Utah mines are especially vulnerable to ‘bumps’ caused by pulling pillars; Murray mine had one

As the effort to rescue six miners in Utah goes on, stories published today suggest more strongly than ever that the mining method used at the mine -- pulling the pillars of coal that support the mine roof -- is the most likely explanation for the massive release of rock known as a "bump," which is usually a roof collapse but can come up from the floor. "Federal studies have found that pulling pillars, especially in the bump-prone mines of Utah, is always particularly dangerous," Ken Ward writes in The Charleston (W.Va.) Gazette.

"A bump occurs because of pressure pushing down onto the mine roof or wall, as opposed to the roof or wall simply falling down," Ward explains. "Very deep mines in the hard sandstone areas of Utah are especially prone to bumps. The hard rock roof and floor of mines adds to the pressure that can cause bumps. At least 80 percent of bumps have been found to occur while operators are performing retreat mining or pulling pillars, according to another Bureau of Mines study published in 1991." (Read more)

The Salt Lake Tribune obtained a memo, and did the map above, showing that operators of Murray Energy Corp.'s Crandall Canyon Mine were trying to work around 'poor roof conditions' before halting mining of the northern tunnels in early March after a "large bump occurred . . . resulting in heavy damage' in those tunnels. The memo indicates that mine operators knew the tremendous pressures of a mountain bearing down on the mine were creating problems with the roof, and they were searching for a way to safely keep the mine from falling in as they cut away the coal pillars supporting the structure."

Robert Ferriter, director of the safety program at the Colorado School of Mines and a 27-year veteran of the U.S. Mine Safety and Health Administration, questioned the role of the agency, which approved "retreat mining," or pillar-pulling, in May. "It's dangerous. Damn dangerous I would say," Ferriter told Robert Gehrke of the Trbune. "What is MSHA doing in all this? They're the ones who are supposed to catch this sort of thing." (Read more)