LOVELOCK —A proposed expansion and equipment upgrade at the Coeur Rochester silver and gold mine in Pershing County could increase production and allow operations to continue into the mid-2030s.
“It will be our largest expansion so far,” said Mike Springfield, Coeur Rochester’s human resources manager.
The mine, about 26 miles northeast of Lovelock along the Black Ridge fault in the Humboldt Mountain Range, includes the main Rochester deposit and adjacent Nevada Packard deposit. Coeur has owned Rochester since 1983, and with the exception of a pause in mining when metal prices dropped in 2007-2011, has been in production at the site since 1986.
Coeur Mining Inc. is a growing precious metals producer based in Chicago. In addition to its operation at Rochester, the company produces from mines in Mexico, South Dakota, Alaska and British Columbia and owns exploration projects throughout North America.
If approved, the Rochester expansion would begin in 2020 to expand waste rock storage areas, extend the Rochester and neighboring Nevada Packard open pits, install a new heap leach facility at Limerick Canyon, and construct new crushing systems in Limerick and Nevada Packard. Improvements also include process plants and miscellaneous infrastructure upgrades.
“We’re basically really constrained in here,” said Greg Robinson, site development manager for Coeur Rochester.
The “greenfield-brownfield” expansion stretches into the neighboring valley because the narrow canyon limited operations. The Rochester pit, which was once Nenzel Hill, will grow in all directions.
“Basically, we move mountains,” Springfield said.
Coeur also plans to go from a core crusher to a high-pressure grinding roll at Rochester in early 2019. With the upgrade, silver recoveries from the rhyolite host rock are expected to improve from 62 percent over 20 years to 70 percent over five years.
“It’s cutting-edge technology in precious metal mining,” Robinson said. “It’s a game changer for us.”
Besides conducting exploration and mining waste rock, the Nevada Packard has not been active since 2007, when ore was hauled from that site to Rochester for processing. The company plans to build another leach pad and crusher at Nevada Packard to increase efficiency and production.
The leach pads at Rochester use the Merrill-Crowe silver and gold recovery process from a cyanide solution by zinc precipitation. Because of mountainous terrain, the leach pad varies in depth from 200 to 400 feet.
“This is where we are complicated ... . It’s what makes Rochester uniquely complicated as far as mines go,” Robinson said, explaining that the mine must be sensitive to crusher operation. “It’s really a choreographed dance.”
The mine is Pershing County’s largest employer, with 300 people working at Coeur Rochester. About 60 percent of the workforce is from Lovelock.
“People genuinely respect each other and work hard,” Robinson said, explaining the company culture promotes communication and employee buy-in. “I think that’s why we have the results we have. Because people get it and they care.”
The company’s safety record as of Oct. 3 was four years, or 2.5 million man-hours, worked without a lost-time incident. This year, Coeur Rochester won the Nevada Mining Association’s third place safety award for a medium surface mine. The association also recognized several individuals from Coeur Rochester for their safety records.
We’re “really proud of our safety culture and the results of that,” said Robinson, a University of Idaho mining engineering graduate.
Underground silver mining began in the Rochester area in about 1910. Coeur has maintained present-day production levels at the site since about 2014.
“We have a really good history of adding resources as we deplete it through mining,” Robinson said.
From 1986 to 2017, Rochester produced 150 million ounces of silver, which “makes us one of the biggest silver mines in the U.S.,” Robinson said. Production rates are approximately 5 million ounces of silver per year and 50,000 ounces of gold per year.
The site placed 4.06 million tons of ore in the third quarter of 2018, according to results released Oct. 9, and the average silver grade was 0.52 ounces per ton. The 2.5 million ounces silver equivalent ounces produced at Rochester represents a 17 percent increase over the same quarter last year due mainly to higher leaching performance.
Over its 30 years in operation, Rochester has had an economic impact of $14 million annually in taxes, employment and labor-related income.
In 2016, the company invested about $60 million to expand its leach pad, increasing capacity to 70 million tons and allowing operations through 2022. Capital investment of the next planned expansion is estimated at $52 million.
We “hope to maintain a presence here for many decades,” Robinson said.