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Why so many sinkholes in the Midstate? - abc27 WHTM

Why so many sinkholes in the Midstate?

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HARRISBURG, Pa. (WHTM) -

What’s under your feet? If you live in the Midstate, best guess way below your home is porous limestone, which is a major factor for sinkholes in the area.

If you head to the top of this website and search for "sinkhole," a bevy of articles will pop up that report on issues in Lancaster, Palmyra, York, Derry Township and, of course, Harrisburg. In essence, sinkholes swarm the Midstate.

William Kochanov, a senior geologist for the state Department of Conservation and Natural Resources, wrote the book on "Sinkholes in Pennsylvania" – literally. The commonwealth’s leading expert met with abc27 in Palmyra, the site where a row of homes fell victim to sinkholes last fall.

"It's like sitting on top of Swiss cheese in a sense," he explained.

Kochanov pointed out that there is a limestone formation that stretches from Adams County to New Jersey. He said this bedrock is buried underneath highly populated urban areas like Carlisle, Harrisburg, Lancaster and Ephrata.

He said what people should understand is sinkholes are very common in the area due to this rock. Between acid rain, rivers, creeks and old infrastructure, water seeps into the sponge-like rock over time.

"Water wants to get down to the water table underground," he said.

As the limestone erodes, the soil just above the bedrock sinks into the hole. The sunken soil underneath creates a bubble above and the surface is without support and eventually caves in.

In the colonial days, farmers were attracted to central Pennsylvania’s soft soil, created by rich minerals and limestone. As communities developed over the centuries, they grew on top of the limestone.

Obviously, the sinkholes cause problems now because of population.

"Not much thought was given to the areas that were developed on," Kochanov said. "The limestone areas were good for farming, they're nice and flat, good transportation."

In most urban settings, water and sewer pipes were built underneath around the early 1900s. Such as the main issue in Harrisburg, failing pipes create water main breaks, which wash the soil away creating those voids that lead to sinkholes.

The problem happens across the viewing area, which begs the question: how can you detect a sinkhole? Kochanov said there are many factors that go into a sinkhole, but homeowners could have a geological inspection of their property.

He said understanding your property’s history, your neighborhood’s water drainage, maintaining your residential pipes and planning accordingly could help prevent sinkholes, but then again they still occur. He said the safe bet is to purchase sinkhole coverage if your homeowner’s insurance doesn’t cover such a situation.

"That little flag pops up when you're in a limestone area to say, 'you may want to consider purchasing [sinkhole] insurance when you purchase your property,' " he said.


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