State DEP Report Says Longwall Mining Caused Subsidence at Dam
Pittsburgh Post-Gazette
17 February 2010
By Don Hopey
A state Department of Environmental Protection investigation has
determined that Consol Energy's Bailey longwall mine in Greene County
caused ground subsidence in July 2005 that cracked the dam in Ryerson
Station State Park and made it unstable.
According to an interim DEP report released Tuesday, the longwall
mining activity was the only thing that could have accounted for the
movement of the dam and the damage that necessitated the draining of
62-acre Duke Lake.
The report excluded the possibilities that either the dam or the
hillside next to it was unstable prior to the mining, and found other
damage caused by longwall mine subsidence in the area of the dam,
including the buckling of a pipeline, and stream and road heaving.
"These findings were based on concrete information from Consol, the
Department of Conservation and Natural Resources, DEP files and months
of site observations," said Michael Terretti, DEP director of mining
operations. "The department stands behind its findings and will now
move into the second phase of its investigation, which is to address
the appropriate remedy."
Consol Energy will appeal the investigation finding to the state
Environmental Hearing Board, according to Joseph Cerenzia, a company
spokesman.
"We're disappointed in the action taken by the DEP and in its finding.
We still believe that the dam problem was not mining related," said Mr.
Cerenzia, who pointed out that the plan for mining near the dam was
approved by the DEP's mining office.
Longwall mining, like that done in the Bailey Mine, is a full
extraction deep mining technique that causes immediate surface
subsidence of up to 4 feet. The subsidence occurs directly above the
mine but also in a wider adjacent land surface. According to state
mining bureau records, the mine was operating outside the presumed
"angle of influence."
But the DEP's report noted that subsidence can also occur at greater
distances from the mine depending on the composition of the rock
overburden between the mine and the surface.
The DEP's investigation was started after the Allegheny County Court of
Common Pleas directed the DCNR to file a claim for damage to the dam
with the DEP. The DCNR had previously filed a claim against Consol in
February 2008 for compensatory damages in excess of $58 million.
According to the DCNR's lawsuit, the cost of replacing the dam built
across the Dunkard Fork of Wheeling Creek in 1960 is in excess of $30
million. In addition, restoring Duke Lake, the centerpiece of the park,
will cost more than $8 million, and the damage to the 1,164-acre park
is estimated at more than $20 million.
Prior to the damage to the dam and the draining of Duke Lake, the park
attracted approximately 160,000 visitors a year, according to the DCNR.