The rockfall that killed an Emery County miner Friday occurred during a process known as retreat mining "pulling pillars" in mining vernacular, according to the federal Mine Safety and Health Administration, which is investigating the accident.
It's the same process that killed six men at the Crandall Canyon Mine in 2007. On Saturday, MSHA spokesman Jesse Lawder said Elam Jones, a continuous mining machine operator at the Rhino coal mine, was struck by a falling slab of rock 10 feet wide by 10 feet long and 22 inches thick.
Retreat mining is a widely used and MSHA-regulated process for removing as much coal as possible from sections of a coal seam.
Once a mining section reaches its limits, and all that's left is a checkerboard series of coal pillars left behind to hold up the roof, crews start at the deepest pillars and start cutting them out in a methodical manner described in detail in MSHA permits. They do this row after row, backing out toward the surface as they go, until most of the recoverable coal has been excavated.
But it is dangerous. MSHA's website has a number of pages devoted to "best practices" for safely pulling pillars, including one that notes that between 1997 and 2008, 29 miners were killed while engaging in this form of mining.
That toll includes the six men who were buried by a catastrophic implosion of the walls in the Crandall Canyon Mine on Aug. 6, 2007. They were pulling pillars in an aged section of that Emery County Mine when the walls blew in, entombing them.
Three more men died and six were injured 10 days later in another implosion.