United States
Environmental Protection
Agency
Industrial Environmental Research'
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S7-84-010 May 1984
&ER& Project Summary
Environmental Assessment of
Surface Mining Methods: Head-
of-Hollow Fill and Mountaintop
Removal
This study was undertaken to assess
the environmental effects of coal
mining and reclamation techniques
employed in Kentucky and West Virginia
mountaintop removal and head-of-
hollow fill construction. The initial
endeavor was divided into four phases:
I. State-of-the-Art Review
II. General Environmental Assessment
of Ten Kentucky and West Virginia
Coal Mine Sites
III. Intensive Mine Site Monitoring
and Environmental Assessment in
Both States
IV. Evaluation and Update of Hollow
Fill Construction Guidelines
The results of Phases Ml, and IVwere
reported in an interim report (EPA-
600/7-79-062) published in July
1979. Phase III results are reported in
this document.
Phase III work consisted of detailed
environmental assessments conducted
at surface coal mine sites in Kentucky
and West Virginia, including study of
rainfall/runoff relationships, water
quality, stream benthic macroinvertebrate
community, and terrestrial vegetation.
Also included were an introductory
investigation into head-of-hollow fill
stability and a study of fugitive dust
emissions generated by Appalachian
coal mines.
A detailed analysis of fill stability was
added to Phase III and completed under
this contract to document the evaluation
of the long-term stability of four head-
of-hollow fills. Three phases of work
included in this part of the effort are:
• Collection of samples of valley fill
material at several locations; deter-
mination of sample moisture con-
tent, density and shear strength;
and application of these parameters
to stability analysis.
• Analysis of water carrying capacity
of rock chimney drains.
• Evaluation of the reliability and
effectiveness of remote data col-
lection techniques.
Volume I of the project report contains
most of the findings of Phase III and
Volume II contains the results of
additional analysis of the long-term
stability of valley fills.
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory. Cincinnati, OH, to
announce key findings of the research
project that is fully described in a
separate, two-volume report of the same
title (see Project Report ordering
information at back).
Site Descriptions for Detailed
Mining Studies
Kentucky Site
The surface mine site in eastern
Kentucky chosen for detailed monitoring
(KY-07-LA) is located in Perry County.
The watershed drains to the Middle Fork
of the Kentucky River immediately
downstream of Buckhorn Lake Dam.
Elevations in this watershed range from
275m (900ft) to 457m (1500ft). The aver-
age watershed slope is 10% with side
slopes as steep as 40%. Prior to mining,
the watershed was undisturbed except
for some nominal disturbance from
exploration activities. Cover type for the
watershed consists of dense forest on the
steep side slopes and small meadow
areas in the bottom land.
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The mine plan for the area called for
conventional contour stripping at a bench
level of approximately 366m (1200ft) to
remove three splits of the Hazard #5A
Seam. At the time this site was mined,
Kentucky did not require backfilling of
exposed highwalls. Since backfilling was
not required, the majority of overburden
removed from the bench level was
pushed into the adjacent hollows to form
hollow fills. For the disposal of excess
overburden, four separate hollow fills
were planned.
Construction of the hollow fills was
accomplished by the end dump and push-
down method. Excess overburden was
hauled to the head of the hollow and
dumped at bench level. The material was
allowed to roll down the outslope to
permit gravity separation of the different
sizes of material. According to Kentucky
regulations, the outslope then was
downgraded to 20 degrees or less every
48 hours to provide stability for the
advancing fill face.
Of the 65 hectares (160 acres) in this
watershed, approximately 24 hectares (58
acres) or 36% of the watershed was
disturbed by mining. Drainage control for
the disturbed areas was provided by a
sedimentation pond located in the
main channel of the unnamed receiving
stream.
Mining activities on this watershed
began in October 1976 with clearing
and grubbing operations. Work on the
first hollow fill began in December and
continued until March 1977. Mining in
the watershed was continuous from
October 1976 to June 1977 when the
mined area was regraded and replanted.
West Virginia Site
The surface mine site in southern West
Virginia chosen for more detailed monitor-
ing (WV-07-SA) is located in Logan
County. The watershed under study is
tributary to the Guyandotte River. Eleva-
tions in the watershed range from 243m
(800ft) to 664m (2180ft). The average water-
shed slope is 15% with side slopes as
steep as 60%. Prior to mining, the portion
of the watershed under study was
undisturbed and consisted of dense
deciduous forest.
The mine area is a small portion of a
large mountaintop removal operation.
The total mining area encompasses
approximately 81 hectares (200 acres)
including mineral area and overburden
disposal (valley fill). Mountain top removal
mining was used at this site for extraction
of the No. 5 Block coal seam at a bench
level of approximately 610m (2000 ft).
Excess overburden was disposed of in a
valley fill located in the upper reaches of
the study watershed. The valley fill was
constructed using the "West Virginia"
method of fill construction in which
material is hauled from bench level to the
toe of the valley fill. Material is placed in
1.22m (4 ft) horizontal lifts and graded by
dozer. In the center of thefill, a continuous
rock "chimney" drain is placed to handle
drainage from the fill surface. The surface
os the fill is graded to direct drainage to
the rock "chimney." Additional 1.22m (4
ft) lifts of fill material are added to the
surface until a 15.2m (50 ft) bench is
constructed. As each lift is added, the
outslope is graded to a 2:1 slope. After a
15.2m (50 ft) bench is completed, the
outslope is revegetated. A 6.1m (20 ft)
terrace is left on the fill surface when the
next bench is constructed.
Of the 20 hectares (49 acres) of this
watershed, approximately 10 hectares
(25 acres) or 50% of the area was
disturbed by mining. Drainage control for
the area was provided by on-bench
methods and by a sedimentation pond in
the stream's main channel. Mining
activities in this watershed began in May
1978 with clearing and grubbing opera-
tions. Active mining in the watershed
continued throughout the monitoring
period which ended in July 1979.
Site Descriptions for Valley Fill
Stability Studies
Kentucky Sites
Site B is the first of two valley fill sites in
the eastern Kentucky coalfields included in
this project. It is located approximately 16
km (10 mi) northwest of the town of
Hazard, Kentucky.
The fill is part of a contour stripping
operation and was constructed simply
by pushing the spoil over the natural
valley slope after clearing and grubbing.
The slope was graded as necessary as
additional fill was placed in order to
comply with regulations in existence at
the time of construction. No specific
internal drainage system comparable to
the West Virginia style rock core chimney
drain was included in the fill.
Lespedeza covers the slope of the
valley fill and the platform. There are no
signs of sloughage within the area.
There is a severe erosion gully which
traverses the face of the fill from the top of
the slope down to the base of the hollow
beyond the toe of the fill. The gully is the
result of a large portion of the platform
drainage being directed to the top edge of
the slope. There is a Iso a pond, situated to
the rear of the platform, which may
influence ground water at the site.
Site Bu is situated on the Breath itt-
Perry County line approximately 27.4
km (17 mi) northwest of Hazard, Kentucky.
It is another contour mining site where
valley fills were utilized for spoil disposal.
The major difference between this site
and Kentucky Site B is the length of the
fill platform, which is approximately 610
m (2,000 ft). The platform is free of any
large trees and the grass cover is sparse
compared to that on the fill outslope.
There are some small trees growing on
the east abutment and a portion of the
eastern slope of the fill. Older hardwood
trees are growing on the west abutment.
No signs of slippage or instability are
evident. However, the erosion which has
taken place is severe. Agully measuring 2
m (6.6 ft) deep by 4 m (13.1 ft) wide has
been eroded along the center of the fill. A
second gully approximately 1.5 m (5 ft)
deep and 1.5 m (5 ft) wide is situated near
the intersection of the fill and the west
abutment. Although the surface drainage
has created these bare areas, there is no
water flowing from the fill.
West Virginia Sites
Site Sp is located approximately 40 km
(25 mi) southeast of Charleston, West
Virginia. This fill is situated in a narrow
hollow, typical of southern West Virginia,
where the relief is 160 m (525 ft).
Geometrically, the fill consists of four
benches and a platform. The slope angle of
the benches varies from 0.45 radians
(25.8°) to 0.63 radians (36°). The vertical
distance between benches varies from
5.79 m (19 ft) to 24.38 m (80 ft). The
outslope is somewhat steeper than
shown on the permit application drawings
and the height between benches does not
agree with the design profile.
The fill surface is well vegetated with
lespedeza and there is a stand of conifers
on Bench D. There is minor surface
erosion on the fill surface, that is, scars
less than 0.15 m (0.5 ft) deep and
occurring only in non-vegetated areas.
The former highwall is completely
backfilled and grass covered except for
one small area north of the fill platform.
Site SpS is located approximately 2.4
km (1.5 mi) north of previously discussed
Site Sp. In fact, mining here was
completed by the same firm and the same
coal seam was mined.
The fill benches and outslopes are
covered by a dense growth of lespedeza
and the natural slopes forming the
abutments are covered with tall hardwood
trees. There are no signs of slippage
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anywhere on the fill surface and the only
noticeable wet area is on the platform
near the drainage pocket at the uppermost
end of the rock chimney drain. The most
noticeable topographic defect is a severe
erosion gully leading from the haul road
along the east side of the fill down to the
lowest bench of the valley fill. The gully
must have been present during construc-
tion since a portion of the lowest bench
leading from the gully to the main drain is
lined with rock similar to that in the
rock chimney drain. Presently there is a
vertical slope along the edge of the haul
road where the gully begins. Except for
the lowest bench which has a slope angle
of 0.63 rad (36°), the slope angles are less
than 0.45 rad (25.8°). The height between
benches is 12.2 m (40 ft) or less.
Results of Detailed Mine Site
Studies
Mine Site Environmental
Assessments
Prior to enactment of the federal
surface mining law, Kentucky require-
ments for excess overburden storage
allowed for downslope disposal of mining
spoil. Employment of downslope disposal
in construction of head-of-hollow or
valley fills prevented concurrent revege-
tation to stabilize exposed surface areas
and led to the construction of long
uninterrupted outslopes, both contribu-
ting to erosion of the fill surface.
From rainfall/runoff relationships
measured at Intensive Site KY-07-LA,
rainfall events occurring during active
mining produced approximately 5% more
runoff than events prior to mining.
The quality of water leaving the mine
area deteriorated following initiation of
mining, as exhibited by an increase in
acid properties and suspended load.
Following the end of mining, the water
was less acid, but carried even more
suspended load. Passage of the water
through the sedimentation pond did not
appear to remove suspended load during
mining. However, the pond was much
more effective in such removal following
the end of mining.
It is difficult to determine whether
cessation of surface mining activity in the
watershed had a significant positive
impact on this stream's macroinvertebrate
community. The number of taxa collected
during the period of active mining (31)
was higher than the number collected
after mining had ceased (13). However,
both collections included mayflies (Ephe-
meroptera), stoneflies (Plecoptera), and
caddisflies (Trichoptera), groups tradition-
ally considered pollution sensitive.
The West Virginia method of head-of-
hollow or valley fill construction appeared
to lead to more stable slopes relative to
erosion potential. Because of the hauldown
method of staged fill construction, the
outslope or face of the fill may be
revegetated prior to the end of construc-
tion. Additionally, the use of terraces
reduces the length of uninterrupted
outslopes susceptible to erosion. For
these reasons, no erosion scars of the
magnitude present on the Kentucky fills
were observed at the West Virginia site.
Changes in quality of water after initia-
tion of mining were evident in weekly
composite sample measurements made
upstream of the sedimentation pond. As
would be expected, pH dropped slightly,
and turbidity, total solids, total iron, and
sulfate increased. Monthly composite
samples indicated that conductivity,
calcium, magnesium, and aluminum
also increased while the trace metals
copper, zinc, cadmium, and nickel remained
nearly the same or declined.
Comparison of values measured above
(influent) and below (effluent) the sedimen-
tation pond allowed approximation of its
efficiency as an instrument of water
quality improvement during active mining.
Turbidity and total solids were substantially
reduced in the water by its passage
through the pond. Total iron, aluminum,
and copper also decreased. However,
conductivity, sulfate, calcium, and mag-
nesium increased.
It is difficult to conclude if surface
mining had an adverse impact on the
stream's benthic macroinvertebrate
community. Although fewer macroinver-
tebrate species were collected in the
stream after initiation of mining, those
species present were not nuisance
species. They included groups traditionally
considered sensitive to environmental
perturbation, mayflies (Ephemeroptera),
stoneflies (Plecoptera), and caddisflies
(Trichoptera). Furthermore, macroinver-
tebrate numerical densities increased
after mining began. It must be note, too,
that the structure of macroinvertebrate
communities is inherently dynamic and
not well understood. What may be loosely
interpreted as community change due to
adverse impact may, in fact, be in
response to unrecognized stimuli.
Valley Fill Subsurface
Investigations
The three fills investigated as part of
this study were composed of dense
material which had not suffered substan-
tial degradation. The ground-water
information indicated that the fills were
free draining and that no water was pond-
ing within the fills. The natural moisture
content of the fill material was that
expected for coarse grained material or
the natural bedrock from which it was
derived. Although no detailed analyses
were performed on the geometry of the
fills, the material comprising the fills, and
the natural overburden conditions led us
to conclude that the fills were stable.
Fugitive Dust Emissions
Investigation
The study of fugitive dust emissions by
high volume sampling revealed large
variation among individual samples, both
spatially and temporally. Haul road traffic
provided the greatest dust emission. At
one mine, drilling, overburden removal,
and coal loading monitored as a joint
operation was nearly as dust-producing
as haul road traffic, with regrading a
distant third. At two other mines,
emissions from drilling, overburden
removal, and coal loading and from
regrading were similar, with those from
haul roads somewhat higher. Fugitive
dust on reclaimed areas at all three mines
was nearly identical and quite low
relative to that measured near active
mining operations. Both mountaintop
removal mines investigated in this
segment of the study were greatly
different in measured densities of fugitive
dust emissions. The contour mine was
intermediate and displayed measured
densities similar to those observed at the
less dust-producing mountaintop removal
mine.
The study of dustfall also revealed
large spatial and temporal variation
among individual samples. No inverse
relationship between source-receptor
distance and mass of dustfall was
observed. There was no large difference
in mass of dustfall between the mountain-
top removal and contour mines.
It would appear that if similar machinery
is used in both mining techniques, as it
was at the mines monitored, differences
in fugitive dust emissions are the result of
local soil types and meteorological
conditions, rather than the result of
mining technique.
Results of Valley Fill Stability
Studies
Surface Inspection
During the summer months, dense
growths of lespedeza and other grasses
made it difficult to walk over the fill slopes
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and, in particular, to detect any surface
defects. However, surface inspection in
the fall was easier because the vegetation
was entering dormancy. Small erosion
channels which had been obscured by
dense summer vegetation were clearly
observable in the fall. The effect of
erosion at various locations on the long-
term stability is difficult to predict. There
is little doubt that it will result in the
continued creation of steep slopes along
the erosion channel which will collapse
and add to the sediment load of streams
below the fill. There is no way of
predicting the occurrence of a massive
slide in the future.
Subsurface Investigations
The drilling of standard test borings to
obtain samples of head-of-hollow fill
material proved satisfactory at the four
sites investigated. Prior to initiation of
this field work, it was thought that boulders
would interfere with the sampling pro-
cedures. However, there was no signifi-
cant difference in the rate of boring ad-
vancement using standard drive casing,
hollow stem augers, or drilled-in casing.
Newer fills, where less material weather-
ing has occurred or where more numerous
large boulders are present, would probably
hamper the advancement of hollow stem
augers.
Field sampling did prove that it was
impossible to obtain undisturbed Shelby
tube samples at any of the drilling
locations because of the numerous rock
fragments. Even a small rock particle can
impede the advancement of this type of a
sampler, which is pushed under hydraulic
pressure.
Seismic and Electrical
Resistivity Surveys
The seismic refraction method was a
most satisfactory geophysical method of
supplementing the data obtained by test
borings. The mobility of the seismic crew
and its equipment made it possible to
obtain subsurface rock profiles where the
terrain made accessibility for a drill rig
impossible.
From the field experience, it is clear
that use of the seismic technique
requires a skilled and knowledgeable
interpreter because of the concave
shaped contact between the fill and the
bedrock. Another absolute requirement
for this type of investigation is a multi-
channel, full wave form recording seis-
mograph in order to obtain reliable data.
Electrical resistivity methods did not
prove satisfactory for a number of
reasons. The length of the fill benches
was too short to obtain penetration to
define the entire depth of the fill. The
drainage core trenches at the West
Virginia sites also distorted the data, and
resulted in negative resistivities.
Laboratory Tests
The most significant problem encoun-
tered in the laboratory testing program
was the size of the samples obtained. The
number of large particles in some
instances made it necessary to combine
samples from more than one boring to
generate sufficient material for remolding
test specimens. Slight differences in the
material types from boring to boring may
have influenced strength test results.
In addition, the density data obtained
using samples from split spoon samplers
may be high because of the disturbance
created by driving the sampler into the
soil.
Site Specific Results
The surface conditions of the West
Virginia fills were generally good. The fill
surfaces had excellent vegetation and
showed little surface erosion. One of the
fills had a significant wet zone on one of
the benches, apparently the result of
either poor grading or fill settlement
causing ponding. At the second fill site,
there was a major erosion scar in a
drainage swale located on one of the fill
abutments.
The valley sites in Kentucky are not as
well vegetated as those investigated in
West Virginia. Both fills had deep erosion
gullies on the outslopes and near the fill
abutments.
Slope Stability
Both West Virginia fills have static
factors of safety greater than 1.0 with and
without seepage forces considered. The
low factor of safety of 1.17 at West
Virginia Site Sp is partially due to the
steepness of the lower benches through
which the critical circle passes. The two
Kentucky valley fills also have stable
slopes. Static factors of safety were
greater than 1.5.
Analysis of Rock Chimney
Drains
The only comment that can be made
relative to the rock chimney drains at the
West Virginia fills is that they are
functioning. Topographic conditions at
the head of the hollow, backfilling of the
highwall, and the location of the haulroads
intercept the overland flow and prevent
the water from reaching the drainage
pockets on the fill platforms.
The Kentucky fills do not contain any
special internal drainage such as the
chimney drain in the West Virginia fills.
This Project Summary was prepared by staff of Skelly and Loy Engineers,
Consultants, Harrisburg, PA 17110.
John F. Martin is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Environmental Assess-
ment of Surface Mining Methods: Head-of-Hollow Fill and Mountaintop
Removal"
"Volume I. •' (Order No. PB 84-146 448; Cost: $19.00)
"Volume II." (Order No. PB 84-146 455; Cost: $13.00)
The above reports will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
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