Twenty-nine miners died that day in the mine, which was operated by Performance Coal Co., a subsidiary of the former Massey Energy Co. The WVOMHS&T report offers a comprehensive look at the fatal incident and its aftermath, covering Upper Big Branch's mining methods, mining history, ventilation and methane drainage, communication and tracking system, organizational structure, causes and contributing factors to the explosion, the chronology of events following the blast and more.

The report outlined the explosion defenses that failed at UBB and offers recommendations for ventilation systems, mine examinations and rock dusting. WVOMHS&T issued a total of 253 violations that covered a range of categories: 147 violations were related to electricity; 15 to ventilation; 11 to equipment; two to coal dust and rock dust; and many more.

"The explosion began after gas, mostly methane, was ignited by frictional impact as the shearer was cutting sandstone roof or by the rock colliding with steel supports or other rock while falling from the sandstone roof behind the longwall shields," the report stated. "The methane explosion quickly transitioned into a coal dust explosion, which severely damaged ventilation controls, conveyor belts, water lines, electrical systems and numerous items in its path until the fuel was consumed and the explosion extinguished itself…"

The report added that the "amount of rock dust being maintained on mine surfaces at the time of the explosion was insufficient to stop a coal dust explosion. The region where the dust explosion started does not appear to have had rock dust periodically applied over the fine coal dust. Periodic applications of rock dust over accumulating fine coal dust are necessary to render such dust harmless."

This report was released on the heels of the news that federal prosecutors have charged Gary May, a former senior mine supervisor with the mine, with felony conspiracy.

To read the report in full, visit http://www.wvminesafety.org/Upper%20Big%20Branch%20Mine%20Accident%20Report.htm.