Utah mine collapse began where miners were removing pillars, seismologists conclude

The Utah mine collapse that claimed nine lives last summer was larger than first thought and started near where miners had been removing pillars of coal in the weeks before the disaster, University of Utah seismologists say in a report that also debunks the mine operator's notion that the collapse could have been caused by an earthquake.

The researchers "estimated the size of the collapse is about four times larger than was thought shortly after the time of the Aug. 6, 2007, disaster that resulted in the deaths of six miners and, 10 days later, three rescuers," a university press release said. "The seismologists’ 53-page report has been submitted to the journal Seismological Research Letters and to federal Mine Safety and Health Administration investigators." MSHA's report on the Crandall Canyon mine is due out this month. "Scientists usually don’t release studies until they are published in journals," the release said. "But in this case, there have been numerous requests for the information, which is a matter of public interest, so researchers released the report now. They delayed the release a couple of weeks at MSHA’s request to give the agency time to inform disaster victims’ families."

Some experts have blamed the collapse on the mine's practice of "robbing pillars," the vertical columns of coal that support the mine roof, and the report lends more credence to that view. It notes that the MSHA-approved mining plan called for "leaving behind pillars about 110 feet long and 60 feet wide. The next phase of the plan was to mine coal in some of these pillars and allowing the roof around the pillars. "The last known working location of the six miners was just east of where those pillars were removed," the release said. The study shows the hypocenter of the collapse, the underground point at which it began, “was right at the edge of where miners were removing pillars in July and early August,” said seismologist Jim Pechmann, the study's lead author and research associate professor of geology and geophysics.

The report also said the scientists are certain that the 3.9-magnitude earthquake recorded at the time of the collapse was the collapse itself, not the cause of the collapse, as contended by Robert Murray of Murray Energy Corp., owner of the mine.