f/EPA
United States
Environmental Protection
Agency
Industrial Environmental Research C
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-093 Mar. 1983
Project Summary
Leachability and Revegetation of
Solid Waste from Mining
M. Lynn Apel
This research was conducted to
assess the effectiveness of various
disposal strategies in the abatement of
pollution from mining solid waste.
Column studies were undertaken to
evaluate the quality and quantity of
leachate generated by the disposal of a
pyrite mine waste under various soil
amelioration and layering configura-
tions and to assess the vegetative
uptake of potentially hazardous mate-
rials from the solid waste.
Columns containing the mine waste
under 0.3 to 1.2 meters (1 to 4 feet) of
cover soil were used to assess the
capability of the cover material to
reduce leachate volume, improve
leachate quality, and enhance the
growth of cover vegetation. Concur-
rently, columns containing neutral-
izing materials were used to determine
if such materials aided in retarding
acid formation and pollutant migration
throughout the soil.
The results of this study illustrate
that the quality of leachate resulting
from the disposal of pyrite mine waste
may be dramatically improved by incor-
porating lime, sewage sludge, and
fertilizer into the upper strata of the
mine waste; layering sewage sludge
and fertilizer on top of the lime-treated
mine waste; or by covering the mine
waste with a relatively thick layer of
cover soil.
The study was conducted by the
Industrial Environmental Research
Laboratory of the U.S. Environmental
Protection Agency (U.S. EPA) in the
greenhouse of the U.S. EPA Test and
Evaluation Facility (T&E Facility) in
Cincinnati, Ohio from August 1980
through January 1981. It should be
noted that the results obtained from
these column studies reflect the
experimental conditions under which
they were obtained and may or may
not be indicative of what would occur
at an actual mine site during the same
period of time.
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 docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The vast amount of solid waste
generated through the mining of mineral
ores must be disposed of in an environ-
mentally safe manner. It has been
estimated that about 1.5 billion tonnes
(1.7 billion tons) of mineral wastes are
discarded annually in the United States
and that total accumulated mineral solid
wastes are approaching 23 billion
tonnes (25 billion tons). Mineral waste
piles currently cover over 800,000
hectares of land (approximately
2,000,000 acres) and represent over 30
percent of the total wastes produced in
the United States.
Depending on the ore being mined
and the processes used, mine wastes
may contain potentially toxic substances
including arsenic, cyanide, mercury, or
heavy metals. These pollutants may be
leached from waste piles and enter
nearby groundwater systems or surface
streams. In addition, lack of a vegetative
cover on the waste piles can be
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conducive to severe wind and water
erosion of the materials, resulting in
wind and waterborne transport of
potentially toxic materials inherent in
the wastes.
Over the past several years the United
States Government has shown an
increasing interest in the proper disposal
of solid wastes generated by the mining
industry. Congress has passed several
pieces of environmental legislation
regulating the treatment and disposal of
solid wastes representing a danger to
public health or the environment. Of
recent concern is the Resource Con-
servation and Recovery Act of 1976,
(RCRA, PL 94-580) and its subsequent
amendments. This act is implemented
and enforced by the U.S. EPA and is
intended to control the disposal of
municipal and industrial solid wastes.
The Surface Mining Control and Recla-
mation Act of 1977 (SMCRA, PL 95-87),
which is implemented and enforced by
the Department of Interior, is intended
to control the environmental effects of
surface coal mining operations and the
surface effects of underground coal
mining operations. The legislation
regulating the disposal of uranium mill
tailings is the Uranium Mill Tailings
Radiation Control Act of 1978 (UMTRCA,
PL 95-604) which is also implemented
by the U.S. EPA but enforced by the
Nuclear Regulatory Commission. These
pieces of legislation have contributed
significantly to the development of solid
waste disposal techniques that are
practical and economically feasible.
This report presents the results of a
series of pilot plant column studies
performed to assess the effectiveness of
various solid waste disposal strategies
in controlling pollution from mine
wastes. The strategies examined in this
research project are currently being
used or have the potential to be used in
the disposal of pyritic mine wastes or
other acidic solid wastes of similar
character and composition. The objec-
tives of these studies included: (1)
determination of the physical and
chemical quality of leachates generated
from test columns containing an acidic
mine waste under various soil ameliora-
tion and layering configurations; (2)
determination of the quantity of leachate
produced relative to water input based
on rainfall statistics of the geographical
location under study; and (3) assessment
of the uptake of potentially hazardous
materials by vegetation growing on the
mine waste or cover soil.
For this study, a pyrite mine waste
was chosen from the Contrary Creek
watershed in Virginia. Contrary Creek is
located in east central Virginia, approxi-
mately 65 kilometers (40.3 miles)
northwest of Richmond and 120 kilo-
meters (74.4 miles) southwest of
Washington, DC. Contrary Creek is
approximately 8 kilometers (5 miles)
long and drains an 18 square kilometer
area (7 square miles) which includes
three abandoned pyrite (iron disulfide -
FeS2) mines and 17 hectares (42 acres)
of pyritic tailings that have remained
since mining ceased in the early 1920s.
Prior to state and federal involvement
in the mid 1970s, this area was barren
of vegetation and the creek was severely
polluted. One of the reasons for federal
involvement in the area was an attempt
to demonstrate the utilization of sewage
sludge to reclaim highly toxic mineral
wastes. Today, most of the tailings piles
have been regraded and vegetated, but
areas still exist, particularly along the
creek bed, where high acidity and
erosion by the stream have prevented
successful reclamation. Material from
these areas was studied in the pilot
plant experiment.
Three approaches were examined for
treating the surface of a disposal area in
order to mitigate the acid mine drainage
resulting from disposal of this pyritic
mine waste. The first approach included
application of digested sewage sludge,
agricultural limestone, and commercial
fertilizer to treat the surface of a waste
pile in order to neutralize the acidic
waste and resulting drainage and
develop a plant growth supporting
medium. The second approach utilized a
layer of cover soil placed over the mine
waste to reduce water infiltration of the
waste and to provide a growth medium.
The third approach involved placement
of a neutralizing layer between the mine
waste and cover soil layer. In each case
the treated surface was vegetated.
Materials and Methods
Column Design
The engineering design of this study
included construction of seventeen
0.30-m (1 -ft) diameter columns ranging
in height from 2.1 m (7 ft) to 3.4m (11 ft)
(Figure 1). Each column consisted of a
0.6-m (2-ft) section of 0.3-m (1-ft)
diameter, schedule 80, polyvinyl chloride
(PVC) pipe secured to a concrete support
platform. A lead support plate was
placed between the PVC pipe and the
platform. Attached to the upper end of
the 0.6-m (2-ft) section of PVC pipe by
means of a PVC/acrylic mounting
flange was a piece of clear, cast acrylic
tubing ranging in height from 1.4m
(4.5ft) to 2.6m (8.5ft). An additional
machined acrylic flange joint was used
in the construction of columns greater
than 1.5m (5ft) in height.
Located within the initial 0.6-m (2-ft)
section of PVC pipe was an internal
leachate collection system made from a
0.3-m (12-in) length of 5.3-cm (2-in)
diameter PVC pipe 'perforated with
0.32-cm (1/8-in) holes and wrapped
with a 200 mesh stainless steel
screen. The function of this screen was
to inhibit the discharge of fines from the
ore or soil material with the leachate. A
5.1-cm (2-in) diameter, plain end, PVC
cap sealed the top of the collection
system and through a series of PVC
linkages, a 0.3-cm (0.5-in) collection
port allowed leachate to flow out of the
column and into an external leachate
holding system. The external system
consisted of a test-tube air trap and an
18.9 liter (5 gallon) polyethylene collec-
tion vessel equipped with a spigot for
draining leachate samples.
The internal leachate collection
system was anchored in concrete
within the 0.6-m (2-ft) section of PVC
pipe. The top surface of the concrete
was coated with an epoxy paint to
prevent reaction with acidic leachates.
At the base of the 5.1 -cm (2-in) diameter
PVC pipe, the concrete was sloped at an
80° angle relative to the pipe to enhance
leachate collection.
Experimental Design
The climatological conditions main-
tained in the greenhouse during the
project study period were based on five-
year mean monthly precipitation, tem-
perature, and humidity data for the
Virginia study area as recorded by the
National Oceanic and Atmospheric
Administration (NOAA, 1974-1980).
Climatic conditions representative of
the Contrary Creek area during the
months of May through October were
simulated. Ten-year, 24-hour storm
events were simulated during weeks 9,
18, 20, and 24 of the 24-week study
period. Distilled water was applied to
the columns weekly and greenhouse
temperature and humidity control
devices were set according to statistics
derived from the NOAA data.
Approximately 3.2 tonnes (3.5 tons) of
waste from a pyrite mine and 1.8 tonnes
(2 tons) of topsoil (cover soil) were
-------
O.D. = 0.31 M
Clear Cast
Acrylic Tubing
O.D. =0.31 M
r
1. 4-2.6 M
I.D. = 0.29 M
T
1.9 CM
Schedule 80 PVC ^
0.61 M Pipe O.D. = 0.34 M
-.15M
t
Machined Acrylic
Flange
- Gasket
. Gasket
1.3 CM PVC Sampling
Outlet
77/777 Greenhouse
///7/7~ Floor
Internal Leachate Collection System Design
5.1 CMI.D.Sch.80
5.7 CM Dia. Plain End
PVC Cap
200 Mesh
Stainless Steel
Screening
1.9 CM Acrylic
1.9CM
5.1 CM PVC
Coupling
PVC Reducer
Bushing 1.3 CM PVC_^
Nipple
1.3 CM x 90° PVC
Elbow
Support Base
Plain End PVC Pump
Perforated with
0.32 CM Drill Holes at
2.5 CM 90° Intervals
•— Clamp Gasket
1 Concrete Coated
with Non-Reactive
Resin
1.3CMI.D. PVC Pipe
j~P/a//7 EndSch. 80
1.3CMI.D.
Concrete Support
^ Lead Support
Plate
Figure 1. Column and collection system design.
To conveit centimeters to inches multiply by 0.39370.
To convert meters to feet multiply by 3.28084.
obtained from the Contrary Creek site.
Soil tests and metal analyses were
performed on representative samples of
these materials. The resulting data
showed that the mine waste contained
approximately 200 mg/g iron, 4 mg/g
lead, 10 mg/g copper, and 2 mg/g zinc.
This compared to approximately 40
mg/g iron, 1 mg/g copper and less than
1 mg/g lead and zinc present in the
cover soil material.
After being air-dried, the waste and
soil were separately passed through a
1.3-cm (0.5-in) screen. The mine waste
was then mixed and placed in the
columns in 0.30-m (12-in) lifts. Each lift
was graded, and a vibrator compactor
was used to achieve a density of
approximately 1600 kg/m3 (100 Ib/ft3).
The cover soil was placed in the
columns in the same manner and
compacted to a density of approximately
800 kg/m3 (50 Ib/ft3). Amendments
were then added to the columns
according to the experimental design
shown in Figure 2. The types and
application rates of the amendments
used in this study were similar to those
used atthe full-scale demonstration site
at Contrary Creek and included agricul-
tural limestone, 15-15-15 commercial
chemical fertilizer, and anaerobically
digested sewage sludge. Sludge used in
the column studies was obtained from
the Cincinnati Municipal Wastewater
Treatment Facility. As a final step, the
columns were then seeded and wrapped
0 Mining Solid Waste
E§ Cover Soil
03 Mining Solid Waste
Lime + Sludge +
Fertilizer
S3 Mining Solid Waste + Lime
Lime
Sludge + Fertilizer
Col 9
Col 10
Col It
Col 12
Col 13
Col 14
Col 15 Col 16 Col 17
Figure 2. Contents of columns 1 through 17.
with brown paper to prevent light from
penetrating into the subsoil.
Surface Treatment
Techniques Studied
Overall, four surface treatment tech-
niques for disposal of the pyrite mine
waste were examined. These techniques
were: (1) the incorporation of sewage
sludge, agricultural limestone and 15-
15-15 commercial fertilizer into the
upper strata of the mine waste, (2) the
layering of sewage sludge and fertilizer
over the lime-treated waste, (3) the
placement of a cover soil layer over the
mine waste, and (4) the placement of a
limestone layer positioned between the
mine waste and cover soil.
-------
Columns 1 and 2 contained 1.2m (4ft)
of the pyrite mine waste only and served
as controls. Columns 3 and 4 contained
1.2m (4ft) of the cover soil material only
and also served as controls.
Columns 5 and 6 simulated the
reclamation work done at the Contrary
Creek Demonstration site. These columns
contained sludge, lime and fertilizer
incorporated into the top 0.15m (0.5 ft)
of the 1.2-m (4-ft) column of pyrite mine
waste. Columns 7 and 8 contained
these same materials in a different
configuration. A 1.2-m (4-ft) layer of the
mine waste was placed in each column.
Lime was incorporated into the top
0.15m (0.5ft) of the mine waste.
Fertilizer and sludge were mixed and
layered on top of the lime-treated mine
waste.
Columns 9 through 14 addressed the
effect of a layer of cover soil placed over
the mine waste. Columns 9 and 10
contained 1.2m (4ft) of the mine waste
under 0.46m (1.5ft) of cover soil.
Similarly, columns 11 and 12 contained
a 0.61 -m (2-ft) layer of cover soil placed
on top of 1.2m (4ft) of the mine waste
while columns 13 and 14 contained
1.2m (4ft) of mine waste under 1.2m
(4ft) of cover soil.
Columns 15 through 17 were used to
examine the effects of placing a neutral-
izing layer between the cover soil and
the mine waste. Column 15 contained
0.61m (2ft) of mine waste, on top of
which was placed 1.6kg (3.5lb) of lime
(approximately 2.5cm (1in) in height). A
0.61-m (2-ft) layer of cover soil was
compacted over the lime. Column 17
was loaded in a similar manner and
contained 3.2kg (7 Ib) of lime (approxi-
mately 5.0cm [2in]) layered between a
0.61-m (2-ft) layer of cover soil and
0.61-m (2-ft) layer of mine waste.
Column 16 contained 0.61m (2ft) of
mine waste under 0.61m (2ft) of cover
soil and served as a control unit. The
contents of each column are shown
schematically in Figure 2.
Methods Used for Data
Analyses and Characterization
After the columns were loaded,
simulation of the climatological condi-
tions of the study area began in the
greenhouse. Distilled water was added
to the columns weekly to simulate
average precipitation conditions. Approx-
imately 24 hours after the water was
added to the columns, leachate samples
were collected from each column and
analyzed for pertinent physical and
chemical properties including acidity,
pH, specific conductance, iron, copper,
lead, and zinc. The resulting data were
then converted to load data (i.e.,
concentration times flow) and these
data were subjected to statistical
analyses.
Vegetative growth was measured
periodically during the project. At the
end of the study period, samples of the
vegetation were analyzed for metal
uptake. Total concentrations of copper,
iron, lead, and zinc in the plant materials
were determined by Atomic Absorption
Spectrophotometry. Mine waste and
cover soil samples were also analyzed at
the end of the study period to assess
metal migration through the mine
waste and cover soil material. As each
column was disassembled, a sample
from each approximately 0.31m (1ft) of
material was obtained and total concen-
trations of the above mentioned metals
were determined.
Results and Discussion
Leachate samples from each column
were collected weekly and analyzed for
pertinent physical and chemical pro-
perties. Quantities of leachate collected
and leachate flow rates were measured
and recorded. The temperature, pH,
turbidity, specific conductance, and
acidity of the lead concentrations in the
acidity of the samples were also
quantified. In addition, iron, copper, zinc
and lead concentrations in the leachate
were determined. The characteristics of
the experimental columns were then
compared to those of the control
columns and the results of each
treatment technique evaluated. Some
of these results are shown in Figures 3
through 8 and Table 1.
Overall, metal migration through the
mine waste and cover soil strata was
minimal during the project study period.
A small portion of the potentially
teachable heavy metal content of the
mine waste was actually leached during
this study. Rough calculations performed
using the data collected from the mine
waste control columns (1 and 2) showed
that approximately 1% of the copper,
10% of the iron, 0.02% of the lead, and
1.5% of the zinc were leached from the
mine waste in these columns.
By the end of the study period,
vegetation was observed on all columns
except those containing the untreated
mine waste. Overall, the rate of vegeta-
500
13579 1113151719212325
Time (Weeks)
1357
9 1113 151719212325
Time (Weeks)
Figure 3. Combined metal and acidity mean load data for columns 1 and 2 containing the
untreated mine waste.
400
3 5
7911 13151719212325
Time (Weeks)
1357
9 11 13151719212325
Time (Weeks)
Figure 4. Combined metal and acidity mean load data for columns 5 and 6 containing the
lime/sludge/fertilizer layered over the lime-treated mine waste.
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13579 1113151719212325
Time (Weeks)
1357
9 1113151719212325
Time (Weeks)
Figure 5. Combined metal and acidity mean load data for columns 7 and 8 containing a
sludge/fertilizer layer over the lime-treated mine waste.
1357911 13151719212325
Time (Weeks)
357
9 11 13151719212325
Time (Weeks)
Figure 6. Combined metal and acidity load data for columns 9 and 10 containing the
mine waste under 0.46m (1.5 ft) of cover soil.
; 3 5
Figure 7.
7 91113151719212325 13579 1113151719212325
Time (Weeks) Time (Weeks)
Combined metal and acidity load data for columns 11 and 12 containing the
mine waste under 0.61m (2 ft) of cover soil.
1604
357
9 l'l 1315 1'7 19 2123 25
Time (Weeks)
Acidity -°-o-
Iron ~*~*~
•400
•300
•9
1 3 5
797/ 13151719212325
Time (Weeks)
Figure 8. Combined metal and acidity load data for columns 13 and 14 containing the
mine waste under 1.2m (4 ft) of cover soil.
live growth was much slower on the
sludge treated columns (5 through 8),
since no cover soil had been applied and
vegetation had to be established on the
surface of the treated mine waste.
However, growth on these columns
indicated that even given the low
application rate of digested wastewater
sludge used, sufficient nutrients were
supplied for vegetation establishment
and growth.
Vegetative metal uptake data were
recorded at the end of the study period.
In general, it was noted that copper
uptake concentrations were predomi-
nately higher when the amendments
were incorporated into the upper
portion of the mine waste (columns 5
and 6} than when layered over the lime-
treated mine waste (columns 8 and 9).
Iron uptake, however, was greater in the
latter case, whereas lead and zinc
uptake showed little differentiation with
respect to either amelioration technique.
Overall, the vegetation on columns
containing the cover soil layered above
the mine waste showed minimal metal
uptake.
Conclusions and
Recommendations
The results of this research indicate
that the quality of leachate emanating
from this pyrite mine waste may be
notably improved by all of the treatment
techniques studied in this experiment,
i.e., incorporating lime, municipal
sludge, and fertilizer into the upper
strata of the mine waste; placing a
mixture of sludge and fertilizer on top of
the lime-treated mine waste; or covering
the mine waste with a 0.6-m to 1.2-m
(2-h to 4-ft) layer of cover soil. Placement
of a soil layer greater than 0.6m (2ft)
over the mine waste, however, was
found to be the best treatment technique.
This technique not only improved
leachate quality but also provided a soil
stratum highly suitable for vegetation.
The utilization of municipal waste-
water sludge in combination with
limestone and fertilizer proved to be
highly beneficial in establishing a
vegetative cover over the mine waste.
This pilot plant observation is in
agreement with the results obtained at
the Contrary Creek field demonstration
site. Reclamation schemes including
the use of sludge and other amend-
ments, such as those studied here, are
recommended for lands containing
wastes which exhibit physical and
chemical characteristics similar to the
mine waste studied in this project.
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These schemes not only provide a
means of sludge disposal but also may
have economic advantages depending
on the extent and location of the waste
material.
Both the layering and incorporation of
sludge, lime and fertilizer into the upper
portion of the pyrite waste resulted in an
improvement in leachatequality compar-
able to that noted when the mine waste
was covered with 1.2m (4ft) of cover
soil. Incorporating the amendments, as
opposed to layering the amendments,
appeared to result in more significant
decreases in leachate acidity and metal
loads.
Placement of a lime layer between the
mine waste and cover soil did not
appear to enhance leachate quality
during the study period; in fact, leachate
quality tended to be worse than that
from the control column. This wasfound
to be correlated to a 15-20% decrease in
flow rate for the experimental columns
as compared to the control column.
As expected, vegetation was quickly
established on the cover soil material
placed above the mine waste, and no
vegetation was established on the
untreated mine waste control columns.
Vegetative growth was much slower
and about 75% less dense on columns
containing the amendments layered
and incorporated into the mine wasteas
compared to the columns containing a
cover soil layer over the mine waste.
Overall vegetative metal uptake by
plants was minimal in all experimental
columns.
It was noted that the adverse condi-
tions of the mine waste (i.e., high acidity,
low pH, high iron content) were greater
deterrents to root penetration into the
mine waste than lack of precipitation, as
often expected. In addition, a thin layer
of lime positioned between the cover
soil and the mine waste materials was
found to be highly conducive to root
penetration into the mine waste layer.
1'able1.
Experimental Column Percent Load Decreases As Compared to the
Untreated Mine Waste Control
Percent Decrease
Columns
Treatments
Mean Mean Mean Mean Mean
Acidity Copper Iron Lead Zinc
Load Load Load Load Load
5 and 6
7 and 8
9 and 10
1 1 and 12
13 and 14
Incorporated lime/sludge/
fertilizer into mine waste
Fertilizer/ sludge layered
over lime-treated waste
0.46-m (1.5- ft) cover soil
0. 6-m (2-ft) cover soil
1.2-m (4-ft) cover soil
77
65
58
71
81
58
44
56
54
64
67
55
50
60
71
53
58
75
79
75
67
51
56
53
69
The EPA author M. Lynn Apel is with the Industrial Environmental Research
Laboratory, Cincinnati, OH 45268.
The complete report, entitled "Leachability and Revegetation of Solid Waste from
Mining," (Order No. PB 83-136010; Cost: $ 17.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U. S. GOVERNMENT PRINTING OFFICE: 1983/659-095/584
-------
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