Federal regulators on Monday halted the use of a controversial type of blocks for underground mine seals, following the second mine disaster this year linked to those seals.The U.S. Mine Safety and Health Administration said it would begin a “reassessment of the structural integrity” of such seals, known as Omega Block. MSHA will also require mine operators to test for the buildup of methane behind such seals, the agency announced.“Until we have answers to our critical questions about the safety of these seals ... coal-mine operators who wish to seal worked-out areas will have to use solid, concrete-block seals, as specified in the regulations,” said David Dye, acting assistant secretary of labor for MSHA.Dye announced the MSHA plans two days after five miners died in a huge explosion in an eastern Kentucky coal mine.The explosion at the Kentucky Darby LLC operation was the first time sine 1981 that the nation has seen one year with two coal-mine disasters, defined as five or more deaths from one accident.Investigators believe the blast at the Darby Mine No. 1 in Harlan County may have occurred near a mined-out area that had been sealed using the controversial foam block material called Omega Block.Potential problems with Omega Block have been linked to the Jan. 2 explosion that led to the deaths of 12 miners at the Sago Mine in Upshur County.
At Sago, the explosion is believed to have occurred inside a sealed area that was walled off with Omega Block.Investigators have not pinpointed the exact problem with the Sago seals.It could be that the blocks were not as strong as MSHA believed when it approved them as an “alternative” seal material more than a decade ago. Investigators are also examining whether the seals were not properly built, and whether the construction specifications themselves were faulty.At the Darby Mine, investigators do not yet know if the explosion occurred inside or outside of the sealed area.
In a prepared statement, MSHA said only that mine rescue team members reported that the seals used in the Darby Mine “failed to withstand an explosion.”“The cause of this mine explosion is currently under investigation,” MSHA said in its statement. But, “preliminary indications” that the seals used at the Darby Mine “were compromised by the blast are of utmost concern to MSHA,” Dye said.Holly McCoy, a spokeswoman for the Kentucky Office of Mine Safety and Licensing, confirmed that the Darby seals were made of Omega Block.Kentucky Gov. Ernie Fletcher said he ordered all the state’s underground coal mines with the seals to monitor them more closely and make sure they’re not leaking.
Under federal law, coal companies that abandoned and seal off mined-out areas must take steps to ensure that these areas are “isolated from the active workings of the mine with explosion-proof seals or bulkheads.”In 1992, MSHA wrote rules to implement the “explosion-proof” criteria. Generally, MSHA required seals to be built with concrete. But it allowed alternate materials if those materials would withstand a blast with the force of 20 pounds per square inch.MSHA cited a 1971 Bureau of Mines report as the source for that number. But, the report itself said that explosions could often be of much more force than that, and noted that other countries require much stronger seals.Dye said that MSHA would require coal companies to “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.”A temporary moratorium on new alternative seals will remain in place until further tests can be conducted to determine those seals’ ability to withstand explosive forces under various conditions, MSHA 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.
Staff writer Ken Ward Jr.’s continued coverage of the Sago Mine disaster and mine safety is being supported by a fellowship from the Alicia Patterson Foundation. To reach Ward, use e-mail or call 348-1702.