Officials at Hecla Mining Co. say they will tunnel a 750-foot bypass at the Lucky Friday Mine to route workers away from a portion of the mile-long corridor where a rock burst injured seven miners last week.
Another rock burst had occurred in the same area on Nov. 16, but it occurred during blasting when no one was in the mine. Residents as far away as Wallace felt that rock burst, which registered as a 2.8-magnitude quake on seismographs.
About 275 people work at the underground silver mine in Mullan, Idaho. Both rock bursts occurred 5,900 feet below the surface in a horizontal corridor that’s used to move workers, ore and equipment.
“It’s one of the main accesses in and out of the mine,” said Mélanie Hennessey, the company’s vice president of investor relations.
“We’re building this bypass, which is significantly far away from where the rock bursts occurred, to be an area that is safe for workers,” she said
Quartzite formations in the Silver Valley are prone to rock bursts. Pressure builds up in the rocks surrounding an underground opening until they suddenly fail. Rock bursts are often associated with blasting. But the Dec. 14 rock burst occurred more than 24 hours after blasting at the mine, Hennessey said.
At the time, miners were installing a steel support system designed to contain rock bursts. Seven of the 11 workers at the scene were injured. Three were hospitalized but have since been released.
The Lucky Friday Mine has been closed since the accident, with no date for a reopening at this time, Hennessey said. Hecla officials closed the mine immediately after the rock burst. The federal Mine Safety and Health Administration, which is investigating the accident, issued a closure order as well.
The new bypass will tunnel through a previously mined area, which will reduce the risk of unstable rock. Company officials anticipate that the bypass will be finished by the end of February, when mining operations will resume at the Lucky Friday.
Most Lucky Friday workers will stay at the mine to work on the bypass or other projects, Hennessey said. Other workers will have a chance to apply for positions at Hecla’s other mining operations.
Even though the bypass will take two months to complete, Hecla officials said they still expect to meet a companywide production goal of 9.5 million ounces of silver in 2012, up from 9 million ounces this year. In addition to the Lucky Friday Mine, Hecla mines silver at its Greens Creek property in Alaska.
Last week’s rock burst followed two fatal accidents at the Lucky Friday this year – one in April and one in November. Prior to this year, the Lucky Friday had an enviable safety record, going 25 years without a fatality, said Phil Baker, Hecla’s president and chief executive officer.
“Our goal, which we will relentlessly pursue, is to re-establish that same safety and operating performance decades into the future,” Baker said in a statement.
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