Feds Illustrate Likely Cause Of Upper Big Branch Mine Blast

Courtesy of the Mine Safety and Health Administration Courtesy of the Mine Safety and Health Administration

That led to excessive sparking, investigators said, as the cutting tool, which is called a shearer, cut into a sandstone layer in the coal. Normally, water sprayers shower the shearer and the area in front of the coal seam. The spray controls coal dust and sparks but the water sprayers weren't fully functional on April 5.

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Investigators tested the water sprayers on the shearer just before Christmas and this video shows the results:

Credit: Courtesy of the Mine Safety and Health Administration

With such little water, a lot of sparks and methane, an ignition developed and it persisted. The failure of the water sprayers left coal dust in the air. And as this mine map shows, investigators found excessive coal dust throughout the area affected by the blast:

Enlarge this image Courtesy of the Mine Safety and Health Administration Courtesy of the Mine Safety and Health Administration

Coal dust, investigators believe, provided the fuel that turned this small methane ignition into a fiery concussive force that traveled more than two miles underground and took 29 lives along the way.

"We still stand by our point that all mine explosions are preventable," concluded Kevin Stricklin, MSHA's mine safety chief.

The maintenance and equipment failures "should have been caught [by Massey Energy] during normal operations," said Joe Main, assistant labor secretary for mine safety and health, rejecting the notion that MSHA's inspection process may have failed.

In a statement, Massey Energy Vice President and General Counsel Shane Harvey repeated the company's theory that a massive and natural infusion of methane or natural gas was the sole cause of the explosion.

"We do not currently believe that there were issues with the bits or the sprays on the shearer that contributed to the explosion," Harvey said. "We likewise do not believe that coal dust played a meaningful role in the explosion."

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MSHA's briefing included a series of slides that purportedly refute Massey's theory about the blast.

(Click here to see more of the reporting that Howard Berkes and other NPR journalists have been doing about Mine Safety In America — including their reports about the April 5 disaster at Massey Energy's Upper Big Branch coal mine in West Virginia, where 29 miners died.)