Monday, May 12, 2014 two miners were killed while performing what is known as “retreat coal mining” at a Patriot Coal mine in in Boone County.

The two miners killed were continuous mining machine operator Eric D. Legg, 48, of Twilight, and roof bolter Gary P. Hensley, 46, of Chapmanville according to the Charleston Gazette. The Gazette also said no other injuries were reported and all other miners were accounted for.

So… What is Retreat Coal Mining?

The idea behind retreat coal mining is fairly simple. As you dig the coal out, you leave pillars of coal standing to support the weight of the ceiling. After the coal has been removed, you remove the pillars, backing out of the mine allowing the area behind the pillars to collapse in. Then the miners take the usable coal from the collapsed pillar and pull back more towards the entrance of the mine. Repeat.


How Dangerous is It?

The Mine Safety and Health Administration (MSHA) says that retreat mining has been historically responsible for 25% of American coal mining deaths, even though it represents only 10% of the industry.

Former mine safety official, now attorney representing miners, Tony Oppegard told West Virginia Public Broadcasting Tuesday:

“All underground coal mining is inherently dangerous but retreat mining is ultrahazardous and operators have to comply religiously with every step of the pillar removal plan to protect the safety of their miners… Most of the time when there is an accident on a pillar section or retreat miner section it’s because there’s not been compliance with the plan or because the miners have not been trained (properly).”

Six miners and three rescuers will killed in a retreat coal mining accident at the Crandall Canyon Mine in Utah in August 2007. Federal investigators eventually concluded that the pillars in that mine “simply were not large enough to support the load.”


What Caused this Accident?

Patriot Coal, the owner of the mine, blames the accident on “a severe coal burst as the mine was conducting retreat mining operations.” That means pressure forced the roof, floor or wall of rock to “burst” into an open area. The Charleston Gazette adds more context:

Various studies have found that coal outbursts or bumps can be especially hard to prevent. But, the studies over many years have also shown, they are not natural occurrences and can be avoided or the risk reduced with proper mine planning and compliance with that planning.

“Inadequate mine planning or incorrect design can increase the occurrence of bumps in underground coal mines,” says one 1991 report by the U.S. Bureau of Mines.

West Virginia Public Broadcasting reports that this particular mine has a “historically bad record of safety violations.”