ICG said although state and federal mine safety authorities had provided approval last week to resume mining operations, the company delayed resumption of coal production until it had announced its initial findings to the families and co-workers of those killed and injured in the accident.
Findings were revealed to families early on Tuesday in a series of private meetings and employees of the Sago Mine were briefed as they reported to work for their regular shifts late Tuesday. Normal coal mining activities will resume on Wednesday, March 15.
ICG president Ben Hatfield said while the company’s investigation was not the final word on the explosion, it was confident that the joint federal-state investigation would reach a similar conclusion.
The company found the January 2 explosion was ignited by lightning and fuelled by methane that naturally accumulated in an abandoned area of the mine that had been recently sealed.
It said the lightning ignition was verified by three independent events: an unusually large lightning strike measured near the Sago Mine by an independent weather monitoring service; a seismic event at the Sago Mine that was detected by a Morgantown area USGS seismic station; and the Sago Mine atmospheric monitoring system signalling a combustion alarm due to presence of carbon monoxide.
ICG said the precise route by which the lightning’s electrical charge travelled from a surface strike location to the sealed area remained under investigation.
“The seals, constructed of Omega block under a plan approved by MSHA and designed to withstand forces of 20 pounds per square inch, were essentially obliterated by the explosion. Calculations indicate that the explosive forces experienced at each seal were substantially greater than 20psi,” ICG said.
“More specifically, the forces at roofline were as high as 30psi at all the seals – and possibly as high as 60psi at some of the seals.”
ICG also reiterated that none of the citations issued at the mine during or prior to the accident were linked to the January 2 explosion.
To prepare the mine for resumption of coal production, more than 80 employees have been working underground for several weeks to repair damage from the explosion. All ventilation controls, including stoppings and overcasts, have been reconstructed.
The formerly sealed area will be ventilated to the surface through two boreholes and a small ventilation shaft that were drilled recently, which will eliminate the need for those seals.
ICG said it had also been participating with the National Institute for Occupational Safety and Health in its underground coal mine communications research effort and had been independently reviewing potential underground communication technology for testing and possible implementation in ICG mines.
ICG’s full investigational results can be found at www.intlcoal.com.