Sinkholes Can Cause Costly Damage

By BRUCE SCHREINER | September 15, 2014

Solid ground isn’t always a certainty. Sinkholes can lurk anywhere, beneath suburban homes, city streets or even football stadiums and museums.

It’s basic geology: Sinkholes open when soil collapses into large holes, caused by flowing water in underground limestone. Their toll can be dramatic, swallowing homes, trees or anything else on the collapsing ground – even prized Corvettes.

credit: National Corvette Museum
credit: National Corvette Museum

The Southeastern U.S. is prime territory for the geological phenomena – a potentially costly game of subterranean roulette.

In Tennessee, a sinkhole opened during renovations on the football stadium at Austin Peay State University. What started as a small hole turned into a chasm 40 feet deep and 40 feet wide as a repair crew dug to find its source.

In Kentucky, a sinkhole gobbled eight classic cars on display at the National Corvette Museum in Bowling Green. Corvettes, piled like toys in a heap of dirt and concrete fragments, became an Internet sensation, boosting museum attendance.

And in Florida – ground zero for sinkholes – Tina and John Furlow were forced from their home near Tampa when a sinkhole caused so much damage that the repairs would have exceeded the value of the three-bedroom house with a nice pool. They now live in a used recreational vehicle.

“It has been miserable,” Tina Furlow said. “It is taking its toll on us. We decided we need to get off this merry-go-round.”

For every sinkhole that causes property damage, scores open in fields and other obscure places.

“In the Southeast U.S., there are hundreds of sinkholes every day and they don’t get reported … or they don’t cause damage,” said Jason Polk, professor of geology and geography at Western Kentucky University.

Earlier this year, sinkholes opened at high-profile spots about an hour and a half apart: the Corvette Museum in south-central Kentucky and the football stadium at Austin Peay State in Clarksville, Tennessee.

During renovations at Austin Peay’s Governors Stadium, a sinkhole was discovered where the football field meets the track. Workers needed seven days to fix it, said Mike Jenkins, superintendent for Nashville-based Bell & Associates Construction. The hole was plugged with layers of boulders, concrete, smaller rocks and a layer of cloth-like material to prevent moisture from seeping through. Then came another application of rocks, capped by asphalt.

“I’m pretty confident that the work we did won’t become an issue again,” Jenkins said.

Austin Peay plays its first football game in the renovated stadium Saturday against Chattanooga.

At the Corvette Museum, the 60-foot-long, 45-foot-wide, 30-foot-deep sinkhole opened in the Skydome display area in mid-February. The place that showcases automotive engineering will highlight another engineering feat when workers fix the hole. The project is expected to last six months and cost millions of dollars, said museum spokeswoman Katie Frassinelli.

The museum will remain open during repairs.

Workers will stabilize the sinkhole walls with metal sheets, then fill it with about 4,000 tons of crushed limestone. Grout – a mixture of sand and cement – will be poured into dozens of holes drilled into the rock, supporting steel and concrete pillars beneath the floor. Concrete flooring will complete the project.

Elsewhere, in one extreme case, a 37-acre sinkhole opened two years ago in southern Louisiana and has been swallowing land ever since. Scientists believe it formed after an underground salt dome cavern had some sort of collapse or breach of its outer supporting sidewall of salt.

In Florida, the nation’s most sinkhole-prone state, a sinkhole in 1981 swallowed sports cars, parts of two businesses, the deep end of a swimming pool and a three-bedroom Winter Park home. In 2013, a Florida man died when a sinkhole opened under his bedroom.

Homeowners often find clues to a sinkhole problem through cracks in the foundation or a shifting floor. When a sinkhole threat has been established, crews can pump a thick grout into the ground to fill the holes.

“There are no typical cases with a sinkhole,” said Sandy Nettles, who owns a geology consulting company in the Tampa, Florida, area. “It just depends on where the building is. We get a lot of them that opened underneath a house. You can run around the house and see no evidence of the sinkhole, but the interior of the house is subsiding or collapsing.”

The Furlows had no clue a sinkhole had formed on their property until John Furlow fell into the hole beside the house, said his wife, Tina.

They tried sticking it out but finally left when her husband developed a lung infection from mold in the house, she said.

“We put every penny into that house thinking we would live and die there,” she said.

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