What Is a Sinkhole? A Scary Threat That’s Rare, but All Too Real

by Michael Mosher on October 30, 2017

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What is a sinkhole? It’s a depression that forms in the ground caused by erosion underneath. Also known as cenotes, shakeholes, swallets, or dolines, sinkholes can be small depressions you’d barely notice or hundred-foot-deep chasms. Scariest of all, they can form gradually or out of the blue, swallowing everything in the vicinity—including you and your home.

Yet while sinkholes are quite frightening, rest assured they’re blessedly rare.

“Your home is much more likely to get struck by lightning than swallowed by a sinkhole,” says Nick Gromicko, founder of the International Association of Certified Home Inspectors. Sinkholes engulf only a few homes a year, out of over 75 million housing units in the U.S. “That means the odds of your home being swallowed by a sinkhole are almost zero,” says Gromicko.

Nonetheless, home buyers and owners should be aware of sinkholes and how and where they form, since certain areas are at greater risk than others.

Where are sinkholes most common?

According to the U.S. Geological Survey, about one-fifth of the United States is at risk of developing sinkholes. They occur most often in areas where carbonate rock (like limestone or dolostone) lie underneath the soil. Since these stones dissolve in water, they can lead to massive underground caves that can collapse, sucking down the earth above.

Florida has the most sinkhole activity, with more than 6,000 occurring per year. Both this state and Tennessee, in fact, have laws requiring home insurance providers to offer sinkhole coverage. But sinkholes are also common in Alabama, Missouri, Kentucky, Pennsylvania, and Texas. And at the end of the day, no place is completely safe, because sinkholes do happen all over the U.S.

“Every state has their own sinkhole activity,” notes Tony Diana, owner of Advanced Pier Technologies and The Sinkhole Guy, a sinkhole and foundation repair company. So, everyone should know the signs of sinkhole activity, particular if they’re purchasing property.

What are some signs of a sinkhole?

According to Gromicko, these are some red flags to look for:

Previously buried items—such as foundations, fence posts, and trees—becoming exposed as the ground sinks
Gullies and areas of bare soil, which are formed as soil moves toward the sinkhole
A circular pattern of ground cracks around the sinking area (“Sudden earth cracking should be interpreted as a very serious risk of sinkhole or earth collapse,” notes Gromicko.)
Formation of small ponds as rainfall accumulates in new areas
Interrupted plumbing or electrical service to a building or neighborhood due to damaged utility lines
Plants that wilt and die because their water’s drawn away by the sinkhole
Slumping or falling trees or fence posts
If you’re interested in purchasing property that’s located in an area known for sinkholes, hire a qualified home inspector to check for them, urges Diana.

“They’ll know the difference between, say, stucco cracking and structural movement,” he says. “They’ll also know if you need to hire a structural engineer or a sinkhole repair company.”

And even after you move in, keep an eye out for potential problems.

“Call an engineer over anything concerning,” Diana says. “It’s better to find out and know what’s going on than be an ostrich with its head stuck in the sand.”

Can a sinkhole be repaired?

Fixing a sinkhole is possible.

“Most of the time, they can simply be filled in with soil,” explains Gromicko. “But sometimes [a repair company] has to dig down to the bedrock and fill in the holes with concrete.”

Putting a stop to minor sinkhole activity runs anywhere from $30,000 to $50,000. If pumping cement into the ground is required, that may boost the cost anywhere from $50,000 to $200,000, depending on the size of your home.

And yet, “the real cost,” adds Gromicko, “is the damage the sinkhole may have done to your property. Some sinkholes have swallowed entire homes in 30 minutes.”

Another caveat? The biggest misconception about sinkholes, adds Gromicko, is that your insurance company will cover all your damages.

“Many homeowner insurance policies don’t cover sinkholes,” he points out. So if you’re concerned, be sure to check, and plan accordingly.



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