WATER POLLUTION CONTROL RESEARCH SERIES
14010 EXA 03/71
Acid Mine Drainage
ENVIRONMENTAL PROTECTION AGENCY • WAT El? QUALITY OFFICE
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WATER POLLUTION CONTROL RESEARCH SERIES
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202^2.
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Pilot Scale Study of Acid Mine Drainage
by
The Ohio State University
Research Foundation
Columbus, Ohio ^3210
for the
WATER QUALITY OFFICE
ENVIRONMENTAL PROTECTION AGENCY
Program # 1^010 EXA
Contract 1^-12-97
March, 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00
Stock Number 6501-0091
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.
Approval does not signify that the contents neces-
sarily reflect the views and policies of the
Environmental Protection Agency, nor does mention
of trade names or commercial products constitute
endorsement or recommendation for use.
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ABSTRACT
A research facility has been developed to study pyrite oxida-
tion and the resulting acid mine drainage on a pilot scale
basis. The test units include a small, long-abandoned drift
mine (the McDaniels Mine), and six 33-inch diameter auger holes,
drilled for the express purpose of furnishing comparable, iso-
lated, experimental units. McDaniels is a single room of
approximately 600 square feet and an average height of three
feet. Four of the auger holes are approximately 200 feet deep,
while the other two are approximately 100 foot each. All units
are in the Middle Kittanning seam and are located within a
radius of 200 yards. They can be opened or sealed at will and
are equipped and instrumented to allow the observation of the
effects of imposed mine atmospheres on the production of acid
mine drainage.
The effect of oxygen concentration on acid production has been
studies in the McDaniels mine. The response time of the mine
to imposed mine atmospheres of varying oxygen concentrations,
mine drainage data, and information derived from bore holes
through the overburden around the mine, provide the basis for
describing sites of pyrite oxidation and the significance of
bacterial catalysis on oxidation rate. Results to date indi-
cate that the major reaction sites are located above the ground
water table where gas, rather than liquid, is the continuous
phase. There is no indication of significant bacterial cataly-
sis of pyrite oxidation.
The six auger holes were drilled in order to provide duplicate
experimental units. By using one or more of the holes as a
reference mine, the fluctuations due to hydrologic variations
can be separated from changes brought about by an imposed change
in environmental conditions, and a more accurate evaluation of
the effect of the environment on mine drainage can be made. The
units also provide experimental flexibility and enhance the
progress of the experimental program which is restricted to one
experiment per year per unit by annual ground water fluctuations
and by the slow response time of underground pyritic systems to
imposed environmental changes.
This report was submitted in fulfillment of Contract No. lU-12-97
(Program #1^010 EXA) under the sponsorship of the Water Quality
Office of EDA.
Key Words: Mine drainage,* pyrite,* sulfides,* Ohio,* auger holes,*
underground mines,* coal,* pollution abatement,
industrial wastes
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TABLE OF CONTENTS
Page
CONCLUSIONS 1
RECOMMENDATIONS 3
INTRODUCTION 5
RESEARCH FACILITIES 9
EXPERIMENTAL PROGRAM 2?
EXPERIMENTAL RESULTS 33
DISCUSSION OF RESULTS 4?
ACKNOWLEDGMENTS 63
REFERENCES, LIST OF PUBLICATIONS 65
GLOSSARY 67
APPENDIX I -- DISCHARGE DATA 69
ABSTRACT CARDS
11
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TABLES
Table Page
I Sulfur Analysis From McDaniels Test Mine 11
II McDaniels Test Mine Operating Conditions 27
III Average Monthly Acid and Sulfate Loads For
McDaniels Mine 3^-
IV Average Monthly Acid and Sulfate Loads For
Auger Holes 35
V Air "Permeability" Measurements ^5
VI Experimental TfWeeping" Rate 50
VII McDaniels Mine Discharge Data 69
VIII Auger Hole No. 1 Discharge Data 77
IX Auger Hole No. 2A Discharge Data 79
X Auger Hole No. 2B Discharge Data 80
XI Auger Hole No. 3 Discharge Data 8l
XII Auger Hole No. k Discharge Data 82
XIII Auger Hole No. 5 Discharge Data 83
XIV Auger Hole No. 6 Discharge Data 8U
111
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FIGURES
Figure Page
1 Planimetric Map of McDaniels Mine and Observation
Wells 10
2 Outcrop Map ih
3 Contour Plat - Floor of McDaniels Mine 15
k Contour Plat - Roof of McDaniels Mine 16
5 Plan View - Auger Hole Placement 18
6 Plan and Elevation - Views of Hole No. 1 19
7 Plan and Elevation - Views of Hole Wo. 2A 20
8 Plan and Elevation - Views of Hole No. 2B 21
9 Plan and Elevation - Views of Hole No. 3 22
10 Plan and Elevation - Views of Hole No. k 2.3
11 Plan and Elevation - Views of Hole No. 5 2k
12 Plan and Elevation - Views of Hole No. 6 25
13 Oxygen Concentration McDaniels Mine 28
Ik Monthly Average Acid and Sulfate Loads for
McDaniels Mine 36
15 Monthly Average Acid and Sulfate Loads for
Auger Hole No. 1 37
16 Monthly Average Acid and Sulfate Loads for
Auger Hole No. 2A 38
17 Monthly Average Acid and Sulfate Loads for
Auger Hole No. 2B 39
18 Monthly Average Acid and Sulfate Loads for
Auger Hole No. 3 kO
19 Monthly Average Acid and Sulfate Loads for
Auger Hole No. k ki
IV
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FIGURES (continued)
Figure Page
20 Monthly Average Acid and Sulfate Loads for
Auger Hole No. 5 ^2
21 Monthly Average Acid and Sulfate Loads for
Auger Hole No. 6 ^3
22 Depth of Water in Well No. 6 vs. Mine Drainage
Flow Rate ^
23 Model of Underground Pyritic System 52
v
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CONCLUSIONS
1. Field data from underground mines indicate that the major sites of
pyrite oxidation lie above the ground water table, in regions where
gas rather than liquid is the continuous phase. Oxygen transport to
the pyrite oxidation site occurs by both convection and diffusion
through the gas phase.
2. Since pyrite oxidation sites are located above the ground water
table, the transport of oxidation products away from the pyrite is a
slow process. With product transport being limited to either l) molecu-
lar diffusion along water films, 2) seepage ("weeping") induced by the
hygroscopic nature of the oxidation products, 3) occasional downward
percolation of precipitation, and k} flushing of restricted regions by
annual changes in ground water table elevations, the retention time of
oxidation products in the mine varies widely with the specific location
of the pyrite being oxidized. In the case of the small abandoned drift
mine studies in this work, one hydrologic cycle does not remove all
oxidation products from the system, and it is unlikely that complete
removal is obtained even after three or four cycles.
2. There are direct indications that a significant portion of the
water flowing into the mined-out volume from the surrounding ground
water flow regions is essentially free of acid, i.e., most of the
drainage has never come in direct contact with active pyrite oxidation
sites.
h. There is no evidence of significant bacterial catalysis of pyrite
oxidation in the mines under investigation. While autotrophic iron-
oxidizing bacteria are active in the drainage after it has left the
pyrite oxidation sites and has been diluted with ground water, bacteria
are not present in sufficient numbers at the oxidation sites to signifi-
cantly affect the rate of pyrite oxidation. The predominant mode of
pyrite oxidation is the direct oxidation of pyrite by oxygen (oxygena-
tion).
5. The six recently drilled auger holes were designed to have a high
degree of similarity, allowing one to be used as a control and the re-
maining five to be available for controlled experimentation. However,
the six units differ widely in regard to both drainage quality and
quantity. This is due to differences in the amount of ground water
flow intercepted by the various holes.
6. The auger holes, although two years old, have not yet reached a
stable acid production rate because of the long period of time required
to reach a steady-state relation between pyrite oxidation rate and
product removal rate. It now appears that at least four years will be
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required for the product removal rate to reach 90 percent of the
ultimate steady-state value.
7. Analysis of underground•pyritic systems is hampered by lack of de-
tailed information on the physical, chemical, and microbiological
conditions at reaction sites. There is obviously a wide range of con-
ditions in respect to oxygen concentration, water flow, and dispersal
rate of oxidation products, depending on the location of a reaction
relative to the strata and to distance from the working face. However,
it is experimentally impossible to directly measure these conditions.
Therefore, interpreting the effects of imposed environmental changes on
acid production rates in accordance with a realistic model of an under-
ground pyritic system appears to offer the best approach to quantita-
tively evaluating such a system. Since accurate data on the effect of
imposed changes must be available for this interpretation, an experi-
mental facility of the type described in this report is required to
obtain sufficiently reliable information.
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RECOMMENDATIONS
Many of the difficulties in interpreting mine drainage field data are
related to the slow time response of natural systems to imposed environ-
mental changes, and the erratic output due to hydrologic variations.
These factors make it impossible to draw reliable conclusions based on
data from a single mine's discharge data over a one or two-year period.
Precise, reliable data are required to determine the kinetics of mine
drainage discharge. Only one type of experimental facility, the
multiple mine complex, is capable of providing data of the type needed
for interpretation of mine drainage kinetics. By using one of the
multiple mines as a reference or base control, the effect of hydrologic
variations can be determined and separated from changes caused by
planned alterations in environment in the other mines.
We, therefore, recommend that work at the multiple mine complex (the
McDaniels research facility) be continued with immediate studies made
as outlined below:
1. McDaniels mine be maintained under a nitrogen atmosphere
for at least two more years in order to more accurately
evaluate response time (and, therefore, information on
the relative importance of the various removal mechan-
isms) and to reduce inventory of stored oxidation products
so that the effect of a step change in oxygen concentra-
tion can be more accurately evaluated.
2. A tracer gas should be added to Auger Hole No. h and the
drainage asymmetry evaluated by observing the concentra-
tion of the tracer dissolved in the discharge from Holes
3 and 5-6. (Holes 5 and 6 will be treated as one experi-
mental unit for reasons discussed in Section VII). If
essentially the same quantity of the tracer is removed
in the discharge from Hole 3 and in Holes 5-6, the effect
of drainage asymmetry, which must exist due to the natural
dip of strata in the area, is negligible in regard to
drainage of reactive volumes of individual auger holes,
3. Since the auger holes have not yet reached "steady-state"
conditions, we recommend that three of the holes be used
as controlsj and three be used for experimentation.
4. The following environmental conditions are recommended
for study:
a. Sealing, with maintenance of a slight partial
pressure of ethylene oxide in an otherwise
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normal atmosphere. This will eliminate bacterial
catalysis of pyrite oxidation if it is present,
and will allow a more direct determination of the
significance of bacterial activity than is pres-
ently possible.
b. Sealing, with maintenance of a carbon dioxide
atmosphere. This could be coupled with the
application of carbon dioxide with an internal
burner, operated in response to barometric
pressure changes.
c. Sealing, with cyclic pressurization to amplify
the effect of breathing. By positive control
of the breathing component of the oxygen trans-
port process, and observation of the resulting
effect on acid production rate, it may be
possible to separate breathing and diffusional
transport, and to obtain a more quantitative
description of both processes.
We recommend that one of the reference auger holes be used
to see if it can be operated as a large respirometer. If
successful, a direct determination of oxygen consumption
could be made. This would be a "breakthrough" in the study
of natural systems, both in terms of time required to evalu-
ate experimental programs and in the accumulation of data
to assist in describing the kinetics of mine drainage pro-
duction. In order to operate a hole as a respirometer, a
method to eliminate the effects of atmospheric pressure
changes ("breathing") on gas phase transport to the mine
must be provided. We hope to accomplish this by use of
inflatable bags to change the volume of the mine in re-
sponse to atmospheric pressure change so that there will
be no flow of gas in or out of the mine.
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INTRODUCTION
The phenomenon of acid drainage formation and discharge from underground
mines has long been the subject of intensive study. These investigations
have been either l) laboratory scale investigations in which the reactive
material was removed from its natural environment, or 2) demonstration
type studies in which the effect of proposed abatement measures have been
observed on full-scale mining operations. While yielding valuable in-
formation, it has not been possible to extrapolate laboratory findings
to the field, nor to interpret demonstration efforts in terms of basic
mechanisms. The use of available laboratory and demonstration project
data and the development of engineering procedures for the abatement of
acid mine drainage at the source depend on the identification of the rate
controlling mechanisms in the mine environment. Thus it is necessary to
determine the nature of the reaction, the location of the reaction sites,
the conditions prevailing at the reaction sites which determine the nature
of the reaction, and the mechanisms by which reactants and products are
transferred to and from the sites.
The specific objectives of this project were to:
1. Determine the effect of oxygen concentration in the mine
on the rate of acid discharge (see page 55).
2. Determine the effect of microbiological factors on the
rate of acid discharge from the mine (see page 57).
3. Determine the location of reaction sites in relation
to the exposed coal surface and the characterization
of conditions predominating at the reaction site
(see page 1+8).
h. Determine the mechanisms of reactant and product trans-
port to and from the reaction sites by "time response"
studies (see page ^9).
The proven inability of laboratory and demonstration scale studies to
provide concrete answers to the above objectives points to the conclu-
sion that such answers will be obtained only by using pilot scale
facilities, situated in representative coal seams, and intermediate in
scale between laboratory studies and demonstration projects. Such
natural environment facilities should be viewed as pilot-scale reactors
in which the kinetics of the reaction taking place within the reactor
can be varied beyond the normal operational range in order to develop
fundamental information on reaction kinetics, a situation not possible
in demonstration projects. Previous work with this type of system is
limited to studies by the Ohio State University at the McDaniels Test
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Mine, located in Vinton County, Ohio. Active research, at this site has
been in progress since 196^ (?)• Experience with this facility has
indicated the applicability of the pilot scale approach to accomplishment
of the objectives outlined above, and a tentative conceptual model of
the physical characteristics of the reaction system has been derived from
the preliminary data (U). Equally important, techniques and limitations
pertinent to the use of this type of facility have been defined. The
major limitation is the severe restriction on the rate at which data can
be collected from a single unit. The natural ground water hydrologic
cycle results in increasing drainage flows during four to five months of
the year, the peak flows usually being attained in May. During periods
of increasing flow, mine drainage acidities reflect both pyrite oxidation
rate and the rate of release of previously stored oxidation products by
the increased flows.
On the other hand, during periods of dropping ground water levels and
decreasing flows, the slow seepage of highly acid solutions downward to
flowing ground water channels will not keep pace with the changing ground
water flow patterns. This will result in a lag in product removal, and
the accumulation of oxidation products in the system. Thus, acidity
appearing in mine drainage is not in equilibrium with the rate of pyrite
oxidation. Over a long period of time a "steady state" condition will
be reached in which the amount of oxidation product removal will be equal
to amount of product formed over the same time period.
The slow transport of acid products to the mine effluent will cause prob-
lems in the interpretation of mine effluent data following the alteration
of environmental conditions within the mine. There will be a response
time delay before the effluent will begin to reflect the change, and the
approach toward a new "steady-state" value may be quite slow.
With regard to data interpretation, experience with the McDaniels Mine
has shown that "base-line" information is erratic; that is, it is a func-
tion of the hydrologic characteristics of the system, particularly as
reflected in the ground water influx rate to the mine. These rates are
subject to major fluctuations. The use of a reference or control mine
to smooth out the effect of base line fluctuations in acid production
with varying flows may overcome this problem. A reference mine implies
the necessity of similar multiple units.
Due to annual cyclic fluctuations of ground water flow, discharge data
can only be compared with regard to the annual pattern. For example,
acid loads at the time of maximum ground water flow in the Spring, and
minimum flow in the Fall are two sets of reference points frequently used
for comparison of discharge data. Note that the comparison is made
between points essentially one year apart. With comparative data
restricted to a one year interval, and with slow response to impressed
environmental changes, one alteration in test conditions per year is the
most that can be carried out with a single unit. These restrictions,
together with the difficulties in obtaining base line data, point to the
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desirability of having multiple pilot-scale facilities, thereby allowing
the objectives of the project to be attained more accurately and quickly.
The decision was made to construct the multiple unit pilot scale facil-
ity. Alternative approaches to the construction of such a facility were
examined in detail. The most satisfactory solution from both an opera-
tional and economical point of view was found to be a series of auger
holes drilled into an exposed high wall located in the same hollow as the
McDaniels Test Mine.
Specific advantages of this arrangement are:
1. The auger holes are in the same coal seam as the McDaniels Test Mine
and only a matter of several hundred feet away, and thus the variability
of coal seam and overburden characteristics are held to a minimum. The
duplication of geologic and geometric features is an extremely important
feature of the multiple-unit concept, impossible to achieve by the use
of selected abandoned mines.
2. By using an auger rather than conventional mining procedures, a much
higher ratio of reaction sites to mined volume is achieved, and it is
possible to drive relatively far back into the coal seam without creating
an excessively large volume. A small volume is desirable because, in
controlled atmosphere composition experiments, the volume will be a
determining factor, along with leakage rate, in the amount of gas and
time required to reach the desired composition. Conventional mining
procedures would result in a mine of not less than twelve foot width,
having a high volume to surface area ratio. From this standpoint, aban-
doned mines would also be less desirable.
3. The nature of the auger holes makes them much more easily and eco-
nomically sealed than units mined by conventional methods. In addition,
seals of the type applicable to augered holes can be relocated at will
within the hole with a minimal expenditure of time and material.
U. The location of the multiple units in proximity to the McDaniel' mine
makes available existing electrical service and on-site laboratory space,
and facilitates efficient operation and maintenance of the research
program.
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RESEARCH FACILITIES
McDaniels Mine
Major renovation and instrumentation of the McDaniels mine was completed
under Project No. A-001-OHIO, Office of Water Resources Research, U. S.
Department of Interior (7). A brief description of this phase of the
project is given below.
Preparation of Site
Prior to May 8, 1965, the mine had been flooded to a depth of approxi-
mately three feet above the outlet valve in the mine seal (which was
constructed in 1957)« On May 8, the valve was opened and the mine
drained. Before draining the mine, samples were taken of the atmosphere
in the mine above the impounded water. During the draining operation,
samples were taken of the drainage which was concurrently treated with
slaked lime to decrease deterioration of water quality in the stream
below the mine. On May 18, the manhole cover in the seal was removed,
and the interior of the mine was examined. The mine was found to be
structurally sound, and plans were made for an accurate planimetric survey
of the mine interior. Reference spads were set in the mine roof, and a
reference line extended through the seal into the open area in front of
the mine. The planimetric survey was finished on June 35 and reference
points were placed on the hillside above the mine. The outline of the
mine was traced on the hillside, which allowed the selection of sites
for five of six observation wells. The location of the sixth well was
determined at the time of the drilling of the wells. A planimetric map
of the mine and the prepared observation wells is given in Figure 1.
After the locations of the wells were determined, the requisite depths of
the wells were estimated, and it was found that the budget would allow
the holes to be cored, thereby yielding the maximum possible amount of
detailed information on the sub-surface geology of the area surrounding
the mine. The drilling was completed during the first week in August.
Boring log plus soil sample and rock cores indicate that the 2^' to 35'
of sandstone overlaying the coal seam is the primary aquifer supplying
the McDaniels Mine. The observation wells provide a means of establishing
the approximate contour of the ground water table. Only one well (No. 6)
shows a significant head of water above the coal.
Samples of the coal and of the shale and clay partings at three points
in the mine were collected and examined for "forms of sulfur." Results
of analyses are presented in Table I.
9
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HOLE » 6
EL. 61'
HOLE "2
EL. 41'
HOLE "4
O EL. 37'
HOLE '3
O EL 35 '
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HOLE "1 ,
EL. 27' i
1
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1
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c
^ [
N.
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I x
\ X
V. -
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uB
) °
u
H /
/
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_ .1
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HOLE "s
POSITIONS OF OBSERVATION
WELLS AROUND MC DANIELS TEST UINE
ELEVATIONS GIVEN IN FT. ABOVE LOWER
LIMIT OF COAL BED
SCALE: I-20'
STREAM
Fig. 1 - Planimetric Map of McDaniels Mine and Observation Wells
10
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Table I. Sulfur Analysis from McDaniels Test Mine
Drill (Face) Samples:
Sample Location No. 1 (Ten feet to left of entrance)
Percent of Sulfur*
Level
Overburden
Top 1/3
Top 1/3
Shale parting
Shale parting
Middle 1/3
Middle 1/3
Lower 1/3
Lower 1/3
Sample Location No,
Top 1/3
Middle 1/3
Shale Parting
Lower 1/3
Sample Location No.
Top 1/3
Top 1/3
Middle 1/3
Lower 1/3
Core Samples
Core No. 1
Description
Top-above
Shale
Shale parting
Middle coal
Bottom coal
Depth
0-3 "
0-3""
3-12"
0-3 "
3-12"
0-3 "
3-12"
0-3 "
3-12"
2 (Left-center
0-3""
0-3 "
0-3 "
0-3 "
Total Sulfate
7-7^ 0.97
2.02 0.21
1.8l 0.19
1+.26 0.86
10 . 7)4 o . 93
1.9k 0.20
2.78 0.29
3.1+9 0.60
14.05 0.79
, back wall)
2.1+5 0.28
2.82 0.28
2.28 0.08
3.52 0.^9
3 (28 feet from entrance along
0-3 "
3-12"
0-3 "
0-3 "
Level
26.6'
26.8'
27-29.5'
29.5-30.2'
U.35 0,51
3.26 o.ki
3.16 0.1+6
2.55 0.31
Percent of
Total Sulfate
9.69 0.66
5.18 1.15
1+.20 O.kO
3-53 0.^9
Pyritic
6.1+3
1.10
0.91
3.03
9.51
0.91
1.61
2.37
2.68
1.1+9
1.86
1.87
2.36
right wall)
3-12
2.18
2.05
1.59
Sulfur
Pyritic
8.58
14-03
3-25
2.^6
Organic
0.3^
0.71
0.71
0.37
0.30
0.83
0.88
0.52
0.59
0.68
0.68
0.33
0,67
0.72
0.67
0.65
0.65
Organic
9.69
0.00
0.55
0.58
11
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Table I. (continued)
Core No. 2
Percent of Sulfur*
Description
Top coal layer
Middle coal
Shale parting
Bottom coal
Core No. 3
Top h" coal
Shale parting
Level
( approx .
6")
(6" from
bottom)
(last 6")
1+" from
top
Total
5.98
5.10
o.i+o
3.07
8.87
11.30
Sulfate
0.90
o.i+o
0.03
0.31
0.6k
1.11+
Fyritic
l+.l+l
4.07
0.12
2.20
7.83
9-98
Organic
0.67
0.63
0.25
0.56
o.Uo
0.18
Middle layer
Shale parting
Bottom coal
Core No. h
Top 1+"
Middle coal
Shale parting
Bottom coal
Core No. 5
Very top
Top shale
Middle coal
Shale parting
Bottom coal
Core No. 6
Top coal
Shale parting
Middle coal
Shale parting
5-05
(!+" thick,6"
from bottom)
(6" from
bottom)
(first 4")
(V from
top)
(6" from
bottom)
(lower 6")
Bottom coal
*Moisture-Free Sulfur
. 18
6.63
i+.4o
1.06
2.80
16.96
+-27') 0.72
(2U.1+-271) 5-05
(27.5') 0.61
(27.5-28.0') 2.62
6.11
1.01+
4.81
0.26
2.98
12
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In addition to planimetric mapping of the mine's interior (Figures 3 and
U), elevation bench marks have been established in the Big Four Hollow
in which the mine is located, and out-crop elevations determined down to
State Highway 2?8 (Figure 2). The dip of strata and topography in the
general area of the mine have thus been established.
During the latter stages of active mining, gob from the operation was
piled against the coal faces not being worked instead of being carted
from the mine. In order to have a good measure of the coal seam exposed
and to gain a better-defined environment within the mine, it was decided
to remove this refuse. The job was completed early in September, 1965.
Construction of an adit was completed soon after the gob was removed.
The adit replaced the frame structure which originally covered the mine
seal and consisted of a small cement block building enclosing the seal,
with an adjoining 8' by 8' room equipped for use as an analytical labo-
ratory and housing for recording instruments. A single phase 220 VAC
power line was contracted and run back to the adit to provide a sufficient
source of electrical power for the multiple mine complex.
The original seal was constructed of hollow concrete block and painted
with "Thoroseal". When preparing the front wall of the box entry
(Figure 3) for mounting the sampling line panel, it was discovered that
the second and third tier of block were disintegrating from the inside
out due to the action of acid water which had leaked into the hollow
core of these blocks. Where the block core had been grouted, no evidence
of attack was apparent. Damaged portions of the box entry were replaced
with solid block, and the entire surface coated with a bituminous sealer.
The main wall of the seal was in excellent condition and required little
repair.
A new pressure type manhole cover was purchased and installed and a
stainless steel panel for mounting sampling lines was mounted in the
front wall of the box entry.
The "permeability" of the mine to air was determined by raising the pres-
sure in the mine to approximately 20 cm. of water and observing the rate
of pressure decline. From these data it was possible to calculate the
amount of gas required to maintain a given pressure differential between
mine and atmosphere.
Assuming no net change in atmospheric pressure over a week's period, it
was found that 600 cu.ft. of air per week would be lost if a differential
pressure of 1.0 mm. of water was maintained. This is equivalent to
slightly less than 3 "K" cylinders of oxygen or nitrogen, which may be
readily transported and installed once a week.
A rain gauge and water level recorder for Well Wo. 6 were installed at
the site.
13
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mi
Figure 2
Outcrop map showing measured
elevations at bottom of coal, and , ,
r 'x y elevations from mine maps
\
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Outline Shows Section
at El. 2.48.
Scale in Feet
Contour Intervals O.I Ft.
Elevation 0.0 is Slightly Lower
Than Lowest Point in Mine,and
Corresponds to 838.0'MSL
Fig. 3 - Contour Plat - Floor of McDaniels Mine
15
-------
'OUTLINE SHOWS
'SECTION AT EL.2.48
SCALE: I" = 5'
CONTOUR INTERVAL =0.1 ft
ELEVATION 0.0 IS SLIGHTLY
BELOW LOWEST POINT
ON FLOOR OF MINE,AND
CORRESPONDS TO 838-0'MSL
4.75
MINE SEAL
Contour Plot - Roof of McDaniels Mine
16
-------
Auger Holes
Figure 5 shows a plan view of the auger hole placement. All seven holes
were drilled in an old strip mine high wall, on the north side of the
valley containing the McDaniels Mine. The McDaniels Mine, not shown in
the figure, is dug into the coal outcrop on the south side of the valley,
and lies approximately 1^-0 feet south of Hole No. 1. A small intermittent
stream entering the valley between Holes 2-B and Hole 3 makes the highwall
discontinuous at this point, and effectively isolates Hole 2-B from Hole 3.
Figures 6 through 12 show the plan and elevation views of Holes 1 through
6, respectively. The diameter of each hole is approximately 33 inches,
and while it was intended that the holes stay in the coal for their entire
length, it was not possible to accomplish this, due to the tendency of
the auger to drop into the clay. The dip of the coal strata to the
southeast is evident in comparing elevations from hole to hole.
The sequence of material adjacent to the Middle Kittanning (No. 6) coal
bed is relatively consistent. The coal is underlain by blue clay, and
overlain by sandstone. A lightly variable shale parting exists near the
top of the coal seam, and a consistent shale parting of 1/2 to 1 inch
thickness is present in the coal about 6 inches above the under clay.
17
-------
I-1
00
CONTOUR INTERVAL «ZO'
Fig. 5 - Plan View - Auger Hole Placement
-------
PLAN
0
o-
10
-o—
20
-O O O-
30 40 50 60
70
80 90
101
-oo
HOLE* I SCALE:
HORIZ
VERT
I
10 20
30
SANDSTONE-
H
844.0
SANDSTONE
843,0
O
I
UJ
8420 -
841.0 -
840.0
ELEVATION
i i i i i i i
6 - Plan and Elevation - Views of Hole No. 1
-------
PLAN
50
—o—
60 64
—o o
ELEVATION
842,0
o 841.0
840.0
839.0
838,0
J L
HOLE #2-A
I I I I I
J SCALE: I I I i
HORI2. L
I
10' 20'
VERT. L
2'
30'
J
3'
Fig. 7 - Plan and Elevation - Views of Hole No. 2A
20
-------
PLAN
0 10
20 30
—-o O O—
40 50 60
—O O O——O O ©-
70
—o—
79
-o
ELEVATION
843.0
842.0 -
841.0 -
840.0 -
LJ 839,0 -
838.0 -
837.0
HOLE* 2-B
I I I I 1
SCALE:
HORIZ.
VERT.
J 1
0
10'
I
20' 30'
I i
r 2- 3'
Fig. 8 - Plan and Elevation Views of Hole Wo. 2B
21
-------
PLAN
ELEVATION
840,0
833.0 I-
832.0
Fig. 9 - Plan and Elevation - Views of Hole No. 3
-------
PLAN
20 30 40 50 60 70
180 190
837.0
SANDSTONE
ELEVATION
CO
830.0 I L
Fig. 10 - Plan and Elevation - Views of Hole No.
-------
PLAN
0 10 20 30 40 5O 60 70 80 9O IOO 110 120 130 140 150 ISO 170
188
ELEVATION
-pr
836.0
835.0
0 834.0
|
833.0
832,0
831,0 -
83O.O
H h
H 1 1 1 1 1 1 1 1 1 1 h
VERT
11.00
Fig. 11 - Plan and Elevation - Views of Hole No. 5
-------
PLAN
10 20 30 4O 5O 60 70 80 9O 100 110 120 130 140 ISO I6O
170
828.0
HOLE #6 SCALE:
(
HORIZ.
10
I
20
I
30
I
0
VERT. L_
Fig. 12 - Plan and Elevation •- Views of Hole Wo. 6
-------
EXPERIMENTAL PROGRAM
For both the McDaniels drift mine and the auger holes, data were first
collected to establish "base" flows and effluent quality. The "base" or
reference condition for the McDaniels mine was the unsealed and contin-
uously draining mine. Oxygen concentration in the mined-out volume was
21$, and the water ponded on the clay floor was estimated to be less
than 300 gallons.
The original intent was to let all the auger holes drain continuously
and monitor the discharges. However, the quantity of water ponded in
the back of the holes—up to 3000 gallons in the case of Hole No. 6—
meant that sudden changes in concentration of water flowing into the
ponded water would be "swamped" by the ponded water, thereby further
decreasing the response of the discharge to changes taking place within
the mine.
The operating conditions finally selected for establishing "base" rates
in auger holes 2A, 2B, 35 ^5 55 and 6 were the unsealed or open holes
with 21$ oxygen throughout, and the ponded water pumped on a weekly
schedule. The flow rates reported for these holes were determined by
measuring the volume of water pumped and dividing this volume by the
time elapsed since the previous pumping. Hole No. 1 did not dip toward
the back and had very little ponded water, so it was allowed to drain
continuously for its "base" operating condition.
Variation in Oxygen Concentration
The atmosphere within McDaniels mine was controlled at different oxygen
levels by: l) the addition of pure oxygen; 2) constant air input; or
3) nitrogen purging. The time periods for these operational modes are
given in Table II. Oxygen concentrations are plotted in Figure 13. An
uncontrolled mode was also used in which the mine was closed as with a
conventional "air seal" and the gas composition within the mine allowed
to reach a steady-state value.
Table II. McDaniels Test Mine Operating Conditions
Time Period
Aug. 10, 1965
Oct. 6, 1966 -
Aug. 1, 196? -
Nov. 18, 1967
Aug. 16, 1968
Sept. 22, 1969
- Oct. 6, 1966
Aug. 1, 1967
Nov. 18, 1967
- Aug. 16, 1968
- Sept. 22, 1969
- Present
Operational Mode
Base Conditions
Nitrogen Purge
Oxygen Addition
Air Purge
Air Seal
Nitrogen Purge
Oa Cone.
21$
1 to 2$
21 - 35$
21$
21 to 10$
0.25 to Oo5$
27
-------
60n
(V)
oo
=5 50-
o
O 4O
•t^f
2
LJ
O
X
O
30
20
10
\
\
s.
1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 ?">
ASONOJFMAMJJAGONDlj
An,
™° \ A
1 1 T^lAfVs
Nl
v\
^~^^\
1 1 1 ! 1 i 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1 1 1 1 1 iNi i I 1 . I I i .1 I l I
MAMJJASONDJFMAMJJASONOJFMAMJJASONOJFMAMJJAS
1965
1966
1967
1968
1969
1970
Fig. 13 - Oxygen Concentration - McDaniels Mine
-------
During nitrogen purge, a water manometer was installed with one leg open
to the atmosphere and the other to the interior of the mine. A wire
contact was set to operate a sensitive relay which controlled a magnetic
valve on the nitrogen supply line. The wire contact maintained a slight
positive pressure of approximately 0.5 mm H20 in the mine.
The original manometric control used during the Oct0 6, 1966 to August 1,
1967, nitrogen purge was somewhat erratic since water vapor from the
mine would sometimes condense in the tubing leading to the manometer or
in the water of the manometer itself, thus changing the set point of the
control. The redesigned manometer system had a slow nitrogen flow
through the tubing connecting the mine to the manometer to prevent dif-
fusion of water and subsequent condensation of water in the manometric
system.
Test Holes
A number of small test holes were drilled around the periphery of the
McDaniels mine to determine the environmental conditions at points well
back of the worked face. These consisted of twelve vertical, one-inch
diameter holes drilled through the overburden to the coal seam at varying
distances up to 100 feet back of the mined volume. In only two cases
was the section between sandstone and coal (the upper shale layer) tight
enough to "hold" water used for drilling. Two holes were fitted with
1/V aluminum pipe down to the coal and cemented in just above the shale
overlying the coal. The pipe was capped in preparation for water and
gas phase sampling.
Water was sampled by running sections of 3/l6" brass tubing joined by
leak-tight connectors, to the bottom of the holes. A serum cap was
mounted on top of the string of tubing and water pulled into the tubing
using a hypodermic syringe. Since the hole was over 30 feet deep in
each case, water could not be drawn to the top, but the water contained
in the tubing when withdrawn was adequate for analysis by atomic adsorp-
tion spectroscopy.
Gas samples were taken in the same manner, but due to the comparatively
large gas volume of the tubing in relation to size of gas sample collected
for gas chromatographic analysis, the values obtained for oxygen concen-
tration are not believed to accurately represent conditions at the bottom
of the hole. The procedure has been revised for future sampling.
Air "Permeability" Measurements
The McDaniels mine and auger holes were tested for air tightness or
"permeability" by pressurizing the holes with air to 10 to 20 inches of
water, then observing the rate of pressure decline. A cannister type
vacuum sweeper was used as the air compressor. The seal on the McDaniels
29
-------
mine was used without alterations except to plug the water trap during
pressurization. The auger holes were tested with a packer -type seal.
A truck tire inner tube was contained between two plywood disks of
slightly smaller diameter than the auger holes. The circumference of
the hole at the depth the seal was to be made was coated with patching
plaster, the seal positioned and the inner tube pumped to 10-15 psi
before the plaster hardened „
When testing auger holes 2A and 2B, two seals were required. Because
the thin section between the two holes was highly permeable, seals were
set in both holes at the same depth, and the pair was pressurized by
adding air to either 2A or 2B. Pressure decline curves were obtained
on both holes.
Derivation of the "permeability" value (K/V) from pressure decline data
plotted as log AP vs. time is given below.
Change in moles of gas, dn, in constant volume, V, with change in pres-
sure, dp, using the- perfect gas law (pV = nRT):
Vdp = RTdn
From mass transfer equation:
dn = kA(P0-P)dt
= K(AP)dt
Substituting for dn and separating variables :
dp = rar dt
AP v
Integrating :
In ^L = £ RT(t2-tx) = 2.3 (logAP2-logAPi)
(APi) V
but:
—SvA^jg gvArJ! _ S]_Ope o-f line On log AP vs. time plot
JT o i->* j/
^S ~ "1
S°'' K = 2.3(slope) = c
V RT
K Cu. ft. of air
Units
V (hrO(cm. H20)(ft3)
30
-------
where:
V = volume of mine in cubic feet
R = gas constant = 75l(ft3)(cm.H20)/lb-mole,°R
•T = Temp.,°R
P = Pressure in cm. of H20
t = Time in minutes
K = kA - "permeability" constant
n = number of moles
A = Cross-sectional area for mass transfer
Note: plot of log AP vs. Time; AP in cm. of H20,
t in minutes
Analytical Procedures
Acidity (Total Acidity): Hot titration to the phenolphthalein end
point was the method used to determine acidity. Values are
reported as ppm (or mg/jj) calcium carbonate equivalent.
Sulfate: Sulfate was determined by standard gravimetric procedures
such as those presented by Scott (3).
Total Iron: If only total iron was to be determined, the concen-
tration was found using an Atomic Adsorption Spectrometer.
If ferric and ferrous ions were to be determined, the total
was taken as the sum of ferric and ferrous ions.
Ferrous Iron: The Zimmerman-Reinhardt method as described by Hille-
brand (l), p. 396, using diphenylamine indicator, was applied
to the sample as received.
Ferric Iron: The ferric ion was determined by reduction with
titanous chloride using procedures described by Hillebrand (l)
p. 398.
31
-------
EXPERIMENTAL RESULTS
Discharges from the McDaniels mine and the auger holes are given as
monthly averages of acid and sulfate discharge in Tables III and IV, and
graphically in Figures lU to 21.
Data collected on individual sampling dates are given in Tables VII
through XIV in Appendix I.
The flow rates for the McDaniels mine from August, 1965, through
December, 1967, were "corrected" using Figure 22. This was advisable
since the drain from the air trap on McDaniels Mine was frequently
plugged with "yellow boy" when the oxygen concentration within the mine
was 10$, or higher. The "corrected" flow was determined by noting the
water level in Well No. 6, then using the flow rate corresponding to
this level as given by Figure 22 as the "corrected" flow.
The air permeability of the auger holes was checked at various depths.
As seen in Table V the difference in permeability with depth is usually
less than the reproducibility of the permeability measurements. The
values tabulated are the average of three or more measurements. For any
one position, repeatability of pressure decline curves was good. However,
use of patching plaster along the line of contact of the seal with the
mine wall did not eliminate leakage behind the plaster through the more
porous stratao This source of leakage was variable and unrelated to the
depth of the seal.
Permeability measurements were made during the winter months when the
overburden was relatively saturated (with water), thus the permeabilities
are lower than if tested during the summer or early fall when the over-
burden is normally drier.
33
-------
Table III. Average Monthly Acid and Sulfate Loads (ibs/day)
For McDaniels Mine
Month
8/65
9/65
10/65
11/65
12/65
1/66
2/66
3/66
4/66
5/66
6/66
7/66
8/66
9/66
10/66
11/66
12/66
1/67
2/67
3/67
4/67
5/67
6/67
7/67
8/67
9/67
10/67
11/67
12/67
1/68
2/68
3/68
4/68
5/68
6/68
7/68
8/68
9/68
10/68
Acid Load
.1452
.1767
.1968
.2333
.2935
.2839
.4929
.5032
.4567
.5710
.3022
.2994
.2222
.1520
.1328
.1402
-1273
.1256
.2679
.4935
.4200
.3677
.2106
.1183
.0643
.0760
.1110
.1478
.1387
.1910
.3160
.4204
.7660
1.3168
.5596
-4153
• 3797
.2428
.1856
Sulfate Load - Month Acid Load Sulfate Load
11/68
12/68
1/69
2/69
3/69
4/69
5/69
6/69
7/69
8/69
9/69
10/69
11/69
12/69
1/70
2/70
3/70
4/70
5/70
6/70
7/70
8/70
.2970
.1617
.1806
.2638
.4255
.3254
.8457
.6913
.3402
.2245
.1342
.1077
.1150
.0925
.0820
.1052
.1725
.2823
.4167
.4955
.2582
,1710
1668
.2865
.3987
.6362
.4892
1.1183
1.1437
.5726
.4193
.3605
.2420
.2222
.2118
.2035
.2235
.3063
.4658
.6123
.7010
.4978
.3306
.3212
34
-------
Table IV. Average Monthly Acid and Sulfate Loads (ibs/day)
For Auger Holes
Month
3/69
4/69
5/69
6/69
7/69
8/69
9/69
10/69
11/69
12/69
1/70
2/70
3/70
4/70
5/70
6/70
7/70
8/70
Month
3/69
V69
5/69
6/69
7/69
8/69
9/69
10/69
11/69
12/69
1/70
2/70
3/70
4/70
5/70
6/70
7/70
8/70
Acid
Load
(Alk)
.178
.1704
.1427
.2619
.1500
.0852
.0780
.0570
.0820
.2096
.1680
.4413
.3843
.4820
.2580
.231+0
.3030
Acid
Load
.1657
.4383
.0060
(Alk)
(Alk)
(Alk)
(Alk)
.1345
.4483
.3637
.4907
.9325
.1090
.0310
.1216
l
Sulfate
Load
• 3537
.7687
.6609
.U185
.5564
.4i4o
.2190
.2550
.2790
.4450
.6943
.5895
1.0660
.9310
.9527
.5250
.4550
.5900
4
Sulfate
Load
• 3205
.861+7
.1455
.0880
.0800
.0880
.0840
.4893
.9690
.7740
1.0690
1 . 7200
,5760
.1730
.3620
2A
Acid
Load
.0979
.2882
.3238
.1718
.0352
• 0255
.0080
.0040
.0150
.1475
.3145
.4770
.1+170
• 5500
.1050
.0820
.1320
Acid
Load
.0378
.0278
.0120
.0163
.0210
.0250
.01+45
.0398
.0573
.0833
.1067
-3390
.0790
.01460
.0600
Sulfate
Load
.1709
.4855
.4350
.21(60
.0705
.0360
.0197
.0120
.0200
.2162
• 3885
• 5740
.4825
.6900
.1300
.1180
.1700
5
Sulfate
Load
.2334
.11+51
.0927
.0880
.0813
.0840
.1265
.1040
.1453
.1986
.2403
.5430
.2090
.1250
.i4oo
2B
Acid
Load
.0090
.0690
.0480
.0088
.0240
.0048
.0028
.0175
.0470
.0828
.0478
.0660
.1250
.1300
.0520
.0420
.1990
6
Acid
Load
.2224
.8215
• 9976
.5973
.4490
.0570
.0493
.0210
.0240
.0450
.1370
.8887
1.4890
1.3600
2.1300
.7280
.4o6o
.7180
Sulfate
Load
.0781
.2709
.2067
.0385
.0792
.0310
.0277
.0630
.1200
.1893
.1800
.2925
.2758
.4050
.1150
.1020
.3290
Sulfate
Load
.9402
2.1385
2.5283
1.5580
1.1450
.5480
• 3333
.2198
.2403
.3500
.5586
1.6960
3.5387
2.8300
3.6933
1.8000
• 9770
1.4290
Acid
Load
.3888
.3423
.0018
.0115
.0048
.0065
.2083
.8820
.6930
• 5863
.8700
.i4oo
.o4io
.1940
3
Sulfate
Load
.6133
.4971
.1368
.0698
.0665
.0668
.0845
.5883
1.3490
1.1115
.9607
1.5067
.3280
.2090
.3850
35
-------
u>
110-
100-
8 so-
x
80
70
60
50
" 40
o
< 30
g
< 20
10
ACID LOAD
SULFATE LOAD
y?
fc-\
\
,\
V
\,
OHr
ASONDljFM A M J JASON D| J F M A M J J A S 0 N D J F M A M J J A S 0 N OTj F M A M J J A S 0 N DJJ FMAMJJ ASONO
1965 1966 ' 1967 ' 1968 ' 1969 ' 1970
Fig. l4 - Monthly Average Acid and Sulfate Loads for McDaniels Mine
-------
-q
AUG '69 SEP '69 OCT '69 NOV '69 DEC '69 JAN '70 FEB '70 MAR '70 APR '70 MAY '70 JUN '70 JUL'70 AUG '70
DATE
Fig. 15 - Monthly Average Acid and Sulfate Loads for Auger Hole No. 1
-------
LO
co
no
Q 100
X
-8 90
-------
UO
vo
MOr
O 100
o
X
>, 90
o
s. 80
70
UJ
60
Q
2
O
O
ACID LOAD
SULFATE LOAD
50
40
30
20
10
AUG'69 SEP'69 OCT'69 NOV'69 DEC'69 JAN'70 FEB'70 MAR'70 APR'70 MAY'70 JUN'70 JUL'70 AUG'70
DATE
Fig. 17 - Monthly Average Acid and Sulfate Loads for Auger Hole No. 2B
-------
140
130
120
110
0 100
o 90
TD
8. 80
- 70
LU
£ 60
50
Q
O
40
ACID LOAD
SULFATE LOAD
AUG'69 SEP'69 OCT'69 NOV'69 DEC'69 JAN'70 FEB'70 MAR'70 APR'70 MAY'70 JUN'70 JUL'70 AUG'70
DATE
Fig. l8 - Monthly Average Acid and Sulfate Loads for Auger Hole No. 3
-------
HOr
8
>s
o
•o
O)
QL
JD
UJ
5*
_1
r>
-------
MOr
ro
8
o
TO
90
S. 80
en
-Q
LU
C/)
9
o
<
70
6O
50
40
30
ACID LOAD —
SULFATE LOAD
AUG'69 SEP'69 OCT'69 NOV'69 DEC'69 JAN'70 FEB'70 MAR'70 APR'70 MAY'70 JUN'70 JUL '70 AUG*70
DATE
Fig. 20 - Monthly Average Acid and Sulfate Loads for Auger Hole No. 5
-------
LO
400 r
300
200
8 100
x
& 90
CL 80
70
to
-Q
UJ
Q
UJ
Q
UJ
(-
X
UJ
UJ
ACID LOAD
SULFATE LOAD
0
AUG
'69 SEP'69 OCT'69 NOV'69 DEC'69 JAN'70 FEB'70MAR'70 APR'70 MAY'70 JUN'70 JUL'70 AUG'70
DATE
Fig. 21 - Monthly Average Acid and Sulfate Loads for Auger Hole No. 6
-------
21
10
*
UJ
20
2 19
a:
UJ
CO
m
0 18
o
o
UJ
o
m
Q_
UJ
O
cc
UuJ
I
17
16
15
0 100 200 300 400 500 600 700
MINE DRAINAGE FLOW RATE , GALLONS PER DAY
Fig. 22 - Depth, of Water in Well Wo. 6 vs. Mine Drainage Flow Rate
-------
Table V. Air "Permeability" Measurements
Hole
Wo.
1
1
1
2A
2B
3
3
k
k
5
5
6
6
McDaniels
Depth of
Seal
(ft)
85
27
87
la
i*
13
30
22
^3
7
ia
30
57
-
Slope of
Plot
(cm H20/min)
0.12
0.19
0.095
0.76
0.1*3
0.69
0.73
2.3
0.^8
0.93
0.2^
0.30
0.32
0.068
"Permeability"
(K/V x io2)
1.6
2.5
1.3
10.1
5.7
9.1
9.7
30.5
6.U
12.3
3.2
U.O
U.2
0.90
-------
DISCUSSION OF RESULTS
General
A few general comments should be made concerning effluent data from
McDaniels mine and the auger holes. For the purpose of this project,
we are interested in monitoring that value which will give the best meas-
ure of the quantity of pyrite oxidized. According to the stoichiometry
usually quoted for the oxidation of pyrite, either sulfate or total acid-
ity might be used to measure products of oxidation. Practically, the
non-titratable calcium and magnesium should be included in the equivalent
acidity to arrive at the stoichiometric quantity of total acid.
For older, stabilized pyritic systems such as the McDaniels mine, either
total acidity or sulfate content of effluent waters appears to be a reli-
able indication of pyrite oxidation products contained in the effluent
water. For the newly drilled auger holes, total acidity alone is not
adequate. Calcite inclusions, together with the "buffering" or ion-
exchange capacity of freshly exposed clay, "neutralize" the acidity pro-
duced, resulting in "alkaline" discharges with high sulfate contents.
A more reliable estimate of pyrite oxidation is given by the sulfate
analysis although there is, no doubt, some sulfate produced in the break-
down of clay minerals by acid waters. Sulfate is also lost in the pre-
cipitate found on the floor and in flow channels of the mine. These
precipitates contain iron hydroxy-sulfates of variable compositions„
The above discussion implies that the initial acidity data from the auger
holes are not a reliable indication of pyrite oxidation products in the
effluent. Later data show a more consistant relation between total acid-
ity and sulfate content.
To assist in understanding the interpretation of data and discussion of
results given in this section, a conceptual model of an underground
pyritic system is described in the following paragraphs. This model was
developed from basic reaction kinetic studies described by Smith and
Shumate(6) together with observations made in conjunction with the project
discussed herein. At this point the model is presented without experi-
mental justification. The interpretation of data leading to the formu-
lation of the conceptual model and experimental evidence proving its
validity are given in the following sections.
Conceptual Model of Underground (Drift) Mines
"Acid" production rate or "acid" load from an underground mine is deter-
mined from flow rate and acid (or sulfate) concentration of the mine's
discharge. The observed rate of production is the result of two inde-
pendent processes: l) rate of acid formation (or rate of pyrite oxidation)
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and 2) transport of oxidation products to the discharge waters.
Pyrite Oxidation
The pyrite oxidation reaction will be examined first. There are two
factors which may determine oxidation rate, depending on which is con-
trolling: 1) the chemical reaction and/or 2) rate of transport of reactant
(oxygen) to the reaction site. Before this concept can be explained,
the "reaction site" must be defined. Basically it is an exposed pyrite
surface together with the gas, liquid, and solid interfaces at this sur-
face. Its characteristics are described by the interfacial area per unit
volume of pyritic material and the conditions at this surface, i.e. oxygen
concentration, ferric/ferrous ratio (as determined by number and activity
of bacteria), temperature, etc. In other words, the reaction site con-
sists of those factors described by Smith & Shumate (6) which determine
the rate of pyrite oxidation.
Oxidation rate is either (approximately) first order (i.e. varies directly
with oxygen concentration), or it is zero order down to 2 or 3 percent oxygen,
depending on whether the oxidation is predominately chemical (first order)
or biological (zero order). Below 2 percent oxygen, the rate is first order in
respect to oxygen in both biological and chemical systems. Regardless
of the nature of the reaction, a finite concentration of oxygen must be
present at the pyrite surface before the pyrite surface can be termed a
"reaction site".
Assuming the mined-out volume of a mine has an oxygen concentration of 21
percent, reaction sites will be exposed to oxygen concentrations varying
from 21 percent at the working face to 0 percent back into the coal strata.
The oxygen concentration gradient in a particular stratum will depend on
the void volume (porosity),the exposed surface area of pyrite per unit
volume of the stratum, and the order of the chemical reaction. The cal-
culation of the oxygen concentration gradient is simply a problem of
diffusion plus chemical reaction for which quantitative mathematical
solutions are available.
Note that "reaction sites" extend as far into the strata as oxygen dif-
fuses. The greater the void volume, or porosity, of a pyrite-containing
stratum, the greater the rate of oxygen diffusion because of the larger
cross-sectional area available for diffusion. At the same time, more
pyrite surfaces will be exposed in a porous material simply because of
the greater total surface exposed to the vapor phase. Conversely, the
tighter the formation, the lower the quantity of oxygen which will diffuse
through it, and the less oxygen available for oxidation per unit volume
of material.
Since oxygen diffusivity in water is 1 x 10~4 that in air, essentially
all oxygen must be transported to the reaction site as a vapor. Diffusion
through water is too slow, and the quantity of dissolved oxygen in water
entering an underground mine is too small to produce a significant "acid"
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load. The diffusion mechanism therefore helps define the location of
reactive sites: they are exposed to vapor; they can not be submerged
under more than a quarter inch of water, or more precisely, there can
not be more than the equivalent of a quarter inch of stationary or
laminar flowing water between the pyrite surface and the source of
oxygen through which oxygen must move by molecular diffusion or diffu-
sion of oxygen becomes rate-determining.
Another fact is brought out by the conceptual model that must be kept in
mind when interpreting discharge data: the quality of effluent water is
not directly related to the quality of water at reaction sites. That
is, discharged water does not describe the aqueous environment at reaction
sites in terms of concentration of oxygen, oxidation products, ferric/
ferrous ratio, or other factors influencing the oxidation rate. The
water in contact with most reaction sites has a high concentration of
oxidation products, probably at or near saturation. The discharge water
is a mixture of these waters from reaction sites and the ground water
entering through major flow channels. The ground water usually contacts
few if any reaction sites.
Removal of Oxidation Products
The rate which pyrite oxidation products enter the effluent stream is
determined by three basic mechanisms:
1. Flushing by a rising water table.
2. Percolation by water flowing down through open channels or fractures
during or after periods of heavy precipitation.
3. Diffusion or "weeping" of saturated solutions of reaction products
caused by water condensing on reaction sites due to the lowered vapor
pressure of the highly concentrated solutions at these locations.
The particular removal mechanism (or mechanisms) involved at a specific
reaction site will depend on its location in respect to the water table
and/or flow channels through which water percolates. If a reaction site
is isolated from these sources of direct removal, oxidation products
will build-up until the degree of saturation at the site and surrounding
area is high enough that the rate of transport to points of direct
removal by percolation or flushing is equal to the oxidation rate. The
build-up of oxidation products has no effect on the oxidation rate (6).
Obviously the instantaneous rate of oxidation product removal is inde-
pendent of the rate at which the oxidation products are formed. At steady
state conditions the long term rates are equal; that is, over a three
or four year period, the total amount of oxidation products removed will
be equal to the total amount of oxidation product formed, but the daily
or weekly acid loads as measured from the discharge cannot be related
to the rate of pyrite oxidation.
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All three of the above removal mechanisms have been observed either in
the laboratory or in the mines. The flushing and percolation mechanisms
are self-evident. The diffusion, or 'Veeping" process is too slow to be
observed directly. To determine its effectiveness as a transport mech-
anism the 'Veeping" rate was measured in the laboratory by supporting a
(roughly) 120 cc. cube of coal several inches above a layer of distilled
water in a vented flask. After allowing several months for the system
to reach steady-state, the water was analyzed for acid and sulfate content
and the experiment resumed. Several months later the water was again
analyzed yielding the results given in Table VI.
Table VI. Experimental "Weeping" Rate
Rate of Transport Equivalent*
Component (mg/day) (^g-mole/day) Oxygen(^g-mole/day)
Acidity 5.5 55 96
Sulfate U.2 ^3 7^
*0xygen required to produce the acidity (or sulfate) by oxidation
of pyrite
A large Warburg-type apparatus was used to determine oxygen up-take rate
for the same sample. The rate of oxygen consumption was 80 ± 20 [ig-mole/
day, the same, within experimental error, as the Equivalent Oxygen shown
in Table VI. These data show that at steady state, the diffusion or
"weeping" mechanism will transport reaction products from reaction sites
at the same rate they are formed. Of course, the time to reach-steady
state depends on the distance and diffusion path between the reaction
site and the receiving water.
Physical Model
Keeping in mind the concepts discussed above, a physical model of a drift
mine such as the McDaniels Mine or the auger holes can be described.
Referring to Figure 23, the oxygen concentration gradient (and therefore
relative oxidation rates), and removal rates can be qualitatively evalu-
ated in relation to boundaries fixed by the working face of the mine, the
extent of oxygen diffusion, and the water table.
To illustrate the situation which exists in each more or less homogeneous
geologic stratum let us examine the shale parting which occurs between
the sandstone overburden and coal measures.
50
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SANDSTONE
OVERBURDE
HIGH WATER TABLE
*•
LOW WATER TABLE
Fig. 23 - Model of Underground Pyritic System
At reaction site "A", oxygen concentration is essentially the same as in
the mine, but as we move back into the shale parting toward "B", diffusion
of oxygen cannot keep up with the consumption of oxygen by the oxidation
reactions, so that the concentration of oxygen decreases. Note that re-
action sites "A" and "B" are exposed to a vapor phase*; that is, there is
a continuous vapor path to the source of oxygen and the reaction site
itself is exposed to vapor. Oxygen can, therefore, be transported to
these reaction sites through the vapor phase.
Point "C" on the other side of the high water table, is under water of
essentially zero dissolved oxygen during the high water period. Under
Sese conditions no oxidation occurs and point "C" is not a reacts site.
During the low water period, if oxygen diffusion is sufficient to supply
oxygen to point "C", oxidation will occur at this point.
Removal of oxidation products from each of these reaction sites is by
different mechanisms. "A" is not near any water source that provides
Srect Removal. The slow diffusion of saturated solutions from "A" by
*The so-called "vapor phase" oxidation does not imply the absence of
liquid water which, according to Smith and Shumate (6) must be present
before oxidation can proceed. At the near 100 percent relative humidity
which exists in an underground mine, the pores and capillaries of the
pyritic material are full of a saturated aqueous phase.
51
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the "weeping" mechanism eventually carries the products of oxidation to
the effluent stream. Point "B" is on the extension of a fracture in the
sandstone overburden which is a water flow channel during periods of
heavy precipitation. Oxidation products are periodically washed from
"B" and carried by the percolation mechanism to the effluent water.
Point "C" is flushed of its oxidation products as the water table rises
and falls during the hydrological year. Oxidation products do not build
up to the extent reached at Point "A" which is never subjected to direct
removal by water, but do reach a higher concentration than Point B which
is washed by percolation at more frequent intervals.
Reaction site "B" as defined in this discussion is a very unique point.
Most reaction sites would not be on a flow channel, but some distance
away—varying from a fraction of an inch to several feet—from direct
contact by flowing water. In other words, the overall removal rate of
oxidation products from most sites is a combination of mechanisms: diffu-
sion and percolation, plus flushing if affected by rise and fall of the
water table.
The data collected from the auger holes and McDaniels mine will be dis-
cussed within the framework of this brief, qualitative description of
kinetic factors which affect acid discharge.
Auger Holes
The outstanding feature of the discharge data from the seven auger holes
is their individuality. Although one might expect Holes 1, 2A, and 2B
to be different, Holes 3? ^3 55 and 6 are about as physically identical
as one can reasonably expect. However, large differences in flow rates
and acid concentration were observed. Acid and sulfate loads were not
as different as flow rates or concentrations taken individually, but here
also the differences were greater than anticipated.
The most unique auger hole is No. 5- Flows (see Table XIII) are much
lower than Holes h and 6 which are located on either side of No. 5. The
probable explanation is that Hole 5 stays in the coal or, in other words,
above the clay for almost all of its length, contrary to holes k and 6.
The reason this influences discharge rates is explained below.
Observations made in mines and auger holes in the Middle Kittanning (No.
6) coal, as well as reports of miners who have worked the area, indicate
that the major water flow into the mines is through partings between the
coal and clay bottom. It may be seen from Figs. 10, 11, and 12 that only
the last 50 feet of Hole 5 intercepts this water flow between the coal
and clay, while in Holes k- and 6, over 120 feet are in the clay. Also
the coal seam is more highly fractured near the front of the auger holes,
so that the water flow from the sandstone overburden through the coal to
the coal-clay parting would be greater near the entrance, where Holes h
and 6 are in the clay and Hole 5 is entirely in the coal.
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The only obvious relationship among the holes is the relative seasonal
change in flows, concentration, and acid loads (see Figs. 15-21). While
absolute values differ greatly, the shapes of the curves, or relative
acid loads, are similar.
Effect of Asymmetry
With the general slope or dip of strata which exists in this area as
evidenced in Figures 6 through 12, there will be some degree of nonuni-
formity or nonsymmetry in drainage areas covered by the auger holes.
For example, all other factors being equal, Hole k will drain more area
on the up-dip side of the hole than on the down-dip side. The degree
of drainage asymmetry will depend on the level of the water table between
the holes as well as the entry point of water into the holes. If highly
asymmetrical, the drainage into (for example) Hole k could originate
from pyritic material oxidized by oxygen entering from Hole 3. Since
lateral diffusion of oxygen or other gaseous components would be symmet-
rical about the center-line of the auger hole it enters, and drainage is
not symmetrical, the effect of a change in gas phase composition imposed
in one auger hole may influence the discharge of the hole on the down-
dip side. Although we do not believe the drainage asymmetry is great
enough to produce a significant distortion in acid or sulfate loads in
two adjoining holes, this possibility will be checked when the holes are
sealed by adding a gaseous tracer such as helium or ethylene oxide to
Hole h and determining the relative amount dissolved in the discharges
from Hole 33 ^, and 5-6 (see below). If the quantity discharged from
3 and 5-6 are the same, there is no effect of asymmetry on drainage. If
there were none of the tracer in Hole 3 and as much in 5-6 as in Hole U,
this would indicate all drainage down-dip of Hole k goes to 5-6.
Another way of estimating the relative drainage area serviced by each
hole is in terms of acid or sulfate load (as Ibs/day) from each hole.
The penetration of oxygen into the different pyrite-bearing strata will
be symmetrical about the center line of the hole, the depth of penetration
depending on the oxidation rate, oxygen diffusivity, and porosity of the
strata. Oxygen penetration and therefore pyrite oxidation will be shown
(see Section 7D) to extend at least 15 to 25 feet into the hill. The
extent of oxygen penetration may be termed the hole's "reactive volume".
This "reactive volume" should be proportional to the hole depth since
oxygen diffusion rate is essentially uniform in a specific stratum
throughout the test site. If drainage were also uniform, the acid load
from the holes would be proportional to depth of the hole since the same
drainage area would produce the same acid load in the discharge.
Sulfate loads are approximately proportional to depth for Holes 1, 2A,
2B, 3 and k-, indicating reasonably uniform drainage. However, when Holes
5 and 6, which have the same depth, are compared, the sulfate load from
Hole 6 is from five to ten times greater than Hole 5.
53
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If Holes 5 and 6 are considered as a unit, that is if the sulfate load
from Hole 5 plus Hole 6 is compared to that from the other holes, the
combined sulfate load is approximately that which would be expected for
a 200 ft. plus 200 ft. = 1+00 ft. hole. The fact that Hole 5 does not
enter the clay until the last 50 feet, and therefore does not intercept
the major water flow path as explained above, probably accounts for the
difference in drainage area serviced by Hole 5 and Hole 6.
Based on these observations, it is possible to use the holes as sets as
originally intended; i.e. as comparable experimental units. Set A would
be Holes 1 and 2A-2B and Set B Holes 3, k and 5-6. One hole from each
set could be used as a reference hole and the others used for different
experiments.
Steady-State Conditions
Data from the auger holes show that they have not yet reached steady-
state conditions. Acid loads for corresponding periods of the hydrologic
year are increasing drastically (see Table IV). Considering the response
time observed in the McDaniels mine (see Section 7D) steady state is not
to be expected for several years. In the case of the auger holes, build-
up of oxidation products in areas not subject to periodic flushing has
not reached the point where the removal mechanisms have attained a yearly
rate equivalent to that of formation. Until the removal per year is
equal to the yearly formation, annual acid and sulfate loads will increase.
It would be ideal to collect base rate data for several years until steady
state conditions are reached. However, valuable time would be lost.
Therefore we recommend that three of the five units available be used
as "reference" mines, rather than only one, as originally proposed. By
this means it will be possible to correct for the changes in relative
acid loads which will occur. With the non-uniform drainage patterns
observed, relative acid loads will change during the approach to steady
state since areas of higher oxygen concentration will reach steady-state
concentrations of oxygen products more rapidly than remote areas. There-
fore the holes servicing the high oxygen areas will not only reach steady-
state sooner, but their relative sulfate loads, compared to that of the
slower holes, will change with time. Thus the concept of comparable exper-
imental units is not valid unless this change in relative sulfate loads
is determined by using two and preferably three holes as reference mines.
While this procedure may not provide quantitative answers to change in
relative loads, it will at least provide an indication of the error
introduced by assuming a constant ratio of sulfate or acid loads.
McDaniels Mine
Discharge data from McDaniels mine show a surprisingly slow "time response"
to imposed changes in atmosphere within the mine. When the plan to main-
tain a continuous positive pressure of nitrogen was first conceived, we
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expected that results due to the change in oxygen concentration would
reach steady state values in a few months. Data collected to date indi
cate this time period will be several years. For example, the McDaniels
mine has been maintained at less than 1 percent oxygen since September,
1969--one year, at the time of this writing. Acid loads have decreased
to 60 or 70 percent of the values observed during corresponding flow
periods of the previous year. This is approximately one-half the de-
crease to be expected when steady-state is reached. Maintaining less
than 1 percent oxygen concentration in the vapor phase should cause the
acidity of the discharge to drop to a relatively constant value under
25 ppm. Referring to Table III, this would correspond to an average
acid load varying from 0.10 Ib/day for the high flows in May, to 0.0^
Ib/day for the low flows in late Fall. The figure of 25 ppm acid is
based on 2 to 3 ppm dissolved oxygen in ground water entering the pyritic
material around the mine, plus oxidation due to the (less than) 1 percent
oxygen in the mine.
The mine and its "reactive volume" may be considered a storage area for
pyrite oxidation products. If all oxygen to the mine could be eliminated
so that no further oxidation would occur, the removal of stored products
may be approximated by the familiar "exponential decay" curve. Assuming
that ko percent of the remaining products are removed per year as indi-
cated by the past year's data, four and one-half years would be required
to remove 90 percent of the oxidation products present at the time oxygen
was eliminated from the mine.
Referring to the conceptual model described in Section 7B, the time re-
sponse data confirm that the majority of reaction sites are not on or
near water flow channels feeding the effluent stream, but are instead
some distance away from flowing water. If the reaction sites were
located where direct removal of oxidation products occurs, time response
would be measured in weeks rather than years. These data also confirm
the "vapor phase" oxidation concept; that is, the reaction sites are
exposed to a vapor, rather than a continuous liquid, phase. Since one-
quarter inch of water offers the same resistance to molecular diffusion
as one mile of air, mass transport kinetics require a vapor phase trans-
port path for oxygen. Oxygen transport rates in a submerged liquid
environment are too low to account for the acid loads observed in
McDaniels mine or the auger holes.
The concentration gradient of oxygen indicated by the model has also
been observed both directly and indirectly. Air samples taken from
drill holes ko feet back of the coal face show a definite oxygen concen-
tration, although the actual numerical values are not quantitatively
reliable. Change in water quality with distance from the working face
is also an indication of the oxygen concentration gradient. Water taken
from Well No. 6 (see Fig. l) 120 feet from the working face is essenti-
ally the same as ground water in the area; pH = 6.0, alkalinity = 10 ppm,
sulfate = 55 ppm, while the water sampled from Well No. 2, 30 feet from
the face, taken at the same time, had a pH = 5.8, acidity of 15 ppm, and
sulfate of 125 ppa. These data demonstrate that pyrite is being oxidized
55
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in remote areas, well removed from the working face of the mine, access-
ible only to oxygen transported through the vapor phase. The quantity
of dissolved oxygen in ground water is too small to account for the
amount of oxidation products found in the water from the wells or bore
holes.
Principle Reaction Zone
The zone of greatest reactivity in the Middle Kittanning (No. 6) coal
seam is the shale layer between the sandstone overburden and the coal.
This strata contains 9 "to l6 percent (as $S) pyritic sulfur. But more
important, this shale layer has a high void volume, or porosity, as ob-
served during drilling operations when drilling water was lost as soon
as the shale layer was entered. With the high void volume, oxygen dif-
fusion through this strata is high. The exposed surface of pyrite per
unit volume of shale would also be high due to porosity and high pyrite
content. In addition, the shale layer is the uppermost pyrite-containing
strata so that more of it would be above the water table than any other
pyritic strata.
Removal of Oxidation Products
The individual sample data (Appendix l) provide further information on
the location of reaction sites and mechanism of product removal. Although
not entirely consistent, the acid or sulfate load is generally more con-
stant than either flow rate or concentration over a one or two week
period. This is due to the essentially constant diffusion or "weeping"
rate for transport of oxidation products to the effluent stream. Although
the solutions transported by diffusion are saturated, they are diluted
by water percolating through the flow channels which intercept the diffu-
sion paths. This water is further diluted by water entering between the
coal and the underlying clay to produce the final discharge. An increase
in water flow into the mine, such as might occur after a day or two of
light rain, will simply act to dilute the normal, steady flow of oxidation
products and the acid load will stay nearly constant. However, if heavy
or prolonged precipatation occurs so that secondary flow channels are
used for percolation and the water table rises, then a greater portion
of the reactive volume is subject to direct removal by flowing water,
the diffusion paths from reaction sites are shortened and the acid loads
will increaseo This is the situation which exists in the Spring when
acid loads reach their maximum values. As water flows recede, fewer flow
channels are used, the water table drops, diffusion paths again lengthen,
and acid loads reach their minimum values until a "steady-state" diffusion
rate is again established. This accounts for the low acid loads in late
Summer and early Fall seen in Figures lU through 21.
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Microbiological Effects
From the standpoint of biological catalysis, two important environmental
conditions which exist at the reaction sites are;
a) relatively little water compared to surface area of pyrite
exposed, i.e., low water-to-pyrite ratio, and
b) highly concentrated, high acid solutions in contact with
pyrite.
Both of these conditions make it difficult to believe that microbial
catalysis of pyrite oxidation can be a significant factor in the formation
of acid mine drainage,, As pointed out by Smith and Shumate (6), oxidation
of pyrite may occur by two independent mechanisms: l) Oxygenation, in
which oxygen is directly adsorbed on a pyrite surface and becomes the
immediate oxidizing agent (electron acceptor), and 2) ferric ion oxidation
in which ferric ions produced in solution by aerobic microbial activity
are adsorbed on the pyrite surface and become the immediate oxidizing
agent. For the oxygenation reaction the major variable (for a given
pyrite surface area), is the partial pressure of oxygen. At low pH's
neither pH nor solution concentrations have a significant effect on oxy-
genation rate. For the ferric ion oxidation reaction, the rate of pyrite
oxidation is determined by the ferric/ferrous ratio in solution as well
as solution concentration and pH (see Ref. 6 for a more detailed discus-
sion of the kinetics of this reaction).
Lau, et al.(2) have shown experimentally that both low water-to-pyrite
ratios and a high concentration of acid and salts in solution reduce the
number and activity of bacteria to the point that the ferric ion oxidation
of pyrite is insignificant compared to oxygenation„ Both of these con-
ditions pertain to reaction sites in underground mines where, as shown
above, vapor phase oxidation must be involved.
At first glance, it would appear that the importance of microbial oxida-
tion could be quickly and positively identified by simply analyzing the
solution at the reaction site, i.e.,the water in contact with the pyrite
surface. However, such an analysis is not possible simply because the
quantity of water on the pyrite surface is much too small to either
collect or analyze.
The closest approach to direct analysis of the ferric/ferrous ratio at
the pyrite surface is obtained by washing the surface of a pyritic sample
(an exposed coal face for example) with dilute acid and analyzing the
wash water. The ferric/ferrous ratio obtained thereby could be much
higher and in no case will be less than that ratio which exists in solu-
tion at the reaction site, for the following reasons: the majority of
the salts collected in the wash will originate from solutions which are
not in contact with the surface of pyrite. Even insignificant microbial
activity—that is, insignificant in relation to oxygenation of pyrite—
could raise the ferric/ferrous ratio in these solutions not in contact
57
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with pyrite to very high levels. But these solutions have little effect
on the overall pyrite oxidation rate for three reasons: l) there is
little solution and therefore few ferric ions involved, 2) according to
the stoichiometry, 1^4 mole of ferric ions are required to oxidize one
mole of pyrite (FeS2), and 3) the diffusion rate of these solutions is
very slow so that the rate at which solutions of high ferric/ferrous
ratios move to the pyrite surfaces is low.
Three different sections of coal in Auger Hole No. 2B were washed with
distilled water and the washings collected. The ferric/ferrous ratios
of the washings were 0.10, 0.^3, and 0.28 (9.^, 30, and 22 percent ferric
iron). The section having the highest pyritic sulfur content had the
lowest (0.10) ferric/ferrous ratio, while the higher ferric/ferrous ratios
were found in the washings from the coal section having low pyrite con-
centration. This is to be expected since coal of higher pyrite content
will have a greater percentage of its adsorbed water in contact with a
pyrite surface.
The only real "evidence" based on field observations, to support the
widely held premise that bacteria have a major role in the formation of
acid drainage is that the effluent from many underground mines has a
high concentration of Ferrobaccillus ferrooxidans and a high ferric/
ferrous ratio. Obviously bacteria are active or the ferrous ions would
not be oxidized to ferric at the low pH's found. For example, the dis-
charge from McDaniels mine when under 10 to 20 percent oxygen has a ferric/
ferrous ratio of 10/1 to 20/1 (90 to 95 percent" ferric).
However, as pointed out before, the effluent water is in no way represen-
tative of the water in contact with reaction sites. Another important
point should be made: the bacteriaHy enhanced ferrous-to-ferric oxida-
tion reaction occurs in the aqueous solution, not on the pyrite surface
(see Reference 6). With these points in mind, the role of bacteria and
their influence on discharge water from McDaniels mine and auger holes
can be explained.
Let us first state that the high ferric-ferrous ratio observed in the
discharge from McDaniels mine and the auger holes is generated after
contact with pyritic material, and then prove the validity of this state-
ment by examining data obtained.
According to Smith and Shumate (6), if the ferric-ferrous ratio of a
solution in contact with pyritic material is less than 0.3 (2k percent
ferric) the oxygenation rate in air is five times greater than the ferric
ion oxidation rate. At a ferric/ferrous ratio of 2.2 (70 percent ferric)
the oxygenation and ferric ion oxidation rate are approximately equal.
The important question to be answered is where the water of high ferric/
ferrous ratios is found. If ferric/ferrous ratios above 0.3 are gener-
ated after the water passes through the pyritic material these waters do
not have a significant effect on the rate of pyrite oxidation or there-
fore on acid discharge. Data described below indicate that the high
ferric/ferrous ratios observed in effluent water from McDaniels mine and
58
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the auger holes is generated in water ponded on the clay floor, out of
contact of pyritic material, and that the water coming through the work-
ing face of the mine into the ponded area has a ferric/ferrous ratio
under 0.25 (20 percent ferric).
The ferric/ferrous ratios of the auger hole discharges increase with
longer residence time in the holes. For example, water flowing from
Hole No. 6, before weekly pumping was started, had a ferric/ferrous ratio
varying from 3.0 to 9.0. Average residence time of water without pumping
was approximately a month. When weekly pumping operations were started,
the ferric/ferrous ratio dropped to 0.25 (20 percent ferric).
When other auger holes were pumped, the water that flowed into the hole
immediately after the hole was pumped down had a ferric/ferrous ratio
under 0.3, even when the pumped water had a ratio over 5.0.
These data show that the major increase in ferric-ferrous ratio occurs
in the ponded water and that the ferric/ferrous ratio of water entering
the ponds is relatively low. Data obtained from McDaniels mine after
nitrogen was added and the oxygen concentration was reduced to less than
1 percent indicate that the ferric/ferrous ratio of water behind the
working face, on the reaction sites, has a low ferric/ferrous ratio.
As noted above, the effluent from McDaniels when the mine was open to
air had a ferric/ferrous ratio above 10. When oxygen dropped below 1
percent, the ferric/ferrous ratio dropped below 0.1 (10 percent ferric)
immediately. The salts appearing in the effluent when the mine is under
nitrogen were formed during the previous period when the oxygen concen-
tration was 21 percent. The ferric/ferrous ratio of these products was
determined by the condition prevailing when formed. While some reduction
of ferric ions is likely when solutions are transported over pyrite to
reach the effluent water, reduction to less than 10 percent ferric is
very unlikely if the initial ferric-ferrous ratio were over 0.25 (20
percent ferric). From these data it would appear that the ferric/ferrous
ratio of solutions behind the working face have ferric/ferrous ratios
around 0.1 or 0.15.
Other analyses of the underground pyritic system will lead to the same
conclusion--ferric/ferrous ratios of water at the majority of reaction
sites are too low to make ferric ion oxidation significant. The steady-
state ferric/ferrous ratio reached in a solution in contact with pyrite
will depend on the relative rates of two reactions: l) rate of ferric
ion generation by microbial oxidation of ferrous ions and 2) the rate of
ferric ion reduction by reaction with pyrite. Increasing the number or
activity of bacteria relative to the surface area of pyrite exposed to
the solution will increase the ferric/ferrous ratio„ That is, if a rela-
tively constant concentration and activity of bacteria are assumed per
unit volume of solution, then the greater the volume of water per unit
surface area of exposed pyrite, the higher the ferric/ferrous ratio in
solution will be. Also, the closer the solution is to a pyrite surface,
the lower the ferric/ferrous ratio will be up to the point where ferric
ions are so close to the pyritic that no resistance to mass transfer is
presento In other words, solutions in direct contact with a pyritic sur-
face have the lowest ferric/ferrous ratio. As solutions become more
dilute and further removed from contact with pyrite, ferric/ferrous ratios
increase. ,__
-------
Let us trace the path of water in contact with a reaction site. Regard-
less of its location the water (solution) will tend to diffuse and "weep"
downward under the influence of gravity. As the solution adsorbs moisture
from the air the volume increases and the solution moves away from the
pyrite surface. The ferric/ferrous ratio will increase if any microbio-
logical activity is present. Additional contact with pyritic material
may be made, but increased volume of solution will reduce contact time
so that the overall or general trend will be an increase in ferric-ferrous
ratio with movement toward the flow channels. Once the solution does
reach the point where it is either removed by percolation or flushing,
dilution as well as pH would increase, allowing further increase in the
ferric/ferrous ratio of the water with which we started. This shows that
the ferric-ferrous ratio of water entering the effluent stream of a mine
has, on the average, the highest ferric/ferrous ratio to be found in
water which contacted pyritic material on its way to the discharge stream.
Experimental data have shown that water behind the working face of a
mine has a low ferric/ferrous ratio (0.25 or 20 percent ferric or lower).
At such ferric/ferrous ratios, microbial induced oxidation is small com-
pared to oxygenation. Therefore acid mine drainage produced as the
result of microbial activity is small compared to that produced by oxy-
genation, which is independent of microbial activity.
Discussion of Future Work
One of the general objectives of this and future work at the McDaniels
research complex is to develop a fundamental understanding of the kinetics
of mine drainage in underground pyritic systems. This encompasses both
the kinetics of formation (i.e. pyrite oxidation) and the removal or
transport of pyrite oxidation products to the receiving stream.
The basic kinetics of formation have been determined in a laboratory.
The application of these basic data require a knowledge of the range of
environmental conditions which exist at reaction sites in a natural system.
A quantitative model of a natural system requires that the relative number
of reaction sites exposed to a given set of environmental conditions be
known. A model, based on the hydrologic and geologic features of the
area under study, can be quantified only on the basis of meaningful field
data.
Field data are equally important to evaluating removal mechanisms and
their kinetics. One of the major unknowns in underground pyritic systems
is the relative importance of the different product transport mechanisms.
Here again, the only logical procedure to use in evaluating these mech-
anisms is interpretation of data from real systems.
To be useful, field data must be capable of precise interpretation. The
following example may be used to illustrate the importance of good data.
Following the change in acid load caused by decreasing oxygen concentra-
tion to zero is one method of evaluating removal mechanisms. Without
60
-------
the formation of oxidation products, acid load due to diffusion and
"flushing" mechanisms (after peak flow) drop to zero, while the load
due to percolation would stay approximately the same for at least six
months to a year (since the percolate is a saturated solution). Only
a 30 to kO percent change in acid load occurs during the first year
after oxygen concentration is dropped to zero. Hydrologic variations
from one year to the next may cause a similar change in acid load.
Therefore, in order to determine the change in acid load due to change
in oxygen, some way of separating the effect of hydrologic conditions
and oxygen composition is necessary. The multiple mine facility pro-
vides the means of determining change in acid load due only to hydrologic
variation since the only variable examined in the reference mine is the
hydrologic conditions. There is no other type of experimental facility
capable of providing data in a reasonable period of time that may be
interpreted with the precision required to determine mine drainage
kinetics of underground pyritic systems.
61
-------
ACKNOWLEDGMENTS
The authors, Professors Edwin E. Smith, Department of Chemical Engineer-
ing, and K. S. Shumate, Department of Civil Engineering appreciate the
help given by the many students and faculty who have assisted in the
development of the McDaniels research complex.
The valuable assistance of part-time student employees, who spent many
long Saturdays in all kinds of weather "at the mines" is sincerely
appreciated. We are particularly indebted to James Wood, Mark McLaughlin,
William Syverson, and Michael Neibler for their reliable support.
Much of the analytical work was ably performed by or under the direction
of Mr. Paul Smith, Research Associate, Engineering Experiment Station.
The financial support of the Federal Water Quality Administration
through Contract lU-12-97 (program #1*4-010 EXA) and the help provided
by Mr. Ronald D. Hill, project officer, is gratefully acknowledged.
63
-------
REFERENCES
1. Hillebrand, Lundell, Bright, Heffman, "Applied Inorganic Analysis,"
2nd Edition, J. Wiley & Sons, Inc., New York (1953).
2. Lau, C. M., Shumate, K. S., Smith, E. E., "The Role of Bacteria in
Pyrite Oxidation Kinetics," Third Symposium of Coal Mine Drainage,
Mellon Institute.
3. Scott, W. W., "Standard Methods of Chemical Analysis," 5th Edition,
Vol. I, p. 908, D. Van Nostrand Co., Inc., New York (1939).
k. Shumate, K. S., Smith, E. E., Brant, R. A., "A Model for Pyritic
Systems," ACS Division of Fuel Chemistry Symposium, Preprints,
157th National Meeting 13, No. 2 (1969).
5. Shumate, K. S., Smith, E. E., "Development of a Natural Laboratory
for the Study of Acid Mine Drainage Production," Second Symposium
on Coal Mine Drainage, Preprints, Mellon Institute, Pittsburgh,
Pa., (May, 1968).
6. Smith, E. E., Shumate, K. S., "Sulfide-to-Sulfate Reaction Mechan-
ism," Water Pollution Control Research Services, 1^010 FPS 02/70
(1970).
7. Smith, E. E., Shumate, K. S., "Development of a Natural Laboratory
for the Study of Acid Mine Drainage Production," Final Report,
U. S. Department of Interior (1968).
LIST OF PUBLICATIONS
Shumate, K. S., Smith, E. E., "Development of a Natural Laboratory for
the Study of Acid Mine Drainage Production," Second Symposium on
Coal Mine Drainage, Preprints, Mellon Institute, Pittsburgh, Pa.,
May 1^-15, 1968.
Shumate, K. S., Smith, E. E., Brant, R. A., "A Model for Pyritic Systems,"
ACS Division of Fuel Chem. Symposium, Preprints, 157the National
Meeting 13, No. 2, (1969).
65
-------
GLOSSARY
ACID (AM) SULFATE) LOAD
Rate of acid (or sulfate) discharged in units of pounds per day.
Acidity expressed in pounds of equivalent CaCOs.
FERRIC ION OXIDATION
One of the two basic modes of pyrite oxidation„ The other mode
is "oxygenation." Ferric ion oxidation occurs when a ferric ion
is adsorbed on a pyrite surface, accepts an electron from the
pyrite and is thereby reduced to the ferrous state. Ferric ions
are the immediate oxidizing agent. When oxygen is adsorbed and
becomes the immediate electron acceptor, the oxidation mode is
termed oxygenation.
QXYGEKATION
(see Ferric Ion Oxidation)
REACTION SITE
Surface of pyrite exposed to oxygen in which the oxygen may be
present as dissolved (inaqueous solution) oxygen or in a humid
atmosphere.
RESPONSE TIME
(For the type of analysis used in this report) Time that a system
requires to reach (e.g. 90$ of) steady-state after a step change
in operating conditions.
SULFATE LOAD
(see Acid Load)
VAPOR PHASE OXIDATION
Oxidation which occurs when the reaction site is exposed to a con-
tinuous vapor phase so that the transport of oxygen is through a
gaseous rather than liquid or solid phase. This does not imply
the absence of liquid water which is always present as adsorbed
water in a natural system,,
67
-------
APPENDIX I
DISCHARGE DATA
Table VII
1965 MCDAMTFLS MJNF DATA
DATE
FLDWjGPO
ACID,
AUG
AUG
AUG
AUG
AUG
AUG
SEPT
SEPT
SFPT
SEPT
SFPT
SEPT
SFPT
SFPT
SEPT
OCT
OCT
ncT
GCT
MOV
NOV
NOV
DEC
OFC
DEC
DFC
OFC
1
1
7
9
24
2
2
3
1
1
2
2
1
2
3
1
7
1
1
?
2
5
6
1
1
2
7
a
o
5
6
1
3
Q
5
3
0
6
3
0 •
4
1
8
1
9
324.
31 2.
292.
274.
795.
29?.
29?.
777.
284.
287.
286.
307.
290.
793.
295.
793.
278.
307.
283.
284.
790.
2ff6.
295.
289.
?83 .
731 .
781.
0
0
0
0
o
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
o
n
0
65
65
55
55
55
59
70
70
59
64
60
73
78
73
77
8?
71
100
77
89
op
98
17?
116
130
119
137
.0
.0
. 0
. 0
. 0
. 0
.0
. 0
.0
.0
. 0
.0
. 0
. 0
.0
. 0
.0
.0
. 0
.0
. 0
. 0
.0
. 0
.0
.0
. o
-------
Table VII (continued)
1966 MCDANIELS MINE DATA
DATE
FLOVv'»GPD
ACID,PPM S04,PPM
JAN
JAN
JAN
FEB
FFB
MAR
MAR
MAR
MAR
APR
APR
APR
APR
APR
MAY
MAY
MAY
MAY
JUNE
JUNE
JUNE
JUNE
JUNE
JULY
JULY
JULY
AUG
AUG
AUG
SEPT
SEPT
SEPT
ncT
ncT
TCT
OCT
OCT
ncT
OCT
MOV
MOV
NOV
vov
DEC
DEC
DEC
DEC
DEC
8
15
22
12
26
5
12
18
25
2
9
16
23
30
7
14
21
27
4
11
15
25
29
8
14
21
6
11
26
2
16
30
6
8
12
15
18
21
29
5
12
l
-------
Table VII (continued)
1967 MCOAMTELS MINE OATA
DATF
F L 0 W, G P D
AT ID, PPM S04*PPM
JAN
JAN
JAN
MAR
APR
APR
APR
APR
APR
MAY
MAY
MAY
MAY
JUNE
JUNE
JUNE
JUNb
JUNE
JUNE
JUNE
JULY
JULY
JULY
JULY
J UL Y
AUG.
AUG
AUG
AUG
A UG
^EPT
SEPT
SEPT
SEPT
PCT
nc.T
OCT
nr.T
^CT
NOV
NOV
MUV
NGV
PEC
DEC
DEC
DEC
7
14
21
25
1
8
15
22
2^
6
13
20
27
3
10
14
16
20
24
27
1
8
13
15
?0
10
12
19
23
26
2
q
16
23
1
11
14
21
28
4
11
18
25
2
9
16
23
211.0
214.0
207.0
342.0
339.0
375.0
404.0
398.0
368.0
377.0
485.0
502.0
477.0
503.0
444.0
404.0
400.0
368.0
334.0
318.0
306.0
274.0
?66.0
24°. 0
240.0
202.0
196.0
199.0
198.0
195.0
192.0
1 92.0
188.0
1 R 7 . 0
104.0
184.0
187- 0
184.0
185.0
1 P 5 . 0
182.0
188.0
184.0
181 .0
179.0
184.0
182.0
75. 0
80,0
60. 0
128. 0
212.0
124. 0
112.0
1 32.0
84. 0
102.0
108.0
96. 0
76.0
70.0
65.0
60.0
56. 0
68.0
68.0
62. 0
54.0
58.0
44.0
58.0
50. 0
32.0
42. 0
34. 0
50.0
34. 0
42. 0
49.0
46. 0
53.0
66. 0
72.0
70. 0
76.0
86. 0
98. 0
86. 0
82. 0
100. 0
94.0
88.0
^2.0
86.0
71
-------
Table VII (continued)
1068 MC.OANIFLS MINE DATA
DATE
AGIO,
S04
JAN
JAN
JAN
FER
FER
FFB
FFR
M AP
MAR
MA«
MAP
MAR
APR
APR
APR
APR
MAY
MAY
MAY
MAY
•MAY
JUNE
JUNE
JUNE
JUNE
JUNF
JULY
JULY
JUL Y
JULY
Aur,
AUG
A IK;
SEPT
SFPT
SEPT
6
20
?7
3
1.0
17
24
2
O
16
?5
?S
6
q
13
?7
4
1 1
I ft.
25
27
1
6
14
18
28
1
5
10
26
2
0
23
10
13
17
230.0
237.0
288.0
775.0
177.0
105.0
105.0
LH9.0
1^4.0
240.0
254.0
405.0
345.0
345.0
300.0
390.0
330.0
345.0
495.0
675.0
788.0
600.0
455.0
300.0
188. n
203.0
248.0
203.0
315,0
270.0
203.0
203.0
263.0
248.0
233.0
2 3 T . n
8fi.O
88.0
06.0
270.0
160. 0
1 46 . 0
106. 0
114. 0
106.0
246. 0
200.0
248 .0
280.0
240. 0
204. 0
318. 0
?60.0
2«5. 0
325.0
201.0
316. 0
246. 0
200. 0
100. 0
2?5.0
181.0
i n.n
1 84.0
186. 0
181.0
171.0
161.0
150.0
115.0
1 4 ?_ . 0
1 36. 0
72
-------
Table VII (continued)
MCOANIELS MIME DATA
DATE
FIOW,GPO
AC 10, PPM S04,PPiM
SEPT
SFPT
OCT
ncT
ncj
OCT
OCT
NQV
NOV
NOV
NOV
NQV
NOV
NOV
NOV
NOV
DFC
DEC
DFC
DEC
DFC
DEC
DEC
DFC
20
24
8
12
19
26
29
2-
5
9
12
16
19
23
26
30
5
7
10
17
20
23
28
31
240.0
221.0
2 1 3 . 0
220.0
19P. 0
193.0
17Q.O
160. n
149.0
198.0
1 9 P . 0
1 9 R . 0
202.0
202. 0
190.0
205.0
198,0
200.0
200.0
198.0
?07.0
204.0
224.0
207.0
115.0
1 13. 0
112.0
116.0
1 10. 0
95.0
105.0
Q7. 0
90.0
125. 0
100. 0
100. 0
92.5
97.5
P7.0
R2. 0
97.0
97.0
95. 0
100.0
95.0
125. 0
140.0
95.0
1 76. 0
17ft.0
167.0
179.0
73
-------
Table VII (continued)
1969 MCDANIELS MINE DATA
DATE
FLOWtGPD
AC ID,PPM S04,PPM
JAN
JAN
JAN
JAN
JAN
FEB
FEB
FFfi
FEB
f EB
MAR
MAR
MAR
MAR
MAR
APR
APR
APR
ADR
APR
MAY
MAY
MAY
MAY
MAY
MAY
MAY
MAY
JUNE
JUNF
JUNE
JUNE
JUNF
JULY
JULY
JULY
4
11
18
25
28
1
8
15
22
25
L
3
15
22
29
5
a
12
22
26
3
6
10
13
17
2 ft
20
31
6
9
12
21
26
3
17
24
207.0
212.0
182.0
231,0
251.0
289.0
274.0
274-. 0
243.0
224.0
224.0
724.0
194.0
176.0
285.0
326.0
327.0
31V.O
440.0
411.0
356.0
334.0
422.0
49 f.u
378. 0
347.0
365.0
0.0
319.0
296.0
294.0
315.0
282.0
274.0
226.0
23J .0
137. 0
204.0
92. 0
157. 0
135.0
235. 0
265.0
195.0
155.0
182.0
145. 0
145.0
135.0
140. 0
280.0
240.0
270. 0
260.0
260.0
232.0
212.0
195. 0
282.0
235. 0
18"?. 0
1 79.0
197.0
173. 0
150.0
140. 0
135.0
127. 0
125.0
110.0
102.0
107.0
172.0
242.0
225.0
324.0
335.0
276.0
245.0
274.0
240.0
234.0
226.0
234.0
360.0
332 .0
359.0
343.0
350.0
331.0
2^8.0
292.0
382.0
322.0
286.0
243.0
288.0
305.0
23Q.O
237.0
224.0
227.0
212,0
206.0
199.0
1 8 6 -. 0
-------
Table VII (continued)
1969 MCOANIFLS .MINT OATA
DATE FLOWtOPD AC ID,PPM S04,PPM PH
JULY
JULY
AUG
AUG
AUG
AUG
SFPT
SEPT
SFPT
OCT
OCT
DCT
OCT
NOV
N'OV
NOV
NOV
DFC
DEC
28
30
8
15
?0
27
3
17
25
4
11
18
25
1
8
2?
29
6
20
266.0
260.0
240.0
236.0
260.0
205.0
Ifi5.0
193.0
193.0
176.0
176.0
160.0
220.0
213.0
180.0
1*2,0
160.0
1«0,0
180.0
9 y . o
95.0
77. 0
87. 0
95.0
82. 0
72.0
67. (}
65. 0
72.0
67.0
100. 0
67.0
6?. 0
60.0
57.0
62. 0
65. 0
55.0
191.0
183. 0
?OQ.O
178.0
182.0
164.0
155.0
155,0
148.0
148.0
148.0
148.0
141 .0
143.0
137.0
134.0
138.0
133,0
139.0
3.2
3.4
3.2
-------
Table VII (continued)
1970 MCDANIELS MINE DATA
DATE
FLOW,GPD
AClD,PPf: SG4,PPM
PH
JAN
JAN
JAN
JAN
FEB
F68
FEB
FEB
MAR
MAR
MAR
MAR
APR
APR
APR
APR
MAY
MAY
MAY
MAY
JUNt
JUNE
JUNE
JUNE
JULY
JULY
JULY
JULY
JULY
JULY
JULY
AUG
AUG
AUG
AUG
AUG
SEPT
SEPT
SEPT
SEPT
OCT
3
17
24
31
7
14
21
28
7
14
21
27
4
11
18
25
2
16
23
30
6
13
17
26
1
7
13
17
22
24
29
1
6
12
19
26
2
10
16
29
5
188
180
160
213
225
235
210
202
282
274
290
310
260
255
285
418
430
*
*
.
»
*
*
9
*
m
*
9
*
*
9
*
*
.
400.
365
420
365
330
285
320
242
272
272
242
242
270
234
270
250
258
251
219
231
250
243
243
220
*
m
*
*
*
*
,
•*
*
*
«
*
.
*
*
*
.
•
,
•
«
*
*
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
60
55
57
95
92
100
105
82
117
107
*
•
*
*
^
,
•
9
•
*
135.
110
145
140
132
175
157
155
142
135
105
105
105
83
87
90
75
80
85
75
75
80
87
92
75
65
67
77
67
80
55
•
*
•
•
*
»
*
.
*
•
•
*
*
*
*
•
*
*
*
*
*
«
•
.
•
•*
•
.
,
+
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
137.
129.
133.
174,
174.
173.
175.
151.
193.
181.
210.
190.
220.
216.
205.
250.
220.
207.
211.
196.
180.
183.
185.
199.
169.
165.
142.
155.
158.
154.
154.
153.
154.
160.
154.
151.
144.
145.
138.
128.
124.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
3
3
3
2
2
2
3
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
4
3
3
.25
.2
.2
,0
.95
.9
.85
.05
.94
.95
.9
,9
.9
.15
.45
.3
.25
.5
.25
.35
.0
.45
.45
.4
.4
.5
.75
.35
.7
.2
.8
. 35
.85
.95
.•9
.68
.8
.0
.22
.72
.68
76
-------
Table VIII
1969 AUGER HOLF 1 DMA
DATE
FLOW,GPD ACID,PPM S04,PPM
JULY
AUG
AUG
AUG
AUG
AUG
SEPT
SEPT
SEPT
SEPT
OCT
OCT
NOV
NOV
NOV
NOV
DEC
DEC
1970
JAN
JAN
JAN
FEB
FEB
FEB
FEB
MAR
MAR
MAR
MAR
APR
APR
APR
APR
MAY
MAY
MAY
MAY
30
4
8
15
20
27
3
10
18
25
11
25
7
8
22
?9
6
?0
AUGER
3
17
31
7
14
21
28
7
14
21
28
4
11
18
25
2
16
23
30
123.0
770.0
87.0
114.0
100.0
76.0
66. 0
60.0
52.0
58,0
68.0
61.0
61.0
75.0
1 14,0
81.0
175.0
1 11.0
HDLF 1
167.0
165.0
251.0
215.0
213.0
195.0
148.0
342.0
365.0
367,0
324.0
385.0
245.0
240.0
470,0
290.0
405.0
202.0
230,0
HATA
250.0
250.0
162.0
187.0
245.0
160.0
242
265
205
222
100,
102,
105,
65.
60,
65,
75. 0
110,
42,
200,
105,
140,
100.
60.
152.
145,
190.
115,
145,
100.
117-0
162.0
217. 0
237.0
177.0
160.0
,0
.0
,0
,0
,0
,0
,0
, 0
,0
,0
,0
,0
0
56R.O
645.0
557.0
501.0
572
475
591
637
562.0
587.0
507,0
437.0
426.0
426.0
386.0
386.0
381.0
362.0
424.0
339.0
493.0
378.0
404.0
358.0
310.0
370.0
355.0
404.0
332.0
351.0
323.0
343,0
320.0
424.0
434.0
382.0
355.0
2,75
2.72
3.0
2.7
2.7
2.83
2.8
2.7
2.7
2.5
2.8
3. 15
2.95
2.95
3.45
3,45
3.4
3.05
3.0
3.4
2.65
2.8
2.8
2.85
2.85
2,87
2.87
2.8
3.0
2.85
2.95
3.0
2.9
2.85
3.2
2.85
2.85
77
-------
Table VIII (continued)
1970 AUGER HOLE 1 DATA
DATE
FLQW,GPD ACID,PPM
SG4,PPM
PH
JUNE
JUNE
JUNE
JULY
JULY
JULY
JULY
JULY
AUG
AUG
AUG
SEPT
SEPT
SEPT
SEPT
OCT
6
13
26
1
7
13
17
22
6
12
19
2
10
16
29
5
137,0
105.0
92.0
104.0
100.0
106.0
98.0
88,0
106.0
182.0
106,0
61,0
107.0
107.0
122.0
64,0
180,0
237, 0
208,0
390.0
255,0
252.0
270.0
242,0
265,0
322,0
210.0
195.0
230.0
230.0
195.0
140.0
403.0
486.0
515.0
670.0
534.0
467.0
563.0
517,0
533.0
584.0
468,0
473.0
509,0
525.0
456.0
403,0
2,75
2,75
2.9
2.7
2.65
2.75
2.75
2.8
2.8
2.75
2.8
2,8
2,9
2.75
3.00
3.02
78
-------
Table IX
1969 AUGER HOLE ?A HAT A
DATE
FLOW,GPD AC1D»PPM S04-fPPM
PH
JULY 30
AUG 4
AUG 8
AUG 15
A UG 20
AUG 27
SEPT 3
SEPT 10
SEPT 17
SEPT 17
SEPT 25
OCT 4
OCT 11
OCT 18
OCY 25
NOV 1
NOV 8
NQV 22
NOV 29
DEC 6
DEC 20
1970 AUGER
JAN 30
JAN 17
JAN 24
JAW 31
FEB 7
FEB 14
FEB 21
FEB 28
MAR 7
MAR 14
MAR 21
MAR 28
APR 11
APR 18
APR 25
MAY 16
MAY 23
MAY 30
JUNE 13
JUNE 17
JUNE 26
JULY 1
JULY 7
JULY 17
AUG 12
AUG 19
SEPT 2
SEPT 16
SEPT 29
30. ?
8.2
4-2
2.2
4.2
?.4
4.8
1. 1
1. 1
1.0
1.0
1.6
2.8
2.0
2.0
2.2
n.5
2.0
2.5
6.0
HOLF 2A
9.6
10.6
12.0
28,0
19,4
28.0
25.0
21.6
31.0
47.0
35.0
35,0
30.0
33.0
44.0
14,0
13.0
3.0
14.0
12.0
7.0
12.0
10.0
7.0
4.2
847.0
1675.0
1191.0
967. 0
840.0
832.0
^5.0
787. 0
797. 0
500. 0
22.0
490.0
512. 0
350.0
430. 0
325, 0
227.0
305. 0
302.0
482.0
DATA
1510. 0
1155.0
1082.0
1110.0
1435.0
1662,0
1890.0
1355.0
1660.0
1442.0
1617.0
1520.0
1972.0
1240.0
1367.0
662.0
1300. 0
1005.0
910,0
895.0
1115.0
837. 0
1017.0
790.0
1665.0
1165.0
1222.0
980. 0
995.0
2484.0
2055,0
2011 .0
1620.0
1687.0
1637.0
1647.0
1701.. 0
1537.0
537,0
1435.0
1353.0
1 3 1" 3 . 0
1031.0
1255.0
964.0
692.0
917.0
940.0
1996.0
1841.0
1690.0
1600.0
1906.0
2010.0
2282.0
1679.0
1981.0
1778.0
1949,0
1786.0
2185,0
1524,0
1643.0
793.0
1526.0
1278,0
1236.0
1260.0
1505.0
1172.0
1478.0
1180.0
2108.0
1555.0
1698.0
1480.0
2.8
2.61
2.65
2.71
2.50
2.56
2.60
2.70
2.7
2.9
2. 5
2.75
?. P
2-9
2.85
2.^
3. 1
3. 1
3. 1
2.8
2.6
2.5
2.55
2.4
2,3
2,25
2.25
2.4
2.55
2.50
2.4
2.4
2.45
2.6
2.5
2.85
2.5
2.45
2.5
2.7
2.7
2.6
2.5
2.6
2,55
2,55
2.65
2.6
79
-------
Table X
1969 AUGER HOLE 23 DATA
DATE FLOW,GPO AC ID, PPM S04,PPM PH
OCT
SEPT
AUG
AUG
AUG
AUG
SEPT
SEPT
SFPT
OCT
OCT
OCT
NOV
NOV
NOV
MOV
PEC
DEC
4
25
4
p
20
27
3
10
17
11
18
25
1
P
22
29
6
20
10.
9.
40.
21.
24.
19.
15.
12,
9.
18.
37.
9.
9 f
33.
26.
35.
13.
72.
ft
6
I
1
3
q
0
5
9
5
0
2
6
5
0
0
1
1
15.
22.
68.
50.
60.
45.
42.
62.
47.
27.
242.
30.
7.
1 05.
115.
50.
30.
152.
n
0
0
o
0
0
0
o
n
0
0
0
0
0
0
0
0
0
252.
255.
331.
306.
266.
246.
263.
360.
313.
271.
299.
227.
363.
308.
227.
207.
361.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4.
3.
3.
3.
3.
3.
3.
3.
3.
4.
4.
5,
3.
2.
3.
3.
2.
14
71
27
42
6
4
7
8
0
05
1
05
Q5
5
B
q
1970 AUGER HOLE 2B DATA
JAN
JAN
JAN
JAN
FFR
FEB
FPB
FEB
MAR
MAR
MAR
MAR
APR
APR
APR
APR
MAY
JUNE
JUNE
JUNE
JUNE
JULY
JULY
JULY
AUG
AUG
SFPT
SEPT
SEPT
•3
17
24
3 1
7
14
21
2.8
7
14
21
1
1
1
1
1
1
60.
63.
86.
30.
35,
28.
30.
30.
84.
6
0
0
0
+
+
+
0
+
302. +
0V
ERFl. QW
28 OVERF
4
11
18
25
30
6
13
17
26
1
11
17
12
19
2
16
29
LOW
OVERFLOW
0V
ERF LOW
OVERF
0V
2
1
1
1
LOW
ERFLOW
20.
05.
51.
25.
52.
44.
51.
66.
82.
98.
40.
22.
2«.
0
0
0
0
0
0
0
0
0
0
o
4
6
120,
175.
52.
130.
55.
30.
50.
40.
52.
27.
25.
32.
50.
15.
17.
20.
17.
35.
42.
67.
196.
57.
52.
150.
200.
115.
85.
62.
100.
0
0
0
0
0
it
ti
a
if
!t
%
0
0
0
0
n
0
0
0
n
0
0
0
0
300.
2
2
24.
13.
309.
2
1
1
1
1
1
1
1
1
1
1
\
1
1
1
2
1
1
2
90.
44.
69.
56.
68,
35.
28.
26.
31.
96.
03 .
03.
00.
25.
60.
84.
04.
71 .
87.
92.
307.
2
?
2
2
37.
10.
02.
58.
0
0
0
0
0
a
$
#
4
q
#
0
0
0
0
0
0
0
0
0
0
0
0
0
3.
3.
3.
2.
3.
2.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3.
3 .
2.
2.
2 .
3.
3.
3.
0
3
35
3
2
4
2
8
23
6
6
4
2
q
9
8
7
4
45
2
4
4
3
9
P
95
2
3
2
'VF^FLii'.-i V^Ll.'hS Hh.KF APPARENTLY
pi iiu pj-1; \//\ Lll f-S
80
-------
Table XI
1969 AUGER HOLE 3 OATA
DATF
FLQW,GPD ACID,PPM
S04fPPM
PH
AUG
AUG
AUG
AUG
AUG
SEPT
SEPT
SEPT
SEPT
OCT
OCT
OCT
OCT
NOV
MOV
NOV
NOV
DEC
DEC
4
8
15
20
27
3
10
17
25
4
11
18
25
1
8
22
29
6
20
1970 AUGER
JAN
JAN
JAN
FEB
FEB
FEB
FEB
MAR
MAR
MAR
MAR
APR
APR
APR
MAY
JUNE
JUNE
JULY
JULY
AUG
AUG
AUG
SEPT
SEPT
17
24
31
7
14
21
28
7
14
21
28
11
18
25
30
6
17
1
22
12
19
26
10
16
43.0
5R.3
47.0
42.7
38.6
35.3
31 .2
2B.5
27 .6
26.7
27. 0
28.1
23.9
25.0
27.0
29.0
29.0
30.0
37.0
HOLE 3
62.0
47.5
116.0
181.0
153.0
279.0
133.0
212.0
236.0
322.0
335.0
323.0
128.0
565.0
450.0
165.0
85.0
75.0
63.0
97.0
120.0
65.0
49.0
37.4
17.0
5. 0
5. 0
5.n
2.0
79. ( ALK )
37. (ALK)
52. (ALK )
30. (ALK)
2. 0
32.0
40. (ALK)
42. ( ALK )
36. { ALK)
5. 0
6.( >UK )
43. (ALK )
7. 0
DATA
175.0
57.0
530.0
835.0
827.0
405. 0
245.0
392.0
245.0
297.0
287,0
277.0
170.0
177.0
172.0
150.0
90.0
65,0
77.0
270.0
272.0
170. 0
75.0
97.0
,0
,0
,0
428.0
439.0
325.0
377,
282,
300,
252.0
256.0
231.0
285.0
31 2.0
304.0
311.0
295.0
288,0
294.0
288.0
272 .0
329.0
3.85
3.95
5.6
5.42
6. 10
6. 0
715
500
1240
1228
1096
673
527
611
427
483
441
448
315
285
290
327
294
267
477
491.0
538.0
407.0
319.0
360.0
5.7
5.8
5.9
5.6
2.9
3.4
2.5
2.4
2.35
2.48
2.67
2.67
3. 1
2.7
2,7
2.7
3.0
2.9
2.8
2.9
3,3
3.35
3.35
2.8
2.75
3.0
3.6
3,4
81
-------
Table XII
1969 AUGFR HOLF 4 DATA
DATE FLOwtGPD ACID,P"M so4,ppM PH
1970 AUGER HOLE 4 DATA
AUG
AUG
AUG
AUG
AUG
SEPT
SEPT
SEPT
SFPT
OCT
OCT
OCT
OCT
NOV
NOV
MOV
NOV
DEC
DEC
4
8
15
20
27
3
10
17
25
4
11
18
25
1
8
22
29
6
20
40
36
36
39
35
31
29
27
26
26
27
27
26
25
27
29
33
31
30
. 1
.5
.7
. 1
.3
.5
.8
.7
.3
.2
.0
.5
.9
.9
. 5
.0
.0
.6
.7
62.
0.
55.
60.
60.
77.
57.
50.
?.
10,
70.
60.
2.
14,
5.
( ALK
17.
5.
( ALK
(ALK
(ALK
7.
( ALK
10.
( ALK
(ALK
(ALK
(ALK
( ALK
(ALK
(ALK
0
0
0
)
0
0
)
)
)
0
)
0
)
)
)
)
)
)
H
333
531
300
373
604
334
423
346
371
3 I 3
405
334
360
331
324
482
339
323
323
*
*
9
»
*
*
•
«
•
^
•
•
*
•
•
.
*
^
•
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Q
0
0
0
0
6
4
5
4
6
6
6
.24
.62
.6
.40
.3
.1
.4
JAN
JAN
JAN
JAN
FEB
FEB
FEB
FEB
MAR
MAR
MAR
MAR
APR
APR
APR
JUNE
JUNE
JUNE
JULY
JULY
JULY
AUG
SEPT
SEPT
SEPT
3
17
24
31
7
14
21
28
7
14
21
28
4
11
18
6
13
17
1
7
17
12
2
10
16
43.3
44.5
39.0
168. 0
173,0
270.0
91.0
68.0
193.0
170,0
228.0
217.0
471.0
202.0
140.0
237.0
98.0
78.0
45.0
51.0
36.0
96.0
65.0
41.0
35.4
107.0
120.0
10.0
325.0
435.0
360.0
305. 0
220.0
192.0
222.0
205.0
245,0
132.0
265.0
235. 0
75.0
122.0
120,0
65.0
100.0
85,0
152,0
215. 0
182.0
72,0
898.0
977.0
527.0
786.0
1022.0
640,0
770.0
670,0
445,0
504. 0
419,0
482.0
272.0
538.0
617.0
459.0
540,0
588,0
407.0
485.0
537.0
453,0
662,0
453.0
430.0
3.5
3.5
5.5
2.65
2,6
2.6
2,6
2.83
2.83
2.9
3.0
2.7
2.85
2.75
2.95
2.9
3.2
3.3
3.65
3.35
3.3
3.05
3.0
3.5
3.55
82
-------
Table XIII
1969 AUGER HDLF 5
DATE FLOW,GPD ACTS),PPM SU4,PPM PH
AUG
AUG
AUG
AUG
AUG
SPET
SEPT
SEPT
SEPT
GCT
nc,T
DCT
OCT
NOV
NOV
MOV
NOV
OFC
DEC
4
8
15
20
27
3
10
17
25
4
11
18
25
1
8
22
2P
6
20
26
25
25
25
25
30
20
20
IB
18
1Q
19
18
18
10
21
22
30
22
,
„
.
.
.
,
.
,
.
.
,
.
,
.
.
.
.
.
.
9
q
2
9
2
q
2
2
P
8
2
7
2
4
0
0
5
7
6
1
1
1
1
1
1
I
1
I
3.
53.
55.
85.
35.
42.
87-
37.
00.
25.
22.
25.
50.
67.
37.
95.
82.
222.
1
72.
0
0
0
n
0
o
0
0
n
0
0
0
n
0
0
0
0
n
0
289.
524.
459.
398.
364.
340.
476.
632.
497.
516.
513.
413.
61 7.
413.
479.
577,
514.
61 R.
504.
0
0
0
0
0
0
0
0
0
o
0
0
0
0
0
0
0
0
0
5
3
3
3
3
3
3
2
2
2
2
3
2
3
2
2
2
2
2
.75
.39
.4
. 30
.52
.4
. 1
,9
.9
.9
.9
. 1
,95
. 15
.9
.75
.95
.9
.9
1970 AUGER HOLE 5 DATA
JAN
JAN
JAN
JAN
FEB
FEB
FhB
FEB
MAR
MAR
MAR
APR
APR
APR
APR
MAY
JUNE
JUNE
JUNE
JULY
JULY
AUG
SEPT
SEPT
SEPT
3
17
24
31
7
14
21
28
7
14
21
4
11
18
25
30
6
13
20
1
17
6
10
16
29
25.3
26. 8
26.0
28.4
28.4
40.0
32.7
48.3
34,0
35.0
35,0
39,0
43.0
40.0
532.0
62.0
59.0
42.0
33.0
30.0
29.0
32.0
27.5
25.0
27.0
160.0
195.0
157. 0
130,0
155.0
172.0
220.0
187. 0
267.0
232.0
362. 0
302.0
255,0
195. 0
1050.0
275.0
265.0
147.0
162.0
185.0
191.0
225. 0
265.0
220,0
220.0
457.0
493.0
483,0
442.0
483.0
296.0
572.0
526.0
662,0
586,0
816.0
689.0
628.0
512, 0
0.0
610.0
582.0
471.0
531.0
508.0
506.0
525.0
565.0
541.0
518.0
2.9
2.8
2.9
2.85
2.8
2.75
2,65
2.79
2.73
2.85
2.7
2,70
2,75
2.95
2,65
2.7
2. 75
2.90
2.95
3.0
2.75
2.85
2.95
2.82
2.95
83
-------
Table XIV
1969 AUGER HOLE 6 DATA
OATE
FLOW,GPD ACID, PPM S04,PPM
PH
AUG
AUG
AUG
AUG
SEPT
SEPT
SEPT
OCT
OCT
OCT
NOV
NOV
NDV
DEC
DEC
4
8
15
27
3
17
25
4
18
25
1
22
29
6
20
133.
99,
101.
97.
82,
68.
63.
60.
61,
56.
54.
61.
66,
65.
60.
0
4
5
2
5
0
0
1
0
7
3
0
5
7
0
1
37
70
100
102
132
5
57
62
7
10
R?
45
66
1 3?
.
.
.
.
.
.
.
.
.
.
•
«
.
.
.
n
0
0
0
o
0
0
0
0
0
n
0
0
0
0
438.
577 .
633.
781.
688.
796.
401.
576,
437.
352.
412.
646.
515-
363.
669.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
5
•3
3
3
3
3
6
3
4
6
5
3
4
6
3
*
•
.
•*
•
•
•
«
*
•
•
•
•
*
*
79
80
30
20
2
0
1
6
5
05
2
3
3
1
05
1970 AUGER HdLF 6 DATA
JAN
JAN
JAN
FEB
FEB
FEB
FEB
MAR
MAR
MAR
MAR
APR
APR
APR
MAY
JUNE
JUNE
JUNE
JUNE
JULY
JULY
JULY
AUG
AUG
AUG
SEPT
SEPT
SEPT
3
24
31
7
14
21
28
7
14
21
28
4
11
18
30
6
13
20
26
1
7
17
6
19
26
10
16
29
78.0
83.0
91.0
103.0
205.0
247.0
191.0
238.0
335.0
370.0
450.0
450.0
312.0
312'.0
450.0
425.0
362.0
277.0
229.0
197.0
165.0
141.0
200.0
102.0
304.0
134.0
114.0
105.0
115.0
355.0
120.0
515.0
900.0
490. 0
357,0
530.0
520.0
537,0
480. 0
475.0
415.0
225.0
325.0
330.0
167.0
338.0
241.0
272.0
300.0
306. 0
347.0
647,0
405.0
392.0
267. 0
235.0
661.0
1116,0
626.0
1400.0
1570.0
1074.0
967.0
1130.0
1127.0
1085.0
984.0
949.0
860.0
563.0
644.0
676.0
620,0
736.0
630,0
650.0
720,0
745.0
757.0
1229,0
783.0
810.0
720.0
655.0
3.1
2.75
3.0
2.5
2.5
2.5
2.65
2.65
2.75
2.65
2.6
2.9
2.65
2.95
2.8
2.65
2.75
2.8
2.9
2,85
2.7
3.7
2,8
2.6
2.8
2.9
2.75
2.90
-------
BIBLIOGRAPHIC: The Ohio State University Research
Foundation
Pilot Scale Study of Acid Mine Drainage
Publication No. 11*010 EXA
A research facility has been developed to study
pyrite oxidation and resulting acid mine drainage on
a pilot scale basis. The test units include a small,
long-abandoned drift mine (McDaniels mine) and six
33 inch diameter auger holes drilled in order to have
comparable, isolated, experimental "mines." All units
are in the Middle Kittanning coal seam in southeastern
Ohio. The effect of oxygen concentration on acid pro-
duction has been studied in the McDaniels mine. Exper-
imental data and observations have shown the location
of major reaction zones and indicated that bacterial
catalysis of pyrite oxidation is not a significant
factor in production of acid mine drainage. The auger
holes are being monitored to determine the degree of
similarity between holes. When the correspondence
ACCESSION NO:
KEY WORDS:
Mine Drainage
Pyrite
Sulfides
Coal
Pollution Abatement
Industrial Waste
Ohio
Auger Holes
Underground Mines
BIBLIOGRAPHIC: The Ohio State University Research
Foundation
Pilot Scale Study of Acid Mine Drainage
Publication No. lit010 EXA
A research facility has been developed to study
pyrite oxidation and resulting acid mine drainage on
a pilot scale basis. The test units include a small,
long-abandoned drift mine (McDaniels mine) and six
33 inch diameter auger holes drilled in order to have
comparable, isolated, experimental "mines." All units
are in the Middle Kittanning coal seam in southeastern
Ohio. The effect of oxygen concentration on acid pro-
duction has been studied in the McDaniels mine. Exper-
imental data and observations have shown the location
of major reaction zones and indicated that bacterial
catalysis of pyrite oxidation is not a significant
factor in production of acid mine drainage. The auger
holes are being monitored to determine the degree of
similarity between holes. When the correspondence
ACCESSION NO:
KEY WORDS:
Mine Drainage
Pyrite
Sulfides
Coal
Pollution Abatement
Industrial Waste
Ohio
Auger Holes
underground Mines
BIBLIOGRAPHIC: The Ohio State University Research
Foundation
Pilot Scale Study of Acid Mine Drainage
Publication No. lit010 EXA
A research facility has been developed to study
pyrite oxidation and resulting acid mine drainage on
a pilot scale basis. The test units include a small,
long-abandoned drift mine (McDaniels mine) and six
33 inch diameter auger holes drilled in order to have
comparable, isolated, experimental "mines." All units
are in the Middle Kittanning coal seam in southeastern
Ohio. The effect of oxygen concentration on acid pro-
duction has been studied in the McDaniels mine. Exper-
imental data and observations have shown the location
of major reaction zones and indicated that bacterial
catalysis of pyrite oxidation is not a significant
factor in production of acid mine drainage. The auger
holes are being monitored to determine the degree of
similarity between holes. When the correspondence
ACCESSION NO:
KEY WORDS:
Mine Drainage
Pyrite
Sulfides
Coal
Pollution Abatement
Industrial Waste
Ohio
Auger Holes
Underground Mines
-------
between holes has "been established, one hole will be
used as a reference mine so that fluctuations due to
hydrologic variations can be separated from effects of
experimentally imposed changes in the other holes.
between holes has been established, one hole will be
used as a reference mine so that fluctuation due to
hydrologic variations can be separated from effects of
experimentally imposed changes in the other holes.
between holes has been established, one hole will be
used as a reference mine so that fluctuations due to
hydrologic variations can be separated from effects of
experimentally imposed changes in the other holes.
-------
Accession Number
w
Subject Field & Group
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
Water Quality Office, Environmental Protection Agency
Title
Pilot Scale Study of Acid Mine Drainage
1Q Authors)
Ohio State University
Research Foundation
16
21
Project Designation
Water Quality Office, EPA 1*
tOlO EXA
Note
22
citation Water pollution Control Research Series, 1^010 EXA 03/71
Environmental Protection Agency, Water Quality Office
Washington, D. C., March 1971
23
Descriptors (Starred First)
Mine Drainage,* Pyrite,* Sulfides,* Coal*
Pollution Abatement, Industrial Waste
25
Identifiers (Starred First)
Ohio,* Auger Holes,* Underground Mines*
27
A bstract
A research facility has been developed to study pyrite oxidation and resulting acid
mine drainage on a pilot scale basis. The test units include a small, long-abandoned
drift mine (McDaniels mine) and six 33 inch diameter auger holes drilled in order to
have comparable, isolated, experimental "mines. " AH units are in the Middle
Kittanning coal seam in southeastern Ohio. The effect of oxygen concentration on acid
production has been studied in the McDaniels mine. Experimental data and observations
have shown the location of major reaction zones and indicated that bacterial catalysis of
pyrite oxidation is not a significant factor in production of acid mine drainage. The
auger holes are being monitored to determine the degree of similarity between holes.
When the correspondence between holes has been established, one hole will be issed
as a reference mine so that fluctuations due to hydrologic variations can be separated
from effects of experimentally imposed changes in the other holes.
Abstractor
> Smith
Institution
The Ohio State University
WR:102 (REV. JULY 1969)
WRSI C
SEND. WITH COPY OF DOCUMENT, TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D.C. 20240
* GPO: 1 970-389-930
------- |