Barrick adds safety liner at old Wood Gulch mine

MOUNTAIN CITY, NEV. — Tucked away in the mountains near a small town in northeast Nevada is the played-out Wood Gulch Mine, where renewed reclamation efforts include 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 during a recent visit to the site.

Barrick returned to the site this summer to install the liner to prevent melting snow from traveling through the leach pad and picking up old cyanide solution at the small mine near Mountain City that hasn't produced gold since the end of 1990.

The pads are used in the heap-leaching process in which ore is crushed and placed on the pads where a cyanide solution is applied to the surface and then percolates down through the ore to separate the gold from the waste rock.

Barrick is spending roughly $1 million on the project, which Brito said was spurred by company monitoring.

"We were still seeing a large volume of drain-down solution from the snow so we're trying to cut off any more water from entering the pad," she said.

Susan Elliott, a U.S. Forest Service geologist for the Humboldt-Toiyable National Forest, called the project a good example of a company stepping in to address water issues.

"Any problem that has come up has been addressed," said Darin McDoniel, Forest Service mine engineer.

Rory Lamp, a supervisory wildlife biologist for the Nevada Department of Wildlife, said the original concern at Wood Gulch was that contaminated water would reach a nearby stream, which could threaten the red band trout in Badger Creek.

"They are trying to resolve that risk," Lamp said.

Brito called the work a one-summer project, explaining that Barrick couldn't leave the leach pad exposed over the winter so the project was 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 heavy equipment and the liner. Sierra Geosynthetic Services Inc. installed the special liner supplied by Agru and 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 worked to finish covering the liner with waste rock that will then be recovered with topsoil and reseeded. The company earlier removed topsoil on the pad, regraded and compacted the material so the liner could be laid and welded to an original liner under the pile of rock and ore.

Wood Gulch was a small mine, so the leach pad covers only 12 acres. 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 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 Barrick.

Reclamation began in 1991. The heap was rinsed in 1991 and 1992, and horizontal drains were drilled in 1993 before the pit highwall resloped, and the heap was covered with growth soil and seeded.

The small pit and a waste-rock dump are above the leach pad, and Brito said plans called for regrading and reseeding.

She said the decision to install the liner over the Wood Gulch leach pad made sense for the location.

"This is very site specific," she said, adding that others in the mining industry were concerned the Barrick work would set a costly precedent.

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 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 plan.

Dave Gaskin, chief of the Environmental Protection Division's Bureau of Mining Regulation and Reclamation, said he was visiting the site to view the project.

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Information from: Elko Daily Free Press, http://www.elkodaily.com