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“There is a whole smorgasbord of things you can do for a mine fire,” said Stanley Michalski, a professional geologist at GAI Consultants, Incorporated, “but not all of them are going to work.” Michalski described the most recent Pennsylvania fire he helped to extinguish in the Percy Mine near Pittsburgh. Michalski’s team first built a series of barriers in the mine, isolating the fire from the surrounding fuel, and then completely filled the barricaded space with a self-hardening concrete made from coal combustion ash. “Not only did we put the fire out, but we filled the mine workings. We prevented subsidence from the ground surface,” Michalski said. “We feel certain that the fire is extinguished.” The procedure cost the state $3.2 million. Every previous attempt had failed and the fire had burned for 31 years.
The fire triangle is the same in the mining industry and the Boy Scouts. Fires need three elements to burn: air, heat, and fuel. Remove one completely and stop the fire. Many firefighting strategies target the first on this list, the oxygen needed for combustion. Firefighters try sealing the mine, forcing the fire to suffocate itself in its own carbon dioxide exhalations. They dig boreholes from the surface “flushing” the fire either with pure water or “whatever is the mixture of the day,” as Edwards described it. For Centralia they tried water and culm, a slurry of fragmented coal, rock, and soil. They try using those same boreholes to pump high concentrations of inert gases like nitrogen, bringing giant tankers to dump millions of dollars into the depths of the earth. For Loveridge Mine in West Virginia, they even removed the thrusters from an old Soviet jet engine, backed it up to the mine entrance and let it run for 10 days, filling the cavern with an exhaust of carbon dioxide, nitrogen, and water.
Each of these techniques has benefits and risks; unlike flushing a mine with water, the jet engine method, though successful in the 2003 Loveridge attempt, will not cool a mine, so it must remain sealed. Only as the heat slowly dissipates into the surrounding rock, sometimes over many months, does the fire’s threat disappear.
These seals are in fact crucial for all of the techniques, and make success difficult. “The mine is a natural system with a lot of fractures . . . just about impossible to seal,” Edwards said. He explained that fire itself can crack the earth above as it gasps for more oxygen: “It bakes the rocks into almost a fractured pottery and even more air gets in.” If the mine isn’t sealed, inert gases leak out and oxygen leaks in. The fire rages on.
Lignite, subbituminous, bituminous, and anthracite—each type of coal has a rank according to its carbon content and purity. Anthracite, the hardest, and the purest at almost 85 percent carbon, is king. It is also the most rare. Though the energy contained in its molecular bonds may be less than in bituminous, anthracite has long been praised for the purity of its clean burn. The only anthracite mined in the United States comes from northeastern Pennsylvania, formed 300 million years ago in the Alleghany Orogeny from the same intense pressure that thrust out the region’s mountainous terrain. This violent birth also gave anthracite seams their unique shape. David DeKok, the author of two books on Centralia, the second, Fire Underground, published in October of 2009, describes the four seams—Buck, Seven Foot, Skidmore, and Mammouth—under the abandoned town. In an interview, he compares them to concentric bowls, layered one on top of the other: “They plunge down deep and come back up again—forming a big nest.” In Centralia, firefighters tried a variety of methods to stop the fire, spending over $3 million from 1962 to 1978 before finally evacuating the town in 1984. These anthracite bowls posed part of the problem, as their sloping sides give mineshafts a steep pitch that makes fighting fires with any type of liquid difficult.
Today, one of the relatively cheap methods for fighting mine fires involves nitrogen-laced foam, dispersed through boreholes. “It’s like soapsuds, with nitrogen,” Smith said. He spends summers testing such techniques in an underground laboratory in a limestone cavern about 80 kilometers south of Pittsburgh. The only coal in Smith’s Lake Lynn Experimental Mine is the coal Smith and his colleagues have placed there, but otherwise the cavern mimics the dimensions and equipment standard in a commercial coal mining operation. One summer, Smith’s colleagues successfully flooded Lake Lynn with so much nitrogen foam that a white tide rushed from the facility’s entrance, rising to researchers’ knees. Using the foam is usually cheaper than pure nitrogen and requires less water than flushing the mine with liquid alone. But foam too has problems. “If you have any slopes in your mine, you can’t stop the flow, and it will just run like a river,” Smith said. Without some type of backstop it can never fill the mine, cover the burning walls and ceiling, and snuff out the oxygen-filled tunnels.
These tunnels themselves make fighting mine fires difficult. As miners search for more coal, Smith explained, they create intricate paths. “It becomes like a city and spreads out for several miles in some cases,” he said. To get coal from multiple anthracite seams, miners would also dig through separating rock, down from one bowl to the next, creating connections that, when the mines were operational, allowed coal to get out and oxygen in. The same tunnels that allowed miners to breath in active mines now fan the fires and allow them to move from one vein to another. “Those fires start to spread and the amount of thermal energy is just enormous,” Smith said.
But even if firefighters had charts of every official mining location and could effectively seal them around a fire, these mines might still have other oxygen paths. The coal left in the abandoned mines proved too much of a temptation for the families living above them. Often “bootleggers” would pick away at the cavern’s support system, gathering fuel for their fires and heat for their homes. In a mine fire, these uncharted passageways are intractable sources of oxygen. Eating away at the mine’s support system, bootleg mining also weakened the mine’s ceiling, sometimes so much that the surface fell down into the cavern below. Such subsidences can also appear during active fires, when the mine’s coal support columns burn into piles of ash. As mine ceilings fall, they create openings to the sky above, gulping oxygen and, on an infamous Valentine’s Day in 1981, almost swallowing Centralia’s 12-year-old Todd Domboski.
Whenever Centralia is in the limelight, the boy who fell into the ground is the media’s favorite story. Fixing a motorcycle in his grandmother’s backyard, Domboski noticed smoke in a neighboring lawn. He went to investigate, bringing a cousin who would end up saving his life. “I was in over my head when he finally grabbed me . . . It was unbearably hot, and it sounded like the wind howling down there,” a teenage Domboski said to Renée Jacobs, the author of Slow Burn, a photography book first published in 1986 and recently re-issued in a new edition. “Ever since, I’ve had terrible nightmares about falling in that hole.”
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