United States
Environmental Protection
Agency
Environmental Monitoring
and Support Laboratory
P.O Box 15027
Las Vegas NV 89114
EPA-600/7-79-024
January, 1979
Research and Development
xvEPA
Groundwater Quality
Monitoring of Western
Coal Strip Mining:
Identification and
Priority Ranking of
Potential Pollution Sources
Interagency
Energy-Environment
Research
and Development
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 categories
were established to facilitate further development and application of environmental
technology. Elimination of traditional grouping was consciously planned to foster
technology transfer and a maximum interface in related fields. 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
8. "Special" Reports
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 systems. The goal of the Pro-
gram is to assure the rapid development of domestic energy supplies in an environ-
mentally-compatible manner by providing the necessary environmental data and
control technology. Investigations include analyses of the transport of energy-related
pollutants and their health and ecological effects; assessments of, and development of,
control technologies for energy systems; and integrated assessments of a wide range
of energy-related environmental issues.
This document is available to the public through the National Technical Information
Service, Springfield, Virginia 22161
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EPA-600/7-79-024
January 1979
GROUNDWATER QUALITY MONITORING
OF WESTERN COAL STRIP MINING:
Identification and Priority Ranking of Potential
Pollution Sources
Edited by
Lome G. Everett
General Electric Company—TEMPO
Center for Advanced Studies
Santa Barbara, California 93102
Contract No. 68-03-2449
Project Officer
Leslie G. McMillion
Monitoring Systems Research and Development Division
Environmental Monitoring and Support Laboratory
Las Vegas, Nevada 89114
ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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DISCLAIMER
This report has been reviewed by the Environmental Monitoring and Support
Laboratory-Las Vegas, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or recom-
mendation for use.
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FOREWORD
Protection of the environment requires effective regulatory actions
which are based on sound technical and scientific information. This infor-
mation must include the quantitative description and linking of pollutant
sources, transport mechanisms, interactions, and resulting effects on man
and his environment. Because of the complexities involved, assessment of
specific pollutants in the environment requires a total systems approach
which transcends the media of air, water, and land. The Environmental Moni-
toring and Support Laboratory-Las Vegas contributes to the formation and
enhancement of a sound monitoring data base for exposure assessment through
programs designed to:
• Develop and optimize systems and strategies for monitoring
pollutants and their impact on the environment
• Demonstrate new monitoring systems and technologies by
applying them to fulfill special monitoring needs of the
Agency's operating programs.
This report presents the initial phases of a study to design and imple-
ment groundwater quality monitoring programs for Western coal strip mining.
The development of a preliminary priority ranking of potential pollution
sources and the pollutants associated with these sources is presented.
The results of this report are the initial segment of the design and
field implementation effort. The priority ranking will be combined in sub-
sequent study phases with evaluations of deficiencies in existing or proposed
monitoring efforts and alternative monitoring technologies to design a cost-
effective groundwater quality monitoring program.
The research program, of which this report is part, is intended to pro-
vide basic technical information and a planning format for the design of
groundwater quality monitoring programs for Western coal strip mining opera-
tions. As such, the study results may be used by coal developers and their
consultants, as well as the various local, State, and Federal agencies with
responsibilities in environmental monitoring and planning.
ill
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Further information on this study and the subject of groundwater
quality monitoring in general can be obtained by contacting the Monitoring
Systems Design and Analysis Staff, Environmental Monitoring and Support
Laboratory, U.S. Environmental Protection Agency, Las Vegas, Nevada.
Georgjg Bi Morgan
Director
Environmental Monitoring and Support Laboratory
Las Vegas
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PREFACE
General Electric-TEMPO, Center for Advanced Studies, is conducting a 5-
year program dealing with the design and implementation of an exemplary ground-
water quality monitoring program for Western coal strip mining. The coal strip
mining activity discussed in this report is located in Campbell County, Wyoming.
In addition to mining impacts, the report discusses secondary water resource
impacts of municipal and industrial support programs which accompany the mining
effort. The report follows a stepwise monitoring methodology developed by
TEMPO.
This report represents the initial phase of this research program. De-
scribed herein is the development of a preliminary priority ranking of potential
pollution sources and their associated pollutants. This priority ranking will
be utilized in subsequent phases of the research as the basis for defining mon-
itoring needs and for ultimately designing the monitoring program.
In the next phases of this research program, a preliminary monitoring
design is to be developed and implemented in the field^ Initial field study
results may result in a reevaluation of the priority ranking presented in this
report. The final product of the 5-year program will be a planning document
which will provide a technical basis and a methodology for the design of ground-
water quality monitoring programs for coal development companies and the various
governmental agencies concerned with environmental planning and protection.
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SUMMARY
General Electric-TEMPO has developed a methodology for designing ground-
water quality monitoring programs. This was a conceptual design which
involved a series of data compilations and evaluation steps leading to a moni-
toring system in place. General Electric-TEMPO is now applying that method-
ology to design a system to monitor the impact of western coal strip mining on
groundwater quality. This document reports the field survey and literature
research performed during the first phase of the design process. The goal of
this phase is to identify and rank the major sources of groundwater quality
degradation. The site for which the monitoring system is being designed
follows the outcrop of the Fort Union Formation in Campbell County, Wyoming.
In addition to the City of Gillette, Wyoming, the project area includes the
following mines: Carter North Rawhide, AMAX Eagle Butte, Wyodak, AMAX Belle
Ayr, Sun Oil Cordero, Kerr-McGee Jacobs Ranch, and ARCO Black Thunder.
The priority ranking is based on a sequence of data compilation and
evaluation steps. These steps include identification of potential pollution
sources, methods of waste disposal, and potential pollutants associated with
the various waste sources; and an assessment of the potential for infiltra-
tion and subsequent mobility of these pollutants in the subsurface. The
three basic criteria used to develop the source-pollutant ranking are:
• Mass of waste, persistence, toxicity, and concentration
• Potential mobility
• Known or anticipated harm to water use.
The information base and related assessments utilized to develop rank-
ings based on the above methodology are summarized in the main body of this
report.
Available background information and field reconnaissance were employed
to describe the hydrogeology and water quality of the study area. These data
were used in concert with the source-pollutant characterization to assess the
potential for pollutant mobility.
Three major classifications of potential pollution sources have been
inventoried: Agricultural, Industrial, and Municipal. Agricultural sources
were found to be insignificant due to their diffuse nature. Irrigated farm-
land is practically nonexistent and dryland farming, which is economically
marginal, is the general method.
The Industrial classification includes Construction, Oil and Gas
vi
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Extraction, Coal Strip Mining, and Coal Conversion activities. Of these four,
coal strip mining and coal conversion are the most significant in terms of
potential groundwater quality degradation. Almost all of the wastes associ-
ated with the construction industry are either disposed of in the Gillette
landfill, and as a result come under the Municipal wastes category, or are
disposed of with mine solid wastes on the leases. The same can be said for
sanitary wastes from the construction industry where the City or mine dis-
posal facilities are utilized.
The oil and gas extraction industry is probably a major potential ground-
water pollution source, however, it will not be investigated in a regional
sense in this study. On mine leases where oil and gas wells exist or have
existed, potential groundwater impacts are of minor concern since they are few
in number and closely scrutinized because of their proximity to the mining
operations.
Coal strip mining and its related sources have considerable potential to
produce groundwater quality degradation. On the majority of mines, pollu-
tant source-specific monitoring does not eixst. Where monitoring of sources
has been conducted it has not been source oriented but directed toward assess-
ing background quality levels, with the hope that eventually any changes in
quality due to pollutants will show up in the monitoring program.
The above approach is the traditional approach utilized, but it is con-
trary to the objectives of Public Laws 92-500 and 93-523, which are aimed at
preventing, reducing, and eliminating groundwater quality degradation. Once
pollutants show up in a background quality monitoring system, in many cases,
it is too late to institute controls. Source monitoring is the key to deter-
mining which controls to implement and whether they are working.
For active mining, the pit discharge represents a potential source of
groundwater pollution. Much of the pit discharge is derived from native
groundwater; however, explosives, sewage effluents, spoils, coal, and other
sources can contribute pollutants.
The relocation of spoils produces a changing chemical environment that
will be a permanent potential source. Some groundwater will likely always
be in contact with the lower parts of the emplaced spoils. Also, some stream-
flow will generally be rerouted, after mining, over the spoils along the
former floodplains and percolation will occur in some areas. Holding ponds
placed on the spoils would be transitory in nature. Groundwater contacting
the spoils will tend to occur indefinitely in specific parts of the reclaimed
areas. In any area where groundwater was present in or above the coal seam
prior to mining, the spoils will generally be in contact with groundwater
after mining ceases. Spoils placed below the water table have top priority
among mining sources for the following reasons:
• The soil and vadose zone are bypassed; thus there is no
pollutant attenuation in these zones
• Generally, materials with the highest pollution potential
are placed at the bottom of the spoils, and it is this
vii
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area that will be contacted by groundwater
• This source is permanent in a sense and can contribute
pollutants over decades or centuries.
Another priority for mining sources would be for rerouted surface water
percolating into the spoils. The extent of this problem depends largely on
the chemical nature and hydraulic head ultimately established in the spoils
and underlying materials and the permeability of spoils beneath the stream
channel. This source will also be permanent and can contribute pollutants
for many decades or centuries after mining ceases. A third priority for
mining sources would be percolation of streamflow below points of pit dis-
charge. The extent of this problem is presently poorly known due to a lack
of adequate monitoring of pit discharge. Dilution due to mixing with surface
water from natural runoff would limit the potential groundwater pollution.
The quality of surface water can also be adversely impacted because in
some parts of the leases the groundwater contributes to surface water flow.
Over the long term, substantial increases in the salinity of surface water
could occur. This, in turn, could exert profound adverse impacts on down-
stream users of surface water.
Of the three coal conversion activities projected to be implemented in
the project area, steam electric power generation, gasification, and liquifi-
cation, only steam electric power generation is being implemented on a large
scale. This plant is located on the Wyodak lease and most of its waste pro-
ducts will be disposed of in the mine pits. The primary waste will be fly
ash, which will be disposed of both in ponds and as landfill. Secondary
wastes, e.g., sewage effluent and sludge, will also be disposed of in ponds
or as landfill.
Top priority should be given to fly ash landfill disposal in the pit at
levels which will lie below groundwater level. This top priority is based on:
• The disposal is basically permanent, and pollutants can
be produced for decades or centuries
• Certain trace elements may well qualify fly ash as a
hazardous waste
• The soil and vadose zone are bypassed and thus pollutant
attenuation in these zones will not occur
• Large volumes of fly ash will be disposed of.
Second priority should be given to-the fly ash slurry pond. This prior-
ity is based on:
• The wastewater disposed to this pond presents a ready
source of water for leaching pollutants to the groundwater
• This source contains a variety of pollutants, including
vi i i
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salinity from brine disposal and metals from the fly
ash.
Third priority should be given to fly ash landfilled above the water
table and beneath rerouted streams. This priority is based on:
• A ready source of water is available for leaching
• The fly ash may well qualify as a hazardous waste.
The principal potential municipal sources of groundwater pollution are
the landfill, sewage treatment plant, and water treatment plant. Only limit-
ed monitoring has been done on the landfill, sewage treatment plant, or water
treatment plant. Individual wells within the City's well field are subject
to damage from any of these three sources and, in the long term, from the
mining operations.
The complete priority ranking is shown in Table 1. A great deal of
effort has been expended on the study of the hydrogeology of the study area
and a large amount of research has been conducted on coal strip mine develop-
ment and environmental effects. However, significant information voids exist
with regard to potential pollutant characterization and the mobility of these
materials in the hydrosphere. Hence, professional judgment plays a large
role in proposing this preliminary source-pollutant ranking.
This ranking will serve as the basis for the design of a monitoring plan
for western coal strip mine development. The next phase of the design pro-
gram includes evaluation of existing monitoring programs, identification of
alternative monitoring approaches to address the source-pollutant ranking,
and selection of a monitoring program for field implementation. This imple-
mentation will be used to verify (and quite probably revise) the preliminary
ranking provided here.
IX
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TABLE 1. PROJECT AREA POTENTIAL POLLUTION SOURCE PRIORITY RANKING BY MAJOR CATEGORY
Coal strip mining
Coal conversion
Municipal
1. Spoils (below water table)
2. Spoils (above water table
below ponds or streams)
3. Pit discharge (to streams)
1. Fly ash (below water table)
2. Fly ash slurry pond
3. Fly ash solids (above water
table)
1. Hazardous wastes at landfill
2. Disposal well water treatment
plant
3. Oily waste ponds at landfill
4. Garbage trench at landfill
5. Sewage effluent to Donkey Creek
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CONTENTS
Foreword i i i
Preface v
Summary vi
Figures xiii
Tables xvi
List of Abbreviations xx
Acknowledgments xxii
Section
1 Introduction 1
Criteria for selecting the monitoring area 2
Selection of the project area 3
Implementation of the priority ranking scheme 5
2 Potential Sources of Pollution and Methods of Disposal 7
Agriculture 7
Industry 8
Oil and gas extraction 15
Construction 15
Coal conversion 18
Municipal sources of pollution 24
3 Potential Pollutants 30
Agriculture 30
Coal strip mining 30
Oil and gas extraction 54
Construction 54
Coal conversion , 56
Municipal 62
4 Groundwater Usage 74
Municipal usage 74
Rural domestic usage 75
Industrial usage 76
Agricultural usage 77
5 Hydrogeologic Framework 78
Surface water hydrology 78
Soils 94
Geology 106
Hydrogeology 110
Modified hydrogeology 155
XI
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6 Existing Groundwater Quality 164
Regional 164
Municipal 184
7 Infiltration Potential 191
Coal strip mining 191
Coal conversion 194
Municipal sources 194
8 Pollutant Mobility in the Vadose Zone 198
Coal strip mining 198
Coal conversion 202
Municipal 203
9 Pollutant Mobility in the Saturated Zone 214
Coal strip mining 214
Coal conversion 216
Municipal sources 217
10 Priority Ranking of Potential Groundwater Pollution
Sources 222
Agricultural activities 222
Industrial 222
Municipal 226
References 229
Appendix A 237
xn
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FIGURES
Number Page
1-1 Major coal fields of Wyoming 4
2-1 Oil and gas fields associated with the Eastern Powder River
Basin, Wyoming 16
2-2 Hole bottom locations (Hoe Creek Experiment No. 1) 22
2-3 Comparison of measured and calculated water production rates
for the Hoe Creek Experiment No. 1 site 23
2-4 Water levels at several locations within the fracture zone 23
2-5 Plan view of the packed-bed experiment 24
5-1 Watershed map 80
5-2 Physiographic divisions and drainage of Campbell County, Wyo. 81
5-3 Flow duration curves for selected Wyoming streams 84
5-4 Relations for estimating flow characteristics in region 2 by
using drainage area 85
5-5 Relations for estimating flow characteristics in region 3 by
using drainage area 86
5-6 Hydrologic regions at monitoring area 87
5-7 Surface water quality measurement sites 88
5-8 Block diagram showing positions of some major kinds of aridisols
and their associates 99
5-9 Soil associations of Campbell County, Wyoming 100
5-10 Generalized map showing the Powder River Basin in relation to
nearby structural features 107
5-11 Correlation of coal beds in the Powder River Coal Basin 109
5-12 Aquifer relationships 111
xi i i
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Number
5-13 Plots of results from four pump tests near Belle Ayr Mine 116
5-14 Isopach map of unconsolidated deposits along Cabal lo Creek 118
5-1 5 Hydrographs of three wells 119
5-16 Water level fluctuations in well N-3, April 26 - July 1, 1974 120
5-17 Water level fluctuations in well 481, May 10 - July 4, 1974 121
5-18 Geologic cross section from the center of the east line,
section 22, to the NE corner, SE%, NE%, section 27, T5IN, R72W 125
5-19 Geologic cross section along west side of section 21, T51N,
R72W 126
5-20 Monthly water level elevations in instrumented monitor wells 130
5-21 Monthly water level elevations in instrumented monitor wells 131
5-22 Potenti ometric surface map, ARCO Black Thunder Lease 135
5-23 Groundwater flow in Roland aquifer 136
5-24 Monitor well locations, ARCO Black Thunder Lease 137
5-25 Kerr-McGee Jacobs Ranch mine, Thunder Creek area 145
5-26 Kerr-McGee Jacobs Ranch mine cross section K-K 147
5-27 Static water levels- Jacobs Ranch mine 148
5-28 Static water levels- Jacobs Ranch mine 149
5-29 Kerr-McGee Jacobs Ranch mine well locations 150
5-30 Water levels of monitor holes at Sun Oil Cordero mine 153
5-31 Idealized east-west cross section of Wyodak site 154
5-32 Contours of water table, Wyodak area 156
5-33 Effect of 50 years of mining in Wyodak north pit upon 157
water table
5-34 Locations of monitoring wells, Wyodak mine 158
6-1 Groundwater gaging network at the Black Thunder Site 178
xiv
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Number Page
8-1 Mobility of copper, lead, beryllium, zinc, cadmium, nickel,
and mercury through 10 soils series 205
8-2 Mobility of selenium, vanadium, arsenic, and chromium through
10 soils series 205
xv
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TABLES
Number Page
2-1 Other Municipalities 28
3-1 Site-specific Topsoil Characteristics 31
3-2 Concentrations of Trace Elements Boron, Cadmium, Lead,
and Mercury in Soils on the Eagle Butte Mine Property 31
3-3 Site-specific Overburden Characteristics 33
3-4 Sulfur and Trace Element Concentrations in Coal Samples 35
3-5 Hypothetical Quality of Wastewater from the Gillette
Treatment Plant 37
3-6 Representative Septic Tank Effluent Concentrations and
Percent Removed 39
3-7 Aerobic Tank Effluent Concentrations 40
3-8 Range of Chemical Composition of Sanitary Landfill Leachate 43
3-9 A Sample List of Nonradioactive Hazardous Compounds 45
3-10 Chemical Analysis of Incinerator Fly Ash 46
3-11 Chemical Analysis of Incinerator Fly Ash 47
3-12 Incinerator Residues 47
3-13 Incinerator Wastewater Data 48
3-14 Chemical and Physical Data: Three Overburden Grab Samples 50
3-15 Trace Element Content of Coal and Associated Rocks,
Core BT249 52
3-16 Comparison of Average Trace Element Concentrations (ppm) 53
3-17 Analyses of Overburden Materials 55
xvi
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Number Page
3-18
(a) Predicted Operating Conditions and Emissions from Unit 5 and
the New Plant Under 100 Percent Load 57
(b) Peak Ground Level Contaminants from Existing Plant 57
(c) Predicted Combined Ground Level Pollutant Concentrations from
New Plant and Existing Unit 5 . 58
(d) Projected Constituents of Ash from the New Plant and Existing
Unit 5 58
3-19 Byproduct Water Analysts from Synthane Gasification of
Various Coals 60
3-20 Mass Spectrometrie Analysis of Benzene-Soluble Tars 61
3-21 Hypothetical Quality of Wastewater, Gillette Treatment Plant 63
3-22 Septic Tank Septage Characteristics as Reported in the Literature 65
3-23 Typical Chemical Composition of Raw and Anaerobically Digested
Sludge 67
3-24 Metals in Sludge, 1971-1973 68
3-25 Analysis of Runoff Sample in Third Trench at the City of
Gillette Landfill in June 1977 71
3-26 June 1977 Analysis of Water from Stone Pile Creek Behind
Gillette Water Treatment Plant 72
3-27 Quantity and Characteristics of Contaminants in Urban Runoff 73
4-1 Major Mine Site Water Usage 76
5-1 Representative Chemical Measurements for Surface Water Quality 90
5-2 Drainage Areas for Lease Sites, Mean Annual Runoff, and
25-Year Peak Discharge 95
5-3 Soil Series Classification of Campbell County 98
5-4 Hydrologic Soil Classifications 105
5-5 Approximate Area! Percentages of Hydrologic Soil Groups 106
5-6 Aquifer Parameters in the Belle Ayr Mine Vicinity 115
5-7 Well Completion Data, WRRI Groundwater Observation Wells,
AMAX Belle Ayr South 122
xvi i
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Number Page
5-8 Summary of Aquifer Test Data I27
5-9 Static Water Levels Measured on Uninstrumented Wells 129
5-10 Monitor Well Inventory for AMAX's Eagle Butte Mine 132
5-11 Calculated Values of Transmissivity and Storage Coefficient
in Roland Formation 134
5-12 Summary of Elevation of Water Level in Roland Coal, Smith
Coal, and Overburden Compared to Elevation of Top of Roland
Coal and Smith Coal 138
5-13 Inventory of Wells and Springs, Rawhide Block Near Gillette,
Wyoming 140
5-14 Summary of Aquifer Test Data, Kerr-McGee Jacobs Ranch Mine 146
5-15 Description of Monitor Well Completions at Jacobs Ranch Mine 151
5-16 Wyodak Groundwater Monitoring Stations 159
6-1 AMAX Belle Ayr Water Quality Data — Wasatch Formation Above
the Coal 166
6-2 AMAX Belle Ayr Water Quality Data-Wyodak Coal
168
AMAX Belle Ayr Water Quality Data-Scoria Pit-Wasatch
6-3 Formation Above the Coal 170
6-4 AMAX Belle Ayr Water Quality Data - Fort Union Formation Below
Coal 171
6-5 Minimum and Maximum Values for Water Quality Parameters at
AMAX Eagle Butte Lease (all aquifers) 173
6-6 Summary of Water Sampling Procedures During Tests of Various
Wells at the Eagle Butte Mine 174
6-7 Results of Chemical Analyses of Groundwater from Wasatch Wells 175
6-8 Results of Chemical Analyses of Groundwater from Roland Coal
Seam Waters 176
6-9 Summary of Water Quality at Black Thunder Site Surface and
Groundwater 179
6-10 Water Quality Analyses of Water Wells on the Rawhide Lease 180
xv i i i
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Number Page
6-11 Minimum and Maximum Values at Carter Oil North Rawhide Lease
for Water Quality Parameters (coal aquifers) 181
6-12 Chemical Analysis of Water from Wells within 6 Miles of Property
Boundary of Proposed Kerr-McGee Jacobs Ranch Coal Mine 182
6-13 Laboratory Analysis of Water from Stock and Domestic Wells
Drilled Prior to Granting of Lease to Kerr-McGee 183
6-14 Groundwater Quality, Hayden Residence, Sun Oil Cordero Lease 185
6-15 Groundwater Quality, Well Number 11, Sun Oil Cordero Lease 186
6-16 Minimum and Maximum Values for Wyodak Mine Water Quality
Parameters 187
6-17 Water Quality Analysis Summary 188
6-18 Water Quality Analysis Summary- Gillette, Wyoming, Water
Supply, 1976 189
8-1 Characteristics of the Soils 211
10-1 Project Area Potential Pollution Source Priority Ranking by
Major Category 228
xix
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LIST OF ABBREVIATIONS
ANFO ammonium nitrate-fuel oil
BOD biochemical oxygen demand
CEC cation exchange capacity
COD chemical oxygen demand
DEQ Department of Environmental Quality
DMA designated monitoring agency
DO dissolved oxygen
DOC dissolved organic carbon
EC electrical conductivity
ECe EC of soil paste extract
ED electrodialysis
EIS environmental impact statement
EPA Environmental Protection Agency
ESP exchangeable sodium percentage
I/I infiltration/inflow
JTU
(turbidity) Jackson turbidity units
ILL Lawrence Livermore Laboratories
MBAS methylene blue active substances
nd no date
NPDES National Pollution Discharge Elimination System
PAH polycyclic aromatic hydrocarbons
RO reverse osmosis
SAR sodium adsorption ratio
SCS Soil Conservation Service
SV solids suspended volatile solids
TDS total dissolved solids
TOC total organic carbon
TPD tons per day
xx
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Chemi cal s and Eements
As
Be
Ca
Cd
CdS
Cr
Cu
CuS
Fe
FeS
Hg
HgS
Mo
NH|
Ni
N02
NOX
Pb
PbS
arsenic
beryllium
calcium
cadmium
cadmium sulfide
chromium
copper
copper sulfide
iron
ferrous sulfide
mercury
mercurous sulfide
mercuric sulfide
molybdenum
ammonium
nickel
nitrogen dioxide
mixed nitrogen oxides
lead
lead sulfide
Se selenium
sulfur dioxide
U uranium
V vanadi urn
Zn zinc
ZnS zinc sulfide
xx i
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ACKNOWLEDGMENTS
Dr. Lome G. Everett of General Electric-TEMPO was responsible for manage-
ment and technical guidance of the project under which this report was prepared.
Dr. Richard M. Tin!in, Camp Verde, Arizona, was responsible for the organiza-
tion and presentation of the report. Principal TEMPO authors were:
Mr. James D. Brown
Dr. Lome G. Everett
Mr. Edward W. Hoy!man
Dr. Guenton C. Slawson, Jr.
Principal consultant authors were:
Dr. S.N. Davis
Ms. Margery A. Hulburt
Mr. Louis Meschede
Dr. Roger Peebles
Dr. Kenneth D. Schmidt
Dr. John L. Thames
Dr. Richard M. Tin!in
Dr. David K. Todd
Dr. Donald L. Warner
Dr. L. Graham Wilson
xxn
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SECTION 1
INTRODUCTION
Groundwater is an important natural resource in the United States. It
supplies an estimated 68 billion gallons* per day to .the nation's fresh water
supply (Murray and Reeves, 1972). Nearly half of the nation's population
receives its drinking water from groundwater sources (U.S. Environmental
Protection Agency, 1976a).
Emphasis on the need to protect groundwater quality has been provided by
the United States Congress through the Federal Water Pollution Control Act
Amendments of 1972 (Public Law 92-500) and the Safe Drinking Water Act of 1974
(Public Law 93-523). These laws give the U.S. Environmental Protection Agency
(EPA) a major responsibility for preventing degradation of groundwater re-
sources.
Coal is one of the nation's most abundant energy sources. Because of its
low sulfur content, Western coal is generally preferred over Eastern coal for
environmental reasons. As a result, Western coal is being strip mined at
unprecedented rates.
Traditionally, groundwater monitoring activities have been designed to
assess the quantity and quality of groundwater for a particular use. To pre-
vent, reduce, and eliminate groundwater quality degradation, as called for in
P.L. 92-500, a monitoring program must do more than this. It must provide a
systematic approach for detecting and delineating groundwater pollution before
the pollution reaches points of groundwater use, and preferably before the
pollutants enter the ground. It must focus on identifying the pollution
sources, specific pollutants, and their respective mobilities through the
hydrogeologic system. Whether a pollutant reaches a point of water use can
no longer be the determining factor as to what constitues groundwater quality
•degradation.
In response to the high priority placed on Western coal development, the
U.S. Environmental Protection Agency awarded a 5-year contract to General
Electric-TEMPO of Santa Barbara, California, based on its systematic approach
to predictive groundwater quality monitoring. The approach provides for the
utilization of a 15-step methodology (Todd et al., 1976) which includes the
identification, quantification, and ranking for monitoring of the important
sources of groundwater quality degradation within a given study area.
* See Appendix A for conversion to metric units. English units were used in
this report because of their current usage and familiarity in industry and
the hydrology-related sciences.
1
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CRITERIA FOR SELECTING THE MONITORING AREA
In 1969, the important coal-producing States in the West - Arizona,
Colorado, Montana, New Mexico, North Dakota, Utah, and Wyoming - had 36 strip
mines which averaged about 400,000 tons yearly per mine. By 1972, the number
of mines had dropped to 28, but production had increased to about 1 million
tons per mine. Presently there are approximately 60 existing coal mines in the
Western States (excluding Washington, Texas, and Oklahoma), and 1976 production
was somewhere on the order of 100 million tons. The Federal Energy Adminis-
tration estimates that Western coal mines in 1985 will produce approximately
570 million tons from about 150 mines.
The coal strip mining activities within this seven-State area were review-
ed by the EPA in order to locate candidate study areas. Once this was accom-
plished, the candidate areas were rated in terms of the degree of attention
they were getting in terms of groundwater quality monitoring activities.
Out of the several candidate areas, the coal field along the eastern edge
of the Powder River Basin, located within the State of Wyoming and mostly with-
in Campbell County, was selected for study. Campbell County is reported to
contain about 50 percent of Wyoming's coal resources and approximately 84
percent of its known strippable coal. At least 20 billion tons lies within
200 feet of the surface and, therefore, is recoverable by strip mining methods
(Breckenridge et al., 1974).
One important long-term objective of this study is to develop a reference
manual for use in developing monitoring programs to assess the impact of coal
strip mining on groundwater quality in other areas of the Western coal-
producing region undergoing similar development. It is anticipated that
monitoring activities developed using this manual will eventually become part
of a State's overall environmental monitoring program - air, land, and water.
As a result, the selection of the areas ideally should be made within a State,
by the appropriate State water pollution control agency that, in cooperation
with the EPA, carries out the mandates of P.L. 92-500 and P.L. 93-523.
The basis for selecting these areas will be governed, collectively, by a
combination of administrative, physiographic, and priority considerations.
These factors are reviewed in the following paragraphs and then applied in
exemplary fashion specifically to the project area to illustrate the area
selection process.
Administrative Considerations
The initiation of a monitoring program requires that a locally designated
monitoring agency be specified. In many situations, the requisite agency with
the necessary technical staff may be a county, district, State, or regional
water organization. Thus, the area to be monitored can often be made to corres-
pond to the jurisdictional area of the designated monitoring agency(DMA).
Selection of the DMA may involve a review of a State's institutional
structure. In some instances, it will be readily apparent which agency should
be designated as the monitoring agency. In other instances, several agencies
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may have overlapping responsibility and authority. Situations such as this may
require organizational changes to provide an efficiently operated DMA.
Physiographic Considerations
The physiographic basis for selecting monitoring areas results from the
fact that groundwater basins are distinct hydrographic units containing one or
more aquifers. Such basins usually, but not always, coincide with major sur-
face water drainage basins. By establishing a monitoring area related to a
groundwater basin, total hydrologic inflows to and outflows from the basin are
fully encompassed.
Priority Considerations
Resource administrators at all levels, Federal, State, and local, are
faced with a common problem - how to allocate monetary resources equitably to
deal with a host of environmental problems. For political reasons, these
individuals must be attentive to the needs of all areas under their jurisdic-
tion. Rarely are funds available in a timely manner to deal with more than
just a fraction of the problems brought to their attention. A procedure for
establishing priorities for both existing and potential environmental impacts
for monitoring and control would be particulalry useful.
The following discussion details the application of the administrative,
physiographic, and priority considerations to the selection of Campbell County
as the project area, and this is followed by a description of how the priority
establishment scheme works, before presenting the results of the first attempt
to rank the sources identified in the project area for monitoring.
SELECTION OF THE PROJECT AREA
The eastern part of the Powder River Basin will be subject to the most
intensive strip mine development in Wyoming. The major coal fields are loca-
ted in Figure 1-1. The coal beds along the eastern edge of the basin outcrop
along a line trending roughly southeast to northwest. Almost all the
strippable coal in these beds is located within Campbell County. In order to
select that portion of the coal field best suited to meeting the goals of this
research effort, the generalized administrative, physiographic, and priority
considerations previously discussed are now applied specifically to the selec-
tion of the project area.
Administrative Considerations
A primary administrative consideration is the selection of the DMA. In
Wyoming, several candidate organizations for the DMA exist - the State
Engineer's Office, the State Geological Survey, and the Department of Environ-
mental Quality (DEQ).
The DEQ, because of its assigned responsibilities for environmental qual-
ity, is the State agency most suited to become the DMA. The DEQ has divided
the-State into five physiographic basins - Big Horn Basin, the Northeast
Basin, the Platte River Basin, the Green River Basin, and the Bear and Snake
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MONTANA
COLORADO
50
MILES
100
=d
MAJOR COAL BEARING AREAS
STRIPPABLECOAL
PROJECT AREA
Figure 1-1. Major coal fields of Wyoming (adapted from U.S. Geological Survey, 1974a)
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River Basins. The Northeast Basin encompasses the project area and consists
of three subbasins - the Powder River, Belle Fourche, and Cheyenne River.
The Northeast Basin has an engineer in charge of overseeing environmental
monitoring activities. He works with the various county and city governments
in the execution of the DEQ's responsibilities.
Campbell County lies completely within the Northeast Basin. One impor-
tant factor in determining the size of the project was to confine the study to
a single political unit and to within short distances from an urban center, in
this case the City of Gillette. Campbell County provides an area large enough
to obtain the necessary regional perspective to provide results which are
representative of the impacts on groundwater quality due to coal strip mining
in the Powder River Basin and many areas of the Western States.
Physiographic Considerations
Initially, a rectilinear boundary was established to serve as the project
boundary until proper physiographic boundaries could be identified. This
boundary is shown in Figure 5-1, by the dotted line. The initial boundaries
were later superseded by the physiographic boundaries of the five watersheds
delineated in Figure 5-1, by heavy black lines. Locally within the above
watershed areas, the recharge and shallow groundwater table conforms to the
topography and local geology. The coal seams in the area, however, are region-
al in extent and dip gently in the opposite direction or westerly direction
from surface flows.
Priority Considerations
The emphasis of the monitoring program is on water quality changes direct-
ly associated with the strip mining of coal. However, various nonmining
activities associated with the development of the coal are included in the
scope of the program.
The major sources not directly attributed to the mines are municipal
(sewage treatment, water treatment, landfills and dumps, and urban runoff),
agricultural and livestock production (fertilizers, soil amendments, pesti-
cides, irrigation, stockpiles, and animal wastes), and various industries
(e.g., oil and gas extraction and the construction inoustry).
IMPLEMENTATION OF THE PRIORITY RANKING SCHEME
The priority ranking scheme which follows is designed to progress through
the groundwater quality monitoring methodology (Todd et al., 1976) three
times, each time at a different level of intensity, each time progressing
further into the later steps of the monitoring methodology, and each time
accomplishing a different goal.
Level One
The first time through the ranking scheme, several objectives are met:
to review the existing data and information on known sources and causes of
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groundwater pollution, to identify potential sources and causes of ground-
water pollution, to identify the potential pollutants associated with both
of these pollution source groupings, to evaluate the hydrogeological frame-
work insofar as it relates to these known and potential sources and causes
of pollution, and to superimpose these sources and pollutants on the hydro-
geologic framework to determine their mobilities. The final goal in this
first pass through the scheme will be assignment of monitoring priorities to
those sources which appear to present the greatest threat to the area's
groundwater quality.
Level Two
Implementation of the monitoring program will require a return to the
initial methodology steps. This time the objective will be to verify the
preliminary priority ranking of sources with hard data and will involve
designing monitoring approaches for each source under investigation. This
exercise will require considerable time, depending on the number of sources
involved and the size of the area - perhaps several years to a decade or more
to reach a mature stage. It is likely that the intensive monitoring will
result in a revision of the original priorities. In time, some monitoring
activities will need to be decreased or completely eliminated, while others
will need to be intensified.
When the results of this second pass through the ranking scheme are used,
a much more accurate estimate of the threat to the area's groundwater quality
will be available, and controls can be devised to deal, with the threat. If
the need for instituting controls is obvious after the first assignment of
priorities, they should be implemented immediately. The implementation of
controls will again require funding by the appropriate State agency.
Level Three
The final pass through the priority ranking scheme will involve monitor-
ing to check on the effectiveness of the controls implemented. If these
controls are proven effective, then the intensity of monitoring can be re-
duced and eventually dropped if the threat can be shown to no longer exist.
New sources of potential pollution will continually appear. The monitor-
ing program should plan to include these sources. They should be brought
into the program through the orderly process of Environmental Impact Reviews
by State and Federal agencies.
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SECTION 2
POTENTIAL SOURCES OF POLLUTION
AND METHODS OF DISPOSAL
The basic TEMPO classification scheme for potential sources in the proj-
ect area includes three major categories: Agricultural, Industrial, and
Municipal.
Agricultural activities in the project area are relatively minor. The
major agricultural activities are grazing cattle and some dryland farming.
Groundwater usage was, and still is, meager for these purposes.
The major emphasis in this study is on coal strip mining, which falls
under the Industrial source grouping. A closely related Industrial activity
is coal conversion via steam power generation, gasification, or liquefaction.
To meet the needs of the coal mining and allied industries, the City of
Gillette, outlying communities, and construction camps will need to provide
additional services, e.g., disposal and treatment of liquid and solid wastes,
and expanded municipal water supply and treatment facilities. The result of
this expansion will be a greater number of potential pollution sources. The
impact of these sources has been given detailed review, in particular those
related to the City of Gillette.
The potential pollution source inventory which follows summarizes the
result of an intensive review of all the published material available in the
project area related to proposed development of the seven mines of interest,
and numerous discussions with the environmental staffs for those mines. Many
discussions were also held with city, county, and State personnel involved
in meeting the needs of the coal development and providing adequate environ-
mental controls for this development.
AGRICULTURE
Ninety-four percent of the land in Campbell and Converse Counties is
pastureland; consequently, most farming is conducted by livestock operations.
The major crops are hay and forage. Very little farmland is irrigated.
According to the Farmer's Cooperative in Gillette, which is the major
outlet for agricultural products in Campbell County, very few, if any, soil
amendments are used in the county. The County Agricultural Agent stated that
very little fertilizer is used. Herbicides are used in the County in small
amounts, primarily along highway rights-of-way, and very few pesticides are
normally used.
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According to the U.S. Bureau of Land Management (1974), grazing of range
beef cattle and sheep is the predominant land use in Campbell County. The
average ranch is about 260 animal units, one animal unit being year-round
support for one cow and calf or five sheep.
The County Agricultural Agent stated (personal communication) that al-
though there is a large amount of livestock in Campbell County, there are no
feedlots in the County at this time. The County Agricultural Agent also
stated that dead animals are generally left where they fall to be consumed by
predators.
INDUSTRY
Two main groupings were used to examine th6 impacts of potential pollu-
tion sources from coal strip mining on groundwater quality, active mining
sources, and reclaimed area sources. Active mining sources are those sources
which result from the actual mining operations and are of a transitory nature.
Reclaimed area sources are those sources which are the result of reclamation
activities following the completion of active mining. These sources are ex-
pected to remain in place indefinitely.
Active Mining Potential Pollution Sources
Stockpiles-
Stockpiles can act as groundwater pollution sources when rainfall or
melted snow percolates through the stored material, dissolving pollutants' and
transporting them to the groundwater system. They are also subject to leach-
ing due to seepage from ponded surface waters or artificially applied waters.
Classes of material that may be stored in stockpiles during the active
mining phase are topsoil, overburden, coal, coal refuse, coaly waste, and the
partings that occur between coal seams. Stockpiles may be very temporary or
they may exist for the life of a mine.
Topsoil -
In all Powder River Basin coal mines some topsoil will be selectively
removed and stockpiled before being replaced on top of graded overburden.
Commonly, topsoil from the first area to be mined will be stockpiled because
there is no place to use this topsoil at the beginning of mining. For exam-
ple, in the case of one mine, the topsoil removed from the first area to be
mined will be stockpiled until it is used to cover the final area to be mined
in about the year 2000. Topsoil might also be stockpiled for blending to up-
grade the quality of reclamation soil cover.
Overburden-
As described here, overburden is that material lying between the topsoil
and the mineable coal beds. In the area of study, the mineable coal lies at
or near the top of the Fort Union Formation and the overburden is sandstone,
shale, carbonaceous shale, and thin or impure coal beds of the Wasatch or
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uppermost Fort Union Formations. In local areas, along the outcrops of coal
beds, a unique rock type has been formed by the baking of shale and siltstone
by burning coal beds. The baked material is commonly called scoria or clinker
and it may also be incorporated in the overburden. An additional type of
overburden is the alluvium found in the stream valleys. It consists of sand,
silt, and clay derived from the bedrock units. Overburden thicknesses in
operating and proposed mines range from none at the outcrop of the mineable
coal', up,to perhaps 300 feet as the coal beds are traced westward into the
Powder River Basin. The thickness of overburden that can be removed at a mine
is based on economics and available technology.
During the mining, the overburden is removed, the coal extracted, and the
overburden then replaced and graded to the desired topography. Overburden is
removed during early development of a mine and is stockpiled because there is
no previously mined area in which to place it.
Coal, Coal Refuse, and Coaly Waste-
Coal, coal refuse, and coaly waste are considered together since they are
geologically and chemically similar. Coal refuse is used here to mean the
fine coal and waste material removed during the coal preparation process.
Coaly waste is used here to describe the thin coal seams, impure coal, and
carbonaceous shale that may occur in the overburden and within the partings
between coal seams. However, these materials are identified separately, in
spite of their geological and chemical similarity, because they are handled
differently and, therefore, have different water pollution potentials.
Coal, the commercial product, is handled carefully. It is mined soon
after exposure by stripping and is not allowed to weather or to have much
water percolate through it to pick up pollutants. After mining, it will
usually be processed in some manner. Common steps in coal processing include
crushing, screening, and washing. Coal at Powder River Basin mines is usu-
ally only crushed. After crushing, coal is temporarily stored in silos,
bunkers, or open piles. Although open piles are the exception, they may
occasionally be used.
Coaly waste is considered separately from the remainder of the over-
burden because it usually has a different type and amount of water pollution
potential. Its geochemical properties also affect its potential as a soil-
-forming material. Such materials commonly form toxic soils and are thus
segregated from the other overburden during mining. A frequent method of
handling is to attempt to place the coaly waste at or near the bottom of the
spoil. In order to selectively place the coaly waste, it may be necessary
to stockpile it temporarily.
Partings-
Partings that occur between coal seams could be considered along with
the overburden, rather than as a separate category. The reason for consider-
ing partings separately is that they are likely to be different from the
"average" overburden because they tend to be principally shale and carbona-
ceous shale and because their location may be cause for handling them
-------
differently from the overburden. Partings might be stockpiled temporarily to
allow for selective placement in the spoils.
Explosives-
Either the overburden or coal, or both, may be blasted at a mine, depend-
ing on the degree of consolidation of the material. The principal explosive
now being used for blasting at the strip mines is an ammonium nitrate-fuel oil
mixture known as ANFO. In the case of a complete explosion during blasting,
the solid ammonium nitrate would be entirely converted to gaseous forms and
ultimately be lost to the atmosphere. In the case of an incomplete explosion,
some ammonium nitrate residual will occur. Apparently no studies have been
made to determine precisely the amount of residual to be commonly expected in
the project area.
Solid Wastes for Road Construct!on-
A common practice in strip mine development is to construct access and
haulage roads from overburden. It has been observed at the mines visited that
most permanent roads are being constructed of scoria, or clinker. However,
some roads have been constructed of overburden.
Discharges into Pit and Methods of Disposal -
Water entering pits can originate from a number of sources, each of which
may already contain pollutants derived in a number of ways. Pit water thus
would generally be expected to contain some pollutants.' Pit water is even-
tually disposed by several different methods. As such, the pit discharge is
itself a potential source of pollution. The following discussion lists the
sources of pit water as well as the methods of disposal of pit discharge.
Water in the pits may come from a number of sources, such as:
• Direct precipitation in the pit
• Runoff into the pit
• Water percolating from nearby stream channels, generally
through alluvium along the floodplain
• Liquid wastes (such as septic tank effluent)
• Groundwatar in the overburden
• Groundwater in spoils
• Groundwater in the coal seam being mined
• Groundwater in underlying coal seams and strata.
For mines in the Gillette area, the method of disposal for most of the
pit discharge will be dust control. Secondarily, the pit discharge will be
10
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used for irrigation of reclaimed spoils during the early stages of reclamation.
Discharge to surface water will also commonly occur when there is excess pit
water compared to potential use.
Supplemental Sources of Water-
Supplemental water for dust control and coal processing may be obtained
from pumpage of deep wells or by importing sewage effluent or both.
Pumpaqe of deep groundwater-It is theoretically possible for poor qual-
ity waters pumped from deep aquifers to pollute shallow groundwater systems.
However, in the project area, the deeper waters are generally of better qual-
ity than shallow waters. Available data indicate that the shallow Wasatch
Formation waters have the poorest quality of any waters in the area.
Pumpage from the deep aquifers in the project area is limited to a few
subdivisions and the coal mines. All drinking water supply wells for the
mines produce from the Fort Union Formation.
Imported sewage effluent-The principal source of sewage effluent for
importation in the project area is from the City of Gillette treatment plant.
This plant receives not only domestic wastes from the City, but also periodic
discharges of industrial wastes.
Sewage flows from the City of Gillette treatment facilities may impact
on the quality of groundwater in two ways: (1) seepage losses in Donkey
Creek and (2) direct drainage into mine pits. Seepage loss is a function of
such factors as temperature and entrained substances. Temperature affects
infiltration through viscosity relationships. Entrained substances, parti-
cularly sediment, orgam'cs, and microorganisms may clog the surface of the
channel, reducing intake rates.
The problem of seepage losses in Donkey Creek will be largely eliminated
following the completion of a pipeline which will transmit effluent from the
City of Gillette to a reverse osmosis (RO) unit at the Wyodak mine. However,
seepage losses in the pipeline must also be considered a potential source.
Water treated in the RO unit wil.l be used as process water in the nearby
Neil Simpson Power Plant. Brine from the RO unit will be discharged to an
evaporation pond for disposal. Leakage from the pond should be considered as
a potential source.
Surplus sewage effluent (above requirements for the RO plant) will be
used for dust control.
Mine Sanitary Wastes-
Three types of treatment facilities may be used to treat sewage generated
in the mine site: septic tanks, package plants, and oxidation ponds.
Septic tanks-Overflow for septic tanks is generally discharged into
leaching fields. Areal requirements for leaching fields with continuous
11
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inundation should be 0.5 gallon per square feet (gal/ft ) per day for inter-
mittent operation. Effluent percolating beneath a leach field poses a threat
to groundwater quality, particularly if the vadose zone consists of fractured
rock. Sludge must be pumped from the septic tank units periodically. Sludge
could be used as a soil conditioner, possibly leading to pollution.
Package plants-Prefabricated package plants are generally used to treat
sewage for small subdivisions, schools, and other installations, with loadings
of 1 million gallons per day (mgd) or less. Package plants operate to provide
extended aeration of sewage -a variant of the activated sludge process.
Units consist of two compartments: a clarifier chamber and an aerator tank,
where air is forced into raw and recycled sewage.
Two problems exist with package plants, vis-a-vis potential impacts on
water quality of the receiving stream or groundwater. First, package plants
are very sensitive to shock loading, e.g., rapid changes in diurnal flow rates.
Treatment becomes relatively ineffective following shock loading such that
effluent quality released from the plant becomes very poor. Secondly, because
primary settling is generally omitted in commercial plants, discharge of sol-
ids may become objectionable.
Oxidation ponds-Oxidation ponds are commonly used in small communities
to treat raw sewage. In fact, if designed properly, ponds may attain second-
ary treatment (U.S. Environmental Protection Agency. 1976b). Three types of
ponds are commonly used: aerobic ponds (mechanical aerators), facultative
ponds (aerobic-anaerobic) and anaerobic ponds. Basically, aerobic ponds rely
on a symbiotic relationship between bacteria and algae to stabilize sewage.
Ponds may leak if inadequately sealed and possibly contribute to ground-
water pollution. Generally, a natural seal is induced in time by infiltrating
organics.
Mine Solid Wastes-
Solid wastes generated by mining operations (excluding spoil) may be
disposed of by one or more of the following:
• Onsite landfills
• Offsite disposal by landfills
• Incorporation in mine spoils
• Incineration followed by land disposal of residue.
Onsite disposal may be accomplished using open dumps or sanitary land-
fills. Open dumps, as the name implies, consist of dumping solid wastes on
the surface of the ground, or over embankments. Occasionally, open dumps are
burned. An advantage of onsite landfills, properly designed and constructed,
is that the solid waste is concentrated at one place. Monitoring of types of
solid wastes is facilitated, as well as groundwater monitoring.
12
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The same discussion given above for onsite disposal applies to offsite
solid waste disposal sites.
Solid wastes generated by mining activities are often incorporated with
mine spoils and dumped into the mine pit. Groundwater moving into the spoil
piles is potentially capable of leaching solid wastes, producing leachate.
In contrast to onsite or offsite disposal, solid wastes are generally placed
haphazardly in the spoils. Consequently, groundwater monitoring becomes a
difficult operation.
Combustible solid wastes may be incinerated to reduce bulk. The residual
ash may then be placed in landfills or into spoil piles. Leaching of buried
ash may subsequently occur by surface or groundwater influx into the landfill
and spoil pile.
Fly ash removed by the incinerator gas stream may settle on the ground
surface for considerable distances from the incinerator. Settled ash repre-
sents a potential source of surface and groundwater contamination.
Liquid Shop Wastes-
Maintenance and servicing of mine equipment will be likely to produce
some liquid wastes, such as oil and wash water. In most cases the mining
companies have simply stated that liquid shop wastes will be disposed of in
a manner complying with State and Federal regulations, but no details have
been given.
Much of the equipment will probably be washed outside, with the water
running off onto the ground. Possible pollutants include salts in the mate-
erial being washed off of the equipment, soap or detergent that may be used,
and salts or toxic elements in the water used for washing. Washing will
probably be concentrated in a relatively small area near the building and shop.
Spills and Leaks—
Wherever liquids are held, there is the potential for leaks. The mines
keep liquids such as gasoline, oil, and diesel fuel in storage tanks, either
buried or above ground, and in some cases, pipelines connect these storage
tanks with points of use. Package treatment plants, with associated pipe-
lines, and storage vessels for ammonium nitrate and fuel oil also have a po-
tential for leaks.
Spills can occur in the process of transporting all of the above mate-
rials and during loading and unloading storage tanks. Lubricants and other
materials used for servicing equipment have the potential of being spilled
both in the shop and at the pit, depending upon where servicing is taking
place.
Reclaimed Area Potential Pollution Sources
Site reclamation fill materials are those that will be within or closely
associated with the mined area. After mining, the overburden (spoils) will
13
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be replaced within the mined area. The spoils will consist of various sub-
categories of geologic materials including coaly waste, interseam partings,
and refuse from coal preparation, if any is produced. Various solid wastes
may also be disposed of within the spoils. This was observed to be the prac-
tice at many of the mines, which are reported to be licensed landfills. Top-
soil that is determined to be of good quality for plant growth will be spread
on the graded spoils. Poor quality soils will be incorporated within the
spoils.
These fill material sources may contribute to groundwater pollution in
several ways. As with stockpiles, precipitation may percolate through the
materials, dissolving soluble chemicals and carrying them to the groundwater
system. Additional mechanisms of pollution are percolation of surface water
from streams, ponds, and lakes, and the movement of groundwater through the
mined area. A common circumstance in Powder River Basin mines is the pres-
ence of a stream that passes through the mine area. The streams are being
diverted during the course of mining, but subsequently will be rechanneled
through mined areas. Ponds and lakes may be developed within the mined area.
Some mining plans include a lake in the final strip cut.
Reclamation Aids-
Fertilizers and soil amendments have some potential for groundwater pol-
lution. The AMAX Belle Ayr South mine is reported to be planning application
of not more than 20 pounds per acre of nitrogen in the form of ammonium ni-
trate; in most cases, 20 pounds of phosphorus in the form of superphosphate,
essentially monocalcium phosphate. Wood fiber and straw mulches are commonly
used in the project area to reduce soil loss and conserve moisture.
The primary fertilizer dealer in Campbell County is the Farm Bureau
Co-op. There, nitrogen (ammonium nitrate) is available with a fertilizer
grade of 34-0-0, and as a mixture with superphosphate, having an analysis of
18-46-0. One mine buys the 34-0-0 and 18-46-0 fertilizer grades and mixes
these to obtain a higher nitrogen content of the applied fertilizer. The
Farm Bureau employee was of the opinion that Campbell County is now in the
experimental stages of fertilizer application, with some farmers believing
strongly in its benefits, and others disclaiming them. Fertilizer is used
primarily in Campbell County on wheat, barley, and some grasses.
Ammonium nitrate is manufactured for use in explosives and as a fertil-
izer. Because it is very soluble in water when used as a fertilizer, it
leaves no residue in the soil if sufficient moisture exists to stabilize it.
Because the two types of nitrogen salt which compose this fertilizer have
the ability to move up and down in the soil solution, it should be consider-
ed a potential pollutant.
The cationic nature of ammonium ions permits adsorption and retention
by soil colloidal material if the exchange capacity of the soil is sufficient-
ly high; otherwise it will be removed in percolating water.
Once ammonium is nitrified, it is subject to leaching as it is completely
mobile in soils. Under conditions of excessive rain and high water table it
14
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may reach the groundwater. This downward migration is likely to occur near
streams. Where evapotranspiration is greater than precipitation, nitrogen
salts may migrate vertically upward to the land surface.
Because the phosphate ion is almost immobile in the soil, phosphorus
moves very slowly from the point of placement.
OIL AND GAS EXTRACTION
Oil and gas have been discovered in 210 fields in the Eastern Powder
River Basin, Figure 2-1. The remaining recoverable reserves in these fields
have been conservatively estimated at 221 million barrels of oil and 508
billion cubic feet of natural gas. Ninety percent of the oil is produced
from the early Cretaceous Muddy Sandstone and the Minnelusa Formation of
Pennsylvanian age.
According to the Consolidated Oil and Gas Co. (personal communication),
in most cases, oil and gas occur together. An oil/gas mixture is pumped out
of the well, and the two are separated on the surface. The gas is piped off,
while the oil is collected in an onsite battery of storage tanks. When the
tanks are full, the oil is tested for water content and is then transported
to the customer via pipeline.
A local rancher has reported that leakage from storage tanks is a con-
tinuing problem; the oil has polluted the surface water in local drainage.
He also reported that during drilling the sides of the mud pits, used for
circulating water and drilling mud, broke open several times, releasing mud,
water, and oil into a nearby stream. Leaks and spills of this type appear
to be an important potential pollution source associated with oil and gas
extraction.
Other potential sources of pollution include seepage through the bottom
of the mud pit and the entrance of water into shallow aquifers through leaks
in the casings of injection or disposal wells.
Every oil well and test hole that has been drilled had a mud pit associ-
ated with the well at the time of drilling. These mud pits are used for mix-
ing drilling mud and for circulating water used in drilling. When a well or
test hole is abandoned, the mud pit must be filled in and "reclaimed." No
site-specific information is available at this time on evaporation ponds or
brine disposal wells.
CONSTRUCTION
Campbell County is the fastest growing area in the State of Wyoming.
This growth rate is reflected in large-scale construction activity in the
area. Approximately 1,000 housing starts per year are anticipated by the
City of Gillette, 600 within the City during 1977 and the balance in adjacent
county areas. Also, numerous duplexes and apartment buildings are slated to
be built in the coming years.
Industrial construction is also active. A large shopping area is planned
15
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" RRR RRR RRR RRRR RR
79W 78W 77* 76W 75W 74W 73W 72W 71W 70W 69W 68W 67W 66W 65W 64W
T58N
T57N
Oil and gas field
(Abd)
Abandoned field
Oil pipeline
Gas pipeline
A
Refinery
T32N
10
20
30 40
50 M.les
0 10 20 30 40 50 Kilometers
Figure 2-1. Oil and gas fields associated with the Eastern Powder River Basin,
Wyoming (U.S. Department of Interior, 1974)
16
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near the (£ut-across Road, south of Interstate 90. East of this planned shop-
ping center, a motel is being built. The facility is scheduled for comple-
tion in fall 1978. North of Gillette along Wyoming Highway 14-16, new steel
buildings are being erected. The newest building will be a parts depot for
mining equipment. Tractor dealerships, welding shops, and other businesses
occupy other recently constructed buildings. The Gillette-Campbell County
airport is also growing. One company is building new hangars and office fa-
cilities, and some individuals are building hangars for their private planes.
Road construction is occurring in the project area. The gravel road
from the AMAX Belle Ayr South mine south to the ARCO Black Thunder mine par-
allels a new railroad line. The road has been widened, new culverts have
been installed, and graders keep the surface smooth.. The road will eventually
be oiled and graveled. Bridges have been replaced on Wyoming Highway 59 near
Reno Junction, and road-patching crews operated countywide through the summer
of 1977. Wyoming Highway 59, north of Gillette, is being rerouted past the
AMAX Eagle Butte mine and the Carter North Rawhide mine.
A north-south railroad line is being constructed from Gillette to the
southern end of the project area. The line is complete to approximately 12
miles south of the Sun Oil Cordero mine, and the operating mines have com-
pleted spur lines to the main railroad. Field observations indicate that the
railroads will be as far south as ARCO's Black Thunder mine by winter 1977.
The most active construction efforts are associated with the surface
coal mines in Campbell County. Although many mines will eventually extract
Federal and/or private coal, only seven mines within the project area have
begun substantial construction.
Methods of Construction Waste Disposal
Construction projects primarily generate solid waste, with limited
amounts of waste oil and grease. Housing construction projects dispose of
their solid waste at the Gillette Sanitary Landfill. Nonmining industrial
construction waste is also deposited at the landfill.
Railroad and highway construction projects use water for dust control.
Water service companies haul water to unlined storage pits, from which the
construction drivers withdraw water for dust control. Field observations
indicate that the water used for these purposes may often be oil field waste-
water, or other nonpotable water. The storage pits for this water are usu-
ally centrally located for easy access. Leaks and spills from storage tanks
are always possible, but few such problems have been observed in the area.
Construction of the surface coal mines generates solid waste and small
amounts of waste oil and grease. The mining companies have obtained permits
to treat the mining pits as landfills. Therefore, solid wastes and all other
wastes generated are dumped into the mining pit and are covered with backfill
material. Personnel from the City of Gillette (Jeff Smith, Gillette City
Engineer, personal communication, 1977) stated that a large amount of mine
construction material is disposed of at the City landfill.
17
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COAL CONVERSION
Steam Electric Power Plants
One air-cooled, coal-fired power plant is currently operating in Campbell
County and another, under construction, is scheduled to go on-line in June
1978.
The operating power plant is Neil Simpson Station, owned by Black Hills
Power and Light Co., and Pacific Power and Light Co., and operated at the
Wyodak mine site. Burning about 400 tons of coal per day, it is capable of
producing 30 megawatts of electricity. When the power plant currently under
construction begins operation, part of the existing facility will be retired.
Combustion products from burning the coal are heat, gaseous carbon di-
oxide, water vapor, sulfur dioxide, and impurities such as suspended inorganic
noncombustibles. These combustion products and excess air pass through the
boiler as flue gases. Next the gases pass through a regenerative air heater
where some of the heat is transferred from the flue gases to incoming combus-
tion air. The flue gases then enter an electrostatic precipitator, where
suspended fly ash particles are charged by an electrical field. The parti-
cles are then attracted to grounded collector plates and are moved down the
plates into a hopper by mechanical vibration of the plates. The electro-
static precipitator will remove about 99 percent of the fly ash and may en-
train as much as 10 percent sulfur dioxide with the ash. It is designed to
treat about 4 million pounds of flue gas per hour. The treated gases will
be discharged through a 400-foot stack at an exit velbcity of about 90 feet
per second during full load operating conditions.
Potential sources of pollution from the power plants include the follow-
ing:
• Atmospheric emissions
• Fly ash from the electrostatic precipitators
• Neutralized demineralizer regeneration wastes
• Sewage treatment plant effluent
• Floor and equipment drainage and wash water
• Boiler blowdown
• Bottom ash sluicing water
• Pyrites from the pulverizer
• Bottom ash from the boiler
• Ash from the economizer.
18
-------
The major power plant waste material is fly ash. It is predicted that
the new plant will produce approximately 28,000 pounds of fly ash per hour,
or nearly 400 tons per day. The ash will be disposed of by using it as fill
in both the north and south pits of the Wyodak mine. Once it is deposited
in the pit, it will be covered with spoil. Water sprays will be employed at
all transfer points in order to minimize dust during ash handling.
Water for boiler makeup will be treated for dissolved solids removal by
two parallel demineralizer trains, each consisting of a cation exchange unit
and a mixed bed ion exchanger. Periodic chemical regeneration of the demin-
eralizers will be required. Regeneration wastes will be collected in a sump
for neutralization to a pH of 6.5 to 8, and will then be disposed of in an
ash pond located in the north pit. Bottom ash sluicing water, boiler blow-
down, and floor and equipment wash water will also be conveyed to the ash
pond. Black Hills Power and Light Co. (1973) states that because the pond
will be located on top of a clay bed no seepage of pond water is anticipated.
During construction of the new plant, sanitary wastes.from the station
and from a nearby residential community are being treated in an extended
aeration treatment facility. Following construction, a packaged treatment
plant, including primary settling, extended aeration, and gas postchlorina-
tion, will be used. It will be designed to treat about 3,500 gallons per
day with a 4,000-gallon aeration, tank, a 1,000-gallon settling tank, and a
1,200-gallon sludge tank. Treated effluent will be discharged to the ash
pond.
Additional solid wastes generated by the power plants are pyrites from
the pulverizer, bottom ash from the boiler, and ash from the economizer.
Black Hills Power and Light Co. (1973) stated that these will be disposed
of onsite.
Gasification
The extensive coal resources of the Powder River Basin, coupled with the
need for easily transportable and usable fuels to high-use regions, create
the potential for development of coal conversion facilities in Campbell County.
Although three types of conversion processes (coal gasification, coal lique-
faction, and solvent refined coal) are currently being studied in the United
States, no commerical-scale facilities are planned for Campbell County for
the immediate future. However, since 1974 Lawrence Livermore Laboratories
(LLL) has been conducting experimental in situ coal gasification studies.
Their experimental site in the Hoe Creek watershed southwest of Gillette is
the only coal conversion activity identified in the study region.
The LLL approach for in situ coal gasification conceptually involves
conversion in a thick-50 feet or more-coal seam at depths of 500 to 3,300
feet. Permeability of the reaction zone is created using chemical explosives.
A permeable, fractured coal bed surrounded by relatively impermeable strata
promotes heat transfer and enhances contact of coal and reactants. LLL
anticipates that this will also minimize leakage of reactants and products
from the fractured zone. In this sense, the LLL concept has been termed an
underground packed-bed reactor.
19
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The fractured zone is ignited at the top. Ignition is initially accom-
panied by oxygen injection which is replaced by a steam-oxygen mixture after
the combustion zone is established. Some of the coal burns to produce process
heat, and the steam is a hydrogen source for the gasification reaction. Col-
lection wells are drilled to the bottom of the fractured zone to collect the
product gases (methane, carbon monoxide, hydrogen and carbon dioxide). Under
commercial operation, these products would be upgraded to pipeline quality
in surface facilities.
With the exclusion of surface upgrading facilities the preceding para-
graphs provide the salient features of both a commercial-scale in situ gasi-
fication facility and the small experimental operation presently existing
near Gillette. The remainder of this discussion deals with the specifics
of the experimental program as it may result in pollution sources.
The actual gasification phase of Hoe Creek Experiment No. 1 occurred in
October 1976. Activities leading to the actual burn included:
• Hydrologic and geologic exploration
• Fracturing of the coal seam
* Placement of inlet, outlet, dewatering and environmental
monitoring wells
« Dewatering of fractured zone
• Gasification experiment.
These activities are to varying degrees potential causes of pollution.
Prior to development of the gasification experiments, exploratory holes
were drilled at the Hoe Creek area to characterize the site geology and hy-
drology (Stone and Snoeberger, 1976). Pump and observation wells were in-
stalled for pump tests. These were subsequently used for dewatering and
environmental monitoring. Potential sources of pollution from these activ-
ities include discharge from pump tests and interconnection of aquifers from
faulty well construction.
Fracturing of the Coal Seam-
Prior to gasification, the coal seam was fractured to enhance permea-
bility and product recovery efficiency. A slurry of explosive material
called Pourvex EL-836 was used (Stephens and Madsen, 1977). The composition
of this explosive is not available. However, explosive residues are a poten-
tial pollutant. Additionally, the fracturing of the coal seam altered the
hydrologic characteristics of the formation and may lead to enhanced move-
ment of gasification byproducts from the area.
Placement of Experimental Wells—
To provide access to the fractured zone and adjacent strata, a variety
20
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of injection (gas), outlet (product), dewatering, and environmental monitor-
ing wells were constructed (Figure 2-2). These wells are potential pollution
sources by acting as conduits between different aquifers, from the burn zone
to other aquifers, and from the burn zone (or aquifers) to the surface.
Dewatering-
After the coal seam was fractured, this zone was dewatered by pumping the
six dewatering wells and well P-l. Pumping was continued with only short
interruption throughout the entire experiment. Water production rates are
shown in Figure 2-3 and water level response in the various site wells is pre-
sented in Figure 2-4. The method of disposal of this water is unspecified.
At equilibrium, the dewatering produced less than 10 gallons per minute (gpm).
Gasification Experiment-
The fractured coal bed for Hoe Creek Experiment No. 1 was ignited on
October 15, 1976. After one day of operation, an override occurred and essen-
tially only the top layer of the fractured zone was gasified. An override had
been predicted from the results of post-fracturing analyses. Gasification
ended October 26, 1976. Approximately 130 tons of coal (16 percent of the
fractured zone) had been consumed. Although the burned zone for this experi-
ment was small, a source of release of the byproducts of pyrolysis, carboniza-
tion and coking of coals, and partial combustion byproducts was created.
Subsequent water movement into and through the burned zone may affect the
water quality of area aquifers. Releases at the surface by dewatering wells
during subsequent pumping are, for environmental monitoring purposes, also a
potential source of pollution.
Subsidence of the burned area after fracturing and gasification is a
possibility. Subsidence may alter the alignment of shallower strata creating
conditions of either aquifer interconnection or blockage. Surface subsidence
may also disrupt runoff patterns and affect recharge.
Hoe Creek Experiment No. 2-
The gasification phase of Hoe Creek Experiment No. 2 is expected to take
place in October 1977. The Hoe Creek 2 site is located about 330 feet from
the site of Hoe Creek Experiment No. 1. The coal seam is approximately 25
feet thick with the top located 118 feet below the surface.
Whereas Hoe Creek Experiment No. 1 was a small-scale two-hole gasifica-
tion project, Hoe Creek Experiment No. 2 will be carried out with a five-spot
array (Figure 2-5). One injection well will be centrally located with four
collection wells arranged around it in a square pattern. Approximately 1,500
pounds of chemical explosives will be used for fracturing in the central in-
jection well and in each of four other explosives holes, arranged in a square
pattern rotated 45 degrees from the square defined by the collection wells.
The explosives holes are arranged to maximize resource recovery by placing the
areas of highest permeability in the longest flow paths. Small explosive
charges may also be placed in the outer flow-holes to reduce flow resistance
in the regions where flow lines converge. The dewatering holes will also be
placed to maintain symmetry and maximize resource recovery.
21
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• THERMOCOUPLE WELLS
O DEWATERING OR MONITORING WELLS
O
10-OW
O
12-OW
P-2°
(HFEM)
O^U o
vP*w
DW-5
0
1-7
0
HE
O^ — AIR
O
8-OW
(HFEM)
•
1-6 ±
O
9-OW
(HFEM)
12
DW-3
•!-!
• • •
1-4 CB-2 ,.8
GAS OUT «*-O
O
DW-2
0 5 10ft.
0123m
.
Figure 2-2. Hole bottom locations (Hoe Creek Experiment No. 1)
(Lawrence Livermore Laboratory, 1977).
22
-------
I
80
70
60
< SO
c
40
30
II I I
I I I I
• SIMPLE CYLINDRICAL MODEL
A TWO-DIMENSIONAL ZONED MODEL
• MEASURED VALUES
AIR
INJECTION
200
Figure 2-3. Comparison of measured and calculated water production
rates for the Hoe Creek Experiment No. 1 site (Lawrence
Livermore Laboratory, 1977).
TIME (h)
Figure 2-4. Water levels at several locations within the fracture zone
as a function of time after the start of dewatering; levels
indicated on the right are those reached after 3 to 5 days
of pumping (Lawrence Livermore Laboratory, 1977).
23
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LEGEND
• DEWATERING HOLES
O EXHAUST HOLES WITH SMALL LIQUID PUMPS
O EXPLOSIVE FRACTURING HOLES
• EXPLOSIVELY FRACTURED GAS INJECTION HOLE
Figure 2-5. Plan view of the packed-bed experiment
(Lawrence Livermore Laboratory, 1977).
The coal will be ignited in the center explosive well at the top of the
seam and burned down and outward using an oxygen/steam blast. Condensed liq-
uids (primarily water) that precede the flame front will be removed through
the exhaust holes. The dewatering holes may be used as back-up exhaust holes
if needed.
MUNICIPAL SOURCES OF POLLUTION
Sanitary Wastes
Sewage Treatment Plant Effluent—
The City of Gillette treatment plant receives not only domestic wastes
from the City, but also periodic discharges of industrial wastes and snow
melt. Its capacity as of May 1977 was about 1.7 mgd. The treatment plant
was originally intended to be a secondary-type facility. Primary treatment
is minimal, however, with only a screen provided to remove the solids. A
follow-up grit chamber and sedimentation tank were not included. Thus, the
secondary unit comprising activated sludge aeration tanks functions in part
also for primary treatment. The capacity of these tanks has been reduced by
accumulation of sand and other material. Because of ineffective treatment
in the aeration tanks, the clarifier or final settling tanks are also
24
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overloaded. Effluent discharging from the plant is piped to a "polishing"
lagoon which may or may not function as an oxidation pond.
Because of the high water table at the plant, leakage from the aeration
and clarifier tanks may be occurring, introducing essentially raw sewage into
groundwater. Leakage from distribution lines onsite and seepage from the
oxidation pond should also be regarded as potential sources.
Effluent discharging from the pond drains into Donkey Creek. Aerial pho-
tography of the area (U.S. Environmental Protection Agency, 1976d) indicates
that effluent may flow for a considerable distance downstream in the creek.
Sewage flows from the Gillette treatment facilities may impact on the
quality of groundwater in two ways: (1) seepage losses in Donkey Creek, and
(2) direct drainage into mine pits. Seepage loss is a function of such fac-
tors as temperature and entrained substances. Temperature affects infiltra-
tion through viscosity relationships. Entrained substances, particularly
sediment, organics, and microorganisms may clog the surface of the channel,
reducing intake rates.
Sewage Sludge-
Sewage sludge consists of a mixture of sewage and settled or suspended
solid matter issuing from the final sewage treatment process. The quantity
and character of sludge depends to a large extent on the treatment process.
For example, sludge from the secondary settling tanks of an activated sludge
process may contain 13,500 gallons of sludge per million gallons of sewage
(Health Education Service, nd), and a moisture content of 98 percent. The
nominal weight of dry solids from the process is 2,250 pounds per million gal-
lons (Health Education Service, nd). The process of sludge digestion is
intended to reduce the volume of liquid, thereby reducing the total volume;
and also to stabilize the organic matter.
A number of methods are available for disposing of sludge, including
landfilling, incineration, and application to cropland.
The technique for handling sludge at the Gillette treatment plant
involves settling in a pond and/or flooding onto a nearby field. No plans
are currently underway to use the sludge for agriculture because of fears
.that zinc or other heavy metals may cause crop damage.
Sludge disposed of by the Gillette treatment plant may impact ground-
water through seepage from the settling pond and during spreading in the
nearby field.
Sewerline Leakage-
Leak-free sewage systems are nonexistent. It is difficult to prevent
small leaks in new systems, and older systems develop cracks and leaks with
age. Most sewerline leaks are quite minor, and can often go totally unde-
tected. Major sewerline leaks can be detected by puddling of sewage and/or
odor problems.
25
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According to City officials, sewerline leakage is not a major problem in
Gillette. No problems of this type have been reported during 1977. However,
potential leakage problems are developing. Sewerlines in the older parts of
town are approximately 40 to 50 years old and they are probably in poor repair.
In summary, sewerline leaks are potential sources of pollution. During
spring runoff periods, much puddling of surface runoff occurs, and infiltrat-
ing waters could conceivably carry sewerline leakage to the groundwater body.
However, shallow groundwater in the Wasatch Formation is discontinuous, and
the infiltrating pollutant might never reach groundwater. Moisture curves in
the vadose zone would have to be determined before a complete analysis would
be performed; the apparent minor nature of this problem, however, discounts
the use of the procedures.
Septic Tanks-
Although septic tanks are in both Campbell County and the City of Gil-
lette (as well as package plants), an inventory of numbers and locations is
not currently available.
Water Treatment Plant
The water supply for the City of Gillette is drawn from more than 25
wells located north of the City. These wells are generally described as
"hard" or "soft" water wells. The number of hard water wells exceeds soft
water wells. Total hardness ranges from a trace (in soft water wells) to
2,425 parts per million (ppm), as CaCOs (Nelson et a!., 1976). Recently
(June 1977), average hardness of raw water entering the Gillette Water Treat-
ment Plant was 128 ppm, CaCOs-
The Gillette Water Treatment Plant was described by TOUPS, Inc. (1977)
as follows:
The Gillette water treatment facilities are located
along the north edge of the City...They consist of a
degasifier, a raw water storage tank, a lime softening
plant, and an electrodialysis plant, all constructed in
1972. The general condition of the treatment facilities
is poor, showing a need for substantial repair and
maintenance work.
Water from the soft water wells is pumped directly
into the treated water storage tanks with no treatment
other than chlorination, thus bypassing the water treat-
ment facilities.
Water from the Fox Hills and hard water wells is
pumped to the first step in the treatment process, which
is a Permutit tray degasifier, designed to remove carbon
dioxide, hydrogen sulfide, and the oxidation of iron.
Water flows by gravity from the degasifier to the raw
water storage tank, which is a 42-foot diameter steel
reservoir with a capacity of 250,000 gallons. A valve
26
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vault at the base of the tank can be used to control the
flow of water to the next step, which is pretreatment by
partial lime-softening and iron removal.
A chlorine feed system for the water supply is lo-
cated near the main pump station. Metering equipment
consists of three Fischer and Porter chlorinators. The
chlorine feed equipment and accessory equipment do not
meet minimum standards set by the' State of Wyoming.
As of June 1977 the electrodialysis plant was not operating because of
severe coating of the electrodialysis (ED) plates with precipitated salt.
Apparently, raw water was introduced to the system without prior softening.
Sludge from the water softening process, consisting of calcium and mag-
nesium salts, is presently taken to the City of Gillette landfill for disposal.
Slurry discharged from the softening process is discharged into Stone Pile
Creek (Burlington Ditch) immediately to the north of the plant creating a
direct source of potential groundwater pollution.
Landfill or Dumps
The Gillette landfill is located southwest of the City on a hill. In
the southwest corner of the site are stockpiled the so-called "white goods,"
mainly metals such as automobiles, 55-gallon oil drums, discarded tires,
wooden furniture, etc. North of the metal disposal area is a pit in which
oily wastes have been dumped, along with some metals. Pesticide containers
and wastes are accepted. Runoff enters this pit from a local area. Near the
pit is an area where open burning is permitted. Down the hill, on'the north
end, are three long parallel trenches. Each is about 30 to 40 feet wide, 400
to 500 feet long and a maximum of 20 to 30 feet deep. The coal almost extends
up to the land surface and was removed and piled on the sides of each trench.
Surface runoff readily flows into the trenches and possibly into the buried
solid wastes.
West of the two lower trenches is another pit, about 100 feet long and
200 feet wide-the so-called dead animal pit. South and east of the three
trenches and up nearer the 2-million gallon City water tank are two additional
pits. These pits contain oily wastes and septic tank pumpage. Garbage also
is scattered about.
South and slightly up the hill from the oily waste ponds is an area mark-
ed for "tires only." Oily wastes have also been discharged into this area.
The presence of surface water running into the landfill trenches is ideal
for the production of leachate. In fact, leachate plumes in the shallow aqui-
fers should be considered a definite possibility.
Urban Runoff
Urban runoff and related pollution sources in the Gillette area include
the runoff itself, traffic-associated pollutants, and street and highway
27
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deicing salts. Specific sources in urban runoff include settled dust, fly
solids from off-street mud, automotive exhaust, organic debris from tree
leaves, grass trimming, and discarded litter (McElroy et a!., 1976). Another
primary source in the urban environment is fecal matter from domesticated and
indigenous animals. Motor traffic contributes particulate materials and
nutrients which accumulate in the surfaces of roadways. Deicing salt is
applied to roadways during winter and spring months.
Miscellaneous Potential Pollution Sources
Miscellaneous potential sources of groundwater contamination in the City
of Gillette include: (1) sources relating to recreational activities, e.g.,
leakage from Gillette Fishing Lake; and (2) discharge of sources to washes,
e.g., road oil leaking from containers near the City of Gillette Treatment
Plant into Stone Pile Wash.
Other Municipalities
The major population centers outside the Gillette city limits are:
Rawhide Village, Collins Heights, Wyodak Construction Camp, Hidden Valley,
Westridge, Heritage Village, and Wright, Wyoming. Table 2-1 details the
methods of waste disposal at each of these areas.
TABLE 2-1. OTHER MUNICIPALITIES
Sewage treatment
Development
Rawhide Village
and Trailer Park
Collins Heights
Wyodak Construction
camp
Hidden Valley
Westridge
Wright
Heritage Village
Water supply
Fort Union wells
Fort Union wells
Fort Union wells
Fort Union wells
Fort Union wells
Fort Union wells
Fort Union wells
^••••••••^••••••••••••••(•••••••(••••••••^•••••MMIIH
Sewage effluent
Small , ephemeral
channel
None
Donkey Creek
Small , ephemeral
channel
None
Small , ephemeral
channel
Small , ephemeral
channel
•M«M_WM^^___|H»MIHnMMIMH^^HBHvai|MII
Sewage sludge
Trucked to City
treatment plant
None
Trucked to City
plant
Trucked to City
treatment plant
None
Uncertain
Trucked to City
treatment plant
iWBIHHHHHHIIIflHHIIBHHIIIgHHHIHHVIIV,^H^H^^HHMMHIBHIII
Septic
tanks
None
1 tank/
1 acre lot
None
None
1 tank/
1 acre lot
None
Some in
early sub-
division
(Anderson)
M^M«HWWMV-«*«^HB**l«
Dumps
None
None
None
None
None
None
None
•••^•^^^•^••^^
Virtually all the water supply is from wells drilled into the deep Fort
Union aquifers. The waters are low total dissolved solids (TDS), sodium
bicarbonate types that are superior to the City of Gillette's municipal supply.
28
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Sewage disposal is achieved by package sewage treatment plants or septic
tanks. Treatment plants are located at Rawhide, Wyodak, Hidden Valley, Heritage
Village, and Wright. Liquid effluents are discharged into small holding ponds
which empty into local ephemeral channels. Sewage sludge is, as a rule, truck-
ed to the City of Gillette sewage treatment plant and is disposed with the
City's sewage sludge. Septic tank areas include Westridge, Collins Heights,
and the Anderson subdivision (adjacent to Heritage Village).
No dumps or landfills are located at the subdivisions. Garbage and trash
are collected and hauled to the Gillette-Campbell County landfill. Plans for
such facilities at Wright, Wyoming, are currently being contemplated.
Local runoff is uncontrolled and, in all cases, runs downhill to the
nearest stream channel. Due to the small size of most of these subdivisions,
and also due to their suburban character, the pollution potential of local run-
off is minimal.
In summary, monitoring programs dealing with the subdivisions should
concentrate on the effluents discharged by the package sewage treatment plants.
Sewage sludge and solid waste are disposed of at City facilities, strengthen-
ing the need for monitoring at these locations.
29
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SECTION 3
POTENTIAL POLLUTANTS
AGRICULTURE
Major potential pollutants from the use of fertilizers in Campbell County
are nitrogen, phosphorus, and possibly potassium. The major pollutants asso-
ciated with livestock in Campbell County are nitrates and organic components
of animal waste. The major weed killer used is 2,4-D. Potential groundwater
pollutants resulting from irrigation and leaching include primarily the solu-
ble salts calcium, magnesium, sodium chloride, sulfate, and bicarbonate; how-
ever, irrigation is limited in the project area.
COAL STRIP MINING
Active Mining Sources
Active mining sources identified in this report include stockpiles con-
sisting of topsoil, overburden, coal ore, coal refuse,'coaly waste, and part-
ings. These materials are discussed in the following paragraphs.
Topsoil-
Certain trace elements may be present in topsoils in the Powder River
Basin that can be significant groundwater pollutants. Summary analyses of
trace elements in near-surface materials in the Powder River Basin are given
by the U.S. Geological Survey (Keefer and Hadley, 1976).
Soluble salts that have been concentrated in some soil series are poten-
tial water pollutants. These salts have been concentrated by ponding and
evaporation of runoff, by evapotranspiration of soil moisture, and by lack of
leaching in soils of low permeability. Soil salinity values are given in the
Eastern Powder River Coal Basin environmental impact statement (EIS) and in
some mine EISs.
Topsoil characteristics for four mines are summarized in Table 3-1.
Ranges for the sodium adsorption ratio (SAR), electrical conductivity, and
pH along with the number of samples analyzed are given. No data are avail-
able for ARCO Black Thunder, Carter North Rawhide, and Kerr-McGee Jacobs
Ranch mines.
Major soil series on the Eagle Butte lease were analyzed for boron, cad-
mium, lead, and mercury concentrations (see Table 3-2). In another analysis
boron was found to range from zero to 1.01 ppm with an average of 0.47 ppm
30
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on Sun Oil's Cordero mine. Selenium found at the Wyodak mine ranges from less
than 0.01 to 0.06 ppm averaging 0.01 ppm with boron concentrations between 0.2
and 2.0 ppm averaging 0.81 ppm. Trace element analyses are not available for
the other mines.
TABLE 3-1. SITE-SPECIFIC TOPSOIL CHARACTERISTICS
Mine
AMAX Belle Ayr South
AMAX Eagle Butte
Sun Oil Cordero
Wyodak
Sodium
jnin.
0.2
0.3
0.18
0.5
adsorption ratio Conductivity
max. ave. min. max. ave.
7.5
5.1
16.18
8.9
2.62
2.19
5.62
5.0
0.13
0.13
0.13
0.0
1.53
-
21.3
2.18
0.81
1.04
5.68
0.052
min.
7
7
6
7
.2
.6
.2
.3
PH
max.
8.1
8.2
8.2
9.2
Number of
ave. samples
7.6
7.95
7.6
8.4
86
20
58
43
Conductivity measured in mmhos/cm.
TABLE 3-2. CONCENTRATIONS (ppm) OF TRACE ELEMENTS BORON,
CADMIUM, LEAD, AND MERCURY IN SOILS ON THE
EAGLE BUTTE MINE PROPERTY
Terry series
Vona series
Maysdorf series
Renohill series
Bidman series
Goshen series
Arvada series
Shingle series
B
0.18
0.12
0.08
0.29
0.25
0.48
1.94
0.13
Cd
0.52
0.52
0.50
0.66
0.53
0.57
0.56
0.54
Pb
1.95
1.99
2.36
2.65
2.00
1.81
3.28
2.44
Hg
0.27
0.31
0.39
0.36
0.18
0.32
0.40
0.58
Overburden-
As is the case with topsoil, a potential water pollutant in overburden is
soluble salts. For example, the soluble salt content of six overburden sam-
ples from the Sun Oil Company Cordero mine ranged from 0.04 to 0.88 percent by
weight (Dames and Moore, 1974). Using these values, and an assumed dry weight
of 1.5 tons per cubic yard for overburden, there would be from 1.2 to 26.4
pounds of soluble salt per cubic yard. Each acre-foot of overburden contains
1,613 cubic yards. Therefore, each acre-foot of overburden might contain from
1,936 to 42,583 pounds of soluble salts.
31
-------
The possibility of trace elements in the overburden becoming important
groundwater pollutants has been and still is of concern. Because of this,
trace element analyses have been performed on overburden from most, if not
all, of the Powder River Basin mines that now exist or are under active devel-
opment. The significance of the analyses remains to be interpreted.
Analysis of conductivity, sodium adsorption ratio, cation exchange capac-
ity, pH, and trace elements from cores of the overburden taken throughout the
study area are summarized in Table 3-3. Trace element analyses also are
available for ARCO Black Thunder and Wyodak mines.
Electrical conductivity (EC) maximum values range from 4.2 to 8.0 micro-
mhos per centimeter (mmhos/cm) throughout the study area. Values less than
8.0 mmhos/cm are indicative of only moderately saline conditions (Wiram, nd).
High EC values are found for samples taken within 5 feet of the surface on the
Belle Ayr South mine. For deeper overburden, salt concentrations are usually
less than 2.0 mmhos/cm which is considered to be insignificant (Wiram, nd) and
would have negligible effect on plant growth.
The major anions responsible for the observed EC values on the Eagle
Butte lease are, in order of abundance: sulfate, chloride, bicarbonate, and
nitrate. The major source of sulfate is gypsum and epsomite (MgS04~FH20).
Sodium chloride and other evaporites are sources of chloride and calcium
carbonate and complex carbonate sulfates are sources of bicarbonate. Soluble
nitrates may be formed by the nitrification of exchangeable ammonium nitrogen
(Power et al., 1974).
High SAR values were also found in the uppermost 5 feet. The maximum
value was 17.6. According to Wiram (nd), SAR values greater than 12.0 indi-
cate potential problems in permeability and structural stability. They are
indicative of an imbalance between sodium and calcium plus magnesium ions
within the montmorillonite clay, which reduces permeability to practically
zero. For deeper overburden, SAR values average 3.5, indicating that the clay
minerals are saturated with calcium and magnesium. Shales and mudstones, in
general, were found to have slightly higher SAR values than associated sand-
stones.
High cation exchange capacity (CEC) values were found for all shales and
mudstones. The average is 16.8 milliequivalents per 100 grams (meq/100 g)
with a maximum value greater than 30 meq/100 g. These values reflect a high
content of montmorillonite clay. CEC values for unconsolidated sands and
sandstones are considerably lower, averaging 8.5 meq/100 g.
Wiram (nd) suggested that continued surveillance will be required if any
irrigation is done during revegetation of stockpiled or backfilled overburden.
Without the use of proper soil amendments, toxic saline and soil permeability
problems can be anticipated.
Almost all of the overburden samples were found to have a pH greater
than 7, with the values ranging from 3.6 to 8.7. Wiram (nd) states that a pH
greater than 8.2 could result in an undesirable soluble carbonate content and
low solubility of calcium salts.
32
-------
TABLE 3-3. SITE-SPECIFIC OVERBURDEN CHARACTERISTICS
CO
CO
Mine
AMAX Belle Ayr South
AMAX Eagle Butte
ARCO Black Thunder
Carter North Rawhide
Kerr-McGee Jacobs Ranch
Sun Oil Cordero
Wyodak
No. of Conductivity3 SAR CECb pH Elementsc
samples Min. Max. Avg. Min. Max. Avg. Hin. Max. Avg. Hin. Max. Avg. Cd Hg Pb Zn Ni Cu S As Se
74 - 6.2 - - 17.6 3.5 - 30.0 16.8 5.3 8.2 0.23 0.08 --1.0
92 - 6.5 3.3 12.8 36.0 27.5 5.0 8.5 0.17 0.05 0.43
41d 3.44 0.12 35 - - 33.8 - 0.8
11 0.7 4.2 1.9 - - 13.033.0 7.4 8.7 ----- 1.7 168 -
55 0.5 5.5 - - - 11.0 32.0 22.7 7.8 8.4 ----- 0.88 167 -
89 0.5 8.0 - 0.3 7.2 - 3.9 48.4 - 3.6 - 0.1 0.07 4.3 14.8 2.1 : - -
7d 0.47 487 <0.1
Conductivity in mmhos/cm
Cation exchange capacity meq/100 g
""Average concentrations in ppm
Trace element analysis only
-------
Five overburden samples from Belle Ayr South were found to have a total
sulfur content greater than 1.0 percent, with the others rarely exceeding 0.3
percent. Of the five samples, two contained fine-grained pyrite and others
had large amounts of gypsum and carbonaceous matter. Gypsum crystals and
soluble sulfate salts are the major sources of sulfur in the overburden. Sul-
fate concentrations were found to range from 20 to 40 meq/liter. It is
present primarily in the form of the mineral selenite (CaS04 • 21^0).
A potential problem of trace element concentrations of cadmium and
mercury may arise. Several examples are shown in Table 3-3 and exceed
natural background levels. Other trace element concentrations are summa-
rized in Table 3-3. Arsenic was found on the Black Thunder lease ranging
from less than 0.05 to 7.75 ppm, averaging 0.80 ppm. Selenium was found
in concentrations less than 0.1 ppm for all samples taken on the Wyodak
mi ne.
Coal, Coal Refuse, and Coaly Waste-
Coal, coal refuse, and coaly waste probably contain some soluble salts,
although no analysis of the soluble salt content of these materials has been
found in the literature or in unpublished reports. The soluble salts are
expected to be principally in the form of crystals of gypsum or similar miner-
als formed in open fractures. Intergranular pores are not present in the coal
and coaly strata as they are in the rest of the overburden.
Sulfur is universally found in coal and carbonaceous strata, but in dif-
ferent forms and in varying amounts of those forms. The two general forms of
sulfur that occur in and with coal are inorganic sulfur and organic sulfur.
Inorganic sulfur occurs primarily as pyrite or marcasite, which are both
iron disulfide (FeS2).
Acid drainage from coal strip mines is an important problem in eastern
coal mining states, but has not been recognized as a serious problem in most
western coal mining areas. One of the characteristics of Powder River Basin
coals is the low sulfur content. This is probably the reason that acid
drainage has not been a problem in the area. However, some pyrite oxidation
does occur as is evidenced by the spontaneous combustion of coal piles along
the base of the high wall of the Wyodak mine. Apparently the acid that does
form from oxidation of pyrite in Powder River Basin coal and associated car-
bonaceous strata is rapidly neutralized, probably by carbonate minerals in the
soil and overburden, and does not cause measurable lowering of the pH of sur-
face water and groundwater. It will, however, contribute dissolved solids in
the form of sulfates, probably principally calcium and magnesium. The acid
that is formed might also dissolve some trace metals before it is neutralized.
As far as is known, no studies have been made of the amount of acid formed in
Powder River Basin strata as a result of coal strip mining and of the fate of"
the acid that is formed.
A number of measurements have been made of the trace elements in Powder
River Basin coals. Keefer and Hadley (1976) presented a summary of analyses
of 15 coal samples from the Wyodak mine and 11 samples from the Belle Ayr
34
-------
mine. A few trace elements are present in coals in amounts greater than in
the overburden and the earth's crust as a whole, but these trace elements
have not yet been identified as actual water pollutants so far as is known.
Trace element and sulfur content of coal samples are summarized in Table 3-4.
TABLE 3-4. SULFUR AND TRACE ELEMENT CONCENTRATIONS IN COAL SAMPLES
Sulfur
<*)
AMAX Belle Ayr South3
AMAX Eagle Butteb
ARCO Black Thunder0
Carter North Rawhide0
Kerr-McGee Jacobs Ranch0
Sun Oil Cordero
Wyodak0
0.
0.
0.
0.
25-0. 6e
14-1. Oe
09-0. 59e
28-0. 52e
1.06
0.30
0.59
Cd
0
0
<0
0
.1
-
.36
-
.001
.66
0.1-0.16f
Average trace element
-------
Explosives—
The primary potential pollutants from explosives appear to be ammonia-
nitrogen, nitrate-nitrogen, fuel oil, and possibly trace organics.
Pit Discharge—
The potential pollutants in pit discharge originate from a number of
sources. All of the potential pollutants from explosives can be in the pit
discharge, namely, ammonium-nitrogen, nitrate-nitrogen, fuel oil, and trace
organics. Most of the major inorganic chemical constituents and some trace
elements can originate from groundwater percolating through the coal, over-
burden, and underlying beds. At the Decker Mine, in Montana, high contents of
sodium, bicarbonate, and sulfate were found in pit discharge. Calcium, mag-
nesium, chloride, boron, and fluoride are additional potential pollutants.
At the Big Horn Mine, high contents of iron, manganese, zinc, and copper were
found in pit discharge. Cadmium, chromium, arsenic, lead, molybdenum, vana-
dium, uranium, thorium, radium, and selenium are additional potential pollu-
tants. Organic materials from the coal and related beds also comprise
potential pollutants.
Gasoline and oil can be introduced by heavy equipment working in the pit.
Bacteriological pollutants can be introduced from domestic wastewater, runoff,
and solid wastes disposed of in or near the pits.
Supplemental Sources of Water—
As discussed in the pollution source inventory, Section 2, no pollution
is anticipated from deep groundwater. The mines are using water from the
deeper part of the Fort Union Formation, and quality is not a problem. Use
of Fox Hills water by the City of Gillette could introduce small amounts of
fluoride into shallow systems, but the relative volume of Fox Hills water used
in the project area is minimal.
Imported Sewage Effluent—
The principal source of imported sewage effluent is from the City of
Gillette Treatment Plant. At the present time (summer 1977) construction is
being completed on a pipeline to transport effluent to the Wyodak Mine.
Effluent will be delivered from two locations: (1) from the line leading into
the "oxidation" pond from the aerobic digesters; and (2) from the "oxidation"
pond discharge line. Wastewater imported into the Wyodak Mine will be a blend
of these sources. At the present time, effluent discharged into Donkey Creek
from the oxidation pond is diverted at Wyodak for road spraying. The RO unit
at the Neil Simpson power plant will drastically alter the quality of effluent
piped to Wyodak.
A representative analysis of wastewater from the treatment plant is not
available at this time. As an approximation, the analysis on Table 3-5 was
developed assuming: (1) wastewater is essentially of the same quality as
incoming sewage because treatment is minimal; (2) composition of medium-
strength domestic sewage reported by Metcalf and Eddy (1972) are applicable;
36
-------
and (3) analysis of carrier water is similar to that for Gillette domestic
water reported by Nelson et al. (1976). This latter assumption neglects
infiltration/inflow (I/I) in the Donkey Creek line and changes in salt content
as a result of domestic usage.
TABLE 3-5. HYPOTHETICAL QUALITY OF WASTEWATER FROM THE
GILLETTE TREATMENT PLANT
Concentration
Constituent (ppm)
Suspended solids, total
Fixed
Volatile
BOD (5-day)
TOC
COD
Nitrogen (total as N)
Organic
Free ammonia
Nitrites
Nitrates
Phosphorus (total as P)
Organic
Inorganic
Alkalinity (as CaC03)
Grease
Potassium
Calcium
Magnesium
Sodium
Sulfate
Chloride
Bicarbonate
TDS
200
50
150
200
200
200
40
15
25
0
0
10
3
7
100
100
9.5
305
158
220
920
36
660
1888
The constituents and related concentrations in Table 3-5 are possibly
representative of wastewater entering the "oxidation" pond from the aerobic
digesters. As indicated above, this water will also be diverted to wyodak.
High total organic carbon (TOC) and chemical oxygen demand (COD) [as well as
high 5-day biochemical oxygen demand (BOD)] values indicate that organics
are a potential contaminant. However, during pipeline flow some additional
breakdown of organics may occur. Other constituents beyond desirable limits
37
-------
include sulfate, nitrogen, IDS, and grease. Flow in the pipeline may be
conducive to nitrification, in which case nitrite values niay increase. The
wastewater may contain excessive levels of coliform organisms (including
fecal), viruses and other intestinal organisms.
Heavy metal concentrations may not be excessive because such metals tend
to concentrate in the sludge.
Observation of the "oxidation" pond at the Gillette Treatment Plant
shows that the pond actually functions as an overloaded facultative pond
with operating characteristics of an anaerobic lagoon. Consequently, waste-
water undergoes anaerobic digestion. According to the Missouri Basin Engineer-
ing Health Council (1971), anaerobic lagoons are capable of reducing BOD
levels between 60 percent to 80 percent. However, "high concentrations of
BOD, suspended solids, and sometimes hydrogen sulfide occur in the effluents
depending upon the initial characteristics of the incoming wastewaters"
(Missouri Basin Engineering Health Council, 1971). It is highly probably that
the pond at Gillette is a poorly operating anaerobic facility. However, if
the treatment effectiveness is similar to a pond in Saskatchewan (reported by
the Missouri Basin Engineering Health Council, 1971), the following removal
efficiencies may exist: suspended solids, 70 percent; BOD, 55 percent; COD,
60 percent; and grease, 75 percent. Using these efficiencies and the corres-
ponding values in Table 3-5, resultant effluent concentrations may be: BOD,
90 ppm; COD, 200 ppm; and grease, 25 ppm. The chemical constituents will
remain about the same, although some change in sulfate should occur due to the
formation of hydrogen sulfide (H2S). Also, because of anaerobic conditions,
nitrogen constituents will remain about the same concentration. The presence
of bacterial colonies floating on the surface on the pond suggests the pond
effluent contains organisms such as coliform bacteria, viruses, and parasitic
organisms. Reducing condition promotes the mobility of heavy metals which may
have escaped the chelating effects of sludge constituents.
Since the pond effluent will be diverted to Wyodak in a pipeline, mixing
will occur with wastewater diverted from the pond inlet line. Also, some
decomposition will occur in the line, reducing COD and BOD (organics) some-
what and possibly promoting nitrification.
Mine Sanitary Wastes-
Septic tanks-Septic tanks reduce the BOD and solids content of sewage
but not necessarily the loading of microorganisms and viruses. Discharge
from a septic tank (to a leach field) contains nutrients, salts, and suspend-
ed solids. Table 3-6, reproduced from a paper by Silberman (1977), is a
representative analysis of septic tank effluent concentrations. The COD and
TOC values suggest that organics might be moderately high in effluent. Also
note the concentration of total coliform organisms. No information is avail-
able on heavy metals, but presumably metals in the carrier water will settle
with sludge in the tank or be carried out with suspended solids.
Further treatment occurs in the leaching field, two conditions are
possible: (1) if the field is overloaded and in tight soils, anaerobic con-
ditions may result; (2) if good air circulation prevails, the leaching field
38
-------
will remain aerobic. The state of aeration may have an effect on sources.
Aerobic conditions will increase nitrate levels in wastewater but lead to a
stabilization of organics and destruction of obligate anaerobics.
TABLE 3-6. REPRESENTATIVE SEPTIC TANK EFFLUENT CONCENTRATIONS
AND PERCENT REMOVED (Silberman, 1977)
Parameter
Value'
Percent removed
or increased
pH (units)
Dissolved oxygen
Biochemical oxygen demand
Chemical oxygen demand
Total organic carbon
Total phosphorus
Phosphates
MBAS
Total solids
Total suspended solids
Total nitrogen as N
Ammonia nitrogen
Organic nitrogen
Nitrate
Nitrite
Chlorides
Alkalinity
Col i forms - total (105/100 cc)
- fecal
7.1±
0
160
323
129
18
34
7.6
378
90
32
27
8
0.14
0.061
95
390
11-110+
0.17
—
—
27
47
46
40
240 increase
67
46
70
8
8 increase
20
increase
increase
111 increase
225 increase
—
—
Units are ppm except as noted.
Anaerobic decomposition of septic tank effluent may reduce nitrate levels
(assuming that nitrification has occurred). Anaerobiosis and associated reduc-
ing conditions may lead to production of methane and hydrogen sulfide gases,
carbon dioxide, and volatile compounds of mercury (Hg) and arsenic (As)
(Fuller, 1977). Hydrogen sulfide (I^S) is reactive with heavy metals as sul-
fides of iron (FeS), zinc (ZnS), cadmium (CdS), lead (PbS), copper (CuS), and
mercury (Hg2$ or HgS). Reducing conditions increase the mobility of the
majority of trace contaminants (Fuller, 1977). For example, reduced iron
becomes soluble and highly mobile.
39
-------
Organic acid production increases under anaerobic conditions The
resultant lowering of pH will increase the mobility of cationic heavy metals.
In addition, chelation will also promote the movement of heavy metals and
soluble organics.
In summary, aerobic leach fields are possible sources of nitrate, ammo-
nia, phosphorus, potassium, chloride, any heavy metals present in abundance,
organics, bacteria, and viruses. Anaerobic leach fields may also be sources
of these constituents but the characteristics of the source would show the
effect of anaerobic conditions on the solubility of indigenous heavy metal
compounds, including those of lead, iron, manganese, copper, and mercury.
Package plants-The types and importance of potential pollutants associ-
ated with package plant effluent are the same as those for septic tanks
(Todd et al., 1976). A representative analysis of effluent from package
plants, reported by Silberman (1977) is shown in Table 3-7. This analysis
does not include other chemical parameters which may be high in effluent,
including sulfate, chloride, hardness, bicarbonate, calcium, and possibly
trace metals. Viruses may also be present in the effluent.
TABLE 3-7. AEROBIC TANK EFFLUENT CONCENTRATIONS (Silberman, 1977)
Parameter Val ue
pH (units) 7.7
Dissolved oxygen 2.76
Biochemical oxygen demand 41
Chemical oxygen demand 158
Total organic carbon 40
Phosphates (as P) 37
Total suspended solids 57
Nitrate .(as" N) 8
Nitrite (as N) 2
Coliforms (105/100 cc) 72
aUm'ts are ppm except as noted.
Operation of package plants may require the removal of solids at infre-
quent intervals. Solids will consist mainly of grit, with perhaps some plas-
tic and other organic matter.
Treatment ponds—The design and operation of waste treatment ponds is
such that quality varies laterally from inlet to outlet and vertically from
water surface to the benthic layers. In general, the overall quality is a
40
-------
function of loading rate, temperature, hours of sunshine, wind action, etc.
Quality is also a function of the type of pond operation, e.g., aerated
pond, anaerobic pond, or facultative pond.
According to the publication, "Waste Treatment Lagoons-State of the
Art," by the Missouri Basin Engineering Health Council (1971), aerated lagoons
are capable of meeting the 30 ppm BOD, 30 ppm suspended solids criteria of
EPA. However, aerated lagoons are not very efficient in removing nitrogen
and phosphorus. The reason is that aerated lagoons operate on the principle
that solids are not removed. Potential pollutants, therefore, comprise some
unstabilized organics, phosphorus and nitrate, and bacteria and viruses, as
well as heavy metals introduced with the raw sources. Metals will concen-
trate in the sludge.
Anaerobic lagoons are not normally effective for secondary treatment,
and effluents could lead to pollution (Missouri Basin Engineering Health
Council, 1971). Effluent quality depends on the source of wastewater, but
BOD concentrations of 100 ppm to 300 ppm have been observed in anaerobic
lagoon effluents from domestic sources. The ratio of discharged effluent to
incoming wastewater BOD values ranges from 0.40 to 0.70. Nutrients are not
appreciably reduced in anaerobic lagoons. For example, incoming organic-N
and NH^-N are not nitrified, although incoming nitrate may be denitrified.
In addition to potential pollutants within the wastewater itself,
anaerobic lagoons may potentially release pollutants present in the benthic
region soil. That is, anaerobic and reducing conditions may increase the
solubility of cationic heavy metals in the soil. Sources related to anaero-
bic lagoons will include incoming nutrients and other chemical constituents
(chloride, sulfate, bicarbonate, carbonate, calcium, magnesium, sodium, etc.)
and organic-N, organic-P, ammonia and phosphorus compounds, bacteria, and
viruses.
Facultative ponds may not attain the required standard: 30 ppm BOD, 30
ppm suspended solids, and 200 coliform per 100 cubic centimeters (cc). BOD
is transformed from incoming organics into algal tissue, and suspended solids
reflect algal concentrations. Algae are capable of reducing nutrients and
heavy metals which, however, are released with the death and lysing of algal
cells. Because of algal activity, the pH of lagoon water increases, with
concomitant alteration of the bicarbonate-carbonate system. The dissolved
oxygen in overlying layers may become supersaturated, while oxygen deficiency
and anaerobic conditions prevail in the benthos. An abundance of dissolved
oxygen (DO) in the upper part of the pond presents optimal conditions for
nitrification. In addition, reactions with soil material (see above) may
lead to generation of heavy metal sources. Also, under very cold or freezing
conditions, such as occur in the Gillette area, facultative ponds may become
anaerobic, producing sources discussed above.
For normal operation, the potential pollutants relating to facultative
ponds include BOD (organics), suspended solids (organics), chemical constitu-
ents in incoming carrier water, nitrate (some of which is reduced to nitrogen
gas in the benthos), a flourishing bacteria population, and viruses. In
addition, heavy metals may be generated in the anaerobic and reduced benthic-
soil interface.
41
-------
Two mines planning to use pond pretreatment are the Wyodak mine, where
an aerated sewage lagoon will be used (no data are available on expected
quality) and the AMAX Belle Ayr South mine, where a "lagoon type aeration
plant" will be used. The only information on quality of the pond system
reported in the EIS (U.S. Department of Interior, 1975) is: "Effluent will
meet...standards such as pH, iron, manganese, and TDS." A sand filter will
reduce suspended solid concentrations.
Solid Wastes-
Solid waste management offers the following options:
• Onsite landfill
• Offsite disposal facility
• Incorporation in mine spoils
• Incineration followed by land disposal of residue.
Onsite landfills comprise special areas set aside on the mine specifically
for landfills; offsite disposal facilities may consist of a central landfill,
such as that operated by the City of Gillette; and incorporation in mine
spoils is self-explanatory. Both onsite and offsite disposal facilities are
centralized and allow more control. Wastes incorporated in the spoils piles
will be distributed randomly, without control on the amount or nature of
wastes. Incineration may create pollutants relating to flyash or gas genera-
tion as well as producing concentrated solid waste.
In general, no matter how disposed, solid wastes will contain the same
potential pollutants. According to Todd et al. (1976), major types of ground-
water pollutants associated with solid wastes include:
Physical — Minor
Inorganic chemicals - Primary
Trace elements — Primary
Organic chemicals - Primary
Bacteriological - Minor
Radiological - Minor.
Some sources present in landfills are reflected in leachates, generated
by the action of water with solid wastes. The range in leachate quality,
such as found in municipal landfills, is shown in Table 3-8 as reported by
Pohland and Engelbrecht (1976). These authors point out that leachate is most
objectionable from a pollution viewpoint when containing high concentrations
of organic matter, high TDS, and low pH. Decreasing pH increases the solubil-
ity of heavy metals present in the waste. In addition, anaerobic reducing
conditions in the soil-landfill interface will also dissolve indigenous heavy
metals. Microbial (and virus) growth in leachate appears to be inhibited by
initial elevated temperature and other inactivating properties.
The quality of leachate changes with time because of changes in composi-
tion of substrate and biological communities. Consequently, high organic
concentrations in the leachate will disappear, pH will return to neutral and
leachate will be less objectionable from the viewpoint of organics. Changes
42
-------
TABLE 3-8. RANGE OF CHEMICAL COMPOSITION OF SANITARY LANDFILL
LEACHATE (Pohland and Engelbrecht, 1976)
Constituent
Chemical oxygen demand
5-day biochemical oxygen demand
Total organic carbon
pH (units)
Total solids
Total dissolved solids
Total suspended solids
Specific conductance (ymho/cm)
Total alkalinity (as CaC03)
Total hardness (as CaCO^)
Total phosphorus (as P)
Orthophosphorus (as P)
Ammonia nitrogen (as N)
Nitrate + nitrite (as N)
Calcium
Chlorine
Sodium
Potassium
Sulfate
Manganese
Magnesium
Iron
Zinc
Copper
Cadmium
Lead
Range of
40
81
256
3.7
0
584
10
2,810
0
0
0
6.5
0
0.2
50
4.7
0
28
1
0.09
17
0
0
0
< 0.03
< 0.10
analyses3
- 89,520
- 33,360
- 28,000
- 8.5
- 59,200
- 44,900
- 700
- 16,800
- 20,850
- 22,800
- 130
- 85
- 1,106
- 10.29
- 7,200
- 2,467
- 7,700
- 3,770
- 1,558
- 125
- 15,600
- 2,820
- 370
- 9.9
- 17
- 2
Values are in ppm unless otherwise noted
43
-------
in inorganics are less predictable. Pohland and Engelbrecht (1976) point out
the danger of extrapolating the environmental impact of leachate based on
single sample analyses.
In addition to municipal-type wastes, hazardous wastes from mines may be
disposed of in landfills. Information on specific hazardous wastes is not
available at this time. As an initial approximation, Table 3-9 [reproduced
from "Decision Makers Guide in Solid Waste Management," (U.S. Environmental
Protection Agency, 1976b)] is included. This table is a sample list of non-
radioactive hazardous compounds which can be considered as hazardous to public
health and the environment.
Incineration followed by landfilling is an alternative waste disposal
technique. Pavoni et al. (1975) review the general principles and methods
employed in municipal incineration operations. Similarly, Scurlock et al.
(1975) discuss requirements and precautions for incineration of hazardous
wastes. Incineration releases gases and particulate matter to the atmosphere
unless trapped and scrubbed. Waste gases may contain nitrogen, carbon diox-
ide, and water vapor. During periods of incomplete combustion, the following
gases may be present: nitrogen dioxide, nitric oxide, sulfur dioxide, sulfur
trioxide, and carbon monoxide (Pavoni et al., 1975). Acids or other com-
pounds may be formed during reaction of rainwater with these gases. Chlorine
containing organics may emit hydrogen chloride gas upon incineration which is
highly corrosive (Scurlock et al., 1975).
Fly ash produced in municipal refuse incinerators is largely inorganic
and consists of oxides of aluminum, calcium, iron, and silicon (Pavoni e't al.,
1975). A chemical analysis of incinerator fly ash is reproduced in Tables
3-10 and 3-11.
Incinerator residue contains soluble organic and inorganic constituents.
Although a complete analysis by constituents was not presented, Pavoni et al.
(1975) gave the general breakdown shown in Table 3-12. Scurlock et al.
(1975) noted that organic materials may contain such heavy metals as mercury,
arsenic, selenium, lead, and cadmium. These heavy metals may exist as oxides
in the ash. "Landfilling of the ash...should be examined with care to ensure
that health hazards or environmental degradation do not occur due to leach-
ing of toxic metal ions to subsurface waters " (Scurlock et al., 1975)
Fly ash may be treated with water to facilitate transportation to a
final disposal site. The slurry will contain undesirable constituents, such
as heavy metals. Table 3-13, reproduced from Pavoni et al. (1975), shows
representative wastewater data from the incineration process.
Information on solid waste management was given for the following mines
in the project area, in the associated environmental impact statements.
Solid wastes may be buried at the Kerr-McGee Jacobs Ranch mine. Possi-
ble contaminants in leachate are shown in Table 3-8.
44
-------
TABLE 3-9. A SAMPLE LIST OF NONRADIOACTIVE HAZARDOUS COMPOUNDS
(U.S. Environmental Protection Agency, 1976b)
Miscellaneous Inorganics
Ammonium chromate
Ammonium dichromate
Antimony pentafluoride
Antimony trifluoride
Arsenic trichloride
Arsenic trioxide
Cadmium (alloys)
Cadmium chloride
Cadmium cyanide
Cadmium nitrate
Cadmium oxide
Cadmium phosphate
Cadmium potassium
cyanide
Cadmium (powdered)
Cadmium sulfate
Calcium arsenate
Calcium arsenite
Calcium cyanides
Chromic acid
Copper arsenate
Copper cyanides
Cyanide (ion)
Decaborane
Diborane
Hexaborane
Hydrazine
Hydrazine azide
Lead arsenate
Lead arsenite
Lead azide
Lead cyanide
Magnesium arsenite
Manganese arsenate
Mercuric chloride
Mercuric cyanide
Mercuric diammonium
chloride
Mercuric nitrate
Mercuric sulfate
Mercury
Nickle carbonyl
Nickle cyanide
Pentaborane-9
Pentaborane-11
Perchloric acid (to 72%)
Phosgene (carbonyl
chloride)
Potassium arsenite
Potassium chormate
Potassium cyanide
Potassium dichromate
Selenium
Silver azide
Silver cyanide
Sodium arsenate
Sodium arsenite
Sodium bichromate
Sodium chromate
Sodium cyanide
Sodium monofluoro-
acetate
Tetraborane
Thallium compounds
Zinc arsenate
Zinc arsenite
Zinc cyanide
Halogens and Interhalogens
Bromine pentafluoride
Chlorine
Chlorine pentafluoride
Chlorine trifluoride
Fluorine
Perchloryl fluoride
Miscellaneous Organias
Acrolein
Alkyl leads
Carcinogens (in general)
Chloropicrin
Copper acetylide
Copper chlorotetrazole
Cyanuric tri azide
Diazodinitrophenol
(DDNP)
Dimethyl sulfate
Dinitrobenzene
Dinitro cresols
Dinitrophenol
Dinitrotoluene
Dipentaerythritol
hexanitrate (DPEHN)
GB (propoxy (2)-
methylphosphoryl
fluoride)
Gelatinized nitro-
cellulose (PNC)
Glycol dinitrate
Gold fulminate
Lead 2,4-dinitroresor-
cinate (LDNR)
Lead styphnate
Lewisite (2-chloro-
ethenyl dichloroar-
sine)
Mannitol hexanitrate
Nitroaniline
Nitrocellulose
Nitrogen mustards
(2,2',2" trichloro-
triethyl amine)
Nitroglycerin
Organic mercury
compounds
Pentachlorophenol
Picric acid
Potassium dinitrobenz-
furoxan (KDNBF)
Silver acetylide
Silver tetrazene
Tear gas (CN)(chloro-
acetophenone)
Tear gas (CS)(2-chloro-
benzylidene malo-
nonitrile)
Tetrazene
VX (ethoxy-methyl phos-
phoryl N,N dipropoxy-
(2-2), thiocholine)
Organic Halogen Compounds
Aldrin
Chlorinated aroma tics
Chlordane
Copper acetoarsenite
2,4-D(2,4-dichloro-
phenoxyacetic acid)
DDD
DDT
Demeton
Dieldrin
Endrin
Ethylene bromide
Fluorides (organic)
Guthion
Heptachlor
Lindane
Methyl bromide
Methyl chloride
Methyl parathion
Parathion
Polychlorinated-
biphenyls (PCB)
45
-------
TABLE 3-10. CHEMICAL ANALYSIS OF INCINERATOR FLY ASH
(Pavoni et al., 1975)
-
Component
Carbon
Organic
Inorganic
Silicon as SiO«
Si
w 1
Aluminum as AlJk
Al c *
Iron as Fe,0,
Fe
Sulfur as SO,
S 3
Calcium as CaO
Ca
Magnesium as MgO
Mg
Titanium as Ti07
Ti
Ni
Na
Zn
Ra
Cr
Cu
Mn
Sn
B
Pb
Be
Ag
V
IT - -
Gansevoort
incinerator,
New York City3
(% by weight)
14.5
85.5
36.0
27.7
10.0
9.7
-
8.5
-
3.4
.
_
_
_
.
_
-
-
-
-
-
-
-
-
-
— ^ — ~—
South Shore
incinerator, Arlington,
New York Citya VAa
{% by weight) (%)
10.4 11.62
89.6
36.1
18.64
22.4
10.79
4.2
2.13
7.6 Small or
trace
8.6
4.70
2.1
0.98
-
2.24
Small or
trace
Small or
trace
Small or
trace
Small or
trace
Small or
trace
Small or
trace
Small or
trace
Small or
trace
- -
Small or
trace
-
Small or
trace
- -
Jens-Rehm Kaiser
study b study0
-
5+
1-10
0.5-8.0
""
*•
—
1.0+
1-10
~
0.5-5.0
1-10
1-10
1-10
0.1-1.0
0.1-1.0
0.1-1.0
0.1-1.0
0.05-0.5
0.01-0.1
0.01-0.1
0.001-0.01
0.001-0.01
0.001-0.01
-
36.3
t
25.7
7.1
8.0
-
8.8
-
2.8
Of\
.9
-
-
-
-
-
-
-
-
-
-
-
-
-
—
Sources:
a Municipal Refuse Disposal. Inst. for Solid Wastes, Amer. Public Works Assn.,
1970.
b Jens, W., and F.R. Rehm. Municipal Incinerator and Air Pollution Control.
Proc. Nat'l. Incin. Conf., Amer. Soc. Mech. Eng., 1966, p. 74.
c Kaiser, E.R. Refuse Composition and Flue-Gas Analyses from Municipal
Incinerators. Proc. Nat'l. Incin. Conf., Amer. Soc. Mech. Eng., 1964, p. 35.
46
-------
TABLE 3-11.
CHEMICAL ANALYSIS OF INCINERATOR FLY ASH
(Pavoni et al., 1975)
Component
Sodium and potassium
oxides
Na as Na,0
Na i
K
Ga
Hg
Mo
Ta
Apparent specific
gravity
Ignition loss
Gansevoort
incinerator,
New York City*
(% by weight)
4.7
-
-
-
-
-
-
-
2.58
"
South Shore
incinerator, Arlington,
New York City3 VA»
(% by weight) (%)
19.0
-
Small or
trace
Small or
trace
Small or
trace
Small or
trace
Small or
trace
Small or
trace
-
14.45
Kaiser
studyb
(%)
.
10.4
-
-
-
-
-
,
-
-
"
Sources:
a Municipal Refuse Disposal. Inst. for Solid Wastes, Amer. Public Works
Assn., 1970.
Kaiser, E.R. Refuse Composition and Flue-Gas Analyses from Municipal
Incinerators. Proc. Nat'l. Incin. Conf., Amer. Soc. Mech. Eng.,
1964, p. 35.
TABLE 3-12. INCINERATOR RESIDUES (Pavoni et al., 1975)
Material
Washington, D.C.,a
Metro-Average
grate-type municipal
Incinerators
(% dry weight)
Rotary-kiln Incinerator
Tin cans
Mill scale and small iron
Iron wire
Massive iron
Nonferrous metals
Stones and bricks
Ceramics
Unburned paper and charcoal
Partially burned organics
Ash
Glass
17.2
6.8
0.7
3.5
1.4
1.3
0.9
8.3
0.7
15.4
44.1
19.3
10.7
0.5
1.9
0.1
.
0.2
3.4
-
57.0
-
+ 6.5 (nonmetallics)
(charcoal )
Sources:
a Kenahan, C.B., and P.M. Sullivan. Let's Not Overlook Salvage. AWPA
Rep., Vol. 34, No. 3, 1967, p. 5.
Rampacek, G. Reclaiming and Recycling Metals and Minerals Found in
Municipal Incinerator Residues. Proc., Mineral Waste Utilization Symp.,
March 27-28, 1968, LIT Research Institute, p. 129.
47
-------
TABLE 3-13. INCINERATOR WASTEWATER DATA
(Pavoni et al., 1975)
Characteristic
pH
Diss. solids, ppm
Susp. solids, ppm
Total solids, % volatile
Hardness (CaC03),
ppm
Sulfate (504), ppm
Phosphate (.Pfy), pDm
Chloride (C), ppm
Alkalinity (CaC03)
5-day BOD @ 20° C
•
, ppm
max.
11.6
9,005
2,680
53.6
1,574
430
55.0
3,650
1,250
--
Plant 1
min.
8.5
597
40
18.5
216
no
0.0
50
2.5
— —
avg.
3
10.4
,116
671
36.3
752
242
23.3
627
516
— —
max.
7
1
1
11.7
,897
,274
51.6
,370
Plant 2
min.
1
780
212.5
2
1
,420
,180
— —
6.0
,341
7
10.5
112
115
1.0
76
292
— *•
avg.
10.5
4,283
372
31.2
889
371
23.5
763
641
— —
Characteristic
PH
Diss. solids, ppm
Susp. solids, ppm
max.
6.5
1,364
398
PI
ant
min.
7
4.8
,818
208
Plant 6
avg.
8
5.8
,838
325
Total solids, % volatile
Hardness (CaC03),
Sulfate (504), ppm
ppm
Phosphate (P04), ppm
Chloride (C), ppm
Alkalinity (CaC03), ppm
5-day BOD @ 20° C
2,780
1,350
15.0
3,821
28
13.5
2
1
3
,440
,125
11.5
,077
16
6.2
2
1
3
,632
,250
13.0
,543
23
8.8
max.
6
2
4.7
,089
,010
24.69
3
2
,780
862
76.2
,404
4
—
min.
5
4.5
,660
848
23.26
3
2
,100
625
32.2
,155
0
—
avg.
4.6
5,822
1,353
23.75
3,437
725
51.5
2,297
1.33
—
Sources:
Plants 1 and 2,
Incinerator
Plants 5 and 6,
USPHS
System
USPHS
Report on the Municipal
of the
District
unpublished
Plant 1 - 110 TPD3Residue Quench
Plant 2 - 125 TPD
Plant 5 - 200 TPD
Plant 6 - 300 TPD
Residue Quench
Cont.
Cont.
data
Sol
id Wastes
of Columbia, 1967.
(SW-llts) (SW-12ts).
(Batch).
(Batch).
Feed-Flyash
Feed-Flyash
Effl
Effl
uent.
uent.
TPD = tons per day
43
-------
Inert sludge from the package plant at the Sun Oil Cordero mine will be
buried in topsoil and graded in the spoil. Sludge may contain concentrated
levels of trace metals due to the affinity of metals to organics (Council for
Agricultural Science and Technology, 1976). Possible metals may include:
manganese, iron, aluminum, chromium, arsenic, selenium, antimony, lead, mer-
cury, cadmium, copper, molybdenum, nickel, and zinc (Council for Agricultural
Science and Technology, 1976).
Ash.produced by incineration at the Wyodak mine will be interlayered with
overburden and buried. Potential contaminants are shown in Tables 3-12 and
3-13. Solid wastes will also be buried, and potential pollutants in leachate
are listed in Table 3-8.
Reclaimed Area Sources
Fill Materials—
The pollution potential of the fill materials, topsoil, and spoils has
been discussed previously in the subsection "Stockpiles." The chemistry and
amount of pollutants dissolved from the topsoil and spoils during movement of
water through these materials will depend on the locations of the various sub-
categories of these materials replaced within the mined area and their rela-
tion to the modified hydrogeologic system that exists after mining. The max-
imum available quantities of soluble salts and trace metals can be estimated,
as has been indicated, but the potential mobility of the trace elements and
rates of dissolution of the soluble salts and trace metals from topsoils have
not been defined.
Spoil will consist of a heterogeneous mixture of overburden material
originally present in the indigenous vadose zone and shallow aquifer systems.
Overburden consists of sandstone, shale, and thin or impure coal beds of the
Wasatch or uppermost Fort Union Formations. Scoria, or baked shale and silt-
stone may also, be present, together with alluvial material. Partings or coaly
wastes above or between coal beds may constitute potential sources of pollu-
tion at many sites. Some parting materials have been found with pH values in
the acidic range and containing high concentrations of certain constituents.
As an example, analyses of three grab samples of overburden material are
shown in Table 3-14, as reported by McTernan (1974). Samples I and II were
sandy loam and Sample III was a silty clay loam ("Blue-Shale"). Compared to
.Samples I and II, the silty clay loam had a low pH, 3.9, and higher concen-
trations of sulfur, iron, copper, and magnesium. The low pH is of signifi-
cance in that heavy metals become more soluble in the acidic range. In con-
trolled laboratory experiments, McTernan observed the bacterial oxidation of
sulfur with a subsequent increase of pH to about 6.3. After about 50 days,
pH values once again decreased.
Several of the mine environmental impact statements indicate that clay
partings will be buried in the spoil piles, i.e., below the reclaimed soil
zone. Such a procedure will position potential sources of pollution within
the vadose zone.
49
-------
TABLE 3-14. CHEMICAL AND PHYSICAL DATA: THREE OVERBURDEN
GRAB SAMPLES (McTernan, 1974)
Characteristic
Sulfur (ppm)
Iron (ppm)
Copper (ppm)
Calcium (ppm)
Magnesium (ppm)
NOo (ppm)
PH
Texture
Sample I
70
5.1
0.6
1,900
330
2.0
8.1
Sandy loam
Sample II
630
4.2
0.3
1,500
310
3.0
8.1
Sandy loam
Sample III
(blue-shale)
1,200
46
722
1,400
670
2.0
3.9
Silty clay loam
In addition to partings, isolated lenses of precipitated gypsum (e.g.,
as selenite) or marcasite (iron sulfide) have been observed. Tait (1976), for
example, noted the presence of both gypsum and marcasite within fractures of
coal aquifers on the Coal Creek property of ARCO. Relatively pure specimens
of selenite have been observed on the sides of a landfill trench, near the
City of Gillette.
The vadose zone developed within spoil piles will include the following
potential sources: (1) sources exposed on fresh surfaces of replaced over-
burden; (2) sources on layers of compacted partings, coaly wastes, or toxic
strata; and (3) sources within buried solid wastes.
In his studies of strip-mine spoils in the Powder River Basin, Rahn (1976)
observed that samples of water from spoils are significantly more concentrated
in total salt than native groundwater. Particularly high concentrations of
calcium and sulfate were observed. He attributed increased salt content
to the dissolution of salts exposed on the spoils blocks. Calcium and
sulfate levels were high because of the presence of gypsum crystals - gypsum
is the most soluble of exposed salts. High concentrations of magnesium were
also observed. Manganese was high in most samples examined by Rahn (1976),
possibly reflecting the weathering of pyrolusite or psilomelane. Excessive
levels of sodium were noted in some samples. The pH values of spoil water
samples were generally in the alkaline range.
Specific pollutants related to solid wastes (including sludge) buried
within the modified vadose zone are discussed elsewhere. In summary, leachate
generated in such wastes could run the gamut from hazardous substances to
excessive concentrations of heavy metals.
Environmental impact statements for several of the mine sites indicate
that parting material, coaly wastes, or toxic strata will be buried within the
spoils. The major pollutants in these layered-in deposits are heavy metals -
although high concentrations of calcium sulfate may also be present These
layers may be more compacted than the overlying spoil, possibly leading to the
formation of perched water tables following surface flooding. Anaerobic con-
ditions brought about by the water table conditions may have an influence on
heavy metals movement.
50
-------
In particular, the following effects may occur:
• Reducing conditions may increase the mobility of cationic
heavy metals. That is, "...trace contaminants arsenic,
beryllium, chromium, copper, iron, nickel, selenium,
vanadium, and zinc are much more mobile under anaerobic
soil conditions, all other factors the same" (Fuller, 1977)
• Reducing conditions lead to the formation of hydrogen
sulfide and consequently heavy metal sulfides. These
metals are relatively insoluble.
Since these two factors are counteractive, the net movement of metals may
be hard to predict. Other conditions should also be taken into account. For
example, partings from several mine sites have low pH values. Metals are more
mobile in the acid range (Fuller, 1977). However, the pH of partings may
change before being inundated, particularly if an organic source of energy is
available for bacteria capable of oxidizing sulfur (McTernan, 1974).
The EIS for the Belle Ayr South mine indicates high values of organic
copper, zinc, and selenium in overburden samples. In addition, certain sample
profiles disclosed higher EC and SAR values within the upper five feet. Table
3-14 (McTernan, 1974) includes analyses from three overburden samples. Obvi-
ously, Sample III (blue-shale) contained the highest concentrations of sulfur,
iron, copper, and magnesium. The pH for Sample III was 3.9.
Analyses of saturation extracts from sample holes at the Eagle Butte mine
site showed high values for both chloride and sulfate. Regarding heavy metals
in overburden, the EIS stated: "There exists no definable trend of trace
metals within the overburden... For all overburden samples, cadmium (Cd) val-
ues range from a minimum 0.03 ppm to a maximum 0.85 ppm and average 0.174 ppm.
Mercury (Hg) ranges from 1.63 ppm to 51.63 ppm... With exception of 16 samples
which possess measured lead concentrations ranging from 1.056 to 2.96 ppm, all
remaining samples disclose concentrations less than 1 ppm. For all samples,
lead (Pb) concentrations range from 0.003 to 2.96 ppm and average 0.43 ppm."
Since native soils normally contain between 40 and 70 ppm lead (Fuller, 1977),
these values are not excessive. One .sample of partings contained a pH of 4.5.
Drever et al. (1977) reported that heavy metals were strongly enriched
near the margins of coal seams at the Black Thunder mine. Table 3-15, repro-
duced from their report, illustrates relative magnitudes of heavy metals and
sulfur in the overburden core samples. Note the concentration of metals
between 77 and 79 feet. Relative to the other core samples, samples in this
range contained high levels of arsenic, cadmium, calcium, mercury, molybdenum,
lead, uranium, and sulfur. Table 3-16 compares average trace metal concen-
trations from cores at the Black Thunder mine with values for average U.S.
coal, average shale, and Okefenokee peat. The upper interface region contained
higher values of beryllium, calcium, lead, and uranium than other samples.
However, Drever et al. (1977) pointed out that "...the trace element concen-
trations in the interface region are not outstandingly high in comparison to
average shale or coal."
51
-------
TABLE 3-15. TRACE ELEMENT CONTENT OF COAL AND ASSOCIATED ROCKS,
CORE BT249 (coal analyses reported on whole coal
basis)(Drever et al., 1977)
•*- • —
Depth
L-ayer (feet)
Overburden
10
13
16
19
22
25
27
32
33
36
39
42
45
48
51
54
57
60
63
65
70
73
76
76
77.3
77.3
78.3
Overburden
78.6
Coal seam
78.6
82
92
100
106
114
120
128
136
146
Coal seam
149
Floor
149
151.5
152
153.5
153.5
154.5
156.5
157
158.3
159.5
As
(ppm)
<0.05
0.13
<0.05
<0.05
<0.05
<0.05
0.08
<0.05
0.08
0.45
0.13
<0.05
0.30
0.60
0.40
0.40
0.55
2.5
-
1.0
0.35
7.5
4.0
0.60
0.50
0.25
0.63
0.78
1.0
0.02
0.02
0.02
0.04
<0.1
0.09
0.07
0.02
0.15
0.20
<0.1
1.1
0.15
0.35
0.54
1.6
0.37
0.09
1.0
-
*— _^ — -~^—
Be
(ppm)
5
4
4
3
4
3
6
6
5
5
3
<2
5
4
5
4
5
5
5
4
3
<2
10
11
7
6
10
20
3.6
0.5
0.48
0.14
0.15
0.2
0.26
0.09
0.28
0.3
1.9
6
5
8
9
4
11
9
11
7
8
• II. mml
Cd
(ppm)
<4
<4
<4
<4
<4
<4
<4
<4
<4
<4
0
0
<4
<4
<4
<4
<4
<4
<4
<4
<4
<4
<4
<4
10
<3
6
<4
2
<0
<0
<0
<0
<0
<0
<0
<0
<0
0
<4
<2
<4
<4
<2
<2
<2
<4
<4
0
.5
.2
.0
.3
.4
.4
.4
.4
.4
.4
.4
.4
.05
.3
Cu
(ppm)
25
15
13
11
12
15
21
18
21
20
10
8
14
30
25
24
25
27
20
25
15
14
70
63
72
43
120
54
26
7.4
9
12
6
8.3
4
3
5
4.5
83
55
58
33
33
25
48
35
160
75
30
Hg
(ppm)
0.10
0.13
0.03
0.03
0.04
0.04
0.23
0.11
0.18
0.14
0.06
<0.02
0.09
0.10
0.10
0.08
_
0.02
<0.02
0.10
0.15
0.04
0.05
-
1.07
0.02
-
0.66
0.37
0.06
0.06
0.05
0.05
0.06
0.02
0.05
0.04
0.04
0.05
<0.02
0.47
<0.02
0.08
-
2.0
0.48
0.49
0.78
-
Mo
(ppm)
5
<4
<4
6
<4
<4
6
<4
<4
5
5
<4
5
5
6
5
5
8
<4
5
6
7
20
10
23
<20
<20
54
5.3
<2
<2
<2
<2
<1
<1
<2
<2
<1
4.1
<20
9
<20
<20
9
27
20
<20
15
<20
Pb
(ppm)
33
30
20
30
30
30
35
50
35
50
30
20
30
23
28
33
32
31
32
25
40
30
100
73
100
55
145
46
19
5.8
6
7
5
4.3
5
4
5
4.5
21
80
69
80
100
36
47
38
120
60
80
U
(ppm)
2
3
2
-
3
-
4
5
5
-
-
-
5
6
11
6
9
12
3
0.06
0.35
0.26
0.16
0.41
0.15
0.06
0.12
0.10
4
4
5.3
6
2
6
12
—
-
S
-
-
-
-
-
-
-
-
-
-
0.25 '
0.22
0.44
0.03
0.15
1.03
0.89
0.63
0.51
0.48
0.32
0.35
0.26
0.24
0.25
0.52
0.46
0.03
0.44
0.01
-
-
-
-
-
-
Ash
W
92.3
94.8
96.5
95.7
92.3
92.2
92.2
97.5
88.2
-
91.4
93.5
89.9
90.7
89.6
93.4
93.1
96.7
85.0
69.8
45.2
85.3
85.4
39.9
13.2
5.3
5.4
4.2
3.8
4.5
4.4
2.8
3.8
4.5
11.9
83:2
43.1
89.1
90.7
44.5
26.7
31.9
70.0
50.5
92.1
52
-------
co
TABLE 3-16. COMPARISON OF AVERAGE TRACE ELEMENT CONCENTRATIONS (ppm)
(Drever et al., 1977)
Sample
Coal seam
excluding margins
Upper interface
region
Average
U.S. coal
Average shale
Okefenokee peat
Be
0.3
11
1.6
3
-
Cu
6.6
70
15
45
25
Mo
1
21
7.5
2.6
-
Pb
5
87
35
20
13
As
0.05
2.5
14
13
-
Hg
0.05
0.3
0.2
0.4
0.4
U
0.2
8
4.0
3.7
-
-------
Analyses of overburden, included in the EIS for the Rawhide Mine, clear-
ly show that partings between coal seams have low pH values and sometimes
high concentrations of heavy metals. Table 3-17, reproduced from the EIS
from the Rawhide Mine, illustrates that a low pH value of 4.9 was reported
for partings in hole NRH-76C (202-212.4 feet). Relative to some other
samples, the concentrations of zinc, iron, and molybdenum were higher in the
sample from NRH-76C.
Data on specific pollutants at the Kerr-McGee Jacobs Ranch Mine site are
limited. There are no reported seams in the overburden with low pH values.
High concentrations of calcium, magnesium, and sulfur were present in a
reported analysis.
The EIS for the Cordero Mine states that no significant amounts of toxic
substances have been found in either the topsoil or overburden analyses and
none is anticipated. Despite this statement, results of analyses of over-
burden samples in the Mining and Reclamation Plan illustrate some samples had
low pH values. For-example, the sample from 19 to 21 feet at location 75-14-2
had a pH of 4.5 and higher than normal levels of phosphorus, nitrate nitro-
gen, iron, and cadmium.
^OIL AND GAS EXTRACTION
Potential groundwater pollutants derived from oil and gas extraction in-
clude oil, from casing leaks, surface leaks and spills, and seepage from the
mud pit; nitrates from incomplete explosions in shot holes; bentonite and
organics from drilling muds such as Revert; salts from'brines and formation
waters encountered during drilling; and hydrocarbons, which have fallen to the
ground from atmospheric emissions.
CONSTRUCTION
Construction waste is usually solid waste, and is disposed of in land-
fills at the mine or in the Gillette Landfill. Landfill pollutants are
discussed under municipal sources. Some of these pollutants come from decom-
posing and/or disassociating construction wastes.
Pollutants introduced by construction include, but are not limited to,
the following:
TDS Chloride
Calcium Sulfate
Iron COD
Copper BOD
Zinc pH (acid generation)
Chromium Oil and grease
Manganese (Other trace metals)
The above list includes the most common contaminants introduced by dete-
rioration of construction wastes. An exact appraisal of the pollutants
generated would require a detailed listing of discarded material.
54
-------
TABLE 3-17. ANALYSES OF OVERBURDEN MATERIALS (U.S. Geological Survey, 1974b)
cn
Hole No.
NRH-45C
NRH-46C
NRH-76C
NRH-76C
NRH-76C
HRH-79C
NRH-79C
NRH-92C
NRH-98C
NRH-99C
NRH-112C
NRH-112C
NRH-126C
Depth of
staple (ft)
•••HM^B^W^^^BMM^^^B^^B
24-34
7-14
111.5-119.5
119.5-121.4
204-212.4
51-59
59-62
31-43
30-40
120-130
45-55
129-137.3
171-178.5
Sample
description
•i^~_«»»^^^^__^^_
Sllty clay
(overburden)
Clay
(overburden)
Sllty clay
loan
(overburden)
Sllty clay
Sllty clay
(parting
between
coal sea*s)
Sllty clay
loan
(overburden)
Sllty clay
low
(overburden)
Sandy clay
(overburden)
Sllty clay
(overburden)
Sllty clay
lOM
(overburden)
Sllty clay
(overburden)
Clay
(overburden)
Sllty clay
loan
(parting
between
coal seam)
£
"2°
8.1
8.2
8.3
8.7
4.9
7.5
7.6
8.1
8.0
8.3
8.5
7.4
6.8
H
~Salt
7.7
7.5
7.8
8.0
4.7
7.4
7.5
7.9
7.8
7.9
7.9
7.1
6.2
CEC
(•eg/
100 g)
25
20
15
15
73
31
33
24
25
19
21
13
11
Salt
(•rims/
1.3
0.7
1.0
0.7
2.4
4.2
4.2
2.4
2.4
"
1.3
0.8
1.7
0.8
Na
(•eg/
100 g)
0.9
0.5
0.5
0.5
1.1
0.6
0.6
0.6
1.2
1.1
1.6
1.2
1.0
Lie*
(X)
6.7
0.3
3.1
3.*
0
2.4
1.7
7.9
5.0
7.7
5.8
0.5
0
Organic
autter
(X)
0.8
0.9
0.6
0.6
5.5
0.8
1.3
0.5
1.6
1.5
2.2
4.6
4.1
Available nutrients (pp»)
*>3
29
1.0
9.0
11
3.0
10
16
4.0
4.0
10
4.0
1.0
1.0
NH4
1.2
0
0.3
0.3
0.8
0.4
1.0
0.1
0.3
0.8
0.4
0.2
0.2
P
2.0
68
1.0
1.0
1.0
1.0
1.0
1.0
1.0
2.0
3.0
1.0
1.0
K
210
150
140
130
270
160
160
160
270
270
340
280
240
Ca
2500
2100
1700
1700
2600
3900
3800
3200
2900
2000
2000
1300
860
Mg
1000
720
410
410
790
1100
1400
630
790
620
660
460
380
S
^^^^BHHHflBV
180
62
160
180
200
200
200
200
200
200
62
200
39
B
0.6
1.3
0.4
0.6
4.8
0.3
0.2
0.3
0.3
0.3
0.2
0.5
0.7
Zn
PM^^HHMMH
1.7
1.7
3.3
3.9
7.8
0.6
3.0
0.9
2.2
2.5
3.8
20
1.6
Fe
•••V^VHUHIIIIII
13
50
16
15
50
18
10
8.8
14
37
40
46
31
gggg^igggg^^^
7.0
0.5
3.2
3.5
7.0
2.1
0.6
2.9
6.3
4.8
11
10
2.0
Cu
^HH^B^V
2.1
6.6
0.7
0.3
8.2
0.4
1.2
0.2
2.2
1.1
0.7
3.2
1.6
-------
COAL CONVERSION
Steam Electric Power Plants
Analyses are available for atmospheric emissions and fly ash from the ex-
isting power plant. Potential pollutants from packaged sewage treatment
plants of the type that the power plant will employ are discussed in another
section.
The major pollutants found in atmospheric emissions are sulfur dioxide
(S02), nitrogen dioxide (N02), and particulates.
Sulfur dioxide in the flue gas is produced by oxidation of sulfur in the
coal. Some of the sulfur is recovered as pyrites, and some of the sulfur
dioxide formed is removed from the flue gas after reacting with alkaline fly
ash. At this time, it is not anticipated that wet scrubbers for sulfur removal
will be required to meet State and Federal air quality standards; however,
provisions have been made for the addition of scrubbers should they become
necessary. On the basis of an average sulfur content in coal of 0.50 percent
and about 4 percent sulfur removal in the furnace, S02 emissions from the new
unit will be less than the allowable limit of 1.2 pounds per million Btu of
heat input. Tests on Unit 5 show greater than 30 percent sulfur removal.
Nitrogen oxides (NOX) are formed by oxidation of nitrogen in the combus-
tion of air and fuel, a process which is influenced by firing conditions in
the boiler. NOX emissions from the boiler in the new plant are guaranteed by
the boiler manufacturer not to exceed 0.7 pound of NO per million Btu of heat
input.
Table 3-18(a) shows expected operating conditions for 100 percent load and
predicted emissions from both existing Unit 5 and the new plant. Table 3-18(b)
shows peak ground level concentrations of sulfur dioxide, nitrogen dioxide, and
particulates from the existing plant, while Table 3-18 (c) shows predicted
ground level concentrations for the new plant together with Unit 5. Table
3-18(d) gives an analysis of the projected ash from Unit 5 of the existing power
plant.
Gasification
The potential pollutants associated with the Hoe Creek in situ coal gasi-
fication experiment are related to the water quality of the aquifers of the
area, nature of explosives used in fracturing, and material created or released
during the gasification burn. Pollutants associated with hydro!ogic-geologic
exploration, placement of experimental wells, and dewatering are related to
aquifer water quality which is described, in Section 6 (Existing Groundwater
Quality). Characteristics of explosives used are unknown at this time but
they could create pollutants associated with fracturing of the coal seam and
dewatering of the fractured zone. The gasification process itself is the major
potential pollution source. Descriptions of possible pollutants follow.
Containment of potential pollutants produced as gasification byproducts
may be a major problem of in situ processing. Principal pollutants expected
5G
-------
TABLE 3-18(a). PREDICTED OPERATING CONDITIONS AND EMISSIONS FROM
UNIT 5 AND THE NEW PLANT UNDER 100 PERCENT LOAD
(Black Hills Power and Light Co., 1973)
Parameters
Unit 5
New plant
Fuel rate (Ib/h)
Flue gas rate (Ib/h)
Heating value (Btu/h)
Heat input (Btu/h)
Predicted emissions (Ib/h)
S02
N02
Particulates
32,000
295,400
8,255
266 million
320
288
90
440,000
4.07 million
8,255
3.6 billion
4,240
2,526
281
TABLE 3-18(b)
PEAK GROUND LEVEL CONTAMINANTS FROM EXISTING PLANT
(Black Hills Power and Light Co., 1973)
Contaminants
so2
3-h avg
24-h avg
Annual avg
N02
Annual avg
Parti culates
24-h avg
Annual avg
Peak
concentration
0.233 ppm
0.055
0.0049
0.0056 ppm
309.1 yg/m3
29.5
Wyomi ng
standard
0.5 ppm
0.1
0.02
0.05 ppm
150 pg/m
60
Federal
primary standard
0
0
0
260
75
.14 ppm
.03
.05 ppm
yg/m
57
-------
TABLE 3-18(c). PREDICTED COMBINED GROUND LEVEL POLLUTANT
CONCENTRATIONS FROM NEW PLANT AND
EXISTING UNIT 5 (Black Hills Power and Light
Co., 1973)
Peak Federal
0
Contaminants concentration 2 standard
so2
3-h avg
24-h avg
Annual avg
0.078 ppm
0.0109
0.0007
0.5 ppm
0.10
0.02
Annual avg
Parti culates
24-h avg
Annual avg
0.0006 ppm
10.61 yg/m3
0.73
0.05 ppm
3
150 yg/m
60
TABLE 3-18(d). PROJECTED CONSTITUENTS OF ASH FROM THE
NEW PLANT AND EXISTING UNIT 5(Black Hills
Power and Light Co., 1973)
Compound Percent
Phosphorus pentoxide
Silica
Ferric oxide
Alumina
Titania
Lime
Magnesia
Sulfur tri oxide
Potassium oxide
Sodium oxide
Undetermined
0.9
39.5
6.3
22.6
1.4
21.4
5.3
0.7
0.5
0.7
0.7
58
-------
are hydrogen sulfide, ammonia, hydrogen cyanide, phenols, benzenes, and oils.
High levels of dissolved salts (including chlorides and fluorides) may also
be released from the coal reaction. Results of analysis of byproduct water
from synthane gasification (a surface process) are shown in Table 3-19. These
data may be representative of in situ byproducts.
The indicated high levels of organic matter in byproduct water may con-
tain a variety of compounds:
Tar (phenols, cresols, pyridines, anilines, catechols)
Intermediate, and high boiling point aromatics (e.g., naphthalenes)
Saturates
Olefins
Thiophenes
Light oil and/or naphtha, BTX (benzene-toluene-xylene),
naphthalene, thiophene, condensed light hydrocarbons, and
disulfide carbon.
Organic compounds tentatively identified in pilot plant studies are
phenol, £ and m cresol, dimethyl phenol (2,4; 2,5; 2,6; 3,4), a naphthol,
and 1,2 dihydronaphthalene. Results of benzene-soluble tars produced as gasi-
fication byproducts are shown in Table 3-20. Coke oven tars are known to con-
tain relatively high levels of carcinogenic organic compounds. Considering
that coke ovens operate in the same temperature range as some gasification
processes (although at lower pressures than surface gasifiers), similar prod-
ucts may be formed during coal gasification.
The trace compounds which may be formed during coal gasification have
been extensively evaluated. Many of the compounds potentially formed are
organometallic compounds, such as:
metal-porphyrins
metal-carbonyIs
metallocenes
arene carbonyIs
metal alkyls
organohydrides
metal chelates.
The biological origin of coal makes it likely that porphyrin compounds are
present. Porphyrins are known to bind metals such as vanadium and nickel.
High partial pressures of carbon monoxide may lead to metal-carbonyl formation
(e.g., carbonyls of nickel, iron and cobalt). These toxic compounds are un-
stable at high temperatures but trace amounts may be produced. Metallocenes
of iron, nickel, chromium, vanadium, tantalum, molybdenum, and tungsten may
be formed. Carbon monoxide pressure may also enhance formation of arene car-
bonyls which are more stable than metal!ocenes and hence may be common species.
Although metal alloys are generally unstable, they may be important in the
mobility of trace metals in the gasification zone. Stable organohydrides of
lead, tin, germanium and silica may be formed in the reducing gasification en-
vironment. Metal chelates formed from phenolics, carboxylic acids and ami no
groups may be important to the mobilization and release of metals.
59
-------
CT>
O
TABLE 3-19. BYPRODUCT WATER ANALYSIS FROM SYNTHANE GASIFICATION OF VARIOUS COALS (Jones et al.,1977)
Water
constituent0
pH
Suspended solids
Phenols
COD
Thiocyanate
Cyanide
Ammonia
Chloride
Carbonate
Bicarbonate
Total sulfur (S04)
Coke
plant
9
50
2,000
7,000
1,000
100
5,000
--
—
—
— —
Illinois
no. 6 coal
8.6
600
2,600
15,000
152
0.6
8,100a
500
6,000b
ll,000b
1,400
Wyoming sub-
bituminous coal
8.7
140
6,000
43,000
23
0.23
9,520
--
—
—
— —
Illinois
char
7.9
24
200
1,700
21
0.1
2,500
31
--
—
North Dakota
lignite
9.2
64
6,600
38,000
22
0.1
7,200
—
__
—
--
Western
Kentucky coal
8.9
55
3,700
19,000
200
0.5
10,000
_ ...
—
--
Pittsburgh
seam coal
9.3
23
1,700
19,000
188
0.6
11,000
__
— —
-_
„
a 85 percent free NH3
b Not from same analysis
c
Units ppm except for pH
-------
TABLE 3-20. MASS SPECTROMETRIC ANALYSIS OF BENZENE-SOLUBLE TARS
(units are percent by volume) (Jones et al. 1977)
Illinois
Structural type No. 6 coala
Benzenes
Indenes
Indains
Naphthalenes
Fluorenes
Acenaphthenes
3- ring aroma tics
Phenyl naphthalenes
4-ring peri condensed
4-ring catacondensed
Phenols
Naphthols
Indanols
Acenaphthenols
Phenatheols
Dibenzofurans
Benzongohthothi ophenes
- B-heterocyclics
Average molecular weight
2.1
8.6b
1.9
11.6
9.6
13.5
13.8
9.8
7.2
4.0
2.8
ob
0.9
—
2.7
6.3
1.7
10.8
212
Montana sub-
Lignite bituminous coal
4.1
1.5
3.5
19.0
7.2
12.0
10.5
3.5
3.5
1.4
13.7
9.7
1.7
2.5
—
5.2
--
3.8
173
3.9
2.6
4.9
15.3
9.7
11.1
9.0
6.4
4.9
3.0
5.5
9.6
1.5
4.6
0.9
5.6
—
5.3
230
Pittsburgh
coal
1.0
6.lb
2.1
16.5
10.7
15.8
14.8
7.6
7.6
4.1
3.0
ob
0.7
2.0
—
4.7
--
8.8
202
a Spectra indicates traces of 5-ring aromatics
b Includes any naphthol present (not resolved in these spectra)
c Data on N-free basis since isotope corrections were estimated
61
-------
Because of the aromatic characteristics of coal, polycyclic aromatic
hydrocarbons (PAH) are found in coal conversion products. Some of these com-
pounds are known to be carcinogenic in experimental animals and in humans.
Trace metals in coal may also be mobilized during gasification and thus
are potential pollutants. Analyses by Attari (1973) of pilot plant opera-
tions indicated substantial losses of mercury, selenium, arsenic, tellurium,
lead, and cadmium from solid residues. Other metals, such as antimony, vana-
dium, nickel, and beryllium, remained in the solid phase. The characteris-
tics and transport of the metals mobilized during gasification and the
mobility of those remaining in the solid phase are largely unknown. According
to Jones et al. (1977), trace elements of primary concern in coal gasifi-
cation are:
antimony
arsenic
barium
beryllium
boron
cadmi urn
chlorine
chromium
copper
fluorine
lead
mercury
molybdenum
nickel
selenium
sulfur
tellurium
uranium
vanadium
zinc.
MUNICIPAL
City of Gillette
Sewage Treatment Plant-
Sources at the Gillette Wastewater Treatment Plant include leakage from
aeration, secondary clarifier and aerobic digester tanks, seepage from the
sludge holding pond, and seepage from the oxidation pond. Sources related to
the sludge holding pond are described elsewhere.
Leakage from the tanks may have about the same quality as incoming
sewage, although the quality of basal sludge may be superimposed. No data
are available on the quality of wastewater in the Gillette wastewater treat-
ment plant. A first estimate based on information from Metcalf and Eddy
(1975) on the typical composition of medium strength domestic sewage is in-
cluded in Table 3-21.
Also included in Table 3-21 are possible values of chemical constituents
in the "carrier" water. These values were given by Nelson et al. (1976) for
the City of Gillette water supply. It is assumed that no changes in concen-
tration occur during domestic uses. Also, possible effects of infiltration
from the Donkey Creek line are neglected. The high COD, TOD, and BOD values
indicate that organics constitute a potential contaminant in the shallow
groundwater system. Similarly, total nitrogen is high.
Since the groundwater flow system is anaerobic, however, nitrate values
should remain low. Another chemical constituent in the carrier water which
is beyond recommended limits is sulfate.
62
-------
TABLE 3-21. HYPOTHETICAL QUALITY OF WASTEWATER, GILLETTE
TREATMENT PLANT (Nelson et al.,1976)
Constituent Concentration (ppm)
Suspended solids - total 200
- fixed 50
- volatile 150
BOD (5-day) 200
TOC 200
COD 500
Nitrogen - total as N 40
- organic 15
- free ammonia 25
- nitrites 0
- nitrates 0
Phosphorus - total as P 10
- organic 3
- inorganic 7
Alkalinity - as CaC03 10°
100
Grease
9.5
Potassium
r i • 305
Calcium
158
Magnesium
220
Sodium
920
Sulfate
36
Chloride
660
Bicarbonate
TDS
63
-------
Sludge settled in the base of aeration, clarifier, and digester tanks
may also contribute heavy metals to groundwater. Other constituents entering
groundwater from the tanks include fecal bacteria and virus. Also present
are amoeboid cysts, intestinal worm eggs, and parasitic fungi.
The "oxidation" pond appears to be an overloaded facultative system with
operating characteristics of an anaerobic lagoon. Consequently, wastewater
undergoes some anaerobic digestion. The quality of water in the pond may be
a blend of incoming and outgoing wastewaters.
Wastewaters entering the "oxidation" pond from the aerobic digesters
will reflect the quality of treatment in the activated sludge process. Such
treatment is minimal in the Gillette Treatment Plant. Therefore, as a first
approximation, the values for medium concentration sewage given in Table 3-21
are assumed also to be representative of wastewater entering the lagoon.
According to the Missouri Basin Engineering Health Council (1971),
treatment effectiveness of a pond in Saskatchewan was as follows: suspended
solids, 70 percent; BOD, 55 percent; COD, 60 percent; and grease, 75 percent.
If Gillette's pond shows similar efficiencies and the corresponding values
are used along with those values shown in Table 3-21, resultant effluent
concentrations would be BOD, 90 ppm; COD, 200 ppm; and grease, 25 ppm. The
high BOD and COD values reflect organics which should be considered a pollu-
tant present in the pond. Chemical constituents increase in concentration
because of evaporation. However, changes in sulfate concentrations will occur
because of the formation of H2S. Also, because of anaerobic condition, nitro-
gen constituents will remain about the same.
Digestion in anaerobic ponds leads to the formation of organic acids,
lowering the pH. Similarly, the reducing conditions in anaerobic ponds also
increase heavy metal mobility (Fuller, 1977). Lund et al. (1976) observed
heavy metals in soil solution extracts 3 meters below the base of effluent
ponds constructed in coarse-textured soils. Metal concentrations were lower
than corresponding values found in extracts beneath sludge ponds, because
sludges tend to accumulate heavy metals. Nevertheless, the possibility of
contamination of groundwater beneath the lagoon at Gillette by heavy metals
should be considered a real possibility. Analyses (courtesy of Ms. Paddock,
Supervisor, water and wastewater plants, City of Gillette) of heavy metals
in "treatment plant water" suggest that high zinc levels might be present in
lagoon water (see section on "Sludges").
The lagoon at the Gillette Treatment Plant might contribute bacteria,
viruses, and other pathogenic organisms to the shallow groundwater system.
It appears that the septic tank septage (material remaining in the tank
and not discharged to leach fields) is disposed of mainly at the City of
Gillette landfill. However, it is entirely possible that septage is occa-
sionally discharged into the sewer system. In this case, shock concentra-
tions may reach the treatment plant. Table 3-22 shows septage characteristics
reported by Silberman (1977).
In addition to the constituents found in normal sewage (and septage), the
64
-------
TABLE 3-22.
SEPTIC TANK SEPTAGE CHARACTERISTICS AS REPORTED
IN THE LITERATURE (all units in ppm, except pH)
(Silberman, 1977)
Septage characteristics3
Total solids
Total fixed solids
Total volatile solids
Total suspended solids
Fixed suspended solids
Volatile suspended solids
Biochemical oxygen demand
Chemical oxygen demand
Ammonia nitrogen
Nitrite nitrogen
Nitrate nitrogen
Organic nitrogen
Total phosphorus
Orthophosphate
Chromium
Alkalinity
Iron
Manganese
Zinc
Cadmi urn
Nickel
Mercury
Hexane extractabl es
Copper
PH
Aluminum
TOC
Grease
Lead
Minimum
6,380
1,880
4,500
5,200
1,600
3,600
3,780
24,700
40
0.2
0.87
26
20
10
1
1,020
163
5.0
50
0.2
1.0
0.022
9,561
8.5
4.2
50
15,000
9,600
2
Maximum
130,000
59,100
71,400
93,400
9,000
30,100
12,400
62,500
150
1.3
9.0
26
310
170
1
1,020
200
5.4
62
0.2
1.0
0.1
9,561
8.5
9
-
-
-
-
aMinimum and maximum values are presented to show that
septage characteristics vary substantially.
65
-------
Gillette Treatment Plant receives industrial wastes of an unknown nature.
These should be considered as potential pollutants. Table 3-22 lists hazard-
ous wastes which are possibly discharged into the Gillette sewer system.
Sewage sludge-According to Todd et al. (1976), the ranking of pollu-
tants associated with sewage sludge is:
Physical - Minor
Inorganic chemical - Primary
Trace elements - Primary
Organic chemical - Primary
Bacteriological - Primary
Radiological - Minor.
Sludge from the activated sludge process normally contains up to 99
pounds of water per pound of sludge solids (U.S. Environmental Protection
Agency, 1974). Consequently digestion occurs under anaerobic conditions.
The solid matter in sludge may consist of 70 percent organic and 30 percent
inorganic substances (Health Education Service, nd). However, Sommers et al.
(1976) reported 50 percent organic matter in sludge collected from eight
Indiana cities.
A breakdown of the composition of raw and anaerobically digested sludge,
reproduced from a report by Wyatt and White (1975), is given in Table 3-23.
The high alkalinity and organic acid levels should be noted. Sommers et al.
(1976) found that the predominant form of N in sludges was organic -N, and
that NH,-N constituted greater than 90 percent of the total inorganic N in
sludges examined from eight Indiana cities. Ammonia concentration in wet
sludges fell within the range 200 to 500 ppm in the same study. With drying
of the sludge, therefore, one would expect production of considerable N03-N.
This could be a source at the Gillette sludge disposal pond.
Organic matter in sludge has an affinity for the heavy metals in waste-
water (Council for Agricultural Science and Technology, 1976). For example,
Mitchell (1964) reported that copper, cobalt and chromium chelates were found
in the fulvic acid fraction of organic matter. Concentrations of heavy metals
vary widely from city to city, depending for example on degree of industriali-
zation, storm water volumes, etc. Table 3-24 presents metals found in sludges
(Dean and Smith, 1973). All metals are present in excessive concentrations;
however, levels of lead, copper, and zinc are particularly high. Regarding
mobility of heavy metals in sludge, studies by Lund et al. (1976) demon-
strated that heavy metals migrated to depths as great as 3 meters below
anaerobically digested sludge holding ponds. The metals examined were Zn, Cd,
Cu, Cr, and Ni. The soils were coarse-textured. The authors found that re-
distribution of metals was closely related to changes in COD of soil samples
with depth. Metal movement was thus attributed to the formation of organic
chelates. Other possible factors promoting metal migration include pH and oxi-
dation reduction potential. For example, during the first stage of anaerobic
digestion of sludge, organic acid formation lowers the pH to a value of about
5.1 (Health Education Service, nd). The lower pH promotes the flux of
catiomc heavy metals (Fuller, 1977). Also, reducing conditions in soil pro-
motes the movement of As, Be, Cr, Cu, Cn, Fe, and Zn, but has little effect on
66
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TABLE 3-23. TYPICAL CHEMICAL COMPOSITION OF RAW AND
ANAEROBICALLY DIGESTED SLUDGE (Hyatt and
White, 1975)
Item
Total dry solids (TS), %
Volatile solids (% of TS)
Grease and fats (ether
soluble, % of TS)
Protein (% of TS)
Nitrogen (N, % of TS)
Phosphorus (P205, % of TS)
Potash (K20, % of TS)
Cellulose (% of TS)
Iron (not as sulfide)
Silica (Si02, % of TS)
PH
Alkalinity (ppm as
CaC03)
Organic acids (ppm
as HAc)
Thermal content (Btu/lb)
Raw primary
Range
2.0-7.0
60-80
6.0-30.0
20-30
1.5-4.0
0.8-2.8
0-1.0
8.0-15.0
2.0-4.0
15.0-20.0
5.0-8.0
500-1,500
200-2,000
6,800-10,000
sludge
Typical
4.0
65
( )
25
2.5
1.6
0.4
10.0
2.5
( )a
6.0
600
500
7,600b
Digested sludge
Range
6.0-12.0
30-60
5.0-20.0
15-20
1.6-6.0
1.5-4.0
0.0-3.0
8.0-15.0
3.0-8.0
10.0-20.0
6.5-7.5
2,500-3,500
100-600
2,700-6,800
Typical
10.0
40.0
( )a
18
3.0
2.5
1.0
10.0
4.0
( )a
7.0
3,000
200
4,000C
aData not shown in reference cited
K
Based on 65 percent volatile matter
cBased on 40 percent volatile matter
67
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the movement of Cd, Pb, and Hg (Fuller, 1977).
TABLE 3-24. METALS IN SLUDGE, 1971-1973
(Dean and Smith, 1973)
Li terature
Element
Cd
Cu
Hg
Ni
Pb
Zn
Geometri c
mean
(ppm)
61
906
14.5
223
404
2420
Spread9
5.89
2.66
5.24
4.54
4.13
2.78
Atomic absorption
geometric
mean
(ppm)
93
1840
3.2
733
2400
6380
aSpread is antilog of standard deviation of log-
normal distribution.
Anaerobic conditions obviously occur in both the sludge lagoon and "oxi-
dation" pond at the Gillette wastewater treatment plant. Because of the shal-
low water table at the site, heavy metals may be introduced almost directly
into the aquifier. A mitigating factor, however, is that the benthic deposits
may have clogged the bottoms of both the sludge pond and "oxidation" pond.
Twenty samples of water at the Gillette wastewater treatment plant were
analyzed in July 1976 for the following heavy metals: Pb, Zn, Cd, Cr, and Hg.
According to the results (courtesy MS. Paddock), values of Cd, Cr, and Hg were
consistently below detection limits. One sample showed a lead concentration
of 0.5 ppm and the remaining 19 were less than 0.1 ppm in lead. In contrast
to these metals, the concentrations of Zn averaged 0.289 ppm. Undoubtedly,
all metals are more highly concentrated in Gillette plant sludge, and the con-
centration of zinc may be excessively high.
In addition to chemical pollutants, sludge contains high concentrations
of fecal coliform bacteria and viruses, and lesser quantities of intestinal
and respiratory organisms (Dean and Smith, 1973). Also amoeboid cysts, in-
testinal worm eggs and parasitic fungi may be present (Dean and Smith, 1973).
Such organisms remain viable in sludge.
Sewerline 1eakage —Sewer leaks allow raw sewage to enter the subsurface
environment. The sewage comes from households and businesses in the community
and, in the case of Gillette, industry as well. Seasonal variation of sewage
composition can occur due to varying proportions of domestic and industrial
waste. Gillette wastes have a higher domestic fraction during the summer
68
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because summer populations are higher than winter populations. Industry
levels are relatively stable year round.
Dissolved minerals in Gillette sewage include all major constituents
(Ca, Na, K, Mg, HCC>3, $04, Cl) and several trace constituents (principally
Fe, Cu, Mn). Diluted organics include nitrogen forms such as ammonium,
nitrate, urea, and proteins. Settleable solids include grit, sand, soaps,
greases, tars, animal fats, hair, oil, and other organic matter. All of
these species can be thought of as potential pollutants, although the mobil-
ity of the various substances will vary considerably.
Septic Tanks-
The characteristics of septic tanks as potential pollution sources were
presented earlier under the discussion of mine sanitary wastes.
Landfills or Dumps-
The Gillette landfill site encompasses the following sources:
Metal disposal area
Oil waste disposal site
Dead animal pit
Garbage trenches
Oily wastes and septic tank pumpage sites
Tire disposal site
Covered dump.
Metal disposal area-This area is used for disposal of metal objects,
such as refrigerators, old cars, and barrels. Also tires, batteries, and
wooden items are included. Potential pollutants associated with metal items
(e.g., in alloys) could include any or all heavy metals, such as manganese,
iron, aluminum, chromium, antimony, lead, copper, cadmium, nickel, and zinc.
Since hazardous wastes of all types are permitted at the waste disposal
site, the metal drums could contain residues ranging from oil to pesticides.
Oily waste disposal area-Waste oils in the disposal pit may include
crankcase oil, transmission fluid, gear lubricants, hydraulic oils, and
possibly kerosene and other solvents. Representative assays of crankcase
drain oils indicate the presence of the following: carbon, nitrogen, sulfur,
lead, zinc, barium, calcium, phosphorus, and iron. Additives included with
the original lubricating oil, such as detergents and pour-depressants, may
be present in crankcase oil. The organic fraction of additives may be dissi-
pated by combustion or reactions with the oil, but inorganics concentrate.
According to Weinstein (1974), drain oils contain significant amounts of
unchanged polyisobutylene and polymethacrylate additives. The percent by
weight of nitrogen in crankcase drain oils may range from 0.13 to 0.21
(Weinstein, 1974).
The solution resulting from flushing service station gasoline tanks may
be dumped into the oil waste pit. Such waste could include high organic and
lead concentrations. Because of the lack of restrictions at the landfill, it
69
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is possible that hazardous wastes could be disposed of in the oil waste pit.
Table 3-22 lists possible hazardous wastes.
Open burning is permitted near the oil waste disposal site. Pesticide
containers and other wastes are accepted. Burning of these items could create
fly ash with high concentrations of organics and possibly heavy metals.
Dead animal pit-The dead animal pit is a source of high BOD, COD, and
TOC, as well as lesser amounts of chemical constituents. The high TOC sug-
gests that organics could migrate from the pit. Pathogenic organisms and
virus are possibly present in abundance. Substances used in the euthanasia of
the animals will also be present in unknown concentrations.
Garbage disposal site-Garbage is disposed of in two active trenches,
each about 30 to 40 feet wide, 400 to 500 feet long, and 20 to 30 feet deep.
A third trench of the same dimensions is used to provide backfill for the
above trenches. Surface drainage runs into the pits.
The range in quality observed in municipal landfill leachate is shown in
Table 3-8, reproduced from a paper by Pohland and Engelbrecht (1976). These
authors point out that leachate is most objectionable from a pollution view-
point when containing high concentrations of organic matter, high TDS, and low
pH. As shown on Table 3-8, the following constituents are potential contami-
nants: organics, nitrate, calcium, chloride, sodium, potassium, sulfate, man-
ganese, magnesium, iron, zinc, copper, cadmium, and lead. Decreasing pH
increases the solubility of heavy metals present in the waste. Similarly,
anaerobic conditions at the soil-landfill interface will promote the mobility
of heavy metals indigenous to the soil. The population of microorganisms in
leachate may be limited by the initially elevated temperatures together with
other inactivating properties (Pohland and Engelbrecht, 1976). In other words,
pathogenic organisms might not be of concern as polluting sources in leachate.
The problem of leachate production and associated potential contaminants
is aggravated at the Gillette disposal site by surface runoff into the
trenches. Not only does such runoff promote leachate formation, but also con-
taminants are introduced with the runoff water. For example, the overburden
layers immediately above the coal seam exposed by the trench were observed to
contain free sulfur and gypsum. A water sample of runoff was collected from a
pool at the base of the third trench in June 1977, the day after a thunder-
storm in the area. Table 3-25 shows the results of an analysis of the sample.
The sample was not preserved (except by freezing); consequently, results for
pH, C03, HC03, NH4> and N03 are questionable. An equivalents per million
(epm) balance shows that the ratio of cations to anions is 1.23. Sulfate
values are questionable because of the method used (Hach Kit) and errors are
introduced by dilution to bring results within the range of the instrument.
However, the values illustrate that probably high concentrations of chloride,
sulfate, sodium, and calcium are introduced into solid waste during runoff.
If the pH is as low as the value shown, runoff water may also contain heavy
metals and promote the mobility of heavy metals in leachate.
70
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TABLE 3-25. ANALYSIS OF RUNOFF SAMPLE IN THIRD TRENCH AT
THE CITY OF GILLETTE LANDFILL IN JUNE 1977
(ppm except for pH)
Water constituent Water constituent
PH
EC
C>
co3
HC03
so4
4.95
32.0
545
0
78.1
1,500
Na
K
Ca
Mg
NH4
N03
338
18
499
226
6.16
2.80
Oil waste and septic^ tajikjjumpage pits—Two pits at the Gillette disposal
site are used to dispose of oil wastes and septic tank pumpage. Observation
of the types of wastes disposed of in these pits suggests that hazardous
wastes are also included.
The type of oily wastes and associated contaminants are probably the same
as those disposed of in the oil waste disposal pit, and hazardous wastes are
probably among those given in Table 3-22.
No information is available on the quality of the septage disposed of in
the septic tank pumpage pit. The characteristics of septage are known to vary
considerably, particularly in communities which do not regulate the collec-
tion and disposal of septage (U.S. Environmental Protection Agency, 1974).
"In these cases, septage haulers will indiscriminately include septic tank
contents along with raw wastewater collected from pit toilets, wastes from
camping trailer pump-out stations, waste motor oil from service stations, cut-
ting oil and other hard-to-treat or toxic wastes from small industries through-
out the communities" (U.S. Environmental Protection Agency, 1974).
Table 3-22 indicates the possible large range in septage characteristics.
The high TOC and COD values illustrate that organics are a possible contami-
nant. Other constituents of concern are: nitrogen, chromium, iron, manga-
nese, zinc, cadmium, nickel, copper, and aluminum. Septage may also contain
high concentrations of parasite microorganisms and viruses.
Tire disposal site-Up the hill from the oily waste and septage disposal
pits is an area for disposal of tires. Oil wastes are also evident in this
pit, with associated potential contaminants. Tires are basically nonbiode-
gradable. Fecal matter from rodents may constitute a pollution source as do
the remains of dead rodents. Tires are also a potential fire hazard. Con-
stituents in fly ash from burning tires may be potential sources of contamina-
tion. Possibly included are organics and heavy metals.
71
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Covered dump-No information is available on the area! extent and composi-
tion of solid wastes in the covered dump at the landfill site. Using present
practices as a guide, it is possible that any or all of the contaminants dis-
cussed above are present.
Water Treatment Facility-
. The two potential pollutants related to the City of Gillette water treat-
ment plant are precipitated solids from the lime softening process and con-
centrated wastewater. Precipitated solids comprise CaC03 and are disposed of
in the landfill.
A sample of treatment plant wastewater was obtained from Stone Pile Creek,
directly behind the plant, in June 1977. The sample was not preserved (except
by freezing). The resultant analysis of major constituents and other charac-
teristics of the water sample are shown in Table 3-26. The ratio of cations
to anions is 0.84, indicating errors in analyses, principally sulfate, or the
presence of undetermined constituents. On the basis of this analysis, however,
it appears that sulfate is the principal contaminant.
TABLE 3-26. JUNE 1977 ANALYSIS OF WATER FROM STONE PILE
CREEK BEHIND GILLETTE WATER TREATMENT PLANT
(pptn except for pH)
Water constituent Water constituent
PH
EC
Cl
co3
HC03
8.5
1.70
14
3.0
109.8
so4
Na
K
Ca
Mg
1,350
55
11
134
165
Urban Runoff-
Sartor and Boyd (1977) reported on studies to determine the nature and
concentrations of contaminants in urban runoff. Results were based on samples
collected for a number of studies throughout the U.S. Among the more signifi-
cant conclusions with respect to pollutants were the following:
• Runoff from street surfaces is generally highly contaminated.
In fact, it is similar in many respects to sanitary sewage.
• The major constituents of street surface contaminants were con-
sistently found to be inorganic, mineral-like matter, similar
to common sand and silt.
72
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• The quantity of contaminant material existing at a given test
site was found to depend upon the length of time which had
elapsed since the site was last cleaned, intentionally (by
sweeping or flushing) or by rainfall.
• The quantity of contaminated material existing on street sur-
faces was found to vary widely depending upon a range of
factors.
Quantity and characteristics of contaminants observed in urban runoff in
the studies by Sartor and Boyd (1977) are shown in Table 3-27. Note particu-
larly the high concentrations of total solids, coliforms, zinc, copper, lead,
and chromium.
Urban runoff for Gillette will also contain high concentrations of ordi-
nary salt used for clearing roads.
Other Municipalities
The only identified potential pollution sources at outlying municipalities
are sewage treatment plants. The sewage effluents at these point sources will
be similar to wastes generated at the City of Gillette treatment plant, and
the reader is referenced to that section of the report. Total dissolved solids
may be lower at outlying municipalities, due to the lower TDS of the water
supply itself. However, the actual makeup of the sewage effluents depends
on the design and operation of the particular package plant.
TABLE 3-27. QUANTITY AND CHARACTERISTICS OF CONTAMINANTS
IN URBAN RUNOFF (Sartor and Boyd, 1977)
Weight means
for all samples
Measured constituents (Ib/curfa mile)
Total solids 1400
Oxygen demand
BODc ' 13.5
COD 95
Volatile solids 100
Algal nutrients
Phosphates 1.1
Nitrates 0.094
Kjeldahl nitrogen 2.2
Bacteriological Q
Total coliforms (org/curb mile) 99 * 10*
Fecal coliforms (org/curb mile) 5.6 * 10
Heavy metals
Zinc 0.65
Copper 0.20
Lead 0.57
Nickel 0.05
Mercury 0.073
Chromium 0.11
Pesticides ,
p.p-DDD 67 x 10'°
p.p-DDT 61 - 10'°
Dieldrin 24 * 10'°
Polychlorinated biphenyls 1100 * 10~°
73
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SECTION 4
GROUNDWATER USAGE
Campbell County receives an average of only 15 inches of precipitation per
year, much of which is in the form of snow. Most of the streams are ephemeral,
but even.permanent rivers, such as the Belle Fourche, are used only for stock
watering and a small amount of irrigation. The primary water supply for all
uses is groundwater.
Groundwater usage can be divided into four broad categories: municipal,
industrial, agricultural, and rural domestic. The only major municipality
within the project area is the City of Gillette. The core city is supplied with
water through a City distribution system, while trailer courts and subdivisions
on the periphery have each developed its own water system. The town of Wright,
located at Reno Junction, also has its own water supply system. Major
industries which use groundwater include coal strip mining, electric power gen-
eration, experimental gasification, and secondary oil recovery. Agricultural
water uses include stock watering and some irrigation.
MUNICIPAL USAGE
City of Gillette
The primary location of municipal water usage is the City of Gillette. Now
supporting a population of 13,000, most of the City itself is supplied through
a central distribution system. Pump station logs and City meter records show
that in 1976 average daily usage was approximately 105 gallons per capita and
that the maximum daily usage was about 240 gallons per capita (Nelson, et al.
1976). Roughly 3 million gallons of water per day flow through the water treat-
ment plant, of which approximately 1.7 mgd enter the sewage treatment plant
(Jeff Smith, City Engineer, personal communication, 1977).
The City water comes from a mixture of hard and soft water wells. There
are currently 20 operational hard water wells, all except 2 of which are locat-
ed in a single well field northwest of the City and north of the railroad, in
Sections 21 and 22, T50N, R72W. The wells range from 182 to 355 feet in depth
and draw water from the Wasatch Formation. When they were drilled in 1969,
water levels ranged from 60 to 80 feet below ground surface, and individual well
yields were generally from 50 to 100 gpm (Anderson and Kelly, 1977). In 1976,
the hard water wells were found to be producing at 75 percent of their original
capacity (Nelson et al., 1976), and in September 1977, water levels were found
to range between 78 and 94 feet below ground surface.
74
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The hard water well system is clearly inadequate to meet the needs of
Gillette's growing population. Not only is the water table as a whole declin-
ing, but the cones of depression from neighboring wells are interfering with
one another (Nelson et al., 1976). The wells are in poor repair, with broken
flow meters and pressure gages and valves that have rusted shut. There is no
monitoring of the well system at this time.
In 1976, a consulting firm (Nelson et al., 1976) was hired by the City of
Gillette to study the water supply situation. At their urging, the City expand-
ed its soft water well system during 1977. The City currently has 12 soft
water wells, 7 of which have been drilled into the Fort Union Formation during
the past year. The City is not yet using these new wells because of sand pro-
blems. The five original Fort Union wells range in depth from 930 to 1,215
feet and have a total pumping capacity of 310 gpm. In 1976, these wells were
found to be operating at 100 percent capacity (Nelson et al., 1976).
In addition, the City has three wells drilled into the Fox Hills
Formation. They range in depth from 3,479 to 8,505 feet and have a total
rated capacity of 575 gpm for two of them and a rated capacity of 75 gpm
for the third. Two of the wells (#1 and #2) have been plugged back and
perforated in the Fort Union Formation.
The City of Gillette has recently turned its attention to the Madison For-
mation as a potential municipal water supply. Although the Madison limestone
is found at about 11,000 feet below the ground surface in the Gillette area, it
is considerably closer to the surface east of Gillette. In July 1977, Pacific
Power and Light Company, the Joint Powers Board of Campbell County, and the City
of Gillette jointly began drilling a test well in the Madison Formation 10 miles
northwest of Keyhole Reservoir. The well was drilled to 2,625 feet, and water
rose to within 400 feet of the surface. If production and quality are found to
be suitable, the City of Gillette has the option of developing a well field on
40 acres around this site. The City would then construct a pipeline to
Gillette, a distance of about 50 miles.
Subdivisions and Trailer Courts
Subdivisions and trailer courts are springing up around the periphery of
Gillette. Rather than hooking up to the City distribution system, these new
developments are drilling their own wells. As of November 1976, records from
the State Engineer's Office showed that water rights permits had been granted
to 26 subdivisions and trailer parks for a total of 4,650 acre-feet annually
(afa).
RURAL DOMESTIC USAGE
Campbell County now has a rural population of about 2,000. Again, on the
basis of a typical household usage of about 105 gallons per capita per day, usage
is roughly 210,000 gallons per day (gpd).
The State Engineer has on file water rights permits for 238 domestic wells
in the project area. Most of the wells range from 100 to 500 feet in depth,
with three wells over 1,000 feet deep, and yields vary between 2 and 25 gpm.
75
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INDUSTRIAL USAGE
Coal Strip Mining
The major use of water at the mines is for road dust suppression. Other
uses include drinking, bathing, etc., and equipment wash water. All of the
mines will be obtaining water both from pit discharge and from deep wells.
Table 4-1 summarizes water requirements for dust suppression and cleaning/
domestic usage.
TABLE 4-1. MAJOR MIME SITE WATER USAGE
Mine
AMAX Belle Ayr South
AMAX Eagle Butte
ARCO Black Thunder
Carter North Rawhide
Dust suppression
(gallons per day)
80,000
(sunnier)
100,000
50,000 - 225,000
200,000
(summer)
Source
pit discharge
pit discharge
pit discharge
and settling
pond
mine drainage
and sewage
treated efflu-
ent
Cleaning/domestic
(gallons per day)
2,500 - 4,000
(wash house only)
55,000
60.000 - 100.000
31,000
Source
local wells
deep wells
4 wel 1 s
1 well
Kerr-McGee Jacobs Ranch
Sun Oil Cordero
Wyodak
100,000
350,000
(storage tank)
60,000
pit discharge
pit discharge
and package
treatment plant
effluent
pit discharge
15,000
(domestic only)
10,000
(domestic only)
wells 300 to
1,000 feet deep
9 wells in Fort
Union Formation
Water requirements for dust suppression vary seasonally with peak water
usage during the summer months. In addition, extremely heavy traffic or wind
conditions can increase water demands. Excess industrial water during the
winter months will be pumped into holding tanks or mine settling ponds The
U.S. Geological Survey (1975) states that excess pit discharge from AMAX's
Belle Ayr South mine will be diverted to Donkey Creek.
Water for cleaning and domestic purposes is being supplied by local ground-
water wells. This includes water for plant wash, steam cleaning, and personal
usage. AMAX estimates personal usage to be about 50 gpd per employee.
Steam Electric Power Generation
Although both the operating power plant and the one under construction are
designed to be air-cooled, water losses occur in the following areas: boiler
blowdown, dermneralizer, evaporation from ash pond, sanitary wastes, equipment
wash water, and floor and equipment drainage. Anticipated water requirements
for the two power plants are 200 to 300 gpm. The current source of water is
from wells in the Fort Union and Fox Hills Formations. When the new plant goes
76
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on line in June 1978, the major water supply will be treated sewage effluent.
from the Gillette sewage treatment plant (Black Hills Power and Light Co., 1973).
Coal Gasification
Lawrence Livermore Laboratories is currently conducting in situ coal gasi-
fication experiments at the Hoe Creek site south of Gillette. The first experi-
ment, carried out in October 1976, produced 66,067 gallons of water from the
dewatering wells beyond that actually used in the gasification process. In
addition, half of that amount again was produced as steam. It is not known at
this time how the excess water is disposed of (Lawrence Livermore Laboratory.
1977).
Secondary Oil Recovery
According to the U.S. Bureau of Land Management (1974), estimated ground-
water used for secondary oil recovery, exclusive of oil produced water, in
Campbell County was 8,500 acre-feet in 1973. Little change was expected for
the future. In northeastern Campbell County, water is obtained mostly from
Inyan Kara rocks and the Minnelusa Formation; while in southeastern and western
Campbell County, most of the secondary recovery water comes from the Fort Union
and Lance Formations and the Fox Hills sandstone.
AGRICULTURAL USAGE
Agricultural water usage consists primarily of stock watering, with minor
irrigation. As of November 1976, water rights permits were on file with the
State Engineer for 439 stock wells in the project area. These range in depth
from 1 to 640 feet, with the majority between 10 and 200 feet. The yields are
mostly under 10 gpm, but range from 2 to 100 gpm. There are also 129 combined
stock and domestic wells, 5 stock and irrigation wells, and 12 wells combining
stock watering with commercial or industrial uses. In the last case, water is
sold for construction, oil exploration, or other purposes.
The Wyoming Water Planning Program (1973) stated that in Campbell County
consumptive water use can be assumed to be approximately 15 gpd for cattle and
3 gpd for sheep. The Wyoming Department of Agriculture (personal communica-
tion) reported that as of January 1976, there were 85,000 cattle and calves
and 84,000 sheep in Campbell County. Using these figures, total water consump-
tion for stock watering in Campbell County is approximately 1.5 mgd. Roughly
60 percent of this total is provided by groundwater. Therefore, a rough esti-
mate of groundwater used for stock watering in Campbell County is 0.9 mgd.
Records from the State Engineer's Office (November 1976) show nine irriga-
tion wells in the project area. Most of these are used by schools, cemeteries,
etc., and have yields ranging from 30 to 100 gpm. Two of the wells are agri-
cultural and have yields of 600 and 350 gpm. There are also five wells used
for both irrigation and stock watering. These have yields ranging from 20 to
200 gpm.
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SECTION 5
HYDROGEOLOGIC FRAMEWORK
This section is intended to provide the source-specific background infor-
mation for the hydrogeologic framework upon which the various potential pollu-
tion sources identified in Section 2 are to be superimposed. Data and infor-
mation gaps exist for many individual sources. These gaps will need to be
filled before a complete assessment of the potential impact of these sources
on groundwater quality can be made.
The section has been arranged according to five major interest areas -
surface water hydrology, soils, geology, existing hydrogeology, and the modi-
fied hydrogeologic practices of the coal strip mining firms. The order of
these areas of interest is of significance because, as the potential pollu-
tants enter the system, they are usually subject to the influence of at least
one of these interest areas.
SURFACE WATER HYDROLOGY
This discussion covers the surface hydrology and its relation to ground-
water in the study area at present. Conditions during and after mining will
also be discussed in the general framework. A detailed site-specific treat-
ment of surface hydrology cannot be made until the mines provide complete
access to their hydrologic data.
Precipitation and Evapotranspiration
The Powder River Basin is semi arid. Average annual rainfall is 15 inches;
average potential evapotranspiration is 25 to 30 inches. Rainfall varies
widely from year to year and is distributed unevenly during the year. Most
rain comes from thunderstorms in the spring and early summer. Thunderstorm
rainfall is very localized, intense, and of short duration.
Little naturally occurring surface water is found in the basin. Most
rain received in the basin is carried back to the atmosphere by evapotrans-
piration. Only a small portion runs off as streamflow, or moves deep into
the subsurface to recharge aquifers. Some small, shallow intermittent lakes
can be found after rainfall. Only the Belle Fourche River and two of its
tributaries, Donkey and Caballo Creeks, flow for extended periods of time
during the year.
-------
Watershed and Stream Morphology
The topography of the eastern Powder River Basin is gently rolling.
Surface relief varies from east to west, particularly east of the coal burn
line that marks the boundary between the Wasatch and Fort Union Formations.
Elevations in the basin range from 4,500 to 5,000 feet.
Figure 5-1 shows the area selected for the monitoring study and the
major watersheds intersected by the monitoring area. The monitoring area
was arbitrarily divided into five watersheds: Rawhide Creek, which flows to
the Powder River; the Belle Fourche River and two of its tributaries, Caballo
and Donkey Creeks; and Little Thunder Creek, which flows to the Cheyenne River.
Drainage net structure appears to be dendritic. The basin has two re-
gional joint sets trending northwest and northeast and, in some areas, drain-
age net development appears to slightly favor these directions. Major stream
gradients are gentle. As an example, the Belle Fourche River has a gradient
of 8 feet per mile just west of the Sun Oil Cordero lease.
Streams generally occupy grassy swales or narrow floodplains. Meander-
ing is very well developed on all but the smallest streams and meander scars
are conspicuous in aerial photographs. Dry stream beds are grass covered
and appear to contain little moveable coarse material.
Intermittent lakes that mark areas of internal drainage occur on all
watersheds. Numerous stock water impoundments (stock tanks) are also con-
structed along smaller streams. Several stream reaches contain sequences of
closely spaced tanks.
The northern third of Campbell County is a deeply dissected upland, with
a similar but less severely eroded continuation of this upland occupying the
western side of the County (number 4 in Figure 5-2). The relief of this
dissected area is rolling to steep and broken, with numerous butte-like hills
of scoria characterizing this upland. The entire area of this physiographic
division is drained by the Powder River, the Little Powder River, and their
tributaries.
South and east of the deeply dissected upland is a rolling divide (num-
ber 1 in Figure 5-2), the crest of which parallels the north-south Highway 59.
This area in 'the central and southern parts, as well as the Rochelle Hills
(number 2 in Figure 5-2), which border the eastern edge of this rolling di-
vide, are drained by the Belle Fourche River and tributaries of the South
Fork Cheyenne River. The predominantly gently sloping plains and tablelands
of this rolling divide have local relief of 200 feet to 400 feet, with rem-
nants of the old Missouri Plateau rising sharply from 100 to more than 1,000
feet about the divide.
East of the rolling divide is a broad, rough, broken, and in places,
badlandlike escarpment that is locally called the Rochelle Hills (number 2
in Figure 5-2). It was formed by the burning of Wyodak coal in the outcrop,
which protected the underlying Fort Union strata, thus forming this striking
and prominent flat-topped ridge (U.S. Geological Survey, 1974a).
79
-------
LEGEND
WATERSHED
BOUNDARY
EPHEMERAL OR
INTERMITTENT
""" STREAM
INTERMITTENT
— OR PERENNIAL
STREAM
MONITORING
AREA
gi PROJECT COAL
LEASE AREAS
1 CARTER NORTH
RAWHIDE
2 AMAX EAGLE
BUTTE
3 WYODAK
4 AMAX BELLE
AYR
5 SUN OIL
CORDERO
6 KERRMcGEE
JACOBS
RANCH
7 ARCO BLACK
THUNDER
Figure 5-1. Watershed map.
80
-------
^ Murky jMiint
|
Figure 5-2. Physiographic divisions and drainage of
Campbell County, Wyo.: (1) rolling di-
vide; (2) Roche!le Hills escarpment;
(3) eastward sloping plain; (4) deeply
dissected upland (Soil Conservation
Service, 1939).
81
-------
The Rochelle escarpment drops 300 to 400 feet to a relatively low east-
ward sloping plane (number 3 in Figure 5-2). Streams are well entrenched
throughout this plain, but the land is severely dissected only in local areas.
On the whole, the surface is gently rolling, but it is modified in places by
steep valley slopes and a few rough broken areas.
Areas of alluvial lands border most of the larger and many of the smaller
drainage ways in the four physiographic divisions already described. Areas
along the Powder, the Little Powder, and the Belle Fourche Rivers attain a
width exceeding 3 miles in some locations.
The alluvial lands include both alluvial terraces and floodplains. Ter-
races occupy about 70 percent of the alluvial lands, having been formed before
streams became so deeply entrenched. Some of the higher terraces are gently
sloping and partly covered by alluvial fans built up by deposits from small
drains issuing from the uplands. The lower terraces are nearly level; few
of them are more than 30 feet above the adjoining floodplains.
These varying physiographic divisions within Campbell County produce
varying soil properties of which the following are commonly found to be re-
lief related: (1) depth of the solum; (2) thickness and organic matter con-
tent of the A horizon; (3) relative moisture content of the profile; (4) color
of the profile; (5) degree of horizon differentiation; (6) soil reaction;
(7) soluble salt content; (8) kind and degree of "pan" development; (9) temp-
erature; and (10) character of the initial material (Buol et a!., 1973).
Undoubtedly, several of these factors have contributed to soil develop-
ment in Campbell County.
Intermittent Lakes
Areas of internal drainage to small closed basins occur in all water-
sheds in the project area. During heavy or long duration rains, surface run-
off collects in these basins to form shallow ponds or lakes. The lakes are
intermittent because they quickly dry as water is lost by evaporation.
The areal distribution of intermittent lakes shows a pattern that fol-
lows the occurrence of shallow, strippable coal. They tend to occur where
the Wasatch beds overlying the Fort Union coals are thin and they show a
trend that follows the coal "outcrop."
These small closed basins have probably been formed by subsidence. The
mechanism causing subsidence is believed to be compaction (diagenesis) of the
thick coal seams during recent geologic time. This explanation is supported
by the obvious correlation between the location of these basins and the thick,
shallow coal beds.
Because these basins do not drain, salts brought in by runoff concen-
trate at the surface and in the soil. Soil maps show many of these basins
contain a highly alkaline and sodic acid called McKenzie clay. These soils
may contribute to the deterioration of groundwater quality when disturbed
by mining.
82
-------
Recharge from intermittent lakes is probably insignificant. The soils
in the lake basins have a clay content and are often sodic, which probably
has the effect of sealing the basin floors when water ponds on these soils.
Streamflow Characteristics
Streams may be classed as ephemeral, intermittent, or perennial. Ephem-
eral streams are dry except for very brief periods when they flow in response
to heavy rainfall, which is usually caused by intense, short-duration thunder-
storms. Intermittent streams flow for extended periods during the year but
are dry for some period, usually during the summer when evapotranspiration
rates are high and there is little or no rain. Perennial streams flow through-
out the year.
Virtually all streams in the area are ephemeral or intermittent. Peren-
nial flow occurs only during wet years in the lower reaches of the Belle
Fourche River, the largest stream in the project area. Figure 5-3 shows a
flow-duration curve for the 'Belle Fourche at Moorcroft, just east of the
project area. This curve shows, for example, that discharge is greater than
0.5 cubic feet per second (ft3/s) only 40 percent of the time.
Streamflow is variable and unpredictable. Mean values of discharge and
peak flow return periods are obtained from sparse data and are almost useless
for prediction. The best and most up-to-date work on Streamflow characteris-
tics is by Lowham (1976), who is the source for Figures 5-4 and 5-5. The
figures show discharge-drainage area relations for streams in two hydrologic
regions that occur in the monitoring area. These regions are shown in Figure
5-6.
Lowham1s (1976) graphs give mean annual discharge (Qa) and peak discharge
for various return periods (PI00 = peak with 100-year return period). He
states that these graphs are not applicable where stream characteristics have
been altered by man and a few data discussed next suggest that streamflows
in the monitoring area have been greatly altered by stock watering tanks.
By storing water the tanks reduce runoff volumes. At AMAX Eagle Butte,
discharge in the Little Rawhide Creek where it enters and leaves the lease
was 110 and 85 acre-feet respectively for the period March 1974 to June 1975
(U.S. Geological Survey, 1976). Note that flow volume decreased in the down-
stream direction. Based on drainage areas at these two points, Lowham's
graphs for Region 3 (Figure 5-5) give mean annual flow volumes of 1,800 and
2,200 acre-feet. Aerial photos of the Little Rawhide Creek watershed upstream
of the lease show at least 31 stock tanks in the 22-square-mile drainage area,
and their presence may explain the very large difference between the estimated
and observed flow volumes.
Stock tanks are found in great numbers throughout the monitoring area.
Streamflow records at other mine sites also show flow volumes that are much
lower than Lowham's estimates. Lowham's graphs give a mean discharge of 8
ft3/s for the Belle Fourche at Sun Oil Cordero, but the Cordero Mining Co.
(1976) reports-that the river is dry for long periods and normally flows at
less than 5 ft /s.
83
-------
Ploins streams
10,000
O
2
O
O
UJ
V)
UJ
UJ
O
CD
O
1U
O
cc
<
x
O
V)
1,000
too
J I
i i i I—n—[—i—rj r
(FlOCiJ'lOOO Lime Missouri River
neor AlzOdO , Mont.
fGlOC38G500 Cheyenne River neor
Sr-wrer.
fH)OG396000 Lonce CreeK ol
Spencer.
rno6"2GbOO Se'ie Furche River
below Moorcroft.
(T)063r»«000 Beaver CreeK neor
Newcastle.
• Ol .1 I to SO SO 3$ ??9 9999
PERCENTAGE OF TIME DISCHARGE WAS EQUALED
OR EXCEEDED.
Figure 5-3. Flow duration curves for selected Wyoming streams
(U.S. Bureau of Land Management, 1974).
84
-------
DRAINAGE AREA, IN SQUARE KILOMETERS
50,000
10,000
o
o
UJ
CO
ce.
1000
CO
=3
O
oc
-------
DRAINAGE AREA, IN SQUARE KILOMETERS
5 10 50 100 5001000 500010,000
50,000
10,000 r
o
o
UJ
a:
UJ
CO
3
O
C3
Q£
to
I—t
a
1000 r
I 'I I Mill 1—I I I Ilil
1 10 100 1000
DRAINAGE AREA, IN SQUARE MILES
10,000
Figure 5-5. Relations for estimating flow characteristics in region 3
by using drainage area (from Lowham, 1976).
86
-------
GILLETTE V^V*^
I y"T*DONKEY
LEGEND
BOUNDARY LINE
BETWEEN EPHEMERAL
AND INTERMITTENT
STREAMS
WATERSHED
BOUNDARY
EPHEMERAL OR
- INTERMITTENT
STREAM
INTERMITTENT
OR PERENNIAL
STREAM
MONITORING
AREA
PROJECT COAL
LEASE AREAS
1 CARTER NORTH
RAWHIDE
2 AMAX EAGLE
BUTTE
3 WYODAK
4 AMAX BELLE
AYR
5 SUN OIL
CORDERO
6 KERRMcGEE
JACOBS
RANCH
7 ARCO BLACK
THUNDER
Figure 5-6. Hydro!ogic regions at monitoring area.
87
-------
Surface Water Quality
Surface water is sampled for chemical quality at several locations in
the Powder River Basin by the U.S. Geological Survey. Sampling sites and
type of analysis are shown in Figure 5-7. No sites are located within the
monitoring area.
t
106°,
106324500
105"
• .
~
20
40 60
SCALE (miles)
80
100
i MONITORING AREA
-• 09234500 CHEMICAL-MEASUREMENT SITE
•• 09234500 TEMPERATURE.MEASUREMENTSITE
i 09217000 BIOLOGICAL-MEASUREMENT SITE
f 09217000 SEDIMENT -MEASUREMENT SITE
Figure 5-7. Surface water quality measurement sites (adapted from
Water Resources Data for Wyoming, Part 2. Water
Quality Records, U.S. Geological Survey, 1974a).
88
-------
To show the range of constituents included in a chemical analysis,
results from station 06428500 on the Belle Fourche River for 1974 are shown
in Table 5-1. During this year, dissolved solids concentration ranged from
about 750 to 2,000 ppm. The major dissolved constituent was sulfate, which
ranged from 450 to 1,300 ppm. Calcium and bicarbonate were next in abun-
dance. Their concentrations, which tended to be about equal, ranged from
100 to 400 ppm.
Surface water quality is also reported for streams on several mine
lease sites in environmental impact studies where quality data have been
collected as part of a program to gather baseline information. Their analysis
generally shows sulfate as the major dissolved solids constituent followed by
calcium, bicarbonate and, in some cases, sodium.
Surface Mater—Groundwater Relationships
Strip mining of coal may have a great impact on shallow groundwater sys-
tems. The occurrence and movement of groundwater in these systems is directly
related to the surface hydrology. This is the case both under natural condi-
tions which prevail at the present and under modified conditions that will
occur during and after stripping of the coal.
A general picture of the relationship between surface water and ground-
water is provided by the streamflow characteristics of the project area.
Ephemeral streams lose water to the streambed and are sources of recharge to
groundwater. Intermittent streams lose water at certain times and receive
groundwater at others. They are alternatively sources of recharge and points
of groundwater discharge. Discharge of groundwater to intermittent streams
is often not sufficient to cause flow but may provide enough water to sustain
ponds in the streambed. Perennial streams are points of groundwater dis-
charge at all times.
Streams in the project area generally grade from ephemeral to perennial
with increasing watershed size. Higher elevations on the watershed are areas
of recharge, both in ephemeral streams and in interstream areas. Recharge
along stream channels is probably enhanced by seepage from stock tanks. Seep-
age takes place both through the tank bottom and often through the face of
the dam, which causes water to pond in the channel for some distance down-
stream from the dam face.
At lower elevations on larger watersheds, groundwater may discharge to
streams and sustain intermittent or perennial flow. Perennial flow appears
only on large watersheds. The largest watershed in the project area, the
Belle Fourche River, has intermittent flow at the Sun Oil Cordero lease where
the drainage area is about 500 square miles.
Relative quantitives of runoff and recharge under premining conditions
in the basin are poorly defined. Lowham's (1976) drainage area-discharge
relations for Region 3 (Figure 5-5) give mean annual runoff values for 10-
and 100-square-mile areas at 1.6 and 5.5 ft3/s or 2.1 and 0.7 inches. As
indicated earlier, these values are likely to be high. Smith (1974) esti-
mates average annual headwater runoff to be 0.3 inch. Runoff at the AMAX
89
-------
TABLE 5-1. REPRESENTATIVE CHEMICAL MEASUREMENTS FOR SURFACE WATER QUALITY (U.S. Geological Survey, 1974a)
CHEYENNE RIVER BASIN
06428500 BELLE FOURCHE RIVER AT WYOMING-SOUTH DAKOTA STATE LINE
LOCATION. Lat 44°44'59", in NEWMtlWV sec. 18, T.9 N., R.I E.. Butte County, S. Dak., at county bridge, 4.0 mi northwest of Belle Fourche,
S. Dak., and 8.0 mi downstream from gaging station.
DRAINAGE AREA. 3,280 mi2, approximately (at gaging station).
PERIOD OF RECORD. Chemical analyses: October 1965 to September 1974. Water temperatures: October 1965 to September 1974.
EXTREMES: 1973-1974:
Specific Conductance -Maximum daily observed, 2,620 micromhos Jan. 14; minimum daily, 726 micromhos Mar. 6.
Water Temperatures -Maximum, 31.0°C June 19; minimum, freezing point on many days during November to March.
Period of Record:
Specific Conductance -Maximum daily, 2,840 micromhos Jan 17, 1970; minimum daily, 461 micromhos Apr. 12, 1971.
Water Temperatures -Maximum, 31.0°C June 19, 1974; minimum freezing point on many days during winter period.
CHEMICAL ANALYSES, WATER YEAR OCTOBER 1973 TO SEPTEMBER 1974
Date
Oct.
24...
Nov..
15...
Dec.
06...
Jan.
10...
Feb.
14...
Mar.
14...
Apr.
25...
May
08...
June
06...
July
04...
Aug.
08...
Sep.
12...
Instantaneous
Time discharge
(cfs)
0800
0800
1410
1700
1710
1315
1715
1815
1000
0900
1415
0900
34
53
35a
8.0a
80a
122-
229
106
67
133
106
33
Dissolved
silica
(SiO?)
(mg/T)
7.0
9.8
11
13
11
8.6
10
15
8.0
6.3
5.3
4.5
Dissolved
Calcium
(Ca)
(mg/1)
230
220
260
370
250
170
130
190
215
130
99
170
Dissolved
Magnesium
(Mg)
(mg/1)
75
66
93
110
38
47
38
57
74
29
34
63
Dissolved
sodium
(Na)
(mg/1 )
92
70
96
140
79
50
50
68
100
100
98
110
Dissolved
Potassium
(K)
(mg/1)
7.7
6.7
7.4
9.5
7.7
8.6
6.7
6.3
8.6
6.7
7.4
8.4
Bicarbonate
(HC03)
(mg/T)
174
203
235
378
215
185
170
207
183
122
189
210
Cirbonate
I Oh)
(mj/1 )
0
0
0
0
0
0
0
0
0
0
0
0
Dissolved Dissolved Dissolved
sulfate chloride fluoride
(S04) (Cl) (F)
(mg/1) (mg/1) (mg/1)
910
790
1000
1300
770
570
440
660
900
550
430
740
4.6
5.5
7.6
9.2
5.3
6.1
'3.8
3.8
3.6
5.4
7.3
7.3
0.7
0.7
0.7
0.8
0.6
0.5
0.6
0.6
0.7
0.7
0.6
0.7
aDaily mean discharge.
(continued)
-------
TABLE 5-1 (continued)
<£>
CHEYENNE RIVER BASIN
06428500 BELLE FOURCHE RIVER AT WYOMING-SOUTH DAKOTA STATE LINE
Dissolved Total
n»*o n1 trate phosphorus
Date (N) (P)
(mg/1 ) (mg/1 )
°3:.. °-05
"iS:.. o-11 °-°2
Dec- 0 05 0 01
06...
JJQ' 0.11 0.02
Fj4- 0.18 0.04
"^ 0.36 0.01
A^' 0.18 0.02
"Q* 0.07 0.01
Jpge 0.05 0.01
J^y 0.38 0.02
Aol:.. °-°7 °-01
SjP- 0.00 0.00
(sum of
:onstituents)
1410
1270
1610
2160
1260
956
760
1100
1400
890
775
1200
Date
Oct. 24...
Jan. 10...
Apr. 25...
July 04...
Dissolved Dissolved
solids sol Ids
(tons/ (tons/
acre-ft) day)
1.92
1.73
2.19
2.94
1.71
1.30
1.03
1.50
1.90
1.21
1.05
1.63
129
182
152
46.7
272
315
470
315
253
320
222
107
FIELD
Instantaneous
Time discharge
(cfs)
0800
1700
1715
0900
Ale. «.Uiiwi
34
8.0a
229
133
Hardness r,rhona ,e Sodium DH Specific
(Ca,Mg) 'A^™ adsorption , p" , conductance
(mg/1) (mg/f) ratio Iun1ts) (micromhos)
890
830
1000
1400
780
630
480
710
840
440
380
680
DETERMINATIONS
Turbidity
(JTU)
9
3
170
90
750 1.3 8.2 1750
660 1.1 8.2 1610
810 1.3 8.1 1940
1100 1.6 7.9 2470
600 1.2 8.0 1570
480 0.9 7.9 1260
340 1.0 8.0 1020
540 1.1 8.3 1300
690 1.5 8.2 1730
340 2.1 7.7 1220
230 2.2 8.2 1100
510 1.8 8.2 1510
Dissolved Fecal
oxygen col i form
(mg/1) (col. /100ml)
9.5 110
9.5 10&
7.5 145
7.2 2700
Temperature
rc)
10.5
1.0
0.5
0.0
0.0
6.0
16.0
17.0
15.5
17.5
23.5
10.0
bNon-ideal counting conditions
(continued)
-------
TABLE 5-1 (continued)
06428500
CHEYENNE RIVER BASIN
BELLE FOURCHE RIVER AT WYOMING-SOUTH DAKOTA STATE LINE
ro
DAY
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
IS
20
23
22
23
24
25
26
27
23
29
30
31
MONTH
SPECIFIC CONDUCTANCE (ml crambos/cm AT
OCT NOV DEC JAN FEB
1690
1670
1650
1670
1700
1740
1780
1800
1700
1640
1570
1460
1640
1680
1710
1700
1740
1730
1720
1720
1720
1750
1760
1750
1780
1780
1790
1750
1640
1580
1750
1700
1650
1630
1610
1590
1680
1630
1700
1710
1630
1680
1680
1740
1620
1630
1590
1700
1700
1680
1680
1760
1820
1900
2030
2020
2020
2000
1960
1970
1940
1960
—
1760
1500
1840
1760
1950
1850
1790
1990
1890
1980
1780
1730
1940
1910
1890
1920
1940
1950
1960
1970
1980
1980
1840
1980
1910
1850
1890
1800
1960
1960
1980
2000
1910
2050
2150
2210
2230
2260
2320
2360
2310
2480
2500
2520
2600
2590
2620
1560
1180
1200
1200
1410
993
1110
1060
895
1020
922
926
1000
1020
1130
1230
1250
1690
1280
1370
1360
1330
1410
1460
1530
1600
1640
1680
1580
1660
1600
1550
1590
1490
1470
1500
1480
1440
1390
1100
1200
1120
1160
1090
1100
1300
—
—
—
1410
25-C). HATER YEAR OCTOBER 1973 TO SEPTEHBER 1974
MAR APR HAY JUN JUL AUG
1320
1500
1590
1600
1140
726
870
847
872
983
1120
1190
1240
1260
1380
1400
1420
1470
1520
1600
1680
1670
1610
1650
1720
1640
1640
1620
1670
1750
1710
1400
1700
1730
1700
1730
1720
1680
1620
1720
1700
1700
1660
1550
1600
1700
1730
1720
1700
1620
1620
1450
1380
1510
995
1030
994
1200
1260
1530
1240
1210
—
1520
1260
1330
1370
1440
1430
1440
1450
1450
1510
1470
1510
1550
1450
1570
1620
1640
1650
1730
1680
1660
1670
1660
1680
1830
1670
1680
1700
1650
1740
1750
1760
1580
1880
1740
1640
1620
1540
1740
1740
1760
1860
1840
1820
1830
1800
1780
1820
1870
1940
1940
1840
1880
1670
1820
1850
1970
1890
2000
1980
1890
2050
1980
--
1830
1450
1840
1690
1120
1120
1090
1120
1100
1110
1110
1120
1140
1130
1130
1130
1130
1120
1120
1020
980
920
760
850
990
1080
1110
1140
1110
1120
1120
1130
1130
1130
1120
1120
1110
1100
1000
975
956
1020
1010
985
1070
1060
1060
1040
1070
1090
1140
1150
1190
1240
1220
1220
1210
1210
1240
1280
1320
1290
1360
1480
1140
SEP
1350
1340
1350
1330
1350
1370
1380
1420
1470
1520
1570
1590
1620
1660
1660
1710
1780
1820
1870
1900
1950
1990
1980
2000
2030
2040
2060
2060
2080
2060
-•
1710
YEAR: MAX - 2620; MIN - 726; MEAN - 1570
(continued)
-------
TABLE 5-1 (continued)
06428500
CHEYENNE RIVER BASIN
BELLE FOURCHE RIVER AT WYOMING-SOUTH DAKOTA STATE LINE
CO
TEMPERATURE (°C) OF WATER, WATER YEAR OCTOBER 1973 TO SEPTEMBER 1974
(ONCE-DAILY MEASUREMENT)
DAY
OCT
NOV
DEC
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
MONTH
19.0
15.0
13.0
14.0
14.0
15.0
15.5
13.0
12.0
5.0
5.0
7.0
12.0
11.0
10.5
14.0
12.0
13.0
14.0
14.0
14.5
14.5
12.0
12.0
11.0
9.0
9.0
7.0
7.0
7.0
6.5
11.5
4.0
3.5
2.5
1.0
0.5
0.5
0.0
0.0
0.0
0.5
2.0
5.0
6.5
5.0
4.5
4.0
6.0
2.0
0.5
0.5
0.0
0.0
0-0
0.0
0.0
0.0
0.0
0.5
0.5
0.0
—
1.5
3.0
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.5
0.5
0.0
0.5
0.0
0.0
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
—
--
—
0.0
0.5
8.0
6.0
8.5
4.0
1.0
3.0
0.5
3.0
3.0
1.0
0.0
1.0
1.0
4.0
2.5
7.0
7.0
1.0
0.5
0.5
0.5
0.5
1.0
2.0
4.0
6.0
8.0
11.0
11.0
8.0
3,5
10.0
7.0
5.5
7.0
8.0
8.0
8.0
10. 6
12.0
8.0
3.0
3.5
5.0
6.0
8.0
8.0
11.0
15.0
15.0
7.0
10.0
12.5
11.0
15.0
16.0
16.0
14.0
13.0
14.0
17.0
--
10.0
18.0
12.0
13.0
15.0
18.0
18.0
18.0
19.0
19.0
18.0
16.0
14.0
12.0
11.0
12.0
10.0
12.0
15.5
17.0
16.0
17.0
17.0
16.0
21.0
23.0
20.0
22.0
14.0
15.0
17.0
16.0
19.0
21.0
22.0
22.0
18.0
20.5
16.5
20.0
18.0
21.0
22.0
25.0
26.0
27.0
27.0
27.0
26.0
30.0
31.0
30.0
30.0
22.0
27.0
27.0
27.0
27.0
27.0
28.0
28.0
28.0
--
24.5
26.0
21.0
21.5
24.0
25.0
24.5
27.0
25.0
28.0
25.0
25.0
25.0
29.5
27.0
27.0
27.0
27.0
27.0
29.0
28.5
28.0
27.0
27.0
27.0
25.0
25.0
26.0
25.0
24.0
24.0
23.0
26.0
22.0
22.0
23.0
23.0
24.0
22.0
20.0
20.0
10.5
20.5
20.0
22.5
20.0
20.0
22.0
22.0
24.5
24.0
24.0
25.0
24.0
23.0
23.0
23.5
25.5
25.6
23.0
21.0
19.0
16.0
16.5
22.0
14.0
16.5
17.5
19.0
18.0
22.0
21.0
17.0
14.0
14.0
14.0
14.0
16.5
18.0
20.0
20.0
19.0
21.0
18..0
25.5
16.0
17.0
17.0
17.5
15.0
15.0
13.0
14.0
15.0
14.0
—
17.0
YEAR: MAX - 31.0; MIN - 0.0; MEAN - 11.0
-------
Eagle Butte lease mentioned earlier was 0.09 inch from March 1974 to June
1975 (100 acre-feet from 22 square miles).
Recharge estimates vary widely. Lowry (1972) estimates that 10 per-
cent of rainfall (1.5 inches) recharges the shallow aquifers. Rechard and
Hasfurther (1976) estimate that average annual recharge and runoff do not
exceed 1 inch. Other estimates of recharge range from one percent of pre-
cipitation (Davis, 1976) to 0.5 inch (U.S. Geological Survey, 1976).
Relative quantities of recharge from interstream areas, stream beds,
and stock tanks are now known. Lowry (1972) believes that most recharge
takes place in interstream areas. He notes that in the spring the soil thaws
and is "frost cultivated." Under this condition, soil permeability is great-
ly increased and it is possible that large amounts of water infiltrate during
the first spring rains.
Recharge through ephemeral or intermittent stream channels is probably
significant, especially where well-developed meanders result in stream
channel lengths that greatly exceed the length between two points along the
longitudinal axis of the floodplain. Recharge by seepage from stock tanks is
also likely to be significant, in particular where they are closely spaced
along a stream.
The surface hydrology at specific mines depends in a general sense on
the position of a site on a watershed. The watershed area that drains through
a mine site will decrease as the location of the mine approaches the head-
waters of the watershed. Streamflow is ephemeral for small drainage areas
and flow volumes are relatively small. The headwaters of the watershed tend
to be recharge areas and water tables are relatively deep. At lower eleva-
tions on the watershed, Streamflow is intermittent and flow volumes can be
large; the water table tends to be shallow and groundwater discharges to
streams under wet conditions.
Four mines in the monitoring area are located high on their watersheds
and drainage areas upstream of the sites tend to be small. These are AMAX
Eagle Butte and Carter North Rawhide on the Rawhide Creek watershed and
ARCO Black Thunder and Kerr-McGee Jacobs Ranch on Little Thunder Creek water-
shed (Figure 5-1). The mines on Donkey and Caballo Creeks and the Belle
Fourche River watersheds (Figure 5-1) have larger upstream drainage areas.
Table 5-2 summarizes drainage areas for the lease sites and gives mean
annual runoff and peak discharge for a 25-year period estimated using Lowham's
(1976) methods.
SOILS
This subsection is intended to provide an insight into the relationship
of the soil environment to the hydrogeologic framework of the project area
which is located within Campbell County. Good quality soil information and
data are paramount to the task of completing a comprehensive environmental
assessment of the effects of surface coal mining on soil properties. For '
example, because soil properties will be completely changed by the mining
94
-------
<£>
TABLE 5-2. DRAINAGE AREAS FOR LEASE SITES, MEAN ANNUAL RUNOFF, AND 25-YEAR PEAK DISCHARGE
(from Lowham, 1976)
Hydrologic Drainage area Mean annual
region upstream of runoff
Mine (Lowham, 1976) Stream lease (mi2) (ft3/s)
ARCO
Black Thunder
Carter
North Rawhide
AMAX
Eagle Butte
Sun Oil
Kerr-McGee
2
3
3
2
2
Little Thunder Creek
N. Prong Little Thunder Creek
Rawhide Creek
Little Rawhide Creek
Little Rawhide Creek
Dry Fork Little Powder River
Belle Fourche River
N. Prong Little Thunder Creek
58
43
60
30
22
17
494
50
. 2.3
2.0
4.5
3.0
2.6
2.4
8.0
2.0
25-year peak
(ft3/s)
1,500
1,200
3,300
2,800
2,000
1,900
3,000
1,200
Jacobs Ranch
Wyodak
Donkey Creek
100
3.1
1,700
-------
process, knowledge of the premining soil situation is necessary to evaluate
the revegetation and infiltration potentials of the spoil material after the
land has been disturbed. In some cases, replaced spoil material will be a
source of pollution by virtue of its high concentration of soluble salts
which may leach to the groundwater.
Existing Soil Environment
Soil formation is largely a function of external processes which alter
the parent material of a soil both chemically and physically. Five major
factors control the kinds of soil that develop. These are: (1) the nature
of the parent material, including its chemical and mineralogical composition,
texture, and structure; (2) the climate under which the soil has formed,
particularly temperature and precipitation; (3) the living organisms which
interact with the soil, especially the native vegetation; (4) the topography
of the area when the soil is formed; and (5) the time that the parent mate-
rials are subjected to soil formation.
The soils of Campbell County are mostly residual, formed from weathered
sedimentary material, mostly sandstone and shale. In general, soils formed
from sandstone are of coarse texture (especially in surface horizons), and
highly permeable. Soils formed from shales are generally fine textured,
relatively impermeable, and consequently poorly leached.
The soils of Campbell County reflect the character of the bedrock to
a marked degree. Areas of sandy and medium-textured soils are underlain
by sandstone and sandy shale, and heavy soils are underlain by clayey sha'le.
The sandy loam and loam soils absorb moisture readily. They have fri-
able or only moderately compact subsoils, and they are thicker than the
heavy or fine-textured soils. Surface layers are well supplied with organic
matter and are neutral or only slightly alkaline. Lower subsoils are cal-
careous and are represented by a lime carbonate accumulation at depths of
16 to 30 inches.
The gray, heavy clay shale weathers slowly, and the soils developed -
from it are shallow. The shallow soils have a medium- to fine-textured
surface and a dense, compact subsoil. They absorb moisture slowly, and
runoff is rapid on the more sloping areas. On the steeper slopes, little
or no soil development has taken place due to geologic erosion.
Soils developed from scoria (clinker) were formed in the past by the
burning of thick coal beds of the Fort Union Formation, are characterized
by a reddish-brown to a light-red friable surface horizon and a red or reddish-
brown friable subsoil containing a layer of lime carbonate accumulation.
Alluvial soils are developed from a variety of material washed from
the uplands and high landscapes and redeposited along stream courses. They
occupy comparatively narrow, elongated, continuous, or broken strips along
most of the main drainages. The soils have a grayish-brown to dark grayish-
brown friable surface that contains a fair amount of organic matter, and
they are calcareous at or near the surface.
96
-------
Miscellaneous areas of soil include rough broken land, rock land, gul-
lied land, and rock outcrops occupying lands of steep relief characterized
by exposed beds of sandstone, shale, and clinker. A complex soil pattern
occurs as residual soils between the dissections. The forces of nature are
the controlling factors of these landscapes.
The natural vegetation of Campbell County is mainly short grasses com-
mon to much of the northern part of the Great Plains region. Some areas in
the northern and eastern parts of the County support variable stands of trees.
Grass is generally more luxuriant and abundant in the northern than in the
southern part of the County due to the slightly greater precipitation in the
north. Also, grass grows better on the sandy soils than silty or clayey
soils, and better on the smooth areas than on those steeply sloping. Due
to the semiarid climate and vegetative conditions, organic matter is accumu-
lated slowly, and soils have developed light-colored surfaces.
Classification of Soil Series of Campbell County-
The present classifications of all soil series published in the 1939
reconnaissance soil survey of Campbell County have been determined, and are
included in Table 5-3. As more detailed soil mapping is completed by indi-
vidual mines, new series are expected to be identified in the County, and
the classifications of these series will be included in a subsequent report.
The majority of soil acreage of Campbell County belongs to the soil order
aridisols. These are primarily soils of dry places, with an achric epipedon
(light-colored surface horizon), with one or more additional diagnostic sub-
surface horizons. The climatic regime in which aridisols form can be charac-
terized as one in which the potential evapotranspiration greatly exceeds the
precipitation during most of the year and no water percolates through the
soil.
Because of the limited amount of water available in the profile, the
chemical and physical reactions which are important in aridisol profiles
are relatively less intense than those in humid regions. Because of this,
the soils inherit much of their morphology from the parent material and the
lack of leaching has left the profiles with a high base status.
The aridisols are separated from the Inceptisols, soils with one or
more diagnostic horizons that are thought to form rather quickly, and that
do not represent significant illuviation, eluviation, or extreme weathering,
by the circumstance that unless irrigated they are usually dry or have a
saturated extract conductivity or more than 2 mmhos/cm at 25° C in the 18-
to 50-cm layer (Buol et al., 1973).
The occurrence of an argillic (clay) subsurface horizon relates to age
and position on the landscape as well as to soil management. The presence
or absence or an argillic horizon in aridisols is used as the basis for di-
viding the order into two suborders, argids (with argillic horizons) and
orthids (without argillic horizons).
97
-------
TABLE 5-3. SOIL SERIES CLASSIFICATION OF CAMPBELL COUNTY
(after Soil Conservation Service, 1939)
Soil Series
Soil Classification
Arvada
Banks
Bridgeport
Di11i nger
Fort Col\ins
Goshen
Laurel
McKenzie
Manvel
Pierre
Renohill
Rough Broken Land
Sarpy
Searing
Terry
Ulm
Wibaux
Ustollic Natrargid, fine, montmorillonitic, mesic
Ustic Torriofluvent, sandy, mixed, calcareous mesic
Fluventic Hapustoll, fine-silty, mixed, mesic
Pachic Hapustoll, fine-loamy, mixed, mesic
Ustollic Haplargid, fine-loamy, mixed, mesic
Pachic Arguistoll, fine-silty, mixed, mesic
Aquollic Salorthid, fine-loamy, mixed, mesic
Typic Haplaquept, fine, montmorillonitic (calcare-
ous), frigid
Ustic Torriorthenth, fine-silty, mixed (calcareous),
mesic
Usteric Camborthid, very-fine, montmorillonitic,
mesic
Ustollic Haplargid, fine, montmorillonitic, mesic
«
Unclassified and Ustic Torriorthenths, loamy and
clayey, montmoriHorn'tic, calcareous, mesic and
shallow
Typic Udipsamment, mixed, mesic
Ustollic Haplargid, fine-loamy, mixed mesic
Ustollic Haplargid, coarse-loamy, mixed, mesic
Ustollic Haplargid, fine-loamy, mixed, mesic
Ustic Torriorthenth, loamy-skeletal over fragmental,
mixed mesic
98
-------
The argids have formed on the oldest geomorphic surfaces, as on the
crests of alluvial fans. Orthids are found on geologically younger side
slopes and surfaces of intermediate age (Figure 5-8). Soils of the young-
est surfaces in the dry region, both the steep mountain slopes and recent
alluvial bottoms, have not developed any diagnostic subsurface horizons and
are classified as entisols.
PALEARGIOS
and HAPLUSTOLLS
LITHIC
HAPLORTHENTS
PALEARGIDS
HAPLARGIOS
andKAPLORTHIDS
HAPLORTH1DS
River
5
NATRARGIDS'
TORRIFLUVENTS HAPLORTHIDS
Figure 5-8. Block diagram showing positions of some major
kinds of aridisols and their associates (after
Buol et al., 1973).
Major Soil Associations of Campbell County-
The nature of soil associations is basically a grouping of soils similar
to each other according to pattern and position and not on the basis of capa-
bility or expected response. Soil associations are named according to the
dominant soil series occurring within the delineations. Figure 5-9 illus-
trates 10 of these associations.
The soil survey of Campbell County separates soils into six groups for
purposes of discussion, based on the soils' position on the landscape and the
parent material from which they were derived. Their divisions include: soils
of the uplands and terraces derived from sandy and slightly silty shales; soils
of the uplands and terraces derived from gray clayey shales and clays; soils of
the uplands and terraces derived from dark-gray Pierre shale; soils of the
uplands derived from sandstone; soils of the uplands and terraces derived from
red, burned shale (scoria); and soils of the bottom lands.
Soils of the uplands and terraces derived from sandy and slightly silty
shales-The soils of this group include the Ulm, Fort Collins, Goshen, and
99
-------
R76W I R75W | R74W [ R7JW | R72W | R71W | R70W | R&9W
MONTANA
T
42
LEGEND
||NT
ULM-RENOHiLL
mm
WiBAUX-SEARiNG
ARVAOA RENOHILL
MANVEL MOLING-
RENOHILL-ULM
PIERRE-ORMAN
d]
ARVAOA-LAUREL
BRlDGEPORT-
BANKS-SARPY
ROUGH
BROKEN UNO
R76W | R75W [ R74W | R73W | R72W | R71W | R70W | R69W
Figure 5-9. Soil associations of Campbell County, Wyoming
(Soil Conservation Service, 1939).
100
-------
Bridgeport, which occupy undulating to gently rolling uplands, colluvial
slopes, and nearly level stream terraces. All of them are loamy or slightly
sandy in their surface layers, and they are friable and silty or only moderate-
ly clayey in their subsoils.
Soils of the uplands and terraces derived from gray clayey shales and
clays-The soils of this group-the Renohill, Arvada, Manvel, Moline, and
McKenzie-occupy upland areas that are underlain by moderately heavy clayey
shale, as well as stream terraces and upland slopes and depressions consisting
of alluvium washed chiefly from areas of heavy upland soils.
Renohill soil occupies 24.5 percent of the County. It has a light-
colored, moderately friable surface horizon with a somewhat heavy compact,
slowly permeable subsoil. Arvada soil occupies 4.2 percent of the County and
has a clay pan which causes slow external and internal natural drainage. The
McKenzie soil has no surface drainage and occupies playas throughout the
County.
Soils of the uplands and terraces derived from dark-gray Pierre shale-
The Pierre and Orman are the only soils in this group. They occupy only a
small acreage in the northeastern corner of the County near Rocky Point. The
internal drainage of these soils is very slow, due to a very dense, compact
clay subsoil. Free calcium carbonate ranges from 6 to 15 inches because of
this slow drainage. This area is shown in Figure 5-9 as the Pierre-Orman
Association.
Soils of the uplands derived from sandstone-The Terry is the only soil
series in this group. Terry soil occupies large areas in the central and
southern parts of the County and, subsequently, occupies a fair amount of
acreage on some of the mine lease sites. It has a moderately sandy to sandy
surface horizon and a sandy subsoil. Due to its rapid internal drainage, it
is leached of calcium carbonate to a depth of 25 to 50 inches.
Soils of the uplands and terraces derived from red, burned shale (scoria)-
The soils of this group include the Searing, Wibaux, and Oil linger. They have
formed from scoria, the red, burned shale that resulted from the burning of
thick coal beds of the Fort Union Formation in the past.
The soils are friable and generally shallow to bedrock, with medium to
r.apid internal drainage.
Soils of the bottom lands-The soils of the bottom lands are the Banks,
Laurel, and Sarpy. They are on floodplains of various widths that have develop-
ed along practically all of the creeks and rivers. Many mine lease sites have
creeks or rivers which transect them, giving rise to soils of these types on
their properties.
The Banks and Sarpy soils have rapid internal drainage, but the Banks is
calcareous whereas the Sarpy is not. The Laurel soil is medium textured,
light grayish brown, friable, and calcareous.
101
-------
Salinity and Alkalinity in Soils-
Many soils in the western United States are affected by excessive con-
centrations of either soluble salts or exchangeable sodium, or both, resulting
in reduced crop production.
The term "saline soil" is defined as a nonsodic soil containing soluble
salts in such quantities that they interfere with growth of most plants. The
exchangeable sodium percentage (ESP) is less than 15 and the electrical con-
ductivity of the saturated soil paste extract (ECe) is greater than 4 mmhos/
cm. The term "sodic soil" (formerly called "alkali soil") refers to a condi-
tion in which the soil contains sufficient exchangeable sodium to interfere
with the growth of most crop plants, either with or without appreciable quan-
tities of soluble salts. Another condition which commonly occurs in semiarid
and arid regions is known as a "non-saline-sodic soil." This type of soil
contains sufficient exchangeable sodium to interfere with the growth of most
crops and does not contain appreciable quantities of soluble salt. The ESP
is greater than 15 and the ECe is less than 4 mmhos/cm. The pH usually is
greater than 8.5 (Fuller and Halderman, 1975).
Rhoades (1974) has indicated that the primary sources of soluble salts in
agricultural soils are: (1) irrigation waters, (2) salt deposits present in
soil parent materials, (3) agricultural drainage waters (both surface and sub-
surface) drainage from upper-lying lands, and (4) shallow water tables.
Rhoades (1974) has listed additional sources of soluble salts, termed "second-
ary" which include: (5) fertilizers, agricultural amendments, or livestock
and poultry manures applied to soils, (6) weathering soil minerals, and (7)
rain and snow.
Undoubtedly, several of these sources have contributed to the formation
of saline and sodic soils in Campbell County in the past, and will contribute
to salt accumulation in the future once spoils have been reclaimed.
Of primary concern to a monitoring program is the pollution potential of
these saline and sodic soils as a consequence of their disruption and place-
ment in designated burial sites. Because of the importance of these types of
soil material as a source of pollution, this section of the report attempts
to characterize the soils of Campbell County which exhibit saline and/or sodic
soil conditions, based largely on information available in the 1939 reconnais-
sance soil survey of Campbell County, and a meager amount of laboratory data.
It should be noted that all of the land mapped as a soil series and designated
as exhibiting saline and/or sodic soil conditions, may not in fact possess
these properties. In many instances these phenomena are highly localized in
various microenvironments, largely a function of position on the landscape,
proximity to the water table, and the nature of the parent material.
Arvada series-Saline drainage water accumulates on this soil, and on its
evaporation, a sodic salt deposit results. This soil possesses a compact
claypan-like subsoil which causes poor drainage by impeding the downward
movement of water and thus contributing to the salinization and alkalization
of the soil. Calcium carbonate is present in the subsoil in streaks and
102
-------
seams which occur below an average depth of 15 inches. In some areas of the
County, wind erosion has removed the surface soil and exposed the heavy,
saline clay subsoil, resulting in scabby spots, barren of vegetation or marked
by the presence of salt-tolerant plants such as greasewood and saltgrass.
This soil occupies extensive areas throughout the County and occurs on
all coal leases and, therefore, is considered a likely candidate for burial
in reclamation operations.
Bridgeport series-This soil is calcareous at or near the surface down-
ward, but has no horizon of calcium carbonate accumulation. Some sodic salts,
seldom concentrated enough to injure vegetation, are present in nearly all
areas where this soil has been mapped, with the areas most strongly affected
occuring along Wildcat Creek. Due to the small total area that this soil
series occupies, it is not considered a potential source of pollution.
Laurel series-The soil of the Laurel series has developed from calcar-
eous recent alluvium washed from the soils of the sandstone, shale, and lime-
stone uplands, therefore, it has accumulated soluble salts.
The lower parts of the subsoil and substratum are splotched and streaked
with white accumulations of calcium carbonate and other salts to a depth of 5
feet or more. This soil is not extensive in the County, and occurs mainly
along the Belle Fourche River and South Fork Wildcat, Horse, and Bitter Creeks,
with small areas along many of the small drains.
Manvel series-Many small areas of soil included with this soil type
contain free salts. The so-called "white salts," chlorides, and sulfates, are
most common, especially in the surface horizon; but sodium carbonate, or
"black alkali," occurs in small quantities in the subsoil and substrata.
McKenzie series—This soil varies widely in stage of development, as is
indicated by its layers of calcium carbonate accumulation. In some places
this carbonate-bearing layer is within a few inches of the surface; in others
it may be at depths as great as 3 feet. This soil occupies playas or
depressions in the central and south-central parts of the County and,
therefore, has been mapped on several lease sites.
Orman series-The surface soil of this series is commonly leached free of
salts, but they have accumulated in numerous flat or slightly depressed spots
in quantities sufficient to injure certain types of vegetation or prevent
their growth. Some crystalline gypsum and other salts are present in the sub-
soil in most areas.
Because only a few small areas of Orman clay are mapped in the County, it
is not considered a significant pollution source.
Pierre clay-The surface horizon of this soil is noncalcareous, with the
subsoil being a compact cloddy clay in which some white streaks of calcium
carbonate have accumulated. Some of the shale contains little calcium carbon-
ate, and the soil developed from it is noncalcareous or only slightly cal-
careous. Gypsum is usually present in varying quantities in the lower part
103
-------
of the subsoil and in the substratum.
Renohill series-The upper subsoil of this series typically contains no
free calcium carbonate, but the lower subsoil is more friable and has an
abundance of calcium carbonate.
Dim series-Calcium carbonate has accumulated in the lower subsoil of
this series but, because they have adequate drainage and excellent tilth,
they are considered some of the most productive soils of the uplands.
p
Hydrologic Soil Classification
Soil properties influence the process of generation of runoff from rain-
fall. Runoff from a plot on a small natural watershed occurs when the rate
of rainfall exceeds the infiltration capacity. Kohnke (1968) has indicated
that the actual relationship of these three hydrologic factors is complicated
by interception storage, depression storage, and surface detention of the
water and that, if considered over longer periods, evaporation and transpira-
tion as well as condensation and adsorption must also be considered.
Although such a complex analysis of surface runoff is not warranted at
this time, an attempt has been made to at least provide general insight into
this parameter, by delimiting areas of soil on particular watersheds that
exhibit similar infiltration characteristics.
This task was accomplished by first defining a watershed which encom-
passes (all or in part) the coal leases to be monitored. The defined water-
sheds were then superimposed on soil maps corresponding to the same areas of
interest, thereby yielding a soils map of the watershed. Once this was accom-
plished, the soils occupying a given watershed were classified in hydrologic
soil groups as defined by Soil Conservation Service (SCS) soil scientists.
The hydrologic soil groups are as follows:
• (Low runoff potential). Soils having high infiltration
rates even when thoroughly wetted and consisting chiefly
of deep, well-to-excessively drained sands or gravels.
These soils have a high rate of water transmission.
• Soils having moderate infiltration rates when thoroughly
wetted and consisting chiefly of moderately deep-to-deep,
moderately well-to-well-drained soils with moderately
fine to moderately coarse textures. These soils have a
moderate rate of water transmission.
• Soils having slow infiltration rates when thoroughly
wetted and consisting chiefly of soils with a layer that
impedes downward movement of water, or soils with
moderately fine to fine texture. These soils have a
slow rate of water transmission.
• (High runoff potential). Soils having very slow infil-
tration rates when thoroughly wetted and consisting'
104
-------
chiefly of clay soils with a high swelling potential,
soils with a permanent high water table, soils with a
clay pan or clay layer at or near the surface, and
shallow soils over nearly impervious material. These
soils have a very slow rate of water transmission.
The hydrologic classification of soils occurring in Campbell County was
derived from the SCS National Engineering Handbook (1971), and is presented
in Table 5-4. Areal extents of the four soil groups were determined for each
of the five watersheds by placing a grid (or "dot counter") over the map,
determining the number of grid intersections falling on each group, and then
computing the particular group percentages of the entire watershed. These
percentages are listed in Table 5-5 and are considered to be approximate.
TABLE 5-4. HYDROLOGIC SOIL CLASSIFICATIONS
Soil series
Arvada
Banks
Bridgeport
Dillinger
Fort Collins
Goshen
Laurel
McKenzie
Manvel-Moline
Orman
Pierre
Renohill
Rough Broken Land
Sarpy
Searing
Terry
Ulm
Wibaux-Searing
Map symbol
Aa, Ab, Ac
Ba
Bb
Da
Fa, Fb
Ga, Gb
La
Mb
Ma
Oa
Pa
Ra, Rb, Re, Rd, Re
Rf, Rg, Rh
Sa
Sb
Ta, Tb
Ua, Ub, Uc, Ud, Ue
Wa
Hydrologic
soil classification
D
A
B
B
B
B
C
D
C
C
D
C
D
A
B
B
B
C
105
-------
TABLE 5-5. APPROXIMATE AREAL PERCENTAGES OF
HYDROLOGIC SOIL GROUPS
Watershed
Belle Fourche River
Cabal lo Creek
Donkey Creek
Little Thunder Creek
Rawhide Creek
Areal
A -
B -
C -
D -
A -
B -
C -
D -
B -
C -
D -
B -
C -
D -
B -
C -
D -
percent
1.7
56.8
22.3
19.2
0.5
42.0
39.2
18.3
33.4
30.6
36.2
41.1
26.3
32.6
37.7
23.9
38.4
GEOLOGY
Regional Geology
The study area is located along the eastern edge of the Powder River
Basin, a structural and topographic basin which is approximately 250 miles
long and 100 miles wide. The basin is bounded by the Bighorn Mountains on
the west, the Black Hills Uplift on the east, and a series of arches and
uplifts to the south. As shown in Figure 5-10, the basin extends north into
Montana. The thick assemblage of sedimentary rocks underlying the basin
reaches nearly 12,000 feet in thickness. Paleozoic sediments rest on crystal-
line Pre-Cambrian rocks. Although there are at least six unconformities in
the sequence, the Paleozoic assemblages are approximately 2,500 feet thick
(U.S. Geological Survey, 1974a). Most are either limey sandstones, sand-
stones, or marine limestones. These formations have outcrops in the Bighorn
Mountains to the west.
The Mesozoic accumulations in the Eastern Powder River Basin include
shales and claystones which were deposited in the Upper Jurassic and Creta-
ceous periods. Thin conglomerate sequences and one thin limestone unit are
also present. The Mesozoic sequence is about 7,000 feet thick in the study
area.
106
-------
^
BIGHORN
—vs—
UPLIFT •. .
•\ \ \ \OSHERIDAN
EXPLANATION
O BELLEFOURCHE
*'',..
GILLETTE \ HILLS
UPLIFT
WIND RIVER BASIN\V^ _
'• *' ""''•, ^V^V
SWEETWATER '"''. ^>
•f A* **'
'fi.t . »i* »
'••-".IMH11 .»•
HARTVILLE .
LARAMIE UPLIFTf( i \\ \
• B^ L
'O
: RAPID CITY
SOUTH DAKOTA
. t 1 I I
ModifiMi front tlw Ttctooic MAP
of the Unittd Statn.
Figure 5-10. Generalized map showing the Powder River Basin
in relation to nearby structural features.
This study is primarily concerned with Cenozoic deposits. Tertiary
deposits are the most important in that they contain the coal formations and
that they outcrop in the study area. In the study area, the Tertiary deposits
are approximately 2,500 feet thick, and consist of siltstones, claystones,
coal beds, and discontinuous sandstones. Quaternary deposits consist of allu-
vium and colluviurn which occur in local drainage areas.
The two formations of particular importance to this study are the Wasatch
and Fort Union.
An angular unconformity exists between these formations in the study
area. This is probably indicative of a^large surge of Laramide uplift. The
lower Wasatch is composed of arkosic sands which were probably derived from
uplifted Pre-Cambfian strata (Davis, 1976). The study area is approximately
75 miles from the Bighorn range and most of the Wasatch rocks outcropping out
in the area are sandy shales and shales. Local lenticular sandstone units
found in the area are indicative of paleo-stream channels. Small swamps
existed during the Eocene period in this area, and some thin to moderately
thick coal beds exist in the Wasatch. These coals, with the exception of the
Felix coal, are not as continuous as the Fort Union coals. The Wasatch For-
mation crops out in the western part of the study area. The Fort Union
107
-------
outcrops in the eastern part of the area, and it is in this area that the
major coal stripping operations are taking place.
The Fort Union Formation is comprised of three members: the Tullock,
the Lebo Shale, and the Tongue River. The Tullock member is predominately
composed of shales and claystones with a few thin discontinuous coal beds in
its upper part. These fine-grained rocks were derived from the uplifted
margins of the Powder River Basin after the gentle Laramide Orogeny of late
Cretaceous age. The Lebo Shale member is characterized by a thick mudstone
assemblage which was probably associated with a surge in uplift of the
Bighorns. Again there are a few thin, discontinuous coal beds in this member.
The Tongue River member comprises more than half of the Fort Union Formation
(1,500 to 1,800 feet thick) and has the most persistent and thick coal seams
in the area (Glass, 1976). The strata which separate the various coal beds
are shales and clays, although there are many discontinuous sandy areas
which indicate past drainages. The Fort Union coals are shown in the fence
diagram presented as Figure 5-11.
Geologic history contains numerous instances where coal beds have burn-
ed. When the coal outcrop is ignited, the burn proceeds downdip under the
overburden. The overburden is subsequently "baked" and its geologic charac-
ter is altered. The new rock, called scoria or clinker, is usually reddish
orange and is quite resistant to weathering. As a result, many of the hills
in the area are capped by clinker zones. Field observation shows that the
clinker reaches a considerable depth and eventually reaches a contact with
the coal seam.
Structure
The Powder River Basin is an asymmetric, gently sloping structural and
topographic depression in northeastern Wyoming. In the study area, dips range
from three to five degrees to the west. There are few faults or folds of any
significance in the area. However, large scale compaction structures exist in
the northern part of the area. These structures were discussed in a paper by
Law (1976). As the coal beds are compacted by overburden, buried stream chan-
nel elastics experience less compaction and exist as topographically high
areas. Law (1976) shows that small normal faults occur in these areas.
Geologic History
The geologic history of the region was as follows:
• There was Paleozoic accumulation of limestone, sandstone
and shale in shallow seas as the basin was slowly down-
warped.
• Transgression of the sea during the Mesozoic allowed the
deposition of thick shales. Various transgressions and
regressions are evident from limestone and conglomeratic
phases.
108
-------
LITTLC POWMR
•IVU COAL
Marl
PUMPKIN IUTTI1 "e"«
COAL FIELD
COMPILED »NO MODIFIED FMOU
PUBLISHED REPORTI AND OPEO-
FILE REPORTS OF THE U.I.
SEOL06ICAL SURVEY
Figure 5-11.
Correlation of coal beds in the Powder River Coal Basin
(Glass, 1976).
109
-------
• The Laramide Orogeny shaped the current Powder River
Basin
• During the Orogeny, Paleocene swamps occupied the basin,
and thick accumulations of coal developed in the Tongue
River Member of the Fort Union Formation.
• Wasatch Formation elastics originated in areas uplifted by
the final Laramide activity. A few thin coal beds occur
in this formation.
• The Oligocene White River Formation contained terrestrial
elastics which have been eroded in the study area.
• Recent conditions have shaped the surface topography and
have allowed the deposition of alluvium in surface drainage
areas.
HYDROGEOLOGY
The hydrogeology of the project study area is complex and subject to many
local variations. For this reason, a general overview of the hydrogeology is
presented first, followed by a mine-by-mine, site-specific discussion. The
data and information presented here are a summary of published records sub-
mitted to Federal agencies by the mining companies, supplemented with some
field observations. The quality of this report, therefore, is limited to the
quality of information released by the mines. Up-to-date hydrogeologic infor-
mation must be made available for TEMPO to evaluate pollutant relationships
with local hydrogeology.
Shallow Aquifers
Five different types of shallow aquifers exist in the study area: alluvial,
Wasatch Formation, scoria, coal seam, and the Fort Union aquifers below the coal
seams. Their relationships are fairly complex, as shown in Figure 5-12.
Alluvial Aquifers-
Alluvial material is found in stream drainages throughout the study area.
Most of the unconsolidated alluviums are fine grained, subangular sediments
which have been derived from Wasatch or Fort Union shales and sandstones. Some
larger clasts of locally derived clinker detritus may be present. Alluvial
transmissivities may range around 500 gpd/ft (Davis, 1976) but they have not
been extensively tested. The units seldom exceed 50 feet of thickness and
storage coefficients are probably 10~2 to 10~1.
The alluvial aquifers can have recharge-discharge relationships with every
other type of aquifer in the area. The interaction of surface water and ground-
water systems in the alluvium is very important, but is not well understood.
110
-------
£;WASATCH
RECHARGE-OISCHARGE
POINTS
POSSIBLE EXCHANGE AREAS
Figure 5-12. Aquifer relationships (modified from Davis, 1976)
-------
Surface runoff associated with precipitation recharges the alluvium and it
may be transmitted to the coal aquifers, or it may move downgradient in the
stream channel and eventually be evaporated. During dry periods, the alluvial
aquifers are probably recharged from the beds which overlie the coal. This
water seldom appears as base flow in the stream, as it probably moves down the
streambed as underflow. Much of the water in the alluvium is discharged by
evaporation. Mater budget studies should be used to try to quantify the volume
of water which is lost through this process, although such a study would have to
quantify all of the inflows to and outflows from the other aquifer systems.
This might prove to be a very difficult process. Well yields from alluvial
aquifers vary greatly due to local differences in permeability and aquifer thick-
ness, and there are relatively few wells in the alluvial systems.
Wasatch Formation Aquifers -
These units are quite variable, and can be good to very poor aquifers.
There are many paleochannels where relatively permeable sandstones transmit
enough water for successful water wells. Elsewhere, numerous clay layers can
effectively perch water. These layers make it very difficult to describe re-
gional aquifer characteristics. Also, numerous thin coal beds are located in
the Wasatch formation. The thickness of the Wasatch formation ranges from near
zero in the coal outcrop regions to approximately 300 feet at the western edge
of the study area.
Although the units dip to the west, local topography exerts a large influ-
ence on groundwater flow directions. Approximately 1 to 5 percent of annual
rainfall is estimated to reach Wasatch groundwater systems. This water gen-
erally moves according to gradients which lead to local drainages. Numerous
small stock wells have openings in these strata, and most water level maps of
the area reflect the effects of gradients established by local drainages. In
addition to rainfall infiltration, the units may be recharged by water in al-
luvial channels in the western part of the study area, and by water transmitted
through clinker-overburden contacts. Natural discharge occurs in the alluvial
valleys in the eastern part of the study area and downward leakage accounts for
the remainder of the natural discharge. Most wells in the Wasatch are low
yield stock wells, but wells which penetrate sandstone strata might produce up
to 100 gpm. The percentage of the total discharge attributable to extraction
from wells is not known, although it might be significant.
Scoria Aquifers -
The scoria (clinker) areas are probably the most interesting hydrogeologic
phenomena in the study area. When shales which overlie coal beds are baked, a
scoria-type rock is formed. These expanded rock masses can collapse into the
void left by the burned coal. Also, gases produced during the burn will rise,
and some of the scoria are vesicular. The result of these combined effects
can be a very permeable aquifer. Coal outcrop fires were quite extensive in
the past, and the clinker zones in the study area are fairly continuous and may
extend laterally underground for as much as a mile (U.S. Geological Survey,
1974a). Transmissivities can range from 102 to 106 gpd/ft (Davis, 1976), and
there is evidence to support values near the upper end of the range. A Wyoming
Highway Department pumping test referred to in Rahn (1976) reported specific
112
-------
capacities of 18 gpm/ft. Other estimates of clinker transmissivity (Dr. J.
Harshbarger, University of Arizona, oral communication, 1977) are on the
order of at least 106 gpd/ft. Storage coefficients generally reflect uncon-
fined conditions and probably range around 10-1.
The recharge-discharge relationships of the scoria aquifers are not well
understood. Although they have extensive outcrop areas, many areas may have
developed soil horizons with large clay fractions and poor infiltration poten-
tial. The fact that most of the areas are hilly would indicate fairly rapid
runoff of surface water, also lowering infiltration potential. However, some
scoria areas intersect alluvial valleys. These are probably recharge areas.
The water-bearing characteristics of the clinker areas indicate that they do
receive substantial recharge, and the exact mechanisms should be closely stud-
fed in the future. Scoria discharge areas depend upon the local arrangement of
the system. The coal seams probably receive some amount of clinker discharge.
In areas where alluvium is intercepted, the recharge-discharge relationship de-
pends on the head relationships of the two systems. When the clinker has more
head, it will discharge into the alluvium, and the water may eventually evapo-
rate. The converse situation would exist when the alluvium has more head than
the clinker. Minor amounts of scoria discharge may leak into the lower members
of the Fort Union Formation. Discharge related to human activity is relatively
small. In areas where the clinkers are mined for use as road paving materials,
there is loss of water from storage. Due to the hard rock character of the
clinker, very few wells withdraw water from the scoria aquifers.
Coal Seam Aquifers —
The regional environmental impact statement (U.S. Geological Survey,
1974c) emphasizes the point that the coal seams are the best aquifers in the
area. The reason for this observation is that the coals are by far the most
regionally extensive sedimentary layers in the basin. The permeability of the
coal is due to extensive fractures, Transmissivities range from 102 to 104
gpd/ft, and are related to the thickness of the coal seam and the extent of
local fracturing. Wells in the coal seams seldom yield more than 20 gpm, and
most of them range around 10 gpm. Transmissivities and storage coefficients
for the coal aquifers vary widely, depending on the nature and occurrence of
the fractures in the coal.
The coal seams are near the surface in the eastern part of the study area.
•Most of the actual outcrop areas have been burned, so clinker zones line the
outcrop pattern. These are recharge areas for the coal seam aquifers. The
clinker beds are quite permeable, and they may act as "head tanks" above the
coals. Also, the coal seams may receive recharge as downward leakage from
overlying Wasatch strata. These overlying beds are relatively impermeable and
they act as leaky aquitards. The local occurrence of sandy zones in the over-
burden makes it difficult to discuss regional aquitard characteristics. The
coals are also recharged in drainage areas. In the study area, coal seams
often lie directly beneath alluvium, and they generally dip away from the
drainage (see Figure 5-12). The alluvium receives water from surface events
and from local groundwater discharge of the Wasatch beds. The alluvial stream
beds are probably very important interchange areas in the groundwater system
in the Eastern Powder River Basin.
113
-------
Natural discharge areas are less obvious than recharge areas. Depth to
the coals increases as they dip to the west. Some water is lost as downward
leakage to the lower members of the Fort Union Formation. Most of the water
in the coal seam generally moves westward under a small gradient under con-
fined or semiconfined conditions. Water wells account for most of the
discharge from the coal seam aquifers. Although the overlying sediments may be
just as permeable as the coal in some areas (Rahn, 1976), most wells have been
completed in the coals because of their local reputation as water-bearing zones.
The majority of water wells in the study area are small stock watering wells
which are pumped with windmills. There are also a number of domestic wells.
Seepage from the coal seams will occur when they are mined. As a rule of thumb,
most companies predict that they will have to pump about 70,000 to 120,000 gpd
from their pits.
Fort Union Aquifers Below the Coal Seams —
Groundwater occurs at various depths below the Wyodak-Anderson coal seams.
Strata immediately beneath the coal seams are predominantly clay-rich, and
these units can confine deeper Fort Union water. Most of the mines claim that
little or no upward leakage is expected to enter the mine pit through these
confining layers. At greater depths, however, aquifers containing relatively
good quality water exist. The City of Gillette has many "soft water" wells
completed approximately 600 feet below the base of the coal seam. Transmis-
sivities are on the order of 104 gpd/ft, and storage coefficients reflect con-
fined conditions. All of the mines are completing their supply wells in these
deeper Fort Union aquifers.
These aquifers may receive downward leakage from overlying strata, but
their predominant source of recharge is from their outcrop areas to the east.
Discharges from the aquifers include pumpage, and upward or downward leakage to
adjacent aquifers.
Site Specific Hydrogeology
Hydrogeologic descriptions of each of the seven mines in the project area
follow.
AMAX Belle Ayr South-
The Belle Ayr South mine is located approximately 20 miles south of Gil-
lette. The mine began producing coal in 1975. Hydrogeologic changes at this
mine may be indicative of similar changes to watch for at the other mines in
the area.
Wasatch overburden in the vicinity of the Belle Ayr South mine is selec-
tively saturated with groundwater. Wet areas are characterized by sandstone
lithologies, while the dry areas are shales or siltstones. The Wasatch Forma-
tion thickens to the west of the present pit, and it is anticipated that more
saturated sandstone paleochannels will be encountered as mining continues.
Pump test data for Wasatch wells are shown in Table 5-6 and Figure 5-13. The
low transmissivities and semiconfined storage coefficients are similar to the
results of other pump tests in Wasatch wells.
114
-------
TABLE 5-6. AQUIFER PARAMETERS IN THE BELLE AYR MINE VICINITY
(AMAX Coal Co., 1977)
err
Well No.
N-l
M-3
N-5
N-6
N-9
N-ll
N-13
N-14
481
WRRI-7A
WRRI-10
Aquifer
compl eted
Wyodak
Wyodak
Uasatch
Wyodak
Open hole
through
Wyodak
(uncased)
Uasatch
Uasatch
Open hole
through
Uyodak
(uncased)
Uyodak
Fort Union
Uyodak
Average values
Azimuth
to observation
well
-
N-S
E-U
-
-
N-S
-
E-U
E-U
-
Pump test
Transmlssivity
(gpd/ft)
1353
6175
-
-
3495
™
-
1528
3542
3218
results
Storage
coefficients
.
0.01
0.0018
-
-
0.0054
'
-
0.0022
0.0038
0.0046
Transmissivity
(gpd/ft)
recharge (in/yr)
524
9894
187
2755
1140
1959
2368
4133
1677
488
-
2512
Calculated Aquifer
recharge Calculated thickness
(in/yr) porosity (ft)
0.12 65
0.14 NA 62
33.0 0.04 100
65
95?
50
1.48 - 54
80
0.13 60
3.13 0.12 60
90
-
-------
en
1.0
U)
0. I
IO
'3
LEGEND
A WRRI-7A
• N-5
x WRRI - 10
+ N-I3A
RECOVERY DATA
CIRCLED
T
WRRI -7A
MATCH
POINT
©
0
© ©
-WRRI-10
MATCH
POINT
® X
N-5-MATCH
POINT
®x
©
e +
-+- N-I3A
1 MATCH
POINT
©
e.'
N-5
W(u)=l
l/u = IO
WRRI- WRRI
N-I3A 10 7A
rs=3.5
t /min
^-2
1-1
10
Figure 5-13. Plots of results from four pump tests near Belle Ayr Mine (AMAX Coal Co., 1977)
-------
Scoria aquifers are locally significant at this mine. Initial cuts into
scoria hills for road gravel encountered water and some water is still being
pumped from these areas. AMAX is trying to determine the source of this
water in order to evaluate the problem (Ted Terrell, AMAX Coal Co., person-
al communication, 1977). As mining progresses to the west, no significant
scoria areas will be encountered and large inflows to the pit from clinkers
are not anticipated.
Figure 5-14 is an isopach map of the alluviated areas along Caballo
Creek. The alluvium is seldom thicker than 30 feet, with channel widths
ranging from 400 to 2,000 feet (AMAX Coal Co., 1977). AMAX has not publish-
ed the results of any aquifer tests in the alluvium, except to say that such
tests show low permeabilities in the alluvium (AMAX Coal Co., 1977).
The coal seams at Belle Ayr South are moist and some of the fractures
conduct significant groundwater flow. Field observations note that at the
highwall some fractures discharged approximately 15 gpm. AMAX estimates that
approximately 100,000 gpd is pumped from the mine (U.S. Geological Survey,
1975). Coal transmissivities and storage coefficients are given in Table
5-6. Such data are local, and will vary with the number of water-bearing
fractures which are penetrated.
Well hydrographs for wells in the Wasatch Formation, the coals, and the
alluvium are shown in Figures 5-15 through 5-17. Monitoring wells have been
installed by the Wyoming Water Resources Institute at the locations described
in Table 5-7.
AMAX Eagle Butte-
The Eagle Butte Mine, located just south of the North Rawhide Mine, has a
hydrogeologic situation similar to that of the Rawhide Mine. Groundwater oc-
curs above, below, and in the coal seams, as well as in the alluvial areas and
in clinker deposits.
The Wasatch Formation contains some groundwater but cannot be thought of
as a regional aquifer. Some overburden wells drilled on the lease, such as
wells D-534 and C-592, encountered no water in the Wasatch Formation (see Fig-
ures 5-18 and 5-19). As shown on the geologic cross-sections, Figures 5-18
and 5-19, lithologies within the Wasatch Formation are discontinuous. There-
fore, the aquifer parameters shown in Table 5-8 are probably not representative
of the entire Wasatch Formation. Transmissivities listed for two pump tests
were 30 gpd/ft and 177 gpd/ft. More tests are needed to verify these results.
Storage coefficients will most often reflect unconfined conditions, although
the 0.003 figure of Table 5-8 indicates some locally confined areas.
Scoria'deposits are located at most of the topographically high areas on
the Eagle Butte lease area, and adjacent to the coal, as shown on Figures 5-18
and 5-19. AMAX has not indicated the extent of their drilling program in
scoria, nor have they discussed the percentage of scoria areas which are wet
or dry. The pump test on well GN-8, which penetrated a scoria zone, yielded
relatively high transmissivities (140,000 gpd/ft) as shown in Table 5-8.
Storage coefficients should reflect unconfined conditions.
117
-------
00
21 T47N
COAL TEST HOLE
ISOPACH OF UNCONSOLIDATED
DEPOSITS, DASHED WHERE
APPROXIMATED
STREAM
PROPERTY BOUNDARY
105°22'30"
Figure 5-14. Isopach map of unconsolidated deposits along Caballo Creek (AMAX Coal Co., 1977).
-------
0)
Lu
oe
§
is
o
_i
LU
CO
a.
LU
O
10
15
y 30
35
45
115
120
125
1974
WRRI-12 UNCONSOLIDATED DEPOSITS
N-5 WASATCH AND COAL
N-l COAL
1975
1976
Figure 5-15. Hydrographs of three wells (AMAX Coal Co., 1977),
119
-------
po
o
u.
QC
t/>
Q
Z
O
-------
116.5
116.6
*>
£116.7
116.8
ff>
O
116.9
O
oc
O
§ 117.0
ro
a.
ui
Q
_i
ui
oc
LU
117.1
117.2
117.3
117.4
117.5
I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I
10
15
20
MAY
15
31 1
10
15
JUNE
20
25
30 1 4
JULY
Figure 5-17. Water level fluctuations in well 481, May 10 - July 4, 1974 (AMAX Coal Co., 1977).
-------
ro
ro
TABLE 5-7. WELL COMPLETION DATA, WRRI GROUNDWATER OBSERVATION
WELLS, AMAX BELLE AYR SOUTH (AMAX Coal Co., 1977)
Well No.
WRRI-2
WRRI-3
WRRI-5
WRRI -5- A
WRRI-7
WRRI-7-A
WRRI-8
Location
SE>s,SE%,NW»s
Sec! 35*
T48N.R71W
Sec! 27*
T48N.R71W
Sec! 34
T48N.R71W
Sec! 34*
T48N.R71W
NW%,SWJj,SW»i
Sec! 27*
T48N.R71W
NW%,SWJs,SW>s
Sec. 27
T48N.R71W
Sec! 33*
T48N.R71W
Initial
Total Perforated Depth to water
depth depths coal level
Formation (feet) (feet) (feet) (ft.bl.g.s.)
Cast 36 30-36 NA 30
overburden
Wyodak 206 166-206 166 186
seam
Wyodak 135 75-135 70 76
seam
r
Wyodak 135 75-35 70 76
seam
Fort Union 329 257-329 170 245
Fort Union 329 257-329 170 245
Alluvium 20 NA NA 9
Present
water
level
(ft.bl.g.s.) Remarks
18 Located ^60' N of
stream south of mine
NA Plugged off at 122'
NA Plugged off at 70'
with bentonite mud
76 Located =20' S of
WRRI-5, SEAM project
108 Coal 1s cased off.
107 Located 35' W of
WRRI-7
9 75' N of bridge abut-
ments. SEAM project
WRRI-9 Stfc.NE^.NE*
Sec. 35
T48N.R71W
Alluvium 18
NA
NA
-20' E of ponded
Caballo Creek. SEAM
project
(continued)
-------
TABLE 5-7 (continued)
ro
oo
Well No.
WRRI-10
WRRI-10-A
WRRI-11
WRRI-12
N-l
N-3
N-3-A
N-5-A
Total Perforated Depth to
depth depths coal
Location Formation (feet) (feet) (feet)
NE%,NE>$,SW>i Wyodak 281 188-281 188
Sec. 31 seam
T48N.R71W
NEH.NEJs, SW% Wyodak 281 200-281 188
Sec. 31 seam
T48N.R71W
NESs,NE»i,SWJs Wasatch 194 90-124 NA
Sec. 31 174-194
T48N.R71W
NE%,NE»i,SW»4 AlluviUm 20 0-20 NA
Sec. 31
T48N.R71W
SWINE'S, SW% Wyodak 190 130-190 130
Sec. 27 seam
T48N.R71W
SW^,NW»s,NWJs Wyodak 122 50-122 44
Sec. 3 seam
T47N.R71W
SWs,NWs,NW% Wyodak 110 50-110 46
Sec. 3 seam
T47N.R71W
SE%, SE>sSE% Wasatch 135 40-135 NA
Sec. 28
T48N.R71W
Initial Present
water water
level level
(ft.bl.g.s.) (ft.bl.g.s.) Remarks
30.2 30.2 Located 47
WRRI-12
30.2 30.2 Located 47
WRRI-12
6.8 6.8 Located 66
WRRI-10
9 9 Located 60
streamgage
project
168 119 Core hole
reamed out
85 69 Core hole
85 69 Located 38
1 N of
1 N of
1 N of
' NW of
. SEAM
that was
and cased
1 of N-3
40 41 Offset of core hole
(continued)
-------
TABLE 5-7 (continued)
no
Well No. Location
N-5-B SE%, SENSE'S
Sec. 28
T48N.R71W
N-6 SEJj.SEJs.SEJg
Sec. 33
T48N.R71W
N-ll SWSj.NWJs.NWsj
Sec. 28
T48N.R71W
N-13 SEJ" SW'' SE5-
Sec! 29*
T48N.R71W
N-13-A SE5s,SW>s,SEJs
Sec. 29
T48N.R71W
481 SWs SE% SEk
Sec! 27*
T48N.R71W
* •
Formation
i Wasatch
; Wyodak
seam
i Wasatch
: Wasatch
Wasatch
Wyodak
seam
— '
Total
depth
(feet)
135
140
207
190
190
160
-- .-.-.-
Perforated
depths
(feet)
40-135
75-140
140-200
80-170
80-170
100-160
Depth to
coal
(feet)
NA
70
207
190
190
95
Initial
water
level
(ft.bl.g.s.)
40
93
NA
NA
NA
110
Present
water
level
(ft.bl.g.s.)
41
37
85
60.5
60
118
Remarks
Located 50' W of
N-5-A
Core hole.
SEAM project
Offset of core hole.
SEAM project
Offset of core hole.
SEAM project
Located 28.5' N of
N-l. SEAM project
Core hole
-------
4500-
en
'r- 4400
co
E
OJ
O
4300-
2 4200
UJ
4100-
4000-
NORTH
O
(0
I
O
I
BROADUS HIGHWAY
SOUTH
o>
m
m
o
l
ro
«n
1
o
1
0
in
i
o
i
ro
i
O
I
o>
o
1
00
fO
1
Q
1
in
ro
i
a
i
Sh
Figure 5-18.
Geologic cross section from the center of the east line, section 22, to the NE corner,
SE%, NE%, section 27, T51N, R72W. Well numbers are indicated across top. Dotted
unit in hole D-459C is same scoria encountered in nearby well GN-8. Static water
level is marked by dotted line between inverted triangles (AMAX Coal Co., 1977a).
-------
NORTH
SOUTH
-------
TABLE 5-8. SUMMARY OF AQUIFER TEST DATA (AMAX Coal Co., 1977a)
ro
Test
well
No.
BAN-1A
BAN- 3
BAN- 4
BAN- 5
GN-6
GN-7
GN-8
GN-9
D-305
Date
of
test
12-23-75
12-12-75
8-18-75
8-18-75
8-18-75
23-28-75
1-6-76
1-6-76
1-7-76
1-7-76
6-27-74
6-27-74
Type
test
Sp. Cap.
Pump
Sp. Cap.
Sp. Cap.
Sp. Cap.
Sp. Cap.
Sp. Cap
Pump
Sp. Cap.
Sp. Cap.
Sp. Cap.
Pump
. Length
Observ . of
well test
No. (hrs.)
3.42
BAN-1 3.42
0.50
0.88
0.82
0.35
4.63
GN-7B 4.63
0.78
0.33
10.25
D-305A 10.25
Prod.
rate
(gpm)
0.63
-
7.5
7.2
3.5
0.8
2.1
-
13
0.05
1.6
-
Final
draw-
down
(ft)
27.0
0.50
28.9
57.9
3.2
29.2
11.1
0.27
0.1
30
-
0.56
Spec.
cap.
(gpm/ft)
0.02
-
0.26
0.12
1.1
0.027
0.19
-
130
0.002
-
-
Geol.
fm.
Was.
Was.
Coal
Coal
Coal
Coal
Coal
Coal
Coal & Burn
FU
-
-
Trans,
(gpd/ft)
30
177
240
130
1200
20
300
676
140,000
5
-
1280
Aquif.
Thick.
(ft)
30
30
101
100 ?
100 ?
33
140
140
58
40
113
113
Perm.
(gpd/ft2)
1
5.9
2.4
1.3
12
0.61
2.1
4.8
2400
0.125
-
11
Storage
coeff. Comments
-
0.003 r = 55'; Bound. Effects
-
-
-
-
-
0.0011 r * 124'; Leaky Aquifer
-
- Pumped by air jet
-
0.0022 r = 38.5
-------
The major occurrence of alluvium on the lease is in the channel of Little
Rawhide Creek. The streambed alluvium trends north through the lease area.
There is also some alluvium in the Dry Fork Little Powder River streambed at
the extreme southeastern corner of the Eagle Butte mine. The thickness of the
alluvium is probably not greater than 40 feet at any point on the lease (AMAX
Coal Co., 1977a). No pump test data have been published by AMAX for the
alluvial areas.
The coal seams on the Eagle Butte lease yield water to wells. The coal
thins towards the north (Figures 5-18 and 5-19) and is generally 75 feet thick
throughout the lease area. Permeability in the coal is secondary in that all
water flows through fractures. AMAX has not indicated that fracture orienta-
tion or developments have been studied. Hydraulic characteristics include
transmissivities ranging from 20 to 1,200 gpd/ft (Table 5-8), and semiconfined
storage coefficients (0.0011).
The water levels in all formations on the Eagle Butte lease are relative-
ly stable. Annual fluctuations are generally less than 3 feet, as shown by
Table 5-9. The well hydrographs (Figures 5-20 and 5-21) show that seasonal
variations are slight, and that premining water levels are fairly stable.
The potentiometric surface in the Roland coal is continuous with the sur-
face shown at the North Rawhide Mine. A groundwater mound exists at the west
central edge of the lease, indicating a possible recharge area or poorly con-
fined conditions. The primary direction of groundwater flow on the lease is
northwest.
AMAX has published data on 30 monitor wells being used on the Eagle Butte
property. Completion information can be found in Table 5-10. The well loca-
tions are also given in the table.
ARCO Black Thunder -
Fairly extensive groundwater investigations have been conducted on the
Black Thunder lease by Atlantic Richfield and by the University of Wyoming.
These researchers have paid considerable attention to the Roland coal aquifer,
Wasatch aquifers, and pre-Roland aquifers. Scoria and alluvial aquifers are
relatively unstudied.
Wasatch aquifers on the lease are local phenomena. Lenticular sandstones
transmit small amounts of water (usually less than 15 gpm) to wells. No pump
tests have been run on Wasatch wells. The Wasatch overburden thickens from
east to west on the mine site, and where groundwater does exist, such waters
are unconfined.
Scoria units exist to the east of ARCO's proposed mine. For this reason,
minimal study of these clinker units has occurred. ARCO notes that such scoria
beds have high permeabilities, with water transmitting capabilities similar to
those of gravels. Alluvium exists in the valleys of Little Thunder and North
Prong Creeks. The alluvium has not been studied to any extent, but ARCO indi-
cates that lithologies include unconsolidated gravels, sands, and clays.
128
-------
TABLE 5-9. STATIC WATER LEVELS MEASURED ON UNINSTRUMENTED WELLS (AMAX Coal Co., 1977a)
Static water levels (ft below casing top)
Well No.
BAN- 3
BAN- 4
BAN- 5
GN-6A
GN-6B
GN-6
GN-7
GN-7A
GN-7B
GN-7(OB)
GN-8
GN-9
GN-9A
GN-9(C)
GNH-1
GNH-3
GNH-4
GNH-5
GNH-6
GNH-10
GNY-11
GNH-12
0305A
AMAX #8
8/18/75
74.6
37.1
79.2
-
-
-
-
-
-
-
-
-
-
-
8.1
6.6
13.4
11.6
9.0
8.3
-
2.9
-
-
12/18/75 to
12/4/75 1/7/76 1/10/76
75.0 (Casing cut 1.5')-
29.0
79.0
Dry hole — not cased
-
25.8
7.0
10.1
6.9
7.3
63.4
72.3
11.3
28.0
9.5
8.6
15.4
13.3
9.7
8.9
9.7
4.1
-
- -
2/13/76 3/2/76
74.5
28.9
78.9
-
-
26.7
6.5
-
6.8
7.3
77.9
68.2
9.9
-
7.6
4.9
'11.6
11.3
6.5
8.5
10.7
4.1
79.0
13.1
3/31/76
78.8
28.7
-
-
-
26.4
6.1
7.0
6.7
-
63.9
63.3
9.9
-
6.7
4.3
9.8
9.7
6.6
11.9
10.5
3.9
-
20 ?
5/5/76
73.6
28.3
80.0
-
-
26.6
-
_
.
-
-
60.1
9.9
-
6.2
2.1
9.9
10.5
6.4
8.0
9.4
3.5
-
-
6/15/76
74.0
20.6
78.9
19.8
-
26.4
6.7
7.0
7.0
-
63.5
-
-
-
6.0
3.9
7.4
11.0
7.9
7.9
Casing
3.4
77.5
-
7/2/76
74.3
28.6
79.1
-
-
25.8
6.9
7.3
7.3
-
63.5
57.0
10.0
~
6.2
4.5
9.7
-
-
8.2
broken
4.9
78.6
-
8/1/76 9/1/76
-
29.3
79.2
20.1
-
24.8
7.6
7.9
5.8
-
64.9
54.6
9.7
-
8.6
7.5
Casing
12.5
9.4
8.9
-
Plugged
-
-
10/13/76
-
29.8
79.0
-
-
25.0
7.5
8.1
7.6
-
64.4
54.1
9.5
-
9.1
6.5
broken
12.4
9.8
9.0
10.0
-
-
-
11/1/76 12/2/76
75.8
29.9
79.1
-
-
25.5
7.2
7.8
7.2
-
63.5
56.6
-
-
6.7
4.1
-
13.8
13.2
12.5
-
-
-
-
-------
4260
4250
4240
oo
o
D-305
D-376
4210
4200
i i i i i i i
_ BAN-2
J i*"T""i""" i"~i'
Q-' K > o
UJ O O LU
w o z o
1974
1975
1976
Figure 5-20. Monthly water level elevations in instrumented monitor wells. The rise in
water level in D-376 during summer and fall of 1975 is probably due to a
change in monitoring personnel (AMAX Coal Co., 1977a).
-------
4270
2 4260
4250
BAN-1
flARSHALL N0.1
D-409
I I I I I I I I I I I I I I I 1 I I I I I I I I I i i
Si h' 5i M z pi of g: >- z j d p: J; 5j cj a: d ge of >- z J d p: K >
1974
1975
1976
Figure 5-21. Monthly water level elevations in instrumented monitor wells. The sharp drops
in water levels in D-409 during fall 1975 are probably due to a change in
monitoring personnel (AMAX Coal Co., 1977a).
-------
TABLE 5-10.
MONITOR WELL INVENTORY FOR AMAX'S EAGLE BUTTE MINE. ELEVATION SOURCES.ARE
LEVELINE SURVEY (S), TOPOGRAPHIC MAPS (T), AND COMBINATIONS OF THE TWO (Tc)
(AMAX Coal Co., 1977a)
oo
ro
Location
Well No.
BAN-1
BAN-1A
BAN- 2
BAN- 3
BAN- 4
BAN- 5
GN-6
GN-6A
GN-7
GN-7(OB)
GN-7A
GN-7B
GN-8
BN-9
GN-9(C)
\*> • J \ V* f
GN-9A
D-305
0-305 A
D-376
D-409A
GNH-1
GNH-3
GNU- 4
GNH-5
GNH-6
GNH-10
GNH-11
fiNH-1?
UI1M w i L,
Marshall #1
AMAX #8
Coordinates (ft)
1720 fel
1670 fel
2000 fnl
728 fnl
2770 fnl
1775 fnl
1290 fnl
20 fnl
1280 fsl
1280 fsl
1460 fsl
1660 fsl
1620 fsl
1620 fsl
1620-fsl
1620 fsl
2620 fsl
2581 fsl
680 fnl
Swenr
520 fsl
160 fsl
810 fsl
2340 fsl
2540 fsl
2830 fsl
1640 fsl
3120 fsl
2730 fsl
NW, NW,
, 150
, 160
, 2050
, 2160
, 1880
, 20
, 20
, 20
, 60
, 60
, 60
, 60
, 20
, 770
, 770
, 830
, 2210
, 2210
00
, 2650
, 2230
, 3020
, 2820
, 3530
, 2910
, 2890
, 2890
, 70
NW, NE
fnd
fnd
fel
fel
fwl
fwl
fwl
fwl
fwl
fwl
fwl
fwl
fwl
fel
fel
fel
fel
fel
fwl
fwl
fwl
fwl
fwl
fwl
fwl
fwl
fwl
fwl
Sec
22
22
26
16
16
16
21
21
21
21
21
21
23
28
28
28
27
27
23
16
16
16
16
16
16
16
16
27
28
T
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
BIN
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
51N
R
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
72W
Elevation
Ground
(ft.msl)
4349
4345
4336
4227.8
4202.8
4276.8
4290.6
_
4252.5
4252.5
4252.2
4252.1
4312.9
4279.3
4279.3
4277
4330.3
4328.8
4291.4
4319.5
4200.2
4202.7
4197.7
4187.9
4182.2
4182.81
4191.9
4177.0
4283.4
4275
Source
S
S
T
S
S
S
T
_
S
S
S
S
S
S
S
T
S
S
S
S
S
S
S
S
S
S
S
S
T
T
Casing
height
(ft)
0.7
1.5
1.0
1.6
2.1
0.8
3.0
0.0
1.4
1.3
0.6
1.3
1.4
2.0
2.2
2.1
l."5
1.4
0.7
0.4
0.8
1.0
3.5
1.1
3.2
1.1
3.5
1.7
0.0
1.9
Total
depth
(ft)
210
218
390
224
173
160
76
117
260
74
260
157
117
313
261
320
356
365
330
330
17
13
15
17
31
18
15
15
—
58
Casing
depth
(ft)
0-195
0-218
0-240
0-224
0-173
0-160
0-76
None
0-260
0-74
0-26
0-20
0-117
0-307
0-183
0-107
0-240
0-240
0-158
0-155.
17
12
14
15
14
12
11
llh
58
Cement
or
packer
depth
(ft)
Surf.
Surf.
240
82
54
123
42
_
76
_
76
—
60
263
None
57
240
240
158
155
None
None
None
None
None
None
None
—
—
30
Perf.
interval
(ft, depth)
95-195
118-218
Open hole
164-244
123-173
125-160
42-75
_
180-260
54-74
18-260
0-20
60-307
307-267
163-183
67-107
240-356
240-365
158-330
155-330
14-17
9-12
11-14
12-15
11-14
9-12
8-11
8%-llh
—
30-58
Formation
aWas.
Was.
Coal
Coal
Coal
Coal
Coal
_
Coal
bQal.
Coal
Qal.
Coal&Burn
CPU
Coal
Was.
Coal & FU
Coal & FU
Coal
Coal & FU
Qal.
Qal.
Qal.
Qal .
Qal .
Qal .
Qal.
Qal.
Coal
Logs
(X-same)
hole)
D482
D482.X
0339.X
X
X
H167
X
X
X
GN-7
GN-7
GN-7
D459C
X
GN-9
GN.-9
GN-9.X
D-305
X
X
X
X
X
X
X
X
X
X
5070
C421
Casing
desc.
4" PVC
4" PVC
4" PVC
4" PVC
4" PVC
4" PVC
5" PVC
None
5" PVC
1" Stl
5" PVC
5" PVC
5" PVC
5" PVC
1" Stl
5" PVC
5" PVC
5" PVC
5" PVC
5" PVC
IV Stl
iy sti
IV Stl
IV Stl
IV Stl
IV Stl
IV Stl
IV Stl
4" PVC
5" PVC
Date
drilled
6-18-74
6-20-74
6-21-74
9-75
9-75
9-75
12-75
12-75
12-75
12-75
12-75
12-75
12-75
12-75
12-75
12-75
6-22-74
6-24-74
6-25-74
6-21-74
9-75
9-75
9-75
9-75
9-75
9-75
9-75
9-75
1973(?)
1-76
"Wasatch
Quaternary Alluvium
cFort Union
-------
The pre-Roland aquifer is composed of fractured shales and other fine-
grained materials. These materials have low permeabilities, but they are satu-
rated. The University of Wyoming study indicates that the pre-Roland aquifer
is confined, but the nature and/or location of the confining layer is unclear.
It is assumed that the strata directly beneath the Roland seam must act as the
confining layer. The University of Wyoming study indicates that some upward
leakage may occur through this confining layer. As shown by Table 5-11, one
pump test in the pre-Roland material did not yield interpretable data. A second
pump test did give a transmissivity value of 7,200 gpd/ft, indicating that the
pre-Roland material may be as permeable or more so than the Roland coal itself.
The Roland coal has been pump tested many times as indicated by Table 5-11.
Transmissivity values ranged from 32 to 25,000 gpd/ft, with an average value of
35,000 gpd/ft, and storage coefficients generally reflected confined conditions
or semiconfined conditions. ARCO has indicated in its Mining Plan Update (1977)
that the coal is virtually full of water except for some areas in the eastern
part of the lease. In these areas, water table or semiconfined conditions are
expected. The Roland seam is approximately 70 feet thick over the lease area.
The potentiometric surface map submitted by ARCO in its 1977 Mining Plan
Update shows levels monitored in 1974 (Figure 5-22). Groundwater flow in the
Roland aquifer generally had a westward component, as supported by carbon-14
age information submitted by the University of Wyoming (Figure 5-23). ARCO has
increased its number of monitoring wells since 1974 and, hopefully, is studying
interaquifer exchanges and potentiometric surface changes. Figure 5-24 shows
monitor well locations.
Carter North Rawhide —
The groundwater systems beneath Carter's Rawhide Mine lease are described
in the company's May 1977 Mining Plan Update. Groundwater exists in the Wasatch
Formation, the scoria hills, the alluvium, the coal seams, and above and below
the coal seams as indicated by Table 5-12.
Approximately 50 percent of the Wasatch overburden is composed of sand-
stones. These sandstones are interbedded with the clays, shales, and silt-
stones which comprise the remainder of the Wasatch Formation. The discontinuous
character of and the questionable hydraulic connections between the sandstone
units limit their performance as prolific water-bearing systems. The Wasatch
•aquifers generally have an unconfined potentiometric surface, although local
shales or clays may confine the water for short distances.
The scoria deposits at the Rawhide mine bear close inspection. In late
1976, a scoria hill was breached during construction excavation. Carter had
to pump 6,000 gpm for several days to dewater the hill. Water levels were
measured frequently throughout this dewatering, and the declines were analyzed
to get an idea of the hydraulic properties of the scoria. Transmissivity
values on the order of 10& gpd/ft were calculated. Not all clinker (scoria)
deposits are saturated, however, and additional data are required to adequate-
ly assess scoria hydrogeology.
133
-------
TABLE 5-11.
CO
CALCULATED VALUES OF TRANSMISSIVITY AND STORAGE COEFFICIENT
IN ROLAND FORMATION (ARCO, 1977)
Pumped
Rl
R2
R2
R5
R5
R6
R7
R8
R9
R10A
RIGA
R12
R12A
R12B
PR12E
R17A
R151
R153
R154
Silo #2
Stuart
Ranch
" • ' 1 - Ill — nil —•nil-.
Obser-
vation Aquifer
_
—
R2A
—
R-5A
—
—
-
_
_
R10D
_
R12B
RI2C
—
R17
_
_
_
_
—
Roland
Roland
Roland
Rol and
Roland
Roland
Roland
Roland
Roland
Roland
Roland
Roland
Roland
Roland
Pre-
Roland
Roland
Roland
Roland
Roland
Pre
Roland
—
Test
method
Jacob9
Jacob
Leaky
aquifer
Jacob
The is-
Jacob
Jacob-
Jacob
Jacob
Jacob
Jacob
Jacob
Jacob
Theis
Data
Theis
Jacob
Jacob
Jacob
Jacob
Jacob
— — ..-[. r.
Obser-
vation Flow
radious rate
(ft) (gpm)
—
—
93
_
93
—
—
—
_
_
60
_
24.
39.
too
100.
_
_
_
—
—
6.8
21.4
21.4
21.8
21.8
15.0
20.0
30.0
5.0
5.0
50.0
5.0
5 5.0
5 15.0
erratic to
0 12.0
23.2
6.0
4.0
50.0
50.0
•' '" • •"•• • ..-nil.
Average
trans- Storage
missivity co-
(gpd/ft) efficient
4,600b
5,600b
3,400
3,800b
5,600
100C
3,800b
4,500b
1 ,300C
4,400b
25,000d
450b
750d
650
analyze
300
600b
32C
32 b
7,200b
790
Comments
— Data erratic; results questionable
_
4.4 x lO'4
*»
2.5 x 10-*
Data skewed
Leaky condition
_
Slightly skewed data
- Data skewed; results questionable
_
Data skewed at end
- ~Data erratic between drawdown and
_
^
7.0 x lO-3
_
2.0 x 10-3
1.5 x 10-6
6.0 x 10-4
_
_
_
-
—
recovery
Data erratic
Data skewed
Data slightly skewed
Data erratic
Data reasonable
Data did not fit curve well
Data fit Theis better than
Data erratic
Data skewed
Data somewhat erratic
Data skewed slightly
Data skewed
leaky
a
Jacob method works well only in homogeneous and isotropic artesian aquifers with a small radius and a large
time period (Walton, 1970). May be a reason for skewed and erratic test data and results.
^Average value between drawdown and recovery test analyses
°Recovery test only analyzed
dDrawdown test only analyzed
-------
LEGEND
MONITORING WELL WITH
STATIC WATER LEVEL
6000 FEET
Figure 5-22. Potentiometric surface map, ARCO Black Thunder Lease
(ARCO, 1977).
135
-------
R 70 W
R-2 (30,000 ± 2430)
R-5 (24,220 ± 3400)
R-7 (33,740 ±4100)
R-IO (17,300 ± 580)
R-ll (26,270 ± 1380)
R-15 (14,330 ± 440)
SILO (PRE-(I 1,170 ± 430)
ROLAND)
(PRE-ROLAND)
LEGEND
CARBON-14 AGE DATES (years)
8000 FEET
Figure 5-23. Groundwater flow in Roland aquifer
(University of Wyoming, 1976).
136
-------
R,,WI »R2 R3
17 16
(R)a commercial well
R 7.0 W
W2
BT-77
LEGEND
• MONITORED WELLS ON SITE
A STOCK WATER WELLS
CONTINUOUS RECORDER ON
ROLAND FORMATION WELL
SOOO FEET
Figure 5-24.
Monitor well locations, ARCO Black Thunder Lease
(University of Wyoming, 1976).
137
-------
CO
00
TABLE 5-12. SUMMARY OF ELEVATION OF WATER LEVEL IN ROLAND COAL, SMITH COAL,
AND OVERBURDEN COMPARED TO ELEVATION OF TOP OF ROLAND COAL AND
SMITH COAL (Carter Oil Co., 1977)
Roland coal
elevation
Well
site
NRH- 1
NRH- 2
NRH- 3
NRH- 4
NRH-239
NRH-241
NRH-242
NRH-243
NRH-244
NRH-245
NRH-246
NRH-247
NRH-268
Coal Water
top, level,
(ft) Cft)
4,245 4,259
4,171 4,241
4,232 4,363b
4,128 4,155
— —
— —
4,172 4,180
4,235 4,218
4,111 4,123
4,090 4,155
4,017 4,150
4,106 4,204
4,256 4,248
Differ-
ence9
Cft)
+ 14
+ 70
+131b
+ 27
—
—
+ 8
- 17
+ 12
+ 65
+133
+ 98
- 7
Smith coal
elevation
Coal
top,
Cft)
—
4,140
4,195
4,095
4,274
4,131
4,140
4,200
4,065
4,041
3,981
—
4,223
Water
level ,
Cft).
_
4,164
4,187
4,146
4,197
4,113
4,153
4,155
4,129
4,180
4,140
—
4,203
Differ-
ence3
Cft)
_
+ 24
- 8
+ 51
- 77
- 18
+ 13
- 45
+ 64
+139
+159
-
- 20
Roland coal
C+) above
C-) below
Smith coal
water level ,
Cft)
_
+ 77
+176b
+ 9
-
—
+ 27
+ 63
- 6
- 25
+ 10
—
+ 45
Overburden
water leyel
elevation,
Cft)
—
4,244
—
-
-
-
4,126
4,244
-
—
-
4,198
4,276
Hfater level (+) above (-) below top of coal
3Water level questionable
-------
Alluvial aquifers are an important part of the hydrogeologic conditions
at the Rawhide mine. Composed of silt, sand, and gravel, these units are
moderately permeable. Saturated thicknesses range from 20 feet at Rawhide
Creek to 40 feet along Dry Fork Little Powder River (Carter Oil Co., 1977).
The alluviaraquifer systems are 100 to 1,000 feet wide, and roughly follow
the meandering courses of the streams.
The coal seams carry groundwater in their fractures. The development of
the fractures determines the water-bearing characteristics of the coal aqui-
fer. In its mining plan update, Carter Oil Co. (1977) published pump test
information for only one well, #NRH-2, showing values of 115 gpd/ft for trans-
missivity in the Roland coal and of 310 gpd/ft for the Smith coal. Storage
coefficients were 0.0002 and 0.003 for the Roland and Smith coals, respective-
ly. These storage coefficients indicate confined conditions, although water
level measurements show that the coal seams are not fully saturated in some
areas. Storage coefficients in these unsaturated areas will be in the range
from 0.001 to 0.10.
The Carter Oil Co. (1977) Plan Update notes that circulation patterns are
complex and not very well understood. Relationships among all four aquifers
will have to be studied and reported. Water well descriptions are contained
in Table 5-13.
Kerr-McGee Jacobs Ranch-
The Jacobs Ranch mine is relatively dry when compared with mines in the
northern part of the study area. Groundwater occurs primarily in the Wasatch
overburden and in the coal seams. There is no significant alluvial area,
and according to Kerr-McGee Coal Corp. (1977), no extensively saturated
scoria regions have been encountered.
As shown on Figure 5-25, a scoria-coal contact exists on the eastern and
southern sides of the lease. Field observations of cuts into the scoria found
that the scoria was essentially dry. However, Kerr-McGee has not drilled ex-
tensively in the scoria, and the possibility of encountering saturated, highly
permeable material should not be discounted. Indeed, as the pump test at well
#2 indicates (Table 5-14), scoria in this area contributed water through coal
fractures to establish relatively large transmissivity figures.
Figure 5-26 indicates that the coal seams at Jacobs Ranch dip to the west.
Confined or semiconfined flow through fractures is probably westward. Aquifer
thicknesses on the order of 70 feet yielded transmissivity values ranging from
50 to 400 gpd/ft. However, discharge was not adequately controlled, and these
figures should be substantiated with additional data. Storage coefficients
computed at observation wells are indicative of confined aquifer conditions.
Water levels in monitor wells on the Jacobs Ranch mine have remained
relatively stable for 3 years (see Figures 5-27 and 5-28). As a potentiojnet-
ric surface map for the mining plan update, Kerr-McGee submitted a summary of
water levels from water rights adjudication data. No contours were drawn, and
the completion depths of the wells were not consistent. Monitor well informa-
tion at Jacobs Ranch is shown on Figure 5-29 and in Table 5-15.
139
-------
TABLE 5-13.
INVENTORY OF WELLS AND SPRINGS, RAWHIDE BLOCK NEAR GILLETTE, WYOMING
(Carter Oil Co., 1977) (see pages 142, 143, and 144 for explanation
of column headings and supplementary notes)
Ranch or house
Well number identification
(D (2)
51-71-6CBA-1 Mador
51-71 -6CBA-2 Mador
51-71 -CBA-3 Mador
51-71-30BAC Marshall
51-72-4AAC Wagensen
51-72-4CDC Oedekoven
51-72-4BAA Wagensen
51-72-5ADD-1 Oedekoven
51-72-5ADD-2 Oedekoven
51-72-7AAC Wagensen
51-72-7ACA School house
51-72-7DAC Daly
51-72-9CCD Wagensen
51-72-11DDA -Carter
51-72-13DDA Marshall
51-72-16BDD Wagensen
51-72-17CDB Hardy
51-72-18DAA Wagensen
51-72-20AAB Coulter
51-72-20ACB-1 Wandler
51-72-20ACB-2 Wandler
51-72-20ADB-1 Harned
51-72-20ADB-2 Harned
51-72-20BDC Vandekoppel
51-72-20CBA Vandekoppel
al. Alluvium
2. Above Roland coal
3. Roland coal
4. Smith coal
5. Base of burned coal
6. Below Smith coal
Use
(3)
D
D
D
S
S
S
D
D
S
S
D
S
S
S
S
S
D
S
D
D
D
D
S
D
S
Depth Year
• (feet) completed
(4) (5)
208.5
400R
Spring -
Spring -
Spring
149.7
352R
450R 1958R
_ _
Spring -
_ _
_ _
Spring
78.3
60.9
Spring -
127R
Spring
— —
60R 1966R
118R 1973R
250R 1970R
60R
""*" "™"
Type of
power
(6)
None
EP
_
_
—
WM
EP
EP
WM&EP
EP
WM
EP
EP
—
EP
EP
EP
EP
WM
EP
WM
MP
elev.
(feet)
(7)
4168
...
_
4275
4200
4215
_
—
_
4200
—
_
4190
4275
4232
4350
—
—
—
:
Depth to
feet
(8)
51.64
—
_
0
0
80.76
30-40R
160R
—
0
5.6
—
70.12
14.07
92R
—
—
^
—
30R
water
date
(9)
5-25-73
—
_
—
4- 6-73
4- 6-73
-
—
—
—
9-26-73
—
6-25-73
6-24-73
1973
~
~"
-
^
-
GPM Date
(10) (11)
_ —
_ —
6R
200R 9-27-73
5E
— —
10R
10R
— ~"
60-70R -
_ —
-" """
0.5 9-26-73
~~ "™
7.5
100R
~ ~
10R
Probable
producing
Used? horizon or
(12) zone3
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
\g
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Vac
TcS
«j
Yes
Yes
\t A A
Yes
MM
NO
Yes
6
6
6
5
1
6
'
1
3
2
7
f
2
1?
7
(continued)
-------
TABLE 5-13 (continued)
Ranch or house
Well number identification Use
(1) (2)
51-72-200CDB Hladkey
51-72-20DDB Hladkey
51-72-21BCB Coulter
51-72-22DAC AMAX coal
51-72-22DCC
51-72-28DAB-1 AMAX coal
51-72-280AB-2 AMAX coal
51-72-29DBB Hladkey
51-73-13ADB Daly
52-72-24BAA Rourke
52-72-25BOB Clark
52-72-26AD Clark
52-72-29DBD Thorpe
52-73-24DDD
52-73-25DCC
(3)
S
S
D
S
S
O.S
S
D
S
S
D,S
S
S
S
D.S
Depth Year
(feet) completed
(4) (5)
68
— —
48R
— —
149.7 1973E
- -
— —
- -
77.0
48.9
Spring
— —
Spring -
115.6
— —
Type of
power
(6)
MM
UM
EP
WM
WM
EP
WM
EP
WM
WM
—
—
—
EP
WM
MP
elev.
(feet)
(7)
4275
—
_
_
4270
—
—
—
4295
4055
-
—
—
—
—
DeDth to water
feet
(8)
12
12
_
_
24.55
—
_
—
60.4
12.09
—
6+
(See
25,09
—
date
(9)
_
—
_
_
6-24-73
—
_
—
7- 7-73
6-24-73
—
9-27-73
notes)
4- 6-73
—
GPM Date Used?
(10) (11) (12)
- - No
Yes
Yes
- - No
— —
Yes
No
Yes
Yes
Yes
10R - Yes
Yes
Yes
2.0+ 4- 6-73 Yes
- - No
Probable
producing
horizon or
zone3
1
?
6
?
2
?
7
?
2
6
6
?
2
2
?
al. Alluvium
2. Above Roland coal
3. Roland coal
4. Smith coal
5. Base of burned coal
6. Below Smith coal
-------
TABLE 5-13 (continued)
Explanation of column headings:
( 1) 51-71-6CBA-1 example: 51 = T 51 N, 71 = R 71 W, 6 = Section,
CBA = HE% NWJj SW%, 1 = well number 1 in this location.
( 2) Tentative information based on currently available information.
(3) D = domestic, S = stock
( 4) Distance in feet from measuring point (MP) to static water level.
(5) R = reported. E = estimated by Fisk.
(6) EP = electric power. WM = windmill.
(7) MP = measuring point (usually top of casing). Plus or minus 10 feet
accuracy.
( 8) Distance in feet from measuring point to static water level.
( 9) Date of water level observation data.
(10) GPM = gallons per minute. R = reported. E = estimated. + = plus,
or more than.
(11) Date of yield data.
(12) Present use status. Yes = currently used. No = currently not used.
Supplementary Notes:
51-71-6DBA-1. USGS card data. Valley side slope. Drilled well in pit about
8 feet deep, 6-inch casing, no pump, no power. MP about 8 feet below land
surface. Water temperature 55° F(bailer sample),conductivity 1050 on
5-25-73.
51-71-6CBA-2. USGS map data. New well about 10 feet north of well 51-71-
6DBA-1. Conductivity 1000 on 5-25-73. Photo by Fisk on 9-26-73.
51-71-6DBA-3. USGS map data. Conductivity 500 on 5-25-73. Photo by Fisk on
9-26-73.
51-71-30BAC. USGS map data. Spring flowing out of hillside. Evidently the
source of the Little Powder River. Discharge about 0.5 second feet (visual
estimate by Fisk on 9-27-73). Three photos by Fisk on 9-27-73. Norman King
of USGS (Denver) believes that this spring indicates the rate of underflow
through the coal from the south.
51-72-4AAC. USGS card data. Developed spring in bottom of upland swale.
Water temperature 42° F, conductivity 2350, pH 6.0 on 4-6-73.
51-72-4CDC. USGS card data. Upland near ridge top. Drilled well with 6 inch
casing. MP about 0.5 feet above land surface. Good measurements. Water
temperature 46.5° F, conductivity 1700, pH 6.0 on 4-6-73.
142
-------
TABLE 5-13 (continued)
51-72-4BAA. Pump setting 160 feet reported. Photo by Fisk on 9-27-73.
51-72-5ADD-1. Pump setting 200 feet reported. Good quality water, slight show
of gas reported. Discharge reported about 10 gpm for one hour, then pump is
off for 15 to 20 minutes, then 10 gpm for an hour, etc. Photo by Fisk on
9-26-73.
51-72-5ADD-2. Photo by Fisk on 9-26-73.
51-72-7AAC. Reported yield of 60-70 gpm for 2 or 3 months, then dry-up for
several months repeat cycle. Photo by Fisk on 9-26-73, no visible flow at that
time.
51-72-7ACA. School well in shed behind school. MP about 0.5 feet above land
surface. Two photos by Fisk on 9-26-73. Water softener used.
51-72-7DAC. Photo by Fisk on 9-27-73.
51-72-9CCD. Discharge about 0.5 second feet (visual estimate by Fisk) on
9-26-73.
51-72-11DDA. USGS card data. Upland. Drilled well with 6-inch casing. MP
about 2.6 feet above land surface. Conductivity 3600 on 6-25-73. Photo by
Ftsk on 9-26-73.
51-72-13DDA. USGS card data. Valley side slope. Stream (Little Powder River)
in valley. Drilled well with submersible pump, 6 inch casing. MP about
13 feet above land surface. Water temperature 50.5° F, conductivity 925 on
6-24-73. Old homestead no longer occupied. Evidently owned by Carter.
51-72-16BDD. Two-inch steel pipe extends to stock tank about 4 feet wide and
12 feet long, half-full of water on 9-26-73. Photo by Fisk.
51-72-17CDB. USGS card data. Well on top of ridge. Submersible electric
pump. Conductivity 1350, pH 6.4 on 4-6-73. Photo by Fisk on 9-26-73.
51-72-18DAA. Trickle from pipe on 9-26-73. Photo by Fisk.
51-72-20AAB. Drilled by Ruby. Trench was being dug on 9-26-73 for pipe from
well to prefab houses. Photo by Fisk.
51-72-20ACB-1. Well drilled with rotary, on top of coal, gravel packed. Water
potable but has some rust. Photo by Fisk on 9-26-73.
51-72-20ACB-2. Drilled by Western Exploration, 60 feet of sand, 5%-inch casing.
Described as "real gusher." Photo by Fisk on 9-26-73.
51-72-20ADB-1. Drilled by Ruby. Photo by Fisk on 9-26-73.
51-72-20ADB-2. Photo by Fisk on 9-26-73.
51-72-20BDC. Reported pump set at about 40 feet. Reported that yield might
be more with larger pump. Good quality water. Photo by Fisk on 9-26-73.
51-72-20CBA. Photo by Fisk on 9-26-73.
51-72-20CDB. USGS map data. Photo by Fisk on 9-26-73.
51-72-20DDB. Photo by Fisk on 9-26-73.
143
-------
TABLE 5-13 (continued)
51-72-21BCB. Drilled by Buck Williams. Well near new house on hill. Described
as "real good well." Water quality good. Photo by Fisk on 9-26-73.
51-72-22CAC. Photo by Fisk on 9-26-73.
51-72-22DCC. USGS card data. Upland valley bottom. MP 0.9 feet above land
surface. Cylinder pump, 6 inch casing. Water temperature 55° F (bailer sample),
conductivity 1875. Photo by Fisk on 9-26-73.
51-72-28DAB-1. Photo by Fisk on 9-26-73.
51-72-28DAB-2. Photo by Fisk on 9-26-73.
51-72-29DBB. Photo by Fisk on 9-26-73.
51-73-13ADB. USGS card data. Upland valley bottom. Drilled well, cylinder
pump, 6-inch steel casing. MP 0.4 feet above land surface. Static water mea-
sured with electric tape. Water obviously high in iron. Water temperature
49.5° F, conductivity 3400, pH 6.4 on 4-7-73.
52-72-24BAA. USGS card data. Upland valley bottom. Cylinder pump, 6-inch
steel casing. MP 1.4 feet above land surface. Water temperature 53° F (Bailer
sample), conductivity 1050 on 6-24-73.
52-72-25DBB. Stock tank located immediately below spring on hillside. Domes-
tic water piped from spring to Mrs. Clark's white house east of Highway 59 and
to Mrs. Clark's old red house west of highway. Photo by Fisk on 9-27-73.
52-72-26ADD. Not sure if supplied by pipe from spring 52-72-25DBB. Photo'by
Fisk on 9-27-73.
52-72-20DBD. Water flows from spring into stock tank. Reported to flow year
around. Flow on 9-26-73 about 0.1 gpm. Photo by Fisk.
52-73-24DDD. USGS card data. Valley side slope. Drilled well, 6-inch steel
casing, submersible pump. MP 0.4 feet above land surface. Good measurements.
Water temperature 51.5° F, conductivity 790, pH 6.4 on 4-6-73.
52-73-25DCC. Photo by Fisk on 9-27-73.
144
-------
-p*
en
? CLINKER EDGE (shading toward clinker)
LEASE AREA
AFFECTED AREA
Figure 5-25. Kerr-McGee Jacobs Ranch mine, Thunder Creek area (Kerr-McGee Coal Corp., 1977)
-------
TABLE 5-14.
SUMMARY OF AQUIFER TEST DATA, KERR-McGEE JACOBS RANCH MINE
(Kerr-McGee Coal Corp., 1977)
-£»
cn
Test
well
No.
36-7
37-3
28-1
12
13
Date
of
test
?
12-5-74
12-5-74
12-7-74
12-7-74
9-28-74
9-28-74
Type Observ.
of well
test No.
Pump _
Sp cap _
Pump 9C-3
Sp cap -
Pump 4C-1
Sp cap -
Sp cap
Length
of test
(min.)
0.5
60
1060
30
164
1440
1440
Prod.
rate
(gpm)
2
5
5
5
1.8
42
49
Final
draw-
down
(ft)
?
22
—
15.5
_
0.4?
145
1 Day
spec.
cap.
(gpm/
ft)
0.17
_
0.04
-
105.0
0.34
Aquifer parameters
Geol.
fin*
Sc & Co
Co
Co
Co
Co
Co
FU
Trans.
(gpd/ft)
400
52
100
112
100.000
500
Aquif.
thick.
(ft)
10
70
60
70
38
108
55
Perm.
(gpd/
ft<0
5.7
0.9
1.4
2.9
930
9
Storage
coeff. Comments
_ SWL at pump bowls -no
recovery after 30 min.
- Erratic pump rate
2.1 x 10-4 Erratic pump rate
- Erratic pump rate
1.3 x 10-5 Erratic pump rate
— No packer-possible leak-
age from overlying scoria
- -
aSc =
Co =
W =
FU =
Scoria
Coal
Wasatch
Fort Union
-------
4600
"K"
Figure 5-26. Kerr-McGee Jacobs Ranch mine cross section K-K (Kerr-McGee Coal Corp., 1977).
-------
o
to
oo
p +'
«c
LJJ CD
UJ
i
o
1
I
J—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—I—l—f-
FEB APR JUN AUG OCT DEC FEB APR JUN AUG OCT DEC FEB APR JUN AUG OCT
1974 1975 1976
Figure 5-27. Static water levels - Jacobs Ranch mine (Kerr-McGee Coal Corp., 1977).
-------
VD LU
_l
UJ
>
LU
_l
CtL
LU
-------
en
O
Figure 5-29. Kerr-McGee Jacobs Ranch mine well locations (Kerr-McGee Coal Corp., 1977).
-------
TABLE 5-15.
DESCRIPTION OF MONITOR WELL COMPLETIONS AT JACOBS RANCH MINE
(Kerr-McGee Coal Corp., 1977)
en
Location
Well No. a
1C-1
1C-7
1C-15
3C-11
4C-1
5C-2
5C-3
9C-2
9C-3
9C-10
28-1
36-7
37-3
37-7
38-7
39-7
98C-15
102C-15
#2W
#3W
North
1115288
2223011
1107229
1113220
1119276
1115375
1115336
1119281
1119093
1112533
1119114
1112770
1119000
1112775
1112768
1112870
1104610
1104240
1109070
1104590
aC = Converted core
W = Water
well
East'
486954
492322
476318
482038
487046
489363
474966
481732
476362
478736
487102
492819
476474
492886
492598
492464
479250
476450
841920
480900
hole
Sec.
1
7
15
11
1
2
3
2
3
10
1
7
3
7
7
7
15
15
11
14
bSc
Co
(JO
43
43
43
43
43
43
43
43
43
43
43
43
43
43
43
43
43
43
43
43
m
70
69
70
70
70
70
70
70
70
70
70
69
70
69
69
69
70
70
70
70
Grd.
eley.
(ft
\ » **
abv.
msl)
4341.3
4892.2
4756.2
4804.8
4875.4
4820.9
4773.4
4854.8
4807.6
4800.6
4877.4
4847.7
4810.5
4842.4
4869.9
4882.9
4660
4642
4683
4683
Total
180
140
185
160
180
195
220
200
240
170
160
80
240
76
120
140
81
50
180
679
Csg.
180
140
185
160
180
195
220
200
240
170
160
80
240
76
120
140
-
-
163
645
Depths
Packer
base
None
None
None
None
None
None
None
None
None
None
90
None
160
None
None
None
-
-
25
190
(ft.)
Perf.
intv.
80-180
40-140
85-185
60-160
80-180
95-195
120-220
100-200
140-240
70-170
88-160
40-80
160-240
36-76
82-120
100-140
-
-
55-163
413-600
Gravel
pack
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
-
-
X
-
Type
'/ r""-
of
hole
.
_
.
-
_
_
-
_
-
_
C
C
C
C
C
C
-
.
W
W
Diameters (in.)
Geol
fmb
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Coal
Sc & Co
Coal
Sc
Coal
Coal
-
-
Sc
Sand
Drill
bit
4
4
4
4
4
4
4
4
4
4
9
9
9 •
5-1/8
5-1/8
5-1/8
4-3/4
5
7-7/8
8-3/4
Csg.
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
1-1/4
5
5
5
2
1-1/4
2
-
-
6
6-5/8
Type
csg.
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
PVC
-
-
-
-
Steel
Steel
State
permit
28904
28905
28906
28907
28908
28909
28910
28911
28912
28913
28708
28706
28707
28709
28710
28711
-
-
29425
29426
= Scoria
= Coal
-------
Sun Oil Cordero -
Groundwater at the Cordero mine has not received extensive treatment in the
Corderc mining plans or impact statements. Brief descriptions of the occurrence
and quality of water have been offered, but supporting maps are not presented.
Groundwater exists in the Wasatch Formation, the coal beds, the alluviated
area of the Belle Fourche River, and probably in the scoria. Cordero has not
published any pump test results to aid in the evaluation of these aquifers, al-
though the environmental impact statement states that aquifer characteristics
are probably sinrlar to those at Belle Ayr South (U.S. Geological Survey,
1976). Field observations at Cordero indicate that the overburden is gener-
ally dry, with the exception of several lenticular sandstone beds. Some water
does emanate from the coal seams, and Cordero estimates that it will pump
between 70,000 and 100,000 gpd from the pit. No information on scoria aqui-
fers or alluvial aquifers has been located.
Water levels were fairly stable during premining activity, as shown on
Figure 5-30. These levels were published in Cordero Mining Co. (1976).
Wyodak -
The Wyodak mine has been mining coal since 1925. When compared with the
planned mines on Federal leases, Wyodak is a relatively small strip mine. How-
ever, because mining has proceeded for a long period of time, Wyodak's hydro-
geology bears scrutiny.
Wasatch and alluvial aquifers are given minimal treatment in Wyodak
Resource Development Corp. (1977). Wasatch aquifers are described as having
"low permeability," although no pump test data are given to substantiate this
statement. Donkey Creek runs north past the south Wyodak pit and turns to the
east just in front of the Neil Simpson Power Plant at Wyodak. From field
observations, it is estimated that there is no more than 20 feet of alluvium
along the streambed of Donkey Creek. Although parts of the alluvium are
saturated, the alluvial aquifer is a minor one.
Three separate scoria aquifers are beneath Wyodak leased lands. As shown
on Figure 5-31, these are the East Burn, the "21" Burn, and the Ditto Lake Burn
(Wyodak Resource Development Corp., 1977). Saturated thicknesses in the East
Burn are on the order of 20 to 30 feet. Wyodak feels that a relatively imper-
vious layer of slaked coal and ash separates the coal beds from the highly
permeable East Burn scoria. The "21" Burn is bordered by coals on the east
and by layers of clays, fine sands, and fluvially deposited ash, slaked coal,
and scoria to the west. Wyodak's consultants feel that this layered material
to the west has a low permeability and serves to isolate Wyodak's coal beds
from the Ditto Lake aquifer. The Ditto Lake Burn, covering 688 acres, is the
largest of the Wyodak scoria areas, and it also has the most water in storage.
Ditto Lake receives internal drainage from local high areas, and this runoff
serves to recharge the scoria aquifer. Pumping tests indicated porosities of
13 percent (Wyodak Resource Development Corp., 1977) and specific capacities
of 18 gpm/ft (Rahn, 1976). The aquifer discharges to the coal at the western
152
-------
LU
§
UJ
50
60
70
80
90
100
110
120
130
140
150
160
o
a- 170
O
180
'
190
200
210
220
230
8
, 10
~" Plug ^
\
A "'
*
\
\
..-——..
4,—-'4--?5»C
v ^
' Dry (Total dtp*)
LEGEND
7 = MONITORING WELL
<
456789 10 1112 1 23456789 10 11 12 12345 678
1974 1975 1976
Figure 5-30. Water levels of monitor holes at Sun Oil Cordero mine
(Cordero Mining Co., 1976).
153
-------
en
WEST
WEST LINE
T50N R71W
WEST LIMIT OF
PROPOSED MINING
EAST
BARRIER
EAST BURN LINE
WYODAK MINE
*"^T" - ~__L FT. UNION CLAYS AND SANDS
APPROXIMATELY 4 MILES - NOT TO SCALE
Figure 5-31. Idealized east-west cross section of Wyodak site
(Wyodak Resources Development Corp., 1977).
-------
edge of the burn, to the layered rocks at the eastern edge, and to evapo-
transpiration.
The coal aquifers at Wyodak are characterized by low permeability according
to Wyodak Resources Development Corp. (1977).
The north pit is reported to make "very little water" even though water
levels are 90 feet above the pit floor only 2,300 feet to the west (Wyodak
Resources Development Corp., 1977). Observations at the south pit indicate
that the largest flows are from fractures near parting layers between the
Roland and Smith coals.
As its potentiometric surface map for its 1977 Mining Plan Update, Wyodak
submitted a partial copy of a U.S. Geological Survey map by King (1974). This
map (Figure 5-32) included few points on or near the mine, and much of the data
was from wells with openings in more than one aquifer.
Wyodak Resources Development Corp. (1977) states that there is a ground-
water divide at the mine. Flows west of the mine are said to be confined in
the coal seam. To the east, water is said to be unconfined and flowing to the
east in Wasatch Formation aquifers. Figure 5-33 shows the effects of 50 years
of mining on water levels near the Wyodak pit.
Wyodak1s groundwater monitoring stations and monitoring schedules are shown
on Figure 5-34 and in Table 5-16.
MODIFIED HYDROGEOLOGY
Watershed Character!sti cs
Mining of coal will result in several changes in the surface water system
and its relation to groundwater. The most conspicuous change will be a general
lowering of the land surface where the coal seams are removed. The overall de-
crease in volume of material (coal and overburden) disturbed by mining will be
slightly less than the volume of coal removed because the overburden increases
slightly in volume when broken up and replaced.
The lowering of the land surface will increase areas of internal drainage,
or closed basins, on all watersheds affected by mining. The water budget of a
closed basin created by mining will determine if the basin forms a perennial
lake or becomes dry for long periods. Surface runoff is a critical factor in
the budget and will determine if a basin that lies below the water table be-
comes a sink for groundwater or a source of recharge. Existing methods of sur-
face runoff prediction may greatly overestimate runoff volumes (Lowham, 1976).
If runoff volume is much less than estimated, a basin may be a groundwater sink
and concentrate all salts brought in by surface and subsurface flow.
Recharge quantities under postmining conditions currently are unknown. In
interstream areas, recharge will depend on modified hydrologic properties of
replaced soil and the configuration of the soil surface. The surface may be
artificially pitted to encourage infiltration and storage of soil water for
plants. It is not known if this water will move deep into the subsurface.
Most or all of the water may be consumed by evapotranspiration.
155
-------
en
cr>
Figure 5-32. Contours of water table, Wyodak area (from U.S. Geological Survey map I-848-F, King, 1974),
-------
DITTO LAKE
NORTH PIT
01
— 4410 ft.
^ \4311 ft.
4300ft.
Figure 5-33. Effect of 50 years of mining in Wyodak north pit upon water table
(after Wyodak Resources Development Corp., 1977).
-------
' \f
DRILLHOLE
__-": ' »* \>V '•<; *
- ^ * * *?i- N- *A
^ .cW
(^r- (>v3/'
v(A, - ^ .••;u(
• \ lx* c-; --'s^-./C'-'/
•. •— / ••<7. S^^LS
si : v\ '.-;-1 c.--j,"
>>^oV\\;';. f
>r •• -'jLLibL-^-^V-
-.-GRAVEl ^G^RAVEL
.^m^^m^, • -
,-<-v ^V-V- V POWFR PI AWTr _ r ^-*
> POWER PLANT
^- —*t iT^
USUBSTA ,^"~ fuj ;
Figure 5-34.
Locations of monitoring wells, Wyodak mine
(Wyodak Resources Development Corp., 1977),
158
-------
TABLE 5-16. WYODAK GROUNDWATER MONITORING STATIONS
(Wyodak Resources Development Corp., 1977)
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Name
3-76
5-76
13-76
11-76
USGS
Ditto Ob-2
Ditto Ob-1
Wi ndmi 1 1
8-76
14-76
15-76
Wi ndmi 1 1
USGS #1
USGS #2
USGS #3
Wyodak #5
Wi ndmi 1 1
Zone monitored
Wyodak coal
Wyodak coal
Sands above coal
Sands above coal
Wyodak coal
Scoria
Scoria
Wyodak coal
Wyodak coal
Sands below coal
Sands above coal
Wyodak coal
Alluvium
Lower Wyodak bed
Upper Wyodak bed
400-foot: sands
below coal
Scoria
Water quality
Every 6 mos.
Start 1992
Every 6 mos.
Start 1992
Every 6 mos.
Start 1992
Every 6 mos.
Start 1992
Every 6 mos.
Start 1992
No check
planned
Every 6 mos.
Start 1992
Every 6 mos.
Start 1992
Every 6 mos!
Start 1992
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
No check
planned
No check
planned
No check
planned
Every 6 mos.
Start 1977
Every 6 mos.
Water level
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mps.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
No check
planned
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
Every 6 mos.
Start 1977
No check
planned
159
-------
Along streambeds established in the soil, infiltration and recharge
quantities will depend on modified stream properties, such as streambed
composition, sediment loads, and material beneath the streambed.
It is possible that overall quantities of recharge to the deep subsur-
face from rainfall and surface runoff will decrease if near-surface permeable
clinker and well-sorted alluvial deposits are destroyed.
The surface hydrology and its relation to groundwater under postmining
conditions can be seen to be speculative. Too few data exist to make reliable
predictions at this time. Better prediction is expected as mining prog-
resses and more data are gathered.
Soils and Infiltration Characteristics
Determining infiltration characteristics will be necessary when there is
a possibility of water percolating from the surface through reclaimed areas
to depths where free water may be present or where there would be free water
buildup. Of particular concern are the pollutants which may be picked up and
transported by these percolating waters.
The depths to which the water might percolate on a reclaimed mine site
depend upon:
• The configuration of the surface, including slope
inclination, slope length, surface roughness, and
surface geometry
• The physical characteristics (including porosity,
texture, depth structure, and collodial content)
of spoil and topsoil material used for dressing
• The amount, temporal distribution, and intensity of
rainfall and snowmelt; and the rates of evaporation,
including potential demand and the influence of
vegetation.
Rahn (1976) determined infiltration, spoils moisture content, grain size
analysis, field density of spoils, overburden lithology, and laboratory calcu-
lations of permeability on samples from several mines in the Powder River
Basin. Results of permeability tests are of interest as estimates of the
hydraulic conductivity of the disturbed vadose zone deposits and the leach-
ing potential. Data for two mines in the project area are given below.
Laboratory permeability values on six samples of overburden from the
Wyodak mine ranged from 6.6 to 38.0 gal/day per ft2, with an average of 14.8
gal/day per ft2 (Rahn, 1976). Rahn also points out that the overburden at
the Wyodak mine is very thin so that the final open pit will be large but
with little spoils. Since the water table is high, the end result will be
mainly a lake in the abandoned pit. Thus, the final vadose zone will be of
minimal thickness.
160
-------
Laboratory permeameter test results for overburden samples from the
Belle Ayr South mine ranged from 1.8 to 38.7 gal/day per ft2, with an average
of 12.9 gal/day per ft2.
Vadose Zone Characteristics
The vadose zone present in spoil following reclamation will consist of
a heterogeneous mixture of overburden material originally present in the
indigenous vadose zone, and shallow aquifer systems. The overburden material
consists of sandstone, shale, carbonaceous shale, and thin or impure coal beds
of the Wasatch or uppermost Fort Union Formations. Scoria, or baked shale and
siltstone, may also be present, together with alluvial material.
Two consequences of modifying the vadose zone area are: (1) increased hy-
draulic conductivity, and (2) exposure of fresh mineral surfaces to percolating
water (Rahn, 1976). The increase in hydraulic conductivity is a reflection of
the overall increase in volume and porosity of spoil formations as compared to
natural formations. Obviously, the new vadose zone will be highly heteroge-
neous and anisotropic. For example, spoil dumped into the pit by truck will
tend to separate out by gravity as it tumbles down the embankment. The method
of placing spoils in the pit also appears to have an effect on hydraulic pro-
perties. For example, Rahn (1976) obtained an average permeability of 450 gpd/
ft2 at the Hidden Water Creek mine with dragline-emplaced spoils, but only
4 gpd/ft2 at the Bighorn coal mine with scraper- and bulldozer-emplaced spoils.
A consequence of the increased hydraulic conductivity of the vadose zone
is that infiltrated surface water will migrate more readily through the depos-
its, leaching salt into the shallow aquifers. Rahn (1976) described the mech-
anism involved in leaching as follows:
"Rocks are generally broken during mining, thus allowing
fresh mineral surfaces to be exposed to percolating wa-
ters. While precise hydro-geochemical reactions are
difficult to predict, it can be stated ... that the equi-
librium soil-water-mineral conditions which had been
established ... over thousands of years are changed by
mining, and with the infiltration of infiltrating rain-
water or percolating groundwater in the spoils, more
rapid weathering reactions can commence."
Observations by Rahn at several mine sites in the Powder River Basin il-
lustrated that the salinity of water samples from the spoils was markedly
greater than in native groundwater.
The manner in which surface water is applied to the spoil pile area may
have an effect on leaching in the vadose zone. If the area becomes inundated,
for example by flood water, water will move downward in the saturated state,
leaching and transporting salts through large cracks or pores. With rainfall
.or light application of surface water, however, water will move downward in
the unsaturated state. Consequently, water movement will be preferentially in
the smaller pore spaces. Field experiments (Biggar and Nielsen, 1967) on
leaching have shown that greater leaching occurs with unsaturated flow than
161
-------
with saturated flow. That is, the potential effect on groundwater quality by
unsaturated flow following a rain is much greater than from surface inundation.
However, because of the slow velocity of unsaturated flow, the effects may not
be evident for years or centuries.
Another consequence of modifying the hydrogeologic properties of the
vadose zone at mine sites is possible. In particular, perching layers may be
disrupted by stripping. Consequently, water moving laterally through mounds
in the vadose zone will intersect and flow into the modified region, and move
downward toward the water table. Leaching will, therefore, result around the
periphery.
Aquifer Characteristics
In general, considerable disruption of aquifer characteristics can occur
during mining. As the coal aquifer commonly is the most productive and the coal
is to be removed, in one sense the aquifer is destroyed. However, in this dis-
cussion, the concern is with the reclaimed area, namely the spoils. In a sense,
the aquifer will remain, but the materials will be different than those origi-
nally present and the hydraulic characteristics will be different. Modifica-
tions of the vadose zone have been previously described. Groundwater at most
mines is in the coal, in the underlying materials, and sometimes in the over-
burden. The coal and overburden vary greatly in the degree of consolidation;
however; groundwater is generally considered to be moving through fractured con-
solidated rock except for the alluvium.
Three major cases to consider are:
• Removal of coal and replacement with spoils;
• Removal of alluvium and replacement with spoils; and
• Removal of overburden and replacement with spoils.
Rahn (1976) reported on two pump tests in spoils near Sheridan, Wyoming.
However, the test at the Big Horn Mine yielded very questionable results and
the reported values of transmissivity are considered unreliable. At the Hidden
Creek Mine, a 27-hour pump test was conducted on a well tapping about 33 feet
of spoils. About 21 gpm were pumped and the specific capacity was 1.7 gpm per
foot of drawdown. The transmissivity was about 11,000 gpd per foot and the
storage coefficient was 0.12. With an average saturated thickness of 24.5
feet, the permeability of the spoils was 450 gpd per square foot. Laboratory
permeabilities reported by Rahn for spoils probably have little meaning with
respect to aquifer characteristics. Additional pump tests are needed to assess
the hydraulic characteristics of spoils.
Removal of Coal -
Transmissivities for coal aquifers in the Gillette area commonly range
from about 100 to 3,500 gpd per foot. Values less than 1,000 gpd per foot are
common and are typical of fractured hard rock. Replacement of coal by spoils
would appear to result in an increased transmissivity, particularly if
162
-------
coarse-grained overburden is predominant in the spoils. However, a predomi-
nance of fine-grained overburden could result in a lower transmissivity.
Also, the spoils are unconsolidated in macrostructure. Small pieces of
relatively consolidated, fractured materials may remain in the spoils. In
any case, the net surface area exposed would appear to be greatly increased.
Also, groundwater may flow through spoils as if it were a granular porous
medium as opposed to a fractured hard rock aquifer. The storage coefficient
would appear to be much greater for spoils than for coal, and obviously the
porosity of spoils would be greater. The geochemical composition of the
spoils is greatly different from that of coal.
Removal of Alluvium —
The hydraulic characteristics of alluvium are poorly known in the Gillette
area. However, the transmissivity is likely low because of the small saturated
thickness. Presently, the alluvium serves as the point of interchange between
surface water and groundwater. That is, percolating streamflow in some areas
passes through the alluvium to underlying formations. Also, groundwater moving
from underlying formations in some areas passes through the alluvium and enters
streams to become surface water. The replacement of alluvium with spoils could
have profound effect on surface water as well as groundwater. More or less
percolation from streamflow could occur than under the original conditions.
Also, base flow conditions in the streams could be increased or decreased. It
is likely that the spoils are less permeable than the alluvium. The geochem-
ical composition of the spoils is generally different than that of the alluvium.
Removal of Overburden —
Transmissivities of several hundred to several thousand gpd per foot are
common for the Fort Union and Wasatch Formations. When the materials overlying
the coal are broken up and replaced as spoils, both permeability and storage
coefficient should be increased. The geochemical composition of the spoils is
basically the same; however, the surface area exposed is greatly increased.
163
-------
SECTION 6
EXISTING GROUNDWATER QUALITY
REGIONAL
Shallow groundwaters in the project area have poor chemical quality. Analy-
ses performed by the coal companies cover a large part of the project area, and
these results indicate that few of the shallow groundwaters meet EPA drinking
water standards. Other analyses of shallow waters, published by Hodson (1971),
indicate that water quality can vary widely in the project area. Regional water
quality was studied by the U.S. Geological Survey (King, 1974) and most waters
in the area were determined to be of marginal quality. This work did not speci-
fy which analyses were from coal aquifers or from Wasatch Formation aquifers.
Preliminary field tests of City of Gillette Wasatch Formation wells yielded TDS
values between 1,200 and 3,800 ppm. The City mixes this poor water with higher
quality water from deeper Fort Union Formation aquifers to meet drinking water
standards.
Groundwaters in the Wasatch Formation are usually of the calcium sulfate
type. Analyses published by the coal companies, the State of Wyoming, and the
U.S. Geological Survey indicate that TDS ranges from 500 to 6,000 ppm, with
most analyses falling in the 2,000- to 4,000-ppm range. The lowest values are
often found in wells near surface streams, and probably reflect the interaction
of the groundwater and surface water. pH values for Wasatch waters range from
7.7 to 8.1. Trace element studies conducted on Wasatch water samples by the
coal companies indicate that problems possibly may exist with the following ele-
ments: arsenic, cadmium, lead, selenium, and possibly uranium.
Coal-seam waters can have dynamic characteristics, changing from calcium
sulfate waters to sodium bicarbonate waters as the water migrates downdip. The
ARCO Black Thunder mine's groundwater quality contains a good example of this
change. Coal-seam TDS values for the project area range from 500 to 3,500 ppm
with most values in the 1,000- to 3,000-ppm interval. Values for pH range from
6.9 to 8.2 in coal aquifer waters, indicating that coal aquifer waters are
neutral to slightly alkaline. Trace elements of concern include, but are not
limited to, arsenic, cadmium, copper, lead, and selenium.
The following discussions are based on data published by the mining com-
panies in various documents. To properly execute the TEMPO methodology, exist-
ing groundwater quality must be studied directly adjacent to the pollution
source, so that changes induced by the source can be determined. The data
presented in this section yield interesting background information, but existing
groundwater quality at each important pollution source must be accumulated.
164
-------
During their first 2-1/2 years of operation, AMAX Belle Ayr workers
have collected numerous groundwater quality samples. Although detailed
sample collection procedures were not outlined in the AMAX Coal Co. (1977)
mining plan update, results of several analyses were reported. Tables 6-1
through 6-4 show the maxima and minima of these results, as well as the mean
values. Significant deviations occur for some parameters, indicating a
dynamic quality situation or sampling and analytical inconsistencies.
In its mining plan update, AMAX states that the dominant water types
within the Wasatch Formation are sodium sulfate and sodium bicarbonate.
However, selected samples from the Wasatch Formation (Table 6-1) would be
classified as a calcium sulfate water. AMAX should include analyses which
reflect the reported sodic quality of their Wasatch waters. Sodic waters are
shown to exist in the Wyodak coal seam. Table 6-2 indicates that water types
vary from sample to sample and that the coal seam waters can be either sodic
or calcic. These results confirm the need for further testing to pinpoint
water quality types on the Belle Ayr lease. AMAX's deep Fort Union water at
well station WRRI 7 has very high sulfate contents for a potable water
source. AMAX did not present data on other Fort Union wells which are report-
edly used for office and shop requirements. The analyses presented for the
scoria pit (Table 6-3) has a close epm balance (0.97), but the reported elec-
trical conductivity is inconsistent with the rest of the results. If this
inconsistency is ignored, the scoria pit water appears to be of fairly good
quality. However, the relative amounts of groundwater inflow and surface
runoff that make up this pit water are unknown, and it is assumed that
groundwater within the scoria is not as good as this analysis might indicate.
AMAX has, published water quality data for its Eagle Butte mine in its
Federal environmental impact statement and in its AMAX Coal Co. mining plan
update (1977a). This summary is based primarily on the data shown in the
mining plan update. Analyses were performed by the Wyoming Department of
Agriculture, and equivalent balances ranged from 0.94 to 1.31. Maximum and
minimum values for water on the Eagle Butte lease are given in Table 6-5.
Sample collection procedures are given in Table 6-6.
The chemical quality data presented by AMAX indicate that large varia-
tions can exist in groundwater quality at the Eagle Butte lease. Although
some waters are low in total dissolved solids, most waters exceed drinking
water recommended standards for dissolved minerals. Eagle Butte waters are
predominantly of the calcium sulfate type. AMAX has published a single
analysis for each well at the lease. Quality variations with time are re-
portedly being studied (AMAX Coal Co., 1977a).
ARCO and the University of Wyoming have conducted fairly extensive
groundwater quality tests. The University received funding from the EPA to
conduct its research at Black Thunder. Tables 6-7 and 6-8 show the analysis
presented in ARCO's Final Environmental Assessment (University of Wyoming,
1976). Figure 6-1 gives the well locations; Table 6-9 summarizes these data.
Cation-anion balances for selected analyses yield ratios ranging from 0.84
to 1.20, indicating fairly good analytical control.
165
-------
TABLE 6-1. AMAX BELLE AYR WATER QUALITY DATA-WASATCH FORMATION
ABOVE THE COAL (AMAX Coal Co., 1977)
Parameter
Field pH (units)
Calcium
Magnesium
Sodium
Potassium
Carbonate
Bicarbonate
Oil and grease
Sulfide
Arsenic
Barium
Boron
Cadmium
Copper
Total chromium
Chromium-Cr'f6
Total iron
Dissolved iron
Lead
Manganese
Mercury
Nickel
Selenium
Number of
analyses
1
12
12
12
11
12
10
12
4
5
5
5
5
5
4
1
8
8
5
5
4
5
4
Maximum
value
7.5
279.
208.
200.
13.0
610.
705.
21.6
0.9
0.007
0.5
0.6
0.014
0.01
0.1
0.01
5.7
5.0
0.1
0.27
0.001
0.1
0.002
Minimum
value
7.5
180.
59.0
113.
0.0
0.0
500.
0.0
0.0
0.007
0.5
0.0
0.01
0.01
0.1
0.01
0.1
1.8
0.01
0.1
0.001
0.1
0.001
Mean
7.5
213.
145.
164.
9.52
101.
604.
2.55
0.3
0.007
0.5
0.164
0.0108
0.01
0.1
0.01
2.59
3.20
0.082
0.180
0.001
0.1
0.0013
Standard
deviation
-
30.6
37.2
27.6
4.80
237.
51.0
6.08
0.408
-
-
0.246
0.0018
-
-
1.70
1.19
0.0402
0.0623
_
-
0.0005
Notes: Values in ppm unless specified
Well station N-5
June 1972 to June 1976
(continued)
166
-------
TABLE 6-1 (continued)
Number of Maximum
Parameter analyses value
Silver
Zinc
Kjeldahl nitrogen
*
Conductivity (mmhos)
Ammonia
Organic nitrogen
Nitrate + Nitrite
Chloride
Fluoride
Cyanide
Sulfate
Phenol
NBAS
BOD
COD
Total dissolved solids
Suspended solids
Suspended volatile solids
Lab pH
Turbidity (JTU)
Total carbonate (CO,)
Hardness (CaCOj)
Alkalinity (CaC03)
5
5
11
12
6
1
1
12
9
4
12
5
5
1
12
12
7
6
11
7
11
12
3
0.5
'0.12
1.0
2760.
0.0
0.9
0.0
46.0
0.6
0.02
1369.
0.034
0.14
31.0
28.4
2300.
178.
100.
7.9
29.0
310.
1550.
516.
Minimum
value
0.05
0.01
0.3
1580.
0.0
0.9
0.0
16.0
0.3
0.008
650.
0.0
0.1
31.0
0.4
1480.
8.0
0.0
7.2
1.3
250.
742.
346.
Mean
0.41
0.052
0.682
2211.
0.0
0.9
0.0
21.9
0.511
0.011
980.
0.0074
0.108
31.0
8.71
1877.
38.4
22.3
7.53
10.9
294.
1138.
454.
Standard
deviation
0.201
0.0432
0.252
310.
-
-
-
8.17
0.105
0.006
205.
0.0149
0.0179
-
9.19
250.
61.7
38.7
0.211
9.76
16.7
211.
93.8
Notes: Values in ppm unless specified
Well station N-5
June 1972 to June 1976
167
-------
TABLE 6-2. AMAX BELLE AYR WATER QUALITY DATA-WYODAK COAL
(AMAX Coal Co., 1977)
Parameter
Field pH (units)
Calcium
Magnesium
Sodium
Potassium
Carbonate
Bicarbonate
Oil and grease
Sulfide
Arsenic
Barium
Boron
Cadmium
Copper
Total chromium
Chromium-Cr
Total iron
Dissolved iron
Lead
Manganese
Mercury
Nickel
Selenium
Number of Maximum
analyses value
1
12
12
12
10
12
12
12
4
5
5
5
5
4
4
1
9
7
5
5
4
5
4
7.0
360.
320.
640.
14.0
0.0
560.
12.1
1.1
0.007
0.5
1.1
0.01
0.01
0.1
0.01
5.1
2.5
0.1
2.0
0.001
0.1
0.001
Minimum
value
7.0
180.
12.0
103.
8.8
0.0
290.
0.0
0.1
0.007
0.5
0.0
0.001
0.01
0.1
0.01
0.2
1.49
0.02
0.1
0.001
0.1
0.001
Mean
7.0
208.
91.4
210.
11.7
0.0
510.
2.34
0.525
0.007
0.5
0.27
0.0082
0.01
0.1
0.01
2.19
2.07
0.084
0.774
0.001
0.1
0.001
Standard
deviation
-
49.1
75.2
138.
1.44
-
74.1
3.55
0.505
-
-
0.465
0.004
-
-
1.65
0.379
0.0358
0.839
-
-
-
Notes: Values in ppm unless specified
Well station N-3
June 1972 to June 1973
(continued)
168
-------
TABLE 6-2 (continued)
Number of Maximum
Parameter analyses value
Silver
Zinc
Kjeldahl nitrogen
Conductivity (mnhos)
Ammonia
Organic nitrogen
Nitrate + Nitrite
Chloride
Fluoride
Cyanide
Sulfate
Phenol
MBAS
BOD
COD
Total dissolved solids
Suspended solids
Suspended volatile solids
Lab pH
Turbidity (JTU)
Total carbonate (CO,)
Hardness (CaCOg)
Alkalinity (CaC03)
5
5
11
12
6
1
1
12
10
4
12
5
5
1
12
12
8
6
11
8
11
12
3
0.5
2.3
3.9
4740.
1.3
3.1
0.0
31.0
1.3
0.02
3400.
0.005
0.16
20.0
345.
5160.
232.
40.0
7.9
125.
270.
2200.
450.
Minimum
value
0.05
0.08
1.1
1720.
0.0
3.1
0.0
3.6
0.4
0.008
680.
0.001
0.1
20.0
28.0
1400.
8.0
6.0
7.0
5.0
140.
530.
225.
Mean
0.41
0.56
2.59
2077.
0.283
3.1
0.0
9.16
0.75
0.011
940.
0.0026
0.112
20.0
71.6
1785.
68.2
21.8
7.23
29.4
251.
896.
373.
Standard
deviation
0.201
0.974
0.856
841.
0.523
-
-
7.46
0.222
0.006
774.
0.0013
0.0268
-
88.4
1063.
74.7
11.9
0.246
40.0
37.7
422.
128.
Notes: Values in ppm unless specified
Well station N-3
June 1972 to June 1973
169
-------
TABLE 6-3. AMAX BELLE AYR WATER QUALITY DATA-SCORIA PIT-WASATCH
FORMATION ABOVE THE COAL (AMAX Coal Co., 1977)
Number of
Parameter analyses
Field pH (units)
Calcium
Magnesium
Sodium
Potassium
Carbonate
Bicarbonate
Cadmi urn
Copper
Total iron
Lead
Manganese
Mercury
Silver
Zinc
Conductivity (mmhos)
Chloride
Sulfate
Hardness
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
Maximum
value
7.6
160.
25.0
45.0
18.0
0.0
156,
0.001
0.01
0.07
0.01
0.002
0.002
0.05
0.02
504.
29.0
456.
21.0
Minimum
value
7.6
160.
25.0
45.0
18.0
0.0
156.
0.001
0.01
0.07
0.01
0.002
0.002
0.05
0.02
504.
29.0
456.
21.0
Mean
7.6
160.
25.0
45.0
18.0
0.0
156.
0.001
0.01
0.07
0.01
0.002
0.002
0.05
0.02
504.
29.0
456.
21.0
Notes: Values in ppm unless specified
Well station scoria pit
dune 1972 to June 1976
170
-------
TABLE 6-4. AMAX BELLE AYR WATER QUALITY DATA-FORT UNION
FORMATION BELOW COAL (AMAX Coal Co., 1977)
Parameter
Field pH (units)
Calcium
Magnesium
Sodium
Potassium
Carbonate
Bicarbonate
Oil and grease
Sulfide
Arsenic
Barium
Boron
Cadmium
Copper
Total chromium
+6
Chromium-Cr
Total iron
Dissolved iron
Lead
Manganese
Mercury
Nickel
Selenium
Number of Maximum
analyses value
1
12
12
12
9
12
12
12
4
5
5
5
5
5
4
1
8
8
5
5
4
5
4
7.7
227.
85.0
243.
10.0
0.0
440.
6.0
3.0
0.02
0.5
0.6
0.01
0.01
0.1
0.01
2.2
1.9
0.1
0.23
0.001
0.1
0.001
Minimum
value
7.7
121.
36.0
154.
8.8
0.0
331.
0.0
0.0
0.007
0.5
0.0
0.001
0.01
0.1
0.01
0.1
0.27
0.01
0.0
0.001
0.1
0.001
Standard
Mean deviation
7.7
157.
46.4
220.
9.33
0.0
398.
1.72
1.07
0.0096
0.5
0.158
0.0082
0.01
0.1
0.01
0.788
0.853
0.082
0.118
0.001
0.1
0.001
-
26.1
12.6
23.3
0.377
-
25.1
2.01
1.39
0.0058
-
0.249
0.004
-
-
-
0.709
0.537
0.0402
0.0823
-
-
-
Notes: Values in ppm unless specified
Well station WRRI 7
(continued)
171
-------
TABLE 6-4 (continued)
Number of Maximum
Parameter analyses value
Silver
Zinc
Kjeldahl nitrogen
Conductivity (mmhos)
Ammonia
Organic nitrogen
Nitrate + Nitrite
Chloride
Fluoride
Cyanide
Sulfate
Phenol
MBAS
BOD
COD
Total dissolved solids
Suspended solids
Suspended volatile solids
Lab pH
Turbidity (JTU)
Total carbonate (CO,)
Hardness (CaC03)
Alkalinity (CaC03)
4
5
11
12
6
1
1
12
9
4
12
5
5
1
11
12
7
6
11
7
11
12
3
0.5
0.44
3.5
1870.
0.3
1.5
0.0
46.0
1.6
0.02
770.
0.047
0.5
9.0
18.0
1500.
206.
108.
7.8
44.0
220.
700.
300.
Minimum
value
0.05
0.04
0.4
1600.
0.0
1.5
0.0
3.6
0.3
0.000
600.
0.001
0.1
9.0
1.2
1270.
4.0
0.0
7.3
0.7
190.
450.
162.
Mean
0.387
0.132
1.81
1791.
0.05
1.5
0.0
12.1
0.555
0.011
728.
0.012
0.18
9.0
8.16
1400.
47.7
29.3
7.48
10.0
199.
572.
274.
Standard
deviation
0.225
0.172
0.785
80.1
0.122
-
-
11.7
0.397
0.006
47.5
0.0197
0.178
-
6.30
62.9
72.6
44.0
0.166
15.3
8.39
58.4
96.9
Notes: Values in ppm unless specified
Well station WRRI 7
172
-------
TABLE 6-5. MINIMUM AND MAXIMUM VALUES FOR WATER QUALITY PARAMETERS AT
AMAX EAGLE BUTTE LEASE (all aquifers) (AMAX Coal Co., 1977a)
Constituent3
Silica
Calcium
Magnesium
Sodium
Potassium
Bicarbonate
Carbonate
Sulfate
Chloride
Fluoride
Nitrate
Boron
TDS
Hardness (Ca + Mg)
Specific conductance
(mmhos)
pH (units)
Minimum
14
79
20
11
2.8
150
0
73
1.2
0.7
0.1
0
336
240
507
7.1
Maximum
38
375
420
540
44
1300
0
2800
25
1.5
23
3.6
6600
2600
9960
8.0
JValues in ppm unless specified otherwise
173
-------
TABLE 6-6. SUMMARY OF WATER SAMPLING PROCEDURES DURING TESTS OF VARIOUS
WELLS AT THE EAGLE BUTTE MINE (AMAX Coal Co., 1977a)
Well
No.
BAN-1A
BAN-3
BAN- 4
BAN-5
GN-6
GN-7
GN-8
GN-9
GNH-6B
Spring
•••••••••••IMH^HMMH
Date
12/23/75
8/19/75
8/19/75
8/19/75
12/18/75
1/6/75
1/7/75
1/7/75
8/19/75
8/18/75
(••^••••PV^HIlmVI^^^HI^M^HIV^BHIV^-^
Aqui f er
Wasatch?
Coal
Coal
Coal
Coal
Coal
Coal
Ft. Union
Alluvium
Alluvium?
•^•MI^Hh4*MH11M«^1111111l«p4BIIIII^— ^^IBBI^^^—a
Elapsed
pumping
time
(hrs)
3.42
0.63
0.88
0.65
0.80
4.50
0.65
10.33
1.33
Artesian
flow?
^MI^^^HIHh^H.vailBW»«_4v^Mh^^^*Bl*«
Volume
water
produced
(gal)
41a
285
413
133
57
567
532b
1C
112
—
Well site tests
Specific
conductance
(mmhos)
2800
3220
1800
1310
1370
1700
1750
—
—
MIIIM>*VIIIIIWMIIIII1IP«MIIIII*IPqlMIIMV*IIIW*IMIIIH«
PH
8.0
7.0
7.2
7.2
8.0
7.8
7.4
—
7.4
7.9
•HKII*MI«IIIIHM-milllllllllHWIIII««
Temp
TO
11.7
13.9
15.5
13.3
11.7
11.7
11.1
--
15.0
13.3
•HIIHII^tfklllllllllWIIIIIWIIIIVIHffMAA
Final
drawdown
(ft)
30
28.9
57.9
3.2
27.2
10.5
•x.0.1
^30
—
- - •. IP :mamf— •— ••a— •»
Yellow color
1169 gallons pumped on 1/6/75
Drilling fluid, not sampled
-------
TABLE 6-7. RESULTS OF CHEMICAL ANALYSES OF GROUNDWATER FROM
WASATCH WELLS (University of Wyoming, 1976).
Sample
W-l
W-2
W-2
W-3
W-4
W-4
W-5
W-5
W-6
W-6
W-7
W-7
W-10
W-10
W-ll
R-15A
Average
Minimum
Maximum
Sampl e
date
9/19/73
3/31/73
2/26/75
10/4/73
10/3/73
12/3/73
10/4/73
12/3/73
10/4/73
12/3/73
7/3/73
12/3/73
5/8/73
2/26/74
10/4/73
12/3/73
Laba
ARCO
ARCO
UW
ARCO
ARCO
UW
ARCO
UW
ARCO
UW
ARCO
UW
ARCO
UW
ARCO
UW
ppm
318
340
155
316
764
700
510
452
238
245
200
269
420
395
281
67
354
67
764
ppm ppm
- 121
- 710
0.18 458
8
385
23 484
- 197
90 186
49
7 19
47
8 34
100
0.3 128
33
9 156
20 195
0.18 8
90 710
ppm
82
230
222
112
346
479
46
55
58
22
49
25
66
56
24
57
120
22
479
Alkb
ppm
454
200
-
159
647
660
157
161
634
465
785
804
433
-
805
166
480
159
805
S04=
ppm
610
3100
1900
1160
3200
3456
1650
1440
275
238
52
35
990
630
51
598
1220
50
3500
cr
ppm
84
47
14
11
113
183
39
14
46
28
53
37
34
7
46
2
47
2
183
Si02
ppm
9
8
-
5
21
20
5
9
10
11
13
13
13
-
10
12
11
5
21
TDSc'd
ppm
(1680)
1610
(4635)
4340
3290d
(1770)
1206
(5476)
4823
6000
(2604)
2340
2408
(1310)
1250
1035
1200
1225
(2056)
1890
2094d
(1250)
675
1067
2440
1035
6000
PH
7.4
7.7
7.5
7.4
6.6
-
7.4
-
7.3
-
7.5
-
7.6
7.8
7.5
-
-
-
-
aARCO, Atlantic Richfield Co.; UW, University of Wyoming.
Nitration alkalinity reported as HCO-3.
cValues in parentheses obtained by summing individual constituents.
Alkalinity (calculated by difference) used to compute TDS.
175
-------
TABLE 6-8. RESULTS OF CHEMICAL ANALYSES OF GROUNDWATER FROM
ROLAND COAL SEAM WATERS (University of Wyoming, 1976)
Sample
R-l
R-2
R-3
R-4
R-5
R-6
R-7
R-8
R-8
R-8
R-8
R-9
R-9
R-10A
R-10D
R-ll
R-12A
R-12C
Sample
date
9/19/73
10/4/73
10/3/73
10/4/73
8/31/73
8/31/73
10/4/73
7/3/73
9/11/73
9/19/73
12/3/73
7/3/73
12/3/73
7/3/73
12/3/73
5/31/73
6/15/73
12/3/73
Lab3
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
ARCO
UW
ARCO
UW
ARCO
ARCO
UW
Na+ K*
ppm ppm
217 -
127 -
87 -
214 -
165 -
290 -
251 -
410 -
260 -
235 -
249 8
400 -
407 13
65 -
100 57
380 -
150 -
211 14
Ca++
ppm
38
49
283
45
55
360
57
305
72
43
26
103
85
380
294
82
150
203
ppm
43
174
132
21
49
145
33
123
34
27
27
49
46
145
211
35
59
75
Alkb
ppm
781
1049
201
750
790
520
833
475
780
802
600
875
700
585
760
1080
710
514
S04=
ppm
23
410
1160
58
<5
1530
90
1670
210
11
180
550
620
1130
1152
167
340
706
cr
ppm
57
31
33
27
40
40
33
25
25
59
13
30
13
23
2
40
23
3
SiOo
Ppm
8
9
12
8
8
13
8
6
8
8
11
11
12
30
18
7
14
14
TDSc*d
ppm
(1167)
774
(1848)
836
(1908)
2210
(1120)
616
(1110)
680
(2430)
2660
(1305)
777
(3010)
2810
(1390)
1030
(1185)
744
1115
(2020)
1790
1896
(2360)
2390
2594
(1791)
1160
(1446)
1100
1740
PH
7.3
7.5
7.3
7.6
7:2
7.0
7.5
7.3
7,1
7.4
-
7.1
-
6.8
-
7.7
7.2
-
aARCO, Atlantic Richfield Co.; UW, University of Wyoming.
Titration alkalinity reported as HCO-,.
c
Values in parentheses obtained by summing individual constituents.
Alkalinity (calculated by difference) used to compute IDS.
(continued)
176
-------
TABLE 6-8 (continued)
Sample
Na+ K+ Ca++ Mg++ Alkb S04= CT Si02 TDSc'd
Sample date Lab ppm ppm ppm ppm ppm ppm ppm ppm ppm pH
(1438)
1130 7.4
R-12D 10/4/73 ARCO 34 - 148
R-12E 7/3/73 ARCO 140 - 30
R-13 5/31/73 ARCO 490 - 230
R-14 5/24/73 ARCO 375 - 119
R-14 2/26/74 UW 300 0.24 97
R-15B 5/31/73 ARCO 340 - 72
R-17A 7/3/73 ARCO 264 - 200
49 512 670 20
18 420 45 50
91 1240 886 54
( 711)
8 500 7.8
(3000)
2380 7.4
8
20
872 380 60 22
(1848)
1440 7.7
33 - 355 9 - 1600d 7.9
I
35 1040 160 40 10
73
(1700)
1170 7.6
(1970)
530 850 40 10 1765 7.0
(1655)
R-151 7/27/73
R-151 2/26/74
R-153 7/27/73
R-153 12/3/73
R-154 8/31/73
R-156 10/9/73
R-156 12/3/73
Average
Minimum
Maximum
ARCO
UW
ARCO
UW
ARCO
ARCO
UW
130
90
126
85
185
68
100
217
34
490
0.11
-
6
.
_
8
13
0.11
57
220
203
305
203
430
152
247
165
26
430
80
83
114
76
230
80
103
79
18
230
520
450
0
670
162
485
658
0
1240
650
560
1050
883
1750
660
808
616
<5
1750
40
8
30
15
40
16
2
29
2
59
15
17
24
20
120
30
17
4
120
1270
1509d
(2090)
2050
1292
(3325)
3100
(1260)
954
1783
1770
711
3325
7.4
6.9
7.9
-
7.2
7.3
-
-
-
ARCO, Atlantic Richfield Co.; UW, University of Wyoming.
Titration Alkalinity reported as HCO~3. ,
cValues in parentheses obtained by summing individual constituents.
dAlkalinity (calculated by difference) used to compute IDS.
177
-------
^_f R 70 W
A
17
(R)« commercia
A
R4
W3
16
1 well
R5«W4
20
R7
W5
R8 •
|
n O '
21
W6A _
RI7A
•21
•
•
W9
W
A
LEGEND
m MONITORED WELLS ON SITE
W2
BT-77
A
1_
L-i
1 — •
R9»W7 »RIOA
3
IWI2
Rj54 Sil° 2
BT-66 * *(PR)
(R)
• • RI53
RI5I •
RI2A«(PR) «RI56
RI4
IDA
t
RI3
34 * 35 _
R'.5B T43N
Wll T42N
3 2
A STOCK WATER WELLS
CONTINUOUS RECORDER ON
* ROLAND FORMATION WELL
0 4000 BOOO FEET
SCALE
Figure 6-1. Groundwater gaging network at the Black Thunder Site
(PR = Pre-Roland well; R = Roland well; W = Wasatch well)
(University of Wyoming, 1976)
178
-------
TABLE 6-9. SUMMARY OF WATER QUALITY AT BLACK THUNDER SITE SURFACE AND
GROUNDWATER (values in ppm) (University of Wyoming, 1976)
Range in Range in
Roland coal Wasatch
Water quality characteristics aquifer aquifer
Major constituents
Calcium 26-430 8-710
Magnesium 18-230 22-479
Sodium 34-490 67-764
Sulfate <5-1750 50-3500
Chloride 2-59 2-183
Silicon dioxide 4-120 5-21
Potassium 0.11-57 0.18-90
Chemical and physical properties
Total alkalinity 0-1240 159-805
Hardness (Ca + Mg)
pH (units) 6.9-7.9 6.6-7.8
Total dissolved solids (TDS) 711-3325 6-75-6000
Specific conductance
(mmhos/cm)
Trace elements
Arsenic <5-<10 <5-<10
Beryllium <1 <1
Cadmium <0.02-5 <0.02-1.1
Copper 0.5-4.2 0.5-1.4
Lead 0.6-4.6 1-3.9
Mercury <0.1-<0.5 <0.1-<0.5
Molybdenum
-------
The ARCO sampling program has been more extensive and comprehensive than
the programs at the other mines. As a result, a clear picture of groundwater
quality in each aquifer has been presented. Wasatch water quality is highly
variable. Water types are predominantly calcium or sodium sulfate, but two
samples were of the sodium bicarbonate type. Roland coal seam waters have
either calcium sulfate or sodium bicarbonate characters. In its Final Envi-
ronmental Assessment (University of Wyoming, 1976), ARCO states that the
waters in the eastern part of the lease are more often of the calcium sulfate
type, and that as the waters move northwest, the character changes to sodium
bicarbonate. ARCO speculates that exchange mechanisms cause this change in
water type. However, surface chemical reactions probably are not the major
contributor to the change. The highly concentrated calcium sulfate waters are
at or near saturation, and precipitation of these elements as gypsum is prob-
ably occurring as the water moves to the west. ARCO has not presented chemi-
cal data on alluvial or scoria aquifer waters.
No groundwater quality data were published in the Carter North Rawhide
Environmental Impact Statement (U.S. Geological Survey, 1974b). Four analy-
ses were published in Carter's mining plan update (1977). Table 6-10 shows
these analyses. Equivalent balances indicate that the ratio of cations to
anions ranges from 0.97 to 1.01. Maximum and minimum data for selected con-
stituents are given in Table 6-10.
TABLE 6-10. WATER QUALITY ANALYSES OF WATER WELLS ON THE RAWHIDE LEASE
(Carter Oil Co., 1977)
Sample
Chemical analyses (ppm)
Calcium
Magnesium
Sodium
Carbonate
Bicarbonate
Sulfate
Chloride
Silicon dioxide
Hardness (CaC03)
Total solids
Evaporated solids
Suspended solids
Volatile suspended solids
pH (units)
Specific conductance
(micromhos/cc)
Turbidity (JTU)
NRH-2
Roland
545
209
118
<0.1
640
1,740
74
19
2,200
3,188
3,180
8.5
<0.1
7.7
3,190
15
NRH-2
Smith
114
54
435
<0.1
1,570
100
65
10
502
1,760
1,760
<0.1
<0.1
7.7
1,920
2
Clinker
well
504
183
133
0
390
1,950
12
_
2,010
4,002
_
_
^
7.7
3,300
_
Main supply
well
7
4
124
0
354
3
12
_
34
329
_
_
8.2
480
3
180
-------
TABLE 6-11. MINIMUM AND MAXIMUM VALUES AT CARTER OIL NORTH RAWHIDE
LEASE FOR WATER QUALITY PARAMETERS (coal aquifers)
(Carter Oil Co., 1977)
Constituent3
Minimum Maximum
Silica
Calcium
Magnesium
Sodium
Bicarbonate
Carbonate
Sulfate
Chloride
Hardness as CaC03
pH Cunits)
10
7
4
118
354
0
3
12
34
7.7
19
545
209
435
1,570
0
1,740
74
2V200
8.2
In ppm except as shown for pH
These data are not definitive, yet they indicate that the coal waters can
have calcium sulfate or sodium bicarbonate characters. Clinker water is gen-
erally regarded to be of poor quality, and this feature is supported by the
Carter analysis. Fort Union deep wells produce waters with good quality char-
acteristics. The low TDS figure, coupled with the softness of the water, indi-
cate that the best quality water on the Carter lease can be found in deep wells.
Chemical data for groundwater on or near the Kerr-McGee Jacobs Ranch lease
have been continuously collected since as early as 1966. Reports included in
Kerr-McGee's Jacobs Ranch Mining Plan Update (1977) include data from samples
analyzed by Kerr-McGee and by the University of Wyoming. Equivalent balances
on some of the analyses indicated that cation-anion ratios ranged near 1.00.
Representative analyses are given in Tables 6-12 and 6-13.
Some of the waters analyzed may have been composite samples from both the
Wasatch and coal aquifers. Completion data for the KM series of wells were
not included in the Mining Plan Update (1977). With the exception of KM-3, all
of the wells at the Jacobs Ranch mine area have calcium sulfate waters. No
analyses were presented for alluvial or scoria wells.
In its Mining Plan Update (1977), Kerr-McGee states that although TDS
values are high, salt tolerant crops should survive if irrigated with Jacobs
Ranch groundwater. Sodium adsorption ratios are expectedly low, and boron con-
centrations are all less than 1 ppm. Selenium, cadmium, and lead concentra-
tions exceed EPA drinking water standards in the following: KM-3, 4, 5, 11, 12
wells.
181
-------
TABLE 6-12.
CHEMICAL ANALYSIS OF WATER FROM WELLS WITHIN 6 MILES OF PROPERTY BOUNDARY
OF PROPOSED KERR-McGEE JACOBS RANCH COAL MINE (Hodson, 1971)
00
ro
Location/ constituent
Well location9
Well depth (ft)
Date of sample
Temperature (deg C)
Silica (S102)(ppm)
Total Iron (Fe)(ppm)
Calcium (Ca)(ppm)
Magnesium (MgHppm)
Sodium (Na)(ppm)
Potassium (K)(ppm)
Bicarbonate (HC03)(ppm)
Carbonate (C03)(ppm)
Sulfate (S04)(ppm)
Chloride (Cl)(ppm)
Fluoride (F)(ppm)
Nitrate (N03)(ppm)
Boron (B)(ppm)
Dissolved solids
(residue at 180° C)
Dissolved solids (sum
of constituents)
Hardness (Ca,Mg)(ppm)
Non-carbonate hardness
(ppm)
Specific conductance
(mmhos )
pH (units)
•BVW^^WH«^^^BI^^^_^^_^_
Fort Union
42N069W07BAC 1
120
07-08-68
_
7.7
0.550
32
17
161
7.8
370
13
185
4.4
0.4
0.9
50
610
613
149
—
951
8.4
^^^^^^^^^^M^fliMfltfMHHHMaaM
Formation
43N069W19AB 1
170
08-07-68
11.0
5.6
0.490
61
30
385
9.2
300
16
828
4.0
0.6
0.3
10
1450
1490
276
—
2080
8.5
•MHBflVMl^MM^MMMlaM^^^^^^^^^^BllpB
42N070W05DDD 1
233
07-09-68
12.0
37
1.300
414
919
720
6.8
254
0
5940
35
1.0
0.2
60
8620
8200
4810
-
7660
8.1
Wasatch
43N070U11DA 1
455
08-07-68
11.0
28.0
0.030
244
66
83
18
227
0
885
2.8
0.9
1.6
-
1450
1440
880
-
1720
8.1
• ••••III ^^^~^ . ^••••^•••^•^^^^^M
Formation
44N070W28CBC 1
261
08-07-68
11.0
8.9
0.440
40
9.7
221
5.2
345
10
306
13
1.0
0.2
10
792
785
140
-
1180
8.5
_. — -
44N071W100D 1
124
07-08-68
11.0
14
0.030
299
110
74
7.0
242
0
1080
5.8
0.4
1.9
60
1860
1710
1200
-
2040
7.9
aWell location, 42N069W07BAC 1 = Township 42 North; Range 69 West; section F; quarter, quarter,
quarter section BAC respectively.
-------
TABLE 6-13. LABORATORY ANALYSIS OF WATER FROM STOCK AND DOMESTIC WELLS
DRILLED PRIOR TO GRANTING OF LEASE TO KERR-McGEE
(Kerr-McGee Coal Corp., 1977)
Location/date/
constituent
Location
Section
T (N)
R (w)
Date sampled
Constituents (ppm)
pH (units)
Temp (° C)
TDS
TSS
Hardness (CaC03)
Elect. Cond. (mmhos)
Ca
Mg
Na
K
As
B
Pb
Si
Zn
Mn
Ni
Cr
Cd
Hg
Cu
Fe (total)
C03
HC03
S04
Cl
N03
F
KM
NE, SE
11
43
70
8-7-68
8.1
11.0
1440
-
880
1720
244
66
83
18
-
0.570
0.570
28
-
_
_
_
-
-
-
0.030
0
227
885
2.8
1.6
0.9
#11
SE, NW
19
43
69
8-7-68
8.5
11.0
1490
-
276
2080
61
30
385
9.2
-
0.010
0.010
5.6
-
-
-
*•
-
-
-
0.490
16
300
828
4.0
0.3
0.6
Well
KM #4
SE
33
44
70
2-?-75
7.3
-
4072
5
1410
-
-
-
-
0.005
0.04
0.04
-
0.4
0.3
0.04
0.04
0.01
0.001
0.04
0.1
-
-
-
_
-
-
KM #9
SE
32
44
70
2-?-75
7.4
-
1152
n
360
-
-
-
-
0.005
0.1
0.03
-
0.6
0.09
0.1
0.01
0.003
0.001
0.06
0.6
—
-
-
-
-
M
KM #1
NE
29
44
70
2-7-75
7.7
••
460
86
90
-
-
-
-
0.005
0.01
0.005
-
0.05
0.01
0.005
0.001
0.001
0.001
0.05
0.05
-
-
-
-
-
183
-------
TEMPO monitoring efforts will be aided by the water quality samples
that have been analyzed at Jacobs Ranch. Information on well-drilling tech-
niques, well completions, and sampling and analytical procedures will aid in
evaluating the usefulness of the previously collected data.
. Although Sun Oil Cordero has been shipping coal since March 1977, its
groundwater monitoring program is not well developed. In the Cordero Mining
Co. Mining Plan Update (1976), officials indicated the existence of only four
groundwater quality monitoring wells. These include three water wells and
one stock well. All are Wasatch Formation wells. Groundwater quality values
for these wells are shown on Tables 6-14 and 6-15.
Cordero reported that these samples show stable values, and that they are
usable data. However, the stock well sample was not a pumped sample, and no
field sampling techniques were discussed. Also, the Hayden well is less than
1,000 feet from a major tributary to the Belle Fourche River. The low quantity
of dissolved solids in this water is probably due to hydraulic connection with
low TDS surface water.
Cordero has reportedly designed a new monitoring plan (Tim Richmond,
Cordero Mining Co., oral communication, 1977). This plan is not yet avail-
able, but when it is acquired, further analysis can be undertaken.
In the Wyodak Resource Development Corp. Mining Plan Update (1977), chem-
ical analyses of water obtained from four wells on the lease were presented.
Two of the wells are located near the ash pit, one was at a coal completion
monitoring well near the southern end of Wyodak1s property, and the fourth
well supplies domestic water from deep Fort Union aquifers. Analytical prob-
lems are indicated by cation-anion ratios which ranged from 0.75 to 5.5 for
the analyses presented. Table 6-16 presents maximum and minimum values of
dissolved constituents in Wyodak water.
These sparse data presented by Wyodak allow little interpretation. The
analyses are consistent with regional trends, in that the shallow waters are
soft and potable. Background quality monitoring must be undertaken near pollu-
tion source areas so that future aquifer degradations can be recognized.
MUNICIPAL
City of Gillette Existing Groundwater Quality
The City of Gillette uses water from the Wasatch Formation, the Fort Union
Formation, and the Fox Hills Formation. The Wasatch wells are considered hard
water wells, and the Fort Union wells soft water wells. The Fox Hills waters
are of marginal quality, with high TDS, hi.gh fluoride concentrations, and some
associated hydrogen sulfide gas being the problem parameters. The waters from
all three systems are blended to produce a potable municipal supply. Tables
6-17 and 6-18 summarize analyses of the City wells, as performed by Nelson et
al. (1976).
-------
TABLE 6-14. GROUNDWATER QUALITY, HAYDEN RESIDENCE, SUN OIL
CORDERO LEASE (Cordero Mining Co., 1976)
^ L— — j— -L" •-,----• — — -— — - T- - - -- — j in : j im nnij M» wimp ii an T— i i ••••^••••iiim«iiail*»iir-|— ; -MI n — •wvnmirji — rr -i _ - _m _L_I _--LT._ - _ _-jn- - -_•_•-•-••- j- mTiui TT — i mrmaimwi^a^a^aMan-^MI
Date
Constituent (ppra)
Total dissolved solids
Suspended solids
Hardness
Bicarbonate-as HC03
Carbonate-as CCu
Sulfate
Chloride
Nitrate
Fluoride
Sodium
Calcium
Iron
Lithium
Arsenic
Selenium
Boron
Zinc
Mercury
Cadmium
Copper
Lead
Chromium
Molybdenum
Nickel
Aluminum
pH-field (units)
-lab (units)
Alkalinity as CaC03
Sep 3, 1974 Nov 25, 1974
328 360
6
44 45
385 377
<1 0
<5 3
7 9
1.5 2.9
1.5 1.0
118 133
10
0.24
0.01
<0.01
0.011
0.11
0.14
<0.5
<5
-
-
-
-
-
-
-
7.9 7.8
309
Feb 9, 1975
390
-
47
403
0
<1
10
1.6
1.9
150
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
7.58
8.1
—
May 22, 1975
354
-
85
506
0
4
18
1.5
1.1
122
-
0.05
0.04
0.00
0.00
0.00
0.03
0.000
0
0.00
0.00
0.00
0.00
0.00
0.0
-
-
-
185
-------
TABLE 6-15. GROUNDWATER QUALITY, WELL NUMBER 11, SUN OIL
CORDERO LEASE (Cordero Mining Co., 1976)
Constituent (ppm)
Total dissolved solids
Hardness
Bicarbonate-as HC03
-as CaC03
Carbonate-as C03
-as CaC03
Sulfate
Chloride
Nitrate
Fluoride
Sodium
Calcium
Iron
Lithium
Arsenic
Selenium
Boron
Zinc
Mercury
Cadmium
Copper
Lead
Chromium
Molybdenum
Nickel
Aluminum
pH-field (units)
-lab (units)
Alkalinity as CaC03
Nov 25, 1974
(a)
(a)
412
0
900
8
13.2
0.58
415
56
0.028
-
-
-
0.14
-
-
-
-
-
-
-
-
*»
-
8.1
337
Date
Feb 9, 1975
2000
920
770
0
910
12
0.90
0.53
440
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
7.6
7.9
—
May 22, 1975
2160
925
1010
0
959
19
0.7
0.48
321
-
0.03
0.10
0.00
0.00
0.01
0.00
0.000
0.00
0.00
0.00
0.00
0.00
0.04
0.00
-
-
-
aSample not sufficient to analyze.
186
-------
TABLE 6-16. MINIMUM AND MAXIMUM VALUES FOR WYODAK MINE WATER QUALITY
PARAMETERS3 (Wyodak Resource Development Corp., 1977)
Constituent5
Calcium
Magnesium
Sodium
Potassium
Bicarbonate
Carbonate
Sulfate
Chloride
Nitrate
TDS
pH (units)
Minimum
179
47
220
7
163
0
110
2
0
1714
7.3
Maximum
599
327
330
33
396
6
3825
110
2.7
4652
8.5
aBased on only four samples available.
Expressed in ppm except for pH.
187
-------
TABLE 6-17. WATER QUALITY ANALYSIS SUMMARY (Nelson et al., 1976)
Source
Lance
Fox Hills
Well
No. 2
Wasatch
UP! i
nc I I
No. 17
Fort
Union
_^ Well
oo No. 6
oo
Pre-
treatment
plant
product
E.D.
1 .
plant
product
City tap
water
Arsenic
allowable
0.05
NDa
(0.01)
NO
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
Barium
allowable
1.0
ND
(0.05)
ND
(0.05)
ND
(0.05)
ND
(0.05)
ND
(0.05)
ND
(0.05)
Cadmium
allowable
0.01
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
Chromium
allowable
0.05
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
Lead
allowable
0.05
ND
(0.
ND
(0.
ND
(o.
ND
(0.
ND
(o.
ND
(0.
05)
05)
05)
05)
05)
05)
Ni trate
Mercury as (N) Selenium
allowable allowable allowable
0.002 10.0 0.01
ND
(0.001)
ND
(0.001)
ND
(0.001)
ND
(0.001)
ND
(0.001)
ND
(0.001)
ND
0.98 (0.
ND
0.19 (0.
ND
0.11 (0.
ND
0.94 (0.
ND
0.23 (0.
ND
0.93 (0.
01)
01)
01)
01)
01)
01)
Silver
allowable
0.05
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
ND
(0.01)
Fluoride
allowable
(1.8)
11.2
ND
(0.1)
1.4
3.9
1.0
2.6
aND = Not detected at level indicated; Example = ND(O.Ol) = Not detected at level of 0.01 (ppm)
Note: Allowable limits indicated are mandatory as set by National interim primary drinking water regulations.
-------
TABLE 6-18.
oo
WATER QUALITY ANALYSIS SUMMARY-GILLETTE, WYOMING, WATER SUPPLY, 1976
(Nelson et al., 1976)
Source
Fox Hills
No. 1
Fox Hills
No. 2
Fox Hills
No. 3
H-l
H-7
H-8
H-10
H-12
H-13
H-14
H-15
H-16
H-17
H-18
H-19
H-20
H-21
H-22
H-23
H-24
H-25
H-26
H-27
S-2
SH-3
S-4
S-5
S-6
S-7
City water
at tap
Calculated
composite
hard water
Sampled
composite
hard water
gpm
56
210
340
41
41
48
56
82
52
82
52
96
56
59
41
56
41
37
82
74
85
59
65
83
65
75
50
55
1560
K
6
4
5
7
10
7
14
18
12
13
14
11
8
14
17
15
11
7
6
9
7
5
6
5
9
9.5
8
Ca
40
trace
3
161
321
321
291
602
552
432
502
402
221
462
552
562
311
341
6
462
20
15
15
15
131
305
216
Mg
24
trace
trace
82
188
148
127
182
255
145
170
248
18
170
194
200
109
145
2
94
30
12
12
6
70
158
103
so4
256
8
2
412
910
1320
1200
1920
2050
1300
1650
1620
460
1550
1920
2050
1150
1250
3
1180
10
12
8
8
565
920
668
Cl
64
56
36
16
170
28
8
16
24
36
28
44
44
16
20
20
12
28
12
16
28
16
16
20
32
36
44
Na
483
489
358
108
18
144
34
72
58
89
90
69
333
72
114
95
117
52
119
14
142
102
132
105
164
220
122
CO 3
1098
1074
903
647
537
390
98
500
488
586
500
537
1000
476
512
354
342
281
329
403
537
342
427
317
427
666
586
IDS
1414
1146
849
1105
1881
2160
1722
3056
3191
2304
2700
2658
1577
2518
3069
3116
1878
1961
310
1973
501
330
399
315
1181
1888
1450
Nad
1063
919
647
829
1479
1545
1213
2137
2285
1647
1909
1957
1131
1784
2162
2184
1321
1402
237
1365
406
260
312
246
867
1369
1077
PH
7.8
8.2
8.1
7.1
7.4
7.3
6.9
7.7
7.1
7.4
7.4
7.4
8.0
7.4
7.6
7.7
7.6
7.3
7.3
7.3
7.5
7.5
7.5
7.5
7.8
7.7
7.5
Conduc-
tivity
1960
1700
1242
—
2000
—
—
2810
2775
2225
2350
2625
2083
2450
2950
2985
2000
1925
435
2060
775
476
585
410
1550
1793
1950
Hardness
CaC03
199
trace
7.50
740
1574
1410
1248
2250
2425
1674
1951
2022
625
1851
2174
2224
1224
1447
23.0
1539
174
87
87
62
615
1248
963
Alka-
linity
CaCOs
901
981
740
_
441
.
-
410
400
480
410
440
820
415
420
290
280
231
270
331
441
281
350
260
350
589
481
Notes: 1. All figures are in ppm with the exception of pH and conductivity. Conductivity is in mmhos/cm^.
2. TDS = Total dissolved solids.
3. NaCl = Salt equivalent of TDS. COMPOSITE «
4. Calculated composite hard water includes weighted contribution from all hard water wells.
5. Sampled composite hard water represents a sample taken from raw water tank. [i:'ti(GPHri)(PRQPERTYn)l
6. Soft water well waters bypass raw water tank and flow directly into city water system. z'nfGPM)
-------
The Wasatch waters (prefix H) are generally nonpotable. Extremely high
sulfate concentrations make these waters particularly undesirable. Some
hydrogen sulfide gas is associated with the Wasatch waters. IDS values range
from 830 to 2,300 ppm, pH values range from 6.9 to 8.0, and the Wasatch
waters are virtually all of the calcium sulfate type.
The City of Gillette has no wells which draw water from fractured coal
seams. Therefore, the contribution from shallow aquifers, as defined in this
study, is the hard water Wasatch wells. Table 6-18 also includes data from
Fox Hills and deep Fort Union wells (prefix S). The deep Fort Union wells
yield the best product in the project area. These high-quality sodium bicar-
bonate waters are being developed more extensively as the City of Gillette
expands it drilling program.
190
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SECTION 7
INFILTRATION POTENTIAL
A necessary step in estimating the impact of the pollutants associated
with the various potential sources is to determine the volume of water leaving
the source and passing through the vadose zone into the zone of saturation.
This volume will vary with the method of waste disposal used, e.g., disposal
at the land surface, burial in the vadose zone, or burial below the water table,
and the infiltration characteristics of the soil.
Based on the limited source monitoring currently being carried out in
the project area collectively by the mines, the City of Gillette, and various
State and Federal agencies, only exemplary estimates of infiltration potential
for a few select sources can be made. These sources fall under three major
categories: coal strip mining, coal conversion, and municipal.
;
COAL STRIP MINING
Sufficient information is available in the project area to provide some
estimate of the infiltration potential of pit discharge and spoils materials.
Pit Discharge (Active Mining Area Source)
As discussed previously in Section 2 (Potential Sources of Pollution and
Methods of Disposal), the primary methods of disposal of pit discharge and
their hydrologic source classifications are:
t Dust control - diffuse
• Irrigation of reclaimed spoils - diffuse
• Discharge to surface water and subsequent percolation - line.
In the case of discharge to surface water, holding ponds are commonly
used to retain the pit discharge prior to release. These holding ponds thus
comprise a potential point source of groundwater pollution.
Pit discharge is used for dust control primarily in the months when precipi-
tation is low and the land surface is relatively dry. This water is applied to
haul roads in the pit, haul roads between the pit and the coal storage silos,
and to other unpaved roads around the plant. Such roads are commonly built on
natural soil or disturbed overburden, and sometimes on the coal itself in the
pit. Most of this water is applied during periods of maximum potential
191
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evapotranspiration. The surfaces to which the water is applied are relatively
compacted due to heavy equipment traffic. Thus, virtually none of the applied
water would be expected to infiltrate and percolate beneath the surficial
materials, but would largely be lost to evapotranspiration. However, pollu-
tant constituents in the applied water are largely retained in the surficial
materials. These constituents could later be leached to groundwater as a
result of excessive watering of the roads or as a result of rainfall causing
runoff to carry the potential pollutants into the ditches.
The infiltration potential of pit discharge used for irrigation of reclaim-
ed spoils is discussed under Spoils (Reclaimed Area Source).
The primary method of disposal of pit discharge in the winter, when use of
water for dust control is minimal or unnecessary, is to streams near the mines.
This water usually mixes with other surface water which is present in the winter.
As streamflow, there is potential for percolation, particularly in areas down-
gradient from the mines. Streamflow can percolate to aquifers whose water
levels are below the channel bottom. This is a potential line source of pollu-
tion in the hydrologic context and may be from several to tens of miles long,
depending on the streamflow and infiltration characteristics. Since much pit
discharge water is disposed of in winter months when evapotranspiration rates
are low, less opportunity exists for disposal by evapotranspiration.
Holding ponds for pit discharge may overlie native materials, such as
alluvium beneath a floodplain, or disturbed materials such as spoils. The
amount of infiltration depends to a large extent on the permeability of the
underlying materials. In general, the future locations of holding ponds and
the underlying materials are poorly known for most mines and, thus, their
infiltration potential is also poorly known. Better knowledge could be gained
by the careful measurement of flow volumes for pit discharge and the disposi-
tion of pit discharge. This, in combination with knowledge of precipitation
and evapotranspiration rates, would allow water budget calculations to deter-
mine wastewater loading and infiltration for each method of disposal.
Spoils (Reclaimed Area Source)
Four primary sources of water may eventually contact the spoils. These
sources can be grouped into point, line, and diffuse in the hydrologic context.
The sources are:
§ Precipitation or applied irrigation water - diffuse
t Streamflow - line
t Ponded water above spoils - point
t Groundwater - diffuse.
Little precipitation is expected to percolate past the topsoil due to the
relatively high potential evapotranspiration rates as compared to the precipi-
tation rate. As discussed under the modified hydrogeology portion of Section
5 (Hydrogeologic Framework), the presence of free lime in undisturbed soils
192
-------
suggests that under natural conditions little or no precipitation infiltrates
past the topsoil.
The spoils will be dressed with topsoil or equivalent. Parts of the
spoils will contain a high percentage of broken and pulverized shale that
decomposes rapidly. Such spoils will generally have a high clay content and
are expected to have low permeability. Other parts of the spoils will contain
broken and pulverized sandstone and alluvium and may be more permeable. The
structure of the soil used for surface dressing will be destroyed in handling
and this material will generally have a higher infiltration capacity than the
underlying spoils.
However, after settlement, the surface dressing will probably have a
lower infiltration capacity than the natural soils. Thus, it is unlikely
that infiltrating water from precipitation will percolate past the topsoil on
areas other than those that receive surface runoff.
Water availability will be a limiting factor in irrigating spoils during
the first several years of reclamation. The relatively low aquifer transmis-
sivities and well yields limit large scale water applications for irrigation.
However, there is some potential for downward percolation of return flow from
irrigation, depending on the amount of water applied compared to the evapo-
transpiration. Measurement of water application will enable estimates to bp
made of potential infiltration by the water budget method.
Many mining plans call for removal of coal beneath present-day flood-
plains. During mining, the stream is temporarily diverted around the active
pit. After mining, when the spoils are in place, the streams are to be
reestablished to simulate natural conditions. In this situation, spoils mate-
rials will be returned in place of natural alluvium beneath the stream
channels. Geomorphic processes will then act to reestablish a hydraulic
equilibrium. For example, alluvium may be carried into the area from up-
gradient lands, or some spoils. This will depend on the permeability of the
spoils and top dressing, the possible presence of organic deposits in the
channel infiltration, and the turbidity of the flowing water. Although the
spoils will probably have a lower infiltration capacity than the alluvium,
seepage from streamflow could be a major source of water coming into contact
with the spoils. In this case, water available for infiltration depends on
streamflow. The amount of infiltration through the channel bottom depends
not only on the subsurface materials, but on the hydraulic head distribution.
If groundwater levels are higher than the channel bottom, little or no infil-
tration will occur. Present data indicate that the natural channels in and
near the mine leases are both gaining and losing, depending on the area and
reach of the stream. The same situation may also prevail after the alluvium
is removed.
If water is temporarily ponded above spoils, then a point source of
groundwater pollution may result from leaching. In this case, the amount of
water available for infiltration can greatly exceed the evapotranspiration
rate. If groundwater levels are of sufficient depth, then percolation of
the water past the topsoil can readily occur. The infiltration rate will
depend on permeability of the spoils, the amount of organic deposits in the
193
-------
pond bottom due to biologic activity, and turbidity and temperature of the
stored water. This particular source would probably be of limited duration
for holding ponds, but if large bodies of standing water are formed on the
dressed spoils due to topographic conditions, a source of long-term duration
could be established.
In the case of groundwater migrating laterally through the spoils, the
topsoil and vadose zone are bypassed, and there is no need to discuss infil-
tration potential from the land surface.
COAL CONVERSION
Potential Pollution Sources
Of the three important types of coal conversion anticipated to be imple-
mented in the project area - steam electric, gasification, and liquification -
only steam electric currently is operating at a level where significant impacts
are expected.
Steam Electric Power Plant -
The existing and planned power plants at Wyodak will generate wastes from
a number of sources. Presently, fly ash and some other wastes are discharged
to a slurry pond in the North Pit. Future plans call for disposal of virtually
all wastes from the power plant in the two pits at the Wyodak mine. The wastes
to be disposed of are fly ash as solid fill in the pits, and liquids and other
wastes in a pond in the North Pit.
Fly ash in the solid form could be emplaced at any depth in the pit. This
disposal method is similar to that for spoils, in that some material could be
considerably above groundwater, but still be subject to leaching.
A number of types of liquid wastes, including sewage effluent, apparently
will be disposed of in the existing pond in the North Pit and may constitute'
an abundant source of water for leaching. Although an extensive clay bed report-
edly underlies the coal at Wyodak, the infiltration potential of wastes from
this pond is poorly known. A water budget analysis could be made if the volume
of flow and solid fly ash were known.
MUNICIPAL SOURCES
The City of Gillette is the principal municipality in the project area.
Three primary potential sources of groundwater pollution are associated with
the City: the landfill, the sewage treatment plant, and the water treatment
plant. A matter of regional concern is the potential impact of the coal strip
mining on the City's water-well field. Currently, only limited information is
available on the first three potential sources, and insufficient information is
available to discuss the impact of mining on the well field.
Landfill
Sources located at the landfill site include: a metal disposal area, oil
194
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waste disposal area, dead animal pit, garbage trenches, oily waste and septic
tank pumpage sites, tire disposal area, and a covered dump. Except for the
garbage trenches,(these pits and disposal areas terminate within overburden
overlying a shallow coal seam. The garbage trench is constructed within the
coal bed.
Metal Disposal Area -
The metal disposal area serves as a repository of refrigerators, old cars,
metal drums, other discarded metals, and tires. These solid wastes are dis-
carded on the land surface. Consequently, infiltration occurs across the
indigenous soil surface. Infiltration is probably optimal because of the mini-
mal disturbance of the soil surface.
Oily Waste Disposal Area -
Wastes disposed of in this area include primarily petroleum byproducts,
and possibly some hazardous substances. Infiltration may be inhibited by the
movement of sludge sediment and fines into the pores and cracks of the over-
burden. In addition, certain organic fluids may preclude capillary uptake.
Dead Animal Pit -
Infiltration beneath the dead animal pit is probably similar to that for
undisturbed materials, except possibly for slight clogging by organics.
Garbage Disposal Site -
The garbage disposal trench infiltrates into the fractured coal seam. The
surface of the seam may be disturbed by the operation of heavy equipment,
impeding intake rates. Surface runoff into the trench may carry down fine
sediments which would also tend to seal off the surface. The penetration of
landfill leachate with high concentrations of calcium and sulfate might lead to
the formation of gypsum deposits within seam fractures, again reducing infil-
tration. Precipitation of limonite [Fe(OH)2] would have a similar effect. The
degree of infiltration reduction by these mechanisms may depend greatly on the
size of fracture openings.
Pits for Oily Waste and Septic Tank Pumpage -
Infiltration characteristics are similar to those of the oily wastes dis-
posed of in the same area and may restrict infiltration.
Covered Dump -
Surface infiltration into the covered dump may be similar to that for
native material. Movement of pollutants from the base of the dump into the
native vadose zone is governed, to some extent, by processes similar to those
discussed for the active landfill.
195
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Sewage Treatment Plant
Potential sources of groundwater contamination associated with waste-
water treatment in Gillette include: (1) treatment plant facilities; (2) an
oxidation pond; (3) a sludge disposal pond; and (4) Donkey Creek.
Treatment Plant Facilities-
Treatment plant facilities include aeration, secondary clarifiers, and
aerobic digestion tanks.
Discussion with wastewater management officials for the City indicate
that the aeration, clarifier, and digestion tanks may leak directly into the
shallow groundwater system at the plant site. No data are available, however,
on the magnitude of seepage.
Oxidation Pond—
Wastewater entering the "oxidation" pond probably has received minimal
treatment in the wastewater treatment plant. Additional treatment in the
pond probably occurs under anaerobic rather than aerobic conditions.
Infiltration from the pond may be minimal because of the penetration of
benthic materials into the pores of the underlying soils - an effect observ-
ed in established ponds (Deming, 1963). An exact value will necessitate a
water balance study (Todd et a!., 1976).
Sludge Disposal Pond-
The infiltration potential of the sludge pond will be restricted by the
movement of organics and fine sediments into the pores underlying vadose zone
materials. In fact, the infiltration rate may be essentially zero.
Donkey Creek—
Wastewater discharged from the oxidation pond enters Donkey Creek,
essentially a line source of potential groundwater contamination. The qual-
ity of wastewater will change somewhat during flow in the creek. For
example, nitrates may increase because of aeration due to algal activity,
wind action, etc. In addition, periodic discharge events resulting from
flash floods or snowmelt may dilute pollutants.
Infiltration into the Donkey Creek streambed will generally decrease
over time because of clogging of the channel deposits with organics and
fines. However, periodic discharge events may scour the channel and tempo-
rarily increase intake rates. In addition to infiltration, another factor
to consider is the consumption of water from the vadose zone by riparian
vegetation along the channel. The amount of recharge into the saturated
zone will consequently be reduced during the growing season of such vege-
tation. Evapotranspirative losses may also occur directly from the shal-
low groundwater system.
196
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Water Treatment Plant
Water treatment facilities for the City of Gillette include a degasifier,
a raw water storage tank, a lime softening plant, and an electrodialysis plant
(Nelson et al., 1976). Wastewater from the lime softening plant and electro-
dialysis plant is discharged directly into the Stone Pile Creek or into a
nearby hand-dug brine disposal well. Most of the wastewater goes into Stone
Pile Creek. The disposal well is filled with filter sand and occasionally
refilled as it subsides.
Brine from the electrodialysis plant probably contains excessively high
concentrations of major chemical constituents together with trace contami-
nants. Organics and microorganisms probably are not present in significant
quantities. Sulfate is the principal contaminant in wastewater from the lime
softening process.
Wastewater discharged into the disposal well probably bypasses the
entire vadose zone and enters directly into a shallow aquifer. "Infiltra-
tion," thus, refers to seepage of wastes out of the well into the aquifer.
In effect, the well functions as a type of recharge well. Intake rates of
such wells are affected mainly by entrained air, sediment, precipitation of
salts, and microbial activity. Intake rates in the brine disposal well are
probably affected by sediment, salt precipitation, and entrained air.
Infiltration of wastewater in Stone Pile Creek may be decreased by the
precipitation of salt in the stream channel; by clogging resulting from
microbial activity; or by sedimentation. Periodic discharge events in the
Creek from snowmelt or flash floods may scour the channel and improve intake
rates. Some water loss may occur in the channel and underlying alluvium by
evapotranspiration. Such losses may increase salt concentration of infil-
trating wastewater.
197
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SECTION 8
POLLUTANT MOBILITY IN THE VADOSE ZONE
This section discusses the movement of pollutants which have infiltrated
the vadose zone. The pollution sources discussed fall under the major cate-
gories of coal strip mining, coal conversion, and municipal.
COAL STRIP MINING
The primary methods of disposing of strip mining pit discharge water are
to use the water for dust control on mining roads during the dry season, dis-
charging surplus water to streambeds during the wet season, and using the water
for irrigation of reclaimed spoils. Pollutant mobility of water infiltrating
into the vadose zone from these uses is discussed in this subsection in terms
of water movement and pollutant transport and attenuation mechanisms.
Pit Discharge (Active Mining Area Source)
When using pit discharge water for dust control, the amount applied is not
sufficient to mobilize any pollutants in the water downward from the surface.
However, road wetting in a pit can result in pollutants that remain at the
bottom of the pit or are later emplaced in subsurface spoils, enhancing their
potential for groundwater pollution. The pollutants will be comprised of those
that are indigenous to the native groundwater plus any added by mining opera-
tions.
Discharge of pit water to the surface will usually be to an alluvial
channel where the vadose zone is typically very thin. In some future situa-
tions, the discharge could be to a stream overlying spoils in a reclaimed area.
Shallow groundwater levels may prevent percolation in the channel of stream-
flow, or mixing with other surface water may attenuate pollutants substantially
before reaching a point downstream where percolation or evapotranspiration does
occur. Such a determination can be made only by accurate measurement of the
rate of waste discharge and the rate of flow upstream and downstream from the
discharge point.
Pollutant-attenuation mechanisms in the chemical sense are poorly known
because the lithology of the alluvium has not been adequately established.
Little pollutant attenuation may occur in sandy areas, while substantial pollu-
tant attenuation may occur in clay areas. Some pollutants could be removed
from the discharge area by streamflow that does not percolate and become con-
centrated downstream. Alternatively, the pollutants could migrate downward
near the point of discharge and concentrate in local aquifers.
198
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Spoils (Reclaimed Area Source)
Several sources of water may enter the vadose zone In the spoils. These
include return flow of water used for irrigation during reclamation of spoils,
streamflow percolation in former floodplain areas, and seepage from holding
ponds constructed on the spoils.
Mann (1976) discusses hydrologic interactions for wastewater in the vadose
zone of arid regions. The vertical distribution of materials comprising spoils
will affect downward movement of water in the vadose zone. Poor topsoils, dis-
turbed overburden, waste coal, shale interlayers, buried refuse, and other
materials will be somewhat haphazardly emplaced as spoils. Perching layers may
be formed and result in saturated conditions and lateral movement of percolat-
ing water in the vadose zone. Under present conditions, water flow in the
vadose zone is apparently largely through fractured consolidated rocks. Because
the spoils are largely comprised of broken up rocks, the modified flow may be
through a medium more similar to granular, porous media and this unconsolidated
material will be more subject to leaching as water passes through it. Virtually
nothing is presently known about the hydrologic characteristics of the existing
natural vadose zones or those that will exist after the spoils are emplaced.
However, the characteristic depth to water is likely to be 100 to 200 feet.
Little excess irrigation water is expected to percolate past the topsoil
during reclamation. However, the volume of applied water can be measured to
determine potential percolation past the topsoils, and the water budget can be
calculated to determine if the water application, hydrologic characteristics of
the spoils and dressing material, and climatic factors at a given location
appear to result in a net excess.
Leaching potential from streamflow percolation may be substantial in the
former floodplain areas after emplacement of spoils. Accurate measurements of
flow at stream-gaging stations along certain reaches of these areas can be used
to determine seepage losses. Depending upon the water table depth, virtually
all of the water passing through a stream channel could be absorbed. However,
groundwater beneath the floodplains could be ultimately consumed by evapotrans-
piration. Perching layers above the water table could result in horizontal
movement of the recharged water some distance away from the stream channel.
Substantial volumes of water may seep from holding ponds constructed on
spoils to the water table. Perching layers above the water table may spread
recharge water horizontally and increase the impacted groundwater area beyond
that of the surface source.
Although slightly different combinations of pollutants may be introduced
by the different sources of water, vadose zone pollutants derived from spoils
will be similar regardless of the source of water. Most of the additional
pollutants that will be in pit discharge water used for irrigation are covered
by the parameters of concern for the spoils. Thus the following discussion
generally applies to all three sources of water applied to the spoils. Poten-
tial pollutants include inorganic chemical, organic chemical, and radiological
types.
199
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Potential Mining and Reclamation Pollutants
Major inorganic chemical groundwater pollutant constituents that can
enter the vadose zone are calcium, magnesium, sodium, potassium, carbonates,
chlorides, sulfates, boron, fluorides, iron, manganese, nitrogen oxides, and
phosphorous oxides. Inorganic chemical trace elements are barium, chromium,
copper, lead, lithium, nickel, strontium, vanadium, zinc, zirconium, arsenic,
cobalt, cadmium, mercury, beryllium, selenium, molybdenum, titanium, bromine,
tin, tellurium, and silver. Organic chemical compounds (total organic carbon,
or TOC) can also migrate through the vadose zone, as can the radiological com-
pounds of uranium, thorium, and radium-226.
Runnels (1976) discusses the geochemical interactions of wastewater in
the vadose zones of arid regions.
The bacteriological content of water leaving the vadose zone should be low
due to pollutant attenuation in the topsoil and vadose zone.
Of the major inorganic chemical constituents, sodium and chloride are rela-
tively mobile. Calcium, magnesium, bicarbonate, and sulfate may be precipitat-
ed out in the vadose zone. However, these and other constituents may be
dissolved from minerals by water percolating through the vadose zone. Nitrate
is relatively mobile and iron and manganese are generally immobile under
aerobic conditions.
At least three major sources of data can be used to assess trace element
mobility in the vadose zone. First, numerous leaching studies have been per-
formed for specific elements applied to specific soils. Second, the general
geochemical behavior for many trace elements in natural water systems is fairly
well defined. Third, the occurrence of selected trace elements in groundwater
is generally known.
Keeney and Wildung (1977) summarize soil interactions with trace metals.
Fuller (1977) presents a detailed discussion of trace element mobility in soils.
He states that numerous factors control pollutant mobility, but in general the
following are most significant:
• Soil texture or particle size
• Pore space distribution in the soil
• Content and distribution of iron, aluminum, and manganese
oxides and hydroxides in the soil
• pH of the soil and percolating waters
• Oxidation-reduction potential in the soil
• Organic matter content of soils and percolating waters
• Concentration of trace elements.
200
-------
Selenium was found to be relatively mobile under aerobic conditions such
as might be present in the vadose zone. Iron, zinc, lead, copper, and beryl-
lium were moderately mobile. Arsenic, cadmium, chromium, and mercury were
slowly mobile.
Hem (1970) discusses the occurrence of a number of trace elements in natu-
ral waters. Beryllium is generally not present in dissolved form in such waters
because of its low solubility. Strontium contents are greatly limited by sul-
fate contents as high as those in the groundwater of the Gillette area. Barium
can also be adsorbed by metal oxides or hydroxides and thus generally occurs in
only small concentrations in groundwater. Titanium is not present in high con-
centrations in natural water because of the low solubility of its oxides and
hydroxides. Vanadium appears to be soluble in groundwater under anaerobic con-
ditions and may be present in significant concentrations if a source is present.
Numerous instances of chromium contamination of groundwater have been
documented. The anionic species are apparently relatively stable in many ground-
water systems. Molybdenum is predominantly present in the anionic form in
groundwater. There appears to be no effective solubility control over molybde-
num concentrations and thus large values may be found if a source is present.
Cobalt content in groundwater is likely controlled by manganese or iron oxides
and hydroxides and generally is low in groundwater. The general geochemical
behavior of nickel is similar to that of cobalt.
The solubility of cupric oxide and hydroxy-carbonate minerals tends to
limit the content of copper in groundwater to low values. Silver content is
limited by the solubility of silver oxide and silver chloride. In dilute
aerated water the equilibrium concentration of silver should be less than 0.01
ppm. Concentrations of zinc exceeding 1 ppm can be in groundwater. Cadmium
contents in groundwater are generally very low; however, some cases of
cadmium contamination have been documented for groundwater. Very few natural
waters contain detectable concentrations of mercury.
Lead content is controlled by bicarbonate and sulfate contents. Lead
sulfate is relatively insoluble, particularly in aerobic situations. Arsenic
can be present in the anionic form over the pH range of most natural waters.
Numerous occurrences of arsenic in groundwater under anaerobic conditions have
been documented. The sorption of arsenate on ferric hydroxide or other active
surfaces is likely an important factor limiting arsenic contents in natural
waters. The stable form of selenium in aerobic groundwater is the anion form
but little information is available on selenite solubility. Bromide has a geo-
chemical behavior similar to chloride, and thus can occur in relatively high
contents in groundwater.
Groundwater quality studies throughout the U.S. indicate that the trace
elements chromium, vanadium, arsenic, cadmium, selenium, molybdenum, and bromine
have been found in high concentrations in certain hydrogeologic situations. All
of these elements readily form anions in the soil-groundwater system and may be
mobile in the vadose zone. Studies of hazardous waste disposal summarized by
the U.S. Environmental Protection Agency (1976c)indicate that the results of
soil-leaching studies are consistent with these observations. These consti-
tuents should thus be given priority over other trace elements in a monitoring
program.
201
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Organic chemicals may move with percolating water through the vadose zone.
However, the organic chemicals to be expected in water that contacts materials
such as coaly wastes have not been well defined. Leenheer and Huffman (1976)
have proposed a classification scheme for organic solute characterization. The
scheme begins with dissolved organic carbon and is further divided on the basis
of solute sorption and acid-base characteristics. Little is known about the
mobility of the organic chemical fraction of wastes that comprise the spoils.
COAL CONVERSION
Anticipated Conversion Mechanisms
Of the three important types of coal conversion anticipated to be imple-
mented in the project area - steam electric, gasification, and liquification—
only steam electric currently is operating at a level where significant impacts
are expected.
Steam Electric Power Plants
Water disposal at the Wyodak power plant consists of solid fly ash land-
filled in the pits and fly ash slurry which is disposed of in a pond.
Pollutant mobility in the vadose zone for fly ash disposed of above the
water table is somewhat similar, in the hydrologic sense, to that for spoils.
The cases of primary concern would be point or line sources superimposed on the
buried fly ash. At Wyodak this could be percolation of Donkey Creek streamflow
after spoils and fly ash are emplaced. Also, holding or* storage ponds could
permit large amounts of percolation in local areas. Little is known about the
hydrologic characteristics of a vadose zone comprised of landfilled fly ash.
For the fly ash slurry pond in the North Pit, the introduction of sub-
stantial amounts of water is planned, and this can be an important source of
water for leaching materials in the slurry pond to the water table.
For fly ash, major potential inorganic chemical pollutants include calcium,
magnesium, sodium, potassium, carbonates, chlorides, sulfates, boron, fluorides,
iron, manganese, nitrogen oxides, and phosphorus oxides. Trace elements in-
clude vanadium, nickel, copper, zinc, arsenic, selenium, lead, antimony, tita-
nium, rubidium, strontium, barium, cadmium, cobalt, chromium, molybdenum,
cesium, bromine, silver, tungsten, iodine, mercury, lithium, zirconium, beryl-
lium, and tellurium. Radiological pollutants are uranium, thorium, and radium.
The discussion on pollutant attenuation in the vadose zone for spoils is
generally applicable to fly ash. However, in fly ash, the concentrations of
some trace metals are particularly high and are of concern. Vanadium, molybde-
num, and cadmium occur in high concentration and are possibly mobile. Arsenic,
selenium, bromine, and iodine should receive priority for monitoring of waters
contacting fly ash. The major constituents, total dissolved solids, fluorine,
and boron should also receive priority.
202
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MUNICIPAL
The three major municipal pollution sources are the Gillette landfill,
sewage treatment plant, and water treatment plant.
Landfill
For convenience, the mobility of pollutants underlying the following areas
are treated together: (1) metal disposal area and the tire disposal area; (2)
oily waste disposal areas and the septic tank pumpage area; (3) the dead animal
pit; and (4) the garbage disposal area.
Metal Disposal Area and Tire Disposal Area -
Potential pollutants in the metal disposal area may consist of trace con-
taminants from metals; organics in hazardous waste containers; freons, and
possibly microorganisms. Pollutants in the tire disposal area may consist pri-
marily of oily wastes, since tires are relatively stable.
The vadose zone underlying the metal disposal and tire disposal areas is
undefined at this time. However, extrapolating from the profile exposed in the
garbage trenches, it appears that the soil profile is relatively thin and under-
lain by bedrock sandstones or shales. In turn, overburden may merge at a
shallow depth with a coal seam. Water movement in both the overburden and coal
occurs primarily through fractures. Depth to water table is unknown. Because
the landfill is located on a knoll, however, it would appear that water levels
may be fairly deep, perhaps as much as 100 to 200 feet.
Mobility of trace contaminants through the relatively thin soil profile
may be governed primarily by the factors listed by Korte et al. (1977) as soil
texture, surface area, percentage of free oxides, and pH. The figures of
Korte et al. (1977), reproduced as Figures 8-1 and 8-2, will be used to estimate
the mobility of trace elements. Assuming also that the soils at the disposal
site are similar to Mohave sandy loam, the mobilities of copper and lead will
be low; and beryllium, zinc, cadmium, nickel, and mercury mobilities will be
moderate. Similarly, the mobilities of selenium, vanadium, arsenic, and
chromium may be high in the landfill soils.
Movement of trace contaminants in the shale or sandstone overburden may
occur primarily through cracks and fissures. The interactions of contaminants
with the solid matrix may not be as significant as those occurring during flow
through the soil. It is known, for example, that salts are more readily leach-
ed through a well-structured soil by unsaturated rather than saturated flow
(Biggar and Nielsen, 1967). Iron-oxide coatings have been observed in over-
burden samples from the mine sites. If such deposits occur in the landfill,
overburden trace contaminants may become sorbed (Keeney and Wildung, 1977).
Because of insufficient data, it is not possible to quantitatively
describe the movement and attenuation of trace contaminants in the coal seam.
However, trace metals may accumulate ;at the interface between overburden and
coal by some undefined process. Drever et al. (1977), for example, noted
such an accumulation of trace metals in a coal-overburden interface on the
203
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Black Thunder mine. The presence of partings above the coal with low pH
values suggests that the mobilities of cationic metals may have been augment-
ed in this region.
Movement of trace metals in the coal seam will occur through fractures.
Again, data are not available to permit the prediction of metal attenuation.
Movement of organics may be moderated by the following mechanisms: sorp-
tion, lowering of the pH into the acid range, and microbial decomposition.
Sorption may be a factor in the soil profile, but may be insignificant in the
remainder of the vadose zone. The action of microorganisms may be of primary
importance in attenuating organics from the source. Details are discussed
below in the section on oily wastes.
Movement of pesticides from containers scattered throughout the area is
difficult to predict without soils data. Davidson et al. (1976) point out
that "...pesticide movement through the soil and into the groundwater may be
increased significantly owing to adsorption-desorption characteristics of a
pesticide at high concentrations." Davidson et al. (1976) used the Freundlich
equation to characterize pesticide mobility in a silty clay loam soil.
Movement of microorganisms in the vadose zone underlying the metal disposal
and tire areas may be restricted primarily by sorption and filtration with the
shallow soil profile. Further movement into the underlying fractured bedrock
may not be inhibited by those effects. The presence of pesticides at waste or
container concentrations may reduce or stop the activity of otherwise viable
soil microorganisms (Davidson et al., 1976).
Oily Waste Disposal Areas and Septic Tank Pumpage Area -
Oily wastes probably consist of spent petroleum substances such as lubri-
cants, transmission fluid, as well as additives, and some hazardous wastes.
Because of decomposition of organics, inorganics tend to concentrate. Trace
contaminants may also accumulate.
The disposal pits for these areas appear to be constructed in bedrock.
Consequently, the ameliorating effects of the soil profile on pollutant mobility
may be minimal.
Because surface reactions of pollutants within bedrock cracks and fissures
are probably minimal, the mobility of macro-constituents within the vadose zone
may be restricted primarily by precipitation reactions. For example, calcium
carbonate and calcium sulfate may precipitate. Precipitated gypsum is evident
in the coal seam within the garbage trench. Similarly, precipitates of limonite
[Fe(OH)2] may occur. Precipitates may clog fractures to the point that infil-
tration will be inhibited-thus restricting mobility. Because of anaerobic
conditions within the pits, nitrogen will tend to remain in the organic or
ammonium forms. Leakage of wastes into the vadose zone, however, may expose
these nitrogenous forms to sufficient oxygen to permit nitrification to take
place. Nitrates will then flow farther into the vadose region.
Mobility of trace contaminants (e.g., lead in oily waste) may be affected
204
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Pb I Be I Zn I Cd I Ni
j l^^^/^^^>C^^v>^X\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\Ni
Figure 8-1. Mobility of copper, lead, beryllium, zinc, cadmium, nickel,
and mercury through 10 soils series (from Korte et al.,
1977).
Figure 8-2. Mobility of selenium, vanadium, arsenic, and chromium
through 10 soils series (from Korte et al., 1977).
205
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by the presence of organic acids within the oily waste and septic disposal
ponds. Lowering the pH tends to increase the mobility of cationic heavy metals.
Reducing conditions will also favor the mobility of such constituents as arse-
nic, beryllium, chromium, copper, iron, and zinc (Fuller, 1977). The presence
of sulfides, however, will act to precipitate FeS, ZnS, CdS, PbS, CuS, Hg2$,
and HgS. However, sulfate reduction to sulfide is restricted at lower pH
values and mobilities of trace contaminants may not be too inhibited by the
formation of precipitates.
Organics in oily wastes and septic tank pumpage will be subjected to micro-
bial decomposition. The rate of decomposition may be fairly slow, however,
because of anaerobic conditions in the pit and because of the chemical complex-
ity of the waste. According to Grove (1975): "...buried oily waste will remain
unchanged for hundreds of years." Streng (1976), however, notes microbial
decomposition of refinery sludge, buried with domestic solid waste, by the
evolution of carbon dioxide and methane gases. Both gases are evolved under
anaerobic conditions.
The subsurface movement of microorganisms is a particular problem in the
septic tank pumpage sites. Because filtration and sorption mechanisms afforded
by the soil will be bypassed, microorganisms flow directly into cracks and
fissures. If these cracks are fine enough, some filtration may be affected.
However, attenuation will occur primarily by effects such as pH, temperature,
and salt content on the viability of microorganisms.
Dead Animal Pit -
The dead animal pit also appears to be excavated into bedrock. However,
dead animals are covered with crushed overburden. Principal contaminants with-
in the dead animal pit are principally organics and pathogenic organisms.
Mobility of these constituents will be governed by the same mechanisms for the
oily wastes and septic tank pumpage areas. In addition, the crushed overburden
may afford a certain degree of filtration of organics and bacteria.
Garbage Disposal Area -
Domestic and commercial solid wastes generated in the Gillette area are
disposed of in the garbage trenches at the landfill site. The trenches may
be as much as 33 feet deep and are excavated through the overburden into the
coal seam. Leachate production in the solid wastes buried in the landfill is
favored by surface runoff into the trenches and by groundwater seepage through
the coal seams.
Pohland and Engelbrecht (1976) provide the following useful description
of leachate:
Sanitary landfill leachate is very likely to have a
very high concentration of both organic and inorganic con-
stituents, including heavy metals; accordingly, the concen-
tration of total dissolved solids will be high. The pH of
leachate is most often in the acidic range. However, the
exact nature of leachate will depend upon such factors as
206
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the composition of the solid wastes placed in the landfill
and the degree of chemical and biological activity. These
factors, along with residence time or the age of the
material in the landfill, largely influence the chemical
and physical characteristics of leachate. The presence of
pathogenic or infectious agents will be a function of:
(1) the density and nature of the pathogens placed in a
landfill; (2) the ability of the pathogens to survive or
to retain their infectivity in the landfill environment or
the leachate; and (3) the ability of the pathogens to move
through the landfill with the leachate into the surrounding
environment. Because of its chemical, physical and/or
biological properties, leachate can potentially impair the
surrounding environment, i.e., nearby surface water or
groundwater.
Because leachate will move from the base of the landfill trenches into a
fractured rather than porous matrix, attenuating mechanisms, such as those
associated with soils, may be minimal. In fact, internal modifications within
the landfill may be more important in attenuating pollutants. Such modifi-
cations are described by Pohland and Engelbrecht (1976). Internal modification
of leachate will occur via undefined physical-chemical reactions among liquid,
solid, and gaseous phases. "Chemical changes occurring may involve oxidation-
reduction reactions, coagulation, and acid-base reactions, while physical
changes may result from filtration, ion exchange, sorption and precipitation."
As a result of such reactions, solid wastes will become stabilized and the
quality of leachate will change. The concentration of organic matter and phys-
ical and chemical constituents will gradually decrease.
Leachate initially contains excessive concentrations of the major chemical
constituents, calcium, magnesium, sodium, potassium, sulfate, and bicarbonate.
The mobilities of certain of these constituents are controlled to some extent
by microbial activity within the landfill. In particular, biological stabili-
zation of organics results in carbon dioxide (C02) production and leads to the
formation of carbonic acid. The pH of leachate is reduced into the acid range.
The solubility of calcium carbonate is increased by carbon dioxide production
and a lowered pH so that the mobilities of calcium and bicarbonate ions will be
augmented. Eventually, however, the pH may be increased in the vadose zone
flow system such that calcium carbonate will precipitate. High concentrations
of sulfate observed in runoff water within the garbage trench suggest that
precipitation of gypsum may occur within the coal seam. Both calcium and sul-
fate would then be removed from the flow system.
The solubility of magnesium carbonate is also influenced by the presence
of carbon dioxide and free movement within the vadose zone would be expected.
Similarly, sodium and potassium salts are soluble unless concentrations are
increased to several thousand parts per million. Mobilities of these salts
will probably be slight.
The anaerobic environment within the landfill will prohibit nitrification
of organic and ammonium nitrogen. However, both nitrogen and ammonium nitrogen
may move to some extent into the coal seam. Sorption of ammonium nitrogen will
207
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be minimal because clays are not present. If sufficient oxygen becomes avail-
able in the flow system, nitrification of ammonium nitrogen may eventually
occur.
The mobility of trace elements in the vadose zone will be of particular
concern in the initial leachate. At that time, carbon dioxide evolution by
microorganisms will be at a maximum, resulting in the production of carbonic
acid. Organic acids will also be abundant. As pointed out above, the mobili-
ties of cationic metals are enhanced in lower pH ranges. Similarly, if reducing
conditions are obtained, the mobility of the following trace contaminants will
be increased: arsenic, beryllium, chromium, copper, cyanide, iron, and zinc
(Fuller, 1977). Organic acids may also favor the production of organic complex-
es with trace contaminants, increasing their mobilities. In contrast to these
mechanisms favoring the mobility of trace metals, precipitation of certain
metals will occur in the presence of sulfides, including FeS, ZnS, CdS, PbS,
CuS, Hg2S and HgS. In order for such sulfides to form, however, it will be
necessary for the pH to increase into a range favorable to sulfur-reducing
microorganisms.
The mobility of organics in landfill leachate will probably not be inhibit-
ed by sorption. The relatively high TDS of leachate, however, may favor the
flux of organics (Metcalf and Eddy, 1975). Possibly the principal mechanism for
retarding the movement of organics will be microbial stabilization. A secondary
effect may be that some organics may precipitate in low pH leachate. Leenheer
and Huffman (1976) note the formation of an organic precipitate upon acidifica-
tion of a groundwater sample for an oil shale area in Wyoming.
Regarding microorganisms, Pohland and Engelbrecht (1976) indicate: "...a
significant reduction in the population of microorganisms can be expected with
time... The decrease in density of biological indicators of fecal pollution
would indicate that leachate would not likely show many, if any, pathogenic
microorganisms. Examination of leachate for enteric viruses has confirmed this;
further, it has been demonstrated that leachate, because of certain of its
chemical constituents, has the capacity to inactivate pathogenic bacteria and
enteric viruses... As a consequence, the chemical and physical characteristics
of leachate are probably potentially more significant in terms of impact on the
surrounding environment than its biological properties."
From the above it appears that the leachate initially flowing into the
vadose zone will mainly contribute microorganisms. Again, because of the
limited capability of the coal seam to filter and sorb organisms, mobility may
be relatively unrestricted. Some sedimentation of bacteria may occur and
environmental conditions may be conducive to die-off. Viruses, however, would
probably flow for a considerable distance.
Sewage Treatment Plant
Section 7 discusses the infiltration potential of several potential sources
of groundwater pollution. The following discussions generalize on the mecha-
nisms which govern the mobility of the pollutants entering the vadose zone.
208
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Treatment Plant Facilities -
Lack of field data precludes an exact definition of the nature and extent
of the vadose zone at the plant site. Also, if the supposition of City of
Gillette officials is correct, the vadose zone may be completely bypassed dur-
ing leakage of pollutants from the tanks. As a first estimate, therefore,
attenuation of these pollutants in the vadose zone is minimal.
Oxidation Pond -
The factors and constituents discussed below will greatly influence the
mobility of pollutants carried by seepage from the oxidation pond.
Macroconstituents - The principal macroconstituents in lagoon seepage
will be similar to those discussed previously for leakage from the wastewater
tanks: calcium, sodium, phosphate, sulfate, bicarbonate, and nitrogen. Reac-
tions will be similar except as moderated by aerobic conditions within the
unsaturated flow regime. Calcium will tend to form precipitates with bicar-
bonate and sulfate and compete with sodium for exchange sites on clay and
organic surfaces. Phosphate mobility is strongly restricted because of inter-
action with carbonates, hydrous oxides, and silicate minerals (Keeney and
Wildung, 1977).
In the anaerobic environment of the "oxidation" pond, organic nitrogen may
be mineralized to ammonia but nitrification will be inhibited. Migration of
ammonia into the vadose zone may be restricted because of sorption on the
organics within the benthos. Further below the benthos-soil interface, ammonia
may become fixed on clay mineral surfaces or become involved in exchange reac-
tions. If oxygen levels are sufficiently high in the unsaturated media and if
a source of organic food supply is available, nitrification may occur. How-
ever, because of the shallow depth to the water table at the pond site, it is
difficult to predict the extent of nitrification.
Trace pollutants - The possibility of polluting the groundwater beneath
the lagoon at Gillette with heavy metals was pointed out previously in the
discussion above on trace pollutants. For example, Lund et al. (1976) observ-
ed heavy metals in soil solution extracts 10 feet below the base of effluent
ponds constructed in coarse textured soils. Metal concentrations in the infil-
tration from the pond will be lower, however, than the corresponding levels
in infiltration from the sludge pond, because sludges accumulate heavy metals.
Levels of zinc may be particularly high (Ms. Paddock, Supervisor, water and
wastewater plants, City of Gillette, personal communication).
Fuller (1977) listed the following 10 general factors as important in
migration of heavy metals in soils: hydrogen ion activity (pH), oxidation
reduction, particle size distribution of soils (surface area), pore size dis-
tribution, lime, organic matter, concentration of ions or salts, certain
hydrous oxides, climate (weathering), and aerobic and anaerobic conditions.
In controlled laboratory experiments, Korte et al. (1977) found that the
following soil properties were dominant in influencing trace pollutant mobil-
ity: soil texture and surface area, percentage of free oxides, and pH.
209
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As a first estimate of the mobility of heavy metals in the vadose zone
underlying the pond, the figures developed by Korte et al (1977) on the
relative mobility of cations in the seven most prominent soil orders in the
U S. are utilized. These figures are reproduced as Figures 8-1 and 8-2.
Characteristics of the soils used in the study by Korte et al. (1977) are
reproduced in Table 8-1. Comparing soils in Table 8-1 with soils in the
Gillette area, it appears that of the soils evaluated by Korte (Figures 8-1
and 8-2), the Mohave sandy loam is the most comparable to the Gillette area
soils. Figure 8-1 shows that copper and lead have low mobilities; beryllium,
zinc, cadmium, nickel, and mercury have moderate mobilities. Similarly,
Figure 8-2 shows that the following metals have high mobility: selenium,
vanadium, arsenic, and chromium.
i ^
Regarding the mobility of zinc, Fuller (1977) indicates that Zn forms
slowly soluble precipitates with carbonate, sulfides, silicate, and phosphate
ions. (The presence of sulfide in water seeping from the pond is highly
likely.)
The mobility of trace metals in soils will be moderated by the presence
of organics. Digestion in anaerobic ponds leads to the formation of organic
acids, lowering the pH. The mobility of cationic heavy metals increases as
the pH decreases. Consequently, metals may penetrate the vadose zone beneath
the pond to the depth that organic acids are neutralized.
Finally, the formation of metal-organic chelates may increase the mobility
of some trace contaminants.
Organic pollutants - The mobility of organics is affected by the factors
discussed under Treatment Plant Facilities: sorption, pH, TDS, and micro-
organisms. Of possible relevance to the migration of organics beneath the pond
are results of studies by Schaub et al. (1975) on rapid infiltration of waste
water. In particular, soil samples from active cells were observed to contain
high levels of TOC and heavy metals in a "black asphaltic" layer at a depth of
about 18 inches.
Microorganisms - Mobility of microorganisms will be influenced by filtra-
tion, sedimentation, and sorption mechanisms. The flux of viruses, in parti-
cular, will be affected by salt concentration,adsorption, pH, organic matter,
and infiltration rates. Quantitative data are needed to determine the relative
effect of these mechanisms on virus movement in the vadose zone underlying the
Gillette pond site.
Sludge Disposal Pond -
Factors affecting the mobility of contaminants in the vadose zone are
essentially identical to those discussed above for the "oxidation" pond.
However, the levels of heavy metals will be greater because of the tendency of
sludges to accumulate metals. All metals are present in excessive concentra-
tion, but the levels of lead, copper, and zinc are particularly high.
210
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TABLE 8-1. CHARACTERISTICS OF THE SOILS (from Korte et al., 1977)
ro
Soil
Wag ram
(N. Carolina)
Ava
(Illinois)
Kalkaska
(Michigan)
Davidson
(N. Carolina)
Molokai
(Hawaii)
Chalmers
(Indiana)
Nicholson
(Kentucky)
Fanno
(Arizona)
Mohave
(Arizona)
Mohave
(Arizona)
Anthony
(Arizona)
Order
Utisol
Alfisol
Spodosol
Ultisol
Oxisol
Mollisol
Alfisol
Alfisol
Aridisol
Aridisol
Entisol
CEC
pH (me/100 g)
4.2
4.5
4.7
6.2
6.2
6.6
6.7
7.0
7.3
7.8
7.8
2
19
10
9
14
26
37
33
10
12
6
EC
(vimhos/cm)
225
157
237
169
1,262
288
176
392
615
510
328
Surface
area
(m2/g)
8.0
61.5
8.9
51.3
67.3
125.6
120.5
122.1
38.3
127.5
19.8
Free
iron Total
oxides Mn Sand
(percent) (ppm) (percent)
0.6
4.0
1.8
17
23
3.1
5.6
3.7
1.7
2.5
1.8
50
360
80
4,100
7,400
330
950
280
825
770
275
88
10
91
19
23
7
3
35
52
32
71
Silt
(percent)
8
60
4
20
25
58
47
19
3/
28
14
Clay Texture
(percent) class
4
31
5
61
52
35
49
46
11
40
15
loamy sand
silty clay
loam
sand
clay
clay
silty clay
loam
silty clay
clay
sandy loam
clay loam
sandy loam
Predominant .
clay minerals
Kaolinite,
chlorite
Vermiculite,
kaolinite
Chlorite,
kaolinite
Kaolinite
Kaolinite,
gibbsite
Montmoril lonite,
vermiculite
Vermiculite
Montmorillonite,
mica
Mica, kaolinite
Mica,
montmoril lonite
Montmoril lonite,
mica
alisted in order of importance.
-------
Studies by Lund et al. (1976) demonstrated that heavy metals migrate to
depths as great as 10 feet below anaerobically digested sludge holding
ponds. The metals examined were zinc, cadmium, copper, chromium, and nickel.
The soils were coarse textured. The authors found that redistribution of
metals was closely related to change in COD of soil samples with depth. Metal
movement was thus attributed to the formation of organic chelates. Other
passible factors promoting metal migration include pH and oxidation reduction
potential. For example, during the first stage of anaerobic digestion of
sludge, organic acid formation lowers the pH to a value of about 5.1 (Health
Education Service, nd). The lower pH promotes the flux of cationic heavy
metals (Fuller, 1977). Also, according to Fuller, reducing conditions in soil
promote the movement of arsenic, beryllium, chromium, copper, cyanide, iron,
and zinc, but have little effect on the movement of cadmium, lead, and mercury.
Anaerobic conditions obviously occur in both the sludge lagoon and "oxida-
tion" pond at the Gillette wastewater treatment plant. Because of the shallow
water table at this site, heavy metals may be introduced almost directly into
the aquifer.
Donkey Creek -
Mobility of pollutants in the vadose zone will be affected by mechanisms
discussed in detail for treatment plant facilities, the "oxidation" pond, and
the sludge disposal pond. However, the area! extent of the vadose zone con-
tacted by the pollutants is far greater than for the essentially point sources.
As a result, attenuation mechanisms associated with exchange, sorption, etc.,
are enhanced.
Periodic flows of snowmelt or rainfall runoff may dilute or flush out the
vadose zone to some extent. The exchange capacity, or sorption sites, may be
rejuvenated by such dilution. However, snowmelt may increase the mobility of
viruses. Lance et al. (1976) observed the desorption and migration of viruses
in soil columns following application of deionized water. Columns were pre-
viously flooded with secondary sewage effluent.
Water Treatment Plant
The hand dug disposal well essentially bypasses the vadose zone. Most
wastewater is disposed of into Stone Pile Creek. Wastewater infiltration
into Stone Pile Creek will enter the vadose zone as a line source. The vadose
zone is probably about 80 feet thick in the vicinity of the water treatment
plant. No information is available on the lithology of the vadose zone.
However, some floodplain alluvium may be present in the vicinity of Stone Pile
Creek. The alluvium probably merges with bedrock at a shallow depth. Water
movement in the bedrock may be restricted primarily to cracks or fissures.
Attenuation of major chemical constituents in the alluvium may be govern-
ed to some extent by processes observed in soils, e.g., sorption and exchange
reactions, and precipitation-solution reactions. The high concentrations of
salts or brine from the electrodialysis plant may favor the formation of
calcium and magnesium carbonates, gypsum, and even some sodium precipitates.
The mobility of chloride will not be affected. The exchange complex of the
212
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limited amount of clays in the alluvium probably would be quickly swamped.
Precipitation may similarly limit the movement of major constituents into the
fractured bedrock underlying the alluvium.
The mobility of constituents in the lime softener wastewater will be
greater than for the electrodialysis brine because the relatively low salt
concentrations will not favor precipitation. Some sorption or exchange reac-
tions may occur; however, movement into the underlying bedrock will probably
be inhibited.
Mobility of tract constituents will be governed by such factors as pH,
reducing conditions, presence of hydrous oxides, and sorption. If the dis-
charge of electrodialysis brine or softening plant wastewater is fairly
continuous, anaerobic conditions will develop in a shallow subsurface zone of
the channel. A characteristic of such a regime is that sulfate will be re-
duced to sulfide, leading to the formation of insoluble precipitates such as
iron sulfate, cadmium sulfate, zinc sulfate, lead sulfate, copper sulfate,
and mercury sulfate. In contrast, however, reducing conditions increase the
mobility of arsenic, beryllium, chromium, copper, cyanide, iron, and zinc.
Cyanide will denitrify and evolve as a gas (Fuller, 1977). Organic acids,
formed for example from decaying channel vegetation, may lower the pH suffi-
ciently that the mobilities of cationic trace metals will be increased.
Chelation of metals with organics will also increase mobility.
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SECTION 9
POLLUTANT MOBILITY IN THE SATURATED ZONE
Pollutants which are conservative in nature or manage to pass through the
various attenuation mechanisms present in the vadose zone are of concern in
this section. These pollutants are still subject to the attenuating mechanisms
of the saturated zone, i.e., buffering, chemical precipitation, filtering, and
dilution.
If upon entering the zone of saturation a pollutant becomes immobile due
to one of these mechanisms, it becomes a philosophical question as to whether
groundwater quality degradation has taken place or whether the assimilative
capacity of the subsurface environment is being utilized. The solution to
this question lies in the proximity of existing or potential usage to the depos-
ited pollutant.
Pollutants which prove to be mobile in the saturated zone may eventually
result in damage to existing or future groundwater usage. The concentration
and toxicity of a particular pollutant and the proximity of a discharge point
for usage to the point of entry of the pollutant to the zone of saturation will
greatly influence the threat associated with a particular source.
COAL STRIP MINING
The two sources in this class which are expected to result in pollutants
reaching the saturated zone are pit discharges disposed of in certain ways,
and spoils.
Pit Discharge (Active Mining Area Source)
For pit discharge, the primary processes of concern for monitoring in the
saturated zone are percolation from polluted streamflow and seepage from hold-
ing or storage ponds. In the case of disposal to surface water, the primary
method of pollutant transport is by surface water flow. Although NPDES (Na-
tional Pollution Discharge Elimination System) permits are required for such
discharges, they are designed for surface water considerations rather than
their effect on groundwater. In addition, the present discharge requirements
are fragmentary in nature and are not comprehensive. Although pollutants
could be carried some distance downstream from the point of discharge, sub-
stantial dilution could also occur at the same time. Rates of groundwater
movement in the alluvial aquifers have been discussed under the following
material on spoils. Monitor wells should generally be placed as close to the
stream channel as possible. For percolation from holding ponds (a point
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source), considerations discussed under the following discussion on spoils
will be applicable. That is, flow rates in the consolidated formations are
generally slow and monitor wells must be located in immediate proximity to
the source. J
Spoils (Reclaimed Area Source)
Two major types of waste disposal involving spoils can be considered:
t Direct emplacement of spoils below the equilibrium water
level (after pit dewatering is ceased)
• Movement of liquids through the spoils to the water table.
This latter type has been previously addressed in Section 7 (Infiltration
Potential) and Section 8 (Mobility of Pollutants in the Vadose Zone). Again,
mobility can be discussed in terms of (1) water movement, and (2) pollutant
transport and attenuation mechanisms.
For spoils directly emplaced into areas that will be below the ground-
water level after active mining stops, no pollutant attenuation will have pre-
viously occurred. As groundwater contacts the spoils, numerous pollutants
will directly enter the groundwater. In situations where spoils are in contact
with fractured rock, such as at the bottom of former pits, pollutants may be
directly introduced to groundwater in fractures. Less pollutant attenuation
due to physical and biologic factors may occur under this circumstance than any
other. An important factor is that the lower part of the spoils will often be
the depository for materials with the highest pollution potential. Examples
are toxic soils, clay layers near the coal or interlayers, and waste coal.
Some constituents in liquids moving through all or part of the vadose zone
in the spoils will have the opportunity for substantial attenuation. However,
numerous pollutants will likely be picked up by the percolating water. The
major important cases would be for streamflow percolation and for seepage from
holding or storage ponds on the spoils.
Polluted groundwater in the spoils can be viewed as a diffuse source in
the hydrologic sense in that, after mining is completed, large areas could be
affected. The rate of movement of the polluted groundwater depends on aquifer
transmissivity, porosity, and the hydraulic gradient. Aquifers potentially
impacted include shallow alluvium, nearby downgradient coal beds, nearby down-
gradient overburden, and formations underlying the spoils. Surface water can
also be impacted because in some areas the groundwater discharges to surface
water.
Hydraulic characteristics of the spoils are poorly known and no aquifer
tests have been reported for mines near Gillette. However, Rahn (1976) report-
ed a transmissivity of 11,000 gpd per foot and a storage coefficient of 0.12
for a 27-hour pump test on a 33-foot thickness of saturated spoils at the
Hidden Creek mine near Sheridan, Wyoming. Additional pump tests are necessary
to adequately determine aquifer parameters for spoils in the Gillette area.
Transmissivity of the Fort Union and Wasatch Formations, including the coal
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beds, commonly range from several hundred to several thousand gpd per foot.
Based on present data, it appears that both the transmissivity and storage
coefficient of spoils will generally be several times larger than those of
the undisturbed consolidated formations. Aquifer characteristics for the
alluvial aquifers are generally unknown.
The hydraulic gradient to be expected in spoils is unknown. However,
King (1974) noted that hydraulic gradients in the more permeable aquifers of
the Gillette area range from 10 to 25 feet per mile. Hydraulic gradients in
the least permeable aquifers may exceed 100 feet per mile. The average hy-
draulic gradient for consolidated rock aquifers is probably about 40 to 50
feet per mile. The University of Wyoming (1976) reported on the extensive
groundwater monitoring at the ARCO Black Thunder mine. The hydraulic gra-
dient for the coal aquifer ranged from 15 to 40 feet per mile.
Porosities for different aquifer materials are not well known. However,
an independent analysis of groundwater flow rate can be obtained from the
results of carbon-14 age dating of groundwater at the Black Thunder mine.
Ages in the range of 11,000 to 34,000 years for groundwater within several
miles of the recharge point indicate very slow travel times, in the range of
only several feet per year. Assuming a porosity of 0.10 for fractured con-
solidated rock, a groundwater flow rate of about 35 feet per year is calcu-
lated, based on average values for transmissivity and hydraulic gradient.
Flow rates of groundwater in the spoils are generally unknown.
The rate of groundwater flow in the consolidated rock aquifers implies
that polluted groundwater entering these aquifers would generally move very
slowly. Thus monitor wells would have to be located very close to a poten-
tial source of pollution. It might require a thousand years for such water
to flow only one-quarter of a mile. The key conclusion is that little effect
on groundwater quality would be noticeable over the short term except in the
immediate proximity of the source. Flow rates in the alluvial aquifers
(underflow) could be much greater; however, these are generally unknown due
to lack of data on aquifer characteristics and hydraulic gradient.
The monitoring of point and line sources would necessitate having wells
as close to the surface as possible. For monitoring a diffuse source, such
as the spoils, the wells can be constructed directly in the spoils. Vadose
zone monitoring and land surface monitoring can provide information on travel
times to the saturated zone and an indication of when polluted water might be
expected to reach the water table.
The chemical aspects of pollutant transport and attenuation are not con-
sidered further because of the relatively slow groundwater flow rates, which
exert the controlling factor on pollutant mobility in the saturated zone.
COAL CONVERSION
The one coal conversion activity of particular importance in the project
area is steam electric power generation.
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Steam Electric Power Generating Plants
At the Wyodak power plant, there are two methods of disposal to consider:
solid fly ash landfilled in the pits, and the fly ash slurry pond. For the
solid fly ash disposal, materials may be placed below the equilibrium water
level. Thus, such materials would be in the saturated zone after mining ceases.
Virtually no pollutant attenuation will have previously occurred. Previous
discussions in Section 7 (Infiltration Potential) and Section 8 (Mobility of
Pollutants in the Vadose Zone) apply to solid fly ash disposed above the
equilibrium water level and to the fly ash slurry pond.
As groundwater enters the buried fly ash, a number of pollutants will
directly enter the groundwater. In situations where solid fly ash is in con-
tact with fractured rock, such as at the bottom of the pit, pollutants may be
directly introduced to groundwater in fractures. Less pollutant attenuation
due to physical and biologic factors may occur under this circumstance than
any other. The solid fly ash disposal can be viewed as a diffuse source, as
it will occur over a relatively large area. The rate of movement of ground-
water in saturated fly ash is generally unknown.
A number of pollutants could be picked up as water moves vertically through
the fly ash beneath the slurry pond, which can be viewed as a point source. For
pollutants reaching the water table, similar considerations apply as those dis-
cussed for mining spoils pollutants. That is, groundwater movement in the con-
solidated rock aquifers is generally slow and monitor wells would have to be
placed in immediate proximity to the pond.
MUNICIPAL SOURCES
All three sources discussed previously in Sections 7 and 8 also have poten-
tial for the production of pollutants which are likely to be mobile in the zone
of saturation and thus may result in groundwater quality degradation.
Landfill
Relatively little information is available on the groundwater system
beneath the landfill. According to a regional potentiometric surface map pre-
sented by Keefer and Hadley (1976), groundwater movement probably occurs in a
northerly direction beneath the site. Consequently, pollutants moving into
the groundwater flow system will move as a plume towards the City of Gillette
well field. Because of slow velocities, however, the effect may not be notice-
able for a considerable time.
Dilution may occur in the flow system, but, again, data are insufficient
at this time to facilitate predictions, for example, by flow net analyses.
An extensive scoria deposit appears to underlie the northeastern region of
the landfill site. Field observations suggest that this scoria deposit is
highly permeable. For example, when the water tank above the landfill was
drained onto the land surface recently, it was noted that the water infiltrated
rapidly. Within a day, water was observed to bubble out at the base of the pit
(courtesy Ms. Paddock). This observation suggests that snowmelt or runoff water
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may flow into the scoria and possibly into the underlying shallow aquifer
system. Dilution of a leachate plume would subsequently result.
Sewage Treatment Plant
Again, because of the lack of data, mechanisms for attenuating pollu-
tants in the saturated zone can be speculated upon only qualitatively at this
time. As pointed out by Todd et al . (1976), similar mechanisms may be opera-
tive in both the vadose zone and saturated zone. In addition, a pollutant
plume in the saturated region will be moderated by dilution with native ground-
water.
Treatment Plant Facilities -
For convenience, potential treatment plant pollutants will be categorized
as: macroinorganic, trace elements, organics, and microorganisms. It will also
be assumed that the shallow aquifer system is within floodplain alluvium, so
that flow occurs in a porous matrix, rather than through fractures.
Macroconstituents - Based on estimated wastewater quality for the City
of Gillette (see Section 3, Table 3-18), it appears that the principal macro-
constituents include calcium, sodium, sulfate, bicarbonate, phosphate, and
nitrogen. Chemical controls on the mobility of calcium are reviewed by Hem
(1970), including the tendency of calcium to precipitate with bicarbonate and
sulfate.
For the flow system beneath the treatment plant, it may be possible to use
a method developed by Hem (1970), Back and Hanshaw (1965), and Bower et al .
(1965) to determine the tendency of CaC03 to precipitate. In addition to pre-
cipitation, calcium mobility may be limited by exchange reactions on clays.
For this case, calcium will be in competition with sodium for exchange sites.
The relative degree of sodium adsorption on clays is described by the sodium
adsorption ratio, SAR:
SAR = Na+ /[(Ca++ + Mg++)/2]1/2
Sulfate and bicarbonate mobilities are linked to reactions with calcium
and magn'esium. In addition, sulfate may be sorbed to a minor extent on the
aquifer matrix and be retained by hydrous oxides of iron (Keeney and Wildung,
1977). The latter reactions, however, require low pH values. The presence
of organic acids in tank seepage may have a local effect in reducing pH and
consequently on sulfate mobility.
Phosphate retention and mobilities are discussed by Keeney and Wildung
(1977). In acid soil, phosphorus is sorbed on the surface of Fe- and Al-
containinq minerals to form surface compounds. As pointed out above, organic
acids presentin tank leakage may have a local effect on lowering pH values and
consequently promote the above reaction. However, eventually, organic acids
will be neutralized in the predominantly alkaline groundwater system. For
alkaline conditions, sorption of P on CaCOs or formation of Ca phosphate miner-
als may occur (Keeney and Wildung, 1977). Phosphate retention on clays and
hydrous oxides may also be important in the saturated flow system.
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Nitrogen mobility in the saturated system will involve only the organic-N
and NH4-N forms. That is, nitrification will be inhibited in the anaerobic
environment. Organic-N may be removed by filtration or become involved in
metal complexation reactions. Mobility of the ammonia form will be restricted
primarily by exchange reactions on clay surfaces.
Trace pollutants - The flux of trace pollutants (i.e., heavy metals and
trace metals) from the wastewater tanks will probably be markedly reduced
because of the tendency of sludge to concentrate such metals. The metals enter-
ing the groundwater system will be affected by reactions in anaerobic systems.
At the outset, it should be noted that the mobility of trace metals is greater
in anaerobic than aerobic systems (Fuller, 1977). Thus, "Reducing conditions
in soil promote mobility of most of the trace contaminants. Cadmium, lead,
and mercury mobility may be little affected by the lack of oxygen as compared
with As, Be, Cr, Cu, Cn, Fe, and Zn, which will migrate at a greater rate"
(Fuller, 1977). If sulfides are present, however, anaerobic conditions may
lead to the formation of relatively insoluble compounds such as FeS, ZnS, CdS,
PbS, CuS, HggS, and HgS. The presence of organic acids also affects the mobil-
ity of trace contaminants because cationic metals are mobile in the lower pH
ranges. However, the flux of arsenic, selenium, and cyanide will not be
appreciably affected. Organic acids may also favor the production of organic
complexes with trace contaminants increasing their mobility.
The mobility of trace contaminants will be moderated also by exchange with
clays and organic matter and adsorption reactions with hydrous oxides of Fe and
Al.
Organics - High COD, TOC, and BOD values are undoubtedly present in tank
seepage. Specifying the mobility of organics is difficult because quantitative
studies have only recently been reported. One problem is that analytical proce-
dures to identify organics are still being developed. Research is needed to
improve capabilities to analyze samples comprehensively so that significance of
trace organics in the environment can be determined (Donaldson, 1977). Recent-
ly, Leenheer and Huffman (1976) described the development of the dissolved
organic carbon (DOC) technique for fractionating organics into hydrophobic and
hydrophilic components using macroreticular resins. The technique was applied
to several natural waters. This technique has advantages over other methods,
such as activated carbon, for concentrating organics. For example, Robertson
et al. (1974) reported that only 10 percent of organics present in ground-
water beneath a landfill in Oklahoma were identified using carbon adsorption
followed by carbon chloroform and carbon alcohol extraction.
Because of the limited information on attenuation of organics in a porous
medium, only qualitative estimates of mobility can be presented at this time.
Sorption may be an important factor in attenuation. It is known, for
example, that PCB's tend to be strongly adsorbed by soil and are also insoluble
in water (Robertson et al., 1974). Leenheer and Huffman (1976) indicate that
both hydrophobic and hydrophilic organics may be sorbed by sediment.
Leenheer and Huffman (1976) noted the formation of an organic precipitate
upon acidification of a groundwater sample from an oil shale area near Rock
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Springs, Wyoming. Raising the pH dissolved the precipitate. Possibly, in a
localized situation, organic acids may lower the pH sufficiently that precipi-
tation may be a factor. However, neutralization of acids would preclude pre-
cipitation of organics.
The relatively high IDS of wastewater may affect the mobility of organ-
ics. For example, in leaching studies on spent shale using a high IDS "foul
water," Metcalf and Eddy (1975) observed about 55 percent reduction in organ-
ics expressed as TOC.
Finally, microorganisms may effect a removal of organics, for example,
by the formation of methane, carbon dioxide, and other gases.
Microorganisms - Microorganisms entering groundwater from the tanks in-
clude fecal coliform, fecal strep, virus, amoeboid cysts, intestinal worm eggs,
and parasitic fungi. The cysts, eggs, and fungi will be removed by filtration.
Bacteria may be attenuated near the interface with the aquifer by filtration,
sedimentation, and adsorption. Migration of virus may be moderated by adsorp-
tion rates (Gilbert et al., 1976). Studies by Schaub et al. (1975) on virus
mobility in coarse soils of high-rate infiltration cells, indicated that
viruses are capable of bypassing filtration and sorption mechanisms and pene-
trating groundwater. In fact, viruses were observed to migrate horizontally
more than 600 feet from the source. Migration of viruses may occur in a
similar fashion away from the tanks.
Dilution effects - The effects discussed above for attenuating the,inor-
ganic, organic, and microbiological sources will be supplemented by dilution
in the water-bearing formation. The magnitude of dilution will require field
data (currently not available) on volume of wastewater entering the water
table, waste loading, areal hydraulic head distribution, transmissivity of the
aquifer, vertical and horizontal hydraulic conductivity values, quantity and
quality of recharge from other surfaces, and pumpage in the area (Todd et al.,
1976).
Oxidation Pond -
The mechanisms of transport for pollutants from this source are similar
to those discussed above for treatment plant facilities.
Sludge Disposal Pond -
The mechanisms of transport for pollutants from this source are also simi-
lar to those discussed above for treatment plant facilities.
Donkey Creek -
Mechanisms for attenuating pollutants in the shallow saturated region
will be similar to those discussed above for treatment plant facilities.
However, dilution effects may be magnified because of the larger surface
area of the aquifer contacted by percolating wastewater. Also, periodic
flows of snowmelt and thunderstorm discharge will enhance dilution.
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Water Treatment Plant
Definitive information is not available on the hydraulic properties of the
aquifer which receives recharge from the brine disposal well or from Stone Pile
Creek. The potentiometric water surface is also unknown. Consequently, it is
not possible to develop flow nets to estimate dilution of pollutants at this
time. Mechanisms operating in the vadose zone may also contribute to attenua-
tion of pollutants but, again, data are not available.
The regional potentiometric map of the aquifer system in the Gillette
area by Keefer and Hadley (1976) shows that groundwater moves in a northerly
direction. As a consequence, recharged electrodialysis brine or softening
plant wastewater will flow toward the City of Gillette well field, which is
a relatively short distance away.
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SECTION 10
PRIORITY RANKING OF POTENTIAL GROUNDWATER POLLUTION SOURCES
Three major classifications of potential pollution sources have been
inventoried, Agricultural, Industrial, and Municipal. The principal thrust
of this inventory has been to review the existing information and data to
determine what is known about the potential impact of the sources within
these major classes on groundwater quality, and then make a preliminary
(Level One) ranking based on this information.
AGRICULTURAL ACTIVITIES
Agricultural activities in the project area were inventoried for poten-
tial groundwater pollution sources. These sources were found to be insigni-
ficant due to their diffuse nature. Irrigated farmland is practically non-
existent and dryland farming is the general method. Most farming in the area
is economically marginal. Cattle ranching is the primary agricultural acti-
vity- On the mine leases funds may become available which could result in
reclamation activities which approach intensive agricultural activities. This
could result in the presence of potential agricultural-related groundwater
pollution sources such as leaching of inorganic nitrogen from mine spoils by
irrigation waters used to establish vegetative cover, and from feedlots.
Based on the above observation,agricultural activities currently will
require only limited surveillance, e.g., through aerial photography.
INDUSTRIAL
The Industrial classification includes Construction, Oil and Gas Extrac-
tion, Coal Strip Mining, and Coal Conversion activities. Of these four, coal
strip mining and coal conversion are apparently the most significant in terms
of potential groundwater quality degradation.
Construction
During the course of the potential pollution source inventory, it was
observed that almost all of the wastes associated with the construction
industry are either disposed of in the Gillette landfill, and as a result
come under the Municipal wastes category, or are disposed of with mine solid
wastes on the leases. The same can be said for sanitary wastes from the
construction industry where the City or mine disposal facilities are utilized.
The construction industry will continue to be given only limited surveillance
to ensure that no changes in practice occur.
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011 and Gas Extraction
The oil and gas extraction industry clearly has considerable potential
as a problem area. Field observations and conversations with farmers and
ranchers indicate that good practices for handling oil field wastes are not
in force. Infiltration pits and ponds are still commonly used for disposal of
oil field wastes and brines. The Gillette landfill is also used for disposal
of oily wastes and brines where these fluids are allowed to freely percolate
into the subsurface. A reportedly common practice for disposal of oil field
wastes is to truck the material to an isolated stretch of road and open the
discharge valve whi-le moving.
The Wyoming Oil and Gas Commission has been contacted to identify their
involvement in monitoring. It was found, however, that this agency is in-
volved in leasing matters and compilation of exploration and production sta-
tistics and that little monitoring is done.
The oil and gas extraction industry is probably a major potential ground-
water pollution source, however, it will not be investigated in a regional
sense in this study. On mine leases where oil and gas wells exist or have
existed, potential groundwater impacts win be evaluated. Based on informa-
tion collected so far, these wells are of minor concern because they are so
few in number, and are under close scrutiny because of their proximity to the
mining operations.
Coal Strip Mining
Coal strip mining and its related sources have considerable potential to
produce groundwater quality degradation. Certain sources have considerably
more potential for harm than others. As should be evident from the discussion
in the previous sections, only limited monitoring has been carried out on the
sources identified in Section 2. Where monitoring of sources has been con-
ducted it has not been source oriented but directed toward assessing back-
ground quality levels, with the hope that eventually any changes in quality
due to pollutants will show up in the monitoring program.
The above approach is the traditional approach utilized, but it is con-
trary to the objectives of Public Laws 92-500 and 93-523, which are aimed at
preventing, reducing, and eliminating groundwater quality degradation. Once
pollutants show up in a background quality monitoring system, in many cases,
it is too late to institute controls. Source monitoring is the key to
determining which controls to implement and whether they are working.
Seven coal strip mining operations in various stages of development were
inventoried in Section 2 for potential groundwater pollution sources. Dif-
ferences in the kinds of sources present exist as well as in the methods of
disposal used. Sufficient information does not exist to develop a priority
ranking for each individual mine site nor for all the sites collectively. No
monitoring is underway on many of the sources. As a result, the preliminary
ranking which follows will relate only to two major coal strip mining related
sources: pit discharges, and spoils.
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For active mining, the pit discharge represents a potential source of
groundwater pollution. Much of the pit discharge is derived from native
groundwater, and this may not appear to be an important source. However, a
number of potential pollutants can enter the pit discharge. Explosives, sew-
age effluents, spoils, coal, and other sources can contribute pollutants to
pit discharge. Pit discharge as a source is transitory in nature; that is,
holding ponds would generally be moved from place to place as mining proceeds.
Pit discharge to surface water will generally be done throughout mining and will
move from place to place, but will be concentrated along the alluvial channels.
The relocation of spoils produces a changing chemical environment that
will be a permanent potential source. Some groundwater will likely always
be in contact with the lower parts of the emplaced spoils. Also, some stream-
flow will generally be rerouted, after mining, over the spoils along the for-
mer floodplains and percolation will occur in some areas. Holdi-ng ponds placed
on the spoils would be transitory in nature. Groundwater contacting the spoils
will tend to occur indefinitely in specific parts of the reclaimed areas. In
any area where groundwater was present in or above the coal seam prior to min-
ing, the spoils will generally be in contact with groundwater after mining
ceases. Spoils placed below the water table have top priority among mining
sources for the following reasons:
• The soil and vadose zone are bypassed, thus there is no pollutant
attenuation in these zones
• Generally, materials with the highest pollution potential are placed
at the bottom of the spoils, and it is this area that will be contacted
by groundwater
• This source is permanent in a sense and can contribute pollutants over
decades and centuries.
Another priority for mining sources would be for rerouted surface water
percolating into the spoils. The extent of this problem depends largely on
the chemical nature and hydraulic head ultimately established in the spoils
and underlying materials and the permeability of spoils beneath the stream
channel. This source will also be permanent and can contribute pollutants for
many decades or centuries after mining ceases. A third priority for mining
sources would be percolation of streamflow below points of pit discharge. The
extent of this problem is presently poorly known due to a lack of adequate
monitoring of pit discharge. Dilution due to mixing with surface water from
natural runoff would limit the potential groundwater pollution.
The quality of surface water can also be adversely impacted because in
some parts of the leases the groundwater contributes to surface water flow.
Over the long term, substantial increases in the salinity of surface water
could occur. This in turn could exert profound adverse impacts on downstream
users of surface water. This factor alone necessitates continual monitoring
of groundwater near the mines.
Groundwater in the coal and overlying formations is generally poor qual-
ity, and probably suitable only for industrial use (with treatment), oil field
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injection, or stock use. Alternative supplies are often available from deeper
formations; however, the costs of drilling and pumping could be greatly in-
creased. Similarly, potential water uses in the future that are presently un-
known could be adversely impacted by lowered groundwater quality. For ex-
ample, toxic substances could make the local groundwater unusable for stock
use. Secondly, there is generally a downward head gradient in the sedimentary
formations. Underlying aquifers utilized for drinking water, stock, industrial,
and other uses could be adversely impacted.
Coal Conversion
Of the three coal conversion activities projected to be implemented in
the project area, steam electric power generation, gasification, and liquifi-
cation, only steam electric power generation is being implemented on a large
scale. This plant is located on the Wyodak lease and most of its waste pro-
ducts will be disposed of in the mine pits. The primary waste will be fly ash,
which will be disposed of both in ponds and as landfill. Secondary wastes,
e.g., sewage effluent and sludge, will also be disposed of in ponds or as land-
fill.
Fly Ash Ponds-
Fly ash disposal at Wyodak in the future is presently not well known.
Past disposal has been in slurry form to a pond in the North Pit. Future dis-
posal will apparently be of two types: (1) fly ash solid landfill ing in the
pit, and (2) fly ash slurry pond. The fly ash slurry pond will be the deposi-
tory for a number of types of wastes, many of which are liquid.
Top priority should be given to fly ash disposal in the pit at levels
which will lie below groundwater level. This top priority is based on:
• The disposal is basically permanent, and pollutants can be produced
for decades or centuries
• Certain trace elements may well qualify fly ash as a hazardous waste
• The soil and vadose zone are bypassed and thus pollutant attenuation
in these zones will not occur
• Large volumes of fly ash will be disposed of.
Second"priority should be given to the fly ash slurry pond. This priority
is based on:
• The waste water disposed to this pond presents a ready source of
water for leaching pollutants to the groundwater
• This source contains a variety of pollutants, including salinity from
brine disposal and metals from the fly ash.
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Third priority should be given to fly ash land-filled above the water table
and beneath rerouted streams. This priority is based on:
• A ready source of water is available for leaching
• The fly ash may well qualify as a hazardous waste.
MUNICIPAL
The principal potential municipal sources of groundwater pollution are
the landfill, sewage treatment plant, and water treatment plant. Individual
wells within the City's well field are subject to damage from any of these
three sources and in the long term from the mining operations. Currently not
enough is known about the regional hydrogeology of the area or the long-term
impacts of the mines on water to estimate what damages to the City's well
field might result.
Only limited monitoring has been done on the landfill, sewage treatment
plant, or water treatment plant. As a result, the following priority ranking
had to be based on knowledge of what has happened under similar circumstances
for the same source type at other locations. Only when more detailed informa-
tion is available will it be possible to develop a ranking which has a high
degree of validity.
Landfill
The City of Gillette landfill is the recipient of pollution-yielding
sources rang.ing from domestic solid waste to a wide gamut of hazardous wastes.
Because no records are kept of incoming wastes, the volume and concentrations
of specific pollutants are unknown. Regulations found in the Resource Conser-
vation and Recovery Act of 1976 will, hopefully, change this in the near future.
The oily waste areas represent point sources of organic wastes as well as macro-
constituents and trace contaminants. Leakage of these pollutants into the
underlying coal seam may be occurring if the sealing action of sludges and
sediments is not effective. In fact, seepage may have been considered as the
prime method for maintaining pit capacity. The dead animal pit and the septic
tank disposal area also may introduce microorganisms into shallow groundwater.
The garbage trenches receive direct surface runoff during storm periods, pro-
moting leachate generation and subsequent movement into the exposed, fractured
coal seam. Some attenuation of pollutants may occur within the landfill proper,
particularly microorganisms. Nevertheless, excessive levels of macroconsti-
tuents and microconstituents and organics enter with the initial leachate. The
problem of groundwater contamination from pollutants at the landfill may be
accentuated by the final hydraulic heads imposed by the elevation of the site
and by movement through scoria and fractures.
Sewage Treatment Plant
The municipal sewage treatment plant sources consist of leaking tanks,
sludge disposal pond, an oxidation pond, and flow of effluent into Donkey
Creek. Leakage of raw effluent and entrained organic loads and microorganisms
226
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into the shallow groundwater system may be particularly insidious. Effluent
flow into Donkey Creek will recharge over a fairly large area. Dilution of
effluents may mitigate pollution to a considerable extent. Windmill wells
which are still at the demonstration stage of development may be using this
blended source at this time. Wastewater beyond the treatment facility will
eventually be diverted to Wyodak and will then be removed largely from the list
of pollutant sources (except for pipe leakage).
Water Treatment Plant
The prime source associated with the water treatment plant is brine from
the desalination plant, particularly if this brine is discharged into a well.
That is, pollutants are introduced directly into water-bearing strata, by-
passing the entire vadose zone. Because of poor operation, however, the
electrodialysis plant is generally inoperative. Seepage of brine into Stone
Pile Creek may also introduce pollutants into a shallow water-table aquifer.
Wastewater in the lime softening plant is not a particularly severe source
because the quality is not too different from natural groundwater.
Septic Tanks
A final possible source is septic tank leach fields in the outlying
trailer courts. This source may be particularly harmful to nearby privately-
owned water supply wells.
There is little question that the above ranking for the major sources
presented in Table 10-1 are very preliminary. This should not be surpris-
ing in view of the limited monitoring which has been done on the sources
identified in Section 2. These sources probably represent only part of the
problem, but do provide a starting point around which a complete monitoring
program can be designed.
Data and information gaps are almost total for many of the sources iden-
tified throughout the project area. The one area of knowledge showing some
degree of completeness is the geologic framework at the seven mine sites.
This is not the case for the three major potential pollution sources for the
Gillette area.
The next phase of the study will involve designing a monitoring program
which includes the limited monitoring which has taken place thus far. The
information obtained from this program will be used to verify and update the
priority ranking, to identify and implement controls, and to monitor the
effectiveness of these controls.
227
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TABLE 10-1. PROJECT AREA POTENTIAL POLLUTION SOURCE PRIORITY RANKING BY MAJOR CATEGORY
ro
ro
oo
Coal strip mining
Coal conversion
Municipal
1. Spoils (below water table)
2. Spoils (above water table
below ponds or streams)
3. Pit discharge (to streams)
1. Fly ash (below water table)
2. Fly ash slurry pond
3. Fly ash solids (above water
table)
1. Hazardous wastes at landfill
2. Disposal well water treatment
plant
3. Oily waste ponds at landfill
4. Garbage trench at landfill
5. Sewage effluent to Donkey Creek
-------
REFERENCES
229
-------
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232
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233
-------
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234
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V
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236
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APPENDIX A
237
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APPENDIX A
METRIC CONVERSION TABLE*
Non-metric units
inch (in)
feet (ft) 2
square feet (ft )
yards
square yards
mi 1 es
square miles
acres
gallons
cubic feet (ft3)
barrels (oil)
acre/ft
gallons/square foot per minute
cubic feet/second
gallons/minute**
gallons/day
million gallons/day
pounds
tons (short)
pounds/acre
parts per million (ppm)
Multiply by
Metric units
25.4
2.54
0.3048
0.290 >
91.44
0.914
10
.6093
.599
.047 >
3.
3.
3.
1,
.785 x
.785 x
.785
.590 x
1.108 x
40.74
3.532 x
6.308 x
3.785
28.32
0.028
0.454
4.536 x
9.072 x
0.907
1.122
1
-2
10
4.047 x 10
10
10
107
10'
10'
10
-1
3
-3
-2
10
-4
(m2)
millimeters (mm)
centimeters (cm)
meters (m)
square meters
centimeters (cm)
square meters (m2)
kilometers (km)
square kilometers
square meters
hectares (ha)
cubic centimeters
cubic meters
liters
liters
liters
liters/square meter per minute
liters/second
liters/second
liters/day
liters/second
cubic meters/second
kilograms
tons (metric)
kilograms
tons (metric)
kilograms/hectare
milligrams per liter (mg/1)
**
* English units were used in this report because of their current usage and
familiarity in industry and the hydrology-related sciences.
1 gpm = 1.6276 afa.
238
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Abbreviations for Units of Measure
afa acre-feet annually
Btu British thermal units
cc cubic centimeters
epm equivalents per million
g grams
h hour
meq mi Hi equivalents
mmhos/cm micromhos per centimeter
ppm parts per million
s seconds
239
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-024
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
GROUNDWATER QUALITY MONITORING OF WESTERN COAL STRIP
MINING: Identification and Priority Ranking of
Potential Pollution Sources
5. REPORT DATE
January 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Lome G. Everett (editor)
8. PERFORMING ORGANIZATION REPORT NO.
GE77TMP-50
9. PERFORMING ORGANIZATION NAME AND ADDRESS
General Electric Company-TEMPO
Center for Advanced Studies
Santa Barbara, California 93102
10. PROGRAM ELEMENT NO.
1NE625
11. CONTRACT/GRAN1
68-03-2449
NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
U.S. Environmental Protection Agency-Las Vegas, NV
Office of Research and Development
Environmental Monitoring and Support Laboratory
Las Vegas, NV 89114
14. SPONSORING AGENCY CODE
EPA/600/07
15. SUPPLEMENTARY NOTES
EMSL-LV Project Officer for this report is Leslie G. McMillion.
Commercial telephone (702) 736-2969, x241, or FTS 595-2969, x241.
i6.ABSTRACT y^g rep0r^ -js the first in a series of several to come out of a 5-year
study to assess the impact on groundwater quality of coal strip mining in the Western
United States. Presented is a preliminary priority ranking of potential sources of
groundwater pollution in an area within Campbell County, Wyoming, overlying one of
the major coal fields in the Powder River Basin.
The priority ranking was developed by making a thorough review of the existing
data available from monitoring activities of mining companies and various county,
State, and Federal agencies. Potential pollution sources and methods of waste dis-
posal at seven operating mines and also in the vicinity of the City of Gillette were
inventoried. The data were carefully reviewed to identify the potential pollutants
associated with each source. Groundwater usage was inventoried. An appraisal of the
hydrogeologic framework and existing groundwater quality was developed. By super-
imposing the identified potential groundwater pollution sources on the hydrogeologic
framework and making estimates of pollutant mobilities from these sources, the pre-
liminary priority ranking was developed. The study has revealed a major data and
information gap in the understanding of pollutant mobilities and, thus, the priority
ranking presented will likely undergo considerable revision as the program progresses.
This report was submitted in partial fulfillment of Contract #68-03-2449 by General
Electric-TEMPO, Center for Advanced Studies, under the sponsorship of the U.S.
Environmental Protection Aaencv.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Groundwater
Groundwater quality
Water pollution sources
Coal mines
Mine wastes
Waste disposal
Strip mining
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Groundwater movement
Monitoring methodology
Pollutant identification
Pollutant source ranking
08D
08H
081
15B
8. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO OF PAGES
264
20. SECURITY CLASS (This page)
UNCLASSIFIED
22.
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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