Roof bolter operator David Sizemore died April 22 of this year when he and fellow crew member Marvin Music were working at Osaka Mining’s Mine No. 1 in Wise County when a portion of the mine roof and rib collapsed.

“The accident occurred while Music was operating a remotely controlled continuous mining machine loading coal and rock into a shuttle car,” MSHA said, adding that both workers were at the No. 7 entry about 17.5ft outby the last row of permanent roof supports as Sizemore observed Music perform the work.

“Rock fell from the mine roof and rib between the right rib and three installed 72-inch torque tension roof bolts … one of the roof bolts broke at the time of the fall,” the agency said.

“The portion of the mine roof and rib that fell, striking both miners, measured approximately 6 feet long and 3 feet wide at the inby end and 19 inches wide at the outby end by up to 14 inches thick.”

MSHA found that the accident occurred because the company was not utilising angle compensating devices in its roof bolt process, which resulted in the bolt bending and fracturing during installation and subsequently having a reduced loading capacity.

Additionally, the agency felt insufficient controls were in use by the bolt manufacturer for the chemical composition during its steel manufacturing process, which consequently left the roof bolts with poor toughness properties.

Lastly, MSHA noted that Sizemore was “unnecessarily in close proximity” to the unit operator while working underground that day.

MSHA ordered that the mine operator make several changes as a result of its investigation, and the operator has already instituted the use of a specialised washer to its pattern bolt assembly.

Additionally, the operator was ordered to submit a revised roof control plan to the federal agency, which it did on April 28 of this year and received approval on it the following day.

“All persons will be in a safe location, outby the continuous mining machine operator, while coal is to be cut, mined or loaded,” the amendment stated.

“The number of persons positioned at the continuous mining machine will be limited to those necessary to facilitate the mining process.

“When persons other than those necessary to facilitate the mining process enter the area, the mining process will stop. Persons shall not be allowed to congregate in the area surrounding the continuous mining machine when coal is being cut, mined or loaded.”

The mine reported to MSHA that the plan was reviewed with all personnel on April 29 and 30.

The mine’s non-fatal days lost (NFDL) injury incidence rate for 2007 was 2.28, versus a national rate of 4.64.