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Bull Mountain coal mine closed pending probe of 3 roof collapses

Bull Mountain coal mine closed pending probe of 3 roof collapses

Inspectors and engineers are on site

  • Updated

The Bull Mountain coal mine near Roundup has been closed pending an investigation into three roof falls in the past week.

Amy Louviere, public-affairs director with the federal Mine Safety and Health Administration, said Wednesday that the underground mine is under a closure order so workers can install supplemental roof supports.

“Mining may resume on a limited basis once the areas of greatest concern have been re-supported while they install even more support,” Louviere said in an email.

There have been no injuries associated with the roof falls themselves, but one miner was injured when he was hit in the head by a post while shoring up the underground roof on July 19. The miner was cleared to resume work.

Roof falls occurred on July 18, 22 and 25, Louviere said.

MSHA inspectors and engineers are on the site. MSHA has been conducing a regular safety and health inspection since July 5.

John DeMichiei, president and CEO of Signal Peak Energy, the mine’s owner, said the mine already was implementing a plan for increased roof support when the first roof fall occurred.

The closure order came Monday, shortly after the mine reported the first roof fall, he said. Mining regulations requires a roof fall to be reported within 15 minutes of occurring. The company has been working with MSHA and a consultant to address the issue, he said.

DeMichiei did not know when mining would resume but said workers are making “good progress” and expected the agency to allow mining soon.

Two of the falls happened near the face of mine, where the longwall mining machine was removing coal, while the third happened in an area almost four miles away, DeMichiei said.

In longwall mining, a machine moves back and forth across a panel of coal, cutting the coal, which falls onto a conveyor for transportation to the surface. The roof in mined-out areas collapses as the machine advances. The collapse can cause the land surface above to sink or subside.

Signal Peak began mining a new, second panel on June 6, DeMichiei said.

The July 18 and July 25 roof falls happened about 600 feet in from where the longwall machine was cutting coal. No one was was exposed to the roof fall, DeMichiei said.

The area is about 800 feet below the surface, which is about double the normal depth of previous mining, he said.

“Up until that time, we had seen absolutely no impact” of mining that far below the ground, he said.

DeMichiei said he thinks the weight of the ground cover and “rock mechanics” caused the roof fall. The first roof fall was about 100 feet long, and the second fall extended it by about 20 feet, he said.

The mine immediately began installing additional roof support, he said.

“We have developed a plan to address those areas where we have that type of a cover,” DeMichiei said. More roof supports will be installed in places where there is 600 feet or more of overburden, he said.

The July 22 incident happened in another area of the mine 3.9 miles away from the other roof falls, DeMichiei said. A portion of a roof in a tunnel system for ventilation fell during excavation work, he said.

Workers encountered a lot of water and got to within eight or nine feet of a coal seam, which is weaker than rock, causing the roof to deteriorate and fall, he said.

“We put a lot of emphasis on safety. It’s been paramount,” he said. The mine had gone more than 150 days without a lost-time accident, he said.

So far in 2011, Signal Peak has logged more than 349,000 hours worked and mined about 1.8 million tons of coal. In 2010, the mine operated about 637,000 hours and mined 4.3 million tons of coal, MSHA’s website said. The coal is hauled to an Ohio utility.

Contact Clair Johnson at cjohnson@billingsgazette.com or 657-1282.

Contact Clair Johnson at cjohnson@billingsgazette.com or 657-1282.

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