Technical and Regulatory Support to Develop a 

Rulemaking to Potentially Modify the NESHAP 

Subpart W Standard for Radon Emissions from 

Operating Uranium Mills 

(40 CFR 61.250) 

U.S. Environmental Protection Agency 

Office of Radiation and Indoor Air 

1200 Pennsylvania Avenue, N.W. 

Washington, DC 20460 

February 2014 
 

TABLE OF CONTENTS 

Acronyms and Abbreviations ....................................................................................................... vii

1.0 Executive Summary .............................................................................................................1

1.1 Introduction, History, and Basis ..............................................................................1

1.2 The Uranium Extraction Industry Today .................................................................2

1.3 Current Understanding of Radon Risk .....................................................................3

1.4 Evaluation of Subpart W Requirements ..................................................................4

1.5 Economic Impacts ....................................................................................................5

2.0 Introduction, History, and Basis ..........................................................................................6

2.1 Document Contents and Structure ...........................................................................7

2.1.1 The Uranium Extraction Industry Today .....................................................7

2.1.2 Current Understanding of Radon Risk .........................................................8

2.1.3 Evaluation of Subpart W ..............................................................................8

2.1.4 Economic Impact Analysis ..........................................................................8

2.2 History of the Development of the Subpart W NESHAP ........................................9

2.2.1 The 1977 Amendments to the Clean Air Act .............................................11

2.2.2 Regulatory Activities between 1979 and 1987 ..........................................11

2.2.3 Regulatory Activities between 1987 and 1989 ..........................................13

2.2.4 1989 Radionuclide NESHAPs Reconsideration Rulemaking....................13

2.2.5 1990 Amendments to the Clean Air Act ....................................................14

2.3 Basis for the Subpart W 1989 Risk Assessment and Results ................................15

2.3.1 Existing Impoundments .............................................................................16

2.3.2 New Impoundments ...................................................................................17

3.0 The Uranium Extraction Industry Today: A Summary of the Existing and Planned 

Uranium Recovery Projects ...............................................................................................17

3.1 The Uranium Market ..............................................................................................18

3.2 Conventional Uranium Mining and Milling Operations ........................................21

3.2.1 Sweetwater Mill, Kennecott Mining Company, Red Desert, 

Wyoming....................................................................................................23

3.2.2 White Mesa Mill, Energy Fuels Corporation, Blanding, Utah ..................25

3.2.3 Shootaring Canyon Mill, Uranium One Incorporated, Garfield 

County, Utah ..............................................................................................28

3.2.4 Piñon Ridge Mill, Bedrock, Colorado .......................................................29

3.2.5 Conventional Mill Tailings Impoundments and Radon Flux Values ........30

3.3 In-Situ Leach Uranium Recovery (Solution Mining) ............................................31

3.3.1 Radon Emission from Evaporation and/or Holding Ponds ........................36

3.4 Heap Leaching .......................................................................................................38

3.4.1 Sheep Mountain Mine, Energy Fuels, Fremont County, Wyoming ..........40

3.5 Method 115 to Monitor Radon Emissions from Uranium Tailings .......................41

4.0 Current Understanding of Radon Risk ...............................................................................44
 

4.1 Radon and Dose Definitions ..................................................................................44

4.2 Radon Risk Factors ................................................................................................45

4.3 Computer Models...................................................................................................46

4.4 Uranium Recovery Facility Radon Dose and Risk Estimates ...............................47

4.5 Summary of Radon Risk ........................................................................................51

5.0 Evaluation of Subpart W Requirements ............................................................................51

5.1 Items Reviewed and Key Issues ............................................................................51

5.1.1 Existing and Proposed Uranium Recovery Facilities ................................52

5.1.2 RCRA Comparison ....................................................................................54

5.1.3 Regulatory History .....................................................................................55

5.1.4 Tailings Impoundment Technologies ........................................................55

5.1.5 Radon Measurement Methods ...................................................................56

5.1.6 Risk Assessment ........................................................................................60

5.2 Uranium Recovery Source Categories ...................................................................61

5.3 The GACT Standard ..............................................................................................61

5.4 Uranium Recovery Categories and GACT ............................................................63

5.5 Other Issues ............................................................................................................65

5.5.1 Extending Monitoring Requirements .........................................................65

5.5.2 Clarification of the Term “Operation” .......................................................66

5.5.3 Clarification of the Term “Standby” ..........................................................66

5.5.4 The Role of Weather Events ......................................................................67

6.0 Economic Impacts Associated with Revision/Modification of the Subpart W 

Standard .............................................................................................................................68

6.1 1989 Economic Assessment ..................................................................................69

6.1.1 Reducing Post-Closure Radon Emissions from 20 pCi/(m2-sec) ..............70

6.1.2 Reducing Radon Emissions During Operation of Existing Mills ..............71

6.1.3 Promulgating a Work Practice Standard for Future Tailings 

Impoundments ............................................................................................71

6.1.4 Economic Impacts ......................................................................................74

6.2 U3O8 Recovery Baseline Economics .....................................................................74

6.2.1 Conventional Mill Cost Estimate ...............................................................76

6.2.2 Heap Leach Facility Cost Estimate ............................................................79

6.2.3 In-Situ Leach (Long) Facility Cost Estimate .............................................81

6.2.4 In-Situ Leach (Short) Facility Cost Estimate .............................................83

6.2.5 Cost Estimate Sensitivities .........................................................................84

6.2.6 Annual Total U3O8 Cost Estimates ............................................................87

6.3 Economic Assessment of Proposed GACT Standards ...........................................90

6.3.1 Method 115, Radon Flux Monitoring ........................................................90

6.3.2 Double Liners for Nonconventional Impoundments .................................93

6.3.3 Maintaining 1 Meter of Water in Nonconventional Impoundments ........100

6.3.4 Liners for Heap Leach Piles .....................................................................105

6.3.5 Maintaining Heap Leach Piles at 30% Moisture .....................................108
 

6.3.6 Summary of Proposed GACT Standards Economic Assessment ............112

6.4 Environmental Justice ..........................................................................................115

6.4.1 Racial Profile for Uranium Recovery Facility Areas ...............................115

6.4.2 Socioeconomic Data for Uranium Recovery Facility Areas ....................117

6.5 Regulatory Flexibility Act ...................................................................................118

7.0 References ........................................................................................................................120

LIST OF TABLES 

Table 1: U3O8 Market Value and Cost to Produce (Nondiscounted)..............................................6

Table 2: Partial Timeline of EPA’s Radiation Standards ...............................................................9

Table 3: Conventional Uranium Mining and Milling Operations ................................................22

Table 4: Proposed New Conventional Uranium Milling Facilities ..............................................23

Table 5: Sweetwater Mill Radon Flux Testing Results ................................................................24

Table 6: White Mesa Mill’s Annual Radon Flux Testing, Tailings Cells 2 & 3 ..........................26

Table 7: Mill Tailings Impoundments and Average/Calculated Radon Flux Values* .................31

Table 8: Operating ISL Facilities ..................................................................................................33

Table 9: ISL Facilities That Are Restarting, Expanding, or Planning for New Operations .........34

Table 10: ISL Evaporation Pond Data Compilation .....................................................................35

Table 11: Anticipated New Heap Leach Facilities .......................................................................38

Table 12: Uranium Recovery Sites Analyzed ...............................................................................47

Table 13: Calculated Maximum Total Annual RMEI, Population Dose and Risk .......................49

Table 14: Calculated Average Total Annual RMEI, Population Dose and Risk ..........................49

Table 15: Dose and Risk to an Average Member of the Population ............................................50

Table 16: Current Pre-December 15, 1989 Conventional Impoundments ...................................53

Table 17: Radon Risk Resulting from Alternative Work Practices (Committed Cancers) ..........73

Table 18: Uranium Recovery Baseline Economics (Nondiscounted) ..........................................75

Table 19: Conventional Mill Cost Estimate ..................................................................................77

Table 20: Heap Leach Facility Cost Estimate ...............................................................................80

Table 21: In-Situ Leach (Long) Facility Cost Estimate ................................................................82

Table 22: In-Situ Leach (Short) Facility Cost Estimate ................................................................84

Table 23: Uranium Ore Grade ......................................................................................................85

Table 24: U3O8 Market Value and Cost to Produce (Nondiscounted) ..........................................85

Table 25: Assumed Case 4 U3O8 Production Breakdown by Mine Type .....................................89

Table 26: Case 4 (Mixed Uranium Recovery Facilities) Economic Projections 

(Nondiscounted) ........................................................................................................89

Table 27: Data Used to Develop Method 115 Unit Costs ............................................................92

Table 28: Method 115 Unit Costs .................................................................................................92

Table 29: Geomembrane (HDPE) Liner Unit Costs .....................................................................94
 

Table 30: Drainage Layer (Geonet) Unit Costs ............................................................................94

Table 31: Geosynthetic Clay Liner (GCL) Unit Costs .................................................................95

Table 32: Nonconventional Impoundment Areas .........................................................................96

Table 33: Base Facility Nonconventional Impoundment Double Liner Capital and 

Installation Costs .......................................................................................................97

Table 34: Mean Base Facility Nonconventional Impoundment Double Liner Capital and 

Installation Cost Breakdown .....................................................................................97

Table 35: Projected Nonconventional Impoundment Double Liner 

Annualized Capital and Installation Costs ................................................................98

Table 36: Base Facility Nonconventional Impoundment Double Liner Annual 

Operation and Maintenance Costs .............................................................................98

Table 37: Projected Nonconventional Impoundment Double Liner 

Annual Operation and Maintenance Costs ................................................................99

Table 38: Projected Nonconventional Impoundment Double Liner Total Annual Costs .............99

Table 39: Comparison of Double Liner to Total U3O8 Production Costs .....................................99

Table 40: Makeup Water Unit Costs ..........................................................................................102

Table 41: Summary of Base Facility Characteristics ..................................................................103

Table 42: Base Facility Annual Makeup Water Cost .................................................................103

Table 43: Base Facility Makeup Water Cost per Pound of U3O8 ...............................................103

Table 44: Projected Annual Makeup Water Cost .......................................................................104

Table 45: Comparison of Cost to Maintain 1 Meter of Water in the Impoundments to Total 

U3O8 Production Cost ..............................................................................................104

Table 46: Annual Dose and Risk Reduction from Maintaining 1 Meter of Water in the 

Impoundments .........................................................................................................105

Table 47: Heap Pile Double Liner Capital and Installation Costs ..............................................107

Table 48: Mean Heap Pile Double Liner Capital Cost Breakdown ............................................107

Table 49: Heap Pile Double Liner Annual Costs ........................................................................108

Table 50: Heap Pile Annual Makeup Water Cost .......................................................................110

Table 51: Projected Annual Heap Pile Makeup Water Cost .......................................................111

Table 52: Annual Dose and Risk Comparison for Maintaining 30% Moisture Content in 

the Heap Pile ............................................................................................................111

Table 53: Proposed GACT Standards Costs per Pound of U3O8 ................................................112

Table 54: Proposed GACT Standards Reference Facility Annual Costs ....................................113

Table 55: Proposed GACT Standards National Annual Costs ...................................................113

Table 56: Proposed GACT Standards Summed National Costs .................................................114

Table 57: Racial Profile for Uranium Recovery Facility Counties .............................................116

Table 58: Regional and National Racial Profiles ........................................................................116

Table 59: Socioeconomic Data for Uranium Recovery Facility Counties .................................117
 

LIST OF FIGURES 

Figure 1: Historical Uranium Prices .............................................................................................19

Figure 2: Uranium Production and Demand from 1945 to 2005 ..................................................20

Figure 3: Uranium Supply Scenario from 2008 to 2030 ...............................................................20

Figure 4: Typical Conventional Uranium Mill .............................................................................21

Figure 5: Sweetwater – Aerial View .............................................................................................24

Figure 6: White Mesa – Aerial View ............................................................................................26

Figure 7: Shootaring Canyon – Aerial View ................................................................................28

Figure 8: Piñon Ridge – Aerial View ...........................................................................................30

Figure 9: In-Situ Leach Uranium Recovery Flow Diagram .........................................................32

Figure 10: Typical Heap-Leaching Uranium Recovery Facility ..................................................40

Figure 11: Sheep Mountain – Aerial View ...................................................................................41

Figure 12: Uranium Decay Series .................................................................................................44

Figure 13: Diffusion Coefficient as a Function of Moisture Saturation .......................................57

Figure 14: Emanation Coefficient as a Function of Moisture Content and Moisture 

Saturation ...................................................................................................................59

Figure 15: Radon Flux as a Function of Moisture Saturation and Moisture Content ...................60

Figure 16: U.S. Average Annual Precipitation .............................................................................67

Figure 17: U.S. Mean Annual Evaporation ..................................................................................68

Figure 18: Estimated Cash Balance – Reference Cases ................................................................78

Figure 19: Cumulative U3O8 Projections – Reference Cases .......................................................79

Figure 20: Estimated Cash Balance – Sensitivity Cases ...............................................................86

Figure 21: Cumulative U3O8 Projections – Sensitivity Cases ......................................................87

Figure 22: Nuclear-Generated Electricity Projections ..................................................................88

Figure 23: U.S. and Foreign Contribution to U3O8 Purchases ......................................................90

Figure 24: Typical Double-Lined Impoundment with Leak Collection Layer .............................93

Figure 25: Typical Double Liner Anchor System .........................................................................96

Figure 26: Typical Heap Pile Liner ............................................................................................106
 

ACRONYMS AND ABBREVIATIONS 

ACE Army Corps of Engineers 

AEA Atomic Energy Act 

AIRDOS AIR DOSe 

ALARA as low as reasonably achievable 

AMC American Mining Congress 

ANPR Advance Notice of Proposed Rulemaking 

BaCl2 barium chloride 

BEIR Biological Effects of Ionizing Radiation 

BID background information document 

CAA Clean Air Act 

CAP88 Clean Air Act Assessment-1988 

CFR Code of Federal Regulations 

CHP certified health physicist 

Ci/yr curies per year 

cm centimeter 

cm/sec centimeter per second 

cm2/sec square centimeter per second 

CPI consumer price index 

CPP Central Processing Plant 

DARTAB Dose And Risk TABulation 

DOE Department of Energy 

EDF Environmental Defense Fund 

EIA Energy Information Administration 

EIS environmental impact statement 

EPA Environmental Protection Agency 

E-PERM Electric Passive Environmental Radon Monitor 

FGR Federal Guidance Report 

FR Federal Register 

ft feet 

g/cc gram per cubic centimeter 

G&A general and administrative 
 

GACT generally available control technology 

GCL geosynthetic clay liner 

GHG Greenhouse Gas 

gpm gallons per minute 

gpm/ft2 gallons per minute per square foot 

H2SO4 sulfuric acid 

HAP hazardous air pollutant 

HDPE high-density polyethylene 

HRTM Human Respiratory Tract Model 

ICRP International Commission on Radiological Protection 

in/yr inches per year 

ISL in-situ leach 

ISR in-situ recovery 

km kilometer 

L liter 

LAACC large-area activated charcoal collector 

lb pound 

LCF latent cancer fatalities 

L/d liters per day 

LLDPE linear low-density polyethylene 

LoC line of credit 

m2

 square meters 

m3

/hr cubic meters per hour 

m/sec meters per second 

MACT maximum achievable control technology 

MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual 

mi mile 

MIR maximum individual risk 

mph miles per hour 

mrem millirem 

mSv millisievert 

N.C. not calculated 

NESHAP National Emission Standard for Hazardous Air Pollutants 
 

N.G. not given 

NMA National Mining Association 

NRC Nuclear Regulatory Commission 

NRDC Natural Resources Defense Council 

O&M operation and maintenance 

ORISE Oak Ridge Institute for Science and Education 

pCi picocurie 

pCi/(ft2

-sec) picocurie per square foot per second 

pCi/g picocurie per gram 

pCi/L picocurie per liter 

pCi/(m2-sec) picocurie per square meter per second 

PIPS passive implanted planar silicon 

POO Plan of Operation 

PVC polyvinyl chloride 

R&D research and development 

Ra radium 

RADRISK RADiation RISK 

RCRA Resource Conservation and Recovery Act 

rem roentgen equivalent in man 

RMEI reasonably maximally exposed individual 

Rn radon 

RSO radiation safety officer 

SC Sierra Club 

SF square foot 

tpd tons per day 

U uranium 

U3O8 triuranium octoxide 

UMTRCA Uranium Mill Tailings Remedial Control Act 

WCS Waste Control Specialists, LLC 

WL working level 

WLM working level month 

ZnS(Ag) silver doped zinc sulfide 
 1 

1.0 EXECUTIVE SUMMARY 

The purpose of this report is to present the reader with an understanding of the facilities being 

regulated under this National Emission Standard for Hazardous Air Pollutant (NESHAP). The 

report also presents the technical bases that the Environmental Protection Agency (EPA or the 

Agency) has used for evaluating the risks from existing facilities and for determining that the 

prescribed work practice standards represent generally available control technology (GACT), as 

required by section 112(d) of the 1990 amendments to the Clean Air Act (CAA). 

The Agency is also defining the scope of its review of the Subpart W NESHAP to include the 

waste impoundments at in-situ leach (ISL) uranium recovery facilities and heap leach recovery 

operations, since all post-1989 impoundments, which potentially contain uranium byproducts, 

are considered to be under the NESHAP. The Agency has defined the scope of the review to 

include regulation of the heap leach pile, as it believes the pile contains byproduct material 

during operations. 

1.1 Introduction, History, and Basis 

After a brief introduction, this report describes the events that led the Agency to promulgate a 

NESHAP for radon emissions from operating uranium mill tailings on December 15, 1989, in 

Section 40 of the Code of Federal Regulations (40 CFR) Part 61, Subpart W. The 1977 

amendments to the CAA include the requirement that the Administrator of EPA determines 

whether radionuclides should be regulated under the act. In December 1979, the Agency 

published its determination in the Federal Register (FR) that radionuclides constitute a 

hazardous air pollutant (HAP) within the meaning of section 112(a)(1). In 1979, the Agency also 

developed a background information document (BID) to characterize “source categories” of 

facilities that emit radionuclides into ambient air, and in 1983, EPA proposed radionuclide 

NESHAPs for four source categories based on the results reported in a new BID. On 

September 24, 1986, the Agency issued a final NESHAP for operating uranium mill tailings, 

establishing an emission standard of 20 picocuries per square meter per second (pCi/(m2

-sec)) 

for radon (Rn)-222 and a work practice standard requiring that new tailings be disposed of in 

small impoundments or by continuous disposal. Between 1984 and 1986, the Environmental 

Defense Fund (EDF), the Natural Resources Defense Council (NRDC), the Sierra Club (SC), and 

the American Mining Congress (AMC) filed various court petitions seeking modifications to the 

NESHAPs. 

In a separate decision, the U.S. District Court for the District of Columbia outlined a two-step 

decision process that it would find acceptable, first establishing a standard based solely on an 

acceptable level of risk, and then considering additional factors, such as costs to establish the 

“ample margin of safety.” 

Section 112(q)(1) of the 1990 CAA Amendments requires that certain emission standards shall 

be reviewed, and if appropriate, revised to comply with the requirements of section 112(d). 

Subpart W is under review/revision in response to that requirement. Section 112(d) of the 1990 

CAA Amendments lays out requirements for promulgating technology-based emissions 

standards for new and existing sources. In accordance with section 112(d), the Administrator has 
 2 

elected to promulgate standards that provide for the use of GACT or management practices to 

regulate radon emissions from uranium recovery facility tailings impoundments noted in 

Subpart W. 

1.2 The Uranium Extraction Industry Today 

From 1960 to the mid-1980s, there was considerable uranium production in the states of 

Colorado, Nebraska, New Mexico, South Dakota, Texas, Utah, Wyoming, and Washington. In 

the early years, the uranium recovery industry consisted of mines (open pit and underground) 

that were associated with conventional uranium milling operations. Because of overproduction, 

the price of uranium rapidly declined in the 1980s. The declining uranium market could not 

support the existing number of uranium recovery operations, and many of the uranium recovery 

facilities in the United States were closed, decommissioned, and reclaimed. In the mid- to late 

1980s, several uranium recovery projects employing the solution, or ISL, mining process came 

on line. However, because of a need for clean energy, a need to develop domestic sources of 

energy, and other reasons, current forecasts predict growth in the U.S. uranium recovery industry 

over the next decade and continuing into the future. 

Conventional uranium mining and milling facilities are one of two types of uranium recovery 

facilities that currently possess state or federal licenses to operate. Representative of the extent of 

the conventional uranium milling operations that currently exist and are licensed in the United 

States are the mills at Sweetwater, Wyoming; Shootaring Canyon, Utah; and White Mesa, Utah. 

Only the White Mesa mill is currently in operation. A conventional mill at Piñon Ridge, 

Colorado, is currently in the planning and licensing stage. Additionally, a total of six potentially 

new conventional mill facilities are being discussed in New Mexico, Wyoming, Utah, and 

Arizona. 

The radon data for the conventional mill tailings impoundments indicate that the radon 

exhalation rates from the surfaces are generally within the Subpart W standard of 

20 pCi/(m2

-sec), but occasionally the standard may be exceeded. When that occurs, the tailings 

are usually covered with more soil, and the radon flux is reduced. 

Solution, or ISL, mining is defined as the leaching or recovery of uranium from the host rock by 

chemicals, followed by recovery of uranium at the surface. ISL mining was first conducted in 

Wyoming in 1963. The research and development projects and associated pilot projects in the 

1980s demonstrated solution mining to be a viable uranium recovery technique. Ten ISL 

facilities are currently operating (see Table 8, page 33), and about 23 other facilities are 

restarting, expanding, or planning for new operations. 

Uranium is leached into solution through the injection into the ore body of a lixiviant. A lixiviant 

is a chemical solution used to selectively extract (or leach) uranium from ore bodies where they 

are normally found underground. The injection of a lixiviant essentially reverses the geochemical 

reactions that are associated with the uranium deposit. The lixiviant ensures that the dissolved 

uranium, as well as other metals, remains in solution while it is collected from the mining zone 

by recovery wells. 
 3 

During typical solution mining, a portion of the lixiviant is bled off in order to control the 

pressure gradient within the wellfield. The liquid bled from the lixiviant is sent to an evaporation 

pond, or impoundment. Since radium (Ra)-226 is present in the liquid bled from the lixiviant, 

radon will be generated in and released from the ISL’s evaporation/holding ponds/

impoundments. The amount of radon released from these evaporation/holding ponds has been 

estimated and found to be small. (See Section 3.3.1.) 

Heap leaching is a process by which chemicals are used to extract the economic element (for the 

purposes of Subpart W, uranium) from the ore. A large area of land is leveled with a small 

gradient, and a liner and collection system are installed. Ore is extracted from a nearby surface or 

underground mine and placed in heaps atop the liner. A leaching agent (usually an acid) will then 

be sprayed on the ore. As the leaching agent percolates through the heap, the uranium is 

mobilized and enters the solution. The solution will flow to the bottom of the pile and then along 

the gradient into collecting pools, from which it will be pumped to an onsite processing plant. In 

the past, a few commercial heap leach facilities operated but none is now operating. Planning 

and engineering have been undertaken for two heap leach facilities, one in Wyoming and the 

other in New Mexico. 

A brief review of Method 115, “Monitoring for Radon-222 Emissions” (40 CFR 61, 

Appendix B) (SC&A 2008), demonstrated that its use can still be considered current for 

monitoring radon flux from conventional uranium tailings impoundments. It is not an option for 

measuring radon emissions from evaporation or holding ponds because there is no solid surface 

on which to place the monitors. 

1.3 Current Understanding of Radon Risk 

A description of how the understanding of the risk presented by radon and its progeny has 

evolved since the 1989 BID was published examines three parameters: (1) the radon progeny 

equilibrium fraction, (2) the epidemiological risk coefficients, and (3) the dosimetric risk 

coefficients. Additionally, SC&A (2011) used the computer code CAP88 version 3.0 (Clean Air 

Act Assessment Package-1988) to analyze the radon risk from eight operating uranium recovery 

sites, plus two generic sites. 

The lifetime (i.e., 70-year) maximum individual risk (MIR)1

 calculated using data from eight 

actual uranium recovery sites was determined to be between 2.45×10-5 to 2.59×10-4. The low end 

of the range is lower than the 3×10-5 lifetime MIR reported in the 1989 rulemaking for existing 

impoundments, while the high end of the range is slightly higher than the 1.6×10-4 lifetime MIR 

reported in the 1989 rulemaking for new impoundments. (SC&A 2011) 

To protect public health, EPA strives to provide the maximum feasible protection by limiting 

radon exposure to a lifetime MIR of approximately 1 in 10 thousand (i.e., 10-4). Although the 

calculated high end of the lifetime MIR range is above 10-4, there are several mitigating factors. 

First, the highest MIR was calculated for a hypothetical mill at an eastern generic site. If an 

actual mill were to be located at the Eastern Generic site, it would be required to reduce its radon 

 1

 In this BID all risks are presented as mortality risks. If it is desired to estimate the morbidity risk, simply 

multiply the mortality risk by 1.39. 
 4 

emissions as part of its licensing commitments. Also, the assumptions that radon releases occur 

continuously for 70 years and that the same reasonably maximally exposed individual (RMEI) is 

exposed to those releases for the entire 70 years are very conservative. 

Likewise, the risk assessment estimated that the risk to the population from all eight real uranium 

sites is between 0.0005 and 0.0009 fatal cancers per year, or approximately one case every 1,080 

to 1,865 years to the 1.8 million persons living within 80 kilometers (km) of the sites. For the 

1989 rulemaking, the estimated annual fatal cancer incidence to the 2 million people living 

within 80 km (50 miles) was 0.0043, which was less than one case every 200 years, for existing 

impoundments and 0.014, or approximately one case every 70 years, for new impoundments. 

1.4 Evaluation of Subpart W Requirements 

EPA has determined that radon releases from uranium recovery facilities are HAPs, as defined 

by the CAA. Furthermore, no radionuclide (including radon) releases have met the CAA’s 

definition of major sources, and thus radon releases from uranium recovery facilities are 

classified as area sources. (See Section 5.3.) Under section 112(d) of the CAA, the EPA 

Administrator may elect to promulgate standards or requirements applicable to area sources that 

provide for the use of GACTs or management practices to reduce emissions of HAPs. For the 

four source categories of radon releases from uranium recovery facilities, the Administrator has 

elected to promulgate GACTs as follows: 

Conventional Impoundments – Constructed on or before December 15, 1989 

GACT The flux standard of 20 pCi/(m2

-sec) contained in the current 40 CFR 61.252(a) 

will no longer be required; require that these conventional impoundments be 

operated to meet one of two work practices: phased disposal and continuous 

disposal, contained in the current 40 CFR 61.252(b). 

Conventional Impoundments – Constructed after December 15, 1989 

GACT Retain the standard that conventional impoundments be designed, constructed, 

and operated to meet one of two work practices: phased disposal and continuous 

disposal, contained in the current 40 CFR 61.252(b). 

Nonconventional Impoundments – Where uranium byproduct material (i.e., tailings) are 

contained in ponds and covered by liquids 

GACT Retain the design and construction requirements of 40 CFR 192.32(a)(1), with no 

size/area restrictions, and require that during the active life of the pond, at least 

1 meter of liquid be maintained in the pond. 
 5 

Heap Leach Piles 

GACT Retain the design and construction requirements of 40 CFR 192.32(a)(1), and 

require that the moisture content of the operating heap be maintained at or greater 

than 30 percent. 

Additionally, the analyses provided in this BID support the following findings: 

 Subpart W continues to be the appropriate regulatory tool to implement the 

Administrator’s duty under the CAA for operating uranium mill tailings. 

 By requiring that conventional impoundments be designed, constructed, and operated to 

meet one of two 40 CFR 61.252(b) work practices (i.e., phased disposal and continuous 

disposal), adoption of an emission limit (e.g., 20 pCi/(m2

-sec)) is not necessary to protect 

public health. 

 The requirement that conventional impoundments use either phased or continuous 

disposal technologies is appropriate to ensure that public health is protected with an 

ample margin of safety, and is consistent with section 112(d) of the 1990 CAA 

Amendments that require standards based on GACT. 

 The standard should be clarified to ensure that all owners and operators of uranium 

recovery facilities (conventional mills, ISL, and heap leach) are aware that all of the 

structures/facilities they employ to manage uranium byproduct material (i.e., tailings) are 

regulated under Subpart W. 

1.5 Economic Impacts 

The economic impact analysis to support any potential revision of the Subpart W NESHAP is 

presented in four distinct areas: 

(1) A review and summary of the original 1989 economic assessment and supporting 

documents are provided. 

(2) The baseline economic costs for development of new conventional mills, ISL facilities, 

and heap leach facilities are developed and presented. 

(3) The anticipated costs to the industries versus the environmental and public health benefits 

to be derived from each of the four proposed GACTs are discussed. 

(4) Finally, information is provided on the economic impacts to disadvantaged and tribal 

populations and on environmental justice. 

The baseline costs were estimated using recently published cost data for actual uranium recovery 

facilities. For conventional mills, data from the proposed new mill at the Piñon Ridge project in 

Colorado were used. Data from two proposed new ISL facilities were used; the first was the 

Centennial Uranium project in Colorado and the second was the Dewey-Burdock project in 

South Dakota. The Centennial project is expected to have a 14 to 15-year production period, 
 6 

which is a long duration for an ISL facility, while the Dewey-Burdock project is expected to 

have a shorter production period of about 9 years, which is more representative of ISL facilities. 

For the heap leach facility, data from the Sheep Mountain project in Wyoming were used. Table 

1 summarizes the unit cost (dollars per pound) estimates for all four uranium recovery facilities. 

As shown, on a unit cost basis, heap leach facilities are projected to be the least expensive, and 

the two ISL facilities the most expensive. 

Table 1: U3O8 Market Value and Cost to Produce 

(Nondiscounted) 

Average U3O8 Price ($/lb) $65.00

Average U3O8 Cost ($/lb) w/ LoC w/o LoC

Conventional $51.56 $47.24

ISL (Long) $53.89 $51.81

ISL (Short) $52.49 $51.46

Heap Leach $46.08 $42.87

Because the four proposed GACTs are not expected to change the manner in which any of the 

uranium recovery facilities are designed, built, or operated, no additional economic benefits or 

costs are associated with the proposed Subpart W revisions. 

At 10 of the 15 existing or proposed uranium recovery sites analyzed, the percentage of Native 

Americans in the population exceeds the national norm, while at nine sites, the percentage of 

Native Americans in the population exceeds the regional norm. At 11 of the 15 sites, the 

percentage of the population that is white exceeds both the national and regional norms. Finally, 

the percentage of the population at all uranium recovery sites that is either African-American or 

Other is less than the national norm, while the percentage of African-Americans and Others is 

less than the regional norm at all but one site. The analysis found that uranium recovery facilities 

are located in areas that are very poor (i.e., ranked in the lowest 0.6% in the country) to areas that 

are more economically advantaged (i.e., ranked in the 91.2 percentile). Six of the 15 sites are 

located in areas that have per capita nonfarm wealth that is above the United States’ 50th

percentile. On the other hand, five sites are located in areas where the per capita nonfarm wealth 

is below the country’s 10th percentile. 

2.0 INTRODUCTION, HISTORY, AND BASIS 

On December 15, 1989, EPA promulgated a NESHAP for radon emissions from operating 

uranium mill tailings (40 CFR 61, Subpart W). Section 112(q) of the CAA, as amended, requires 

EPA to review, and if appropriate, revise or update the Subpart W standard on a timely basis 

(within 10 years of passage of the CAA Amendments of 1990). Soon after the original 

promulgation of the standard, the uranium industry in the United States declined dramatically. 

However, recent developments in the market for uranium have led to some companies expressing 

their intention to pursue licensing of new facilities, and therefore, EPA is reviewing the necessity 

and adequacy of the Subpart W regulations before these proposed facilities become operational. 
 7 

Two separate standards are defined in Subpart W. The first states that existing sources (facilities 

constructed before December 15, 1989) must ensure that emissions to the ambient air from an 

existing uranium mill tailings pile shall not exceed 20 pCi/(m2

-sec) or 1.9 picocuries per square 

foot per second (pCi/(ft2

-sec)) of Rn-222. To demonstrate compliance with this emission 

standard, facilities are required to monitor emissions in accordance with Method 115 of 40 CFR 

61, Appendix B, and file an annual report with EPA showing the results of the compliance 

monitoring. The second Subpart W standard prescribes that for new sources (facilities 

constructed on or after December 15, 1989), no new tailings impoundment can be built unless it 

is designed, constructed, and operated to meet one of the two following work practices: 

(1) Phased disposal in lined tailings impoundments that are no more than 40 acres in 

area and meet the requirements of 40 CFR 192.32(a) as determined by the 

U.S. Nuclear Regulatory Commission (NRC). The owner or operator shall have 

no more than two impoundments, including existing impoundments, in operation 

at any one time. 

(2) Continuous disposal of tailings such that tailings are dewatered and immediately 

disposed of with no more than 10 acres uncovered at any time and operated in 

accordance with 40 CFR 192.32(a) as determined by the NRC. 

The work practice standard also applies to operations at existing sources, once their existing 

impoundments can no longer accept additional tailings. 

The facilities covered by Subpart W are uranium recovery facilities, also licensed and regulated 

by the NRC or its Agreement States. The NRC becomes involved in uranium recovery 

operations once the ore is processed and chemically altered. This occurs either in a uranium mill 

(the next step from a conventional mine) or during ISL or heap leach. For this reason, the NRC 

regulates ISL facilities, as well as uranium mills and the disposal of liquid and solid wastes from 

uranium recovery operations (including mill tailings), but does not regulate the conventional 

uranium mining process. The NRC regulations for the protection of the public and workers from 

exposure to radioactive materials are found in 10 CFR 20, while specific requirements for the 

design and operation of uranium mills and disposition of tailings are found in 10 CFR 40, 

Appendix A. 

2.1 Document Contents and Structure 

This report is divided into six sections. The first two sections are the Executive Summary and 

this introduction, which includes discussions of the history of the development of Subpart W 

(Section 2.2) and the basis for the 1989 risk assessments (Section 2.3). Four technical sections, 

the contents of which are summarized below, follow this introductory section. 

2.1.1 The Uranium Extraction Industry Today 

After a brief history of the uranium market, Section 3.0 identifies both the uranium recovery 

facilities that are licensed today and those that have been proposed to be built in the future. 

For currently existing impoundments, Section 3.0 presents the following information: 
 8 

 Data on the configuration of current impoundments. 

 Results of compliance monitoring. 

Section 3.0 also presents a description of the Method 115 radon monitoring method. 

2.1.2 Current Understanding of Radon Risk 

Section 4.0 presents a qualitative analysis of the changes that have occurred in the understanding 

of the risks associated with Rn-222 releases from impoundments. Emphasis is on the changes to 

the predicted radon progeny equilibrium fractions and the epidemiological and dosimetric 

lifetime fatal cancer risk per working level (WL). Section 4.0 also discusses how the current 

analytical computer model, CAP88 Version 3.0, evolved from and differs from the models used 

for the 1989 risk assessment (i.e., AIRDOS-EPA, RADRISK, and DARTAB). Finally, 

Section 4.4 presents dose and risk estimates for several current uranium recovery facilities. 

2.1.3 Evaluation of Subpart W 

The evaluation of Subpart W requirements required the analyses of some key issues to determine 

if the current technology has advanced since the 1989 promulgation of the rule. The key issues 

include: existing and proposed uranium recovery facilities, Resource Conservation and Recovery 

Act (RCRA) comparison, regulatory history, tailings impoundment technologies, radon 

measurement methods, and risk assessment. Section 5.0 discusses these key issues, in order to 

determine whether the requirements of Subpart W are necessary and sufficient. 

Based on the evaluation of the key issues and in keeping with section 112(d) of the CAA, 

Section 5.0 also presents GACT radon emission control standards for three categories of uranium 

recovery facilities: 

(1) Conventional impoundments. 

(2) Nonconventional impoundments, where uranium byproduct material (i.e., tailings) is 

contained in ponds and covered by liquids. 

(3) Heap leach piles. 

In addition to the key issues, several issues that need clarification in order to be more fully 

understood are presented and described. The issues in need of clarification include extending 

monitoring requirements, defining when the closure period for an operating facility begins, 

interpretation of the term “standby,” the role of weather events, and monitoring reporting 

requirements. 

2.1.4 Economic Impact Analysis 

Section 6.0 of the document reviews and reassesses all the additional economic impacts that may 

occur due to the extension and revision of the Subpart W NESHAP and specifically addresses 

the following: 
 9 

 A review and summary of the original 1989 economic assessment and supporting 

documents are provided. 

 The baseline economic costs for the development of new conventional mills and ISL and 

heap leach facilities are developed and presented. 

 The anticipated costs to industries versus environmental and public health benefits to be 

derived from each of the four proposed GACTs are discussed. 

 Finally, information is provided relating to economic impacts on disadvantaged 

populations and tribal populations and to environmental justice. 

2.2 History of the Development of the Subpart W NESHAP 

The following subsections present a brief history of the development of environmental radiation 

protection standards by EPA, with particular emphasis on the development of radionuclide 

NESHAPs. 

Table 2 presents a partial time line sequence of EPA’s radiation standards with emphasis on the 

NESHAPs, including Subpart W. 

Table 2: Partial Timeline of EPA’s Radiation Standards 

January 13, 1977 EPA publishes 40 CFR 190 – Environmental Protection Standards for Nuclear Power 

Operations. 

August 1979 EPA publishes first BID, Radiological Impacts Caused by Emission of Radionuclides into 

Air in the United States, EPA 520/7-79-006. 

December 27, 1979 EPA determines radionuclides constitute a HAP – (section 112(a)(1) amendments to the 

CAA. 

January 5, 1983 EPA under UMTRCA promulgates, 40 CFR 192, Subpart B “Standards for Cleanup of 

Land and Buildings Contaminated with Residual Radioactive Materials from Inactive 

Uranium Processing Sites,” that for inactive tailings or after closure of active tailings, the 

radon flux should not exceed an average release rate of 20 pCi/(m2

-sec). 

March 1983 EPA publishes draft report, Background Information Document Proposed Standards for 

Radionuclides, EPA 520/1-83-001, and proposes radionuclide NESHAPs for: 

1. DOE and Non-NRC-Licensed Federal Facilities. 

2. NRC-Licensed Facilities. 

3. Elemental Phosphorus Plants. 

4. Underground Uranium Mines. 

September 30, 1983 EPA issues standards under UMTRCA (40 CFR 192, Subparts D and E) for the 

management of tailings at locations licensed by the NRC or the States under Title II of the 

UMTRCA. These standards do not specifically limit Rn-222 emissions until after closure 

of a facility; however, they require ALARA procedures for Rn-222 control. 

February 17, 1984 SC sues EPA (District Court for Northern California) and demands EPA promulgate final 

NESHAP rules for radionuclides or find that they do not constitute a HAP (i.e., “de-list”" 

the pollutant). In August 1984, the court grants the SC motion and orders EPA to take 

final actions on radionuclides by October 23, 1984. 

October 22, 1984 EPA issues Final Background Information Document Proposed Standards for 

Radionuclides, EPA 520/1-84-022-1and -2. 

October 23, 1984 EPA withdraws the proposed NESHAPs for elemental phosphorus plants, DOE facilities, 

and NRC-licensed facilities. 
 10 

Table 2: Partial Timeline of EPA’s Radiation Standards 

December 1984 District Court finds EPA in contempt. EPA and SC submit motion to court with schedule 

(August 5, 1985). Court orders EPA to issue final standards for Rn-222 emissions from 

licensed uranium mills and mill tailings impoundments by May 1, 1986 (later moved to 

August 15, 1986). 

February 6, 1985, to 

September 24, 1986 

EPA promulgates NESHAPs for: 

1. DOE Facilities (February 1985). 

2. NRC-Licensed Facilities and Non-DOE Federal Facilities (February 1985). 

3. Elemental Phosphorus Plants (February 1985). 

4. On April 17, 1985, Rn-222 emissions from underground uranium mines added. 

5. On September 24, 1986, Rn-222 from licensed uranium mill tailings added – 

20 pCi/(m2

-sec) and the work practice standard for small impoundments or 

continuous disposal. 

November 1986 AMC and EDF file petitions challenging the NESHAPs for operating uranium mills. 

July 28, 1987 The Court of Appeals for the District of Columbia remanded to EPA the NESHAP for 

vinyl chloride (see text). Given the decision, EPA petitioned the court for a voluntary 

remand of standards and asked that the pending litigation on all issues relating to its 

radionuclide NESHAPs be placed in abeyance during the rulemaking. EPA also agreed to 

reexamine all issues raised by parties to the litigation. The court granted EPA’s petition on 

December 8, 1987. 

September 14, 1989 EPA promulgates NESHAPs for benzene, etc. Importantly, EPA establishes the “fuzzy 

bright line.” That is, EPA’s approach to residual risk under section 112 (as advanced in 

the Hazardous Organic NESHAPs and approved by the District of Columbia Circuit in 

NRDC v. EPA) as essentially establishing a “fuzzy bright line” with respect to 

carcinogens, whereby EPA must eliminate risks above one hundred in one million 

(1 in 10,000) , does not have to address risks below one in one million (1 in 1,000,000), 

and has discretion to set a residual risk standard somewhere in between (Jackson 2009). In 

a second step, EPA can consider whether providing the public with “an ample margin of 

safety” requires risks to be reduced further than this “safe” level, based on EPA’s 

consideration of health information and other factors such as cost, economic impact, and 

technological feasibility (Jackson 2009). 

September 1989 EPA publishes the NESHAPs for radionuclides. The agency prepared an EIS in support of 

the rulemaking. The EIS consisted of three volumes: Volume I, Risk Assessment 

Methodology; Volume II, Risk Assessments; and Volume III, Economic Assessment.

December 15, 1989 EPA promulgates NESHAPs for: 

 Subpart B: National Emission Standards for Radon Emissions from Underground 

Uranium Mines. 

 Subpart H: Emissions of Radionuclides Other than Radon from DOE Facilities. 

 Subpart I: National Emissions of Radionuclides Other than Radon from DOE 

Facilities by NRC and Federal Facilities Not Covered by Subpart H. 

 Subpart K: Radionuclide Emissions from Elemental Phosphorus Plants. 

 Subpart Q: Radon Emissions from DOE Facilities. 

 Subpart R: Radon Emissions from Phosphogypsum Stacks. 

 Subpart T: Radon Emissions from the Disposal of Uranium Mill Tailings. 

(rescinded effective June 29, 1994; published in the FR July 15, 1994). 

 Subpart W: Radon Emissions from Operating Uranium Mill Tailings Piles. 

November 15, 1990 President signs the CAA Amendments of 1990. Part of the act requires that some 

regulations passed before 1990 be reviewed and, if appropriate, revised within 10 years of 

the date of enactment of the CAA Amendments of 1990. The amendments also instituted a 

technology-based framework for HAPs. Sources that are defined as large emitters are to 

employ MACT, while sources that emit lesser quantities may be controlled using GACT. 
 11 

2.2.1 The 1977 Amendments to the Clean Air Act 

On January 13, 1977 (FR 1977), EPA established environmental protection standards for nuclear 

power operations pursuant to its authority under the Atomic Energy Act (AEA). The standards in 

40 CFR 190, which covered all licensed facilities that are part of the uranium fuel cycle, 

established an annual limit on exposure to members of the public. The NRC or its Agreement 

States, which licenses these facilities, has the responsibility for the enforcement of the Part 190 

standards. Additionally, the NRC imposes the requirement that licensees keep all exposures “as 

low as reasonably achievable” (ALARA). The Part 190 standards exempted Rn-222 from the 

annual limit because of the uncertainties associated with the risk of inhaled radon. 

After the promulgation of 40 CFR 190, the 1977 amendments to the CAA were passed. These 

amendments included the requirement that the Administrator of EPA determine whether 

radionuclides should be regulated under the CAA. 

In December 1979, the Agency published its determination in the Federal Register (FR 1979) 

that radionuclides constitute a HAP within the meaning of section 112(a)(1). As stated in the FR, 

radionuclides are known to cause cancer and genetic defects and to contribute to air pollution 

that may be anticipated to result in an increase in mortalities or an increase in serious, 

irreversible, or incapacitating reversible illnesses. The Agency further determined that the risks 

posed by emissions of radionuclides into the ambient air warranted regulation and listed 

radionuclides as a HAP under section 112. 

Section 112(b)(1)(B) of the CAA requires the Administrator to establish NESHAPs at a “level 

which (in the judgment of the Administrator) provides an ample margin of safety to protect the 

public health” or find that they are not hazardous and delist them. 

2.2.2 Regulatory Activities between 1979 and 1987 

To support the development of radionuclide NESHAPs, the Agency developed a BID to 

characterize “source categories” of facilities that emit radionuclides into ambient air (EPA 1979). 

For each source category, EPA developed information needed to characterize the exposure of the 

public. This included characterization of the facilities in the source category (numbers, locations, 

proximity of nearby individuals); radiological source terms (curies/year (Ci/yr)) by radionuclide, 

solubility class, and particle size; release point data (stack height, volumetric flow, area size); 

and effluent controls (type, efficiency). Doses to nearby individuals and regional populations 

caused by releases from either actual or model facilities were estimated using computer codes 

(see Section 2.3). 

In 1983, EPA proposed radionuclide NESHAPs for four source categories based on the results 

reported in a new BID (EPA 1983). These four source categories were the Department of Energy 

(DOE) and non-NRC-licensed federal facilities, NRC-licensed facilities, elemental phosphorus 

plants, and underground uranium mines. For all other source categories considered in the BID 

(i.e., coal-fired boilers, the phosphate industry and other extraction industries, uranium fuel-cycle 

facilities, uranium mill tailings, high-level waste disposal, and low-energy accelerators), the 

Agency found that NESHAPs were not necessary. In reaching this conclusion, the Agency found 

that either the levels of radionuclide emissions did not cause a significant dose to nearby 
 12 

individuals or the regional populations, the additional effluent controls were not cost effective, or 

the existing regulations under other authorities were sufficient to keep emissions at an acceptable 

level. 

During the public comment period on the proposed NESHAPs, the Agency completed its 

rulemaking efforts under the Uranium Mill Tailings Remedial Control Act (UMTRCA) to 

establish standards (40 CFR 192) for the disposal of uranium mill tailings. With respect to the 

emission of Rn-222, the UMTRCA standards established a design standard calling for an Rn-222 

flux rate of no more than 20 pCi/(m2

-sec). 

In February 1984, the SC sued EPA in the U.S. District Court for Northern California (Sierra 

Club v. Ruckelshaus, No. 84-0656) (EPA 1989), demanding that the Agency promulgate final 

NESHAPs or delist radionuclides as a HAP. The court sided with the plaintiffs and ordered EPA 

to promulgate final regulations. In October 1984, EPA withdrew the proposed NESHAPs for 

elemental phosphorus plants, DOE facilities, and NRC-licensed facilities, finding that existing 

control practices protected the public health with an ample margin of safety (FR 1984). EPA also 

withdrew the NESHAP for underground uranium mines, but stated its intention to promulgate a 

different standard and published an Advance Notice of Proposed Rulemaking (ANPR) to solicit 

additional information on control methods. It also published an ANPR for licensed uranium 

mills. Finally, the FR notice affirmed the decision not to regulate the other source categories 

identified in the proposed rule, with the exception that EPA was doing further studies of 

phosphogypsum stacks to see if a standard was needed. 

In December 1984, the U.S. District Court for Northern California found EPA’s action of 

withdrawing the NESHAPs to be in contempt of the court’s order. Given the ruling, the Agency 

issued the final BID (EPA 1984) and promulgated final standards for elemental phosphorus 

plants, DOE facilities, and NRC-licensed facilities in February 1985 (FR 1985a), and a work 

practice standard for underground uranium mines in April of the same year (FR 1985b). 

The EDF, the NRDC, and the SC filed court petitions seeking review of the October 1984 final 

decision not to regulate the source categories identified above, the February 1985 NESHAPs, 

and the April 1985 NESHAP. The AMC also filed a petition seeking judicial review of the 

NESHAP for underground uranium mines. 

On September 24, 1986, the Agency issued a final NESHAP for operating uranium mill tailings 

(FR September 24, 1986), which established an emission standard of 20 pCi/(m2

-sec) for Rn-222 

and a work practice standard requiring that new tailings be disposed of in small impoundments 

or by continuous disposal. One justifications for the work practices was that, while large 

impoundments did not pose an unacceptable risk during active operations, the cyclical nature of 

the uranium milling industry could lead to prolonged periods of plant standby and the risk that 

the tailings impoundments could experience significant drying, with a resulting increase in 

Rn-222 emissions. Furthermore, the Agency believed that the two acceptable work practices 

actually saved the industry from the significant costs of constructing and closing large 

impoundments before they were completely filled. With the promulgation of the NESHAP for 

operating uranium mill tailings, three EPA regulations covered the releases of radionuclides into 
 13 

the air during operations and tailings disposal at uranium mills: 40 CFR 190; 40 CFR 192; and 

40 CFR 61, Subpart W. 

In November 1986, the AMC and the EDF filed petitions challenging the NESHAP for operating 

uranium mill tailings. 

2.2.3 Regulatory Activities between 1987 and 1989 

While the petitions filed by the EDF, NRDC, SC, and AMC were still before the courts, the U.S. 

District Court for the District of Columbia, in NRDC v. EPA (FR 1989b), found that the 

Administrator had impermissibly considered costs and technological feasibility in promulgating 

the NESHAP for vinyl chloride. The court outlined a two-step decision process that it would find 

acceptable, first establishing a standard based solely on an acceptable level of risk and then 

considering additional factors, such as costs, to establish the “ample margin of safety.” Given the 

court’s decision, the Agency reviewed how it had conducted all of its NESHAP rulemakings and 

requested that the court grant it a voluntary remand for its radionuclide NESHAPs. As part of an 

agreement with the court and the NRDC, the Agency agreed to reconsider all issues that were 

currently being litigated, and it agreed that it would explicitly consider the need for a NESHAP 

for two additional source categories: radon from phosphogypsum stacks and radon from DOE 

facilities. The subsequent reconsideration became known as the radionuclide NESHAPs 

reconsideration rulemaking. 

2.2.4 1989 Radionuclide NESHAPs Reconsideration Rulemaking 

In the radionuclide NESHAPs reconsideration rulemaking, the Administrator relied on a “bright 

line” approach for determining whether a source category required a NESHAP. This meant that 

no NESHAP was required if all individuals exposed to the radionuclide emissions from the 

facilities in the source category were at a lifetime cancer risk of less than 1 in 1,000,000, and less 

than 1 fatal cancer per year was estimated to be incurred in the population. For source categories 

that did not meet this “bright line” exclusion, the Agency adopted a two-step, multi-factor 

approach to setting the emission standards. 

The first step established a presumptively acceptable emissions level corresponding to an MIR of 

about 1 in 10,000 lifetime cancer risk, with the vast majority of exposed individuals at a lifetime 

risk lower than 1 in 1,000,000, and with less than 1 total fatal cancer per year in the exposed 

population. If the baseline emissions from a source category met these criteria, they were 

presumed adequately safe. If they did not meet these criteria, then the Administrator was 

compelled by his nondiscretionary duty to determine an emission limit that would correspond to 

risks that were adequately safe. 

After baseline emissions were determined to be adequately safe or an adequately safe alternative 

limit defined, the analysis moved to the second step, where reduced risks for alternative emission 

limits were evaluated, along with the technological feasibility and costs estimated to be 

associated with reaching lower levels. In the two-step approach, the Administrator retained the 

discretion to decide whether the NESHAP should be set at these lower limits. 
 14 

2.2.5 1990 Amendments to the Clean Air Act 

NESHAP Subpart W is under consideration for revision because section 112(q)(1) requires that 

certain emission standards in effect before the date of enactment of the 1990 CAA Amendments 

shall be reviewed and, if appropriate, revised to comply with the requirements of section 112(d). 

As stated previously, soon after the original promulgation of the standard, the uranium industry 

in the United States declined dramatically, negating the need to perform the Subpart W review. 

However, as discussed in Section 3.1, recent developments in the market for uranium have led to 

forecasts of growth in the uranium market over the next decade and continuing for the 

foreseeable future. Therefore, EPA is reviewing the necessity and adequacy of the Subpart W 

regulations at this time, before facilities developed in response to those forecasts become 

operational. 

Section 112(d) of the 1990 CAA Amendments lays out requirements for promulgating 

technology-based emissions standards for new and existing sources. Section 112(c) lists 

radionuclides, including radon, as an HAP, while section 112(a) defines two types of HAP 

sources: major sources and area sources. Depending on whether the source is a major or area 

source, section 112(d) prescribes standards for the regulation of emissions of HAPs. 

The regulation of HAPs at major sources is dictated by the use of maximum achievable control 

technology (MACT). Section 112(d) defines MACT as the maximum degree of reduction in 

HAP emissions that the Administrator determines is achievable, considering the cost of 

achieving the reduction and any non-air-quality health and environmental impacts and energy 

requirements. With respect to area sources, section 112(d)(5) states that, in lieu of promulgating 

an MACT standard, the Administrator may elect to promulgate standards that provide for the use 

of GACT or management practices to reduce HAP emissions. 

EPA has determined that radon emissions from uranium recovery facility tailings impoundments 

are an area source and that GACT applies (see Section 5.3). The Senate report on the legislation 

(U.S. Senate 1989) contains additional information on GACT and describes GACT as: 

...methods, practices and techniques which are commercially available and 

appropriate for application by the sources in the category considering economic 

impacts and the technical capabilities of the forms to operate and maintain the 

emissions control systems. 

Determining what constitutes a GACT involves considering the control technologies and 

management practices that are generally available to the area sources in the source category. It is 

also necessary to consider the standards applicable to major sources in the same industrial sector 

to determine if the control technologies and management practices are transferable and generally 

available to area sources. In appropriate circumstances, technologies and practices at area and 

major sources in similar categories are considered to determine whether such technologies and 

practices could be generally available for the area source category at issue. Finally, as noted 

above, in determining GACTs for a particular area source category, the costs and economic 

impacts of available control technologies and management practices on that category are 

considered. 
 15 

2.3 Basis for the Subpart W 1989 Risk Assessment and Results 

In the 1989 NESHAP for operating uranium mill tailings, exposures and risks were estimated 

using a combination of actual site data for existing impoundments and model or representative 

facilities for future impoundments and computer models. The 1989 risk assessment reflected the 

estimated risks to the regional (0-80 km [0-50 mile]) populations associated with the 11 

conventional mills that were operating or in standby2 at that time. Mathematical models were 

developed to simulate the transport of radon released from the mill tailings impoundments and 

the exposures and risks to individuals and populations living near the mills. Those models were 

programmed into three computer programs for the 1989 risk assessment: AIRDOS-EPA, 

RADRISK, and DARTAB. The paragraphs that follow briefly discuss each of these computer 

programs. 

AIRDOS-EPA was used to calculate radionuclide concentrations in the air, rates of deposition on 

the ground, concentrations on the ground, and the amounts of radionuclides taken into the body 

via the inhalation of air and ingestion of meat, milk, and vegetables. A Gaussian plume model 

was used to predict the atmospheric dispersion of radionuclides released from multiple stacks or 

area sources. The amounts of radionuclides that are inhaled were calculated from the predicted 

air concentrations and a user-specified breathing rate. The amounts of radionuclides in the meat, 

milk, and vegetables that people ingest were calculated by coupling the atmospheric transport 

models with models that predict the concentration in the terrestrial food chain. 

RADRISK computed dose rates to organs resulting from a given quantity of radionuclide that is 

ingested or inhaled. Those dose rates were then used to calculate the risk of fatal cancers in an 

exposed cohort of 100,000 persons. All persons in the cohort were assumed to be born at the 

same time and to be at risk of dying from competing causes (including natural background 

radiation). RADRISK tabulated estimates of potential health risk due to exposure to a known 

quantity of approximately 500 different radionuclides and stored these estimates until needed. 

These risks were summarized in terms of the probability of premature death for a member of the 

cohort due to a given quantity of each radionuclide that is ingested or inhaled. 

DARTAB provided estimates of the impact of radionuclide emissions from a specific facility by 

combining the information on the amounts of radionuclides that were ingested or inhaled (as 

provided by AIRDOS-EPA) with dosimetric and health effects data for a given quantity of each 

radionuclide (as provided by RADRISK). The DARTAB code calculated dose and risk for 

individuals at user-selected locations and for the population within an 80-km radius of the 

source. Radiation doses and risks could be broken down by radionuclide, exposure pathway, and 

organ. 

Of the 11 conventional mills that were operating or in standby at that time, seven had unlined 

impoundments (the impoundments were clay lined, but not equipped with synthetic liners), while 

five had impoundments with synthetic liners. As the NESHAP revoked the exemption to the 

liner requirement of 40 CFR 192.32(a), the mills with unlined impoundments had to close the 

 2

 “Standby” means the period of time when a facility may not be accepting new tailings but has not yet 

entered closure operations. 
 16 

impoundments and move towards final reclamation and long-term stabilization of the tailings 

impoundments. 

2.3.1 Existing Impoundments 

The NESHAP for operating uranium mill tailings addressed both existing and future tailings 

impoundments. For the existing impoundments, the radon emissions and estimated risks were 

developed using site-specific data for each of the 11 mills that were operating or in standby at the 

time the assessment was made. These data included the average Ra-226 content of the tailings, 

the overall dimensions and areas of the impoundments (developed from licensing data and aerial 

photographs), areas of dry (unsaturated) tailings, the existing populations within 5 km of the 

centers of the impoundments (identified by field enumeration), 5–80 km populations derived 

from U.S. Census tract data, meteorological data (joint frequency distributions) from nearby 

weather stations, mixing heights, and annual precipitation rates. 

The AIRDOS-EPA code was used to estimate airborne concentrations based on the calculated 

Rn-222 source term for each facility. Rn-222 source terms were estimated on the assumption that 

an Rn-222 flux of 1 pCi/(m2

-sec) results for each 1 picocurie per gram (pCi/g) of Ra-226 in the 

tailings and the areas of dried tailings at each site. The radon flux rate of 1 pCi/(m2-sec) per 

pCi/g Ra-226 was derived based on theoretical radon diffusion equations and on the lack of 

available radon emissions measurements. 

For each sector in the 0–80 km grid around each facility, the estimated Rn-222 airborne 

concentration was converted to cumulative working level months (WLMs), assuming a 

0.50 equilibrium fraction between radon and its decay products, an average respiration rate 

appropriate for members of the general public, and the assumption of continuous exposure over a 

70-year lifetime. Using a risk coefficient of 760 fatalities/106 WLM, lifetime risk, fatal cancers 

per year, and the risk distribution were calculated for the exposed population. 

The baseline risk assessment for existing uranium tailings showed an MIR of 3×10-5 which was 

below the benchmark level of approximately 1×10-4 and is, therefore, presumptively safe. 

Additionally, the risk assessment calculated 0.0043 annual fatal cancers in the 2 million persons 

living within 80 km of the mills. The distribution of the cancer risk showed that 240 persons 

were at risks between 1×10-5 and 1×10-4, and 60,000 were at risks between 1×10-6 and 1×10-5. 

The remainder of the population of about 2 million was at a risk of less than 1×10-6. Based on 

these findings, EPA concluded that baseline risks were acceptable. 

The decision on an ample margin of safety considered all of the risk data presented above plus 

costs, scientific uncertainty, and the technical feasibility of control technology necessary to lower 

emissions from operating uranium mill tailings piles. As the risks from existing emissions were 

very low, EPA determined that an emission standard of 20 pCi/(m2-sec), which represented 

current emissions, was all that was necessary to provide an ample margin of safety. The 

necessity for the standard was explained by the need to ensure that mills continued the current 

control practice of keeping tailings wet and/or covered. Finally, to ensure that ground water was 

not adversely affected by continued operation of existing piles that were not synthetically lined 
 17 

or clay lined, the NESHAP ended the exemption to the requirements of 40 CFR 192.32(a), which 

protects water supplies from contamination. 

2.3.2 New Impoundments 

The 1989 risk assessment for new mill tailings impoundments was based on a set of model mills, 

defined so that the impact of alternative disposal strategies could be evaluated. For the purpose 

of estimating the risks, the model mills were characterized to reflect operating mills, and the 

dispersion modeling and population exposures were based on the arid conditions and sparse 

population density that characterize existing impoundments in the southwestern states. 

For new impoundments, a baseline consisting of one large impoundment (116 acres, which is 

80% wet or ponded during its 15-year active life) was modeled (i.e., the continuation of the 

current practice). The baseline results indicated an MIR of 1.6×10-4, a fatal cancer incidence of 

0.014 per year, and only 20 persons at a risk greater than 1×10-4. Given the numerous 

uncertainties in establishing the parameters for the risk assessment and in modeling actual 

emissions and exposures, the Administrator found that the baseline emissions for new tailings 

impoundments met the criteria for presumptively safe. 

The decision on an ample margin of safety for new tailings considered two alternatives to the 

baseline of one large impoundment: phased disposal using a series of small impoundments and 

continuous disposal. The evaluation of these alternatives showed a modest reduction in the MIR 

and the number of fatal cancers per year, but a significant increase in the number of individuals 

at a lifetime risk of less than 1×10-6. The costs estimated for the two alternatives showed that 

phased disposal would lead to an incremental cost of $6.3 million, while continuous disposal was 

believed to actually result in a modest cost saving of $1 million. 

Given the large uncertainties associated with the risk and economic assessments performed for 

the new tailings impoundments, and considering the boom and bust cycles that the uranium 

industry has experienced, EPA determined that a work practice standard was necessary to 

prevent the risks from increasing if an impoundment were allowed to become dry. Finally, 

although continuous disposal showed slightly lower overall risks and costs than phased disposal, 

the Administrator recognized that it was not a proven technology for disposal of uranium mills 

tailings. Therefore, he determined that the work practice standard should allow for either phased 

disposal (limited to 40-acre impoundments, with a maximum of two impoundments open at any 

one time) or continuous disposal. 

3.0 THE URANIUM EXTRACTION INDUSTRY TODAY: A SUMMARY OF THE 

EXISTING AND PLANNED URANIUM RECOVERY PROJECTS 

Section 3.1 describes the historical uranium market in the United States. In the 1950s and 1960s, 

the market was dominated by the U.S. government’s need for uranium, after which the 

commercial nuclear power industry began to control the market. The next three sections describe 

the types of process facilities that were and continue to be used to recover uranium. Section 3.2 

describes conventional mills and includes descriptions of several existing mines, while 

Section 3.3 describes ISL facilities. Heap leach facilities are described in Section 3.4. Finally, 
 18 

Section 3.5 discusses the applicability of the Subpart W recommended radon flux monitoring 

method. 

3.1 The Uranium Market 

The uranium recovery industry in the United States is primarily located in the arid southwest. 

From 1960 to the mid 1980s, there was considerable uranium production in the states of 

Colorado, Nebraska, New Mexico, South Dakota, Texas, Utah, Wyoming, and Washington. The 

majority of the uranium production at that time was associated with defense needs, while a lesser 

amount was associated with commercial power reactor needs. Without exception, the uranium 

recovery industry consisted of mines (open pit and underground) that were associated with 

conventional uranium milling operations. The conventional uranium mining/milling process is 

described in Section 3.2. 

When the demand for uranium could not support the existing number of uranium recovery 

operations, there was a movement to decommission and reclaim much of the uranium recovery 

industry in the United States. 

The UMTRCA Title I program established a joint federal/state-funded program for remedial 

action at abandoned mill tailings sites where tailings resulted largely from production of uranium 

for the weapons program. Now there is Federal ownership of the tailings disposal sites under 

general license from the Nuclear Regulatory Commission (NRC). Under Title I, the Department 

of Energy (DOE) is responsible for cleanup and remediation of these abandoned sites. The NRC 

is required to evaluate DOE’s design and implementation and, after remediation, concur that the 

sites meet standards set by EPA. 

The UMTRCA Title II program is directed toward uranium mill sites licensed by the NRC or 

Agreement States in or after 1978. Title II of the act provides – 

 NRC authority to control radiological and nonradiological hazards. 

 EPA authority to set generally applicable standards for both radiological and 

nonradiological hazards. 

 Eventual state or federal ownership of the disposal sites, under general license from 

NRC.3

In the mid- to late 1980s, several commercial uranium recovery projects employing the solution, 

or ISL, mining process came on line. Section 3.3 describes the uranium ISL mining process. The 

uranium ISL projects and the data that they collected served as the industry standard. This 

industry saw an increase in activity as the conventional mine/milling operations were being shut 

down. 

This shift in the method of uranium mining was associated with economic conditions that existed 

at the time. The price of uranium rapidly declined in the 1980s. The decline in price was 

associated with overproduction that took place during the earlier years. The peak in production 

was associated with Cold War production and associated contracts with DOE. However, as the 

 3

 http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/mill-tailings.html 
 19 

Cold War came to an end, the need for uranium began to diminish. The amount of uranium that 

was needed for DOE projects was greatly diminished and, therefore, the price of uranium saw a 

decline. Figure 1 shows the spot prices for natural uranium. Note the price decline in the early 

1980s. 

Figure 1: Historical Uranium Prices 

Additionally, inexpensive uranium appeared on the worldwide market associated with the 

foreign supplies of low-grade and rather impure yellowcake. Only minimal purification and 

associated refinement was necessary to produce a yellowcake feedstock that could supply 

domestic and worldwide uranium needs from the low-grade foreign supply. Finally, the 

megatons to megawatts downblending program also supplied large supplies of uranium, both 

domestically and worldwide. Classical supply and demand economic principles established a 

market that had oversupply, constant demand and, therefore, a declining price. Consequently, the 

uranium industry in the United States saw a production decline. Although the number of uranium 

operations and production of domestic supply of uranium declined, several domestic uranium 

projects remained active, primarily supplying foreign uranium needs. These projects were 

generally located in the ISL mining production states of Nebraska, Texas, and Wyoming. This 

represented a significant shift in the method that was used to recover uranium, from conventional 

mines to ISL mines. 

Numerous forecasts of worldwide uranium supply and demand exist. Perhaps one of the best 

graphical representations is from the World Nuclear Association. Figure 2 shows the actual 

uranium production rates from 1945 to 2005, as well as the demand trend that was established 

based on these production numbers. Figure 2 indicates that, from the 1960s to the present, the 

worldwide uranium demand has continued to increase even though the U.S. price for uranium 

has decreased. 
 20 

Source: WNA 2010 

Figure 2: Uranium Production and Demand from 1945 to 2005 

Figure 3 shows the uranium supply scenario forecast by the World Nuclear Association. The 

three potential requirement curves shown are based on a variety of factors. The figure indicates 

that current production, as well as planned future worldwide production, may begin to fall short 

of demand in the next few years. 

Source: WNA 2010 

Figure 3: Uranium Supply Scenario from 2008 to 2030 

In summary, all forecasts are for the uranium industry to show growth in the next decade and 

continuing for the foreseeable future. Drivers for this trend are a worldwide need for clean 

energy resources, the current trend to develop domestic sources of energy, and the investment of 

foreign capital in the United States, which is recognized as a politically and economically stable 

market in which to conduct business. 
 21 

3.2 Conventional Uranium Mining and Milling Operations 

Conventional uranium mining and milling facilities are one of two types of uranium recovery 

facilities that currently possess state or federal licenses to operate. There are currently no 

licensed heap leach facilities. Conventional uranium mining and milling operations are in the 

minority and are a carryover from the heavy production days of the 1970s and 1980s. 

Sweetwater Mill, Shootaring Canyon Mill, and White Mesa Mill represent the extent of the 

current conventional uranium milling operations that exist in the United States. 

A conventional uranium mill is generally defined as a chemical plant that extracts uranium using 

the following process: 

 Trucks deliver uranium ore to the mill, where it is crushed into smaller particles before 

the uranium is extracted (or leached). In most cases, sulfuric acid (H2SO4) is the leaching 

agent, but alkaline solutions can also be used to leach the uranium from the ore. In 

addition to extracting 90–95% of the uranium from the ore, the leaching agent also 

extracts several other “heavy metal” constituents, including molybdenum, vanadium, 

selenium, iron, lead, and arsenic. 

 The mill then concentrates the extracted uranium to produce a material called 

“yellowcake” because of its yellowish color. 

 Finally, the yellowcake is transported to a uranium conversion facility, where it is 

processed through the stages of the nuclear fuel cycle to produce fuel for use in nuclear 

power reactors. 

Figure 4 shows a schematic of a typical conventional uranium mill. 

Figure 4: Typical Conventional Uranium Mill 
 22 

Currently, there are three domestic licensed conventional uranium mining and milling facilities 

and a newly licensed facility that has yet to be constructed, as shown in Table 3. 

Table 3: Conventional Uranium Mining and Milling Operations 

Mill Name Licensee Location Website 

Sweetwater 

Kennecott Uranium 

Co/Wyoming Coal 

Resource Co 

Sweetwater County, 

Wyoming None identified 

Shootaring Canyon Uranium One 

Americas Garfield County, Utah http://www.uranium1.com/

indexu.php?section=home 

White Mesa EFR White Mesa LLC San Juan County, Utah http://www.energyfuels.com/

white_mesa_mill/ 

Piñon Ridge Energy Fuels 

Resources Corp. 

Montrose County, 

Colorado 

http://www.energyfuels.com/

projects/pinon-ridge/index.html 

Mill Name Regulatory Status Capacity (tons/day) 

Sweetwater Standby,* license expires November 2014 3,000 

Shootaring Canyon Standby,* license expires May 2012 750 

White Mesa Operating, license expires March 2015 2,000 

Piñon Ridge Development, license issued January 2011 500 (design) 

* Standby means the period of time when a facility may not be accepting new tailings, but has not yet entered 

closure operations. 

Instead of processing uranium ore, the conventional mills shown in Table 3 may process 

alternate feed stocks. These feed stocks are generally not typical ore, but rather materials that 

contain recoverable amounts of radionuclides, rare earths, and other strategic metals. These feed 

stocks are processed, the target materials are recovered, and the waste tailings are discharged to 

the tailings impoundment. The two facilities shown in Table 3 as being in standby (Sweetwater 

and Shootaring Canyon) have had their operating licenses converted into “possession only” 

licenses. Prior to recommencing operation, those facilities will be required to submit a license 

application to convert back to an operating license. EPA will review that portion of the license 

application associated with NESHAP to ensure that all Subpart W requirements are incorporated 

into the appropriate licensing documents and operating procedures.

As described in Section 3.1, the rapid rise in energy costs, increased concerns about global 

warming, and the tremendous worldwide surge in energy use have all led to renewed interest in 

uranium as an energy resource. At the spring 2010 joint National Mining Association (NMA)/ 

NRC Uranium Recovery Workshop, the NRC identified numerous projects that have filed or are 

expected to file applications for new licenses, expansions of existing operations, or restarts of 

existing operations, including several proposals for conventional uranium recovery facilities. 

Contacts with the NRC and state regulatory agencies indicate that permitting and licensing 

actions are associated with the proposed conventional uranium milling and processing projects 

shown in Table 4. Although a significant uranium producer, at present, Texas has no interest in 

conventional uranium milling operations. The potential new mill at Piñon Ridge, Colorado, is not 

shown in Table 4, since its development is advanced and it has already been listed in Table 3. 
 23 

Table 4: Proposed New Conventional Uranium Milling Facilities 

Company Site (Estimated) 

Application Date State 

Uranium Energy Corp Anderson Project N.A. AZ 

Rio Grande Resources Mt. Taylor FY14 NM 

Strathmore Minerals Corporation Roca Honda 12-Sep NM 

Uranium Resources, Inc. Juan Tafoya FY 14 NM 

Oregon Energy, LLC Aurora Uranium Project 13-Dec OR 

Virginia Uranium Coles Hills N.A. VA 

Strathmore Minerals Corporation Gas Hills 12-Sep WY 

N.A. = not available 

No new construction has taken place on any milling facilities shown in Table 4; however, as with 

all industries, planning precedes construction. Considerable planning is underway for existing 

and new uranium recovery operations. As with facilities currently in standby, EPA will review 

the license application to ensure that all Subpart W requirements are incorporated into the 

appropriate licensing documents and operating procedures for these proposed new mills. 

No specific information is available on the type of tailings management systems intended for the 

proposed new conventional mills. To limit radon that could be emitted from the tailings 

impoundments, Subpart W requires that the tailings be disposed of in a phased disposal system 

with disposal cells not larger than 40 acres, or by continuous disposal in which not more than 

10 acres of exposed tailings may accumulate at any time. Regardless of the type of tailings 

management system the new milling operations select, they will all also have to demonstrate that 

their proposed tailings impoundment systems meet the requirements in 40 CFR 192.32(a)(1). 

3.2.1 Sweetwater Mill, Kennecott Mining Company, Red Desert, Wyoming 

The Sweetwater project is a conventional uranium recovery facility located about 42 mi 

northwest of Rawlins, Wyoming, in Sweetwater County. The site is very remote and located in 

the middle of the Red Desert. The approximately 1,432-acre site includes an ore pad, overburden 

pile, and the milling area (see Figure 5). The milling area consists of administrative buildings, 

the uranium mill building, a solvent extraction facility, and a maintenance shop. There is also a 

60-acre tailings management area with a 37-acre tailings impoundment that contains 

approximately 2.5 million tons of tailings material. The Sweetwater impoundments are 

synthetically lined, as required in 40 CFR 192.32(a). The facility is in a standby status and has a 

possession only license administered by the NRC. The future plans associated with this facility 

are unknown, but the facility has been well maintained and is capable of processing uranium. 

The standby license for this facility is scheduled to expire in 2014. The licensee and/or regulator 

will decide whether to renew or to terminate this license.
 24 

Figure 5: Sweetwater – Aerial View 

To demonstrate compliance with Subpart W, testing on the facility’s tailings impoundment for 

radon emissions is conducted annually (KUC 2011). Table 5 shows the results of that testing. 

The lower flux readings measured in 2009 and 2010 are a direct result of the remediation work 

(regrading and lagoon construction in the tailings impoundment) performed in 2007 and 2008. 

Table 5: Sweetwater Mill Radon Flux Testing Results 

Test Date Radon Flux 

(pCi/(m2

-sec)) Test Date Radon Flux 

(pCi/(m2

-sec))

August 7, 1990 9.0 August 14, 2001 6.98 

August 13, 1999 5.1 August 13, 2002 4.10 

August 5, 1992 5.6 August 12, 2003 7.11 

August 24, 1993 5.0 August 17, 2004 6.38 

August 23, 1994 5.0 August 16, 2005 7.63 

August 15, 1995 3.59 August 15, 2006 3.37 

August 13, 1996 5.47 August 13, 2007 6.01 

August 26, 1997 4.23 August 5, 2008 4.59 

August 11, 1998 2.66 July 30, 2009 1.60 

August 10, 1999 1.27 August 10, 2010 1.44 

August 8, 2000 4.05 

Source: KUC 2011, p. 6 
 25 

Summary of Results 

Air monitoring data were reviewed for a 26-year period (1981 to 2007). Upwind Rn-222 

measurements, as well as downwind Rn-222 values, were available. The average upwind radon 

value for the period of record was 3.14 picocuries per liter (pCi/L). The average downwind radon 

value for the same period was 2.60 pCi/L. These values indicate that there is no measurable 

contribution to the radon flux from the mill tailings that are currently in the lined impoundment. 

This monitoring program remains active at the facility. 

 

Approximately 28.3 acres of tailings are dry with an earthen cover; the remainder of the tailings 

is continuously covered with water. The earthen cover is maintained as needed. One hundred 

radon flux measurements were taken on the exposed tailings, as required by Method 115 for 

compliance with Subpart W. The mean radon flux for the exposed beaches was 8.5 pCi/(m2-sec). 

The radon flux for the entire tailings impoundment was calculated to be 6.01 pCi/(m2

-sec). The 

calculated radon flux from the entire tailings impoundment surface is approximately 30% of the 

20.0 pCi/(m2

-sec) standard. 

3.2.2 White Mesa Mill, Energy Fuels Corporation, Blanding, Utah 

The White Mesa project is a conventional uranium recovery facility located about 6 mi south of 

Blanding, Utah, in San Juan County. The approximately 5,415-acre site includes an ore pad, 

overburden pile, and the milling area (see Figure 6). The mill area occupies approximately 

50 acres and consists of administrative buildings, the uranium milling building, and ancillary 

facilities. The facility used a phased disposal impoundment system, and two of the 40-acre cells 

are open. The facility has operated intermittently in the past, and this type of operation continues 

on a limited basis. The amount of milling that takes place, as well as the amount of uranium that 

is being produced, is a small fraction of the milling capacity. The uranium recovery project has 

an active license administered by the Utah Department of Environmental Quality, Division of 

Radiation Control. 
 26 

Figure 6: White Mesa – Aerial View 

To demonstrate compliance with Subpart W, the radon flux from tailings surfaces is measured 

and reported to the State of Utah annually. As Table 6 shows, these data consistently demonstrate 

that the radon flux from the White Mesa Mill’s tailings cells are below the criteria. 

Table 6: White Mesa Mill’s Annual Radon 

Flux Testing, Tailings Cells 2 & 3 

Year Radon Flux (pCi/(m2

-sec)) 

Cell 2 Cell 3 

1997 12.1 16.8 

1998 14.3 14.9 

1999 13.3 12.2 

2000 9.3 10.1 

2001 19.4 10.7 

2002 19.3 16.3 

2003 14.9 13.6 

2004 13.9 10.8 

2005 7.1 6.2 

Source: Denison 2007, p. 116

The Table 6 radon flux values for 2001 and 2002 were elevated when compared to the prior 

years. Denison believes that these radon fluxes were largely due to the drought conditions in 

those years, which reduced the moisture content in the interim cover placed over the inactive 

portions of tailings Cells 2 and 3. In addition, the beginning of the 2002 mill run, which resulted 

in increased activities on the tailings cells, may have contributed to these higher values. As a 

result of the higher radon fluxes during 2001 and 2002, additional interim cover was placed on 
 27 

the inactive portions of Cells 2 and 3. While this effort was successful, additional cover was 

applied again in 2005 to further reduce the radon flux (Denison 2007). 

Summary of Results 

Air monitoring data were reviewed for a 2-year period (2006 to 2008). The White Mesa site 

utilized the MILDOS code to calculate radon concentrations (ANL 1998), in the same 

calculation process that had been used since 1995. As a comparison, Denison Mines reactivated 

the six air monitoring stations that were used at the site. Data from these stations were collected 

for a 2-year period. The upwind and downwind measurements showed no definable trends. At 

times, the upwind concentrations were the higher values, while at other times, the downwind 

concentrations were the greatest. However, all values were within regulatory standards. 

The tailings facilities at the White Mesa facility consist of the following impoundments/cells 

(Denison 2011): 

 Cell 1, constructed with a 30-millimeter (mil) PVC earthen-covered liner, is used for the 

evaporation of process solution (Cell 1 was previously referred to as Cell 1-I, but is now 

referred to as Cell 1). 

 Cell 2, constructed with a 30-mil PVC earthen-covered liner, is used for the storage of 

barren tailings sands. Cell 2 has 67 acres of surface area. Because 99% of the cell has a 

soil cover over the deposited tailings, only 0.7 acres of tailings are exposed as tailings 

beaches. 

 Cell 3, constructed with a 30-mil PVC earthen-covered liner, is used for the storage of 

barren tailings sands and solutions. Cell 3 has 71 acres of surface area, and 54% of the 

cell has a soil cover over the deposited tailings. The remainder of the cell consists of 

tailings beaches (19%) and standing liquid (26%). 

 Cell 4A, constructed with a geosynthetic clay liner, a 60-mil high-density polyethylene 

(HDPE) liner, a 300-mil HDPE Geonet drainage layer, a second 60-mil HDPE liner, and 

a slimes drain network over the entire cell bottom. This cell was placed into service in 

October 2008. 

 Cell 4B, constructed with a geosynthetic clay liner, a 60-mil HDPE liner, a 300-mil 

HDPE Geonet drainage layer, a second 60-mil HDPE liner, and a slimes drain network 

over the entire cell bottom. This cell was placed into service in February 2011. 

One hundred radon flux measurements were collected on the Cell 2 beach area, and an additional 

100 measurements were taken on the soil-covered area in accordance with Method 115 for 

Subpart W analysis. The data were used to calculate the mean radon flux for the exposed beaches 

and the soil-covered area. The average radon flux for all of Cell 2 was calculated to be 

13.5 pCi/(m2

-sec), or about 68% of the 20.0 pCi/(m2-sec) standard. 
 28 

At Cell 3, 100 radon flux measurements were collected from each of the soil cover and the beach 

areas, as required by Method 115. The data were used to calculate the mean radon flux for the 

exposed beaches and the soil-covered area. The radon flux from the standing liquid-covered area 

was assumed to be zero. The average radon flux for all of Cell 3 was calculated to be 

8.9 pCi/(m2-sec), or about 46% of the 20.0 pCi/(m2-sec) standard. 

3.2.3 Shootaring Canyon Mill, Uranium One Incorporated, Garfield County, Utah 

The Shootaring Canyon project is a conventional uranium recovery facility located about 3 mi 

north of Ticaboo, Utah, in Garfield County. The approximately 1,900-acre site includes an ore 

pad, a small milling building, and a tailings management system that is partially constructed (see 

Figure 7). The mill circuit operated for a very short time and generated only enough tailings to 

cover 7 acres of the impoundment. Although the milling circuit has been dismantled and sold, 

the facility is in a standby status and has a possession only license administered by the Utah 

Department of Environmental Quality, Division of Radiation Control. The future plans for this 

uranium recovery operation are unknown. Current activities at this remote site consist of 

intermittent environmental monitoring by consultants to the parent company. The standby license 

for this facility is scheduled to expire in 2014. The licensee and/or the regulator will decide 

whether to renew or to terminate this license. 

Figure 7: Shootaring Canyon – Aerial View 

Summary of Results 

Air monitoring data were reviewed for a 2-year period (2009 to 2010). Continuous air 

monitoring is not conducted at the site; rather, a 20- to 24-hour sampling event is required once 

per quarter as a condition of the license. The high-volume air sampler is located downwind of the 

tailings facility. Many sampling events during a 2-year period indicate that the downwind 
 29 

Rn-222 concentrations are around 1% of the allowable effluent concentration limit. The two 

years of data reviewed indicated no trends. 

The Shootaring Canyon facility operated for approximately 30 days. Tailings were deposited in a 

portion of the upper impoundment. A lower impoundment was designed but has not been built. 

Milling operations in 1982 produced 25,000 cubic yards of tailings, deposited in an area of 

2,508 m2

 (0.62 acres). The tailings are dry except for moisture-associated occasional 

precipitation events; consequently, there are no beaches. The tailings have a soil cover that is 

maintained by the operating company. The impoundment at Shootaring Canyon is synthetically 

lined, as required in 40 CFR 192.32(a). 

One hundred radon flux measurements were collected on the soil-covered tailings area in 

accordance with Method 115. The 2009 sampling results indicated that average flux from the 

covered tailings was 23.3 pCi/(m2

-sec), which exceeded the allowable 20 pCi/(m2-sec) 

regulatory limit. In response to this result, the licensee notified the Utah Division of Radiation 

Control and placed additional soil cover on the tailings. The soil cover consisted of local borrow 

materials in the amount of 650 cubic yards. More sampling took place during the week of 

November 7, 2009. An additional 100 sample results were collected and showed that the average 

radon flux was reduced to 18.1 pCi/(m2

-sec). Sampling for 2010 took place in April. Again, 

100 radon flux measurements were collected. The average radon flux revealed by this sampling 

was 11.9 pCi/(m2-sec). 

3.2.4 Piñon Ridge Mill, Bedrock, Colorado 

The Piñon Ridge project is a permitted conventional uranium recovery facility in development. 

The permitted location is located about 7 mi east of Bedrock, Colorado, and 12 mi west of 

Naturita, Colorado, in Montrose County (see Figure 8). The approximately 1,000-acre site will 

include an administration building, a 17-acre mill site, a tailings management area with 

impoundments totaling approximately 90 acres, a 40-acre evaporation pond with proposed 

expansion of an additional 40-acre evaporation pond as needed, a 6-acre ore storage area, and 

numerous access roads. The design of the tailings management area is such that it can meet the 

work practice standard with a synthetically lined impoundment, a leak detection system, and a 

surface area that does not exceed 40 acres. The facility has not been constructed, but is fully 

licensed and administered by the Colorado Department of Public Health and Environment. Also, 

EPA has approved the facility’s license to construct under NESHAP Subpart A of 40 CFR 61. 

Current activities at the site are maintenance of pre-operational environmental monitoring. 
 30 

Figure 8: Piñon Ridge – Aerial View 

3.2.5 Conventional Mill Tailings Impoundments and Radon Flux Values 

In summary, the radon data for the active mill tailings impoundments indicate that the radon 

exhalation rates from the measured surfaces have exceeded the regulatory standard of 

20 pCi/(m2

-sec) at times. Two instances exist in the records that were reviewed. One instance 

was in 2007, when a portion of the Cotter Corporation impoundment did not have sufficient soil 

cover. Monitoring results showed a flux rate of 23.4 pCi/(m2-sec). The tailings surface was 

covered with a soil mixture, and the flux rate was reduced to 14.0 pCi/(m2-sec). The second 

instance in which the regulatory standard was exceeded was recorded during the 2009 sampling 

event at Shootaring Canyon Mill. This sampling event indicated that average flux from the 

covered tailings was 23.3 pCi/(m2

-sec), caused by insufficient soil cover. Although covering 

tailings piles with various other materials (e.g., synthetics, asphalt, soil-cement mixtures) has 

been studied, covers made of earth or soil have been shown to be the most cost effective in 

reducing radon emissions (EPA 1989, NRC 2010). In both cases when monitoring indicated 

radon fluxes in excess of the standard, additional soil cover was added to the tailings, and the 

radon flux rates were reduced to below the regulatory standards. 

Table 8 shows the average/calculated radon flux values, as reported by the uranium recovery 

operators. 
 31 

Table 7: Mill Tailings Impoundments and Average/Calculated Radon Flux 

Values* 

Facility 

Radon Flux (pCi/(m2

-sec)) Calculated Tailings 

Impoundment Average 

Radon Flux (pCi/(m2 Soil-Covered Area Tailings Beach -sec)) 

Sweetwater Mill No soil-covered 

area 

8.5 6.01 

White Mesa Mill, Cell 2 13.1 50.2 13.5 

White Mesa Mill, Cell 3 13.9 6.7 8.9 

Shootaring Canyon Mill 15 

2-year average Not applicable 15 

2-year average 

Piñon Ridge Mill Not applicable Not applicable Not applicable 

* The respective uranium recovery operators supplied all data and calculations. 

3.3 In-Situ Leach Uranium Recovery (Solution Mining) 

Solution, ISL or in-situ recovery (ISR), mining is defined as the leaching or recovery of uranium 

from the host rock (typically sandstone) by chemicals, followed by recovery of uranium at the 

surface (IAEA 2005). Leaching, or more correctly the remobilization of uranium into solution, is 

accomplished through the injection into the ore body of a lixiviant. The injection of a lixiviant 

essentially reverses the geochemical reactions associated with the uranium deposit. The lixiviant 

ensures that the dissolved uranium, as well as other metals, remains in solution while it is 

collected from the mining zone by recovery wells. 

ISL mining was first conducted in Wyoming in 1963. The research and development projects 

and associated pilot projects of the 1980s demonstrated solution mining as a viable uranium 

recovery technique. Initial efforts at the solution mining process were often less than ideal: 

 Lixiviant injection was difficult to control, primarily because of poor well installation. 

 Laboratory-scale calculations did not always perform as suspected in geological 

formations. 

 Recovery well spacing was poorly understood, causing mobilized solutions to migrate in 

unsuspected pathways. 

 Restoration efforts were not always effective in re-establishing reducing conditions; 

therefore, some metals remained in solution and pre-mining ground water conditions were 

not always achievable. 

Additional research and development work indicated that mining solutions could be controlled 

with careful well installation. The use of reducing agents during restoration greatly decreased the 

amount of metals that were in solution. As a result of these modifications in mining methods, 

solution mining of uranium became a viable method to recover some uranium deposits, many of 

which could not be economically mined by the open pit methods typically employed by the 

uranium industry. Additionally, the economics of solution mining were more favorable than 

conventional mining and milling. Because of these factors, solution mining and associated 

processing began to dominate the uranium recovery industry. Figure 10 shows a schematic of a 

typical ISL uranium recovery facility. 
 32 

Figure 9: In-Situ Leach Uranium Recovery Flow Diagram 

During typical solution mining, a portion of the lixiviant is bled off in order to control the 

pressure gradient within the wellfield. As Figure 10 shows, the liquid bled from the lixiviant is 

sent to an evaporation pond, or impoundment. The pond/impoundment may be used to dispose of 

the liquid via evaporation, or it may be used simply to hold the liquid until a sufficient amount 

has been accumulated so that other means may be used to dispose of it (e.g., land application or 

irrigation, deep well disposal). Since Ra-226 is present in the water bled from the lixiviant, radon 

will be generated in and released from the solution mining facility’s evaporation/holding ponds 

or impoundments. 

The 1989 NESHAP risk assessment (EPA 1989), although not conducted specifically for 

solution mining sites, is applicable to ponds/impoundments at solution mining facilities. All of 

the ponds at solution mining facilities are synthetically lined. Because of the presence of liners, 

none would be required to be closed. The solution mining industry is more transient in that the 

impoundment life is less than those at conventional uranium mining and milling sites. Typically, 

the impoundments are in the range of 1–4 acres and are built to state-of-the-art standards. 

Two types of lixiviant solutions, loosely defined as acid or alkaline systems, can be used. In the 

United States, the geology and geochemistry of most uranium ore bodies favor the use of 

“alkaline” lixiviants or bicarbonate-carbonate lixiviant and oxygen. Other factors in the choice of 
 33 

the lixiviant are the uranium recovery efficiencies, operating costs, and the ability to achieve 

satisfactory ground water restoration. The acid systems once used in the United States are still 

used in Eastern Europe and Asia and were used recently in Australia on ore bodies in saline 

aquifers (IAEA 2005). 

The four major types of uranium deposits in the United States are: strata-bound (roll front), 

solution breccia pipe, vein, and phosphatic deposits (EPA 1995). Of these, ISL is the uranium 

recovery technique used mostly on strata-bound ore deposits. Strata-bound ore deposits are ore 

deposits contained within a single layer of sedimentary rock. They account for more than 90% of 

the recoverable uranium and vanadium in the United States and are found in three major 

geographic areas: the Wyoming Basin (Wyoming and Nebraska), Colorado Plateau or Four 

Corners area (northwestern New Mexico, western Colorado, eastern Utah, and northeastern 

Arizona), and southern Texas. A discussion of the origin of the uranium ore, including ore body 

formation and geochemistry, may be found in the reference, Technical Resource Document 

Extraction and Beneficiation of Ores and Minerals, Volume 5, “Uranium” (EPA 1995). Much of 

the recoverable uranium in these regions lends itself to ISL because of the physical and 

geochemical properties of the ore bodies. 

Four times a year, the Energy Information Administration (EIA) publishes data on the status of 

U.S. ISL facilities. EIA (2013) identified six ISL facilities that were recovering uranium and 

producing yellowcake in the 2nd quarter of 2013. Table 8 shows these facilities. These operations 

are located in NRC-regulated areas, as well as in Agreement States. 

Table 8: Operating ISL Facilities 

Plant Owner Plant Name County, State 

Cameco Crow Butte Operation Dawes, Nebraska 

Power Resources, Inc. dba 

Cameco Resources 

Smith Ranch-Highland 

Operation 

Converse, Wyoming 

Uranium Energy Corp. dba 

South Texas Mining Venture 

Hobson ISR Plant Karnes, Texas 

La Palangana Duval, Texas 

Mestena Uranium LLC Alta Mesa Project Brooks, Texas 

Uranium One USA, Inc. Willow Creek Project 

(Christensen Ranch and 

Irigaray) 

Campbell and 

Johnson, Wyoming 

The two major geographical areas of ISL mining and processing have been Texas and Wyoming. 

These areas are well suited to this ISL mining technology, in that the geology associated with the 

mineralized zone is contained by layers of impervious strata. Texas is the major producer of 

uranium from ISL operations, followed by Wyoming. ISL operations in South Dakota and 

Nebraska recover lesser amounts of uranium. 

For the 2nd quarter of 2013, EIA (2013) identified the ISL facilities shown in Table 9 as being 

developed, or partially or fully permitted and licensed, or under construction. As discussed, the 

economics of ISL uranium recovery are conducive to lower grade deposits or deeply buried 

deposits that could not be economically recovered with conventional open pit or underground 

mining actions. 
 34 

As the data in Table 9 show, there is considerable interest in ISL mining operations in the U.S. 

uranium belt. Many of the existing ISL operations are planning for expansion by preparing the 

license applications and other permitting documents. It is apparent that most domestic uranium 

recovery will be associated with existing and new ISL operations. 

Table 9: ISL Facilities That Are Restarting, Expanding, or 

Planning for New Operations

Plant Owner Plant Name County, State (existing 

and planned locations) 

Status, 2nd 

Quarter 2013 

Powertech Uranium Corp Dewey Burdock Project Fall River and Custer, 

South Dakota 

Developing 

Uranium One Americas, Inc. Jab and Antelope Sweetwater, Wyoming Developing 

Hydro Resources, Inc. Church Rock McKinley, New Mexico Partially Permitted 

And Licensed 

Hydro Resources, Inc. Crownpoint McKinley, New Mexico Partially Permitted 

And Licensed 

Strata Energy Inc Ross Crook, Wyoming Partially Permitted 

And Licensed 

Uranium Energy Corp. Goliad ISR Uranium 

Project 

Goliad, Texas Permitted And 

Licensed 

Uranium One Americas, Inc. Moore Ranch Campbell, Wyoming Permitted And 

Licensed 

Lost Creek ISR, LLC Lost Creek Project Sweetwater, Wyoming Under 

Construction 

Uranerz Energy Corporation Nichols Ranch ISR 

Project 

Johnson and Campbell, 

Wyoming 

Under 

Construction 

Table 10 shows the size of the surface impoundments at ISL facilities. It is noteworthy that the 

operation of these facilities does not require impoundments nearly as large as the impoundments 

used at conventional mills. The impoundments are utilized for the evaporative management of 

waste water. The impoundments are small because a minimal percentage of the process water 

needs to be over-recovered to maintain solution flow to the recovery wells. The solution mining 

industry has used deep well injection for most of the waste water. All signs indicate that this type 

of waste water disposal will continue in the future. 

Table 10 shows that all of the solution mining sites reviewed are using the deep well injection 

method.
 35 

Table 10: ISL Evaporation Pond Data Compilation 

Operation Evaporation pond? Date pond was constructed Size of pond Synthetic liner under pond? Leak detecti

system? 

Cameco, Smith Ranch East and west ponds 1986 8.6 acres Yes Yes, ponds h

had leaks 

Cameco, Crow Butte 3 commercial ponds and 2 R&D ponds R&D ponds 1990 

Pond 1, 2, 5 

850×200 ft Yes Yes 

Pond 3, 4 

700×250 ft 

Hydro Resources, Crown Point 

Project is licensed with the NRC, but no construction has taken place (personal conversation with Urani

Hydro Resources, Church Rock 

Project is licensed with the NRC, but no construction has taken place (personal conversation with Urani

Uranium Resources Inc., Kingsville Dome Two 120×120 ft ponds 1990 120×120 ft Yes Yes Uranium Resources Inc., Vasquez Two 150×150 ft ponds 1990 150×150 ft Yes Yes Uranium Resources Inc., Rosita Two 120×120 ft ponds 1985 120×120 ft Yes Yes Mestena, Alta Mesa Evaporation data not found STMV, La Palangana Evaporation data not found 
 36 

3.3.1 Radon Emission from Evaporation and/or Holding Ponds 

Unlike conventional mills, ISL facilities do not produce tailings or other solid waste products. 

However, they do generate significant amounts of liquid wastes during uranium extraction and 

aquifer restoration. During extraction, an extraction solution (lixiviant), composed of ground 

water enhanced by an oxidant and carbonate/bicarbonate, is injected through wells into the ore 

zone. This lixiviant moves through pores in the ore body and mobilizes the uranium. The 

resulting “pregnant” lixiviant is withdrawn by production wells and pumped to the processing 

plant, which recovers the uranium. To prevent leakage of the lixiviant outside the production 

zone, it is necessary to maintain a hydraulic cone of depression around the well field. This is 

accomplished by bleeding off a portion of the process flow. Other liquid waste streams are from 

sand filter backwash, resin transfer wash, and plant washdown. One method to dispose of these 

liquid wastes is to evaporate them from ponds. Deep well injection and land application 

(i.e., irrigation) are other methods for disposing of the liquid wastes. For these disposal methods, 

the waste liquid is collected in holding ponds until a quantity sufficient for disposal has been 

accumulated. 

As defined by the AEA of 1954, as amended, byproduct material includes tailings or waste 

produced by the extraction or concentration of uranium from any ore processed primarily for its 

source material content (42 USC 2014(e)(2)). Clearly, waste water generated during solution 

mining is within this definition of byproduct material and is thus subject to the requirements of 

Subpart W. 

The waste water contains significant amounts of radium, which will radiologically decay and 

generate radon gas. Radon diffuses much more slowly in water than it does in air. For example, 

the radon diffusion coefficient in water is about 10,000 times smaller than the coefficient in air 

(i.e., on the order of 10-5 square centimeters per second (cm2

/sec) for water and 10-1 cm2/sec for 

air (Drago 1998, as reported in Brown 2010)). Thus, if the tailings piles are covered with water, 

then most of the radon would decay before it could diffuse its way through the water. However, 

since over time periods comparable to the half-life of radon, there is considerable water 

movement within a pond, advective as well as diffusive transport of radon from the pond water 

to the atmosphere must be considered. The water movement is partly caused by surface wind 

currents, thermal gradients, mechanical disturbance from the mill discharge pipe, and biological 

disturbances (animals, birds, etc.). Dye movement tests indicate that for shallow (less than 

1 meter) pond water, advective velocities may exceed 1–2 millimeters per minute, resulting in 

virtually no radon containment by the surface water. If shallow water movement is sufficient to 

remove radon from the tailings-water interface and transport it to the atmosphere in a short time 

(several hours), the radon flux from the shallow tailings is nearly as great as that from similar 

bare saturated tailings; hence, no significant radon attenuation is gained by covering the tailings 

with water (Nielson and Rogers 1986). Consequently, in order for a pond covering a tailings pile 

to be effective at reducing the release of radon, the pond water must be greater than 1 meter in 

depth. 

Additionally, if there is radium in the pond water, radon produced from that radium could escape 

into the atmosphere. A review of the various models used for estimating radon flux from the 
 37 

surface of water bodies indicates that the stagnant film model (also known as the two bottleneck 

model (Schwarzenbach et al. 2003)), coupled with a wind correction equation, can be used to 

estimate the radon flux based on the concentration of radium in the pond’s water and the 

assumption that radon is in secular equilibrium with the radium. The radon flux from the surface 

of an evaporation pond, as a function of the wind speed (for winds less than 24 miles per hour 

(mph)), can be estimated using this model with the following equation: 

J = -0.351V w

-4

C

e

1.4810 (3-1)

Where J = Radon flux (pCi/(m2

-sec)) 

Cw = Concentration of radium in the water (pCi/L) 

V = Wind speed (m/sec) 

Implicit in this model is the fact that in pond water the radon diffusion coefficient is 10-5 cm2

/sec 

and that the thickness of the stagnant film layer can be estimated by an exponential relationship 

with wind speed (Schwarzenbach et al. 2003). 

Baker and Cox (2010) measured the radium concentration in an evaporation pond at the 

Homestake Uranium Mill Site at 165 pCi/L. Assuming a direct conversion to Rn-222 (165 

pCi/L), the flux is estimated from equation 3-1 at 1.65 pCi/(m2-sec). This is comparable to 

measurements of the flux, which averaged 1.13 pCi/(m2-sec). However, the Homestake 

measurement method did not allow the measurement of wind-generated radon fluxes, as the 

collar used to float the canister makes the wind speed zero above the area being measured. No 

data were found for measurements of the radon flux on evaporation ponds versus wind speed. 

The model should not be used for wind speeds above 10 meters per second (m/sec) (24 mph). 

However, this is not expected to be a major limitation for estimating normal radon releases and 

impacts from operational evaporation ponds. 

Using actual radium pond concentrations and wind speed data in equation 3-1, the radon pond 

flux was calculated from several existing ISL sites (SC&A 2010). Results showed that the radon 

flux ranged from 0.07 to 13.8 pCi/(m2

-sec). This indicates that the radon flux above some 

evaporation ponds can be significant (e.g., can exceed 20 pCi/(m2

-sec)). If such levels occur, 

there are methods for reducing the radium concentration in the ponds, the most straightforward 

being dilution. However, this solution is temporary, as evaporation will eventually increase the 

concentration. A second method is to use barium chloride (BaCl2) to co-precipitate the radium to 

the bottom of the pond. The radon generated at the depths of the bottom sediments will decay 

before reaching the pond surface. 

Again using actual ISL site data, the total annual radon release from the evaporation ponds was 

calculated and compared to the reported total radon release from three sites. The evaporation 

pond contribution to the site’s total radon release was small (i.e., less than 1%). 

Two additional sources of radon release were investigated: the discharge pipe and evaporation 

sprays. The discharge pipe is used to discharge bleed lixiviant to the evaporation pond. Radon 
 38 

releases occur when the bleed lixiviant exits the pipe and enters the pond. The investigation 

found that these radon releases are normally calculated using the methodology in NUREG-1569, 

Appendix D (NRC 2003); thus, this source is currently included in the total radon releases 

reported for an ISL site. For a “typical” ISL, with a purge water radon concentration of 

3.2×105 pCi/L and a purge rate of 5.5×105 liters per day (L/d) or about 100 gallons per minute 

(gpm), NUREG-1569, Appendix D, calculated the radon released from the discharge pipe to be 

64 Ci/yr. 

Spray systems are sometimes used to enhance evaporation from the ponds. A model to calculate 

radon releases during spray operation was developed (SC&A 2010). Also, data from ISL ponds 

were used to estimate this source of radon release. The radon releases from spray operations 

were reported to range from <0.01 to <3 pCi/(m2

-sec) (SC&A 2010). Furthermore, operation of 

the sprays would reduce the radon concentration within the pond; therefore, the normal radon 

release would be depressed once the sprays are turned off (until the radon has had an opportunity 

to re-equilibrate with the radium). Hence, operation of spray systems to enhance evaporation is 

not expected to significantly increase the amount of radon released from the pond. 

3.4 Heap Leaching 

Heap leaching is a process by which chemicals are used to extract the uranium from the ore. A 

large area of land is leveled with a small gradient, layering it with HDPE or linear low-density 

polyethylene (LLDPE), sometimes with clay, silt or sand beneath the plastic liner. Ore is 

extracted from a nearby surface or an underground mine. The extracted ore will typically be run 

through a crusher and placed in heaps atop the plastic. A leaching agent (often H2SO4) will then 

be sprayed on the ore for 30–90 days. As the leaching agent percolates through the heap the 

uranium will break its bonds with the oxide rock and enter the solution. The solution will then 

flow along the gradient into collecting pools from which it will be pumped to an onsite 

processing plant. 

In the past, there have been a few commercial heap leach facilities, but currently none are 

operating. However, this type of facility can be rapidly constructed and put into operation. 

Planning and engineering have begun for two heap leach facilities. At the spring 2010 joint 

NMA/NRC Uranium Recovery Workshop, the NRC identified two proposed heap leach projects, 

one in Wyoming and the other in New Mexico, as shown in Table 11. In addition to these two 

projects, Cotter has indicated to the Colorado Department of Public Health and Environment that 

it intends to retain the use of the secondary impoundment at its Cañon City site for heap leaching 

in the future (Hamrick 2011). 

Table 11: Anticipated New Heap Leach Facilities 

Owner Site State 

Energy Fuels4 Sheep Mountain Wyoming 

Uranium Energy Corporation Grants Ridge New Mexico 

Source: NMA 2010 

 4

 Energy Fuels acquired the Sheep Mountain Project through its acquisition of Titan Uranium Inc. in 

February 2012 (http://www.energyfuels.com/development_projects/sheep_mountain/, accessed 9/25/2013). 
 39 

Higher uranium prices will likely lead to the processing of low-grade ore currently found in the 

uranium districts in Wyoming and New Mexico. Much of the low-grade ore currently exists in 

spoil piles that were not economical to truck to milling operations. Little processing equipment is 

necessary to bring heap leach operations on line. Additionally, minimal personnel are necessary 

to operate and monitor such an operation. However, the application of NESHAP Subpart W to 

heap leach facilities should be clarified (see Section 5.0). At a minimum, it is expected that these 

types of facilities will be limited in acreage according to the Subpart W standard and will be 

required to have synthetic liners with monitored leak detection systems. 

Attempts have been made at heap-leaching low-grade uranium ore, generally by the following 

process: 

 Small pieces of uncrushed ore are placed in a pile, or “heap”, on an impervious pad of 

plastic, clay, or asphalt, to prevent uranium and other chemicals from migrating into the 

subsurface. 

 An acidic solution is then sprayed onto the heap, which dissolves the uranium as it 

migrates through the ore. 

 Perforated pipes under the heap collect the uranium-rich solution, and drain it to 

collection basins, from where it is piped to the processing plant. 

 At the processing plant, uranium is concentrated, extracted, stripped, and dried to produce 

a material called “yellowcake.” 

 Finally, the yellowcake is packed in 55-gallon drums to be transported to a uranium 

conversion facility, where it is processed through the stages of the nuclear fuel cycle to 

produce fuel for use in nuclear power reactors. 

Figure 10 shows a schematic of a typical heap-leaching uranium recovery facility. 
 40 

Figure 10: Typical Heap-Leaching Uranium Recovery Facility 

Heap-leaching was not an industry trend; rather, it was an attempt to process overburden that 

contained a minimal concentration of uranium. Production records associated with this 

processing technique were not maintained, but certainly the technique represented less than 1% 

of the recovered uranium resources. Almost all of the conventional uranium recovery operations 

were stand-alone facilities that included the mining, milling, processing, drying, and 

containerization of the yellowcake product. The yellowcake product was then trucked to 

processing facilities that refined the raw materials into the desired product. 

3.4.1 Sheep Mountain Mine, Energy Fuels, Fremont County, Wyoming 

The Sheep Mountain mine, located at approximate 42o 24’ North and 107o 49’ West, has 

operated as a conventional underground mine on three separate occasions. Mining on the Sheep 

Mountain property started in 1956 and continued in several open pit and underground operations 

until 1982. The Sheep I shaft was sunk in 1974, followed by the Sheep II shaft in 1976. 

Production from the Sheep I shaft in 1982 was reported to be 312,701 tons at an average grade of 

0.107% U3O8 (triuranium octoxide). In 1987, an additional 12,959 tons at 0.154% U3O8 were 

produced, followed by 23,000 tons at 0.216% U3O8 in 1988. The Sheep II shaft has had no 

production. The Congo Pit is essentially a single open pit which was being readied for 

development in the early 1980s, but plans were never realized because of the collapse of the 

uranium market. Feed from Sheep Mountain was processed at the Split Rock Mill, which was 

located north of Jeffrey City. Figure 11 shows the Sheep Mountain mine. 
 41 

Figure 11: Sheep Mountain – Aerial View 

Energy Fuels plans to develop the Sheep Mountain mine with both conventional underground 

and open pit mining, followed by heap leach extraction of the uranium with an ion-exchange 

recovery plant producing up to 1.5 million pounds of U3O8 per year. Energy Fuels’ plans include 

the development of both the Sheep I and Sheep II underground mines, with access from twin 

declines. At its peak production, the underground mine will produce approximately 1.0 million 

pounds U3O8 per year. The Congo Pit will also be developed, producing an average of 

500,000 pounds U3O8 per year. Recovery of the uranium will include heap leach pads using 

H2SO4 and a conventional recovery plant, through to yellowcake production on site. Assuming 

no re-use of heap pads, there will be 100 heap leaching cells, each with a capacity of 66,000 tons 

of material stacked to a height of 25 feet (ft) over an area of 40 ft by 100 ft. The mineral 

processing rate will be 500,000 tons per year or greater (Titan Uranium 2010). 

Currently, the Wyoming Department of Environmental Quality has issued a fully bonded mining 

permit to Titan (now Energy Fuels). Energy Fuels is in the process of developing a source 

material license application for submittal to the NRC around mid-2011. The review and approval 

process is expected to take about 2 years (i.e., the NRC will complete it in mid-2013). Finally, 

the Plan of Operation (POO) is being developed and expected to be submitted to the U.S. Bureau 

of Land Management also around mid-2011. Submittal of the POO will trigger development of 

an environmental impact statement (EIS). This POO/EIS process is expected to be completed by 

the end of 2012 (Titan Uranium 2011). 

3.5 Method 115 to Monitor Radon Emissions from Uranium Tailings 

Subpart W (40 CFR 61.253) requires that compliance with the existing emission standards for 

uranium tailings be achieved through the use of Method 115, as prescribed in Appendix B to 

40 CFR 61. Method 115 consists of numerous sections that discuss the monitoring methods that 
 42 

must be used in determining the Rn-222 emissions from underground uranium mines, uranium 

mill tailings piles, phosphogypsum stacks, and other piles of waste material that emits radon. 

For uranium tailings piles, Method 115, Section 2.1.3, specifies the minimum number of flux 

measurements considered necessary to determine a representative mean radon flux value for each 

type of region on an operating pile: 

 Water covered area—no measurements required as radon flux is assumed to be 

zero. 

 Water saturated beaches—100 radon flux measurements. 

 Loose and dry top surface—100 radon flux measurements. 

 Sides—100 radon flux measurements, except where earthen material is used in 

dam construction. 

The requirement of 300 measurements may result in more measurements then are necessary 

under the Subpart W design standards. For example, under design standard 40 CFR 61.252(b)(2) 

for continuous disposal, only 10 acres are uncovered at one time. The 300 flux measurements on 

a 10-acre area translate into one measurement every 1,500 ft2

, or one every 40 ft. At the time 

Method 115 was developed and amended to Appendix B (i.e., 1989), the uranium tailings areas 

were much larger than the Subpart W design standards presently allow. For example, 

DOE/EIA-0592 (1995) indicates that some mills had tailings areas of over 300 acres (although 

not necessarily in a single pile). 

Method 115, Section 2.1.6, indicates that measuring “radon flux involves the adsorption of radon 

on activated charcoal in a large-area collector.” Since 1989, there have been advances in methods 

of measuring radon flux. George (2007) is particularly relevant in terms of radon measuring 

devices: 

In the last 20 years, new instruments and methods were developed to measure 

radon by using grab, integrating, and continuous modes of sampling. The most 

common are scintillation cell monitors, activated carbon collectors, electrets, ion 

chambers, alpha track detectors, pulse and current ionization chambers, and 

solid state alpha detectors. 

In George (2007) radon detection is divided into: 

I. Passive integrating radon measurements 

(1) Activated carbon collectors of the open face or diffusion barrier type. 

Charcoal canisters often employ a gamma spectrometer to count the radon 

daughters as surrogates (bismuth-214, for example). Liquid scintillation vials 

also use alpha and beta counting. About 70% of radon measurements in the 

United States are canister type. 
 43 

(2) Electret ion chambers are being used for 2–7 days duration to measure the 

voltage reduction (drop). The voltage drop on the electrets is proportional to 

the radon concentration. About 10%–15% of radon measurements use this 

methodology. 

(3) Alpha track detectors are used for long-term measurements. Alphas from 

radon penetrate a plastic lattice, which is etched with acid, and the resulting 

tracks are counted. There is some use in the United States, but this is more 

popular in Europe. 

II. Passive or active continuous radon measurements 

(1) Scintillation cell monitors mostly include the flow-through type. 

(2) Current and pulse ionization chambers (mostly passive). 

(3) Solid state devices are either passive or active if they use a pump to move air 

through the sensitive volume of the monitor like the RAD 7, which uses a 

solid state alpha detector (passive implanted planar silicon (PIPS) detector). 

Additionally, the Oak Ridge Institute for Science and Education (ORISE) compared various 

radon flux measurement techniques (ORISE 2011), including activated charcoal containers, the 

Electric Passive Environmental Radon Monitor (E-PERM) electret ion chamber, the 

AlphaGUARD specialized ionization chamber, semiconductor detectors to measure radon 

daughters, and ZnS(Ag) (silver doped zinc sulfide) scintillation detectors. ORISE stated that the 

last two techniques were not yet commercially available and that the AlphaGUARD detector was 

“expensive,” and thus they are not currently candidates for radon flux monitoring of uranium 

tailings. Comparing the activated charcoal containers to the E-PERM, ORISE found that while 

both were easy to operate and relatively inexpensive, the E-PERM showed smaller variations in 

measurements, and the activated charcoal containers had higher post-processing costs. The only 

disadvantage of the E-PERM was that its Teflon disks must be replaced after each use. Based on 

this comparison, ORISE recommended that for a large number of measurements, such as those 

needed to comply with Subpart W, E-PERM flux monitors would be best. 

This brief review of Method 115 demonstrates that its use can still be considered current for 

monitoring radon flux from uranium tailings. However, it is important to note that the specific 

design protocols were developed for use at larger tailings impoundments. Alternatively, many 

commercial enhancements to that design are widely available and in use today. Other forms of 

passive detectors, as well as active measurement detectors, are also acceptable alternatives to 

demonstrate conformance with the standard. In addition, the method as currently written has 

some elements and requirements that should be reviewed and possibly revised, particularly the 

location and the frequency of measurement. These would be better based on statistical 

considerations or some other technical basis. Additional discussion of the continued applicability 

of Method 115 appears in SC&A 2008, ORISE 2011, and George 2007. 
 44 

4.0 CURRENT UNDERSTANDING OF RADON RISK 

Subpart W regulates the emission of radon from operating uranium recovery facility tailings. To 

enhance the understanding of the need for Subpart W, this section presents a qualitative review 

and analysis of changes in the analysis of the risks and risk models associated with radon 

releases from uranium recovery tailings since the publication of the 1989 BID (EPA 1989). After 

presenting some brief radon basics, the analysis focuses on three areas that have evolved: radon 

progeny equilibrium fractions, empirical risk factors, and the development of dosimetric risk 

factors. Finally, Section 4.4 presents the results of a risk assessment performed using current 

methodology (i.e., CAP88, Version 3 (TEA 2007)), 2011 estimated population distributions, and 

historical radon release data. Section 4.4 also discusses and compares the current calculated risks 

to the 1989 risk assessment results, presented in Section 2.3. 

4.1 Radon and Dose Definitions 

Rn-222 is a noble gas produced by radioactive decay of Ra-226. As shown in Figure 12, one of 

the longer-lived daughters in the uranium (U)-238 decay series, Ra-226 is a waste product in 

uranium tailings and liquids from uranium recovery facilities. These include mills, evaporation 

and surge ponds, typically found in ISL facilities, and heap leach piles. Radium (and its daughter 

radon) is also part of the natural radiation environment and is ubiquitous in soils and ground 

water along with its parent uranium. 

Figure 12: Uranium Decay Series 

Radon, with a half-life of 3.8 days, decays into a series of short half-life daughter products or 

progeny. Being chemically inert, most inhaled radon is quickly exhaled. Radon progeny, 

however, are charged and electrostatically attach themselves to inhalable aerosol particulates, 

which are deposited in the lung or directly onto lung tissue. These progeny undergo decay, 
 45 

releasing alpha, beta, and gamma radiation that interacts directly with lung tissue. Of these 

interactions, alpha particles from polonium-218 and polonium-214 are the most biologically 

damaging. The resulting irritation of lung cell tissue particularly from these alpha particles 

enhances the risk of developing a lung cancer. Determining an estimate of the risk of developing 

a cancer is of primary importance to establishing the basis for any regulatory initiatives. 

4.2 Radon Risk Factors 

In 1988, the National Research Council’s Committee on the Biological Effects of Ionizing 

Radiation (BEIR) presented a report on the health risks of radon (BEIR IV, NAS 1988). BEIR IV 

derived quantitative risk estimates for lung cancer from analyses of epidemiologic data from 

underground miners. The risk factor presented in BEIR IV for radon was 350 cancer deaths per 

million person-WLMs5

 of exposure. 

The International Commission on Radiological Protection (ICRP), in its Publication 50 

(ICRP 1987), addressed the question of lung cancer risk from indoor radon daughter exposures. 

The ICRP Task Group took a direction quite different from that of the BEIR Committee. The 

Task Group reviewed published data on three miner cohorts: U.S., Ontario, and Czech uranium 

miners. When the ICRP 50 relative risk model was run with the 1980 U.S. life table and vital 

statistics, the combined male and female reference risk was calculated in the 1989 BID to be 

4.2×10-4 cancer deaths per WLM. 

In the 1989 BID, EPA averaged the male and female BEIR IV and ICRP 50 risk coefficients and 

adjusted the coefficients for background, so that the risk of an excess lung cancer death for a 

combined population (men and women) was 3.6×10-4 WLM-1, with a range from 1.4×10-4 to 

7.2×10-4 WLM-1 (EPA 1989). 

In addition to epidemiological radon risk coefficients, dosimetric models have been developed as 

a widely acceptable approach to determine the effects of exposures to radon progeny. One of the 

principal dosimetric models used to calculate doses to the lung following inhalation of radon and 

its daughters is the ICRP Human Respiratory Tract Model (HRTM), first introduced in ICRP 

Publication 66 (ICRP 1994). The ICRP used the HRTM to develop a compilation of effective 

dose coefficients for the inhalation of radionuclides, presented in Publication 72 (ICRP 1996). 

Shortly after the publication of ICRP Publication 72, and using the information in that report, 

EPA developed Federal Guidance Report 13 (FGR 13) (EPA 1999)6

. In addition to the risk 

factors given in FGR 13 itself, the FGR 13 CD Supplement (EPA 2002) provides dose factors, as 

well as risk factors, for various age groups. For this study, the dose and risk factors from the 

 5

 Radon concentrations in air are commonly expressed in units of activity (e.g., picocuries (pCi) or 

becquerels) per unit volume (e.g., liters (L)); however, radon progeny concentrations are commonly expressed as 

working levels (WLs). In a closed volume, the concentration of short-lived radon progeny will increase until 

equilibrium is reached, under these conditions, each pCi/L of radon will give rise to (almost precisely) 0.01 WL, or 

100 pCi/L = 1 WL (EPA 2003). Exposure to 1 WL for 1 month (i.e., 170 hours) is referred to as 1 working level 

month (WLM). 6

 Since FGR 13 was published, several organizations have produced updated radiation risk estimates. EPA 

2011 reviewed the update risk estimates and concluded that the new mortality estimates do not differ greatly from 

those in FGR-13. 
 46 

FGR 13 CD Supplement were used to calculate the dose and risk due to exposure to 1 WLM of 

radon and its progeny. The calculation assumed a radon airborne concentration of 100 pCi/L, a 

radon progeny equilibrium fraction of 0.4, a breathing rate of 0.9167 cubic meters per hour 

(m3

/hr), and an exposure duration of 170 hours. 

The results of this calculation demonstrate that the FGR 13 based radon progeny lung dose 

conversion factor is between about 2.1 to 7.0 millisieverts (mSv)/WLM, depending on the age of 

the individual being exposed. The results also show that the lifetime fatality coefficient from 

lung exposure is between about 6×10-4 to 2.4×10-3 WLM-1, depending on the exposed 

individual’s age. This agrees well with the factor calculated from empirical data. 

In conclusion, the radon progeny risk factor from FGR 13 of 6×10-4 WLM-1 used in this analysis 

falls within the risk factor range identified in the 1989 BID (i.e., 1.4×10-4 to 7.2×10-4 WLM-1), 

and is about 67% larger than the 3.6×10-4 WLM-1 radon progeny risk factor used in the 1989 

BID. Thus, the radon progeny risk factor used in this Subpart W analysis updates the risk factor 

used in the 1989 BID to reflect the current understanding of the radon risk, as expressed by the 

ICRP and in FGR 13. 

4.3 Computer Models 

Various computer models that could be used to calculate the doses and risks due to the operation 

of conventional and ISL uranium mines were compared. Seven computer programs were 

considered for use in the uranium tailings radon risk assessment: CAP88 Version 3.0, RESRADOFFSITE, MILDOS, GENII, MEPAS, AIRDOS, and AERMOD. A detailed selection process 

was used to select the program from the first five programs listed. AIRDOS was not included in 

the detailed selection process, since it is no longer an independent program, but has been 

incorporated into CAP88 Version 3.0. Because it calculates only atmospheric dispersion, but not 

radiological doses or risks, AERMOD was also not included. The five remaining programs 

received a score between 0 and 5 for each of the following 11 criteria: (1) Exposure Pathways 

Modeled, (2) Population Dose/Risk Capability, (3) Dose Factors Used, (4) Risk Factors Used, 

(5) Meteorological Data Processing, (6) Source Term Calculations, (7) Verification and 

Validation, (8) Ease of Use/User Friendly, (9) Documentation, (10) Sensitivity Analysis 

Capability, and (11) Probabilistic Analysis Capability. Also, each criterion had a weighting 

factor of between 1 and 2. The total weighted score was calculated for each code, and CAP88 

was selected for use in this evaluation. A more complete discussion of the selection of the risk 

assessment computer code appears in SC&A 2010. 

As described in Section 2.3, the 1989 BID used the computer codes AIRDOS-EPA, RADRISK, 

and DARTAB to calculate the risks due to radon releases from uranium tailings. Subsequent to 

the publication of the 1989 BID, CAP88 Version 3.0 was produced. CAP88 Version 3.0 was 

originally composed of the AIRDOS-EPA and DARTAB computer codes and the dose and risk 

factors from RADRISK (see Section 2.3). CAP88 Version 3.0 was first used for DOE facilities 

to calculate effective dose equivalents to members of the public to ensure compliance with the 

then-issued NESHAP Subpart H rules (TEA 2007). Currently, CAP88 Version 3.0 incorporates 

the dose and risk factors from FGR 13 for determining risks from radionuclides, including the 

radon decay daughters. 
 47 

When calculating doses and risk from Rn-222, CAP88 Version 3.0 can be run in two different 

modes, either normally or in the “radon only” mode. When run in the normal mode, CAP88 

Version 3.0 treats radon and its progeny as any other radionuclide and its progeny would be 

treated. That is, the radon is decayed as it travels from the release point to the dose receptor 

location, and the in-growth of the progeny is calculated. At the dose receptor location, doses are 

calculated assuming all the normal exposure pathways, including inhalation and air submersion, 

that are normally associated with radon doses, and also the exposure pathways from the longer 

lived radon progeny that deposit onto the ground, including ground shine and food ingestion. To 

perform these calculations, CAP88 Version 3.0 used the dose and risk factors from FGR 13. 

In the “radon only” mode, CAP88 Version 3.0 calculates the risk from the radon WL 

concentration, but not the dose. The annual risk to an individual or population at a location is 

simply the WL concentration multiplied by a risk coefficient. The risk coefficient used by 

CAP88 Version 3.0 is 1.32 cancer fatalities per year per WL. Although this risk coefficient is not 

documented in any of the CAP88 Version 3.0 user manuals, so its origin is unknown, it can be 

derived from the CAP88 Version 3.0 output files. A risk coefficient of 1.32 WL-year-1 is 

equivalent to 2.56×10-2 cancer deaths per WLM, which is about two orders of magnitude larger 

than the risk coefficient discussed in Section 4.2. Thus, CAP88’s “radon only” mode was not 

used to calculate the risk estimates that are summarized in the next section. Rather, the risk 

estimates are based on CAP88’s atmospheric transport model (for radon decay and progeny 

buildup) and the radionuclide-specific risk factors from FGR 13. 

4.4 Uranium Recovery Facility Radon Dose and Risk Estimates 

To perform the CAP88 dose/risk analysis, three types of data were necessary: (1) the distribution 

of the population living within 80 km (50 mi) of each site, (2) the meteorological data at each 

site, particularly the wind speed, wind direction, and stability class, and (3) the amount of radon 

annually released from the site. 

Dose/risk assessments were performed for the uranium recovery sites identified in Table 12, 

which include conventional uranium mills and ISL mines, plus two hypothetical generic sites 

developed to represent the western and eastern United States. 

Table 12: Uranium Recovery Sites Analyzed

Mill / Mine Type State Regulator Latitude Longitude

deg min sec deg min sec

Crow Butte In-Situ Leach NE NRC 42 38 41 -103 21 8

Western Generic Conventional NM NRC 35 31 37 -107 52 52

Alta Mesa 1, 2, 3 In-Situ Leach TX State 26 53 59 -98 18 29

Kingsville Dome 1,3 In-Situ Leach TX State 27 24 54 -97 46 51

White Mesa Mill Conventional UT State 37 34 26 -109 28 40

Eastern Generic Conventional VA NRC 38 36 0 -78 1 11

Smith Ranch - Highland In-Situ Leach WY NRC 43 3 12 -105 41 8

Christensen/Irigaray In-Situ Leach WY NRC 43 48 15 -106 2 7

Sweetwater Mill Conventional WY NRC 42 3 7 -107 54 41
 48 

Normally, the population doses and risks are calculated out to a distance of 80 km (50 mi) from 

the site. Therefore, it was necessary to know the population to a distance of 80 km from each site 

in each of the 16 compass directions. This information is not normally available from U.S. 

Census Bureau data. However, in 1973, EPA wrote a computer program, SECPOP 

(Sandia 2003), which would convert census block data into the desired 80-km population 

estimates for any specific latitude and longitude within the continental United States. The NRC 

adopted this program to perform siting reviews for license applications and has updated the 

program to use the 2000 census data. SC&A (2011) used the SECPOP program to estimate the 

population distribution around each site; that population was then modified to account for 

changes in the population from 2000 to 2010. 

For those sites where site-specific meteorological data were identified, those site-specific data 

were used. For other sites, CAP88 Version 3.0 is provided with a weather library of 

meteorological data from over 350 National Weather Service stations. For sites without sitespecific meteorological data, data from the National Weather Service station nearest the site were 

used. 

Annual radon release estimates were determined for each site based on the available 

documentation for the site. For example, some sites reported their estimated radon release in 

their semiannual release reports, while other sites calculated their radon release as part of their 

license application or renewal application. Finally, for some sites, the annual radon release 

estimates were obtained from the NRC-produced, site-specific environmental assessment. If 

multiple documents provided radon release estimates for a particular site, the estimate from the 

most recent document was used. Consistent with the 1989 assessment, in order to bound the 

risks, radon releases were estimated from both process effluents and impoundments. Likewise, if 

both theoretical and actual radon release values were identified for a site, the actual radon release 

value was given preference. 

Additional descriptions of each site’s population, meteorology, and radon source term may be 

found in SC&A 2011. Doses and risks to the RMEI and to the population living within 80 km of 

the facility were calculated. The RMEI is someone who lives near the facility and is assumed to 

have living habits that would tend to maximize his/her radiation exposure. For example, the 

RMEI was assumed to eat all of his/her vegetables from a garden located nearest the facility, 

which is contaminated with radon progeny as a result of radon releases from the facility. On the 

other hand, population doses and risks are based on the number of individuals who live within 

80 km of the facility. These people are also assumed to eat locally grown vegetables, but not 

necessarily from the garden located nearest the facility. The RMEI’s dose and risk are included 

within the population dose and risk, since he/she lives within the 80-km radius. 

Table 13 presents the RMEI and population doses and risks due to the maximum radon releases 

estimated for each uranium site. 
 49 

Table 13: Calculated Maximum Total Annual RMEI, Population Dose and Risk 

Uranium Site

Maximum 

Radon 

Release (Ci/yr)

Annual Dose LCF(a, b) Risk (yr-1)

Population 

(person-rem)

RMEI 

(mrem) Population RMEI

Sweetwater 2,075 0.5 1.2 2.9E-06 6.0E-07

White Mesa 1,750 5.2 12.0 3.4E-05 6.4E-06

Smith Ranch - Highlands 36,500 3.7 1.5 2.3E-05 7.7E-07

Crow Butte 8,885 2.7 3.3 1.7E-05 1.7E-06

Christensen/Irigaray 1,600 3.8 1.9 2.4E-05 9.9E-07

Alta Mesa 740 21.6 11.5 1.3E-04 6.1E-06

Kingsville Dome 6,958 58.0 11.3 3.8E-04 6.1E-06

Eastern Generic 1,750 200.3 28.2 1.4E-03 1.6E-05

Western Generic 1,750 5.1 6.0 2.7E-04 7.7E-06

(a)Latent Cancer Fatalities 

(b)In this table all risks are presented as LCF risks. If it is desired to estimate the morbidity risk, simply multiply the LCF risk 

by 1.39. 

Table 14 presents the RMEI and population doses and risks due to the average radon releases 

estimated for each uranium site. The risks were based on average radon releases to make it easier 

to convert these annual risk values into lifetime risk values. This conversion is done by simply 

multiplying the Table 14 values by the number of years that the facility operates for the 

population risk, or by the length of time that the individual lives next to the facility for the RMEI 

risk. 

Table 14: Calculated Average Total Annual RMEI, Population Dose and Risk 

Uranium Site

Average Rado

n Release 

(Ci/yr)

Annual Dose LCF(a) Risk (yr-1)

Population 

(person-rem)

RMEI 

(mrem)

Populatio

n

RMEI

Sweetwater 1,204 0.3 0.7 1.7E-06 3.5E-07

White Mesa 1,388 3.0 7.0 2.0E-05 3.7E-06

Smith Ranch - Highland

s 21,100 2.2 0.9 1.3E-05 4.5E-07

Crow Butte 4,467 1.6 1.9 1.0E-05 1.0E-06

Christensen/Irigaray 1,040 2.2 1.1 1.4E-05 5.7E-07

Alta Mesa 472 12.5 6.7 7.6E-05 3.6E-06

Kingsville Dome 1,291 33.6 6.6 2.2E-04 3.5E-06

Eastern Generic 1,388 116.3 16.4 7.9E-04 9.2E-06

Western Generic 1,388 3.0 3.5 1.6E-04 4.4E-06

(a)Latent Cancer Fatalities

The dose and risk to an average member of the population within 0–80 km of each site may be 

calculated by dividing the population doses and risks from Table 13 and Table 14 by the 

population for each site. Table 15 shows the results of that calculation. 
 50 

Table 15: Dose and Risk to an Average Member of the Population 

Uranium Site

Dose (mrem) LCF(a) Risk (yr-1)

Average 

Release

Maximum 

Release

Average 

Release

Maximum 

Release

Sweetwater 0.03 0.05 1.6E-07 2.7E-07

White Mesa 0.15 0.25 9.6E-07 1.6E-06

Smith Ranch - Highlands 0.03 0.05 1.7E-07 2.9E-07

Crow Butte 0.05 0.08 3.1E-07 5.3E-07

Christensen/Irigaray 0.06 0.11 3.8E-07 6.6E-07

Alta Mesa 0.03 0.05 1.6E-07 2.7E-07

Kingsville Dome 0.07 0.13 4.8E-07 8.3E-07

Eastern Generic 0.05 0.09 3.7E-07 6.4E-07

Western Generic 0.04 0.07 2.2E-06 3.8E-06

(a)Latent Cancer Fatalities

As Table 15 shows, the annual latent cancer fatality (LCF) risk to an average member of the 

population surrounding a uranium site ranges from 1.6×10-7 to 1.6×10-6 for the seven actual sites, 

and from 3.7×10-7 to 3.8×10-6 for the two hypothetical generic sites. 

The study estimated that the annual fatal cancer risk to the RMEI ranges from 3.5×10-7 to 

6.4×10-6 for the seven actual sites, and from 4.4×10-6 to 1.6×10-5 for the two hypothetical generic 

sites. The highest annual individual risk occurred at the Eastern Generic site, which is not 

surprising considering that the nearest individual was assumed to reside only about 1 mi from the 

hypothetical site. It is likely that during the site selection process for an actual facility, a site this 

close to residences would be eliminated and/or the design of the facility would include features 

for reducing radon emissions in order to reduce the RMEI risk. 

The lifetime risk would depend on how long an individual was exposed. For example, for the 

seven actual sites analyzed, assuming that the uranium mill operates for 10 years, then the 

lifetime fatal cancer risk to the RMEI would be 3.5×10-6 to 3.7×10-5. Alternatively, if it is 

assumed that an individual was exposed for his/her entire lifetime (i.e., 70 years), then the 

lifetime fatal cancer risk to the RMEI would be 2.45×10-5 to 2.59×10-4. For the two hypothetical 

generic sites, the lifetime fatal cancer risk to the RMEI would be 4.4×10-5 to 9.2×10-5 assuming 

10 years of mill operation, or 3.1×10-5 to 6.44×10-5 assuming 70 years of mill operation. The 

lifetime risk calculation uses only the average radon release results, because while the maximum 

could occur for a single year, it is unlikely that the maximum would occur for 10 or 

70 continuous years. 

The study also estimated that the risk to the population from all seven real uranium sites is 

between 0.0005 and 0.0009 fatal cancers per year, or approximately one case every 1,080 to 

1,865 years to the 1.8 million persons living within 80 km of the sites. 
 51 

4.5 Summary of Radon Risk 

This section described the evolution in the understanding of the risk presented by radon and its 

progeny since the 1989 BID was published. Additionally, the computer code CAP88 Version 3.0 

was used to analyze the radon risk from seven operating uranium recovery sites and two generic 

sites. 

The lifetime MIR calculated using data from seven actual uranium recovery sites was determined 

to be between 2.45×10-5 to 2.59×10-4. The low end of the range is lower than the 3×10-5 lifetime 

MIR reported in the 1989 rulemaking for existing impoundments (see Section 2.3.1), while the 

high end of the range is slightly higher than the 1.6×10-4 lifetime MIR reported in the 1989 

rulemaking for new impoundments (see Section 2.3.2). 

In protecting public health, EPA strives to provide the maximum feasible protection by limiting 

radon exposure to approximately 1 in 10,000 (i.e., 10-4) the lifetime MIR. Although the 

calculated high end of the lifetime MIR range is above 10-4, the assumptions that radon releases 

occur continuously for 70 years and that the same RMEI is exposed to those releases for the 

entire 70 years are very conservative. 

Similarly, the risk assessment estimated that the risk to the population from all seven real 

uranium sites is between 0.0005 and 0.0009 fatal cancers per year, or approximately one case 

every 1,080 to 1,865 years among the 1.8 million persons living within 80 km of the sites. For 

the 1989 rulemaking, the estimated annual fatal cancer incidence to the 2 million people living 

within 80 km of the sites was 0.0043, which was less than one case every 200 years for existing 

impoundments, and 0.014, or approximately one case every 70 years for new impoundments (see 

Sections 2.3.1 and 2.3.2). 

5.0 EVALUATION OF SUBPART W REQUIREMENTS 

The evaluation of Subpart W requirements required analyses of several items to determine if the 

current technology had advanced since the promulgation of the rule. These topics are listed 

below, along with the key issues addressed in this report to determine whether the requirements 

of Subpart W are necessary and sufficient. 

5.1 Items Reviewed and Key Issues 

Each of these items will be reviewed with reference to the relevant portions of this document: 

(1) Review and compile a list of existing and proposed uranium recovery facilities and the 

containment technologies being used, as well as those proposed. 

Key Issue – The standard should be clarified to ensure that all owners and operators of 

uranium recovery facilities (conventional mills, ISL, and heap leach) are aware that all 

of the structures and facilities they employ to manage uranium byproduct material (i.e., 

tailings) are regulated under Subpart W. 
 52 

(2) Compare and contrast those technologies with the engineering requirements of 

hazardous waste impoundments regulated under RCRA Subtitle C disposal facilities, 

which are used as the design basis for existing uranium byproduct material (i.e., tailings) 

impoundments. 

Key Issue – All new impoundments shall adopt the design and engineering standards 

referred to through 40 CFR 192.32(a)(1). 

(3) Review the regulatory history. 

Key Issue – NESHAP Subpart W continues to be the appropriate regulatory tool to 

implement the Administrator’s duty under the CAA for operating uranium mill tailings. 

(4) Tailings impoundment technologies. 

Key Issue – The emission limit for impoundments that existed as of December 15, 1989, 

has been demonstrated to be both achievable and sufficient to limit risks to the levels 

that were found to protect public health with an ample margin of safety. 

The requirement that impoundments opened after December 15, 1989, use either phased 

or continuous disposal technologies as appropriate to ensure that public health is 

protected with an ample margin of safety, which is consistent with section 112(d) of the 

1990 Amendments of the CAA, which requires standards based on GACT. 

(5) Radon measurement methods used to determine compliance with the existing standards. 

Key issue – The approved method (Method 115, 40 CFR 61, Appendix B) of monitoring 

Rn-222 to demonstrate compliance with the emission limit for impoundments that 

existed as of December 15, 1989, is still valid. 

(6) Compare the 1989 risk assessment with current risk assessment approaches. 

Key Issue – Adoption of a lower emission limit is not necessary to protect public health, 

as the current limit has been shown to be protective of human health and the 

environment. Impact costs associated with the limit are considered to be acceptable. 

5.1.1 Existing and Proposed Uranium Recovery Facilities 

Sections 3.2, 3.3, and 3.4 describe the three types of uranium recovery facilities: conventional 

mills, ISL facilities, and heap leach facilities. Each facility type is briefly described below. 

Conventional Mills 

Section 3 of this report presents a review of the existing and proposed uranium recovery 

facilities. As indicated, there are five conventional mills at various stages of licensing, with 

various capacities to receive tailings. Of these five conventional mills, only White Mesa is 
 53 

operational. Some of these were constructed before December 15, 1989, and fall under the 

Subpart W monitoring requirement. Table 16 shows the current conventional mills with preDecember 15, 1989 conventional impoundments. 

Table 16: Current Pre-December 15, 1989 Conventional Impoundments 

Conventional 

Mill Name Regulatory Status Pre-December 15, 1989 

Impoundments 

Sweetwater Standby,* license expires November 2014 37 acres not full 

Shootaring Canyon Standby,* license extension May 2013 Only 7 acres of impoundment filled 

White Mesa Active, license expires March 2015 Cell 2 closed, Cell 3 almost full 

* Standby means the period of time when a facility may not be accepting new tailings, but has not yet entered 

closure operations. 

The White Mesa Mill (see Section 3.2.2) has one pre-1989 cell (Cell 3) that is authorized to 

accept tailings and is still open. Cell 2 is closed. Both cells are monitored for radon flux. The 

average radon flux for Cell 2 was calculated at 13.5 pCi/(m2

-sec), while that at Cell 3 was 

8.9 pCi/(m2-sec). The mill also uses an impoundment constructed before 1989 as an evaporation 

pond. 

The Sweetwater Mill (see Section 3.2.1) has a 60-acre tailings management area with a 37-acre 

tailings impoundment of which 28 acres are dry with an earthen cover. The remainder is covered 

by water. The radon flux from this impoundment is monitored yearly. The average flux (using 

Method 115) for the entire impoundment was 6.01 pCi/(m2-sec), including the water-covered 

area, which had an assumed flux of zero. 

The Shootaring Canyon Mill (see Section 3.2.3) had plans for an upper and lower impoundment, 

but only the upper impoundment was constructed. As the mill operated for approximately 

30 days, only about 7 acres of tailings were deposited in the upper impoundment. These have a 

soil cover. The average radon flux from the covered tailings was measured using Method 115 at 

11.9 pCi/(m2-sec) in April 2010. 

The Piñon Ridge Mill (see Section 3.2.4) is a permitted conventional uranium recovery facility in 

Montrose County, Colorado. The facility has not been constructed; however, there are current 

activities at the site, including a pre-operational environmental monitoring program. 

In-Situ Recovery 

As discussed in Section 3.3, ISL was first conducted in 1963 and soon expanded so that by the 

mid-1980s, a fair proportion of the recovered uranium was by ISL. Table 8shows the ISL 

facilities in the United States that are currently operational. As previously discussed, the 

economics of ISL uranium recovery are conducive to lower grade deposits or deeply buried 

deposits that could not be economically recovered with conventional open pit or underground 

mining. Thus, approximately 23 facilities are restarting, expanding, or planning for new 

operations (see Table 9). 

Of particular importance to Subpart W are the impoundments that are an integral part of all ISL 

facilities. These impoundments are required to maintain the hydrostatic gradient toward the leach 
 54 

field to minimize excursions referred to as “flare,” a proportionality factor designed to estimate 

the amount of aquifer water outside of the pore volume that has been impacted by lixiviant flow 

during the extraction phase. While these impoundments typically do not reach the size and scale 

of conventional tailings piles, they are an integral component of ISL, contain various amounts of 

radium, and can function as sources of radon gas. Section 3.3.1 provides the mathematical 

framework for estimating the quantity of radon being emitted from an impoundment. The 

subsequent discussion of Subpart W, including a proposed standard for impoundments 

constructed after December 15, 1989, will further evaluate this radon flux. 

Heap Leach Facilities 

The few commercial heap leach facilities established in the 1980s have been shut down. 

Recently, however, two heap leach facilities have been proposed: one in Wyoming (Sheep 

Mountain – Energy Fuels) and one in New Mexico (Grants Ridge, Uranium Energy Corporation) 

(see Section 3.4). If the price of uranium increases, then recovery of uranium from heap-leaching 

low-grade ores will become economically attractive and will likely lead to additional facilities. 

The question to be addressed from the standpoint of Subpart W is the radon flux released from 

the active heap leach pile. Also, once the uranium is removed from the ore in the heap leach pile, 

the spent ore becomes a byproduct material much like the tailings, albeit not mobile. This spent 

ore contains radium that releases radon. As the heap leach pile is constructed to allow lixiviant to 

“trickle through” the pile, these same pathways could allow for radon release by diffusion out of 

the spent ore and then through the pile, which is addressed under Subpart W. 

5.1.2 RCRA Comparison 

Both alternative disposal methods presented in Subpart W (work practices) require that tailings 

impoundments constructed after December 15, 1989, meet the requirements of 

40 CFR 192.32(a)(1). Tailings impoundments include surface impoundments, which are defined 

in 40 CFR 260.10: 

Surface impoundment or impoundment means a facility or part of a facility which 

is a natural topographic depression, man-made excavation, or diked area formed 

primarily of earthen materials (although it may be lined with man-made 

materials), which is designed to hold an accumulation of liquid wastes or wastes 

containing free liquids, and which is not an injection well. Examples of surface 

impoundments are holding, storage, settling, and aeration pits, ponds, and 

lagoons. 

The above definition encompasses conventional tailings ponds, ISL ponds, and heap leach piles. 

The last is included as it is assumed that the heap leach pile will be diked or otherwise 

constructed so as not to lose pregnant liquor coming from the heap. 

This being the case, 40 CFR 264.221(a) states that the impoundment shall be designed and 

constructed and installed to prevent any migration of wastes out of the impoundment to the 

adjacent subsurface soil or ground water or surface water at any time during the active life of the 

impoundment. Requirements of the liner system listed in 40 CFR 264.221(c) include: 
 55 

(1)(i)(A) A top liner designed and constructed of materials (e.g., a geomembrane) to prevent 

the migration of hazardous constituents into such liner during the active life. 

(1)(i)(B) A composite bottom liner, consisting of at least two components. The upper 

component must be designed and constructed of materials (e.g., a geomembrane) to 

prevent the migration of hazardous constituents into this component during the active 

life and post-closure care period. The lower component must be designed and 

constructed of materials to minimize the migration of hazardous constituents if a 

breach in the upper component were to occur. The lower component must be 

constructed of at least 3 ft (91 centimeters (cm)) of compacted soil material with a 

hydraulic conductivity of no more than 1×10−7

 centimeters per second (cm/sec). 

The regulation also requires a leachate collection system: 

(2) The leachate collection and removal system between the liners, and immediately 

above the bottom composite liner in the case of multiple leachate collection and 

removal systems, is also a leak detection system. This leak detection system must be 

capable of detecting, collecting, and removing leaks of hazardous constituents at the 

earliest practicable time through all areas of the top liner likely to be exposed to waste 

or leachate during the active life and post-closure care period. 

Other requirements for the design and operation of impoundments, given in 40 CFR 264 

Subpart K, include construction specifications, slope requirements, and sump and removal 

requirements. The above requirements are important to new uranium containment/impoundment 

systems because of the potential that water will be used to limit the radon flux from a 

containment/impoundment. Thus, it is also important to minimize the potential for ground water 

or surface water contamination. For conventional mill tailings impoundments, the work practices 

require a soil cover. With heap leach piles, the moisture in the heap would limit radon during 

operations, and after operations, a degree of moisture would be required to ensure that the radon 

diffusion coefficient is kept low (see Section 5.4). 

5.1.3 Regulatory History 

Section 2.0 reviewed the regulatory history of Subpart W. This review indicates that NESHAP 

Subpart W continues to be the appropriate regulatory tool to implement the Administrator’s duty 

under the CAA. The following presents the use of GACT (see Section 5.3) in detail and 

describes its use in conventional and other than conventional uranium recovery. 

5.1.4 Tailings Impoundment Technologies 

Sections 2.3.1 and 2.3.2 discuss tailings impoundment technologies. The two primary changes to 

the technology as it was previously practiced were first that owners and/or operators of 

conventional mill tailings impoundments must meet the requirements of 40 CFR 192.32(a)(1) 

and second that they must adhere to one of the two work practices previously discussed (for 
 56 

impoundments constructed after December 15, 1989). Within these limits, tailings impoundment 

technologies have had no fundamental changes. 

5.1.5 Radon Measurement Methods 

As previously described, Subpart W defines two separate standards. The first states that existing 

sources (as of December 15, 1989) must ensure that emissions to the ambient air from an 

existing uranium mill tailings pile shall not exceed 20 pCi/(m2

-sec) of Rn-222. To demonstrate 

compliance with this emission standard, facilities are required to monitor emissions in 

accordance with Method 115 of 40 CFR 61, Appendix B, and file an annual report with EPA that 

shows the results of the compliance monitoring (see Section 3.5). As pointed out in Appendix B, 

the focus of the monitoring was on the beaches, tops, and sides of conventional piles. The radon 

flux from the water-covered portion of the tailings pile was assumed to be zero. Although 

regulated under Subpart W, it is unclear how to monitor the radon flux off the surface of 

evaporation ponds at conventional mills, ISLs, or heap leach facilities. Since these ponds are 

considerably smaller than tailings impoundments, the solution was to specify that as long as the 

water cover is 1 meter or more during the active life of the pond, no monitoring is necessary (see 

Section 3.3.1). 

Section 3.3.1 also shows that, for evaporation ponds at ISL facilities, the radon flux from the 

surface is a function of the wind speed and the concentration of radium in the water. Estimates 

using actual ISL data showed the contribution to the sites’ total radon release to be less than 1% 

of the total. In any case, the radon flux can also be reduced by co-precipitating the radium using 

barium chloride (BaCl2) co-precipitation treatment to reduce the radium concentration. 

For impoundments constructed on or after December 15, 1989, monitoring is not required. 

Rather, Subpart W requires that these impoundments comply with one of two work practice 

standards: the first practice limits the size of the impoundment to 40 acres or less, which limits 

the radon source, while the second practice of continuous disposal does not allow uncovered 

tailings to accumulate in large quantities, which also limits radon emissions. 

For evaporation ponds or holding ponds as in the pre-December 15, 1989, case, a 1-meter cover 

of water should be sufficient to limit the radon flux to the atmosphere (see Section 3.3.1). Thus, 

the proposed GACT is that these impoundments meet the design and construction requirements 

of 40 CFR 192.32(a)(1), with no size or area restriction, and that during the active life of the 

pond at least 1 meter of liquid be maintained in the pond. 

The last facility is the potential heap leach pile. Subpart W applies to the material in the pile as 

byproduct material is being generated. Considering a small section of the pile as the leach (acid 

or base) solubilizes the uranium, the material left is byproduct material. The result is a material 

similar to tailings and the heap is also wet. It is assumed that if the moisture content is greater 

than 30%, the heap is not dewatered. As long as the heap is not dewatered, the radon diffusion 

coefficient is such that minimal radon will escape the heap leach pile. 
 57 

Heap Leach Radon Flux 

A possible source of radon from a heap leach pile is from the surface of the pile. Assuming that 

the heap pile is more than 1 or 2 meters thick, the radon flux from this configuration can be 

estimated from the following formula (NRC 1984): 

J = 104

 R ρ E ඥߣ ܦ) ௘5-1 (

Where J = radon flux (pCi/(m2-sec)) 

104 = units conversion (cm2

/m2) 

R = specific activity of radium (pCi/g) 

ρ = dry bulk density of material (1.8 g/cc) 

E = emanation coefficient 

λ = radon decay constant (2.11×10-6 sec-1) 

De = radon diffusion coefficient (cm2

/sec) 

 = D0 p exp[-6 m p -6 m14 p] (5-2) 

D0 = radon diffusion coefficient in air (0.11 cm2

/sec) 

 m = moisture saturation fraction 

 p = total porosity 

The above empirical expression for the radon diffusion coefficient was developed by Rogers and 

Nielson (1991), based on 1,073 diffusion coefficient measurements on natural soils. Figure 13 

shows that the diffusion coefficient calculated using the empirical expression agrees well with 

the measured data points over the whole range of moisture saturation at which diffusion 

coefficient measurements were made. 

Source: Rogers and Nielson 1991, as reported in Li and Chen 1994 

Figure 13: Diffusion Coefficient as a Function of 

Moisture Saturation 
 58 

Figure 13 also demonstrates that as the moisture increases, the radon diffusion coefficient 

decreases significantly. This is because radon diffuses 10,000 times more slowly in water than it 

does in air (Drago 1998, as reported in Brown 2010). Therefore, adding moisture to the 

radium-containing material (whether it be a tailings pile or a heap pile) would decrease the 

diffusion coefficient, thereby increasing the time it takes for radon to diffuse out of the material 

and allowing more radon to decay before it can be released. As Figure 13 shows, the decrease in 

the radon diffusion coefficient can be significant, especially at high moisture levels. 

However, in addition to the radon diffusion coefficient, the radon emanation coefficient is 

sensitive to the amount of moisture present. When a radium atom decays, one of three things can 

happen to the resulting radon atom: (1) it may travel a short distance and remain embedded in the 

same grain, (2) it can travel across a pore space and become embedded in an adjacent grain, or 

(3) it is released into a pore space. The fraction of radon atoms released into the pore space is 

termed the “radon emanation coefficient” (Schumann 1993). As soil moisture increases, it affects 

the emanation coefficient by surrounding the soil grains with a thin film of water, which slows 

radon atoms as they are ejected from the soil grain, increasing the likelihood that the radon atom 

will remain in the pore space. Research by Sun and Furbish (1995) describes this relationship 

between moisture saturation and the radon emanation rate: 

The greater the moisture saturation is, the greater the possible radon emanation 

rate is. With moisture contents from 10% up to 30%, the recoil emanation rates 

quickly reach the emanation rate of the saturated condition. As the moisture 

reaches 30%, a universal thin film on the pore surface is formed. This thin film is 

sufficient to stop the recoil radon from embedding into another part of the pore 

wall. 

Figure 14 shows that the radon emanation coefficient can vary considerably for different tailings 

piles. Figure 14 also agrees with Sun and Furbish (1995) in that it shows that the emanation 

coefficient tends to level off when the moisture saturation level is above approximately 30%. 
 59 

Source: NRC 1984 

Figure 14: Emanation Coefficient as a Function of Moisture 

Content and Moisture Saturation 

In conclusion, a moisture saturation level of up to about 30% tends to increase the radon 

emanation coefficient and decrease the radon diffusion coefficient, such that the amount of radon 

released from the pile could increase with increasing moisture. Above about 30% moisture 

saturation, the radon emanation coefficient is unchanged by increasing moisture, while the radon 

diffusion coefficient continues to decrease. Figure 15 shows the total effect of moisture on the 

radon flux. Equation 5-1 was used to develop Figure 15, along with the Rogers and Nielson 

(1991) empirical equation for the diffusion coefficient, an approximation of the Vitro Sand 

emanation coefficient from Figure 14, and a porosity of 0.39. Figure 15 does not show the radon 

flux values, since they would vary depending on the radium concentration and would not affect 

the shape of the curve. 
 60 

Figure 15: Radon Flux as a Function of Moisture Saturation and 

Moisture Content 

Figure 15 shows that the radon flux starts low and increases as the moisture saturation increases 

due to the emanation coefficient. At between 20% and 30% moisture saturation, the flux reaches 

a peak that is about 21⁄2 times the flux at zero moisture, after which the diffusion coefficient takes 

control and the flux decreases. Figure 15 is consistent with the results reported by Hosoda et al. 

(2007) in their study of the effect of moisture on the emanation of radon and thoron gases from 

weathered granite soil: 

A sporadic increase in the radon and thoron exhalation rates was caused by the 

increase in the moisture content up to 8% [27% moisture saturation]. However, 

the exhalation rates showed a decreasing tendency with the increase in moisture 

content over 8%..., both measured and calculated radon exhalation rates had 

similar trends with an increase in the moisture content in the soil. 

The final point from Figure 15 is that the radon flux with a moisture content of 70% or greater is 

less than the flux at zero moisture, and that with a porosity of 0.39, 70% moisture saturation is 

equivalent to 27% moisture by weight. Thus, 30% moisture by weight would result in a radon 

flux significantly below the zero moisture flux. 

5.1.6 Risk Assessment 

Section 4.4 presents the results of a risk assessment performed for seven actual uranium recovery 

sites plus two generic uranium recovery sites. This risk assessment used the CAP88 Version 3.0 

analytical computer model, which, as described in Section 4.0, evolved from and differs from the 

models used for the 1989 risk assessment (i.e., AIRDOS-EPA, RADRISK, and DARTAB). 

Additionally, this assessment used the latest radon dose and risk coefficients (i.e., millirem 
 61 

(mrem)/picocurie (pCi) and LCF/pCi) from FGR 13. Both the 1989 assessment and this 

assessment used site-specific meteorological data. This assessment used 2000 census data, 

updated to 2010, whereas the 1989 assessment used 1983 data. Finally, as stated above, this 

assessment used actual historical radon releases from the uranium recovery sites, whereas 

because of the lack of site-specific data, the 1989 assessment assumed a radon release rate based 

on 1 pCi/(m2-sec) Rn-222 emitted per pCi/g Ra-226 during both the operating, standby, drying, 

and/or disposal phase, and either 20 pCi/(m2

-sec) or the design flux (if known) during the 

post-disposal phase. 

Section 4.4 presents the doses and risks calculated by the current risk assessment, and 

Section 4.5summarizes them. Additional information on the current risk assessment appears in 

SC&A 2011. 

5.2 Uranium Recovery Source Categories 

The preceding items and key issues are the basis for categorizing the major uranium recovery 

methods that will lead to methods of reducing radon emissions. The next section, which 

addresses the GACT standard, further discusses the applicability of the control measures. The 

following source categories represent a logical breakdown of the current uranium recovery 

industry: 

Conventional Impoundments – Conventional impoundments are engineered structures for 

storage and eventual permanent disposal of the fine-grained waste from mining and milling 

operations (i.e., tailings). All conventional uranium recovery mills have one or more 

conventional impoundments. Table 3 shows conventional uranium milling facilities that are 

either built or licensed. This category will also include future conventional milling facilities. 

Nonconventional Impoundments – At nonconventional tailings impoundments, tailings 

(byproduct material) are contained in ponds and covered by liquids. These impoundments are 

normally called “evaporation ponds” or “holding ponds.” Nonetheless, they contain byproduct 

material and, as shown in Section 3.3.1, can generate radon gas. This category is usually 

associated with ISL facilities (i.e., process waste water resulting from ISL operations (see 

Section 3.3)), but can also be associated with conventional facilities or heap leach facilities. 

While these ponds do not meet the work practices for conventional mills, they still must meet the 

requirements of 40 CFR 192.32(a)(1). 

Heap Leach Piles – While no heap leach facilities are currently operating in the United States, at 

least one potential operation is expected to go forward (see Section 3.4). Heap leach piles contain 

byproduct material, which is the residue of the operation. That is, as the lixiviant mobilizes the 

uranium, the remaining part of the ore becomes byproduct. As stated above, the design and 

operation of the heap leach is expected to follow the requirements of 40 CFR 192.32(a)(1). 

5.3 The GACT Standard 

Section 112(d) of the CAA requires EPA to establish NESHAPs for both major and area sources 

of HAPs that are listed for regulation under CAA section 112(c). Section 112(c) lists 
 62 

radionuclides, including radon, as a HAP, while section 112(a) defines two types of HAP 

sources: major sources and area sources. Depending on whether the source is a major or area 

source, section 112(d) prescribes standards for regulation of emissions of HAP. A “major 

source,” other than for radionuclides, is defined as any stationary source or group of stationary 

sources located within a contiguous area and under common control that emits or has the 

potential to emit, in the aggregate, 10 tons per year or more of any HAP. For radionuclides, 

major source shall have the meaning specified by the Administrator by rule. An area source is a 

stationary source that is not a major source. 

The regulation of HAPs at major sources is dictated by the use of MACT. Section 112(d) defines 

MACT as the maximum degree of reduction in HAP emissions that the Administrator determines 

is achievable, considering the cost of achieving the reduction and any non-air-quality health and 

environmental impacts and energy requirements. With respect to area sources, section 112(d)(5) 

states that, in lieu of promulgating a MACT standard, the Administrator may elect to promulgate 

standards that provide for the use of GACT or management practices to reduce HAP emissions. 

In 2000, EPA provided guidance to clarify how to apply the major source threshold for HAPs as 

defined in section 112(b) of the CAA Amendments of 1990. The guidance stated how to apply 

the major source threshold specifically for radionuclides: 

There have been some questions about determining the major source threshold 

for sources of radionuclides. Section 112(a)(1) allows the Administrator to 

establish different criteria for determining what constitutes a major source of 

radionuclides since radionuclides emissions are not measured in units of tons. 

This, however, would not preclude a known radionuclide emitter that is 

collocated with other HAP-emitting activities at a plant site from being 

considered a major source due to the more common, weight-based threshold. The 

July 16, 1992, source category list notice did not include any sources of 

radionuclides because no source met the weight-based major source threshold, 

and the Agency had not defined different criteria. At the current time, there 

remain no listed major source categories of radionuclide emissions. [EPA 2000b] 

Based on this guidance, radon emissions from uranium recovery facility tailings impoundments 

are not a major source, and therefore, they are area sources for which the GACT standard is 

applicable. Unlike MACT, the meaning of GACT, or what is “generally available” is not defined 

in the act. However, section 112(d)(5) of the CAA Amendments for 1990 authorizes EPA to: 

Promulgate standards or requirements applicable to [area] sources...which 

provide for the use of generally available control technologies or management 

practices by such sources to reduce emissions of hazardous air pollutants. 

The Senate report on the legislation (U.S. Senate 1989) provides additional information on 

GACT and describes it as: 

...methods, practices and techniques which are commercially available and 

appropriate for application by the sources in the category considering economic 
 63 

impacts and the technical capabilities of the forms to operate and maintain the 

emissions control systems. 

Determining what constitutes GACT involves considering the control technologies and 

management practices that are generally available to the area sources in the source category. 

Also considered are the standards applicable to major sources in the same industrial sector to 

determine if the control technologies and management practices are transferable and generally 

available to area sources. In appropriate circumstances, technologies and practices at area and 

major sources in similar categories are also reviewed to determine whether such technologies 

and practices can be considered generally available for the area source category at issue. Finally, 

as noted above, in determining GACT for a particular area source category, the costs and 

economic impacts of available control technologies and management practices on that category 

are considered. 

Thus, as presented above, “Promulgate standards or requirements ... ” does not limit EPA to 

strict “standard setting” in order to provide for the use of GACT. Rather, it allows EPA to 

promulgate at least two types of rules: rules that set emission levels based on specific controls or 

management practices (this is analogous to the MACT standard setting), and rules that establish 

permitting or other regulatory processes that result in the identification and application of GACT 

standards. 

5.4 Uranium Recovery Categories and GACT 

For conventional impoundments, the 1989 promulgation of Subpart W contained two work 

practice standards, phased disposal and continuous disposal (see Section 2.0, page 7). The work 

practice standards limit the size and number of the impoundments at a uranium recovery facility 

in order to limit radon emissions. The standards cannot be applied to a single pile that is larger 

than 40 acres (for phased disposal) or 10 uncovered acres (for continuous disposal). This 

approach was taken in recognition that the radon emissions from these impoundments could be 

greater if the piles were left dry and uncovered. The 1989 Subpart W also included the 

requirements in 40 CFR 192.32(a), which include design and construction requirements for the 

impoundments as well as requirements for preventing and mitigating ground water 

contamination. 

As discussed earlier, it is no longer believed that a distinction needs to be made for conventional 

impoundments based on the date when they were design and/or constructed. The existing 

impoundments at both the Shootaring Canyon (Section 3.2.3) and Sweetwater (Section 3.2.1) 

facilities can meet the work practice standards in the current Subpart W regulation. 

Impoundments at both these facilities have an area of less than 40 acres and are synthetically 

lined as required in 40 CFR 192.32(a). Also, the existing Cell 3 at the White Mesa mill will be 

closed in 2012 and replaced with impoundments that meet the phased disposal work practice 

standard (Section 3.2.2). Therefore, there is no reason not to apply the work practice standards 

required for impoundments designed or constructed after December 15, 1989, to these older 

impoundments. By incorporating these impoundments under the work practice standards, the 

requirement of radon flux testing is no longer needed and will be eliminated. 
 64 

For the proposed GACT, the requirements of 40 CFR 192.32(a) as they pertain to the Subpart W 

standards were evaluated. Liner requirements in use for the permitting of hazardous waste land 

disposal units under RCRA are contained in 40 CFR 264.221. Since 40 CFR 192.32(a)(1) 

references 40 CFR 264.221, it is the only requirement necessary for Subpart W, as the RCRA 

requirements are effective methods of containing tailings and protecting ground water while also 

limiting radon emissions. The regulation in 40 CFR 264.221 contains safeguards to allow for the 

placement of tailings and also provides for an early warning system in the event of a leak in the 

liner system. Therefore, the proposed GACT for conventional impoundments retains the two 

work practice standards and the requirements of 40 CFR 192.32(a)(1), because they have proven 

to be effective methods for limiting radon emissions while also protecting ground water. The 

NRC considers the requirements of 40 CFR 192.32(a) in its review during the licensing process. 

For nonconventional impoundments, where tailings (byproduct material) are contained in ponds 

and covered by liquids, a new GACT is proposed. These facilities, called “evaporation ponds” or 

“holding ponds,” also must meet the requirements of 40 CFR 192.32(a)(1). Specifically, these 

are the design and operating requirements for the impoundments. Because of the general 

experience that a depth of greater than 1 meter of liquid essentially reduces the radon flux of 

ponds to negligible levels, no monitoring is required for this type of impoundment. Given these 

factors, the following GACT is proposed: 

Nonconventional impoundments meet the design and construction requirements 

of 40 CFR 192.32(a)(1), with no size/area restriction, and during the active life of 

the pond, at least 1 meter of liquid be maintained in the pond. 

For the last category, heap leach piles, an approach similar to that for nonconventional 

impoundments is proposed. As previously noted, these facilities contain byproduct material, 

which is the residue of the operation. That is, as the lixiviant mobilizes the uranium, the 

remaining part of the ore becomes byproduct material, which is regulated under Subpart W. As 

for nonconventional impoundments, the design and operation of the heap leach pile is expected 

to follow the requirements of 40 CFR 192.32(a)(1). This also will prevent the loss of pregnant 

liquor (lixiviant with dissolved uranium) from spillage or leakage. 

The byproduct material that makes up the volume of the spent heap leach pile is typically wet. 

As Figure 15 shows, as material goes from dry to wet the radon flux first increases before it 

decreases (the reasons for this are discussed in Section 5.1.5). While it is impossible to maintain 

a completely wet state, it is possible to maintain a sufficient percentage of moisture content to 

meet a goal that the radon flux in the wetted material is below what the flux would be if the 

material was dry. This percentage is related to the state or material being “dewatered.” By way of 

definition, 40 CFR 61.251(c) states: 

Dewatered means to remove the water from recently produced tailings by 

mechanical or evaporative methods such that the water content of the tailings 

does not exceed 30 percent by weight. 

Thus, the proposed GACT for heap leach piles is that, in addition to meeting 

40 CFR 192.32(a)(1), operating heap leach piles must maintain a moisture content greater than 
 65 

30% (equivalent to about 70% to 80% moisture saturation, as described in Section 5.1.5). This 

would, as indicated, ensure that the radon flux from the surface of the pile is quite low, i.e., at or 

below what the flux would be if the material in the pile was dry. 

Since the purpose of this GACT is to control the radon emissions, it may not be critical to 

maintain the 30% moisture content in the lower levels/lifts of the pile. The reason for this is twofold; first, radon generated in the lower levels would have to travel further in the pile before it 

would escape to the atmosphere, thereby giving it more time to decay within the pile, and 

second, radon from the lower layers will be slowed due to the 30% moisture content in the upper 

levels. Additionally, if inter-lift liners are provided when the pile is composed of multiple lifts, 

the inter-lift liner would act as a barrier to radon from the lower lifts, and thus mitigate the need 

for those lower lifts to maintain the 30% moisture content. On the other hand, because radon 

emission do not stop when active uranium leaching has ceased, it will be necessary to continue 

wetting the pile to maintain the 30% moisture content until a final reclamation cover (including a 

radon barrier layer) has been constructed over the pile. 

5.5 Other Issues 

During the review of Subpart W, several additional issues were identified. These are identified 

and discussed in this section. 

5.5.1 Extending Monitoring Requirements 

In reviewing Subpart W, EPA examined whether radon monitoring should be extended to all 

impoundments constructed and operated since 1989 so that the monitoring requirement would 

apply to all impoundments containing uranium byproduct material (i.e., tailings). EPA also 

reviewed how this requirement would apply to facilities where Method 115 is not applicable, 

such as at impoundments totally covered by liquids. As the rule currently exists, only pre-1989 

conventional tailings impoundments are required to monitor for radon emissions, the requirement 

being an average flux rate of not more than 20 pCi/(m2

-sec). This is because, at the time of 

promulgation of the 1989 rule, EPA stated that the proposed work practice standards would be 

effective in reducing radon emissions from operating impoundments. Since the work practice 

standards could not be applied to pre-1989 facilities, and since EPA determined that it is not 

feasible to prescribe an emissions standard for radon emissions from a tailings impoundment 

(54 FR 9644 (FR 1989a)), the improved work practice standards would limit radon emissions by 

limiting the amount of tailings exposed. 

Thus, it is not necessary to require radon monitoring at facilities constructed after the current 

Subpart W was promulgated (i.e., December 15, 1989). With respect to tailings and the amount 

of water used to cover them, the work practice standards (now proposed as GACTs) are also 

protective in preventing excess radon emissions. Further, for nonconventional impoundments, 

where there is no applicable radon monitoring method, the standing liquid requirement will 

effectively prevent all radon emissions from holding or evaporation ponds. 
 66 

5.5.2 Clarification of the Term “Operation” 

As currently written, 40 CFR 61.251(e) defines the operational period of a tailings impoundment. 

It states that “operation” means that an impoundment is being used for the continuing placement 

of new tailings or is in standby status for such placement [which means that as long as the 

facility has generated byproduct material at some point and placed it in an impoundment, it is 

subject to the requirements of Subpart W]. An impoundment is in operation from the day that 

tailings are first placed in the impoundment until the day that final closure begins. 

There has been some confusion over this definition. For example, a uranium mill announced that 

it was closing a pre-December 15, 1989, impoundment. Before initiating closure, however, it 

stated that it would keep the impoundment open to dispose of material generated by other closure 

activities at the site that contained byproduct material (liners, deconstruction material, etc) but 

not “new tailings.” The company argued that since it was not disposing of new tailings the 

impoundment was no longer subject to Subpart W. We disagree with this interpretation. While it 

may be true that the company was no longer disposing of new tailings in the impoundment, it has 

not begun closure activities; therefore, the impoundment is still open to disposal of byproduct 

material that emits radon and continues to be subject to all applicable Subpart W requirements. 

To prevent future confusion, we are proposing to amend the definition of “operation” in the 

Subpart W definitions at 40 CFR 61.251 as follows: 

Operation. Operation means that an impoundment is being used for the continued 

placement of uranium byproduct material or tailings or is in standby status for 

such placement. An impoundment is in operation from the day that uranium 

byproduct materials or tailings are first placed in the impoundment until the day 

that final closure begins. 

5.5.3 Clarification of the Term “Standby” 

In the past, there has been confusion as to whether the requirements of Subpart W apply to a 

uranium recovery facility that is in “standby” mode. Although not formally defined in 

Subpart W, “standby” is commonly taken to be the period of time when a facility may not be 

accepting new tailings, but has not yet entered closure operations. This period usually takes place 

when the price of uranium is such that it may not be cost effective for the facility to continue 

operations, and yet the facility fully intends to operate once the price of uranium rises to a point 

where it is cost effective for the facility to re-establish operations. As shown in Table 3, the 

Sweetwater and Shootaring Canyon mills are currently in standby. While in standby, a uranium 

recovery facility can change its license from an operating license to a possession only license, 

thereby reducing its regulatory obligations (and costs). 

The addition of the following definition of “closure” into the Subpart W definitions at 

40 CFR 61.251 would eliminate confusion: 

Standby. Standby means the period of time that a facility may not be accepting 

new tailings, but has not yet entered closure operations. 
 67 

5.5.4 The Role of Weather Events 

In the past, uranium recovery facilities have been located in the western regions of the United 

States. In these western regions, the annual average precipitation (see Figure 16) falling on the 

impoundment is less than the annual average evaporation (see Figure 17) from the impoundment. 

Also, these facilities are located away from regions of the country where extreme rainfall events 

(e.g., hurricanes or flooding) could jeopardize the structural integrity of the impoundment, 

although there is a potential for these facilities to be affected by flash floods, tornadoes, etc. 

However, recent uranium exploration in the United States shows the potential to move eastward, 

into more climatologically temperate regions of the country. South central Virginia is now being 

considered for a conventional uranium mill (e.g., the Coles Hills, see 

Table 4). To determine whether additional measures would be needed for impoundments 

operating in areas where precipitation exceeds evaporation, a review of the existing requirements 

was necessary. 

Figure 16: U.S. Average Annual Precipitation 
 68 

Figure 17: U.S. Mean Annual Evaporation 

Subpart W requires owners and operators of uranium tailings impoundments to follow the 

requirements of 40 CFR 192.32(a). That particular regulation references the RCRA surface 

impoundment design and operations requirements of 40 CFR 264.221. At 40 CFR 264.221(g) 

and (h) are requirements that can be used to ensure proper operation of tailings impoundments. 

Section 264.221(g) states that impoundments must be designed, constructed, maintained, and 

operated to prevent overtopping resulting from normal or abnormal operations; overfilling; wind 

and rain action; rainfall; run-on; malfunctions of level controllers, alarms and other equipment; 

or human error. Section 264.221(h) states that impoundments must have dikes that are designed, 

constructed, and maintained with sufficient structural integrity to prevent massive dike failure. In 

ensuring structural integrity, it must not be presumed that the liner system will function without 

leakage during the active life of the unit. 

Uranium recovery facilities are already operating under the requirements of 

40 CFR 192.32(a)(1), including compliance with 40 CFR 264.221(g) and (h), which will provide 

protection against the weather events likely to occur in the eastern United States. 

6.0 ECONOMIC IMPACTS ASSOCIATED WITH REVISION/MODIFICATION OF 

THE SUBPART W STANDARD 

This section contains the following economic impact analyses necessary to support any potential 

revision of the Subpart W NESHAP: 

 Section 6.1 provides a review and summary of the original 1989 economic assessment 

and supporting documents. 

 The baseline economic costs for development of new conventional mills and ISL and 
 69 

heap leach facilities are developed and presented in Section 6.2. 

 Section 6.3 presents the anticipated industry costs versus environmental and public health 

benefits to be derived from each of the four proposed GACT standards. 

 Finally, Section 6.4 provides demographic data regarding the racial and socioeconomic 

composition of the populations surrounding uranium recovery facilities. 

To assess the economic impacts of potential revisions to the Subpart W NESHAP, capital costs 

(including equipment costs), labor costs, taxes, etc., were obtained from actual recent cost 

estimates that have been prepared for companies planning to design, develop, construct, and 

operate uranium recovery facilities. For ISL facilities, two recent cost estimates were used as the 

basis for this analysis, while for conventional mills and heap leach facilities, a single cost 

estimate was used for each type of facility. Other necessary data, such as a discount rate, 

borrowing, and interest rates, were assumed, as described in Section 6.2. 

Where feasible and appropriate, the economic models and recommendations from EPA’s 

“Guidelines for Preparing Economic Analyses” (EPA 2010) were followed in assessing these 

economic impacts. 

The cost and economic impact estimates described in Section 6.2 and 6.3 are based on industry 

data compiled in 2010-2011. Therefore, some of the analytical input values would differ 

somewhat if they were updated to reflect the latest information available. For example, the 

current long-term market price of uranium is approximately 17 percent lower than the $65 

estimate that is used in the analysis (Cameco, 2013). The uranium mining industry is currently 

experiencing a volatile period resulting from the aftereffects of the Fukushima nuclear disaster. 

In particular, uranium demand has suffered from nearly all of Japan’s workable reactors 

remaining offline since the March 2011 earthquake and tsunami triggered multiple meltdowns at 

the Fukushima Dai-ichi plant. Given the atypical post-Fukushima uranium market situation of 

the last couple of years and the prospects for a return to more normal market activity in the midterm future,7

 we have decided not to update the analysis to incorporate the latest industry data. 

The results of the analyses described in this section are judged to be realistic estimates of the 

mid- to long-term impacts of the proposed Subpart W NESHAP. 

6.1 1989 Economic Assessment 

When Subpart W was promulgated in 1989, EPA performed both an analysis of the standard’s 

benefits and cost and an evaluation of its economic impacts. Those analyses appear in the 1989 

BID, Volume 3, Sections 4.4 and 4.5 (EPA 1989). This section briefly summarizes the 

Subpart W economic assessments performed in 1989. 

 7

These prospects include: the conclusion of the U.S.-Russia program that annually removes 24 million 

pounds of ex-military highly enriched uranium from the market via down-blending for use as U.S. nuclear fuel; the 

60 nuclear power plants that are currently under construction throughout the world; efforts to reduce climate change 

emissions; and expectations that Japan will slowly begin restarting its 50 nuclear plants. 
 70 

In these 1989 assessments, EPA evaluated the benefits and costs associated with three separate 

decisions. The first decision concerned a limit on allowable radon emissions after closure. The 

options evaluated included reducing radon emissions from the 20 pCi/(m2

-sec) limit to 

6 pCi/(m2

-sec) and 2 pCi/(m2-sec). 

The second decision that EPA investigated was the means by which the emissions from active 

mills could be reduced to the 20 pCi/(m2

-sec) limit while operations continue. Emissions could 

be reduced by applying earth and water covers to portions of the dry areas of the tailings piles, 

which could reduce average radon emissions for the entire site to the 20 pCi/(m2

-sec) limit. 

While the first two decisions were focused on tailings piles that existed at the time the standard 

was promulgated, the third concerned future tailings impoundments. EPA evaluated alternative 

work practices for the control of radon emissions from operating mills in the future. Options 

investigated include the replacement of the traditional single-cell impoundment (i.e., the 1989 

baseline) with phased disposal or continuous disposal impoundments. 

6.1.1 Reducing Post-Closure Radon Emissions from 20 pCi/(m2-sec) 

The 1989 BID estimated the total annual tailings piles radon emissions for standards of 20, 6, 

and 2 pCi/(m2-sec) and calculated the cancers that could result from those emissions. It found 

that over a 100-year analysis period, the 6 pCi/(m2

-sec) option could lower local and regional 

risks by 3.6 cancers, while the incremental benefit of lowering the allowable flux rate from 6 to 

2 pCi/(m2-sec) was estimated at 1.0 cancer. 

The increased costs associated with reducing the allowable flux rate from 20 to 6 pCi/(m2

-sec) 

were estimated to be between $113 and $180 million (1988$) ($205 and $327 million (2011$)), 

while attainment of a 2 pCi/(m2-sec) flux rate was estimated to result in added costs of $216 to 

$345 million (1988$) ($393 to $627 million (2011$)). 

The 1989 BID does not make any statement regarding the monetized value of reduced cancer 

risks. Nor does it explicitly weigh the costs and benefits of the alternative standards. As the 

following excerpt from the preamble to the standard shows, for tailings piles at operating mills, 

EPA’s decision was based on the very low risks associated with 20 pCi/(m2-sec), rather than on a 

comparison of the benefits versus the costs of the alternative emission standards: 

... the risks from current emissions are very low. A NESHAP requiring that 

emissions from operating mill tailings piles limit their emissions to no more than 

20 pCi/(m2

-sec) represents current emissions. EPA has determined that the risks 

are low enough that it is unnecessary to reduce the already low risks from the 

tailings piles further. [FR 1989a, page 51680] 

While for tailings impoundments at inactive mills, the preamble presented a quantitative 

cost-benefit comparison as justification for maintaining the radon emission level at 

20 pCi/(m2

-sec): 
 71 

EPA examined these small reductions in incidence and maximum individual risk 

and the relatively large costs of achieving Alternative II [6 pCi/(m2

-s)], $158 

million capital coat and $33 million in annualized costs and determined that 

Alternative I [20 pCi/(m2

-s)] protects public health with an ample margin of 

safety. [FR 1989a, page 51682]

6.1.2 Reducing Radon Emissions During Operation of Existing Mills 

The 1989 BID estimated the reduction in total risk that could be obtained by reducing radon 

emissions from active mills operating at that time to 20 pCi/(m2-sec) through the application of 

an earthen cover and/or by keeping the tailings wet. The 1989 BID, Table 4-41, reported the risk 

reduction to be 0.17 fatal cancers for all active mills over their assumed 15-year operational life. 

The 1989 BID, Table 4-42B, reported that the cost for providing the earthen covers and for 

keeping the tailings wet over the 15-year operating period was estimated to be $13.166 million 

(1988$) ($23.94 million in 2011$). 

The 1989 BID does not make any statement regarding the monetized value of reduced cancer 

risks. Nor does it explicitly weigh the costs and benefits of the alternative standards. EPA 

nonetheless decided that without these standards the risks were too high, as the following 

segment from the preamble to the standard indicates: 

... EPA recognizes that the risks from mill tailings piles can increase dramatically 

if they are allowed to dry and remain uncovered. An example of how high the 

risks can rise if the piles are dry and uncovered can be seen in the proposed rule, 

54 FR 9645. That analysis assumed that the piles were dry and uncovered and the 

risks were as high as 3×10-2 with 1.6 fatal cancers per year. Therefore, EPA is 

promulgating a standard that will limit radon emissions to an average of 

20 pCi/m2-s. This rule will have the practical effect of requiring the mill operators 

to keep their piles wet or covered. ... [FR 1989a, page 51680] 

6.1.3 Promulgating a Work Practice Standard for Future Tailings Impoundments 

Section 4.4.3.1 of the 1989 BID provides the following explanations of the phased and 

continuous disposal options: 

Phased Disposal 

The first alternative work practice which is evaluated for model new tailings 

impoundments is phased disposal. In phased or multiple cell disposal, the tailings 

impoundment area is partitioned into cells which are used independently of other 

cells. After a cell has been filled, it can be dewatered and covered, and another 

cell used. Tailings are pumped to one initial cell until it is full. Tailings are then 

pumped to a newly constructed second cell and the former cell is dewatered and 

then left to dry. After the first cell dries, it is covered with earth obtained from the 

construction of a third cell. This process is continued sequentially. This system 
 72 

minimizes emissions at any given time since a cell can be covered after use 

without interfering with operations as opposed to the case of a single cell. 

Phased disposal is effective in reducing radon-222 emissions since tailings are 

initially covered with water and finally with earth. Only during a drying-out 

period of about 5 years for each cell are there any [significant] radon-222 

emissions from the relatively small area. During mill standby periods, a water 

cover could be maintained on the operational cell. For extended standby periods, 

the cell could be dewatered and a dirt cover applied. 

Continuous Disposal 

The second alternative work practice, continuous disposal, is based on the fact 

that water can be removed from the tailings slurry prior to disposal. The 

relatively dry dewatered (25 to 30% moisture [by weight]) tailings can then be 

dumped and covered with soil almost immediately. No extended drying phase is 

required, and therefore very little additional work would be required during final 

closure. Additionally, ground water problems are minimized. 

To implement a dewatering system would introduce complications in terms of 

planning, design, and modification of current designs. Acid-based leaching 

processes do not generally recycle water, and additional holding ponds with 

ancillary piping and pumping systems would be required to handle the liquid 

removed from the tailings. Using trucks or conveyor systems to transport the 

tailings to disposal areas might also be more costly than slurry pumping. Thus, 

although tailings are more easily managed after dewatering, this practice would 

have to be carefully considered on a site-specific basis. 

Various filtering systems such as rotary vacuum and belt filters are available and 

could be adapted to a tailings dewatering system. Experimental studies would 

probably be required for a specific ore to determine the filter media and 

dewatering properties of the sand and slime fractions. Modifications to the typical 

mill ore grinding circuit may be required to allow efficient dewatering and to 

prevent filter plugging or blinding. Corrosion-resistant materials would be 

required in any tailings dewatering system due to the highly corrosive solutions 

which must be handled. ... 

The committed fatal cancer risk8

 from the operation of model baseline (single-cell), phased 

disposal, and continuous disposal impoundments, as determined by the 1989 BID, is shown in 

Table 17. Table 17 shows the following: 

[during] the operational period the risk of cancer is reduced, relative to the single 

cell baseline, by 0.129 if phased disposal is adopted and by 0.195 if the 

continuous single cell method is used. The risk reduction associated with using 

the continuous single cell relative to the phased approach is 0.066. In the 

post-operational phase, phased disposal raises the risk by 0.012 relative to the 

 8

 “Committed fatal cancer risk” is the likeliness that an individual will develop and die from cancer at 

some time in the future due to their current exposure to radiation. “Committed fatal cancer risk” is sometimes 

referred to as “latent cancer fatality risk.” 
 73 

baseline, while the continuous single cell approach lowers it by 0.017 relative to 

the baseline and by 0.028 relative to phased disposal. [EPA 1989, 

Section 4.4.3.3] 

Table 17: Radon Risk Resulting from Alternative Work 

Practices (Committed Cancers) 

Baseline 

(Single Cell)

Phased 

Disposal

Continuous 

Disposal

Operational Period 

(0 to 20 years) 0.282 0.153 0.087

Post-Operations 

(21 to 100 years) 0.264 0.276 0.247

Total 0.546 0.429 0.334

Source: EPA 1989, Table 4-45 

Concerning the cost to implement the work practices, the 1989 BID indicates the following: 

the phased ... disposal impoundment is the most expensive design ($54.02 million 

[1988$]), while the single cell ... impoundment ($36.55 million [1988$]) is the 

least expensive. Costs for the continuous single cell design ($40.82 million 

[1988$]) are only slightly more than those of the single cell impoundment, 

although the uncertainties surrounding the technology used in this design are the 

largest. [EPA 1989, Section 4.4.3.4] 

The 1989 BID does not make any statement regarding the monetized value of reduced cancer 

risks. Nor does it explicitly weigh the costs and benefits of the alternative standards. However, as 

the following excerpt from the preamble to the standard shows, EPA was concerned about the 

uncertainty of the benefits and costs analysis that had been performed for this portion of the 

regulation. Ultimately, the Agency based its decision on the small cost to implement the work 

practices, rather than on weighing the benefits versus the costs: 

The uncertainty arises because it assumes a steady state industry over time. If the 

uranium market once again booms there would be increased risks associated with 

Alternative I [one large impoundment (i.e., baseline)]. If the industry then 

experienced another economic downturn, the costs of Alternative I would increase 

because of the economic waste that occurs when a large impoundment is 

constructed and not filled. The risks can also increase if a company goes bankrupt 

and cannot afford the increased costs of closing a large impoundment and the pile 

sits uncovered emitting radon. The risks can also increase if many new piles are 

constructed, creating the potential for the population and individual risks to be 

higher than EPA has calculated. 

These uncertainties significantly affect the accuracy of the [benefits and costs]

analysis and given the small cost of going to Alternatives II [phased disposal] and 

III [continuous disposal], EPA has determined that in order to protect the public 
 74 

with an ample margin of safety, both now and in the future, new mill tailings 

impoundments must use phased or continuous disposal. [FR 1989a, page 51680] 

6.1.4 Economic Impacts 

To determine the economic impacts of the proposed Subpart W on the uranium production 

industry, the 1989 BID evaluated two extreme cases; in the first, it was assumed that “no portion 

of the cost of the regulation can be passed on to the purchaser of U3O8,” and in the second, it was 

“assumed that the uranium production industry is able to recover the entire increase in the 

tailings disposal cost by charging higher U3O8 prices.” These two cases provided the lower and 

upper bound, respectively, of the likely economic impacts of Subpart W on the uranium 

production industry. 

As described in Section 3.1, from 1982 to 1986, the uranium production industry had been 

contracting and experiencing substantial losses because of excess production capacity. The 1989 

Subpart W economic impact assessment concluded that if the industry had to absorb the costs of 

implementing the regulation, the present value cost at that time would be about five times the 

industry losses from 1982 to 1986, or equal to about 10% of the book value of industry assets at 

that time, or about 15% of industry’s liabilities. 

Alternatively, if the uranium production industry could pass on the Subpart W implementation 

costs to its electric power industry customers, who would likely pass on the costs to the 

electricity users, the 1989 economic impact assessment concluded: 

The revenue earned by the [electric power] industry for generating 2.4 trillion 

kilowatt hours of electricity in 1986 was 121.40 billion dollars. The 1987 present 

value of the regulation (estimated to be $250 million) is less than 1 percent 

(.06%) of the U.S. total electric power revenue for the same year. [EPA 1989, 

Section 4.5.1]

The 1989 BID drew no conclusions regarding what effects, if any, these impacts would have on 

the uranium production industry’s financial health. 

6.2 U3O8 Recovery Baseline Economics 

This section presents the baseline economics for development of new conventional mills, ISL 

facilities, and heap leach facilities. EPA’s economic assessment guidelines define the baseline 

economics as “a reference point that reflects the world without the proposed [or in the case of 

Subpart W, the modified] regulation. It is the starting point for conducting an economic analysis 

of potential benefits and costs of a proposed [or modified] regulation” (EPA 2010, Section 5). 

The baseline costs were estimated using recently published cost data for actual uranium recovery 

facilities. For the conventional mill, data from the proposed new mill at the Piñon Ridge project 

in Colorado were used. For the ISL facility, data from two proposed new facilities were used: the 

first was the Centennial Uranium project in Colorado and the second was the Dewey-Burdock 

project in South Dakota. The Centennial project is expected to have a 14- to 15-year production 
 75 

period, which is a long duration for an ISL facility, while the Dewey-Burdock project is expected 

to have a shorter production period of about 9 years, which is more representative of ISL 

facilities. For the heap leach facility, data from the Sheep Mountain project in Wyoming were 

used. Sections 6.2.1 through 6.2.4 provide details of how the project-specific cost data were 

converted into base case economic data, and Section 6.2.5 presents a short sensitivity study for 

the conventional mill and heap leach cost estimates. Because two projects were analyzed, a 

sensitivity analysis of the ISL cost estimates was not performed. 

Next it was necessary to estimate the annual amount of U3O8 that is currently used and how 

much would be required in the future. For these estimates, data from the Energy Information 

Administration (EIA) were used. Section 6.2.6 describes how the EIA data were coupled with 

specific cost data for the uranium recovery facilities to determine the cost and revenue estimates 

provided in Table 18. 

Table 18: Uranium Recovery Baseline Economics (Nondiscounted) 

Cost / Revenue

2009 ($1,000) 2035 Projections ($1,000)*

2009$ 2011$ Reference 

Nuclear

Low Nuclear 

Production

High Nuclear 

Production

Ref Low 

Import

U3O8 Revenue $347,000 $462,000 $502,000 $473,000 $605,000 $706,000

U3O8 Cost $298,000 $372,000 

Conventional $398,000 $375,000 $480,000 $560,000

In-Situ Leach $396,000 $373,000 $477,000 $557,000

Heap Leach $356,000 $335,000 $429,000 $501,000

Mixed Facilities $392,000 $368,000 $472,000 $553,000

* See the discussion below and in Section 6.2.6 for a description of these cases. 

Table 18 presents uranium production industry cost and revenue for six cases. The first two cases 

are based on the actual amount of U3O8 produced in the United States in 2009 (the last year for 

which data are available). The two 2009 cases differ in that the first is based on 2009 dollars, 

including the weighted-average price of $48.92 per pound for uranium of U.S. origin, while the 

second was based on assumptions used in this analysis (i.e., 2011 dollars and a U3O8 price of $65 

per pound). The remaining four cases in Table 26 are all based on the assumptions used in this 

analysis, but differ in the amount of U3O8 assumed to be produced in the United States in 2035. 

The first through third 2035 cases are for the Reference, Low Nuclear Production, and High 

Nuclear Production projected 2035 nuclear power usage, as estimated by the EIA (see 

Section 6.2.6). It should be noted that most of the U3O8 used in the United States is from foreign 

suppliers. The fourth 2035 case (Ref Low Import) increases the percentage of U.S.-origin 

uranium to 20% for the reference nuclear power usage estimate. 

For each of the four 2035 projection cases, four assumptions were made regarding the source of 

the U3O8: (1) all U3O8 is from conventional mills, (2) all U3O8 is from ISL (recovery) facilities, 

(3) all U3O8 is from heap leach facilities, and (4) the U3O8 is from a mixture of uranium recovery 

facilities (see Section 6.2.6, page 87, for a definition of the mixture). Table 19 shows that the 

type of uranium recovery facility assumed makes only about a 15% difference between the 

lowest cost (heap leach) and the largest cost (ISL) recovery type facility. 
 76 

6.2.1 Conventional Mill Cost Estimate 

The base case economic costs for development of a new conventional mill were developed using 

data from the proposed new mill at Piñon Ridge in Colorado (Edge 2009). Although cost 

estimates for other conventional mills were reviewed, e.g., Coles Hill (Lyntek 2010), Church 

Rock (BDC 2011), the Piñon Ridge cost estimate was selected for the base case because it is 

believed to be the furthest advanced. Specific cost data obtained from the Piñon Ridge project 

(i.e., Edge 2009, Tables 7.1-1 and 7.1-2) were for land acquisition and facility construction, 

operating and maintenance, decommissioning, and regulatory oversight. While the Piñon Ridge 

project supplied the mill design parameters and the overall magnitude of the cost, additional data 

on the breakdown of the capital and operating costs were taken from the Coles Hill uranium 

project located in Virginia (Lyntek 2010). 

Assumptions used to develop the conventional mill base case cost estimate include: 

 As per the Piñon Ridge project, the mill design processing capacity is1,000 tons per day 

(tpd), and the licensed operating processing rate is 500 tpd. 

 The operating duration is 40 years, as per the Piñon Ridge project. 

 Because they were more detailed, the Coles Hill cost data (Lyntek 2010) were used to 

generate a percentage breakdown of the Piñon Ridge cost estimates (Edge 2009). For 

example, the Piñon Ridge operating cost estimate was divided into labor, power and 

water, spare parts, office and lab supplies, yellowcake transportation, tailings operating, 

and general and administration (G&A) using Coles Hill percentages. Thus, the Coles Hill 

data affected the detailed breakdown of the cost estimate, but not its magnitude. 

 Ore grades are 0.142% and 0.086% for underground and open-pit mined uranium, based 

on data from the EIA (EIA 2010, Table 2). The base case analysis did not use the Piñon 

Ridge project’s average ore grade of 0.23%. 

 The U3O8 recovery rate is 96% per the Piñon Ridge project. 

 A line of credit (LoC) of $146 million has an annual interest rate of 4%, with a 20-year 

payback period. 

 The price for U3O8 is $65 per pound (SRK Consulting 2010a, SRK Consulting 2010b, 

Berger 2009). 

 Taxes, claims, and royalties total 11.5% of revenue. 

 The discount rates are 3% and 7%, consistent with EPA’s economic analysis guidelines 

(EPA 2010). 
 77 

The Piñon Ridge project data do not include the costs to develop and/or operate a uranium mine. 

Rather, it is assumed that these costs are included in the cost of the uranium ore purchased for 

processing at the Piñon Ridge mill. Mine development and operating costs are included for the 

conventional mill based on an average of the open pit and underground mine costs developed for 

the heap leach facility (see Section 6.2.2). 

Table 19 presents the cost estimates that were developed for the conventional uranium mill.

Table 19: Conventional Mill Cost Estimate 

Component

Discount Rate

None 3% 7%

Resource mined (1,000 tons) 7,000 N.C. N.C.

U3O8 Recovered (1,000 lb) 15,958 N.C. N.C.

Revenues/Costs ($1,000)

Gross Revenue on U3O8 $1,037,299 $617,406 $369,925

Line of Credit (LoC) $146,000 $154,891 $167,155

Mine Costs 

Development $82,553 $49,136 $29,440 

Operating $261,195 $155,465 $93,148 

Mill Costs 

Construction $134,073 $139,870 $147,761

Mill Direct $53,136 $55,434 $58,562 

Mill Indirect $9,547 $9,960 $10,522 

Mill Contingency $15,671 $16,348 $17,271 

Tailings $55,718 $58,128 $61,407 

Operating and Maintenance $124,397 $74,042 $44,363

Labor (All inclusive) $59,267 $35,276 $21,136 

Power & Water $19,400 $11,547 $6,919 

Spare Parts $15,883 $9,454 $5,664 

Office and Lab Supplies $5,117 $3,045 $1,825 

Yellowcake Transportation $2,239 $1,332 $798 

Tailings Operating $22,492 $13,387 $8,021 

G&A $8,634 $5,139 $3,079 

Taxes, Claims, and Royalties $119,289 $71,002 $42,541 

Regulatory Oversight $11,800 $7,191 $4,541 

Decommissioning/Closure $12,000 $3,679 $801 

Repay LoC, plus Finance Costs $214,859 $169,561 $130,302 

Total Cost $968,801 $675,085 $495,978
 78 

The cash balance for the conventional mill (as well as the other uranium recovery facilities) is 

shown in Figure 18. Figure 18 shows that until production year 18, when the LoC has been paid 

off, the conventional mill is just breaking even. 

Figure 18: Estimated Cash Balance – Reference Cases 

Figure 19 shows the assumed annual U3O8 production from the conventional mill (as well as the 

other uranium recovery facilities). Based on the assumptions used for the base case, the 

conventional mill produces the least amount of U3O8 annually. 
 79 

Figure 19: Cumulative U3O8 Projections – Reference Cases 

6.2.2 Heap Leach Facility Cost Estimate 

The base case economic costs for development of a new heap leach facility were developed 

using data from the proposed new facility at Sheep Mountain in Wyoming (BRS 2011). Specific 

assumptions used to develop the base case cost estimate for the heap leach facility include: 

 The operating duration is 13 years, as per the Sheep Mountain project’s uranium 

production schedule. The annual amount of ore processed averaged 491,758 tons, with 

maximum and minimum annual processing rates of 916,500 and 74,802 tons, respectively 

(BRS 2011, page 86). 

 The U3O8 production rates were not adjusted to achieve equivalent production rates with 

the other types of facilities because to do so might affect the facility capital costs in a 

manner that would be inconsistent with the estimates provided for the Sheep Mountain 

project. If additional uranium ore production is to be modeled, a second (or more) and 

identical heap leach facility should be assumed, either concurrently or sequentially with 

the first facility. 

 Consistent with the Sheep Mountain project cost assumptions, capital investment, totaling 

$14.177 million, was assumed during the operational period to add more heap leach pads 

and to replace underground mine equipment. Two additional heap pads were assumed, 

the first after approximately one-third of the ore is processed, and the second after 

two-thirds is processed. 

 Ore grades were 0.142% and 0.086% for underground and open-pit mined uranium, 

based on data from the EIA (EIA 2010, Table 2). The Sheep Mountain project’s ore 
 80 

grades averaged 0.132% for underground and 0.085% for open-pit produced uranium 

(BRS 2011, page 86). 

 The U3O8 recovery rate varied between 89% and 92%, depending on the year of 

operation, as per the Sheep Mountain project (BRS 2011, page 86). 

 The cost of open pit mining is $19.28 per ton of ore, while the cost of underground 

mining is $52.24 per ton, and the cost of heap leach processing is $13.51 per ton (BRS 

2011, pages 87 and 88). 

 The price for U3O8 is $65 per pound (SRK Consulting 2010a, SRK Consulting 2010b, 

Berger 2009). 

 An LoC of $125 million has an annual interest rate of 4%, with a 15-year payback period. 

 Taxes, claims, and royalties total 11.5% of revenue. 

 The discount rates are 3% and 7%, consistent with EPA’s economic analysis guidelines 

(EPA 2010). 

Table 20 presents the cost estimates developed for the heap leach facility. 

Table 20: Heap Leach Facility Cost Estimate 

Component

Discount Rate

None 3% 7%

Resource mined (1,000 tons) 

Open Pit 2,895 N.C. N.C.

Underground 3,498 N.C. N.C.

U3O8 Recovered (1,000 lb) 13,558 N.C. N.C.

Revenues/Costs ($1,000)

Gross Revenue on U3O8 $881,266 $764,878 $643,637

Line of Credit (LoC) $125,000 $136,591 $153,130

Open Pit Mine 

Capital Costs $14,590 $14,590 $14,590

Operating Costs $55,817 $49,594 $42,879

Underground Mine 

Capital Costs $60,803 $59,880 $58,997

Operating Costs $182,723 $156,753 $130,078

Heap Pads/Processing Plant 

Capital Costs $51,885 $50,788 $49,690

Operating Costs $86,367 $74,973 $63,130
 81 

Table 20: Heap Leach Facility Cost Estimate 

Component

Discount Rate

None 3% 7%

Shared Costs

Predevelopment $10,630 $11,149 $11,874

Reclamation Costs $17,000 $14,755 $12,416

Taxes, claims, and royalties $101,346 $87,961 $74,018

Repay LoC/Finance Costs $168,640 $146,659 $125,441

Total Cost $749,801 $667,102 $583,114

Figure 18 end of year cash balance for the heap leach facility (as well as for the other uranium 

recovery facilities). Figure 18 shows that by production year 4, the heap leach facility has a 

positive cash balance. Figure 19 shows the assumed annual U3O8 production from the heap leach 

facility (as well as from the other uranium recovery facilities). Based on the assumptions used for 

the base case, the heap leach facility consistently produces the largest quantity of U3O8 annually. 

6.2.3 In-Situ Leach (Long) Facility Cost Estimate 

The base case economic costs for development of a new ISL facility were estimated using data 

from the proposed new Centennial project in Weld County, Colorado (SRK Consulting 2010b). 

The Centennial project is expected to have a production period of 14–15 years, which is a long 

duration for an ISL facility. Annual cost estimates for the Centennial project are provided on 

pages 117 through 123 of SRK Consulting 2010b. SRK Consulting 2010b, Section 17.11, 

discusses the basis for the Centennial project cost estimate. Specific assumptions used to develop 

the ISL (Long) facility base case cost estimate for this analysis include: 

 The operating duration is 15 years, as per the Centennial project’s uranium production 

schedule (SRK Consulting 2010b, pages 117 and 120). The facility produces about 

700,000 lb of U3O8 annually in the first 12 years, then reduces production until only 

92,000 lb is produced in the last (15th) year. 

 The U3O8 production rates were not adjusted to achieve equivalent production rates with 

the other types of facilities because to do so might affect the ISL facility capital costs in a 

manner that would be inconsistent with the estimates provided for the Centennial project. 

If additional U3O8 production is to be modeled, a second (or more) and identical ISL 

(Long) facility should be assumed, either concurrently or sequentially with the first 

facility. 

 Ground water restoration of a mining unit is assumed to begin as soon as practicable after 

mining in the unit is complete (SRK Consulting 2010b, pages 17–24). Funds for 

restoration are set aside beginning in the second production year and continuing until the 

end of the project (i.e., year 19 after the start of production). 

 The price for U3O8 is $65 per pound (SRK Consulting 2010a, SRK Consulting 2010b, 

Berger 2009). 
 82 

 An LoC of $85 million has an annual interest rate of 4%, with a 10-year payback period. 

 Taxes, claims, and royalties total 11.5% of revenue. 

 The discount rates are 3% and 7%, consistent with EPA’s economic analysis guidelines 

(EPA 2010). 

Table 21 presents the cost estimates that were developed for the ISL (Long) facility. 

Table 21: In-Situ Leach (Long) Facility Cost Estimate 

Component

Discount Rate

None 3% 7%

U3O8 Recovered (1,000 lb) 9,522 N.C. N.C.

Revenues/Costs ($1,000)

Gross Revenue on U3O8 $618,930 $501,943 $390,820

Line of Credit (LoC) $85,000 $87,550 $90,950

Operating Cost Summary 

Central Plant/Ponds $66,536 $52,000 $38,805

Satellite/Well Field $126,708 $109,218 $90,279

Restoration $11,257 $8,353 $5,844

Decommissioning $14,818 $9,175 $5,017

G&A Labor $16,379 $12,849 $9,732

Corporate Overhead $6,350 $4,969 $3,761

Contingency $48,410 $39,313 $30,687

Total Operating Costs $290,458 $235,877 $184,124

Capital Cost Summary 

CPP/General Facilities $55,097 $54,027 $52,739

Well Fields $14,209 $13,868 $13,450

G&A $13,605 $13,428 $13,212

Mine Closure $12,585 $7,244 $3,555

Miscellaneous $14,246 $11,055 $8,202

Contingency $21,948 $19,924 $18,232

Total Capital Costs $131,690 $119,546 $109,390

Severance, Royalty, Tax $71,177 $57,723 $44,944

Repay LoC/Finance Costs $104,797 $92,076 $78,758

Total Cost $598,122 $505,223 $417,216

Figure 18 shows the end of year cash balance for the ISL (Long) facility (as well as for the other 

uranium recovery facilities). Figure 18 shows that by the second year of production, the ISL 

(Long) facility has a positive cash balance. Figure 19 shows the assumed annual U3O8

production from the ISL (Long) facility (as well as from the other uranium recovery facilities). 

Based on the assumptions used for the base case, the ISL (Long) facility produces an annual 
 83 

amount of U3O8 that is midway between the amounts produced by the conventional mill and 

heap leach facility. 

6.2.4 In-Situ Leach (Short) Facility Cost Estimate 

The base case economic costs for development of a new ISL facility were estimated using data 

from the proposed new Dewey-Burdock project in South Dakota (SRK Consulting 2010a). The 

Dewey-Burdock project is expected to have a production period of about 9 years, which is 

representative for an ISL facility. SRK Consulting 2010a, pages 96 through 105, presents annual 

cost estimates for the Dewey-Burdock project, and Section 17.11 of that report discusses the 

basis for the Dewey-Burdock project cost estimate. Specific assumptions used to develop the ISL 

(Short) facility base case cost estimate for this analysis include: 

 The operating duration is 9 years, as per the Dewey-Burdock project’s uranium 

production schedule (SRK Consulting 2010a, pages 117 and 120). The facility produces 

about 1,010,000 lb of U3O8 annually in the first 6 years, then production declines until 

only 533,000 lb is produced in the last (9th) year. 

 The U3O8 production rates were not adjusted to achieve equivalent production rates with 

the other types of facilities because to do so might affect the ISL facility capital costs in a 

manner that would be inconsistent with the estimates provided for the Dewey-Burdock 

project. If additional U3O8 production is to be modeled, a second (or more) and identical 

ISL (Short) facility should be assumed, either concurrently or sequentially with the first 

facility. 

 Ground water restoration of a mining unit is assumed to begin as soon as practicable after 

mining in the unit is complete (SRK Consulting 2010a, pages 17–18). Funds for 

restoration are set aside beginning in the first production year and continuing for 2 years 

after production ends (i.e., production year 11). 

 The price for U3O8 is $65 per pound (SRK Consulting 2010a, SRK Consulting 2010b, 

Berger 2009). 

 An LoC of $70 million has an annual interest rate of 4%, with a 5-year payback period. 

 Taxes, claims, and royalties total 11.5% of revenue. 

 The discount rates are 3% and 7%, consistent with EPA’s economic analysis guidelines 

(EPA 2010). 

Table 22 presents the cost estimates developed for the ISL (Short) facility. 
 84 

Table 22: In-Situ Leach (Short) Facility Cost Estimate 

Component

Discount Rate

None 3% 7%

U3O8 Recovered (1,000 lb) 8,408 N.C. N.C.

Revenues/Costs ($1,000)

Gross Revenue on U3O8 $546,520 $491,065 $431,098 

Line of Credit (LoC) $70,000 $72,100 $74,900 

Operating Cost Summary 

Central Plant/Ponds $31,036 $27,485 $23,754 

Satellite/Well Field $130,056 $116,074 $100,788 

Restoration $6,159 $5,207 $4,234 

Decommissioning $11,614 $8,594 $5,835 

G&A Labor $9,750 $8,637 $7,500 

Corporate Overhead $3,900 $3,450 $2,994 

Contingency $38,503 $33,889 $29,021 

Total Operating Costs $208,558 $186,696 $162,811 

Capital Cost Summary 

CPP/General Facilities $49,338 $50,297 $51,598 

Well Fields $37,127 $36,951 $36,787 

G&A $2,507 $2,463 $2,414 

Mine Closure $22,460 $16,640 $11,314 

Miscellaneous $9,565 $8,253 $6,927

Contingency $19,707 $19,593 $19,545 

Total Capital Costs $140,705 $134,197 $128,586 

Severance, Royalty, Tax $83,444 $74,899 $65,698 

Repay LoC/Finance Costs $78,619 $74,171 $68,984 

Total Cost $511,326 $469,963 $426,079 

Figure 18 shows the end of year cash balance for the ISL (Short) facility (as well as for the other 

uranium recovery facilities). Figure 18 shows that in its first year of production, the ISL (Short) 

facility has a positive cash balance. Figure 19 shows the assumed annual U3O8 production from 

the ISL (Short) facility (as well as from the other uranium recovery facilities). Based on the 

assumptions used for the base case, the ISL (Short) facility produces an annual amount of U3O8

that is midway between the amounts produced by the ISL (Long) and heap leach facilities. 

6.2.5 Cost Estimate Sensitivities 

The uranium recovery facility base case cost estimates developed in Sections 6.2.1 through 6.2.4 

were based on the specific assumptions presented in each section. One of the key parameters for 

the determination of the conventional mill and heap leach facility cost estimates is the assumed 

ore grade. Table 23 presents the average ore grades reported by the EIA for U.S.-origin uranium 

during 2009. These are the ore grades assumed for the conventional mill and heap leach facility 

cost estimates. As noted in Section 6.2.2, the ore grades assumed in the Sheep Mountain project 
 85 

cost estimate (BRS 2011) were very similar to the Table 23 values. However, as noted in Section 

6.2.1, the Piñon Ridge project cost estimate used an ore grade of 0.23%, which is considerably 

higher than the Table 23 EIA values (Edge 2009). 

Table 23: Uranium Ore Grade 

Mine Type Ore Output 

(1,000 tons) Ore Grade

Underground 76,000 0.142%

Open Pit 54,000 0.086%

In-Situ Leach 145,000 0.08%

Total 275,000 0.10%

Source: EIA 2011b 

Table 24 summarizes the cost estimates for all four uranium recovery facilities developed in 

Sections 6.2.1 through 6.2.4. It includes the heap leach facility and conventional mill sensitivity 

cost estimates based on the alternate ore grade and ore processing assumptions just described. 

Table 24: U3O8 Market Value and Cost to Produce 

(Nondiscounted) 

Average U3O8 Price ($/lb) $65.00

Average U3O8 Cost ($/lb) w/ LoC1 w/o LoC2

Conventional $51.56 $47.24

ISL (Long) $53.89 $51.81

ISL (Short) $52.49 $51.46

Heap Leach $46.08 $42.87

Conventional as Designed $26.57 $25.45

Heap Leach w/ High Grade Ore $22.13 $20.59 1

 Total cost minus LoC revenue divided by the pounds of U3O8 produced 2

 Total cost minus LoC revenue minus finance charge divided by the 

pounds of U3O8 produced. 

The Piñon Ridge mill is being designed to process 1,000 tpd of uranium ore but, because of 

current market conditions, is currently being licensed to process only 500 tpd. The cost estimate 

in Section 6.2.1 is based on a conventional mill processing 500 tpd. As an alternative, the 

conventional mill cost estimate is recalculated using an ore grade of 0.23% and an ore processing 

rate of 1,000 tpd. These results have been included in Table 24. 

So that the facilities maintain a positive cash flow, the analyses in Sections 6.2.1 through 6.2.4 

assumed that each facility would be provided with an LoC to cover the construction and 

development costs. The amount of the LoC was determined by how much cash was necessary to 

maintain a positive cash balance. The interest on the LoC was assumed to be 4%, and the period 

to repay the LoC varied for each facility, depending on the amount of the LoC. The interest paid 

on the LoC is included in the facility cost estimates developed in Sections 6.2.1 through 6.2.4. 
 86 

The right hand column of Table 24 shows what the facility-specific cost estimates would be 

without an LoC (and if the cash flow was allowed to be negative), or if the interest rate was 0%. 

Figure 20 shows the effect of alternative assumptions on the cash balance. 

Figure 20: Estimated Cash Balance – Sensitivity Cases 

Figure 21 shows the effect of the alternative assumptions on the U3O8 production. The obvious 

conclusion is that the higher the ore grade, the more U3O8 is produced, and therefore, the 

uranium recovery facility is more profitable. 
 87 

Figure 21: Cumulative U3O8 Projections – Sensitivity Cases 

6.2.6 Annual Total U3O8 Cost Estimates 

In Sections 6.2.1 through 6.2.4, base case cost estimates were developed for a conventional mill, 

a heap leach facility, and two ISL facilities. These individual uranium recovery facility cost 

estimates are used together with the actual 2009 (the last year for which data are available) and 

projected 2035 U.S.-origin uranium production. 

For 2009, the EIA reports that 7,100 thousand pounds of U3O8 was produced in the United States 

(EIA 2011b). For this analysis, the total produced was divided between conventional mills and 

ISL facilities using the EIA-provided ore outputs, shown in Table 23, which resulted in 

3,356,000 lb for conventional mills and 3,744,000 lb for ISL facilities. No heap leach facilities 

were operating in 2009, so the heap leach production is zero. The 2009 uranium recovery facility 

total cost and revenue estimates given in Table 18 (page 75) are based on these U3O8 production 

figures and the individual facility unit cost estimates given in Table 24. 

These calculated 2009 economic data are based on 2011 dollars (e.g., $65 per pound of U3O8). 

The 2009 calculated economic data are adjusted to 2009 dollars by assuming an average U3O8

price of $48.92 lb-1 (EIA 2010) and adjusting the costs by the ratio of the 2009 energy consumer 

price index (CPI, 202.301) to the 2011 energy CPI (252.661) (BLS 2011, Table 25). Table 18 

(page 75) also gives the 2009 economic data estimates based on 2009 dollars for uranium 

recovery facilities. 

The next part of the analysis was to estimate the future value of the U.S. uranium recovery 

industry. To this end, it was necessary to estimate the future size of the nuclear power industry. 

The EIA (2011a) analyzed the U.S. energy outlook for 2011 and beyond, including the 

contribution from nuclear power. The EIA analyzed a reference case, plus 46 alternative cases, 
 88 

and determined the nuclear power contribution for each. The EIA reported that in 2010, nuclear 

power produced 803×109

 kilowatt-hours of electricity and projected that for the reference case, 

nuclear power would produce 874×109 kilowatt-hours in 2035 (EIA 2011a). Of the 46 alternative 

cases, the Greenhouse Gas (GHG) Price Economywide and Integrated High Technology cases 

had the largest and smallest projected nuclear power contributions in 2035, respectively. The 

GHG Price Economywide case was projected to contribute 1,052×109

 kilowatt-hours in 2035, 

while the Integrated High Technology case was projected to contribute 823×109

 kilowatt-hours. 

Figure 22 shows and compares the EIA projections. 

 Source: EIA 2011a 

Figure 22: Nuclear-Generated Electricity Projections 

It is assumed that the 2035 to 2009 U3O8 requirements would have the same ratio as the 2035 to 

2010 EIA (2011a) nuclear power estimates. Thus, for the EIA Reference Nuclear, Low Nuclear 

Production (Integrated High Technology), and High Nuclear Production (GHG Price 

Economywide) cases, the total U3O8 requirements in 2035 are estimated to be 7,728, 7,277, and 

9,302 thousand pounds, respectively. Costs were estimated for four cases, with each case 

assuming a different type of uranium recovery facility responsible for producing the required 

U3O8. The cases are (1) only conventional mills, (2) only ISL facilities, (3) only heap leach 

facilities, and (4) a mixture of all three types of facilities. 

To divide the total U3O8 requirement among the three types of uranium recovery facilities for 

Case 4, it is assumed that one reference heap leach facility would be operational, and that the 

remainder of the U3O8 would be divided between conventional mills and ISL facilities with the 

same ratio as in 2009. The total amount of U.S.-origin U3O8 for each of the 2035 projections is 

shown in Table 25 for Case 4. For the remaining three cases, the total 2035 projections given in 

Table 25 were assumed to be produced by the particular mine type associated with the case. 
 89 

Table 25: Assumed Case 4 U3O8 Production Breakdown by Mine Type 

Mine Type

U3O8 Produced (1,000 lb)

2009

2035 Projections

Reference 

Nuclear Low Nuclear 

Production

High Nuclear 

Production

Ref Low 

Import

Conventional 3,356 3,159 2,947 3,903 4,642

In-Situ Leach 3,744 3,525 3,287 4,355 5,178

Heap Leach ― 1,043 1,043 1,043 1,043

Total 7,100 7,728 7,277 9,302 10,862

Source: EIA 2011b 

The 2035 total cost and revenue estimates for uranium recovery facilities appear in Table 18 

(page 75) and are based on the Table 25 U3O8 productions and the individual facility unit cost 

estimates given in Table 24. Refer to Section 6.2 for a discussion of the Table 18 total cost and 

revenue estimates. Table 26 gives a breakdown by facility type for Case 4, the mixed uranium 

recovery facility case. 

Table 26: Case 4 (Mixed Uranium Recovery Facilities) Economic Projections 

(Nondiscounted) 

Cost/Revenue

2035 Projections ($1,000)

Reference 

Nuclear

Low Nuclear 

Production

High Nuclear 

Production Ref Low Import

U3O8 Revenue $502,305 $472,994 $604,605 $706,057

Conventional $205,407 $191,551 $253,767 $301,726

In-Situ Leach $229,108 $213,653 $283,048 $336,541

Heap Leach $67,790 $67,790 $67,790 $67,790

U3O8 Cost $391,584 $368,411 $472,461 $552,668

Conventional $162,932 $151,941 $201,292 $239,334

In-Situ Leach $180,590 $168,409 $223,108 $265,273

Heap Leach $48,062 $48,062 $48,062 $48,062

The EIA (2010, Table S1a) shows that most of the U3O8 purchased in the United States is of 

foreign origin (see Figure 23). In 2009, the 7,100 thousand pounds of U3O8 produced in the 

United States amounted to only 14.2% of the total amount of U3O8 purchased. Since the total 

cost and revenue estimates in Table 18 (page 75) are based on the 2009 U.S.-produced U3O8, 

then those estimates include the assumption that 85.8% of the U.S.-purchased U3O8 is of foreign 

origin. As Figure 23 shows, the amount of foreign origin U3O8 has fluctuated over time. If all of 

the U3O8 that is purchased in the United States were to be supplied domestically, then the total 

cost and revenue estimates shown in Table 18 would increase by a factor of 7 (i.e., 1/0.142 = 7). 

However, this is considered to be unrealistic and is unsupported by the data shown in Figure 23. 

As an alternative, the Ref Low Import case shown in Table 18 assumes that 20% of the 2035 

EIA Reference case U3O8 needs would be met domestically. 
 90 

 Source: EIA 2010, Table S1a 

Figure 23: U.S. and Foreign Contribution to U3O8 Purchases 

6.3 Economic Assessment of Proposed GACT Standards 

EPA is proposing to revise Subpart W by introducing three categories related to how uranium 

recovery facilities manage byproduct materials during and after the processing of uranium ore. 

are presented and described in Section 5.4 presents and describes the proposed GACTs for each 

category. This section presents the costs and benefits associated with the implementation of the 

various components of the GACTs. The first category is the standards for conventional mill 

tailings impoundments. The second category consists of requirements for nonconventional 

impoundments where uranium byproduct material (i.e., tailings) is contained in ponds and 

covered by liquids. Examples of this category are evaporation or holding ponds that exist at 

conventional mills and ISR and heap leach facilities. Requirements in this second category are 

that the nonconventional impoundments be provided with a double liner (Section 6.3.2) and that 

liquid at a depth of 1 meter be maintained in the impoundment (Section 6.3.3). The third 

category of revised Subpart W would require that heap leach piles be provided with a double 

liner (Section 6.3.4) and that the pile’s moisture content be maintained above 30% by weight 

(Section 6.3.5). Additionally, the revised Subpart W would remove the requirement to monitor 

the radon flux at conventional facilities constructed on or prior to December 15, 1989 (Section 

6.3.1). 

6.3.1 Method 115, Radon Flux Monitoring 

Existing Subpart W regulations require licensees to perform annual monitoring using 

Method 115 to demonstrate that the radon flux at conventional impoundments constructed before 

December 15, 1989, is below 20 pCi/(m2

-sec). The elimination of this monitoring requirement 
 91 

would result in cost savings for the three facilities to which this requirement still applies: 

Sweetwater, White Mesa, and Shootaring Canyon.9

Radon Flux Monitoring Unit Costs 

Method 115 requires that multiple large-area activated charcoal collectors (LAACCs) be 

employed to make radon flux measurements. The first step in preparing this cost estimate was to 

develop the cost for making a single LAACC radon flux measurement. Unit cost data for 

performing LAACC radon flux measurements were obtained from three primary sources: the 

“Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)” (EPA 2000a), 

KBC Engineers (KBC 2009), and Waste Control Specialists (WCS 2007). Weston Solutions 

provided fully loaded billing rates for radiation safety officers (RSOs) and certified health 

physicists (CHPs) (WS 2003). 

MARSSIM (EPA 2000a)―MARSSIM is a multivolume document that presents methodologies 

for performing radiation surveys. Appendix H to MARSSIM describes field survey and 

laboratory analysis equipment, including the estimated cost per measurement. Included in 

Appendix H is the cost estimate for performing an LAACC measurement. The MARSSIM 

estimated cost range for LAACC radon flux measurements is $20 to $50 per measurement, 

including the cost of the canister. Since MARSSIM, Revision 1, was published in August 2000, 

it is assumed that this cost estimate is in 2000 dollars. MARSSIM does not estimate the cost for 

deploying the canisters or for final report preparation. 

KBC Engineers (KBC 2009)―In November 2009, KBC Engineers prepared a revised “Surety 

Rebaselining Report” for the Kennecott Uranium Company’s Sweetwater Uranium Project, 

which included an estimate for the cost of performing Method 115 radon flux monitoring. KBC 

based the canister testing cost of $50 per canister on past invoices received from Energy 

Laboratories, Inc. (a commercial analytical laboratory). In addition to the cost for the laboratory 

work, KBC included estimates for setting up and retrieving canisters in the field and for data 

analysis and report preparation. KBC estimated that a technician/engineer with a fully loaded 

billing rate of $100 per hour would require 40 hours to set up and retrieve 110 canisters, or 

$36.36 per canister. Also, KBC estimated that an engineer/scientist with a fully loaded billing 

rate of $105 per hour would require 20 hours for data analysis and report preparation for the 

110 canisters, or $19.06 per canister. The KBC unit cost estimates are in 2009 dollars. 

Waste Control Specialists (WCS 2007)―In its application to construct and operate a byproduct 

material disposal facility,10 Waste Control Specialists, LLC (WCS) included a closure plan and 

corresponding cost estimate. As part of the final status survey, the radon flux through the 

disposal unit cap will be measured using LAACCs. WCS used the MARSSIM value as the cost 

for testing the canister. In addition, WCS included the cost of an RSO at $75 per hour to conduct 

the survey and prepare report and the cost of a CHP at $104 per hour to review the survey data. 

For the 100 canisters assumed, WCS assumed the RSO would require 40 hours for a cost of $30 

 9

 Cotter Corporation has indicated that the primary impoundments at its Cañon City site are no longer 

active, and thus, it has stopped performing Subpart W radon flux monitoring at that site (Thompson 2010). 10 The WCS facility is not a conventional tailings facility or a uranium recovery facility. It was specially 

constructed to handle the K-65 residues that were stored at DOE’s Fernald site. 
 92 

per canister and the CHP would require 10 hours, or $10.40 per canister. The WCS unit costs are 

in 2004 dollars. 

Weston Solutions (WS 2003)―Weston Solutions did not estimate the cost associated with 

Method 115 radon flux monitoring, but it did include the fully loaded hourly billing rates for 

radiation supervisors (equivalent to RSOs) and CHPs of $78 and $133, respectively. These 

billing rates are in 2003 dollars. 

Unit Costs―Table 27 summarizes the data provided in the four source documents. The first step 

was to adjust all of the data to constant 2011 dollars. The CPI (DOL 2012) was used to make this 

adjustment. The right side of Table 27 shows the adjusted cost data. 

Table 27: Data Used to Develop Method 115 Unit Costs 

Data as Provided Adjusted to November 2011 

(CPI = 226.23)

Source Date CPI

Cost per Canister Cost per Canister

Testing Setup/

RSO

Analysis/

CHP Testing Setup/

RSO

Analysis/

CHP

EPA 2000a Aug-00 172.8 $20.00 N.G. N.G. $26.18 N.G. N.G.

 $50.00 N.G. N.G. $65.46 N.G. N.G.

WS 2003 Dec-03 184.3 N.G. $31.20 $13.30 N.G. $38.30 $16.33

WCS 2007 May-07 207.949 $25.00 $30.00 $10.40 $27.20 $32.64 $11.31

 $50.00 $54.40 

KBC 2009 Nov-09 216.33 $50.00 $36.36 $19.09 $52.29 $38.03 $19.96

N.G. = not given in the source document 

Based on the data from Table 27, minimum, average, and maximum unit costs for performing 

Method 115 radon flux monitoring were estimated and are shown in Table 28. 

Table 28: Method 115 Unit Costs 

Type LAACC Unit Cost ($/Canister) 

Testing Setup/RSO Analysis/CHP Total

Minimum $26.18 $32.64 $11.31 $70.14

Average $45.11 $36.32 $15.87 $97.29

Maximum $65.46 $38.30 $19.96 $123.72

Total Annual Cost Savings (Benefit) 

Method 115 requires 100 measurements per year as the minimum number of flux measurements 

considered necessary to determine a representative mean radon flux value. Additionally, if there 

are exposed beaches or soil-covered areas (as is likely at White Mesa), then an additional 

100 measurements are necessary. Thus, for the three sites still required to perform Method 115 

radon flux monitoring, the average annual cost to perform that monitoring (based on the Table 28 

LAACC unit costs) is estimated to be about $9,730 per site per year for Shootaring and 
 93 

Sweetwater, and $19,460 for White Mesa. For all three sites the total annual average cost is 

estimated to be $38,920 yr-1, with a range from approximately $28,000 to $49,500 yr-1. 

6.3.2 Double Liners for Nonconventional Impoundments 

Uranium byproduct materials are often stored in onsite impoundments at uranium recovery 

facilities, including in holding ponds and evaporation ponds. These ponds can be collectively 

referred to as nonconventional impoundments, to distinguish them from conventional tailings 

impoundments. This section provides an estimate of the cost to provide these nonconventional 

impoundments with a double liner, including a leak collection layer. Figure 24 shows a typical 

design of an impoundment double liner. 

Source: Golder 2008, Drawing 8

Figure 24: Typical Double-Lined Impoundment with Leak Collection Layer 

Double Liner Unit Costs 

Unit costs, per square foot of liner, have been estimated for the three components of the double 

liner system: the geomembrane (HDPE) liner, the drainage (Geonet) layer, and the geosynthetic 

clay liner (GCL). 

HDPE Unit Cost―The geomembrane (HDPE) liner installation unit cost estimates shown in 

Table 29 were obtained from the indicated documents and Internet sites. The Table 29 unit costs 

include all required labor, materials, and manufacturing quality assurance documentation costs 

(Cardinal 2000, VDEQ 2000). Where necessary, the unit costs were adjusted from the year they 

were estimated to year 2011 dollars using the CPI. The Table 29 geomembrane (HDPE) liner 

mean unit cost is $0.95 ft-2, the median cost is $0.74 ft-2, while the minimum and maximum costs 

are $0.45 and $2.35, respectively. 
 94 

Table 29: Geomembrane (HDPE) Liner Unit Costs 

Data Source Unit Cost (ft-2) Thickness - Area As Given 2011$

Foldager 2003 $0.37 $0.45 Not Specified

Vector 2006 $0.45 $0.50 60 mil

Cardinal 2000 $0.39 $0.51 60 mil - 470,800 SF 

Cardinal 2000 $0.40 $0.52 60 mil - 138,920 SF 

Earth Tech 2002 $0.45 $0.57 60 mil

Cardinal 2000 $0.47 $0.61 60 mil - 118,800 SF 

VDEQ 2000 $0.48 $0.63 60 mil 

Duffy 2005 $0.60 $0.70 40 mil

Get-a-Quote $0.70 $0.70 40 mil

Cardinal 2000 $0.54 $0.71 60 mil - 60,600 SF 

MWH 2008 $0.70 $0.74 40 mil

Project Navigator 2007 $0.70 $0.76 60 mil

MWH 2008 $0.80 $0.84 80 mil

Get-a-Quote $0.86 $0.86 60 mil

EPA 2004 $0.80 $0.96 60 mil

Get-a-Quote $1.04 $1.04 80 mil

Free Construction $1.05 $1.05 40 mil

Free Construction $1.69 $1.69 60 mil

Foldager 2003 $1.40 $1.72 Not Specified

Free Construction $2.00 $2.00 80 mil

Lyntek 2011 $2.35 $2.35 80 mil

Drainage Layer (Geonet) Unit Cost―Some of the documents reviewed included unit cost 

estimates for installation of the drainage (Geonet) layer, as shown in Table 30. As with the 

geomembrane (HDPE) liner unit costs, the drainage (Geonet) layer unit costs were adjusted from 

the year they were estimated to year 2011 dollars using the CPI. The Table 30 drainage layer 

(Geonet) mean unit cost is $0.64 ft-2, the median cost is $0.57 ft-2, while the minimum and 

maximum costs are $0.48 and $1.02, respectively. 

Table 30: Drainage Layer (Geonet) Unit 

Costs 

Data Source Unit Cost (ft-2)

As Given 2011$

EPA 2004 $0.40 $0.48

Project Navigator 2007 $0.45 $0.49

Earth Tech 2002 $0.45 $0.57

MWH 2008 $0.60 $0.63

Duffy 2005 $0.88 $1.02
 95 

Geosynthetic Clay Liner (GCL) Unit Cost―Some of the documents reviewed also included 

unit cost estimates for installation of the GCL, as shown in Table 31. As for the geomembrane 

(HDPE) liner unit costs, the CPI was used to adjust the GCL unit costs from the year they were 

estimated to year 2011 dollars. The Table 31 GCL mean unit cost is $0.69 ft-2; the median cost is 

$0.65 ft-2; and the minimum and maximum costs are $0.45 and $1.12, respectively. 

Table 31: Geosynthetic Clay Liner 

(GCL) Unit Costs 

Data Source Unit Cost (ft-2)

As Given 2011$

Vector 2006 $0.40 $0.45

EPA 2004 $0.40 $0.48

Earth Tech 2002 $0.52 $0.65

Project Navigator 2007 $0.70 $0.76

Lyntex 2011 $1.12 $1.12

Some designs may choose to use a compacted clay layer beneath the double liner (e.g., Figure 

26). However, Sandia (1998) has found that “[r]eplacing the 60 cm thick clay (amended soil) 

barrier layer with a GCL drastically reduced the cost and difficulty of construction.” This savings 

was due to avoiding the expense of obtaining the bentonite clay and the difficulties of the clay 

being “sticky to spread and slippery to drive on,” plus “compaction was extremely difficult to 

achieve.” For these reasons, it is believed that GCL will be used in most future applications and 

is thus appropriate for this cost estimate. 

Design and Engineering―The cost estimates include a 20% allowance for design and 

engineering for the mean and median estimates, and a 10% and 20% allowance for the minimum 

and maximum estimates, respectively. The design and engineering cost has been calculated by 

multiplying the capital and installation cost by the allowance factor. 

Contractor Oversight―The cost estimates include a 20% allowance for contractor oversight 

for the mean and median estimates, and a 15% and 25% allowance for the minimum and 

maximum estimates, respectively. The contractor oversight cost has been calculated by 

multiplying the capital and installation cost by the allowance factor. 

Overhead and Profit―The cost estimates include a 20% allowance for overhead and profit for 

the mean and median estimates, and a 15% and 25% allowance for the minimum and maximum 

estimates, respectively. The overhead cost and profit has been calculated by multiplying the sum 

of the capital and installation, design and engineering, and contractor oversight costs by the 

allowance factor. 

Contingency―The cost estimates include a contingency factor of 20% for the mean and median 

estimates, and 15% and 25% for the minimum and maximum estimates, respectively. The 

contingency has been calculated by multiplying the sum of all of the other costs by the 

contingency factor. 
 96 

Double Liner Capital and Installation Cost 

Impoundment Areas―Figure 25 shows that in order to anchor the upper liner and drainage 

layer (Geonet), an additional 8.5 ft of material is required on each side of the impoundment. 

Similarly, an additional 6 ft of material is required on each side of the impoundment to anchor 

the lower liner and the GCL. 

Source: Golder 2008, Drawing 8

Figure 25: Typical Double Liner Anchor System 

Section 6.2 describes base facilities for each type of uranium recovery facility: conventional, 

ISR, and heap leach. Since they are not given in Section 6.2, Table 32 shows the impoundment 

surface areas for each of the base facilities, plus the areas of the upper liner, drainage layer 

(Geonet), lower liner, and GCL. The liner areas include additional material in order to anchor the 

liner, plus an additional 10% to account for the sloping of the sides and waste. 

Table 32: Nonconventional Impoundment Areas 

Facility Type Impoundment 

Type Number

Area (acres)

Surface Upper Liner 

& Geonet

Lower Liner 

& GCL

Conventional Evaporation 10 4.13 4.94 4.82

(Golder 2008) Total 10 41.30 49.39 48.22

ISR Water Storage 10 7.20 8.41 8.26

(Powertech 2009) Process Water 1 3.31 3.98 3.88

Total 11 75.31 88.05 86.50

Heap Raffinate 1 0.9 1.17 1.11

(Titan 2011) Collection 1 1.5 1.88 1.81

Evaporation 1 5.7 6.71 6.58

Total 3 8.10 9.75 9.50

Impoundment Double Liner Cost―Based on the above estimated quantities of material and 

unit costs, Table 33 presents the median, minimum, and maximum capital costs for installing the 
 97 

double liner beneath the impoundments of each of the three types of uranium recovery facilities: 

conventional, ISR, and heap leach. 

Table 33: Base Facility Nonconventional Impoundment 

Double Liner Capital and Installation Costs 

Cost Type Conventional ISR Heap

Mean $13,800,000 $24,700,000 $2,700,000 

Median $11,500,000 $20,600,000 $2,300,000 

Minimum $6,500,000 $11,600,000 $1,300,000 

Maximum $32,900,000 $58,900,000 $6,500,000 

Mean, w/o Upper Liner $6,800,000 $12,100,000 $1,300,000 

To demonstrate the individual component contribution to the total capital and installation cost, 

Table 34 presents the calculated mean capital cost breakdown by category. 

Table 34: Mean Base Facility Nonconventional Impoundment 

Double Liner Capital and Installation Cost Breakdown 

Liner Component Unit Cost 

(ft-2)

Mean Impoundment Double Liner 

Capital and Installation Cost

Conventional ISR Heap

Upper Liner $0.95 $2,040,654 $3,638,014 $402,799 

Drainage (Geonet) $0.64 $1,370,814 $2,443,844 $270,581 

Lower Liner $0.95 $1,992,191 $3,573,958 $392,414 

GCL $0.69 $1,455,818 $2,611,714 $286,761 

Design & Engineering 20% $1,371,895 $2,453,506 $270,511 

Contractor Oversight 20% $1,371,895 $2,453,506 $270,511 

Overhead & Profit 20% $1,920,654 $3,434,908 $378,715 

Contingency 20% $2,304,784 $4,121,890 $454,459 

Total ― $13,828,706 $24,731,338 $2,726,751 

Table 33 includes capital and annual cost estimates for a mean, without upper liner case. This 

case was added because, even if not required to comply with 40 CFR 192.32(a)(1), the design of 

nonconventional impoundments at uranium recovery facilities would include at least a single 

liner. The reason is that the NRC, in 10 CFR 40, Appendix A, Criterion 5(A), requires that “... 

surface impoundments (...) must have a liner that is designed, constructed, and installed to 

prevent any migration of wastes out of the impoundment to the adjacent subsurface soil, ground 

water, or surface water ... .” Thus, the Mean, w/o Upper Liner case estimates the cost to upgrade 

a single liner to a double liner system (i.e., the cost of the upper liner and the GCL have been 

removed). 

Double Liner Total Annual Cost 

Section 6.2.6 (Table 25) provided projections of the U3O8 requirements in the year 2035 for four 

different nuclear usage scenarios: Reference Nuclear – 7,728,000 lb; Low Nuclear Production – 

7,277,000 lb; High Nuclear Production – 9,302,000 lb; and Reference Low Import – 10,862 lb. 
 98 

Table 35 presents the calculated annualized cost for installation of a double liner in a 

nonconventional impoundment for the 2035 projected U3O8 productions. The annualized cost 

was calculated by first dividing the capital cost of the double liner by the total amount of U3O8

expected to be produced during the lifetime of each uranium recovery facility, and then 

multiplying by the projected amount of U3O8 produced annually. Table 35 presents four cases. In 

the first three cases, it was assumed that a single type of uranium recovery facility would 

produce all of the U3O8 required in 2035, while in the fourth case, it was assumed that a mixture 

of uranium recovery facilities would be operating in 2035. For the fourth case, Table 25 gives the 

contribution to the total U3O8 required in 2035 by each type of facility. 

Table 35: Projected Nonconventional Impoundment Double Liner 

Annualized Capital and Installation Costs 

Cost Type Projected 2035 

U3O8 Production

Annualized Capital and Installation Cost ($/yr)

Conventional ISR Heap Mix

Mean Reference Nuclear $6,700,000 $22,700,000 $1,600,000 $14,800,000 

Median Reference Nuclear $5,600,000 $18,900,000 $1,400,000 $12,400,000 

Minimum Low Nuclear Production $2,900,000 $10,000,000 $700,000 $6,500,000 

Maximum Reference Low Import $22,400,000 $76,100,000 $5,500,000 $49,300,000 

Mean, w/o Upper Liner Reference Nuclear $3,300,000 $11,100,000 $800,000 $7,300,000 

In addition to the annualized capital and installation costs, the total annual cost includes the costs 

associated with the operation and maintenance (O&M) of the double liner. For the double liner, 

O&M would consist of daily inspection of the liner and repair of the liner when rips or tears are 

observed above the water level or when water is detected in the leak detection layer. Since daily 

inspections of the nonconventional impoundments are part of the routine operation of the 

uranium recovery facility (Visus 2009), the only additional O&M cost associated with the double 

liner would be the repair costs. It was assumed that the annual O&M cost for the 

nonconventional impoundments would be 0.5% of the total capital cost for installing the liners 

(MWH 2008 and Poulson 2010). Using the Table 33 base facility cost estimates for installation 

of the double liner, Table 36 shows the calculated double liner O&M costs for each base facility. 

Table 36: Base Facility Nonconventional Impoundment Double Liner Annual 

Operation and Maintenance Costs 

Cost Type O&M 

Allowance 

Base Facility Annual O&M Cost ($/yr)

Conventional ISR Heap

Mean 0.5% $68,000 $120,000 $13,000 

Median 0.5% $56,000 $100,000 $11,000 

Minimum 0.25% $16,000 $29,000 $3,200 

Maximum 1.0% $330,000 $590,000 $65,000 

Mean, w/o Upper Liner 0.5% $34,000 $61,000 $6,700 

Table 37 shows annual O&M costs for the projected 2035 U3O8 productions. The Table 37 

annual O&M costs were calculated by dividing the Table 36 costs by each base facility’s annual 

U3O8 production and then multiplying by the projected 2035 U3O8 production. 
 99 

Table 37: Projected Nonconventional Impoundment Double Liner 

Annual Operation and Maintenance Costs 

Cost Type Projected 2035 

U3O8 Production

Annual Operation and Maintenance Cost ($/yr)

Conventional ISR Heap Mix

Mean Reference Nuclear $1,300,000 $990,000 $50,000 $1,100,000 

Median Reference Nuclear $1,100,000 $830,000 $39,000 $950,000 

Minimum Low Nuclear Production $300,000 $230,000 $11,000 $250,000 

Maximum Reference Low Import $9,000,000 $6,900,000 $330,000 $7,600,000 

Mean, w/o Upper Liner Reference Nuclear $700,000 $500,000 $24,000 $560,000 

The total annual cost for a double liner in a nonconventional impoundment is simply the sum of 

the annualized capital (Table 35) and installation cost plus the annual O&M cost (Table 37). 

Table 38 shows these total annual costs for the five cost types and four assumed uranium 

recovery facility cases. 

Table 38: Projected Nonconventional Impoundment Double Liner Total Annual Costs 

Cost Type Projected 2035 

U3O8 Production

Total Annual Cost ($/yr)

Conventional ISR Heap Mix

Mean Reference Nuclear $8,000,000 $23,700,000 $1,700,000 $16,000,000 

Median Reference Nuclear $6,700,000 $19,800,000 $1,400,000 $13,300,000 

Minimum Low Nuclear Production $3,200,000 $10,200,000 $700,000 $6,800,000 

Maximum Reference Low Import $31,400,000 $83,000,000 $5,800,000 $56,900,000 

Mean, w/o Upper Liner Reference Nuclear $3,900,000 $11,700,000 $800,000 $7,800,000 

Section 6.2, Table 18 (page 75), shows that the total estimated cost to produce all of the U3O8

projected for 2035 by the Reference Nuclear projection. Table 39 compares those total U3O8

production costs to the double liner total costs given in Table 38. As Table 39 shows, the cost to 

install a double liner is less than 6% of the total cost to produce U3O8, while the cost to upgrade 

from a single liner to a double liner is less than 3% of the total cost. 

Table 39: Comparison of Double Liner to Total U3O8 Production Costs 

Facility Type

2035 Projection Reference Nuclear Cost 

(million 2011$)

Liner 

Contribution

Total Annual 

(Table 18)

Double Liner 

(Table 38)

Single to Double 

(Table 38)

Double 

Liner

Single to 

Double

Conventional $398 $8.0 $3.9 2.0% 1.0% 

In-Situ Leach $411 $23.7 $11.7 5.8% 2.8% 

Heap Leach $356 $1.7 $0.8 0.5% 0.2% 

Mixed Facilities $396 $16.0 $7.8 4.0% 2.0% 

Finally, the conventional, ISR, and heap leach base uranium recovery facilities (see Section 6.2) 

include a double liner, with drainage layer (Geonet) collection system for their onsite 
 100 

impoundment designs. Thus, there is no additional cost for the Section 6.2 base uranium 

recovery facilities to meet the design and construction requirements at 40 CFR 192.32(a)(1) for 

onsite nonconventional impoundments. 

Benefits from a Double Liner for a Nonconventional Impoundment 

Including a double liner in the design of all onsite nonconventional impoundments that would 

contain uranium byproduct material would reduce the potential for ground water contamination. 

Although the amount of the potential reduction is not quantifiable, decision makers should 

consider this benefit because of the significance of ground water as a source of drinking water. 

6.3.3 Maintaining 1 Meter of Water in Nonconventional Impoundments 

As shown in Section 3.3.1, as long as a depth of approximately 1 meter of water is maintained in 

the pond, the effective radon emissions from the pond are so low that it is difficult to determine 

if there is any contribution above background radon values. This section estimates the cost to 

maintain 1 meter of water in the impoundment. 

In order to maintain 1 meter, or any level, of water within a pond it is necessary to replace the 

water that is evaporated from the pond. If the evaporated water is not replaced by naturally 

occurring precipitation, then it would need to be replaced with makeup water supplied by the 

pond’s operator. The replacement process is assumed to be required as part of the normal 

operation of the uranium recovery facility, which would occur regardless of the GACT. Thus, 

this cost estimate does not include process water replacement. 

Unit Cost of Water 

Three potential sources of pond makeup water were considered: municipal water suppliers, 

offsite non-drinking-water suppliers, and onsite water. 

Municipal Water Supplier (Black & Veatch 2010)―In 2009/2010, a survey of the cost of 

water in the 50 largest U.S. cities was performed (Black & Veatch 2010). The survey compiled 

typical monthly bill data for three residential (3,750, 7,500, and 15,000 gallon/month), a 

commercial (100,000 gallon/month), and an industrial (10,000,000 gallon/month) water users. 

For this study, the commercial and industrial data were normalized to dollars per gallon, and the 

higher of the two values was used. 

The survey found that the cost of water ranged from $0.0012 gallon-1 in Sacramento, California, 

to $0.0066 gallon-1 in Atlanta, Georgia, with a mean of $0.0031 gallon-1 and a median of $0.0030 

gallon-1. Looking at only those cities located within states potentially producing uranium 

(i.e., Arizona, Colorado, New Mexico, and Texas; the survey included no cities in Utah or 

Wyoming), the survey found that the cost of water ranged from $0.0016 gallon-1 in Albuquerque, 

New Mexico, to $0.0045 gallon-1 in Austin, Texas, with a mean and median of $0.0031 gallon-1. 

Offsite Non-Drinking-Water Suppliers (DOA 2004)―The water supplied by municipal water 

suppliers has been treated and is suitable for human consumption. It is not necessary for 
 101 

impoundment evaporation makeup water to be drinking water grade. Therefore, using the data 

from the 50-city survey would likely overestimate the impoundment makeup water cost. 

Unfortunately, no data could be found as to the cost of non-drinking-water grade water for use as 

impoundment makeup water. However, another large scale use of non-drinking-water grade 

water is for crop irrigation, and the U.S. Department of Agriculture has compiled data on the cost 

of irrigation water for crops (DOA 2004). 

For offsite sources of irrigation water, the Department of Agriculture states that the “31.6 million 

acre-feet of water received from off-farm water suppliers ... cost irrigators $579 million, for an 

average cost of $18.29 per acre-foot of water ...” (DOA 2004, page XXI), or $0.000056 gallon-1. 

Onsite Water (DOA 2004)―The Department of Agriculture identifies both wells (43.5 million 

acre-feet) and surface water (11.8 million acre-feet) as sources of onsite water. The cost for both 

sources is essentially the cost to pump the water from its source to where it is used. 

Unfortunately, the Department does not provide separate pumping costs for each onsite source, 

but instead states: 

There were 497,443 irrigation pumps of all kinds used on 153,117 farms in 2003 

irrigating 42.9 million acres of land. These pumps were powered by fuels and 

electricity costing irrigators a total of $1.55 billion or an average of $10,135 per 

farm. The principal energy source used was electricity, for which $953 million 

was spent to power 319,102 pumps that irrigated 24.1 million acres at an average 

cost of $39.50 per acre. Solar energy was reported as the source for pumping 

wells on 360 farms irrigating 16,430 acres. [DOA 2004, page XXI]

From these data, it is possible to determine that the mean cost for pumping onsite water from 

both sources is $0.000086 gallon-1. Also, on a per acre basis, the cost of using electricity to pump 

the water is slightly higher than the total average cost (i.e., $39.50 versus $36.13), and the use of 

solar energy to pump water is very rare (i.e., only about 0.03%). 

Unit Costs―Table 40 shows the makeup water unit costs that have been estimated for this 

study. As described, the municipal water source costs are taken from Black & Veatch 2010, 

while the mean costs for offsite non-drinking and onsite water sources were taken from DOA 

2004. All unit water costs were adjusted to 2011 dollars. 

Although the Department of Agriculture did not present sufficient data to allow for the 

calculation of minimum, maximum, and median unit water costs, these costs were estimated by 

assuming that the cost of offsite non-drinking and onsite water sources have variation in costs 

similar to the variation in municipal supplier costs. Table 40 also shows these estimated makeup 

water unit costs. 
 102 

Table 40: Makeup Water Unit Costs 

Area Source Makeup Water Unit Costs (gallon-1)

Minimum Mean Median Maximum

United States Municipal Supplier $0.0013 $0.0033 $0.0032 $0.0069

Offsite Non-Drinking $0.000027 $0.000069 $0.000067 $0.000144

Onsite Source $0.000041 $0.00011 $0.00010 $0.00022

Potential Uranium 

Producing States 

(AZ, CO, NM, TX)

Municipal Supplier $0.0017 $0.0032 $0.0033 $0.0047

Offsite Non-Drinking $0.000035 $0.000068 $0.000068 $0.000099

Onsite Source $0.000054 $0.00010 $0.00010 $0.00015

Additionally, Edge (2009) presents the discounted cost of estimated consumptive water use for 

the Piñon Ridge conventional mill. With 3% and 7% discount rates, the 40-year cost of water 

was presented as $58,545 and $33,766, respectively, which translates into an annual cost of 

$2,533. Edge (2009, page 7-2) indicates that the Piñon Ridge mill is estimated to use 

227 acre-feet of water per year. This gives a water unit cost of $0.000034, which is consistent 

with the Table 40 offsite non-drinking and onsite water sources unit costs. 

Total Annual Cost to Maintain 1 Meter of Water 

Required Water Makeup Rate (Net Evaporation Rate)―As stated above, in order to 

maintain the water level within a nonconventional impoundment, it is necessary to replace the 

water that is evaporated from the impoundment. Some (and in some places all) of the evaporated 

water will be made up by naturally occurring precipitation. Figure 17 shows the annual 

evaporation (inches per year (in/yr)) of the lower 48 states, while Figure 16 shows the annual 

precipitation (in/yr). To determine the annual required water makeup rate, the Figure 16 data is 

simply subtracted from the Figure 17 data. A positive result indicates that evaporation is greater 

than precipitation, and makeup water must be supplied, whereas a negative result indicates that 

precipitation is sufficient to maintain the impoundment’s water level. 

The U.S. Army Corps of Engineers (ACE) has published net lake evaporation rates for 152 sites 

located in the United States (ACE 1979, Exhibit I). The ACE found that the net evaporation 

ranged from -35.6 in/yr in North Head, Washington, to 96.5 in/yr in Yuma, Arizona, with a mean 

of 10.8 in/yr and a median of 0.9 in/yr. At 82 sites, the evaporation rate exceeds the precipitation 

rate, and makeup water would be required to maintain the impoundment’s water level. 

Looking at only those 22 sites located within states potentially producing uranium (i.e., Arizona, 

Colorado, New Mexico, Texas, Utah, and Wyoming), the ACE found that the net evaporation 

rate ranged from 6.1 in/yr in Houston, Texas, to 96.5 in/yr in Yuma, Arizona, with a mean of 

45.7 in/yr and a median of 41.3 in/yr. The evaporation rate exceeded the precipitation rate at all 

22 sites in the potentially uranium-producing states included in the ACE study. 

Uranium Recovery Facility Pond Size―As described in Section 6.2, a base facility was 

assumed for each of the three types of uranium recovery facilities. Table 41 gives information for 

each base facility that is necessary to calculate the annual makeup water cost (i.e., the surface 

area of the onsite impoundments and the annul U3O8 production). 
 103 

Table 41: Summary of Base Facility Characteristics 

Parameter Conventional ISR Heap

Impoundment Surface Area (acres) 41.3 75.3 8.1

U3O8 Production (lb/yr) 400,000 930,000 2,200,000 

Total Annual Cost―The only cost associated with maintaining the water level within the 

impoundment is the cost of the water. It is assumed that existing piping will connect the 

nonconventional impoundment to the water source, and that the water level will be visually 

checked at least once per day (Visus 2009). 

The makeup water unit cost data from Table 40, the net evaporation rates from above (page 102), 

and the impoundment areas from Table 41 are combined to calculate annual makeup water cost 

estimates provided in Table 42. 

Table 42: Base Facility Annual Makeup Water Cost 

Cost 

Type

Water Cost 

($/gal)

Net Evaporation 

(in/yr)

Makeup Water Cost ($/yr)

Conventional ISR Heap

Mean $0.00010 45.7 $5,313 $9,687 $1,042

Median $0.00010 41.3 $4,840 $8,826 $949

Minimum $0.000035 6.1 $240 $438 $47

Maximum $0.00015 96.5 $16,337 $29,790 $3,204

The annual cost of makeup water from Table 42 was divided by the base facility U3O8 annual 

production rate from Table 41 to calculate the makeup water cost per pound of U3O8 produced, 

shown in Table 43. 

Table 43: Base Facility Makeup Water Cost per 

Pound of U3O8

Cost Type Makeup Water Cost ($/lb)

Conventional ISR Heap

Mean $0.0133 $0.0104 $0.00047 

Median $0.0121 $0.0095 $0.00043 

Minimum $0.00060 $0.00047 $0.000021 

Maximum $0.041 $0.032 $0.0015 

Section 6.2.6 (Table 25) provided projections of the U3O8 requirements in the year 2035 for four 

different nuclear usage scenarios: Reference Nuclear – 7,728,000 lb; Low Nuclear Production – 

7,277,000 lb; High Nuclear Production – 9,302,000 lb; and Reference Low Import – 10,862 lb. 

Table 44 shows the makeup water costs which were calculated for the U3O8 production projected 

for 2035. The first three cost estimates assume that a single type of uranium recovery facility 

would be responsible for producing all of the projected U3O8, while the last estimates assume 

that a mix of uranium recovery type facilities is used, as described in Section 6.2.6. 
 104 

Table 44: Projected Annual Makeup Water Cost 

Cost Type Projected 2035 

U3O8 Production

Makeup Water Cost ($/yr)

Conventional ISR Heap Mix

Mean Reference Nuclear $102,630 $80,489 $3,660 $88,979 

Median Reference Nuclear $93,500 $73,329 $3,334 $81,063 

Minimum Low Nuclear Production $4,366 $3,424 $156 $3,780 

Maximum Reference Low Import $443,678 $347,963 $15,821 $381,053 

Table 18 (page 75) shows the total estimated cost to produce all of the U3O8 projected for 2035 

by the Reference Nuclear projections. Table 45 compares those total U3O8 production costs to 

the costs for maintaining 1 meter of water in the impoundments given in Table 44. As Table 45 

shows, the cost to maintain 1 meter of water in the impoundments is much less than 1% of the 

total cost to produce U3O8 for all four cases analyzed. 

Table 45: Comparison of Cost to Maintain 1 Meter of Water 

in the Impoundments to Total U3O8 Production Cost 

Facility Type

2035 Projection Reference 

Nuclear Cost (million 2011$) 1 Meter Water 

Total Annual Contribution

(Table 18)

1 Meter Water 

(Table 44)

Conventional $398 $0.103 0.026%

In-Situ Leach $411 $0.080 0.019%

Heap Leach $356 $0.004 0.001%

Mixed Facilities $396 $0.089 0.022%

Total Annual Benefits from Maintaining 1 Meter of Water 

By requiring a minimum of 1 meter of water in all nonconventional impoundments that contain 

uranium byproduct material, the release of radon from these impoundments would be reduced. 

Nielson and Rogers (1986) present the following equation for calculating the radon attenuation: 

ܣ ൌ ݁ቆି൤

ఒ

஽൨

బ.ఱ

ௗቇ

(6-1) 

Where: A = Radon attenuation factor (unitless) 

λ = Radon-222 decay constant (sec-1) 

 = 2.1×10-6 sec-1 

 D = Radon diffusion coefficient (cm2

/sec) 

 = 0.003 cm2

/sec in water 

 d = Depth of water (cm) 

 = 100 cm 

Solving the above equation shows that 1 meter of water has a radon attenuation factor of about 

0.07. To demonstrate the impact that a 1-meter water cover would have, the doses and risks 

reported in Section 4.4, Table 13 (page 49), have been recalculated. In this recalculation, it was 

assumed that an additional 1 meter of water covered all of the radon sources. Table 46 shows the 

results of this recalculation, in terms of the dose and risk reduction attributable to covering the 
 105 

source area with 1 meter of water. Table 46 shows both the original radon release (as reported in 

Table 13, page 49) and the radon release after the source area has been covered with 1 meter of 

water. 

Table 46: Annual Dose and Risk Reduction from Maintaining 1 Meter of Water in the 

Impoundments 

Uranium Site

Radon 

Release (Ci/yr)

Annual Dose 

Reduction

LCF(a) Risk Reduction 

(yr-1)

Table 13 1 Meter 

Water

Population 

(person-rem)

RMEI 

(mrem) Population RMEI

Sweetwater 2,075 147 0.5 1.1 2.7E-06 5.6E-07

White Mesa 1,750 124 4.8 11.1 3.2E-05 5.9E-06

Smith Ranch - Highlands 36,500 2,590 3.4 1.4 2.1E-05 7.2E-07

Crow Butte 8,885 630 2.5 3.1 1.6E-05 1.6E-06

Christensen/Irigaray 1,600 114 3.5 1.8 2.2E-05 9.2E-07

Alta Mesa 740 52 20.1 10.7 1.2E-04 5.7E-06

Kingsville Dome 6,958 494 53.9 10.5 3.5E-04 5.7E-06

* LCF = latent cancer fatalities 

6.3.4 Liners for Heap Leach Piles 

Designing and constructing heap leach piles to meet the requirements at 40 CFR 192.32(a)(1) 

would minimize the potential for leakage of uranium enriched lixiviant into the ground water. 

Specifically, this would require that a double liner, with drainage collection capabilities, be 

provided under heap piles. Figure 26 shows a typical design of a heap leach pile double liner. 

Although Figure 26 shows a clay-amended layer beneath the double liner, for the reasons given 

in Section 6.3.2, this cost estimate has assumed that a GCL would be used beneath the double 

liner, as shown in Figure 24. 
 106 

Source: Titan 2011

Figure 26: Typical Heap Pile Liner 

Double Liner Unit Costs 

The unit costs for installing a double liner, with a leakage collection system, to a heap leach pile 

are assumed to be the same as the units costs developed in Section 6.3.2 for nonconventional 

impoundments. 

The base heap leach facility utilizes a conveyor to deliver crushed material to the pile 

(Titan 2011). However, if material is delivered to the pile by truck, then the truck would put 

additional stress on the liner. Additional costs would be incurred to protect the liner from the 

additional stress. Because this analysis uses a range of liner unit costs, the additional costs for 

protecting the liner if truck loading is employed have been enveloped. 

Total Cost of Heap Leach Pile Double Liner 

Section 6.2.2 base heap leach facility (i.e., Sheep Mountain in Wyoming) includes two 80-acre 

heap piles. Using the same method described for the nonconventional impoundment (page 96), it 

was estimated that 90.3 acres of material would be required for the upper liner and drainage 

(Geonet) layer, and 89.6 acres of material for the lower liner and GCL. With these quantities of 

material and the unit costs from Section 6.3.2, Table 47 presents the median, minimum, and 

maximum capital and installation costs for installing the double liner beneath the two 80-acre 

heap piles. 
 107 

Table 47: Heap Pile Double Liner 

Capital and Installation Costs 

Cost Type Capital and 

Installation Cost

Mean $25,200,000 

Median $20,600,000 

Minimum $11,900,000 

Maximum $60,700,000 

Mean, w/o Upper Liner $12,900,000 

Table 47 includes capital and annual cost estimates for a Mean, w/o Upper Liner case. This case 

was added because even if not required to meet the requirements at 40 CFR 192.32(a)(1), the 

design of the heap leach pile would include at least a single liner to collect the lixiviant flowing 

out of the heap. The reason is that since the lixiviant flowing out of the heap contains the 

uranium, it is in the licensee’s economic interest to recover as much of it as possible, and since 

the rinsing liquid would be mixed with the lixiviant, it too would be recovered. Thus, the Mean, 

w/o Upper Liner case estimates the cost to upgrade a single liner to a double liner system (i.e., 

the cost of the upper liner and the GCL have been removed). 

To demonstrate the individual component contribution to the total capital and installation cost, 

Table 48 presents a breakdown by component of the calculated mean capital and installation 

cost. 

Table 48: Mean Heap Pile Double Liner Capital Cost 

Breakdown 

Liner Component Unit Cost 

(ft-2)

Mean Heap Pile Double 

Liner Capital Cost

Upper Liner $0.95 $3,730,077 

Drainage (Geonet) $0.64 $2,505,687 

Lower Liner $0.95 $3,702,230 

GCL $0.66 $2,579,315 

Design & Engineering 20% $2,503,462 

Contractor Oversight 20% $2,503,462 

Overhead & Profit 20% $3,504,847 

Contingency 20% $4,205,816 

Total ― $25,234,896 

Table 49 presents the heap pile double liner annual cost estimates. The total annual cost is the 

sum of the annualized capital and installation cost and the annual O&M cost. The annualized 

capital cost was calculated by first dividing the capital cost of the double liner by the total 

amount of U3O8 expected to be produced during the lifetime of the heap leach facility, and then 

multiplying by the amount of U3O8 produced annually. The U3O8 annual production was based 

on 2035 projections made in Section 6.2.6. 
 108 

Table 49 presents two cases. In the first case, it was assumed that all of the U3O8 required in 

2035 would be produced by heap leach facilities, while in the second case, it was assumed that 

heap leach facilities would be part of a mixture of uranium recovery facilities operating in 2035. 

For the second case, Table 25 gives the heap leach facility contribution to the total U3O8 required 

in 2035. 

Table 49: Heap Pile Double Liner Annual Costs 

Case Cost Type Annualized 

Capital Cost 

Annual O&M 

Cost 

Total Annual 

Cost 

Heap Only Mean $15,100,000 $220,000 $15,300,000 

Median $12,300,000 $180,000 $12,500,000 

Minimum $6,700,000 $60,000 $6,800,000 

Maximum $51,100,000 $1,340,000 $52,400,000 

Mean, w/o Upper Liner $7,700,000 $110,000 $7,800,000 

Mix Mean $340,000 $5,000 $350,000 

Median $280,000 $4,000 $280,000 

Minimum $160,000 $1,000 $160,000 

Maximum $1,600,000 $43,000 $1,600,000 

Mean, w/o Upper Liner $170,000 $3,000 $170,000 

Table 18 (page 75) shows that the total estimated cost to produce all of the U3O8 projected for 

2035 by the Reference Nuclear projection is $356 million. Thus, the cost for installing a double 

liner under the heap leach pile is about 4% of the total cost of heap leach U3O8 production 

(i.e., $15.3 million/$356 million), while the cost to change from a single liner to a double liner is 

about 2% of the total cost of heap leach U3O8 production (i.e., $7.8 million/$356 million). 

Finally, the Section 6.2.2 base heap leach facility design includes a double liner, with drainage 

layer (Geonet) collection system, as shown in Figure 26. Thus, there is no additional cost for the 

Section 6.2.2 base heap leach facility to meet the design and construction requirements at 

40 CFR 192.32(a)(1). 

Benefits from a Double-Lined Heap Leach Pile 

Including a double liner in the design of all heap leach piles would reduce the potential for 

ground water contamination. Although the amount of the potential reduction is not quantifiable, 

it is important for decision makers to consider this benefit because of the significance of ground 

water as a source of drinking water. 

6.3.5 Maintaining Heap Leach Piles at 30% Moisture 

As described in Section 5.4, the goal of this GACT is to maintain 30% moisture content in the 

heap leach pile so that the radon flux will be no larger than the flux from dry ore. 

Simply adding water to the surface of the heap leach pile will replenish and maintain the 

moisture content in the surface layer. The moisture content in the remainder of the heap leach 
 109 

vertical profile will be a function of the ore materials ability to retain moisture. The field 

moisture capacity of any earthen material is a function of the grain size and the mineralogy of the 

materials. Accordingly, the 30% moisture content should be attained with all low grade ore 

materials, due to the presence of significant fine-grained materials. Furthermore, it may not be 

necessary to maintain the entire pile at 30% moisture content, but only the upper portion of the 

pile. The exact depth to which the 30% moisture content requirement would apply would be 

determined on a site by site basis. The cost to supply the water to replenish the pile’s moisture 

content has been estimated below. 

It is also recognized that imposing a 30% moisture content requirement on the pile might (and 

likely, would) require certain design changes to the pile. Principal concerns to be addressed 

during pile design are slope stability and the liquefaction potential. Regarding slope stability, 

many leach piles are provided with containment dikes which provide structural support to the 

pile. The 30% moisture content requirement will have little or no effect on the moisture 

associated with the containment dikes, and thus the dikes would continue to provide support. 

Additionally, the pile design may be altered to increase its stability. For example, lower slopes, 

higher confinement dikes, the construction of stair-step pad grade, or the installation of textured 

(as opposed to smooth) geomembrane liner in critical areas would enhance pile stability. 

Regarding liquefaction potential, it has been estimated that liquefaction is unlikely if the degree 

of saturation in the pile is less than about 85% (Sassa 1985, as referred to in Smith 2002, Thiel 

and Smith 2004). Assuming a 2.7 ratio between moisture content and saturation (NRC 1984), the 

30% moisture content require translates into 81% saturation, which is slightly below the level 

required for liquefaction. Needless to say, with the increase in the saturation that will result from 

the imposition of the 30% moisture content requirement, more attention will need to be paid to 

the pile design to minimize the liquefaction potential. 

The costs associated with these design changes have not been included in the following cost 

estimate because any design change would depend very much on the site’s characteristics, and in 

many cases the design change might be inexpensive to implement if it is identified during the 

design phase. For example, using a textured rather than smooth liner, constructing higher 

containment dikes, and using stair-step pad grade could all be incorporated into the pile’s design 

at minimal, if any, additional cost. 

Unit Water Cost 

The unit costs for providing water to a heap leach pile are assumed to be the same as the unit 

costs developed in Section 6.3.3 (page 100) for providing water to nonconventional 

impoundments. 

Cost of Soil Moisture Meters 

Soil moisture sensors have been used for laboratory and outdoor testing purposes and for 

agricultural applications for over 50 years. They are mostly used to measure moisture in gardens 

and lawns to determine when it is appropriate to turn on irrigation systems. Soil moisture sensors 

can either be placed in the soil or held by hand. 
 110 

For example, one system would bury soil moisture sensors to the desired depth in the heap. 

Then, a portable soil moisture meter would be connected by cable to each buried sensor one at a 

time, i.e., a single meter can read any number of sensors (Irrometer 2010). The portable soil 

moisture meter costs about $350, and each in-soil sensor about $35 or $45, depending on the 

length of the cable (either 5 or 10 ft) (Ben Meadows 2012). 

Alternatively, with a handheld soil moisture meter, two rods (up to 8 inches long) that are 

attached to the meter are driven into the soil at the desired location, and a reading is taken. A 

handheld meter of this type costs about $1,065, and replacement rods about $58 for a pair 

(Spectrum 2011, Spectrum 2012). 

Total Annual Cost to Maintain 30% Moisture in the Heap Leach Pile 

The only cost associated with maintaining the moisture level within the pile is the cost of the 

water. It is assumed that existing piping (used to supply lixiviant to the pile during leaching) 

would be used to supply water necessary for maintaining the moisture level. Also, it is assumed 

that the in-soil method for moisture monitoring would be used, and that the above costs are 

insignificant. Finally, it is assumed that moisture readings would be performed during the daily 

inspections of the heap pile (Visus 2009), with no additional workhours. 

The base heap leach facility includes a heap pile that will occupy up to 80 acres at a height of up 

to 50 ft. With an assumed porosity of 0.39 (see Section 5.1.5, page 56) and a moisture content of 

30% by weight, the effective surface area of the liquid within the heap pile is 33.7 acres. 

Table 50 presents the calculated cost for makeup water to maintain the moisture level in the heap 

pile, such that the moisture content is at 30% by weight, or greater. The unit costs for water and 

the net evaporation rates derived in Section 6.3.3 were used for this estimate. 

Table 50: Heap Pile Annual Makeup Water Cost 

Cost 

Type

Water Cost 

($/gal)

Net Evaporation 

(in/yr)

Makeup Water 

Cost ($/yr)

Makeup Water 

Rate (gpm/ft2

)

Mean $0.00010 45.7 $4,331 2.3E-05

Median $0.00010 41.3 $3,946 2.1E-05

Minimum $0.000035 6.1 $196 3.0E-06

Maximum $0.00015 96.5 $13,318 4.8E-05

To place this amount of makeup water in perspective, during leaching and rinsing of the pile, 

liquid is dripped onto the pile at a rate of 0.005 gallons per minute per square foot (gpm/ft2

) 

(Titan 2011), or about 4,220 in/yr. This application rate is almost two orders of magnitude larger 

than the mean net evaporation rate, and is over a factor of 40 larger than the maximum net 

evaporation rate, shown in Table 50, and should be sufficient to maintain the moisture content 

within the pile 
 111 

Section 6.2.6 and Table 25 (page 89) present projections of the U3O8 production for the year 

2035. Table 51 presents the annual cost for makeup water to maintain the heap pile’s moisture 

content. Table 51 presents two cases. In the first case, Heap Only, it was assumed that heap leach 

facilities would produce all of the U3O8 required in 2035, while in the second case, it was 

assumed that heap leach facilities would be part of a mixture of uranium recovery facilities 

operating in 2035. For the second case, Table 25 gives the heap leach facility contribution to the 

total U3O8 required in 2035. 

Table 51: Projected Annual Heap Pile Makeup Water Cost 

Cost Type Projected 2035 

U3O8 Production

Makeup Water Cost ($/yr)

Heap Only Mix

Mean Reference Nuclear $15,000 $300 

Median Reference Nuclear $14,000 $300 

Minimum Low Nuclear Production $650 $20 

Maximum Reference Low Import $66,000 $2,100 

Table 18 (page 75) shows that the total estimated cost to produce all of the U3O8 projected for 

2035 by the Reference Nuclear projection is $356 million. Thus, the cost for maintaining 30% 

moisture in the heap leach pile is well under 1% of the total cost of heap leach U3O8 production 

(i.e., $15,000/$356,000,000). 

Total Annual Benefits from Maintaining 30% Moisture in the Heap Leach Pile 

By requiring a minimum 30% by weight moisture content in the heap leach pile, the release of 

radon from these piles would be reduced by up to about a factor of 21⁄2, as shown in Figure 15. 

From the base case production profile (BRS 2011, page 86), it can be determined that the heap 

pile ore has a mean U-238 concentration of 213 pCi/g, and a range of 135 to 321 pCi/g. 

Assuming the normalized radon flux from a heap pile with 30% moisture content is 

1 pCi/(m2

-sec) per pCi/g Ra-226, and that the Ra-226 is in equilibrium with the U-238, then the 

mean annual radon release from the 80-acre heap pile would be 2,180 Ci/yr. A comparable 

annual radon release from a dryer heap pile could be as high as 5,450 Ci/yr. Table 52 shows a 

comparison of annual doses and risks using these heap pile annual radon releases and the release 

to dose/risk relationship for the Western Generic site from Table 13. 

Table 52: Annual Dose and Risk Comparison for Maintaining 

30% Moisture Content in the Heap Pile 

Heap Pile 

Moisture Content 

(by Weight)

Radon 

Release 

(Ci/yr)

Annual Dose LCF(a) Risk (yr-1)

Population 

(person-rem)

RMEI 

(mrem) Population RMEI

>30% 2,180 6.3 7.5 3.4E-04 9.6E-06 

<30% 5,450 16 19 8.4E-04 2.4E-05 

* LCF = latent cancer fatalities 
 112 

Of course the exact reduction will depend upon the specific heap pile. For example, if a heap pile 

is operating at 20% moisture content without the GACT, then according to Figure 15, imposing 

the GACT would result in a radon flux reduction of about a factor of 1.6. Also, as Figure 14 

shows, the response of the radon emanation coefficient to increasing moisture is very dependent 

on the material. This relationship between the emanation coefficient, moisture content, and 

material also influences the amount of reduction provided by the GACT. 

6.3.6 Summary of Proposed GACT Standards Economic Assessment

Sections 6.3.2 through 6.3.5 presents the details of the economic assessment that was performed 

for implementing each of the four proposed GACT standards. Table 53 presents a summary of 

the unit cost (per pound of U3O8) for implementing each GACT at each of the three types of 

uranium recovery facilities. In addition to presenting the GACT costs individually, Table 53

presents the total unit cost to implement all relevant GACTs at each type of facility. 

A reference facility for each type of uranium recovery facility is developed and described in 

Section 6.2, including the base cost estimate to construct and operate (without the GACTs) each 

of the three types of reference facilities. For comparison purposes, the unit cost (per pound of 

U3O8) of the three uranium recovery reference facilities is presented at the bottom of Table 53. 

Table 53: Proposed GACT Standards Costs per Pound of U3O8

Unit Cost ($/lb U3O8) 

Conventional ISL Heap Leach 

GACT – Double Liners for 

Nonconventional Impoundments $1.04 $3.07 $0.22

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $0.013 $0.010 $0.0010

GACT – Liners for Heap Leach Piles ― ― $2.01

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $0.0043

GACTs – Total for All Four $1.05 $3.08 $2.24

Baseline Facility Costs (Section 6.2) $51.56 $52.49 $46.08

Based on the Table 53, implementing all four GACTs would result in unit cost (per pound of 

U3O8) increases of about 2%, 6%, and 5% at conventional, ISL, and heap leach type uranium 

recovery facilities, respectively. 

Included in the Section 6.2 descriptions is the operational duration and amount of uranium 

produced by each reference facility. This information from Section 6.2 has been used to calculate 

an annual U3O8 production rate for each type facility, which in turn has been coupled with the 

unit costs provided in Table 53, to generate the annual cost for implementing each GACT at 

each reference facility. These annual costs are presented in Table 54. Again for comparison the 

baseline cost (without the GACTs) is provided at the bottom of Table 54 for each type facility. 
 113 

Table 54: Proposed GACT Standards Reference Facility Annual Costs

Reference Facility Annual Cost ($/yr) 

Conventional ISL Heap Leach 

GACT – Double Liners for 

Nonconventional Impoundments $410,000 $2,900,000 $230,000

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $5,300 $9,700 $1,100

GACT – Liners for Heap Leach Piles ― ― $2,100,000

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $4,500

GACTs – Total for All Four $420,000 $2,900,000 $2,300,000

Baseline Facility Costs $21,000,000 $49,000,000 $48,000,000

Based on EIA (EIA 2011a) nuclear power productions, Section 6.2.6 estimated the U.S. U3O8

productions until the year 2035. Using those EIA-based production estimates for 2011 and 2035 

and the unit cost values from Table 53, Table 55 presents the estimated national annual cost for 

implementing the proposed GACTs. 

Table 55: Proposed GACT Standards National Annual Costs

National Annual Cost ($1,000/yr) 

2011 U3O8 Production 

Conventional ISL Heap Leach Total 

GACT – Double Liners for 

Nonconventional Impoundments $3,500 $12,000 $0 $15,000

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $45 $40 $0 $85

GACT – Liners for Heap Leach Piles ― ― $0 $0

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $0 $0

GACTs – Total for All Four $3,600 $12,000 $0 $15,000

Baseline Facility Costs $180,000 $200,000 $0 $380,000

2035 U3O8 Production 

Conventional ISL Heap Leach Total 

GACT – Double Liners for 

Nonconventional Impoundments $3,300 $11,000 $230 $14,000

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $42 $37 $1.1 $80

GACT – Liners for Heap Leach Piles ― ― $2,100 $2,100

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $4.5 $4.5

GACTs – Total for All Four $3,300 $11,000 $2,300 $17,000

Baseline Facility Costs $160,000 $190,000 $48,000 $400,000

Since no facilities were operating, it was assumed that all 2011 U3O8 production was divided 

between conventional and ISL facilities with the 2009 ratio, as shown in Table 25 (i.e., 47.3% 

conventional and 52.7% ISL). As described in Section 6.2.6, for 2035 it was assumed that one 
 114 

heap leach facility would be operational, and that the remainder of the U3O8 production would be 

divided between conventional and ISL facilities with the 2009 ratio. 

Of course, if the amount of U3O8 produced by each type facility changes the annual cost to 

implement the GACTs changes as well. For example if in 2035 all U3O8 is produced by ISL 

facilities, then the national annual cost to implement the GACTs would increase from $17 

million (as shown in Table 55) to $24 million. Alternatively, if all 2035 U3O8 is produced by 

conventional facilities, then the national annual cost to implement the GACTs would decrease to 

$8.1 million. Because the baseline U3O8 production costs are fairly constant across all three types 

of uranium recovery facilities (see Table 53 and Sections 6.2.1 through 6.2.4), the 2035 baseline 

U3O8 production national annual cost would remain fairly constant around $400 million, 

regardless of how the U3O8 is produced. 

Table 56 presents the national cost for the implementation of the four proposed GACTs summed 

over the years 2011 to 2035. As with the Table 55 annual national costs, the Table 56 summed 

national costs are based on EIA (EIA 2011a) nuclear power productions, as described in Section 

6.2.6. 

Table 56: Proposed GACT Standards Summed National Costs 

National Cost, Summed from 2011 to 2035 ($1,000) 

Non-Discounted 

Conventional ISL Heap Leach Total 

GACT – Double Liners for 

Nonconventional Impoundments $81,000 $270,000 $5,800 $350,000

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $1,000 $910 $27 $2,000

GACT – Liners for Heap Leach Piles ― ― $52,000 $52,000

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $110 $110

GACTs – Total for All Four $82,000 $270,000 $58,000 $410,000

Baseline Facility Costs $4,000,000 $4,600,000 $1,200,000 $9,800,000

Discounted @3% 

Conventional ISL Heap Leach Total 

GACT – Double Liners for 

Nonconventional Impoundments $58,000 $190,000 $4,100 $250,000

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $740 $650 $19 $1,400

GACT – Liners for Heap Leach Piles ― ― $37,000 $37,000

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $80 $80

GACTs – Total for All Four $59,000 $190,000 $41,000 $290,000

Baseline Facility Costs $2,900,000 $3,300,000 $850,000 $7,000,000
 115 

Table 56: Proposed GACT Standards Summed National Costs 

National Cost, Summed from 2011 to 2035 ($1,000) 

Discounted @ 7% 

Conventional ISL Heap Leach Total 

GACT – Double Liners for 

Nonconventional Impoundments $40,000 $130,000 $2,900 $170,000

GACT – Maintaining 1 Meter of Water in 

Nonconventional Impoundments $510 $450 $13 $970

GACT – Liners for Heap Leach Piles ― ― $26,000 $26,000

GACT – Maintaining Heap Leach Piles at 

30% Moisture ― ― $55 $55

GACTs – Total for All Four $41,000 $130,000 $29,000 $200,000

Baseline Facility Costs $2,000,000 $2,300,000 $590,000 $4,800,000

As with the Table 55 annual national costs, if the amount of U3O8 assumed to be produced by 

each type facility changes the Table 56 summed national costs to implement the GACTs changes 

as well. For example if all U3O8 is produced by ISL facilities, then the non-discounted summed 

national cost to implement the GACTs would increase from $410 million (as shown in Table 56) 

to $590 million. Alternatively, if all U3O8 is produced by conventional facilities, then the nondiscounted summed national cost to implement the GACTs would decrease to $200 million. 

Similar to the baseline annual national costs, the baseline U3O8 production non-discounted 

summed national cost would remain around $9.8 billion, regardless of how the U3O8 is produced. 

6.4 Environmental Justice 

Concerning environmental justice, EPA’s economic assessment guidelines state: 

Distributional analyses address the impact of a regulation on various 

subpopulations. Minority, low-income and tribal populations may be of particular 

concern and are typically addressed in an environmental justice (EJ) analysis. 

Children and other groups may also be of concern and warrant special attention 

in a regulatory impact analysis. [EPA 2010, Section 10] 

6.4.1 Racial Profile for Uranium Recovery Facility Areas 

This section presents information on the racial (e.g., tribal populations) and economic (e.g., low 

income) profiles of the areas surrounding existing and proposed uranium recovery facilities. 

Table 57 presents the racial profiles in the immediate areas (i.e., counties) surrounding the 

existing and proposed uranium recovery facilities, while Table 58 presents the profiles in the 

surrounding regional area (i.e., states) and on a national basis. A comparison of Table 57 to 

Table 58 indicates whether the racial population profile surrounding the uranium recovery 

facilities conform to the national and/or regional norms. 
 116 

Table 57: Racial Profile for Uranium Recovery Facility Counties 

Existing/Proposed 

Facility

Facility 

Type County, State White Black Native American Others

Juan Tafoya Conventional McKinley, NM 22.2% 0.4% 75.4% 2.0% 

White Mesa Mill Conventional San Juan, UT 42.7% 0.1% 55.8% 1.3% 

Grants Ridge Heap Leach Cibola, NM 56.2% 1.0% 40.9% 1.8% 

Sheep Mountain Heap Leach Fremont, WY 78.3% 0.1% 19.8% 1.8% 

Crow Butte In-Situ Leach Dawes, NE 94.5% 0.9% 3.0% 1.6% 

Piñon Ridge Conventional Montrose, CO 96.6% 0.4% 1.4% 1.7% 

Sweetwater Mill Conventional Sweetwater, WY 96.3% 0.8% 1.1% 1.9% 

Christensen / Irigaray In-Situ Leach Campbell, WY 97.4% 0.2% 1.0% 1.4% 

Smith Ranch - Highland In-Situ Leach Converse, WY 97.5% 0.1% 1.0% 1.4% 

Shootaring Canyon Conventional Garfield, CO 97.2% 0.5% 0.8% 1.6% 

Kingsville Dome In-Situ Leach Kleberg, TX 92.8% 3.9% 0.8% 2.6% 

Goliad In-Situ Leach Goliad, TX 93.6% 5.0% 0.7% 0.7% 

Palangana In-Situ Leach Duval, TX 98.3% 0.6% 0.7% 0.4% 

Alta Mesa In-Situ Leach Brooks, TX 98.8% 0.4% 0.6% 0.3% 

Source: http://www.census.gov/popest/counties/asrh/ 

Table 58: Regional and National Racial Profiles 

State White Black Native 

American Others

New Mexico NM 85.4% 2.1% 9.8% 2.7% 

Wyoming WY 95.1% 0.8% 2.3% 1.8% 

Utah UT 94.0% 0.9% 1.4% 3.7% 

Colorado CO 90.7% 4.0% 1.2% 4.1% 

Nebraska NE 92.7% 4.1% 0.9% 2.3% 

Texas TX 83.7% 11.8% 0.7% 3.9% 

United States US 81.1% 12.7% 0.9% 5.3% 

Source: http://www.census.gov/popest/counties/asrh/ 

At 10 of the 15 sites, the percentage of Native Americans in the population exceeds the national 

norm, while at nine sites, the percentage of Native Americans in the population exceeds the 

regional norm. At 11 of the 15 sites, the percentage of the population that is White exceeds both 

the national and regional norms. Finally, the percentage of the population at all uranium recovery 

sites that is either Black or Other is less than the national norm, while the percentage of Blacks 

and Others is less than the regional norm at all but one site. 

For all of the sites considered together, the data in Table 57 do not reveal a disproportionately 

high incidence of minority populations being located near uranium recovery facilities. However, 

certain individual sites may be located in areas with high minority populations. Those sites 

would need to be evaluated during their individual licensing processes. 
 117 

6.4.2 Socioeconomic Data for Uranium Recovery Facility Areas 

Table 59 shows the socioeconomic data for the immediate areas (i.e., counties) surrounding the 

existing and planned uranium recovery facilities. Specifically, the socioeconomic data shown in 

Table 59 is the fraction of land that is farmed, the value of that farmland, and the nonfarm per 

capita wealth. The percentages shown next to the value of that farmland and the nonfarm per 

capita wealth indicate where the site ranks when compared to all other counties in the United 

States. 

Table 59: Socioeconomic Data for Uranium Recovery Facility Counties 

Existing/Proposed 

Facility

Facility 

Type County, State Farm Land

Farm Value 

Per Hectare

Per Capita 

Nonfarm Wealth

White Mesa Mill Conventional San Juan, UT 31.1% $670 4.0% $103,073 0.6% 

Juan Tafoya Conventional McKinley, NM 90.9% $185 0.0% $115,603 1.9% 

Alta Mesa In-Situ Leach Brooks, TX 72.8% $1,423 13.2% $117,693 2.2% 

Grants Ridge Heap Leach Cibola, NM 58.2% $378 0.7% $118,862 2.4% 

Palangana In-Situ Leach Duval, TX 74.1% $1,792 17.5% $132,493 6.9% 

Crow Butte In-Situ Leach Dawes, NE 88.0% $895 6.9% $144,291 15.1% 

Kingsville Dome In-Situ Leach Kleberg, TX 0.0% $1,478 13.9% $149,865 20.4% 

Goliad In-Situ Leach Goliad, TX 92.6% $2,244 22.0% $162,584 35.4% 

Piñon Ridge Conventional Montrose, CO 23.3% $2,916 30.1% $181,133 59.5% 

Sheep Mountain Heap Leach Fremont, WY 42.6% $768 5.3% $186,775 65.4% 

Shootaring Canyon Conventional Garfield, CO 21.4% $3,195 34.3% $200,316 76.7% 

Smith Ranch - Highland In-Situ Leach Converse, WY 92.5% $381 0.7% $208,583 82.1% 

Christensen/Irigaray In-Situ Leach Campbell, WY 97.3% $437 1.1% $225,858 89.3% 

Sweetwater Mill Conventional Sweetwater, WY 22.2% $242 0.1% $232,504 91.2% 

The discussion first focuses on the per capita nonfarm wealth. For comparison, the per capita 

nonfarm wealth in the United States ranges from $39,475 (Slope County, North Dakota) to 

$618,954 (New York County, New York). Table 59 shows that uranium recovery facilities are 

located in areas that are very poor (i.e., ranked in the lowest 0.6% in the country) to areas that are 

very well to do (i.e., ranked in the 91.2 percentile). Six of the 15 sites are located in areas that 

have per capita nonfarm wealth that is above the 50th percentile in the United States. On the other 

hand, five sites are located in areas in which the per capita nonfarm wealth is below the country’s 

10th percentile. 

Table 59 shows that eight of the sites have more than 50% of their land devoted to farming. 

However, the Table 59 farm value data show that the farmland for all 15 sites is below the 35th

percentile farmland value in the United States. This could indicate that the farmland is of poor 

quality, or simply that the land is located in an economically depressed area. For comparison, 

farmland in the United States ranges in value from $185 per hectare (McKinley County, New 

Mexico, which is the location of the proposed Juan Tafoya uranium recovery facility) to 

$244,521 per hectare (Richmond County, New York). 
 118 

For all of the sites combined, the data provided in Table 59 do not reveal a disproportionately 

high incidence of low-income populations being located near uranium recovery facilities. 

However, certain individual sites may be located within areas of low-income population. Those 

sites would need to be evaluated during their individual licensing processes. 

6.5 Regulatory Flexibility Act 

The Regulatory Flexibility Act requires federal departments and agencies to evaluate if and/or 

how their regulations impact small business entities. Specifically, the agency must determine if a 

regulation is expected to have a significant economic impact on a substantial number of small 

entities. Small entities include small businesses, small organizations, and small governmental 

jurisdictions. 

If a rulemaking is determined to have a significant economic impact on a substantial number of 

small entities, then the agency must conduct a formal regulatory flexibility analysis. However, if 

the agency determines that a rulemaking does not have a significant economic impact on a 

substantial number of small entities, then it makes a certification of that finding and presents the 

analyses that it made to arrive at that conclusion. 

To evaluate the significance of the economic impacts of the proposed revisions to Subpart W, 

separate analyses were performed for each of the three proposed GACTs. 

The GACT for uranium recovery facilities that use conventional milling techniques proposes that 

only phased disposal units or continuous disposal units be used to manage the tailings. For either 

option, the disposal unit must be lined and equipped with a leak detection system, designed in 

accordance with 40 CFR 192.32(a)(1) (see Section 5.4). If phased disposal is the option chosen, 

the rule limits the disposal unit to a maximum of 40 acres, with no more than two units open at 

any given time. If continuous disposal is chosen, no more than 10 acres may be open at any 

given time. Finally, the agency is proposing to eliminate the distinction made in the 1989 rule 

between impoundments constructed pre-1989 and post-1989, since all of the remaining pre-1989 

impoundments comply with the proposed GACT. The elimination of this distinction also 

eliminates the requirement that pre-1989 disposal units be monitored annually to demonstrate 

that the average Rn-222 flux does not exceed 20 pCi/(m2

-sec). 

The conventional milling GACT applies to three existing mills and one proposed mill that is in 

the process of being licensed. The four conventional mills are the White Mesa mill and the 

proposed Piñon Ridge mill owned by Energy Fuels; the Shootaring Canyon mill owned by 

Uranium One, Inc.; and the Sweetwater mill owned by Kennecott Uranium Co. . Of the three 

companies that own conventional mills, one, Energy Fuels, is classified as a small business, on 

the basis that they have fewer than 500 employees (EF 2012 states that Energy Fuels has 255 

active employees in the U.S.). 

Energy Fuels’ White Mesa mill uses a phased disposal system that complies with the proposed 

GACT. When its existing open unit is full, it will be contoured and covered. Then, a new unit, 

constructed in accordance with the proposed GACT, will be opened to accept future tailings. 
 119 

Energy Fuels is proposing a phased disposal system to manage its tailings; this system also 

complies with the proposed GACT. 

Section 5.4 describes the proposed GACTs. Because both the White Mesa mill and the proposed 

Piñon Ridge mill are in compliance with the proposed GACT, it can be concluded that the 

rulemaking will not impose any new economic impacts on small business (i.e., Energy Fuels). 

For White Mesa, the proposed rule will actually result in a cost saving as Energy Fuels will no 

longer have to perform annual monitoring to determine the average radon flux from its 

impoundments. 

The GACT for evaporation ponds at uranium recovery facilities requires that the evaporation 

ponds be constructed in accordance with design requirements in 40 CFR 192.32(a)(1) and that a 

minimum depth of 1 meter of liquid be maintained in the ponds during operation and standby. 

The key design requirements for the ponds are for a double liner with a leak detection system 

between the two liners. 

In addition to the four conventional mills identified above, the GACT for evaporation ponds 

applies to ISL facilities and heap leach facilities. Currently, there are six operating ISLs (as 

shown in Table 8) and no operating heap leach facilities. The operating ISLs are Crow Butte and 

Smith Ranch owned by Cameco; Alta Mesa owned by Mestena Uranium, LLC; Willow Creek 

owned by Uranium One, Inc.; and Hobson and La Palangana owned by Uranium Energy Corp. 

Again, using the criterion of fewer than 500 employees, Mestena Uranium, LLC, and Uranium 

Energy Corp. are small businesses, while both Cameco and Uranium One, Inc., which is owned 

by Rosatom, are large businesses. 

All of the evaporation ponds at the four conventional mills and the six ISLs were built in 

conformance with 40 CFR 192.32(a)(1). Therefore, the only economic impact is the cost of 

complying with the new requirement to maintain a minimum of 1 meter of water in the ponds 

during operation and standby. 

In addition to the operating ISLs listed above, Table 9 shows that there are nine ISLs have been 

proposed for licensing. These are: Dewey Burdock owned by Powertech Uranium Corp.; 

Nichols Ranch owned by Uranerz Energy Corp.; ‘Jab and Antelope’ and Moore Ranch owned by 

Uranium One Americas, Inc., a subsidiary of Rosatom; Church Rock and Crownpoint owned by 

Hydro Resources, Inc. a subsidiary of Uranium Resources, Inc.; Ross owned by Strata Energy 

Inc., a subsidiary of Australian-based Peninsula Energy Limited; Goliad owned by Uranium 

Energy Corp.; and Lost Creek owned by Lost Creek ISR, LLC a subsidiary of Ur-Energy. All of 

these companies, except Rosatom, are small businesses. 

According to the licensing documents submitted by the owners of the proposed ISLs, all will be 

constructed in conformance with 40 CFR 192.32(a)(1). Therefore, the only economic impact is 

the cost of complying with the new requirement to maintain a minimum of 1 meter of water in 

the ponds during operation and while in standby status. 

The requirement to maintain a minimum of 1 meter of liquid in the ponds is estimated to cost up 

to $0.03 per pound of U3O8 produced. Considering that the current (i.e., January 30, 2012) price 
 120 

of U3O8 is $52 per pound (UxC 2012), this cost does not pose a significant impact to any of these 

small entities. 

The GACT for heap leach facilities applies the phased disposal option of the GACT for 

conventional mills to these facilities and adds the requirement that the heap leach pile be 

maintained at a minimum 30-percent moisture content by weight during operations. Although no 

heap leach facilities are currently licensed, the small business Energy Fuels is expected to submit 

a licensing application for the Sheep Mountain Project. From the preliminary documentation that 

has been presented (Titan 2011), the Energy Fuels facility will have an evaporation pond, a 

collection pond, and a raffinate pond. All three ponds will be double lined with leak detection. 

Based on the unit and facility cost comparisons presented in Table 53 and Table 54, 

respectively, the implementation of the proposed GACTs at a heap leach facility (such as Sheep 

Mountain) would increase the U3O8 production cost by about 5%. Based on this small increase, 

the Sheep Mountain Project would: 1) remain competitive with U3O8 production cost for other 

types of facilities, and 2) continue to provide Energy Fuels with a profit. Energy Fuels is the only 

entity known to be preparing to submit a license application for a heap leach facility. 

Of the 20 uranium recovery facilities identified above, 13 are owned by small businesses. As 

documented above in this report, those 13 facilities are either already in compliance with the 

proposed GACTs, with no additional impact, or compliance with the GACTs would not pose a 

significant impact to any of the small businesses (e.g., $52.03 lb-1 versus $52 lb-1). Thus, after 

considering the economic impacts of this proposed rule on small entities, it is concluded that this 

action will not have a significant economic impact on a substantial number of small entities. 

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