Plan is aimed at stopping Bradenville mine subsidence

July 07--George Piper, owner of Zeb's Towing in Bradenville, nearly lost one of his tow trucks last year when a sinkhole opened and swallowed its rear tires.

"The back end dropped in, and the right rear tires fell through," he said.

Piper was able to salvage the truck with the help of a Derry Township crew, but the memory of the sinkhole, likely caused by mine subsidence, is still fresh.

The hole on Westmoreland Street is now covered with a heavy metal plate -- a temporary fix. But the state Department of Environmental Protection hopes to make permanent repairs.

With $55.6 million in new funding from the federal government, the DEP's Bureau of Abandoned Mine Reclamation is proposing a mine subsidence control project designed to stabilize 140 homes in Bradenville.

Bureau personnel explained the large-scale project to residents at meetings in June and, so far, have right-of-entry consent from 95-100 homeowners.

"We still have time to get more homes signed up," said Dean Baker, environmental program manager for the bureau's office in Cambria County.

The project will consist of drilling four to six injection boreholes, each about four inches in diameter, around the homes and filling them with a cement-like grout material, Baker explained.

The method using flowable fill has been used with about 3,000 homes in Pennsylvania.

"It's something we've used over the years. We get very good coverage and a good success ratio," he said.

Workers will drill into the mine void below the houses in hopes of preventing future subsidence. Baker said there have been 17 "subsidence events" in Bradenville, a former coal town, in the past 20 years.

"We have had to stabilize a home here or there," he said. "There are some areas where homes have damage and cracks in the foundation. ... We also know that the strata above the mine is not strong enough to hold up the homes and stop subsidence. We confirmed that with the exploratory drilling."

The DEP collected core samples from the drilling in 2012 but got no further with the project.

Derry Township Supervisor Vincent DeCario said the township was informed in 2012 that the project would be put on a waiting list for when funding became available.

"I think it's a good thing," he said. "What this does is it gives people peace of mind."

The area under Bradenville was mined by the Latrobe-Connellsville Coal & Coke Co. until the early 1940s, Baker said. The Derry No. 1 Deep Mine accessed the Pittsburgh coal seam, extracting coal through the room-and-pillar method.

Mine subsidence occurs when the ground above an old or abandoned mine cavity collapses. Subsidence usually is not an issue with new mines.

Cracked foundations, collapsed walls and even homes sinking into the ground are all possible impacts of underground mine subsidence, which is not typically covered by homeowner's insurance policies .

"Underground mining has a long history in Pennsylvania, and historic mines can still cause subsidence today," DEP Secretary Patrick McDonnell said in May when the funding was announced.

The project design is expected to be completed by September, and bids are expected to be awarded in February 2019. Construction will take place during the 2019/2020 construction seasons and is expected to be completed by October 2020.

Funding for the project is coming from the 2018 Abandoned Mine Land Grant Fund, which is supported by the mining industry via a fee on coal mined across the country.

Stephen Huba is a Tribune-Review staff writer. Reach him at 724-850-1280, [email protected] or via Twitter @shuba_trib.

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