GeoEngineers run tests on sinkhole in Harrison, Arkansas

HARRISON, Ark. - You might remember the sinkhole that opened up off Chelsea Circle in Harrison.

"Three collapses in the sinkhole. Each time they fill it it re-collapses, so we know we have a sizable cavity underneath the bedrock," said Principal GeoEngineer Gary Pendergrass.

The first time it opened was in April of 2017. The latest collapse was just a few months ago, and it took down a shed.

"This one has about a six or eight-foot drop. So it is a public safety hazard in that sense, and that's certainly why the city of Harrison wants to jump in and help get it fixed," Pendergrass said.

After seeing KY3 and KSPR's story about it opening up again, the GeoEngineers decided to come take a look for themselves.

"The geophysical methods we're using today will characterize the bedrock. It'll tell us how big the hole is, what the configuration is and that will help us decide how to seal it permanently," the principal GeoEngineer said.

Pendergrass said this type of testing takes all day. And then it could be a couple weeks before they give the results to the city.

The tests also give clues as to how the hole was created.

"Dry soil is pretty strong," Pendergrass said. "Wet soil is not so strong. You see a lot of these types of collapses after major rainfall events. It could be surface water since we're next to a creek that has wet the soil. It could be water coming up from underneath from the cave system."

For the GeoEngineers, this isn't their first rodeo.

"We worked on the big collapse at Top Of The Rock," he said. "The big one Nixa had a few years back. So at least this one's smaller and hopefully more manageable than those ones were."

The principal geological engineer said they've fixed dozens of these and have never had to go back and fix one again.