PALMER TWP., Pa. -- Work is underway to fill a 50-foot-deep sinkhole in Palmer Township. It was supposed to be done Friday, but PennDOT says inclement weather pushed that date back to early next week. The same area on Main Street has seen sinkholes before.
Geology experts say some of these have natural causes and others are prompted by human activity.
What causes a sinkhole? Penn State Professor Sanjay Srinivasan studies just that.
"You're talking about carbonate or limestone geology, which when contacted by fresh water or groundwater, it starts, it triggers some dissolution mechanism and can lead to these kinds of cave formation," said Sanjay Srinivasan, an energy and mineral engineering professor and the director at the EMS Energy Institute at Penn State.
Pressure on those rock formations lead them to collapse. That process can be accelerated by several things. Some are natural, like excessive rainfall and erosion, and others are manmade, like "when you are pumping a lot of water from the groundwater," said Srinivasan.
Palmer Township is seemingly prone to sinkholes. Two of them opened on Main Street within weeks.
Some question whether all of that warehouse development is playing a role.
"I would be a little bit skeptical about that," said Srinivasan.
Srinivasan says there are lots of rules, including those from the PA DEP, that builders have to follow, though he acknowledges things do happen, and open sinkholes can expand.
"If there are heavy vehicles passing in the road, that adds to the load, and that can cause, you know, that can trigger increased activity," said Srinivasan.
The thought makes some uneasy as they drive by.
PennDOT tells us its geotech unit has investigated the area and found no indication of cracks or subsidence that could be hazardous to motorists. A spokesperson adds the agency is following all of its regulations.
"I think that every one of these incidents needs to be investigated," said Srinivasan.
The goal there is to see if anything can be done to prevent more from opening up.
"There are new advancements and monitoring technologies," said Srinivasan. "There's a network that has been commissioned by Penn State, for example, to monitor seismic activities across the state."
As of Friday, the hole itself was filled up. Crews are aiming to reopen all lanes of traffic on Monday or Tuesday.
