In a statement issued Wednesday, a spokesman for Alpha Natural Resources, which bought Massey effective June 1, again declined to say what it believes caused the disaster.
"We welcome any additional information that will help reconstruct what happened at Massey's Upper Big Branch Mine," said Alpha spokesman Ted Pile. "But we also ask for time to conduct our own assessment of all the findings published to date as well as proprietary or confidential information we didn't have access to prior to the acquisition of Massey."
MSHA officials told the miners' families they have completed a more than 200-page draft report that they hope to have finalized by sometime this fall. Among other things, investigators are still making final determinations about which of the "multitude" of violations they discovered would be classified as having "contributed" to the deaths.
The massive investigation of the worst U.S. mining disaster in nearly 40 years has involved 300 witness interviews, 84,000 pages of documents, nearly 1,000 separate maps, 23,000 photographs and 1,060 pieces of physical evidence, officials said.
MSHA investigators criticized Massey for "chronic ventilation problems" at Upper Big Branch, saying the company engineered the mine in an "ad hoc" fashion, without long-term planning and by repeated "trial and error" efforts to provide adequate fresh-air to working sections.
Agency officials also blasted the routine use at the mine of ventilation doors that can be left open and are subject to damage and leakage that can short-circuit fresh-air flow underground. MSHA also repeated previous findings that water sprays meant to control dust and ignitions were missing or inoperable, and often clogged with sediment from improperly filtered river water.
Federal investigators found inadequate use by Massey of "rock dust," or crushed limestone, which controls the buildup of explosive coal dust underground. In one case, MSHA said, one end of the longwall section had never been rock-dusted since the longwall machine started work in the fall of 2009. In other instance, MSHA said, roof conditions and mine floor buckling made it impossible to use a mechanized rock-duster in portions of the Upper Big Branch tunnels.
Investigators reported that miners at Upper Big Branch were intimidated into not voicing safety concerns, and that local mine managers were threatened with losing their jobs if they ever allowed a safety problem to slow down coal production.
MSHA officials said mine foremen at Upper Big Branch routinely did not record key methane gas and other readings. They noted that one company safety examiner who was supposed to check for methane the day of the explosion had turned off his methane monitor in mid-March and not turned it back on again until about four hours after the April 5 explosion.
Stricklin said Wednesday MSHA has not been able to find any evidence that Massey took recommended safety precautions following previous methane problems in 1997, 2003 and 2004 at Upper Big Branch. But, Stricklin conceded, there is also no record that MSHA pushed the company to do so.
Staff writer Gary A. Harki contributed to this report.
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.