TVA
EPA
Tennessee
Valley
Authority
Energy Demonstrations and
Cuchnology
Chattanooga, TN 37401
EDT-111
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-80-066
March 1980
Effects of Coal-ash
Leachate on Ground
Water Quality
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
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The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
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9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
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EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
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This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-80-066
March 1980
Effects of Coal-ash Leachate
on Ground Water Quality
by
Jack D. Milligan and Richard J. Ruane
TVA Project Director: Hollis B. Flora II.
Tennessee Valley Authority
1140 Chestnut Street, Tower II
Chattanooga, Tennessee 37401
EPA Interagency Agreement No. D5-E721
Program Element No. INE624A
EPA Project Officer: Michael C. Osborne
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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DISCLAIMER
This report was prepared by the Tennessee Valley Authority and
has been reviewed by the Office of Energy, Minerals, and Industry,
United States Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the Tennessee Valley Authority or
the United States Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
iii
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ABSTRACT
The four objectives of this research are: (1) to develop a
methodology for the field collection of coal-ash leachate;
(2) chemically characterize ash leachates from fossil-fueled power
plants using different coal sources; (3) determine the character-
istics of the hydrogeochemical environment in which the leachate
occurs; and (4) determine the attenuation of coal-ash leachate by
various soil types.
Groundwater monitoring wells were installed around the ash
ponds at two TVA coal-fired steam plants. Continuous soil-core sam-
ples were collected and analyzed for physical and chemical parameters,
.Groundwater samples were collected and analyzed periodically. Ash
leachate was percolated through different clays and soil types in
the laboratory to study attenuation rates. Results indicate that:
1. Coal-ash leachate is a highly variable solution, but character-
istically is high in dissolved solids, boron, iron, calcium,
aluminum, and sulfate. Ash leachate can be acidic, with pH
values as low as 2 measured. Ash leachate is a chemically
reducing solution.
2. The different coal sources associated with this study produced
ash leachate with similar characteristics.
3. The use of an inert gas lift pump proved an effective means
of collecting anoxic groundwater samples while minimizing
oxidation.
4. Differences were found in the characteristics of leachate
samples obtained by extracting the interstitial soil water
and samples collected from monitoring wells. Interstitial
water samples contained higher concentrations of metals and
were more acidic than well samples.
5. The flux of metals from coal-ash leachate was found negligible
when compared to the mass of metals discharged by the ash pond
surface overflow (even though concentrations in the ground
water were highest) because the surface discharge was much
greater than the groundwater flow.
IV
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This report was submitted by the Tennessee Valley Authority,
Office of Natural Resources, in partial fulfillment of Energy
Accomplishment Plan 80 BDO under terms of Interagency Agreement
EPA-IAG-D5-E-721 with the Environmental Protection Agency. Work was
completed as of November 1979.
v
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CONTENTS
Abstract iv
Figures vii
Tables ix
Acknowledgments xi
1. Introduction 1
2. Conclusions and Recommendations 2
3. Literature Review 4
4. Description of Ash Disposal Areas H
Plant J 11
Plant L 13
5. Methodology 15
Field investigation 15
Plant J - groundwater sampling well
design and installation 15
Groundwater sample collection 19
Plant L - groundwater sampling 22
Laboratory attenuation studies 22
6. Coal Ash Leachate Field Investigations 28
Soil core analyses 28
Interstitial water analysis 39
Groundwater analysis 43
Aluminum 47
Iron 53
Copper, lead, zinc, and other metals 57
7. Hydrology 61
8. Laboratory Attenuation Studies 73
Attenuation by natural soil collected
at plant L 73
Attenuation by natural soil collected
at plant J 80
Attenuation by kaolinite 85
Discussion of leachate attenuation study 90
9. Theoretical Considerations 93
References 96
Appendices
A. Analytical methods 99
B. Vertical profiles of substratum at plants J and L 103
C. Analytical results of column attenuation studies 107
D. Chemical characteristics of clay minerals used in
column attenuation studies 112
vi
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FIGURES
Number
1 Effects of fly ash with lime on pH and dissolved
oxygen of distilled water (after Theis) 7
2 Effects of fly ash with lime on pH and dissolved
oxygen of distilled water (after Theis) 8
3 Plant J - groundwater sampling well locations 12
4 Plant L - groundwater sampling well locations 14
5 Cross section of interstitial water extractor 16
6 Cross section of groundwater sampling well 20
7 Column elution apparatus 26
8 Solubility of microcrystalline gibbsite as a function
of pH, at 25 C, and 1 atmosphere total pressure
(from Roberson and Hem, 1969) 50
9 Solubility of microcrystalline gibbsite as a function
of sulfate concentration. Ionic strength 0.10 for
25 C, and 1 atmosphere total pressure (from Roberson
and Hem, 1969) 51
10 Solubility of iron in relation to pH and Eh at 25°C
and 1 atm. Total dissolved sulfur 10 M;
bicarbonate species 10 M (Hem 1969) 54
11 Fields of stability of sulfur species likely to
occur in natural water (Hem 1969) 56
12 Groundwater table elevation in sampling wells at
plant J, March 9, 1977 62
13 Groundwater table elevation in sampling wells at
plant L, February 22, 1977 63
14 Cross section of ash disposal area at plant J 64
15 Cross section of the clay-silt and sand strata at
plant J, showing mean horizontal permeabilities (K)
for locations J4, J5, and J6 66
Vll
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FIGURES (continued)
Number Page
16 Cross section of substratum below plant J's
ash disposal area - plant J ............... 68
17 Tracer test of conductance and chloride vs.
pumping time ...................... 72
18 Concentrations of magnesium, sodium, and potassium
in the effluent from plant L's soil column ...... 74
19 Concentrations of copper, zinc, and nickel in the
effluent from plant L's soil column .......... 75
20 Concentrations of aluminum and barium in the
effluent from plant L's soil column . ......... 76
21 Concentration of sulfate in the effluent from
plant L's soil column ................. 77
22 Concentrations of magnesium, sodium, and potassium
in the effluent from plant J's soil column ....... 81
23 Concentrations of copper, zinc, and nickel in the
effluent from plant J's soil column .......... 82
24 Concentrations of aluminum and barium in the effluent
from plant J's soil column ............... 83
25 Concentrations of magnesium, sodium, and potassium in
the kaolinite clay column effluent ........... 86
26 Concentrations of copper, zinc, and nickel in the
kaolinite clay column effluent ............. 87
27 Concentrations of aluminum and barium in the kaolinite
clay column effluent
28 Schematic of coal ash leachate generation and
attenuation ...................... 94
viii
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TABLES
Number Page
1 Chemical Characteristics of Coal Ash Shaker
Test Supernatant 5
2 Comparison of Coal Ash Leachate Obtained
By Different Techniques 10
3 Permeability, Density, Grain-Size Distribution, and
Moisture Content of Subsoils Collected From Ash
Disposal Site - Plant J 18
4 Groundwater Sampling Well Depths, Water Table
Elevations, and Subsoil Stratum Sampled at Plant J . . . 21
5 Comparison of Dissolved Oxygen Concentrations in
Groundwater Samples Collected by Pumping With
Nitrogen and Air at Plant J 21
6 Groundwater Sampling Well Depths, Water Table
Elevations, and Subsoil Stratum Sampled at Plant L . . . 23
7 Permeability, Density, Grain-Size Distribution, and
Moisture Content of Subsoils Collected From Ash
Disposal Site - Plant L 24
8 Constituents Analyzed in Column Attenuation Studies ... 27
9 Chemical Analysis Performed on Split-Spoon Soil Cores . . 28
10 Soil-Core Analyses at Plant J 29
11 Soil-Core Analyses at Plant L 32
12 Ranges of Concentrations With Each Soil Type and at
Each Sampling Location for the Soil-Core Samples
Analyzed From Plant J 36
13 Ranges of Concentrations Within Each Strata at Each
Sampling Location for the Soil-Core Samples
Analyzed From Plant L 37
14 Concentration in Ash Samples Collected From Ash
Disposal Areas - Plants J and L 38
15 Analysis of Extracted Interstitial Water From Plant J . . 40
16 Analysis of Extracted Interstitial Water From Plant L . . 42
ix
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TABLES (continued)
Number
Page
17 Analysis of Groundwater Samples Collected From
Sampling Wells at Plant J - July 2, 1976 44
18 Analysis of Groundwater Samples Collected February 22,
1977, From Sampling Wells at Plant L 46
19 Comparison of Concentrations Measured in Groundwater
Sampling Wells, Extracted Interstitial Water, and
Solid Substratum Material - Plants J and L 48
20 Solubility Product Constants for Iron, Aluminum,
Copper, Lead, and Zinc Compounds 59
21 Flux of Selected Constituents Through Substrata at
Plant J 69
22 Mass Balance of Plant L's Soil Column Influent and
Effluent 79
23 Mass Balance of Plant J's Soil Column Influent and
Effluent 84
24 Mass Balance of Kaolinite Packed Column Influent and
Effluent 89
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ACKNOWLEDGMENTS
This study was initiated by TVA as part of a project entitled
"Characterization of Effluents from Coal-Fired Utility Boilers,"
and is supported under Federal Interagency Agreement Numbers
EPA-IAG-D5-E-721 and TV-41967A between TVA and EPA for energy related
environmental research. Thanks are extended to EPA project officers,
Julian W. Jones, Michael C. Osborne, and Dr. Ron A. Venezia, and TVA
project director, Dr. H. B. Flora II. Appreciation is also extended
to Salvatore Magliente, Kenneth L. Ogle, Frank G. Parker, and Randall
L. Snipes. A special appreciation is extended to Tien-Yung J. Chu for
his conceptualization of this study. Thanks are also extended to
Rebecca L. Carpenter, Ralph D. Gillespie, J. E. Liner, B. C. Sinor,
and V. E. Vandergriff for their technical assistance.
XI
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SECTION 1
INTRODUCTION
The increasing use of coal for power generation will result in an
increasing potential for adverse environmental impacts. Realizing the
importance of knowing what impacts power generating facilities may have
on the environment and anticipating the forthcoming Federal regulations
applying to solid waste disposal (Resource Conservation and Recovery
Act, P.L. 94-580), the Tennessee Valley Authority (TVA) in conjunction
with the Environmental Protection Agency (EPA) initiated a study to
characterize the various effluents associated with coal-fired generating
facilities. As a part of that study, entitled "Characterization of
Effluents from Coal-Fired Utility Boilers," the impact of coal-ash
leachate on groundwater quality at two TVA fossil-fueled power plants
was investigated.
TVA's coal-fired generating system produces approximately 650 tons
of coal ash for every 1000 megawatts generated. During 1977, TVA's 12
coal-fired power plants produced approximately 6.7 million tons of ash.
The ash consists of various proportions of fly ash and bottom ash
depending on the methods of firing and ash collection systems used at
the plants. Once collected, the ash is sluiced with raw river water to
nearby settling ponds. After settling, overflow from the settling pond
is discharged to adjacent receiving streams in compliance with the EPA
National Pollutant Discharge Elimination System permit.
Ash leachate is generated by the infiltration of ponded sluicing
water into the settled ash, and its subsequent percolation through the
ash where it eventually acquires the characteristics of ash leachate.
The dry disposal of coal-ash, or ash ponds that are no longer inundated,
such as a filled pond, can generate ash leachate with water from direct
precipitation and/or rainfall runoff. Once the leachate is generated
and has entered the subsurface environment below the deposited ash, its
chemical characteristics can be affected by various attenuation phenomena.
This report presents the results of a field and laboratory project
performed to characterize coal-ash leachate and its attenuation by
selected soil types at two TVA power plants. The major objectives of
the project were to: (1) develop a methodology for the field collection
of coal-ash leachate, (2) chemically characterize ash leachate from
fossil-fueled power plants using different coal sources, (3) determine
the characteristics of the hydrogeochemical environment in which the
leachate occurs, and (4) determine the attenuation of coal-ash leachate
by various soil types.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
Results of the ash pond leachate investigation indicate:
1. Coal-ash leachate is a highly variable solution, but charac-
teristically is high in dissolved solids, boron, iron, calcium,
aluminum, and sulfate.
2. Several constituents in ash leachate were found to exceed
EPA's criteria for drinking water. These include cadmium,
chromium, iron, manganese, and lead. Dissolved solids and
pH also did not meet these criterion.
3. Ash leachate can be acidic, with pH values as low as 2.0
measured. This acidity was found at two steam plants even
though one generated an alkaline ash.
4. Ash leachate is a chemically reduced solution.
5. The different coal sources associated with this study produced
ash leachate with similar characteristics. However, the acidic
ash at one plant produced higher concentrations of metals in
the leachate than the alkaline ash at another plant.
6. The use of an inert gas lift pump provides a means of collecting
anoxic groundwater samples while minimizing oxidation.
7. Differences found in the characteristics of leachate samples
obtained by extracting the interstitial soil water and those
of samples from monitoring wells include: (a) interstitial
water samples were more acidic than well samples, (b) inter-
stitial water samples contained higher concentrations of
metals than well samples and, (c) the collection of inter-
stitial water samples by compressing soil samples is a time
consuming and costly technique relative to the collection of
water samples via monitoring wells. Further investigation
into groundwater and leachate sampling techniques and their
effects on sample integrity is needed to ensure accurate
evaluations of leachate impacts.
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8. Coal-ash leachate migration and/or attenuation in subsoils
cannot be accurately determined by analyzing total soil
samples for leachate constituents. Fractionization and
analysis of specific particle sizes may be necessary to
reduce the large variation associated with total soil
sample analysis.
9. The mass of metals in the ash pond leachate entering adjacent
surface water was found negligible when compared to the
mass discharged by the ash pond surface overflow (even though
concentrations in the ground water were higher) because surface
flows were much larger.
10. Soils containing a large percentage of clay provide a better
medium for attenuating metals from ash leachate than soils
with more sand.
11. The anoxic leachate attenuation system, developed during this
investigation, is a viable approach for studying leachate
attenuation by soils under anoxic conditions.
12. Further work on the speciation chemistry of coal-ash leachate
needs to be performed to determine if toxic metal species are
present.
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SECTION 3
LITERATURE REVIEW
The solubilization of ions from coal ash during the percolation of
water through ash disposal areas and their potential for groundwater
contamination, have long been recognized. In a study conducted during
1951 and 1952 by Merz and Snead,1 the leaching of soluble salts and
alkaline compounds from incinerator ash dumps was investigated. Their
studies indicated that salts and alkaline compounds would leach from ash
during the percolation of water from direct precipitation and/or ground-
water movement through the ash; however, the leaching rate would be very
low. The study also found that chlorides, nitrates, and sulfates were
the most readily leached anions, and sodium and potassium were the most
readily leached cations. Calcium and magnesium were found to leach, but
very slowly. A limited number of leachate samples were also analyzed
for copper, aluminum, lithium, manganese, vanadium, barium, boron, and
strontium. Only boron and strontium were found in quantities above one
milligram per liter.
In a much later report, Rohrman2 discussed a comprehensive ash
study which involved 12 fossil-fueled power plants. One of the major
findings of this study was that all the ponded ash sluice waters con-
tained boron and phosphorus, and data was presented showing that many of
the elements in coal ash were present in the oxide form. In one of the
first studies to determine the major chemical elements of coal-ash
leachate, O'Connor, et al.,3 mixed 50 grams of fly ash of different ages
with 500 milliliters of demineralized water and analyzed the liquid for
extracted solutes. This study indicated that the coal-ash extract could
be characterized as an alkaline solution of calcium sulfate. The pH of
the extracts ranged from 7.5 to 11.1, calcium ranged from 27 to 288
mg/1, and sulfate from 45 to 600 mg/1. An additional finding was that
the pH of the extract decreased with increasing age of the ash, but a
reason for this is unknown. As a further part of this study, coal ash
was placed into columns and subjected to repeated elutions with demin-
eralized water. In this experiment, the highest concentrations of
solids were observed during the first elutions and most of the readily
soluble constituents were eluted with the first three liters of elutant.
Calcium and sulfate were found to be the most abundant ions in all the
elutants. Between pH 10.0 and 11.5, calcium was equal to the total
hardness. At a pH below 10.0, calcium accounted for approximately half
the hardness, indicating the solubilization of other hardness-producing
ions.
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In a study by Weeter, et al.,4 500 grains each of fly ash and bottom
ash were mixed with two liters of distilled water for 48 hours. The
liquid of this mixture was then analyzed for the extracted solutes. The
results of their analysis is presented in Table 1. The calcium and
sulfate concentrations in fly ash samples ranged from 400 to 600 mg/1
and from 1300 to 2000 mg/1, respectively, somewhat higher concentrations
than those found by O'Connor, et al. However, in the O'Connor study a
smaller concentration of ash was used in the mixing experiment. The
concentration of solutes in a water-ash mixture has been shown by Weeter
to be dependent on ash concentration. Batch mixing studies performed by
Weeter indicated that the supernatant concentrations of sulfate, alka-
linity, calcium, and iron increase with increasing fly ash loading, and
steady-state concentrations for these constituents were found to occur
within a mixing time of one hour. This indicates that the most readily
soluble constituents in coal ash are loosely bound to sites on the
surface of the ash particle.
TABLE 1. CHEMICAL CHARACTERISTICS OF COAL-ASH SHAKER TEST SUPERNATANT3
(after Weeter. et al.)
Parameter
Iron
Potassium
Calcium
Magnesium
Titanium
Arsenic
Boron
Aluminum
Sodium
Sulfate
Phosphate
Silica
Fly ashb
0.1-1.8
33-112
400-600
1-19
Trace
0.01
3-10
1.5-6.8
15-90
1300-2000
0.1-0.6
3-40
Bottom ash
0.05-0.15
0.4-6.6
8-135
0.8-7.1
0.1
0.01-0.8
0.1-0.2
0.05-0.5
0.8-7.8
12-60
0.1-0.5
1-2
a500 grams of ash with 2 liters of distilled water; shaken for 48 hours.
Values in mg/1.
In batch shake tests similar to those performed by Weeter, Theis
and Wirth5 mixed various weights of fly ash that were collected from
different plants with one liter of distilled water and determined the
equilibrium pH of the supernatant. Their experiments indicated that
equilibrium pH levels were achieved with an ash concentration of 1 to 2
grams per liter. They also discovered that some ashes induced alkaline
conditions in the supernatant, while others produced acidic conditions.
An analysis of the supernatant for trace metals showed that the highest
concentrations were present in the acidic ash mixture, indicating
increased solubilization as would be expected with the depressed pH.
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In addition to changes in the pH and metals concentrations, changes
in the dissolved oxygen concentration resulting from the addition of fly
ash, have been found. In Figures 1 and 2, from Theis,^ it can readily
be seen that after mixing fly ash with water the original dissolved
oxygen concentration is depressed, and the pH either increased or
decreased. The decreased dissolved oxygen concentration may be a result
of oxygen depletion by a sulfite ion oxidation reaction, and may be
expressed by:
S03"2 + 1/2 02 * S04~2
The rate of this reaction is normally very slow:7 however, the
catalytic effects of metal ions in this reaction are well known, and the
reaction rate may also be affected by certain organic compounds. Increases
in pH are likely a result of the solubilization of calcium oxide (lime)
present on the surface of the ash particles. Upon mixing with water,
calcium oxide becomes hydrated as follows:
CaO + H2 Ca(OH)2 hydrated lime formation (1)
Ca(HC03)2 -> Ca+2 + 2HC03~ (2)
C0"2 + H+ (3)
HCO ~ + OH~ (4)
Equations 3 and 4 effectuate the increase in pH by removing hydrogen
ions in equation 3 and increasing hydroxide ions in equation 4. These
reactions, along with others, were utilized by Chu8 in a study to demon-
strate the efficacy of lime-soda ash softening of ash pond water for
closed-cycle water reuse in power plants.
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I 2 3
TIME (DAYS)
13.0
- 12.0
- 11.0
- 10.0
x
Q.
- 6.0
5.0
Fipure 1. Effects of fly ash with lime on pH
and dissolved oxygen of distilled
water (after Theis).
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a.
2.0
2 3
TIME (DAYS)
Figure 2. Effects of fly ash with lime on pH and dissolved
oxygen of distilled water (after Theis).
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Certain ashes may contain high concentrations of transition metal
oxides, concurrent with low quantities of lime. Under these circum-
stances the acidic character of the transition metals, especially iron,
can cause decreases in solution pH. In addition, salts of metal ions
show varying degrees of acidity when dissolved in water; hydrolysis of
these ions effectuates acidic conditions. For example:
Fe(H20)5 OH+2 + H20 + Fe(H20)4(OH)2+ + H30+ (7)
Decreased solution pH could present a potential water quality
problem if a portion of the metals associated with coal ash were present
on the surface of the ash particle where they could be easily solu-
bilized. The sorption properties of fly ash were also investigated by
Theis, and his findings indicated that surface coatings of amorphous
iron, manganese, or aluminum oxides could provide a sorptive medium for
trace metals.
Reed, et al.,9 performed mixing studies using various concentra-
tions of fly ash. From these studies he concluded that equilibrium
concentrations were established within 20 minutes of contact. He also
noted that the equilibrium concentrations achieved under his batch study
were considerably lower than concentrations found by Burnett,10 during a
column percolation study in which fly ash from the same location was
used.
In another column study performed by Brown,11 distilled water was
percolated through plastic columns filled with coal ash. Successive
volumes of the percolate were then analyzed for various elements. The
concentrations found in the percolate by Brown were considerably higher
than concentrations found by previous investigators using batch mixing
techniques. Column percolation studies tend to allow greater contact
time and higher ash-to-water ratios than batch tests. These investi-
gations indicate that column studies may be a more accurate method of
predicting actual coal-ash leachate quality.
Harriger, et al.,12 in one of the few recent studies to charac-
terize coal-ash leachate by analyzing groundwater samples, reported
highly variable concentrations of calcium, sulfate, alkalinity, iron,
and magnesium in groundwater samples collected in an ash disposal area,
and much higher values overall as compared to samples collected away
from the ash disposal area. Some of their values are presented in
Table 2 for comparison with values obtained in laboratory studies using
batch and column techniques.
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TABLE 2. COMPARISON OF COAL ASH LEACHATE OBTAINED BY DIFFERENT TECHNIQUES
Parameter
Calcium, mg/1
Sulfate, mg/1
Alkalinity, mg/1
as CaCO~
Iron, mg/1
Magnesium, mg/1
Arsenic, mg/1
Mixed batch
a
extraction
20-280
18-740
42-190
0.03-0.1
1-19
0.01
Column elutipn
extraction
490
39,000
390
0.1
80
0.13
Leachate well
sample
91-660
345-4000
56,000-
985,500
0.04-10.4
2.6-16.8
0.01-0.19
weeter (see references).
Brown (see references).
f\
Harriger (see references).
10
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SECTION 4
DESCRIPTION OF ASH DISPOSAL AREAS
This section describes the coal-ash disposal areas at plants
J and L, and provides some detailed information regarding coal use and
ash generation. In addition, the geological stratigraphy beneath both
disposal areas is described.
PLANT J
Plant J is a coal-fired power generating facility located on a
peninsula formed by two reaches of the Clinch and Emory Rivers in eastern
Tennessee. The facility was put into full operation in December 1955,
and has a rated power generating capacity of 1700 megawatts. The plant
utilizes coal produced in eastern Tennessee and eastern Kentucky which
has an average of 2.0 percent sulfur and 19 percent ash. During 1972 the
plant consumed 3.9 million metric tons of coal, and generated 711,682
metric tons of ash. The ash consisted of 560,002 metric tons of fly ash,
and 151,680 metric tons of furnace bottom ash. The fly ash is collected
by mechanical collectors and electrostatic precipitators installed in
series, with an overall efficiency of 98 percent. The bottom ash is
collected in hoppers located at the bottom of the furnace. The ashes
required 30,112 million liters of raw river water to sluice it from the
collection systems at the plant to a nearby ash settling pond for disposal.
The original coal-ash disposal area at plant J (ash pond A) con-
sisted of a 242,800 m2 settling pond. This pond was completely filled
with ash by 1972 and is no longer in use. The current disposal pond has
an area of approximately 594,900 m.2 The pond is situated adjacent to
the Emory River (see Figure 3) with the pond retainer dike separating the
pond and river. The pond overflow is discharged over a weir into a small
embayment of Watts Bar Reservoir.
The thickness of the ash in plant J's disposal area ranges from
0.5 meters near the pond's overflow weir to 14 meters in the original
242,800 m2 pond. The whole disposal area is underlain by (1) a clay-silt
stratum immediately below the ash ranging in thickness from 2.4 to 6.1
meters, (2) a deeper alluvial sand stratum ranging in thickness from 1.5
to 3.6 meters, and (3) low permeability shale.*3 The thickness of the
shale is not accurately known.
11
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Figure 3. Plant J - ground water
sampling well locations,
i
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The ash pond dike itself is composed of a variety of materials with
varying compositions, mostly silty clay, but deposits of ash are present.
The height of the dike from the original ground surface to the top of the
dike was approximately 4.5 meters.
PLANT L
Plant L began commercial operation in 1952, with three coal-fired
units generating about 420 megawatts. By 1975, five additional units had
been added bringing the total full load generating capacity of the plant
to about 1965 megawatts. The facility is located on the Tennessee River
in northeastern Alabama. The plant burns coal obtained from areas in
western Kentucky and north Alabama which averages about 2.8 percent
sulfur and 16 percent ash. During 1972, the plant consumed 3.3 million
metric tons of coal and produced 432,361 metric tons of ash consisting of
107,228 metric tons of bottom ash and 325,133 metric tons of fly ash.
The fly ash is collected by electrostatic precipitators or mechanical
collectors and the bottom ash is collected in hoppers located at the
bottom of each furnace. The volume of raw river water required to
sluice the ash from the collection systems to nearby ash settling ponds
during 1972 was about 27,725 million liters.
Plant L originally had two principal disposal areas (see Figure 4),
ponds 1 and 2. Pond 1 is no longer active or inundated and has begun to
revegetate. Currently, all the ash discharged from the plant is received
by pond 2. This pond is 95 percent full and acts merely as a conduit to
transport the ash to pond 3, which is the latest ash pond constructed.
Some settling occurs in pond 2, but it is mostly the very coarse, heavy
material. Most of the ash is settled in pond 3. The total ash disposal
area, including ponds 1, 2, and 3, is approximately 1,032,000 m2.
The thickness of the ash in plant L's ash disposal area ranges up to
11 meters in depth. The greatest ash depths occur in the older ponds 1
and 2. Underlying the ash disposal areas, there are three geological
formations present:14 (1) recent deposits of river alluvium, (2) older
river terrace deposits, and (3) limestone.
The material overlying the limestone bedrock in the disposal area
was deposited by the Tennessee River. There is no clear-cut delineation
between the alluvium and the terrace deposits. Both are composed mostly
of clay and silt with some sand and gravel mixtures. In the ash disposal
area, these deposits vary in thickness from 3.8 to 9.0 meters. The
underlying bedrock in the area is Ordovician age limestone several
hundred feet thick. Its composition is mainly shaly limestone with
interbeds of purer limestone and zones of varicolored siltstone or
argillite. There are numerous cavities in the limestone resulting from
its dissolution by ground water.
Pond No. 3's dike material is composed of a highly compacted clay of
low permeability. The thickness of the dike from its interface with the
original ground surface to the top of the dike is approximately 10 meters.
13
-------
Op SCRUBBER SLUDGE POND
4 ASH POMD # 2 I |_L6
(ACTIVE) r<*
-------
SECTION 5
METHODOLOGY
This section describes the methods and procedures used to obtain
data on ash leachates, groundwater contamination, leachate migration,
and leachate attenuation by soils. The project involved field investi-
gations at two power plants with different coal sources and subsurface
soil conditions, and a laboratory simulation of leachate attenuation
using leachate collected at one of the power plants.
FIELD INVESTIGATION
Plant J - Groundwater Sampling Well Design and Installation
During March and April 1976, groundwater sampling wells were
installed at eight locations in and around the ash disposal pond at
plant J (see Figure 3). Two of the eight sampling sites (Jl and J8)
are located hydraulically upgradient from the ash disposal area and
function as background locations. Site J2 was located in an older
section of the disposal area, which is no longer inundated and is
presently used as an equipment storage area. Site J3 was located in
an area of the active disposal pond that had recently been filled and
was stable enough to support drilling equipment. Sites J4, J5, J6,
and J7 were located on the peripheral retainer dike downgradient from
the active disposal area and were spaced in such a manner as to inter-
cept any lateral flow of ash leachate from the ash disposal area.
To install a sampling well, a "split-spoon" soil sampler with a
diameter of 5.1 cm was first used to obtain a soil sample and then a
hollow-stem auger having a 30.5 cm outside diameter and powered by a
hydraulic drill was used to drill the well hole. The soil samples
were collected continuously by alternating the downward movement of
soil sampler and auger until an impermeable substratum was encountered.
After extracting the soil from the split-spoon sampling device, the
outermost layers of the soil core were cut away, so as to eliminate
any contamination from the sampling device, and a portion of the
residual soil sample preserved in a plastic container for later labora-
tory analysis. The remainder of the residual soil sample was then
15
-------
METAL FRAME--
0-ftlNO
POROUS PLATE
MATCWAL-NYLON
ORCULARTUGE
GLASS FIBER
FILTER
EXTRACTED VWTER
COLLECTION
VESSEL
FIGURE 5. CROSS-SECTION OF
INTERSTITIAL WATER EXTRACTOR
16
-------
hydraulically compressed with the nylon interstitial water extraction
device illustrated in Figure 5. It was necessary to perform the
extraction as soon as possible because any delay could alter the
composition of the interstitial water, and no technique for preserva-
tion was available. A portion of the extracted interstitial water
was then immediately analyzed for pH, conductivity, sulfate, alka-
linity, and hardness. The remaining water was filtered through a
0.45 micron filter pad and acidified (HNO,,) for later laboratory
analysis of metals.
The interstitial water extraction device was made of inert nylon.
All parts were machined to fit with little or no water loss during
operation. Actually, however, after many hours of use, extracted water
began to leak out between the solid plunger and its sheath (the circu-
lar tube). This was a result of sand getting between the plunger and
circular tube and the subsequent scoring of each during operation. A
harder material, perhaps teflon, and more precise machine work would
undoubtedly correct some of this problem. Operation of the extraction
device was quite simple, but required a great deal of strength for
optimum results. To operate the device, the solid plunger was removed
from the circular tube and glass fiber filters (usually two) placed over
the porous plate. A portion of subsoil sample collected within the zone
of saturation was then placed inside the circular tube. The amount of
subsoil compressed at one time varied depending on its composition. Clay
material often required compression of several portions of a sample in
order to obtain the needed volume of water, while a larger quantity of
sand could be compressed with the same result. The amount of subsoil
used per compression ranged from approximately 400 to 800 grams. After
placing the subsoil in the circular tube, the solid plunger was inserted
and the whole extraction device installed in the metal holding frame. A
three-ton hydraulic jack was then used to force the base and plunger
together, compressing the subsoil and forcing the water through the glass
fiber filters to the collection vessel.
The volume of interstitial water obtained in this manner ranged from
6 to 30 milliliters per compression, or, by rough estimate, 4 to 15
percent of the subsoil's moisture content.
At all locations except Jl and J8, and at selected elevations
(usually upon encountering a change in strata), undisturbed soil samples
were collected for laboratory determinations of horizontal and vertical
permeabilities, grain size classification, moisture content, and bulk
density. (The results of these determinations are presented in Table 3,
and the analytical methods in appendix A.) This was normally done by
offsetting from the original sampling bore hole and drilling down to the
predetermined sampling depth. The undisturbed samples were collected by
hydraulically pushing a cylindrical tube (a Shelby tube) having a length
of 76 cm and a diameter of 8.9 cm through the desired sampling area. The
Shelby tube, with sample, was then extracted from the well hole and both
ends sealed with paraffin wax to prevent moisture loss.
17
-------
oo
TABLE 3. PERMEABILITY, DENSITY, GRAIN-SIZE DISTRIBUTION, AND MOISTURE CONTENT
OF SUBSOILS COLLECTED FROM ASH DISPOSAL SITE - PLANT J
Sampling
Location
J2
J3
J4
J4
J5
J6
J6
J7
J7
Depth
(m)
15.
14.
7.
9.
6.
7.
14.
12.
5.
3
1
4
7
6
4
5
9
1
Vertical
permeability
(cm/s)
6
1
2
3
4
4
1
6
1
.3xl(T 8
.3xlO~6
.8xl(T 7
.lxlO~6
.OxlQ-7
.4xlO~7
.4xlO-6
.IxlO-6
.7xlO-7
Horizontal
permeability
(cm/s)
7.4xlQ-8
7. 4x10" 5
6. 6xlO~ 8
8.8xlO-6
2.8xlO~7
2.5xlO~6
1.3xlO~6
1.4xlO-5
2.6xlO~7
Gravel
(%)
0
3
0
0
0
0
0
0
0
Sand
(%)
8
25
40
80
33
29
82
69
25
Silt
(%)
54
63
41
14
45
51
13
24
47
Clay
(%)
38
9
19
6
22
20
5
7
28
Density
(R/cm3)
1.48
1.42
1.68
1.60
1.60
1.48
1.79
1.45
1.56
Moisture
(%)
25.7
24.6
20.9
22.6
24.3
26.7
13.9
20.7
23.0
*Textural classification of soil fractions as per American Society for Testing and Materials designation,
where: clay <0.005 mm, silt 0.005-0.074 mm, sand 0.074-4.75 mm, and gravel >4.75 mm.
-------
After the original split-spoon sampling was completed, the void that
had been produced by the action of the hollow-stem auger was cleaned out
and a groundwater monitoring well installed. Each well was constructed
of schedule 80 (0.64 cm wall thickness) polyvinyl chloride (PVC) pipe
that had an outside diameter of 11.4 cm. The bottom 45 cm of each PVC
well was perforated with 0.95 cm drill holes to allow groundwater
inflow. Each PVC well was lowered to the bottom of the well hole
and the annular space created between the perforated PVC pipe and the
side of the well hole filled with pea gravel to some approximate height
above the perforations, usually about 0.6 meters; this served to filter
the inflow of solids into the well and prevent clogging. A layer of
fine sand (approximately 0.3 meters thick) was placed in the annular
space above the pea gravel filter. This functioned as a barrier between
the pea gravel filter and a bentonite slurry placed in the annular space
above the sand. The bentonite slurry extended from the top of the fine
sand upwards to the surface of the water table and served to prevent
water from channeling down the side of the PVC pipe. The remaining
annular space above the bentonite slurry was filled with soil extracted
from the original hole. At the point where the well casing entered the
ground, a 0.5 meter diameter concrete apron, sloping away from the well,
was constructed. This was done to further inhibit water from channeling
down the side of the casing.
Fourteen wells were installed at the eight locations at plant J.
Multiple wells were installed at locations J2, J3, J4, J5, J6, and J7 to
enable the sampling of leachate from different substrata. Table 4 gives
the depth of each well, the water table elevation at time of installa-
tion, and the type of stratum sampled.
Groundwater Sample Collection
To ensure that contamination of monitoring well samples did not
occur from lowering a sampling device into the wells, groundwater samples
were collected with a gas lift pump as illustrated in Figure 6. Cylin-
ders of commercial argon or nitrogen gas containing less than 0.5 ppm
oxygen were used during sample collection to minimize oxidation of the
samples.
The gas cylinders were equipped with a pressure regulator and hose.
With the hose attached to the Shrader valve at the well head, the regu-
lator was adjusted to deliver 4218 to 7031 kgs/sq meter (6 to 10 psi).
The gas flowed down the quarter-inch flexible tubing and into the bottom
of the half-inch rigid plastic pipe, and lifted the water in the pipe to
the surface where it was collected. To avoid collecting a water sample
that may have set in a well for several weeks (and no longer would be
representative of the surrounding ground water), at least one water
volume of each well was pumped out prior to collecting a sample for
analysis. After collection, water samples were preserved and shipped to
the laboratory for analysis (see section 5).
19
-------
PLASTIC CAPS
1/2" RIGID PLASTIC PIPE
' 1/4" FLEXIBLE TUBING
1/4 PERFORATIONS
ON FOUR SIDES
PEA GRAVEL
FIGURE 6. CROSS-SECTION OF
GROUNDWATER SAMPLING WELL
20
-------
TABLE 4. GROUNDWATER SAMPLING WELL DEPTHS, WATER TABLE ELEVATIONS,
AND SUBSOIL STRATUM SAMPLED AT PLANT J
Well
Jl
J2
J3
J3A
J4
J4A
J5
J5A
J5B
J6
J6A
J7
J7A
J8
Well depth
(meters)
8.5
14.0
12.8
8.2
7.6
3.6
8.5
3.6
8.2
4.1
11.8
14.0
4.2
7.5
Elevation at
well bottom
224.8
219.4
216.7
221.4
221.6
225.6
220.7
225.7
221.1
224.4
216.8
213.4
223.0
226.6
Water table
elevation
231.28
230.19
227.75
227.81
225.11
c
225.64
c
c
224.15
c
226.10
226.10
230.90
Type of stratum
sampled
Shale
Silty clay
Silty sand
Coal ash
Sand
Clayey silt
Sand
Clayey silt
Sand
Sand
Clayey silt
Clay
Sand
Shale
Elevation above mean sea level (meters).
Monitoring well casing perforated within these strata.
'Not measured.
TABLE 5. COMPARISON OF DISSOLVED OXYGEN CONCENTRATIONS
IN GROUNDWATER SAMPLES COLLECTED BY PUMPING
WITH NITROGEN AND AIR AT PLANT J
In situ
Dissolved oxygen in sample
Well
J2
J3
J3A
J4
J4A
dissolved oxygen
0.5 mg/1
0.2 mg/1
0.5 mg/1
0.6 mg/1
0.6 mg/1
Pumped with nitrogen
1.0 mg/1
0.5 mg/1
0.2 mg/1
0.2 mg/1
0.7 mg/1
Pumped with air
20 mg/1
8.3 mg/1
7.4 mg/1
-
In situ concentration after recovery from wasting one well water volume.
21
-------
The validity of using a gas, such as nitrogen, to collect ground-
water samples is supported by the data in Table 5. These data indicate
that less change will occur in the dissolved oxygen concentration in the
ground water by using nitrogen gas to pump the wells rather than by
using air, and that the difference is quite significant.
Plant L - Groundwater Sampling
Groundwater monitoring wells were installed at 11 locations in and
around the coal-ash disposal area at plant L (Figure 4). Two of the
eleven locations, L10 and Lll, are located hydraulically upgradient
from the ash disposal area and function as background locations. Sites
L6, L8, and L9 are in successively older sections of the ash disposal
area and for the most part are no longer inundated. Locations L8 and L9
have some vegetative cover, while L6 is barren and partially inundated.
Location L7 is hydraulically downgradient from the disposal area and LI,
L2, L3, L4, and L5, are situated along the active disposal area's
peripheral retainer dike.
Eighteen groundwater monitoring wells were installed at plant L.
Multiple wells were installed at seven locations in order to sample
different substrata. The depth of each well, the water table elevation,
and the type of substratum from which water samples were collected are
presented in Table 6.
Plant L's monitoring well design, and procedures for their installa-
tion, are essentially the same as described for plant J. However, at
plant L, several of the monitoring wells were constructed using schedule
40 PVC pipe (0.32 cm wall thickness) with an outer diameter of 8.8 cm
(3-1/2 inches). This smaller pipe proved to be easier to handle and
install with no observed loss in sampling performance. Split-spoon soil
sample collections, interstitial water extractions, undisturbed Shelby
tube samples, and groundwater sample collection procedures at plant L
are the same as described for plant J. The results of the permeability,
density, grain, size distribution, and moisture content determinations
on the undisturbed soil samples collected at plant L are presented in
Table 7.
LABORATORY ATTENUATION STUDIES
During the project design phase, several possibilities were
considered for generating, or simulating, an ash leachate in the
laboratory suitable for use in an attenuation study. However, after
the groundwater sampling wells were installed and leachate samples
analyzed, it became apparent that the most representative water to
use, and the most easily obtainable, was the actual coal-ash leachate
collected in situ. The coal-ash leachate used in the laboratory
attenuation studies was collected from groundwater sampling well
L6A, at plant L. This well is approximately 10.6 meters deep and
22
-------
TABLE 6. GROUNDWATER SAMPLING WELL DEPTHS, WATER TABLE ELEVATIONS,
AND SUBSOIL STRATUM SAMPLES AT PLANT L
Well
LI
L1A
L2
L2A
L3
L3A
L4
L4A
L5
L5A
L6
L6A
L7
L8
L9
L9A
L10
Lll
Well depth
(m)
10.67
6.10
13.72
6.10
13.41
12.50
15.85
6.10
15.24
8.53
14.33
10.67
8.84
11.89
8.53
5.49
19.51
17.68
Elevation at
well bottom3
179.72
184.28
177.81
185.76
178.13
178.98
176.03
185.44
175.89
182.77
179.23
182.54
175.04
179.51
183.13
186.04
177.06
174.97
Water table
elevation3
183.22
182.22
186.50
181.51
181.48
182.52
182.60
183.03
186.58
186.85
186.81
182.10
187.55
189.08
189.58
183.98
183.50
Type of stratum
sampled
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Silt-clay
Elevation above mean sea level (m).
23
-------
TABLE 7. PERMEABILITY, DENSITY, GRAIN-SIZE DISTRIBUTION, AND MOISTURE CONTENT
OF SUBSOILS COLLECTED FROM ASH DISPOSAL SITE - PLANT L
Sampling
location
L2
L2A
L3
L3A
L3A
L4
L4
L4A
L5
L5
L6
L6
L7
L8
L8
L8
L9A
L10
Lll
Depth
(m)
13.8
5.8
13.4
6.6
11.0
13.4
13.9
10.1
8.3
9.0
10.7
12.7
8.8
3.0
0.8
5.1
5.9
16.6
5.9
Vertical
permeability
(cm/s)
1.4xlO-8
6.3xlO-8
6. 7xlO~ 8
6.9xlO-9
2. 7x10- 8
3.7xlO-8
4.4xlO-8
1.9xlO-8
1.4xlO-8
4.3xlO-8
6.6xlO-6
1.2xlO-8
55.2x10-8
5. 6x10" 8
3. 0x10- 4
1.9xlO-8
2.0xlO-8
2.3xlO-8
6.3x10-8
Horizontal
permeability
(cm/s)
0.2x10-8
1.7xlO-7
5.8xlO-8
l.lxlO-8
1.2xlO-8
5.5xlO-8
3.4xlO-8
2.0xlO-8
1.7xlO-8
7.4xlO-9
5.6xlO-6
5. 7x10- 9
45.0xlO-8
2 . 3xlO"8
1.5x10-^
7 . 4xlO-9
1.9xlO-8
4.7xlO-8
2.8xlO-8
Sand
(%)
23
30
15
27
10
14
4
23
15
29
54
13
10
14
37
1
9
5
30
Silt
(%)
48
18
31
24
15
21
54
28
34
26
42
31
65
41
58
22
36
15
28
Clay
(%)
29
31
50
36
68
43
42
41
51
40
4
56
25
45
1
77
55
80
42
Density
(g/cm3)
1.72
1.66
1.03
1.77
1.43
1.28
1.23
1.72
1.64
1.60
1.45
1.62
1.06
1.57
1.18
1.44
1.55
1.34
1.64
Moisture
(%)
19.2
18.7
56.1
17.5
31.6
36.5
38.0
18.0
23.2
22.0
24.3
24.2
57.5
24.6
35.2
32.7
26.5
37.3
22.9
*Textural classification of soil fractions as per American Society for Testing and Materials designa-
tion, where: clay <0.005 mm, silt 0.005-0.074 mm, sand 0.074-4.75 mm, and gravel >4.75 mm.
-------
terminates at the interface of the ash and the original soil. Only
the bottom 45 cm of the well is perforated to allow leachate inflow.
The water collected at this well has thus percolated downward through
approximately 10 meters of ash. Leachate from plant L was selected
because it could be transported to the laboratory the quickest.
After deciding that field collection was the optimum method for
obtaining a leachate sample, there were collection problems that
needed to be surmounted.
Preliminary in situ measurements indicated that anoxic conditions
existed in the leachate environment, and if these conditions were not
maintained during collection, transportation, and storage, alterations
in the chemical characteristics of the leachate would result (simply
allowing the leachate to come in contact with air would cause pre-
cipitates to form). This problem was alleviated by using argon gas
to pump the leachate to the well head. At the well head, tygon tubing
was connected to the 1.27 cm pipe that expelled the sample, and the
other end to a 20-liter plastic receiving carboy, which was closed to
the atmosphere. After wasting one well volume, the collection appara-
tus was purged with argon gas and then connected to the well head for
sample collection. By sampling in this manner it was possible to
maintain anoxic conditions in the leachate. After sample collection
was completed, an argon atmosphere was maintained over the leachate
in the carboy during transportation to the laboratory. Argon gas
was used in place of nitrogen in the attenuation study because it
contained less oxygen (<0.1 mg/1). In addition, argon is heavier
than nitrogen and air and tended to form a blanket over the leachate
to aid in the maintenance of anoxic conditions.
In the laboratory, the carboy was placed into a controlled
temperature compartment maintained at 20 C under an atmosphere of
argon. Once temperature equilibrium was established (approximately
two days), attenuation studies were performed with the following
materials: (1) soil taken from the ash pond dike at plant L, (2)
soil taken from the ash pond dike at plant J, and (3) kaolinite.
Each of these materials was homogenized and mixed with equal volumes
of silica and rehomogenized prior to packing into columns. It was
necessary to mix these materials with silica so that flow through
the columns could be sustained. The fine clay material tended to
swell and clog upon wetting, inhibiting or completely stopping the
flow of leachate. The silica increased the permeability of the
mixture and allowed the maintenance of flow through the column.
The effect of the silica was not determined in this study, but it
was assumed to be negligible because of the nonreactive nature of
the silica particles, and the fact that each column had the same
amount of silica, so the relative effects would be nearly the
same.
Into each column (a 25-ml buret with an inside diameter of
1.2 cm), 11.64 grams of soil-silica mixture (1:1 volume ratio) was
packed, at a density approximating the field conditions of 1.6 grams
25
-------
GLASS TUBING
PLASTIC TUBING
TEST TUBES
FRACTION COLLECTOR
-EFFLUENT
-GLASS BEADS
-GLASS WOOL
-SOIL
-GLASS WOOL
-GLASS BEADS
-INFLUENT
h*-GLASS TUBING--
PLASTIC TUBING
FLOW DIRECTION
PUMP
ANOXIC
ASH POND
LEACHATE
-CONTROLLED TEMPERATURE
ENVIRONMENT
/REGULATOR
-ARGON GAS
FIGURE 7. COLUMN ELUTION APPARATUS
-------
per cubic centimeter. Both ends of the soil-silica mixture were
packed with glass wool and glass beads to maintain the integrity
of the soil column. The column was set up in a controlled tem-
perature chamber (see Figure 7) to maintain 20 C. The leachate
was pumped from the plastic carboy with a low flow, teflon-coated
pump, up through the soil column to allow air to escape and ensure
saturation. The effluent from the column was then collected in
glass test tubes predosed with 0.1 ml nitric acid. Effluent flow
was adjusted as needed to approximately 0.1 ml per minute.
Sample collection was accomplished by photoelectrical measurements of
the column effluent volume, coupled with a rotating automatic fraction
collector. Effluent samples were collected during the three attenuation
studies until the calcium exchange capacity of each soil-silica mixture
was theoretically exceeded (this was estimated from calculation). The
effluent from each column was collected in 30 ml test tubes which were
composited to make up 6 effluent samples per column. After compositing,
the samples were analyzed for the constituents listed in Table 8.
Procedures for these analyses are given in appendix A. In addition,
each of the soils and clays were subjected to powder X-ray diffraction
analysis for their relative amounts of montmorillite, kaolinite, illite,
and quartz. Each was also analyzed for the constituents listed in
Table 8 (see appendix A for description of soil procedure).
TABLE 8. CONSTITUENTS ANALYZED IN COLUMN
ATTENUATION STUDIES
Calcium Copper
Magnesium Chromium
Sodium Zinc
Potassium Nickel
Iron Cadmium
Manganese Lead
Sulfate Aluminum
Barium Beryllium
Mercury Selenium
27
-------
SECTION 6
COAL ASH LEACHATE FIELD INVESTIGATIONS
In this section, the results of analyses performed on soil core,
interstitial water, and groundwater samples collected at plants J and L
are presented.
SOIL CORE ANALYSES
The split-spoon soil cores collected at plants J and L, as described
in the section on Methodology, were analyzed in the laboratory for the
chemical constituents listed in Table 9. The analytical procedures
used in these analysis are described in appendix B.
TABLE 9. CHEMICAL ANALYSIS PERFORMED ON SPLIT-SPOON SOIL CORES
Aluminum
Arsenic
Barium
Beryllium
Calcium
Cadmium
Chromium
Copper
Iron
Magnesium
Mercury
Nickel
Lead
Selenium
Sulfate
Zinc
At nearly all sampling locations at plants J and L, soil-core
samples were taken from ground surface to bedrock at various vertical
intervals depending on the type of substratum encountered. The pur-
pose for analyzing these vertical strata profiles for the constituents
in Table 9 was to determine the extent of leachate migration downward
and away from the ash disposal area by comparing the vertical and
horizontal distribution of constituents in the substrata. In addi-
tion, the concentration differentials between various strata were
used to compare their relative capacities for attenuating ash
leachate.
The data presented in Tables 10 and 11 are a result of the chemical
analyses performed on the soil cores collected at plants J and L,
respectively.
28
-------
TABLE 10. SOIL-CORE ANALYSIS AT PLANT J*
VO
Sampling Depth
location (mj
Jl 0.7
1.3
1-9
2.5
3-2
3.7
4.0
J2 1.3
3.3
5.7
8.1
13.5
14.0
14.1
14.6
15.0
15.5
16.0
16.4
16.9
17.3
17-8
J3 2.2
3.2
4.4
10.2
11.0
11.1
11.5
12.1
13.4
14.1
14.5
14.9
15.0
Strata
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Ash
Ash
Ash
Ash
Clay-silt
Clay-silt
Clay- silt
Clay- silt
Clay-silt
Clay-silt
Sand
Sand
Sand
Sand
Sand
Ash
Ash
Ash
Clay-silt
Sand
Sand
Sand
Sand
Sand
Sand
Sand
Sand
Shale
Al
l6o
140
160
150
64
160
120
60
56
83
470
83
21,OOO
620
9,4OO
79
2,200
420
3,900
240
1,000
360
4,900
44.0OO
20,000
8.0OO
4,200
4,500
_
2,300
2,700
2,9OO
-
6,9OO
16,000
As
11
-
11
-
-
-
<4
48
-
-
-
-
12
-
-
-
_
-
-
-
_
-
_
-
_
6
22
-
-
_
_
-
-
-
Ba
130
130
240
180
l4o
140
120
130
100
l4o
110
130
260
130
130
89
39
37
74
42
_
47
79
470
31
91
53
77
_
30
45
32
86
180
Be
.
-
-
-
-
-
-
_
-
-
_
-
-
-
<1
-
-
-
<1
_
-
-
<1
4
_
_
< 0.1
< 1
_
_
_
< 1
_
<1
2
Ca Cd
1,200 <1
1,600 <1
4,100 <1
4,200 <1
3,300 <1
3,900 <1
4,800 <1
2.20O <1
3,700 <1
2,400 <1
2,000 <1
1,200 <1
5,200
1,000 <1
970 <1
1,000 <1
510
1,000 <1
350
-------
TABLE 10 (continued)8
GO
o
Sampling Depth
location (m)
J4 1.7
3.5
5.0
6.5
8.0
9-6
11.1
J5 3-9
7.6
10.0
11.8
12.2
12.3
J6 1.9
4.8
8.2
9-6
11.5
12.8
14.1
aValues in jig/g.
Not analyzed.
Strata
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Sand
Sand
Shale
Clay-silt
Clay-silt
Clay-silt
Sand
Shale
Shale
Ash
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Sand
Al As
4,100 60
5,100
11,000
6,300 <4
3,900
1,300
11,000
12,000
7,OOO
3,800
4,300
20,000
17,000
8,900
11,000
5,900
-
3,800
6,300
1,700
Ba Be
75
46
54 <1
23
54 <1
12
140 3
32 1
36
-------
TABLE 11. SOII^COSE ANALYSES AT PLANT L
Sampling
location
JY
J8
Depth
(nO
O.Y
1.6
2.5
3.5
4.5
5.0
6.8
7.9
8.8
10.0
11.2
11.8
13.4
3.3
4.0
4.8
6.3
7.8
9.2
Strata
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Clay-silt
Shad
Sand
Sand
Sand
Sand
Sand
Shale
Shale
Shale
Shale
Shale
Shale
Shale
Al As
14,000
14,000
16,OOO
12,000
12,000
14,000
5,100
6,200
5,900
2,200
2,700
1,300
1,500
17,000
18,000
15,000
18,000
12,000
18,000
Ba
220
300
280
190
57
58
31
25
29
< 10
15
<10
430
100
no
200
310
200
180
Be
1
1
-
-
<1
-
<1
-
-
< 1
-
<1
2
2
1
-
1
-
1
Ca
4,100
15,000
22,000
14,000
1,OOO
1,500
150
470
550
120
240
160
2,300
21,000
4,100
4,6OO
11,000
7,100
4,200
Cd
<1
<1
-
-
< 1
-
<1
-
-
< 1
-
<1
1
2
2
_
1
_
1
Cr
31
31
51
33
12
12
10
26
11
<5
8
<5
39
35
43
42
46
32
44
Cll
22
22
21
17
9
8
2
10
6
< i
6
2
4
68
12
4
42
14
27
Fe
21,OOO
19,000
29,000
26,000
17,000
25,000
18,000
8,900
8,400
22,000
2,300
1,800
21,000
18,000
21,000
27,000
22,000
22,000
24,000
Hg
0.37
0.37
< 0,1
<0.1
-
< 0.1
-
<0.1
< 0.1
0.23
< 0.1
0.15
1.1
0.27
-
< 0.1
-
<0.1
0.28
Mg
6,400
6,600
6,700
5,000
1,100
110
500
120
960
250
370
250
6,100
5,200
7,000
7,300
8,500
6,000
8,600
Ni
42
42
43
44
5
12
<5
9
10
<5
<5
<5
57
70
41
45
43
34
51
Pb
15
15
24
20
30
17
2k
16
13
19
6
17
29
33
24
17
28
10
22
Se
<2
<2
_
_
_
_
_
-
-
<2
-
<2
<2
<2
-
_
-
1
<2
SO,
140
240
490
290
350
470
120
<4
<4
37
76
93
7,000
7,000
3,600
200
160
180
93
Zn
59
59
71
48
25
35
19
29
18
18
9
8
77
70
67
77
76
51
74
-------
TABLE 11. SOIL-CORE ANALYSES AT PLANT L
to
Sampling
location
LI
L2
L3
LU
Depth
(m)
2.1*
l*-3
6.7
7-3
9.1
10.1*
11.6
2.1
6.7
10.1*
11.0
12.8
13-5
13.6
3-7
6.7
9-5
10.1
11.9
13.7
ll*.9
3.7
6.7
9.7
9-8
10.8
12.8
ll*.6
15-9
Strata
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Al As
13,000 <1
17,000 <1
15,000 <1
16,000 <1
16, COO 3
18,000 <1
10,OOO <1
10,000 <1
17,000 <1
20,000 1
15,000 <1
12,000 <1
11,000 <1
3,800
-------
TABLE 13. (continued)
00
Sampling Depth
location (m)
L5 2.1
5.2
6.7
8.2
10.1
11.9
15.2
L6 0.9
1.5
2.1
3.7
5-2
6.7
8.2
8.8
10.1
10.7
11.3
11.9
12.5
13-1
13-7
14.2
L7 0.9
2.4
3.7
5.2
6.7
8.2
Strata
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Ash
Ash
Ash
Ash
Ash
Ash
Ash
Ash
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Al
12,000
11,000
17,000
18,000
10,000
10,000
12,000
11,000
15,000
14,000
10,000
14,000
15,000
12,000
15,000
15,000
22,000
18,OOO
14, OOO
19,000
20,000
25.0OO
17,000
17,000
22,000
22,000
18,000
1O,OOO
18,000
As
9
<1
1
<1
-------
TABLE 11 (continued)
U>
Sampling
location
L8
L9
L10
Lll
Depth
(m)
0.9
1.5
2.1
2.7
3-1+
5.2
7.6
10.1
11.9
0.9
1.8
2.7
3-7
U.6
5.5
6.1
7.9
10.5
2.1
5.2
8.2
12.3
17.1*
20.1*
3.7
6.7
9.8
12.8
17.1+
Strata
Ash
Ash
Ash
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Ash
Ash
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Silty clay
Al As
12,000 <1
15,OOO <1
5,500 <1
13,000 <1
16,000 <1
15,000 ll+
13,000 <1
12,000 <1
10,000 3
10,000 <1
12,000 <1
13,000 <1
5,600 1
7,000 20
6,300 <1
11,000 <1
15,000 <1
15,000 <1
11,000 11
It, 500 <1
1*,100 <1
11,000 21+
10,000 16
13,000 <1
9,900
-------
The most notable characteristic about the data from plant J
(Table 10) is that the concentrations of most constituents are highly
variable, both within and between sampling locations. The concentration
of mercury, with two exceptions, was found to be below 1.0 yg/g. At
sampling locations Jl and J8, the least variability (in terms of absolute
differences) in concentrations was observed for most constituents. This
is not surprising since both these locations were hydraulically upgradient
from the ash disposal area and have homogeneous stratum types throughout
their vertical profiles, albeit different from one another. The variable
nature of the data is further illustrated in Table 12. This table gives
the ranges of concentrations in each soil type measured at locations J2
through J7 combined, and also the ranges within each location. These
data indicate that the more variable values are associated with the
clay-silt, ash, and shale materials, while the sand contained a narrower
range of concentrations. Locations Jl and J8 were omitted from the soil
type comparisons because of their previously mentioned homogeneity.
However, in the bottom portion of Table 12, where ranges of values are
given for each sampling location, the lower variability at locations Jl
and J8 relative to other locations is again indicated. At sampling
locations J2 through J7, the magnitude of the variability is dependent
on the constituent under consideration. For example, location J2 has
the widest range of aluminum values, location J4 has the widest range of
calcium values, and location J7 has the widest range of chromium
concentrations.
The data from plant L (Table 11), although not nearly as variable
as plant J's, exhibits some variability, both within and between, samp-
ling locations. Beryllium, cadmium, and selenium values, like plant J's
data, are less than or near their analytical detection limits, while
concentrations of mercury were all measured below 0.5 yg/g. However,
unlike the data from plant J, the two hydraulically upgradient sampling
locations at plant L (L10 and Lll) are no less variable than sampling
locations downgradient from the ash disposal area. It should be noted
that the strata types present at plant L consisted mostly of a homoge-
neous silty-clay material throughout the vertical profile. The varia-
tion in plant L's soil core concentrations is also illustrated in
Table 13, where the range of concentration in each stratum measured
and the ranges within each location are given.
The data in this table indicate that, except for selenium, sulfate,
and zinc, the highest constituent concentrations are associated with the
silty-clay material. At the bottom of Table 13, the range in concen-
tration within each sampling location indicates that, unlike the control
locations at plant J, plant L's upgradient control locations (L10 and
Lll) are nearly as variable as the sampling locations downgradient from
the ash disposal area. Several parameters (iron, copper, chromium,
zinc, lead, and nickel) actually demonstrate higher maximum concen-
trations in the control locations than several of the hydraulically
downgradient locations.
35
-------
TABLE 12.
UJ
tn
RANGES OF CONCENTRATIONS WITH EACH SOIL TYPE AND AT EACH SAMPLING LOCATION
FOR THE SOIL COBE SAMPLES ANALYZED FROM PLftBT f'
Soil type
Clay- si It
Sand
Shale
Ash
Sampling
locations
Jl
J2
J3
J4
J5
J6
J7
J3
Al
64-21,000
240-6900
1500-20,000
56-44,000
64-160
56-21,000
2300-44,000
1300-11,000
3800-20,000
17OO-11,OOO
13OO-l6,OOO
12,000-18,000
As
<4-60
22
-
48
<4-ll
12-48
6-22
<4-6o
-
-
-
"
Ba
16-300
< 10-86
10O-430
31-470
120-240
37-260
30-470
12-140
16-190
28-160
< 10-430
100-310
Be
< 1-1.0
<1-*5
<5-l6
39-70
6-56
25-45
<5-22
<5-56
<5-53
<5-58
5-18
<5-57
34-70
Pb
<5-8l
<5-38
8-33
<5-69
14-81
<5-38
<5-69
3-51*
<5-26
<5-25
6-30
10-33
Se
-------
TABLE 13. RANGES OF CONCENTRATIONS WITHIN EACH STRATA AT EACH SAMPLING LOCATION
FOR THE SOIL COUE SAMPLES ANALYZED FBOM PLANT La
Strata
Ash
Silty clay
Sampling
location
LI
L2
L3
IA
L5
L6
L7
L8
L9
L10
Lll
Al As
5,500-15,000 *5
12-51
22-29
18-1*8
25-1*8
12-39
28-31*
19- "*5
17-32
19-1+2
17-l»2
17-1*5
33-51
Cu
13-35
1+-35
9-21+
1+-18
6-22
1*-20
7-18
1+-35
9-35
5-25
8-33
6-28
7-22
Fe
11,000-65,000
6,100-97,000
17,000-31,000
6,200-39,000
8,600-97,000
6,100-30,000
25, 000- 3!+, 000
11,000-65,000
16, 000-1+1*, 000
33,000-63,000
13,000-63,000
13,000-1*1,000
19,000-50,000
Hg
< 0.1-0. 3
< 0.1-0.1*
0.1-0.2
< 1-0.2
<1-0.2
< 1-0 . 2
<0.1-C.2
<1
' 0.01-0.3
0.2-0.1*
0.1-0.2
0.2-0.1*
Mg
61+0-11+00
120-15,000
620-5300
1+1+0-3200
710-15,OOO
1*00-81*00
1300-3200
160-2800
1300-6500
600-3600
690-3300
120-530
210-11+03
Ni
16-1+2
<5-5^
6-28
8-32
8-57
<5-32
7-13
8-1*2
8-37
7-28
^5-32
' 5-23
<5-37
Pb Se
8-31
-------
TABLE 14. CONCENTRATIONS IN ASH SAMPLES COLLECTED FROM ASH DISPOSAL AREAS - PLANTS J AND
u>
oo
Constituent
Aluminum
Arsenic
Barium
Beryllium
Calcium
Cadmium
Chromium
Copper
Iron
Magnesium
Mercury
Nickel
Lead
Selenium
Sulfate
Zinc
Mean
9,938.4
48
151.4
2.5
2,828.6
1.3
21.3
33.1
12,785.7
1,563.3
0.3
19.4
19.0
2.0
1,161.4
28.0
Plant J
Range
56-44,000
48
79-470
<1.0-4
1,200-4,600
<1.0-3
6-47
21-72
4,900-30,000
290-3,000
<0.1-0.7
6-56
<5-69
<2-2
230-3,600
5-90
Mean
12,346.2
2.3
186.9
1.5
7,815.4
1.2
30.2
23.6
42,769.2
995.4
0.2
27.8
16.2
1.2
1,200.5
74.3
Plant L
Range
5,500-15,000
<1.0-5
110-320
<1.0-2
2,200-14,000
<1.0-2
19-45
12-35
11,000-65,000
640-1,800
<0.1-0.3
16-42
8-31
<1.0-2
36-5,500
17-140
values in mg/L.
-------
The mean concentrations and range of values for the constituents
listed in Table 9 were calculated for all ash samples collected at
plants J and L. At plant J, ash samples were collected over various
vertical intervals at sampling locations J2 and J3, and at plant L
sampling locations L6, L8, and L9. The results of these calculations
indicate (Table 14) that the mean concentrations of aluminum, barium,
calcium, chromium, iron, nickel, sulfate, and zinc are highest in ash
from plant L. Plant J, however, had the higher mean concentrations of
arsenic, beryllium, cadmium, copper, mercury, lead, selenium, and
magnesium. There are a multitude of reasons why the above elements
would be partitioned as they are between the two plants; different coal
sources, methods of firing the coal, and ash collection systems are
the major reasons related to plant operations. The sample collection
is undoubtedly another factor to consider. The age of the ash sample
and its particle size characteristics may also affect concentrations
within the sample. The longer coal ash has been exposed to the leach-
ing process the more opportunity for the dissolution of ions, and at
least one investigator** has shown that smaller ash particles contain
higher concentrations of certain elements.
The variable nature of the constituents measured in the soil cores
from plants J and L, precluded the use of this data for determining the
extent of leachate migration. The natural variation of soils resulting
from spatial differences in mineralology, organic content, and soil
particle sizes makes the effects of leachate on constituent concentra-
tions in the soil difficult or impossible to define. Determining
differences in the attenuation capacity of the various substrata also
suffers because the highly variable soil makes results ambiguous. In
order to utilize soil core data to determine the magnitude of leachate
migration, some means of eliminating or minimizing the natural variation
will be needed. One approach may be to analyze only a certain particle
size fraction of a sample for a contaminant. Another might be to sepa-
rate the various components of a soil sample, such as organic and
inorganic, and analyze separately. There are many approaches which
might be considered, but the measurement of constituents in total soil
samples, as this investigation indicates, does not appear to be a
viable one.
INTERSTITIAL WATER ANALYSIS
During the collection of soil core samples from plants J and L,
certain cores were selected for extraction and analysis of their inter-
stitial water (the extraction methodology is given in section 4). The
basis for selecting which cores were to be extracted was the apparent
moisture content of the core and the density of the material under
consideration. Both of these factors were evaluated in the field,
based on field soil testing techniques, previous experience, and
intuition. In all, 23 soil-core extractions were analyzed from
plant J, and seven at plant L. The fewer number of samples extracted
39
-------
TABLE 15. ARALYSIS OF EXTRACTED DlTEESTniAL WATER FROM PLANT J
Well locations
Depth, m
Strata
Aluminum, mg/L
Barium, mg/L
Beryllium, mg/L
Calcium, mg/L
Cadmium, mg/L
£* Chromium, mg/L
O .
Copper, mg/L
Iron, mg/L
Magnesium, mg/L
Mercury, mg/L
Nickel, mg/L
Lead, mg/L
Selenium, mg/L
Sulfate, mg/L
Zinc, mg/L
pH, std. units
Conductivity,
J3
13-it
Sand
3.2
<0.1
-
56
-
<0.01
0.3
15
lit
-
<0.5
-
-
-
0.7
7.3
J3
llt.l
Sand
3.15
-
-
15.5
< 0.001
0.008
0.02
0.82
-
<0.01
<0.05
< 0.006
-------
TABLE 15 (continued)
Well locations
Depth, m
Strata
Aluminum, mg/L
Barium , mg/L
Beryllium, mg/L
Calcium, mg/L
Cadmium, mg/L
Chromium, mg/L
Copper, mg/L
Iron, mg/L
Magnesium, mg/L
Mercury, mg/L
Nickel, mg/L
Lead, mg/L
Selenium, mg/L
Sulfate, mg/L
Zinc, mg/L
pH, std. units
Conductivity,
J6
8.2
Clay- silt
2.5
<0.1
-
62
0.006
< 0.001
<0.1
38
12
<0.02
<0.5
0.07
<0.05
260
0.5
7.1
J6
11.5
Clay-silt
6.1*
-
-
78
0.006
0.015
0.07
25
-
<0.01
<0.05
0.018
<0.05
-
0.53
2.3
J6
12.8
Clay-silt
9-1
<0.1
-
130
-
0.01
<0.1
61t
19
<0.02
<0.5
-
-
<100
2.2
2.7
J7
1.6
Clay-silt
1.15
-
-
1*20
< 0.001
< 0.001
0.01
1.1*
-
<0.01
0.11
< 0.002
< 0.02
-
0.03
7.2
J7
U.5
Clay-silt
3.5
<0.1
-
660
-
<0.01
<0.1
0.8
63
<0.02
<0.5
-
-
1500
5.0
6.8
J7
5.0
Clay- silt
2.8
1.9
-
510
0.002
0.003
0.3
50
1*1
<0.02
<0.5
O.OOl*
<0.10
-
2.6
1.7
J7
6.8
Clay- si It
and sand
3.6
-
-
37
O.OOl*
0.005
0.06
2.7
-
-
0.09
0.016
<0.05
-
0.38
1.7
J7
7.9
Clay-silt
and sand
8.1*
<0.1
-
51
-
<0.01
0.2
8.1
20
<0.02
<0.05
16
-
100
0.9
1.5
J7
8.8
Clay- si It
and sand
8.1
1.8
-
58
-
0.02
0.2
5.2
32
<0.02
<0.05
-
-
230
2.5
1.1*
J7
1C
Clay- si It
and sand
23
-
-
59.5
0.005
0.09
0.03
92
-
<0.01
0.12
0.07
<0.05
-
0.1*3
2.1
J7
11.2
Clay-silt
and sand
11
2.3
-
73
0.003
0.021
<0.1
85
15
<0.01
<0.5
0.035
<0.05
-
1.7
2.2
575
2200
2750
1950
2700
1200
1*500
20,000
9500
3550
-------
TABLE 16. ANALYSIS OF EXTRACTED INTERSTITIAL WATER FROM PLANT L
Constituents
Depth, meters
Strata
Aluminum, mg/1
Barium, mg/1
Beryllium, mg/1
Calcium, mg/1
Cadmium, mg/1
Chromium, mg/1
Copper, mg/1
Iron, mg/1
Mercury, mg/1
Magnesium, mg/1
Manganese, mg/1
Nickel, mg/1
Lead, mg/1
Zinc, mg/1
pH, standard units
L3
15.0
Silt-clay
2.2
0.400
<0.010
96
0.010
<0.050
<0.010
1.9
<0.004
21
0.140
<0.050
0.050
0.070
7.5
Conductivity, ymhos/cm 880
Alkalinity, mg/1
as CaCO
Sulfate, mg/1
320
100
L6
8.0
Ash
8.4
0.600
<0.010
220
0.080
0.110
0.110
9.5
<0.004
3.8
0.550
0.100
0.050
1.8
3.5
1180
900
Sampling
L6
8.8
Ash
8.6
0.600
<0.010
280
0.040
0.050
0.090
6.3
<0.004
6.3
0.450
0.070
0.050
0.620
3.6
1130
900
locations
L6
10.0
Ash
2.0
0.500
<0.010
320
0.020
<0.050
0.020
8.8
<0.004
16
1.6
0.120
0.050
0.690
6.5
1040
920
L6
10.6
Ash
8.2
0.600
<0.010
210
0.010
0.060
0.060
19
<0.004
12
1.2
0.090
0.120
0.640
4.1
3000
600
L7
8.2
Silt-clay
7.7
0.600
<0.010
200
0.020
<0.050
0.070
8.9
<0.004
14
3.5
0.080
0.100
0.400
2.9
6400
500
L8
0.9
Ash
4.1
0.200
<0.010
170
0.020
<0.050
0.030
3.5
<0.004
9.8
0.580
0.090
0.050
0.330
3.4
1650
860
-------
at plant L was because the compacted nature of the soils precluded the
extraction of enough water for laboratory analysis. In Tables 15 and
16, the results of analyses on the interstitial waters from plants J
and L, respectively, are presented. The dashes that appear in these
tables indicate analyses were not performed because an insufficient
amount of extracted water was available to accommodate the analyti-
cal evaluation. The minimum detection limits shown for the same
elements are also a result of insufficient sample volume.
One of the most striking features about the data in Tables 15 and
16 is the low pH values observed. At plant J, 16 of the 23 pH measure-
ments were less than 5.0, and 13 of the values were below 3.0. At plant
L, five of the seven measurements for pH were below 5.0, and one less
than 3.0. The data do not, however, indicate any trends in pH, such as
with depth or stratum type. In addition, the constituent concentrations
in these tables do not always track with variations in pH, as would be
expected from solubility relationships. For example, iron concentra-
tions at sampling location J7 (Table 15) are not inversely proportional
to pH, and zinc concentrations at location J4 demonstrate similar
behavior. The solubilities of the elements in Tables 15 and 16 in
relation to other matrices in which they were measured are obviously a
factor to consider and this subject is discussed later in the report.
GROUNDWATER ANALYSIS
In Tables 17 and 18, the results of the laboratory analysis per-
formed on groundwater samples collected from the wells at plant J and L,
respectively, are presented. Samples were collected from all sampling
locations at plant J, except Jl, on July 2, 1976, and from all locations
except J3 and J3A on March 9, 1977. These sample omissions were a
result of sampling well malfunctions. Groundwater samples were collected
from all sampling locations at plant L, on February 22, 1977.
For comparative purposes, the EPA's domestic water supply criteria16
are also listed in Tables 17 and 18. Although these criteria are not
applicable to leachate from solid waste disposal sites, they are used
here, and elsewhere in this report, as a screening process to identify
water quality constituents that may deserve environmental consideration.
Of the constituents measured in samples from plant J, five were found to
exceed EPA's criteria for iron, manganese, lead, dissolved solids (as
sulfate), and pH. Samples from all wells except Jl, a background well,
exceeded the criterion for iron; samples from all wells in the March
collection exceeded the manganese criterion; and the criterion for
dissolved solids was exceeded in March at locations J4, J4A, J5A, J7A,
and J8. Lead exceeded the criterion in July at locations J6, and the
pH was not within the criterion at wells J3, J4, J5B, J6, J6A, and J7.
At plant L, the data indicate that the criterion for iron was
exceeded in samples analyzed from wells, L3A, L6A, L7, L8A, and L9A.
Dissolved solids, as sulfate, exceeded the criterion in samples from
43
-------
TABLE 17. ANALYSIS OF GROUNDWATEE SAMPLES COLLECTED FROM SAMPLING WELLS AT PLANT J - JULY 2, 1976
Parameter
Aluminum, mg/L
Beryllium, mg/L
Cadmium, mg/L
Calcium, mg/L
Chromium, mg/L
Copper, mg/L
Iron, mg/L
Lead, mg/L
Mercury, mg/L
Nickel, mg/L
Selenium, mg/L
Dissolved solids,
total, mg/L
Zinc, mg/L
pH, standard units
J2
0.8
<0.01
-------
TABLE 17 (continued)
Parameter
Aluminum, mg/L
Arsenic, mg/L
Boron, mg/L
Barium, mg/L
Beryllium, mg/L
Calcium, mg/L
Cadmium, mg/L
Chromium, mg/L
Copper, mg/L
Iron, mg/L
Mercury, mg/L
Magnesium, mg/L
Manganese, mg/L
Nickel, mg/L
Lead, ng/L
Selenium, mg/L
Sulfate, mg/L
Sulfide, mg/L
Dissolved solids,
total, mg/L
Volatile solids,
total, mg/L
Zinc, mg/L
pH, standard units
Oxidation reduction
potential, MV~
Conductivity, nmhos/cm2
Alkalinity, mg/L
as CaC03
Water table
elevation, m
Jl
0.3
< O.OOlt
0.16
< 0.1
<0.01
62
< 0.001
< 0.005
<0.01
<0.05
< 0.002
17
0.13
<0.05
<0.01
< 0.001
68
0.08
itio
10
<0.02
7.5
--130
It70
192
230. it8
J2
<0.2
0.026
5.6
< 0.1
<0.01
110
< 0.001
< 0.005
<0.01
16
< 0.002
U2
it. 6
<0.05
<0.01
< 0.001
65
<0.02
lltOO
70
<0.01
7-1
-135
790
390
228.55
Jit
<0.2
< 0. 00'4
0.2
< 0.1
<0.01
110
< 0.001
< 0.005
<0.01
<0.05
< 0.002
16
o.6;t
<0.05
<0.01
< 0.001
310
<0.02
900
ItO
<0.01
6.8
-70
510
-
224.79
J4A
<0.2
< O.OOlt
0.26
< 0.1
<0.01
itio
< 0.001
< 0.005
<0.01
U20
< 0.002
120
44
0.08
<0.01
< 0.001
2100
0.07
ItOOO
570
<0.01
6.6
-100
2200
-
22lt.03
J5
March
<0.2
< O.OOlt
0.09
< 0.1
<0.01
19
< 0.001
< 0.005
<0.01
0.57
< 0.002
12
0.2lt
<0.05
< 0.01
< 0.001
30
<0.02
210
10
<0.01
7.0
-130
180
81
22lt.70
J5A
9, 1977
<0.2
0.006
0.6l
< 0.1
<0.01
260
< 0.001
< 0.005
<0.01
2200
< 0.002
100
63
0.06
< 0.01
< 0.001
3400
0.13
4900
500
0.05
6.5
-110
2900
108
223.75
J5B
O.lt
< O.OOlt
0.13
<0.01
18
< 0.001
< 0.005
<0.02
3.7
< 0.002
10
It. 5
<0.05
O.Olt
< 0. 001
130
<0.02
390
50
0.2
3.3
-i-SOO
360
-
221.16
J6
<0.2
< O.OOlt
0.2
< 0.1
<0.01
110
< 0.001
< 0.005
<0.01
1.6
< 0.002
15
3.5
<0.05
<0.01
< 0,001
120
<0.02
950
50
<0.01
7.4
-100
520
237
220.19
J6A
<0.2
< 0.004
0.2
< 0.1
<0.01
100
< 0.001
< 0.005
<0.01
77.0
< 0. 002
18
7.3
<0.05
<0.01
< 0.001
150
<0.02
1200
70
0.02
6.9
-160
680
320
22lt . 36
J7A
< 0.2
< 0.002
2.0
< 0.1
<0.01
520
< 0.001
< 0.005
<0.01
7.0
< 0.002
96
18
0.08
< 0.01
< 0.001
1700
0.03
3^00
250
0.01
7.0
-110
1900
320
225.13
J8
<0.2
< 0.002
0.16
< 0.1
<0.01
360
< 0.001
< 0.005
< 0.01
0.2lt
< 0. 002
70
2.2
<0.05
<0.01
< 0.001
890
<0.02
2700
120
0.02
7.6
-^150
1460
295
228.22
DWSCa
b
0.05
b
1.0
b
b
0.01
0.05
1.0
0.3
0.002
b
0.05
b
0.05
0.01
250
b
250
b
5.0
5.9
b
b
b
b
^Domestic Water Supply Criteria, EPA, 1976.
Not analyzed.
-------
TABLE 18. AHALYSIS OF GKOUNDHATER SAMPLES COLLECTED FEBBUARY 22. 1977. FROM SAMPLING WELLS AT FLAHT L
Parameter
Altrnnnum, mg/L
Arsenic, mg/L
Boron, mg/L
Beryllium, mg/L
Calcium, mg/L
Cadmium, mg/L
Chromium, mg/L
Copper, mg/L
Iron, mg/L
Mercury, mg/L
Magnesium, mg/L
Manganese, mg/L
Bicfcel, mg/L
Lead, mg/L
Selenium, mg/L
Sulfate, mg/L
Sulfide, mg/L
Dissolved solids,
total, mg/L
Zinc, mg/L
pE, standard units
Oxidation reduction
potential, MV
Conductivity,
^mhos/cm2
Alkalinity, mg/L
as CaCOo
Water table
elevation, m
LI
0.8
<0.002
0.15
<0.01
55
< 0.001
< 0.005
<0.01
<0.05
< 0.002
4.4
0.75
<0.05
<0.01
< 0.001
8.0
0.33
190
<0.01
7.7
+70
280
198
183.21
L2
0.5
< 0.002
0.35
<0.01
81
< 0.001
< 0.005
<0.01
<0.05
< 0.002
7.1
O.U5
<0.05
<0.01
< 0.001
10
o.o4
180
<0.01
7.8
+390
325
230
182.20
L2A
<0.2
< 0.002
0.23
<0.01
6U
< 0.001
<0.005
0.04
<0.05
<0.002
6.1
2.9
<0.05
<0.01
-------
wells L8, L8A, and L9A. The pH in well L8A was not within the
criterion, and manganese exceeded the criterion in all wells sampled,
including the background wells.
The data also indicate that pH values measured in samples collected
from the sampling wells (Tables 17 and 18) were generally higher than
values obtained from the extracted interstitial water samples (Tables 14
and 15). Samples from the wells were generally.neutral to alkaline,
with only two depressed pH values observed (wells L8A and J5B), while
the pH of the interstitial water was generally very acidic (a pH of 1.4
was measured), but ranged to alkaline. Although the methods of collec-
tion differ between the interstitial water and the well water, it was
possible to compare samples collected by both methods from the same
location and depth. These comparisons are given in Table 19, along with
the soil core sample concentrations for the same locations and depth.
The table shows that in all cases where measurable quantities of a
constituent were found the concentration in the interstitial water
sample was greater than that found in the well sample. This comparison
indicates that the measurement of interstitial water may be a more
accurate method of determining groundwater contamination by leachates
than utilizing groundwater monitoring wells of the design used in this
study. However, more research is needed to economize and standardize
this technique. Specific reactions and chemistry of selected
constituents in Table 19 are discussed below.
Aluminum
In aqueous systems, aluminum is strongly influenced by its tendency
to form soluble complexes with fluoride, hydroxide, sulfate, phosphate,
and some organic ligands: its solubility is affected by the concentra-
tions of these ligands. The solubility of aluminum, as a function of
pH, in a hydroxide equilibrium environment, is illustrated in Figure 8.
On the alkaline.side of the curve, the main species present is mono-
valent AL(OH)4 , while under acidic conditions the main species is the
trivalent form Al . However, in aqueous solutions such as the inter-
stitial water in Table 19, other complexing ligands in addition to
hydroxide may alter the solubility of aluminum through complexation.
For example, the concentration of sulfate in an interstitial water
sample collected from location J4 was measured at 2300 mg/1, with a pH
of 4.3. Roberson and Hem18 studied the solubility of aluminum in the
presence of different concentrations of sulfate and at different pH's,
and Figure 9 illustrates the solubility of microcrystalline gibbsite
(A1(OH)3) as a function of sulfate concentrations over the ranges of
pH from their studies. Using the data from location J4, at 2300 mg/1
sulfate and a pH of 4.3, the relationship presented in Figure 9 indi-
cates that approximately 270 mg/1 of aluminum could be soluble in the
interstitial water sample. In addition, using values from location J4
at 310 mg/1 sulfate and a pH of 6.8 for the well water sample, 0.04
mg/1 of soluble aluminum could be present in the well water according
47
-------
TABLE 19. COMPARISON OF CONCENTRATIONS MEASURED IN GROUNDWATER SAMPLING WELLS,
EXTRACTED INTERSTITIAL WATER, AND SOLID SUBSTRATUM MATERIAL,
PLANTS J AND L
CD
Sampling location and site
Location J3 (13. 1+ m)
Constituent
pH, standard units
Alkalinity, mg/L
as CaCOj
Oxidation reduction
potential, MV
Dissolved solids ,
total, mg/L
Volatile solids,
total, mg/L
Aluminum, mg/L
Arsenic, mg/L
Boron, mg/L
Barium, mg/L
Beryllium, mg/L
Calcium , mg/L
Cadmium , mg/L
Chromium, mg/L
Copper, mg/L
Iron, mg/L
Mercury, mg/L
Magnesium, mg/L
Manganese, mg/L
Nickel, mg/L
Lead, mg/L
Selenium, mg/L
Sulfiate, mg/L
Sulfide, mg/L
Zinc, mg/L
Groundwater
sampling wells
9-5
-
150
_
5.0
-
-
-
<0.01
27
< 0.001
< 0.005
0.08
9-3
< 0.0002
-
-
<0.05
0.011
< 0.001
_
-
0.09
Extracted
interstitial
water
7.3
-
-
_
3.2
-
-
< 0.1
-
56
_
-------
TABLE 19 (continued)
Sampling location and
Constituent
pH, standard units
Alkalinity, mg/L
as CaCOj
Oxidation reduction
potential, MV
Dissolved solids,
total, mg/L
Volatile solids,
total, mg/L
Aluminum, mg/L
Arsenic, mg/L
Boron, mg/L
Barium, mg/L
Beryllium, mg/L
Calcium, mg/L
Cadmium, mg/L
Chromium, mg/L
Copper, mg/L
Iron, mg/L
Mercury, mg/L
Magnesium, mg/L
Manganese, mg/L
Nickel, mg/L
Lead, mg/L
Selenium, mg/L
Sulfate, mg/L
Sulfide, mg/L
Zinc, mg/L
Lcc
Groundwater
sampling wells
8.0
235
+120
180
_
0.3
< 0.002
0.2
-
<0.01
61*
< 0.001
< 0.005
o.oU
0.06
< 0.002
15
0.69
<0.05
<0.01
< 0.001
22
0.1
<0.01
ation L3 (15.0 m
Extracted
interstitial
water
7.5
320
_
-
_
2.2
_
_
0.1*
<0.01
96
0.01
<0.05
<0.01
1.9
-------
-2
-3h
-4
ui
O
O
o>
O
-51
-61
8
10
Figure 8.
PH
Solubility of microcrystalle gibbsite as a function of pH, at 25° C.,
and 1 atmosphere total pressure (from Roberson and Hem, 1969).
-------
-r
-6
-5
o
o>
.3-3
-2
-1
n
i i i
-
i i i
i
|
i
-
-
-
-
-
-
\ j
* i i
-I
-3 -4 -5 -6
Log CAI
-7 -8
-7
-6
-5
PH3.5
-2
-I
4.5 5.0 5.5 6.0
1 \
-I -2 -3 -4 -5 -6
Log CAI
-7
FlRure 9. Solubility of microcrystalline gibbsite as a function of sulfate concentration
Ionic strength 0.10 for 25 C, and 1 atmosphere total pressure
(from Roberson and Hem, 1969).
51
-------
to the relationship expressed in Figure 9. From Table 19, the concen-
trations of aluminum actually measured in the interstitial and well water
samples at location J4, are 60 and <0.20 mg/1 respectively. The concen-
tration of aluminum in the well water sample may agree with the value
predicted from Figure 9, but it cannot be verified because the detectable
limit is higher than the predicted value. The concentration of aluminum
in the interstitial water sample (60 mg/1), however, is A. 5 times less
than the predicted value (270 mg/1) . It might be postulated that 60
mg/1 was all the aluminum available for solubilization; however, a
return to Table 19, location J4, shows that 3900 yg/g of aluminum was
present in the (soil) substratum. The soil moisture content was approxi-
mately 20 percent (see Table 3) , and if all the aluminum were to dis-
solve, calculations indicate that a 624 mg/1 aluminum solution would
result more than enough to meet the predicted value.
Thus, it appears that other factors besides the sulfate concen-
trations affected the solubility of aluminum in the interstitial water
samples from location J4. The type of matrix in which the aluminum is
chemically bound, incomplete soil-water contact, and competition with
other metal ions for the sulfate ligand are factors which might affect
aluminum solubility. Further analysis of the data indicates that com-
petition for the sulfate ligand may indeed be the limiting factor. The
competition for the sulfate ligand by other metal ions, such as magne-
sium, calcium, barium, and lead, may force the hydroxide solubility to
be limiting for aluminum. The following calculations tend to verify
this point:
"}3 = K = 10~32 (1)
so
10~14 (2)
{Al+3} = 2.2 x 10~3 moles/liter (3)
apparent v '
PH = -log {H+} =4.3 (4)
{OH~} = 10~/{H} (5)
{OH~} = 10~14/5.0 x 10~5
{OH"}aPParent = 1«" X
Substitution of 3 and 5 into 1 yields:
{Al+3} _ {OH~}3 ^ = 1.7 x 10~32 (6)
apparent apparent
52
-------
The calculated solubility (6), using the measured values of alumi-
num and pH from Table 19, is close to the theoretical solubility con-
stant (1). These data suggest that the system is in equilibrium and it
is the hydroxide solubility that is controlling the aluminum concentra-
tion in the interstitial water and, as stated earlier, the predominate
form at a pH of 4.3 would be Al .
It should be pointed out that the characteristics of the samples
from location J4 are not necessarily indicative of all locations at
plant J or L. For example, at location J3 (Table 19), the aluminum
concentration in both the interstitial water and well water exceeds its
hydroxide solubility (Kapparent - 9.4 x 10-25 and Kapparent = 2.3 x icr"
respectively) indicating either the occurrence of complexation or the
presence of a system not in equilibrium, while for location L6, calcu-
lations indicate the concentration of aluminum in the interstitial water
has not reached the limit imposed by the hydroxide solubility constant
(K = 6.0 x 10~34), even though the concentration is higher than
apparent
at location J3. This suggests that the acidic conditions (pH 4.1) at
location L6 are allowing more aluminum in solution, but not enough is
present to attain maximum equilibrium concentrations.
It should be noted that the simplistic approach used in the equili-
brium discussions herein minimizes the effects of ionic strength,
temperature, and medium on K
s o
Iron
There are two oxidation states in which iron normally occurs, the
ferrous form (Fe+2), and the ferric form (Fe+3). Under oxidizing condi-
tions and near neutral pH (5 to 8), iron is precipitated as the highly
insoluble (Kso = 6.0 x 10~38) ferric hydroxide, Fe(OH)3. The solubility
of iron is dependent on pH and oxidation-reduction potential (Eh). Its
chemical behavior is also influenced by its ability to form complex ions
with sulfides, sulfates, oxides, hydroxides, chlorides, fluorides, carbon-
ates, phosphates, and organic material. The ferrous form (Fe+3) forms
weaker complexes than the ferric, and forms few stable inorganic com-
plexes. It is the predominate oxidation state in reducing and/or acidic
environments.19
Figure 10 illustrates the relationships between pH and Eh that
define the conditions under which specific ionic species of iron domi-
nate. This is known as an Eh-pH, or stability field, diagram. Specific
areas where species dominate are delineated by thermodynamic computa-
tions, in which the Nernst equation is the fundamental relationship that
establishes the dividing line between oxidized and reduced species. A
thorough discussion of Eh-pH diagrams is given by Garrels,20 where this
familiar form of the Nernst equation is utilized.
53
-------
WATER REDUCED
HFe02
Figure 10. Solubility of iron in relation to pH and Eh at 25° C.,
and 1 atm. Total dissolved sulfur 10"^ M: bicarbonate
species 10~2 M (Hem,
54
-------
Where:
Eh = oxidation reduction potential
E° ~ standard oxidation potential for half-cell reaction
R = universal gas constant (1.987 calories/degree mole)
T = temperature in degrees Kelvin
n = number of electrons involved in chemical reaction
F = Faraday constant (96,484 coulombs)
{ox} = activity of oxidized ions
{red} = activity of reduced ions
This equation can be used with thermodynamic data to generate the
stability field diagrams of the type illustrated in Figure 10, for any
of the various metal equilibriums one would care to examine. They were
not presented for all the metal ions measured during this study because
the variable nature of the data, both between and within sampling
locations, would require a voluminous exposition.
As Figure 10 indicates, ferrous iron (Fe ) can be produced by the
oxidation of pyrite (FeS2), reduction of ferric species (Fe+3), dissolu-
tion of ferrous hydroxide (Fe(OH)2)> or dissolution of siderite (FeCO.,).
Additionally, the kinetics and formation of intermediate species may
affect the formation of ferrous iron. The FeS2 equilibrium is a feasible
condition because of the high concentration of sulfate present in several
of the sampling wells, the low pH values of the interstitial water, and
the presence of pyrite (FeS2) in coal. In Figure 11, the stability
fields for five different sulfur species are illustrated. The dotted
line indicates the ferrous-ferric boundary and demonstrates that sulfate
is the predominate form of sulfur stable in the ferric region.
At a pH less than about 8.0, and under reducing conditions, the
H2S .and S° forms predominate. Oxidation of l^S will produce the S°
form, which upon further oxidation, forms 80^2. xhe H2S form has the
notorious "rotten egg" odor, which was noticeable during the collection
of water samples from several of the wells at both plants. This quali-
tative analysis indicates the potential presence of a reducing environment
in the ground water at certain sampling locations. It was most notice-
able in samples collected from wells downgradient from the ash disposal
areas, and least, if at all, in the upgradient or background wells. In
addition, the odoriferous wells upon inspection were found to have a
black deposit (possibly FeS) on the 1.27 cm rigid PVC pipe installed
inside the well. This deposit was most concentrated at the interface
of the groundwater surface with the atmosphere and may be a result of
55
-------
8 10 12 14
PH
Figure 11. Fields of stability of sulfur species
likely to occur in natural water (Hem, 196
56
-------
oxidation within the well casing. Solubility product calculations
were performed for the FeS, Kso = 2.6 x 10 equilibrium, using
iron and sulfide data from Tables 17 and 18. The calculations
indicated that concentrations of iron and sulfide in samples from
three locations at plant J (J5A, J4A, and J7A) exceeded the solu-
bility product for FeS, and at plant L, wells L3, L3A, L4, L5, L6,
L6A, L7, L8, L8A, L9A, and L10 exceeded the FeS solubility. The
water sampled from these wells was thus unstable (not at equili-
brium) with regard to the ferrous sulfide equilibrium, and
precipitation of FeS could be expected, which may account for the
black deposits on the aforementioned PVC pipe.
A potentially important aspect of the speciation chemistry of iron-
sulfate equilibrium, as it relates to coal-ash leachate, is the oxidation
of pyrite present in the ash disposal area. In a study by Cox, et al,21
to characterize the runoff from coal storage piles, the production of
ferrous iron and acidity from pyrite oxidation was shown to be the major
factor effectuating the solubilization of iron. The oxidation of pyrite
results in the production of ferrous iron and acidity via the following
reactions:
+2 + 4
2 FeS + 70 + 2 H0 -> 2 Fe + 4H+ 4 SC> (1)
4 Fe+2 + 02 + 4H+ + 4 Fe+3 + 2H20 (2)
At this stage the ferric iron can either hydrolyze to form insoluble
ferric hydroxide,
Fe+3 + 3 H20 -> Fe(OH)3 + 3H+, (3)
or oxidize pyrite directly producing more ferrous iron and acidity:
FeS2 + 14 Fe+3 + 8 H20 -> 15 Fe+2 + 2 S04~2 + 16 H+ (4)
The speciation chemistry of the iron-sulfate equilibrium is a
complex process, and may be worthy of further study in relation to
ash pond leachate due to its potential for decreasing pH and sub-
sequent solubilization of trace metals.
Copper, Lead, Zinc, and Other Metals
At pH values below 7.3, the predominate form of soluble copper is
Cu+2s while at higher values CuOff*" is most prevalent. Copper is strongly
complexed with inorganic ligands such as carbonates, hydroxides, and
57
-------
chlorides and with organic matter. The low pH values observed in the
interstitial water samples indicate the Cu+2 form would prevail, while
at the higher pH values in the well samples it would precipitate as
Cu(OH)2 or Cu2(OH)2C03. In solution at the higher pH values, it
could be in the form of Cu(OH)^=, or CuO =.
Solubility calculations were performed for the copper equilibriums
CuS, CuC03, and Cu(OH)2 using data in Tables 17 and 18 and the stabi-
lity constants listed in Table 20. The calculations indicated that all
well water samples that contained measurable amounts of copper and sul-
fide were unstable (nonequilibrium) with regard to Cu+2. The solubility
limiting equilibrium was found to be CuS as the following calculation
using the data from location L6A, demonstrates:
{Cu+ } = 0.02 mg/1 = 3.1 x 10~7 mole/liter
{S=} = 0.11 mg/1 = 3.4 x 10~6 mole/liter
{C03=} = 1.62 mg/1 = 2.7 x 10~5 mole/liter
{OH*} = 3.1 x 10~7 mole/liter
Sulfide solubility:
{Cu+2}{S=} = 1.0 x 10~12
Hydroxide solubility:
4-9 7
{Cu }{OH } = 2.9 x 10
Carbonate solubility:
{Cu+2}{C03=> = 8.3 x 10"12
exceeds solubility product,
system unstable, precipitation
occurring
equal to solubility product,
system stable, in equilibruim
less than solubility product,
system unstable, available Cu"1"2
The calculations indicate that the water sample from L6A is
in equilibrium with regard to Cu(OH)2 and not at equilibrium with
regard to CuCC>3. Above a pH of approximately 7.5 such as at many
of the sampling locations at plants J and L, the Cu(OH)~ solubility
is exceeded and precipitation occurs.
In waters with pH values below 6.0, the predominate ionic species
of lead is the divalent Pb+2 form. The solubility of lead can be influ-
enced by complexation with hydroxides, chlorides, and organic material.
58
-------
In association with sulfates, carbonates, or phosphate anions under
alkaline conditions, soluble compounds will readily be formed resulting
in the precipitation of lead. Solubility calculations for the PbS
equilibrium, Kgo = 7.0 x 10~29, using data from Tables 17 and 18,
indicate that the water sample collected from sampling well L9A
at plant L is chemically unstable with regard to the PbS equilibrium,
K = 7.2 x 10" 13, and precipitation is occurring.
apparent » r r &
Where:
K = solubility product at equilibrium
K = solubility product of the measured solution
apparent
TABLE 20. SOLUBILITY PRODUCT CONSTANTS FOR IRON, ALUMINUM,
COPPER, LEAD, AND ZINC COMPOUNDS
*a
Compound _ Solubility product _
FeS 2.6 x 10~22
Fe(OH) 5.0 x 10~15
OQ
Fe(OH)3 6.0 x 10
FeC03 2.0 x 10"11
Al(OH) 1.0 x 10~32
Cus 7.9 x 10~37
-?n
Cu(OH)2 1.5 x 10 u
CuC03 2.3 x 10~10
PbS 7.0 x 10~29
Pb(OH)2 1.5 x 10~17
PbC03 7.2 x 10~14
ZnS 7.9 x 10~26
Zn(OH)2 5.0 x 10~17
ZnC03 2.0 x 10~U
a
Adapted from: Sillen, L. G., and A. E. Kartell, "Stability
Constants of Metal-Ion Complexes." London: The Chemical
Society, Burlington House, W. E. (1964).
59
-------
Generally, the dominating ionic zinc species in solutions of low
PH (<7.0) is Zn+2, with the anionic forms Zn(OH)3~ and Zn(OH)^ ^ being
the soluble species at high pH (ll.O).23 The carbonate is the most
soluble form, K = 2.0 x 10, with the hydroxide following at Kgo =
5.0 x 10'^. The least soluble zinc compound is the ZnS form with K =
SO
7.9 x 10~26. Solubility calculations, again using the data in Tables 17
and 18, indicate that in the well samples where measurable zinc and
sulfide concentrations were found (L4, L8A, Lll, J5A, and J7A), unstable
conditions (K >K ) with regard to zinc solubility were present,
apparent so
and precipitation was occurring. With measured pH values less than 11,
no hydroxo-zinc complexing would be expected; thus, any dissolved zinc
species measured in the sampling wells would be predominately the
divalent Zn+2.
The concentrations of beryllium, cadmium, chromium, mercury, and
selenium measured in the sampling wells at plants J and L, as Tables 17
and 18 indicate, were all less than or near their analytical detection
limits. This contrasts with interstitial water analysis in Tables 15
and 16, where concentrations of cadmium, chromium, and mercury were
present in measurable quantities.
Arsenic was present in measurable quantities in samples collected
from wells J2, J5A, L6, L7, L8A, and L9A. Boron was present in all well
samples collected from plants J and L, on March 9 and February 22,
respectively. In addition, the concentration of boron in samples from
wells J2, J7A, L6A, L8, L8A, L9, and L9A were found to exceed the EPA's
quality criteria for water16 of 0.750 mg/1 for irrigation (at one loca-
tion, L8A, by more than 26 times).
As a result of the comparisons between the data listed in Tables
15, 16, 17, 18, and 19, the solubility calculations that were made using
these data, and observations made from the selected Eh-pH diagrams,
several trends have become apparent. First, in general these data
indicate that the concentrations of metals in the interstitial water
samples were higher than concentrations measured for the same consti-
tuents in samples taken from the sampling wells; second, interstitial
water samples tended to have lower pH values than well samples, perhaps
indicating a more reducing environment in the former; third, the
predominate form of iron, copper, zinc, and lead ions present in solu-
tion was as the divalent species, while aluminum was in the trivalent
form; and fourth, the metal-sulfide equilibrium played a dominant role
in controlling the solubility of metals (with the exception of aluminum,
which was limited by the hydroxide solubility due to its +3 valence
state).
60
-------
SECTION 7
HYDROLOGY
The ash disposal areas at plants J and L are located adjacent to
reservoirs in which the water levels in winter are drawn down several
feet for flood control. As a result, groundwater discharge to the river
is greatest during this period. During the late spring and summer
months the reservoir levels are higher, with minor daily variations in
elevation. The higher reservoir levels during this time reduce the
water table gradient toward the river, resulting in a decreased rate of
groundwater discharge to the reservoir.
Although seasonal variations in groundwater flow beneath the ash
disposal areas at both plants occur, the net groundwater movement is to
the adjacent reservoir. In Figures 12 and 13, water table elevations in
the sampling wells at plants J and L, measured respectively on March 9
and February 22, 1977, are plotted along with the average elevation of
the associated reservoir levels observed in 1977 (far right horizontal
axis). The sampling locations are plotted on the graph from left to
right in order of decreasing distance from the river. An estimated line
of best fit through the points (dashed line) indicates a riverward
gradient and thus, the net direction of groundwater flow at the two
disposal areas is toward the river.
Figure 14, is a geologic section and water table profile of the ash
pond area at plant J, showing the water table gradient toward the river.
The figure also shows a condition that may be common to ash disposal
areas where the perimeter dike is constructed of a low permeable material.
Subsurface water might be impounded behind the closed perimeter dike
continuous with the pond's bottom, both of low permeability (which is
the current design). After raising the dike several times to accommo-
date additional ash, a large bowl with low permeability sides would
result. Water in the bottom of this bowl would tend to be passed around
by ambient groundwater flows and mixing would be minimal. Static water
in this zone would undoubtedly be of poorer quality than water merely
passing through coal ash once, acquiring some characteristics of ash
leachate, and then flowing on to mix with unaffected ground or surface
waters or acted on by attenuation dynamics of the surrounding subsoils.
The water in the dead space of the bowl would have a prolonged ash
contact time, allowing for maximum dissolution of ions and the formation
61
-------
235 r
230
cc
g 225
I
ESTIMATED BEST FIT
UJ
UJ
03
<
QC
UJ
I
220
215
210
TOWARD RIVER
j i i
Jl J8 J2 J4 J5 J6 J7 RIVER
ELEVATION
SAMPLING LOCATIONS
Figure 12. Groundwater table elevation in sampling
wells at plant J, March 9, 1977
62
-------
195;
CO
uj 1901
185
LJ
Ul
CD
ffi 1801
S
ESTIMATED BEST FIT
TOWARD RIVER
175
LIO LI I L9 L8 L7 L6 L5 L4 L3 L2 LI RIVER
ELEVATION
SAMPLING LOCATIONS
Figure 13. Groundwater table elevation in sampling
wells at plant L, February 22, 1977
63
-------
Ash Pond A
(abandoned)
Asn Pond B
(active)
Watts Bar
Res. -
Shale---I--^=.-L-L~_--I~ -
|i -..'. ; .,.'.-'. -^_i ! OIIUIC
500
1000
1500
2000
2500
Distance.m
Figure 14. Cross section of ash disposal area at plant J.
-------
of an acidic, highly reducing environment. The potential impact of a
hidden condition such as this on local groundwater quality may warrant
determination of whether the phenomenon exists.
In Figure 13, the water table elevations in the abandoned ash ponds
at plant L (locations L8 and L9), are higher than the surrounding water
table elevations, including the background locations. This is the type
of data that would indicate a leachate bowl. Inflows into the bowl
would not be able to equilibrate with the surrounding water table if
the bowl's sides and bottom were of low permeability (permeability of
the soil below the deposited ash at locations L8 and L9, averages 10~^
cm/sec), and the water level inside the bowl would tend to rise above the
ambient groundwater table. The phenomena is speculative at this point;
more data would be required for confirmation.
The permeability of the ash pond dike and subsoil beneath the ash
at plant J, was measured in the laboratory in both the vertical and
horizontal directions. The vertical permeabilities ranged from 6.3
x 10~8 to 1.3 x 10~6 cm/sec (see Table 3), while horizontal permeabi-
lities ranged from 7.4 x 10~° to 7.4 x 10~^ cm/sec. Subsoil samples
with lower permeabilities contained larger fractions of clay,* while
samples with higher permeabilities contained larger fractions of sand
(Table 3). The density of the soils ranged from 1.42 to 1.79 g/cm3.
Sample density increased with sand content. Moisture content of plant J
soils ranged from 13.9 to 25.7 percent. Generally, the soil samples
from plant J, consisting mostly of sand with a moderate moisture
content, were of moderate permeability and medium to high density.
At plant L, vertical permeabilities ranged from 6.9 x 10~" to 3.0 x
10 cm/sec, and horizontal permeabilities ranged from 5.7 x 10 to
1.5 x 10"^ cm/sec (see Table 7). The sample with 10"^ cm/sec permea-
bility was an ash sample collected at location L8. In general^ soil
samples from plant L having the lowest permeability also contained
a large percentage of clay, while the higher permeable samples con-
tained more sand (with the exception of L8, which was ash at 0.8
meters). The densities of the soil material at plant L ranged from
1.03 to 1.77 g/cm3; moisture ranged from 17.5 to 57.5 percent. Soil
samples from plant L, consisting mostly of highly compacted silty
clay, were generally of low permeability and high moisture content.
Figure 15 shows an idealized cross section of the ash pond dike
at plant J; the superimposed values are mean horizontal permeabilities
(K) as measured on samples of the clay-silt and sand strata collected
at locations J4, J5, and J6. The permeabilities of both strata were
*
Textural classification of soil fractions as per American Society for
Testing and Materials designation, where: clay <0.005 mm, silt 0.005
to 0.074 mm, sand 0.074 to 4.75 mm, and gravel >4.75.2tt
65
-------
ELEV 227.4 m /
ASH POND 7 CLAY-SILT \ ELEV ZZ5.6 m
K« 9.4 x I0"7cm/s \ RESERVOIR
SAND
K=5.0xlO~6cm/s
Q
SHALE
Figure 15. Cross section of the clav-silt and sand strata
at plant .1, showing mean horizontal permeabilities
(K) for locations J4, J5, and J6.
66
-------
very low, with the permeability of clay-silt stratum being the lower
of the two. Using a modification of Darcy's law, the flow through a
discrete saturated substratum, such as the clay-silt substratum, is:
Q = TIW (5)
Where: T = coefficient of transmissibility, volume per unit time
per unit length of stratum width
I = hydraulic gradient, unitless
W = width of the vertical section through which the flow
occurs, unit length
and, T = Km (6)
Where: K = average coefficient of permeability from top to bottom of
stratum, volume per unit time
m = thickness of stratum, unit length
For example, in the clay-silt stratum at locations J4, J5, and J6,
the average horizontal coefficient of permeability (from Table 3) was
9.4 x 10"' cm/sec, and the average thickness of the stratum was 9.8
meters. Conversion of the coefficient of permeability to liters per
day gives 0.83 liters per day, per square meter. Substitution into
equation 6 produces a coefficient of transmissibility of 7.9 liters
per meter of stratum width for the clay-silt stratum. The width of
the vertical section through which the flow occurs (W) corresponds to
the linear length of the ash pond dike adjacent to the reservoir, and
was measured to be approximately 1718 meters. The hydraulic gradient
(I) of the water table was 0.5. Substituting into equation 5:
Q = (7.95 ) (Q.5) (1718 m)
day-m
Q = 6824 liters per day (1803 gallons per day)
gives the total groundwater flow passing through this cross-sectional
area of the clay-silt stratum. A similar calculation for the sand
stratum, where the average permeability was 5.0 x 10~6 cm/ sec and the
average stratum thickness for locations J4, J5, and J6 was 2.5 meters,
indicates a total flow through this stratum of 9265 liters per day.
Combining the flows through the clay-silt and sand strata gives a total
flow through both strata of 16,090 liters per day. This compares to a
surface discharge from the ash disposal pond at plant J, of from 59.4
67
-------
Figure 16. Cross section of substratum below plant J's ash disposal area.
-------
TABLE 21. FLUX OF SELECTED CONSTITUENTS THROUGH SUBSTRATA AT PLANT J
Constituent
Aluminum
Calcium
Cadmium
Chromium
Copper
Iron
Magnesium
Nickel
Lead
Sulfate
Zinc
Concentration
in clay-silt
mg/1
98
301
<0.002
<0.005
0.113
506
79.3
0.18
0.036
1883
0.90
Clay-silt
flux
g/24 hr.
671
2054
0.013
0.034
0.773
3457
541
1.27
0.247
12,851
6.14
Concentration
in sand
mg/1
3.2
98
0.001
0.007
0.053
38.9
14.3
0.05
0.032
153
0.110
Sand
flux
g/24 hr.
30
914
9.26
0.064
0.494
360
132
0.494
0.293
1420
1.02
Total
ground water
flux g/24 hr.
701
2968
9.27
0.098
1.26
3817
673
1.76
0.540
14,271
7.16
Concentration
in ash pond
discharge mg/1
1.4
22.5
0.0015
<0.005
0.06
2.35
3.1
<0.05
<0.01
88.5
0.05
Ash pond
discharge
flux g/24 hr.
142,088
2,283,567
152
-
6089
238,505
314,624
-
-
8,982,033
5074
-------
to 16.2 million liters per day during 1976. It should be noted that the
flow (Q) is dependent on the hydraulic gradient (I), while transmissi-
bility (T) and width (W) remain constant. The hydraulic gradient
fluctuates with time according to the elevation of the adjacent reser-
voir, subsequently increasing or decreasing subsurface discharge.
Figure 16 shows a cross section of the ash pond and substrata at
plant J and illustrates the spatial relationships between the ash,
clay-silt, sand, and shale materials. The total flux of aluminum,
calcium, cadmium, chromium, copper, iron, magnesium, nickel, lead,
sulfate, and zinc were calculated for the combined flows in the clay-
silt and sand strata illustrated in Figure 16 (detailed vertical
profiles of the substratum at plants J and L are presented in appendix
B). These fluxes are compared (see Table 21) to the total mass of the
same constituents discharged from the ash pond's surface effluent. The
fluxes in the groundwater were obtained by averaging the concentrations
measured (Table 17) at locations J4A, J5A, and J6A for the clay-silt
flux, and J4, J5, and J6, for the sand flux. The product of the average
concentrations and the clay-silt and sand flows calculated above, gives
the 24-hour flux in each strata. The summation of these two fluxes
provides the total groundwater flux of each constituent. These cal-
culations were made assuming concentration homogeneity within each
stratum, and disregarding attenuation processes. The mass constituent
discharged from the ash pond via the surface effluent was determined by
averaging the concentrations measured in two samples collected during
1976, and multiplying this value by the average 1976 daily effluent
discharge.
Comparison of the columns in Table 21 shows that the total flux of
aluminum, calcium, copper, iron, magnesium, nickel, and zinc was great-
est in the clay-silt stratum, while in the sand stratum cadmium, chromium,
lead, and sulfate flux were greatest. Comparison of the total flux
through both strata with the total mass from the ash pond surface dis-
charge shows that the flux through both strata combined was a small
percentage (less than 1 percent) of the total mass discharged from the
ash pond surface effluent. Albeit, with the exception of copper, con-
stituent concentrations were higher in the groundwater than in the ash
pond discharge. The significant factor effectuating the total mass in
the ash pond surface discharge as compared to the groundwater flux was
flow. Flow from the ash pond during 1976 averaged 1.0 x 10 liters per
day, whereas, the calculated total flow through the combined clay-silt
and sand strata was 16,909 liters per dayonly 0.016 percent of the ash
pond discharge.
The physical measurements of the predominantly clay-silt sub-
strata necessary to quantify groundwater flow at plant L, were not made
because the large area involved would have required numerous and costly
70
-------
exploratory borings. The low permeabilities measured in the clay-silt
substratum (less than 10 cm/sec) would, however, tend to minimize
leachate movement if a generalization can be made from the calculations
made with plant J's data.
As previously mentioned in the geological description (section 3),
the primary material underlying the ash disposal area at plant L, is a
mixture of alluvial and terrace deposits. In certain areas, such as
location L4, these deposits consist of unconsolidated materials con-
taining as much as 40 percent gravel. This type of material could not
be collected in a Shelby tube for the determination of permeability. In
order to determine the groundwater flow in this material, two wells were
installed 1.5 meters apart with perforations transecting the pervious
gravel material vertically. The difference in hydraulic head between
the two wells was 3.1 meters. Nineteen liters of a saturated sodium
chloride solution were then injected into the upgradient well. The
downgradient well was then pumped and samples collected periodically for
the measurement of conductance and chloride. Figure 17 shows a plot of
chloride concentration and conductivity versus pumping time for the
downgradient well. The figure indicates that the chloride concentration
increased substantially within 24 minutes and reached a maximum at
approximately 75 minutes. The plot of conductance versus time presents
a shape nearly identical to the chloride plot, with a slight decrease in
the beginning and a slower return to baseline being the only differences.
The slow return to baseline of both parameters is thought to be a result
of lateral dispersion of the solute.
Under the conditions of this test, if the time required to reach
maximum concentration is assumed to be the flow time between the two
wells, then 0.03-cm/sec would be the velocity of the ground water in
this material. Using Darcy's law, this velocity converts to a per-
meability (K) of 0.14 cm/sec, substantially higher than values measured
in the laboratory on other subsurface materials. At plant L, there are
two locations (L4 and L5) where this highly permeable alluvial material
was found. The water quality at both these locations, however, was not
significantly different from the background wells 10CW and 11CW. This
seemed to indicate that attenuation processes in the overlying clay-silt
stratum were precluding ash leachate from infiltrating the porous alluvial
material. However, if the ash leachate should ever enter the highly
permeable alluvium, minimal attenuation, characteristic of this type of
material, would allow the rapid lateral spread of ash leachate.
71
-------
Figure 17
N3
Cone CP
(Pf>»n)
TRACER TEST OF CONDUCTANCE AND CHLORIDE
vs
PUMPING TIME
Condvctonc*
umhoi/
8 16 24 32 40 48 56 64 72 80 88 96 104 112 120 128 136 144 152 160 176 168 184 192 200 208
TIME
(Minutes)
-------
SECTION 8
LABORATORY ATTENUATION STUDIES
This section presents the results of the soil column attenuation
studies performed on natural soils from plants L and J, and kaolinite
clay.
ATTENUATION BY NATURAL SOIL COLLECTED AT PLANT L
A sample of the ash pond dike material from plant L was one of
three soil materials used in the attenuation experiment described in
section 4. As previously mentioned in that section, samples of the soil
column effluent were analyzed for the constituents listed in Table 8.
These data are tabulated, along with an analysis of the ash leachate
used in the attenuation studies, and are presented in appendix C. The
soil sample from plant L, was also analyzed by X-ray diffraction for
quartz, and the clay minerals montmorillonite, kaolinite, and illite.
The analysis found the clay minerals present in the following relative
abundance: kaolinite > montmorillonite > illite, and quarts was the
most predominate crystalline phase present.
Figures IS, 19, 20, and 21 are plots of plant L's soil column
effluent concentrations for magnesium, sodium, potassium, aluminum,
barium, copper, zinc, nickel, and sulfate, versus the cumulative
effluent volumes. Also shown on these plots are the "initial" influent
leachate concentrations for the above parameters. In Figure 18, mag-
nesium, sodium, and potassium are plotted. The illustration shows that
the concentrations of magnesium and sodium in the column effluent ex-
ceeded the initial influent concentration for the duration of the
experiment, indicating solubilization of these elements occurred in the
soil. Potassium, however, initially had a concentration less than the
influent, which increased above the influent in subsequent samples and
eventually equilibrated (concentration in equaled concentration out)
with the initial leachate concentration. This seems to indicate that
potassium was initially attenuated by the soil, and later merely passed
through the column unaffected. This is further illustrated in Table 22,
where mass balances have been calculated on twelve parameters including
those illustrated in Figures 18 through 21.
73
-------
20
16
o>
E
12
8-
*
INITIAL LEACHATE CONCENTRATION
MAGNESIUM
SODIUM
POTASSIUM
180 360 540 720 900 1080
CUMULATIVE ELUATE VOLUME (ml)
1260
18. Concentrations of magnesium, sodium, and potassium
in the effluent from plant L's soil column.
-------
1.0 r-
o>
E
-o
Cn
.01
0.004
INITIAL LEACHATE CONCENTRATION
COPPER
ZINC ---
NICKEL
_L
180
360
540 720
900 1080 1260
CUMULATIVE ELUATE VOLUME (ml)
Figure 19. Concentrations of cooper, zinc, and nickel
in the effluent from plant L's soil column.
-------
1.0
r
ALUMINUM
BARIUM --
O.I
INITIAL LEACHATE CONCENTRATION
.01
180 360 54O 720 900 1080
CUMULATIVE ELUATE VOLUME (ml)
1260
Figure 20. Concentrations of aluminum and barium
In Che effluent from plant L's soil
column.
-------
400
300
o>
uj 200
IOO
INITIAL LEACHATE CONCENTRATION
ISO 360 540 720 900 1080
CUMULATIVE ELUATE VOLUME (ml)
1260
Figure 21. Concentration of sulfate in the effluent
from plant L's soil column.
-------
The mass input to the soil columns was determined by multiplying
the total volume of eluate that passed through the column by the initial
influent concentration. To determine the mass output of the column, the
volume of each composite eluate sample was multiplied by the concentra-
tion of the constituent measured therein, and these values summed. The
difference between the mass in and mass out is the amount retained, or
contributed by the soil column. These data indicate that magnesium and
sodium had, respectively, 16 and 5 percent increases in mass between the
influent and effluent of the soil column, while 3 percent of the
potassium was removed in the soil.
In Figure 19, copper, nickel, and zinc concentrations in the soil
column effluent are plotted. Copper concentrations were less than the
initial leachate concentration in all samples analyzed, and gradually
decreased with the volume eluted. Zinc showed a trend similar to
copper. With the exception of the first sample, all samples analyzed
for zinc were less than the initial leachate concentration. The con-
centration of nickel in the leachate was less than the analytical
detection limit, which accounts for effluent values not plotted below
the initial leachate concentration line. However, samples of the soil
column effluent did contain some measureable quantities of nickel indi-
cating solubilization from the soil. In Table 22, the data indicate
that copper and zinc had, respectively, 97 and 40 percent removal during
the test. Calculations were not performed for nickel because it was not
detected in the leachate.
The concentrations of aluminum and barium in the effluent from
plant L's soil column are illustrated in Figure 20, and the plot for
sulfate in Figure 21. All of the effluent samples analyzed for barium
and aluminum had concentrations less than the initial leachate value,
with the first eluate volume for aluminum being the only exception. The
data in Table 22, show that 70 percent of the aluminum and 57 percent of
the barium were removed in the soil column. The sulfate plot in Figure
21, indicates solubilization occurring within the soil column. This
indication is supported by the mass balance data in Table 22, which
shows a 15 percent increase in sulfate mass between the soil column
influent and effluent.
Calcium, manganese, iron, and mercury data are not plotted, but
from the mass balance data in Table 22, it is indicated that 11 percent
of the calcium, 85 percent of the manganese, essentially 100 percent of
the iron, and 87 percent of the mercury were removed in the soil column.
Cadmium, chromium, lead, beryllium, and selenium were all less than the
minimum detectable limits in all samples, including the initial leachate
sample, and for that reason were not addressed in this analysis.
Also presented in Table 22, are the number of chemical equivalents
removed from the leachate and the number added to the soil column efflu-
ent, with the sum of both listed at the bottom of the table. These
78
-------
TABLE 22. MASS BALANCE OF PLANT L'S SOIL COLUMN INFLUENT AND EFFLUENT
10
Constituent
Magnesium
Sodium
Potassium
Copper
Zinc
Aluminum
Barium
Sulfate
Calcium
Manganese
Iron
Mercury
Mass IN
(mg)
8.66
8.44
15.96
0.16
0.05
0.07
0.26
273.6
210.9
4.79
17.1
0.0023
Mass OUT
(mg)
10.03
8.87
15.45
0.01
0.03
0.02
0.11
315.3
187.8
0.74
<0.01
0.0003
Percent
removal
0
0
3
97
40
70
57
0
11
85
>99
87
Equivalents
removed
0
0
0.01
0.004
0.0004
0.01
0.002
0
1.16
0.15
0.92
1.9 x 10~5
Percent
increased
16
5
0
0
0
0
0
15
0
0
0
0
Equivalents
added
0.11
0.02
0
0
0
0
0
0.87
0
0
0
0
Total
2.26
1.00
-------
data indicate that 2.26 meq (milliequivalents) were removed in the soil
column, while 1.0 meq was added to the column effluent. This amounted
to a net decrease of 1.26 meq through the soil column.
ATTENUATION BY NATURAL SOIL COLLECTED AT PLANT J
A sample of plant J's ash pond dike material was used to determine
the attenuation of coal-ash leachate by a natural soil type being used
in ash pond construction, as was the soil from plant L, previously dis-
cussed. The soil sample from plant J, contained a percentage of clay
minerals that when subjected to X-ray diffraction analysis were found to
be present in the following relative abundance: illite > kaolinite >
montmorillonite. In addition to these clay minerals, the soil con-
tained quartz as the most predominant crystalline phase. The cation
exchange capacity of the soil was 17.0 meq per 100 grams, as determined
by the method of Bascomb, which is described in appendix A.
In Figures 22 through 24, plant J's soil column effluent concen-
trations are plotted against the cumulative effluent volumes for
magnesium, sodium, potassium, aluminum, barium, copper, zinc, and
nickel. The initial leachate concentrations for the above parameters
are also shown in these plots. In Figure 22, magnesium, sodium, and
potassium are plotted. The illustration shows that the concentrations
of magnesium and sodium in the soil column effluent exceeded the influ-
ent concentration in all samples analyzed during the experiment.
Again, as with plant L's soil column study, the plots indicated solu-
bilization of these elements within the soil column. The plot for
potassium is similar to the one generated from plant L's attenuation
data. Initially the effluent concentration was less than the influent,
and then gradually increased to nearly the same concentration, but never
quite equilibrated with the influent. This indicates that potassium was
being attenuated, to some degree, for the duration of the experiment.
This is also illustrated in Table 23, where mass balances have been
calculated on eleven constituents, in a manner previously described. As
the data in this table indicate, magnesium and sodium had, respectively,
20 and 10 percent increases in mass between the influent and effluent of
the soil column, while 12 percent of the potassium was removed in the
soil.
Figure 23 illustrates the plotted concentrations of copper, zinc,
and nickel in plant J's soil column effluent. Copper concentrations
fluctuated, but were always less than the influent value. The zinc
concentration in the column effluent initially was higher than the
influent, but immediately declined to remain less than the influent
value for the experiment's duration. The mass balance data from Table
23 show that copper and zinc, respectively, had 94 and 57 percent
removal of mass in the soil column. A balance on nickel could not be
calculated because it was not detected in most samples.
80
-------
20
16
12
8-
4-
INITIAL LEACH ATE CONCENTRATION
MAGNESIUM
SODIUM -
POTASSIUM «
300 600 900 1200 1500 1800
CUMULATIVE ELUATE VOLUME (ml)
22. Concentrations of maeneslum, sodium, and potassium
in the effluent from nlant J's soil column.
-------
2.0
1.0
= C.i
o>
CO
ro
0.01
e*o £*»«
iNITiAL LEACHATC CONC£i\" i RATION
COPPER-
ZINC «
NICKEL
0.004]
300 600 900 1200 1500 1800
CUMULATIVE ELUATE VOLUME (ml)
Figure 23. Concentrations of cooper, zinc, and nickel
In the effluent from plant J's soil column.
-------
1.0
00
a. o.i
E
0.01
INITIAL LEACHATt CONCENTRATION
ALUMINUM
BARIUM
I
I
300 600 900 1200 1500 1800
CUMULATIVE ELUATE VOLUME (ml)
Figure 24. Concentrations of aluminum and barium
in the effluent from plant J's soil
column.
-------
TABLE 23. MASS BALANCE OF PLANT J'S SOIL COLUMN INFLUENT AND EFFLUENT
oo
Constituent
Magnesium
Sodium
Potassium
Copper
Zinc
Aluminum
Barium
Calcium
Manganese
Iron
Mass IN
(mg)
13.00
12.31
23.94
0.24
0.07
0.10
0.39
316.35
7.18
26.65
Mass OUT
(mg)
15.65
13.59
21.18
0.01
0.04
0.11
0.27
261.30
1.77
0.08
Percent
removal
0
0
12
94
57
0
32
17
75
=100
Equivalents
removed
0
0
0.07
0.01
0.0009
0
0.001
2.75
0.20
1.38
Percent
increased
20
10
0
0
0
10
0
0
0
0
Equivalents
added
0.22
0.06
0
0
0
0.001
0
0
0
0
Total 4.41 0.28
-------
Aluminum, however, began with an effluent concentration greater
than the influent, then decreased to below the influent value where it
remained for all samples except the last which was again greater in
concentration than the influent. Barium had 32 percent removal within
the soil column, according to the data in Table 23. Aluminum had a 10
percent increase in mass between influent and effluent.
Although the data for calcium, manganese, and iron were not plotted,
the mass balance data in Table 23 indicate that 17 percent of the cal-
cium, 75 percent of the manganese, and nearly 100 percent of the iron
was removed in the soil column. Cadmium, chromium, lead, beryllium,
mercury, and selenium were all less than their analytical detection
limits in nearly all samples. Not enough sample was collected for
sulfate analysis. Table 23 also shows that 4.41 chemical meq were
removed in the soil column from plant J, while 0.28 meq were added to
the column effluent. Thus, a net decrease of 4.13 meq occurred between
the soil column influent and effluent.
ATTENUATION BY KAOLINITE
In natural soils there are three major clay minerals that may be
present in relative amounts depending on the geographical location; they
are kaolinite, montmorillonite, and illite. Each of these clays has the
ability to attenuate pollutants from aqueous solutions, although selec-
tively and at different rates.25 Attempts were made to study the attenua-
tion of coal-ash leachate by each of these clays. However, expansion of
the clay minerals montmorillonite and illite upon wetting inhibited
percolation to such a degree that experiments with these two clays were
abandoned. It was possible, however, to study the attenuation capa-
bilities of kaolinite. The results of that investigation are presented
in Figures 25 through 27, and Table 24.
In Figure 25, column effluent concentrations of magnesium, sodium,
and potassium are plotted against the cumulative eluate volume from the
kaolinite clay column. The illustration shows that concentrations of
magnesium and sodium in all effluent samples analyzed, except the last,
exceeded the influent leachate concentration. This indicates that
solubilization of these two elements occurred within the clay column.
Potassium, on the other hand, had concentrations in the column effluent
which exceeded the influent concentrations in all samples except the
first and last. This would seem to indicate that potassixim is also
being solubilized to some degree within the clay column. In Table 24,
mass balance data agree with the plotted data, in that magnesium,
sodium, and potassium respectively, had 23, 17, and 9 percent increases
in mass between the clay column influent and effluent.
Figure 26 illustrates the plotted concentrations of copper, zinc,
and nickel in the kaolinite column effluent. Copper concentrations were
less in the column effluent than in the influent for all samples except
85
-------
20 h
00
16
12
o>
E
8
r
..
*
-INITIAL LEACHATE CONCENTRATIONS
MAGNESIUM
SODIUM
POTASSIUM
e
180 360 540 720 900 1080
CUMULATIVE ELUATE VOLUME (ml)
1260
Figure 25. Concentrations of magnesium, sodium, and pottasium
in the kaolinite clav column effluent.
-------
t.o
*
0»
£
CD
-J
-INITIAL LEACHATE CONCENTRATIONS
0.0!
COPPER-
Zi'JC
NICKEL
0.04,
_L
180 360 540 720 900 1080 1260
CUMULATIVE ELUATE VOLUME (ml)
Figure 26. Concentrations of copper, zinc, and nickel
in the kaolinite clay column effluent.
-------
1.0
-IN'TIAI LEACHATF CONCFNTRATIONS
00
00
0>
E
0.!
L
ALUMINUM-
BARIUM '
0.01
i
180 360 540 720 900 1080
CUMULATIVE ELUATE VOLUME (ml)
1260
Figure 27. Concentrations of aluminum and barium
in the kaolinite clay column effluent.
-------
TABLE 24. MASS BALANCE OP KAOLINITE PACKED COLUMN INFLUENT AND EFFLUENT
C on s t i tuen t s
Magnesium
Sodium
Potassium
Copper
Zinc
Aluminum
Barium
Calcium
Manganese
Iron
Mercury
Sulfate
Mass IN
(mg)
9.12
8.64
16.80
0.17
0.05
0.07
0.28
222.00
5.04
18.00
0.0024
345.60
Mass OUT
(mg)
11.21
10.11
18.24
0.07
0.03
0.05
0.20
180.00
0.99
0.05
0.0003
429.60
Percent
remova 1
0
0
0
56
50
30
29
19
80
99.7
88
0
Equivalents
removed
0
0
0
0.003
0.001
0.002
0.001
2.09
0.14
0.96
0.000021
0
Percent
increased
23
17
9
0
0
0
0
0
0
0
0
24
Equivalents
added
0.17
0.06
0.03
0
0
0
0
0
0
0
0
1.75
Total
3.20
2.01
-------
the last. All effluent zinc samples analyzed were less than the influ-
ent leachate concentration. The concentration of nickel in the column
effluent initially exceeded the column influent, then decreased to
equilibrate with the influent concentration, which was nickel's minimum
detectable limit. Copper and zinc removal within the clay column, based
on mass balance data in Table 24, was respectively 56 and 50 percent. A
balance on nickel was not calculated because it was not detected in the
influent and most of the effluent samples.
Plots of aluminum and barium concentration in the kaolinite column
effluent are illustrated in Figure 27. All samples analyzed for barium
had concentrations less than the initial leachate concentration. Alu-
minum concentrations were less than the influent in the early eluate
volumes, then gradually increased to become equal with the influent
concentration. The data from Table 24 indicates that aluminum and
barium were reduced in the kaolinite column by 30 and 29 percent,
respectively.
For calcium, manganese, iron, and mercury, the mass balance data in
Table 24 indicate that 19 percent of the calcium, 80 percent of the
manganese, nearly 100 percent of the iron, and 80 percent of the mercury
was removed in the kaolinite clay column. Sulfate had a 24 percent
increase in mass from influent to effluent.
In Table 24, the data also indicates that 3.20 chemical meq were
removed in the kaolinite column, while 2.01 meq were added to the column
effluent. As a result, a net of 1.19 chemical meq were attenuated from
the initial leachate influent by the kaolinite clay column.
DISCUSSION OF LEACHATE ATTENUATION STUDY
The attenuation processes that occur in soils are a potential
major influence precluding groundwater contamination by leachate from
coal ash disposal areas. In an attempt to determine the extent of ash
leachate attenuation by various soils, the laboratory investigations
reported on above were conducted. Other investigators have used this
technique to determine the attenuation of various aqueous wastes by
different soils, clays, and other porous material.2°,27,28
For example, in a study by Griffin, et al,26 the attenuation of
pollutants in municipal landfill leachate by the clay minerals mont-
morillonite, kaolinite, and illite was investigated. Their study
determined the following clay mineral hierarchy for attenuation capa-
bilities, montmorillonite > illite > kaolinite, and that the principal
attenuation mechanism for lead, cadmium, mercury, and zinc was precipi-
tation in the soil columns surface layers. In a study by Fetter27 to
determine attenuation of secondarily treated wastewater by a calcareous
glacial outwash soil, the findings suggested that heavy metals removal
was through ion exchange. Still other investigators, such as Leeper,28
consider the adsorption reactions with hydrous oxides of iron, aluminum,
90
-------
and manganese to be the major mechanism for the attenuation of metals in
soil. As one can see from this small, but representative sampling, the
literature is inconclusive as to which mechanism is the major factor
influencing attenuation by soils. Indeed, no one mechanism is univer-
sally responsible for the attenuation processes that occur in soils
receiving liquid wastes or leachate. In fact, the mechanisms may vary
for each situation depending on the characteristics of the soil, the
characteristics of the liquid waste or leachate, and the hydrological
conditions.
The major mechanism influencing attenuation of ash leachate in this
study is not readily discernable from the previously discussed data. It
may be concluded with a certain degree of confidence, however, that ion
exchange is not solely responsible for the removal of constituents from
the ash leachate, for the following reason.
The two natural soils from plants L and J, and the kaolinite clay
used in the column tests had cation exchange capacities, respectively,
of 20.0, 17.0, and 16.0 meq per 100 g (the cation exchange capacity of
the silica was negligible at 1.2 meq/ 100 g) . Five grams each of the
soils and clay material was used in each column, which yielded a total
exchange capacity for the columns of 1.0 meq plant L material, 0.85 meq
plant J material, and 0.80 meq for the kaolinite column. The number of
meq's attenuated by these same respective columns was 1.26, 4.13, and
1.19 meq. Each column has thus exceeded its available exchange capac-
ity; consequently, ion exchange is not the only mechanism accounting for
attenuation in this study. Actually, ion exchange may be only a minor
influence, and precipitation and/or adsorption may be the major influ-
encing mechanisms affecting attenuation, but the data do not differentiate
between these two mechanisms.
A comparison of the mass balance data in Tables 22, 23, and 24
shows that magnesium and sodium had a net increase in mass between the
column influent and effluent for all three attenuation experiments.
This indicates that these two elements were solubilized by the ash'
leachate as it passed through the soil columns. Of the three materials
used in this study, the kaolinite clay released the most magnesium and
sodium. Potassium was also released from the kaolinite, while the two
natural soils, from plants J and L, attenuated potassium.
Copper and zinc were both retained in all three attenuation columns
copper more so than zinc. Copper was attenuated the least by the kaoli-'
nite clay. The two natural soils attenuated greater than Qn n r + *
the copper. Barium was attenuated in all thre^ columns? bu? ?he Soli
e attened I
. - i
with esentially 0 peL^remo^nr0: h' T C°nStitUentS
with 75 percent plus attenuation * C°1Umn; man^anese
91
-------
In general, soils that are composed of high percentages of clay
minerals will, by one mechanism or another, tend to attenuate solutes
more so than will materials containing high percentages of sand.
92
-------
SECTION 9
THEORETICAL CONSIDERATIONS
Using information reported in the literature to date regarding
coal-ash leachate and the attenuation of leachates in general, the
results of this study, and some fundamental knowledge of the hydro-
geochemical environment, a schematic diagram of ash pond leachate
generation and attenuation was prepared (see Figure 28). This diagram
illustrates some of the basic concepts associated with solid waste
disposal in general and presents some details relating to coal-ash
disposal in particular. The diagram does not necessarily indicate
conditions and mechanisms associated with all ash disposal sites,
but is designed to relate some of the physical and chemical pro-
cesses that may be pertinent to an environmental evaluation of
groundwater degradation at coal-ash disposal areas.
In this illustration, fly ash, bottom ash, and pyrites are sluiced
to the ash pond, along with other miscellaneous plant discharges, such
as acidic coal-pile drainage. Once in the disposal pond, the ash and
other heavy particles settle out, with the supernatant overflowing into
an adjacent surface water. Supernatant that does not leave the pond via
the surface overflow infiltrates into the settled ash, carrying with it
any solutes picked up during sluicing of the ash from the plant and
mixing with other wastes discharged to the pond. After infiltration,
the pond supernatant percolates down through the saturated aerobic zone
where readily soluble ions of calcium, magnesium, sodium, and sulfate
are added to solution. Some slight dissolution of certain metals may
occur, and sulfite, if not already in solution, solubilizes.
Further downward percolation leads to the anoxic zone, which is
created by the depletion of dissolved oxygen by sulfite or other oxi-
dation processes. It is in the anoxic zone, which occurs either below
the water table or deep enough to prevent surface aeration, where the
percolating water acquires the culmination characteristics of coal-ash
leachate. The anoxic zone is a reducing acidic environment in which
dissolution of metals can occur, sulfides are formed, and high concen-
trations of ferrous iron may occur. It is also in this zone where the
hydraulic gradient of the groundwater begins to exert its energy poten-
tial on the leachate, altering the direction component of its velocity
from strictly downward to lateral.
93
-------
ASH SLUICING PIPE FROM PLANT
(CONTAINS FLY ASH,BOTTOM ASH.PYRITE.RAH SURFACE HATER,LOW DISS. METALS,HIGH TOTAL METALS)
DIRECT PRECIPITATION
X
ORIGINAL
GROUND WATER TABLE'
SUPERNATE
INFILTRATION
ASH POND SUPERNATE DISCHARGE
(MUST MEET NPDES REQUIREMENTS)
SATURATED
kAEROBIC ZONE
DISSOLUTION OF Cd*«,Mq_+* SCfi ,
TDS INCREASES SOME METAL?
AND SO \ PRODUCED
ASH DISPOSAL POND
GROUND WATER FLOW
D.O. DEPLETES S03 »
ANOXIC ZONE DISSOLUTION OF METALS.LOW/
pH,REDUCING ENVIRONMENT/
FORMATION OF SULFIOE
% HIGH CONCENTRATION Fe*t/
\INFILTRATION OF LEACHATE INTO SUBSURFACE
I I
SH POND DIKE
'(LOW PERMEABILITY)\
CLAY-SILT STRATUM LEACHA\E ATTENUATION 06CURIHG HERE
(LOW HYDRAULIC CONDUCTIVITY (ASSORPTIORyPRECIPITATION.MN EXCHANGE
HIGHCATION EXCHANGE CAPACITY SOMEXLUTION) \
HIGH ADSORPTION SITES) ^^ X
SURFACE WATER-LAKE OR RIVER
(NORMALLY SUPPLIES RAH WATER
FOR ASH SLUICING)
OXIDATION AND PRECIPITATION OF
vLEACHATE ENTERING SURFACE !-;ATER
-- LEACHATE MIGRATION FRONT
"(HIGH^CONC. OF EXCHANGEABLE DIVALENT CATIONS
PRECEEDS LEACHATE FRONT,TERMED "HARDNESS HALO")
SAND STRATUM
(HIGH. HYDRAULIC CONDUCTIVITY
.OU CATION EXCHANGE CAPACITY
.OW ADSORPTION SITES)
GROUND WATER FLOW
MINIMAL ATTE'lUATIOii HERE
IMPERMEABLE
BEDROCK
FIGURE 28. SCHEMATIC OF COAL-ASH
LEACHATE GENERATION AND ATTENUATION
-------
Eventually the leachate begins to infiltrate the bottom of the ash
disposal area. This may occur at a relatively high rate if the pond
bottom is of a highly permeable material, such as sand, or at a lower
rate if the material is a low permeable clay-silt, such as illustrated
in Figure 28. In the clay-silt stratum attenuation of solutes in the
leachate will begin to occur. Attenuation mechanisms, such as ion
exchange, chemical precipitation, and physical adsorption, will act to
lessen the leachate migration. As the leachate plume advances through
the subsurface environment, metal ions with an affinity for adsorption
and exchange sites will replace weakly-bound divalent cations, such as
calcium and magnesium. These displaced divalent cations will move along
preceding the leachate plume and create what has been termed a "hardness
halo." Conservative constituents, such as chloride and sulfate, may
even precede this hardness halo. The rate of leachate migration will
depend on the hydraulic conductivity and the rate of attenuation.
If the leachate plume should reach a highly permeable stratum such
as the sand stratum depicted in Figure 28, then the potential for in-
creased groundwater degradation can occur. A sand stratum or aquifer
offers little in the way of attenuation capacity and much as an avenue
for leachate migration. Hydraulic conductivities of sandy material are
normally greater than those of clay, and the number of adsorption and
exchange sites are fewer, which will tend to decrease the rate of
attenuation.
Leachate studies thus far suggest that coal-ash disposal sites, and
perhaps solid waste disposal sites in general, might be constructed in
such a manner as to allow leachate to percolate downward through an
attenuation blanket. The attenuation blanket would need to be of design
and material t'hat would allow optimum flow and attenuation, thus acting
as a treatment system.
95
-------
REFERENCES
1. Merz, R. C., and J. R. Snead. "Investigation of Leaching of
Ash Dumps." State Water Pollution Control Board, Sacramento,
California, 1952.
2. Rohrman, F. A. "Analyzing the Effect of Fly Ash on Water
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3. O'Connor, J. T., M. H. Virshbo, C. J. Cain, and C. J. O'Brien.
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Paper presented at the ASCE National Environmental Engineering
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8. Chu, T.-Y. J., W. R. Nicholas, and R. J. Ruane. "Complete
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Paper presented at the 68th Annual Meeting of the AIChE
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96
-------
9. Reed, G. D., D. T. Mitchell, and D. G. Parker. "Water Quality
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West LaFayette, Indiana, May 4-6, 1976.
10. Burnett, J. Master's Thesis, Civil Engineering Department,
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Fuel Ash in Water Supply Catchment Areas." Water Research, 10,
1976. pp. 1115-1121.
12. Harriger, T. L., W. M. Barnard, D. R. Corbin, and D. A. Watroba.
"Impact of a Coal Ash Landfill on Water Quality in Northcentral
Chautauqua County, New York." Departments of Geology and
Chemistry, State University College, Fredonia, New York, 1977.
13. Benziger, C. P., and J. M. Kellberg. "Preliminary Geological
Investigation for Eastern Area Steam Plant." TVA Division of
Water Control Planning, Knoxville, Tennessee, February 1951.
14. Kellberg, J. M., and C. P. Benziger. "Geology of the Widows Creek
Steam Plant Site." TVA Division of Water Control Planning,
Knoxville, Tennessee, April 1950.
15. Davison, R. L., D. F. S. Natusch, and J. R. Wallace. "Trace
Elements in Fly Ash Dependence of Concentration on Particle
Size." Environmental Sci. and Technol., JJ(13), December 1974.
pp. 1107-1113.
16. Quality Criteria for Water. U.S. Environmental Protection Agency,
EPA-440/9-76-023, Washington, D.C., 1976.
17. Hem, J. D. "Graphical Methods for Studies of Aqueous Aluminum
Hydroxide, Fluoride, and Sulfate Complexes," Chemistry of
Aluminum in Natural Water. Geological Survey Water-Supply
Paper 1827-B, 1968.
18. Roberson, C. E., and J. D. Hem. "Solubility of Aluminum in
the Presence of Hydroxide, Fluoride, and Sulfate." Chemistry
of Aluminum in Natural Water. Geological Survey Water-Supply
Paper 1827-C, 1969.
19. Hem, J. D., and W. H. Cropper. "Survey of Ferrous-Ferric Chemical
Equilibria and Redox Potentials." Chemistry of Iron in Natural
Water. Geological Survey Water-Supply Paper 1459, 1962.
20. Hem, J.D. "Equilibrium Chemistry of Iron in Groundwater. "
Principles and Applications of Water Chemistry, S.D. Frost and J. V.
Hunter, eds. John Wiley, pub. , 1967. (Proceedings from 4th
Rudolph Research Conference, 1965.)
97 (Rev. 3/81)
-------
21. Hem, J.D. "Some Chemical Relationships Among Sulfur Species and
Dissolved Ferrous Iron. " Chemistry of Iron in Natural Water, Geo-
logical Survey Water-Supply Paper 1459, 1962.
22. Garrels, R.M. Mineral Equilibria. Harper and Brothers, publishers,
New York, 1960
23. Cox, D. B., T.-Y. J. Chu, and R. J. Ruane. "Characteriza-
tion of Coal Pile Drainage." Paper prepared for Office of
Energy, Minerals, and Industry, Office of Research and
Development, U.S. Environmental Protection Agency,
Washington, D.C., 1978.
24 Federal Water Quality Administration. Oxygenation of Ferrous Irons.
U.S. Government Printing Office, Washington, D.C., 1970.
25. Hem, J. D., "Chemistry and Occurrence of Cadmium and Zinc in Surface
Water and Groundwater." Water Resources Research, .8(3), June 1972.
pp. 661-679.
26. 1976 Annual Book of ASTM Standards, Part 19, Soil and Rock;
Building Stones; Peats. American Society for Testing and
Materials, Philadelphia, Pennsylvania, 1976.
27. Griffin, R. A., N. F. Shimp, J. D. Steele, R. R. Ruch, W. A. White,
and G. Hughes. "Attenuation of Pollutants in Municipal Landfill
Leachate by Passage Through Clay." Environmental Sci. and Techno!..
10(13), December 1976.
28. Ibid._
29 Fetter, C. W. "Attenuation of Waste Water Elutriated Through
' Glacial Outwash." Ground Water, .15(5), September-October 1977.
30 Leeper, G. W. "Reactions of Heavy Metals with Soil with Special
' Regard To Their Application in Sewage Waste." Department Army
Corps of Engineers Rep. Cont. No. DACW 73-73-C-0026, 1970.
31 cronHard Methods for the Examination of Water and Wastewater.
14th ed., 1975.
32 M°tb"Hg for Chemical Analysis of Water and Wastes. Environmental
Monitoring and Support Laboratory, EPA-625-16-74-003a, 1976.
(Rev. 3/81)
-------
APPENDIX A
ANALYTICAL METHODS
99
-------
APPENDIX A
ANALYTICAL METHODS
The elements, aluminum, barium, beryllium, calcium, cadmium,
chromium, copper, iron, magnesium, manganese, nickel, and lead in the
interstitial water, soil column effluents and groundwater well samples,
were measured by direct atomic absorption spectrophotometry using
techniques described in Standard Methods29 and by EPA.30 Mercury was
determined by the cold vapor technique recommended by EPA. Arsenic
and selenium were measured using the gaseous hydride method, also
recommended by EPA.
Sulfate was measured using the turbidimetric method, and pH values
were obtained in the field using the glass electrode. Conductivity and
alkalinity were also measured in the field using established procedures.29'30
Soil core samples were analyzed for aluminum, barium, beryllium,
calcium, cadmium, chromium, copper, iron, magnesium, manganese, nickel,
and lead by first undergoing a wet acid digestion followed by direct
measurement with atomic adsorption spectrophotometry.30 Mercury was
measured in the soil core samples using EPA's recommended methods.30
Arsenic and selenium were set digested and then determined by the
gaseous hydride method previously mentioned.
Standard powder X-ray diffraction techniques were used to determine
the relative amounts of quartz, kaolinite, montmorillinite, and illite
present in the soils.
Oxidation-reduction potentials were determined with a silver-silver
chloride electrode.
Vertical and horizontal permeabilities of soil samples were deter-
mined by encasing soil specimens 3.5 cm in diameter and approximately
7.6 cm long in a rubber membrane and placing in a triaxial chamber.
Back pressure to 70,310 kgs/m2 (100 psi) was applied to assure specimen
saturation. The average coefficient of permeability was then determined
under a constant head test method by measuring the quantity of water
flowing through the specimen in a given time.
The moisture content of soil samples was determined as per ASTM
procedure D-2216. Bulk densities were determined by weighing a soil
specimen 15 cm long and 8.9 cm in diameter, then coating the specimen
with paraffin and submerging in water to determine its volume. The
moisture content of the specimen was then determined and the bulk
density calculated using the specimen's weight, volume, and moisture
content.
100
-------
Grain size classifications were determined by sieve separation of
large particles followed by the hydrometer technique for the silt and
clay fraction.
Dissolved oxygen concentrations in groundwater samples were deter-
mined in situ by lowering a membrane electrode into the monitoring
wells. The membrane electrode was also used on groundwater samples
brought to the surface for dissolved oxygen determinations.
101
-------
DETERMINATION OF CATION EXCHANGE CAPACITY
Reagents
Triethanolamine solution: Triethanolamine (commercial) 90 ml
diluted to 1:1, and pH adjusted to 8.1 by adding 2N-hydrochloric acid
(140-150 ml). This solution is diluted to 2:1. Protect from carbon
dioxide during storage.
Barium chloride solution: BaCl2, 2H20 244 g per 1 (approximately 2N).
Buffered barium chloride reagent: Mix equal volumes of the above
solutions.
Magnesium sulphate solution: MgSO,, 7H 0 6.2 g per 1 (approximately
0.05N).
EDTA solution: Sequestric acid disodium salt 3.723 g per 1 (0.02N).
Catechol Violet indicator: 0.1 g dissolved in 100 ml of water.
Method
Transfer 5 g of soil (<2 mm air-dry, of known moisture content) to
a tightly stoppered polythene centrifuge bottle. Note the weight oi
bottle plus soil (W.). Treat calcareous soils with aPP*oxim*f 1\1°°
of the buffered barium chloride reagent, preferably with S*^6 *f ^
for 1 hr. Centrifuge at 1500 rpm (RCF) 415) for 15 mm. and discard the
supernatant liquid. For noncalcarous soils this f irst .w^hl^an be
omitted. Treat with a further 200 ml of reagent overnight ^ntrifuge
and again discard the supernatant liquid. Add ;PP«*IM"^?J £ f
distilled water and shake for a few minutes to break up thfo!°ji "**'
Centrifuge and discard the supernatant liquid. Weigh the bottle with
content. (W.). Pipette into the bottle 100 ml of magnesxum sulphate
solution and shake the stoppered bottle occasionally over a period of 2
hr. Centrifuge and transfer the clear liquid immediately to a stoppered
flask.
To a 5-ml aliquot of the solution add 6 drops of 2N-aq. ammonia and
titrate with standard EDTA solution using 2 drops of Catechol Violet
indicator. The end-point is indicated by a color change from clear blue
to reddish purple (Titre AI ml). This titre must be corrected for the
effect of the volume (not chloride content) of liquid retained by the
centrifuged soil after the wash water:
Corrected titre (A ) = A.^100 4- W2 W^/100 ml
Aliquots of 5 ml of the original magnesium sulphate solution are
also titrated under similar conditions (Titre B) .
CEC of the soil = 8(B - A ) meq/100 g
*Bascomb, C. L. "Rapid Method for the Determination of Cation-Exchange
Capacity of Calcareous and Noncalcareous soils." J. of Sci. Food and
Agric., 15, 1964. pp. 821-823.
102
-------
APPENDIX B
VERTICAL PROFILES OF SUBSTRATUM AT PLANTS J AND L
103
-------
VERTICAL PROFILE OF THE SUBSTRATUM AT PLANT J's MONITORING WELL LOCATIONS
Jl
J2
J3
J4
CLAY/SILT
SHALE
CLAY/SILT
SAND
SHALE
1= - i
^
J5
- -^
4.1
ASH
CLAY/SILT
SHALE
CLAY/SILT
10.2
11.8
SAND
SHALE
i .
J6
i i
= ±|
" '
ASH
CLAY/SILT
13.4 SAND
16.0
18.4
SHALE
CLAY/SILT
1 1.4 SAND
14.5
SHALE
j
J7
HS
CLAY/SILT
9.7 SAND
II. 1
15.0
SHALE
SHALE
8.8
13.4
==
=
J8
3 U~ WUUNL
SUKI-AUt
8.0
10.9 j
DEPTH
(METERS)
0- GROUND
9.3
i
DEF
(MET
SURFACE
1
TH
ERS)
-------
VERTICAL PROFILE OF THE SUBSTRATUM AT PLANT L's MONITORING WELL LOCATIONS
LI
CLAY/SILT
LIMESTONE
10.8
L4
CLAY/SILT
GRAVELLY SAND
GRAVELLY CLAY -vft;
9.8
14.2
CLAY/SILT
LIMESTONE
13.7
L5
CLAY/SILT
GRAVELLY SAND
CLAY/SILT
LIMESTONE
7.8
10.8
16.3
L3
CLAY/SILT
GRAVELLY CLAY
LIMESTONE
0- GROUND SURFACE
11.6
13.4
DEPTH
(METERS)
L6
ASH
CLAY/SILT
LIMESTONE
-0-GROUND SURFACE
10.5
14.4
DEPTH
(METERS)
-------
VERTICAL PROFILE OF THE SUBSTRATUM AT PLANT L's MONITORING WELL LOCATIONS
L7
CLAY/SILT
LIMESTONE
8.9
L8
ASH
CLAY/SILT
LIMESTONE
2.6
11.7
L9
ASH
CLAY/SILT
LIMESTONE
0-GROUND
5.4
10.8
SURFACE
DEPTH
(METERS)
LIO
CLAY/SILT
GRAVELLY CLAY
CLAY/SILT
LIMESTONE
6.7
12.3
21.1
-0-GROUNDSURWCE
CLAY/SILT
DEPTH
(METERS)
18.1
LIMESTONE
-------
APPENDIX C
ANALYTICAL RESULTS OF COLUMN ATTENUTATION STUDIES
107
-------
TABLE C-l. ANALYSIS OF COAL ASH LEACHATE USED IN SOIL
ATTENUATION STUDY
Constituent
Value
Constituent
Value
pH, std. units 7.8
Eh, millivolts -280
Temperature, °C 17
Conductivity, (Jtnhos/cm2 1800
Alkalinity, mg/1
as CaC03 340
Calcium, mg/1 185
Magnesium, mg/1 7.6
Iron, mg/1 15
Copper, mg/1 0.14
Zinc, mg/1 0.04
Nickel, mg/1 <0.05
Aluminum, mg/1 0.06
Cadmium, mg/1 <0.01
Mercury, mg/1 0.002
Chromium, mg/1 <0.05
Lead, mg/1 <0.010
Beryllium, mg/1 <0.002
Barium, mg/1 0.23
Manganese, mg/1 4.2
Sodium, mg/1 7.2
Potassium, mg/1 14
Selenium, mg/1 <0.002
Total dissolved
solids, mg/1 720
Sulfide, mg/1 0.07
Sulfate, mg/1 240
Nitrite and Nitrate
as nitrogen, mg/1 0.02
Phosphate as
Phosphorus, mg/1 0.08
108
-------
TABLE C-2. ANALYTICAL RESULTS OF COLUMN ATTENUATION STUDIES
o
vO
Composite volume, ml
Total volume
eluted, ml
Calcium, mg/L
Magnesium, mg/L
Sodium, mg/L
Potassium, mg/L
Iron, mg/L
Manganese, mg/L
Copper, mg/L
Zinc, mg/L
Nickel, mg/L
Sulfate, mg/L
Cadmium, mg/L
Lead, mg/L
Chromium, mg/L
Aluminum, mg/L
Barium, mg/L
Beryllium, mg/L
Mercury, mg/L
Selenium, mg/L
180
180
120
9.0
8.6
6.3
<0.005
0.48
0.02
<0.05
0.18
300
0.009
<0.05
<0.005
0.09
0.1
<0.005
0.03
<0.004
Analysis
150
330
180
9.0
7.9
13
<0.005
0.06
0.008
<0.01
0.05
300
<0.005
<0.05
<0.005
<0.02
0.08
<0.005
0.0005
<0.002
of effluent
180
510
190
9.3
8.2
14
<0.005
0.26
0.007
0.19
0.05
300
<0.005
<0.05
<0.005
<0.02
0.07
<0.005
0.0003
<0.002
from soil column Plant
150
660
180
9.4
8.1
15
<0.005
0.44
0.007
<0.01
0.09
240
<0.005
<0.05
<0.005
<0.02
0.08
<0.005
0.0002
<0.004
150
810
180
9.6
8.6
15
<0.005
0.650
<0.005
<0.01
<0.05
310
<0.005
<0.05
<0.005
<0.02
0.1
<0.005
0.0003
<0.002
L
180
990
180
9.6
8.2
14
<0.005
0.83
<0.005
0.14
<0.05
280
<0.005
<0.05
<0.005
<0.02
0.12
<0.005
0.0003
<0.002
120
1110
170
9.2
7.9
14
<0.005
0.86
0.007
<0.01
0.07
270
<0.005
<0.05
<0.005
<0.02
0.13
<0.005
0.0002
<0.01
-------
TABLE C-2 (continuech
Analysis of effluent from
Composite volume, ml
Total volume
eluted, ml
Calcium, mg/L
Magnesium, mg/L
Sodium, mg/L
Potassium, mg/L
Iron, mg/L
Manganese, mg/L
Copper, mg/L
Zinc, mg/L
Nickel, mg/L
Sulfate, mg/L
Cadmium, mg/L
Lead, mg/L
Chromium
Aluminum, mg/L
Barium, mg/L
Beryllium, mg/L
Mercury
Selenium, mg/L
300
300
160
10
8.9
10
0.12
0.5
0.02
0.1&
1.1
*
<0.001
0.032
<0.005
0.1
0.12
<0.005
<0.0008
<0.004
270
570
160
9.4
8.0
12
0.068
0.49
0.006
0.03
<0.05
*
<0.001
<0.01
<0.005
0.05
0.13
<0.005
<0.0008
<0.004
soil column Plant J
300
870
160
9.5
8.0
12
0.063
0.77
0.02
0.02
<0.05
*
<0.001
<0.01
<0.005
0.04
0.1
<0.005
<0.0008
<0.004
270
1140
160
9.5
8.2
13
0.053
1.1
0.006
0.03
<0.05
*
<0.001
<0.01
<0.005
0.05
0.16
<0.005
<0.0008
<0.004
300
1440
160
9.7
8.4
13
0.039
1.1
0.007
0.02
<0.05
*
<0.001
<0.01
<0.005
<0.02
0.17
<0.005
<0.0008
<0.004
270
1710
150
9.2
8.2
12
0.03
0.94
0.022
0.02
<0.05
*
<0.001
<0.01
<0.005
0.17
0.16.
<0.005
<0.0008
<0.004
-------
TABLE C-2 (continued)
Analysis of effluent from kaolinite clay column
Composite volume, ml
Total volume
eluted, ml
Calcium, mg/L
Magnesium, mg/L
Sodium, mg/L
Potassium, mg/L
Iron, mg/L
Manganese , mg/L
Copper, mg/L
Zinc, mg/L
Nickel, mg/L
Sulfate, mg/L
Cadmium, mg/L
Lead, mg/L
Chromium, mg/L
Aluminum, mg/L
Barium, mg/L
Beryllium, mg/L
Mercury, mg/L
Selenium, mg/L
180
180
130
9.0
9.6
14
0.046
0.75
0.045
<0.01
0.96
*
<0.005
<0.05
<0.005
0.04
0.13
<0.0005
<0.0002
<0.004
180
360
150
9.9
8.5
16
0.013
0.22
0.056
<0.01
0.18
*
<0.005
<0.05
<0.005
<0.02
0.15
<0.0005
<0.0002
<0.004
180
540
150
9.9
8.5
16
0.013
0.25
0.046
<0.01
0.07
*
<0.005
<0.05
<0.005
<0.02
0.16
<0.0005
<0.0002
<0.004
180
720
160
9.5
8.3
15
0.022
0.96
0.039
<0.01
0.07
*
<0.005
<0.05
<0.005
0.03
0.19
<0.0005
<0.0002
<0.004
180
900
160
9.2
7.8
15
0.099
1.1
0.081
<0.01
0.05
*
<0.005
<0.05
<0.005
0.07
0.17
<0.0005
0.0003
<0.004
180
1080
170
10
8.8
16
0.063
1.3
0.04
<0.01
0.05
*
<0.005
<0.05
<0.005
0.06
0.2
<0.0005
0.0003
<0.004
120
1200
120
7.2
7.0
14
0.014
0.92
0.16
0.12
<0.05
*
<0.005
<0.05
<0.005
0.06
0.14
<0.0005
0.0003
<0.01
*Not enough sample for analysis.
-------
APPENDIX D
USED IN COLUMN ATTENUATION STUDIES
112
-------
TABLE D-l. CHEMICAL CHARACTERISTICS OF CLAY MINERALS
USED IN COLUMN ATTENUATION STUDIES
Constituent
Chlorine, mg/1
Sulfate, mg/1
Bromine
Calcium, |Jg/g
Magnesium, |Jg/g
Sodium, (Jg/g
Potassium, (Jg/g
Iron, (Jg/g
Total Manganese, (Jg/g
Copper, |jg/g
Value
460.0
480.0
1.2
4000
2500
300
5300
6100
65
52
Constituent Value
Zinc, ug/g 17
Nickel, (Jg/g 26
Cadmium, (Jg/g <1.0
Lead, |jg/g 12.0
Chromium, (Jg/g <5.0
Aluminum, (Jg/g 7700
Barium, (Jg/8 830
Beryllium, (Jg/g 5.0
Mercury, (Jg/g 0.27
Arsenic, H8/8 1-2
Selenium, (Jg/g <1.0
Kaolinite
Constituent
Chlorine, mg/1
Sulfate, mg/1
Bromine
Calcium, |Jg/g
Magnesium, (Jg/g
Sodium, |Jg/g
Potassium, (J8/8
Iron, (Jg/g
Total Manganese, (Jg/g
Copper, ng/g
Value
30.0
120.0
<0.2
120
110
60
70
1400
830
15
Constituent Value
Zinc, (jg/g 52
Nickel, (Jg/g 21
Cadmium, (Jg/g <1.0
Lead, (Jg/g 10.0
Chromium, (Jg/g <5.0
Aluminum, (Jg/8 840
Barium, (Jg/g 6l
Beryllium, (Jg/g 3.0
Mercury, (Jg/g 0.60
Arsenic, |Jg/g 10.0
Selenium, (Jg/g <1.0
Constituent
Montmorillonite
Value
Chlorine, mg/1
Sulfate, mg/1
Bromine
Calcium, (Jg/g
Magnesium, (Jg/g
Sodium, (jg/g
Potassium, |Jg/g
Iron, (Jg/g
Total Manganese, (Jg/g
Copper, M8/8
26.0
1800.0
<0.2
770
3400
1100
200
1700
22
3
Constituent Value
Zinc, |Jg/g 70
Nickel, (Jg/8 <5-0
Cadmium, (Jg/g <1.0
Lead, (Jg/g 48.0
Chromium, (Jg/g <5.0
Aluminum, (Jg/g 2900
Barium, (Jg/g 13
Beryllium, (Jg/g 2.0
Mercury, (Jg/g 0.17
Arsenic, (Jg/g 2.3
Selenium, (Jg/g <1.0
113
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-80-066
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Effects of Coal-ash Leachate on Ground Water
Quality
5. REPORT DATE
March 1980
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jack D. Milligan and Richard J. Ruane
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Tennessee Valley Authority
1120 Chestnut Street, Tower II
Chattanooga, Tennessee 37401
10. PROGRAM ELEMENT NO.
INE624A
11. CONTRACT/GRANT NO.
EPA Interagency Agreement
D5-E721
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 5/75-11/79
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES ffiRL-RTP prOJCCt OfflCCr IS
919/541-2547. TVA project director is Hollis B.
Michael C. Osborne, Mail Drop 62,
Flora H.
16. ABSTRACT
The report gives results of research to: (1) develop methodology for the
field-collection of coal-ash leachate; (2) chemically characterize ash leachates from
power plants using different coal sources; (3) determine the characteristics of the
hydrogeochemical environment in which the leachate occurs; and (4) determine the
attenuation of coal-ash leachate by various soil types. Groundwater monitoring wells
were installed around ash ponds at two TVA plants. Continuous soil-core samples
were collected and analyzed periodically. Ash leachate was percolated through dif-
ferent clays and soils to study attenuation rates. Results include indications that: (1)
coal-ash leachate is highly variable, but characteristically high in dissolved solids,
B, Fe, Ca, Al, and SO4; ash leachate is acidic, with measured pH as low as 2; (2)
the coal sources associated with the study produced ash leachate with similar char-
acteristics; (3) an inert-gas lift pump was effective in collecting anoxic groundwater
samples while minimizing oxidation; (4) differences were found in the characteristics
of leachate samples obtained by extracting the interstitial soil water and samples col-
lected from the monitoring wells; interstitial water samples contained higher concen-
trations of metals and were more acidic than well samples; and (5) the flux of metals
in the ash pond leachate was negligible compared to ash pond surface overflow.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Leaching
Water Quality
Ground Water
Coal
Ashes
Pollution Control
Stationary Sources
Coal Ash
13B
07D,07A
08H
21D
2 IB
B. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
125
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
114
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