DUNMORE - Investigators from the state Department of Environmental Protection's Bureau of Abandoned Mine Reclamation on Monday determined a subsidence on Butler Street to be mine-related.
Despite that determination, the question of whether a broken water main or an abandoned mine caused the subsidence amounts to a "chicken and egg" scenario, according to Bernard Walko, planning unit engineering manager for the Bureau of Abandoned Mine Reclamation..
"We'll never know," he said, whether the subsidence caused the main break or the main break caused a liquefaction of soils resulting in the subsidence.
Either way, though, 20 feet of soil sat atop 5 feet of rock over an abandoned mine, the only place for that soil to go.
"All that we can say is that in the end result, that material had to go someplace, and the only place really for that material to go was the old workings that we know had to be in the area," Mr. Walko said.
Mr. Walko received a call at 10:30 p.m. Sunday to respond to the subsidence in the 500 block of Butler Street.
The relatively small surface hole along the curb at 510 Butler St. belies a greater danger: Mr. Walko said a 30-foot-wide void extends about 15 feet across the street underground at an average depth of 15 feet.
The residents of 510 and 511 Butler St. vacated their homes Sunday night, according to Mr. Walko.
Beneath the road separating the two properties lies the void that breached the Underwood Colliery's No. 2 Dunmore coalbed, a mine last operated in 1936, according to Robert Sorokas, a project manager for the federal Office of Surface Mining's anthracite branch in Wilkes-Barre.
Dunmore police closed the 500 block of Butler Street, which could remain closed for weeks depending on the severity of the subsidence.
A thin layer of pavement hung over the hole Monday and water continued to spray from a cracked 6-inch water main until the afternoon, with mist rising out and turning to frost on the street.
Susan Turcmanovich, a spokeswoman for Pennsylvania American Water, said the company shut off service to 510 and 511 Butler St. Monday afternoon.
Mr. Walko said it did not appear to him that the structures at 510 and 511 Butler St. were in any immediate danger, though stopping the flow of water into the subsidence was crucial in assuring that.
Dom Brominski, a spokesman for UGI Pennsylvania Natural Gas, said a gas line in the area was not affected by the subsidence and service continued uninterrupted. The company is "continually monitoring" the exposed line, he added, and a UGI crew was on scene Monday to close the exposed line's valve should that become necessary.
For Mr. Walko's office, the next step in the reclamation process will be a new one.
Prior to Oct. 1, the Office of Surface Mining handled emergency situations caused by mine-related subsidences, according to Michael Kuhns, supervisor general engineer for the Office of Surface Mining's anthracite branch.
The federal government now deems mine-related subsidences a state responsibility
The Office of Surface Mining provided technical assistance to the DEP in determining the cause of the Dunmoree subsidence, Mr. Kuhns said, but now with that first step out of the way the job belongs to the DEP.
"We're relatively new at this," Mr. Walko said. "Typically this is a project that would have been taken care of by the OSM emergency program ... Sometimes we can't act as quickly as OSM did but we're doing the best we can."
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