The safe storage of mining waste has been a critical part of the debate over a lithium mine in northern Nevada, and now environmental advocates are pointing to a report warning that flawed analysis of the mine may lead to failures that could unleash toxic slurry into the state’s watershed.
Lithium Nevada, a subsidiary of Canada based Lithium Americas, plans to build a lithium mine near the Oregon-Nevada border, after securing federal approval early last year. The mine has also secured a number of state permits required to begin construction of the project.
On Tuesday, one of those state permits was unsuccessfully challenged by the Great Basin Resource Watch, a conservation group that has strongly opposed the mine.
The Nevada State Environmental Commission’s five-member appeals board ruled against the conservation group’s appeal of a state permit allowing the mine to produce and store at least 60 million tons of toxic mining waste on Nevada’s landscape.
However, the group argues a major report they commissioned detailing flaws in Lithium Nevada’s plan to contain contaminated water waste produced by the mine was stricken from the hearing after Lithium Nevada objected to its inclusion on procedural grounds.
During the hearing, representatives for the Great Basin Resource Watch repeatedly alluded to the report, saying they could not argue their case to the panel after their central evidence was blocked.
Representatives for the Nevada Division of Environmental Protection, however, said the report submitted by the conservation group contained “falsely generated catastrophic concerns.”
At the center of the conflict is whether or not clay, a porous material, retains more water than sand.
Lithium Nevada says that the mine at Thacker Pass will be a “zero-water discharge” facility, meaning that toxic water used for mining will be captured, purified, and recycled rather than dumped back into the environment and waterways.
The mine says it plans to store much of its waste using a “dry stack” method, an emerging technology that some environmental nonprofits and mining experts argue will better prevent water pollution. The method involves miners removing water from waste and working it into a sandy mixture that’s left over once minerals are extracted, which is then put on a liner and covered with soil and vegetation.
But the report prepared for Great Basin Research Watch by Steven Emerman, an associate professor of Hydrology for Utah Valley University who has evaluated mining projects from North America to Asia, has left conservationists troubled about the viability of the mine’s strategy for containing toxic water waste.
Moisture content for waste using the dry stack method is typically around 23%, according to Emerman, as storage facilities for mining waste using the drier technique are not designed to keep large amounts of contaminated water from seeping through. But the moisture content of the waste produced by Thacker Pass would be 46% — twice that of conventional “tailings” or rock waste.
“It would probably have greater water content than any tailings storage facility ever constructed,” wrote Emerman in the report. “Although this should be a zero-discharge facility, seepage rates …would be tens to thousands of gallons per minute and would continue for decades after closure with no provisions for management of the seepage.”
That’s because the mine is planning to extract lithium from clay‐rich soil that retains much more water than the sand found in other environments. According to the report, the saturation rate of clay used for dry stacking could be up to 52%—“an unprecedented practice for filtered tailings,” writes Emerman.
“The filtration of clay tailings is a new technology and there are no operating mines with filtered clay tailings anywhere in the world,” Emerman wrote.
‘Just a bad process’
During the hearing, attorneys for the Nevada Division of Environmental Protection said Lithium Nevada’s infrastructure plan for water seepage was “more than sufficient to ensure complete containment and no degradation to the state’s water.”
Representatives for the division detailed a separate report by Lithium Nevada that found seepage would not be an issue as a result of the company’s drying method for tailings.
“The permit issued here is a zero discharge permit, meaning no contaminated water is permitted to be discharged in the state’s water,” said deputy attorney general for the division, Andrew Bell. “The Division received and reviewed multiple credible reports that showed the project will not contaminate the state’s water.”
Attorneys representing Lithum Nevada also said they would monitor fluid levels in the reclaim pond — which is designed to capture water waste — daily and that any water collected would not be discharged into the environment.
In his report Emerman says his findings show that “even if seepage could be managed through the reclaim pond” the amount of water waste produced by the porous clay tailings would make the reclamation pond “entirely inadequate.”
The Nevada Division of Environmental Protection also argued there are precedents for dry stacking with clay-rich soil, such as the Pumpkin Hollow copper mine near Yerington.
Representatives for Great Basin Resource Watch maintained that all precedents named by the division are either not in operation or processing hard-rock ores rather than extracting metal from clay deposits, as planned at the Thacker Pass mine.
The conservation group argued the division should have “exercised extra due diligence” to address possible water pollution due to the “unique nature” of the mine and carefully reviewed all analysis before granting permits.
“To us, it’s just a bad process,” said John Hadder, director of the Great Basin Resource Watch. “We wish the agency would have held off on finalizing the permit until more information was in.”
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