MOUNTAIN CITY — Tucked away in the mountains near the town of Mountain City is the mined-out Wood Gulch Mine, where renewed reclamation includes a first for Nevada mines.
“This is the first time a leach pad has been covered with a synthetic liner in Nevada,” Melissa Ann Brito, a closure manager with Barrick Gold of North America, said Tuesday during a visit to the site.
Barrick went back this summer to install the liner to prevent snow melt from traveling through the leach pad and picking up old cyanide solution at the small mine that hasn’t produced gold since the end of 1990.
Barrick is spending roughly $1 million on the project, which Brito said was “self-directed.” The company had been monitoring the reclaimed site for years and saw the need to take action.
“We were still seeing a large volume of drain-down solution from the snow so we’re trying to cut off anymore water from entering the pad,” she said.
“This is a good example of a company stepping in. The whole point is to address water issues. I am really looking forward to the results from this,” said Susan Elliott, the Humboldt-Toiyable National Forest geologist for the U.S. Forest Service.
“I think it’s a first-class project. Any problem that has come up has been addressed,” said Darin McDoniel, a mine engineer for the Forest Service.
Rory Lamp, a supervisory wildlife biologist for the Nevada Department of Wildlife, said the original concern at Wood Gulch was that bad water would reach a stream down below. This in turn would threaten the red band trout in Badger Creek, but no contaminated water has reached the stream.
“They are trying to resolve that risk,” Lamp said of the Barrick project.
“This is a one-summer project,” Brito said, explaining that Barrick couldn’t leave the leach pad exposed over the winter so the project is targeted for completion by Sept. 15.
Work started in July, once the narrow road to the high-elevation site was dry enough to bring in the heavy equipment and the liner, which Sierra Geosynthetic Services Inc. installed. Agru supplied the special liner designed for better drainage.
Logan Jensen of the engineering firm Knight Piesold said roughly 430,000 square feet of liner went on the pad.
High Mark Construction was working Tuesday to finish covering the liner with waste rock that will then be recovered with topsoil and reseeded. The company earlier removed the topsoil that was on the pad, regraded the pad and compacted the material so the liner could be laid over the pad and welded to the original liner under the heap.
Wood Gulch was a small mine so the leach pad covers only 12 acres, and the mine was the first and only one Homestake Mining Co. developed under a small mines division, Brito said. Barrick acquired Wood Gulch when it acquired Homestake in 2001.
The mine started up in mid-1988, closed for the 1988-89 winter and went into continuous operation from April 1989 to November 1990. During operation, the mine produced 34,852 ounces of gold and 66,955 ounces of silver, according to a Barrick history of the project.
Reclamation began in 1991. The heap was rinsed in 1991 and 1992, and horizontal drains were drilled into the heap in 1993. Drainage was conveyed to a bio-cell system, the pit highwall resloped, and the heap was covered with growth soil and seeded back then.
The small pit and a waste-rock dump are above the leach pad, and Brito said “we will regrade the waste-rock dump as much as we can and we’ll also reseed that.”
She said the decision to install the liner over the Wood Gulch leach pad “made sense for this location,” but Barrick is getting “a little backlash” from the mining industry, which fears the project will set a precedent that could be costly to the industry.
“This is very site specific,” she said.
Modern mines place synthetic liner down before starting a heap leach pad or expanding an existing pad, but they cap the heaps with soil mixtures.
Lamp said Nevada mines continue to learn from leach-pad closures, but Wood Gulch was reclaimed years ago.
“We have 20 years of information now. It’s been a learning process as we go along,” he said.
Brito said that while the synthetic liner topping a leach pad is a first for mining in Nevada, the liner has been used for a couple of mine projects elsewhere and is commonly used at landfills.
“We borrowed the idea,” she said.
Brito said the project took two years of planning and risk assessment, and Elliott said the Forest Service worked with Barrick for a year. The Nevada Division of Environmental Protection also was regularly involved and approved the closure plan.
Dave Gaskin, chief of NDEP’s Bureau of Mining Regulation and Reclamation, said he was visiting the Barrick project to see what the company is doing.
The summer project in the remote location also is a camping experience for the High Mark Construction crew, said Jensen of Knight Piesold and Ron Ricken, who is overseeing the work for Barrick. Choch Zaga of High Mark said the company has 11 people on site.