Benld, IL — The way a few teachers tell it, the elementary school in the central Illinois farming town suddenly started giving off freakish cracking and popping sounds on a Saturday not too long ago. Walls sprouted lightning bolt-shaped cracks and floors buckled, dooming the building on a day no students were inside.
The culprit: A long-abandoned coal mine hundreds of feet below whose pillars had given way. It’s a wildly unpredictable phenomenon all too common across coal country, where over the years scores of homes, schools, businesses and roads have cropped up over closed mines and threatened their stability.
The problem, called subsidence — the lowering of the land surface because of changes underground — has been around for more than a century, though recent figures pinpointing its national scale are lacking.
Comprehensive federal reports often are decades old. One report dated 1979 estimated that more than eight million acres of U.S. land had been burrowed out by mining, with subsidence affecting about one-fourth of it. Those numbers are certain to be stale.
Subsidence experts say the problem has been documented in more than 30 states and on lands belonging to six American Indian tribes, creating costly headaches for people like Jerry Niswonger.
Just last month, the auto body shop owner in Hopkins County, Ky., was forced with his wife from their decade-old, three-bedroom home when it dropped 17 inches on one side within days after the mine below settled. “It’s just like it’s running downhill,” Niswonger said of the house.
Niswonger, 57, always assumed a mine lurked nearby but never knew for sure until calamity came. “That’s the chance you take,” he shrugged. He expects to salvage the home, covering some of the expense through his subsidence insurance but knowing “I’ll have to dip into my own pocket.” An early estimate put the damage at $150,000.
On a road in Pennsylvania’s Washington County, subsidence Aug. 6 caused anything but a pothole. The 12-foot-wide, 20-foot-deep sinkhole blamed on a mine below opened up on the state’s Route 88, forcing continued detours for motorists as crews try to mend the crater.
In Illinois, more than a million acres — 3 percent of the state — have been mined out for coal as of 2007, including 827,000 acres of underground burrowing, according to the Illinois State Geological Survey. More than 178,000 acres of that is occupied by homes or industry, according to state figures dating to 1991.
Those numbers are the latest available and certain to be outdated as urban sprawl gobbles up one-time mine lands.
Avoiding those mines in central and southern Illinois is very difficult, said Bob Gibson, a subsidence expert with the Illinois Department of Natural Resources’ abandoned mine lands unit. His team has monitored every subsidence event in southern Illinois since the late 1970s.
In the 1,500-resident town of Benld, the district’s leaders knew the school sat above a mine even before it was built seven years ago to replace an 82-year-old school next door also damaged from a mine below. But they didn’t hire collapse-predicting specialists, buy extra insurance or backfill the mines with noncompressible waste material or concrete, a very pricey proposition.
In fact, they’re not required to. Illinois has no state building regulations that mandate a complete study of the prospect of mine collapse.
Then on March 28, pillars in what had been Superior Coal Co.’s No. 2 mine collapsed and filled in those tunnels with tons of soil and rock, dooming the elementary school.
In the gymnasium, a two-inch-wide crack zigzags along the floor, then juts outside and across the parking lot. Red circular metal posts shoring up some entryways are the only things keeping the roof from caving in, said Paul Skeans, the district’s superintendent.
“The entire frame of the building is being twisted. At some point, it’s all gonna come down,” Skeans said, shaking his head. “Whenever I come down here, I get sad all over again.”