A sinkhole in a Marriottsville road has been covered for safety; officials say large sinkholes are limited to select areas of Carroll County.
When Julie Rosenthal came home to Stoneridge Court off Melstone Valley Way in Marriottsville on Monday evening, she could tell something was wrong. A 5-by-5-foot space around a sinking section of asphalt had been marked off with orange cones while she was at work, and it appeared someone had added asphalt to the depression.
By 6:30 that evening, the sinkhole opened back up.
"My husband came home … And went to walk the dogs and said, 'There's a hole in the ground!'" Rosenthal said. "That's when we took the video of it just pouring in. It obviously sank deeper than when they left it. You can't just leave asphalt on nothing."
In the video Rosenthal submitted to the Carroll CountyTimes, loose asphalt can be seen sliding into the hole at the center of a pooling depression of road, its ultimate depth unseen from the camera's point of view.
"It had to be 3 to 4 feet deep in the center, we could see into it," she said. "We were concerned because it was wider than the cones and we were afraid that somebody would drive into it and if they had driven into it, they couldn't get out of it."
Rosenthal called the Carroll County Sheriff's Office to report the sinkhole. A county road crew had placed a steel plate over the hole Tuesday.
Deputy director of Carroll County Public Works Jeff Topper said that while he was not personally aware of the sinkhole Rosenthal reported, the department does seek the public's help in identifying new sinkholes.
"We hope people report them to us when they find this sort of thing," he said. "We may have to cordon it off and get the crews out there and get it fixed and keep things safe for drivers."
Sinkholes take precedence over run-of-the-mill potholes when it comes to repair, according to Topper. Potholes may be annoying and even damaging to a vehicle, but sinkholes can be truly dangerous.
"Typically, a sinkhole will be of a much greater depth — you'll be able to look down in there and it will be black. It could be some feet deep," Topper said. "You are not sure at that point how big is the void under the asphalt. You certainly don't want to be driving over it."
While the sinkhole Rosenthal encountered could certainly have been dangerous for drivers, it is unlikely to widen into a nightmarish gaping maw, and that's because it's just not that type of sinkhole, according to Tom Devilbiss, deputy director of the Carroll County Department of Land Use, Planning and Development.
"There are different types of sinkholes and reasons for them forming," he said. "There are natural sinkholes that are related to the geology and the marble or limestone bedrock. There are also things that are basically the result of human activity."
Natural sinkholes are the kind that can grow large, but Devilbiss said that in Carroll, sinkholes are mostly limited to the valley stretching from southeast Westminster along Route 31 toward New Windsor, Union Bridge and Route 75. That valley sits on the geological formation called the Wakefield Marble, and Devilbiss said his department has logged and mapped more than 500 sinkholes formed by weakened portions of this bedrock.
Sinkholes found outside of the Wakefield Marble area are generally the result of some human activity that has created a void in the ground, according to Devilbiss, such as old wells or cisterns whose aged and buried wooden covers finally rot through, or where loose landfill and buried debris shift, rot and give way to the mass of the earth above them.
"Most of the [sinkholes] in the road … are associated with pipe failures," Devilbiss said. "We historically put in the ground corrugated metal pipes, and their life spans are limited to 30 to 40 years."
A pipe leak will then hollow the ground around the leaking pipe and create a void beneath the road surface, potentially dangerous for motorists but not a massive hole by any means.
"The reason you see those big ones in Baltimore City is that they don't have the bedrock, but what they have is sand and gravel. So when one of those pipes fails, it washes out a huge area under the ground," Devilbiss said. "That's a third type of sinkhole, basically."
Rosenthal's sinkhole might be something of a hybrid. When she first moved into her home 30 years ago, she said the development was initially laid out with gravel roads in the wrong positions.
"I am not surprised the road is sinking," she said. "This is our second sinkhole on this poor little road. We had another in the center of the court about two years ago."