A list of mine explosions appears at the end of this story.
CHARLESTON, W.Va. -- Late on the morning of March 9, 1976, a huge explosion ripped through the Scotia Mine in Letcher County, Ky. Fifteen workers died. Two days later, 11 more were killed in a second blast.
Federal investigators traced the first fatal explosion to sparks from a battery-powered locomotive being used in a fresh-air intake tunnel in the underground mine.
Air in the tunnel should have been free of explosive methane and coal dust. But various ventilation violations by Scotia Coal Co. allowed methane to build up in the tunnel.
And use of the battery-powered locomotive, with gears, air brakes and a compressor that could have easily created sparks, was perfectly legal -- then and now.
In most parts of an underground coal mine, operators must use only explosion proof, or "permissible" electrical equipment. Such special gear is not required in fresh-air intake tunnels, which are supposed to be free of explosive gases and dust.
But in the three decades since Scotia, at least seven other major coal-mining explosions were caused by the use in intake airways of electrical equipment not designed to prohibit sparks, according to federal government reports.
Over the last 34 years, nearly half of the deaths from mine explosions occurred in intake airways, the reports show. Some were ignited by miners smoking, or by sparks from rock hitting rock in a roof fall. But in most cases, those intake tunnel explosions were traced to the perfectly legal use of regular electrical vehicles, circuit breakers, belt controls, cables and other gear, instead of specially designed explosion-proof equipment.
The issue is a "considerable problem," according to Tom Dubaniewicz, an electrical engineer who has researched intake airway explosions for the National Institute for Occupational Safety and Health.
Dubaniewicz wrote two papers for NIOSH about the problem, one in September 2007 and another in January 2009. Both papers, widely available to the mining industry and its regulators, called for reforms in the type of electrical equipment allowed in intake airways in underground coal mines.
"There really is no law applicable to sparking equipment in the intakes," Dubaniewicz said in an interview last week.
And so far, despite the 34-year record of deadly explosions, no one has proposed any changes in federal law or U.S. Mine Safety and Health Administration regulations to address the problem.
Asked last week if the agency was aware of the NIOSH research, thought it revealed a serious problem, or planned any action in response, MSHA officials issued a two-sentence statement.
"We will take a look at the findings of the report, and see where they're at with their recommendations," the statement said. "Then we will meet with NIOSH officials to discuss where we go from here."
Investigators have yet to begin sifting through evidence underground to pinpoint the ignition source in the April 5 explosion that killed 29 miners at Massey Energy's Upper Big Branch Mine in Raleigh County. It will be many months before conclusions are drawn or reports made public about the worst U.S. coal-mining disaster in 40 years.
A preliminary MSHA report, ordered by President Barack Obama, blamed the blast on an ignition of methane that was probably made far worse by a buildup of highly explosive coal dust.
Investigators say they are starting out focused on two theories about possible ignition points: One is in the "gob," or the unsealed, mined-our area where the roof caves in behind Upper Big Branch's longwall mining machine; The other is in a "development section," where continuous mining machines prepare for the longwall to work. One possibility, investigators said, is that the ignition could have occurred in an intake airway in that development section.
But regardless of where the Upper Big Branch explosion was ignited, mine safety experts last week said the two reports Dubaniewicz prepared for NIOSH offered stark evidence of another area where mine safety rules have not kept up with clearly known problems that lead to large numbers of deaths.