Geology Reference
In-Depth Information
SIDEBAR 1.5 DECEMBER 18, 1981: EASTOVER MINING
COMPANY, HARLAN COUNTY, KENTUCKY
On December 18, 1981, Eastover Mining Company's Hollow No. 3
combined refuse disposal site failed, releasing about 25 million gallons of
saturated coal refuse. The operation had been permitted to dispose of
layers of coarse coal refuse and dewatered slurry "filter cake," which
contained approximately 30 percent moisture, behind an embankment
(see discussion of disposal techniques in Chapter 7 ) and, at a height of
192 feet, had reached 90 percent of its planned capacity. Several factors
contributed to the increased pore water pressure in the dewatered fine
refuse zone, including: (1) the filter cake layers had not been allowed
sufficient time to dry before additional material was added; (2) layers of
filter cake were not completely covered with coarse coal refuse; (3) a
stream flowed into the impounded material, increasing saturation; and (4)
material used in construction of the embankment did not allow water to
seep out. The failure released a mudflow approximately 5 feet deep that
traveled 4,400 feet downstream (500 feet in vertical distance) into the
community of Ages, Kentucky. One resident was killed, three houses were
destroyed, and 30 homes were damaged.
SOURCE: Cannon, 1981.
SIDEBAR 1.6 APRIL 8, 1987: PEABODY COAL COMPANY,
RALEIGH COUNTY, WEST VIRGINIA
On April 8, 1987, a breach developed in the principal spillway pipe in
the Lower Big Branch impoundment at Peabody's Montcoal No. 7
complex in Raleigh County, West Virginia. The 36-inch-diameter pipe ran
through the impoundment and under part of the embankment at a depth of
55 feet. The rupture released nearly 23 million gallons of water, slurry,
and fine coal refuse.
The exact cause of the accident was not identified but was probably a
combination of factors: (1) Heavy snowfall (16 inches of snow with a
rainfall equivalent of 1.9 inches), followed by rapid temperature increases
and snowmelt, sent excessive amounts of water through the pipe. (2) Two
landslides occurred in the slope above the rupture. Although the relative
timing of the landslides and the breach is not known, the slides could have
caused the pipe to collapse or separate. (3) Erosion of particles near the
pipe connections could have reduced the bearing strength of the pipe. (4)
The strength of an "elbow" in the piping may have been exceeded by
massive and rapid fluid flow. In addition, a sinkhole that developed from
the rupture threatened the stability of the embankment. The sinkhole
came within 100 feet of several upstream-constructed additions to the
cross-valley embankment before stability was maintained through
mitigation of the breach.
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