Un.ted States Eastern Environmental EPA 520'l-83-007
Environmental Protection Radiation Facility June 1963
Agency P C Bo« 3009
ol Radiation Programs Monlgornery AL 36193
&EPA
Radiation
Potential Health and
Environmental Hazards of
Uranium Mine Wastes
Report To The Congress
Of The United States
Volume 2 of 3 Volumes
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EPA 520/1-6-83-007
POTENTIAL HEALTH AND ENVIRONMENTAL
HAZARDS OF URANIUM MINE WASTES
A Report to the Congress of the United States
in Response to Public Law 95-604
June 10, 1983
U.S Environmental Protection Agency
Office of Radiation Programs
Washington, D.C. 20460
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CONTENTS
Page
Foreword ............ xxix
1.0 Introduction ........•• 1-1
1.1 Purpose .......... 1-1
1.1.1 Contents ......... 1-1
1.2 Uranium Ore Production and Future Uranium Needs . . 1-2
1.2.1 Past Production 1-2
1.2.2 Projected Needs for Uranium 1-2
1.3 Overview of Uranium Mining Operations .... 1-5
1.3.1 General ......... 1-5
1.3.2 Surface Mining 1-12
1.3.3 Underground Mining ....... 1-16
1.3.4 In Situ Leaching ....... 1-19
1.3.5 Other Mining Methods 1-27
1.3.5.1 Heap Leaching ....... 1-27
1.3.5.2 Mine Water Recirculation .... 1-28
1.3.5.3 Borehole Slurry Mining 1-29
1.3.5.4 Uranium as a By-Product .... 1-30
1.4 Current Applicable Standards and Regulations . . 1-30
1.4.1 Federal Regulations 1-30
1.4.1.1 Federal Laws, Regulations and Guides for.
Protection of Health and Environment . . 1-31
1.4.1.1.1 Air Quality 1-31
1.4.1.1.2 Water Quality 1-33
1.4.1.1.3 Land Quality 1-34
1.4.1.2 Federal Mineral Leasing and Location/Patent
Laws 1-35
1.4.1.2.1 Prospecting and Mining Rights . . 1-36
1.4.1.2.2 Mining and Environmental Plans . . 1-36
1.4.1.3 Laws Having Potential Applicability . . 1-36
ii
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Page
1.4.2 State Regulations 1-42
1.4.2.1 Colorado 1-45
1.4.2.2 New Mexico 1-47
1.4.2.3 Texas 1-49
1.4.2.4 Utah 1-49
1.4.2.5 Washington 1-50
1.4.2.6 Wyoming 1-51
1.5 References ; . 1-53
2.0 Inventory of Uranium Mines 2-1
2.1 References 2-16
3.0 Potential Sources of Contaminants to the Environment and
Man ............ 3-1
3.1 Background Concentrations of Radionuclides and Trace
Metals 3-1
3.1.1 Naturally Occurring Radionuclides .... 3-1
3.1.2 Stable Elements ....... 3-6
3.2 Water-Related Aspects of Uranium Mining . . . 3-11
3.2.1 Previous and Ongoing Hydrologic and Water Quality
Studies Related to Uranium Mining .... 3-11
3.2.2 Mine Water Management 3-13
3.2.3 Water Quality Effects of Mine Water Discharge . 3-23
3.2.3.1 Behavior of Contaminants in the Aqueous
Environment 3-23
3.2.3.1.1 Dilution and Suspended Sediment
Transport 3-25
3.2.3.1,2 Sorption and Desorption . . . 3-25
3.2.3.1.3 Precipitation 3-28
3.2.3.1.4 Biological Assimilation and
Degradation 3-30
3.2.3.1.5 Complexation 3-31
3.2.3.2 Results of Field Studies in Uranium
Mining Areas 3-32
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Page
3.2.3.2.1 Colorado 3-32
3.2.3.2.2 Wyoming 3-34
3.2.3.2.3 Texas 3-38
3.2.3.2.4 New Mexico 3-39
3.2.3.3 Summary ........ 3-43
3.3 Surface Mining .......... 3-44
3.3.1 Solid Wastes . 3-44
3.3.1.1 Overburden Piles 3-45
3.3.1.2 Ore Stockpiles 3-54
3.3.1.3 Sub-Ore Piles 3-60
3.3.1.4 Reclamation of Overburden Piles . . . 3-62
3.3.2 Mine Water Discharge 3-63
3.3.2.1 Data Sources 3-63
3.3.2.2 Quantity and Quality of Discharge . . . 3-64
3.3.3 Hydraulic and Water Quality Effects of Surface
Mine Discharge 3-68
3.3.3.1 Runoff and Flooding in the Model Surface
Mine Area 3-68
3.3.3.1.1 Study Approach 3-68
3.3.3.1.2 Description of Area ..... 3-70
3.3.3.1.3 Method of Study 3-72
3.3.3.1.4 Discussion of Results .... 3-77
3.3.3.2 Impacts of Seepage on Groundwater . . . 3-89
3.3.4 Gases and Dusts from Mining Activities . . . 3-93
3.3.4.1 Dusts and Fumes 3.93
3.3.4.2 Radon-222 from the Pit, Storage Piles, and
Ore Handling 3.99
3.4 Underground Mining 3-107
3.4.1 Solid Wastes 3-107
3.4.1.1 Waste Rock Piles 3-109
3.4.1.2 Ore Stockpiles 3_110
3.4.1.3 Sub-Ore Piles 3_112
iv
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Page
3.4.2 Mine Water Discharge 3-113
3.4.2.1 Data Sources 3-113
3.4.2.2 Quality and Quantity of Discharge . . . 3-114
3.4.3 Hydraulic and Water Quality Effects of Underground
Mine Discharge 3-120
3.4.3.1 Runoff and Flooding in the Model Underground
Mine Area 3-120
3.4.3.1.1 Study Approach 3-120
3.4.3.1.2 Description of Area 3-122
3.4.3.1.3 Estimate of Sub-basin Flood Flow . . 3-124
3.4.3.1.4 Prediction of Sub-basin Water Quality . 3-132
3.4.3.2 Impacts of Seepage on Groundwater . . . 3-149
3.4.4 Gases and Dusts from Mining Activities . . . 3-155
3.4.4.1 Radon-222 in Mine Exhaust Air .... 3-155
3.4.4.2 Aboveground Radon-222 Sources .... 3-157
3.4.4.3 Dusts and Fumes ....... 3-159
3.5 In Situ Leach Mining 3-168
3.5.1 Solid Wastes 3-159
3.5.2 Associated Wastewater 3-172
3.5.3 Airborne Emissions 3-174
3.5.4 Excursion of Lixiviant ....... 3-178
3.5.5 Restoration and Reclamation 3-179
3.6 Other Sources 3-185
3.6.1 Mineral Exploration 3-185
3.6.1.1 Environmental Considerations .... 3-187
3.6.1.2 Radon Losses from Drill Holes .... 3-192
3.6.1.3 Groundwater 3-193
3.6.1.4 Fumes 3-193
3.6.1.5 Model Drilling 3-194
3.6.2 Precipitation Runoff from Uranium Mines . . . 3-194
3.7 Inactive Mines ..... 3-204
3.7.1 Inactive Surface Mines 3-204
3.7.1.1 Waste Rock Piles 3-213
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Page
3.7.1.2 Radon-222 from the Mine Area .... 3-216
3.7.1.3 Land Surface Gamma Radiation .... 3-222
3.7.2 Inactive Underground Mines 3-227
3.7.2.1 Waste Rock Piles 3-229
3.7.2.2 Radon-222 from the Mine Area .... 3-232
3.7.2.3 Land Surface Gamma Radiation .... 3-237
3.8 References 3-242
4.0 Description of Model Mines ....... 4-1
4.1 Surface Mine 4-1
4.2 Underground Mine ........ 4-4
4.3 In Situ Leach Mine 4-7
4.4 Inactive Surface Mine 4-8
4.5 Inactive Underground Mine 4-9
5.0 Potential Pathways 5-1
5.1 General .......... 5-1
b.1.1 Vegetation 5-1
5.1.2 Wildlife 5-1
5.1.3 Land Use 5-2
5.1.4 Population Near Mining Areas 5-2
5.1.5 Population Statistics of Humans and Beef Cattle . 5-12
5.2 Prominent Environmental Pathways and Parameters for
Aqueous Releases 5-12
5.2.1 Individual Committed Dose Equivalent Assessment . 5-13
5.2.2 Collective (Population) Dose Equivalent Assessment . 5-15
5.3 Prominent Environmental Pathways and Parameters for
Atmospheric Releases 5-16
5.3.1 Individual Committed Dose Equivalent Assessment . 5-16
5.3.2 Collective (Population) Dose Equivalent Assessment . 5-18
5.4 Mine Wastes Used in the Construction of Habitable
Structures 5-19
5.5 References 5-20
6.0 Health and Environmental Effects 6-1
6.1 Health Effects and Radiation Dosimetry .... 6-1
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Page
6.1.1 Radioactive Airborne Emissions 6-1
6.1.2 Nonradioactive Airborne Emissions .... 6-26
6.1.2.1 Combustion Products 6-26
6.1.2.2 Nonradioactive Gases 6-28
6.1.2.3 Trace Metals and Particulates in the Form
of Dust 6-28
6.1.3 Radioactive Aquatic Emissions ..... 6-35
6.1.4 Nonradioactive Aquatic Emissions .... 6-42
6.1.5 Solid Wastes 6-44
6.1.5.1 Radium-226 Content 6-44
6.1.5.2 Estimates of Potential Risk .... 6-45
6.1.5.3 Using Radium Bearing Wastes in the Construction
of Habitable Structures 6-46
6.1.5.3.1 Use of Uranium Mine Wastes . . . 6-48
6.2 Environmental Effects ....... 6-48
6.2.1 General Considerations ...... 6-48
6.2.2 Effects of Mine Dewatering 6-52
6.2.3 Erosion of Mined Lands and Associated Wastes . . 6-54
6.2.4 Land Disturbance from Exploratory and
Development Drilling ...... 6-56
6.2.5 Land Disturbance from Mining ..... 6-59
6.2.5.1 Underground Mines ...... 6-59
6.2.5.2 Surface Mines 6-59
6.2.6 Retirement Phase 6-59
6.3 References ......... 6-73
7.0 Summary and Recommendations ....... 7-1
7.1 Overview .......... 7-1
7.2 Sources and Concentrations of Contaminants . . . . 7-1
7.2-1 Surface and Underground Mines ..... 7-1
7.2.2 In Situ Leach Mines 7-7
7.2.3 Uranium Exploration ....... 7-8
7.3 Exposure Pathways ........ 7-8
7.4 Potential Health Effects 7-9
Vll
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Page
7.4.1 Radioactive Airborne Emissions ..... 7-9
7.4.2 Nonradioactive Airborne Emissions .... 7-13
7.4.3 Radioactive Aqueous Emissions 7-13
7.4.4 Nonradioactive Aqueous Emissions .... 7-15
7.4.5 Solid Wastes 7-16
7.5 Environmental Impacts ....... 7-16
7.5.1 Land and Water Contamination ..... 7-17
7.5.2 Effects of Mine Dewatering 7-22
7.5.3 Erosion of Mined Lands and Associated Wastes . . 7-22
7.5.4 Exploratory and Development Drilling . . . 7-23
7.5.5 Underground Mining . . . . . - 7-23
7.5.6 Surface Mining 7-24
7.6 Regulatory Perspective ....... 7-25
7.7 Conclusions and Recommendations ..... 7-25
7.7.1 Conclusions ........ 7-26
7.7.1.1 Solid Wastes 7-26
7.7.1.2 Airborne Effluents 7-26
7.7.1.3 Waterborne Effluents . 7-27
7.7.1.4 Exploratory and Development Drilling . . . 7-27
7.7.2 Recommendations to Congress . . . . . 7-28
7.8 Other Findings 7-28
7.9 References 7-29
Appendixes (See Volume 3)
A. Summary of Federal Laws Potentially Affecting Uranium Mining
B. Federal Water Programs and Rights Activities
C. Congressionally Approved Compacts that Apportion Water
D. State Laws, Regulations, and Guides for Uranium Mining
E. Active Uranium Mines in the United States
F. Inactive Uranium Mines in the United States
G. General Observations of Uranium Mine Sites in Colorado,
New Mexico, Texas, and Wyoming.
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H. Influence of Mine Drainage on Seepage to Groundwater
and Surface Water Outflow
I. Computation of Mass Emission Factors for Wind Erosion
J. Aquatic Dosimetry and Health Effects Models and Para-
meter Values
K. Airborne Pathway Modeling
L. Health Risk Assessment Methodology
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FIGURES
Page
1.1 Uranium mining regions in the western United States . . 1-4
1.2 The percent of $50 U30Q reserves located in the principal
mining states 1-8
1.3 The percent of $50 U30g reserves located in the various
mining regions .....•>••• 1-9
1.4 Artist's conception of open pit mining operation and
support facilities ......... 1-13
1.5 Generalized underground mine showing modified room and
pillar method of mining . . . . . . . . 1-17
1.6 Diagrams of some common injection-recovery well patterns
used in uranium in situ leach mining 1-26
2.1 Location of active and inactive uranium mines and principal
uranium mining districts in Colorado ..... 2-6
2.2 Location of active and inactive uranium mines and principal
uranium mining districts in the Uravan Mineral Belt of
western Colorado 2-7
2.3 Location of active and inactive uranium mines in the Grants
Mineral Belt and other areas of New Mexico .... 2-8
2.4 Location of active, inactive, and proposed surface and in
situ uranium mines in Texas ....... 2-9
2.5 Location of uranium mines and mining districts in Utah . . 2-10
2.6 Location of uranium mines and principal uranium mining
districts in southeastern Utah 2-11
2.7 Location of active and inactive uranium mines and principal
uranium mining areas in Wyoming ...... 2-12
2.8 Location of active and inactive uranium mines in the Gas Hills
and Crooks Gap-Green Mountain areas of central Wyoming . . 2-13
2.9 Location of active and inactive uranium mines in the Shirley
Basin, South Powder River Basin, and Pumpkin Buttes areas
of Wyoming 2-14
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Page
3.1 The uranium decay series showing the half lives and mode of
decay 3-2
3.2 The thorium decay series showing the half lives and mode of
decay 3-3
3.3 Disposition of drainage water from active surface and under-
ground uranium mines 3-14
3.4 Location of mines, ore and waste storage areas and monitoring
stations at the Morton Ranch mine, South Powder River Basin,
Wyoming 3-37
3.5 Location of study areas, sampling stations and uranium mines,
Poison Canyon area, McKinley County, New Mexico . . . 3-41
3.6 Sample locations for radionuclides and select trace metals
in sediments, San Mateo mine, New Mexico .... 3-42
3.7 Potential sources of environmental contamination from active
open pit uranium mines ........ 3-46
3.8 Storage pile configurations assumed at surface and underground
mines 3-48
3.9 Sketch of sub-basin, basin, and regional basin showing orien-
tation of principal drainage courses, areas of drainage, and
location of mines ......... 3-69
3.10 Average monthly flows for the Cheyenne River and Lance Creek
near Spencer, Wyoming, for the period 1948-1970 . . . 3-71
3.11 Suspended sediment concentration to discharge, Salt Wells
Creek and Tributaries, Wyoming 3-75
3.12 Relation of discharge and specific conductance to time at
Salt Wells Creek, Green River Basin, Wyoming .... 3-76
3.13 Periods of no flow in Lance Creek and the Cheyenne River
near Riverton, Wyoming, for the period 1948-1978. . . . 3-82
3.14 Configuration of open pit model mines 3-105
3.15 Potential sources of environmental contamination from active
underground uranium mines ....... 3-108
XI
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Page
3.16 Sketch of sub-basin, basin, and regional basin showing
orientation of principal drainage courses, areas of drain-
age, and location of mines in the New Mexico model area . 3-121
3.17 Average monthly flows for the period of record for the Rio
San Jose and the Rio Puerco in New Mexico .... 3-129
3.18 Periods of no flow in the Rio San Jose and Rio Puerco . . 3-131
3.19 Total flow volumes in one-day periods for floods of various
recurrence intervals in the sub-basin and basins in New
Mexico ........... 3-133
3.20 Total flow volumes in seven-day periods for floods of various
recurrence intervals in the sub-basin and basins in New
Mexico ........... 3-134
3.21 Principal streams and surface water sampling stations in the
Churchrock and Gallup areas ....... 3-145
3.22 Average depth of exploratory drilling in the U.S. uranium
industry from 1948 to present 3-188
3.23 Annual waste to ore ratios for surface mining of uranium
(1948 to 1979) 3-209
3.24 Cross section of model inactive surface mine . . . 3-214
3.25 Results of gamma exposure rate survey at the 1601 pit and
environs, Morton Ranch uranium mine, Converse County,
Wyoming 3_226
3.26 Waste to ore ratios for inactive underground uranium mines
from 1932 to 1977 3-228
3.27 Radon-222 concentrations in mine air discharged by natural
ventilation 3_236
3.28 Gamma radiation survey around an inactive underground uranium
mine in New Mexico 3-240
5.1 Potential airborne pathways in the vicinity of uranium
mines 5_17
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Page
6.1 Average indoor radon-222 decay product measurements (In
working levels) as a function of average radium-226 con-
centration in soil 6-47
6.2 Example of natural reclamation of drill sites . . . 6-57
6.3 Inactive underground mine site 6-60
6.4 Example of active and inactive surface mining activities . 6-63
6.5 Mine wastes eroded by ephemeral streams in the Mesa Mon-
tanosa area, New Mexico 6-64
6.6 Basal erosion of a uranium mine waste pile by an ephemeral
stream in the Mesa Montanosa area, New Mexico . . . 6-65
6.7 Scattered piles of mine waste at the Mesa Top mine, Mesa
Montanosa, New Mexico 6-66
6.8 Close up view of easily eroded sandy and silty mine waste
from the Mesa Top mine, Mesa Montanosa, New Mexico . . 6-66
6.9 Gullying and sheet erosion of piled and spread mine wastes
at the Dog Incline uranium mine, Mesa Montanosa, New Mexico . 6-67
6.10 Recent erosion of unstabilized overburden piles at the
inactive Galen mine, Karnes County, Texas .... 6-68
6.11 Unstabilizied overburden piles and surface water erosion at
the Galen mine, Karnes County, Texas 6-68
6.12 Aerial view of the Manka mine, Karnes County, Texas . . 6-70
6.13 Overburden pile showing the weak vegetative cover and
gullying associated with improper stabilization at the
Manka mine, Karnes County, Texas, 6-70
6.14 Inactive Hackney mine, Karnes County, Texas .... 6-72
Appendix G
G.I Plan view of inactive underground uranium mine No. 1, related
waste rock piles, and surface gamma exposure rates, Uravan
Mineral Belt, Colorado G-3
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Page
G.2 Sectional view of inactive underground uranium mine No. 2,
related waste rock piles, and surface gamma exposure rates,
Uravan Mineral Belt, Colorado 6-4
G.3 Plan, view of inactive underground uranium mine No. 3, re-
lated waste rock piles, and surface gamma exposure rates,
Uravan Mineral Belt, Colorado G-6
G.4 Sectional view of inactive underground uranium mine No. 4,
related waste rock piles, and surface gamma exposure rates,
Uravan Mineral Belt, Colorado 6-7
G.5 Plan view of inactive underground uranium mine No. 5, re-
lated waste rock piles, and surface gamma exposure rates,
Uravan Mineral Belt, Colorado G-8
G.6 Plan view of inactive underground uranium mine No. 6, re-
lated waste rock piles, and surface gamma exposure rates,
Uravan Minera^Belt, Colorado G-9
G.7 Plan view of inactive underground uranium mine No. 7, re-
lated waste rock piles, and surface gamma exposure rates,
Central City District, Colorado ...... G-ll
G.8 Plan view of inactive underground uranium mine No. 8, re-
lated waste rock piles, and surface gamma exposure rates,
Central City District, Colorado G-12
G.9 Plan view of inactive underground fluorspar uranium mine No.
9, related waste rock piles, and surface gamma exposure rates,
near Jamestown, Colorado G-13
G.10 Plan view of inactive underground uranium mine No. 10, related
waste rock piles, and surface gamma exposure rates, Central
City District, Colorado G-15
G.ll Typical mine waste pile associated with a small- to medium-
sized inactive underground uranium mine, Uravan Mineral
Belt, Colorado G-16
G.12 Side view of a typical underground uranium mine located on
the rim of a sandstone mesa, Uravan Mineral Belt, Colorado . G-16
xiv
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Page
G.13 Mine waste accumulations near the portal of a typical under-
ground rim-type uranium mine, western Colorado . . . G-17
G.14 Mine waste dump associated with a typical rim-type under-
ground uranium mine, western Colorado G-17
G.15 Movement of fluorspar-uranium mine wastes from a tailings
pile into a stream, Jamestown area, Colorado .... G-19
G.16 1972 aerial photograph of the Galen and Pawelek open pit
mines, Karnes County, Texas . G-27
G.17 1978 aerial photograph of the Galen and Pawelek open pit
mines, Karnes County, Texas 6-27
G.18 Results of gamma exposure rate survey at the 1601 pit and
environs, Morton Ranch uranium mine, Converse County, Wyoming G-31
G.19 Location of sampling stations at the Morton Ranch mine, South
Powder River Basin, Wyoming G-33
G.20 Sample locations for radionuclides and select trace metals in
sediments, San Mateo mine, New Mexico ..... G-34
Appendix H
H.I Wyoming model area sub-basin drainage system H-3
H.2 Model area stream cross section ...... H-3
H.3 New Mexico model area sub-basin drainage system H-9
Appendix J
J.I Surface stream flow pattern within drainage area J-3
J.2 Conservation of mass relationship for resuspension model . J-13
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TABLES
Page
1.1 Domestic uranium production by state from 1948 to
January 1, 1979 1-3
1.2 Projected annual nuclear capacity (GWe) in the U.S. . 1-6
1.3 Domestic uranium reserves by state as of January 1, 1979 1-7
1.4 The quantities of U30g produced in 1978 by the various
mining methods ......••• 1-10
1.5 The predicted methods of mining ore reserves . . . 1-10
1.6 Summary of current in situ leaching operations as of
January 1, 1978 ........ 1-21
1.7 Trace metal concentrations of recirculated acid and
alkaline lixiviants 1-25
1.8 Federal laws, regulations, and guides for uranium mining 1-32
1.9 Requirements to obtain rights to prospect or explore
by federal, state and private lands .... 1-37
1.10 Requirements to obtain rights to mine ore by federal,
state and private lands 1-39
1.11 Requirements for mining and environmental plans by
federal, state and private lands 1-41
1.12 State laws, regulations, and guides for uranium mining . 1-43
2.1 Type of U.S. uranium properties 2-3
2.2 The location and type of active uranium properties . 2-4
2.3 The location and type of inactive uranium properties . 2-5
2.4 Cumulative ore production through January 1, 1979 . . 2-15
3.1 Gamma-ray energy released by one gram of rock . . 3-4
3.2 Radionuclide content and dose equivalent rates from
common rocks and soil 3-4
3.3 Average dose equivalent rates due to terrestrial
radiation in western nininq states ..... 3-5
3.4 Radionuclide concentrations in surface and groundwater
in the vicinity of a proposed uranium project . . 3-7
3.5 Concentrations of selected elements in igneous and
sedimentary rocks 3-8
xvi
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Page
3.6 Concentrations of selected elements in surface water at
five locations in the vicinity of a proposed uranium
project 3-9
3.7 Concentrations of selected elements in groundwater at six
locations in the vicinity of a proposed uranium project. 3-10
3.8 Estimated average concentrations of three metals in
U.S. streams 3-6
3.9 Summary of feed water sources for active U.S. uranium
mills 3-17
3.10 Current and projected uranium mine discharges in the
Grants Mineral Belt, New Mexico 3-21
3.11 Estimated surface areas associated with overburden piles 3-50
3.12 Particle size distributions of mill tailings and mine
overburden 3-52
3.13 Natural radionuclide concentrations in various common
rock types 3-52
3.14 Annual average airborne radionuclide concentrations
• in the vicinity of an open pit uranium mine . . . 3-53
3.15 Uranium and stable element concentrations measured in rock
and soil samples from two uranium mines .... 3-55
3.16 Concentration of radionuclides and stable elements in
overburden rock from the model surface mines . . . 3-56
3.17 Estimated average areas of ore pile surface and pad . 3-57
3.18 Distribution of ore reserves by the type of host . . 3-59
3.19 Average stable element concentrations in sandstone
ores of New Mexico ........ 3-59
3.20 Estimated average surface areas of sub-ore piles during
the 17-year active mining period 3-61
3.21 Summary of average discharge and water quality data for
uranium mines in Wyoming and a comparison with NPDES
limits .......... 3-65
3.22 Water quality associated with surface and underground
mines in various stages of construction and operation . 3-67
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3.23 Peak discharge and total volume for floods of 2, 5, 10,
25, 50 and 100 year recurrence intervals . . . 3-78
3.24 Summary of calculated total flow in the Wyoming model
area sub-basin using the USGS and SCS methods . . 3-79
3.25 Annual contaminant loading from one uranium mine and
resulting concentrations in floods within the sub-basin
for return periods of 2 to 100 years .... 3-84
3.26 Concentrations in basin and regional basin streams as a
result of surface mine discharge ..... 3-86
3.27 Comparison of potable and irrigation water standards and
surface water quality affected by surface mine drainage 3-87
3.28 Northeastern Wyoming groundwater sources . . . 3-91
3.29 Groundwater quality of wells sampled by the three major
uranium producers in the South Powder River Basin,
Wyoming .......... 3-92
3.30 Estimated air pollutant emissions from heavy-duty
equipment at surface mines ...... 3-94
3.31 Average annual dust emissions from mining activities . 3-97
3.32 Average annual emissions of radionuclides (pCi) and stable
elements (kg) from vehicular dust at the model surface
mines 3-100
3.33 Average annual emissions of radionuclides (yCi) and stable
elements (kg) from mining activities at the model surface
mines 3-101
3.34 Average annual emissions of radionuclides ( yCi) and stable
elements (kg) in wind suspended dust at the model surface
mines 3-102
3.35 Radon-222 releases during surface mining . . . 3-107
3.36 Estimated average surface areas of waste rock piles at
underground mines ........ 3-111
3.37 Estimated surface areas of ore stockpiles at underground
mines 3-111
3.38 Estimated average surface areas of sub-ore piles at
underground mines ........ 3-113
xvi 1
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3.39 Summary of average discharge and water quality data for
underground uranium mines in the Colorado Plateau Region
(Colorado, New Mexico, Utah) and a comparison with NPDES
limits 3-116
3.40 Water quality associated with underground mines in
various stages of construction and operation . . . 3-119
3.41 Total flow volume for sub-basin floods of 1- and 7-day
durations and return periods of 2, 5, 10, and 25 years . 3-126
3.42 Summary of area, discharge, and irrigated acreage for
the sub-basin, basin, and regional basin hydrographic
units in New Mexico 3-127
3.43 Dilution factors for the Rio San Jose, Rio Puerco, and
Rio Grande for 1-day flood flows with a 2-year recurrence
interval 3-135
3.44 Annual contaminant loading from 14 uranium mines and
resulting concentrations in sub-basin floods and in the
average annual flow of the Rio San Jose, Rio Puerco, and
Rio Grande ......... 3-137
3.45 Comparison of potable and irrigation water standards
and surface water quality affected by underground
mine drainage 3-140
3.46 Radiochemical and stable element/compound water quality for
selected acid and alkaline leach uranium mill tailings
ponds in the United States . . . . . . 3-142
3.47 Summary of flood runoff water quality and uranium mill pond
quality 3-143
3.48 Flow and water quality in the Puerco River near Churchrock
and Gallup, New Mexico 3-146
3.49 Groundwater quality in principal aquifers in the Grants
Mineral Belt, New Mexico 3-151
3.50 Groundwater quality associated with the San Mateo Creek
and Rio Puerco (west) drainages in the Grants Mineral
Belt, New Mexico 3-154
xix
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Page
3.51 Estimated annual radon-222 emissions from underground
uranium mining sources ....... 3-158
3.52 Estimated air pollutant emissions from heavy-duty equipment
at underground uranium mines ...... 3-161
3.53 Estimated average annual dust emissions from underground
mining activities 3-163
3.54 Average annual emissions of radionuclides (y Ci) and
stable elements (kg) from mining activities at the
model underground mines. .....-• 3-165
3.55 Average annual emissions of radionuclides (yCi) and
stable elements (kg) in wind suspended dust at the model
underground mines ........ 3-166
3.56 Average annual emissions of radionuclides (pCi) and stable
elements (kg) from vehicular dust at the model underground
mines .......... 3-167
3.57 Estimated quantities of wastewater produced by an in situ
leaching operation ........ 3-173
3.58 Estimated average concentrations and annual accumulation
of some contaminants in waste water .... 3-175
3.59 Estimated average annual airborne emissions from the
hypothetical in situ leaching facility .... 3-176
3.60 Estimated average concentrations and annual and total
accumulations of some contaminants in restoration waste-
water 3-181
3.61 A comparison of contaminant concentrations in pre-mining
groundwater and pre-restoration mine water . . . 3-182
3.62 Estimates of exploratory and development drill holes
(1948-1979) 3-189
3.63 Estimated source terms per bore hole for contemporary
surface drilling for uranium 3-195
3.64 Airborne dusts produced at an average mine site from
exploratory and development drilling .... 3-196
xx
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Page
3.65 Estimates of emissions from drill rig diesel power
source 3-196
3.66 Sediment yields in overland flow from uranium mining
areas 3-202
3.67 Consolidated list of inactive uranium producers by State
and type of mining . . . . . . . . 3-206
3.68 Uranium mine waste and ore production .... 3-207
3.69 Cumulative uranium mine waste and ore production . . 3-211
3.70 Average annual emissions of radionuclides (yCi) and stable
elements (kg) in wind suspended dust at the model inactive
surface mine . . . . . . . . 3-217
3.71 Average radon flux of inactive uranium mill tailings
piles 3-218
3.72 Average radon flux measured at inactive uranium mine
sites 3-220
3.73 Background radon flux estimates ..... 3-221
3.74 Summary of estimated radon-222 releases from inactive
surface mines ......... 3-223
3.75 Summary of land surface gamma radiation surveys in New
Mexico, Texas, and Wyoming ...... 3-225
3.76 Average annual emissions of radionuclides (yCi) and
stable elements (kg) in wind suspended dust at the model
inactive underground mine ...... 3-231
3.77 Summary of radon-222 releases from inactive underground
mines .......... 3-238
3.78 Summary of land surface gamma radiation surveys in
Colorado and New Mexico ....... 3-239
5.1 Number of uranium mines and population statistics for
counties containing uranium mines. . . . . . 5-3
5.2 Population statistics for humans and beef cattle . . 5-12
5.3 Aquatic environmental transport pathways initially
considered ......... 5-14
xxi
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Page
6.1 Annual release rates (Ci) used in the dose equivalent
and health effects computations for active uranium
mines .....«•••• 6-2
6.2 Annual release rates (Ci) used in the dose equivalent
and health effects computations for inactive uranium
mines .......... 6-4
6.3 Annual working level exposure from radon-222 emissions
from model uranium mines 6-6
6.4 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model average
surface uranium mine 6-7
6.5 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model average
large surface uranium mine ...... 6-8
6.6 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model average
underground uranium mine ....... 6-9
6.7 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model average
large underground uranium mine 6-10
6.8 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model inactive
surface uranium mine ....... 6-11
6.9 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model inactive
underground uranium mine 6-12
6.10 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a hypothetical
in situ uranium solution mine 6-13
6.11 Individual lifetime fatal cancer risk for one year of
exposure and estimated additional fatal cancers to the
regional population due to annual radioactive airborne
emissions from model uranium mines 6-15
xxn
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Page
6.12 Individual lifetime fatal cancer risk due to lifetime
exposure to radioactive airborne emissions from model
uranium mines 6.16
6.13 Genetic effect risk to descendants for one year of parental
exposure to atmospheric radioactive airborne emissions from
model uranium mines 6-17
6.14 Genetic effect risk to descendants for a 30-year parental
exposure to atmospheric radioactive airborne emissions
from model uranium mines 6-18
6.15 Percent of the fatal cancer risk for the maximum individual
due to the sources of radioactive emissions at model ura-
nium mines 6-20
6.16 Percent of the fatal cancer risk for the average individual
in the regional population due to the sources of radioactive
emissions at model uranium mines 6-21
6.17 Percent of fatal cancer risks due to radon-222 daughter con-
centrations at model uranium mine sites .... 6-22
6.18 Percent of the fatal cancer risk for principal nuclides and
pathways due to radioactive particulate and Rn-222 emissions
at model uranium mines ....... 6-23
6.19 Natural background concentrations and average urban concen-
trations of selected airborne pollutants in the United
States 6-27
6.20 Combustion product concentrations at the site of the maximum
individual with comparisons 6-29
6.21 A comparison of the airborne concentrations of nonradioactive
gases at the hypothetical in situ leach site with threshold
limit values 6-30
6.22 Stable trace metal airborne concentrations at the site of
the maximum individual 6-32
6.23 Comparison of stable trace metal airborne concentrations
at the location of the maximum individual with natural
background concentrations and average urban concentrations
of these airborne pollutants ...... 6-33
xxi n
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Page
6.24 Comparison of trace metal airborne concentrations at the
site of the maximum individual with threshold limit values
(TLV's) in the workroom environment adjusted for continuous
exposure to the general public 6-34
6.25 Annual radiation dose equivalent rates due to aquatic
releases from the New Mexico model underground mine . 6-36
6.26 Annual radiation dose equivalent rates due to aquatic
releases from the Wyoming model surface mine . . . 6-37
6.27 Individual lifetime fatal cancer risk and committed fatal
cancers to the population residing within the assessment
areas .......... 6-38
6.28 Genetic risks to succeeding generations of an individual
and committed genetic effects to descendants of the present
population residing within the assessment area . . 6-41
6.29 Comparison of nonradiological waterborne emissions from
uranium mines with recommended agricultural water quality
limits . . . . . . . . . . 6-43
6.30 Estimated lifetime risk of fatal lung cancer to individuals
living in homes built on land contaminated by uranium mine
wastes 6-45
6.31 Gamma radiation anomalies and causes .... 6-49
7.1 Distribution of United States uranium mines by type of
mine and state 7-2
7.2 Sources of contaminants at uranium mines . . . 7-3
7.3 Concentration of contaminants in waste rock (overburden),
ore, and sub-ore 7-6
7.4 Summary of harm from radioactive airborne emissions of
model uranium mines 7_H
7.5 Percent additional lifetime fatal cancer risk for a lifetime
exposure to the individual and the percent additional cancer
deaths in the regional population per year of exposure esti-
mated to occur as a result of uranium mining . . . 7-12
xxiv
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Page
7.6 Summary of the fatal cancer risks caused by radioactive
aqueous emissions from model uranium mines . . . 7-14
7.7 Estimated lifetime risk of fatal lung cancer to the average
person living in a home built on land contaminated by uranium
mine wastes 7-16
7.8 Summary of contaminant loading and stream water quality from
a model surface uranium mine 7-20
7.9 Summary of contaminant loading and stream water quality
from a model underground uranium mine . . . 7-21
Appendix A
A.I Federal laws, regulations, and guides for uranium mining A-l
Appendix D
D.I State laws, regulations, and guides for uranium mining . D-l
Appendix E
E.I Active uranium mines in the United States . . . E-l
Appendix F
F.I Inactive uranium mines in the United States F-l
Appendix G
G.I Uravan and Jamestown areas G-14
G.2 Inactive uranium mine sites surveyed in New Mexico . G-21
G.3 Status and location of uranium mines in Texas. . . G-25
G.4 Trace elements and radionuclides in water in the south
fork of Box Creek drainage at UNC Morton Ranch lease . G-35
G.5 Radionuclides and trace metals in sediments in the south
fork of Box Creek at UNC Morton Ranch lease . . . G-36
G.6 Radionuclides and trace metals in soils near the 1601
open pit mine, UNC Morton Ranch lease, Wyoming . . G-37
xxv
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Page
G.7 Radionuelides and trace metals in soil profiles at the
open pit mines, UNC Morton Ranch lease, Wyoming . . G-38
G.8 Radionuclides and trace metals in sediments from the
drainage of the San Mateo mine and from San Mateo
Creek, New Mexico S-40
G.9 Radium-226 and trace elements in water from San Mateo
Creek near San Mateo mine discharge point . . . G-40
Appendix H
H.I Characteristics of the sub-basin containing the model
mines .......... H-2
H.2 Seepage and outflow calculations for the Wyoming model
mine drainage system ....... H-6
H.3 Characteristics of the sub-basin hydrographic unit in the
model underground uranium mine area .... H-8
H.4 Seepage and outflow calculations for the New Mexico
model mine area drainage system H-ll
Appendix J
J.I Aquatic environmental transport pathways examined . . J-6
J.2 Characteristics of the generic sites .... J-20
J.3 Stream data for Valencia County ..... J-23
J.4 Estimation of meat production in Valencia County for
1977 ........... J-25
J.5 Estimates of meat production in Converse County,
Wyoming for 1976 j-26
J.6 Annual radionuclide release rates to streams for active
uranium mines j_29
J.7 Freshwater fish concentration factors .... J-29
J.8 Normalized human intake rate factors for radionuclide
uptake via plant root systems |. j-3i
J.9 Irrigated land usage j_31
xxvi
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Page
J.10 Soil removal rate constants and radioactive decay
constants j_33
J.ll Milk and beef concentration factors .... J-33
0.12 Dose equivalent conversion factors J-36
J.13 Health effects conversion factors for internal pathways. J-37
0.14 Health effects conversion factors for external pathways. 0-37
Appendix K
K.I Characteristics of the generic sites K-l
K.2 Animal and vegetable crop distribution for use with
AIRDOS-EPA K-3
K.3 Sources of food for the maximum individual (percent) . K-4
K.4 Selected input parameters to AIRDOS-EPA K-5
K.5 Selected terrestrial pathway parameters by radionuclide. K-7
K.6 Effective radioactive decay constants .... K-8
Appendix L
L.I Radionuclide dose rate and health effect risk conversion
factors used in uranium mine assessments . . . L-4
L.2 Additional input data used by DARTAB in the health im-
pact assessment of airborne emissions .... L-21
L.3 Example input data file for DARTAB L-22
L.4 Maximum individual fatal cancer risk for one year of ex-
posure to atmospheric radioactive emissions from model
uranium mines ......... L-23
L.5 Fatal cancer risk to an average individual in the regional
population for one year of exposure to atmospheric radio-
active emissions from model uranium mines . . . L-24
L.6 Fatal cancer risk to the population for one year of ex-
posure to atmospheric radioactive emissions from model
uranium mines L-25
xxvn
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Page
L.7 Genetic effect risk to descendants of maximum exposed
individual for one year of parental exposure to atmo-
spheric radioactive particulate and Rn-222 emissions from
model uranium mines L-26
L.8 Genetic effect risk to descendants of average individual
of the population for one year of parental exposure to
atmospheric radioactive particulate and Rn-222 emissions
from model uranium mines 1-27
L.9 Genetic effect risk to descendants of the regional popu-
lation for one year of parental exposure to atmospheric
radioactive particulates and Rn-222 emissions from model
uranium mines ......... L-28
xxvm
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FOREWORD
The Uranium Mill Tailings Radiation Control Act of 1978 stipulates
that "...the Administrator, in consultation with the Commission, shall
provide to the Congress a report which identifies the location and
potential health, safety, and environmental hazards of uranium mine
wastes together with recommendations, if any, for a program to eliminate
these hazards." It is our understanding that the intent of Congress was
to determine if remedial actions similar to those for uranium mill
tailings are required for mine wastes.
The report was prepared by the Office of Radiation Programs and
addresses potential health effects caused by air emissions, water
effluents, and solid wastes at active and inactive uranium mines. It is
probably the single most comprehensive report on the subject. The
effects from other mining activities such as exploration, site
preparation, and in situ leaching were evaluated in proportion to their
potential significance and the amount of available information about
them. Comments on this report from the uranium mining industry, States,
and the Nuclear Regulatory Commission have also been considered.
The conclusions and recommendations are in the Executive Summary and
Chapter 7 of the report. The principal findings of this report are as
follows:
1. No problems were identified that require Congressional action.
2. Standards are probably needed to control human exposure from
radioactive emissions from underground uranium mines. We have proposed a
standard for underground uranium mines under the Clean Air Act program to
develop radionuclide standards.
3. Regulations should be considered for maintaining the control of
solid wastes at active uranium mines to prevent off-site use and to
minimize the health risks from these materials. This is part of the
overall agency consideration of mining wastes and is being carried out
under the auspices of the Solid Waste Disposal Act.
4. The report also identifies additional studies that are needed to
completely elucidate the potential for local adverse effects as a result
of possible misuse of the mine waste materials in construction of
buildings. Preliminary reports of field studies by EPA identifying
possible sites at which mine wastes may have been utilized in
construction or around buildings have been sent to the States for
follow-up studies.
Glen L. Sjoblom, Director
Office of Radiation Programs
XXIX
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ACKNOWLEDGEMENTS
The following persons of the Office of Radiation Programs made
substantial contributions to this report.
R. L. Blanchard, EERF, Montgomery, AL*
G. G. Eadie, ORP-Las Vegas, NV* P. J. Magno, CSD, Washington, DC
T. W. Fowler, EERF, Montgomery, AL J. M. Moore, ORP-Las Vegas, NV
M. M. Gottlieb, TAD, Washington, DC D. Nelson, CSD, Washington, DC
J. M. Hans, Jr., ORP-Las Vegas, NV* M. F. O'Connell, ORP-Las Vegas, NV
T. R. Morton, EERF, Montgomery, AL C. M. Petko, EERF, Montgomery, AL
T. L. Hurst, ORP-Las Vegas, NV J. E. Regnier, CSD, Washington, DC
R. F. Kaufmann, ORP-Las Vegas, NV* J. S. Silhanek, CSD, Washington, DC
J. M. Smith, EERF, Montgomery, AL
* Principal Authors
The following persons provided data and information used in this report.
L. V. Beal, U.S. Geological Survey, Albuquerque, NM
R. Beckman, U.S. Dept. of Labor, Denver, CO
J. D. Borland, U.S. Geological Survey, Albuquerque, NM
T. Buehl, Nev/Mexico Environmental Protection Agency, Santa Fe, NM
T. Bullock, Utah Industrial Commission, Salt Lake City, UT
A. J. Carroll, U.S. Dept. of Interior, Denver, CO
T. Chung, U.S. Dept. of Energy, Grand Junction, CO
L. M. Cook, Texas Dept. of Health, Austin, TX
J. T. Dale, USEPA, Region VIII, Denver, CO
J. G. Dudley, NM Environmental Improvement Div., Santa Fe, NM
W. H. Engelmann, U.S. Bureau of Mines, Twin Cities, MI
J. R. Giedt, USEPA, Region VIII, Denver, CO
A. L. Hornbaker, Colorado Geological Survey, Denver, CO
S. J. Hubbard, IERL, USEPA, Cincinnati, OH
R. G. Kirby, USEPA, Effluent Guidelines Division, Washington, DC
xxx
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0. L. Kunkler, U.S. Geological Survey, Santa Fe, NM
H. W. Lowham, U.S. Geological Survey, Cheyenne, WY
H. D. May, USEPA, Region VI, Dallas, TX
R. Meehan, U.S. Dept. of Energy, Grand Junction, CO
A. T. Mull ins, TVA, Chattanooga, TN
G. E. Niewiadomski, U.S. Geological Survey, Washington, DC
B. L. Perkins, New Mexico Energy and Minerals Department, Santa Fe, MM
C. R. Phillips, USEPA, EERF, Montgomery, AL
H. G. Plimpton, MSHA, Salt Lake City, UT
T. J. Price, Bendix Field Engineering Corp., Grand Junction, CO
J. G. Rank!, U.S. Geological Survey, Cheyenne, WY
R. F. Reed, U.S. Bureau of Mines, Washington, DC
G. C. Ritter, Bendix Field Engineering Corp., Grand Junction, CO
P. B. Smith, USEPA, Region VIII, Denver, CO
J. P. Stone, U.S. Dept. of Interior, Washington, DC
A. B. Tanner, U.S. Geological Survey, Reston, VA
S. Waligora, Eberline Inst. Co., Albuquerque, NM
R. E. Walline, USEPA, Region VIII, Denver, CO
T. Willingham, USEPA, Region VIII, Denver, CO
T. Wolff, New Mexico Environmental Protection Agency, Santa Fe, NM
A. F. Wright, (formerly) U.S. Geological Survey, Albuquerque, NM
The authors express their appreciation to Mrs. Winnifred Schupp,
ORP-Las Vegas, NV, and Mrs. Annette Fannin, EERF, Montgomery, AL, for
typing the report and to Mrs. Edith Boyd, ORP-Las Vegas, NV, for pre-
liminary editing of the report.
xxxi
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SECTION 1
INTRODUCTION
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1-1
1.0 Introduction
1.10 Purpose
This report was prepared in response to Section 114(c) of Public Law
95-604 dated November 8, 1978 (USC78). This Section of the Law stipulates
that, "Not later than January 1, 1980, the Administrator, in consultation with
the Commission, shall provide to the Congress a report which identifies the
location and potential health, safety, and environmental hazards of uranium
mine wastes together with recommendations, if any, for a program to eliminate
these hazards." The purpose of this report is to comply fully with this re-
quest, as accurately and completely as available information will permit.
1.1.1 Contents
This volume has seven major sections. The content of each section is
described generally below:
Section 1: Brief reviews of predicted future uranium production require-
ments; descriptions of methods of extracting uranium from the earth;
and presently enforced standards and regulations governing uranium
mining.
Section 2: A description of the active and inactive uranium mine in-
ventory with a discussion of its limitations. The actual mine listings
are presented in Appendixes E and F.
Section 3: A comprehensive discussion of potential sources of radio-
active and stable contaminants to the environment and man from uranium
mining operations. Annual release rates of contaminants from the identi-
fied sources computed on a generic basis.
Section 4; A description of model underground, surface, and in situ
leach mines with operational parameters and source terms. Both active
and inactive model underground and surface mines are described.
Section 5: A brief and general discussion of the environment that
exists about uranium mines, including vegetation, wildlife, domestic
animals, and human populations. The potential atmospheric and aquatic
pathways of contaminants from the mines to man are also defined.
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1-2
Section 6: Computation of individual and population dose equivalents
and potential health effects from mine wastes and effluents based on
the source terms developed in Section 3, the model mines defined in
Section 4, and the pathways described in Section 5. A qualitative
description of the environmental effects based on site visits is
also presented.
Section 7: A brief summary of the report followed by the conclusions
and recommendations.
1.2 Uranium Ore Production and Future Uranium Needs
1.2.1 Past Production
Table 1.1 lists the quantities of ore mined and uranium (UoOg) produced
in the various uranium mining states between 1948 and January 1, 1979. Two
states, New Mexico and Wyoming, have been the source of about 64 percent of
the uranium mined in the United States. The Colorado Plateau, which includes
parts of New Mexico, Arizona, Colorado, and Utah (see Figure 1.1), has been
the largest source area of mined uranium, accounting for about 70 percent of
the U30g production through 1976 (ST78). During this same period, the Gas
Hills and the Shirley and Powder River Basins of Wyoming produced about 22
percent of the total U30g (ST78).
To produce 302,370 MT of U30g required the mining of 145,811,000 MT of
uranium ore during the 31-year period from 1948 to 1979(DOE79). The average
grade of ore, reported as percent of U-Og, was 0.208 percent during this
period.
1.2.2 Projected Needs for Uranium
The expected growth in the use of nuclear energy for the production of
electric power in the United States during the remainder of this century will
require an expansion of the uranium mining industry. However, the magnitude
of this expansion is difficult to estimate, because the forecasts that pre-
dict the growth of the nuclear power industry differ considerably (AEC74,
ERDA75, EPA76, NRC76, NUS76, Cu77, He77, NEP77, Ew78, Ni78, and St78).
However, all forecasts predict a continued growth of the industry. Expansion
of the uranium mining industry will be influenced also by decisions regarding
fuel reprocessing and commercial utilization of breeder reactors.
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1-3
Table 1.1 Domestic uranium production by state
from 1948 to January 1, 1979 (DOE79)
State
New Mexico
Wyoming
Others ^
Total
Ore
Production, MT
59,977,000
36,263,000
49,571,000
145,811,000
Contained
U308, MT
123,560
68,400
110,410
302,370
^Includes minor, non-ore sources.
Includes Alaska, Arizona, California, Colorado, Florida, Idaho, Montana,
Nevada, New Jersey, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah,
and Washington.
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1-4
Northern and
Central Basin
& Range
Figure 1.1 Uranium mining regions in the western United States
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1-5
Table 1.2 gives examples of four typical forecasts. The Nuclear Regu-
latory Commission's (NRC) projected annual nuclear capacity is far below
former predictions. This lower projection, which is in line with the admin-
istration's National Energy Plan (NEP77), is believed to be more realistic in
view of recent drops in demand for electricity, labor problems, equipment
delays, litigations initiated by environmental groups, the absence of a
publicly accepted waste disposal program, and concern over nuclear prolif-
eration. The Department of Energy predicts that 293,120 MT of U,00 will be
o o
required to provide nuclear generating capacity through 1990 (DOE79). This
assumes no uranium or plutonium recycling.
Table 1.3, which gives domestic uranium reserves by state, shows that
the reserves are near the areas already mined. Figure 1.2 shows the distri-
bution of $50 ore reserves by state, and Fig. 1.3 shows reserves by resource
region (see Fig. 1.1 for region locations). Future major mining activities
probably will be in the same general areas that have already been mined. To
obtain the 834,600 MT of $50 U00Q reserves will require mining about 1.14 x
Q JO
10 MT of ore with an average grade of 0.073 percent U30g.
1.3 Overview of Uranium Mining Operations
1.3.1 General
The two major uranium mining methods used in the United States are
underground mining and surface (open pit) mining. These two methods ac-
counted for more than 98 percent of the uranium mined in the United States in
1971 (AEC74). This has decreased only slightly to about 93 percent in 1978
(DOE79). However, various types of solution mining are currently being
tested and probably will be employed commercially more frequently.
Table 1.4 shows the current production capacities of U30g for the var-
ious mining methods. Although underground mines are far more numerous than
surface mines, production by the two methods is nearly equal. This is be-
cause surface mines have a much larger capacity. During 1978, 305 under-
ground mines accounted for about 46 percent (8,350 MT) of the U30g production
while 63 surface mines produced about 47 percent (8,710 MT) of the U30g. In
situ leaching, heap leaching, mine water extraction, and other alternative
methods accounted for the remaining 7 percent (1,270 MT).
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1-6
Table 1.2 Projected annual nuclear capacity (GWe) in the U.S.
Source
ERDA (ERDA75)
USEPA (EPA76)
Electric World (EW78)
NRC (NRC79)^
1980
71-92
80
92
61
1985
160-245
188
160
127
1990
285-470
350
194
195
1995
445-790
578
237
280
2000
625-1250
820
380
^'Schedule assumed for this document.
Note.—The actual nuclear capacity realized in 1977 was 49 GWe.
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1-7
Table 1.3 Domestic uranium reserves by state
as of January 1, 1979
State
New Mexico
Wyoming
Texas
Arizona,
Colorado,
& Utah
Others^
Total
Ore, MT
482,200,000
431,300,000
83,400,000
107,300,000
35,700,000
1,139,900,000
Ore
Grade, % U-Og
0.09
0.06
0.05
0.07
0.07
0.073{b)
U308, MT
434,000
258,800
41,700
75,100
25,000
834,600
% Total U30g
52
31
5
9
3
100
(a)
Includes Alaska, California, Idaho, Montana, Nevada, North Dakota,
Oregon, South Dakota and Washington.
^ 'Weighted average.
Note.—The uranium reserves in this table include ore from which U30g can
be obtained at a forward cost of $50 per pound or less. Costs do not include
profits or cost of money.
Source: DOE79.
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1-8
Figure 1.2 The percent of $50 U 3 O 8 reserves located in the
principal mining states (DOE 79)
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1-9
Colorado Plateau (54%
Northern PlajnsjVKO
Other (9%)
Wyoming Basins (31%)
Figure 1.3 The percent of $50 U 3 O 8 reserves located in the
various mining regions (DOE 79)
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1-10
Table 1.4 Quantities of U30g produced in 1978
by the various mining methods
Mining Method
Underground Mines (305)^a'
Surface Mines (63)
MT of U308
8350
8710
Percent^
46
47
Other (23): In situ leaching,
heap leaching, & mine water 1270 7
Total 18,330 100
^a'The number of mines or sites are given in parentheses.
' 'Rounded to total 100 percent.
Source: DOE79.
Table 1.5 Predicted methods of mining ore reserves
Mining Method
Underground Mining
Surface Mining
Other: In situ leaching,
heap leaching, & mine water
Total
MT of U308
547,000
260,400
27,200
834,600
Percent
66
31
3
Note.--These are reserves of the $50 per pound U,0g or less cost category.
Source: DOE79.
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1-11
Although some mines produced much more than others, one can compute a
rough estimate of the average capacity of underground and surface mines as
follows. The average grades of ore removed from underground and surface
mines in 1978 were reported to be 0.155 percent and 0.120 percent U30g,
respectively (DOE79). Dividing the annual U308 productions (Table 1.4) of
the two mining methods by their respective grades indicates that the 305
underground mines accounted for 5,387,100 MT of ore while 7,258,300 MT were
removed from the 63 surface mines. Hence, the average ore production capac-
ities of underground and surface mines are about 1.8 x 104 MT and 1.2 x 105
MT, respectively. From this assessment, the average ore capacity of a sur-
face mine is about seven times that of an underground mine.
The trend during the past few years of an increasing percentage of U~0a
being mined underground will continue, because shallow deposits of high grade
ore have tended to be surface mined first. Table 1.5, which displays the
distribution of $50 reserves by mining method, shows the continued increase
in the proportion of UoOg mined by the underground method. By the Department
of Energy predictions, future production from underground mines will more
than double that from surface mines. The NRC predicts UgOg production by in
situ leaching to peak in 1990 at about 4000 MT/yr and total 76,000 MT by the
year 2000 (NRC79). If this prediction is realized, this resource will un-
doubtedly draw from those assigned to underground and surface mining in Table
1.5. The production of LLOg by heap leaching and mine water extraction is
predicted to be relatively small.
It is very difficult to predict how much U30g will be produced as a
by-product from other mineral mines, but by-product production should in-
crease total IL00 production during the next 20 years. Approximately 180 MT
•3 o
of ILOo are currently recovered each year from the phosphoric acid production
at wet phosphate plants. The NRC predicts that this will increase to 1800
MT/yr by 1985 and possibly to 7000 MT/yr by the year 2000 (NRC79). If planned
leaching facilities are actually built at copper waste dumps at Yerington,
Nevada; Butte, Montana; and Twin Buttes, Arizona, to supplement the operating
facility at Bingham Canyon, Utah, recovery of U308 from these operations
could reach 900 MT/yr (NRC78). Hence, by-product U30g production could
conceivably account for about eight percent of the required annual U30Q pro-
duction by the year 2000.
-------
1-12
Although the depth of the ore deposit is the fundamental consideration
in selecting the mining method to be applied to a particular ore body, the
size and grade of the deposit are also important factors. The shape of the
deposit, the overburden rock strength, environmental considerations, and
other factors may also influence the selection. Surface mining is generally
used for relatively shallow deposits; rarely for those below 400 feet (St78).
However, under some conditions, it may be cheaper to mine a small, shallow,
high-grade ore deposit by underground methods; whereas, a larger low-grade
deposit at a greater depth may be cheaper to mine by surface mining. Because
productivity is greater by surface mining, it is generally preferred when
conditions are favorable. Other factors must be examined when considering
the use of in situ leaching (see Section 1.3.4).
1.3.2 Surface Mining
The use of surface (open pit) mining methods is most prevalent in the
Gas Hills Region and the Shirley and Powder River Basins in Wyoming, the
Laguna District of New Mexico, the coastal plains in south Texas, and some
areas of Colorado and Utah (St78). Fig. 1.4 illustrates a typical open pit
mine.
In surface mining, an open pit is dug to expose the uranium deposits.
After the topsoil is removed and stockpiled nearby, the overburden is removed
by the method best suited to the nature of the rock. If the rock is easily
crumbled, it is removed by tractor-mounted ripper bars, bulldozers, shovels,
or pushload scrapers; if it is not, blasting and drilling are required. The
broken rock is then trucked to a nearby waste dump. Occasionally, dikes and
ditches are constructed around these waste piles to collect runoff and divert
it to sedimentation ponds. Overall, an area of a hundred or more acres may
be covered by stored overburden wastes (AEC74).
As mining progresses, the overburden is used as it is removed to back-
fill mined out areas of the pit. When an area is completely backfilled, it
is graded to conform to the surrounding topography and to restore the natural
drainage patterns. The area is then covered with topsoil and seeded to blend
with the natural terrain. Most of the older surface mines were not back-
filled (see Section 3.7.1), and neither are many of the currently active
surface mines.
-------
Figure 1.4 Artist's conception of open pit mining operation and support facilities (TVA78a)
i
i—•
LO
-------
1-14
Contact with the ore zone is determined by gamma and x-ray detection
instruments, usually Geiger-Muller counters that have been calibrated to in-
dicate the uranium content of the rock. Since uranium is usually in sand-
stone formations, the ore is easily removed. Large backhoes and front-end
loaders are often used to remove ore that has been loosened with tractor-
mounted rippers. Large ore trucks carry the ore from the pit to stockpiles
at the mine or the mill. Uranium ore is usually stockpiled by grade, e.g.,
high-grade, average-grade, low-grade. Sub-ore grade rock is also usually
stored separately in piles. This is rock that contains UgOg at a concen-
tration below what the mill will now accept, but which might later be worth
recovering.
Drifts (small tunnels) are sometimes driven into the pit wall to recover
small, narrow ore pods. The drifts are generally short, sometimes less than
30 meters. The mining techniques in these drifts are like those used in
underground mining (see Section 1.3.3).
Surface mining requires a network of roads from and around the pit area
and to the mill. Heavy vehicles operating on these roads, and the digging
itself, produce a certain amount of rock and ore dust. However, the dust can
be kept down by routinely sprinkling the roads with water or using other dust
suppressants. Treated water from the sedimentation ponds is sometimes used
for this purpose.
The ratio of overburden to the ore produced in an open pit mine can vary
from 10:1 to as high as 80:1 (St78). One source has estimated the average
ratio as 30:1 (Le77). A recent study of eight large open pit uranium mines
reported a ratio of 77 (+ 36) to 1 (Ni79). Since the latter study did not
consider the many smaller surface mines where the overburden to ore ratio is
likely to be smaller than 77 to 1, this report will assume an average ratio
of 50:1. Considering that the average ore capacity of an open pit mine is
approximately 1.2 x 105 MT/yr (see Section 1.3.1), about 6 x 106 MT of over-
burden must be removed annually and initially stored on the surface until
reclamation procedures can be initiated.
-------
1-15
Since most uranium deposits lie below the water table, groundwater must
be prevented from flooding the mining area. One method is to surround the
pit with several large capacity wells to lower the water table near the pit.
This water is discharged directly into the natural surface drainage system,
in accordance with the National Pollutant Discharge Elimination System
(NPDES) discharge permit issued to the mining company. Water that does
collect in the pit (mine sump water) is pumped to a sedimentation pond for
solids removal and, if necessary, for subsequent treatment prior to discharge
into the natural drainage system. Another mine dewatering procedure often
used consists of ditches dug along the interior perimeter of the pit floor to
channel the water to sumps located at the lowest levels of the pit floor.
Water that collects in the sumps is pumped to one or more sedimentation
basins for solids removal, possible treatment, and final discharge into the
existing natural drainage system in accordance with water quality standards
specified in the NPDES permit. The rates at which mines are dewatered range
from 0.28 m3/min to 288 m3/min (AEC74, TVA78a, NRC77a, NRC77b).
Barium chloride, to coprecipitate radium, and a flocculent (an agent
causing aggregate formation) to remove other contaminants are usually added
to pond water before it is discharged. Water with a high concentration of
dissolved uranium is often run through ion exchange columns, and the resin
regenerant solution containing the uranium is sent to the mill for pro-
cessing. The precipitated sludge that collects on the pond bottom consists
primarily of ferric and calcium hydroxides, calcium sulfate, and barium
sulfate with coprecipitated radium. At some sites, this precipitated sludge
is transferred to the mill tailings pond at the end of the mining operation.
A small amount of uncontrolled seepage may occur through the bottom of
sedimentation ponds and, depending upon soil permeability and direction of
flow, may enter the water table. For example, the seepage rate through the
bottoms of two settling ponds totaling 4.9 hectares at one site was less than
0.57 m3/min (NRC77a). In addition, seepage can be reduced by lining the
ponds (well-compacted bentonite clay is sometimes used for this purpose) and
by the sludge that accumulates on the pond bottom.
-------
1-16
During active surface mining operations, a total of several thousand
hectares of land area will be disturbed (St78, Th79). When all uranium has
been mined and the operation is completed, a pit remains. The walls of the
pit may be contoured and allowed to fill with water, creating a small man-
made lake.
1.3.3 Underground Mining
Underground mining is much less disruptive to the surface terrain than
open pit mining. The surface affected generally involves less than 41 hect-
ares, but the mine may extend laterally underground for more than a mile and
at several depths. Figure 1.5 illustrates a typical large, contemporary
underground mine.
In underground mining, access to the ore body is gained through one or
more vertical shafts, generally sunk to a slightly greater depth than the ore
body, or through inclines, declines, or adits, all cut through waste rock.
The waste rock is removed to a spoils area that may be, but usually is not,
surrounded by a ditch to contain runoff, as discussed above.
The sizes of the accesses vary considerably. The vertical haulage shaft
may vary from less than 8 feet in diameter, sufficient to accommodate one
small ore skip (a large bucket), to a diameter of 20 feet, which will accom-
modate dual ore skips as well as a man and material skip. In some cases, the
near horizontal accesses are sufficiently large to allow passage of large
diesel-powered vehicles.
Underground mines are developed in a way that minimizes the removal of
waste rock, resulting in much smaller spoil storage piles than those at
surface mines. It is estimated that the ore to waste rock ratio generally
ranges from 20:1 to 1:1 (ACE74, Th79). At seven presently active mines, the
ore to waste rock ratio ranges from 1.5:1 to 16:1 with an average ratio of
9.1:1 (Ja80). Using the average ratio and the average annual ore capacity of
an underground mine (see Section 1.3.1), each year the average underground
mine will produce about 2.0 x 10 MT of waste rock that is removed and stored
on the surface. Initially all waste rock is transported to the surface, but,
-------
GENERALIZED UNDERGROUND URANIUM MINE
MODIFIED ROOM AND PILLAR METHOD OF MINING
Figure 1.5 Generalized underground mine showing modified room and pillar method of mining (TVA78b)
-------
1-18
as mining progresses, it is sometimes transported to mined-out areas of the
mine and retained beneath the surface. This practice may diminish as lower
grade sub-ore becomes more economical to mill. Since waste rock may contain
sub-ore, some waste rock will likely be kept available for milling.
Ore deposits, outlined by development drilling, are followed as closely
as possible. When ore lies in narrow, long deposits, drifts are cut through
the ore body and raises or stopes are driven from the drift to reach small
ore pods. Crosscuts are driven from the haulage drifts when necessary to
reach nearby deposits. Large area deposits are commonly mined by the "room
and pillar" method. This involves mining out blocks of ore while leaving ad-
jacent pillars of ore or waste as support for the roof. The size of the
rooms depends on the roof condition. The roof is usually strengthened by
bolts, wire mesh, timbersets, and steel arches. When an area is completely
mined, the ore pillars are removed in a systematic sequence that allows safe
retreat.
Ore is usually broken by drilling and blasting. The broken ore is
removed and transferred to mine rail cars. The ore is then carried by rail
cars or wheeled vehicles either directly to the surface or to a skip at the
bottom of the haulage shaft and lifted to the surface. Haulage in large area
mines is often accomplished by large diesel-powered loaders, haulers, and
trucks. When the ore is sufficiently soft, it may be removed with continuous
mining machines instead of drilling and blasting techniques; however, most
ore bodies are too small and irregular to mine economically this way.
Ventilating systems are required in underground uranium mines to remove
blasting fumes and radon-222 (Rn-222) that emanates from the ore and mine
water and to control temperature. Fresh air is usually forced down the main
haulage shaft and along the main haulage drifts to the working areas. The
mine air is exhausted through ventilation shafts to the surface. The venti-
lation air is diverted from inactive areas of the mine to reduce air contam-
ination. Inactive areas are usually sealed with airtight bulkheads to pre-
vent radon gas in those areas from circulating. The ventilation rate should
be sufficient to maintain the radon daughter concentration of the mine air
at, or below, levels that meet federal and state occupational exposure stan-
-------
1-19
dards. The rate will vary depending upon mine size (volume), grade of ex-
posed ore, size of the active working areas, rock characteristics (diffusion
rate of Rn-222), effectiveness of bulkhead partitions, atmospheric pressure,
and other factors. Ventilation rates in active mines vary from a few hundred
3 3
m /min to over a hundred thousand m /min. For example, the ventilation rates
for seven uranium mines in the Grants, New Mexico area ranged from 4.4 x 103
to 1.1 x 10 m /min, with an average of 7.4 x 103 m3/min (Ja79).
Because ore bodies often lie in or beneath major aquifers, dewatering
operations similar to those practiced in surface mining are required. These
operations commence during the initial shaft-sinking process and may continue
throughout the working life of the mine. Water is pumped from wells that are
driven into the water-bearing strata near the mining operation and discharged
either directly into the natural surface drainage system, in accordance with
an NPDES permit, or to settling ponds. Water that collects in the mine is
diverted to sumps and pumped to a settling pond. The impounded mine water is
treated similarly to that described above at surface mines (see Section
1.3.2). The discharge of water from these ponds is in accordance with water
quality standards specified in the NPDES permit. (Note.--About one-half of
the active New Mexico mine discharges have NPDES permits that are presently
under adjudication and, therefore, are not necessarily in accord with dis-
charge limits [Pe79a].)
1.3.4 In Situ Leaching
In situ leaching has less adverse impact on the environment than con-
ventional uranium mining and milling methods. It also may permit economical
recovery of currently unrecoverable low-grade uranium deposits (NRC78).
Though in situ leach mining currently produces only a small amount of the
annual U.S. output of U30g, variations of this technique are being widely
tested for uranium extraction and have potential for becoming commercially
significant (La78, NRC78, TVA78b, Ka78). Table 1.6 lists in situ leaching
operations for uranium as of January 1, 1978. The operations are concen-
trated on the coastal plain of southwest Texas and in the Wyoming basin
regions. Most commercial sized operations are in southern Texas, where
recent expansion is expected to increase the production of U30g by this
-------
1-20
technique to about 900 MT annually (TVA78b). Two Texas sites alone, Bruni
and Lamprecht, are expected to produce annually 110 and 230 MT of U^Og,
respectively (Wy77). A number of projects are currently testing the effec-
tiveness of the in situ leaching technique. Though these studies usually last
about 18 months to 3 years, some feasibility tests require up to 6 years
before expanding to full or commercial scale operations (La78). Excellent
reviews of this mining method are available (La78, Ka78).
Uranium extraction by in situ leaching probably will not be restricted
to one or two geographical areas. Uranium deposits potentially suitable for
mining by this method are prevalent in almost all of the established uranium
mining areas in the United States. Uranium deposits are potential candidates
for in situ mining if they meet the following criteria: (1) the ore deposit
is located in a zone saturated with water; (2) the ore deposit lies above
and preferably between geological layers impervious to water; (3) the
deposit is adequately permeable to water; and (4) the uranium in the ore
deposit is in a Teachable state. Colorado and New Mexico already have in situ
leaching activities at the pilot scale, and the mining industry has inquired
about additional pilot-scale research and development sites in South Dakota,
Arizona, Utah, and Montana (La78).
In the in situ leaching method, a leaching solution (lixiviant) is in-
jected through wells into the uranium-bearing ore body. It forms chemical
complexes with the uranium, which dissolves in the solution. Production
wells bring the uranium-bearing solution to the surface where the uranium is
extracted. The barren lixiviant can then be reconstituted and reused. To
control groundwater flow, the production (pumped) well operates as a sump or
pressure sink in the formation, which produces a flow of groundwater and
lixiviant from the injection wells to the production well. Also, some of the
barren lixiviant is not reinjected. This reduces the water level in the well
field, allowing groundwater to migrate into the mining zone. This inflow
prevents the flow of the lixiviant away from the field area.
Lixiviants for in situ mining contain salts of anions (negatively
charged chemical groups), such as sulfate, carbonate, bicarbonate, and am-
monium, that form stable aqueous complexes with hexavalent (positively
-------
1-21
Table 1.6 Summary of current in situ leaching operations as of
January 1, 1978
Name
Sundance
Project
Red Desert
Site I
Red Desert
Site II
Charl ey
Site
Highland
Site
Double Eagle
Site
North Rolling
Pin Site
Collins Draw
Site II
Bear Creek
Site
Nine Mile
Lake Site
Red Desert
Site
Irigaray Site
Site No. I
Site No. 2
Crownpoint
Project
Location
Crook
County, WY
Sweetwater
County, WY
Sweetwater
County, WY
Johnson
County, WY
Converse
County, WY
Carbon
County, WY
Camp be 1 1
County, WY
Campbel 1
County, WY
Converse
County, WY
Natrona
County, WY
Sweetwater
County, WY
Johnson
County, WY
McKinley
County, NM
Sandoval
County, NM
McKinley
County, NM
Pattern
5-SP
5-SP
5-SP
5-SP
7-SP
5-SP
5-SP
5-SP
5-SP
5-SP
5-SP
ND
4-SP
4-SP
4-SP
Scale of(b)
Operation
RD-PS
RD-I
RD-PS
RD
RD-C
RD
RD-I
RD
RD-I
RD-PS
PS
C
PS- 1
PS- 1
RD
Flow Rate(c)
(m3/min)
.(«
ND
ND
ND
4.54
ND
ND
0.38-0.57
ND
0.38
0.38
6.06
ND
ND
ND
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1-22
Table 1.6 Summary of current in situ leaching operations as of
January 1, 1978 (continued)
Name
Grover Site
Palangana Dome
Site
O'Hern Site
Bruni Site
Lamprecht
Site
Zamzow Site
Boots/Brown
Site
Clay West
Site
Burns Ranch
Site
Moser Site
We]1(a) Scale of(b)
Location Pattern Operation
Weld County, 5-SP PS-C
CO
Duval County, ND^ ' C
TX
Duval County, ND C
TX
Duval County, ND C
TX
Bee County, ND C
TX
Live Oak ND C
County, TX
Live Oak ND C
County, TX
Live Oak ND C
County, TX
Live Oak ND C
County, TX
Live Oak ND C
County, TX
Flow Rate'c^
(m /min)
0.76
ND
ND
ND
0.76
ND
ND
ND
ND
ND
^ 'Well pattern: 5-SP indicates one or more 5-spot pattern(s), etc. See
Figure 1.6.
^ 'Given are past or present operations - planned future operations: RD-
research and development, PS - pilot scale, C - commercial scale, I - presently
inactive.
^c'Flow rate of leachate to processing plant in m /min.
(d)
No data.
Source: La78; Du79.
-------
1-23
charged in the +6 state) uranium. An oxidant, such as air, oxygen, hydrogen
peroxide, sodium chlorate, sodium hypochlorite, or potassium permanganate, is
added to oxidize the uranium to the hexavalent state. For example:
U02 + H202
Unfortunately, there is no lixiviant specific for uranium. Consequently,
other minerals commonly associated with uranium deposits, such as iron, sele-
nium, vanadium, molybdenum, and arsenic, may also be dissolved. This tends
to contaminate the leach solution and deplete the lixiviant. Lixiviant
agents and their concentrations are selected to maximize uranium recovery and
minimize undesirable secondary reactions. Acidic solutions (pH 2) are
avoided because they are less selective. Neutral or basic lixiviants (pH
6-10), such as ammonium or sodium carbonate or bicarbonate, are often used.
Many variables affect the accumulation of trace elements in leaching
solutions, particularly the chemical and physical nature of the host for-
mation. Table 1.7 illustrates relative contaminant levels in the two lixi-
viant types in a laboratory experiment. Except for Ra-226, significantly
greater trace element concentrations occur in the acid lixiviant; the total
dissolved solids is about eight times higher than in the alkaline solution.
Hence, it would be necessary to bleed much larger volumes of acidic lixiviant
from the system prior to reinjection in order to maintain acceptable levels
of these undesirable constituents. Large volumes of liquid wastes containing
higher toxic metal concentrations are generally produced when acidic lixi-
viants are employed. Also, because calcium minerals are abundant in geologic
strata and carbonate minerals are highly soluble in acid solutions, partic-
ularly calcium carbonate, large amounts of calcium accumulate in recirculated
acid lixiviant, and they must be removed by a purification process prior to
reinjection. However, acid lixiviants leach more rapidly than alkaline ones,
yield higher uranium recoveries — about 90 percent with sulfuric acid com-
pared to 60 to 70 percent with a bicarbonate solution — and generally ex-
tract less radium (Wy77).
The number of wells, their spacing, and their pattern depend upon the
-------
1-24
size and hydrologic characteristics of the formation. Figure 1.6 shows
diagrams of some common well patterns. Several hundred injection wells with
several recovery wells may be employed. Well spacing may vary from 10 to 60
m. In addition, a number of monitoring wells are driven a short distance
from the well field to detect any excursion of lixiviant from the leach
field. A commercial-size operation may require a well field area of 20
hectares or more (TVA78b).
The pregnant (containing uranium) leachate from the production wells is
filtered through a sand filter to remove suspended particulates, then passed
through a surge tank (storage reservoir) to ion-exchange resin beds that se-
lectively remove the uranium complex. The uranium is washed from the resin
beds, precipitated, filtered, dried (at most sites), and packaged.
Some processes of solution mining produce liquid and solid wastes. The
volume of liquid wastes produced is much smaller, per weight of U30g produced,
than that from the dewatering activities of conventional mining methods.
There is also no waste rock. Residues obtained from drilling are a solid
waste. Those that traverse the ore zone will contain some uranium ore. If
calcium or sulfate control of the lixiviant is necessary, additional solid
wastes are impounded in waste ponds under a liquid seal to minimize atmo-
spheric dispersion. Precipitation compounds will also be produced as evap-
oration concentrates the impounded waste solutions.
Liquid waste streams include lixiviant, filter and resin washes, resin
eluant bleed, and water used in cleaning the injection wells. The total
o
production rate of these waste streams may vary between 0.19 to 0.38 m/min
(Ka78, Wy77, TVA78b). At most sites, all liquid wastes flow to waste ponds
and evaporate. Pond size depends on the flow rate of the wastes and the
evaporation rate. The pond bottoms are usually lined with clay, asphalt, or
a continuous plastic sheet to minimize the seepage rate, although some seep-
age may inadvertently occur. Deep-well injection is also used, principally
in Texas, to dispose of liquid wastes from in situ leaching (Du79).
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1-25
Table 1.7 Trace metal concentrations of recirculated acid and
alkaline lixiviants
Trace Metal
Arsenic
Chromium
Cobalt
Copper
Iron
Lead
Manganese
Molybdenum
Nickel
Selenium
Strontium
Vanadium
Zinc
Zirconium
Radium-226^
TDS(e)
Acidic(a)
<0.05
0.15
0.2
1.0
25.4
0.7
1.2
NR
0.6
NR
3.7
1.0
4.3
3.3
390
7.8
Concentrations, mgA
Alkaline(b)
<0.05
0.07
NR(c)
0.04
0.6
0.2
NR
0.9
0.06
1.6
1.5
NR
0.1
0.9
1750
1.0
^Composition - 5 g/£ H2S04 and 0.1 g/£ NaC103<
(b)Composition - 8 gA, NH4HC03 and 1 g/£ \\flr
- Not Reported.
(d)
Units - pCi/£.
^e'Total dissolved solids in grams.
Source: Ka78.
-------
o
1-26
O
o
FIVE SPOT PATTERN
9
i • •
__^__^ 6..
MULTIPLE FIVE-SPOT PATTERN
O
--6
O
O
O
O
O
O X
V
o
• o
o
o
O o
SEVEN SPOT PATTERN
r Y T
i • i • i
A.
x» •
T
• i • i •
A A
^ -V ^ -X,
T Y Y
* • i • i
^ A
MULTIPLE SEVEN-SPOT PATTERN
KEY
INJECTION WELL
PRODUCTION WELL
X=10-60M
o o
o
ORE BODY CONFIGURATION PATTERN
Figure 1.6 Diagrams of some common injection-recovery
well patterns used in uranium in situ leach mining
-------
1-27
Atmospheric emissions from in situ leaching include Rn-222 that is
vented mainly from the pregnant lixiviant surge tanks and particulate matter
that may escape from the scrubbers (exhaust filters) of the yellowcake
(uranium product) drying and packaging units. Radon-222 emanation from the
waste ponds is probably negligible, since the sediment which contains the
radium remains submerged and little Radon-222 will diffuse through the water
and escape to the atmosphere.
When the mining operation is completed, the water volume of the leach
zone will be restored to limits set by regulatory agencies. The primary
method of aquifer restoration is flushing the zone with groundwater by
pumping from the production wells and/or the injection wells. This process
may produce up to 1.70 m /min additional liquid wastes that contain a high
concentration of dissolved solids (NRC78). This contaminated water passes
through an ion-exchange unit and then discharges to the waste ponds. The
barren effluent can be further treated by desalination and reinjected to the
formation. Also, a barium chloride solution can be injected into the leach
zone to coprecipitate radium from the aquifer water prior to the groundwater
sweeps.
1.3.5 Other Mining Methods
1.3.5.1 Heap Leaching
Ore of a grade too low to be economically extracted in the mill opera-
tion is sometimes treated by heap leaching. In this process, the low grade
ore is placed in large, rectangular, open-air piles on a specially prepared
pad. To construct the heap-leach pad, the topsoil is first removed and the
cleared area graded to a 2 percent to 3 percent slope. The graded area is
then covered by a plastic sheet. Perforated plastic pipe is placed on the
plastic parallel to the slope and covered with approximately 30 cm of clean,
coarse gravel. A collecting trough is formed at the base of the slope and a
berm surrounds the pile area.
When the ore is dumped on the pad, large solution reservoirs are formed
on the top. Acidic or alkaline mine water is pumped into the reservoirs and
-------
1-28
percolates through the pile. The percolated water is collected in the trough
and recirculated until the concentration of uranium in solution is sufficient
to be economically extracted. The leaching process may require up to six
months to recover approximately 80 percent of the uranium in the ore
(NRC77a). The heap-leach pile at one mine contained an annual accumulation of
approximately 360,000 MT of low-grade ore (NRC77a). The pile measured 300 m
x 90 m x 7.6 m with solution reservoirs of 22 m x 90 m x 1.5 m.
After leaching operations are completed, the leached pile is neutralized
with lime to a pH of about 7. The site is then contoured to blend with the
surrounding terrain, covered with layers of subsoil and topsoil, and seeded
to control wind and water erosion.
Because necessary information is unavailable and the contribution of
heap leaching to the total uranium production is very minor and not expected
to become significant (NRC79), an assessment of the environmental impact of
heap-leached piles has not been conducted. However, the NRC has recently
concluded that, although the hazard of tailings produced by heap leaching
will be much less than the hazard of tailings at conventional uranium mills,
the same tailings management and disposal criteria should possibly apply
(NRC79).
1.3.5.2 Mine Water Recirculation
At several sites mine water is recirculated to leach "worked-out areas"
of underground mines (Pe79b). In the early uranium mining years, ore with
less than about 0.15 percent U,0g was not mined. This grade is relatively
high compared to present day markets. Consequently, significant quantities
of uranium remain in these abandoned areas. Because the roofs of these areas
collapsed during the initial mining retreat, this ore is difficult to re-
trieve by conventional methods. To recover a portion of this uranium, holes
are drilled to the top of the collapsed zone and mine water is sprayed from
these holes onto the shattered ore. Water for leaching may be sprayed from
the mine floor if the abandoned area is accessible to the workers (Pe79a).
The oxidized uranium (uranyl ion) is leached by the slightly alkaline mine
water, which flows to collection sumps. The enriched water is pumped to a
resin ion-exchange unit to extract the uranium, and then it is recycled.
-------
1-29
After the available oxidized uranium has been leached, the process is dis-
continued for a few weeks to allow more uranium to oxidize. Mine water is
then circulated again through the ore.
This process increases the recovery of uranium with minor effort and
expense, but it contributes little to the total domestic uranium production
(NRC79). In addition, the quality of the stored mine water used will be en-
hanced after passing through the resin ion-exchange unit. Hence, mine water
recirculation has little impact on the environment. It was not assessed in
this study.
1.3.5.3. Borehole Slurry Mining
Hydraulic borehole slurry mining is a recently proposed technique for
extracting uranium ore (Ka78, St78). As the name suggests, this method uses
pressurized water to loosen and combine with ore-bearing material to form a
watery mixture known as 'slurry' that is transported from the borehole and
then conventionally milled. This method could be applied to sandstone de-
posits at depths of 30 m to about 100 m. By present estimates, yellowcake
from ore containing 0.06 percent U30« and mined at a 60 m depth by this
method would cost $42 per pound (Ka78). This method presently is not as
economical as the more conventional methods of uranium mining.
The process consists of drilling a 45-cm diameter hole to approximately
2 m below the uranium-bearing strata. A cutting jet assembly is positioned
in the hole at the end of a rigid service column containing conduits for the
pressurized water and slurry transport. The slurry pump is placed at the
bottom of the hole. The underground mining operation is started with the jet
set at the lowest position. The rotating jet cuts material through an arc of
somewhat less than 360° for a distance of up to 25 m, depending upon the
design of the jet system. The segment of unmined ore acts to support the
overlying strata. After the material is removed as a slurry, the jet is
raised to the next level of ore and the process is repeated. After milling,
the decanted water from the slurry is recycled for slurrying more ore. The
tailings from the milling operation are used to backfill the borehole cavi-
ties and minimize subsidence.
-------
1-30
A 15 m to 25 m radius borehole can be mined in an 8- to 24- hour period
(Ka78). Large ore bodies might be mined by drilling, slurrying, processing,
and backfilling in a systematic pattern that leaves ore in between boreholes
for support. These areas could be mined in a second phase after the original
boreholes are backfilled.
Borehole mining for uranium is currently only a proposed method with no
pilot or commercial scale units in operation. Thus, the possible environ-
mental impact from this process was not assessed in this study.
1.3.5.4. Uranium as a By-Product
The recovery of uranium as a by-product from other mineral mining and
milling operations was discussed briefly in Section 1.3.1. Since recovery is
basically from the milling operation, any environmental problem that might
exist is associated with milling rather than mining. Therefore, it was not
assessed in this study.
1.4 Current Applicable Standards and Regulations
1.4.1 Federal Regulations
Health, safety, and environmental hazards associated with uranium mining
are regulated by Federal and State laws. This review focuses on laws and
regulations applicable to mine operations. Nuclear Regulatory Commission
regulations for milling operations apply to in situ leach extraction and are
therefore included. Some laws and regulations on exploration rights also
cover the environmental impact of mining operations and wastes.
Prior to the National Environmental Policy Act (NEPA) of 1969, there
were few regulations protecting the environment of lands not controlled or
owned by the Federal Government. Even with NEPA, much Federal authority on
environmental problems was unused until recently. This Act established a
national policy concerning the environment. Section 102(2) (C) states that
every agency of the Federal Government must "include in every recommendation
or report on proposals for legislation and other major Federal actions signi-
ficantly affecting the quality of the human environment, a detailed state-
ment" of the environmental impact of such an action. Major Federal actions
-------
1-31
"... includes actions with effects that may be major and which are poten-
tially subject to Federal control and responsibility ... actions include new
and continuing activities, including projects and programs entirely or partly
financed, assisted, conducted, regulated, or approved by Federal agencies;
new or revised agency rules, regulations, plans, policies, or procedures; and
legislative proposals (Sections 1506.8, 1508.17) .... Approval of specific
projects, such as construction or management activities located in a defined
geographic area. Projects include actions approved by permit or other regula-
tory decision as well as federal and federally-assisted activities"(40 CFR
1500).
1.4.1.1 Federal Laws, Regulations, and Guides for Protection of Health and
Environment
Table 1.8 provides an overview of federal laws and regulations for the
protection of health or environment and the administering agencies. Federal
agency responsibilities for water use, conservation laws, and exploration and
mining rights are indicated in columns 1-4. Laws and regulations for environ-
mental quality and health and safety are indicated in columns 5-10. See
Appendix A for an itemized list of the laws and regulations shown generally
in Table 1.8.
1.4.1.1.1 Air Quality
Regulations on air quality have been promulgated pursuant to the Clean
Air Act (42 U.S.C. 1857 et seq), which includes the Clean Air Act of 1963
(Public Law 88-206) and amendments by the following: Public Law 89-272,
Public Law 89-675, Public Law 90-148, Public Law 91-604, Public Law 92-157,
Public Law 93-319, Public Law 95-95, and Public Law 95-190. The Environ-
mental Protection Agency establishes National Ambient Air Quality Standards,
New Source Performance Standards, and National Emissions Standards for Haz-
ardous Air Pollutants under the Clean Air Act (CAA). Primary standards are
set to protect public health and secondary standards are set to protect
public welfare from known or anticipated adverse effects.
National Ambient Air Quality Standards (NAAQS) have been established for
seven pollutants in 40 CRF 50. The Administrator of EPA is authorized to set
emission standards for hazardous air pollutants for which no ambient air
quality standard is applicable. Asbestos, beryllium, mercury, and vinyl
-------
Table 1.8 Federal laws, regulations, and guides for uranium mining
Genera
Water
Federal Agency Use
1
Conservation-
Preservation
Statutes
Mining
Permits Environmental Quality Health
Exploration Mining Water Land and
Ridhts Riahts Air Surf UG Solids Reel am Safety
Dept. of Int. X
BIA(a)
BLM(a)
USGSCa)
Dept. of Energy
Dept. of Agr. X
USFS(a)
EPA X
AIR-OAQPS(a)
Water
Surface OWPS(a)
Ground OSW(a)
Land-OSW(a)
Rad1ation-ORP(a)
U.S. Army
Corps of Engrs. X
Dept. of Labor
MSHA(a)
OSHA(a) ,.,
Nuclear Reg. Comm. ;
X
X
X
X
X
X
X
X
XX X
XX X
XX X
X X
XX X
X
XX X
X XXX
X
X
X
XX XX
XXX XX X
X X
X
V '
X i*
t\
X X XXX
(a)
BIA-Bureau of Indian Affairs
BLM-Bureau of Land Management
USGS-United States Geological Survey
USFS-United States Forest Service
OWPS-Office of Water Planning and Standards
OSW-Office of Solid Waste
ORP-Office of Radiation Programs
MSHA-Mining Safety and Health Administration
..-.OAQPS-Office of Air Quality, Planning and Standards OSHA-Occupational Safety and Health Administration
' 'Nuclear Regulatory Commission (NRC) regulations and guides for milling do apply to in situ extraction or mining
but not conventional surface or underground mining where NRC has no authority.
-------
1-33
chloride emission standards are in subparts, B, C, E, and F of 40 CFR 61,
respectively. Section 122 of the CAA directed the Administrator to determine
whether emissions of radioactive pollutants, cadmium, arsenic, and polycyclic
organic matter (such as benzene) into ambient air will cause or contribute to
air pollution and endanger public health. If they do, EPA must propose emis-
sion standards for them within 180 days after that decision. The EPA has
listed radionuclides as "hazardous pollutants" under Section 112 of the Clean
Air Act in December 1979 (44FR76738, December 27, 1979). To date, no
standards for radionuclide emissions in air have been promulgated.
The particulate concentration values of the NAAQS apply to mining oper-
ations. Emissions (including dust) must be controlled to meet the standards.
Dust from mining operations was excluded from any air quality impact assess-
ment for prevention of significant air quality deterioration (PSD) (see 43
F.R. 26395). However, as a result of the court decision in Alabama Power
Company v. Costle, 13 ERC 1225, EPA has proposed amendment of PSD regulations
(44 F.R. 51924, September 5, 1979).
The emission of radioactive substances or gases from gaseous release is
controlled by NRC regulations 10 CFR Parts 20 and 40 for uranium milling and
in situ leaching. The NRC does not have this authority over mining. There
are no Federal regulations for radioactive pollution of air from mining at
this time. However, MSHA enforces standards for radioactivity in air inside
mines (30 CFR 57.5-37 through 57.5-42). Health and Safety standards of MSHA
for Metal and Nonmetallic Mine Safety are given in 30 CFR Parts 55, 57, and
58.
1.4.1.1.2 Water Quality
Standards for water quality are promulgated by EPA under the Federal
Water Pollution Control Act (FWPCA) of 1948 (as amended) and the Safe
Drinking Water Act (SDWA) (as amended). The FWPCA and SDWA regulate surface
water quality and groundwater quality, respectively.
-------
1-34
The Federal Water Pollution Control Act Amendments of 1972(Public Law
92-500) established that no one has a right, without permit, to discharge
pollutants into navigable waters of the nation. The Act provides for the
establishment of both water quality standards and effluent limitations. In
addition to requiring effluent standards for existing sources, it required
EPA to set new source performance standards for uranium mining. The fol-
lowing standards and guidelines apply to uranium mining and milling: Regu-
lations on Policies and Procedures for the National Pollutant Discharge
Elimination System (40 CFR 125), Effluent Guidelines - Mining and Processing
(40 CFR 116), Effluent Guidelines and Standards for Mining and Processing (40
CFR 436), and Protection of the Environment-Ore Mining and Dressing - Point
Source Category (40 CFR Part 440). Table 1.12 lists other pertinent regu-
lations and guides.
The Safe Drinking Water Act primarily protects municipal water systems.
Part C of the Act requires that states establish underground waste water in-
jection programs according to EPA regulations. Most mining operations dis-
pose of waste water through surface discharges subject to the NPDES permit
program and to the FWPCA. However, if a mine or mill seeks to dispose of
polluted water by injection and such injection may endanger public drinking
water supplies, then the Safe Drinking Water Act would apply. Finally, EPA
will be developing regulations pursuant to Subtitle C of the Resource Con-
servation and Recovery Act that will provide controls on hazardous uranium
mining wastes, including protection of groundwater resources. Section 4004
criteria, promulgated on September 13, 1979, apply to the nonhazardous
portion of the wastes.
The NRC's water quality standards for radioactivity in discharges from
uranium milling to the environment are in 10 CFR Parts 20 and 40. These
would apply to in situ mining licensed by NRC or an agreement state.
1.4.1.1.3 Land Quality
Federal regulations on solid waste disposal and land reclamation speci-
fically for uranium mining wastes are being developed pursuant to the Solid
Waste Disposal Act (as amended). The Surface Mining Control and Reclamation
Act of 1977 only applies to coal mining. Uranium mining occurs on Federal
-------
1-35
lands, where the Departments of Interior and Agriculture require reclamation.
A large part of the western states is Federally owned land: Arizona (43 per-
cent), California (45 percent), Colorado (36 percent), Idaho (64 percent),
Montana (30 percent), Nevada (87 percent), New Mexico (34 percent), Texas (2
percent), Utah (66 percent), Washington (29 percent), and Wyoming (48 per-
cent). State laws and local zoning ordinances may affect waste disposal.
Many states authorize counties to regulate land use outside incorporated
areas. Likewise, many states allow cities, towns, and villages to enact
zoning ordinances for land use within their boundaries. Thus, mining oper-
ations in each state are subject to different reclamation requirements,
depending upon land ownership and location.
Regulations for hazardous uranium mining wastes have been proposed by
the EPA pursuant to Subtitle C of the Solid Waste Disposal Act as sub-
stantially amended by the Resources Conservation and Recovery Act of 1976
(Public Law 94-580). These were published in the Federal Register (43 F.R.
58946-59028) on December 18, 1978. Waste rock and overburden from uranium
mining are listed as hazardous wastes, because they contain radioactive
substances that meet the definition of hazardous wastes given in Section 1004
(5) of the Act. Special waste standards (Part 250.46-4) were proposed for
the treatment, storage, and disposal of overburden and waste rock.
1.4.1.2 Federal Mineral Leasing and Location/Patent Laws
Some Federal regulations govern mineral exploration and mining rights.
The Mining Law of 1872 (30 USC §§ 21-50) permits persons to enter public
lands to discover, locate, and mine valuable minerals. The law has no pro-
visions for facility siting, surface protection, or reclamation. Free use of
water and timber for the mining operation and land for a mill site are ancil-
lary rights granted by the law. Most subsequent mineral leasing laws are
similar, designed to provide an orderly system for locating, removing, and
utilizing valuable mineral deposits on federally owned and controlled lands.
Pursuant to Section 603 (C) of the Federal Land Policy and Management Act of
1976, DOI has proposed specific environmental protection regulations (43 CFR
3800) for mining activities in potential or identified wilderness study areas
(44 FR 2620).
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1-36
1.4.1.2.1 Prospecting and Mining Rights
Consideration of environmental impacts may be required before obtaining
the right to prospect or explore. Depending upon land category, prospectors
may have to assess the environmental impact of mineral exploration before
being permitted to explore. Table 1.9 summarizes these requirements. Pros-
pectors on private lands simply must have permission from the owner of record
of mineral estate. On the other hand, Tribal and Indian lands, National
Forest System lands, and public lands (not public domain) all have specific
approval systems that require exploration plans or other appropriate consid-
erations.
Obtaining rights to mine usually involves the same Government agency
involved with prospecting rights. Table 1.10 summarizes applicable Federal
laws and regulations.
1.4.1.2.2 Mining and Environmental Plans
Before mining begins certain operating or mining and reclamation plans
must be submitted and approved. Table 1.11 summarizes these. The require-
ments parallel those for prospecting and mining rights.
1.4.1.3 Laws Having Potential Applicability
Federal laws require regulation for quality of air, water, and land. In
addition, though their direct influence has not been evaluated in this re-
port, federal laws protecting wildlife and cultural resources could affect
uranium mining activities.
Water use is also of potential concern in regard to uranium mining.
However, except for in situ mining, uranium mining operations have modest
needs for water. In fact, most mines typically dispose of significant
quantities from necessary dewatering. Appendix B lists federal water pro-
grams and rights activities and the lead agencies administering them; and
Appendix C lists Congressionally approved compacts that apportion water.
These compacts apportion water to the affected states, and each state in turn
allocates its share of the water among intrastate users on the basis of its
own system of water rights.
-------
Table 1.9 Requirements to obtain rights to prospect or explore by federal,
state and private lands
Land Category
Requirements
Federal:
Tribal,
Prospecting permit issued by BIA with consent of tribe. 25 CFR 171.27a.
Technical examination of environmental effects of prospecting by BIA, 25
CFR 177.4. Exploration plan submitted to USGS. Approval of plan by USGS
required, 25 CFR 177.6. Enforcement of plan by USGS, 25 CFR 177.10.
Allotted Indian.... No specific provisions for prospecting. Procedure for leasing to prospect
is same as for mining. If allotted land has been patented, treat same as
private land.
Public Domain,
Acquired Public...,
Withdrawn Public..,
Reserved Public...,
No restriction on prospecting. Entry under General Mining Law of 1872 (30
USC 22, 43 USC 1744, 43 CFR Part 3810), uranium included, 43 CFR 37461.
Prospecting permit from BLM, 43 CFR 3510.0-3 and 3511.2-1. Acquired lands not
subject to prospecting permits are listed in 43 CFR 3501.2-1. If acquired
land is not under BLM jurisdiction, consent of governmental entity having
jurisdiction is required before permit issued by BLM (43 CFR 3501.2-6).
Public domain land withdrawn for power development is open to entry and lo-
cation under General Mining Law of 1872, 30 USC 621. Agency having control
of withdrawn land reports any objections to mining activity based on land
use for which withdrawal was made. If controlling agency recommends stipu-
lations in the permit, they are included (43 CFR 3501.3-1 (a), (c).
Some Federal lands are disposed of with minerals reserved to the Govern-
ment; e.g., see 43 USC 299, 43 CFR 3814.1, 30 USC 50. For these lands,
permit issued.by BLM requires conformance with law under which reservation
was made, 43 CFR 35013-2(2). For lands reserved or segregated for partic-
ular purpose, special requirements may be made by BLM for protection and
use of land for purpose that it was reserved or segregated. Leases
from Dept. of Energy may be possible under 42 USC 2097.
CO
-------
Table 1.9 (Continued)
Land Category
Requirements
National Forest System...Public domain lands inside National Forest System boundaries are subject
to General Mining Law of 1872, with the following conditions: (a) If Dept.
of Agriculture requires operations plan, it must be submitted. Dept. of
Agriculture approves plan, 36 CFR 252.1; (b) Operations must minimize
environmental impact on surface resources in System lands, 36 CFR 252.8;
(c) Surface inspection and securing compliance with plan is responsibility
of Dept. of Agriculture, 36 CFR 252.7. Acquired National Forest System
land same as Acquired Public Land.
State Lease obtained from appropriate State Agency according to state law.
Private Permission given by owner of record of mineral estate.
Source:San Juan Basin Regional Uranium Study, Working Paper No. 28, Legal Infrastructure Related to
Uranium Mining in the San Juan Basin, United States Department of Interior.
co
00
-------
Table 1.10 Requirements to obtain rights to mine ore by
federal, state, and private lands
Land Category Requirements
Federal:
Tribal Secretary of Interior has general authority for leases, 25 USC 396a. Tribe
must approve. Leases given by bid. Approval of Secretary of Interior re-
quired, 25 CFR 171.2. Tribe may negotiate lease if Secretary grants per-
mission. Secretary has discretion to reject lease negotiated by Tribe, 25
CFR 171.2. Secretary may issue charter of incorporation to Tribe which may
include authority for Tribe to negotiate mining leases without approval.
Allotted Indian Leases given by bid. If Secretary of Interior approves, leases may be nego-
tiated by Indian owners, but negotiated lease subject to rejection by Secre-
tary, 25 CFR 172.4 and 172.6. Approval of allottee required. If patented,
treat same as private land.
Public Domain No lease required. Location of mineral deposit (staking a claim) after min-
eral has been discovered, 43 CFR 3831.1 and 3841.3. File locations with BLM
and in accordance with 43 USC 1744. Also record in accordance with State law.
Obtain patent for land claimed, 30 USC 29, 43 CFR Part 3860. Mill sites may
be claimed by location and patenting, 30 USC 42, 43 CFR Subpart 3844. If claim
has been patented, treat same as private land.
Acquired Public Mineral estate on acquired lands can be leased by BLM, 43 CFR 3501.3-1, subject
to exceptions (43 CFR 3501.1-5 and 3501.2-1). Permittee who prospected and
discovered is entitled to preference right lease, 43 CFR 3520.1-l(a)(3). BLM
leases land which contains valuable minerals on competitive basis, 43 CFR
3520.1-2(a). If land is not under BLM jurisdiction, consent of governmental
entity having jurisdiction is required before lease issues. '•p
CO
Withdrawn Public... For public domain land withdrawn for power development, laws are same as for
land in Public Domain, 30 USC 621. If withdrawal does not preclude mining,
BLM can lease mineral estate. Agency having jurisdiction of withdrawn land
reports any objections to mining activity, based on land use for which with-
drawal was made. If controlling agency recommends stipulations in lease,
they are included, 43 CFR 3501.3-l(a)(c). Leases from Dept. of Energy
on lands withdrawn for DOE use under 42 USC 2097.
-------
Table 1.10 (Continued)
Land Category
Reserved Public
Requirements
Some Federal lands are disposed of with minerals reserved to the government; see
e.g. 43 USC 299, 43 CFR 3814.1 and 30 USC 50. For these lands, lease issued by
BLM requires conformance with law under which reservation was made, 43 CFR 3501.
3-2(2). For lands reserved or segregated for particular purpose, special require-
ments may be made by BLM for protection and use of land for purpose that it was
reserved or segregated.
Public Domain land inside National Forest System boundaries are subject to Gen-
eral Mining Law of 1872, with the following exceptions: 36 CFR 252.1, (a) If
Department of Agriculture requires operations plan, it must be submitted.
Department of Agriculture approves plan; (b) Operations must minimize environ-
mental impact on surface resources on System Lands, 36 CFR 252.8; (c) Surface
reclamation required, 36 CFR 252.8(g); (d) Inspection and compliance with plan
responsibility of Department of Agriculture, 36 CFR 252.7. Acquired National
Forest System Land same as Acquired Public Land.
Leases obtained from appropriate State Agency according to state law.
Lease of mineral estate (or total estate) by private negotiation.
6.
7. National Forest
System
8.
9.
State
Private
Source: San Juan Basin Regional Uranium Study, working Paper No. 28, Legal Infrastructure Related
to Uranium Mining in the San Juan Basin, United States Department of Interior.
-------
Table 1.11 Requirements for mining and environmental plans by federal,
state, and private lands
Land Category Requirements
Federa1:
Tribal Mining plan must be approved by USGS. If lease requires revegetation, the
revegetation work is included in mining plan. Mining plan can be changed
by mutual consent of USGS and operator, 25 CFR 177.6. BIA evaluates environ-
mental effect of proposed operations and formulates environmental mitigation
requirements. BIA consults with USGS, 25 CFR 177.4.
Allotted Indian Same as Tribal Land, 25 CFR 177.1., unless allotted land has been patented. If
patented, treat same as private land.
Public Domain Plan same as acquired public land.
Acquired Public Geological survey approval of mining plan to mitigate adverse
environmental effects for federal leases, 30 CFR 231.10.
Withdrawn Public Stipulations can be put in the lease by the agency for whom the
land was withdrawn. These could affect operations but no formal
submission of plans required, 30 CFR 231.10.
Reserved Public Lessee must conduct operations in conformance with such require-
ments as may be made by BLM. Requirements will conform to pur-
poses for which land was reserved, 43 CFR 350.3-2(b). Approval
of mining plan required, 30 CFR 231.10.
National Forest System...Operations plan submitted to District Ranger, Department of Agri-
cultural, if he deems it necessary, 36 CFR 252.4. Reclamation
of surface required under opertor's plan, 36 CFR 252.8(g). Com-
pliance with Federal and State environmental laws, preserve
scenic values, wildlife, etc., 36 CFR 252.8. District Ranger,
Department of Agriculture, inspects and assures compliance
with operations plan, 36 CFR 252.7.
State Mine plan filed with and approved by State.
Private Same as State Land.
Note.—Some states require submission of mining and reclamation plans for all land.
Source: San Juan Basin Regional Uranium Study, Working Paper No. 28, Legal Infrastructure
Related to Uranium Mining in the San Juan Basin, United States Department of Interior.
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1-42
1.4.2. State Regulations
Federal statutes and regulations control many areas of environmental
quality. Most state licensing or regulatory authority is often the result of
a Federal-State agreement. However, land reclamation for uranium mining on
federal and nonfederal lands is principally under state control. Table 1.12
shows the regulatory scheme for six states with uranium mining, and Appendix
D lists the specific laws, regulations, and guides indicated generally in
Table 1.12.
Agreement states have made formal arrangements with the NRC to develop
programs to issue by-product, source material, and processing licenses. The
Atomic Energy Act (Sec. 274), as amended, requires agreement states to pro-
vide by 1981 regulatory programs that are equivalent to or more stringent
than the federal requirements for mill operations. Much of the environmental
regulation of mining operations outside of federally controlled lands, espec-
ially for reclamation activities, currently depends upon state or local
requirements. No NRC licenses are required for mining, except in situ.
The Federal Water Pollution Control Act amendments of 1972 give EPA
National Pollution Discharge Elimination System (NPDES) permitting authority.
However, Section 402 provides for approval of a state or interstate program
to permit. The Administrator has established guidelines specifying pro-
cedural and other elements that must be present to obtain approval (40 CFR
124). Where states have not been approved, applicants apply for discharge
permits from EPA. However, EPA asks what state requirements should also be
certified so that state standards are met. Column 2 of Table 1.12 lists
states that are approved to issue NPDES permits.
The Clean Air Act (CAA) amendments of 1970 and 1977 require, under
Section 110, that State Implementation Plans (SIP's) must be submitted for
approval to EPA for implementation of CAA on a local level. The approval and
implementation of State plans are given in 40 CFR 52. In areas where NAAQS
are violated, SIP's must produce compliance by 1982. If a state fails to
enforce its plan, EPA may enforce it. There are currently no emission stan-
dard regulations specific for uranium mining by State governments.
-------
Table 1.12 State laws, regulations, and guides for uranium mining
General
State
NRC
Agreement
State
NPDES
Permit
State
Mining
Permits
Water Exploration Mining
Use Rights Rights Air
Environmental Quality
Water
Surf UG
Health
Land and
Solids Reel am Safety
COLORADO Yes Yes
Department of Health
Water Quality Control Div.
Air Quality Control Div.
Department of Natural Resources
Div. of Water Reserves (State
Board of Land Commissioners
Mined Land Reel am Bd -
Division of Mines
NEW MEXICO Yes No
State Land Commission
Dept. of Energy and Minerals
Dept. of Natural Resources
Env. Improvement Div.
TEXAS Yes No
Dept. of Water Resources
R.R. Commission of Texas
General Land Office
Dept. of Health
Air Control Board
UTAH No No
State Engineer
Dept. of Social Services
Division of Health
Water Pollution Control Bd.
Dept. of Natural Resources
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
OJ
-------
Table 1.12 (continued)
GENERAL
Permits
State
NRC NPDES
Agreement Permit Water ExplorationMining
State State Use Rights Rights Air
Mining
Environmental
Water
Surf
UG
Qua
Land
Health
and
Solids Reel am
WASHINGTON Yes
Dept. of Natural Resources
Dept. of Ecology
Office of Water Programs
Dept of Social Services & Health -
Health Services Division
Air Quality Division
Yes
(No)
WYOMING
State Inspector of Mines
State Engineers Office
Dept. of Env. Quality
Air Quality Div.
Water Quality Div.
Land Quality Div.
Solid Waste Management
No
Yes
x
x
Note.—An "x indicates the existence of one or more controlling laws, regulations, or guides.
the specific laws, regulations, or guides.
See Appendix D for a list of
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1-45
Applicable laws, regulations, and guidelines that apply to uranium
mining in Colorado, New Mexico, Texas, Utah, Washington, and Wyoming are
discussed below. Laws and regulations of other previously mined or potential
uranium mining states, such as Arizona, California, Idaho, Montana, and South
Dakota, are not reviewed. However, the basic environmental considerations
of uranium mining should not be significantly different for other states.
1.4.2.1. Colorado
Colorado is an NRC "Agreement State" and has been approved by the EPA to
issue NPDES discharge permits. Both radiation and water quality regulatory
activities are under the jurisdiction of the Colorado Department of Health.
The Health Department's Radiation and Hazardous Wastes Control Division
administers radiation control activities and the control of hazardous wastes
disposal. However, there are no operable rules or regulations for mining.
Water quality is the responsibility of the Water Quality Control Commission
(affiliated with the Health Department), which promulgates water quality
standards and control regulations, and the Health Department's Water Quality
Control Division, which administers and enforces the Commission's regulations
and issues NPDES permits, as well as being responsible for numerous other
water quality activities.
Colorado's permitting of discharges to "navigable" waters has been ap-
proved by EPA. Unlike most states, Colorado has promulgated specific "Guide-
lines for Control of Water Pollution from Mine Drainage" (November 10, 1970).
These guidelines have the status of regulation since the State does not issue
the NPDES permit unless the guidelines will be met. Colorado also has "Rules
for Subsurface Disposal Systems" that, in conjunction with other rules, may
assure protection of groundwater. These "Rules" cover all wastes that are
disposed of underground, whether by direct or indirect means. "Wastes"
include "any substance, solid, liquid, or gaseous, including radioactive
particles thereof, which pollute or may tend to pollute any waters of the
State." Solid waste and other land disposals are covered by Section
25-8-501, CRS 1973, as amended. In cases where these regulations do not
control, the rules for subsurface disposal systems may apply.
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1-46
The Colorado Department of Natural Resources administers water use in
Colorado. As with most Western States, water is not in great abundance in
Colorado. Determination of priority of water rights to surface and tributary
groundwater is under the jurisdiction of a system of Water Courts, while the
Division of Water Resources (State Engineer) administers and controls the
allocation of actually available waters on an annual basis according to water
rights priorities.
There are no State air quality standards or regulations that apply
specifically to uranium mining. However, the National Ambient Air Quality
Standards and various State emission control regulations apply to uranium
mining activities as they do to all other types of emission sources. Colo-
rado's air quality activities are the responsibility of the State Health
Department's affiliated Air Quality Control Commission and its Air Quality
Control Division. The Commission defines State air quality policy and prom-
ulgates air quality ambient standards and emission control regulations, while
the Division administers and enforces the air quality regulations and issues
emission permits.
The Board of Land Commissioners, affiliated with the Colorado Department
of Natural Resources, issues permits for prospecting and controls leases for
mining on State lands. The Board has policies and regulations concerning
environmental impacts on prospected or leased lands.
The Colorado Mined Land Reclamation Board was created in 1976. It is
adminstered by the Department of Natural Resources. The Board issues permits
for all mining operations on all Federal and non-Federal lands in the State.
The stated intent for Colorado Mined Land Reclamation Law is "to allow for
the continued development of the mining industry in this State, while re-
quiring those persons involved in mining operations to reclaim land affected
by such operations so that the affected land may be put to a use beneficial
to the people of this State. It is the further intent...to conserve natural
resources, aid in the protection of wildlife and aquatic resources, and
establish agricultural, recreational, residential, and industrial sites and
to protect and promote the health, safety, and general welfare of the
people...." The Board has established rules and regulations to implement the
-------
1-47
law. Rule 5 (Prospecting Notice and Reclamation Requirements) considers
prospecting a separate activity, but still covered by certain reclamation
requirements. The reclamation performance standards of Rule 6 have specific
requirements for grading, hydrology and water quality, wildlife safety and
protection, topsoiling, and revegetation. Rule 7 ("Surety") assures rec-
lamation. Before the Board issues any permit and before any Notice of Intent
to Prospect is valid, the applicant must post surety with the Board. The
amount of surety, established by the Board, is to be sufficient to fully
reimburse the State for all expenses it would incur in completing the rec-
lamation plan in the event of default by the operator.
Colorado also has regulations that apply for health and safety in mining
operations. For each invidual employee of any mining operation within the
state a lifetime history is maintained on exposure to radon daughter concen-
trations when certain minimum values are reached. The State Department of
Natural Resources Division of Mines administers these.
1.4.2.2 New Mexico
In New Mexico, a mine plan must be filed with and approved by the State
Mining Inspector before he will issue a permit. The State Mining Inspector
does not review the plan for environmental impact. Groundwater use rights
are established by the State Engineer, and the Land Commission handles ex-
ploration and mining rights. The engineer's office issues a permit for bene-
ficial use of any water pumped from uranium mines. However, the Navajo tribe
claims jurisdiction of the State's groundwater in the northwest region of New
Mexico. It is likely that the Departments of Interior and Justice will
eventually become involved in this dispute as Trustees for the tribe.
Approval status has been given, with some exceptions, by EPA to New Mex-
ico's plan for the attainment and maintenance of national air standards (40
CFR 52.1622). However, neither Federal nor State regulations include speci-
fic emission standards for uranium mining. But "Ambient Air Quality Stan-
dards" (40 CFR 50.6) on suspended particulates apply to all sources of air
pollution.
-------
1-48
New Mexico is an NRC agreement state, but it is not an approved NPDES
state. Part 2 of the amended Water Quality Control Commission regulations
applies to any discharge that is not subject to a permit under the NPDES sys-
tem. The State requires approved discharge plans for discharges that could
contaminate groundwater. However, the applicable NPDES regulations (Subpart
E-Uranium, Radium and Vanadium Ores Subcategory, 40 CFR 440.50) have been
challenged by some mine operators. They claim that discharges to a dry
arroyo do not constitute "the discharge of pollutants into the navigable
water, water of the continguous zone, and the oceans." Because more than
half of active New Mexico mine discharges have NPDES permits that are now
under adjudication, there is no enforcement and discharges may not be in
accordance with Standards. If the NPDES challenge is sustained, then New
Mexico's Part 2 regulations could be applied, even though they are not par-
ticularly suitable for uranium mining discharges. Possibly only the regu-
lations on chemical oxygen demand and settling of heavy metal solids would
apply to uranium mine wastes. The Part 3 "Regulations for Discharges onto or
below the Surface of the Ground" (3-100) that are designed to "protect all
groundwater" would also be important. A discharge plan is required for ef-
fluent discharges that move directly or indirectly into groundwater, if the
effluent contains any of the contaminants listed in Section 3-103 a, b, and
c, or toxic pollutants. Since the list of contaminants includes uranium and
radium, New Mexico can approve only discharge plans meeting the drinking
water standards.
There are no state regulations for solid wastes and land reclamation for
mining operations. The mining plan and bonding requirements associated with
mining permits determine the extent of mining reclamation.
Radiation safety requirements (Sections 74-3-1 et seq NMSA 1978) apply
to both mining and milling. Air quality monitoring in underground mines cur-
rently involves potential duplication of effort by the New Mexico Mine In-
spector (69-5-7 et seq NMSA 1978) and the Federal Mine Safety and Health
Administration (30 CFR 57.5-37).
-------
1-49
1.4.2.3 Texas
Texas is an NRC agreement state, but not an EPA approved NPDES permit
state. The Department of Water Resources controls water use. Even though
much of the water used in Texas comes from wells, there are no regulations on
pumping groundwater. However, some counties have regulations that limit
groundwater withdrawal to control subsidence.
Specific regulations for in situ uranium mining are enforced by the
Texas Department of Health (TDH). Since Texas is an agreement state, its
regulations reflect all appropriate NRC regulations. The TDH also implements
the Safe Drinking Water Act (SDWA) and monitors groundwater to assure that
its provisions for radium and selenium concentrations are met.
The General Land Office (6LO) issues prospecting permits and mining
leases on state-owned lands. Mining and reclamation plans for uranium mining
on state-owned lands are reviewed for approval by GLO. The "Texas Uranium
Surface Mining and Reclamation Act" exempts state-owned lands from regulation
by the Railroad Commission.
Surface mining is regulated by the Railroad Commission. All require-
ments of state and federal laws must be fulfilled before a permit is issued.
Mining and reclamation plans must be submitted and approved. A bond is
required to assure reclamation after mining.
The Texas Air Control Board administers provisions of the Clean Air Act.
Except for suspended particulates, there are no applicable standards, i.e.,
there are no state source standards, for uranium mining.
The Texas Guides and Regulations for Control of Radiation (TRCR) do not
apply to surface uranium mining. They do apply to in situ mining due to NRC
agreement state licensing. The radioactive content of water discharged from
all mines to the environment must not exceed TRCR limits.
1.4.2.4 Utah
Utah is neither an NRC agreement state nor an NPDES permit approved
state. The Utah State Engineer's Office is responsible for approval of water
-------
1-50
use rights. The Department of Natural Resources oversees exploration and
mining rights on State lands.
The Division of Oil, Gas, and Mining of the Department of Natural Re-
sources issues permits for uranium mining operations, except in situ mining
licensed by the NRC. A mining and reclamation plan must be approved. Rule
M-10 standards include consideration of land use, public safety and welfare,
impoundment, slopes, high walls, toxic materials, roads and pads, draining,
structures and equipment, shafts and portals, sediment control, revegetation,
dams, and soils. Bonding requirements assure reclamation.
Discharges to surface waters are regulated under the EPA administered
NPDES system and the Utah Water Pollution Committee. Utah does have separate
regulations administered by the Department of Social Services. These are
applied to mining operations such as non-discharging waste water systems and
in situ mining where no NPDES permit is required.
No sources of pollution will be allowed to cause groundwaters to exceed
drinking water standards. The applicable standards for classes 1A and IB
domestic water sources are given in Wastewater Disposal Regulations, Part II.
Utah is developing radiation safety regulations. We do not expect that
they will apply to uranium mining, since they are based on the model state
suggested regulations.
1.4.2.5 Washington
Washington is an NRC agreement state and an NPDES approved permit state.
The Department of Ecology regulates water use and water quality. Washington
has no regulations for groundwater. These waters could be protected under
the Safe Drinking Water Act.
The Department of Natural Resources controls exploration and mining
rights for state-owned lands only. The mineral lease law covers both surface
and underground mining but not in situ or heap leaching. The State Rec-
lamation Act applies to state and private lands only. A mining and recla-
mation bond is required before a permit is issued. Reclamation is assured
through bonding requirements.
-------
1-51
Washington has a Clean Air Act under which regulations have been prom-
ulgated consistent with the Federal Clean Air Act. No source emission stan-
dards have been issued for uranium mining. National Ambient Air Quality
Standards could apply to suspended particulates.
Washington has rules and regulations for radiation protection, but they
do not apply to uranium mining.
1.4.2.6 Wyoming
Wyoming is an approved NPDES permitting State but not an NRC Agreement
State. The State Engineer's Office controls water use rights. Control is
primarily on the quantity of water used, but there is some statutory respon-
sibility regarding sedimentation. Discharges to surface waters are regulated
by the Water Quality Division of the Department of Environmental Quality. The
construction of any water or waste water facility requires a construction
permit. Groundwater regulations have been proposed. These include ground-
water quality standards for any activity. Permitting requirements specific
to in situ uranium operations is one of a group of special process dis-
charges.
The Land Quality Division of the Wyoming Department of Environmental
Quality is the principle agency responsible for enforcing environmental pro-
tection standards and reclamation standards with respect to uranium mining
operations. The Division also enforces mineral exploration regulations that
afford protection to groundwater and restoration of significant surface dis-
turbances.
Wyoming law requires that uranium mined land must be restored to a use
at least equal to its highest previous use (W.S. 35-ll-402(a)(i) and (ii))
and mining operations must be conducted to prevent pollution of waters of the
State (W.S. 35-ll-402(a)(v1)). Before a mining operation receives a permit
it must submit to the Department a mining and reclamation plan that demon-
strates compliance with the law and associated rules and regulations. The
plan must contain a plan for the disposal of all acid-forming, toxic mat-
erials or materials constituting a fire, health, or safety hazard uncovered
-------
1-52
or created by the mining process: radioactive material is included (W.S.
35-ll-406(b)(1x)).
An operator must also, in accord with his approved mine and reclamation
plan, cover, bury, impound, contain, or dispose of toxic, acid-forming, or
radioactive material determined to be hazardous to health and safety or con-
stitute a threat of pollution to surface or subsurface waters (W.S.
35-ll-415(b)(iv)). A required surety bond assures that the operator will re-
claim the land according to his approved plan. If the bond is forfeited, the
State is responsible for reclamation.
Wyoming has legislated authority for a position on radiological res-
toration of mined lands. It is described in the Division's Guideline No. 1,
Section III. The Division is presently drafting regulations for radiation
protection on uranium mined lands and handling of uranium mine wastes. These
regulations shall set standards.
Wyoming also has a solid waste management program that presently regu-
lates only refuse generated at mines. Solid waste disposal sites are per-
mitted at these facilities. Solid waste regulations could be promulgated
that affect mining.
In Wyoming, Ambient Air Quality Standards are applied to mining oper-
ations, and fugitive emissions are controlled to the extent that these stand-
ards are met. An Air Quality Permit is required for the construction of a
uranium mining and/or processing facility, and the applicant is required to
demonstrate that applicable ambient and PSD (Prevention of Significant Deter-
ioration) provisions are met.
Wyoming has radiation protection regulations for the safety of mines
while they are actually in process. These regulations are under the juris-
diction of the State Inspector of Mines. According to Wyoming Law, the pro-
tection of miners from hazardous exposure to radioactivity must conform to
the American Standards Association revised Publication N 13.8, "Radiation
Protection in Uranium Mines and Mills." The uranium regulations (94-R-ll)
are found in Chapter 3, Article 4 of Title 30 - Mines and Minerals.
-------
1-53
1.5 References
AEC74 U.S. Atomic Energy Commission, Directorate of Licensing, Fuels and
Materials, 1974, "Environmental Survey of the Uranium Fuel Cycle",
WASH-1248.
Cu77 Culler, F. L., 1977, "An Alternate Perspective on Long Range Energy
Options", Conference on U.S. Options for Long Term Energy Supply, Den-
ver, Colorado, Atomic Industrial Forum Report, Vol. 3.
DOE79 U.S. Department of Energy, 1979, "Statistical Data of the Uranium
Industry", GJO-100(79).
Du79 Durler, D.L., U.S. Steel Corporation, Texas Uranium Operations, Corpus
Christi, TX, 12/4/79 personal communication.
EPA76 U.S. Environmental Protection Agency, Office of Radiation Programs,
1976, "Final Environmental Statement for Environmental Radiation Pro-
tection Requirements for Normal Operations of Activities in the Uranium
Fuel Cycle", EPA 520/4-76-016.
ERDA75 Energy Research and Development Adminstration, Office of the Assis-
tant Administrator for Planning and Analysis, 1975, "Total Energy, Elec-
tric Energy and Nuclear Power Projections, United States".
EW78 Electrical World, 1978, "Annual Electrical Industry Forecast".
He77 Hetland, D. L. and Wilbur, D. 6., 1977, "Potential Resources",
presented at the Uranium Industry Seminar, Grand Junction, Colorado.
Ja79 Jackson, P. 0., Perkins, R. W., Schwendiman, L. C., Wogman, N. A.,
Glissmeyer, J. A. and Enderlin, W. I., 1979, "Radon-222 Emissions in
Ventilation Air Exhausted From Underground Uranium Mines", Battelle
Pacific Northwest Laboratory Report, PNL-2888 REV., NUREG/CR-0627.
-------
1-54
Ja80 Jackson, P. 0., Battelle Pacific Northwest Laboratory, Richland, WA.,
12/80, Personal Communication.
Ka75 Kallus, M. F., 1975, "Environmental Aspects of Uranium Mining and Mil-
ling in South Texas", U.S. Environmental Protection Agency Report, EPA-
906/9-75-004.
Ka78 Kasper, D., Martin, H. and Munsey, L., 1978, "Environmental Assessment
of In Situ Mining", Report prepared by PRC Toups Corp. for the U.S. De-
partment of the Interior, Bureau of Mines, Contract No. J0265022.
La78 Larson, W.C., 1978, "Uranium In Situ Leach Mining in the United States",
U.S. Department of the Interior, Bureau of Mines Information Circular 8777.
Le77 Lee, H. and Peyton, T.O., 1977, "Potential Radioactive Pollutants Re-
sulting from expanded Energy Programs", U.S. Environmental Protection
Agency Report, EPA 600/7-77-082.
NEP77 National Energy Plan (NEP), April 1977.
Ni78 Nininger, R. D., 1978, Atomic Industrial Forum Conference, "Fuel Cycle
'78", New York, NY.
Ni79 Nielson, K. K., Perkins, R. W., Schwendiman, L. C. and Enderlin, W. I.,
1979, "Prediction of the Net Radon Emission from a Model Open Pit Uran-
ium Mine", Battelle Pacific Northwest Laboratory Report, PNL-2889 Rev.,
NUREG/CR-0628.
NRC76 U.S. Nuclear Regulatory Commission, Office of Nuclear Material, Safety
and Safeguards, 1976, "Final Generic Environmental Statement on the Use
of Recycled Plutonium in Mixed Oxide Fuel in Light Water Cooled Reactors",
NUREG-0002, Vol. 3.
NRC77a U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety
and Safeguards, 1977, "Draft Environmental Statement Related to Operation
of Sweetwater Uranium Project", NUREG-0403, Docket No. 40-8584.
-------
1-55
NRC77b U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety
and Safeguards, 1977, "Final Environmental Statement Related to Operation
of Bear Creek Project", NURG-0129, Docket No. 40-8452.
NRC78 U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety
and Safeguards, 1978, "Draft Environmental Statement related to Opera-
tion of Highland Uranium Solution Mining Project", NUREG-0404, Docket No.
40-8102.
NRC79 U.S. Nuclear Regulatory Commission, Office of Nuclear Material Safety
and Safeguards, 1979, "Draft Generic Environmental Impact Statement on
Uranium Milling", NUREG-0511, Vol. 1.
NUS76 NUS Corporation, 1976, "Technical Assessment for Specific Aspects of
EPA Proposed Environmental Radiation Standard for the Uranium Fuel Cycle
(40CFR190) and its Associated Documentation", A Report Prepared for the
Atomic Industrial Forum, AIF/NESP-011.
Pe79a Perkins, B.L., Energy and Minerals Department, State of New Mexico,
12/13/79, personal communication.
Pe79b Perkins, B. L., 1979, "An Overview of the New Mexico Uranium Industry",
New Mexico Energy and Minerals Department Publication, Santa Fe, New Mexico.
St78 Stone and Webster Engineering Corp., 1978, "Uranium Mining, and Milling -
The Need, The Processes, The Impacts, The Choices", A Contract Prepared
for the Western Interstate Energy Board, U.S. Environmental Protection
Agency Report, EPA-908/1-78-004.
Th79 Thomasson, W. N., 1979, "Environmental Development Plan for Uranium
Mining, Milling and Conversion", U.S. Department of Energy, DOE/EDP-0058.
Th78 Thompson, W. E., 1978, "Ground-Water Elements of In Situ Leach mining
of Uranium", A Contract Prepared by Geraghty and Miller, Inc., for the
U.S. Nuclear Regulatory Commission, NUREG/CR-0311.
-------
1-56
TVA78a Tennessee Valley Authority, 1978, "Final Environmental Statement -
Morton Ranch Uranium Mining".
TVA78b Tennessee Valley Authority and the U.S. Department of the Interior,
1978, "Draft Environmental Statement - Crownpoint Uranium Mining Project".
USC78 U.S. Congress, 1978, "Uranium Mill Tailings Radiation Control Act of
1978", Public Law 95-604.
Wy77 Wyoming Mineral Corporation, 1977, "Environmental Report - Irigaray
Project, Johnson County, Wyoming", Wyoming Mineral Corporation, 3900 S.
Wadsworth Blvd., Lakewood, Colorado 80235.
-------
SECTION 2
INVENTORY OF URANIUM MINES
-------
2-1
2.0 Inventory of Uranium Mines
To inventory the numbers, types, and locations of uranium mines in
the United States, we used data from the Department of Energy, Grand Junction
Office (DOE-GJO). We produced the inventory of uranium mines presented in
this section and Appendixes E and F of this report from the DOE-GJO master
data file (DOE79a) and personal communications with DOE-GJO (Ch80, MESOa,
MESOb). These two sources combined yielded our own EPA master data file,
which we divided into two parts - active and inactive mines.
Table 2.1 classifies active and inactive U.S. uranium properties accor-
ding to the method of uranium production (mine type) based on data that were
current as of 1978 (MeSOa). The major mining methods are surface and under-
ground mines (DOE79b). The remaining mining methods are only minor contrib-
utors to the total uranium ore production (DOE79b).
Table 2.1 shows a total of 340 active mines. This final total, which is
52 less than the original total of 392 active mines provided by DOE-GJO
(MeSOa), was derived, in consultation with DOE-GJO (MeSOb), by eliminating 43
mines that were duplicated on the list and 9 that were small producers (i.e.,
producing only a few tons of ore for the entire year of 1978). Most (if not
all) of the 52 eliminated mines were either underground or surface mines.
The original totals of 305 active underground mines and 63 active sur-
face mines (DOE79b), whose combined total of 368 mines accounts for the later
eliminated 52 mines that were duplicate listings or small producers, were the
totals we used in modeling the average underground and surface mines in this
study. The differences between these totals and the smaller Table 2.1 totals
of 256 active underground mines and 60 active surface mines are insignificant
compared with other uncertainties in predicting health effects. The smaller
totals for underground and surface mines would introduce differences of less
than 17% and less than 5% for the active average underground and average
surface model mines, respectively.
Table 2.2 gives locations and types of active uranium mines by state.
With respect to the number of mines, Colorado and Utah dominate the inven-
tory, especially for underground mines. However, since New Mexico and
-------
2-2
Wyoming have large mines (underground in New Mexico, and surface in Wyoming)
and dominate ore production, New Mexico is the site of our model active
underground mines and Wyoming is the site of our model active surface mines.
Our model in situ leaching operation is also sited in Wyoming, which is one
of two states mining uranium with that method. Appendix E gives a complete
inventory of active uranium mines.
The numbers of inactive uranium mines according to state and mining
method are given in Table 2.3. Colorado and Utah have the greatest number of
inactive mines, but Arizona, Wyoming, New Mexico, and South Dakota also
contain significant numbers. Since New Mexico and Wyoming have dominated ore
production over the past 10 years (DOE79b), New Mexico (because of its large
underground mines) is our model site for inactive underground mining and
Wyoming (because of its large surface mines) is the site of our model inact-
ive surface mine. Appendix F gives a complete inventory of inactive uranium
mines.
Figures 2.1 through 2.9 are maps showing the locations, status, and
types of uranium mines in Colorado, New Mexico, Texas, Utah, and Wyoming
(Ch77, Co78a, Co78b, Co78c, Ea73, G175, Hi69, Pe79, Ut77). Since it is not
always possible to show all the mines in a given district, the maps indicate
only the area and number of mines in some major mining districts, partic-
ularly for Colorado and Utah. The maps do not show the location of many small
mines started during the uranium boom of the 1950's because their exact
locations are unknown. In Colorado alone there are over a thousand such
mines.
Table 2.4 shows total ore production through January 1, 1979 for active
and inactive surface and underground mines. The larger mines (>910 MT ore
production) dominate the list of active mines, and the smaller mines (<910
MT ore production) dominate the inactive list. If remedial action becomes
necessary for inactive mines, the information in Table 2.4 could help esti-
mate the magnitude of such an action, at least affording a way to make rough
estimates of waste rock, sub-ore, and overburden that are present at the
inactive site. A recent DOE report (DOE79c) contains additional information
on mining waste tonnage and acreage of specific properties.
-------
2-3
Table 2.1 Type of U.S. uranium properties
Uranium Number of Number of
Production Methocr3' Active ProDert.ip* Tnartiwa 0*™
Surface mine
Underground mine
Mine water production
Heap leach - dumps
Heap leach - ores
Dumps
Sub-ore
In-situ leaching
Miscellaneous
Tailings dump
Unknown
60
256
2
1
0
1
1
11
0
2
6
J.IIVKWWIVW I i vp\- 1 V 1 W. J
1252
2036
1
7
1
42
12
2
23
0
13
TOTAL 340 3389
^'Categories listed in this column are modifications of the originals
(DOE79a). Copper by-product and surface-underground combination categories
were eliminated because they contained no properties. The miscellaneous-
phosphate by-product category was reduced to miscellaneous because most phos-
phate by-product properties were not included in the DOE-6JO master data file
(DOE79a). The low grade or protore category was changed to sub-ore to be con-
sistent with the rest of this report.
-------
Table 2.2 The location and type of active uranium properties
Surface
State Mine
Arizona
Colorado
New Mexico
Texas
Utah
Washington
Wyoming
TOTAL
1
5
4
16
13
2
19
60
Underground
Mine
1
106
35
0
108
0
6
256
Mine
Water Heap-Leach
Production Dumps
0
0
2
0
0
0
0
2
0
0
0
0
0
0
1
1
Heap-Leach
Ores Dumps
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
1
Sub-ore
0
0
0
0
0
0
1
1
In-Situ
Leaching
0
0
0
8
0
0
3
11
Tail ings
Miscellaneous Dump
0
0
0
0
0
0
0
0
0
1
0
1
0
0
0
2
Unknown Total
0
3
0
0
3
0
0
6
2
115
42
25
124
2
30
340
-------
Table 2.3 The location and type of inactive uraniun properties
Surface
State Mine
Alaska
Arizona
California
Colorado
Florida
Idaho
Minnesota
Montana
Nevada
New Jersey
New Mexico
N. Dakota
Oklahoma
Oregon
S. Dakota
Texas
Utah
Washington
Wyoming
Unknown
0
135
13
263
0
2
0
9
9
0
34
13
3
2
111
38
378
13
223
6
Underground
Mine
1
189
10
902
0
4
0
9
12
1
142
0
0
1
30
0
698
0
32
5
Mine
Water
Production
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
Heap-Leach
Dumps
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6
0
Heap-Leach
Ores Dumps
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
35
0
0
0
0
0
0
0
0
0
0
0
0
7
0
0
0
Sub-ore
0
0
0
1
0
0
0
0
0
0
8
0
0
0
0
0
1
0
2
0
In-Situ
Leaching
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
0
0
0
0
Miscellaneous
0
0
0
10
1
0
1
0
0
0
1
0
0
0
0
0
6
0
2
2
Tail ings
Dump
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Unknown Total
0
1
0
6
0
0
0
0
0
0
2
0
0
0
0
1
3
0
0
0
1
326
23
1217
1
6
1
18
21
1
188
13
3
3
141
42
1093
13
265
13
TOTAL
1252
2036
42
12
23
13
3389
-------
4 Active mines
10 Inactive mines
MOFFAT ^[ 00
QDENVER
m GRANDMJNCTION
^>
TELH .COLORADO
SPRINGS
ELPXkSO
GUNNISON
MONTRdSE
locations of
mines in this
area shown
|in figure2£
u FREMONT
OURAY
I
a
^INSDALE
13 Inactive mines
LEGEND
• ACTIVE MINES, TYPE UNKNOWN
o IN ACTIVE MINES. TYPE UNKNOWN
D
p fORTEZ JQ LAPLATA
* /'nJL
DURANGO
I ARCHULETA
Figure 2.1 Location of active and inactive uranium mines and
principal uranium mining districts in Colorado
K3
I
-------
2-7
COLORADO
LEGEND
A, • ACTIVE MINES, TYPE UNKNOWN
I, D INACTIVE MINES, TYPE UNKNOWN
Kilometers
Figure 2.2 Location of active and inactive uranium mines
and principal uranium mining districts in the
Uravan Mineral Belt of western Colorado
-------
©
CROWN POINT
MARIANO LAKE
©
Ambrosia Lake
•i-.:.-..
McKINLEY COUNTY
VALENCIA COUNTY
F 7 ' r '
of I f \
OO.~,., 1 „ | | 1
:%fjrV
:.±:-^ >
! -J 9 >0 • -'WriOMfTt**
-.,rA.f'' L! 1
: i \ \
"1 (
' SANDOVAL COUNT'
©i !
SAN_MATEO _|_ "© MARQUEZ
©
GRANTS
20
•KILOMETERS
LEGEND
| Grants Mineral Belt
Active mine, type unknown
Inactive mine, type and
status unknown
Mines outside Grants Mineral
Belt. Primarily inactive.
©
LACUNA
Figure 2.3 Location of active and inactive uranium mines in
the Grants Mineral Belt and other areas of New Mexico
K3
CO
-------
2-9
38
5 PLANNED IN-SITU OPERATIONS
AND 1 PLANNED OPEN PIT MINE
4 ACTIVE IN-SITU OPERATIONS
Karnes City
KARNES CO
*
Three Rivers
LIVE OAK CO.
23C
LEGEND
A ACTIVE SURFACE MINE
© PLANNED SURFACE MINE
A INACTIVE SURFACE MINE
g) ACTIVE IN-SITU OPERATION
0) PLANNED IN-SITU OPERATION
Scalel
Kilometers
2B(
Figure 2.4 Location of active, inactive, and proposed
surface and in situ uranium mines in Texas
-------
2-10
114°
113°
1120/
ir
w:;::x;:i:| EMERY' '#$#&$&. GRAND v&&
:::::::::x:::::::::::::::::::::::::;:::::::::3t::;::::: M da b '£%
yfftfy* MINES IN THIS AREA XvX
YNE'':!:!:!:SHOWN IN FIGURE 2.6 :8x':
Cedar City
'I*''**!'**''***"*'"''1***1'1*1'***'*''*1*1'*'**'****'*!***!1''
x::::;:;::::: SAN JUAN :::::::
40 80 120 160 200
SCALE
KILOMETERS
LEGEND
•-8 DISTRICT CONTAINING SPECIFIED NUMBER OF MINES, TYPE AND STATUS UNKNOWN
A SINGLE MINE LOCATION: TYPE AND STATUS UNKNOWN
Figure 2.5 Location of uranium mines and mining districts in Utah
-------
2-11
CRCCN RIVtft
AND SAN RAFAfi
MINING DISTRICTS
-------
NORTHERN SLACK
HILLS
SWEETWATE
LARAMIE
CheyenneQ
110°
109°
108
107C
106C
105
LEGEND
A Active Surface Mine
V Inactive Surface Mine
• Active Underground Mine
D Inactive Underground Mine
Figure 2.7 Location of active and inactive uranium mines
and principal uranium mining areas in Wyoming
r-o
i
-------
2-13
V V
A
A
V
A
V V
A v
• A
Gas Hills
--43°
*
Jeffery City
Crooks Gap --Green Mountain
Split Rock
LEGEND
A Active Surface Mine
V Inactive Surface Mine
• Active Underground Mine
D Inactive Underground Mine
5 10 15 20 25 30
KILOMETERS
Figure 2.8 Location of active and inactive uranium mines in the Gas
Hills and Crooks Gap-Green Mountain areas of central Wyoming
-------
2-14
Tea Pot Dome
*
South Powder River Basin
-43°
*
Douglas
LEGEND
A Active Surface Mine
V Inactive Surface Mine
• Active Underground Mine
D Inactive Underground Mine
10 20
40
Kilometers
8
Figure 2.9 Location of active and inactive uranium mines
in the Shirley Basin, South Powder River Basin,
and Pumpkin Buttes areas of Wyoming
-------
Table 2.4 Cumulative Ore Production
through January 1, 1979
Active
Inactive
Ore Production
MT No. Mines
Under- Under-
of total) Surface ground No. Mines (% of total) Surface ground
< 91
91-910
910-91,000
> 91,000
Total
16
33
188
103
340
(4.7)
(9.7)
(55.3)
(30.3)
(100.0)
8
5
15
32
60
3
24
165
64
256
1553
753
986
97
3389
(45.8)
(22.2)
(29.1)
(2.9)
(100.0)
899
134
180
39
1252
628
588
766
54
2036
ro
t—»
01
-------
2-16
2.1 References
Ch77 Chapman, Wood, and Griswold, Inc., 1977, "Geologic Map of Grants Uran-
ium Region," New Mexico Bureau of Mines and Mineral Resources Geological
Map 31 (rev.).
Ch80 Personal communication with William L. Chenoweth (DOE-GJO), January 1980.
Co78a Colorado Geological Survey, Department of Natural Resources, State of Col-
orado, 1978, James L. Nelson-Moore, Donna Bishop Collins, and A. L. Horn-
baker, "Radioactive Mineral Occurrences of Colorado and Bibliography", Bul-
letin 40.
Co78b Collier, J.D., Hornbaker, A.L., and Chenoweth, W.L., 1978, "Directory of
Colorado Uranium and Vanadium Mining and Milling Activities", Colorado Geo-
logical Survey Map Series 11.
Co78c Cook, L.M., 1978, "The Uranium District of the Texas Gulf Coastal Plain",
Texas Department of Health, Austin, Texas.
DOE79a Department of Energy, Grand Junction Office, 1979, magnetic computer tape
of selected information on U.S. uranium mines.
DOE79b Department of Energy, 1979, "Statistical Data of the Uranium Industry", GJO-
100(79), Grand Junction, Colorado.
DOE79c Department of Energy, 1979, "Report on Residual Radioactive Materials on
Public or Acquired Lands of the United States", DOE/EV-0037, Washington, D.C.
Ea73 Eargle, D.H., Hunds, G.W., and Weeks, A.M.D., 1973, "Uranium Geology and
Mines, South Texas", Bureau of Economic Geology Guidebook 12, University
of Texas at Austin.
G175 Glass, 6.B., Wendell, W.G., Root, F.K, and Breckenridge, R.M., 1975, "En-
ergy Resources Map of Wyoming", Wyoming Geological Survey.
-------
2-17
Hi69 Hilpert, L.S., 1969, "Uranium Resources of Northwestern New Mexico", US6S
Professional Paper 603.
MeSOa Letter from Robert J. Meehan (DOE-GJO) to Thomas R. Horton (EPA-EERF),
dated January 16, 1980.
Me80b Personal communication with Robert J. Meehan (DOE-GJO), January 1980.
Pe79 Perkins, B.L., 1979, "An Overview of the New Mexico Uranium Industry", New
Mexico Energy and Minerals Department, Santa Fe, New Mexico.
Ut77 State of Utah, Department of Natural Resources, Utah Geological and Mineral
Survey, 1977, "Energy Resources Map of Utah", Map 44.
-------
SECTION 3
POTENTIAL SOURCES OF CONTAMINANTS
TO THE ENVIRONMENT AND MAN
-------
3-1
3.0 Potential Sources of Contaminants to the Environment and Man
3.1 Background Concentrations of Radionucli'des and Trace Metals
3.1.1 Naturally Occurring Radionuclides
Potassium-40 and radionuclides in the decay chains of uranium-238 and
thorium-232 are the principal sources in the earth's crust of background
radiation. Figures 3.1 and 3.2 show the uranium-238 and thorium-232 decay
chains. Potassium-40 constitutes 0.0118 percent of naturally occurring po-
g
tassium. Its half-life is 1.26 x 10 years and, upon decay, potassium-40
emits a 1.46 MeV gamma ray in 11 percent of its disintegrations. Table 3.1
lists the average concentration of and gamma-ray energy released by these
radionuclides in one gram of rock. Table 3.2 lists the radionuclide content
and dose equivalent rates from common rocks and soils. Potassium-40 and the
thorium-232 decay chain each contribute about 40 percent of the dose rate at
3 feet above the ground while the uranium-238 decay chain contributes approxi-
mately 20 percent of the total dose rate.
Radon-222 occurs in the uranium-238 decay chain and has a half-life of
3.8 days. It is a noble gas and, upon decay, produces a series of short-
lived, alpha-emitting daughters (see Fig.3.1). The average atmospheric radon
concentration in the continental U.S. is 0.26 pCi/liter (Oa72). Under most
conditions, the radon daughters contribute less than 10 percent (a few tenths
of a prem/hr) to the terrestrial external dose equivalent rate. However,
inhaled radon daughters contribute a large fraction of the total dose equiva-
lent rate to the respiratory tract: about 50 percent (90 mrem/yr) to the lung
and nearly all of the dose (450 mrem/yr) to the segmental bronchioles
(NCRP75).
Eighty-five percent of the surface area of the United States, and nearly
all of its population, is underlain by rocks and soils of sedimentary origin.
However, the correlation between the bedrock activity and the aboveground
activity is not clear.
In most soils, the amount of water varies from 5 to 25 percent. The
soil moisture attenuates gamma radiation from the soil. The potassium-40
dose equivalent rate can decrease by 30 percent when the soil water content
increases from 0 to 30 percent (OA72). Moisture can retard the diffusion of
radon into the atmosphere and reduce the exposure to airborne radon daugh-
ters. Since radon daughters account for 95 percent of the gamma-ray energy
from the uranium-238 series, their accumulation in the ground increases
-------
3-2
URANIUM — 238 DECAY SERIES
238(J
92 W
4.5 x 10' yr
a
234
9flTh
24. Ida
234
9lPa
1.2 min.
' &.y
T2U
2.5 x 105 yr
f&.y
a,T
230
90Th
8.0 x 104 yr
a,y
226
88Ra
1 602 yr
a,y
222D
86""
3.8 da '
a,y
218
84Po
3.0 min.
a
214 210
84Po 84Po
1.6 x lO^sec 138da.
/ /
™« , /&iy a'v 21303B.' r *'y
19.7 min.' 5,0da
M £ '
214
82 p"
26.8 min.
/0,y 210 / (3,7 206
' 82Kt> f 82 Pb
22 yr. Stable
Figure 3.1 The uranium decay series showing the half lives and mode of decay.
-------
3-3
THORIUM - 232 DECAY SERIES
Figure 3.2 The thorium decay series showing the half lives and mode of decay.
-------
3-4
Table 3.1 Gamma-ray energy released by one gram of rock
Isotope
Uranium-238 (in equi
decay products)
Uranium-235 (in equi
decay products)
Thorium-232 (in equi
decay products)
Potass ium-40
Other Elements
Source: Oa72.
Table 3.2
Rock Type
Igneous^ ' basic
Silicic (granite)
Sedimentary^ '
Shale
Sandstone
Limestone
Upper crustal
average
U.S. surficial
average^ ^
Average Energy,
Concentration, KeV/sec.
Percent
librium with «
2.98 x 10 68.2
librium with *
0.02 x 10 1.53
1 ibrium with »
11.4 x 10 87.8
3.0 149
2.7
Radionuclide content and dose equivalent rates from
common rocks and soil
Uranium Thorium Potass ium-40
ppm mrem/yr^a' ppm mrem/yr^ ppm mrem/yr
0.9 5.2 2.7 7.3 1.2 14.7
4.7 26.9 20.0 53.8 5.0 61.3
3.7 21.2 12.0 32.3 3.2 39.2
0.45 2.6 1.7 4.6 1.1 13.5
2.2 12.6 1.7 4.6 0.32 3.9
2.8 16.0 10 26.9 2.4 29.4
1.8 10.3 9.0 24.2 1.8 21.8
Total
mrem/yr
27.2
142.0
92.7
20.7
21.1
72.3
56.3
(a)
(b)
(c)
(d)
mrem/yr/ppm: uranium, 5.73; thorium, 2.69; potassium-40, 12.3 (Be68).
Source: C166.
Uranium and thorium averages (Ph64); potassium (He69).
Source: Lo64.
-------
3-5
the exposure from this series. Thus, soil moisture decreases the
potassium-40 and thorium-232 dose equivalent rates and increases or leaves
unchanged the uranium-238 series dose equivalent rate.
Snow cover also affects the terrestrial dose equivalent rate and the
radon emanation rate. Gamma radiation attenuates exponentially as a function
of the density and thickness of the snow cover (Oa72). However, the overall
influence of snow on population exposure is negligible since, in most popu-
lated areas, there is relatively little snowfall that remains for long
periods of time.
Table 3.3 shows the average dose equivalent rate due to radiation in
some Western mining states (Oa72). Terrestrial radiation in the Western
uranium mining states is higher than in the rest of the nation due to the
greater concentration of the uranium-238 series.
Table 3.3 Average dose equivalent rates due to terrestrial
radiation in western mining states
Terrestrial Dose,
State mrem/yr
Arizona 45.6
Colorado 65.8
New Mexico 51.7
South Dakota 45.6
Texas 29.0
Utah 45.6
Wyoming 45.6
Concentrations of radionuclides measured in surface and groundwater
samples collected on a proposed uranium project site are listed in Table 3.4
(NRC79a). The large variations among concentrations at different collection
-------
3-6
sites are typical of surface water concentrations. (Concentrations in sea
water are more uniform.) Hence, generalizations about background concen-
trations of radionuclides in fresh water systems are impractical. Extensive,
site-specific studies over an extended period of time are necessary to obtain
meaningful background concentrations for a site.
3.1.2 Stable Elements
Concentrations of metals occurring in the earth's crust generally range
from several parts-per-billion (ppb) to a few parts-per-million (ppm).
Measured concentrations vary widely from site to site and often in different
samples taken from the same site. Table 3.5 lists the results of measure-
ments for selected elements. It should be emphasized that these are general
estimates of element composition of rocks in the United States and do not
reflect large variations that occur within the different rock types.
Concentrations of metals measured in surface and groundwater samples
collected from different locations on a proposed uranium project site are
listed in Tables 3.6 and 3.7, respectively. There are large differences in
the composition of surface and groundwaters. Table 3.8 shows the average
concentrations of three trace metals that are sometimes associated with mine
discharge water. These values, which were taken from the results of an
extensive study (Tu69), approximate average concentrations in United States
streams. Background concentrations at any specific site could be much
different.
Table 3.8 Estimated average concentrations (ppb) of three
metals in U.S. streams
Element
Chromium
Molybdenum
Selenium
Turekian's
Results
1.4
1.8
0.2
Other results from
Literature
1.0
1.0
0.2
Source: Tu69.
-------
Table 3.4 Radionuclide concentrations In surface and groundwater
in the vicinity of a proposed uranium project
Concentrations
Radionucl ide Location 1
U-238 9.8
Ra-226 0.4
Rn-222 145
Th-230 <0.1
Th-232 <0.1
U-238 2.0
Location 2
4.0
0.5
108
0.2
4.5
, pd'A
Location 3 Location 4 Location 5 Location 6
2
42
0
2
Surface Water
.5 1.8 1.6
.1 0.08 <0.1
<4 <4
Groundwater
.3 3.2 3.8 1.2
Source: NRC79a,
co
-------
Table 3.5 Concentrations of selected elements in igneous and sedimentary rocks, (ppm)
Element
Aluminum
Arsenic
Boron
Barium
Cadmium
Cobal t
Chromium
Copper
Iron
Mercury
Potassium
Manganese
Molybdenum
Nickel
Lead
Antimony
Selenium
Vanadium
Zinc
Igneous rocks^3'
1.8
10
425
0.2
25
100
55
56,300
0.08
20,900
950
1.5
75
12.5
0.2
0.05
135
70
Shales(b)
80,000
13
100
580
0.04
19
90
45
47,200
0.04
26,600
850
2.6
68
20
1.5
0.6
130
95
Sandstones^
25,000
1
3.5
50
0.05
0.3
35
5
9,800
0.03
10,700
50
0.2
2
7
0.05
0.05
20
16
Limestone^ '
4,200
1
20
120
0.035
0.1
11
4
3,800
0.04
2,700
1,100
0.4
20
9
0.2
0.08
20
20
U)
\a )(•_..— — — . T-*CA OO
(^
Source: Tu69.
-------
Table 3.6 Concentrations of selected elements in surface water at five locations
in the vicinity of a proposed uranium project
Concentrations,
Element
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Cobalt
Chromium
Copper
Lead
Mercury
Molybdenum
Nickel
Selenium
Vanadium
Zinc
Location 1 Location 2
2.4
<0.01
<0.01
0.06
0.001
<0.001
0.01
0.005
0.019
<0.001
0.0007
0.002
0.03
0.03
0.03
0.04
3.0
0.01
0.01
1.4
0.001
0.001
0.01
0.001
0.017
0.001
0.0008
0.002
0.02
0.03
0.02
0.05
Location 3
50
<0.01
0.07
6.6
0.04
<0.001
0.10
0.066
0.18
0.020
0.0007
0.002
0.12
<0.01
0.45
0.35
mq/ji
Location 4
1
<0.01
<0.01
0.5
<0.001
<0.001
<0.01
0.003
0.002
<0.001
0.0005
0.002
<0.01
<0.01
0.01
<0.01
Location 5
2
<0.01
<0.01
0.5
<0.001
0.001
0.01
0.003
0.005
<0.001
0.0006
0.002
<0.01
<0.01
0.02
0.01
co
i
Source: NRC79a,
-------
Table 3.7 Concentrations of selected elements in groundwater at six locations
in the vicinity of a proposed uranium project
Concentrations, mq/i
Element
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Cobal t
Chromium
Copper
Lead
Mercury
Molybdenum
Nickel
Selenium
Vanadium
Zinc
Location 1
<0.1
<0.01
<0.01
<0.1
0.001
<0.001
<0.01
<0.001
0.003
0.003
<0.0004
0.001
<0.01
0.06
0.01
4.4
Location 2
1
<0.01
<0.01
0.5
<0.001
<0.001
<0.01
0.003
0.003
<0.001
0.0012
0.002
<0.01
<0.01
0.01
0.07
Location 3 Location 4
0.8
<0.01
<0.01
0.5
<0.001
<0.001
<0.01
0.003
0.006
<0.001
0.0005
0.002
0.01
<0.01
0.02
0.21
14.7
<0.01
<0.01
0.2
0.003
<0.001
0.01
0.004
0.027
0.003
<0.001
0.001
0.02
<0.01
0.01
0.07
Location 5
0.2
<0.01
0.01
0.3
0.001
<0.001
<0.01
0.001
<0.001
<0.001
<0.0004
0.001
<0.01
0.13
0.02
0.01
Location 6
10
<0.01
0.04
0.7
<0.001
<0.001
<0.01
0.003
0.006
0.002
0.0017
0.003
<0.01
<0.01
0.08
0.02
Source: NRC79a.
CO
I—»
O
-------
3-11
3.2 Water-Related Aspects of Uranium Mining
3.2.1 Previous and Ongoing Hydro!ogic and Mater Quality Studies Related
to Uranium Mining
In the late 1950's and early 1960's, the U.S. Public Health Service con-
ducted field studies to determine the water quality impacts of the uranium
mining and milling industry. The studies emphasized uranium milling rather
than mining. The Federal Water Pollution Control Administration conducted
extensive stream surveys to assess the effects of uranium milling (but not
mining) on the main stem and principal tributaries of the Colorado River.
Subsequent stream survey work in Colorado by the Water Pollution Control
Commission and the U.S. Geological Survey (Mo74, We74) mentioned a portion of
the Uravan Mineral Belt and uranium mines therein, but the work did not
emphasize uranium mines. Significant amounts of acidity and total trace
metal concentrations were found in streams from 18 different mining areas.
Dilution and chemical precipitation below mine drainages decreased concen-
tration and increased the pH. Given enough time and distance, the streams
recover naturally, but the accumulations of trace metals in the sediments
increase. Field observations in 1971-72 of streams in most of Colorado
indicated that approximately 724 km of streams in 25 different mining areas
were adversely affected by mine drainage (We74).
Discussions of the impacts of uranium mining on water quality or quan-
tity are incidental in numerous impact statements and environmental reports
prepared by industry and (or) the U.S Nuclear Regulatory Commission as an
integral part of licensing or relicensing uranium mills. Coverage on mining
is usually minor as the principal focus is on milling impacts. The same is
true for the recently prepared generic EIS on regulation of uranium milling
(NRC79b).\
Radiochemical assessment of surface and groundwater in uranium mining
districts of New Mexico is done by self-monitoring programs associated with
NPDES permits. Also, radiochemical assessment studies have been funded
recently by the New Mexico Environmental Improvement Division and U.S Environ-
mental Protection Agency. Self-monitoring, particularly in the pre-
operational phase, characterizes mining and milling operations in all of the
concerned States. These, together with results of surveys by State per-
sonnel, have resulted in extensive files of water quality data, flow measure-
-------
3-12
merits, field observations of mine conditions, and exchanges between industry,
regulatory agencies, and the public. Rarely are the data assembled and
interpreted for dissemination outside a given agency. States experiencing
rapid growth in uranium mining and milling are undoubtedly placing first
priority on activities directly related to licensing, monitoring, and other-
wise implementing regulations. Unfortunately, there is no concerted effort
to prepare broad assessments of the cumulative impacts of mining and milling.
Texas, New Mexico, and Wyoming are cases in point. Critical review and syn-
thesis of these types of data can produce rather useful information. For
example, the publication "Water Quality Impacts of Uranium Mining and Milling
Activities in the Grants Mineral Belt, New Mexico" (EPA75) addresses the
groundwater and surface water changes as the result of extensive uranium
mining and milling production in a relatively confined area.
Some states have since initiated review of their data files, conducted
field studies, and, in some cases, contracted study teams to investigate
similar water quality changes. For example, a recent report by the Wyoming
Department of Environmental Quality summarizes 16 years of aqueous radium and
uranium data. The study reports that significant amounts of Ra-226 and
uranium were present in surface water in the Shirley Basin as a result of
inadequate mine water treatment (Ha78).
In Texas, surface water and groundwater monitoring conducted by indus-
try, as well as by State and Federal agencies, reveal little or no change of
chemical quality attributable to uranium mining and milling (Ge77, Ka76).
This conclusion is based on 586 samples collected from 198 stations over a
period of 39 years but primarily from 1961 to 1975. The State monitoring
program by several agencies is continuing, but either summary reports are not
issued or are two years overdue, depending on the agency. Not all of the
findings exonerate the industry. One survey (It75) showed that none of the
mine water from the 10 lakes that were sampled was suitable for human use.
The lakes were also unsuitable for irrigation due to mineralization of the
water by sulfate, chloride, and TDS. One of the 10 was suitable for stock
watering.
The conditions or limits in the NPDES permits consider the quality of
water being discharged, the quality of receiving water, and available, prac-
tical, treatment technology. Industry is required to monitor the discharges
-------
3-13
on a periodic basis, usually daily, weekly, or monthly, and report results to
EPA. The NPDES permits and related monitoring data help to estimate the
quantity and quality of discharge allowed to enter the off-site environment.
Intensive studies of the influence of uranium mining on water quality
and availability have not been conducted. Most investigations to date have
been site-specific, of relatively short duration, and focused on the influ-
ence of surface discharge or subsurface seepage on water quality. Baseline
studies from specific projects typically consist of quarterly or semi-annual
sampling and are oriented toward milling instead of mining activities. The
effects of dewatering on depleted water supplies or on water quality shifts
in the aquifers of an area are rarely considered, and, then only on a mine-
by-mine basis. Rarely are soil, stream sediment, and biologic samples
collected in the preoperational period for radiologic analysis.
3.2.2 Mine Water Management
Figure 3.3 shows a scheme for considering the fate of water discharged
from underground and open pit mines, including principal sources and sinks,
most of which affect both water flow and quality. Broken lines in Fig. 3.3
indicate less important sequences with respect to water quality. For ex-
ample, those mines that handle all water by on-site evaporation are likely to
involve small volumes of water, and impacts on groundwater as a result of
seepage are also likely to be small.
Mine drainage is surface water or groundwater flowing from a mine or an
area affected by mining activities. Mine related point and nonpoint pollu-
tion sources can contaminate both surface water and groundwater throughout
all phases of mining, that is, during mineral exploration, mine development,
mineral extraction, processing, transport, and storage, and waste disposal.
While mine-related point pollution sources usually include only milling and
processing plant discharges and mine dewatering discharges, nonpoint sources
can occur during any or all phases of mining. The chemical and physical
characteristics and the mode of transfer of these nonpoint sources are vari-
able and depend upon, among other things, the mineral being mined, its geo-
-------
Mine
Drainage
Evaporated
on Site
Ion Exchange
Plant U Removal
Uranium Mill
Process Water
Settling
Ponds
Radium removed with
Barium Chloride
Discharge to
Streams and
Dry Washes
Discharge to
Streams and
Dry Washes
Agricultural
Use
Discharge to
Mill Tailings
Ponds
Discharge to
Streams and
Washes
Discharge to
Streams and
Washes
Figure 3.3. Disposition of drainage water from active surface and underground uranium mines
US
I
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3-15
logic environment, the interrelations of all associated hydrologic systems
(both surface water and groundwater), and the type of processing, trans-
portation, storage, and waste disposal methods. Some mine-related nonpoint
pollution sources are as follows (EPA77a):
1. suspended solids carried by immediate surface runoff
2. dissolved solids carried by immediate surface runoff
3. suspended and dissolved solids in proximate subsurface
water seepage
4. dissolved solids in groundwater recharge
5. dissolved solids in groundwater discharge
6. uncontrolled contributions from mine-related point sources:
a. high instantaneous concentrations of regulated pollutants
in excess of effluent discharge guidelines, but falling
within the NPDES instantaneous and daily average discharge
limitations
b. unregulated minor contaminants in point source discharges
which are not specifically included under NPDES effluent
limitations
c. untreated mine dewatering discharges during or following
major storm events (NPDES point source treatment systems
may be bypassed during storm events of greater than a 10-
year, 24-hour intensity)
7. reclaimed mine area and undisturbed area drainage diversion
discharges
8. surface water and groundwater contamination and degradation
induced by mine-related hydrologic disturbances and imbalances
Typically, waters affected by mine drainage are chemically altered by an
increase in iron, sulfate, acidity (or alkalinity), hardness, IDS, and
various metals, and are physically altered by an increase in suspended solids
such as silt and sediment (Anon69,Hi68).
Many but not all uranium mines dewater at rates of 1 to perhaps 20
m3/min. Typically, the water from the mine goes to settling ponds and then
either to the mill or a nearby stream, dry wash, river, etc. Depending on
the amount of mine water recycled in the mill and the amount of water pumped
from the mines, there may or may not be any release to streams or arroyos.
In at least one instance in the Grants Mineral Belt, mine water is totally
recycled through the mine to enhance solubilization of uranium which is
removed with ion exchange columns. Large evaporation ponds and some seepage
losses help maintain a water balance and minimize releases to streams,
arroyos, etc. Increasing competition for water in the western states is
likely to induce maximum mine water reuse (in the mill), reinjection, or use
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3-16
for potable supplies (H177) or power plant cooling.
When mill tailings ponds are used for final disposal of mine water,
there is significant addition of chemical and radiochemical contaminants to
the water in the course of milling. After treatment to reduce suspended
solids, mine water may be recycled for use in the milling process or released
to nearby streams, necessitating radium removal and reduction of suspended
solids. Dissolved uranium in mine water, if present in concentrations ex-
ceeding about 3 mg/ju is recovered by ion exchange columns. Settling ponds at
the mines remove suspended solids. The water is then conveyed to receiving
streams or to the mills for uranium recovery and (or) to satisfy mill feed
water requirements. There are rather rigid requirements for release to
surface water compared to groundwater.
A recent survey of 20 U.S. uranium mills (Ja79a) found large variation
in the degree of water recycling. Where mine water is readily available, it
probably is reused less than in water-short areas. More efficient water use
by uranium mills possibly could increase the amount of (relatively) high
quality mine water being discharged to the environment; lessen adverse impacts
of mill tailings disposal by reducing the amount of liquid; and make mine
water available as a source of potable water (after treatment) in water-short
areas such as Churchrock and Gallup, New Mexico (Hi77). To date, water qual-
ity deterioration related to seepage and accidental release of tailings to
surface streams has received the most study and has been the focus of regu-
latory programs. In the future, it is likely that water quantity issues will
become increasingly important, particularly in areas where water supplies are
already limited and where extensive dewatering necessarily accompanies
mining.
Of 20 uranium mills surveyed, 6 reported part or all of the mill feed
water came from mine drainage (Ja79a). In New Mexico, 19 of 30 mines sur-
veyed by the State Environmental Improvement Division (J. Dudley, written
o
communication) had off-site discharge to arroyos ranging up to 19 m per
minute. Those mines with no discharge utilized evaporation ponds or used the
water for dust control. Most of the mines discharged to arroyos. In several
instances, however, water was piped to a nearby mill at flow rates of 5 to 8
m per minute. Relatively small quantities of mine water were used for sand
backfill of mines, in-situ leaching of old workings, and irrigation of grass-
lands. In summary, New Mexico mines discharge 66 m3 per minute off-site.
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3-17
3
Of this, 12 m per minute is routed to mills, and the balance is discharged
directly off-site from the mine. Average discharge to streams and arroyos
for the active underground mines in the Grants Mineral Belt on the whole was
3
1.8 m /min, whereas 12 mines in the Ambrosia Lake District averaged 1.7
m /min. In New Mexico, all mines discharging to an arroyo practice radium
removal with approximately 90% efficiency. Uranium removal from mine water
discharge occurs in all but two active mines. Future trends are likely to
reflect increased discharge from the mine to the environment. Settling
ponds, radium removal, or both will be used to meet discharge permit require-
ments.
In Wyoming, discharge from both surface and underground mines may be
used as process water for uranium mills, discharged to surface streams, or
used for irrigation. For example, at the North Morton underground mining
3
operation, approximately 2 m per minute of mine water discharge will be used
to irrigate 800 hectares of alfalfa. At the South Morton surface mine oper-
ation, a like amount of discharge will become mill feed water.
A survey of all active U.S. uranium mills showed that 14 of 20 make no
use of mine water (Ja79a). This may reflect mines where water simply is not
encountered or the fact that mines and mills are not co-located. Most mills
depend on deep wells, except in New Mexico where mine water is the main mill
water supply. Table 3.9 summarizes water sources for U.S. uranium mills.
Proposed NRC regulations on mill tailings disposal (44 Fed. Reg. 50012-59)
purport to make long-term tailings isolation the primary consideration in
mill siting. In areas subject to severe natural erosive or dispersive
forces, this may mean that mills cannot be sited in the vicinity of mines.
This may have effects on use of mine water for milling.
Table 3.9 Summary of feed water sources for active U.S. uranium mills
Water SourceNo. of Mills~~
Rivers, Reservoirs 4
Wells 8
Springs 1
Unknown 1
Mine Water 3
Mine Water and Wells 1
20
Source: Ja79a.
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3-18
Although underground mining is now dominant in the Grants Mineral Belt,
the greatest number of mines are small stripping operations that have long
been inactive. This type of mining activity has apparently had little ad-
verse impact on water resources. Few data are available on drainage assess-
ment of large open pit mines such as the Jackpile-Paguate. The St. Anthony
pit discharges about 0.076 m3 per minute. Usually, the ore is above the
water table. Any water present on the mine floor presumably is flood runoff
or discharge from a nearby underground mine. Other strip mines in the
Mineral Belt were not studied; hence, no conclusions were drawn (J. L. Kunk-
ler, USGS, in preparation).
Mine dewatering is done either by pumping the mine pit/shaft directly or
by drilling high capacity wells peripheral to the mine and pumping a suf-
ficient volume of water to at least partially dewater the sediments. Because
of the great volume of water that must be removed from an aquifer, the latter
method is impractical for deep underground uranium mines. This is partic-
ularly true for the artesian aquifers of most of the deeper mines in the
Grants Mineral Belt. More commonly this method is reserved for shaft sinking
and open pit mines to depths of several hundred feet. Most underground mines
are dewatered by pumping the water that collects in the mine itself. Borings
("longholes") made into the ore body for assay work and explosives facilitate
drainage. There is considerable difference in the quality of water depending
on the dewatering method used. Water removed from wells adjacent to the mine
typically is representative of natural quality, but water removed from the
mine can be high in radionuclides, stable elements, and suspended solids. In
large part this is due to the disruptive nature of mining. However, more
subtle, chemical processes of oxidation and bacterial action, aided by
evaporation and free flow of air in the mine, are also operative.
The extent to which uranium exploration adversely impacts water re-
sources is not well understood. Land surface disruption from drilling pads
and access roads obviously affects erosion rates and results in mud pits and
piles of contaminated cuttings on or near the land surface. Subsurface
effects are less obvious. A potentially serious one is interaquifer connec-
tion via exploratory boreholes. In Wyoming, 6 million meters of exploratory
drilling took place in 1979. Although State law requires mining companies to
plug the holes after drilling, it is common practice to install only a
surface plug and to rely on the drilling mud to effect a seal at depth.
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3-19
Similar situations are likely in New Mexico and Texas. Shortages of funds
and personnel to oversee proper completion and abandonment exist at the State
level.
Hydraulic effects of water released from mines, whether from pumping or
gravity flow, include increased surface discharge, recharge of shallow
aquifers by infiltration, and decline of static water levels in formations
intersected by the mine or related cone of depression. Of most concern are
the effects relating to mine water discharge on downstream users and any
influences, direct or indirect, of pumping/dewatering on water quality in the
ore body and contiguous strata. In some locations, the Grants Mineral Belt,
for example, the ore body is also a major regional artesian aquifer; hence,
dewatering affects present water levels and will affect water levels at least
to the year 2000, with complete recovery taking much longer. The extent and
significance of uranium mine dewatering are as yet poorly documented. Recent
studies have been made in New Mexico where dewatering is of concern because
of the influence on regional groundwater availability for municipal use and
in relation to return flows to the San Juan River (NRC79b; Ly79). In
Wyoming, static water levels in wells on ranches adjacent to uranium mines
owned by Exxon, Kerr-McGee, Rocky Mountain Energy Co., and other companies
southwest of Douglas and between Pumpkin Buttes and Douglas have reportedly
dropped 7 to 10 meters (Anon79). Water quality changes associated with
dewatering generally are unknown and not specifically monitored regardless of
the mining area location.
Water quality associated with dewatering is generally good, although
suspended solids may be high, as expected. Discharge from dewatering wells
will be low in suspended solids because of filtering by soil and rock
aquifers. Overall water quality from dewatering wells, particularly for
underground mines, is likely to be representative of ambient conditions in
the ore body and, to a lesser extent, the adjacent formations that may also
be dewatered.
Recent USGS work on groundwater in the San Juan Basin Region has in-
dicated that mining expansion will have a significant impact on the water
yield of the Morrison Formation (Ly79). In this study, although no water
quality data are derived, the recharge and mine dewatering parameters that
impact the expected drawdowns in the aquifer imply that a total of 7.03 x 108
m3 of water will be produced by the 33 planned or announced mines by the year
-------
3-20
2000. If the projected development of 72 mines occurs, dewatering would
exceed 1.48 x 109 m3. The model also estimates that flow in the San Juan
River will decline very slightly (0.05 m3/min). Similarly, flow in the Rio
Grande Valley would be reduced by 0.85 m /min. The impacts will continue
after mining and dewatering cease.
Table 3.10 summarizes New Mexico uranium mine discharge in relation to
mine type, depth, and status (active or proposed). Note that projected
mining is primarily underground and represents an average increase in mine
depth of 275 percent and an increase in dewatering rate from 2.4 to 13.8 m
per minute. One would expect numerous water quality and quantity issues to
arise if these projections materialize. For example, competition for water
supply is likely to be widespread throughout the Upper Colorado River Basin,
and uranium mines/mills are already relatively large water users. Dewatering
and discharge require no water rights under State water laws in New Mexico,
but the water is essentially wasted. Use of water in mills constitutes a
beneficial use of water, and state water laws therefore require filing for
water rights. Such filings may be denied upon protest from existing water
users.
Inactive uranium mines and related wastes also influence water quality,
particularly as a result of chemical and physical transport by surface water
runoff. The main reasons why mine waste piles erode more quickly than un-
disturbed soils are lack of topsoil, steep angle of slopes, presence of toxic
elements and buildup of salt in the near surface, and poor water retention
characteristics. Usually, inactive surface and underground uranium mines are
not a source of direct discharge of water, be it contaminated or of ambient
quality, because of the low rainfall-high evaporation characteristics of the
western uranium regions, static groundwater levels deep below the land sur-
face in mining areas, and, in a few instances, recontouring of mined lands
such that drainage is internal. Whether mines contaminate groundwater by
groundwater leaching or by recharge contacting exposed oxidized ore bodies is
poorly documented. Preliminary feasibility studies by the U.S. Geological
Survey (Hi77) indicate generally good quality water from one inactive under-
ground mine in the Churchrock area of New Mexico. It is possible that this
water may be used as a municipal water supply for Gallup, New Mexico.
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3-21
Table 3.10 Current and projected uranium mine discharges
in the Grants Mineral Belt, New Mexico
Mine Type
Active
Underground
Open pit
Proposed
Underground
Open pit
Number of
Mines
33
3
46
0
Average
Depth (m)
248
48
681
N/A
Average Discharge
(m/min)
2.42
0.045
13.8
N/A
Source: Environmental Improvement Division, State of New Mexico.
For most uranium regions, the volume of discharge from inactive mines to
surface water bodies, though poorly documented, is believed to be less signi-
ficant than that from active mines. The degree to which inactive mines
contribute contaminants, directly or indirectly, to adjacent water resources
can only be qualitatively assessed. The significance of inactive mines is
highly dependent on regional setting and mine type.
Inactive surface mines in Texas are, with rare exception, not a source
of direct discharge to surface water. It is unknown if there is any adverse
impact from standing water in the mine pits, the most recent of which have
been final-contoured with an internal drainage plan. Various observers
suspect that water quality deteriorates when overland flow crosses mine
spoils associated with overburden piles (It75 and He79). Water in the mine
pits is unsuitable for potable and stock use due to high stable element
contents, but it is generally acceptable in terms of radioactivity. Water in
Texas open pit mines is a combination of runoff and groundwater. Before
release from a mine, water is put in retention ponds to reduce total sus-
pended solids. Holding ponds are used for storing mine water, and discharge
is not allowed unless such discharge does not adversely affect the receiving
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3-22
water. Usually, water in the holding pond is returned to the mine for perm-
anent impoundment. Dilution by runoff and direct rainfall and concentration
by evaporation affects water quality, which the Texas Health Department (L.
Cook, personal communication, 1979) reports as meeting radium standards for
potable water. However, one survey of water in mine impoundments revealed
that none of it would be suitable for potable or stock water use (It75).
Whereas 50 to 100 pCi'A, of radium-226 is common in active open pit mines and
concentrations of several hundred picocuries per liter may be present in
groundwater within the ore body, concentrations in the ponds are between 1
and 5 pCi/£ after abandonment and reclamation. Over the long term, sedi-
mentation and sorption processes in the surface impoundments are likely to
improve the quality of surface water and the water that recharges the ground-
water system (L. Cook, personal communication, 1979).
Harp (1978) recently presented a historical recap of water quality
impacts from uranium mining and milling in the Shirley Basin area and on the
Pathfinder Mine in particular. Self-monitoring data had been collected since
1959. Also available were results of one-time water quality and biological
surveys by Wyoming Fish and Game Department and the Environmental Protection
Agency, as well as self-monitoring data for NPDES permits, and various other
reports, investigative studies, and miscellaneous reports. The study con-
cluded that significant increases in ambient uranium and radium has occurred
in nearby stream water and sediments. Initial strip mining and mill pro-
cessing operations were primarily to blame, but previous acid-leach solution
mining also had a decided impact. The major, continuing source of contam-
ination to the Little Medicine Bow/Medicine River System is the mine de-
watering effluent from Pathfinder Mines Corporation (a mine/mill complex) (J.
Giedt, USEPA, written communication, 1980).
Little is known concerning drainage from inactive mines in Wyoming and
Utah. It is likely that at least some of those in Utah are draining, an-
alogous to the situation in Colorado. Few active surface mines in Wyoming
drain to surface water. In the Front Range of Colorado, it is estimated that
perhaps half of the mines discharge at least part of the year; whereas, in
the Uravan Mineral Belt very few mines drain, and those that do are located
in the lowland areas and (or) are deeper than the average for the area.
From the North Park area southward to Durango mines occasionally drain,
particularly those intersecting the Entrada Sandstone. Flow rates are highly
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3-23
variable, ranging from slight seepage to perhaps 8.5 to 17 m3 per minute (D.
Collins, personal communication, 1979). In the Yellow Cat area of Grand
County, Utah, a westward extension of the Uravan Mineral Belt, the streams
are ephemeral, and the few springs in the area drain inactive uranium mines
dating back to at least 1950 (Ca64; D. Collins, personal communication,
1979).
The foregoing analysis indicates that (1) U.S. uranium mills make little
use of mine water; (2) mine drainage is primarily to the environment, with
occasional use for agriculture, sand backfilling of mines, construction, and
potable supply; (3) a few active surface mines in Wyoming and many under-
ground mines in New Mexico have the greatest discharge to the off-site en-
vironment; (4) inactive surface mines do not appear to adversely impact
groundwater quality, although the effects of spoils piles may be a source of
surface water contamination; and (5) selected inactive underground mines in
Colorado and possibly adjacent portions of Utah may discharge water enriched
in radionuclides and trace elements. Inactive mines may effect groundwater
in New Mexico. Not enough as yet is known about oxidizing conditions,
aquifer connections, etc. to reach definitive conclusions. Subsequent sec-
tions of the report quantify the volume and quality of mine discharge from
existing mines in Wyoming and Texas and deep underground mines in New Mexico.
In New Mexico, both the United Nuclear Corporation and Kerr-McGee Nuclear
Corporation mills get all their water from mines. Three future mills will
all use mine water, hence mine water is important for milling in New Mexico
(B. Perkins, State of New Mexico, written communication, 1979). Analysis of
the hydraulic and chemical effects of mine discharge in terms of environ-
mental quality and public health are of considerable concern.
3.2.3 Water Quality Effects of Mine Water Discharge
3.2.3.1 Behavior of Contaminants in the Aqueous Environment
Mine drainage in general can cover a broad range of pH values. Drainage
from uranium mines is usually alkaline and not considered as detrimental as
acidic mine drainage, which occurs when acid producing minerals are assoc-
iated with the ore body. In the western states, overburden material is often
highly alkaline or saline and creates the potential for alkaline drainage.
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3-24
Environmental problems associated with alkaline and saline drainages are not
well documented (Hi73).
Water quality impacts from uranium mining are a function of both quality
and quantity of discharge. Underground and surface mines commonly require
dewatering prior to or during the ore removal phase, although there is con-
siderable variation from one area or mine to another. In New Mexico, large
and medium sized mines are essentially dry, whereas mines in Texas and
Wyoming require extensive dewatering. Regardless of location, underground
mines rarely are dry and many require extensive dewatering. Considering the
variety of water management measures, regional differences in contaminants
and receiving waters, and geochemical characteristics of ore bodies, detailed
discussion of the effects of mine drainage or mining, in general, on water
quality must await further site - or area - specific study. It is ques-
tionable if sufficient data on mine drainage exist to assess effects on biota
and the fate of contaminants in surface or sub-surface water bodies.
Limited data from Colorado, Texas, Wyoming, and New Mexico suggest
adverse impacts on water quality from discharge of mine water. Effects of
dewatering on deep groundwater quality are very poorly documented; hence, no
conclusion as to relative significance is drawn. With respect to surface
water resources, discharge of mine water and overland movement of water and
suspended or dissolved contaminants may be significant. Because of the
dearth of data on overland flow, emphasis herein is on contaminants dis-
charged via mine drainage water. Substantial studies to evaluate sediment
yield and quality from lands mined for uranium, particularly from areas of
surface mining, have not been conducted, although recent work in Texas (He79)
is a notable exception.
Elements such as uranium, radium, molybdenum, selenium, zinc, and vana-
dium may be enriched in point and nonpoint discharges from uranium mines.
The dispersal, mobility, and uptake of such elements are directly relevant to
the subject of this report. We reviewed selected literature and field data
to at least qualitatively understand what processes and elements are most
significant and to thereby strengthen some of the underlying source term
assumptions in the transport and health effects modeling. Despite the annual
chemical load introduced to ephemeral streams by both dissolved and suspended
constituents in mine effluent and overland flow from mined lands, waste piles
etc., a number of processes affect the concentrations in the ambient environ-
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3-25
ment. These include dilution, suspended sediment transport, sorption and
desorption, precipitation, ion exchange, biological assimilation or de-
gradation, and complexation.
3.2.3.1.1 Dilution and Suspended Sediment Transport
In many uranium mining regions there is flooding or flash flooding. Such
storms may well be the only runoff event for a year or more at a time. It is
worthwhile then to consider some of the effects of such events on mobili-
zation of contaminants associated with uranium mining wastes. Typically
there is significant interdependence between the physical and chemical pro-
cesses.
A principal physical process is dilution. This will reduce concen-
trations of pollutants released to surface waters, but is considered to play
a relatively minor role over the short term for water percolating through the
soil to sources of groundwater in arid or semiarid regions.
Transport of suspended sediments in floods is another dominant process.
Suspended load is largely a result of physical, hydraulic processes, hence
elements that are rapidly and thoroughly removed from solution as a result of
solubility limits, precipitation with other ions, ion exchange, and sorption
may well be transported in the suspended load. In metal mining areas of
central Colorado, total and dissolved metal loads in streams are greater
during high flow periods, apparently a result of flushing from mines and
tailings piles and scouring of chemical precipitates from stream substrates
(Mo74). Typically, total and dissolved loads decrease downstream, regardless
of discharge. Increase in iron in the downstream direction reflects scouring
of precipitate—an amorphous, hydrated ferric oxide. Dispersal occurs for
quite a distance downstream.
3.2.3.1.2 Sorption and Desorption
Sorption can play an extremely important role in purifying waters,
particularly if infiltration or percolation is involved. This is especially
true when contaminant concentrations are too low to undergo precipitation
reactions. Virtually every ionic species will be sorbed and removed to some
extent except for chloride and, to a lesser extent, sulfate and nitrate.
These seem to pass through soils and alluvium without significant sorption
(Ru76). Sorption processes can be highly specific, depending on the type of
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3-26
contaminant and the physical and chemical properties of both the solution and
the porous medium.
There have been numerous laboratory studies on the sorption, leach-
ability, and mobility of stable elements in various types of soil. A recent
review of the literature on radionuclide interactions in soils specifically
discusses radium, thorium, and uranium, which are especially pertinent to
uranium mining (Am78). Distribution coefficients, the ratio of concentration
in soil to that in water, ranged between 16 and 270 for uranium in various
soil-river water systems, between 200 and 470 for radium, and on the order of
105 for thorium at pH6. These observations appear consistent with the
generally accepted ideas that uranium is relatively mobile, thorium extremely
immobile, and radium somewhere in between in natural water systems (NRC79b;
Ku79; Ga77a).
Adsorption is believed to be important for cadmium, copper, lead, and
nickel, insofar as these are transported in the suspended fraction, whereas
manganese and zinc are primarily in the dissolved fraction. Adsorption of
metals onto precipitated manganese oxides or hydroxides at elevated pH is
probably insignificant in the case of most uranium mine discharges insofar as
these are alkaline and, furthermore, discharge to or co-mingle with other
streams that are alkaline.
Radium sorption and desorption tests done on uranium mill waste solids
and river sediments collected from several locations in the Colorado Plateau
(Sh64) and in Czechoslovakia (Ha68) showed that leaching is primarily con-
trolled by the liquid-to-sol id ratio, i.e., the volume of leaching liquid per
unit weight of suspended solids. Natural leaching from mining and milling
waste solids freely introduced to rivers in the past is one of the major
factors in radium contamination of rivers (Ru58). Although settling ponds
are now used to remove or at least reduce suspended solids from active mine
discharges, the dissolved radium load sorbed on sediments presents a source
term that may be somewhat analogous to river sediments contaminated by dis-
solved and suspended milling and mining wastes. The manner in which the
radium is mobilized and the significance is poorly understood and bears
further investigation. Apparently there is a "leap frog" transport mechanism
involving combined chemical and physical weathering processes. There should
be a marked downstream attenuation of both dissolved and sorbed/precipitated
radium inventories insofar as sediment burial and dilution take place and
Teachability limits are reached, i.e., no more radium can be removed regard-
-------
3-27
less of the duration, frequency, or intensity of agitation. Should the
stream eventually discharge into a reservoir, it is unlikely that renewed
leaching will take place. Shearer and Lee (Sh64) did not account for some
factors that may be locally significant, such as bio-uptake along the stream/
river, use of water for irrigation, number of uranium facilities discharging,
and other local factors.
Experiments were conducted in Japan (Ya73) to determine uranium adsorp-
tion and desorption using carbonate solutions and three soil types (alluvial,
sandy, volcanic ash). Very high adsorption ratios and very low desorption
ratios of uranium characterized the various soil types in contact with stream
water and help explain the decrease in soluble uranium with flow distance
from mines (Ma69). When wastewater flows into streams at the maximum per-
missible concentration (1.8 mg U/A ) recommended (ICRP64), Yamamoto et al.
(Ya73) conclude that the uranium behaves as a uranyl carbonate complex anion
and that essentially complete sorption readily occurs in the presence of
(Japanese river) water which contains 15 to 39.9 mg/£ bicarbonate. Since
this is similar to concentrations in surface waters of uranium regions in the
western states, similar results are expected.
Sorption or desorption of heavy metals such as Co, Ni, Cu, and Zn in
soils and fresh water sediments occurs in response to the aqueous concen-
tration of metal, aqueous concentration of other metals, pH, and amount and
strength of organic chelates and inorganic complex ion formers in solution
(Je68). Other controls on the heavy metal concentrations in soil and fresh
water include organic matter, clays, carbonates, and oxide and hydroxide
precipitates.
To what degree solubility acts as a limit on stable element concen-
trations in natural waters is unclear. The crystal!ographic form or even the
chemical composition of a precipitate are often unknown. Elements such as
iron, aluminum, manganese, and titanium form insoluble hydroxides and are
likely to exceed equilibrium solubility limits (An73). Hem (He60) partially
disagrees, saying "it is not unreasonable to assume equilibirum for the iron
species in water." Whether mine discharges or overland flow from mined areas
are in equilibrium is unknown, but it is doubtful considering the underground
or flash-flood origin of such waters. The non-equilibrium aspects of certain
peak runoff events has been documented for major streams of the world (Durum
and Haffty, 1963). Metals such as iron, aluminum, manganese, and titanium,
-------
3-28
which readily form rather insoluble hydroxides as particulates or colloids,
may be dissolved from suspended minerals during high flow conditions.
Organics present in such flood waters may assist through formation of soluble
complexes. Resulting metal concentrations may be higher than solubility and
redox relationships alone would indicate.
3.2.3.1.3. Precipitation
Probably one of the most significant processes affecting stable element
solubility in natural water systems is adsorption on hydrous ferric and
manganese oxides. Jenner (Je68) believes this is the principal control on
the fixation of Co, Ni, Cu, and Zn (heavy metals) in soils and fresh water
sediments. For example, ferric hydroxide adsorbs one to two orders of magni-
tude more SeO., per unit weight than clays, and 90 to 99 percent adsorption is
possible at a pH of seven to eight typical of most western streams (Ho72). At
neutral or slightly alkaline pH, both iron and manganese are poorly soluble
in oxidizing systems and, in general, exhibit very similar chemical behavior,
although manganese is slightly more soluble. Fixation of selenium in soils,
particularly by iron oxide or as ferric selenite, renders it unavailable to
agricultural and forage crops, although specific selenium-accumulating plants
can remove the element and, upon decomposition, release it in water soluble
forms, such 'as selenate and organic selenium compounds, available to other
plants (Ro64). The behavior and mechanism of selenium adsorption (as selen-
ium oxyanion) by hydrous ferric oxides is readily extended to the inter-
pretation of other similarly bound minor elements (Ho72). Mobile selenium
oxyanion in slightly alkaline waters might be carried to streams by surface
runoff or in groundwater. Selenite selenium sorbed upon ferric hydroxide
should be transported in surface waters at neutral or slightly acid pH. Other
metals forming highly insoluble hydroxides in the pH range of 6 to 9 include
copper (above pH 6.5), zinc (above pH 7.5), and nickel (above pH 9). Molyb-
denum is thought to hydrolyze to the bimolybdate ion under acid conditions
and precipitate with iron and aluminum. Aerobic or oxidizing conditions in
the vadose zone are favorable for the development of many of these oxides
(Cu, Fe, Mn, Hg, Ni, Zn, Pb). Reducing conditions deep in saturated zones
generally lead to increased mobility of these metals.
Reducing conditions that can exist in the presence of organic material
(bituminous or lower ranking coals, anaerobic bacteria, fluidized humates)
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can lead to precipitation reactions favorable for removing contaminants from
mine waters. Reduction of uranium to the quadrivalent state and its fixation
on clays would play the major role in protecting groundwater supplies from
uranium if the appropriate reducing agents were present in soils (Ga77a;
Ku79). Inorganic reducing agents could include ferrous iron and hydrogen
sulfide produced by the action of an aerobic bacteria on sulfates. Natural
reducing conditions can also, theoretically, cause the formation of such
native elements as arsenic, copper, mercury, selenium, silver, and lead,
which are all quite insoluble in their elemental form (Ru76). Hydrogen
sulfide or other sulfides, if available, will serve to reduce the concen-
trations of such metals as arsenic, cadmium, copper, iron, lead, mercury,
molybdenum, nickel, silver, and lead.
The metal-scavenging of hydrated iron oxide precipitate has been docu-
mented in a mined area of Colorado where relatively acid schists and gneisses
give rise to acid runoff that dissolves large quantities of aluminum, mag-
nesium, and zinc. Runoff from a nearby drainage basin underlain by basic
rocks containing base and precious metal veins carries considerably less
metal. However, manganese oxide precipitated with iron oxide contains large
quantities of metals. Ferric hydroxide precipitates from aerated water
solutions containing more than 0.01 ppm iron at pH values of 4.5 and above,
aluminum hydroxide precipitates in the pH range of 5 to 7, and manganese
hydroxide precipitates above pH8 (He60; Ch54). Considering the alkaline pH
of most uranium mine discharges and overland flow from non-point sources such
as mine waste piles, precipitation of iron and possibly manganese seems
certain. The scavenging effect of iron hydroxide at neutral to alkaline pH is
considerably less than that of manganese hydroxide precipitate.
The extensive studies of mine drainage in Colorado by Morgan and Wentz
(1974) revealed the effects of solubility on stable element transport. In
the downstream direction, dilution and neutralization of the acid mine drain-
age by bicarbonate caused dissolved metal to decrease due to dilution,, chem-
ical precipitation, and probably adsorption onto ferric hydroxide preci-
pitate. The latter creates a coating on the stream substrate for a con-
siderable distance during low flow periods. Subsequently, flood events scour
and transport the precipitates. Manganese and zinc remain primarily in the
dissolved phase for a considerable distance, whereas cadmium, copper, iron,
lead, and nickel concentrate in the suspended fraction and, when turbulence
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3-30
decreases, precipitate. The mobility sequence for the metals studied in
Colorado generally follows the order Mn s Zn > Cu > Cd >Fe>Ni> Pb. Ferric
hydroxide precipitation and scavenging seems to be more important at neutral
than at acidic pH's (Je68).
3.2.3.1.4 Biological Assimilation and Degradation
Biological uptake and the role it has on stable element concentrations
in water is not predictively understood (An73). Plant uptake of stable
elements and resulting phytotoxicity is not merely a function of. how much is
present in the soils or water. In the case of arsenic, the chemical form of
arsenic appears more important than the total soil arsenic (Wo71). For ex-
ample, water-soluble arsenic in soil created more phytotoxic effects than
those with no detectable water-soluble arsenic. Soils high in reactive
aluminum remained less phytotoxic, despite heavy applications of arsenic,
than soils with low reactive aluminum. Selenium in soils can be present as
elemental selenium, selenates, pyritic selenium, ferric selenites, and or-
ganic selenium compounds of unknown composition. Selenates and organic
compounds are most available to plants, although slow hydrolysis of the other
forms can occur such that they become available for plant uptake. The im-
portance of water soluble selenium versus total selenium as the major factor
affecting plant uptake has been demonstrated (La72; Gr67). Where sufficient
selenium is present in plant-available form, all species will take it up in
sufficient amounts to be harmful to animals (La72). Naturally occurring
soils containing such available forms are geographically confined to semiarid
regions or areas of impeded drainage. Such soils are not hazardous to humans
and only locally are they a threat to animals.
Despite numerous examples of high selenium (up to 2.7 ppm) in surface
water, particularly that associated with drainage from seleniferous soils in
agricultural areas, Rosenfeld and Beath (Ro64) reported only a few cases of
water-related selenosis in man or livestock. Water high in selenium is
typically unpalatable to livestock and certainly to man. Lakin (La72) con-
cluded that environmental contamination due to selenium is increasing, but
hazardous concentrations are unlikely; mining and industrial wastes may cause
local problems; and the effect of added selenium in waters in combination
with other contaminants bears further study.
Uranium uptake by several species of native plants in the southeastern
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3-31
Utah portion of the Colorado Plateau varied, sometimes strikingly, with the
species, time of year, part of plant, availability of uranium in the soil,
and chemical composition of the underlying rocks (Ca57). The type of rooting
system and the soil moisture conditions also were influential. In some
cases, there was no consistent relationship between the amount of uranium in
the soil versus that in the plant ash. Plants are much less selective with
respect to cadmium uptake, and it has been conclusively demonstrated that
plants absorb cadmium from cadmium containing solutions and soils (Pa73;
Fu73). Phytotoxic effects vary considerably with plant species. Cadmium and
zinc sulfides tend to concentrate in the organic matter of soils. Upon
oxidation to sulfate, plant availability increases along with solubility.
Under alkaline conditions (pH8), cadmium is taken up rapidly by biota and by
sediments. However, modeling of cadmium transport and its deposition in
aquatic systems is very complex and encompasses many variables, most impor-
tant of which are pH, carbonate content, chemical form, and competing ions.
3.2.3.1.5 Complexation
Published data on Gibbs free energies, enthalpies, and entropies of 42
dissolved uranium species and 30 uranium-bearing solid phases were recently
reviewed (La78). Uranium in natural waters is usually complexed with car-
bonate, hydroxide, phosphate, fluoride, sulfate, and perhaps silicate. Such
complexes greatly increase the solubility of uranium minerals and increase
uranium mobility in groundwater and surface water. In waters with typical
concentration of chloride, fluoride, phosphate, and sulfate, intermediate
Eh's, neutral to alkaline pH's, and the presence of phosphate or carbonate,
uranyl phosphate or carbonate complexes form and increase mineral solubility
by several orders of magnitude. Sorption of the uranyl minerals carnotite,
tyuyamunite, autunite, potassium autunite, and uranophane onto natural mater-
ials is greatest in the pH range of 5 to 8.5. Uranium content of small
streams, in particular, can exhibit wide spatial and temporal variations due
to pH and oxidation state of the water, concentrations of complex-forming
species such as carbonate or sulfate, and presence of highly sorptive mater-
ials such as organic matter, certain metallic hydroxides, and clays (La78).
Whereas sorption is probably a dominant control on stable element concen-
trations in low temperature aqueous conditions, there is insufficient infor-
mation concerning specific sorbents to allow accurate prediction.
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3-32
3.2.3.2 Results of Field Studies in Uranium Mining Areas
3.2.3.2.1 Colorado
Extensive studies of the effect of mine drainage on stream water quality
and biota were done in central Colorado (Mo74). Although uranium was mined
in 14 of the 25 areas studied, other metals were the principal products.
Most of the ores were high in iron sulfides, and associated drainage was
acidic. Also studied, but less intensely, was the Uravan district of western
Colorado where the principal products are uranium and vanadium from Mesozoic
sandstone. The Uravan Mineral Belt is different in terms of principal pro-
duct and geologic features from other mining areas studied in Colorado. For
these other areas, the drainage is acidic and heavily enriched in heavy
metals and, therefore, somewhat atypical of most Colorado uranium mines in the
Uravan area.
After a preliminary field survey of the temperature, specific conduc-
tivity, pH, stream-bottom conditions, and aquatic biota at 995 stream sites,
192 were chosen for detailed sampling and analysis during 1971-1972. The
data indicate the contamination of approximately 711 kilometers of streams in
25 different areas, mostly in the Colorado Mineral Belt. The water quality
effects in these areas arise from many varied causes, including active and
inactive mine drainage, tailings pond seepage, drainage tunnels, and milling
operations. The length of the streams affected is not absolute as it varies
with the time of the year and flow conditions (Mo74).
The general findings indicate that Mn, Se, and SO, concentrations, and
specific conductivity are poor indicators of mine drainage as natural sources
can cause high values for these parameters even in undisturbed areas. Uranium
mines make at least some contribution to problems of contaminated streams in
central Colorado. In central Colorado, the exact impact of uranium mining on
stream water quality is unknown but believed to be less important or signif-
icant in most areas as compared to impact from other mining, with the pos-
sible exception of the Boulder-Jamestown area (J. Goettl and D. Anderson,
Colorado Game, Fish, and Parks Division and Water Pollution Control
Commission, respectively, personal communication). Cadmium, As, and Pb
exceed the U.S. Public Health Service toxicity limits, respectively, 12.5
percent, 1.4 percent, and 2.1 percent of the time. Mercury and Ag limits
were never exceeded, and Cr was never detected. Iron and Mn standards were
-------
3-33
frequently exceeded by large percentages, however, these limits are only
based on aesthetics. Concerning the negative impacts of the various
constituents, Cu and Zn (exceeding the limits 7.8 and 9.0 percent of the
time, respectively) pose the greatest threat to resident aquatic life.
Mining operations in the Uravan area are a relatively minor source of metals
for the San Miguel River (Mo74). Potential problem areas are settling ponds
and tailings piles associated with the mining operation. Although not a
source of acid drainage, these sources did cause increased concentrations of
copper, iron, manganese, nickel, vanadium, and zinc in the river. Only
manganese exceeded the standard for drinking water, and no metal concen-
trations exceeded the biological criteria. Seepage (0.003 m /s, pH 6.8, 3300
mgA,HC03) from a mine tailings area into Atkinson Creek, a tributary of the
San Miguel River, observed in December 1972 caused no adverse impacts.
Because of its size, proximity to population, and effects on surface
water quality, extensive surface water quality investigations to assess the
impacts of mine water discharge from the Schwarzwalder mine have been made
(EPA72). Grab samples of the mine effluent taken in 1972 revealed 15 mg/£
uranium and 80 pCi/£ radium-226. As of 1972, overflow and seepage from the
settling ponds used to treat the mine effluent significantly degrade the
radiochemical quality of nearby Ralston Creek. This was confirmed by both
EPA and the State/Denver Water Boards monitoring program. With 20-fold dilu-
tion, Ralston Creek downstream of the mine contained 3 pCi/£ and 82 yg/£
dissolved radium-226 and uranium, respectively. With no dilution, as during
July, concentrations were 81 pCi/£ and 20,300 ygA. Influx of contaminated
stream water to nearby Long Lake raised dissolved radium-226 to 0.8 pCi/£
(4-fold increase over background) and uranium to 230yg/£ (20 times back-
ground). From these data, conclusions were reached that the mine water
caused a 5 percent increase in the radiation dose to consumers in a local
water system (based on FRC and NCRP standards and daily consumption of 1.0
liter water). If the 4.5 mg/& uranium limit proposed by ICRP was used, the
estimated dose increases to nearly 40 percent of the dose limit for a popu-
lation group. Since 1972, the effluent has been treated for radium-226 and
uranium removal. Trace metals analysis of water samples collected from the
creek and the water treatment plants revealed concentrations comparable to or
greater than those in the effluent as of July 20, 1978. Concentrations
-------
(ug/x, ) were as follows:
3-34
Mine Effluent
Ralston Creek (avg)
Water treatment plants (avg)
*mgA,
As
5
5
5
F*
1
1.3
0.55
Pb
15
32
97
Se
<2
<2
2
Zn
18
56
146
3.2.3.2.2 Wyoming
We assessed the effects of mine drainage by literature review and a
limited field study in the Spring of 1979. Results of the latter conclude
this section of the report. The effects of mine dewatering, in situ
leaching, and mill tailings seepage on surface water quality in the Shirley
Basin were previously studied by the Wyoming Department of Environmental
Quality (Ha78). Sixteen years of data on aqueous radium and uranium indicated
significant amounts of radium-226 and uranium reached streams because of
inadequate -mine dewater treatment, mill tailings pond seepage, and improper
operation of a precipitation treatment unit. Uranium concentrations in
stream water increased 60-fold because of mine water discharge and possible
tailings pond seepage. The effects of past loadings of uranium and radium on
fish propagation or migration are not clear, although biologic uptake of
uranium and radium has occurred. Phytoplankton, algae, and bottom fauna
organisms also do not appear to have been adversely affected, but no studies
have been conducted since 1962. Long-term effects of increased radioactivity
levels are known and merit further study: "There exists real need for addi-
tional studies to determine the mechanisms involved in the dispersion and
ultimate disposal of uranium loaded into the drainage basin...Only after
additional studies have been completed, may we understand the total and long
range impact that the company's activities have had on the aqueous environ-
ment" (Ha78). This latter finding related specifically to the current (1978)-
loading of uranium from treated mine discharge.
Previous studies by the State of Wyoming (Ha78) found that solution
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3-35
mining by the Pathfinder Uranium Company noticeably affected ambient uranium
concentrations in the study areas. A 1968 survey by the Department of
Environmental Quality (Ha78) indicated relatively high loadings of soluble
uranium and radium on stream sediments near the mine dewatering outfall.
Analysis of fish skeletons indicated radium uptake corresponding to dissolved
radium-226 concentration exceeding 1 pCi/ji. Resampling in 1970 showed a
decrease in radioactivity values in sediment but a tenfold increase in fish
uptake of uranium relative to other fish populations in the basin. Radio-
activity concentrations in fish tissue were highest near the mine effluent
outfalls but did not constitute a major source of radioactive intake by
consumers.
In June 1971, the EPA Radiological Activities Section of Region VIII
(Denver) made a field reconnaissance of uranium mining and milling activities
in the Shirley Basin area. Radiological analyses of water and sediment sam-
ples in the Shirley Basin and in the Bates Hole drainage basin to the north
unquestionably indicated significant increases in radioactivity levels in
water, sediment, and fish because of effluent discharge from mines and mill
tailings. Concentrations of dissolved radium-226 and uranium in mine efflu-
ent were well above background. The discharges were not considered a source
of radiation dose to the populace (residents and transients) because of
remoteness and lack of water use, but toxic effects on fish were of concern
(M. Lammering, written communications, 1979). Monitoring in 1972 by the
Wyoming Game and Fish Department showed water quality effects as far as seven
miles downstream. From 1970 to 1972, radium-226 concentrations remained
stable, but uranium increased. Fish samples collected in 1972 showed in-
creased amounts of radium in the flesh compared to the 1970 results. Soil
samples from a creek that received mine effluent indicated relatively large
transport and enrichment of uranium and radium. Radium in particular was
enriched in the sediments and showed temporal variations indicative of suc-
cessive scouring and removal, presumably in flood flows. Precipitation of
uranium compounds was not apparent, probably because oxidized uranyl species
are quite soluble in natural water.
To further our understanding of the role aqueous pathways play in con-
taminant dispersal, we monitored stable and radioactive trace elements in the
Spring of 1979 in surface runoff from ore, sub-ore, and overburden piles from
the Morton Ranch area of active mining in Wyoming. EPA personnel selected
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3-36
the basic study areas and assisted in sample collecting. Most of the samp-
ling, analysis, and interpretation was done under contract with Battelle,
Pacific Northwest Laboratories and is the subject of a draft report (Wo79).
Appendix G contains a more complete discussion and listing of the data.
Since runoff samples were unavailable, the sampling program emphasized the
collection of soil samples in well-defined runoff gullies originating at
surface stockpiles of minerals. Where the drainage systems intersected
flowing water, upstream and downstream samples were collected. Most of the
samples consisted of the top five centimeters of soil in the bottom of the
drainage channels and three core profiles. Samples of the source material
were also collected.
Trace element and radionuclide analyses of runoff from the Morton Ranch
area are primarly based on surface sediments and vertical sediment profiles
from the dry stream beds, since few streams or other forms of runoff were
encountered. Figure 3.4 shows the waterways surrounding the inactive 1601
pit area and the semi-active 1704 pit area.
Three vertical soil profile samples were collected, two in an erosional
drainage area from the ore and waste pits south of the 1601 pit and one in an
erosional drainage bed on the east side of the waste pile of the 1704 pit.
The radionuclide and chemical constituents of these samples along with analy-
ses of other soil samples are reported in Appendix 6. The results indicate
aqueous leaching based on the radium/uranium ratios of about 12 in rede-
posited material in the alluvial fan area of the drainage, compared to a
corresponding ratio of 0.9 in the undisturbed (sub-surface) material in the
top alluvium profile.
Trace element data also indicate limited transport of mine contamination
with respect to uranium, and to a lesser extent, Se and V. The profile
samples containing 140 and 21 ppm U resulted from material transported from
the adjacent ore piles. The aqueous samples similarly showed no unusual
characteristics indicative of mine wastes.
An aqueous sample and the soil profiles collected near the 1704 pit
similarly showed no evidence of mine-related pollution or leaching of uran-
ium. This observation is based on the water and particulate analyses and the
radionuclide analyses. These samples constitute a worst case, since the
sediment samples were collected in the redeposited material of the waste pile
drainage and should show greater levels of pollutants there than would fin-
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3-37
LEGEND
• W Water
• S Soil
^ G -Stream sediment
A P 76 cm soil profile
0200
1000
Figure 3.4 Location of mines, ore and waste storage areas and monitoring stations at the
Morton Ranch mine. South; Powder River Basin, Wyoming.
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3-38
ally reach the South Fork Creek bed.
Pollutant releases from the Morton Ranch, Wyoming uranium mining oper-
ations were not observable in water drainages of the surrounding area. The
only significant movement of mine-related wastes was the transport of the
stockpiled ore in erosional drainage areas on and immediately adjacent to the
waste pile of the 1601 pit. Long-distance transport of these pollutants
(primarily uranium) into the South Fork of Box Creek was not observable. The
strongest evidence that mine wastes are a source of local soil and water
contamination is the radiochemical data, and uranium in particular. Pol-
lutant transport is almost entirely confined to the immediate area of the
mines, although there has been some dispersal via water in the ephemeral
streams. There is considerable disequilibrium between radium and uranium
which may indicate leaching and remobilization of uranium. The possibility
of natural disequilibrium in the ore body should not be overlooked.
3.2.3.2.3 Texas
A very comprehensive field and literature survey of elements associated
with uranium deposits in south Texas (He79) revealed high to very high con-
centrations of molybdenum, arsenic, and selenium in areas of shallow miner-
alization; drainages adjacent to older, abandoned mines; and in some re-
claimed areas. Areas of shallow mineralization have concentrations of
several tens of ppm molybdenum and arsenic and up to 14 ppm selenium. Near
surface material exposed by mining may have several hundred ppm molybdenum
and arsenic. Waterborne transport of suspended or dissolved solids away from
open pit mines resulted from mine water discharge and (or) surface runoff and
erosion of abandoned spoil piles. Molybdenum from the mining areas could
potentially aggravate natural soil problems leading to molybdenosis (Kab79).
Additional careful study is suggested, particularly of areas receiving mine
drainage as pumped water or overland flow.
Lakes or ponds associated with 10 mine locations in Karnes and Live Oak
counties contained water unsuitable for drinking without prior treatment
(It75). Generally, mineralization was also excessive and rendered the water
unfit for irrigation. Air and terrestrial sampling revealed no health haz-
ards from mining wastes and mined lands, but insects and other bottom fauna
in the lakes concentrated radium-226 400 to 800 times the water concentration
based on dry weight of the organisms.
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3.2.3.2.4 New Mexico
The principal investigations of the influence of uranium mining on water
quality includes EPA and contracted (Wo79) work by the U.S. Environmental
Protection Agency, the Department of Interior (Ku79), and ongoing studies by
the State of New Mexico (J. Dudley, oral communication, 1979). Because of
the co-location of mining and milling facilities, it is difficult to identify
impacts from one versus the other.
Survey of groundwater and surface water quality in close proximity to
the Jackpile-Paguate, Ambrosia Lake, and Churchrock mining areas (EPA75)
revealed extensive discharges of mine water to the ambient environment, use
of unlined ponds for settling suspended solids from mine dewatering, use of
contaminated mine water as a potable supply (one facility), and failure of
all facilities discharging to streams to have a valid NPDES permit. The
volume of mine discharge, particularly in the Churchrock area and from a mine
near Mount Taylor, led to use of the water for irrigation and stock. In
other areas of Ambrosia Lake and near Churchrock, infiltration of mine water
mixed with seepage from mill tailings ponds is causing local contamination of
shallow, potable aquifers, but the problem is not considered serious and
ongoing studies are underway. The State of New Mexico has installed a moni-
toring well network to determine temporal and spatial trends in groundwater
quality. The U.S. Geological Survey, in particular, is monitoring surface
flows and water quality in the Ambrosia Lake and Churchrock areas.
As part of the San Juan Basin Regional Uranium Study, the Department of
Interior (DOI79) assisted by the U.S. Geological Survey (Ku79) examined
selected water quality impacts from mining and milling and concluded that
much of the mine effluent is suitable for irrigation, stock, and industrial
use. Locally, it supports aquatic life and wildlife. Additional data on
stream sediments are needed to evaluate the impact on water resources of
erosion of waste rock from mines and mill tailings. It is preliminarily
suggested (Ku79) that such erosion may be difficult to detect at distances of
more than a few miles from the source because of the large amount of
(natural) regional soil erosion. The results of the study are presently in
draft form and may therefore be revised.
As part of the present study on uranium mining wastes, two New Mexico
areas containing inactive mines were surveyed in the Spring of 1979. Stable
and radioactive trace elements were monitored in surface runoff from sub-ore
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3-40
and overburden piles in Ambrosia Lake and in the nearby Poison Canyon area.
EPA staff selected the basic study areas and assisted in sample collection.
The bulk of the sampling, analytical, and interpretation phases was done by
Battelle, Pacific Northwest Laboratories (Wo79). Appendix G contains the
data and discussion. As in the case of the Wyoming study area, the sampling
program emphasized stream sediment sampling, cores, and shallow (5 cm thick)
grab samples at the land surface. Samples of the source material were also
collected. Figures 3.5 and 3.6 show the location of the study areas and
sampling stations in New Mexico. Samples of the source material were col-
lected at one of the two New Mexico drainage systems investigated. One
system in Poison Canyon, New Mexico, was adjacent to several small surface
operations as well as an underground mine site. For this system, no single
source could be defined for the runoff constituents.
The Poison Canyon mine drainage system is a dry creek bed. The course
of this creek passes an abandoned underground mine site from which it can
receive runoff water. It then passes through a dirt roadway and follows a
course adjacent to some small open pit mines. After a distance of several
hundred kilometers, it joins a second branch drainage that originates next to
a waste pile from one of the open pit mines. Samples were collected along
this waterway starting with a background sample upstream of the underground
mine about 200 m from the road. The first downstream sample was collected
about 130 m downstream from the roadway. This was upstream of the runoff
source originating in the open pit mine. The remaining samples were col-
lected along the drainage way (Fig. 3.5), below contamination sources from
the open pit operations.
A second site, the San Mateo Mine and environs, is located in the south-
east portion of the Ambrosia Lake mining district. Large mine waste piles, a
heap leaching operation, and a mine drainage pond are prominent at the site,
which drains northward to San Mateo Creek.
Soil composites were collected at the waste pile and heap leach pile.
These represent the source term for possible contamination of the watershed.
The drainage samples were collected following one channel down the waste pile
face to the intersection with San Mateo Creek, which was followed for a
distance of 500 to 600 m from the site. Additional samples were collected in
the gullies leading from the heap leach area and one of the off-site gullies.
The latter represents blank soil upstream of the drainage water. Sampling
sites are noted in Fig. 3.6. No significant contamination from the under-
-------
X
Area #2 . , „_
Area. #3
Inactive
Surface Mines
LEGEND
• Active Underground Mine
a Inactive Underground Mine
^-!-3 Surface Mine
'v—^ Ephemeral Stream Course
® Well Water Sample
• Soil Sample
N.M. Highway 53
Kilometer
Figure 3.5 Location of study areas, sampling stations and uranium mines, Poison Canyon area, McKinley County,
New Mexico.
LO
I
•P-
-------
3-42
103
Heap Leach 105
Pond (Dry) x^
106
Figure 3.6 Sample locations for radionuclides and select trace metals in sediments,
San Mateo mine, New Mexico.
-------
3-43
ground site was detected. The Ra-226 content of the soil was about two times
the background level at the furthest downstream site. This sample was col-
lected about 130 m from the apparent source.
In summary, at the New Mexico inactive mine drainages the most prominent
indicator of runoff from above-ground mineral storage is radium-226 in stream
bed sediments. Concentrations in the source material are almost two orders
of magnitude higher than those measured in the background soils. Elements
such as uranium and selenium also have as large a concentration gradient,
with concentrations decreasing downstream. At Poison Canyon, the radium-226
concentration diminished to two times background in a distance of approxi-
mately 100 m, while at the San Mateo site the distance was about 400 to 500
m. This may reflect either a more rapid transport by faster flowing water at
the San Mateo site or, more likely, the larger source term there relative to
background. At the San Mateo mine, radium-226 concentrations in water and
sediments are significantly elevated downstream relative to upstream of the
mine drainage.
3.2.3.3 Summary
The field studies conducted to date on the impacts of uranium mining on
water quality are somewhat contradictory. Although no cases of gross, wide-
spread contamination of groundwater or streams can be documented for uranium
mining, there are cases of local contamination of water and sediments. From
standpoints of theory and field data, there is need for cautious optimism in
the use of local soil and water resources as sinks for waste discharge.
Although numerous studies indicate that considerable reliance can be placed
on the various physical and chemical processes to protect natural waters from
contamination, investigations generally warn against using such studies to
predict what may happen in other situations (Ru76; NRC79b; Ku79; Fu77; Am78).
Laboratory results are highly dependent on the chemical properties of the
fluid matrix and the physical and chemical properties of the particular soil
studied. Results of field studies are site and time specific and have often
suffered from inconsistent and undefined sampling and sample preservation
techniques and questionable analytical measurements (Ku79; Ha78; Si77).
Our analyses reveal that there have been local water quality problems
from mine water and wastes. Although widespread hazards have not been iden-
tified, this may be false security insofar as the present status of knowledge
concerning trace element mobility in aqueous settings representative of
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3-44
uranium mining areas is rather unclear from both theoretical and real-data
standpoints. Most often, effects of mining are interspersed with and masked
by impacts from uranium milling. This complicates or renders impossible any
meaningful interpretation of the mining-related data. Despite the attempt to
sort out some of the information on trace element mobility, there is in-
sufficient understanding at this time to dismiss or otherwise reduce the
significance of trace element contributions (from mining activities) to
surface streams and, to a lesser extent, to groundwater.
We conclude that there is considerable information on the topics of
trace element chemistry. It is also clear that trace element concentrations
in natural fresh water are highly variable on both macro and micro geographic
scales. There is great difficulty in correlating concentrations with such
characteristics as streamflow or lithologic environment. Accurate prediction
of the behavior and cycling of trace elements through water and sediments
first involves characterization of physical states such as particle size and
form (chelate, colloid, complex ion, precipitate, etc.), speciation, and
availability to plants and animals (An73). Andelman concludes "...that there
can be large differences in trace element concentrations [in water], on both
a macro and micro geographic scale, and that such variations often occur in
an unsystematic and nonpredictable fashion."
We recommend additional studies of spatial and temporal variations,
sources and sinks of trace elements, chemical interactions within the hydro-
geologic system, interactions between surface and groundwater systems,
effects on aquatic biota, and effects on water use (human consumption, stock
watering, irrigation). Periodic monitoring in certain areas would allow for
the detection of the long-term trends of potential changes that would accom-
pany anticipated increases in future mining activity — during a period of
increased competition for scarce water resources.
3.3 Surface Mining
3.3.1 Solid Wastes
Surface mining consists of removing materials, separating them into ore,
sub-ore, and overburden, and storing them in separate piles on the surface
near the mine for various periods of time (Section 1.3.2). The various
storage piles are managed differently, vary in size and level of contami-
nants, and exist for varying periods of time. All are potential sources of
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3-45
contamination to the environment via dusts suspended and transported by the
wind, precipitation runoff, and Rn-222 emanation (Fig. 3.7).
3.3.1.1 Overburden Piles
Surface mining produces spoils at a rate of millions to tens-of-millions
of tons per year. Unless this material is used to backfill the pit, large
surface areas — 40 hectares to over 400 hectares -- are covered to depths
varying from a few meters to over 100 meters (Ka75, NRC77a, NRC77b, DOA78,
Pe79).
Most of the mines begun since the early to mid 1970's use overburden to
backfill mined-out areas of the pit (Ka75). Since older mines usually did
not, erosion of their storage piles by water and wind may present an environ-
mental problem (Ka75). In addition, the large amounts of overburden that
past and present mines have used for road and dike construction and backfill
also may present an environmental problem.
The annual average ore production of the 63 surface mines operating in
the United States in 1978 was 1.2 x 105 MT (Section 1.3.1). Assuming an
overburden to ore ratio of 50:1 (Section 1.3.2), the average annual pro-
duction of overburden was about 6.0 x 10 MT per mine. A recent study of the
eight large mines that accounted for 68 percent of the total 1977 United
States U000 production from surface mines recommends the following average
o o
production parameters (Ni79):
5
1. ore production = 5.1 x 10 MT/yr
2. average ore grade =0.11 percent U,0g
3. overburden:ore ratio = 77
4. overburden production = 4.0 x 10 MT/yr
5. mining days/yr =330 d/yr
Surface areas of hypothetical overburden piles were computed using the
above 63-mine and 8-mine overburden production rates and the following assump-
tions:
3
1. an average density of 2.0 MT/m - reported values vary between
1.6 and 2.7 (Ro78, DOA78, NRC78a, Ni79)
2. the dumps are on level terrain
3. a rectangular waste dump with the length twice the width, and
sides that slope at 45° angles (Fig. 3.8a)
-------
Figure 3.7 Potential sources of environmental contamination from active open pit uranium mines.
-------
3-47
4. a waste dump in the shape of a truncated right-circular cone with
45° angled sides (Fig. 3.8b)
5. a bulking factor of 25% or 1.25 (Burns, E., Navajo Engineering
and Construction Authority, Shiprock, NM, 2/80 personal communi-
cation)
Table 3.11 lists the surface areas of the hypothetical overburden piles
in the following three cases:
Case 1 - one year production with no backfilling
Case 2 - backfilling concurrent with mining - assumes 7 pits
opened in a 17-year mine life with overburden from each
successively mined pit used to backfill a previously com-
pleted pit, resulting in an equivalent of one pit of over-
burden (2.4-yr production) stored on the surface (Ni79)
Case 3 - no backfilling during the 17-year mine life
The quantities of dust and Rn-222 that become airborne are directly
proportional to the surface areas of waste piles. Table 3.11 shows the large
variations possible between surface areas of waste piles at some active
mines. Waste piles also cover various areas of terrain. However, for the
same volumes, there are no significant differences in surface area or area of
terrain covered for the two configurations of waste piles used in this study.
Case 2 approximates recently activated mines, and Case 3 approximates older
mines.
The type of rock in overburden spoil piles depends on the locations of
the ore zones. Common rock types of New Mexico, Wyoming, and Texas mines in-
clude sandstone, claystone, siltstone, shale, and limestone, and unconsoli-
dated silt, gravel, and sand (Co78, Pe79, Wy77, Ri78). In Texas, there are
also lignite beds, tuffaceous silts, and some nearly pure volcanic ash
-------
3-48
W
a) A rectangular pile with length twice the width and 45 degree sloping sides
b) A frustum of a regular cone with 45 degree sloping sides
Figure 3.8 Storage pile configurations assumed at surface and underground mines.
-------
3-49
(Ka75). Coal veins are often present in Wyoming and New Mexico (Wy77, Ri78).
However, the most abundant material in waste rock dumps will probably be
clastic sedimentary rocks: sandstone, siltstone, and shale.
There .is great variation in the particle size of material in waste
piles, and this variation is important. Large particles (>30pm)*, because
they usually settle within a few hundred feet of their origin, do not con-
tribute to the airborne dust concentration (EPA77b). The potential for human
respiration of the wind suspended dusts is also strongly influenced by the
mean particle diameter (ICRP66).
Overburden rock is as large as available equipment can load and haul to
the storage area. Rocks too large to handle with available equipment are
broken into manageable sizes by small, explosive charges. Hence, rock parti-
cles will vary from less than a ym to a meter or more in diameter. Since
weathering eventually breaks down the larger stones, the fraction of smaller
particles increases over time.
Particle size distributions of material in waste rock piles at uranium
mines have not been determined. It is likely that this material has a
greater fraction of larger particles than that associated with crushed uran-
ium mill tailings. Table 3.12 shows an example of the particle size distri-
bution in the latter and the mean particle size distribution from a study of
shale overburden removed from a surface mine in Pennsylvania (Ro78). Al-
though the distribution fractions differ, a gross comparison can be made
between the particle size of mill tailings and overburden waste. About 28
percent of the tailings were less than 50 urn in diameter, and only about 12
percent of the particles in the overburden pile had similarly small dia-
meters. Because only particles smaller than 30 ym are likely to remain
suspended by the wind for any significant distance (EPA77b), probably less
than 10 percent of the overburden is a potential source of environmental
contamination via wind erosion.
Table 3.13 shows the natural radionuclide concentrations in common rock
types in the United States. In sedimentary rocks, which are common in the
major uranium mining regions, the U-238 concentrations vary from less than 1
ppm** to about 4 ppm. Natural radioactivity usually is somewhat higher in
the western states, and the uranium content in overburden prior to mining
= micrometer = 10" meters.
**ppm = parts-per-million = 10"6 grams per gram of rock.
-------
3-50
Table 3.11 Estimated surface areas associated with overburden piles
Pile
Management^9' Height,
Overburden Surface Area
m Volume^, m3 of Pile, m2
Terrain
Covered, Hectares
Rectangular Pile'c^
Case 1
Case 2
Case 2
Case 3
Case 1
Case 2
Case 2
Case 3
Truncated
Case 1
Case 2
Case 2
Case 3
Case 1
Case 2
Case 2
Case 3
65
65
30
65
65
65
30
65
Cone^
65
65
30
65
65
65
30
65
Average Large Mine^ '
2.5 x 107
6.0 x 107
6.0 x 107
4.2 x 108
( e)
Average Minev '
3.8 x 106
9.0 x 106
9.0 x 106
6.4 x 107
Average Large Mine^ '
2.5 x 107
6.0 x 107
6.0 x 107
4.2 x 108
Average Mine'6'
3.8 x 106
9.0 x 106
9.0 x 106
6.4 x 107
5.2 x 105
1.1 x 106
2.2 x 106
7.1 x 106
1.0 x 105
2.2 x 105
3.6 x 105
1.2 x 106
5.2 x 105
1.1 x 106
2.1 x 106
7.1 x 106
1.1 x 105
2.2 x 105
3.5 x 105
1.2 x 106
48
106
209
682
10
20
34
113
46
104
208
683
9
18
33
110
-------
3-51
Table 3.11 (continued)
^'Management:
Case 1 - one year production with no backfilling
Case 2 - backfilling concurrent with mining - assumes 7 pits
opened in a 17-year mine life and equivalent of one-
pit overburden (2.4 year production) remains on surface
Case 3 - no backfilling during 17-year mine life
^ 'Volume = production (MT/yr) x production years x bulking factor (1.25)
* by density (2.0 MT/m3).
^'Length of pile is twice the width and the sides slope at a 45° angle
(Fig. 3.8a)
I
(e)
^ - - *j - - - — — i ,
^ 'Overburden production = 4.0 x 10 MT/yr.
Average 1978 overburden production of all 63 surface mines, assuming an
overburdenrore ratio of 50/1, 6.0 x 10 MT/yr per mine.
* 'A frustum of a regular cone with 45° sloping sides (Fig. 3.8b).
is about 4 ppm (Ni79). However, during mining, some low-grade ore mixes with
the overburden and may increase the concentration of the pile to as high as
20 ppm U30g (Ni79). This is equivalent to 12.6 disintegrations per minute
(dpm) per gram of overburden. The progeny of the uranium will contribute
additional radioactivity. Although there are local disequilibria between
U-238 and its principal daughters, Th-230 and Ra-226, in ore-bearing rock,
secular equilibrium will be assumed (Wo79). Small quantities of Th-232 and
progeny will provide additional radioactivity. There is no apparent rela-
tionship between the Th-232 and U-238 decay chains. Th-232 concentrations in
ores and host rock range from less than a pCi/g to a few pCi/g regardless of
the U-238 concentration (Wo79).
-------
3-52
Table 3.12 Particle size distributions of mill tailings
and mine overburden
Mill
Particle Size,
Mm
250
125-250
53-125
44-53
20-44
7-20
1.4-7
< 1.4
^'Source:
(^Source:
'The conc<
Tailings(a)
Weight
Percent
60.3
7.5
4.2
3.8
7.8
7.2
9.1
0.0
Sc79.
Ro78.
entration of
Conc.(c)
Avg. Cone.
0.15
0.03
0.03
0.03
0.75
1.5
4.6
radionuclides
Overburden^ '
Particle Size, Weight
ym Percent
>2000 75
50-2000 13
2-50 8
<2 4
in that fraction divided by the
average concentration.
Table 3.13 Natural radionuclide concentrations in various
common rock types
U-238
Rock Type
Igneous
Basic
Granite
Sedimentary
Shale
Sandstone
Limestone
ppm
0.9
4.7
3.7
0.45
2.2
pCi/g
0.3
1.6
1.2
0.15
0.7
Th-232
ppm
2.7
20
12
1.7
1.7
pCi/g
0.3
2.2
1.3
0.2
0.2
K-40
ppm
1.2
5.0
3.2
1.1
0.32
pCi/g
8.4
35
22
7.7
2.2
Source: Oa72.
-------
3-53
Table 3.14 shows the results of an extended airborne particle sampling
program near a surface mine in New Mexico (Ea79). Although the on-site
source of the radioactivity measured on these filters is undetermined, ore
and sub-ore piles, waste rock piles, and mining activity all probably con-
tribute. The higher activities reflect a greater contribution from ore
dusts. From these air measurements, the above assumed average uranium con-
centration in overburden, 12.6 dpm/g (s 6 pCi/g), appears reasonable. These
data also indicate that the progeny of U-238 through Ra-226 are in near
secular equilibrium. The Th-232 concentration is about 1 pCi/g and, as
indicated above, independent of the uranium concentration. Considering all
available data, the radioactive source terms for overburden piles will be as
follows: (1) U-238 and progeny = 6 pCi/g (0.0020 percent U30g; (2) activity
ratio (dust:overburden) = 2.5 (Section 3.3.1.2); and (3) Th-232 and progeny
= 1 pCi/g. Figures 3.1 and 3.2 show the uranium and thorium decay series.
Table 3.14 Annual average airborne radionuclide concentrations
in the vicinity of an open pit uranium mine, pCi/g
Location
Jackpile Housing
Paguate
Bibo
Mesita
Old Laguna^3^
U-238
76
13
9
3
5
Th-230
80
12
7
2
2
Ra-226
70
13
5
3
3
Th-232
1.2
1.3
1.3
0.7
0.4
U-238/Th-232
63
10
7
4
13
'^Background location
Source: Ea79.
-------
3-54
Little information is available on stable element concentrations in
overburden rock. Table 3.15 summarizes the analyses of a few grab samples of
soil and rock from a uranium mine in New Mexico and one in Wyoming (Wo79).
Except for possibly Se, V, and As, there are no significant concentrations of
stable elements attributable to uranium mining. Considering the typically
high natural Se and V contents of many minerals common to these areas and the
limited number of analyses, the inference of pollution is indefinite. A
relationship between uranium and the stable element concentrations does not
appear to exist. Thus, the stable element concentrations in overburden from
the model surface mine will be the average concentrations of samples 6, 7, and
8 in Table 3.15. Table 3.16 lists the average concentrations.
3.3.1.2 Ore Stockpiles
Ore is often stockpiled at the mine as well as the mill. Although ore
stockpiles are much smaller than the overburden waste piles, the concen-
trations of most radioactive contaminants are much greater in ore-bearing
rock than in overburden. In addition, ore is stockpiled at the mine for
shorter periods of time than waste rock. Ore stockpile residence times vary
from mine to mine and range from a few days to a few months. The recent
study of 8 large surface mines cited 41 days as an average ore stockpile
residence time (Ni79). We will use this value to estimate the average area
of ore stockpiles.
The average of the 63 operating surface mines produced 1.2 x 10 MT of
ore during 1978. Assuming 330 working days per year and a 41-day ore stock-
pile residence time, a 1.5 x 10 MT ore stockpile would exist at the average
mine. In comparison, the recent Battelle study reported that the average of
eight large surface mines produced 1550 MT of ore per day, which would yield
a 6.3 x 10 MT ore storage pile, assuming the same residence time (Ni79).
The ore piles vary in height at different mines and different times. One
study reports a maximum pile height of 9.2 m (30 ft) (Ni79), and at another
site the maximum and equilibrium ore pile heights are estimated to be 6.7 m
and 3.1 m, respectively (NRC78a). Using these parameters and a bulking
factor of 1.25 (Burn's, E., Navajo Engineering and Construction Authority,
Shiprock, NM, 2/80, personal communciation), the pile surface and pad areas
were computed for the two production rates and two pile heights, 9.2 m and
-------
Table 3.15 Uranium and stable element concentrations measured in rock and soil samples from
two uranium mines
Concentrati on ,ug/g
Sample
Wyoming
1. Top Soil Piles
2. Sub-ore
3. Ore
New Mexico
4. Background Soil
5. Background Soil
6. Waste Pile
7. Waste Pile
8. Sub-ore + waste
9. Ore
As
3.2
<1.8
5.4
4.1
2.3
7.8
14
4.1
6.0
Ba
700
6800
800
450
440
540
280
45
64
Cu
13
9
9
12
9
11
21
22
27
Cr
46
<36
<27
<23
<20
<28
<43
<51
<48
Fe(a)
1.3
1.2
1.1
0.9
0.8
0.8
0.7
0.3
0.4
Hg
<4
10
<7
<4
<4
<5
<8
<6
<6
K(a)
2.2
2.3
2.3
1.8
1.6
1.4
0.5
0.1
0.2
Mn
190
140
180
200
190
260
750
446
673
Mo
2.9
<2.2
<2.9
5.5
4.9
2.5
<2.8
<1.8
<1.8
Pb Se
23 <1
22 2.1
16 28
12 <1
13 <1
10 <1
31 3.1
25 <1.4
31 1.5
Sr
89
128
94
72
50
99
178
179
323
V
60
<100
200
<50
<50
<70
180
<55
<55
Zn
37
25
25
22
19
23
23
13
14
U
6
61
370
<5
<5
8
189
57
---
Source: Wo79.
^a'Units are percent.
co
i
01
CD
-------
3-56
Table 3.16 Concentration of radionuclides (pCi/g) and stable elements
in overburden rock from the model surface mines
Element
Arsenic
Barium
Copper
Chromium
Iron(a)
Mercury
Potassiunr3'
Manganese
Molybdenum
Lead
Concentration
9
290
18
<51
0.6
<8
0.7
485
2.5
22
Element
Selenium
Strontium
Vanadium
Zinc
U-238
Th-230
Ra-226
Pb-210
Po-210
Th-232
Concentration
2
150
100
20
6
6
6
6
6
1
^ 'Units are percent.
3.1 m, assuming the same geometric configurations as for the overburden piles
(Fig. 3.8). Table 3.17 gives the results. The computed surface areas of an
average ore stockpile vary with volume of ore stored and pile height, but
they are relatively independent of the pile shape.
Uranium deposits exist in sedimentary, metamorphic, and igneous for-
mations. Sedimentary formations, primarily sandstone, siltstone, mudstone,
and limestone generally host stratiform ore deposits often accompanied by
carbonaceous material. Vein-type deposits usually occur in fractures of
igneous and metamorphic formations. In the Rocky Mountain mining regions,
about 98 percent of the recovered UoOg comes from sandstone and related-type
rock (St78). Sedimentary formations, principally sandstone, have been the
predominant host for uranium in South Texas (Ka75).
-------
3-57
Table 3.17 Estimated average areas of ore pile surface and pad
Pile
Configuration^3'
Rectangular
Truncated Cone
Rectangular
Truncated Cone
Rectangular
Truncated Cone
Rectangular
Truncated Cone
Pile
Height, m
Average
9.2
9.2
3.1
3.1
Average
9.2
9.2
3.1
3.1
Surface Area
of Pile, m2
Large Mine^ '
6,300
6,200
14,000
13,700
Mine(c)
1,860
2,000
3,660
3,590
Ore Pad
2
Area, m
5,700
5,300
13,500
13,200
1,820
1,580
3,420
3,340
U)
(b)
See Figure 3.8.
Volume of ore = 6.3 x 10 MT (41 day production) x 1.25 (bulking factor)
* 2.0 MT/m3 = 3.9 x 104 m3.
(c)
Volume of ore = 1.5 x 10 MT (41 day production) x 1.25 (bulking factor)
* 2.0 MT/m3 = 9.4 x 103m3.
-------
3-58
The DOE does not expect the mineralogical characteristics of uranium ore
to change appreciably in the future, since the known reserves are mainly in
sandstone or a related host (DOE79). This fact is apparent from the data in
Table 3.18, which gives the distribution of ore reserves in the United States
by type of host rock. More than 97 percent of the uranium reserves are in
sedimentary formations, primarily sandstone. Hence, it is reasonable to
assume that ore stockpiles in the future will continue to consist mainly of a
friable (easily crumbled) sandstone rock.
No data are presently available on the particle size distribution of
material in ore stockpiles. Thus, the particle size distribution of ore will
be assumed to be similar to that of overburden rock.
The average grade of ore mined in 1978 was about 0.14 percent UjOg, but
this will decline in future years (DOE79). The average grades of ore associ-
ated with tnn "30 and $50 reserves are 0.10 percent and 0.07 percent UgOg,
respectively (DOE79). Assuming the average grade of ore mined in the next
decade to be about 0.10 percent UgOg, the average uranium concentration in
ore stockpiles will be 285 pCi/g (632 dpm/g). Although secular equilibrium
in the uranium decay chain may not totally exist in some cases due to
leaching by groundwater with subsequent redeposition, it appears reasonable
to assume that radioactive equilibrium exists in a general assessment.
As discussed earlier, ambient Th-232 concentrations in the vicinity of a
uranium mine range between 1 to 2 pCi/g. However, a concentration of 0.01
percent thorium is typical for ore from some surface mines (Mi76). This
concentration is equivalent to 11 pCi Th-232/g of ore.
Uranium occurs in many ores as a secondary deposition. In a reducing
environment, the soluble uranyl ion converts to insoluble uranium oxide and
deposits preferentially on the smaller particles. (The total surface area of
a given mass of smaller particles is greater than for larger particles.)
Therefore, dusts that consist primarily of small particles have a greater
specific concentration than ore as a whole (Table 3.12). The common pro-
cedure for computing uranium concentration in dust is to multiply the average
concentration in the ore by 2.5 (NRC77a, NRC78a).
-------
3-59
Table 3.18 Distribution of ore reserves by the type of host
Host Type
Sedimentary^
Lignite Materials
Limestone
Igneous and Metamorphic
Totals
MT of
Ore (106)
1,143.2
2.2
1.3
32.7
1,179.4
MT of
U3°8
810,000
3,000
1,200
20,400
834,600
Percent Total
Tons, U30g
97.1
0.4
0.1
2.4
100.0
^'Principally sandstone, but includes conglomerates, shale, mudstone, etc.
Note.—The reserves are $50 or less per pound U308, effective January 1,
1979 (DOE79).
Table 3.19 Average stable element concentrations in sandstone
ores of New Mexico
Metal
Arsenic
Barium
Cadmium
Cobalt
Copper
Chromium
Iron
Mercury
Potassium
Magnesium
Concentration, ug/g^a'
86 (10-890)
920 (150-1500)
ND^
16 (3-150)
61 (15-300)
20 (7-70)
15,700 (3,000-70,000)
ND
25,000 (7,000-30,000)
3,500 (700-15,000)
Metal Concentration, vg/g^a'
Manganese
Molybdenum
Nickel
Lead
Ruthenium
Selenium
Strontium
Vanadium
Zinc
960 (70-3,000)
115 (3-700)
20 (7-70)
78 (3-300)
ND
110 (1-625)
130 (1.5-300)
1410 (70-7,000)
29 (10-70)
of concentrations given in parentheses.
- not detected
Note.--Ore samples are Dakota and Morrison sandstone from 25 uranium
mines (Hi69).
-------
3-60
In accord with the above discussion, we assume the following estimated
average radionuclide source terms for ore stockpiles: (1) U-238 and progeny =
285 pCi/g ore (0.10 percent U308); (2) Activity ratio (dust:ore) = 2.5; and
(3) Th-232 and progeny = 10 pCi/g ore.
Stable elements -- molybdenum, selenium, arsenic, manganese, vanadium,
copper, zinc, and lead — often associated with uranium ore at elevated
concentrations may cause deleterious environmental and health effects. Mer-
cury and cadmium are present only on rare occasions (Th78). However, as
discussed above, there is no apparent relationship between concentration of
stable elements and ore grade (Wo79). Table 3.19 lists measured (Hi69)
concentrations of stable elements in 25 sandstone ores from New Mexico and
average concentrations computed from these data. We assume the average
concentration for the ore from the model surface mine.
3.3.1.3 Sub-ore Piles
All mines recover some rock containing uranium ore that at the time of
mining is uneconomic to mill. The grade of this "sub-ore" varies with the
"cutoff" level assigned by the mill. Some mines process sub-ore by heap
leaching, which changes the chemical properties and constituents of the pile
(Section 1.3.5.1). However, most mines store the sub-ore in separate piles
and recover it when it becomes economically feasible.
The sizes of sub-ore dump piles vary with the quantity of ore mined and
its grade. One study suggests that the sub-ore accumulation rate equals the
ore production rate (Ni79), a ratio similar to that reported for the Sweet-
water uranium mining operation (NRC77a). Using this assumption with the ore
production rates given above for the average large mine and average mine, 5.1
x 10 MT/yr and 1.2 x 10 MT/yr, respectively, the average sizes of sub-ore
piles generated at a constant rate during the 17-year active life of a mine
were based on an 8.5 year accumulation and a bulking factor of 1.25. Figure
3.8 shows the shapes of the piles assumed, and Table 3.20 gives the results
for piles 30 m high. The surface areas of the two pile configurations differ
very little.
The mineralogical characteristics of ore and sub-ore are very similar.
Thus, the distribution in Table 3.18 will apply to sub-ore. This study
considers the particle size distribution of sub-ore the same as for over-
burden and ore.
-------
3-61
In the early mining years, the ore cutoff grade was usually about 0.15
percent U30g. However, this has continually decreased until today the cutoff
ore grade .is about 0.03 percent U30g (Ni79, NRC77a). Hence the ore content of
these piles will be less than 0.03 percent U30g, and the average content has
been estimated to be one-half the cutoff grade, or 0.015 percent U30g (Ni79),
which is equivalent to 43 pCi U-238/g (95 dpm/g). Also, the uranium in the
sub-ore, as in ore, is assumed to be in secular equilibrium with its progeny.
Because the occurrence of uranium in sub-ore is the same as in ore and the
mineralogies are similar, the uranium in sub-ore should be concentrated on
small particles by the same factor as in ore, 2.5.
The Th-232 concentration in sub-ore is between the ambient level and
that in the associated ore, 1 pCi/g to 11 pCi/g. For lack of measured Th-232
concentrations, we assume that less than 2 pCi/g of Th-232 will be present
(Table 3.14). The radiological significance of an error in this assumption
will be small.
From the above discussion, we assume the following estimated average
radionuclide source terms for sub-ore piles: U-238 and progeny = 40 pCi/g
(0.015 percent U30g); activity ratio (dust:sub-ore) = 2.5; and Th-232 and
progeny = 2 pCi/g. Figures 3.1 and 3.2 show the uranium and thorium progeny.
Table 3.20 Estimated average surface areas of sub-ore piles during
the 17-year active mining period
Pile Surface Area Terrain
?
Configuration^' of Pile, m Covered, Hectares
Rectangular
Truncated Cone
Average Large Mine^ '
1.2 x 105
1.2 x 105
11
11
(c)
Average Mine
Rectangular
Truncated Cone
3.5 x 104
3.6 x 104
3.2
3.0
Fig. 3.8.
(^Volume of sub-ore = 8.5 yr x 5.1 x 105 MT/yr x 1.25 4 2.0 MT/m3 = 2.7
x 106 m3.
Volume of sub-ore = 8.5 yr x 1.2 x 105 MT/yr x 1.25 * 2.0 MT/m3 = 6.4
x 105m3.
-------
3-62
Stable elements observed in ore will also be present in sub-ore. Because
stable element concentrations specific to sub-ore are unavailable and are
unrelated to ore grade, concentrations in the sub-ore from the model surface
mine will be assumed equal to those in the ore (Table 3.19).
3.3.1.4 Reclamation of Overburden Piles
Reclamation is usually done only for overburden piles. Ore stockpiles
are continually being disturbed and their residence time is short. Also,
sub-ore piles generally are not stabilized in anticipation of recovering the
uranium at a later time. Hence, only overburden and waste rock piles are
considered for stabilization and reclamation. Section 1.3.2 gives a brief
description of these practices.
Backfilling mined out areas of the pit is necessary for an adequate
reclamation program. Because of the swelling of earthern material once
mined, sufficient material should be available to completely fill the pit
when mining is completed. However, even though backfilling is generally
being performed at most recently active mine sites, sufficient overburden is
often not replaced to eliminate the pit.
Improperly stabilized spoil piles may become sources of contaminants to
the environment. The wind can suspend and transport small-sized particles
containing elevated levels of contaminants. Radon-222, produced by the
radioactive decay of Ra-226 contained in the rocks, can emanate from the pile
surfaces. Precipitation runoff from the piles can carry particulate matter
and dissolved contaminants into the natural surface drainage system if
rainfall exceeds the infiltration and holding capacity of the pile. The
general procedure for reducing wind and water erosion is to grade the piles
to conform to the natural terrain, cover the area with a layer of topsoil,
and seed it with a native grass.
These spoils consist of unweathered and unconsolidated rock, coarse
gravels, and sands and allied materials isolated from the natural processes
that occur on surface soils. Consequently, spoils have poor textural prop-
erties and low water-holding capacities. Having no established flora to
aerate the surface and make nutrients available, spoils are barren of nut-
rients required for plant growth. Hence, to sustain vegetation on these
piles may be difficult because of poor soil quality and the arid conditions
-------
3-63
In the principal mining regions. Therefore, all plant growth depends on the
topsoil cover, which is generally less than 30 cm thick (Re76). This is
often inadequate to store sufficient water and nutrients to sustain plant
growth during extended dry periods. Soil irrigation and fertilization may be
required for several years until plants can sustain themselves.
Proper grading of the spoil piles, with water management and conser-
vation, can help reclamation. The piles should have less than a 3:1 slope to
reduce surface water runoff and erosion (St78). Forming catchment basins and
terraces to hold water on the spoils and reduce water erosion will also
increase the amount of runoff available to the plants. It also has been
determined that vegetation on north-facing slopes requires about half the
applied water of that on south-facing slopes (Re76). Water requirements of
vegetation on horizontal surfaces and east and west slopes are about inter-
mediate between those of the north and south slopes. Hence, spoil piles with
long, north slopes will conserve water and reduce the irrigation required.
Locating piles on leeward slopes and away from natural drainage will also
reduce wind and water erosion.
The reestablishment of native grasses and shrubs is essential for con-
trolling wind and water erosion and providing wildlife habitat. Wyoming
requires a pre-mining vegetation inventory for use in evaluating post-mining
reclamation (Wy76). Similar statutes governing mine reclamation are in
effect in other states (Section 1.4). The Soil Conservation Service has
recommended seed mixtures that are best suited to climatic and soil con-
ditions in different areas of the West (St78). Newly seeded areas are usu-
ally protected from grazing by fencing for at least two growing seasons to
allow the plants to become established.
Abandoned pits fill with water and form small lakes that livestock and
wildlife can use for drinking water, if the water is uncontaminated. But,
unless properly managed, final pits may be hazards to people and wildlife.
Therefore, steep walls should be graded to give safe access into the pit, and
after grading, the pit banks should be seeded to minimize erosion and prevent
the sides from sloughing off.
3.3.2 Mine Water Discharge
3.3.2.1 Data Sources
The principal sources of information used to model the mining region in
-------
3-64
Wyoming are the site-specific EIS's and ER's for active and proposed mining/
milling operations and the NPDES permit data on discharge volume and quality.
Several reports by state and federal agencies supplemented the foregoing,
particularly with respect to estimating ambient water quality and flood
volumes for various return periods and annual or monthly flows in principal
streams of the region. Foremost among these is work by the State (Ha78), the
U.S. Geological Survey (Cr78, Ho73), and the Soil Conservation Service
(DOA75).
Self-monitoring data collected by industry and reported to EPA were also
checked to ascertain compliance with NPDES permit conditions. Unfortunately,
the permits do not specify limits on the volume of discharge; hence, the
total mass or flux per unit of time may or may not agree with the values
originally estimated by the discharges in the EIS, ER, or license appli-
cation.
3.3.2.2 Quantity and Quality of Discharge
The purpose of this section is to identify water quality associated with
surface uranium mining in the Wyoming Basin. This area was selected for
detailed source term characterization and pathways analysis because of past
and ongoing uranium production, primarily by surface mining. A subsequent
section (3.4.2) similarly addresses underground mining. The analysis to
follow is incomplete and preliminary, owing to the limited existing data, the
lack of opportunity for significant new investigations in the time of this
study, and the decision to pursue the objectives on a "model area/model mine"
approach. So many variables of ore occurrence, mining practices, climate,
geology, and hydrology exist that a detailed investigation is unrealistic.
Table 3.21 summarizes water quality data for seven surface and three
underground mines in Wyoming. Uranium averages 0.62 mg/£ and ranges from
0.02 to 1.3 mg/£ . Dissolved radium-226 is typically less than 4 pCi/£ ,
although one mine reportedly discharged 10.66 pd'/JU Suspended solids
average 24.9 mg/a . There is considerable variation from one facility to
another; the observed range is 2.7 to 87.2 mgA, . Zinc is the only stable
element consistently monitored, probably because the NPDES permit addresses
it. Concentrations average 0.04 mg/£ and are well below the 0.5 mgA limit in
the permits. Barium and arsenic are less frequently monitored but appear to
be in the range of 0.05 mg/& for barium to 0.005 mgA for arsenic. Both of
these values are well below the discharge limits.
-------
Table 3.21 Summary of average discharge and water quality data for uranium mines
in Wyoming and a comparison with NPDES limits
Radioactivity
Mine
Project Type
1
2
3
4
5
6
7
8
9
10
U
U
U
S
S
S
S
S
S
S
All Mine Types (
Average:
Standard
Deviation
Underground
Average
Standard
Deviation
•
Discharge
m /min
0.
6.
0.
1.
3.
5.
3.
1.
0.
4.
85
57
70
89
60
68
52
21
10
55
Total U Ra-226
mg/£
0.
0.
0.
1.
0.
0.
0.
0.
1.
95
41
02
30
63
02
98
14
14
pCi/i
3.
2.
7.
10.
3.
2.
0.
3.
3.
92
28
41
66
94
85
67
03
6
TSS
87.
2.
8.
5.
11.
10
19.
17.
62.
so4
2
7 234
8
0
1
4 875
3
5
Major and trace constituents, mg/j,
Zn
0.
0.
0.
0.
0.
0.
0.
0.
0.
Fe Ba Cd As
08 1.25
02 0.02 0.05
01
01
14
05
05 0.004 0.005
02
16
1 through 10):
2.87
2.25
0.
0.
62
50
4.
3.
26
00
24.
29.
9 555
5 453
0.
0.
06 0.64 0.05 0.004 0.005
06 0.87 -
Mines (1 through 3):
•
•
Surface Mines (4
Average
Standard
Deviation
Summary of
•
NPDES
Daily Average /Da
2.71
3.35
through
2.94
1.96
Permit
10):
Limits
ily Maximum
0.
0.
0.
0.
46
47
70
53
2/4
4.
2.
4.
3.
54
62
1
4
i *\
3/10va/
10/30
Total
32.
47.
20.
21.
9 234
1
88 875
04
20/30
0.
0.
0.
0.
0.
04 0.64 0.05
04 0.87
071 0.004 0.005
063 - w
i
CT>
5/10 -/2 -/I 0.05/0.1 0.5/1 on
Radium
(a)
Total Ra-226 limit is not monitored.
Source: NPDES permits from Region VIII (R. Walline, written communciation), site-specific
reports (EIS, ER), and self-monitoring data.
-------
3-66
Mean values from six surface mining projects in Wyoming were the basis
for estimating the effects of mine discharge on water quality. Values from
mines in the South Powder River Basin model area compare very well with the
Wyoming mines, thus supporting adoption of a model mine in the Basin. There
were no strong differences in water quality between surface and underground
mines. Table 3.21 shows that discharge is highly variable, ranging from 0.1
3 3
to 6.57 m /min, with an average of 2.87 m /min. In surface mining projects,
the average is 2.94 m /min, with a standard deviation of 1.96, indicating
considerable discharge variation among facilities. This study'assumes an
overall average flow of 3 m /min from each surface mine in the calculations
of chemical loading of local and regional streams (see Section 3.3.3 and
Appendix H).
Table 3.22 shows water quality and flow rates associated with open pit
mines in other areas and in various stages of operation. Ongoing development
of an open pit mine in Colorado involves 28 m /min discharge and is therefore
well above the average. Radium, uranium, and suspended solids are relatively
low. Producing open pit mines in New Mexico are usually dry or nearly so and
are dewatered at rates of 0.6 m /min or less. The water is used for dust
control. Radium concentrations can be very high (New Mexico Projects) due to
long residence time of groundwater in the ore body and the concentrating
effects of evaporation. Similary, groundwater associated with ore bodies in
Texas and Wyoming may contain several hundred picocuries per liter.
Mine dewatering has the greatest potential for adverse environmental and
public health impacts. Although contaminant concentrations in the effluent
conform to NPDES requirements, there is long-term contaminant loading to the
ambient environment. Contaminants concentrate on stream sediments because of
sorption and evaporation and become available for transport by flood water.
Regional or at least local dewatering of ore bodies may deplete high quality
groundwater. Theoretically, dewatering may induce horizontal or vertical
influx of poorer quality groundwater into productive or potentially pro-
ductive aquifers, but the extent of this phenomenon is poorly documented. We
strongly recommend further study because the work done to date is largely
oriented toward determining engineering feasibility versus the overall en-
vironmental impact.
-------
Table 3.22 Water quality associated with surface and underground mines in various stages of
construction and operation
Milligrams per liter
Project
Discharge
m /min
Total U
mg/s.
Dissolved
Ra-226
pCi/£
Pb-210 TSS S04 As
pCi/£
Mo Se
Colorado
Open pit mine:
Development stage 28 1.044 4.10
New Mexico
Producing open pit
mine, seepage to
pit 0.13 2.5 180
Open pit mine,
ponded inflow water 0.58 2.6 220
Texas
Active open pit mine
holding pond. 50 to 100
17
26
16.2
168
23
2151 0.005
842 0.005
380 < 0.01
0.018 0.019
0.545 0.043
<0.01 <0.01
co
i
-------
3-68
Overland flow is not dismissed herein as a significant pathway, although
its impact is of lesser importance according to data from April 1979 field
studies in New Mexico and Wyoming (see Section 3.2.3.2 and Appendix G). A
recent U.S. Geological Survey study for the Bureau of Indian Affairs (Ku79)
addresses projected effects of runoff over long time periods if wastes and
sub-ore are not stabilized or covered. The study concludes, with essentially
no real data, that stream flows are too small in the sub-basin to transport
wastes. In the larger basins, such as the Rio Puerco, sediment loads are so
great that addition of tailings and, presumably, mine wastes would be insig-
nificant. It is our opinion that additional field study is needed. Overland
flow in a long time period could move radionuclides in the wastes into the
main stream channels. Since this source will be available for many years
after mine closure, if wastes are not stabilized, it may become a major one.
Seepage of contaminated water from mine holding ponds, which are op-
erated to reduce suspended solids concentrations in mine discharge water, is
believed to be insignificant. Since the ponds have relatively small areas,
their seepage losses are small compared to losses by infiltration of releases
to the watercourses. In some mining areas, such as the Powder River Basin,
shallow groundwater quality is naturally poor. Maximum attenuation of con-
taminants is expected in the shallow, poorly permeable bedrock strata of the
Wasatch and Fort Union Formations.
3.3.3 Hydraulic and Water Quality Effects of Surface Mine Discharge
3.3.3.1 Runoff and Flooding in the Model Surface Mine Area
3.3.3.1.1 Study Approach
Precipitation and runoff estimation for the model surface mine scenario
in Wyoming considers three hydrographic units: sub-basin, basin, and
regional basin. Respective surface areas are 11.4, 5,400, and 13,650 square
o
kilometers (km ). The mine is located in the sub-basin. The sub-basin, the
basin, and the regional basin are all drained by ephemeral streams. The
latter is drained by a major regional river that has wide seasonal variations
in flow and is dry or nearly so about 180 days each year. The sub-basin has
similar flow variability. Figure 3.9 depicts the mine in relation to the
sub-basin, basin, and regional basin.
-------
3-69
CAMPBELL COUNTY
i SOUTH
i DAKOTA
Sub-basin area
containing model
mines
I NEBRASKA
CONVERSE COUNTY x--_.-''
20
40
I
(km)
Sub-basin boundary(approximate)
Basin boundary
Regional basin boundary
Figure 3.9 Sketch of sub-basin, basin, and regional basin showing orientation of principal drainage
courses, areas of drainage, and location of mines.
-------
3-70
The first general approach defined quality and volume of mine water
discharge. Hypothetical hydrographic basins were then delineated and flood
flows calculated for return periods ranging from 2 to 100 years. The indi-
vidual and collective effects of discharge from three mines were then evalu-
ated in terms of perennial flow, flood flow, and chemical transport. Of key
importance was an estimation of the extent of perennial streams created by
mine discharge and the influence of contaminants on water quality in the
river draining the regional basin.
3.3.3.1.2 Description of Area
We selected an area of active mining and milling in the South Powder
River Basin of Wyoming for analysis. The area has four active or imminently
active uranium mills and a number of open pit mines. Available data on the
geology, hydrology, and water quality of the area are sparse, but because of
the mining and milling activity are relatively well known for a remote region
like northeastern Wyoming. The study team chose one mining and milling pro-
ject in the area for field investigation in April 1979; hence, additional
data became available and are used herein as appropriate.
Terrain in the area has low rolling hills and an average elevation of
1414 m (MSL datum). Since the climate is not very different from that of
nearby Casper, Wyoming, meteorological data from that station are fairly
representative of the region. There are no relatively large seasonal and
annual variations in precipitation intensity, frequency, and duration. Mean
annual precipitation over a 30-year record period is 28.5 cm and occurs
mainly as scattered thunderstorms in late spring and early summer. These
thunderstorms supply 25 to 50 percent of the total annual precipitation and
are usually of high intensity, short duration, and can be quite local.
Potential pan evaporation averages 110 cm per year and greatly exceeds pre-
cipitation.
Streams in the study area are ephemeral and only exhibit measurable
surface flow during snowmelt and heavy thunderstorm activity. Average total
monthly flow for the period 1948 through 1970 for Lance Creek and the Chey-
enne River at Spencer, Wyoming reveal distinct high- and low-flow periods in
the year (Fig. 3.10). We believe that the streams represent the basin and
regional basin hydrographic units used herein. Large watersheds usually
exhibit measurable surface flow for about 180 days per year. Small water-
sheds, 30 to 40 square kilometers, may not flow at all for several consec-
-------
3-71
Cheyenne River
mean annual flow
Lance Creek
mean annual flow
3 mines mean
monthly flow
2 mines mean
monthly flow
1 mine mean
monthly flow
MONTH
Figure 3.10 Average monthly flows for the Cheyenne River and Lance Creek near Spencer, Wyoming, for the period
1948-1970. (DOI59, DOI64, DOI69, DOI73)
-------
3-72
3
utive years. Mean annual runoff is 0.8 to 1.3 cm or 0.0023 to 0.004 m /sec
2
per km .
Peak flows in the regional basin and basin area are a result of snowmelt
in at least 50 percent of the cases. This is commonly due to temporary but
rapid melting from January to March. High flows can also result from wide-
spread summer storms, but these are the exception. For small basins on the
order of forty square kilometers or less, peak flows occur because of thunder-
storms in the summer months. Thus peak flows in small basins versus the
basin or regional basin commonly occur for different reasons and at different
times in the year. A period of peak runoff from the sub-basin might coin-
cide with a low flow or zero discharge condition in the basin or regional
basin.
In the area of the Morton Ranch project (DOA75) there are 14 sub-basins,
2
the average of which is about 11.4 km . Channel slopes are 11.4 to 31.4 m/km
(average 21.2 m/km), and basin slopes are about 88 m/km. These are tributary
to larger streams with channel slopes of 2.17 to 17.0 m/km (average 6.63
2
m/km), and which drain basins with an area of 5,400 km and a mean annual
flow of 0.80 m /sec. These, in turn, are tributary to a regional basin with
2 3
an area of 13,650 km and mean annual flow of 1.47 m /sec. All three hydro-
graphic units are drained by ephemeral streams. The main stem of the re-
gional system is dry an average of 180 days per year. The basin drains into
the regional basin, assumed here to be the Cheyenne River Basin, which drains
2
an area of 13,650 km (Da75, Lo76, Ra77).
Surface water in the model area is used mainly for stock watering and
irrigation. The amount of irrigated area in the basin is 1400 hectares,
compared to 2800 in the regional basin. Because of extreme variability in
surface flow volume and water quality, almost all municipal water comes from
wells completed in bedrock. Stock water is from both wells and impoundments,
whereas single-family domestic supplies are primarily from wells.
3.3.3.1.3 Method of Study
Because of dilution considerations, flow volume rather than peak dis-
charge rate is of prime concern. For the basin and regional basin areas,
only peak flow rate can be readily estimated on a probability basis for
annual and longer time periods of perhaps 2, 5, 10, etc. years. Peak flow in
the larger hydrographic areas commonly does not coincide with that in the
-------
3-73
smaller basins. Also, there is poor correlation between peak flow rate (Q)
and total flow volume (V) for streams draining large basins. Total flow
volume in the larger basins can be estimated from partial duration flow data.
That is, we can estimate the percentage of the time, during the year, flow
will be of a given magnitude.
Relationships among runoff volume, rainfall, and surface area in small
basins (encompassing less than 30 square kilometers) in the Powder River
Basin have been developed by the U.S. Geological Survey (Cr78) and the Soil
Conservation Service (DOA75). Peak discharge and total annual flow in the
basin and regional basin units were measured by the U.S. Geological Survey
for Lance Creek at Spencer, Wyoming and for the Cheyenne River near Spencer.
We analyzed the effects of perennial or chronic mine discharge on chang-
ing existing ephemeral streams in the sub-basin, basin, and regional basin to
perennial streams using a crude seepage and evaporation model. The basic
equations and approach, explained in Appendix H, are similar to those used in
the Generic Environmental Impact Statement on Uranium Milling (NRC79b).
Adjustments were made for mine discharge rates and infiltration and evap-
oration losses. The main output of the model is an estimate of which stream
segments might become perennial and what the net discharge would be from a
number of mines operating in the same sub-basin. Water quality impacts can
only be very roughly assessed. For the time being, we assume that infil-
tration and evaporation decrease flow but do not effect the chemical mass in
the system. That is, we assume contaminants in mine drainage are deposited
on or in the stream/wash substrate and remain available for transport by
flood water.
The sub-basin is as shown in Fig. H.I (Appendix H) and contains three
3
active uranium mines, each of which discharges 4,320 m /day. Quaternary
alluvium constituting the channel is assumed to have a porosity of 40 per-
cent. The sub-basin contains seven streams or wash segments, three receiving
mine water directly. Water from the mines dissipates by infiltration, evap-
oration, and as surface flow that may leave the sub-basin entirely. Appendix
H shows the basic equations and assumptions and gives a complete summary of
"losses" due to seepage and evaporation as well as any net outflow from the
sub-basin.
-------
3-74
Precipitation-runoff in the Wyoming study area correlates rather closely
to basin size. Basins of about 10,000 km2 area have an annual unit-area
o
runoff of 0.43 cm/yr; whereas an area of perhaps 25 km might have a runoff
of only 5 cm/yr. Decreased runoff (on a unit area basis) associates with
larger basins and reflects water storage, channel losses, and evapo-
transpiration that occur mainly in the tributaries. Impoundments are rarely
on the main stem of streams, where washouts are a problem, but rather on
tributaries. The average impoundment is located about every 130 square
kilometers, is rather small, and is used for stock water. Very infrequently,
small flood-irrigation projects may use impounded water for grasslands.
Seventy-five percent of the annual runoff occurs during the summer thunder-
storm activity in May, June, and July. Snowmelt occurs rather slowly and is
captured in the headwater areas, whereas rainfall events are rather intense
and localized, causing excess flows that reach the main stem, Lance Creek and
Cheyenne River. Sediment loads are high in both the tributary and main stem
streams.
Contaminant concentrations in overland and channel flow during peak run-
off events in the sub-basin are expected to follow the pattern shown in Fig.
3.11, the data for which are from the U.S. Geological Survey (H. Lowham, in
preparation) for a small basin, Salt Wells Creek, in the Green River Basin of
southwestern Wyoming.
Note in the inset of Fig. 3.11 that the washoff peak, that portion of
the runoff enriched in dissolved and suspended materials, precedes the runoff
peak. Runoff in small basins is typically associated with brief but intense
thunderstorms that flush the land surface. Total suspended solids (TSS)
concentrations are disproportionately high in the peak flow events. Dis-
o
charges of 170 m /min carry 100,000 mg/a TSS; whereas flows of 1 cfs might
carry only 500 mg/£. The leading edge of the high flow has the greatest
concentration of suspended solids and dissolved chemical load. Figure 3.12
depicts discharge and specific conductance values as a function of time for
the same small basin in Wyoming. Specific conductance (SC) is a rough mea-
sure of the total dissolved solids (DS) content, following the approximate
relationship: DS = 0.71 SC. Note that the first rise in the flow hydrograph
occurs about three hours after the peak for specific conductance, indicating
the presence of a contaminated "front" laden with salts and other suspended
and soluble materials. The second peak on the flow hydrograph similarly
precedes and is associated with degraded water quality due to this flushing
-------
200,000-
100,000_
50,000-
10,000-
5,000-
I
s
1,000-
500-
i—~%
I
8
CO
100.
0.1
A A
General sediment-transport
characteristics of stream
after flushing by leading
edge of flood wave.
Example hydrograph
showing flushing
action of floodwave.
TIME-
LEGEND
• Low-flow conditions
D Medium-flow conditions, Spring snowmelt
runoff..
• High-flow conditions, rainstorm runoff.
A Samples obtained by automatic sampler of
leading (rising) edge of floodwave.
0.5
T
1
—r
10
—r-
50
—I—
100
T
500 1,000
DISCHARGE, IN CUBIC FEET PER SECOND
I
•^J
U1
Figure 3.11 Suspended sediment concentration to discharge, Salt Wells Creek and tributaries, Wyoming (From U.S.
Geological Survey data, H Lowham, in preparation)
-------
w
o z
i—t •->
w 7
o L
CO
t-H
Q
1.
0
"FLUSHING" OF ACCUMULATED SALTS AND
'MATERIAL FROM DRAINAGE
Specific conductance
N,
Discharge
«
3,000
o
o
LO
C-J
2,000'
to
o
1,000^
8
1800 2400
July 19 I
0600 1200 1800
July 20
TIME (HOURS)
2400 0600 1200
I July 21
1800
Figure 3.12 Relation of discharge and specific conductance to time at Salt Wells creek. Green River Basin, Wyoming.
(From U.S. Geological Survey data, H. Lowham, in preparation.)
-------
3-77
action. About 33 hours after precipitation begins, runoff water quality and
flow very nearly approximate antecedent conditions. This indicates
rather thorough flushing, most of which occurred in an 18-hour period.
Assuming similarity between the surface mining area and the situation
described above, we believe intense flows of rather short duration flush most
of the contaminants from the land surface and stream channels. Although
sub-basin floods are expressed in terms of return period for Wyoming and in
terms of partial duration (1-day, 7-days) and varying return periods for New
Mexico, we believe the basic approaches (total flow vs. partial duration) to
be rather similar because of the "flashy" nature of runoff in both study
areas. In the New Mexico case, the mean discharge rate and the flow volume
for the 7-day event are very often less than that for the 1-day event for the
same return period. This also confirms the intense, short-term nature of
runoff processes in the Wyoming and New Mexico model areas.
3.3.3.1.4 Discussion of Results
This section addresses the interaction between mine drainage and flood
waters. Flood magnitude is addressed first, followed by calculation of water
quality effects due to mine water. The U.S. Geological Survey technique
(Cr78) for estimating floods in small basins in northeastern Wyoming was used
to estimate peak discharge and total flow volume in the sub-basin. Multiple
regression analysis reveals that the variables of area, slope, and relief
provide roughly 90 percent correlation between rainfall and runoff (Cr78).
Considering the numerous assumptions made throughout the analysis, only the
area variable is used herein. It accounts for 70 percent of the flow. Table
3.23 shows the peak discharge rate and total flow volume from the sub-basin
for floods with recurrence intervals (r) of 2 to 100 years. The basic equa-
tion for calculating discharge rate or flow volume is--
0 or V = a Abl (3.1)
r r
where a = regression constant
b, = drainage area coefficient for area: peak discharge area: volume
relationships
A = basin area
= 11.4 km2
0 V discharge rate and flow volume for flooding events with return
yr' r
periods of 2, 5, 10, 25, 50, 100 years.
-------
3-78
The flow volume for the two-year flood is 32,921 m , and the instan-
taneous peak flow rate is 387 m /min. For comparison, we assume that the
o 63
model mine discharges 3.00 m /min or 1.6 x 10 m per year. Assuming the
^j
annual flood volume is 30,000 m , it is apparent that annual dilution is
essentially nil and can be expected to be zero for perhaps 8 to 10 months of
the year when there is no natural runoff. As Table 3.24 shows, flow volumes
calculated using the Soil Conservation Service (DOA75) methodology average
1.5 times greater than those derived using the USGS approach. The latter are
used herein in the interests of conservatism, i.e., there is less volume for
dilution of contaminants.
Table 3.23 Peak discharge and total volume for floods of 2, 5, 10, 25, 50
and 100 year recurrence intervals
Recurrence
Interval , r,
in years
2
5
10
25
50
100
Regression
Constant, a
9.62
18.08
24.87
34.71
42.82
51.58
0.
0.
0.
0.
0.
0.
bl
689
713
727
739
748
756
Volume
(m3)
32921
64116
90009
127862
159920
194937
Regression
Constant, a
96.
199.
292.
441.
575.
731.
21
6
8
1
4
1
b
0
0
0
0
0
0
1
.582
.612
.632
.660
.679
.699
Peak
Discharge
(m /min. )
387
840
747
1269
2674
3500
Peak flood discharges in the basin and regional basin range from 4,053
3
to 31,401 m /min for recurrence intervals of 25 years or less. For 50- and
100- year flooding events, peak discharge approximates 19,370 to 44,860
3 3
m /min. In the regional basin, discharge is 1.7 m /min or less approximately
3
eight months of the year and equals or exceeds 17 m /min for about three
months of the year, typically in the winter and early spring.
-------
3-79
Maximum discharge from the basin and sub-basin is expected in the late
spring and early summer months because of thunderstorms. At this time, flow
in the river draining the regional basin is also at or near maximum, thus
there is high probability for considerable dilution of runoff contaminated by
mine drainage.
Total flow volumes for the basin and regional basin were estimated from
U.S. Geological Survey records for the period 1948 to 1970. Figure 3.10
shows average monthly flows in cubic meters for the Cheyenne River and Lance
Creek near Spencer, Wyoming. Immediately apparent is the close similarity in
overall runoff pattern for the year.
Table 3.24 Summary of calculated total flow in the Wyoming model area
sub-basin using the USGS and SCS methods
Recurrence
Interval, r,
in years
Sub-basin
Total flow (m3)(a)
Sub-basin
Total flow (m3)(b)
2
5
10
25
50
100
^Source: Cr78.
(b)Source: DOA75.
'C'NC = Not calcul
32,921
64,116
90,009
127,862
159,920
194,937
a ted.
14,467
NC(c)
98,419
170,815
231,618
295,257
Minimum flows occur in November, December, and January, and peak runoff in
both basins occurs in May, June, and July. Long-term average annual flow in
the basin is 2.18 x 107 m3 and 5.64 x 107 m3 in the Cheyenne River. These
2
are almost exactly proportional to the respective basin areas of 5,360 km
and 13,650 km2, indicating similar climatic and runoff conditions.
-------
3-80
Assuming there are 3 mines operating for a 17-year period and that each
o
mine discharges on the average 3.00 m/min continuously, total annual flow
fi o
volume from the mines is 4.7 x 10 m . Cumulative discharge from the sub-
basin is 7.04 m3/min or 3.7 x 106 m3/yr, which causes development of a
perennial stream 12.8 km long within the basin. Insofar as the basin channel
length is 141 km, the perennial stream ceases to flow well within the basin.
Appendix H explains the methodology and intermediate steps involved in
deriving these foregoing values. Mine drainage water is not expected to flow
the full length of Lance Creek or reach the Cheyenne River. However, on the
basis of total monthly flow, the volume of mine drainage from one mine ex-
ceeds the flow in Lance Creek and the Cheyenne River for three months of the
year, whereas flow from three mines exceeds basin flow for five months and
regional basin flow for four months each year (Fig. 3.10).
The aqueous pathway for mine drainage is considered in terms of chronic,
perennial transport in the mine water, per se, and transport by flood waters
that periodically scour the channels where most of the sorbed contaminants
would be located. Considering the random nature of flooding and the re-
sulting uncertainty as to when the next 2-, 5-, or 10-year, etc. flood may
occur, it is assumed that most contaminants accumulate on an annual basis and
are redissolved by floods of varying return periods (2 to 10 years) and
volumes. Many combinations of buildup and flooding are possible, such as
buildup for 5 years or 10 years with perhaps several 2-year storms and one
5-year storm. Insofar as numerous assumptions are made in calculating volume
and quality of mine discharge, basin runoff, and fate of the contaminants in
the aqueous system, use of annual accretion and varying flood volumes in the
sub-basin is considered adequate for estimating flood water quality.
Dilution of contaminated flows originating in the sub-basin and ex-
tending into the basin were conservatively calculated by assuming that the
total flow during the low period equaled the mean annual flow. Thus, high
flows and associated increased dilution are ignored, tending to make the
analysis conservative. Contaminated flows from the sub-basin are diluted
into these adjusted mean annual flows. Definition of the source term on an
annual basis is most compatible with the radiation dose and health effects
calculations in Section 6. Use of the low flow segment of the total annual
-------
3-81
flow regime is decidedly conservative since total flow during the five months
of low flow conditions amounts to 111,610 m3 and 218,336 m3 for the basin and
regional basin, respectively. Average annual flow for the period of record
(22 years) is considerably higher, amounting to 2.184 x 107 m3 for the basin
7 3
and 5.64 x 10 m for the regional basin.
Runoff in the basin and regional basin is expected to markedly dilute
contaminated flood flows originating in the basin. Such floods would scour
contaminants from about 23 kilometers of channel affected by contaminants
from the three active mines. Peak runoff events in the sub-basin are most
likely in the late spring-early summer season when runoff in the basin and
regional basin is the maximum or near maximum, on the average. However, peak
runoff from the sub-basin could also occur when the basin and regional basin
are at low flow or zero discharge. Such contrasts are present between the
basin and regional basin flow regimes. From September through December,
Lance Creek can be expected to have no discharge from 45 to 65 percent of the
time, whereas the Cheyenne River will be dry, on the average, from 65 to 85
percent of the time (Fig. 3.13). Thus there is a distinct chance that
contaminants transported in Lance Creek would not be immediately diluted upon
reaching the Cheyenne River.
Before discussing the calculated concentrations of contaminants in the
basin and regional basin streams, several other conditions need to be men-
tioned. In water-short regions like Wyoming, extensive use is made of im-
poundments to capture and store runoff. On Lance Creek, the model for the
c o
basin, the volume of existing impoundments is 15.78 x 10 m or 72 percent of
the annual average runoff. In the regional basin, modeled after the Cheyenne
7 ^?
River, there are 4.2 x 10 m of storage volume, which is 74 percent of the
average flow of 56.4 x 106 m . Thus, it is very likely that discharge from
the sub-basin or basin will not exit the basin, particularly in the periods
of low flow. Contaminant concentrations, particularly those affected by
sorption and precipitation reactions, are likely to be reduced as a result of
sedimentation and long residence time in the impoundments, although there is
some potential for overtopping, disturbance by cattle, and so on. Signif-
icant adverse impacts are not likely considering precipitation and sorption
reactions which are likely to remove contaminants from the food chain. Proof
of this is lacking and we recommend confirmatory studies for the stable ele-
ments. Previous studies (Ha78; Wh76) emphasized radiological contaminants.
-------
100 —
90 —
o 80 —
C£
cr
a:
70 —
60
o
£ 50 —
o
40 —
30 —
20 —
10 —
UJ
a:
UJ
D_
0
Cheyenne River
(Annual 0-Flow days X=55.7%)
Lance Creek
(Annual 0-Flow days X=42.9%)
JAN
j
FEB | MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
I
oo
to
Figure 3.13 Periods of no flow in Lance Creek and the Cheyenne River near R iverton, Wyoming for the period 1948-1978
(Summarized from flow records provided by H. Lowham, U.S. Geological Survey, Cheyenne, WY.)
-------
3-83
Radium-226 is strongly sorbed onto stream sediments and (or) it is
subject to precipitation. Partial re-solution in subsequent floods occurs
but it is assumed that only 10 percent of the mass deposited on an annual
basis goes back into solution in flood waters. The rationale for this
assumption is based on laboratory studies (Sh64; Ha68), field data from New
Mexico (Ka75; Ku79), and review of the literature. Pertinent field and
laboratory data specific to surface water quality in the Wyoming uranium
mining areas are scarce, although studies by the State (summarized by Harp,
1978) are noteworthy. Sulfate is regarded herein as rather mobile and, as
such, most of it infiltrates the shallow aquifer. Therefore, only 20 percent
of the mass from a given mine on an annual basis is assumed available for
re-solution in flood waters. The fate of zinc, arsenic, and cadmium is in-
sufficiently understood to predict what fraction in the mine discharge will
be removed from solution versus remain available for re-solution. Studies
along these lines are necessary. Similarly, not all of the contaminants
potentially present in mine waters from Wyoming are necessarily shown in
Tables 3.21 and 3.25, which were developed based on available data from NPDES
permits, environmental reports, and environmental impact statements. In the
case of suspended solids, there is no calculation of non-point source con-
tributions from mined lands. Sediment loads from such sources could be
locally significant, but mined land reclamation and natural recovery seems to
effectively mitigate problems. Only suspended solids from mine drainage, per
se, are considered.
Table 3.25 shows the flood flow volumes (in the sub-basin) associated
with events having return periods of 2, 5, 10, 25, 50, and 100 years. Also
shown are the contaminant concentrations calculated from the annual contami-
nant loading diluted into the foregoing floods. As expected, concentrations
are high because of the low dilution volumes associated with the small sub-
basin. Surface water in the sub-basin might be impounded therein for use by
stock or, less possibly, irrigation, but it is more likely that the principal
impoundments would be in the larger hydrographic unit, the basin. The flood
flow volumes shown represent runoff from the entire sub-basin. When the
second and third mines begin to discharge, the annual loading and concen-
tration values shown would have to be doubled or tripled. The reader should
remember that background concentrations already present in flood runoff would
be additive to the values in Table 3.25. However, these have been assumed
-------
Table 3.25 Annual contaminant loading from one uranium mine and resulting concentrations
in floods within the sub-basin for return periods of 2 to 100 years
Contaminant and
concentration in
mine effluent
Total uranium 0.070
Radium- 226 4.1
Total sus-
pended solids
Sulfate
Zinc
Cadmi urn
Arsenic
20.9
875
0.071
0.004
< 0.005
mg/ a
pCi/ a
mg/
mg/
mg/
mg/
mg/
£
t
i.
t
t
Chemical mass available
•Flood flow volumes (m ) and contaminant concentrations associated
with return periods of 2 to 100 years^0'
for transport on an annual V_ = 32921 V& = 64116
basis Cy C5
110
0.00065
32,955
275,940
112.0
6.31
7.88
kg/yr
Ci/yr(a)
kg/yr
kg/yr
kg/yr
kg/yr
kg/yr
3.34 1.72
19.7 10.1
1001 514
8381 4304
3.40 1.75
0.192 0.098
0.239 0.123
VIQ = 90009
C10
1.22
7.2
366
3066
1.24
0.070
0.088
V25 = 127862
C25
0.86
5.1
258
2158
0.876
0.049
0.062
V5Q = 159920
C50
0.69
4.1
206
1723
0.700
0.039
0.049
V100 = 194937
C100
0.
3.
169
1416
0.
0.
0.
56
3
575
032
040
Ten percent of the annual loading is assumed available for solution. The balance is assumed sorbed onto sediments or present in
insoluble precipitates.
^ 'Twenty percent of the annual loading is assumed available for transport and the balance is assumed to have infiltrated to the water
table or it is present as an insoluble precipitate.
^C'V and C refer to, respectively, flood volume, in cubic meters, and concentration in milligrams per liter or picocuries per liter for an ^
r-year flood. Concentrations are in milligrams per liter except radium-226, in
Note.—Assumptions: Mine discharges continuously at a rate of 3.00 m /min and concentrations are the average of those shown in Table 3.21.
All suspended and dissolved contaminants remain in or on the stream sediments and are mobilized by flood flow.
-------
3-85
equal to zero in order to estimate incremental increases due to mining and to
simplify the calculations.
Table 3.26 shows contaminant concentrations in the basin and regional
basin streams from the discharge of one mine. For cases involving two or
more mines, the concentration shown would be scaled up by a factor of two or
more. Basically, the table shows the effects of taking contaminated flood
waters from the sub-basin and diluting them in the low flow volume of the
basin and regional basin. As expected, concentrations decrease with floods of
greater volume and longer return period. Additional dilution occurs when
discharge from the basin enters the regional basin. Taking the two-year
runoff event in the sub-basin, for example, uranium is diluted from 3.34 mg/£
(Table 3.25) to 0.76 mgA in the basin and then to 0.44 mg/£ in the regional
basin. There is some question as to whether the lesser sub-basin floods,
particularly those with return periods of 25 years or less, would actually
flow the length of the basin and enter the regional basin. Because much of
the 22.7 km reach of stream directly affected by mine discharge is located in
the basin, it is conservatively assumed that the contaminants will reach the
basin and eventually the regional basin. The foregoing analysis is struc-
tured as a worst-case, maximum-concentration scenario.
Concentrations of contaminants in flood waters affected by mine drainage
are compared to water standards for potable and irrigation uses (Table 3.27).
Radium-226 concentrations in the basin and regional basin streams (Table
3.27) range from 1.6 to 4.5 pCi'A and are below the drinking water standard
(for Ra-226 + Ra-228) of 5 pCi/£. Uranium concentrations range from 0.26 to
0.76 mg/e, , which is roughly equivalent to 176 to 514 pCi/£. On the basis of
chemical toxicity alone, such concentrations would probably present no prob-
lem for short periods, but radioactivity is another matter. Reevaluation of
the standard for uranium in potable water is presently receiving attention
within the Agency (R. Sullivan and J. Giedt, USEPA, oral communication,
1980). Briefly, there is consensus that the radiotoxicity of uranium is
similar to that of radium-226 and 228. For continuous ingestion at a rate of
2 liters per day, it is suggested that potable water contain no more than 10
pCi/£ (0.015 mg/£) natural uranium to reduce the incidence of fatal cancers
to no more than 0.7 to 3 per year per million population (Office of Drinking
Water guidance to the State of Colorado, July 7, 1979). Realizing that the
-------
Table 3.26 Concentrations In basin and regional basin streams as a result of surface mine discharge
Parameter
Concentrations (mgA ; pCi£ in the case of radium)
in basin discharge under low flow conditions due
to influx of sub-basin floods with 2, 25, and 100
year return periods^'
C2 C25 C100
Concentrations {mgA ; pCiA in the case of radium) in regional
basin discharge under low-flow conditions due to influx of basin
discharge, also under low-flow conditions, and sub-basin floods
with 2, 25, and 100 year return periods
(b)
"lOO
Total Uranium
Radium-226
Total Susp. Solids
Sulfate
Zinc
Cadmium
Arsenic
0.76
4.5
228
1909
0.774
0.044
0.054
0.46
2.7
138
1152
0.468
0.026
0.033
0.36
2.1
107
900
0.366
0.020
0.025
0.44
2.6
131
1098
0.445
0.025
0.031
0.32
1.9
95
797
0.324
0.018
0.023
0.26
1.6
79
668
0.271
0.015
0.019
^'Calculated as follows: Assuming a two year flood, uranium concentration in the outflow from the sub-basin equals 3.34 mg/i and flow
equals 32,921 m (see Table 3.25). Average total flow for 5 months of low flow conditions in the basin equals 111,610 m . The concentration
in the basin outflow, after dilution of the contaminated inflow from the sub-basin for floods of varying recurrence intervals equals:
''Basin
(b)
Hence,
VSub-bas1n x°Sub-bas1n
0.76 mg/j.
(32921 itT) (3.34 mg/i )
Basin) 32921 m3 + 111610 m3)
a" above, except average total flow volume for 5 months of low flow in the regional basin equals 218,336
Regional basin
(Sub-basin
Calculations similar to "»"
C,
M r
Sub-basin x Sub-basin
V V
(Sub-basin + Regional Basin)
oo
CTv
-------
Table 3.27 Comparison of potable and irrigation water standards and surface water quality affected by surface mine drainage
Parameter
Range of contaminant concen-
trations in flood flow
affected by mine discharge^'
Basin Regional Basin
Min. Max. Min. Max.
Potable water standards
(b)
Irrigation
(c)
Maximum Permissable
Concentration
)
Recommended Limiting
Concentration
Recommendations for maximum concentration
for continuous use on all soils (mg/j )
Total U
Ra-226 + 228
TSS
Sul fate
Zinc
Cadmium
Arsenic
0.36
2.1
107
900
0.366
0.02
0.025
0.76
4.5
228
1909
0.774
0.044
0.054
0.26
1.6
79
668
0.271
0.015
0.019
0.44
2.6
131
1098
0.445
0.025
0.031
0.015/3. 5/0. 21(d)
5 pCi/jj,
— —
250
5.0
0.01
0.05 0.01
—
5 pCi/£
—
200
2.0
0.010
0.10
^'Concentrations in milligrams per liter, except Ra-226 -228 which are in picocuries per liter.
* ^Sources: U.S. Environmental Protection Agency (EPA76) and, in the case of uranium, suggested guidance from the National Academy of
Sciences (NAS79) to the USEPA and from USEPA (Office of Drinking Water) to the State of Colorado (La79).
(^Source: NAS72.
' '0.015 mg/s, : Suggested maximum daily limit based on radiotoxicity for potable water consumed at a rate of 2 liters per day on a
continuous basis.
3.5 mgA : Suggested maximum 1-day limit based on chemical toxicity and intake of 2 liters in any one day.
0.21 mgA : Suggested maximum 7-day limit based on chemical toxicity and intake of 2 liters per day for 7 days.
00
-------
limit of 10 pCi/£ (0.015 mg/A ) may not be cost effective, the Agency is
contracting to develop the economic and technical basis for a uranium (in
water) standard. The National Academy of Science, at the request of the
Agency, evaluated the chemical toxicity of uranium. A maximum, 1-day concen-
tration of 3.5 mg/j, (7 mg/day based on daily intake of 2 liters) is the
"Suggested No Adverse Response Level" (SNARL). The corresponding concen-
tration for a 7-day period is 0.21 mg/£ .
There are numerous complicating factors surrounding the foregoing sug-
gested radiotoxicity and chemical toxicity limits for uranium. These include
economic justification, technical feasibility, gut to blood transfer factors,
and overall health of the receptor, to name a few. Of importance is the fact
that a stricter standard for uranium in water is likely and that present
NPDES limits of 1 mg/£ or previous drinking water limits on the order of 5 to
8 mg/£ are or will be superseded. For these reasons, the calculated uranium
concentrations in the aqueous pathway are considered relative to the more
recent, suggested limits of 0.015, 3.5, and 0.21 mg/£ .
Although mine effluents are not considered potable water, they infil-
trate shallow aquifers that are potable in terms of the Safe Drinking Water
Act. The extent to which shallow aquifers in uranium mining areas are used
for potable water supply is presently small, but accurate surveys of well lo-
cations and water quality are scarce. If a limit of 0.015 mg/£ for uranium
in potable water is set, it appears that uranium instead of radium-226 may be.
the primary pollutant of concern in both surface runoff and related shallow
groundwater.
Of the remaining contaminants, sulfate and possibly cadmium might exceed
drinking water standards. Cadmium may also limit use of the water for irri-
gation. These results provide only a rough estimate of water quality ef-
fects. There are other stable toxic elements to consider, but there are
insufficient data. Multiple mine sources would increase the concentration,
but ion exchange, sorption, etc. would reduce them. The net effect is simply
unknown. It does appear that uranium, in particular, deserves additional
study in light of new interpretations concerning radiotoxicity.
-------
3-89
3.3.3.2 Impacts of Seepage on Groundwater
The previous analysis assumed no infiltration (to groundwater) of dis-
solved or suspended contaminants, thereby creating a maximum or worst-case
situation with respect to transport via floodwaters. In fact, contaminants
will also infiltrate through the stream deposits. Anions and selected stable
elements like uranium, selenium, and molybdenum are most likely to migrate
downward. Insofar as the alluvial, valley fill aquifer may be used locally,
particularly in the case of larger drainage basins and the regional basin,
some analysis of potential impacts is offered herein.
Effects of mine drainage impoundments used to settle suspended solids
are excluded from the present analysis. Such impoundments are relatively
small, commonly less than 1 or 2 hectares, and tend to become self-sealing
due to settling of fines. Potable water supplies at the mines are usually
from deep exploration borings converted to water wells or from mine water.
Problems may exist with such water being contaminated, as has been documented
in the Grants Mineral Belt (EPA75), but we do not believe seepage from set-
tling ponds to be a factor.
Infiltration of water discharged to ephemeral stream courses was not
calculated separately. It was combined into a lumped term incorporating
infiltration and evaporation. Both losses are, in part, a function of sur-
face area. Infiltration takes place primarily in the basin. When three
mines are operating, 22.7 km of perennial stream is created and extends into
a portion of the basin. Infiltration of the mine effluent adds primarily to
the amount of water in storage in the alluvium, versus acting as a source of
recharge to the deeper, consolidated strata.
As with many of the intermontane basins in Wyoming, water in the South
Powder River Basin is primarily groundwater recharged by sporadic runoff from
limited precipitation (Ke77). Some stock ponds that collect surface runoff
are supplemented by groundwater from wells or springs. Mine water discharged
from one underground mine is used to irrigate approximately 65 hectares of
native grass, alfalfa, oats, and barley. In general, groundwater is not used
for irrigation (Ho73). Groundwater use for domestic supplies is largely
confined to the Dry Fork of the Cheyenne River (Ke77). The number of wells is
close to a density of one per 400 ha (Ke77). Typical wells are completed in
the alluvium and yield less than 100 £ /min.
-------
3-90
Geological formations in the southern portion of the Powder River Basin
include in descending order and increasing age; the 1) Alluvium, 2) Wasatch
Formation, 3) Fort Union Formation, 4) Lance Formation, 5) Fox Hills Forma-
tion, and 6) older rocks too deep to be affected by uranium mining (NRC78c).
Table 3.28 shows the well depth for each formation, anticipated well yields,
and the total dissolved solids content in the vicinity of an active uranium
mining and milling project in the South Powder River Basin.
Water quality in the Wasatch and Fort Union Formations ranges widely and
appears to correlate with the permeability of the water-bearing sand and
proximity to outcrops. No relation of water quality to depth is apparent.
Analyses of water from Cenozoic rocks show dissolved solids ranging from less
than 100 to more than 8000 mgA, (Ho73). Of the 258 analyses performed by the
USGS, 55 showed dissolved solids less than 500 mg/a , 133 less than 1000 mg/£,
and 125 more than 1000 mg/jj, . Sodium, sulfate, and bicarbonate are the dom-
inant ions, and water is usually excessively hard. Iron is character-
istically a problem in water from the Wasatch and Fort Union Formations
(Ho73). Element distributions show considerable variability due to clay
lenses in the sandy units (NRC78c). The clays act as barriers to groundwater
movement and preferentially concentrate some elements. Table 3.29 shows the
ambient groundwater quality in the immediate area of three active mills in
\ the South Powder River Basin.
3
In the Wyoming model mine sub-basin, total inflow equals 9 m /min or
CO C O
4.73 x 10 m /yr, and total annual infiltration loss equals 4.65 x 10 m
(calculated in Appendix H). Restated, 98.2 percent of the discharge infil-
trates and the remainder evaporates.
6 3
Infiltration of 4.65 x 10 m /yr is not likely to continue for the full
duration of mining unless the bedrock strata have the same or similar perme-
ability as the alluvium and (or) there is an extensive zone of unsaturated
alluvium to provide storage. The alluvium in the Wyoming study area is
concentrated along the stream axes, is relatively thin, and is underlain by
less permeable bedrock strata. It is probable that a zone of saturated
alluvium will gradually develop and extend downstream as mine discharge con-
tinues. Recharge from the alluvium to the underlying Wasatch or Fort Union
Formations will occur but at a low rate compared to infiltration. Water
quality in the alluvium is highly variable (Table 3.29); it may or may not be
affected by mine drainage. Adverse impacts, if any, are likely to be a
result of uranium, sulfate, and mobile elements.
-------
Table 3.28 Northeastern Wyoming groundwater sources
Geologic Period
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Pennsylvanian
Mississippian
Ordovician
Cambrian
Aquifer
Alluvium
Wasatch
Fort Union
Lance
Fox Hills
Mesaverde
Cody
Frontier
Dakota
Sundance
Spearfish
Minnelusa
Pahasapa
Bighorn
Flathead
Depth Range
of Wells, m
3-30
12-300
45-180
45-365
210-700
12-915
30-335
20-610
75-1830
120-210
6-275+
75-1980
150-2320
0-60
20-1800
Anticipated Well Yield, £pm
Common
20-945
4-150
4-110
4-190
75-260
57-150
4-20
4-20
95-380
4-20
4-115
95-950
380-9460
3785
760
High
1140-2270
380-2370
380
1900
760-1900
225-265
380-760
380-1135
760-3410
95
380-760
1860-7470
26,500-35,600
3785
Total Dissolved
Solids, mg/fc
106-7340
160-6620
484-3250
450-3060
1240-3290
550-1360
6392-12,380
390-2360
218-1820
894-2310
2590
255-3620
290-3290
427-3219
124
Source: NRC78b.
CO
I
-------
3-92
Table 3.29 Groundwater quality of wells sampled by the three major
uranium producers in the South Powder River Basin, Wyoming
Parameter
Range of Concentration Reported
Kerr-McGee
(a)
TVA
(b)
Exxon
(c)
PH
Spec. cond.
umhos/cm
Ca
Mg
Na
HC03
so4
Cl
Zn
Fe
Ba
Radium (pd/a)
Uranium (mg/£)
7.4-8.0
210-1100
28-343
8-81
5-71
30-380
28-980
<5-57
0.006-18.0
0.41 - 5.18
< 0.002- 2.3
7-4 - 8.5
250-1300
10-200
2-80
10-300
70-110
8-1000
11-25
0.03 -3
0.2 -20
0.2 -18
0.002-60
7.3-8.1
290-600
26-150
1-13
54-121
90-412
58-575
6-16
ND- 0.14^
0.01- 1.64
ND- 0.05
0.4 -12.0
0.0004 - 0.21
^'Shallow wells up to 61 meters depth, Tables 2.6-7 through 2.6-10 of
reference Ke77.
(b)
(c)
(d)
From Figs. Cl and C3 of reference NRC78b.
Table 2.12 of reference NRC78d.
ND: Not detectable.
-------
3-93
An actual example of this saturated front developing and moving down-
gradient is present at the Kerr-McGee Nuclear Corporation's Bill Smith Mine
in South Powder River Basin (Ke77). The mine discharges to a tributary of
Sage Creek at a rate of about 1.7 m /min. From the period January 1974 to
late 1976, a flow front 23 km long developed as a result of infiltration into
the sandy alluvium. The discharge water maintains a high groundwater level
in the stream bed. Unfortunately, no information is available on the geo-
metry of the stream channel to evaluate the volume of water that has infil-
trated in the three-year period or on any water quality changes that have
occurred.
In summary, additional field data are needed to properly address the
water quality effects of infiltration. Both theory and at least one field
example indicate extensive infiltration of effluent containing at least some
mobile stable and radioactive contaminants. Therefore, we recommend addi-
tional field investigations to determine, at the minimum, any hydraulic and
water quality effects of mine discharge on shallow aquifers and the influence
of dewatering on regional water levels and water quality, regardless of pre^
existing or anticipated local water use patterns.
3.3.4 Gases and Dusts from Mining Activities
Dusts and toxic gases are generated from routine mining operations.
Combustion products are produced by large diesel and gasoline-powered equip-
ment in the mine and by trucks transporting the overburden, ore, and sub-ore
from the pit to storage pile areas. Dusts are produced by blasting,
breaking, loading, and unloading rock and ore and by haulage trucks moving
along dirt roads. Finally, Rn-222 will emanate from exposed ore in the pit
and from the ore as it is broken, loaded, and unloaded. These sources will
be discussed individually.
3.3.4.1 Dusts and Fumes
Most vehicular emissions are from the combustion of hydrocarbon fuels in
heavy-duty, diesel-powered mining equipment. Surface mines produce con-
siderably more emissions than underground mines, since the overburden must be
removed before the ore can be mined. The principal emissions are parti-
culates, sulfur oxides, carbon monoxide, nitrogen oxides, and hydrocarbons.
The quantity of these combustion products released to the atmosphere depends
on the number, size, and types of equipment used.
-------
3-94
The EPA estimates the following emissions from mining 1350 MT of ore per
day from a surface mine (Re76).
Emissions per Operating Day, kq/d
Pollutant Mining Operations Overburden Removal
Particulates 17.0 18.9
Sulfur oxides 35.4 39.3
Carbon monoxide 294.2 327.4
Nitrogen oxides 484.6 538.4
Hydrocarbons 48.4 53.8
Assuming a 330 operating-day-year (Ni79), we adjusted these emission rates to
ore production for the average surface mine (1.2 x 10 MT/yr) and the average
large surface mine (5.1 x 10 MT/yr) as described in Sections 1.3.1 and
3.3.1. Table 3.30 shows the total airborne combustion product emissions.
These estimated emission rates are somewhat higher than rates previously
suggested by the U.S. Atomic Energy Commission (AEC74).
Table 3.30 Estimated air pollutant emissions from heavy-duty
equipment at surface mines
Pollutant
Particulates
Sulfur oxides
Carbon monoxide
Nitrogen oxides
Hydrocarbons
Average Mine^ '
3
7
55
91
9
Emissions, MT/yr^a'
Average Large Mine^c'
14
28
235
387
39
^a'Based on (Re76) and 330 operating days per year (N179).
bW production = 1.2 x 105 MT/yr.
c\ 5
'Ore production = 5.1 x 10 MT/yr.
-------
3-95
Dust is produced from blasting, scraping, loading, transporting, and
dumping ore, sub-ore, and overburden. Additional dust is produced when the
ore is reloaded from the stockpile for transportation to the mill. Dust
emissions vary widely, depending upon moisture content, amount of fines,
number and types of equipment operating, and climatic conditions. Because
ore is usually wet, the relative amounts of dust produced from mining and
handling it are usually small. We selected the following emission factors
from those suggested by the EPA for the above listed mining activities (Hu76,
Ra78, Da79):
Blasting = 5 x 10"4 kg dust/MT
Scraping and bulldozing = 8.5 x 10 kg dust/MT
Truck loading = 2.5 x 10"2 kg dust/MT
_2
Truck dumping = 2 x 10 kg dust/MT
We applied these emission factors to the ore, sub-ore, and overburden
production rates of the average mine and average large mine and estimated
average annual dust emissions for these mining activities (see Table 3.31).
These are probably maximum emission rates because blasting is not always
required, and some emission factors appear to have been based upon data from
crushed rock operations, which would contain more fines than rock removed
from surface mines. One-half the emission factor values were applied to ore
and sub-ore because they are usually wet, except when reloading ore from the
stockpile, in which case it is assumed to have dried during the 41-day resi-
dence period (Section 3.3.1.2).
The movement of heavy-duty haul trucks is probably the largest single
source of dust emissions at surface mines. An emission factor (EF) for this
source can be computed by the following equation (EPA77b).
EF = 2.28 x 10'4 (s) M 365_w (TF) (f) (3.2)
48 365"
where,
EF = Emission factor, MT/vehicle kilometer traveled (MT/VKmt),
S = Silt content of road surface, percent,
-------
3-96
M2
V = Vehicle velocity, kmph [Note: This term becomes 143
for velocities less than 48 km/hr (EPA77b, DA79)]}
W = Mean annual number of days with 0.254 mm or more rainfall,
TF = Wheel correction factor, and
f = Average fraction of emitted particles in the <30 ym diameter sus-
pended particle size range; particles having diameters greater
than 30 ym will settle rapidly near the roadway.
Values selected for these terms in the solution of Equation 3.2 are --
S = 10 percent (Da79),
V = 32 km/hr for heavy-duty vehicles and 48 km/hr for light vehicles
p
(therefore, the velocity term is (32/48) and (48/48), respectively),
W = 90 days (EPA77b),
TF = 2.5 (Da79) (heavy-duty vehicles only), and
f = 0.60, since the weight percent of particles of less than 30 ym
and greater than 30 y m in diameter is generally considered to
be 60 and 40 percent, respectively (EPA77b).
•3
Substituting these values into Equation 3.2 yields 1.15 x 10 MT/VKmT and
_3
1.03 x 10 MT/VKmt for the emission factors of heavy-duty haul trucks and
light duty vehicles, respectively.
Table 3.31 shows estimated dust emissions for the movement of heavy-duty
haul trucks using the following information:
-------
Table 3.31 Average annual dust emissions from mining activities
Dust Emissions, MT/yr
Mining Activity
Blasting
Scrapi ng/bul 1 dozi ng
Truck Loading
Total at Pit Site
Truck Dumping
Reloading stockpiled ore^6j
Total at Pile Sites
Vehicular dust^ '
Wind suspended dust
from storage piles
Average Mine^3'
Ore(c)
0.03
NA(d^
1.5
1.53
1.2
1 3.0
4.2
14
10
Sub-ore^ '
0.03
NA
1.5
1.53
1.2
NA
1.2
14
3
Overburden
3.0
51
150
204
120
NA
120
304
30
Average Large Mine^ '
Ore(c)
0.13
NA
6.4
6.53
5.1
13
18.1
59
44
fcl
Sub-orev '
0.13
NA
6.4
6.53
5.1
NA
5.1
59
10
Overburden
20
340
1000
1360
800
NA
800
2020
94
on annual production rates of 1.2 x 10 MT of ore and sub-ore and 6.0 x 10 MT of overburden,
^ 'Based on annual production rates of 5.1 x 10 MT of ore and sub-ore and 4.0 x 10 MT of overburden.
ir\
v 'Assumed wet.
(d)
(e)
(f)
NA - not applicable.
Assumed dry.
Dust emissions from heavy-duty vehicular traffic along ore, sub-ore and overburden haul roads.
-------
3-98
EF = 1.15 x 10"3 MT/VKmt,
Truck capacities = 31.8 MT for ore and sub-ore and
109.1 MT for overburden (Da79),
Round-trip haul distance = 3.2 km to ore and sub-ore piles
and 4.8 km to overburden dump, and
Annual production rates = given in Section 3.3.1 and in the
footnotes of Table 3.31.
Additional dust emissions will occur from the movement of light-duty
vehicles along access roads. Using the emission factor derived above (1.03 x
10 MT/VKmT) and assuming that there are 24 km of access roads traveled 4
times a day for 330 operating days per year, about 33 MT of dust will be
produced from this source annually. Emissions during haulage road main-
tenance is relatively small and will not be considered.
Table 3.31 also shows average annual dust emissions from wind erosion of
overburden, sub-ore, and ore piles at the model surface mines. For these
computations, we assumed the model overburden pile to be that of Case 2 and
in the shape of a 65-m high truncated cone (Table 3.11). The same was
assumed for the average mine, except the pile height was 30 m. The sub-ore
piles of both mines were assumed to have a truncated cone configuration
(Table 3.20). The same configuration was also assumed for the ore piles, but
the pile heights were 9.2 m for the average large mine and 3.1 m for the
average mine (Table 3.17).
Emission factors, computed in Appendix I, are 0.850 MT/hectare-yr for
overburden and sub-ore piles and 0.086 kg/MT for the ore stockpiles. The
first emission factor was multiplied by the overburden and average sub-ore
pile areas; the second factor was multiplied by the annual ore production.
In computing the Table 3.31 dust emissions, we assumed no effective dust
control program and that there was no vegetation on overburden and sub-ore
piles. Haul roads are normally sprinkled routinely during dry periods, and
stabilizing chemicals are applied primarily to ore haul roadways at some
mines. Sprinkling can reduce dust emissions along haul roads by 50 percent,
and up to 85 percent by applying stabilizing chemicals (EPA77b, Da79).
-------
3-99
The dust emissions from vehicular traffic (Table 3.31) (transportation)
were summed with those produced by light vehicular traffic (33 MT/yr) and
considered as one source of emissions. Concentrations of contaminants in the
dust are unknown. Some spillage of ore and sub-ore along haul roads will
undoubtedly raise uranium levels in roadbed dust. As an estimate, uranium
and daughter concentrations in the dust were considered to be twice back-
ground, 8 ppm (2.7 pCi/g), while concentrations of all other contaminants
were considered to be similar to those in overburden rock (Section 3.3.1.1,
Table 3.16). Table 3.32 shows the annual emissions computed with these
assumptions.
Table 3.33 lists annual contaminant emissions from mining activities
(scraping, loading, dumping, etc.) according to source location, at the pit
and at the piles. Contaminant emissions were computed by multiplying the
total annual dust emissions at each pile (Table 3.31) by the respective
contaminant concentrations in each source ~ overburden (Section 3.3.1.1.;
Table 3.16), sub-ore (Section 3.3.1.3; Table 3.19) and ore (Section 3.3.1.2;
Table 3.19). Contaminant emissions at the site of the pit were computed by
multiplying the total annual dust emissions of ore, sub-ore, and overburden
(Table 3.31) by their respective contaminant concentrations. The three pro-
ducts of the multiplication were then summed to give the values in the 4th
and 8th data columns of Table 3.33. The health impact of the sources at each
location will be assessed separately in Section 6.1.
Table 3.34 lists annual contaminant emissions due to wind suspension and
transport of dust. These values were computed by multiplying the annual mass
emissions (Table 3.31) by the contaminant concentrations in overburden,
sub-ore, and ore listed in Sections 3.3.1.1, 3.3.1.3, and 3.3.1.2, respec-
tively. The uranium and uranium daughter concentrations were also multiplied
by an activity ratio (dust/source) of 2.5 (Section 3.3.1.2). Although some
metals may also be present as secondary deposits, it was believed that there
were insufficient data to justify multiplying their concentrations by the 2.5
ratio.
3.3.4.2 Radon-222 from the Pit, Storage Piles, and Ore Handling
Rn-222 will be released from the following sources during surface mining
operations:
-------
3-100
Table 3.32 Average annual emissions of radionucl ides (yCi)
and stable elements (Kg) from vehicular dust at
the model surface mines
Contaminant
Arsenic
Barium
Copper
Chromium
Iron
Mercury
Potassium
Manganese
Molybdenum
Lead
Selenium
Strontium
Vanadium
Zinc
Uranium-238 and
each daughter
Thorium-232 and
each daughter
Average Large
Surface Mine^a'
20
630
39
<111
13,030
<17
15,200
1,050
5.4
48
4.3
330
220
43
5,860
2,170
Average
Surface Mine' '
3.3
106
6.6
<19
2,190
<2.9
2,560
177
0.9
8.0
0.7
55
37
7.3
990
370
(b)
Mass emissions = 2,170 MT/yr.
Mass emissions = 365 MT/yr.
-------
Table 3.33 Average annual emissions of radionuclides (yCi) and stable elements
(kg) from mining activities at the model surface mines
Average Surface Mine^
Overburden
Contaminant Pile Site
Arsenic
Barium
Cobalt
Copper
Chromium
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Potassium
Selenium
Strontium
Vanadium
Zinc
Uranium-238 &
each daughter
Thorium-232 &
each daughter
1.1
35
NR^b^
2.2
<6
720
2.6
NR
58
0.3
NR
840
0.2
18
12
2.4
1,800
120
»
Sub-ore Ore Pit Site
Pile Site Pile Site
0.10
1.1
0.02
0.07
0.02
19
0.09
4.2
1.2
ND(c>
0.14
0.02
30
0.13
0.16
1.7
0.04
120
2.4
0.36
3.9
0.07
0.26
0.08
66
0.33
15
4.0
ND
0.48
0.08
105
0.46
0.55
5.9
0.12
2,990
42
2.1
62
0.05
3.9
<10
1,270
4.7
11
102
0.86
0.06
1,500
0.74
31
25
4.2
4,300
220
Average Large Surface Mine^ '
Overburden Sub-Ore Ore Pit Site
Pile Site Pile Site Pile Site
7.2
232
NR
14
<41
4,800
18
NR
388
<6.4
2.0
NR
5,600
1.6
120
80
16
12,000
800
0.44
4.7
0.08
0.31
0.10
80
0.40
18
4.9
ND
0.59
0.10
128
0.56
0.66
7.2
0.15
510
10
1.6
17
0.29
1.1
0.36
284
1.4
63
17
ND
2.1
0.36
453
2.0
2.4
26
0.52
12,900
180
13
406
0.21
25
<70
8,360
31
46
672
4.9
0.26
9,850
4.2
206
154
28
25,700
1,440
^a'
Mass emissions from Table 3.31.
NR - Not reported.
ND - Not detected.
co
i
-------
Table 3.34 Average annual emissions of radionuclides (yCi) and stable elements
Contaminant
Arsenic
Barium
Cobalt
Copper
Chromium
Iron
Mercury
Potassium
Magnesium
Manganese
Molybdenum
Nickel
Lead
Selenium
Strontium
Vanadium
Zinc
Uranium-238 &
each daughter
Thorium-232 &
each daughter
Average
Overburden
Pile
0.85
27
NR^a)
1.7
<4.8
564
<0.75
660 '
NR
46
0.24
NR
2.1
0.19
14
9.4
1.9
1,410
94
Large Surface Mine
Sub-Ore
Pile
0.86
9.2
0.16
0.61
0.20
157
ND(b)
250
35
9.6
1.2
0.20
0.78
1.1
1.3
14
0.29
1,000
20
Ore
Stockpile
3.8
40
0.70
2.7
0.88
690
ND
1,100
154
42
5.0
0.88
3.4
4.8
5.7
62
1.3
31,300
440
Average Surface Mine
Overburden
Pile
0.27
8.7
NR
0.54
<1.5
180
<0.24
210
NR
15
0.08
NR
0.66
0.06
4.5
3.0
0.60
450
30
Sub -Ore
Pile
0.26
2.8
0.05
0.18
0.06
47
ND
75
11
2.9
0.35
0.06
0.23
0.33
0.39
4.2
0.09
300
6.0
Ore
Stockpile
0.86
9.2
0.16
0.61
0.20
157
ND
250
35
9.6
1.2
0.20
0.78
1.1
1.3
14
0.29
7,100
100
oo
i
- Not reported.
- Not detected.
-------
3-103
1. Ore, sub-ore, and overburden during rock breakage and loading
in the pit and unloading on the respective piles. (Since rock
breakage, loading, transporting, and unloading usually occur in
a short time period, they are considered one release.)
2. Ore during reloading from the stockpile after a 41-day residence
time (Section 3.3.1.2).
3. Exposed surfaces of overburden, ore, and sub-ore in the active
pit area.
4. Overburden, ore, and sub-ore pile surfaces.
The annual quantities of Rn-222 released from sources 1 and 2 above were com-
puted using the following factors and assumptions:
1. Rn-222 is in secular equilibrium with U-238.
2. The density of ore, sub-ore, and overburden is 2.0 MT/m .
3. Annual production rates of ore, sub-ore, and overburden are those
given previously in this Section and in footnotes "a" and "b" of
Table 3.31.
4. All Rn-222 present, 0.00565 Ci/m per percent U30g, is available
with an emanation coefficient of 0.27. [Although an emanation co-
efficient of 0.2 is commonly used (Ni79), recent emanation-coeffi-
cient measurements for 950 samples of domestic uranium ores by
the Bureau of Mines indicate a value between 0.25 and 0.3 to be
more appropriate (Au78, Tanner, A.B., Department of Interior, Geo-
logical Survey, Reston, VA, 11/79, personal communication).
Therefore, an emanation coefficient of 0.27 was selected.]
5. The quantities of UgOg present in ore, sub-ore, and overburden are
0.10, 0.015, and 0.0020 percent, respectively.
Substituting these values into the following equation yields the Rn-222 re-
leases given in Table 3.35 for the average mine and the average large mine.
Ci
Rn-222 (Ci/yr) = (Percent U) 3 J (0.27)
X (Production Rate, MT )
f
(3.3)
The quantities of Rn-222 that emanate from exposed overburden, ore, and
sub-ore surfaces in the pit were estimated by the following method. Exposed
-------
3-104
surface areas of ore and sub-ore are assumed equal since equal quantities of
each are mined. The computation assumes an ore plus sub-ore zone 12 m thick
(hj) in the shape of a truncated cone with 45 degree sloping sides (Fig.
3.14). The radii of the zone, r1 and r2, can be computed using the following
equation from the relationship ro = rl + 12 and the volumes of ore P^us
sub-ore mined in a 2.4 year period — 1.22 x 106m3 and 2.8 x 105m3 at the
average large mine and average mine, respectively (the bulking factor is not
considered in computing the pit volume).
2 2
V (ore + sub-ore zone) = 1/3 „• hj (r^ +^1^2+r2 ) ^3'4^
The computed radii, r, and r2, were 174 m and 186 m at the average large
mine and 80 m and 92 m at the average mine. The surface areas (Sft) of
exposed ore and sub-ore in the pit are then one-half that given by the
equation,
SA = 1/2TT (dj + d2)(slant height) +rr r^, (3.5)
where d, and d^ are the diameters related to r. and r^. Exposed surface
areas of ore and sub-ore were computed to be equal and 57,170 m at the
2
average large mine and 14,650 m at the average mine.
The shape of the overburden zone was assumed to be the same as the ore
and sub-ore zone (Fig. 3.14). The thickness, hp, and radius, r3, of this
zone can be computed using the following equation with the relationship, r, =
73 fi 3
r2 + h2, and knowing the volume--4.8 x 10 m and 7.2 x 10 m —at the
average large mine and average mine, respectively.
V (overburden) = 1/3 TT h2 (r22 + r2r3 + r32) (3.6)
Since r2 was computed above to be 186 m at the average large mine and 92 m at
the average mine, Equation 3.6 becomes
4.8 x 107 = 1.087 x 105h2 + 584h22 + 1.047h23 (3.7)
for the average large mine, and
-------
Ore plus sub-ore Zone
Figure 3.14 Configuration of open pit model mines.
o
Ul
-------
3-106
7.2 x 106 = 2.659 x 104h2 + 289 h£2 + 1.047h23 (3.8)
for the average mine.
Solving these equations yields the following parameters:
average large mine 188 m 374 m 186 m
average mine 105 m 197 m 92 m
The surface area (SJ of the exposed overburden is then given by the
following equation.
SA = 1/2 * (d2 + d3) (slant height), (3.9)
where d. and d0 are the diameters related to r9 and r,. Areas computed were
52 52
4.68 x 10 m and 1.34 x 10 m for the average large mine and average mine,
respectively.
Multiplying the exposed ore, sub-ore, and overburden areas by their U,0g
contents (0.10%, 0.015% and 0.002%, respectively) and by a Rn-222 exhalation
2
rate of 0.092 Ci/m per year per percent UoOg* and summing gives the annual
Rn-222 releases shown in Table 3.35.
The emanation of Rn-222 from overburden, sub-ore, and ore storage piles
2
is based on an exhalation rate of 0.092 Ci/m per yr per percent ILOo (Ni79),
and ore grades of 0.002 percent, 0.015 percent, and 0.10 percent, respec-
tively. The surface areas used were those computed previously for the case 2
model mines and listed in Tables 3.11, 3.17 and 3.20. The areas for the
fi 7 R ?
average large mine and average mine are 1.1 x 10 m and 2.2 x 10 m for
52 42
overburden piles, 1.2 x 10 m and 3.6 x 10 m for sub-ore piles, and 6.2 x
32 32
10 m and 3.6 x 10 m for the ore piles, respectively. Applying these para-
meters, the annual Rn-222 emissions from the overburden, sub-ore, and ore
piles at the average mine and average large mine were computed. Table 3.35
presents the results.
The total annual Rn-222 released during surface mining operations is the
sum of the releases from the sources considered: 331 Ci from the average
mine and 1261 Ci from the average large mine. Considering ore production and
*The average value of measured exhalation rates at surface uranium mines
(N179).
-------
3-107
Table 3.35 Radon-222 releases during surface mining, Ci/yr
Source
Ore loading and unloading
Reloading ore from stockpile
Sub-ore loading and unloading
Overburden loading and unloading
Exposed surface of overburden,
ore, and sub-ore in the pit
Ore stockpile exhalation
Sub-ore pile exhalation
Overburden pile exhalation
Total
Average Mine
9
9
1
9
180
33
50
40
331
Average Large Mine
39
39
6
61
691
57
166
202
1261
grade differences, these values agree reasonably well with those computed by
other procedures (Tr79).
3.4 Underground Mining
3.4.1 Solid Wastes
During underground mining, like surface mining, materials are removed,
separated according to ore content, and stored on the surface for various
periods of time (Section 1.3.3). These separate piles consist of waste rock
produced from shaft sinking operations and from cutting inclines, declines,
and haulage drifts through barren rock, sub-ore, and ore. The waste rock is
similar to overburden removed at surface mines, except much smaller quan-
tities are involved and none are returned to the mine. However, as mining
progresses, waste rock is sometimes used to backfill mined out areas of the
mine and retained beneath the surface. The ore and sub-ore will also be
similar in nature to those described previously for surface mines, as is their
potential to be sources of contamination to the environment (Fig. 3.15).
-------
Figure 3.15 Potential sources of environmental contamination from active underground uranium mines.
o
en
-------
3-109
3.4.1.1 Waste Rock Piles
Much smaller quantities of waste rock accumulate at underground mines
than overburden at surface mines. The weight ratio of waste rock to ore
depends mainly upon the size, depth, and age of the mine. During the initial
mining stages, all material removed is waste rock. As entry into the ore
body occurs and ore mining begins, the quantity of waste rock removed per
metric ton of ore decreases sizably. Once in the ore body, as little waste
rock as possible is mined. The ratio of ore to waste rock removed from
underground mines varies considerably. At seven presently active underground
mines, the ore to waste rock ratio varies from 1.5:1 to 16:1, with an average
ratio of 9.1:1 (Jackson, P.O., Battelle Pacific Northwest Laboratory,
Richland, WA, 12/79, personal communication). As future mines become larger
and deeper, the overall ore to waste rock ratio will probably decrease.
4
Since the annual average ore capacity of underground mines was 1.8 x 10
MT in 1978 (Section 1.3.1), the average of the 305 underground mines would
3
have produced 2.0 x 10 MT of waste rock during that year, assuming the
average 9.1:1 ore to waste rock ratio. This will be considered the pro-
duction rate of the "average underground mine." Like surface mines, rela-
tively few of the 305 active underground mines account for a significant
portion of the total ore produced by the underground method. Also, future
underground mines are expected to have larger capacities than many of the
current mines (Th79). Therefore, a second underground mine will be con-
sidered, which is defined as the "average large mine." Its annual ore pro-
5
duction rate is assumed to be 2 x 10 MT, the average ore capacity of five
large underground operations (Ja79b, TVA79, TVA76, TVA78a, TVA78b). The
quantity of waste rock removed annually will be 2.2 x 10 MT, assuming the
ore to waste rock ratio to be the same as for the average mine. Assuming the
3
density of waste rock to be about 2.0 MT/m and a bulking factor of 1.25
(Burn's, E., Navajo Engineering Construction Authority, Shiprock, N.M., 2/80,
personal communication), the average mine and average large mine will produce
3343
waste rock at an annual rate of 1.3 x 10 m and 1.4 x 10 m , respectively.
Since waste rock is not presently used to backfill mined-out areas, this rate
of accumulation will continue for the life of the mine, which is assumed to
be the same as that for an open pit mine, 17 years.
Table 3.36 lists estimated average surface areas of the waste rock piles
during the lifetimes of the two mines defined above. The following para-
meters were used:
-------
3-110
Parameter Average Mine Average Large Mine
Waste rock production rate, MT/yr
Rock density, MT/m
Bulking factor
3
Waste rock volume, m /yr
Active mine life, yr
Pile height, m
• ~*
2.0 x 103
2.0
1.25
1.3 x 103
17
6
A
2.2 x 10H
2.0
1.25
1.4 x 104
17
12
These estimated areas assume no backfilling and that the piles are on
level terrain. Because waste rock is sometimes used to backfill and is often
dumped into a gorge or ravine, these surface areas represent maximum
conditions.
The mineralogy, physical characteristics, and composition of waste rock
from underground mines are assumed to be identical to the overburden removed
from open pit mines (Section 3.3.1.1). Also, reclamation procedures for
waste rock piles at underground mines should be similar to those described in
Section 3.3.1.4 for overburden dumps.
3.4.1.2 Ore Stockpiles
Because ore is often stockpiled at the mine and/or at the mill, it be-
comes a potential source of contamination to the mine environment during the
storage period. These piles will be smaller than the waste rock piles, but
the concentration of most contaminants in the ore-bearing rock will be much
greater.
Ore stockpile residence times can vary considerably with time and ore
management. Residence times commonly range from a few days to a few months.
The same residence time will be assumed for underground mines as was selected
above for surface mines, 41 days. Assuming a 330 operating-day-year and a
1.25 bulking factor, the ore stockpiles of the average mine and average large
3 3
mine will contain 1,400 m and 15,500 m of ore, respectively. The surface
areas of the ore stockpiles were computed using these volumes and assuming
3.1 m high rectangular piles (NRC78a). Table 3.37 lists the estimated
surface areas.
-------
3-111
Table 3.36 Estimated average surface areas of waste
rock piles at underground mines
Average Surface Area
Mine Size Accumulation/9' m of Pile, m2
Average mine' ' 1.1 x 10 2,700
f c\ c
Average large minev ' 1.2 x 10 14,100
Surface Area
of Pad, m2
2,460
12,800
'a'Assumes average volume of waste rock accumulated during 17-yr. mine
life with no backfilling (1/2 total volume accumulation).
/ L. \ O
* 'Annual waste rock production = 2.0 x 10 MT.
(c) 4
x 'Annual waste rock production = 2.2 x 10 MT.
Note. --Waste rock piles are rectangular with length twice the width
and sides sloping at 45° (Fig. 3.8 a).
Table 3.37 Estimated surface areas of ore stockpiles
at underground mines
Steady State Surface Area Surface Area
Mine Size Accumulation,'9^ m3 of Pile, m2 of Pad, m
n • (b)
Average minev '
/c\
Average large minev '
1,400
15,500
680
5,800
620
5,480
^'Assume 41-day residence time.
^'Annual ore production = 1.8 x 10 MT.
^'Annual ore production = 2 x 10 MT.
Note.—Ore stockpiles are rectangular with length twice the width and
sides sloping at 45° (Fig. 3.8 a). Pile height is assumed to be 3.1 m
(NRC78a).
-------
3-112
The mineralogy, physical characteristics, and composition of ore from
underground mines are assumed to be identical to the ore removed from surface
mines (Section 3.3.1.2). The U30g grade of ore may average somewhat higher
from underground mines than from surface mines. However, a grade of 0.1
percent IkCL probably approximates reasonably well the ore reserves minable
by the underground method (DOE79). Uranium and its decay products in air-
borne dust from these ore piles will be concentrated by a factor of 2.5
(Section 3.3.1.2).
3.4.1.3 Sub-Ore Piles
The quantity of sub-ore mined at an underground mine, as at a surface
4
mine, is considered to be about equal to the quantity of ore mined, 1.8 x 10
5
MT at the average mine and 2 x 10 MT at the average large mine. Assuming
sub-ore to have a density of 2.0 MT/m and after removal a bulking factor of
1.25, the average .volume of sub-ore to be on the surface during the 17-yr
operational life of the average mine and average large mine will be 9.6 x 10
o c o
m and 1.1 x 10 m , respectively (i.e., one-half the total of 17-yr accumu-
lation).
Although sub-ore is often placed on top of piles of previously mined
waste rock (Perkins, B.L., New Mexico Energy and Minerals Department, Santa
Fe, NM, 12/79, personal communication), we assumed separate rectangular piles
in computing the surface areas of the piles at the model mines. Table 3.38
lists the estimated surface and pad areas of the sub-ore piles. These compu-
tations were based on pile heights of 6 m at the average mine and 12 m at the
average large mine.
At underground mines, the cutoff grade ranges from 0.02 to 0.05 percent
U30g, yielding an average sub-ore grade of 0.035 percent U30g (99 pd'/g)
(Perkins, B.L., New Mexico Energy and Minerals Department, Santa Fe, N.M.,
12/79, personal communication). The mineralogy, physical characteristics,
and other constituents of sub-ore from underground mines are assumed ident-
ical to the sub-ore removed from surface mines (Section 3.3.1.3).
-------
3-113
Table 3.38 Estimated average surface areas of sub-ore
piles at underground mines
Average Surface Area Surface Area
Mine Size Accumulation.'a^ m3 of Pile, m2 of Pad, m2
Average mine^ '
ic\
Average large minev '
9.6 x
1.1 X
104
106
18,800
104,900
17,700
99,400
^a'0ne-half that which will accumulate during the 17-yr mine life.
^ 'Annual sub-ore production = 1.8 x 10 MT.
(c\ c
v 'Annual sub-ore production = 2.0 x 10 MT.
Note.--Sub-ore piles are rectangular with length twice the width and
sides sloping at 45° (Fig. 3.8a).
3.4.2 Mine Water Discharge
3.4.2.1 Data Sources
Information concerning the amount and quality of water discharged from
underground uranium mines in New Mexico is from field surveys conducted in
1975 (EPA75, P. Frenzel, USGS, written communication, 1979) and Wogman
(Wo79), from site-specific environmental impact statements and reports, from
NPDES permits, and from a State study (Pe79).
Many mining companies maintain that permits are not required because the
formerly ephemeral streams into which discharge occurs are, in effect, a
result of the discharges and do not meet the definition of navigable bodies
of water. Nevertheless, the companies have applied for permits, together
with a request to the courts for a ruling concerning their necessity.
The New Mexico district office of the U.S. Geological Survey (L. Beal,
USGS, written communication, 1979) provided discharge rate and volume for the
regional drainage systems, namely the Rio San Jose, Rio Puerco (east), and
the Rio Grande. We followed procedures developed by the USGS (Bo70) to
calculate runoff from ungaged basins.
-------
3-114
3.4.2.2 Quality and Quantity of Discharge
To estimate average or typical conditions for mine water discharge, 11
projects in Colorado, New Mexico, and Utah were selected. Table 3.39 shows
the summarized flow and water quality data. The center of current domestic
underground mining is in the Colorado Plateau and the San Juan Basin. In
this area, there is an increasing trend toward underground mining. In
Wyoming, both underground and surface mining activity are significant. In
Texas, surface mining and, to a lesser extent, in situ leaching are the
principal methods used. Climatic and geologic characteristics and land and
water use patterns in the Colorado-Utah-New Mexico uranium area are broadly
similar; and the Grants Mineral Belt in general and the Ambrosia Lake Dis-
trict in particular are representative of this area. There are many comp-
licating variables such as the geologic and geochemical characteristics of
the ore body and host rock. Water-yield and quality associated with mines
also vary within the region, as do the size and relative location of the
populace. The Grants Mineral Belt scenario is conservative. The mines
discharge relatively large amounts of water to streams that are used for
irrigation and stock watering and that flow by or through local centers of
population.
Table 3.39 shows discharge from selected underground uranium mines in
the Colorado Plateau areas of Colorado, New Mexico, and Utah. On the aver-
3 ^
age, discharge is 2.78 m /min, with a standard deviation of 4.34 m /min. The
selected underground mines discharge an amount of water similar to that from
the Wyoming surface mines. In the Grants Mineral Belt area, average flow
from 28 underground mines is 2.4 m /min (J. Dudley, New Mexico Environmental
Improvement Division, written communication). Of the 27 active underground
mines being dewatered, 17 discharge to the environment at an average rate of
3.2 m /min. The remainder are in a closed circuit. That is, their discharge
is used as mill feed water. The range for 17 mines is 0.2 to 19 m3/min.
Average discharges from New Mexico underground mines are significantly
greater than those from mines in Colorado and Utah, which average 0.68
3
m /min. Most of the ore production in New Mexico has been from mines 200 to
300 meters deep. In recent years, mines have become progressively deeper and
involve more dewatering. For example, the Gulf Mount Taylor mine, which is
3
not yet producing ore, discharges 15 m /min and will produce ore from a depth
-------
3-115
of 1,200 meters. Most of the water is now diverted to a nearby ranch for
irrigation and stock watering. When the mill goes on line, most of the mine
water will be used there.
Of the 16 active mines in the Ambrosia Lake district, 13 discharge to
offsite areas at an average rate of approximately 1.6 m /nrin. For modeling
and to be conservative, we assumed that 14 active mines are present in the
o
model mine area and that the average discharge rate per mine is 2.0 m /min.
This is somewhat less than the average condition for the Grants Mineral Belt
(3.2 m /min) as a whole in terms of discharge rate, but the high density of
mines assumed present in the model area partly compensates for the differ-
ence.
For the New Mexico project shown in Table 3.39, numbers 4, 5, 6, and 7
have discharge that comes directly from the mine portal to settling ponds
before discharge. Neither ion exchange for uranium recovery nor barium
chloride treatment for radium removal is used. Facilities 8 through 11 use
ion exchange columns for uranium removal before discharge. Settling may or
may not be used, depending on the suspended solids content of the particular
discharge. Project number 10 removes radium prior to discharge. Radium
concentrations in the combined effluent from two active mines in the Church-
rock area (projects 8 and 4), both of which use settling ponds as the only
treatment, have ranged from 1.9 to 8.9 pCi/£ since 1975. In the first survey
(EPA75), effluent from these same mines contained 30.8 and 7.9 pCi/ a . The
combined discharge from both mines was sampled by the U.S. Geological Survey
in 1975, 1977, and 1978 (P. Frenzel, written communciation) and by the EPA
(EPA75) in 1975. Concentrations were 30, 14, 2.6, and 2.6 pCi/ji ,
respectively.
It is apparent that there are marked temporal trends in mine water
quality and quantity. Major factors responsible include changes in the
dewatering rate accompanying shaft sinking versus actual ore production.
Simultaneously, there are changes in the mineral quality and leaching rate of
strata as the ore body is approached and then penetrated. Mining practices,
oxidation of the ore body and possibly bacterial action may also assist in
the solubilization of toxic stable and radioactive trace elements. Sample
handling and analytical procedures can also markedly affect results. For
example, if suspended solids are high and a sample is acidified prior to
filtering, soluble radium, uranium, and other trace constituents typically
-------
Table 3.39 Summary of average discharge and water quality data for underground
uranium mines in the Colorado Plateau Region (Colorado, New Mexico,
Utah) and a comparison with NPDES limits
Dissolved
Radioactivity
Di
Project
Utah(a)
r
Colorado
2
3
New Mexico
4
5
6
7
8, ,
9/\
1° til
n(a)
Average
Standard
Deviation
scharge
m /min
0.67
1.31
0.06
14.67
3.79
1.89
0.95
0.18
0.82
6.06
0.216
2.78
4.34
Total U,
mgA
1.35
2.20
0.25
1.0
0.67
0.02
0.18
4.2
1.9
1.1
2.6
1.41
1.25
Ra-226,
pCiA
1.25
0.53
10.00
89 1 \
23 r
14(c)
0.1
1.9
4.7
2.3
4.3
13.7
25.9
Pb-210,
pCi/£
15
33
15
0
9.7
16
14
14
14.6
9.1
TSS
7.5
14.3
144.9
25.4
2.6
51.5
1
1.08
2.2
27.8
46.9
Major and
S04 Zn
872 0.02
0.065
60.6
213.7
744
1045
67.2
675
705
837
580
368
trace
Ba
0.19
2.13
0.88
0.17
0.66
0.81
0.80
constituents, mg/s,
Cd As
< 0.01 <0.01
0.003 0.055
<0.005 <
0.011
0.005
<0.005
<0.005 <
0.011
< 0.005
0.012
0.012
0.015
Mo
0.4
0.054
0.01
0.24
0.05
= 0.01
0.45
0.62
0.79
0.29
0.29
Se
0.03
0.008
0.004
0.002
0.094
0.407
0.027
0.036
0.076
0.137
CO
I
-------
Table 3.39 (continued)
Summary of NPDES permit limits for daily average/daily maximum, mg/j, except Ra-226, pCi/£
State
New Mexico
Utah
Colorado
Dissolved
Radium-226
3/10
10/30 Total
Radium
3/10
and
3/10
and
Dissolved Total Total
Uranium Suspended Dissolved
Solids Solids Zinc
2/4
2/4
and
3/5
and
2/4
50/150(dayT 0.5/1.0
20/30(month)
20/30^e) NA/650 0.5/1.0
3500
20/30 48990/,f) 0.5/1.0
kg/day
Barium Cadmium Arsenic Vanadium
1/2 0.05/0.1 1/2 5/10
and and
-/I 0.5/1
^'Average discharge rate per mine is shown. Two or more mines constitute the project.
(b),
(c)
(d)
BaCl2 treatment for radium removal faulty; repaired in late 1979.
Values shown are for untreated water. BaCK treatment now used.
Applies to discharge associated with shaft construction.
(e)
v 'Maximum of 10 mg/£ for 30-day period and 20 mgA for 7-day period effective July 1, 1980.
(f)
Receiving water standard.
Source: Chemical analyses from in-house studies (EPA75) and State of New Mexico (J. Dudley, Environmental
Improvement Division, written communication). NPDES permit data from Regions VI, VIII (H. May, R. Walline,
written communication). Other references include site-specific reports (EIS,ER) and company monitoring data.
oo
i
-------
3-118
will increase, as compared to samples that are filtered prior to acidifi-
cation (Ka77). Therefore, development of "average" or "typical" trace ele-
ment concentration data is questionable and may be erroneous without detailed
knowledge of the many variables affecting the final results.
Despite the foregoing difficulties, available chemical data assembled in
Table 3.39 provide much of the source term input data used in subsequent cal-
culations. The reader should bear in mind that uranium concentrations are
likely to be less than 3 mgA, simply because it is economically practical to
use ion exchange recovery for concentrations greater than this level. Daily
average radium-226 concentrations on the order of 3 pCi/Ji are specified in
valid NPDES permits, and reliable data from USGS, EPA, and state sources re-
veal stream concentrations near the point of discharge to be on the order of
3 to 14 pCi/& in recent years. Therefore, the "average" radium-226 concen-
tration of 13.7 pCi/2, used in the subsequent modeling calculations is at
least slightly conservative. Actual concentrations of stable elements (Zn,
Ba, Cd, etc.) appear to be well below the NPDES limits, which were also de-
veloped from analysis of uranium mine effluent. Thus, it is presumed that
the average values in Table 3.39 for these elements are reasonably correct.
The variables of mine size, age, host rock, and water treatment (ion ex-
change, barium chloride, settling ponds) are reflected in the data. Water
quality for mines examined in Utah and Colorado generally agrees with the New
Mexico cases, with the exception of Project Number 3 mine, which is being
dewatered and may, therefore, temporarily have excessive suspended solids.
We recommend that the NPDES data for uranium mine discharges be evaluated and
that additional compliance monitoring be conducted to confirm .the quality of
mine discharge. Such studies should focus on situations where mine water is
being used for irrigation and stock watering.
Table 3.40 shows discharge and water quality characteristics for under-
ground mines under construction and not yet producing ore. The first example
involves water pumped from a deep mine shaft under construction. Consid-
erable water is encountered above the ore body; water quality is good and
representative of natural conditions; and suspended solids are high as a
result of construction. The second case is similar except that flow is re-
duced, but radium and suspended solids concentrations are greatly elevated
due to construction and possible ore body oxidation. The third case involves
-------
Table 3.40 Water quality associated with underground mines in various
stages of construction and operation
Discharge
Project m /min
New Mexico
1. Underground mine 5.76
shaft construction;
dewatering
2. Underground mine 1.73
shaft construction;
dewatering
3. Underground mine; 1.43
dewatering wells
4. Underground mine 0
recirculating leach
solution from stopes
(after ion exchange)
Dissolved
Total U Ra-226 Pb-210
mgA pCi/Ji pCi'A TSS
0.03 0.07 10 23.8
<0.01 29 0 554
0.08 0.2 0 1
0.32 29 17 1.1
Concentration, mg/£
S04 As Mo Se
134 <0.005 0.01 0.003
527 0.012 0.007 0.005
144 <0.005 0.01 0.003
1060 <0.005 3.2 0.268
Source: J. Dudley, State of New Mexico, written communication, 1979.
co
i
-------
3-120
dewatering wells used to dewater the ore body before mining. There is no
oxidation and suspended solids are very low as is radium-226. Dissolved
radium-226 in the ore body is on the order of 10 pCiA or less in the natural
state, but concentrations rise to 100 pCi/£ or more after mining takes place,
possibly due to oxidation and bacterial action in the workings (EPA75).
Project Number 4, in the Ambrosia Lake district, is an inactive underground
mine now used as a type of in situ leach facility. Mine water is recir-
culated through the workings. Leached uranium is selectively recovered using
ion exchange. The process is a closed one, hence no effluent is involved.
Water quality after uranium removal reflects the buildup in radium, lead-210,
sulfate, molybdenum, and selenium.
3.4.3. Hydraulic and Water Quality Effects of Underground Mine Discharge
3.4.3.1 Runoff and Flooding in the Model Underground Mine Area
3.4.3.1.1 Study Approach
We chose to study an area of rather concentrated underground mining,
similar to the Ambrosia Lake district of New Mexico. All of the mines in the
district dewater to different degrees because the principal ore body is in
the Westwater Canyon Member of the Morrison Formation, which is also a major
aquifer. In the analysis, flows from some 14 active mines discharge to
formerly dry washes and dissipate downstream by evaporation and, more impor-
tantly, infiltration. Suspended and dissolved constituents persist at the
land surface and become available for resuspension and transport in surface
floods with recurrence intervals of 2 to 25 years. Contaminated runoff from
the sub-basin is then diluted in average annual flows of progressively larger
streams and rivers of the region.
Similar to the analysis presented for surface mines in Wyoming, there is
a three-basin hierarchy: sub-basin, basin, and regional basin (Fig. 3.16).
These correspond to Arroyo del Puerto-San Mateo Creek, Rio San Jose and Rio
Puerco, and the Rio Grande. Of these, the Rio Puerco is distinctly ephe-
meral. The Rio Puerco drains into the Rio Grande, which is perennial, due in
large part to the heavily regulated flows and storage reservoirs. Because
-------
3-121
MCKINLEY COUNTY
Sub-basin area containing
model mines
0 10 20 30 40
50
(km)
""" ™"""""x «•..
^* «••
Sub-basin boundary
Boundary of a portion of the Rio San Jose basin
upstream from the sub-basin
Rio Puerco basin boundary
± USGS gauging station
Note: Boundary of the Rio Grande regional basin above Bernardo is not
shown.
Figure 3.16 Sketch of sub-basin, basin, and regional basin showing orienta-
tion of principal drainage courses, areas of drainage, and loca-
tion of mines in the New Mexico model area
-------
3-122
the Rio Grande is the major regional river and the basis of extensive irri-
gation projects, it is included in the analysis. The mining area is well
away from the Rio Grande Valley, and it is unlikely that noticeable changes
in flow or water quality because of mining would occur.
Flow volumes for the sub-basin and open file USGS data (L. Beal, written
communication, 1979) for flows in the basin and regional basin are used to
transport and dilute contaminants originating in the mine effluent. It is
initially assumed that all contaminants are available for transport by sur-
face flow so as to deliberately create a worst-case situation. Section
3.4.3.2 reviews infiltration of water and solute for possible effects on
groundwater.
We do not address the effects of seepage from settling ponds because
such ponds are relatively small, tend to be self-sealing, and are well away
from inhabited areas. Supposedly, settled solids from these ponds are
removed and incorporated with uranium mill tailings. Limited field studies
to determine whether such ponds cause groundwater contamination is warranted.
In some instances, the ponds have synthetic liners, and leakage is expected
to be minimal. The influence of mine dewatering (by wells, shafts, and
pumping of mine workings) on groundwater quality or availability is not
addressed primarily because of the lack of data. We strongly recommend
further study of the hydraulic and groundwater quality effects of dewatering.
This aspect of mining is coming under increased scrutiny by regulatory
agencies at the State and Federal level because of the influence on water
quality and availability.
In summary, our approach defines the quality and volume of mine water
discharge; outlines hydrographic basins; and calculates flood flows for
various return periods ranging from 2 to 25 years in the sub-basin. These
flows are then diluted into the average annual flow in the basin and regional
basin. The principal objective is to develop a rough estimate of contaminant
loads resulting from mine discharge.
3.4.3.1.2 Description of Area
The Grants Mineral Belt of northwestern New Mexico is in the Navajo and
Datil sections of the Colorado Plateau physiographic province (Fe31). Char-
acteristic landforms in the study area include rugged mountains, broad, flat
-------
3-123
valleys, mesas, cuestas, rock terraces, steep escarpments, canyons, lava
flows, volcanic cones, buttes, and arroyos (Ki67; Co68). Elevations in the
area range from 1,980 m at Grants to an average of 2,160 m near Ambrosia
Lake. Just north of Grants is Mount Taylor, the highest point in the region.
It rises from Mesa Chivato to an elevation of 3,471 m (Co68).
The study area has a mild, semiarid, continental climate. Precipitation
averages 25.4 cm/year, and there is abundant sunshine, low relative humidity,
and a comparatively large annual and diurnal temperature range. Average
annual precipitation at Gallup, Bluewater, and Laguna is 27.12, 24.55, and
22.31 cm, respectively. In the higher elevations, the average is 51 cm or
more because of thunderstorms in July, August, and September and snow accumu-
lations in the winter months (Co68, Go61, Jo63). Only thunderstorms are
significant in the lowlands. Heavy summer thunderstorms (40 to 70 in number)
of high intensity and local extent can result in 5 cm of rain with local,
damaging flash floods.
2
The watersheds of the Rio San Jose and Rio Puerco encompass 19,037 km .
Most of the larger communities in the basin are located in the floodplain of
the Rio Grande and principal tributaries. Extensive irrigation with surface
water occurs in the watersheds of the Rio San Jose, Rio Puerco, and Rio
Grande. In the sub-basin, there was no perennial flow before mining and,
thus no irrigation, but increasing use is being made of the mine discharge,
which is regarded as an asset in a water-short area. Subsequent sections
summarize the surface water quantity at some of the principal gauging
stations in the Middle Rio Grande Basin and the irrigated areas below these
stations. Groundwater is used for essentially all public water supplies as
the temperature, quality, and year-round availability are assured. Numerous
wells scattered across the landscape, particularly in the stream valleys, are
used for stock water and, to a lesser extent, for potable use on the scat-
tered ranches and Indian settlements.
Under completely natural conditions, streams in the study area were
distinctly ephemeral, and many of the smaller ones did not experience flow
for periods of several years. The Rio Grande experiences peak flows in the
April-June period when snowmelt and precipitation cause gradual rises to
moderate discharge levels involving large volumes of flow and long durations.
Peak discharge rates (volume per time) occur in the summer flash floods.
-------
3-124
Construction of dams and conveyance channels to eliminate flooding problems
has been extensive. In the tributaries such as the Rio San Jose and upper
reaches of the Rio Puerco, there is considerable streamflow regulation to
minimize flood damage and maximize use of available water for irrigation.
Conditions in the Ambrosia Lake district with respect to the type of
mining operations and discharge of effluent to ephemeral streams are dupli-
cated elsewhere in the Grants Mineral Belt. In the Churchrock district, two
3
mines discharge to the Rio Puerco at rates of 4.7 to 15 m /min. Most of the
4.7 m3/min discharge from one mine is now used in a nearby mill. At Mariano
Lake, located between Ambrosia Lake and Churchrock, and at the Marquez and
Rio Puerco mines east of Ambrosia Lake, mines are expected to discharge 0.8
•5
to 4.5 m /min to various ephemeral streams. Another large mine will soon
o
discharge up to 5.3 m /min northward into the San Juan River Basin. In the
mid 1980's, construction is expected to begin on five large underground
mining projects that will have a combined discharge on the order of 71
3
m /min. Most discharge will be into the San Juan Basin, reflecting the trend
of mines becoming deeper and requiring more dewatering as the mining center
moves from the south flank of the San Juan Basin into more interior portions.
3.4.3.1.3 Estimate of Sub-basin Flood Flow
Since we use a dilution-model, emphasis is on flow volume rather than
peak discharge rate in the sub-basin, basin, and regional basin hydrographic
units. Gaging records from the U.S. Geological Survey WATSTORE system (L.
Beal, written communication, 1979) provide average discharge rates for runoff
events with various return periods and durations. The latter specify the
time, in days, and the associated flow rate that will be equaled or exceeded.
Flows for arbitrary periods of time ranging from 1 to 183 days are specified.
Probability can be stated in terms of N-year recurrence interval. By
combining discharge rate (volume per time) and time (partial duration), flow
volume can be calculated.
In the ungaged sub-basin, runoff volumes associated with events having
return periods of 2, 5, 10, and 25 years were calculated from regression
equations developed by the USGS (Bo70). The equations were generated from
multiple regression of discharge records from gaged basins against various
basin characteristics. These are area (A), precipitation (P ), longitude
-------
3-125
at the center of the sub-basin (Lo), soils infiltration index (Si), and mean
basin elevation (Em). Through use of appropriate constants and coefficients
(Bo70), flow volumes can be calculated for 1-day and 7-day events with return
periods of 2, 5, 10, and 25 years. For the sub-basin, the basic equation has
the following form:
FV = a Abi Pab9 uA* S^5 Embl* (3.10)
p
where A = 95 mi
P = 2.9 inches
a
Lo = 7.85 (longitude in decimal degrees minus 100)
Si = 8.5
E = 7.0 thousand feet
Table 3.41 contains the regression coefficients and total flow volume data.
Short-term, 1-day and 7-day, events were of main interest because these would
be expected to provide greater flushing of contaminants stored at or near the
water-substrate interface in the streams receiving mine discharge.
The extent to which mine discharge transforms existing ephemeral streams
into perennial ones is evaluated with a crude seepage and evaporation model
(see Appendix H). The basic equations and approach are patterned after a
similar analysis in the Generic Environmental Impact Statement on Uranium
Milling (NRC79b).
Figure 3.16 shows the relationship of the sub-basin, basin,.and regional
basin boundaries and the principal drainage courses and gaging stations. The
confluence of the Rio Puerco and Rio San Jose is shown approximately 55 km
closer to the Rio Grande than is actually the case in order to simplify flow
routing and to reduce the number of dilution calculations. Table 3.42 sum-
marizes the key characteristics of these basins in terms of catchment area,
discharge, and irrigated farmlands downstream from points where mine dis-
charge might be tributary to the streams. Mine discharge occurs in the
sub-basin which in turn discharges to the Rio San Jose and then to the Rio
Puerco. No mine discharge and no significant runoff are associated with that
portion of the basin tributary to San Mateo Creek between the Rio San Jose
and the sub-basin. For modeling, flooding within and runoff from the sub-
-------
Table 3.41 Total flow volume for sub-basin floods of 1- and 7-day durations
and return periods of 2, 5, 10, and 25 years
Flood
Vol ume
FV l,2(a)
FV 1,5
FV 1,10
FV 1,25
FV 7,2
FV 7,5
FV 7,10
FV 7,25
Regression Coefficients
a
1.
1.
5.
2.
8.
2.
8.
3.
08 x
27 x
07 x
39 x
60 x
99 x
97 x
06 x
io-4
ID'3
io-3
lO"2
io-7
ID'4
io-4
io-3
bl
0.
0.
0.
0.
0.
0.
0.
0.
931
941
953
972
965
904
910
922
b9
1.83
1.40
1.17
0.929
2.36
2.55
2.37
2.17
b!4
-1.43
-1.89
-2.18
-2.51
-1.61
-2.09
-2.39
-2.76
b!5
4.09
4.07
4.02
3.95
4.22
3.53
3.61
3.68
Vo
b4
2.
6.
1.
1.
1.50 5.
8.
1.
2.
lume
(m3)
16 x
23 x
02 x
76 x
95 x
79 x
43 x
26 x
io4
IO4
IO5
IO5
IO3
IO3
IO4
io4
'FV 1,2 indicates a flood of 1-day duration and a return period of 2 years.
r\>
-------
Table 3.42 Summary of area, discharge, and irrigated acreage for the sub-basin, basin, and
regional basin hydrographic units in New Mexico
USGS
Station
Number
Area (km )
p o
Number of km Average m /min Average Annual
o
Period of Under Irrigation Discharge (for Discharge (m)
Record Yrs. Below Station Period of Record) for Period of Record
Sub-basin
Basins
Rio San Jose
near Grants
Rio Puerco
near Bernardo
Regional Basin
Rio Grande at
Bernardo
246
3435 5957 42
(2927 non-contributing)
3530 19037 38
(2927+ non-contributing)
3320 49810 41
(7610 non-contributing)
2.43+
11.09
81.05
1649.35
5.83 x 10l
4.26 x 10'
86.69 x 10'
= Not Calculated.
t\3
-------
3-128
basin is, in effect, routed without change in flow and quality and allowed to
enter the Rio San Jose. Flow from the San Jose is further diluted in the Rio
Puerco, then diluted again in the Rio Grande. In actuality, flow from the
Ambrosia Lake district rarely, if ever, enters the Rio San Jose because flood
volumes are small and infiltration losses are large. This departure from
true conditions is justified within the context of the modeling approach
used. Basically, the model draws from a specific area but does not attempt
to closely duplicate its conditions. If a specific area were exactly repre-
sented, the model would still be incorrect to varying degrees for other
areas, and the generic value of the assessment would depreciate.
Of special interest is the effect of contaminated flows on irrigation
projects present on the Rio San Jose and Rio Grande. An extensive system of
dams and conveyance channels regulates flow in the Rio Grande, and partial
duration flow data are unavailable. Instead, the average annual flow volume
is used to provide the final dilution estimate. For the sub-basin in which
the mines are located, flood volumes are calculated using the USGS regression
equations (Bo70). The maximum return period for which flows are calculated
is 50 years. The remainder of this section first considers the flow or
hydraulic aspects of the surface water pathway. Finally, several factors
concerning the quality of runoff water are mentioned to balance conservatism
and realism in the pathway analysis and, subsequently, in the health effects
modeling to follow. The emphasis here is on surface water impacts, and we
assume maximum transport for this pathway. The influence of infiltrating
mine water is discussed in Section 3.4.3.2.
All of the streams, except the Rio Grande and certain reaches of the Rio
San Jose are distinctly ephemeral under natural conditions. In the sub-
basin, there is perennial flow because of mine discharge. In Fig. 3.17 are
the average monthly and annual discharges for the Rio San Jose and the Rio
Puerco in comparison to cumulative annual flow from 14 mines, each dis-
3
charging at 2 m /min. The monthly data reveal pronounced seasonal variations
approaching 1 to 2 orders of magnitude. The streams do not show the same
seasonal variations, further attesting to varied patterns of runoff, irri-
gation diversion, and control features such as impoundments and conveyance/
irrigation channels. Figure 3.18 shows the percentage of each month during
-------
•
•
.
•
u£
<«
m
m
«i
i
M
4
*Vi
•i
•
4
•
••
VI
•••
4MB
-
,
0
LEGEND
3-129
RIO han Jose near drants N.M
•••• Rio Puerco at
j ------
Rio Puerco, N.M.
\ssssssssssss\ Rio Puerco near Bernardo, N.M.
T
S
S
s!
s
s,
s
s
Jan
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JS
%.
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Nov
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Srv] :;
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ixi
Dec
Figure 3.17 Average monthly flows for the period of record for the Rio San Jose
and the Rio Puerco in New Mexi^"'Q""""arized from flow records provided by
L. Seal, U.S. Geological Surve erque).
-------
3-130
which there is no flow in the Rio San Jose and Rio Puerco. The average
period of annual or monthly no flow is as follows:
Rio San Jose near Grants: 0 Percent
Rio Puerco at Rio Puerco: 45 Percent
Rio Puerco at Bernardo : 71 Percent
It is also assumed that flow from the sub-basin reaches the first major
stream, the Rio San Jose, with no change in flow or quality. Runoff is
minimal in the lower reaches of San Mateo Creek because of internal drainage
and considerable infiltration. Historical evidence indicates that only
rarely, if ever, would flood runoff from Ambrosia Lake enter the Rio San
Jose. In the interests of conservatism, total flow laden with contaminants
is transported to the Rio San Jose. Dilution first occurs within the sub-
basin and then, successively, in the Rio San Jose, Rio Puerco, and Rio
Grande. The latter is the regional basin.
There is an infinite number of combinations of flood volumes and dilu-
tion volumes for the sub-basin, basin, and regional basin streams. Use of
average annual discharge volumes in the receiving streams simplifies what
would otherwise be a burdensome, confusing series of calculations. Flushing
action from the sub-basin is handled on a probabilistic basis in terms of
flow duration and return period. Concentration values are based on 14 mines,
a loading period of two years, and flow and water quality data shown in Table
3.39. When, for example, 5-year or 10-year events are considered, it is
conservatively assumed that events with shorter return periods do not occur.
The accretion period remains constant (2 years), and only the return period
and duration are varied, resulting in varying flow volumes. It is conceiv-
able that contaminants could concentrate for 3, 4, or 5 years and then be
flushed by a 2-year event, but this was not evaluated.
Minimum and maximum return periods for floods from the sub-basin were
set at 2 and 25 years, respectively, for several reasons. The 2-year event,
i.e., runoff volume over a duration of 1 day or 7 days and occurring on the
average of every 2 years, is expected to occur rather frequently over the
life of the mines (17 years). The intermediate-sized storms with return
periods of 5 or 10 years would result in considerable contaminant transport,
-------
100
o 90
80
!70
-6
<« 60
3 50
'3 40
30
m
o
8
?H
-------
3-132
but concentrations would be low owing to dilution and to annual or semiannual
scouring provided by smaller floods. The 25-year event is a practical maxi-
mum expected to occur during the lifetime of the mining district. Still
larger floods, with return periods of 50 or 100 years, can be calculated but
are less important because of their infrequent occurrence. Figures 3.19 and
3.20 show calculated flow volumes from the sub-basin for 1-day and 7-day
durations and return periods of 2 years to 50 years. The extreme range in
flow volume is from 2.16 x 104 m3 to 2.55 x 10 m .
Figures 3.19 and 3.20 show flow values in the Rio San Jose and Rio
Puerco for 1-day and 7-day durations and return periods of 1 to 100 years.
For the Rio San Jose, 1-day volumes range from 1.24 x 10 m to 1.68 x 10
3 3
m . The mean annual discharge rate in the Rio San Jose is 11.09 m /min. Flow
from the Rio San Jose enters the Rio Puerco where corresponding flows (1-day
fi y o
duration) range from 0.6 x 10 to 2.15 x 10 m at the point of inflow to the
Rio Grande. Average daily discharge in the Rio Grande seasonally ranges from
8.87 x 10 m to 59.5 x 10 m . Average annual flows rather than peak 1-day
or 7-day flows were used in the subsequent calculations.
The maximum probability for peak runoff from the sub-basin and resulting
contaminant transport is in the summer months, at which time the Rio Puerco
has no flow about 22 to 75 percent of the time. Flow in the Rio San Jose and
Rio Puerco from June through September ranges from 3.96 x 10 to 1.97 x 10
3
m per month for the period of record (Fig. 3.17).
3.4.3.1.4 Prediction of Sub-basin Water Quality
Table 3.43 outlines dilutions based on the foregoing discussion of flow
patterns and discharges and considering only the 1-day sub-basin flood event
with a 2-year recurrence interval. The dilution constant is the ratio of
concentration in the receiving water to that in the contaminated (relatively)
inflow. It is more commonly expressed as the dilution factor, which is the
reciprocal. Thus, in the case of the sub-basin flood flow entering the mean
annual flow of the Rio San Jose, there is a 271:1 dilution (Table 3.43).
With development of the foregoing (mine water) source term and surface
water pathway, the remaining discussion emphasizes contaminant concen-
trations in surface water. This, in turn, serves as input data to health
effects modeling for the water pathway. Chemical concentrations in the Rio
-------
3-133
10 (
K)
6
3
U,
tLc
BH
O
a
LEGEND
O Sub-basin (Arroyo del
Puerto @ San Mateo Creek)
A Basin (Rio San Jose near
Grants, #3435)
O Basin (Rio Puerco near
Bernardo, #3530)
NOTE: Total flood flow for
one day duration not calcu-
lated for regional basin
(Rio Grande).
lO'
10
25
50
100
RECURRENCE INTERVAL (YEARS)
Figure 3.19 Total flow volumes in one-day periods for floods of various
recurrence intervals in the sub-basin and basins in New Mexico (Summarized
from flow records provided by L Seal, U.S. Geological Survey, Albuquerque).
-------
5_
4.
3.
2.
10'
9,
8—|
7.
6—I
10
4-
3_
10'
7.
6.
LEGEND
o Sub-basin (Arroyo del Puerto
San Mateo Creek)
A Basin (Rio San Jose near
Grants, #3435)
O Basin (Rio Puerco
near Bernardo, #3530)
NOTE: Total flood for seven days
duration not calculated for regional
basin (Rio Grande).
5 10 25
RECURRENCE INTERVAL fYEARSI
50
100
Figure 3.20 Total flow volumes in seven-day periods for floods of various
in thf <;i i
and
in MO
-------
Table 3.43 Dilution factors for the Rio San Jose, Rio Puerco, and Rio Grande
for 1-day flood flows with a 2-year recurrence interval
Hydrographic Basins
Rio San Jose near Grants^3'
Rio Puerco' '
Rio Grande near Bernardo*0'
Flow Ratio
(m3/m3)
2.16 x 104
5.83 x 106 + 2.16 x 104
2.16 x 104
4.26 x 107 + 2.16 x 104
2.16 x 104
Dilution
Constant
0.0037
0.00051
0.000025
Dilution
Factor
271
1973
40135
86.69 x 107 + 2.16 x 104
^'Calculated using mean annual flow in the Rio San Jose (near Grants, NM) station:
Dilution - Sub-basin flood flow .
Rio San Jose flow + Sub-basin flood flow
^ 'Assumes Rio San Jose enters the Rio Puerco at Bernardo:
Dilution
Sub-basin flood flow
Rio Puerco flow (includes Rio San Jose flow) + Sub-basin flood flow
(^Dilution = Sub-basin flood flow
Rio Puerco flow + Rio Grande flow (at Bernardo) + Sub-basin flood flow
co
i
CO
en
-------
3-136
San Jose, Rio Puerco (at Bernardo), and in the Rio Grande (near Bernardo) are
shown in Table 3.44 along with 1-day and 7-day flood flow volumes from the
sub-basin for return periods of 2, 5, 10, and 25 years. These flood volumes
are diluted into the mean annual flow of the Rio San Jose (near Grants), Rio
Puerco (at Bernardo), and Rio Grande (near Bernardo). The principal reason
for using mean annual flow is that the radiation dose and health effects
model (Section 6.0) stresses estimating average annual dose to the population
over the duration of mining activity.
For example, the 1-day duration flood flow (with a 2-year return period)
contains 1920 mg/a uranium, which decreases to 7.09 mg/a in the Rio San Jose
and 0.973 mg/£ in the Rio Puerco. Because of the short duration of most
floods in the sub-basin, there is little difference in flow volume and, thus,
dilution between the 1-day and 7-day events. With progressive dilution down-
stream, the difference in size between sub-basin floods of varying durations
and return periods becomes insignificant relative to the mean annual flow
volumes of the basin and regional basin streams. As a result, concentrations
tend to reach a minimum and remain unchanged at this degree of accuracy.
As in the case of the Wyoming surface-mine scenario, we assume
that most contaminants in the mine water collect on or near the land
surface and are available for transport. This assumption is open to ques-
tion, but field data are scarce to support contentions as to the fraction of
contaminant load that becomes unavailable. For example, extensive field
studies along the Animas, San Miguel, and Dolores Rivers in Colorado con-
cluded that "...once radium becomes a part of a stream's environment, it
constitutes a relatively long-term and continuous source of water and aquatic
biota contamination" (Si66). However, cessation of uranium mill discharges
to the Colorado River tributaries effectively negated this source, which is
now believed to be buried behind the Lake Powell and Lake Mead impoundments.
Similarly, dissolved radium reverts to background levels of several pico-
curies per liter in natural streams receiving mine water in Colorado and New
Mexico. Although it is likely that flood waters resuspend precipitates and
sediments with sorbed radium, laboratory experiments (Sh64; Ha68) indicate
that only minor re-solution takes place. This phenomenon is supported by
recent surface water data collected in the Grants Mineral Belt of New Mexico
(Ku79). Therefore, concentrations of dissolved radium in flood water are
-------
Table 3.44 Annual contaminant loading from 14 uranium mines and resulting concentrations in sub-basin floods and in the
average annual flow of the Rio San Jose, Rio Puerco, and Rio Grande
Contaminant
concentration
in mine
effluent (mgA
except as noted)
Total Uranium
1.41
Radium-226
13.7 pCi/4
Lead-210
14.6 pCi/l
Cadmium
0.007
Arsenic
0.012
Selenium
0.076
Mass available 1- and 7-day flood flow volumes (m3) and contaminant concentrations associated with return periods of 2 to 25 years*
for transport 1-Day 7-Day
(kg/yr exceot .
as noted } U) V,=2.16xl04
C2
1480 1920
7.09
0.973
0.0456
0.00144 Ci/yr 1870
6.9
0.95
0.044
0.00153 Ci/yr 19800
73.1
10.0
0.470
7 9
0.03
0.004
0.0002
13 17
0.063
0.0086
0.00040
80 100
0.38
0.053
0.0026
V,=6.23xl04
C5
665
7.03
0.971
0.0456
647
6.8
0.95
0.044
6880
72.7
10.0
0.471
3
0.03
0.004
0.0002
5.8
0.061
0.0085
0.00040
36
0.38
0.052
0.0026
Vin=1.02xl05
1 r
°10
406
6.98
0.970
0.0455
395
6.8
0.94
0.044
4200
72.2
10.0
0.471
2
0.03
0.005
0.0002
3.6
0.062
0.0086
0.00040
22
0.38
0.052
0.0026
V9,=1.76xl05
" r
45
235
6.89
0.967
0.0455
229
6.7
0.94
0.044
2430
71.2
10.0
0.470
1
0.03
0.004
0.0002
2.1
0.062
0.0086
0.00041
13
0.37
0.052
0.0026
V,=5947 Vc=8794
r P
C2 °5
6970 4710
7.10 7.09
0.973 0.972
0.0456 0.0455
6780 4580
6.9 6.9
0.95 0.95
0.044 0.044
72000 48700
73.4 73.3
10.0 10.1
0.471 0.471
30 20
0.03 0.03
0.004 0.004
0.0002 0.0002
61 41
0.062 0.062
0.0085 0.0085
0.00040 0.00040
376 254
0.38 0.38
0.053 0.053
0.0026 0.0026
Vin=1.43xl04
1U -
4o
2900
7.10
0.973
0.0456
2820
6.9
0.95
0.044
30000
73.4
10.1
0.472
10
0.02
0.003
0.0002
25
0.061
0.0084
0.00039
156
0.38
0.053
0.0026
V,c=2.26xl04
"r
°25
1830
7.07
0.970
0.0456
1780
6.9
0.94
0.044
19000
73.4
10.1
0.472
9
0.03
0.005
0.0002
16
0.062
0.0085
0.00040
99
0.38
0.053
0.0026
-------
Table 3.44 (continued)
Contaminant Mass available
concentration for transport
in mine (kg/yr except,.
effluent (mg/i as noted)v<
except as noted)
Molybdenum 300
0.29
Barium 850
0.81
Zinc 45
0.043
Sulfate 1.22 x 105
580
Total Suspended 29000
Solids
27.8
1- and 7-day flood flow volumes (m) and contaminant concentrations associated with
1-Day
i} V2=2.16xl04
390
1.4
0.20
0.0093
1100
4.1
0.56
0.026
58
0.21
0.029
0.0014
1.58 x 105
584
80
3.8
38000
140
19
0.90
V,=6.23xl04
5 C5
130
1.4
0.19
0.0089
380
4.0
0.55
0.026
20
0.21
0.029
0.0014 •
5.48 x 104
580
80
3.8
13000
140
19
0.89
V1Q=1.02xl05
82
1.4
0.20
0.0092
230
4.0
0.55
0.026
12
0.21
0.029
0.0014
3.35 x 104
574
80
3.7
8000
140
19
0.90
V25=1.76xl05
48
1.4
0.20
0.0091
140
4.1
0.58
0.027
7.2
0.21
0.030
0.0014
1.94 x 104
568
80
3.8
4600
130
19
0.89
V2=5947
1400
1.4
0.20
0.0092
4000
4.1
0.56
0.026
210
0.21
0.029
0.0014
5.74 x 105
586
80
3.8
140000
140
20
0.92
Vc=8794 V
C5
960
1.4
0.20
0.0093
2700
4.1
0.56
0.026
140
0.21
0.029
0.0014
3.88 x 105
584
80
3.8
92000
140
19
0.89
return periods of 2 to 25 years' '
7-Day
10=1.43xl04
C10
590
1.4
0.20
0.0091
1700
4.2
0.57
0.027
88
0.22
0.030
0.0014
2.38 x 105
582
80
3.7
57000
140
19
0.90
V25=2.26xl04
C25
370
1.4
0.20
0.0092
1100
4.2
0.58
0.027
56
0.22
0.030
0.0014
1.51 x 105
584
80
3.8
36000
140
19
0.89
(a)
(bk
Mass values shown are on an annual, per-mine basis.
'V and C refer respectively to flood volume, in cubic meters, and concentration in runoff for an r-year flood. Concentrations are in
mg/4, except for radium-226 and lead-210, which are in pCi/*. Concentrations shown are from accretion or loading In the sub-basin for 2, 5, 10,
25 years, yielding the first value shown in each set. The next three values below this initial value represent, In downward order, concentrations
In the flood flow as diluted by the mean annual flow in 1) the Rio San Jose near Grants (5.83 x 10 m ), 2) the Rio Puerco at Bernardo (4.26 x 10
m3), and 3) the Rio Grande near Bernardo (86.69 x 107 m3).
Note.—Assumptions: Mines discharge continuously at a rate of 2.0 m3/min. Concentrations are the average of those shown in Table 3.39. Except
for radium and sulfate, all suspended and dissolved contaminants remain in or on the stream sediments and are mobilized by flood flow. Twenty per-
cent of the sulfate and 10 percent of the radium are available for resolution.
00
-------
3-139
arbitrarily set at 0.00144 Ci/yr or 10 percent of the annual loading from the
model mine.
Sulfate is also considered an important exception in the total "trans-
port" concept. Because sulfate can be a highly mobile anion, it is assumed
that 80 percent of the load enters the shallow groundwater reservoirs and 20
percent is available for solubilization and chemical transport in surface
flows. No distinct pattern of groundwater contamination from mine water, per
se, was documented in an earlier Grants Mineral Belt survey (EPA75), but
recent data from the State indicate groundwater deterioration as a result of
mine drainage (J. Dudley, New Mexico Environmental Improvement Division, oral
communication, 1979). It is likely that considerable fractionation of other
stable and radioactive trace elements occurs, but field data specific to the
uranium mining regions are quite scarce, with the exception of Texas (He79),
where only stable elements were studied. Because of our imperfect, non-pre-
dictive understanding of trace element transport in aqueous systems, our
analysis assumes total transport for most constituents in lieu of numerous,
equally unfounded assumptions for resuspension factors, fractionation, etc.
Floods of 1-day and 7-day duration and return periods of 2, 5, 10, and 25
years are arbitrarily selected as providing the necessary flushing action
associated with intense, short-term runoff events. It is likely that storms
of shorter (less than 1-day) duration and possibly greater discharge rate
also transport contaminants. The flow volume and thus the dilution cannot be
estimated for these events.
Calculated water quality in basin and regional basin streams is shown in
Table 3.45 along with established and suggested standards for selected con-
taminants. For uranium, concentrations in the basin exceed the suggested
limits based on chemical toxicity and radiotoxicity. Radium-226/228 exceeds
the standard in the basin but is well below the standard for the regional
basin. The same is true for sulfate, cadmium, arsenic, barium, and selenium.
Zinc is the only contaminant consistently below the potable and irrigation
water standards. As in the case of the surface mine scenario for Wyoming,
uranium is apparently well above suggested limits and warrants further study,
as do the stable toxic elements in the basin area(s) closest to the mining
centers.
With the exception of radium-226 and sulfate, the concentrations of
radionuclides and other parameters shown in Tables 3.44 and 3.45 reflect no
-------
Table 3.45 Comparison of potable and Irrigation water standards and
surface water quality affected by underground mine drainage
Parameter
Range of contaminant concen-
trations in flood flow , ,
affected by mine discharge^'
Basin Regional Basin
Min. Max. Min. Max.
Potable water standards (mg/{, r '
Maximum Permissable Recommended Limiting
Concentration Concentration
Irrigation^
Recommendations for maximum concentration
for continuous use on all soils (mg/s. )
Total U
Ra-226 +
TSS
Sulfate
Zn
Cd
As
Ba
Se
6.
228 6.
130
574
0.
0.
0.
4.
0.
9
7
21
03
061
0
37
7.
6.
140
584
0.
0.
0.
4.
0.
1
9
22
03
063
2
38
0.045
0.044
0.89
3.7
0.0014
0.0002
0.00039
0.026
0.0026
0.046
0.044
0.92
3.8
0.0014
0.0002
0.00041
0.027
0.0026
0.015/3.
-.
__
WH
—
0.
0.
1
0.
5/0.2(d)
-.
_
_
-
01
05
01
5 pCIA
250
5.0
---
0.01
--"
.
5 pC
-
200
2.
0.
0.
-
0.
„
i /o
—
0
010
10
—
02
^''Concentrations in milligrams per liter, except Ra-226 -228 which are in picocuries per liter. Data shown apply to the Basin (Rio San
Jose near Grants) and Regional Basin (Rio Grande near Bernardo) streams (Table 3.44).
* 'Sources: U.S. Environmental Protection Agency (EPA76) and, in the case of uranium, suggested guidance from the National Academy of
Sciences (NAS79) to the USEPA and from USEPA, (Office of Drinking Water) to the State of Colorado (La79).
(c)
(d).
Source: (NAS72).
'0.015 mgA. :Suggested maximum daily limit based on radiotoxicity for potable water consumed at a rate of 2 liters per day on a continuous basis
3.5 mg/t: Suggested maximum daily limit based on chemical toxicity and intake of 2 liters in any one day
0.21 mg/£: Suggested maximum daily limit based on chemical toxicity and intake of 2 liters per day for 7 days
-------
3-141
reductions for ion exchange, precipitation, or sorption. Rather, a simple
dilution model is used in which the mass loading from mine discharge is
calculated as the product of concentration and discharge (volume). There are
problems with this approach. In some cases, the calculated concentrations in
flood waters probably exceed the solubility limits, as in the case of sulfate
in the presence of barium. In other instances, precipitation of barium
sulfate or iron and manganese hydroxides might greatly reduce the concen-
tration of radium and uranium, both of which would coprecipitate. Thus the
stream concentrations shown in Table 3.44 are probably high (conservative).
To improve the analysis, additional comparisons or parallels were drawn using
mill tailings solutions and stream water quality as affected by mine drainage
and a mill tailings spill.
Contaminant concentrations in uranium mill tailings liquids provide an
upper limit estimate of runoff concentrations insofar as the solvent action
of tailings solutions maximize dissolution of minerals present in the ore (J.
Kunkler, USGS, written communication, 1979). Table 3.46 is a compilation of
mill tailings water quality data from numerous previous reports and sum-
marized by EPA and USGS staff (Ka79; Ku79). It is apparent that there are
wide variations as a function of mining region and whether an acid or alka-
line leach mill circuit is used. The Nuclear Regulatory Commission (NRC79b)
assumption for the composition of a "typical" acid leach mill is shown along
with other average or representative analyses. A conservative (worst qual-
ity) analysis for uranium mill pond water quality is estimated as follows
(Table 3.47) and compared to the average concentrations calculated from the
mixing of mine effluent and flood volumes (Table 3.44).
The data in Table 3.47 suggest that calculated concentrations in the
sub-basin almost without exception exceed those in uranium mill tailings
solutions. Thus, the calculated values are probably erroneously high. Calcu-
lated concentrations in flood waters of the basin and regional basin streams
are considerably less and are in rough agreement with field data, at least
for the stable constituents. Radium-226 and lead-210, however, still seem
excessively high considering the various natural processes of sorption,
precipitation, and so on. To understand the degree to which natural streams
transport contaminants, we reviewed water quality data from selected New
Mexico streams receiving mine drainage.
-------
Table 3.46 Radiochemical & stable element/compound water quality for selected acid & alkaline leach uranium mill tailings ponds in the United States
i.
2.
.
4.
5.
6.
7.
.
9.
10.
Tailings Pile U Th-230
Location (mg/O
Split Rock, WY 10.5 41600
(acid)
Canon City, CO — —
(acid)
Mstah ilT O (\ £fl
nuau j U 1 £.. \J 3U
United Nuclear, 14 —
NM (acid)(a)
Anaconda Inj. 130 —
Well Feed, NM
Kerr-McGee, NM 32
(acid)(a)
UN-HP, Grants, 150
NM (alkaline)
•j. — _ _ — _ UV C. O A T 1 f\
Humeca, WY bo. 4 liu
(acid)
USNRC-Uranium 8.0 150000
Milling ElS(acid)
Representative
acid mi 11 pond, «
v.. Uju i " • \B J
in New Mexico —
"Average" (Exclusive
of 9 and 10) 58 13920
Maximum value:
"Average" versus
NRC GEIS 58 150000
Ra-226 Pb-210 Po-210 As
(pCi/z)
4800 — 940 1.1
10.1
inn -_- ~i A
1UU --- ... /.U
38
53
58
52
o/in
£W — - — -
400 400 400 0.2
i
760 — — 6
760 400 400 6
Mn Cu Se Mo V SO Na Fe TDS NH Ca NO Cl
(cngA )
15.5 0.2 1 0.05 280 11810 374 560 43.5 65
25.0 18 0.6 190 7.1 34000 19000 280 77400 — 380 140 6500
_ _ _ _ inn mnnnn — - — — ^00
50 3 0.005 3 30 — 300 1000 700
340 — 0.03 — 6.3 4900 1200 — — 69 — 7.4
30 5 0.18 7 10 — 500 1000 - 300
0.92 70 6.8 4300 4300 4.4 — 4.4 2
OA fi t ... ... ___ CCA A 1 1 *7Afi ft c _._. Afif\ — — — ic i cnnn
500 50 20 100 0.1 30000 500 1000 35000 500 500 — 300
160 6.5 0.32 54 10 10000 6200 510 80000 227 485 40 1700
500 50 20 100 10 30000 6200 1000 80000 500 500 40 1700
(b)
Source: Ku79.
Ammonium ion.
-------
Table 3.47 Summary of flood runoff water quality and
uranium mill pond quality
Parameters
Uranium (mg/£)
Radium-226 (pCi/£)
Lead-210 (pC1/i)
Polonium-210 (pCi/£)
Arsenic (mg/£)
Manganese (mg/a )
Copper (mg/£)
Selenium (mg/£ )
Molybdenum (mg/£)
Vanadium (mg/£ )
Sulfate (mg/£)
Concentration in
uranium mill
tailings solution
58
760
400
400
6
500
50
20
100
10
30,000
Concentration in
flood waters of the
sub-basiVa'
235 - 6970
229 - 6780
2430 - 72000
NC(b)
2.1 - 61
NC
NC
11 - 220
48 - 2400
NC
9.7 x 104 - 2.87 x 106
Concentration in
flood waters of the
Rio San Jose
7
6.9
73
NC
0.062
NC
NC
0.34
1.4
NC
2901
^Refer to Table 3.44.
calculated.
co
i
to
-------
3-144
The USGS, by water sampling in the Churchrock area of New Mexico (J.L.
Kunkler, USGS, written communication, 1979), determined water quality in an
ephemeral stream receiving rather large and continuous mine discharges. Data
are also available from the Schwarzwalder Mine near Golden, Colorado (EPA72).
Until 1972, this mine discharged effluent high in uranium, radium, and trace
elements to Ralston Creek and subsequently to two lakes/reservoirs used for
irrigation and potable supply (Section 3.2.3.2.1).
The way in which surface runoff water quality is created or affected by
mine discharge is complex. In the Churchrock area, numerous water quality
changes occur as the mine discharges flow toward Gallup (Fig. 3.21 and Table
3.48). As in other uranium mining areas in New Mexico, stream volume con-
stantly decreases with flow distance, but water quality changes are erratic.
Infiltration, discussed in more detail in the following section of the report
and in Appendix H, amounts to about 90 percent or more of the water loss.
The balance is by evaporation. On a percentage basis, similar losses occur
in the principal drainage courses in Ambrosia Lake. Dissolved Ra-226 de-
creases from 30 to 0.88 pCi/£ in a reach of 9.2 km and, on a later date, from
14 to 0.95 pCi/£ in a distance of 26.7 km. Based on the limited flow and
water quality data, it appears that radium is strongly sorbed onto the stream
sediments. In October 1975, soluble uranium decreased from 1150 to 740 yg/
in the reach immediately below the mine discharges, yet in July 1977 and May
1978 uranium increased in the downstream direction from 580 to 860 ug/t and
from 970 to 2800 yg/£. These changes bear no consistent relation to fluctu-
ations in dissolved or suspended solids along the flow path. Both of the
latter parameters appear to increase in the direction of flow and may be a
result of flash floods in lower reaches of the basin. Uranium appears to
undergo little change and may actually increase in the downstream direction.
Of the stable trace elements, vanadium, selenium, iron, molybdenum, and zinc
show no consistent change with distance.
A third approach used to assess surface runoff quality involved a brief
review of some of the data collected to monitor a July 1979 tailings accident
in New Mexico. The mill tailings dam at the Churchrock mill breached and
dumped 223,000 m of liquid and 1,000 metric tons of solids into the Rio
Puerco drainage system. The catastrophe immediately spurred numerous water
quality studies by State and Federal agencies. Numerous inter-
-------
O Twin Lakes
station Name
Q/Manuelito
Mine Effluent; KM & UNC mines and Puerco River tributary
below mines.
Pipeline Canyon at Trestle near Churchrock, N.M.
Effluent from Pipeline Canyon, N.M.
Puerco River near Springstead, N.M.
Puerco River at the Hogback near Gallup, N.M.
Puerco River at Gallup, N.M.
Puerco River at Manuelito, N.M.
Puerco River near state line of N.M. and Ariz.
CO
l
i—»
-P-
Ln
Figure 3.21 Principal streams and surface water sampling stations in the Churchrock and Gallup areas
-------
Table 3.48 Flow and water quality in the Puerco River near Churchrock and Gallup, New Mexico
Location and
(Station Number)
Oct. 16, 1975
Puerco River tributary
below mines - (1)
Puerco River near
Springstead, NH -(4)
Puerco River at
Gallup, MM - (6)
Puerco River at
Manuelito - (7)
July 6, 1977
Puerco River tributary
below mines - (1)
Puerco River at the
3
U nat.
nr/min ng/j, as U,0_
14.5
12.4
5.11
6.8(est)
11.55
6.47
1150
740
—
540
580
860
Ra-226
pCI/jt
30
0.88
0.52
0.25
14
0.95
Total
Dissolved
430
480
640
800
410-
520
Solids, ma/ j
Suspended
410
1600
2300
2800
260
15000
Suspended solids,
metric tons
per day Ba Cd
9.5
8.67
5.14
—
800 1
100 1
Concentrations ug/i
Cr Pb Mo V Zn Se As Fe
21-27 - 20
13-25 - 30
5.7 - 26 - 40
... -_ .__
06 - - 0 25 1(3) 10
0 11 - - 50 20 1(19) 80
Hogback, near Gallup,
NN - (5)
Puerco River near 15.5
State line (NM/AZ) - (8)
83
0.27 600
44000
1700 4 02
30 5 6(7) 90
CO
I
-------
Table 3.48 (Continued)
Location and ,
(Station Number) nT/min
May 25, 1978
Effluent from Kerr 10.9
McGee and United Nuclear
Mines, Churchrock, NM-
(1)
Effluent from Pipeline 9
Canyon, NM - (3)
Puerco River near 10.88
Springstead, NM - (4)
(sampled 5/18/78)
July 11-12, 1978
Pipeline Canyon at 14.45
trestle near Churchrock,
NM - (2)
Effluent from Pipeline 14.3
Canyon, NM - (3)
Puerco River near —
Springstead, NM - (4)
U nat. Ra-226
ug/i as U308 pCi/t
807 2.6
2800 1.5
1100 0.8
940 8.6
1120 1.3
1130 2.2
Suspended solids,
Total Solids, mq/4 metric tons Concentrations ug/4
Dissolved Suspended per day Ba Cd Cr Pb Mo V Zn Se
. ... 12 19 - 4
- ... 820 28 - 110
- ... 12 16 - 0
./
- - 230 11 -
- ... 260 6 - 11
- - - - 240 9 13
As Fe
-
-
- 15
- 540
- 70
- 40
Source: New Mexico District office of the U.S. Geological Survey (Peter Frenzel, written communication, 1979 and Kunkler, 1979).
-------
3-148
pretations of the data have led to some confusion, compounded in some
instances by inconsistent sample collection and preservation. However,
several general findings seem true. Dissolution of stable and radioactive
trace contaminants in flood waters does not seem significant providing that
pH of the flood is in the range of 4 to 7. After several days, the mill
tailings liquid was diluted and neutralized and contaminant concentrations
decreased -- sometimes to levels lower than before the accident (J. Kunkler,
USGS, written communication, 1979). At a downstream sampling station near
Gallup, some 30 kilometers from the spill, dissolved uranium and radium-226
about 36 hours after the spill were 3.1 mg/ji and 0.95 pCi'A, respectively.
Suspended sediments contained 19 ppm uranium and 0.72 pCi/g radium-226. For
the latter, this is less than background.
The surface water quality data pertaining to discharge of mine effluents
and to the July 1979 spill seem to indicate rapid and thorough removal of
radium-226 as a result of sorption, precipitation, pH adjustment, etc. How-
ever, stream sediment analyses in the Grants Mineral Belt are scarce, and
there are no analyses of suspended solids in flood waters. Stream-bed sedi-
ment analyses by the USGS indicate less sorbed radium-226 and uranium than
expected (Ku79). During this spill incident, uranium and selenium were
relatively mobile in surface streams.
From the foregoing review of the literature and field data and prelim-
inary calculations of runoff quality (Table 3.44), the following general con-
clusions are offered:
1. Radium-226 is removed from surface water in the New Mexico study
area at rates of 0.5 to 3 pCi/£ per kilometer of stream. Final concen-
trations are on the order of 0.25 pCi/£. Resolution in successive surface
flows occurs, but it is not significant.
2. Uranium and certain stable trace elements, such as selenium, van-
adium, molybdenum, and iron, show no consistent reduction with flow distance
and may show an increase, at times.
3. Considerable more data collection is needed to understand the fate
of dissolved and suspended contaminants from mine drainage. The present data
base is rather limited in terms of sampling frequency, variety of contam-
inants measured, and types of measurements, for example, suspended solids
analyses for flood waters.
-------
3-149
4. With the exception of radium-226, the preliminary calculations of
runoff quality in Table 3.44 are believed to be a first approximation of
field conditions. Additional studies specific to the principal mining dis-
tricts are needed.
5. Dissolved radium-226 concentrations in runoff are believed to be
several picocuries per liter or less under natural conditions.
6. Uranium is fairly mobile and probably the most significant radio-
nuclide in uranium mine effluent.
3.4.3.2 Impacts of Seepage on Groundwater
The principal use of groundwater in the immediate area of the mines is
for stock water. Wells in the highland areas are typically one to two hun-
dred meters deep and completed in underlying bedrock strata (Co68; Ka75).
Contamination of such wells by mine discharge is considered extremely un-
likely. Shallow wells are few in number and located along major drainages
that are typically ephemeral. Such shallow wells are susceptible to con-
tamination if located downgrade from mine discharges. Municipal water
supplies are usually developed from wells because groundwater is consistently
available and has acceptable suspended and dissolved mineral contents. The
aquifers tapped by municipal wells are mostly either quaternary lava flows or
deeper mesozoic sandstone and carbonate sequences. Considering the distance
from the mining centers to the communities and the hydrogeologic conditions,
it is unlikely that mining will cause measurable deterioration of municipal
water quality. The greatest likelihood for contaminated groundwater is in the
shallow, alluvial aquifer beneath streams receiving mine drainage. It is
extremely unlikely that water quality in deeper, artesian aquifers will be
adversely affected by mine discharge or overland flow affected by solid
wastes. Shallow wells in these locations have been constructed in the past,
but there are only a few and they are used for stock watering. It is poss-
ible that recharge of substantial quantities of mine water to the shallow
aquifer will encourage additional use of it, in which case water quality will
be of concern.
Table 3.49 shows average and extreme concentrations of various common
and trace constituents in groundwater and other measures of water quality.
The data are composited from a previous study (EPA75) and from unpublished
-------
3-150
analyses by the New Mexico Environmental Improvement Division (J. Lazarus,
NMEID, oral communication, 1979). We have categorized the data according to
principal aquifers, which are in areas where the groundwater is not believed
to be contaminated by mining. Because it is common for a well to tap more
than one aquifer, the differences in water quality in Table 3.49 are approxi-
mate at best. The data reveal no sharp differences in water quality amongst
the three major aquifers. The San Andres Limestone, a major aquifer for
municipal and industrial uses in the Grants and Milan areas, has equal or
greater concentrations of most constituents as compared to the Westwater
Canyon Member and Gallup Sandstone units, which are closely associated with
uranium mineralization.
Theoretical analysis of radionuclide transport in groundwater beneath
and adjacent to a uranium mill tailings pond reveals very limited migration
of radionucl ides in groundwater (Se75). Using a seepage rate of 4 x 10"
cm/sec and a 10 percent loss of soluble radionuclides, numerical solutions
for steady state flow and transport into unconsolidated sand for periods of 5
years and 20 years reveal up to several meters movement of radium-226, thor-
ium-230/ 234, uranium, and lead-210 after 20 years of leaching. For example,
radium in groundwater to a depth of 3 meters is 10 percent of that in the
tailings pond. Because the other isotopes tend to have even greater sorption,
migration distances are further reduced. Although field studies at three
uranium mill tailings piles in the Grants Mineral Belt substantiate only
local migration of radionuclides (EPA75), extensive lateral migration of
stable chemical species has been observed at uranium mills in Colorado,
Wyoming, and Washington (Ka79, Ka78a, He79). For example, with respect to
the old Cotter uranium mine at Canon City, Colorado, the Colorado Department
of Health has stated in its Final Executive Licensing Summary, August 17,
1979, that "contamination attributed to tailings liquid was observed in an
off-site water well ten years after the mill began depositing tailings, a
[migration] rate of over five hundred feet per year." With respect to the
same site, one researcher has stated that "the soluble uranium content of
Lincoln Park ground waters is highly elevated with respect to Arkansas River
water and exceeds suggested thresholds below which ecological and health
effects are not expected. Molybdenum concentrations in these ground waters
greatly exceed irrigation standards as well as the ALG based on health and
ecological effects...." (Dr79). Near neutral pH and relatively low concen-
-------
3-151
Table 3.49 Groundwater quality in principal aquifers in the
Grants Mineral Belt, New Mexico
Parameter
PH
Spec. cond.
ymhos/cm
IDS
Cl
mg/n
Se
mg/ji.
V
mgA
Radium-226
pCi/£
Uranium,
mgA,
Th-230,
pCi/£
Th-232,
PCI/*
Po-210,
pCi/£
San Andres
Limestone
7.2
(6.9 - 7.5)
1900
(720 - 3500)
1680
(490 - 4500)
98
(<0.2 - 270)
0.31
(0.01 - 1.52)
0.88
(0.4 - 1.3)
0.47
(0.11 - 1.92)
1.31
(0.04 - 2.6)
0.12
(0.017 - 0.52)
0.11
(0.0053-0.54)
0.75
(0.070 - 2.3)
Aquifer
Westwater Canyon
Member, Morrison Fm.
and
Gallup Sandstone
7.9
(6.7 - 9.15)
1800
(550 - 4250)
1160
(340 - 2300)
15
(0 - 98)
0.02
(0.01 - 0.13)
0.3
(0.3 - 0.3)
0.71
- (0.07 - 3.7)
0.35
(0.02 - 1.0)
0.030
(0.015 - 0.053)
0.015
(<0. 01-0. 036)
0.42
(0.19 - 0.79)
Quaternary
Alluvium, Tertiary
Volcanics, and
Chinle Formation
7.6
(6.25 - 8.8)
1715
(700 - 4000)
1240
(490 - 3800)
57
(6.2 - 260)
0.59
(0.02 - 1.06)
0.55
(0.3 - 1.3)
0.22
(0.05 - 0.72)
4.72
(0.07 - 14)
0.212
(0.018 - 0.65)
0.123
(0.0094-0.99)
0.193
(0.010 - 0.55)
^a'Mean and range of values shown.
Note.--Selenium, vanadium, and uranium values for the limestone and alluvium/
chinle aquifers are based on 4 to 5 analyses and must be regarded as tentative.
-------
3-152
trations in mine effluents, together with low hydraulic heads, indicate short
migration distances in groundwater for radionuclides and most stable trace
elements in mine effluents.
Discharge of water pumped from mines to arroyos has both hydraulic and
water quality impacts on shallow groundwater in the alluvial aquifer. The
seepage model (Appendix H) and scattered field measurements in the Grants
Mineral Belt substantiate that significant groundwater recharge is associated
with mine discharge. Water quality effects on groundwater are poorly docu-
mented, however. We do not address the influence of impoundments used to
remove suspended solids from mine effluents before discharge. Seepage water
losses from such impoundments are believed to be small, especially when
compared to infiltration losses in the arroyos and open fields receiving most
of the wastes not piped to mills for process water. The impoundments are
rather small and tend to become self-sealing due to settlement of fines. In
at least one instance in Ambrosia Lake, the mine pond is lined to prevent
seepage.
Unpublished flow and water quality data from the U.S. Geological Survey
(P. Frenzel, written communication, 1979) document conditions in the Rio
Puerco drainage near Churchrock and Gallup, New Mexico. Figure 3.21 shows
the sampling station locations, and the chemical data are in Table 3.47.
From October 1975 gaging data, seepage and evaporation reduce flow 9.39
3 3
m /min in a reach of 30.2 km, a loss of 0.31 m /min/km. Conservatively
o
assuming 20 percent of this is by evaporation, seepage is 7.5 m /min or 3.94
fi q
x 10 m /yr. Gaging data for July 1977 and May 1978 similarly indicate
average bed losses of 0.24 m /min/km. In the Ambrosia Lake district (data
not shown), discharges (to San Mateo Creek and Arroyo del Puerto) from about
fi -3
a dozen mines total about 10.8 x 10 m /year, and the total length of
/
perennial stream is about 15 kilometers. Assuming an average stream width of
one meter and the above evaporation rate, evaporation and infiltration are
3 3
0.06 m /min and 7.54 m /min, respectively. In this case, infiltration
amounts to 99 percent of total loss. Dissolved solids range from 520 to 1231
mg/£ (mean 743 mg/a ), and Ra-226 ranges from 0.2 to 23 pCi/£ (mean 6.6 pCiA,),
Selenium and molybdenum average 0.010 and 0.22 mg/ji, respectively.
Considering these two areas, evaporation averages about 4 percent of
mine discharge versus the value of one percent calculated in Appendix H.
Obviously, increased evaporation is accompanied by decreased infiltration.
-------
3-153
Infiltration ranges from at least 90 percent to perhaps 99 percent of mine
discharge, or from 1.8 to 1.98 m /min per mine. The foregoing field data and
the more theoretical approach used in Appendix H show reasonable agreement on
the relative amounts of infiltration and evaporation. We conclude then that
most of the mine effluent infiltrates within relatively short distances of
the mine(s) and recharges the shallow water table. The dissolved, generally
nonreactive contaminants such as chloride and sulfate are expected to reach
the water table, but reactive contaminants such as radium-226 and most trace
metals would sorb or precipitate in the soil (substrate) in the course of
infiltration.
The influence of mine discharge on groundwater quality beneath formerly
ephemeral streams now receiving the discharge is currently under investi-
gation by the New Mexico Environmental Improvement Division. Monitoring
wells have been installed at several locations along the Rio Puerco (west) in
the Churchrock area and San Mateo Creek in the Ambrosia Lake district. Table
3.50 summarizes partial results of samples taken in the last 12 to 18 months.
In the Ambrosia Lake district, marked deterioration in water quality between
the Lee Ranch and Sandoval Ranch stations on San Mateo Creek is a result of
either natural causes and (or) mine drainage from a nearby deep underground
uranium mine. Between Sandoval Ranch and Otero Ranch even more pronounced
changes occur. In this short reach of 2.5 km, contaminated flows from uranium
mines, ion-exchange plants, and seepage from an acid leach uranium mill enter
Arroyo del Puerto, a tributary of San Mateo Creek. Additional study of
surface water quality in the Arroyo del Puerto is recommended to further
characterize the obviously interconnected surface water and groundwater
systems.
In the Churchrock area, drained by the Rio Puerco, groundwater quality
changes in the downstream direction are not readily apparent (Table 3.50).
Although there is an acid leach mill also adjacent to the Rio Puerco trib-
utary receiving the mine discharges, the mill is relatively new (1978 start-
up) and may not yet influence stream quality. Most of the discharge from one
of the two mines is used as mill feed water, thereby causing decreased dis-
charge from the mines to the stream. Nevertheless, the reach of the perennial
stream is increasing, indicating infiltration of remaining mine effluent and
addition of water to storage in the shallow aquifer. Storage changes have
been confirmed by static groundwater level measurements in the area east of
-------
3-154
Table 3.50 Groundwater quality associated with the San Mateo Creek
and Rio Puerco (west) drainages in the Grants Mineral
Belt, New Mexico
Station
Sulfate
(mg/ a )
Molbdenum
Selenium Uranium
San Mateo Creek
Lee Ranch
Sandoval Ranch
Otero Ranch
125.7
225-274
463-989
103-235
350-516
< 5 <10
4-14.7 293-400
33-59 680-860
Rio Puerco (west)
Hwy. 566 Bridge on
N. Fork Rio Puerco
Rio Puerco at
Fourth St. Bridge,
Gallup
101-223
163-244
<10-284
<10-215
20-22
9-26
530-760
550-625
Source: Based on unpublished 1978 data developed by the New Mexico
Environmental Improvement Division (J. Lazarus, oral
communication, 1979).
Gallup. A massive spill of mill tailings into the Rio Puerco occurred in July
1979 and will complicate water quality investigation, insofar as the mine and
mill influences are now superimposed in terms of both solid and liquid waste
loadings in the watershed. The tailings "flood," estimated to contain about
360,000 m of fluid and 1000 MT of solids, was traced into Arizona.
In summary and considering the high volume of dilute mine discharges,
-------
3-155
which are enriched in certain stable and radioactive toxic trace elements
(EPA75; Hi77), we recommend that water quality effects of mine discharge be
very carefully evaluated in at least a few selected areas. Available stream-
flow data indicate that infiltration is the principal means of disposal, yet
the water quality data base, in particular, is rather weak to assess whether
adverse impacts are likely. It is expected that future discharges in the
Churchrock area alone will amount to about 40 m3/min and will contain less
than 400 mgA dissolved solids, most of which is sodium and bicarbonate.
Dissolved concentrations of uranium, radium, iron, selenium, and vanadium are
elevated relative to drinking water limits and infiltration of uranium,
selenium, and possibly other stable elements warrants study. Use of settling
ponds and barium chloride treatment greatly reduces the suspended solids,
uranium, and radium concentrations. The final composition and ultimate
disposal of pond sediments and added chemicals is essentially undocumented
and bears additional investigation. Lastly, mine dewatering creates marked
regional cones of depression and reduces the flow of water to existing supply
wells and the baseflow component in major drainage systems such as the San
Juan River (Ly79).
3.4.4 Gases and Dusts from Mining Activities
3.4.4.1 Radon-222 in Mine Exhaust Air
Unlike surface mines, large capacity ventilating systems are required in
underground uranium mines, primarily to dilute and remove Rn-222 that em-
anates from the ore (Section 1.3.3). Ventilation rates vary from a few
hundred to a few hundred thousand cubic meters of air per minute, and mea-
sured Rn-222 concentrations in mine vent air range from 7 pCi/£ to 22,000
pCi/£ (Ja79b). The concentration of Rn-222 in mine exhaust air varies de-
pending upon ventilation rate, mine size (volume) and age, grade of exposed
ore, size of active working areas, rock characteristics (moisture content and
porosity), effectiveness of bulkhead partitions, barometric pressure, ore
production rates, and mining practices. The emanation of Rn-222 dissolved in
water that seeps into most mines may also contribute to Rn-222 in the exhaust
air.
-------
3-156
Because of the numerous variables that affect Rn-222 concentrations in
mine air, it is difficult to confidently model radon releases from under-
ground mines. A useful model would be one that would relate radon emissions
to the production of ILOR. Measurements relating radon emissions to ore
O O
production have been made at seven underground uranium mines in New Mexico
(Ja79b). The results of these measurements varied at the different mines
from 1,380 to 23,500 Ci Rn-222 per APR*, with an average rate of 4,300 Ci
Rn-222 per APR. The higher emission rates were noted to occur at the older
mines. This was believed due to larger surface areas of exposed ore and
sub-ore in the older mines. That is, inactive mined-out areas increase with
mine age, and the ceiling, floors, and walls of these areas still contain
certain amounts of ore and sub-ore. Radon emanating from these surface areas
tend to increase the Rn-222 content of exhausted mine air unless these in-
active areas of the mine (rooms, stopes, drifts, etc.) are effectively
sealed. Because the radon emission factor is so variable in terms of Ci per
APR, an emission rate based on cumulative ILOR mined has been proposed for
modeling purposes (Ja79b). It is believed that this relationship would
reduce the apparent dependence of the emission rate on the mine age. However,
data are not presently available to make this latter correlation.
Although the average measured Rn-222 exhaust factor of 4,300 Ci/AFR is
tentative and may be improved by studies in progress (Ja79b), it is the only
value currently available for modeling purposes and will, therefore, be used
in the present assessment. Assuming that 1 APR is equivalent to 245 MT** of
U308 (Ja79b), 0.017 Ci of Rn-222 will be released from the mine vents per
metric ton of 0.1 percent grade ore mined. This emission rate will include
all underground sources, i.e., emanation from exposed ore and blasting,
slushing, loading, and transporting ore bearing rock. Radon-222 emissions
were estimated for the two model underground mines by multiplying their
*AFR = Annual Fuel Requirement for a 1000 MWe LWR.
**The APR value on which the exhaust factor was based.
-------
3-157
respective annual ore capacities by the above emission rate. Table 3.51
lists the results.
The estimated annual radon release computed for the average underground
mine is compared below with releases reported elsewhere. Agreement is rea-
sonably good.
Source
This Study
Tr79
TVA78a
TVA78b
TVA79
Th79
Annual Release of Rn-222, Ci
306
289 - 467^
1577
180
215
87
' Adjusted for 0.1 percent ore grade.
By properly capping the exhaust vents and sealing the shaft and mine
entrance, radon emission rates from inactive mines will be a negligible
fraction of the radon release rate that occurs during active mining.
3.4.4.2 Aboveqround Radon-222 Sources
Radon-222 will be released from the following aboveground sources.
1. Dumping ore, sub-ore, and waste rock from the ore skip into haul
trucks and unloading them on their respective piles.
2. Reloading ore from the stockpile after a 41-day residence time.
3. Emanation from waste rock, sub-ore, and ore storage pile surfaces.
The annual quantities of Rn-222 released by sources 1 and 2 were esti-
mated using the following factors and assumptions.
Radon-222 is in secular equilibrium with U-238.
The density of ore, sub-ore, and waste rock is 2.0 MT/m .
Annual production rates of ore and sub-ore are equal and
assumed to be 1.8 x 104 MT at the average mine and 2 x 10
MT at the average large mine (Sections 3.4.1.1 to 3.4.1.3).
The production rate ratio of ore to waste rock is 9.1:1 (Sec-
tion 3.4.1.1).
All Rn-222 present is available for release, 0.00565 Ci/m per
-------
3-158
Table 3.51 Estimated annual radon-222 emissions from
underground uranium mining sources
AverageAverage Large
Source Mine^, Ci/yr Mine^, Ci/yr
Underground"
Mine vent air 306 3,400
Aboveground
Ore loading and
dumping
Sub-ore loading
and dumping
Waste rock loading
and dumping
Reloading ore from
stockpile
Ore stockpile exhalation
Sub-ore pile exhalation
Waste rock pile exhalation
Total
1.4
0.5
0.003
1.4
6.3
61
0.5
377
15.3
5.3
0.03
15.3
53
338
2.6
3830
^'Annual production of ore and sub-ore = 1.8 x 10 MT, waste rock =
2.0 x 103 MT.
x 104 MT.
' 'Annual production of ore and sub-ore = 2 x 10 MT, waste rock = 2.2
-------
3-159
percent U30fl (Ni79), with an emanation coefficient of 0.27
(Au78, Tanner, A.B., Department of Interior, Geological
Survey, Reston, VA., 11/79, personal communication).
The quantities of U30g present in ore, sub-ore, and waste
rock are 0.10 percent, 0.035 percent and 0.0020 percent,
respectively (Sections 3.4.1.1 to 3.4.1.3).
Substituting the above values into the following equation yields the
Rn-222 releases given in Table 3.51 for the average mine and the average
large mine. , \
Rn-222 (Ci/yr) = (percent U,0a) 10.00565 Ci 1(0.27) / m3
13 I I
\m . percent/ 12.0 MT
x (Production Rate, MT) ' (3.11)
These releases are maximum values since very little time will have elapsed
between the underground (blasting, slushing, loading, etc.) and surface
operations. A significant amount of the radon that is available for release
will emanate during the underground operations and invalidate the first
assumption above concerning radioactive equilibrium. Nevertheless, these
estimated maximum releases are very small in comparison to the radon released
from the mine exhaust vents.
The emanation of Rn-222 from waste rock, sub-ore, and ore piles is based
on an exhalation rate of 0.092 Ci/m2-yr-percent U30g (Ni79) and ore grades of
0.002 percent, 0.035 percent, and 0.10 percent, respectively. Surface areas
of the ore piles (Table 3.37), sub-ore piles (Table 3.38), and waste rock
piles (Table 3.36) were used in these calculations. Applying these para-
meters, the annual Rn-222 emissions from the waste rock, sub-ore, and ore
piles at the average mine and average large mine were computed. Table 3.51
gives the results. Total annual Rn-222 emissions during underground mining
operations is the sum of the releases from all sources considered: 377 Ci
from the average mine and 3830 Ci from the average large mine. More than 80%
of the Rn-222 emissions results from the mine vent air.
3.4.4.3 Dusts and Fumes
Vehicular emissions resulting from the combustion of hydrocarbon fuels
in gasoline and diesel-powered equipment are considerably less at underground
mines than at surface mines (Section 3.3.4.1). The principal emissions are
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3-160
participates, sulfur oxides, carbon monoxide, nitrogen oxides, and hydro-
carbons. The quantity of these combustion products released to the atmosphere
depends on the number, size, and types of equipment used, all of which are
directly related to ore production.
EPA has estimated the following emissions from mining 1350 MT of ore per
day from an underground mine (Re76).
Pollutant Emissions per Operating Day, Kg/d
Particulates 2.4
Sulfur Oxides 5.0
Carbon Monoxide 41.9
Nitrogen Oxides 68.1
Hydrocarbons 6.9
Assuming a 330 operating-day year (Ni79), these emissions were adjusted
according to the annual ore production of the average mine (1.8 x 10 MT) and
the average large mine (2 x 10 MT). Table 3.52 lists the total airborne
combustion product emissions. These emissions are small compared to those at
surface mines (Table 3.30). For example, these estimates indicate that the
emissions of combustion products at the average surface mine are more than
100 times greater than those at the average underground mine.
At underground mines, dust is produced by both underground and surface
operations. No measurements have been made of dust concentrations in mine
exhaust air. Because underground mines are wet, which greatly reduces dust
production, and since a large portion of the dust produced would probably
deposit underground, dust emissions from underground operations are probably
relatively small. Hence, dust emissions from underground operations will not
be assessed.
Aboveground sources of dust include dumping ore, sub-ore, and waste rock
from the skip into haul trucks; dumping these materials onto their respective
piles; reloading ore from the stockpile; using dirt haul roads by vehicular
traffic; and dust suspended by the wind from the waste rock, sub-ore, and ore
piles. These sources will be assessed as was done previously for surface
mines (Section 3.3.4.1).
-------
3-161
Table 3.52 Estimated air pollutant emissions from heavy-duty
equipment at underground uranium mines
Pollutant
Particulates
Sulfur oxides
Carbon monoxide
Nitrogen oxides
Hydrocarbons
Average Mine^ '
32
67
560
910
92
Emissions, Kg/yr'a'
Average Large Mine^0'
350
740
6,210
10,100
1,020
^Based on Re76 and 330 operating days per year.
(b),
(c).
^ 'Annual ore production = 1.8 x 10 MT.
'Annual ore production = 2 x 10 MT.
Dust emissions will vary over a wide range depending upon moisture
content, amount of fines, number and types of equipment operating, and cli-
matic conditions. Because ore is generally wet, the relative amounts of dust
produced from its mining and handling are usually small. The following
emission factors were selected from those suggested by the EPA for loading
and dumping operations (Hu76, Ra78, Da79):
2
truck loading = 2.5 x 10 kg/MT; and
truck dumping = 2.0 x 10 kg/MT.
Average annual dust emissions were estimated for the aboveground mining
activities by applying these emission factors to the ore, sub-ore, and waste
rock production rates of the average mine and average large mine. Table 3.53
lists the results. One-half the emission factor values were applied to ore
and sub-ore because they are generally wet, except when reloading ore from
the stockpile. In that case, it is assumed to have dried during the 41-day
residence period (Section 3.4.1.2). Also, the emission factor for truck
loading was assumed valid for loading the haul trucks from the mine skip. The
dust emission for truck dumping may be high since it was based on dumping of
aggregate, which would have a smaller particle size distribution than the
ore, sub-ore, or waste rock (Hu76).
-------
3-162
The movement of heavy-duty trucks is a large source of dust at most
uranium mines. The magnitude of this source depends upon a number of
factors, including the particle size distribution and moisture content of the
road bed material, vehicular speed and distance traveled, and meteorological
conditions. Emission factors for heavy-duty haul trucks (1.15 kg/VKmT) and
light duty vehicles (1.03 kg/VKmt) are the same as those computed for these
vehicles at surface mines (Section 3.3.4.1). Dust emissions for the movement
of heavy-duty haul trucks were estimated using the appropriate emission
factor and assuming --
31.8 MT truck capacities;
round-trip haul distances of 1.61 km to the ore and sub-ore
piles and 3.22 km to the waste rock pile; and
the annual production rates given in Sections 3.4.1.1, 3.4.1.2
and 3.4.1.3.
Table 3.53 lists the results.
Additional dust emissions will occur from light-duty vehicular traffic
along access roads. Using the emission factor derived in Section 3.3.4.1
(1.03 kg/VKmt) and assuming that there are 16 km of access roads traveled 4
times a day during the 330 operating days per year, about 22 MT of dust will
be produced from this source annually. Emissions that occur during haulage
road maintenance is relatively small and will not be considered.
Heavy-duty, haul truck traffic at underground uranium mines produces
considerably less dust than at surface mines. This is to be expected because
of the vast quantities of overburden that must be transported as well as
larger ore and sub-ore capacities at surface-type mines.
The dust emissions computed above for transportation assume no effective
dust control program. But, haul roads are normally sprinkled routinely
during dry periods, and stabilizing chemicals are applied to roadways,
usually to the ore haul roads. Dust emissions along haul roads can be
reduced by 50 percent from sprinkling and up to 85 percent by the application
of stabilizing chemicals (EPA77b, Da79).
Table 3.53 also lists average annual dust emissions caused by wind
erosion of waste rock, sub-ore, and ore piles at the model underground mines.
Emission factors, computed in Appendix I, are 2.12 MT/hectare-yr for waste
rock and sub-ore piles and 0.040 kg/MT for the ore stockpiles. The first
emission factor was multiplied by the waste rock and sub-ore pile surface
-------
Table 3.53 Estimated average annual dust emissions from underground mining activities
Source^ '
Loading truck from
skip at mine shaft
Truck dumping at
piles
Reloading stock-
(e)
piled orev '
Wind suspended dust
from piles
Transportation^
/ .
Average Mineu
Ore(cJ Sub-ore^
0.23 0.23
0.18 0.18
0.45 NA^
0.72 4.0
1.0 1.0
Dust
Emissions, MT/yr
*' Average Large Mine^ '
Waste Rock
0.05
0.04
NA
0.57
0.23
Ore^c^
2.5
2.0
5.0
8.0
11.6
Sub-ore^
2.5
2.0
NA
22
11.6
Waste Rock
0.6
0.4
NA
3.0
2.6
^Based on annual production rates of 1.8 x 10 MT of ore and sub-ore, and 2.0 x 10 MT of waste rock.
5 4
Based on annual production rates of 2 x 10 MT of ore and sub-ore, and 2.2 x 10 MT of waste rock.
Assumed wet.
Aboveground activities.
Assumed dry.
NA - Not applicable.
emissions from heavy-duty, vehicular traffic along ore, sub-ore, and waste rock haul roads.
(d)
(e)
CO
CO
-------
3-164
areas given in Tables 3.36 and 3.38, respectively, while the second
factor was multiplied by the annual ore production.
Table 3.54 shows annual contaminant emissions caused by mining activ-
ities (loading and dumping) according to source location, at the mine shaft
and at the piles. Contaminant emissions were computed by multiplying the
total annual dust emissions at each pile (Table 3.53) by the respective
contaminant concentrations in each source—waste rock (Section 3.4.1.1;
Table 3.16), sub-ore (Section 3.4.1.3; Table 3.19), and ore (Section 3.4.1.2;
Table 3.19). Contaminant emissions at the site of the mine shaft were com-
puted by multiplying the annual dust emissions of ore, sub-ore, and over-
burden (loading truck from skip - Table 3.53) by their respective contaminant
concentrations. The three products of the multiplication were then summed to
give the values listed in the 4th and 8th data columns of Table 3.54. The
health impact of the sources at each location will be assessed separately in
Section 6.1.
Annual contaminant emissions due to wind suspension and transport of
dust are listed in Table 3.55. These values were computed by multiplying the
annual mass emissions (Table 3.53) by the contaminant concentrations in waste
rock, sub-ore, and ore listed in Sections 3.4.1.1, 3.4.1.3, and 3.4.1.2,
respectively. The uranium and uranium daughter concentrations in dusts from
all sources were also multiplied by an activity ratio (dust/source) of 2.5
(Section 3.3.1.2). Although some metals may also be present as secondary
deposits, it was believed that there were insufficient data to justify multi-
plying their concentrations by the 2.5 ratio.
The dust emissions from vehicular traffic listed in Table 3.53 (trans-
portation) were summed with that produced by light vehicular traffic (22
MT/yr) and considered one source of emissions. Concentrations of contam-
inants in haul road dust have not been measured and are not known. Some
spillage of ore and sub-ore along haul roads will undoubtedly raise uranium
levels in roadbed dust. As an estimate, uranium and daughter concentrations
in the dust were considered to be twice background, 8ppm (2.7 pCi/g), while
concentrations of all other contaminants were considered to be similar to
those in the waste rock (Section 3.4.1.1). Table 3.56 shows the annual
emissions computed with these assumptions.
-------
Table 3.54 Average annual emissions of radionucl ides (pCi) and stable elements (kg) from
mining activities at the model underground mines
Average Underground Mine'3'
Contaminant
Arsenic
Barium
Cobalt
Copper
Chromium
Iron
Mercury
Potassium
Magnesium
Manganese
Molybdenum
Nickel
Lead
Selenium
Strontium
Vanadium
Zinc
Uram'um-238 and
each daughter
Thorium-232 and
each daughter
Waste Rock
Pile Site
0.0004
0.012
NR(b)
0.0007
< 0.002
0.24
< 0.0003
0.28
NR
0.02
0.0001
NR
0.0009
0.0001
0.006
0.004
0.0008
0.6
0.04
Sub-ore
Pile Site
0.02
0.17
0.003
0.01
0.004
2.8
ND(C)
4.5
0.63
0.17
0.02
0.004
0.01
0.02
0.02
0.25
0.005
45'
0.4
Ore
Pile Site
0.05
0.58
0.01
0.04
0.01
9.9
ND
16
2.2
0.60
0.07
0.01
0.05
0.07
0.08
0.89
0.02
450
6.3
Mine
Site
0.04
0.44
0.007
0.03
<0.01
7.5
<0.001
12
1.6
0.47
0.05
0.009
0.04
0.05
0.07
0.65
0.01
222
2.8
Average Large Underground Mine^
Waste Rock
Pile Site
0.004
0.12
NR
0.007
<0.02
2.4
< 0.003
2.8
NR
0.19
0.001
NR
0.009
0.001
0.06
0.04
0.008
6
0.4
Sub-ore
Pile Site
0.17
1.8
0.03
0.12
0.04
3.1
ND
50
7.0
1.9
0.23
0.04
0.16
0.22
0.26
2.8
0.06
495
4
Ore
Pile Si
0.60
6.4
0.11
0.43
0.14
110
ND
175
25
6.7
0.81
0.14
0.55
0.77
0.91
9.9
0.20
4,990
70
Mine
te Site
0.44
4.8
0.08
0.32
< 0.13
82
0.005
129
18
5.1
0.58
0.10
0.40
0.55
0.74
7.1
0.16
2,410
31
emissions from Table 3.53.
Not reported.
Not detected.
CTl
cn
-------
Table 3.55 Average
(kg) in
annual emissions of radionucl ides (yCi) and stable elements
wind suspended dust at the model underground mines
Average Large Underground Mine
Waste
Contaminant Pi
Arsenic
Barium
Cobalt
Copper
Chromium
Iron
Mercury
Potassium
Magnesium
Manganese
Molybdenum
Nickel
Lead
Selenium
Strontium
Vanadium
Zinc
Uranium-238 and
each daughter
Thorium-232 and
each daughter
Rock
le
0.03
0.87
NR(a)
0.05
<0.15
18
<0.02
21
NR
1.5
0.008
NR
0.07
0.006
0.45
0.30
0.06
45
3
Sub-Ore
Pile
1.9
20
0.35
1.3
0.44
345
ND(b)
550
77
21
2.5
0.44
1.7
2.4
2.9
31
0.64
5,450
44
Ore
Stockpile
0.69
7.4
0.13
0.49
0.16
126
ND
200
28
7.7
0.92
0.16
0.62
0.88
1.0
11
0.23
5,700
80
Average Underaround Mine
Waste Rock
Pile
0.005
0.17
NR
0.01
< 0.03
3.4
< 0.005
4.0
NR
0.28
0.001
NR
0.01
0.001
0.09
0.06
0.01
9
0.6
Sub-Ore
Pile
0.34
3.7
0.06
0.24
0.08
63
ND
100
14
3.8
0.46
0.08
0.31
0.44
0.52
5.6
0.12
990
8
Ore
Stockpile
0.06
0.66
0.01
0.04
0.01
11
ND
18 -
2.5
0.69
0.08
0.01
0.06
0.08
0.09
1.0
0.02
513
7.2
- Not reported.
- Not detected.
co
i
CTi
-------
3-167
Table 3.56 Average annual emissions of radionuclides (yCi) and
stable elements (kg) from vehicular dust at the model
underground mines
Contaminant
Arsenic
Barium
Copper
Chromium
Iron
Mercury
Potassium
Manganese
Molybdenum
Lead
Selenium
Strontium
Vanadium
Zinc
Uranium-238 and
each daughter
Thorium-232 and
each daughter
^Mass emissions
* 'Mass emissions
Average Large
Underground Mine^
0.43
14
0.86
<2.4
287
<0.38
335
23
0.12
1.1
0.10
7.2
4.8
0.96
129
48
=47.8 MT/yr.
= 24.2 MT/yr.
Average
Underground Mine^ '
0.22
7.0
0.44
<1.2
145
<0.19
170
12
0.06
0.53
0.05
3.6
2.4
0.48
65
24
-------
3-168
3.5 In Situ Leach Mining
Because in situ leaching of uranium (see general description in Section
1.3.4) is in its infancy, a data base for performing a detailed generic
environmental assessment does not presently exist. The fact that the para-
meters for assessing this process are so site specific and depend upon oper-
ational procedures further impedes a generic assessment. Current research
projects may help to resolve many of the present uncertainties and provide
the data needed to better quantify the potential source terms (La78).
In view of the expected future expansion of this uranium mining method
(Section 1.3.4), a qualitative assessment that can be modified later when
additional data become available was deemed necessary. This assessment was
possible because of recent laboratory experiments and field measurements at
pilot-scale plants (Wy77, Ka78b, NRC78b, Tw79).
Similar to other uranium mining methods, in situ leaching also produces
liquid, solid, and airborne wastes. However, the quantities of these wastes
and their characteristics differ considerably from those produced at surface
or underground mines. Also, because the recovery, drying, and packaging of
the U30g produced is often performed at the mine site, wastes from these
processes should probably be included in the mine assessment.
This assessment uses the parameters of a hypothetical "typical" com-
mercial-sized in situ solution mine. Unlike surface or underground mines,
relatively few in situ facilities exist, and they are all somewhat different
because of site specificity and the rapid development of new or modified
techniques. The following parameters for the hypothetical mine were based
upon those of the Highland, Crownpoint, and Irigaray uranium projects and
those reported by Kasper et al. (1978) (Wy77, NRC78b, TVA78b).
The Hypothetical In Situ Solution Mine
(1) Size of deposit = 52.6 hectares
(2) Average thickness of ore body = 8 m (Ka78b, NRC78b)
(3) Average ore grade = 0.06 percent U30g (Ka78b, Tw79)
(4) Mineralogy = Sandstone
-------
3-169
(5) Ore density = 2 MT/m3
(6) Ore body depth = 153 m
(7) Mine life = 10 years (2-yr leach period in each of
5 sectors)
(8) Well pattern = 5 spot (NRC785, TVA78b, Ka78b)
Injection wells = 260
Production wells = 200
Monitoring wells = 80
(9) Annual U30g production = 227 MT (Wy77, NRC78b, Ka78b)
(10) Uranium leaching efficiency = 80 percent (Ka78b)
(11) Lixiviant = Alkaline
(12) Lixiviant flow capacity = 2,OOOVmin (Ka78b, Wy77, NRC78b)
(13) Lixiviant bleed = SOVmin (2.5 percent) (Wy77, NRC78b, TVA78b)
(14) Uranium in Lixiviant = 183 mg/A (TVA78b, Ka78b, NRC78b)
(15) Calcite (CaCO,) removal required = 2 kg calcite per kg U-00
o 0 o
(Wy77)
The solid, liquid, and airborne wastes generated by this facility are
described below. Wastes and quantities generated, as well as operations and
procedures selected, will naturally differ to varying degrees from those at
some operating sites.
3.5.1 Solid Wastes
The quantity of solid wastes generated depends upon the leachate, the
ore body, and operational procedures that effect the mobilization of ore
constituents. Little information is available on the quantities of solids
generated because of this site dependence, the newness of the process, and
the apparent relatively small quantities that are produced. Examples of
solid wastes that might be expected to be generated by the alkaline leach
process are listed below:
(1) Materials filtered from the lixiviant line
(2) Sediments from the surge tanks
(3) Calcium carbonate from the calcium control unit
-------
3-170
(4) Barium sulfate from the contaminant control in the
elution/precipitation circuit of the recovery process
(5) Materials deposited in the evaporation ponds
(6) Drill hole residues
(7) Solids from aquifer restoration
Sources 1 and 2
No information concerning quantities of solids from these two sources
could be found in the literature, but they are described as being relatively
small compared to other sources (NRC78b). These wastes are transferred to
evaporation ponds and retained beneath a liquid seal.
Source 3
One of the larger sources of solids is the calcium control unit (Wy77).
Calcite, CaC03, which is removed prior to injection of the refortified lixi-
viant, coprecipitates radium and any residual uranium. It has been reported
that the amount of calcite produced is less than 2.8 kg per 1 kg of U.,0g
recovered (Wy77). Assuming this ratio to be 2.0, and if Ra-226 is in secular
equilibrium with U-238 in the ore, and 2.5 percent is solubilized by the
lixiviant (Wy77, NRC78b), 454 MT of calcite will be produced annually and
contain a total of 1.6 Ci of Ra-226. Also, calcite has been observed to
contain between 1 to 2 percent ILOg by weight (Wy77). Assuming an average of
1.5 percent U30g, about 1.9 Ci (6.8 MT U30g) of U-238 may also be present in
the calcite waste.
Radium-226 and its daughter, Rn-222, are probably the most radiologically
significant radionuclides associated with uranium mine wastes, and the small
amount of Ra-226 retrieved by in situ leaching is a distinct advantage.
Conventionally mining the quantity of ore assumed for the hypothetical in
situ mine would contribute 64 Ci of Ra-226 per year to the surface. Because
of the insolubility of RaSO^, acid lixiviants containing H^SO. mobilize even
less radium than alkaline lixiviants. It is reported that the latter mobi-
lizes up to 4.5 times the radium as acid leach solutions (Wy77).
If practical, the calcite waste is transferred to the mill to recover
the coprecipitated uranium. Otherwise, the waste is transferred to an evap-
oration pond and retained beneath a liquid seal to minimize atmospheric dis-
persion and radon emanation.
-------
3-171
Source 4
If necessary, the sulfate concentration in the eluant circuit of the
uranium recovery unit may be controlled by the precipitation of BaSO,. There
are no data on the contaminant levels expected in the BaSO. waste, although
less than 730 MT per year are anticipated (Wy77). These wastes are impounded
beneath a liquid seal of an evaporation pond.
Source 5
An assortment of precipitation compounds will be produced by evaporative
concentration of impounded waste solutions. The principal products expected
are alkali chlorides, carbonates, and sulfates. The quantity of solids pro-
duced by this mechanism and their rate of accumulation on the pond bottom has
not been reported.
Source 6
Residues produced from drilling the numerous wells required for in situ
leaching constitute another solid waste. The hypothetical in situ leaching
facility defined above requires a total of 540 wells drilled to a depth of
153 m: 200 production, 260 injection, and 80 monitoring wells. A diameter of
10.2 cm will be assumed for all wells, although 5.1 cm, 12.7 cm, and-15.2 cm
diameter wells have been used (Wy77). To accommodate a concrete and steel
casing, a drill hole of approximately 20 cm will be required. The residue
from drilling the monitoring wells will consist mostly of barren rock; how-
ever, an equivalent of an 8-m section of each injection and recovery well
will contain 0.06 percent grade ore. Hence, drill hole residues will consist
of 4,960 MT of barren waste rock and 230 MT of ore containing 138 kg of U30g.
These wastes are in relatively small quantities and should be-manageable. The
waste rock and ore, if mixed and stored in a 2-m-high rectangular pile, would
only cover an area of about 0.15 hectares and average 0.0027 percent U30g.
Source 7
During the active mining period, all solid wastes are generally
retained beneath a liquid seal in lined evaporation ponds to minimize atmo-
spheric dispersion and radon emanation. A plan for the final disposal of
solid wastes has not been determined. Suggested procedures are to transport
the wastes to a conventional uranium mill for further treatment to recover
any U30g present, treat the effluent as mill wastes, construct long-term
tailings ponds on the site, or ship the wastes to a licensed off-site burial
ground. Solid wastes probably comprise the least significant type waste
relative to health and the environment. Solid wastes generated from recla-
mation procedures will be discussed in Section 3.5.5.
-------
3-172
3.5.2 Associated Wastewater
Water flushed through the leached area when restoring the well field is
the largest source of wastewater (see Section 3.5.5). The principal sources
of wastewater generated by the hypothetical facility during the leaching and
recovery operations are as follows:
(1) Lixiviant bleed -- barren lixiviant removed from the
leach circuit to produce a net inflow into the well-field
area and to control contaminant concentrations
(2) Resin wash -- water to wash resin of excess NH.C1 used to
regenerate the resin. Lixiviant bleed is sometimes used for
this operation, and it reduces the total quantity of waste-
water produced (Ka78b)
(3) Eluant bleed -- barren eluant removed to control salt accum-
ulation, principally NaCl and Na^COg, and maintain proper
volume
(4) Well cleaning — water used to flush injection wells to pre-
vent clogging
The sources of wastewater and the quantities produced vary at different
sites, depending upon the lixiviant and recovery circuit chemistry as well as
the production rates. However, estimates were made of the quantities of
wastewater generated by the four principal sources for the hypothetical in
situ facility, and they are listed in Table 3.57. It is assumed that waste
from backwashing the sand filters is lixiviant bleed waste water and does not
contribute to the total wastewater generated. The total volume of wastewater
4 3
estimated to be generated is 8.43 x 10 m /yr. Assuming the evaporation
ponds are 3.05 m deep with a 0.604 m freeboard (Wy77) and a natural evap-
oration rate of 142 cm/yr (TVA78b), a pond capacity of 34,770 m3/yr which
would encompass a surface area of about 1.4 hectares/yr would be required.
Using evaporation data assumed for the Irigaray Uranium Project, about 75
percent of the annual wastewater inventory would evaporate, which would leave
4 3
2.11 x 10 m /yr and require a surface area of 0.85 hectares/yr. If
necessary, the pond size can be reduced by using mechanical evaporators.
-------
3-173
Table 3.57 Estimated quantities of wastewater produced by an
in situ leaching operation
Source
Lixiviant bleed (2.5%)
Resin wastr3^
Eluant bleed
Well cleaning^ '
Total
Flow Rate,
( Vroin)
50
26
17
__
Annual Accumulation,
(m3/yr)
2.63 x 104
1.37 x 104
8.9 x 103
3.54 x 104
8.43 x 104
may be included in the lixiviant bleed.
^ 'Assumes 260 injection wells flushed twice each month with 5680 liters
of water.
Source: Data from Wy77 and Ka78b proportioned to an annual U30g production
of 227 MT and a lixiviant flow of 2000j?/min; aquifer restoration is excluded
(Section 3.5.5).
-------
3-174
The liquid wastes are generally brines. They contain large amounts of
sodium chloride consisting of 1,500 to 5,000 mg/£ total dissolved solids
(TDS), trace metals ranging from 0 to 10 mg/i, and small quantities of radio-
activity. The quantities of contaminants generated each year were estimated
for the hypothetical solution mine by using the annual mass emissions esti-
mated for the Highland Uranium Project and adjusting the flow rates to pre-
dict the concentrations (NRC78b). Table 3.58 lists these estimated concen-
trations and annual emissions. Because the contaminants from the lixiviant
bleed were not included in the source document, the trace metals that are
mobilized by the leachate do not appear in the tabulation, and Ra-226
presence is grossly underestimated (Table 1.7, Section 1.3.4). Considering
possible trace metal concentrations and their toxicities, their presence in
the lixiviant bleed wastewater may be significant. Assuming that 2.5 percent
of the Ra-226 in the ore is extracted, the pregnant leachate will contain
about 1,520 pCiA , yielding 1.6 Ci/yr. However, it is assumed that most of
this radium will be removed by the calcium control unit.
There are no planned releases of liquid wastes to the environment at in
situ solution mines. The contaminants dissolved in the liquid wastes will
accumulate on the pond bottoms as the liquid evaporates. Barring dike fail-
ure and seepage through the lined pond bottoms, no impact should be imposed
upon the environment by this source during operation.
Another method, other than evaporation, to remove wastewater from an in
situ site is deep well injection. This is the dominant method of wastewater
removal at operations in South Texas (Durler, D.L., U.S. Steel Corporation,
Texas Uranium Operations, Corpus Cristi, TX, 9/79, written communication).
3.5.3 Airborne Emissions
Airborne emissions from an in situ solution mining operation will origi-
nate from three principal sources: the uranium recovery and processing unit,
the waste storage evaporation ponds, and the radon released from the pregnant
leach surge tanks. The primary radioactive species emitted is Rn-222. The
nonradioactive species emitted are a function of the lixiviant and the
uranium recovery processes employed. Fugitive dust emissions, primarily from
vehicular traffic, will also occur on the site. However, because very little
heavy equipment is used, the potential for adverse environmental impact from
this source will not be significant and is not considered in this assessment.
-------
3-175
Table 3.58 Estimated average concentrations and annual
accumulation of some contaminants in wastewater
Contaminant
Calcium
Chlorine
Carbonate
Bicarbonate
Magnesium
Sodium
Uranium- 238
Radium-226
Thorium- 230
Concentration, mg/£
64
2,070
31
36
24
1,320
1
21(a)
6U)
Annual Accumulation, kg
5,380
173,880
2,600
3,020
2,020
110,880
84
1.
0.
8(b)
5(b)
Units are pCi/£
Units are mCi.
Note.—Mass emissions estimated for the Highland Uranium Project
(NRC78b), adjusted for flow rates and U30g production of the hypothetical
solution mine.
Estimated average annual airborne emissions were computed for the hypo-
thetical facility using data supplied by the Irigaray and Highland Uranium
Projects and from the report of Kasper, et al. (1978) (Wy77, NRC78b). Table
3.59 gives the results, proportioned to a production rate of 227 MT/ yr.
The major sources of emissions from the uranium recovery plant are
by-products of combustion from the dryers, volatilized solution residuals,
and U-00 fines generated during product drying. Carbon dioxide is the major
3 8
combustion product emitted, although sulfur dioxide may also be significant
if oil is used to fuel the dryers. Ammonium salts, used in the precipitation
of uranium and resin regeneration, will volatilize as both ammonia and
ammonium chloride during yellow cake drying. Airborne particulates that
include uranium and some decay products are generated during the drying and
packaging processes. The emission rates of U30Q and daughter products were
computed on the basis of an average release rate of 363 kg of U30g per year
-------
3-176
Table 3.59 Estimated average annual airborne emissions from the
hypothetical in situ leaching facility
Source
Annual Release Rate
Recovery
Uranium-238
Uranium-234
Uranium-235
Thorium-230
Radium- 2 26
Lead-210
Polonium-210
Ammonia
Ammonium chloride
Carbon dioxide
1.0 x 10"1 Ci
1.0 x 10"1 Ci
4.8 x 10"3 Ci
1.7 x 10"3 Ci
1.0 x 10"4 Ci
1.0 x 10"4 Ci
1.0 x 10"4 Ci
3.2 x 10° MT
1.2 x 101 MT
6.8 x 102 MT
Surge Tank
(b)
Radon-222
fc\
Storage Pondsv '
Ammonia
Ammonium chloride
Carbon dioxide
6.5 x 10^ Ci
1.0 x 10^ MT
3.0 x 102 MT
7.5 x 101 MT
^Includes the calcium control unit.
^ 'Assumes all radon formed dissolves in the lixiviant and 100 percent
is released on contact with the atmosphere.
^Based on a release rate of 14.6 MT/yr of NH3> 10.6 MT/yr of C02 and
42.0 MT/yr of NH^Cl per hectare of pond surface (Wy77), and an average pond
surface area of 7.1 hectares (1.42 ha/yr x 5 yrs).
-------
3-177
from a 227 MT/yr facility (Wy77, Ka78b). High efficiency filters and scrub-
bers are used, which significantly reduce the releases from the uranium
recovery plant.
Emission rates from the wastewater storage ponds are determined by the
composition of the waste solutions, evaporation rate, feed rate to the ponds,
and the water temperature. The principal emissions from storage ponds ser-
vicing an alkaline leach process, as defined for the hypothetical facility,
are ammonia, ammonium chloride, and carbon dioxide. Different atmospheric
releases would result from waste ponds servicing an acid leach facility. The
release of Rn-222 from the pond surfaces has not been measured. The emission
rate of Rn-222 resulting from the decay of Ra-226 contained in the pond
sediments will be inhibited by the liquid seal maintained over the entire
surface area of the pond. Because of its low solubility in the unagitated
pond water, it is reasonable to conclude that the rate of release for radon
from the water surface will be small compared to that from the pregnant leach
surge tanks. The liquid seal maintained over the pond area minimizes air-
borne particulate emissions from the storage ponds.
The principal source of airborne radioactive emissions is the release of
Rn-222 from the pregnant leach surge tanks. Rn-222 is mobilized from the ore
zone during solution mining and will be largely soluble in the lixiviant
under the very high pressure (-15 atm) that exists at the ore zone depth
(-500 ft). Upon reaching the atmosphere at the surge tank, nearly complete
release of the absorbed radon will take place. Since nearly all Ra-226
remains underground in the leach zone—only 2.5 percent is assumed to be
extracted--Rn-222 will continue to be generated in areas leachred of uranium.
Consider a 2-year leach period in each of 5 sectors that is 80 percent
efficient and yields an average of 227 MT of U30g per year. If U-238 and
Ra-226 are initially in secular equilibrium and 97.5 percent of the Ra-226
remains underground, 156 Ci of Ra-226 will be continually available for
Rn-222 production. This quantity of Ra-226 will yield a lixiviant concen-
tration in the 252,800 m3 aquifer (Section 3.5.5) of 6.18 x 105 pCi/£ ,
assuming a maximum emanating power of 100 percent. The latter assumption
will result in a maximum Rn-222 concentration in the lixiviant. A high
emanating power is probable considering the conditions that exist in the
aquifer: high pressure, high permeability due to leaching, the presence of
water in the rock pores, radium present on grain surfaces, and the flow rate
of water through the ore zone (Ta78, Tanner, A.B., Department of Interior,
-------
3-178
Geological Survey, Reston, Va, 11/79, personal communication). Therefore,
applying these maximizing conditions with a pumping rate of 2,000 Ji/min, 650
Ci/yr of Rn-222 will be released at the pregnant leachate surge tanks.
Apparently very few measurements of Rn-222 concentrations in pregnant
leachates have been made at operating facilities. One investigator reports
that measured concentrations range from 10,000 pC1/A to over 500,000 pCi/ji
and may vary with time at the same well by factors greater than ten
(Waligora, S., Eberline Instrument Corp., Albuquerque, N.M., 1979, personal
communication). The concentration computed above for the model facility lies
above the observed range.
3.5.4 Excursion of Lixiviant
A production zone excursion refers to the event when the leach solution
flows from the leach field contaminating the surrounding aquifer. Production
zone excursions are usually prevented by bleeding a small fraction (2 to 7
percent) of the lixiviant before reinjection. This imposes an imbalance in
the injection-recovery volumes and causes groundwater to flow into the leach
field from the surrounding stratum.
Production zone excursions are detected by wells placed 60 m to 300 m
from the well field. These wells are routinely monitored, generally bi-
weekly, to detect concentration increases of one or more constituents of the
lixiviant. Lixiviant constituents monitored may be chloride, ammonia, bi-
carbonate, sulfate, calcium, or uranium. In addition, conductivity and pH
measurements are usually included. When one or more of the indicators ex-
ceeds a maximum limit specified in the operator's permit, the observation is
verified by resampling. If positive, sampling frequency is increased, appro-
priate government agencies are notified and corrective actions are begun.
An excursion from the production zone may be terminated by one of the
following suggested methods (Wy77):
(1) Overpumping - increasing the flow rate of the recovery
wells to increase the inward flow of native groundwater
(2) Reordering - applying different pumping rates of the recovery
wells to different areas of the well field, providing a
greater inflow of native groundwater at specific points
-------
3-179
(a variation of overpumping)
(3) Reducing Injection - another method of increasing the ratio
of recovery flow to injection flow providing the same effect
as overpumping
(4) Ceasing to Pump - stopping both recovery and injection flows
(migration is then due entirely to natural groundwater flow,
which is many orders of magnitude less than with wells pumping)
(5) Begin Restoration - initiated when all other efforts have
failed to stop the migration of lixiviant from the leach
field (Section 3.5.5)
Excursions are likely to occur during the operation of an in situ leach
mine. Adverse consequences of an excursion will be determined by its extent,
the rate of outward flow, contamination levels, aquifer hydrology, and the
effectiveness of corrective measures applied.
3.5.5 Restoration and Reclamation
Restoration is the process by which the in situ leach site is returned
to an environmentally acceptable state after mining is complete. Surface
restoration consists of removing all structures, pipelines, and so on and
sealing the evaporation ponds. Subsurface restoration, the primary area of
concern, is done by discontinuing lixiviant injection and continuing pumping
to sweep fresh groundwater from the surrounding area through the leached ore
zone. It is anticipated that this process will flush out the remaining lixi-
viant and chemical compounds or elements that have adsorbed or reacted with
the mineral content of the aquifer. The water recovered can be purified by
chemical precipitation, ion exchange, reverse osmosis, or other processes,
and then recycled. This reduces considerably the quantity of water that must
be managed. Between 75 and 80 percent of the water can be reinjected while
the remainder containing the contaminants is transferred to an evaporation
pond (Wy77, NRC78b). During the initial restoration process, it is generally
cost effective to recover the uranium from the process wastewater.
Aquifer restoration continues until the groundwater quality in the
mining zone meets a criterion established on a basis of the premining water
quality. In many cases, the premining groundwater quality criterion is diffi-
cult to establish because water quality can vary considerably over the ore
zone region and may contain high natural levels of contaminants. Samples of
water from wells monitored prior to mining in Texas contained concentrations
-------
3-180
of Rn-222 approaching 20,000 pCi/£ (Tanner, A.B., Department of Interior,
Geological Survey, Reston, Va, 11/79, personal communication), and it is
probably unrealistic to attempt to restore an aquifer to a better quality
than existed naturally before mining. Wells and flow rates used in this
process must be carefully selected and controlled to provide efficient
groundwater sweeps and to insure that all affected areas of the leach zone
are restored.
The affected aquifer volume that is to be restored may be estimated by
the following equation:
affected volume = area of well field x aquifer thickness (3.12)
x (porosity)
•
100 percent
Assuming a porosity for sandstone of 30 percent (NRC78b), the affected volume
of the hypothetical in situ solution mine defined in Section 3.5 would be:
affected volume = 52.6 hectares x 8 m x
c o
30 percent/100 percent = 1.26 x 10 m .
Because of mixing leach solution with the incoming sweep water and the grad-
ual desorption of some contaminants from clays present in the ore body, more
water is required to adequately flush the contaminants than one pore volume.
It has been estimated that five to seven pore volumes of water would be
required, for adequate restoration (Wy77, NRC78b). Using the seven pore
volume value and assuming that 80 percent of the sweep water is reinjected
fi ^
after purification, a total of 1.76 x 10 m of wastewater having high TDS
would be transferred to the evaporation ponds during the restoration phase.
If the aquifer is swept at a flow rate of 2,000 £/min, restoration would take
8 years (1.6 yr per sector), and wastewater will accumulate at about 2.22 x
5 3
10 m /yr during this period. With careful control, restoration can be con-
current with leaching in different areas of the well field.
Table 3.60 lists estimated average concentrations of contaminants in the
restoration wastewater (NRC78b) and annual accumulation rates of the con-
taminants based on a flow rate of 2,000 £/min. In the last column are esti-
mates of the total mass of substances produced by restoration that would
become sediments in the evaporation ponds. Data were not provided for cal-
cium, magnesium, chloride, and ammonium ions, even though the latter two are
major constituents expected from an alkaline leach process (Wy77). These
concentrations reflect average values, but concentrations in the wastewater
during the initial phase of the restoration process will be much higher. For
-------
3-181
Table 3.60 Estimated average concentrations and annual and total accumula
tions of some contaminants in restoration wastewater
Contaminant
Concentration
Annual
(a)
Total
Accumulation, Kg Accumulation,
Arsenic
Calcium
Chloride
Carbonate
Bicarbonate
Magnes i urn
Sodium
Ammonium
Selenium
Sulfate
Uranium-238
Thorium-230
Radium- 2 26
Radon-222
0.2
NA(C)
NA
450
550
NA
550
NA
0.10
150
< l^d)
100
75(e)
618,000
210
NA
NA
473,000
578,000
NA
578,000
NA
100
157,000
<900
o.io8(f)
0<6(f)
5,200^
^'Produced only during the estimated 8-yr restoration period.
' 'Total accumulation during the estimated 8-yr restoration period.
A - Data not available.
^ 'Concentration after uranium extraction.
' '
are
Units are Ci/yr or total curies.
Source: Concentrations based on those estimated for the Highland Urani-
um Project (NRC78b), adjusted for a flow rate of 2,000 £/min.
-------
3-182
Table 3.61 A comparison of contaminant concentrations in pre-mining
groundwater and pre-restoration mine water (Wy77)
Contaminant
Arsenic
Barium
Boron
Cadmium
Chromium
Copper
Manganese
Mercury
Nickel
Selenium
Silver
Zinc
Lead
Chloride
Ammonia
Bicarbonate
Uranium (UgOg)
Radium-226
Total dissolved solids
Pre-mining
Water, mg/£
<0.0025
0.12
0.16
<0.005
0.0135
0.019
0.12
0.0028
0.018
0.013
<0.005
0.003
0.0035
10.75
<1.0
139
0.098
27(a)
793
Pre-restoration
Water, mgA
0.021
0.069
0.283
0.014
0.002
0.220
0.97
<0.0002
0.218
1.75
0.015
0.22
0.110
524
235
805
24.4
371(a)
1324
are pCi/ju
-------
3-183
example, Table 3.61 compares concentrations of substances in the groundwater
before mining with those after mining but before restoration. These data are
from tests conducted for the Irigaray Project (Wy77) and indicate those sub-
stances whose groundwater concentrations may be elevated by in situ leaching.
Radon emission during the restoration process has not been considered
(Wy77, NRC78b, Ka78b). Because essentially all Ra-226 remains in the ore
zone (about 97.5 percent), it appears reasonable to expect Rn-222 emissions
to continue during restoration. A leached-out sector of the model mine will
contain 156 Ci of Ra-226 in an aquifer volume of 2.53 x 105 m3 (1.26 x 106
o
m * 5). Although no measurements have been made, it would appear that the
restoration wastewater will contain about the same Rn-222 concentration as
the pregnant leachate during leaching, 6.18 x 10 pCi/Ji (Section 3.5.3).
Assuming a pumping rate of 2,000 Vmin, a maximum of 650 Ci of Rn-222 will be
released during each year of restoration, resulting in a maximum total re-
lease of 5,200 Ci during the estimated 8-yr restoration.
Restoration is presently in the experimental stages. No com-
mercial-sized facility has reached that phase of operation. Although restor-
ation by flushing appears feasible, there have been problems when alkaline
lixiviants were used, particularly those containing ammonium ions. Ammonium
is the preferred cation because sodium causes the clays to swell and plug the
formation, and calcium forms an insoluble sulfate that also decreases the
permeability of the formation. However, ammonium ions adsorb tightly on to
clays by replacing the calcium and magnesium atoms in the clays. Mont-
morillonite, prevalent in the Texas mining areas, has extensive surface areas
that result in very large ion-exchange capacities. Once adsorbed, the
ammonium ions desorb at a very slow rate and prolong the restoration. It has
been reported that after sweeping a leached ore zone with 10 ore zone volumes
of water, the ammonium concentration of the water was reduced to 15 to 25 mg^
(Ka78b). This concentration of ammonium may not be significant, although,
under aerobic conditions, ammonium ions can be oxidized to the more toxic
nitrate. In a deep aquifer, this oxidation process is not likely to occur,
and, because of the very low Teachability of ammonium ions from clays, any
ammonium retained after restoration will move to surrounding aquifers at a
very slow rate.
Several ongoing research studies are trying to solve the ammonium prob-
lem (Ka78b). Potassium is being tested as a cation replacement for ammonium
-------
3-184
in hopes that its adsorption and swelling characteristics will be favorable.
Sweep solutions enriched in calcium and magnesium are being tested to deter-
mine if they will facilitate the flushing of the ammonium ion by replacing it
on the clays by ion-exchange.
Restoration of the aquifer after mining stops is in the research stage.
The adequacy of the restoration process and the procedures required will
depend on a number of factors: the lixiviant used, concentration of specific
ions in the lixiviant, the physical character of the stratigraphic unit, and
the geochemical nature of the ore deposit. Undoubtedly, research will im-
prove the process in the next few years. If the criteria of the restoration
process are met, it is unlikely that there will be any adverse environmental
impact from a properly restored aquifer.
Generally, the goal of reclaiming the site"surface is to return the area
to a state similar to that which existed naturally before mining. This often
means one suitable for livestock grazing and wildlife habitat. The following
site reclamation actions have been proposed (Wy77):
(1) Remove all structures and exposed pipes and plug all wells with
concrete.
(2) After all impounded liquids have completely evaporated, cover
the remains with overburden to a depth [2 m has been suggested at the
Irigaray site (Wy77)J that will support plant growth and suppress
Rn-222 emissions or transport and deposit the remains in a mill tailings
impoundment.
(3) Before backfilling, dispose of the solids containing sufficient
radioactivity to warrant removal by one of the methods suggested in
Section 3.5.1.
(4) Grade surfaces of the backfilled ponds and all other barren areas
to create a suitable topography and then revegetate them.
(5) Irrigate and fertilize sites to develop adequate plant cover.
(6) Maintain fences to prevent grazing by livestock until stable vege-
tative cover becomes established.
(7) Monitor reclaimed sites for radiation, verification of vegetative
cover, and the absence of adverse erosion.
(8) Sample monitoring wells one year after restoration to verify aquifer
restoration.
-------
3-185
3.6 Other Sources
3.6.1 Mineral Exploration
During early exploration, uranium was identified by its mineral color,
i.e., pitchblende from the Central City District in Colorado and carnotite in
the Uravan Mineral Belt in Utah and Colorado. It was usually mined in con-
junction with other metals and minerals. Later, when portable radiation
survey meters became available, a substantial portion of the uranium findings
(generally outcrops) were made by non-geologic prospectors (UGS54). Current
uranium exploration uses extensive geological studies to locate formations
with a strong potential for uranium ore content. These formations are then
explored and field surveyed to verify the presence of ore. Much of the
current exploratory activity is directed at expanding known deposits and
mining areas.
As the surface and near-surface uranium deposits are found, mined, and
depleted, exploration for reserves must be conducted at greater depths. The
deeper uranium deposits, however, offer few radiometric clues on the surface
regarding their location. In these cases, geologic studies and field work
postulate the existence of promising geological formations. Actual explor-
ation must be done by drilling. Drilling is also used to extend and explore
known uranium producing areas.
There are two categories of drilling: exploratory and developmental.
Exploratory drilling is used to sample a promising formation to determine if
uranium ore is present. The drilling is generally done on a grid with the
drill holes spaced 60 m to 1.6 km or more apart. Development drilling, to
define the size and uranium content of the ore body, occurs when ore is
struck in an exploratory hole. The development hole spacing ranges from 8 m
to 100 m, depending on the characteristics and depth of the ore body.
Usually, the same drilling equipment is used for both the exploratory and
development drilling.
Ordinarily, there are three vehicles in a drilling unit. One vehicle
carries and operates the drill rig, the second carries the drill rods, and
the third carries water. Although the drill rig is a well-engineered, com-
pact design, its physical size is increasing to meet the demands of deeper
drilling (Personal communication with G. C. Ritter, 1979, Bendix Field En-
gineering Corp., Grand Junction, CO).
-------
3-186
Early drilling (1948-1956) was predominantly done with percussion
drills. These drills could drill to depths of about 76 m using 2.8 cm dia-
meter drill steel. The drill bit was cooled and cuttings were removed from
the drill hole by forcing air down the center of the drill stem. The
cuttings (chips, sands, and dusts) were carried up and out of the drill hole
by the air stream with velocities of 914-1520 m per minute (Ni76). The chips
and coarse sands collected near the bore hole while the fine sands drifted
and deposited around the drill site. Dusts, however, were free to drift with
the winds.
Rotary drilling, used for boring deep holes, generally has replaced
percussion drilling. Drill stems of 7.3 cm diameter are used to bore holes
to depths of about 1300 m. Stems with diameters of 11.4 cm and larger are
used for drilling holes in excess of 1300 m. The rotary drill bits are
cooled generally in the same manner as percussion drills. When groundwater
is encountered, water is used as a drilling medium and for removing cuttings.
The cuttings are removed from the drill hole in the form of a slurry or
drilling mud. They are usually stored in basins, either fabricated or dug in
the ground. If unavailable, water is hauled to the drill site by truck. The
drilling muds and water are stored in portable tanks or an earth impoundment
for recirculation. After the drilling is completed, very often the cuttings
are scattered and the drilling mud left at the site. This practice has been
discouraged over the past 10 years in the Uravan area (Personal communication
with G.C. Ritter, 1979, Bendix Field Engineering Corp., Grand Junction, CO).
In some cases, the cuttings are disposed of in a trench and covered up with
earth. Drilling muds are also sometimes covered. In either case,
containment of the drilling wastes does not appear to be a prevalent
practice.
Development drilling is conducted if ore is struck in an exploratory
hole. The offset distance (i.e, the distance between development drill
holes) is dependent on the previous history of the ore body sizes in the
area. Offsetting may occur as soon as ore is struck, or it may be delayed
until the exploratory drilling is completed.
-------
3-187
The ore body may be evaluated by bore hole logging or by examining and
analyzing cores. Core drilling, if used, usually begins at the top of the
ore horizon. Ore (cores and cuttings) removed from the bore hole are some-
times removed from the drill site. In cases where the ore is not removed
from the drill site, it remains with the dry cuttings or in the drilling
muds. The drill hole collar is sometimes plugged with 0.9 - 1.5 m of concrete
after the bore hole has been evaluated. In some states, the drill hole must
be plugged to seal off aquifers in order to minimize groundwater
contamination.
3.6.1.1 Environmental Considerations
By 1977, the uranium industry had completed 101 x 10 meters of surface
drilling, with an all-time yearly high of 12 x 10 meters (DOE79). From
1958-1977, about 821,900 surface holes were drilled, resulting in 87.8 x 106
meters of bore holes. No statistics are available on the number of holes
drilled from 1948-1958, but the annual and cumulative meters drilled for that
period is known (DOE79). In order to estimate the number of drill rig place-
ments for that period, the total annual meters of drilling was divided by the
annual average bore hole depth. The average depth per bore hole was esti-
mated by plotting the average annual bore hole depths for 1958-1977 then
using that data to estimate the annual bore hole depths for 1948-1957 by
linear regression analysis (Fig. 3.22).
The data points in Fig. 3.22 appear to fall into two groups: 1958-1966
and 1966-1977. The average drilling depth of the 1966-1977 group of data
points probably reflects the deep drilling in the Grants, New Mexico area
that became significant in 1969. Using this information, the 1948-1958
average drilling depths were estimated from regression analysis using the
1958-1966 data points only. Table 3.62 is a summary of the DOE drilling data
and the number of estimated bore holes by type and year.
-------
175
1948
1952
1956
1960
1964 1968
YEAR
1972
1976
1980
LO
I
I—1
oo
00
Figure 3.22 Average depth of exploratory drilling in the U.S. uranium industry from 1948 to present.
-------
3-189
Table 3.62 Estimates of exploratory and development drill holes (1948-1979)
Surface Drilling (106 Meters)
Year
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
TOTAL
Exploration
0.052
0.110
0.174
0.329
0.415
1.11
1.24
1.61
2.22
2.24
1.15
0.722
0.427
0.402
0.451
0.268
0.294
0.354
0.549
1.67
4.97
6.25
5.49
3.47
3.60
3.29
4.88
5.03
5.94
7.89
10.8
9.94
286
Development
0.012
0.016
0.063
0.106
0.091
0.112
0.169
0.232
0.457
0.564
1.06
1.00
1.28
0.972
0.741
0.604
0.381
0.289
0.731
1.62
2.30
2.86
1.69
1.23
1.10
1.70
1.83
2.74
4.48
4.45
5.24
5.18
149
Average Hole
Depth(Meters)
38.1(a}
«:i(i)
42.7^3x
42.7U)
44.2(9)
45-7^
45.7(a)
45.7
48.2
53.9
50.0
61.9
39.6
42.4
47.5
67.7
110
125
120
122
121
128
146
168
139
154
132,
155,^
158 a
Number of Holes
Exploration
1,360^
2,880 °
4,380 b
8,000 °
10,100)^
26,100^
29 000
36,300^
48,600^
25*300
16,300
7,340
8,260
6,440
8,470
5,970
6,230
5,750
12,800
38,500
47,900
44,000
28,400
26,900
22,600
27,400
34,300
40,400
62,600,.,
69,200^
62,700
823,000
Development
320(b)
424^
M$«
' (h}
2,220^
2,620tD;
(b)
5;260(b)
10*000
12*300^
22^900
19,600
24,400
19,300
12,900
13,500
9,910
7,330
13,200
16,900
19,500
28,000
14,900
10,400
9,710
11,700
12,300
21,600
27,200
30,900,.,
33,700>^
32,700
454,000
^Indicates estimated average depth from Fig. 3.22.
^Indicates number of drill holes estimated by dividing the annual
exploration and surface drilling depths by the average hole depth.
-------
3-190
Cuttings produced by drilling can degrade the drill site area and the
local air quality. For convenience of evaluation, the cuttings are divided
into two general categories—dusts and wastes. The dusts are drilling fines
that become airborne, and wastes are drilling chips and sands deposited
around the borehole. The maximum dust production occurs when compressed air
is used solely for cleaning the boreholes. Generally the drilling industry
uses foaming agents injected into the compressed air stream to help remove
drill cuttings. The foam traps and contains the fine particulates and sub-
stantially reduces the airborne dust. In practice, the drillers minimize
airborne dust, because it causes excessive wear on engines and compressors.
Dust production also indicates improper drilling energy being used to grind
up cuttings in the borehole rather than bore. Occasionally some water may
also be injected into the air stream to remove cuttings and to keep the drill
hole from collapsing when loose materials are encountered.
There are some estimates of airborne dust production and general assump-
tions concerning drilling practices (Private communication with Mr. T. Price,
Bendix Corp., Grand Junction, CO and E. Borgerding, Borgerding Drilling Co.
Inc., Montrose, CO). They are as follows:
(1) The ratio by weight of the chips, sands, and dusts produced by
drilling is approximately 60:37:3, respectively (i.e., 3 Kg of every 100 Kg
of cuttings removed from a borehole is available as airborne dust).
(2) Fifty percent of all drill holes are wet (mud) drilled and 50 per-
cent are air drilled; ninety-five percent of the latter are drilled using
mist or foam (i.e., 2.5 percent are dry-drilled).
(3) The first 6.6 m of all drill holes are drilled dry (i.e., no mist
or foam is used).
We estimated dust production from contemporary drilling by averaging
drilling data from Table 3.62 for the years 1975 through 1979. The average
depth of the holes for this period is 148 m. The annual average numbers of
exploration and development holes are 53,800 and 29,200, respectively. Air-
borne dust production from those holes that are drilled with mud (wet), foam,
or mists (97.5 percent of both the exploratory and development holes) will
originate only from the first 6.6 m depth. The weight of dust generated per
hole will be as follows:
3 "3
Airborne dust (kg) = Volume of borehole (m ) x density (kg/m ) x air-
borne dust fraction (.03) per drill hole
-------
3-191
= ( Trr2h) (2000kg)(0.03) where h = 6.6 m
3
m r = 0.0865 m (assumed average rad-
ius of 2 bit sizes r = 7.3 cm
and 10 cm) (Pe79)
= (3.14)(7.48 x 10"3) m2 x 6.6 m x 2000 kg x 0.03
m3
=9.3 kg
The average weight of airborne dust (kg) produced from all contemporary
annual drilling (first 6.6 m) is
83,000 drill holes x 9.3 kg = 7.7 x 105 kg.
drill hole
The annual total weight (kg) of airborne dust produced from 2.5 percent
of the annual number of drill holes bored (dry) where no mud, mists, or foams
are used
= 83,000 drill holes x 148 m x 0.025 x 47 kg cuttings x
drill hole m
0.03 kg dust/kg cuttings = 4.3 x 105 kg/yr. (3.13)
The total weight of airborne dust produced annually from each dry-drilled
borehole is 209 kg.
Assuming that each development hole penetrates the 3.6 m ore body, the
total amount of airborne ore and sub-ore dust produced from development
drilling annually is
29,200 drill holes x 3.6 m (ore and sub-ore) x 47 kg cuttings x
yr drill hole m
0.03 kg dust/kg cutting x 0.025 = 3.7 x 103 kg. (3.14)
The total weight of airborne ore and sub-ore dust produced from each develop-
ment drill hole (no mud, mists, or foams used) is 5.1 kg.
The estimated annual quantity of ore and sub-ore brought to the surface
by contemporary drilling equals:
29,200 drill holes x 3.6 m x 47 kg cuttings (3.15)
yr drill hole m
= 4.9 x 106 kg or 4.9 x 103 MT
yr yr '
Most of the ore will remain at the drill site with drilling muds or with
the drilling wastes around the drill holes. Since the ore most usually will
be the last material removed from the boreholes, it will be deposited on the
-------
3-192
surface of the cuttings and drilling muds. This will expose the ore to the
elements and subject it to erosion.
3.6.1.2 Radon Losses from Drill Holes
When the development drill penetrates an ore body, some of the ore and
sub-ore bearing formations will be exposed to air in the drill hole. Some of
the radon gas produced in the ore can enter into the air in the drill hole
and escape to the atmosphere. The mechanisms affecting the release rate of
radon from boreholes are poorly understood. Tanner observed a wide variation
in radon concentrations as a function of depth in an open borehole as com-
pared to a closed borehole (Ta58). Tanner also noted that strong winds could
significantly reduce the total radon content of an uncovered borehole. Since
so little is known about radon discharges from development boreholes, radon
losses in this report are assessed on a "worst case" basis using the fol-
lowing assumptions:
1. The drill hole is not plugged.
2. About 3.6 m of ore and sub-ore were drilled.
3. All radon released into the borehole escapes to the
atmosphere.
4. The average grade of the ore and sub-ore is 0.17 percent.
- 5. No water accumulates in the borehole.
The surface area of the borehole passing through the ore and sub-ore body
is
2 Trrh = 2 x 3.14 x 0.0865 m x 3.6 m = 2.0 m2. (3.16)
The radon release rate is estimated for ore and sub-ore in the borehole using
2
an exhalation rate of 0.092 Ci/m per year per percent of U30ft (Ni79). The
quantity of radon (Q) per development hole escaping per unit time is
0.092 Ci x 0.17% x 2.0 m2 x - - - x 1012 = 990 pCi/sec (3.17)
m2 yr % 3.15 xlO7 sec/yr C1
The total quantity of radon per annum escaping from all development holes
drilled through 1979
11 holes x
sec-drill hole
= 4.5 x 105 drill holes x 990 pCi x 3.15 x 107 sec/yr
1
1012pCi
Ci
= 14,000 Ci/yr (3.18)
-------
3-193
The "worst case" estimate can be modified by assuming 50 percent of the
holes are wet and 30 percent of the remaining holes are plugged or have
collapsed. In this case, the total source term would be about 4,900 Ci/yr.
Since about 31 percent of the development drill holes are at surface mines
and are consumed by the pits, the annual Rn-222 release from the remaining
holes will be 3,400 Ci/yr.
3.6.1.3 Groundwater
Progressively deeper holes are being drilled as the ore bodies near the
surface become depleted. As the drilling depths increase, one or more
aquifers may be intercepted by a drill hole, and an aquifer with poor water
quality may be connected with an aquifer with good water quality. Depending
on the direction of flow, the quality of water may be downgraded in a good
aquifer. Most states require some plugging of the drill holes to seal the
aquifer in order to maintain water quality. Adequate plugging of the drill
holes requires a conscientious effort on the part of the driller and the
regulatory agency. Since the movement of groundwater is relatively slow, the
change in the quality of water in an aquifer will not be apparent for some
time. Thus, it may take a long time to correct the quality of water in a
downgraded aquifer.
3.6.1.4 Fumes
It is estimated (Pe79) that 11.2 liters of diesel fuel are needed to
drill 1.0 m. In 1979, the average borehole depth was estimated to be 158 m
and would require about 1770 liters of diesel fuel. This fuel would be
burned at a rate of approximately 173 liters per hour. Some individual
holes, however, are drilled in excess of 914 m and require 10,200 liters of
diesel fuel. It is estimated that about 170 million liters of diesel fuel
were consumed for all 1979 drilling.
The principal emissions from the drilling power sources are partic-
ulates: sulfur oxides, carbon monoxide, nitrogen oxides, and hydrocarbons.
Because of the transient nature of the drilling, these releases are not ex-
pected to substantially lower air quality over time.
-------
3-194
3.6.1.5 Model Drilling
About 1.3 x 106 holes have been drilled and bored for all uranium mining
from 1948 through 1979 for approximately 3000 mines. This would amount to
about 430 holes per mine. Thirty-six percent of the holes were for develop-
ment drilling, and 64 percent were for exploratory drilling. Assuming that
50 percent of the exploratory and development holes are air drilled (see
Section 3.6.1.1), the airborne dust production for an average mine may be
estimated as follows:
Airborne dust from all drill holes (first 6.6 m of depth air drilled dry)
= 430 drill holes x 9.3 kg = 4000 kg. (3.19)
drill hole
Airborne dust from all dry air drilling, less the first 6.6 m, (3.20)
= (430 drill holes x 209 kg dust x 0.5 x 0.05) - 100 kg = 2100 kg.
drill hole
Airborne ore and sub-ore dust produced by dry air drilling
= 430 drill holes x 0.36 x 0.5 x 0.05 x 5.1 kg dust = 20 kg. (3.21)
drill hole
Total airborne dust produced from all drilling at an average mine site
= 4000 kg + 2100 kg = 6100 Kg = 6.1 MT. (3.22)
Twenty kilograms of the total dust produced will be ore and sub-ore
dusts. The Rn-222 emissions from the bore holes at an average mine site would
be
430 drill holes (0.5)(0.36) (990 pCi ) = 7.7 x 104 £Ci_, (3.23)
sec-drill hole sec
or 2.4 Ci/yr.
Development drill holes at a surface mine would be consumed by the pit.
Tables 3.63—3.65 show airborne particulate source terms for uranium
drilling for individual drill holes and for an average uranium mine. Table
3.63 lists the airborne dust produced for each type exploratory and develop-
ment borehole; Table 3.64 summarizes the quantity of airborne dust produced
by all types of drilling at an average mine site; and Table 3.65 lists the
pollutants emitted from a drill rig power source.
3.6.2 Precipitation Runoff from Uranium Mines
Unquestionably, overland flow or surface runoff from precipitation
transports dissolved and suspended contaminants from mining areas to the
offsite environment. Unfortunately, the significance of this pathway rela-
-------
Table 3.63 Estimated source terms per borehole for contemporary surface drilling for uranium
Thickness of Ore
and
Type of Drilling
Exploratory
Air (dry)
Air (mist or foam)
Wet (mud)
Development
Air (dry)
Air (mist or foam)
Wet (mud)
Sub-ore Bodies
(m)
NA
NA
NA
3.6
3.6
3.6
Ai rborne
Total (kg)
209
9.3
9.3
209
9.3
9.3
Dust Production
Rate(k9/m1n>la)
0.27
0.27
0.27
0.27
0.27
0.27
Airborne Ore and Sub-Ore
Dust Production
Total
NA
NA
NA
5.1
NA
NA
(kg) Rate(kg/min)^a)
NA
NA
NA
0.27
NA
NA
(b)
'Based on an air drilling rate of 11.5 m/hr.
NA - not applicable.
CO
I
ID
cn
-------
3-196
Table 3.64 Airborne dusts produced at an average mine site
from exploratory and development drilling
Type of Drilling
Quantity of Airborne Dust (kg)
All types (first 6.6 m depth)
Air drilling (dry)
Total
4,000
2.100
6,100 kg
(a)
^'Twenty kg of the total will be ore and sub-ore dusts.
Table 3.65 Estimates of emissions from drill rig
diesel power source
Pollutant
Carbon monoxide
Hydrocarbons
Nitrogen oxides
Aldehydes
Sulfur oxides
Particulates
I i
Production Rate
(kg/103 liters fuel)
12.2
4.49
56.2
0.84
3.74
4.01
Quantity ^a'
(kg/drill hole)
20.2
7.4
93
1.39
6.2
6.6
Rate(a)
(kg/hr)
1.5
0.55
6.9
0.10
0.46
0.49
v 'Based on a drilling rate of llm/hr,
Source: EPA77b.
-------
3-197
tive to uranium mines is highly site specific and poorly understood. Very few
field studies of runoff from uranium mining areas have been conducted, and
what field data do exist frequently relate to the combined and probably
greater influences of mine water discharge and milling. Most of the NRC
regulations apply to mill operations, since mining is generally exempt from
the agency's charter. The EPA regulations (Environmental Radiation Pro-
tection Standards for Nuclear Power Operations; 40 CFR Part 190) applicable
to the uranium fuel cycle establish dose limits for individuals to provide
protection for populations living in the vicinity of uranium mills. Uranium
mines are excluded, and so are liquid effluent guidelines for ore mining and
dressing (40 CFR 440, Subpart E). Regulations being developed under the
Resource Conservation and Recovery Act (RCRA) of 1976 apply to radioactive
wastes not covered by the Atomic Energy Act of 1954, as amended. Solid and
liquid waste categories will be defined in forthcoming EPA regulations de-
veloped under RCRA, but it is not anticipated that runoff from mined lands
will meet the waste characteristics in the regulations. Similarly, the
Federal Water Pollution Control Act Amendment of 1972, the Clean Water Act of
1977, the Safe Drinking Water Act, and State regulations in general do not
address surface runoff effects of mining. Without the regulatory base,
studies and field data are, not surprisingly, rather scarce. In New Mexico,
the State's 208 Water Quality Management Plan calls for, among other things,
improved data collection on runoff from active and inactive tailings piles
and from drilling, exploration, and development activities such as access
road and drill site construction (So79).
We have not estimated chemical transport by overland flow because of the
limited time for the study. But, it is reasonable to expect that such trans-
port may be quite significant in an arid and semiarid climate where much of
the precipitation that does infiltrate is discharged back into the atmosphere
as water vapor. This has been well demonstrated in the case of uranium mill
tailings (K178). Water moving back out of the soil transports dissolved
salts that are deposited on the soil surface when the carrier (water) evap-
orates. Subsequent precipitation further transports these salts downward
into the soil and laterally to offsite areas. So-called "blooms" of salt
crystals, composed mainly of sulfate and chloride compounds, characterize
uranium ore bodies, mill tailings piles, and mine wastes in a number of
Western States, and we must presume that such salts solubilize in runoff.
-------
3-198
This also indicates that there may be large concentrations of contaminants
available for plant uptake. Molybdenum, in particular, is one of the toxic
elements on such blooms, and uranium is also highly suspect. Selenium,
arsenic, and vanadium may also be present, since their anions are mobile
under oxidizing conditions characteristic of the near-surface, unsaturated
zone (Fu78).
Overburden has been used extensively to backfill surface mines operating
since the early to mid 1970's, but this is not true at many if not most older
and now inactive mines. Erosion of these piles by water and wind may present
the greatest problem (Ka75). Using overburden to construct access roads and
dikes distributes contaminants in the local environment and may aggravate air
and water pollution. Considering that 75 percent of the overburden has a
grain size exceeding 2000 ym (see Table 3.12), it is unlikely that widespread
physical transport will result from overburden piles. However, using over-
burden for roads decreases the grain size. The association of uranium and
progeny with the smaller sediment-size fractions, by a factor of 2.5, in-
creases the potential for transport by overland flow.
Tables 3.15, 3.16, and 3.19 show stable and radioactive trace elements
in ores; sub-ore, and overburden from uranium mines. Understandably, uran-
ium, thorium, and radium are high. Arsenic, selenium, vanadium, and moly-
bdenum are almost always closely associated with uranium. Barium, zinc,
manganese, copper, iron, and potassium may also be associated in certain
mineral provinces and districts. Mercury and cadmium are occasionally pre-
sent (Th78). There is no consistent relationship between ore grade and trace
metal content in selected New Mexico and Wyoming study areas (Wo79).
Particularly in the case of active or recently active mines, surface
runoff is collected with dikes and ditches that route water to settling
ponds. Water spray or chemical additives can control road dust. They are
commonly used in the active mining stage, but almost never used during ex-
ploratory drilling. Grading piles to a slope of 3:1 or less also helps to
reduce runoff (St78), and this practice is becoming common in Texas and
Wyoming. Proper planting techniques further reduce runoff by increasing
infiltration and decreasing sediment transport.
The significance of surface runoff from mining areas as a dispersal
mechanism was investigated as part of this study (Wo79) (see also Section
3.2.3.2). We examined stable and radioactive trace elements in soils
-------
3-199
affected by runoff from ore, sub-ore, and mine waste/overburden piles from
one active surface mining area in Wyoming and two inactive areas (surface and
underground mines) in New Mexico. Although there was evidence of offsite
movement of uranium and radium at all sites, transport is limited and de-
creases with distance from the site. In Wyoming, pollutant releases from the
mine studied do not reach nearby water courses although onsite transport of
stockpiled ore as a result of precipitation runoff does occur.
A U.S. Bureau of Mines (BOM, no date) study of strip and surface mining
operations and their effects in the United States involved questionnaires,
literature survey, and onsite examinations of 693 selected sites, among which
were uranium mines in New Mexico and Wyoming. At 60 percent of the sites, on
a national basis, there were no serious problems because vegetation was
reestablished and the slope of the land was gentle both before and after
mining. Thirty percent of the sites had eroded to depths of 0.3 m or less,
and the remainder were gullied to greater depths. There were sediments from
mined lands in 56 percent of the ponds and 52 percent of the streams on or
adjacent to the sample sites. Spoil bank materials ranged in pH from 3 to 5
at 47 percent of the sites and are thus not amenable to plant growth. Field
observations substantiate that mined land areas, be they former forests or
grasslands, did not return to the pre-mining condition. Idle land increased
almost fourfold because of mining. The study concluded that natural pro-
cesses need to be strongly supplemented if mined sites are to revert to
former uses. Since only 6.3 percent of lands mined for uranium were re-
claimed from 1930 through 1971 (Pa74), it seems reasonable to conclude that
there are increased sediment loads, gullying, and poor revegetation at most
older inactive mines that were poorly stabilized, if at all.
The Bureau of Mines study concluded that peak sediment loads in runoff
are characteristic of areas with high intensity storms and steep slopes,
particularly during and shortly after mining. Such problems are less severe
in arid regions, but large quantities of sediment are discharged from mine
workings, spoil heaps, and access roads. In some instances, effects of wind
and water erosion on steep spoil banks in arid lands are evident many years
after abandonment. In areas outside Appalachia, 86 percent of the areas
investigated had sufficient runoff control, and those areas where there was a
problem almost exclusively involved coal, phosphate, manganese, clay, and
gold. v
-------
3-200
Incidences of radioactive contamination of local surface water have been
documented for the Shirley Basin uranium mine (Utah International, Inc.) in
Wyoming (Ha78). The most pronounced changes in water and stream sediment
quality coincided with initial strip mining and mill processing operations.
Early acid-leach solution mining also had a decided impact. Pollutant
loadings from overland flow, per se, were not determined but are presumed to
be minor compared to aqueous discharges from mines and mills. These findings
contradict those of an earlier study (Wh76) of the same mine. Soil and
vegetation collected from 1971 through 1975 at 28 stations in the vicinity of
the mine were analyzed for gross alpha and gross beta (1971 to 1974) and
total uranium, Ra-226 and Pb-210 (1975). The study (Wh76) concluded that—
1. concentrations of the foregoing parameters were extremely variable
but reasonably consistent with previously reported information;
2. there is no evidence that radionuclide concentration in soil or
vegetation collected from routine monitoring stations are changing
with time;
3. concentrations of radioactivity in soil and vegetation correlate
with distance from the mill area to a distance of 1.2 miles; and
4. measurable ecological effects from radiation in the environs of
the Shirley Basin mine cannot be demonstrated.
The absence of statistically significant soil and vegetation contamination
from the mine versus the mill is noteworthy. Overall, vegetation tends
toward higher alpha and beta concentrations than soil, except at the
close-in, upwind sampling areas. This selective concentration in vegetation
suggests aerial deposition of contaminated dust particles on vegetation, with
some additional possibility for root uptake.
Estimates of surface drilling for uranium reveal that relatively large
land areas are involved. The volume of cuttings removed from borings in the
period 1948 through 1979 is calculated using 286 x 10 m of exploratory
drilling and 104 x 10 m of development drilling (from Table 3.62). We
assumed that 30 percent of the mines are surface mines, which eliminates the
borings and related debris. Thus the value of 149 x 10 (in Table 3.62) is
reduced by 30 percent. Average diameter for 8.5 x 10 m of borings in the
period 1948 through 1956 is 2.8 cm versus 7.3 cm for the period 1957 through
1979 (see Section 3.6.1) when 426 x 106 m of drilling took place. A sample
calculation for the volume removed from borings made in the period 1975-1979
follows:
-------
3-201
V = Trr h / \ (3.24)
= (3.14)17.43 cm2 (146m)
\ 2 /
= 0.632 m3
Assuming a bulk density of 2000 Kg per m3, each boring results in 1265 Kg of
cuttings at land surface. There were 415,300 borings, resulting in 263,000
m of cuttings. Assuming that the average thickness of cuttings is 0.5 m,
526,000 m or 0.53 Km is affected. The inclusive area affected by drilling
from 1948 through 1979 is 3.6 Km2.
Table 3.66 summarizes the surface areas affected by mine wastes, ore
piles, and exploration and development activities. Maximum use was made of
data developed elsewhere in this report on the number of mines, waste pile
dimensions and surface areas, and the summary of exploration and development.
The estimate is, at best, a first approximation and needs considerable re-
finement.
For example, grain size, degree of consolidation, slope, vegetative
cover, and other characteristics may vary considerably between ambient soil
and rock materials versus mine wastes. The latter very often occur in steep,
urwegetated piles and are composed of easily-eroded, friable sandstone,
boulders, and fines. It is likely, therefore, that the sediment yield on a
mass per time per area basis exceeds that of the surrounding areas; thus the
estimate developed below may well be on the low side.
Sediment yields from areas affected by various mining 'operations are
roughly estimated from consideration of land areas affected and unit soil
loss values for the surrounding regions. Actual values for individual tail-
ings or waste piles may be considerably different, but refining the values
given will require additional analysis beyond the scope of the present study.
Potential coal mining lands in the Northeastern Wyoming range lose soil
at rates of 4.8 to 167 m3/Km2/yr (Ke76). Upland erosion and stream channel
erosion in the Gillette study area are not generally serious problems, since
land dissection is presently minimal and vegetative cover is well estab-
lished. The potential for increased sediment yield is large, if vegetative
cover were to be reduced or eliminated and slopes steepened because of
mining. Certainly, during active mining, these conditions will be at least
locally present. Erosion rates of 600 to 1,100 m3/Km2/yr from mined lands in
the South Powder River Basin are expected, and they are reasonably close to
-------
Table 3.66 Sediment yields in overland flow from uranium mining areas
Source Term
Active Mines
Underground
Ore piles
Sub-ore piles
Waste rock piles
Surface
Ore piles
Sub-ore piles
Overburden piles
Factor
603 m2/mine
26,700 m2/mine
26,700 m2/mine
4.15 x 103 m2/mine
67 x 103 m2/mine
380 x 103 m2/mine
No. Installations
251 mines
251 mines
251 mines
36 mines
36 mines
36 mines
Cumulative
2
Source, Km
0.15
6.7
6.7
0.15
2.4
13.7
Annual Sediment
Loading, m
143
6385
6385
143
2287
13056
Inactive Mines
Underground
Waste piles and
sub-ore
4.07 x 103 m2/mine
2108 mines
0.86
820
Surface
Overburden and
sub-ore
6.73 x 104 m2/mine
944 mines
64
61000
CO
ro
o
ro
-------
Table 3.66 (Continued)
Source Term
Exploration and
Drilling
1948-1979
1975-1979
Access roads
pads
Factor
Devel opment
435 x 106 m
1265 kg/boring
and
1.25 acres or
0.5 ha/boring
Cumulative Annual Sediment
? 3(a)
No. Installations Source, Km Loading, m v '
1.28 x 106 borings 3.6 3431
415,300 0.53 506
1.28 x 106 6500 6.2 x 106
^'Assumes average sediment yield of 953 m /Km .
Note.—Data in this table are based on average mine vs. average large mine as defined in Section 3 of
report.
CO
o
CO
-------
3-204
natural, pre-mining conditions (R. Loeper, Soil Conservation Service, 1979,
personal communication). At the Bear Creek mine, the reclamation design
32
calls for maximum losses from overburden piles of 1,100 m /Km /yr initially
and 600 m3/Km2/yr after the first 3 years. In general, erosion and soil loss
from uranium mining in this part of Wyoming is not a significant problem,
mainly because of reclamation by industry. Sediment yields in the Grants
Mineral Belt range from 95 to 240 m3/Km2/yr in the area of the large Jack-
pi le-Paguate surface mine to 500 to 1,400 m3/Km/yr near the underground
mining centers around Smith Lake, Ambrosia Lake, and Churchrock (P. Boden,
Soil Conservation Service, 1979, personal communication). Considering both
the Wyoming and New Mexico model mine areas, this study used an overall
average annual soil loss rate of 953 m /Km. This average sediment yield
rate is based on studies by the Soil Conservation Service of large areas in
New Mexico, Wyoming, and other Western States.
In summary, the total land area directly affected by uranium mining is
? 32
about 6600 Km. Assuming an overall average sediment yield of 953 m /Km ,
fi o
annual sediment transported by overland flow is approximately 6.3 x 10 m .
Obviously exploration and development activities affect the greatest area
2
(6500 Km ), but they do not necessarily have the greatest impact.
Exploration and development, for example, affect large areas, but most of the
area affected is a result of constructing access roads and drill pads.
Whereas sediment yields from ore, sub-ore, overburden, and waste rock is
3
estimated at 90,000 m per year. Surface mining, although it supplies only
about 30 percent of U.S. production, affects the second greatest area (80
2
Km ). We have not attempted to characterize the quality of sediment runoff.
The fate of these sediments is very poorly understood and has not been the
subject of intensive investigation. Further study in the area of intensive
surface mining such as in Texas and Wyoming is needed to determine changes in
erosion rates resulting from mining and to quantify the contaminant flux and
fate.
3.7 Inactive Mines
3.7.1 Inactive Surface Mines
For generic purposes, a model inactive open pit or surface uranium mine
must be defined in order to estimate the environmental impact from this type
-------
3-205
of mining. We have assumed that an inactive surface mine has a single hole
or pit in the ground, with all of the materials (wastes) stacked into piles
adjacent to the pit area. The size or volume of the pit would be approxi-
mately equal to the volume of the ore and wastes removed from it. Since only
6.3 percent of all of the land used for uranium mining has been reclaimed
from 1930 through 1971 (Pa74), no credit for reclamation is given to the
model mine.
Ideally, the model mine size could be established by averaging the ore
and waste production for each inactive surface mine. Unfortunately, these
statistics are either not thoroughly documented or they are retained as
company confidential information. In lieu of specific information, the model
surface mine size was established from annual ore and waste production sta-
tistics for all surface mines, divided by the number of inactive surface
mines.
Table 3.67 is a summary of inactive mines, obtained from the Department
of Energy mine listing. The mines are listed by type, surface and under-
ground. Most of the inactive surface mines are in Colorado, Utah, Arizona
and New Mexico. For model derivation purposes, we assumed that there are
presently 1250 inactive surface uranium mines.
Table 3.68 lists mine waste and ore production information from 1932 to
1977. Uranium mine waste and ore production statistics, on an annual basis,
were available from both surface and underground uranium producers from 1959
to 1976 (DOI59-76). Annual uranium ore production statistics for each
uranium mining type (surface and underground) are available for 1948 to 1959
(DOE79) and for combined uranium production from 1932 to 1942 (DOI32-42). In
order to estimate waste production for the years prior to 1956, the annual
mine type ore production records were multiplied by waste-to-ore ratios.
These ratios were estimated from published 1959 to 1976 ore and waste produc-
tion statistics (DOI59-76). Very little uranium ore was mined from 1942 to
1948, since most of the uranium was obtained by reprocessing vanadium and
radium tailings (personal communication with G. Ritter, Bendix Field Engi-
neering Corp., Grand Junction, CO, 1979). The annual waste production for
surface mining from 1948 to 1959 was estimated by extrapolating known
waste-to-ore ratios (1959 to 1976) through the 1948 to 1959 time period using
a "best fit" regression analysis (Fig. 3.23). This method cannot be used to
estimate waste-to-ore ratios because the waste production is finite and will
always occu<"s and also surface mining for uranium essentially began in 1950.
-------
3-206
Table 3.67 Consolidated list of inactive uranium producers by
State and type of mining
State
AL
AZ
CA
CO
ID
MT
NV
NO
NM
ND
OK
OR
SD
TX
UT
WA
WY
Surface
0
135
13
263
2
9
9
0
34
13
3
2
111
38
378
13
223
Underground
1
189
10
902
4
9
12
1
142
0
0
1
30
0
698
0
32
Percent of Total
Surface Mines
0.0
11
1.0
21
0.16
0.72
0.72
0.0
2.7
1.0
0.24
0.16
8.9
3.0
30
1.0
18
Percent of Total
Underground Mines
<0.1
9.3
0.49
44
0.20
0.44
0.59
<0.1
7.0
0.0
0.0
<0.1
1.5
0.0
34
0.0
1.6
Total
1246
2031
-------
Table 3.68 Uranium mine waste and ore production (MT x 1000)
Surface Mining
Underground Mining Surface Mining
Underground
Mining
Total Ore
Produced By
Surface and/or
Year Crude Ore
1977
1976
1975
1974
1973
1972
1971
1970
1969
1968
1967
1966
1965
1964
1963
1962
1961
1960
1959
1958
1957
1956
1955
1954
5059
4238
3809
3510
3800
3447
2656
2490
1653
1989
1393
905
1630
2344
3578
2895
3051
2691
2494
2139
1462
1131
339
241
Waste
237800
190700
139700
129700
182300
155100
120200
76870
81000
31360
32510
24400
17710
26680
33120
44640
42500
73570
46790
19240
11700
9048
2650
1930
Crude Ore
4305
3569
2485
2222
1614
2439
2836
3304
3171
3382
2897
2777
3055
3227
3575
4892
5017
5104
3796
2558
1888
1595
1043
762
Waste
3487
2605
2195
1424
934
593
858
962
1184
1163
1024
863
809
941
946
1087
1117
1868
941
690
510
414
271
198
Waste/Ore
47
45
37
37
48
45
45
31
49
16
23
27
11
11
9.0
15
14
27
19 , x
9.0(a)
8.0
8.0
8.0
8.0
Waste/Ore
0.81
0.73
0.88
0.64
0.58
0.24
0.30
0.29
0.37
0.34
0.35
0.31
0.26
0.29
0.26
0.22
0.22
0.37
0.25,. ,
0.27(b)
0.27
0.26
0.26
0.26
Underground Mines
9364
7807
6295
5732
5414
5886
5492
5794
4824
5371
4290
1768
4685
5571
7153
7787
8068
7795
6290
4697
3350
2726
1382
1003
co
i
ro
o
-------
Table 3.68 (continued)
Surface Mining
Underground Mining Surface Mining
Underground
Mining
jfjwaste to ore ratios from 1950 - 1958 estimated from 1959 - 1972 ratios.
lD;Waste to ore ratios from 1932 - 1958 estimated from 1959 - 1972 ratios.
Total Ore
Produced By
Surface and/or
Year Crude Ore Waste
1953 162 1300
1952 59 472
1951 25 203
1950 21 167
1949
1948
1947
1946
1945
1944
1943
1942
1941
1940
1939
1938
1937
1936
1935
1934
1933
1932
Crude Ore Waste Waste/Ore
503
341
289
207
156
34
0
0
0
0
0
0
0.824
0.7221
5.68
3.89
1.55
1.31
1.03
0.230
0.047
0.0553
126 8.0
85 8.0
73 8.0
50 8.0
37
8.3
0.181
0.151
1.19
0.817
0.310
0.261
0.207
0.0461
0.00896
0.0105
Waste/Ore
0.25
0.25
0.25
0.24
0.24
0.24
0.24
0.23
0.23
0.23
0.22
0.22
0.22
0.21
0.21
0.21
0.20
0.20
0.20
0.20
0.19
0.19
Underground Mines
665
400
314
228
156
34
0.824
0.722
5.68
3.89
1.55
1.31
1.03
0.230
0.047
0.0553
CO
I
rv>
o
00
-------
DC
60 r_
50 —
40
30
OO
•=C
20
10
0
1948
I
NO
o
VO
1952
1956
1960
1968
1972
1964
YEAR
Figure 3.23 Annual waste to ore ratios for surface mining of uranium (1948 to 1979).
1976
1980
-------
3-210
Since early surface mines recovered ore bodies very close to the sur-
face, the ore-to-waste ratio would be expected to be relatively small. A
range of waste to ore ratios of 8:1 to 35:1 for surface mining has been
estimated (C174). The lower ratio was selected to be typical for surface
mining from 1948 to 1957 and was used to estimate the waste production for
that period. The increase in waste-to-ore ratios from 1959 to 1976 was
probably due to several reasons. The gradual depletion of near surface ore
deposits required mining deposits at increasing depths, and the development
of surface mining equipment now permits economical recovery of ore at greater
depths below grade. The waste-to-ore ratios for 1976 to 1977 were projected
with the previous regression analysis line fit.
The estimated annual cumulative waste production from uranium surface
mining for 1950 to 1978 (Table 3.69) is 1.73 x 109 MT. A crude estimate of
the waste production for the model inactive surface mine can be made by
dividing the total waste produced to 1978 by the number of inactive mines.
But, this overestimates waste production because some of the contemporary
wastes are being produced by active mines, and the waste production per mine
has increased with increasing contemporary waste-to-ore ratios. To adjust
the contemporary waste production for the active mines and the increasing
waste-to-ore ratios, we assumed a cutoff date of 1970, based on the descrip-
tion of a contemporary active surface mine (Ni79). The model mine age is
about 1 year as of June 1978, and has an expected life of approximately 17
years. Those mines that were active in 1970 are all assumed to have become
inactive between 1970 and 1978. Their percentage of the annual waste of
about 12.5 percent was assumed to decrease linearly with time from 1970-1978.
For example, all of the wastes produced by surface mines in 1970 (i.e., 7.69
x 10 MT) were produced by surface mines that would be inactive by 1978. The
waste production for the following years (1971-1977) was: 1.05 x 10® MT in
1971; 1.16 x 108 MT in 1972; 1.14 x 108 MT in 1973; 6.49 x 107 MT in 1974;
5.24 x 107 MT in 1975; 4.77 x 107 MT in 1976; 2.97 x 107 MT in 1977. The ore
production was calculated in the same manner as for the wastes and was 3.27 x
10 MT in 1970. The ore production for the following years was: 2.32 x 10
MT in 1971; 2.58 x 106 MT in 1972; 2.38 x 106 MT in 1973; 1.76 x 106 MT in
1974; 1.43 x 106 MT in 1975; 1.06 x 106 MT in 1976, and 6.32 x 105 MT in
1977. The adjusted cumulative wastes from surface mining from 1950-1978 was
9 7
1.11 x 10 MT, and the adjusted cumulative ore production was 4.49 x 10 MT.
-------
Table 3.69 Cumulative uranium mine waste and ore production
Year
1977
1976
1975
1974
1973
1972
1971
1970
1969
1968
1967
1966
1965
1964
1963
1962
1961
1960
1959
1958
1957
1956
1955
Su rf ace
1733000
1496000
1305000
1165000
1036000
853200
698100
577800
501000
420000
388600
356200
331800
314000
287300
254200
209600
167100
93510
46720
27470
15770
6720
Waste (103MT)
Underground
29250
24950
21380
19180
17760
16820
16240
15370
14410
13220
12060
11040
10180
9369
8425
7479
6391
5273
3406
2466
1776
1266
852
Surface
59220
54160
49920
46110
42600
38800
35350
32700
30200
28550
26560
25170
24260
22640
20290
16720
13810
10770
8075
5580
3442
1979
848
Ore (103MT)
Underground
73100
68840
65210
62760
60500
58960
56510
53600
50330
47160
43810
40910
38090
35000
31750
28210
23310
18320
13150
9433
6839
4943
3356
co
IX)
-------
Table 3.69 (Continued)
Year
1954
1953
1952
1951
1950
1949
1948
1947
1946
1945
1944
1943
1942
1941
1940
1939
1938
1937
1936
1935
1934
1933
1932
Waste (103MT)
Surface Underground
4071 580
370 171
842 257
370 171
167 98.9
48.6
11.4
3.18
3.18
3.18
3.18
3.18
3.18
3.18
3.00
2.85
1.67
0.844
0.533
0.272
0.0656
0.0195
0.0105
Ore (103MT)
Surface Underground
509 2313
46.3 702
105 1043
46.3 702
20.9 413
206
49.8
15.3
15.3
15.3
15.3
15.3
15.3
15.3
14.5
13.8
8.12
4.24
2.68
1.37
0.333
0.102
0.0553
CO
I
rv>
-------
3-213
Using these adjusted waste and ore values, the model inactive uranium surface
mine produced 8.88 x 105 MT of waste and 3.59 x 104 MT of ore.
The volume of the remaining pit of the model surface mine would be equal
to the total of the volume of wastes and ore that were removed from the mine.
Assuming a density of 2.00 MT/m , the volume of wastes and ore removed from
the mine pit would be 4.44 x 105 and 1.80 x 104 m3, respectively. The pit
was assumed to have the shape of an inverted truncated cone with a wall angle
of 45° (Fig. 3.24). The ore body was assumed to be a solid right cylinder
with a radius of 43.7 m and height of 3.0 m. The pit depth (ground surface
to bottom of ore bed) was 36.7 m, and the ground surface area of the pit
opening was calculated to be 2.03 x 10 m .
3.7.1.1 Waste Rock Piles
Overburden and sub-ore wastes from surface mines have been handled in
several ways in the past. In one case, the sub-ore (generally the last
material removed from the pit) was piled on top of the overburden. In an-
other case the sub-ore was piled separately and blended with higher grade ore
for shipment to the ore buying stations or mills. If the quantity of sub-ore
was in excess of that required for blending, it was also dumped on top of the
overburden (personal communication with 6. Ritter, Bendix Field Engineering
Corp.," Grand Junction, CO, 1979). The earlier surface mining practices,
therefore, generally produced waste piles with their cores containing over-
burden and their outer surface containing a mixture of overburden and
sub-ore.
The actual method of removing and stacking overburden and sub-ore varies
from mine to mine. In many cases the wastes were dumped in depressions or
washes or stacked in more than one pile. For calculation purposes, we assume
that wastes are stacked on a single pile in the shape of a solid truncated
cone 10 m high with a 45 degree slope. It is further assumed that the
sub-ore removed from the pit is placed evenly on top of the stacked over-
burden. The area and depth of the sub-ore placed on the waste pile is esti-
mated by determining the areas of the base and top of the pile by iteration,
computing the exposed surface area of the pile, computing the volume of the
sub-ore, and calculating the depth of the sub-ore.
The areas of the base and top of the waste pile (truncated cone) were
determined from the following equation:
-------
80.4
43.7
Figure 3.24 Cross section of model inactive surface mine (meters).
u>
I
-------
3-215
V = h. (AR + Ay +V"ABAy) wnere v = volume of wastes (overburden (3.25)
3 and sub-ore) (m3)
AB = area of the base (m2)
Ay = area of the top (m )
h = perpendicular distance between
the base and top (10 m)
Different values of Ag were substituted into the equation until the value of
V was equal to the combined volumes of the overburden and sub-ore (i.e; 5.55
x 10 m ) using a bulking factor of 25%. The area of the cone top was com-
puted (assuming a 45 degree slope) from the diameter of the top (Dy), which
is equal to the diameter of the base (DD), minus 20 meters or D, = D0 - 20.
b I D
The calculated diameters, Dy and DB> are 256 m and 276 m, respectively.
The exposed surface area of the waste pile was calculated using the
following equation:
S = S, + Sy where S. = lateral surface area (m ) (3.26)
c __L /r . p \
\ ^~2 ILB LT}
and ST = area of the top (m )
T .2
S = J^ (CB + CT) + Trry where CB = circumference of the base (m)
2 CT = circumference of the top (m)
L = slant height (m)
rT = radius of the top (m)
S = 14.1 (irDT +irDD) + Trr2 where DT = diameter of the top (m)
~- T B D^ = dimeter of the base (m)
S = 14.1 (3.14) (256 + 276) + 3.14 (16384)
2
S = 6.33 x 104 m2 (exposed surface area of waste pile)
The volume of sub-ore removed from the pit is assumed to be equal to the
volume of ore removed from the pit. The thickness (T) of the sub-ore plate on
the overburden is—
T = Vo = 2.25 x 104m3 = 0.36m.
S 6.33 x 10V <3-27)
-------
3-216
In summary, the waste pile produced at an inactive uranium surface mine
is to be in the shape of a truncated cone having a surface area of 6.33 x 10
2
m . The pile is assumed to have an inner-core of overburden plated with 0.36
m of sub-ore on its exposed surface. In practice, the plate would be a
mixture of overburden and sub-ore with the sub-ore concentrations increasing
towards the pile surface.
Table 3.70 lists average annual emissions of contaminants due to wind
erosion of the overburden pile. To compute these values, an emission factor
of 0.850 MT/hectare-yr, computed in Appendix I, was multiplied by the pile
surface area, 6.33 hectares, and the stable element concentrations listed in
Table 3.19. Uranium and thorium concentrations were assumed to be 110 pCi/g
and 2 pCi/g, respectively.
3.7.1.2 Radon-222 from the Mine Area
After the termination of active mining, Rn-222 will continue to exhale
from the wall and floor of the pit. Since all of the ore has been removed,
the Rn-222 will originate from the overburden and sub-ore surfaces. The sur-
face area of the sub-ore region of the pit is estimated from the volume of
ore and sub-ore (3.6
following equations:
ore and sub-ore (3.6 x 10 m ) and the shape and size of the pit using the
V = 1/3 h (AT + AB +\/A^ )where: A? = ff r2 (3.28)
S = 1/2 L (CB + Cb) + AB AB = rrr2 (3.29)
The terms in the equations are defined in the previous Section. By sub-
stituting the terms rg + h for r^ in Equation 3.28, h can be solved by
iteration.
V = 3.6 x 104 m3 = 1/3 h [ir (rg + h)2 + TT r 2 +
TT (rg + h)2 ( Trr2) ]when h = 5.3 m
The exposed surface area of the pit that contains the sub-ore is
Ss = 1/2 (7.50) 7r(87.4 + 98.0) + 6000 = 8.18 x 103 m2,
and the surface area of the overburden section of the pit is
SQ = 1/2 (44.4) (IT) (98.0 + 161.0) = 1.81 x 104 m2.
-------
3-217
Table 3.71 shows the results of radon flux measurements made at 20 of
the tailings piles at inactive uranium mill sites. Also shown is the esti-
mated average Ra-226 content of the tailings and the average Ra-226 content
Table 3.70 Average annual emissions of radionuclides (pCi) and stable
elements (kg) in wind suspended dust at the model inactive
surface mine
Contaminant
Arsenic
Barium
Cadmium
Cobalt
Copper
Chromium
Iron
Mercury
Potassium
Magnesium
Manganese
Overburden
Pile(a)
0.46
4.9
ND(b)
0.09
0.33
0.11
84
ND
135
19
5.2
Contaminant
• Molybdenum
Nickel
Lead
Ruthenium
Selenium
Strontium
Vanadium
Zinc
Uranium-238 and
each daughter
Thorium-232 and
each daughter
Overburden
Pile(a)
0.62
0.11
0.42
ND
0.59
0.70
7.6
0.16
1480
11
Emissions = 5.38 x 10 g/yr.
- Not detected.
-------
3-218
Table 3.71 Average radon flux of inactive uranium mill tailings piles
Location
ARIZONA
Monument Valley
Tuba City
COLORADO
Durango
Grand Junction
Gunnison
Maybell
Naturita
New Rifle
Old Rifle
Slick Rock
IDAHO
Lowman
NEW MEXICO
Ambrosia Lake
Shiprock
OREGON
Lakeview
SOUTH DAKOTA
Edgemont
TEXAS
Falls City
Ray Point
UTAH
Green River
Mexican Hat
Salt Lake City
WYOMING
Spook Site
Average All Sites
Average
Radon Flux^a'
(pCi/m -sec)
20
193
197
359
470
86
1446
458
553
70
125
173
340
660
143
65
430
77
290
1200
1770
466
Estimated
Ra-226(b)
Tailings Content
(pCi/g)
50
924
840
784
420
252
756
504
980
171
—
760
700
420
—
448
518
140
784
896
356
563
Average
Ra-226
Background
Soils(a)(pCi/g)
0.95
0.95
1.48
1.52
1.48
1.52
1.48
1.52
1.52
1.48
1.12
1.02
1.7
0.81
1.33
0.93
0.93
1.43
0.83
1.4
0.99
1.26
Reference^3
)
FBD-6JT-4 (1977)
FBD-GJT-5 (1977)
FBD-GJT-9
FBD-GJT-9
FBD-GJT-12
FBD-GJT-11
1977)
1977)
1977)
1977
FBD-GJT-8 (1977
FBD-GJT-10 1
[1977
FBD-GJT-10 (1977
FBD-GJT-7 (1977
FBD-GJT-17 (1977)
FBD-GJT-13 (1977)
Bernhardt et al.
(1975)
FBD-GJT-18 (1977)
FBD-211 (1978)
FBD-GJT-16 (1977)
FBD-GJT-20 (1977)
FBD-GJT-14 (1977)
FBD-GJT-3 (1977)
Bernhardt et al.
(1975)
FBD-GJT-15 (1977)
WFBD77.
Sw76.
-------
3-219
measured in representative background soils for each site. The average radon
exhalation rate per average Ra-226 content of tailings material from these
data is 0.83 pCi of Rn/m -sec per pCi of Ra/g.
Data analysis by Schiager (Sc74) indicates a radon exhalation rate of
2
1.6 pCi of Rn/m -sec per pCi of Ra/g. This value has often been used in the
environmental impact statements to assess the radon flux from tailings mater-
ials.
Table 3.72 summarizes data obtained during radiological surveys of
inactive uranium mine sites in New Mexico and Wyoming during the spring of
1979 (Wo79). Radon exhalation rates were measured with charcoal cannisters
and the radium-226 concentrations were determined for composite surface
samples taken from overburden, sub-ore, and waste rock piles. The average
radon-222 exhalation rate per average radium-226 content of the overburden,
p
sub-ore, and waste rock piles was 0.27, 0.11, and 0.12 pCi of Rn/m -sec per
pCi of Ra-226/g, respectively.
Measurements of the background flux and Ra-226 content of typical back-
ground soils were reported for the Edgemont, South Dakota site (FBD78).
2
These data indicate a value of 1.05 pCi of Rn/m -sec per pCi of Ra/g. Table
3.73 summarizes background radon flux estimates for several regions of the
United States. Considering the average U.S. background flux to be 0.82 pCi
of Rn/m2-sec (Tr79) and the average U.S. background soil Ra-226 content to be
1.26 pCi of Ra/g (Oa72), the average U.S. background radon exhalation rate is
estimated to be 0.65 pCi of Rn/m2-sec per pCi of Ra/g. The average back-
ground radon exhalation rate for New Mexico and Wyoming (Table 3.72) was 0.33
pCi of Rn/m2-sec per pCi of Ra/g. Therefore, the grand average U.S. back-
ground radon exhalation rate has been estimated to be 0.68 pCi of Rn/m -sec
per pCi of Ra/g, and the grand average U.S. background soil Ra-226 content
has been estimated to be 1.6 pCi/g.
We estimated the total radon released from the model abandoned surface
mine area from the following parameters:
1. Radon exhalation from the sub-ore surface area of the pit—
. the exposed sub-ore surface area (Ss) = 8.18 x 10 m ;
. the average radium-226 content of the sub-ore = 110 pCi/g; and
. the radon flux rate for sub-ore = 12 pCi of Rn/m -sec.
-------
Table 3.72 Average radon flux measured at inactive uranium mine sites
Location
Underground Mines
San Mateo Mine,
New Mexico
Barbara J # 1 Mine,
New Mexico
Surface Mines
Poison Canyon 1,
New Mexico
Poison Canyon 2,
New Mexico
Poison Canyon 3,
New Mexico
Morton Ranch
(Pit 1601),
Wyoming
Grand Averages
Area
Waste pile
Heap leach pond
Background
Waste pile
Background
Sub-ore
Overburden piles
Background
Sub-ore
Overburden pile
Sub-ore
Sub-ore
Overburden
Background
Sub-ore
Overburden
Waste Rock
Background
Average Radon
Flux (pCi/m2-sec)
18
38
0.29
7.9
0.41
7.0
6.7
0.33
5.3
9.8
11
24
9.7
2.3
12
8.7
13
0.83
Number of
Flux Measurements
11
3
1
6
1
1
5
1
3
6
2
12
4
2
Average Radium-226
Content of Surface
Sample (pCi/g)
117
81
0.77
110
3
43
62
2.1
—
— _
170
23
3
110
32
110
2.2
co
ro
rv>
o
Source: Wo79.
-------
3-221
Table 3.73 Background radon flux estimates
Radon Flux
2
Location pCi/m -sec
Background Soils of the U.S.
Champaign County, Illinois 1.4
Argonne, Illinois 0.56
Lincoln, Massachusetts 1.3
Socorro, New Mexico 0.90
Socorro, New Mexico 1.0
Socorro, New Mexico 0.64
Yucca Flat, Nevada 0.47
Texas 0,27
2
Average U.S. Background Radon Flux = 0.82 pCi/m-sec.
Source: Tr79.
Therefore, the radon released from the sub-ore surface area of the pit is
8.18 x 103 m2 x 12 pCi of Rn/m2-sec x 86400 sec/day = 8.48 mCi of Rn/day.
2. Radon exhalation from the overburden surface area of the pit—
. the exposed overburden surface area (S ) =
1.81 x 104 m2;
. the average radium-226 content of the overburden = 32 pCi/g; and
2
. the radon flux rate for overburden is 8.7 pCi of Rn/m -sec.
Therefore, the radon released from the overburden surface area of the pit is
1.81 x 104 m2 x 8.7 pCi of Rn/m2-sec x 86400 sec/day = 13.6 mCi of Rn/day.
-------
3-222
3. Radon exhalation from the overburden pile remaining at the pit--
. the exposed surface area of the waste pile (S) =
4 ? w
6.33 x 1(T m ;
. the Ra-226 'content of the surface of the overburden pile is
the same as the sub-ore content = 32 pCi/g; and
. the radon flux rate for the overburden pile is 8.7 pCi
2
of Rn/m -sec.
4
Therefore, the radon exhalation rate from the overburden pile is 6.33 x 10
? 9
m x 8.7 pCi of Rn/m -sec x 86400 sec/day = 47.6 mCi of Rn/day.
The total radon release rate at the abandoned surface mine site is the
sum of the above three source terms, 69.7 mCi/day. The estimated radon
release rate for background soils for an undisturbed area equivalent to the
surface mine area uses the following parameters:
. the ground surface area equivalent to the area of the pit opening
(2.03 x 104 m2) and the overburden pad area (5.98 x 104 m2) = 8.01
4 2
x 10 m , and
. the radon flux rate for background soils in uranium mining
2
areas = 0.83 pCi of Rn/m -sec (Table 3.72).
Therefore, the radon exhalation rate from an undisturbed area equivalent to
the model surface mine is
8.01 x 10 m x 0.83 pCi of Rn/m -sec x 86400 sec/day =
5.7 mCi of Rn/day.
Table 3.74 summarizes the annual radon-222 release from the model
inactive uranium surface mine and all inactive uranium surface mines.
3.7.1.3 Land Surface Gamma Radiation
The surface mine uranium overlying strata must be removed in order to
gain access to the uranium-bearing host materials and the ore body. The ore
body consists of ore and sub-ore, and the sub-ore is simply that fraction of
the ore body that contains ore uneconomical to recover. The end result of
the mining is that the residues (sub-ore) enhance natural radioactive
materials. That is, they are exposed or brought to the earth's surface. The
enhancement will cause, in most cases, increased aboveground radiation
-------
3-223
Table 3.74 Summary of estimated radon-222 releases from
inactive surface mines
Source
Estimation Method
Annual Release, Ci
Mine Pit
Sub-ore area
Overburden area
Total
Overburden Pile
Background
Model Mine
All Inactive
Mines
Model mine and limited field
measurements
Model mine and limited field
measurements
Model mine and limited field
measurements
Rn-222 flux measurements and
projected surface areas of
model mine pit and overburden
pile
Net Rn-222 release
Annual net Rn-222 release from
model times 1250 mines
3.1
5.0
8.1
17.4
2.1
23.4
29,000
-------
3-224
exposure rates around the mining area. Ore and sub-ore lost through handling
are subject to wind and water erosion. This effectively increases the mine
site area in a radiological sense. The gamma radiation exposure levels on
and around a mine site can be high enough to restrict use of the area after
mining.
Gamma radiation surveys were conducted at some inactive uranium surface
mining areas. Table 3.75 lists the ranges of exposure rates found. Appendix
G contains more specific information concerning the surveys. The residual
exposure rate levels would probably preclude unrestricted use of the pits,
waste piles, and overburden.
Figure 3.25 depicts gamma radiation measurements made on radials ex-
tending outward from an inactive surface mine pit. The measurements were
made with a pressurized ion chamber (PIC) at approximately 61 m intervals on
each radial. As expected, the exposure rate decreases with distance away from
the pit, indicating surface contamination from wind and water erosion of the
spoils and ore piles. Some of the contamination may also have originated
from ore and sub-ore dust losses during mining.
Since the pit resides over a former ore body and connecting or adjacent
ore bodies may be located near the mine, some caution is necessary when
interpreting the gamma exposure rates as indicative of surface contamination.
Development drilling, indicating the presence of ore bodies, is prevalent
throughout the north, west, and south areas around the pit. The northeast,
east, and southeast areas around the pit have exploratory drill holes only.
They indicate the probable absence of ore bodies. Although the north, north-
west, west, and southwest radials cross below grade ore bodies, it is not
reflected by the gamma measurements. Unless the ore body is very close to
the surface, its gamma radiation will not be measured (i.e., the 1/10 value
layer for earth shielding is about 0.3 m). The south radial, however, did
cross an ore outcropping.
If the exposure rate measurements made at the end points of the radials
(south radial excepted) are assumed to be near background, their mean value
is 14.4]jR/hr with a 2 sigma error of 1.6y R/hr.
Assuming all measurements in excess of 14.4 + 1.6 y R/hr or 16.0 yR/hr
are a result of eroded ore and sub-ore from the mining activities, an iso-
exposure rate line enclosing the eroded materials can be constructed around
the mine site. The line is constructed on Fig. 3.25 and is qualitatively
-------
3-225
Table 3.75 Summary of land surface gamma radiation surveys
in New Mexico, Texas and Wyoming
Gamma Radiation
Location Area Exposure Rate (y R/hr)
Poison Canyon, Pits 40 to 190
New Mexico Waste piles 65 to 250
Overburden 25 to 65
Texas Pits 5 to 400
Morton Ranch, Wyoming Pit 16 to 63
(1601 Pit) Ore piles 200
Overburden 59 to 138
Source: Wo79 for New Mexico and Wyoming and Co77 for Texas.
adjusted on the south radial to compensate for the ore outcropping. The line
bulges into the southeast quadrant indicating erosion by the predominant
2
northwest winds and contamination of about 0.3 km .
In summary, it appears that the residual gamma radiation exposure levels
at surface mining pits and overburden piles would preclude these areas from
unrestricted use. It also appears that wind and water erosions of the spoils,
ore, and sub-ore are occurring and causing land contamination far removed
from the mining area. Several surface mines were gamma surveyed in New
Mexico. The mines could not be individually gamma radiation surveyed because
of their close proximity, cross contamination from eroded ore and sub-ore,
and possible ore outcrops.
-------
13.9
14.1
13.9
15.3
14.5
14.9
14.6 14.4 15.2
13.9
154
14.9
220 22.4,^22.0 18.6 18.3 17.3 17.016.116.2 16.0 15.6 13.2
\
I
34.4
23.1
GROSS GAMMA EXPOSURE RATE
36
59.8
38.5
19.5
17.8
18.8
17.4
19.2
17.7
19.6
20.9
54.2
16.9
17.9
17.0
/ 18.3
15.4
Figure 3.25 Results of gamma exposure rate survey at the 1601 pit and environs, Morton Ranch uranium mine,
Converse County, Wyoming (^
I
S3
-------
3-227
3.7.2 Inactive Underground Mines
The model inactive underground mine is basically defined by dividing the
total reported volumes of ore and waste removed by inactive underground
mining by the number of inactive underground mines. The number of inactive
underground mines has been obtained from the U.S. Department of Energy mine
listing in Table 3.67. Table 3.67 lists the mines by state and type of mine.
Forty-four percent of the inactive underground mines are located in Colorado,
34 percent in Utah, 9.3 percent in Arizona, and 7.0 percent in New Mexico.
For modeling purposes, we assume that there are presently 2030 inactive
underground uranium mines. Table 3.69 lists the estimated underground mine
waste and ore production for 1932 to 1977. Uranium mine waste and ore pro-
duction statistics, on an annual basis, were available for underground pro-
ducers from 1959 to 1977 (DOI59-76). Annual uranium ore production statis-
tics for underground mining are available from 1948 to 1959 (DOE79) and from
1932 to 1942 (00132-42.). We estimated the mine waste production for the period
of 1932 to 1960 from underground mining waste-to-ore ratios and established
waste-to-ore ratios using the published ore and wastes production statistics
from 1959 to 1976 (DOI59-76). These ratios were fitted with a line by re-
gression analysis in order to estimate the waste-to-ore ratios from 1932 to
1959 (Fig. 3.26). Two lines were fitted to the known waste-to-ore ratios
because of the abrupt change in the ratios from 1972 to 1976. We assumed
that the steeper slope was caused by increased waste production from the
larger and deeper underground mines operated during this time. The estimated
annual waste-to-ore ratios were multiplied by the published annual ore pro-
duction values to estimate the annual waste production from 1932 to 1959. We
assumed that no ore was produced from 1942 to 1948 because most of the uran-
ium was obtained by reprocessing vanadium and radium tailings during that
period (Private communication with G. C. Ritter, 1979, Bendix Field Engi-
neering Corporation, Grand Junction, Colorado). Table 3.69 lists the cumu-
lative annual waste production from underground mining from 1932 through
1977. The total waste produced for this period was 2.92 x 10 MT, and the
total ore produced was 7.31 x 10 MT.
A simplistic way to identify a model inactive underground mine would be
to divide the cumulative tonnage of ore and wastes by the number of inactive
mines. We estimated the number of inactive mines from the U.S. Department of
Energy mine listing (Section 2.0 and Table 3.67). The model inactive under-
-------
1.2-
0.8_
0.6—
LLJ
at.
O
0.4—
0.2—
1932
T I I I I I I
1937 1942 1947 1952 1957 1962 1967
YEAR
Figure 3.26 Waste to ore ratios for inactive underground uranium mines from 1932 to 1977.
1972
1977
OJ
I
NJ
K>
00
-------
3-229
ground mine produced 3.60 x 10 MT of ore and 1.44 x 10 MT of waste. Unfor-
tunately, some of the contemporary waste and ore production has been produced
by Hoth active and inactive mines. In order to adjust the contemporary ore
and waste production for that portion of the ore and wastes generated by
active mining, we assumed a model active mine having a mining life of 15
years (St79). The mid-life of the mine was assumed to have occurred in 1978,
with production beginning in 1971.
We also assumed that some of the mines became inactive during the
1971-1978 period and that their numbers decreased linearly. For example,
2.44 x 10 MT of ore was produced in 1972 and 85.7 percent of that ore pro-
duced was from mines that were inactive by 1978. Therefore, adjusted ore
production was 2.09 x 10 MT for 1971. The ore production for 1973 was 1.15
x 106 MT and 1.27 x 106 MT in 1974; 1.06 x 106 MT in 1975; 1.02 x 106 MT in
1976; and 6.16 x 10 MT in 1977. The adjusted waste production was: 5.08 x
105 MT in 1972; 6.67 x 105 MT in 1973; 8.13 x 105 MT in 1974; 9.43 x 105 MT
in 1975; 7.43 x 105 MT in 1976; and 4.99 x 105 MT in 1977.
Through 1978, the cumulative adjusted ore production from inactive
underground mines was 6.37 x 10 MT, and the cumulative adjusted waste pro-
duction was 2.04 x 10 MT. The model inactive underground mine was assumed
4 4
to have produced 3.14 x 10 MT of ore and 1.00 x 10 MT of waste. Assuming a
3 4
density of 2.0 MT per m , the volume of ore and waste removed were 1.6 x 10
and 5.0 x 10 m , respectively.
Fifty percent of the waste volume mined we assumed to be sub-ore. The
volume of waste rock (i.e., containing no sub-ore) removed during the mining
3 3
is 2.5 x 10 m . Assuming an entry dimension of 1.83 m x 2.13 m, about 615 m
of shafts and haulways are in the model mine. The ore body we assumed to
have an average thickness of 1.8 m with a length and width of 91.2 m each.
3 2
The surface area of the passages would be 4.83 x 10 m . The surface area of
4 2
the mined-out ore body would be 1.71 x 10 m .
3.7.2.1 Waste Rock Piles
Wastes produced from underground uranium mining were generally cast or
dumped near the mine entries. Those wastes that were dumped on relatively
flat terrain formed dome-shaped piles. Wastes cast from rim mines generally
formed long, thin sheets down the canyon slopes. Since most of the inactive
underground mines are in the Uravan Mineral Belt, the waste pile shape (dome)
-------
3-230
is assumed to be predominant (see Appendix 6.1.2) and is used for the
calculations of the waste pile dimensions.
The waste produced at a typical underground mine consists of waste rock
and sub-ore. The waste rock is assumed to be on the bottom of the waste pile
since it was generally removed first. Sub-ore, which was removed later, is
assumed to cover or plate the waste pile. The waste piles are assumed to be
dome shaped, covering a circular area of 0.40 hectares. The dome is assumed
to be a spherical segment with a height (b) and base (c) of 71.8 m. The
volume (V) of the spherical segment, 6.3 x 103 m3 when corrected for bulking,
is equal to the volume of wastes and is expressed as
V =1 Trb (3c2 + 4b2). (3.30)
24
The surface area of the spherical segment is given by the expression
S = I Tr(4b2 + c2) where S = Surface area (m2). (3.31)
4
The term b is solved by substitution and iteration in the former equation and
is substituted in the latter equation to determine the surface area of the
wastes:
V = 6.3 x 103 m3 = _! TT b (15465 + 4b2) where: b = 3.1 m. (3.32)
24
The surface area of the waste pile is
1
4
S = 1 Tr(4b2 + c2) (3.33)
= 1 (3.14) (38 + 5155)
4
= 4.08 x 103 m2.
The thickness (T) of sub-ore on the surface of the waste pile is
volume of sub-ore = 3.2 x 10V „ QJB m< (3>34)
area of waste pile 4.08 x 103nr
In summary, the waste pile at an inactive underground uranium mine is
assumed to have the shape of a spherical segment with a surface area 4.08 x
3 2
10 m . The pile is assumed to have an inner core of waste rock covered or
plated with 0.78 m of sub-ore on its exposed surface. It is expected that
the plate of sub-ore on the waste pile would be more pronounced than the
sub-ore plates on overburden piles at surface mines because of diminished
-------
3-231
blending, mining practices, and the lower waste-to-ore ratio. The grand
average of the radium-226 concentrations in the waste rock and overburden
piles (Table 3.72) appear to confirm this expectation.
Table 3.76 lists average annual emissions of contaminants due to wind
erosion of the waste rock pile. These values were estimated by multiplying
an emission factor of 2.12 MT/hectare-yr, derived in Appendix I, by the waste
pile surface area, 0.408 hectares, and the stable element concentrations
given in Table 3.19. We assumed uranium and thorium concentrations to be 110
pCi/g and 2 pCi/g, respectively.
Table 3.76 Average annual emissions of radionuclides (uCi) and stable elements
(kg) in wind suspended dust at the model inactive underground mine
Contaminant
Arsenic
Barium
Cadmium
Cobal t
Copper
Chromium
Iron
Mercury
Potassium
Magnesium
Manganese
Waste Rock
Pile(a)
0.07
0.80
ND(b)
0.01
0.05
0.02
14
ND
22
3.0
0.83
Contaminant
Molybdenum
Nickel
Lead
Ruthenium
Selenium
Strontium
Vanadium
Zinc
Uranium-238 and
daughter
Thorium-232 and
daughter
Waste Rock
Pile(a)
0.10
0.02
0.07
ND
0.10
0.11
1.2
0.03
each
238
each
1.7
'a'Mass emissions = 8.65 x 105 g/yr.
(b)
ND - Not detected.
-------
3-232
3.7.2.2 Radon-222 from the Mine Area
We estimated the total radon released from the model inactive under-
ground mine from the following parameters:
1. Radon exhalation from the waste rock pile—
3 2
. the exposed surface area of the waste pile = 4.1 x 10 m ;
. the average Ra-226 content of the waste pile is 110 pCi/g; and
2
. the radon flux rate for the waste pile is 13 pCi of Rn/m -sec.
Therefore, the radon released from the waste pile is
4.1 x 103 m2 x 13 pCi of Rn/m2-sec x 86400 sec/day = 4.6 mCi of Rn/day.
2. Typical background release rate--
. the ground surface area equivalent to the area covered by
3 2
the waste pile = 4.1 x 10 m , and
. the radon flux rate for background soils in uranium mining
areas = 0.83 pCi of Rn/m2-sec (Table 3.72).
Therefore, the radon exhalation rate from an undisturbed area equivalent to
the waste pile of a model underground mine is
4.1 x 103 m2 x 0.83 pCi of Rn/m2-sec x 86400 sec/day = 0.29 mCi of Rn/day.
The net radon release rate due to the waste pile at the inactive underground
mine is 4.6 minus 0.29 or about 4.3 mCi of Rn/day above normal background.
Natural ventilation will occur in most mines and usually is considered
by mine ventilation engineers when planning the forced ventilation systems.
The natural force that can maintain a natural air flow due to temperature
differences is thermal energy. The thermal energy added to a system is
converted into a pressure difference. If the pressure difference is suffi-
cient to overcome head losses, a flow of air will occur.
Natural ventilation depends upon the difference between the temperature
inside and outside of a mine and the difference between the elevation of the
mine workings and the surface. Air flow by natural ventilation is generally
small (140 - 566 m /min) in shallow mines (Pe52). In deep mines, natural
ventilation flows may range from 1,420 to 4,250 m3/min (Pe52). The flow in
either the shallow or deep mines depends upon the depth, size, and number of
-------
3-233
openings. The intensity of thermal energy-induced natural pressure usually
ranges from a few hundredths to a few tenths cm of water in shallow (less
than 460 m deep) mines (Pe52). The maximum pressure drop per 305 m of depth
in deep mines is about 2.54 cm of water in winter and about 0.84 cm during
the summer (Pe52).
In general, natural ventilation is subject to considerable fluctuation.
It usually increases to a maximum in winter and a minimum in summer for deep
mines. The typical inactive underground uranium mine would be shallow;
therefore, the natural ventilation would be expected to reach its maximum in
the winter and summer and its minimum in the spring and fall (air temperature
in the mine closely approaches the outside temperature during the spring and
fall).
A first approximation of the annual release of Rn-222 from an inactive
underground mine simply would be that all Rn-222 released into the mine air
will be exhausted by natural ventilation before a significant radioactive
decay occurs. That is, the quantity of radon released into the mine is equal
to the quantity of radon released from the mine. The quantity of Rn-222
released from the sub-ore surfaces remaining in the mined-out ore body is
Q MLRn.222) =Ax ^ (3>35)
sec
where A is the surface area of the mined out
2
ore body (m )
= exhalation rate of the Rn-222 from
•
sub-ore per unit area per unit time, 12
pCi (Section 3.7.1.2)
m -sec
Q = (1.71 x 104 m2) (12 pCi) = 2.1 x 105 pCi/sec.
2
m -sec
It should be noted that * is the average radon flux physically mea-
sured from sub-ore bodies in inactive surface mines (Section 3.7.1.2). Be-
cause of safety considerations, no measurements were made from sub-ore bodies
in inactive underground mines during the April 1979 field surveys. The annual
Rn-222 source term from the mined-out ore body in an inactive underground
uranium mine, using the preceding assumptions, is
-------
3-234
Q (Ci) = 2.1 x 105 £Ci x 3.6 x 103 sec x 24 hr x 365 d. x
yr sec hr d yr
1 = 6.6 Ci
1012£C_i yr * (3-36)
Ci
The annual Rn-222 source term (Q) from the passageways, assuming an exhalation
rate of 8.7 pCi for overburden, is (Section 3.7.1.2)
m -sec
(4.8 x 103 m2) (2.7 x 10"4 Ci ) = 1.3 CI. (3.37)
yr-m yr
The air flow rate from the mine, assuming 140 m /min for an average shallow
mine, will exchange the mine air every three hours. The average annual
radon-222 concentration will be
7.9 Ci/yr x 1 x 1 = 107 pCi/£.
7.4 x 107 m3/yr 1000 a/m3
The radon daughter concentration will be about 87 percent of equilibrium with
the radon, assuming a mean residence time of the radon in the mine to be 1.5
hours.
Several inactive mines in the Grants, New Mexico area were monitored for
radon discharges by natural ventilation. One of the mines monitored was
relatively small and had a vertical shaft access. Five cased 30 cm diameter
vents were found and were assumed to be connected with the mine. The shaft
was covered with steel plate, but access holes were cut in the plate and one
corner had been pried up. Four vents were capped with buckets. Just one
cover was gas tight. One vent was partially covered with a piece of wood.
Only very small flow rates due to natural ventilation were measured at the
shaft and vents. The maximum radon emission from the mine per day was esti-
3
mated to be 2.8 x 10 yCi. This low radon discharge rate is probably due to
partial blockage of the vents and water in the mine. The mine was partially
flooded, and flowing water could be seen at the bottom of the shaft. The
-------
3-235
effect of the water would be to partially or completely close off the mine
workings and substantially reduce natural ventilation. The water would also
dissolve and substantially suppress the radon exhaling from the surface areas
of the mine. Thus, we believe that the radon discharges from wet inactive
mines via natural ventilation will be minimal.
Investigation at another inactive mine revealed that it was connected to
three other inactive mines that were subsequently connected to two active
mines. Ventilation fans at the connecting active mines were usually shut
down after the end of the day shift and on weekends. Mine air was exhausted
by natural ventilation through the shaft (highest opening) and vents of the
mine investigated. A flow rate up to 88 m /min was observed coming from the
shaft, and radon-222 concentrations reached 11,000 pCi/£. The average flow
rate observed over a weekend was 75 m /min, with an average radon-222 concen-
tration of 9,800 pCi/£. The average radon emission was 1.1 Ci/day.
Figure 3.27 is a plot of the changes in the Rn-222 concentration in the
air from the shaft of the inactive mine investigated. The average of the
3
measurements of the air flow rate from the shaft was about 76 m /min. The
Rn-222 concentration increased almost linearly with time for about 20 hours
after the fans were shut down at the end of the day shift on April 27, 1979.
The Rn-222 concentrations also leveled off at about '10, 000 pCi/«, . A dip,
presumed to have been caused by high winds, occurred in the Rn-222 concen-
tration curve from about 1000 to 1600 hours on April 28, 1979.
Since the curve is relatively flat at 10,000 pCi/£, it is assumed that
the rate of production of the Rn-222 is equal to the rate of removal of the
Rn-222 from the six mines. The average residence time of the radon in the
mine air is assumed to be approximately 10 hours, and the radon daughters
would be in near-equilibrium (assumed to be s 90 percent). Assuming that all
six interconnecting mines contributed equally to the source term measured,
the release rate of Rn-222 for a single mine will be
10,000 pCi/A x 76,000 £/min x 1440 min/day x 10"12Ci/pCi * 6
= 0.18 Ci/day.
Based on the preceding estimation of Rn-222 and progeny released from a
typical mine on the Colorado plateau and physical measurements at six con-
nected mines, the annual radon release rate may range from 7.9 to 66 Ci/yr.
These source term estimates, of course, are based on a single mine. Many mine
workings are, in fact, interconnected. If these interconnected workings are
assumed to constitute a single mine, then the upper limit of Rn-222 and
-------
Ventilation
Fans Operating
.Ventilation
Fans Not Operating
14000
12000
10000
O
Q.
C
CD
O
C
O
o
cs
CM
CM
C
O
"O
(D
tr
6000
4000
2000
April 27,1979
April 28,1979
April 29,1979
April 30,1979
o
o
o
o
o
o
o
o
o
o
o
o
o
ID
Time
O
o
O
o
-------
3-237
progeny discharge known at this time will be about 10,000 pCi/£ with an
annual Rn-222 source term of about 400 Ci/yr. For example, 67 percent of all
inactive underground uranium mines are in or near the Uravan mineral belt and
are probably dry. Their aggregate Rn-222 discharge by natural ventilation is
estimated to be
1360 mines x 66 Ci Rn-222 = 9.0 x 104 Ci/yr.
yr-mine
In summary, there is little information available on the discharge of
Rn-222 and its progeny from the vents and entries of inactive uranium mines
by natural ventilation. Some physical measurements indicate that the dis-
charges may be substantial. It is known, through surveys conducted to
support this study, that a large majority of the inactive uranium mines are
not isolated from the atmosphere and are capable of discharging their Rn-222
and progeny into the local environment. It is also known that some self-
sealing will probably occur at some of the mines, due to flooding, cave-ins,
and subsidence. Table 3.77 summarizes estimates of the annual radon-222
releases from inactive underground uranium mines. This potential source of
exposure could be practically eliminated by proper sealing of the inactive
mines.
3.7.2.3 Land Surface Gamma Radiation
Gamma radiation surveys were conducted around underground mining areas
in Colorado and New Mexico. Table 3.78 lists the ranges of gamma radiation
exposure rates measured at some of the mines. The elevated gamma ray ex-
posure rates on the waste piles are due primarily to plating those piles with
sub-ore removed during the mining process.
Some radioactive materials originating from ore and sub-ore handling can
be lost into the local environment around a mine site. Erosion of the mine
wastes can also disperse contaminants into the local environment. Figure 3.28
illustrates gross gamma radiation exposure rate measurements around an in-
active underground uranium mine in New Mexico. Background gamma-ray exposure
rate measurements made around the mine area ranged from 12 to 15 yR/hr.
According to the measurements made, exposure rate levels exceeded background
from 50 to more than 100 meters from the waste piles. The area that has been
contaminated far exceeds the area physically disturbed at the mine site.
Gross gamma exposure rates measured on the waste piles averaged about 95
-------
3-238
Table 3.77 Summary of radon-222 releases from inactive underground mines
Source
Estimation Methods
Annual Release, Ci
Model Mine
Waste Rock Piles
Underground workings
Sub-ore Surfaces
Passageways
Background
Model Mine
Actual Mine
Underground workings
(dry)
Underground workings
(wet)
Waste rock piles
Calculated volume & surface 1.7
area; limited field measure-
ments of radon flux
Radon release based on natural
ventilation rate for shallow
mines
Calculated surface area; limited
radon flux measurements of sub-ore 6.6
Calculated passageway surface
area; limited measurements of
radon flux from overburden 1.3
Field measurements of radon flux;
and projected area of waste
rock pile
Total radon source minus back-
ground
Field measurements
Field measurements
Calculated volume & surface area;
Limited field measurements of
radon flux
0.11
9.5
66
1.1
1.7
-------
3-239
Table 3.78
Summary of land surface gamma radiation surveys in
Colorado and New Mexico
Location
Area
Gamma Radiation
Exposure Rate (y R/hr)
Boulder, Colorado
Uravan, Colorado
Waste piles
Waste piles
40 to 100
50 to 220
San Mateo, New Mexico
Waste pile
Ore
Overburden
Background
35 to 275
100 to 350
20 to 120
10 to 13
Mesa Top Mines,
New Mexico
Waste piles
25 to 290
Barbara J #1 Mine,
New Mexico
Waste piles
Background
21 to 170
12 to 15
Source: Wo79.
-------
15
0 25 50 75
METERS Vent
GROSS GAMMA RAY EXPOSURE RATE -(/zR/hr)
' Figure 3.28 Gamma radiation survey around an inactive underground uranium mine in New Mexico.
N
-p-
o
-------
3-241
yR/hr, which would make them unsuitable for unrestricted use.
In summary, wastes from underground uranium mining technologically
enhance natural radioactivity and may .be considered low-level radioactive
wastes. Improperly controlled wastes will be dispersed into the surrounding
environment by the mining activities and erosion.
-------
3-242
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3-244
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-------
3-24'5
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-------
3-250
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3-251
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3-252
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-------
3-253
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-------
3-254
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3-255
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3-256
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3-257
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3-258
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Research, 14, 219-224.
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SECTION 4
DESCRIPTION OF MODEL MINES
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4 - 1
4.0 Description of Model Mines
Section 1.3 describes uranium mines and their operations, and Section 3
describes the potential sources of contamination at the principal types of
active and inactive mines. These discussions include an analysis of the
potential sources of contamination, quantities of contaminants associated
with the different sources, variations in the sources, and estimates of the
values needed to define the impact that these sources may impose upon the
environment and nearby populations. We attempted to define these terms and
mining parameters in a way that would reflect a general view of the uranium
mining industry and permit a generic assessment. The parametric values that
we have chosen for this assessment are listed below. The sections of this
report from which they were derived are given in parentheses.
4.1 Surface Mine
The model open pit (surface) mine will be located in Wyoming. It is the
mine defined in Section 3.3 as the "average large mine." However, to define
the total impact of all 63 open pit mines operating in the United States in
1978 we used the parameters developed in Section 3.3 for the "average mine."
Parameter
Ore, MT/yr
Sub-ore, MT/yr
Overburden, MT/yr
Production Parameters (1.3.1, 3.3.1)
Average Large Mine
5.1 x 105
5.1 x 105
4.0 x 107
Parameter
Mining days
per year
Mine life, yr
Ore stockpile
residence time, days
Overburden
management
Mining Parameters (3.3.1)
Average Large Mine
330
17
41
Case 2*
Average Mine
1.2 x 105
1.2 x 105
6.0 x 106
Average Mine
330
17
41
Case 2*
*Case 2—Backfilling concurrent with mining - assumes 7 pits opened in 17-yr.
mine life and the equivalent of one-pit overburden (2.4 yr. production)
remains on the surface.
-------
4-2
Parameter
Average grade,
percent U,CL
Th-232 concentration,
pCI/g
Activity ratio
(dust/ore)
Mineralogy
Density, MT/m3
Surface area of
2
stockpile, m
Area of pad, m
Stockpile height, m
Thickness of ore
zone, m
Ore Parameters (3.3.1,2)
Average Large Mine
0.1
10
2.5
Sandstone
2.0
6,200
5,300
9.2
12
Average Mine
0.1
10
2.5
Sandstone
2.0
3,590
3,340
3.1
12
Parameter
Average grade,
percent IL00
6 o
Th-232 concentration,
pCi/g
Activity ratio
(dust/sub-ore)
Mineralogy
3
Density, MT/m
Surface area of
2
stockpile, m
Stockpile height, m
Area of pad, hectares
Sub-Ore Parameters (3.3.1.3)
Average Large Mine
0.015
2.5
Sandstone
2.0
120,000
30
11
Average Mine
0.015
2
2.5
Sandstone
2.0
36,000
30
3
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4 - 3
Parameter
Average grade,
percent ILOg
Th-232 concentration,
pCi/g
Mineralogy
3
Density, MT/m
Surface area of
2
dump, m
Dump height, m
Area of terrain,
hectares
Overburden Parameters (3.3.1.1)
Average Large Mine
0.0020
Sedimentary
2.0
1.1 x 10
65
104
6
Average Mine
0.0020
1
Sedimentary
2.0
3.5 x 105
30
33
. Wastewater Discharge Parameters (3.3.2.2)
Parameters (mg/£ except as noted) Average Mine
Discharge volume, 2.94
o
m /min (Assumed value of 3.0)
Total uranium 0.07
Radium-226, pCi/ji ^ 0.41
Total suspended solids 20.88
Sulfate
-------
4 - 4
Airborne Source Terms (3.3.4)
Section 3.3.4 identifies and describes potential sources of airborne
contamination at surface mines. The principal sources are dusts produced
by mining operations and wind erosion and Rn-222 released by exposed uranium
in the pit and overburden, sub-ore, and ore piles. The tables of Section
3.3.4 present the average annual emissions of contaminants from these sources
during active mining.
Source
Combustion Products
Vehicular Dusts
Dust from Mining Activities
Wind Suspended Dust
Rn-222 Emissions
4.2 Underground Mine
The model underground mine, defined in Section 3.4 as the "average large
mine," will be located in New Mexico. However, to determine the total impact
of all 305 underground uranium mines in the United States we used the
parameters developed in Section 3.4 for the "average mine."
Parameter
Ore, MT/yr
Sub-ore, MT/yr
Waste rock, MT/yr
Production Parameters (1.3.1, 3.4.1)
Average Large Mine
2 x 105
2 x 105
2.2 x 104
Average Mine
1.8 x 104
1.8 x 104
2.0 x 103
Parameter
Mining days per year
Mine life, yr
Ore stockpile residence
time, days
Waste rock management
Mining Parameters (3.4.1)
Average Large Mine
330
17
41
No backfill
Average Mine
330
17
41
No backfill
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4 - 5
Ore Parameters (3.4.1.2)
Parameter Average Large Mine
Average grade,
percent U30g 0.10
Th-232 concentration,
pCi/g 10
Activity ratio
(dust/ore) 2.5
Mineralogy Sandstone
Density, MT/m3 2.0
Surface area of
stockpile, m2 5,800
Stockpile height, m 3.1
2
Area of pad, m 5,480
Sub-Ore Parameters (3.4.1.3)
Parameter Average Large Mine
Average grade,
percent U~0R 0.035
Th-232 concentration,
pCi/g 2
Activity ratio
(dust/sub-ore) 2.5
Mineralogy Sandstone
Density, MT/m3 2.0
Surface area of
dump, m2 104,900
Dump height, m 12
Area of pad, m2 99,400
Average Mine
0.10
10
2.5
Sandstone
2.0
680
3.1
620
Average Mine
0.035
2
2.5
Sandstone
2.0
18,800
6
17,700
-------
4-6
Waste Rock Parameters (3.4.1.1)
Parameters
Average grade,
percent U-jOg
Th-232 concentration,
pCi/g
Mineralogy
Density, MT/m3
Surface area of
2
dump, m
Dump height, m
2
Area of terrain, m
Average Large Mine
0.0020
1
Sedimentary
2.0
14,100
12
12,800
Average Mine
0.0020
1
Sedimentary
2.0
2,700
6
2,460
Wastewater Discharge Parameters (3.4.2.2)
(a)
Parameter (mgA except as noted)
Discharge volume,
m /min
Total Uranium
Radium-226,
Lead-210, pCi/a
Total suspended solids
Sulfate(b)
Zinc
Barium
Cadmium
Arsenic
Molybdenum
Selenium
Average Mine
2.78
(assume value of 2.0)
1.41
1.37
1.46
27.8
116
0.043
0.81
0.007
0.012
0.29
0.076
^'Concentrations of Ra-226 and its daughters are reduced to 10 per-
cent of the amount actually released due to irreversible sorption and pre-
cipitation.
^ 'Concentrations of sulfate are reduced to 20 percent of the amount
actually released due to irreversible sorption and precipitation.
-------
4 - 7
Airborne Source Terms (3.4.4)
Section 3.4.4 identifies and describes potential sources of airborne
contamination at underground mines. The principal sources are contaminated
dusts due to mining operations and wind erosion and Rn-222 that is released
from the mine exhaust vents during mining and from waste rock, sub-ore, and
ore pile surfaces. Average annual emissions of contaminants from these
sources during active mining operations are presented in the following tables
of Section 3.4.4.
Source
Combustion Products
Vehicular Dusts
Dust from Mining Activities
Wind Suspended Dust
Rn-222 Emissions
4.3 In Situ Leach Mine
The following parameters are for a model (hypothetical) in situ solution
mine as defined in Section 3.5:
1. Size of deposit =52.6 hectares
2. Average thickness of ore body = 8 m
3. Average ore grade = 0.06 percent U^Og
4. Mineralogy = Sandstone
5. Ore density - 2 MT/m3
6. Ore body depth = 153 m
7. Mine life » 10 years (2-yr leach period in each of 5 sectors)
8. Well pattern = 5 spot
Injection wells = 260
Production wells = 200
Monitoring wells = 80
9. Annual U30g production = 227 MT
10. Uranium leaching efficiency = 80 percent
11. Lixiviant = Alkaline
12. Lixiviant flow capacity = 2,000 «/min
13. Lixiviant bleed = 50 Vmin (2.5 percent)
14. Uranium in Lixiviant = 183 mg/&
15. Calcite (CaCOJ removal required = 2 kg calcite per kg U30g
-------
4-8
Data were insufficient to estimate aqueous releases of contaminants from
these type mines. However, since these facilities are planned to operate
with no aqueous discharges, releases of contaminants via this pathway, except
for possible excursions, should be small. Annual releases of contaminants to
the atmosphere were computed in Section 3.5.3 for the model mine and listed
in Table 3.59. These estimated annual airborne releases will be used to
compute dose and indicate adverse health effects that might be associated
with in situ leach mining.
4.4 Inactive Surface Mine
The model inactive surface mine will be located in Wyoming. It is
defined in Section 3.7.1. The model mine parameters are listed below.
Mine Parameters
1. Period of active mining = 17 years
2. Total waste rock production = 8.88 x 10 MT
4
3. Total ore production = 3.59 x 10 MT
o
4. Density of ore and waste rock = 2.0 MT/m
5. Size of abandoned pit:
Volume = 4.62 x 105 m3
4 2
Ground surface area = 2.03 x 10 m
Pit bottom area = 6.00 x 103 m2
Depth = 36.7 m
6. Surface area and composition of waste rock pile =
4 2
6.33 x 10 m uniformly covered to a depth of
0.36 m with sub-ore
7. Reclamation = none
Airborne Source Terms
Sections 3.7.1.1 and 3.7.1.2 identify and describe potential sources of
airborne contamination at inactive surface uranium mines. The principal
sources are contaminated, wind-suspended dust from the waste rock pile and
Rn-222 released from exposed ore and sub-ore bearing surfaces in the pit and
the waste rock pile. Tables 3.70 and 3.74 show average annual emissions of
contaminants from these sources.
-------
4 - 9
4.5 Inactive Underground Mine
The model inactive underground mine will be located in New Mexico. It is
defined in Section 3.7.2, and its parameters are listed below.
Mine Parameters
1. Period of active mining = 15 yrs
2. Total waste rock production = 1.00 x 10 MT
3. Total ore production = 3.14 x 104 MT
4. Density of ore and waste rock = 2.0 MT/m
5. Surface area and composition of waste rock pile =
3 2
4.08 x 10 m uniformly covered to a depth of
0.78 m with sub-ore
6. Mine entrance and exhaust vents not sealed
Airborne Source Terms
Sections 3.7.2.1 and 3.7.2.2 identify and define potential sources of
airborne contamination at inactive underground uranium mines. The principal
sources are contaminated, wind-suspended dust from the waste rock pile and
Rn-222 released from the unsealed mine entrance and exhaust vents and the
waste rock pile. Tables 3.76 and 3.77 list average annual emission of con-
taminants from these sources.
-------
SECTION 5
POTENTIAL PATHWAYS
-------
5-1
5.0 Potential Pathways
5.1 General
5.1.1 Vegetation
Airborne participate radioactivity may be deposited directly on the
edible foliar surfaces of crops or on the soil and then migrate through the
soil into the plant's root system and into an edible crop. Such crops may be
consumed directly by man or by animals which are ultimately consumed by man.
The use of contaminated water (either groundwater or surface) to irrigate
crops may also lead to the ingestion of radionuclides from either the direct
consumption of the crop or the crop-to-animal-to-man pathway.
The reconnaissance surveys of some inactive uranium mine sites indicated
that no crops for human consumption were being farmed at or near any of the
sites. Although the potential for man's ingestion of radionuclides in edible
crops due to the direct deposition or the root uptake of either airborne par-
ticulates or contaminated mine water is a greater possibility near the active
mines, farming in such areas is not extensive.
Almost every inactive and active mine site visited had range cattle and/
or sheep grazing on the natural vegetation growing at the site; hence, the
possible consumption of such animals could be a potential pathway for man's
ingestion of radionuclides released into the environment surrounding the mine
sites.
5.1.2 Wildlife
There are numerous species of mammals, birds, reptiles, and amphibians
at both active and inactive uranium mine sites. Though mining may destroy
their natural habitat, there are no significant radiological impacts on
wildlife in these areas. Dewatering and drainage from active mines sometimes
create ponds or streams that may be used by migratory waterfowl and local
wildlife as a source of water, but, when mining is completed, the ponds dry
up, probably without leaving any permanent or significant radiological impact
on wildlife. The small lakes formed in inactive surface mine pits, however,
may remain for a long period of time and have a significant environmental
impact. It would be expected that sedimentation and eutrophication of the
lakes would progressively diminish the impact with time by reducing the con-
tact of ore bodies with the biosphere. The potential food pathway of animal-
-------
5-2
toman via wildlife hunting at these sites is also minimal. Hunting is poor
and hunting restrictions are usually observed at the mine sites.
5.1.3 Land Use
Most uranium mining activities have been conducted in areas away from
population centers. Most mines are located on private property or are on
Federal lands such as national forests. The predominant land use is as
rangeland (or forest) and only minor areas are cropland. The fraction of land
o
used for vegetable crop production for Wyoming and New Mexico is 1.59 x 10
and 1.38 x 10~3, respectively. This fraction is based on the assumption that
the statewide fractions apply to uranium mining areas within each state.
Average population densities are typically rural, i.e., less than one person
2
per 2.6 km.
5.1.4 Population Near Mining Areas
Uranium mines occur in clusters throughout many western states and are
somewhat scattered throughout the eastern states. In order to estimate the
number of persons residing within 50 miles (80km) of a mine, we used county
populations where there either is or has been mining. Table 5.1 lists the
states and their respective mining counties plus the numbers of inactive and
active surface and underground uranium mines in each county. We derived the
county population statistics from U.S. Department of Commerce census data
(DOC78), which are January 1, 1975 estimates. The county areas were obtained
from the same reference.
2
The area, 20,106 km , within a circle with a radius of 80 km usually
exceeds the area of most counties. Because of this, the number of persons
residing within 80 km of a mine will be underestimated using county popula-
tion statistics. In other words, we consider the estimates of populations
within the mining regions to be somewhat low.
Persons residing in a mining area are likely to be exposed from more
than one mine because of the aforementioned clustering. To account for this,
Table 5.1 lists the product (person-mines) for both active and inactive uran-
ium mines. The total number of person-mines for inactive mines is approxi-
mately 82,000,000 persons. The total number of person-mines for active mines
is approximately 14,000,000 persons. The combined equivalent population
exposed to inactive and active uranium mining is approximately 96,000,000
persons.
-------
Table 5.1 Number of uranium mines and population statistics for counties
containing uranium mines
State
Alaska
Arizona
California
County
Southeast^3*
Apache
Cochise
Coconino
Gila
Graham
Haricopa
Mohave
Navajo
Pi ma
Santa Cruz
Yavapai
Imperial
Inyo
Kern
Las sen
Number of
Uranium Mines
Inactive Active
1
140
2
113
18
1
3
5
35
2
3
3
2
1
6
2
0
0
0
0
0
0
0
6
1
1
0
0
0
0
0
0
Population County
Density County Area Population
o 2
(persons/km ) (km) (persons)
0.03
1.1
3.8
1.0
2.4
1.4
41.
0.76
2.3
19.
4.3
1.8
6.8
0.77
17
1.4
44,501
28,930
16,203
48,019
12,297
11,961
23,711
34,232
25,666
23,931
3,227
20,956
10,984
26,237
21,113
11,816
1,282
32,304
61,918
48,326
29,255
16,578
971,228
25,857
59,649
443,958
13,966
37,005
74,492
17,259
349,874
16,796
Person-Mines Person-Mines
Inactive Active
1,282
4,522,560
123,836
5,460,838
526,590
16,578
2,913,684
129,285
2,088,715
887,916
41,898
111,015
148,984
17,259
2,099,244
33,592
0
0
0
0
0
0
0
0
59,649
443,958
0
0
0
0
0
0
-------
Table 5.1 (Continued)
State County
California Madera
Mono
Riverside
San Bernardino
Sierra
Tuolumne
Colorado Boulder
Clear Creek
Custer
Dolores
Eagle
El Paso
Fremont
Garfield
Gil pin
Grand
Number of
Uranium Mines
Inactive Active
1
1
5
3
A
1
7
4
3
6
2
1
25
10
4
4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Population
Density
/
(persons/km'
7.5
0.51
25.
14
1.2
4.6
68
4.8
0.59
0.62
1.7
42
6.6
2.3
5.0
0.86
County Area
?) (km)2
5,556
7,840
18,586
52,103
2,481
5,832
1,937
995
1,909
2,657
4,353
5,587
4,022
7,759
383
4,802
County
Population
(persons)
41,519
4,016
456,916
696,871
2,842
25,996
131,889
4,819
1,120
1,641
7,498
235,972
26,545
17,845
1,915
4,107
Person-Mines Person-Mines
Inactive Active
41,519
4,016
2,284,580
2,090,613
2,842
25,996
923,223
19,276
3,360
9,846
14,996
235,972
663,625
178,450
7,660
16,428
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-------
Table 5.1
(Continued)
State County
Colorado Gunnison
Hi ns dale
Huerfano
Jefferson
La Plata
Larimer
Mesa
Moffat
Montezuma
Montrose
Park
Pitkin
Pueblo
Rio Blanco
Saguache
San Juan
Number
Uranium
Inactive
1
1
2
13
3
5
185
18
6
479
7
1
1
26
13
2
of
Mines
Active
0
0
0
1
0
0
20
3
1
63
0
0
0
0
1
0
Population
Dens i ty
o
(persons/km )
1.2
0.19
1.6
120
5.4
17
7.3
0.77
2.7
3.5
0.77
3.5
20
0.77
0.39
0.77
County Area
(km)2
8,339
2,729
4,077
2,028
4,358
6,762
8,549
12,284
5,423
5,796
5,599
2,520
6,228
8,451
8,142
1,012
County
Population
(persons)
10,006
519
6,590
235,368
23,533
114,954
62,407
9,459
14,642
20,286
4,311
8,820
124,560
6,507
3,175
779
Person-Mines
Inactive
10,006
519
13,180
3,059,784
70,599
574,770
11,545,295
170,262
87,852
9,716,994
30,177
8,820
124,560
169,182
41,275
1,558
Person-Mines
Active
0
0
0
235,368
0
0
1,248,140
28,377
14,642
1,278,018
0
0
0
0
3,175
0
-------
Table 5.1
(Continued)
State
Colorado
Idaho
Montana
Nevada
County
San Miguel
Teller
Custer
Lemhi
Broadwater
Carbon
Fallon
Hill
Jefferson
Madison
Clark
Elko
Humbol dt
Lander
Lincoln
Lyon
Number of
Uranium Mines
Inactive Active
339
3
5
1
1
11
1
1
3
1
2
3
1
2
2
2
25
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Population
Density County Area
n *\
(persons/km ) (km)
0.77
3.9
0.23
0.39
0.82
1.5
0.96
2.3
1.5
0.55
16.2
0.31
0.25
0.39
0.19
1.9
3,322
1,432
12,766
11,862
3,090
5,325
4,229
7,581
4,278
9,138
20,393
44,452
25,128
14,558
27,114
5,257
County
Population Person-Mines Person-Mines
(persons) Inactive Active
2,557
5,584
2,967
6,395
2,526
7,797
4,050
17,358
6,839
5,014
330,714
13,958
6,375
2,992
2,647
10,508
866,823
16,752
14,835
6,395
2,526
85,767
4,050
17,358
20,517
5,014
661,428
41,874
6,375
5,984
5,294
21,016
63,925
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
-------
Table 5.1 (Continued)
State
Nevada
Hew Jersey
New Mexico
County
Mineral
Nye
Was hoe
Sussex
Catron
Dona Ana
Grant
Harding
Hidalgo
McKinley
Mora
Quay
Rio Arriba
Sandoval
San Juan
San Miguel
Santa Fe
Number of
Uranium Mines
Inactive Active
2
1
6
1
4
1
3
1
1
73
1
3
8
3
41
3
2
0
0
0
0
0
0
0
0
0
35
0
0
0
0
0
0
0
Population
Dens i ty
o
(persons/km )
0.71
0.12
8.9
73
0.12
7.1
2.1
0.25
0.53
3.5
0.93
1.5
1.9
2.3
4.6
1.8
13
County Area
(km)2
9,751
46,786
16,487
1,364
17,863
9,852
10,282
5,527
8,927
14,138
5,025
7,446
15,133
9,619
14,245
12,279
4,926
County
Population
(persons)
7,051
5,599
144,750
99,299
2,198
69,773
22,030
1,348
4,734
49,483
4,673
10,903
28,752
22,123
65,527
21,951
64,038
Person-Mines
Inactive
14,102
5,599
868,500
99,299
8,792
69,773
66,090
1,348
4,734
3,612,259
4,673
32,709
230,016
66,369
2,686,607
65,853
128,076
Person-Mines
Active
0
0
0
0
0
0
0
0
1,731,905
0
0
0
0
0
0
0
-------
Table 5.1
(Continued)
State
New Mexico
North Dakota
Oklahoma
Oregon
South Dakota
County
Sierra
Socorro
Taos
Valencia
Billings
Slope
Stark
Cad do
Custer
Crook
Lake
Butte
Custer
Fall River
Harding
Lawrence
Pennington
Inact
6
7
1
19
9
1
3
2
1
1
2
3
10
93-
28
2
5
Number of
Uranium Mines
ive Active
0
0
0
4
0
0
0
.0
0
0
0
0
0
0
0
0
0
Population
Density
2
(persons/km)
0.67
0.57
3.0
3.1
0.39
0.39
5.8
8.8
8.3
1.3
0.34
1.3
1.2
1.9
0.39
8.4
8.3
County Area
(km)2
10,790
17,102
5,843
14,649
2,950
3,172
3,408
3,294
2,538
7,705
21,318
5,827
4,032
4,514
6,946
2,072
7,198
County
Population
(persons)
7,189
9,763
17,516
45,411
1,153
1,360
19,650
28,931
21,040
9,985
7,158
7,825
5,196
8,066
1,879
17,453
59,349
Person-Mines
Inactive
43,134
68,341
17,516
862,809
10,377
1,360
58,950
57,862
21,040
9,985
14,316
23,475
51,960
750,138
52,612
34,906
296,745
Person-Mines
Active
0
0
0
181,644
0
0
0
0
0
0
0
0
0
0
0
0
0
00
-------
Table 5.1
(Continued)
State County
Texas Bri scoe
Burnet
Crosby
Garza
Gonzales
Karnes
Live Oak
Utah Beaver
Box Elder
Duchesne
Emery
Garfield
Grand
Iron
Juab
Kane
Number
Uranium
Inactive
2
1
1
6
2
23
6
9
1
4
186
131
164
1
4
3
of
Mines
Active
0
0
0
0
0
10
5
1
0
0
18
15
17
0
0
0
Population
Density
o
(persons/km )
1.2
4.4
3.9
2.8
5.8
6.6
2.3
0.77
1.9
1.5
0.39
0.39
0.77
1.4
0.52
0.39
County Area
(km)2
2,264
2,577
2,359
2,367
2,735
1,963
2,732
6,692
14,512
8,430
11,497
13,359
9,536
8,547
8,837
10,111
County
Population
(persons)
2,794
11,420
9,085
6,611
16,342
12,955
6,453
5,152
28,129
12,645
4,483
5,210
7,342
12,177
4,574
3,943
Person-Mines
Inactive
5,588
11,420
9,085
39,666
32,684
297,965
38,718
46,368
28,129
50,580
833,838
682,510
1,204,088
12,177
18,296
11,829
Person-Mines
Active
0
0
0
0
0
129,550
32,265
5,152
0
0
80,694
78,150
124,814
0
0
0
-------
Table 5.1
(Continued)
State
Utah
Washington
Wyoming
County
Piute
San Juan
Sevier
Uintah
Washington
Wayne
Pend Ore me
Spokane
Stevens
Albany
Big Horn
Campbel 1
Carbon
Converse
Crook
Fremont
Number of
Uranium Mines
Inactive Active
10
241
2
14
6
32
3
9
1
4
9
55
16
31
23
65
0
24
0
0
0
0
0
0
2
0
0
0
3
5
0
13
Population
Density
o
(persons/km)
0.77
0.77
2.3
1.5
2.7
0.39
1.9
67
3.5
2.3
1.5
1.2
0.77
0.77
0.77
1.2
County Area
(km)2
1,952
19,961
4,996
11,621
6,285
6,438
3,631
4,553
6,425
11,002
8,176
12,318
20,473
11,087
7,464
23,817
County
Population
(persons)
1,503
15,369
11,490
17,431
16,969
2,510
7,361
306,338
22,489
25,304
12,264
14,781
15,764
8,536
5,747
28,580
Person-Mines
Inactive
15,030
3,703,929
22,980
244,034
101,814
80,320
22,083
2,757,042
22,489
101,216
110,376
812,955
252,224
264,616
132,181
1,857,700
Person-Mines
Active
0
368,856
0
0
0
0
0
0
44,978
0
0
0
47,292
42,680
0
371,540
-------
Table 5.1
(Continued)
State County
Wyoming Johnson
Natrona
Nlobrara
Sublette
Sweetwater
Washakie
We s ton
Number of Population County
Uranium Mines Density County Area Population Person-Mines
2 2
Inactive Active (persons/km ) (km) (persons) Inactive
15
16
13
1
4
2
1
0
2
0
0
2
0
0
0.39
3.9
0.39
0.39
1.2
1.5
1.0
Average Population
Density
2
4.4 persons/km
10,813
13,835
6,770
12,564
27,011
5,858
6,234
4,217 63,255
53,956 863,296
2,640 34,320
4,899 4,899
32,413 129,652
8,787 17,574
6,307 6,307
Person-Mines
Active
0
107,912
0
0
64,826
0
0
Total County Total Person-Mines Total Person-Mines
Area (km)2 Population (Inactive) (Active)
1,492,136 6,625,099 82,327,885 14,035,161
Note.—Population statistics from (DOC78).
^Congressional District.
-------
5-12
5.1.5 Population Statistics of Humans and Beef Cattle
Table 5.2 lists some population statistics for humans in New Mexico and
Wyoming, humans in all uranium mining states, and beef cattle in New Mexico
and Wyoming.
Table 5.2 Population statistics for humans and beef cattle
Total Human and Beef Cattle Population Within 80 km Radius of Mines
New Mexico Wyoming All Uranium Mining States
Human 447,412 224,195 6,625,099
Beef cattle 753,000 905,000
Average Human and Beef Cattle Population Densities Within 80 km Radius
of Uranium Mines (number/km )^a'
Human
Beef Cattle
2.4
4.1
1.3
5.1
4.4
(a^Areas taken from Table 5.1: New Mexico = 183,646 km2; Wyoming = 177,422
2 2
km , and the total county area = 1,492,136 km .
5.2 Prominent Environmental Pathways and Parameters for Aqueous Releases
From a computer code prepared within EPA, we calculated annual committed
dose equivalents to individuals and annual collective dose equivalents to a
population for these assessments. Table 5.3 lists the aqueous pathways that
were initially considered potential pathways of exposure. As indicated in
Table 5.3, these pathways result in computation of dose equivalents due to
inhalation, ingestion, ground surface exposure, and air submersion. For above
surface crop ingestion, milk ingestion, and beef ingestion (pathways 3, 4,
and 5), we considered only uptake through the plant root systems to predict
-------
5-13
concentrations of radionuclides in crops, since essentially all irrigation is
ditch irrigation. Appendix J contains a detailed explanation of the
environmental transport and dosimetry models used in these analyses.
The maximum individual for the aquatic pathways is the individual at
maximum risk. He is exposed to radionuclides discharged in mine effluent
through pathways 2 through 10 of Table 5.3. The water contributing radionu-
cl ides to these pathways comes from a creek into which a mine discharges. The
average individual is exposed to the average risk of all persons included in
the population of the assessment area. He is exposed to radionucl ides dis-
charged in mine effluent through pathways 2 through 8 and 10 of Table 5.3.
The water contributing radionuclides to these pathways is taken from the
regional river after the creek water has been diluted in this river. The
population considered in the assessment of the aquatic pathways is obtained
by multiplying the regional assessment area size by the population density
within this area. This assessment area contains the drainage basin for the
mine effluent stream, the creek and the regional river discussed in defining
the maximum and average individuals.
5.2.1 Individual Committed Dose Equivalent Assessment
Section 6 of this report contains the computed dose equivalents to the
maximum individual and to the average individual. For the maximum indi-
vidual, we included all pathways in Table 5.3 except drinking water (pathway
1). It is known that the releases to the aquatic environment occur through
discharge of mine water to surface streams. Potentially, drinking water
could be one of the most significant pathways for the maximum individual dose
equivalents, if surface water containing mine wastes was drunk. However, it
appears that all drinking water for both the New Mexico and the Wyoming sites
comes from wells (Robert Kaufmann, 1979, U.S. Environmental Protection
Agency, Las Vegas, NV, personal communication). Thus, the only way mine
discharges can enter human drinking water is by percolating through the soil.
Since we do not know the soil chemistry for these sites well enough to
predict the ion-exchange parameters for the soil, we can not predict,
realistically, the quantity of mine-related radionuclides that would reach
the groundwater. We expect that these ion-exchange factors would be large
for several of the radionuclides considered in these analyses and that
groundwater concentrations of radionuclides discharged in mine water
-------
5-14
would be quite small compared to concentrations in the surface water down-
stream from the mines. Further study is needed before dose equivalents for
the maximum individual by drinking groundwater can be adequately addressed.
The following are other assumptions used to calculate maximum individual
dose equivalents:
1. Ground surface concentrations of radionuclides (used for
pathways 6 through 8) are for 8.5 years, the assumed
midpoint of mine life. The assumed period of mine oper-
ation is 17 years. The organ annual dose equivalents for
the external surface exposure pathway are based on the
ground concentrations after the 8.5 years buildup time.
2. For inhaled or ingested radionuclides, the dose equivalents
are the annual committed dose equivalents that will be
accumulated over 70 years after intake for an adult.
We calculated dose equivalents to the average individual in the assess-
ment area by taking the population dose equivalents (discussed in Subsection
5.2.2) and dividing by the population living in the area.
Table 5.3 Aquatic environmental transport pathways initially considered
Pathway No. Pathway
1 Drinking water ingestion
2 Freshwater fish ingestion
3 Above surface crops ingestion - irrigated cropland
4 Milk ingestion - cows grazing on irrigated pasture
5 Beef ingestion - cows grazing on irrigated pasture
6 Inhalation - material resuspended which was deposited
during irrigation
7 External dose due to ground contamination by material
originally deposited during irrigation
8 External dose due to air submersion in resuspended
material originally deposited during irrigation
9 Milk ingestion - cows drinking contaminated
surface water
10 Beef ingestion - cows drinking contaminated surface
water
-------
5-15
5.2.2 Collective (Population) Dose Equivalent Assessment
For the population dose equivalent assessment calculations, we concluded
that the pathways of concern are pathways 2, 3, 4, 5, 6, 7, 8, and 10 of
Table 5.3 (detailed discussion in Appendix J, subsection J2). The size of
? 2
the assessment areas for New Mexico is 19,037 km and 13,650 km for Wyoming.
We used the following considerations to calculate population dose equivalents
for the assessment area:
1. Ground surface concentrations of radionuclides are for 8.5
years, the assumed midpoint mine life. (The period of
mine operation is 17 years.) The organ annual collective
dose equivalent rates for the external surface exposure
pathway are based on the ground concentrations after the
8.5 year buildup time.
2. For inhaled or ingested radionuclides, the dose equivalents
are the annual collective dose equivalents that will be ac-
cumulated over the 70 years after intake for adults.
3. The population distributions around the sites are based
on estimates by county planners (John Zaboroc, 1979,
Converse Area Planning Office, Douglas, Wyoming, personal
communication) and agricultural personnel (Tony Romo, 1979,
Valencia County Agent, Los Lunas, New Mexico, personal
communication) for 1979. The populations, assumed to remain
constant in time, were estimated to be 16,230 and 64,950
persons in the Wyoming and New Mexico assessment areas,
respectively.
4. Average agricultural production data for the county which con-
tains a major portion of the assessment area are used.
5. The population in the assessment area eats food from the as-
sessment area. We assume that any imported food is free of
radionuclides.
As mentioned previously, Appendix J contains the details regarding the
models and values for parameters used in these analyses.
-------
5-16
5»3 Prominent Environmental Pathways and Parameters for Atmospheric Releases
We used the AIRDOS-EPA (Mo79) computer code to calculate radionuclide
air and ground concentrations, ingestion and inhalation intakes, and working
level exposures; and we used the DARTAB (Be80) computer code to calculate dose
and risk from the AIRDOS-EPA intermediate output using dose and risk factors
from the RADRISK (Du80) computer code. We calculated working levels associ-
ated with Rn-222 emissions assuming that Rn-222 decay products were 70 per-
cent in equilibrium with Rn-222, a value considered representative of indoor
exposure conditions (Ge78). Appendix K contains a detailed discussion of the
application of the AIRDOS-EPA and RADRISK computer codes.
Figure 5.1 shows the general airborne pathways evaluated for uranium
mines. We calculated doses due to air immersion, ground surface exposure,
inhalation, and ingestion of radionuclides, but we did not address the resus-
pension pathway, since the AIRDOS-EPA code did not provide a method for cal-
culating resuspended air concentrations or subsequent redeposition to the
ground surface. We used the modification to the AIRDOS-EPA computer code
made by Nelson (Ne80) to include the effect of environmental removal of
radioactivity from the soil. For ingestion, transfers associated with both
root uptake and foliar deposition on food and forage are considered.
5.3.1 Individual Committed Dose Equivalent Assessment
We assessed the maximum individual on the following basis:
1. The maximum individual for each source category is intended
to represent an average of the individuals living close to
each model uranium mine. The individual is assumed to be
located about 1600 meters from the center of the model site.
2. Ground surface concentrations of radionuclides used in the
assessment are those that would occur during the midpoint of
the active life of the model uranium mine. Buildup times
used in the assessment are 8.5 years for active surface and
underground mines, 5 years for the in situ leach mine, and
26.5 years for the inactive surface and underground mines.
The 26.5-year buildup time for the inactive mines is chosen
to represent the midpoint of the 53-year exposure time that
a resident living a lifetime in the region around the model
mine is estimated to experience. The organ dose equivalent
rates for the external surface exposure pathway are based on
-------
Airborne Radionuclides and Trace Metal Contaminants
Inhalation
Soil
Vegetation
Ingestion
Animals
Ul
I
Figure 5.1 Potential airborne pathways in the vicinity of uranium mines.
-------
5-18
the concentrations for the indicated buildup time.
3. For inhaled or ingested radionuclides, the dose equivalent
rates are actually the 70-year committed dose equivalent
rates for an adult receptor, i.e., the internal dose equiva-
lent that would be delivered up to 70 years after an intake.
The individual dose equivalent rates in the tables are in
units of mrem/yr.
4. The individual is assumed to home grow a portion of his or
her diet consistent with the rural setting for each model
uranium mine site. Appendix K contains the actual fractions
of home-produced food consumed by individuals for the model
mine sites. The portion of the individual's diet that was
not locally produced is assumed to be imported and uncontam-
inated by the assessment source.
5.3.2 Collective (Population) Dose Equivalent Assessment
The collective dose equivalent assessment to the population out to 80 km
from the facility under consideration is performed as follows:
1. The population distribution around the model mine sites is
based on the 1970 census. The population is assumed to re-
main constant in time.
2. Ground surface concentrations and organ dose equivalent rates
for the external surface exposure pathway (as for the individ-
ual case) are those that would occur over the active life of
the model mine.
3. Average agricultural production data for the state in which the
model uranium mine is located are assumed.
4. The population in the assessment area eats food from the assess-
ment area to the extent that the calculated production allows,
and any balance is assumed to be imported without contamination
by the assessment source.
5. Seventy-year committed dose equivalent factors for an adult
receptor (as for the individual case) are used for ingestion
and inhalation.
-------
5-19
5.4 Mine Wastes Used In the Construction of Habitable Structures
Using uranium mine wastes under or around habitable structures or
building habitable structures on land contaminated with uranium mine wastes
can result in increased radiation exposures to individuals occupying these
structures. The radium-226 present in these wastes elevates the concen-
trations of radon-222 and its decay products and produces increased gamma
radiation inside these structures. The health risk to individuals occupying
these structures is generally much greater from inhaling radon-222 decay
products than the risk received from gamma radiation.
Radon-222, formed from the decay of radium-226, is an inert gas that
diffuses through the soil and migrates readily through foundations, floors,
and walls and accumulates in the inside air of a structure. Breathing
radon-222 and its short-lived decay products (principally polonium-218,
bismuth-214, and polonium-214) exposes the lungs to radiation.
The radon-222 decay product concentration (working level) inside a
structure from radon-222 gas diffusing from underlying soil is extremely
variable and influenced by many complex factors. These would include the
radium-226 concentration of the soil, the fraction of radon-222 emanating
from the soil, the diffusion coefficient of radon-222 in soil, the rate of
influx of radon-222 into the structure, the ventilation rate of the
structure, and the amount of plate-out (adsorption) of radon-222 decay
products on inside surfaces.
The potential risks of fatal lung cancer that could occur to individuals
living in homes built on land contaminated by uranium mine wastes have been
estimated using measurements and calculational methodology relating radon-222
decay product concentrations inside homes to the radium-226 concentrations in
outside soil (He78, Wi78). These estimates are shown in Section 6.1.5.
-------
5-20
5.5 References
Be80 Begovich, C.L., Eckerman, K.F., Schlatter, E.G. and Ohr, S.Y., 1980,
"DARTAB: A Program to Combine Airborne Radionuclide Environmental Exposure
Data with Dosimetric and Health Effects Data to Generate Tabulations of
Predicted Impacts," Oak Ridge National Laboratory Rept., ORNL-5692 (Draft).
DOC78 U.S. Department of Commerce, Bureau of Census, 1978, "County and
City Data Book, 1977," (U.S. Government Printing Office, Washington,
D.C.).
Du80 Dunning, D.E. Jr., Leggett, R.W., and Yalcintas, M.G., 1980, "A Com-
bined Methodology for Estimating Dose Rates and Health Effects from
Exposure to Radioactive Pollutants," Oak Ridge National Laboratory
Rept., ORNL/TM-7105.
Ge78 George, A.C. and Breslin, A.J., 1978, "The Distribution of Ambient Radon
and Radon Daughters in Residential Buildings in the New Jersey-New York
Area," presented at the symposium on the Natural Radiation Environment III,
Houston, Texas, April 23-28.
He78 Healy, J.W. and Rodgers, J.C., 1978, "A Preliminary Study of Radium-
Concentrated Soil," Los Alamos Scientific Laboratory Report, LA-7391-
MS.
Mo79 Moore, R.E., Baes, C.F. Ill, McDowell-Boyer, L.M., Watson, A.P.,
Hoffman, F. 0., Pleasant, J.C. and Miller, C.W., 1979, "AIRDOS-EPA:
A Computerized Methodology for Estimating Environmental Concentrations
and Dose to Man from Airborne Releases of Radionuclides," U.S. Environ-
mental Protection Agency Report, EPA 520/1-79-009 (Reprint of ORNL-
5532).
Ne80 Nelson, C.B., 1980, "AIRDOS-EPA Program Modifications," internal
memorandum dated February 12, 1980, U.S. Environmental Protection
Agency, Office of Radiation Programs, Washington, D.C..
Wi78 Windham, S.T., Phillips, C.R., and Savage, E.D., 1978, "Florida
Phosphate Land Evaluation Criteria," U.S. Environmental Protection
Agency Draft Report, unpublished.
-------
SECTION 6
HEALTH AND ENVIRONMENTAL EFFECTS
-------
6 - 1
6.0 Health and Environmental Effects
6.1 Health Effects and Radiation Doslmetry
6.1.1 Radioactive Airborne Emissions
We used data on radioactive emissions (Section 3) to estimate the
public health impact of these emissions. Our assessments include estimates
of the following radiation exposures and health risks:
1. Dose equivalent rates and working level exposures to the
most exposed individuals (maximum individual) and to the
average exposed individuals in the regional population
(average individual)
2. Collective dose equivalent rates and working level exposures
to the regional population
3. Lifetime fatal cancer risks to the maximum and average indi-
viduals in the regional population
4. Genetic effect risk to the descendants of the maximum and
average individuals in the regional population
5. The number of fatal cancers committed in the regional popu-
lation per year of model mine operation
6. The number of genetic effects committed to the descendants of
the regional population per year of model mine operation
The somatic health impact risks estimated in this report are for fatal
cancers only. For whole body exposure, the risk of nonfatal cancer is
about the same or slightly less than for fatal cancer. Thus, for whole
body doses, it is conservatively estimated that one nonfatal cancer could
occur for each additional fatal cancer. The somatic health impact for the
regional population (additional cancers per year) is calculated at equi-
librium for continuous exposure and this is equal to the additional cancers
committed over all time per year of exposure; thus we used the term
committed additional cancers (see Appendix L).
The genetic effect risks estimated in this report are for effects in
descendants of an irradiated parent or parents. Genetic effects per year
in the regional population due to radionuclide releases from the mines are
calculated for an equilibrium exposure situation. The calculated genetic
effects per year at equilibrium is equal to the genetic effects committed
over all time from one year exposure. Thus, the calculated additional
-------
Table 6.1 Annual release rates (Ci) used in the dose equivalent and health
effects computations for active uranium mines
Classifi-
cation
Mining
activities
Ore
Sub-ore
Overburden/
waste rock
Vehicular
dust
Total
Location
Pit/mine site
Pile site
Pile site
Pile site
Mining area
All sources
Average Surface Mine^3'
U
4.3E-3
1.01E-2
4.2E-4
2.25E-3
9.9E-4
1.81E-2
Th
2.2E-4
1.42E-4
8.4E-6
1.50E-4
3.7E-4
8.90E-4
Rn-222
1.99E+2
4.2E+1
5.0E+1
4.0E+1
0
3.31E+2
Average Large Surface Mine ^a'
U
2.57E-2
4.42E-2
1.51E-3
1.34E-2
5.86E-3
9.07E-2
Th
1.44E-3
6.20E-4
3.00E-5
8.94E-4
2.17E-3
5.15E-3
Rn-222
7.97E+2
9.6E+1
1.66E+2
2.02E+2
0
1.26E+3
}?]Release rates taken from Tables 3.32 to 3.35.
lD;Release rates taken from Tables 3.51 and 3.54 to 3.56.
o>
I
ro
-------
Table 6.1 (cont.)
Average
U
2.22E-4
9.63E-4
1.04E-3
9.6E-6
6.5E-5
2.30E-3
Underground
Th
2.8E-6
1.35E-5
8.4E-6
6.4E-7
2.4E-5
4.93E-5
Mine W
Rn-222
3.08E+2
7.7
6.1E+1
5.0E-1
0
3.77E+2
Average
U
2.41E-3
1.07E-2
5.95E-3
5.10E-5
1.29E-4
1.92E-2
Large Underground Mine * '
Th Rn-222
3.10E-5 3.42E+3
1.50E-4 6.83E+1
4.8E-5 3.38E+2
3.40E-6 2.6
4.80E-5 0
2.80E-4 3.83E+3
In Situ
U
l.OE-1
j • i
N.A. (Q>
N.A.
N.A.
N.A.
l.OE-1
Leach Mine
Th
0
1 N.A.
N.A.
N.A.
N.A.
0
(c)
Rn-222
6.50E+2
N.A.
N.A.
N.A.
N.A.
6.50E+2
(c)
(d)
Release rates taken from Table 3.59.
N.A.- Not Applicable.
Note.—Columns labeled U and Th include each daughter of the decay chain in secular equilibrium.
cr>
u>
-------
6-4
Table 6.2 Annual release rates (Ci) used in the dose equivalent and health
effects computations for inactive uranium mines
Location
Pit/vents-
portals
Waste rock/
sub-ore pile
Surface Mine ^ Underground Mine ^D;
U Th Rn-222 U Th Rn-222
0 0 8.1 0 0 7.55
1.48E-3 1.1E-5 1.74E+1 2.38E-4 1.7E-6 1.7
'a'
^ '
Release rates taken from Tables 3.70 and 3.74.
Release rates taken from Tables 3.76 and 3.77,
Note.—Column headings U and Th include each daughter of the decay chain
in secular equilibrium.
-------
6-5
genetic effects are commltted effects to all future generations for one
year of exposure to the regional population.
We calculated individually each major source of radionuclide airborne
emissions for each model uranium mine site so that we could determine the
extent that each source contributed to the total health impact. Tables 6.1
and 6.2 contain the annual release rates for each source classification (or
location) that we used to calculate dose equivalent rates and health
effects for active and inactive uranium mines.
The estimated annual working level exposures from Rn-222 emissions by
the model uranium mines are listed in Table 6.3. The working level ex-
posures presented for the maximum individual are the Rn-222 decay product
levels to which an individual would be continuously exposed for an entire
year. Working level exposure to the regional population is the sum of the
exposures to all individuals in the exposed population from the annual
release from the model mine.
We estimated radiological impacts of radioactive airborne emissions
from the model uranium mines with the AIRDOS-EPA (Mo79), RADRISK (Du80),
and DARTAB (Be80) computer codes. Appendixes K and L contain explanations
of our use of these computer codes.
Where emissions for U-238 plus daughters and Th-232 plus daughters
were reported (Section 3), a source term for both the parent and important
daughters were input into the AIRDOS-EPA code. For example, a reported
emission rate of 0.01 Ci/yr of U-238 plus daughters (U in Tables 6.1 and
6.2) would be input into the AIRDOS-EPA code as 0.01 Ci/yr of U-238, 0.01
Ci/yr of U-234, 0.01 Ci/yr of Th-230, 0.01 Ci/yr of Ra-226, 0.01 Ci/yr of
Pb-214, 0.01 Ci/yr of Bi-214, 0.01 Ci/yr of Pb-210, and 0.01 Ci/yr of
Po-210. A reported emission rate of 0.01 Ci/yr of Th-232 plus daughters
(Th in Tables 6.1 and 6.2) would be input into the AIRDOS-EPA code as 0.01
Ci/yr of Th-232, 0.01 Ci/yr of Ra-228, 0.01 Ci/yr of Ac-228, 0.01 Ci/yr of
Th-228, 0.01 Ci/yr of Ra-224, 0.01 Ci/yr of Pb-212, 0.01 Ci/yr of Bi-212,
and 0.0036 Ci/yr of Tl-208. The Tl-208 source term is approximately one-
third that of Bi-212 because of the branching ratio.
The maximum individual, average individual, and population dose equiv-
-------
Table 6.3 Annual working level exposure from radon-222
emissions from model uranium mines
Source
Average Surface Mine
Average Large
Surface Mine
Average Underground
Mine
Average Large
Underground Mine
Inactive Surface
Mine
Inactive Underground
Mine
In Situ Leach Mine
Maximum
Individual
(WL)(a)
2.3E-4
8.4E-4
4.6E-4
4.7E-3
1.8E-5
1.1E-5
4.5E-4
Average
Individual
(WL)
4.5E-7
1.7E-6
2.1E-6
2.1E-5
3.5E-8
5.1E-8
8.9E-7
Regional
Population
(person-WL)
6.5E-3
2.5E-2
7.5E-2
7.6E-1
5.0E-4
1.8E-3
1.3E-2
Working level.
CT>
CTt
-------
6 - 7
Table 6.4 Annual radiation dose equivalents due to atmospheric radioactive
particulate and Rn-222 emissions from a model average surface
uranium mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
LLI(a) wall
Kidney
Bladder wall
ULI(b) wall
SI(c) wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
2.4
3.4E+1
1.2E+1
5.5E-1
1.6
9.7E-2
5.2E-1
4.6E-1
4.2
3.0E-1
2.1E-1
9.4E-2
5.1E-1
5.4E-1
6.4
5.1E-1
5.2E-1
5.4E-1
4.9
Average
Individual
(mrem/yr)
5.4E-3
7.5E-2
6.3E-3
2.0E-3
6.3E-3
8.9E-5
1.9E-3
1.6E-3
1.8E-2
9.7E-4
5.2E-4
1.2E-4
1.9E-3
1.9E-3
2.8E-2
1.9E-3
1.9E-3
1.9E-3
5.5E-3
Population
(person-rem/yr)
7.7E-2
1.1
9.0E-2
2.7E-2
9.1E-2
1.3E-3
2.7E-2
2.3E-2
2.5E-1
1.4E-2
7.4E-3
1.7E-3
2.7E-2
2.7E-2
4.0E-1
2.7E-2
2.7E-2
2.7E-2
7.8E-2
Lower large intestine wall.
( Upper large intestine wall.
c> Small intestine wall.
-------
6-8
Table 6.5 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model average
large surface uranium mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
LLI wall
Kidney
Bladder wall
ULI wall
SI wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
1.35E+1
1.9E+2
6.6E+1
3.0
8.9
5.4E-1
3.0
2.5
2.1E+1
1.7
1.1
5.2E-1
2.8
3.0
3.5E+1
2.8
2.9
3.0
2.7E+1
Average
Individual
(mrem/yr)
2.7E-2
3.8E-1
3.1E-2
9.6E-3
3.2E-2
4.5E-4
9.6E-3
8.2E-3
9.0E-2
4.9E-3
2.6E-3
6.0E-4
9.6E-3
9.6E-3
1.4E-1
9.6E-3
9.6E-3
9.6E-3
2.7E-2
Population
(person-rem/yr)
3.9E-1
5.4
4.5E-1
1.4E-1
4.6E-1
6.4E-3
1.4E-1
1.2E-1
1.3
7.0E-2
3.8E-2
8.6E-3
1.4E-1
1.4E-1
2.0
1.4E-1
1.4E-1
1.4E-1
3.8E-1
-------
6 - 9
Table 6.6 Annual radiation dose equivalents due to atmospheric radio-
active particulate and Rn-222 emissions from a model average
underground uranium mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
LLI wall
Kidney
Bladder wall
ULI wall
SI wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
5.1E-1
7.2
2.9
1.2E-1
3.5E-1
2.0E-2
1.1E-1
9.4E-2
9.1E-1
6.4E-2
4.3E-2
2.0E-2
1.1E-1
1.1E-1
1.4
1.1E-1
1.1E-1
1.1E-1
1.1
Average
Individual
(mrem/yr)
8.3E-4
1.2E-2
5.0E-3
2.3E-4
7.2E-4
2.8E-5
2.2E-4
1.8E-4
2.0E-3
1.2E-4
7.3E-5
2.8E-5
2.2E-4
2.3E-4
3.1E-3
2.2E-4
2.2E-4
2.3E-4
2.0E-3
Population
(person-rem/yr
2.9E-2
4.1E-1
1.8E-1
8.3E-3
2.7E-2
l.OE-3
8.0E-3
6.5E-3
7.4E-2
4.4E-3
2.7E-3
l.OE-3
8.0E-3
8.0E-3
1.1E-1
7.9E-3
8.0E-3
8.1E-3
7.1E-2
-------
6-10
Table 6.7 Annual radiation dose equivalents due to atmospheric radioactive
particulate and Rn-222 emissions from a model average large
underground uranium mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
III wall
Kidney
Bladder wall
ULI wall
SI wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
4.2
6.0E+1
2.5E+1
9.7E-1
2.9
1.7E-1
9.4E-1
7.8E-1
7.7
5.4E-1
3.6E-1
1.6E-1
9.2E-1
9.4E-1
1.2E+1
9.2E-1
9.4E-1
9.4E-1
9.8
Average
Individual
(mrem/yr)
6.9E-3
9.6E-2
4.7E-2
1.9E-3
6.0E-3
2.3E-4
1.8E-3
1.5E-3
1.7E-2
l.OE-3
6.0E-4
2.3E-4
1.8E-3
1.8E-3
2.6E-2
1.8E-3
1.8E-3
1.9E-3
1.8E-2
Population
(person-rem/yr
2.5E-1
3.5
1.7
6.9E-2
2.2E-1
8.5E-3
6.8E-2
5.5E-2
6.2E-1
3.6E-2
2.2E-2
8.4E-3
6.6E-2
6.8E-2
9.2E-1
6.6E-2
6.7E-2
6.8E-2
6.2E-1
-------
6-11
Table 6.8 Annual radiation dose equivalents due to atmospheric radioactive
particulate and Rn-222 emissions, from a model inactive surface
uranium mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
LLI wall
Kidney
Bladder wall
ULI wall
SI wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
2.1E-1
2.9
9.5E-1
5.6E-2
1.4E-1
1.5E-2
5.4E-2
4.4E-2
3.5E-1
3.3E-2
2.4E-2
1.4E-2
5.2E-2
5.5E-2
5.3E-1
5.2E-2
5.3E-2
5.5E-2
3.9E-1
Average
Individual
(mrem/yr)
4.8E-4
6.8E-3
5.0E-4
1.8E-4
5.5E-4
1.1E-5
1.8E-4
1.4E-4
1.5E-3
9.2E-5
4.7E-5
1.3E-5
1.8E-4
1.8E-4
2.3E-3
1.8E-4
1.8E-4
1.8E-4
4.7E-4
Population
( person- rem/yr
6.9E-3
9.8E-2
7.2E-3
2.6E-3
7.8E-3
1.6E-4
2.6E-3
2.0E-3
2.1E-2
1.3E-3
6.7E-4
1.8E-4
2.5E-3
2.6E-3
3.3E-2
2.5E-3
2.5E-3
2.6E-3
6.8E-3
-------
6 - 12
Table 6.9 Annual radiation dose equivalents due to atmospheric radioactive
particulate and Rn-222 emissions from a model inactive underground
uranium mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
LLI wall
Kidney
Bladder wall
ULI wall
SI wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
5.8E-2
8.0E-1
2.7E-1
1.6E-2
3.9E-2
4.0E-3
1.5E-2
1.2E-2
9.7E-2
9.1E-3
6.6E-3
3.7E-3
1.4E-2
1.5E-2
1.5E-1
1.4E-2
1.5E-2
1.5E-2
1.1E-1
Average
Individual
(mrem/yr)
9.3E-5
1.3E-3
3.4E-4
2.9E-5
7.9E-5
5.2E-6
2.8E-5
2.2E-5
2.1E-4
1.6E-5
l.OE-5
4.9E-6
2.7E-5
2.8E-5
3.2E-4
2.7E-5
2.8E-5
2.8E-5
1.5E-4
Population
(person-rem/yr
3.4E-3
4.6E-2
1.3E-2
l.OE-3
2.8E-3
1.8E-4
l.OE-3
8.0E-4
7.6E-3
5.8E-4
3.7E-4
1.8E-4
9.7E-4
l.OE-3
1.2E-2
9.8E-4
l.OE-3
l.OE-3
5.7E-3
-------
6-13
Table 6.10 Annual radiation dose equivalents due to atmospheric radioactive
particulate and Rn-222 emissions from a hypothetical in situ
uranium solution mine
Organ
Red marrow
Endosteal
Pulmonary
Muscle
Liver
Stomach wall
Pancreas
LLI wall
Kidney
Bladder wall
ULI wall
SI wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Weighted mean
Maximum
Individual
(mrem/yr)
1.6E-1
2.8
3.9E+1
8.4E-3
1.9E-2
1.6E-2
7.6E-3
6.1E-1
3.3E-1
4.8E-3
2.0E-1
3.6E-2
7.3E-3
8.9E-3
4.6E-2
7.4E-3
7.9E-3
8.4E-3
1.2E+1
Average
Individual
(mrem/yr)
2.7E-4
5.0E-3
2.0E-2
2.2E-5
5.4E-5
5.7E-5
2.1E-5
2.5E-3
l.OE-3
1.2E-5
8.1E-4
1.4E-4
2.1E-5
2.2E-5
1.8E-4
2.1E-5
2.1E-5
2.1E-5
6.2E-3
Population
(person-rem/yr
3.8E-3
7.1E-2
2.9E-1
3.1E-4
7.7E-4
8.1E-4
3.0E-4
3.5E-2
1.5E-2
1.6E-4
1.2E-2
2.0E-3
3.0E-4
3.1E-4
2.5E-3
3.0E-4
3.0E-4
3.1E-4
8.8E-2
-------
6 - 14
alent rates* due to atmospheric radioactive participate and Rn-222 emis-
sions from the model uranium mine sites are presented in Tables 6.4 through
6.10. The Rn-222 dose equivalent rate is only for the inhalation and air
immersion pathways and excludes Rn-222 daughters. The impact from Rn-222
daughters is addressed separately with a working level calculation. The
dose equivalent estimates are for the model sites described for use with
the AIRDOS-EPA code in Appendix K. Assumptions about food production and
consumption for the maximum individual were selected for a rural setting.
The maximum individual dose equivalent rate occurred about 1600 meters
downwind from the center of the model site. The term "population" refers
to the population living within a radius of 80 kilometers of the source.
Population dose equivalents are the sum of the exposures to all individuals
in the exposed population for the annual release from the model uranium
mine.
Dose equivalent rates in Tables 6.4 through 6.10 indicate that the red
marrow, endosteal cells, lung, kidneys, and spleen are generally the
highest exposed target organs. A dose equivalent rate is presented for the
"weighted mean" target organ, but this calculated result was not used in
the health effect calculations. We calculated "weighted mean" dose equiv-
alents by using organ dose equivalent weighting factors (see Appendix L)
and summing the results. The weighted mean dose equivalent rate was pre-
sented instead of the total body dose equivalent rate.
Individual lifetime fatal cancer risks and estimated additional fatal
cancers to the regional population due to atmospheric radioactive emissions
from the model uranium mine sites are presented in Tables 6.11 and 6.12.
The individual lifetime risks in Table 6.11 are those that would result
from one year of exposure (external and internal) and the working levels
estimated for those individuals. Except for the in situ leach mine, the
individual lifetime risks in Table 6.12 are those that would result from a
lifetime of exposure (71 years average life expectancy). The individual
lifetime risks in Table 6.12 for the in situ leach mine are based on an
exposure time of 18 years, which is the expected life, including restor-
ation, of this type of model uranium mine.
*The dose equivalent rates were not used to calculate risk and are only
presented for perspective purposes. Risks of health impact were calcu-
lated directly from external and internal radionuclide exposure data.
-------
6-15
Table 6.11 Individual lifetime fatal cancer risk for one year of exposure
and estimated additional fatal cancers to the regional popula-
tion due to annual radioactive airborne emissions from model
uranium mines
Source
Maximum
Exposed
Individual
Average
Exposed
Individual
Regional
Population
Average surface mine
Particulates and Rn-222 6.7E-7
Radon-222 daughters 5.5E-6
Total 6.2E-6
Average large surface mine
Particulates and Rn-222 3.7E-6
Radon-222 daughters 1.9E-5
Total 2.3E-5
Average underground mine
Particulates and Rn-222 1.6E-7
Radon-222 daughters 1.1E-5
Total 1.1E-5
Average large underground mine
Particulates and Rn-222 1.4E-6
Radon-222 daughters 1.1E-4
Total 1.1E-4
Inactive surface mine
Particulates and Rn-222 5.5E-8
Radon-222 daughters 4.2E-7
Total 4.7E-7
Inactive underground mine
Particulates and Rn-222 1.5E-8
Radon-222 daughters 2.71-7
Total 2.8E-7
In situ leaching facility
Particulates and Rn-222 1.6E-6
Radon-222 daughters 1.1E-5
Total 1.3E-5
7.5E-10
1.1E-8
1.2E-8
3.7E-9
4.1E-8
4.5E-8
2.8E-10
4.9E-8
4.9E-8
2.5E-9
5.0E-7
5.0E-7
6.4E-11
8.3E-10
8.9E-10
2.0E-11
1.2E-9
1.2E-9
8.7E-10
2.1E-8
2.2E-8
1.1E-5
1.6E-4
1.7E-4
5.4E-5
5.9E-4
6.4E-4
l.OE-5
1.7E-3
1.7E-3
9.0E-5
1.8E-2
1.8E-2
9.1E-7
1.2E-5
1.3E-5
7.4E-7
4.4E-5
4.5E-5
1.2E-5
3.0E-4
3.1E-4
-------
6-16
Table 6.12 Individual lifetime fatal cancer risk due to lifetime exposure
to radioactive airborne emissions from model uranium mines
Source
Maximum
Exposed
Individual
Average
Exposed , x
Individual {C}
Average surface mine^ '
Particulates and Rn-222
Radon-222 daughters
Total
Average large surface
Particulates and Rn-222
Radon-222 daughters
Total
Average underground rnine^3'
Particulates and Rn-222
Radon-222 daughters
Total
Average large underground mine
Particulates and Rn-222
Radon-222 daughters
Total
Inactive surface mine^ '
Particulates and Rn-222
Radon-222 daughters
Total
Inactive underground mine^ '
Particulates and Rn-222
Radon-222 daughters
Total
In situ leaching facility^ '
Particulates and Rn-222
Radon-222 daughters
Total
(a)
1.4E-5
1.2E-4
1.3E-4
6.6E-5
3.5E-4
4.2E-4
3.5E-6
2.0E-4
2.0E-4
2.5E-5
1.9E-3
1.9E-3
3.9E-6
3.0E-5
3.4E-5
1.1E-6
1.9E-5
2.0E-5
1.6E-5
2.0E-4
2.2E-4
1.6E-8
2.3E-7
2.5E-7
6.6E-8
7.4E-7
8.1E-7
5.8E-9
9.0E-7
9.1E-7
4.4E-8
8.6E-6
8.6E-6
4.5E-9
5.9E-8
6.3E-8
1.4E-9
8.5E-8
8.6E-8
8.7E-9
3.8E-7
3.9E-7
^'Considers exposure for 17 years to active mining and 54 years to
inactive mine effluents.
^ 'Considers exposure for 71 years to inactive mine effluents.
^'Considers the average individual in the regional population within an
80-km radius of the model mine.
(d)
Considers 10-year operation and 8-year restoration.
-------
6-17
Table 6.13 Genetic effect risk to descendants for one year of parental
exposure to atmospheric radioactive airborne emissions from
model uranium mines
Source
Descendants of Descendants of
Maximum Exposed Average Exposed
Individual Individual
(effects/ (effects/
birth) birth)
Descendants of
Regional
Population
(effects/yr)
Average surface mine
Average large surface mine
Average underground mine
Average large underground mine
Inactive surface mine
Inactive underground mine
In situ leach facility
6.3E-7
3.7E-6
1.4E-7
1.1E-6
6.0E-8
1.6E-8
8.0E-9
2.6E-9
1.3E-8
2.9E-10
2.4E-9
2.4E-10
3.4E-11
2.7E-11
1.6E-5
7.9E-5
4.4E-6
3.6E-5
1.4E-6
5.0E-7
1.6E-7
-------
6-18
Table 6.14 Genetic effect risk to descendants for a 30-year parental
exposure to atmospheric radioactive airborne emissions from
model uranium mines
Effects/birth
Source
Descendants of
Maximum Exposed
Individual
Descendants of
Average Exposed
Individual(c)
Average surface rnine^9'
Average large surface mine^3'
Average underground mine^ '
Average large underground mine^3'
Inactive surface mine^ '
Inactive underground mine^ '
In situ leach facility^
1.2E-5
6.4E-5
2.6E-6
2.0E-5
1.8E-6
5.0E-7
1.4E-7
4.6E-8
2.2E-7
5.4E-9
4.0E-8
7.2E-9
5.8E-10
4.8E-10
^Considers exposure to 17 years active mining and 13 years inactive
mine effluents.
(b)
Considers exposure for 30 years to inactive mine effluents.
f c)
v 'Considers the average individual in the regional population within an
80-km radius of the model mine.
(d)
Considers 10-year operation and 8-year restoration.
-------
6-19
Genetic effect risks due to atmospheric radioactive emissions from the
model uranium mine sites are presented in Tables 6.13 and 6.14. The risks
to descendants in Table 6.13 are those that would result from one year of
exposure to the parent or parents of first generation individuals. The de-
scendant risks in Table 6.14 are those that would result from 30 years ex-
posure to the first generation parent or parents, except for the in situ
leach mine where we used an 18-year exposure time. The 30-year time period
represents the mean years of life where gonadal doses are genetically
significant.
We estimated the health impact risks with the DARTAB code using ex-
posure data from the AIRDOS-EPA code. The dose equivalent and risk con-
version factors that we used with the DARTAB code are tabulated in Appendix
L. The somatic risk conversion factors are based on a lifetime (71 years
average lifetime) exposure time, and the genetic effect risk conversion
factors are based on a 30-year exposure time. When the exposure time for
calculated risks was only one year, we calculated the risk by multiplying
the risk calculated by DARTAB with the ratio of the one year exposure time
to the exposure times used to calculate the risk conversion factors (1/71
for somatic effects and 1/30 for genetic effects to descendants of maximum
and average exposed individuals).* Appendix L contains a discussion of the
health risk assessment methodology.
We developed several tables to present the calculated health impact
risk. The percentage contributions to the fatal cancer risks for indi-
vidual sources at each model uranium mine site are contained in Table 6.15
for the maximum individual and Table 6.16 for the average individual. The
fatal cancer risks by source term for one year of exposure which we used to
calculate percentage contributions are contained in Tables L.4 to L.6 in
Appendix L. Tables L.7 to L.9 contain genetic risks by source term at each
model uranium mine site. The percent of the fatal cancer risk due to
radon-222 daughter concentrations at model uranium mine sites is indicated
in Table 6.17. The percent of the fatal cancer risk for principal nuclides
and pathways due to radioactive particulate and Rn-222 emissions at each
model uranium mine site are contained in Table 6.18.
*A correction factor was not needed for DARTAB calculated genetic
effects committed per year to the regional population.
-------
Table 6.15 Percent of the fatal cancer risk for the maximum individual
due to the sources of radioactive emissions at model uranium
mines
Percent of fatal cancer risk * ' '
Mining
Mine type Activities
Average surface mine
Average large surface mine
Average underground mine
Average large underground mine
Inactive surface mine
Inactive underground mine
In situ leach facility
56 (95)
59 (93)
80 (slOO)
89 (=100)
28(cJ (100)
77(C) (100)
100 (87)
Ore
18 (66)
14 (41)
3 (79)
2 (76)
0
0
0
Sub-ore
14 (98)
12 (98)
17 (97)
9 (96)
0
0
0
Spoils
12 (89)
14 (86)
<1 (96)
<1 (96)
72 (84)
23 (77)
0
Vehicular
Dust
<1 (0)
1 (0)
<1 (0)
<1 (0)
0
0
0
Table L. 4, Appendtx L,
^ 'Values in parentheses are percent contribution of radon-222 daughters.
^Emissions from abandoned pit (surface mine) or vents and portals (underground mine).
I
rv>
o
-------
Table 6.16 Percent of the fatal cancer risk for the average individual
in the regional population due to the sources of radioactive
emissions at model uranium mines
Percent of fatal cancer risk^a> '
Mine type
Average surface mine
Average large surface mine
Average underground mine
Average large underground mine
Inactive surface mine
Inactive underground mine
In situ leach facility
Mining
Activities
58 (97)
60 (96)
81 (1100)
89 (S100)
29(c) (100)
80^ (100)
100 (96)
Ore
16 (78)
11 (64)
2 (93)
2 (91)
0
0
0
Sub-ore
14 (99)
12 (99)
16 (99)
9 (99)
0
0
0
Spoils
12 (93)
16 (92)
<1 (99)
<1 (99)
71 (90)
20 (92)
0
Vehicular
Dust
<1 (0)
1 (0)
<1 (0)
<1 (0)
0
0
0
(a)
(b)
(c)
See Table L.5, Appendix L.
Values in parentheses are percent contribution of radon-222 daughters.
*
Emissions from abandoned pit (surface mine) or vents and portals (underground mines).
en
ro
-------
6-22
Table 6.17 Percent of fatal cancer risks due to radon-222
daughter concentrations at model uranium mine
s i tes
Source Percent fatal cancer
Average surface mine 89
Average large surface mine 84
Average underground mine 99
Average large underground mine 99
Inactive surface mine 88
Inactive underground mine 95
In situ leach facility 87
^'Remainder due to radioactive particulate and Rn-222 emissions,
-------
Table 6.18 Percent of the fatal cancer risk for principal nuclides and pathways due to radioactive
— - •-•• -••• _ •
Percent of
fatal cancer risk
Internal Pathways
Mine Type
Average
Surface Mine
Average Large
Surface Mine
Average
Underground Mine
Average Large
Underground Mine
Inactive , .
Surface MineUJ
Inactive , ,
Underground Mine^ '
In situ
Leaching Facility
Receptor
Max. Individual
Av. Individual
or population
Max. Individual
Av. Individual
or Population
Max. Individual
Av. Individual
or Population
Max. Individual
Av. Individual
or Population
Max. Individual
Av. Individual
or Population
Max. Individual
Av. Individual
or Population
Max. Individual
Av. Individual
or Population
Principal Nucl ides
U-238(20.0), U-234(22.1), Th-230(31.7),
Ra-226(7.94), Po-210(7.33)
U-238(9.17), U-234(10.1), Th-230(22.7),
Ra-226(21.3), Pb-210(6.92), Po-210(22.4)
U-238(20.0), U-234(22.2), Th-230(31.8),
Ra-226(7.98)
U-238(9.19), U-234(10.1), Th-230(22.7),
Ra-226(21.4), Pb-210(6.94), Po-210(22.4)
U-238(17.9), U-234(19.8), Th-230(28.4),
Ra-226(7.14), Po-210(6.59), Rn-222(13.6)
U-238(12.0), U-234(13.2), Th-230(20.1),
Ra-226(7.24), Po-210(7.31), Rn-222(34.6)
U-238(17.5), U-234(19.3), Th-230(27.7),
Ra-226(6.97), Po-210(6.43), Rn-222(16.0)
U-238(11.2), U-234(12.4), Th-230(18.8),
Ra-226(6.76), Po-210(6.83), Rn-222(39.2)
U-238(19.5), U-234(21.6), Th-230(31.0),
Ra-226(9.4), 81-214(5.31), Po-210(7.17)
U-238(8.76), U-234(9.68), Th-230(21.7)
Ra-226(26.1), Pb-210(6.77) , Po-210(21.4)
U-238(19.6), U-234(21.6), Th-230(31.1),
Ra-226(9.45), Bi-214(5.33), Po-210(7.21)
U-238(17.0), U-234(18.8), Th-230(28.5),
Ra-226(12.7), Bi-214(4.81), Po-210(10.4)
U-238(45.2), U-234(50.0), U-235(2.21)
U-238(43.3), U-234(47.8), U-235(2.12)
Inges-
tion
15.8
60.1
15.9
60.5
14.0
16.9
13.6
15.7
16.8
62.2
16.9
26.3
0.46
3.50
Inhal-
ation
80.2
38.1
80.0
37.7
82.5
80.6
82.9
82.0
75.4
34.3
75.2
66.6
99.5
96.5
External
Air
Immersion
0.003
0.005
0.002
0.004
0.025
0.063
0.029
0.071
0.002
0.003
0.001
0.004
0.002
0.009
Pathways
Ground
Surface
4.02
1.81
4.05
1.83
3.52
2.43
3.39
2.25
7.85
3.48
7.88
7.09
0.039
0.038
(a)
Spoils source term only.
-------
6-24
The fatal cancer health risk at each of the model uranium mine sites
is dominated by the lung cancer risk from radon-222 daughter exposures (see
Table 6.17). Radioactive particulates and Rn-222 contributed to a little
over 10 percent of the total fatal cancer health risk at the model surface
mines and at the in situ leaching facility (see Table 6.11). Essentially
all the risks from the model underground mines are due to radon-222 daugh-
ter exposures. The fatal cancer health risks from the active model under-
ground mines are greater than the risks from the active model surface mines
because of the larger quantity of Rn-222 released. The risks are similar
at inactive surface and underground mines.
The largest fatal cancer risk is from the average large underground
mine (see Tables 6.11 and 6.12)—an estimated 1.9E-3 lifetime fatal cancer
risk to the maximum exposed individual for a lifetime exposure. The life-
time fatal cancer risk to the average individual in the regional population
is estimated to be 8.6E-6 for a lifetime exposure period. The number of
estimated additional fatal cancers in the regional population per year of
mine operation is estimated to be 1.8E-2.
For the active surface mines, about 60 percent of the radon daughter
impact is from the exposed pit surfaces (see Table L.4). For the active
underground mines, the predominate radon daughter impact is from mine vent
air. For the inactive surface mine, about 70 percent of the radon daughter
impact is from waste rock pile exhalation and about 30 percent was from the
pit interior surfaces. About 80 percent of the radon daughter impact for
the inactive underground mine was due to radon releases from the mine vents
and entrance. The release of radon from the pregnant leach surge tanks was
the predominate source of the radon daughter health impact risk for the
model in situ leach mine. Detailed percentages of the lifetime fatal
cancer risks by source term for each model uranium mine are contained in
Tables 6.15 and 6.16.
The health impact from particulate radionuclides and Rn-222 was pre-
dominately due to U-238 and daughter radionuclides (see Table 6.18). Thor-
ium-232 and daughters were only minor contributors to the particulate and
Rn-222 fatal cancer risk with Rn-222 only contributing significantly (14 to
40 percent) at active underground mines. The majority of the exposure to
individuals around the model uranium mines is received from the internal
pathways. Inhalation was the most important internal pathway except for
the average individual and regional population impact at surface mines
-------
6-25
where ingestion was the major pathway (see Table 6.18). For active surface
mines, about 52 percent of the particulate and Rn-222 impact to the maximum
individual was from the ore source term, and about 25 percent of the
health impact was from the mining activities source term (see Table L.4).
For active underground mines, between 28 and 46 percent of the particulate
and Rn-222 impact was from the ore source term and between 26 and 41 per-
cent of the particulate and Rn-222 impact was from the sub-ore source term.
The predominant source of the particulate and Rn-222 impact from the in-
active mines was particulate radionuclides in wind-suspended dust from the
waste rock pile. The release of particulate radionuclides from the uranium
recovery plant was the predominant source of the particulate health impact
risk for the model in situ leach mine.
For perspective, the calculated fatal cancer risks can be compared to
the estimated cancer risk from all causes. The American Cancer Society
estimates the risk of cancer death from all causes to be 0.15 (Ba79). The
maximum exposed individual around the model average large underground mine
is estimated to incur an additional lifetime fatal cancer risk of 0.0019
(1.3 percent) due to radioactive airborne emissions from the model mine.
There is a regional population of 36,004 persons for the model average
large underground mine site located in New Mexico. The cancer death rate
for the State of New Mexico for whites of both sexes was 154.5 deaths per
year for 1973 to 1976 per 100,000 people (NCI78). Applying this statistic
to the regional population, about 56 cancer deaths are estimated to occur
each year in the regional population from all causes. Applying the approxi-
mate fatal cancer risk coefficient of 0.15 to the regional population of
36,004 persons, about 5,400 people in the regional area would normally die
of cancer. About 0.018 additional cancer deaths (0.00033 percent) in the
regional population are estimated per year of operation from radioactive
airborne emissions at the model average large underground mine.
The risk of genetic effects from radiation exposure at model uranium
mine sites is very small compared to the normal occurrence of hereditary
disease. The national incidence of genetic effects is 60,000 per 10 births
(NAS72). The normal occurrence of hereditary disease for the descendants of
the regional population of 14,297 at the model average large surface mine
in Wyoming is 0.06 effects per birth and 12.1 effects per year, based on
202 live births per year in the regional population. (We present sta-
tistics for the site of the average large surface mine since the largest
-------
6-26
genetic risk for all the evaluated model uranium mines occurred at this
site [see Tables 6.13 and 6.14]). We estimated the genetic effect risk to
the descendants of the maximum exposed individual to be an additional
6.4E-5 effects/birth (0.1 percent increase) for a 30-year exposure period.
The genetic effect risk to the descendants of the average exposed indi-
vidual in the regional population is estimated to be an additional 2.2E-7
effects/birth (0.00036 percent increase) for a 30-year exposure period.
The number of additional genetic effects committed to the descendants of
the regional population per year of operation of the average large surface
mine is estimated to be 7.9E-5. The additional committed genetic effects
constitute a very small increase to the 12.1 effects that will normally
occur each year in the live births within the regional population.
6.1.2 Nonradioactive Airborne Emissions
To calculate atmospheric concentrations at the location of the maximum
individual, we used the data on nonradioactive air pollutant emissions from
Section 3. We compared these pollutant air concentrations with calculated
nonoccupational threshold limit values, natural background concentrations,
and average urban concentrations of selected airborne pollutants in the
United States.
The "natural" background atmospheric concentration has been defined
(Va71) as the concentration of pollutants in areas absent of activities by
man which cause significant pollution. Variations in background levels may
result from differences in mineral content of the soil, vegetation, wind
conditions, and the proximity to the ocean or metropolitan areas. Based on
an extensive literature survey and consideration of the abundance and dis-
tribution of the chemical elements in the ocean and earth's crust, a set of
"natural" background airborne concentrations has been developed for the
United States (Va71). Natural background airborne concentrations for
selected pollutants are listed in the second column of Table 6.19. Also
listed in the table are average concentrations of airborne pollutants in
urban areas. The latter are arithmetic mean concentrations obtained from
measurements taken over a period of several years (Va71).
6.1.2.1 Combustion Products
Airborne concentrations of combustion products released from diesel
and gasoline-powered equipment were estimated for the site of the maximum
-------
6-27
Table 6.19 Natural background concentrations and average urban
concentrations of selected airborne pollutants in
the United States
Natural Background 3 Average Urban
Pollutant Concentration, y g/m Concentration, y g/m
Gases
CO 100 7000
NO 40 141
NH* 10 80
SO^ 5 62
COC 594,000, , NR
Hydrocarbons NR^a; 500
Suspended particles
Total
As
Ba
Cd
Co
Cr
Cu
Hg
Fe
Pb
Mg
Mn
Mo
Ni
Se
Sr
Th
U
V
Zn
Zr
20 - 40
0.005
0.005
0.0001
0.0001
0.001
0.01
0.0005
0.2 - 0.5
0.001
0.1
0.01
0.0005
0.001
0.001
0.005
0.0005
0.0001
0.001
0.01
0.001
105
0.02 ( 1)
NR
0.002
0.0005
0.015
0.09
0.1
1.58
0.79
NR
0.1
0.005
0.034
NR
NR
NR
NR
0.05
0.67
NR
(a)NR - Not Reported.
Source: Va71; except for C02, Ba76.
-------
6-28
individual. The concentrations were computed using the annual release
rates given in Tables 3.30 and 3.52 with dispersion parameters applicable
for the model underground (New Mexico) and surface (Wyoming) mining areas
(Appendix K). The estimated combustion product concentrations are low
compared to the natural background and average urban concentrations (see
Table 6.20). A conservative threshold limit value (TLV) was computed, as
described in Section 6.1.2.3 for S02, CO, and N02. Of these pollutants,
only the nitrogen oxide concentrations at the average large surface mine
exceed the nonoccupational TLV. Considering these comparisons and the
conservative nature of the analyses, combustion products released from
heavy uranium mining equipment do not appear to pose a health hazard.
6.1.2.2 Nonradioactive Gases
Airborne concentrations of the three principal nonradioactive gases
released from the hypothetical in situ leach mining site were computed
using the source terms from Table 3.59 and the meteorological parameters
and dispersion model described in Appendix K. Table 6.21 shows the esti-
mated atmospheric concentrations at the location of a maximum individual;
occupational threshold limit values (TLV's); adjusted TLV's applicable to
nonoccupational exposures; and the percent the estimated concentrations are
of the adjusted TLV's. The occupational TLV's have been conservatively
adjusted. They were adjusted on the basis of a 168-hr week, instead of a
40-hour week and a safety factor of 100.
The results of this analysis indicate that two of the estimated con-
centrations fall below their respective TLV's, and the concentration of
ammonium chloride is approximately equal to its TLV. Considering the
conservative nature of the adjusted nonoccupational TLV on which the com-
parisons were made, none of the nonradioactive gases appear to be at con-
centrations that might pose a serious health hazard. The ammonia level is
about 80 percent of the estimated "natural" background concentration and
only about 10 percent of the average urban concentration (Table 6.19).
6.1.2.3 Trace Metals and Particulates in the Form of Dust
We identified seventeen trace metals and particulates in the form of
dust as potential airborne emissions from uranium mines. Table 6.22 pre-
sents projected airborne concentrations of the metals and particulates at
the site of the maximum individual for six mine classifications. As might
-------
Table 6.20 Combustion product concentrations at the site of the maximum individual
3
with comparisons, yg/m
Pollutant
Particulates
of combustion
sox
CO
NOX
Hydrocarbons
Average
underground
mine
1.4E-3
1.2E-2
9.7E-2
1.6E-1
1.6E-2
Average large
underground
mine
1.6E-2
1.3E-1
1.1E+0
1.8E+0
1.8E-1
Average
surface
mine
9.7E-2
5.5E-1
4.3E+0
7.1E+0
7.1E-1
Average large
surface
mine
4.5E-1
2.2E+0
1.8E+1
3.0E+1
3.1E+0
Natural
background
concentration^8'
NR(C)
5E+0
l.OE+2
4.0E+1
NR
Average
urban
concentration^3'
NR
6.2E-H
7.0E+3
1.4E+2
5.0E+2
Non-
occupational
NR
3.1E-H
1.3E+2
2.1E+1
NR
(a}See Table 6.19.
(^Nonoccupational TLV = TLV (mg/m3) x 40 hr/168 hr x 10"2 x 103 yg/mg (ACGIH76),
i \
(c)
NR - Not reported.
CT>
I
ro
\o
-------
6-30
Table 6.21 A comparison of the airborne concentrations of nonradioactive
gases at the hypothetical in situ leach site with threshold
limit values
Contaminant
NH3
NH4C1
co2
Atmospheric
Concentration^ '
( v g/m3)
8.1
24
60
TLV^
(mg/m )
18
10
9000
Non-
(c)
occupational v '
TLV (yg/m3)
43
24
21,400
Percent of
Nonoccupational
TLV
19
100
0.3
(a)
(b)
Location of maximum individual.
Source: ACGIH76.
^Nonoccupational TLV = TLV (mg/m3) x 40 hr/168 hr x 10"2 x 103 ug/mg.
-------
6-31
be expected, large surface mine emissions usually have the greatest concen-
trations, and those from inactive underground mines the least. Projected
metal concentrations range from a low of about 5 x 10"7 ygm/m3 of cobalt
frum inactive underground mines to a high of about 1 ygm/m3 of potassium
from large surface mines.
Table 6.23 shows where particulates (dust) or trace metal air concen-
trations are estimated to exceed natural background or average urban air
concentrations (Table 6.19). Several trace metal air concentrations exceed
"natural" background; however, only the estimated air concentration of par-
ticulates (dust) exceeds the air concentration of airborne pollutants in
urban areas.
We evaluated the significance of these concentrations by comparing
them with threshold limit values (TLV's) for workroom environments pub-
lished by the American Conference of Governmental Industrial Hygienists
(ACGIH76). These TLV's, which are for occupational workers and a 40-hour
workweek, were adjusted by multiplying by 40/168 to convert them to con-
tinuous exposure values and dividing by 100 to make them applicable to the
general public. Table 6.24 is a tabulation of the adjusted TLV's, the pro-
jected concentrations of metals and particulates (from Table 6.22), and the
ratio of these concentrations to the adjusted TLV's. The sums of these
ratios provide a measure of whether a mixture of the metals would be a
significant problem, a sum greater than one indicating that the "composite"
TLV has been exceeded.
Table 6.24 shows that in no case does a single metal exceed its TLV,
nor do any of the mixtures exceed a "composite" TLV. Although TLV's were
not available for potassium and strontium, their low toxicity and low con-
centrations make it unlikely that their addition to the sums would change
this conclusion. For the worst case, large surface mines, the sum of
ratios is only about 17 percent of the limit.
Particulates, on the other hand, present a different picture. The TLV
for nonspecific particulates, nuisance dust, was chosen for comparison. It
t
can be seen that the TLV is exceeded by a factor of six at the large model
surface mine and nearly exceeded at the average model surface mine. About
50% of the exposure to dust is from vehicular traffic, and about 30% re-
sults from mining activities within the pit.
In summary, specific trace metal airborne emissions from uranium mines
do not appear to present a significant hazard, either singly or as com-
-------
Table 6.22 Stable trace metal airborne concentrations at the site of the maximum
individual,
Trace Avg. under-
metal ground mine
As
Ba
Co
Cu
Cr
Fe
Hg
K
Mg
Mn
Mo
Ni
Pb
Se
Sr
V
In
Part*
3.1E-5
5.1E-4
4.0E-5
3.3E-5
5.0E-5
9.7E-3
7.2E-6
1.3E-2
9.4E-4
7.1E-4
3.3E-5
4.9E-6
4.1E-5
* 3.1E-5
1.7E-4
4.7E-4
2.6E-5
•b) 1.2
Avg. large
underground mine
1.9E-4
1.8E-3
3.1E-5
1.5E-4
1.4E-4
4.1E-2
1.5E-5
6.3E-2
6.9E-3
2.8E-3
2.3E-4
3.9E-5
2.0E-4
2.2E-4
5.5E-4
3.0E-3
9.6E-5
3.9
Avg. surface
mine
2.6E-4
7.0E-3
1.1E-5
4.4E-4
1.1E-3
1.4E-1
1.8E-4
1.7E-1
2.5E-3
1.1E-2
1.4E-4
1.4E-5
5.4E-4
1.2E-4
3.4E-3
2.2E-3
4.6E-4
2.3E+1
Avg. large Inactive under-
surface mine ground mine
1.5E-3
4.2E-2
4.7E-5
2.5E-3
6.9E-3
8.5E-1
1.1E-3
1.0
l.OE-2
6.8E-2
6.7E-4
5.8E-5
3.2E-3
5.9E-4
2.1E-2
1.8E-2
2.8E-3
1.4E+2
3.1E-6
3.6E-5
4.5E-7
2.2E-6
8.9E-7
6.3E-4
NA(a)
9.8E-4
1.3E-4
3.7E-5
4.5E-6
8.9E-7
3.1E-6
4.5E-6
4.9E-6
5.4E-5
1.3E-6
3.9E-2
Inactive surface
mine
1.5E-5
1.6E-4
2.9E-6
1.1E-5
3.6E-5
2.7E-3
NA
4.4E-3
6.2E-4
1.7E-4
2.0E-5
3.6E-6
1.4E-5
1.9E-5
2.3E-5
2.5E-4
5.2E-6
1.7E-1
(b)
- Not available.
Part. - Particulates (dust).
u>
ro
-------
6-33
Table 6.23 Comparison of stable trace metal airborne concentrations at the
location of the maximum individual with natural background con-
centrations and average urban concentrations of these airborne
pollutants
Exceed Natural Background
(a)
Exceed Average Urban Concentration'
Average Large Surface Mine
Ba, Cr (possible), Fe, Hg (possible),
Mn, Mo, Pb, Sr, V,
particulates
Average Surface Mine
Ba, Cr (possible), Mn, V
Average Large Underground Mine
V
Particulates
None
None
Average Underground Mine
None
None
(a)
See Tables 6.19 and 6.22.
-------
Table 6.24 Comparison of trace metal airborne concentrations at the site of the maximum individual with threshold limit values
(TLV's) in the workroom environment adjusted for continuous exposure to the general public, pg/m
Trace Adjusted^'
metal TLV
As 1.2
Ba 1.2
Co 0.24
Cu 0.48
Cr 1.2
Fe 12
Hg 0.12
K NA
Mg 24
Mn 12
Mo 12
Ni 0.24
Pb 0.36
Se 0.48
Sr NA
V 1.2
Zn 12
Total of ratios
Particulates:
Oust 24(c)
(a)Adjusted
^ Average Average Large
Underground Mine Underground mine
Cone. Cone. /TLV
3.1E-5 3E-5
5.1E-4 4E-4
4.0E-6 2E-5
3.3E-5 7E-5
5E-5 4E-5
9.7E-3 8E-4
7.2E-6 6E-5
1.3E-2 —
9.4E-4 4E-5
7.1E-4 6E-5
3.3E-5 3E-6
4.9E-6 2E-5
4.1E-5 1E-4
3.1E-5 6E-5
1.7E-4
4.7E-4 4E-4
2.6E-5 2E-6
2E-3
1.2E+0 5E-2
TLV = Occupational
Cone. Cone. /TLV
1.9E-4
1.8E-3
3.1E-5
1.5E-4
1.4E-4
4.1E-2
1.5E-5
6.3E-2
6.9E-3
2.8E-3
2.3E-4
3.9E-5
2.0E-4
2.2E-4
5.5E-4
3.0E-3
9.6E-5
3.9E+0
TLV (mg/m3)
2E-4
2E-3
1E-4
3E-4
1E-4
3E-3
1E-4
3E-4
2E-4
2E-5
2E-4
6E-4
5E-4
--
2E-3
8E-6
1E-2
2E-1
Average
Surface Mine
Average Large
Surface mine
Cone. Cone. /TLV Cone. Cone. /TLV
2.6E-4
7.0E-3
1.1E-5
4.4E-4
1.1E-3
1.4E-1
1.8E-4
1.7E-1
2.5E-3
1.1E-2
1.4E-4
1.4E-5
5.4E-4
1.2E-4
3.4E-3
2.2E-3
4.6E-4
2.3E+1
2E-4
6E-3
5E-5
9E-4
9E-4
1E-2
2E-3
1E-4
9E-4
1E-5
6E-5
2E-3
2E-4
--
2E-3
4E-5
3E-2
1E+0
3
x 40 hr/168hr x 10 yg/m(
1.5E-3
4.2E-2
4.7E-5
2.6E-3
6.9E-3
8.5E-1
1.1E-3
l.OE+0
l.OE-2
6.8E-2
6.7E-4
5.8E-5
3.2E-3
5.9E-4
2.1E-2
1.8E-2
2.8E-3
1.4E+2
J x 1/100.
1E-3
4E-2
2E-4
5E-3
6E-3
7E-2
9E-3
4E-4
6E-3
6E-5
2E-4
9E-3
1E-3
--
2E-2
2E-4
1.7E-1
6E+0
Inactive
Underground mine
Cone. Cone. /TLV
3.1E-6
3.6E-5
4.5E-7
2.2E-6
8.9E-7
6.3E-4
NA
9.8E-4
1.3E-4
3.7E-5
4.5E-6
8.9E-7
3.1E-6
4.5E-6
4.9E-6
5.4E-5
1.3E-6
3.9E-2
3E-6
3E-5
2E-6
5E-6
7E-7
5E-5
___ _
5E-6
3E-6
4E-7
4E-6
9E-6
9E-6
--
4E-5
1E-7
2E-4
2E-3
Inactive
Surface mine
Cone.
1.5E-5
1.6E-4
2.9E-6
1.1E-5
3.6E-6
2.7E-3
NA
4.4E-3
6.2E-4
1.7E-4
2.0E-5
3.6E-6
1.4E-5
1.9E-5
2.3E-5
2.5E-4
5.2E-6
1.7E-1
Cone. /TLV
1E-5
1E-4
IE- 5
2E-5
3E-6
2E-4
__
3E-5
IE- 5
2E-6
2E-5
4E-5
4E-5
--
2E-4
4E-7
7E-4
7E-3
WNA - Not available.
^'Limit for nuisance dust - total mass.
Source: Workroom TLV's from ACGIH76.
-------
6-35
posite mixtures, when evaluated against adjusted threshold limit values.
However, particulate emissions, at least for surface mines, require further
evaluation. If model predictions can be verified by measurement, control
measures are indicated.
6.1.3 Radioactive Aquatic Emissions
We used the data on radioactive releases from mine dewatering (Sec-
tions 3.3.3 and 3.4.3) to estimate the public health impact of mining
operations at a typical active underground mining site (New Mexico) and a
typical active surface mining site (Wyoming). The health risks estimated
in this section are of fatal cancers and genetic effects to succeeding
generations. Dose equivalents and health risks per year of active mine
operation are estimated for the maximum and average individuals and for the
population of each assessment area. These calculated dose equivalents and
health risk estimates are believed to be higher than the actual dose equiv-
alents and health risks because of the conservative ass .ptions required to
predict movement of radionuclides in surface waters (see Section J.2 of
Appendix J). Very few data are available on aquatic releases from inactive
mines; hence, the significance of these releases, particularly for Colorado
and Utah where inactive mines are numerous, could not be determined.
The individual and population dose equivalents presented in this sec-
tion are computed using the models and parameters discussed in Appendix J.
The health risk estimates are generated by the following procedures:
a. For inhalation or ingestion of radionuclides, the quantity
of radionuclides taken into the body is determined as part
of the dose equivalent calculations. This quantity is mul-
tiplied by a health risk per unit intake conversion factor.
b. For external irradiation from ground deposited radionuclides
or from air submersion, the dose equivalents are calculated
and multiplied by a health risk per unit dose equivalent con-
version factor.
The health risk per unit intake and health risk per unit external dose
equivalent conversion factors for aquatic releases are listed in Tables
J.13 and J.14, Appendix J. This appendix also discusses the health risk
assessment methodology used to obtain the risks presented in this section.
Uranium and Ra-226 releases are given for both active mining sites. It is
assumed that the stated uranium releases are entirely U-238 and that U-234
is in equilibrium with the U-238 but that Th-230 precipitates out of the
mine water.
-------
6-36
Table 6.25 Annual radiation dose equivalent rates due to aquatic releases
from the New Mexico model underground mine
Organ
Endosteal
Red Marrow
Lung
Liver
Stomach Wall
LLI Wall^a)
Thyroid
Kidney
Muscle
Ovaries
Testes
Weighted Mean
Maximum Individual
Dose Rate (mrem/y)
5.6E+1
2.0
1.3
5.5E-1
1.9E-1
9.4E-1
4.5E-1
2.8E+1
4.9E-1
4.1E-1
4.7E-1
2.2
Average Individual
Dose Rate (mrem/y)
5.0
1.6E-1
2.1E-3
2.9E-2
3.8E-3
6.6E-2
2.5E-2
2.4
2.5E-2
2.4E-2
2.4E-2
1.5E-1
Population Dose
Rate (person-rem/y
3.2E+2
1.1E-H
1.4E-1
1.9
2.5E-1
4.3
1.6
1.6E+2
1.6
7.8E-1
7.8E-1
9.9
^a'Lower large intestine wall
-------
6-37
Table 6.26 Annual radiation dose equivalent rates due to aquatic releases
from the Wyoming model surface mine
Organ
Endosteal
Red Marrow
Lung
Liver
Stomach Wall
LLI Wall(a)
Thyroid
Kidney
Muscl e
Ovaries
Testes
Weighted Mean
Maximum Individual
Dose Rate (mrem/y)
6.8E-1
3.8E-2
2.3E-2
3.0E-2
l.OE-2
2.9E-2
1.8E-2
4.0E-1
1.9E-2
1.5E-2
1.8E-2
4.0E-2
Average Individual
Dose Rate (mrem/y)
2.1E-1
7.4E-3
l.OE-4
2.8E-3
2.8E-4
7.7E-3
1.4E-3
1.1E-1
1.5E-3
1.5E-3
1.4E-3
7.1E-3
Population Dose
Rate (person-rem/y
3.4
1.2E-1
1.7E-3
4.5E-2
4.6E-3
1.3E-1
2.3E-2
1.8
2.4E-2
1.2E-2
1.2E-2
1.2E-1
Lower large intestine wall
-------
Table 6.27 Individual lifetime fatal cancer risk and committed fatal cancers to the population
residing within the assessment areas
Source
Maximum exposed individual
lifetime fatal cancer risk
for operation of the mine
1 yr.
17 yrs.
Average exposed individual
lifetime fatal cancer risk
for operation of the mine
1yr. 17 yrs.
Committed fatal cancers
for the assessment area
population for operation
of the mine
1 yr. 17 yrs.
Underground
mine site
(New Mexico)
Surface mine
Site (Wyoming)
3.3E-7
7.1E-9
5.6E-6
1.2E-7
2.0E-8
9.6E-10
3.4E-7
1.6E-8
1.3E-3
1.6E-5
2.2E-2
2.7E-4
The average individual risk is the cumulative population risk divided by the population
residing within the assessment area.
CO
00
-------
6 - 39
Also, it is assumed that Rn-222, Pb-214, Bi-214, Pb-210, and Po-210 are in
equilibrium with the Ra-226. For example, a reported release rate of 0.01
Ci/yr of U-238 would be reflected in the analyses as 0.01 Ci/yr of U-238
and 0.01 Ci/yr of U-234. In like manner, a release of 0.001 Ci/yr of
Ra-226 would be reflected in the analyses as 0.001 Ci/yr Ra-226, 0.001
Ci/yr Rn-222, 0.001 Ci/yr Pb-214, 0.001 Ci/yr Bi-214, 0.001 Ci/yr Pb-210,
and 0.001 Ci/yr Po-210.
The maximum individual, average individual, and population annual dose
equivalent rates due to release of mine water containing radionuclides are
given in Tables 6.25 and 6.26 for the two active uranium mine sites. The
population dose equivalent rates are the sum of the dose equivalent rates
to all individuals residing within the assessment areas due to the annual
release from the model uranium mine. Average individual dose equivalent
rates are computed by dividing the population dose equivalent rates by the
number of persons in the assessment area.
The dose equivalent rates in Tables 6.25 and 6.26 indicate that the
endosteal cells and kidney are the highest exposed target organs. Inges-
tion is the predominant exposure mode for both the endosteal cells and the
kidney.
Individual lifetime fatal cancer risks and committed fatal cancers to
the population within the assessment area for radionuclide releases due to
mine dewatering are presented in Table 6.27. The maximum and average indi-
vidual lifetime risks (columns 2 and 3, respectively) and the committed
fatal cancers to the population within the assessment area (column 4) are
shown for both one year of release of radionuclides due to mine dewatering
and, in parenthesis, for the cumulative release over the 17 years of mine
operation. To compute the 17-year risks, the one-year risks are multiplied
by 17, which assumes equal annual radionuclide discharges. At both the
model underground (New Mexico) and surface (Wyoming) mines, the majority of
the risk is from releases of U-238, U-234, and Po-210.
A perspective on the additional fatal cancers estimated for the popu-
lation (Table 6.27) can be gained by realizing that the probability of an
individual dying of cancer of all types is 0.15 (Ba79). Taking the New
Mexico assessment area (64,950 persons) as an example, the expected number
of deaths from all forms of cancer for this population is 9,743 persons.
For the 17 years of mine operations, the estimated increase in the number
of deaths from cancer in the assessment area population is 0.022 deaths
-------
6-40
(Table 6.27). This represents a 0.00023 percent increase in the expected
fatal cancer occurrences in the assessment area population as a result of
operation of the underground mine in New Mexico over its 17-year active
life. For the Wyoming assessment area (16,230 persons), the estimated
increase in the expected fatal cancer deaths due to operation of the sur-
face mine for 17 years is 0.000011 percent.
Table 6.28 presents the genetic risks to succeeding generations, for
exposure to both individuals and the population within the assessment area,
caused by mine dewatering radionuclide releases. The genetic risks to
succeeding generations of maximum and average exposed individuals (columns
2 and 3, respectively) and the committed genetic effects to the descendants
of the present population within the assessment area (column 4) are shown
for one year of releases. The mechanics and assumptions used to estimate
the genetic effects are similar to those used to estimate fatal cancer
risks (see Appendix J). For both the model underground (New Mexico) and
surface (Wyoming) mines the majority of the risk is from releases of U-238,
U-234, and Po-210.
The risks of additional genetic effects due to the discharge of con-
taminated mine water from model uranium mine sites are very small when com-
pared to the normal occurrence of hereditary diseases. As given in Section
6.1.1, the natural incidence of genetic effects is 60,000 per million
births (NAS72), or 0.06 effects per birth. This natural incidence rate is
equivalent to 848 effects per year per million persons, considering a birth
rate of 0.01413 births per person-year. Taking the New Mexico site as an
example, the normal incidence of genetic effects for the assessment area
population (64,950 persons) during the 17 years of operation of the mine
would be 936 genetic effects. The increase in genetic effects committed to
the assessment area population during the 17 years of operation is 0.015
genetic effects committed. Thus, the genetic effects committed due to
aquatic wastes released during the operation of the New Mexico underground
mine are only 0.0016% of the genetic effects which occur due to other
causes during the mine operating life. For the Wyoming site (16,230 per-
sons), the genetic effects committed due to aquatic wastes released during
the operation of the model surface mine are only 0.0001% of the genetic
effects which occur due to other causes during the mine operating life. It
-------
Table 6.28 Genetic risks to succeeding generations of an individual and committed genetic effects
to descendants of the present population residing within the assessment area
Source
Genetic effects committed to succeeding
generations of an individual for operation
of the mine for 1 year
(a)
Maximum Individual
Average Individual
Genetic effects committed to the
descendants of the present population
for operation of the mine for 1 year
Underground mine
site (New Mexico)
4.5E-7
3.3E-8
9.0E-4
Surface mine
site (Wyoming)
1.4E-8
2.0E-9
1.4E-5
^a'Genetic effects assume 1 birth per person.
en
i
-------
6 - 42
should be noted that genetic effect risks to descendants of individuals
cannot be added to somatic effect risks for these individuals.
6.1.4 Nonradioactive Aquatic Emissions
Data on nonradiological emissions from uranium mines via the water
pathway are limited. Table 6.29 presents available estimates of concen-
trations of four trace metals plus sulfate and suspended solids in dis-
charge streams from the model surface mine located in Wyoming and seven
trace metals plus sulfate and suspended solids from the model underground
mine located in New Mexico. These concentrations are calculated after
dilution in the first order tributaries (Appendix J) and represent average
concentrations for the assessment areas. The concentrations presented in
Table 6.29 are conservative since, with the exception of sulfates, loss of
contaminants due to precipitation, adsorption, and infiltration to shallow
aquifers are not considered. The concentrations are calculated by diluting
discharges from a mine into the first order surface streams with no losses.
For sulfate, a more realistic approach is taken since only 20 percent of it
is assumed to remain in solution in the surface stream, as discussed in
Section 3.3.3.1.4.
Also presented in Table 6.29 are recommended agricultural water con-
centration limits for livestock and irrigation for several of these ele-
ments (EPA73). Drinking water limits are not presented because public
water supplies are normally derived from groundwater rather than surface
water, so drinking water would not be a pathway of concern for the average
individual in the assessment area. Though drinking water would be a po-
tentially significant pathway for the maximum individual, the data avail-
able for this analysis did not allow a reliable prediction of groundwater
concentrations due to mine dewatering (Appendix J). For this reason, the
impact of nonradioactive waterborne emission on the maximum exposed indi-
vidual could not be evaluated. The ratios of the average water concen-
trations to these limits are also listed in Table 6.29 and show that only
molybdenum from the underground mine approaches its limit (irrigation).
Also, the sums of the ratios being less than one indicate that mixtures of
the metals would not exceed a "composite limit" for an average individual
in the assessment area.
-------
Table 6.29 Comparison of nonradiological waterborne emissions from uranium mines with
recommended agricultural water quality limits
Parameter
Arsenic
Barium
Cadmium
Molybdenum
Selenium
Zinc
Uranium
Sul fate
Recommended
Livestock
0.2
NA(a)
0.05
NA
0.05
25
NA
NA
Total suspended solids NA
Totals
(a*NA - Not
(b)Excluding
available.
molybdenum.
Limits, mg/j.
Irrigation
0.1
NA
0.01
0.01
0.02
2.0
NA
NA
NA
Model Surface Mine
Avg. Water Ratio Ratio, Avg./ Avg. Water
Cone., mg/j. Avg. /Livestock Irrigation Conc.,mg/
Limit Limit
1.4E-4 0.0007 0.0014 3.1E-4
2.0E-2
1.1E-4 0.0022 0.011 1.6E-4
7.0E-3
1.6E-3
4.8E-4 0.00002 0.00024 1.1E-3
2.0E-3 3.5E-2
4.9 2.9
5.8E-1 6.8E-1
0.0029 0.013
Model Underground
Ratio
£ Avg. /Livestock
Limit
0.0016
0.0032
0.032
0.00004
0.037
Mine
Ratio, Avg./
Irrigation
Limit
0.0031
0.016
0.70
0.08
0.00055
0.80
01
CO
-------
6-44
Because of the limited number of data available, it is difficult to
evaluate the significance of these discharges. Although molybdenum could
be a problem, it is not possible to quantify the risk from molybdenum to
the maximum individual without having estimates of drinking water con-
centrations. Uranium, the metal estimated to be in highest concentration
(Table 6.29), has no established limits based on chemical toxicity in the
United States. In Canada, the maximum acceptable concentration for uranium
in drinking water based on chemical toxicity has been set at 0.02 mg/£
(0.04 mg/day), considering a continuous lifetime intake rate of 2 liters of
water per day (HWC78). It is reasonable to assume that limits for uranium
in water used for irrigation and to water livestock would exceed the
drinking water limit. Hence, based on the estimated uranium concentrations
at surface (0.002 mg/£ ) and underground (0.035 mg/£ ) uranium mines, the
water would probably be acceptable for irrigation and livestock watering.
The other constituents, such as solids and sulfates, for which limits are
not available, have minimal or no toxic properties.
It is premature to conclude the health hazard caused by non-
radiological waterborne emissions from uranium mines. Before definitive
conclusions can be reached, additional information is needed. Of par-
ticular interest would be data on water use patterns in the vicinity of the
mines and the degree to which the mine discharges may infiltrate ground-
water supplies.
6.1.5 Solid Hastes
6.1.5.1 Radium-226 Content
Solid wastes, consisting of sub-ore, waste rock, and overburden, at
active and inactive uranium mines contain elevated concentrations of
radium-226.* The sub-ore may contain as much as 100 pCi/g of radium-226.
Even though the overburden and waste rock contain lower concentrations than
the sub-ore, most of these wastes contain concentrations of radium-226 in
quantities greater than 5 pCi/g (see Sections 3.3.1, 3.4.1, 3.7.1, and
3.7.2).
* The radium-226 concentration in natural soil and rock is about 1 pCi/g.
-------
6-45
Uranium mine wastes containing radium-226 in quantities greater than 5
pCi/g have been designated as "hazardous wastes" in a recently proposed EPA
regulation (43FR58946, December 18, 1978) under the Resource Conservation
and Recovery Act (RCRA). This is primarily due to the fact that the use of
these wastes under or around habitable structures could significantly
increase the chance of lung cancer to individuals occupying these struc-
tures.
6.1.5.2 Estimates of Potential Risk
We have estimated the risk of fatal lung cancer that could occur to
individuals living in houses built on land contaminated by uranium mine
wastes (Table 6.30). Risks were estimated for homes built on land con-
taining radium-226 soil concentrations ranging from 5 to 30 pCi/g. The
relationship between the indoor radon-222 decay product concentration and
the radium-226 concentration in soil under a structure is extremely vari-
able and depends upon many complex factors. Therefore, the data in Table
6.30 only illustrate the levels of risks that could occur to individuals
living in structures built on contaminated land. These data should not be
interpreted as establishing a firm relationship between radium-226 concen-
trations in soil and indoor radon-222 decay product concentrations.
Table 6.30 Estimated lifetime risk of fatal lung cancer to
individuals living in homes built on land
contaminated by uranium mine wastes
226Ra in Soil
(pCi/g)
5
10
20
30
Indoor Working Levels
(WL)
0.02
0.04
0.08
0.12
Lifetime Risk of
Fatal Lung Cancer^
(per 100 persons)
2.5
5.0
10
15
a)
Based on an individual being inside the home 75 percent of the time,
-------
6-46
The working level concentrations in Table 6.30 were derived from
calculations made by Healey (He78), who estimated that 1 pCi/g of
radium-226 in underlying loam-type soil would result in about 0.004 WL
inside a house with an air change rate of 0.5 per hour. These calculated
working levels are in reasonable agreement with measurements made by EPA
(Fig. 6.1) at 21 house sites in Florida (S.T. Windham, U.S. Environmental
Protection Agency, Written Communication, 1980). The Florida data were
derived from the average radium-226 concentration in soil (core samples
were taken to a maximum depth of three feet at each site) and the average
radon-222 decay product concentration inside each structure.
6.1.5.3 Using Radium Bearing Wastes In The Construction of Habitable
Structures
Wastes containing elevated levels of radium-226 have been used at a
number of locations in the construction of habitable structures. In Grand
Junction, Colorado, uranium mill tailings were widely used as landfill
under and around the foundations of homes and other structures causing high
radon-222 decay product concentrations inside many structures. To remedy
this situation, Public Law 92-314 was passed in 1972 to establish a fed-
eral-state remedial action program to correct the affected structures. In
Mesa County, Colorado, which includes Grand Junction, uranium mill tailings
were identified at about 6,000 locations. About 800 of these locations are
expected to receive corrective action because the radon decay product
concentrations inside buildings constructed at these locations, exceeded the
remedial action criteria (DOE79). According to the criteria, dwellings and
school houses would be recommended for remedial action if the indoor radon
decay product concentration exceeded 0.01 WL above background; other struc-
tures would be recommended for remedial action if the indoor radon decay
product concentration exceeded 0.03 WL above background.
In central Florida, structures have been built on reclaimed phosphate
land. The reclaimed land is composed of phosphate mining wastes that con-
tain elevated radium-226 concentrations. EPA estimates that about 1,500 to
4,000 residential or commercial structures are located on 7,500 acres of
the total 50,000 acres of reclaimed phosphate-mined lands (EPA79). A
survey of 93 structures built on reclaimed phosphate land showed that about
40 percent of the structures had indoor radon-222 decay product concen-
trations in excess of 0.01 WL and about 20 percent had concentrations in
-------
6-47
O)
c
_
o
u.
o
o
•o
c
0.001
0.01
10 15
Radium-226 in soil (pCi/g)
20
Figure 6.1 Average indoor radon-222 decay product
measurements (in working levels) as a function of
average radium-226 concentration in soil.
-------
6-48
excess of 0.03 WL (EPA79). Lifetime residency in a structure with a
radon-222 decay product concentration of 0.03 WL could result in twice the
normal 3 to 4 percent risk of fatal lung cancer.
6.1.5.3.1 Use of Uranium Mine Wastes
We do not know to what extent the wastes from uranium mines have been
removed from mining sites and used in local and nearby communities. How-
ever, while surveying in 1972 for locations with higher-than-normal gamma
radiation in the Western States to locate uranium mill tailings material
used in local communities, EPA and AEC identified more than 500 locations
where "uranium ore" was believed to be the source of the elevated gamma
radiation (ORP73). The specific type of ore (mill-grade, sub-ore, low-grade
waste rock) was not determined as this was beyond the scope of the survey.
At some locations, however, surveyors attempted to characterize the ore by
using such terms as "ore spillage," "ore specimens," "low-grade crushed
ore," or "mine waste dump material." Some locations were identified as
sites of former ore-buying stations (ORP73).
Since it is unlikely that valuable mill-grade ore would have been
-widely available for off-site use, we suspect that uranium mine waste
(perhaps sub-ore) may be the source of the elevated gamma radiation levels
at many of the locations where large quantities of ore material are pre-
sent. Table 6.31 shows the locations where higher-than-normal gamma radi-
ation levels were detected during these surveys and the suspected sources
of the elevated levels.
6.2 Environmental Effects
6.2.1 General Considerations
Minerals are necessary to augment man's existence and welfare; in
order to obtain them, some form of mining is necessary. The very nature of
mining requires disturbing the land surface, but may be considered tran-
sitory. To discuss the environmental effects of uranium mining in partic-
ular, it is convenient to divide the mining operations into three phases.
The first phase includes the exploration for, and the delineation of, the
ore body. This involves, in most cases, substantial exploratory and de-
velopment drilling. The second phase involves the preparation of the mine
site and the mining process itself. This phase includes the construction
of service areas, dewatering impoundments, and access roads, digging or
drilling of mine entries, etc. During the actual mining process, waste
-------
6-49
Table 6.31
Gamma radiation anomalies and causes
Location
Arizona / »
Cane Valley^'
Cameron
Cutter
Tuba City
State Total
Colorado' '
Cameo
Canon City
Clifton
Coll bran
Craig
Debeque
Delta
Dove Creek
Durango
Fruita
Gateway
Glade Park
Grand Valley
Gunnison
Leadville
Loma
Mack
Mesa
Mesa Lakes
Molina
Naturita
Nucla
Palisade
Plateau City
Rifle
Sal Ida
Slick Rock
Uravan
Whitewater
State Total
Idaho
Idaho City
Lowman
Salmon
State Total
Number of
Anomalies
Detected
19
3
5
17
44
3
187
1083
145
86
109
43
83
354
1276
17
1
110
47
91
199
90
123
3
43
33
13
939
28
810
64
9
209
55
6253
3
12
77
92
Cause of Anomaly
Uranium Radioactive
Tailings
15
7
22
1
36
159
4
8
2
1
59
118
58
12
1
10
3
18
10
6
1
10
3
107
1
168
6
3
208
1013
9
1
10
Ore
4
1
4
9
24
31
2
7
3
17
18
47
1
2
8
2
3
2
1
15
6
36
20
2
5
4
256
2
2
Source
1
1
3
2
49
1
1
1
1
1
5
3
7
1
75
Natural
Radioactivity
3
3
99
14
46
1
29
2
67
26
28
65
4
1
2
14
1
52
2
453
2
65
70
Unknown
2
7
9
2
28
876
139
25
106
10
3
102
1144
3
98
7
6
181
82
120
3
43
2
2
779
27
614
4
1
49
4456
1
9
10
-------
6-50
Table 6.31 (continued)
Location
New Mexico
Bluewater
Gamerco
Grants
Milan
Shiprock
State Total
Oregon
Lakeview
New Pine Creek
State Total
South Dakota
Edgemont
Hot Springs
Provo
State Total
Texas
Campbell ton
Coughran
Falls City
Fashing
Floresville
George West
Karnes City
Kenedy
Panna Maria
Pawnee
Pleasanton
Poth
Three Rivers
Til den
Whitsett
Number of
Anomalies
Detected
2
5
101
41
9
158
18
4
22
55
45
4
104
7
1
5
1
16
10
10
22
3
1
21
15
5
11
1
Cause of Anomaly
Tailings
1
7
5
8
21
43
3
46
2
2
1
1
Uranium Radioactive
Ore Source
1
49 1
23 4
1 0
74 5
2
1
3
2 1
3
1
5 2
1
1
1
1
1 2
Natural
Radioactivity
5
25
1
31
10
10
1
17
18
6
1
3
14
10
6
13
3
17
14
2
11
1
Unknown
19
8
27
6
3
9
8
25
33
2
2
7
1
1
2
State Total
129
101
15
-------
6 - 51
Table 6.31 (continued)
Location
Utah
Blanding
Bluff
Cisco
Crescent Junction
Green River
Magna
Mexican Hat
Mexican Hat
(Old Mill)
Moab
Monticello , .
Salt Lake Cityvc>
Thompson
State Total
Washington
C res ton
Ford
Reardan
Springdale
State Total
Wyomi ng
Hudson
Jeffery City
Lander
Riverton
Shirley Basin
State Total
Totals
Number of
Anomalies
Detected
38
2
2
2
23
27
5
14
125
59
225
30
552
3
1
10
2
16
8
28
86
86
9
217
7587
Cause of Anomaly
Tailings
10
1
1
10
15
31
70
26
164
13
4
15
9
41
1323
Uranium
Ore
21
1
2
1
14
1
4
1
76
16
10
3
150
2
9
8
14
33
537
Radioactive
Source
1
1
2
7
3
5
0
19
1
1
1
3
107
Natural
Radioactivity
3
1
21
1
6
76
108
3
1
10
2
16
5
3
53
33
94
904
Unknown
4
1
1
7
3
21
9
64
1
111
1
2
20
23
46
4716
(a'Frnm FPA rpnort ORP/IV-75-2. Auaust 1975. Cane Vallev was not included in initial
gamma survey program.
^Excluding Grand Junction where non-tailings anomalies were not sub-categorized
according to source.
^c'Salt Lake City was not completely surveyed.
Source: ORP73.
-------
6-52
piles are produced, mine vents drilled or reamed, and pits opened and
sometimes closed. In the third or retirement phase, the site is subject to
deterioration from weathering ad infinitum. The extent of the deter-
ioration depends somewhat on the amount and quality of reclamation con-
ducted during this phase.
6.2.2 Effects of Mine Dewatering
Both surface and underground mines are dewatered in order to excavate
or sink shafts and to penetrate and remove the ore body. Dewatering is by
ditches, sumps, and drill holes within the mine or by high capacity wells
peripheral to the mine and associated shafts. Dewatering rates up to 4 x
5 3
10 m /day have been reported in the literature. Average discharge for the
3
surface and underground mines modeled herein are 3.0 and 2.0 m /min-
ute/mine, respectively. Between 33 and 72 new mines are projected in the
San Juan Basin of New Mexico alone. Total annual discharge is expected to
9 3
exceed 1.48 x 10 m . Calculated effects include decreased flow in the San
3 3
Juan (0.05 m /min) and the Rio Grande (0.85 m /min) rivers. Future mining
will be primarily underground and the average mine depth will increase 275
percent, i.e., from 248 m to 681 m. Average mine discharge is expected to
3 3
increase from 2.42 m /min to 13.8 m /min.
Aside from the hydraulic and water quality effects of discharging
copious quantities of mine water to typically ephemeral streams, dewatering
impacts are receiving increasing scrutiny because of the observed and cal-
culated impacts on regional water availability and quality. Declines of
water levels in regionally-significant aquifers of New Mexico and reduced
base flow to surface streams are expected. Water quality effects relating
to inter-aquifer connection and water transfer as a result of both de-
watering and exploratory drilling have not been evaluated in any uranium
mining area. In several Texas uranium districts, the effects of massive
dewatering associated with surface mining are beginning to receive atten-
tion, but definitive studies have not yet begun and regulatory action is
not expected in the near future. With respect to in situ leach mining,
dewatering is not necessary and hence is not a concern. There is, however,
some question concerning the practice of pumping large volumes of ground-
water to restore aquifers. It is likely that both dewatering and aquifer
restoration practices will come under increasing State regulation in water-
short areas, particularly in areas of designated groundwater basins or
where aquifers connect with fully-appropriated surface streams. The un-
certainties surrounding environmental impacts of mining in this area can be
-------
6-53
expected to increase, and additional, comprehensive investigations of the
effects of mine dewatering and wastewater discharge are needed. Expansion
in Wyoming and Texas surface and in situ leaching operations is similar,
and these areas should be included in future investigations.
Uranium in water removed from mines through deliberate pumping or
gravity flow is extracted for sale when the concentration is 2 to 3 mg/£ or
more. If there is subsequent discharge to surface water, radium-22(> is
also removed down to concentrations of 2 to 4 pd'A to comply with NPDES
permit conditions. Use of settling ponds at the mines also reduces total
suspended solids and may reduce other dissolved constituents as a result of
aeration and coprecipitation. Seepage from such settling ponds is believed
to be low and, therefore, environmentally insignificant relative to ground-
water. Management of waterborne solid wastes is inconsistent from one mine
to another. In some cases, the solids are collected and put in with mill
tailings, but in most cases they remain at the mine portal and are covered
over.
For surface versus underground mines, we recognize certain inconsis-
tencies in the parameters chosen to calculate contaminant loading of
streams. Contaminant loadings from a model surface uranium mine were
calculated for uranium, radium, TSS, sulfate, zinc, cadmium, and arsenic.
As noted in Section 3.3.1, molybdenum, selenium, manganese, vanadium,
copper, zinc, and lead are commonly associated with uranium deposits;
however, there were too few data for the latter elements to develop an
"average" condition. In addition, barium, iron, and magnesium can be
abundant in New Mexico uranium deposits. There were insufficient data for
these elements in the case of surface uranium mines in Wyoming, hence
contaminant loadings were not calculated. Regional differences dictate
which parameters are monitored for baseline definition and NPDES purposes.
Not all • potential contaminants are important in every region. For this
reason and others, State and industry monitoring programs are inconsistent
with respect to parameters. Since the scope of this study did not permit
extensive field surveys, maximum reliance was placed on published, readily-
available data.
In terms of parameters and concentrations, NPDES permit limits are in-
consistent from one EPA Region to another and from one facility to another
in a given Region. In part, this reflects previous screening of the efflu-
ent discharge data and natural variations in the chemistry of ore bodies.
-------
6-54
However, the inconsistencies in parameters included and concentration
limits are sufficiently large as to suggest Devaluating NPDES permits and
specifying more consistent limits that more closely reflect contaminant
concentrations and volumes of mine discharge.
Infiltration of most of the mine discharge in Wyoming and New Mexico
is confirmed by field observations from these States. The modeling results
agree with these field data. Furthermore, the modeling results, i.e.,
maximum infiltration, are consistent with those in the generic assessment
of uranium milling (NRC79). Potable aquifers are defined under the Safe
Drinking Water Act as those which contain less than 10,000 mg/£ IDS.
Shallow groundwater throughout the uranium regions of the U.S. meets this
criterion.
Considering that essentially all of the mine effluent infiltrates and
is a source of recharge to shallow potable aquifers, NPDES limits should be
influenced by the drinking water regulations and ambient groundwater qual-
ity. The latter is essentially never considered with respect to mine dis-
charges. Extensive use of soils in both the saturated and unsaturated zones
as sinks for significant masses of both water and toxic chemical constit-
uents originating in the mine discharge necessitates further evaluation of
the fate of these elements. Present understanding of fractionation and
resuspension processes affecting stable and radioactive trace elements
greatly limits accurate prediction of health and environmental effects of
mine discharge.
6.2.3 Erosion of Mined Lands and Associated Wastes
Increased erosion and sediment yield result from mining activities
ranging from initial exploration through the postoperative phase. Access
roads and drilling pads and bare piles of overburden/waste rock and sub-ore
constitute the most significant waste sources. Dispersal is by overland
flow originating as precipitation and snowmelt. To a lesser extent, wind
also transports wastes and sub-ore to the offsite environment. Underground
mining is much less disruptive to the surface terrain than is surface
mining. Documentation of the processes and removal rates is scarce and
consists of isolated studies in Texas, Wyoming, and New Mexico. Conser-
vatively assuming that sediment yields characteristic of the areas con-
taining the mines also apply to the mine wastes, yields of overburden,
3
waste rock, ore, and sub-ore amount to 90,000 m per year. Total sediment
-------
6-55
yield from all mining sources, including exploration and development
activities, is estimated at 6.3 x 10 m .
Actual erosion rates from specific sources could be considerably above
or below, this value owing to such variables as pile shape and slope, degree
of induration and grain size, vegetative cover, and local climatic patterns
and cycles. Slope instability does present serious uranium mine waste
problems throughout the mountainous uranium mining areas of Colorado (S.M.
Kelsey, State of Colorado, written communication, 1979). Field obser-
vations in four western states confirm that some erosion characterizes
essentially every pile but that proper reclamation, particularly grading
and plant cover, provides marked improvement and may actually reduce sedi-
ment loss to below pre-mining levels. Unstabilized overburden, waste rock,
and sub-ore piles revegetate rather slowly, even in areas of ample rainfall
such as south Texas.
Stable trace metals such as molybdenum, selenium, arsenic, manganese,
vanadium, copper, zinc, and lead are commonly associated with uranium ore
and may cause deleterious environmental and health effects. Mercury and
cadmium are rarely present. There is no apparent relationship between the
concentration of trace metals and ore grade. In New Mexico ores, selenium,
barium, iron, potassium, magnesium, manganese, and vanadium are most abun-
dant. Presently, very few data are available to characterize the trace
metal concentrations in overburden rock. Results of trace metal analyses
of a few grab samples from several uranium mines in New Mexico and one in
Wyoming show that except for selenium, vanadium, and arsenic, no signif-
icant trend attributable to uranium mining was present (N.A. Wogman,
Battelle Pacific Northwest Laboratory, Written Communication, 1979).
Considering the background concentration for these elements and the limited
number of analyses, the inference of offsite contamination based on these
elements is indefinite.
Ore storage piles, used to hold ore at the mine for periods averaging
one month, are potential sources of contamination to the environment via
dusts suspended and transported by the wind, precipitation runoff, and
Rn-222 exhalation—all of which can be significantly reduced by proper
management. Similarly, spoil piles remaining as a result of overburden,
waste rock, or sub-ore accumulations left on the land surface after mining
constitute a source of contaminants for transport by wind and water. Waste
particles enriched in stable and radioactive solids and Rn-222 can be
-------
6-56
transported by wind and precipitation runoff. Such transport can be re-
duced through proper grading and installation of soil covers protected by
vegetation or rip-rap.
Soil samples collected from ephemeral drainage courses downgrade from
inactive uranium mines in New Mexico and Wyoming generally revealed no
significant offsite movement of contaminants (See Appendix 6). For the New
Mexico mines studied, Ra-226 was elevated to about twice local background
at distances of 100 to 500 meters from the mine. Water and soil samples
from a surface mining site in Wyoming showed no significant offsite move-
ment of mine-related pollution although some local transport of stockpiled
ore was evident in drainage areas on and immediately adjacent to one mine
pit. The strongest evidence that mine wastes are a source of local soil
and water contamination is the radiochemical data and uranium in partic-
ular. Substantial disequilibrium between radium and uranium may indicate
leaching and remobilization of uranium, although disequilibrium in the ore
body is also suspect.
6.2.4 Land Disturbance from Exploratory and Development Drilling
About 1.3 x 10 exploratory and development drill holes have been
drilled through 1977 by the uranium mining industry (see Section 3.6.1).
Using the estimated land area of 0.51 hectares disturbed per drill hole
(Pe79), about 6.5 x 10 hectares of land have been disturbed by drilling
through 1977. To further refine the estimates of land areas disturbed, we
reviewed some recent drilling areas at three mine sites. From observing
187 recent drill sites, it was concluded that 0.015 ± 0.006 hectares per
drill pad were physically disturbed. The error term for the estimates is
at the 95 percent confidence level. The land area disturbed by roads to
gain access to the drill sites was also estimated from aerial photography
and amounts to 0.17 ± 0.11 hectares. The error term for this estimate is
also at the 95 percent confidence level. The total area disturbed per
drill site (drill pad and access roads) is 0.19 ± 0.11 hectares. Using the
latter estimates from aerial photography, the total land area disturbed
from all drilling through 1977 ranges from about 1000 to 4000 km with a
2
mean of about 2500 km . Drilling wastes removed from the boreholes can
disturb additional land areas through wind and water erosion. Ore and
sub-ore remaining in the drilling wastes can, in a radiological sense,
disturb land areas around the drill site from erosion. The extent of the
-------
6 - 57
. -.
Figure 6.2 Example of natural reclamation of drill sites.
-------
6-58
radiological contamination at drill sites is not known and cannot presently
be estimated.
Some reversal of the initial environmental damage at older drill sites
was also observed from aerial photographs. Figure 6.2 contains a typical
medium-to-large surface uranium mine and some adjacent drilling areas that
show the effects of weathering. New drill sites are in the upper left-hand
corner of the photograph. The access roads and drill pads are plainly
visible. It also appears that exposed drilling wastes remain at the drill
site. The area left of center in the photograph shows drill sites that are
probably intermediate in age. The drilling wastes remaining have very
little voluntary vegetation growing on them, and appear to have been sub-
ject to wind erosion. Weathering of the drill pads and access roads is
obvious, as they are hardly discernible. It appears, in these cases, that
weathering may be considered a natural reclamation phenomenon. Old drill
holes are located in the lower left corner of the photograph. The drilling
wastes appear to be isolated dots; the drill pads and roads are almost
indistinguishable from the surrounding terrain. It appears that weathering
and volunteer plant growth tend to obscure scarring caused by roads located
in relatively level areas. In Figure 6.3, an underground mine site, the
access roads to the adjacent drill sites required extensive excavation
because of the topography. These more severe excavation "scars" will
probably remain for a long period of time.
In summary, the average number of drill holes per mine can be esti-
mated by dividing the total number of holes drilled through 1977 by the
number of active and inactive mines in existence in 1977:
1.3 x 106 drill holes ~ 400 drill holes. (6.1)
3300 mines mine
The total land area physically disturbed from drilling per mine is
400 drill holes x 0.19 hectares x km2 = 0.76 km2
" "' •
mine drill hole 100 hectares mine (6.2)
In some instances, weathering and volunteer plant growth (natural recla-
mation) tend to restore the land areas disturbed by drilling. In others,
especially on rugged topography where extensive excavation has occurred,
weathering may promote extensive erosion rather than natural reclamation.
Any ore or sub-ore remaining at the drill sites is subject to erosion.
-------
6 - 59
6.2.5 Land Disturbance from Mining
6.2.5.1 Underground Mines
At underground mines, some land area must be disturbed to accommodate
equipment, buildings, wastes, vehicle parking, and so on. The disturbed
area may range widely between mines in the same area or in different geo-
graphical areas. The land area disturbed by 10 mines was estimated from
aerial photographs. Nine of the mines were in New Mexico and one was in
Wyoming. The disturbed land area averaged 9.3 hectares per mine site and
ranged from 0.89 to 17 hectares. Access roads for each mine site consumed
about 1.1 hectares on the average and ranged from 0.20 to 2.59 hectares.
Subsidence or the collapse of the underground workings also causes some
2
land disturbances. An estimated 2.8 km of land has subsided as a result
of uranium mining in New Mexico from 1930-71 (Pa74). A crude estimate of
the land disturbed from subsidence per mine can be made by dividing the
subsided area by the number of inactive underground mines in New Mexico.
This amounts to about 1.5 hectares per mine. The total area (mine site,
access roads, and subsidence) disturbed by an underground mine is estimated
to be 12 hectares.
6.2.5.2 Surface Mines
An estimate of land disturbed from surface mining was also made from
aerial photographs of eight mining sites in New Mexico and two in Wyoming.
The area estimates are for a single pit or a group of interconnected pits,
including the area covered by mine wastes. The average disturbed area was
estimated to be about 40.5 hectares and ranged from 1.1 to 154 hectares.
2
Access roads for the pits averaged 2.95 hectares (0.03 km ) and ranged from
0.18 to 18 hectares. The total area disturbed per mine site is about 44
hectares.
6.2.6 Retirement Phase
The actual exploration and mining of the uranium ore constitutes a
very small portion of the total existence time of a mine when considered
over a large time frame. The natural forces of erosion and weathering, as
well as plant growth, will eventually change any work or alterations that
man has made on the landscape. For example, underground mines may even-
tually collapse and fill with water if they are in a water table; waste
piles erode and disperse in the environment; the sharp edges of pits become
-------
6 - 60
Figure 6.3 Inactive underground mine site.
-------
6-61
smooth from wind and water erosion; lakes that are produced in pits fill up
with sediment; vents and mine entries collapse, etc.
Perhaps one of the more important considerations associated with
allowing a mine site to be naturally reclaimed is the dispersal of the mine
wastes. Their removal from underground and subsequent storage on the
surface constitute a technological enhancement of both radioactive mater-
ials and trace metals, creating a low-level radioactive materials disposal
site. It appears that containment of the wastes would be preferred over
their dispersal. Wastes from underground mines deposited near the entries
are subject to substantial erosion. Figure 6.3 is an aerial photograph of
an inactive underground uranium mine. The large light area is the waste
pile and the small pile nearby is a heap-leach area. Erosion is occurring
on both. A possible solution to this problem is to minimize the amount of
wastes brought to the surface by backfilling mined-out areas. Another
technique to minimize the dispersal of wastes into the environment by
containment is to stabilize them. Unfortunately, a substantial quantity of
wastes from past mining activities have been dumped in depressions and
washes, which, in essence, enhances their dispersion into the environment.
In retrospect, the wastes should have been stored in areas where minimal
erosion would occur and then covered with sufficient topsoil to promote
plant growth.
In surface mining, radiological containment can be accommodated by
keeping the topsoil, waste rock, and sub-ores segregated during their re-
moval. When backfilling, the materials can be returned to the pit in the
order they were removed or in an order that would enhance the radiological
quality of the ground surface. In this manner, the wastes would be con-
tained and essentially removed from the biosphere. Figure 6.4 shows some
examples of inactive and active surface mines. Some weathering and natural
revegetation are noticeable around the inactive pits. Revegetation, on the
other hand, appears to be relatively sparse at other inactive pits.
Erosion in inactive mining areas in New Mexico and Texas can result in
deep gullying of mine waste and overburden piles. The mine wastes blan-
keting the foreground of Figure 6.5 are incised by an ephemeral stream that
has been subsequently crossed by a roadbed in the immediate foreground.
This particular mine, located in the Mesa Montanosa area immediately south
of Ambrosia Lake, New Mexico, was active from 1957 to 1964. Thus, erosion
occurred in about 15 years. In the background is a large mine waste pile,
-------
6-62
the toe of which is being undercut by the same ephemeral stream (Fig. 6.6).
No deliberate revegetation of the mine wastes dumped in either discrete
piles or spread over the landscape (Fig. 6.7) is occurring, due in large
part to the unfavorable physical and chemical characteristics of the
wastes. The wastes are devoid of organic matter and are enriched in stable
and radioactive trace elements, some of which are toxic to plant life. Low
rainfall and poor moisture retention characteristics further suppress
vegetative growth. As shown in Fig. 6.7, there is a sharp contrast between
the vegetative cover on mine wastes versus that on the undisturbed range-
land in the background. Waste rock from many if not most of the mines in
New Mexico, Utah, and Colorado is weakly cemented sandstone with numerous
shale partings. Physical breakdown to loose, easily-eroded soil unsuitable
for plant life is common (Fig. 6.8), and transport by overland flow and
ephemeral streams occurs both during and long after the period of active
mining (Fig. 6.9).
Depending on the degree of reclamation, if any, inactive surface mines
in Texas vary considerably in the degree of erosion and revegetation. For
example, the deep gullying shown in Fig. 6.10 developed in a period of one
year. The mine wastes in this case were not contoured or covered to mini-
mize gamma radiation, excessive erosion, or revegetation. In fact, the
wastes were disturbed and shifted very recently in the course of construc-
ting the holding pond (for mine water pumped from an active mine to the
right of the picture) in the background. Drainage in this instance is
internal, i.e., to a holding pond. In the background are more recent mine
waste piles also showing deep gullying, scant vegetation, and lack of
protective soil covering. Mine wastes in Texas are not completely returned
to the mine primarily because of the excessive cost. As in the case of
most mining operations, the bulking factor makes it physically impossible
to completely dispose of the wastes in the mines.
Surface mines in Texas, particularly the older ones, also have assoc-
iated overland flow to the offsite environment. Shown in Fig. 6.11 is a
principal channel floored by unstabilized mine wastes and draining toward
nearby grazing lands. Numerous deer and doves also were observed in the
area and are actively pursued by sportsmen. The unstabilized mine in this
photograph was last active several years ago, but most activity stopped in
1964. Vegetation has been very slow to reestablish and is essentially
limited to a very hardy, drought-resistant willow shown in the center of
the picture.
-------
6 - 63
. #»* . • •-
V-. "•
«*>•'.
:. *•••/,
Figure 6.4 Example of active and inactive surface mining activities.
-------
6 - 64
f^.
Figure 6.5 Mine wastes eroded by ephemeral streams in the Mesa
Montanosa area, New Mexico.
-------
6 - 65
.
Figure 6.6 Basal erosion of a uranium mine waste pile by an ephemeral
stream in the Mesa Montanosa area, New Mexico.
-------
6 - 66
Figure 6.7 Scattered piles of mine waste at the Mesa Top Mine, Mesa
Montanosa, New Mexico. Note the paucity of vegetation. Colum-
nar object in background is a ventilation shaft casing.
>
..
f t:
•* f' ^
3 - ~**:
- ]>s'
J
i V >X ^^" '* /
-i*i*.^ f ** -<,^^2;/'>/-> :••* rf
Figure 6.8 Close-up view of easily eroded sandy and silty mine waste from
the Mesa Top Mine, Mesa Montanosa, New Mexico.
-------
6 - 67
.
Figure 6.9 Gullying and sheet erosion of piled and spread mine wastes at
the Dog Incline uranium mine, Mesa Montanosa, New Mexico.
-------
6 - 68
• __
Figure 6.10 Recent erosion of unstabilized overburden piles at the inactive
Galen mine, Karnes County, Texas.
Figure 6.11 Unstabilized overburden piles and surface water erosion at the
Galen Mine, Karnes County, Texas.
-------
6-69
Mines stabilized within the last few years feature improved final con-
touring and use of topsoil and seeding to stimulate revegetation. The
reclaimed spoil piles are then available for grazing. Because backfill
cannot be complete (due to economic and bulking factors), part of the mine
pit remains as shown in Figs. 6.12 and 6.13, which are of the same mine. The
aerial view shows extensive patches of light colored soil devoid of vegeta-
tion. Here topsoil is missing and revegetation is minimal despite the 5
years elapsed since mining. Figure 6.13 is a closeup of one portion of the
mine showing deep gullying, a thin layer of dark topsoil over relatively
infertile sand and silt, and the vertical mine walls. Excavations like
this must be fenced. They are a hazard to livestock and people. It is
likely that erosion will continue to spread away from the mine, but the
rate and consequence is unknown.
Although a mine site can be reclaimed to produce an acceptable aesthe-
tic effect, it may not be suitable in a radiological sense. At the conclu-
sion of surface mining, the remaining pit will contain exposed sub-ore on
some of the pit walls and pit floor. Because most mines at least partly
fill with water and the ore zone is thereby covered, gamma radiation and
radon diffusion should be markedly reduced. Although water accumulation in
the pit would be expected to have elevated concentrations of trace metals
and radioactive materials, this condition would probably be temporary
because of the eventual covering of the pit by sedimentation from inflow of
surface water and materials sloughed from the pit walls. The natural
reclamation process could be enhanced by tapering the pit Wjal.ls to a more
gradual slope and depositing the materials on the pit floor. If sub-ores
are allowed to remain near the surface, gamma exposure rates may be suffi-
cient to prevent unlimited land use and, even if enough stabilizing mater-
ials were used to suppress the gamma radiation, radon exhalation probably
could prevent unrestricted land use also. Some of the possible radiation
problems could be reduced by separating the waste rock and sub-ore when
hauled to the surface. The waste rock could then be used as a blanket for
tfi'e sub-ore. Away from the pit proper, surface gamma readings must be
below 62 yR/hr to comply with Texas State regulations. It is reasoned that,
since background is about 5y R/hr, surface gamma radiation of 57yR/hr or
less would cause a total body dose of 500 mrem/yr or less.
A number of the older mines in Texas were active in the late 1950's
and early 1960's«before there were requirements for stabilization. Such
-------
6 - 70
Figure 6.12 Aerial view of the Manka Mine, Karnes County, Texas. Note
the extent of the mine pit and associated waste piles with poor
vegetative growth on bare wastes or those with insufficient top-
soil cover.
Figure 6.13 Overburden pile showing the weak vegetative cover and
gullying associated with improper stabilization at the Manka
Mine, Karnes County, Texas. Mine stabilized in 1974.
-------
6 - 71
mines, one of which is shown in Fig. 6.14, are relatively shallow, contain
shallow pools of water, and have high associated gamma radiation on the
order of 80 to 100 uR/hr and as much as 140 to 250 yR/hr in some areas.
The particular mine in Fig. 6.14 has maximum readings of 400uR/hr on the
mine waste piles. In addition, the mine was used for illegal disposal of
toxic wastes, primarily styrene, tars, and unidentified ceramic or re-
fraction nodules. Some of the drums containing the wastes are shown in the
rear center and right of the photograph.
Mine wastes may be used for construction and other purposes if they
are not controlled or restricted (see Sections 5.4 and 6.1.5.3.1). These
wastes have been used for fill in a yard and park (Appendix G). Possibly
they have also been used in a school area and fairgrounds (Th79). Their
use in dwelling construction has also been reported (Ha74). It is also
common practice to use mine wastes for road ballast and fill in areas
around mine sites. This type of usage is evident from the roads immed-
iately adjacent to and located north and northeast of the mine shown in
Fig. 6.3.
In summary, only about six percent of the land used for uranium mining
has been reclaimed from 1930-71 (Pa74). For the most part, the wastes at
the mine sites are spreading as a result of weathering and erosion. It
appears that the wastes can be controlled or disposed of by altering some
mining practices, which would require very little effort or expense on the
part of the mining industry. Any reclamation of the mine sites should be
keyed to long-term, natural reclamation that will continue indefinitely.
Careful planning can hasten the natural reclamation process and insure
long-term stability of the mine sites. Measures should be taken to prevent
the removal of mine wastes.
-------
6 - 72
^Hfcgfeg-i'i
Figure 6.14 Inactive Hackney Mine, Karnes County, Texas. Drums in back-
ground contained toxic liquid wastes and styrene. Mine was
active in late 1950's and early 1960.
-------
6-73
6.3 References
ACGIH76 American Conference of Governmental and Industrial Hygienists, 1976,
"TLV's - Threshold Limit Values for Chemical Substances and Physical Agents
in the Workroom Environment with Intended Changes for 1976," American Con-
ference of Governmental and Industrial Hygienists, Cincinnati, Ohio.
Ba76 Baes, C.F., Goeller, H.E., Olson, J.S. and Rotty, R.M., 1976, "The Global
Carbon Dioxide Problem," Oak Ridge National Laboratory Report, ORNL-5194.
Ba79 Battist, L., Buchanan, J., Congel, F., Nelson, C., Nelson, M., Peterson, H.,
and Rosenstein, M., 1979, Ad Hoc Population Dose Assessment Report, "Popu-
lation Dose and Health Impact of the Accident at the Three Mile Island Nu-
clear Station," A preliminary assessment for the period March 28 through
April 7, 1979 (Superintendent of Documents, U.S. Government Printing Office,
Washington, D.C.).
Be80 Begovich, C. L., Eckerman, K.F., Schlatter, E.C. and Ohr, S.Y., 1980, "DAR-
TAB: A Program to Combine Airborne Radionuclide Environmental Exposure Data
with Dosimetric and Health Effects Data to Generate Tabulations of Predicted
Impacts", Oak Ridge National Laboratory Report, ORNL-5692 (Draft).
DOE79 U.S. Department of Energy, 1979, "Progress Report on the Grand Junction
Uranium Mill Tailings Remedial Action Program," DOE/EV-0033.
DOI68 U.S. Department of the Interior, Federal Water Pollution Control Admin-
istration, 1968, "Water Quality Criteria: Report of the National Technical
Advisory Committee to the Secretary of the Interior."
Du80 Dunning, D.E. Jr., Leggett, R.W. and Yalcintas, M.G., 1980, "A Combined
Methodology for Estimating Dose Rates and Health Effects From Exposure to
Radioactive Pollutants," Oak Ridge National Laboratory Report, ORNL/TM-
7105.
EPA73 U.S. Environmental Protection Agency, 1973, "Water Quality Criteria-1972,"
U.S. Environmental Protection Agency Report, EPA-R3/73-033.
-------
6 - 74
EPA79 U.S. Environmental Protection Agency, 1979, "Indoor Radiation Exposure
Due to Radium-226 in Florida Phosphate Lands," EPA-520/4-78-013.
Ha74 Hans, J. and Douglas, R., 1974, "Radiation Survey of Dwellings in Cane
Valley, Arizona and Utah, for the Use of Uranium Mill Tailings," Office
of Radiation Programs, U.S. Environmental Protection Agency.
He78 Healy, J.W. and Rodgers, J.C., 1978, "A Preliminary Study of Radium-Con-
centrated Soil," LA-7391-MS.
HWC78 Health and Welfare Canada, 1978, "Guidelines for Canadian Drinking Water
Quality," Canadian Government Publishers Centre, Supply and Services Canada,
Hull, Quebec, Canada, K1AOS9.
Mo79 Moore, R.E., Baes, C.F. Ill, McDowell-Boyer, L.M., Watson, A.P., Hoffman,
P.O., Pleasant, J.C. and Miller, C.W., 1979, "AIRDOS-EPA: A Computerized
Methodology for Estimating Environmental Concentrations and Dose to Man
from Airborne Releases of Radionuclides," U.S. Environmental Protection
Agency Report, EPA 520/1-79-009 (Reprint of ORNL-5532).
NAS72 National Academy of Sciences, National Research Council, 1972, "The Ef-
fects on Populations of Exposure to Low Levels of Ionizing Radiation,"
Report of the Advisory Committee on the Biological Effects of Ionizing
Radiations (BEIR Report).
NCI78 National Cancer Institute, 1978, "SEER Program: Cancer Incidence and
Mortality in the United States 1973-1976," Prepared by Biometry Branch,
Division of Cancer Cause and Prevention, National Institutes of Health,
National Cancer Institute, Bethesda, Maryland.
NRC79 U.S. Nuclear Regulatory Commission, 1979, "Draft Generic Environmental
Impact Statement on Uranium Milling, Volume I, Appendices," NUREG-0511.
ORP73 Office of Radiation Programs, 1973, "Summary Report of Radiation Surveys
Performed in Selected Communities," U.S. Environmental Protection Agency.
-------
6 - 75
Pa74 Paone, J., Morning, J. and Giorgetti, L., 1974, "Land Utilization and Rec-
lamation in the Mining Industry, 1930-71," U.S. Bureau of Mines, Washington,
O.C.
Pe79 Perkins, B.L., 1979, "An Overview of the New Mexico Uranium Industry," New
Mexico Energy and Minerals Department, Santa Fe, New Mexico.
Th79 Thrall, J., Hans, J. and Kallemeyn, V., 1980, "Above Ground Gamma-
Ray Logging of Edgemont, South Dakota and Vicinity," U.S. Environmental Pro-
tection Agency, Office of Radiation Programs - Rept., ORP/LV80-2.
Va71 Vandergrift, A.E., Shannon, L.J., Gorman, P.G., Lawless, E.W., Sal lee, E.E.
and Reichel, M., 1971, "Particulate Pollutant System Study - Volume 1 - Mass
Emissions," EPA Contract to Midwest Research Institute, Kansas City, Missouri,
Contract No. CPA 22-69-104.
-------
SECTION 7
SUMMARY AND RECOMMENDATIONS
-------
7-1
7.0 Summary and Recommendations
7.1 Overview
This report describes the potential health and environmental effects
caused by uranium mines. It considers all contaminants—solid, liquid, and
airborne—and presents doses and health effects caused by wastes at both
active and inactive mines. In addition to outlining the various methods of
mining uranium, the report graphically depicts mine locations and lists the
U.S. total of 340 active and 3,389 inactive urainum mines (Appendixes E and
F) according to mine name, owner, location (state, county,
section-township-range), and total ore production. Table 7.1 summarizes
the mine lists.
Several facts and limitations helped shape the method and approach of
this study. Little information on uranium mines is available; measurement
information that is available on uranium mine wastes is frequently influ-
enced (biased) by nearby uranium mills; there are inherent variations
between uranium mines, especially between in situ mines, that complicate
generic assessments of uranium mine wastes; and, finally, the law (P.L.
95-604) that mandated this study allotted only a short time in which to
complete it. To accommodate these facts in our study plan, we decided to
develop conceptual models of uranium mines and to make health and
environmental projections from them, based upon available data from the
literature; to employ conservative (maximizing) assumptions when necessary;
and to supplement available information with information from discussions
with persons inside and outside the agency and by doing several field
studies in Texas, New Mexico, and Wyoming. Table 7.2 summarizes the
sources of uranium mine contaminants that were modeled in this study.
7.2 Sources and Concentrations of Contaminants
7.2.1 Surface and Underground Mines
We calculated released radioactivity for two models of active under-
ground and surface uranium mines. The average-large mine, the first model,
reflects new and predicted future mines. The average mine, the second
model, reflects the regional impact of multiple mines. The quality and
-------
Table 7.1 Distribution of United States uranium mines by type of mine and state
Active
State
Alaska
Arizona
California
Colorado
Florida
Idaho
Minnesota
Montana
Nevada
New Jersey
New Mexico
N. Dakota
Oklahoma
Oregon
S. Dakota
Texas
Utah
Washington
Wyoming
Unknown
Total
Surface
0
1
0
5
0
0
0
0
0
0
4
0
0
0
0
16
13
2
19
0
60
Under-
ground
0
1
0
106
0
0
0
0
0
0
35
0
0
0
0
0
108
0
6
0
256
In situ
leaching
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
8
0
0
3
0
11
All^
Others
0
0
0
4
0
0
0
0
0
0
3
0
0
0
0
1
3
0
2
0
13
Surface
0
135
13
263
0
2
0
9
9
0
34
13
3
2
111
38
378
13
223
6
1252
Inactive
Under-
ground
1
189
10
902
0
4
0
9
12
1
142
0
0
1
30
0
698
0
32
5
2036
All
Other(a)
0
2
0
52
1
0
1
0
0
0
12
0
0
0
0
4
17
0
10
2
101
ro
(a)
Includes mine water, heap leach dumps, miscellaneous, and unknown.
-------
7-3
Table 7.2. Sources of contaminants at uranium mines
Active
Source Underground
Waste Rock (Overburden) Pile
Wind suspended dust
Rn-222 emanation
Precipitation runoff
Sub-Ore Pile
Wind suspended dust
Rn-222 emanation
Precipitation runoff
Ore Stockpile
Wind suspended dust
Rn-222 emanation
Precipitation runoff
Abandoned Mine Area Surfaces
Rn-222 emanation
Mining Activities
Dusts
Combustion products
Rn-222
Wastewater
Surface discharge
Seepage
M
M
C
M
M
C
M
M
C
M
M
M
M
M
C
Active
Surface
M
M
C
M
M
C
M
M
C
M
M
M
M
M
C
Inactive
Underground
M
M
C
M
M
C
M
M
C
M
NA
NA
NA
NA
C
Inactive
Surface
M
M
C
M
M
C
M
M
C
M
NA
NA
NA
NA
C
Note.—M, Source modeled;C, considered but not modeled due to lack of
information; NA, not applicable.
-------
7-4
flow rates that were determined for water discharges from typical surface
and underground mines in Wyoming and New Mexico, respectively, were used to
calculate chemical loading of streams in three hydrographic units: sub-
basin (containing the mines), basin, and regional basin. Infiltration of
mine water to potable groundwater and suspension/solution of contaminants
in flood waters are the main components of the aqueous pathway. Crude
dilution and infiltration models were used to evaluate aqueous discharge
from active mines. Off-site movement from inactive mines is primarily by
overland flow, the contamination significance of which was evaluated with
limited field and literature surveys.
Concentrations of radionuclides and stable elements in waste rock,
sub-ore, and ore, selected from only a few measurements, are shown in Table
7.3. Average annual airborne emissions for the sources listed in Table 7.2
were computed for active and inactive mines using the concentrations listed
in Table 7.3 and the geological and meteorological information appropriate
for each region. Source terms were maximized by assuming no dust control
and no spoils pile restoration. Annual emissions of airborne contaminants
estimated for the various sources are given in the following tables of
Section 3.
Tables on Active Mines
Tables on Inactive Mines
Source
Combustion Products
Vehicular Dusts
Dust from Mining
Activities
Wind Suspended Dust
Radon-222 Emissions
Surface
3.30
3.32
3.33
3.34
3.35
Underground
3.52
3.56
3.54
3.55
3.51
Surface Underground
—
—
3.70 3.76
3.74 3.77
Annual emissions in mine water discharged to the surface by the model
average underground and surface mines are listed below.
-------
7-5
Parameter
Surface Mine
(Wyoming)
(a)
(b)
Underground Mine
(New Mexico)
3
Flow rate, m /min
Uranium-238, Ci/yr
Uranium- 2 34, Ci/yr
Radium-226, Ci/yr
Radon-222 and each
short-lived daughter, Ci/yr
Lead-210, Ci/yr
Polonium-210, Ci/yr
Arsenic, Kg/yr
Barium, Kg/yr
Cadmium, Kg/yr
Molybdenum, Kg/yr
Selenium, Kg/yr
Sulfate, MT/yr'b'
Zinc, Kg/yr
Total suspended solids, MT/yr
3.0
0.037
0.037
0.00065
0.00065
0.00065
0.00065
7.9
ND(a)
6.3
ND
ND
276
112
33.0
2.0
0.49
0.49
0.0014
0.0014
0.0014
0.0014
13
850
7
300
70
122
45
29
No data available.
The values shown for radium-226 and sulfate are 10 percent and 20 per-
cent, respectively, of those released on an annual basis. Radium is assumed
to be irreversibly sorbed, and sulfate readily infiltrates.
-------
7-6
Table 7.3. Concentration of contaminants in waste rock (overburden), ore, and
sub-ore
Nonradioactive
Stable
Element
Arsenic
Barium
Cadmium
Cobalt
Copper
Chromium
Iron
Mercury
Magnesium
Concentration
Waste Rock
9
290
NA
NA
18
<51
6,000 15
<8
NA 3
, uq/q
Ore and
Sub-ore
86
920
ND
16
61
20
,700
ND
,500
Stable
Element
Manganese
Molybdenum
Potassium
Lead
Ruthenium
Selenium
Strontium
Vanadium
Zinc
Concentration.
Waste Rock
485
2.5
7,000
22
NA
2
150
100
20
, uq/q
Ore and
Sub-ore
960
115
25,000
78
ND
110
130
1,410
29
Radioactive
Radioactive
Contaminant
U-238 and each daughter
Th-232 and each daughter
Waste rock
6
1
Concentration,
Sub-ore
(a)
2
pCi/g
Ore
285
10
^a'The concentration of U-238 and each daughter was assumed to be 99 pCi/g
at active underground mines, 40 pCi/g at active surface mines, and 110 pCi/g
at inactive mines of both types.
Note.--NA, Not available; ND, Not detected.
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7-7
7.2.2
In Situ Leach Mines
The sources of airborne releases that we assessed at our model in situ
leach mine were the uranium recovery and packaging unit, the evaporation
ponds, and the surge tank. The annual releases for these sources are listed
below.
Source
Annual Airborne Release Rate
Recovery Plant
Uranium-238
Uranium-234
Uranium-235
Thorium-230
Radium-226
Lead-210
Polonium-210
Ammonia
Ammonium chloride
Carbon dioxide
0.10 Ci
0.10 Ci
0.0048 Ci
0.0017 Ci
0.00010 Ci
0.00010 Ci
0.00010 Ci
3.2 MT
12 MT
680 MT
Surge Tank
Radon-222
650 CI
Storage Ponds
Ammonia
Ammonium chloride
Carbon dioxide
100 MT
300 MT
80 MT
Since in situ mining is site specific and relatively new, little
information is available on its wastes. Thus, only airborne releases were
assessed quantitatively; liquid and solid wastes were discussed quali-
tatively.
Several characteristics of in situ mining, especially regarding its
liquid and solid wastes, tend to minimize its release of contaminants.
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7-8
First, only a small fraction of Ra-226 is leached (2.5 percent assumed);
second, all liquid wastes are impounded with no planned releases; third,
much of the liquid waste evaporates, except at a few sites in Texas where
the wastes are injected into deep wells; and, finally, at in situ mines
solid wastes accumulate at a much lower rate than they do at conventional
mines. Aquifer restoration and underground excursion of the leaching
solution were also discussed qualitatively. Although restoration has not
yet been done at a commercial scale site, preliminary experiments indicate
that proper aquifer restoration is possible. During the restoration
process, Rn-222 will continue to be purged from the aquifer and should be
considered a possible source of exposure.
7.2.3 Uranium Exploration
During exploration and developmental drilling, dusts are produced,
Rn-222 and combustion products from drilling equipment are released, and
approximately 0.2 hectares of land surface are disturbed per drill hole.
The average mine site produces an estimated 6,100 kg of airborne dust, 20
kg of which is ore and subore. About 3400 Ci of Rn-222 are released annu-
ally from all development holes drilled since 1948 (4.5 x 10 ), which is
similar to that released from one operating mine. Combustion product
releases are small.
7.3 Exposure Pathways
Exposures were assessed for a hypothetical most exposed individual
living about 1600 m (1-mile) from the center of the mine and for a
population residing within an 80-km (50-mile) radius of the mine. The
meteorological and geological parameters used were those appropriate to the
respective sites.
Aqueous releases were modeled through a basin, sub-basin, and regional
basin hydrographic area. Dilution by precipitation, snowmelt, and periodic
flooding (typical of semi arid regions) was analyzed but not used in the
model. For the model we assumed that the average annual release of
contaminants is diluted by the average annual flow rate of the stream being
considered. The pathways that we assessed are listed below.
-------
7-9
Air Pathways
Water Pathways
1. Breathing
a. Radioactive particulates
and radon-222
b. Radon-222 daughters
1. Breathing
a. Resuspended contaminants
deposited from irrigation
water
2. External Exposure
a. Submersion
b. Surface deposited
radioactivity
2. External Exposure
a. Submersion in resuspended
contaminants deposited
from irrigation water
3. Eati ng
a. Above-surface foods
grown in the area
b. Milk and beef cattle
grazing in the area
3. Eating
a. Above-surface foods grown
in the area
b. Milk and beef cattle grazing
in the area and drinking
contaminated water
c. Fish
In addition to the risks caused by wastes at or discharged directly
from the mines, we assessed the risks to occupants of habitable structures
built on land containing uranium mine wastes. The radium-226 in these
wastes increases the concentrations of radon-222 and its decay products and
the gamma radiation inside these structures.
7.4 Potential Health Effects
7-4.1 Radioactive Airborne Emissions
The risks of fatal cancer were estimated for radioactive airborne
emissions. They include the lifetime risk to the most and average exposed
individuals in the regional population and the number of additional fatal
cancers in the regional population caused per year of model mine operation
(see Table 7.4).
-------
7-10
The major fatal cancer risk at each of the model uranium mines is the
risk of lung cancer from Rn-222 daughter exposures (Tables 6.11 and 6.12).
At surface and in situ mines, radioactive particulates plus Rn-222 con-
tribute only a little over 10 percent of the total fatal cancer risk. The
principal radionuclides in the airborne particulate emissions are U-238,
U-234, Th-230, Ra-226, and Po-210. The contribution from Th-232 and its
daughters is minor. At underground mines, essentially all the risks are
due to Rn-222 daughter exposures. Fatal cancer risks at active underground
mines are greater than those at active surface mines because of the larger
quantity of Rn-222 daughter products released. For inactive mines, the
risks are similar at surface and underground sites.
Most of the exposure to individuals around the model uranium mines is
received internally, usually by breathing. However, the average person in
the region around surface mines receives most of his exposure by eating
contaminated foods. The largest contributors to the radioactive partic-
ulate plus Rn-222 impact are ore and overburden at active surface mines and
ore and sub-ore at the active underground mines. For the model in situ
mine, the uranium processing plant was the main source of particulate
radionuclides.
Of 'all evaluated model uranium mines, the average large underground
mine (Table 7.4) causes the largest fatal cancer risk and the largest
number of additonal cancers in the regional population. Compared to the
natural occurrence of fatal cancer from all causes (Table 7.5), we estimate
an increase of 1.3 percent (0.0019) in fatal cancers over the lifetime of
the maximum individual and a 0.0003 percent (0.018) increase in fatal
cancers in the regional population per year. Increases in expected fatal
cancers are less at all other model mine sites.
Compared to a normal occurrence of genetic effects of 0.06
effects/birth and 12.1 effects/year in the regional population (Wyoming),
the computed risk of additional genetic effects from radiation exposure at
the model uraninum mines is very small. The average large surface mine
produces the largest increase in genetic effects. We estimate the genetic
risk to the descendants of the most exposed individual to be an additional
6.4E-5 effects/birth (0.1 percent increase) for a 30-year parental ex-
posure; 2.2E-7 effects/birth (0.00036 percent increase) to the descendants
of the average exposed individual in the regional population for the same
-------
Table 7.4 Summary of fatal cancer risks from radioactive air-
borne emissions of model uranium mines
Source Most exposed Average exposed
individual life- individual life-
time fatal cancer time fatal cancer
risk (a) risk (a)
Average Surface 1.3E-4 2.5E-7
Mine
Average Large 4.2E-4 8.1E-7
Surface Mine
Average Under- 2.0E-4 9.1E-7
ground Mine
Average Large 1.9E-3 8.6E-6
Underground Mine
Inactive Surface 3.4E-5 6.3E-8
Mine
Inactive Under- 2.0E-5 8.6E-8
ground Mine
In Situ Leach Mine 2.2E-4 3.9E-7
Fatal cancers
cancers caused in
regional population
per year
1.7E-4
6.4E-4
1.7E-3
1.8E-2
1.3E-5
4.5E-5
3.1E-4
Lifetime exposures were calculated as follows:
Surface and underground mines: Exposure for 17 years to active mining and 54 years to
inactive mine effluents.
Inactive mines: Exposure for 71 years to inactive mine effluents.
In situ leach mine: .Exposure for 10-year operation and 8-year restoration.
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7-12
Table 7.5 Percent additional lifetime fatal cancer risk for a
lifetime exposure to the individual and the percent
additional cancer deaths in the regional population
per year of exposure estimated to occur as a result
of uranium mining
Source
Average surface mine
Average large surface
mine
Average underground
mine
Average large
underground mine
inactive surface mine
Inactive underground
Most
Exposed
Individual
8.7E-2
2.8E-1
1.3E-1
1.3
2.3E-2
1.3E-2
Average
Exposed
Individual
1.7E-4
5.4E-4
6.1E-4
5.7E-3
4.2E-5
5.7E-5
Regional
Population
7.9E-6
3.0E-5
3.1E-5
3.3E-4
6.1E-7
8.3E-7
mine
In situ leach mine
1.5E-1
2.6E-4
1.4E-5
Note.—Comparisons are based on the risks given in Table 7.4, a national
cancer risk from all causes of 0.15, and an estimate of the cancer death rate
from all causes to the regional populations of New Mexico (5,400 deaths) and
Wyoming (2,140 deaths).
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7-13
exposure period; and 7.9E-5 additional genetic effects committed to the
descendants of the regional population per year of mine operation. The
latter increase is very small compared to the 12.1 effects that will norm-
ally occur each year in the live births of the regional population.
7.4.2 Nonradioactive Airborne Emissions
Atmospheric concentrations of nonradioactive air pollutants were
calculated at the location of the most exposed individual. The concen-
trations were compared with calculated nonoccupational threshold limit
values, natural background concentrations, and average urban concentrations
of selected airborne pollutants in the United States.
Of the pollutant sources investigated, three produced insignificant
health hazards:
1. airborne stable trace metals
2. airborne combustion products from heavy equipment operation
3. nonradioactive gas emissions at in situ leach mines
However, at active surface mines, dust particulates (produced mainly
by vehicular traffic) equal or exceed conservatively calculated nonoccu-
pational threshold limit values and, therefore, are a potential nuisance.
7 .-4.3 Radioactive Aqueous Emissions
The only water from active uranium mines is that pumped from the mines
and released to surface streams. The largest radiation dose* from this
water to individuals in the assessment regions is to the endosteal cells
(bone) (see Tables 6.25 and 6.26). It primarily comes from" eating foods
grown on land irrigated by streams fed by discharged mine water. Signifi-
cant, but of lesser importance, are exposures due to breathing wind sus-
pended material from irrigated land, eating fish caught in streams near the
site, and external gamma radiation from land irrigated by streams fed by
mine water discharges. We estimate only a small risk from eating beef and
milk from cattle grazing on irrigated pasture and drinking water contami-
nated by mine discharges (<2 percent of the total risk from aqueous
emissions). The radionuclides of major importance in the risk analyses are
U-238 and U-234.
*In Section 7, "dose" is to be read as "dose equivalenf—absorbed
radiation (dose) multiplied by a quality factor.
-------
7-14
The risks of fatal cancer were estimated for radioactive aqueous dis-
charges to surface streams from active uranium mines. The estimates in-
cluded, for the 17-years of active mine operation, the cumulative risk to
the most and average exposed individuals in the assessment area and the
number of fatal cancers caused to persons residing within the assessment
area (Table 7.6). Aqueous emissions from inactive mines and from in situ
leach mines were not modeled due to a lack of data. However, we believe
aqueous source terms from these mines would be low.
Drinking water may be an important source of exposure for the most
exposed individual living near a uranium mine. However, we did not esti-
mate it because we could not quantify radionuclide concentrations in pot-
able groundwater with available information. Also, mine water probably is
not consumed directly by man.
Table 7.6 Summary of the fatal cancer risks caused by radioactive
aqueous emissions from model uranium mines
Source
Most exposed
individual's life-
time fatal cancer
risk for 17 years
of mine operation
Average exposed
individual's life
time fatal cancer
risk for 17 years
of mine operation
Fatal cancers
caused in the
assessment area
population from
17 years of
mine operation
5.6E-6(3.7E-35&)(a) 3.4E-7(2.3E--4%) 2.2E-2(2.3E-4%)
Underground
mine site
(New Mexico)
Surface mine
site
(Wyoming)
1.2E-7(8.0E-5%)
2.6E-4(l.lE-55£)
All "risks" in this table are in addition to the 0.15 risk of fatal
cancer from all causes.
Although aqueous discharges from the model underground mine produce
greater risks than those from the model surface mine, primarily because of
greater releases of U-238 and U-238 daughters, aqueous releases at either
mine cause only very small cancer risks (see Table 7.6) beyond the 0.15
-------
7-15
natural risk of fatal cancer. For example, in New Mexico (assessment
population 64,950) and Wyoming (assessment population 16,230), 9,742 and
2,434 deaths from cancer from all causes are projected to occur. Aqueous
mine discharges in these areas will add only 0.022 and 0.00026 estimated
deaths, respectively, to these totals.
The largest increase in estimated genetic effects occurs at the under-
ground mine site. However, compared to the natural occurrence of heredi-
tary disease, the overall risk of additional genetic effects due to radio-
nuclides discharged in water from the model mines is very small. Based on
a natural occurrence of 0.06 effects/birth, there will be 936 genetic
effects in the regional population of New Mexico during 17 years of mine
operation. In contrast, there will be only 0.015 additional effects to all
the descendants of the regional population because of the 17-year exposure
period.
7.4.4 Nonradioactive Aqueous Emissions
Aqueous concentrations of nonradioactive pollutants were calculated
for stream water we assumed was used by the average individual within the
assessment area. The pathways considered are those listed in Section 7.3.
Drinking water might be a significant pathway for the most exposed indi-
vidual. However, we could not make a reliable prediction of increased
groundwater concentrations due to mine dewatering with the available data.
A comparison of the water concentrations of several pollutants with
recommended EPA limits for livestock and irrigation usage (see Table 6.29)
showed that only molybdenum from the underground mine approaches its limit
for irrigation. The sums of the ratios of the average water concentrations
to the recommended limits are less than one, indicating that mixtures of
the metals would not exceed a "composite limit" for an average individual
in the assessment areas. Constituents such as solids and sulfates, for
which limits are unavailable, have minimal or no toxic properties.
More information is needed before definitive conclusions can be
reached about health hazards caused by nonradioactive waterborne emissions.
Uranium, the metal estimated to be in highest concentration, has no es-
tablished limits based on chemical toxicity in the United States. Of
particular interest would be data on water use patterns near the mines and
the degree to which mine discharges may infiltrate groundwater supplies.
-------
7-16
7.4.5 Solid Wastes
We estimated the risk of fatal lung cancer to individuals living in
houses built on land contaminated by uranium mine wastes as a function of
the Ra-226 concentration in the wastes (see Table 7.7). How much mine waste
has been used for homesite land fill as well as its level(s) of contami-
nation are unknown. Because of the cost, it is unlikely that mill-grade
ore would be available for off-site use. It is more likely that waste
rock, perhaps mixed with some sub-ore, would be the material used. Con-
sidering the Ra-226 content of sub-ores and the likelihood of its being
diluted with waste rock and native soil, mine wastes in residential areas
would probably contain between 5 to 20 pCi/gm of Ra-226.
Table 7.7 Estimated lifetime risk of fatal lung cancer to the
average person living in a home built on land contami-
nated by uranium mine wastes
226Ra in Soil Indoor Working Levels Lifetime Risk of
(pCi/g) (WL) Fatal Lung Cancer^
5 0.02
10 0.04
20 0.08
30 0.12
0.025
0.050
0.10
0.15
^a'Based on the average individual being inside his home 75 percent of the
time.
7.5 Environmental Impacts
We evaluated the environmental effects of uranium mining, including
exploration, by reviewing completed studies, extensive communications with
State and Federal agencies, field studies in Wyoming and New Mexico, re-
connaissance visits to Wyoming, Colorado, New Mexico, and Texas, and
imagery collection and interpretation. Underground and surface mines were
examined to develop a sense of an average or typical condition with respect
to mine size, land areas affected, quality and quantity of airborne and
-------
7-17
waterborne releases, and general, qualitative appreciation for the effects
of such operations on surface streams, groundwater, disturbed land areas,
and natural recovery processes. In many instances, conditions can be
documented, but the significance remains highly subjective and thus weakens
the justification for corrective action, particularly for inactive mines.
7.5.1 Land and Water Contamination
We conclude that (1) U.S. uranium mills make little use of mine water;
(2) mine drainage is to the environment, with occasional use for agri-
culture, sand backfilling, construction, and potable supply; (3) active
surface mines in Wyoming and underground mines in New Mexico have the
greatest discharge to the offsite environment; (4) inactive surface mines
do not appear to adversely affect groundwater quality, although water in
such mines is typically contaminated and runoff from surface accumulation
of overburden and sub-ore may be a source of surface water contamination;
and (5) selected inactive underground mines in Colorado and possibly adja-
cent portions of Utah may discharge water enriched in radionuclides and
trace elements. Since the mining industry now uses terrestrial ecosystems
extensively as sinks for mining-related contaminants, an appropriate govern-
ment agency should monitor active mines for groundwater quality, sorption of
contaminants on stream sediments, and the flushing action of flooding
events.
Before and during surface and underground uranium mining, contaminated
mine water is frequently discharged to arroyos and pasture lands adjacent
to the mines. Less frequently, mine water is used in nearby uranium mills,
in which case ultimate disposal is to the mill tailings pile where evap-
oration and seepage occur. However, despite this practice of mine water
discharge to land and despite the existence of over 3,000 active and in-
active mines and the accelerating level of exploration and mining, there
are many more studies and surveys on the interaction of uranium mills and
water resources than there are on uranium mines and water resources. With
few exceptions, monitoring mine water quality has been related to NPDES
permits.
When mines discharge water to open lands and water courses, 90 percent
or more of it infiltrates the soil and the balance evaporates. Stable and
radioactive contaminants subject to sorption are selectively concentrated
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7-18
in nearby soils, which become a local sink. Mobile constituents such as
sulfate and chloride probably percolate to the water table along with the
bulk of the water, which recharges nearby shallow aquifers downgrade from
the mines. Although many areas in New Mexico, Texas, Colorado, Wyoming,
and Utah have received mine water discharge, studies of contaminant
accretion on soils and deterioration of groundwater quality have been
rather limited. Widespread contamination of groundwater has not been
documented, but there are indications that local surface water and ground-
water quality have been adversely effected in Colorado, Wyoming, and Texas.
Studies underway in New Mexico reveal, in at least two mining districts,
groundwater deteriorating because of mine drainage. Significant increases
in ambient uranium and radium occurred in the Shirley Basin uranium dis-
trict of Wyoming because of initial strip mining and mill processing and,
to a lesser extent, in situ leaching. The long-term significance of soil
loading with stable and radioactive contaminants and their cycling through
the terrestrial ecosystem, including the human food chain, has not been
determined for uranium mining operations.
Discharges from model active surface and underground mines average 2
to 3 m /minute. In most cases, complete infiltration takes place in stream
beds within 5 to 10 kilometers of the mines. However, when discharges from
several mines are combined or if single mine discharge is several cubic
meters per minute or more, infiltration and storage capacity of the
alluvium in nearby channels is exceeded and perennial flows are created for
distances of 20 to 30 kilometers. For example, underground uranium mines
in the Grants Mineral Belt of New Mexico currently discharge 66 m per
3
minute. Of this, only 12 m per minute are used in uranium mills; the
balance is discharged to nearby washes or arroyos. Fourteen of the 20
active uranium mills make no use of mine water, which is associated with
essentially every active underground mine and most active surface mines,
particularly in Texas and Wyoming.
Annual contaminant loading from continuous discharge at a rate of 3
m / minute from one surface mine in the Wyoming model area and dilution in
flood flows with recurrence intervals of 2 to 25 years produce the loading
and stream concentration values in Table 7.8. Chemical loading was calcu-
lated on a mass-per-time basis to estimate the effects of mine drainage.
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7-19
For assessing environmental impacts, we assume that most contaminants
remain on or near the land surface and are available for resuspension in
periodic flash flooding in the sub-basin. Sorption, precipitation, and so
on are assumed to render 90 percent of the radium-226 unavailable for
further transport. Eighty percent of the sulfate is assumed to infiltrate
and also becomes unavailable for further transport in flood waters.
Stream concentrations for uranium, zinc, cadmium, and arsenic are
likely to be less than those shown because there will not be 100 percent
resuspension of sorbed contaminants, and flood events with lesser return
periods are also likely to disperse contaminants. The loading data are
believed to be quite realistic; it is the temporal distribution and re-
distribution of the contaminants that constitute a significant unknown.
These preliminary results indicate contamination of surface water with
uranium, radium, sulfate, and, to a lesser extent, with cadmium and arsenic
in stream waters near the mine outfall. Subsequent dilution of these
initial concentrations will occur as the flow merges with that of pro-
gressively larger streams in the downgrade direction, but cadmium and
sulfate may exceed the drinking water standard in flood waters as far as
the regional basin. Impoundment of these initial flows can be expected
considering water management practices in semiarid rangeland areas like
Wyoming. Therefore, further pathway investigations, based on field data,
are needed.
For the model underground mining area, we selected the Ambrosia Lake
District of New Mexico. We assumed that 14 mines discharged an average of
2 m3/minute and that loading took place for two years prior to each flood.
We then calculated concentrations in flood water for eight different
cases-for 2, 5, 10, and 25 year floods (larger numbers indicating larger
floods), with concentrations for each flood being calculated on the basis
of both a 1-day and 7-day flood duration (see Table 7.9). Based upon these
assumptions and calculations, it appears that concentrations in flood
waters, particularly in the basin, may exceed established or suggested
standards for uranium, radium, cadmium, arsenic, selenium, barium, and
sulfate. However, precipitation and sorption, in addition to dilution
farther downstream, probably will reduce these concentrations enough so
that quality standards for drinking and irrigation water can be met. But
-------
Table 7.8 Summary of contaminant loading and stream water quality from a model surface uranium mine
Annual Loading
Per Mine (a)
(Kg/yr)
Uranium
110
Radium-226
0.00065 Ci/yr
TSS
32,955
Sulfate
2.76 x 105
Zinc
112.0
Cadmi urn
6.31
Arsenic
7.88
Drinking Water Concentrations in Basin and Regional Basin
Standard Flood Flows for Floods of 2, 25, and 100
(mq/£) Years Return Period,
Bas i n
Min Max
0.015/3. 5/0. 21(b) 0.36 0.76
5 2.1 4.5
pCi/£ pCi/£ pCi/£
107 228
250 900 1909
5.0 0.366 0.774
0.01 0.02 0.044
0.05 0.025 0.054
mg/l
Regional
Min
0.26
1.6
pCi/£
79
668
0.271
0.015
0.019
Basin
Max
0.44
2.6
pCi/£
131
1098
0.445
0.025
0.031
^Loading values shown for radium and sulfate are reduced to 10 percent and 20 percent, respectively,
of the amount actually released by a mine. Irreversible sorption and precipitation affect radium and
sulfate infiltrates to the water table.
^ ^0.015 mg/£ : Suggested maximum daily limit based on radiotoxicity for potable water consumed at a
rate of 2 liters per day on a continuous basis. 3.5 mg/£ : Suggested maximum daily limit based on chemical
toxicity and intake of 2 liters in any one day. 0.21 mg/£ : Suggested maximum daily limit based on chemical
toxicity and intake of 2 liters per day for 7 days.
INJ
O
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Table 7.9 Summary of contaminant loading and stream water quality from
a model underground uranium mine
Drinking
Annual Loading, Water
Per Mine(a) Standard
(Kg/yr) (mg/£)
Uranium 1480 0.015/3. 5/0. 21^
Radium-226
0.0014 Ci/yr 5 pCi/£
Lead- 210
0.0014 Ci/yr
Cadmium 7 0.01
Arsenic 13 0.05
Selenium 80 0.01
Molybdenum 300 —
Barium 850 1.0
Zinc 45 5.0
Sulfate 1.22 x 105 250
TSS 29,000
Concentrations in Basin and Regional Basin for 1-day and
7-day Floods of 2 to 25 Years Return Period, mg/£
Min
6.9
6.7 pCi/£
71.2 pCi/£
0.03
0.061
0.37
1.4
4.0
0.21
574
130
Basin
Max
7.1
6.9 pCi/£
73.4 pCi/£
0.03
0.063
0.38
1.4
4.2
0.22
584
140
Regional
Min
0.045
0.044 pCi/£
0.470 pCi/£
0.0002
0.00039
0. 0026
0.0089
0.26
0.0014
3.7
0.89
Basin
Max
0.046
0.044 pCi/£
0.0472 pCi/£
0.0002
0.00041
0.0026
0.0093
0.27
0.0014
3.8.
0.92
(a)Loading values shown for radium and sulfate are reduced to 10 percent and 20 percent, respectively,
of the amount actually released by a mine. Irreversible sorption and precipitation affect radium and sulfate
infiltrates to the water table.
*• ^0.015 mg/£ : Suggested maximum daily limit based on radiotoxicity for potable water consumed at a
rate of 2 liters per day on a continuous basis. 3.5 mg/£ : Suggested maximum daily limit based on
chemical toxicity and intake of 2 liters in any one day. 0.21 mg/£ : Suggested maximum daily limit
based on chemical toxicity and intake of 2 liters per day for 7 days.
i
r>o
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7-22
more theoretical and field evaluations are needed to confirm this.
In situ leaching has contaminated local groundwater reservoirs. We
expect that this will continue because leach solution excursions from the
well field do occur and because injected constituents, especially ammonium,
can not be fully recovered. The NRC and agreement States recognize this
situation but consider the adverse impacts outweighed by the benefits of
recovering additional uranium and developing a relatively new technology.
7.5.2 Effects of Mine Dewatering
Underground mines and most surface mines are dewatered to allow for
excavation or shaft sinking and ore removal. The resulting low concen-
tration and, oftentimes, large volume effluent discharges introduce sub-
stantial masses of stable and radioactive trace elements to local soil and
water systems. This extensive use of soils in both the saturated and
unsaturated zones as water and contaminant sinks requires further study to
'determine the environmental fate of those elements. In addition to local
effects, the long-term impacts on regional water availability and quality
are also important. The NPDES limits relating to surface discharges are,
in terms of-parameters and concentrations, different from one EPA region to
another and should be reevaluated to more closely reflect the impact of
contaminant concentration and mine discharge. In general, the uncer-
tainties about the environmental impact of mine dewatering can be expected
to increase; and additional, comprehensive investigations of its effects
are necessary.
7.5.3 Erosion of Mined Lands and Associated Wastes
From initial exploration through retirement, mining, particularly
surface mining, increases erosion and sediment yield. The most significant
waste sources are access roads, drilling pads, and piles of over-
burden/waste rock and sub-ore. Sediment and associated contaminants are
dispersed mostly through the overland flow of precipitation and snowmelt
water. Erosion rates vary considerably with the characteristics of the
source area, i.e., pile geometry, soil and rock characteristics, amount and
type of vegetative cover, topography, and local climate. There is some
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7-23
erosion of all mine waste sources, although studies of ephemeral drainage
courses downgrade from inactive mines in New Mexico and Wyoming usually
reveal only local soil and water contamination and no significant off-site
dispersal of contaminants. Proper reclamation, particularly grading and
revegetation, markedly reduce erosion and, consequently, contaminant trans-
port.
7.5.4 Exploratory and Development Drilling
The uranium industry has drilled approximately 1,300,000 exploratory
and development drill holes through 1977. This amounts to about 430 drill
holes per mine if averaged over all active and inactive mines. During the
course of drilling, some land areas are disturbed to provide access roads
to the drill sites and pads for the drill-rig placements. This has dis-
turbed about 2500 km2 (960 mi2) of land for all drilling through 1977.
Drilling wastes accumulate at each drill site. Although these wastes
are sometimes placed in trenches and backfilled after drilling, the general
industry practice (observed from field studies and aerial photography),
apparently, is to allow the wastes to remain on the surface, subject to
erosion. The extent of radiological contamination from erosion of the
remaining ore and sub-ore at development drill holes is not known.
The average drilling depth has increased with time and will probably
continue to do so in the future. Deeper drilling will tend to increase the
probability that several aquifers may be penetrated by each drill hole.
Aquifers with good quality water may be degraded by being connected, via
the drill holes, with aquifers of poor quality water. Current regulations
require drill holes to be plugged to prevent interaquifer exchange, but
often only the first one and one-half meters of the borehole will be
plugged, and regulations do not effect past drill holes. Finally, it appears, from
mine site surveys and aerial photography, that very few drill sites have
been reclaimed.
7.5.5 Underground Mining
The land disturbed by individual underground mines varies from 0.89 to
17 hectares (2.2 to 42 acres) with an average of 9.3 hectares (23 acres).
In addition, access roads to the mines consume about 1.1 hectares (2.7
acres), and mine subsidence disturbs about 1.5 hectares (3.7 acres). A
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7-24
total of about 12 hectares (30 acres) of land are disturbed by an average
underground mine.
All underground uranium mining through 1977 has produced about 2.9 x
7 73
10 MT or about 1.8 x 10 m of wastes. Some of these wastes, the sub-
ores, contain elevated concentrations of naturally occurring radionuclides.
The sub-ores usually are removed last in the mining process and dumped on
top of the waste rock where they are subject to erosion. Some radiation
surveys conducted around waste piles indicate that the sub-ores are eroding
and contaminating land in addition to that disturbed by the mining activ-
ities.
During our field studies in Texas, New Mexico, Wyoming, and Colorado,
we saw very few mine sites where reclamation had been completed or was in
progress—especially at the inactive mine sites.
7.5.6 Surface Mining
The cumulative waste from surface mining uranium between 1950 and 1978
9 93
amounts to about 1.7 x 10 MT (1.1 x 10 m ). Overburden is usually used
to backfill mined-out pits during contemporary mining. At older inactive
mines, the mine wastes were either used for pit backfill or completely
disregarded. Erosion of these waste piles may cause substantial environ-
mental problems.
The amount of land physically disturbed at a surface mine is highly
variable. The area disturbed at ten surface mines was estimated to range
from 1.1 to 154 hectares (2.7 to 380 acres), averaging about 41 hectares
(101 acres) per mine site. Access roads disturb about 3 hectares (7.4
acres) per mine site, bringing the total average area physically disturbed
to about 44 hectares (109 acres). Field surveys of inactive mine sites
indicate that mine wastes (sub-ores) erode and contaminate land areas
greater than those physically disturbed. The land contamination appears to
have been caused by erosion of ore stockpiles, erosion of sub-ores, and
dust losses from the actual mining process.
Very few if any inactive mine sites were reclaimed. Reclamation of
any mine site will have to address the radiological aspects of the mine and
its wastes.
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7-25
7.6 Regulatory Perspective
Except for in situ leach mining, licensed by the Nuclear Regulatory
Commission (NRC), uranium mining is not licensed, per se, by a Federal
agency. However, three Federal statutes have particular relevance to
uranium mining. First, the Federal Water Pollution Control Act as
amended (1972) requires a permit for discharges to navigable waters.
Second, the Clean Air Act amendments of 1977 require a permit for
pollutant air emissions. Third, proposed regulations under the Resource
Conservation Recovery Act of 1977 identify hazardous wastes and
stipulate their disposal for uranium mining. When promulgated, these
latter regulations will strengthen current Federal and State reclamation
requirements.
In situ uranium mining is licensed by those states having
agreement-state status with NRC. National Pollution Discharge
Elimination System (NPDES) permits are issued by EPA approved states. No
state issues mining licenses per se. However, most states require mining
and reclamation plans, including bonding fees, for at least
state-controlled lands. Most reclamation requirements provide erosion
control through slope and vegetation standards. Arizona is the only
uranium mining state without reclamation requirements.
7.7 Conclusions and Recommendations
The evaluation of the potential impacts of uranium mining was
performed largely by means of analytical studies of model facilities. We
believe that the results give an adequate representation of the
industry. In order to determine the extent of possible problems, our
studies were specifically designed to give conservative results. It
should be recognized that actual mines may operate under conditions
producing substantially smaller impacts than the results presented.
Compared to uranium milling, health and environmental effects of
mining are not as well understood, despite the existence of over
3000 active and inactive mines. We have noted throughout this report
instances of the absence or inadequacy of pertinent information.
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7-26
7.7.1 Conclusions
7.7.1.1 Solid Wastes
Solid uranium mining wastes are potentially hazardous when used as
building materials or when buildings are constructed on land containing
such wastes. The hazard arises principally from increased risk of lung
cancer due to radon-222. In a 1972 survey of communities in uranium
mining regions, EPA and the former Atomic Energy Commission found more
than 500 locations where such wastes had been used.
7.7.1.2 Airborne Effluents
a) Individuals living very near active underground mine exhaust
vents would have an increased risk of lung cancer caused by exposure to
radon-222 emissions. Surface mines and in situ mines are less hazardous,
and inactive mines do not have significant radon-222 emissions. Other
airborne radioactive emissions from all types of mines are judged to be
smaller.
b) The number of additional cancers committed per year in the
regional populations due to radionuclide air emission from the
approximately 340 active mines and 3300 inactive mines was estimated to
be about 0.6 cancers in 1978. This number of estimated additional
cancers is small, about one-third of the estimated additional cancers in
regional populations due to radon emissions from the 24 inactive uranium
mill tailings piles addressed by Title I of the Uranium Mill Tailings
Radiation Control Act (EPA 80). (These mill tailings piles represent
about 13 percent of all tailings currently existing due to U.S. uranium
miTling and mining). These potential effects are not of sufficient
magnitude to warrant corrective measures, especially considering the
large number of sites involved.
c) The following were judged to cause an insignificant health risk
for all types of mines:
1. airborne nonradioactive trace metals.
2, airborne combustion products from heavy-duty
equipment operations.
3. nonradioactive emissions from in situ leach sites.
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7-27
d) Airborne dust near large surface mines (primarily caused by
vehicular traffic) may exceed the National Ambient Air Quality Standard
for particulate matter.
7.7.1.3 Waterborne Effluents
a) We estimate that an insignificant health risk accrues to
populations from waterborne radioactivity from an average existing mine.
b) Uranium mine dewatering and water discharges, which are
increasing as more and deeper mines are created, may in the future have
significant effects on water quality. Current treatment practices are
controlling the release of radioactivity into surface waters.
c) Water in inactive surface and underground mines usually contains
radionuclides and trace elements in concentrations comparable to
groundwater in contact with ore bodies. Some abandoned underground mines
in certain areas of Colorado and Utah probably discharge such waters to
nearby streams and shallow aquifers. Available data is not sufficient to
conclude whether or not there is a problem.
d) We could not determine, using models, that there is no health
hazard to individuals who drink water drawn from such surface or
underground sources. Water discharges from active mines to nearby
streams and stream channels may extensively recharge shallow aquifers,
many of which are either now used or could be used for drinking water.
Such determinations must be made on a site-specific basis, and take
account of the additive effects of multiple mines. These studies can be
made easily a part of State or utility surveillance programs.
7.7.1.4 Exploratory and Development Drilling
Harm from effluents due to exploratory and developmental drilling is
probably small compared to effects of operating mines. Under current
regulations and practices, however, aquifers penetrated at different
levels can mix, creating the potential for degrading high quality
groundwater.
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7-28
7.7.2 Recommendations to Congress
1) Based on this study, we do not believe at this time that
Congress needs to enact a remedial action program like that for uranium
mill tailings. This is principally because uranium mine wastes are lower
in radioactivity and not as desirable for construction purposes as
uranium mill tailings. Nonetheless, some mining waste materials appear
to have been moved from the mining sites but not to the extent that mill
tailings were.
2) Some potential problems were found that might require regulatory
action but none of these appear to require new Congressional action at
this time.
7.8 Other Findings
1) Regulations may be needed to control wastes at active uranium
mines to preclude off-site use and to minimize the health risks from
these materials. These regulations would need to address the use of the
materials for construction purposes as well as ultimate disposal of the
materials.
EPA proposed such regulations in 1978 under the Resource
Conservation and Recovery Act (RCRA). In 1980, Congress amended RCRA to
require further EPA studies before promulgating general regulations for
mining wastes. An EPA study by the Office of Solid Wastes on all types
of mines, including uranium mines, is currently being conducted. The
amendment did not restrict EPA's authority to regulate use of uranium
mine wastes in construction or reclamation of lands containing such
wastes.
2) Standards are needed to control human exposure from radioactive
air emissions from uranium mines. This is principally because of
potential exposure to individuals living near large underground uranium
mines rather than concerns regarding the exposure of regional
populations. We have proposed such standards under Section 112 of the
Clean Air Act.
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7-29
3) EPA has conducted two field studies in 1972 and 1978 which
define possible sites at which mine wastes may have been used in
construction or around buildings. The information developed in these
studies has been sent to State health departments. The States should
conduct follow-up studies, as appropriate, to determine whether there are
problems at these sites.
4) The adequacy with which NPDES permits protect individuals who
may obtain drinking water near the discharge points for uranium mine
dewatering should be evaluated by States. Under the Public Water Systems
provision of the Safe Drinking Water Act, radionuclide standards now
exist for drinking water.
5) Some site specific studies should be considered by States to
determine the extent to which inactive uranium mines are significant
water pollution sources.
6) States with uranium mines should determine the feasibility of
control of fugitive dust from large surface mines and incorporate the
recommendations in State Implementation Plans.
7) States should require borehole plugs in drilling operations that
will prevent interaquifer mixing (exchange) and also seal drilling holes
at the surface.
7.9 References
EPA80 U.S. Environmental Protection Agency, 1980, "Draft Environmental
Impact Statement for Remedial Action Standards for Inactive Uranium
Processing Sites (40 CFR 192), "EPA 520/4-80-011.
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