Tuesday, July 27, 2021

The Thacker Pass Mine is Indeed Benign, Compared to Most Gold and Copper Mines in Nevada


In a previous piece, I noted that the proposed Thacker Pass mine will be relatively benign in comparison to other large mines in Nevada, primarily gold and copper mines. As a critic of the mining industry for nearly 40 years, I and colleagues have stressed the importance of reclamation of mine sites, particularly since all mines ultimately close, and the legacy of poorly closed mines is all too common in the West.   

True reclamation means leaving a mined area with a productive post mining land use, eliminating any long-term water quality or safety issues and in a manner that is visually consistent with the surrounding landscape. Few gold and copper mines meet this standard, and water quality issues from heap drainage, leaking tailings facilities and pit lakes exist at many, if not most, of these sites, to the point that management of these mined sites will be required for decades to centuries.  

The Thacker Pass mine, as presently planned, will not have a pit lake, will not penetrate the groundwater, will not have any heap drainage or a problematic tailings facility. As discussed below, this mine is indeed relatively benign but will be a major source of lithium, which is critical for mitigating the transportation contribution to carbon buildup in the atmosphere and the resulting climate change. Overall, I feel that this mine is environmentally beneficial, due to the importance of the metal, and the projected lack of long term problems that are common in other mines.

Reclamation at the Thacker Pass mine will occur concurrently with mining, due to the unique nature of the ore body. Mining will occur in trenches that will move across the ore body, but those trenches will partially be refilled and reclaimed as mining for each trench is completed. Gold and copper mines do not have this opportunity, since they are following an ore body that is much less uniform than the lithium ore body at Thacker Pass.   

While the trenches will not be completely refilled at Thacker Pass, the plan is to produce a reclaimed area that will have similar vegetation as presently exists and will return the land to wildlife habitat. Notable is the fact that some of the very best sage grouse habitat is in the Montana Mountains, above the area to be mined, and the company has committed to not mine in that habitat, although they do have the bulk of the claims in that area.   Proposals to protect that sage grouse habitat are currently under discussion.

Gold mines often have strip ratios of waste to ore that are large- often well over 5 tons of waste to 1 ton of ore. The Thacker Pass mine will have a waste to ore ratio that is 1.6 tons of waste to 1 ton of ore. This low waste to ore ratio will reduce the size of the pit correspondingly, since much of the material removed from the pit will be ore.  

Groundwater contamination is always a concern with mines, but is less so at Thacker Pass, since no mining will occur below the groundwater table for about 20 years under the proposed state reclamation permit. In the later decades ahead, the mine may go below the groundwater table, but that action will require further analysis through a State agency permitting process with the benefit of data from the early years of operation. 

The tailings impoundment is where the extracted clay ore will be placed. This is a completely lined facility and will indeed be large, but will contain neutralized clay waste that has been filtered to remove as much water as possible. The filtered and extracted clay waste will be placed in the tailings facility in a “dry stack” method, where the filtered clay will be compressed to minimize empty space. Clay is very often used as a sealant in a variety of applications, and the clay tailings will itself limit penetration of water through the waste clay.  Even then, the residual contaminant load will be primarily calcium sulfate, often called gypsum, which is a soil amendment used in nearby agriculture to reduce the pH of alkaline agricultural soils on the order of one ton per acre. The tailings facility will ultimately be reclaimed to wildlife habitat.

Concerns of odors have been expressed regarding the large amount of sulfur that will be brought to the site.  However, this same type of sulfur has been used for decades for disease control in crops, and odor has not been a reported issue. Sulfur will be shipped to the Thacker Pass mine in closed containers from rail heads in Winnemucca. The sulfur will be burned in closed systems to produce sulfuric acid for extraction of the ore. As discussed previously the acidified solutions used to extract the lithium ores will be neutralized prior to disposal of the clays in the tailings facilities.  

Water rights have been purchased from agricultural water rights owners, so the amount of groundwater removed from the basin will not change, although the points of diversion will change. Any alterations in groundwater levels will need to be measured on a regular basis, and impacts on current water users need to be assessed and mitigated.  

The impacts on the local community during construction and mining of Thacker Pass are certainly not trivial, and increased truck traffic will occur, and associated traffic patterns and safety requirements need to be implemented. There is no question that this large mine will change the community character of the Quinn River Valley, since it will be the site of one of the largest lithium mines in the nation. The discussion of those impacts will need to be a continuing discussion topic as the mine evolves.

Ultimately, those who live in the western United States are increasingly aware of the issues that climate change will bring. The record number of 100 degree days in June in Northern Nevada and the very early major fires are a good indication of what we can expect, but even more importantly, the environmental effects from climate change are going to be more severe to the aboriginal communities throughout the world that do not have the option of turning on air conditioners. Permafrost melting in the northern latitudes will force communities to move somewhere, and we can all expect to see major impacts on species of animals that will no longer survive in those altered environments. Those who view this mine as a major loss of habitat simply need to consider how much habitat is being lost from the dramatically increased forest fires worldwide (and also in the western U.S.). Five thousand acres of mined land that will ultimately be reclaimed is small, compared to over 200,000 acres that have been burned in Nevada, California and Oregon in the last three weeks.

Lithium will not solve all of the climate change problems, but it is a significant method for storing electricity, and will enable travel to use renewable energy sources rather than carbon-based energy sources. Batteries will also allow storage of grid electricity when the sun does not shine or wind does not blow. Mitigating climate change is so very critical for maintaining the health of human communities and reducing species extinction. The Thacker Pass mine is an important mitigation measure to slowing the U.S. contribution to climate change.  We should all remember that the U.S., on a per capita basis, is still one of the world’s highest contributors to climate change. We will also be one of the largest consumers of lithium batteries, and need to contribute to the sourcing of the basic material needed to manufacture those batteries.  

Glenn C. Miller, is Professor Emeritus, Dept. of Natural Resources and Environmental Science, University of Nevada Reno.

Top photo caption and credit: The proposed site of the Thacker Pass lithium mine in north-central Humboldt County, Nevada on April 10, 2021 – photo: Brian Bahouth/the Ally

The opinions expressed above are not necessarily those of the Sierra Nevada Ally. Our newsroom remains entirely independent of our opinion page. Published opinions further public conversation to fulfill our civic responsibility to challenge authority, act independently of corporate or political influence.