Series of mine lightning strikes largely ignored
Federal regulators largely ignored a string of eight mine explosions caused by lightning strikes near U.S. coal mines between 1993 and 2001, according to a new independent report on the Sago Mine disaster.
No one connected the dots to determine how the lighting strikes were making their way into underground mine passages. Little was done to come up with ways to protect mines from lightning.
Nor did anyone make the crucial link between the strikes — which hit sealed areas in mines in Alabama and West Virginia — and a federal rule that undermined a law requiring seals to be “explosion proof,” according to the new Sago disaster report.
“There would have been no disaster if the explosion had been contained by the supposedly explosion-proof seals,” said the report, prepared for Gov. Joe Manchin by longtime mine safety advocate Davitt McAteer.
The 97-page report, released Wednesday, concludes that lighting “probably” ignited the Jan. 2 explosion that led to the deaths of 12 Sago miners.
Multiple lighting strikes — at least two and perhaps three — occurred in the vicinity of the mine at almost precisely the same time as the mine explosion.
“More remains to be learned, however, about how lightning made its way into the sealed area where the methane ignition took place, and, depending on how that question is answered, specific steps must then be taken to protect miners against the risk of lightning-ignited methane ignitions,” McAteer said in his report.
The report cited nine explosions in U.S. coal mines between August 1993 and May 2001 that investigators blamed on lightning. Four of those occurred in West Virginia, and four in Alabama. No one was injured in any of the eight blasts.
McAteer, now a vice president at Wheeling Jesuit University, said that a review of U.S. Mine Safety and Health Administration reports on those explosions “is an unsettling exercise.”
“In contrast to other MSHA investigation reports which provide a measure of engineering certainty, these are more speculative, containing phrases like ‘probable cause was lightning’ or ‘it is reasonable to conclude that lightning may have ignited methane,’” McAteer reported. “We need prompt research on the role lightning plays in underground mine explosions and ways to prevent it.”
In an interview Thursday, McAteer acknowledged that most of the lightning strikes at mines occurred while he was running MSHA from 1994 to 2000 during the Clinton administration. He said he should have forced a closer examination of the issue.
“This scared everybody — it scared me,” McAteer said.
During a news conference Wednesday in Buckhannon, McAteer explained the importance of the issue.
“We have miners in mines today, and every time a thunderstorm comes by, are they at risk?” he said. “The answer is ‘we don’t know.’
“Those [explosion reports] haven’t been compiled in a way to say ‘how do we address this?’” McAteer said. “We need to address those questions and we need to address them quickly.”
In examining the previous lightning strikes, MSHA investigators found that, in most cases, seals constructed of various materials had been partially blown out by the blasts.
After these incidents, the National Institute for Occupational Safety and Health in 2001 issued a bulletin to alert the mining industry to the apparent hazard of lightning-triggered ignitions.
The report noted that, in at least one case, the force of the explosion exceeded 20 pounds per square inch. In 1969, Congress had decreed that all seals in underground mines be “explosion proof,” and in 1992, MSHA adopted the 20-psi standard to define that term.
“Unfortunately, NIOSH concluded that if lightning as a potential source of ignition could not be eliminated, the only alternative would be to eliminate flammable concentrations or reduce the volume of the flammable mixture present in the sealed area,” McAteer’s report said. “Other steps, such as eliminating wires or other conductors and removing potential ignition sources such as old batteries from sealed areas, were also recommended.
“But, neither NIOSH nor MSHA, despite their acknowledgement that sealed-area explosions could generate more than 20 psi, recommended reconsidering the 20-psi standard for ‘explosion-proof’ bulkheads in the light of accumulating experience.”
And in his report, McAteer concludes that MSHA probably should have never adopted the 20-psi standard in its 1992 rules anyway.
In a legal memo to McAteer, West Virginia University law professor Pat McGinley wrote that the standard “is inconsistent with the unambiguous statutory mandate of the Mine Act that coal mine seals be ‘explosion proof.’”
MSHA based the regulation entirely on a 1971 federal Bureau of Mines study that “makes for deeply disturbing reading in the wake of the Sago disaster,” McGinley explained.
But in doing so, McGinley wrote, MSHA “ignored contradictory evidence in the report itself” and offered a “meager explanation” for a standard that is “totally implausible.”
The Bureau of Mines study, written by the late researcher Donald W. Mitchell, reviewed mine explosions in the U.S. and abroad, noting that blast pressure had been measured as high as 127 pounds per square inch. Mitchell wrote, though, that pressures 200 feet or more from the origin of the explosion seldom exceeded 20 psi.
“That statement, while not documented anywhere in the report, appears to be the rationale for his conclusion that bulkheads may be considered ‘explosion-proof’ if they can withstand a static load of 20 psi,” the McAteer report said.
McAteer noted that seal standards of 50 psi and greater have been adopted in various other mining countries, including the United Kingdom, Canada, Australia and South Africa. Also, the U.S. government in 1921 had adopted a standard of 50 psi for coal mines on federal land.
At the same time, the McAteer report notes, the test used to qualify the foam blocks used at Sago for the 20-psi standard were faulty. NIOSH tested how well the seals stood up to a sideways, glancing blow, rather than a head-on hit as occurred at Sago.
McAteer concluded that standards for seals must be improved in West Virginia and across the country.
On Wednesday, MSHA announced that it was issuing a memo to overturn the 1992 regulation that defined “explosion proof” as withstanding a 20-psi blast. Instead, MSHA said, seals must now withstand at least a 50-psi explosion.
MSHA said seals must also now be certified by a professional engineer and construction must be certified by a senior mine manager. As for existing seals, MSHA said it would examine them with operators “to determine whether additional measures are necessary to protect miners.”
McAteer recommended that mine operators should be required to replace existing foal or other alternative block seals with concrete seals or take steps to ventilate sealed areas of dangerous gases.
“Until measures such as these have been taken, every sealed area in every underground coal mine in West Virginia and throughout the United States should be considered a potential time bomb — and treated accordingly,” McAteer said in his report.
The McAteer report is available online at www.wvgov.org/SagoMineDisasterJuly2006FINAL.pdf.
Staff writer Ken Ward Jr.’s continued coverage of the Sago Mine disaster is being supported by a fellowship from the Alicia Patterson Foundation. To contact Ward, use e-mail or call 348-1702.