A mixture of coal ash and cement will be used to douse the 58-acre Percy Mine fire in North Union Township, Fayette County, a stubborn and crafty blaze that has been burning for 31 years.
The state Department of Environmental Protection on Wednesday awarded a $3.2 million contract to control and extinguish the underground mine fire to GAI Consultants, a civil and environmental engineering consulting firm, headquartered in Homestead.
The Percy fire was discovered in July 1974 in the Youngstown area of North Union Township, about one-half mile west of Route 119 near the former Uniontown state police barracks, just north of the city.
State officials say the fire was ignited by a trash fire in a small hole above ground. The conflagration subsequently worked its way underground into the air shafts and tunnels. The Percy Mine, once operated by Landman Coal & Coke Co., closed in 1923.
The fire went undetected for several years until residents observed smoke coming from the ground, cooking the earth and making it hot enough to melt snow in the dead of winter.
The fill material will be delivered to the site in a moist state in order to minimize dust, and then mixed with water and cement to form a slurry that will be pumped into the mine through a series of boreholes.
"It's the process as much as the material used, which makes us optimistic of success," said Tom Rathbun, spokesman for the state environmental protection agency.
Previous efforts to contain the fire have been unsuccessful. In 1984, the federal Department of the Interior spent $2.4 million to build an underground clay containment wall between the fire and homes in Youngstown. By the early 1990s, the fire began to spread as it reached around the wall, baked the clay and caused it to crack.
The fire is about 970 feet underground at its deepest point. The blaze has burned along the roof of the coal seam -- not on the floor -- rendering any flushing process with water useless.
Rathbun said the fill used to fight the fire has been used widely as a structural fill material, and was used previously by the state Department of Transportation at Pittsburgh International Airport. He said the combustible ash has a high limestone content, and will be supplied by Reliant Energy's Elrama plant in Cheswick.
There are currently 112 underground mine fires burning nationwide, including 39 in Pennsylvania. Rathbun said there are nine underground fires burning in Fayette County, seven in Allegheny County, three in Washington County and one in Westmoreland County.
