Last week's fatal coal mine explosion might never have reached the operational part of the mine if operators had sealed off unused areas with traditional concrete barriers instead of a weaker industrial foam product, experts say.
In a media briefing Wednesday, officials from the federal Mine Safety and Health Administration acknowledged that large abandoned sections of the Sago Mine were sealed off with barriers constructed from Omega block, which weighs and costs less than standard concrete designs.
They said preliminary investigations indicate that the explosion began in the unused portion of the mine and blew the seal outward, releasing the smoke and dangerous gases, eventually killing 12 men.
A similar explosion in sealed-off parts of a Pineville, W.Va., mine in 1995 shook the unused area but was stopped by seals made of concrete. "When we went in, the seals weren't damaged or anything," said Gary Trout, a United Mine Workers representative.
Trout said it appeared that lightning had struck a nearby gas pipe that ran into the Pineville mine, igniting the gases collected there. In the abandoned area, temporary ventilation barriers called stoppings had been destroyed, suggesting the blast had considerable force.
Officials investigating the Sago disaster have advanced the theory that lightning striking a gas well ignited that explosion also. But at Sago, the shattered seals allowed the blast to reach and destroy stoppings in the working mine, disrupting the ventilation system and preventing workers from finding a clean-air escape route.
The mine agency requires that seals withstand 20 pounds per square inch of explosive pressure, but two recent studies by the National Institute for Occupational Safety and Health suggest concrete barriers survive much stronger blasts, while foam structures similar to those at Sago withstand about 20 psi.
"Foam is easier to handle, and it probably costs less," said Steve Webber, former head of West Virginia's mine safety agency. He said some explosions could be stopped by concrete seals, but not by the foam material.
Mine administration officials said Wednesday that they had obtained documents relating to the seal, and that it would be one focus of their investigation.