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1
Introduction
On October 11, 2000, near Inez, Kentucky, a breakthrough occurred in
which a 72-acre surface impoundment of waste materials from coal process-
ing at Martin County Coal Corporation released approximately 250 million
gallons of slurry into a nearby underground coal mine. The slurry flowed
through the mine, into nearby creeks and rivers, flooding stream banks to a
depth of 5 feet. The spill caused no loss of human life. However, environ-
mental damage was significant, and local water supplies, taken from the
rivers, were disrupted for days. This report develops numerous suggestions
and recommendations to reduce the potential for similar accidents in the
future. In this chapter, we review the processes that lead to the generation of
coal waste and the impoundments used to store it, and then we turn to a
description of accidents and incidents involving coal waste facilities. Finally,
we review the tasks and activities of this committee.
COAL PRODUCTION AND USE IN THE UNITED STATES
Coal is the largest single source of fuel for domestic energy production.
In the United States, 90 percent of the coal produced is used in power plants
(Freme and Hong, 2000~. Coal accounts for about 33 percent of the total
energy production (Chircop, 1999~. In 2000, coal accounted for 51.4 percent
of electric power generation (Freme, 2001~. Industries and manufacturing
plants also use coal directly, especially those that produce chemicals, cement,
paper, ceramics, and various metal products. On average, about 20 pounds of
coal are utilized per day per capita in the United States (Chircop, 1999~.
The United States has approximately 26 percent of the world's coal
reserves (BP Global, 2001) (Table 1.1~. More than 400 coalfields and small
deposits underlie a total of 458,600 square miles in 38 states, nearly evenly
1,
7
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18
TABLE 1.1 Major World Coal Reserves, 2000
Country
Reserves in Percentage
million short tons of world total
United States
246,643
Former USSR 230,178
China 114,500 11.6
India 74,733 7.6
South Africa 55,333 5.6
Australia 90,400 9.2
Germany 67,000 6.8
Poland 14,309 1.5
Canada 8,623 0.9
Indonesia 5,220 0.5
United Kingdom 1,500 0.2
Mexico 1,211 0.1
Others 74,561 7.6
SOURCE: Data extracted from BP Global, 2001.
COAL WASTEIMPOUNDMENTS
split between the Eastern and Western regions (Chircop, 1999~. Although
some 300 different coal beds are mined each year, almost 47 percent of total
production comes from just 10 of the largest deposits.
Important coal deposits east of the Mississippi, are found in 10 states
(Alabama, Illinois, Indiana, Kentucky, Maryland, Ohio, Pennsylvania,
Tennessee, Virginia, and West Virginia). In the West, the Wyodak coal bed,
the nation's leading source of coal, underlies part of the Powder River Basin
of Wyoming and Montana. Other active Western coal reserves are found in
Colorado, Utah, New Mexico, Arizona, and Alaska (Chircop, 1999~. ~ the
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INTRODUCTION
19
interior states, coal occurs in several separate basins Tom Michigan to
Texas. According to data Tom the U.S. Energy Information Administration,
coal beds throughout the United States produced 1.08 billion tons of coal in
2000, the 12th consecutive year in which 900 million tons or more were
mined. In recent years, U.S. coal production has exhibited the following
trends:
Western mines account for an increasing share of total production
(Figure 1.1~.
Fewer coal mines are operating, but those mines are larger.
Surface mines produce all increased proportion of coal overall.
· Longwall mining produces an increased Faction of coal mined
underground.
1 ,200
1 ,000
~ 800
o
s 600
c 400
200
o
US
Appalachian
Western
Interior
1990 1992 1994 1996 1998 2000
FIGURE l.l Coal production by region, 1989-2000. From Energy Information Admini-
stration, 2001.
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20
COAL WASTEIMPOUNDMENTS
ADVANCED COAL CLEANING
Increased mechanization in the underground coal mining industry has
decreased selectivity and increased the volume of refuse. Equipment, such as
continuous miners or longwall shearers, often takes roof and floor rock in
addition to in-seam partings (Sidebar 1.1~. Equipment currently used to mine
and transport coal produces more fine coal particles than did earlier
equipment. Rotating cutter heads, feeder-breakers, and transfer points in
SIDEBAR 1.1 Underground Coal Mining Methods in the United States
About 39 percent of coal produced in the' United States comes from
underground mines (Chircop, 1999~. Underground coal is mined by the following
methods: conventional, longwall, continuous, and shortwall. Longwall and
continuous mining are used effectively in combination (Chircop, 1999~.
Conventional mining processes include drilling and blasting the coal.
This method, one of the oldest mining methods, can be effective in certain
geologic areas. Today, it is used for only 5 percent of underground coal
mining (Chircop, 1999~.
More than 45 percent of underground coal is mined by longwall mining
(Chircop, 1999~. This method is gaining in popularity because it can improve
coal recovery to 80 percent, and it enhances miners' safety (Peterson et al.,
2001~. Production rates depend on the width of the block, the thickness of the
coal seam, and the technology used to transport the raw coal out of the mine.
Rotating drums, steel plows, or mounted shearers traverse back and forth
across the block width and excavate blocks 600 to 1,200 feet wide and 5,000
to 7,500 feet long (Chircop, 1999; Peterson et al., 2001~. Longwall length
capabilities have been steadily increasing: some Western operations now
achieve lengths of over 10,000 feet (e.g., Twentymile in Colorado and
SUFCO in Utah). The miners and mining equipment are protected by moving
hydraulic roof supports called shields (Chircop, 1999~. After an area has been
mined, the roof collapses.
Continuous mining is a mechanized method utilizing mechanical cutting
machinery. Although longwall mining has moved to the forefront (Chircop,
1999; NRC, 2001), continuous mining is still important in coal production.
Continuous mining equipment is used to develop the areas for longwall
mining. The continuous mining method uses a room-and-pillar system,
whereby mined-out "rooms" are supported by coal "pillars." An operator, who
maintains visual contact with the machine, can control this machinery
remotely, thereby increasing miners' safety.
Shortwall mining refers to mining with a continuous mining machine,
moving roof supports, and excavating blocks 150 to 200 feet wide and more
than one half mile long (Chircop, 1999~. This method is currently not used to
any appreciable extent.
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INTRODUCTION
21
conveyor belt systems all break up the coal, producing quantities of fine coal
particles whose recovery requires special processing and cleaning
techniques.
The characteristics of the in-situ coal (e.g., ash and sulfur content) vary
spatially. The product that emerges from a mine often includes, not only
randomly distributed impurities and the non-coal material known as partings
(see Sidebar 1.2 for a description of the processes that deposit coal and
create the impunties), but also material Tom the roof and floor layers. Thus,
the characteristics of mined coal vary considerably.
End-use plants are engineered for optimal combustion to burn feedstock
of a particular ash, sulfur, and energy content requirements rarely met by
the n~n-of-mine coal or by coal from a single source (Figure 1.2~. These
combustion requirements have been the impetus for all upstream process
changes, including the search for coal of low sulfur content, improved coarse
and fine coal cleaning processes, in addition to several disposal and
environmental laws.
SIDEBAR 1.2 Coal Geology
Coal is a combustible material consisting of organic matter and minor
amounts of inorganic materials. It is derived from a heterogeneous mixture of
plant remains and associated minerals, which have undergone chemical and
physical changes by geological and biological processes without free access
to air. Coal has a highly variable composition, affecting both its chemical and
physical properties. Except for the anthracite region in eastern Pennsylvania,
coal beds usually occur as nearly horizontal or gently folded strata. A coal
seam is a composite of several layers, each of which may consist of a
different mixture of coal material and mineral matter. Occasionally, these
layers may be completely inorganic, such as shale, or high in mineral matter.
Such layers are referred to respectively as partings and bony coal. Coal and
associated rocks may contain significant amounts of sulfur, arsenic, and other
materials whose presence in the waste engenders environmental concems.
The depositional environments that produced the coalfields of the
Eastem United States were predominantly coastal-deltaic. Large volumes of
sediment were deposited from the Appalachian Mountains into rivers, which
emptied into bays and coastal seaways. These conditions engendered the
development of vast, laterally extensive peat swamps along the coastlines
and delta platforms. Periodically, sea level rose and shallow marine environ-
ments flooded the swamps, depositing marine shales and limestones. The
cyclic repetition of these sedimentary environments has resulted in some of
the most complex stratigraphic sequences in the geologic record.
SOURCE: Rice et al., 1979.
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22
COAL WASTEIMPOUNDMENTS
Resources
Coal type
Anthracite
Bituminous
Subbituminous
Lignite
Coal
characteristics
Sulfur
Ash
Moisture
Heat content
Minerals
Coking index
%~%
Mining
Underground
Conventional
Continuous
Longwall
Surface
Open-pit
Area
Contour
Auger
Mountaintop
Preparation
Crushing
Screening
Conventional cleaning
Deep cleaning
Blending
Transportation
Train
Regular freight
Unit train
Barge
Truck
Conveyor belt
Slurry lines
End Use
Customer
Utilities
Metallurgical plants
Industry
Residential/commercial
Environmental
Issues
Air
Water
Land
Waste/residuals
Wildlife
Aesthetics
Economy
On-site
Off-site
FIGURE 1.2 Coal system components. Dotted arrows indicate important feedback to
mining feasibility. Modified Tom Office of Technology Assessment, 1979.
Limitations on sulfur dioxide (SO2) emissions from coal-fired power
plants have also contributed to the need for advanced coal-cleaning tech-
nology. Power plants require coal of consistent quality (e.g., sulfur, ash, and
heat content) to comply with these regulations. In an effort to produce coals
that allow power plant operators to comply win standards established by the
Clean Air Act, various methods of removing pyrite (FeS2) from the coal
have been developed. In the past, much of this material would have entered
the combustion chamber with the coal and would have resulted in additional
ash. Now, the pyrite is removed, but it adds to the waste the preparation
plant generates.
Finally' the quality of coal being mined in the Eastem United States has
declined as higher quality reserves have been depleted. Therefore, tech-
niques have been implemented to upgrade the coal product quality.
Previously, coal was cleaned by dry methods; however, a combination
of factors, such as particle size, dust, transport, health, safety, and noise, and
the better performance of wet processes have contributed to the near
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INTRODUCTION
23
abandonment of dry coal cleaning processes in recent years. The increased
use of water to control dust in underground mines, and the increased
efficiency of wet cleaning methods have continued the sharp decline in dry
coal cleaning methods.
Coal preparation (colloquially referred to as "washing") separates non-
combustible materials from coal. Processing the run-of-mine coal may
include: removing extraneous materials, crushing, sizing, blending coal from
several locations, and concentration. A coal preparation plant separates the
material it receives into a product stream and a reject stream, which may be
further divided into coarse and fine refuse streams. Depending on the source,
20 to 50 percent of the material delivered to a coal preparation plant may be
rejected (Leonard, 1991~. One of the reject streams is slurry, a blend of
water, coal fines, silt, sand, and clay particles, which is most commonly
disposed of in an impoundment.
COAL REFUSE IMPOUNDMENTS IN THE UNITED STATES
Coal refuse disposal impoundments are constructed for the permanent
disposal of any coal, rock, and related material removed from a coal mine in
the process of mining. Standard classification of coal slurry impoundments
includes the following:
· Active In operation and receiving slurry.
· Inactive—Not in operation or receiving slurry. Inactive impound-
ments may receive slurry in the future, becoming active again, and
therefore have not been closed permanently.
Abandoned Not in operation and closed. These impoundments
usually have been filled to capacity and have been closed and
reclaimed.
Grandfathered or "Pre-law"—Not in operation since promulgation
of the 1977 Surface Mining Control and Reclamation Act (SMCRA)
regulation. These impoundments are reclaimed under the Abandoned
Mine Lands Program.
As of August 2001, MSHA oversees 713 active fresh-water and slurry
impoundments in the United States (T. Bentley, Mine Safety and Health
Administration, personal communication, 2001~. Most coal waste impound-
ments in the United States are found in the East, predominantly in West
Virginia, Pennsylvania, Kentucky, and Virginia. The thicker Western coal
seams being mined now contain fewer in-seam partings and out-of-seam
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24
COAL WASTEIMPOUNDMENTS
rock, and most of that coal is shipped raw without extensive processing.
Consequently, coal waste impoundments are rarely used in the West. In the
Eastem coalfields, however, the majority of the coal from underground
mines is processed before sale. Of the 1.1 billion tons of coal mined in the
United States per year, about 600-650 million tons are processed to varying
degrees. Typically 350-400 million tons are handled in wet-processing
systems that, on average, produce 70-90 million tons of fine refuse in a
slurry. (C. Raleigh, CQ Inc., personal communication, 2001~. Much of that
material is stored in coal waste impoundments.
Disposal methods for coarse and fine coal refuse developed along
separate lines. Even before the days of modern coal preparation plants,
laborers picked rock from the run-of-mine coal and discarded it in refuse
piles. Sometimes coarse refuse was resumed to the mine, but more
commonly it was deposited on the surface.
When fine coal cleaning came into widespread use, it became necessary
to deal with the refuse. One way is to pump the slurry into an impoundment
and allow the particles to settle. Another is to concentrate or dewater the
slurry and/or to mix it with coarse refuse or other additives (e.g., lime, sodium
silicate, elastomeric polymers, resinous adhesives) to provide stability
(Osborne, 1988), and then dispose of it in a landfill or impoundment.
DISPOSAL OF FINE REFUSE IN IMPOUNDMENTS
To impound fine coal slurry, embankments are constructed with
compacted coarse coal refuse material. Prior to an accident in 1972, the
Buffalo Creek disaster (Sidebar 1.3), little consideration was given to control
of water entering an impoundment from a preparation plant or as runoff
from the watershed above. Indeed, the coarse coal refuse used for
embankment construction provides a filter to limit impacts to the quality of
the water entering nearby streams (D'Appolonia Consulting Engineers,
1975~. In most impoundments, the embankment is constructed of coarse coal
refuse, according to a design that is approved by regulatory authorities (see
Chapter 2~.
In the mountainous Appalachian region, the coarse refuse embankments
are usually constructed across a valley, enclosing a basin that holds the coal
refuse. In flatter Midwestern terrain, beamed and incised impoundments may
be constructed. They typically have a larger surface area and are shallower.
The slurry is pumped into the impoundment, where the fine particles in the
slurry settle by gravity beneath a pool of clear water. In many impoundments,
this clear water is pumped back to the coal processing plant and is reused.
,_
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INTRODUCTION
SIDEBAR 1.3 February 26,1972: Buffalo Mining Company,
Buffalo Creek, West Virginia
On February 26, 1972, the most destructive flood in West Virginia's
history occurred when a coal waste impounding structure collapsed on the
Buffalo Creek tributary of Middle Fork. Shortly before 8:00 a.m., the
impounding structure collapsed, releasing approximately 132 million gallons
of water. The water passed through two more piles of coal waste blocking the
Middle Fork. At that time, there were no federal standards requiring either
impoundments or hazardous refuse piles to be constructed and maintained in
an approved manner.
Around 1957, as part of its surface mining operations, the Buffalo Mining
Company (a subsidiary of the PiKston Coal Company) had begun depositing
mine waste consisting of rock and coal in Middle Fork. Buffalo Mining
constructed its first impounding structure, near the mouth of Middle Fork in
1960. Six years later, it added a second impounding structure, 600 feet
upstream. By 1968, the company was depositing more waste another 600
feet upstream. By 1972, the height of this third impounding structure ranged
from 45 to 60 feet.
Between February 24 and 26, 1972, the National Weather Service
measured 3.7 inches of rain in the area of Logan County and Buffalo Creek.
The impounding structure probably failed because foundation deficiencies led
to sliding and slumping of the front face of the refuse bank. The waterlogged
refuse bank accelerated the failure. The slumping lowered the top of the
refuse bank and allowed the impounded water to breach and then rapidly
erode the crest of the bank. Upon failure of the refuse bank, the floodwater
moved into pockets of burning coal waste.
As result of the flood, 125 people were killed, 1,100 were injured, and
more than 4,000 were left homeless. In addition, the flood completely
demolished 1,000 cars and trucks, 502 houses, and 44 mobile homes, and
damaged 943 houses and mobile homes to varying extents. Property damage
was estimated at $50 million.
SOURCE: W. E. Davies et al., 1972
FINES DISPOSAL PROBLEMS IN OTHER MINING SECTORS
The problem of slurry disposal is not unique to the coal industry; it is a
consideration for many base and precious metals industries, as well. For
example, in the aluminum industry, disposal of massive quantities of bauxite
tailings (called red mud) creates similar problems (Wagh and Desai, 1987~.
Disposing of the red mud in settling ponds in dilute, fine mud-sar~d slurries
of about 20 percent solids (Downs and Stocks, 1977) brings with it a number
of problems including very slow settling time and low bearing strength. The
25
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26
COAL WASTE IMPOUNDMENTS
search for alternative disposal technologies (e.g., thickened t60 percent
solids] high-density residue stacking), as well as for processing and
utilization of the red mud, have been underway for some time (Wagh and
Desai, 1987~.
The disposal of the tremendous volume of waste sand and clay in the
beneficiation process of phosphate mining is another example of these
problems. The clay is pumped to a settling area in a dilute stream (3 percent
solids) or sent to a Sickener to increase the solids content (15 percent solids)
(Garlanger arid Fuleihan, 1983~. Fine sediment disposal also is a problem in
base metal mining and smelting operations.
COAL WASTE IMPOUNDMENT FAILURES
Coal waste facilities have been involved in several accidents or
incidents since 1972. She incidents reviewed here demonstrate Me range of
the types of failures that can affect coal waste impoundments and of impacts
of such failures. They are not a complete list of incidents. The first event
was the Buffalo Creek accident (Sidebar 1.3), the most serious because it
resulted in the loss of 125 lives and extensive damage to property down-
s~eam of Me refuse piles and impoundments. Following that accident,
regulations were promulgated to govern the design of the embankment
structures used in figure impoun~nents. Since ~en, no engineered embar~k-
ments have failed, although other incidents and accidents have occulted.
Sidebars 1.4 to 1.12 describe selected events.
SIDEBAR 1.4 August 14, 1977: Island Creek Coal Company,
Boone County, West Virginia
An embankment under construction failed at Island Creek Coal
Company's impoundment in Boone County, West Virginia, on August 14,
1977. Heavy rainfall overflowed a temporary diversion ditch, causing the
water level in the impoundment to rise. Because the embankment was still
under construction, storage capacity had not yet reached the required
minimum, and the sudden influx of additional water overtopped the
embankment. Meanwhile, the water eroded the embankment, reducing its
height 23 feet during a two-day period. During this time, 6.8 acre-feet of
material was released, which clogged a drainage pipe downstream.
SOURCE: Owens, 1977.
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INTRODUCTION
27
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 embank-
ment before stability was maintained through mitigation of the breach.
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28
COAL WASTEIMPOUNDMENTS
The impoundment, upstream from several communities, was rated at the
time as high hazard. A 50-mile stretch of Coal River from Montcoal to its
mouth at St. Albans was visibly affected, and five water plants were shut
down. Although 1,700 customers' water supply was disrupted in the Racine
Public Service District, no human injuries or fatalities occurred as a- result of
this incident.
SOURCE: Owens, 1987.
SIDEBAR 1.7 January 28, 1994: Consolidation Coal Company,
Morgantown, West Virginia
On January 28, 1994, a 5-foot earthen berm failed at a slurry refuse
impoundment at the Arkwright Mine in Granville, West Virginia. Heavy rain
and melting snow resulted in 30 inches of water collecting behind the berm; it
was determined that the 4-inch discharge pipe and rock underdrain at the site
were insufficient to prevent water accumulation. The incident released
375,000 gallons of water into the town of Granville. Although no one was
injured, three residences directly downstream were damaged.
SOURCE: Betoney, 1994.
SIDEBAR 1.8 May 22, 1994: Martin County Coal Corporation,
Davella, Kentucky
On May 22, 1994, a breakthrough occurred at Martin County Coal
Corporation's Big Hollow slurry impoundment in Davella, Kentucky. Nearly 32
million gallons of black water inundated an abandoned and sealed-off portion
of the mine. The breakthrough resulted either from collapse or water
penetration of the Coalburg coal seam bordering the impoundment. Slurry
had been impounded 32 feet higher than the coal seam's elevation. The
mine's 16-inch concrete-block seals held the black water inundating the mine,
but water broke through portal seals and a coal seam outcrop barrier.
Although the slurry level dropped by 6 feet, the embankment structure was
not damaged, and no injuries or fatalities occurred.
SOURCE: Stewart and Robinson, 1994.
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INTRODUCTION
29
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 1 920s to the 1 980s.)
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.
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30
COAL WASTEIMPOUNDMENTS
SIDEBAR 1.11 November 26, 1996: Consolidation Coal Company,
Oakwood, Virginia
On November 26, 1996, the Buchanan No.1 impoundment in Buchanan
County, Virginia, failed. In the 1 960s, the Kennedy coal seam at the site had been
excavated by both surface area mining and underground auger mining. After the
impoundment was constructed (1984), another company mining underground in
the adjacent drainage area apparently intersected the historic auger mine
workings, providing a conduit for the slurry.
Coal refuse and slurry from the impoundment broke into an abandoned
underground mine and discharged about 1,000 gallons per minute at its peak
through two mine portals into the adjacent North Branch Hollow of the Levisa
Fork of the Big Sandy River. There was no detrimental impact on the
embankment, and no one was killed or injured.
SOURCE: Michalek et al., 1996.
SIDEBAR 1.12 October 11, 2000: Martin County Coal Corporation,
Inez, Kentucky
On October 11, 2000, a coal waste impoundment of the Martin County
Coal's preparation plant near Inez, Kentucky, released slurry containing an
estimated 250 million gallons of water and 31 million gallons of coal waste into
local streams. Reportedly, the failure was caused by the collapse of the slurry
pond into underground coal mine workings next to the impoundment. The slurry
broke through an underground mine seal and discharged from mine entrances 2
miles apart into two different watersheds (wolf Creek and Coldwater Fork).
Although no human life was lost, the release killed aquatic life along the Tug
Fork of the Big Sandy River and its tributaries. Public water supplies were
disrupted when communities along the rivers in both Kentucky and West Virginia
shut down water plants to prevent contamination with black water. Anencan
Electric Power had to close its massive generating plant, and numerous
properties and residences were damaged.
SOURCE: Vanous issues of the Herald Leader, the CounerMoumal, and the
Charleston Gazette (2000, 2001~; Dennis Hatfield, Martin County Coal
Corporation, personal communication, 2001.
Two of the events resulted from leaks or failures of drainage pipes.
However, the majority of the incidents involved failures in the basin area.
Inaccurate mine maps and inadequate characterization of the basin area most
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INTRODUCTION
31
likely contributed to at least some of these incidents. This report deals with
both of these issues in detail (Chapters 4 and 5~.
IMPOUNDMENT HAZARD RANKING SYSTEMS
MSHA bases its hazard potential rating system on the height of the
embankment, the volume of material impounded, and the downstream
effects of an impoundment failure (MSHA, 1974, 1983~. The resulting three
classifications are:
Low Hazard Po ten tint Facilities in rural areas where failure would
cause only slight damage, such as to farm buildings, forest,
agricultural land, or minor roads.
Moderate Hazard Potential Facilities in predominately rural areas
where failure may damage isolated homes or minor railroads,
disrupting services or important facilities.
· High Hazardt Potential Facilities whose failure could reasonably
be expected to cause loss of human life, serious damage to houses,
industrial and commercial buildings, important utilities, highways,
and railroads.
The MSHA guidelines indicate that design criteria become more
conservative as the hazard potential increases. For example, design criteria
for the maximum precipitation (flood) event increase as the hazard
classification moves from low to high. Thus, storm design criteria for a long-
term high-hazard-potential impoundment require that the impoundment be
designed to contain the probable maximum precipitation that is reasonable
for the region (MSHA 1974, 1983~. In addition, piezometers are generally
required to monitor and verify the water saturation conditions within the
embankment for moderate and high hazard sites.
MSHA guidelines further state that the stability of an embankment
should normally have minimum static and seismic factors of safety of at
least 1.5 and 1.2, respectively, under maximum anticipated phreatic condi-
tions. The guidelines require extra attention to seismic events for high
hazard impoundments in certain regions (MSHA, 1974, 1983~.
On December 1, 1997, after two unintentional releases of slurry in
Virginia in a two-month period, MSHA introduced a second classification
system that addresses the potential for the unintentional release of water or
slurry from impoundments into active or abandoned mines (Sidebars 1.9 and
1.10~. This classification system allows the coal mine operator to evaluate
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COAL WASTEIMPOUNDMENTS
the proximity of underground workings; to determine whether the recom-
mendations of Bureau of Mines Information Circular 8741 (Babcock and
Hooker, 1977), which provides guidelines for mining under bodies of water,
are met; and to assess the potential impact if a breakthrough were to occur.
For example, the impact may threaten the safety of miners or the safety of
the general public (MSHA, 1997~. A priority rating is assigned to each
impoundment based on its breakthrough potential- whether low, medium,
or high and a potential impact of a breakthrough. The purpose of this
classification system is to evaluate whether the impoundment plan
adequately addresses the breakthrough potential (MSHA, 1997~. These
ranking systems are based on the proximity of the basin to underground
workings as well as the potential downstream impacts were a basin to fail.
However, they do not assess the probability of failure. It is a completely
separate ranking than that which is done for the embankment structure.
In addition, the Federal Emergency Management Agency ranks embank-
ments based on potential impacts should a failure occur (U.S. Bureau of
Reclamation, 1988~. This inventory lists more than 76,000 dams. The Office
of Surface Mines (OSM) and the state delegate programs use a similar
system to rank earth dams and reservoirs by whether they are located in rural
areas and the amount of damage failure could cause (U.S. Department of
Agriculture, 1976~. Neither of these organizations has a ranking system for
breakthrough potential.
STUDY AND REPORT
Concern about the potential for accidents like the one at Inez, Kentucky
(October 2000), motivated Congress to direct MSHA to commission an
independent study of current coal waste disposal methods and an exploration
of alternatives for future disposal of coal waste. In addition, Congress
directed that the study examine engineering standards for coal waste
impoundments, and recommend ways to improve the stabilization of
impoundment structures.
The National Research Council (NRC) established the Committee on
Coal Waste Impoundments to undertake this study. The committee consists
of 14 experts from academia, industry, and state government with expertise
in coal mining, geology, geophysics, geochemistry, hydrology, mining
regulations, environmental law, mining health and safety, land-use planning,
and geotechnical and geological engineering. Brief biographies of the
committee members appear in Appendix A.
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INTRODUCTION
The overall objectives of this study are:
.
33
to examine engineering standards for coal waste impoundments;
· to provide recommendations for improving impoundment structure
stabilization;
to determine the adequacy of mine maps; and
to evaluate potential alternatives for future coal waste disposal,
including the benefits of each alternative.
The Statement of Task lists the following specific tasks:
Engineering Standards/Barrier Stability/Monitoring
Examine current engineering practices for coal waste impound-
ments and provide recommendations for improving engineering
practices, including impoundment structure stabilization.
What alternative means are available to evaluate or confirm the
safety of the designed barriers protecting slurry impoundments?
What options can be developed to effectively monitor the status of
coal barriers left to protect slurry impoundments?
Site Characterization
Evaluate the adequacy of mine maps and explore ways to improve
mapping and surveying practices in general for the mining industry.
What is the best way to three-dimensionally conceptualize and
delineate the impoundment area, including the extent of under-
ground mine works beneath or adjacent to the slurry disposal area?
Alternative Technologies
Evaluate potential alternatives for future coal waste disposal, in-
cluding the benefits of each alternative.
Are there other methods to wash and process coal that would reduce
the amount of slurry disposal needed?
What are the options for the coal waste product to be refined further
in order to produce a marketable product?
To address the charge, the committee gathered, synthesized, and
analyzed information by working in subgroups based on the three main
topics in the Statement of Task (geotechnical aspects, site characterization,
and alternative technologies). The committee held eight information-
gathenng meetings, including six subgroup meetings, between March and
June 2001. The meetings included presentations by, and discussions with the
sponsor, personnel from other government programs, and representatives of
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34
COAL WASTEIMPOUNDMENTS
industry, academia, environmental organizations, labor organizations, and
citizens' groups (Appendix B). To obtain input from the public, the com-
mittee held eight town meetings throughout the Eastern coal-mining region.
Finally, the full committee met twice in closed session for discussion and
writing. As background material, the committee reviewed relevant govem-
ment documents and materials, pertinent NRC reports, and other technical
reports and literature published through July 2001.
This report is intended for multiple audiences. It contains advice for
MSHA, OSM, other federal agencies, and state regulatory agencies, as well
as policy makers, the coal industry and its consultants, scientists, and
engineers. Chapter 2 gives an overview of the regulatory framework for coal
waste impoundments. Chapter 3 examines issues related to the engineering
design for coal refuse facilities. Chapter 4 discusses site characterization,
including mine mapping, map storage and preservation, and surveying.
Chapter 5 addresses techniques, such as geophysical methods, to locate
abandoned mines and other voids, and hydraulic testing to establish the
thickness of barrier pillars. Chapter 6 discusses ways to limit potential
failure modes for the embankment and basin area. Chapter 7 addresses
alternatives to slurry impoundments, including alternative mining and coal
preparation methods, direct utilization of slurry, and alternative disposal
techniques. Chapter 8 summarizes the committee's conclusions and recom-
mendations. Technical terms are defined in the glossary (Appendix C).
It is important to recognize that this charge specifically directs the
committee to focus its analysis on the engineering and characterization of
coal waste impoundments. The committee was not asked to consider other
factors related to potential impacts of disposing of coal wastes in an
impoundment, or any other disposal option. For example, these factors
might include potential long-term effects on water quality; land use issues,
including long-term stewardship of closed impoundments; and economic
and cost-benefit analyses of alternatives. The committee also was not asked
to evaluate the risks of individual impoundments, examine the qualifications
and training of inspectors, or comment on coal mining policy issues not
directly related to impoundments. Although important, such issues are well
beyond the charge to this committee. Furthermore, a comprehensive analysis
of these issues would require considerably more time than was available for
the present study.
=
Representative terms from entire chapter:
coal refuse
