Three sinkholes have been discovered in the Centre Region in four days, the latest on Saratoga Drive in Ferguson Township.
It’s a rate that Todd Giddings, a hydrogeologist and owner of Todd Giddings Associates, said is not a cause for alarm.
“I think such occurrences get more notoriety and attention than they once did, and there have been years wetter with more sinkholes,” he said.
The first of the three sinkholes formed after a stormwater pipe collar separated and allowed water to erode the soil under Memorial Field, which will reopen Wednesday evening after having been closed since the discovery Thursday. It was 4 feet wide by 4 feet deep.
A sinkhole also formed on Bigler Road and was discovered Saturday on the Penn State campus. The Saratoga Drive sinkhole was discovered Sunday.
The cause of most sinkholes is excessive rainfall, particularly in short bursts.
“It’s usually the result of three necessary factors,” Giddings said. “Excessive precipitation is No. 1.”
Through Monday, July has thus far been the wettest in 120 years of record keeping, according to Penn State meteorology data, with 5.36 inches of rain. June was also particularly rainy, with 6.81 inches of rain having fallen, the 12th wettest June on record.
“So, we have had a lot of excess rain in quantity, and if it comes down so hard and intense it can drain away and cause ponding,” Giddings said. “That is the second element or factor. The deeper the ponding is, the more seepage pressure there is exerted on the soil.”
Giddings said the third factor is a float pathway.
“Normally, rainfall percolates through soil by first moving through the pore spaces in soil grains, and this moisture is held by capillary attraction, which is stronger than gravity,” he said. “If there is a pathway, man-made or natural, like something as simple as an old, decomposed root, the water will seep along that pathway. This creates a bigger opening as more water and soil debris go down it, and that can erode soil exponentially to cause a sinkhole.”
Giddings said the formation of sinkholes depends on the weather.
“If we had a six-, seven-, eight-year drought they’d be much less frequent and prevalent,” he said.
Ferguson Township Manager Mark Kunkle said in an email that the sinkhole on Saratoga Drive is 20 feet by 20 feet and 15 feet deep. The road will be closed between Gwenedd Lane and Bristol Avenue for the repairs, which are expected to be complete Tuesday.
Kunkle said there is a history of sinkholes on the roadway and along the adjacent stormwater basin.
“Access to properties along the closed sections of Saratoga Drive will be available via other local streets around the closures,” the release said.
The township has asked that drivers avoid Saratoga Drive until the repairs are completed.
The sinkhole on the Penn State campus has closed Bigler Road between McKean and Pollock roads until about Aug. 2 so that crews from the Office of Physical Plant can make repairs.