It has been a little more than two months since an underground fire forced Consol Energy to shut down its Blacksville No. 2 deep mine along the Pennsylvania-West Virginia border, and neither the company nor the federal agency in charge of mine safety oversight knows what caused it.
And they may never know.
Cecil-based Consol Energy received federal approval of its plan to reopen the mine Thursday, and approximately 650 employees, including 450 miners from United Mine Workers Local 1702, will start returning to work in the mine today and Saturday, with full production slated to begin Monday.
But the cause of the fire that closed the mine March 12, when smoke was discovered pouring out of an exhaust fan at the Orndoff Shaft in Wayne, will likely remain a mystery.
"I'm not sure we'll ever be able to tell the public succinctly what caused the fire because that area is now all behind the seals that the company constructed," said Kevin Stricklin, coal mine safety administrator in the U.S. Department of Labor's Mine Safety and Health Administration. "Our investigation team will eventually come up with a list of possibilities but we can't, and won't, know for sure."
Possibilities include a spark from a telephone in the area or from a roof fall that could have set off an explosion that ignited coal dust, or even a lightning strike, Mr. Stricklin said. He said after the fire was discovered, MSHA inspectors never got into the part of the mine that was burning because the heat was too intense and it was too smoky.
Lynn Seay, a Consol spokeswoman, said she expects the company will eventually figure out what caused the fire, based on tests of material from the burned area of the mine, but Thursday afternoon said the company had not made any determination.
According to a statement released by Ms. Seay, because the fire occurred in an inactive and previously mined area of the 900-to-1,000-foot deep mine, Consol did not lose any minable Pittsburgh seam coal reserves in the mine, which has a 39-square-mile underground footprint. The mine normally produces approximately 400,000 tons of coal a month.
When the fire was discovered, Consol moved fast to contain it to the previously mined section and protect its coal reserves, Mr. Stricklin said.
"When a company wants to put out a mine fire or prevent it from increasing in size to protect its holdings, we can't and wouldn't tell them to stop," he said. "Consol acted quickly and by doing so saved millions of dollars of coal and reduced the possibility of injuries from fighting the fire."
According to Mr. Stricklin, Consol was fortunate the fire occurred in a down-dip or low point in the Pittsburgh Seam. That allowed the company to pump millions of gallons of water into the mine, filling passageways adjacent to the area that was burning and cutting off oxygen to the fire.
The company then drilled bore holes into the area of the mine that was on fire and injected nitrogen gas to reduce the oxygen content in that section of the mine to less than 10 percent and prevent the fire from growing. Subsequently, metal sheets were put in place as temporary seals to further reduce the air flow into the fire area.
Consol began pumping cement into the mine in mid-April to construct the permanent seal walls, each 5 to 6 feet thick and able to withstand 50 pounds per square inch of pressure, around the area that had been on fire. It completed the last of the 21 seals May 7.
According to Consol, approximately 4 million square feet of the mine was sealed off.
"I don't want to say Consol was lucky because it did have a fire, but luck was on its side because of the location of the fire in a dip in the seam," Mr. Stricklin said. "Because of that, they were able to roof the water and cut off its oxygen supply. Without the dip Consol would have lost much more of the mine."
Phil Smith, a spokesman for the United Mine Workers International, said the union was glad the mine is getting back into production so quickly, even if the cause of the fire isn't known.
"We're very happy that our members will be getting back to work tomorrow because the guys have been going without a paycheck for a while," Mr. Smith said. "As for the fire, it could have been caused by any number of things, and with the area now flooded and sealed we may never know."
Don Hopey: firstname.lastname@example.org or 412-263-1983.