By Erich Hiner, CG Editor-in-Chief
Residents of the Village of Sugarcreek, Ohio, hadn’t given much thought to the town’s old coal mine before May 2009, but their memories were violently jogged when a home began to sink. The land beneath the house sagged, cracking the building’s façade and walls. The middle of the brick-front ranch-style house bowed, and cracks began to run through the bricks and drywall. The family living there had to abandon their home while village officials looked on helplessly.
“It all happened within about three or four days,” Sugarcreek Village Administrator Dick Rausch said. “It didn’t seem like there was much anybody could do except let it run its course.”
An investigation by the Ohio Department of Natural Resources Division of Mineral Resources Management revealed that mine subsidence, the bowing or collapse of earth due to unstable, underground mining voids, was to blame.
Records from the ODNR Division of the Geological Survey showed that the old coal mine ran under large portions of Sugarcreek, unbeknownst to many residents.
Workers started the mine in the early 1900s and cleared vast coal deposits over several decades. Like more than 99 percent of coal mines in eastern Ohio, it was eventually abandoned.
After the mine closed in 1960, Sugarcreek grew and dozens of new homes were built. Today, nearly 2,200 people live in the town about 100 miles northeast of Columbus.
“It’s a neighborhood, and the whole area is completely undermined,” said Mac Swinford, assistant chief of the ODNR Division of the Geological Survey. “The people that built there had no idea their houses were above an abandoned underground mine.”
Although mine subsidence affects relatively few Ohioans annually, thousands of residents live above or near abandoned underground mines, or AUMs, and are not aware of the empty space beneath their homes.
According to data from the geological survey office, Ohio is now home to about 5,000 documented AUMs. As many as 2,000 additional AUMs might exist for which there are no records.
Known AUMs are present in 35 of Ohio’s 88 counties. Most AUMs are in Ohio’s coal-rich Appalachian counties.
The mines run under 2 percent of Ohio’s surface, roughly 800 square miles. They account for a combined area about three-fourths the size of Rhode Island.
The subsidence incident at Sugarcreek is not unique. Hundreds of subsidence events have occurred in the state, and the government has spent millions of dollars to repair subsidence damage caused by AUMs.
Ohio is ranked 12th in the nation for subsided land. About 350 acres have been logged in the Office of Surface Mining’s Abandoned Mine Land Inventory System. Ohio is ranked sixth in the nation for spending on subsidence reclamation projects after Wyoming, Pennsylvania, West Virginia, North Dakota and Kentucky.
The state has responded to more than 400 subsidence events since 1985, reinforcing more than 177 acres of land at a cost of $14.7 million.
In some cases, Ohio towns or cities have been built over or near abandoned mines. In other cases, land under existing towns has been mined.
Terry Van Offeren, deputy chief of the ODNR Division of Mineral Resources Management, said subsidence events can be dangerous but are difficult to predict.
“You don’t know where it’s going to take place, when it’s going to take place or what the magnitude is going to be,” Van Offeren said.
Subsidence holes and sags can happen in backyards and under homes, Swinford said. Mines tend to suck in soil from the surrounding area when they cave, endangering buildings that might not be directly over subsidence sites.
AUM subsidence also threatens Ohio’s roadways. In March 1995, a subsidence opened a 6-foot hole in the eastbound lane of Interstate 70 in Guernsey County, causing an accident and costing the state $3.6 million in repairs.
More than 550 lane miles of Ohio’s roads run over AUMs, said Kirk Beach, geology program manger at the Ohio Department of Transportation’s Office of Geotechnical Engineering. Every lane mile requires $4.2 million to repair or reinforce, Beach said.
From 1995 to 2004, ODOT spent $31.8 million to repair roads or reinforce AUMs to prevent problems. The recent bypass project near Nelsonville in Athens County cost the state $30 million in mine remediation, Beach said.
Ohio’s AUMs are mostly overseen, observed and reclaimed by the state with financial help from the federal government.
Tim Jackson, AML emergency program administrator for the ODNR Division of Mineral Resources Management, responds to sudden subsidence events that pose a threat to public safety. To confirm an AUM, workers bore holes into the ground around the area of a suspected subsidence. Although advanced technologies exist to detect mines, the only foolproof way to find them is to drill, Jackson said.
If workers find a mining void and determine it to be the cause of the subsidence, the void is filled with cement, grout or gravel.
Mines located less than 90 feet below the surface are more likely to cause what geologists refer to as “pit subsidence,” wide but shallow openings in the ground that appear suddenly because of mine cave-ins. Mines with roofs deeper than 90 feet create sagging on the surface and can damage structures, but do not typically create holes.
Smaller projects can take up to 90 days, Jackson said, and stabilizing subsided land under a house can take several months. A small sinkhole in a yard can cost from $2,000 to $5,000. Stabilizing a house can cost from $50,000 to $90,000, Jackson said.
Thankfully for Ohio residents, that cost is covered almost entirely by the state. The ODNR pays to stabilize the ground, and the state offers cheap subsidence insurance coverage through the Ohio Mine Subsidence Insurance Underwriting Association.
Subsidence insurance is required by law in 26 Ohio counties, but it is offered to homeowners for $1 per year. In 11 Ohio counties, homeowners have the option to buy subsidence insurance for $5 a year. Subsidence insurance covers up to $300,000 in repairs.
Officials agree that mine subsidence is likely to worsen as timber mine supports wear down. Natural wear and tear stresses some older mines to the breaking point.
“As the mines age, the potential could be become greater in the future,” said T.A. Brininger, the OMSIUA claims representative who handled the Sugarcreek claim.
While cases such as the one in Sugarcreek are rare, and Ohio has had no major injuries from subsidence on private property, officials warn precautions are necessary.
Chief among the recommendations is to avoid building above known AUMs.
“The possibility is always there. These are sudden events,” Jackson said. “Any underground mine has the potential to fill and collapse.”
The state is focusing on educating residents about the dangers of subsidence. Online resources include an abandoned mine land development guide and an interactive abandoned mine locater that residents can use to find out if their homes lie above AUMs.
Swinford said being aware of AUMs is the best way for the public to be prepared.
“This is a public safety issue, period. These subsidence holes can open up in people’s backyards, and people can be injured,” Swinford said. “They need to know these underground mines exist in their area.”
Editor’s Note: College Green Editor-in-Chief Erich Hiner was interning with the Scripps Howard Foundation Wire in Washington, D.C. when he wrote this article. Article and photo courtesy of SHFW. Reprinted with permission.