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6560-50-P

ENVIRONMENTAL PROTECTION

40 CFR Part 63

[EPA-HQ-OAR-2011-0797; FRL-???]

RIN 2060-AQ92

National Emissions Standards for Hazardous Air Pollutants: Primary

Aluminum Reduction Plants

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

SUMMARY: The EPA is proposing amendments to the national emissions 

standards for hazardous air pollutants for Primary Aluminum Reduction 

Plants to address the results of the residual risk and technology 

review that the EPA is required to conduct by the Clean Air Act. If 

finalized, these proposed amendments would address previously 

unregulated emissions (i.e., carbonyl sulfide (COS) emissions from 

new and existing potlines and polycyclic organic matter (POM) 

emissions from new and existing prebake potlines and existing pitch 

storage tanks); remove the vertical stud Soderberg one (VSS1) potline 

subcategory; reduce the MACT limits for POM emissions from horizontal 

stud Soderberg (HSS) and VSS2 potlines; eliminate the startup, 

shutdown and malfunction exemption in accordance with recent actions 

by the United States Court of Appeals for the District of Columbia 

Circuit; add provisions for facilities to avail themselves of an 

affirmative defense in the event of a malfunction under certain 
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conditions; and make certain technical and editorial changes. The 

proposed emissions limits for POM and COS are based on maximum 

achievable control technology (MACT). While the proposed 

modifications would result in some reduction in actual emissions of 

POM from existing pitch storage tanks, reduce the potential emissions 

of POM from Soderberg potlines, and prevent increases in emissions of 

COS and sulfur dioxide, the health risks posed by actual emissions 

from this source category are currently within the acceptable range 

and would not be reduced appreciably by the proposed 

modifications.These proposed amendments:

 Reduce emissions limits for Polycyclic Organic Matter (POM)for 

Soderberg potlines;

 Establish POM emission limits for existing and new prebake 

potlines, which were previously unregulated for POM;

 Establish a carbonyl sulfide (COS) emission limit for potlines, 

which were previously unregulated for COS;

 Require existing pitch storage tanks to meet the same standard as 

new pitch storage tanks;

 Add work practice standards for periods of startup for potlines;

 Require anode bake furnaces and pitch storage tanks to comply with 

the MACT standards during periods of startup and modify the MACT 

standard for anode bake furnaces to include startup practices;

 Revise applicability to include existing pitch storage tanks;
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 Revise the incorporation by reference section to include a method 

for measurement of sulfur in coke;

 Add a definition of affirmative defense and remove the definition 

of Vertical stud Soderberg one (VSS1) potlines; and

 Make technical and editorial changes.

DATES: Comments must be received on or before [INSERT THE DATE 45 

DAYS AFTER THE DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE 

FEDERAL REGISTER]. Under the Paperwork Reduction Act, comments on the 

information collection provisions are best assured of receivinghaving

full considerationeffect if the Office of Management and Budget (OMB) 

receives a copy of your comments on or before [INSERT THE DATE 30 

DAYS AFTER THE DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE 

FEDERAL REGISTER].

Public Hearing. If anyone contacts the EPA requesting to speak 

at a public hearing by [INSERT THE DATE 10 DAYS AFTER THE DATE OF 

PUBLICATION IN THE FEDERAL REGISTER], a public hearing will be held 

on [INSERT THE DATE 15 DAYS AFTER THE DATE OF PUBLICATION IN THE 

FEDERAL REGISTER].

ADDRESSES: Submit your comments, identified by Docket ID Number EPAHQ-OAR-2011-0797, by one of the following methods:

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

submitting comments.

 Email: a-and-r-docket@epa.gov, Attention Docket ID Number EPAHQ-OAR-2011-0797.

 Fax: (202) 566-9744, Attention Docket ID Number EPA-HQ-OAR-2011-

0797.
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 Mail: U.S. Postal Service, send comments to: EPA Docket Center, 

EPA West (Air Docket), Attention Docket ID Number EPA-HQ-OAR2011-0797, U.S. Environmental Protection Agency, Mail Code:code:

2822T, 1200 Pennsylvania Ave., NW, Washington, DC 20460. Please 

include a total of two copies. In addition, please mail a copy 

of your comments on the information collection provisions to the 

Office of Information and Regulatory Affairs, Office of 

Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th

Street, NW, Washington, DC 20503.

 Hand Delivery: U.S. Environmental Protection Agency, EPA West 

(Air Docket), Room 3334, 1301 Constitution Ave., NW, Washington, 

DC 20004, Attention Docket ID Number EPA-HQ-OAR-2011-0797. 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 Number EPA-HQOAR-2011-0797. The EPA‘s policy is that all comments received will be 

included in the public docket without change and may be made 

available on-line at http://www.regulations.gov, including any 

personal information provided, unless the comment includes 

information claimed to be confidential business information (CBI) or 

other information whose disclosure is restricted by statute. Do not 

submit information that you consider to be CBI or otherwise protected 

through http://www.regulations.gov or email. The 

http://www.regulations.gov website is an ―anonymous access‖ system, 

which means the EPA will not know your identity or contact 

information unless you provide it in the body of your comment. If you 

send an email comment directly to the EPA without going through 

http://www.regulations.gov, your email address will be automatically 

captured and included as part of the comment that is placed in the 
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public docket and made available on the Internet. If you submit an 

electronic comment, the 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 the EPA cannot read your comment due to 

technical difficulties and cannot contact you for clarification, the 

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 the 

EPA‘s public docket, visit the EPA Docket Center homepage at 

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

Docket. The EPA has established a docket for this rulemaking 

under Docket ID Number EPA-HQ-OAR-2011-0797. All documents in the 

docket are listed in the http://www.regulations.gov index. Although 

listed in the index, some information is not publicly available, 

e.g., CBI or other information whose disclosure is restricted by 

statute. Certain other material, such as copyrighted material, is not 

placed on the Internet and will be publicly available only in hard 

copy. Publicly available docket materials are available either 

electronically in http://www.regulations.gov or in hard copy at the 

EPA Docket Center, 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 EPA Docket Center is (202) 566-1742.
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Public Hearing. If a public hearing is held, it will begin at 

10:00 a.m. on [INSERT THE DATE 15 DAYS AFTER THE DATE OF PUBLICATION 

OF THIS PROPOSED RULE IN THE FEDERAL REGISTER] and will be held at 

the EPA‘s campus in Research Triangle Park, North Carolina, or at an 

alternate facility nearby. Persons interested in presenting oral 

testimony or inquiring as to whether a public hearing is to be held 

should contact Ms. Virginia Hunt, Office of Air Quality Planning and 

Standards, Sector Policies and Programs Division, (D243-02), U.S. 

Environmental Protection Agency, Research Triangle Park, North 

Carolina 27711; telephone number: (919) 541–0832.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 

action, contact Mr. David Putney, Sector Policies and Programs 

Division (D243-02), Office of Air Quality Planning and Standards, 

U.S. Environmental Protection Agency, Research Triangle Park, North 

Carolina 27711, telephone (919) 541-2016; fax number: (919) 541-

3207; and email address: putney.david@epa.gov. For specific 

information regarding the risk modeling methodology, contact Dr. 

Michael Stewart, Office of Air Quality Planning and Standards, Health 

and Environmental Impacts Division, Air Toxics Assessment Group 

(C504–06), U.S. Environmental Protection Agency, Research Triangle 

Park, NC 27711; telephone number: (919) 541–7524; fax number: (919) 

541–0840; and email address: stewart.michael@epa.gov. For information 

about the applicability of the proposed or current national emission 

standards for hazardous air pollutants (NESHAP) for primary aluminum 
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reduction plants to a particular entity, contact the appropriate 

person listed in Table 1 of this preamble.

Table 1. List of EPA Contacts for theFor The NESHAP Addressed in 

thisIn This Proposed Action

NESHAP for: OECA Contact1 OAQPS Contact2

Primary Aluminum 

Reduction Plants

Patrick Yellin, 

(202)564-2970

yellin.patrick@epa.gov

David Putney,

(919) 541-2016, 

putney.david@epa.gov

1 EPA Office of Enforcement and Compliance Assurance.

2 EPA Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION:

Preamble Acronyms and Abbreviations

Several acronyms and terms used to describe industrial 

processes, data inventories, and risk modeling are included in this 

preamble. While this may not be an exhaustive list, to ease the 

reading of this preamble and for reference purposes, the following 

terms and acronyms are defined here for reference::

ADAF age-dependent adjustment factors

AEGL acute exposure guideline levels

AERMOD air dispersion model used by the HEM-3 model

AMOS ample marginAmple Margin of safetySafety

ANPRM advance notice of proposed rulemaking

ATSDR Agency for Toxic Substances and Disease Registry

BACT best available control technology

BLDS bag leak detection system

CAA Clean Air Act

CBI Confidential Business Information

CEMS continuous emissions monitoring system

CFR Code of Federal Regulations

COS carbonylCarbonyl sulfide

CTE central tendency exposure

EJ environmental justice
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EPA Environmental Protection Agency

ERPG Emergency Response Planning Guidelines

ERT Electronic Reporting Tool

HAP hazardous air pollutants

HEM-3 Human Exposure Model, Version 3

HEPA high efficiency particulate air

HHRAP Human Health Risk Assessment Protocols

HI Hazard Index

HQ Hazard Quotient

ICR information collection request

IRIS Integrated Risk Information System

Km kilometer

LAER lowest achievable emissions rate

lb/yr pounds per year

MACT maximum achievable control technology

MACT Code Code within the NEI used to identify processes included

in a source category

MDL method detection level

mg/acm milligrams per actual cubic meter

mg/dscm milligrams per dry standard cubic meter

mg/m3 milligrams per cubic meter

MIR maximum individual risk

MRL minimum risk level

NAC/AEGL

Committee National Advisory Committee for Acute Exposure Guideline 

Levels for Hazardous Substances

NAICS North American Industry Classification System

NAS National Academy of Sciences

NATA National Air Toxics Assessment

NEI National Emissions Inventory

NESHAP National Emissions Standards for Hazardous Air Pollutants

NOAEL no observed adverse effects level

NRC National Research Council

NTTAA National Technology Transfer and Advancement Act

O&M operation and maintenance

OAQPS Office of Air Quality Planning and Standards

ODW Office of Drinking Water

OECA Office of Enforcement and Compliance Assurance

OHEA Office of Health and Environmental Assessment
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OMB Office of Management and Budget

PB-HAP hazardous air pollutants known to be persistent and bioaccumulative in the environment

PM particulate matter

POM polycyclic organic matter

ppmv parts per million volume

RACT reasonably available control technology

RBLC RACT/BACT/LAER Clearinghouse

REL reference exposure level

RFA Regulatory Flexibility Act

RfC reference concentration

RfD reference dose

RIA Regulatory Impact Analysis

RTR residual risk and technology review

SAB Science Advisory Board

SBA Small Business Administration

SCC Source Classification Codes

SOP standard operating procedures

SSM startup, shutdown, and malfunction

TEQ toxic equivalency quotient

TOSHI target organ-specific hazard index

TPY tons per year

TRIM Total Risk Integrated Modeling System

TTN Technology Transfer Network

UF uncertainty factor

μg/m3 microgram per cubic meter

UL upper limit

UMRA Unfunded Mandates Reform Act

UPL upper predictive limit

URE unit risk estimate

WHO World Health Organization

WWW worldwide web

Organization of this Document. The information in this preamble is 

organized as follows:

I. General Information

A. What is the statutory authority for this action?

B. Does this action apply to me?
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C. Where can I get a copy of this document and other related 

information?

D. What should I consider as I prepare my comments for the EPA?

II. Background

A. What is this source category and how did the MACT standard 

regulate its HAP emissions?

B. What data collection activities were conducted to support this 

action?

III. Analyses Performed

A. How did we address unregulated emission sources?

B. How did we estimate risks posed by the source category?

C. How did we consider the risk results in making decisions for this 

proposal?

D. How did we perform the technology review?

E. What other issues are we addressing in this proposal?

IV. Analytical Results and Proposed Decisions

A. What are the results of our analyses and proposed decisions 

regarding unregulated emissions sources?

B. What are the results of the risk assessments?

C. What are our proposed decisions regarding risk acceptability and 

ample margin of safety?

D. What are the results and proposed decisions based on our 

technology review?

E. What other actions are we proposing?

F. Compliance dates

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

VI. Request for Comments

VII. Submitting Data Corrections

VIII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and 

Executive Order 13563: Improving Regulation and Regulatory 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
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G. Executive Order 13045: Protection of Children from Environmental 

Health Risks and Safety Risks

H. Executive Order 13211: Actions Concerning Regulations That 

Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer and Advancement Act

J. Executive Order 12898: Federal Actions to Address Environmental 

Justice in Minority Populations and Low-Income Populations

I. General Information

A. What is the statutory authority for this action? 

Section 112 of the CAA establishes a two-stage regulatory 

process to address emissions of hazardous air pollutants (HAP) from 

stationary sources. In the first stage, after the EPA has identified 

categories of sources emitting one or more of the HAP listed in 

section 112(b) of the CAA, section 112(d) of the CAA calls for us to 

promulgate national emission standards for hazardous air pollutants 

(NESHAP) for those sources. ―Major sources‖ are those that emit or 

have the potential to emit (PTE) 10 tons per year (tpy) or more of a 

single HAP or 25 tpy or more of any combination of HAP. For major 

sources, these technology-based standards must reflect the maximum 

degree of emission reductions of HAP achievable (after considering 

cost, energy requirements and nonair quality health and environmental 

impacts) and are commonly referred to as maximum achievable control 

technology (MACT) standards.

MACT standards are to reflect application of measures, 

processes, methods, systems or techniques including, but not limited 

to, measures which (1) reduce the volume of or eliminate emissions of 

pollutants through process changes, substitution of materials or 
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other modifications, (2) enclose systems or processes to eliminate 

emissions, (3) capture or treat pollutants when released from a 

process, stack, storage or fugitive emissions point, (4) are design, 

equipment, work practice or operational standards (including 

requirements for operator training or certification) or (5) are a 

combination of the above. CAA section 112(d)(2)(A)-(E). The MACT 

standard may take the form of a design, equipment, work practice or 

operational standard where the EPA first determines that either (1) a 

pollutant cannot be emitted through a conveyance designed and 

constructed to emit or capture the pollutant or that any requirement 

for, or use of, such a conveyance would be inconsistent with law, or 

(2) the application of measurement methodology to a particular class 

of sources is not practicable due to technological and economic 

limitations. CAA sections 112(h)(1)-(2).

The MACT ―floor‖ is the minimum control level allowed for MACT 

standards promulgated under CAA section 112(d)(3) and may not be 

based on cost considerations. For new sources, the MACT floor cannot 

be less stringent than the emission control that is achieved in 

practice by the best-controlled similar source. The MACT floors for 

existing sources can be less stringent than floors for new sources, 

but they cannot be less stringent than the average emission 

limitation achieved by the best-performing 12 percent of existing 

sources in the category or subcategory (or the best-performing five 

sources for categories or subcategories with fewer than 30 sources). 
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In developing MACT standards, we must also consider control options 

that are more stringent than the floor. We may establish standards 

more stringent than the floor (―beyond the floor‖ standards) based on 

the consideration of the cost of achieving the emissions reductions 

and any nonair quality health and environmental impacts and energy 

requirements. No beyond the floor standards are proposed in this 

rulemaking action.

The EPA is then required to review these technology-based 

standards and to revise them ―as necessary (taking into account 

developments in practices, processes, and control technologies)‖ no 

less frequently than every 8 years, under CAA section 112(d)(6). In 

conducting this review, the EPA is not obliged to completely 

recalculate the prior MACT determination. NRDC v. EPA, 529 F.3d 1077, 

1084 (D.C. Cir. 2008).

The second stage in standard-setting focuses on reducing any 

remaining ―residual‖ risk according to CAA section 112(f). This 

provision requires, first, that the EPA prepare a Report to Congress

discussing (among other things) methods of calculating risk posed (or 

potentially posed) by sources after implementation of the MACT 

standards, the public health significance of those risks, and the 

EPA‘s recommendations as to legislation regarding such remaining 

risk. The EPA prepared and submitted this report (Residual Risk 

Report to Congress, EPA–453/R–99–001) in March 1999. Congress did not 

act in response to the report, thereby triggering the EPA‘s 
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obligation under CAA section 112(f)(2) to analyze and address 

residual risk.

CAA section 112(f)(2) requires us to determine, for source 

categories subject to MACT standards, whether the emissions standards 

provide an ample margin of safety to protect public health. If the 

MACT standards for HAP ―classified as a known, probable, or possible 

human carcinogen do not reduce lifetime excess cancer risks to the 

individual most exposed to emissions from a source in the category or 

subcategory to less than 1-in-1 million,‖ the EPA must promulgate 

residual risk standards for the source category (or subcategory), as 

necessary, to provide an ample margin of safety to protect public 

health. In doing so, the EPA may adopt standards equal to existing 

MACT standards if the EPA determines that the existing standards are 

sufficiently protective. NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 

2008). (―If EPA determines that the existing technology-based 

standards provide an ―ample margin of safety,‖ then the agency is 

free to readopt those standards during the residual risk 

rulemaking.‖) The EPA must also adopt more stringent standards, if 

necessary, to prevent an adverse environmental effect1 but must 

consider cost, energy, safety and other relevant factors in doing so.

 

1

―Adverse environmental effect‖ is defined in CAA section 112(a)(7) as any 

significant and widespread adverse effect, which may be reasonably 

anticipated to wildlife, aquatic life or natural resources, including 

adverse impacts on populations of endangered or threatened species or 

significant degradation of environmental qualities over broad areas.
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Section 112(f)(2) of the CAA expressly preserves our use of a 

two-step process for developing standards to address any residual 

risk and our interpretation of ―ample margin of safety‖ developed in 

the National Emission Standards for Hazardous Air Pollutants: Benzene 

Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, 

Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product 

Recovery Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). 

The first step in this process is the determination of acceptable 

risk. The second step provides for an ample margin of safety to 

protect public health, which is the level at which the standards are 

set (unless a more stringent standard is required to prevent, taking 

into consideration costs, energy, safety, and other relevant factors, 

an adverse environmental effect).

The terms ―individual most exposed,‖ ―acceptable level,‖ and 

―ample margin of safety‖ are not specifically defined in the CAA. 

However, CAA section 112(f)(2)(B) preserves the interpretation set 

out in the Benzene NESHAP, and the United States Court of Appeals for 

the District of Columbia Circuit in NRDC v. EPA, 529 F.3d 1077, 

concluded that the EPA‘s interpretation of subsection 112(f)(2) is a 

reasonable one. See NRDC v. EPA, 529 F.3d at 1083 (―[S]ubsection 

112(f)(2)(B) expressly incorporates the EPA‘s interpretation of the 

Clean Air Act from the Benzene standard, complete with a citation to 

the Federal Register‖). (D.C. Cir. 2008). See also, A Legislative 

History of the Clean Air Act Amendments of 1990, volume 1, p. 877 
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(Senate debate on Conference Report). We notified Congress in the 

Residual Risk Report to Congress that we intended to use the Benzene 

NESHAP approach in making CAA section 112(f) residual risk 

determinations (EPA–453/R–99–001, p. ES–11).

In the Benzene NESHAP, we stated as an overall objective:

* * * in protecting public health with an ample margin of 

safety, we strive to provide maximum feasible protection against 

risks to health from hazardous air pollutants by, (1) protecting 

the greatest number of persons possible to an individual 

lifetime risk level no higher than approximately 1-in-1 million; 

and (2) limiting to no higher than approximately 1-in-10 

thousand [i.e., 100-in-1 million] the estimated risk that a 

person living near a facility would have if he or she were 

exposed to the maximum pollutant concentrations for 70 years.

The agency also stated that, ―The EPA also considers incidence 

(the number of persons estimated to suffer cancer or other serious 

health effects as a result of exposure to a pollutant) to be an 

important measure of the health risk to the exposed population. 

Incidence measures the extent of health risk to the exposed 

population as a whole, by providing an estimate of the occurrence of 

cancer or other serious health effects in the exposed population.‖ 

The agency went on to conclude that ―estimated incidence would be 

weighed along with other health risk information in judging 

acceptability.‖ As explained more fully in our Residual Risk Report 
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to Congress, the EPA does not define ―rigid line[s] of 

acceptability,‖ but considers rather broad objectives to be weighed 

with a series of other health measures and factors (EPA–453/R–99–001, 

p. ES–11). The determination of what represents an ―acceptable‖ risk 

is based on a judgment of ―what risks are acceptable in the world in 

which we live‖ (Residual Risk Report to Congress, p. 178, quoting the 

Vinyl Chloride decision at 824 F.2d 1165) recognizing that our world 

is not risk-free.

In the Benzene NESHAP, we stated that ―EPA will generally 

presume that if the risk to [the maximum exposed] individual is no 

higher than approximately 1-in-10 thousand, that risk level is 

considered acceptable.‖ 54 FR 38045. We discussed the maximum 

individual lifetime cancer risk (or maximum individual risk (MIR)) as 

being ―the estimated risk that a person living near a plant would 

have if he or she were exposed to the maximum pollutant 

concentrations for 70 years.‖ Id. We explained that this measure of 

risk ―is an estimate of the upper bound of risk based on conservative 

assumptions, such as continuous exposure for 24 hours per day for 70 

years.‖ Id. We acknowledge that maximum individual lifetime cancer 

risk ―does not necessarily reflect the true risk, but displays a 

conservative risk level which is an upper-bound that is unlikely to 

be exceeded.‖ Id.

Understanding that there are both benefits and limitations to 

using maximum individual lifetime cancer risk as a metric for 
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determining acceptability, we acknowledged in the 1989 Benzene NESHAP 

that ―consideration of maximum individual risk * * * must take into 

account the strengths and weaknesses of this measure of risk.‖ Id.

Consequently, the presumptive risk level of 100-in-1 million (1-in-10 

thousand) provides a benchmark for judging the acceptability of 

maximum individual lifetime cancer risk, but does not constitute a 

rigid line for making that determination.

The agency also explained in the 1989 Benzene NESHAP the 

following: ―In establishing a presumption for MIR, rather than a 

rigid line for acceptability, the agency intends to weigh it with a 

series of other health measures and factors. These include the 

overall incidence of cancer or other serious health effects within 

the exposed population, the numbers of persons exposed within each 

individual lifetime risk range and associated incidence within, 

typically, a 50-kilometer (km) exposure radius around facilities, the 

science policy assumptions and estimation uncertainties associated 

with the risk measures, weight of the scientific evidence for human 

health effects, other quantified or unquantified health effects, 

effects due to co-location of facilities and co-emission of 

pollutants.‖ Id.

In some cases, these health measures and factors taken together 

may provide a more realistic description of the magnitude of risk in 

the exposed population than that provided by maximum individual 

lifetime cancer risk alone. As explained in the Benzene NESHAP, 
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―[e]ven though the risks judged ―acceptable‖ by the EPA in the first 

step of the Vinyl Chloride inquiry are already low, the second step 

of the inquiry, determining an ―ample margin of safety,‖ again 

includes consideration of all of the health factors, and whether to 

reduce the risks even further.‖ In the ample margin of safety 

decision process, the agency again considers all of the health risks 

and other health information considered in the first step. Beyond 

that information, additional factors relating to the appropriate 

level of control will also be considered, including costs and 

economic impacts of controls, technological feasibility, 

uncertainties and any other relevant factors. Considering all of 

these factors, the agency will establish the standard at a level that 

provides an ample margin of safety to protect the public health, as 

required by CAA section 112(f). 54 FR 38046.

As discussed in the previous section of this preamble, we apply 

a two-step process for developing standards to address residual risk. 

In the first step, the EPA determines whether risks are acceptable. 

This determination ―considers all health information, including risk 

estimation uncertainty, and includes a presumptive limit on maximum 

individual lifetime [cancer] risk (MIR)2 of approximately 1-in-10 

thousand [i.e., 100-in-1 million].‖ 54 FR 38045. In the second step 

of the process, the EPA sets the standard at a level that provides an 

 

2

Although defined as ―maximum individual risk,‖ MIR refers only to cancer 

risk. MIR, one metric for assessing cancer risk, is the estimated risk were 

an individual exposed to the maximum level of a pollutant for a lifetime.
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ample margin of safety ―in consideration of all health information, 

including the number of persons at risk levels higher than 

approximately 1-in-1 million, as well as other relevant factors, 

including costs and economic impacts, technological feasibility, and 

other factors relevant to each particular decision.‖ Id.

In past residual risk determinations, the EPA presented a number 

of human health risk metrics associated with emissions from the 

category under review, including: the MIR; the numbers of persons in 

various risk ranges; cancer incidence; the maximum noncancer hazard 

index (HI); and the maximum acute noncancer hazard. In estimating 

risks, the EPA considered source categories under review that are 

located near each other and that affect the same population. The EPA 

provided estimates of the expected difference in actual emissions 

from the source category under review and emissions allowed pursuant 

to the source category MACT standard. The EPA also discussed and 

considered risk estimation uncertainties. The EPA is providing this 

same type of information in support of these actions.

The agency acknowledges that the Benzene NESHAP provides 

flexibility regarding what factors the EPA might consider in making 

our determinations and how they might be weighed for each source 

category. In responding to comment on our policy under the Benzene 

NESHAP, the EPA explained that: ―The policy chosen by the 

Administrator permits consideration of multiple measures of health 

risk. Not only can the MIR figure be considered, but also incidence, 
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the presence of noncancer health effects, and the uncertainties of 

the risk estimates. In this way, the effect on the most exposed 

individuals can be reviewed as well as the impact on the general 

public. These factors can then be weighed in each individual case. 

This approach complies with the Vinyl Chloride mandate that the 

Administrator ascertain an acceptable level of risk to the public by 

employing [her] expertise to assess available data. It also complies 

with the Congressional intent behind the CAA, which did not exclude 

the use of any particular measure of public health risk from the 

EPA's consideration with respect to CAA section 112 regulations, and, 

thereby, implicitly permits consideration of any and all measures of 

health risk which the Administrator, in [her] judgment, believes are 

appropriate to determining what will  ̳protect the public health.‘‖

For example, the level of the MIR is only one factor to be 

weighed in determining acceptability of risks. The Benzene NESHAP 

explains ―an MIR of approximately 1-in-10 thousand should ordinarily 

be the upper end of the range of acceptability. As risks increase 

above this benchmark, they become presumptively less acceptable under 

CAA section 112, and would be weighed with the other health risk 

measures and information in making an overall judgment on 

acceptability. Or, the agency may find, in a particular case, that a 

risk that includes MIR less than the presumptively acceptable level 

is unacceptable in the light of other health risk factors.‖ 

Similarly, with regard to the ample margin of safety analysis, the 
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Benzene NESHAP states that: ―EPA believes the relative weight of the 

many factors that can be considered in selecting an ample margin of 

safety can only be determined for each specific source category. This 

occurs mainly because technological and economic factors (along with 

the health-related factors) vary from source category to source 

category.‖

B. Does this action apply to me?

The regulated industrial source category that is the subject of 

this proposal is listed in Table 2 of this preamble. Table 2 of this 

preamble is not intended to be exhaustive, but rather provides a 

guide for readers regarding the entities likely to be affected by 

this proposed action. These standards, once finalized, will be 

directly applicable to affected sources. Federal, State, local, and 

tribal government entities are not affected by this proposed action. 

As defined in the source category listing report published by the EPA

in 1992, the Primary Aluminum Reduction Plant source category is 

defined as any facility which produced primary aluminum by the 

electrolytic reduction process.

Table 2. NESHAP and Industrial Source Categories Affected by thisBy 

This Proposed Action

Source Category NESHAP NAICS 

code1

MACT 

code2

Primary Aluminum 

Reduction Plants

Primary Aluminum 

Reduction Plants

331312 0023

1 North American Industry Classification System

2 Maximum Achievable Control Technology
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C. Where can I get a copy of this document and other related 

information?

In addition to being available in the docket, an electronic copy 

of this proposal will also be available on the World Wide Web (WWW) 

through the EPA‘s Technology Transfer Network (TTN). Following 

signature by the EPA Administrator, 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/atw/rrisk/rtrpg.html. The TTN provides 

information and technology exchange in various areas of air pollution 

control.

Additional information is available on the residual risk and 

technology review (RTR) webpage at: 

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. This information 

includes source category descriptions and detailed emissions 

estimates and other data that were used as inputs to the risk 

assessments.

D. What should I consider as I prepare my comments for the EPA?

Submitting CBI. Do not submit information containing CBI to the 

EPA through http://www.regulations.gov or email. Clearly mark the 

part or all of the information that you claim to be CBI. For CBI 

information on a disk or CD ROM that you mail to the 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 
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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. If you submit a CD ROM or disk that 

does not contain CBI, mark the outside of the disk or CD ROM clearly 

that it does not contain CBI. Information not marked as CBI will be 

included in the public docket and the EPA‘s electronic public docket 

without prior notice. Information marked as CBI will not be disclosed 

except in accordance with procedures set forth in 40 CFR part 2. Send 

or deliver information identified as CBI only to the following 

address: Roberto Morales, OAQPS Document Control Officer (C404-02), 

Office of Air Quality Planning and Standards, U.S. Environmental 

Protection Agency, Research Triangle Park, North Carolina 27711, 

Attention Docket ID Number EPA-HQ-OAR-2011-0797.

II. Background

A. What is this source category and how did the MACT standard 

regulate its HAP emissions?

The NESHAP (or MACT rule) for the Primary Aluminum Reduction 

Plants waswere promulgated on October 7, 1997 (62 FR 52407) and 

amended on November 2, 2005 (70 FR 66285). The rule is applicable to 

facilities with affected sources associated with the production of 

aluminum by electrolytic reduction. Aluminum is produced from refined 

bauxite ore (also known as alumina), using an electrolytic reduction 

process in a series of cells called a ―potline.‖ The raw materials 
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include alumina, coke, pitch and fluoride salts. According to 

information available on the website of The Aluminum Association, 

Inc. (www.aluminum.org) approximatelyApproximately 50 percent of the 

aluminum produced in the U.S. comes from primary aluminum facilities. 

The two main potline types are prebake (a newer, higher efficiency, 

lower-emitting technology) and Soderberg (an older, lower efficiency, 

higher-emitting technology). There are currently 15 facilities 

located in the United States that are subject to the requirements of 

this NESHAP: 14 primary aluminum production plants and one carbononly prebake anode production facility. These 14 primary aluminum 

production plants have approximately 53 potlines that produce 

aluminum. Each plant has a paste production operation, and 12 of the 

14 plants have anode bake furnaces. Twelve of the 14 facilities 

utilize prebake potlines; the other 2 utilize Soderberg potlines. 

According to The Aluminum Association, Inc., due to a decrease in 

demand for aluminum, fourFour of the 14 facilities are currently 

idle, including 1 Soderberg facility. The major HAPs emitted by these 

facilities are carbonyl sulfide (COS), hydrogen fluoride (HF), and 

polycyclic organic matter (POM), specifically polycyclic aromatic 

hydrocarbons (PAH).

The standards promulgated in 1997 and 2005 apply to emissions of 

HF, measured using total fluorides (TF) as a surrogate, from all 

potlines and anode bake furnaces and POM (as measured by methylene 

chloride extractables) from Soderberg potlines, anode bake furnaces, 
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paste production plants and pitch storage tanks associated with 

primary aluminum reduction. Affected sources under the rules are each 

potline, each anode bake furnace (except for one that is located at a 

facility that only produces anodes for use off-site), each paste 

production plant, and each new pitch storage tank.

The NESHAP designated seven subcategories of existing potlines 

based primarily on differences in the process operation and 

configuration. The control of primary emissions from the reduction 

process is typically achieved by the installation of a dry alumina 

scrubber (with a baghouse to collect the alumina and other 

particulate matter). The MACT control technology typically used for 

anode bake furnaces is a dry alumina scrubber, and a capture system 

vented to a dry coke scrubber is used for control of paste production

plants. See Table 3 for the emission limits.

Table 3. Summary of Current MACT Emission Limits for Existing Sources

underUnder the 1997 NESHAP, and the 2005 Amendments.

Source Pollutant Emission Limit

Potlines1

CWPB1 potlines

CWPB2 potlines

CWPB3 potlines

SWPB potlines

VSS1 potlines

 

VSS2 potlines

 

HSS potlines

TF

TF

TF

TF

TF

POM

TF

POM

TF

POM

0.95 kg/Mg (1.9 lb/ton) of aluminum produced

1.5 kg/Mg (3.0 lb/ton) of aluminum produced

1.25 kg/Mg (2.5 lb/ton) of aluminum produced

0.8 kg/Mg (1.6 lb/ton) of aluminum produced

1.1 kg/Mg (2.2 lb/ton) of aluminum produced

1.2 kg/Mg (2.4 lb/ton) of aluminum produced

1.35 kg/Mg (2.7 lb/ton) of aluminum produced

2.85 kg/Mg (5.7 lb/ton) of aluminum produced

1.35 kg/Mg (2.7 lb/ton) of aluminum produced

2.35 kg/Mg (4.7 lb/ton) of aluminum produced

Paste Production POM Install, operate, and maintain equipment for 

capture of emissions and vent to a dry coke 
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scrubber

Anode Bake Furnace 

(collocated with a 

primary aluminum 

plant)

TF

POM

0.10 kg/Mg (0.20 lb/ton) of green anode

0.09 kg/Mg (0.18 lb/ton) of green anode

1CWPB1=Center-worked prebake potline with the most modern reduction cells; includes all

center-worked prebake potlines not specifically identified as CWPB2 or CWPB3. 

CWPB2=Center-worked prebake potlines located at Alcoa in Rockdale, Texas; Kaiser Aluminum in 

Mead, Washington; Ormet Corporation in Hannibal, Ohio; Ravenswood Aluminum in Ravenswood, 

West Virginia; Reynolds Metals in Troutdale, Oregon; and Vanalco Aluminum in Vancouver, 

Washington.

CWPB3=Center-worked prebake potline that produces very high purity aluminum, has wet

scrubbers as the primary control system, and is located at the primary aluminum plant 

operated by NSA in Hawesville, Kentucky.

HSS=Horizontal stud Soderberg potline.

SWPB=Side-worked prebake potline.

VSS1=Vertical stud Soderberg potline at Northwest Aluminum in The Dalles, Oregon, or at

Columbia Aluminum in Goldendale, Washington.

VSS2=Vertical stud Soderberg potlines at Columbia Falls Aluminum in Columbia Falls, Montana.

Table 4. Summary of Current MACT Emission Limits for New Sources

underUnder the 1997 NESHAP and 2005 Amendments

Source Pollutant Emission Limit

All Potlines TF 0.6 kg/Mg (1.2 lb/ton) of aluminum produced

VSS1, VSS2, and HSS 

potlines

POM 0.32 kg/Mg (0.63 lb/ton) of aluminum produced

Paste Production POM Install, operate, and maintain equipment for 

capture of emissions and vent to a dry coke 

scrubber

Anode Bake Furnace

(collocated with a 

primary aluminum plant)

TF

POM

0.01 kg/Mg (0.020 lb/ton) of green anode

0.025 kg/Mg (0.05 lb/ton) of green anode

Pitch storage tanks POM Emission control system designed and operated to 

reduce inlet emissions by 95 percent or greater.

The 1997 NESHAP for primary aluminum reduction plants 

incorporates new source performance standards for potroom groups; 

these emission limits are listed in Table 4. The limits for new 

Soderberg facilities apply to any Soderberg facility that adds a new 

potroom group to an existing potline or is associated with a potroom 

Formatted: Line spacing: single
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group that meets the definition of a modified or reconstructed 

potroom group. Since these POM limits are very stringent, they 

effectively preclude the operation of any new Soderberg potlines.

Compliance with the emission limits in the current rule is 

demonstrated by performance testing which can be addressed 

individually for each affected source or according to emissions 

averaging provisions. Monitoring requirements include monthly 

measurements of TF secondary emissions, quarterly measurement of POM 

secondary emissions and annual measurement of primary emissions, 

continuous parameter monitoring for each emission control device, a

monitoring device to track daily weight of aluminum produced, daily 

inspection for visible emissions, and daily inspection of wet roof 

scrubbers. Recordkeeping for the rule is consistent with the General 

Provisions requirements with the addition of recordkeeping for daily 

production of aluminum, records supporting emissions averaging and 

records documenting the portion of TF measured as particulate matter 

or gaseous form.

B. What data collection activities were conducted to support this 

action?

For the Primary Aluminum Reduction Plant source category, we 

compiled a preliminary dataset using available information, reviewed 

the data, and made changes where necessary. The preliminary dataset 

was based on data in the 2002 National Emissions Inventory (NEI) 

Final Inventory, Version 1 (made publicly available on February 26, 
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2006), and the 2005 National Emissions Inventory (NEI), version 2.0 

(made publicly available in October 2008). The NEI is a database that 

contains information about sources that emit criteria air pollutants, 

their precursors, and HAP. The NEI database includes estimates of 

annual air pollutant emissions from point and volume sources, 

emission release characteristic data such as height, velocity,

temperature and location latitude/longitude coordinates.

We reviewed the NEI datasets, corrected geographic coordinates

and stack parameters in consultation with the facilities, and made 

changes based on available information. We also reviewed the 

emissions and other data to identify data anomalies that could affect 

risk estimates. The 2005 NEI was then updated to develop the 2005 

National Air Toxics Assessment (NATA) Inventory. Subsequently, in 

April 2011, we received test data and other information through an 

Information Collection Request (ICR) from 11 of the 15 facilities in 

the source category. These ICR data were then used along with the 

2005 NATA inventory data to develop the emissions dataset for this 

source category, which includes our best estimates of actual 

emissions of HAP for the facilities. This dataset was then used in 

the risk modeling analyses to estimate the risks due to actual 

emissions for the source category.

POM emissions were allocated to specific POM compounds on the 

basis of the fractional contributions of these compounds to the 

actual POM emissions, as determined (as appropriate) from an average 
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of test data for two prebake potlines and an average of data from two 

Soderberg facilities. Based on knowledge of the industry and previous 

testing, we could reasonably expect emissions of approximately 23 POM 

specific POM compounds from primary aluminum production facilities. 

The allocation incorporated POM emissions at 50 percent of the 

detection limit for those compounds ―reported as below detection 

limit.‖ The use of 50 percent of the detection limit is more 

conservative than assuming that these compounds were not present; an 

assumption that the compounds were present at the detection limit 

would be an overestimation. The assumption that these compounds were 

present at 50 percent of the detection limit represented the midpoint 

of two extreme options. For Soderberg potline stacks, six out of 38 

measurements were below the detection limit. For Soderberg potroom 

roof vents, 10 out of 38 measurements were below the detection limit.

For prebake potline stacks, 21 out of 38 measurements were below the 

detection limit. For prebake potroom roof vents, 25 out of 38 

measurements were below the detection limit.

To estimate allowable emissions, we analyzed the emissions data 

gathered from the 2002 NEI, the 2005 NEI and responses to the ICR 

described above. Based on that analysis, we estimated that allowable 

emissions were generally about 1.5 times higher than actual 

emissions. Therefore, to calculate allowable emissions we assumed 

that allowable emissions were 1.5 times greater than actual emissions

for all facilities except for one idle Soderberg facility (Columbia 
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Falls). For Columbia Falls, which has the highest potential for 

emissions of all the facilities, we evaluated site-specific data and 

estimated that allowable emissions were about 1.9 times higher than 

actual emissions.1.8 times higher than actual emissions. The POM 

emissions were then allocated to specific compounds on the basis of 

the fractional contributions of these compounds to the actual POM 

emissions, as determined from an average of test data from two 

Soderberg facilities. The allocation incorporated POM emissions at 50

percent of the detection limit for those compounds for which 

measurements were below the detection limit.

Actual emissions of COS for the industry are estimated to be 

about 4,400 tons per year (tpy), with an average of about 330 tons 

per facility. Actual emissions of HF are estimated to be about 1,900 

tpy with an average of about 160 tpy per facility. Estimated 

emissions of speciated compounds of POM were much lower. Estimated 

actual emissions of identified POM species totaled approximately 180

tpy for the industry. Moreover, POM emissions are much higher from 

Soderberg facilities compared to prebake facilities. The average POM 

emissions from prebake facilities are about 4.5 tpy per facility, and 

the average POM emissions for Soderberg facilities are about 60 tpy

per facility. We estimate that approximately one-third of the 

emissions of POM for both types of potrooms come from the control 

device stack, and the remainder are secondary emissions emitted from 

potroom vents. This estimate is based on a summary of emissions 
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derived from reports of emission testing conducted at two prebake 

facilities and two Soderberg facilities (―Industry Review of Draft 

POM Speciation and Emissions Data,‖ December 19, 2007).fugitives 

emitted from potroom vents.

The emissions data, calculations and risk assessment inputs for 

the Primary Aluminum Reduction Plant source category are described 

further in Draft Development of the RTR Emissions Dataset for the 

Primary Aluminum Production Source Category which is available in the 

docket for this proposed rulemaking.

III. Analyses Performed

In this section we describe the analyses performed to support 

the proposed decisions for the RTR for this source category.

A. How did we address unregulated emissions sources?

In the course of evaluating the Primary Aluminum Reduction Plant

source category, we identified certain HAP for which we failed to 

establish emission standards in the original MACT. See National Lime 

v. EPA, 233 F. 3d 625, 634 (D.C. Cir. 2000) (the EPA has ―clear 

statutory obligation to set emissions standards for each listed 

HAP‖).

We evaluated establishing emissions limits for COS for the 

source category and for POM for various emissions points that had not 

been regulated in the 1997 MACT rule or in the 2005 amendments. 

Section 112(d)(3)(B) of the CAA requires that the MACT standards for 

existing sources be at least as stringent as the average emissions
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limitation achieved by the best performing five sources (for which 

the Administrator has or could reasonably obtain emissions 

information) in a category with fewer than 30 sources. The Primary 

Aluminum source category consists of fewer than 30 sources.

The EPA must exercise its judgment, based on an evaluation of 

the relevant factors and available data, to determine the level of 

emissions control that has been achieved by the best performing 

sources under variable conditions. It is recognized in the case law

that the EPA may consider variability in estimating the degree of 

emissions reduction achieved by best-performing sources and in 

setting MACT floors. See Mossville Envt‘l Action Now v. EPA, 370 F.3d 

1232, 1241–42 (D.C. Cir 2004) (holding that the EPA may consider 

emissions variability in estimating performance achieved by bestperforming sources and may set the floor at a level that a bestperforming source can expect to meet ―every day and under all 

operating conditions‖). More details on how we calculate MACT floors 

and how we account for variability are described in the Draft MACT 

Floor Analysis for the Primary Aluminum Source Category which is 

available in the docket for this proposed action.

Carbonyl sulfide (COS) was not regulated in the 1997 NESHAP or 

in the 2005 amendments for Primary Aluminum Reduction Plants. In this 

action we analyzed the available data and evaluated options for 

developing MACT standards for this HAP. As mentioned above, COS is 

the HAP emitted in largest quantities. Based on all our analyses, 
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which are described in section IV.A of this preamble, we concluded 

that establishing a standard based on a mass balance equation would 

be the most appropriate approach. Therefore, we are proposing MACT 

standards for COS in today‘s action based on use of a mass balance 

equation to derive COS emissions based on data on anode coke sulfur 

content, anode consumption and aluminum production..

Polycyclic organic matter (POM) emissions from prebake potlines

were also not regulated in the 1997 NESHAP or in the 2005 amendments.

We are proposing MACT limits for new and existing prebake potlines in 

today‘s action based on available data. Finally, the 1997 NESHAP 

included MACT standards for new pitch storage tanks, which required a 

95 percent reduction in emissions. However, the rule had no limits 

for existing storage tanks. We are proposing that existing tanks will 

be subject to the same standard (i.e., minimum of 95 percent

reduction of POM emissions). for these tanks. At least three 

facilities are currently achieving this level of control on existing 

tanks..

Further details about the analyses, the results and proposed 

decisions regarding the proposed MACT limits pursuant to CAA section 

112(d)(2) and 112(d)(3) are presented in section IV.A of this 

preamble.

B. How did we estimate risks posed by the source category?

The EPA conducted risk assessments that provided estimates of 

the MIR posed by the HAP emissions for each source in the category, 
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the HI for chronic exposures to HAP with the potential to cause 

noncancer health effects, and the hazard quotient (HQ) for acute 

exposures to HAP with the potential to cause noncancer health 

effects. The assessments also provided estimates of the distribution 

of cancer risks within the exposed populations, cancer incidence and 

an evaluation of the potential for adverse environmental effects for 

each source category. The risk assessments consisted of seven primary 

steps, as discussed below. The docket for this rulemaking contains 

the following document which provides more information on the risk 

assessment inputs and models: Draft Residual Risk Assessment for the 

Primary Aluminum Reduction Plant Source Category. The methods used to 

assess risks (as described in the seven primary steps below) are 

consistent with those peer-reviewed by a panel of the EPA‘s Science 

Advisory Board (SAB) in 2009 and described in their peer review 

report issued in 20103; they are also consistent with the key 

recommendations contained in that report.

1. Establishing the nature and magnitude of actual emissions and 

identifying the emissions release characteristics

As discussed in section II.B of this preamble, we used a dataset 

consisting ofbased on the estimated actual and allowable emissions as 

the basis for the risk assessment. In addition to the quality 

 

3

U.S. EPA SAB. Risk and Technology Review (RTR) Risk Assessment 

Methodologies: For Review by the EPA‘s Science Advisory Board with Case 

Studies – MACT I Petroleum Refining Sources and Portland Cement 

Manufacturing, May 2010.
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assurance (QA) of the emissions and associated parametersfacilities

contained in the dataset, we also checked the coordinates of every 

facility in the dataset through visual observations using tools such 

as Google Earth and ArcView. Where coordinates were found to be 

incorrect, we identified and corrected them to the extent possible. 

We also performed QA of the emissions data and release 

characteristics to ensure there were no outliers.

2. Establishing the relationship between actual emissions and MACTallowable emissions levels

The available emissions data in the MACT dataset include

estimates of the mass of HAP actually emitted during the specified 

annual time period. These ―actual‖ emission levels are often lower 

than the emission levels that a facility might be allowed to emit and 

still comply with the MACT standards. The emissions level allowed to 

be emitted by the MACT standards is referred to as the ―MACTallowable‖ emissions level. This represents the highest emissions 

level that could be emitted by the facility without violating the 

MACT standards.

We discussed the use of both MACT-allowable and actual emissions 

in the final Coke Oven Batteries residual risk rule (70 FR 19998–

19999, April 15, 2005) and in the proposed and final Hazardous 

Organic NESHAP residual risk rules (71 FR 34428, June 14, 2006, and 

71 FR 76609, December 21, 2006, respectively). In those previous 

actions, we noted that assessing the risks at the MACT-allowable 
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level is inherently reasonable since these risks reflect the maximum 

level sources could emit and still comply with national emission 

standards. But we also explained that it is reasonable to consider 

actual emissions, where such data are available, in both steps of the 

risk analysis, in accordance with the Benzene NESHAP. (54 FR 38044, 

September 14, 1989.)

Further explanation is provided in the document Draft

Development of the RTR Emissions Dataset for the Primary Aluminum 

Production Source Category which is available in the docket for this 

proposed rulemaking.

3. Conducting dispersion modeling, determining inhalation exposures 

and estimating individual and population inhalation risks

Both long-term and short-term inhalation exposure concentrations 

and health risks from each facility in the source category addressed 

in this proposal were estimated using the Human Exposure Model (HEM)

(Community and Sector HEM–3 version 1.1.0). The HEM–3 performs three 

primary risk assessment activities: (1) conducting dispersion 

modeling to estimate the concentrations of HAP in ambient air, (2) 

estimating long-term and short-term inhalation exposures to 

individuals residing within 50 km of the modeled sources and (3) 

estimating individual and population-level inhalation risks using the 

exposure estimates and quantitative dose-response information.

The dispersion model used by HEM–3 is AERMOD, which is one of 

the EPA‘s preferred models for assessing pollutant concentrations 
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from industrial facilities.

4

To perform the dispersion modeling and to 

develop the preliminary risk estimates, HEM–3 draws on three data 

libraries. The first is a library of meteorological data, which is 

used for dispersion calculations. This library includes 1 year (1991) 

of hourly surface and upper air observations for more than 158 

meteorological stations, selected to provide coverage of the United 

States and Puerto Rico. A second library of United States Census 

Bureau census block

5

internal point locations and populations provides 

the basis of human exposure calculations (Census, 2000). In addition, 

for each census block, the census library includes the elevation and 

controlling hill height, which are also used in dispersion 

calculations. A third library of pollutant unit risk factors and 

other health benchmarks is used to estimate health risks. These risk 

factors and health benchmarks are the latest values recommended by 

the EPA for HAP and other toxic air pollutants. These values are 

available at http://www.epa.gov/ttn/atw/toxsource/summary.html and 

are discussed in more detail later in this section.

In developing the risk assessment for chronic exposures, we used 

the estimated annual average ambient air concentration of each of the 

HAP emitted by each source for which we have emissions data in the 

source category. The air concentrations at each nearby census block 

 

4

U.S. EPA. Revision to the Guideline on Air Quality Models: Adoption of a 

Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and 

Other Revisions (70 FR 68218, November 9, 2005).

5

A census block is generally the smallest geographic area for which census 

statistics are tabulated. 
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centroid were used as a surrogate for the chronic inhalation exposure 

concentration for all the people who reside in that census block. We 

calculated the MIR for each facility as the cancer risk associated 

with a continuous lifetime (24 hours per day, 7 days per week, and 52 

weeks per year for a 70-year period) exposure to the maximum 

concentration at the centroid of an inhabited census block. 

Individual cancer risks were calculated by multiplying the estimated 

lifetime exposure to the ambient concentration of each of the HAP (in 

micrograms per cubic meter) by its unit risk estimate (URE), which is 

an upper bound estimate of an individual‘s probability of contracting 

cancer over a lifetime of exposure to a concentration of 1 microgram 

of the pollutant per cubic meter of air. For residual risk 

assessments, we generally use URE values from the EPA‘s Integrated 

Risk Information System (IRIS). For carcinogenic pollutants without 

the EPA IRIS values, we look to other reputable sources of cancer 

dose-response values, often using California EPA (CalEPA) URE values, 

where available. In cases where new, scientifically credible doseresponse values have been developed in a manner consistent with the 

EPA guidelines and have undergone a peer review process similar to 

that used by the EPA, we may use such dose-response values in place 

of, or in addition to, other values, if appropriate.

Polycyclic organic matter (POM), a carcinogenic HAP with a 

mutagenic mode of action, is emitted by the facilities in this source 
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category.

6

For this compound group,

7

the age-dependent adjustment 

factors (ADAF) described in the EPA‘s Supplemental Guidance for 

Assessing Susceptibility from Early-Life Exposure to Carcinogens

8

were 

applied. This adjustment has the effect of increasing the estimated 

lifetime risks for POM by a factor of 1.6. In addition, although only 

a small fraction of the total POM emissions were not reported as 

individual compounds, the EPA expresses carcinogenic potency for 

compounds in this group in terms of benzo[a]pyrene equivalence, based 

on evidence that carcinogenic POM has the same mutagenic mechanism of 

action as benzo[a]pyrene. For this reason, the EPA‘s Science 

Policy Council

9

recommends applying the Supplemental Guidance to all 

carcinogenic polycyclic aromatic hydrocarbons for which risk 

estimates are based on relative potency. Accordingly, we have applied 

the ADAF to the benzo[a]pyrene equivalent portion of all POM 

mixtures.

Incremental individual lifetime cancer risks associated with 

emissions from the source category were estimated as the sum of the 

 

6

U.S. EPA. Performing risk assessments that include carcinogens described 

in the Supplemental Guidance as having a mutagenic mode of action. Science 

Policy Council Cancer Guidelines Implementation Work Group Communication II: 

Memo from W.H. Farland, dated October 4, 2005.

7

See the Risk Assessment for Source Categories document available in the 

docket for a list of HAP with a mutagenic mode of action.

8

U.S. EPA. Supplemental Guidance for Assessing Early-Life Exposure to 

Carcinogens. EPA/630/R-03/003F, 2005. 

http://www.epa.gov/ttn/atw/childrens_supplement_final.pdf.

9

U.S. EPA. Science Policy Council Cancer Guidelines Implementation 

Workgroup Communication II: Memo from W.H. Farland, dated June 14, 2006.
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risks for each of the carcinogenic HAP (including those classified as 

carcinogenic to humans, likely to be carcinogenic to humans and 

suggestive evidence of carcinogenic potential

10

) emitted by the 

modeled source. Cancer incidence and the distribution of individual 

cancer risks for the population within 50 km of any source were also 

estimated for the source category as part of these assessments by 

summing individual risks. A distance of 50 km is consistent with both 

the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the 

limitations of Gaussian dispersion models, including AERMOD.

To assess risk of noncancer health effects from chronic 

exposures, we summed the HQ for each of the HAP that affects a common 

target organ system to obtain the HI for that target organ system (or 

target organ-specific HI, TOSHI). The HQ for chronic exposures is the 

estimated chronic exposure divided by the chronic reference level, 

which is either the EPA reference concentration (RfC), defined as ―an 

estimate (with uncertainty spanning perhaps an order of magnitude) of 

a continuous inhalation exposure to the human population (including 

sensitive subgroups) that is likely to be without an appreciable risk 

 

10

These classifications also coincide with the terms "known carcinogen, 

probable carcinogen and possible carcinogen," respectively, which are the 

terms advocated in the EPA's previous Guidelines for Carcinogen Risk 

Assessment, published in 1986 (51 FR 33992, September 24, 1986). Summing the 

risks of these individual compounds to obtain the cumulative cancer risks is 

an approach that was recommended by the EPA's SAB in their 2002 peer review 

of EPA's NATA entitled, NATA - Evaluating the National-scale Air Toxics 

Assessment 1996 Data -- an SAB Advisory, available at: 

http://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/

$File/ecadv02001.pdf.
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of deleterious effects during a lifetime,‖ or, in cases where an RfC 

from the EPA‘s IRIS database is not available, a value from the 

following prioritized sources: (1) the agency for Toxic Substances 

and Disease Registry Minimum Risk Level, which is defined as ―an 

estimate of daily human exposure to a substance that is likely to be 

without an appreciable risk of adverse effects (other than cancer) 

over a specified duration of exposure‖; (2) the CalEPA Chronic 

Reference Exposure Level (REL), which is defined as ―the 

concentration level at or below which no adverse health effects are 

anticipated for a specified exposure duration;‖ or (3) as noted 

above, a scientifically credible dose-response value that has been 

developed in a manner consistent with the EPA guidelines and has

undergone a peer review process similar to that used by the EPA, in 

place of or in concert with other values.

Screening estimates of acute exposures and risks were also 

evaluated for each of the HAP at the point of highest off-site 

exposure for each facility (i.e., not just the census block 

centroids), assuming that a person is located at this spot at a time 

when both the peak (hourly) emission rates from each emission point 

at the facility and worst-case dispersion conditions occur. The acute 

HQ is the estimated acute exposure divided by the acute dose-response 

value. In each case, acute HQ values were calculated using best 

available, short-term dose-response values. These acute dose-response 

values, which are described below, include the acute REL, acute 
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exposure guideline levels (AEGL) and emergency response planning 

guidelines (ERPG) for 1-hour exposure durations. As discussed below, 

we used conservative assumptions for emission rates, meteorology and 

exposure location for our acute analysis.

As described in the CalEPA‘s Air Toxics Hot Spots Program Risk 

Assessment Guidelines, Part I, The Determination of Acute Reference 

Exposure Levels for Airborne Toxicants, an acute REL value 

(http://www.oehha.ca.gov/air/pdf/acuterel.pdf) is defined as ―the 

concentration level at or below which no adverse health effects are 

anticipated for a specified exposure duration.‖ Acute REL values are 

based on the most sensitive, relevant, adverse health effect reported 

in the medical and toxicological literature. Acute REL values are 

designed to protect the most sensitive sub-populations (e.g., 

asthmatics) by the inclusion of margins of safety. Since margins of 

safety are incorporated to address data gaps and uncertainties, 

exceeding the acute REL does not automatically indicate an adverse 

health impact.

AEGL values were derived in response to recommendations from the 

National Research Council (NRC). As described in Standing Operating 

Procedures (SOP) of the National Advisory Committee on Acute Exposure 

Guideline Levels for Hazardous Substances

(http://www.epa.gov/opptintr/aegl/pubs/sop.pdf),

11

―the NRC‘s previous 

 

11

NAS, 2001. Standing Operating Procedures for Developing Acute Exposure 

Levels for Hazardous Chemicals, page 2.
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name for acute exposure levels—community emergency exposure levels—

was replaced by the term AEGL to reflect the broad application of 

these values to planning, response, and prevention in the community, 

the workplace, transportation, the military, and the remediation of 

Superfund sites.‖ This document also states that AEGL values 

―represent threshold exposure limits for the general public and are 

applicable to emergency exposures ranging from 10 minutes to eight 

hours.‖ The document lays out the purpose and objectives of AEGL by

stating (page 21) that ―the primary purpose of the AEGL program and 

the National Advisory Committee for Acute Exposure Guideline Levels 

for Hazardous Substances is to develop guideline levels for once-ina-lifetime, short-term exposures to airborne concentrations of 

acutely toxic, high-priority chemicals.‖ In detailing the intended 

application of AEGL values, the document states (page 31) that ―[i]t 

is anticipated that the AEGL values will be used for regulatory and 

nonregulatory purposes by U.S. Federal and state agencies and 

possibly the international community in conjunction with chemical 

emergency response, planning, and prevention programs. More 

specifically, the AEGL values will be used for conducting various 

risk assessments to aid in the development of emergency preparedness 

and prevention plans, as well as real-time emergency response 

actions, for accidental chemical releases at fixed facilities and 

from transport carriers.‖
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The AEGL–1 value is then specifically defined as ―the airborne 

concentration of a substance above which it is predicted that the 

general population, including susceptible individuals, could 

experience notable discomfort, irritation, or certain asymptomatic 

nonsensory effects. However, the effects are not disabling and are 

transient and reversible upon cessation of exposure.‖ The document 

also notes (page 3) that, ―Airborne concentrations below AEGL–1 

represent exposure levels that can produce mild and progressively 

increasing but transient and nondisabling odor, taste, and sensory

irritation or certain asymptomatic, nonsensory effects.‖ Similarly, 

the document defines AEGL–2 values as ―the airborne concentration 

(expressed as ppm or mg/m3) of a substance above which it is 

predicted that the general population, including susceptible

individuals, could experience irreversible or other serious, longlasting adverse health effects or an impaired ability to escape.‖

ERPG values are derived for use in emergency response, as 

described in the American Industrial Hygiene Association‘s document 

entitled, Emergency Response Planning Guidelines (ERPG) Procedures 

and Responsibilities

(http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf)which 

states that, ―Emergency Response Planning Guidelines were developed 

for emergency planning and are intended as health based guideline 
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Page 46 of 149

concentrations for single exposures to chemicals.‖

12

The ERPG–1 value 

is defined as ―the maximum airborne concentration below which it is 

believed that nearly all individuals could be exposed for up to 1

hour without experiencing other than mild transient adverse health 

effects or without perceiving a clearly defined, objectionable odor.‖ 

Similarly, the ERPG–2 value is defined as ―the maximum airborne 

concentration below which it is believed that nearly all individuals 

could be exposed for up to 1 hour without experiencing or developing 

irreversible or other serious health effects or symptoms which could 

impair an individual‘s ability to take protective action.‖

As can be seen from the definitions above, the AEGL and ERPG 

values include the similarly defined severity levels 1 and 2. For 

many chemicals, a severity level 1 value AEGL or ERPG has not been 

developed; in these instances, higher severity level AEGL–2 or ERPG–2 

values are compared to our modeled exposure levels to assess

potential for acute concerns.

Acute REL values for 1-hour exposure durations are typically 

lower than their corresponding AEGL–1 and ERPG–1 values. Even though 

their definitions are slightly different, AEGL–1 values are often 

similar to the corresponding ERPG–1 values, and AEGL–2 values are 

often similar to ERPG–2 values. Maximum HQ values from our acute 

screening risk assessments typically result when basing them on the 

 

12

ERP Committee Procedures and Responsibilities. November 1, 2006. American 

Industrial Hygiene Association.
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acute REL value for a particular pollutant. In cases where our 

maximum acute HQ value exceeds 1, we also report the HQ value based 

on the next highest acute dose-response value (usually the AEGL–1 

and/or the ERPG–1 value).

To develop screening estimates of acute exposures, we developed 

estimates of maximum hourly emission rates by multiplying the average 

actual annual hourly emission rates by a factor to cover routinely 

variable emissions. Acute risk modeling is conducted under the 

assumption that peak emissions are ten times greater than long term 

average emissions, in the absence of information regarding the 

variability of the emissions.

With respect to routine variable emissions, primary aluminum 

potlines have a more consistent emissions profile than many other 

sources because these emissions actually reflect the average of the 

emissions from approximately 100 individual pots which operate in 

cycles that are not in phase with each other. Thus any variability 

associated with aluminum levels or electrode replacement for a 

particular pot may be damped out by the other pots at different 

stages. Alcoa provided to EPA a series of hourly hydrogen fluoride 

concentration data for two potlines at their Wenatchee facility. 

Approximately 2,075 consecutive hourly readings were provided based 

on Fourier Transform Infrared measurements at the roof vents. Alcoa 

found that the ratio of the maximum HAP emission rate to the average 

HAP emission rate for these two potlines were 2.7 and 5.6. Only one 
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value out 2,075 consecutive hour samples (0.05 percent) was more than 

5 times the average (i.e., 99.95 percent of values were less than 5

times the average).

This dataset was then combined and subjected to two statistical 

analysis techniques: the upper prediction limit (UPL) calculated 

assuming a log-normal distribution after adjusting for temporal 

correction and extreme value theory. The average of the concentration 

values is 514 μg/m3. The 99 percent UPL was calculated at 2,215 μg/m, 

which corresponds to 4.3 times the mean.

Using the extreme value theory, the 99.9 percentile estimate of 

the generalized extreme value distribution (corresponding to 1 

observation in 1000) was 2,306 μg/m3, which corresponds to 4.5 times 

the mean. Based on these data, a source category factor of 5 times 

the average hourly emissions rate, rather than the default factor of 

10, was used in the acute screening assessment.

When worst-case HQ values from the initial acute screen step 

were less than 1, acute impacts were deemed negligible and no further 

analysis was performed. In cases where an acute HQ value from the 

screening step indicated the potential for acute risk, we further 

analyzed these values by considering additional site-specific data to 

develop a relatively more refined estimate of the potential for acute 

impacts of concern. This site-specific data includes the facility 

layout that was used to distinguish facility property from an area 

where the public could be exposed. These refinements are discussed in 
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the Draft Residual Risk Assessment for the Primary Aluminum 

Production Source Category document, which is available in the docket

for this proposed rulemaking.

Ideally, we would prefer to have continuous measurements over 

time to see how the emissions vary by each hour over an entire year. 

Having a frequency distribution of hourly emission rates over a year 

would allow us to perform a probabilistic analysis to estimate 

potential threshold exceedances and their frequency of occurrence. 

Such an evaluation could include a more complete statistical 

treatment of the key parameters and elements adopted in this 

screening analysis. However, we recognize that having this level of 

data is rare, hence our use of the multiplier approach.

To better characterize the potential health risks associated 

with estimated acute exposures to HAP, and in response to a key 

recommendation from the SAB‘s peer review of the EPA‘s RTR risk 

assessment methodologies,

13 we generally examine a wider range of 

available acute health metrics than we do for our chronic risk 

assessments. This is in response to the SAB‘s acknowledgement that 

there are generally more data gaps and inconsistencies in acute 

reference values than there are in chronic reference values. 

Comparisons of the estimated maximum off-site 1-hour exposure levels 

are not typically made to occupational levels for the purpose of 

 

13 The SAB peer review of RTR Risk Assessment Methodologies is available at: 

http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/

$File/EPA-SAB-10-007-unsigned.pdf.
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characterizing public health risks in RTR assessments. This is 

because they are developed for working age adults and are not 

generally considered protective for the general public. We note that 

occupational ceiling values are, for most chemicals, set at levels 

higher than a 1-hour AEGL-1.

4. Conducting multi-pathway exposure and risk screening

The potential for significant human health risks due to 

exposures via routes other than inhalation (i.e., multi-pathway 

exposures) and the potential for adverse environmental impacts were 

evaluated in a three-step process. In the first step, we determined 

whether any facilities emitted any PB-HAP (HAP known to be persistent 

and bio-accumulative in the environment). There are 14 PB-HAP 

compounds or compound classes identified for this screening in the 

EPA‘s Air Toxics Risk Assessment Library (available at 

http://www.epa.gov/ttn/fera/risk_atra_vol1.html). They are cadmium 

compounds, chlordane, chlorinated dibenzodioxins and furans, 

dichlorodiphenyldichloroethylene, heptachlor, hexachlorobenzene, 

hexachlorocyclohexane, lead compounds, mercury compounds, 

methoxychlor, polychlorinated biphenyls, POM, toxaphene and 

trifluralin.

Since POM is a PB-HAP and is emitted by all facilities in this 

source category, we proceeded to the second step of the evaluation to 

screen for potentially significant multi-pathway risks due to POM 

emissions. In this step, we determined whether the facility-specific 
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emission rates of POM were large enough to create the potential for

significant non-inhalation human or environmental risks under 

reasonable worst-case conditions. To facilitate this step, we have 

developed emission rate thresholds for each PB–HAP using a 

hypothetical worst-case screening exposure scenario developed for use 

in conjunction with the EPA‘s TRIM.FaTE model. The hypothetical 

screening scenario was subjected to a sensitivity analysis to ensure 

that its key design parameters were established such that 

environmental media concentrations were not underestimated (i.e., to 

minimize the occurrence of false negatives or results that suggest 

that risks might be acceptable when, in fact, actual risks are high)

and to also minimize the occurrence of false positives for human 

health endpoints. We call this application of the TRIM.FaTE model 

TRIM-Screen. The facility-specific emission rates of POM were 

compared to the TRIM-Screen emission threshold values for POM to 

assess the potential for significant human health risks or 

environmental risks via non-inhalation pathways.

5. Assessing risks considering emissions control options

In addition to assessing baseline inhalation risks and screening 

for potential multi-pathway risks, where appropriate, we also 

estimated risks considering the potential emission reductions that 

would be achieved by the particular control options under 

consideration. In these cases, the expected emissions reductions were 

applied to the specific HAP and emissions sources in the source 
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category dataset to develop corresponding estimates of risk 

reductions.

6. Conducting other risk-related analyses: facility wide assessments

To put the source category risks in context, for our residual 

risk reviews, we also typically examine the risks from the entire 

―facility,‖ where the facility includes all HAP-emitting operations 

within a contiguous area and under common control. In these facility 

wide assessments we examine the HAP emissions not only from the 

source category of interest, but also emissions of HAP from all other 

emissions sources at the facility. Eleven of the primary aluminum 

reduction plants are collocated with secondary aluminum production 

operations. Based on a general knowledge of these facilities, we 

believe that the Primary Aluminum sources are the largest sources of 

HAP emissions at each of them. Moreover, we plan to do a facility 

wide assessment for each of these eleven facilities in an upcoming 

RTR rulemaking for the Secondary Aluminum source category. Therefore, 

we did not perform a facility wide risk assessment for these eleven 

facilities as part of today‘s action. For the four primary aluminum 

facilities that are not collocated with secondary aluminum production 

operations, the risk assessment performed as part of today‘s 

actioncontained herein is a facility wide risk assessment.

7. Considering uncertainties in risk assessment

Uncertainty and the potential for bias are inherent in all risk 

assessments, including those performed for the Primary Aluminum 
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source category addressed in this proposal. Although uncertainty 

exists, we believe that our approach, which used conservative tools 

and assumptions, ensures that our decisions are health-protective. A 

brief discussion of the uncertainties in the emissions datasets, 

dispersion modeling, inhalation exposure estimates and dose-response 

relationships follows below. A more thorough discussion of these 

uncertainties is included in the risk assessment documentation 

(referenced earlier) available in the docket for this action.

a. Uncertainties in the emissions datasets

Although the development of the MACT dataset involved QA/quality 

control processes, the accuracy of emissions values will vary 

depending on the source of the data, the degree to which data are 

incomplete or missing, the degree to which assumptions made to 

complete the datasets are inaccurate, errors in estimating emissions 

values and other factors. The emission estimates considered in this 

analysis generally are annual totals for certain years that do not 

reflect short-term fluctuations during the course of a year or 

variations from year to year.

The estimates of peak hourly emission rates for the acute 

effects screening assessment were based on a multiplication factor of 

5 applied to the average annual hourly emission rate, which is 

intended to account for emission fluctuations due to normal facility 

operations. 

b. Uncertainties in dispersion modeling
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While the analysis employed the EPA‘s recommended regulatory 

dispersion model, AERMOD, we recognize that there is uncertainty in 

ambient concentration estimates associated with any model, including 

AERMOD. In circumstances where we had to choose between various model 

options, where possible, model options (e.g., rural/urban, plume 

depletion, chemistry) were selected to provide an overestimate of 

ambient air concentrations of the HAP rather than underestimates. 

However, because of practicality and data limitation reasons, some 

factors (e.g., meteorology, building downwash) have the potential in 

some situations to overestimate or underestimate ambient impacts. For 

example, meteorological data were taken from a single year (1991),

and facility locations can be a significant distance from the sites

where these data were taken. Despite these uncertainties, we believe 

that at off-site locations and census block centroids, the approach 

considered in the dispersion modeling analysis should generally yield 

overestimates of ambient HAP concentrations.

c. Uncertainties in inhalation exposure

The effects of human mobility on exposures were not included in 

the assessment. Specifically, short-term mobility and long-term 

mobility between census blocks in the modeling domain were not 

considered.

14

The assumption of not considering short or long-term 

population mobility does not bias the estimate of the theoretical 

 

14

Short-term mobility is movement from one micro-environment to another over 

the course of hours or days. Long-term mobility is movement from one 

residence to another over the course of a lifetime.
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MIR, nor does it affect the estimate of cancer incidence since the 

total population number remains the same. It does, however, affect 

the shape of the distribution of individual risks across the affected 

population, shifting it toward higher estimated individual risks at 

the upper end and reducing the number of people estimated to be at 

lower risks, thereby increasing the estimated number of people at 

specific risk levels.

In addition, the assessment predicted the chronic exposures at 

the centroid of each populated census block as surrogates for the 

exposure concentrations for all people living in that block. Using 

the census block centroid to predict chronic exposures tends to overpredict exposures for people in the census block who live further 

from the facility, and under-predict exposures for people in the 

census block who live closer to the facility. Thus, using the census 

block centroid to predict chronic exposures may lead to a potential 

understatement or overstatement of the true maximum impact, but it is 

an unbiased estimate of average risk and incidence.

The assessments evaluate the cancer inhalation risks associated 

with continuous pollutant exposures over a 70-year period, which is 

the assumed lifetime of an individual. In reality, both the length of 

time that modeled emissions sources at facilities actually operate 

(i.e., more or less than 70 years) and the domestic growth or decline 

of the modeled industry (i.e., the increase or decrease in the number 

or size of United States facilities) will influence the risks posed 
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by a given source category. Depending on the characteristics of the 

industry, these factors will, in most cases, result in an 

overestimate both in individual risk levels and in the total 

estimated number of cancer cases. However, in rare cases, where a 

facility maintains or increases its emission levels beyond 70 years, 

residents live beyond 70 years at the same location, and the 

residents spend most of their days at that location, then the risks 

could potentially be underestimated. Annual cancer incidence 

estimates from exposures to emissions from these sources would not be 

affected by uncertainty in the length of time emissions sources 

operate.

The exposure estimates used in these analyses assume chronic 

exposures to ambient levels of pollutants. Because most people spend 

the majority of their time indoors, actual exposures may not be as 

high, depending on the characteristics of the pollutants modeled. For 

many of the HAP, indoor levels are roughly equivalent to ambient 

levels, but for very reactive pollutants or larger particles, these 

levels are typically lower. This factor has the potential to result 

in an overstatement of 25 to 30 percent of exposures.

15

In addition to the uncertainties highlighted above, there are 

several other factors specific to the acute exposure assessment. The 

accuracy of an acute inhalation exposure assessment depends on the 

 

15

U.S. EPA. National-Scale Air Toxics Assessment for 1996. (EPA 453/R–01–

003; January 2001; page 85.)
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simultaneous occurrence of independent factors that may vary greatly, 

such as hourly emissions rates, meteorology, and human activity 

patterns. In this assessment, we assume that individuals remain for 1 

hour at the point of maximum ambient concentration as determined by 

the co-occurrence of peak emissions and worst-case meteorological 

conditions. These assumptions would tend to overestimate actual 

exposures since it is unlikely that a person would be located at the 

point of maximum exposure during the time of worst-case impact.

d. Uncertainties in dose-response relationships

There are uncertainties inherent in the development of the doseresponse values used in our risk assessments for cancer effects from 

chronic exposures and noncancer effects from both chronic and acute 

exposures. Some uncertainties may be considered quantitatively, and 

others generally are expressed in qualitative terms. We note as a 

preface to this discussion a point on dose-response uncertainty that 

is brought out in the EPA 2005 Cancer Guidelines; namely, that ―the 

primary goal of the EPA actions is protection of human health; 

accordingly, as an agency policy, risk assessment procedures, 

including default options that are used in the absence of scientific 

data to the contrary, should be health protective.‖ (EPA 2005 Cancer 

Guidelines, pages 1–7.) This is the approach followed here as 

summarized in the next several paragraphs. A complete detailed 

discussion of uncertainties and variability in dose-response 
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relationships is given in the residual risk documentation, which is 

available in the docket for this action.

Cancer URE values used in our risk assessments are those that 

have been developed to generally provide an upper bound estimate of 

risk. That is, they represent a ―plausible upper limit to the true 

value of a quantity‖ (although this is usually not a true statistical 

confidence limit).

16

In some circumstances, the true risk could be as 

low as zero; however, in other circumstances, the risk could also be 

greater.

17

When developing an upper bound estimate of risk and to 

provide risk values that do not underestimate risk, health-protective 

default approaches are generally used. To err on the side of ensuring 

adequate health-protection, the EPA typically uses the upper bound 

estimates rather than lower bound or central tendency estimates in 

our risk assessments, an approach that may have limitations for other 

uses (e.g., priority-setting or expected benefits analysis).

Chronic noncancer reference (RfC and reference dose (RfD)) 

values represent chronic exposure levels that are intended to be 

health-protective levels. Specifically, these values provide an 

estimate (with uncertainty spanning perhaps an order of magnitude) of 

daily oral exposure (RfD) or of a continuous inhalation exposure 

(RfC) to the human population (including sensitive subgroups) that is 

 

16

IRIS glossary (http://www.epa.gov/NCEA/iris/help_gloss.htm).

17

An exception to this is the URE for benzene, which is considered to cover 

a range of values, each end of which is considered to be equally plausible 

and which is based on maximum likelihood estimates.
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likely to be without an appreciable risk of deleterious effects 

during a lifetime. To derive values that are intended to be ―without 

appreciable risk,‖ the methodology relies upon an uncertainty factor 

(UF) approach (U.S. EPA, 1993, 1994) which includes consideration of 

both uncertainty and variability. When there are gaps in the 

available information, UF are applied to derive reference values that 

are intended to protect against appreciable risk of deleterious 

effects. The UF are commonly default values,

18

e.g., factors of 10 or 

3, used in the absence of compound-specific data; where data are 

available, UF may also be developed using compound-specific 

information. When data are limited, more assumptions are needed and 

more UF are used. Thus, there may be a greater tendency to 

overestimate risk in the sense that further study might support 

development of reference values that are higher (i.e., less potent) 

because fewer default assumptions are needed. However, for some 

 

18

According to the NRC report, Science and Judgment in Risk Assessment

(NRC, 1994) ―[Default] options are generic approaches, based on general 

scientific knowledge and policy judgment, that are applied to various 

elements of the risk assessment process when the correct scientific model is 

unknown or uncertain.‖ The 1983 NRC report, Risk Assessment in the Federal 

Government: Managing the Process, defined default option as ―the option 

chosen on the basis of risk assessment policy that appears to be the best 

choice in the absence of data to the contrary‖ (NRC, 1983a, p. 63). 

Therefore, default options are not rules that bind the Agency; rather, the 

Agency may depart from them in evaluating the risks posed by a specific 

substance when it believes this to be appropriate. In keeping with EPA‘s 

goal of protecting public health and the environment, default assumptions 

are used to ensure that risk to chemicals is not underestimated (although 

defaults are not intended to overtly overestimate risk). See EPA, 2004, An 

Examination of EPA Risk Assessment Principles and Practices, EPA/100/B–

04/001 available at:

http://www.epa.gov/osa/pdfs/ratf-final.pdf.
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pollutants, it is possible that risks may be underestimated. While 

collectively termed ―uncertainty factor,‖ these factors account for a 

number of different quantitative considerations when using observed 

animal (usually rodent) or human toxicity data in the development of 

the RfC. The UF are intended to account for: (1) variation in 

susceptibility among the members of the human population (i.e., 

inter-individual variability); (2) uncertainty in extrapolating from 

experimental animal data to humans (i.e., interspecies differences); 

(3) uncertainty in extrapolating from data obtained in a study with 

less-than-lifetime exposure (i.e., extrapolating from sub-chronic to 

chronic exposure); (4) uncertainty in extrapolating the observed data 

to obtain an estimate of the exposure associated with no adverse 

effects; and (5) uncertainty when the database is incomplete or there 

are problems with the applicability of available studies. Many of the 

UF used to account for variability and uncertainty in the development 

of acute reference values are quite similar to those developed for 

chronic durations, but they more often use individual UF values that 

may be less than 10. UF are applied based on chemical-specific or 

health effect-specific information (e.g., simple irritation effects 

do not vary appreciably between human individuals, hence a value of 3 

is typically used), or based on the purpose for the reference value 

(see the following paragraph). The UF applied in acute reference 

value derivation include: (1) heterogeneity among humans; (2) 

uncertainty in extrapolating from animals to humans; (3) uncertainty 
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in lowest observed adverse effect (exposure) level to no observed 

adverse effect (exposure) level adjustments; and (4) uncertainty in 

accounting for an incomplete database on toxic effects of potential 

concern. Additional adjustments are often applied to account for 

uncertainty in extrapolation from observations at one exposure 

duration (e.g., 4 hours) to derive an acute reference value at 

another exposure duration (e.g., 1 hour).

Not all acute reference values are developed for the same 

purpose, and care must be taken when interpreting the results of an 

acute assessment of human health effects relative to the reference 

value or values being exceeded. Where relevant to the estimated 

exposures, the lack of short-term dose-response values at different 

levels of severity should be factored into the risk characterization 

as potential uncertainties.

Although every effort is made to identify peer-reviewed 

reference values for cancer and noncancer effects for all pollutants

emitted by the sources included in this assessment, some HAP continue 

to have no reference values for cancer or chronic noncancer or acute 

effects. Since exposures to these pollutants cannot be included in a 

quantitative risk estimate, an understatement of risk for these 

pollutants at environmental exposure levels is possible. For a group 

of compounds that are either unspeciated or do not have reference 

values for every individual compound (e.g., glycol ethers), we 
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conservatively use the most protective reference value to estimate 

risk from individual compounds in the group of compounds.

Additionally, chronic reference values for several of the 

compounds included in this assessment are currently under the EPA 

IRIS review, and revised assessments may determine that these 

pollutants are more or less potent than the current value. We may reevaluate residual risks for the final rulemaking if these reviews are 

completed prior to our taking final action for this source category

and a dose-response metric changes enough to indicate that the risk 

assessment supporting this notice may significantly understate human 

health risk.

e. Uncertainties in the multi-pathway and environmental effects 

screening assessment

We generally assume that when exposure levels are not 

anticipated to adversely affect human health, they also are not 

anticipated to adversely affect the environment. For each source 

category, we generally rely on the site-specific levels of PB-HAP 

emissions to determine whether a full assessment of the multi-pathway 

and environmental effects is necessary. For this source category, we 

only performed a multi-pathway screening assessment for PB-HAP. Thus, 

it is important to note that potential PB-HAP multi-pathway risks are 

biased high.

C. How did we consider the risk results in making decisions for this 

proposal?
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In evaluating and developing standards under section 112(f)(2),

as discussed in section I.A of this preamble, we apply a two-step 

process to address residual risk. In the first step, the EPA

determines whether risks are acceptable. This determination 

―considers all health information, including risk estimation 

uncertainty, and includes a presumptive limit on maximum individual 

lifetime [cancer] risk (MIR)19 of approximately 1-in-10 thousand 

[i.e., 100-in-1 million]‖ (54 FR 38045). In the second step of the 

process, the EPA sets the standard at a level that provides an ample 

margin of safety ―in consideration of all health information, 

including the number of persons at risk levels higher than 

approximately 1-in-1 million, as well as other relevant factors, 

including costs and economic impacts, technological feasibility, and 

other factors relevant to each particular decision‖ (Id.)

In past residual risk actions, the EPA has presented and 

considered a number of human health risk metrics associated with 

emissions from the category under review, including: the MIR; the 

numbers of persons in various risk ranges; cancer incidence; the 

maximum non-cancer hazard index (HI); and the maximum acute noncancer hazard (72 FR 25138, May 3, 2007; 71 FR 42724, July 27, 2006). 

In more recent proposals (75 FR 65068, October 21, 2010, and 75 FR 

 

19 Although defined as ―maximum individual risk,‖ MIR refers only to 

cancer risk. MIR, one metric for assessing cancer risk, is the 

estimated risk were an individual exposed to the maximum level of a 

pollutant for a lifetime.
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80220, December 21, 2010), the EPA also presented and considered 

additional measures of health information, such as estimates of the 

risks associated with the maximum level of emissions which might be 

allowed by the current MACT standards (see, e.g., 75 FR 65068, 

October 21, 2010, and 75 FR 80220, December 21, 2010). The EPA also 

discussed and considered risk estimation uncertainties. The EPA is 

providing this same type of information in support of the proposed 

actions described in this Federal Register notice.

The agency is considering all available health information to 

inform our determinations of risk acceptability and ample margin of 

safety under CAA section 112(f). Specifically, as explained in the 

Benzene NESHAP, ―the first step judgment on acceptability cannot be 

reduced to any single factor‖ and thus ―[t]he Administrator believes 

that the acceptability of risk under [previous] section 112 is best 

judged on the basis of a broad set of health risk measures and 

information‖ (54 FR 38046). Similarly, with regard to making the 

ample margin of safety determination, as stated in the Benzene NESHAP 

―[in the ample margin decision, the agency again considers all of the 

health risk and other health information considered in the first 

step. Beyond that information, additional factors relating to the 

appropriate level of control will also be considered, including cost 

and economic impacts of controls, technological feasibility, 

uncertainties, and any other relevant factors.‖ Id.
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The agency acknowledges that the Benzene NESHAP provides

flexibility regarding what factors the EPA might consider in making 

determinations and how these factors might be weighed for each source 

category. In responding to comment on our policy under the Benzene 

NESHAP, the EPA explained that: ―The policy chosen by the 

Administrator permits consideration of multiple measures of health 

risk. Not only can the MIR figure be considered, but also incidence, 

the presence of non-cancer health effects, and the uncertainties of 

the risk estimates. In this way, the effect on the most exposed 

individuals can be reviewed as well as the impact on the general 

public. These factors can then be weighed in each individual case. 

This approach complies with the Vinyl Chloride mandate that the 

Administrator ascertain an acceptable level of risk to the public by 

employing [her] expertise to assess available data. It also complies 

with the Congressional intent behind the CAA, which did not exclude 

the use of any particular measure of public health risk from the

EPA's consideration with respect to CAA section 112 regulations, and, 

thereby, implicitly permits consideration of any and all measures of 

health risk which the Administrator, in [her] judgment, believes are 

appropriate to determining what will  ̳protect the public health‘‖ (54 

FR 38057).

Thus, the level of the MIR is only one factor to be weighed in 

determining acceptability of risks. The Benzene NESHAP explained that 

―an MIR of approximately 1-in-10 thousand should ordinarily be the 
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upper end of the range of acceptability. As risks increase above this 

benchmark, they become presumptively less acceptable under CAA 

section 112, and would be weighed with the other health risk measures 

and information in making an overall judgment on acceptability. Or, 

the agency may find, in a particular case, that a risk that includes 

MIR less than the presumptively acceptable level is unacceptable in 

the light of other health risk factors‖ (Id. at 38045). Similarly, 

with regard to the ample margin of safety analysis, the EPA stated in 

the Benzene NESHAP that: ―...the EPA believes the relative weight of 

the many factors that can be considered in selecting an ample margin 

of safety can only be determined for each specific source category. 

This occurs mainly because technological and economic factors (along 

with the health-related factors) vary from source category to source 

category‖ (Id. at 38061).

D. How did we perform the technology review?

Our technology review focused on the identification and 

evaluation of developments in practices, processes, and control 

technologies that have occurred since the Primary Aluminum Reduction 

Plant NESHAP was promulgated.

Based on our analyses of the data and information collected from 

industry and the trade organization representing all facilities 

subject to the NESHAP, our general understanding of the industry, and 

other available information in the literature on potential controls 

for this industry, we identified no new developments in practices, 
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processes, and control technologies. For the purpose of this 

exercise, we considered any of the following to be a ―development‖:

 Any add-on control technology or other equipment that was not 

identified and considered during development of the 1997 Primary 

Aluminum Reduction Plant NESHAP.

 Any improvements in add-on control technology or other equipment 

(that were identified and considered during development of the 

1997 Primary Aluminum Reduction Plant NESHAP) that could result 

in significant additional emissions reduction.

 Any work practice or operational procedure that was not 

identified or considered during development of the 1997 Primary 

Aluminum Reduction Plant NESHAP.

 Any process change or pollution prevention alternative that 

could be broadly applied to the industry and that was not 

identified or considered during development of the 1997 Primary 

Aluminum Reduction Plant NESHAP.

We also consulted the EPA‘s RACT/BACT/LAER Clearinghouse (RBLC)

to identify potential technology advances. Control technologies 

classified as RACT (Reasonably Available Control Technology), BACT 

(Best Available Control Technology), or LAER (Lowest Achievable 

Emissions Rate) apply to stationary sources depending on whether the 

sources exist or new and on the size, age, and location of the 

facility. BACT and LAER (and sometimes RACT) are determined on a 
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case-by-case basis, usually by State or local permitting agencies. 

The EPA established the RBLC to provide a central database of air 

pollution technology information (including technologies required in 

source-specific permits) to promote the sharing of information among 

permitting agencies and to aid in identifying future possible control 

technology options that might apply broadly to numerous sources 

within a category or apply only on a source-by-source basis. The RBLC 

contains over 5,000 air pollution control permit determinations that 

can help identify appropriate technologies to mitigate many air 

pollutant emissions streams. We searched this database to determine 

whether it contained any practices, processes, or control 

technologies for the types of processes covered by the Primary 

Aluminum Reduction Plant NESHAP. No such practices, processes, or 

control technologies were identified in this database.

E. What other issues are we addressing in this proposal?

In addition to the analyses described above, we also reviewed 

other aspects of the MACT standards for possible revision as 

appropriate and necessary. Based on this review we have identified 

aspects of the MACT standards that we believe need revision.

This includes proposing revisions to the startup, shutdown and 

malfunction (SSM) provisions of the MACT rule in order to ensure that 

they are consistent with a recent court decision in Sierra Club v. 

EPA, 551 F. 3d 1019 (D.C. Cir. 2008). In addition, we are proposing 

other changes to the rule which are not based on residual risk. These 
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include establishing MACT floor-based standards for POM emissions 

from prebake potlines, COS emissions from all potlines, and design 

standards for control of POM emissions from existing pitch storage 

tanks. We are also proposing changes to the rule related to 

affirmative defense for exceedance of an emission limit during a 

malfunction. The analyses and proposed decisions for these actions 

are presented in section IV of this preamble.

IV. Analytical Results and Proposed Decisions

This section of the preamble provides the results of our RTR for 

the Primary Aluminum Reduction Plant source category and our proposed 

decisions concerning changes to the Primary Aluminum Reduction Plant

NESHAP.

A. What are the results of our analyses and proposed decisions 

regarding unregulated emissions sources?

The current MACT rule has no standards for POM from prebake

potlines. Prebake facilities have significantly lower POM emissions

compared to Soderberg facilities. Nevertheless, these emissions are 

not negligible. We are proposing to establish MACT emission limits 

for POM from prebake potlines in this action. The typical controls 

used on these prebake potlines to limit the primary (i.e., stack) 

emissions, and which reflect the MACT floor level of control, are dry 

alumina scrubbers (with a baghouse). We calculated MACT floor limits 

for these potlines based on the limited available data. We also 

considered possible controls beyond the MACT floor, such as wet roof 
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scrubbers, but we estimated that these beyond-the-floor controls 

would only achieve approximately an additional 30 percent reduction 

in secondary (i.e., roof vent) emissions and that the costs of these 

additional controls would be quite high (e.g., well over $100 million 

in capital costs for the industry). We estimate that the cost of 

controlling POM from prebake potroom secondary emissions would be 

approximately $800,000 per ton. Therefore, we are proposing emission 

limits for POM from prebake potlines, after considering variability 

in emissions using a 99% upper prediction level approach, based on 

the MACT floor. We are proposing a POM emission limit for new prebake 

potlines equal to the lowest limit for existing prebake potlines 

(developed from data obtained from the best performing sources 

(center-worked prebake one) facilities). More details about the data 

and analyses used to derive the MACT limits, and explanation of the 

beyond-the-floor analyses, are provided in the technical document 

Draft MACT Floor Analysis for the Primary Aluminum Production Source 

Category which is available in the docket for this proposed action.

The proposed limits for prebake potlines are shown in Table 5.

Table 5. Proposed Emission Limits for New and Existing Prebake 

Potlines

Source Pollutant Emission Limit
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Existing Prebake

CWPB1 potlines

CWPB2 potlines

CWPB3 potlines

SWPB potlines

New Prebake

All prebake 

potline types

POM

POM

POM

POM

POM

0.310.33 kg/Mg (0.62(0.66 lb/ton) of aluminum 

produced

0.650.73 kg/Mg (1.3(1.45 lb/ton) of aluminum 

produced

0.63 0.73 kg/Mg (1.26(1.45 lb/ton) of 

aluminum produced

0.33 kg/Mg (0.65(0.66 lb/ton) of aluminum 

produced

0.310.32 kg/Mg (0.62 (0.63 lb/ton) of 

aluminum produced

As mentioned above, the current MACT rule has no standards for 

COS. It is very difficult and quite expensive to measure total COS 

emissions because the concentrations of secondary emissions are below 

the detection limit of the EPA reference method. However, stack tests 

are feasible and have been completed. Moreover, emissions studies 

have been completed using an experimental test method to estimate COS 

emissions from these secondary emissions sources (Determination of 

COS to SO2 Ratio in Smelting Process Emissions at the Alcoa Warrick 

Operations, 4 August 1995).. We have been able to use the 

experimental test results along with stack test data to estimate 

total COS emissions. Based on these studies and data on sulfur 

content of input materials to estimate total COS emissions. We, we

have determined that there is a direct relationship between the COS 

emissions and the sulfur content of raw materials. The results of 

these studies indicate that an estimated 8 percent of the sulfur 

Formatted: Line spacing: single
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present in the coke (used to make anodes) is converted to COS

emissions.

Given the technical difficulties of measuring secondaryfugitive

COS emissions directly, and given that there is a direct relationship 

between sulfur content of input materials and COS emissions, we 

developed a mass balance equation for calculating COS emissions. 

Using this approach, we developedcalculated a proposed MACT standard 

for COS usingvia the mass balance equation. The equation derives 

monthly COS emission rates based and available data on anode coke 

sulfur content, anode consumptionproduction and aluminum production, 

as follows: from each facility using the following equation:

 

 

 

 

 

 

 

Where:

ECOS = the facility wide emission rate of COS during the calendar 

month in pounds per ton of aluminum produced;

K = factor accounting for molecular weights and conversion of sulfur 

to carbonyl sulfide = 234;

Y = the tons of anode used at the facility during the calendar month;

Z = the tons of aluminum produced at the facility during the calendar 

month; and

%S = the weighted average sulfur content of the anode coke utilized 

in the production of aluminum during the calendar month (e.g., if the 
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weighted average sulfur content of the anode coke utilized during the 

calendar month was 2.5%, then %S = 0.025).

Using this method, we are proposing ahave determined that the

MACT floor limit for COS for existing facilities atis 3.9 pounds of 

COS per ton of aluminum produced (lb/ton Al), based on data obtained 

from the five facilities with the lowest calculated COS emissions and 

adjustment to account for variability using a 99% upper prediction 

limit approach.. With regard to costs for this standard, we estimate 

that all facilities will be able to meet this limit with minimal 

adjustments of their raw materials and with minimal additional costs

(e.g., calculating COS emissions and the associated monitoring, 

recordkeeping and reporting).. With regard to new sources, the MACT 

floor limit for COS for new facilities is proposed at 3.1 lb COS/ton 

Al, based on data obtained from the facility with the lowest 

calculated COS emissions and adjustment to account for variability.

We also considered beyond-the-floor options for COS. For 

example, we assessed the feasibility and costs of proposing that all 

existing facilities meet a limit of 3.1 lb COS/ton Al. We estimate 

that a limit at this level would impact 5 facilities, result in 220 

tpy reductions of COS emissions, at a total cost of $13,000,000 (or 

$2.6 million per facility) per year. However, there are significant 

uncertainties regarding the future availability and costs of the 

associatedrequired lower-sulfur anode coke. The Primary Aluminum 

industry obtains most of their coke as a by-product from the gas and 
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oil refinery industry. It is our understanding that currently 

available coke with low sulfur contents could be very hard to obtain 

in the future and will likely be much more expensive. This situation 

is expected due to the following: (1) the type of crude oil input at 

refineries in the future is generally expected to be heavier and, 

therefore, less likely to result in ―anode grade coke‖ that has the 

structure necessary for use in anode production; (2) the type of 

crude oil input at refineries in the future is generally expected to

have higher sulfur content because the per barrel cost of heavy sour 

(i.e., high-sulfur) crude oil is so much lower than light sweet 

(i.e., low-sulfur) crude oil; (3) refineries initially designed to 

process light sweet crude oil are being converted to process heavy 

sour crude oil at a rapid pace worldwide due to refinery economics; 

(4) refineries are designed to desulfurize the product streams 

(gasoline, diesel, etc.), not the crude oil input, and the sulfur in 

the crude oil tends to concentrate in the petroleum coke (i.e., the 

―bottoms‖); (5) unwillingness of refineries to preferentially process

light sweet crude oil in place of heavy sour crude oil due to 

unfavorable economics (i.e., refineries will not modify their 

operations to change the quality of a by-product such as petroleum 

coke); and (6) the lack of leverage that primary aluminum companies 

have over the quality of this by-product, as coke is a very low 

profit item for refineries and anode grade coke represents less than 

20% of all the petroleum coke produced worldwide. Thus, based on 
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future availability of low-sulfur coke, the true long term costs 

could exceed the present estimated cost of $13,000,000 per year.

We also evaluated the feasibility and costs of another beyondthe-floor option of requiringproposing that all existing facilities 

meet a limit of 3.5 lb COS/ton Al. We estimate that a limit at this 

level would impact 2 facilities, result in 52 tpy reductions of COS 

emissions, at a total cost of $2,000,000 (or $1 million per facility)

per year. Once again, these estimated costs could be significant 

underestimates of the true long-term costs. The uncertainties and 

concerns about the future availability and costs of the required lowsulfur content coke that are described above for the 3.1 lb COS/ton 

Al option are also a concern for this 3.5 lb COS/ton Al option.

We also considered control options including incineration and 

scrubbing of COS. The cost of incineration would be quite high due to 

the volume (typically millions of cubic feet per minute) and the 

relatively low temperature of the exhaust stream (typically less than 

200 °F). Incineration also involves the disadvantage of the generation 

of sulfur dioxide and other pollutants. Similarly, the cost of 

scrubbers would be quite high and involve the disadvantage of 

generating a waste sludge stream.

Given the analyses and conclusions described above, we are 

proposing a MACT standard for COS for existing facilities based on 

the MACT floor analysis, which is a limit of 3.9 lb COS/ton Al. With 
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regard to new sources, we are proposing a MACT standard for COS based 

on the MACT floor analysis, which is a limit of 3.1 lb COS/ton Al.

With regard to POM emissions from pitch storage tanks, the 1997 

NESHAP included MACT standards for new pitch storage tanks, which 

required a 95 percent reduction in POM emissions. However, the 1997 

NESHAP had no limits for existing storage tanks. We are proposing in 

today‘s action that existing tanks will be subject to the same 

standard (i.e., minimum of 95 percent reduction of POM emissions).

for these tanks. At least three facilities are currently achieving 

this level of control. We estimate that eight facilities would be 

affected by this standard and would need to add controls, at a total 

annualized cost of about $21,000 per facility.year. We also estimate 

that this would achieve 1.62.3 tons reductions in POM emissions per 

year.

A non-contact single stage, refrigerated, water cooled condenser 

system was considered as a beyond the floor option for POM from pitch 

storage tanks. However, we believe the associated cost (estimated at 

$184,000 per year, per facility) is not justified by the incremental 

control of HAP (estimated at 0.081 tons per year for the industry).

B. What are the results of the risk assessments?

For the Primary Aluminum source category, we conducted an 

inhalation risk assessment for all HAP emitted. We also conducted 

multi-pathway screening analyses for PB-HAP emitted (i.e., POM).

Results of the risk assessment are presented briefly below and in 
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more detail in the residual risk documentation referenced in section

III of this preamble, which is available in the docket for this 

action.

Table 6 of this preamble provides an overall summary of the 

results of the inhalation risk assessment.

Table 6. Primary Aluminum Reduction Plant Inhalation Risk Assessment 

Results

Maximum

Individual

Cancer Risk

(in 1 million)1

Estimated 

Population

at 

increased 

Risk of 

cancer ≥ 

1-in-1 

Million

Estimated 

Annual

Cancer

Incidence 

(cases 

per year)

Maximum

Chronic Non-cancer

TOSHI2

Worstcase 

Maximum 

Refined 

Screening

Acute 

Noncancer 

HQ3

Based on 

Actual 

Emissions 

Level

Based on 

Allowable 

Emissions 

Level4,5

Based on 

Actual 

Emissions 

Level

Based on 

Allowable 

Emissions 

Level

30 100 41,000 0.005 0.4 0.6

HQREL 10

(HF)

HQAEGL-1 4

(HF)

1 Estimated maximum individual excess lifetime cancer risk due to HAP emissions from 

the source category.

2 Maximum TOSHI. The target organ with the highest TOSHI for the primary aluminum 

source category is the skeletal system.

3 See section III.B of this preamble for explanations of acute dose-response values.

4 The facility with the highest MIR based on allowable emissions is the Columbia 

Falls facility. Notably, this facility has not operated in approximately 2 years 

and therefore, the EPA did not generate risk estimates (i.e., MIR, TOSHI, and acute 

screening values) based on actual emissions for this facility.

5 The highest MIR based on allowable emissions from an operating facility is 

estimated to be up to 50 in one million, for the operating Soderberg facility.

The results of the chronic inhalation cancer risk assessment 

indicate that, based on estimates of current actual emissions, the 

maximum individual lifetime cancer risk (MIR) could be up to 30 in

one million, with emissions of POM20 primarily from potline roof vents 

(secondary emissions) and anode bake furnaces driving these risks.

The highest MIR of up to 30 in one million based on actual emissions 

 

20 Most all POM emitted by this source category are PAHs.

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is due to POM emissions from the one currently operating Soderberg 

facility. The highest MIR due to actual emissions from prebake

facilities was estimated to be up to 20 in one million; the next 

highest MIR for an operating prebake facility is estimated to be up 

to 6 in one million.million. The total estimated cancer incidence 

from this source category based on actual emission levels is 0.005

excess cancer cases per year or one case in every 200 years, with 

emissions of POM contributing approximately 9990 percent to this 

cancer incidence. In addition, we note that approximately 41,000

people are estimated to have cancer risks greater than 1 in one

million, and approximately 900 people are estimated to have risks 

greater than 10 in one million. When considering the risks associated 

with MACT-allowable emissions, the MIR could be up to 100 in one

million if the Columbia Falls facility (a Soderberg type facility) 

were to resume its primary aluminum operations (see note 4 on Table 

6). The MIR based on allowable emissions from the one currently 

operating Soderberg facility (Massena East facility) was up to 50 in 

one million. The highest MIR based on allowable emissions from any of 

the prebake facilities was up to 30 in one million.

The maximum modeled chronic non-cancer TOSHI value is 0.4 based 

on actual emissions, driven primarily by HF emissions. When 

considering MACT allowable emissions, the maximum chronic non-cancer 

TOSHI value could be up to 0.6. For this source category, there were 

two HAP that had relevant acute health effect screening values: 
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carbonyl sulfide (COS) and hydrofluoric acid (HF). Acute health 

effect screening is performed using actual emissions data. The 

Columbia Falls facility has not operated in about 2 years and has not 

operated at capacity since about 1999. Therefore, suitable actual 

emission data was not available for this facility and its acute 

health effects are not included in this discussion. Further, the 

carbon-only prebake anode production facility does not emit COS or 

HF. Therefore, this discussion addresses the acute health effects of 

only the 13 remaining facilities subject to this NESHAP. With respect 

to COS, we did not find any potential for acute health concerns for 

the 13 facilities based on their actual emissions. However, HF

emissions did not screen out with respect to potential acute health 

effects. The highest refined worst-case HQ for HF based on a REL is 

10, based on an AEGL-1 is 4, and based on an ERPG-1 is 2. Moreover, 8 

of the 13 facilities show the potential for worst-case acute HQ 

values greater than 1 based on the REL, 46 of the 13 facilities show 

the potential for worst-case acute HQ values greater than or equal to

1 based on the AEGL-1 and 4 of the 13 facilities show the potential 

for worst-case acute HQ values greater than or equal to 1 based on 

the ERPG-1.21 Nevertheless, it is important to note that all the 

 

21 Individual facility acute HQ values for all facilities can be found in 

Appendix 5, Table 4, of the risk assessment document that is included in the 

docket for this proposed rulemaking. Acute HQ values exceeding a value of 1 

based on the REL were as follows: 10, 10, 9, 9, 5, 3, 2 and 2. Acute HQ 

values greater than a value of 1 based on the AEGL-1 were as follows: 4, 4, 

3 and 3. Acute HQ values greater than or equal to a value of 1 based on the 

ERPG-1 were as follows: 2, 2, 1 and 1.
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worst-case acute HQs are based on conservative assumptions (e.g., 

worst-case meteorology coinciding with peak short-term one-hour 

emissions from each emission point, with a person located at the 

point of maximum concentration during that hour).

In addition to the analyses presented above, to screen for 

potential multi-pathway effects from emissions of POM, we compared 

the estimated actual PAH emission rates from 14 facilities in this 

source category to the multi-pathway screening rate for PAHs 

described in section III.B. Results of this worst-case screen

estimate that actual PAH emissions from all 14 facilities exceed the 

PAH multi-pathway screening rate. With respect to these exceedances 

of the worst-case multi-pathway screening rate for PAHs, we note that 

this only indicates the potential for multi-pathway-related cancer 

risks of concern from PAHs. Moreover, due to data limitations, we 

were not able to refine our multi-pathway analysis beyond the worstcase screening assessment. Thus, we note that these results are 

biased high for purposes of screening and are subject to significant 

uncertainties. As such, they do not necessarily indicate that multipathway risks from POM are significant, only that we cannot rule out 

the possibility that they might be significant.

C. What are our proposed decisions regarding risk acceptability and 

ample margin of safety?

1. Risk acceptability
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As noted in section III.C of this preamble, we weigh all health 

risk factors in our risk acceptability determination, including the 

MIR, the numbers of persons in various risk ranges, cancer incidence, 

the maximum noncancer HI, the maximum acute noncancer hazard, the 

extent of noncancer risks, the potential for adverse environmental 

effects, distribution of risks in the exposed population, and risk 

estimation uncertainties (54 FR 38044, September 14, 1989).

For the Primary Aluminum Reduction source category, the risk 

analysis we performed indicates that the cancer risk to the 

individual most exposed due to actual emissions is well below 100 in

one million, and the cancer incidence is low (1 case in every 200 

years). The potential risks due to allowable emissions are higher 

with an estimated MIR of up to 100 in one million which is the 

presumptive upper limit of acceptable risk.

With regard to noncancer risks, the analysis indicates that

chronic noncancer health risks are negligible due to both actual and 

allowable emissions. The assessment of potential acute noncancer 

effects (described in the previous section) suggests that there may 

be potential for some acute risks due to HF emissions with worst-case 

HQs up to 10 (based on the REL). In characterizing the potential for 

acute noncancer impacts of concern, it is important to remember the 

upward bias of these worst-case exposure estimates and to consider 

the results along with the rather large uncertainties related to the 

emissions estimates and screening methodology.
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With regard to multi-pathway exposures and risks, results of the 

screening analysis indicate that actual PAH emissions from all the 

facilities exceed the worst-case multi-pathway screening rate for 

PAHs, indicating the potential for possible multi-pathway-related 

cancer risks of concern from PAHs. We note that these screening 

results do not necessarily indicate that significant multi-pathway 

risks actually exist at primary aluminum facilities, only that we 

cannot rule them out as a possibility.

Overall, in determining whether risk is acceptable, we 

considered all the available health risk information, as described 

above. In this case, because the MIRs due to actual emissions are 

well below 100-in-1 million risk, and since the one facility that 

could pose possible risks due to allowable emissions of up to 100 in

one million is not operating, and because a number of other factors 

indicate relatively low risk concern (e.g., low cancer incidence and 

low potential for chronic noncancer risks), and given the 

conservative, worst-case screening level characteristics of the acute 

and multi-pathway assessments, and various uncertainties, we are 

proposing to determine that the risks due to HAP emissions from this 

source category are acceptable.

2. Ample margin of safety analysis

We next considered whether the existing MACT standard provides 

an ample margin of safety (AMOS). Under the ample margin of safety 

analysis, we evaluate the cost and feasibility of available control 
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technologies and other measures (including the controls, measures and 

costs reviewed under the technology review) that could be applied in 

this source category to further reduce the risks (or potential risks) 

due to emissions of HAP identified in our risk assessment, along with 

all of the health risks and other health information considered in 

the risk acceptability determination described above. 

First, we evaluated the feasibility to reduce the potential 

risks due to allowable POM emissions from Soderberg facilities. As 

described above, the potential cancer MIR from Soderberg facilities 

is estimated to be up to 100 in one million due to allowable 

emissions. These risks are driven by POM emissions from a Soderberg 

facility within the vertical stud Soderberg (VSS2) subcategory. The 

current emissions limit (from the 2005 NESHAP amendments) for POM 

from potlines in this VSS2 subcategory is 2.85 kg of POM per Mg of 

Aluminum produced (2.85 kg/Mg, or 5.7 lbs/ton). Based on sitespecific emissions data submitted by the company in early 2008 for 

this facility, the estimated actual emissions from this facility were 

about 2 lbs/ton during the most recent years of operation (see 

Document EPA-HQ-OAR-2002-0031-0029, which is available in the docket 

for this rulemaking).

After considering variability in emissions, which is appropriate 

for establishing MACT limits (as described in section III.A above), 

we calculated, using a 99% upper prediction level approach, that an 

emissions limit of 3.8 lbs/ton could be achieved by this facility 
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without any additional controls and therefore no additional costs.

This would result in a reduction of approximately 33 percent for the

allowable emissions from VSS2 potlines, and would reduce the 

potential cancer MIR due to allowable emissions to about 70 in one 

million. We also evaluated potential controls to reduce these risks 

further (such as requiring wet roof scrubbers). We determined that 

these controls would be quite costly (approximately $4 million per 

ton of organic HAP), with estimated capital costs of about $40 

million for this one facility, and would only achieve about an 

additional 9.6 tons of HAP per year (30 percent) reduction in POM 

emissions. These controls and costs are described in more detail 

below.

We also evaluated the POM emissions from the one operating 

Soderberg facility (which is in the HSS subcategory) as part of our 

AMOS analyses. Based on the risk assessment, we estimated that this 

facility posed a cancer MIR of up to 30 in one million based on 

actual emissions and an MIR of up to 50 in one million based on 

allowable emissions. The current emissions limit for POM from 

potlines for this HSS subcategory is 2.35 kg/Mg (or 4.7 lbs/ton). 

Based on site specific emissions data for this facility, the actual 

emissions from this facility are estimated to be about 1.5 lbs/ton.

After considering variability in emissions, we determined that an 

emissions limit of 3.0 lbs/ton could be achieved by this facility 

with no additional controls and, therefore, no additional costs. This 
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would result in a reduction of approximately 36 percent for the 

allowable emissions from these HSS potlines, and would reduce the 

potential cancer MIR due to allowable emissions from this facility to 

about 30 in one million.

We identified wet roof scrubbers as one possible control 

technology that could be applied to further reduce allowable and 

actual emissions of POM from potlines, to reduce the cancer risks due 

to actual and allowable POM emissions, and to reduce the potential 

risks due to multi-pathway exposures to POM. One facility in the 

source category currently has this type of scrubber. These controls 

can also be used to reduce HF emissions and, thus, would reduce the 

potential for acute noncancer risks. However, the costs for these 

controls are high. For example, we estimate that the capital costs 

for the typical facility would be more than $40 million, with 

annualized costs of $13 million. Industry wide this would result in 

total capital costs of over $400 million, with estimated annualized 

costs of over $150 million. These controls would achieve reductions 

of secondary emissions of about 30 to 50 percent. Given the high 

costs (estimated at approximately $140,000 per ton of HAP) and 

relatively low emissions and risk reductions, we proposeconclude that 

it is not appropriate or necessary to establishpropose these 

additional controls under 112(f)(2). Therefore, based our AMOS 

analysis, we are proposing under section 112(f)(2) of the CAA to 

lower the POM emissions limit for VSS2 potlines from 5.7 to 3.8 
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lbs/ton and to lowerreduce the POM limit for HSS potlines from 4.7 to 

3.0 lbs/ton. Pursuant to CAA section 112(f)(4), we are proposing that 

these changes apply 90 days after the effective date of this 

rulemaking. We did not identify any other cost-effective controls to 

further reduce HAP emissions for this source category under the AMOS 

analyses.

In accordance with the approach established in the Benzene 

NESHAP, the EPA weighed all health risk measures and information 

considered in the risk acceptability determination, along with the 

costs and economic impacts of emissions controls, technological 

feasibility, uncertainties and other relevant factors in 

proposingmaking our ample margin of safety determination. Considering 

the health risk information and the costs of the options identified, 

we propose that the existing MACT standards, along with the proposed 

lower POM limits for potlines at Soderberg facilities (VSS2 and HSS 

subcategories) described above, will provide an ample margin of 

safety to protect public health.

Pursuant to CAA section 112(f)(4), we are proposing that these 

changes (i.e., lower emission limits for potlines at Soderberg 

facilities) apply 90 days after the effective date of this 

rulemaking. See CAA section 112(f)(4)(A).

Nevertheless, we solicit comment and information on the 

feasibility, costs and appropriateness of any additional controls or 
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options to further reduce the potential risks due to emissions of 

HAP, especially POM andor HF.

D. What are the results and proposed decisions based on our 

technology review?

As described above, dry alumina scrubbers (with baghouses) are 

the typical controls used to minimize primary emissions of HF and POM 

from the potlines. However, some facilities use wet scrubbers and 

ESPs to control these emissions. The MACT control technology 

typically used for anode bake furnaces is also a dry alumina 

scrubber, and a capture system vented to a dry coke scrubber is used 

for control of paste production plants. These facilities further 

reduce HAP emissions from anode bake furnaces by implementation of 

certain practices during periods of startup (e.g., development of an 

anode bake furnace startup schedule, operation of the associated 

control system(s) within normal parametric limits prior to the 

startup of the anode bake furnace). To further control potline 

secondary emissions, one facility has wet roof scrubbers to get 

additional control of HF and POM. As described in the AMOS section 

above, it would be quite costly to require wet roof scrubbers on 

other facilities.

Overall, based on our technology review, we determined that 

there have been no developments in practices, processes, and control 

technologies that would be considered feasible and cost-effective to 

apply to this source category since promulgation of the Primary 
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Aluminum Reduction Plant NESHAP, other than the anode bake furnace 

startup practices mentioned above. We propose to modify the MACT 

requirements for anode bake furnaces to include implementation of the 

startup practices mentioned above. Further, based on an analysis of 

recent emissions data, we believe that the practices, processes and 

control technologies currently in use by this source category allow 

for a reduction in the POM emission limits for Soderberg potlines 

(please refer to the ample margin of safety analysis in section

IV.C.2 of this preamble).

Additional details regarding these analyses can be found in the 

following technical document for this action which is available in 

the docket: Draft Technology Review for the Primary Aluminum 

Reduction Plant Source Category.

E. What other actions are we proposing?

1. Startup, shutdown and malfunctions

The United States Court of Appeals for the District of Columbia 

Circuit vacated portions of two provisions in the EPA‘s CAA section 

112 regulations governing the emissions of HAP during periods of 

startup, shutdown and malfunction (SSM). Sierra Club v. EPA, 551 F.3d 

1019 (D.C. Cir. 2008), cert. denied, 130 S. Ct. 1735 (U.S. 2010). 

Specifically, the Court vacated the SSM exemption contained in 40 CFR 

63.6(f)(1) and 40 CFR 63.6(h)(1), that are part of a regulation, 

commonly referred to as the ―General Provisions Rule,‖ that the EPA

promulgated under CAA section 112. When incorporated into CAA section 
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112(d) regulations for specific source categories, these two 

provisions exempt sources from the requirement to comply with the 

otherwise applicable CAA section 112(d) emissions standard during 

periods of SSM.

We are proposing the elimination of the SSM exemption in this 

rule. Consistent with Sierra Club v. EPA, the EPA is proposing 

standards in this rule that apply at all times. We are also proposing 

several revisions to Appendix A to subpart LL of part 63 (the General 

Provisions Applicability table). For example, we are proposing to 

eliminate the incorporation of the General Provisions‘ requirement 

that the source develop an SSM plan. We also are proposing to 

eliminate or revise certain recordkeeping and reporting requirements 

related to the SSM exemption. The EPA has attempted to ensure that we 

have not included in the proposed regulatory language any provisions 

that are inappropriate, unnecessary, or redundant in the absence of 

the SSM exemption. We are specifically seeking comment on whether 

there are any such provisions that we have inadvertently incorporated 

or overlooked.

In proposing the standards in this rule, the EPA has taken into 

account startup and shutdown periods and, for the reasons explained 

below, the EPA is proposing in some cases different standards for 

startup periods.

The 1997 MACT rule allowed for periods of up to six months for 

startup of existing potlines that had been previously shutdown. These 
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long startup periods for potlines are recognized as part of the 

normal operations during which emissions testing is not feasible. The 

current MACT emission limits are not applicable during these startup 

periods. Thus, we are proposing MACT standards for these periods in 

today‘s action. Given that it is economically and technically 

infeasible to measure emissions during these startup periods, we are 

proposing detailed work practice standards that will minimize HAP 

emissions and ensure proper operation of the processes and control 

equipment during startup periods. The proposed work practices include

bringing the potline scrubbers and exhaust fans on line prior to 

energizing the first cell being restarted, ensuring that the primary 

capture and control system is operating at all times during startup, 

and keeping pots covered during startup as much as practicable to 

include, but not limited to, minimizing the removal of covers or 

panels of the pots on which work is being performed. Moreover, 

facilities must inspect potlines daily during startup and perform 

additional work practices, including resealing pot crust as often and 

as soon as practicable, reducing cell temperatures to as low as 

practicable, and adjusting pot parameters to their optimum levels to 

include, but not limited to, the following parameters: alumina 

addition rate, exhaust air flow, cell voltage, feeding level, anode 

current, and liquid and solid bath levels.

The 1997 MACT rule allowed for startup periods for new or 

reconstructed anode bake furnaces and pitch storage tanks and for 
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anode bake furnaces that had been previously shutdown. Based on 

information received from industry, we believe that these sources can

comply with their MACT standards during startup periods. Therefore, 

we are removing the provisions for startup of anode bake furnaces and 

pitch storage tanks. However, we have added startupwork practices for 

anode bake furnace startup periods to help ensure that the standards 

will beare met. These startupwork practices will minimize HAP 

emissions and ensure proper operation of the processes and control 

equipment during startup periods (please refer to the discussion of 

the technology review in section IV.D of this preamble).

Shutdown emissions are not expected to be different from those 

during normal operation; therefore, no separate standard or work 

practice is warranted. We propose that the numerical MACT limits 

described in previous sections of this preamble (established for 

normal operations) will apply during shutdown periods. We also 

propose that the MACT limits for all other affected units besides 

potlines (bake furnaces, pitch tanks, and paste production plants) 

apply at all times, including during startups and shutdowns.

Information on periods of startup and shutdown received from the 

industry indicate that emissions during startup (except for potlines) 

and shutdown periods are no greater than emissions during normal 

operations. Therefore, the continued operation of the existing 

control devices and emission capture systems will, in conjunction 

with the detailed proposed startup practices and work practices 
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described above, be consistent with maximum achievable control 

technology and will be adequate, along with all the other standards 

described above, to ensure that risks will be acceptable and the rule 

will provide an ample margin of safety.

Periods of startup, normal operations, and shutdown are all 

predictable and routine aspects of a source‘s operations. However, by 

contrast, malfunction is defined as a ―sudden, infrequent, and not 

reasonably preventable failure of air pollution control and 

monitoring equipment, process equipment or a process to operate in a 

normal or usual manner * * *‖ (40 CFR 63.2). The EPA has determined 

that CAA section 112 does not require that emissions that occur 

during periods of malfunction be factored into development of CAA 

section 112 standards. Under CAA section 112, emissions standards for 

new sources must be no less stringent than the level ―achieved‖ by 

the best controlled similar source and for existing sources generally 

must be no less stringent than the average emissions limitation 

―achieved‖ by the best performing 12 percent of sources in the 

category. There is nothing in CAA section 112 that directs the agency 

to consider malfunctions in determining the level ―achieved‖ by the 

best performing or best controlled sources when setting emissions 

standards. Moreover, while the EPA accounts for variability in 

setting emissions standards consistent with the CAA section 112 case 

law, nothing in that case law requires the agency to consider 

malfunctions as part of that analysis. Section 112 of the CAA uses 
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the concept of ―best controlled‖ and ―best performing‖ unit in 

defining the level of stringency that CAA section 112 performance 

standards must meet. Applying the concept of ―best controlled‖ or 

―best performing‖ to a unit that is malfunctioning presents 

significant difficulties, as malfunctions are sudden and unexpected 

events.

Further, accounting for malfunctions would be difficult, if not 

impossible, given the myriad different types of malfunctions that can 

occur across all sources in the category and given the difficulties 

associated with predicting or accounting for the frequency, degree, 

and duration of various malfunctions that might occur. As such, the 

performance of units that are malfunctioning is not ―reasonably‖ 

foreseeable. See, e.g., Sierra Club v. EPA, 167 F. 3d 658, 662 (D.C.

Cir. 1999) (EPA typically has wide latitude in determining the extent 

of data-gathering necessary to solve a problem. We generally defer to 

an agency's decision to proceed on the basis of imperfect scientific 

information, rather than to "invest the resources to conduct the 

perfect study."). See also, Weyerhaeuser v. Costle, 590 F.2d 1011, 

1058 (D.C. Cir. 1978) (―In the nature of things, no general limit, 

individual permit, or even any upset provision can anticipate all 

upset situations. After a certain point, the transgression of 

regulatory limits caused by  ̳uncontrollable acts of third parties,‘ 

such as strikes, sabotage, operator intoxication or insanity, and a 

variety of other eventualities, must be a matter for the 

Formatted: No underline
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administrative exercise of case-by-case enforcement discretion, not 

for specification in advance by regulation‖). In addition, the goal 

of a best controlled or best performing source is to operate in such 

a way as to avoid malfunctions of the source, and accounting for 

malfunctions could lead to standards that are significantly less 

stringent than levels that are achieved by a well-performing nonmalfunctioning source. The EPA‘s approach to malfunctions is 

consistent with CAA section 112 and is a reasonable interpretation of 

the statute.

In the event that a source fails to comply with the applicable 

CAA section 112(d) standards as a result of a malfunction event, the 

EPA would determine an appropriate response based on, among other 

things, the good faith efforts of the source to minimize emissions 

during malfunction periods, including preventative and corrective 

actions, as well as root cause analyses to ascertain and rectify 

excess emissions. The EPA would also consider whether the source's 

failure to comply with the CAA section 112(d) standard was, in fact, 

―sudden, infrequent, not reasonably preventable‖ and was not instead 

―caused in part by poor maintenance or careless operation‖ 40 CFR 

63.2 (definition of malfunction).

Finally, the EPA recognizes that even equipment that is properly 

designed and maintained can sometimes fail and that such failure can 

sometimes cause an exceedance of the relevant emissions standard. 

(See, e.g., State Implementation Plans: Policy Regarding Excessive 
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Emissions During Malfunctions, Startup, and Shutdown (Sept. 20, 

1999); Policy on Excess Emissions During Startup, Shutdown, 

Maintenance, and Malfunctions (Feb. 15, 1983)). The EPA is therefore 

proposing to add to the final rule an affirmative defense to civil 

penalties for exceedances of emissions limits that are caused by 

malfunctions. See 40 CFR 63.842 (defining ―affirmative defense‖ to 

mean, in the context of an enforcement proceeding, a response or 

defense put forward by a defendant, regarding which the defendant has 

the burden of proof, and the merits of which are independently and 

objectively evaluated in a judicial or administrative proceeding). We 

also are proposing other regulatory provisions to specify the 

elements that are necessary to establish this affirmative defense; 

the source must prove by a preponderance of the evidence that it has 

met all of the elements set forth in 40 CFR 63.855 (see also 40 CFR 

22.24). The criteria ensure that the affirmative defense is available 

only where the event that causes an exceedance of the emissions limit 

meets the narrow definition of malfunction in 40 CFR 63.2 (sudden, 

infrequent, not reasonably preventable and not caused by poor 

maintenance and or careless operation). For example, to successfully 

assert the affirmative defense, the source must prove by a 

preponderance of the evidence that excess emissions ―[w]ere caused by 

a sudden, infrequent, and unavoidable failure of air pollution 

control and monitoring equipment, process equipment, or a process to 

operate in a normal or usual manner....‖ The criteria also are designed 
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to ensure that steps are taken to correct the malfunction, to 

minimize emissions in accordance with 40 CFR sections 63.843(f) and 

63.844(f) to prevent future malfunctions. For example, the source 

must prove by a preponderance of the evidence that ―[r]epairs were 

made as expeditiously as possible when the applicable emissions

limitations were being exceeded...‖ and that ―[a]ll possible steps were 

taken to minimize the impact of the excess emissions on ambient air 

quality, the environment and human health....‖ In any judicial or 

administrative proceeding, the Administrator may challenge the 

assertion of the affirmative defense and, if the respondent has not 

met its burden of proving all of the requirements in the affirmative 

defense, appropriate penalties may be assessed in accordance with CAA 

section 113 (see also 40 CFR 22.27).

The EPA included an affirmative defense in the proposed rule in 

an attempt to balance a tension, inherent in many types of air 

regulation, to ensure adequate compliance while simultaneously 

recognizing that despite the most diligent of efforts, emission 

limits may be exceeded under circumstances beyond the control of the 

source. The EPA must establish emission standards that ―limit the 

quantity, rate, or concentration of emissions of air pollutants on a 

continuous basis.‖ 42 U.S.C. §7602(k)(defining ―emission limitation 

and emission standard‖). See generally Sierra Club v. EPA, 551 F.3d 

1019, 1021 (D.C. Cir. 2008) Thus, the EPA is required to ensure that 

section 112 emissions limitations are continuous. The affirmative 
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defense for malfunction events meets this requirement by ensuring 

that even where there is a malfunction, the emission limitation is 

still enforceable through injunctive relief. While ―continuous‖ 

limitations, on the one hand, are required, there is also case law 

indicating that in many situations it is appropriate for EPA to 

account for the practical realities of technology. For example, in 

Essex Chemical v. Ruckelshaus, 486 F.2d 427, 433 (D.C. Cir. 1973), 

the D.C. Circuit acknowledged that in setting standards under CAA 

section 111 ―variant provisions‖ such as provisions allowing for 

upsets during startup, shutdown and equipment malfunction ―appear 

necessary to preserve the reasonableness of the standards as a whole 

and that the record does not support the  ̳never to be exceeded‘ 

standard currently in force.‖ See also, Portland Cement Association 

v. Ruckelshaus, 486 F.2d 375 (D.C. Cir. 1973). Though intervening 

case law such as Sierra Club v. EPA and the CAA 1977 amendments 

undermine the relevance of these cases today, they support the EPA‘s 

view that a system that incorporates some level of flexibility is 

reasonable. The affirmative defense simply provides for a defense to 

civil penalties for excess emissions that are proven to be beyond the 

control of the source. By incorporating an affirmative defense, the 

EPA has formalized its approach to upset events. In a Clean Water Act 

setting, the Ninth Circuit required this type of formalized approach 

when regulating ―upsets beyond the control of the permit holder.‖ 

Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 (9th Cir. 1977). But 

see, Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 
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1978) (holding that an informal approach is adequate). The 

affirmative defense provisions give the EPA the flexibility to both 

ensure that its emission limitations are ―continuous‖ as required by 

42 U.S.C. § 7602(k), and account for unplanned upsets and thus 

support the reasonableness of the standard as a whole.

Specifically, we are proposing the following rule changes:

 Add general duty requirements in 40 CFR sections 63.843 and 

63.844 to replace General Provision requirements that reference 

vacated SSM provisions.

 Add replacement language that eliminates the reference to SSM 

exemptions applicable to performance tests in 40 CFR section 

63.847(d).

 Add paragraphs in 40 CFR section 63.850(d) requiring the 

reporting of malfunctions as part of the affirmative defense 

provisions.

 Add paragraphs in 40 CFR section 63.850(e) requiring the keeping 

of certain records during malfunctions as part of the 

affirmative defense provisions.

 Revise Appendix A to subpart LL of part 63 to reflect changes in 

the applicability of the General Provisions to this subpart 

resulting from a court vacatur of certain SSM requirements in 

the General Provisions.

2. Electronic reporting.
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The EPA must have performance test data to conduct effective 

reviews of CAA sections 112 and 129 standards, as well as for many 

other purposes including compliance determinations, emissions factor 

development, and annual emissions rate determinations. In conducting 

these required reviews, the EPA has found it ineffective and time 

consuming, not only for us, but also for regulatory agencies and 

source owners and operators, to locate, collect, and submit 

performance test data because of varied locations for data storage 

and varied data storage methods. In recent years, though, stack 

testing firms have typically collected performance test data in 

electronic format, making it possible to move to an electronic data 

submittal system that would increase the ease and efficiency of data 

submittal and improve data accessibility.

Through this proposal the EPA is presenting a step to increase 

the ease and efficiency of data submittal and improve data 

accessibility. Specifically, the EPA is proposing that owners and 

operators of Primary Aluminum Reduction Plant facilities submit 

electronic copies of required performance test reports to the EPA‘s

WebFIRE database. The WebFIRE database was constructed to store 

performance test data for use in developing emissions factors. A 

description of the WebFIRE database is available at 

http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main.

As proposed above, data entry would be through an electronic 

emissions test report structure called the Electronic Reporting Tool. 
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The ERT would be able to transmit the electronic report through the 

EPA‘s Central Data Exchange network for storage in the WebFIRE 

database making submittal of data very straightforward and easy. A 

description of the ERT can be found at 

http://www.epa.gov/ttn/chief/ert/ert_tool.html.

The proposal to submit performance test data electronically to 

the EPA would apply only to those performance tests conducted using 

test methods that will be supported by the ERT. The ERT contains a 

specific electronic data entry form for most of the commonly used EPA

reference methods. A listing of the pollutants and test methods 

supported by the ERT is available at 

http://www.epa.gov/ttn/chief/ert/ert_tool.html. We believe that 

industry would benefit from this proposed approach to electronic data 

submittal. Having these data, the EPA would be able to develop 

improved emissions factors, make fewer information requests, and 

promulgate better informed regulations.

One major advantage of the proposed submittal of performance 

test data through the ERT is a standardized method to compile and 

store much of the documentation required to be reported by this rule. 

Another advantage is that the ERT clearly states what testing 

information would be required. Another important proposed benefit of 

submitting these data to the EPA at the time the source test is 

conducted is that it should substantially reduce the effort involved 

in data collection activities in the future. When the EPA has 
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performance test data in hand, there will likely be fewer or less 

substantial data collection requests in conjunction with prospective 

required residual risk assessments or technology reviews. This would 

result in a reduced burden on both affected facilities (in terms of 

reduced manpower to respond to data collection requests) and the EPA

(in terms of preparing and distributing data collection requests and 

assessing the results).

State, local, and tribal agencies could also benefit from more 

streamlined and accurate review of electronic data submitted to them. 

The ERT would allow for an electronic review process rather than a 

manual data assessment making review and evaluation of the source 

provided data and calculations easier and more efficient. Finally, 

another benefit of the proposed data submittal to WebFIRE 

electronically is that these data would greatly improve the overall 

quality of existing and new emissions factors by supplementing the 

pool of emissions test data for establishing emissions factors and by 

ensuring that the factors are more representative of current industry 

operational procedures. A common complaint heard from industry and 

regulators is that emissions factors are outdated or not 

representative of a particular source category. With timely receipt 

and incorporation of data from most performance tests, the EPA would 

be able to ensure that emissions factors, when updated, represent the 

most current range of operational practices. In summary, in addition 

to supporting regulation development, control strategy development, 
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and other air pollution control activities, having an electronic 

database populated with performance test data would save industry, 

state, local, tribal agencies, and the EPA significant time, money, 

and effort while also improving the quality of emissions inventories 

and, as a result, air quality regulations.

Records must be maintained in a form suitable and readily 

available for expeditious review, according to 63.10(b)(1). 

Electronic recordkeeping and reporting is available for many records, 

and is the form considered most suitable for expeditious review if 

available. Electronic recordkeeping and reporting is encouraged in 

this proposal and some records and reports are required to be kept in 

electronic format.

F. Compliance dates

We are proposing that existing facilities must comply with the 

proposed revised emissions limits for Soderberg potlines (which are 

being proposed under CAA sections 112(f)(2) for all affected 

sources), no later than 90 days after the date of publication of the 

final rule. We are proposing that existing facilities must comply 

with all other changes proposed in this action (other than 

affirmative defense provisions and electronic reporting which are 

effective upon promulgation of the final rule) no later than 3 years 

after the date of publication of the final rule. All new or 

reconstructed facilities must comply with all requirements in this 

rule upon startup.
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V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

The affected sources are new and existing potlines, new and 

existing pitch storage tanks, new and existing anode bake furnaces

(except for one that is located at a facility that only produces 

anodes for use off-site), and new and existing paste production 

plants.

B. What are the air quality impacts?

The proposed rule will require the POM emissions from existing

uncontrolled pitch storage tanks to be reduced by a minimum of 95 

percent. This is estimated to result in a reduction of 1.62.3 tons

per year (tpy) of POM. In addition, the proposed lower Soderberg 

potline POM limits would reduce POM emissions from the two Soderberg 

facilities, assuming production at plant capacity, by approximately 

300 tpy, combined.

C. What are the cost impacts?

Under the proposed amendments, 8 facilities would be required to 

install or upgrade, and operate emissions control systems (such as 

activated carbon adsorbers or condensers) to control emissions of HAP

from pitch storage tanks at total estimated cost of $167,832 per 

year, or $20,979 per facility. In addition, 12 facilities will have 

to conduct periodic performance tests for POM emissions from 45 

prebake potlines at an estimated total cost of $90,000 per year for 
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the source category, or $7,500 per year per facility. The total 

estimated cost of the rule is $258,000 per year.

D. What are the economic impacts?

We performed an economic impact analysis for the proposed 

modifications in this rulemaking. That analysis estimates total 

annualized costs of approximately $257,832 at 13 facilities and cost 

to revenue of less than 0.02% for the Primary Aluminum Production 

source category. For more information, please refer to the Draft 

Economic Impact Analysis for this proposed rulemaking that is 

available in the public docket for this proposed rulemaking.

E. What are the benefits?

This proposed rule will achieve about 1.62.3 tons per year 

reductions in POM emissions, which may result in a slight health 

benefit.emissions. The proposed limits of 3.9 pounds of COS per ton 

of aluminum produced (lb COS/ton Al) for existing facilities and 3.1 

lb COS/ton Al for new facilities will prevent increases in COS 

emissions and prevent increases in SO2 emissions as a co-benefit. The 

proposed COS standard will likely result in the use of lower sulfur 

content coke in the anode production processes. This reduction in 

anode coke sulfur content would result in decreases in emissions of 

both COS and sulfur dioxide (SO2). We estimate that SO2 emissions will 

decrease by 12 tons for each ton of COS reduction.

VI. Request for Comments
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We are soliciting comments on all aspects of this proposed 

action. In addition to general comments on this proposed action, we 

are also interested in any additional data that may help to reduce 

the uncertainties inherent in the risk assessments and other 

analyses. We are specifically interested in receiving corrections to 

the site-specific emissions profiles used for risk modeling. Such 

data should include supporting documentation in sufficient detail to 

allow characterization of the quality and representativeness of the 

data or information. Section VII of this preamble provides more 

information on submitting data.

VII. Submitting Data Corrections

The site-specific emissions profiles used in the source category 

risk and demographic analyses are available for download on the RTR 

web page at: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The data 

files include detailed information for each HAP emissions release 

point for the facility included in the source category.

If you believe that the data are not representative or are 

inaccurate, please identify the data in question, provide your reason 

for concern, and provide any ―improved‖ data that you have, if 

available. When you submit data, we request that you provide 

documentation of the basis for the revised values to support your 

suggested changes. To submit comments on the data downloaded from the 

RTR Web page, complete the following steps:
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1. Within this downloaded file, enter suggested revisions to the 

data fields appropriate for that information. The data fields that 

may be revised include the following:

Data Element Definition

Control Measure Are control measures in place? (yes or no)

Control Measure Comment Select control measure from list provided, 

and briefly describe the control measure

Delete Indicate here if the facility or record 

should be deleted

Delete Comment Describes the reason for deletion

Emissions Calculation 

Method Code For Revised 

Emissions

Code description of the method used to 

derive emissions. For example, CEM, 

material balance, stack test, etc.

Emissions Process Group

Enter the general type of emissions process 

associated with the specified emissions 

point

Fugitive Angle

Enter release angle (clockwise from true 

North); orientation of the y-dimension 

relative to true North, measured positive 

for clockwise starting at 0 degrees 

(maximum 89 degrees)

Fugitive Length

Enter dimension of the source in the eastwest (x-) direction, commonly referred to 

as length (ft)

Fugitive Width

Enter dimension of the source in the northsouth (y-) direction, commonly referred to 

as width (ft)

Malfunction Emissions Enter total annual emissions due to 

malfunctions (tpy)

Malfunction Emissions Max 

Hourly

Enter maximum hourly malfunction emissions 

here (lb/hr)

North American Datum

Enter datum for latitude/longitude 

coordinates (NAD27 or NAD83); if left 

blank, NAD83 is assumed

Process Comment Enter general comments about process 

sources of emissions

REVISED Address Enter revised physical street address for 

MACT facility here

REVISED City Enter revised city name here

REVISED County Name Enter revised county name here

REVISED Emissions Release 

Point Type

Enter revised Emissions Release Point Type 

here

REVISED End Date Enter revised End Date here

REVISED Exit Gas Flow 

Rate

Enter revised Exit Gas Flowrate here 

(ft3/sec)
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Data Element Definition

REVISED Exit Gas 

Temperature Enter revised Exit Gas Temperature here (F)

REVISED Exit Gas Velocity Enter revised Exit Gas Velocity here 

(ft/sec)

REVISED Facility Category 

Code

Enter revised Facility Category Code here, 

which indicates whether facility is a major 

or area source

REVISED Facility Name Enter revised Facility Name here

REVISED Facility Registry 

Identifier

Enter revised Facility Registry Identifier 

here, which is an ID assigned by the EPA 

Facility Registry System

REVISED HAP Emissions 

Performance Level Code

Enter revised HAP Emissions Performance 

Level here

REVISED Latitude Enter revised Latitude here (decimal 

degrees)

REVISED Longitude Enter revised Longitude here (decimal 

degrees)

REVISED MACT Code Enter revised MACT Code here

REVISED Pollutant Code Enter revised Pollutant Code here

REVISED Routine Emissions Enter revised routine emissions value here 

(tpy)

REVISED SCC Code Enter revised SCC Code here

REVISED Stack Diameter Enter revised Stack Diameter here (ft)

REVISED Stack Height Enter revised Stack Height here (ft)

REVISED Start Date Enter revised Start Date here

REVISED State Enter revised State here

REVISED Tribal Code Enter revised Tribal Code here

REVISED Zip Code Enter revised Zip Code here

Shutdown Emissions Enter total annual emissions due to 

shutdown events (tpy)

Shutdown Emissions Max 

Hourly

Enter maximum hourly shutdown emissions 

here (lb/hr)

Stack Comment Enter general comments about emissions 

release points

Startup Emissions Enter total annual emissions due to startup 

events (tpy)

Startup Emissions Max 

Hourly

Enter maximum hourly startup emissions here 

(lb/hr)

Year Closed Enter date facility stopped operations

2. Fill in the commenter information fields for each suggested 

revision (i.e., commenter name, commenter organization, commenter 

email address, commenter phone number, and revision comments).
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3. Gather documentation for any suggested emissions revisions 

(e.g., performance test reports, material balance calculations).

4. Send the entire downloaded file with suggested revisions in 

Microsoft® Access format and all accompanying documentation to Docket 

ID Number EPA-HQ-OAR-2011-0797 (through one of the methods described 

in the ADDRESSES section of this preamble). To expedite review of the 

revisions, it would also be helpful if you submitted a copy of your 

revisions to the EPA directly at RTR@epa.gov in addition to 

submitting them to the docket.

5. If you are providing comments on a facility, you need only 

submit one file for that facility, which should contain all suggested 

changes for all sources at that facility. We request that all data 

revision comments be submitted in the form of updated Microsoft® 

Access files, which are provided on the RTR Web Page at: 

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.

VIII. Statutory and Executive Order Reviews

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 because it raises novel 

legal and policy issues. Accordingly, the 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 
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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 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 the EPA has 

been assigned the EPA ICR number 2447.01. The information collection 

requirements are not enforceable until OMB approves them. The 

information requirements are based on notification, recordkeeping, 

and reporting requirements in the NESHAP General Provisions (40 CFR 

part 63, subpart A), which are mandatory for all operators subject to 

national emissions standards. These recordkeeping and reporting 

requirements are specifically authorized by CAA section 114 (42 

U.S.C. 7414). All information submitted to the EPA pursuant to the 

recordkeeping and reporting requirements for which a claim of 

confidentiality is made is safeguarded according to agency policies 

set forth in 40 CFR part 2, subpart B.

We are proposing new paperwork requirements forto the Primary

Aluminum Reduction Plant source category in the form of a one-time 

requirement to prepare design specifications for existing pitch 

storage tank controls, and submissions of test reports and 

calculations for demonstration of compliance with prebake potline POM 

limits.
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For this proposed rule, the EPA is adding affirmative defense to 

the estimate of burden in the ICR. To provide the public with an 

estimate of the relative magnitude of the burden associated with an 

assertion of the affirmative defense position adopted by a source, 

the EPA has provided administrative adjustments to this ICR to show 

what the notification, recordkeeping and reporting requirements 

associated with the assertion of the affirmative defense might 

entail. The EPA‘s estimate for the required notification, reports and 

records for any individual incident, including the root cause 

analysis, totals $3,141 and is based on the time and effort required 

of a source to review relevant data, interview plant employees, and 

document the events surrounding a malfunction that has caused an 

exceedance of an emissions limit. The estimate also includes time to 

produce and retain the record and reports for submission to the EPA. 

The EPA provides this illustrative estimate of this burden because 

these costs are only incurred if there has been a violation and a 

source chooses to take advantage of the affirmative defense.

Given the variety of circumstances under which malfunctions 

could occur, as well as differences among sources' operation and 

maintenance practices, we cannot reliably predict the severity and 

frequency of malfunction-related excess emissions events for a 

particular source. It is important to note that the EPA has no basis 

currently for estimating the number of malfunctions that would 

qualify for an affirmative defense. Current historical records would 
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be an inappropriate basis, as source owners or operators previously 

operated their facilities in recognition that they were exempt from 

the requirement to comply with emissions standards during 

malfunctions. Of the number of excess emissions events reported by 

source operators, only a small number would be expected to result 

from a malfunction (based on the definition above), and only a subset 

of excess emissions caused by malfunctions would result in the source 

choosing to assert the affirmative defense. Thus we believe the 

number of instances in which source operators might be expected to 

avail themselves of the affirmative defense will be extremely small.

With respect to the Primary Aluminum Production source category, 

the emissions controls are operational before the associated emission 

source(s) commence operation and remain operational until after the 

associated emission source(s) cease operation. Also, production 

operations would not proceed or continue if there is a malfunction of 

a control device and the time required to shut down production 

operations (i.e., on the order of a day) is small compared to the 

averaging time of the emission standards (i.e., monthly, quarterly 

and annual averages). Thus, we believe it is unlikely that a control 

device malfunction would cause an exceedance of any emission limit. 

Therefore, sources within this source category are not expected to 

have any need or use for the affirmative defense and we believe that 

there is no burden to the industry for the affirmative defense 

provisions in the proposed rule.
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We expect to gather information on such events in the future and 

will revise this estimate as better information becomes available. We 

estimate 15 regulated entities are currently subject to subpart LL 

and will be subject to all proposed standards. The annual monitoring, 

reporting, and recordkeeping burden for this collection (averaged 

over the first 3 years after the effective date of the standards) for 

these amendments to subpart LL is estimated to be $148,000 per year. 

This includes 1,558 labor hours per year at a total labor cost of 

$148,000 per year, and total non-labor capital and operation and 

maintenance (O&M) costs of $500 per year. This estimate includes 

performance tests, notifications, reporting, and recordkeeping 

associated with the new requirements for existing pitch storage tanks 

and new and existing potlines. The total burden for the Federal 

government (averaged over the first 3 years after the effective date 

of the standard) is estimated to be 120 hours per year at a total 

labor cost of $11,400 per year. Burden is defined at 5 CFR 1320.3(b).

An agency may not conduct or sponsor, and a person is not 

required to respond to, a collection of information unless it 

displays a currently valid OMB control number. The OMB control 

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

9. When these ICRs are approved by OMB, the agency will publish a 

technical amendment to 40 CFR part 9 in the Federal Register to 

display the OMB control numbers for the approved information 

collection requirements contained in the final rules.
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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, the EPA has established a public 

docket for this rule, which includes this ICR, under Docket ID number 

EPA-HQ-OAR-2011-0797. Submit any comments related to the ICR to the 

EPA and OMB. See the ADDRESSES section at the beginning of this 

notice for where to submit comments to the 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 the EPA. Since OMB is required to make a 

decision concerning the ICR between 30 and 60 days after [INSERT THE 

DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL REGISTER], a 

comment to OMB is best assured of having its full effect if OMB 

receives it by [INSERT THE DATE 30 DAYS AFTER THE DATE OF 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.

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 
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small businesses, small organizations, and small governmental 

jurisdictions.

For purposes of assessing the impacts of this proposed rule on 

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

defined by the Small Business Administration‘s (SBA) regulations at 

13 CFR 121.201; (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 that is 

independently owned and operated and is not dominant in its field. 

For this source category, which has the NAICS code 331312, the SBA 

small business size standard is 1,000 employees according to the SBA 

small business standards definitions. There are no small entities 

subject to subpart LL.

After considering the economic impacts of today‘s 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 will not impose any requirements on 

small entities. We continue to be interested in the potential impacts 

of the proposed rule on small entities and welcome comment on issues 

related to such impacts.

D. Unfunded Mandates Reform Act.

This proposed rule does not contain a Federal mandate under the 

provisions of Title II of the Unfunded Mandates Reform Act of 1995 
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(UMRA), 2 U.S.C. 1531-1538 for State, local, or tribal governments or 

the private sector. The proposed rule would not result in 

expenditures of $100 million or more for State, local, and tribal 

governments, in aggregate, or the private sector in any 1 year. The 

proposed rule imposes no enforceable duties on any State, local or 

tribal governments or the private sector. Thus, this proposed rule is 

not subject to the requirements of sections 202 or 205 of the UMRA.

This proposed 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 or operated by State 

governments, and, because no new requirements are being promulgated, 

nothing in this 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 the 

EPA policy to promote communications between the EPA and State and 
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local governments, the EPA specifically solicits comment on this 

proposed rule from State and local officials.

F. Executive Order 13175: Consultation and Coordination with Indian 

Tribal Governments.

This proposed rule does not have tribal implications, as 

specified in Executive Order 13175 (65 FR 67249, November 9, 2000). 

None of the provisions of this proposed rule will result in increased

emissions of any hazardous air pollutant from any facility. The more 

stringent limitations of POM emissions from horizontal stud Soderberg 

potlines may result in decreased risk to Indian tribal populations.

Thus, Executive Order 13175 does not apply to this action.

The 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.

This proposed rule is not subject to Executive Order 13045 (62 FR 

19885, April 23, 1997) because it is not economically significant as 

defined in Executive Order 12866. Moreover, the agency does not 

believe the environmental health risks or safety risks addressed by 

this action present a disproportionate risk to children.

Nevertheless, the public is invited to submit comments or identify 

peer-reviewed studies and data that assess effects of early life 

exposure to HAP from Primary Aluminum sources. The EPA will typically 
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accord greater weight to studies and data that have been peer 

reviewed.

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 

under Executive Order 13211, ―Actions Concerning Regulations That 

Significantly Affect Energy Supply, Distribution, or Use‖ (66 FR 

28355, May 22, 2001), because it is not likely to have significant 

adverse effect on the supply, distribution, or use of energy. This 

action will not create any new requirements and therefore no 

additional costs for sources in the energy supply, distribution, or 

use sectors.

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 (15 U.S.C. 

272 note), directs the EPA to use voluntary consensus standards (VCS) 

in its regulatory activities unless to do so would be inconsistent 

with applicable law or otherwise impractical. VCS 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 the EPA to 

provide Congress, through OMB, explanations when the agency decides 

not to use available and applicable VCS.
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This proposed rulemaking involves technical standards. The EPA 

proposes to use ASTM D3177-02 (2007) Standard Test Methods for Total 

Sulfur in the Analysis Sample of Coal and Coke. This is a voluntary 

consensus method. This method can be obtained from the American 

Society for Testing and Materials, 100 Bar HarborHarbour Drive, West 

Conshohocken, Pennsylvania 19428 (telephone number (610) 832-9500). 

This method was proposed because it is commonly used by primary 

aluminum reduction facilities to demonstrate compliance with sulfur 

dioxide emission limitations imposed in their current Title V 

permits. The EPA welcomes comments on this aspect of this proposed 

rulemaking and, specifically, invites the public to identify 

potentially-applicable voluntary consensus standards and to explain 

why such standards should be used in this regulation.

J. Executive Order 12898: Federal Actions to Address Environmental 

Justice in Minority Populations and Low-Income Populations.

Executive Order 12898 (59 FR 7629, February 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.
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For the primary aluminum source category, EPA has determined 

that the current health risks posed to anyone by actual emissions 

from this source category are within the acceptable range, and that 

the proposed rulemaking will not appreciably reduce these risks 

further. As a result, this proposed rule will not have 

disproportionately high and adverse human health or environmental 

effects on minority or low-income populations.

To examine the potential for any environmental justice issues 

that might be associated with each source category, we evaluated the 

distributions of HAP-related cancer and non-cancer risks across 

different social, demographic, and economic groups within the 

populations living near the facilities where this source category is

located. The methods used to conduct demographic analyses for this 

rule are described in the document Draft Residual Risk Assessment for 

the Primary Aluminum Reduction Plant Source Category which may be 

found in the docket for this rulemaking. The development of 

demographic analyses to inform the consideration of environmental 

justice issues in the EPA rulemakings is an evolving science. The EPA 

offers the demographic analyses in today‘s proposed rulemaking as 

examples of how such analyses might be developed to inform such 

consideration, and invites public comment on the approaches used and 

the interpretations made from the results, with the hope that this 

will support the refinement and improve utility of such analyses.
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In the demographics analysis, we focused on populations within 

50 km of the facilities in this source category with emissions 

sources subject to the MACT standard. More specifically, for these 

populations we evaluated exposures to HAP that could result in cancer 

risks of 1 in one million or greater. We compared the percentages of 

particular demographic groups within the focused populations to the 

total percentages of those demographic groups nationwide. The results 

of this analysis are documented in the document Draft Residual Risk 

Assessment for the Primary Aluminum Reduction Plant Source Category

in the docket for this proposed rulemaking. Formatted: Font: Bold, Underline
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National Emission Standards for Hazardous Air Pollutants: Primary 

Aluminum Reduction Plants

List of Subjects in 40 CFR Part 63

Environmental protection, Air pollution control, Hazardous 

substances, Incorporation by reference, Reporting and recordkeeping 

requirements.

____________________________

Dated:

____________________________

Lisa P. Jackson,

Administrator.
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For the reasons stated in the preamble, part 63 of title 40, 

chapter I, of the Code of Federal Regulations is proposed to be 

amended as follows:

PART 63—[AMENDED]

1. The authority citation for part 63 continues to read as 

follows:

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

Subpart LL – [AMENDED]

2. Section 63.840 is amended by revising paragraph (a) to read 

as follows:

Section 63.840 Applicability

(a) Except as provided in paragraph (b) of this section, the 

requirements of this subpart apply to the owner or operator of each 

new or existing pitch storage tank, potline, paste production plant 

and anode bake furnace associated with primary aluminum production 

and located at a major source as defined in section 63.2.

3. Section 63.841 is amended by adding paragraph (a)(3) to read 

as follows:

Section 63.841 Incorporation by reference.

* * * * * 

(a) * * *

(3) ASTM D3177-02 (2007) Standard Test Methods for Total Sulfur 

in the Analysis Sample of Coal and Coke.

* * * * * 
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4. Section 63.842 is amended by removing the definition for 

―Vertical stud Soderberg one (VSS1)‖ and adding definitions for 

―affirmative defense‖ and ―startup of an anode bake furnace‖ to read 

as follows:

Section 63.842 Definitions.

* * * * * 

Affirmative defense means, in the context of an enforcement 

proceeding, a response or defense put forward by a defendant, 

regarding which the defendant has the burden of proof, and the merits 

of which are independently and objectively evaluated in a judicial or 

administrative proceeding.

* * * * *

Startup of an anode bake furnace means the process of initiating 

heating to the anode baking furnace where all sections of the furnace

have previously been at ambient temperature. The startup or re-start 

of the furnace begins when the heating begins. The startup or restart concludes at the start of the second anode bake cycle.when 

fires begin to move to additional furnaces.

* * * * *

5. Section 63.843 is amended by revising paragraphs (a)(1)(v) 

and (a)(2)(i) through (iii) and adding paragraphs (a)(2)(iv) through 

(a)(2)(vii), (d), (e), and (f) read as follows:

Section 63.843 Emission limits for existing sources.

* * * * *
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(a) * * *

(a)(1) Emissions of TF must not exceed:

* * * * *

(v) Reserved;

* * * * *

(a)(2) Emissions of POM must not exceed:

(i) 1.5 kg/Mg (3.0 lb/ton) of aluminum produced for each HSS 

potline;

(ii) Reserved;

(iii) 1.9 kg/Mg (3.8 lb/ton) of aluminum produced for each VSS2 

potline;

(iv) 0.310.33 kg/Mg (0.62(0.66 lb/ton) of aluminum produced for 

each existing CWPB1 prebake potline;

(v) 0.650.73 kg/Mg (1.3(1.45 lb/ton) of aluminum produced for 

each existing CWPB2 prebake potline;

(vi) 0.630.73 kg/Mg (1.26(1.45 lb/ton) of aluminum produced for 

each existing CWPB3 prebake potline;

(vii) 0.33 kg/Mg (0.65(0.66 lb/ton) of aluminum produced for 

each existing SWPB prebake potline;

* * * * *

(d) Pitch storage tanks. Each pitch storage tank shall be 

equipped with an emission control system designed and operated to 

reduce inlet emissions of POM by 95 percent or greater.
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(e) COS limit. Emissions of COS must not exceed 3.9 lb/ton of 

aluminum produced.

(f) At all times, the owner or operator must operate and 

maintain any affected source, including associated air pollution 

control equipment and monitoring equipment, in a manner consistent 

with safety and good air pollution control practices for minimizing 

emissions. Determination of whether such operation and maintenance 

procedures are being used will be based on information available to 

the Administrator which may include, but is not limited to, 

monitoring results, review of operation and maintenance procedures, 

review of operation and maintenance records, and inspection of the 

source.

6. Section 63.844 is amended by revising paragraph (a)(2) and 

adding paragraphs (a)(3), (e) and (f) to read as follows:

Section 63.844 Emission limits for new or reconstructed sources.

* * * * *

(a) * * *

(3)(2) POM limit. Emissions of POM from Soderberg and prebake 

potlines must not exceed 0.310.32 kg/Mg (0.62(0.63 lb/ton) of 

aluminum produced.

* * * * *

(e) COS limit. Emissions of COS must not exceed 3.1 lb/ton of 

aluminum produced.
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(f) At all times, the owner or operator must operate and 

maintain any affected source, including associated air pollution 

control equipment and monitoring equipment, in a manner consistent 

with safety and good air pollution control practices for minimizing 

emissions. Determination of whether such operation and maintenance 

procedures are being used will be based on information available to 

the Administrator which may include, but is not limited to, 

monitoring results, review of operation and maintenance procedures, 

review of operation and maintenance records, and inspection of the 

source.

7. Section 63.846 is amended by revising paragraphs (b) and (d) 

and adding paragraphs (e) and (f) to read as follows:

Section 63.846 Emission averaging.

* * * * *

(b) Soderberg Potlines. The owner or operator may average TF 

emissions from potlines and demonstrate compliance with the limits in 

Table 1 of this subpart using the procedures in paragraphs (b)(1) and 

(b)(2) of this section. The owner or operator also may average POM 

emissions from potlines and demonstrate compliance with the limits in 

Table 2 of this subpart using the procedures in paragraphs (b)(1) and 

(b)(3) of this section. * * *

(d) * * *

(2) * * *
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(iv) The test plan for the measurement of TF or POM emissions in 

accordance with the requirements in sections 63.847(b) and (k); * * *

(4) * * *

(ii) The inclusion of any emission source other than an existing 

potline or existing anode bake furnace or the inclusion of any 

potline or anode bake furnace not subject to the same operating 

permit; or

(iii) The inclusion of any potline or anode bake furnace while 

it is shut down, in the emission calculations.

(iv) Reserved.

* * * * *

(e) TF emissions from Prebake Potlines. The owner or operator 

may average TF emissions from potlines and demonstrate compliance 

with the limits in Table 1 of this subpart using the procedures in 

paragraphs (e)(1) and (e)(2) of this section.

(1) Monthly average emissions of TF must not exceed the 

applicable emission limit in Table 1 of this subpart. The emission 

rate must be calculated based on the total emissions from all 

potlines over the period divided by the quantity of aluminum produced 

during the period, from all potlines comprising the averaging group.

(2) To determine compliance with the applicable emission limit 

in Table 1 of this subpart for TF emissions, the owner or operator 

must determine the monthly average emissions (in lb/ton) from each 

potline from at least three runs per potline each month for TF 
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secondary emissions using the procedures and methods in sections

63.847 and 63.849. The owner or operator must combine the results of 

secondary TF monthly average emissions with the TF results for the 

primary control system and divide total emissions by total aluminum 

production.

(f) POM Emissions from Prebake Potlines. The owner or operator 

also may average POM emissions from potlines and demonstrate 

compliance with the limits in Table 2 of this subpart using the 

procedures in paragraphs (f)(1) and (f)(2) of this section.

(1) Average emissions of POM for each compliance demonstration 

period, must not exceed the applicable emission limit in Table 2 of 

this subpart. The emission rate must be calculated based on the total

emissions from all potlines divided by the quantity of aluminum 

produced during the period, from all potlines comprising the 

averaging group.

(2) To determine compliance with the applicable emission limit 

in Table 2 of this subpart for POM emissions, the owner or operator 

must determine the emissions (in lb/ton) from each potline using the 

procedures and methods in sections 63.847 and 63.849. The owner or 

operator must combine the results of measured or calculated secondary 

POM emissions with the POM emissions from the primary control system 

and divide total emissions by total aluminum production.

8. Section 63.847 is amended by revising paragraphs (a), (b), 

(b)(6), (c)(1), (c)(2), (c)(2)(i) through (iii), (c)(3), (c)(3)(i) 
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and (ii), (d)(2), (e)(2) and (g) and adding paragraphs (d)(5),(e)(8), 

(i),(j), (k) and (l) to read as follows:

Section 63.847 Compliance Provisions.

(a) Compliance dates. The owner operator of a primary aluminum 

reduction plant must comply with the requirements of this subpart by:

(1) Except as noted in paragraph (2) of this section, the 

compliance date for an owner or operator of an existing plant or 

source subject to the provisions of this subpart is October 7, 1999.

(2) The compliance dates for existing plants and sources are:

(i) [Insert date 90-days after date of publication of final 

rule] for Soderberg potlines subject to emission limits in sections 

63.843(a)(2)(i) and (iii) which became effective [insert date of 

publication of final rule].

(ii) [Insert date 3 years after date of publication of final 

rule] for prebake potlines subject to emission limits in sections 

63.843(a)(2)(iv) through (vii) and section 63.848(n) which became 

effective [insert date of publication of final rule].

(iii) [Insert date 3 years after date of publication of final 

rule] for potlines subject to the work practice standards in section 

63.854 which became effective [insert date of publication of final 

rule].

(iv) [Insert date 3 years after date of publication of final 

rule] for anode bake furnaces subject to the startup practices in 
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section 63.847(m) which became effective [insert date of publication 

of final rule].

(v) [Insert date 3 years after date of publication of final 

rule] for compliance with the pitch storage tank POM limit provisions 

of section 63.843(d) and the COS emission limit provisions of 

sections 63.843(e) and 63.844(e).

(vi) [Insert date of publication of final rule] for the 

malfunction provisions of sections 63.850(d)(2) and (e)(4)(xvi) and 

(xvii), the affirmative defense provisions of section 63.855, and the 

electronic reporting provisions of sections 63.850(c) and (f).

(3) Upon startup, for an owner or operator of a new or 

reconstructed source.

* * * * *

(b) Test plan for TF from all anode bake furnaces and potlines 

and POM from Soderberg potlines. The owner or operator shall prepare 

a site-specific test plan prior to the initial performance test 

according to the requirements of section 63.7(c) of this part. The 

test plan must include procedures for conducting the initial 

performance test and for subsequent performance tests required in 

section 63.848 for emission monitoring. In addition to the 

information required by section 63.7, the test plan shall include: * 

* *

(6) Reserved.

* * * * *
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(c) * * *

(1) During the first month following the compliance date for an 

existing potline (or potroom group), anode bake furnace or pitch 

storage tank;

(2) By the 180th day following startup for a potline or potroom 

group for which the owner or operator elects to conduct an initial 

performance test. The 180-day period starts when the first pot in a 

potline or potroom group is energized.

* * * * *

(2)(i) Reserved.

(2)(ii) Reserved.

(2)(iii) Reserved.

(3) By the 180th day following startup for a potline or potroom 

group that was shut down at the time compliance would have otherwise 

been required and is subsequently restarted. The 180-day period 

starts when the first pot in a potline or potroom group is energized.

(3)(i) Reserved.

(3)(ii) Reserved.

* * * * *

(d) Performance test requirements. The initial performance test 

and all subsequent performance tests must be conducted in accordance 

with the requirements of the general provisions in subpart A of this 

part, the approved test plan, and the procedures in this section. 
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Performance tests must be conducted under such conditions as the 

Administrator specifies to the owner or operator based on 

representative performance of the affected source for the period 

being tested. Upon request, the owner or operator must make available 

to the Administrator such records as may be necessary to determine 

the conditions of performance tests. * * *

* * * * *

(2) POM emissions from Soderberg potlines. For each Soderberg 

(HSS, and VSS2) potline, the owner or operator must measure and 

record the emission rate of POM exiting the primary emission control 

system and the rate of secondary emissions exiting through each roof 

monitor, or for a plant with roof scrubbers, exiting through the 

scrubbers. Using the equation in paragraph (e)(2) of this section, 

the owner or operator must compute and record the average of at least 

three runs each quarter (one run per month) for secondary emissions 

and at least three runs each year for the primary control system to 

determine compliance with the applicable emission limit. Compliance 

is demonstrated when the emission rate of POM is equal to or less 

than the applicable emission limit in sections 63.843, 63.844 or 

63.846.

* * * * *

(d) * * *

(5) POM emission from prebake potlines. POM emissions from 

prebakePrebake potlines. For each prebake potline, the owner or 

Formatted: Underline, Complex Script Font:

11 pt

Formatted: Underline, Complex Script Font:

11 pt
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operator shall measure and record the emission rate of POM exiting 

the primary emission control system. The owner or operator shall 

compute and record the average of at least three runs every five 

years. For each prebake potline for which the owner or operator 

chooses to demonstrate compliance using the provisions of section

63.847(e)(2), the owner or operator shall measure and record the 

emission rate of secondary emissions exiting through each roof 

monitor, or for a plant with roof scrubbers, exiting through the 

scrubbers. The owner or operator shall compute and record the average 

of at least three runs every five years for secondary emissions. The 

owner or operator shall calculate POM emissions in accordance with 

sections 63.847(e)(2) or (8). Compliance is demonstrated when the 

emission rate of POM is equal to or less than the applicable emission 

limit in sections 63.843, 63.844 or 63.846.

* * * * *

(e) * * *

(2) Compute the emission rate of POM from each Soderberg 

potline, and from those prebake potlines for which the owner or 

operator chooses to measure secondary emissions, using Equation 1,

Where:

Ep = emission rate of POM from the potline, kg/mg (lb/ton); and

Cs = concentration of POM, mg/dscm (mg/dscf). POM emission data 

collected during the installation and startup of a cathode must not 

be included in Cs.
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* * * * *

(8) Compute the rate of POM from each prebake potline for which 

the owner or operator does not choose to determine the measure the 

secondary emissions using Equation 3:

 

 

 

 

 

 

 (Equation 3)

Where:

Epp = emission rate of POM from a potline, kg/Mg (lb/ton);

Cpp1 = concentration of POM from the primary control system, mg/dscm 

(mg/dscf);

Q1 = volumetric flow rate of effluent gas from the primary control 

system dscm/hr (dscf/hr);

CpF2 = concentration of TF from the secondary control system or roof 

monitor, mg/dscm (mg/dscf);

CpF1 = concentration of TF from the primary control system, mg/dscm 

(mg/dscf); and

Q2 = volumetric flow rate of effluent gas from the secondary control 

system or roof monitor, dscm/hr (dscf/hr).

* * * * *

(g) Pitch storage tanks. The owner or operator must demonstrate 

initial compliance with the standard for pitch storage tanks in 

sections 63.843(d) and 63.844(d) by preparing a design evaluation or 

by conducting a performance test. The owner or operator shall submit 

for approval by the regulatory authority the information specified in 
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paragraph (g)(1) of this section, along with the information 

specified in paragraph (g)(2) of this section where a design 

evaluation is performed or the information specified in paragraph 

(g)(3) of this section where a performance test is conducted.

* * * * *

(i) Reserved.

(j) COS Emissions. The owner operator of each plant must 

calculate the facility wide emission rate of COS for each calendar 

month of operation using the following equation:

 

 

 

 

Where:

ECOS = the facility wide emission rate of COS during the calendar 

month in pounds per ton of aluminum produced;

K = factor accounting for molecular weights and conversion of sulfur 

to carbonyl sulfide = 234;

Y = the tons of anode used at the facility during the calendar month;

Z = the tons of aluminum produced at the facility during the calendar 

month; and

%S = the weighted average sulfur content of the anode coke utilized 

in the production of aluminum during the calendar month (e.g., if the 

weighted average sulfur content of the anode coke utilized during the 

calendar month was 2.5%, then %S = 0.025).
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Compliance is demonstrated if the calculated value of ECOS is 

less than the applicable standard for COS emissions in sections 

63.843(e) and 63.844(e).

(k) Test plan POM from prebake potlines. The owner or operator 

must prepare a site-specific test plan prior to the initial 

performance test according to the requirements of section 63.7(c) of 

this part. The test plan must include procedures for conducting the 

initial performance test and for subsequent performance tests 

required in section 63.848 for emission monitoring. In addition to 

the information required by section 63.7 the test plan shall include:

(1) Procedures to ensure a minimum of three runs are performed 

for the primary control system for each source;

(2) For a source with a single control device exhausted through 

multiple stacks, procedures to ensure that at least three runs are 

performed by a representative sample of the stacks satisfactory to 

the applicable regulatory authority;

(3) For multiple control devices on a single source, procedures 

to ensure that at least one run is performed for each control device 

by a representative sample of the stacks satisfactory to the 

applicable regulatory authority;

(4) For plants with roof scrubbers, procedures for rotating 

sampling among the scrubbers or other procedures to obtain 

representative samples as approved by the applicable regulatory 

authority.
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(l) Potlines. The owner or operator shall develop a written 

startup plan as described in section 63.854 that contains specific 

procedures to be followed during startup periods of potline(s). 

Compliance with the applicable standards in section 63.854 will be 

demonstrated through site inspection(s) and review of site records by 

the applicable regulatory authority.

(m) Anode bake furnaces. If you own or operate a new or existing 

primary aluminum reduction affected source, you must develop a 

written startup plan as described in paragraphs (m)(1) through (4) of 

this section. Compliance with the startup plan will be demonstrated 

through site inspection(s) and review of site records by the 

applicable regulatory authority. The written startup plan must

contain specific procedures to be followed during startup periods of 

anode bake furnaces, including the following:

(1) A requirement to develop an anode bake furnace startup

schedule prior to startup of the first anode bake furnace.

(2) Records of time, date, duration and any nonroutine actions 

taken during startup of the furnaces.

(3) A requirement that the associated emission control system 

should be operating within normal parametric limits prior to startup

of the first anode bake furnace.

(4) A requirement to shut down the anode bake furnaces 

immediately if the associated emission control system is off line at 

any time during startup.
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9. Section 63.848 is amended by revising paragraph (b) and 

adding paragraph (n) to read as follows:

Section 63.848 Emission monitoring requirements.

* * * * *

(b) POM emissions from Soderberg potlines. Using the procedures 

in section 63.847 and in the approved test plan, the owner or 

operator shall monitor emissions of POM from each Soderberg (HSS and 

VSS2) potline every three months. The owner or operator shall compute 

and record the quarterly (3-month) average from at least one run per 

month for secondary emissions and the previous 12-month average of 

all runs for the primary control systems to determine compliance with 

the applicable emission limit. The owner or operator must include all 

valid runs in the quarterly (3-month) average. The duration of each 

run for secondary emissions must represent a complete operating 

cycle. The primary control system must be sampled over an 8-hour 

period, unless site-specific factors dictate an alternative sampling 

time subject to the approval of the regulatory authority.

* * * * *

(n) POM emissions from prebake potlines. Using the procedures in 

section 63.847 and in the approved test plan, the owner or operator 

must monitor emissions of POM from each prebake potline every five 

years. The owner or operator must compute and record the sum of the 

average primary and secondary emissions using the procedures of 

sections 63.847(e)(2) or (e)(8).
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10. Section 63.849 is amended by adding paragraph (f) to read as 

follows:

Section 63.849 Test methods and procedures.

* * * * *

(f) The owner or operator must use ASTM Method D3177 – 02 (2007) 

for determination of the sulfur content in anode coke shipments to 

determine compliance with the applicable facility wide emission limit 

for COS emissions.

11. Section 63.850 is amended by revising paragraphs (c), (d) 

and (e)(iii) and adding paragraphs (e)(xvi) and (xvii) and (f) to 

read as follows:

Section 63.850 Notification, reporting and recordkeeping 

requirements.

* * * * *

(c) As of January 1, 2012 and within 60 days after the date of 

completing each performance test, as defined in section 63.2, and as 

required in this subpart, the owner or operator must submit 

performance test data, except opacity data, electronically to the 

EPA‘s Central Data Exchange by using the ERT (see 

http://www.epa.gov/ttn/chief/ert/erttool.html/) or other compatible 

electronic spreadsheet. Only data collected using test methods 

compatible with ERT are subject to this requirement to be submitted 

electronically into the EPA‘s WebFIRE database.
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(d) Reporting. In addition to the information required under 

section 63.10 of the General Provisions, the owner or operator must 

provide semi-annual reports containing the information specified in 

paragraphs (d)(1) through (d)(2) of this section to the Administrator 

or designated authority.

(1) Excess emissions report. As required by section 63.10(e)(3), 

the owner or operator must submit a report (or a summary report) if 

measured emissions are in excess of the applicable standard. The 

report must contain the information specified in section 

63.10(e)(3)(v) and be submitted semiannually unless quarterly reports 

are required as a result of excess emissions.

(2) If there was a malfunction during the reporting period, the

owner or operator must submit a report that includes the number, 

duration, and a brief description for each type of malfunction which 

occurred during the reporting period and which caused or may have 

caused any applicable emission limitation to be exceeded. The report 

must also include a description of actions taken by an owner or 

operator during a malfunction of an affected source to minimize 

emissions in accordance with sections 63.843(f) and 63.844(f), 

including actions taken to correct a malfunction.

* * * * * 

(e) * * *

(e)(4) * * *

(iii) Reserved.
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(e)(4) * * *

(xvi) Records of the occurrence and duration of each malfunction 

of operation (i.e., process equipment) or the air pollution control 

equipment and monitoring equipment.

(xvii) Records of actions taken during periods of malfunction to 

minimize emissions in accordance with sections 63.843 and 63.844, 

including corrective actions to restore malfunctioning process and 

air pollution control and monitoring equipment to its normal or usual 

manner of operation.

(f) All reports required by this subpart not subject to the 

requirements in paragraph (b) of this section must be sent to the 

Administrator at the appropriate address listed in section 63.13. If 

acceptable to both the Administrator and the owner or operator of a 

source, these reports may be submitted on electronic media. The 

Administrator retains the right to require submittal of reports 

subject to paragraph (b) of this section in paper format.

12. Section 63.854 is added to read as follows:

Section 63.854 Work Practice Standards for Periods of Startup.

(a) Startup of potlines. If you own or operate a new or existing 

primary aluminum reduction affected source, you must comply with the 

requirements of paragraphs (a)(1) through (7) of this section during 

startup for each affected potline.

(1) Develop a potline startup schedule before starting up the 

potline.
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(2) Keep records of number of pots started per day.

(3) Bring the potline scrubbers and exhaust fans on line prior 

to energizing the first cell being restarted.

(4) Ensure that the primary capture and control system is 

operating at all times during startup.

(5) Keep pots covered during startup as much as practicable to 

include but not limited to minimizing the removal of covers or panels 

of the pots on which work is being performed.

(6) Inspect potlines daily during startup and perform the 

following work practices as specified in paragraphs (a)(6)(i) through 

(iv) of this section.

(i) Identify unstable pots as soon as practicable but in no case 

more than 12 hours from the time the pot became unstable;

(ii) Reduce cell temperatures to as low as practicable, but no 

higher than the maximum temperature specified in the operating plan 

described in paragraph (a)(7) of this section;

(iii) Reseal pot crusts that have been broken as often and as 

soon as practicable but in no case more than 24 hours from the time 

the crust was broken; and

(iv) Adjust pot parameters to their optimum levels, as specified 

in the operating plan described in paragraph (a)(7) of this section,

including, but not limited to, the following parameters: alumina 

addition rate, exhaust air flow, cell voltage, feeding level, anode 

current and liquid and solid bath levels.
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(7) Prepare a written operating plan to minimize emissions 

during startup to include, but not limited to, the requirements in 

(a)(1) through (6) of this section.

13. Section 63.855 is added to read as follows:

Section 63.855 Affirmative defense for exceedance of emission 

limit during malfunction.

In response to an action to enforce the standards set forth in 

this subpart, you may assert an affirmative defense to a claim for 

civil penalties for exceedances of such standards that are caused by 

malfunction, as defined at section 63.2. Appropriate penalties may be 

assessed, however, if you fail to meet your burden of proving all of 

the requirements in the affirmative defense. The affirmative defense 

shall not be available for claims for injunctive relief.

(a) To establish the affirmative defense in any action to 

enforce such a limit, you must timely meet the notification

requirements in section 63.850 of this subpart, and must prove by a 

preponderance of evidence that:

(1) The excess emissions:

(i) Were caused by a sudden, infrequent, and unavoidable failure 

of air pollution control and monitoring equipment, process equipment, 

or a process to operate in a normal or usual manner; and

(ii) Could not have been prevented through careful planning, 

proper design or better operation and maintenance practices; and
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(iii) Did not stem from any activity or event that could have 

been foreseen and avoided, or planned for.

(iv) Were not part of a recurring pattern indicative of 

inadequate design, operation, or maintenance; and

(2) Repairs were made as expeditiously as possible when the 

applicable emissions limitations were being exceeded. Off-shift and 

overtime labor were used, to the extent practicable to make these 

repairs; and

(3) The frequency, amount and duration of the excess emissions 

(including any bypass) were minimized to the maximum extent 

practicable during periods of such emissions; and

(4) If the excess emissions resulted from a bypass of control 

equipment or a process, then the bypass was unavoidable to prevent 

loss of life, personal injury, or severe property damage; and

(5) All possible steps were taken to minimize the impact of the 

excess emissions on ambient air quality, the environment and human 

health; and

(6) All emissions monitoring and control systems were kept in 

operation if at all possible, consistent with safety and good air 

pollution control practices; and

(7) All of the actions in response to the excess emissions were 

documented by properly signed, contemporaneous operating logs; and

(8) At all times, the affected source was operated in a manner 

consistent with good practices for minimizing emissions; and
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(9) A written root cause analysis has been prepared, the purpose 

of which is to determine, correct, and eliminate the primary causes 

of the malfunction and the excess emissions resulting from the 

malfunction event at issue. The analysis shall also specify, using 

best monitoring methods and engineering judgment, the amount of 

excess emissions that were the result of the malfunction.

(b) Notification. The owner or operator of the affected source 

experiencing an exceedance of its emissions limit(s) during a 

malfunction, shall notify the Administrator by telephone or facsimile 

transmission as soon as possible, but no later than two business days 

after the initial occurrence of the malfunction, if it wishes to 

avail itself of an affirmative defense to civil penalties for that 

malfunction. The owner or operator seeking to assert an affirmative 

defense, shall also submit a written report to the Administrator 

within 45 days of the initial occurrence of the exceedance of the 

standards in this subpart to demonstrate, with all necessary 

supporting documentation, that it has met the requirements set forth 

in paragraph (e) of this section. The owner or operator may seek an 

extension of this deadline for up to 30 additional days by submitting 

a written request to the Administrator before the expiration of the 

45 day period. Until a request for an extension has been approved by 

the Administrator, the owner or operator is subject to the 

requirement to submit such report within 45 days of the initial 

occurrence of the exceedance.
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14. Reserved sections are amended to read as follows:

Sections 63.856 - 63.859 [Reserved]

15. Table 1 to Subpart LL of Part 63 is amended to read as 

follows:

Table 1 to Subpart LL of Part 63—Potline TF Limits for Emission Averaging

Type

Monthly TF limit (1b/ton)

[for given number of potlines]

2 lines 3 lines 4 lines 5 lines 6 lines 7 lines 8 lines

CWPB1 1.7 1.6 1.5 1.5 1.4 1.4 1.4

CWPB2 2.9 2.8 2.7 2.7 2.6 2.6 2.6

CWPB3 2.3 2.2 2.2 2.1 2.1 2.1 2.1

VSS2 2.6 2.5 2.5 2.4 2.4 2.4 2.4

HSS 2.5 2.4 2.4 2.3 2.3 2.3 2.3

SWPB 1.4 1.3 1.3 1.2 1.2 1.2 1.2

16. Table 2 to Subpart LL of Part 63 is amended to read as 

follows:

Table 2 to Subpart LL of Part 63—Potline POM Limits for Emission Averaging

Type

POM limit (lb/ton)

[for given number of potlines]

2 lines 3 lines 4 lines 5 lines 6 lines 7 lines 8 lines

HSS 3.5 3.2 3.1 3.0 3.0 2.9 2.8

VSS2 3.5 3.3 3.2 3.1 3.0 2.9 2.9

CWPB1 0.63 0.56 0.52 0.52 0.48 0.48 0.48

CWBP2 1.4 1.35 1.31 1.31 1.26 1.26 1.26

CWBP3 1.33 1.28 1.28 1.26 1.26 1.26 1.26

SWPB 0.63 0.56 0.52 0.52 0.48 0.48 0.48

17. Appendix A to subpart LL of part 63 is amended to read as 

follows:
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Appendix A to Subpart LL of Part 63—Applicability of General 

Provisions (40 CFR Part 63, Subpart A)

Reference

Section(s) ...

Applies to 

subpart LL

Comment

63.1 Yes

63.2 Yes

63.3 Yes

63.4 Yes

63.5 Yes

63.6(a), (b), (c) Yes

63.6(d) No Section reserved.

63.6(e)(1)(i) No See sections 63.843(f) and 

63.844(f) for general duty 

requirement.

63.6(e)(1)(ii) No

63.6(e)(1)(iii) Yes

63.6(e)(2) No Section reserved.

63.6(e)(3) No

63.6(f)(1) No

63.6(g) Yes

63.6(h) No No opacity limits in rule.

63.6(i) Yes

63.6(j) Yes

63.7(a) through (d) Yes

63.7(e)(1) No See section 63.847(d)

63.7(e)(2) through (e)(4) Yes

63.7(f), (g), (h) Yes

63.8(a) and (b) Yes

63.8(c)(1)(i) No See sections 63.843(f) and 

63.844(f) for general duty 

requirement.

63.8(c)(1)(ii) Yes

63.8(c)(1)(iii) No

63.8(c)(2) through (d)(2) Yes

63.8(d)(3) Yes, 

except for 

last 

sentence

63.8(e) through (g) Yes

63.9(a),(b),(c),(e),(g),(h)(1)

through (3), (h)(5) and (6), 

Yes

Formatted Table
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Reference

Section(s) ...

Applies to 

subpart LL

Comment

(i) and (j)

63.9(f) No

63.9(h)(4) No Reserved

63.10(a) Yes

63.10(b)(1) Yes

63.10(b)(2)(i) No

63.10(b)(2)(ii) No See sections 63.850(e)(4)(xvi) 

and (xvii) for recordkeeping of 

occurrence and duration of 

malfunctions and recordkeeping 

of actions taken during 

malfunction.

63.10(b)(2)(iii) Yes

63.10(b)(2)(iv) and (b)(2)(v) No

63.10(b)(2)(vi) through 

(b)(2)(xiv)

Yes

63.(10)(b)(3) Yes

63.10(c)(1) through (9) Yes

63.10(c)(10) and (11) No See sections 63.850(e)(4)(xvi) 

and (xvii)for recordkeeping of 

malfunctions.

63.10(c)(12) through (c)(14) Yes

63.10(c)(15) No

63.10(d)(1) through (4) Yes

63.10(d)(5) No See section 63.850(d)(2) for 

reporting of malfunctions.

63.10(e) and (f) Yes

63.11 No Flares will not be used to 

comply with the emission 

limits.

63.12 through 63.15 Yes

Formatted Table