the site, which is several miles out Eagle Meadow Road, also known as Forest Road 5N01 at the 5N33 spur.
The site is at 8,500 feet in elevation in Tuolumne County and drains into Red Rock Creek, which flows to the Middle Fork Stanislaus River near Kennedy Meadows Resort, Dennis Geiser, a regional environmental engineer with the Forest Service in Vallejo, said Wednesday.
Scientists say uranium mines, uranium ore and uranium waste can remain radioactive for centuries.
A June 2014 study by scientists at Lawrence Livermore National Laboratory, sponsored by the National Nuclear Security Administration, Department of Energy, found uranium content and compositions of contaminated Red Rock Creek headwaters, relative to mine tailings of the Juniper Mine, suggesting uranium weathered from the mine and deposited in the creek.
The findings from a national lab sponsored by the U.S. Department of Energy were not mentioned in a closure construction summary report submitted to the U.S. Forest Service in September 2014.
Geiser said Wednesday was the first time he heard of the report “Investigating uranium distribution in surface sediments and waters: a case study of contamination from the Juniper Uranium Mine, Stanislaus National Forest, CA" by four scientists at Lawrence Livermore National Laboratory, Chemical Sciences Division.
Geiser said the Department of Energy collected samples in 2010, which was before the Forest Service did site restoration and built the repository.
“So everything they are discussing is what was happening before we did the site work,” Geiser said. “Essentially what they are saying is that, based on the uranium levels in the creek waters, in addition to the types of radionuclides that DOE detected in the downstream creek waters, uranium is being released from the site. This is being done via erosion of the waste rock and by dissolving the uranium into the waters.”
Back in June 2003, The Union Democrat reported the Forest Service announced the abandoned Juniper Uranium Mine was emitting more gamma radiation than previously thought.
The U.S. Environmental Protection Agency said the levels were potentially harmful to people and closed the area. A federal Superfund cleanup was planned to put the mining waste back in the open mining pit and bury it, and it was delayed several years.
Construction activities began in 2011 with the installation of a toe berm and underdrain. In September 2012, the cleanup was delayed by torrential late-summer rains near the crest of the Sierra Nevada.
Construction of a geosynthetic cover, soil cover and drainage and erosion controls were completed in 2013. The $1.5 million project was authorized under the Comprehensive Environmental Response, Compensation and Liability Act, also known as the Superfund.
“When we closed the site and followed EPA prescrip, we took all waste rock and put it back in the pit, we built an underdrain to catch any water that was seeping out of the sidewall of the pit,” Geiser said Wednesday.
“You want to keep the waste rock dry. You don’t want water flowing through because that’s when you get material leaching out,” Geiser said. “We covered it with an impermeable cap, a synthetic material. It’s made of HDPE, high-density polyethylene.”
The Superfund cleanup was intended to minimize residual radiation from the waste rock, Geiser said.
“Anything residual, we had to dig down to a clean level, where the radiation levels are below the risk threshold,” Geiser said. “All the contaminated material went into the repository.”
When the Juniper Uranium Mine was operating, miners dug down to where they found uranium deposits and it was sent to Salt Lake City for processing, Geiser said.
Natural uranium can be radioactive for centuries, Geiser said.
Summarizing the Superfund closure of the mine that concluded in 2013, Geiser said, “the cleanup work we performed at Juniper was building a mine waste repository in the former open pit mine and then consolidating the contaminated waste rock in said repository.”
The repository has an impermeable cover system with surface water and drainage control features, Geiser said. Cover systems like this require monitoring and inspections to check for potential damage to the cover system and drainage features and to ensure the remedy is intact and performing as designed. This includes checking for erosion damage, which may impact the cover, clogging or settlement in surface water channels or damage from unauthorized public access.
“For the lack of a better term, what we have is a mine waste landfill, and they have to be maintained for perpetuity,” Geiser said.
Work scheduled at Juniper Uranium Mine later this month and next month is to repair perimeter storm water channels that have clogged with sediment washing down from site, to restore drainage flow in the top deck perimeter channel and eliminate ponding observed earlier this year, to remove decomposing channel riprap and replace with rock, and widen riprap placement in one perimeter channel to ensure offsite surface water and snowmelt stay off the cap and cover system, Geiser said.
“With any type of repository like this we can have periodic maintenance needs,” Geiser said. “As the cover system gets settled and the vegetation better established, these needs decrease over time.”
Other work at the site that will continue includes a surface and groundwater monitoring program.
The Juniper Uranium Mine produced about 500 tons of uranium ore for nuclear power and nuclear weapons between 1956 and 1966. The heavy, radioactive material occurs naturally in the Sierra Nevada mountains.
For more information, call Stanislaus National Forest headquarters in Sonora at (209) 532-3671.