Introduction - Coal Waste Impoundments: Risks, Responses, and Alternatives - page 13

SIDEBAR 1.9 AUGUST 9, 1996: LONE MOUNTAIN
PROCESSING INCORPORATED, ST. CHARLES, VIRGINIA
On August 9, 1996, there was a breakthrough at Lone Mountain
Processing's Miller Cove slurry impoundment. The evening before the
failure, approximately 2.75 inches of rain had fallen, and most of it within
an hour and a half. Approximately 1 million gallons of black water were
released into Gin Creek through an abandoned mine. (Underground
mines had operated in areas adjacent to the impoundment from the 1920s
to the 1980s.)
Excavation of the breach showed that the leak occurred in an area
where available mine maps indicated a barrier of at least 25 feet of solid
coal between the outcrop and the underground mine workings. Further
exploration revealed that the barrier was in fact less than 2 feet thick. It is
believed that hydrostatic pressure from the slurry opened cracks in the
coal seam and began a piping-type failure. The thin coal barrier was
progressively eroded, allowing slurry to flow uncontrolled into the
abandoned mine.
SOURCE: Michalek et al., 1996.
SIDEBAR 1.10 OCTOBER 24, 1996: LONE MOUNTAIN
PROCESSING INCORPORATED, ST. CHARLES, VIRGINIA
On October 24, 1996, a second breakthrough occurred at Lone
Mountain Processing's Miller Cove impoundment, but in another area of
the abandoned mine. This release was more serious than the event in
August ( Sidebar 1.9 ) because the water contained more solids.
Approximately 6 million gallons of water and slurry exited the abandoned
mine into Gin Creek and flowed 11 miles, where it entered the Powell
River's North Fork. Reportedly, the river was discolored for more than 40
miles.
The failure resulted from two large sinkholes that had developed on
the northwestern end of the impoundment. When the site was excavated
to locate the breach, it was determined that the slurry had entered through
a fracture in the mine roof that coincided with these sinkholes.
SOURCE: Michalek et al., 1996.