BUCKHANNON, W.Va. -- The force of an explosion behind a sealed off section at Sago mine that trapped 13 miners, killing 12 of them, may have been more than four times greater than the federal standard those seals are required to withstand.
That was the analysis of a consultant hired by International Coal Group, which owns Sago, based on the extent metal plates and hangers were deformed by the blast.
One seal "saw a minimum peak pressure of 60 psi [pounds per square inch] that could have been as high as 90 psi," said Stephen Gerard Sawyer, a structural engineer.
"All the other seals saw at least 25 psi."
Currently, mine operators who want to seal off a mined out area must construct a wall that can withstand a static pressure of 20 psi.
Another expert hired by ICG, Thomas Novak, presented his case for lightning being the most likely cause for igniting the methane behind the seal, although he later acknowledged that "it's not a definitive conclusion."
The two men laid out their findings during the second day of a public hearing about the Jan. 2 blast, being held at West Virginia Wesleyan College.
The hearing will conclude today.
Both men said they are continuing their research, which they hope to finish this summer.
Crucial to Mr. Sawyer's work are test explosions being conducted at the Lake Lynn Laboratory Mine near Fairchance, Fayette County.
In a recent test, Omega block seals similar to those used at Sago withstood a 20 psi explosion passing by from the side. While replicating the original Omega block tests, they did not send a blast directly at the seals, as happened at Sago.
Those tests will continue in coming weeks and months.
A Pittsburgh Post-Gazette story in March noted that other industrialized countries, such as Australia, require that seals withstand a force of 50 psi.
Yesterday, Bennett Hatfield, president and chief executive officer of ICG, said he thinks the 20 psi federal standard for seals may not be high enough.
ICG officials first declared March 14 that their preliminary findings had led them to believe lightning had ignited the methane, based on the explosion coinciding with a strong lightning strike, evidence of a seismic event at the mine and a carbon monoxide alarm.
The company reopened the mine the next day and Mr. Hatfield explained that officials wanted to assure their workers about the probable cause quickly rather than wait for the state and federal investigations.
Yesterday, using diagrams of the mine and surrounding area, Mr. Novak speculated that a major lightning strike on a tree at about 6:28 a.m. on Jan. 2 was within 300 feet of a power line that fed into the Sago mine two miles away.
With the conveyor structure held by chain supports and wire mesh bolted to the roof inside the mine, "now you have a continuous metallic path from within 300 feet of the lightning strike to within a few feet of the seals," Mr. Novak said.
Mr. Novak said he also based his theory on the belief that two other possible causes -- friction caused by a roof fall or a spontaneous combustion -- did not occur based on examination of the area.
"From the post-explosion investigation, those have been eliminated," Mr. Novak said.
That prompted questions from panelists, who pointed out that the area had been sealed off only weeks before because of roof problems.
And when asked what implication the lightning ignition theory might have for the thousands of other sealed areas in mines across the United States, Mr. Novak replied, "That's a very good question."
In his presentation to panelists, Mr. Novak hewed in large part to the findings in a report he provided to ICG regarding three theories of how lightning could have reached into the mine.
But he did not mention one aspect of that report cited earlier, which pointed to an area inside the sealed section that bore "an unusual set of intersecting streaks."
ICG, in releasing what it called its preliminary findings on the cause of the blast, said the streaks "appear to have an associated increase in magnetism, which would suggest the passage of electrical energy across or through the rock."
But James Dean, acting director of the West Virginia Office of Miners Health Safety and Training, said the markings, after being tested at an independent laboratory, were declared to be fossils.
Dennis O'Dell, an official with the United Mine Workers of America, said he had also been advised of those findings and kept a sample of the streaks.
"It just looked like a tree. It looks like bark -- tree bark," Mr. O'Dell said.
ICG's early release of its findings was bitterly criticized yesterday by Sara Bailey, daughter of George Hamner, one of the miners who died.
She accused the company of prematurely blaming the blasts on lightning "in an attempt to influence public opinion" and deflect responsibility from conditions at the mine before the Mine Safety and Health Administration or the state of West Virginia could issue a definitive report on the cause of the blast.
A final report on the disaster is expected sometime this summer.Martha Rial, Post-Gazette
Stephen Gerard Sawyer, an International Coal Group consultant, displays a belt hanger, part of a coal mine's metallic roof, during the Sago hearings yesterday.
Click photo for larger image.
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