After a violent rock burst at the Lucky Friday Mine on Nov. 16, federal inspectors ordered mine managers to conduct twice-daily monitoring to check if stress was building up in the rocks.

The rock burst had registered as a 2.8-magnitude quake on seismographs. No one was in the mine when it occurred, but residents as far away as Wallace reported feeling the earth rumble.

On Dec. 14, mine managers failed to conduct the second daily reading, according to documents from the Mine Safety and Health Administration. Another rock burst occurred that evening, injuring seven miners, one of whose pelvis was broken in the accident.

“The company disregarded the safety of the miners by failing to do the required testing,” a federal inspector wrote in his report.

The report was part of 300-plus pages of inspection documents obtained by The Spokesman-Review through a Freedom of Information Act request. The underground silver mine in Mullan, Idaho, is owned by Coeur d’Alene-based Hecla Mining Co.

Hecla is appealing the inspector’s conclusion and a company spokeswoman declined to comment.

According to documents, mine superintendent Jeff Jordan told inspectors that he didn’t think rock-stress readings could be taken because workers were installing a steel liner over stress gauges in that area. But the gauges contained extended wires so they could be read during the installation of the liner, which was intended to contain unstable rock, the documents said.

Conditions in the Lucky Friday’s main shaft are also described in the inspection reports, along with other safety hazards flagged by inspectors. The reports offer more details about the December inspection that led to a yearlong shutdown of the Lucky Friday during a period of record silver prices. On Jan. 6, federal inspectors closed the primary shaft, citing safety concerns. Hecla officials expect the mine to reopen in early 2013, after repairs are made to the shaft, which carries workers and ore into and out of the mine.

Among the findings:

• Inspectors said loose concrete deposits in the mile-deep shaft were a hazard, with the potential to fall and injure or kill workers traveling in the shaft. The deposits were the result of leaking pipes that carry sand and cement into the mine. Some concrete chunks were as large as 2 feet by 3 feet. Inspectors also raised concerns about 400 feet of pipe in the shaft that wasn’t properly secured.

The weekly shaft inspections done by Hecla employees were inadequate, federal inspectors said. The Lucky Friday didn’t have systematic procedures for testing or inspecting the shaft or keeping up with shaft maintenance, the reports said.

• Several work areas didn’t have a secondary escape route. Inspectors said miners could be trapped underground if their only escape route was blocked by falling rock.

• Inspectors cited numerous areas where mesh fencing to contain unstable rock had holes torn in it. The Lucky Friday was cited more than 40 times for the same problem in the past two years, the reports said.

• In one area, inspectors snapped pictures of a port-a-potty located directly underneath an overhead chute.

• About 70 pages of inspection documents were withheld because they’re related to an ongoing investigation of last summer’s arson fires at the mine.

Hecla plans to spend $50 million on capital projects at the Lucky Friday over the next year, including $30 million for shaft repairs and upgrades. The company’s goal is to surpass the federal safety requirements and operate as safely and efficiently as possible, Hecla spokeswoman Melanie Hennessey said in an interview last week.

Since a fatal accident at the mine last April, Hecla has added geotechnical engineering staff at both the Lucky Friday Mine and the Greenscreek Mine in Alaska, she said.