Mine rescue team members responding to the disaster at the Darby mine in Kentucky on May 20 reported that the alternative seals had failed to withstand the explosion.
The cause of the explosion is currently under investigation. However, preliminary indications that the seals used at the Darby mine were compromised by the blast are of utmost concern to MSHA, agency acting administrator David Dye said.
“While MSHA investigates this tragedy to determine the cause and location of the explosion, we are concerned that the alternative seals did not withstand a blast and exposed miners to unacceptable hazards,” Dye said.
Dye on Monday said MSHA will begin a reassessment of the structural integrity of existing alternative seals and will require testing of the atmosphere behind the seals. For those alternative seals with structural issues in which the atmosphere behind them is potentially explosive, MSHA officials will require additional precautions to protect miners.
Dye also announced a moratorium on new construction of alternative seals under the 1992 MSHA standard. He is directing MSHA district managers not to approve requests to construct alternative seals in underground coal mines. This moratorium will be effective immediately while further review and testing on each of the previously approved alternative seals under this 1992 standard is conducted.
“MSHA will require that coal mine operators immediately examine the structural integrity of all of their alternative seals and test the atmosphere behind these seals to protect against hazardous conditions for miners,” Dye said.
“In addition, MSHA is issuing a temporary moratorium on the construction of alternative seals to protect America’s underground coal miners following the second disaster this year in which these seals failed to withstand an explosion. Until we have answers to our critical questions about the safety of these seals, as approved under the 1992 alternative seals standard, coal mine operators who wish to seal worked-out areas will have to use solid, concrete-block seals, as specified in the regulations.”
The temporary moratorium will remain in place until further tests of alternative seals can be conducted to determine the seals’ ability to withstand explosive forces under various conditions.
