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ENVIRONMENTAL PROTECTION AGENCY 6560-50-P

40 CFR Part 61

[EPA-HQ-OAR-2008-0218; FRL-9816-2]

RIN 2060-AP26 

Revisions to National Emission Standards for Radon 

Emissions from Operating Mill Tailings 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Proposed rule. 

___________________________________________________________ 

SUMMARY: The Environmental Protection Agency (EPA) is 

proposing to revise certain portions of the National 

Emission Standards for Hazardous Air Pollutants (NESHAP) 

for radon emissions from operating uranium mill tailings. 

The proposed revisions are based on EPA’s determination as 

to what constitutes generally available control technology 

or management practices (GACT) for this area source 

category. We are also proposing to add new definitions to 

this rule, revise existing definitions and clarify that the 

rule applies to uranium recovery facilities that extract 

uranium through the in-situ leach method and the heap leach 

method. 

Deleted: _XXXX-X
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DATES: Comments must be received on or before [insert 

date], 90 days after publication in the Federal Register. 

ADDRESSES: Submit your comments, identified by Docket ID 

No. EPA-HQ-OAR-2008-0218, by one of the following methods: 

 www.regulations.gov: Follow the on-line instructions 

for submitting comments. 

 Email: a-and-r-docket@epa.gov

 Fax: 202-566-9744 

 Mail: Air and Radiation Docket, Environmental 

Protection Agency, Mailcode: 2822T, 1200 Pennsylvania 

Ave., NW, Washington, DC 20460. 

 Hand Delivery: EPA West Building, Room 3334, 1301 

Constitution Ave., NW Washington, DC 20004. Such 

deliveries are only accepted during the Docket’s 

normal hours of operation, and special arrangements 

should be made for deliveries of boxed information. 

Instructions: Direct your comments to Docket ID No. EPAHQ-OAR-2008-0218. EPA's policy is that all comments 

received will be included in the public docket without 

change and may be made available online at 

www.regulations.gov, including any personal information 

provided, unless the comment includes information claimed 

to be Confidential Business Information (CBI) or other 

Comment [RJR1]: OMB suggested 60 days but 

communications from stakeholders suggest they will 

ask for another 30 day extension. 
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information whose disclosure is restricted by statute. Do 

not submit information that you consider to be CBI or 

otherwise protected through www.regulations.gov or e-mail. 

The www.regulations.gov website is an “anonymous access” 

system, which means EPA will not know your identity or 

contact information unless you provide it in the body of 

your comment. If you send an e-mail comment directly to 

EPA without going through www.regulations.gov your e-mail 

address will be automatically captured and included as part 

of the comment that is placed in the public docket and made 

available on the Internet. If you submit an electronic 

comment, EPA recommends that you include your name and 

other contact information in the body of your comment and 

with any disk or CD-ROM you submit. If EPA cannot read 

your comment due to technical difficulties and cannot 

contact you for clarification, EPA may not be able to 

consider your comment. Electronic files should avoid the 

use of special characters, any form of encryption, and be 

free of any defects or viruses. For additional information 

about EPA’s public docket visit the EPA Docket Center 

homepage at http://www.epa.gov/epahome/dockets.htm

Docket: All documents in the docket are listed in the 

www.regulations.gov index. Although listed in the index, 

some information is not publicly available, e.g., CBI or 
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other information whose disclosure is restricted by 

statute. Certain other material, such as copyrighted 

material, will be publicly available only in hard copy. 

Publicly available docket materials are available either 

electronically in www.regulations.gov or in hard copy at 

the Office of Air and Radiation Docket, EPA/DC, EPA West, 

Room 3334, 1301 Constitution Ave., NW, Washington, DC. The 

Public Reading Room is open from 8:30 a.m. to 4:30 p.m., 

Monday through Friday, excluding legal holidays. The 

telephone number for the Public Reading Room is (202) 566-

1744, and the telephone number for the Air and Radiation 

Docket is (202) 566-1792. 

FOR FURTHER INFORMATION CONTACT: Reid J. Rosnick, Office 

of Radiation and Indoor Air, Radiation Protection Division, 

Mailcode 6608J, U.S. Environmental Protection Agency, 1200 

Pennsylvania Ave., NW Washington, DC 20460; telephone 

number: 202-343-9290; fax number: 202-343-2304; email 

address: rosnick.reid@epa.gov.

SUPPLEMENTARY INFORMATION: 

Outline. The information in this preamble is organized as 

follows: 

I. General Information 

A. Does this action apply to me? 

B. What should I consider as I prepare my comments to 

EPA? 

C. Acronyms and Abbreviations Deleted: a
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D. Where can I get a copy of this document? 

E. When would a public hearing occur? 

II. Background Information for Proposed Area Source 

Standards 

A. What is the statutory authority for the proposed 

standards? 

B. What criteria did EPA use in developing the 

proposed GACT standards for these area sources?

C. What source category is affected by the proposed 

standards? 

D. What are the production operations, emission 

sources, and available controls? 

E. What are the existing requirements under Subpart W? 

F. How did we gather information for this proposed 

rule? 

G. How does this action relate to other EPA standards? 

H. Why did we conduct an updated risk assessment? 

III. Summary of the Proposed Requirements 

 A. What are the affected sources? 

 B. What are the proposed requirements? 

C. What are the monitoring requirements? 

D. What are the notification, recordkeeping and 

reporting requirements? 

E. When must I comply with these proposed standards? 

IV. Rationale for this Proposed Rule 

A. How did we determine GACT? 

B. Proposed GACT standards for operating mill tailings 

V. Other Issues Generated by Our Review of Subpart W 

A. Clarification of the Term “standby” 

B. Amending the definition of “operation” for 

conventional impoundments 

C. Weather Events 

D. Applicability of 40 CFR 192.32(a) to Subpart W 

VI. Summary of Environmental, Cost and Economic Impacts 

 A. What are the air impacts? 

 B. What are the cost and economic impacts? 

 C. What are the non-air environmental impacts? 

VII. Statutory and Executive Order Review 

A. Executive Order 12866: Regulatory Planning and 

Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation and 

Coordination with Indian Tribal Governments 

Deleted: proposed standards?

Deleted: initial and subsequent

Deleted: s
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G. Executive Order 13045: Protection of Children from 

Environmental Health and Safety Risks 

H. Executive Order 13211: Actions Concerning 

Regulations 

That Significantly Affect Energy Supply, 

Distribution or Use 

I. National Technology Transfer Advancement Act 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and 

Low-Income Populations 

I. General Information

A. Does this Action Apply to Me?

The regulated categories and entities potentially 

affected by the proposed standards include: 

Category NAICS 

code1

Examples of regulated 

Entities 

Industry: 

Uranium Ores Mining 

and/or Beneficiating 

212291 Area source facilities 

that extract or 

concentrate uranium 

from any ore processed 

primarily for its 

source material content 

Leaching of Uranium, 

Radium or Vanadium 

Ores 

212291 Area source facilities 

that extract or 

concentrate uranium 

from any ore processed 

primarily for its 

source material content 1

 North American Industry Classification System. 

 This table is not intended to be exhaustive, but 

rather provides a guide for readers regarding entities 

likely to be affected by this proposed action. If you have 

any questions regarding the applicability of this action to 

a particular entity, consult either the air permit 
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authority for the entity or your EPA regional 

representative as listed in 40 CFR 61.04 of subpart A 

(General Provisions).

B. What should I consider as I prepare my comments for 

EPA?

1. Submitting CBI. Do not submit this information to 

EPA through www.regulations.gov or e-mail. Clearly mark 

the part or all of the information that you claim to be 

CBI. For CBI information in a disk or CD ROM that you mail 

to EPA, mark the outside of the disk or CD ROM as CBI and 

then identify electronically within the disk or CD ROM the 

specific information that is claimed as CBI. In addition 

to one complete version of the comment that includes 

information claimed as CBI, a copy of the comment that does 

not contain the information claimed as CBI must be 

submitted for inclusion in the public docket. Information 

marked as CBI will not be disclosed except in accordance 

with procedures set forth in 40 CFR part 2. 

2. Tips for Preparing Your Comments. When submitting 

comments, remember to: 

• Identify the rulemaking by docket number and 

other identifying information (subject heading, 

Federal Register date and page number). 

• Follow directions - The agency may ask you to 

Deleted: S

Deleted: C

Deleted: P

Deleted: M

Deleted: C
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respond to specific questions or organize 

comments by referencing a Code of Federal 

Regulations (CFR) part or section number. 

• Explain why you agree or disagree, suggest 

alternatives, and substitute language for your 

requested changes. 

• Describe any assumptions and provide any 

technical information and/or data that you used. 

• If you estimate potential costs or burdens, 

explain how you arrived at your estimate in 

sufficient detail to allow for it to be 

reproduced. 

• Provide specific examples to illustrate your 

concerns, and suggest alternatives. 

• Explain your views as clearly as possible, 

avoiding the use of profanity or personal 

threats. 

Make sure to submit your comments by the comment period 

deadline identified.

C. Acronyms and Abbreviations

We use many acronyms and abbreviations in this document. 

These include: 

AEA – Atomic Energy Act 

ALARA – As low as reasonably achievable 

BID – Background information document 
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CAA – Clean Air Act 

CAAA – Clean Air Act amendments of 1990 

CCAT – Colorado Citizens Against Toxic Waste 

CFR – Code of Federal Regulations 

Ci – Curie, a unit of radioactivity equal to the amount of 

a radioactive isotope that decays at the rate of 3.7 × 1010

disintegrations per second. 

DOE – U.S. Department of Energy 

EIA – economic impact analysis 

EO – Executive Order 

EPA – U.S. Environmental Protection Agency 

FR – Federal Register

GACT – Generally Available Control Technology 

gpm - Gallons Per Minute 

HAP – Hazardous Air Pollutant 

ICRP – International Commission on Radiological Protection 

ISL – In-situ leach uranium recovery, also known as in-situ 

recovery (ISR)

LCF - Latent Cancer Fatality – Death resulting from cancer 

that became active after a latent period following exposure 

to radiation

NAAQS – National Ambient Air Quality Standards 

NCRP – National Council on Radiation Protection and 

Measurements 

mrem – millirem, 1 x 10-3 rem 

MACT – Maximum Achievable Control Technology 

NESHAP – National Emission Standard for Hazardous Air 

Pollutants 

NRC – U.S. Nuclear Regulatory Commission 

OMB – Office of Management and Budget 

pCi – picocurie, 1 x 10-12 curie 

Ra-226 - Radium-226 

Rn-222 – Radon-222 

Radon flux - A term applied to the amount of radon crossing 

a unit area per unit time, as in picocuries per square 

centimeter per second (pCi/m2/sec). 

RCRA – Resource Conservation and Recovery Act 

Subpart W – National Emission Standards for Radon Emissions 

from Operating Mill Tailings at 40 CFR 61.250-61.256 

TEDE – Total Effective Dose Equivalent 

UMTRCA – Uranium Mill Tailings Radiation Control Act of 

1978 

U.S.C. – United States Code 

D. Where can I get a copy of this document?
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 In addition to being available in the docket, an 

electronic copy of this proposed action will also be 

available on the Worldwide Web (WWW) through the Technology 

Transfer Network (TTN). Following signature, a copy of 

this proposed action will be posted on the TTN’s policy and 

guidance page for newly proposed or promulgated rules at 

the following address: http://www.epa.gov/ttn/oarpg/. The 

TTN provides information and technology exchange in various 

areas of air pollution control. 

E. When would a public hearing occur?

 If anyone contacts EPA requesting to speak at a public 

hearing concerning this proposed rule by [INSERT DATE 90

DAYS AFTER PUBLICATION IN THE FEDERAL REGISTER], we will 

hold a public hearing on [INSERT DATE DAYS AFTER 

PUBLICATION IN THE FEDERAL REGISTER]. If you are 

interested in attending the public hearing, contact Mr. 

Anthony Nesky at (202) 343-9597 to verify that a hearing 

will be held. If a public hearing is held, it will be held 

at...WILL BE ADDED LATER 

II. Background Information for Proposed Area Source 

Standards 

A. What is the statutory authority for the proposed 

standards?
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 Section 112(q)(1) of the Clean Air Act (CAA) requires 

that National Emissions Standards for Hazardous Air 

Pollutants (NESHAP) “in effect before the date of enactment 

of the Clean Air Act Amendments of 1990 [Nov. 15, 1990]. . 

. shall be reviewed and, if appropriate, revised, to comply 

with the requirements of subsection (d) of . . . section 

[112].” EPA promulgated 40 CFR Part 61, Subpart W, 

“National Emission Standards for Radon Emissions From 

Operating Mill Tailings,” (“Subpart W”) on December 15, 

1989.1

 EPA is conducting this review of Subpart W under CAA 

section 112(q)(1) to determine what revisions, if any, are 

appropriate. 

Section 112(d) of the CAA requires EPA to establish 

emission standards for major and area source categories 

that are listed for regulation under CAA section 112(c). A 

major source is any stationary source that emits or has the 

potential to emit 10 tons per year (tpy) or more of any 

single hazardous air pollutant (HAP) or 25 tpy or more of 

any combination of HAP. An area source is a stationary 

source of HAP that is not a major source. For the purposes 

 

1

 On April 26, 2007, Colorado Citizens Against Toxic Waste and Rocky 

Mountain Clean Air Action filed a lawsuit against EPA (EPA-HQ-OAR-2008-

0218-0013) for EPA’s alleged failure to review and, if appropriate, 

revise NESHAP Subpart W under CAA section 112(q)(1). A settlement 

agreement was entered into between the parties in November 2009(EPA-HQOAR-2008-0218-0019). 

Deleted: (Docket Reference)

Deleted: (Docket reference)
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of Subpart W, the HAP at issue is radon-222 (hereafter 

referred to as "radon"). We presently have no data or 

information that shows any other HAPs being emitted from 

these impoundments. Calculations of radon emissions from 

operating uranium recovery facilities have shown that 

facilities regulated under Subpart W are area sources. 

(EPA-HQ-OAR-2008-0218-0001, 0002) 

 Section 112(q)(1) does not dictate how EPA must 

conduct its review of those NESHAP issued prior to 1990. 

Rather, it provides that the Agency must review, and if 

appropriate, revise the standards to comply with the 

requirements of section 112(d). Determining what 

revisions, if any, are appropriate for these NESHAP is best 

assessed through a case-by-case consideration of each 

NESHAP. As explained below, in this case, we have reviewed 

Subpart W and are revising the standards consistent with 

section 112(d)(5), which provides EPA authority to issue 

standards for area sources. 

 Under CAA section 112(d)(5), the Administrator may 

elect to promulgate standards or requirements for 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.” 

Under section 112(d)(5), the Administrator has the 

Deleted: REFERENCE

Comment [RJR2]: I will provide these sources 

when we submit to OMB. PROVIDED 

OMB also asks: Are there any other HAPs that need 

to be considered? Response: We believe that radon is 

the only HAP emitted from the impoundments we 

regulate under Subpart W as we presently have no 

data that shows any other HAPs being emitted from 

these impoundments. We do not have data to 

determine whether HAP are emitted from other 

processes or structures at these facilities. 
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discretion to use generally available control technology or 

management practices (GACT) in lieu of maximum achievable 

control technology (MACT) under section 112(d)(2) and 

(d)(3), which is required for major sources. Pursuant to 

section 112(d)(5), we are proposing revisions to Subpart W 

to reflect GACT. 

B. What criteria did EPA use in developing the 

proposed GACT standards for these area sources?

 Additional information on generally available control 

technologies or management practices (GACT) is found in the 

Senate report on the legislation (Senate Report Number 101–

228, December 20, 1989), which 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 firms to 

operate and maintain the emissions control 

systems. 

Consistent with the legislative history, we can consider 

costs and economic impacts in determining GACT, which is 

particularly important when developing regulations for 

source categories, like this one, that may have small 

businesses.

 Determining what constitutes GACT involves considering 

the control technologies and management practices that are 

generally available to the area sources in the source 
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category. We also consider the standards applicable to 

major sources2

 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, we may also consider 

technologies and practices at area and major sources in 

similar categories to determine whether such technologies 

and practices could be considered generally available for 

the area source category at issue. Finally, as noted above, 

in determining GACT for a particular area source category, 

we consider the costs and economic impacts of available 

control technologies and management practices on that 

category. 

C. What source category is affected by the proposed 

standards?

As defined by EPA pursuant to the CAA, the source 

category for Subpart W is “facilities licensed [by the U.S. 

Nuclear Regulatory Commission (NRC)] to manage uranium 

byproduct material during and following the processing of 

uranium ores, commonly referred to as uranium mills and 

their associated tailings.” 40 CFR 61.250. Subpart W 

defines “uranium byproduct material or tailings” as “the 

waste produced by the extraction or concentration of 

 

2 None of the sources in this source category are major sources.
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uranium from any ore processed primarily for its source 

material content.3

” 40 CFR 61.251(g). For clarity, in this 

proposed rule we refer to this source category by the term 

“uranium recovery facilities” and we are proposing to add 

this phrase to the definitions section of the rule. Use of 

this term encompasses the existing universe of facilities 

whose HAP emissions are currently regulated under Subpart 

W. Uranium recovery facilities process uranium ore to 

extract uranium. The HAP emissions from any type of uranium 

recovery facility that manages uranium byproduct material 

or tailings is subject to regulation under Subpart W. This 

currently includes three types of uranium recovery 

facilities: (1) conventional uranium mills; (2) in-situ 

leach recovery facilities; and (3) heap leach facilities. 

Subpart W requirements specifically apply to the affected 

sources at the uranium recovery facilities that are used to 

manage or contain the uranium byproduct material or 

tailings. Common names for these structures may include, 

 

3 Pursuant to the Atomic Energy Act of 1954, as amended, the Nuclear 

Regulatory Commission defines “source material” as “(1) Uranium or 

thorium or any combination of uranium or thorium in any chemical or 

physical form; or (2) Ores that contain, by weight, one-twentieth of 

one percent (0.05 percent), or more, of uranium or thorium, or any 

combination of uranium or thorium.” (10 CFR 20.1003) For a uranium 

recovery facility licensed by the Nuclear Regulatory Commission under 

10 CFR Part 40, “byproduct material” means the “tailings or wastes 

produced by the extraction or concentration of uranium or thorium from 

ore processed primarily for its source material content, including 

discrete surface wastes resulting from uranium solution extraction 

processes.” (10 CFR 20.1003 and 40.4)

Deleted: that 

Deleted: A
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but are not limited to, impoundments, tailings 

impoundments, evaporation or holding ponds, and heap leach 

piles. However, the name itself is not important for 

determining whether Subpart W requirements apply to that 

structure; rather, applicability is based on the use of 

these structures to manage or contain uranium byproduct 

material. 

D. What are the production operations, emission sources, 

and available controls?

As noted above, uranium recovery and processing 

currently occurs by one of three methods: (1) conventional 

milling; (2) in-situ leach (ISL); and (3) heap leach. Below 

we present a brief explanation of the various uranium 

recovery methods and the usual structures that contain 

uranium byproduct materials. 

(1) Conventional Mills. 

Conventional milling is one of the two primary recovery 

methods that are currently used to extract uranium from 

uranium-bearing ore. Conventional mills are typically 

located in areas of low population density. Only one 

conventional mill in the United States is currently 

operating; all others are in standby, in decommissioning 

(closure) or have been decommissioned. Deleted: already 
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A conventional uranium mill is a chemical plant that 

extracts uranium using the following process: 

(A) Trucks deliver uranium ore to the mill, where it is 

crushed before the uranium is extracted through a 

leaching process. In most cases, sulfuric acid is the 

leaching agent, but alkaline solutions can also be used 

to leach the uranium from the ore. The process generally 

extracts 90 to 95 percent of the uranium from the ore. 

(B) The mill then concentrates the extracted uranium to 

produce a uranium oxide material which is called 

"yellowcake" because of its yellowish color.4

(C) 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. 

(D) The extraction process in (A) and (B) above produces 

both solid and liquid wastes (i.e., uranium byproduct 

material, or “tailings”) which are transported from the 

extraction location to an on-site tailings impoundment or 

a pond for temporary storage. 

 

4

 The term “yellowcake” is still commonly used to refer to this 

material, although in addition to yellow the uranium oxide material can 

also be black or grey in color.
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Uranium byproduct material/tailings are typically 

created in slurry form during the crushing, leaching and 

concentration processes and are then deposited in an 

impoundment or "mill tailings pile" which must be carefully 

monitored and controlled. This is because the mill tailings 

contain heavy metal ore constituents, including radium. The 

radium decays to produce radon, which may then be released 

to the environment. Because radon is a radioactive gas 

which may be inhaled into the respiratory tract, EPA has 

determined that exposure to radon and its daughter products 

contributes to an increased risk of lung cancer. 5 

The holding or evaporation ponds at this type of 

facility hold liquids containing byproduct material from 

which HAP emissions are also regulated under Subpart W. 

These ponds are discussed in more detail in the next 

section. 

 (2) In-Situ Leach/Recovery 

In-situ leach or recovery sites (ISL/ISR, in this 

document we will use ISL) represent the majority of the 

uranium recovery operations that currently exist. The 

research and development projects and associated pilot 

projects of the 1980s demonstrated ISL as a viable uranium 

 

5 http://www.epa.gov/radon/risk_assessment.html

Deleted: Its presence is of 

particular concern in confined 

areas (such as mines or homes),6

but radon can also be a health risk 

in open spaces.
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recovery technique where site conditions (e.g., geology) 

are amenable to its use. Economically, this technology 

produces a better return on the investment dollar (EPA-HQOAR-2008-0218-0087); therefore, the cost to produce uranium 

is more favorable to investors. Due to this, the trend in 

uranium production has been toward the ISL process. 

In-situ leaching is defined as the underground 

leaching or recovery of uranium from the host rock 

(typically sandstone) by chemicals, followed by recovery of 

uranium at the surface. Leaching, or more correctly the 

re-mobilization of uranium into solution, is accomplished 

through the underground injection of a lixiviant (described 

below) into the host rock (i.e., ore body) through wells 

that are connected to the ore formation. A lixiviant is a 

chemical solution used to extract (or leach) uranium from 

underground ore bodies. 

The injection of a lixiviant essentially reverses the 

geochemical reactions that resulted in the formation of the 

uranium deposit. The lixiviant assures that the dissolved 

uranium, as well as other metals, remains in the solution 

while it is collected from the ore zone by recovery wells 

which pump the solution to the surface. At the surface, the 

uranium is recovered in an ion exchange column and further 

processed into yellowcake. The yellowcake is packaged and 
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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. 

Two types of lixiviant solutions can be used, loosely 

defined as “acid” or “alkaline” systems. In the U.S., the 

geology and geochemistry of the majority of the uranium ore 

bodies favors the use of alkaline lixiviants such as 

bicarbonate-carbonate lixiviant and oxygen. Other factors 

in the choice of the lixiviant are the uranium recovery 

efficiencies, operating costs, and the ability to achieve 

satisfactory ground water restoration. 

After processing, lixiviant is recharged (more 

carbonate/bicarbonate or dissolved carbon dioxide is added

to the solution) and pumped back down into the formation 

for reuse in extracting more uranium. However, a small 

amount of this liquid is held back from reinjection to 

maintain a proper hydraulic gradient7

 within the wellfield. 

The amount of liquid held back is a function of the 

characteristics of the formation properties (e.g., 

permeability, hydraulic conductivity, transmissivity). This

excess liquid is sent to an impoundment (often called an 

 

7

 The hydraulic gradient determines which direction water in the 

formation will flow, which in this case limits the amount of water that 

migrates away from the ore zone.

Deleted: pressure

Formatted: Font: (Default) Courier New, Not

Superscript/ Subscript

Formatted: Font: (Default) Courier New
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evaporation pond or holding pond) on site or injected into 

a deep well for disposal. These impoundments, since they 

contain uranium byproduct material, are subject to the 

requirements of Subpart W.8 With respect to the lixiviant 

reinjected into the wellfield, there is a possibility of 

the lixiviant spreading beyond the zone of the uranium 

deposit (excursion), and this produces a threat of groundwater contamination. The operator of the ISL facility 

remediates any excursion by pumping large amounts of water 

in or out of the formation (at various wells) to contain 

the excursion, and this water (often containing byproduct 

material either before or after injection into or 

withdrawal from the formation) is often stored in the 

evaporation or holding ponds.9

 Although the excursion 

control operation itself is not regulated under Subpart W, 

the ponds that contain byproduct material are regulated 

under that subpart since they are a potential source of 

radon emissions. After the ore body has been depleted, 

restoration of the formation (attempting to return the 

formation back to its original geochemical and geophysical 

properties) is accomplished by flushing the host rock with 

 

8

 As described later in this preamble, the design requirements for these 

impoundments are derived from the RCRA requirements for impoundments.

9

 By controlling the hydraulic gradient of the formation the operator 

controls the direction of flow of water, containing the water within 

specified limits of the formation.

Deleted: ponds

Comment [RJR3]: OMB would like to discuss 

whether the ponds are subject to RCRA or CWA. 

The evaporation ponds are not subject to RCRA as 

long as the wastes contained in the ponds are 

generated solely from mineral extraction or 

beneficiation. We understand this is the case for the 

evaporation ponds at the uranium recovery facilities 

covered by subpart W. If, however, a facility adds 

other wastes to the evaporation ponds, the ponds 

could become subject to RCRA. RCRA 

applicability in these circumstances could only be 

determined on a case-by-case basis. 

Whether the evaporation ponds at a particular 

uranium recovery facility are subject to the CWA 

depends on the facts of the particular situation. 

Impoundments can be jurisdictional under the CWA 

but that is a case-by-case determination. Similarly, 

whether a facility is discharging a regulated pollutant 

is also a case-by-case determination. Thus, EPA 

could only determine CWA applicability at a 

particular facility on a case-by-case basis.

 

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water and sometimes additional chemicals. Since small 

amounts of uranium are still contained in the returning 

water, the restoration fluids are also considered byproduct 

material, and are usually sent to evaporation ponds for 

disposition. 

(3) Heap Leaching 

In addition to conventional uranium milling and ISL, 

some facilities may use an extraction method known as 

heap leaching. In some instances uranium ore is of such low 

grade or the geology of the ore body is such that it is not 

cost-effective to remove the uranium via conventional 

milling or through ISL.10 In this case a heap leaching 

method may be utilized. 

No such facilities currently operate to recover 

uranium in the U.S. However, there are plans for at least 

one facility to open in the U.S. within the next few years. 

Heap leach operations involve the following process: 

A. Small pieces of ore are placed in a large pile, or 

"heap," on an impervious geosynthetic liner with 

perforated pipes under the heap. For the purposes of 

Subpart W the impervious pad will meet the 

 

10 The ore grade is so low that it is not practical to invest large sums 

of capital to extract the uranium. Heap leach is a much more passive

and relatively inexpensive system.

Deleted: T

Deleted: pad of plastic, clay, or 

asphalt,

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requirements for design and construction of 

impoundments found at 40 CFR 192.32 (a). 

B. An acidic solution is then sprayed11 over the ore to 

dissolve the uranium it contains. 

C. The uranium-rich solution drains into 

the perforated pipes, where it is collected and 

transferred to an ion-exchange system. 

D. The heap is “rested,” meaning that there is a 

temporary cessation of application of acidic solution 

to allow for oxidation of the ore before leaching 

begins again. 

E. The ion-exchange system extracts the uranium from 

solution where it is later processed into 

a yellowcake12. 

F. Once the uranium has been extracted, the remaining 

solution still contains small amounts of uranium 

byproduct material (the extraction process is not 100% 

effective), and this solution is either piped to the 

heap leach pile to be reused or piped to an 

evaporation or holding pond. In the evaporation pond 

it is subject to the Subpart W requirements. 

 

11 Other technology includes drip systems, sometimes used at gold 

extraction heaps, and flooding of the heap leach pile. 12 It is our understanding that either ion exchange or solvent 

extraction techniques can be used to recover uranium at heap leach 

facilities. The decision to use one type or the other depends largely 

on the quality of the ore at a particular site. 

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G. 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. 

H. Finally, there is a final drain down of the heap 

solutions, as well as a possible rinsing of the heap. 

These solutions will contain byproduct material and 

will be piped to evaporation or holding ponds, where 

they become subject to the Subpart W requirements. 

The heap leach pile will be closed in place according 

to the requirements of 40 CFR 192.32. 

Today we are proposing to regulate the HAP emissions 

from heap leach uranium extraction under Subpart W, in 

addition to conventional impoundments and evaporation 

ponds, which are already regulated under this Subpart. Our 

rationale (explained in greater detail in Section IV.D.4.) 

is that from the moment uranium extraction takes place in 

the heap, uranium byproduct material is left behind. 

Therefore the byproduct material must be managed with the 

same design as a conventional impoundment, with a liner and 

leak detection system prescribed at 40 CFR 192.32(a), and 

an effective method of limiting radon emissions while the 

heap leach pile is being used to extract uranium. 

Deleted: packed in 55-gallon drums 

to be 

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As described above, there may also be holding or 

evaporation ponds at this type of facility. In many cases 

these ponds hold liquids containing byproduct material. The 

byproduct material is contained in the liquids used to 

leach uranium from the ore in the heap leach pile as well 

as draining the heap leach pile in preparation for closure. 

The HAP emissions from these fluids are currently regulated 

under Subpart W. 

E. What are the existing requirements under Subpart W?

Subpart W was promulgated on December 15, 1989 (54 FR 

51654). At the time of promulgation the predominant form of 

uranium recovery was through the use of conventional mills. 

There are two separate standards required in Subpart W. The 

first standard is for “existing” impoundments, e.g., those 

in existence and licensed by the NRC (or it’s Agreement 

States) on or prior to December 15, 1989. Owners or 

operators of existing tailings impoundments must ensure 

that emissions from those impoundments do not exceed a 

radon (Rn-222) flux standard of 20 picocuries per meter 

squared per second (pCi/m2

/sec). As stated at the time of 

promulgation: “This rule will have the practical effect of 

requiring the mill owners to keep their piles wet or 

Deleted: se
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covered.13” Keeping the piles (impoundments) wet or covered 

with soil would reduce radon emissions to a level that 

would meet the standard. This is still considered an 

effective method to reduce radon emissions at all uranium 

tailings impoundments. 

The method for monitoring for compliance with the 

radon flux standard was prescribed as Method 115, found at 

40 CFR Part 61, Appendix B. The owners or operators of 

existing impoundments must report to EPA the results of the 

compliance testing for any calendar year by no later than 

March 31 of the following year. 

There is currently one existing operating mill with 

impoundments that pre-date December 15, 1989, and two mills 

that are currently in standby mode. 

The second standard applies to “new” impoundments 

designed and/or constructed after December 15, 1989. The 

requirements applicable to new impoundments are work 

practice standards that regulate either the size and number 

of impoundments, or the amount of tailings that may remain 

uncovered at any time. After December 15, 1989, 40 CFR 

61.252(b) states that no new tailings impoundment can be 

built unless it is designed, constructed and operated to 

meet one of the following two work practices: 

 

13 See 54 FR 51689
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1. Phased disposal in lined impoundments that are no 

more than 40 acres in area and meet the 

requirements of 40 CFR 192.32(a) as determined by 

the 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 that are 

dewatered and immediately disposed 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 basis of the work practice standards is to (1) 

limit the size of the impoundment, which limits the radon 

source; or (2) utilize the continuous disposal system, 

which prohibits large accumulations of uncovered tailings, 

limiting the amount of radon released. 

The work practice standards described above were 

promulgated after EPA considered a number of factors that 

influence the emissions of Rn-222 from tailings 

impoundments, including the climate and the size of the 

impoundment. For example, for a given concentration of Ra226 in the tailings, and a given grain size of the 

tailings, the moisture content of the tailings will control 

the radon emission rate; the higher the moisture content 
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the lower the emission rate. In the arid and semi-arid 

areas of the country where most impoundments are located or 

proposed, the annual evaporation rate is quite high. As a 

result, the exposed tailings (absent controls like 

sprinkling) dry rapidly. In previous assessments, we 

explicitly took the fact of rapid drying into account by 

using a Rn-222 flux rate of 1 pCi/m2

/s per pCi/g Ra-226 to 

estimate the Rn-222 source term from the dry areas of the 

impoundments. (Note: The estimated source terms from the 

ponded (areas completely covered by liquid) and saturated 

areas of the impoundments are considered to be zero, 

reflecting the complete attenuation of the Rn-222). 

Another factor we considered was the area of the 

impoundment, which has a direct linear relationship with 

the Rn-222 source term, more so than the depth or volume of 

the impoundment. Again, assuming the same Ra-226 

concentration and grain sizes in the tailings, a 100-acre 

dry impoundment will emit 10 times the radon of a 10-acre 

dry impoundment. This linear relationship between size and 

Rn-222 source term is one of the main reasons that Subpart 

W imposed size restrictions on all future impoundments (40 

acres per impoundment if phased disposal is chosen and 10 

acres total uncovered if continuous disposal is chosen). 

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Subpart W also mandates that all tailings impoundments 

at uranium recovery facilities comply with the requirements 

at 40 CFR 192.32(a). EPA explained the reason for adding 

this requirement in the preamble as follows: 

“EPA recognizes that in the case of a tailings pile 

which is not synthetically or clay lined (the clay 

lining can be the result of natural conditions at the 

site) water placed on the tailings in an amount 

necessary to reduce radon levels, can result in ground 

water contamination. In addition, in certain 

situations the water can run off and contaminate 

surface water. EPA cannot allow a situation where the 

reduction of radon emissions comes at the expense of 

increased pollution of the ground or surface water. 

Therefore, all piles will be required to meet the 

requirements of 40 CFR 192.32(a) which protects water 

supplies from contamination. Under the current rules, 

existing piles are exempt from these provisions, this 

rule will end that exemption.” 

54 FR 51654, 51680 (December 15, 1989). Therefore, all 

impoundments are required to meet the requirements at 40 

CFR 192.32(a). 

Section 192.32(a) includes a cross-reference to the 

surface impoundment design and construction requirements of 

hazardous waste surface impoundments regulated under the 

Resource Conservation and Recovery Act (RCRA), found at 40 

CFR 264.221. Those requirements state that the impoundment 

shall be designed, 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 
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time during the active life of the impoundment. Briefly, 40 

CFR 264.221(c) requires that the liner system must include: 

1. A top liner designed and constructed of materials 

(e.g., a geomembrane) to prevent the migration of 

hazardous constituents into the liner during the 

active life of the unit. 

2. 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 of the unit. 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 three feet of compacted soil material with a 

hydraulic conductivity of no more than 1 x 10-7 cm/sec. 

3. A leachate collection and removal system between 

the liners, which acts as a leak detection system. 

This system must be capable of detecting, collecting 

and removing hazardous constituents at the earliest 

practicable time through all areas of the top liner 

likely to be exposed to the waste or liquids in the 

impoundment. 
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There are other requirements for the design and operation 

of the impoundment, and these include construction 

specifications, slope requirements, sump and liquid removal 

requirements.14

F. How did we gather information for this proposed rule?

This section describes the information we used as the 

basis for making the determination to revise Subpart W. We 

collected this information using various methods. We 

performed literature searches, where appropriate, of the 

engineering methods used by existing uranium recovery 

facilities in the United States as well as the rest of the 

world. We used this information to determine whether the 

technology used to contain uranium byproduct material had 

advanced since the time of the original promulgation of 

Subpart W. We reviewed and compiled a list of existing and 

proposed uranium recovery facilities and the containment 

technologies being used, as well as those proposed to be 

used. We compared and contrasted those technologies with 

the engineering requirements of hazardous waste surface 

impoundments regulated under Subtitle C of the Resource 

Conservation and Recovery Act (RCRA), which are used as the 

 

14 For detailed information on the design and operating requirements, 

refer to 40 CFR Part 264 Subpart K – Surface Impoundments. 

Deleted: D

Deleted: W

Deleted: G

Deleted: I

Deleted: P

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design basis for existing uranium byproduct material 

impoundments. 

We collected information on existing uranium mills and 

in-situ leach facilities by issuing information collection 

requests authorized under section 114(a) of the CAA to 

seven uranium recovery facilities. At the time, this 

represented 100% of existing facilities. Since then, Cotter 

Corp. has closed its Cañon City facility. These requests 

required uranium recovery companies to provide detailed 

information about the uranium mill and/or in-situ leaching 

facility, as well as the number, sizes and types of 

affected sources (tailings impoundments, evaporation ponds 

and collection ponds) that now or in the past held uranium 

byproduct material. We requested information on the history 

of operation since 1975, ownership changes, whether the 

operation was in standby mode and whether plans existed for 

new facilities or reactivated operations were expected.15 We 

also reviewed the regulatory history of Subpart W and the 

radon measurement methods used to determine compliance with 

the existing standards. Below is a synopsis of the 

information we collected and our analyses. 

1. Pre-1989 Conventional Mill Impoundments 

 

15 Section 114(a) letters and responses can be found at 

http://www.epa.gov/radiation/neshaps/subpartw/rulemaking-activity.html

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We have been able to identify three facilities, either 

operating or on standby,16 that have been in operation 

since before the promulgation of Subpart W in 1989. These 

existing facilities must ensure that emissions from their 

pre-1989 impoundments17 not exceed a radon (Rn-222) flux 

standard of 20 pCi/m2

/sec. The method for monitoring for 

compliance with the radon flux standard was prescribed as 

Method 115, found at 40 CFR Part 61, Appendix B. These 

facilities must also meet the requirements in 40 CFR 

61.252(c), which cross-references the requirements of 40 

CFR 192.32(a). 

The White Mesa Conventional Mill in Blanding, Utah, 

has one pre-1989 impoundment (known by the company as Cell 

3) that is currently in operation and near capacity but is 

still authorized and continues to receive tailings. The 

company is now pumping any residual free solution out of 

the cell and contouring the sands. It will then be 

determined whether any more solids need to be added to the 

cell to fill it to the specified final elevation. It is 

expected to close in the near future. (EPA-HQ-OAR-2008-

 

16 “Standby” is when a facility impoundment is licensed for the 

continued placement of tailings/byproduct material but is currently not 

receiving tailings/byproduct material. See Section V.A. for a 

discussion of this definition that we are proposing to add to Subpart 

W.

17 In this preamble when we use the generic term “impoundment,” we are 

using the term as described by industry. 

Deleted: The company has placed as 

much tailings sands into it as 

possible at this time. 

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0218-0069) The mill also uses an impoundment constructed 

before 1989 as an evaporation pond (known as Cell 1). To 

the extent this evaporation pond contains byproduct 

material, its HAP emissions are also regulated by Subpart 

W. 

The Sweetwater conventional mill is located 42 miles 

northwest of Rawlins, Wyoming. The mill operated for a 

short time in the 1980s and is currently in standby status. 

Annual radon values collected by the facility indicate that 

there is little measurable radon flux from the mill 

tailings that are currently in the lined impoundment. This 

monitoring program remains active at the facility. 

According to company records, of the 37 acres of tailings, 

approximately 28.3 acres of tailings are covered with soil; 

the remainder of the tailings are continuously covered with 

water. The dry tailings have an earthen cover that is 

maintained as needed. During each monitoring event one 

hundred radon flux measurements are taken on the tailings 

continuously covered by soil, as required by Method 115 for 

compliance with Subpart W. The mean radon flux for the 

exposed tailings over the past 21 years was 3.5 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 thus 

Deleted: Since it most likely

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approximately 30% of the 20.0 pCi/m2

/sec standard. (EPA-HQOAR-2008-0218-0087) 

The Shootaring Canyon project is a conventional mill 

located about 3 miles north of Ticaboo, Utah, in Garfield 

County. The approximately 1,900-acre site includes an ore 

pad, a small milling building, and a tailings impoundment 

system that is partially constructed. The mill operated 

for a very short period of time. Shootaring Canyon did 

pre-date the standard, but the mill was shut down prior to 

the promulgation of the standard. The impoundment is in a 

standby status and has an active 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. (EPA-HQOAR-2008-0218-0087) 

The Shootaring Canyon mill operated for approximately 

30 days. Tailings were deposited in a portion of the upper 

impoundment. A lower impoundment was conceptually designed 

but has not been built. Milling operations in 1982 

produced 25,000 cubic yards of tailings, deposited in a 

2,508 m2

 (0.62 acres) area. The tailings are dry except for 

moisture associated with occasional precipitation events; 

Deleted: Reference

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consequently, there are no beaches18. The tailings have a 

soil cover that is maintained by the operating company. 

Radon sampling for the 2010 year took place in April. 

Again, one hundred radon flux measurements were collected. 

The average radon flux from this sampling event was 

11.9 pCi/m2

-sec. 

A fourth mill is Cotter Corporation in Cañon City, 

Colorado. The mill no longer exists, and the pre-1989 

impoundments are in closure. 

2. 1989-Present Conventional Mill Impoundments 

There currently is only one operating conventional mill 

with an impoundment that was constructed after December 15, 

1989. The White Mesa conventional mill in Utah has two 

impoundments (Cell 4A and Cell 4B: Cell 4A is currently 

operating as a conventional impoundment and Cell 4B is 

being used as an evaporation pond) designed and constructed 

after 1989. The facility uses the phased disposal work 

practice. 

There are several conventional mills in the planning 

and/or permitting stage and conventional impoundments at 

these mills will be required to utilize one of the current 

work practice standards. 

 

18 The term “beaches” refers to portions of the tailings impoundment 

where the tailings are wet but not saturated or covered with liquids.

Deleted: for the less than one acre 

surface area

Deleted: A reclamation plan exists 

but is under revision as part of 

license renewal. Since the 

impoundments are in closure, the 

impoundments are not subject to 

Subpart W but instead are subject 

to the long-term closure and 

decommissioning requirements in 

their license issued by the state 

of Colorado, an NRC agreement 

State.
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3. In-Situ Leach Facilities 

After 1989 the price of uranium began to fall, and the 

uranium mining and milling industry essentially collapsed, 

with very few operations remaining in business. However, 

several years ago the price of uranium began to rise so 

that it became profitable once more for companies to 

consider uranium recovery. ISL has become the preferred 

choice for uranium extraction where suitable geologic 

conditions exist. 

Currently there are five ISL facilities in operation: 

(1) the Alta Mesa project in Brooks County, Texas; (2) the 

Crow Butte Operation in Dawes County, Nebraska; (3) the 

Hobson/La Palangana Operation in South Texas; (4) the 

Willow Creek (formerly Christensen Ranch/Irigaray Ranch) 

Operation in Wyoming; and (5) the Smith Ranch-Highland 

Operation in Converse County, Wyoming.19 These facilities 

use or have used evaporation ponds to hold back liquids 

containing uranium byproduct material from reinjection to 

maintain a proper hydraulic gradient within the wellfield.20

These ponds are subject to the Subpart W requirements and 

range in size from less than an acre to up to 40 acres. 

 

19 Source: U.S. Energy Information Administration, 

http://www.eia.gov/uranium/production/quarterly/html/qupd_tbl4.html

20 The Alta Mesa operation uses deep well injection rather than 

evaporation ponds.

Deleted: Subpart W was promulgated,

Deleted: , because of renewed 

interest in nuclear power,

Deleted: pressure
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Based on the information provided to us the ponds meet the 

requirements of 40 CFR 61.252(c). 

There are approximately 11 additional ISL facilities 

in various stages of licensing or on standby. It is 

anticipated that there could be approximately another 20-30 

license applications over the next 5-10 years21. 

4. Heap Leach Facilities 

 As stated earlier, there are currently no operating 

heap leach facilities in the United States. We are aware of 

two or three potential future operations. The project most 

advanced in the application process is the Sheep Mountain 

facility in Wyoming. Energy Fuels has announced its intent 

to submit a license application to the NRC in December 

2013. One or two other as yet to be determined operations 

may be located in Lander County, Nevada and/or a site in 

New Mexico.22

5. Flux Requirement versus Management Practices for 

Conventional Impoundments in operation before December 15, 

1989. 

In performing our analysis we considered the 

information we received from all the existing conventional 

 

21 Source: http://www.nrc.gov/materials/uranium-recovery/licenseapps/ur-projects-list-public.pdf. 22 http://www.nrc.gov/materials/uranium-recovery/license-apps/urprojects-list-public.pdf. 

Deleted: 2

Deleted: (REFERENCE)

Deleted: Titan Uranium

Deleted: mid 2012

Deleted: Work Practice Standards

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impoundments. We also looked at the compliance history of 

the existing conventional impoundments. After this review 

we considered two specific questions: 1) Are any of the 

conventional impoundments using any novel methods to reduce 

radon emissions? 2) Is there now any reason to believe that 

any of the existing conventional impoundments could not 

comply with the management practices for new conventional 

impoundments, in which case would we need to continue to 

make the distinction between conventional impoundments 

constructed before or after December 15, 1989? We arrived 

at the following conclusions: First, we are not aware of 

any conventional impoundment that uses any new or different

technologies to reduce radon emissions. Conventional 

impoundment operators continue to use the standard method 

of reducing radon emissions by limiting the size of the 

impoundment and covering tailings with soil or keeping 

tailings wet. These are very effective methods for limiting 

the amount of radon released to the environment. 

Second, we believe that only one existing operating 

conventional impoundment designed and in operation before 

December 15, 1989, could not meet the work practice 

standards. This impoundment is Cell 3 at the White Mesa 

mill, which is expected to close in 2014 (Personal

communication with Utah Department of Environmental 

Comment [RJR4]: OMB would like to discuss 

why these two questions were considered. We asked 

these two questions as part of our overall efforts to 

determine whether revisions were necessary (i.e. part 

of our effort to “review, and if necessary, revise” the 

standards). The statute does not mandate we ask 

these two particular questions. But as part of our 

efforts to determine whether a revision was 

necessary, these are logical questions to ask. We 

describe the statutory authorities we are working 

under in Sections II.A. and B. What we describe 

here is just part of that process.

Deleted: work practice standards 

Deleted: novel
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Quality, May 16, 2013, EPA-HQ-2008-0218-0081). We were very 

clear in our 1989 rulemaking that all conventional mill 

impoundments must meet the requirements of 40 CFR 

192.32(a), which in addition to requiring ground-water 

monitoring also required the use of liner systems to ensure 

there would be no leakage from the impoundment into the 

ground water. We did this by removing the exemption for 

existing piles from the 40 CFR 192.32(a) requirements (54 

FR 51680). However, we did not require those existing 

impoundments to meet either the phased disposal or 

continuous disposal work practice standards, which limit 

the exposed area and/or number of conventional 

impoundments, thereby limiting the potential for radon 

emissions. This is because at the time of promulgation of 

the rule, conventional impoundments existed that were 

larger in area than the maximum work practice standard of 

40 acres used for the phased disposal work practice, or 10 

acres for the continuous disposal requirement. This area 

limitation was important in reducing the amount of exposed 

tailings that were available to emit radon. However, we 

recognized that by instituting a radon flux standard we 

would require owners and operators to limit radon emissions 

from these preexisting impoundments (usually by placing 

water or soil on exposed portions of the impoundments). The 

Deleted: ending
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presumption was that conventional impoundments constructed 

before this date could otherwise be left in a dry and 

uncovered state, which would allow for unfettered release 

of radon. The flux standard was promulgated to have the 

practical effect of requiring owners and operators of these 

old impoundments to keep their tailings either wet or 

covered with soil, thereby reducing the amount of radon 

that could be emitted (54 FR 51680). 

We believe that the existing conventional impoundments 

at both the Shootaring Canyon and Sweetwater facilities can 

meet the work practice standards in the current Subpart W 

regulation. The conventional impoundments at both these 

facilities are less than 40 acres in area and are 

synthetically lined as per the requirements in 40 CFR 

192.32(a). We also have information that the new 

conventional impoundments operating at the White Mesa mill 

will utilize the phased work practice standard of limiting 

conventional impoundments to no more than two, each 40 

acres or less in area. We also have information that Cell 3 

at the White Mesa facility will be closed in 2014, and the 

phased disposal work method will be used for the remaining 

cells.(Personal communication with Utah Department of 

Environmental Quality, May 16, 2013, EPA-HQ-2008-0218-0081)

As a result, we find there would be no conventional 

Deleted: 2

Deleted: REFERENCE

Deleted: )

Deleted: that at the time of 

promulgation of this proposed rule 
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impoundment designed or constructed before December 15, 

1989 that could not meet a work practice standard. Since 

the conventional impoundments in existence prior to 

December 15, 1989, appear to meet the work practice 

standards, we are proposing to eliminate the distinction of 

whether the conventional impoundment was constructed before 

or after December 15, 1989. We are also proposing that all 

conventional impoundments (including those in existence 

prior to December 15, 1989) must meet the requirements of 

one of the two work practice standards, and that the flux 

standard of 20 pCi/m2

/sec will no longer be required for the 

impoundments in existence prior to December 15, 1989. We 

ask for comment on this approach. 

G. How does this action relate to other EPA standards?

Under the CAA, EPA promulgated Subpart W, which includes 

standards and other requirements for controlling radon 

emissions from operating mill tailings at uranium recovery 

facilities. Under our authority in the Uranium Mill 

Tailings Radiation Control Act of 1978 (UMTRCA), we have 

also issued standards that are more broadly applicable to 

uranium and thorium byproduct materials at active and 

inactive uranium recovery facilities. NRC (or Agreement 

Deleted: ,
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States23) and DOE implement and enforce these standards at 

these uranium recovery facilities as directed by UMTRCA. 

These standards, located in 40 CFR Part 192, address the 

radiological and non-radiological hazards of uranium and 

thorium byproduct materials in ground water and soil, in 

addition to air. For the non-radiological hazards, UMTRCA 

directed us to promulgate standards consistent with those 

used by EPA to regulate non-radiological hazardous 

materials under RCRA. Therefore, our Part 192 standards 

incorporate the ground-water protection requirements 

applied to hazardous waste management units under RCRA and 

specify the placement of uranium or thorium byproduct 

materials in impoundments constructed in accordance with 

RCRA requirements. Radon emissions from non-operational 

impoundments (i.e., those with final covers) are limited in 

40 CFR Part 192 to the emissions levels of 20 pCi/m2

/sec. We 

are currently preparing a regulatory proposal to update 

provisions of 40 CFR Part 192, with emphasis on groundwater protection for ISL facilities. As explained in 

 

23 An Agreement State is a State that has entered into an agreement with 

the Nuclear Regulatory Commission under section 274 of the Atomic 

Energy Act of 1954 (42 U.S.C. 2021)and has authority to regulate

byproduct materials (as defined in section 11e.(2)of the Atomic Energy 

Act)and the disposal of low-level radioactive waste under such 

agreement.
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previous sections, Subpart W currently contains reference 

to some of the Part 192 standards. 

H. Why did we conduct an updated Risk Assessment?

While not required by or conducted as part of our GACT 

analysis, one of the tasks we performed for our own 

purposes was to update the risk analysis we performed when 

we promulgated Subpart W in 1989. We performed a comparison 

between the 1989 risk assessment and current risk 

assessment approaches, focusing on the adequacy and the 

appropriateness of the original assessments. We did this 

for informational purposes only and not for or as part of 

our GACT analysis. Instead, we prepared this updated risk 

assessment because we wanted to demonstrate that even using 

updated risk analysis procedures (i.e. using procedures 

updated from those used in the 1980s), the existing radon 

flux standard appears to be protective of the public health 

and the environment. We did this by using the information 

we collected to perform new risk assessments for existing 

facilities, as well as two idealized “generic” sites, one 

located in the eastern half of the United States and one 

located in the southwest United States. (These two model 

sites do not exist. They are idealized using representative 

features of mills in differing climate and geography). This 
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information has been collected into one document24 that has 

been placed in the docket (EPA-HQ-OAR-2008-0218-0087) for 

this proposed rulemaking. 

As part of this work, we evaluated various computer 

models that could be used to calculate the doses and risks 

due to the operation of conventional and ISL uranium 

recovery facilities, and selected CAP88 V 3.0 for use in 

this analysis. CAP88 V 3.0 was developed in 1988 from the 

AIRDOS, RADRISK, and DARTAB computer programs, which had 

been developed for the EPA at the Oak Ridge National 

Laboratory (ORNL). 

CAP88 V 3.0, which stands for “Clean Air Act 

Assessment Package-1988 version 3.0,” is used to 

demonstrate compliance with the NESHAP requirements 

applicable to radionuclides. CAP88 V 3.0 calculates the 

doses and risk to a designated receptor as well as to the 

surrounding population. Exposure pathways evaluated by 

CAP88 V 3.0 are: inhalation, air immersion, ingestion of 

vegetables, meat, and milk, and ground surface exposure. 

CAP88 V 3.0 uses a modified Gaussian plume equation to 

estimate the average dispersion of radionuclides released 

 

24 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) 

Deleted: DOCKET REFERENCE
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from up to six emitting sources. The sources may be either 

elevated stacks, such as a smokestack, or uniform area 

sources, such as the surface of a uranium byproduct 

material impoundment. Plume rise can be calculated assuming 

either a momentum or buoyant-driven plume. 

At several sites analyzed in this evaluation only 

site-wide releases of radon were available to us. This 

assessment was limited by the level of detail provided by 

owners and operators of uranium recovery facilities. In 

instances where more specific site data were available, 

site-wide radon releases were used as a bounding estimate. 

Assessments are done for a circular grid of distances and 

directions for a radius of up to 80 kilometers (50 miles) 

around the facility. The Gaussian plume model produces 

results that agree with experimental data as well as any 

comparable model, is fairly easy to work with, and is 

consistent with the random nature of turbulence. A 

description of CAP88 V 3.0 and the computer models upon 

which it is based is provided in the CAP88 V 3.0 Users 

Manual.25

The uranium recovery facilities that we analyzed 

included three existing conventional mills (Cotter, White 

Mesa and Sweetwater), five operating ISL operations (the 

 

25 http://www.epa.gov/radiation/assessment/CAP88 V 3.0/index.html
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Alta Mesa project in Brooks County, Texas; the Crow Butte 

Operation in Dawes County, Nebraska; the Hobson/La 

Palangana Operation in South Texas; the Willow Creek 

(formerly Christensen Ranch/Irigaray Ranch) Operation in 

Wyoming; and the Smith Ranch-Highland Operation in Converse 

County, Wyoming), and two generic sites assumed for the 

location of conventional mills (we chose conventional mills 

because we believe they have the potential for greater 

radon emissions). One generic site was modeled in the 

southwest United States (Western Generic) while the other 

was assumed to be located in the eastern United States 

(Eastern Generic).26 An Eastern generic site was selected 

for the second generic site to accommodate the recognition 

that a number of uranium recovery facilities are expected 

to apply for construction licenses in the future, and to 

determine potential risks in geographic areas of the U.S. 

that customarily have not hosted uranium recovery 

facilities. For this assessment the conventional mills we 

were most interested in were the White Mesa mill and the 

Sweetwater mill. (The Shootaring Canyon mill was not 

analyzed, because the impoundment is very small and is soil 

covered, and the Cotter facility is now in closure). These 

 

26 There is a potential in the future for uranium recovery in areas like 

south-central Virginia.

Deleted: to be
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conventional mills are either in operation or standby and 

are subject to the flux standard of 20 pCi/m2

/sec. The risk 

analyses performed for these two mills showed that the 

maximum lifetime cancer risks from radon emissions from the 

White Mesa impoundments were 1.1 x 10-4 while the maximum 

lifetime cancer risks from radon associated with the 

impoundments at the Sweetwater mill were 2.4 x 10-5. In 

protecting public health, EPA strives to provide the 

maximum feasible protection by limiting lifetime cancer 

risk from radon exposure to approximately 1 in 10,000 

(i.e., 10-4). The analyses also estimated that the total 

cancer risk to the populations surrounding all ten modeled 

uranium sites (i.e., total cancer fatalities) is between 

0.0015 and 0.0026 fatal cancers per year, or approximately 

1 case every 385 to 667 years for the 4 million persons 

living within 80 km of the uranium recovery facilities. 

Similarly, the total cancer incidence for all ten modeled 

sites is between 0.0021 and 0.0036 cancers per year, or 

approximately 1 case every 278 to 476 years. The analyses 

are described in more detail in the background document 

generated for this proposal.27 As stated above, we performed 

this risk assessment for informational purposes only. The 

 

27 All risks are presented as LCF risks. If it is desired to estimate the 

morbidity risk, simply multiply the LCF risk by 1.39. For a more 

detailed analysis of cancer mortality and morbidity, please see the 

Background Information Document, Docket number EPA-HQ-OAR-0218-0087.

Comment [RJR5]: OMB asks “In what 

context(s) does EPA use this cutoff for radon cancer 

risk. Response below. 

Deleted: incidence

Deleted: (DOCKET REFERENCE).

Formatted: Font: (Default) Courier New
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risk assessment was not required or considered during our 

analysis for proposing GACT standards for uranium recovery 

facilities (e.g., conventional impoundments, nonconventional impoundments or heap leach piles). 

III. Summary of the Proposed Requirements 

We are proposing to revise Subpart W to include 

requirements that we have identified are generally 

available for controlling radon emissions in a costeffective manner and are not currently included in Subpart 

W. Specifically, we are proposing to require that nonconventional impoundments and heap leach piles must 

maintain minimum liquid levels to control their radon 

emissions from these affected sources. 

 Additionally, we are revising Subpart W to propose 

GACT standards for the affected sources at conventional 

uranium mills, ISL facilities and heap leach facilities. 

Given the evolution of uranium recovery facilities over the 

last 20 years, we believe it is appropriate to revise 

Subpart W to tailor the requirements of the rule to the 

different types of facilities in existence at this time. 

We are therefore proposing to revise Subpart W to add 

appropriate definitions, standards and other requirements 

that are applicable to HAP emissions at these uranium 

recovery facilities. 
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 Our experience with ensuring that uranium recovery 

facilities are in compliance with Subpart W also leads us 

to propose three more changes. First, we are proposing to 

remove certain monitoring requirements that we believe are 

no longer necessary for demonstrating compliance with the 

proposed GACT standards. Second, we are proposing to 

revise certain definitions so that owners and operators 

clearly understand when Subpart W applies to their 

facility. Third, we are proposing to clarify what specific 

liner requirements must be met under subpart W.28

Taken altogether, the proposed revisions to Subpart W 

are appropriate for updating, clarifying and strengthening 

the management of radon emissions from the uranium 

byproduct material generated at uranium recovery 

facilities. 

A. What are the affected sources?

Today we are proposing to revise Subpart W to include 

requirements for affected sources at three types of 

operating uranium recovery facilities: (1) conventional 

uranium mills; (2) ISL facilities; and (3) heap leach 

 

28 Under its CAA authority, EPA requires facilities subject to Subpart 

W to build impoundments in a manner that complies with the requirements 

found in 40 CFR 192. As a matter of convenience, EPA cross-references 

the Part 192 requirements in Subpart W instead of copying them directly 

into Subpart W. This cross-referencing convention is often used in 

rulemakings.

Comment [RJR6]: OMB asked for this 

paragraph to be removed. We would prefer to retain 

it. It is simply a summary paragraph, and we believe 

it sums up the section. 
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facilities. The affected sources at these uranium recovery 

facilities include conventional impoundments, nonconventional impoundments where tailings are contained in 

ponds and covered by liquids (examples of these affected 

sources are evaporation or holding ponds that may exist at 

conventional mills, ISL facilities and heap leach 

facilities), and heap leach piles. The proposed GACT 

standards and the rationale for these proposed standards 

are discussed below and in Section IV. We request comment 

on all aspects of these proposed requirements. 

B. What are the proposed requirements?

1. Conventional impoundments. 

 In the 1989 promulgation of Subpart W we created two 

work practice standards, phased disposal and continuous 

disposal, for uranium tailings impoundments designed and 

constructed after December 15, 1989. The work practice 

standards, which limit the exposed area and/or number of 

conventional impoundments at a uranium recovery facility, 

require that these impoundments be no larger than 40 acres 

(for phased disposal) or 10 uncovered acres (for continuous 

disposal). We also limited the number of conventional 

impoundments operating at any one time to two. We took this 

approach because we recognized that the radon emissions 

from very large conventional impoundments could impose 
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unacceptable health effects if the piles were left dry and 

uncovered. The 1989 promulgation also included the 

requirements in 40 CFR 192.32(a), which include design and 

construction requirements for the impoundments as well as 

requirements for prevention and mitigation of ground-water 

contamination. 

As discussed earlier, we no longer believe that a 

distinction needs to be made for conventional impoundments 

based on the date when they were designed and/or 

constructed. We believe that the existing conventional 

impoundments at both the Shootaring Canyon and Sweetwater 

facilities can meet the work practice standards in the 

current Subpart W regulation. The conventional impoundments 

at both these facilities are less than 40 acres in area and 

are synthetically lined as per the requirements in 40 CFR 

192.32(a)(1). The existing cell 3 at the White Mesa mill 

will undergo closure in 2014 and will be replaced with the 

impoundments currently under construction that meet the 

phased disposal work practice standard. Therefore, there is 

no reason not to subject these older impoundments to the 

work practice standards required for impoundments designed 

or constructed after December 15, 1989. By incorporating 

these impoundments under the work practices provision of 

Subpart W, it is no longer necessary to require radon flux 

Deleted: bring

Deleted: under the umbrella of 
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monitoring, and we are proposing to eliminate that 

requirement. 

The proposed elimination of the monitoring requirement 

in 40 CFR 61.253 applies only to those facilities currently 

subject to the radon flux standard in 40 CFR 61.252(a), 

which applies to only the three conventional impoundments 

in existence prior to the original promulgation of Subpart 

W on December 15, 1989. While we are proposing to eliminate 

the radon monitoring requirement for these three 

impoundments under Subpart W, this action does not relieve 

the owner or operator of the uranium recovery facility of 

the monitoring and maintenance requirements of their 

operating license issued by the NRC or its Agreement 

States. These requirements are found at 10 CFR Part 40, 

Appendix A, Criterion 8 and 8A. Additionally, NRC, through 

its Regulatory Guide 4.14, may also recommend incorporation 

of radionuclide air monitoring at operating facility 

boundaries.

 Further, when the impoundments formally close they are 

subject to the radon monitoring requirements of 40 CFR 

192.32(a)(3), also under the NRC licensing requirements. 

From a cost standpoint, by not requiring radon 

monitoring we expect that for all three sites the total 

annual average cost savings would be $29,200, with a range 

Deleted: e
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from about $21,000 to $37,000. More details on economic 

costs can be found in Section IV.B of this preamble. 

For the proposed rule we also evaluated the requirements 

of 40 CFR 192.32(a) as they pertain to the Subpart W 

standards. The requirements of 40 CFR 192.32(a) are 

included in the NRC’s regulations and are reviewed for 

compliance by NRC during the licensing process for a 

uranium recovery facility. We determined that the 

requirements at 40 CFR 192.32(a)(1), which reference the 

RCRA requirements for design and operation of surface 

impoundments at 40 CFR 264.221, are the only requirements 

necessary for EPA to incorporate for Subpart W as they are 

effective methods of containment of tailings and protecting 

ground water while also limiting radon emissions. This 

liner requirement, described earlier in this preamble, 

remains in use for the permitting of hazardous waste land 

disposal units under RCRA. The requirements at 40 CFR 

192.32(a)(1) contain safeguards to allow for the placement 

of tailings and yet provide an early warning system in the 

event of a leak in the liner system. We are therefore 

proposing to retain the two work practice standards and the 

requirements of 40 CFR 192.32(a)(1) as GACT for 

conventional impoundments because these methods for 
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limiting radon emissions while also protecting ground water 

have proven effective for these types of impoundments. 

2. Non-conventional impoundments where tailings are 

contained in ponds and covered by liquids. 

Today we are proposing a GACT standard specifically 

for non-conventional impoundments where uranium byproduct 

materials are contained in ponds and covered by liquids. 

Common names for these structures may include, but are not 

limited to, impoundments and evaporation or holding ponds. 

These affected sources may be found at any of the three 

types of uranium recovery facilities. 

These units meet the existing applicability criteria 

in 40 CFR 61.250 to classify them for regulation under 

Subpart W. The holding or evaporation ponds located at 

conventional mills, ISL facilities and potentially heap 

leach facilities contain uranium byproduct material, either 

in solid form or dissolved in solution, and therefore their 

emissions are regulated under Subpart W. As defined at 40 

CFR 61.251(g), uranium byproduct material or tailings means 

the waste produced by the extraction or concentration of 

uranium from any ore processed primarily for its source 

material content. Therefore, emissions for the ponds at 

uranium recovery facilities that contain either uranium 

byproduct material in solid form or radionuclides dissolved 
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in liquids are regulated under Subpart W. Today we are 

again stating that determination and proposing a GACT 

standard specifically for these impoundments. 

Evaporation or holding ponds, while sometimes smaller 

in area than conventional impoundments, perform a basic 

task. They hold uranium byproduct material until it can be 

disposed. Our survey of existing ponds shows that they 

contain liquids, and, as such, this general practice has 

been sufficient to limit the amount of radon emitted from 

the ponds, in many cases, to almost zero. Because of the 

low potential for radon emissions from these impoundments, 

we do not believe it is necessary to monitor them for radon 

emissions. We have found that as long as approximately one 

meter of liquid is maintained in the pond, the effective 

radon emissions from the pond are so low that it is 

difficult to determine whether there is any contribution 

above background radon values. EPA has stated in the Final 

Rule for Radon-222 Emissions from Licensed Uranium Mill 

Tailings: Background Information Document (August, 1986): 

“Recent technical assessments of radon emission rates 

from tailings indicate that radon emissions from 

tailings covered with less than one meter of water, or 

merely saturated with water, are about 2% of emissions 

from dry tailings. Tailings covered with more than one 

meter of water are estimated to have a zero emissions 

rate. The Agency believes this calculated difference 

between 0% and 2% is negligible. The Agency used an 

emission rate of zero for all tailings covered with 
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water or saturated with water in estimating radon 

emissions.” 

Therefore, we are proposing as GACT that these 

impoundments meet the design and construction requirements 

of 40 CFR 192.32(a)(1), with no size/area restriction, and 

that during the active life of the pond at least one meter 

of liquid be maintained in the pond. 

We are also proposing that no monitoring be required 

for this type of impoundment. We have received information 

and collected data that show there is no acceptable radon 

flux test method for a pond holding a large amount of 

liquid. (Method 115 does not work because a solid surface 

is needed to place the large area activated carbon 

canisters used in the Method). Further, even if there was 

an acceptable method, we recognize that radon emissions 

from the pond would be expected to be very low because the 

liquid acts as an effective barrier to radon emissions; 

given that radon-222 has a very short half-life (3.8 days), 

there simply is not enough time for most of the radon 

produced by the solids or from solution to migrate to the 

water surface and cross the water/air interface before 

decaying.(EPA-HQ-OAR-2008-0218-0087) It therefore appears 

that monitoring at these ponds is not necessary for 

demonstrating compliance with the proposed standards. We 

Deleted: REFERENCE
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do, however, ask for comment and supporting information on 

three issues: (1) whether these impoundments need to be 

monitored with regard to their radon emissions, and why; 

(2) whether these impoundments need to be monitored to 

ensure at least one meter of liquid is maintained in the 

pond at all times, and (3) if these impoundments do need 

monitoring, what methods could a facility use (for example, 

what types of radon collection devices, or methods to 

measure liquid levels), at evaporation or holding ponds. 

3. Heap Leach Piles. 

The final impoundment category for which we are 

proposing GACT standards is heap leach piles. We are 

proposing to require that heap leach piles meet the phased 

disposal work practice standard set out in Section III B. 

1. of this preamble (which limits an owner/operator to no 

more than two operating heap leach piles of no more than 40 

acres each at any time) and the design and construction 

requirements at 40 CFR 192.32(a)(1) as GACT. We are also 

requiring heap leach piles to maintain minimum moisture 

content of 30% so that the byproduct material in the heap 

leach pile does not dry out, which would increase radon 

emissions from the heap leach pile. 

As noted earlier in the preamble, there are currently 

no operating uranium heap leach facilities in the United 
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States. We are aware that the one currently proposed heap 

leach facility will use the design and operating 

requirements at 40 CFR 192.32(a)(1) for the design of its 

heap. Since this requirement will be used at the only 

example we have for a heap leach pile, it, along with the 

phased disposal work practice standard (limiting the number 

and size of heap leach piles), will be the emission 

standards that we propose as GACT for heap leach piles. The 

premise is that the operator of a heap would not want to 

lose any of the uranium-bearing solution; thus, it is cost 

effective to maintain a good liner system so that there 

will be no leakage and ground water will be protected. 

Also, use of the phased disposal work practice standard 

will limit the amount of exposed uranium byproduct material 

that would be available to emit radon. If we assume that 

uranium ore (found in the heap leach pile) and the 

resultant leftover byproduct material after processing emit 

radon at the same rate as uranium byproduct material in a 

conventional impoundment (a conservative estimate), we can 

also assume that the radon emissions will be nearly the 

same as two 40 acre conventional impoundments. 

We recognize that owners and operators of conventional 

impoundments also limit the amount of radon emitted by 

keeping the tailings in the impoundments covered, either 
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with soil or liquids. At the same time, however, we 

recognize that keeping the uranium byproduct material in 

the heap in a saturated or near-saturated state (in order 

to reduce radon emissions) is not a practical solution as 

it would be at a conventional tailings impoundment. In the 

definitions at 40 CFR 61.251(c) we have defined “dewatered” 

tailings as those where the water content of the tailings 

does not exceed 30% by weight. We are proposing today to 

require operating heaps to maintain moisture content of 

greater than 30% so that the byproduct material in the heap 

is not allowed to become dewatered which would allow more 

radon emissions. We are specifically asking for comment on 

the amount of liquid that should be required in the heap, 

and whether the 30% figure is a realistic objective. We are 

also asking for comments on precisely where in the heap 

leach pile this requirement must be met. The heap leach 

pile may not be evenly saturated during the uranium 

extraction process. The sprayer/drip system commonly used 

on the top of heap leach piles usually results in a semisaturated moisture condition at the top of the pile, since 

flow of the lixiviant is not uniformly spread across the 

top of the pile. As downward flow continues, the internal 

areas of the pile become saturated. We are requesting 
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information and comment on where specifically in the pile 

the 30% moisture content should apply. 

C. What are the monitoring requirements?

As the rule currently exists, only mills with existing 

conventional impoundments in operation on or prior to 

December 15, 1989, are currently required to monitor to 

ensure compliance with the radon flux standard. The reason 

for this is because at the time of promulgation of the 1989 

rule EPA stated that no flux monitoring would be required 

for new impoundments because the proposed work practice 

standards would be effective in reducing radon emissions 

from operating impoundments by limiting the amount of 

tailings exposed (54 FR 51681). Since we have now 

determined that existing older conventional impoundments 

can meet one of the two work practice standards, we are 

proposing to eliminate the radon flux monitoring 

requirement. 

In reviewing Subpart W we looked into whether we 

should extend radon monitoring to all affected sources 

constructed and operated after 1989 so that the monitoring 

requirement would apply to all conventional impoundments, 

non-conventional impoundments and heap leach piles 

containing uranium byproduct materials. We also reviewed 

how this requirement would apply to facilities where Method 
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115 is not applicable, such as at impoundments totally 

covered by liquids. We concluded that the original work 

practice standards (now proposed as GACT) continue to be an 

effective practice for the limiting of radon emissions from 

conventional impoundments and from heap leach piles. We 

also concluded that by maintaining an effective water cover 

on non-conventional impoundments the radon emissions from 

those impoundments are so low as to be difficult to 

differentiate from background radon levels at uranium 

recovery facilities. Therefore, we are proposing today that 

it is not necessary to require radon monitoring for any 

affected sources regulated under Subpart W. We seek 

comment on our conclusion that radon monitoring is not 

necessary for any of these sources as well as on any 

available cost-effective options for monitoring radon at 

non-conventional impoundments totally covered by liquids. 

D. What are the notification, recordkeeping and reporting 

requirements?

New and existing affected sources are required to 

comply with the existing requirements of the General 

Provisions (40 CFR part 61, subpart A). The General 

Provisions include specific requirements for notifications, 

recordkeeping and reporting, including provisions for 

Comment [RJR7]: OMB asks “The evaluation of 

the effectiveness of the 30% moisture content of 

heap leach piles has a number of uncertainties (e.g., 

the heterogeneity of the water content and lack of 

measured effectiveness data) that seem to make it 

difficult to justify the absence of monitoring. Can 

EPA better justify why heap leach piles should not 

be monitored? 

EPA response: With no facilities to use as a guide, 

EPA is proposing this method of compliance for 

heap leach piles. Since this is a proposed rule, we 

have asked for comment on this approach, as well as 

suggestions for other methods. 
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notification of construction and/or modification and 

startup as required by 40 CFR 61.07, 61.08 and 61.09. 

Today we are also proposing that all affected sources 

will be required to maintain certain records pertaining to 

the design, construction and operation of the impoundments, 

both including conventional impoundments, and 

nonconventional impoundments, and heap leach piles. We are 

proposing that these records will be retained at the 

facility and contain information demonstrating that the 

impoundments and/or heap leach pile meet the requirements 

in section 192.32(a)(1), including but not limited to, all 

tests performed that prove the liner is compatible with the 

material(s) being placed on the liner. For nonconventional 

impoundments we are proposing that this requirement would 

also include records showing compliance with the continuous 

one meter of liquid in the impoundment29; for heap leach 

piles, we are proposing that this requirement would include 

records showing that the 30% moisture content of the pile 

is continuously maintained. Documents showing that the 

impoundments and/or heap leach pile meet the requirements 

in section 192.32(a)(1) are already required as part of the 

pre-construction application submitted under 40 CFR 61.07, 

 

29 The one meter liquid requirement pertains to having one meter of 

liquid cover any and all solid byproduct material. We do not anticipate 

a large quantity of solid byproduct material in these nonconventional 

impoundments. (EPA-HQ-OAR-2008-0218-0088) Deleted: REFERENCE
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so these records should already be available. Records 

showing compliance with the one meter liquid cover 

requirement for nonconventional impoundments and records 

showing compliance with the 30% moisture level required in 

heap leach piles can be created and stored during the daily 

inspections of the tailings and waste retention systems 

required by the NRC (and Agreement States) under the 

inspection requirements of 10 CFR 40, Appendix A, Criterion 

8A. 

Because we are proposing new record-keeping 

requirements for uranium recovery facilities, we are 

required by the Paperwork Reduction Act (PRA) to prepare an 

estimate of the burden of such record-keeping on the 

regulated entity, in both cost and hours necessary to 

comply with the requirements. We have submitted the 

Information Collection Request (ICR) containing this burden 

estimate and other supporting documentation to the Office 

of Management and Budget (OMB). See Section VII.B for more 

discussion of the PRA and ICR. 

We believe the record-keeping requirements proposed 

today will not create a significant burden for operators of 

uranium recovery facilities. As described earlier, we are 

proposing to require retention of three types of records: 

(1) records demonstrating that the impoundments and/or heap 

Deleted: must also submit an 

Deleted: at the time this proposal 

is published in the Federal 

Register
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leach pile meet the requirements in section 192.32(a)(1) 

(e.g. the design and liner testing information); (2) 

records showing that one meter of water is maintained to 

cover the byproduct material stored in nonconventional 

impoundments; and (3) records showing that heap leach piles 

maintain a moisture content of at least 30%. 

Documents demonstrating that the affected sources 

comply with section 192.32(a)(1) requirements are necessary 

for the facility to obtain regulatory approval from NRC (or 

an NRC Agreement State) and EPA to construct and operate 

the affected sources (this includes any revisions during 

the period of operations). Therefore, these records will 

exist independent of subpart W requirements and will not 

need to be continually updated as a result of this recordkeeping requirement in subpart W; however, we are proposing 

to include this record-keeping requirement in subpart W to 

require that the records be maintained at the facility 

during its operational lifetime (in some cases the records 

might be stored at a location away from the facility, such 

as corporate offices). This might necessitate creating 

copies of the original records and providing a location for 

storing them at the facility. 

Keeping a record to provide confirmation that water to 

a depth of one meter is maintained above the byproduct 
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Page 66 of 133

 

material stored in nonconventional impoundments should also 

be relatively straightforward. This would involve placement 

of a measuring device or devices in or at the edge of the 

impoundment to allow observation of the water level 

relative to the level of byproduct material in the 

impoundment. Such devices need not be highly technical and 

might consist of, for example, measuring sticks with 

easily-observable markings placed at various locations, or 

marking the sides of the impoundment to illustrate 

different water depths. As noted earlier, NRC and Agreement 

State licenses require operators to inspect the facility on 

a daily basis. Limited effort should be necessary to make 

observations of water depth and record the information in 

inspection log books that are already kept on site and 

available to inspectors. 

Similarly, daily inspections would provide a mechanism 

for recording moisture content of heap leach piles. 

However, because no heap leach facilities are currently 

operating, there is more uncertainty about exactly how the 

operator will determine that the heap has maintained a 30% 

moisture content. As discussed in more detail in Section 

IV.E.4 of this preamble, soil moisture probes are readily 

available and could be used for this purpose. Such probes 

could be either left in the heap leach pile, placed at 
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locations that provide a representative estimate for the 

heap as a whole, or facility personnel could use handheld 

probes to collect readings. The facility might also employ 

mass-balance estimates to provide a further check on the 

data collected. 

We estimate the burden in hours and cost for uranium 

recovery facilities to comply with the proposed 

recordkeeping requirements are as follows: 

Table 1: Burden Hours and Costs for 

Proposed Recordkeeping Requirements 

(Annual figures except where noted) 

Activity Hours Costs 

Maintaining Records 

for the section 

192.32(a)(1) 

requirements 

20* $1,360* 

Verifying the one 

meter liquid 

requirement for 

nonconventional 

impoundments 

288 $12,958 

Verifying the 30% 

moisture content at 

heap leach piles 

using multiple soil 

probes 

2,068 $86,548 

*These figures represent a one-time cost to the facility. 

Burden levels for heap leach piles are most uncertain 

because they depend on the chosen method of measurement 

(e.g., purchasing and maintaining multiple probes or a 

smaller number of handheld units) as well as the personnel 
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training involved (e.g., a person using a handheld unit 

will likely need more training than someone who is simply 

recording readings from already-placed probes). We request

comment on our estimates of burden, as well as suggestions 

of methods that could readily and efficiently be used to 

collect the required information. More discussion of the 

ICR and opportunities for comment may be found in Section 

VII.B. 

E. When must I comply with these proposed standards? 

All existing affected sources subject to this proposed 

rule would be required to comply with the rule requirements 

upon the date of publication of the final rule in the 

Federal Register. To our knowledge, there is no existing 

operating uranium recovery facility that would be required 

to modify its affected sources to meet the requirements of 

the final rule; however, we request any information 

regarding affected sources that would not meet these 

requirements. New sources would be required to comply with 

these rule requirements upon the date of publication of the 

final rule in the Federal Register or upon startup of the 

facility, whichever is later. 

IV. Rationale for this Proposed Rule 

A. How did we determine GACT?

Deleted: invite
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 As provided in CAA section 112(d)(5), we are proposing 

standards representing GACT for this area source category. 

In developing the proposed GACT standards, we evaluated the 

control technologies and management practices that are 

available to reduce HAP emissions from the affected sources 

and identified those that are generally available and 

utilized by operating uranium recovery facilities. 

As noted in Section II.F., for this proposal we 

solicited information on the available controls and 

management practices for this area source category using 

written facility surveys (surveys authorized by section 

114(a) of the CAA), reviews of published literature, and 

reviews of existing facilities (EPA-HQ-OAR-0218-0066). We 

also held discussions with trade association and industry 

representatives and other stakeholders at various public 

meetings30. Our determination of GACT is based on this 

information. We also considered costs and economic impacts 

in determining GACT (See Section VI.). 

We identified two general management practices that 

reduce radon emissions from affected sources. These general 

management practices are currently being used at all 

existing uranium recovery facilities. First, limiting the 

 

30 See http://www.epa.gov/radiation/neshaps/subpartw/rulemakingactivity.html for a list of presentations made at public meetings held 

by EPA and at various conferences open to the public.

Deleted: REFERENCE
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area of exposed tailings in conventional impoundments 

limits the amount of radon that can be emitted. The work 

practice standards currently included in subpart W require 

owners and operators of affected sources to implement this 

management practice by either limiting the number and area 

of existing, operating impoundments or covering dewatered 

tailings to allow for no more than 10 acres of exposed 

tailings. This is an existing requirement of Subpart W and 

of the NRC licensing requirements; hence, owners and 

operators of uranium recovery facilities are already 

incurring the costs associated with limiting the area of 

conventional impoundments (and as proposed, heap leach 

piles) to 40 acres or less (as well as no more than two 

conventional impoundments in operation at any one time), or 

limiting the area of exposed tailings to no more than 10 

acres. 

Second, covering uranium byproduct materials with 

liquids is a general management practice that is an 

effective method for limiting radon emissions. This general 

management practice is often used at nonconventional 

impoundments, which, as stated earlier, are also known as 

evaporation or holding ponds. These nonconventional 

impoundments also contain byproduct material, and thus 

their HAP emissions are regulated under Subpart W. They are Deleted: as such we have 

Deleted: them 
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also regulated under the NRC operating license. While they 

hold mostly liquids, they are still designed and 

constructed in the manner of conventional impoundments, 

meaning they meet the requirements of section 192.32(a)(1). 

While this management practice of covering uranium 

byproduct materials in impoundments with liquids is not 

currently required under subpart W, facilities using this 

practice have generally shown its effectiveness in reducing 

emissions in both conventional impoundments (that make use 

of phased disposal) and nonconventional impoundments (i.e. 

holding or evaporation ponds). We are therefore proposing 

to require the use of liquids in nonconventional 

impoundments as a way to limit radon emissions. 

Therefore after review of the available information 

and from the evidence we have examined we have determined 

that a combination of the management practices listed above 

will be effective in limiting radon emissions from this 

source category, and will do so in a cost effective manner. 

We also believe that since heap leach piles are in many 

ways similar to the design of conventional impoundments, 

the same combination of work practices (limitation to no 

more than two operating heap leach piles, each one no more 

than 40 acres) will limit radon emissions in heap leach 
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piles. We discuss our reasons supporting these conclusions 

in more detail in Section IV.B. 

B. Proposed GACT standards for operating mill tailings.

1. Requirements at 40 CFR 192.32(a)(1)

As an initial matter, we determined that the 

requirements at 40 CFR 192.32(a)(1), which reference the 

RCRA requirements for the design and construction of liners 

at 40 CFR 264.221, continue to be an effective method of 

containment of tailings for all types of affected sources. 

(EPA-HQ-OAR-2008-0218-0015) The liner requirements, 

described earlier in this document, remain in use for the 

permitting of hazardous waste land disposal units under 

RCRA. Because of the requirement for nearly impermeable 

boundaries between the tailings and the subsurface, and the 

requirement for leak detection between the liners, we have 

determined that the requirements contain enough safeguards 

to allow for the placement of tailings and also provide an 

early warning system in the event of a leak in the liner 

system.( EPA-HQ-OAR-2008-0218-0015) For this reason we are 

proposing to require as GACT that conventional 

impoundments, non-conventional impoundments and heap leach 

piles all comply with the liner requirements in 40 CFR 

192.32(a)(1). Previously, Subpart W contained this 

requirement but included a more general reference to 40 CFR 

Deleted: S

Deleted: O

Deleted: M

Deleted: T

Deleted: REFERENCE IMPOUNDMENT STUDY

Comment [RJR8]: OMB has asked for a copy of 

this document. It will be sent to them. 

Deleted: REFERENCE IMPOUNDMENT STUDY
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192.32(a); we are proposing to replace that general 

reference with a more specific reference to 40 CFR 

192.32(a)(1) to narrow the requirements under this proposed 

rule to only the design and construction requirements for 

the liner of the impoundment contained in 40 CFR 

192.32(a)(1). 

 The estimated average cost of the liner requirement 

for each type of impoundment at uranium recovery facilities 

is listed in the table below (EPA-HQ-OAR-2008-0218-0087): 

Table 2: Estimated Liner Costs 

Table 2: 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

Table 2 presents a summary of the unit cost (per pound 

of U3O8) for implementing each GACT at each of the three 

Deleted: REFERENCE

Comment [RJR9]: OMB asks, “Is this a total 

cost or per facility – please specify? If per facility, 

what are the estimated total cost? 

Deleted: Type of Impoundment ... [1]

Formatted: Indent: First line: 0.5", Line

spacing: Double
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types of uranium recovery facilities. In addition to 

presenting the GACT costs individually, Table 2 presents 

the total unit cost to implement all relevant GACTs at each 

type of facility.

Based on the Table 22, implementing all four GACTs 

would result in unit cost (per pound of U3O8) increases of 

about 2%, 6%, and 5% at conventional mills, ISL, and heap 

leach type uranium recovery facilities, respectively.

In making these cost estimates, we have assumed the 

following: (1) a conventional impoundment is no larger than 

40 acres in size, which is the maximum size allowed for the 

phased disposal option; (2) a nonconventional impoundment 

is no larger than 80 acres in size (the largest size we 

have seen); and (3) a heap leach pile is no larger than 40 

acres in size (again, the maximum size allowed under the 

phased disposal work practice standard, although as with 

conventional impoundments the owner or operator is limited 

to two of these affected sources to be in operation at any 

time). 

We do not have precise data for the costs associated 

with the liner requirements at conventional impoundments 

using the continuous disposal work practice standard 

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spacing: Double

Deleted: Table 
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because currently none exist, but a reasonable maximum 

approximation would be the costs for the 80 acre 

nonconventional impoundment, since it is the largest we 

have seen. We believe that no additional costs would be 

incurred for building a conventional impoundment that will 

use the continuous disposal option above what we estimated 

for building a nonconventional impoundment but we ask for 

comment on whether this assumption is reasonable. We also 

ask for data on the costs of building a conventional 

impoundment using continuous disposal, and how those costs 

would differ from the estimates provided above, or whether 

the costs we have listed for building a conventional 

impoundment using phased disposal are a reasonable 

approximation of the costs for building a conventional 

impoundment using continuous disposal. 

These liner systems are already required by 40 CFR 

192.32(a)(1), which, as explained above, are requirements 

promulgated by EPA under UMTRCA that are incorporated into 

NRC regulations and implemented and enforced by NRC and NRC 

Agreement States through their licensing requirements. 

Therefore, we are not placing any additional liner 

requirements on facilities or requiring them to incur any 

additional costs to build their conventional or 

nonconventional impoundments or heap leach piles above and 
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beyond what an owner or operator of these impoundments must 

already incur to obtain an NRC or NRC Agreement State 

license. 

 The liner systems we are proposing that heap leach 

piles must use are the same as those used for conventional 

and nonconventional impoundments. We estimate that the 

average costs associated with the construction of a 40 acre 

liner that complies with 40 CFR 192.32(a)(1)is 

approximately $15.3 million. When compared to the baseline 

capital costs associated with the facility (estimated at 

$356 million)(EPA-HQ-OAR-2008-0218-0087), the costs for 

constructing this type of liner system per facility is 

about 4% of the total baseline capital costs of a heap 

leach pile facility (EPA-HQ-OAR-2008-0218-0087).31 

 2. Conventional Impoundments. 

 

31 For our purposes, baseline conditions are defined as a reference point 

that reflects the world without the proposed regulation. It is the 

starting point for conducting an economic analysis of the potential 

benefits and costs of a proposed regulation. The defined baseline 

influences first the level of emissions expected without regulatory 

intervention. It thereby also influences the projected level of 

emissions reduction that may be achieved as a consequence of the 

proposed regulation. Baselines have no standard definition besides the 

fact that they simply provide a reference scenario against which 

changes in economic and environmental conditions (in this case radon 

emissions) can be measured. In some instances, baselines have been 

established based on the assumption that economic, environmental and/or 

other conditions will continue on the present path or trend, purely as 

time dependant extensions of presently observed patterns. In other 

instances, baselines are derived from elaborate modeling projections. 

Because in all cases their purpose is to project a view of the world 

without the proposed regulatory intervention, baselines have are 

sometimes termed "do nothing" or "business as usual" scenarios.

Deleted: REFERENCE

Deleted: REFERENCE
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In the 1989 promulgation of Subpart W we required new 

conventional impoundments to comply with one of two work 

practice standards, phased disposal or continuous disposal. 

These work practice standards contain specific limits on 

the exposed area and/or number of operating conventional 

impoundments to limit radon emissions because we recognized 

that radon emissions from very large impoundments could 

impose unacceptable health effects if the piles were left 

dry and uncovered. We are proposing as the GACT standard 

that all conventional impoundments – both existing 

impoundments and new impoundments - comply with one of the 

two work practice standards, phased disposal or continuous 

disposal, because these methods for limiting radon 

emissions by limiting the area of exposed tailings continue 

to be effective methods for reducing radon emissions from 

these impoundments (reference EPA 520-1-86-009, August 

1986). We are proposing that existing impoundments also 

comply with one of the two work practice standards because, 

as discussed earlier, we no longer believe that a 

distinction needs to be made for conventional impoundments 

based on the date when they were designed and/or 

constructed. 

We are also not aware of any conventional impoundments 

either in existence or planned that use any other 
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technologies or management practices to reduce radon 

emissions. Operators continue to use the general management 

practices discussed above for reducing radon emissions from 

their conventional impoundments, i.e., limiting the size 

and/or number of the impoundments, and covering the 

tailings with soil or keeping the tailings wet. These 

management practices form the basis of the work practice 

standards for conventional impoundments and continue to be 

very effective methods for limiting the amount of radon 

released to the environment. 

These work practice standards are a cost-effective 

method for reducing radon emissions from conventional 

impoundments. In addition, the liner requirements for 

conventional impoundments are also required by the NRC in 

their licensing requirements at 10 CFR Part40. Therefore, 

we are proposing that GACT for conventional impoundments 

will be the same work practice standards as were previously 

included in Subpart W. 

3. Non-conventional Impoundments where Tailings are 

Contained in Ponds and Covered by Liquids

Today we are proposing a GACT standard specifically 

for use by any operating uranium recovery facility that has 

one or more non-conventional impoundments at its facility 

(i.e., those impoundments where tailings are contained in 
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ponds and covered by liquids). Common names for these 

structures may include, but are not limited to, 

impoundments, evaporation ponds and holding ponds. These 

ponds contain uranium byproduct material and the HAP 

emissions are regulated by Subpart W.

Industry has argued in preambles to responses to the 

CAA section 114(a) letters32 and elsewhere that Subpart W 

does not, and was never meant to, include these types of 

evaporation or holding ponds under the Subpart W 

requirements. Industry has asserted that the original 

Subpart W did not specifically reference evaporation or 

holding ponds but was regulating only conventional mill 

tailings impoundments. They argue that the ponds are 

temporary because they hold very little solid material but 

instead hold mostly liquids containing dissolved 

radionuclides (which emit very little radon), and at the 

end of the facility’s life they are drained, and any solid 

materials, along with the liner system, are disposed in a 

properly licensed conventional impoundment. 

EPA has consistently maintained that these nonconventional impoundments meet the existing applicability 

criteria for regulation under Subpart W. As defined at 40 

 

32 http://www.epa.gov/radiation/neshaps/subpartw/rulemakingactivity.html

Deleted: asserts
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CFR 61.251(g), uranium byproduct material or tailings means 

the waste produced by the extraction or concentration of 

uranium from any ore processed primarily for its source 

material content. The holding or evaporation ponds located 

at conventional mills, ISL facilities and potentially heap 

leach facilities contain uranium byproduct materials, 

either in solid form or dissolved in solution, and 

therefore their HAP emissions are regulated under Subpart 

W. Today we reiterate that position and are proposing a 

GACT standard more specifically tailored for these types of 

impoundments. 

We are proposing that these non-conventional 

impoundments (the evaporation or holding ponds) must 

maintain a liquid level in the impoundment of no less than 

one meter at all times during the operation of the 

impoundment. Maintaining this liquid level will ensure that 

radon-222 emissions from the uranium byproduct material in 

the pond are minimized. We are also proposing that there is 

no maximum area requirement for the size of these ponds 

since the chance of radon emissions is small. Our basis for 

this determination is that radon emissions from the pond 

will be expected to be very low since the liquid in the 

ponds acts as an effective barrier to radon emissions; 

given that radon-222 has a very short half-life (3.8 days), 
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there simply is not enough time for approximately 93% of 

the radon produced by the solids or from the solution to 

migrate to the water surface and cross the water/air 

interface before decaying. 

By requiring a minimum of one meter of water in all 

nonconventional impoundments that contain uranium byproduct 

material, the release of radon from these impoundments 

would be greatly reduced. Nielson and Rogers (1986) present 

the following equation for calculating the radon 

attenuation: 

ܣ ൌ ݁ቆି൤ఒ

஽൨

బ.ఱௗቇ

Where: A = Radon attenuation factor (unit

less) 

λ = Radon-222 decay constant (sec1

) 

 = 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 

The above equation indicates that the attenuation of 

radon emanation by water (i.e., the amount by which a water 

cover will decrease the amount of radon emitted from the 

impoundment) depends on how quickly radon-222 decays, how 

quickly radon-222 can move through water (the diffusion 
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coefficient), and the thickness of the layer of water.33

Solving the above equation shows that one meter of water 

has a radon attenuation factor of about 0.07. That is, 

emissions can be expected to be reduced by about 93% 

compared to no water cover. 

The benefit incurred by this requirement is that 

significantly less radon will be released to the 

atmosphere. The amount varies from facility to facility 

based on the size of the nonconventional impoundment, but 

across existing facilities radon can be expected to be 

reduced by approximately 24,600 curies, a decline of 

approximately 93%. 

The estimated cost associated with complying with the 

proposed one meter of liquid that would be required to 

limit the amount of radon emissions to the air vary 

according to the size of the impoundment and the geographic 

area in which it is located. We estimate that this 

requirement will cost owners or operators of 80 acre 

nonconventional impoundments between $1,042 and $9,687 per 

year. This value varies according to the location of the 

impoundment, which will determine evaporation rates, which 

 

33 For a detailed discussion of this topic, which includes the effects 

of pond water mixing, wind and convection, please see “Risk Assessment 

Revision for 40 CFR Part 61 Subpart W-Radon Emissions from Operating 

Mill Tailings, Task 5 Radon Emission from Evaporation Ponds,”(EPA-HQOAR-2008-0218-0080)

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determines how much replacement water will be required to 

maintain the minimum amount of one meter. If the evaporated 

water is not replaced by naturally occurring precipitation, 

then it would need to be replaced with make-up water 

supplied by the nonconventional impoundment’s operator. 

The most obvious source of water is what is known as 

“process water” from the extraction of uranium from the 

subsurface. Indeed, management of this process water is 

one of the primary reasons for constructing the impoundment 

in the first place, as the process water contains uranium 

byproduct material that must also be managed by the 

facility. It is possible that an operator could maintain 

one meter of water in the impoundment solely through the 

use of process water. If so, this would not create any 

additional costs for the facility as the cost of the 

process water can be attributed to its use in the uranium 

extraction process. However, for purposes of estimating the 

economic impacts associated with our proposal, our cost 

estimate does not include process water as a source of 

water potentially added to the impoundment to replace water 

that has evaporated. Instead, we estimated the costs of 

using water from other sources. This method results in the 

most conservative cost estimate for compliance with the one 

meter requirement. 

Comment [RJR10]: OMB asks: “Could 

operators use surfactants or other substances to 

reduce evaporation and hence costs when process 

water is not available? Also, some evaporation 

reduction schemes employ water column mixing to 

decrease the temperature of the water at the surface. 

It seems like this practice would be problematic for 

reducing radon emissions.” 

Reply: The use of surfactants or other substances to 

reduce evaporation would defeat the purpose of an 

evaporation pond, so we have not included this in the 

analysis. It is reasonable to assume that when the 

facility is in operation there are significant amounts 

of water available (bled off from the well field 

withdrawal to maintain an effective hydraulic 

gradient) to release into the ponds. Also, we have 

done a detailed analysis of water column mixing, 

effects of wind and other physical processes in the 

determination of radon flux from evaporation ponds. 

This analysis is contained in the document “Risk 

Assessment Revision for 40 CFR Part 61 Subpart WRadon Emissions form Operating Mill Tailings, Task 

5 Radon Emission from Evaporation Ponds,” EPA 

Docket number EPA-HQ-OAR-2008-0218-0080, 

which will be included in the submission to OMB.
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In performing the cost impacts for this requirement, 

three potential sources of impoundment make-up water were 

considered: (1) municipal water suppliers; (2) offsite nondrinking-water suppliers; and (3) on-site water. (EPA-HQOAR-2008-0218-0087) Depending on the source of water 

chosen, we estimate that this requirement will cost owners 

or operators of nonconventional impoundments between 

$1,042.00 and $9,687.00 per year.34 

 This value also varies according to the size and 

location of the nonconventional impoundment. Such 

impoundments currently range up to 80 acres in size. The 

requirement to maintain a minimum of one meter of liquid in 

the ponds is estimated to cost approximately $0.03 per 

pound of uranium produced. The annual cost of makeup water 

was divided by the base case facility yellowcake annual 

production rate to calculate the makeup water cost per 

pound of yellowcake produced (EPA-HQ-OAR-2008-0218-0087). 

We conclude that this proposed requirement is a costeffective way to significantly reduce radon emissions from 

nonconventional impoundments, and is therefore appropriate 

 

34 Municipal sources were the most expensive, with average unit costs 

of $0.0033 per gallon. Offsite non-drinking water sources were the 

cheapest, at $0.000069 per gallon on average. Various references were 

used for the comparisons. For more detail, please see Section 6.3.3 of 

the Background Information Document. 

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to propose as a GACT standard for nonconventional 

impoundments. 

4. Heap Leach Piles 

The final affected source type for which we are 

proposing GACT standards is heap leach piles. While there 

are currently no operating uranium heap leach facilities in 

the United States, we are proposing to regulate the HAP 

emission at any future facilities using this type of 

uranium extraction under Subpart W since the moment that 

uranium extraction takes place in the heap, uranium 

byproduct materials are left behind. During the process of 

uranium extraction on a heap, as the acid drips through the 

ore, uranium is solubilized and carried away to the 

collection system where it is further processed. At the 

point of uranium movement out of the heap, what remains is 

uranium byproduct materials as defined by 40 CFR 61.251(g). 

In other words, what remains in the heap is the waste 

produced by the extraction or concentration of uranium from 

ore processed primarily for its source material content. 

Thus, Subpart W applies because uranium byproduct materials 

are being generated during and following the processing of 

the uranium ore in the heap. 

As a result, we are proposing GACT standards for heap 

leach piles. We are proposing that these piles conform to 
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the phased disposal work practice standard specified for 

conventional impoundments in 40 CFR 61.252(a)(1)(i)(which 

limits the number of active heap leach piles to two, and 

limits the size of each one to no more than 40 acres) and 

that the moisture content of the uranium byproduct material 

in the heap leach pile be greater than or equal to 30% 

moisture content. We believe that the phased disposal 

approach can be usefully applied here because it limits the 

amount of tailings that can be exposed at any one time, 

which limits the amount of radon that can be emitted. The 

phased disposal work practice standard is applicable for 

heap leach piles because heap leach piles are expected to 

be managed in a manner that is similar in many respects to 

conventional impoundments. Based on what we understand 

about the operation of potential future heap leach 

facilities, after the uranium has been removed from the 

heap leach pile the uranium byproduct material that remains 

would be contained in the heap leach structure which would 

be lined according to the requirements of 40 CFR 

192.32(a)(1). The heap leach pile would also be covered 

with soil at the end of its operational life to minimize 

radon emissions. 

 This is what is required to occur at conventional 

impoundments using the phased disposal standard. Limiting 
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the size of the operating heap leach pile to 40 acres or 

less (and the number of operating heap leach piles at any 

one time to two) has the same effect as it does on 

conventional impoundments; that is, it limits the area of 

exposed uranium byproduct material and therefore limits the 

radon emissions from the heap leach pile. While we believe 

that the 40 acre limitation is appropriate for heap leach 

piles, we are requesting comment on what should be the 

maximum size (area) of a heap leach pile. 

We are also proposing as GACT that the heap leach pile 

constantly maintain a moisture content of at least 30% by 

weight. By requiring a moisture content of at least 30%, 

the byproduct material in the heap leach pile will not 

become dewatered, and we think that the heap leach pile 

will be sufficiently saturated with liquid to reduce the 

amount of radon that can escape from the heap leach pile.

However, we request further information on all the chemical 

mechanisms in place during the leaching operation, and 

whether the 30% moisture content is sufficient for 

minimizing radon emissions from the heap leach pile. We 

also request comment on the amount of time the 30% moisture 

requirement should be maintained by a facility. We are 

proposing the term “operational life” of the facility. We 

are aware of several operations that take place during the 
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uranium extraction process at a heap leach pile. After an 

initial period of several months of allowing lixiviant to 

leach uranium from the pile, the heap leach pile is allowed 

to “rest,” which enables the geochemistry in the pile to 

equilibrate. At that point the heap leach pile may be 

subjected to another round of extraction by lixiviant, or 

it may be rinsed to flush out any remaining uranium that is 

in solution in the heap leach pile. After the rinsing, the 

pile is allowed to drain and a radon barrier required by 40 

CFR 192.32 can be emplaced. We are proposing that the 

operational life of the heap leach pile be from the time 

that lixiviant is first placed on the heap leach pile until 

the time of the final rinse. We believe this incorporates a 

majority of the time when the heap leach pile is uncovered

(no radon barrier has been constructed over the top of the 

heap) and when the ability for radon to be emitted is the 

greatest. We ask for comment on this approach. 

Because there is no “process water” component to a heap 

leach operation, as there is for an ISL, water for the heap 

leach pile must be supplied from an outside source. Even if 

an ISL and heap leach operation were to be located at the 

same site, we consider it unlikely that an operator would 

use ISL process water as the basis for an acidic heap leach 

solution. It is possible, in fact likely, that the solution 
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used in the heap will be recycled (i.e., applied to the 

heap more than once), which could reduce the amount of 

outside water needed to some degree, although as we discuss 

later in this section, it would not seem that recycling 

solution would affect the overall moisture content. In 

calculating the high-end costs of heap leaching, we have 

not included this possibility in our estimates of economic 

impacts. 

The unit costs for providing liquids to a heap leach 

pile are assumed to be the same as the unit costs developed 

for providing water to nonconventional impoundments. In 

estimating the cost impacts for this requirement, three 

potential sources of impoundment make-up water were 

considered: (1) municipal water suppliers; (2) offsite nondrinking-water suppliers; and (3) on-site water. The only 

cost associated with maintaining the moisture level within 

the pile is the cost of the liquid. We assume 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, we assume that the facility will use 

the in-soil method for moisture monitoring. The in-soil 

method and its costs are described below. 
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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. 

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. 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). 

Finally, it is assumed that moisture readings would be 

performed during the NRC required daily inspections of the 

heap leach pile, which would require approximately 2,000 

additional work hours per year per facility. Our estimates 

for costs of monitoring the heap include 100 sensors 

located within the heap, with a meter on each sensor. We 

chose 100 sampling stations because heaps are generally the 

same size as conventional impoundments, and Method 115 

prescribed. The total estimated costs for using this 

system, including labor, are approximately $86,500 per year 

per facility. 
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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. a 

minimum of 100 sampling stations for measuring radon. We 

did not estimate costs for this method, as we concluded 

that the length of time required walking around a heap 

leach pile and obtaining these measurements required more 

time than is found in an average work day, and would expose 

workers to potentially hazardous constituents contained in 

the lixiviant. 

The base case heap leach facility includes a heap

leach pile that will occupy up to 80 acres at a height of 

up to 50 feet. With an assumed porosity of 0.39 and a 

moisture content of 30% by weight, the effective surface 

area of the liquid within the heap pile is 33.7 acres.

Table 3 presents the calculated cost for make-up water 

to maintain the moisture level in the heap leach pile, such 

that the moisture content is at 30% by weight, or greater. 

The unit costs for water and the net evaporation rates used 

for these estimates are identical to those derived for 

evaporation ponds. 

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Table 3: Heap Leach 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 make-up water in perspective, 

during leaching and rinsing of the heap leach pile, liquid 

is dripped onto the pile at a rate of 0.005 gallons per 

minute per square foot (gpm/ft2

) (Titan 2011). This rate is 

significantly higher than the make-up water rates necessary 

to maintain the moisture content at 30% by weight, shown in 

Table 3. We conclude from this analysis that the leaching 

solution applied in a typical operation should be 

sufficient to maintain the moisture content of the heap 

leach pile to the required levels, and only in unusual 

circumstances (such as during the final rinse and draindown 

of the heap leach pile) would additional liquids need to be 

applied. However, in a circumstance that would require the 

additional application of liquid to maintain the 30% 

moisture limit, such as excessive evaporation, we estimate 

that the cost of requiring the owner/operator of a heap 

leach pile to maintain 30% moisture content in the pile 

will average approximately $4,000 per year.

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We are asking for comment on exactly where in the pile 

the 30% moisture content should be achieved. We are also 

soliciting comments on whether the leaching operation 

itself liberates more radon into the air than the 

equivalent of a conventional impoundment. We assume that 

because low-grade ore is usually processed by heap leach, 

there would be less radon emitted from a heap leach pile 

than from a conventional impoundment of similar size. We 

request information on whether this is a correct 

assumption.

We are also aware that there could be a competing 

argument against regulating the heap leach pile under 

Subpart W while the lixiviant is being placed on the heap 

leach pile. While not directly correlative, the process of 

heap leach could be defined as active “milling.” The 

procedure being carried out on the heap is the extraction 

of uranium. In this view, the operation is focused on the 

production of uranium rather than on managing uranium 

byproduct materials. Therefore, under this view, the heap 

meets the definition of tailings under 40 CFR 61.251(g) 

only after the final rinse of the heap solutions occurs and 

the heap is preparing to close. In this scenario the heap 

leach pile would close under the requirements at 40 CFR 
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Part 192.32 and Subpart W would never apply. We are 

requesting comments on the relative merits of this 

interpretation. 

It bears noting that, as with ISL facilities, 

collection and/or evaporation ponds (nonconventional 

impoundments) may exist at heap leach facilities that will 

also contain uranium byproduct materials. These ponds HAP 

emissions will be regulated under Subpart W regardless of 

whether the heap leach pile is also subject to regulation 

under that subpart. 

V. Other Issues Generated by Our Review of Subpart W 

During our review of Subpart W we also identified 

several issues that need clarification in order to be more 

fully understood. The issues that we have identified are: 

 Clarification of the term “standby” and how it relates 

to the operational phase of an impoundment; 

 Amending the definition of “operation” of an 

impoundment so that it is clear when the owner or 

operator is subject to the requirements of Subpart W; 

 Determining whether Subpart W adequately addresses 

protection from extreme weather events; 
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 Revising 40 CFR 61.252(b) and (c) to accurately 

reflect that it is only 40 CFR 192.32(a)(1)that is 

applicable to Subpart W; and 

 Removing the phrase “as determined by the Nuclear 

Regulatory Commission” in 40 CFR 61.252(b)(1) and (2). 

A. Clarification of the Term “Standby”

There has been some confusion over whether the 

requirements of Subpart W apply to an impoundment that is 

in “standby” mode. This is the period of time that an 

impoundment may not be accepting tailings, but has not yet 

entered the “closure period” as defined by 40 CFR 

192.31(h). This period of time usually takes place when the 

price of uranium is such that it may not be cost effective 

for the uranium recovery facility to continue operations, 

and yet the facility has not surrendered its operating 

license and may re-establish operations once the price of 

uranium rises to a point where it is cost effective to do 

so. Since the impoundment has not entered the closure 

period, it could continue to accept tailings at any time; 

therefore, Subpart W requirements continue to apply to the 

impoundment. 

Today we are proposing to add a definition to 40 CFR 61.251 

to define “standby” as: 

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Standby means the period of time that an impoundment 

may not be accepting uranium byproduct materials but 

has not yet entered the closure period. 

B. Amending the definition of “Operation” for a

conventional impoundment

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 

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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 today 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. 

C. Weather Events

In the past, uranium recovery facilities have been 

located in the western regions of the United States. In 

these areas, the annual precipitation falling on the 

impoundment, and any drainage area contributing surface 

runoff to the impoundment, has usually been less than the 

annual evaporation from the impoundment. Also, these 

facilities have been located away from regions of the 

country where extreme rainfall events (e.g., hurricanes or 

flooding) could jeopardize the structural integrity of the 
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impoundment, although there is a potential for these 

facilities to be affected by flash floods, tornadoes, etc. 

Now, however, uranium exploration and recovery in the U.S. 

has the potential to move eastward, into more 

climatologically temperate regions of the country, with 

south central Virginia being considered for a conventional 

uranium mill. In determining whether additional measures 

would be needed for impoundments operating in areas where 

precipitation exceeds evaporation, a review of the existing 

requirements was necessary. 

The proposed revisions to Subpart W will continue to 

require owners and operators of all impoundments to follow 

the requirements of 40 CFR 192.32(a)(1). 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 ensure proper 

design and 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 (e.g., a two foot freeboard 

requirement); rainfall; run-on; malfunctions of level 

controllers, alarms and other equipment; and human error. 

Section 264.221(h) states that impoundments must have dikes 
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that are designed, constructed and maintained with 

sufficient structural integrity to prevent massive failure 

of the dikes. In ensuring structural integrity, it must not 

be presumed that the liner system will function without 

leakage during the active life of the unit. 

Since impoundments at uranium recovery facilities have 

been and will continue to be required to comply with the 

requirements of 40 CFR 192.32(a)(1), they are already 

required to be designed to prevent failure during extreme 

weather events. As we stated in Section IV B.2., we believe 

the requirements of 40 CFR 192.32(a)(1) contain enough 

safeguards to allow for the placement of tailings and yet 

provide an early warning system in the event of a leak in 

the liner system. Therefore, we are proposing to include 

these requirements in the Subpart W requirements without 

modification. 

D. Applicability of 40 CFR 192.32(a) to Subpart W

The requirements at 40 CFR 61.252(b) and (c) require 

compliance with 40 CFR 192.32(a). However, we are now 

proposing to focus the Subpart W requirements on the 

impoundment design and construction requirements found 

specifically at 40 CFR 192.32(a)(1). The remainder of 40 

CFR 192.32(a) goes beyond this limited scope by including 
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requirements for ground-water detection monitoring systems 

and closure of operating impoundments. These other 

requirements, along with all of the Part 192 standards, are 

implemented and enforced by the NRC through its licensing 

requirements for uranium recovery facilities at 10 CFR part 

40, Appendix A. However, when referenced in Subpart W, the 

requirements in 40 CFR 192.32(a)(1) would also be 

implemented and enforced by EPA as the regulatory authority 

administering Subpart W under its CAA authority. Therefore 

today we are proposing to revise 40 CFR 61.252 (b) and (c) 

to specifically define which portions of 40 CFR 192.32(a) 

are applicable to Subpart W. At the same time we are 

proposing to eliminate the phrase “...as determined by the 

Nuclear Regulatory Commission” from 40 CFR 61.252(b). This 

should eliminate confusion regarding what an applicant must 

submit to EPA under the CAA in its pre-construction and 

modification approval applications as required by 40 CFR 

61.07 and better explain that EPA is the regulatory agency 

administering Subpart W under the CAA. This proposed change 

will have no effect on the licensing requirements of the 

NRC or its regulatory authority under UMTRCA to implement 

the Part 192 standards through its licenses. 

VI. Summary of Environmental, Cost and Economic Impacts 

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As discussed earlier, uranium recovery activities are 

carried out at several different types of facilities. We 

are proposing to revise Subpart W based on how uranium 

recovery facilities manage uranium byproduct materials 

during and after the processing of uranium ore at their 

particular facility. As discussed in Sections III and IV, 

we are proposing GACT requirements for three types of 

affected sources at uranium recovery facilities: (1) 

conventional impoundments; (2) nonconventional 

impoundments; and (3) heap leach piles. 

For purposes of analyzing the impacts of the proposed 

rule, we assumed that approximately five conventional 

milling facilities, 50 ISL facilities (although this is 

only a projection since only 12 currently exist) and one 

heap leach facility, each with at least one regulated 

impoundment, would become subject to the proposed rule. The 

following sections present our estimates of the proposed 

rule’s air quality, cost and economic impacts. For more 

information, please refer to the Economic Impact Analysis 

report that is included in the public docket for this 

proposed rule. (EPA-HQ-OAR-2008-0218-0087) 

A. What are the air quality impacts? 

 We project that the proposed requirements will 

maintain or improve air quality surrounding the regulated 

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facilities. The GACT standards being proposed today are 

based on control technologies and management practices that 

have been used at uranium recovery facilities for the past 

twenty or more years. These standards will minimize the 

amount of radon that is released to the air by keeping the 

impoundments wet or covered with soil and/or by limiting 

the area of exposed tailings. The requirements in this 

proposed rule should eliminate or reduce radon emissions at 

all three types of affected sources. 

B. What are the cost and economic impacts?

Table 24 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 24 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 4.

Comment [RJR11]: OMB requests: “Can you 

add a table of the cost/cost savings for each of the 

provisions and the total estimated costs of the 

proposed rule? 

Added 

Formatted: Indent: First line: 0.5"

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Table 4: Proposed GACT Standards Costs per Pound of U3O8

Unit Cost ($/lb U3O8)

Conventiona

l 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 24, 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.

The baseline costs were estimated using recently 

published cost data for actual uranium recovery facilities. 

For the model conventional mill, we used data from the 

recently licensed new mill at the Piñon Ridge project in 

Colorado. For the model ISL facility, we used data from two 

proposed new facilities: (1) the Centennial Uranium project 

in Colorado; and (2) the Dewey-Burdock project in South 

Dakota. The Centennial project is expected to have a 14- to 

15-year production period, which is a long duration for an 

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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, we used data from the proposed Sheep 

Mountain project in Wyoming. 

Existing Subpart W required facilities to perform 

annual monitoring using Method 115 to demonstrate that the 

radon flux standard at conventional impoundments 

constructed before December 15, 1989 was below 20 pCi/m2

-

sec. The proposed removal of this monitoring requirement 

would result in a cost saving to the three facilities for 

which this requirement still applies: (1) Sweetwater; (2) 

White Mesa; and (3) Shootaring Canyon. Method 115 requires 

100 measurements as the minimum number of flux measurements 

considered necessary to determine a representative mean 

radon flux value. For the three sites that are still 

required to perform Method 115 radon flux monitoring, the 

average annual cost to perform that monitoring is estimated 

to be about $9,730 for Shootaring and Sweetwater, and 

$19,460 for White Mesa. For all three sites the total 

annual average cost is estimated to be $38,920 per year, 

with a range from approximately $28,000 to $49,500 per 

year. For all three sites the total annual average cost 
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savings resulting from removal of the flux monitoring 

requirement would be $39,920. 

Baseline costs (explained in Section IV.B) for 

conventional impoundment liner construction35 will remain 

the same, since the proposed rule does not impose 

additional requirements. Liners meeting the requirements at 

40 CFR 192.32(a)(1) are already mandated by other 

regulations and, therefore, built into the baseline cost 

estimate. Therefore there are consequently no costs (or 

benefits) resulting from the inclusion of these 

requirements in Subpart W. 

The average cost to construct one of these 

impoundments is $13.8 million. We estimate that this cost 

is approximately 3% of the total baseline capital costs to 

construct a conventional mill, estimated at $372 million. 

We have estimated that for an average 80 acre 

nonconventional impoundment the average cost of 

construction of an impoundment is $23.7 million. Requiring 

 35 These liner systems (conventional, nonconventional and heap 

leach piles)are already required by 40 CFR 192.32(a)(1), which, as 

explained above, are requirements promulgated by EPA under UMTRCA that 

are incorporated into NRC regulations and implemented and enforced by 

NRC through their licensing requirements. Therefore, we are not placing 

any additional liner requirements on facilities or requiring them to 

incur any additional costs to build their conventional or 

nonconventional impoundments or heap leach piles above and beyond what 

an owner or operator of these impoundments must already incur to obtain 

an NRC license. Therefore, there are no projected costs (or benefits) 

beyond the baseline resulting from the inclusion of these requirements 

in Subpart W. 
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impoundments to comply with the liner requirements in 40 

CFR 192.32(a)(1) will contain the uranium byproduct 

material and reduce the potential for ground water 

contamination. The only economic impact attributable to the 

proposed rule is the cost of complying with the new 

requirement to maintain a minimum of one meter of water in 

the nonconventional impoundments during operation and 

standby. As shown in Section IV.B.3. of this preamble, as 

long as approximately one meter of water is maintained in 

the nonconventional impoundments the effective radon 

emissions from the ponds are so low that it is difficult to 

determine if there is any contribution above background 

radon values. In order to maintain one meter of liquid 

within a pond, it is necessary to replace the water that is 

evaporated from the pond. Depending on the source of water 

chosen36, we estimate that this requirement will cost owners 

or operators of nonconventional impoundments between $1,042 

and $9,687 per year. This value also varies according to 

the size of the nonconventional impoundment, up to 80 

acres, and the location of the impoundment. Evaporation 

rates vary by geographic location. However, the cost to 

maintain the one meter of liquid in a nonconventional 

 

36 Municipal sources were the most expensive, with average unit costs of 

$0.0033 per gallon. Offsite non-drinking water sources were the 

cheapest, at $0.000069 per gallon on average. For more detail, please 

see Section 6.3.3 of the Background Information Document.
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impoundment is estimated to be less than 1% of the total 

annual production costs, estimated at $23.7 million. The 

requirement to maintain a minimum of one meter of liquid in 

the ponds is estimated to cost approximately $0.03 per 

pound of uranium produced. 

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 leach piles. Baseline costs (explained 

in Section IV.B) for heap leach pile liner construction 

will remain the same, since the proposed rule does not 

impose additional requirements. Liners meeting the 

requirements at 40 CFR 192.32(a)(1) are already mandated by 

other regulations and, therefore, built into the baseline 

cost estimate. Therefore there are consequently no costs 

(or benefits) resulting from the inclusion of these 

requirements in Subpart W. Baseline costs for construction 

will be essentially the same as for conventional 

impoundments. Since the liner systems are equivalent to the 

systems used for conventional and nonconventional 

impoundments, we have been able to estimate the average 

costs associated with the construction of heap leach pile 
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impoundments that meet the liner requirements we are 

proposing, and compare them to the costs associated with 

the total production of uranium produced by the facility. 

The average cost of constructing such an impoundment is 

estimated to be approximately $15.3 million. The costs of 

constructing this type of liner system are about 4% of the 

estimated total baseline capital costs of a heap leach 

facility estimated at $356 million.

For heap leach piles, when the soil moisture content 

in the heap leach pile falls below about 30% by weight, the 

radon flux out of the heap leach pile increases because 

radon moves through the air faster (with less opportunity 

to decay) than through water. We concluded from our 

analysis that the leaching solution applied in a typical 

operation should be sufficient to maintain the moisture 

content of the heap leach pile to the required levels, and 

only in unusual circumstances would additional liquids need 

to be applied. However, in a circumstance that would 

require the additional application of liquid to maintain 

the 30% moisture limit, such as excessive evaporation, we 

estimate that the cost of requiring the owner/operator of a 

heap leach pile to maintain 30% moisture content in the 

pile will average approximately $4,000 per year. We also 

estimate that it will cost approximately $86,500 per year 
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(which includes labor of approximately 2,000 hours) to 

perform the tests required to verify that the moisture 

content is being maintained. These costs are less than one 

percent of the total baseline capital costs of a heap leach 

facility, estimated at $356 million. 

In summary, we estimate that for conventional 

impoundments there will be no additional costs incurred 

through this proposed rule. There will be a cost savings of 

approximately $39,900 per year for the three existing 

conventional impoundments that are currently required to 

monitor for radon flux through the use of Method 115, since 

we are proposing to eliminate this requirement. For 

nonconventional impoundments we estimate that the 

additional costs incurred by this proposed rule will be to 

maintain one meter of liquid in each nonconventional 

impoundment, and we have estimated those costs between 

approximately $1,040 and $9,680 per year. For heap leach 

piles, additional costs incurred by this proposed rule 

would be for the maintaining and monitoring of the 

continuous 30% moisture content requirement, which we 

estimate will impose a one-time cost of approximately 

$35,000 for equipment and approximately $86,000 per year to 

monitor the moisture content. 

C. What are the non-air environmental impacts?
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Water quality would be maintained by implementation of 

this proposed rule. This proposed rule does contain 

requirements (by reference) related to water discharges and 

spill containment. In fact, the liner requirements cross 

referenced at 40 CFR 192.32(a)(1) will significantly 

decrease the possibility of contaminated liquids leaking 

from impoundments into ground water (which can be a 

significant source of drinking water). Section 192.32(a)(1) 

includes a cross-reference to the surface impoundment 

design and construction requirements of hazardous waste 

surface impoundments regulated under the Resource 

Conservation and Recovery Act (RCRA), found at 40 CFR 

264.221. Those requirements state that the impoundment 

shall be designed, 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. There are 

other requirements for the design and operation of the 

impoundment, and these include construction specifications, 

slope requirements, sump and liquid removal requirements. 

These liner systems (conventional, nonconventional and 

heap leach piles)are already required by 40 CFR 

192.32(a)(1), which, as explained above, are requirements 

promulgated by EPA under UMTRCA that are incorporated into 

Deleted: ground water 

Comment [RJR12]: OMB asked for this 

paragraph to be removed. We prefer to retain it, 

because we believe it is important to explain why 

these provisions in Subpart W do not impose an 

additional cost. 
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NRC regulations and implemented and enforced by NRC through 

their licensing requirements. Therefore, we are not placing 

any additional liner requirements on facilities or 

requiring them to incur any additional costs to build their 

conventional or nonconventional impoundments or heap leach 

piles above and beyond what an owner or operator of these 

impoundments must already incur to obtain an NRC license. 

Including a double liner in the design of all onsite 

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, it is important to take this into 

consideration due to the significant use of ground water as 

a source of drinking water. 

VII. Statutory and Executive Orders Review

A. Executive Order 12866: Regulatory Planning and Review 

and Executive Order 13563: Improving Regulation and 

Regulatory Review. 

 Under Executive Order 12866 (58 FR 51735, October 4, 

1993), this action is a "significant regulatory action.” 

The Executive Order defines “significant regulatory action” 

as one that is likely to result in a rule that may “raise 

novel legal or policy issues arising out of legal mandates, 

Comment [RJR13]: OMB asked for this 

sentence to be removed. We prefer to retain it, 

because we believe it is important to explain why 

these provisions in Subpart W do not impose an 

additional cost. 

Deleted: Baseline costs (explained in 

Section IV.B) for liner 

construction will remain the same, 

since the proposed rule does not 

impose additional requirements. 

Liners meeting the requirements at 

40 CFR 192.32(a)(1) are already 

mandated by other regulations and, 

therefore, built into the baseline 

cost estimate. Therefore there are 

consequently no costs (or benefits) 

resulting from the inclusion of 

these requirements in Subpart W.¶
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the President’s priorities, or the principles set forth in 

the Executive Order.” 

Accordingly, EPA submitted this action to the Office of 

Management and Budget (OMB) for review under Executive 

Orders 12866 and 13563 (76 FR 3821, January 21, 2011) and 

any changes made in response to OMB recommendations have 

been documented in the docket for this action. 

B. Paperwork Reduction Act 

 The information collection requirements in this 

proposed rule have been submitted for approval to the 

Office of Management and Budget (OMB) under the Paperwork 

Reduction Act, 44 U.S.C. 3501 et seq. The Information 

Collection Request (ICR) document prepared by EPA has been 

assigned EPA ICR number 2464.01. 

The information to be collected for the proposed 

rulemaking today is based on the requirements of the Clean 

Air Act. Section 114 authorizes the Administrator of EPA to 

require any person who owns or operates any emission source 

or who is subject to any requirements of the Act to: 

- Establish and maintain records 

- Make reports, install, use, and maintain monitoring 

equipment or method 

- Sample emissions in accordance with EPA-prescribed 

locations, intervals and methods 
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- Provide information as may be requested 

EPA’s regional offices use the information collected 

to ensure that public health continues to be protected from 

the hazards of radionuclides by compliance with health 

based standards and/ or Generally Available Control 

Technology (GACT). 

The proposed rule would require the owner or operator 

of a uranium recovery facility to maintain records that 

confirm that the conventional impoundment(s), 

nonconventional impoundment(s) and heap leach pile(s) meet 

the requirements in section 192.32(a)(1). Included in these 

records are the results of liner compatibility tests, 

measurements confirming that one meter of liquid has been 

maintained in nonconventional impoundments and records 

confirming that heap leach piles have constantly maintained 

at least 30% moisture content during the operating life of 

the heap leach pile. This documentation should be 

sufficient to allow an independent auditor (such as an EPA 

inspector) to verify the accuracy of the determination made 

concerning the facility's compliance with the standard. 

These records must be kept at the mill or facility for the 

operational life of the facility and, upon request, be made 

available for inspection by the Administrator, or his/her 

authorized representative. The proposed rule would not 
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require the owners or operators of operating impoundments 

and heap leach piles to report the results of the 

compliance inspections or calculations required in Section 

61.255. The recordkeeping requirements require only the 

specific information needed to determine compliance. We 

have taken this step to minimize the reporting requirements 

for small business facilities. 

The annual proposed monitoring and recordkeeping 

burden to affected sources for this collection (averaged 

over the first three years after the effective date of the 

proposed rule) is estimated to be 10,400 hours with a total 

annual cost of $400,000. This estimate includes a total 

capital and start-up cost component annualized over the 

facility’s expected useful life, a total operation and 

maintenance component, and a purchase of services 

component. We estimate that this total burden will be 

spread over 21 facilities that will be required to keep 

records. Of this total burden, however, 4,150 hours (and 

$93,000) will be incurred by the one heap leach uranium 

recovery facility, due to the requirements for purchasing, 

installing and monitoring the soil moisture sensors, as 

well as training staff on how to operate the equipment. 

Burden is defined at 5 CFR 1320.3(b). An agency may 

not conduct or sponsor, and a person is not required to 
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respond to, a collection of information unless it displays 

a currently valid OMB control number. The OMB control 

numbers for EPA's regulations in 40 CFR are listed in 40 

CFR Part 9. 

 To comment on the Agency's need for this information, 

the accuracy of the provided burden estimates, and any 

suggested methods for minimizing respondent burden, EPA has 

established a public docket for this rule, which includes 

this ICR, under Docket ID number EPA-HQ-OAR-2008-0218. 

Submit any comments related to the ICR to EPA and OMB. See 

ADDRESSES section at the beginning of this notice for where 

to submit comments to EPA. Send comments to OMB at the 

Office of Information and Regulatory Affairs, Office of 

Management and Budget, 725 17th Street, NW, Washington, DC 

20503, Attention: Desk Office for EPA. Since OMB is 

required to make a decision concerning the ICR between 30 

and 60 days after [Insert date of publication in the 

Federal Register.], a comment to OMB is best assured of 

having its full effect if OMB receives it by [Insert date 

30 days after publication in the Federal Register.]. The 

final rule will respond to any OMB or public comments on 

the information collection requirements contained in this 

proposal. 

C. Regulatory Flexibility Act 
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 The Regulatory Flexibility Act (RFA) generally 

requires an agency to prepare a regulatory flexibility 

analysis of any rule subject to notice and comment 

rulemaking requirements under the Administrative Procedure 

Act or any other statute unless the agency certifies that 

the rule will not have a significant economic impact on a 

substantial number of small entities. Small entities 

include small businesses, small organizations, and small 

governmental jurisdictions. 

For purposes of assessing the impacts of today's rule 

on small entities, small entity is defined as: (1) a small 

business whose company has less than 500 employees and is

primarily engaged in leaching or beneficiation of uranium, 

radium or vanadium ores as defined by NAIC code 212291; (2) 

a small governmental jurisdiction that is a government of a 

city, county, town, school district or special district 

with a population of less than 50,000; and (3) a small 

organization that is any not-for-profit enterprise which is 

independently owned and operated and is not dominant in its 

field. 

After considering the economic impacts of this 

proposed rule on small entities, I certify that this action 

will not have a significant economic impact on a 

substantial number of small entities. This proposed rule is 
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estimated to impact approximately 18 uranium recovery 

facilities that are currently operating or plan to operate 

in the future. 

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 Part 192.32(a)(1). 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 that was 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 on an annual basis to demonstrate that the 

average Rn-222 flux does not exceed 20pCi/sec/sq. meter. 
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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 owned by Energy Fuels Resources (USA); the 

Shootaring Canyon mill owned by Uranium One, Inc.; the 

Sweetwater mill owned by Kennecott Uranium Co.; and the 

proposed Piñon Ridge mill owned by Energy Fuels, Inc. Of 

the four companies that own conventional mills, two, 

Dennison Mines and Energy Fuels, are classified as small 

businesses using fewer than 500 employees as the 

classification criterion. 

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 

and a new unit, constructed in accordance with the proposed 

GACT, will be opened to accept future tailings. Energy 

Fuels is proposing a phased disposal system to manage its 

tailings; this system also complies with the proposed GACT. 

Based on the fact that both small entities are in 

compliance with the proposed GACT, we conclude that the 

rulemaking will not impose any new economic impacts on 

either facility. For Energy Fuels Mines, the proposed rule 

will actually result in a cost saving as it will no longer 

Deleted: Denison Mines’

Deleted: Denison
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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 Part 

192.32(a)(1) and that a minimum of 1 meter of liquid be 

maintained in the ponds during operation and standby. The 

key design requirements for the ponds are for a doubleliner 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 in-situ 

leach (ISL) facilities and heap leach facilities. 

Currently, there are five operating ISLs and no operating 

heap leach facilities. The operating ISLs are Crow Butte 

and Smith Ranch owned by Cameco Resources, Alta Mesa owned 

by Mestena Uranium, LLC, Willow Creek owned by Uranium One, 

Inc., and Hobson owned by Uranium Energy Corp. Again using 

the fewer than 500 employees’ criterion, Mestena Uranium, 

LLC and Uranium Energy Corp are both small businesses, 

while Cameco Resources and Uranium One, Inc. are both large 

businesses. 

All of the evaporation ponds at the four conventional 

mills and the five ISLs were built in conformance with Part 

192.32(a)(1). Therefore the only economic impact is the 
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cost of complying with the new requirement to maintain a 

minimum of 1 meter of water in the ponds during operation 

and standby. 

The proposed revisions to Subpart W apply to five 

currently operating ISLs. The operating ISRs are Crow Butte 

(Nebraska) and Smith Ranch (Wyoming), owned by Cameco 

Resources; Alta Mesa (Texas), owned by Mestena Uranium, 

LLC; Willow Creek (Wyoming), owned by Uranium One, Inc.; 

and Hobson (Texas), owned by Uranium Energy Corp. Again 

using the fewer than 500 employees’ criterion, Mestena 

Uranium, LLC and Uranium Energy Corp are both small 

businesses, while Cameco Resources and Uranium One, Inc. 

are both large businesses. 

In addition to the five operating ISLs, three 

additional ISRs have been licensed, all in the state of 

Wyoming. These are: Lost Creek, owned by Ur-Energy Inc.; 

Moore Ranch, owned by Uranium One, Inc.; and Nichols Ranch, 

owned by Uranez Uranium Corp. Of these three companies, 

both Ur-Energy Inc. and Uranez Uranium Corp. are small 

businesses. 

Eleven other ISLs have been proposed for licensing. 

These include: Dewey-Burdock (South Dakota) and Centennial 

(Colorado), both owned by Powertech Uranium Corp.; and 

Kingsville Dome, Los Finados, Rosito, and Vasques (Texas), 

Deleted: R

Deleted: R

Deleted: Twelve

Deleted: R

Deleted: Benavidas, 
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all owned by Uranium Resources Inc.; Crownpoint (New 

Mexico), also owned by Uranium Resources Inc., Church Rock 

(New Mexico), owned by Strathmore Minerals; Ross (Wyoming), 

owned by Strata Energy, Inc., Goliad (Texas), owned by 

Uranium Energy Corp.; and Antelope-Jab (Wyoming), owned by 

Uranium One, Inc. All of these companies, except for 

Uranium One, Inc. are small businesses. 

According to the licensing documents submitted by the 

owners of the proposed ISLs, all will be constructed in 

conformance with Part 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. 

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. This cost is not a significant 

impact on any of these small entities. 

Although there are no heap leach facilities currently 

licensed, Energy Fuels, Inc. is expected to submit a 

licensing application for the Sheep Mountain Project. From 

the preliminary documentation that Titan has presented, the 

facility will have an Evaporation Pond, a Collection Pond, 

and a Raffinate Pond. All three ponds will be double lined 

with leak detection. However, as Energy Fuels is a large Deleted: Titan Uranium
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business, it does not affect the determination of impacts 

on small businesses. 

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. 

As noted previously, there are no heap leach 

facilities currently in existence, and the only one that is 

known to be preparing to submit a license application is 

being proposed by Energy Fuels, which is a large business. 

Of the 20 facilities identified above, 15 are owned by 

small businesses. No small organizations or small 

governmental entities have been identified that would be 

impacted by the proposed GACTs. We continue to be 

interested in the potential impacts of the proposed rule on 

small entities and welcome comments on issues related to 

such impacts.

D. Unfunded Mandates Reform Act 

This rule does not contain a Federal mandate that may 

result in expenditures of $100 million or more for State, 

local and tribal governments, in the aggregate, or the 

private sector in any one year. The proposed rule imposes 

no enforceable duties on any State, local or Tribal 

Deleted: Titan Uranium
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governments or the private sector. Thus, this rule is not 

subject to the requirements of sections 202 or 205 of UMRA. 

This rule is also not subject to the requirements of 

section 203 of UMRA because it contains no regulatory 

requirements that might significantly or uniquely affect 

small governments because it contains no requirements that 

apply to such governments nor does it impose obligations 

upon them. 

E. Executive Order 13132: Federalism 

This proposed rule does not have federalism 

implications. It will not have substantial direct effects 

on the States, on the relationship between the national 

government and the States, or on the distribution of power 

and responsibilities among the various levels of 

government, as specified in Executive Order 13132. None of 

the facilities subject to this action are owned and 

operated by State governments, and, nothing in the proposed 

rule will supersede State regulations. Thus, Executive 

Order 13132 does not apply to this proposed rule. 

In the spirit of Executive Order 13132 and consistent 

with EPA policy to promote communications between EPA and 

State and local governments, EPA specifically solicits 

comment on this proposed rule from State and local 

officials. 
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F. Executive Order 13175: Consultation and Coordination 

with Indian Tribal Governments 

This action does not have tribal implications, as 

specified in Executive Order 13175 (65 FR 67249, November 

9, 2000). The action imposes requirements on owners and 

operators of specified area sources and not tribal 

governments. Thus, Executive Order 13175 does not apply to 

this action. 

EPA specifically solicits additional comment on this 

proposed action from tribal officials. 

G. Executive Order 13045: Protection of Children from 

Environmental Health Risks and Safety Risks 

 EPA interprets EO 13045 (62 FR 19885, April 23, 

1997) as applying to those regulatory actions that 

concern health or safety risks, such that the analysis 

required under section 5-501 of the Order has the 

potential to influence the regulation. This action is 

not subject to EO 13045 because it is based solely on 

technology performance. 

H. Executive Order 13211: Actions Concerning Regulations 

That Significantly Affect Energy Supply, Distribution, or 

Use 

 This action is not a “significant energy action” as 

defined in Executive Order 13211 (66 FR 28355 (May 22, 
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2001)), because it is not likely to have a significant 

adverse effect on the supply, distribution, or use of 

energy. This proposed rule will not adversely directly 

affect productivity, competition, or prices in the energy 

sector.

I. National Technology Transfer and Advancement Act 

 Section 12(d) of the National Technology Transfer and 

Advancement Act of 1995 (“NTTAA”), Public Law No. 104-113, 

12(d) (15 U.S.C. 272 note) directs EPA to use voluntary 

consensus standards in its regulatory activities unless to 

do so would be inconsistent with applicable law or 

otherwise impractical. Voluntary consensus standards are 

technical standards (e.g., materials specifications, test 

methods, sampling procedures, and business practices) that 

are developed or adopted by voluntary consensus standards 

bodies. NTTAA directs EPA to provide Congress, through 

OMB, explanations when the Agency decides not to use 

available and applicable voluntary consensus standards. 

 This proposed rulemaking does not involve technical 

standards. Therefore, EPA is not considering the use of any 

voluntary consensus standards. 

 We request public comment on this aspect of the 

proposed rulemaking, and specifically, ask you to identify 

potentially applicable voluntary consensus standards and to 
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explain why such standards could be used in this 

regulation. 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and LowIncome Populations. 

 Executive Order 12898 (59 FR 7629 (Feb. 16, 1994))

establishes federal executive policy on environmental 

justice. Its main provision directs federal agencies, to 

the greatest extent practicable and permitted by law, to 

make environmental justice part of their mission by 

identifying and addressing, as appropriate, 

disproportionately high and adverse human health or 

environmental effects of their programs, policies, and 

activities on minority populations and low-income 

populations in the United States. 

 EPA has determined that this proposed rule will not 

have disproportionately high and adverse human health or 

environmental effects on minority or low-income populations 

because it increases the level of environmental protection 

for all affected populations without having any 

disproportionately high and adverse human health or 

environmental effects on any population, including any 

minority or low-income population. This proposed rule 

would reduce toxics emissions of radon from nonconventional 
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impoundments and heap leach piles and thus decrease the 

amount of such emissions to which all affected populations 

are exposed. 

 
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National Emission Standards for Radon Emissions From 

Operating Mill Tailings 

List of Subjects in 40 CFR Part 61 

Environmental protection, Air pollution control, Hazardous 

substances, Radon, Tailings, Byproduct, Uranium, Reporting 

and recordkeeping requirements. 

_________________________ 

Dated: 

_________________________ 

Gina McCarthy, 

Administrator. 

 

Deleted: Lisa P. Jackson
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For the reasons stated in the preamble, the Environmental 

Protection Agency proposes to amend title 40, Chapter I of 

the Code of Federal Regulations as follows: 

PART 61—-[National Emissions Standards for Hazardous Air 

Pollutants] 

1. The authority citation for part 61 continues to read as 

follows: 

Authority: 42 U.S.C. 7401 et seq. 

Subpart W—[National Emission Standards for Radon Emissions 

From Operating Mill Tailings] 

2. Section 61.251 is amended by revising definition e and 

adding new definitions h-m as follows: 

§61.251 Definitions

* * * * *

(e) Operation. Operation means that an impoundment is being 

used for the continued placement of uranium byproduct 

materials 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.

(h) Conventional Impoundment. A conventional impoundment is 

a permanent structure located at any uranium recovery 

facility which contains mostly solid uranium byproduct 

material from the extraction of uranium from uranium ore. 

These impoundments are left in place at facility closure. 

Deleted: AMENDED

Deleted: AMENDED

Deleted: revised

Deleted: amending one 

Deleted: amended by 

Deleted: in alphabetical order

Formatted: Line spacing: Double
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(i) Non-Conventional Impoundment. A non-conventional 

impoundment can be located at any uranium recovery facility 

and contains uranium byproduct material suspended in and/or 

covered by liquids. These structures are commonly known as 

holding ponds or evaporation ponds. They are removed at 

facility closure. 

(j) Heap Leach Pile. A heap leach pile is a pile of uranium 

ore placed on an engineered structure and stacked so as to 

allow uranium to be dissolved and removed by leaching 

liquids. 

(k) Standby. Standby means the period of time that an 

impoundment may not be accepting uranium byproduct 

materials but has not yet entered the closure period. 

(l) Uranium Recovery Facility. A uranium recovery facility 

means a facility licensed by the NRC or an NRC Agreement 

State to manage uranium byproduct materials during and 

following the processing of uranium ores. Common names for 

these facilities are a conventional uranium mill, an insitu leach (or recovery) facility and a heap leach facility 

or pile. 

(m) Heap Leach Pile Operational Life. The operational life 

of a heap leach pile means the time that lixiviant is first 

placed on the heap leach pile until the time of the final 

rinse. 

Deleted: (l) Operation. Operation 

means that an impoundment is being 

used for the continued placement of 

uranium byproduct materials 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.¶

Deleted: m

Deleted: n
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3. Section 61.252 is revised to read as follows: 

§61.252 Standard. 

(a) Conventional Impoundments. 

 (1) Conventional impoundments shall be designed, 

constructed and operated to meet one of the two following 

management: 

(i) Phased disposal in lined tailings impoundments 

that are no more than 40 acres in area and shall 

comply with the requirements of 40 CFR 192.32(a)(1). 

The owner or operator shall have no more than two 

conventional impoundments, including existing 

impoundments, in operation at any one time. 

(ii) Continuous disposal of tailings such that 

tailings are dewatered and immediately disposed with 

no more than 10 acres uncovered at any time and 

shall comply with the requirements of 40 CFR 

192.32(a)(1). 

(b) Non-Conventional Impoundments. Non-conventional 

impoundments shall meet the requirements of 40 CFR 

192.32(a)(1). During operation and until final closure 

begins, the liquid level in the impoundment shall not be 

less than one meter. 

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(c) Heap Leach Piles. Heap leach piles shall comply with 

the phased disposal management practice in 40 CFR 

61.252(a)(1)(i). Heap leach piles shall be constructed in 

lined impoundments that are no more than 40 acres in area 

and shall comply with the requirements of 40 CFR 

192.32(a)(1). The owner or operator shall have no more than 

two heap leach piles, including existing heap leach piles, 

in operation at any one time. Heap leach piles shall also 

comply with the requirements of 40 CFR 192.32(a)(1). The 

moisture content of heap leach piles shall be maintained at 

30% or greater. The moisture content shall be determined on 

a daily basis, and performed using generally accepted 

geotechnical methods. The moisture content requirement 

shall apply during the heap leach pile operational life. 

§61.253 [Removed]

4. Section 61.253 is removed.

§61.254 [Removed]

5. Section 61.254 is removed.

6. Section 61.255 is revised to read as follows: 

§61.255 Recordkeeping requirements 

(a) The owner or operator of any uranium recovery facility 

must maintain records that confirm that the conventional 

impoundment(s), nonconventional impoundment(s) and heap 

leach pile(s) at the facility meet the requirements in 40 

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CFR 192.32(a)(1). These records shall include, but not be 

limited to, the results of liner compatibility tests. 

(b) The owner or operator of any uranium recovery facility 

with nonconventional impoundments must maintain records 

that include measurements confirming that one meter of 

liquid has been maintained in the nonconventional 

impoundments at the facility. 

(c) The owner or operator of any heap leach facility shall 

maintain records confirming that the heap leach piles 

maintained at least 30% moisture content by weight during 

the heap leach pile operational life. 

(d) The records required in paragraphs (a), (b) and (c) 

above must be kept at the uranium recovery facility for the 

operational life of the facility and must be made available 

for inspection by the Administrator, or his authorized 

representative. 
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Type of Impoundment Average Cost ($Millions) 

Conventional Impoundment 13.8 

Nonconventional Impoundment 23.7 

Heap Leach 15.3