Officials had initially assumed that the source of the methane was the Lower Eagle Seam, which lies below the Eagle Seam at vertical distances that vary form five to 25 feet.
But further investigation determined that, "The Lower Eagle Seam may simply represent an impermeable cap-rock for a larger gas trap," according to the MSHA documents.
"Natural gas may be ponded in structural highs beneath the Lower Eagle Seam, after rising into domes and subsequently being trapped from further rise by relatively impermeable coal or shale," according to one MSHA report, dated May 4, 2004.
Another MSHA reported, dated July 15, 2004, concluded that, "methane trapped in zone below the Eagle Coal Seam could be released into the mine through fractures opened by longwall coal extraction."
That memo, written by several MSHA staffers for then-acting District Manager Stephen Gigliotti, was prepared to summarize a May 26, 2004, meeting where agency officials and Massey representatives discussed the problem and outlined possible solutions.
Previously, Massey had told MSHA the company planned to drill degasification wells into the Lower Eagle Seam prior to subsequent longwall mining "in an attempt to decrease the potential for future outbursts." MSHA concluded, "This appears to be a reasonable plan."
After the May 2004 meeting, MSHA outlined a variety of other potential steps, including increased airflow to help sweep any methane out of the mine, better training for miners to be aware of warning signs of an impending methane outburst, and a plan for sealing off portions of the mine floor where fractures and methane leaks were likely to occur.
None of the MSHA documents indicate what, if any, of these steps were ultimately taken by the company or mandated by the agency.
Shane Harvey, Massey's general counsel, said the company is reviewing the matter.
"We are looking at it," Harvey said. "I don't know the details of what was done."
MSHA records appear to indicate that Massey was cited for a minor violation of its ventilation plan after the 2004 incident. The company paid a $525 fine. Agency records do not appear to contain any citations for the 2003 incident.
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.