PennDOT has solution for Palmyra sinkholes - abc27 WHTM

PennDOT has solution for Palmyra sinkholes

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The word for the Midstate landscape is: Karst. That means that we are built on an area rich in limestone, underground water, and even caves. Researchers are realizing that simply plugging up sinkholes wont fix a 100 million-year-old problem.

Last Friday served as a reminder that when the earths foundation gives way, a family's foundation can easily go with it.

That's what happened when concrete parted on Cherry Street in Palmyra. Nine families were forced out of their homes.

Cherry Street runs parallel to Rt. 422 where repairs have been taking place on those sinkholes since the 1930's.

"We tried to plug the throat of a sinkhole with rock and concrete and yet we were coming back months later having to do other fixes and repairs," said PennDOT Spokesperson, Greg Penny.

There's a reason why this traditional quick fix method doesn't work.

That's where Dan Woodderll comes into play;

"In this case the rocks were migrating down deeper and we'd put more rock in and they'd migrate," he explained.

Woodderll serves as the district Soils Manager.

"The geology is karst. It's limestone with a lot of voids and cracks in it where water can flow through," he said.

That underground water will find a way to run and erode no matter what.

And that sparked an idea.

It's simple really.

"We would put the slab across to bridge it," Woodderll said.

In theory, the plan is to let the underground water flow.

"A 17 inch concrete slab to bridge the area and it will act basically like an underground bridge," he added.

The underground support would be built under route 422.

Pioneering a solution that could one day keep the entire Midstate above ground.

A Geophysics test was used to determine the depth and stability of the soil below the roadway. Supports for the underground bridge will be installed on shallow areas of bedrock.

The cost of the project is $1.3 million dollars. PennDot savings will be used to fund it.

Construction is expected to begin late next summer.


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