[Federal Register Volume 79, Number 235 (Monday, December 8, 2014)]
[Proposed Rules]
[Pages 72914-72965]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-27499]



[[Page 72913]]

Vol. 79

Monday,

No. 235

December 8, 2014

Part IV





Environmental Protection Agency





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40 CFR Part 63





National Emissions Standards for Hazardous Air Pollutants: Primary 
Aluminum Reduction Plants; Proposed Rule

  Federal Register / Vol. 79, No. 235 / Monday, December 8, 2014 / 
Proposed Rules  

[[Page 72914]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2011-0797; FRL-9917-44-OAR]
RIN 2060-AQ92


National Emissions Standards for Hazardous Air Pollutants: 
Primary Aluminum Reduction Plants

AGENCY: Environmental Protection Agency.

ACTION: Supplemental proposed rulemaking.

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SUMMARY: This action supplements our proposed amendments to the 
national emission standards for hazardous air pollutants (NESHAP) for 
the Primary Aluminum Production source category published in the 
Federal Register on December 6, 2011. In that action, the Environmental 
Protection Agency (EPA) proposed amendments based on the initial 
residual risk and technology reviews (RTR) for this source category, 
and also proposed certain emission limits reflecting performance of 
Maximum Achievable Control Technology (MACT). Today's action reflects a 
revised technology review and a revised residual risk analysis for the 
Primary Aluminum Production source category and proposes new and 
revised emission standards based on those analyses, newly obtained 
emissions test data, and comments we received in response to the 2011 
proposal, including certain revisions to the technology-based standards 
reflecting performance of MACT. This action also proposes new 
compliance requirements to meet the revised standards. This action, if 
adopted, will provide improved environmental protection regarding 
potential emissions of hazardous air pollutant (HAP) emissions from 
primary aluminum production facilities.

DATES: Comments. Comments must be received on or before January 22, 
2015. A copy of comments on the information collection provisions 
should be submitted to the Office of Management and Budget (OMB) on or 
before January 7, 2015.
    Public Hearing. If anyone contacts the EPA requesting to speak at a 
public hearing by December 15, 2014, a public hearing will be held on 
December 23, 2014 at the U.S. EPA building at 109 T.W. Alexander Drive, 
Research Triangle Park, NC 27711. If you are interested in requesting a 
public hearing or attending the public hearing, contact Ms. Virginia 
Hunt at (919) 541-0832 or at [email protected]. If the EPA holds a 
public hearing, the EPA will keep the record of the hearing open for 30 
days after completion of the hearing to provide an opportunity for 
submission of rebuttal and supplementary information.

ADDRESSES: Comments. Submit your comments, identified by Docket ID No. 
EPA-HQ-OAR-2011-0797, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 
Follow the online instructions for submitting comments.
     Email: [email protected]. Include Attention Docket ID 
No. EPA-HQ-OAR-2011-0797 in the subject line of the message.
     Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2011-0797.
     Mail: Environmental Protection Agency, EPA Docket Center 
(EPA/DC), Mail Code: 28221T, Attention Docket ID No. EPA-HQ-OAR-2011-
0797, 1200 Pennsylvania Avenue NW., Washington, DC 20460. 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/Courier Delivery: EPA Docket Center, Room 3334, EPA 
WJC West Building, 1301 Constitution Avenue NW., Washington, DC 20004, 
Attention Docket ID No. 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 No. EPA-HQ-OAR-
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 
online 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 
www.regulations.gov or email. The http://www.regulations.gov Web site 
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 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 not include special characters or 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/dockets.
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2011-0797. All documents in the docket are 
listed in the 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 regulations.gov or in 
hard copy at the EPA Docket Center, Room 3334, EPA WJC West Building, 
1301 Constitution Avenue 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.
    Public Hearing: If anyone contacts the EPA requesting a public 
hearing by December 15, 2014, the public hearing will be held on 
December 23, 2014 at the EPA's campus at 109 T.W. Alexander Drive, 
Research Triangle Park, North Carolina. The hearing will begin at 10:00 
a.m. (Eastern Standard Time) and conclude at 5:00 p.m. (Eastern 
Standard Time). There will be a lunch break from 12:00 p.m. to 1:00 
p.m. Please contact Ms. Virginia Hunt at 919-541-0832 or at 
[email protected] to register to speak at the hearing or to inquire 
as to whether or not a hearing will be held. The last day to pre-
register in advance to speak at the hearing will be December 22, 2014. 
Additionally, requests to speak will be taken the day of the hearing at 
the hearing registration desk, although preferences on speaking times 
may not be able to be accommodated. If you require the service of a 
translator or

[[Page 72915]]

special accommodations such as audio description, please let us know at 
the time of registration. If you require an accommodation, we ask that 
you pre-register for the hearing, as we may not be able to arrange such 
accommodations without advance notice. The hearing will provide 
interested parties the opportunity to present data, views or arguments 
concerning the proposed action. The EPA will make every effort to 
accommodate all speakers who arrive and register. Because these hearing 
are being held at U.S. government facilities, individuals planning to 
attend the hearing should be prepared to show valid picture 
identification to the security staff in order to gain access to the 
meeting room. Please note that the REAL ID Act, passed by Congress in 
2005, established new requirements for entering federal facilities. If 
your driver's license is issued by Alaska, American Samoa, Arizona, 
Kentucky, Louisiana, Maine, Massachusetts, Minnesota, Montana, New 
York, Oklahoma or the state of Washington, you must present an 
additional form of identification to enter the federal building. 
Acceptable alternative forms of identification include: Federal 
employee badges, passports, enhanced driver's licenses and military 
identification cards. In addition, you will need to obtain a property 
pass for any personal belongings you bring with you. Upon leaving the 
building, you will be required to return this property pass to the 
security desk. No large signs will be allowed in the building, cameras 
may only be used outside of the building and demonstrations will not be 
allowed on federal property for security reasons. The EPA may ask 
clarifying questions during the oral presentations, but will not 
respond to the presentations at that time. Written statements and 
supporting information submitted during the comment period will be 
considered with the same weight as oral comments and supporting 
information presented at the public hearing.
    Docket: The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2011-0797. All documents in the docket are 
listed in the www.regulations.gov index. Although listed in the index, 
some information is not publicly available, e.g., CBI or other 
information whose disclosure is restricted by statute. Certain other 
material, such as copyrighted material, will be publicly available only 
in hard copy. Publicly available docket materials are available either 
electronically in www.regulations.gov or in hard copy at the EPA Docket 
Center, EPA WJC West Building, Room 3334, 1301 Constitution Ave. NW., 
Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 
p.m., Monday through Friday, excluding legal holidays. The telephone 
number for the Public Reading Room is (202) 566-1744, and the telephone 
number for the Air Docket is (202) 566-1742.

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, Environmental 
Protection Agency, Research Triangle Park, NC 27711; telephone (919) 
541-2016; fax number: (919) 541-3207; and email address: 
[email protected]. For specific information regarding the risk 
modeling methodology, contact Mr. Jim Hirtz, Health and Environmental 
Impacts Division (C539-02), Office of Air Quality Planning and 
Standards, U.S. Environmental Protection Agency, Research Triangle 
Park, NC 27711; telephone number: (919) 541-0881; fax number: (919) 
541-0840; and email address: [email protected]. For information about 
the applicability of the NESHAP to a particular entity, contact Mr. 
Patrick Yellin, Office of Enforcement and Compliance Assurance, U.S. 
Environmental Protection Agency, EPA WJC West Building, Mail Code 
2227A, 1200 Pennsylvania Avenue NW., Washington, DC 20460; telephone 
number: (202) 564-2970 and email address: [email protected].

SUPPLEMENTARY INFORMATION: 
    Preamble Acronyms and Abbreviations. We use multiple acronyms and 
terms in this preamble. While this list may not be exhaustive, to ease 
the reading of this preamble and for reference purposes, the EPA 
defines the following terms and acronyms here:

As arsenic
ADAF age-dependent adjustment factor
AEGL acute exposure guideline levels
AERMOD air dispersion model used by the HEM-3 model
ATSDR Agency for Toxic Substances and Disease Registry
BLDS bag leak detection system
BTF beyond-the-floor
CAA Clean Air Act
CalEPA California EPA
CBI Confidential Business Information
Cd cadmium
CE Cost Effectiveness
CFR Code of Federal Regulations
COS carbonyl sulfide
Cr chromium
Cr\+3\ trivalent chromium
Cr\+6\ hexavalent chromium
CWPB1 center-worked prebake one
CWPB2 center-worked prebake two
CWPB3 center-worked prebake three
D/Fs polychlorinated dibenzo-p-dioxins and polychlorinated 
dibenzofurans
EF Emission Factors
EJ environmental justice
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guidelines
ERT Electronic Reporting Tool
FR Federal Register
HAP hazardous air pollutants
HEM-3 Human Exposure Model, Version 1.1.0
HF hydrogen fluoride
Hg mercury
HI Hazard Index
HQ Hazard Quotient
HSS horizontal stud Soderberg
IRIS Integrated Risk Information System
km kilometer
LOAEL lowest-observed-adverse-effect level
LOEL lowest-observed-effect level
MACT maximum achievable control technology
MCEM methylene chloride extractable matter
mg/dscm milligrams per dry standard cubic meter
mg/kg-day milligrams per kilogram-day
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
Mn manganese
MRL Minimal Risk Level
NAAQS National Ambient Air Quality Standards
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
Ni nickel
NOAEL no-observed-adverse-effect level
NRC National Research Council
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
OMB Office of Management and Budget
PAH polycyclic aromatic hydrocarbons
Pb lead
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PCB polychlorinated biphenyls
PEL probable effect level
PM particulate matter
POM polycyclic organic matter
ppm parts per million
RDL representative method detection level
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SBA Small Business Administration
SSM startup, shutdown and malfunction
SWPB side-worked prebake
TF total fluorides
TOSHI target organ-specific hazard index
TPY tons per year

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TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and 
Ecological Exposure model
TTN echnology Transfer Network
UF uncertainty factor
[mu]g/dscm micrograms per dry standard cubic meter
[mu]g/m\3\ micrograms per cubic meter
UMRA Unfunded Mandates Reform Act
UPL Upper Prediction Limit
URE unit risk estimate
VCS voluntary consensus standards
VSS1 vertical stud Soderberg one
VSS2 vertical stud Soderberg two

    Organization of this Document. The information in this preamble is 
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related 
information?
    C. What should I consider as I prepare my comments for the EPA?
II. Background Information
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP 
regulate its HAP emissions?
    C. What is the history of the Primary Aluminum Production source 
category risk and technology review?
    D. What data collection activities were conducted to support 
this action?
III. Analytical Procedures
    A. For purposes of this supplemental proposal, how did we 
estimate the post-MACT risks posed by the Primary Aluminum 
Production source category?
    B. How did we consider the risk results in making decisions for 
this supplemental proposal?
    C. How did we perform the technology review?
IV. Revised Analytical Results and Proposed Decisions for the 
Primary Aluminum Production Source Category
    A. What actions are we proposing pursuant to CAA sections 
112(d)(2) and 112(d)(3)?
    B. What are the results of the risk assessment and analyses?
    C. What are our proposed decisions regarding risk acceptability, 
ample margin of safety and adverse environmental effects based on 
our revised analyses?
    D. What are the results and proposed decisions based on our 
technology review?
    E. What other actions are we proposing?
    F. What compliance dates are we proposing?
V. Summary of the Revised 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
    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. Does this action apply to me?

    Table 1 of this preamble lists the industrial source category that 
is the subject of this supplemental proposal. Table 1 is not intended 
to be exhaustive but rather to provide a guide for readers regarding 
the entities that this proposed action is likely to affect. The 
proposed standards, once promulgated, will be directly applicable to 
the affected sources. Federal, state, local and tribal government 
entities would not be affected by this proposed action. As defined in 
the ``Initial List of Categories of Sources Under Section 112(c)(1) of 
the Clean Air Act Amendments of 1990'' (see 57 FR 31576, July 16, 
1992), the ``Primary Aluminum Production'' source category is any 
facility which produces primary aluminum by the electrolytic reduction 
process.\1\
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    \1\ U.S. EPA. Documentation for Developing the Initial Source 
Category List--Final Report, EPA/OAQPS, EPA-450/3-91-030, July, 
1992.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
------------------------------------------------------------------------
         Source category                  NESHAP          NAICS code \a\
------------------------------------------------------------------------
Primary Aluminum Production......  Primary Aluminum               33131
                                    Reduction Plants.
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\a\ 2012 North American Industry Classification System.

B. 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 action is available on the Internet through EPA's Technology 
Transfer Network (TTN) Web site, a forum for information and technology 
exchange in various areas of air pollution control. Following signature 
by the EPA Administrator, the EPA will post a copy of this proposed 
action at: http://www.epa.gov/ttn/atw/alum/alumpg.html. Following 
publication in the Federal Register, the EPA will post the Federal 
Register version of the proposal and key technical documents at this 
same Web site. Information on the overall RTR program is available at 
the following Web site: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.

C. 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 CBI. In addition to 
one complete version of the comments that includes information claimed 
as CBI, you must submit a copy of the comments that does not contain 
the information claimed as CBI 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 Code of Federal Regulations (CFR) part 2. Send or deliver 
information identified as CBI

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only to the following address: Roberto Morales, OAQPS Document Control 
Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, 
Research Triangle Park, North Carolina 27711, Attention Docket ID No. 
EPA-HQ-OAR-2011-0797.

II. Background Information

A. What is the statutory authority for this action?

    Section 112 of the Clean Air Act (CAA) establishes a two-stage 
regulatory process to address emissions of HAPs from stationary 
sources. In the first stage, after the EPA has identified categories of 
sources emitting one or more of the HAP listed in CAA section 112(b), 
CAA section 112(d) requires us to promulgate technology-based NESHAP 
for those sources. ``Major sources'' are those that emit or have the 
potential to emit 10 tons per year (tpy) or more of a single HAP or 25 
tpy or more of any combination of HAPs. For major sources, the 
technology-based NESHAP must reflect the maximum degree of emission 
reductions of HAPs achievable (after considering cost, energy 
requirements and non-air quality health and environmental impacts) and 
are commonly referred to as MACT standards.
    MACT standards must reflect the maximum degree of emissions 
reduction achievable through the application of measures, processes, 
methods, systems or techniques, including, but not limited to, measures 
that (1) reduce the volume of or eliminate pollutants through process 
changes, substitution of materials or 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) through (E). The MACT standards may take the form of 
design, equipment, work practice or operational standards where the EPA 
first determines either that (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 section 112(h)(1) and (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 emissions control that is achieved in practice by 
the best-controlled similar source. The MACT floor for existing sources 
can be less stringent than floors for new sources but not less 
stringent than the average emissions 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). In developing MACT 
standards, the EPA must also consider control options that are more 
stringent than the floor. We may establish standards more stringent 
than the floor based on considerations of the cost of achieving the 
emission reductions, any non-air quality health and environmental 
impacts and energy requirements.
    The EPA is then required to review these technology-based standards 
and revise them ``as necessary (taking into account developments in 
practices, processes, and control technologies)'' no less frequently 
than every 8 years. CAA section 112(d)(6). In conducting this review, 
the EPA is not required to recalculate the MACT floor. Natural 
Resources Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 
2008). Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667, 
672-73 (D.C. Cir. 2013).
    The second stage in standard-setting focuses on reducing any 
remaining (i.e., ``residual'') risk according to CAA section 112(f). 
CAA section 112(f)(1) required that the EPA prepare a report to 
Congress discussing (among other things) methods of calculating the 
risks 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 the Residual Risk Report to 
Congress, EPA-453/R-99-001 (Risk Report) in March 1999. CAA section 
112(f)(2) then provides that if Congress does not act on any 
recommendation in the Risk Report, the EPA must analyze and address 
residual risk for each category or subcategory of sources 8 years after 
promulgation of such standards pursuant to CAA section 112(d).
    Section 112(f)(2) of the CAA requires the EPA to determine for 
source categories subject to MACT standards whether the emission 
standards provide an ample margin of safety to protect public health. 
Section 112(f)(2)(B) of the CAA expressly preserves the EPA's use of 
the two-step process for developing standards to address any residual 
risk and the agency's interpretation of ``ample margin of safety'' 
developed in the National Emissions 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 EPA notified Congress in the Risk 
Report that the agency intended to use the Benzene NESHAP approach in 
making CAA section 112(f) residual risk determinations (EPA-453/R-99-
001, p. ES-11). The EPA subsequently adopted this approach in its 
residual risk determinations and in a challenge to the risk review for 
the Synthetic Organic Chemical Manufacturing source category, the 
United States Court of Appeals for the District of Columbia Circuit 
upheld as reasonable the EPA's interpretation that CAA section 
112(f)(2) incorporates the approach established in the Benzene NESHAP. 
See NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008) (``[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.''); see also, A Legislative History of the Clean 
Air Act Amendments of 1990, vol. 1, p. 877 (Senate debate on Conference 
Report).
    The first step in the process of evaluating residual risk is the 
determination of acceptable risk. If risks are unacceptable, the EPA 
cannot consider cost in identifying the emissions standards necessary 
to bring risks to an acceptable level. The second step is the 
determination of whether standards must be further revised in order to 
provide an ample margin of safety to protect public health. The ample 
margin of safety is the level at which the standards must be set, 
unless an even more stringent standard is necessary to prevent, taking 
into consideration costs, energy, safety and other relevant factors, an 
adverse environmental effect.
1. Step 1--Determination of Acceptability
    The agency in the Benzene NESHAP concluded that ``the acceptability 
of risk under section 112 is best judged on the basis of a broad set of 
health risk measures and information'' and that the ``judgment on 
acceptability cannot be reduced to any single factor.'' Benzene

[[Page 72918]]

NESHAP at 38046. 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'' (Risk Report at 178, quoting NRDC v. EPA, 824 F. 2d 
1146, 1165 (D.C. Cir. 1987) (en banc) (``Vinyl Chloride''), 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 one in 10 thousand, that risk level is considered 
acceptable.'' 54 FR 38045, September 14, 1989. 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 
acknowledged 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 
the MIR as a metric for determining acceptability, we acknowledged in 
the 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. Further, in the 
Benzene NESHAP, we noted that:

``[p]articular attention will also be accorded to the weight of 
evidence presented in the risk assessment of potential 
carcinogenicity or other health effects of a pollutant. While the 
same numerical risk may be estimated for an exposure to a pollutant 
judged to be a known human carcinogen, and to a pollutant considered 
a possible human carcinogen based on limited animal test data, the 
same weight cannot be accorded to both estimates. In considering the 
potential public health effects of the two pollutants, the Agency's 
judgment on acceptability, including the MIR, will be influenced by 
the greater weight of evidence for the known human carcinogen.''

Id. at 38046. The agency also explained in the Benzene NESHAP that:

    ``[i]n 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 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. At 38045. 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 noted earlier, in NRDC v. EPA, the court held that CAA section 
112(f)(2) ``incorporates the EPA's interpretation of the Clean Air Act 
from the Benzene Standard.'' The court further held that Congress' 
incorporation of the Benzene standard applies equally to carcinogens 
and non-carcinogens. 529 F.3d at 1081-82. Accordingly, we also consider 
non-cancer risk metrics in our determination of risk acceptability and 
ample margin of safety.
2. Step 2--Determination of Ample Margin of Safety
    CAA section 112(f)(2) requires the EPA to determine, for source 
categories subject to MACT standards, whether those standards provide 
an ample margin of safety to protect public health. As explained in the 
Benzene NESHAP, ``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 . . . . 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 section 112.'' 54 
FR 38046, September 14, 1989.
    According to CAA section 112(f)(2)(A), 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 
one in one 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 (i.e., the MACT 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 effect,\2\ but must consider cost, energy, safety 
and other relevant factors in doing so.
---------------------------------------------------------------------------

    \2\ ``Adverse environmental effect'' is defined 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. CAA section 112(a)(7).
---------------------------------------------------------------------------

    The CAA does not specifically define the terms ``individual most 
exposed,'' ``acceptable level'' and ``ample margin of safety.'' In the 
Benzene NESHAP, 54 FR 38044-38045, September 14, 1989, we stated as an 
overall objective:

    In protecting public health with an ample margin of safety under 
section 112, EPA strives 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 
plant would have if he or she were exposed to the maximum pollutant 
concentrations for 70 years.

    The agency further stated that ``[t]he 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 risks 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.'' Id. at 38045.
    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, including the incremental risk reduction 
associated with standards more stringent than the MACT standard or a 
more stringent standard that the EPA

[[Page 72919]]

has determined is necessary to ensure risk is acceptable. In the ample 
margin of safety analysis, the agency considers additional factors, 
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, September 14, 1989.

B. What is this source category and how does the current NESHAP 
regulate its HAP emissions?

    The NESHAP for Primary Aluminum Reduction Plants were promulgated 
on October 7, 1997 (62 FR 52407), codified at 40 CFR part 63, subpart 
LL (referred to as subpart LL or MACT rule in the remainder of this 
preamble), and amended on November 2, 2005 (70 FR 66285). The MACT rule 
is applicable to facilities with affected sources associated with the 
production of aluminum by electrolytic reduction. These facilities are 
described in the following paragraph and collectively comprise what is 
commonly known as the Primary Aluminum Production source category.
    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 include alumina, petroleum 
coke, pitch and fluoride salts. According to information available on 
the Web site of The Aluminum Association, Inc. (http://www.aluminum.org), approximately 40 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 13 facilities located in the United 
States that are subject to the requirements of this NESHAP: 12 primary 
aluminum production plants and one carbon-only prebake anode production 
facility. These 12 primary aluminum production plants have 
approximately 45 potlines that produce aluminum. Ten primary aluminum 
production plants have a paste production operation, and 10 of the 12 
primary aluminum production plants have anode bake furnaces. Eleven of 
the 12 primary aluminum facilities use prebake potlines; the other 
plant uses Soderberg potlines. Due to a decrease in demand for 
aluminum, four of the facilities are currently idle, including the 
Soderberg facility. The major HAPs emitted by these facilities are 
carbonyl sulfide (COS), hydrogen fluoride (HF), particulate HAP metals 
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, 
paste production plants and pitch storage tanks associated with primary 
aluminum production. 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 a dry alumina scrubber (with a 
baghouse to collect the alumina and other particulate matter (PM)). The 
control technology typically used for anode bake furnaces is a dry 
alumina scrubber. A capture system vented to a dry coke scrubber is 
used for control of paste production plants. See Tables 2 and 3 for the 
applicable emission limits established under the 1997 NESHAP and the 
2005 Amendments.

  Table 2--Summary of Current MACT Emission Limits for Existing Sources
             Under the 1997 NESHAP, and the 2005 Amendments
------------------------------------------------------------------------
            Source                  Pollutant          Emission limit
------------------------------------------------------------------------
Potlines \1\
    CWPB1 potlines............  TF...............  0.95 kg/Mg (1.9 lb/
                                                    ton) of aluminum
                                                    produced.
    CWPB2 potlines............  TF...............  1.5 kg/Mg (3.0 lb/
                                                    ton) of aluminum
                                                    produced.
    CWPB3 potlines............  TF...............  1.25 kg/Mg (2.5 lb/
                                                    ton) of aluminum
                                                    produced.
    SWPB potlines.............  TF...............  0.8 kg/Mg (1.6 lb/
                                                    ton) of aluminum
                                                    produced.
    VSS1 potlines.............  TF...............  1.1 kg/Mg (2.2 lb/
                                                    ton) of aluminum
                                                    produced.
                                POM..............  1.2 kg/Mg (2.4 lb/
                                                    ton) of aluminum
                                                    produced.
    VSS2 potlines.............  TF...............  1.35 kg/Mg (2.7 lb/
                                                    ton) of aluminum
                                                    produced.
                                POM..............  2.85 kg/Mg (5.7 lb/
                                                    ton) of aluminum
                                                    produced.
    HSS potlines..............  TF...............  1.35 kg/Mg (2.7 lb/
                                                    ton) of aluminum
                                                    produced.
                                POM..............  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
                                                    scrubber.
Anode Bake Furnace (collocated  TF...............  0.10 kg/Mg (0.20 lb/
 with a primary aluminum                            ton) of green anode.
 plant).
                                POM..............  0.09 kg/Mg (0.18 lb/
                                                    ton) of green anode.
------------------------------------------------------------------------
\1\CWPB1 = 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 Century Aluminum primary aluminum plant in Kentucky.
HSS = Horizontal stud Soderberg potline (no facilities remain in the
  U.S.).
SWPB = Side-worked prebake potline.
VSS1 = Vertical stud Soderberg potline (no facilities remain in the
  U.S.).
VSS2 = Vertical stud Soderberg potlines (located at an idle facility
  known as Columbia Falls Aluminum in Columbia Falls, Montana).


[[Page 72920]]


 Table 3--Summary of Current MACT Emission Limits for New Sources Under
                the 1997 NESHAP, and the 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  TF...............  0.01 kg/Mg (0.020 lb/
 with a primary aluminum                            ton) of green anode.
 plant).
                                POM..............  0.025 kg/Mg (0.05 lb/
                                                    ton) of green anode.
Pitch storage tanks...........  POM..............  Emission control
                                                    system designed and
                                                    operated to reduce
                                                    inlet POM 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 3. 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 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. We expect any new potline would need to 
be a prebake potline to comply with the new source limits in the 
NESHAP.
    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 parametric 
monitoring for each emission control device, a monitoring device to 
track daily weight of aluminum produced and daily inspection for 
visible emissions. 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 PM or gaseous 
form.

C. What is the history of the Primary Aluminum Production source 
category risk and technology review?

    Pursuant to section 112(f)(2) of the CAA, in 2011 we conducted an 
initial evaluation of the residual risk associated with the NESHAP for 
Primary Aluminum Reduction Plants. At that time, we also conducted an 
initial technology review pursuant to section 112(d)(6) of the CAA. 
Finally, we also reviewed the 2005 MACT rule to determine whether other 
amendments were appropriate. Based on the results of that initial RTR, 
and the MACT rule review, we proposed amendments to the NESHAP (also 
known as subpart LL) on December 6, 2011 (76 FR 76260) (referred to as 
the 2011 proposal in the remainder of this FR document). The proposed 
amendments in the 2011 proposal which we are revisiting in today's 
supplemental proposal include the following:
     Proposed emission limits for POM from prebake potlines;
     Amendments to the monitoring, notification, recordkeeping 
and testing requirements; and
     Proposed provisions establishing an affirmative defense to 
civil penalties for violations caused by malfunctions.
    As explained below, we are also proposing provisions which have no 
analogue in the 2011 proposal.
    The comment period for the December 2011 proposal opened on 
December 6, 2011, and ended on February 1, 2012. We received 
significant comments from industry representatives, environmental 
organizations and state regulatory agencies. After reviewing the 
comments, and after consideration of additional data and information 
received since the 2011 proposal, we determined it is appropriate to 
revise some of our analyses and to publish a supplemental proposal. 
After collecting and reviewing additional data, we are proposing 
technology-based emission limits pursuant to CAA sections 112(d)(2) and 
(3) for PM, as a surrogate for particulate HAP metals, for new and 
existing potlines, anode bake furnaces and paste plants. We are also 
proposing revised technology-based emissions limits for POM emissions 
from prebake potlines and amendments to the monitoring, notification, 
recordkeeping and testing requirements to implement these emission 
limits. Pursuant to CAA section 112(f)(2), we are also proposing risk-
based emission standards for POM, nickel (Ni) and arsenic (As) 
emissions from potlines in the VSS2 subcategory and proposing testing 
and monitoring requirements to demonstrate compliance with the 
standards for Ni and As. We are also proposing revisions to the testing 
and compliance requirements for COS emissions.
    In addition, we are withdrawing our 2011 proposal to include an 
affirmative defense in this rule in light of a recent court decision 
vacating an affirmative defense in one of the EPA's CAA section 112(d) 
regulations. NRDC v. EPA, 749 F. 3d 1055 (D.C. Cir. 2014) (vacating 
affirmative defense provisions in CAA section 112(d) rule establishing 
emission standards for Portland cement kilns).
    Today's supplemental proposed rulemaking will allow the public an 
opportunity to review and comment on the revised analyses and revised 
proposed amendments described above.
    However, we also proposed other requirements in the 2011 proposal 
(listed below) for which we have made no revisions to the analyses, are 
not proposing any changes and are not reopening for public comment. 
These are:
     POM standards for existing pitch storage tanks and related 
monitoring, reporting and testing requirements;
     Emissions limits for COS from potlines;
     Elimination of startup, shutdown and malfunction (SSM) 
exemptions; and
     Electronic reporting.
    The comment period for the December 2011 proposal opened on 
December 6, 2011, and ended on February 1, 2012. We will address the 
comments we received during the public comment period for the 2011 
proposal at the time we publish final RTR amendments for the Primary 
Aluminum Production source category based on the 2011 proposal and 
today's supplemental proposal.

[[Page 72921]]

D. What data collection activities were conducted to support this 
action?

    The 2011 risk assessment was based on estimates of PAH emissions 
derived from test measurements conducted in the 1990's on facilities 
that may not have been representative of current operating practices 
and using test methods that were inferior to those currently available. 
In addition, data available to estimate emissions of HAP metals from 
potlines were very limited, and no data were available to estimate HAP 
metals emissions from anode bake furnaces and paste plants. 
Furthermore, no data were available to estimate dioxin/furan (D/F) and 
polychlorinated biphenyl (PCB) emissions from potlines, anode bake 
furnaces and paste plants.
    The proposed emission limits for POM from prebake potlines included 
in the 2011 proposal were based on extremely limited data. Also lacking 
were reliable data on which to base MACT standards for PM (as a 
surrogate for HAP metals) emissions from potlines, anode bake furnaces 
and paste plants.
    Therefore, in March 2013 we sent an information request to the 
primary aluminum companies pursuant to section 114 of the CAA to gather 
additional relevant emissions test data. In response to this request, 
selected facilities provided the following data:
     Additional emission test data for POM emissions from 
prebake potlines;
     Additional emission test data for PM emissions from 
prebake potlines, Soderberg potlines (which have subsequently shut 
down), anode bake furnaces and paste plants;
     Additional emission test data for speciated PAH, speciated 
HAP metals, speciated PCBs and speciated polychlorinated dibenzo-p-
dioxins and polychlorinated dibenzofurans from potlines, anode bake 
furnaces and paste plants.

III. Analytical Procedures

A. For purposes of this supplemental proposal, how did we estimate the 
post-MACT risks posed by the Primary Aluminum Production source 
category?

    The EPA conducted a risk assessment that provides estimates of the 
MIR posed by the HAP emissions from each source in the source category, 
the hazard index (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 assessment also provides estimates of the distribution of 
cancer risks within the exposed populations, cancer incidence and an 
evaluation of the potential for adverse environmental effects. The 
eight sections that follow this paragraph describe how we estimated 
emissions and conducted the risk assessment. The docket for this 
rulemaking contains the following document which provides more 
information on the risk assessment inputs and models: Residual Risk 
Assessment for the Primary Aluminum Production Source Category in 
Support of the 2014 Supplemental Proposal. The methods used to assess 
risks (as described in the eight 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 2010; 
\3\ they are also consistent with the key recommendations contained in 
that report.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    Using the test reports from the 2013 information request we 
calculated annual emission rates of PAHs, D/Fs, PCBs and HAP metals 
from primary and secondary potline exhausts, anode bake furnace 
exhausts and paste plant exhausts. Where no test data were available we 
calculated and applied emission factors (EF) for these pollutants and 
emission points based on average emission rates from similarly operated 
sources to estimate emissions. However, it is important to note that 
only two facilities tested for D/F and PCBs. Furthermore, many of the 
test results for D/Fs and PCBs were below detection limits. More than 
half of the mercury (Hg) emissions tests results were also below 
detection limit. Therefore, there are greater uncertainties regarding 
D/F, PCB and Hg emissions compared to the other HAP. To estimate 
emissions in cases where some, but not all, data were below the 
detection limit, we assumed the undetected emissions were equal to one-
half the detection limit, which is the established approach for dealing 
with non-detects in the EPA's RTR program when developing emissions 
estimates for input to the risk assessments. Subsequently, we developed 
EF based on these limited data to estimate emissions at the other 
facilities. We believe the emissions estimates for D/F and PCBs are 
quite conservative (i.e., more likely to be overestimated rather than 
underestimated) because we assumed undetected emissions were equal to 
one half the detection limit. We note that EPA may, but is not 
obligated to amend MACT standards. In the case of D/F, Hg and PCB, 
where many of the emissions tests were below detection limit, and given 
the uncertainties and limitations of the data (for example, we have 
test data for D/F and PCBs for only one of the 11 prebake facilities), 
the EPA is choosing not to propose standards for these HAP at this 
time.
    We also obtained test data from recent compliance tests for TF and 
estimated HF emissions from primary and secondary potline exhausts and 
anode bake furnace exhausts. We estimated COS emissions as described in 
the 2011 risk assessment. We did not receive any additional test data 
for COS. Thus, the emissions estimates for COS have not changed since 
the 2011 proposal. As noted above, we are not accepting further comment 
on either this analysis or the proposed emission limit for COS.
    We also verified information regarding emissions release 
characteristics such as stack heights, stack gas exit velocities, stack 
temperatures and source locations. In addition to the quality assurance 
(QA) of the source data for the facilities contained in the dataset, we 
also checked the coordinates of every emission source in the dataset 
using tools such as Google Earth. Where coordinates used in the 2011 
risk assessment were found to be incorrect, we identified and corrected 
them. We also performed a QA assessment of the emissions data and 
release characteristics to ensure the data were reliable and that there 
were no outliers. The emissions data and the methods used to estimate 
emissions from all the various emissions sources are described in more 
detail in the technical document: Revised Draft Development of the RTR 
Emissions Dataset for the Primary Aluminum Production Source Category, 
which is available in the docket for this action (Docket ID No. EPA-HQ-
OAR-2011-0797).
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during the specified annual time 
period. In some cases, these ``actual'' emission levels are lower than 
the emission levels required to comply with the current MACT standards. 
The emissions level allowed to be emitted by the MACT standards is 
referred to as the ``MACT-allowable'' emissions level. We discussed the 
use of both MACT-allowable and actual

[[Page 72922]]

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 actions, we noted 
that assessing the risks at the MACT-allowable level is inherently 
reasonable since these risks reflect the maximum level facilities could 
emit and still comply with national emission standards. 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 approach.
    For this supplemental proposal, we evaluated allowable emissions 
based on responses to the information request. We estimated that 
allowable emissions for the currently regulated HAP (i.e., PAHs and HF) 
were generally about 1.5 times higher than the actual emissions. 
Therefore, to calculate allowable emissions of PAHs and HF, we assumed 
that allowable emissions were 1.5 times the actual emissions for all 
facilities except for one idle Soderberg facility (Columbia 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 for the regulated HAP (i.e., PAHs and HF) were 
about 1.9 times higher than estimated actual emissions when the plant 
is operating. Regarding unregulated HAP, the NESHAP currently includes 
no standards for COS, PCB, D/F and HAP metal emissions. Since there is 
no standard in place for these HAP and, therefore, no defined level of 
``MACT allowable'' emissions levels, we assumed that allowable 
emissions for COS, PCB, D/F and HAP metal emissions were equal to 
estimated actual emissions. Further explanation is provided in the 
technical document: Revised Draft Development of the RTR Emissions 
Dataset for the Primary Aluminum Production Source Category, which is 
available in the docket (Docket ID No. EPA-HQ-OAR-2011-0797).
3. How did we conduct dispersion modeling, determine inhalation 
exposures and estimate individual and population inhalation risks?
    Both long-term and short-term inhalation exposure concentrations 
and health risks from the source category addressed in this proposal 
were estimated using the Human Exposure Model (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 
kilometers (km) of the modeled sources,\4\ and (3) estimating 
individual and population-level inhalation risks using the exposure 
estimates and quantitative dose-response information.
---------------------------------------------------------------------------

    \4\ This metric comes from the Benzene NESHAP. See 54 FR 38046.
---------------------------------------------------------------------------

    The air dispersion model used by the HEM-3 model (AERMOD) is one of 
the EPA's preferred models for assessing pollutant concentrations from 
industrial facilities.\5\ 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 (2011) of 
hourly surface and upper air observations for more than 800 
meteorological stations, selected to provide coverage of the United 
States and Puerto Rico. A second library of United States Census Bureau 
census block \6\ internal point locations and populations provides the 
basis of human exposure calculations (U.S. Census, 2010). 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://www2.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants and are discussed in 
more detail later in this section.
---------------------------------------------------------------------------

    \5\ 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).
    \6\ A census block is the smallest geographic area for which 
census statistics are tabulated.
---------------------------------------------------------------------------

    In developing the risk assessment for chronic exposures, we used 
the estimated annual average ambient air concentrations of each HAP 
emitted by each source for which we have emissions data in the source 
category. The air concentrations at each nearby census block 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 inhabited census blocks. 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 
([mu]g/m\3\)) by its unit risk estimate (URE). The URE 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 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 dose-response 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.
    In the case of Ni compounds, to provide a health-protective 
estimate of potential cancer risks, we used the IRIS URE value for Ni 
subsulfide in the assessment for the 2011 proposed rule for the Primary 
Aluminum Production source category. Based on past scientific and 
technical considerations, the determination of the percent of Ni 
subsulfide was considered a major factor for estimating the extent and 
magnitude of the risks of cancer due to Ni-containing emissions. Nickel 
speciation information for some of the largest Ni-emitting sources 
(including oil combustion, coal combustion and others) suggested that 
at least 35 percent of total Ni emissions may be soluble compounds and 
that the URE for the mixture of inhaled Ni compounds (based on Ni 
subsulfide, and representative of pure insoluble crystalline Ni) could 
be derived to reflect the assumption that 65 percent of the total mass 
of Ni may be carcinogenic.
    Based on consistent views of major scientific bodies (i.e., 
National Toxicology Program (NTP) in their 12th Report of the 
Carcinogens (ROC),\7\ International Agency for Research on

[[Page 72923]]

Cancer (IARC) \8\ and other international agencies) \9\ that consider 
all Ni compounds to be carcinogenic, we currently consider all Ni 
compounds to have the potential of being carcinogenic to humans. The 
12th Report of the Carcinogens states that the ``combined results of 
epidemiological studies, mechanistic studies, and carcinogenic studies 
in rodents support the concept that Ni compounds generate Ni ions in 
target cells at sites critical for carcinogenesis, thus allowing 
consideration and evaluation of these compounds as a single group.'' 
Although the precise Ni compound (or compounds) responsible for the 
carcinogenic effects in humans is not always clear, studies indicate 
that Ni sulfate and the combinations of Ni sulfides and oxides 
encountered in the Ni refining industries cause cancer in humans (these 
studies are summarized in a review by Grimsrud et al., 2010 \10\). The 
major scientific bodies mentioned above have also recognized that there 
are differences in toxicity and/or carcinogenic potential across the 
different Ni compounds.
---------------------------------------------------------------------------

    \7\ National Toxicology Program (NTP), 2011. Report on 
Carcinogens. 12th ed. Research Triangle Park, NC: US Department of 
Health and Human Services (DHHS), Public Health Service. Available 
online at http://ntp.niehs.nih.gov/ntp/roc/twelfth/roc12.pdf.
    \8\ International Agency for Research on Cancer (IARC), 1990. 
IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 
Chromium, nickel, and welding. Vol. 49. Lyons, France: International 
Agency for Research on Cancer, World Health Organization Vol. 
49:256.
    \9\ World Health Organization (WHO, 1991) and the European 
Union's Scientific Committee on Health and Environmental Risks 
(SCHER, 2006).
    \10\ Grimsrud TK and Andersen A. Evidence of Carcinogenicity in 
Humans of Water-soluble Nickel Salts. J Occup Med Toxicol 2010, 5:1-
7. Available online at http://www.ossup-med.com/content/5/1/7.
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    In the inhalation risk assessment for this supplemental proposal, 
we chose to take a conservative approach: we considered all Ni 
compounds to be as carcinogenic as Ni subsulfide and applied the IRIS 
URE for Ni subsulfide without a factor to reflect the assumption that 
100 percent of the total mass of Ni may be as carcinogenic as pure Ni 
subsulfide. However, given that there are two additional URE values 
\11\ derived for exposure to mixtures of Ni compounds, as a group, that 
are 2-3 fold lower than the IRIS URE for Ni subsulfide, the EPA also 
considers it reasonable to use a value that is 50 percent of the IRIS 
URE for Ni subsulfide for providing an estimate of the lower end of the 
plausible range of cancer potency values for different mixtures of Ni 
compounds.
---------------------------------------------------------------------------

    \11\ Two UREs (other than the current IRIS values) have been 
derived for nickel compounds as a group: One developed by the 
California Department of Health Services (http://www.arb.ca.gov/toxics/id/summary/nickel_tech_b.pdf) and the other by the Texas 
Commission on Environmental Quality (http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf).
---------------------------------------------------------------------------

    The EPA estimated incremental individual lifetime cancer risks 
associated with emissions from the facilities in the source category as 
the sum of the 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 \12\) emitted 
by the modeled sources. Cancer incidence and the distribution of 
individual cancer risks for the population within 50 km of the sources 
were also estimated for the source category as part of this assessment 
by summing individual risks. A distance of 50 km is consistent with 
both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044, 
September 14, 1989) and the limitations of Gaussian dispersion models, 
including AERMOD.
---------------------------------------------------------------------------

    \12\ 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 the 
EPA's National Air Toxics Assessment (NATA) titled, 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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    To assess the risk of non-cancer 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 is the estimated exposure 
divided by the chronic reference value, which is a value selected from 
one of several sources. First, the chronic reference level can be the 
EPA reference concentration (RfC) (http://www.epa.gov/riskassessment/glossary.htm), 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 of deleterious effects during a 
lifetime.'' Alternatively, in cases where an RfC from the EPA's IRIS 
database is not available or where the EPA determines that using a 
value other than the RfC is appropriate, the chronic reference level 
can be a value from the following prioritized sources: (1) The Agency 
for Toxic Substances and Disease Registry (ATSDR) Minimum Risk Level 
(MRL) (http://www.atsdr.cdc.gov/mrls/index.asp), which is defined as 
``an estimate of daily human exposure to a hazardous substance that is 
likely to be without an appreciable risk of adverse non-cancer health 
effects) over a specified duration of exposure''; (2) the CalEPA 
Chronic Reference Exposure Level (REL) (http://www.oehha.ca.gov/air/hot_spots/pdf/HRAguidefinal.pdf), which is defined as ``the 
concentration level (that is expressed in units of micrograms per cubic 
meter ([mu]g/m\3\) for inhalation exposure and in a dose expressed in 
units of milligram per kilogram-day (mg/kg-day) for oral exposures), 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.
    POM, a carcinogenic HAP with a mutagenic mode of action, is emitted 
by the facilities in this source category.\13\ For this compound 
group,\14\ the EPA's analysis applies the age-dependent adjustment 
factors (ADAF) described in the EPA's Supplemental Guidance for 
Assessing Susceptibility from Early-Life Exposure to Carcinogens.\15\ 
This adjustment has the effect of increasing the estimated lifetime 
risks for POM by a factor of 1.6. In addition, although primary 
aluminum facilities reported most of their total POM emissions 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 \16\ recommends applying the Supplemental Guidance to all 
carcinogenic PAH 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.
---------------------------------------------------------------------------

    \13\ 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.
    \14\ See the Risk Assessment for Source Categories document 
available in the docket for a list of HAP with a mutagenic mode of 
action.
    \15\ 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.
    \16\ U.S. EPA. Science Policy Council Cancer Guidelines 
Implementation Workgroup Communication II: Memo from W.H. Farland, 
dated June 14, 2006.
---------------------------------------------------------------------------

    As mentioned above, in order to characterize non-cancer chronic 
effects, and in response to key

[[Page 72924]]

recommendations from the SAB, the EPA selects dose-response values that 
reflect the best available science for all HAP included in RTR risk 
assessments.\17\ More specifically, for a given HAP, the EPA examines 
the availability of inhalation reference values from the sources 
included in our tiered approach (e.g., IRIS first, ATSDR second, CalEPA 
third) and determines which inhalation reference value represents the 
best available science. Thus, as new inhalation reference values become 
available, the EPA will typically evaluate them and determine whether 
they should be given preference over those currently being used in RTR 
risk assessments.
---------------------------------------------------------------------------

    \17\ 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.
---------------------------------------------------------------------------

    The EPA also evaluated screening estimates of acute exposures and 
risks for each of the HAP (for which appropriate acute dose-response 
values are available) at the point of highest potential off-site 
exposure for each facility. To do this the EPA estimated the risks when 
both the peak hourly emissions rate and worst-case dispersion 
conditions occur. We also assume that a person is located at the point 
of highest impact during that same time. In accordance with the mandate 
of section 112(f)(2) of the CAA, we use the point of highest off-site 
exposure to assess the potential risk to the maximally exposed 
individual. The acute HQ is the estimated acute exposure divided by the 
acute dose-response value. In each case, the EPA calculated acute HQ 
values using best available, short-term dose-response values. These 
acute dose-response values, which are described below, include the 
acute REL, acute exposure guideline levels (AEGL) and emergency 
response planning guidelines (ERPG) for 1-hour exposure durations. As 
discussed below, we used conservative assumptions for emissions rates, 
meteorology and exposure location.
    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.'' Id. at page 2. Acute 
REL values are based on the most sensitive, relevant, adverse health 
effect reported in the peer-reviewed medical and toxicological 
literature. Acute REL values are designed to protect the most sensitive 
individuals in the population through the inclusion of margins of 
safety. Because margins of safety are incorporated to address data gaps 
and uncertainties, exceeding the 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/oppt/aegl/pubs/sop.pdf),\18\ ``the NRC's previous 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.'' 
Id. at 2. 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.'' Id. at 2.
---------------------------------------------------------------------------

    \18\ National Academy of Sciences (NAS), 2001. Standing 
Operating Procedures for Developing Acute Exposure Levels for 
Hazardous Chemicals, page 2.
---------------------------------------------------------------------------

    The document lays out the purpose and objectives of AEGL by stating 
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-in-a-lifetime, 
short-term exposures to airborne concentrations of acutely toxic, high-
priority chemicals.'' Id. at 21. In detailing the intended application 
of AEGL values, the document states 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.'' Id. at 31.
    The AEGL-1 value is then specifically defined as ``the airborne 
concentration (expressed as ppm (parts per million) or mg/m\3\ 
(milligrams per cubic meter)) of a substance above which it is 
predicted that the general population, including susceptible 
individuals, could experience notable discomfort, irritation, or 
certain asymptomatic non-sensory effects. However, the effects are not 
disabling and are transient and reversible upon cessation of 
exposure.'' Id. at 3. The document also notes 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, non-sensory 
effects.'' Id. Similarly, the document defines AEGL-2 values as ``the 
airborne concentration (expressed as parts per million or milligrams 
per cubic meter) of a substance above which it is predicted that the 
general population, including susceptible individuals, could experience 
irreversible or other serious, long-lasting adverse health effects or 
an impaired ability to escape.'' Id.
    ERPG values are derived for use in emergency response, as described 
in the American Industrial Hygiene Association's Emergency Response 
Planning (ERP) Committee document titled, ERPGS Procedures and 
Responsibilities (https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERP-SOPs2006.pdf), which states that, ``Emergency Response Planning 
Guidelines were developed for emergency planning and are intended as 
health based guideline concentrations for single exposures to 
chemicals.'' \19\ Id. at 1. 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.'' Id. at 2. 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 
one hour without experiencing or developing irreversible or other 
serious health effects or symptoms which could impair an individual's 
ability to take protective action.'' Id. at 1.
---------------------------------------------------------------------------

    \19\ ERP Committee Procedures and Responsibilities. November 1, 
2006. American Industrial Hygiene Association.
---------------------------------------------------------------------------

    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 
because the types of

[[Page 72925]]

effects for these chemicals are not consistent with the AEGL-1/ERPG-1 
definitions; in these instances, we compare higher severity level AEGL-
2 or ERPG-2 values to our modeled exposure levels to screen for 
potential acute concerns. When AEGL-1/ERPG-1 values are available, they 
are used in our acute risk assessments.
    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 the same as 
the corresponding ERPG-1 values, and AEGL-2 values are often equal to 
ERPG-2 values. Maximum HQ values from our acute screening risk 
assessments typically result when basing them on the 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 in the absence of 
hourly emissions data, generally, we first develop estimates of maximum 
hourly emissions rates by multiplying the average actual annual hourly 
emissions rates by a default factor to cover routinely variable 
emissions. We choose the factor to use partially based on process 
knowledge and engineering judgment reflecting, where appropriate, 
circumstances of the particular source category at issue. The factor 
chosen also reflects a Texas study of short-term emissions variability, 
which showed that most peak emission events in a heavily-industrialized 
four-county area (Harris, Galveston, Chambers and Brazoria Counties, 
Texas) were less than twice the annual average hourly emissions rate. 
The highest peak emissions event was 74 times the annual average hourly 
emissions rate, and the 99th percentile ratio of peak hourly emissions 
rate to the annual average hourly emissions rate was 9.\20\ Considering 
this analysis, to account for more than 99 percent of the peak hourly 
emissions, we apply a conservative screening multiplication factor of 
10 to the average annual hourly emissions rate in our acute exposure 
screening assessments as our default approach. However, we use a factor 
other than 10 if we have information that indicates that a different 
factor is appropriate for a particular source category.
---------------------------------------------------------------------------

    \20\ See http://www.tceq.state.tx.us/compliance/field_ops/eer/index.html or the docket to access the source of these data.
---------------------------------------------------------------------------

    For the Primary Aluminum Production source category, information 
was available to determine process-specific factors. The processes in 
this source category are typically equipped with controls which will 
not allow startup of the emission source until the associated control 
device is operating and will automatically shut down the emission 
source if the associated controls malfunction. Further, some processes, 
for example, the potlines, operate continuously so there are no 
significant spikes in emissions. We, thus, believe emissions from the 
potlines are relatively consistent over time with minimal fluctuation. 
However, we realize that emissions vary over time. Furthermore, as 
described above, we estimate the maximum allowable emissions for this 
source category are about 1.5 times higher than the average long-term 
actual emissions for these sources. Therefore, we assume that hourly 
emissions rates from potlines could occasionally increase by a factor 
of up to 1.5 times the average hourly emissions, which, for the reasons 
stated above, we believe is a valid multiplier to estimate maximum 
acute emissions from potlines. Other processes, for example paste 
production and anode baking, may have specific cycles, with peak 
emissions occurring for a part of that cycle. We assume these peak 
emissions could be as high as 2 times the average emissions for paste 
plants and bake furnaces. As discussed in sections II.D and III.A.1 of 
this preamble, above, we collected data regarding the emissions from 
these processes. Those emissions data represent emissions during 
periods of normal operations (as opposed to during periods of peak 
emissions).
    Therefore, based on the modes of operation and other factors 
described above, we applied an acute emissions multiplier of 1.5 to all 
potline emissions for input to the acute risk assessment, and for paste 
production and anode baking we applied an acute emissions multiplier of 
2. We regard these factors as conservative (i.e., they are designed not 
to underestimate variability). Even with data available to develop 
process-specific factors, our assessment of acute risk reflects 
conservative assumptions, in particular in its assumptions that every 
potline operates at the same hour and that every potline has emissions 
1.5 times higher than the average at the same hour, that this is the 
same hour as the worst-case dispersion conditions, and that a person is 
at the location of maximum concentration during that hour. This results 
in a conservative exposure scenario.
    As part of our acute risk assessment process, for cases where acute 
HQ values from the screening step were less than or equal to 1 for 
modeled HAPs (even under the conservative assumptions of the screening 
analysis), acute impacts were deemed negligible and no further analysis 
was performed for these HAPs. In cases where an acute HQ from the 
screening step was greater than 1, for some modeled HAPs additional 
site-specific data were considered to develop a more refined estimate 
of the potential for acute impacts of concern. These refinements are 
discussed more fully in the Residual Risk Assessment for the Primary 
Aluminum Production Source Category in Support of the 2014 Supplemental 
Proposal, which is available in the docket for this action (Docket ID 
No. EPA-HQ-OAR-2011-0797). 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 emissions 
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. Recognizing that this level of data is rarely 
available, we instead rely on the multiplier approach.
    As noted above, the agency may choose to refine the acute screen by 
also assessing the exposure that may occur at a centroid of census 
block. For this source category we first used conservative assumptions 
for emissions rates, meteorology and exposure location for our acute 
analysis. We then refined the acute assessment by also estimating the 
HQ for As at centroids of census blocks.
    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,\21\ we generally examine a wider range of 
available acute health metrics (e.g., RELs, AEGLs) 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. In some cases, when Reference Value Arrays \22\ for 
HAP have

[[Page 72926]]

been developed, we consider additional acute values (i.e., occupational 
and international values) to provide a more complete risk 
characterization.
---------------------------------------------------------------------------

    \21\ 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.
    \22\ U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference 
Values for Formaldehyde in Graphical Arrays of Chemical-Specific 
Health Effect Reference Values for Inhalation Exposures (Final 
Report). U.S. Environmental Protection Agency, Washington, DC, EPA/
600/R-09/061, and available online at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003.
---------------------------------------------------------------------------

4. How did we conduct the multipathway exposure and risk screening?
    The EPA conducted a screening analysis examining the potential for 
significant human health risks due to exposures via routes other than 
inhalation (i.e., ingestion). We first determined whether any sources 
in the source category emitted any HAP known to be persistent and 
bioaccumulative in the environment (PB-HAP). The PB-HAP compounds or 
compound classes are identified for the screening from the EPA's Air 
Toxics Risk Assessment Library (available at http://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library).
    For the Primary Aluminum Production source category, we identified 
emissions of cadmium (Cd) compounds, D/F, POM, divalent Hg compounds 
and HF. However, as we explained in section III.A.1 of this preamble, 
many of the emissions tests for mercury and D/F were below detection 
limit or detection limit limited. Nevertheless, we estimated emissions 
of these HAP based on the conservative assumption that undetected 
emissions were equal to one half the detection limit. Therefore, we 
consider the estimates for D/F and Hg to be conservative (i.e., more 
likely to be overestimated rather than underestimated).
    Because one or more of the PB-HAP are emitted by at least one 
facility in the Primary Aluminum Production source category, we 
proceeded to the next step of the evaluation. In this step, we 
determined whether the facility-specific emissions rates of the emitted 
PB-HAP were large enough to create the potential for significant non-
inhalation human health risks under reasonable worst-case conditions. 
To facilitate this step, we developed emissions rate screening levels 
for several PB-HAP using a hypothetical upper-end screening exposure 
scenario developed for use in conjunction with the EPA's Total Risk 
Integrated Methodology.Fate, Transport, and Ecological Exposure 
(TRIM.FaTE) model. The PB-HAP with emissions rate screening levels are: 
Cd, lead, D/F, Hg compounds and POM. We conducted a sensitivity 
analysis on the screening scenario to ensure that its key design 
parameters would represent the upper end of the range of possible 
values, such that it would represent a conservative, but not impossible 
scenario. The facility-specific emissions rates of these PB-HAP were 
compared to the emission rate screening levels for these PB-HAP to 
assess the potential for significant human health risks via non-
inhalation pathways. We call this application of the TRIM.FaTE model 
the Tier 1 TRIM-screen or Tier 1 screen.
    For the purpose of developing emissions rates for our Tier 1 TRIM-
screen, we derived emission levels for these PB-HAP (other than lead 
(Pb) compounds) at which the maximum excess lifetime cancer risk would 
be 1-in-1 million (i.e., for D/F and POM) or, for HAP that cause non-
cancer health effects (i.e., Cd compounds and Hg compounds), the 
maximum HQ would be 1. If the emissions rate of any PB-HAP included in 
the Tier 1 screen exceeds the Tier 1 screening emissions rate for any 
facility, we conduct a second screen, which we call the Tier 2 TRIM-
screen or Tier 2 screen.
    In the Tier 2 screen, the location of each facility that exceeded 
the Tier 1 emission rate is used to refine the assumptions associated 
with the environmental scenario while maintaining the exposure scenario 
assumptions. A key assumption that is part of the Tier 1 screen is that 
a lake is located near the facility; we confirm the existence of lakes 
near the facility as part of the Tier 2 screen. We then adjust the 
risk-based Tier 1 screening level for each PB-HAP for each facility 
based on an understanding of how exposure concentrations estimated for 
the screening scenarios for the subsistence fisher and the subsistence 
farmer change with meteorology and environmental assumptions.
    PB-HAP emissions that do not exceed these new Tier 2 screening 
levels are considered to pose no unacceptable risks. When facilities 
exceed the Tier 2 screening levels, it does not mean that multipathway 
impacts are significant, only that we cannot rule out that possibility 
based on the results of the screen.
    If the PB-HAP emissions for a facility exceed the Tier 2 screening 
emissions rate, and data are available, we may decide to conduct a more 
refined Tier 3 multipathway assessment. There are several analyses that 
can be included in a Tier 3 screen depending upon the extent of 
refinement warranted, including validating that the lake is fishable 
and considering plume-rise to estimate emissions lost above the mixing 
layer. If the Tier 3 screen is exceeded, the EPA may further refine the 
assessment. For this source category, we conducted 3 Tier 3 screening 
assessments at Alcoa (Ferndale, WA), Alumax (Goose Creek, SC) and 
Reynolds Metals (Massena, NY). The Reynolds Metals facility is a 
Soderberg facility which was operating at the time we sent out the 
information request and when we collected the emissions data and 
initiated the modeling assessment. However, recently this facility 
permanently shut down all their Soderberg potline operations. It is our 
understanding that this facility will either convert to a prebake 
facility or remain permanently shut down. A detailed discussion of the 
approach for this multipathway risk assessment can be found in Appendix 
9 (Technical Support Document: Human Health Multipathway Residual Risk 
Screening Assessment for the Primary Aluminum Production Source 
Category) of the risk assessment document.
    In evaluating the potential multipathway risk from emissions of Pb 
compounds, rather than developing a screening emissions rate for them, 
we compared maximum estimated chronic inhalation exposures with the 
level of the current National Ambient Air Quality Standard (NAAQS) for 
Pb.\23\ Values below the level of the primary (health-based) Pb NAAQS 
were considered to have a low potential for multipathway risk.
---------------------------------------------------------------------------

    \23\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring among other 
things that the standard provide an ``ample margin of safety''). 
However, the lead NAAQS is a reasonable measure of determining risk 
acceptability (i.e., the first step of the Benzene NESHAP analysis) 
since it is designed to protect the most susceptible group in the 
human population--children, including children living near major 
lead emitting sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. 
In addition, applying the level of the primary lead NAAQS at the 
risk acceptability step is conservative, since the primary lead 
NAAQS reflects an adequate margin of safety.
---------------------------------------------------------------------------

    For further information on the multipathway analysis approach, see 
the Residual Risk Assessment for the Primary Aluminum Production Source 
Category in Support of the 2014 Supplemental Proposal, which is 
available in the docket for this action (Docket ID No. EPA-HQ-OAR-2011-
0797).
5. How did we assess risks considering the revised emissions control 
options?
    In addition to assessing baseline inhalation risks and potential 
multipathway risks, we also estimated risks considering the emission

[[Page 72927]]

reductions that would be achieved by the control options under 
consideration in this supplemental proposal (i.e., emission reductions 
reflecting the proposed standards reflecting MACT). In these cases, the 
expected emission reductions were applied to the specific HAP and 
emission points in the RTR emissions dataset to develop corresponding 
estimates of risk that would exist after implementation of the proposed 
amendments in today's action.
6. How did we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect
    The EPA conducts a screening assessment to examine the potential 
for adverse environmental effects as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
b. Environmental HAP
    The EPA focuses on seven HAP, which we refer to as ``environmental 
HAP,'' in its screening analysis: Five PB-HAP and two acid gases. The 
five PB-HAP are Cd, D/F, POM, Hg (both inorganic Hg and methylmercury) 
and Pb compounds. The two acid gases are hydrogen chloride (HCl) and 
HF. We have no data indicating primary aluminum plants emit HCl. 
Therefore, our analysis for this source category does not reflect HCl 
emissions. The rationale for including the remaining six HAP in the 
environmental risk screening analysis is presented below.
    The HAP that persist and bioaccumulate are of particular 
environmental concern because they accumulate in the soil, sediment and 
water. The PB-HAP are taken up, through sediment, soil, water and/or 
ingestion of other organisms, by plants or animals (e.g., small fish) 
at the bottom of the food chain. As larger and larger predators consume 
these organisms, concentrations of the PB-HAP in the animal tissues 
increase as does the potential for adverse effects. The five PB-HAP we 
evaluate as part of our screening analysis account for 99.8 percent of 
all PB-HAP emissions nationally from stationary sources (on a mass 
basis from the 2005 National Emissions Inventory).
    In addition to accounting for almost all of the mass of PB-HAP 
emitted, we note that the TRIM.FaTE model that we use to evaluate 
multipathway risk allows us to estimate concentrations of Cd compounds, 
D/F, POM and Hg in soil, sediment and water. For Pb compounds, we 
currently do not have the ability to calculate these concentrations 
using the TRIM.FaTE model. Therefore, to evaluate the potential for 
adverse environmental effects from Pb compounds, we compare the 
estimated HEM-3 modeled exposures from the source category emissions of 
Pb with the level of the secondary NAAQS for Pb.\24\ We consider values 
below the level of the secondary Pb NAAQS as unlikely to cause adverse 
environmental effects.
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    \24\ The secondary lead NAAQS is a reasonable measure of 
determining whether there is an adverse environmental effect since 
it was established considering ``effects on soils, water, crops, 
vegetation, man-made materials, animals, wildlife, weather, 
visibility and climate, damage to and deterioration of property, and 
hazards to transportation, as well as effects on economic values and 
on personal comfort and well-being.''
---------------------------------------------------------------------------

    Due to its well-documented potential to cause direct damage to 
terrestrial plants, we include the acid gas HF emitted by primary 
aluminum sources, in the environmental screening analysis. In addition 
to the potential to cause direct damage to plants, high concentrations 
of HF in the air have been linked to fluorosis in livestock. Air 
concentrations of these HAP are already calculated as part of the human 
multipathway exposure and risk screening analysis using the HEM3-AERMOD 
air dispersion model, and we are able to use the air dispersion 
modeling results to estimate the potential for an adverse environmental 
effect.
    The EPA acknowledges that other HAP beyond the seven HAP discussed 
above may have the potential to cause adverse environmental effects. 
Therefore, the EPA may include other relevant HAP in its environmental 
risk screening in the future, as modeling science and resources allow. 
The EPA invites comment on the extent to which other HAP emitted by the 
source category may cause adverse environmental effects. Such 
information should include references to peer-reviewed ecological 
effects benchmarks that are of sufficient quality for making regulatory 
decisions, as well as information on the presence of organisms located 
near facilities within the source category that such benchmarks 
indicate could be adversely affected.
c. Ecological Assessment Endpoints and Benchmarks for PB-HAP
    An important consideration in the development of the EPA's 
screening methodology is the selection of ecological assessment 
endpoints and benchmarks. Ecological assessment endpoints are defined 
by the ecological entity (e.g., aquatic communities including fish and 
plankton) and its attributes (e.g., frequency of mortality). Ecological 
assessment endpoints can be established for organisms, populations, 
communities or assemblages and ecosystems.
    For PB-HAP (other than Pb compounds), we evaluated the following 
community-level ecological assessment endpoints to screen for organisms 
directly exposed to HAP in soils, sediment and water:
     Local terrestrial communities (i.e., soil invertebrates, 
plants) and populations of small birds and mammals that consume soil 
invertebrates exposed to PB-HAP in the surface soil;
     Local benthic (i.e., bottom sediment dwelling insects, 
amphipods, isopods and crayfish) communities exposed to PB-HAP in 
sediment in nearby water bodies; and
     Local aquatic (water-column) communities (including fish 
and plankton) exposed to PB-HAP in nearby surface waters.
    For PB-HAP (other than Pb compounds), we also evaluated the 
following population-level ecological assessment endpoint to screen for 
indirect HAP exposures of top consumers via the bioaccumulation of HAP 
in food chains:
     Piscivorous (i.e., fish-eating) wildlife consuming PB-HAP-
contaminated fish from nearby water bodies.
    For Cd compounds, D/F, POM and Hg, we identified the available 
ecological benchmarks for each assessment endpoint. An ecological 
benchmark represents a concentration of HAP (e.g., 0.77 ug of HAP per 
liter of water) that has been linked to a particular environmental 
effect level through scientific study. For PB-HAP we identified, where 
possible, ecological benchmarks at the following effect levels:
     Probable effect levels (PEL): Level above which adverse 
effects are expected to occur frequently;
     Lowest-observed-adverse-effect level (LOAEL): The lowest 
exposure level tested at which there are biologically significant 
increases in frequency or severity of adverse effects; and

[[Page 72928]]

     No-observed-adverse-effect levels (NOAEL): The highest 
exposure level tested at which there are no biologically significant 
increases in the frequency or severity of adverse effect.
    We established a hierarchy of preferred benchmark sources to allow 
selection of benchmarks for each environmental HAP at each ecological 
assessment endpoint. In general, the EPA sources that are used at a 
programmatic level (e.g., Office of Water, Superfund Program) were used 
in the analysis, if available. If not, the EPA benchmarks used in 
regional programs (e.g., Superfund) were used. If benchmarks were not 
available at a programmatic or regional level, we used benchmarks 
developed by other federal agencies (e.g., National Oceanic and 
Atmospheric Administration (NOAA)) or state agencies.
    Benchmarks for all effect levels are not available for all PB-HAP 
and assessment endpoints. In cases where multiple effect levels were 
available for a particular PB-HAP and assessment endpoint, we use all 
of the available effect levels to help us to determine whether 
ecological risks exist and, if so, whether the risks could be 
considered significant and widespread.
d. Ecological Assessment Endpoints and Benchmarks for Acid Gases
    The environmental screening analysis also evaluated potential 
damage and reduced productivity of plants due to direct exposure to 
acid gases in the air. For acid gases, we evaluated the following 
ecological assessment endpoint:
     Local terrestrial plant communities with foliage exposed 
to acidic gaseous HAP in the air.
    The selection of ecological benchmarks for the effects of acid 
gases on plants followed the same approach as for PB-HAP (i.e., we 
examine all of the available chronic benchmarks). For HCl, the EPA 
identified chronic benchmark concentrations. We note that the benchmark 
for chronic HCl exposure to plants is greater than the reference 
concentration for chronic inhalation exposure for human health. This 
means that where the EPA includes regulatory requirements to prevent an 
exceedance of the reference concentration for human health, additional 
analyses for adverse environmental effects of HCl would not be 
necessary.
    For HF, the EPA identified chronic benchmark concentrations for 
plants and evaluated chronic exposures to plants in the screening 
analysis. High concentrations of HF in the air have also been linked to 
fluorosis in livestock. However, the HF concentrations at which 
fluorosis in livestock occur are higher than those at which plant 
damage begins. Therefore, the benchmarks for plants are protective of 
both plants and livestock.
e. Screening Methodology
    For the environmental risk screening analysis, the EPA first 
determined whether any facilities in the Primary Aluminum Production 
source category emitted any of the seven environmental HAP. For the 
Primary Aluminum Production source category, we identified emissions of 
five of the PB-HAP (Cd, Hg, Pb, D/F and POM) and one acid gas (HF).
    Because one or more of the seven environmental HAP evaluated are 
emitted by the facilities in the source category, we proceeded to the 
second step of the evaluation.
f. PB-HAP Methodology
    For Cd, Hg, POM and D/F, the environmental screening analysis 
consists of two tiers, while Pb compounds are analyzed differently as 
discussed earlier. However, as we explained in section III.A.1 above, 
there are greater uncertainties in the emissions estimates for Hg or D/
F because of the limitations in the available data and because a large 
portion of emissions tests results were below the detection limit for 
those HAP. Nevertheless, to be conservative (i.e., more likely to 
overestimate risks rather than underestimate risks), we have included 
emissions estimates of Hg and D/F in the PB-HAP risk screen based on 
conservative assumptions (i.e., emissions of one half the detection 
limit were assumed for those tests where no pollutants were detected).
    In the first tier, we determined whether the maximum facility-
specific emission rates of each of the emitted environmental HAP were 
large enough to create the potential for adverse environmental effects 
under reasonable worst-case environmental conditions. These are the 
same environmental conditions used in the human multipathway exposure 
and risk screening analysis.
    To facilitate this step, TRIM.FaTE was run for each PB-HAP under 
hypothetical environmental conditions designed to provide 
conservatively high HAP concentrations. The model was set to maximize 
runoff from terrestrial parcels into the modeled lake, which in turn, 
maximized the chemical concentrations in the water, the sediments and 
the fish. The resulting media concentrations were then used to back-
calculate a screening level emission rate that corresponded to the 
relevant exposure benchmark concentration value for each assessment 
endpoint. To assess emissions from a facility, the reported emission 
rate for each PB-HAP was compared to the screening level emission rate 
for that PB-HAP for each assessment endpoint. If emissions from a 
facility do not exceed the Tier 1 screening level, the facility 
``passes'' the screen, and, therefore, is not evaluated further under 
the screening approach. If emissions from a facility exceed the Tier 1 
screening level, we evaluate the facility further in Tier 2.
    In Tier 2 of the environmental screening analysis, the emission 
rate screening levels are adjusted to account for local meteorology and 
the actual location of lakes in the vicinity of facilities that did not 
pass the Tier 1 screen. The modeling domain for each facility in the 
Tier 2 analysis consists of eight octants. Each octant contains 5 
modeled soil concentrations at various distances from the facility (5 
soil concentrations x 8 octants = total of 40 soil concentrations per 
facility) and one lake with modeled concentrations for water, sediment 
and fish tissue. In the Tier 2 environmental risk screening analysis, 
the 40 soil concentration points are averaged to obtain an average soil 
concentration for each facility for each PB-HAP. For the water, 
sediment and fish tissue concentrations, the highest value for each 
facility for each pollutant is used. If emission concentrations from a 
facility do not exceed the Tier 2 screening level, the facility passes 
the screen, and is typically not evaluated further. If emissions from a 
facility exceed the Tier 2 screening level, the facility does not pass 
the screen and, therefore, may have the potential to cause adverse 
environmental effects. Such facilities are evaluated further to 
investigate factors such as the magnitude and characteristics of the 
area of exceedance.
g. Acid Gas Methodology
    The environmental screening analysis evaluates the potential 
phytotoxicity and reduced productivity of plants due to chronic 
exposure to HF (we have no data regarding HCl emissions from primary 
aluminum facilities and, therefore, HCl was not analyzed). The 
environmental risk screening methodology for HF is a single-tier screen 
that compares the average off-site ambient air concentration over the 
modeling domain to ecological benchmarks for each of the acid gases. 
Because air concentrations are compared directly to the ecological 
benchmarks, emission-based screening levels are not calculated for HF 
as they

[[Page 72929]]

are in the ecological risk screening methodology for PB-HAPs.
    For purposes of ecological risk screening, the EPA identifies a 
potential for adverse environmental effects to plant communities from 
exposure to acid gases when the average concentration of the HAP around 
a facility exceeds the LOAEL ecological benchmark. In such cases, we 
further investigate factors such as the magnitude and characteristics 
of the area of exceedance (e.g., land use of exceedance area, size of 
exceedance area) to determine if there is an adverse environmental 
effect.
    For further information on the environmental screening analysis 
approach, see the Residual Risk Assessment for the Primary Aluminum 
Production Source Category in Support of the 2014 Supplemental 
Proposal, which is available in the docket for this action (Docket ID 
No. EPA-HQ-OAR-2011-0797).
7. How did we conduct facility-wide assessments?
    To put the source category risks in context, we 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 other words, 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 for which we have data. We analyzed 
risks due to the inhalation of HAP that are emitted ``facility-wide'' 
for the populations residing within 50 km of each facility, consistent 
with the methods used for the source category analysis described above. 
The Residual Risk Assessment for the Primary Aluminum Production Source 
Category in Support of the 2014 Supplemental Proposal, available 
through the docket for this action, provides the methodology and 
results of the facility-wide analyses, including all facility-wide 
risks.
8. How did we consider uncertainties in risk assessment?
    In the Benzene NESHAP, we concluded that risk estimation 
uncertainty should be considered in our decision-making under the ample 
margin of safety framework. Uncertainty and the potential for bias are 
inherent in all risk assessments, including those performed for this 
proposal. Although uncertainty exists, we believe that our approach, 
which used conservative tools and assumptions, ensures that our 
decisions are health protective and environmentally protective. A brief 
discussion of the uncertainties in the RTR emissions dataset, 
dispersion modeling, inhalation exposure estimates and dose-response 
relationships follows below. A more thorough discussion of these 
uncertainties is included in the Revised Draft Development of the RTR 
Emissions Dataset for the Primary Aluminum Production Source Category, 
and the Residual Risk Assessment for the Primary Aluminum Production 
Source Category in Support of the 2014 Supplemental Proposal, which is 
available in the docket for this action (Docket ID No. EPA-HQ-OAR-2011-
0797).
a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions 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 accurate, errors in emission estimates and other 
factors. The emission estimates considered in this analysis generally 
are annual totals for certain years, and they 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 an emission adjustment factor for 
each emission process group and applied to the average annual hourly 
emission rates, which are intended to account for emission fluctuations 
due to normal facility operations.
    As described above and in the Revised Draft Development of the RTR 
Emissions Dataset for the Primary Aluminum Production Source Category, 
we gathered a substantial amount of emissions test data from currently 
operating facilities (plus test data from a then-operating, now closed 
Soderberg facility). Required testing under the CAA section 114 request 
included measurements of HAP metal emissions from primary and secondary 
potline exhausts at seven facilities, as well as measurements of HAP 
metal emissions from three anode bake furnace exhausts and three paste 
plant exhausts. We also received additional POM emissions data from 
eight facilities. Furthermore, we received speciated PAH, PCB and D/F 
emissions data from primary and secondary exhausts of two potlines (one 
Soderberg potline and one prebake potline), as well as exhausts from 
one anode bake furnace and one paste plant. We used these data to 
estimate emissions from emission points for which we had no emissions 
test data. Also, there is additional uncertainty concerning the 
estimated emissions of Hg and D/F since, as discussed in sections 
III.A.1 and IV.A of this preamble, a substantial portion of the 
emissions test results for those HAP were reported as below laboratory 
detection limits. Finally, we received hexavalent chromium (Cr\+6\) 
emissions stack test data from primary and secondary potline exhausts 
at two facilities and an anode bake furnace and a paste plant at one 
facility. We used the average results from these tests to apportion 
emissions of Cr\+6\ and trivalent chromium (Cr\+3\) for the remaining 
facilities that did not test. Therefore, there are some uncertainties 
regarding the split between Cr\+6\ and Cr\+3\ for these remaining 
facilities. Nevertheless, we believe the test data we used are 
representative. Thus, the uncertainties are not significant. 
Furthermore, since we used the average results of the available tests, 
the values we used as input for the risk assessment are equally likely 
to be overestimates or underestimates of the actual speciated 
emissions.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration 
estimates associated with any model, including the EPA's recommended 
regulatory dispersion model, AERMOD. In using a model to estimate 
ambient pollutant concentrations, the user chooses certain options to 
apply. For RTR assessments, we select some model options that have the 
potential to overestimate ambient air concentrations (e.g., not 
including plume depletion or pollutant transformation). We select other 
model options that have the potential to underestimate ambient impacts 
(e.g., not including building downwash). Other options that we select 
have the potential to either under- or overestimate ambient levels 
(e.g., meteorology and receptor locations). On balance, considering the 
directional nature of the uncertainties commonly present in ambient 
concentrations estimated by dispersion models, the approach we apply in 
the RTR assessments should yield unbiased estimates of ambient HAP 
concentrations.
c. Uncertainties in Inhalation Exposure
    The EPA did not include the effects of human mobility on exposures 
in the assessment. Specifically, short-term mobility and long-term 
mobility between census blocks in the modeling

[[Page 72930]]

domain were not considered.\25\ The approach of not considering short 
or long-term population mobility does not bias the estimate of the 
theoretical MIR (by definition), nor does it affect the estimate of 
cancer incidence because 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 high risk levels (e.g., 1-in-10 thousand 
or 1-in-1 million).
---------------------------------------------------------------------------

    \25\ 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.
---------------------------------------------------------------------------

    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 over-predict 
exposures for people in the census block who live farther 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 is an unbiased estimate 
of average risk and incidence. We reduce this uncertainty by analyzing 
large census blocks near facilities using aerial imagery and adjusting 
the location of the block centroid to better represent the population 
in the block, as well as adding additional receptor locations where the 
block population is not well represented by a single location.
    The assessment evaluates the cancer inhalation risks associated 
with pollutant exposures over a 70-year period, which is the assumed 
lifetime of an individual. In reality, both the length of time that 
modeled emission 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 
domestic facilities) will influence the future risks posed by a given 
source or 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 the unlikely scenario where a facility 
maintains, or even increases, its emissions levels over a period of 
more than 70 years, residents live beyond 70 years at the same 
location, and the residents spend most of their days at that location, 
then the cancer inhalation risks could potentially be underestimated. 
However, annual cancer incidence estimates from exposures to emissions 
from these sources would not be affected by the length of time an 
emissions source operates.
    The exposure estimates used in these analyses assume chronic 
exposures to ambient (outdoor) 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, 
indoor levels are typically lower. This factor has the potential to 
result in an overestimate of 25 to 30 percent of exposures.\26\
---------------------------------------------------------------------------

    \26\ U.S. EPA. National-Scale Air Toxics Assessment for 1996. 
(EPA 453/R-01-003; January 2001; page 85.)
---------------------------------------------------------------------------

    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that the EPA 
conducts as part of the risk review under section 112(f) of the CAA 
that should be highlighted. The accuracy of an acute inhalation 
exposure assessment depends on the simultaneous occurrence of 
independent factors that may vary greatly, such as hourly emissions 
rates, meteorology and the presence of humans at the location of the 
maximum concentration. In the acute screening assessment that we 
conduct under the RTR program, we assume that peak emissions from the 
source category and worst-case meteorological conditions co-occur, 
thus, resulting in maximum ambient concentrations. These two events are 
unlikely to occur at the same time, making these assumptions 
conservative. We then include the additional assumption that a person 
is located at this point during this same time period. For the primary 
aluminum source category, these assumptions would tend to be 
conservative worst-case actual exposures as it is unlikely that a 
person would be located at the point of maximum exposure during the 
time when peak emissions and worst-case meteorological conditions occur 
simultaneously.
    For the primary aluminum source category, we refined the acute 
exposure assessment by estimating the HQ at a centroid of a census 
block. This reduces the uncertainty in the assessment because we are 
evaluating the potential for exposures to occur at locations where 
people could actually live, rather than at the point of maximum off-
site concentration.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and non-cancer 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's Guidelines for Carcinogen Risk Assessment 
(EPA/630/P-03/001B, March 2005); namely, that ``the primary goal of 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'' (Guidelines for Carcinogen Risk Assessment, 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 relationships is given in the Residual 
Risk Assessment for the Primary Aluminum Production Source Category in 
Support of the November 2014 Proposal, which is available in the docket 
for this action (Docket ID No. EPA-HQ-OAR-2011-0797).
    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).\27\ In some circumstances, the true risk could be as 
low as zero; however, in other circumstances the risk could be greater. 
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

[[Page 72931]]

limitations for other uses (e.g., priority-setting or expected benefits 
analysis).
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    \27\ IRIS glossary (http://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary).
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    Chronic non-cancer 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 a continuous 
inhalation exposure (RfC) or a daily oral exposure (RfD) to the human 
population (including sensitive subgroups) that is 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 considers uncertainty, variability and gaps in the 
available data. The UF are applied to derive reference values that are 
intended to protect against appreciable risk of deleterious effects. 
The UF are commonly default values,\28\ 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 pollutants, it is possible that risks may be 
underestimated.
---------------------------------------------------------------------------

    \28\ 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 the 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.
---------------------------------------------------------------------------

    While collectively termed ``UF,'' 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. The 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 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 appropriate human health 
effect dose-response assessment values for all pollutants emitted by 
the sources in this risk assessment, some HAP emitted by this source 
category are lacking dose-response assessments. Accordingly, these 
pollutants cannot be included in the quantitative risk assessment, 
which could result in quantitative estimates understating HAP risk.
    To help to alleviate this potential underestimate, where we 
conclude similarity with a HAP for which a dose-response assessment 
value is available, we use that value as a surrogate for the assessment 
of the HAP for which no value is available. To the extent use of 
surrogates indicates appreciable risk, we may identify a need to 
increase priority for new IRIS assessment of that substance. We 
additionally note that, generally speaking, HAP of greatest concern due 
to environmental exposures and hazard are those for which dose-response 
assessments have been performed, reducing the likelihood of 
understating risk.
e. Uncertainties in the Multipathway Assessment
    For each source category, we generally rely on site-specific levels 
of PB-HAP emissions to determine whether a refined assessment of the 
impacts from multipathway exposures is necessary. This determination is 
based on the results of a three-tiered screening analysis that relies 
on the outputs from models that estimate environmental pollutant 
concentrations and human exposures for four PB-HAP. Two important types 
of uncertainty associated with the use of these models in RTR risk 
assessments and inherent to any assessment that relies on environmental 
modeling are model uncertainty and input uncertainty.\29\
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    \29\ In the context of this discussion, the term ``uncertainty'' 
as it pertains to exposure and risk encompasses both variability in 
the range of expected inputs and screening results due to existing 
spatial, temporal and other factors, as well as uncertainty in being 
able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the selected models are 
appropriate for the assessment being conducted and whether they 
adequately represent the actual processes that might occur for that 
situation. An example of model uncertainty is the question of whether 
the model adequately describes the movement of a pollutant through the 
soil. This type of uncertainty is difficult to quantify. However, based 
on feedback received from previous EPA SAB reviews and other reviews, 
we are confident that the models used in the screen are appropriate and 
state-of-the-art for the multipathway risk assessments conducted in 
support of RTR.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the multipathway screen, we configured the models to avoid 
underestimating exposure and risk. This was

[[Page 72932]]

accomplished by selecting upper-end values from nationally-
representative datasets for the more influential parameters in the 
environmental model, including selection and spatial configuration of 
the area of interest, lake location and size, meteorology, surface 
water and soil characteristics and structure of the aquatic food web. 
We also assume an ingestion exposure scenario and values for human 
exposure factors that represent reasonable maximum exposures. The 
multipathway screens include some hypothetical elements, namely the 
hypothetical farmer and fisher scenarios. It is important to note that 
even though EPA conducted a multipathway assessment based on these 
scenarios, no data exist to verify the existence of either the farmer 
or fisher scenario outlined above.
    In Tier 2 of the multipathway assessment, we refine the model 
inputs to account for meteorological patterns in the vicinity of the 
facility versus using upper-end national values and we identify the 
actual location of lakes near the facility rather than the default lake 
location that we apply in Tier 1. By refining the screening approach in 
Tier 2 to account for local geographical and meteorological data, we 
decrease the likelihood that concentrations in environmental media are 
overestimated, thereby increasing the usefulness of the screen. The 
assumptions and the associated uncertainties regarding the selected 
ingestion exposure scenario are the same for Tier 1 and Tier 2.
    For both Tiers 1 and 2 of the multipathway assessment, our approach 
to addressing model input uncertainty is generally cautious. We choose 
model inputs from the upper end of the range of possible values for the 
influential parameters used in the models, and we assume that the 
exposed individual exhibits ingestion behavior that would lead to a 
high total exposure. This approach reduces the likelihood of not 
identifying high risks for adverse impacts.
    Despite the uncertainties, when individual pollutants or facilities 
do screen out, we are confident that the potential for adverse 
multipathway impacts on human health is very low. On the other hand, 
when individual pollutants or facilities do not screen out, it does not 
mean that multipathway impacts are significant, only that we cannot 
rule out that possibility and that a refined multipathway analysis for 
the site might be necessary to obtain a more accurate risk 
characterization for the source category. For further information on 
uncertainties and the Tier 1 and 2 screening methods, refer to the risk 
document Appendix 5, Technical Support Document for TRIM-Based 
Multipathway Tiered Screening Methodology for RTR.
    We completed a Tier 3 multipathway screen for this supplemental 
proposal. This assessment contains less uncertainty compared to the 
Tier 1 and Tier 2 screens. The Tier 3 screen improves the lake 
characterization used in the Tier 2 analysis and improves the screen by 
adjusting for emissions lost to the upper air sink through plume-rise 
calculations. The Tier 3 screen reduces uncertainty through improved 
lake evaluations used in the Tier 2 screen and by calculating the 
amount of mass lost to the upper air sink through plume rise. 
Nevertheless, some uncertainties also exist here. The Tier 3 
multipathway screen and related uncertainties are described in detail 
in section 4 of the Residual Risk Assessment for the Primary Aluminum 
Production Source Category in Support of the 2014 Supplemental 
Proposal, which is available in the docket for this action (Docket ID 
No. EPA-HQ-OAR-2011-0797).
f. Uncertainties in the Environmental Risk Screening Assessment
    For each source category, we generally rely on site-specific levels 
of environmental HAP emissions to perform an environmental screening 
assessment. The environmental screening assessment is based on the 
outputs from models that estimate environmental HAP concentrations. The 
same models, specifically the TRIM.FaTE multipathway model and the 
AERMOD air dispersion model, are used to estimate environmental HAP 
concentrations for both the human multipathway screening analysis and 
for the environmental screening analysis. Therefore, both screening 
assessments have similar modeling uncertainties.
    Two important types of uncertainty associated with the use of these 
models in RTR environmental screening assessments--and inherent to any 
assessment that relies on environmental modeling--are model uncertainty 
and input uncertainty.\30\
---------------------------------------------------------------------------

    \30\ In the context of this discussion, the term 
``uncertainty,'' as it pertains to exposure and risk assessment, 
encompasses both variability in the range of expected inputs and 
screening results due to existing spatial, temporal and other 
factors, as well as uncertainty in being able to accurately estimate 
the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the selected models are 
appropriate for the assessment being conducted and whether they 
adequately represent the movement and accumulation of environmental HAP 
emissions in the environment. For example, does the model adequately 
describe the movement of a pollutant through the soil? This type of 
uncertainty is difficult to quantify. However, based on feedback 
received from previous EPA SAB reviews and other reviews, we are 
confident that the models used in the screen are appropriate and state-
of-the-art for the environmental risk assessments conducted in support 
of our RTR analyses.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the environmental screen for PB-HAP, we configured the models to 
avoid underestimating exposure and risk to reduce the likelihood that 
the results indicate the risks are lower than they actually are. This 
was accomplished by selecting upper-end values from nationally-
representative datasets for the more influential parameters in the 
environmental model, including selection and spatial configuration of 
the area of interest, the location and size of any bodies of water, 
meteorology, surface water and soil characteristics and structure of 
the aquatic food web. In Tier 1, we used the maximum facility-specific 
emissions for the PB-HAP (other than Pb compounds, which were evaluated 
by comparison to the secondary Pb NAAQS) that were included in the 
environmental screening assessment and each of the media when comparing 
to ecological benchmarks. This is consistent with the conservative 
design of Tier 1 of the screen. In Tier 2 of the environmental 
screening analysis for PB-HAP, we refine the model inputs to account 
for meteorological patterns in the vicinity of the facility versus 
using upper-end national values, and we identify the locations of water 
bodies near the facility location. By refining the screening approach 
in Tier 2 to account for local geographical and meteorological data, we 
decrease the likelihood that concentrations in environmental media are 
overestimated, thereby increasing the usefulness of the screen. To 
better represent widespread impacts, the modeled soil concentrations 
are averaged in Tier 2 to obtain one average soil concentration value 
for each facility and for each PB-HAP. For PB-HAP concentrations in 
water, sediment and fish tissue, the highest value for each facility 
for each pollutant is used.
    For the environmental screening assessment for acid gases, we 
employ a single-tiered approach. We use the modeled air concentrations 
and compare those with ecological benchmarks.

[[Page 72933]]

    For both Tiers 1 and 2 of the environmental screening assessment, 
our approach to addressing model input uncertainty is generally 
cautious. We choose model inputs from the upper end of the range of 
possible values for the influential parameters used in the models, and 
we assume that the exposed individual exhibits ingestion behavior that 
would lead to a high total exposure. This approach reduces the 
likelihood of not identifying potential risks for adverse environmental 
impacts.
    Uncertainty also exists in the ecological benchmarks for the 
environmental risk screening analysis. We established a hierarchy of 
preferred benchmark sources to allow selection of benchmarks for each 
environmental HAP at each ecological assessment endpoint. In general, 
EPA benchmarks used at a programmatic level (e.g., Office of Water, 
Superfund Program) were used if available. If not, we used EPA 
benchmarks used in regional programs (e.g., Superfund Program). If 
benchmarks were not available at a programmatic or regional level, we 
used benchmarks developed by other agencies (e.g., NOAA) or by state 
agencies.
    In all cases (except for Pb compounds, which were evaluated through 
a comparison to the NAAQS for Pb and its compounds), we searched for 
benchmarks at the following three effect levels, as described in 
section III.A.6 of this preamble:
    1. A no-effect level (i.e., NOAEL).
    2. Threshold-effect level (i.e., LOAEL).
    3. Probable effect level (i.e., PEL).
    For some ecological assessment endpoint/environmental HAP 
combinations, we could identify benchmarks for all three effect levels, 
but for most, we could not. In one case, where different agencies 
derived significantly different numbers to represent a threshold for 
effect, we included both. In several cases, only a single benchmark was 
available. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we used all of the available 
effect levels to help us to determine whether risk exists and if the 
risks could be considered significant and widespread.
    The EPA evaluates the following seven HAP in the environmental risk 
screening assessment: Cd, D/F, POM, Hg (both inorganic Hg and 
methylmercury), Pb compounds, HCl \31\ and HF, where applicable. These 
seven HAP represent pollutants that can cause adverse impacts for 
plants and animals either through direct exposure to HAP in the air or 
through exposure to HAP that is deposited from the air onto soils and 
surface waters. These seven HAP also represent those HAP for which we 
can conduct a meaningful environmental risk screening assessment. For 
other HAP not included in our screening assessment, the model has not 
been parameterized such that it can be used for that purpose. In some 
cases, depending on the HAP, we may not have appropriate multipathway 
models that allow us to predict the concentration of that pollutant. 
The EPA acknowledges that other HAP beyond the seven HAP that we are 
evaluating may have the potential to cause adverse environmental 
effects and, therefore, the EPA may evaluate other relevant HAP in the 
future, as modeling science and resources allow.
---------------------------------------------------------------------------

    \31\ As noted above, we have no data regarding HCl emissions 
from primary aluminum plants so the EPA did not evaluate HCl in this 
screening assessment for this proposal.
---------------------------------------------------------------------------

    Further information on uncertainties and the Tier 1 and 2 screening 
methods is provided in Appendix 5 of the document ``Technical Support 
Document for TRIM-Based Multipathway Tiered Screening Methodology for 
RTR: Summary of Approach and Evaluation.'' Also, see the Residual Risk 
Assessment for the Primary Aluminum Production Source Category in 
Support of the 2014 Supplemental Proposal, available in the docket for 
this action (Docket ID No. EPA-HQ-OAR-2011-0797).

B. How did we consider the risk results in making decisions for this 
supplemental proposal?

    As discussed in section II.A of this preamble, in evaluating and 
developing standards under CAA section 112(f)(2), 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) 
\32\ of approximately [1-in-10 thousand] [i.e., 100-in-1 million].'' 54 
FR 38045, September 14, 1989. If risks are unacceptable, the EPA must 
determine the emissions standards necessary to bring risks to an 
acceptable level without considering costs. In the second step of the 
process, the EPA considers whether the emissions standards provide 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. The EPA must 
promulgate emission standards necessary to provide an ample margin of 
safety.
---------------------------------------------------------------------------

    \32\ 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.
---------------------------------------------------------------------------

    In past residual risk actions, the EPA considered a number of human 
health risk metrics associated with emissions from the categories under 
review, including the MIR, the number of persons in various risk 
ranges, cancer incidence, the maximum non-cancer HI and the maximum 
acute non-cancer hazard. See, e.g., 72 FR 25138, May 3, 2007; 71 FR 
42724, July 27, 2006. The EPA considered this health information for 
both actual and allowable emissions. See, e.g., 75 FR 65068, October 
21, 2010; 75 FR 80220, December 21, 2010; 76 FR 29032, May 19, 2011. 
The EPA also discussed risk estimation uncertainties and considered the 
uncertainties in the determination of acceptable risk and ample margin 
of safety in these past actions. The EPA considered this same type of 
information in support of this action.
    The agency is considering these various measures of health 
information to inform our determinations of risk acceptability and 
ample margin of safety under CAA section 112(f). 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, September 14, 1989. Similarly, with regard 
to the ample margin of safety determination, ``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.
    The Benzene NESHAP approach provides flexibility regarding factors 
the EPA may consider in making determinations and how the EPA may weigh 
those factors for each source category. In responding to comment on our 
policy under the Benzene NESHAP, the EPA explained that:

``[t]he 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

[[Page 72934]]

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'.''

See 54 FR at 38057, September 14, 1989. 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 one 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.'' Id. at 38045. Similarly, with regard to the 
ample margin of safety analysis, the EPA stated in the Benzene NESHAP 
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.'' Id. at 
38061. We also consider the uncertainties associated with the various 
risk analyses, as discussed earlier in this preamble, in our 
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information 
to date in making residual risk determinations. At this time, we do not 
attempt to quantify those HAP risks that may be associated with 
emissions from other facilities that do not include the source 
categories in question, mobile source emissions, natural source 
emissions, persistent environmental pollution or atmospheric 
transformation in the vicinity of the sources in these categories.
    The agency understands the potential importance of considering an 
individual's total exposure to HAP in addition to considering exposure 
to HAP emissions from the source category and facility. We recognize 
that such consideration may be particularly important when assessing 
non-cancer risks, where pollutant-specific exposure health reference 
levels (e.g., RfCs) are based on the assumption that thresholds exist 
for adverse health effects. For example, the agency recognizes that, 
although exposures attributable to emissions from a source category or 
facility alone may not indicate the potential for increased risk of 
adverse non-cancer health effects in a population, the exposures 
resulting from emissions from the facility in combination with 
emissions from all of the other sources (e.g., other facilities) to 
which an individual is exposed may be sufficient to result in increased 
risk of adverse non-cancer health effects. In May 2010, the SAB advised 
the EPA ``that RTR assessments will be most useful to decision makers 
and communities if results are presented in the broader context of 
aggregate and cumulative risks, including background concentrations and 
contributions from other sources in the area.'' \33\
---------------------------------------------------------------------------

    \33\ The EPA's responses to this and all other key 
recommendations of the SAB's advisory on RTR risk assessment 
methodologies (which is available at: http://yosemite.epa.gov/sab/
sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-
007-unsigned.pdf) are outlined in a memo to this rulemaking docket 
from David Guinnup titled, EPA's Actions in Response to the Key 
Recommendations of the SAB Review of RTR Risk Assessment 
Methodologies.
---------------------------------------------------------------------------

    In response to the SAB recommendations, the EPA is incorporating 
cumulative risk analyses into its RTR risk assessments, including those 
reflected in this proposal. The agency is: (1) Conducting facility-wide 
assessments, which include source category emission points as well as 
other emission points within the facilities; (2) considering sources in 
the same category whose emissions result in exposures to the same 
individuals; and (3) for some persistent and bioaccumulative 
pollutants, analyzing the ingestion route of exposure. In addition, the 
RTR risk assessments have always considered aggregate cancer risk from 
all carcinogens and aggregate non-cancer hazard indices from all non-
carcinogens affecting the same target organ system.
    Although we are interested in placing source category and facility-
wide HAP risks in the context of total HAP risks from all sources 
combined in the vicinity of each source, we are concerned about the 
uncertainties of doing so. Because of the contribution to total HAP 
risk from emission sources other than those that we have studied in 
depth during this RTR review, such estimates of total HAP risks would 
have significantly greater associated uncertainties than the source 
category or facility-wide estimates. Such aggregate or cumulative 
assessments would compound those uncertainties, making the assessments 
too unreliable.
    As discussed in more detail below, based on the results of these 
risk analyses and evaluation of control options, we are proposing 
revised limits for emissions of POM from potlines, and first ever 
emissions limits for emissions of PM (as a surrogate for HAP metals) 
from potlines, anode bake furnaces and paste production plants and for 
emissions of Ni and As, from the VSS2 potline subcategory.

C. 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 MACT standards were promulgated. Where we 
identified such developments, in order to inform our decision of 
whether it is ``necessary'' to revise the emissions standards, within 
the meaning of CAA section 112(d)(6), we analyzed the technical 
feasibility of applying these developments and the estimated costs, 
energy implications, non-air environmental impacts, as well as 
considering the emission reductions. We also considered the 
appropriateness of applying controls to new sources versus retrofitting 
existing sources.
    Based on our analyses of the available data and information, we 
identified potential developments in practices, processes and control 
technologies. For 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 original MACT 
standards.
     Any improvements in add-on control technology or other 
equipment (that were identified and considered during development of 
the original MACT standards) that could result in additional emissions 
reduction.
     Any work practice or operational procedure that was not 
identified or considered during development of the original MACT 
standards.
     Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during

[[Page 72935]]

development of the original MACT standards.
     Any significant changes in the cost (including cost 
effectiveness) of applying controls (including controls the EPA 
considered during the development of the original MACT standards).
    Since we are proposing some first-time MACT standards in this 
action, we considered the same factors with respect to these proposed 
MACT standards. In addition to reviewing the practices, processes and 
control technologies that were considered at the time we originally 
developed (or last updated) the NESHAP, we also reviewed a variety of 
data sources in our investigation of potential practices, processes or 
controls to consider. Among the sources we reviewed were the NESHAP for 
various industries that were promulgated since the MACT standards being 
reviewed in this action. We reviewed the regulatory requirements and/or 
technical analyses associated with these regulatory actions to identify 
any practices, processes and control technologies considered in these 
efforts that could be applied to emission sources in the Primary 
Aluminum Production source category, as well as the costs, non-air 
impacts and energy implications associated with the use of these 
technologies. Additionally, we requested information from facilities 
regarding developments in practices, processes or control technology. 
Finally, we reviewed information from other sources, such as state and/
or local permitting agency databases and industry-supported databases.
    For the 2011 proposal, our initial technology review focused on the 
identification and evaluation of developments in practices, processes 
and control technologies that have occurred since the EPA promulgated 
the 1997 NESHAP. We then made decisions on whether it is necessary to 
propose amendments to the 1997 NESHAP to require standards reflecting 
performance of the identified developments. Based on our analyses of 
the data and information collected and our general understanding of the 
industry and other available information on potential controls for this 
industry, we identified no developments in practices, processes and 
control technologies, other than the proposed startup work practices 
described in the December 2011 proposal (76 FR 76260).
    Additional details regarding the previously conducted technology 
review can be found in the Draft Technology Review for Primary Aluminum 
Reduction Plants (Docket ID No. EPA-HQ-OAR-2011-0797-0149) and are 
discussed in the preamble to the December 2011 proposal (76 FR 76260). 
We conducted an additional review of developments in practices, 
processes and control technologies since the 2011 proposal and updated 
the technology review to reflect changes in the number and type of 
currently operating and idled facilities. As noted, this analysis 
indicates what developments may be possible assuming the EPA adopts the 
proposed amendments to the MACT standards discussed in the following 
section of this preamble. The Revised Draft Technology Review for the 
Primary Aluminum Production Source Category is available in the docket 
(Docket ID No. EPA-HQ-OAR-2011-0797).

IV. Revised Analytical Results and Proposed Decisions for the Primary 
Aluminum Production Source Category

A. What actions are we proposing pursuant to CAA sections 112(d)(2) and 
112(d)(3)?

    As described previously, CAA section 112(d) requires the EPA to 
promulgate technology-based NESHAP for listed source categories, 
including this source category. The EPA did so in the 1997 primary 
aluminum NESHAP. As described above (in section II.B), the 1997 NESHAP 
included MACT standards for TF from all types of existing and new 
potlines and bake furnaces and MACT standards for POM from existing and 
new Soderberg potlines, paste plants, bake furnaces and new pitch 
storage tanks. In the 2011 proposal, we proposed emissions limits 
pursuant to CAA sections 112(d)(2) and (3) for a number of HAP or 
emissions points that were not previously covered by the NESHAP, 
including limits for POM from prebake potlines, COS from prebake and 
Soderberg potlines and POM from existing pitch storage tanks. After 
proposal, in response to the 2013 CAA section 114 information request, 
we received a substantial amount of additional data on POM emissions 
from prebake potlines and therefore we re-analyzed the proposed limits 
for emissions of POM from prebake potlines.\34\ Based on those analyses 
we have determined it is appropriate to propose revised emission limits 
for POM from these existing potlines in these subcategories, and to 
propose different POM limits for new potlines.
---------------------------------------------------------------------------

    \34\ As explained above, the EPA did not have POM emissions data 
for prebake potlines at the time of the December 2011 proposal. The 
EPA developed the POM emissions MACT floor limits for prebake 
potlines in that proposal by estimating POM emissions based on a 
ratio of POM emissions to TF emissions, an approach which found no 
support in the public comments. Today's proposal is based entirely 
on the new emission data obtained since the December 2011 proposal. 
See section II.D, above.
---------------------------------------------------------------------------

    Additionally, after the 2011 proposal, in response to the 2013 CAA 
section 114 information request, we received data regarding PM and HAP 
metals emissions from potlines, anode bake furnaces and paste plants. 
These pollutants are not covered by the 1997 NESHAP. Based on those 
analyses, we have determined it is appropriate to propose emission 
limits for PM, as a surrogate for HAP metals, from existing potlines 
and new potlines, as well as from new and existing anode bake furnaces 
and new and existing paste plants. We have used PM as a surrogate for 
HAP metals in many other NESHAP (e.g., secondary aluminum, see 65 FR 
15692 (March 23, 2000), and Portland cement, 64 FR 31900 (June 14, 
1999)). The agency believes PM is an appropriate surrogate for non-
mercury HAP metals because those metals and particulate are captured 
indiscriminately by PM control technology. See National Lime Ass'n v. 
EPA, 233 F. 3d 625, 639 (D.C. Cir. 2000) (upholding use of PM as a 
surrogate for HAP metal for purposes of CAA section 112(d) MACT 
standard). We do not consider TF to be a suitable surrogate for HAP 
metals since the HF portion of TF is very reactive and controlled very 
effectively via adsorption in dry alumina scrubbers in the Primary 
Aluminum Production source category. The HAP metals would not be as 
effectively controlled via these mechanisms and, therefore, we would 
not expect good correlation, for this source category, between HAP 
metal emissions and TF emissions. Similarly, we do not consider POM to 
be a suitable surrogate for HAP metals as POM is more effectively 
controlled via adsorption in the dry alumina scrubbers than HAP metals. 
Again, we would not expect good correlation, for this source category, 
between HAP metal emissions and POM emissions. See 61 FR 50592 (Sept. 
26, 1996). We expect better correlations may exist between these 
pollutants in some other source categories that use other types of 
control devices to minimize emissions. However, as explained above, we 
do not expect good correlation in the Primary Aluminum Production 
source category, which uses dry alumina scrubbers as a primary control 
technology and is the only source category we are aware of that 
controls emissions with dry alumina scrubbers. Therefore, we are 
proposing MACT limits for both POM and PM for Primary Aluminum 
Production sources in this action.
    In this section, we summarize how we developed the revised proposed

[[Page 72936]]

standards for POM emissions from prebake potlines and the newly 
proposed PM emission standards for potlines, anode bake furnaces and 
paste plants (including how we calculated MACT floors, how we accounted 
for variability in those floor calculations, and how we considered 
beyond-the-floor (BTF) options). For more information on these 
analyses, see the Revised Draft MACT Floor Analysis for the Primary 
Aluminum Production Source Category, which is available in the docket 
for this action (Docket ID No. EPA-HQ-OAR-2011-0797).
    With regard to Hg, D/F and PCBs, as discussed in section III.A.1 of 
this preamble, there are considerable limitations in the emissions data 
for these HAP. For example, many of the available emissions test 
results were reported as below detection limit (BDL) for these HAP. 
Furthermore, we have test data for PCBs and D/F for only one of the 11 
prebake facilities. Nevertheless, based on the available data 
(including applying conservative assumptions that non-detectable Hg is 
actually emitted), we estimate that the total Hg emissions for the 
entire source category are less than 60 pounds per year and the average 
Hg emissions per facility are less than 5 pounds per year. We estimate 
the total D/F toxicity equivalent (TEQ) emissions for the entire source 
category are less than 7 grams per year (again assuming that non-
detectable D/F are actually emitted) and that the average D/F TEQ 
emissions per facility are less than 1 gram per year. Furthermore, 
there are significant uncertainties regarding these emissions and we 
have insufficient data to develop appropriate standards for these HAP. 
As discussed in section III.A.1 of this preamble, the EPA may, but is 
not obligated to, amend MACT standards \35\ and, in the case of D/F, Hg 
and PCB, where data are insufficient to develop appropriate standards, 
the EPA is choosing not to propose standards for these HAP at this 
time.
---------------------------------------------------------------------------

    \35\ See, e.g. Portland Cement Ass'n v. EPA, 665 F. 3d 177, 189 
(D.C. Cir. 2011).
---------------------------------------------------------------------------

1. How do we develop MACT floor limits?
    As discussed in the 2011 proposal (76 FR 76260), the MACT floor 
limit for existing sources is calculated based on the average 
performance of the best performing units in each category or 
subcategory, and also on a consideration of these units' variability. 
The MACT floor for new sources is based on the single best performing 
source, with a similar consideration of that source's variability. The 
MACT floor for new sources cannot be less stringent than the emissions 
performance that is achieved in practice by the best-controlled similar 
source. To account for variability in the operation and emissions, the 
stack test data were used to calculate the average emissions and the 99 
percent upper prediction limit (UPL) to derive the MACT floor limits. 
For more information regarding the general use of the UPL and why it is 
appropriate for calculating MACT floors, see the memorandum titled, Use 
of the Upper Prediction Limit for Calculating MACT Floors (UPL Memo), 
which is available in the docket for this action (Docket ID No. EPA-HQ-
OAR-2011-0797). Furthermore, with regard to calculation of MACT floor 
limits based on limited datasets, we considered additional factors as 
summarized below and described in more detail in the memorandum titled, 
Approach for Applying the Upper Prediction Limit to Limited Datasets 
for the Primary Aluminum Production Source Category (i.e., Limited 
Dataset Memo), which is available in the docket for this action.
2. What is our approach for applying the UPL to limited datasets?
    The UPL approach addresses variability of emissions data from the 
best performing source or sources in setting MACT standards. The UPL 
also accounts for uncertainty associated with emission values in a 
dataset, which can be influenced by components, such as the number of 
samples available for developing MACT standards and the number of 
samples that will be collected to assess compliance with the emission 
limit. The UPL approach has been used in many environmental science 
applications. As explained in more detail in the UPL Memo, the EPA uses 
the UPL approach to reasonably estimate the emissions performance of 
the best performing source or sources to establish MACT floor 
standards.
    With regard to the derivation of MACT limits using limited 
datasets, in a recent DC Circuit Court of Appeals decision in National 
Association of Clean Water Agencies v. EPA (NACWA), 734 F. 3d 1115 
(2013), which involved challenges to the EPA's MACT standards for 
sewage sludge incinerators, questions were raised by the court 
regarding the application of the UPL to limited datasets. We have since 
addressed these questions, as explained in detail in the Limited 
Dataset Memo, which is available in the docket for this action (Docket 
ID No. EPA-HQ-OAR-2011-0797). We seek comments on the approach 
described in the Limited Dataset Memo and whether there are other 
approaches we should consider for such datasets.
3. How did we apply the approach for limited datasets to limited 
datasets in the Primary Aluminum Production source category?
    For the Primary Aluminum Production source category, we have 
limited datasets for the following pollutants and subcategories: POM 
and PM from existing CWPB2 potlines, CWPB3 potlines and SWPB potlines; 
POM and PM from all new potlines; and PM from new anode bake furnaces 
and paste production plants. Therefore, we evaluated these specific 
datasets to determine whether it is appropriate to make any 
modifications to the approach used to calculate MACT floors for each of 
these datasets.
    For each dataset, we performed the steps outlined in the Limited 
Dataset Memo, including: ensuring that we selected the data 
distribution that best represents each dataset; ensuring that the 
correct equation for the distribution was then applied to the data; and 
comparing individual components of each limited dataset to determine if 
the standards based on limited datasets reasonably represent the 
performance of the units included in the dataset. The results of each 
analysis are summarized below and described in more detail in the 
Limited Dataset Memo and in the Revised Draft MACT Floor Analysis for 
the Primary Aluminum Production Source Category document, which are 
available in the docket (Docket ID No. EPA-HQ-OAR-2011-0797).
4. POM Emissions From Potlines
a. Background
    As described above, since the 2011 proposal, we obtained additional 
data on POM emissions from prebake potlines. In particular, we obtained 
data from eight facilities that operate prebake potlines, including at 
least one facility in each prebake potline subcategory. Today's 
proposal is based exclusively on these new data, which the EPA regards 
as much more reliable than the data used in the 2011 proposal because 
the new data are based on direct testing of POM emissions, whereas the 
data used in the 2011 proposal were emissions estimates based on a 
ratio of POM emissions to TF emissions. Data were obtained from 
performance tests conducted by each of these facilities on both its 
primary control system exhaust and its secondary emissions. POM 
emissions are generated from volatilization of organic matter in anodes 
used to reduce alumina. All primary aluminum plants control these

[[Page 72937]]

POM emissions (and PM emissions) by capturing them from the area near 
the pots and directing them through a dry alumina scrubber, except for 
one plant which directs these emissions through wet scrubbers. The one 
plant with wet scrubbers produces a very high purity aluminum, is in a 
subcategory known as the Center-Worked Prebake 3 subcategory, and is 
the only facility in that subcategory. Uncaptured (secondary) emissions 
of POM and PM are emitted from vents in the roof of the potroom. One 
plant operates wet roof scrubbers to control these secondary emissions. 
This is the sole facility in the Side-Worked Prebake subcategory. The 
MACT floor limits were determined based on the sum of the primary and 
secondary emissions. As in the current NESHAP and the 2011 proposal, 
these results are normalized to units of production, and expressed as 
pounds of pollutant (in this case, POM) per ton of aluminum produced 
(lb/ton aluminum).
    Pursuant to CAA sections 112(d)(2) and 112(d)(3), we are proposing 
to revise the 1997 NESHAP to include emission limits for POM emissions 
from prebake potlines. Regarding Soderberg potlines, the 1997 NESHAP 
already includes MACT limits for POM from Soderberg plants. 
Furthermore, the additional emissions data we gathered since the 2011 
proposal do not support any revisions of the MACT limits for POM 
emissions from Soderberg potlines based solely on control technology 
considerations. Therefore, we are not proposing to revise the emissions 
limits for POM emissions from Soderberg potlines under CAA sections 
112(d)(2), 112(d)(3) or 112(d)(6) in today's action. However, as 
described in section IV.C of this preamble, we also evaluated POM 
limits as part of our risk review and based on the results of the risk 
assessment we concluded that it was appropriate to tighten the POM 
limits for Soderberg facilities because of unacceptable risks. 
Therefore, as described in detail in section IV.C., we are proposing 
significantly tighter POM limits for Soderberg facilities based on our 
risk review pursuant to section 112(f) of the CAA.
b. Calculation of MACT Floors for POM for Potlines
    As discussed in the 2011 proposal and in section II.A of this 
preamble, the MACT floor for existing sources is based on the 
performance of best performing existing sources, and the MACT floor for 
new sources is based on the single best performing source. These MACT 
floor values include a calculation of variability calculated from these 
best performers' test runs (76 FR 76260). More specifically, to account 
for normal variability in the operation and emissions, we calculated 
the MACT floors using the 99 percent UPLs. For more information 
regarding the use of the UPL and why it is appropriate for calculating 
MACT floors, see the UPL Memo. For more information on the calculation 
of the MACT floors for the Primary Aluminum Production source category, 
see the Revised Draft MACT Floor Analysis for the Primary Aluminum 
Production Source Category document, which is available in the docket 
(Docket ID No. EPA-HQ-OAR-2011-0797).
    With regard to new sources, as explained above, the MACT floor for 
new sources cannot be less stringent than the emissions performance 
that is achieved in practice by the best-controlled similar source. The 
EPA performed a variability analysis similar to that used for existing 
sources to calculate a 99 percent UPL using the test runs from the 
lowest emitting facility without regard to subcategory to derive the 
new source MACT floor limit. This new source MACT floor limit for POM 
emissions from potlines is lower (i.e., more stringent) than the MACT 
floor limit for POM emissions from existing potlines for all 
subcategories. We are not proposing separate emission limits for 
subcategories for new potlines because we expect that any new potlines 
will be designed to use the cleanest, most efficient technology 
available, or to improve capture and control systems to achieve 
emissions no greater than the best existing plant.\36\ A summary of the 
proposed MACT floor limits for POM is provided in Table 4.
---------------------------------------------------------------------------

    \36\ We are not reconsidering, reopening, or otherwise 
considering comment on the subcategorization structure for existing 
sources in this source category.

   Table 4--Proposed MACT Floor Emission Limits for POM from Potlines
------------------------------------------------------------------------
                                                          Emission limit
                     Affected source                        (in lb POM/
                                                           ton aluminum)
------------------------------------------------------------------------
Existing CWPB1 Potlines.................................            1.1
Existing CWPB2 Potlines.................................           12
Existing CWPB3 Potlines.................................            2.7
Existing SWPB Potlines..................................           19
New or Reconstructed Potlines...........................            0.77
------------------------------------------------------------------------

c. BTF Analysis for POM for Existing Potlines
    The next step in establishing MACT standards is the BTF analysis. 
In this step, we investigate other mechanisms for further reducing HAP 
emissions that are more stringent than the MACT floor level of control 
in order to ``require the maximum degree of reduction in emissions'' of 
HAP. In setting such standards, CAA section 112(d)(2) requires the 
agency to consider the cost of achieving the additional emission 
reductions, any non-air quality health and environmental impacts 
associated with more stringent standards and energy requirements 
associated with more stringent standards. Historically, these factors 
have included factors such as solid waste impacts of a control and the 
energy impacts of various potential control strategies.
    As described below, we considered BTF control options to further 
reduce emissions of POM. The BTF POM control options were developed 
based on the application of wet roof scrubbers to the 11 facilities 
that currently do not have them.
    We estimated the capital costs, annualized costs, emissions 
reductions and cost effectiveness for the BTF limits for this control 
technology. The details regarding how these limits were derived, and 
the estimated costs and expected reductions of POM and POM HAP through 
the installation of wet roof scrubbers, are provided in the Revised 
Draft Cost Impacts for the Primary Aluminum Production Source Category 
document, which is available in the docket (Docket ID No. EPA-HQ-OAR-
2011-0797).
    Under this option (i.e., BTF controls for POM), we estimate the 
capital costs for installation and operation of the wet roof scrubbers 
at the 11 facilities would be $490 million, the annualized costs would 
be $155 million, and the controls would achieve about 1,000 tons per 
year of reductions in POM and 1.9 tons per year in speciated PAHs (a 
subset of POM). This results in an estimated cost effectiveness of 
about $155,000 per ton of POM and $82 million per ton of speciated 
PAHs. We believe our estimated costs are unacceptably high and not cost 
effective. When the primary aluminum NESHAP was proposed in 1996, we 
considered a cost effectiveness of $91,000 per ton of POM to be 
unacceptably high (Basis and Purpose Document for the Development of 
Proposed Standards for the Primary Aluminum Industry, July 19, 1996). 
Furthermore, industry sources provided additional information (Docket 
ID No. EPA-HQ-OAR-2011-0797, Johnson, C.D., Aluminum Association, July 
9, 2014) indicating that most existing prebake facilities would also 
likely require structural modification and reinforcement to accommodate 
the wet roof scrubbers, which could increase our estimated costs by 2 
to 3 times, or

[[Page 72938]]

more. Note also that we have previously determined that there are 
technical problems with using these wet scrubbers at those facilities 
located in colder climates (see 62 FR 52392 (Oct. 7, 1997)). 
Furthermore, based on our memo titled, Economic Impact Analysis for 
National Emissions Standards for Hazardous Air Pollutants: Primary 
Aluminum Reduction Plants, which is available in the docket (Docket ID 
No. EPA-HQ-OAR-2011-0797), we project that this option would pose 
significant economic burden on the companies and that several 
facilities would be at risk of closure under this option. There would 
also be collateral environmental impacts (more waste generated and more 
energy use), although these are not the most significant factors in the 
EPA's proposed decision.
    Based on consideration of all the factors described above, we are 
not proposing BTF limits for POM emissions from existing sources. A 
summary of the estimated costs and reductions for the BTF option of wet 
scrubbers is provided in Table 5.

                         Table 5--Estimated Costs and Reductions for BTF Control Options
----------------------------------------------------------------------------------------------------------------
                                                                      Reduction
       Annualized costs  ($/yr)                 Pollutant             (ton/yr)      Cost  effectiveness  ($/ton)
----------------------------------------------------------------------------------------------------------------
Retrofit Wet Scrubber for Potline
 Secondary Emissions:
    $155 million......................  POM......................           1,000  155,000.
                                        Speciated PAHs...........             1.9  82 million.
                                        PM.......................           2,900  53,000.
                                        PM-HAP metals............              23  6.73 million.
Upgrade filter bags for anode bake
 furnaces:
    $7.9 million......................  PM.......................             7.3  1.1 million.
                                        PM-HAP metals............           0.027  292 million.
Upgrade filter bags for paste plants:
    $560,000..........................  PM.......................            5.31  110,000.
                                        PM-HAP metals............          0.0058  96 million.
----------------------------------------------------------------------------------------------------------------
Note: As described in sections above, the potline control costs shown in Table 5 could be 2 to 3 times higher or
  more because of need for building modifications and reinforcement to support the wet roof scrubbers.

d. BTF Analysis for POM for New Potlines
    We estimate that a new primary aluminum plant of 200,000 ton per 
year capacity could install wet roof scrubbers for $28 million capital 
cost and $11 million per year total annualized cost. This is equivalent 
to $55 per ton of aluminum. Assuming a new or reconstructed plant would 
be similar to the best performing existing source, we estimate that it 
would achieve reductions of 21 tons per year of POM by installing a wet 
roof scrubber. Therefore, the estimated cost effectiveness would be 
$540,000 per ton of POM reductions. We believe these costs and cost 
effectiveness are unacceptably high. Furthermore, the MACT floor level 
of control is based on the best performing existing source which 
already has relatively low POM emissions (which explains the poor cost 
effectiveness of further control). Therefore, we are not proposing BTF 
limits for emissions of POM from new or reconstructed sources.
e. Proposed Standards for POM for Existing, New and Reconstructed 
Potlines
    Based on the results of all our analyses for existing, new and 
reconstructed sources, and after considering the estimated costs and 
reductions of the possible options for existing, new and reconstructed 
sources, we are proposing prebake potline emission standards for POM at 
the MACT floor for existing, new and reconstructed sources (as shown in 
Table 4).
    As discussed earlier, these MACT floor-based standards are based on 
the 99 percent UPL. We estimate that all existing prebake potlines will 
be able to meet these MACT floor limits for POM without the need to 
install additional controls because the performance of all sources in 
the category is similar, all of the potlines within each of the 
subcategories utilize very similar emissions control technology and the 
average emissions from each source are well below the MACT floor limit. 
Therefore, in assessing the costs of the proposed MACT standards for 
potline POM emissions, the only associated additional costs we estimate 
are for compliance testing, monitoring and recordkeeping.
5. PM Emissions From Potlines
a. Background
    The 1997 NESHAP does not contain emission limits for HAP metals (or 
for a surrogate). However, as described above, since the 2011 proposal, 
we obtained significant amounts of data on PM emissions from potlines. 
In particular, we obtained PM data from nine prebake potline facilities 
(including at least one facility in each prebake potline subcategory) 
and one Soderberg facility when the facility was operating. We obtained 
data from each of these facilities from performance tests of both the 
primary control system exhaust and the secondary emissions. The PM 
emissions are generated from suspension of alumina feed material and 
the condensation or precipitation of metals, organic compounds and 
fluoride salts emitted from the pots. The PM includes HAP metals that 
are in particulate form (such as Ni, Cd, Cr, Pb, manganese (Mn) and 
As). The particulate HAP metals emitted by primary aluminum facilities 
are part of their PM emissions, and, as noted above, are captured 
indiscriminately by the PM control equipment. All primary aluminum 
plants control these emissions by capturing them from the area near the 
pots and directing them through a dry alumina scrubber, followed by a 
particulate control device, except for one facility which directs the 
captured emissions through a wet scrubber. This one facility is in the 
Center-Worked Prebake 3 potline subcategory which produces a very high 
purity aluminum and is the only facility in that subcategory.
    The uncaptured (secondary) PM emissions are emitted from vents in 
the roof of the potroom. One plant operates wet roof scrubbers which 
are assumed to provide some control (about a 50 percent reduction) of 
these secondary emissions. This one facility is in the Side-Worked 
Prebake subcategory and is the only facility in the U.S. that is in 
that subcategory.

[[Page 72939]]

    The MACT floor limits were determined based on the sum of the 
primary and secondary emissions. As in the current NESHAP, these 
results were normalized to units of production, and are expressed as 
pounds of pollutant (in this case, PM) per ton of aluminum produced.
    Pursuant to CAA sections 112(d)(2) and (3), we are proposing to 
revise the 1997 NESHAP to include emission limits for PM emissions (as 
a surrogate for particulate HAP metals) from potlines.
b. Calculation of MACT Floor Limits for PM for Potlines
    As described in sections II.A and IV.A.4.b of this preamble, the 
MACT floor limit reflects the performance of best performing sources 
for existing sources (or the single best performing source, for new 
sources), including a calculation of variability. More specifically, to 
account for variability, we calculated the MACT floors using the 99 
percent UPL. For more information on how we calculated the MACT floors, 
see the Revised Draft MACT Floor Analysis for the Primary Aluminum 
Production Source Category document, which is available in the docket 
(Docket ID No. EPA-HQ-OAR-2011-0797).
    With regard to new sources, as explained above, the MACT floor 
cannot be less stringent than the emissions performance that is 
achieved in practice by the best-controlled similar source. The MACT 
floor limit for PM for new potlines was calculated based on the 99 
percent UPL using the test data from the lowest emitting facility 
without regard to subcategory. This new source MACT floor limit for PM 
emissions from potlines is lower (i.e., more stringent) than the MACT 
floor limit for PM emissions from existing potlines. This emission 
limit is based on the best performing source and is equal to the lowest 
emission limit proposed for any existing potline subcategory. We are 
not proposing subcategories for new potlines because we expect that any 
new potlines will be designed to use the cleanest, most efficient 
technology available, or to improve capture and control systems to 
achieve emissions no greater than the best existing plant. We are 
proposing that the MACT floor emissions limit for all types of new 
potlines will be based on the single best performing existing potline, 
which for PM is a potline at the SWPB facility. A summary of the MACT 
floor limits for PM for existing and new potlines is provided in Table 
6.

        Table 6--MACT Floor Emission Limits for PM From Potlines
------------------------------------------------------------------------
                                                           PM emission
                    Affected source                       limit (lb PM/
                                                          ton aluminum)
------------------------------------------------------------------------
Existing CWPB1 Potlines................................              7.2
Existing CWPB2 Potlines................................             11
Existing CWPB3 Potlines................................             20
Existing SWPB Potlines.................................              4.6
Existing VSS2 Potlines.................................             26
New and Reconstructed Potlines.........................              4.6
------------------------------------------------------------------------

c. BTF Analysis for PM for Existing Potlines
    The next step in establishing MACT standards is the BTF analysis. 
In this step, we investigate other mechanisms for further reducing HAP 
emissions that are more stringent than the MACT floor level of control 
in order to ``require the maximum degree of reduction in emissions'' of 
HAP. In setting such standards, CAA section 112(d)(2) requires the 
agency to consider the cost of achieving the additional emission 
reductions, any non-air quality health and environmental impacts 
associated with more stringent standards and energy requirements 
associated with more stringent standards.
    As described below, we considered BTF control options to further 
reduce emissions of PM. The BTF PM control options were developed based 
on the application of wet roof scrubbers to the 11 facilities that 
currently do not have them, which are the same BTF controls assessed 
for POM.
    We estimated the capital costs, annualized costs, emissions 
reductions and cost effectiveness for the BTF limits for this control 
technology. These are the same costs used for estimating POM control 
costs. The details regarding calculation of these estimated costs and 
expected reductions of PM and HAP metals through the installation of 
wet roof scrubbers are provided in the Revised Draft Cost Impacts for 
the Primary Aluminum Production Source Category document which is 
available in the docket (Docket ID No. EPA-HQ-OAR-2011-0797).
    Under this option (i.e., BTF controls for PM and HAP metals), we 
estimate the capital costs for 11 facilities to install and operate wet 
roof scrubbers would be about $490 million, annualized costs of about 
$155 million, and would achieve about 2,900 tons per year of reductions 
in PM, 780 tons per year of PM2.5 and 23 tons per year in 
HAP metals, which results in estimated cost effectiveness of about 
$200,000 per ton of PM2.5 and $6.7 million per ton of HAP 
metals. Furthermore, industry sources provided additional information 
(Docket ID No. EPA-HQ-OAR-2011-0797, Johnson, C.D., Aluminum 
Association, July 9, 2014) indicating that most existing prebake 
facilities would likely require structural modification and 
reinforcement to accommodate the wet roof scrubbers, which could 
increase our estimated costs by 2 to 3 times, or more. Therefore, we 
believe the costs for these BTF controls would be unacceptably high. 
Note also that we have previously determined that there are technical 
problems with using these wet scrubbers at those facilities located in 
colder climates (see 62 FR 52392, October 7, 1997). Furthermore, based 
on our Economic Impact Analysis for National Emissions Standards for 
Hazardous Air Pollutants: Primary Aluminum Reduction Plants, which is 
available in the docket (Docket ID No. EPA-HQ-OAR-2011-0797), we 
project that this option would pose significant economic burden on the 
companies and that several facilities would be at risk of closure. 
There would also be collateral environmental impacts (more waste 
generated and more energy use), although these are not significant 
factors in the EPA's proposed decision.
    Based on consideration of all the factors described above, we are 
not proposing BTF limits for PM emissions from existing sources. A 
summary of the costs and reductions for the BTF option of wet scrubbers 
is provided in Table 5.
d. BTF Analysis for PM for New Potlines
    We estimate that a new primary aluminum plant of 200,000 ton per 
year capacity could install wet roof scrubbers for $28 million per year 
capital cost and $11 million per year total annualized cost. This is 
equivalent to $55 per ton of aluminum. Assuming a new or reconstructed 
plant would be similar to the best performing existing source, we 
estimate that it would achieve 110 tons per year reductions of PM and 
32 tons per year reductions of PM2.5 by installing a wet 
roof scrubber. Therefore, the estimated cost effectiveness would be 
$98,000 per ton of PM reductions and $350,000 per ton of 
PM2.5 reductions. We believe these costs are unacceptably 
high and not cost effective. Therefore, we are not proposing BTF limits 
for PM for new or reconstructed sources.
e. Proposed Standards for PM for Existing, New and Reconstructed 
Potlines
    Based on the results of all our analyses for existing, new and 
reconstructed sources, and after considering the estimated costs and

[[Page 72940]]

reductions of the possible options for existing, new and reconstructed 
sources, we are proposing PM potline emission standards at the MACT 
floor for existing, new and reconstructed sources (as shown in Table 
6). As discussed earlier, these MACT floor-based standards are based on 
the 99 percent UPL. We estimate that all existing prebake potlines will 
be able to meet these MACT floor limits for PM without the need to 
install additional controls because the performance of all sources in 
the category is similar, all of the potlines within each of the 
subcategories utilize very similar emissions control technology, the 
average emissions from each source are well below the MACT floor limit 
and emissions data from every facility that performed emissions testing 
were included in the dataset used to develop the MACT floor. Therefore, 
in assessing the costs of the proposed MACT standards for potline PM 
emissions, the only associated costs we estimate are for compliance 
testing, monitoring and recordkeeping.
6. PM Emissions From Anode Bake Furnaces
a. Background
    The 1997 NESHAP does not contain emission limits for HAP metals (or 
for a surrogate). However, as described above, we obtained significant 
data on PM emissions from anode bake furnaces since the 2011 proposal. 
In particular, we obtained data from 7 of the 8 anode bake furnaces 
presently in operation. Data were obtained by facilities from 
performance tests of their control device exhausts. As in the current 
NESHAP, these results are normalized to units of production, and 
expressed as pounds of pollutant (in this case, PM) per ton of green 
anode. PM emissions are generated from dust and condensed pitch 
hydrocarbons and fluorides generated when green anodes are baked. All 
currently operating anode bake furnaces are controlled with dry alumina 
scrubbers and fabric filters, which capture particulate HAP metals 
indiscriminately as a subset of total captured PM.
    Pursuant to CAA sections 112(d)(2) and (3), we are proposing to 
revise the 1997 NESHAP to include emission limits for PM (as a 
surrogate for HAP metals) from anode bake furnaces.
b. Calculation of MACT Floor Limits for PM for Anode Bake Furnaces
    We followed the same general approach, using the 99 percent UPL, to 
calculate MACT floor limits for anode bake furnaces as we used for the 
potlines (described in section IV.A.4.b of this preamble). Using this 
approach we calculate the MACT floor limit for existing anode bake 
furnaces to be 0.068 lbs PM per ton of green anode (lbs/ton green 
anode). For more information on how we calculated the MACT floors, see 
the Revised Draft MACT Floor Analysis for the Primary Aluminum 
Production Source Category document, which is available in the docket 
(Docket ID No. EPA-HQ-OAR-2011-0797).
    With regard to new sources, as explained above, the MACT floor 
cannot be less stringent than the emissions performance that is 
achieved in practice by the best-controlled similar source. A 
variability analysis similar to that used for existing sources was then 
performed to calculate a 99 percent UPL using the test data from the 
lowest emitting facility. This new source MACT floor limit for PM 
emissions from anode bake furnaces is lower (i.e., more stringent) than 
the MACT floor limit for PM emissions from existing anode bake 
furnaces. The new source MACT floor limit is based on the performance 
of the best existing anode bake furnace. Using this approach, we 
calculate the MACT floor limit for new sources to be 0.036 lbs/ton 
green anode.
c. BTF Analysis for PM for Existing Anode Bake Furnaces
    The next step in establishing MACT standards is the BTF analysis. 
As described above, in this step, we investigate other mechanisms for 
further reducing HAP emissions that are more stringent than the MACT 
floor level of control in order to ``require the maximum degree of 
reduction in emissions'' of HAP.
    We considered BTF control options to further reduce emissions of PM 
from anode bake furnaces. The BTF PM control options were developed 
based on the replacement of cloth filter bags with membrane bags which 
are expected to provide better particulate control.
    We estimated the capital costs, annualized costs, emissions 
reductions and cost effectiveness for the BTF limits for this control 
technology. The details regarding how these limits were derived, and 
the estimated costs and expected reductions of PM and HAP metals 
through the replacement of conventional filter bags with membrane bags 
are provided in the Revised Draft Cost Impacts for the Primary Aluminum 
Production Source Category document, which is available in the docket 
(Docket ID No. EPA-HQ-OAR-2011-0797).
    Under this option (i.e., BTF controls for PM and HAP metals), we 
estimate annualized costs for 10 facilities of about $7.9 million. This 
option would achieve about 7.3 tons per year of reductions in PM and 
0.027 tons per year of HAP metals, which results in estimated cost 
effectiveness of about $1.1 million per ton of PM and $292 million per 
ton of HAP metals. We believe these costs and cost effectiveness are 
unacceptably high. There would also be collateral environmental impacts 
(more waste generated and more energy use), although these are not the 
most significant factors in the EPA's proposed decision. Based on 
consideration of all the factors described above, we are not proposing 
BTF limits for PM emissions from existing sources.
    A summary of the costs and reductions for the BTF option based on 
the performance of fabric filters with membrane bag upgrades is given 
in Table 5.
d. BTF Analysis for PM for New Bake Furnaces
    We estimate that a new primary aluminum plant of 200,000 ton per 
year capacity could use membrane filter bags in fabric filters used to 
control PM from anode bake furnaces for an incremental annualized cost 
of $680,000 per year. Cost effectiveness is expected to be comparable 
to that estimated for existing plants. We believe these costs and cost 
effectiveness are unacceptably high. Therefore, we are not proposing 
BTF limits for PM emissions from new anode bake furnaces.
e. Proposed Standards for PM for Existing, New and Reconstructed Anode 
Bake Furnaces
    Based on the results of all our analyses for existing, new and 
reconstructed sources, and after considering the estimated costs and 
reductions of the possible options for existing, new and reconstructed 
sources, we are proposing a PM emission limit at the MACT floor for 
existing bake furnaces of 0.068 pounds of PM per ton of green anode 
(lbs PM/ton green anode) and we are proposing a MACT floor limit of 
0.036 lbs PM/ton green anode for new and reconstructed sources.
    As discussed earlier, these MACT floor-based standards are based on 
the 99 percent UPL. We estimate that all existing bake furnaces will be 
able to meet these MACT floor limits for PM without the need to install 
additional controls because the performance of all sources in the 
category is similar, all of these furnaces utilize very similar 
emissions control technology and the average emissions from each source 
for which we have reliable data are well below the MACT floor limit. 
Therefore,

[[Page 72941]]

the only additional costs are estimated to be for compliance testing, 
monitoring and recordkeeping. Therefore, in assessing the costs of the 
proposed MACT standards for PM for bake furnaces, the only associated 
costs we estimate are for compliance testing, monitoring and 
recordkeeping.
7. PM Emissions From Paste Plants
a. Background
    The 1997 NESHAP does not contain emission limits for emissions of 
HAP metals (or for a surrogate) from paste plants. However, as 
described above, we obtained a substantial amount of data on PM 
emissions from paste plants since the 2011 proposal. In particular, we 
obtained emissions test data from seven of the eight paste plants 
presently in operation. Data were obtained from tests of control device 
exhausts. As in the current NESHAP, these results are normalized to 
units of production, and expressed as pounds of pollutant (in this 
case, PM) per ton of green anode. All currently operating paste plants 
are controlled with dry coke scrubbers and fabric filters. PM emissions 
are generated from crushing and grinding coke and mixing ground coke 
with heated pitch to produce green anodes.
    Pursuant to CAA sections 112(d)(2) and (3), we are proposing to 
revise the 1997 NESHAP to include emission limits for PM emissions from 
paste plants.
b. Calculation of MACT Floor Limits for PM for Paste Plants
    We followed the same general approach, using the 99 percent UPL, to 
calculate MACT floor limits for paste plants as we used for the 
potlines (described in section IV.A.4.b of this preamble). Using this 
approach, we calculate the MACT floor limit for existing paste plants 
to be 0.082 lbs of PM per ton of green anode. For more information on 
how we calculated the MACT floors, see the Revised Draft MACT Floor 
Analysis for the Primary Aluminum Production Source Category document, 
which is available in the docket (Docket ID No. EPA-HQ-OAR-2011-0797).
    With regard to new sources, a variability analysis similar to that 
used for existing sources was then performed to calculate a 99 percent 
UPL using the test data from the lowest emitting facility. This new 
source MACT floor limit for PM emissions from paste plants is based on 
the best performing existing paste plant and is lower (i.e., more 
stringent) than the proposed MACT floor limit for PM emissions from 
existing paste plants. Using this approach, we calculate the MACT floor 
limit for new paste plants to be 0.0054 lbs of PM/ton green anode.
c. BTF Analysis for PM for Existing Paste Plants
    The next step in establishing MACT standards is the BTF analysis. 
In this step, we investigate other mechanisms for further reducing HAP 
emissions that are more stringent than the MACT floor level of control 
in order to ``require the maximum degree of reduction in emissions'' of 
HAP.
    We considered BTF control options to further reduce emissions of PM 
from paste plants. The BTF PM control options were developed based on 
the replacement of cloth filter bags with membrane bags which are 
expected to provide better particulate control.
    We estimated the capital costs, annualized costs, emissions 
reductions and cost effectiveness for the BTF limits for this control 
technology. We also considered if there were non-air environmental 
impacts or energy usage implications. The details regarding how these 
limits were derived, and the estimated costs and expected reductions of 
PM and HAP metals through the replacement of conventional filter bags 
with membrane bags are provided in the Revised Draft Cost Impacts for 
the Primary Aluminum Production Source Category document which is 
available in the docket (Docket ID No. EPA-HQ-OAR-2011-0797).
    Under this option (i.e., BTF controls for PM and HAP metals), we 
estimate the annualized costs for 11 facilities to be about $560,000, 
and would achieve about 5.3 tons per year of reductions in PM, 1.5 tons 
of reductions in PM2.5 and 0.0058 tons per year of HAP 
metals. This results in estimated cost effectiveness of about $110,000 
per ton of PM, $370,000 per ton of PM2.5 and $96 million per 
ton of HAP metals. We believe these costs and cost effectiveness are 
unacceptably high and minimal HAP reductions would be achieved. There 
would also be collateral environmental impacts (more waste generated 
and more energy use), although these are not significant factors in the 
EPA's proposed decision. Therefore, we are not proposing BTF limits for 
PM emissions from existing paste plants.
    A summary of the costs and reductions for the BTF option of 
membrane bag upgrades is provided in Table 5.
d. BTF Analysis for PM for New Paste Plants
    We estimate that a new primary aluminum plant with the capacity of 
200,000 ton per year could use membrane filter bags in fabric filters 
used to control PM from a paste plant for an incremental annualized 
cost of $51,000 per year, which would achieve approximately 0.0005 tpy 
reductions. This results in estimated cost effectiveness of about $98 
million per ton of HAP metals. We believe these costs and cost 
effectiveness are unacceptably high, especially given that minimal HAP 
reductions would be achieved. Furthermore, the metal HAP emissions are 
already quite low from existing paste plants under the current NESHAP. 
Therefore, we are not proposing BTF limits for PM emissions from new or 
reconstructed paste plants.
e. Proposed Standards for PM for Existing, New and Reconstructed Paste 
Plants
    Based on the results of all our analyses for existing, new and 
reconstructed sources, and after considering the estimated costs and 
reductions of the possible options for existing, new and reconstructed 
sources, we are proposing paste plant PM emission standards at the MACT 
floor for existing, new and reconstructed sources (as shown in Table 
7). Since all of the paste plants utilize similar emissions control 
technology and the average emissions from each source were well below 
the MACT floor, all presently operating facilities are expected to meet 
the proposed MACT floor emission standards without the need to install 
additional controls. Therefore, in assessing the costs of the proposed 
MACT standards for PM for paste plants, the only associated costs we 
estimate are for compliance testing, monitoring and recordkeeping.
    A summary of the proposed MACT standards pursuant to CAA sections 
112(d)(2) and (3) for POM and PM for the various processes at primary 
aluminum reduction plants is provided in Table 7.

[[Page 72942]]



    Table 7--Proposed MACT Emission Limits for POM and PM for Primary
         Aluminum Reduction Plants Pursuant to Section 112(d)(2)
------------------------------------------------------------------------
        Affected source               Pollutant         Emission limit
------------------------------------------------------------------------
Existing CWPB1 Potlines........  POM................  1.1 lb/ton
                                                       aluminum.
Existing CWPB2 Potlines........  POM................  12 lb/ton
                                                       aluminum.
Existing CWPB3 Potlines........  POM................  2.7 lb/ton
                                                       aluminum.
Existing SWPB Potlines.........  POM................  19 lb/ton
                                                       aluminum.
New or Reconstructed Potlines..  POM................  0.77 lb/ton
                                                       aluminum.
Existing CWPB1 Potlines........  PM.................  7.2 lb/ton
                                                       aluminum.
Existing CWPB2 Potlines........  PM.................  11 lb/ton
                                                       aluminum.
Existing CWPB3 Potlines........  PM.................  20 lb/ton
                                                       aluminum.
Existing SWPB Potlines.........  PM.................  4.6 lb/ton
                                                       aluminum.
Existing VSS2 Potlines.........  PM.................  26 lb/ton
                                                       aluminum.
New and Reconstructed Potlines.  PM.................  4.6 lb/ton
                                                       aluminum.
Existing Bake Furnaces.........  PM.................  0.068 lb/ton green
                                                       anode.
New Bake Furnaces..............  PM.................  0.036 lb/ton green
                                                       anode.
Existing Paste Plants..........  PM.................  0.082 lb/ton green
                                                       anode.
New and Reconstructed Paste      PM.................  0.0056 lb/ton
 Plants.                                               green anode.
------------------------------------------------------------------------

B. What are the results of the risk assessment and analyses?

1. Inhalation Risk Assessment Results
    Table 8 provides an overall summary of the results of the 
inhalation risk assessment.

             Table 8--Primary Aluminum Production Source Category Inhalation Risk Assessment Results
----------------------------------------------------------------------------------------------------------------
                                      Estimated
 Maximum individual cancer risk     population at     Estimated annual  Maximum chronic non-   Refined maximum
      (-in-1 million) \a\           increased risk    cancer incidence    cancer TOSHI \b\   acute non-cancer HQ
                                   levels of cancer   (cases per year)                               \c\
----------------------------------------------------------------------------------------------------------------
                                                Actual Emissions
----------------------------------------------------------------------------------------------------------------
70.............................  >= 1-in-1 million:               0.06  1 Cadmium and        HQREL = 10 (Arsenic
                                  881,000.                               Nickel Compounds.    Compounds).
                                 >= 10-in-1 million:                                         Residential.
                                  65,000.
                                 >= 100-in-1
                                  million: 0.
----------------------------------------------------------------------------------------------------------------
                                             Allowable Emissions \d\
----------------------------------------------------------------------------------------------------------------
300............................  >= 1-in-1 million:               0.06  2 Nickel and
                                  950,000.                               Arsenic Compounds.
                                 >= 10-in-1 million:
                                  76,000.
                                 >= 100-in-1
                                  million: 200.
----------------------------------------------------------------------------------------------------------------
\a\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\b\ Maximum TOSHI. The target organ with the highest TOSHI for the Primary Aluminum Production source category
  for actual emissions is the kidney and respiratory system and for allowable emissions is the respiratory,
  immunological and developmental systems.
\c\ The maximum off-site HQ acute value of 10 at a residential location for actuals is driven by emissions of As
  from the potline roof vents. See section III.A.3 of this preamble for explanation of acute dose-response
  values. Acute assessments are not performed on allowable emissions.
\d\ The development of allowable emission estimates can be found in the memoranda titled, Revised Draft
  Development of the RTR Emissions Dataset for the Primary Aluminum Production Source Category which is
  available in the docket.

    The inhalation risk modeling performed to estimate risks based on 
actual and allowable emissions relied primarily on emissions data from 
the information requests. The results of the chronic baseline 
inhalation cancer risk assessment indicate that, based on estimates of 
current actual emissions, the maximum individual lifetime cancer risk 
(MIR) posed by the Primary Aluminum Production source category is 70-
in-1 million, with As, Ni and Cr\+6\ compounds from the potline roof 
vents accounting for 99 percent of the MIR. The total estimated cancer 
incidence from primary aluminum production sources based on actual 
emission levels is 0.06 excess cancer cases per year, with emissions of 
As, Ni and Cr\+6\ compounds contributing 64 percent, 21 percent and 8 
percent, respectively, to this cancer incidence. In addition, we note 
that approximately 900,000 people are estimated to have cancer risks 
greater than or equal to 1-in-1 million as a result of actual emissions 
from this source category, with 65,000 people having cancer risks 
greater than 10-in-1 million.
    When considering MACT-allowable emissions, the maximum individual 
lifetime cancer risk is estimated to be up to 300-in-1 million, driven 
by potential emissions of As, Ni and PAH compounds from the potline 
roof vents of the one idle Soderberg facility. The estimated cancer 
incidence is estimated to be 0.06 excess cancer cases per year. 
Approximately 950,000 people were estimated to have potential cancer 
risks greater than or equal to 1-in-1 million considering allowable 
emissions from primary aluminum plants with 76,000 people with 
potential cancer risks greater than 10-in-1 million and 200 people with 
potential cancer risks greater than 100-in-1 million. The maximum 
modeled chronic non-cancer

[[Page 72943]]

HI (TOSHI) value based on actual emissions was estimated to be 1, for 
both Ni and Cd compounds emissions from the potline roof vents. When 
considering MACT-allowable emissions, the maximum chronic non-cancer 
TOSHI value was estimated to be 2, for both Ni and As compounds from 
potline roof vent emissions.
2. Acute Risk Results
    Worst-case acute HQs were calculated for every emitted HAP that has 
an appropriate acute benchmark. For cases where the screening HQ was 
greater than 1, we further determined the highest HQ value that might 
occur outside facility boundaries. Based on estimated actual peak 
baseline emissions, the highest off-site acute screening HQ is 30 for 
As and the highest off-site acute screening HQ for HF is 3.
    We refined the acute As assessment by evaluating exposures at the 
centroids of census blocks--these are locations around the facilities 
where people could actually live. Based on this refinement, the maximum 
HQ was 10, for As. We estimate that about 170 people could be exposed 
to concentrations leading to an acute HQ of 10 for As, about 1,500 
people could be exposed to a concentration leading to an acute HQ 
greater than 5, and that about 8,500 people could be exposed to a 
concentration leading to an acute HQ greater than 1. This assessment 
still assumes in order to reach an HQ greater than 1 that peak 
emissions from the source category and worst-case meteorological 
conditions co-occur. We then assume further that an individual will be 
present to be exposed at that time. These are a conservative series of 
assumptions. We expect that this would happen for very few hours of the 
8,760 hours that are in a year.
    We did not conduct any refinements to the HF acute screen because 
the maximum off-site HQ of 3 is at a location where we would not expect 
people to be for 1 hour. For more details see the Residual Risk 
Assessment for the Primary Aluminum Production Source Category in 
Support of the 2014 Supplemental Proposal, which is available in the 
docket (Docket ID No. EPA-HQ-OAR-2011-0797).
3. Multipathway Risk Screening Results
    Results of the worst-case Tier 1 screening analysis indicate that 
13 facilities exceeded the PB-HAP emission screening rates (based on 
estimates of actual emissions) for D/F, Hg and PAH with six facilities 
exceeding the screening rate for Cd. For the PB-HAPs and facilities 
that did not screen out at Tier 1, we conducted a Tier 2 screen. The 
Tier 2 screen replaces some of the assumptions used in Tier 1 with 
site-specific data, including the location of fishable lakes, and local 
precipitation, wind direction and speed. The Tier 2 screen continues to 
rely on conservative, high-end assumptions about consumption of local 
fish and locally grown or raised foods (adult female angler at 99th 
percentile consumption for fish \37\ for the subsistence fisherman 
scenario and 90th percentile for consumption of locally grown or raised 
foods \38\ for the farmer scenario) which, as noted above, may not 
occur for this source category. It is important to note that, even with 
the inclusion of some site-specific information in the Tier 2 analysis, 
the multipathway screening analysis is still a very conservative, 
health-protective assessment (e.g., upper-bound consumption of local 
fish and locally grown and/or raised foods) and in all likelihood will 
yield results that serve as an upper-bound multipathway risk associated 
with a facility.
---------------------------------------------------------------------------

    \37\ Burger, J. 2002. Daily Consumption of Wild Fish and Game: 
Exposures of High End Recreationists. International Journal of 
Environmental Health Research 12:343-354.
    \38\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
---------------------------------------------------------------------------

    While the screening analysis is not designed to produce a 
quantitative risk result, the factor by which the emissions exceed the 
threshold serves as a rough gauge of the ``upper-limit'' risks we would 
expect from a facility. Thus, for example, if a facility emitted a PB-
HAP carcinogen at a level 2 times the screening threshold, we can say 
with a high degree of confidence that the actual maximum cancer risks 
will be less than 2-in-1 million. Likewise, if a facility emitted a 
noncancer PB-HAP at a level 2 times the screening threshold, the 
maximum noncancer hazard would represent an HQ less than 2. The high 
degree of confidence comes from the fact that the screens are developed 
using the very conservative (health-protective) assumptions that we 
describe above.
    Based on this Tier 2 non-cancer screening analysis, emissions of Hg 
\39\ and Cd exceeded the site-specific levels for those PB-HAP by a 
factor of 2 from two different facilities. With regard to the Tier 2 
cancer screening analysis, 10 facilities have estimated D/F emissions, 
as 2,3,7,8-tetrachlorodibenzo-p-dioxin TEQ, above the Tier 2 cancer 
screening thresholds and 12 facilities have estimated PAH emissions, as 
benzo(a)pyrene (BaP), above the Tier 2 cancer screening threshold. The 
highest cancer exceedance for D/F was 40 times and 7 times for PAH's 
for the subsistence fisherman scenario (total cancer screen value of 50 
for the MIR site). Thus, these results indicate that the maximum cancer 
risks due to multipathway exposures to D/F and PAH emissions for the 
subsistence fisher scenario are less than 50-in-1 million.\40\ For the 
subsistence farmer scenario, the highest cancer exceedance for D/F was 
10 times and PAHs was 4 times (total cancer screen value of 20 for the 
MIR site).
---------------------------------------------------------------------------

    \39\ As noted earlier, mercury values used in the analysis are 
likely to be inflated because EPA assumed mercury was emitted even 
from sources where no mercury was detected.
    \40\ As noted earlier, D/F emissions used in this analysis are 
likely to be overstated because EPA imputed values for D/F congeners 
even from plants and process units where those D/F congeners were 
not detected in the emissions tests.
---------------------------------------------------------------------------

    Results of the analysis for Pb compounds indicate that based on the 
baseline, actual emissions, the maximum annual off-site ambient Pb 
concentration was below the primary NAAQS for Pb.
4. Environmental Risk Screening Results
    We conducted an environmental risk screening assessment for the 
Primary Aluminum Production source category for the following HAP: Cd, 
Hg, PAHs, D/F and HF. The results of the environmental screening 
analysis are summarized in Table 9.

[[Page 72944]]



                        Table 9--Summary of Environmental Risk Screen Results for the Primary Aluminum Production Source Category
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Number of facilities in category exceeding
                                    Percent of modeled area in category
                                               exceeding \2\
                                 -----------------------------------------------------------------------------------------------------------------------
                  Environmental HAP            Tier 1 Screen
                                             Tier 2 Screen \1\                  NOAEL             LOAEL
                                                                          (%)               (%)
                                 ----------------------------------------------------------------------------
                                                             NOAEL              LOAEL             NOAEL             LOAEL
--------------------------------------------------------------------------------------------------------------------------------------------------------
PB-HAP..........................  D/F................  None               None              ................  ................         0.40            0
                                  MeHg...............  None               None              ................  ................            0            0
                                  Cd.................  1                  1                 None              None                        0            0
                                  PAH................  1                  1                 1                 None                   \4\ NA            0
Acid Gases......................  HF \3\.............  NA                 None              ................  ................           NA          0.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Tier 2 screen is performed for PB-HAP when there are exceedances of the Tier 1 screen. The acid gas screen is a one tier screen.
\2\ A value of 0% indicates that none of the modeled data points exceeded the benchmark. For PB-HAP the percent area is based on the Tier 2 results, if
  a Tier 2 analysis is performed. Otherwise, the percent area is based on the Tier 1 results.
\3\ For HF, we evaluated two benchmarks, one from Canada and the other from the state of Washington. Although, they are both considered to be LOELs_the
  level between a NOAEL and a LOAEL, we have listed the results under the LOAEL column for the Canadian benchmark, which is the more protective of the
  two.
\4\ One facility had a Tier 2 exceedance for the sediment NOAEL benchmark at one lake. For PB-HAP the percent area is calculated for soil benchmarks
  only.
NA = Not Applicable. MeHg = methylmercury.

    In our Tier 1 analysis, emissions of D/F and methylmercury did not 
exceed the threshold emission rates for any of the ecological 
benchmarks for any facility in the source category. In our Tier 1 
analysis, emissions of Cd and PAHs exceeded some ecological benchmarks 
for one facility. Therefore, we performed a Tier 2 analysis. In the 
Tier 2 analysis, emissions of Cd did not exceed the threshold emission 
rates for any of the ecological benchmarks for any facility in the 
source category. In the Tier 2 analysis, emissions of PAHs exceeded the 
NOAEL sediment benchmark for one lake by 2 times, but did not exceed 
the threshold effect level. For HF, the average modeled concentration 
around each facility (i.e., the average concentration of all off-site 
data points in the modeling domain) did not exceed the ecological 
benchmarks. For Pb compounds, we did not estimate any exceedances of 
the secondary Pb NAAQS.
5. Facility-Wide Risk Assessment Results
    The facility-wide chronic MIR and TOSHI are based on actual 
emissions from all sources. Considering facility-wide emissions, the 
MIR is estimated to be 70-in-1 million driven by As, Ni and Cr\+6\ 
emissions and the chronic non-cancer TOSHI value is calculated to be 1 
driven by emissions of Cd compounds. In both cases, the source of these 
emissions are from potline roof vents.
6. Multipathway Refined Risk Results
    In the Tier 2 screening, emissions of Cd exceeded the fisher 
threshold at Alcoa in Ferndale, WA (NEIWA19906), and emissions of Hg 
exceeded the fisher threshold at Alumax in Goose Creek, SC (NEI41217) 
by a factor of 2. We also conducted a refined risk assessment for the 
Reynolds Metals (Alcoa--Massena East) (NEI46970) plant in Massena, NY. 
For more details on these assessments, see the Residual Risk Assessment 
for the Primary Aluminum Production Source Category in Support of the 
2014 Supplemental Proposal, which is available in the docket (Docket ID 
No. EPA-HQ-OAR-2011-0797). We then proceeded to a Tier 3 screen. We 
examined the set of lakes from which the (hypothetical) fisher ingested 
fish. Any lakes that appeared to not be fishable or not publicly 
accessible were removed from the assessment, and the screening 
assessment was repeated. After we made the determination which critical 
lakes were fishable and their respective adjustment to the Tier 2 
values, we analyzed plume rise data. All three of these sites required 
plume rise analysis. Approximately, 33 percent of the Cd emissions at 
NEIWA19906 and six percent of the Hg emissions at NEI41217 were lost 
due to plume rise, resulting in the Tier 2 non-cancer screening values 
for both sites for the fisher scenario going from 2 to 1.
    Reynolds Metals (NEI46970) permanently ceased operating their 
Soderberg process in March of 2014. The multipathway and inhalation 
risk characterization for this site will not be reflective of any 
future operations that may be conducted at this site, but provides 
valuable information showing how, through the use of more efficient and 
cleaner technologies, the industry has improved its environmental 
performance. This facility had the highest Tier 2 cancer screen value 
for the source category based upon actual emissions of PAHs and D/F 
with a value of 70 for the subsistence fisher scenario and a value of 
200 for the subsistence farmer scenario.
    An analysis of the fishable lakes did not change the Tier 2 cancer 
screening values, and analysis of the hourly plume-rise data resulted 
in only 4 percent of the mass being lost to the upper air sink. The 
Tier 3 screen did not reduce the Tier 2 cancer screen values for either 
PAH's or D/F for this facility. The subsistence fisher and subsistence 
farmer scenarios are conservative screens that provide upper bound 
estimates of screening values with high levels of uncertainty. The 
multipathway scenarios for the Tier screens include some hypothetical 
elements, namely the location and actual site-specific ingestion rates 
for exposed individuals. It is important to note that even though the 
multipathway assessment has been conducted, no data exist to verify the 
existence of either the farmer or fisher for each site. With regard to 
the farmer scenario, the uncertainty is even higher due to lack of 
site-specific information on where sustainable farms are located in 
addition to the make-up and quantities of food ingested.
7. Demographic Analysis Results
    To examine the potential for any environmental justice (EJ) issues 
that might be associated with the source category, we performed a 
demographic analysis, which is an assessment of risks to individual 
demographic groups, of the population close to the facilities. In this 
analysis, we evaluated the distribution of HAP-related cancer risks

[[Page 72945]]

and non-cancer hazards from the Primary Aluminum Production source 
category across different social, demographic and economic groups 
within the populations living near facilities identified as having the 
highest risks. The methodology and the results of the demographic 
analyses are included in a technical report, Risk and Technology 
Review--Analysis of Socio-Economic Factors for Populations Living Near 
Primary Aluminum Facilities, which is available in the docket for this 
action (Docket ID No. EPA-HQ-OAR-2011-0797).
    The results of the demographic analysis are summarized in Table 10 
below. These results, for various demographic groups, are based on the 
estimated risks from actual emissions levels for the population living 
within 50 km of the facilities. The results (shown in Table 10) 
indicate there are no significant disproportionate risks to any 
particular minority, low income, or indigenous population. The results 
of the Primary Aluminum Production source category demographic analysis 
indicate that emissions from the source category expose approximately 
881,307 people to a cancer risk at or above 1-in-1 million. The 
percentages of the at-risk population in each demographic group (except 
for White and non-Hispanic) are similar to or lower than their 
respective nationwide percentages.

             Table 10--Primary Aluminum Production Source Category Demographic Risk Analysis Results
----------------------------------------------------------------------------------------------------------------
                                                                             Population with
                                                                            cancer risk at or   Population with
                                                           Nationwide         above 1-in-1       chronic hazard
                                                                                 million         index above 1
----------------------------------------------------------------------------------------------------------------
Total Population.....................................       312,861,265             881,307                    0
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White................................................                72                  80                    0
All Other Races......................................                28                  20                    0
----------------------------------------------------------------------------------------------------------------
                                                 Race by Percent
----------------------------------------------------------------------------------------------------------------
White................................................                71.9                80.1                  0
African American.....................................                13                  13                    0
Native American......................................                 1.1                 0.9                  0
Other and Multiracial................................                14                   6                    0
----------------------------------------------------------------------------------------------------------------
                                              Ethnicity by Percent
----------------------------------------------------------------------------------------------------------------
Hispanic.............................................                17                   5                    0
Non-Hispanic.........................................                83                  95                    0
----------------------------------------------------------------------------------------------------------------
                                                Income by Percent
----------------------------------------------------------------------------------------------------------------
Below Poverty Level..................................                14                  14                    0
Above Poverty Level..................................                86                  86                    0
----------------------------------------------------------------------------------------------------------------
                                              Education by Percent
----------------------------------------------------------------------------------------------------------------
Over 25 and without High School Diploma..............                15                  14                    0
Over 25 and with a High School Diploma...............                85                  86                    0
----------------------------------------------------------------------------------------------------------------

C. What are our proposed decisions regarding risk acceptability, ample 
margin of safety and adverse environmental effects based on our revised 
analyses?

1. Risk Acceptability
    As noted in section II.A.1 of this preamble, the EPA sets standards 
under CAA section 112(f)(2) using ``a two-step standard-setting 
approach, with an analytical first step to determine an `acceptable 
risk' that considers all health information, including risk estimation 
uncertainty, and includes a presumptive limit on maximum individual 
lifetime cancer risk (MIR) of approximately 1 in 10 thousand \[41]\.'' 
(54 FR 38045, September 14, 1989.)
---------------------------------------------------------------------------

    \41\ 1-in-10 thousand is equivalent to 100-in-1 million. The EPA 
currently describes cancer risks as ``n-in-1 million.''
---------------------------------------------------------------------------

    In this proposal, the EPA estimated risks based on both actual and 
allowable emissions from primary aluminum facilities. In determining 
acceptability, we considered risks based on both actual and allowable 
emissions.
a. Estimated Risks From Actual Emissions
    The baseline inhalation cancer risk to the individual most exposed 
to emissions from sources regulated by subpart LL is 70-in-1 million 
based on actual emissions from prebake facilities. The estimated 
incidence of cancer due to inhalation exposures is 0.06 excess cancer 
cases per year, or 1 case every 17 years. Approximately 881,000 people 
face an estimated increased cancer risk greater than 1-in-1 million due 
to inhalation exposure to actual HAP emissions from the Primary 
Aluminum Production source category, and approximately 65,000 people 
face an estimated increased risk greater than 10-in-1 million and up to 
70-in-1 million. The agency estimates that the maximum chronic non-
cancer TOSHI from inhalation exposure is 1. As, Ni, Cd and chromium 
(Cr) are the main HAP contributing to the estimated chronic cancer and 
chronic non-cancer risks.
    The Tier 2 multipathway screening analysis of actual emissions from 
operating plants indicates the potential for PAH and D/F emissions is 
about 50 times the screening level for cancer for the fisher scenario 
and 20 times the cancer threshold for the farming scenario. These 
results indicate that the maximum cancer risks due to multipathway 
exposures to D/F and PAH emissions from this source category are less 
than 50-in-1 million. Non-cancer impacts from Cd and Hg were at the 
Tier 2 screening thresholds,

[[Page 72946]]

which indicates that the maximum HI due to multipathway exposures to Hg 
and Cd emissions from this source category is less than 1.
    As noted above, the Tier 2 multipathway screen is conservative in 
that it incorporates many health-protective assumptions (and, as noted, 
reflects further assumptions here as to amounts of certain HAP being 
emitted). For example, the EPA chooses inputs from the upper end of the 
range of possible values for the influential parameters used in the 
Tier 2 screen and assumes that the exposed individual exhibits 
ingestion behavior that would lead to a high total exposure. A Tier 2 
exceedance cannot be equated with a risk value or a HQ or HI. Rather, 
it represents a high-end bounding estimate of what the risk or hazard 
may be. For example, an exceedance of 2 for a non-carcinogen can be 
interpreted to mean that we have high confidence that the HI would be 
lower than 2. Similarly, an exceedance of 30 for a carcinogen means 
that we have high confidence that the risk is lower than 30-in-1-
million. Confidence comes from the conservative, or health-protective, 
assumptions that are used in the Tier 2 screen.
    The refined multipathway analysis that the EPA conducted for one 
specific Soderberg facility which has recently permanently shut down 
its Soderberg potlines found that the Tier 3 cancer screen resulted in 
the same potential risk as identified in the Tier 2 analysis with a 
cancer screen value of 70 for the subsistence fisher and 200 for the 
subsistence farmer. These results indicate that the maximum cancer 
risks due to multipathway exposures to emissions from that facility 
could have been up to 200-in-1 million. However, since that plant has 
permanently ceased operations of the Soderberg potlines (i.e., the 
emissions sources that were driving the risk at that facility), the 
future risks due to emissions at this location (i.e., if the company 
decides to replace its Soderberg potlines with lower-emitting prebake 
potlines and resume operations) will be substantially less than 100-in-
1 million.
    The assessment of maximum acute inhalation impacts from baseline 
actual peak emissions (i.e., based on the standards in the 1997 NESHAP 
and the proposed standards in the 2011 proposal and this supplemental 
proposal) indicates the potential for As to exceed an HQ value of 1 
based on the REL value, with an estimated maximum off-site acute HQ of 
30 based on the REL value and 10 at a residential location. There are 
no AEGL values for comparison. We refined the acute As assessment by 
evaluating exposures at the centroids of census blocks--these are 
locations around the facilities where people could actually live. Based 
on this refinement, the maximum HQ was 10. We estimate that about 170 
people could be exposed to concentrations leading to an acute HQ of 10, 
about 1,500 people could be exposed to a concentration leading to an 
acute HQ greater than 5, and about 8,500 people could be exposed to a 
concentration leading to an acute HQ greater than 1. This assessment 
still assumes in order to reach an HQ greater than one, peak emissions 
from each emission source at the source category and worst-case 
meteorological conditions co-occur at a time when an individual is 
present. In other words, the analysis includes the conservative 
assumption that every process releases its peak emissions at the same 
hour as the worst-case dispersion conditions. We expect that this would 
happen for very few hours of the 8,760 hours that are in a year.
    We did not conduct any refinements to the HF acute screen because 
the maximum off-site HQ of 3 is at a location where we would not expect 
people to be for 1 hour.
    For more information, refer to Appendix 8 of the Residual Risk 
Assessment for the Primary Aluminum Production Source Category in 
Support of the 2014 Supplemental Proposal (Docket ID No. EPA-HQ-OAR-
2011-0797).
b. Estimated Risks from Allowable Emissions
    The EPA estimates that the baseline inhalation cancer risk to the 
individual most exposed to emissions from sources regulated by subpart 
LL is up to 300-in-1 million based on allowable emissions from 
Soderberg facilities, with As, Ni and POM driving the risks. The EPA 
estimates that the incidence of cancer due to inhalation exposures 
could be up to 0.06 excess cancer cases per year, or 1 case 
approximately every 17 years. About 950,000 people could face an 
increased cancer risk greater than 1-in-1 million due to inhalation 
exposure to allowable HAP emissions from this source category (assuming 
facilities emit at allowable levels for much of their operations, a 
highly conservative assumption), and approximately 76,000 people could 
face an increased risk greater than 10-in-1 million and 200 people to 
excess cancer risks up to 300-in-1 million due to allowable emissions.
    The risk assessment estimates that the maximum chronic non-cancer 
TOSHI from inhalation exposure values is up to 2, driven by allowable 
Ni and As emissions with approximately 30 people exposed at this value.
c. Acceptability Determination
    In proposing a determination of whether risks are acceptable for 
this source category, the EPA considered all available health 
information and risk estimation uncertainty as described above.
    The risk results indicate that actual inhalation cancer risks from 
the Primary Aluminum Production source category to the individual most 
exposed are up to, but no greater than, approximately 70-in-1 million 
and that allowable inhalation cancer risks to the individual most 
exposed are up to, but no greater than, approximately 300-in-1 million, 
which is 3 times higher than the presumptive limit of acceptability. 
The MIR based on actual emissions is well below the presumptive limit, 
while the MIR based on allowable emissions is well above the 
presumptive limit. The maximum chronic non-cancer results show no 
exceedance of the human health values for actual emissions and 
exceedance by up to a factor of approximately 2 based on allowable 
emissions.
    Regarding the acute risks, the refined maximum HQ at a residential 
location is 10 for As. We expect that these exceedances would happen 
for very few hours of the 8,760 hours that are in a year. For HF the 
maximum off-site HQ of 3 is at a location where we would not expect 
people to be for 1 hour.
    The excess cancer risks from the multipathway screen from actual D/
F emissions from operating plants indicate that the risk to the 
individual most exposed could be up to but no greater than 50-in-1 
million for the fisher scenario and 20-in-1 million for the farmer 
scenario. These results (which reflect very conservative assumptions) 
are considerably less than 100-in-1 million, the presumptive limit of 
acceptability. The multipathway Tier 2 screen for non-cancer is at the 
Tier 2 screening value of 1 for Hg and Cd. The estimated cancer risks 
from the multipathway assessment for operating facilities were well 
below 100-in-1 million. The refined multipathway results for the 
Massena East Soderberg plant indicated potential cancer risks of up to 
200-in-1 million at that location. However, since this facility has 
permanently shut down its Soderberg operations, we are not concerned 
about the potential future emissions from this facility.
    Nevertheless, given all the information presented above, the EPA 
proposes that the risks due to potential HAP emissions at baseline from 
the

[[Page 72947]]

Soderberg subcategory are unacceptable due to the allowable cancer 
risks of 300-in-1 million based on potential emissions from the idle 
Soderberg facility (Columbia Falls Aluminum Company).
    Regarding the prebake subcategories, the EPA has some concerns 
regarding the potential acute risks due to As emissions (with a maximum 
acute HQ of 10). However, given the conservative nature of the acute 
analysis (described above), and the fact that the inhalation cancer MIR 
is well below 100-in-1 million (MIR = 70-in-1 million), the chronic 
non-cancer risks are low (e.g., HI = 1) and that the multipathway 
assessment indicated the maximum cancer risks due to multipathway 
exposures to HAP from prebake facilities was no higher than 50-in-1 
million, we propose that the risks due to actual emissions from the 
prebake subcategories are acceptable.
2. Proposed Controls To Address Unacceptable Risks for Soderberg 
Facilities
a. VSS2 Potline Emissions
    In order to ensure that the risks associated with Soderberg 
facilities are acceptable, we evaluated the potential to reduce MACT-
allowable VSS2 potline emissions for the primary HAP driving the cancer 
risks (i.e., POM, As and Ni). Regarding POM, the current NESHAP 
includes an emissions limit for POM of 5.7 lbs/ton of aluminum. As 
noted above, the one facility driving the allowable risks has been idle 
for 5 years. All indications are that this facility will not reopen. 
However, based on available data from the most recent years that they 
were operating, we estimate that if this one VSS2 facility did reopen 
and if they installed wet roof top scrubbers that they could achieve a 
POM emissions limit of 1.9 lb/ton (0.85 Kg/Mg) of aluminum, which would 
be a significant reduction in potential POM emissions. This limit is 3 
times lower than the current limit for POM. Furthermore, given that 
there would be variability in emissions, in order for the facility to 
comply with a limit of 1.9 lbs/ton at all times, they would need to 
have average POM emissions considerably lower than 1.9 lb/ton. 
Therefore, under the authority of CAA section 112(f)(2), we propose a 
POM emission limit for VSS2 potlines of 1.9 lb/ton (0.85 Kg/Mg) of 
aluminum. As mentioned above, the one remaining Soderberg plant has 
been idle for 5 years and we believe it is highly unlikely that the 
facility will reopen, due to its less efficient aluminum production 
method. However, if it does reopen, we estimate that the capital costs 
for the roof top wet scrubbers would be about $30 million and that 
annualized costs would be about $8 million.
    These controls would also achieve reductions of HAP metal 
emissions. We estimate that wet roof scrubbers would achieve a 50 
percent reduction in secondary potline emissions of metals. See CFAC 
BART Analysis in the docket (Docket ID No. EPA-HQ-OAR-2011-0797). 
Nevertheless, to ensure that the primary HAP metals (i.e., As and Ni) 
that are driving the allowable cancer risks are limited to acceptable 
levels of emissions, we are proposing facility-wide total potline 
emissions limits for As and Ni that reflect a 50 percent reduction in 
the estimated facility-wide secondary potline emissions of those 
metals. We are doing so pursuant to CAA section 112(f)(2) in order to 
ensure risks will be acceptable from the VSS2 subcategory. Given that 
these reductions would be achieved using the same controls used for 
POM, there would be no added cost of control, and there would be risk 
reductions associated with reduced HAP metal emissions. Based on our 
analysis of available data, we estimated that, if this facility resumed 
operations, facility-wide emissions of Ni would be less than 0.14 
pounds per ton of aluminum produced and facility-wide emissions of As 
would be less than 0.012 pounds per ton of aluminum produced, using 
their current controls. Assuming wet roof scrubbers are installed, and 
assuming the wet roof scrubbers would achieve a 50 percent reduction in 
HAP metal emissions, and assuming the facility would run 3 potlines, 
which is the most potlines it operated in the past 13 years, we 
estimate that the roof top wet scrubbers would be able to limit 
emissions of Ni and As from potlines to no more than 0.07 pounds of Ni 
per ton of aluminum produced and no more than 0.006 pounds of As per 
ton of aluminum produced, on a facility-wide basis. Therefore, under 
the authority of CAA section 112(f), we are proposing potline emission 
limits of 0.07 pounds of Ni per ton of aluminum produced and 0.006 
pounds of As per ton of aluminum produced. For more information 
regarding the development of these risk-based standards, see the 
memorandum titled, Development of Emissions Standards to Address Risks 
for the Primary Aluminum Production Source Category Pursuant to Section 
112(f) of the Clean Air Act, in the docket for this action (Docket ID 
No. EPA-HQ-OAR-2011-0797).
    Regarding post-control risks, we estimate that with a POM emission 
limit that is 3 times lower than the current POM emission limit and 
with Ni and As emission limits that reflect a 50 percent reduction in 
potential emissions of those metals, that the post control risks would 
be approximately 100-in-1 million, if the plant did reopen.
    Based on our analyses, we conclude that the one existing VSS2 
facility, if it chose to reopen, could meet these limits with the 
installation of wet roof scrubbers on their potrooms. We note that it 
is very unlikely that any new Soderberg plants would be constructed in 
the U.S. because the Soderberg method of aluminum reduction is less 
cost effective than the prebake method and due to the cost that would 
be incurred to comply with the stringent POM limits for any new or 
reconstructed potline in the NESHAP. New or reconstructed sources would 
be subject to a POM limit of 0.77 pounds per ton of aluminum produced 
as opposed to existing sources being subject to a POM limit of 5.7 
pounds per ton of aluminum produced under the 1997 NESHAP, or 1.9 
pounds per ton of aluminum produced if the proposed revised limit of 
1.9 pounds per ton of aluminum produced in this supplemental proposal 
is adopted. Nevertheless, to ensure that any possible future Soderberg 
plant has acceptable metals emissions, we are proposing that any new 
Soderberg potlines would need to meet new source MACT limits for POM 
and the risk-based standards for As and Ni.
    We propose that compliance with the As and Ni emissions limits for 
existing VSS2 potlines and new Soderberg potlines will be demonstrated 
by annual performance testing along with various parametric monitoring 
on a more frequent basis. The proposed compliance testing requirements 
for POM are described in section IV.E of this preamble.
3. Ample Margin of Safety Analysis
    Under the ample margin of safety analysis, we again consider all of 
the health factors and evaluate the cost and feasibility of available 
control 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 due to 
emissions of HAP identified in our risk assessment.
    Under the ample margin of safety analysis, we evaluated possible 
options to reduce HAP metal and POM emissions from the prebake potline 
roof vents. The main option we evaluated is based on requiring most 
prebake facilities to install wet roof scrubbers to reduce secondary 
HAP metals emissions

[[Page 72948]]

from their potline roof vents. Under this option we estimate that post-
control cancer MIR would be 40-in-1 million for prebake facilities 
(down from 70-in-1 million). We estimate that under this option chronic 
non-cancer hazards would be below 1. The As maximum acute HQ would be 
reduced from 10 down to 7. With regard to the acute As exposures, we 
estimate that about 60 people could be exposed to concentrations 
leading to an acute HQ of 7, about 154 people could be exposed to a 
concentration leading to an acute HQ greater than 5, and that about 
3,600 people could be exposed to a concentration leading to an acute HQ 
greater than 1. This assessment still assumes, in order to reach an HQ 
greater than 1, peak emissions from the source category and worst-case 
meteorological conditions co-occur. We expect that this would happen 
for very few hours of the 8,760 hours that are in a year. For HF, the 
maximum off-site HQ would be reduced from 3 to 2 and is at a location 
where we would not expect people to be for 1 hour.
    We estimate that the total capital costs would be at least $415 
million ($46 million per facility), annualized costs would be at least 
$133 million ($15 million per facility), with cost effectiveness (CE) 
of $6 million per ton HAP metals and $130,000 per ton POM or higher. 
This option would also achieve 715 tpy PM2.5 reductions with 
CE of $185,000 per ton PM2.5. We believe these costs are 
substantial. Furthermore, based on our economic analysis, we project 
that this option would pose a significant economic burden on the 
companies and that several facilities would be at risk of closure under 
this option. The option would also be associated with potentially 
adverse environmental effects (more wastewater discharge), and 
increased energy usage (with attendant carbon pollution), although 
these are not the most significant factors in the EPA's proposed 
decision. Therefore, given all the factors described above, we are not 
proposing this option in today's action.
    In regards to the Soderberg facilities, we estimate that the 
actions proposed under CAA section 112(f)(2), as described above to 
address unacceptable risks, will reduce the MIR associated with 
allowable emissions of As, Ni and PAHs from 300-in-1 million to 100-in-
1 million (assuming the highly unlikely scenario wherein the Soderberg 
plant was to resume operation). The potential cancer incidence due to 
allowable emissions from this one facility will be reduced from 0.007 
to 0.003 with a potential of 1 case every 330 years versus 1 case every 
170 years, and the number of people estimated to potentially have 
cancer risks greater than 1-in-1 million will remain the same at 65,000 
people. The chronic noncancer inhalation TOSHI due to allowable 
emissions will be reduced from 2 to 1. Based on our research and 
analysis, we did not identify any cost effective controls beyond those 
proposed above that would achieve further reduction in risk. Therefore, 
we conclude that the controls to achieve acceptable risks (described 
above) will also achieve an ample margin of safety.
4. Adverse Environmental Effects
    Based on the results of our environmental risk screening 
assessment, we conclude that there is not an adverse environmental 
effect as a result of HAP emissions from the Primary Aluminum 
Production source category. We are proposing that it is not necessary 
to set a more stringent standard to prevent, taking into consideration 
costs, energy, safety and other relevant factors, an adverse 
environmental effect.

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

    We updated the technology review conducted for the 2011 proposal 
and 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 the 2011 
proposal. The analysis is very similar to that outlined above with 
respect to potential BTF standards. Additional details regarding the 
technology review can be found in the Revised Draft Technology Review 
for the Primary Aluminum Production Plant Source Category, which can be 
found in the docket (Docket ID No. EPA-HQ-OAR-2011-0797). This same 
information underlies the EPA's determination not to propose BTF limits 
and is summarized above.

E. What other actions are we proposing?

    In addition to the proposed actions described above, we re-
evaluated compliance requirements associated with the 2011 proposed 
amendments to determine whether we should make changes to those 
proposed amendments. Based on this re-evaluation, we are proposing the 
following changes to what was proposed in the 2011 proposal.
1. Frequency for Testing of Prebake Potline POM
    The December 2011 proposal included a testing frequency of once 
every 5 years for POM from prebake potlines and provisions for 
estimating potline roof vent emissions based on potline stack POM 
emissions and potline stack and vent TF emissions. These provisions 
were proposed based on a belief that prebake potline POM emissions 
would be relatively low and that potline vent POM emissions would be 
difficult to determine. Based on the results of testing conducted in 
response to our 2013 information request, we determined that POM 
emissions from prebake potlines are higher than we expected and that 
methods exist for testing prebake vent emissions. As a result, we are 
proposing annual testing of POM emissions from prebake potline stacks 
and testing three times each semiannual period for POM emissions from 
prebake potline roof vents, with compliance demonstrated by summing 
emissions from these two locations.
2. Reduced Testing Frequency for TF From Potlines and POM From 
Soderberg Potlines
    The NESHAP currently requires the owner/operator of an affected 
source to measure and record the emission rate of TF from potline 
stacks at least three times each year and from potline roof vents at 
least three times each month, unless they apply for, and receive, 
authorization to measure and record the roof vent TF emission rate 
three times per quarter. The NESHAP currently requires the owner/
operator to measure and record the emission rate of POM from Soderberg 
potline stacks at least three times each year and from their roof vents 
at least three times per quarter. We are proposing to decrease the 
required frequencies of measuring and recording emission rates of TF 
from potline roof vents and POM from Soderberg roof vents to three 
times each semiannual period because, based on the consistency of 
previous test results and considering the potline work practices 
included in this supplemental proposal, we believe that this testing 
frequency is adequate to determine compliance with these emission 
limits. However, as discussed in section VI of this preamble, we are 
seeking comments regarding other potential testing frequencies.
3. Testing, Monitoring and Reporting for PM, Metals and COS
    We are proposing testing, monitoring and reporting requirements to 
demonstrate compliance with the proposed emission limits for PM, Ni and 
As emissions, including the use of EPA Method 29 for determination of 
the emission rates of Ni and As. Furthermore, based on comments

[[Page 72949]]

received on the December 2011 proposal, we are proposing the use of an 
alternate method of determination of sulfur in coke, for use in 
demonstrating compliance with the potline COS emission limit.
4. Revisions to the Tables of Emission Limits for Averaging
    The current NESHAP allows emissions averaging across similar 
process vents. In this action, we are proposing revised limits 
applicable to the emission averaging to reflect the proposed revised 
and proposed additional emission standards described in section IV.A of 
this preamble.
5. Alternative Emissions Limits for Co-Controlled New and Existing 
Anode Bake Furnaces
    We are proposing alternative emission limits for certain co-
controlled new and existing anode bake furnaces to simplify compliance 
demonstration. This provision will allow a facility which uses one 
control device to control TF and POM emissions from a comingled exhaust 
from new and existing anode bake furnaces to comply with alternative 
production weighted average emission limits for those pollutants. These 
production weighted average emission limits are more protective than 
the emission limits that would otherwise apply to those sources, but 
will simplify compliance determinations and reduce costs for the 
sources because multiple emissions sources can be controlled and 
monitored at a single location.
6. Deletion of Provisions for HSS Potlines
    Following the publication of the December 2011 proposal, the only 
existing HSS potlines were permanently shut down and have been 
dismantled. We are proposing to remove the definition and emissions 
standards for this subcategory.
7. Startup, Shutdown, Malfunction
    In the 2011 proposal, we proposed to eliminate two provisions that 
exempt sources from the requirement to comply with the otherwise 
applicable CAA section 112(d) emission standards during periods of SSM. 
We also included provisions for affirmative defense to civil penalties 
for violations of emission standards caused by malfunctions. Periods of 
startup, normal operations and shutdown are all predictable and routine 
aspects of a source's operations. Malfunctions, in contrast, are 
neither predictable nor routine. Instead they are, by definition 
sudden, infrequent and not reasonably preventable failures of emissions 
control, process or monitoring equipment. As explained in the 2011 
proposal, the EPA interprets CAA section 112 as not requiring emissions 
that occur during periods of malfunction to 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 
emission 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 sources when setting emission 
standards. As the United States Court of Appeals for the District of 
Columbia Circuit has recognized, the phrase ``average emissions 
limitation achieved by the best performing 12 percent of'' sources 
``says nothing about how the performance of the best units is to be 
calculated.'' Nat'l Ass'n of Clean Water Agencies v. EPA, 734 F.3d 
1115, 1141 (D.C. Cir. 2013). While the EPA accounts for variability in 
setting emissions standards, nothing in CAA section 112 requires the 
agency to consider malfunctions as part of that analysis. A malfunction 
should not be treated in the same manner as the type of variation in 
performance that occurs during routine operations of a source. A 
malfunction is a failure of the source to perform in a ``normal or 
usual manner'' and no statutory language compels the EPA to consider 
such events in setting CAA section 112 standards.
    Further, accounting for malfunctions in setting emission standards 
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. Therefore, 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) (``The 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 
administrative exercise of case-by-case enforcement discretion, not for 
specification in advance by regulation.''). In addition, emissions 
during a malfunction event can be significantly higher than emissions 
at any other time of source operation. For example, if an air pollution 
control device with 99 percent removal goes off-line as a result of a 
malfunction (as might happen if, for example, the bags in a baghouse 
catch fire) and the emission unit is a steady state type unit that 
would take days to shut down, the source would go from 99 percent 
control to zero control until the control device was repaired. The 
source's emissions during the malfunction would be 100 times higher 
than during normal operations. Therefore, the emissions over a 4-day 
malfunction period would exceed the annual emissions of the source 
during normal operations. As this example illustrates, accounting for 
malfunctions could lead to standards that are not reflective of (and 
significantly less stringent than) levels that are achieved by a well-
performing non-malfunctioning source. It is reasonable to interpret CAA 
section 112 to avoid such a result. 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.
    Further, to the extent the EPA files an enforcement action against 
a source for violation of an emission standard, the source can raise 
any and all defenses in that enforcement action and the federal 
district court will determine what, if any, relief is appropriate. The 
same is true for citizen enforcement actions.

[[Page 72950]]

Similarly, the presiding officer in an administrative proceeding can 
consider any defense raised and determine whether administrative 
penalties are appropriate.
    As noted above, the 2011 proposal included an affirmative defense 
to civil penalties for violations caused by malfunctions. The EPA 
included the affirmative defense in the 2011 proposal as it had in 
several prior rules in an effort to create a system that incorporates 
some flexibility, recognizing that there is a tension, inherent in many 
types of air regulation, to ensure adequate compliance while 
simultaneously recognizing that despite the most diligent of efforts, 
emission standards may be violated under circumstances entirely beyond 
the control of the source. Although the EPA recognized that its case-
by-case enforcement discretion provides sufficient flexibility in these 
circumstances, it included the affirmative defense in the 2011 proposal 
and in several prior rules to provide a more formalized approach and 
more regulatory clarity. See Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 
1057-58 (D.C. Cir. 1978) (holding that an informal case-by-case 
enforcement discretion approach is adequate); but see Marathon Oil Co. 
v. EPA, 564 F.2d 1253, 1272-73 (9th Cir. 1977) (requiring a more 
formalized approach to consideration of ``upsets beyond the control of 
the permit holder.''). Under the EPA's regulatory affirmative defense 
provisions, if a source could demonstrate in a judicial or 
administrative proceeding that it had met the requirements of the 
affirmative defense in the regulation, civil penalties would not be 
assessed. Recently, the United States Court of Appeals for the District 
of Columbia Circuit vacated an affirmative defense in one of the EPA's 
CAA section 112(d) regulations. NRDC v. EPA, 749 F. 3d 1055 (D.C. Cir. 
2014) 2014 U.S. App. LEXIS 7281 (vacating affirmative defense 
provisions in CAA section 112(d) rule establishing emission standards 
for Portland cement kilns). The court found that the EPA lacked 
authority to establish an affirmative defense for private civil suits 
and held that under the CAA, the authority to determine civil penalty 
amounts lies exclusively with the courts, not the EPA. Specifically, 
the court found: ``As the language of the statute makes clear, the 
courts determine, on a case-by-case basis, whether civil penalties are 
`appropriate.' '' See NRDC v. EPA, 749 F.3d 1055, 1063 (D.C. Cir. 2014) 
(``[U]nder this statute, deciding whether penalties are `appropriate' 
in a given private civil suit is a job for the courts, not EPA.''). In 
light of NRDC, the EPA is withdrawing its proposal to include a 
regulatory affirmative defense provision in this rulemaking. As 
explained above, if a source is unable to comply with emissions 
standards as a result of a malfunction, the EPA may use its case-by-
case enforcement discretion to provide flexibility, as appropriate. 
Further, as the United States Court of Appeals for the District of 
Columbia Circuit recognized, in an EPA or citizen enforcement action, 
the court has the discretion to consider any defense raised and 
determine whether penalties are appropriate. Cf. NRDC v. EPA, 749 F. 3d 
1055, 1064 (D.C. Cir. 2014) (arguments that violation were caused by 
unavoidable technology failure can be made to the courts in future 
civil cases when the issue arises). The same logic applies to the EPA 
administrative enforcement actions.

F. What compliance dates are we proposing?

    In this supplementary proposal we are proposing changes to some of 
the compliance dates that we proposed in 2011. Specifically, we propose 
that facilities must comply with the changes set out in this 
supplementary proposal which are being proposed under CAA section 
112(d) no later than one year after the effective date of the final 
rule. In the 2011 proposal, we proposed that the facilities would be 
allowed up to three years after the effective date of the final rule to 
comply with the proposed changes under CAA section 112(d). Upon further 
review and analysis of available data, we believe that one year will be 
sufficient time to comply with the proposed CAA section 112(d) 
standards, which would include: conducting testing to demonstrate 
compliance with the proposed MACT standards for POM from existing 
prebake potlines and COS emissions from all existing potlines; 
implementing the proposed work practice standards for potlines, paste 
production plants and anode bake furnaces; and installing any necessary 
controls on existing pitch tanks.
    We also believe that one year will be sufficient time to conduct 
testing to demonstrate compliance with the new MACT standards in this 
supplemental proposal for PM emissions from existing potlines, paste 
production plants and anode bake furnaces, since equipment 
modifications will not be necessary.
    Finally, we propose that facilities must comply with the risk-based 
emission limits for POM, Ni and As emissions from VSS2 potlines and new 
Soderberg potlines no later than two years after the effective date of 
the final rule. We believe that it is appropriate to allow the maximum 
amount of time for compliance with these risk-based standards 
permissible pursuant to CAA section 112(f) (i.e., 2 years) since a 
subject facility would be required to install wet roof scrubbers in 
order to comply with those standards.

V. Summary of the Revised 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 plants.

B. What are the air quality impacts?

    We estimate that the proposed lower VSS2 potline POM emissions 
limits would reduce POM emissions from the one VSS2 facility by 
approximately 53 tons per year if the facility were to resume 
operation. Furthermore, we estimate that these proposed standards would 
also result in about 1 tpy reduction of HAP metals and 40 tpy reduction 
of PM2.5 if the one Soderberg facility reopened.

C. What are the cost impacts?

    Under the proposed amendments, prebake facilities would be required 
to conduct annual POM testing on potlines, and all facilities would be 
required to conduct annual PM testing on potlines, anode bake furnaces 
and paste plants. Facilities would also be required to monitor 12 anode 
bake furnaces and 11 paste plants at an estimated cost of $129,375 per 
year. These testing costs are offset by reduced frequency testing of TF 
from all potlines, resulting in a reduction in testing costs of 
$2,050,000 per year. The total estimated cost of the rule is a savings 
of $959,000 assuming that the Columbia Falls Soderberg plant does not 
reopen.
    The one Soderberg facility, if it reopens, will be expected to 
install and operate wet roof scrubbers on their potrooms to comply with 
risk-based standards for POM, As and Ni at a total estimated capital 
cost of $30 million and annual cost of $8 million. This facility, if it 
reopens, would be also required to conduct annual Ni and As emissions 
tests on three potlines. Under this scenario, the total estimated cost 
of the rule is $7,100,000 per year. The memorandum, Revised Draft Cost 
Impacts for the Primary Aluminum Production Source Category includes a

[[Page 72951]]

description of the assumptions used for this analysis and is available 
in the docket (Docket ID No. EPA-HQ-OAR-2011-0797).

D. What are the economic impacts?

    We performed an economic impact analysis for the proposed 
modifications in this action. That analysis estimates a net savings for 
each open facility based on the assumption that the Columbia Falls 
Soderberg facility will not reopen. If Columbia Falls does reopen, the 
total estimated cost of the rule is $7,100,000 per year. For more 
information, please refer to the memo titled, Economic Impact Analysis 
for National Emissions Standards for Hazardous Air Pollutants: Primary 
Aluminum Reduction Plants for this proposed rulemaking that is 
available in the public docket for this proposed rulemaking.

E. What are the benefits?

    If the Soderberg facility were to resume operations, the proposed 
standards in this supplemental proposal would achieve an estimated 
reduction in annual HAP emissions of about 53 tons, which would provide 
significant benefits to public health. In addition to the HAP 
reductions, which would ensure an ample margin of safety, we also 
estimate that this supplemental proposal would achieve about 230 tons 
of reductions in PM (including 40 tons of PM2.5) emissions 
as a co-benefit of the HAP reductions annually (again assuming 
resumption of the Soderberg plant operations).
    This rulemaking is not an ``economically significant regulatory 
action'' under Executive Order 12866 because it is not likely to have 
an annual effect on the economy of $100 million or more. Therefore, we 
have not conducted a Regulatory Impact Analysis (RIA) for this 
rulemaking or a benefits analysis. While we expect that these avoided 
emissions will improve air quality and reduce health effects associated 
with exposure to air pollution associated with these emissions, we have 
not quantified or monetized the benefits of reducing these emissions 
for this rulemaking. This does not imply that there are no benefits 
associated with these emission reductions. We provide a qualitative 
description of benefits associated with reducing these pollutants 
below. When determining whether the benefits of an action exceed its 
costs, Executive Orders 12866 and 13563 direct the agency to consider 
qualitative benefits that are difficult to quantify but nevertheless 
essential to consider.
    Directly emitted particles are precursors to secondary formation of 
fine particles (PM2.5). Controls installed to reduce HAP 
would also reduce ambient concentrations of PM2.5 as a co-
benefit. Reducing exposure to PM2.5 is associated with 
significant human health benefits, including avoiding mortality and 
morbidity from cardiovascular and respiratory illnesses. Researchers 
have associated PM2.5 exposure with adverse health effects 
in numerous toxicological, clinical and epidemiological studies (U.S. 
EPA, 2009).\42\ When adequate data and resources are available and an 
RIA is required, the EPA generally quantifies several health effects 
associated with exposure to PM2.5 (e.g., U.S. EPA, 
2012).\43\ These health effects include premature mortality for adults 
and infants, cardiovascular morbidities such as heart attacks, hospital 
admissions and respiratory morbidities such as asthma attacks, acute 
bronchitis, hospital and emergency department visits, work loss days, 
restricted activity days and respiratory symptoms. The scientific 
literature also suggests that exposure to PM2.5 is 
associated with adverse effects on birth weight, pre-term births, 
pulmonary function and other cardiovascular and respiratory effects 
(U.S. EPA, 2009), but the EPA has not quantified these impacts in its 
benefits analyses. PM2.5 also increases light extinction, 
which is an important aspect of visibility.
---------------------------------------------------------------------------

    \42\ U.S. Environmental Protection Agency (U.S. EPA). 2009. 
Integrated Science Assessment for Particulate Matter (Final Report). 
EPA-600-R-08-139F. National Center for Environmental Assessment--RTP 
Division. Available on the Internet at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=216546.
    \43\ U.S. Environmental Protection Agency (U.S. EPA). 2012. 
Regulatory Impact Analysis for the Final Revisions to the National 
Ambient Air Quality Standards for Particulate Matter. Office of Air 
and Radiation, Research Triangle Park, NC. Available on the Internet 
at http://www.epa.gov/ttn/ecas/regdata/RIAs/finalria.pdf.
---------------------------------------------------------------------------

    The supplemental proposed rulemaking is also anticipated to reduce 
emissions of other HAP, including HAP metals (As, Cd, Cr (both total 
and hexavalent), Pb, Mn and Ni) and PAHs, assuming the Soderberg plant 
resumes operations. Some of these HAP are carcinogenic (e.g., As, PAHs) 
and some have effects other than cancer (e.g., kidney disease from Cd, 
respiratory and immunological effects from Ni). While we cannot 
quantitatively estimate the benefits achieved by reducing emissions of 
these HAP, we would expect benefits by reducing exposures to these HAP. 
More information about the health effects of these HAP can be found on 
the IRIS,\44\ ATSDR,\45\ and California EPA \46\ Web pages.
---------------------------------------------------------------------------

    \44\ US EPA, 2006. Integrated Risk Information System. http://www.epa.gov/iris/index.html.
    \45\ US Agency for Toxic Substances and Disease Registry, 2013. 
Minimum Risk Levels (MRLs) for Hazardous Substances. http://www.atsdr.cdc.gov/mrls/index.html.
    \46\ CA Office of Environmental Health Hazard Assessment. 
Chronic Reference Exposure Levels Adopted by OEHHA as of December 
2008. http://www.oehha.ca.gov/air/chronic_rels.
---------------------------------------------------------------------------

VI. Request for Comments

    As stated above, we are not opening comment on aspects of the 2011 
proposal (76 FR 76260) that have not changed and are not addressed in 
this supplemental proposal. Comments received on the 2011 proposal 
along with comments received on this supplemental proposal will be 
addressed in the EPA's Response to Comment document and final rule 
preamble for the Primary Aluminum Production source category.
    We are soliciting comments on the revised risk assessment and 
technology review and proposed changes to the previously-proposed 
amendments.
    We are seeking comments on an alternative approach for 
demonstrating compliance with the emissions limits for potlines. 
Facilities face challenges when measuring secondary emissions from 
potlines, as these emissions are fugitive in nature. Some facilities 
employ a manifold system which captures a portion of the emissions that 
would exit the roof of the building. These emissions can be sampled 
using standard EPA reference methods, and the results can be 
extrapolated to account for the emissions from the entire roof. Other 
facilities sample the emissions near the roof using a series of 
elevated cassettes that contain removable filters. The EPA has a 
standard reference method for the measurement of TF using these 
cassettes, but there is not a standard reference method for other 
pollutants.
    In the 2013 CAA section 114 information request, we requested 
facilities use filters meeting the requirements of EPA Method 315 in 
the cassettes and then recover and analyze the filters for filterable 
PM and POM using Method 315. In reviewing the results, we noted that 
there was no appreciable difference in the results of facilities that 
tested using the reference method in the manifold and facilities that 
tested using filters in cassettes. We, therefore, think it is 
reasonable to require facilities with manifolds to test at ambient 
conditions instead of heating the filter and probe. We also think it is 
reasonable to allow facilities that

[[Page 72952]]

sample in manifolds to forego the use of the back half of the train 
altogether. In this case, the filterable POM results would be a 
surrogate for total POM, and the measurement data for the cassettes and 
manifolds would be most directly comparable.
    We are seeking comments on the frequency with which the owner/
operator of affected potlines must measure and record emission rates of 
TF, POM and PM from roof vents. The frequency proposed in this action 
is at least three times each semiannual period. However, we are 
considering frequencies of at least three times each quarter or at 
least three times each year. We request that any commenter who would 
like the EPA to consider a different frequency include specific 
rationale and factual basis, including supporting data, for why a 
different frequency would be appropriate.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses and instructions are available for 
download on the RTR Web site at: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The data files include detailed information for each HAP 
emissions release point for the facilities 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 page, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information.
    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).
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations, etc.).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft[supreg] Access format and all accompanying documentation to 
Docket ID No. EPA-HQ-OAR-2011-0797 (through one of the methods 
described in the ADDRESSES section of this preamble).
    5. If you are providing comments on a single facility or multiple 
facilities, you need only submit one file for all facilities. The file 
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[supreg] Excel files that are generated by the 
Microsoft[supreg] Access file. These files are provided on the RTR Web 
site 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

    This action is not a ``significant regulatory action'' under the 
terms of Executive Order 12866 (58 FR 51735, October 4, 1993) and is, 
therefore, not subject to review under Executive Orders 12866 and 13563 
(76 FR 3821, January 21, 2011).

B. Paperwork Reduction Act

    The information collection requirements in this proposed rule have 
been submitted for approval to the 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 EPA ICR number 2447.01.
    We are proposing changes to the paperwork requirements to the 
Primary Aluminum Production source category. In this supplemental 
proposal, we are proposing less frequent testing of POM emissions from 
Soderberg potlines and less frequent testing of TF emissions from all 
potlines. In addition, we are removing from this proposal the burden 
associated with the affirmative defense provisions included in the 
December 2011 proposal.
    We estimate 13 regulated entities are currently subject to subpart 
LL (NESHAP for Primary Aluminum Reduction Plants) and will be subject 
to this action. The annual monitoring, reporting and recordkeeping 
burden for this collection (averaged over the first 3 years after the 
effective date of the standards) as a result of the supplemental 
proposal revised amendments to subpart LL is estimated to be -
$1,179,000 per year.
    This includes -427 labor hours per year at a total labor cost of -
$32,350 per year, and total non-labor capital and operation and 
maintenance costs of -$1,212,000 per year. This estimate includes 
performance tests, notifications, reporting and recordkeeping 
associated with the new requirements for primary aluminum reduction 
plant operations. The total burden for the federal government (averaged 
over the first 3 years after the effective date of the standard) is 
estimated to be 199 hours per year at a total labor cost of $9,072 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.
    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 No. EPA-HQ-OAR-
2011-0797. Submit any comments related to the ICR to the EPA and OMB. 
See ADDRESSES section at the beginning of this preamble 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 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after December 8, 2014, a comment to OMB is best 
assured of having its full effect if OMB receives it by January 7, 
2015. 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 generally requires an agency to 
prepare a regulatory flexibility analysis of any rule subject to notice 
and comment rulemaking requirements under the Administrative Procedure 
Act, or any other statute, unless the agency certifies that the rule 
will not have a significant economic impact on a substantial number of 
small entities. Small entities include small businesses, small 
organizations and small governmental jurisdictions.
    For purposes of assessing the impacts of today's rule on small 
entities, small entity is defined as: (1) A small business 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

[[Page 72953]]

employees according to the SBA small business standards definitions.
    After considering the economic impacts of today's action on small 
entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. None of the 
companies affected by this rule is considered to be a small entity per 
the definition provided in this section.

D. Unfunded Mandates Reform Act

    This action does not contain a federal mandate under the provisions 
of Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), 2 
U.S.C. 1531-1538 for state, local or tribal governments, or the private 
sector. The action 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. This supplemental proposal imposes no 
enforceable duties on any state, local or tribal governments, or the 
private sector. Thus, this action is not subject to the requirements of 
sections 202 or 205 of the UMRA.
    This action 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 as it contains no 
requirements that apply to such governments nor does it impose 
obligations upon them.

E. Executive Order 13132: Federalism

    This action 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 action will 
supersede state regulations. Thus, Executive Order 13132 does not apply 
to this action.
    In the spirit of Executive Order 13132, and consistent with EPA 
policy to promote communication between the EPA and state and local 
governments, the EPA specifically solicits comment on this proposed 
action from state and local officials.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have tribal implications, as specified in 
Executive Order 13175 (65 FR 67249, November 9, 2000) because it does 
not have substantial direct effects on any Indian tribe(s), on the 
relationship between the federal government and Indian tribes or on the 
distribution of power and responsibilities between the federal 
government and Indian tribes. Thus, Executive Order 13175 does not 
apply to this action.
    The EPA specifically solicits comment on this action from tribal 
officials.

G. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    This action is not subject to Executive Order 13045 (62 FR 19885, 
April 23, 1997) because the agency does not believe the environmental 
health risks or safety risks addressed by this action present a 
disproportionate risk to children.
    This rule is expected to reduce environmental impacts for everyone, 
including children. This action establishes emissions limits at the 
levels based on MACT, as required by the CAA. Based on our analysis, we 
believe that this rule does not have a disproportionate impact on 
children.
    The public is invited to submit comments or identify peer-reviewed 
studies and data that assess effects of early life exposure to HAP 
emitted from the Primary Aluminum Production source category.

H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not subject to Executive Order 13211 (66 FR 28355, 
May 22, 2001), because it is not a significant regulatory action under 
Executive Order 12866.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (NTTAA), Public Law 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 VCS bodies. The NTTAA 
directs the EPA to provide Congress, through OMB, explanations when the 
agency decides not to use available and applicable VCS.
    This proposed rulemaking involves technical standards. The rule 
requires the use of either ASTM D3177-02 (2007), Standard Test Methods 
for Total Sulfur in the Analysis Sample of Coal and Coke, or ASTM D-
6376-06, Test Method for Determination of Trace Metals in Petroleum 
Coke by Wavelength Dispersive X-ray Fluorescence Spectroscopy. These 
are voluntary consensus methods. These methods can be obtained from the 
American Society for Testing and Materials, 100 Bar Harbor Drive, West 
Conshohocken, Pennsylvania 19428 (telephone number (610) 832-9500). 
These methods were proposed in the rule because they are commonly used 
by primary aluminum production facilities to demonstrate compliance 
with sulfur dioxide emission limitations imposed in their current Title 
V permits.
    Under 40 CFR 63.7(f) and 40 CFR 63.8(f) of subpart A of the General 
Provisions, a source may apply to the EPA for permission to use 
alternative test methods or alternative monitoring requirements in 
place of any required testing methods, performance specifications or 
procedures in the proposed rule.
    The EPA welcomes comments on this aspect of the proposed rulemaking 
and specifically invites the public to identify potentially applicable 
VCS 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. For the Primary Aluminum Production 
source category, the 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 
provide and ample margin of safety to protect public health of all 
demographic groups.
    The EPA has determined that this proposed rule will not have 
disproportionately high and adverse human health or environmental 
effects on minority, low income or indigenous populations because it 
increases the level of environmental protection for all

[[Page 72954]]

affected populations without having any disproportionately high and 
adverse human health or environmental effects on any population, 
including any minority, low income or indigenous populations.
    These proposed standards will improve public health and welfare, 
now and in the future, by reducing HAP emissions contributing to 
environmental and human health impacts. These reductions in HAP 
associated with the rule are expected to benefit all populations.
    To examine the potential for any environmental justice issues that 
might be associated with the Primary Aluminum Production 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 proposed rule are described in the document, Risk and 
Technology Review--Analysis of Socio-Economic Factors for Populations 
Living Near Primary Aluminum Facilities, which may be found in the 
docket for this rulemaking (Docket ID No. EPA-HQ-OAR-2011-0797).
    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-1 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, Risk and Technology Review--
Analysis of Socio-Economic Factors for Populations Living Near Primary 
Aluminum Facilities, in the docket for this rulemaking.

List of Subjects in 40 CFR Part 63

    Environmental protection, Air pollution control, Hazardous 
substances, Incorporation by reference, Reporting and recordkeeping 
requirements.

    Dated: November 13, 2014.
Gina McCarthy,
Administrator.

    For the reasons stated in the preamble, Title 40, chapter I, of the 
Code of Federal Regulations (CFR) is proposed to be amended as follows:

PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS 
FOR SOURCE CATEGORIES

0
1. The authority citation for part 63 continues to read as follows:

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

Subpart LL--National Emission Standards for Hazardous Air 
Pollutants for Primary Aluminum Reduction Plants

0
2. Section 63.840 is amended by revising paragraph (a) to read as 
follows:


Sec.  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 Sec.  63.2.
* * * * *
0
3. Section 63.841 is amended by:
0
a. Revising paragraphs (a)(1) and (2); and
0
b. Adding paragraphs (a)(3) and (4).
    The revisions and additions read as follows:


Sec.  63.841  Incorporation by reference.

    (a) * * *
    (1) Chapter 3, ``Local Exhaust Hoods'' and Chapter 5, ``Exhaust 
System Design Procedure'' of ``Industrial Ventilation: A Manual of 
Recommended Practice,'' American Conference of Governmental Industrial 
Hygienists, 22nd edition, 1995, IBR approved for Sec. Sec.  63.843(b) 
and 63.844(b);
    (2) ASTM D 2986-95A, Standard Practice for Evaluation of Air Assay 
Media by the Monodisperse DOP (Dioctyl Phthalate) Smoke Test, IBR 
approved for section 7.1.1 of Method 315 in appendix A to this part;
    (3) ASTM D4239-13e1, Standard Test Method for Sulfur in the 
Analysis Sample of Coal and Coke Using High Temperature Tube Furnace 
Combustion; and
    (4) ASTM D6376-10, Standard Test Method for Determination of Trace 
Metals in Petroleum Coke by Wavelength Dispersive X-Ray Fluorescence 
Spectroscopy.
* * * * *
0
4. Section 63.842 is amended by:
0
a. Adding, in alphabetical order, definitions of ``Particulate matter 
(PM),'' and ``Startup of an anode bake furnace'';
0
b. Removing the definitions for ``Horizontal stud Soderberg (HSS) 
process'' and ``Vertical stud Soderberg one (VSS1)''; and
0
c. Revising the definition for ``Paste production plant''.
    The revisions and additions read as follows:


Sec.  63.842  Definitions.

* * * * *
    Particulate matter (PM) means, for the purposes of this subpart, 
emissions of particulate matter that serve as a measure of total 
particulate emissions and as a surrogate for metal hazardous air 
pollutants contained in the particulates, including but not limited to, 
antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, 
manganese, nickel and selenium.
    Paste production plant means the processes whereby calcined 
petroleum coke, coal tar pitch (hard or liquid) and/or other materials 
are mixed, transferred and formed into briquettes or paste for vertical 
stud Soderberg (VSS) processes or into green anodes for a prebake 
process. This definition includes all operations from initial mixing to 
final forming (i.e., briquettes, paste, green anodes) within the paste 
production plant, including conveyors and units managing heated liquid 
pitch.
* * * * *
    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 concludes at 
the start of the second anode bake cycle if the furnace was at ambient 
temperature upon startup. The re-start concludes when the anode bake 
cycle resumes if the furnace was not at ambient temperature upon re-
start.
* * * * *
0
5. Section 63.843 is amended by:
0
a. Revising paragraph (a)introductory text;
0
b. Revising paragraph (a)(1)(iv);
0
c. Removing and reserving paragraph (a)(1)(v);
0
d. Revising paragraph (a)(1)(vi);
0
e. Removing paragraph (a)(1)(vii);
0
f. Removing and reserving paragraphs (a)(2)(i) and (ii);
0
g. Revising paragraph (a)(2)(iii);
0
h. Adding paragraphs (a)(2)(iv) through (vii);
0
i. Redesignating paragraph (a)(3) as (a)(6);
0
j. Adding new paragraph (a)(3)and paragraphs (a)(4) and (5);
0
k. Revising paragraph (b) introductory text;
0
l. Adding paragraph (b)(4);
0
m. Revising paragraph (c) introductory text;
0
n. Revising paragraphs (c)(1) and (2);

[[Page 72955]]

0
o. Adding paragraph (c)(3); and
0
p. Adding paragraphs (d), (e) and (f).
    The revisions and additions read as follows:


Sec.  63.843  Emission limits for existing sources.

    (a) Potlines. The owner or operator shall not discharge or cause to 
be discharged into the atmosphere any emissions of TF, POM, PM, nickel 
or arsenic in excess of the applicable limits in paragraphs (a)(1) 
through (a)(5) of this section.
    (1) * * *
    (iv) 0.8 kg/Mg (1.6 lb/ton) of aluminum produced for each SWPB 
potline; and
    (v) [Reserved]
    (vi) 1.35 kg/Mg (2.7 lb/ton) of aluminum produced for each VSS2 
potline.
    (2) * * *
    (i) [Reserved]
    (ii) [Reserved]
    (iii) 1.9 kg/Mg (3.8 lb/ton) of aluminum produced for each VSS2 
potline;
    (iv) 0.55 kg/Mg (1.1 lb/ton) of aluminum produced for each CWPB1 
prebake potline;
    (v) 6.0 kg/Mg (12 lb/ton) of aluminum produced for each CWPB2 
prebake potline;
    (vi) 1.4 kg/Mg (2.7 lb/ton) of aluminum produced for each CWPB3 
prebake potline; and
    (vii) 9.5 kg/Mg (19 lb/ton) of aluminum produced for each SWPB 
prebake potline.
    (3) PM limits. Emissions of PM shall not exceed:
    (i) 3.6 kg/Mg (7.2 lb/ton) of aluminum produced for each CWPB1 
potline;
    (ii) 5.5 kg/Mg (11 lb/ton) of aluminum produced for each CWPB2 
potline;
    (iii) 10 kg/Mg (20 lb/ton) of aluminum produced for each CWPB3 
potline;
    (iv) 2.3 kg/Mg (4.6 lb/ton) of aluminum produced for each SWPB 
potline; and
    (v) 13 kg/Mg (26 lb/ton) of aluminum produced for each VSS2 
potline.
    (4) Nickel limits. Emissions of nickel shall not exceed 0.07 lb/ton 
from all VSS2 potlines at a primary aluminum reduction plant.
    (5) Arsenic limits. Emissions of arsenic shall not exceed 0.006 lb/
ton from all VSS2 potlines at a primary aluminum reduction plant.
    (6) Change in subcategory. Any potline, other than a reconstructed 
potline, that is changed such that its applicable subcategory also 
changes shall meet the applicable emission limit in this subpart for 
the original subcategory or the new subcategory, whichever is more 
stringent.
    (b) Paste production plants. The owner or operator shall install, 
operate and maintain equipment to capture and control POM and PM 
emissions from each paste production plant.
* * * * *
    (4) PM limits. Emissions of PM shall not exceed 0.041 kg/Mg (0.082 
lb/ton) of green anode.
    (c) Anode bake furnaces. The owner or operator shall not discharge 
or cause to be discharged into the atmosphere any emissions of TF, POM 
or PM in excess of the limits in paragraphs (c)(1) through (3) of this 
section.
    (1) TF limit. Emissions of TF shall not exceed 0.10 kg/Mg (0.20 lb/
ton) of green anode;
    (2) POM limit. Emissions of POM shall not exceed 0.09 kg/Mg (0.18 
lb/ton) of green anode; and
    (3) PM limit. Emissions of PM shall not exceed 0.034 kg/Mg (0.068 
lb/ton) of green anode.
    (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.
    (e) COS limit. Emissions of COS must not exceed 1.95 kg/Mg (3.9 lb/
ton) of aluminum produced for each potline.
    (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.
0
6. Section 63.844 is amended by:
0
a. Revising paragraph (a) introductory text;
0
b. Revising paragraph (a)(2);
0
c. Adding paragraphs (a)(3) through (5);
0
d. Revising paragraph (b) introductory text;
0
e. Adding paragraphs (b)(1) and (2);
0
f. Revising paragraph (c) introductory text;
0
g. Revising paragraphs (c)(1) and (2);
0
h. Adding paragraph (c)(3); and
0
i. Adding paragraphs (e) and (f).
    The revisions and additions read as follows:


Sec.  63.844  Emission limits for new or reconstructed sources.

    (a) Potlines. The owner or operator shall not discharge or cause to 
be discharged into the atmosphere any emissions of TF, POM, PM, nickel 
or arsenic in excess of the applicable limits in paragraphs (a)(1) 
through (a)(5) of this section.
* * * * *
    (2) POM limit. Emissions of POM from potlines must not exceed 0.39 
kg/Mg (0.77 lb/ton) of aluminum produced.
    (3) PM limit. Emissions of PM from potlines must not exceed 2.3 kg/
Mg (4.6 lb/ton) of aluminum produced.
    (4) Nickel limits. Emissions of nickel shall not exceed 0.07 lb/ton 
from all Soderberg potlines at a primary aluminum reduction plant.
    (5) Arsenic limits. Emissions of arsenic shall not exceed 0.006 lb/
ton from all Soderberg potlines at a primary aluminum reduction plant.
    (b) Paste production plants.
    (1) The owner or operator shall meet the requirements in Sec.  
63.843(b)(1) through (3) for existing paste production plants and shall 
not discharge or cause to be discharged into the atmosphere any 
emissions of PM in excess of the limit in paragraph (b)(2) of this 
section.
    (2) Emissions of PM shall not exceed 0.0028 kg/Mg (0.0056 lb/ton) 
of green anode.
    (c) Anode bake furnaces. The owner or operator shall not discharge 
or cause to be discharged into the atmosphere any emissions of TF, PM 
or POM in excess of the limits in paragraphs (c)(1) through (3) of this 
section.
    (1) TF limit. Emissions of TF shall not exceed 0.01 kg/Mg (0.02 lb/
ton) of green anode;
    (2) POM limit. Emissions of POM shall not exceed 0.025 kg/Mg (0.05 
lb/ton) of green anode; and
    (3) PM limit. Emissions of PM shall not exceed 0.018 kg/Mg (0.036 
lb/ton) of green anode.
* * * * *
    (e) COS limit. Emissions of COS must not exceed 3.1 lb/ton of 
aluminum produced for each potline.
    (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.
0
7. Section 63.846 is amended by:

[[Page 72956]]

0
a. Revising paragraph (b) introductory text;
0
b. Revising paragraphs (b)(1) through (3);
0
c. Revising paragraph (c) introductory text;
0
d. Revising paragraphs (c)(1) and (2);
0
e. Revising paragraphs (d)(2)(ii) through (iv);
0
f. Revising paragraphs (d)(4)(i) through (iii); and
0
g. Removing (d)(4)(iv).
    The revisions read as follows:


Sec.  63.846  Emission averaging.

* * * * *
    (b) Potlines. The owner or operator may average emissions from 
potlines and demonstrate compliance with the limits in Tables 1 through 
3 of this subpart using the procedures in paragraphs (b)(1) through (3) 
of this section.
    (1) Annual average emissions of TF shall not exceed the applicable 
emission limit in Table 1 of this subpart. The emission rate shall be 
calculated based on the total primary and secondary emissions from all 
potlines over the period divided by the quantity of aluminum produced 
during the period, from all potlines comprising the averaging group. To 
determine compliance with the applicable emission limit in Table 1 of 
this subpart for TF emissions, the owner or operator shall determine 
the average emissions (in lb/ton) from each potline from at least three 
runs per potline semiannually for TF secondary emissions and at least 
three runs per potline primary control system each year using the 
procedures and methods in Sec. Sec.  63.847 and 63.849. The owner or 
operator shall combine the results of secondary TF average emissions 
with the TF results for the primary control system and divide total 
emissions by total aluminum production.
    (2) Annual average emissions of POM shall not exceed the applicable 
emission limit in Table 2 of this subpart. The emission rate shall be 
calculated based on the total primary and secondary emissions from all 
potlines over the period divided by the quantity of aluminum produced 
during the period, from all potlines comprising the averaging group. To 
determine compliance with the applicable emission limit in Table 2 of 
this subpart for POM emissions, the owner or operator shall determine 
the average emissions (in lb/ton) from each potline from at least three 
runs per potline semiannually for POM secondary emissions and at least 
three runs per potline primary control system each year for POM primary 
emissions using the procedures and methods in Sec. Sec.  63.847 and 
63.849. The owner or operator shall combine the results of secondary 
POM average emissions with the POM results for the primary control 
system and divide total emissions by total aluminum production.
    (3) Annual average emissions of PM shall not exceed the applicable 
emission limit in Table 3 of this subpart. The emission rate shall be 
calculated based on the total primary and secondary emissions from all 
potlines over the period divided by the quantity of aluminum produced 
during the period, from all potlines comprising the averaging group. To 
determine compliance with the applicable emission limit in Table 3 of 
this subpart for PM emissions, the owner or operator shall determine 
the average emissions (in lb/ton) from each potline from at least three 
runs per potline semiannually for PM secondary emissions and at least 
three runs per potline primary control system each year for PM primary 
emissions using the procedures and methods in Sec. Sec.  63.847 and 
63.849. The owner or operator shall combine the results of secondary PM 
average emissions with the PM results for the primary control system 
and divide total emissions by total aluminum production.
    (c) Anode bake furnaces. The owner or operator may average TF 
emissions from anode bake furnaces and demonstrate compliance with the 
limits in Table 4 of this subpart using the procedures in paragraphs 
(c)(1) and (2) of this section. The owner or operator also may average 
POM emissions from anode bake furnaces and demonstrate compliance with 
the limits in Table 4 of this subpart using the procedures in 
paragraphs (c)(1) and (2) of this section. The owner or operator also 
may average PM emissions from anode bake furnaces and demonstrate 
compliance with the limits in Table 4 of this subpart using the 
procedures in paragraphs (c)(1) and (2) of this section.
    (1) Annual emissions of TF, POM and/or PM from a given number of 
anode bake furnaces making up each averaging group shall not exceed the 
applicable emission limit in Table 4 of this subpart in any one year; 
and
    (2) To determine compliance with the applicable emission limit in 
Table 4 of this subpart for anode bake furnaces, the owner or operator 
shall determine TF, POM and/or PM emissions from the control device for 
each furnace at least once each year using the procedures and methods 
in Sec. Sec.  63.847 and 63.849.
    (d) * * *
    (2) * * *
    (ii) The assigned TF, POM or PM emission limit for each averaging 
group of potlines or anode bake furnaces;
    (iii) The specific control technologies or pollution prevention 
measures to be used for each emission source in the averaging group and 
the date of its installation or application. If the pollution 
prevention measures reduce or eliminate emissions from multiple 
sources, the owner or operator must identify each source;
    (iv) The test plan for the measurement of TF, POM or PM emissions 
in accordance with the requirements in Sec.  63.847(b) and (k);
* * * * *
    (4) * * *
    (i) Any averaging between emissions of differing pollutants or 
between differing sources. Emission averaging shall not be allowed 
between TF, POM and PM, and emission averaging shall not be allowed 
between potlines and anode bake furnaces;
    (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.
* * * * *
0
8. Section 63.847 is amended by:
0
a. Revising paragraph (a) introductory text;
0
b. Revising paragraphs (a)(1) and (2);
0
c. Removing and reserving paragraph (a)(3);
0
d. Removing and reserving paragraph (b)(6);
0
e. Revising paragraphs (c)(1) through (3);
0
f. Revising paragraph (d) introductory text;
0
g. Revising paragraph (d)(1);
0
h. Removing and reserving paragraph (d)(2);
0
i. Revising paragraph (d)(4);
0
j. Adding paragraphs (d)(5) and (6);
0
k. Revising paragraphs (e)(1) and (4);
0
l. Adding paragraphs (e)(8) and (e)(9);
0
m. Revising paragraph (f);
0
n. Revising paragraph (g) introductory text;
0
o. Revising paragraphs (g)(2)(ii) and (iv);
0
p. Adding and reserving paragraph (i); and
0
q. Adding paragraphs (j), (k), (l) and (m).
    The revisions and additions read as follows:


Sec.  63.847  Compliance provisions.

    (a) Compliance dates. The owner operator of a primary aluminum

[[Page 72957]]

reduction plant must comply with the requirements of this subpart by 
the applicable compliance date in paragraph (a)(1), (a)(2), (a)(3) or 
(a)(4) of this section:
    (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) [DATE OF PUBLICATION OF FINAL RULE] for the malfunction 
provisions of Sec. Sec.  63.850(d)(2) and (e)(4)(xvi) and (xvii) and 
the electronic reporting provisions of Sec. Sec.  63.850(c) and (f) 
which became effective [DATE OF PUBLICATION OF FINAL RULE].
    (ii) [DATE 1 YEAR AFTER DATE OF PUBLICATION OF FINAL RULE] for 
prebake potlines subject to emission limits in Sec. Sec.  
63.843(a)(2)(iv) through (vii); for potlines subject to the work 
practice standards in Sec.  63.854(a), the COS emission limit 
provisions of Sec.  63.843(e) and the PM emissions limit provisions of 
Sec. Sec.  63.843(a)(3)(i) through (v); for anode bake furnaces subject 
to the startup practices in Sec.  63.847(l) and PM emission limits in 
Sec.  63.843(c)(3); for compliance with the pitch storage tank POM 
limit provisions of Sec.  63.843(d); for paste production plants 
subject to the startup practices in Sec.  63.847(m) and PM emission 
limits in Sec.  63.843(b)(4) which became effective [DATE OF 
PUBLICATION OF FINAL RULE].
    (iii) [DATE 2 YEARS AFTER DATE OF PUBLICATION OF FINAL RULE] for 
Soderberg potlines subject to emission limits in Sec.  
63.843(a)(2)(iii), (a)(4) and (a)(5) which became effective [DATE OF 
PUBLICATION OF FINAL RULE].
    (3) [Reserved]
* * * * *
    (b) * * *
    (6) [Reserved]
* * * * *
    (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.
    (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.
    (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. 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.
    (1) TF, POM and PM emissions from potlines. For each potline, the 
owner or operator shall measure and record the emission rates of TF, 
POM and PM exiting the outlet of the primary control system for each 
potline 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)(1) of this section, the 
owner or operator shall compute and record the average of at least 
three runs semiannually 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 TF is equal to or less than the applicable emission 
limit in Sec.  63.843, Sec.  63.844, or Sec.  63.846.
    (2) [Reserved]
* * * * *
    (4) TF, POM and PM emissions from anode bake furnaces. For each 
anode bake furnace, the owner or operator shall measure and record the 
emission rate of TF, POM and PM exiting the exhaust stacks(s) of the 
primary emission control system for each anode bake furnace. In 
accordance with paragraphs (e)(3), (4) and (8) of this section, the 
owner or operator shall compute and record the average of at least 
three runs each year to determine compliance with the applicable 
emission limits for TF, POM and PM. Compliance is demonstrated when the 
emission rates of TF, POM and PM are equal to or less than the 
applicable TF, POM and PM emission limits in Sec.  63.843, Sec.  
63.844, or Sec.  63.846.
    (5) Nickel Emissions from VSS2 Potlines and new Soderberg potlines. 
(i) For each VSS2 potline, and for each new Soderberg potline, the 
owner or operator must measure and record the emission rate of nickel 
exiting the primary emission control system and the rate of secondary 
emissions of nickel exiting through each roof monitor, or for a plant 
with roof scrubbers, exiting through the scrubbers. Using the procedure 
in paragraph (e)(10) of this section, the owner or operator must 
compute and record the average of at least three runs each year for 
secondary emissions and at least three runs each year for primary 
emissions.
    (ii) Compliance is demonstrated when the emissions of nickel are 
equal to or less than the applicable emission limit in Sec.  
63.843(a)(4) or Sec.  63.844(a)(4).
    (6) Arsenic Emissions from VSS2 Potlines and from new Soderberg 
potlines. (i) For each VSS2 potline, and for each new Soderberg 
potline, the owner or operator must measure and record the emission 
rate of arsenic exiting the primary emission control system and the 
rate of secondary emissions of arsenic exiting through each roof 
monitor, or for a plant with roof scrubbers, exiting through the 
scrubbers. Using the procedure in paragraph (e)(11) of this section, 
the owner or operator must compute and record the average of at least 
three runs each year for secondary emissions and at least three runs 
each year for primary emissions.
    (ii) Compliance is demonstrated when the emissions of arsenic are 
equal to or less than the applicable emission limit in Sec.  
63.843(a)(5) or Sec.  63.844(a)(5).
    (e) * * *
    (1) Compute the emission rate (Ep) of TF, POM or PM from 
each potline using Equation 1:
[GRAPHIC] [TIFF OMITTED] TP08DE14.031



[[Page 72958]]


Where:

Ep = emission rate of TF, POM or PM from a potline, kg/Mg 
(lb/ton);
Cs1 = concentration of TF, POM or PM from the primary 
control system, mg/dscm (mg/dscf);
Qsd = volumetric flow rate of effluent gas corresponding 
to the appropriate subscript location, dscm/hr (dscf/hr);
Cs2 = concentration of TF, POM or PM as measured for roof 
monitor emissions, mg/dscm (mg/dscf);
P = aluminum production rate, Mg/hr (ton/hr);
K = conversion factor, 10\6\ mg/kg (453,600 mg/lb);
1 = subscript for primary control system effluent gas; 
and
2 = subscript for secondary control system or roof 
monitor effluent gas.

* * * * *
    (4) Compute the emission rate of POM from each anode bake furnace 
using Equation 2,

Where:

Eb = emission rate of POM, kg/mg (lb/ton) of green anodes 
produced; and
Cs = concentration of POM, mg/dscm (mg/dscf).
* * * * *
    (8) Compute the emission rate of PM from each anode bake furnace 
using Equation 2,

Where:

Eb = emission rate of PM, kg/mg (lb/ton) of green anodes 
produced; and
Cs = concentration of PM, mg/dscm (mg/dscf).

    (9) Compute the emission rate (EPMpp) of PM from each 
paste production plant using Equation 3,
[GRAPHIC] [TIFF OMITTED] TP08DE14.032

Where:
EPMpp = emission rate of PM, kg/mg (lb/ton) of green 
anodes produced;
Cs = concentration of PM, mg/dscm (mg/dscf);
Qsd = volumetric flow rate of effluent gas, dscm/hr 
(dscf/hr);
Pb = quantity of green anode material placed in the anode 
bake furnace, mg/hr (ton/hr); and
K = conversion factor, 10\6\ mg/kg (453,600 mg/lb).

    (f) Paste production plants. (1) Initial compliance with the POM 
standards for existing and new paste production plants in Sec. Sec.  
63.843(b) and 63.844(b) will be demonstrated through site inspection(s) 
and review of site records by the applicable regulatory authority.
    (2) For each paste production plant, the owner or operator shall 
measure and record the emission rate of PM exiting the exhaust 
stacks(s) of the primary emission control system. Using the equations 
in paragraph (e)(9) of this section, the owner or operator shall 
compute and record the average of at least three runs each year to 
determine compliance with the applicable emission limits for PM. 
Compliance with the PM standards for existing and new paste production 
plants is demonstrated when the PM emission rates are less than or 
equal to the applicable PM emission limits in Sec. Sec.  63.843(b)(4) 
and 63.844(b)(2).
    (g) Pitch storage tanks. The owner or operator must demonstrate 
initial compliance with the standard for pitch storage tanks in 
Sec. Sec.  63.843(d) and 63.844(d) by preparing a design evaluation or 
by conducting a performance test. The owner or operator must submit for 
approval by the regulatory authority the information specified in 
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.
* * * * *
    (2) * * *
    (ii) If an enclosed combustion device with a minimum residence time 
of 0.5 seconds and a minimum temperature of 760 degrees C (1,400 
degrees F) is used to meet the emission reduction requirement specified 
in Sec.  83.843(d) and Sec.  83.844(d), documentation that those 
conditions exist is sufficient to meet the requirements of Sec.  
83.843(d) and Sec.  83.844(d);
* * * * *
    (iv) If the pitch storage tank is vented to the emission control 
system installed for control of emissions from the paste production 
plant pursuant to Sec.  63.843(b) or Sec.  63.844(b)(1), documentation 
of compliance with the requirements of Sec.  63.843(b) is sufficient to 
meet the requirements of Sec.  63.843(b) or Sec.  63.844(d);
* * * * *
    (i) [Reserved]
    (j) COS emissions. The owner operator of each plant must calculate, 
for each potline, the emission rate of COS for each calendar month of 
operation using Equation 5:
[GRAPHIC] [TIFF OMITTED] TP08DE14.033


Where:
ECOS = the 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 consumed in the potline during the calendar 
month;
Z = the tons of aluminum produced by the potline during the calendar 
month; and
S = the weighted average fraction of sulfur in the anode coke 
consumed in the production of aluminum during the calendar month 
(e.g., if the weighted average sulfur content of the anode coke 
consumed during the calendar month was 2.5 percent, then S = 0.025). 
The weight of anode coke used during the month of each different 
concentration of sulfur is used to calculate the overall weighted 
average fraction of sulfur.

    Compliance is demonstrated if the calculated value of 
ECOS is less than the applicable standard for COS emissions 
in Sec. Sec.  63.843(e) and 63.844(e).
    (k) Startup of potlines. The owner or operator must develop a 
written startup plan as described in Sec.  63.854 that contains 
specific procedures to be followed during startup periods of 
potline(s). Compliance with the applicable standards in Sec.  63.854 
will be demonstrated through site inspection(s) and review of site 
records by the regulatory authority.
    (l) Startup of anode bake furnaces. If you own or operate a new or 
existing anode bake furnace, you must develop a written startup plan as 
described in paragraphs (l)(1) through (4) of this

[[Page 72959]]

section. Compliance with the startup plan will be demonstrated through 
site inspection(s) and review of site records by the 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.
    (2) Records of time, date, duration of anode bake furnace startup 
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 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. The anode bake furnace restart may resume once the 
associated emission control system is back on line and operating within 
normal parametric limits.
    (m) Startup of paste production plants. If you own or operate a new 
or existing paste production plant, you must develop a written startup 
plan as described in paragraphs (m)(1) through (3) of this section. 
Compliance with the startup plan will be demonstrated through site 
inspection(s) and review of site records by the regulatory authority. 
The written startup plan must contain specific procedures to be 
followed during startup periods of paste production plants, including 
the following:
    (1) Records of time, date, duration of paste production plant 
startup and any nonroutine actions taken during startup of the paste 
production plants.
    (2) A requirement that the associated emission control system 
should be operating within normal parametric limits prior to startup of 
the paste production plant.
    (3) A requirement to shut down the paste production plant 
immediately if the associated emission control system is off line at 
any time during startup. The paste production plant restart may resume 
once the associated emission control system is back on line and 
operating within normal parametric limits.
0
9. Section 63.848 is amended by:
0
a. Revising paragraphs (a) and (b);
0
b. Removing and reserving paragraph (e);
0
c. Adding paragraphs (f)(6) and (7); and
0
d. Adding paragraphs (n), (o) and (p).
    The revisions and additions read as follows:


Sec.  63.848  Emission monitoring requirements.

    (a) TF and PM emissions from potlines. Using the procedures in 
Sec.  63.847 and in the approved test plan, the owner or operator shall 
monitor emissions of TF and PM from each potline by conducting annual 
performance tests on the primary control system and semiannual 
performance tests on the secondary emissions. The owner or operator 
shall compute and record the average from at least three runs for 
secondary emissions and the average from at least three runs for the 
primary control system to determine compliance with the applicable 
emission limit. The owner or operator must include all valid runs in 
the semiannual average. The duration of each run for secondary 
emissions must represent a complete operating cycle. Potline emissions 
shall be recorded as the sum of the average of at least three runs from 
the primary control system and the average of at least three runs from 
the roof monitor or secondary control device.
    (b) POM emissions from potlines. Using the procedures in Sec.  
63.847 and in the approved test plan, the owner or operator must 
monitor emissions of POM from each potline stack annually and secondary 
potline POM emissions semiannually. The owner or operator must compute 
and record the semiannual average from at least three runs per year for 
secondary emissions and at least three runs per year for the primary 
control systems to determine compliance with the applicable emission 
limit. The owner or operator must include all valid runs in the 
semiannual 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. Potline emissions shall be recorded as the sum of 
the average of at least three runs from the primary control system and 
the average of at least three runs from the roof monitor or secondary 
control device.
* * * * *
    (e) [Reserved]
    (f) * * *
    (6) For emission sources with fabric filters that choose to 
demonstrate continuous compliance through bag leak detection systems 
you must install a bag leak detection system according to the 
requirements in paragraph (o) of this section, and you must set your 
operating limit such that the sum of the durations of bag leak 
detection system alarms does not exceed 5 percent of the process 
operating time during a 6-month period.
    (7) If you choose to demonstrate continuous compliance through a 
particulate matter CEMS, you must determine continuous compliance 
averaged on a rolling 30 operating day basis. All valid hours of data 
from 30 successive operating days shall be included in the average.
* * * * *
    (n) PM emissions from anode bake furnaces and paste production 
plants. Using the procedures in Sec.  63.847 and in the approved test 
plan, the owner or operator shall monitor PM emissions from each anode 
bake furnace and paste production plant on an annual basis. The owner 
or operator shall compute and record the annual average of PM emissions 
from at least three runs to determine compliance with the applicable 
emission limits. The owner or operator must include all valid runs in 
the annual average.
    (o) Bag leak detection system. For each baghouse used to control PM 
emissions, you must install, operate and maintain a bag leak detection 
system according to paragraphs (o)(1) through (3) of this section, 
unless a system meeting the requirements of paragraph (p) of this 
section, for a CEMS and continuous emissions rate monitoring system, is 
installed for monitoring the concentration of particulate matter.
    (1) You must develop and implement written procedures for baghouse 
maintenance that include, at a minimum, a preventative maintenance 
schedule that is consistent with the baghouse manufacturer's 
instructions for routine and long-term maintenance.
    (2) Each bag leak detection system must meet the specifications and 
requirements in paragraphs (o)(2)(i) through (viii) of this section.
    (i) The bag leak detection system must be certified by the 
manufacturer to be capable of detecting PM emissions at concentrations 
of 1.0 milligram per dry standard cubic meter (0.00044 grains per 
actual cubic foot) or less.
    (ii) The bag leak detection system sensor must provide output of 
relative PM loadings.
    (iii) The bag leak detection system must be equipped with an alarm 
system that will alarm when an increase in relative particulate 
loadings is detected over a preset level.
    (iv) You must install, calibrate, operate and maintain the bag leak 
detection system according to the manufacturer's written specifications 
and recommendations.
    (v) The initial adjustment of the system must, at a minimum, 
consist of

[[Page 72960]]

establishing the baseline output by adjusting the sensitivity (range) 
and the averaging period of the device and establishing the alarm set 
points and the alarm delay time.
    (vi) Following initial adjustment, you must not adjust the 
sensitivity or range, averaging period, alarm set points, or alarm 
delay time, except in accordance with the procedures developed under 
paragraph (o)(1) of this section. You cannot increase the sensitivity 
by more than 100 percent or decrease the sensitivity by more than 50 
percent over a 365-day period unless such adjustment follows a complete 
baghouse inspection that demonstrates that the baghouse is in good 
operating condition.
    (vii) You must install the bag leak detector downstream of the 
baghouse.
    (viii) Where multiple detectors are required, the system's 
instrumentation and alarm may be shared among detectors.
    (3) You must include in the written procedures required by 
paragraph (o)(1) of this section a corrective action plan that 
specifies the procedures to be followed in the case of a bag leak 
detection system alarm. The corrective action plan must include, at a 
minimum, the procedures that you will use to determine and record the 
time and cause of the alarm as well as the corrective actions taken to 
minimize emissions as specified in paragraphs (o)(3)(i) and (ii) of 
this section.
    (i) The procedures used to determine the cause of the alarm must be 
initiated within 30 minutes of the alarm.
    (ii) The cause of the alarm must be alleviated by taking the 
necessary corrective action(s) that may include, but not be limited to, 
those listed in paragraphs (o)(3)(ii)(A) through (F) of this section.
    (A) Inspecting the baghouse for air leaks, torn or broken filter 
elements, or any other malfunction that may cause an increase in 
emissions.
    (B) Sealing off defective bags or filter media.
    (C) Replacing defective bags or filter media, or otherwise 
repairing the control device.
    (D) Sealing off a defective baghouse compartment.
    (E) Cleaning the bag leak detection system probe, or otherwise 
repairing the bag leak detection system.
    (F) Shutting down the process producing the particulate emissions.
    (p) Particulate Matter CEMS. If you are using a CEMS to measure 
particulate matter emissions to meet requirements of this subpart, you 
must install, certify, operate and maintain the particulate matter CEMS 
as specified in paragraphs (p)(1) through (4) of this section.
    (1) You must conduct a performance evaluation of the PM CEMS 
according to the applicable requirements of Sec.  60.13, and 
Performance Specification 11 at 40 CFR part 60, Appendix B of this 
chapter.
    (2) During each PM correlation testing run of the CEMS required by 
Performance Specification 11 at 40 CFR part 60, Appendix B of this 
chapter, collect data concurrently (or within a 30- to 60-minute 
period) by both the CEMS and by conducting performance tests using 
Method 5, 5D or 5I at 40 CFR part 60, Appendix A-3 or Method 17 at 40 
CFR part 60, Appendix A-6 of this chapter.
    (3) Perform quarterly accuracy determinations and daily calibration 
drift tests in accordance with Procedure 2 at 40 CFR part 60, Appendix 
F of this chapter. Relative Response Audits must be performed annually 
and Response Correlation Audits must be performed every three years.
    (4) Within 60 days after the date of completing each CEMS response 
audit or performance test conducted to demonstrate compliance with this 
subpart, you must submit the response audit data as specified in Sec.  
63.850(c) and the results of the performance test as specified in Sec.  
63.850(b).
0
10. Section 63.849 is amended by:
0
a. Revising paragraphs (a)(6) and (7);
0
b. Adding paragraphs (a)(8) through (11); and
0
c. Adding paragraph (f).
    The revisions and additions read as follows:


Sec.  63.849  Test methods and procedures.

    (a) * * *
    (6) Method 315 in appendix A to this part or an approved 
alternative method for the concentration of POM where stack or duct 
emissions are sampled;
    (7) Method 315 in appendix A to this part and Method 14A in 
appendix A to part 60 of this chapter or an approved alternative method 
for the concentration of POM where emissions are sampled from roof 
monitors not employing wet roof scrubbers. Method 315 need not be set 
up as required in the method. Instead, replace the Method 14A monitor 
cassette filter with the filter specified by Method 315. Recover and 
analyze the filter according to Method 315;
    (8) Method 5 in appendix A to part 60 of this chapter or an 
approved alternative method for the concentration of PM where stack or 
duct emissions are sampled;
    (9) Method 17 and Method 14A in appendix A to part 60 of this 
chapter or an approved alternative method for the concentration of PM 
where emissions are sampled from roof monitors not employing wet roof 
scrubbers. Method 17 need not be set up as required in the method. 
Instead, replace the Method 14A monitor cassette filter with the filter 
specified by Method 17. Recover and analyze the filter according to 
Method 17;
    (10) Method 29 in appendix A to part 60 of this chapter or an 
approved alternative method for the concentration of nickel and arsenic 
where stack or duct emissions are sampled; and
    (11) Method 29 and Method 14A in appendix A to part 60 of this 
chapter or an approved alternative method for the concentration of 
nickel and arsenic where emissions are sampled from roof monitors not 
employing wet roof scrubbers. Method 29 need not be set up as required 
in the method. Instead, replace the Method 14A monitor cassette filter 
with the filter specified by Method 29. Recover and analyze the filter 
according to Method 29.
* * * * *
    (f) The owner or operator must use either ASTM D4239-13e1 or ASTM 
D6376-10 for determination of the sulfur content in anode coke 
shipments to determine compliance with the applicable emission limit 
for COS emissions.
0
11. Section 63.850 is amended by:
0
a. Revising paragraphs (b), (c) and (d);
0
b. Removing and reserving paragraph (e)(4)(iii);
0
c. Revising paragraphs (e)(4)(xiv) and (xv);
0
d. Adding paragraphs (e)(4)(xvi) and (xvii); and
0
e. Adding paragraph (f).
    The revisions and additions read as follows:


Sec.  63.850  Notification, reporting and recordkeeping requirements.

* * * * *
    (b) Performance test reports. Within 60 days after the date of 
completing each performance test required by this subpart, the owner or 
operator shall submit the results of the performance test following the 
procedure specified in either paragraph (b)(1) or (b)(2) of this 
section.
    (1) For data collected using test methods supported by the EPA's 
Electronic Reporting Tool (ERT) as listed on the EPA's ERT Web site 
(http://www.epa.gov/ttn/chief/ert/index.html) at the time of the test, 
the owner or operator shall submit the results of the performance test 
to the EPA via the Compliance and Emissions Data Reporting Interface 
(CEDRI). (CEDRI can be accessed through the EPA's Central Data Exchange 
(CDX) (http://cdx.epa.gov/epa_home.asp).)

[[Page 72961]]

Performance test data shall be submitted in a file format generated 
through the use of the EPA's ERT. Instead of submitting performance 
test data in a file format generated through the use of the EPA's ERT, 
you may submit an alternate electronic file format consistent with the 
extensible markup language (XML) schema listed on the EPA's ERT Web 
site, once the XML schema is available. Owners or operators who claim 
that some of the performance test information being submitted is 
confidential business information (CBI) shall submit a complete file 
generated through the use of the EPA's ERT (or an alternate electronic 
file consistent with the XML schema listed on the EPA's ERT Web site 
once the XML schema is available), including information claimed to be 
CBI, on a compact disc, flash drive, or other commonly used electronic 
storage media to the EPA. The electronic media shall be clearly marked 
as CBI and mailed to U.S. EPA/OAQPS/CORE CBI Office, Attention: Group 
Leader, Measurement Policy Group, MD C404-02, 4930 Old Page Road, 
Durham, NC 27703. The same ERT or alternate file with the CBI omitted 
shall be submitted to the EPA via the EPA's CDX as described earlier in 
this paragraph.
    (2) For data collected using test methods that are not supported by 
the EPA's ERT as listed on the EPA's ERT Web site at the time of the 
test, the owner or operator shall submit the results of the performance 
test to the Administrator at the appropriate address listed in Sec.  
63.13.
    (c) Performance evaluation reports. Within 60 days after the date 
of completing each CEMS performance evaluation, submit the results of 
the performance evaluation following the procedure specified in either 
paragraph (c)(1) or (2) of this section.
    (1) For performance evaluations of continuous monitoring systems 
measuring pollutants that are supported by the EPA's ERT as listed on 
the EPA's ERT Web site, you must submit the results of the performance 
evaluation to the EPA via the CEDRI. (CEDRI can be accessed through the 
EPA's CDX.) Performance evaluation data must be submitted in a file 
format generated through the use of the EPA's ERT. Instead of 
submitting performance test data in a file format generated through the 
use of the EPA's ERT, you may submit an alternate electronic file 
format consistent with the XML schema listed on the EPA's ERT Web site, 
once the XML schema is available. If you claim that some of the 
performance evaluation information being submitted is CBI, you must 
submit a complete file generated through the use of the EPA's ERT (or 
an alternate electronic file consistent with the XML schema listed on 
the EPA's ERT Web site once the XML schema is available), including 
information claimed to be CBI, on a compact disc, flash drive or other 
commonly used electronic storage media to the EPA. The electronic media 
must be clearly marked as CBI and mailed to U.S. EPA/OAQPS/CORE CBI 
Office, Attention: Group Leader, Measurement Policy Group, MD C404-02, 
4930 Old Page Road, Durham, NC 27703. The same ERT or alternate file 
with the CBI omitted must be submitted to the EPA via the EPA's CDX as 
described earlier in this paragraph.
    (2) For any performance evaluations of continuous monitoring 
systems measuring pollutants that are not supported by the EPA's ERT as 
listed on the EPA's ERT Web site, submit the results of the performance 
evaluation to the Administrator at the appropriate address listed in 
Sec.  63.13.
    (d) Reporting. In addition to the information required under Sec.  
63.10 of the General Provisions, the owner or operator must provide 
semiannual reports containing the information specified in paragraphs 
(d)(1) and (2) of this section to the Administrator or designated 
authority.
    (1) Excess emissions report. As required by Sec.  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 Sec.  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 Sec. Sec.  63.843(f) and 63.844(f), 
including actions taken to correct a malfunction.
    (e) * * *
    (4) * * *
    (iii) [Reserved]
* * * * *
    (xiv) Records documenting any POM data that are invalidated due to 
the installation and startup of a cathode;
    (xv) Records documenting the portion of TF that is measured as 
particulate matter and the portion that is measured as gaseous when the 
particulate and gaseous fractions are quantified separately using an 
approved test method;
    (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; and
    (xvii) Records of actions taken during periods of malfunction to 
minimize emissions in accordance with Sec. Sec.  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 Sec.  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.
0
12. Section 63.854 is added to read as follows:


Sec.  63.854  Work Practice Standards for Potlines.

    (a) Periods of operation other than startup. 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 (4) of this 
section during periods of operation other than startup.
    (1) Ensure the potline scrubbers and exhaust fans are operational 
at all times.
    (2) Ensure that the primary capture and control system is operating 
at all times.
    (3) Keep pots covered 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.
    (4) Inspect potlines daily and perform the work practices specified 
in paragraphs (a)(4)(i) through (iii) 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, and follow 
the written operating plan described in paragraph (b)(4) of this 
section if the cell temperature exceeds the specified high temperature 
limit; and
    (iii) Reseal pot crusts that have been broken as often and as soon 
as practicable.

[[Page 72962]]

    (b) Periods of startup. 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 (4) and (b)(1) through (4) of 
this section during periods of startup for each affected potline.
    (1) Develop a potline startup schedule before starting up the 
potline.
    (2) Keep records of the number of pots started each day.
    (3) Inspect potlines daily and adjust pot parameters to their 
optimum levels, as specified in the operating plan described in 
paragraph (b)(4) of this section, including, but not limited to: 
Alumina addition rate, exhaust air flow rate, cell voltage, feeding 
level, anode current and liquid and solid bath levels.
    (4) Prepare a written operating plan to minimize emissions during 
startup to include, but not limited to, the requirements in (b)(1) 
through (3) of this section. The operating plan must include a 
specified high temperature limit for pots that will trigger corrective 
action.
0
13. Section 63.855 is added to read as follows:


Sec.  63.855  Alternative Emissions Limits for Co-controlled New and 
Existing Anode Bake Furnaces.

    (a) Applicability. The owner or operator of a new anode bake 
furnace meeting the criteria of paragraphs (a)(1) and (2) of this 
section may demonstrate compliance with alternative TF and POM emission 
limits according to the procedures of this section.
    (1) The new anode bake furnace must have been permitted to operate 
prior to May 1, 1998; and
    (2) The new anode bake furnace must share a common control device 
with one or more existing anode bake furnaces.
    (b) TF emission limit. (1) Prior to the date on which each TF 
emission test is required to be conducted, the owner or operator must 
determine the applicable TF emission limit using Equation 6-A,
[GRAPHIC] [TIFF OMITTED] TP08DE14.034


Where:
LTFC = Combined emission limit for TF, lb/ton green anode 
material placed in the bake furnace;
LTFE = TF limit for emission averaging for the total 
number of new and existing anode bake furnaces from Table 4 to this 
subpart;
PE = Mass of green anode placed in existing anode bake 
furnaces in the twelve months preceding the compliance test, ton/
year; and
PN = Mass of green anode placed in new anode bake 
furnaces in the twelve months preceding the compliance test, ton/
year.

    (2) The owner or operator of a new anode bake furnace that is 
controlled by a control device that also controls emissions of TF from 
one or more existing anode bake furnaces must not discharge, or cause 
to be discharged into the atmosphere, any emissions of TF in excess of 
the emission limits established in paragraph (b)(1) of this section.
    (c) POM emission limits. (1) Prior to the date on which each POM 
emission test is required to be conducted, the owner or operator must 
determine the applicable POM emission limit using Equation 6-B,
[GRAPHIC] [TIFF OMITTED] TP08DE14.035


Where:
LPOMC = Combined emission limit for POM, lb/ton green 
anode material placed in the bake furnace.

    (2) The owner or operator of a new anode bake furnace that is 
controlled by a control device that also controls emissions of POM from 
one or more existing anode bake furnaces must not discharge, or cause 
to be discharged into the atmosphere, any emissions of TF in excess of 
the emission limits established in paragraph (c)(1) of this section.
0
14. Table 1 to Subpart LL of Part 63--Potline TF Limits for Emission 
Averaging is revised to read as follows:

                                       Table 1 to Subpart LL of Part 63--Potline TF Limits for Emission Averaging
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Monthly TF limit (lb/ton) [for given number of potlines]
                  Type                   ---------------------------------------------------------------------------------------------------------------
                                              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
SWPB....................................             1.4             1.3             1.3             1.2             1.2             1.2             1.2
VSS2....................................             2.6             2.5             2.5             2.4             2.4             2.4             2.4
--------------------------------------------------------------------------------------------------------------------------------------------------------

0
15. Table 2 to Subpart LL of Part 63--Potline POM Limits for Emission 
Averaging is revised to read as follows:

                                       Table 2 to Subpart LL of Part 63--Potline POM Limits for Emission Averaging
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Quarterly POM limit (lb/ton) [for given number of potlines]
                  Type                   ---------------------------------------------------------------------------------------------------------------
                                              2 lines         3 lines         4 lines         5 lines         6 lines         7 lines         8 lines
--------------------------------------------------------------------------------------------------------------------------------------------------------
CWPB1...................................               1             0.9             0.9             0.9             0.8             0.8             0.8
CWPB2...................................            11.6            11.2            10.8            10.8            10.4            10.4            10.4
CWPB3...................................             2.5             2.4             2.4             2.3             2.3             2.3             2.3

[[Page 72963]]

 
SWPB....................................            16.6            15.4            15.4            14.3            14.3            14.3            14.3
VSS2....................................             3.3             3.1             3.0             2.9             2.9             2.8             2.7
--------------------------------------------------------------------------------------------------------------------------------------------------------

0
16. Table 3 to subpart LL is redesignated as Table 4 to Subpart LL of 
Part 63--Anode Bake Furnace Limits for Emission Averaging and revised 
to read as follows:

               Table 4 to Subpart LL of Part 63--Anode Bake Furnace Limits for Emission Averaging
----------------------------------------------------------------------------------------------------------------
                                                                         Emission limit (lb/ton of anode)
                       Number of furnaces                        -----------------------------------------------
                                                                        TF              POM             PM
----------------------------------------------------------------------------------------------------------------
2...............................................................           0.11             0.17           0.037
3...............................................................           0.09             0.17           0.031
4...............................................................           0.077            0.17           0.026
5...............................................................           0.07             0.17           0.024
----------------------------------------------------------------------------------------------------------------

0
17. New Table 3 to Subpart LL of Part 63--Potline PM Limits for 
Emission Averaging is added to read as follows:

                                       Table 3 to Subpart LL of Part 63--Potline PM Limits for Emission Averaging
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                     Monthly PM limit (lb/ton) [for given number of potlines]
                  Type                  ----------------------------------------------------------------------------------------------------------------
                                             2 lines          3 lines         4 lines         5 lines         6 lines         7 lines         8 lines
--------------------------------------------------------------------------------------------------------------------------------------------------------
CWPB1..................................              5.9             5.6             5.2             5.2             4.9             4.9             4.9
CWPB2..................................             10.6            10.3             9.9             9.9             9.5             9.5             9.5
CWPB3..................................             18.4            17.6            17.6            16.8            16.8            16.8            16.8
SWPB...................................              4               3.7             3.7             3.5             3.5             3.5             3.5
VSS2...................................             25              24.1            24.1            23.1            23.1            23.1            23.1
--------------------------------------------------------------------------------------------------------------------------------------------------------

0
18. Appendix A to Subpart LL of Part 63--Applicability of General 
Provisions is revised to read as follows:

                    Appendix A to Subpart LL of Part 63--Applicability of General Provisions
                                           [40 CFR Part 63, Subpart A]
----------------------------------------------------------------------------------------------------------------
    Reference  section(s) . . .             Requirement         Applies to subpart LL           Comment
----------------------------------------------------------------------------------------------------------------
63.1(a)(1) through (4)............  General Applicability.....  Yes..................
63.5(a)(5)........................  ..........................  Yes..................
63.1(a)(6)........................  ..........................  Yes..................
63.1(a)(7) through (9)............  ..........................  No...................  [Reserved].
63.1(a)(10) through (12)..........  ..........................  Yes.
63.1(b)(1) through (3)............  Initial Applicability       Yes..................  (b)(2) Reserved.
                                     Determination.
63.1(c)(1)........................  Applicability after         Yes..................
                                     standard Established.
63.1(c)(2)........................  ..........................  Yes..................
63.1(c)(3) and (4)................  ..........................  No...................  [Reserved].
63.1(c)(5)........................  ..........................  Yes..................
63.1(d)...........................  ..........................  Yes..................  [Reserved].
63.1(e)...........................  Applicability of Permit     Yes.
                                     Program.
63.2..............................  Definitions...............  Yes.
63.3..............................  Units and Abbreviations...  Yes..................
63.4(a)(1) and (2)................  Prohibited activities.....  Yes.
63.4(a)(3) through (5)............  ..........................  No...................  [Reserved].
63.4(b) and (c)...................  Circumvention/Severability  Yes.
63.5(a)(5)........................  Construction/               Yes.
                                     Reconstruction
                                     Applicability.

[[Page 72964]]

 
63.5(b)(1)........................  Existing, New,              Yes.
                                     Reconstructed Sources
                                     Requirements.
63.5(b)(2)........................  ..........................  No...................  [Reserved].
63.5(b)(3) and (4)................  ..........................  Yes.
63.5(b)(5)........................  ..........................  No...................  [Reserved].
63.5(b)(6)........................  ..........................  Yes.
63.5(c)...........................  ..........................  No...................  [Reserved].
63.5(d)...........................  Application for Approval    Yes.
                                     of Construction/
                                     Reconstruction.
63.5(e)...........................  Approval of Construction/   Yes.
                                     Reconstruction.
63.5(f)...........................  Approval of Construction/   Yes..................
                                     Reconstruction Based on
                                     State Review.
63.6(a)...........................  Compliance with Standards   Yes..................
                                     and Maintenance
                                     Applicability.
63.6(b)(1) through (5)............  New and Reconstructed       Yes.
                                     Source Dates.
63.6(b)(6) and (7)................  ..........................  No...................  [Reserved].
63.6(c)(1)........................  Existing Source Dates.....  Yes.
63.6(c)(2)........................  ..........................  Yes.
63.6(c)(3) and (4)................  ..........................  No...................  [Reserved].
63.6(c)(5)........................  ..........................  Yes.
63.6(d)...........................  ..........................  No...................  [Reserved].
63.6(e)(1)(i).....................  ..........................  No...................  See Sec.  Sec.
                                                                                        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...................  [Reserved].
63.6(e)(3)........................  Startup, Shutdown and       No.
                                     Malfunction Plan.
63.6(f)(1)........................  Compliance with Emissions   No.
                                     Standards.
63.6(f)(1) and (2)................  Methods/Finding of          Yes.
                                     Compliance.
63.6(g)...........................  Alternative Standard......  Yes.
63.6(h)...........................  Compliance with Opacity/VE  Only in Sec.   63.845  Opacity standards
                                     Standards.                                         applicable only when
                                                                                        incorporating the NSPS
                                                                                        requirements under Sec.
                                                                                         63.845
63.6(i)(1) through (14)...........  Extension of Compliance...  Yes.
63.6(i)(15).......................  ..........................  No.                    [Reserved].
63.6(i)(16).......................  ..........................  Yes.
63.6(j)...........................  Exemption from Compliance.  Yes.
63.7(a)...........................  Performance Test            Yes.
                                     Requirements
                                     Applicability.
63.7(b)...........................  Notification..............  Yes.
63.7(c)...........................  Quality Assurance/Test      Yes.
                                     Plan.
63.7(d)...........................  Testing facilities........  Yes.
63.7(e)(1)........................  Conduct of Tests..........  No...................  See Sec.   63.847(d)
63.7(e)(2) through (4)............  ..........................  Yes.
63.7(f),(g), (h)..................  Alternative Test Method...  Yes.
63.8(a)...........................  Monitoring Requirements     Yes.
                                     Applicability.
63.8(b)...........................  Conduct of Monitoring.....  Yes.
63.8(c)(1)(i).....................  ..........................  No...................  See Sec.  Sec.
                                                                                        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)      ..........................  Yes.
 through (3), (h)(5) and (6), (i)
 and (j).
63.9(a)...........................  Notification Requirements   Yes.
                                     Applicability.
63.9(b)...........................  Initial Notifications.....  Yes.
63.9(c)...........................  Request for Compliance      Yes.
                                     Extension.
63.9(d)...........................  New Source Notification     Yes.
                                     for Special Compliance
                                     Requirements.
63.9(e)...........................  Notification of             Yes.
                                     Performance Test.
63.9(f)...........................  Notification of VE/Opacity  Yes.
                                     Test.
63.9(g)...........................  Additional CMS              Yes.
                                     Notifications.
63.9(h)(1) through (3)............  Notification of Compliance  Yes.
                                     Status.
63.9(h)(4)........................  ..........................  No...................  [Reserved].
63.9(h)(5) and (6)................  ..........................  Yes.
63.9(i)...........................  Adjustment of Deadlines...  Yes.

[[Page 72965]]

 
63.9(j)...........................  Change in Previous          Yes.
                                     Information.
63.10(a)..........................  Recordkeeping/Reporting     Yes.
                                     Applicability.
63.10(b)(1).......................  General Recordkeeping       Yes.
                                     Requirements.
63.10(b)(2)(i)....................                              No.
63.10(b)(2)(ii)...................  ..........................  No...................  See Sec.  Sec.
                                                                                        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 (v)...........  ..........................  No.
63.10(b)(2)(vi) through (xiv).....  ..........................  Yes.
63.(10)(b)(3).....................  ..........................  Yes.
63.10(c)(1) through (9)...........  ..........................  Yes.
63.10(c)(10) and (11).............  ..........................  No...................  See Sec.  Sec.
                                                                                        63.850(e)(4)(xvi) and
                                                                                        (xvii)for recordkeeping
                                                                                        of malfunctions.
63.10(c)(12) through (14).........  ..........................  Yes..................
63.10(c)(15)......................  ..........................  No...................
63.10(d)(1) through (4)...........  General Reporting           Yes..................
                                     Requirements.
63.10(d)(5).......................  Startup-Shutdown and        No...................  See Sec.   63.850(d)(2)
                                     Malfunction Reports.                               for reporting of
                                                                                        malfunctions.
63.10(e) and (f)..................  Additional CMS Reports and  Yes..................
                                     Recordkeeping/Reporting
                                     Waiver.
63.11.............................  Control Device/work         No...................
                                     practices requirements
                                     Applicability.
63.12.............................  State Authority and         Yes..................
                                     Delegations.
63.13.............................  Addresses.................  Yes..................
63.14.............................  Incorporation by Reference  Yes..................
63.15.............................  Information Availability/   Yes..................
                                     Confidentiality.
63.16.............................  Performance Track           No...................
                                     Provisions.
----------------------------------------------------------------------------------------------------------------

[FR Doc. 2014-27499 Filed 12-5-14; 8:45 am]
BILLING CODE 6560-50-P