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The Memorial Field Sinkhole Repair Job Hits One Surprise, But Sinkholes Here Are a Fact of Life

by on April 10, 2013 12:40 PM

Take a drive down Frazier St. and you'll see construction crews are now working to stabilize a massive sinkhole under the east bleachers of Memorial Field. Ed Poprik is Physical Plant Director for the State College School District. It's Poprik's job to oversee the work. And there's already been one surprise.

First, a little history.  Memorial Field hosts a variety of athletic events including football soccer, field hockey and lacrosse. According to a booklet compiled by Jo Hays and Margaret Riley, the field sits on a parcel that's just a hair shy of three and-a-half acres. It was built during the Great Depression as a Work Progress Administration project.

The school district bought the land in 1914 for roughly $3,000. Soon after, the school board complained because people were using it as a dump. The first football game was played at Memorial Field in 1937.

 

Now, back to the surprise. Poprik says the initial excavation work uncovered a lot more concrete underground than anybody expected to find. It probably was put there during earlier attempts to solve the sinkhole situation. Crews have already dug 20 feet into the ground in an attempt to locate the bottom of the sinkhole.

Sinkholes can be a costly problem, but not an unusual one in the State College area. One opened up on the Penn State campus this past winter, along Park Ave.

"Sinkholes develop in regions where the geological bedrock is limestone and Nittany Valley has plenty of this rock," says Penn State Professor of Geology Terry Engelder. According to Engelder the ridges around the Nittany valley are sandstone which doesn't dissolve easily. Water runs downhill and hits limestone which tends to dissolve relatively rapidly.  The limestone sitting directly below Tussey Ridge is the Coburn Limestone. A large network of caves has formed along Tussey Mountain from Shingletown Gap to Rock Springs."

"The caves host underground streams which tend to further dissolve the limestone so that natural features like Penn's Cave forms.  Penn's Cave is also in the Coburn Limestone and other limestones just under the Coburn. Eventually the caves grow so large with underground water flowing through then that they can no longer support the rock above them," Engelder said.

"Memorial Field is constructed on... limestone known as the Axemann which is older and thus found at some depth below the Coburn.  One of the best outcrops of the Axemann Limestone can be viewed behind the Hamilton Street Shopping Plaza where Firestone Tire  is located. Basically Memorial Field was built on an underground cave in the Axemann Limestone and this cave could eventually collapse."

According to Poprik, once workers have dug deep enough, they'll install pipes to drain away water from the site. They're also planning to build some temporary bleachers in the vicinity of the sinkhole, in time for fall sports.

The bleacher project will cost $2.3 million. A budget of $600,000 has been allocated to replace the turf.

Even when the sinkhole is filled, it may not be the only sinkhole to pop up in an unwelcome location.

"In central PA, most of the valleys are underlain by carbonate rocks - limestones and dolostones," Penn State professor Eric Kirby explains. "These rock types are composed primarily of minerals that are susceptible to dissolution in groundwater. Over many millennia, these rocks can slowly dissolve and form extensive subterranean networks of caves. When these caves grow large enough, the overlying rock can no longer support its own weight and a sinkhole develops."



Ben Jones covers Penn State football and basketball for StateCollege.com. He's on Twitter as @Ben_Jones88.
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