tales
Environmental Protection
Agency!
Office of
Radiation Programs
Washington. DC ?0460
September 1983
EPA 520/1 83-008-1
Fihal Environmental
Impact Statement
Standards
r the Control
of Byproduct Materials
from Uranium Ore Processing
(40 CFR 192)
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i
Volume I
EP 520/1
83-008-1
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EPA 520/1-83-008-1
Final
Environmental Impact Statement
for
Standards for the Control
of
Byproduct Materials from
Uranium Ore Processing
(40 CFR 192)
Volume I
September 1983
Office of Radiation Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
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CONTENTS
Page
SUMMARY S-l
1. INTRODUCTION 1-1
1.1 Scope of the Standards 1-1
1.2 Contents of the Analysis 1-3
References 1-5
2. THE URANIUM MILLING INDUSTRY 2-1
2.1 History of the Uranium Milling Industry 2-1
2.2 Conventional Milling Processes 2-2
2.3 Waste Management at Uranium Mills 2-5
2.4 Uranium Recovery by Heap-Leaching 2-7
2.5 Currently Licensed Uranium Mills 2-8
2.6 Future Uranium Supply and Demand 2-8
References 2-12
3. ENVIRONMENTAL RELEASES FROM URANIUM MILLING WASTES 3-1
3.1 Composition of Tailings Solids and Pond Liquids 3-1
3.1.1 Radioactivity in Tailings 3-1
3.1.2 Toxic Elements and Other Chemicals in
Tailings 3-4
3.2 Routine Environmental Releases from Tailings 3-4
3.2.1 Air Contamination 3-5
3.2.2 Land Contamination 3-9
3.2.3 Water Contamination , 3-11
3.3 Nonroutine Releases 3-14
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CONTENTS (Continued)
Page
3.3.1 Accidents and Acts of God 3-14
3.3.2 Misuse of Tailings Sands 3-15
3.4 Environmental Releases from Heap-Leaching Operations .. 3-15
References 3-16
4. MODEL SITE AND TAILINGS PILE 4-1
4.1 Model Site 4-1
4.1.1 Meteorology 4-1
4.1.2 Demography 4-1
4.1.3 Hydrology '. 4-6
4.1.4 Agricultural Productivity 4-6
4.2 The Model Tailings Pile 4-6
4.2.1 Physical Description 4-7
4.2.2 Contaminants Present 4-8
4.2.3 Radioactive Emissions to Air 4-8
4.2.4 Emissions of Contaminants to Water 4-8
References 4-11
5. ENVIRONMENTAL PATHWAYS 5-1
5.1 Contaminants 5-1
5.1.1 Particulates 5-1
5.1.2 Radon 5-2
5.1.3 Liquid Contaminants 5-2
5.2 Atmospheric Transport 5-3
5.2.1 Near the Tailings 5-3
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CONTENTS (Continued)
Page
5.2.2 Regional 5-3
5.2.3 National 5-5
5.3 Hydrological Dispersion 5-5
5.3.1 Surface Water 5-5
5.3.2 Groundwater 5-6
5.4 Environmental Concentrations '5-7
5.4.1 Calculational Procedures 5-7
5.4.2 Air Concentrations 5-8
5.4.3 Ground Surface Concentrations 5-10
5.4.4 Dietary Intake 5-16
5.4.5 Water Concentrations 5-17
References 5-21
6. HEALTH IMPACT OF TAILINGS BASED ON MODEL TAILINGS PILE 6-1
6.1 Introduction 6-1
6.1.1 Radon and Its Immediate Decay Products 6-3
6.2 Estimated Effects on Health Due to Radioactive
Releases from the Model Tailings Pile 6-4
6.2.1 Effects of Radioactive Particulate Releases
from the Model Tailings Pile 6-9
6.2.2 Effects of Radon Emissions from
Tailings Piles 6-9
6.2.3 Effects of Gamma Radiation Emissions from
Tailings Piles and Windblown Tailings 6-11
6.3 Effects from Misuse of Tailings 6-11
6.4 Estimated Effects on Health Due to Toxic Releases
from the Model Tailings Pile 6-12
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CONTENTS (Continued)
Page
6.5 Effects Expected in Plants and Animals 6-13
6.6 Total Radon Decay Product Population Risk from the
Uranium Milling Industry 6-13
References 6-16
7. CONTROL OF TAILINGS DURING MILLING OPERATIONS 7-1
7.1 Objectives of Control Measures 7-2
7.1.1 Wind Erosion 7-3
7.1.2 Radon 7-3
7.1.3 Water Contamination 7-3
7.2 Control Methods 7-3
7.2.1 Wind Erosion 7-3
7.2.2 Control of Radon 7-6
7.2.3 Control of Groundwater Contamination 7-6
7.3 Cost and Effectiveness of Control Measures for Model
Tailings Pile 7-7
7.3.1 Control of Wind Erosion of Tailings 7-7
7.3.2 Control of Radon 7-8
7.3.3. Control of Seepage to Groundwater 7-8
7.4 Cost-Effectiveness Analyses 7-11
7.4.1 Wind Erosion 7-11
7.4.2 Control of Radon 7-12
7.4.3 Control of Seepage to Groundwater 7-14
References 7-15
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CONTENTS (Continued)
Page
8. OBJECTIVES AND METHODS FOR TAILINGS DISPOSAL 8-1
8.1 Health and Environmental Protection Objectives 8-1
8.2 Longevity of Control 8-3
8.2.1 Human Intrusion 8-4
8.2.2 Erosion and Gully Intrusion 8-4
8.2.3 Floods and Other Natural Processes 8-5
8.2.4 Longevity of Control 8-8
8.3 Disposal Methods and Effectiveness 8-9
8.3.1 Earth Covers 8-9
8.3.2 Basin and Pond Liners 8-12
8.3.3 Thermal Stabilization 8-14
8.3.4 Chemical Processing 8-15
8.3.5 Soil Cement Covers 8-16
8.3.6 Deep-Mine Disposal 8-16
8.3.7 Solidification in Concrete or Asphalt 8-16
8.4 Selection of Disposal Method for this Analysis 8-17
References 8-18
9. ALTERNATIVE STANDARDS FOR TAILINGS DISPOSAL 9-1
9.1 Form of the Standards 9-1
9.1.1 Dose or Exposure Rate Limits 9-1
9.1.2 Concentration Limits in Air and Water 9-1
9.1.3 Release Rate Limits 9-2
9.1.4 Engineering/Design Standards 9-2
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CONTENTS (Continued)
Page
9.2 Alternative Disposal Standards 9-3
9.3 Estimated Costs of Methods for Alternative Standards .. 9-6
9.3.1 Disposal Methods for Existing Tailings Piles ... 9-7
9.3.2 Disposal Methods for New Tailings Piles 9-6
9.4 Accidental and Radiation-Induced Deaths from Disposal.. 9-10
9.5 Alternative Cleanup Standards for On-site Contaminated
Land 9-14
References 9-17
10. ANALYSIS OF COSTS AND BENEFITS FOR ALTERNATIVE TAILINGS
DISPOSAL ALTERNATIVES AND SELECTION OF THE STANDARD Z 10-1
10.1 Benefits Achievable Through Disposal of Tailings 10-1
10.1.1 Benefits of Stabilization 10-2
10.1.2 Benefits of Radon Control 10-6
10.1.3 Benefits of Protecting Water 10-7
10.2 Benefits and Costs for a Model Tailings Pile 10-7
10.2.1 Baseline Case A 10-7
10.2.2 Alternative Standards B-l, B-2, B-3 10-9
10.2.3 Alternative Standards C-l through C-5 10-9
10.3 The Standard Selected 10-10
APPENDICES
APPENDIX A: Health and Environmental Protection Standards for
Uranium and Thorium Mill Tailings A-l
APPENDIX B: Estimated Costs for Disposal of Active
Uranium Mill Tailings B-l
APPENDIX C: Health Basis for Hazard Assessment C-l
APPENDIX D: Water Management at Uranium Ore Processing Sites ... D-l
viii
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CONTENTS (Continued)
Page
APPENDIX E: Current Estimated Populations Near Active Uranium
Ore Processing Sites E-l
APPENDIX F: Other Mineral Resources in Uranium Mining Regions... F-l
VOLUME II: Final Environmental Impact Statement for Standards
for the Control of Byproduct Materials from
Uranium Ore Processing: Response to Comments
TABLES
2-1 Uranium Production 2-2
2-2 Currently Licensed U.S. Uranium Mills 2-9
2-3 Projections of Industry Demand and Production for Uranium
Yellowcake 2-11
2-4 Projections of Demand, Production, and Inventory of
Uranium Yellowcake 2-11
3-1 Description of Mill Tailings Piles at Licensed Mills 3-6
3-2 Dissolved Substances in Tailings Pond Liquids at
Selected Sites 3-8
3-3 Average Concentration of Elements Found in Inactive Uranium
Mill Tailings 3-10
3-4 Contamination in Shallow Aquifers Compared with Estimated
Background Near Active Tailings Ponds 3-12
3-5 Elements Found in Elevated Concentrations in Groundwater
Near Inactive Tailings Sites 3-14
4-1 Annual Average Joint Frequency Distribution for Winds in
the Model Mill Region 4-2
4-2 Population Distribution at a Remote Uranium Mill
Tailings Site 4-4
4-3 Population Distribution at a Rural Uranium Mill
Tailings Site 4-5
4-4 Summary of Principal Physical Characteristics of the Model
Tailings Pile 4-7
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CONTENTS (Continued)
Page
4-5 Chemical and Radiological Properties of Tailings Wastes
Generated by the Model Mill 4-9
4-6 Radioactive Emissions to Air from Model Tailings Pile 4-10
5-1 Regional Air Concentration of Radionuclides by Distance and
Particle Size (Operational Phase) 5-11
5-2 Regional Population Inhalation Intake and Exposure (per
Operational Year) 5-12
5-3 National Population Exposures and Intakes 5-12
5-4 Regional Air Concentration of Radionuclides by Distance and
Particle Size (Post-Operational Phase) 5-13
5-5 National Population Exposures and Intakes Per Year (Post-
Operational Phase) 5-14
5-6 Regional Ground Surface Concentrations for Radionuclides... 5-14
5-7 Regional Population Ground Surface Exposure for
Radionuclides (per Operational Year) 5-15
5-8 Regional Ground Surface Concentrations for Radionuclides
by Distance (Post-Operational Phase) 5-15
5-9 Regional Food Utilization Factors for an Individual 5-16
5-10 Regional Individual Annual Ingestion for Radionuclides
(Operational Phase) 5-18
5-11 Regional Individual Annual Ingestion for Radionuclides
(Post-Operational Phase) 5-19
5-12 Regional Population Ingestion for Radionuclides
(per Operational Year) 5-20
6-1 Regional Individual Lifetime Risk of Fatal Cancer
(Operational Phase) , 6-5
6-2 Regional Individual Lifetime Risk of Fatal Cancer
(Post-Operational Phase) 6-6
6-3 Number of Fatal Cancers per Operational Year for the
Regional Population 6-7
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CONTENTS (Continued)
Page
6-4 Number of Fatal Cancers per Post-Operational Year for the
Regional Population 6-7
6-5 U.S. Collective Risks due to Radon-222 Release per
Operational Year 6-8
6-6 U.S. Collective Risks due to Radon-222 Release per
Post-Operational Year 6-8
7-1 Chemical Stabilization Agents Used for Dust Suppression ... 7-5
7-2 Costs and Effectiveness of Methods for Controlling
Wind Erosion at a Model Tailings Pile 7-9
7-3 Costs and Benefits of Various Levels of Control of
Dust Emissions for Model Tailings Pile During
Operational Phase 7-12
7-4 Costs and Benefits of Various Levels of Control of Radon
Emissions from Model Tailings Pile During
Operational Phase 7-13
8-1 Estimated Earthen Cover Thickness (in meters) to Reduce
Radon Emissions to 20 pCi/m2s 8-11
8-2 Summary of Radon Flux Measurements Made at Grand Junction
Over a Two-Year Period 8-11
8-3 Percent Reduction in Emanating Ra-226 at Temperatures
from 500° to 1200° C 8-14
9-1 Alternative Standards for Disposal of Uranium Mill Tailings 9-4
9-2 Control Methods Assumed to Satisfy the Alternative
Standards 9-7
9-3 Summary of Cost Estimates for Disposal of Active Uranium
Mill Tailings 9-11
9-4 Accidental and Radiation-Induced Deaths Associated with
Alternative Levels of Tailings Control 9-13
10-1 Benefits of Controlling Uranium Mill Tailings at
Existing Active Sites 10-3
10-2 Benefits of Controlling Uranium Mill Tailings at Active
Mill Sites through the Year 2000 for the Baseline
Estimate 10-4
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CONTENTS (Continued)
Page
10-3 Benefits of Controlling Uranium Mill Tailings at Active
Mill Sites through the Year 2000 for the Low Growth
Estimate 10-5
10-4 Total Costs of Controlling Uranium Tailings at Active Sites 10-8
FIGURES
2-1 Flow Diagram of the Generation of Uranium Tailings Solids
and Liquids from the Acid-Leach Process 2-4
3-1 The Uranium-238 Decay Series 3-2
3-2 Radon Production In a Tailings Pile 3-3
5-1 Radon Concentrations Near the, Pile 5-9
8-1 Recurrence Times Versus Probabilities for Various Periods
of Concern 8-7
8-2 Percentage of Radon Penetration of Various Covers by
Thickness 8-10
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SUMMARY
( ) Draft
( X ) Final Environmental Impact Statement
Environmental Protection Agency
Office of Radiation Programs
1. This action is administrative.
2. The Environmental Protection Agency is establishing public health
and environmental standards (40 CFR 192) for uranium and thorium mill
tailings at licensed mill sites under the Uranium Mill Tailings
Radiation Control Act of 1978 (PL. 95-604). Mills are currently
located in Colorado, New Mexico, South Dakota, Texas, Utah,
Washington, and Wyoming.
These standards are issued to reduce and control the hazards
associated with uranium and thorium mill tailings. Controls are
required both during the operational period of mills and for disposal
of the tailings piles, to assure environmentally sound, long-term
protection of public health and stabilization of the tailings.
These standards will be implemented by the U.S. Nuclear
Regulatory Commission and its Agreement States that have approval to
license uranium or thorium mills. The total cost is estimated to be
about $260 million (1983 dollars) for disposal of existing tailings
and about $390 million (1983 dollars) for disposal of existing
tailings and those projected to be generated to the year 2000.
3. These standards will provide the following public health and
environmental benefits:
(a) Under the post-closure standards, radon emissions from
tailings piles will be reduced by at least 95 percent for 1,000
years, and for a lesser degree beyond that period for a time not
readily estimated. We estimate that this will avoid
approximately 570 lung cancer deaths per century; the total
number of lung cancer deaths avoided over the effective life of
the control is not calculable, but should exceed tens of
thousands. Measures used to achieve these standards will also
prevent spreading of tailings by wind and water erosion, protect
water quality, and should discourage misuse of tailings by
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providing a significant barrier against intrusion for at least a
thousand years.
(b) Existing standards for operating mills are not changed (40
CFR 190, 40 CFR 440, and Federal Radiation Guidance as published
in 1960, 25 FR 4402). Groundwater quality will be protected
through the incorporation of Solid Waste Disposal Act (SWDA)
standards (40 CFR 264) into these standards. Also, uranium and
molybdenum are added to the list of hazardous constituents
controlled under the SWDA standards and specific concentration
limits for alpha emitters in water are added.
4. The following alternatives were considered:
(a) Institutional controls with radon emission limits of:
(B-l) no limit
(B-2) 60 pCi/m2s
(B-3) 20 pCi/m2s
(B-4) 6 pCi/m2s
(b) Passive, engineered controls designed for 1,000 years with
radon emission limits of:
(C-l) no limit
(C-2) 60 pCi/m2s
(C-3) 20 pCi/m2s
(C-4) 6 pCi/m2s
(C-5) 2 pCi/m2s
(c) Passive, engineered, below-grade controls designed for
1,000 years with radon emission limits of:
(D-2) 60 pCi/m2s
(D-3) 20 pCi/m2s
(D-4) 6 pCi/m2s
(D-5) 2 pCi/m2s
(d) Different standards for sites in remote areas.
EPA selected alternative C-3 with an admonishment to regulatory
agencies that alternative D-3 should be seriously considered for any
new tailings impoundments.
5. The following are the major points raised in public comments on
the proposed standards and EPA's resolution of them:
(a) Estimates of health risk from radon
Some commenters thought EPA's estimates were too high. We
reviewed our risk estimates and concluded the original estimates
are reasonable. In any case, uncertainties in these risk
estimates would not lead to different standards.
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(b) Significance of risk from radon from tailings piles
Several commenters argued that EPA failed to demonstrate that
the risks associated with radon emissions from tailings are
significant and compared the risk from radon from tailings to
that from other radon sources and from other causes of deaths,
such as automobile and home accidents. We do not believe these
other risks are relevant to this rulemaking. Both the
individual and the population risks from radon from tailings are
sufficient for EPA to consider controlling radon from tailings.
(c) Standards based on current populations
Some commenters suggested that less restrictive standards are
appropriate for sites that are in currently sparsely populated
areas. Other commenters raised the question of the fairness, or
equity, of protecting a few people less just because of where
they live. We concluded that relaxed standards for "remote"
sites are not feasible based on a demographic basis, i.e., a
remote site is not readily defined, on the lack of clear
delineation between existing sites, and on the unpredictability
of future populations. In addition, the potential cost savings
do not outweigh foregone benefits.
(d) Passive vs. institutional controls
Comments on this issue ranged from strong support of passive
stabilization for thousands of years to protection for only a
few decades with institutional controls. We concluded that
long-term protection should be provided through the use of
passive control methods because the legislative history of the
Act supports this approach, and because the incremental cost of
passive control are well justified in terms of incremental
benefits.
(e) Radon emission limit after closure
Commenters who thought the proposed 20 pCi/m2s limit too high
objected primarily to the high residual risk to individuals
living very close to a pile. This risk is about 1 in 1,000.
Commenters who thought the proposed limit too restrictive
contended the cost was too high in view of the small
contribution radon from tailings makes to total radon and their
view that EPA had overestimated the risk. We selected 20 pCi/m2s
because higher values will not achieve the objectives of the
rulemaking, and these objectives can be cost-effectively
achieved by such a limit. We did not select a lower value since
this limit is already technology forcing, and uncertainty of
predictably attaining lower limits is too great to justify the
benefits that will be achieved.
(f) Relationship to the Clean Air Act requirements
A few commenters argued that EPA is required to provide suitable
health protection under both UMTRCA and the Clean Air Act (CAA)
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and that EPA had not done so in the proposed standards. EPA
therefore considered emissions of radionuclides from tailings
under both UMTRCA and CAA. For the operational period, EPA has
not sufficiently analyzed work practice and tailings management
methods to assure radon emissions will be minimized. Therefore,
EPA is issuing an Advance Notice of Proposed Rulemaking under
the CAA for consideration of the control of radon emissions from
tailings during the mill's operating period. For the post-
closure period, we concluded that these standards fulfilled all
requirements under both UMTRCA and CAA.
(g) Radon concentration vs. emission rate limits
A few commenters believed a radon concentration limit in air
where people are exposed is preferable to an emission limit.
EPA rejected this approach since it could be satisfied by
dispersion, rather than control, through selection of boundaries
and installation of fences, both institutional controls that
would not provide long-term protection.
(h) Cleanup standards
Some commenters argued there is no need to clean up contaminated
land that is to be turned over to a government agency, since the
government can provide any needed protection. We concluded land
included as part of the disposal site should be cleaned up to
satisfy the same objectives of this rulemaking that apply to
disposal of tailings.
(i) Choice of liner material-protection of groundwater quality
Some commenters stated that no liner technology, synthetic or
clay, is capable of achieving the goal of the primary
groundwater protection standard, i.e., no seepage of hazardous
constituents into the groundwater or the soil underlying the
tailings impoundment. During its SWDA rulemaking, EPA reviewed
this matter in detail and decided to require a liner that is
capable of preventing migration of wastes into the ground and
water. Commenters did not establish that tailings impoundments
are sufficiently different from impoundments controlled under
SWDA to justify departures from SWDA rules.
(j) Secondary standard-protection of groundwater quality
Many commenters argued that past practice at uranium mill sites
has led to groundwater contamination at virtually every site
and, under the proposed standards, this will lead to a
requirement for EPA concurrence on alternate standards at most
of these sites. They argued that this amounts to duplicative
licensing. We have modified the standard to authorize the
regulatory agency to issue alternate limits when the secondary
standards will be satisfied within the site boundary or 500
meters, whichever is less.
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6. The following Federal Agencies have commented on the Draft
Environmental Impact Statement:
Department of Energy
Department of Health and Human Services
Department of the Interior
Nuclear Regulatory Commission
Tennessee Valley Authority
7. This Final Environmental Impact Statement was made available to
the public in October 1983. Single copies are available while
quantities last from:
U.S. Environmental Protection Agency
Director, Criteria and Standards Division
Office of Radiation Programs, (ANR-460)
Washington, D.C. 20460
or the National Technical Information Service, 5285 Port Royal Road,
Springfield, Va., 22161.
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Chapter 1: INTRODUCTION
In the Uranium Mill Tailings Radiation Control Act of 1978, Public
Law 95-604, 42 USC 7901 (henceforth designated as "the Act"), Congress
directed the Environmental Protection Agency (EPA) to "promulgate
standards of general application for the protection of the public
health, safety, and the environment from radiological and non-
radiological hazards associated with the processing and with the
possession, transfer, and disposal of byproduct material...at sites at
which ores are processed primarily for their source material content or
which are used for the disposal of such byproduct material." The term
'byproduct material' as defined by the Act means, for these sites,
"...the tailings or wastes produced by the extraction or concentration
of uranium or thorium from any ore processed primarily for its source
material content." The Act assigns the responsibility for imple-
mentation and enforcement of these standards to the Nuclear Regulatory
Commission and its Agreement States through their licensing activities.
The Act also requires EPA to promulgate standards for cleanup and
disposal of uranium tailings at inactive processing sites. EPA issued
standards for cleanup of contaminated open lands and buildings and for
disposal of tailings at inactive uranium processing sites on January 5,
1983 (48 FR 590).
1.1 Scope of the Standards
Standards are required for the control of effluents and emissions
from the tailings both during milling operations and for the final
disposal of tailings. The Act specifies that standards for non-
radioactive hazards must provide protection of human health and the
environment consistent with applicable standards established under
Subtitle C of the Solid Waste Disposal Act, as amended.
The sites that are affected by these standards currently include
about two dozen conventional uranium mills and 4 heap-leaching
locations; these sites are licensed by NRC or its Agreement States.
Approximately 86 percent of all uranium produced in 1980 was produced
from ore mined in underground or open-pit mines and processed in
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conventional uranium mills. Solution mining contributed 8 percent, and
about 5 percent came from heap-leach plants, mine water extraction and
conventional milling of low-grade stockpiles of ore.
Only conventional uranium mills, heap-leaching operations, and
above-ground wastes from solution mining are covered by these proposed
standards. Phosphoric acid byproduct operations are not included
because these operations do not process ore primarily for its source
material (uranium or thorium) content. The Act was directed primarily
toward the solution of environmental problems from the radioactive
tailings piles resulting from conventional milling operations.
A number of environmental standards already apply to tailings.
EPA promulgated 40 CFR Part 190, Environmental Radiation Protection
Standards for Uranium Fuel Cycle Operations, on January 13, 1977 (42 FR
2858). These standards specify the radiation levels below which normal
operations of the uranium fuel cycle must operate. Radiation exposures
due to environmental release of and from uranium byproduct material are
covered by these standards, with the exception of emissions of radon
and its decay products. Under the Clean Water Act, EPA issued effluent
limitations guidelines on December 3, 1982, for new source performance
standards for wastewater discharges from the mining and dressing of
uranium, radium, and vanadium ores (40 CRF 440, 47 FR 54598).
Discharges of both radioactive and nonradioactive materials to surfeice
waters from uranium byproduct materials are covered by these effluent
guidelines. Because these guidelines and proposals have already been
issued, we have not evaluated control measures for discharges to
surface water in this DEIS.
EPA promulgated 40 CFR Part 261, Subpart FGroundwater
Protection, on July 26, 1982 (47 FR 32274) under the Solid Waste
Disposal Act (SWDA), as amended by the Resource Recovery and
Conservation Act. The Act requires that standards for nonradioactive
hazards from uranium byproduct materials be consistent with standards
promulgated under SWDA for such hazards. Also, the Act requires that
the NRG establish general requirements which are, to the maximum extent
practicable, at least comparable to requirements applicable to the
possession, transfer, and disposal of similar hazardous material
regulated by EPA under the SWDA. NRG Agreement States are required by
the Act to adopt standards which are equivalent, to the maximum extent
practicable, or more stringent than, standards adopted and enforced by
the NRC. These responsibilities must be carried out by the NRC whether
or not EPA promulgates standards for groundwater protection. We have
included groundwater protection in this analysis to determine whether
or not the SWDA standards should be supplemented or modified by the
standards promulgated under the Act.
Thorium mill tailings are included in the definition of byproduct
material and must be licensed by the NRC or an Agreement State under the
same provisions of the Act as uranium mill tailings. However, the only
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thorium currently being recovered from ore is as a secondary product at
the W.R. Grace Co. facility near Chattanooga. There are also thorium
byproduct materials at four inactive sites located in New Jersey,
Illinois, Ohio, and West Virginia. The current demand for thorium is
small, and there appears to be little growth potential. The two major
uses of thorium are as a source material in nuclear applications and as a
thin ceramic lantern mantle that gives off a bright light. Neither of
these uses is expected to increase significantly in the next few years.
There are a few other licensed sites contaminated with uranium and
thorium and their decay products. Two or three of these sites may
contain uranium and thorium byproduct material as defined by the Act.
These sites are not included in this analysis, because the quantities of
material are relatively small and would not affect the overall analysis.
There are now about 175 million tons of tailings at the licensed
mill sites. Of these, about 56 million tons were generated under
government contracts. Most of these 56 million tons of tailings are not
separated from other tailings and are commonly designated "commingled"
tailings. The Department of Energy (DOE) has recently issued a report on
commingled tailings in response to Congressional concern over whether the
government or industry should pay for disposal of these tailings
(DOE82). The analysis for these standards is not significantly affected
by this issue. However, government sharing of costs would lead to a
lesser impact on the industry, as reflected, for example, in fewer mills
closing under certain alternatives for environmental requirements. Thus,
government sharing of costs could permit application of more stringent
standards. Our economic analysis assumes the total costs of compliance
will be borne by the industry. Any government sharing of disposal costs
would thus improve industry's economic position compared to that
projected in this analysis.
1.2 Contents of the Analysis
In this document, we examine (1) alternative standards for disposal
of uranium mill tailings, and (2) alternative standards for control of
environmental releases from tailings during the operational phase of
uranium mills. Both radioactive and nonradioactive releases are
considered. Potential effects of tailings on health are estimated, along
with the effectiveness and costs of different control approaches.
In Chapter 2 we briefly describe the uranium industry and summarize
projections of uranium production to the year 2000. Chapter 3 contains a
description of the uranium tailings themselves, with emphasis on their
hazardous components and releases of contaminants to the environment. A
model site and tailings pile is described in Chapter 4 for use in
carrying out the analysis of benefits and costs of control. In Chapter 5,
pathways through which radioactive and hazardous materials may cause
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exposure to man are examined. Based on the information in Chapters 4
and 5, potential health effects are estimated on local, regional, and
national populations in Chapter 6. Chapter 7 contains a review of
emission control measures for the operating period of the mill and
estimates of the effectiveness and costs of these systems.
In Chapter 8 we examine the efficacy and longevity of the principal
methods for disposal of tailings. Chapter 9 contains cost estimates for
representative disposal methods for existing and future tailings at model
sites. In Chapter 10 we analyze costs and benefits for tailings disposal
standards options.
1-4
-------
REFERENCES
DOE82 Department of Energy, "Commingled Uranium Tailings Study,"
DOE/DP-0011, June 1982.
1-5
-------
Chapter 2: THE URANIUM MILLING INDUSTRY^)
2.1 History of the Uranium Milling Industry
The uranium milling industry has undergone considerable change in
the last 35 years, as uranium developed from a commodity of minor
commercial use to one vital for nuclear weapons and for producing
electrical energy. To meet military needs in the early 1940"s, uranium
ore was obtained from the rich pitchblendes (greater than 10 percent
U30g equivalent) of the Belgian Congo and the Great Bear Lake
deposits in Canada, supplemented by production from a few small mines
in the Colorado Plateau area. These high-grade ores and concentrates
were refined by an ether extraction technique adapted from analytical
chemistry procedures. The processes used for low-grade ores were
relatively crude and reflected little change from methods used at the
turn of the century. Milling costs were high and uranium recovery was
relatively inefficient.
After the Atomic Energy Act was passed in 1946, strong emphasis
was placed on the discovery and development of new sources of uranium
and on development of improved processing techniques. The Atomic
Energy Commission (AEC) purchased 3 x ICH MT^) of U30g between
1948 and 1970, with approximately 55 percent from domestic sources.
Table 2-1 illustrates the size of the industry from 1948 to the
present. During the peak production years of 1960 to 1962, there were
up to 26 operating mills (excluding plants producing byproduct uranium
from phosphates) with an annual production rate exceeding 1.5 x 104 MT
of U30g from 7 x 10" MT of ore (average grade of 0.21 percent).
^1'Much of the information in this chapter is based on the Nuclear
Regulatory Commission's "Final Generic Environmental Impact Statement
on Uranium Milling," NRC80, Chapters 2 and 3 and Appendix B. Material
from other sources is separately referenced.
(^Metric ton (MT) or 1000 kg, equivalent to 2200 pounds or 1.1 short
tons (ST).
2-1
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Table 2-1. Uranium Production^)
Year
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
U3°8
(1000 MT)
0.1
0.2
0.4
0.7
0.8
1.1
1.5
2.5
5.4
7.7
11.3
14.7
16.0
15.7
15.4
12.9
10.7
Year
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
U3°8
(1000 MT)
9.5
9.6
10.2
11.2
10.5
11.7
11.1
11.7
12.0
10.5
10.5
11.6
13.6
16.8
17.0
19.8
17.5
(^Adapted from DOE82. Includes 11303 production obtained
by mine water, heap-leaching, solution mining, or as a by-
product of another activity.
Reduced military requirements and the slow development of
commercial nulcear power resulted in fewer operating mills and lower
uranium production in the period from 1963 to 1970. About 3.4 x 1()5
MT of 0303 had been produced by the end of 1981, resulting in about:
1.8 x 10^ MT of tailings. Approximately 15 percent of the tailings
are at 23 inactive mill sites covered under Title I of the Act, and the
balance (85 percent or about 1.5 x 10^ MT) is located at currently
active mill sites considered by this analysis.
Mill capacities in 1978 ranged from 360 to 6300 MT of ore per day,
with an average capacity of 1800 MT per day. In early 1978, 19 mills
were operating; this increased to 21 in early 1980. At the end of
1982, there were 14 mills in operation.
2.2 Conventional Milling Processes
In the uranium milling process, uranium is extracted from the
crude ore and concentrated into an intermediate semirefined product
called "yellowcake." The remainder of the material, essentially the
total mass for low-grade ores, is disposed of in mill tailings piles.
Most of the radioactivity associated with the ore goes ho the tailings
2-2
-------
pile. This radioactivity consists primarily of radium and its decay
products, which are not removed with the uranium during milling.
Historically, about 90 percent or more of yellowcake has been
produced by conventional mills. In 1980 about 15 percent of yellowcake
was produced from solution mining, mine water, copper dump-leach
liquor, or wet process phosphoric acid effluents.
There are two basic conventional processes for removing uranium
from ore: the acid-leach process and the alkaline-leach process.
About 80 percent of the current milling capacity uses a sulfuric acid
leach process. Since it is not economical to leach those ores having a
high alkaline content with acid, these ores are leached with an
alkaline solution. Several mills include circuits for both processes.
Primary emphasis is placed on the acid-leach process in this analysis.
Comments on the alkaline process are limited to differences between the
processes that are pertinent to their environmental releases.
Figure 2-1 is a flow diagram of the process at a conventional mill
leading up to the generation of waste tailings solids and liquids. In
a conventional mill, the first step is grinding the ore to a size
suitable for leaching out the uranium. Ore characteristics and the
leaching process dictate the degree to which ore must be ground. For
the acid leaching of sandstone ores, the ore is ground to the natural
grain size.
Alkaline leaching requires much finer grinding. The ore is
conveyed from the crushing circuit to the grinding circuit by belt
feeders. Samples are taken at points between the crushing and grinding
circuit for routine laboratory analysis. Rod and ball mills are
usually used to grind the ore to approximately 28 mesh (600 microns)
for the acid-leach process or to 200 mesh (74 microns) for the alkaline-
leach process. The ores are wet ground (water added) with the aid of
classifiers, thickeners, cyclones, or screens that size the ore and
return coarser particles for further grinding, resulting in a pulp
density of 50 to 65 percent solids. Water consumption is reduced by
recirculating mill solutions (e.g., by recycling the clarified effluent
from the grinding circuit thickener.) Wet milling can be used in place
of both the crushing and fine grinding. This process uses a rotating
steel cylinder. The tumbling action of the lifters, large pieces of
ore, and a small charge of 8- to 10-centimeter steel balls are used to
break down the ore.
After grinding, the ore is leached to remove uranium. In 1976,
the acid-leach process was used by 82 percent of the industry. Acid
leaching is preferred for ores with 12 percent or less limestone.
Those with more than 12 percent limestone require excessive quantities
of acid and, for economic reasons, are best extracted by alkaline
leaching. The sulphuric-acid leaching process is compatible with
several concentration and purification processes, including ion
exchange, solvent extraction, or a combination of both processes. The
2-3
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Ore
Crushing and
Grinding
Water
Sulfuric
Acid and
*
Sodium Chlorate
Wet
Grinding
Leaching
Tailings Pond
(Tailings sand and slimes,
liquid wastes)
Flocculant
Water
Countercurrent
Decantation
(CCD)
Barren raffinate
Pregnant Liquor
Solvent
Extraction
Further
Processing
Figure 2-1. Flow Diagram of the Generation of Uranium Tailings
Solids and Liquids from the Acid-Leach Process.
2-4
-------
slurry from the grinding operation (50 to 65 percent solids) is
discharged into the leaching circuit, which consists of several tanks
in series. Sulfuric acid is continuously added to maintain the pH
between 0.5 and 2.0. For U.S. ores treated exclusively for uranium
extraction, acid consumption ranges from 20 to 60 kilograms of sulfuric
acid per MT (40 to 120 Ibs/tons) of ore.
An oxidant, either NaCK>3 or MnC>2, is also continuously added
with the sulfuric acid to oxidize tetravalent uranium in the ore to
hexavalent uranium, which is more soluble. Iron must be present in the
solution for NaClO-j or MnC>2 to be an effective oxidant for tetrava-
lent uranium. Either oxidant acts to oxidize ferrous iron to the
ferric state, and the ferric iron in turn oxidizes the uranium. Ore
leaching proceeds at atmospheric pressure and a little above room
temperature. Most of the uranium in the ore is dissolved, as well as
some other materials, such as some uranium daughter products, iron, and
aluminum. The residence time in the leaching tank is about 7 hours.
After ore leaching is completed, the "pregnant" leach liquor
containing the dissolved uranium is removed from the tailings solids.
This is carried out in a countercurrent decantation (CCD) circuit. In
this operation, the slurry is first sent to hydrocyclones (liquid
cyclone separators) that separate the coarse sand fraction as an
underflow, and the sand fraction is subsequently washed in a series of
classifiers. The overflows from the classifier and the hydrocyclone
are combined, and the slimes are washed. Flocculants are added to
promote settling of the suspended solids. The solids are washed with
fresh water and recycled (barren) raffinate from the solvent extraction
circuit. After thorough washing, the sands and slimes are pumped as a
slurry to the tailings pond. After solid-liquid separation in the CCD
circuit, the leach solution is sent to the solvent extraction and
further processing.
The acid-leach and alkaline-leach processes have considerable
chemical differences, and the ore is milled to a smaller size for
carbonate leaching. However, this does not appear to cause any
significant differences in environmental releases. A larger fraction
of the thorium-230 is solubilized in the acid-leach process than in the
carbonate-leach process, but the thorium is precipitated in the
tailings pond when the acidity is reduced. Thus, except in the early
stages of liquid discharges before the solution is neutralized, this
difference is negligible.
2.3 Waste Management at Uranium Mills
During the early history of uranium milling, tailings liquids were
discharged to surface waters. As late as 1975, Sears (Se75) noted that
two mills were discharging liquid effluents to surface waters. In
1981, only the Uravan, Colorado, mill was still discharging treated
liquid effluents directly to surface waters.
2-5
-------
The alternative to discharging liquid effluent is the impoundment
of both solids and liquids in a tailings pond. Initially, tailings
ponds were located near the mill based on economics and accessibility.
The pond areas were formed from dikes built with tailings sands or from
soil and rock from the pond area. As the pond was filled, the dikes
were raised with mill tailings sands, separated from the slurried waste
with cyclone separators. This design was used for most of the inactive
tailings piles (EPA80) and many of the older active piles. Current NRC
regulatory practice discourages the use of tailings for dike materials
(NRCSOa, NRC77). However, this practice still continues for many of
the existing active sites (e.g., Homestake and Kerr-McGee near Grants,
New Mexico). Although the ponds were generally designed as evaporation
ponds, there are instances where seepage has equaled or exceeded the
evaporation rate (Ka75, EPA75). There are still seepage releases to
groundwater and probably to surface water at several mills (See Chapter 3.)
It was not until 1976 that the NRC made a concerted effort to
control uranium mill tailings. Performance objectives were issued in
1977 and again in revised form in Regulatory Guide 3.11 (NRC77). These
objectives provide location criteria, require the elimination of wind-
blown tailings, and require reducing post-reclamation gamma exposure
to offsite areas to essentially background levels. Furthermore, this
guidance discourages the use of upstream dam construction techniques
(the dam is raised in stages on the tailings material) and specifies
minimizing seepage from the tailings ponds by the use of clay or
artificial liners. The guidance requires designs that improve the
tailings stability and reduce the seepage from tailings disposal
systems.
EPA collected information on active mills and waste disposal
practices in 1978 (Ja79). Some of the notable conclusions are:
Tailings and effluent disposal methods practiced in
the United States generally consist of impoundment of
mill wastes in unlined ponds. This disposal method
is not state-of-the-art. It is usually inadequate,
since up to 85 percent of the liquid effluent
impounded may be lost by seepage and, subsequently,
pollute groundwater.
Treatment of mill effluents to reduce pollutant
levels and/or to recover uranium or uranium
byproducts is seldom practiced.
Treatment and discharge as a method of effluent
disposal is practiced at only one of the currently
operating, conventional uranium mills in the United
States.
2-6
-------
o All effluent streams from the mills sampled in this
study, were they to be discharged, would require
treatment to comply with effluent limitation
guidelines for point-source discharges. Currently,
none of the streams sampled is being discharged.
« Unlined ponds, properly located, may be
environmentally acceptable as a means of mill waste
disposal under some local soil and hydrogeological
conditions, because some native soils can mitigate
the adverse effects of seepage, by exhibiting low
permeabilities, thereby reducing seepage rates,
and/or possessing characteristics that favor the
uptake and fixation of seepage-borne contaminants.
Total dependence on native soils above the water
table for purification of seepage from unlined ponds
is not technically sound, since uptake capacity is
both unpredictable and time dependent, and anions
such as sulfate, chloride, and nitrate are not
removed.
Lined ponds represent a recent advance in
state-of-the-art technology for containment of
millwastes, since they afford a greater degree of
seepage prevention than unlined ponds and ensure
protection of groundwater.
Clay or treated clay liners are preferred for lining
ponds containing mill tailings wastes.
After a mill ceases operations, the tailings impoundment will
slowly dry up over a few years. In such a condition, tailings are
continually vulnerable to spreading by wind and water erosion or by
such uses as for fill around buildings. Some of these dry tailings
piles have been the subject of a variety of stabilization schemes
involving earth cover placement and revegetation. Stabilization
attempts to date have not been generally successful, and none has
been designed for the long term.
2.4 Uranium Recovery by Heap-Leaching
Most mills are not designed to process uranium ores of less than
0.04 percent I^Og. However, uranium is often extracted from such
ores by a heap-leach process. Heap-leaching is also used when the ore
body is small or situated far from the milling facilities. Shipping a
high-grade solution or a crude bulk precipitate (the product of heap-
leaching) to the mill is less expensive than hauling low-grade ore to
the mill.
2-7
-------
Uranium recovery by heap-leaching has been used for low-grade
(0.01-0.03 percent ^303) sandstone uranium ores. The ore to be
heap leached is typically placed upon a gently sloped impermeable pad
and saturated from above with a leaching solution. Pad impermeability
is generally achieved by laying down a plastic sheeting, but other
materials such as asphalt and concrete have been used on a pilot
scale. Just above the pad, a network of pipes and drain tiles is put
in place to collect the leachate that percolates to the bottom of the
ore piles. The percolated leachate is collected and recirculated until
the uranium concentration in the solution reaches 0.06 to 0.1 grams of
U30s/per liter. At this point the leachate is sent to resin
ion-exchange columns for extraction of the uranium.
If mine water is used, uranium already in the water, as well as
that extracted from the heap leach, is recovered. The most commonly
used leach reagents are sulfuric acid and ammonium carbonate. In an
efficient operation about 80 percent of the uranium will be extracted
from the ore. Heap-leach piles are commonly about 100 meters long, 6
to 8 meters high, with beams separating the piles in segments about 20
meters wide. After completion of operations, the leached ore may be
limed, graded, and stabilized by covering and revegetating the
surface. A state-of-the-art heap-leaching operation is described in
detail in a recent document (NRC78b).
2.5 Currently Licensed Uranium Mills
There were 27 licensed uranium mills, of which 14 were operating,
in the United States as of December 31, 1982. These mills are listed
in Table 2-2. Edgemont, South Dakota, which is not an operating mill,
has been included since it is licensed and has been excluded from the
designated inactive sites (EPA80). The Tennessee Valley Authority
(TVA) owns the site and had planned to reactivate the mill. However,
TVA is now planning to clean up the site and move the milling
operation. The Ray Point, Texas, site has also been shut down for
several years. The Bokum mill in New Mexico has been constructed and
licensed, but it has never started operation. The data in Table 3-1
summarizes the operational features of the mills with significant
tailings (NRCbOa and Ja79, supplemented with private communications).
2.6 Future Uranium Supply and Demand
Uranium is required for both the nuclear power industry and
defense activities. Projections of uranium needs for nuclear power can
be reasonably accurate for the next 20 years, since 10 to 15 years is
required from the decision to build a reactor until it is producing
power. Power reactors ordered now will not be producing power until
the 1990's. Uranium needs for defense purposes are much more difficult
to project since they are greatly influenced by political considera-
tions. However, it is likely that nuclear power needs will greatly
2-8
-------
Table 2-2. Currently Licensed U.S. Uranium Mills(a)
Location Owner
OPERATING MILLS
Colorado
Canon City Cotter Corporation
New Mexico
Milan Homestake Mining
Ambrosia Lake Kerr-McGee Nuclear
Texas
Panna Maria Chevron Resources
Utah
Blanding Energy Fuels Nuclear
La Sal Rio Algom Corporation
Moab Atlas Minerals
Wyoming
Gas Hills Pathfinder Mines
Gas Hills Union Carbide
Powder River Rocky Mountain Energy
Powder River Exxon Minerals
Red Desert Minerals Exploration Co.
Shirley Basin Pathfinder Mines
Shirley Basin Petrotomics
SHUT-DOWN MILLS
Colorado
Uravan Union Carbide Corporation
New Mexico
Bluewater Anaconda Minerals Company
Seboyeta Sohio-Reserve
Church Rock United Nuclear
Marquez Bokum Resources
South Dakota
Edgemont Tennessee Valley Authority
Texas
Falls City Conoco-Pioneer Nuclear
Ray Point Exxon (Susquehanna-Western)
(continued)
See footnote at end of table.
2-9
-------
Table 2-2. Currently Licensed U.S. Uranium Mills(a)
(Continued)
Location Owner
SHUT-DOWN MILLS (Continued)
Utah
Hanksville Plateau Resources
Washington
Ford Dawn Mining Company
Wellpinit Western Nuclear
Wyoming
Jeffrey City Western Nuclear, Inc.
Gas Hills Federal-American Partners
'a'As of September 1982.
outstrip defense needs during the next 20 years. Thus, only demand for
the nuclear power industry is projected in this analysis.
Projections of uranium demand are made for two cases. A "high"
case is based on the mid-range nuclear generating capacity scenario of
the U.S. Department of Energy (DOE) (DOE81). A "low" case is based on
the DOE installed reactor capacity projection identified as the firm
nuclear base scenario (DOE81). These estimates are presented in Table
2-3.
Yellowcake requirements are calculated by using the NRC
assumptions given in their generic EIS for uranium milling (NRC80a). A
conversion factor of 185 MT U30g in yellowcake per GWe-year is
used. This assumes a 3 percent fuel enrichment, 0.20 percent tails
assay, and an effective average nuclear generating plant capacity
factor of 75 percent.
Conventional mills (as described in Section 2.2) are not assumed
to satisfy the total demand for uranium. About 80 percent of the
present uranium demand is supplied by conventional milling. This
fraction is expected to vary during the next 20 years. The fraction of
uranium assumed to be supplied by conventional milling is listed in
Table 2-3 (NRCSOa). The demand for conventional milling production,
estimated by multiplying the total uranium demand by this fraction, is
presented in Table 2-3 for the 20-year period 1980 to 2000.
Another important factor in projecting demand for uranium is the
inventory held by utilities, reactor manufacturers, and fuel
fabricators. A normal inventory level is about a 1-year level of
consumption. Currently an abnormally large inventory of uranium is
2-10
-------
Table 2-3. Projection of Industry Demand and Production for
Uranium Yellowcake
1983-2000
Year
Industry Demand
103 MT 1)303
Conventional Production
103 MT U308
1983
1985
1990
1995
2000
12.7
17.1
18.1
20.4
26.9
7.5
7.3
9.5
10.5
11.3
Source: Appendix B, Regulatory Impact Analysis of Final Active Mill
Tailings Standard, EPA 520/1-83-010, 1983.
being held. It is assumed that this inventory will be reduced to more
normal levels over a 6-year period. This inventory reduction wil]
result in less uranium production.
The total quantities of tailings produced by conventional nilling
from 1983 to 2000 is projected to be about 175 million tons. (Thp
conversion factor used is 1,075 MT of tailings per MT of l^Og as
yellowcake (NRCSOa) and assumes 0.1 percent uranium in ore and a 93
percent recovery rate during milling.
2-11
-------
REFERENCES
DOE81 Department of Energy, "1980 Annual Report to Congress, Volume
3: Forecasts," DOE/EIS-0173(80)/3, March 1981.
DOE82 Department of Energy, "Statistical Data of the Uranium
Industry," GJ-100(82), Grand Junction Area Office, Colo.
EPA75 Environmental Protection Agency, 1975, "Water Quality Impacts
of Uranium Mining and Milling Activities in the Grants Mineral
Belt, New Mexico," EPA Region VI, Dallas, Texas, EPA
906/9-75-002.
EPA80 Environmental Protection Agency, Office of Radiation Programs,
1980, "Draft Environmental Impact Statement for Remedial
Action Standards for Inactive Uranium Processing Sites,
40 CFR 192," EPA 520/4-80-011, EPA, Washington, D.C..
Ja79 Jackson B., Coleman W., Murray C., and Scinto L., 1979,
"Environmental Study on Uranium Mills," TRW Inc. contract
with the U.S. Environmental Protection Agency, Contract
No. 68-03-2560.
Ka75 Kaufmann, R.E., G.G. Eadie, C.R. Russell, 1975, "Summary of
Groundwater Quality Impacts of Uranium Mining and Milling in
the Grants Mineral Belt, New Mexico," Technical Note
ORP/LV-75-4, U.S. Environmental Protection Agency, Office of
Radiation Programs, Las Vegas Facility, Las Vegas, Nevada.
NRC77 Nuclear Regulatory Commission, 1977, "Design, Construction and
Inspection of Embankment Retention Systems for Uranium Mills,"
Regulatory Guide 3.11, NRC, Washington, D.C.
NRC78a Nuclear Regulatory Commission, 1978, "Final Environmental
Statement Related to the Operation of the Highland Uranium
Solution Mining Project, Exxon Minerals Company, U.S.A.,"
NUREG-0489, NRC, Washington, D.C.
NRC78b Nuclear Regulatory Commission, 1978, "Final Environmental
Statement Related to the Sweetwater Uranium Project, Minerals
Exploration Company," NUREG-0505, NRC, Washington, D.C.
NRCSOa Nuclear Regulatory Commission, 1980, "Final Generic
Environmental Impact Statement on Uranium Milling,"
NUREG-0706, Vol. 1, 2, 3, NRC, Washington, D.C.
NRCSOb Nuclear Regulatory Commission, 1980, "Radiological Effluent
and Environmental Monitoring at Uranium Mills," Regulatory
Guide 4.14, NRC, Washington, D.C.
2-12
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Chapter 3: ENVIRONMENTAL RELEASES FROM URANIUM MILLING WASTES
In this chapter, we discuss the composition of uranium mill
tailings solids (sands and slimes), tailings pond liquids, and heap-
leaching wastes. We also discuss the extent to which radioactive
elements, toxic substances, and other contaminants from these wastes
have been released to the environment through human activity and/or by
natural causes. We defer to Chapter 4 the development of projections
of releases from a model site.
3.1 Composition of Tailings Solids and Pond Liquids
Uranium mill tailings solids and pond liquids contain essentially
all the radioactive and toxic elements of the original uranium ore,
except for about 90 percent of the uranium which is extracted during
the milling process. The tailings also contain a variety of chemicals
used as part of the extraction process described in the previous
chapter.
3.1.1 Radioactivity in Tailings
Most of the uranium recovered from ore is uranium-238, a
radioactive isotope that decays, over billions of years, to become
lead-206, a stable (i.e., nonradioactive) element. The lengthy decay
process includes a number of intermediate stages (called decay
products). These, too, are radioactive. Figure 3-1 traces the steps
in this decay process. Since the ore was formed millions of years ago,
uranium has continued to decay and an inventory of all of these decay
products has built up. There are also radioactive materials from two
other decay processes in uranium ore, the uranium-235 series and the
thorium-232 series, but these are present in much smaller amounts, and
we have concluded that it is not necessary to include them in our
analysis (see Section 4.1).
When ore is processed most of the uranium is removed, and most of
the subsequent decay products become part of the tailings. As a
result, thorium-230 is the radionuclide with the longest half-life'D
^1'A half-life is the time it takes for a given quantity of a
radioactive isotope to decay to half of that quantity. Figure 3-1
shows the half-lives of the members of the uranium-238 decay series.
3-1
-------
(ELEMENT)
(HALF-LIFE)
(PARTICLE OR
RAY EMITTED
I
Polomum-218
3.1 minutes
alpha
I
I
Lead-214
27 minutes
Bismuth-214
20 minutes
X
beta,
/ gamma
Polomum-214
.00016
/ beta,
gamma
alp
gan
Lead-
22 ye
seconds
ha,
ima
\
210
ars
Bismuth-210
5.0 days
X
/beta
/ gamma
Polonium-210
140 days
>beta i u
' alpha,
Lead-206
stable
Figure 3-1. The Uranium-238 Decay Series.
3-2
-------
of significance in tailings. Thorium decays to produce radium-226.
Radium decays in turn to produce radon-222, a radioactive gas. Because
radon gas is chemically inert, some of it escapes from the tailings
particles in which it is produced, diffuses to the pile surface, and is
carried away into the atmosphere. Airborne radon produces a series of
short half-life decay products that are hazardous if inhaled. If the
radon does not escape from the tailings, its decay products remain
there, and the gamma radiation they produce may increase the hazard to
people near tailings.
Since thorium-230 has a much longer half-life than its two
immediate decay products, radium and radon, the amounts of
radioactivity from radium and radon remain the same as that from
thorium. The amount of radon released from a tailings pile, therefore,
remains effectively constant on a year-to-year basis for many thousands
of years, decreasing only as the thorium, with its 77,000-year
half-life, decreases.
In Figure 3-2 we show how the yearly production rate of radon in a
tailings pile will decrease with time. It falls to 10 percent of its
initial value in about 265,000 years. This time scale illustrates the
long-term nature of most of the significant radiological hazards
associated with uranium mill tailings.
cfl 0)
H 4J
4J efl
H pi
3
M a
o
LW -H
O 4-1
O
4-J 3
C Td
0) O
O M
M PH
(U
PH
100
75
50
25
0
1
1
10
100
1,000 10,000
Time (years)
100,000 1,000,000
Figure 3-2. Radon Production in a Tailings Pile.
3-3
-------
When discharged from the mill, tailings have both solid and liquid
components. The solid portion of tailings is composed of particles
ranging in size from coarse sands to fine slimes. In both the acid
process and the alkaline process, the residual uranium and radium
content of slimes is about twice that of sands. In the acid-leach
process, about 95 percent of the thorium in the original ore remains
with the solid tailings, while the balance is dissolved in the tailings
liquids. Less than one percent of the radium is dissolved in the
liquids. In the alkaline process, less than one percent of both the
thorium and radium is dissolved in the tailings liquids.
In Table 3-1 we show, for licensed uranium mills (as of January
1980) with tailings piles, the quantity of tailings, area of the pile,
average ore grade, and estimated average radium content in the solids.
Also included are the estimated radon emissions from each pile and
other factors relevant to emissions from tailings piles. Tailings: at
most future uranium mills are expected to fall within the range of
values shown in Table 3-1. The ore grade at the different mills
typically varies from 0.15 percent to 0.3 percent uranium, and the
radium concentration (and presumably other radionuclides in the
uranium-238 decay series) varies from 200 pCi/g to 900 pCi/g. This
should be compared with the background radium concentration in average
soil from 0.2 pCi/g to 3 pCi/g.
In Table 3-2 we have compiled selected available data on
radioactivity and toxic element levels in tailings pond liquids. Many
levels are more than two orders of magnitude above EPA drinking water
standards (these are listed in Table 3-4), but large variations occur
among the mills. The wide variation is caused by the characteristics
of uranium ore and the process (i.e., acid- versus alkaline-leach).
Again, the values in Table 3-2 are expected to characterize liquid
wastes at future uranium mills.
3.1.2 Toxic Elements and Other Chemicals in Tailings
A number of toxic materials from ore or from chemicals used in
processing have been found in both liquid and solid uranium mill wastes
(Se75, FB76-78). The contaminants present depend on the ore source and
the type of processing. In Table 3-3, we indicate the average concen-
tration of 15 elements commonly found in the solids of 19 inactive
tailings piles (MaSla). The concentrations of these elements show wide
variations among the piles, as well as wide variations above and below
values for "typical soil." This data is believed to be representative
of tailings at active mills as well as tailings to be generated at
future mills. In Table 3-2, we showed the concentration of toxic
substances and other chemicals in tailings pond liquids at existing
uranium mills.
3.2 Routine Environmental Releases from Tailings
Releases from tailings wastes may occur to land, groundwater,
surface water, and air. Land is contaminated chiefly by tailings
3-4
-------
transported by wind and water erosion; groundwater by the leaching of
radionuclides, toxic elements, and other chemicals in solid tailings,
or from seepage of tailings pond liquids; surface water from inputs
from contaminated groundwater and also from runoff over contaminated
areas; air from emissions of radon and fine wind-suspended tailings
particles.
3.2.1 Aijr_jCo n t ami na^iori
Radon Emissions
In the uranium-238 decay series, radon is unique because it is a
chemically inert gas and therefore freely migrates by diffusion from
the tailings into ambient air. Tn Table 3-1 we show calculated radon
emission rates'^) from the 27 active sites. These calculated rates
range from 200 pCi/m^s to 900 pCi/m^s. Radon emission rates from
uncontaminated soils are much lower, averaging close to 1 pCi/m2s,
with a range of perhaps as much as a factor of 2 or 3 higher and
lower. To estimate the annual radon release rates reported in
Table 3-1, we assumed that the radon emission rate per unit area is
1.0 pCi/m^s per pCi/g radium; this value was also used by NRC (NRC80,
Appendix G). It is consistent with the assumption that the piles are
dry, homogeneous, uncovered, and at least 3 meters deep. By way of
comparison, Haywood (Ha77) has calculated values of 0.35, 0.65, and 1.2
pCi/m^s radon per pCi/g radium for wet, moist, and dry tailings,
respectively.
The radon release rates listed in Table 3-1 are likely to be
greater than the actual release rates for active piles because these
piles still contain significant quantities of entrapped water. Many
active piles also contain large areas of standing water on their
surface. Both conditions significantly inhibit the release of radon to
air. In assessing the health impact from active tailings piles, we
have considered the effect of the pond area in reducing radon
emissions. However, with regard to assessing the impact of tailings
piles when the mill is not active, we consider it more reasonable to
assume that, over the time period of interest for the hazards
associated with radon release (hundreds of thousands of years), the
piles would be dry most of the time.
There have been few systematic ambient .air measurements of radon
emissions from tailings piles. However, studies to date (Mo82, PHS69)
demonstrate good agreement between field measurements and the
^ 'The term emission rate is used rather than fluence rate or flux
density, which, although more precise, are terms generally less familiar.
3-5
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prediction of mathematical models. The data in these studies support
the following conclusions:
Radon levels immediately above tailings
piles typically are above 10 pCi/1.
At 0.5 km from some piles, radon
concentration may exceed the average
background by 1 pCi/1.
Significant increases above background have
been measured at distances up to 1.5 km
downwind of tailings piles.
Emision raiAins particles
Tailings piles also release fine tailings particles to the air in
moderate-to-high winds. Schwendiman, et al . , have studied particle
release rates from an active pile (Sc80). Their data show that for
wind speeds from 7 mph to 25 mph, the airborne mass loading downwind
from the pile is roughly 5 x 10~^ g/rn-^. This is an order of
magnitude greater than the mass loading measured just upwind of the
site.
The airborne concentrations of several radioactive and toxic
elements were also measured, confirming that the windblown particles
from a tailings pile contain a variety of radionuclides, as well as the
toxic elements selenium, lead, arsenic, mercury, and molybdenum.
However, the air concentrations of toxic elements observed were well
below the 8-hour threshold limit values to which workers can be
repeatedly exposed without suffering adverse effects. (These values
for occupationally exposed workers were established by the American
Conference of Governmental Industrial Hygienists (AC81).) We conclude,
therefore, that the primary hazard arises from breathing radionuclides,
and their buildup on land surfaces.
3.2.2 ^^ Jl°J^_ami_na t^ion
The action of wind and water can erode tailings from unstabilized
piles onto nearby land. To determine the extent of this contamination
at inactive sites, we conducted gamma radiation surveys at most of the
inactive tailings sites in the spring of 1974 (Do75). We used the
measured gamma radiation levels to estimate the extent of radium
contamination in the surface soil (EPA80). If levels above 5 pCi/g,
averaged over the top 15 centimeters, are considered to represent
significant contamination, then, typically, windblown tailings have
contaminated an area near each pile that is more than three times the
area of the pile itself. It is reasonable to assume that, if
uncontrolled, contamination at existing uranium mills will be
comparable to that at inactive sites within a decade or so after the
existing mills become inactive. Little data is available concerning
contamination of land with windblown toxic materials. However, because
3-9
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whole tailings particles are transported, it is likely that the ratio
of toxic materials to radioactive materials in contaminated land is in
generally the same proportion as the ratio of these materials in the
tailings. Surface runoff may also deposit tailings particles and,
therefore, toxic materials in the vicinity of the pile. In these cases
also, the amount of radioactivity should usually be a reasonably good
indicator of the presence of elevated levels of toxic elements because
like radioactive elements, they are, for the most part, relatively well
fixed in tailings particles.
3.2.3 Water Contamination
Tailings can contaminate both surface and groundwater; we discuss
what is known about each at both active and inactive tailings piles.
As we shall see, the potential for water contamination at inactive
piles is far less than the corresponding potential contamination at
active sites.
Groundwater
Most of the potential for groundwater contamination arises from
seepage of liquid waste from the tailings pile when the mill is
active. Kaufmann, et al. (Ka75), estimated that 30 percent of the
process water from two active tailings ponds in New Mexico had seeped
into the ground. Purtyman, et al. (Pu77), estimated a 44-percent
seepage loss from another pile in New Mexico during its active life.
The NRC (NRC80) assumes that a model site will experience a 40-percent
water loss by seepage and uses a mathematical model to estimate the
movement of the seepage through unsaturated soil, formation of a seepage
"bulb" in the saturated soil zone, and the movement of pollutants with
groundwater. For its model mill in an arid region, where the evapora-
tion rate far exceeds the precipitation rate, the NRC concluded that
about 95 percent of the possible contamination of groundwater would be
associated with the active phase of the pile and only 5 percent with
with long-term loses from an inactive nonstabilized pile (NRC80). A
more detailed description of groundwater contamination can be found in
Appendix D.
Case histories showing water contamination problems near selected
active uranium mills and mines are given in a recent report (UI80).
Contamination that extends up to 8,000 feet from active tailings piles
has been found, but this has been confined to shallow alluvial aquifers
(UI80). Contamination of deep aquifers near these mills has not been
observed. In Table 3-4 we have summarized the data from groundwater
monitoring around these active tailings ponds. In general, the data
support the following conclusions regarding the shallow aquifers:
Unless pond water is contained by a natural clay or
synthetic liner, contamination of groundwater near
the pile may be expected. More than perhaps one-
third of all active tailings piles show at least
limited contamination of a shallow aquifer.
3-11
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Contamination is accompanied by highly elevated
levels of total dissolved solids, with sulfate
being the chief constituent. Such water is
rendered essentially useless for all puposes.
Because of the lack of background data on the aquifers and sites
in question, no other general conclusions can be made. It is often
difficult to prove that tailings are the cause of an elevated
concentration of a substance in groundwater unless the background
concentration of the aquifer is well characterized and there are no
nearby potential sources of additional contamination. This situation
is seldom realized. However, at one mill, heavy molybdenum contamina-
tion has been confirmed. Other sites show strong evidence of
contamination from selenium and uranium (UI80).
There is evidence that groundwater in shallow aquifers is
contaminated near some inactive sites, probably due to seepage of
liquids from tailings ponds during and soon after their active use
(Dr78). Groundwater contaminant concentrations near the inactive mills
have been surveyed (FB76-78). Although it is not possible to positively
ascribe the source of this contamination to tailings, some cases of
elevated concentrations were found.
In Table 3-5, we summarize the toxic elements found in elevated
concentrations in groundwater near inactive tailings piles. Markos has
shown that many of the soluble elements in piles tend to precipitate
and form a barrier when liquids move downward in the pile to the soil
at the tailings-soil interface (Ma79a, MaSlb, MaSlc). This would
prevent contamination of groundwater from tailings piles during the
inactive phase. However, it is not known how long this barrier will
last, and there could be channels through the barrier at locations
other than those sampled. DOE is currently sponsoring additional
studies of these potential routes of groundwater contamination.
Surface Water
Standing water with elevated concentrations of toxic materials has
been reported on and adjacent to some tailings sites (MaSlc, FB76-
78). Usually, these concentrations are intermediate between those
reported for waters within piles and normal levels in surface water.
Surface water runoff from rains and floods can wash surface salt
deposits and tailings from an unprotected pile, causing spread of toxic
and radioactive elements to nearby land and streams. A more likely
route for the contamination of surface water is seepage of contaminated
groundwater into a nearby stream or reservior. Some degradation of
water quality in nearby streams has been reported at active sites.
However, studies of the inactive tailings piles do not show that nearby
streams are being contaminated (FB76-78).
3-13
-------
Table 3-5. Elements Found in Elevated Concentrations in Groundwater
Near Inactive Tailings Sites
Tailings Site
(a)
Elements
(b)
Gunnison, Colorado
Ambrosia Lake, New Mexico
Falls City, Texas
Green River, Utah
Ray Point, Texas
Arsenic, Barium, Chromium, Iron,
Lead, Selenium, Vanadium
Barium, Lead, Vanadium
Arsenic, Barium, Chromium, Iron,
Lead, Selenium, Radium, Vanadium
Arsenic, Chromium, Lead, Selenium
Arsenic
(a)(FB76-78).
^"/At most sites there are other potential sources of this toxic material
contamination; see orginal reports for details.
3.3 Nonroutine Releases
3.3.1 Accidents and Acts of God
The most credible accident that could lead to a widespread release
of tailings solids and pond water is a dam failure at a tailings pond.
This actually occurred at the United Nuclear mill in Church Rock,
New Mexico on July 16, 1979, and 100 million gallons of tailings-pond
water and 1000 tons of solid tailings were released into the Rio
Puerco, a large ephemeral stream. Following the spill, abnormally high
concentrations of radionuclides and toxic elements were recorded as far
as 36 miles downstream. However, after several weeks, water quality of
the Rio Puerco susbstantially improved to within background levels of
contaminants. In addition to surface-water contamination, some
groundwater contamination in shallow wells adjacent to the Rio Puerco
was also detected. Contaminated sediment was found in the Rio Puerco
for several miles downstream of the spill.
The spill prompted a commitment of resources from several Federal
and State agencies to study the failure and to monitor the
contamination. At the urging of the State of New Mexico and the Navajo
Nation, United Nuclear conducted a cleanup of contaminated areas and
supplied the Navajos with replacement water. The ultimate cost of the
entire incident will probably be several million dollars.
3-14
-------
Although the Church Rock tailings-dam failure occurred
spontaneously, natural events could also precipitate such a failure:
most notably severe flooding or an earthquake. In Chapter 8, the
probabilities of such events are discussed, along with engineering and
site selection options for minimizing these probabilities. Also
discussed in Chapter 8 are the impacts of events such as tornadoes and
glaciation on the effectivness of contaminant controls.
3.3.2 Misuse of Tailings Sands
In the recent past, uranium mill tailings have been used
extensively as a building material, chiefly as fill around and under
foundations and concrete slabs. The tailings sands have ideal physical
characteristics for this purpose. However, such use typically results
in building occupants being exposed to high levels of radon decay
products and thereby incurring a significant lifetime risk of lung
cancer. In Grand Junction, Colorado, over 700 buildings have been
identified as contaminated and requiring remedial action. In other
mill towns, it is estimated that more than 350 buildings are
contaminated. In addition to buildings, many thousands of other
locations have been identified (e.g., sidewalks, lawns, gardens,
driveways) in mill towns where tailings have been used. These
buildings and locations were contaminated by tailings from inactive
mills. We have not assessed the extent of existing misuse near active
mills.
3.4 Environmental Releases from Heap-Leaching Operations
The principal solid waste from heap leaching is the barren material
remaining after uranium recovery. Airborne emissions from
heap-leaching operations include particulates suspended by wind erosion
of the pile and radon gas. The particulates will contain toxic
elements and radionuclides in proportion to the ore concentrations.
The amount of radon and particulates given off will be proportional to
the size of the operation. These have been calculated for the
heap-leaching cell covering about 0.5 acre in area described in Chapter 2,
Particulate emissions from the dry portion of a heap-leaching cell
are estimated to be about 1 MT annually. The radon emanation rate from
this operation is calculated to be 25 Ci/y (NRC78). This is less than
one-half as much as a tailings pile per unit acre.
Releases of contaminants to groundwater could result from the
seepage of leachate containing elevated concentrations of radionuclides
and toxic elements. This, however, would not normally pose a problem
during operations since an efficient heap-leaching operation requires
an impermeable pad and all leachate is collected for processing. After
termination of operations, normal rainfall could lead to some leaching
from the piles, but we expect this to be no greater threat than
leaching from an unstabilized conventional tailings pile.
3-15
-------
REFERENCES
AC81 American Conference of Governmental Industrial Hygienists,
"Threshold Limit Values for Chemical Substances in Workroom
Air Adopted by ACGIH for 1981," ACGH, 6500 Glenway Ave., Bldg
D-5, Cincinnati, Ohio
Bo66 Bowen H.J.M., "Trace Elements in Biochemistry," Academic
Press, New York, 1966.
Do75 Douglas R.L. and Hans J.M. Jr., "Gamma Radiation Surveys at
Inactive Uranium Mill Sites, Technical Note ORP/LV-75-5,
Office of Radiation Programs, USEPA, Las Vegas, Nevada, August
1975.
Dr78 Dreesen D.R., Maple M.L. and Kelley N.E., "Contaminant
Transport, Revegetation, and Trace Element Studies at Inactive
Uranium Mill Tailings Studies at Inactive Uranium Mill
Tailings Piles," in: Proceedings of the Symposium on Uranium
Mill Tailings Management," Colorado State University, Fort:
Collins, Colorado, 1978.
EPA80 Environmental Protection Agency, Office of Radiation Programs,
1980, "Draft Environmental Impact Statement for Remedial
Action Standards for Inactive Uranium Processing Sites, 40 CFR
192," EPA 520/4-80-011, EPA, Washington, B.C.
FB76-78 Ford, Bacon & Davis, Utah, Inc., "Phase II-Title I,
Engineering Assessment of Inactive Uranium Mill Tailings," 20
contract reports for Department of Energy Contract No.
E(05-l)-1658, 1976-78.
FB78 Ford, Bacon & Davis, Utah, Inc, "Engineering Assessment of
Inactive Uranium Mill Tailings, Edgemont Site," prepared for
U.S. Nuclear Regulatory Commission, Washington, D.C., 20555,
1978.
Ha77 Haywood F.F., Goldsmith W.A., Perdue P.T., Fox W.F., and
Shinpaugh W.H., "Assessment of Radiological Impact of the
Inactive Uranium Mill Tailings Pile at Salt Lake City, Utah,"
ORNL-TM-5251, Oak Ridge National Laboratory, Tennessee, 1977.
Ka75 Kaufmann R.F., Eadie G.G., and Russell C.R., "Summary of
Ground Waste Quality Impacts of Uranium Mining and Milling in
the Grants Mineral Belt, New Mexico," Technical Note
ORP/LV-75-4, Office of Radiation Programs, USEPA, Las Vegas,
Nevada, 1975.
Ma79a Markos G., "Geochemical Mobility and Transfer of Contaminants
in Uranium Mill Tailings," in: Proceedings of the Second
Symposium on Uranium Mill Tailings Management, Colorado State
University, November 1979.
3-16
-------
REFERENCES (Continued)
Ma81b Markos G. and Bush K.J., "Physico-Chemical Processes in Uranium
Mill Tailings and their Relationship to Contamination,"
Presented at the Nuclear Energy Agency Workshop, Fort Collins,
Colorado, October 1981.
MaSlc Markos G., Bush K.J. and Freeman T., "Geochemical Investigation
of UMTRAP Designated Site at Canonsburg," Number ET-44206, U.S.
Department of Energy, Washington, D.C.
Mo82 Momeni M.H. and Zielen A.J., "Comparison of Theoretical
Predictions and Measured Radon and Radon Daughter
Cencentrations: Toward Validation of the UDAD Code," from
Third Joint Conference on Applications of Air Pollution
Meteorology, American Meteorogical Society, Boston, Mass.
NM80 New Mexico Health and Environment Department, "Water Quality
Data for Discharges from Uranium Mines and Mills in New
Mexico," July 1980.
NRC77 Nuclear Regulatory Commission, "Final Environmental Impact
Statement related to the Operation of the Lucky Me Gas Hills
Uranium Mill," NUREG-0557, Washington, D.C., November 1977.
NRC78 Nuclear Regulatory Commission, "Final Environmental Impact
Statement related to the Operation of Sweetwater Uranium
Project," NUREG-0505, Washington, D.C. 20555.
NRC79 Nuclear Regulatory Commission, "Final Environmental Impact
Statement related to the Operation of Moab Uranium Mill,"
G-0453, Washington, D.C. January 1979.
NRC80 Nuclear Regulatory Commision, "Final Generic Environmental
Impact Statement on Uranium Milling, Volume II," NUREG-0511,
USNRC, Washington, D.C. 1979.
PHS69 Public Health Service, "Evaluation of Radon-222 Near Uranium
Tailings Piles," DER 69-1, Department of Health, Education, &
Welfare, Washington, D.C., 1969.
Pu77 Purtyman W.D., Wienke C.L., and Dreesen D.R., "Geology and
Hydrology in the Vicinity of the Inactive Uranium Mill Tailings
Pile, Ambrosia Lake, New Mexico," LA-6839-MS, Los Alamos
Scientific Laboratory, New Mexico, 1977.
Sc80 Schwendiman L.C., Sehmel G.A., Horst T.W, Thomas C.W. and
Perkins R.W. "A Field Modeling Study of Windblown Particles
from a Uranium Mill Tailings Pile," NUREG/CR-14007, Battelle -
Pacific Northwest Laboratory, Richland, Washington, June 1980.
3-17
-------
REFERENCES (Continued)
Se75 Sears M.B., et al., "Correlation of Radioactive Waste
Treatments Costs and the Environmental Impact of Waste Effuents
in the Nuclear Fuel Cycle for Use in Establishing "As Low as
Practicable' GuidesMilling of Uranium Ores," Report
ORNL-TM-4903, Two Volumes, Oak Ridge National Laboratory,
Tennessee, 1975.
UI80 University of Idaho, "Overview of Ground Water Contamination
Associated with Operating Uranium Mills in the United States,"
College of Mines and Mineral Resources, University of Idaho,
1980.
3-18
-------
Chapter 4: MODEL SITE AND TAILINGS PILE
This chapter summarizes the specific characteristics of the model
site and tailings pile used for the analyses presented in Chapters 5
and 6.
4.1 Model Site
The "model mill" chosen for this analysis is the one developed for
the NRC's Final Generic Environmental Impact Statement on Uranium
Milling (NRC80). The model mill is based on features of uranium mills
in operation in the 1970"s. The characteristics, operating procedures,
and effluents of the model mill were derived from data for existing
mills as described in the technical literature and in environmental
reports (MP80). Since the Act relates only to the tailings resulting
from operation of the mill, the "model site" used for the analysis in
Chapters 5 and 6 is defined as the area within a radius of 80
kilometers from the center of the model mill tailings pile.
4.1.1 Meteorology
The meteorology of the model site is typical of semiarid regions
of the western United States. The average annual precipitation of the
model site is 31 cm (12 inches). Potential evaporation exceeds
precipitation, averaging 150 cm (60 inches) per year. Joint frequency
of the annual average wind speed, direction, and atmospheric stability
for the model site are presented in Table 4-1.
4.1.2 Demography
Two population distributions were used for the model site to
represent a range of potential impacts from the model tailings pile:
(1) the population distribution from the NRC model site (NRC80), and
(2) the population distribution near the tailings pile in Edgemont,
South Dakota (NRC81). The NRC model site represents a location where
only a few people live close to the tailings pile (referred to here as
a "remote" site). The Edgemont site represents a location with a
larger population living near the tailings pile (referred to here as a
"rural" site). Tables 4-2 and 4-3 present these population distribu-
tions as a function of distance and direction from the model tailings
pile.
4-1
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To obtain better information on populations at mill sites, EPA
contracted with Battelle Pacific Northwest Laboratories to count the
number of people within 5 km of these sites. These data are presented
in Appendix E. EPA also obtained data on the number of people living
between 5 and 80 km of these sites based on 1970 census data (Ew73).
These values were then used to estimate the total health risk to local
and regional populations (see Chapter 6) by various weighting
techniques.
4.1.3 Hydrology
The surface waters near the model pile are short-lived streams and
small ranch impoundments used for livestock watering. These ephemeral
streams have their maximum flows in June and July and are dry from
September to February. Rivers and reservoirs are several miles away
from the model pile. In some cases, the nearby surface water is good
(of drinking water quality), but nearby surface water will contain
relatively high concentrations of dissolved solids, making it
unsuitable for many purposes. The groundwater resources near the model
uranium mill tailings pile are an unconfined surface aquifer (often
alluvial) plus deep aquifers separated from the surface by an
impermeable layer. For calculating the movement of contamination from
the model pile, the NRC assumed the water table (the top of the surface
aquifer) is 25 meters below ground level. The deep aquifers often lie
below 300 meters. The surface aquifer is the most commonly used,
chiefly for domestic and stock water.
The deep aquifers are used for large industrial applications.
Uranium mills, for example, often obtain mill process water from deep
aquifers. Water quality of both the surface and deep aquifers is
variable.
4.1.4 Agricultural Productivity
Uniform agricultural productivity rates for vegetables, meat, and
milk in units of kg/y-km2 were applied over the entire area of the
model site except the controlled areas occupied by the mill and
tailings pile. The production rates used are:
Product kg/y-km^
Vegetables 1020
Meat 1180
Milk 1140
These production rates are averages of production rates in States where
uranium milling takes place (NRC80), weighted by the expected uranium
development activity in each state.
4.2 The Model Tailings Pile
The tailings are assummed to be generated by an acid-leach mill.
We generally assume the same characteristics as chosen by the NRC for
their generic assessment of the uranium milling industry (NRC80).
4-6
-------
4.2.1 Physical Description
The model tailings pile is typical of uranium mills in operation
in the 1970's. The model mill generates 1800 MT of solid tailings
slurried in water to about 50 percent solids by weight. When
discharged from the mill, the slurried tailings material is pumped
through pipes to the tailings pond impoundment. The pond is initially
a square basin formed by building low earthen embankments. The initial
embankment is assumed to be 3 meters high, 3 meters broad at the top,
and 15 meters wide at the base. Each side of the square is assumed to
be 947 meters long at the centerline of the embankment. The final
embankments are assumed to be 10 meters high, 13 meters wide at the
top, and 53 meters at the base; the initial centerline dimensions are
unchanged. The total tailings disposal area is about 100 hectares (250
acres) of which 80 hectares contain tailings. It is assumed that,
during operations, one fourth of the tailings area is covered by water,
and another one-eighth is wet.
After milling operations cease, it is assumed a few years pass
before the tailings have dried and settled sufficiently to accommodate
heavy equipment. The ultimate height of the tailings pile is assumed
to be about 8 meters. In this post-operational phase, the emissions
from tailings and the controls are different from those during the
operational phase.
The principal physical characteristics of the model tailings pile
are summarized in Table 4-4.
Table 4-4. Summary of Principal Physical Characteristics
of the Model Tailings Pile
Parameter Value
Operational life of tailings pile 15 years
Operating days per year 310
Dry solid waste generated (tailings) 1800 MT/day
Tailings density (slurry) 1.6 g/cm-*
Gross water flow to tailings pond 1800 MT/day
Tailings pond water recycled 30%
Net water consumption for tailings slurry 1260 MT/day
Area of tailings impoundment 100 ha
Area of tailings 80 ha
Ponded area on tailings (operational) 20 ha
Ponded area on tailings (post-operational) 0 ha
Wet beaches 10 ha
Average depth of tailings (post-operational) 8 m
4-7
-------
4.2.2 Contaminants Present
The ore grade processed by the model mill from 1982 to 2000 is
assumed to average 0.1 percent. The uranium recovery efficiency is
assumed to be 93 percent. These values result in the tailings
radioactivity listed in Table 4-5. Also listed are the assumed
concentrations of toxic substances and other chemicals in the tailings
pond liquids of the model pile (NRC80). The values in Table 4-5 are
representative of tailings piles generated by acid leach mills. For an
alkaline-leach mill, the most significant difference is that the
concentration of thorium-230 in tailings liquids would be more than an
order of magnitude lower.
4.2.3 Radioactive Emissions to Air
Radionuclides are released into air from tailings piles in the
form of small dust particles and radon gas. Table 4-6 lists the
assumed annual release rates of radionuclides from the model tailings
pile. Particulate emissions are listed in two particle size
distributions with characteristic diameters of 5 and 35 microns,
respectively, and a density of 2.4 g/cm3. The Activity Median
Aerodynamic Diameters (AMADs) for these particle size distributions are
7.75 and 54.2 ym, respectively. A detailed description of the methods
used for estimating these release rates is given in Appendix G-l of the
Generic Environmental Impact Statement on Uranium Milling (NRC80).
4.2.4 Emis s io ns of Cont: aminants to Water
For the model pile, it is assumed that there are no routine
releases to surface water. This is achieved through proper siting of
the pile along with the minimal engineered controls required to
substantially eliminate surface water runoff from the tailings pile.
The assumed routine emissions to groundwater are more substantial.
NRC calculates a seepage rate of 0.22 million MT of water per year
during the operational phase, and 5 percent of this value during the
post-operational phase. We have made no estimates of the specific
contaminants released with this water because they will vary with the
ore used, the milling process, the geochemistry of the soil, and other
factors.
4-8
-------
Table 4-5. Chemical and Radiological Properties of
Tailings Wastes Generated by the Model Mill(a)
Parameter
Dry Solids
U3°8 ,^
Uranium (natural) ^b'
Radium- 226
Thorium-230
Tailings Liquid
pH
Aluminum
Ammonia
Arsenic
Calcium
Cadmium
Chloride
Copper
Fluoride
Iron
Lead
Manganese
Mercury
Molybdenum
Selenium
Sodium
Sulfate
Vanadium
Zinc
Total dissolved solids
Uranium (natural)
Radium-226
Thorium-230
Lead-210
Polonium-210
Bismuth- 2 10
Unit
wt%
pCi/g
pCi/g
PCi/g
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
pCi/L
pCi/L
pCi/L
pCi/L
pCi/L
pCi/L
Value(a)
0.007
39
280
280
2
2,000
500
0.2
500
0.2
300
50
5
1,000
7
500
0.07
100
20
200
30,000
0.10
80
35,000
3,300
250
90,000
250
250
250
a(NRC80).
^k/A 1.5 microgram mass of natural uranium has activities of
0.49 pCi each of uranium-238 and uranium-234 and 0.023 pCi of
uranium-235.
4-9
-------
Table 4-6. Radioactive Emissions to Air from Model Tailings Pile
Radionuclide
Radon-222
Operational Phase
Post-Operational Phase
Particulate Emissions , (mCi/y)
Particle size
Uranium-238
Uranium-234
Thorium-230
Radium-226
Lead-210
Polonium- 2 10
5 ym
2.6
2.6
36
36
36
36
35 ym
6.1
6.1
84
84
84
84
5 ym
4.2
4.2
58
58
58
58
35 ym
9.8
9.8
134
134
134
134
Gaseous Emissions (Ci/y)
4400 7000
4-10
-------
REFERENCES
Ew73 Ewing D.R. and Payne J.A., "Computer Access to Geographic
Distribution of the Population," U.S. Department of Commerce,
COM-73-11678, July 1973.
(MP80) J.F. Facer, Jr., "Production Statistics," U.S. Energy Research
and Development Agency, presented at the Uranium Industry
Seminar, Grand Junction, Colorado, 19-20 October 1976.
M.B. Sears, et al., "Correlation of Radioactive Waste
Treatment Costs and the Environmental Impact of Waste
Effluents in the Nuclear Fuel Cycle for Use in Establishing as
Low as Practicable GuidesMilling of Uranium Ores," Oak Ridge
National Laboratory, Oak Ridge, Tenn., ORNL-TM-4903, Vol. 1,
May 1975.
"WIN Reports on Uranium Ore Analysis," National Lead Company,
Inc., Raw Materials Development Laboratory, U.S. AEC Contract
No. 49-6-924; WIN Reports #3, 5, 14, 39, 44, 45, 49, 50, 56,
58, 60, 64, 65, 67, 70, 71, 72, 76, 77, 79, 89, 97, and 106,
dated 7 January 1957 to 10 July 1958.
D. A. Brobst and Pratt W.P. (editors), "United States Mineral
Resources," Geological Survey Professional Paper 820, U.S.
Dept. of the Interior, Geological Survey, 1973.
"Mineral Facts and Problems," U.S. Dept. of the Interior,
Bureau of Mines Bulletin 667, 1975.
"Final Environmental StatementBear Creek Project, Rocky
Mountain Energy Company," U.S. Nuclear Regulatory Commission,
Docket No. 40-8452, NREG-0129, January 1977.
"Draft Environmental StatementLucky Me Uranium Mill, Utah
International, Inc.," U.S. Nuclear Regulatory Commission,
Docket No. 40-2259, NREG-0295, June 1977.
"Draft Environmental StatementMoab Uranium Mill, Atlas
Minerals Division, Atlas Corp.," .U.S. Nuclear Regulatory
Commission, Docket No. 40-3453, November 1977.
"Final Environmental StatementThe Highland Uranium Mill
(Exxon Co., U.S.A.)," U.S. Atomic Energy Commission,
Directorate of Licensing, Docket No. 40-8102, March 1973.
"Environmental ReportSweetwater Uranium Project, Sweetwater
County, Wyoming," Minerals Exploration Company, November 1976.
"Final Environmental StatementShirley Basin Uranium Mill,
Utah International, Inc.," U.S. Atomic Energy Commission,
Directorate of Licensing, Docket No. 40-6622, December 1974.
4-11
-------
REFERENCES (Continued)
NRC80 Nuclear Regulatory Commission, "Final Generic Environmental
Impact Statement on Uranium Milling," NUREG-0706, NRG,
Washington, D.C., 1980.
NRC81 Nuclear Regulatory Commission, "Draft Environmental Statement
Related to the Decommissioning of the Edgemont Uranium Mill,"
NUREG-0846, NRG, Washington, D.C., 1981.
4-12
-------
Chapter 5: ENVIRONMENTAL PATHWAYS
In this Chapter the pathways through which radioactive and toxic
materials from mill tailings may cause exposure of man are examined
and, where possible, quantified. While consideration of the impact'of
tailings piles on man depends on the statusoperational or postopera-
tionalof the mill, the contaminants which are expected to be present
are the same. The projected health impacts of these materials are
developed for the various pathways in Chapter 6, using the results
obtained in this chapter for the model site.
5.1 Co n tami nan t s
The pathway analysis considers three general forms of
contaminants. They are particulates (dust), radon (gas), and liquids
(leachate). An introductory discussion of each form is given first,
and the actual transport mechanisms are presented in the following
sections. The model mill has been described in Chapter 4. The source
terms and other model parameters are more fully described in the Final
Generic Environmental Impact Statement on Uranium Milling (NRC80).
Since the Act addresses only the tailings resulting from mill
operations, only the model mill source terms applicable to the tailings
pile are employed.
5.1.1 Particulates
The mechanism of movement of tailings particles by wind is similar
to the movement of soil and is dependent on wind velocity, physical
properties of the tailings, and the nature of the tailings surface.
Wind forces can generate three basic modes of particle movement:
surface creep, saltation, and airborne suspension. Surface creep,
which spreads the tailings pile, involves particles ranging in size
from 500 to 1000 urn. These particles are rolled along the surface by
the push of strong winds and the exchange of momentum after impact with
smaller particles in saltation. Saltation causes individual particles
to jump and lurch within a few centimeters of the ground. Particles
that saltate are from 100 to 500 ym in size, depending on shape and
density, and are quickly brought back to the ground by gravitational
force. The resulting exchange of momentum with other particles can
initiate surface creep, saltation, or suspension. Particles in
5-1
-------
suspension are small enough (less than about 100 ym) to have a
gravitational velocity of fall lower than the upward velocity of the
turbulent wind. These particles may be carried through the atmosphere
for long time periods and to distances far from their original
location. While airborne, these suspended particles contribute to the
inhalation pathway of exposure of man; when deposited, they contribute
to the ingestion and external surface exposure pathways.
5.1.2 Radon
As shown in Figure 3-1, the radon decay process involves seven
principal decay products before ending with nonradioactive lead. The
four short half-life radioactive decay products immediately following
radon are the most important sources of cancer risk. These decay, for
the most part, within less than an hour. Members of the decay chain
with relatively long half-lives (beginning with lead-210, which has a
22-year half-life) are more likely to be ingested than breathed and
pose much smaller risks.
The principal short half-life products of radon are polonium-218,
lead-214, bismuth-214, and polonium-214. Polonium-218, the first decay
product, has a half-life of just over 3 minutes. This is long enough
for most of the electrically-charged polonium atoms to attach to
microscopic airborne dust particles that are typically less than a
millionth of a meter (pm) across. When breathed, these small particles
have a good chance of sticking to the moist epithelial lining of the
bronchial tubes in the lung.
Exposure to radon decay products is expressed in terms of a
specialized unit called the Working Level (WL). A Working Level is any
combination of short half-life radon decay products that emits 130,000
million electron volts (MeV) of alpha-particle energy in 1 liter of
air. The unit of cumulative exposure to radon decay products is the
Working Level Month (WLM), which is exposure to air containing 1 WL of
radon decay products for a working month, which is defined as 170
hours. (These units were developed to measure radiation exposure of
workers in uranium mines.) Continuous exposure of a member of the
general population to 1 WL for 1 year is equivalent to about 27 WLM.
For exposures occurring indoors, we assume a 75 percent occupancy
factor. Thus, an indoor (residential) exposure to 1 WL for 1 year is
equivalent to about 20 WLM (EPA79a).
5.1.3 Liquid Contaminants
Airborne transport of tailings, with subsequent deposition on the
ground and on surface waters, and transport or leaching of tailings by
water used for drinking or irrigation can lead to exposure of man to
radioactive and toxic substances. Future contamination of surface or
groundwater is also likely if there is erosion of toxic elements from a
pile by rain, by flooding, or, possibly, by the flushing action of
seasonal changes in the water table when it can reach a pile from
5-2
-------
below. Severe floods have a greater, but difficult to evaluate,
potential for producing significant contamination of streams and
rivers. Future groundwater contamination from the seepage and flushing
action of seasonal changes in the water table is uncertain. The degree
of detail with which we can accurately treat these potential pathways
varies. Modeling of water pathways requires site-specific data on
sources and uses of water. The existence of actual water pathways for
radioactive and toxic materials from tailings piles has not yet been
verified, so we discuss these pathways in general terms only.
Concentrations of dissolved substances in the tailings pond water at
the model mill are shown in Table 4-5.
5 . 2 Atmospheric^ Transpo rt
Airborne particulates and radon are analyzed using essentially
the same calculational procedure. For the purpose of evaluating
environmental impact, the analysis has been performed for both regional
and national populations, using appropriate meteorological models for
each. Because of the short half-life of radon, the worldwide impact is
not significantly greater than the sum of the impacts of these two
groups, and is therefore not calculated for this analysis. The term
"regional" is defined to include local and regional populations at
distances up to 50 miles (80 km) from the tailings site and "national"
to cover the remainder of the contiguous United States.
5.2.1 Nearthe
We estimated radon concentrations over and close to the edge of
generic, uncovered tailings piles, which, for calculational
convenience, we take as circular in shape. For these calculations we
assumed that the radon emission rate is a uniform 280 pCi/m^s from
the tailings. Concentrations for other emission rates would be
proportionately higher or lower. The concentration calculations were
made using generic wind data from the NRC GEIS (NRC80) and the
AIRDOS-EPA dispersion model (EPA79b).
5.2.2 Regional
He t eo ro 1 o gy
Airborne transport within the region is governed by meteorological
conditions at the model mill site. These are detailed in Chapter 4.
The transport mechanisms considered are described below.
Pi spears ion
The AIRDOS-EPA code (EPA79b) uses a modified Gaussian plume
equation to estimate airborne dispersion of radionuclides from the
pile. Calculations are site-specific and require detailed knowledge of
the joint wind direction, wind speed, and stability frequencies. Since
the accuracy of these projections decreases with distance, we limit
5-3
-------
calculations with this method to regional (less than 50 miles distant)
locations. Values calculated are annual averages, since we are not
concerned with diurnal or seasonal variations.
Deposition
AIRDOS-EPA estimates the annual average concentration of each
radionuclide in air at ground level (corrected for deposition) as a
function of direction and distance from the source. Deposition rates
at each location are calculated for each radionuclide, and from these,
the ground concentration levels at the desired locations. The
radionuclides are deposited on the ground in the model by both
precipitation and direct dry deposition.
Ingrowth of Radon Decay Products
At the point where radon diffuses out of the tailings, the
atmospheric concentration of associated radon decay products is zero,
because those decay products generated prior to diffusion from the
surface have been captured in earth. As soon as radon is airborne,
atmospheric decay product ingrowth commences and a secular equilibrium
between the amount of radon and £he amount of each decay product is
approached. At such secular equilibrium, there is equal activity of
all the short half-life radon decay products in air, and alpha
radiation per unit of radon concentration is maximized. To account for
incomplete equilibrium before this state is achieved, we define the
"equilibrium fraction" as the ratio of the potential alpha energy from
those decay products actually present to the potential alpha energy
that would be present at complete equilibrium. As radon and its decay
products are transported by the wind, the equilibrium fraction
increases with distance from the pile approacing the theoretical
maximum value. However, depletion processes, such as dry deposition or
precipitation scavenging, selectively remove decay products (but not
radon), so complete equilibrium with the radon is seldom, if ever,
reached.
When radon and its daughters enter a structure, they remain for a
mean time that is inversely proportional to the ventilation rate and
proportional to its half-life. Since the former is much smaller than
the latter, the building ventilation rate is a principal factor
affecting further changes in the equilibrium fraction. It can also be
affected by other considerations, such as the indoor surface-to-volume
ratio and the dust loading in indoor air (Po7b).
We have also assumed that, on the average, Americans spend
approximately 75 percent of their time indoors, mostly in their
homes (Mo76, Oa72). We have weighted the indoor and outdoor equili-
brium fractions for a given location by factors of 0.75 and 0.25,
respectively, to estimate an effective value for calculating exposure
to radon decay products from tailings piles. Since indoor exposure is
the dominant form of exposure due to radon, this effective equilibrium
fraction does not depend strongly on the distance from the tailings
pile. We assume an effective equilibrium fraction of 70 percent for
5-4
-------
exposure of populations, since the majority of all affected individuals
are not close to piles. For maximum exposed individuals close to a
pile, we assume half this value.
5.2.3 National
Ihe inert radon gas emitted from tailings piles can be transported
beyond the 50-mile regional cutoff. A trajectory dispersion model
developed by NOAA (Tr/9) has been used to estimate the national impact
of radon emissions from the model pile. This model calculates the
potential radiation exposure to the United States population for radon
released from four typical mill site locations. (Descriptions of these
typical mill sitesCasper, Wyoming; Falls City, Texas; Grants, New
Mexico; and Wellpinit, Washingtonare given in (Tr79).) Only
exposures taking place beyond the 50-mile regional limit are
considered. Details of the model are given in He75. The model yields
radon concentrations (pCi/L) in air which were converted to decay
product concentrations by assuming that 100 pCi/L of radon corresponds
to a decay product concentration of 0.7 WL.
5.3 Hydrological Dispersion
There are two basic types of water resources considered in the
impact assessments: (1) surface water (water on the surface of the
earth, such as in lakes and rivers) and (2) groundwater (water occurring
below the surface of the earth in a zone of saturation). The impacts
on these two types of water resources in the model region are discussed
in the following subsections for the case of an unlined tailings
disposal area.
5.3.1 Surface Water
Operational
During operation of the mill, seepage from tailings ponds could
add heavy metals, suspended solids, radioactive contaminants, and
soluble salts to surface waters. Three routes of contamination might
occur as a result of this seepage:
1. Seepage water from the tailings pond could intercept an
aquifer and contaminate groundwater. This contamination could also
degrade surface water quality under certain conditions. Irrigation
wells or water supply wells could also penetrate aquifers that have
been contaminated by seepage from tailings ponds. Water pumped from
such wells would normally discharge into a surface water irrigation
ditch or canal and uJtimately into a stream. Contaminated water
extracted via such wells would remain contaminated when it entered a
surface water stream.
2. Seepage Weter could form surface pools downgrade from the
tailings pond. Consideration of the transport time and concentration
data for the seepage pools indicates that the trace materials in the
pools would have the same initial composition as the tailings pond.
5-5
-------
This surface water v>ould be subject to a high rate of evaporation,
which would result in a concentration of the soluble ions as the volume
of seepage water decreases. During periods of local precipitation and
spring runoff, this contaminated water could enter surface streams or
rivers.
3. During dry periods, seepage water might reach the ground
surface and be subject to a high evaporation rate, which would result
in salt deposits. These areas would be exposed to surface runoff
during periods of precipitation or during periods of snowmelt, at which
time the precipitates again would be subject to dissolution and
transport, resulting in a pulse of contaminated water reaching surface
waters. Depending on the amount of materials in the runoff and the
dilution capacity of the existing streamflow, the water quality of some
streams, on rare occasions, could reach toxic levels.
Post-Operational
After mill operations cease, seepage from the tailings would be
substantially reduced since discharge of water from the mill ends. The
permanent seepage rate caused by precipitation falling on uncovered,
abandoned tailings is estimated to be about 5 percent of the rate
during the 15-year operational period (NRC80).
5.3.2 Groundwater
The impacts of uranium milling operations on groundwater are
generally site-specific (because of regional and local variations in
geology and hydrology) and thus are difficult to discuss on a generic
basis. For illustrative purposes, however, a set of geological and
hydrological characteristics has been assumed for the model region.
The effects of mining on groundwater can be fairly extensive and
in many cases cannot be logically separated from the effects of nearby
milling operations. For the model mill, however, we assume that the
mines will be sufficiently far from the tailings pond to have no effect
on effects due to tailings pond seepage.
Operational
By far the greatest impact on groundwater resulting from operation
of a model mill would be from seepage from the tailings pond. The term
"tailings pond" is used in the general sense in this context, and is
intended to include evaporation ponds or any other type of unlined
facility which receives mill waste water. The model mill contains an
unlined tailings disposal area. The principal contaminants in the
acidic tailings pond liquid are radium, thorium, sulfate, iron,
manganese, and selenium (Table 4-5}.
Post-Operational
After mill operations cease, seepage from the tailings would be
substantially reduced because of the cessation of discharge of water
5-6
-------
from the mill. It should be emphasized that this analysis assumes that
no new wells are permitted which would withdraw contaminated
groundwater from the aquifer affected by the seepage.
During the post-operational period, an advancing front of seepage
water containing nonradioactive contaminants would be moving
downgradient. In this analysis, contaminant concentrations have been
calculated on the assumption that there would be no lateral dispersion;
this is a conservative assumption in that it results in overestimation
of downgradient concentrations of contaminants. As these contaminants
disperse downgradient, their concentrations would be reduced.
5.4 Environmental Concentrations
We calculate environmental concentrations, radiation doses, and
health risks due to airborne releases using three computer
codesAIRDOS-EPA (EPA79b), RADRISK (Du80), and DARTAB (Be81).
AIRDOSE-EPA estimates, for a given source term, the amount of
intake of each radionuclide, or the external concentration, at the
point of exposure. RADRISK calculates the radiation dose and risk from
unit intake of a given radionuclide. DARTAB is a control code that
scales the unit estimates of RADRISK to match the actual exposure
levels calculated by AIRDOS-EPA and then displays the results in a
useful format.
5.4.1 Calculational Procedures
The regional environmental concentrations resulting from airborne
emissions presented in this Chapter are obtained using the AIRDOS-EPA
code. The RADRISK and DARTAB health risk calculations are described in
Chapter 6 and Appendix C.
The AIRDOS-EPA code was developed for EPA by the Oak Ridge
National Laboratory. It is a modification of AIRDOS-II, a code in use
for many years, also developed by ORNL. Terrestrial food chain models
used by the code are based on those used by the U.S. Nuclear Regulatory
Commission, as provided in Regulatory Guide 1.109.
A modified Gaussian plume is used to estimate dispersion of as
many as 36 radionuclides from point or area sources. Radionuclide
concentrations in air, rates of deposition on ground surfaces, ground
surface concentrations, and intake rates due to inhalation and
ingestion (meat, milk, fresh vegetables) are then calculated.
Meteorological, population, and other data characteristics of the site
can be used to give more accurate assessments of a specific source.
When a source continually emits long half-life radionuclides, the
environmental concentration levels build up for as long as the source
continues to emit. This is not a significant consideration for air
5-7
-------
concentrations, but is for those concentrations which result from
deposition on the ground surface. Our calculations assume that the
particulates which deposit on the ground surface are removed by
environmental processes, such as leaching, at a rate of 2 percent per
year. (In addition, only 20 percent of the radon which results from
the decay of deposited radium is assumed to escape). Since the
environmental concentrations are not constant, they are calculated for
specific times appropriate to the analysis. For the operational
period, this is at the end of 15 years (the expected duration of mill
operation) for the assessment of individual exposure and at the end of
100 years for the assessment of population exposures. The release
rates used for these calculations are those shown in Table 4-6.
For the post-operational period, the enviromental concentrations
are calculated at the end of 100 years of releases. The release rates
for this period assume the tailings pond no longer exists and that the
entire tailings pile area (80 ha) contributes to the releases. Because
of the 2 percent per year removal rate assumed for deposited
particulates, these concentrations are close to equilbrium.
Radon decay product concentrations (WL) are calculated from the
atmospheric radon concentration (Ci/m-^) using an effective
equilibrium fraction as described in Section 5.2.1.
5.4.2 Air Concentrations
Near the Pile
Average concentrations near the pile are shown in Figure 5-1 for a
small (5 hectares or 12 acres), a medium (20 hectares or 49 acres), and
a large (80 hectares or 196 acres) tailings pile. Our calculations
show that the average concentration near the center of the pile and at
the edge of the pile are relatively insensitive to the size of the
pile. For the 20-hectare pile, Figure 5-1 also shows the results in
the directions for which the concentration is maximum or minimum. The
wind data (and therefore the dispersion) and the shape of the pile at
actual sites would differ from the one used for these calculations.
Although we have not performed site-specific calculations, we believe
that the higher wind direction asymmetry at actual tailings sites would
increase the maximum concentration at the edge of the tailings to about
4 pCi/L. This is the only calculation which uses dimensions different
from those of the model pile described in Chapter 4.
Regional
Regional air concentrations for particulates and radon are shown
in Table 5-1. These concentrations are based on the operational phase
source terms given in Table 4-6. In Table 5-1 and subsequent tables,
the column heading "average" refers to the arithmetic average over the
sixteen directions for which concentrations are calculated. The
heading "maximum" is the value for the direction of maximum risk (see
5-J
-------
100
500
DISTANCE FROM CENTER OF PILE (M)
1000
Figure 5-1. Radon Concentration Near the Tailings Pile.
Radon Emission Rate is 280 pCi/m2s.
5-9
-------
Chapter 6) at that distance. The directions may differ since "risk"
implies that an individual or population is present. In general, the
direction of maximum concentrat ion is the same as that of maximum risk;
in those situations where it is not, the concentration for the
direction of maximum risk does not differ in any practical sense from
that in the direction of maximum concentration. Data in Table 5-1 and
subsequent tables are presented to two significant figures to
facilitate comparisons and not to indicate that environmental values
can be calculated to that level of accuracy.
Table 5-2 shows population inhalation intakes of particulates and
radon decay product exposures, calculated for a year's release during
the operational period. The population distributions are shown in
Tables 4-2 and 4-3. Note that the total intake/exposure values for the
remote site are less than those for the rural one even though the
remote site has a larger regional population. The larger nearby
population of the rural site substantially increases the regional
intakes and exposures for that site. Post-operational regional
concentrations for particulates and radon are shown in Table 5-4. The
entire tailings pile area is assumed to be dry in this period, so the
emissions are 80/50 times the values for the operational phase.
National
National population exposures during the post-operational phase of
the model mill are calculated in the same way as those for the
operational phase. The radon source term, Table 4-6, during this phase
is 7000 curies per year and the exposures shown in Table 5-5 are the
total exposures for each year that the tailings pile continues to exist.
Annual national population exposures to radon emissions during the
operational phase of the model mill are shown in Table 5-3. The total
source term of 4400 curies per year (from Table 4-6) is attributed to
each site in turn; the average value for all sites is also shown.
These exposures assume an equilibrium fraction of 0.7 and exclude the
population living within 50 miles of the sites. The values represent
the total exposure to this population which results from each year's
operation of the mill.
5.4.3 Ground Surface Concentrations
Operational
Table 5-6 shows the regional ground surface concentrations of
radionuclides for the operational phase of the mill. These values are
calculated after 15 years of operation. The "average" and "maximum"
headings again refer to the average for all directions and the
direction of maximum risk for all pathways.
5-10
-------
Table 5-1. Regional Air Concentration (Ci/nr')
of Radionuclides
by Distance and Particle Size
(Operational Phase)
Distance
(meters)
Average
5 ym 35 ym
5
Maximum
ym 3 5 (jin
238Uj 234u
600
1000
2000
3000
4000
5000
10000
20000
600
1000
2000
3000
4000
5000
10000
20000
600
1000
2000
3000
4000
5000
10000
20000
3
1
2
1
7
4
1
3
5
1
3
1
1
6
1
4
.7E-16
.1E-16
.8E-17
.2E-17
.OE-18
.6E-18
.2E-18
.2E-19
£- J \J TV
.2E-15
.6E-15
.9E-16
.8E-16
.OE-16
.6E-17
.6E-17
.6E-18
1.
4.
1.
7.
4.
3.
1.
5.
6
1
3
1
6
4
7
1
l 226
9
2
5
2
9
6
1
1
3E-09
4E-10
4E-10
OE-11
6E-11
4E-11
3E-11
6E-12
.5E-17
.8E-17
.5E-18
.4E-18
.9E-19
.2E-19
.5E-20
.3E-20
Ra, 210Pb,
.3E-16
.5E-16
.OE-17
.OE-17
.8E-18
.OE-18
.1E-18
.9E-19
222Rn
6.
2.
6.
2.
1.
1.
3.
8.
21°Po
9.
3.
9.
4.
2.
1.
4.
1.
3E-16
2E-16
3E-17
9E-17
7E-17
1E-17
OE-18
8E-19
OE-15
1E-15
OE-16
2E-16
4E-16
6E-16
2E-17
3E-17
2
7
2
1
9
6
2
1
1.
5.
1.
5.
2.
1.
3.
5.
2.
7.
1.
7.
4.
2.
4.
7.
.OE-09
.7E-10
.7E-10
.4E-10
.5E-11
.9E-11
.6E-11
.1E-11
5E-16
6E-17
3E-17
5E-18
8E-18
7E-18
1E-19
4E-20
2E-15
9E-16
9E-16
8E-17
OE-17
4E-17
4E-18
7E-19
averaged over all directions.
Value for direction of greatest risk.
5-11
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Table 5-2. Regional Population Inhalation Intake and Exposure
(per Operational Year)
Inhalation
(person-pCi)
Radon Decay
Distance
(km)
20
20-40
40-80
Total
20
20-40
40-80
Total
Number of
Persons
16
4,572
52,840
57,428
2,273
5,314
14,235
21,822
23 Y
5 ym
6.9
4.9
2 . 6E+01
3 . 8E401
2.0E+03
1.2E+01
2.8
2.0E+03
234U
35 ym
Remote
1.5
7.5E-02
7.3E-01
2.3
Rural
1.8E+02
4.4E-01
3.6E-02
1.8E402
23°Th, 226Ra, <
5 y m
Site(a)
l.OE+02
6.9E401
3.7E+02
5.4E+02
Site(a)
2.8E+04
1.8E+02
4.0E+01
2.8E+04
*°Pb, 21°Po
35 um
2.2E+01
1.1
l.OE+01
3.3E+01
2.5E+03
6.3
5. IE -01
2.6E+03
rrouuct
Exposure
(person-WLy)
2.4E-02
1.5E-01
7.3E-01
8.9E-01
7.0
2.0E-01
1.4E-01
7.3
Chapter 4 for description of sites.
Table 5-3. National Population Exposures and Intakes
(per Operational Year)
Exposures
210
Pb Intakes
222
Rn « Radon Decay Product Inhalation
Release Site (person-Ci-y/m ) (person-WLy) (person-Ci)
New Mexico
Grants
Texas
Falls City
Washington
Wellpinit
Wyoming
Casper
Ave rage
3. IE -07
4.8E-07
2.6E-07
3.7E-07
3.5E-07
2.2 7.7E-07
3.3 8.2E-07
1.9 7.9E-07
2.6 9.4E-07
2.5 8.3E-07
Ingestion
(person-Ci)
4.4E-06
2.7E-06
5.3E-06
4.8E-06
4.4E-06
5-12
-------
Table 5-4. Regional Air Concentration
of Radionuclides
by Distance and Particle
(Post-Operational Phase)
Distance
(meters)
600
1000
2000
3000
4000
5000
10000
20000
Average
511 1 C
Mm jj jjm
5
1
4
2
1
7
1
5
.9E-16
.8E-16
.4E-17
.OE-17
.1E-17
.4E-18
.8E-18
.2E-19
1.
2.
5.
2.
1.
6.
1.
2.
238^ 234U
OE-16
8E-17
6E-18
2E-18
1E-18
7E-19
2E-19
1E-20
230Th, 226Ra, 210Pb,
600
1000
2000
3000
4000
5000
10000
20000
600
1000
2000
3000
4000
5000
10000
20000
8
2
6
2
1
1
2
7
.4E-15
.6E-15
.3E-16
.8E-16
.6E-16
.1E-16
.6E-17
.3E-18
2
7
2
1
7
5
2
9
1.
4.
8.
3.
1.
9.
1.
3.
.OE-09
.IE- 10
.2E-10
.1E-10
.4E-11
.4E-11
.OE-11
.OE-12
5E-15
OE-16
OE-17
2E-17
6E-17
6E-18
7E-18
OE-19
222Rn
Maximum
5 pm 35
1
3
1
4
2
1
4
1
.OE-15
.5E-16
.OE-16
.7E-17
.7E-17
.8E-17
.8E-18
.4E-18
2.
8.
2.
8.
4.
2.
4.
8.
/
urn
4E-16
9E-17
1E-17
7E-18
4E-18
7E-18
9E-19
6E-20
210Po
1
5
1
6
3
2
6
2
.4E-14
.OE-15
.4E-15
.7E-16
.9E-16
.6E-16
.8E-17
.OE-17
3
1
4
2
1
1
4
1
3.
1.
3.
1.
6.
3.
7.
1.
.2E-09
.2E-09
.4E-10
.3E-10
.5E-10
.1E-10
.1E-11
.8E-11
5E-15
3E-15
OE-16
2E-16
3E-17
9E-17
OE-18
2E-18
(a)
Value averaged over all directions.
^ 'Value for direction of greatest risk.
5-13
-------
Table 5-5. National Population Exposures and Intakes Per Year
(Post-Operational Phase)
210
222
Rn
_
Radon Decay
Products
Pb Intakes
_ i i.v/uuv.i-0 Inhalation Ingestion
Release Site (person-Ci-y/m ) (person-WLy) (person-Ci) (person-Ci)
New Mexico
Grants
Texas
Falls City
Washington
Wellpinit
Wyoming
Casper
Average
4.9E-07
7.6E-07
4.2E-07
5.8E-07
5.7E-07
3.5
5.3
3.0
4.1
4.0
1.2E-06
1.3E-06
1.3E-06
1.5E-06
1.3E-06
7.0E-06
6.4E-06
8.4E-06
7.7E-06
7.0E-06
Table 5-6. Regional Ground Surface Concentrations (Ci/m^)
for Radionuclides^3'
(Operational Phase)
Distance
(meters)
600
1000
2000
3000
4000
5000
10000
20000
'a' Average:
Maximum:
u,
Average
3.
1.
2.
1.
5.
3.
7.
1.
9E-09
1E-09
4E-10
OE-10
5E-11
5E-11
7E-12
9E-12
U
Maximum
8.1E-09
2.9E-09
7.4E-10
3.2E-10
1.7E-10
1.1E-10
2.4E-11
5.9E-12
value averaged over
value for
direction
Th, '
Average
5
1
3
1
7
5
1
2
all
of
. 5E-08
.6E-08
.5E-09
.5E-09
.8E-10
.OE-10
.1E-10
.7E-11
" Ra
Maximum
1.
4.
1.
4.
2.
1.
3.
8.
2E-07
2E-08
OE.08
6E-09
5E-09
6E-09
5E-10
4E-11
Pb,
Average
5.
1.
3.
1.
7.
4.
1.
2.
3E-08
5E-08
3E-09
4E-09
5E-10
8E-10
1E-10
6E-11
Po
Maximum
1.
4.
1.
4.
2.
1.
3.
8.
1E-07
OE-08
OE-08
4E-09
4E-09
5E-09
3E-10
1E-11
directions.
greatest
risk.
5-14
-------
r\
Table 5-7. Regional Population Ground Surface Exposure (person-Ci/m )
for Radionuclides (per Operational Year)
(km)
20
20-40
40-80
Total
20
20-40
40-80
Total
Persons
16
4,572
52,840
57,428
2,273
5,314
14,235
21,822
238u, 234u
Remote Site
3.3E-08
9.9E-09
5.9E-08
l.OE-07
Rural Site^
5.8E-06
2.9E-08
5.9E-09
5.8E-06
23°Th, 226Ra
[a)
4.7E-07
1.4E-07
8.4E-07
1.5E-06
a)
8.3E-05
4.1E-07
8.4E-08
8.3E-05
21°Pb, 21°Po
4.2E-07
1.2E-07
7.4E-07
1.3E-06
7.3E-05
3.6E-07
7.5E-08
7.3E-05
(a)
See Chapter 4 for description of sites.
Table 5-8. Regional Ground Surface Concentrations (Ci/m )
for Radionuclides by Distance^a^
(Post-Operational Phase)
Distance
(meters)
600
1000
2000
3000
4000
5000
10000
20000
' a' Average: :
Maximum:
U
Average
2
5
1
5
2
1
4
1
.1E-08
.9E-09
.3E-09
.5E-10
.9E-10
.9E-10
.1E-11
.OE-11
value
value
£,*/
U
Maximum
4
1
3
1
9
5
1
3
.3E-08
.6E-08
.9E-09
.7E-09
.2E-10
.9E-10
.3E-10
.2E-11
averaged over
for direction
Th,
Average
2.9E-07
8.4E-08
1.8E-08
7.8E-09
4.2E-09
2.7E-09
5.9E-10
1.5E-10
£_ L.
Ra
Maximum
6
2
5
2
1
8
1
4
.2E-07
.2E-07
.6E-08
.4E-08
.3E-08
.4E-09
.8E-09
.5E-10
Pb,
Average
2
7
1
6
3
2
5
1
.6E-07
.4E-08
.6E-08
.9E-09
.7E-09
.4E-09
.2E-10
.4E-10
£- J.
Po
Maximum
5
2
4
2
1
7
1
4
.5E-07
.OE-07
.9E-08
.2E-08
.2E-08
.4E-09
.6E-09
.4E-10
all directions.
of greatest risk.
5-15
-------
Regional population surface exposures for the operational phase
corresponding to these concentrations are shown in Table 5-7. These
values give the total exposure to the population for each year's
operation of the mill.
The national population dose resulting from deposition of radon
decay products, primarily the long-lived lead-210, is dominated by the
ingestion pathway. For this reason, separate ground surface exposures
are not given here. Intakes due to ingestion are discussed in
Section 5.4.4.
Post 0 p e rat ion a1
Post-operational regional ground surface concentrations are given
in Table 5-8. These representative values are calculated for the end
of a 100-year release period.
Since only the magnitude of the source term is different,
post-operational surface exposures are not listed separately. They
may be obtained by multiplying the values in Table 5-7 by factor 1.6.
Separate national ground exposures are not shown, since they are
not significant compared to ingestion doses, which are given below,
5.4.4 Dietary Intake
Food consumption fractions for the regional population are shown
in Table 5-9. We have assumed that the mill is sited in a region of
low agricultural productivity and that area residents produce the same
amount of their own food supply as urban residents.
Table 5-9. Regional Food Utilization Factors for An Individual
Home Produced Total Annual
Type of Food (Percent) Consumption
Leafy vegetables 7.6 18 kg
Other produce 7.6 176 kg
Milk 0.0 112 L
Meat 0.8 85 kg
5-16
-------
Annual ingestion intakes for an individual residing in the region
are given in Table 5-10 Eor the operational phase and in Table 5-11 for
the post-operational phase. Annual regional population ingestion
values for the operational phase are given in Table 5-12. Since the
only difference is in the source term, values for the post-operational
phase are a factor of 1.6 larger than those in Table 5-12.
Annual national population exposures due to the ingestion of
long-lived radon decay products are dominated by lead-210. Dose and
risk calculations take account of the lead decay products as they build
up within the body following lead-210 intake. Table 5-3 gives the
annual population exposure resulting from dietary intake of lead-210
during the operational phase of the model mill. Post-operational
exposures are shown in Table 5-5.
5.4.5 Water Concentrations
In general, meaningful modeling of water pathways can be done only
on a site-specific basis, since any model depends strongly on the
hydrological and geological characteristics of the area. NRC (NRC80)
has performed a detailed analysis for the model mill based on a set of
assumed parameters. However, the environmental impact of a given
tailings pile depends on so many factors, i.e., wind erosion, floods,
slides into nearby streams, seepage through the pile, runoff of
rainwater, etc., that each must be evaluated on an ad hoc basis.
Surface Water
During operation of the mill, the pathways noted in Section 5.3
could cause the transfer of contaminants to surface waters. However,
based on the rainfall in the model mill region, the quantities of
material washed or leached into flowing surface waters could be so
dispersed and rapidly diluted that it is unlikely that surface water
would pose a significant health problem. Since the moisture content of
the tailings is reduced after mill operations cease, the potential for
surface water contamination is even less.
Under the Clean Water Act, effluent guidelines are already in
effect for uranium mills. In addition, EPA has New Source Performance
Standards for new uranium mills that would eliminate the discharge of
process waste water. In view of this comprehensive regulatory program
for surface water discharges from the uranium milling industry, surface
water contamination is not addressed in this analysis.
Groundwater
The modeling of groundwater contamination by tailings piles
depends strongly on the chemical and physical properties of the
underground environment. The NRC model predicts that, in spite of the
initial presence of radioactive materials in the seepage, no
5-17
-------
O O O
+ + I
W W W
oo CM so rn
_< CM ,-( IA
»?£
Is
m CM i-t
CN .-I ,-1
w w w w
,-1 ,-( \0
CM f-H i-l
W W
so m
-3- -<
O O
I |
Ed w
rt it cn
WWW
w w w
on o\ CM co
en so ^H
5-18
-------
g.s
C 4J
< n3
.-< Dfi
r-H
I M
in o
UJ W W W
w w w w w w
CM ,-< rH
CO ^O
-------
radioactive contamination of groundwater would be expected during or
after mill operation. Based on their parameters, many of the
contaminants present in the acidic tailings pond water would
precipitate out or undergo ion exchange and be removed by soil from the
tailings seepage water. Potential contamination, as indicated by this
model, would be limited to toxic materials having relatively high
mobility. The health aspects of these materials are discussed in
Chapter 6.
Since control of groundwater pollution is already required for
conformance with existing water protection regulations, we have not
performed a detailed analysis for this pathway.
Table 5-12. Regional Population Ingestion (person-pCi)
for Radionuclides (per Operational Year)
Distance
(km)
20
20-40
40-80
Total
20
20-40
40-80
Total
Number of
Persons
16
4,572
52,840
57,428
2,273
5,314
14,235
21,822
238U, 234U 230Th 226Ra
210
Remote
1.4 1.8E+01
4.1E+02 5.3E+03
4.7E+03 6.0E+04
5.1E+03 6.5E+04
Rural Site(5
3.0E+02 3.9E+03
7.1E+02 9.1E+03
1.9E+03 2.4E+04
2.9E+03
3.7E+04
Chapter 4 for description of sites.
5.6E+01
1.6E+04
1.8E+05
2.0E+05
1.2E+04
2.8E+04
6.9E+04
1.1E+05
Pb
210
2.3E+01
6.5E+03
7.5E+04
8.2E+04
4.7E+03
1.1E+04
2.9E+04
4.5E+04
Po
2.7E+01
7.8E+03
9.0E+04
9.8E+04
5.0E+03
1.2E+04
3.1E+04
4.8E+04
5-20
-------
REFERENCES
Be81 Begovich C.L., Eckerman K.F., Schlatter E.G., Ohr S.Y., and
Chester R.O., "DARTAB: A Program to Combine Airborne
Radionuclide Environmental Exposure Data with Dosimetric and
Health Effects Data to Generate Tabulations of Predicted
Health Impacts," ORNL-5692, Health and Safety Research
Division, ORNL, Oak Ridge, Tennessee, 1980.
Du80 Dunning D.E., Leggett R.W., and Yalcintas M.G., "A Combined
Methodology for Estimating Dose Rates and Health Effects from
Exposure to Radioactive Pollutants," ORNL/TM-7105, Health and
Safety Research Division, ORNL, Oak Ridge, Tennessee, 1980.
EPA79a Environmental Protection Agency, "Indoor Radiation Exposure
Due to Radium-226 in Florida Phosphate Lands," EPA
520/4-78-013, Office of Radiation Programs, EPA, Washington,
D.C, July 1979.
EPA79b Environmental Protection Agency, "AIRDOS-EPA: A Computerized
Methodology for Estimating Environmental Concentrations and
Dose to Man from Airborne Releases of Radionuclides,"
EPA 520/1-79-009, Office of Radiation Programs, USEPA,
Washington, D.C., December 1979.
He75 Heffter J.L., Taylor A.D., and Ferber G.J., "A
Regional-Continental Scale Transport, Diffusion, and
Deposition Model," NOAA Tech. Memo, ERL/ARL-50, 1975.
Mo76 Moeller D.W. and Underbill D.W., "Final Report on Study of the
Effects of Building Materials on Population Dose Equivalents,"
School of Public Health, Harvard University, Boston, December
1976.
NRC80 Nuclear Regulatory Commission, "Final Generic Environmental
Impact Statement on Uranium Milling," NUREG-0706, USNRC,
Washington, D.C. 1980.
Oa72 Oakley D.T., "Natural Radiation Exposure in the United
States," ORP/SID 72-1, USEPA, Washington, D.C., 1972.
Po78 Porstendorfer J., Wicke A., and Schraub A., 1978, "The
Influence of Exhalation, Ventilation, and Deposition Processes
Upon the Concentration of Radon, Thoron and Their Decay
Products in Room Air," Health Physics 34- (465).
Tr79 Travis C.C., Watson A.P., McDowell-Boyer L.M., Cotter S.J.,
Randolph M.L., and Fields D.E., "A Radiological Assessment of
Radon-222 Released from Uranium Mills and Other Natural and
Technologically Enhanced Sources," ORNL/NUREG-55, ORNL,
Oak Ridge, Tennessee, 1979.
5-21
-------
Chapter 6: HEALTH IMPACT OF TAILINGS BASED ON MODEL TAILINGS PILES
In this chapter we consider the health impact of material coming
from the model pile. When feasible, projections, based on these
results, for the total impact of the industry are developed in
Chapter 10. Data on the concentrations of radioisotopes for
individuals or populations at various distances from the model pile,
taken from Chapter 5, were combined with the risk coefficients
described in Appendix C to estimate the risks to individuals and
populations living around the model pile. Potential effects on local,
regional, and national populations are estimated.
6.1 Introduction
Among metallic ore wastes, uranium tailings piles are unusual
because of the amount of radioactivity they contain. Radioactivity
probably constitutes the principal source of hazard to health from
these wastes, although nonradioactive toxic chemicals, such as arsenic,
lead, selenium, mercury, sulphates, and nitrates are usually present.
Milling of uranium ore removes about 90 percent of the uranium in the
ore. The remainder, along with most other radioactive materials and
toxic chemicals, is discarded in the liquid and solid wastes discharged
to tailings piles.
The principal isotope of uranium, uranium-238, decays over
billions of years to become lead, a stable nonradioactive element.
This lengthy decay process involves a series of intermediate
radioactive decay products, such as thorium-230, radium-226, and
radon-222. The decay of uranium since the ore was formed millions of
years ago has built up an inventory of these decay products, which are
present in uranium mill tailings in various concentrations.
The dominant hazard from tailings is due to the radioactive decay
products of uranium-238, particularly radium-226 and its short
half-life decay products. Each gram of natural uranium ore contains
about 490 pCi each of uranium-238 and uranium-234 and additionally
about 23 pCi of uranium-235 and 2 pCi of thorium-232. Because they
occur in relatively small proportions and/or pose much less risk to
health, uranium-235 and thorium-232 and their radioactive decay
products may usually be ignored in evaluating the hazard of uranium
tailings.
6-1
-------
Uranium tailings emit three kinds of radiation: alpha particles,
beta particles, and gamma rays. All are forms of ionizing radiation,
which breaks up molecules into electrically charged fragments called
ions. In biological tissues, this ionization can produce harmful
cellular changes. At the low radiation levels usually encountered in
the environment, we expect the effects of such changes to be difficult
to detect. Studies show, however, that people exposed to radiation
have a greater chance of developing cancer. If the ovaries or testes
are exposed, the health or development of future generations of
children may also be impaired due to genetic damage. This genetic
damage includes gene mutations and chromosome aberrations. Effects of
the damage may be conspicuous or invisible, serious or trivial, with a
possibility of occurring in the first generation after exposure or
hundreds of generations in the future (NAS80). Only effects causing
serious handicap at sometime during the lifespan are addressed in this
document .
One cannot predict with precision the increased chance of cancer
or genetic damage after exposure to radiation. We have based our risk
estimates on studies of persons exposed at doses higher than those
usually resulting from tailings and the assumption that at lower doses
the effects will be proportionally less. This assumption may over-
estimate or underestimate the actual risk, but it is the best that can
be done at present (EPA76).
Alpha, beta, and gamma radiations from mill tailings can
cancer or genetic damage. However, the major threat comes from
breathing air containing radon decay products with short half -lives
polonium-218, for example and exposing the lungs and other internal
organs to the alpha radiation these decay products emit. In addition,
people may be directly exposed to gamma rays from radioactive material
in the tailings pile, and radioactive tailings particles may be
transported into the body by breathing or ingestion.
The body's internal organs would still be exposed to radiation
from radionuclides even if uranium tailings piles suddenly disappeared,
because radon, radium, uranium, thorium, and other radioactive elements
occur naturally in the air, rock, and soil. One picocurie of radium
per gram of soil is a typical concentration; outdoor air contains a few
tenths of a picocurie of radon per liter (UN77). Normal eating and
breathing introduce these and other radioactive materials into the
body, Increasing the potential for cancer and genetic damage. This
discussion, therefore, also compares the health risks from tailings to
those from normal exposure not to justify the tailings risk, but to
provide a realistic context for comparison.
Tailings also contain toxic elements that could eventually be
inhaled or ingested by man and animals or absorbed by plants. Windblown
tailings inhaled by man or animals are unlikely to cause any toxicity
problems because the mass of inhaled material is so small. However,
the toxic elements in windblown tailings could be absorbed by plants
6-2
-------
growing near a pile and could be a potential pathway leading to chronic
toxicity diseases in men or animals eating those plants. Moreover,
toxic elements from tailings could leach or seep into water supplies
used for irrigation or drinking. Finally, windblown tailings and radon
decay products could be deposited directly onto some foods, such as
lettuce and spinach.
It is important to distinguish between acute and chronic
toxicity. Acute toxicity (or poisoning) occurs when enough of the
toxic element is consumed to interfere with a vital body or organ
function. The severity of the poisoning is usually proportional to the
amount of the toxic element consumed, and in extreme cases death or
permanent injury will occur. Chronic toxicity is more insidious. It
occurs when small amounts of a toxic element are consumed over a
prolonged period of time. A small fraction of each intake may be
deposited in tissues or organs. Toxic symptoms appear when the
cumulative deposit exceeds a critical level. Alternatively, each
intake of a toxic element may cause a small increment of organ damage.
Symptoms of toxicity become apparent when this damage accumulates to a
critical extent. Symptoms of chronic toxicity may be reversible if
consumption of the toxic element Is stopped, or they may be
irreversible, progressive, or both.
In the case of tailings, acute toxicity would be a problem only if
standing water adjacent to or on a pile is consumed. Chronic toxicity
is more likely and is therefore examined in later discussions.
6.1.1 Radon and its Immediate Decay Products
Since the milling and extraction processes have removed most of
the uranium from the ore, the longevity of the remaining radioactive
members of the uranium series is determined by the presence of
thorium-230, which has a 77,000-year half-life. The thorium-230 decay
product, radium-226, has a 1,600-year half-life. Both thorium and
radium are relatively insoluble and immobile in their usual chemical
forms. However, the decay product of radium-226 is radon-222, an inert
radioactive gas, that readily diffuses through interstitial spaces to
the surface of the tailings pile where it becomes airborne. The
half-life of radon-222 is 3.8 days, so some radon atoms can travel
thousands of miles through the atmosphere before they decay.
As shown in Figure 3-1, the radon decay process involves seven
principal decay products before ending with nonradioactlve lead. The
four short half-life radioactive decay products immediately following
radon are the most important sources of cancer risk. These decay, for
the most part, within less than an hour. Members of the decay chain
with relatively long half-lives (beginning with lead-210, which has a
22-year half-life) are more likely to be ingested than breathed and
represent much smaller risks.
6-3
-------
The principal short half-life products of radon are poloniura-218,
lead-214, bismuth-214, and polonium-214. Polonium-218, the first decay
product, has a half-life of just over 3 minutes. This is long enough
for most of the electrically charged polonium atoms to attach themselves
to microscopic airborne dust particles that are typically less than a
millionth of a meter across. When breathed, these small particles have
a good chance of sticking to the moist epithelial lining of the bronchi.
Most inhaled particles are eventually cleared from the bronchi by
mucus, but not quickly enough to keep the bronchial epithelium from
being exposed to alpha radiation from polonium-218 and polonium-214.
This highly ionizing radiation passes through and delivers radiation
doses to several types of lung cells. The exact doses delivered to
cells that eventually become cancerous cannot be characterized
adequately. Also, we do not have detailed knowledge of the deposition
pattern of the radioactive particles in the lung and the distances'from
them to cells that are susceptible. Further, there is some disagreement
about the types of bronchial cells where cancer originates. Therefore,
we have based our estimates of lung cancer risk on the amount of inhaled
radon decay products to which people are exposed, rather than on the
dose absorbed by the lung.
6.2 Estimated Effects on Health Due to Radioactive Releases from the
Model Tailings Pile
Risk factors from Tables C-3 to C-10 (see Appendix C) were used in
the DARTAB computer code to determine individual and population
lifetime risks for continuous exposure to emissions from the model
tailings pile. The calculated health impact on individuals and
populations is shown in Tables 6-1 through 6-6. The risk averages
given are population averages over the indicated sector. As shown in
these tables, about 99 percent of the inhalation risk is due to radon
and its daughters.
Values in these tables are shown to two significant figures solely
to facilitate comparisons and additional calculations; these projec-
tions have overall uncertainties of at least a factor of 2 or 3. The
individual health risks are for a lifelong exposure to the environmental
concentrations discussed in Chapter 5. A shorter period of exposure
may be assessed by assuming that the risk due to that exposure or
intake had been spread over the individual's lifetime. For example,
the risk from a 15-year exposure would be approximated as 15/70.76
times the lifetime (70.76 years is the expected lifespan of an
individual in the RADRISK cohort). The population health effect values
are the number of cancer deaths per year calculated at equilibrium for
a stationary population living at the calculated environmental
concentration levels. These values are equivalent to the number of
health effects committed per year of operation. (The age distribution
of the stationary population is that for the U.S. life table population
in 1970, assuming a constant birth rate, and no external migration.)
6-4
-------
Cancer
H
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6-5
-------
Cancer
2
«H
o
a
3 'S
II
"3 «
nal Individu
(Post-Opew
-H
HO
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5
1
s
a
f,
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3
V
u
td Suite
tposure
S»
o
lalatlon
ilculates Inl
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4J
(0
0)
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(meters) A\
CM cn in o oo *n
o en CM oo CM o CM
en P*-
-------
Table 6-3. Number of Fatal Cancers per Operational Year for the Regional Population
Distance
(km)
20
20-40
40-80
Total
20
20-40
40-80
Total
Number of
Persons
4,
52,
57,
2,
5,
14,
21,
^a-'See Chapter
Table
Distance
(km)
20
20-40
40-80
Total
20
20-40
40-80
Total
6-4.
16
572
840
428
273
314
235
822
4 for
Ingestion
1.
2.
3.
3.
2.
4.
1.
2.
OE-08
9E-06
4E-05
7E-05
1E-06
9E-06
3E-05
OE-05
description
Number of
Number of
Persons
4,
52,
57,
2,
5,
14,
21,
16
572
840
428
273
314
235
822
Ing
1.
4.
5.
5.
3.
7.
2.
3.
Fatal
estion
6E-08
6E-06
4E-05
9E-05
4E-06
8E-06
1E-05
2E-05
Radioactive
Particulates
Inhalation Ground Surface
2
1
6
1
5
3
7
5
Remote
.OE-06
.3E-06
.9E-06
.OE-05
Rural
.4E-04
.3E-06
.5E-07
. 5E-04
9.4E-06
2.8E-06
1.7E-05
2.9E-05
Site(a)
1.6E-03
8.3E-06
1.7E-06
1.7E-03
Subtotal
1.1E-05
7. OE-06
5.8E-05
7.6E-05
2.1E-03
1.7E-05
1.5E-05
2.3E-03
Radon Decay
Products
5.
3.
1.
2.
1.
4.
3.
1.
7E-04
5E-03
7E-02
1E-02
7E-01
8E-03
3E-03
8E-01
Total
5.8E-04
3.5E-03
1.7E-02
2.1E-02
1.7E-01
4.8E-03
3.3E-03
1.8E-01
of sites.
Cancers per Post-Operational Year
Radioactive
Particulates
Inhalation Ground Surface
3
2
1
1
8
5
1
8
Remote
.2E-06
.1E-06
.1E-05
.6E-05
Rural
. 6E-04
.3E-06
.2E-06
. 8E-04
Site
1.5E-05
4.5E-06
2.7E-05
4.6E-05
Site^a)
2.6E-03
1.3E-05
2.7E-06
2.7E-03
for the
Subtotal
1.8E-05
1.1E-05
9.2E-05
1.2E-04
3.5E-03
2.6E-05
2.5E-05
3.6E-03
Regional Population
Radon
Decay
Products
9.
5.
2.
3.
2.
5.
2.
1E-04
6E-03
7E-02
4E-02
7E-01
7E-03
3E-03
9E-01
Total
9.3E-04
5.6E-03
2.7E-02
3.4E-02
2.7E-01
7.7E-01
5.3E-03
2.9E-01
(a)
See Chapter 4 for description of sites.
6-7
-------
Table 6-5. U.S. Collective Risks due to 222Rn Release
per Operational Year
(Fatal Cancers)
Release Site
New Mexico
Grants
Texas
Falls City
Washington
Wellpinit
Wyoming
Casper
Average
Inhalation
l.OE-04
1.1E-04
1.1E-04
1.3E-04
1.1E-04
210Pb Intake
Ingest ion
2. IE -04
1.3E-04
2.5E-04
2.3E-04
2.1E-04
Total
3.2E-04
2.4E-04
3.6E-04
3.5E-04
3.2E-04
Radon Decay
Product
Exposure
5.2E-02
8.0E-02
4.4E-02
6. IE -02
5.9E-02
Table 6-6. U.S. Collective Risks due to 222Rn Release
per Post-Operational Year
(Fatal Cancers)
Release Site
New Mexico
Grants
Texas
Falls City
Washington
Wellpinit
Wyoming
Casper
Average
Inhalation
1.6E-04
1.8E-04
1.7E-04
2.0E-04
1.8E-04
210 Pb Intake
Ingestion
3.3E-04
2.1E-04
4.0E-04
3.7E-04
3.3E-04
Total
5.0E-04
3.8E-04
5.7E-04
5.7E-U4
5.1E-04
Radon Decay
Product
Exposure
8.2E-02
1.3E-01
7. IE -02
9.8E-02
9.5E-Q2
6-8
-------
6.2.1 Effects of Radioactive Partlculate Releases from the Model
Tailings Pile
Individuals and Regional Populations
Windblown tailings from the model tailings pile may be inhaled by
persons in the vicinity of the pile. They may also be deposited on
soil or vegetation, be transferred to edible plants and ingested by
members of the population around the pile. The contribution of these
two pathways is included in the risk estimates listed in Tables 6-1 to
6-4. The period for greatest risk from windblown particulates is
during the post-operational phase of the mill after the tailings pile
has been allowed to dry (Tables 6-2, 6-4).
The risk (expectation of developing a fatal cancer) to an
individual for a lifelong exposure is shown in Tables 6-1 and 6-2 as a
function of distance from the center of the pile. Risks from all
pathways of exposure are listed for the maximum exposed individual at
each distance. Depending on whether the local population density is
high or low, e.g., a rural site versus a remote site, the expected
number of fatal cancers in the regional population may vary by orders
of magnitude as shown in Tables 6-3 and 6-4.
Genetic effects from windblown particulates were also calculated
for the two site populations. For the rural site, we calculate a
commitment of 7 x 10~4 genetic effects per operational year and
1 x 10~3 genetic effects per year after operations cease. The
corresponding values for the remote site are 1 x 10~4 genetic effects
per operational year and 2 x 10^ thereafter. As indicated in
Appendix C these are order-of-magnitude estimates of the genetic
effects to all future generations.
6.2.2 Effects of Radon Emissions from Tailings Piles
Individuals and Regional Populations
Detailed information is needed to determine the exposure due to
radon decay products in a population. An accurate calculation of the
collective exposure from a particular pile would require, in addition
to the number of people exposed, the site and ventilation
characteristics of each person's residence and work place, the length
of time a person spends at each place, and the average annual
distribution of wind speed and direction.
We have estimated local and regional exposure at the model site
using the methods to estimate exposures described in Section 5.4. The
population data used are those presented in Chapter 4, although future
changes are almost certain. Some population data are updated in
Section 6.6 below.
6-9
-------
The excess risk to people due to exposure to radon decay products
depends on their distance from the pile. Tables 6-1 and 6-2 list
estimated excess risks to individuals for lifetime residency, as a
function of distance from a model pile during operational and
post-operational phases of the pile, respectively. The decay product
concentrations are based on a dispersion factor that depends on the
area of the pile out to a distance of several pile diameters. Beyond
that distance the theoretical pile can be considered as a point source
for the purpose of estimating concentration levels. The estimates for
this pile are based upon the relative risk model and assume a stationary
population. We estimate the maximum lifetime risk of fatal cancer to
an individual living 600 meters from the center of the pile is 1.2 x
10~^ during the operational period and 1.9 x 10~^ during the
post-operational period.
The estimated risk of lung cancer from naturally-occurring radon
decay products found in homes that are not near mill tailings or any
other specifically identified radon source is 0.004 to 4 chances in
1,000 (EPA82). National data on radon decay products in homes (EPA82)
are scanty and vary widely among individual houses. These estimates
are based on the assumption that the average radon decay product
concentration is 0.004 WL in homes and that they are occupied 75
percent of the time. This assumed average level of radon decay
products is based on recent data on 21 houses in New York and New
Jersey (Ge78) and on 26 houses in Florida (EPA79) and is consistent
with data obtained in other countries (UN77). For comparison, these
risks are about 10 percent of the expected lifetime risk of lung cancer
death from all causes (0.029) in a stationary population having 1970
U.S. lung cancer mortality rates.
Effects on the U.S. Population
Radon emissions from a tailings pile may affect the health of
populations beyond 80 kilometers from tailings piles. The aggregate
effect on persons living more than 80 kilometers from the pile is
summarized in Tables 6-5 and 6-6. These results are estimates of the
total risk committed over 100 years to an exposed population of 200
million persons. Although the U.S. population increase has not been
uniform, an increased risk on the order of 20 percent should provide a
rough estimate of the risk to the current population.
Effects from Long-Lived Radioactive Decay Products of Radon
The long-lived decay products of radon, beginning with lead-210
(see Figure 3-1), are also potential hazards. A quantitative estimate
of the impact of eating and breathing long-lived decay products from
the model pile cannot be established without site-specific information
on food sources (Tr79), for example. The only detailed study available
was prepared by Oak Ridge National Laboratory (Tr79) for the four sites
listed in Chapter 5. We used these results in an input to our risk
models to compare their importance to that of the short-lived decay
products of radon. These comparisons are shown in Tables 6-5 and 6-6.
These results should not be taken as quantitative estimates of the
actual risk at specific active sites.
6-10
-------
The four sources of exposure in this analysis are shown in
Tables 6-1 to 6-4. The largest risk is from breathing short-lived
radon decay products; the risk is 100 to 1000 times greater than the
next highest risk, for both individuals and for the regional
population. Persons living more than 80 kilometers from a model pile
are less exposed, and their risk would be considerably below that
indicated in Tables 6-1 to 6-4. But again, the risk from breathing
short-lived radon decay products is about 100 times greater than from
other pathways (Tables 6-5 and 6-6). We conclude that the risks from
these pathways can be ignored compared to that from breathing short-
lived radon decay products.
6.2.3 Effects of Gamma Radiation Emissions from Tailings Piles and
Windblown Tailings
Gamma radiation exposure of individuals depends on how close
to the edge of a pile people live or work and how tailings from the
pile are distributed by the wind. The collective gamma radiation dose
depends on both the number of people exposed and their doses. Potential
individual doses can be approximated from available data, but accurate
estimates cannot be made without a variety of detailed information,
such as where people live and work and the amount of shielding provided
by buildings.
Gamma radiation from tailings exposes the entire body so that all
organs are at risk. The estimated frequency of fatal cancer and
serious genetic effects due to exposure of 1 mrad/y are listed in
Tables C-l and C-2 in Appendix C. People who live or work near
tailings piles will incur additonal risk from long-term exposures in
proportion to the excess of their average lifetime annual dose rate
above the normal background rate (approximately 100 mrem per year).
The estimated contribution of gamma radiation emissions to individuals
and populations in the vicinity of the model tailings pile is shown in
Tables 6-1 to 6-4 in the column headed "Ground Surface."
6.3 Effects from Misuse of Tailings
When tailings are used in building construction, there can be
serious risks to the health of those who live in such buildings. The
Grand Junction experience is an example of what can happen when this
kind of misuse occurs. There, about 700 buildings are contaminated
with enough tailings to increase average indoor radon decay product
levels by at least 0.01 WL; a few houses have levels higher than 0.5 WL.
Assuming that the useful lifetime of these buildings is 70 years, we
estimate about an additional 70-150 lung cancers would occur if
remedial measures were not taken.
The estimated risks to individuals exposed to these high levels of
radon decay products are very large. For persons living in a house
6-11
-------
with a concentration of 0.1 WL, the potential excess lifetime risk of
lung cancer is 0.5 to 1 chance in 10.
Other misuses of tailings, e.g., tailings used in gardens or
underneath detached buildings, can cause effects on health, but these
cannot be estimated easily. The risks depend on the particular way in
which the tailings are used, and effects on health may be due to gamma
radiation, ingestion of radionuclides through food chains, or
inhalation.
6.4 Estimated Effects on Health Due to Toxic Releases from the Model
Tailings Pile
Toxic materials have been considered in this EIS if they are in
substantially greater concentration in tailings than in native rocks or
soils or in a relatively mobile form (as either anions or cations). We
have included materials that are harmful to livestock and plants as
well as those potentially affecting humans directly. Evaluating the
potential risks from nonradioactive toxic substances in tailings
requires different methods from those used for radioactive
substances.CD With nonradioactive toxic materials the type of
effect varies with the material; the severity of the effectbut not
its probability of occurringincreases with the dose. Moreover,
because the body can detoxify some materials or repair the effects of
some small doses, often no toxic effects occur below a threshold dose.
We cannot construct a numerical risk assessment for nonradioactive
toxic substances because we do not have enough information. We can,
however, qualitatively describe risks of toxic substances in terms of
their likelihood of reaching people (or animals, or agricultural
products), concentrations at which they may be harmful, and their toxic
effects.
No acute effectsdeath in minutes or hourscould occur except by
drinking liquid directly from a tailings pond. Severe sickness, or
death within days to weeks, from the use of highly contaminated water
is possible, but very unlikely.
Chronic toxicity from the continuous consumption of contaminants
at low concentrations could be a problem. Toxic substances can
accumulate slowly in tissues, causing symptoms only after some minimum
amount has accumulated. Such symptoms of chronic toxity develop
slowly, over months or years.
(I'Many nonradioactive substances can induce cancer in experimental
animals (Go77, Ve78). However, for nonradioactive substances found in
uranium mill tailings, we do not feel that dose-response relationships
adequate for estimating such risks for oral intake have been developed.
6-12
-------
In Table 4-5 we listed many chemical elements and ions that have
been found in tailings piles. Many of these occur in tailings in only
slightly higher concentrations than in background soils, and they also
have low toxicity when taken orally (Ve78). The following elements are
in this category: lanthanides, including cerium, europium, lanthanum,
and terbium; silicates; and zirconium, scandium, boron, gallium, and
aluminum. Some other elements may be in elevated concentrations in
tailings, but they, too, are not very toxic. These include copper,
manganese, magnesium, cobalt, iron, vanadium, zinc, potassium,
chloride, and sulfate. Some elements and ions at concentrations well
below levels toxic to humans and animals will cause water to have an
objectionable taste and color. Examples are iron, copper, manganese,
chloride, and sulfate.
Other substances are both present in tailings and are regulated
under the National Interim Primary Drinking Water Regulations (NIPDWR).
Listing in the NIPDWR is an indication of a significant need to limit
direct human consumption of these substances. The NIPDWR cover the
following elements: arsenic, barium, cadmium, chromium, lead, mercury,
nitrate, selenium, and silver. The toxicologies of these substances
are discussed in Appendix C. Molybdenum is both toxic and present in
tailings in elevated concentrations; its toxicity is also discussed in
Appendix C. Appendix C also discusses both the chemical and
radiological toxic effects of ingesting radium, thorium, and uranium.
Tailings are not known to be significant sources of other toxic
materials regulated under the NIPDWR, such as organic substances,
microbiological organisms, and man-made radioactivity.
6.5 Effects Expected in Plants and Animals
No significant adverse effects are expected in plants or animals
from radioactive emissions from the model tailings pile.
No attempt to estimate health effects from toxic materials
released from the model tailings pile is made since such estimates
require site-specific data on concentrations in water used for
irrigation or watering livestock, agricultural practices, and so
forth. Data on toxicity and an approach to estimating levels toxic to
plants and animals are detailed in Appendix C. In a properly
controlled tailings pile, there should be no hazard to plants or
animals.
6.6 Total Radon Decay Product Population Risk from the
Uranium Milling Industry
The estimate of the total population risk from radon emissions
from all active tailings piles is presented in this section.
The number of people living within a 5-km radius of each tailings
pile was counted by Battelle Pacific Northwest Laboratories (PNL) and
is presented in Appendix E. The total number of people living within
each annulus is:
6-13
-------
Number of People
Annulus
(km from centroid of piles)
0-0.5
0.5-1.0
1,0-2.0
2.0-3.0
3.0-^.0
4.0-5.0
Total 14,737
The population risk to these people was estimated by multiplying
the number of people in each annulus by the average individual risk of
fatal cancer at the enter of each annulus. This risk was extrapolated
from the values given in Table 6-2, except for the 0-0.5 km annulus
where the maximum individual risk was used. The total risk to the
population within 5 km of tailings piles is estimated to be 0.38 deaths
per year.
The number of people (3,649,271) living within the 5- to 80-km
annulus of each tailings pile was calculated from 1970 Bureau of Census
data (Ew73). A large part of this population was due to six sites: 2
in Texas which are within 80 km of San Antonio, 2 in Washington which
are about 40 km from Spokane, 1 in New Mexico which is within 80 km of
Albuquerque, and 1 in Colorado which includes Pueblo and Colorado
Springs within 80 km. While the total number of people was greater
than an equivalent number of model remote sites (see Table 4-2), the
distribution was similar with most of the people located in the 40 and
80 km annulus. Therefore, it was considered reasonable to estimate the
risk using the model remote site and correcting for the difference in
total populations.
The population risk to the people living in the 5 to 80 km annuli
of the 26 active piles is then:
(26 piles) C0.034 ffgJS) (^fgffg,) - 2.!
-------
The nationwide collective risk is:
t^c. j i \ /A nnc deaths,. _ ._. deaths
(26 piles) (0.095 n7) = 2.47
^ pile/y year
where the risk factor is from Table 6-6.
The total collective risk from existing piles is
0.-5.0 km
5.0-80 km
Nationwide
4.95 deaths/year
The collective risk from new tailings piles is considered to be
most like the risk from remote sites. Most future uranium milling is
likely to occur in New Mexico, Utah, and Wyoming, the currently
developed areas. Thus, the likelihood of a large regional population
is vanishingly small; Albuquerque is the only large city in these
areas. Also, current siting practice prevents locating uranium mills
near heavily populated area, so> the local (within 5 km) population
should be very small. Therefore, the population risk from new piles is
estimated using the remote site risk factor from Table 6-4, the
nationwide risk factor from Table 6-6, and nine new piles as projected
in the RIA:
(9 piles) (0.034 L)+ (9)(0.095 ) = 1.16
v pile/y pile/y year
6-15
-------
REFERENCES
EPA76 Environmental Protection Agency, "ORP Policy Statement on the
Relationship Between Radiation Dose and Effect, March 3, 1975;
Drinking Water Regulations, Radionuclides," Federal Register,
41.28409, July 9, 1976.
EPA79 Environmental Protection Agency, "Indoor Radiation Exposure
Due to Radlu«-226 in Florida Phosphate Lands," EPA
520/4-78-013, Office of Radiation Programs, USEPA, Washington,
D.C., July 1979.
EPA82 Environmental Protection Agency, "Final Environmental Impact
Statement for Remedial Action Standards for Inactive Uranium
Processing Sites," EPA 520/4-82-013-1, Office of Radiation
Programs, USEPA, Washington, D.C., October, 1982.
Ew73 Swing D.R. and Payne J.A., "Computer Access to Geographic
Distribution of the Population," Department of Commerce,
COM-73-11678, July 1973.
6e78 George A.C. and Breslin A.J., "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 in the Environment III, Houston, Texas,
ApriJ 1978.
Go77 Goyer R.A. and Mehlnan M.A., editors, "Advances in Modern
Toxicology," Vol 2: Toxicology of Trace Elements, John Wiley
& Sons, New York, 1977.
NAS80 National Academy of Sciences, "The Effects on Population of
Exposure to Low Levels of Ionizing Radiation," Committee on
the Biological Effects of Ionizing Radiations, NAS, National
Academy Press, Washington, D.C., 1980.
NRC80 Nuclear Regulatory Commission, Final Generic Environmental
Impact Statement on Uranium Milling, NUREG-0706, NRC,
Washington, D.C., 1980.
Tr79 Travis C.C., Watson A.P., McDowell-Boyer L.M., Cotter S.J.,
Randolph M.L., and Fields D.E., "A Radiological Assessment of
Radon-222 Released from Uranium Mills and Other Natural and
Technologically Enhanced Sources," ORNL/NUREG-55, ORNL,
Oak Ridge, Tennessee, 1979.
UN77 United Nations Scientific Committee on the Effects of Atomic
Radiation, "Source and Effects of Ionizing Radiation, Report
to the General Assembly," U.N. Publication E.77.IX.1, United
Nations, N.Y., 1977.
Ve78 Venugopal B. and Luckey T.D., "Metal Toxicity in Mammals,"
Vol. 2, Chemical Toxicity of Metals and Metaloids, Plenum
Press, New York, 1978.
6-16
-------
Chapter 7: CONTROL OF TAILINGS DURING MILLING OPERATIONS
Releases of radioactive and nonradioactlve hazardous materials
from tailings during milling operations are controlled by existing
standards and regulations, for the most part. Control of radioactive
emissions and effluents from tailings is required by the Atomic Energy
Act (AEA) and the Clean Water Act (CWA). Also, UMTRCA requires that
environmental standards for nonradioactive hazardous materials be
consistent with standards under the Solid Waste Disposal Act (SWDA), as
amended. Therefore, we briefly summarize existing standards and
regulations applicable to releases from uranium tailings before we
analyze controls for such releases during the operational phase of
uranium byproduct material management.
EPA promulgated Environmental Radiation Protection Standards for
Nuclear Operations on January 13, 1977 (40 CFR Part 190). These
standards specify the radiation levels below which normal operations of
the uranium fuel cycle are determined to be environmentally
acceptable. Radiation exposure due to releases from uranium byproduct
material is included under these standards with the exception of
emissions of radon and its decay products. Alternative standards for
radon emissions from uranium byproduct material are considered in this
Chapter. We also briefly review controls for radioactive releases
other than radon for the purpose of determining if the existing
standards remain cost effective in requiring their specific protection
levels.
EPA promulgated standards for discharges of process waste water
from uranium mills on December 3, 1982, as Ore Mining and Dressing
Point Source Category; Effluent Limitations Guidelines and New Source
Performance Standards, Subpart E - Uranium, Radium and Vanadium Ores
Subcategory (40 CFR Part 440). The purpose of these rules is to
establish new source performance standards (NSPS) under the Clean Water
Act. The NSPS require that "...there shall be no discharge of process
wastewater from mills using the acid leach, alkaline leach or combined
acid and alkaline leach process for the extraction of uranium or from
mines and mills using in situ leach materials."
7-1
-------
EPA promulgated Standards for Owners and Operators of Hazardous
Waste Treatment, Storage, and Disposal Facilities under Subtitle C of
the Solid Waste Disposal Act (SWDA) on July 26, 1982, (40 CFR Part
264). Radioactive materials controlled under the Atomic Energy Act of
1954, as amended, are not included under the Solid Waste Disposal Act.
However, UMTRCA requires that standards for nonradioactive hazards
under UMTRCA shall provide for the protection of human health and the
environment consistent with the standards required under Subtitle C of
the Solid Waste Disposal Act, as amended, which are applicable to such
hazards.
The Act also required the NRG to insure that management of uranium
byproduct materials is carried out in such a manner as conforms to
general requirements established by the NRG, with the concurrence of
EPA, which are, to the maximum extent practicable, at least comparable
to requirements applicable to the possession, transfer, and disposal of
similar hazardous material regulated by EPA under the SWDA, as amended.
EPA standards under the SWDA, as amended, specify concentration
limits for toxic materials in groundwater and also specify that there
shall be no increase in background levels in groundwater for hazardous
constituents listed in Appendix VIII of 40 CFR Part 261. For the
operating these rules basically require that: 1) a plastic liner
should be placed on the bottom of a tailings pond to prevent seepage of
leachate into the groundwater; 2) an active leachate management program
should be conducted to treat, process, recycle, etc., the leachate
collected from the tailings pond; 3) groundwater adjacent to the liner
should be monitored; and 4) a corrective action plan should be
implemented if hazardous constituents are detected above background.
levels in the groundwater.
The Nuclear Regulatory Commission issued rules on October 3, 1980,
which specify licensing requirements for uranium and thorium milling
activities, including tailings and wastes generated from these
activities (10 CFR Part 40). These rules specify technical, surety,
ownership, and long-term care criteria for the management and final
disposition of uranium byproduct material. Certain of these rules were
suspended in August 1983 following publication of EPA's proposed
standards as required by UMTRCA amendments passed in January 1983.
The NRC also enumerated the authorities reserved to the NRC in
Agreement States under the provisions of UMTRCA, and specified
requirements for Agreement States to implement UMTRCA (10 CFR Part
150). Under the Agreement State program, Agreement States can issue
licenses for uranium processing activities, including uranium byproduct
material generated from these activities.
7.1 Objectives of Control Measures
Releases of radionuclides and toxic elements to air and water from
uranium mill tailings piles during milling operations can be reduced or
eliminated by a variety of control measures. Some of these are
appropriate for temporary control, and others have a more lasting
7-2
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effect. Releases to air are in the form of windblown tailings dust and
radon gas. Releases to water are primarily from seepage from tailings
ponds into underlying aquifers. However, best practicable technology
(BPT) for existing mills permits the discharge of pollutants to surface
waters. New source performance standards (NSPS) prohibit the discharge
of pollutants to surface waters except in areas where annual precipi-
tation exceeds annual evaporation; then the difference between
precipitation and evaporation may be discharged (40 CRF 440). This
section discusses available methods for controlling these releases and
the benefits achievable.
7.1.1 Wind Erosion
Wind can erode exposed tailings embankments and dry beach areas
and transport small tailings particles away from the site. These
releases cause radiation exposures to people living near the tailings
pile, primarily through inhaling the airborne tailings particles.
Radiation exposures can also occur, but to a lesser extent, from
ingesting food contaminated with tailings particles or from external
exposure to offsite tailings deposited on the ground. Tailings also
contain toxic elements that could be ingested eventually by man and
animals or absorbed by plants.
7.1.2 Radon
Since radon-222 is an inert gas, it diffuses through the
interstitial spaces of a tailings pile to the surface, where it escapes
into the air. Radon-222 decay products can cause large radiation doses
to the lungs of people living near tailings piles and, because radon
can travel long distances through the atmosphere before decaying, it
also causes small radiation doses to large numbers of people distant
from tailings piles. Control measures can reduce radon emissions from
the tailings.
7.1.3 Water Contamination
Wind and water flowing over or through tailings can carry
radionuclides and toxic elements to surface or underground water. The
primary concern during milling operations is when water seeps from the
tailings ponds into an underground aquifer, contaminating the water
with radionuclides and toxic elements and presenting potential health
risks to people using the water. The objectives of control measures
for water protection are to eliminate seepage from tailings ponds and
to prevent the contamination of water resources.
7.2 Control Methods
7.2.1 Wind Erosion
Wind erosion can be controlled by stabilizing tailings by any of
the following methods:
7-3
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1. Physical Methodswetting the tailings or covering the
tailings with soil or other restraining materials.
2. Chemical Methodstreating the tailings with a chemical
which interacts with the fine-sized materials to form a
crust.
3. Vegetative Methodsgrowing plants in the tailings or in
cover materials.
4. Staged or below-grade disposal.
During the operational phase of a mill tailings pile,
airborne-dust is usually controlled by wetting the surface of the
tailings or by treating the dry surfaces with chemicals. During the
post-operational phase more permanent methods can be used, either,
physical or vegetative methods, or a combination of these methods..
However, vegetative procedures are unsuitable for many locations
because of the low rainfall and the high alkalinity or acidity of the
tailings.
Keeping tailings surfaces wet with tailings solution or sprinkling
them with water can suppress dusting. This can be done, for example,
by discharging tailings slurry from multiple discharge points, as
opposed to a single point. Alternatively, sprinkling systems or tank
trucks can spray dried areas. Because surfaces of the tailings
impoundment can dry out rapidly, this method of dust suppression
requires continuous attention.
Chemical stabilization involves interaction of a reagent with
tailings to form an air- and water-resistant crust or layer that will
effectively stop dust from blowing. Resinous adhesives; lignosulfonates;
elastomeric polymers; milk of lime; mixtures of wax, tar, and pitch;
potassium and sodium silicates; and neoprene emulsions have been used for
such purposes (De74). In tests by the U.S. Bureau of Mines, resinous
adhesives, lignosulfonates, and elastomeric ploymers were shown to be the
most promising chemicals for stabilizing tailings. Calcium
lignosulfonate (Norleg A) and an elastomeric polymer (DCA-70) were tested
on the tailings at Tuba City, Arizona, with reasonably good results,
although periodic maintenance was needed (Ha69). More recently,
wood-fiber-based materials (Conwed-200) and magnesium chloride (Dust
Guard) have been used effectively for tailings dust control (Mab2).
Table 7-1 lists chemicals that have been used for suppressing tailings
dust and their estimated unit costs.
Various cover materials have been used or tested for stabilizing
tailings and controlling wind erosion, including soil, rock, slag, bark
or straw, vegetation, and synthetic covering such as asphalt. The most
common cover materials used are soil and vegetation because of their
relative ease of application and economy. Although vegetative cover can
sometimes be used by itself, it is normally used in conjuntion with soil
7-4
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Table 7-1. Chemical Stabilization Agents Used for Dust Suppression
(1983 dollars)
Product
Aerospray-70
Soil Card
Dust Binder
Concentrate
Cone rex
Norlig A
Conwed-200
Conwed-200
Type
elastomeric
polymer
elastomeric
polymer
elastomeric
polymer
resinous
adhesive
lignosulfonate
wood fiber
wood fiber
Application
Rate
230 gal/acre
420 gal/acre
240 gal/acre
730 gal/acre
2.4 tons/acre
1.5 tons /acre
0.75 tons /acre
0.75 tons /acre
Unit Cost
($/acre)
$1400
1900
1700
950
280 (a)
190(b)
260
370
& Terra-Tac 1
Dust Guard
Magnesium
Chloride
40 Ibs/acre
12 tons/acre
890
(a'Based on application rate used by Bureau of Mines (Ha69).
estimate (NRC80).
cover or with a chemical stabilizing agent. However, for areas of low
rainfall, vegetative cover will require irrigation.
Several recent tailings impoundment designs have incorporated
progressive reclamation schemes into overall tailings management
programs. These schemes segment large tailings areas into a number of
smaller cells, with sequential construction, filling, and reclamation.
Such schemes substantially reduce dust emissions by reducing the
available surface area of exposed tailings.
Tailings can also be stored and disposed of through the use of
existing open mine pits or special excavations, so that the tailings
are below grade, thus virtually eliminating exposure of the tailings to
surface erosional effects.
7-5
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7.2.2 Control of Radon
Radon releases from uranium mill tailings can be controlled by
minimizing the exposed dry beach areas of tailings by keeping the
tailings covered with water, soil, or some type of synthetic material.
Management practices involving staged reclamation of the tailings are
also a practical way of limiting the area of exposed tailings.
Radon diffusion through tailings is significantly affected by the
moisture content of tailings. Tailings covered by water do not release
any significant quantity of radon to air, and the release rate of radon
from wet beach areas is only about 30 percent of the release from dry
beach areas (NRC81). For most existing older tailings piles, this
method of controlling radon is dependent on the design of the tailings
pile and appears to have limited application. Although radon emissions
can be reduced somewhat by discharging tailings slurry onto the pile
and keeping it wet, large areas of exposed tailings will still exist
because of upstream construction methods and the need to maintain
adequate freeboard. However, for new or future tailings piles, design
and management techniques can be used that will keep all but a small
area of the tailings either wet or covered with water (NRC80).
Radon emissions to the atmosphere can be controlled by covering
the exposed tailings with soil (see Section 8.3). Relatively thick
covers (one meter or more) are needed to reduce radon emissions
significantly (see Figure 8-1). Soil covers to reduce radon emissions
are more applicable to final disposal of the tailings than as an
interim measure to reduce radon emissions during milling operations.
Applying soil covers to tailings beach areas during operations is not
practical because new beach areas are constantly being formed.
Several recent tailings impoundment designs have incorporated
progressive reclamation schemes into overall tailings management
programs. These schemes segment large tailings areas into a number of
smaller cells, with sequential construction, filling, and reclamation.
Such schemes substantially reduce radon emissions by reducing the of
exposed surface area of tailings.
Land restrictions can prevent people from living near tailings
piles and thus reduce the health risks from radon emissions from
tailings. The greatest risks occur to people living close to the
tailings piles (i.e., 0.5 to 1 mile), with the individual risks
decreasing significantly with distance from the pile (see Table 6-1).
7.2.3 Control of Groundwater Contamination
The principal available means for controlling groundwater
contamination from uranium mill tailings is using liners in the
tailings pond to prevent seepage. This method is primarily applicable
to new tailings piles because the liners must be installed when the
tailings impoundment is originally constructed, unless the pile is
7-6
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removed and replaced. Other methods for controlling potential
groundwater contamination involve removing the pollutants from the
tailings liquids or dewatering the tailings before disposal. These
methods also are most applicable to new mills. Methods for controlling
seepage to groundwater under existing tailings piles are limited to
pumping contaminated water back to the tailing pond or to separate,
lined evaporation ponds.
Placing compacted clay over the ground surface under a tailings
pile will act as a sealant and inhibit seepage from the tailings pond.
Furthermore, the ion-exchange characteristics of the clay will further
retard the transport of contaminants to the underlying aquifer. The
sealing property of clay results from its ability to expand when wet.
The expanded clay particles decrease the pore space of the soil,
decreasing its permeability.
Many types of synthetic materials can be used as liners to prevent
seepage from tailings ponds, including plastics, elastomers, and
asphalt coatings. Plastics and elastomers are usually used with
polyester or nylon reinforcement and are flexible liners. Careful
preparation of the tailings pond base and of the protective soil layer
placed after installation of the liner is necessary to avoid damage to
the liner.
Chemical processes which remove pollutants from the tailings
solution could be used to control groundwater contamination. For
example, removing contaminants from the water by lime neutralization or
ion exchange are two such processes (NRC80). Lime neutralization
precipitates radionuclides and most toxic elements as insoluble
hydroxides. Ion-exchange resin can absorb contaminants from the
solution. Information on the practicability of these processes is
limited, and such processes generally have not been used in the uranium
milling industry in the United States (WefcO).
Based on available information, using liners appears to be the
most practical method for preventing groundwater contamination from
tailings piles.
7.3 Cost and Effectiveness of Control Measures for Model Tailings Pile
7.3.1 Control of Wind Erosion of Tailings
During the operational phase of uranium mill tailings piles, wind
erosion of tailings may be most easily controlled by spraying the dry
beach areas with water or treating those areas with a chemical
stabilization agent. During the post-operational phase of a mill
tailings pile (i.e., before final disposal), a thin cover may be used
to prevent wind erosion. Although many types of cover material are
available, soil appears to be the most practicable cover for this
purpose. The cost and estimated efficiency of these control methods
are shown in Table 7-2.
7-7
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For new tailings piles, efficient design and management practices
can reduce the amount of airborne dust released from the piles. Staged
disposal (see Appendix B) can reduce the amount of tailings dust by
about 70 percent (NRC80). Below-grade disposal will shield the dry
tailings areas from wind erosional effects and significantly reduce the
amount of tailings dust. We assign a control efficiency of 90 percent
to the below-grade disposal option described in Appendix B. No direct
costs are assigned to dust control for these management options, since
dust control is obtained at no additional cost when these management
options are selected based on disposal considerations. Appendix B
contains a discussion of the costs of these management options.
7.3.2 Control of Radon
Methods for reducing radon emissions to air from tailings are not
easily applied to existing tailings piles during the operational
phase. Using cover materials is not practical since new tailings beach
areas are continuously being formed. Although radon emissions can. be
reduced by enlarging the area of tailings covered by water, such an
approach is affected by the design of the tailings pile and is a
complex function of seepage, evaporation and recycling rates, and
tailings embankment strength and stability. For purposes of subsequent
analyses, we conclude that using water covers to obtain large
reductions in radon emissions is not generally applicable to existing
tailings piles. By wetting the tailings surfaces with tailings liquids
or by sprinkling with water, a small reduction (20 percent of the total
radon emitted over the operating life of the pile) in the radon
emissions can be achieved (NRC80).
For new tailings piles, the use of staged disposal can reduce
radon emissions by about 70 percent. Designs that maximize the amount
of tailings covered by water can achieve a greater-than 90 percent
reduction of the radon emissions (NRC80). No direct costs are assigned
to these methods for controlling radon, since the control is obtained
at no additional cost when the management option is selected based on
disposal considerations.
7.3.3 Control of Seepage to Groundwater
During the operational phase of the mill, contamination of
groundwater can be controlled by using a plastic or clay liner on the
bottom and sides of the tailings pond. Estimated costs for a synthetic
liner at a new tailings pond are presented in Appendix B for the model
tailings pile as ill.5 million (1983 dollars), which includes 25
percent for overhead and profit. The estimated cost for a synthetic
liner at a new tailings pile using the staged disposal method is $8.1
million, which includes 25 percent for overhead and profit. The staged
disposal method has a lower estimated cost primarily because the
tailings are arranged in a thicker layer than they are for surface
storage, thereby reducing the area requiring a liner.
7-8
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Table 7-2.
Control Method
Costs and Effectiveness of Methods for Controlling
Wind Erosion at a Model Tailings Pile
(1983 dollars in thousands)
Capital Annual Present Estimated Control
Costs Costs Worth Efficiency (%)
Water Spray (Truck)
Water Spray (Piped)
Chemical
Stabilization(a)
Chemical
Stabilization^)
Soil Cover (1 foot)
420
OPERATIONAL PHASE
35
168
260 50 (NRC8Q, PE82)
1,280 90 (PED82)
53 400 80 (NRC80, PE82)
POST-OPERATIONAL PHASE
84
525
318 80 (NRC80, PE82)
525 90-100 (PE82)
(a)Cost based on an annual application of the chemical agent, Norlig A.
Chemical treatment of tailings at a new tailings pond by the
addition of lime is estimated to cost $12.4 million at an acid-leach
mill and $11.3 million at an alkaline-leach mill (We80). The
alkaline-leach tailings are assumed to be blended with acid-leach
tailings before treatment with lime. The key cost item is the sludge
storage lagoon for both acid- and alkaline-leach tailings.
Options for protecting groundwater at existing tailings ponds
varies from site to site. The control costs for groundwater protection
at existing tailings ponds can range from zero, where no action is
needed, to the costs of constructing a new, lined tailings pond as
presented in Appendix B. An intermediate-cost remedial action is being
applied at the Homestake mill in New Mexico. Two rows of wells were
drilled across the groundwater hydraulic gradient down from the
tailings pond. Water is pumped from wells in the first row, closest to
the pond, and recycled. Fresh water is injected into the weils in the
second row to dilute any contaminated groundwater. During September
1978, 3.7 million gallons were injected. The estimated present value
7-9
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of the future costs for this pumping is about $89,000, which includes
capital costs for 15 pumps and drilling 15 wells and an annual
operating cost corrected to present value at a 10 percent discount rate.
The effectiveness of plastic liners results from the physical
barrier that these liners provide. A plastic liner will retain all the
liquid in the tailings pond, including the dissolved hazardous and
toxic materials. This is advantageous since it prevents the seepage
into groundwater of chemical forms of these materials that are highly
soluble and difficult to remove with chemical processes. It also
avails us of the option to issue standards requiring control of
materials that are currently not listed under Subtitle C of the SWDA,
as amended. Protection of groundwater achieved with plastic liners
controls both the hazardous materials listed under Subtitle C of the
SW1JA, as amended, and other potential pollutants found in uranium
tailings.
Molybdenum is found in some uranium ores and is present in
tailings after the ore is processed (see Chapter 3). Molybdenum is
estimated to be potentially toxic to humans and also has a narrow
safety margin, e.g., a low ratio of toxic intake to adult required
intake, as discussed in Appendix C. This inorganic has been found in a
shallow aquifer at the Cotter mill, Canon City, Colorado, at estimated
potentially toxic concentrations, as shown in Chapter 3. Also,
molybdenosis has been observed in cattle grazing on land contaminated
with molybdenum from the processing of uranium ores in North Dakota and
Texas, as noted in Appendix C. All this, in addition to the fact that
molybdenum will be controlled by the same methods used to control toxic
and hazardous materials, allows us to consider control of molybdenum
seepage from uranium tailings storage areas.
Radioactive materials are not included under the SWDA regulations
since most of them are controlled under the Atomic Energy Act and thus
are exempted by the SWDA, as amended. Tailings contain large
quantities of radioactive materials as shown in Chaper 3.
Contamination of groundwater by radioactive materials is controlled
since they are potentially the most hazardous constituents of
tailings. The same methods used to protect groundwater from other
toxic and hazardous constituents will also prevent contamination by
radioactive materials.
Concentration limits for toxic materials in the SWDA regulations
were adopted directly from the National Interim Primary Drinking Water
Regulations (40 CFR Part 141). Thus, the concentration limits for
radionuclides, as specified in the drinking water standards, can be
adopted for application to tailings since this is consistent with
standards under SWDA, as amended. These include limits of 5 pCi of
radium-226 and radium-228 per liter of water and of 15 pCi of gross
alpha particle activity per liter of water. The gross alpha particle
limit excludes uranium which is present in large quantities in tailings
7-10
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and has been found in high concentrations in shallow aquifers as shown
in Chapter 3. However, uranium is indigenous in groundwater in many
uranium producing areas. Therefore, rather than specifying a
concentration limit for uranium, a nondegradation approach is more
suitable. This requires that there would be no increase in the
concentration of uranium above background levels in the local area of
the tailings.
Protecting groundwater by controlling seepage from tailings with a
plastic liner would eliminate seepage as a discharge pathway for excess
wastewater. At some sites this is a significant discharge pathway.
New Source Performance Standards (NSPS) under the Clean Water Act
prohibit the discharge of process wastewater from uranium mills as the
degree of effluent reduction currently attainable. Taken together,
these controls may pose a problem of what to do with excess waste water
at certain locations where average annual precipitation approaches or
exceeds average annual evaporation. At these locations the only
discharge pathway for excess wastewater would be evaporation. It
appears from Table 3-1 that Texas is the only currently developed
uranium producing region where this may be a problem.
However, future uranium producing locations may be developed in
regions where the average annual precipitation exceeds annual average
evaporation. For these situations the NSPS may not apply since these
standards were developed for environmental conditions where the average
annual evaporation exceeds the average annual precipitation. These
standards also contain provisions in the event that the annual
precipitation exceeds the annual evaporation. This potential problem
may also arise for a new tailings impoundment at an existing uranium
processing site. In this case a determination would be required as to
whether a new impoundment would be considered a new source.
7.4 Cost-Effectiveness Analyses
7.4.1 Wind Erosion
The levels of risk to the public from dust particle emissions from
uncontrolled tailings piles are relatively low. During the operational
phase of the model pile, the average lifetime risk of fatal cancer to
the nearest individuals is estimated to be about 3 x 10~5, and the
number of cancer deaths in the population from 15 years of dust
emissions range from 0.03 for a rural site to 0.001 for a remote site.
These risks can be reduced to even lower levels through the use of dust
control measures.
Costs and benefits (health risk reductions) for various levels
of dust control for the model tailings pile for the operational phase
are presented in Table 7-3. A combination of chemical stabilization
and water sprinkling can achieve a 90-percent reduction in dust
7-11
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emissions. This would result in a reduction from 3 x 10~5 to 3 x
10~6 in the lifetime risk of fatal cancer to the nearest individual
and will prevent up to 0.03 fatal cancers (in the population living
around the tailing pile at a rural site) during the operation phase of
the tailings pile, at a cost of fc660 thousand. For new tailings, the
use of staged disposal in combination with chemical stabilization can
achieve a 94 percent reduction in dust emissions. This would result in
a reduction of the risks similar to those just described, but at a
smaller incremental cost of $120 thousand.
7.4.2 Control of Radon
Costs and benefits for controlling radon emissions during the
operational phase of the model pile are presented in Table 7-4. For
existing tailings, keeping the tailings surface wet is the only
practical control method. Water sprinkling would achieve about a
20-percent reduction in the radon emissions. Over the term of the
operational phase this would prevent about 0.7 fatal cancers in the
population at a rural site and 0.2 fatal cancers at a remote site, but
would result in only a small reduction in the lifetime risk of fatal
cancer to the nearest individuals (i.e., from 1.6 x 10~3 to 1.3 x
10-3).
Table 7-3. Costs and Benefits of Various Levels of Control of Dust
Emissions for Model Tailings Pile During Operational Phase
(1983 dollars)
Present
Controls
None
A
B
A & B
B & D
Emission
Reduction
(%)
0
50
80
90
94
Worth
Cost
($1000)
0
260
400
660
120
Lifetime Risk
to Individual
3 . OE-5
1.5E-5
6.0E-6
3.0E-6
1.5E-6
Fatal Cancers
( Cancers /I 5y)
Rural Site Remote Site
3.0E-2 l.OE-3
2.0E-2 5.0E-4
6.0E-3 2.0E-4
3.0E-3 l.OE-4
2.0E-3 6. OE-5
A=Water spray (truck).
B=Chemical Stabilization (Norlig A).
D=Staged Disposal (applicable to new tailings piles only).
Note: See Chapter 4 for description of rural and remote sites.
7-12
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Table 7-4. Costs and Benefits of Various Levels of Control
of Radon Emissions from Model Tailings Pile During Operational Phase
(1983 dollars)
Controls
None
A
D
E
D & E
Emission
Reduction
(%)
0
20
70
90
95
Present
Worth
Cost
($1000)
0
260
0
0
0
,i^ Fatal Cancers(°)
Lifetime Risk
to Individual
1.6E-3
1.3E-3
4.8E-4
1.6E-4
8.0E-5
(Cancers /15y)
Rural Site Remote Site
3.6
2.9
1.1
4.0E-1
2.0E-1
1.2
1.0
4.0E-1
1 . OE-1
6.0E-2
A=Water Sprinkling.
D=Staged Reclamation (applicable to new tailings piles only).
E=Below grade disposal in excavated pit with tailing covered with water
(applicable only to new mills).
Note: See Chapter 4 for description of rural and remote sites.
(a)costs for Controls D and E are not listed since they are inherent
in the disposal method.
(b)Lifetime risk to the average individual located 600 meters from
the center of the pile.
(c)Fatal cancers include those occurring in local, regional, and
national populations (see Tables 6-1 through 6-6 for the proportions
in each).
7-13
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For new tailings, using staged disposal in combination with
below-grade disposal would allow most of the tailings to be covered
with water during the operational phase. This method can achieve a
high level of radon control (i.e., greater than 95 percent). This
would result in a reduction of the lifetime risk of fatal cancer to the
average individuals at 600 m from 1.6 x 10~3 to 8.0 x 10~5 and
would prevent 3.4 fatal cancers in the population at a rural site and
1.1 fatal cancers at a remote site.
Using water covers or wetting the tailing surfaces are not
appropriate radon control methods during the post-operational phase.
The purpose of this predisposal period is to allow the tailings to dry
out to allow final disposal. The only way to reduce radon emissions
during the post-operational phase is to minimize the amount of exposed
tailings through the application of staged reclamation. This method is
applicable to new tailings only and would reduce the radon emissions
during the 5-year post-operational phase by 70 percent for the model
tailings pile. This would result in a reduction of from 1.7 x 10"3
to 5 x 10~4 in the lifetime risk to the average individual at 600 m
(See Table 6-2) and would prevent 1.3 fatal cancers in the population
at a rural site and 0.5 fatal cancer at a remote site.
7.4.3 Control of Seepage to Groundwater
The benefits of groundwater protection are not easily
quantifiable. Maintaining the quality of the groundwater for future
uses is the primary benefit of protecting groundwater. At new tailings
piles, this can be accomplished by a three-step program:
1. Install a liner to prevent seepage of leachate into the
groundwater or, alternatively, select a site with
characteristics that have a high probability of protecting
groundwater, and
2. Conduct monitoring on a schedule that will assure early
identification of any hazardous constituents from the
tailings in the groundwater and perform corrective actions,
as needed..
3. Install a cap to prevent infiltration of precipitation into
the hazardous materials after closure of the impoundment.
The cost of liners ranges from $8 to $12 million to achieve this
benefit. The additional cost of selecting a "good" site are
anticipated to be small compared with the cost of a liner. The cost of
a monitoring program is negligible when compared to liner costs.
At existing tailings piles the benefits of groundwater protection
are the same, i.e., preserving the groundwater quality for future
uses. Costs, however, can range from small, where groundwater is
currently adequately protected due to site characteristics, up to
large, when transfer of tailings to a new, lined tailings pond is
required to protect groundwater.
7-14
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REFERENCES
De74 Dean K.C., Havens R., and Glantz M.W., "Methods and Costs for
Stabilizing Fine-Sized Mineral Wastes," Report No. 7896, Bureau
of Mines, U.S. Department of the Interior, Salt Lake City,
Utah, 1974.
Ha69 Havens R. and Dean K.C., "Chemical Stabilization of the Uranium
Tailings at Tuba City, Arizona," Report 7288, Bureau of Mines,
U.S. Department of the Interior, Salt Lake City, Utah, 1969.
Ma82 Private communication; Paul Magno of the Environmental
Protection Agency with the Nuclear Regulatory Commission, 1982.
NRC80 Nuclear Regulatory Commission, "Final Generic Environmental
Impact Statement on Uranium Milling," NUREG-0706, USNRC,
Washington, B.C., September 1980.
NRC81 Nuclear Regulatory Commission, "Radon Release from Uranium
Mining and Milling and their Calculated Health Effects,"
NUREG-0757, USNRC, Washington, D.C., February 1981.
PE82 PEDCO Environmental, Inc., Evaluation of Costs to Control
Fugitive Dust from Tailings at Active Uranium Mills, EPA
Controct No. 68-02-3173, Task No. 053, USEPA, Washington, D.C.,
March 1982.
We80 Werthman P.H. and Bainbridge K.L., "An Investigation of Uranium
Mill Wastewater Treatability," EPA Contract No. 68-01-4845,
1980.
7-15
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Chapter 8: OBJECTIVES ANb METHODS FOR TAILINGS DISPOSAL
8.1 Health and Environmental Protection Objectives
Based on the results in the preceding chapters, we have identified
the following objectives for these standards.
1. To discourage future use of tailings in or near buildings.
The widespread past use of tailings around foundations or in
construction materials has caused an increase of radon decay
products in buildings, leading to increased risk of
radiation-induced lung cancer.
2. To protect people from radon emanating from tailings piles.
Radon exposure of people living in the vicinity of tailings
piles leads to increased risk of lung cancer. Also, since
radon is a chemically inert gas with a radioactive half-life
of 3.8 days, radon released from tailings can travel long
distances before it decays. As the radon decays, it exposes
large numbers of people to low levels of radiation.
3. To prevent the surface spread of tailings. Tailings may be
spread by wind and water. This can cause radiation exposure
of local residents from both radon decay products and gamma
radiation. In addition, the spread of tailings may
contaminate surface water.
4. To protect groundwater. Contamination of groundwater occurs
when water comes in contact with tailings or leaches
radioactive and toxic materials from the tailings and then
moves into a groundwater aquifer through fissures, percolation,
or by other means. The degree of risk to man and livestock
depends on the concentrations of contaminants in the water and
the uses of the water (human consumption, livestock watering,
irrigation, etc.).
Because of the long lifetimes of the radioactive contaminants in
tailings and the presence of toxic materials (which do not decay), the
8-1
-------
potential for harming people by any of the above pathways will persist
essentially indefinitely. It is therefore necessary to satisfy the
above objectives for as long a period as practical. Many factors
affect the long-term effectiveness of tailings disposal methods. They
include external phenomena, such as erosion by wind and rain,
earthquakes, floods, and glaciers; internal chemical and mechanical
processes in the piles; and human activities. Predictions of the
stability of disposed tailings become less certain as the time period
increases. Beyond several thousand years, long-term geological
processes and climatic change will govern the effectiveness of most
control methods.
These objectives are interrelated. For instance, radon control
may be achieved by placing a thick earth cover over the tailings. This
method also controls the spreading of tailings, attenuates external
gamma radiation, prevents groundwater contamination, and isolates the
tailings so as to discourage misuse.
Methods to prevent radon emissions into the atmosphere range from
the use of simple barriers to delay the release of radon until it has
decayed, to more complex means, such as incorporating tailings into
asphalt or concrete, or chemical processing to remove the radium and
thorium.
Various methods can be used for isolating tailings, ranging from
temporary measures, such as fencing, to more permanent measures, such
as using a simple earthen cover or deep disposal. Greater amounts of
material, such as earth, placed between the tailings and the accessible
environment increase the isolation of the tailings. Isolation is here
taken to mean the degree to which man is discouraged from intruding
into the tailings.
Protection from external gamma radiation is achieved by placing
materials of sufficient mass over the source of the penetrating (gamma)
radiation. Thus, a plastic sheet will have essentially no effect on
gamma levels, whereas a layer of earth is quite effective.
Methods for control of windblown and precipitation-carried
tailings include soil and plastic coverings, chemical and asphalt
binders sprayed on the tailings, grading and contouring to eliminate
steep slopes, rock covers, and revegetation. Some methods, such as
chemical and asphalt sprays, do not last long on tailings and are more
suitable for use during the operating phase of a mill.
Methods for preventing contamination of groundwater fall into four
groups:
1. Placing a barrier between the tailings and the aquifer which
will either prevent the movement of water from the tailings to
the aquifer (or vice versa) or will remove hazardous materials
by adsorption.
8-2
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2. Fixing the tailings into a solid mass that prevents the
leaching of hazardous materials from tailings by water.
3. Contouring and covering to minimize the movement of
precipitation into tailings.
4. Selecting a site that is far removed from aquifers, with
characteristics that minimize the movement of water into or
out of tailings, and/or that provide natural adsorption of
hazardous materials.
Not all these methods are feasible for every tailings pile. Some
are only appropriate for new tailings. A significant factor is that
most existing uranium mills are located in arid areas of the western
United States where natural evapotranspiration generally exceeds
precipitation. The selection of a site can eliminate the need for a
liner, if the soil has the needed permeability and adsorption charac-
teristics. Disposal methods could also be different for mill sites
where abandoned surface mines or natural land depressions are nearby.
8.2 Longevity of Control
Mill tailings will be hazardous for hundreds of thousands of
years. Although economically feasible methods which assure control for
such long-term periods are beyond present knowledge and experience,
enough is known to provide protection at reasonable cost for periods of
hundreds to thousands of years.
Control failures can occur through natural phenomena or through
human intrusion. Natural phenomena, such as erosion and deposition,
flooding, climatic change, earthquakes, vulcanism, and glaciation can
change the landscape. Human disturbance can also take a number of
forms, ranging from constructing buildings to drilling, mining, and dam
building. Not all of these activities would cause control failures,
however; at some sites, human intrusions and natural phenomena may
actually increase isolation of the tailings by depositing additional
materials or soil on the tailings. The longevity of protection
achievable will vary considerably from site to site at existing sites.
In the following discussion controls are grouped into two broad
classes: those that depend on active institutional maintenance, and
those that do not. "Active" measures include fences, guards, repair of
drainage channels, replacement of eroded cover, and maintenance of
vegetative cover. Unfortunately, there is no general consensus on the
length of time human institutions will remain effective or reliable to
continue such active measures. In this regard, failure of institu-
tional controls does not necessarily imply a complete breakdown of
societal structure. The more likely situation would be failure of
institutional controls through program reductions, reorganization,
8-3
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changes in priorities, or through the failure of special funding
mechanisms.
8.2.1 Human Intrusion
The effectiveness of controls in discouraging intrusion over long
time periods is difficult to evaluate. Probably the worst scenario is
the use of tailings as a resource for construction material by
residents of a nearby population center. This can (and has) led to
widespread use of tailings around, under, and in residences, schools,
and other inhabited structures. Easily removable or attractive control
materials may have a potential for promoting misuse. Examples are
fences and easily removed rock covers.
Inhibiting of intrusion for long periods is more likely to be
successful by using passive methods. Thick earth covers, for example,
provide significant long-term passive protection against intrusion.
Other effective "passive" methods include heavy rock cover, deep-mine
disposal, below-grade disposal, solidification in a cement or asphalt
mixture, or coverings of a tailings-cement mix.
8.2.2 Erosion and Gully Intrusion
All surface disposal methods are subject to erosion. Erosion ot
stabilized tailings piles can occur as or be caused by sheet erosion,
gully intrusion or erosion, wind erosion, and differential settlement.
Nelson et al. (Ne83) describe these various modes and discuss long-term
mitigating measuies in some detail.
Sheet erosion is caused by unconcentrated water flowing directly
over the surface of the tailings impoundment and the cover (the
engineering design methods necessary to control such erosive forces).
Sheet erosion is defined as that erosion which occurs as a result of
the impact of raindrops striking the ground surface or water flowing in
small ephermal rills. The amount of sheet erosion that can occur at a
given location depends on the slope of the land, nature of the cover
material, type and density of the cover material, and rainfall duration
and intensity.
Control of sheet erosion can be accomplished by grading the cover
to gentle, flat slopes and placing gravel, cobbles, or rock layers over
the cover, or coarse gravel mixed with finer soil. Such controls can
be considered to duplicate desert landforms that have been stable for
thousands of years and are described as desert pavements or gravel
armor. The design of such controls is quite site specific, however, as
emphasized by Nelson, et al. (Ne83).
Gully erosion is caused by concentrated water flowing over the
tailings tuaL can cut deep channels through embankments or cover
materials and disperse tailings downstream. Gullies can also be
8-4
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initiated off the tailings area and migrate upstream into the
tailings. The formation of gullies depends on topographical features,
such as slope angle and slope length, the existence of stable base
levels on or near the site, erodibility of the soil, and the flood flow
velocity.
The best method of controlling gully erosion is by preventing
gully initiation (Ne83). Topographical features can be altered by
providing gentle and shorter slopes, gradual changes in grade, and
establishing base levels around the site (rock trenches, wing walls,
etc.). Soil erodibility can be reduced by providing larger grained
soils (gravel) and/or natural vegetation. Flood flow velocity can be
reduced or eliminated by providing diversion ditches. Gentle and short
slopes can also reduce this velocity. Depending on a given site's
features, it is likely a combination of these controls will be required.
Wind erosion is caused by suspension of small particles in the air
and by creep of particles moving along the ground surface. Materials
most highly susceptible to wind erosion are fine-grained noncohesive
sands and silts with diameters in the range of 0.02 to 0.10 mm.
Particles less than 0.002 mm, which are classified as clays, are highly
resistant to wind erosion due to cohesion (Neb3).
Wind erosion may be controlled by increasing surface roughness
through vegetation and using different rock sizes. Measures taken to
control water sheet erosion generally should minimize losses by wind
erosion.
Differential settlement is not erosion itself but can initiate
erosion by channelizing runoff. It can also cause failures by cracking
of cover material and by impounding water in depressions. Factors
which cause differential settlement include differences in
compressibility between different grain sizes of tailings,
nonuniformity of tailings in the impoundment, and variation in
compressibility of underlying materials.
Controls for differential settlement are surcharging and grading.
In surcharging, more cover material than necessary is placed over
compressible materials to cause a known amount of settlement within the
material. Grading also places additional cover over compressible
materials, where differential settlement is not expected to be great.
8.2.3 Floods and Other Natural Processes
Natural processes that can destroy the integrity of disposed
tailings piles include floods, winds, and earthquakes. Floods are
probably the greatest hazard to integrity. Methods are available to
protect piles against floods. New piles can be located so as to
minimize disruptions from floods and winds. For existing and new
piles, diversion ditches and embankments can be constructed, rocks
8-5
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can be placed on the slopes of piles (and on top, if needed), and the
tailings can be graded to gradual slopes. Existing piles can also be
moved, if sufficient protection is not afforded by these methods.
These are all passive controls.
The time over which controls should be effective is an important
factor in standards for long-term protection. Specifying this time
directs the design of disposal methods that have reasonable assurance
of providing such effectiveness over this period. The design of a
tailings disposal method is similar to the design of other major
projects, such as dams, bridges, causeways, etc., that are subjected to
natural disruptive processes (Ju83, Neb3, Cob78).
The first design step is to determine the size of the flood that
will be used in the design of the disposal method. This is accom-
plished by a probabilistic analysis. For example, a flood of a certain
magnitude will occur periodically, i.e., a 100-year flood is defined as
a flood that has a recurrence rate of 1/100 each year, or 0.01 in any
one year.
The probability (or likelihood) that a flood equal to or greater
than this 100-year flood will occur in a specified number of years is
given by the formula:
Pt = 1 - (l-t)n
where
Pt = Probability that an event with
recurrence rate of t will occur in
n years.
t = Recurrence rate of an event (1/1)
T = Recurrence time of event in years
n = Period of concern in years.
The probability that a 100-year event (flood) will occur sometime
during a 100-year period is thus 0.63, as is the probability that a
1,000-year event (flood) will occur sometime during a 1,000 year
period. Thus, it is more likely than not that an event with a
recurrence time equal to the period of concern will occur within the
period of concern.
For any period of concern, it is useful to determine a series of
probabilities that events with various recurrence times will occur
within that period of concern. For example, probabilities and
corresponding recurrence times are plotted in Figure 8-1 for three
periods of concern; 100 years, 400 years, and 1,000 years. This plot
8-6
-------
40,000-
10,000-
DC
> 4,000
u.
O
LLJ
§
1-
LU
U
HI
£ 1,000-
o
400-
200^
1000 YEAR PERIOD OF CONCERN
400 YEAR PERIOD OF CONCERN
JOO YEAR PERIOD OF CONCERN
I I
0 .2 .4 .6 .8 1.0
PROBABILITY EVENT WILL OCCUR DURING PERIOD OF CONCERN
Figure 8-1. Recurrence Times Versus Probabilities for
Various Periods of Concern.
8-7
-------
clearly illustrates that the probability is high that an event with a
recurrence time equal to the period of concern will occur during the
period of concern, as noted above.
The most important point shown in Figure b-1, however, is that the
recurrence time becomes very long for low probabilities, regardless of
the period of concern. (The recurrence time defines the size, or
design, of the event (flood), i.e., a recurrence time of a 10,000-year
flood). For example, for a probability of 5 percent the design event
is 2000 years for a 100-year period of concern, is almost 10,000 years
for a 400-year period of concern, and is 20,000 years for a 1,000-year
period of concern. Thus, specifying the period of concern (or the;
period over which protection must be provided) determines the size of
the event (flood) for design purposes, given some reasonably low
probability that the event will occur within the period of concern.
The long recurrence times of these design floods preclude the use
of historical data, which are of too short a duration. Rather the.
design is based on the probable maximum flood (PMF) which in turn is
determined from the probable maximum precipitation (PhP) over the area
that could affect the disposed tailings. The PMP can be obtained from
depth-area-duration relationships developed for the entire United
States by the National Oceanographic and Atmospheric Administration
(NOAA60, NOAA77-78). It is important to recognize that the size of
flood, is not proportioned, in general, to the length of the period of
concern. That is, in most cases the PMF is not significantly larger
than projections of floods for only moderately long periods of concern
(e.g., 1,000-year floods). Nelson, et al. (Neb3) discuss this in
detail, especially in regard to size of the drainage basin contributing
to the PhF at specific sites. They conclude, "To provide for a level
of risk consistent with normal engineering practice for 200-, 500-, or
1,000-year stability periods requires a design storm having a
recurrence interval of several thousand years. Because the PMP is
based on site specific physical meteorological limitations which avoid
the inaccuracies associated with extending limited data bases for long
time periods, it is reasonable and prudent to use a PMF based on the
PMP as the design flood."
8.2.4 Longevity of Control
We have chosen two time periods for evaluating the longevity of
effective control. A short time period of 100 years was chosen for one
case, since this has been proposed as the limit for reliance on
institutional controls (EPA78). A period of about 1,000 years was
selected for the second case. Tnis case displays the difference
between active and passive controls, as well as the expected variation
of effectiveness of controls over longer time periods.
In general, the effectiveness of controls over time can be rated
as follows;
8-8
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Highest - Deep geological disposal.
Below-grade surface disposal.
Above-grade surface disposal, entire area covered
with thick earth and rock cover.
- Above-grade surface dispoal, entire area covered
with thick earth, slopes covered with rock.
- Above-grade surface disposal, entire area covered
with thick earth.
Lowest - Above-grade surface disposal, entire area covered
with thin earth and maintained.
This ranking assumes the tailings pile is located where erosion
occurs. If tailings are located where soil deposition is taking place,
the ranking will be equal for all cases as long as deposition continues.
8.3 Disposal Methods and Effectiveness
8.3.1 Earth Covers
Earth placed over tailings slows the movement of radon into the
atmosphere by various attenuation processes. When the earth is moist,
attenuation increases. Different soils have different attenuation
properties; these can be approximately quantified in terms of a
quantity called the "half-value layer" (HVL). The HVL is that
thickness of cover material (soil) that reduces radon emission to
one-half its value. Figure 8-2 shows the percentage of radon that
would be predicted to penetrate various thicknesses of materials with
different HVLs. These values are nominal; the actual HVL may vary
significantly. From Figure 8-2 it can be seen that 3 meters of sandy
soil (HVL =1.0 meters) is projected to reduce the radon released from
tailings by about 90 percent. Soils with better attenuation properties
would require less thickness to achieve the same reduction. For
example, 1 meter of compacted moist soil (HVL =0.3 meters) would be
predicted to reduce the radon release by about 90 percent.
A more complete treatment of radon attenuation based on the work
of Rogers (Ro81), is given in Appendix P of the NRG Generic E1S for
mill tailings. That analysis concludes that the effectiveness of an
earthen cover as a barrier to radon depends most strongly on its mois-
ture content. Typical clay soils in the uranium milling regions of
western United States exhibit ambient moisture contents of 9 percent tc
12 percent. For nonclay soils, ambient moisture contents range from 6
percent to 10 percent. The following table provides, as an example,
the cover thicknesses needed to reduce the radon emission to 20 pCi/m^s
for the above ranges of soil moisture. Four examples of tailings are
8-9
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PS
w
>
8
fn
o
o
H
H
W
2
100 r
90
80
70
60
50
40
30
20
10
SANDY SOIL (HVL = 1.0 m)
SOIL (HVL = 0.5 m)
COMPACTED, MOIST SOIL
(HVL = 0.3 m)
CLAY (HVL = 0.12 m)
2345
COVER THICKNESS (METERS)
Figure 8-2. Percentage of Radon Penetration of Various
Covers by Thickness.
8-10
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shown that cover the probable extreme values of radon emissions from
bare tailings at existing sites (100 to 1000 pCi/m2s); the most
common values lie between 300 pCi/m2s and 500
Table 8-1. Estimated Earthen Cover Thickness
(in meters) to Reduce Radon Emissions to 20
Radon Emission
from Tailings . ,, . , . . ,. ,
~ Percent Moisture Content of Cover
(pCi/m s) 6 8 10 12
100
300
500
1000
1.7
2.8
3.4
4.1
1.3
2.1
2.6
3.2
1.0
1.5
2.0
2.4
0.7
1.1
1.5
1.8
In practice, design techniques must take account of uncertainties
in the measured values of the specific materials used, the tailings to
be covered, and predicted long-term values of equilibrium moisture
content for the specific location, in order to assure meeting any given
radon emission limit over the long term. The uncertainty in predicting
reductions in radon flux increases rapidly as the required radon
emission limit approaches background. Even at 20 pCi/m^s the
uncertainty may approach a factor of three (Ro83). For example, the
calculated emission rates using Roger's method (RoBl) for four earthen
test plots at Grand Junction, Colorado, are compared to actual
performance in Table 8-2 (Ge81, Ba82, Ha83).
Table 8-2. Summary of Radon Flux Measurements Mode
at Grand Junction Over a Two-Year Period (Ba82)
Average Tailings Average Moisture
Radon Source «Flux Flux? Content
Barrier (pCi/m s) (pCi/m s) (%)
1.2m Mancos Shale/ 619 + 221 1.0 + 1.1 15.8
1.8m Adobe
1.2m Bentonite/ 589 + 285 8.8 + 8.5 20.2
1.8m Adobe
1.2m Compacted Adobe/ 316+1 6.6+10.2 11.9
1.8m Adobe
3m Uncornpacted Adobe 195 + 132 18.3+25.2 6.5
Calculated
Flux 2
(pCi/m s)
2.32
0.07
6.92
14.9
8-11
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Two tests produced results close to the predicted values (the
compacted and uncompacted adobe cases). The test of the Mancos shale and
adobe was more than a factor of 2 less than the predictable value and the
test of the bentonite and adobe was more than a factor of 100 higher than
the predicted value. It should be noted that these test plots are still
far from reaching equilibrium moisture content (representative values in
the area range from 3.3 percent for Mancos shale to 11.0 percent for
bentonite clay).
The thickness of earthen cover needed to provide isolation is not
directly calculable. Perhaps the best approach is to review the depths
to which excavations for common activities are routinely made. Excava-
tions are routinely made to 6 to 8 feet for public utilities (water and
sewer pipes, power lines, telephone lines). Footings for house founda-
tions are often placed at an 8-foot depth. In colder climates it is
important that water lines and foundations be placed below the frost
depth to avoid freezing problems. Graves are also dug to a depth of
6 feet or more.
The amount or thickness of earth that will attenuate gamma radiation
to one-half its initial value is also called a half-value layer (HVL).
As with radon adsorption, the HVL for gamma attenuation depends on soil
composition, compaction, moisture content, and other factors. The
average HVL of compacted soil for gamma radiation from tailings is about
0.1 meter. Therefore, a soil thickness of 0.5 meter will reduce the
gamma radiation to about 3 percent of its initial value from the
uncovered tailings, and 1 meter of soil would reduce it to about 0.1
percent of its initial value.
The model tailings pile is assumed to have a radium-226 concentration
of 280 pCi/g. This produces a gamma-absorbed dose rate in air of about
4,000 mrad/year on top of the uncovered tailings, assuming a homogeneous
distribution of radium-226 in the tailings. An earth covering of 1 meter
would reduce this absorbed dose rate in air to about 7 mrad/year. This
is slightly less than the total gamma dose from the uranium-238 series
under average background conditions.
Earthen covers can also prevent the movement of tailings by wind and
water. A combination of grading and contouring slopes, covering with 0.5
meter of earth, landscaping, and continuing maintenance is considered the
minimum control for these pathways, as long as maintenance is continued.
Longer term protection that does not rely on maintenance can be provided
by use of thicker earth covers, and rock or other forms of surface
stabilization.
8.3.2 Basin and Pond Liners
Liners are materials placed on the botton of a tailings retention
basin or pond to prevent or reduce the seepage of water into the
underlying soil. Liners can be made of clays, asphalts, concretes, and
polymers (plastics), or various combinations of these (Ba81, Bu81, NRC80).
8-12
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Agency policy on the use of liners for groundwater protection was
delineated in recently promulgated regulations under the Solid Waste
Disposal Act (EPA82). A liner placed beneath the waste in a land
disposal unit is often a key element of a general liquids management
strategy. However, liners are just one component of an overall liquid
management system. A liner is a barrier that prevents or greatly
restricts migration of liquids into the ground. No liner, however, can
keep all liquids out of the ground for all time. Eventually, liners will
either degrade, tear, or crack and will allow liquids to migrate out of
the unit. It is, therefore, important that liquids be removed during the
time that the liner is most effective. Leachate collection and removal
systems at landfills and measures to remove free liquids from surface
impoundments at closure are the principal techniques used to remove
liquids.
The Agency view of the function of a liner contrasts with that of
some members of the public and the regulated community. Some view liners
as devices that provide a perpetual seal against any migration from a
waste management unit. The more reasonable assumption, based on what is
known about the pressures placed on liners over time, is that any liner
will begin to leak eventually. Others have argued that liners should be
viewed as a means of retarding the movement of liquids from a unit for
some period of time. While this view accords with how liners do in fact
operate, this represents an incomplete regulatory strategy for ground
water protection because it achieves only a delay of the appearance of
groundwater contamination rather than a permanent solution. Accordingly,
liners should be viewed as a barrier best used to maintain control of
liquids prior to their removal from the waste management unit during its
active life. Assurance of long-term protection is best achieved by a
combination of removal of excess liquids and prevention of influx of new
liquids after disposal.
Thus, while liners may remain effective for preventing migration
from the unit until well after disposal, their principal role occurs
earlier. In final disposal, the Agency believes that a protective cap
becomes the prime element of the liquids management strategy. A
well-designed and carefully maintained cap can be quite effective at
reducing the volume of liquids entering a unit and therefore can
substantially reduce the potential for leachate generation at the unit
for long periods.
The Battelle Pacific Northwest Laboratory group has performed a
comprehensive review of liners for uranium tailings (Bubl). They
selected seven materials for laboratory testing (bafal) on the basis of
their potential usefulness as liners for uranium mill tailings ponds.
These materials were asphalt concrete, asphalt rubber, catalytic airblown
asphalt, Hypalon (a chlorosulphonated polyethylene), sodium-bentonite,
saline seal-100 bentonite, and GSR-6U bentonite. Ihey also tested a
native soil at one of the alternative disposal sites for the Durango,
Colorado, inactive tailings pile. The materials were tested for
permeability (increased permeability is caused by failures through
chemical attack of the asphalts and synthetics or through reduction of
8-13
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the ion exchange capacity of the clays), physical stresses, and radiation
damage. Based on laboatory tests, expected field effectiveness, and a
cost analysis, the liners selected for field studies were a catalytic
airblown asphalt-and-soil amended with sodium-bentonite.
For this analysis, to protect groundwater before the final disposal
of the tailings, we assume a plastic liner is installed on the bottom and
sides of a disposal pit. Earthen cover is assumed to provide an adequate
cap, after disposal, to control influx of water in the arid western
regions typical of U.S. uranium mills. At wet sites typical of the
eastern U.S., however, it would be necessary to prevent infiltration of
precipitation through the cover into the tailings, Thus, a cover that is
less permeable than the liner would be required.
8.3.3 Thermal Stabilization
Tnennal stabilization is a process in which the tailings are
sintered at high temperatures. The Los Alamos National Laboratory has
conducted a series of tests on tailings from four different inactive mill
sites (DrBl). Tailings were sintered at temperatures ranging from 300°
to 1200°C. Tests were then run on the various properties of these
tailings. The results are presented in Table 8-3.
Table 8-3. Percent Reduction in Emanating Ra-226
at Temperatures from 500° to
(b)
Sintering
Temperature
(°c)
500
600
700
800
900
1000
1100
1200
Shiprock,
Sands
(%)
15
29
44
63
83
92
96.4
97.7
N.M., Pile
Fines
U)
16
27
37
58
84
96.1
98.8
99.2
Durango,
Sands
(%)
48
64
76
87
92
95.5
99.0
99.5
Colo., Pile
Fines
U)
61
68
80
86
91
92
99.8
99.8
(a). treated tailings
1 untreated tailings
(b) original emanating Ra-226:
Shiprock sands
Shiprock fines
Source: Dr81.
39 pCi/g.
214 pCi/g.
Durango sands
Durango fines
140 pCi/g.
473 pCi/g.
8-14
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Ihese results indicate that thermal stabilization can be quite
effective in preventing the release (emanation) of radon from
tailings. Ihe authors note that before thermal stabilization can be
considered as a practical disposal method, information is needed on the
following:
1. The long-term stability of the sintered material exposed to
physical degradation and chemical attack (e.g., solubility of
new minerals and amorphous material found in thermally
stabilized tailings).
2. The interactions of the tailings and the refractory materials
lining a kiln.
3. Ihe gaseous and particulate emissions produced during
sintering of tailings.
4. Revised engineering and economic analysis as more information
is developed.
Since gamma radiation is still present, protection against the
misuse of sintered tailings is still required. While the potential
health risk irom external gamma radiation is not as great as that from
the radon decay products, it can produce unacceptably high exposure
levels in and around occupied buildings. Also, the potential for
groundwater contamination may require the use of liners.
8.3.4 Chemical Processing
The Los Alamos National Laboratory has also studied various
chemical processes to remove thorium-230 and radium-22b from the
tailings, along with other minerals (tombi). After removal from the
tailings, the thorium and radium can be concentrated and fixed in a
matrix such as asphalt or concrete. This greatly reduces the volume of
these hazardous materials and allows disposal with a higher degree of
isolation than economically achievable with tailings.
The NRC has considered the processing of uranium ore in a nitric
acid mill (NkCBO). This chemical process would strip a large fraction
of the thorium and radium from the ore, along with uranium and other
minerals. The thorium and radium would then be concentrated, fixed in
a matrix, and disposed of in a manner similar to the process just
described for sulfuric acid treatment of the tailings.
The major question regarding both these processes is whether they
reduce the thorium and radium values in the stripped tailings to safe
levels. If processing efficiencies of faO percent to 90 percent were
attained, radium concentrations in tailings would still be in the 30 to
60 pCi/g range. This concentration can cause excessive levels of radon
decay products in occupied structures if these treated tailings were
8-15
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placed under or around the structures. Thus, careful disposal of the
stripped tailings would still be required to prevent misuse. Another
disadvantage of chemical processing is the cost, although some of the
costs might be recovered from the sale of other minerals recovered in
the processing (Th81). The value of other minerals can be expected to
vary greatly CThbl) from ore to ore.
8.3.5 Soil Cement Covers
A mixture of soil and Portland cement, called soil cement, is
widely used for stabilizing and conditioning soils (.PC79). It is used
to condition subsoils under highway pavements, to serve as a base tor
large parking lots where it is covered with asphalt, and to stabilize
slopes by preventing erosion, among other uses.
The aggregate sizes of tailings appear suitable to make a good
quality soil cement, which is relatively tough, withstands freeze/thaw
cycles, and has a compressive strength of 300 to 800 psi. Vvhen
combined in a disposal system with a 1-meter earth cover over it, soil
(tailings) cement would be likely to provide reasonable resistance to
erosion and intrusion, to substantially reduce radon releases, and to
shield against penetrating radiation. Its costs are expected to be
comparable to triose of thick earth covers.
The long-term performance of soil cement is unknown, especially as
tailings piles shift or subside with age. Also, soil cement cracks at
intervals when placed over large surface areas. The importance of this
cracking on the effectiveness of soil cement has not been evaluated,
but is expected to be small.
8.3.6 Deep-Mine Disposal
Disposal of tailings in worked-out deep mines offers several
advantages and disadvantages compared to surface disposal options. The
probability of intrusion into and misuse of tailings in a deep mine is
much less than that achievable with surface disposal. Radon releases
to the atmosphere would be eliminated, for practical purposes, as would
erosion and external radiation.
The greatest problem with deep mine disposal is the potential
contamination of groundwater. This problem is most difficult to
evaluate, especially over the long term. Also, this method would be
cost-effective for only those mills near deep mines because of the high
cost of transporting tailings.
8.3.7 Solidification in Concrete or Asphalt
This disposal method separates the sands fraction of the tailings
from the slimes fraction. The sands make up the greatest part of the
tailings weight, while most of the radioactive material is in the
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slimes. After separation, the sands are washed and discharged into a
surface pit. The slimes are separated from the water, dried and then
solidified in concrete or asphalt. The solidified slimes can then be
disposed of in the pit with the sands or by other methods offering more
isolation. The NRC analyzed this method in some detail, including a
cost evalution (NRCbO).
Since about 15 percent of the radioactivity is in the sands, this
fraction will contain about 60 pCi/g of radium-226. This concentration
can lead to an excessive buildup of radon in structures if these sands
are misused under and around structures. Thus, the sands fraction will
require a barrier, such as an earth cover, to isolate them and to
prevent misuse . Also, since toxic metals will be present in both
fractions (Coa81), a liner may be needed to protect groundwater from
the sands fraction.
Overall, this method is costly, provides a relatively high level
of protection from 85 percent of the radioactivity in the tailings, but
provides little protection from the remaining radioactivity and toxic
materials unless additional controls are used.
8.4 Selection of Disposal Method For This Analysis
Earthen covers were selected for analysis for the following
reasons:
1. Thick earthen covers are effective in
discouraging misuse of tailings, in reducing
radon emissions, in essentially eliminating gamma
radiation, in protecting groundwater for
long-term periods, and in resisting erosion.
2. Thick earthen covers can be made long lasting by
stabilizing the surface with vegetation and/or
rock.
3. Costs are relatively low and can be estimated
with some degree of certainty.
8-17
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REFERENCES
Ba82 Baker E.G., Freeman H.D., Hartley J.N., and Gee G.W., "Cost and
Effectiveness of Radon Barrier Systems," In: Proceedings of the
Fifth Symposium on Uranium Mill Tailings Management, Fort
Collins, Colorado, December 1982.
Ba81 Barnes S.M., Buelt J.L., and Hale V.Q., "Accelerated Aging Tests
of Liners for Uranium Mill Tailings Disposal," DOE/UMT-0205,
PNL-4049, Pacific Northwest Laboratory, Richland, Washington,
99352, November 1981.
Bu81 Buelt J.L., Hale V.Q., Barnes S.M., and Silviera D.J., "An
Evaluation of Liners for a Uranium Mill Tailings Disposal Site -
A Status Report," DOE/UMT-0200, PNL-3679, May 1981.
Coa81 Cokal E.J., Dreesen D.R., and Williams J.M., "The Chemical
Characteristics and hazard Assessment of Uranium hill Tailings,"
in: Proceedings of the Fourth Symposium on Uranium Mill
Tailings Management, Fort Collins, Colorado, October 1981.
Cob78 Costa J.R., "Holocene Stratigraphy in Flood Frequency Analysis,"
Water Resources Research, pp. 626-632, August 1978.
Dr81 Dreesen D.R., Williams J.M. and Cokal E.J., "Thermal
Stabilization of Uranium Mill Tailings," in: Proceedings of the
Fourth Symposium on Uranium Mill Tailings Management, Fort
Collins, Colorado, October 1981.
EPA78 Environmental Protection Agency, "Criteria for Radioactive
Wastes," Federal Register, 43 FR 53262, November 15, 1978.
EPA82 Environmental Protection Agency, "Hazardous Waste Management
System; Permitting Requirements for Land Disposal Facilities,"
40 CFR Part 264 (47 FR 32274), July 26, 1982.
Ge81 Gee G.W., et al., "Radon Control by Multilayer Earth Barriers:
2. Field Tests," in: Proceedings of the Fourth Symposium on
Uranium Mill Tailings Management, Fort Collins, Colorado,
October 1961.
Ha83 Hartley, J.N., Gee G.W., Baker E.G., and Freeman H.D., "1981
Radon Barrier Field Test at Grand Junction Uranium Mill Tailings
Pile," DOE/UMT-0213, PNL-4539, April 1983.
Ju83 Junge R.W. and Dezman L.E., "An Analysis of Control Standards
for the Long-Term Containment of Uranium Tailings," Transcripts
of Public Hearings on EPA's Proposed 40 CFR 192 Rules, Denver,
June 1983.
8-18
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REFERENCES (Continued)
Ne83 Nelson J.D., Volpe R.L., Wardwell R.E., Schumm S.A., and Staub
W.P., "Design Considerations for Long-Term Stabilization of Uranium
Mill Tailings Impoundments," Colorado State University, NUREG/CR-
3397, August 1983.
NCAA Department of Commerce and USAE, Department of the Army,
Hydrometeorological Reports, Government Printing Office,
Washington, D.C.
#38 (1960). Generalized estimates of probable maximum
precipitation for the United States west of tge 105th meridian.
#49 (1977). Probable maximum precipitation estimates, Colorado
River and Great Basin drainages.
#51 (1978). Probable maximum precipitation estimates, United
States east of the 105th meridian.
NRC80 Nuclear Regulatory Commission, "Final Generic Environmental Impact
Statement on Uranium Milling," NUREG-0706, September 1980.
PC79 Portland Cement Association, "Soil-Cement Construction Handbook,"
EB003.09S, Skokie, 111., 1979.
Ro81 Rogers V.C. and K.K. Nielson, "A Handbook for the Determination of
Radon Attenuation Through Cover Materials," NUREG/CR-2340, Nuclear
Regulatory Commission, Washington, D.C., November 1981.
Ro83 Rogers V.C., Personal communication, 1983.
Th81 Thode, E.F. and D.R. Dreeeen, "Technico-Economic Analysis of
Uranium Mill Tailings Conditioning Alternatives," in: Proceedings
of the Fourth Symposium on Uranium Mill Tailings Management, Fort
Collins, Colorado, October 1981.
Wm81 Williams J.M., Cokal E.J., and Dreesen D.R., "Removal of
Radioactivity and Mineral Values from Uranium Mill Tailings," in:
Proceedings of the Fourth Symposium on Uranium Mill Tailings
Management, Fort Collins, Colorado, October 1981.
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Chapter 9: ALTERNATIVE STANDARDS FOR TAILINGS DISPOSAL
In this chapter we first consider the various quantities which can
be used to express limitations on environmental releases. We then
formulate alternative standards that accomplish, in varying degrees,
the objectives set forth in Chapter 8. Finally, we determine the cost
of controls required to implement each of these alternatives.
9.1 Form of the Standards
9.1.1 Dose or Exposure Rate Limits
Health protection standards based on radiation dose or exposure
have two major advantages. First, the health risk to an individual can
be limited directly. Second, the cumulative risk from all pathways to
humans from the source is included. Partly because of these advantages,
the Federal Radiation Council Radiation Protection Guidance for Federal
Agencies (FRC60) and the Environmental Radiation Protection Standards
for Uranium Fuel Cycle Operations (40 CFR 190) (EPA77), with the
exception of the standards for certain long-lived radionuclides, are in
this form.
However, dose or exposure rate limits are not useful in
establishing health protection standards in connection with the
disposal of uranium mill tailings because they have an inadequate
relationship with some of the principal objectives of disposal, such as
preventing misuse of the tailings and controlling radon emissions from
tailings for a long period of time. Establishing an environmental dose
rate limit (or Working-Level Limit) near a tailings pile gives no
assurance of providing a long-lasting barrier controlling radon or of
inhibiting the use of tailings. In addition, limits on dose imply a
need to know the locations of individuals for long periods of time in-
to the future. Unless an exclusion area can be maintained indefi-
nitely, conformance to a dose limit could not be assured.
9.1.2 Concentration Limits in Air and Water
The primary advantage of standards specifying concentration limits
of hazardous or toxic materials in air or water is ease of compliance.
Most monitoring involves measurements of concentrations in environmental
media. Thus, monitoring results can be compared to concentration
9-1
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limits to determine compliance. This is a useful approach in
evaluating the performance of emissions and effluent controls at
operating facilities.
Concentration limits of radon in air can assure a given level of
performance of control measures. The relationship between radon
emissions from a pile and offsite concentrations of radon in air is
presented in Chapter 5.
Concentration limits are appropriate for the water pathway during
operation and closure, for which the period of concern is, at most,
decades, and which are used to assess the need for corrective actions.
EPA groundwater protection policy, which dictates the form of ground-
water standards, specifies concentration limits. However, they are not
appropriate for other pathways since they could be satisfied largely by
institutional methods, such as acquiring and maintaining control over
land, that are not appropriate in view of the long-term hazard.
9.1.3 Release Rate Limits
This form of standard is useful for controlling emissions when
either total quantities discharged or ambient levels of a pollutant are
of concern. It is also useful for controlling emissions and effluents
when it is desirable to force a specific level of control.
Because of these advantages a release rate limit approach appears
to offer the best choice of accomplishing the primary objectives of
these standards. A release rate limit can assure that an effective and
durable barrier controls radon emissions and isolates the tailings from
the environment. This barrier can also provide significant assurance
that the tailings would not be removed from the site and used in and
around occupiable structures.
9.1.4 Engineering/Design Standards
Engineering or design standards specify methods or procedures and
the critical dimensions or characteristics of the method. Such
standards have the advantage of directly assuring a solution of the
problem. For tailings disposal, a design standard could require that
tailings be covered with a certain type of soil to a minimum thickness
and with a maximum slope. Soil stabilization methods could also be
spelled out, such as rock cover on the slopes and vegetation over the
remainder of the disposal site.
Several disadvantages are inherent in design standards. They tend
to squelch ingenuity and initiative to develop improved and less costly
methods. They do not reflect the variations in local conditions that
may lead to greater health protection if properly utilized or exploited.
They are difficult to change or modify. The disadvantages of design
standards appear to outweigh the advantages for use in the disposal of
uranium mill tailings. In addition, the legislative history of the Act
does not support the use of such standards.
9-2
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A second approach in engineering/design standards can be based on
probabilities considerations. In this form, the primary objective of
the standard is stated clearly. Then, probabilities (in quantified
terms) are assigned for achieving the primary objective during various
future periods. For example, in the near term, the numerical
probability assigned to meeting the primary objective could be high.
For longer periods, the probability could be reduced, reflecting
inability to predict the effectiveness of controls over longer times.
Compliance with a probability-based standard uses models, which
project the future performance of control methods, and expert views.
The advantage of this approach is that it forces an appraisal of the
long-term hazards associated with the tailings. however, the present
state of the art for tailings disposal limits the usefulness of
numerical probability-based design standards.
9.2 Alternative Disposal Standards
We have evaluated a range of alternatives for disposal standards
based on the objectives described in Section 8.1, the most likely
disposal method chosen in Chapter 8, and the form of the standard
considered in Section 9.1. These alternatives are presented in
Table 9-1. The requirements selected to meet the objectives are shown
for each alternative. Most of the requirements are expressed quantita-
tively, and in combination they achieve the overall objective of
reducing risks to people from tailings. The ranges of the controls
vary widely, from no control (Alternative A) to high levels of control
(Alternatives C-5 and D-5).
Uranium mill tailings will remain hazardous for hundreds of
thousands years due to the 75,000-year half-life of thorium-230.
Protecting public health for such periods of time is difficult to
conceptualize, much less assure. On a practical basis, controls
reasonably can be relied on for periods defined as:
Active controla maximum period of about 100 years.
Available and practical engineering controlsa period
extending from a few hundred years to a few thousand years.
Controls featuring great isolationa period of many thousands
of years limited by major geological activity.
These periods will be used in the ensuing discussions of
alternative standards.
In preparing alternatives, it is important to separate active
(institutional) and passive (engineered) controls so that the differ-
ences in benefits and costs are apparent. It is also important to
delineate the differences in benefits and costs for disposal methods
that can be used at new tailings impoundments. Thus, alternatives were
developed as follows:
9-3
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Alternative Type of Control
Group A Base case. No controls.
Group B Institutional (active) controls.
Group C Passive (engineered) controls.
Group D Passive (engineered) controls for
new tailings impoundments.
Within each group the radon emission level was varied (as indicated by
the number following the group letter, i.e., B-l, B-2, etc.) to depict
the cost effectiveness of different levels of radon control.
Alternative A. This alternative is the "no standards" case and
represents conditions if nothing is done. The piles will remain
hazardous for a long time, taking about 265,000 years for the
radioactivity to decay to 10 percent of current levels. The radon
emission rate from a model pile is estimated to be 400 pCi/m^s,
compared to a background rate for typical soils of about 1 pCi/m^s.
We also know that the concentration of some toxic chemicals in the
tailings is hundreds of times background levels in ordinary soils, so
that the potential for contaminating groundwater is present and
continues indefinitely.
Alternative B-l. This alternative specifies that control measures
include a durable cover that is subject to inspection and maintenance
requirements for 100 years. Institutional controls (inspection and
maintenance) would also be required to prevent significant contamina-
tion of groundwater, or groundwater would be treated before use. No
radon emission rate is specified.
Alternative B-2. Control measures require a durable cover that is
subject to inspection and maintenance for 100 years. The radon
emission limit is 60 pCi/m2s. Institutional controls would also be
required to protect groundwater.
Alternative B-3. Control measures require a durable cover that is
subject to inspection and maintenance for 100 years. The radon
emission limit is 20 pCi/m2s. Groundwater would be protected through
the use of institutional controls, such as monitoring and corrective
actions.
Alternative C-l. Control measures are designed so there is
readonable assurance they will be effective for 1,000 years. No
requirement is specified for radon emissions. Water quality is
expected to be protected for about 100 years.
Alternative C-2. Control measures are designed so there is
readonable assurance they will be effective for a few 1,000 years.
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Table 9-1. Alternative Standards for Disposal of Uranium Mill Tailings
Alternative
Standard
Minimum Time
Controls Should
Prevent Erosion
and Misuse
(years)
Radon Emissions
Permitted from
Top of2Pile
(pCi/m -sec)
Expected Time
Controls Should
Protect Groundwater
(years)
None
No limit
None
B-l
B-2
B-3
C-l
C-2
C-3
C-4
C-5
D-2
D-3
D-4
D-5
100
100's
100's
1,000
1,000
Many 1,000
Many 1,000
Many 1,000
1,000
Many 1,000
Many 1,000
Many 1,000
No requirement
60
20
No requirement
60
20
6
2
60
20
6
2
100
luO
100
100
100's
1,000
1,000
1,000
1,000
1,000
1,000
1,000
The radon emission limit is 60 pCi/m2s.
be protected for a few hundred years.
Groundwater is expected to
Alternative C-3. In this alternative control measures are
designed to be effective for 1,000 years. The radon emission limit is
20 pCi/m2s. Water quality is expected to be protected for about
1,000 years.
Alternative C-4. Control measures are designed to be effective
for at least 1,000 years. The radon emission limit is 6 pCi/m2s.
Water quality is expected to be protected for at least 1,000 years.
Alternative C-5. Control measures are designed to be effective
for at least 1,000 years. The radon emission limit is 2 pCi/ia2s.
Water quality is expected to be protected for at least 1,000 years.
Alternative D-2.
Disposal below grade by a staged disposal method
This will provide a significant reduction in radon
Control measures are designed to be
is required.
emissions during mill operations.
9-5
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effective for 1,000 years. The radon emission limit is 60 pCi/m2s.
Water quality is expected to be protected for about 1,000 years.
Alternative D-3. Disposal below grade by staged methods is
required, thus providing reduction of radon emissions during mill
operations. Control measures are designed to be effective for 1,000
years. The radon emission limit is 20 pCi/m2s. Water quality is
expected to be protected for more than 1,000 years.
Alt ernative D-4. Disposal below grade by staged methods is
required, thus providing reduction of radon emissions during mill
operations. Control measures are designed to be effective for at least
1,000 years. The radon emission limit is 6 pCi/m2s. Water quality
is expected to be protected for more than 1,000 years.
Alternative D-5. Disposal below grade by staged methods is
required, thus providing reduction of radon emissions during mill
operations. Control measures are designed to be effective for at least
1,000 years. The radon emission limit is 2 pCi/m2s. Water quality
is expected to be protected for more than 1,000 years.
9.3 Estimated Costs of Methods for Alternative Standards
Costs are estimated for the levels of control which will satisfy
the levels of health protection shown in lable 9-1. A range of
thicknesses of earth covers provides the various radon emission
levels. Various protective materials are used to increase the
long-term effectiveness of the cover.
Because the large differences in the sizes of existing tailings
piles at licensed sites can lead to large cost differences, these piles
have been separated into three groups: 2 million tons (MT), 7 million
tons, and 22 million tons. Their characteristics are given in Appendix B,
This grouping is for costing purposes only. While the divergence in
estimated costs for existing piles is great, the range in potential
health risks is small. Estimates of potential health risks are largely
dependent on the area covered by the tailings. The area of the model
pile (Chapter 4) and a listing of existing piles (Chapter 3) indicate
the areas vary by a factor of only plus or minus 40 percent.
Ratio of Area of
Existing Piles to Area
Area (hectares) of the Model Pile
Model pile 80 1.0
Existing 2 million tons 49 0.61
Existing 7 million tons 73 0.91
Existing 22 million tons 113 1.4
Thus, potential health risk estimates can be treated uniformly,
regardless of the pile size.
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9.3.1 Disposal Methods for Existing Tailings Piles
Method Bl-E
The edges of the square tailings pile are graded and contoured to
a 3:1 (H:V) slope. The entire area is then covered with 0.5 meter of
earth obtained nearby. A 6-feet high, 6-gage aluminum chain link fence
is placed around the exclusionary zone, which is assumed to be 0.5
kilometer from all sides of the pile. The covered pile is
landscaped,assuming that suitable loam or topsoil is available onsite.
The borrow-pit is reclaimed. Maintenance and inspection are added for
a 100-year period. The costs for this method are summarized in
Table 9-2.
Method B2-E
The sides of the tailings piles are graded to 3:1 (H:V) slope.
The tailings are covered with 1.5 meters of earth obtained nearby and
the entire surface is landscaped. A fence is installed to form an
exclusion area 0.5 kilometer wide all around the disposed tailings.
The borrow pit is reclaimed. The costs for this method are shown in
Table 9-2.
Method B3-E
For this method the edges of the square tailings pile are graded
to a 3:1 (H:V) slope. The entire tailings area is covered with 2.4
meters of earth obtained nearby or locally. The entire area (slopes
and top) are landscaped after covering. A fence is installed to form
an exclusion area 0.5 km wide around the edge of the tailings. The
borrow pit is reclaimed. The costs for this option are listed in Table
9-2.
Method Cl-E
The sides of the tailings piles are graded to a 5:1 (H:V) slope,
after which the entire area is covered with 0.5 m of gravelly earth
obtained nearby or locally. The slopes are covered with 0.5-meter rock
cover. No fence is needed. The borrow pit is reclaimed. The costs
for this option are presented in Table 9-2.
Method C2-E
The edges of the tailings piles are contoured to a slope of 5:1
(H:V). The entire area is then covered with 1.5 meters of earth
obtained nearby except the top 0.5-meter of the cover is gravelly
earth. The slopes are covered with a 0.5-meter thick rock cover. No
fence is necessary. The borrow pit is reclaimed. The costs for this
option are presented in Table 9-2.
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Method C3-E
The sides of the tailings piles are graded to a 5:1 (H:V) slope.
The entire area is then covered with 2.4 meters of earth obtained
nearby of which the top 0.5-meter layer is gravelly earth. A 0.5-meter
rock cover is added to the slopes. The borrow pit is reclaimed. The
costs for this method are listed in Table 9-2.
Method C4-E
The sides of the pile are graded to a 5:1 (H:V) slope. The entire
area is covered with 3.4 meters of earth obtained nearby of which the
top 0.5-meter layer is gravelly earth. A 0.5-meter rock cover is
placed on the slopes. No fence is needed. The borrow pit is
reclaimed. The costs for this method are listed in Table 9-2.
Method C5-E
The sides of the pile are graded to a 5:1 (H:V) slope. The entire
area is covered with 4.3 meters of earth obtained locally of which the
top 0.5-meter layer is gravelly earth. A 0.5-meter rock cover is
placed on the slopes. No fence is needed. The borrow pit is
reclaimed. The costs for this method are shown in Table 9-2.
9.3.2 Disposal Methods for New Tailings Piles
Method A
This method is the same as the base case in the NRC analysis
(NRC80). An initial square basin would be formed by building low
earthen embankments along each side of 947 meters length at the
centerline. The mill tailings would be slurried into the basin, and as
the basin filled, the coarse fraction of the tailings (sands) would be
used to raise and broaden the embankments. The final dimensions of the
embankments would be 10 meters high and 13 meters wide at the top.
When the mill ceases operations, no specific control measures for
disposal would be used. The cost for this option is listed in
Table 9-2 and consists only of preparation of the initial basin.
Methods Bl-N, B2-N, and B3-N
These methods use earth covers on the tailings and rely on
institutional controls to prevent misuse and to maintain the covered
pile. A pit is excavated close to the mill and measures 930 meters
square by 2 meters deep. Embankments are constructed along each side,
947 meters long, 10 meters high, and 13 meters wide at the top. The
pit is lined with 1 meter of clay obtained locally. Tailings are
pumped directly into the pit during operation of the mill. It is
assumed that water from the pond will be recycled to the mill, thereby
negating the need for an evaporation pond.
9-8
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At the end of mill life, the embankments are excavated and placed
on top of the tailings. The slopes of the covered tailings are graded
to 3:1 (H:V). The cover thickness is 0.5 meters for Bl-N, 1.5 meters
for B2-N, and 2.4 meters for B3-N. The entire area is landscaped. A
fence is placed around the disposal area and provides a 0.5-kilometer
exclusion zone. Borrow pits are reclaimed. The site is maintained for
100 years by irrigation of the vegetative cover and inspection and
repair of the earth cover and fence. Costs are shown in Table 9-2.
Methods Cl-N, C2-N, C3-N, C4-N and C5-N
Passive controls are used in these methods. These methods use
earth covers, 0.5-meter rock covers on the slopes and 0.5-meter gravel
layers on the top. A pit is prepared and used in the same manner to
that described for methods Bl-N, B2-N, and B3-N, including the liner.
At the end of mill life, the embankments are excavated and placed
on top of the tailings. The cover thickness is 0.5 meters for Cl-N,
1.5 meters for C2-N, 2.4 meters for C3-N, 3.4 meters for C4-N, and 4.3
meters for C5-N. The slopes of the disposed tailings are graded to 5:1
(H:V) and then covered with rock to a depth of 0.5 meter. The top of
the disposed tailings area (that part not covered with rock) is covered
with a 0.5-meter layer of gravelly soil which replaces the top
0.5-meter of earth. No fence is needed. The costs are listed in
Table 9-2.
Methods D2-N, D3-N, D4-N, and D5-N
These methods are somewhat similar to the staged or phased
disposal method described by the NRC's GEIS (NRC80). This method uses
6 pits, each 280 meters square at the bottom and with 2:1 (H:V)
slopes. Two pits are constructed initially and lined with 1 meter of
clay. Tailings are pumped to the first pit until it is full and then
pumped to the second pit. When the first pit is sufficiently dry, the
third or fourth pit is excavated, and the excavated earth is used to
cover the first pit to the original ground contour. The earth cover
thickness is 1.5 meters for D2-N, 2.4 meters for D3-N, 3.4 meters for
D4-N, and 4.3 meters for D5-N. This process continues sequentially
until the end of mill life. An evaporation pond is needed in this
method. Costs for this pond are taken from the NRC GEIS and corrected
for inflation.
At the end of mill life there will likely be four completed pits,
which are covered with earth to the original ground contour and 2
uncovered pits. When sufficiently dry, these last two pits are
covered with excavated earth to the original ground contour. The
disposed tailings area is landscaped. The areas covered by the
evaporation pond and excess excavated earth are restored. The costs
for this method are presented in Table 9-2.
9-9
-------
Cost Estimates
Cost estimates for the disposal of tailings at active uranium
milling sites are presented in Table 9-2 along with a summary of
critical design features. The cost estimate details are developed in
Appendix B, which also includes characteristics of tailings piles, unit
costs, and descriptions of disposal methods.
All cost estimates in Table 9-2 include an increase of 25 percent
for overhead and profit, but do not include the cost of a liner for the
tailings pond. The disposal costs for the model pile are greater than
for the existing 7-MT pile. The difference is due to the larger size
of the model and the costs of preparing the initial tailings
impoundment. The model pile, taken directly from the NRC Generic EIS
(NRC80), appears oversize when compared with industry practice. This
leads to the considerably greater costs for the model pile when
compared to an existing pile containing about the same quantity of
tailings. These cost estimates for the NT methods can be considered
maximum costs.
9.4 Accidental and Radiation-Induced Deaths from Disposal
One of the costs of control is the possibility of accidental
deaths during the disposal of tailings and when moving tailings.
Table 9-3 shows our estimate of the number of accidental deaths that
could be associated with each alternative disposal standard. These
estimates include accidental deaths of workers and premature,
radiation-induced deaths of construction workers at the tailings sites.
In our review of the existing tailings sites, we identified only
two sites that may be vulnerable to flooding. Even for these two
sites, it is not clear that the tailings would have to be moved to
provide protection against flooding. Thus, we have made no estimate of
the number of deaths that might occur, primarily to workers and the
public, from transportation accidents if the tailings piles are moved.
The most important parameter in this simplified analysis of
accidental deaths is the number of person-hours of labor required to do
the job. This is used to estimate the number of construction-related
deaths, as well as the number of premature deaths from radiation
exposure.
The labor required for piles that are to be controlled onsite is
proportional to the amount of earthmoving to be done; a gradual slope
requires more earthmoving than a steep slope, roughly in proportion to
the ratio of the slopes, and a thick cover requires more earthmoving
than a thinner one. Based on figures from a DOE contractor (DeW81), we
estimate that Alternative Bl-N would require about 110 person-years of
labor for the model pile. The labor requirements for C3-N and D3-N
would be 280 person-years. The labor requirements for each alternative
are estimated by scaling directly by the area covered by the tailings
9-10
-------
Table 9-2. Summary of Cost Estimates for Disposal
of Active Uranium Mill Tailings
Costvcl'
(in millions of
Method 1983 dollars)
A(b)
Bl(c)
Cl
C2
C3
C4
C5
D2
-------
Table 9-3. Accidental and Radiation-Induced Deaths Associated
with Alternative Levels of Tailings Control
Radiation-Induced
Method Accidental Deaths Deaths
For a Model Pile
Bl-N
B2-N
B3-N
Cl-N
C2-N and D2-N
C3-N and D3-N
C4-N and D4-N
C5-N and D5-N
For 2-mil lion- ton piles:
(11 piles)
Bl-E
B2-E
E3-E and Cl-E
C2-E
C3-E
C4-E
C5-E
For 7-million-ton piles:
(12 piles)
Bl-E
B2-E
B3-E and Cl-E
C2-E
C3-E
C4-E
C5-E
NEW TAILINGS
0.07
0.13
0.16
0.14
0.16
0.17
0.18
0.19
EXISTING TAILINGS
(As of January 1983)
0.4
0.5
0.7
0.8
1.0
1.1
1.2
0.5
0.7
0.9
1.0
1.2
1.3
1.4
0.04
0.09
0.10
0.08
0.10
0.11
0.12
0.13
0.3
0.4
0.5
0.6
0.7
0.8
0.8
0.3
0.4
0.5
0.6
0.8
0.9
0.9
9-12
-------
Table 9-3. Accidental and Radiation-Induced Deaths Associated
with Alternative Levels of Tailings Control (Continued)
Radiation-Induced
Method Accidental Deaths Deaths
EXISTING TAILINGS
(As of January 1983)
For 22-million-ton piles;
(3 piles)
Bl-E 0.2 0.2
B2-E 0.3 0.2
B3-E and Cl-E 0.4 0.3
C2-E 0.5 0.3
C3-E 0.6 0.4
C4-E 0.7 0.5
C5-E 0.7 0.5
TOTAL:
Bl-E
B2-E
B3-E and Cl-E
C2-E
C3-E
C4-E
C5-E
1.1
1.5
2.0
2.3
2.8
3.1
3.3
0.8
1.0
1.3
1.5
1.9
2.2
2.2
(see Section 9.3), using an effective area of the model pile of 80
hectares.
The occupational deaths resulting from this are estimated from
mortality statistics for the construction industry: 60 deaths per
100,000 worker-years (NS78). This corresponds to 6 x 10"^ accidental
deaths per person-year.
Radiation-induced deaths are difficult to estimate since it is
impossible to anticipate measures that might be used to protect
workers. However, in the worst case, the gamma radiation exposure rate
over a bare tailings pile (typically 1 mrem/h) for a working year would
lead to exposures of about 2 rem/y. Inhalation of radon decay products
would, at most, lead to a comparable risk. In Table 9-3, we have
assumed that the maximum risk of premature, radiation-induced death is
equivalent to the risk from an exposure of 4 reins (whole-body equivalent)
of gamma radiation per person-year of labor. Radiation-induced deaths
9-13
-------
are estimated at the rate of 2 x 10~6 per person-rem. Since radiation
exposures will be significantly reduced as the earth cover is added,
the radiation-induced death estimate was taken as one-half the value
obtained without credit for shielding by the cover.
9.5 Alternative Cleanup Standards for On-site Contaminated Land
We have analyzed four alternative cleanup standards for on-site
contaminated lands. All have requirements that limit the amount of
radium contamination because the presence of radium is a reasonable
index of the health hazard, including that due to toxic chemicals as
well as other radionuclides.
Alternative LI approaches a high-cost nondegradation alternative;
below this proposed radium limit it is usually not possible, using
conventional survey equipment, to accurately distinguish between
contaminated land and land with high naturally-occuring levels of
radium. Alternatives L2 and L3 approximate optimized cost-benefit
standards, but L2 demands a more rigorous cleanup of the soil surface.
Alternative L4 is a least-cost alternative that allows high radiation
levels that are close to Federal Guidance recommendations for exposure
of individuals to all sources of radiation excepting natural background
and medical uses.
The four alternative standards are:
Alternative LI. Land is cleaned up to levels not exceeding an
average 5 pCi/g of radium-226 in any 5-cm layer within 30 cm of
the surface and in any 15-cm layer below 30 cm of the surface.
Alternative L2. Land is cleaned up to levels not exceeding an
average of 5 pCi/g in the 15-cm surface layer of soil, and an
average of 15 pCi/g over any 15-cm depth for buried contaminated
materials.
Alternative L3. Land is cleaned up to levels not exceeding an
average of 15 pCi/g in any 15-cm depth of soil.
Alternative L4. Land is cleaned up to levels not exceeding an
average of 30 pCi/g in any 15-cm depth of soil.
In Table 9-4 we list the estimates of the costs and benefits of
each alternative standard for on-site contaminated land at the 26
existing mill sites. In each standard, the only remedial method for
which we estimated cost was the removal and disposal of contaminated
soil, since this is generally less costly than placing earth cover and
vegetation over contaminated areas and excluding access by fencing.
The benefits are expressed by (1) the number of acres of land that are
cleaned up and returned to productive use, and (2) the typical maximum
residual risk to individuals living in houses that might then be built
on this land.
9-14
-------
The number of acres requiring cleanup under each option was
estimated based on NRC's analysis of land decontamination (NRC80). By
assuming a typical depth profile of the radium contamination, it is
possible to relate the gamma radiation levels measured by the survey to
the areas of land contaminated above a specific concentration level of
radium. If the top 15-cm layer of earth is uniformly contaminated with
30 pCi/g of radium, the gamma field at the surface would be 63 percent
of the gamma flux from an infinitely thick layer, or 34
microroentgens/hr (He78). However, if the 30-pCi/g average in the top
15 cm of earth is due to a thin surface layer of nearly pure tailings
of a few hundred pCi/g, the resulting gamma radiation at the surface
would be about 54 microroentgens/hr. Since we expect windblown
contamination profiles to be somewhere in between these extremes, we
estimate that, on the average, 44 microroentgens/hr above background
(385 mrem/y) implies 30 pCi/g radium contamination in the top 15 cm of
soil (Standard L4). Similar analyses for Alternative Standards LI, L2,
and L3 result in 3, 7, and 22 microroentgens/hr, respectively (or 26,
61, and 193 mrem/y, respectively). Additional deeper contamination
would yield only slightly higher gamma values because of shielding by
the surface layer.
Using these correlations between radium contamination levels and
gamma radiation levels, the areas requiring cleanup under each standard
were estimated based on the NRG analysis. The total costs of cleanup
were then calculated assuming a cleanup cost of $15,300 (1983 dollars)
per acre for heavily contaminated land (ore storage areas) and $2600
(1983 dollars) per acre for land contaminated with windblown tailings.
The highest risk to people living in houses built upon contami-
nated land is due to the inhalation of radon decay products from radon
that seeps into the house. In the worst case, Alternatives LI and L2
would allow thick-surface earth layers with 5 pCi/g contamination,
while Alternatives L3 and L4 would allow thick layers of contaminated
soil at 15 pCi/g and 30 pCi/g, respectively. On the average, houses
built on such 5 pCi/g earth would be expected to have indoor radon
decay product levels of about 0.02 WL. Houses with poorer-than-average
ventilation would have higher levels, while well-ventilated houses
would have lower levels. Houses built on land more heavily
contaminated than 5 pCi/g would have higher average indoor decay
product levels in proportion to the contamination. The estimated risks
due to lifetime exposure from these levels are listed in Table 9-4.
These are maximum estimates since most contaminated land away from the
immediate mill sites (where houses might be built) has only thin layers
(a few tens of centimeters) of contaminated material.
The gamma radiation levels to individuals permitted under the four
alternative standards are 80 mrem/yr for LI and L2, 240 mrem/yr for L3,
and 470 mrem/yr for L4. This assumes a thick layer of contaminated
material over a large area at the maximum permitted levels of radium
concentrations. These doses would lead to increased risk of many kinds
of cancer, but this increase would be small compared to the lung cancer
risks due to radon decay products.
9-15
-------
Table 9-4. Costs and Benefits of Alternative Cleanup
Standards for Land
(in 1983 dollars)
Alterna-
tive
LI
L2
L3
L4
Radium-226
Soil Concentra-
tion Limit
(pCi/g)
5
5 to 15
15
30
Number of
Acres Re-
quiring,,
Cleanup la;
8300
5700
3100
520
Total Cost
(millions of)
dollars)
27.9
21.3
14.6
7.8
Estimated
Residual risk ,, -.
of Lung Cancer^
2 in 100
2 in 100
6 in 100
10 in 100
(a'Areas of land on uranium milling sites that have radium contamina-
tion in excess of the soil concentration limit. It is assumed that
about 20 acres (the ore storage pad) at each site is heavily contami-
nated and must be excavated to 3 feet. The remaining area is
contaminated by windblown tailings and is excavated to 6 inches
(NRC80). These totals are for the 26 existing sites.
lifetime risk of lung cancer to the individual living in a
house built on land contaminated to the limits allowed by the alterna-
tive standards. This is based on the relative-risk model; use of the
absolute-risk model gives risks which are about a factor of two lower.
9-16
-------
REFERENCES
DeWSl Telephone conversation between Michael DeWitt, Sandia
National Laboratories, Albuquerque, New Mexico, and EPA
staff, 1981.
EPA77 Environmental Protection Agency, "Environmental Radiation
Protection Standards for Nuclear Power Operations (40 CFR
190)," January 1977.
EPA82 Environmental Protection Agency, "Hazardous Waste
Management System; Permitting Requirements for Land
Disposal Facilities (40 CFR Part 264)," July 26, 1982.
FRC60 Federal Radiation Council, "Radiation Protection Guidance
for Federal Agencies," Federal Register 4402, May 18, 1960.
NRC80 Nuclear Regulatory Commission, "Final Generic
Environmental Impact Statement on Uranium Milling,"
NUREG-0706, USNRC, Washington, D.C., 1980.
NS78 National Safety Council, "Accident Facts/' 444 N. Michigan
Ave, Chicago, Illinois.
9-17
-------
Chapter 10: ANALYSIS OF COSTS AND BENEFITS FOR TAILINGS
DISPOSAL ALTERNATIVES AND SELECTION OF THE STANDARD
10.1 Benefits Achievable Through Disposal of Tailings
The estimated benefits of disposal of tailings include:
1. Reducing the likelihood of misuse of tailings,
and the resulting risk of lung cancer deaths from
inhaling radon decay products.
2. Reducing the risk of lung cancer deaths caused
by emissions of radon and its decay products.
3. Reducing the contamination of water with
radioactive and other hazardous or toxic materials.
4. Reducing the spread of radioactive and other
hazardous or toxic materials.
5. Eliminating, for practical purposes, exposure
to gamma radiation from tailings.
All of these benefits are achieved by stabilizing the tailings by
adding earthen cover material and instituting protective measures for
groundwater, where needed.
The benefit we are best able to quantify is the number of lung
cancer deaths averted by controlling radon emissions. We can estimate
the reduction in radon emissions resulting from the placement of a
given thickness of earthen cover, and translate this reduction into
lung cancer risk averted (see Chapter 6). The benefits of radon
control are quantified for both the total risk to populations of lung
cancer death that is averted and for the reduction in risk to
individuals living near the piles. These benefits are proportional to
the length of time the control remains effective.
Most of the other benefits of controlling the tailings piles are
not quantifiable, although the goals are well defined: the reduction
of health risks from exposure to the hazardous materials contained in
10-1
-------
the tailings. For example, we are unable to translate flood protection
measures into the number of health effects averted. The missing
linkages are: 1. The translation from specific flood protection
measures to flood damage averted; 2. The translation from flood damage
to the pile to distribution of tailings spread along the downstream
river valley; and 3. The translation from the tailings spread along
the river valley to the number, length, and level of exposures. There
are similar problems with quantifying the chance of misuse. The
permanence of erosion control, i.e., the years of erosional spreading
avoided and the years of water quality protection can be evaluated,
but, the consequences avoided are not readily quantified.
The benefits for each alternative standard are displayed in
Tables 10-1 and 10-2 and are quantified when possible.
The benefits of controlling tailings at existing sites are
summarized in Table 10-1. There were about 175 million tons of
tailings at 26 active mill sites January 1983. Table 10-1 is presented
primarily to show the cost effectiveness of controlling existing
tailings, which may be different than the cost effectiveness of
controlling future tailings.
The benefits of controlling tailings at all sites, both existing
and new, are summarized in Table 10-2. Based on current DOE
projections, it is estimated that another 175 million tons of tailings
will be generated by 2000.
10.1.1 Benefits of Stabilization
The benefits of stabilizing the tailings are expressed in terms of
the reduced chance of misuse and the years of erosional spreading
avoided. The number of health effects averted cannot be estimated.
The major benefit of stabilizing a pile is the inhibition of the
hazards associated with human intrusion and misuse of the tailings
piles; this can be expressed only in qualitative terms. We have
assigned relative values to the probability of misuse, based on the
assumption that thicker covers provide greater inhibition of misuse.
Also, the below-grade disposal method, with a 2.4-meter earth cover up
to the original ground contour, is expected to provide greater
inhibition of misuse than above-grade disposal with the same cover
thickness.
The likelihood of misuse during the period of effectiveness of
these alternatives ranges from most likely for the no-requirements
alternative to unlikely for alternatives with 2.4 meters of earth cover
and very unlikely for the method with 4.3 meters of earth cover.
10-2
-------
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The Grand Junction cleanup program is an example of the kind of
expensive remedial actions that stabilization should prevent. The.
tailings in Grand Junction buildings are now being cleaned up at a cost
of about $23 million, to avoid an estimated 75 to 150 lung cancer
deaths. The additional cost of cleaning up contaminated offsite land
is estimated at $22 million to $31 million.
A second benefit of stabilization is the prevention of erosion.
The benefit of preventing tailings erosion can be expressed in a
semiquantitative way by estimating the number of years that erosional
spreading is prevented. Protection from erosion is estimated to range
from a few hundred years to many thousands of years for the various
alternatives. Since erosion may now be taking place at some sites,
benefits can be derived from any remedial measure that reduces
erosion. For example, EPA estimated the cost for cleanup of
contaminated land around inactive tailings piles at $8,000 (1983
dollars) per acre. The total cost for cleanup of such lands depends on
the area contaminated and the level to which it must be cleaned up.
A third benefit of stabilization is protection against floods
which could wash tailings downstream to flood plains, where land use is
residential and agricultrual. Should this happen, expensive remedial
measures would probably be needed. A recent tailings "spill" (failure
of a dam containing a tailings pile at an active mill) in the Southwest
contaminated hundreds of acres of land (of limited value) over a
distance of about 20 miles. We estimate the cost of cleanup of that
spill to be $1 million to $5 million, depending on the cleanup criteria
used. The total radioactivity spilled was less than 5 percent of that
in an average active pile.
10.1.2 Benefits of Radon Control
The estimated benefits of radon control can be quantified. For
individuals living near a tailings pile, the benefit is a reduction in
health risk. The maximum risk of death to nearby individuals during
their lifetime is estimated to be about 2 chances in 100 for the
no-requirements of Alternative (A). This risk drops to less than 1
chance in 1,000 for Alternatives B-3, C-3, and D-3. The greatest risk
reduction is achieved by Alternatives C-5 and D-5, which have a 2
pCi/m2s radon emission limit and reduce the risk to less than 1
chance in 10,000.
The total national lung cancer death rate from radon emissions
from existing active piles is estimated at 500 per century if no
controls are used. This estimate will increase as additional tailings
are produced if controls are not used. Alternatives with a 20 pCi/m^s
radon emission rate would reduce this rate to about 25 per century for
hundreds to thousands of years. The benefit from a more restrictive
radon emission rate would be the virtual elimination of the radon
risk. Alternatives C-5 and D-5 are estimated to provide greater than
99 percent control of radon for at least 1,000 years.
10-6
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10.1.3 Benefits of Protecting Water
Protection of water quality is a benefit that cannot be
quantified, because future uses of the water cannot be estimated.
Unlike air, which must be breathed, water may or may not be used in
ways that might cause an increase in health risks. Also, water may be
tested for contaminants and, if polluted, it may be cleaned to levels
suitable for its projected use, or may be rejected, if an alternative
is avail?ble. However, after disposal the protective cover, or cap,
over the tailings can be quite effective at reducing the volume of
liquids entering the tailings and therefore can substantially reduce
the potential for contamination of groundwater for long periods.
The benefit of protecting groundwater is the preservation of its
existin6 quality for future uses. These uses are drinking, lifestock
watering, and limited irrigation. A specific benefit of groundwater
protection would be the reduction, or elimination, of molybdenosis in
cattle, \vhich has occurred at a site in Colorado where molybdenum from
a tailiufes pond contaminated groundwater.
Existing uranium tailings are located in areas with low
precipitstion. This means there is little need to discharge waste
water to surface waters. Waste water can be held in ponds, where it
evaporates or can be recycled back to the process. Only one uranium
mill currently has a National Pollution Discharge Elimination System
(NPDES; permit, under the Clean Water Act, for example. However,
uranium milling and milling may occur in wetter areas in the future
where discharges to surface waters may be unavoidable. In these cases,
the operator would be required to obtain a NPDES permit, which would
assure protection of surface water quality.
10.2 Benefits and Costs for a Model Tailings Pile
1'he benefits derived from disposal of tailings have been estimated
as shown in Tables 10-1 and 10-2 for the various alternative
standards. The total costs of these methods have been estimated as
listed in Table 10-3. In this section these benefits and costs are
evaluated for each alternative standard.
10.2.j Baseline Case A
This case is used as a baseline to which the benefits of other
methods can be compared. While this alternative would not achieve the
goals or objectives of the disposal standards, it has the significant
benefit of preventing the flagrant discharge of all tailings into
surface waters. This control has been practiced by the industry for
some time, however, and is considered appropriate as a baseline.
Cancer deaths from radon emissions from uncontrolled piles are
estimated to be 5 per year for existing tailings piles. These deaths
are expected to increase to 6 per year for all the tailings that are
projected to exist by the year 2000, if no controls are implemented.
10-7
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Table 10-3. Total Costs of Controlling Uranium Tailings
at Active Sites
(1983 dollars in millions discounted at 10%)
Alternative Present Worth Costs (10% discount rate)(a)
Standard
A
B-l
B-2
B-3
C-l
C-2
C-3
C-4
C-5
D-2
D-3
D-4
D-5
Existing Tailings
0
117
192
256
115
192
260
336
403
192
260
336
403
Future Tailings
1
83
95
111
95
112
128
146
165
156
160
186
204
Total Cost
1
2.00
287
367
210
304
388
482
568
348
430
522
607
cost estimates assume that two-thirds of the future tailings
generated at existing mills will be placed in existing impoundments and
tat other one-third will be placed in new, lined impoundments. We assume
that the average radium contents of existing and future tailings is 400
pCi/m2s.
10-8
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10.2.2 Alternative Standards B-l, B-2, and B-3
The concept underlying these alternatives is active control and
maintenance. The earth cover, loam, and vegetation would reduce radon
emanation and associated health effects for the 100-year period
maintenance is performed. The total radon deaths avoided would be
1,000 for Alternative B-l, 1,500 for Alternative B-2 and 2,000 for
Alternative B-3. The chance of misuse is small for 100 years because
of a fence and continuing human activities such as maintence and
inspection. Annual inspection and repair actions would provide
protection against windblown and surface water contamination and
external radiation for as long as such actions continue.
Most of the benefits for these alternative are considered to end
when maintenance activities cease. Once the sprinkling (irrigation) of
the vegetation stops, chemicals from the tailings will probably kill
the vegetation, and the cover will be denuded and rapidly eroded.
However, this scenario could be modified by selection of a site where
the deposition of material exceeds the erosion of material. Even in
this case the deposition rate is likely to be low, thus allowing
continued radon releases and significant chances of misuse for a long
period.
The estimated total costs for Alternatives B-l through B-3 are
$200 to $370 million as listed in Table 10-3.
The estimated number of accidental and radiation induced deaths
for Alternative B-l is 3, for Alternative B-2 is 4, and for Alternative
B-3 is 6.
10.2.3 Alternative Standards C-l through C-5
The concept underlying these alternatives is passive, engineered
controls that will provide long-term protection without monitoring,
inspection, and repair. Different thicknesses of earthen covers
control radon emissions by 50 percent (for Alternative C-l) to greater
than 99 percent (for Alternative C-5). The total radon deaths avoided
would range from thousands to tens of thousands for the time periods
that the rock and pebbly soil protected covers would last. The chance
of misuse would be low during an initial period, especially if large
size rock is used on the slopes. However, with the passage of time the
chance of misuse would increase as reasons to avoid the pile (disposed
tailings) were forgotten or became obscure, and the pile became known
as a resource area for rock and sand. It is estimated that this
initial period would be about 100 years, after which the likelihood of
misuse would increase somewhat. The benefits of preventing windblown
and surface water contamination and protecting against external gamma
radiation are estimated to last thousands of years.
The estimated total cost for C Alternatives range from $210 to
$570 million (Table 10-3).
10-9
-------
The estimated number of accidental and radiation induced deaths
for Alternative C-l is 5, for C-2 is 6, for C-3 is 7, C-4 is 8, and for
C-5 is 8. These include control of existing tailings plus all tailings
generated to the year 2000.
10.2.4 Alternative Standards D-2 through D-5
These alternatives would require staged disposal of the tailings,
whereby several tailings storage ponds are used during the lifetime of
a mill. After each pond is filled, it is allowed to dry and is then
covered with earth to the original ground level. This has the
additional benefits of reducing the total quantity of tailings
requiring disposal at the end of mill life and of controlling part: of
the radon emissions during operations. This latter benefit is
discusssed in Chapter 7. Staged disposal is considered feasible for
new impoundments only. Existing tailings piles, which may contain
future tailings, are controlled to levels described in Alternatives C-l
through C-5.
The benefits of this alternative include reductions in radon
deaths, a greatly reduced chance of misuse for thousands of years, and
virtual elimination of surface water and land contamination and
external radiation exposure. The chance of misuse is likely to be less
for these alternatives because the tailings disposal site should be
indistinguishable from the surrounding terrain. By placing the
tailings below grade and covering them to the initial land contour,
there would be no easily identifiable pile with rock covered slopes,
clearly an indication of human activity.
The estimated total costs for these alternatives range from $350
to $600 million for both new and existing tailings sites. Alternatives C-2
through C-5 for existing tailings were used in conjunction with D-2
through D-5 to estimate total costs.
The estimated number of accidental and radiation-induced deaths
for Alternative D-2 is 6, D-3 is 7, D-4 is 8, and D-5 is 8.
10.3 The Standard Selected
Selecting a limit for radon emissions from tailings involves four
public health objectives, in addition to reducing health effects from
radon released directly from the pile. These may all be achieved by
using a thick earthen cover, which serves to inhibit misuse of
tailings, to stabilize tailings against erosion and contamination of
land and water, to minimize gamma exposure, and to avoid contamination
of groundwater from tailings. A radon emission limit of 20 pCi/m2g
or less would require use of a sufficiently thick earthen cover to
achieve all of these objectives. Our analysis shows that a limit of 20
pCi/m2g is also cost-effective for eliminating most health effects in
regional and national populations from radon released directly from the
pile. Such a limit would also reduce maximum individual risks to
10-10
-------
residents near tailings piles to less than one in 1,000. We concluded
that levels higher than 20 pCi/m2s are not justified, based on the
cost-effectiveness of risk reduction to 20 pCi/m2s, and the
unacceptably high maximum individual risks involved at higher levels.
The risk to people who live permanently very close to tailings
piles can still be relatively high, up to 1 in 1,000 for lifetime
residency, for a limit of 20 pCi/m2s. However, the practicability
and cost-effectiveness of providing more radon control by requiring
design for lower levels of emission falls rapidly below 20 pCi/m2s.
We note that no pile has ever been protected by such a cover; that
is, covers with defined levels of control and longevity are
undemonstrated technology. The design of covers to meet a specific
radon emission limit and period of longevity must be based on
measurements of properties of local covering materials and prediction
of local parameters, such as soil and tailings moisture, over the long
term. Because of uncertainties in measuring and predicting these
parameters, the uncertainty of performance of soil covers increases
rapidly as the stringency of the control required increases. Thus, in
the case of lower levels, the primary issue becomes whether conformance
to a design standard for such levels is practicably achievable.
There is some field information available regarding the
practicality of reduction of radon emissions to levels approaching
background. Tests conducted at a pile in Grand Junction, Colorado,
showed that test plots of 3-meter covers made from four different
earthen combinations reduced radon emissions to values ranging from
1.0+1.1 to 18.3+25.2 pCi/m2s. The efficiencies of these covers
ranged from 88.8 percent to 99.7 percent. These results apply to the
first two years after emplacement and do not reflect performance after
long-term moisture equilibrium is achieved (some cover moisture
contents are still considerably elevated over prevailing levels). We
believe ranges like these can generally be expected, because the radon
control characteristics of earthen materials used for covers will vary
from site to site. Three of the four covers studied satisfied 20
pCi/m2s with a reasonable degree of certainty. The other cover
(18.3+25.2 pCi/m2s) was uncompacted, and its poor performance can
therefore be discounted. Exactly how much thicker these covers would
need to be to reliably achieve a lower limit (e.g., 6 or 2 pCi/m2s)
over the required 1,000-year period is not known.
During hearings on the standards, experts commented that although
covers can be designed to meet levels such as 20 pCi/m2s, estimation
models are not reliable at significantly lower emission levels.
We concluded that achieving conformance with a radon emission
standard that is significantly below 20 pCi/m2s (6 or 2 pCi/m2s,
for example) clearly would require designers to deal with unreasonably
great uncertainty for this undemonstrated technology.
10-11
-------
We could also have specified a much shorter period of performance,
such as a few decades, for which the design to a lower emission level
would have been feasible, but the gain in health protection is clearly
greater for a slightly relaxed control level than for such a greatly
relaxed longevity of control.
The risk from radon emissions diminishes rapidly with distance
from the tailings pile (declining by a factor of three for each
doubling of the distance beyond a few hundred meters). There currently
are only about 30 individuals living so near to active piles that they
might be subject to nearly maximum annual post-disposal risks. We
expect that the actual number of people who might experience near
maximal lifetime risk will be smaller, since they would have to
maintain lifetime residence in the land area immediately adjacent to a
tailings pile. In sum, we believe that the probability of a
substantial number of individuals actually incurring these maximum
calculated risks is small.
We conclude that it is not reasonable to reduce the emission
standard below 20 pCi/m2s because of (1) the uncertainty associated
with the feasibility of implementing a requirement for a significantly
lower standard, (2) the small reduction in total health benefit
associated with such thicker covers, (3) the limited circumstances in
which the maximum risk might be sustained, and (4) the uncertain, but
substantial, cost of the added cover thicknesses needed for reasonable
assurance of achieving levels that further reduce individual risk
significantly.
10-12
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APPENDIX A
HEALTH AND ENVIRONMENTAL PROTECTION STANDARDS FOR
URANIUM AND THORIUM MILL TAILINGS
-------
Appendix A: HEALTH AND ENVIRONMENTAL PROTECTION STANDARDS FOR
URANIUM AND THORIUM MILL TAILINGS
In 40 CFR Chapter I, Part 192 is revised by adding Subparts D and
E as follows:
PART 192 - HEALTH AND ENVIRONMENTAL PROTECTION STANDARDS FOR
URANIUM AND THORIUM MILL TAILINGS
Subpart D Standards for Management of Uranium Byproduct Materials
Pursuant to Section 84 of the Atomic Energy Act of 1954, as Amended.
Section
192.30 Applicability
192.31 Definitions and Cross-references
192.32 Standards
192.33 Corrective Action Programs
192.34 Effective Date
Subpart E Standards for Management of Thorium Byproduct Materials
Pursuant to Section 84 of the Atomic Energy Act of 1954, as Amended.
Section
192.40 Applicability
192.41 Provisions
192.42 Substitute Provisions
192.43 Effective Date
A-3
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AUTHORITY: Section 275 of the Atomic Energy Act of 1954, 42 U.S.C. 2022,
as added by the Uranium Mill Tailings Radiation Control Act of 1978,
Pub. L. 95-604, as amended.
Subpart D Standards for Management of Uranium Byproduct Materials
Pursuant to Section 84 of the Atomic Energy Act of 1954, as Amended.
192.30 Applicability
This subpart applies to the management of uranium byproduct materials
under Section 84 of the Atomic Energy Act of 1954 (henceforth designated
"the Act"), as amended, during and following processing of uranium ores,
and to restoration of disposal sites following any use of such sites under
Section 83(b)(l)(B) of the Act.
192.31 Definitions and Cross-references
References in this subpart to other parts of the Code of Federal
Regulations are to those parts as codified on January 1, 1983.
(a) Unless otherwise indicated in this subpart, all terms shall have
the same meaning as in Title II of the Uranium Mill Tailings Radiation
Control Act of 1978, Subparts A and B of this part, or Parts 190, 2.60,
261, and 264 of this chapter. For the purposes of this subpart, the terms
"waste," "hazardous waste," and related terms, as used in Parts 260, 261,
and 264 of this chapter shall apply to byproduct material.
(b) Uranium byproduct material means the tailings or wastes produced
by the extraction or concentration of uranium from any ore processed
primarily for its source material content. Ore bodies depleted by uranium
A-4
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solution extraction operations and which remain underground do not
constitute "byproduct material" for the purpose of this Subpart.
(c) Control means any action to stabilize, inhibit future misuse of,
or reduce emissions or effluents from uranium byproduct materials.
(d) Licensed site means the area contained within the boundary of a
location under the control of persons generating or storing uranium
byproduct materials under a license issued pursuant to Section 84 of the
Act. For purposes of this subpart, "licensed site" is equivalent to
"regulated unit" in Subpart F of Part 264 of this chapter.
(e) Disposal site means a site selected pursuant to Section 83 of
the Act.
(f ) Disposal area means the region within the perimeter of an
impoundment or pile containing uranium byproduct materials to which the
post-closure requirements of Section 192.32(b)(l) of this subpart apply.
(g) Regulatory agency means the U.S. Nuclear Regulatory Commission.
(h) Closure period means the period of time beginning with the
cessation, with respect to a waste impoundment, of uranium ore processing
operations and ending with completion of requirements specified under a
closure plan.
(i) Closure plan means the plan required under Section 264.112 of
this subpart.
(j) Existing portion means that land surface area of an existing
surface impoundment on which significant quantities of uranium byproduct
materials have been placed prior to promulgation of this standard.
A-5
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192.32 Standards
(a) Standards for application during processing operations and prior
to the end of the closure period.
(1) Surface Impoundments (except for an existing portion) subject to
this subpart must be designed, constructed, and installed in such, manner
as to conform to the requirements of Section 264.221 of this chapter,
except that at sites where the annual precipitation falling on the
impoundment and any drainage area contributing surface runoff to the
impoundment is less than the annual evaporation from the impoundment, the
requirements of Section 264.228 (a)(2)(iii)(E) referenced in Section
264.221 do not apply.
(2) Uranium byproduct materials shall be managed so as to conform to
the ground water protection standard in Section 264.92 of this chapter,
except that for the purposes of this subpart:
(i) to the list of hazardous constituents referenced in Section
264.93 of this chapter are added the chemical elements molybdenum and
uranium,
(ii) to the concentration limits provided in Table 1 of Section
264.94 of this chapter are added the radioactivity limits in Table A of
this subpart,
(iii) detection monitoring programs required under Section 264.98
to establish the standards required under Section 264.92 shall be
completed within one (1) year of promulgation,
A-6
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(iv) The regulatory agency may establish alternate concentration
limits (to be satisfied at the point of compliance specified under Section
264.95) under the criteria of Section 264.94(b), provided that, after
considering practicable corrective actions, these limits are as low as
reasonably achievable, and that, in any case, the standards of Section 264.94(a)
are satisfied at all points at a greater distance than 500 meters from
the edge of the disposal area and/or outside the site boundary, and
(v) The functions and responsibilities designated in Part 264
of this chapter as those of the "Regional Administrator" with respect
to "facility permits" shall be carried out by the regulatory agency,
except that exemptions of hazardous constituents under Section
264.93(b) and (c) of this chapter and alternate concentration limits
established under Section 264.94(b) and (c) of this chapter (except as
otherwise provided in Section 192.32(a)(2)(iv)) shall not be effective
until EPA has concurred therein.
(3) Uranium byproduct materials shall be managed so as to conform
to the provisions of:
(a) Part 190 of this chapter, "Environmental
Radiation Protection Standards for Nuclear Power Operations" and
(b) Part 440 of this chapter, "Ore Mining and Dressing Point
Source Category: Effluent Limitations Guidelines and New Source
Performance Standards, Subpart C, Uranium, Radium, and Vanadium Ores
Subcategory."
(4) The regulatory agency, in conformity with Federal Radiation
Protection Guidance (FR, May 18, 1960, pgs. 4402-3), shall make every
effort to maintain radiation doses from radon emissions from surface
A-7
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impoundments of uranium byproduct materials as far below the Federal
Radiation Protection Guides as is practicable at each licensed site.
(b) Standards for application after the closure period.
At the end of the closure period
(1) disposal areas shall each comply with the closure performance
standard in Section 264.111 of this chapter with respect to
nonradiological hazards and shall be designed* to provide reasonable
assurance of control of radiological hazards to
(i) be effective for one thousand years, to the extent
reasonably achieveable, and, in any case, for at least 200 years, and,
(ii) limit releases of radon-222 from uranium byproduct
**
materials to the atmosphere so as to not exceed an average release
f\
rate of 20 picocuries per square meter per second (pCi/m s).
(2) The requirements of Section 192.32(b)(l) shall not apply to
any portion of a licensed and/or disposal site which contains a
concentration of radium-226 in land, averaged over areas of 100 square
* The standard applies to design. Monitoring for radon-222 after
installation of an appropriately designed cover is not required.
**This average shall apply to the entire surface of each disposal
area over periods of at least one year but short compared to 100
years. Radon will come from both uranium byproduct materials and from
covering materials. Radon emissions from covering materials should be
estimated as part of developing a closure plan for each site. The
standard, however, applies only to emissions from uranium byproduct
materials to the atmosphere.
A-8
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meters, which, as a result of uranium byproduct material, does not
exceed the background level by more than
(i) 5 picocuries per gram (pCi/g), averaged over the first
15 centimeters (cm) below the surface, and
(ii) 15 pCi/g, averaged over 15 cm thick layers more than 15
cm below the surface.
192.33 Corrective Action Programs
If the ground water standards established under provisions of
Section 192.32(a)(2) are exceeded at any licensed site, a corrective
action program as specified in 264.100 of this chapter shall be put
into operation as soon as is practicable, and in no event later than
eighteen (18) months after a finding of exceedance.
192.34 Effective Date
Subpart D shall be effective 60 days after promulgation.
Table A
Combined radium-226 and radium-228 5 pCi/liter
Gross alpha-particle activity
(excluding radon and uranium) 15 pCi/liter
Subpart E Standards for Management of Thorium Byproduct Materials
Pursuant to Section 84 of the Atomic Energy Act of 1954, as Amended.
A-9
-------
192.40 Applicability
This subpart applies to the management of thorium byproduct
materials under Section 84 of the Atomic Energy Act of 1954, as
amended, during and following processing of thorium ores, and to
restoration of disposal sites following any use of such sites under
Section 83(b)(l)(B) of the Act.
192.41 Provisions
The provisions of Subpart D of this Part, including Sections
192.31, 192.32, and 192.33, shall apply to thorium byproduct material
and:
(a) provisions applicable to the element uranium shall also apply
to the element thorium;
(b) provisions applicable to radon-222 shall also apply to
radon-220; and
(c) provisions applicable to radium-226 shall also apply to
radium-228.
(d) operations covered under Section 192.32(a) shall be conducted
in such a manner as to provide reasonable assurance that the annual
dose equivalent does not exceed 25 millirems to the whole body, 75
millirems to the thyroid, and 25 millirems to any other organ of any
member of the public as a result of exposures to the planned discharge
of radioactive materials, radon-220 and its daughters excepted, to the
general environment.
A-10
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192.42 Substitute Provisions
The regulatory agency may, with the concurrence of EPA, substitute
for any provisions of Section 192.41 of this subpart alternative
provisions it deems more practical that will provide at least an
equivalent level of protection for human health and the environment.
192.43 Effective Date
Subpart E shall be effective 60 days after promulgation.
A-ll
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APPU4DIX B
ESTIMATED COSTS FOR DISPOSAL OF URANIUM
BYPRODUCT! MATERIALS
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Appendix B: ESTIMATED COSTS FOR DISPOSAL OF URANIUM
BYPRODUCT MATERIALS
CONTENTS
Page
B.I Characteristics of Model Tailings Piles B-5
B.2 Tailings Disposal Unit Costs B-7
B.3 Descriptions and Costs of Disposal Methods B-10
References B-21
TABLES
B-l Unit Costs B-8
B-2 Reclamation Costs for a Borrow Pit on Flat Terrain B-10
B-3 Disposal Cost Summary: Method Bl-E B-12
B-4 Disposal Cost Summary: Method B2-E B-13
B-5 Disposal Cost Summary: Method B3-E B-13
B-6 Disposal Cost Summary: Method Cl-E B-14
B-7 Disposal Cost Summary: Method C2-E B-15
B-8 Disposal Cost Summary: Method C3-E B-16
B-9 Disposal Cost Summary: Method C4-E B-16
B-10 Disposal Cost Summary: Methods C5-E B-17
B-ll Disposal Cost Summary: Methods for Disposal of New Tailings
Piles B-19
B-3
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Appendix B: ESTIMATED COSTS FOR DISPOSAL OF URANIUM
BYPRODUCT MATERIALS
B.I Characteristics of Model Tailings Piles
The costs for disposal of uranium byproduct materials are
estimated in this appendix for alternative disposal standards. The
disposal methods, with one exception, use earth covers of various
thicknesses which are stabilized with vegetation and rock. We believe
this is the most likely method of disposal. The one exception is a
tailings solidification method which is described in detail by the
Nuclear Regulatory Commission (NRC80).
The costs of liners on the bottoms of tailings impoundments are
included for completeness since they represent a significant capital
cost. In practice, a liner is an operational control that protects
groundwater during the operational phase of a tailings pond. Long-term
protection of groundwater is provided by the cover. The estimates are
arranged so that costs of liners can be easily subtracted for analysis
purposes. Additional cost estimates for protecting groundwater are
presented in Chapter 7.
Existing Tailings Piles
In early 1983, there were 26 licensed uranium mills with tailings
piles. An analysis of these piles indicated that since they vary
widely in size, control costs would also vary greatly. Consequently
the piles were grouped into model piles as follows:
a. a 2-million-ton pile on 122 acres with an average
depth of 7.2 feet.
Number of piles in this group = 11
Average tons per pile =1.9 million
(Range = 0 to 3.2 million tons)
Average area covered = 122 acres
(Range = 47 to 200 acres)
B-5
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b. a 7-million-ton pile on 180 acres with an
average depth of 18.5 feet
Number of piles in this group = 12
Average tons per pile = 7.2 million
(Range = 4.5 to 10.9 million tons)
Average area covered = 180 acres
(Range = 85 to 400 acres)
c. a 22-million-ton pile on 279 acres with an
average depth of 36.9 feet
Number of piles in this group = 3
Average tons per pile = 22.5 million
(Range = 19.2 to 27.6 million tons)
Average area covered = 279 acres
(Range = 210 to 328 acres)
Separate calculations are needed for each model pile and for each
disposal method.
Another important feature of the model piles is the additional
area that would be covered by tailings when the sides of the tailings
piles, which consist of the sands (coarse fraction), are sloped or
contoured to provide additional erosion control. Two values are used
for the slopes of the pile edges after grading, 3:1 (H:V) and
5:1 (H:V). The volume of tailings moved is estimated by calculating
the volume of the sloped tailings where the vertical distance is the
average depth of the pile and the horizontal distance is 3 or 5 times
the vertical. The pile is assumed to be square. The amount of
additional land covered and the volume of tailings moved by sloping the
edges of the piles are:
Additional Land Tailings Moved
Covered (acres) (thousands of cubic yards)
Pile Size 3:1 slope 5:1 slope 3:1 slope 5:1 slope
2 million tons
7 million tons
22 million tons
4.6
14.5
36.3
7.7
24.4
61.5
27
215
1,070
45
361
1,810
These values can increase the cost significantly for those methods
involving disposal in place. It may be more economical to move the
tailings into the center of the pile, thereby forming a hemisphere rather
than cover the additonal land area with soil. However, it is not clear
that this method would be less costly, since the grading and shaping of
such large volumes is also costly.
B-6
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New Tailings Piles
Information on tailings to be generated at a model new mill are
taken from the NRC GEIS (NRC80). The NRC model mill has an
ore-processing capacity of 1,800 MT per day. The ore grade is expected
to average 0.1 percent uranium, and the uranium recovery efficiency is
assumed to be 93 percent. The mill is operated 310 days per year (i.e.,
85 percent capacity utilization rate), and the average annual production
is 580 MT yellowcake, which is 90 percent l^Oy. The model pile
covers an area of 198 acres with earth embankments around the tailings,
bringing the total area to 247 acres. The ultimate depth of the tailings
is about 26 feet.
The tailings will be generated at a rate of 1,800 MT per day, or 558
thousand MT per year, or 8.4 million MT during the assumed 15-year
operating period of the mill. The tailings are discharged to an
impoundment in the base case, which is analyzed later in this appendix as
case NT1.
B.2 Tailings Disposal Unit Costs
The most likely methods for disposal of the tailings involve
covering the tailings with earth, as discussed in Chapter 8. The unit
costs for earth work, transportation, fencing, landscaping, rock cover,
and maintenance and inspection are shown in Table B-l. All costs (except
the liner, maintenance, and inspection) were taken from Means (Me83).
The estimated 1980 cost of a Hypalon liner was $8.25 million (See
Alternative 5 in NRC80). Correcting this cost to 1983 and adding 25
percent for overhead and profit, a plastic liner is estimated to cost
§11.5 million for the 80-hectare model impoundment.
Maintenance and inspection costs are calculated for: (1) an
irrigaton system for maintaining vegetation on thin earth covers, (2)
fencing maintenance, and (3) annual inspections, including groundwater
monitoring and repair and revegetation of eroded areas.
Irrigation
The irrigation system design was developed for EPA by PEDCO
Environmental, Inc. (PE82). The design is for a 40-acre site (about 16
hectares) and consists of a 150-hp motor and pump unit, polyethylene
piping, and plastic spray heads. The capital costs of this system are
$127,000, and it is assumed that it must be replaced every 20 years. The
present value of capital requirements for 100 years of operation is
$149,000, using a 10 percent discount rate and replacement at 20, 40, 60,
and 80 years. Annual costs of operation are $12,000 per year for
maintenance and labor; $9,300 a year for electrical power; and $6,000 per
year for overhead, assuming the system is operated 8 hours per week, 8
months per year. The present value of these annual costs is $273,000 for
100 years using a 10-percent discount rate. Therefore, the total
B-7
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Table B-l Unit Costs
(1983 Dollars)
Task
Cost
Jl.07/yd/3
$4.14/yd3
$3.53/yd3
$3.17/yd3
$4.60/yd3
Earth work:
Grading:
Move and spread by scraper.
Placing earthern cover:
Excavate, haul, spread, and
compact by scrapers for 5,000 feet.
Excavate, load, haul by truck for
2 miles off the highway; dump, spread,
and compact.
Excavating pits:
Excavate, haul, and spread, by
scrapers, for 5,000 feet.
Moving tailings:
Excavate by drag line. Load, haul
2 miles off highway, spread, and
compact.
Synthetic liners:
Install flexible membrane liner
in 200-acre impoundment.
Transportation:
Over highway hauling of earth, tailings,
clay, loam, etc. (based on 4-mile roundtrips)
Rock cover:
Machine placed 18" thick.
Bank new gravel from borrow pit
Landscaping:
Fine grading and seeding, including
lime, fertilizer, and seed.
Fencing:
Chain link, 6 feet high,. 6-gauge aluminum.
Maintenance and inspection:
Installation and operation of
an irrigation system for 100 years-
present worth at 10% discount rate.
$11.5 million
$20/yd2
$3.23/yd2
$6,900/acre
$15.25/ft
$ll,000/acre
B-8
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Table B-l. Unit Costs (Continued)
(1983 Dollars)
Task Cost
Maintenance of fencing at 1% of capital 0.10 x capital
cost per year. Present value at 10% cost of
discount rate for 100 years. fencing
Annual inspections including ground- $100,000/site
water monitoring and repair and revegetation
of eroded areas. Present value at 10% discount
rate for 100 years.
present value of providing irrigation for 100 years is $422,000 for a
40-acre site, or $10,500 per acre. This was corrected for inflation
(1981 to 1983) to $11,000 per acre.
Fencing
Maintaining the fence for 100 years is assumed to cost 1 percent
of the installation cost annually. The present value of this
maintenance cost for 100 years at 10-percent discount rate is:
Present Value of Fencing Maintenance = 0.10 x fencing capital cost.
Annual Inspections
The cost for annual inspections at a site is taken directly from
Appendix R of (NRC80). For this purpose, we used NRC Scenario IV,
which requires only limited maintenance. Their inspection costs are
$10,500 annually. This includes $1,000 per year for maintenance of the
fence. Since this cost is already considered, it is subtracted, giving
an annual cost of $9,500 per site. The present value is $95,000 per
site, using a 10 percent discount rate for 100 years. This was
corrected for inflation (1981 to 1983) to $100,000 per site.
Borrow Pit Reclamation
The costs for reclaiming borrow pits were estimated for a borrow
pit in flat terrain. Stripping and saving 15 centimeters of top soil
and revegetation following replacement of the top soil were assumed.
The four side walls in the flat terrain pit are graded to an 8:1 slope
before top soil replacement and revegetation. The costs for the flat
terrain case are presented in Table B-2.
B-9
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Table B-2. Reclamation Costs for a Borrow Pit on Flat Terrain^)
(1983 dollars in millions)
Size of
Tailings Pile
2 million tons
3:1 slope
5:1 slope
Cover
0. 5 meter
0.28
0.29
Thickness
1 meter
0.44
0.45
on Tailings Pile
3 meters
0.91
0.93
5 meters
1.31
1.34
7 million tons
3:1 slope 0.37 0.58 1.24 1.97
5:1 slope 0.38 0.60 1.28 2.04
22 million tons
3:1 slope
5:1 slope
0.50
0.51
0.80
0.84
1.93
2.04
3.06
3.22
it is assumed that 15 cm of topsoil were stripped and saved,
the four side walls of the pit were graded to an 8:1 slope, the top soil
was replaced, and the area revegetated. The size and depth of the pit
varied, depending on the amount of soil needed to cover the tailings;
however, in no case was the borrow pit excavated deeper than 12 yards.
B.3 Descriptions and Costs of Disposal Methods
Calculation Procedures
Several assumptions are made in developing disposal costs.
Assumptions related to determining the thickness of the cover are:
the methods developed by Rogers (Ro81) and used by
the NRC (NRC80) for estimating radon diffusion
through earthen materials reasonably reflect the
movement of radon
the moisture in the cover (earthen material) is
8 percent
the moisture in the tailings is 8 percent
the effective bulk radon diffusion coefficient can
be determined from the moisture content
the total porosity of the tailings is the same as
that of the cover
These assumptions are made in the context that the design of
tailings disposal methods will be conservative so as to provide
reasonable assurance that the radon emission limit will be achieved over
B-10
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the required period. For example, in actual design, soils with better
moisture retention features (clays) are expected to be available at many
sites. NKC reported that equilibrium in moisture in Western clays ranges
from 9 to 12 percent (NRC80). Since the cover moisture will be greater
than 8 percent in many cases, the net result is that the 6 percent
assumed will tend to increase the cover thickness required over that
calculated from "best estimated" values, which would yield an
approximately equal probability of achieving above or below the design
level.
Another conservative factor is related to the moisture content of
the tailings themselves. In actual cases the tailings will usually have
a greater initial moisture content than covers (Ha83). It is also
reasonable to assume that the tailings will retain moisture for long
periods due to their high salt contents. However, designers are expected
to use values for tailings moisture that reflect a reasoned judgement of
what the long-term equilibrium value of moisture will be. The design
methods (Ro82) predict that thicker covers are needed, as tailings
moisture content decreases, to achieve a given level of control. A value
of 8 percent moisture in tailings is assumed for these estimates to
reflect a conservative approach.
Rogers (Ro81) emphasizes that cover moisture is the dominant
variable affecting radon attenuation. Ihe sensitivity of cover thickness
to variations in ore grade, tailings moisture, and porosity ratio
(porosity of tailings to porosity of cover) is generally of secondary
importance compared to cover moisture.
Another factor that must be considered is the uncertainty involved
in measuring the attenuation characteristics of the particular earthen
materials used for the cover. Conservative judgements will also be
required regarding the values for these characteristics for use in actual
calculations.
Existing Tailings Piles
Method Bl-E
The edges of the square tailings pile are graded and contoured to a
3:1 (h:V) slope. The entire area is then covered with 0.5 meter of earth
obtained nearby. A b-feet high, 6-gage aluminum chain link fence is
placed around the exclusionary zone, which is assumed to be 0.5 kilometer
from all sides of the pile. The covered pile is landscaped, assuming
that suitable loam or topsoil is available onsite. The borrow-pit
reclamation cost is taken from Table B-2. Maintenance and inspection are
added for a 100-year period. The costs for this method are summarized in
Table B-3.
B-ll
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Table B-3. Disposal Cost Summary: Method Bl-E
(1983 dollars in millions)
Size of Pile (Ml)
Task 2 7 22
Grading slopes 0.03 0.23 1.14
Excavating, hauling, spreading
and compacting cover material 1.18 1.82 2.95
Fencing 0.34 0.38 0.43
Landscaping 0.87 1.34 2.18
Reclaiming borrow pit 0.28 0.37 0.50
Maintain for 100 years 1.53 2.28 3.61
TOTAL 4.23 6.42 10.81
Composite Unit Costs:
$/MT Tailings 2.12 0.92 0.49
3/MT U308 2,279 989 528
Method B2-E
The sides of the tailings piles are graded to 3:1 (H:V) slope. The
tailings are covered with 1.5 meters of earth obtained nearby and the
entire surface is landscaped. A fence is installed to form an exclusion
area 0.5 kilometer wide all around the disposed tailings. The borrow pit
is reclaimed as described in Section B.2. The costs for this method are
shown in Table B-4.
Method B3-E
For this method the edges of the square tailings pile are graded to
a 3:1 (H:V) slope. The entire tailings area is covered with 2.4 meters
of earth obtained nearby or locally. The entire area (slopes and top)
are landscaped after covering. A fence is installed to form an exclusion
area 0.5 km wide around the edge of the tailings. The borrow pit is
reclaimed as described in Section B.2. The costs for this option are
listed in Table B-5.
B-12
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Table B-4. Disposal Cost Summary: Method B2-L
(1983 dollars in millions)
Size of Pile (MT)
Task
Grading Slopes
Excavating, hauling, spreading
and compacting cover material
Fencing
Landscaping
Reclaiming borrow pit
Mainenance
TOTAL
Composite Unit Costs
$/MT Tailings
$/MT UoOo
J~O
2
0.02
3.55
0.34
0.87
0.56
1.53
6.88
3.44
3,698
7
0.23
5.45
0.38
1.34
0.75
2.28
10.43
1.49
1,602
22
1.14
8.b4
0.43
2.18
1.08
3.61
17.28
0.79
844
Table B-5. Disposal Cost Summary: Method B3-E
(1983 dollars in millions)
Task
Grading slopes
Excavating, hauling, spreading
Fencing
Landscaping
Reclaiming borrow pit
Maintenance
TOTAL
Composite Unit Costs:
$/MT Tailings
2
0.03
5.67
0.34
0.87
0.8
1.53
9.24
4.62
Size of Pile
7
0.23
8.71
0.38
1.34
1.04
2.28
13.98
2.00
(MT)
20
1.14
14.1
0.43
2.18
1.58
3.61
23.04
1.05
4,966 2,150 1,129
B-13
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Method Cl-E
The sides of the tailings piles are graded to a 5:1 (H:V) slope,
after which the entire area is covered with 0.5 m of gravelly earth
obtained nearby or locally. The slopes are covered with 0.5-iueter rock
cover. No fence is needed. The borrow pit is reclaimed as described
in Section B.2. The costs for this option are presented in Table B-6.
Table B-6. Disposal Cost Summary: Method Cl-E
(1983 dollars in millions)
Size of Pile (MT)
Task
22
Grading slopes
Excavating, hauling, spreading,
and compacting cover material
Placing gravel cover
Placing rock cover
Reclaiming borrow pit
TOTALS
Composite Unit Costs:
0.05
1.21
0.39
1.91
1.94
3.18
$/MT Tailings
$/MT U3o8
1.59
1,704
0.90
969
0.62
663
Method C2-E
The edges of the tailings piles are contoured to a slope of 5:1
(H:V). The entire area is then covered with 1.5 meters of earth
obtained nearby except the top 0.5-meter of the cover is gravelly
earth. The slopes are covered with a 0.5-meter thick rock cover. No
fence is necessary. The borrow pit is reclaimed as described in
Section B.2. The costs for this option are presented in Table B-7.
Method C3-E
The sides of the tailings piles are graded to a 5:1 (H:V) slope.
The entire area is then covered with 2.4 meters of earth obtained
nearby of which the top 0.5-meter layer is gravelly earth. A 0.5-meter
rock cover is added to the slopes.
B-14
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No fence is needed. The borrow pit is reclaimed as described in
Section B.2. The costs for this method are listed in Table B-8.
Table B-7. Disposal Cost Summary: Method C2-E
(1983 dollars in millions)
Size of Pile (MT)
Task 2 7 22
Grading slopes 0.05 0.39 1.94
Excavating, hauling, spreading,
and compacting cover material 3.63
Placing gravel cover .87
Placing rock cover .75
Reclaiming borrow pit 0.57
TOTALS 5.87
Composite Unit Costs:
$/MT Tailings 2.94 1.50 0.93
$/MT U30g 3,155 1,616 1,004
Method C4-E
The sides of the pile are graded to a 5:1 (H:V) slope. The entire
area is covered with 3.4 meters of earth obtained nearby of which the
top 0.5-meter layer is gravelly earth. A 0.5-meter rock cover is
placed on the slopes. No fence is needed. The borrow pit is reclaimed
as described in Section B.2. The costs for this method are listed in
Table B-9.
Method C5-E
The sides of the pile are graded to a 5:1 (h:V) slope. The entire
area is covered with 4.3 meters of earth obtained locally of which the
top 0.5-meter layer is gravelly earth. A 0.5-meter rock cover is
placed on the slopes. No fence is needed. The borrow pit is reclaimed
as described in Section B.2. The costs for this method are shown in
Table B-10.
B-15
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Table B-8. Disposal Cost Sumnuuyj Method C3-E
(1983 dollars in millions)
Size of Pile (MT)
Task
Grading slopes
Excavating, hauling, spreading,
and compacting cover material
Placing gravel cover
Placing rock cover
Reclaiming borrow pit
TOTALS
Composite Unit Costs:
$/MT Tailings
$/MT U308
2
0.05
5.81
.87
.75
0.79
8.27
4.14
4,445
7
0.39
9.15
1.27
2.36
1.08
14.25
2.04
2,188
22
1.94
15.24
1.98
5.95
1.68
26.79
1.22
1,309
Table B-9. Disposal Cost Summary: Method C4-E
(1983 dollars in millions)
Task
Grading slopes
Excavating, hauling, spreading,
and compacting cover material
Placing gravel cover
Placing rock cover
Reclaiming borrow pit
TOTAL
2
0.05
8.24
.87
.75
1.01
10.92
Size of Pile
7
0.39
13.0
1.27
2.36
1.43
18.45
(MT)
22
1.94
21.6
1.98
5.95
2.28
33.75
Composite Unit Costs:
$/MT Tailings
$/MT U308
5.46 2.b4 1.53
5,870 2,833 1,649
B-16
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Table B-10. Disposal Cost Summary: Method C5-E
(1983 dollars in millions)
Size of Pile (MT)
Task
Grading slopes
2
0.05
7
0.39
22
1.94
Excavating, hauling, spreading,
and compacting cover material
Placing gravel cover
Placing rock cover
Reclaiming borrow pits
TOTAL
Composite Unit Costs:
$/MT Tailings
U308
10.41
.87
.75
1.2
13.28
16.4
1.27
2.36
1.77
22.19
6.64 3.17 1.82
7,138 3,408 1,954
New Tailings Piles
Method A
This method is the same as the base case in the NRG analysis
(NRC80). An initial square basin would be formed by building low
earthen embankments along each side of 947 meters length at the
centerline. The mill tailings would be slurried into the basin, and as
the basin filled, the coarse fraction of the tailings (sands) would be
used to raise and broaden the embankments. The final dimensions of the
embankments would be 10 meters high and 13 meters wide at the top.
When the mill ceases operations, no specific control measures for
disposal would be used. The cost for this option is listed in
Table B-ll and consists only of preparation of the initial basin.
Methods Bl-N, B2-N, and B3-N
These methods use earth covers on the tailings and rely on
institutional controls to prevent misuse and to maintain the covered
pile. A pit is excavated close to the mill and measures 930 meters
square by 2 meters deep. Embankments are constructed along each side,
947 meters long, 10 meters high, and 13 meters wide at the top. The
pit is lined with a synthetic liner. Tailings are pumped directly into
the pit during operation of the mill. It is assumed that water from
B-17
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the pond will be recycled to the mill, thereby negating the need for an
evaporation pond.
At the end of mill life, the embankments are excavated and placed
on top of the tailings. The slopes of the covered tailings are graded
to 3:1 (H:V). The cover thickness is 0.5 meters for Bl-fr, 1.5 meters
for B2-N, and 2.4 meters for B3-N. The entire area is landscaped. A
fence is placed around the disposal area and provides a 0.5-kilometer
exclusion zone. Borrow pits are reclaimed. The site is maintained for
100 years by irrigation of the vegetative cover and inspection and
repair of the earth cover and fence. Costs are shown in Table B-ll.
Methods Cl-M, C2-N, C3-N, C4-N and C5-N
Passive controls are used in these methods. These methods use
earth covers, 0.5-meter rock covers on the slopes and 0.5-meter gravel
layers on the top. A pit is prepared and used in the same manner to
that described for methods Bl-N, B2-N, and B3-N, including the liner.
At the end of mill life, the embankments are excavated and placed
on top of the tailings. The cover thickness is 0.5 meters for C1--N,
1.5 meters for C2-N, 2.4 meters for C3-N, 3.4 meters for C4-N, and 4.3
meters for C5-N. The slopes of the disposed tailings are graded to 5:1
(H:V) and then covered with rock to a depth of 0.5 meter. The top of
the disposed tailings area (that part not covered with rock) is covered
with a 0.5-meter layer of gravelly soil which replaces the top
0.5-meter of earth. No fence is needed. The costs are listed in Table
B-ll.
Methods D2-N, D3-N, D4-N, and D5-N
These methods are somewhat similar to the staged or phased
disposal method described by the NRC's GEIS (NRC80). This method uses
6 pits, each 280 meters square at the bottom and with 2:1 (H:V)
slopes. Two pits are constructed initially and lined with a synthetic
liner. Tailings are pumped to the first pit until it is full and then
pumped to the second pit. When the first pit is sufficiently dry, the
third or fourth pit is excavated, and the excavated earth is used to
cover the first pit to the original ground contour. The earth cover
thickness is 1.5 meters for D2-N, 2.4 meters for D3-N, 3.4 meters for
D4-N, and 4.3 meters for D5-N. This process continues sequentially
until the end of mill life. An evaporation pond is needed in this
method. Costs for this pond are taken from the NRC GEIS and corrected
for inflation.
At the end of mill life there will likely be four completed pits,
which are covered with earth to the original ground contour and 2
uncovered pits. When sufficiently dry, these last two pits are
covered with excavated earth to the original ground contour. The
disposed tailings area is landscaped. The areas covered by the
evaporation pond and excess excavated earth are restored. The costs
for this method are presented in Table B-ll.
B-16
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Table B-ll. Disposal Cost Summary: Methods for Disposal of New Tailings Piles
(1983 dollars in millions)
Disposal Method
Task
Excavate pit and construct
embankments
Placing liners
Grade slopes
Excavate, haul, spread and
compact cover material^3'
Fence
Landscape
Place rock on slopes
Place gravel on top
Evaporation pond
Reclaim borrow pits
Maintenance for 100 years
TOTAL (includes 0 & P)
Unit Costs:
3/MT Tailings
$/MT U308
A Bl B2
1.26 5.8 5.8
11.5 11.5
0.9 0.9
3.04
0.4 0.4
1.63 1.63
_
- - -
_
0.52
2.7 2.7
1.26 22.93 26.49
0.15 2.73 3.15
161 2,935 3,386
B3 Cl C2
5.8 5.8 5.8
11.5 11.5 11.5
0.9 0.54 0.54
6.64 - 4.0
0.4
1.63
3.68 3.68
1.41 1.41
_
0.93 - 0.6
2.7
30.50 22.93 27.53
3.63 2.73 3.28
3,902 2,935 3,526
C3
5.8
11.5
0.54
7.64
-
-
3.68
1.41
-
0.93
31.50
3.75
4,031
Disposal Method
C4 C5
D2 D3 D4
D5
Excavate pit and construct
embankments
Placing liners
5.8 5.8 26.2 28.5 31.4 34.0
11.5 11.5 8.08 8.08 8.08 8.08
See footnotes at end of table.
B-19
-------
Table B-ll.
Disposal Cost Summary: Methods for Disposal of New Tailings Piles
(1983 dollars in millions)
(Continued)
Task
C4
Disposal Method
C5 D2 D3
D4
D5
Grade slopes
Excavate, haul, spread and
compact cover material^3)
Fence
Landscape
Place rock on slopes
Place gravel on top
Evaporation pond
Reclaim borrow pits
Maintenance for 100 years
0.54 0.54 -
11.6 15.27 1.42 2.3 3.34 4.3
3.68
1.41
-
1.3
3.68
1.41
3.64
1.65
1.06
3.64
1.08 1.11 1.13
3.64 3.64 3.64
TOTAL (includes 0 & P)
35.83 39.85 40.40 43.60 47.57 51.15
Unit Costs:
i/MT Tailings
$/MT U308
4.27 4.74 4.81 5.19 5.66 6.09
4,590 5,096 5,171 5,579 6,084 6,547
(^Disposal Methods Bl and Clthe task is included in grading; for Disposal Methods D2
through D5two pits only, remaining pits are covered during excavation of new pits.
B-20
-------
REFERENCES
Ha83 Hartley J.N., Gee G.W., Baker E.G., and Freeman H.D., "1981
Radon Barrier Field Test at Grand Junction Uranium Mill
Tailings Pile," DOE/UMT-0213, PNL-4539, April 1983.
Me83 "Building Construction Cost Data," 1983, Robert Snow Means Co.,
Inc., 100 Construction Plaza, Duxbury, Mass.
NRC80 Nuclear Regulatory Commission, "Final Generic Environmental
Impact Statement on Uranium Milling," NURLG-0706, Washington,
D.C., September 1980.
PE82 PEDCO Environmental, Inc., "Evaluation of Costs to Control
Fugitive Dust from Tailings at Active Uranium Mills," EPA
Contract No. 68-02-3173, Task No. 053, USEPA, Washington, D.C.,
March 1982.
Ro81 Rogers V.C. and Nielson K.K., "A Handbook for the Determination
of Radon Attenuation Through Cover Materials, NUREG/CR-2340,
RAE 18-1, PNL-4084, December 1981.
B-21
-------
APPENDIX C
HEALTH BASIS FOR HAZARD ASSESSMENT
-------
Appendix C: HEALTH BASIS FOR HAZARD ASSESSMENT
CONTENTS
Page
Introduction C-5
C.I Risk Models for Stochastic Effects C-5
C.I.I The RADRISK Code C-7
C.2 Risk Estimates for Inhaled Radon and Radon-Daughters (Radon
Decay Products C-9
C.2.1 Risk of Lung Cancer from Inhaling Radon Decay Products C-9
C.3 Risk Factors per Unit Exposure C-14
C.4 Risks from Toxic Materials, Nonstochastic Effects C-14
C.4.1 Estimates of Chronic Toxicity in Humans C-22
C.4.2 Estimates of Chronic Toxicity in Animals and Plants ... C-22
References C-24
TABLES
C-l Risk Parameters for Cancers Considered C-8
C-2 Genetic Risk Parameters C-9
C-3 Lifetime Risk of Excess Cancer in a Cohort of 100,000 for
Continuous Exposure to Lead-210 C-14
C-4 Lifetime Risk of Excess Cancer in a Cohort of 100,000 for
Continuous Exposure to Polonium-210 C-l5
C-5 Lifetime Risk of Excess Cancer in a Cohort of 100,000 for
Continuous Exposure to Radium-226 C-16
C-6 Lifetime Risk of Excess Cancer in a Cohort of 100,000 for
Continuous Exposure to Thorium-230 C-17
C-7 Lifetime Risk of Excess Cancer in a Cohort of 100,000 for
Continuous Exposure to Uranium-234 C-18
C-3
-------
CONTENTS (Continued)
Page
C-8 Lifetime Risk of Excess Cancer in a Cohort of 100,000 for
Continuous Exposure to Uranlum-238 C-19
C-9 30-Year Genetic Dose Commitment C-20
C-10 Selected Potentially Toxic Substances Associated with Uranium
Mill Tailings C-22
C-ll Daily Intake Levels of Selected Elements Estimated to be
Toxic C-23
FIGURES
C-l Excess Fatal Lung Cancer iti Various Miner Groups by
Cumulative Exposure C-ll
C-4
-------
Appendix C: HEALTH BASIS FOR HAZARD ASSESSMENT
Introduction
Inhalation or ingestion of radionuclides or toxic chemicals can,
have adverse effects on human and animal health. The adverse effects
can be separated, generally, into stochastic and nonstochastic.
Stochastic effects are those in which the probability of the effect is
proportional to the exposure level, but the severity of the effect is
independent of exposure. Nonstochastic effects are those in which the
severity of the effect is proportional to the exposure level and there
is usually a threshold level of exposure below which no effect is
observed.
Low levels of radiation exposure, such as that associated with
inhalation or ingestion of radionuclides transported into the
environment from tailings piles, generally produce stochastic effects.
Radiation from radionuclide particles deposited on the ground may also
expose people causing stochastic effects. Ingestion or inhalation of
toxic chemicals from tailings piles would cause nonstochastic effects.
For purposes of this analysis, only stochastic effects (e.g.,
cancer and inherited abnormalities) will be considered in the case of
ionizing radiation exposure and only nonstochastic (e.g., acute and
chronic poisoning) in the case of exposure to toxic elements. In
Section C.I below we describe how we estimate the risk due to external
gamma radiation, ingested radioactivity, or inhaled radioactive
particulates that are not radon progeny. In Section C.2 we describe
how we estimate the risk of lung cancer due to the inhalation of radon
and radon progeny.
C.I Risk Models for Stochastic Effects
There are two kinds of risks from the low levels of ionizing
radiation characteristic of exposures to radionuclides released into
the environment. The most important of these is cancer, which is fatal
at least half the time. The other risk is the induction of hereditary
defects in descendants of exposed persons. The severity of these
defects range from fatal to inconsequential. As mentioned above, we
C-5
-------
assume that at low levels of exposure the risk of cancer and hereditary
effects is in proportion to the dose received, and that the severity of
any induced effect is independent of the dose level. That is, while
the probability of a given type of cancer occurring increases with
dose, such a cancer induced at one dose is equally as debilitating as
that same type of cancer induced at another dose. For these effects,
we assume that there is no completely risk-free level of radiation
exposure.
The risks and effects on health from low-level ionizing radiation
were reviewed for EPA by the National Academy of Sciences in reports
published in 1972 and in 1980 (NAS72a, NASSOb). We have used these
studies and others to estimate the risks associated with the radiation
doses described in this report. Byproduct materials from uranium ore
processing are principally alpha particle emitters. Alpha particles
are a form of ionizing radiation that has a high linear energy transfer
(LET). As noted in the 1980 BEIR report, cited above, the dose
response relationship for high LET radiations is linearly proportional
to dose, and biological effects due to high LET radiations may increase
rather than be reduced at low dose rates.
exposed individuals;" these people are located at the point of highest
lifetime risk. The risk to the individual is the risk of premature
death from cancer due to the radiation dose received. The risk
calculation considers all important radionuclides, pathways, and organs
of the body.
The risk to an individual can be subdivided and related to other
parameters. For example, we can determine which part of the risk is
committed by radionuclides moving through a specific pathway or which
organ is at highest risk. This information is helpful when deciding
which control strategies will be the most effective.
The risk to populations can also be estimated; that is, the number
of future effects on health that are committed for each year that the
source operates. The risks are associated with doses delivered to
people over a time period which is longer than the average individual's
lifespan. The dose is not necessarily delivered to people during the
years of release because radionuclides with long half-lives may take a
long time to move through environmental pathways to people.
Like the individual lifetime risk, the total risk to populations
can be subdivided and related to other parameters, such as organ,
radionuclide, or exposure pathway.
The genetic risk is the risk to future generations associated with
the dose equivalent to the gonads of both exposed parents over the
first 30 years of their lives. We calculate the total genetic risk for
the same population for which we calculate the collective potential
fatal cancer risk.
C-6
-------
C.I.I The RADRISK Code
The estimates of cancer and genetic risk are calculated using a
computer code called RADRISK. In RADRISK, the group assumed to be at
risk by the code is a hypothetical cohort of 100,000 people, all born
simultaneously and subject to the same risks throughout their lives.
Each member is assumed to be exposed at a constant rate to a unit
concentration of radionuclides. For each radionuclide and for each
pathway, the code calculates the number of premature deaths due to
radiation and the number of years of life lost due to these deaths.
When radioactive particulates are inhaled, they enter the lung,
and the ICRP Task Group lung model is used to predict where in the lung
they go and how fast they are removed to other parts of the body.
Depending on size and solubility class, there is removal of some of
this material to the gastrointestinal (Gl) tract and absorption by the
blood. A GI tract model is used to estimate how much of the material
reaching the tract is absorbed by the blood.
After absorption by the blood, radionuclides are distributed among
the organs according to uptake and metabolic information supplied to
RADRISK. Dose rates are calculated with the help of models that
simulate the biological processes involved when radionuclides enter and
leave organs.
Cancers do not appear immediately after exposure. There is a
minimum induction time, latent period, before the cancers are observed;
the length, usually years, varies with the type of cancer. Thereafter,
there is a specified period when there is a finite probability of
cancer, a "plateau" period, and it also varies with the type of
cancer. For most cancers the latent period includes the balance of a
person's lifetime. Table C-l lists the risk parameters used in RADRISK.
Lifetime probabilities for many types of cancer, in many organs,
are followed and risks calculated. At the same time, competing risks
unrelated to the radiation exposure are accounted for. The RADRISK
code does this; however, we do not yet understand how accurate these
calculations are. In particular, cancer risks and metabolic parameters
are uncertain, and since relative risk estimates are not available for
all radiation-induced cancers, only an absolute risk estimate is made.
We believe risks are accurate to an order of magnitude only and should
never be reported to more than one significant figure.
Inherited abnormalities (genetic effects), as noted above, do not
occur in those exposed to radiation but in their progeny. The genetic
risk coefficient used in RADRISK is given in Table C-2.
C-7
-------
Table C-l. Risk parameters for cancers considered (Su81)
Leukemia
Bone
Lung
Breast
Liver
Stomach
Pancreas
Lower Large
Intestine
Kidneys
Bladder
Upper Large
Intestine
Small Intestine
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
2
5
10
15
15
15
15
15
15
15
15
15
15
15
15
15
15
2
25
30
110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
45
2.3
0.2
3.0
2.3
0.9
0.5
0.7
0.4
0.2
0.2
0.2
0.1
0.1
0.1
0.1
0.1
0.1
***0.4
**46
4
30
2.3
9
5
7
4
2
2
2
1
1
1
1
1
1
***0.4
0.3
0.03
0.6
0.4
0.2
0.09
0.1
0.07
0.04
0.04
0.04
0.02
0.02
0.02
0.02
0.02
0.02
0.08
*Low-LET.
**Based on a quality factor of 20 for alpha particle irradiation (ICRP-26. In view of the
leukemia incidence observed in persons exposed to bone seeking alpha particle emitters
(Mo79), we believe a quality factor of 20 is highly conservative for leukemia, perhaps by an
order of magnitude.
***0.04 for 131I and longer-lived radioiodine.
C-8
-------
Table C-2. Genetic Risk Parameters
First All
Generation Generations
Risks per one million live- 0.04 0.2
births per mrad low-LET
radiation
A more detailed description of RADRISK can be found in
ORNL/TM-7745, "Estimates of Health Risk from Exposure to Radioactive,
Pollutants" (Su81).
C.2 Risk Estimates for Inhaled Radon and Radon-Daughters (Radon Decay
Products)
An estimate of the health risk from inhaling radon and its
short-lived daughters has been done separately for both historic and
technical reasons.
The history of the health impact of exposure to radon and its
short-lived daughters has its roots in the past, before the discovery
of x-rays or identification of radioactivity. The units of exposure,
Working Level (WL), Working Level Month (WLM), are unusual and do not
fit into the RADRISK computer code. The risk of radon, radon-daughter
exposure has been calculated independently of the RADRISK program
calculations for this analysis.
C.2.1 Risk of Lung Cancer from Inhaling Radon Decay Products
The high incidence of lung cancer mortality among underground
miners is well documented (EPA79a, Ar79, Ar81). Uranium miners are
particularly affected, but lead, iron, and zinc miners exposed to
relatively low levels of radon decay products also show an increased
lung cancer mortality that correlates with exposure to radon decay
products. The type of lung cancer most frequently observed, moreover,
is relatively uncommon in the general population.
Risk estimates for the general public based on these studies of
miners are far from precise. First, and most important, the relatively
small number of miners at risk injects considerable statistical
uncertainty into estimating the number of excess lung cancer cases (see
Figure C-l). Second, although the cumulative lifetime exposure in
contaminated buildings can be comparable to that of some miners, most
of the miners studied were exposed to much higher levels of radon decay
C-9
-------
products than usually occur in the general environment. Third, the
exposure levels are uncertain. Fourth, significant demographic
differences exist between miners and members of the general publicthe
miners were healthy males over 14 years old, many of whom smoked.
However, information from the studies of miners can provide useful
estimates, if not precise predictions, of the risks to the general
population from radon decay products.CD
Since the miners being studied have not all died, their eventual
excess lung cancers must be projected from current data by using
mathematical models. There are two ways to use the observed frequency
of lung cancer deaths among the exposed miners to estimate the risk
from inhaling radon decay products over a person's lifetime. One,
commonly called the relative risk model, yields the percent increase in
the normal incidence of cancer per unit of exposure. The other, called
the absolute risk model, yields the absolute numerical increase in
cancers per unit of exposure. In the relative risk model, it is
assumed that the increased risk is proportional to the age-dependent
natural incidence of the disease for each year an individual remains
alive following exposure. In the absolute risk model, it is assumed
that the added risk is independent of natural incidence, i.e., the risk
is constant each year an individual remains alive following exposure.
As a basis for calculating estimates using the relative risk
model, we conclude that a 3-percent increase in the number of lung
cancer deaths per WLM is consistent with data from the studies of
underground miners. However, because of the differences between adult
male miners and the general population (EPA79a), we estimate that the
risk to the general population may be as low as 1 percent or as high as
5 percent. This is consistent with a recent Canadian study where the
best estimate of excess relative risk was 2.28+0.35 percent (Th82). To
develop absolute risk estimates in earlier reports, we used the
estimate of 10 lung cancer deaths per WLM for 1 million person-years at
risk reported by the National Academy of sciences (NAS76). In a 1978
paper, Land and Norman (La78) reported that in Japanese A-bomb
survivors, radiation-induced lung cancers had a temporal distribution
of occurrence similar to naturally-occurring cancers of the same site.
Further, they concluded the cumulative distribution of
radiation-induced lung cancer across time after exposure was consistent
with a relative risk model of cancer incidence or with an age-specific
absolute risk model.
In a paper at the same symposium, Smith and Doll (Sm78) reported
the risk of cancer developing at most "heavily irradiated" sites in
ee "Indoor Radiation Exposure Due to Radium-226 in Florida
Phosphate Lands" (EPA 79a) for greater detail of such an analysis.
C-10
-------
±
80
70
> 60
o
cc.
LU
O
50
<> 40
z
3 30
oo
H
D
00
E 20
10
All
J(l
Ro
J. AA
kS
O CZECH - URANIUM
0 SWEDEN - LEAD, ZINC (A), IRON (R,J)
A UNITED STATES-URANIUM
A CANADA-URANIUM
X 95% CONFIDENCE LIMITS
I
1
0 100 200 300 400 500 600
CUMULATIVE WORKING LEVEL MONTHS
700
Figure C-l. Excess Fatal Lung Cancer in Various Miner Groups
by Cumulative Exposure (Ar79).
C-ll
-------
ankylosing spondylitic patients treated with x-rays was directly
proportional to the risk of a tumor in the absence of radiation; in
other words, a relative-risk-like response. In the most recent report
on the Japanese A-bomb survivors, Kato and Schull (Ka82) reiterated the
observation that radiation-induced lung cancer develops only after the
survivors attain the age at which this cancer normally develops. The
evidence in these three reports of external radiation exposure points
to relative-risk or age-specific absolute risk models as being
appropriate for radiation-induced lung cancer.
Recent informatioi) from China provides similar evidence for
exposure to radon, radon daughters. Shi-quan and Xiao-ou (Sh82) have
reported that in Chinese tin miners exposed to radon and its daughters,
the lung cancers developed at the. age at which lung cancer normally
develops. Those who started milling at age 8 or 9 had an
induction-latent period about 10 years longer than those who started
mining at age 19 or 20, Here, .gain, a simple absolute risk model will
not fit the observations.
In view of these observations that a simple absolute risk model is
inappropriate for estimating the risk of lung cancer due to radon
daughter exposure, a simple absolute risk estimate was not calculated.
An interagency comparison of risks calculated using the EPA relative-
risk model and th-?. age-specific absolute risk model from BEIR III
(NASSOb) showed them t.o be nearly identical numerically (860
cases/106 person. WKM versus 850 cases/106 person-WLM) (RPC80).
Because of the. similarity in risk estimates, only relative risk
estimates for radon '.--sisfbter exposures are used in this document.
Unless we st:ie
i.e., tboF,-j n«us--(i ':>-.
those frotv M'.Vior CjU
',-terwise, we estimate excess cancer fatalities,
elevated radiation levels that are in addition to
levels of radon 1r, t;r,,; ...
of the 3-T'M LionaJ rlsi- due
uses tl.<« risk coef f Lc t«--uts
the length oi i as>n a f-M-,.;o
survives otVr1 potent I.H.. -
Statist 'CS. T' 10 i .;;<>,
cancer deaths "hat tm>
100,000 person i. v.V
radiation i« not \ ..-
the balance <>*" tr.c-; -
uuber of lung cancer deaths from increased
onment, we have used a life-table analysis
o radiation exposure (Bu81). This analysis
ast discussed. It also takes into account
..;ou is exposed and the number of years a person
cai-ses of death based on 1970 U.S. death rate
i3 expiessed as the number of premature lung
occur >lue to lifetime radiation exposure of
lurcher, that injury caused by alpha
so that exposed persons remain at risk for
Using the c^l
to 0.0.1 WI ( ,.' : w-
additional ch.;j.
was made assurmup,
exposure to radyi
greater ris
r t
3 ''if- !".' P~ *"'
s>}-A~' -i)
we estimate that a person exposed
lit'-ture j.ncurs a 1.7 percent (1 in 60)
> .g a "atal lung cancer. This estimate
e :: more sensitive than adults. If
'.-s curing childhood carries a three times
Hfetiiie relative risk would increase by
«-'.T» a similar lifetable analysis and an
C-12
-------
absolute risk model, we would have estimated that a person exposed to
0.01 WL over a lifetime incurs a 0.7 percent (1 in 140) additional
chance of contracting a fatal lung cancer. Again, equal child and
adult sensitivities are assumed (EPA79a). For comparison, a lifetable
analysis for the same population not exposed to excess radiation yields
a 2.9 percent chance of lung cancer death.
Even though, under either of these models, the risk of
radon-induced lung cancer varies with age, it is sometimes convenient
to express these risks on an average annual basis. We have calculated
a person's average annual risk from a lifetime of exposure by dividing
the lifetime risk estimates given above by an average lifespan of 71
years. {*' Based on the risk model and assumptions just described for
lifetime exposure, we estimate an average of 2.4 lung cancer deaths per
year for each 100 person-working-levels of such exposure. "Person-
working-levels" is the population's collective exposure; that is, the
number of people times the average concentration of radon decay
products (in working levels) to which they are exposed.
For the entire U.S. population, the estimated number of cancers is
large using the relative risk model, but this estimate does not hold
for all locations because the lung cancer rate varies considerably in
different parts of the country. Therefore, we can base our relative
risk estimate for each source on the lung cancer death rate for the
State in which the source is located. Lung cancer death rates are
lower than the national average in several of the States, so at some
localities the relative risk is lower than at others.
Radiation risk can also be stated in terms of years of life lost
due to cancer death. In the relative risk model, the distribution of
ages at which lung cancer caused by radiation occurs is the same as
that for all lung cancer in the general population. Since lung cancer
occurs most frequently in people over 70 years of age, the years of
life lost per fatal lung cancer14.5 years on the averageis less
than for many other fatal cancers. The absolute risk model wrongly
assumes that lung cancer fatalities occur at a uniform rate throughout
life and, therefore, each fatality reduces the lifespan by a larger
amountan average of 24.6 years.
Because we used recent population data, our assessments are for
current conditions. If the population lifestyle, medical knowledge,
and other patterns of living affecting mortality remain unchanged, then
these rates of lung cancer death could persist for the indefinite
future. We have not attempted to assess the effects of future change,
which may either increase or decrease our risk estimates. It is
prudent, we believe, to assume that estimated risks based on current
data could persist over the indefinite future.
(1) Note that this is not the same as applying the risk coefficient for
71 years, since the lifetable analysis accounts for other causes of
death.
013
-------
Table C-3. Lifetime Risk of Excess Cancer in a Cohort
of 100,000 from Continuous Exposure to
Inhalation (1 pCi/y)
Organ
Red Marrow
Endosteum
Pulmonary Lung
Breast
Liver
Stomach Wall
Pancreas
Lower Large
Intestine Wall
Kidneys
0.3 pm
3.6E-4
1 . 8E-4
2.0E-6
4.5E-6
3.4E-4
7.3E-9
l.OE-5
6.8E-8
3.8E-5
Particle Size
7.75 ym
4.1E-4
2.1E-4
3.8E-7
5.0E-6
3.9E-4
1.4E-8
1.1E-5
5.3E-7
4.1E-5
54.2 ym
3.9E-4
2.0E-5
1.8E-7
4.9E-6
3.8E-4
1.4E-8
1.1E-5
6.0E-7
3.9E-5
Ingest ion
(1 pCi/y)
1.3E-4
6.4E-4
3.6E-8
1.6E-6
1.2E-4
1.6E-8
3.6E-6
1.2E-6
1.3E-5
Ground
Deposition
(1 pCi/cm2)
1.3E-3
1 . 4E-4
l.OE-3
9.1E-4
2.0E-4
1 . 3E-4
1.1E-4
5.6E-5
4.9E-5
Bladder Wall
Upper Large
Intestine Wall
Small Intestine
Wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
TOTAL
6.8E-8
3.8E-5
1.5E-6
l.OE-8
2.1E-9
1.5E-6
1.5E-6
1.7E-6
1.5E-6
1.5E-6
l.OE-6
5.3E-7
4.1E-5
1.6E-6
5.9E-8
5.1E-9
1.6E-6
1.6E-6
1.6E-6
1.6E-6
1.6E-6
1.2E-6
6.0E-7
3.9E-5
1.6E-6
6. 6E 8
5.5E-9
1.6E-6
1.6E-6
1.5E-6
1.6E-6
1.6E-6
1.1E-6
1.2E-6
1.3E-5
5.0E-7
1.3E-7
7.8E-9
5.1E-7
5.1E-7
4.9E-7
5.1E-7
5.1E-7
3.6E-7
5.6E-5
4.9E-5
3. 5E-5
3. 5E-5
1.5E-5
3.0E-5
4.6E-5
2.1E-5
6.4E-6
2.5E-5
2.0E-4
9.5E-4
1.1E-3
l.OE-3
3.4E-4
4.3E-3
C.3 Risk Factors per Unit Exposure
Risk factors computed in the RADRISK program or in the radon risk
program for unit exposure are listed in Tables C-2 through C-9.
C.4 Risks From Toxic Materials, Nonstochastic Effects
Toxic materials have been considered in this analysis if they are
in substantially greater concentration in the source than in native
rocks or soils or in a relatively mobile form (anionic or cationic).
Materials that are harmful to livestock and plants as well as those
potentially affecting humans directly have been included. Evaluating
the potential risks from nonradioactive toxic substances requires
C-14
-------
Table C-4. Lifetime Risk of Excess Cancer in a Cohort
of 100,000 from Continuous Exposure to Polonium-210
Inhalation (1 pCi/y)
Organ
Red Marrow
Endosteum
Pulmonary Lung
Breast
Liver
Stomach Wall
Pancreas
Lower Large
Intestine Wall
Kidneys
Bladder Wall
Upper Large
Intestine Wall
Small Intestine
Wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
TOTAL
0. 3 y m
2.6E-4
5.6E-6
4.1E-2
1.6E-5
1.9E-4
8.2E-8
4.8E-5
2.6E-6
2.4E-4
6.8E-6
4.3E-7
3.7E-8
6.8E-6
6.8E-6
2.1E-4
6.8E-6
6.8E-6
3.3E-6
4.2E-2
Particle Size
7. 75 ym
3.8E-4
8.1E-6
5.9E-3
2.3E-5
2.7E-4
1.6E-7
6.9E-5
5.2E-6
3.5E-4
9.8E-6
8.6E-7
7.3E-8
9.8E-6
9.8E-6
3.0E-4
9.8E-6
9.8E-6
4.8E-6
7.4E-3
54.2 ym
3.6E-4
7.6E-6
1.4E-3
2.1E-5
2.6E-4
1.7E-7
6.5E-5
5.5E-6
3.3E-4
9.2E-6
9.2E-7
7.8E-8
9.2E-6
9.2E-6
2.4E-4
9.2E-6
9.2E-6
4.5E-6
2.8E-4
Ingestion
(1 pCi/y)
1.8E-4
3.8E-6
7.0E-12
l.OE-5
1.3E-4
2.0E-7
3.2E-5
6.2E-6
1.6E-4
4.6E-6
l.OE-6
8.8E-8
4.6E-6
4.6E-6
1 . 4E-4
4.6E-6
4.6E-6
2.2E-6
6.9E-4
Ground
Deposition
(1 pCi/cm2)
3.1E-6
3.1E-7
5.1E-6
3.6E-6
1.2E-6
6.9E-7
9.1E-7
4.1E-7
2.9E-7
2.7E-7
2.7E-7
1.2E-7
8.0E-8
1.5E-7
1.6E-7
1.1E-7
l.OE-7
5.6E-7
1.7E-5
C-15
-------
Table C-5. Lifetime Risk of Excess Cancer in a Cohort
of 100,000 from Continuous Exposure to Radium-226
Organ
Red Marrow
Endos teum
Pulmonary Lung
Breast
Liver
Stomach Wall
Pancreas
Lower Large
Intestine Wall
Kidneys
Bladder Wall
Upper Large
Intestine Wall
Small Intestine
Wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Inhalation (1 pCi/y)
Particle Size
7.75 Pm 54.2 ym
8.9E-4
3.6E-4
7.2E-3
1.7E-5
5.8E-5
2.6E-7
4.8E-5
1.1E-5
1.3E-5
6.9E-6
1.3E-6
1.1E-7
6.9E-6
6.9E-6
6.4E-6
6.9E-6
6.9E-6
3.6E-6
8.6E-4
3.4E-4
1.8E-3
1.6E-5
5.6E-5
2.6E-7
4.6E-5
1.2E-5
1.2E-r5
6.6E-6
1.3E-6
1.1E-7
6.6E-6
6.6E-6
6.2E-6
6.6E-6
6.6E-6
3.4E-6
Ingestion
(1 pCi/y)
5.9E-4
2.4E-4
7.0E-7
1.1E-5
3.8E-5
2.5E-7
3.2E-5
1.3E-5
8.5E-6
4.5E-6
1.5E-6
1.1E-7
4.5E-6
4.5E-6
4.2E-6
4.5E-6
4.5E-6
2.3E-6
Ground
Deposition
(1 PCi/cm2)
3.9E-3
4.0E-4
4.5E-3
3.0E-3
l.OE-3
4. 8E-4
5.9E-4
3.2E-4
2.1E-4
1.9E-4
2.1E-4
l.OE-4
7.6E-5
1.8E-4
1.1E-4
8.1E-5
1.1E-4
7.1E-4
TOTAL 8.7E-3 3.1E-3 9.6E-4 1.6E-2
C-16
-------
Table C-6. Lifetime Risk of Excess Cancer in a Cohort
of 100,000 from Continuous Exposure to 230Th
Organ
Red Marrow
Endosteum
Pulmonary Lung
Breast
Liver
Stomach Wall
Inhalation
Particle
7. 75 jam
2.3E-2
1.6E-2
6.6E-2
8.0E-6
1.5E-4
1.7E-7
(1 pCi/y)
Size
54.2 ym
1.5E-2
1.1E-2
1.6E-2
5.2E-6
9.7E-5
1.8E-7
Ingest ion
(1 pCi/y)
2.4E-4
1.7E-4
3.7E-10
8.4E-8
1.6E-6
1.8E-7
Ground
Deposition
(1 pCi/cm2)
2.9E-4
3.0E-5
2.7E-4
2.5E-4
5.3E-5
3.1E-5
Pancreas
Lower Large
Intestine Wall
Kidneys
Bladder Wall
Upper Large
Intestine Wall
Small Intestine
Wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
2.
6.
6.
3.
1.
8.
3.
3.
3.
3.
3.
1.
4E-5
OE-6
9E-6
5E-6
OE-6
5E-8
5E-6
5E-6
5E-6
5E-6
5E-6
8E-6
1.
6.
4.
2.
1.
8.
2.
2.
2.
2.
2.
1.
6E-5
2E-6
5E-6
3E-6
OE-6
8E-8
3E-6
3E-6
3E-6
3E-6
3E-6
1E-6
2.
6.
7.
3.
1.
8.
3.
3.
3.
3.
3.
1.
5E-7
3E-6
3E-8
6E-8
OE-6
9E-8
6E-8
6E-8
6E-8
6E-8
6E-8
8E-8
3.
1.
1.
9.
1.
4.
4.
1.
5.
3.
5.
4.
3E-5
9E-5
2E-5
9E-6
OE-5
9E-6
7E-6
3E-5
7E-6
OE-6
4E-6
6E-5
TOTAL 1.1E-1 4.2E-2 4.2E-4 1.1E-3
C-17
-------
Table C-7. Lifetime Risk of Excess Cancer in a Cohort
of 100,000 from Continuous Exposure to
Organ
Red Marrow
Endosteum
Pulmonary Lung
Breast
Liver
Stomach Wall
Inhalation
Particle
7.75 pm
2.4E-5
1.6E-5
6.7E-2
1.3E-7
4.7E-7
2. OE-7
(1 pCi/y)
Size
54.2 ym
1.6E-5
1.1E-5
1.6E-2
8.4E-8
3.2E-7
2. OE-7
Ingest ion
(1 pCi/y)
2.3E-4
1.5E-4
1.7E-6
1.2E-6
4.5E-6
4.2E-7
Ground
Deposition
(1 pCi/cm2)
1.4E-4
1.5E-5
1.1E-4
1.9E-4
1.6E-5
1.3E-5
Pancreas
Lower Large
3.6E-7
2.5E-7
3.5E-6
1.4E-5
Intestine Wall
Kidneys
Bladder Wall
Upper Large
Intestine Wall
Small Intestine
Wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
6.
1.
5.
1.
9.
5.
5.
5.
5.
5.
2.
1E-6
1E-5
7E-8
OE-6
1E-8
2E-8
2E-8
2E-8
2E-8
2E-8
7E-8
6.
7.
3.
1.
9.
3.
3.
3.
3.
3.
1.
3E-6
5E-6
9E-8
1E-6
2E-8
6E-8
6E-8
6E-8
6E-8
6E-8
8E-8
5.
1.
5.
9.
1.
5.
5.
5.
5.
5.
2.
3E-6
1E-4
5E-7
5E-7
2E-7
OE-7
OE-7
OE-7
OE-7
OE-7
5E-7
1.
3.
2.
2.
1.
1.
9.
1.
7.
1.
1.
OE-5
4E-6
8E-6
8E-6
4E-6
9E-6
6E-6
9E-6
6E-7
6E-6
6E-5
TOTAL
6.7E-2
1.6E-2
5.1E-4
5.4E-4
C-18
-------
Table C-8. Lifetime Risk of Excess Cancer in a Cohort
of 100,000 from Continuous Exposure to 238U
Organ
Red Marrow
Endosteum
Pulmonary Lung
Breast
Liver
Stomach Wall
Pancreas
Lower Large
Intestine Wall
Kidneys
Bladder Wall
Upper Large
Intestine Wall
Small Intestine
Wall
Ovaries
Testes
Spleen
Uterus
Thymus
Thyroid
Inhalation
Particle
7.75 p m
2.0E-5
1.3E-5
6.1E-2
2.7E-7
5.1E-7
2.9E-7
3.8E-7
9.2E-6
9.8E-6
5.4E-8
1.5E-6
1.3E-7
4.8E-8
4.7E-8
5.4E-8
5.0E-8
5.9E-8
5.6E-8
(1 pCi/y)
Size
54.2iim
1.4E-5
9.0E-6
1.5E-2
1.2E-7
3.0E-7
2.1E-7
2.4E-7
7.0E-6
6.7E-6
3.6E-8
1.1E-6
9.6E-8
3.1E-8
3.1E-8
3.4E-8
3.3E-8
3.5E-8
2.6E-8
Ingestion
(1 pCi/y) _
1.9E-4
1 . 3E-4
1.5E-6
1.2E-6
3.9E-6
3.7E-7
3.2E-6
5.1E-6
9.5E-5
4.9E-7
8.7E-7
1.1E-7
4.3E-7
4.3E-7
4.5E-7
4.5E-7
4.5E-7
2.7E-7
Ground
Deposition
(1 pCi/cm2)
7.6E-5
8.3E-6
5.2E-5
1.3E-4
4.6E-6
6.3E-6
7.0E-6
5.8E-6
l.OE-6
7.4E-7
7.9E-7
3.6E-7
9.2E-7
6.8E-6
8.0E-7
1.3E-7
5.3E-7
6.0E-6
TOTAL 6.1E-2 1.5E-2 4.3E-4 3.1E-4
C-19
-------
Table C-9. 30-Year Genetic Dose Commitment
(mrad)
Organ
Ovary
LOW-LET
High-LET
Testis
LOW-LET
High-LET
Ovary
LOW-LET
High-LET
Testis
LOW-LET
High-LET
Ovary
LOW-LET
High-LET
Testis
LOW-LET
High-LET
Lead-
210
9.
2.
9.
2.
9.
2.
9.
2.
3.
7.
2.
7.
6E-5
5E-4
4E-5
5E-4
3E-5
4E-4
1E-5
4E-4
1E-5
8E-5
9E-5
8E-5
Polonium-
210
1.
1.
5.
1.
1.
1.
5.
1.
1.
7.
3.
7.
(7.75
6E-9
7E-3
9E-10
7E-3
(54.2
6E-9
6E-3
6E-10
6E-3
3E-9
8E-4
2E-10
8E-4
Radium-
226
INHALATION
m particle
7.1E-5
1.2E-3
3.9E-5
1.2E-3
m particle
7.1E-5
1.2E-3
f
3.7E-5
1.1E-3
INGEST ION
6.2E-5
7.6-6
2.7E-5
7.1E-4
Radium-
230
size)
2.0E-6
5.8E-4
1.
5.
8E-6
8E-4
size)
1.4E-6
3.8E-4
1.
3.
2.
6.
2.
6.
2E-6
8E-4
OE-7
2E-5
4E-8
2E-6
Thorium-
234
1.
8.
2.
8.
1.
6.
1.
6.
3.
8.
2.
8.
8E-7
8E-6
4E-8
8E-6
8E-7
OE-6
7E-8
OE-6
7E-5
6E-5
2E-7
6E-5
Uranium-
238
6.
7.
5.
7.
2.
5.
1.
5.
1.
7.
1.
7.
7E-6
3R-6
OE-6
4E-6
6E-6
1E-6
9E-6
1E-6
5E-5
2E-5
4E-5
2E-5
GROUND DEPOSITION
Ovary
Testis
4.
7.
OE-2
9E-2
1.
2.
4E-4
6E-4
1.3E-1
3.1E-1
8.
2.
1E-3
3E-2
3.
1.
2E-3
7E-2
1.
1.
6E-3
2E-2
C-20
-------
different methods from those used for radioactive substances.CD As
noted earlier, with nonradioactive toxic materials, the type of effect
varies with the material; the severity of the effectbut not its
probability of occurringincreases with the dose. Moreover, because
the body can detoxify some materials or repair the effects small doses,
often no toxic effects occur below a threshold dose.
We cannot construct a numerical risk assessment for nonradioactive
toxic substances because we do not have enough information. We can,
however, qualitatively describe risks of toxic substances in terms of
their likelihood of reaching people (or animals, or agricultural
products), concentrations at which they may be harmful, and their toxic
effects. No acute effectsdeath in minutes or hoursare expected at
concentrations addressed in this analysis. Severe sickness, or death
within days to weeks, from the use of highly contaminated water is
possible, but unlikely.
Chronic toxicity from the continuous consumption of contaminants
at low concentrations could be a problem. Toxic substances can
accumulate slowly in tissues, causing symptoms only after some minimum
amount has accumulated. Such symptoms of chronic toxicity develop
slowly, over months or years.
An extensive section in the EIS for inactive sites (EPA82-83) was
devoted to toxicity of elements found in uranium mill tailings and
tailings ponds and problems associated with them. Only an abreviated
discussion will be presented here. For the more detailed discussion,
the EIS for remedial action at inactive sites should be consulted.
At active uranium milling sites, inorganic toxic elements are
expected to be the major cause of concern (see Table C-10).
Organic chemicals used in processing ore are recycled and only
fugitive releases to tailings ponds might occur. The principal
organics associated with uranium milling are kerosene, di
(2-ethylhexyl) phosphoric acid (EHPA), tributyl phosphate, tertiary
amines (e.g., almine-336) and isodecanol (NRC80).
Although the organic chemicals used in uranium milling are not
expected to be released with mill tailings to any appreciable extent,
background levels in surface and ground water should be established for
both inorganic and organic potential pollutants. Both inorganic
chemicals and some organic chemicals may be transported long distances
so local levels in water may reflect distant industrial sources of
pollution rather than mill operations.
nonradioactive substances can induce cancer in experimental
animals (Go77, Ve78). However, for nonradioactive substances found in
uranium mill tailings, we do not feel that dose-response relationships
adequate for estimating such risks for oral intake have been developed.
021
-------
Table C-10. Selected Potentially Toxic Substances
Associated with Uranium Mill Tailings
Arsenic
Barium
Boron
Cadmium
Chromium
Copper
Cyanide
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Nitrates
Radium
Selenium
Silver
Thorium
Uranium
Vanadium
C 4.1. Estimates of Chronic Tqxicity in Humans
Data reviewed by the National Academy of Sciences showed that for
elements essential to human nutrition, there is a margin of safety
between the amount required for good nutritiion and the amount which is
toxic. The margin of safety may be narrow; e.g., 10 times the daily
recommended intake of arsenic is toxic; or wide, e.g., 1,000 times the
daily recommended intake of chromium is toxic (NASSOa). Table C-ll
lists selected substances found in uranium mill tailings and estimated
toxic levels. Note that these estimates are derived from a number of
sources of data and are not adjusted for chemical form of the element,
age or sex of subject, or any other factors. The estimates should be
viewed as very broad estimates of where toxicity might be expected.
C.4.2 Estimates of Chronic Toxicity in Animals and Plants
Although there is potential for causing acute toxic conditions to
develop in plants or animals if tailings pond water or other highly
contaminated standing water is used for plants or animals, this is
considered unlikely to occur. Induction of chronic toxicity in plants
or animals by using contaminated surface water, or more likely,
contaminated groundwater is deemed more plausible.
Maintaining water quality no worse than levels specified in the
interim primary (EPA76) or secondary (EPA79b) drinking water
regulations would also protect plants and animals in most cases.
However, these limits may not be adequate to protect dairy cattle, and
C-22
-------
not all possible contaminants would be covered. Likewise, not all
elements potentially toxic to plants would be covered. For a more
extended discussion of elements toxic to plants and animals, the
National Academy of Sciences 1972 publication, "Water Quality
Criteria," (NAS72b) can be consulted.
Table C-ll. Daily Intake Levels of Selected Elements
Estimated to be Toxic (NASSOa, EPA82)
Element
Arsenic
Barium
Boron
Cadmium
Chromium
Copper
Cyanide
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Nitrates
Radium
Selenium
Silver
Tho r ium
Uranium
Vanadium
Ratio of Toxic
Intake to Adult
Potentially Toxic _Int_ake__in Humans (mg)
Required Intake
10
NE
NE
NE
1000
40-135
NE
340-1700
NE
120
NE
10-40
112
NE
NE
100
NE
NE
NE
40-280
Acute
23(3)
550-600(3)
15000-30000(3)
15-30
9
175-200(3)
50-200(3)
70,000+ (3)
9
9
10-200(3)
9
250
8400-42000(3)
9
9
140(a)
9
350(3)
1700-17000(3)
Chronic
0.2-0.5
9
9
0.6
5-200
80-400
10
3000-30000
0.1-3
300-600
0.3-3
2-20
6
10
9
5-20
0.1
9
0.6
1-3
NE - Not reported to be essential in humans.
(a)Deaths are expected.
C-23
-------
REFERENCES
Ar79 Archer V.E., "Factors in Exposure Response Relationships of
Radon Daughter Injury," in Proceedings of the Mine Safety and
Health Administration Workshop on Lung Cancer Epidemiology and
Industrial Applications of Sputum Cytology, November 14-16,
1978, Colorado School of Mines Press, Golden, Colorado, 1979.
Arbl Archer V.E., "health Concerns in Uranium Mining and Milling,"
J. Occup. Med. 23:502, 1981.
Bu81 Bunger B.M., Cook J.R. and Barrick M.K., "Life Table
Methodology for Evaluating Radiation Risk: An Application Based
on Occupational Exposures," in Health Physics, 40:439-455,
1981.
EPA76 Environmental Protection Agency, "National Interim Primary
Drinking Water Regulations," EPA-570/0-76-003, Office of Water
Supply, USEPA, Washington, D.C., 1976.
EPA79a Environmental Protection Agency, "Indoor Radiation Exposure
Due to Radium-226 in Florida Phosphate Lands," EPA
520/6-78-013, Office of Radiation Programs, Washington, D,,C.,
July 1979.
EPA79b Environmental Protection Agency, "National Secondary Drinking
Water Regulations," Federal Register 44:42195-42202, 1979..
EPA82-83 Environmental Protection Agency, "Final Environmental Impact
Statement for Remedial Action Standards for Inactive Uranium
Processing Sites (40 CFR 192)," EPA, Office of Radiation
Programs, Washington, D.C.,1982.
Go77 Goyer R.A. and Mehlman M.A., editors, "Advances in Modern
Toxicology," Vol. 2: Toxicology of Trace Elements, John Wiley
& Sons, New York, 1977.
Ka82 Kato H. and Schull W.J., "Studies of the Mortality of A-Bornb
Survivors. 7. Mortality, 1950-1978: Part 1. Cancer
Mortality." Radiat. Res. 90:395-432 (1982).
La78 Land C.E. and Norman J.E., "Latent Periods of Radiogenic
Cancers Occurring Among Japanese A-Bomb Survivors," pp. 29-47
in Late Biological Effects of Ionizing Radiation, Volume I,
IAEA, Vienna, 1978.
C-24
-------
REFERENCES (Continued)
Mo79 Mole R.H., "Carcinogenesis by Thorotrast and Other Sources of
Irradiation, Especially Other Alpha Emitters," Environmental
Research, Vol. 18, No. 1, p.192, February 1979, Academic
Press, New York.
NAS72a National Academy of Sciences, The Effects on Populations of
Exposure to Low Levels of Ionizing Radiation, Report of the
Advisory Committee on the Biological Effects of Ionizing
Radiation, PB-239 735/AS, NAS, National Technical Information
Service, Springfield, Virginia, 1972.
NAS72b National Academy of Sciences, "Water Quality Criteria,"
EPA-R3-73-033, USEPA, Washington, D.C. 1972.
NAS76 National Academy of Sciences, "Health Effects of Alpha
Emitting Particles in the Respiratory Tract," Report of Ad Hoc
Committee on "Hot Particles" of the Advisory Committee on the
Biological Effects of Ionizing Radiations, EPA Contract No.
68-01-2230, EPA 520/4-76-013, USEPA, Washington, D.C. October
1976.
NAS80a National Academy of Sciences, "Drinking Water and Health,"
Volume 3, NAS, National Academy Press, Washington, B.C., 1980.
NAS80b National Academy of Sciences, "The Effects on Population of
Exposure to Low Levels of Ionizing Radiation," Committee on
the Biological Effects of Ionizing Radiations, NAS, National
Academy Press, Washington, B.C., 1980.
NRC80 Nuclear Regulatory Commission, "Final Generic Environmental
Impact Statement on Uranium Milling," NUREG-0706, Office of
Nuclear Material Safety and Safeguards, USNRC, Washington,
D.C., 1980.
RPC80 Radiation Policy Council, "Report of the Task Force on Radon
in Structures," RPC-80-002, U.S. Radiation Policy Council,
Washington, 1980.
Sh82 Shi-quan S. and Xiao-on Y., "Induction-Latent Period and
Temporal Aspects of Miner Lung Cancer," unpublished report (in
English), 1982.
C-25
-------
REFERENCES (Continued)
Sm78 Smith P.G. and Doll R., "Age- and Time-Dependent Changes in
the Rates of Radiation-Induced Cancers in Patients with
Ankylosing Spondylitis Following a Single Course of X-ray
Treatment," pp. 205-218 in: Late Biological Effects of
Ionizing Radiation, Volume I., IAEA, Vienna, 1978.
Su81 Sullivan R.E., et al., "Estimates of Health Risk from Exposure
to Radioactive Pollutants," ORNL/TM-7745, Oak Ridge National
Laboratory, Oak Ridge, Tennessee, 1981.
Th82 Thomas D.C. and McNeill K.G., "Risk Estimates for the Health
Effects of Alpha Radiation," Prepared for the Atomic Energy
Control Board, Ottawa, Canada, INFO-0081, September 1982.
Ve78 Venugopal B. and Luckey T.D., "Metal Toxicity in Mammals,"
Volume 2, Chemical Toxicity of Metals and Metaloids, Plenum
Press, New York, 1978.
C-26
-------
APPENDIX D
WATER MANAGEMENT AT URANIUM ORE PROCESSING SITES
-------
APPENDIX D: WATER MANAGEMENT AT URANIUM PROCESSING SITES
CONTENTS
Page
D.I Summary D-5
D.2 Introduction D-6
D.3 Uranium Recovery Processes D-6
D.4 Contaminants in Uranium Waste D-7
D.5 Water Use and Retention at Operating Mills D-8
D.6 Design of Tailings Impoundments D-8
D.7 Clay and Synthetic Liners D-9
D.8 Groundwater Monitoring Results D-10
D.8.1 Introduction D-10
D.8.2 Composition of Tailings Ponds D-10
D.8.3 The Neutralization Zone D-ll
D.8.4 Monitoring Groundwater Contamination D-12
D.9 Control of Toxic Materials to Groundwater D-15
References D-lb
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APPENDIX D: WATER MANAGEMENT AT URANIUM ORE PROCESSING SITES
D.I Summary
Operating uranium mills produce effluents containing radioactivity
and toxic materials which are potential contaminants to groundwater.
Large amounts of tailings effluents placed in unlined evaporation ponds
on permeable soil at existing mill sites have seeped into the sandstone
bedrock that contains groundwater. Investigations of the altered
bedrock along the seepage pathways show attenuation of most of the
radionuclides and some of the toxic elements during the neutralization
phase of the leachate. Some of the highly mobile and soluble heavy
metals, (Mo, V, Mn, Pb, As, and Se) have migrated beyond the
neutralization zone into the groundwater. The presence of diagnostic
chemical species related to seepage plumes and higher-than-normal
concentrations of toxic materials above groundwater background levels
disclose the presence of tailings contaminants in the groundwaters
close to the uranium mills.
The characteristics of seepage migration are site specific and
controlled by the relatively complex hydrogeology of the typical
uranium mill site. No satisfactory method exists to abate or predict
contaminant movement from these unlined tailings ponds.
Using synthetic liners, clay liners, or a combination of both in
the tailings pond seems to be the most effective method of confining
mill tailings effluents. The type of liner used is usually determined
by the nature of the waste and conditions of the site. Both clay and
synthetic liners are similar in cost. Synthetic liners are more
impervious and if adequately guarded by clay layer cushions can be
protected from tear or puncture and chemical alteration.
Clay liners, properly designed with structural integrity, can
provide a tight seal by the precipitation of some solids into pore
spaces as a result of neutralization reactions attending the
interaction of acid waste water and the liner materials. However, the
impermeability achieved is somewhat less assured than the synthetic
liners.
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D.2 Introduction
The water used in the recovery of uranium contains toxic materials
that must be effectively managed to prevent potential surface water or
groundwater contamination. It has been estimated that as much as 85
percent of the mill tailings effluents are lost to groundwater during
the mill's operation (Ja79). Thus, confining water during the mill
operating phase is critical in controlling the amount of contaminants
available for potential pollution.
Mill tailings effluents discharged to unlined evaporation ponds
have resulted in seepage loss of some of the contaminants to
groundwater during the operation phase of the mills. Tailings pond
seepage has been detected in the groundwater at a number of sites. The
maximum distance of migration reported at one site was 1.5 miles
(UI80). Within a few years after the mill closes, tailings ponds will
evaporate in the arid to semi-arid climate of western United States;
this leaves a tailings pile vulnerable to wind and water erosion.
Over the past several years, there have been a number of core hole
borings and water monitoring investigations to better understand and
develop methods to mitigate the migration from uranium tailings
impoundments. These site-specific studies have traced the extent and
travel rates of seepage plumes, have identified the attenuation of
radionuclides and toxic material by the geologic media, and have
contributed to the understanding of the physicochemical factors
involved. The migration of highly mobile contaminants requires further
study. Emphasis presently is placed on the confinement and retention
of effluents in the tailings ponds by synthetic liners, clay liners, or
a combination of both; however, some natural media may be impervious to
seepage. Future technology directed toward changing the chemistry of
tailings pond effluents may help contain the mobile toxic materials
that contaminate groundwater.
D.3 Uranium Recovery Processes
There are two basic conventional processes for recovering uranium
from the ore: the acid-leach process and the alkaline-leach process.
The acid-leach process is used when the ore contains less than 12
percent limestone and generally accounts for 80 percent of the uranium
recovery. The alkaline-leach process is used on the remaining 20
percent of the ore milled. Both processes involve an initial dry
crushing and grinding, then water is introduced as the ore is wet
ground to a pulp density of 50 to 65 percent solids. Water consumption
at this step is reduced by recirculating the water.
A leaching process removes the uranium from the crushed ore, with
sulfuric acid as the leaching agent in the acid-leach process; a mixed
sodium carbonate-sodium bicarbonate solution is the leaching agent in
the alkaline-leach process (NRC80a). After ore leaching is completed,
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the "pregnant" leach liquor containing the dissolved uranium is removed
from the tailings solids by a counter current decantation (CCD)
circuit. The leach solution is sent to a solvent extraction for
further processing, and the remaining solids are washed and pumped as a
slurry to the tailings ponds. Water in the tailings ponds generally is
characterized by total dissolved solids in the range of 12,000 to
90,000 mg/L with an abundance of dissolved radionuclides and heavy
metals. The pH of the water averages about 1.8 for mills using the
acid-leach process and about 10.2 for mills that use the alkaline-leach
process.
The acid-leach and alkaline-leach processes have considerable
chemical differences. A larger fraction of thorium is solubilized in
the acid-leach process, but the thorium is precipitated in the tailings
pond when the acidity is reduced. In addition to variations in the
chemical composition from the milling process used, other variations
exist from differences in the composition of the ores related to their
origin.
D.4 Contaminants in Uranium Waste
The waste from the milling operations of uranium ore contains all
the toxic contaminants present in the original ore, about 10 percent of
the uranium not recovered in the process, and a variety of chemicals
used in the extraction process. The nature of the contaminants vary in
relation to the source of the ore and the type of process used.
Radionuclides reported include uranium, thorium, and radium, and toxic
materials include arsenic, lead, molybdenum, and selenium. Other
elements and parameters reported include iron, manganese, sulfate,
chloride, total dissolved substances (TDS), and acidity index (pH).
Many levels of toxic materials are more than two orders of magnitude
above EPA drinking water standards. Additional heavy metals and
chemicals existing in uranium mill wastewater which are locally
important, include Sb, Be, Cd, Cr, Cu, Ni, Zn, V, Mn, Al, and ammonia.
The solid portion of the tailings is comprised of particles
ranging in size from coarse sands to fine slimes. Quartz and feldspar
comprise the major portion of the sands, while fines contain
appreciable amounts of clay minerals, gypsum, calcite, and barite in
addition to quartz and feldspar (Dr81). In both the acid process and
the alkaline process, the residual uranium and radium content of slimes
(fines) is about twice that of sands; this is undoubtedly due to the
greater concentration of sorptive minerals, e.g., clay minerals, in the
slimes. In the acid-leach process, about 95 percent of the thorium in
the original ore remains in the solid tailings waste. Less than one
percent of the radium is dissolved in the liquids. Even more of the
thorium and radium remains in the solid waste from the alkaline-leach
process.
Radon gas is released as a daughter radionuclide from the decay of
radium-226, which is largely retained in the solid waste. Because
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radon is chemically inert, it migrates by diffusion from the tailings
pile to the atmosphere. Radon emissions rates have been calculated at
between 200 to 900 pCi/m2s. Uncontaminated soils average about
1 pCi/m2s by comparison. Standing water and entrapped water in the
tailings pile inhibit the release of radon gas so that calculated
release rates cited may be high.
D.5 Water Use and Retention at Operating Mills
Water conservation is desirable in many mining and milling
operations for uranium recovery. Mine waters are treated to recover
uranium and/or to remove radium, heavy metals, and suspended solids.
The treated mine waters are used at the mill as feed water or
discharged to the watershed. Currently, only the Uravan, Colorado,
mill discharges treated wastes to surface water. Water is used to
slurry the tailings (the wastes) from the mill to an impoundment. This
water can evaporate, be pumped to evaporation ponds, recycled to the
mill, or discharged to surface waters. Water decanted from the ponds
in the impoundment system may be recycled to the mill, decreasing fresh
water usage.
The quantity of water used in milling is variable and depends on
the process used and the degree of recycling. The acid-leach process
requires greater amounts of fresh water than mills using the
alkaline-leach process. Fresh water is usually required in acid leach
mills for ore grinding, leaching (as steam), counter current
decantation washing, and precipitation (Ja79). The alkaline-leach
process normally employs a mixed sodium carbonate-sodium bicarbonate
leach solution in the grinding circuit with fresh water used for
post-leaching filtration and second-stage precipitation (Ja79). The
waste streams from the milling process are partially or totally
segregated for disposal, especially if recycling from the impoundment
system is practiced. Segregation and disposal in separate ponds allow
reuse of less contaminated wastes while providing for containment of
liquid wastes which contain high concentrations of contaminants.
D.6 Design of Tailings Impoundments
The predominant method of disposal of all solid and liquid wastes
generated in the uranium mill today is impoundment of the wastes in a
tailings retention system. This system consists of an earthen dam or
embankment and an evaporation basin or pond behind the dam. The dam is
located to minimize the upstream catchment area. Ditches are also
constructed to direct the water around the impoundment. The
evaporation basin on the upstream side of the dam is lined with a clay
or synthetic liner to prevent seepage loss to the underlying soil.
The NRC has issued Regulatory Guide 3.11, "Design, Construction,
and Inspection of Embankment Retention Systems for Uranium Mills" which
provides the design goals for tailings impoundments (NRC77). The
design takes into consideration the protection of the embankment
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retention systems from the Probable Maximum Flood (PMF). The PMF is
defined as the flood that may be expected from the most severe
combination of critical meteorologic and hydrologic conditions that are
reasonably possible in the region (NRC77). The regulatory guide lists
appropriate guidance for determining the Probable Maximum Flood.
Methods for estimating return intervals of paleofloods in the
particular acute semiarid regions have been described by Kochel and
Baker (Ko82).
D.7 Clay and Synthetic Liners
In the early days of uranium milling, not much attention was given
to the protection of the subsurface hydrogeologic environment. Most of
the mill wastes generated before 1977 are stored in unlined tailings
ponds, and some of these have leaked. Most waste disposal sites are
located in hydrogeologic environments that consist of nonindurated
and/or indurated sediments that were deposited in fluvial
environments. Buried river deposits are coarse grained and difficult
to detect because of their braided, band-like occurrence in such
terrain. High seepage rates of migrating solutions can take place if
such formations occur beneath an unlined uranium mill tailings
evaporation pond.
Since groundwater monitoring was initiated in 1977, seepage from
tailings ponds has been detected in groundwater from a number of sites,
with migration as much as 1.5 miles at one of the sites (UI80). The
seepage plumes were traced by one or more of several chemical
parameters found in the seepage water, particularly sulfate and total
dissolved solids. In some cases, this monitoring effort has identified
contamination problems which require the use of recovery wells to
return contaminated water from seepage plumes back to lined tailings
ponds. (UI80).
The technology of pond liners is a relatively recent development.
Generally speaking, synthetic liners are used for evaporation ponds of
mine waters or less contaminated effluents, and thicker clay liners are
used in tailings ponds. Synthetic liners of polyvinyl chloride (PVC),
chlorinated polyethylene (CPE), and hypalon (synthetic rubber) used at
uranium mills are less permeable (10~10 cm/s) than clay liners
(Ja79). Synthetic liners, however, are subject to loss of seal by
puncture or tearing during installation. Thus, they must be protected
with some layers of clay. The clay layers act as a cushion to prevent
rupture and to neutralize the leachate and potential chemical
alteration of the synthetic liner.
Clay liners, in addition to having structural stability, are
effective in sealing ponds because of their layered structure and their
high sorptive properties. The desorption of Na+ from montmorillonite
in the mill tailings of the Grants Mineral Belt has been described as
being desirable because pollutants are probably being adsorbed in their
place on this clay mineral (Lo82). Leaching of clay into liner pores
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(caused by precipitation) can also increase the impermeability of the
clay liner; this enhances the long-term stability of the clay liners
(Pe82). Natural clays treated with polymeric materials have also been
shown to improve the sealing properties of clay, and permeabilities as
small as 10~6 to lO^8 cm/s have been achieved (Ja79).
The uncertainty of maintaining an acceptable level of
environmental control with unlined tailings ponds warrants the use of
synthetic liners, clay liners, or a combination of clay and synthetic
liners that prevent the seepage of contaminants into groundwater.
D.8 Groundwater Monitoring Results
D.8.1 Introduction
Before 1977 most mill wastes were stored in unlined tailings
ponds. Seepage from these ponds has contaminated groundwater. The
characteristics of seepage movement are site specific, and a number of
methods can identify the pathways and extent of pollution to
groundwater. Some of the data that were collected at uranium mill
disposal sites are incomplete, and some were collected by methods that
are not state of the art. The most reliable method of characterizing,
groundwater contamination is by identifying the chemicals in tailings
ponds that are also in groundwater above background levels.
The methods used to delineate the migration path of the seepage
plume and the actual groundwater monitoring results at the active mill
tailings sites are reviewed in the next section.
D.8. 2 Composition of Tailings Ponds
The dissolved radionuclides of primary concern within most
tailings ponds include radium-226, thorium-230, uranium-238, lead-210,
and polonium-210. Heavy metals found in varying quantities among the
uranium mill sites include molybdenum, arsenic, selenium, lead, iron,
chromium, manganese, magnesium, cobalt, nickel, barium, vanadium, and
copper. Toxic heavy metals are higher in concentration in acid mill
waste than in alkaline mill waste. Anions of toxic heavy metals are
generally more soluble and, thus, potentially more hazardous than the
cationic species of the same element which can be precipitated with
lime or sulfide. Major anions formed by heavy metals in tailings ponds
include species of arsenic, chromium, molybdenum, uranium, and
vanadium. Inorganic anions, notably sulfate, nitrate, and chloride,
are present in significant quantities in acid leach mill wastes. Other
inorganic anions found in minor amounts in most wastewater include
sulfide, cyanide, fluoride, and total dissolved solids (Ja79). Light
elements in tailings ponds include potassium, sodium, aluminum,
beryllium, calcium, magnesium, and titanium.
While organics are widely used in the extraction process, most of
these chemicals are removed, and quantities of organic compounds in
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mill liquid wastes are low. Typical concentrations of total organic
carbon in acid mill waste range from 6 to 24 mg/L in acid mill waste
and 1 to 450 mg/L in alkaline mill waste; oil and grease is generally
1 mg/L in acid mill waste and 3 mg/L in alkaline mill waste; MBAS
surfactants average 0.5 mg/L in acid mill waste and 0.02 mg/L in
alkaline mill waste; phenol is less than 0.2 mg/L for both types of
wastes (Ja79). The pH of the waters in the tailings ponds averages
about 1.8 for mills using the acid-leach process and about 10.2 for
mills using the alkaline extraction process.
D.8.3 The Neutralization Zone
The acid seepage plumes are normally neutralized by carbonate
minerals in the bedrock within a few hundred yards of most tailings
ponds. At a distance of a few hundred yards, the total dissolved
substances can be expected to range from 5,000 to 10,000 mg/L, as
contrasted to the 25,000-35,000 mg/L found in normal tailings pond
water (UI80). The pH change gradually increases to that of the normal
groundwater, and minerals are precipitated that are not generally
native to the bedrock in this same distance of transport.
Several investigators have attempted to characterize the
transition zone between the mill tailings pond water and the point
where it becomes indistinguishable from native groundwater. A recent
investigation describes the interaction between the seepage from the
tailings ponds and the natural soils by thermodynamic principles; this
interaction is based on minerals identified as precipitates and
dissolved minerals (Ma82). Gypsum precipitation, for example, results
when calcite comes in contact with sulfuric acid; carbon dioxide gas is
produced and the calcium reacts with the sulfate to. produce gypsum.
Barium will also precipitate as BaSO^ and in the process remove
radium from solution (Ma82). Conclusions drawn, however, are almost
entirely on solid-phase data, and the liquid-phase chemistry is ignored,
Another line of investigation utilizes an analytical
hydrogeochemical model based upon acid consumption-neutralization front
movement. In this model it is possible to identify and characterize
zones within migrating plumes of tailings-derived water by the chemical
characteristics of the water (Sh82). An investigation of the seepage
from an unlined mill tailings pond in the Wyoming Gas Hills district
describes radionuclide retention within the first 40 to 60 cm beneath
the pond. The neutralization zone to an ll-meter depth is delineated
by typical gypsum precipitation and carbonate removal and increases to
the 8.2 pH background level (Er82).
The foregoing investigations describe the retention of certain
radioactive and toxic materials attending the neutralization of mill
pond seepage and the nature of transition zones. Of major concern is
determining what portion of the seepage has gone beyond the
neutralization zone to become part of groundwater contamination. This
is best determined by groundwater monitoring.
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D.8.4 Monitoring Groundwater Contamination
Several groundwater monitoring investigations of uranium mill
sites have disclosed chemical pollutants above background levels that
are attributed to seepage from unlined mill tailings ponds. A
description of these site-specific monitoring findings follows.
Canon City, Colorado
Before 1979, the Cotter Corporation near Canon City, Colorado,
used the alkaline-leach process and disposed of mill tailings wastes in
a series of unlined tailings ponds. The seepage waste is typical of
both the alkaline and acidic types and is described as concentrated
sodium sulfate waters with high levels of molybdenum, selenium, and
emitters of radiation (UI80).
Concentrations of molybdenum at levels of 16.7 mg/L at a well
approximately 8000 feet from the Cotter tailings pond, within an
isoconcentration delineated zone, are evidence of pollution from a
point source in the tailings pond. The maximum background level of
molybdenum in the vicinity of the mill is 1.1 mg/L, and the Drinking
Water Standard for molybdenum is 0.05 mg/L (U180).
A Soil Conservation Reservoir near the tailings pond (3000 feet)
has elevated levels of sodium, sulfate, radionuclides, and selenium (in
addition to elevated levels of molybdenum) which appear to be related
to the seepage effluents from the pond. The complex nature of the
hydrogeology around the Cotter Mill, however, makes migration pathways
difficult to interpret for engineering corrective measures.
Ford, Washington
The Dawn Mining Company mill near Ford, Washington, has acid-leach
process effluent seepage from existing unlined tailings ponds that has
contaminated the groundwater beneath the site. Sulfate is the primary
tracer of the contamination plume that is easily traced through the
highly permeable sand and gravel glacial sediments to an underlying
glacial lake, derived clay stratum. At the impervious clay stratum, a
groundwater mound gradient is created'that causes discharge in a
direction approximately 0.5 miles west of the tailings pond to a nearby
surface stream (U180). Uranium concentration in the seepage emergence
zone is 0.06 mg/L, whereas uranium in springs not affected by the
tailings pond is 0.004 mg/L. However, the only contaminant in the
seepage emergence zone that exceeds Drinking Water Standards is
nitrate, which occurs in levels of 35 mg/L and is three and one-half
times the maximum permissible concentration specified. Sulfate,
manganese, and total dissolved solids occur in excess of "recommended"
limits for drinking water. Pump-back systems are being considered as
engineering control measures to control the pollution.
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Gas Hills, Wyoming
The Union Carbide Gas Hills, Wyoming, uranium mill near Riverton,
Wyoming, has contributed groundwater contaminants from an unlined
tailings disposal pond containing acid-leach process effluents. Water
quality in the water-bearing horizons of the Wind River Formation used
as background indicator wells barely exceeds the Drinking Water
Standards for total dissolved solids, sulfate, selenium, and radium-226
(UI80).
Monitoring wells around the mill tailings pond indicate that
migration of contaminants is occurring in the upper alluvial layer and
middle sandy layer of the Wind River Formation which has a thickness of
400 feet.
Typical water contamination from a monitoring well to a depth of
140 feet and at a distance of 700 feet from the disposal pond indicate
the following: sulfate 2932 mg/L, with 250 mg/L the irrigation
standard; selenium 0.26 mg/L, with 0.01 mg/L the irrigation standard;
total dissolved solids 5760, with 250 mg/L the irrigation standard;
nitrate 150 mg/L, with 10 mg/L the irrigation standard; aluminum
59 mg/L, with 20 mg/L the irrigation standard; manganese 7 mg/L, with
0.05 mg/L the irrigation standard; chloride 893 mg/L, with 250 mg/L the
irrigation standard (NRCSOb). More monitoring wells would be required
to determine how far the seepage has migrated because of the complex
hydrogeologic conditions and the interpretation of data required.
Jeffrey City, Wyoming
Groundwater has been contaminated by the acid-leach effluent
seepage from the Western Nuclear, Inc., Split Rock uranium mill near
Jeffrey City, Wyoming. The unlined tailings pond leaked contaminants
into the underlying Split Rock Formation comprised of fine-grained
sandstone having a hydraulic conductivity of 1.4 x 10~2 to 1 x 10~^
cm/s (UI80). Groundwater degradation occurs beyond the site boundary
in the direction of Jeffrey City.
Arsenic contamination has been detected up to 2900 feet from the
tailings pond. A chemical analysis of sediments shows a decrease in
contaminants with depth and distance from the tailings pond. Due to
high levels of iron and manganese in the tailings pond (300 mg/L and 17
mg/L respectively), it appears that oxyhydroxides of these elements are
readily formed and coprecipitate other heavy metals under governing
chemical conditions in the host media. The sorption of cationic
species by clay minerals as well as change in redox potential (Eh) and
pH are other factors that control the migration distance of
contaminants. Arsenic is the exception with the media effecting less
control on its migration.
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Fremont County, Wyoming
The Federal American Partners mill tailings pond located in the
Gas Hills area of Fremont County, Wyoming, has leaked seepage to
groundwater beneath the site. The unlined tailings pond is situated on
weathered sandstone of the Wind River Formation. The acid-leach
effluents have migrated approximately 3200 feet with chloride, sulfate,
nitrogen, lead, and total dissolved solids found above background
levels (UI80). Isoconcentration maps delineate the direction of
migration of the contaminants with test data from 27 monitoring wells
ranging in depth from 20 to 105 feet. Seepage migration appears to be
confined to the deeper aquifer. Buried stream channels in the area
could constitute zones of higher hydraulic conductivity so that
groundwater migration could become greater without corrective action.
La Sal, Utah
The Rio Algom Corporation's Lisbon Valley mill tailings pond near
La Sal, Utah, has seeped alkaline-leach process effluents to a perched
groundwater mound in the vicinity of the tailings pond (UI60). The
unlined pond is located on a thin layer of terrestrial deposits (10 feet
or less) that overlie the Dakota-Burro Canyon sandstones. Contami-
nation is restricted to the Dakota-Burro Canyon Formation with Drinking
Water Standards exceeded approximately 1500 ft. away from the tailings
ponds (UI80). Conclusions regarding the migration are based on
isoconcentration maps for alkalinity (CC^), chloride, nitrate sodium,
sulfate, boron, total uranium, and radium-226. A major northwesterly-
trending fault present near the site (3,000 ft. away) may influence the
movement of the seepage plume at the site.
Milan, New Mexico
The Homestake uranium mill near Milan, New Mexico, has sustained
440 m3/d or 6 percent seepage loss of alkaline-leach process
effluents discharged to unlined tailings ponds (Ja79). The seepage has
penetrated the highly permeable and saturated alluvium which blankets
(up to 75 feet thick) the more massive, less permeable Chinli Formation
bedrock of shale and sandstone (Pi81). A mound of contaminated
groundwater underlies the tailings ponds, and elevated levels of
uranium, radium, selenium, and nitrate-nitrogen, in excess of New
Mexico Drinking Water Standards, have been found in surrounding wells
used as drinking water by nearby residents (Pi81).
Selenium ranges up to '2.0 mg/L (limit is 0.05 mg/L);
nitrate-nitrogen, up to 14.1 mg/L (limit is 10.0 mg/L); uranium, up to
5 mg/L (limit is 0.5 mg/L); radium-226, up to 9.5 picocuries/L (limit
is 5.0 picocuries/L). Background levels and preoperational levels of
selenium, nitrate, and sulfate have also at times exceeded New Mexico
Drinking Water Standards. Such variations and potential faults beneath
the tailings piles have made it difficult to determine the extent of
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contamination. Homestake is attempting to mitigate the groundwater
pollution by pumping contaminated alluvial groundwaters back to
tailings ponds and injecting better quality waters into the alluvium
(Pi81). Some monitoring wells show water quality deterioration while
others show improvement (UNHP80). The monitoring program in a complex
hydrogeologic setting is compounded by potential faults which makes an
assessment of the situation exceptionally difficult.
D.9 Control of Toxic Materials to Groundwater
Monitoring investigations of the migration pathways from unlined
mill tailings pond have determined that radionuclides and some of the
toxic heavy metals are attenuated within a few feet of the tailing pond
but that some toxic heavy metals are highly mobile and have
contaminated the groundwater. The mobile species include molybdenum,
selenium, chlorine, sulfate, nitrate, arsenic, lead, and vanadium.
Under existing hydrogeologic conditions and the chemical makeup of the
seepage from the tailings pond, this condition prevails unless
protective controls are utilized. Controls that exist to prevent
groundwater contamination include, (a) complete containment by
impervious seals (clay or synthetic liners), and/or (b) altering the
chemistry of tailings pond effluents.
Synthetic and clay liners were mentioned earlier and are probably
the most positive long-term controls for containment of both the
acid-leach and alkaline-leach process effluents in tailings ponds. The
lon^-terui stability of earthen materials or clay liners in contact with
acid tailings solutions has been investigated by the Pacific Northwest
Laboratory (PNL) under NRG contract (Pe82). The highly acid condition
of the acid-leach tailings slurry (1.8 ph) leach some of the clay. The
PNL laboratory investigation disclosed that materials containing over
30 percent clay showed a decrease in permeability with time (Pe82).
Such findings, however, are limited to laboratory studies and do not
ncessarily reflect long-term field conditions.
The decreases in permeability for a number of clay materials
considered were attributed to pore plugging resulting from the
precipitation of minerals and solids. X-ray diffraction and
geochemical predictions confirm that gypsum, jarosite, and other
minerals precipitate after the tailings solution reacts with the earth
material comprising the liners (Pe82). To ensure that the initial
permeability of the liner is minimized, the liner should be compacted
to at least 90 percent of its maximum capacity as determined by a
standard Proctor test (Pe82). A one-meter clay liner compacted with a
calcium carbonate content of 4 percent or greater could be expected to
impede the pH front advance into the surrounding geologic materials for
hundreds of years and to neutralize the total acidity of a typical
tailings pond (Peb2).
The concept of altering the chemistry of the uranium mill
wastewater by precipitation to control the removal of toxic materials
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in tailings ponds has been investigated by the Environmental Protection
Agency. This study was performed for both acid and alkaline waste
streams and considered a number of processes. The most promising
finding is the combining of acid waste streams with alkaline waste
streams to precipitate metals that occur as anions (We80). Mobile
metals, such as Mo and V, present in anionic form as molybdates and
vanadates, are effectively removed from solution at a pH range of 5.8
to 6.1 achieved by mixing the acid and alkaline mill waste at a 5:3
ratio by volume (We80). Other metals largely removed at this pH
include iron, aluminum, chromium, and nickel. However, few alkaline-
process mills and acid-process mills are located close enough to
accomplish this mixing.
A recent Pacific Northwest Laboratory investigation of the
neutralization, fixation, and specific constituent removal methods for
treatment of uranium mill wastes to mitigate groundwater contamination
found the neutralization process to be the most effective (Sh83).
The fixation process adds materials to mill waste to produce
physically stable compounds that resist leaching of hazardous
materials, but this process is very expensive, not completely effective
over tens of years, and substantially increases the volume and weight
of the wastes. Specific constituent removal methods include ion
exchange processes, selective precipitation, or alternate ore leaching
processes that reduce specific concentrations in tailings solutions.
To date, the only specific constituent removed is radium-226 by
co-precipitation with 83804 when BaCl2 is added to the waste stream
of the acid waste treatment process.
The neutralization process, by contrast to the fixation and
specific constituent methods, limits the pollutants in the tailings
solution at a reasonable cost. In this process, a combnation of
limestone and lime added to the acid leach tailings waste adjusts the
pH to 8.0; this pH constitutes the optimum level found for heavy metal
removal (Sh83).
The neutralization process has been practiced by the Canadians
with 90 percent reduction of dissolved solids and 99 percent reduction
in radionuclides as compared to untreated U.S. tailings solutions.
While Canadian tailings ponds after neutralization contain sulfate,
nitrate, ammonia, and radium-226 in excess of water quality control
standards, it is expected that any effluent discharged through the
substrata to groundwater would attenuate or reduce these pollutants by
natural processes of adsorption and precipitation.
Since the primary goal of groundwater protection is prevention of
contaminant seepage into groundwater, it appears that reliance should
be placed on synthetic liners or a combination of synthetic and clay
liners. While laboratory studies by Pacific Northwest Laboratory show
that permeability decreases in time with clay liners containing over 30
D-16
-------
percent clay, complete reliance cannot be guaranteed for prototype
conditions. Therefore, the state of the art for achievement of least
migration of pollutants from mill tailings ponds appears to be the
synthetic liners with adequate protection from physical rupture using
protective clay layers.
D-17
-------
REFERENCES
DrSl Dressen D.R., Williams J.M., and Cokal E.J., 1981, "Thermal
Stabilization of Uranium Mill Tailings Management," Colorado
State University, Oct. 26-27, 1981.
Er82 Erikson R.L. and Sherwood D.R., "Interaction of Acidic
Leachate with Soil Materials at Lucky McPathfinder Mill, Gas
Hills, Wyoming," Symposium on Uranium Mill Tailings
Management, Fort Collins, Colorado, Dec. 9-10, 1982.
Ja79 Jackson B., Coleman W., Murray C., and Scinto L.,
"Environmental Study on Uranium Mills," TRW Report for EPA,
Contract 68-03-2560, 1979.
Ko82 Kochel C.R. and Baker V.R., 1982, "Paleoflood Hydrology,"
Science, Vol. 215, No. 4531.
Lo82 Longmire P. and Brookins D., "Trace Metals, Major Elements,
and Radionuclide Migration in Groundwater from an Acid
Leaching Uranium Tailings in the Grants Mineral Belt, N.M.,"1
Symposium on Uranium Mill Tailings Management, Fort Collins,
Colorado, Dec. 9-10, 1982.
Ma82 Markos G. and Bush K.J., 1982, "Thermodynamic Calculations and
Phase Diagrams Evaluating Tailings-Soil-Water Interactions,"
Symposium on Uranium Mill Tailings Management, Fort Collins,
Colorado, Dec. 9-10, 1982.
NRC77 Nuclear Regulatory Commission, "Design, Construction and
Inspection of Embankment Retention Systems for Uranium Mills,"
Regulatory Guide 3.11, NRC, Washington, D.C., 1977.
NRCSOa Nuclear Regulatory Commission, "Final Generic Environmental
Impact Statement on Uranium Milling," NUREG-0706, Vol. 1, 2,
3, NRC, Washington, D.C., 1980.
NRC80b Nuclear Regulatory Commission, "Radiological Effluent and
Environmental Monitoring at Uranium Mills," Regulatory Guide
4.14, NRC, Washington, D.C., 1980.
Pe82 Peterson S.R., Erikson R.L., and Gee G.W., "The Long-Term
Stability of Earthen Materials in Contact with Acidic Tailings
Solutions," Pacific Northwest Laboratory, NUREG/CR-2946,
PNL-4463, 1982.
Sh83 Sherwood D.R. and Serne R.J., "Tailings Treatment Techniques
for Uranium Mill Waste: A Review of Existing Information,"
NUREG/CR-2938, PNL-4453, 1983.
D-18
-------
REFERENCES (Continued)
PI81 Pierce J.A., "Groundwater Contamination at the United
Nuclear-Homestake Partners Uranium Mill," State of New Mexico,
Environmental Improvement Division Report of 23 April 1981.
Sh82 Shepherd T.A. and Brown S.E., "A Generic Model of Contaminant
Migration from Uranium Tailings Impoundments," Symposium on
Uranium Mill Tailings Management, Fort Collins, Colorado, Dec.
9-10, 1982.
UI80 University of Idaho, "Overview of Ground Water Contamination
Associated with Six Operating Uranium Mills in the United
States," Mineral Resources Waste Management Team, University
of Idaho, Dec. 30, 1980.
UNHP80 United Nuclear-Homestake Partners, "Review of the -Broadview
Acres Injection System at UNHP Mill near Milan, N.M.,"
Hydro-Engineering Contract, 1980.
We80 Werthman P.M. and Bainbridge K.L., "An Investigation of
Uranium Mill Wastewater Treatment," Environmental Protection
Agency, Contract 68-01-4845, 1980.
D-19
-------
APPENDIX E
CURRENT ESTIMATED POPULATIONS NEAR
ACTIVE URANIUM ORE PROCESSING SITES
-------
Appendix E: Current Estimated Populations Near
Active Uranium Ore Processing Sites
CONTENTS
Page
Appendix E E-5
Tables
E-l Canon City, Colorado E-6
E-2 Uravan, Colorado E-7
E-3 Ambrosia Lake, New Mexico E-8
E-4 Bluewater, New Mexico E-9
E-5 Church Rock, New Mexico E-10
E-6 Marquez, New Mexico E-ll
E-7 Milan, New Mexico E-l2
E-8 Seboyeta, New Mexico E-l3
E-9 Edgemont, South Dakota E-l4
E-10 Panna Maria, Texas E-l5
E-ll Falls City, Texas E-l6
E-12 Ray Point, Texas E-l7
E-13 Blanding, Utah E-l8
E-l4 La Sal, Utah E-l9
E-15 Moab Utah E-20
E-l6 Hanksville, Utah E-21
E-l7 Ford, Washington E-22
E-18 Wellpinit, Washington E-23
E-l9 Powder River, Wyoming E-24
E-20 Gas Hills, Wyoming (Federal-American Partners) E-25
E-21 Red Desert, Wyoming E-26
E-22 Gas Hills, Wyoming (Pathfinder Mines) E-27
E-23 Shirley Basin, Wyoming (Pathfinder) E-28
E-24 Shirley Basin, Wyoming (Petrotomics) E-29
E-25 Powder River, Wyoming (Rocky Mountain Energy) E-30
E-26 UCG-Gas Hills, Wyoming E-31
E-27 Jeffrey City, Wyoming E-32
E-3
-------
APPENDIX E: CURRENT ESTIMATED POPULATIONS NEAR
ACTIVE URANIUM ORE PROCESSING SITES
EPA contracted with Battelle Pacific Northwest Laboratories
(PNL) to count the number of people living near existing tailings
piles. PNL conducted these population counts during May and June
1983.
PNL obtained these data by visiting each site and counting the
occupied dwellings out to 5 kilometers (km) from the center of the
tailings pile. In some of the heavily populated areas, populations
were estimated from census tract and block data, city zoning maps,
information obtained from city planners, and direct observations of
population densities. Census data (1980) on the average number of
persons per household per county were used to translate dwelling
counts to population.
Some difficulties were encountered in determining whether a
habitable dwelling was occupied, as for instance, in houses "for
sale" or seasonal houses. In these cases, PNL used their best
judgment since they did not directly contact any householders.
Also, PNL did not take any road labelled "no trespassing" or any
private road; they relied on visual sitings from public roads.
The data are presented in the following tables in area segments
as determined by annular rings and 16 compass points. The center of
each pile is identified by its geographical coordinates (latitude
and longitude) and is at the centroid of the tailings area. The
radial distances of the annular rings are measured from the centroid.
E-5
-------
Table L-l. Estimated Population Living Near the Tailings Pile at
Canon City, Colorado, June 1983
(Latitude 38O23'46"; Longitude 105O13'45")
Total Population (0.0-5.0 km): 5933
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
L
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0 2.0-3.0
- - 5
124
- - 39
_ _ _
_ _ _
_ _ _
_ «
- - -
_
- - 16
_ _ _
_
_
184
3.0-4.0
935
899
715
88
-
-
-
5
3
-
-
-
-
-
122
2,767
4.0-5.0
1158
715
303
52
-
-
-
~
8
-
-
-
-
47
699
2,982
- Indicates 0.
E-6
-------
Table E-2. Estimated Population Living Near the Tailings Pile at
Uravan, Colorado, June 1983
(Latitude 38<>22'N.; Longitude 105°45'W.)
Total Population (0.0-5.0 km): 349
Radial Distance (km)
Direction
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
w
WNW
NW
NNW
Total
0.0-0.5 0.5-1.0
45
77
- -
11
14
- -
-
-
_ _
- -
_
-
_ _
- -
- -
_ _
147
1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
108
9 - - -
_
- - - -
28
- 6 3 -
_
_ _ _ _
_
- - - -
_ _ _ _
_ _ _ _
_ _ _
48
193 b 3 -
- Indicates 0.
E-7
-------
Table E-3. Estimated Population Living Near the Tailings Pile at
Ambrosia Lake, New Mexico, June 1983
(Latitude 35O23'39"N.; Longitude 107O49'47"W.)
Total Population (0.0-5.0 km): 1
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE ______
NE ______
ENE ______
E - - -
ESE ______
SE ______
SSE ______
S ______
SSW ______
SW ______
WSW ______
W ---___
WNW ______
NW ______
NNW ___i__
Total ___!__
- Indicates 0.
E-8
-------
Table E-4. Estimated Population Living Near the Tailings Pile at
Bluewater, New Mexico, June 1983
(Latitude 35oi6'12"N.; Longitude 107°56'44"W.)
Total Population (0.0-5.0 km): 907
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SE
SE
S
ssw
sw
wsw
w
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0 2.0-3.0
_
- - -
_ _ _
_ _ _
_ _
38
- 6 29
41
- - 6
16
- - 3
- - 3
_ _ _
6 136
3.0-4.0
-
-
_
-
6
10
13
13
171
418
16
19
-
666
4.0-5.0
-
-
_
-
-
13
_
19
-
-
_
54
13
99
- Indicates 0.
E-9
-------
Table E-5. Estimated Population Living Near the Tailings Pile
at Church Rock, New Mexico, June 1983
(Latitude 35038'47"N.; Longitude 108°30'08"W.)
Total Population (0.0-5.0 km): 312
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0
N - -
NNE
NE - -
ENE
E - -
ESE
SE - -
SSE
s - -
SSW
sw - -
WSW
w -
WNW
NW - -
NNW - -
Total
1.0-2.0
7
-
-
-
_
-
-
7
-
-
4
-
-
7
25
2.0-3.0
-
-
-
_
-
4
4
15
4
7
-
11
7
52
3.0-4.0
15
19
7
_
7
11
4
22
-
-
-
-
85
4.0-5.0
-
-
-
15
19
19
22
41
19
15
_
-
-
-
150
- Indicates 0.
E-10
-------
Table E-6. Estimated Population Living Near the Tailings Pile
at Marquez, New Mexico, June 1983
(Latitude 35oi8'59"N.; Longitude 107O16'28"W.)
Total Population (0.0-5.0 km): 15
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE ______
NE ______
ENE ______
E ______
ESE ______
SE ______
SSE ______
S ______
SSW ______
SW ______
WSW ______
W 15
WNW ______
NW ______
NNW ______
Total 15
- Indicates 0.
E-ll
-------
Table E-7. Estimated Population Living Near the Tailings Pile
at Milan, New Mexico, June 1983
(Latitude 35Qi4'3i"N.; Longitude 107°51'46"W.)
Total Population (0.0-5.0 km): 396
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0
N - -
NNE
NE -
ENE
E - -
ESE
SE - -
SSE
S - -
SSW
SW -
WSW
W - -
WNW - -
NW -
NNW
Total
1.0-2.0
-
-
3
-
-
3
51
67
44
22
-
-
-
190
2.0-3.0 3.0-4.0 4.0-5.0
_ _ _
- 3 -
-
-i-
_
_ _
- - -
22
16 29 41
3-10
63 13 6
_ _ _
_
_
- - -
104 45 57
- Indicates 0.
E-12
-------
Table E-8. Estimated Population Living Near the Tailings Pile
at Seboyeta, New Mexico, June 1983
(Latitude 35oii'09"N.; Longitude 107O20'09"W.)
Total Population (0.0-5.0 km): 166
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
_
_
_ _ _ _ _
_
- - - - -
_____
_
_____
32 19
3b
10 70
- - - - -
42 124
- Indicates 0.
E-13
-------
Table E-9. Estimated Population Living Near the Tailings Pile
at Edgemont, South Dakota, June 1983
(Latitude 43oi7'43"N.; Longitude 103<>48'46"W.)
Total Population (0.0-5.0 km): 1,421
Radial Distance (km)
Direction
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
w
WNW
NW
NNW
Total
0.0-0.5 0.5-1.0
-
-
-
_ _
-
-
_ _
- -
-
3
18 20
10 18
-
-
31 38
1.0-2.0
5
3
-
-
_
-
-
-
_
-
20
63
306
612
83
33
1,125
2.0-3.0
8
5
3
_
3
-
_
-
-
-
58
94
-
171
3.0-4.0
8
-
_
3
3
3
_
-
3
_
8
-
-
28
4.0-5.0
10
-
_
-
-
-
3
5
_
-
10
-
28
- Indicates 0.
E-14
-------
Table E-10. Estimated Population Living Near the Tailings Pile
at Panna Maria, Texas, June 1983
(Latitude 28O57'33"N.; Longitude 97O56'31"W.)
Total Population (0.0-5.0 km): 453
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0
3
3
- -
9
9
6
6
6 9
3
- -
- -
_ _
-
-
12 42
2.0-3.0
-
-
6
12
3
-
_
-
-
6
3
-
3
33
3.0-4.0
-
6
21
9
-
_
6
3
12
15
6
3
81
4.0-5.0
.
9
3
18
68
-
3
6
24
6
9
13b
-
-
3
285
- Indicates 0.
E-15
-------
Table E-ll. Estimated Population Living Near the Tailings Pile
at Falls City, Texas, June 1983
(Latitude 28O54'03"N.; Longitude 98°05'40"W.)
Total Population (0.0-5.0 km): 42
Radial Distance (km.)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0
ME 3
NE 3 6
ENE _____
E _____
ESE _____
SE 3
SSE _____
S _____
SSW _____
SW 6
WSW _____
W 3
WNW _____
NW _____
NNW _____
Total 3 12 9
4.0-5.0
3
-
-
-'
3
b
6
-
-
_
-
-
-
18
- Indicates 0.
E-16
-------
Table E-12. Estimated Population Living Near the Tailings Pile
at Ray Point, Texas, June 19b3
(Latitude 28O3i'n"N.; Longitude 98<>06'05"W.)
Total Population (0.0-5.0 km): 130
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0
3
3
- -
6
9
-
-
- -
-
-
_ _
-
_
21
2.0-3.0
9
3
3
3
-
-
3
-
-
-
_
-
-
21
3.0-4.0
6
-
3
9
6
3
-
-
3
_
-
-
-
30
4.0-5.0
14
-
3
6
-
-
_
-
35
_
-
-
-
58
- Indicates 0.
E-17
-------
Table E-13. Estimated Population Living Near the Tailings Pile
at Blanding, Utah, June 1983
(^atitude 37<>31f 37"N., Longitude 109O30'33"W. )
Total Population (0.0-5.0 km): 8
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNL _____ 4
NE ______
ENE ______
y «,
ESE ______
SE ______
SSE _____ 4
S ______
ssw ______
sw ______
wsw ______
w ______
WNW ____--
NW ______
mv -_-_-_
Total _____ 8
- Indicates 0.
E-18
-------
Table E-14. Estimated Population Living Near the Tailings Pile
at Rio Algom Site, La Sal, Utah,
June 1983
(Latitude 38O16'N.; Longitude 109°16'30"W. )
Total Population (0.0-5.0 km): 343
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
w
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
53 85 12
8 28 57 - 40
4
-----
______
_____
_____
-----
_____
_____
_
-----
_____
4
4
20 12 16
8 105 154 32 44
- Indicates 0.
L-19
-------
Table E-15. Estimated Population Living Near the Tailings Pile
at Moab, Utah, June 1983
(Latitude 38O35'59"N.; Longitude 109O35'44"W.)
Total Population (0.0-5.0 km): 2361
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
-
_____
- 6 - - -
33--
9 674 668
420 557
-----
_ _ _
_____
_____
_____
_ _
_
21
_ _ _
- 9 33 1094 1225
- Indicates 0.
E-20
-------
Table E-16. Estimated Population Living Near the Tailings Pile
at hanksville, Utah, June 1^83
(Latitude 37°43'06"N.; Longitude 110°40'51"W.)
Total Population (0.0-5.0 km): 171
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE ______
NE ______
ENE ______
E ______
ESE ______
SE ______
SSE ______
S ______
SSW _____ !7]_
SVI ______
WSW ______
w ______
WNW ______
NW ______
NNW ______
Total ----- 171
- Indicates 0.
E-21
-------
Table E-17. Estimated Population Living Near the Tailings Pile
at Dawn Mill, Ford, Washington,
June 1983
(Latitude 47°54'06"N.; Longitude 117°49'58"W.)
Total Population (0.0-5.0 km): 411
Radial Distance (km)
Direction 0.0-0.5
N
NNE
NE
ENE
E
ESE
SL
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
0.5-1.0 1.0-2.0
20
20
15
29
3
- -
-
_ _
- -
_
-
_
- -
-
9
3 93
2.0-3.0
12
3
I*.
29
_
-
-
3
-
-
3
58
23
3
12
157
3.0-4.0
15
6
20
6
_
-
3
3
9
3
15
6
-
-
96
4.0-5.0
-
12
_
3
35
3
-
3
3
-
-
62
- Indicates 0.
E-22
-------
Table E-18. Estimated Population Living Near the Tailings Pile
at Wellpinit, Washington, June Ib»b3
(Latitude 47052 ' 27 "N. ; Longitude llb°07'00"W. )
Total Population (0.0-5.0 km): 49
___ Radial Distance (km) _
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE ______
NE ______
ENE ______
ESE - - - - 3 6
SE 3
SSE ______
S ______
SSW ----- 3
SW ______
WSW ----- 3
W 26
WNW _____ 5
^fW ______
NNW ______
Total - - - - 32 17
- Indicates 0.
E-23
-------
Table E-19. Estimated Population Living Near the Tailings Pile
at Powder River, Converse County, Wyoming, June 19b3
(Latitude 43<>05'N.; Longitude 105°30'W.)
Total Population (0.0-5.0 km): b
Radial Distance (km)
Direction 0.0-0.3 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.U
N 6
NNE ______
NE ______
ENE ______
E ______
ESE ______
SE ______
SSE ______
S ______
SSW ------
SW ______
WSW ------
W ------
WNW ______
NW ______
NNW ------
Total 6
- Indicates 0.
E-24
-------
Table E-20. Estimated Population Living Near the Tailings Pile
at Gas hills, (Federal American Partners)
Fremont County, Wyoming, June 1963
(Latitude 42O47'59"N.; Longitude 107O30'Ob"W.)
Total Population (0.0-5.0 km): 0
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE ______
NE ______
ENE ______
L" __ «.
ESE ______
SE ______
SSE ______
S ______
SSW ______
sw ______
wsw ______
w ______
VINW ______
NW ______
NNW ______
Total ______
- Indicates 0.
E-25
-------
Table E-21. Estimated Population Living Near the Tailings Pile
at Ked I/esert, Sweetwater County, Wyoming, June 1963
(Latitude 42O02'56"N.; Longitude 107°53'28"W.)
Total Population (O.U-5.0 km): 0
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ---___
NNE ______
NE ______
ENL ______
L ______
ESE ______
SE ______
SSE ______
S ______
SSW ______
SW ______
WSW ______
W ______
WHW ______
NW ______
NNW ______
Total ______
- Indicates 0.
E-26
-------
Table E-22. Estimated Population Living Near the Tailings Pile
(Pathfinder Mxnes) at Gas hills, Fremont County, Wyoming,
June 1983
(Latitude 42°49'55"N. , Longitude 1U7°29'23"W. ;
Total Population (0.0-5.0 km): 0
_ Radial Distance (.km) _
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-^.0 4.0-5.0
NNE
NE
ENE
T?
ESE
SE
SSE
S
SSW
SW
WSW
w
NW
NNW
Total
- Indicates 0.
E-27
-------
Table E-23. Estimated Population Living Near the Tailings Pile
(Pathfinder) at Shirley Basin, Carbon County, Wyoming, June 1983
(Latitude 42<>20'N.; Longitude 106°12'W.)
Total Population (0.0-5.0 km): 0
_ Radial Distance (km) __
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 A. 0-5.0
N --___-
NNE ______
NE ______
ENE
ESE ______
SE ______
SSE _____*
S ____**
SSW ___-**
SW __--**
WSW ___-_*
w ______
WNW ______
NW ______
NNW ____--
Total ______
- Indicates 0.
* Area covered by intersecting Petrotomics Shirley Basin Mill to the
South.
E-28
-------
Table E-24. Estimated Population Living Near the Tailings Pile
(Petrotomics) at Shirley Basin, Carbon County, Wyoming, June 1983
(Latitude 42O20'iM.; Longitude 10b°12'W.)
Total Population (0.0-5.0 km): 357
Radial Distance (km)
Direction
N
NNE
NE
ENE
E
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
HW
NNW
Total
0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
____**
____**
____**
_____*
______
______
______
------
17b
179
______
______
______
______
______
- 357
- Indicates 0.
* Area covered by intersecting Pathfinder Shirley Basin Mill to the
North.
E-29
-------
Table E-25. Estimated Population Living Near the Tailings Pile
(Rocky Mountain Energy) at Powder River, Converse County,
Wyoming, June 1983
(Latitude 43oi6'i>l.; Longitude 105O37'h.)
Total Population (0.0-5.0 km): 0
_ Radial Distance (km) _
Direction 0.0-0.5 0.5-1.0 l.U-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE _-__--
NE ______
ENE ______
ESE
SE
SSE
S
ssw
sw
wsw
w
WNW
NW
NNW
Total
- Indicates 0.
E-30
-------
Table E-26. Estimated Population Living Near the Tailings Pile
at UCC-Gas Hills, Natrona County, Wyoming, June 1983
(Latitude 42°49'45"N.; Longitude 107°2y'34"W. )
Total Population (0.0-5.0 km): 0
__ Radial Distance (km) _
Direction 0.0-0.5 0.5-1.0 1.0-2.0 2.0-3.0 3.0-4.0 4.0-5.0
N ______
NNE ______
Nh ______
ENE ______
ESE
SE
SSE
S
SSW
SW
WSW
W
WNW
NW
NNW
Total
- Indicates 0.
E-31
-------
Table E-27. Estimated Population Living Near the Tailings Pile
at Jeffrey City, Fremont County, Wyoming, June
(Latitude 42O30'32"N.; Longitude 107°47'14"W.)
Total Population (0.0-5.0 km): 906
Radial Distance (km)
Direction 0.0-0.5 0.5-1.0 1.0-2.0
N -
MNE -
NE -
ENE -
hSE - 3 -
SE -
SSE -
s -
ssw -
sw -
wsw -
W -
WNW -
NW -
NNW -
Total - 3 -
2.0-3.0 3.0-4.0 4.0-5.0
_ _ _
_
: : :
21 6 -
3-9
_ _ _
_
14U
551 167
_ ~ _
_
3 - -
3 - -
30 697 176
- Indicates 0.
E-32
-------
APPENDIX F
OTHER MINERAL RESOURCES
IN URANIUM MINING REGIONS
-------
APPENDIX F
OTHER MINERAL RESOURCES IN URANIUM MINING REGIONS
CONTENTS
Page
F. 1 Summary and Conclusions F-5
F.2 Introduction F-6
F.3 Uranium Resources F-6
F.4 Vanadium Resources F-7
F.5 Molybdenum Resources F-7
F .6 Fossil Fuel Resources F-8
F.6.1 Wyoming Basins F-8
F.6.1.1 Powder River Basin F-8
F.6.1.2 Great Divide Basin F-8
F.6.1.3 Shirley Basin F-9
F.6.1.4 Wind River Basin (Gas Hills) F-9
F. 6.2 Western Gulf Coastal Plain F-9
F.7 Other Mineral Resources F-9
F.8 Recreational and Other Activities F-10
F.9 Factors Relating to Mineral Production F-ll
References F-15
F-3
-------
APPENDIX F
OTHER MINERAL RESOURCES IN URANIUM MINING REGIONS
F.1 Summary and Conclusions
Many uncertainties are associated with predicting the continued
isolation of mill tailings piles that are now seemingly remote. Estimates
regarding the continued isolation of uranium mill tailings sites are
obviously speculative and will, therefore, provide only rough estimates to
address the issue.
By the beginning of the twenty-first century, we estimate that mill
tailings piles will be about three times as large as the 1982 volumes.
Possibly one-third of the sites will be relatively isolated. Fevelopment
of other mineral resources on or near the sites will affect population
growth and the degree to which the sites are isolated.
Metal resources that have potential development are those that are
mined as coproducts or byproducts of sedimentary uranium deposits, such as
vanadium and molybdenum. Vanadium resources are associated with uranium
production in the Colorado Plateau resource region. The volume of
vanadium ore mined at some of the current uranium mill sites as a
coproduct or byproduct is five times the volume of uranium ore. Any
increased demand for vanadium and molybdenum could reactivate existing
mills or result in development of these resources near existing uranium
mills.
Other metals such as copper, cobalt, nickel, tungsten, lead, zinc,
silver, and gold also occur within the uranium resource regions and
constitute potential resources that could affect population increases to
the region.
The Wyoming Basins and the Western Gulf Coastal Plain resource
regions contain fossil fuels, generally at greater depth, but within the
sedimentary rock sequence containing the uranium ore. Development of
coal, oil, and gas resources could affect population growth and the degree
of isolation of the tailings piles in these areas.
Potential solar energy expansion in the sun belt and increased
tourist and recreational facilities also influence the potential isolation
of the uranium tailings.
F-5
-------
F.2. Introduction
The purpose of this review is to focus on the probable mineral
developments that could occur in the future near the 27 uranium mill
tailings sites considered in this report. Qualitative judgments will be
based on (a) known reserves of other minerals in the area, (b) probable
mineral resources, based on reconnaissance information and geologic
setting, (c) the possibility of reactivating those uranium mills that have
closed or will close in the next few decades. The effect of recreational
or national park growth on the isolation of the sites is also an important
consideration but will not be part of the qualitative judgement made
regarding future minerals development near the uranium mill sites. The
likelihood of future minerals development at each of the 27 uranium mills
tailings sites is summarized in Table F-l. The qualitative rating
assigned will be considered in the following sections.
The uranium milss being considered are listed in Table F-l in
relation to their location within the uranium resource regions defined by
the Department of Energy (DOE80). This DOE classification is based on
geologic and physiographic characteristics and will simplify discussions
regarding other possible mineral development near the uranium mill sites.
F.3 Uranium Resources
The Colorado Plateau resource region contains most of the uranium
produced in the United States (DOE80). This region contains the Morrison
Formation of Jurassic age in the Grants Mineral Belt of New Mexico and
Uravan Mineral Belt of Utah and Colorado and the Chinli Formation of
Triassic age in Utah and Arizona. The uranium ore occurs in fluvial,
lenticular, cross-bedded, quartzose, or arkosic sandstones associated with
vanadium deposits which today are mined as a byproduct with the uranium
ore.The sandstones containing the uranium deposits are interbedded with
mudstones. The uranium deposits are believed to be transported by
groundwater as a leachate from granitic rocks or volcanic rock exposed
along the margins of the sedimentary basins to the deposition site.
Precipitation of the uranium into the pore spaces of the sandstone
probably occurred under reducing conditions.
The uranium deposits of the Wyoming Basins, Colorado and Southern
Rockies, Great Plains, and Western Gulf Coastal Plain Resource Regions are
similar to the Colorado Plateau resource region in being contained in
sedimentary sandstone formations. The uranium deposits of the Columbia
Plateau resource region are vein type deposits in fissures of the
crystalline bedrock from a primary source rock of nearby Cretaceous
plutons from the resource regions.
The production of uranium ore from the uranium resource regions will
depend on the use of nuclear power as an energy source in the future. At
the very least, uranium will be needed to fuel existing reactors until the
end of their lives. Thus, it is likely that the uranium industry'will
F-6
-------
recover somewhat from its currently depressed condition. While it is
difficult to project the relative contributions the United States and
other uranium producing nations will make to the demand, it is reasonable
to predict a continuing role for the U.S. uranium industry because of the
political stability and proven ability of the United States to produce
uranium (Na83). In this light, the reactivation potential of existing
uranium mills for uranium or uranium byproducts is considered reasonable
for all the uranium mill sites except the skeletonized or removed mills at
Edgemont, South Dakota, and Ray Point, Texas (Table F-l).
F.4. Vanadium Resources
The Colorado Plateau region and the Colorado and Southern Rockies
resource regions are the largest producers of vanadium in the
United States. In 1980, Colorado was the leading producer of vanadium,
with Utah second, and New Mexico fifth. Colorado vanadium is largely a
coproduct or byproduct of uranium production; it averages about 5 pounds
of vanadium oxide for each pound of uranium oxide (BM80).
In 1980 vanadium was produced at uranium mills in Canon City and
Uravan, Colorado, and at uranium mills in Moab and Blanding, Utah (Table
F-l). In New Mexico, vanadium production, although small, doubled in
value and almost doubled in quantity; the vanadium was recovered as a
byproduct of uranium output from uranium-vanadium ores mined in McKinley
County (BM80).
With the increased demand for vanadium in high-strength low-alloy
steels and superalloys by the aerospace industry and other applications,
the production of vanadium may possibly increase in the long term.
Uranium mills in which vanadium was previously a byproduct may be
reactivated, and more Colorado Plateau sites in the Morrison Formation
could also be developed. The long-term effect on population growth will
tend to decrease the isolation of mill tailings piles.
F.5. Molybdenum Resources
The Climax and Henderson, Colorado, mines and the Questa, New Mexico,
mine produced 70 percent of the total output of molybdenum in the
United States in 1980 (BM80). Most of the remainder was supplied as a
byproduct or coproduct of copper mining. A small amount, less than
0.3 percent, was produced as a byproduct from uranium ore at the Ambrosia
Lake uranium mill in the Grants Mineral Belt, McKinley County, New
Mexico. Molybdenum production as a byproduct is also a potential
consideration for some of the other uranium mills in Utah and Colorado.
Molybdenum is one of the metal ores that has potential resource
development near the two uranium mills at Ford, Washington (Dawn Mining
Company), and Wellpinit, Washington (Western Nuclear Corporation), in the
Columbia Plateau Resource Region.
F-7
-------
Molybdenum consumption and uses have gradually increased despite
fluctuations over the last 25 years, and the demand for molybdenum is
expected to continue in the long term.
F.6. Fossil Fuel Resources
F.6.1 Wyoming Basins
The Wyoming Basins contain thick sedimentary rock units that contain
considerable reserves of oil, gas, and coal deposits (DOE82a, DOE82b).
The basins were formed in Cretaceous time, and continental deposits of
Tertiary age were deposited on Paleozoic and Mesozoic sedimentary rock
units. The fossil fuel resources occur within the same vertical sequence
of sedimentary formations as the uranium deposits but from older geologic
formations of greater depth.
F.6.1.1 Powder River Basin
The Rocky Mountain Energy and Exxon uranium mill sites are located in
the Powder River Basin in Converse County, Wyoming. Oil and gas are
produced from Cretaceous sandstones located a few thousand feet below the
uranium-bearing Fort Union Formation of Tertiary age. Coal is produced
from the Fort Union and Wasatch Formation of Tertiary age.
Coal production is limited to one mine which fuels the Pacific Power
and Light Company power plant. The 3.5 million tons of coal mined
annually in Converse County is minor compared to that of Campbell County
(71 m tons), Sweetwater County (21 m tons), Carbon County (8 m tons), and
Lincoln County (5 m tons) (DOE82a). Although current use of coal is low
in Converse County, the mere fact that it has been developed can lead to
additional development and increasing population.
Oil and gas production in the Powder River Basin, however, is
significant with production in billions of barrels and with the likely
discoveries of large deposits in yet unexplored areas (NRC77). Oil is
produced about one mile east of the Rocky Mountain Energy Company uranium
mill. The population may increase with the growth of the oil and gas
production in this area.
F.6.1.2 Great Divide Basin
The Red Desert Uranium Mill of the Minerals Exploration Company is
located in the Great Divide Basin in Sweetwater County, Wyoming. Coal
reserves of this county are estimated at 700 million tons; however, the
deposits are low grade, high sulfur, subbituminous coal (NRC78). The
closest active coal mines are 50 miles away. Oil and gas production is
active in the area with the Bison Basin oil field 20 miles northwest and
the Siberian Ridge gas field 15 miles south (NRC78).
F-8
-------
While development of fossil fuel resources in this basin is not
expected to proceed as rapidly as in other Wyoming basins because of the
quality or quantity of the deposits, it is expected that in the long term
the tailings piles will be less isolated as a result of oil, gas, and coal
production.
F.6.1.3 Shirley Basin
The Pathfinder Mines Mill and Petrotomics Mill are located in the
Shirley Basin in Carbon County, Wyoming. The areas surrounding these
sites are generally large ranch areas and are sparsely populated.
Coal production in Carbon County in 1981 ranked third in the State of
Wyoming with 39 million tons of bituminous coal and 2.2 billion tons of
subbituminous coal (DOE82a). Seven active mines in the county had a
production of 8.6 million tons in 1981. The coal production anticipated
in the long term could be expected to increase the population in this
region and decrease the isolation of the tailings piles.
F.6.1.4 Wind River Basin (Gas Hills)
The Union Carbide Corporation, Pathfinder Mines, Western Nuclear, and
Federal American uranium mills are located in the Gas Hills region of the
Wind River Basin. Mesozoic and Paleozoic formations are important gas and
oil producers in this portion of the Wind River Basin (NRC77). Oil
reserves in Fremont County, where three mill sites are located, are
estimated to be about 60 x 10" bbl, but it is anticipated that oil
production will continue to slowly decline; natural gas production,
however, is expected to increase (NRC80).
Coal is no longer being mined in the Gas Hills area, and the
733 x 106 tons of subbituminous grade coal in Fremont County are not
strippable (NRC80). Coal production is, therefore, not considered a
viable economic potential for this part of the basin in the future.
F.6.2. Western Gulf Coastal Plain
The Falls City, Ray Point, and Panna Maria uranium mills are located
in the Western Gulf Coastal Plain of Texas, a region underlain by thick
sedimentary rock units ranging from Triassic to Tertiary in age. Limited
oil and gas reserves in this relatively dense rural area are not expected
to change the population density significantly in the long term.
F.7. Other Mineral Resources
The ten-year National Uranium Resource Evaluation (NURE) program for
uranium exploration was completed this year by the Department of Energy.
This program, in addition to searching for uranium concentrations,
reported on elements that are associated with uranium and serve as
indicators of uranium concentrations. These elements included molybdenum,
F-9
-------
sulphur, lead, arsenic, vanadium, zinc, copper, nickel, and cobalt, while
other elements such as gold, silver, tin, and tungsten, also tested for,
were analyzed for their own worth (Bo80). If mineral resources near
uranium sites are developed, the isolation of tailings piles could be
affected.
The Colorado Plateau and Colorado and Southern Rockies resource
regions contain areas of potential mineral resources. The uranium mills
at Blanding and Moab, Utah, currently produce copper as a byproduct
material (BM80).
The two uranium mills in the Columbia Plateau resource region are in
a mineralized area containing potential tungsten, molybdenum, silver,
copper, lead, and zinc resources. This area is currently being explored
for its resource potential.
In the Laramide Range to the west of the two uranium mills in the
Powder River Basin, Wyoming, there are indications of potential for
mineral production. Copper, chromium, iron, tungsten, asbestos, and
vermiculite deposits are reported from Pre-Cambrian rocks in the Laramide
Range, as well as traces of gold, silver, beryl, zinc, bismuth, and rare
earths, but the magnitude of these deposits has not been determined
(NRC78).
Wyoming ranked first in the nation in 1980 for production of trona
(sodium carbonate) and bentonite clay and fourth in production of iron
ore, and most of these resources are located in two of the counties
containing uranium mills (BM80). However, these resources probably will
have no influence on the degree of isolation of the tailings piles at
these mills, because of the large size of the counties and the locations
of these resources at appreciable distances from the uranium mills.
F.8. Recreational and Other Activities
Recreational activities and tourism in the scenic West will
undoubtedly affect the isolation of some of the uranium mill tailings
piles. Three of the mill sites are located in scenic southeastern Utah
and one is near the Black Hills area.
The Hanksville, Utah (Plateau Resources), uranium mill is located a
few miles from Lake Powell, a manmade lake on the Colorado River in
southeastern Utah (NRC79). In addition to this recreational area, the
Arches National Park, Canyonlands National Park, Natural Bridges National
Monument, and other unusual and historic sites of this area threaten the
isolation of tailings piles at La Sal, Utah (Rio Algom Corporation),
and Moab, Utah (Atlas Minerals), in the long term. At the Edgemont,
South Dakota (TVA), mill site, the growth of that town could conceivably
double by the mid-1980's as a result of its location near the Black Hills
(NRC81).
F-10
-------
F.9. Factors Relating to Mineral Production
The long term isolation of mill tailings piles depends on the
population growth of the region. An important factor controlling
population growth is the development of other mineral resources in uranium
mining regions.
The uranium mills may be reactivated by demands for uranium or the
metal coproducts or byproducts mined with uranium. The demand for
molybdenum and vanadium could activate at least four of the uranium
mills. Exploration discoveries of molybdenum, vanadium, and other metals
in the geologic formations of these regions could also result in future
production of mineral resources at or near these mill sites.
Coal production in Wyoming was more than 12 percent of the U.S.
production by tonnage in 1981 (TX)E82a) . Coal reserves in the Vyominp
Basins rn extensive, and Sweetwater and Carbon counties rank second and
third in coal production. The population near the tailings piles in these
counties will undoubtedly increase in the long term as a result of
expanding mining activities. Coal production in Converse County (Powder
River Basin) is limited to that needed by a local utility. While
production is expected to remain restricted to that use in the near term,
the abundance of low grade coal could become a resource of production in
the long term.
Gas and oil production is expected to increase in the Powder River
Basin, Great Divide Basin, and the Wind River Basin (Gas Hills) in the
future. While production of this resource moves less population into a
region than coal mining or mining of metals, the activities and production
of gas and oil will contribute to the reduction of the degree of isolation
of uranium tailings piles.
The NURE program has included testing for other metals in addition to
uranium, and other potential metal resources are known in the resource
regions listed in Table F-l. The region surrounding the two Washington
mills and the Laramide Range adjacent to Wyoming mill sites are examples
of potential production of these metals should further exploration prove
their potential.
The southeastern Utah area and Black Hills area may become less
isolated because of recreational and scenic attractions. As solar power
becomes established, these arid sites may become less isolated.
The foregoing factors suggest 'that mineral production is highly
probable in the future. The likelihood of future mineral production at
the 27 uranium mill sites is qualitatively assessed in Table F-l.
F-ll
-------
Table F-l. Potential Resource Development
Near Currently Licensed Uranium Mills
Location/
Owner
Pontential
reactiva-
tion of
mill
Resource Development
Fossil fuels , ,
Oil & Metals '
Gas Coal V Mo Other
Other(b)
activi-
ties
Likelihood
of Future
Minerals
Development
Colorado Plateau Resource Region
New Mexico
Ambrosia Lake
(Kerr-McGee Nuclear)
Bluewater
(Anaconda Minerals Co.)
Church Rock
(United Nuclear Co.)
Marquez
(Bokum Resources)
Milan
(Homestake Mining)
Seboyeta
(Sohio-Reserve)
Utah
Blanding
(Energy Fuels Nuclear)
Utah
Hanksville
(Plateau Resources)
Moab
(Atlas Minerals)
La Sal
(Rio Algom Corporation)
XXX
High
Low
Low
Low
Low
Low
High
High
High
High
See footnotes at end of table.
F-12
-------
Table F-l. Potential Resource Development
Near Currently Licensed Uranium Mills
(Continued)
Location/
Owner
Colorado
Uravan
(Union Carbide
Corporation)
Pontential
reactiva-
tion of
mill
X
Resource Development
Fossil
Oil &
Gas
fuels
Coal V
Metals
Mo Other
X
Colorado and Southern Rockies
Other(b)
activi-
ties
Resource
Likelihood
of Future
Minerals
Development
High
Region
Canon City
(Cotter Corporation)
Wyoming
Gas Hills
(Pathfinder Mines)
Gas Hills
(Union Carbide)
Wyoming
Gas Hills
(Federal-American
Partners)
Jeffrey City
(Western Nuclear)
Powder River
(Rocky Mountain Energy)
Powder River
(Exxon Minerals)
Red Desert
(Minerals Exploration
Company)
X X
Wyoming Basins Resource Region
High
High
High
Medium
Medi urn
High
High
High
See footnotes at end of table.
F-13
-------
Table F-l. Potential Resource Development
Near Currently Licensed Uranium Mills
(Continued)
Location/
Owner
Shirley Basin
(Pathfinder Mines)
Shirley Basin
Pontential
reactiva-
tion of
mill
X
X
Resource Development .
Fossil fuels , > Othervl
Oil & Metals activi-
Gas Coal V Mo Other ties
X *-
X
v Likelihood
of Future
Minerals
Development
High
High
(Petrotomics)
South Dakota
Edgemont
(Tennessee Valley Authority)
Texas
Falls City
(Conoco-Pioneer Nuclear)
Panna Maria
(Chevron Resources)
Ray Point
(Exxon (Susquehanna-
Western))
Washington
Ford
(Dawn Mining Company)
Wellpinit
(Western Nuclear)
Great Plains Resource Region
Western Gulf Coastal Plain Resource Region
Columbia Plateau Resource Region
Low
Medium
Medium
Medium
Medium
Medium
(a)y = Vanadium; Mo = Molybdenum; Other = copper, gold, silver, tungsten, cobalt,
nickel, lead, and zinc.
activities include recreational and tourist establishments.
F-14
-------
REFERENCES
BM80 Bureau of Mines, 1980, "Minerals Yearbook," Vol. II.
Bo80 Bolivar, S.L., 1980, "An Overview of the National Uranium
Resources Evaluation Hydrogeochemical and Stream Sediment
Reconnaissance Program," Open File Report GJBK-220(80), U.S.
Department of Energy, Grand Junction, Colorado, p. 24.
DOE80 Department of Energy, 1980, "An Assessment Report on Uranium in
the United States," Grand Junction Office Report GJO-lll(80).
DOE82a Department of Energy, 1982, "Coal Production," DOE/EIA-0118(81).
DOE82b Department of Energy, 1982, "U.S. Crude Oil, Natural Gas,
and Natural Gas Liquid Reserves," 1981 Annual Report,
DOE/EIA/0216C81).
Na83 Nash, J.T., 1983, "Nuclear Fuels," Geotimes, February 1983,
pp. 28-29.
NRC77 Nuclear Regulatory Commission, 1977, "Lucky Me Gas Hills Uranium
Mill," NUREG-0357.
NRC78 Nuclear Regulatory Commission, 1978, "Highland Uranium Solution
Mining Project," Exxon Minerals Company, Final EIS, NUREG-0489.
NRC79 Nuclear Regulatory Commission, 1979, "Draft Environmental Impact
Statement, Plateau Resources Limited, Shootering Canyon Uranium
Project," NUREG-0504.
NRC80 Nuclear Regulatory Commission, 1980, "Gas Hills Uranium Project,"
Final EIS, NUREG-0702.
NRC81 Nuclear Regulatory Commission, 1981, "Draft Environmental Impact
Statement Related to the Decommissioning of the Edgemont Uranium
Mill," NUREG-0846.
F-15
-------
APPENDIX G
THORIUM MILL TAILINGS
-------
APPENDIX G
THORIUM MILL TAILINGS
CONTENTS
Page
G.I Introduction G-5
G.2 Tailings Piles G-6
G.3 Thoron and its Immediate Decay Products G-6
G.4 Effects of Gamma Radiation from Tailings G-ll
G.5 Groundwater G-12
References G-13
TABLES
G-l Estimated Cover Thickness to Reduce Thoron Emissions to
20 pCi/m2s G-8
G-2 Regional Air Concentration for Radionuclides G-9
G-3 Regional Ground Surface Concentrations for Radionuclides .. G-10
G-4 Release Rates for Thorium Assessment G-10
G-5 Regional Individual Lifetime Risk of Fatal Cancer from
Radon-220 and Decay Products G-ll
G-6 Gamma Radiation Flux Density and Absorbed Dose Rate for the
Uranium and Thorium Series G-ll
FIGURES
G-l Thorium-232 Decay Series G-7
G-3
-------
0655H 7/12/83
Appendix G: THORIUM MILL TAILINGS
G.I Introduction
This Appendix discusses the potential pathways and health effects
which might be connected with thorium tailings piles. As noted in
Chapter 1, there are no large scale commercial thorium milling
operations now in existence, and there appears to be little potential
for future growth. Existing locations at which thorium byproduct
materials are present vary widely in nature and are not susceptible to
generic analysis. In addition, the ores have a wide range of thorium
content and may contain substantial amounts of thorium-232. All these
considerations make it difficult to define a "model" mill in the sense
of the uranium mill described in Chapter 4. Any analysis would be
extremely sensitive, for example, to the thorium content of the tailings
pile since its long half-life (14.1 billion years) would pose a threat
over extremely long periods as compared to its decay products which are
short-lived and essentially decay to negligible levels in about 35
years.
Thorium is found primarily in monazite ore which is an anhydrous
phosphate of the rare earths. Cerium and lanthanum oxides are
generally found in greatest abundance in monazite. Thorium oxide in
monazite is highly variable, ranging between 3 and 10 percent, but as
much as 31 percent has been reported (Me79, Dr58, Be59).
A description of a monazite processing method is included in
Kerr-McGee's "Stabilization Plan-License #STA583-West Chicago,
Illinois" (Ke79). The ore was ground and reacted with excess caustic
soda to separate the phosphate from the rare earths. Selective
dissolution with hydrochloric acid allowed separation of the thorium
from the rare earths. The rare earths were processed through solvent
extraction and, selectively, ion exchange. The thorium fraction, along
with some rare earths not requiring high purity, were processed through
a series of chemical steps using caustic soda, and chloride, fluoride,
and nitrate treatments. Further treatment was also given to produce
oxides of rare earths.
G-5
-------
In order to afford a direct comparison between uranium and thorium
tailings, we have elected to use as a base case a thorium tailings pile
which has physical characteristics similiar to those of the model mill
described in Chapter 4. Instances in which different physical
parameters are used are noted below.
G.2 Tailings Piles
Due to the diversity in thorium ores, content, and the purpose for
which it was processed, it is difficult to postulate a standard
configuration for a thorium mill tailings pile. However, if thorium is
to be mined commercially on a large scale, the milling processes should
be similiar to those involved in uranium milling. Most of the thorium
would be extracted, and the tailings pile would be comprised
predominantly of the radioactive decay products of the thorium series.
Figure G-l depicts the decay chain for this series. There are many
points of similiarity between the uranium and thorium series: both are
long-lived, naturally-occuring radionuclides; each, at one point in the
decay chain, produces a gaseous isotope of radon; the decay products of
both emit gamma radiation; and the decay products in both chains are
isotopes of the same chemical elements. The major difference between
the two series, from a radiological point of view, is the relatively
short half-lives of the decay products of the thorium series as
compared to those of the uranium series. Thus, as may be seen by
comparing Figures 3-2 and G-l, the hazard presented by thorium tailings
would be of much shorter duration if the thorium-232 content were small.
To make a direct comparison between uranium and thorium tailings,
we have assumed a thorium pile with the same basic specifications as
those given in Chapter 4 for the model uranium mill. The speci-
fications required for the thorium analysis are primarily those
regarding the meteorology and physical charateristics of the pile; this
does not fepresent a composite of existing thorium piles, most of which
are smaller, have higher decay product concentrations, and retain
appreciable amounts of thorium. Radiological differences occasioned by
the behaviour of thorium and its decay products are discussed in the
following sections. Since, the chemical elements in the thorium series
are identical to those in the uranium series, nonradiological
considerations would be similar to those discussed in the text.
G.3 Thoron and its Immediate Decay Products
One of the decay prducts in the thorium series is a gaseous
isotope of radon, radon-220, usually referred to as thoron to
distinguish it from the radon-222 of the uranium series. Since the
thoron is also a chemically inert gas, it can diffuse through the
tailings pile and be transported, with its decay products, through the
atmosphere. While the transport and decay processes are roughly
analogous to those of radon, the short half-lives of thoron (55.6
seconds) and its precursor, radium-224 (3.62 days) significantly affect
the nature of these processes.
G-6
-------
(DECAY MODE)
t
Polonium - 212
(298 nano
seconds)
Figure G-l. Thorium-232 Decay Series.
G--7
-------
A general expression for the thoron (or radon) source term (Ro81)
is
Q - R pb E A
where
R = radium-224 content (pCi/g)
Pb = bulk density (g/m^)
E = emanating power
A = decay constant for thoron
Since the same equation holds for radon ( A= 2.1xlO~6/sec), the
thoron ( x=l«25xlO~2/Sec) production rate will be in the same ratio
as the decay constants or nearly 6,000 times larger, for the same
radium density, than that for radon. The higher thoron production rate
is, however, offset by its shorter half-life since, once the thoron has
decayed, it no longer migrates freely through the tailings or cover
material. For example, the thoron flux at the surface of a bare
tailings pile containing 280 pCi/g of radium-224 is about 21,600 pCi/
m2s rather than the 280 pCi/m^s of radon for the same radium-226
density. The analytical techniques described in Section 8.3.1 may also
be used to determine the thickness of an earthen cover required to
attenuate the thoron flux. Based on the nominal thoron flux value
given above, some typical thoron reduction thicknesses are shown in
Table G-l.
Table G-l. Estimated Cover Thickness (in meters)
to Reduce Thoron Emissions to 20 pCi/m2s
Thoron Emission
from Tailings Percent Moisture Content of Cover
(pCi/m s) 6 8 10 12
10,000
20,000
30,000
40,000
0.0826
.0918
.0972
.1010
0.0637
.0708
.0750
.0779
0.0491
.0546
.0578
.0601
0.0379
.0421
.0446
.0463
The epidemiology and dosimetry of thoron and its decay products
have recently been reviewed by the International Commission on
Radiological Protection (ICRP81). They concluded that, because of the
short half-life of thoron and its first decay product, the radiation
hazard from the short lived progeny of thoron is normally well
represented by the potential alpha energy exposure of lead-212 and
bismuth-212. Based on this conclusion, the effective dose equivalent
for the thoron decay products is about one-third that of the short-lived
radon decay products.
G-8
-------
Effects of Thoron Emissions from Tailings Piles
Regional air concentrations for thoron and its decay products due
to atmospheric transport are shown in Table G-2 (ground surface
concentrations are in Table G-3). These were calculated using the
computer programs described in Chapter 5 and assuming the same
meteorology and physical characteristics described for the operational
phase of the model mill in Chapter 4. The source term is based on a
thoron surface flux, as given above, of 21,600 pCi/m^s which yields a
total emission rate of 3.39x10^ Ci/y (see Table G-4) from the bare
tailings pile. The calculated health impact for airborne thoron and
its decay products is shown in Table G-5. These risks are calculated
on the same basis as those described in Chapter 6. The risk due to
windblown tailings material has not been included in this table since
no information is available regarding possible particle size
distributions.
Table G-2. Regional Air Concentration (Ci/m3)
for RadionuclidesCa)
212,
Distance
(meters)
600
1000
2000
3000
4000
5000
10000
20000
(a Average:
Maximum :
Average
7.2E-9
1.1E-9
4.2E-11
2.6E-12
2.2E-13
2.1E-14
2.7E-19
1.5E-28
Rn
Maximum
1.5E-8
2.7E-9
1.2E-10
7.8E-12
6.6E-13
6.2E-14
8.3E-19
4.6E-28
value averaged over
value for direction
Pb ,
Average
1
4
1
5
3
2
8
2
all
of
.2E-10
.2E-11
.2E-11
.9E-12
.7E-12
.6E-12
.OE-13
.7E-13
Bi
Maximum
2.
7.
2.
1.
7.
5.
1.
5.
OE-10
4E-11
5E-11
2E-11
9E-12
5E-12
7E-12
9E-13
Tl
Average
4
1
4
2
1
9
2
9
.4E-11
.5E-11
.3E-12
.1E-12
.3E-12
.3E-13
.9E-13
.6E-14
Maximum
7
2
8
4
2
2
6
2
.IE -11
.7E-11
.9E-12
.5E-12
.8E-12
.OE-12
.2E-13
.1E-13
directions.
greatest risk.
Effects of Ground Deposited Decay Products of Thoron
Although the half-lives in the thoron series are shorter than those
of the uranium series, there is still a potential for ground deposition
and buildup of the thorium decay products. Regional ground
concentrations of these isotopes due to airborne deposition are given in
Table G-3. The corresponding health impact is included in Table G-5
which contains the external irradiation hazard due to both ground
deposition and airborne material. The ingestion pathway has been omitted
since it is negligible compared to the external pathway. No attempt has
G-9
-------
Table G-3. Regional Ground Surface Concentrations (Ci/m2)
for Radionuclides^a)
Distance
(meters)
600
1000
2000
3000
Average
1.3E-8
4.4E-9
1.3E-9
6.6E-10
Tb
Maximum
2.0E-8
7.8E-9
2.7E-9
1.4E-9
Bi
Average
1.4E-8
4.8E-9
1.4E-9
7.1E-10
Maximum
2.2E-8
8.5E-9
2.9E-9
1.5E-9
*v«T]
Average
4.9E-9
1.7E-9
5.2E-10
2.6E-10
L
Maximum
8.0E-9
3.1E-9
1.1E-9
5.5E-10
4000
5000
10000
20000
4.2E-10
3.0E-10
9.7E-11
3.4E-11
9.0E-10
6.4E-10
2.1E-10
7.6E-11
4.6E-10
3.2E-10
1.1E-10
3.7E-11
9.8E-10
7.0E-10
2.3E-10
8.2E-11
1.6E-10
1.2E-10
3.8E-11
1.3E-11
3.5E-10
2.5E-10
8.4E-11
3.0E-11
'Average: value averaged over all directions.
Maximum: value for direction of greatest risk.
Table G-4. Release Rates for Thorium Assessment
Nuclide
Release Rate
(Ci/y)
Radon-220
Lead-212
Bismuth-212
Thallium-208
3.39E+5
493.
493.
177.
G-10
-------
Table
Distance
(meters)
600
1000
2000
3000
4000
5000
10000
20000
(^Average:
Maximum :
G-5. Regional Individual Lifetime Risk of Fatal Cancer
from Radon-220 and Decay Products
Inhalation External Total
Average Maximum Average Maximum Average Maximum
7
2
6
3
2
1
4
1
.4E-3
.4E-3
.7E-4
.3E-4
.1E-4
.4E-4
.4E-5
.5E-5
1.2E-2
4.3E-3
1.4E-3
6.9E-4
4.4E-4
3.1E^
9 . 6E-5
3.3E-5
value averaged over
value for direction
4
1
4
2
1
9
3
1
all
of
.3E-5
.5E-5
.3E-6
.1E-6
.3E-6
.5E-7
.OE-7
.OE-7
6.
2.
8.
4.
2.
2.
6.
2.
9E-5
6E-5
8E-6
5E-6
9E-6
OE-6
5E-7
3E-7
7
2
6
3
2
1
4
1
.5E-3
.4E-3
.8E-4
.3E-4
.IE -4
.5E-4
.5E-5
.5E-5
1
4
1
7
4
3
9
3
.2E-2
.4E-3
.4E-3
.OE-4
.4E-4
.1E-4
.8E-5
.3E-5
directions .
greatest risk.
been made to calculate national impact since the short half-lives of
the thoron and daughter products should make this contribution
relatively small.
G.4 Effects of Gamma Radiation from Tailings
As noted in Section 6.2.3, gamma radiation exposure depends on the
proximity of individuals to the tailings pile as well as the distribu-
tion of windblown material. Individual doses can only be assessed on a
case-by-case basis since details on shielding and distance are critical
to the calculation. The remaining considerations noted in that Section
will, in general, hold true for thorium tailings. The thorium series,
however, has a higher gamma flux density than the uranium series. The
properties of the gamma radiation field at one meter above the ground
surface have been calculated for both series (NCRP75) and are shown in
Table G-6.
Table G-6. Gamma Radiation Flux Density and Absorbed Dose Rate for the
Uranium and Thorium Series
Radionuclide
Series
Ground
Concentration
(pCi/g)
Gamma Flux
Density
( Y/cm s)
Absorbed
Dose Rate
(mrad/y)
Uranium and
Decay Products
Thorium and
Decay Products
2.82
3.81
13.9
21.6
(a)uranium-238.
(b)Thorium-232.
G-ll
-------
The absorbed dose rates for the thorium series are seen to be about
fifty percent greater than those for the uranium series.
G.5 Groundwater
As with uranium mill tailings, the effect on groundwater of
thorium milling operations would be highly site specific and depend on
the ore constituents and beneficiation process. If the site character-
istics of the model mill are used, the radiological impact of the
thorium decay products would be negligible due to the short half-lives
of the decay products, the absence of nearby aquifers, and the long
transport times involved in movement through the environment. The
nonradiological impact, in the absence of detailed information on the
extraction process and ore constituents, would be expected to be
similiar to that for uranium tailings discussed in Section 6.4.
G-12
-------
REFERENCES
Be59 Berry L.G. and B. Mason, Mineralology, W.H. Freeman and Co.,
San Francisco, 1959.
Dr58 Dryden L., Monazite in Part of the Southern Atlantic Coastal
Plain, Geological Survey Bulletin 1042-L, U.S. Geological
Survey, 1958.
Me79 Mertie J.B., Jr., Monazite in the Granitic Rocks of the
Southeastern Atlantic StatesAn Example of the Use of Heavy
Minerals in Geologic Exploration, Geological Survey
Professional Paper 1094, U.S. Geological Survey, 1979.
Ke79 Kerr-McGee Chemical Corp., Plan for Decommissioning the
Factory Site and Stabilizing under License the Disposal Site
of the Kerr-McGee West Chicago Rare Earths Facility,
Kerr-McGee Chemical Corp., 1979.
ICRP81 International Commission on Radiological Protection, Limits
for Inhalation of Radon Daughters by Workers, ICRP-32,
Pergamon Press, Oxford, 1981.
NCRP75 National Council on Radiation Protection and Measurements,
Natural Background Radiation in the United States, NCRP-45,
NCRP, Washington, D.C., 1975.
Ro81 Rogers V.C. and K.K. Nielson, A Handbook for the Determination
of Radon Attenuation Through Cover Materials, NUREG/CR-2340,
RAE 18-1, PNL-4084, November 1981.
G-13
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA Report 520/1-83-008-1
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Final Environmental Impact Statement for Standards for
the Control of Byproduct Materials from Uranium Ore
Processing (40 CFR 192)
5. REPORT DATE
September 1983
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
U.S. Environmental Protection Agency
Office of Radiation Programs (ANR-460), Washington, D.C.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Environmental Protection Agency has issued health and environmental
protection standards for the control of uranium and thorium tailings during ore
processing operations and for final disposal. 'These standards will apply to tailings
licensed by the U.S. Nuclear Regulatory Commission and the States under Title II of
the Uranium Mill Tailings Radiation Control Act of 1978 (Public Law 95-604). This
Final Environmental Impact Statement examines health, environmental, technical, and
cost considerations and other factors important to developing the standards.
Volume II of this document contains the Agency responses to comments received
as a result of the public review that is part of the regulatory process.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
uranium mill tailings
radioactive waste disposal
radon radium thorium
hazardous constituents
Uranium Mill Tailings Radiation Control Act
Resource Conservation and Recovery Act
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Focm 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
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