Crandall Canyon: six men, then three more who went in after them

HUNTINGTON, Utah — At 2:48 a.m. on August 6, 2007, the roof of a working section at the Crandall Canyon mine came down in a single violent event. Six miners were underground. The collapse registered on seismographs across the region.

The mine was retreat mining: pulling the pillars that had held the roof up while the coal was taken out, and letting the ground come down behind the crew. The roof fall that killed the six was later described by seismologists as a mining-induced event, not an earthquake, and the mine's owner spent months insisting otherwise.

Ten days later, rescuers working to reach the men were hit by another collapse in the same area. Three of them were killed, including an MSHA inspector, and six more were injured. The mine never produced another ton. Nine men died in a mountain in Emery County.

The reviews that followed were uncomfortable for the regulators as well as the operator. MSHA's own internal review and an independent panel convened by the Department of the Interior in 2008 both concluded that the mining plan had been allowed to proceed into a configuration that experts inside and outside the agency had warned was dangerous.

Crandall Canyon is the case that mine engineers still cite in any discussion of retreat mining, pillar design and the limits of a rescue when the ground itself is the hazard. It is also a case about how much authority an operator should have to design a mining sequence that the regulator signs off on without independent engineering.

No federal rule changed afterwards. What changed was the argument: retreat mining had to justify itself on a plan, and rescue attempts had to account for the possibility that the rescuers are standing in the second collapse.