Document ID: EPA-HQ-OAR-2011-0797-0001
Agency: epa
Document Type: Proposed Rule
Title: National Emissions Standards for Hazardous Air Pollutants: Primary Aluminum Reduction Plants
Posted Date: 2011-12-06T05:00Z

[Federal Register Volume 76, Number 234 (Tuesday, December 6, 2011)]
[Proposed Rules]
[Pages 76260-76291]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-29881]

[[Page 76259]]

Vol. 76

Tuesday,

No. 234

December 6, 2011

Part III

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. 76 , No. 234 / Tuesday, December 6, 2011 / 
Proposed Rules  

[[Page 76260]]

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ENVIRONMENTAL PROTECTION

40 CFR Part 63

[EPA-HQ-OAR-2011-0797; FRL-9491-3]
RIN 2060-AQ92

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The EPA is proposing amendments to the national emissions 
standards for hazardous air pollutants for Primary Aluminum Reduction 
Plants to address the results of the residual risk and technology 
review that the EPA is required to conduct by the Clean Air Act. If 
finalized, these proposed amendments would address previously 
unregulated emissions (i.e., carbonyl sulfide (COS) emissions from new 
and existing potlines and polycyclic organic matter (POM) emissions 
from new and existing prebake potlines and existing pitch storage 
tanks); remove the vertical stud Soderberg one (VSS1) potline 
subcategory; reduce the MACT limits for POM emissions from horizontal 
stud Soderberg (HSS) and VSS2 potlines; eliminate the startup, shutdown 
and malfunction exemption in accordance with recent actions by the 
United States Court of Appeals for the District of Columbia Circuit; 
add provisions for facilities to avail themselves of an affirmative 
defense in the event of a malfunction under certain conditions; and 
make certain technical and editorial changes. The proposed emissions 
limits for POM and COS are based on maximum achievable control 
technology (MACT). While the proposed modifications would result in 
some reduction in actual emissions of POM from existing pitch storage 
tanks, reduce the potential emissions of POM from Soderberg potlines, 
and prevent increases in emissions of COS and sulfur dioxide, the 
health risks posed by actual emissions from this source category are 
currently within the acceptable range and would not be reduced 
appreciably by the proposed modifications.

DATES: Comments must be received on or before January 20, 2012. Under 
the Paperwork Reduction Act, comments on the information collection 
provisions are best assured of receiving full consideration if the 
Office of Management and Budget (OMB) receives a copy of your comments 
on or before January 5, 2012.
    Public Hearing. If anyone contacts the EPA requesting to speak at a 
public hearing by December 16, 2011, a public hearing will be held on 
December 21, 2011.

ADDRESSES: Submit your comments, identified by Docket ID Number EPA-HQ-
OAR-2011-0797, by one of the following methods:
     http://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     Email: a-and-r-docket@epa.gov, Attention Docket ID Number 
EPA-HQ-OAR-2011-0797.
     Fax: (202) 566-9744, Attention Docket ID Number EPA-HQ-
OAR-2011-0797.
     Mail: U.S. Postal Service, send comments to: EPA Docket 
Center, EPA West (Air Docket), Attention Docket ID Number EPA-HQ-OAR-
2011-0797, U.S. Environmental Protection Agency, Mail Code: 2822T, 1200 
Pennsylvania Ave. NW., Washington, DC 20460. Please include a total of 
two copies. In addition, please mail a copy of your comments on the 
information collection provisions to the Office of Information and 
Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk 
Officer for EPA, 725 17th Street, NW., Washington, DC 20503.
     Hand Delivery: U.S. Environmental Protection Agency, EPA 
West (Air Docket), Room 3334, 1301 Constitution Ave. NW., Washington, 
DC 20004, Attention Docket ID Number EPA-HQ-OAR-2011-0797. Such 
deliveries are only accepted during the Docket's normal hours of 
operation, and special arrangements should be made for deliveries of 
boxed information.
    Instructions. Direct your comments to Docket ID Number EPA-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 
on-line at http://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be confidential business information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov 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 avoid the use of special characters, any form of encryption, and 
be free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID Number EPA-HQ-OAR-2011-0797. All documents in the docket are 
listed in the http://www.regulations.gov index. Although listed in the 
index, some information is not publicly available, e.g., CBI or other 
information whose disclosure is restricted by statute. Certain other 
material, such as copyrighted material, is not placed on the Internet 
and will be publicly available only in hard copy. Publicly available 
docket materials are available either electronically in http://www.regulations.gov or in hard copy at the EPA Docket Center, EPA West, 
Room 3334, 1301 Constitution Ave. NW., Washington, DC. The Public 
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the EPA 
Docket Center is (202) 566-1742.
    Public Hearing. If a public hearing is held, it will begin at 10 
a.m. on December 21, 2011 and will be held at the EPA's campus in 
Research Triangle Park, North Carolina, or at an alternate facility 
nearby. Persons interested in presenting oral testimony or inquiring as 
to whether a public hearing is to be held should contact Ms. Virginia 
Hunt, Office of Air Quality Planning and Standards, Sector Policies and 
Programs Division, (D243-02), U.S. Environmental Protection Agency, 
Research Triangle Park, North Carolina 27711; telephone number: (919) 
541-0832.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Mr. David Putney, Sector Policies and Programs Division 
(D243-02), Office of Air Quality Planning and Standards, U.S. 
Environmental

[[Page 76261]]

Protection Agency, Research Triangle Park, North Carolina 27711, 
telephone (919) 541-2016; fax number: (919) 541-3207; and email 
address: putney.david@epa.gov. For specific information regarding the 
risk modeling methodology, contact Dr. Michael Stewart, Office of Air 
Quality Planning and Standards, Health and Environmental Impacts 
Division, Air Toxics Assessment Group (C504-06), U.S. Environmental 
Protection Agency, Research Triangle Park, NC 27711; telephone number: 
(919) 541-7524; fax number: (919) 541-0840; and email address: 
stewart.michael@epa.gov. For information about the applicability of the 
proposed or current national emission standards for hazardous air 
pollutants (NESHAP) for primary aluminum reduction plants to a 
particular entity, contact the appropriate person listed in Table 1 of 
this preamble.

 Table 1--List of EPA Contacts for the NESHAP Addressed in This Proposed
                                 Action
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         NESHAP for:            OECA Contact \1\      OAQPS Contact \2\
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Primary Aluminum Reduction    Patrick Yellin,       David Putney,
 Plants.                      (202) 564-2970,       (919) 541-2016,
                               yellin.patrick@epa.   putney.david@epa.go
                               gov.                  v
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\1\ EPA Office of Enforcement and Compliance Assurance.
\2\ EPA Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION: 

Preamble Acronyms and Abbreviations

    Several acronyms and terms used to describe industrial processes, 
data inventories, and risk modeling are included in this preamble. 
While this may not be an exhaustive list, the following terms and 
acronyms are defined here for reference:

ADAF age-dependent adjustment factors
AEGL acute exposure guideline levels
AERMOD air dispersion model used by the HEM-3 model
AMOS ample margin of safety
ANPRM advance notice of proposed rulemaking
ATSDR Agency for Toxic Substances and Disease Registry
BACT best available control technology
BLDS bag leak detection system
CAA Clean Air Act
CBI Confidential Business Information
CEMS continuous emissions monitoring system
CFR Code of Federal Regulations
COS carbonyl sulfide
CTE central tendency exposure
EJ environmental justice
EPA Environmental Protection Agency
ERPG Emergency Response Planning Guidelines
ERT Electronic Reporting Tool
HAP hazardous air pollutants
HEM-3 Human Exposure Model, Version 3
HEPA high efficiency particulate air
HHRAP Human Health Risk Assessment Protocols
HI Hazard Index
HQ Hazard Quotient
ICR information collection request
IRIS Integrated Risk Information System
Km kilometer
LAER lowest achievable emissions rate
lb/yr pounds per year
MACT maximum achievable control technology
MACT Code Code within the NEI used to identify processes included in 
a source category
MDL method detection level
mg/acm milligrams per actual cubic meter
mg/dscm milligrams per dry standard cubic meter
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
MRL minimum risk level
NAC/AEGL Committee National Advisory Committee for Acute Exposure 
Guideline Levels for Hazardous Substances
NAICS North American Industry Classification System
NAS National Academy of Sciences
NATA National Air Toxics Assessment
NEI National Emissions Inventory
NESHAP National Emissions Standards for Hazardous Air Pollutants
NOAEL no observed adverse effects level
NRC National Research Council
NTTAA National Technology Transfer and Advancement Act
O&M operation and maintenance
OAQPS Office of Air Quality Planning and Standards
ODW Office of Drinking Water
OECA Office of Enforcement and Compliance Assurance
OHEA Office of Health and Environmental Assessment
OMB Office of Management and Budget
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PM particulate matter
POM polycyclic organic matter
ppmv parts per million volume
RACT reasonably available control technology
RBLC RACT/BACT/LAER Clearinghouse
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RIA Regulatory Impact Analysis
RTR residual risk and technology review
SAB Science Advisory Board
SBA Small Business Administration
SCC Source Classification Codes
SOP standard operating procedures
SSM startup, shutdown, and malfunction
TEQ toxic equivalency quotient
TOSHI target organ-specific hazard index
TPY tons per year
TRIM Total Risk Integrated Modeling System
TTN Technology Transfer Network
UF uncertainty factor
[micro]g/m \3\ microgram per cubic meter
UL upper limit
UMRA Unfunded Mandates Reform Act
UPL upper predictive limit
URE unit risk estimate
WHO World Health Organization
WWW worldwide web

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

I. General Information
    A. What is the statutory authority for this action?
    B. Does this action apply to me?
    C. Where can I get a copy of this document and other related 
information?
    D. What should I consider as I prepare my comments for the EPA?
II. Background
    A. What is this source category and how did the MACT standard 
regulate its HAP emissions?
    B. What data collection activities were conducted to support 
this action?
III. Analyses Performed
    A. How did we address unregulated emission sources?
    B. How did we estimate risks posed by the source category?
    C. How did we consider the risk results in making decisions for 
this proposal?
    D. How did we perform the technology review?
    E. What other issues are we addressing in this proposal?
IV. Analytical Results and Proposed Decisions
    A. What are the results of our analyses and proposed decisions 
regarding unregulated emissions sources?
    B. What are the results of the risk assessments?
    C. What are our proposed decisions regarding risk acceptability 
and ample margin of safety?
    D. What are the results and proposed decisions based on our 
technology review?
    E. What other actions are we proposing?
    F. Compliance dates
V. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
VI. Request for Comments

[[Page 76262]]

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. What is the statutory authority for this action?

    Section 112 of the CAA establishes a two-stage regulatory process 
to address emissions of hazardous air pollutants (HAP) from stationary 
sources. In the first stage, after the EPA has identified categories of 
sources emitting one or more of the HAP listed in section 112(b) of the 
CAA, section 112(d) of the CAA calls for us to promulgate national 
emission standards for hazardous air pollutants (NESHAP) for those 
sources. ``Major sources'' are those that emit or have the potential to 
emit (PTE) 10 tons per year (tpy) or more of a single HAP or 25 tpy or 
more of any combination of HAP. For major sources, these technology-
based standards must reflect the maximum degree of emission reductions 
of HAP achievable (after considering cost, energy requirements and 
nonair quality health and environmental impacts) and are commonly 
referred to as maximum achievable control technology (MACT) standards.
    MACT standards are to reflect application of measures, processes, 
methods, systems or techniques including, but not limited to, measures 
which (1) reduce the volume of or eliminate emissions of pollutants 
through process changes, substitution of materials or other 
modifications, (2) enclose systems or processes to eliminate emissions, 
(3) capture or treat pollutants when released from a process, stack, 
storage or fugitive emissions point, (4) are design, equipment, work 
practice or operational standards (including requirements for operator 
training or certification) or (5) are a combination of the above. CAA 
section 112(d)(2)(A)-(E). The MACT standard may take the form of a 
design, equipment, work practice or operational standard where the EPA 
first determines that either (1) a pollutant cannot be emitted through 
a conveyance designed and constructed to emit or capture the pollutant 
or that any requirement for, or use of, such a conveyance would be 
inconsistent with law, or (2) the application of measurement 
methodology to a particular class of sources is not practicable due to 
technological and economic limitations. CAA sections 112(h)(1)-(2).
    The MACT ``floor'' is the minimum control level allowed for MACT 
standards promulgated under CAA section 112(d)(3) and may not be based 
on cost considerations. For new sources, the MACT floor cannot be less 
stringent than the emission control that is achieved in practice by the 
best-controlled similar source. The MACT floors for existing sources 
can be less stringent than floors for new sources, but they cannot be 
less stringent than the average emission limitation achieved by the 
best-performing 12 percent of existing sources in the category or 
subcategory (or the best-performing five sources for categories or 
subcategories with fewer than 30 sources). In developing MACT 
standards, we must also consider control options that are more 
stringent than the floor. We may establish standards more stringent 
than the floor (``beyond the floor'' standards) based on the 
consideration of the cost of achieving the emissions reductions and any 
nonair quality health and environmental impacts and energy 
requirements. No beyond the floor standards are proposed in this 
rulemaking action.
    The EPA is then required to review these technology-based standards 
and to revise them ``as necessary (taking into account developments in 
practices, processes, and control technologies)'' no less frequently 
than every 8 years, under CAA section 112(d)(6). In conducting this 
review, the EPA is not obliged to completely recalculate the prior MACT 
determination. NRDC v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008).
    The second stage in standard-setting focuses on reducing any 
remaining ``residual'' risk according to CAA section 112(f). This 
provision requires, first, that the EPA prepare a Report to Congress 
discussing (among other things) methods of calculating risk posed (or 
potentially posed) by sources after implementation of the MACT 
standards, the public health significance of those risks, and the EPA's 
recommendations as to legislation regarding such remaining risk. The 
EPA prepared and submitted this report (Residual Risk Report to 
Congress, EPA-453/R-99-001) in March 1999. Congress did not act in 
response to the report, thereby triggering the EPA's obligation under 
CAA section 112(f)(2) to analyze and address residual risk.
    CAA section 112(f)(2) requires us to determine, for source 
categories subject to MACT standards, whether the emissions standards 
provide an ample margin of safety to protect public health. If the MACT 
standards for HAP ``classified as a known, probable, or possible human 
carcinogen do not reduce lifetime excess cancer risks to the individual 
most exposed to emissions from a source in the category or subcategory 
to less than 1-in-1 million,'' the EPA must promulgate residual risk 
standards for the source category (or subcategory), as necessary, to 
provide an ample margin of safety to protect public health. In doing 
so, the EPA may adopt standards equal to existing MACT standards if the 
EPA determines that the existing standards are sufficiently protective. 
NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008). (``If EPA determines 
that the existing technology-based standards provide an ``ample margin 
of safety,'' then the agency is free to readopt those standards during 
the residual risk rulemaking.'') The EPA must also adopt more stringent 
standards, if necessary, to prevent an adverse environmental effect \1\ 
but must consider cost, energy, safety and other relevant factors in 
doing so.
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    \1\ ``Adverse environmental effect'' is defined in CAA section 
112(a)(7) as any significant and widespread adverse effect, which 
may be reasonably anticipated to wildlife, aquatic life or natural 
resources, including adverse impacts on populations of endangered or 
threatened species or significant degradation of environmental 
qualities over broad areas.
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    Section 112(f)(2) of the CAA expressly preserves our use of a two-
step process for developing standards to address any residual risk and 
our interpretation of ``ample margin of safety'' developed in the 
National Emission Standards for Hazardous Air Pollutants: Benzene 
Emissions From Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, 
Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product 
Recovery Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The 
first step in this process is the determination of acceptable risk. The 
second step provides for an ample margin of safety to protect public 
health, which is the level at which the standards are set (unless a 
more

[[Page 76263]]

stringent standard is required to prevent, taking into consideration 
costs, energy, safety, and other relevant factors, an adverse 
environmental effect).
    The terms ``individual most exposed,'' ``acceptable level,'' and 
``ample margin of safety'' are not specifically defined in the CAA. 
However, CAA section 112(f)(2)(B) preserves the interpretation set out 
in the Benzene NESHAP, and the United States Court of Appeals for the 
District of Columbia Circuit in NRDC v. EPA, 529 F.3d 1077, concluded 
that the EPA's interpretation of subsection 112(f)(2) is a reasonable 
one. See NRDC v. EPA, 529 F.3d at 1083 (``[S]ubsection 112(f)(2)(B) 
expressly incorporates the EPA's interpretation of the Clean Air Act 
from the Benzene standard, complete with a citation to the Federal 
Register''). (D.C. Cir. 2008). See also, A Legislative History of the 
Clean Air Act Amendments of 1990, volume 1, p. 877 (Senate debate on 
Conference Report). We notified Congress in the Residual Risk Report to 
Congress that we intended to use the Benzene NESHAP approach in making 
CAA section 112(f) residual risk determinations (EPA-453/R-99-001, p. 
ES-11).

    In the Benzene NESHAP, we stated as an overall objective:
    * * * in protecting public health with an ample margin of 
safety, we strive to provide maximum feasible protection against 
risks to health from hazardous air pollutants by, (1) protecting the 
greatest number of persons possible to an individual lifetime risk 
level no higher than approximately 1-in-1 million; and (2) limiting 
to no higher than approximately 1-in-10 thousand [i.e., 100-in-1 
million] the estimated risk that a person living near a facility 
would have if he or she were exposed to the maximum pollutant 
concentrations for 70 years.

    The agency also stated that, ``The EPA also considers incidence 
(the number of persons estimated to suffer cancer or other serious 
health effects as a result of exposure to a pollutant) to be an 
important measure of the health risk to the exposed population. 
Incidence measures the extent of health risk to the exposed population 
as a whole, by providing an estimate of the occurrence of cancer or 
other serious health effects in the exposed population.'' The agency 
went on to conclude that ``estimated incidence would be weighed along 
with other health risk information in judging acceptability.'' As 
explained more fully in our Residual Risk Report to Congress, the EPA 
does not define ``rigid line[s] of acceptability,'' but considers 
rather broad objectives to be weighed with a series of other health 
measures and factors (EPA-453/R-99-001, p. ES-11). The determination of 
what represents an ``acceptable'' risk is based on a judgment of ``what 
risks are acceptable in the world in which we live'' (Residual Risk 
Report to Congress, p. 178, quoting the Vinyl Chloride decision at 824 
F.2d 1165) recognizing that our world is not risk-free.
    In the Benzene NESHAP, we stated that ``EPA will generally presume 
that if the risk to [the maximum exposed] individual is no higher than 
approximately 1-in-10 thousand, that risk level is considered 
acceptable.'' 54 FR 38045. We discussed the maximum individual lifetime 
cancer risk (or maximum individual risk (MIR)) as being ``the estimated 
risk that a person living near a plant would have if he or she were 
exposed to the maximum pollutant concentrations for 70 years.'' Id. We 
explained that this measure of risk ``is an estimate of the upper bound 
of risk based on conservative assumptions, such as continuous exposure 
for 24 hours per day for 70 years.'' Id. We acknowledge that maximum 
individual lifetime cancer risk ``does not necessarily reflect the true 
risk, but displays a conservative risk level which is an upper-bound 
that is unlikely to be exceeded.'' Id.
    Understanding that there are both benefits and limitations to using 
maximum individual lifetime cancer risk as a metric for determining 
acceptability, we acknowledged in the 1989 Benzene NESHAP that 
``consideration of maximum individual risk * * * must take into account 
the strengths and weaknesses of this measure of risk.'' Id. 
Consequently, the presumptive risk level of 100-in-1 million (1-in-10 
thousand) provides a benchmark for judging the acceptability of maximum 
individual lifetime cancer risk, but does not constitute a rigid line 
for making that determination.
    The agency also explained in the 1989 Benzene NESHAP the following: 
``In establishing a presumption for MIR, rather than a rigid line for 
acceptability, the agency intends to weigh it with a series of other 
health measures and factors. These include the overall incidence of 
cancer or other serious health effects within the exposed population, 
the numbers of persons exposed within each individual lifetime risk 
range and associated incidence within, typically, a 50-kilometer (km) 
exposure radius around facilities, the science policy assumptions and 
estimation uncertainties associated with the risk measures, weight of 
the scientific evidence for human health effects, other quantified or 
unquantified health effects, effects due to co-location of facilities 
and co-emission of pollutants.'' Id.
    In some cases, these health measures and factors taken together may 
provide a more realistic description of the magnitude of risk in the 
exposed population than that provided by maximum individual lifetime 
cancer risk alone. As explained in the Benzene NESHAP, ``[e]ven though 
the risks judged `acceptable' by the EPA in the first step of the Vinyl 
Chloride inquiry are already low, the second step of the inquiry, 
determining an `ample margin of safety,' again includes consideration 
of all of the health factors, and whether to reduce the risks even 
further.'' In the ample margin of safety decision process, the agency 
again considers all of the health risks and other health information 
considered in the first step. Beyond that information, additional 
factors relating to the appropriate level of control will also be 
considered, including costs and economic impacts of controls, 
technological feasibility, uncertainties and any other relevant 
factors. Considering all of these factors, the agency will establish 
the standard at a level that provides an ample margin of safety to 
protect the public health, as required by CAA section 112(f). 54 FR 
38046.
    As discussed in the previous section of this preamble, we apply a 
two-step process for developing standards to address residual risk. In 
the first step, the EPA determines whether risks are acceptable. This 
determination ``considers all health information, including risk 
estimation uncertainty, and includes a presumptive limit on maximum 
individual lifetime [cancer] risk (MIR) \2\ of approximately 1-in-10 
thousand [i.e., 100-in-1 million].'' 54 FR 38045. In the second step of 
the process, the EPA sets the standard at a level that provides an 
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.
---------------------------------------------------------------------------

    \2\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk were an individual exposed to the maximum level 
of a pollutant for a lifetime.
---------------------------------------------------------------------------

    In past residual risk determinations, the EPA presented a number of 
human health risk metrics associated with emissions from the category 
under review, including: The MIR; the numbers of persons in various 
risk ranges; cancer incidence; the maximum noncancer hazard index (HI); 
and the maximum acute noncancer hazard. In estimating risks, the EPA 
considered

[[Page 76264]]

source categories under review that are located near each other and 
that affect the same population. The EPA provided estimates of the 
expected difference in actual emissions from the source category under 
review and emissions allowed pursuant to the source category MACT 
standard. The EPA also discussed and considered risk estimation 
uncertainties. The EPA is providing this same type of information in 
support of these actions.
    The agency acknowledges that the Benzene NESHAP provides 
flexibility regarding what factors the EPA might consider in making our 
determinations and how they might be weighed for each source category. 
In responding to comment on our policy under the Benzene NESHAP, the 
EPA explained that: ``The policy chosen by the Administrator permits 
consideration of multiple measures of health risk. Not only can the MIR 
figure be considered, but also incidence, the presence of noncancer 
health effects, and the uncertainties of the risk estimates. In this 
way, the effect on the most exposed individuals can be reviewed as well 
as the impact on the general public. These factors can then be weighed 
in each individual case. This approach complies with the Vinyl Chloride 
mandate that the Administrator ascertain an acceptable level of risk to 
the public by employing [her] expertise to assess available data. It 
also complies with the Congressional intent behind the CAA, which did 
not exclude the use of any particular measure of public health risk 
from the EPA's consideration with respect to CAA section 112 
regulations, and, thereby, implicitly permits consideration of any and 
all measures of health risk which the Administrator, in [her] judgment, 
believes are appropriate to determining what will `protect the public 
health.' ''
    For example, the level of the MIR is only one factor to be weighed 
in determining acceptability of risks. The Benzene NESHAP explains ``an 
MIR of approximately 1-in-10 thousand should ordinarily be the upper 
end of the range of acceptability. As risks increase above this 
benchmark, they become presumptively less acceptable under CAA section 
112, and would be weighed with the other health risk measures and 
information in making an overall judgment on acceptability. Or, the 
agency may find, in a particular case, that a risk that includes MIR 
less than the presumptively acceptable level is unacceptable in the 
light of other health risk factors.'' Similarly, with regard to the 
ample margin of safety analysis, the Benzene NESHAP states that: ``EPA 
believes the relative weight of the many factors that can be considered 
in selecting an ample margin of safety can only be determined for each 
specific source category. This occurs mainly because technological and 
economic factors (along with the health-related factors) vary from 
source category to source category.''

B. Does this action apply to me?

    The regulated industrial source category that is the subject of 
this proposal is listed in Table 2 of this preamble. Table 2 of this 
preamble is not intended to be exhaustive, but rather provides a guide 
for readers regarding the entities likely to be affected by this 
proposed action. These standards, once finalized, will be directly 
applicable to affected sources. Federal, State, local, and Tribal 
government entities are not affected by this proposed action. As 
defined in the source category listing report published by the EPA in 
1992, the Primary Aluminum Reduction Plant source category is defined 
as any facility which produced primary aluminum by the electrolytic 
reduction process.

                Table 2--NESHAP and Industrial Source Categories Affected by This Proposed Action
----------------------------------------------------------------------------------------------------------------
               Source category                            NESHAP               NAICS code \1\     MACT code \2\
----------------------------------------------------------------------------------------------------------------
Primary Aluminum Reduction Plants...........  Primary Aluminum Reduction                331312              0023
                                               Plants.
----------------------------------------------------------------------------------------------------------------
\1\ North American Industry Classification System.
\2\ Maximum Achievable Control Technology.

C. Where can I get a copy of this document and other related 
information?

    In addition to being available in the docket, an electronic copy of 
this proposal will also be available on the World Wide Web (WWW) 
through the EPA's Technology Transfer Network (TTN). Following 
signature by the EPA Administrator, a copy of this proposed action will 
be posted on the TTN's policy and guidance page for newly proposed or 
promulgated rules at the following address: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The TTN provides information and technology exchange 
in various areas of air pollution control.
    Additional information is available on the residual risk and 
technology review (RTR) Web page at: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. This information includes source category descriptions and 
detailed emissions estimates and other data that were used as inputs to 
the risk assessments.

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

    Submitting CBI. Do not submit information containing CBI to the EPA 
through http://www.regulations.gov or email. Clearly mark the part or 
all of the information that you claim to be CBI. For CBI information on 
a disk or CD ROM that you mail to the EPA, mark the outside of the disk 
or CD ROM as CBI and then identify electronically within the disk or CD 
ROM the specific information that is claimed as CBI. In addition to one 
complete version of the comment that includes information claimed as 
CBI, a copy of the comment that does not contain the information 
claimed as CBI must be submitted for inclusion in the public docket. If 
you submit a CD ROM or disk that does not contain CBI, mark the outside 
of the disk or CD ROM clearly that it does not contain CBI. Information 
not marked as CBI will be included in the public docket and the EPA's 
electronic public docket without prior notice. Information marked as 
CBI will not be disclosed except in accordance with procedures set 
forth in 40 CFR part 2. Send or deliver information identified as CBI 
only to the following address: Roberto Morales, OAQPS Document Control 
Officer (C404-02), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711, Attention Docket ID Number EPA-HQ-OAR-2011-0797.

II. Background

A. What is this source category and how did the MACT standard regulate 
its HAP emissions?

    The NESHAP (or MACT rule) for the Primary Aluminum Reduction Plants 
was promulgated on October 7, 1997 (62 FR 52407) and amended on 
November 2, 2005 (70 FR 66285). The rule is applicable to facilities 
with affected sources associated with the production of aluminum by 
electrolytic reduction. Aluminum is produced from refined

[[Page 76265]]

bauxite ore (also known as alumina), using an electrolytic reduction 
process in a series of cells called a ``potline.'' The raw materials 
include alumina, coke, pitch and fluoride salts. According to 
information available on the Web site of The Aluminum Association, Inc. 
(http://www.aluminum.org) approximately 50 percent of the aluminum 
produced in the U.S. comes from primary aluminum facilities. The two 
main potline types are prebake (a newer, higher efficiency, lower-
emitting technology) and Soderberg (an older, lower efficiency, higher-
emitting technology). There are currently 15 facilities located in the 
United States that are subject to the requirements of this NESHAP: 14 
primary aluminum production plants and one carbon-only prebake anode 
production facility. These 14 primary aluminum production plants have 
approximately 53 potlines that produce aluminum. Each plant has a paste 
production operation, and 12 of the 14 plants have anode bake furnaces. 
Twelve of the 14 facilities utilize prebake potlines; the other 2 
utilize Soderberg potlines. According to The Aluminum Association, 
Inc., due to a decrease in demand for aluminum, four of the 14 
facilities are currently idle including 1 Soderberg facility. The major 
HAPs emitted by these facilities are carbonyl sulfide (COS), hydrogen 
fluoride (HF), and polycyclic organic matter (POM), specifically 
polycyclic aromatic hydrocarbons (PAH).
    The standards promulgated in 1997 and 2005 apply to emissions of 
HF, measured using total fluorides (TF) as a surrogate, from all 
potlines and anode bake furnaces and POM (as measured by methylene 
chloride extractables) from Soderberg potlines, anode bake furnaces, 
paste production plants and pitch storage tanks associated with primary 
aluminum reduction. Affected sources under the rules are each potline, 
each anode bake furnace (except for one that is located at a facility 
that only produces anodes for use off-site), each paste production 
plant, and each new pitch storage tank.
    The NESHAP designated seven subcategories of existing potlines 
based primarily on differences in the process operation and 
configuration. The control of primary emissions from the reduction 
process is typically achieved by the installation of a dry alumina 
scrubber (with a baghouse to collect the alumina and other particulate 
matter). The MACT control technology typically used for anode bake 
furnaces is a dry alumina scrubber, and a capture system vented to a 
dry coke scrubber is used for control of paste production plants. See 
Table 3 for the emission limits.

  Table 3--Summary of Current MACT Emission Limits for Existing Sources
             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        POM..............   ton) of green anode.
 plant).                                           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 primary aluminum plant operated by NSA in Hawesville,
  Kentucky.
HSS = Horizontal stud Soderberg potline.
SWPB = Side-worked prebake potline.
VSS1 = Vertical stud Soderberg potline at Northwest Aluminum in The
  Dalles, Oregon, or at Columbia Aluminum in Goldendale, Washington.
VSS2 = Vertical stud Soderberg potlines at Columbia Falls Aluminum in
  Columbia Falls, Montana.

 Table 4--Summary of Current MACT Emission Limits for New Sources Under
                   the 1997 NESHAP and 2005 Amendments
------------------------------------------------------------------------
            Source                  Pollutant          Emission limit
------------------------------------------------------------------------
All Potlines..................  TF...............  0.6 kg/Mg (1.2 lb/
                                                    ton) of aluminum
                                                    produced.
VSS1, VSS2, and HSS potlines..  POM..............  0.32 kg/Mg (0.63 lb/
                                                    ton) of aluminum
                                                    produced.
Paste Production..............  POM..............  Install, operate, and
                                                    maintain equipment
                                                    for capture of
                                                    emissions and vent
                                                    to a dry coke
                                                    scrubber.
Anode Bake Furnace (collocated  TF...............  0.01 kg/Mg (0.020 lb/
 with a primary aluminum        POM..............   ton) of green anode
 plant).                                           0.025 kg/Mg (0.05 lb/
                                                    ton) of green anode.
Pitch storage tanks...........  POM..............  Emission control
                                                    system designed and
                                                    operated to reduce
                                                    inlet emissions by
                                                    95 percent or
                                                    greater.
------------------------------------------------------------------------

[[Page 76266]]

    The 1997 NESHAP for primary aluminum reduction plants incorporates 
new source performance standards for potroom groups; these emission 
limits are listed in Table 4. The limits for new Soderberg facilities 
apply to any Soderberg facility that adds a new potroom group to an 
existing potline or is associated with a potroom group that meets the 
definition of a modified or reconstructed potroom group. Since these 
POM limits are very stringent, they effectively preclude the operation 
of any new Soderberg potlines.
    Compliance with the emission limits in the current rule is 
demonstrated by performance testing which can be addressed individually 
for each affected source or according to emissions averaging 
provisions. Monitoring requirements include monthly measurements of TF 
secondary emissions, quarterly measurement of POM secondary emissions 
and annual measurement of primary emissions, continuous parameter 
monitoring for each emission control device, a monitoring device to 
track daily weight of aluminum produced, daily inspection for visible 
emissions, and daily inspection of wet roof scrubbers. Recordkeeping 
for the rule is consistent with the General Provisions requirements 
with the addition of recordkeeping for daily production of aluminum, 
records supporting emissions averaging and records documenting the 
portion of TF measured as particulate matter or gaseous form.

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

    For the Primary Aluminum Reduction Plant source category, we 
compiled a preliminary dataset using available information, reviewed 
the data, and made changes where necessary. The preliminary dataset was 
based on data in the 2002 National Emissions Inventory (NEI) Final 
Inventory, Version 1 (made publicly available on February 26, 2006), 
and the 2005 National Emissions Inventory (NEI), version 2.0 (made 
publicly available in October 2008). The NEI is a database that 
contains information about sources that emit criteria air pollutants, 
their precursors, and HAP. The NEI database includes estimates of 
annual air pollutant emissions from point and volume sources, emission 
release characteristic data such as height, velocity, temperature and 
location latitude/longitude coordinates.
    We reviewed the NEI datasets, corrected geographic coordinates and 
stack parameters in consultation with the facilities, and made changes 
based on available information. We also reviewed the emissions and 
other data to identify data anomalies that could affect risk estimates. 
The 2005 NEI was then updated to develop the 2005 National Air Toxics 
Assessment (NATA) Inventory. Subsequently, in April 2011, we received 
test data and other information through an Information Collection 
Request (ICR) from 11 of the 15 facilities in the source category. 
These ICR data were then used along with the 2005 NATA inventory data 
to develop the emissions dataset for this source category, which 
includes our best estimates of actual emissions of HAP for the 
facilities. This dataset was then used in the risk modeling analyses to 
estimate the risks due to actual emissions for the source category.
    POM emissions were allocated to specific POM compounds on the basis 
of the fractional contributions of these compounds to the actual POM 
emissions, as determined (as appropriate) from an average of test data 
for two prebake potlines and an average of data from two Soderberg 
facilities. Based on knowledge of the industry and previous testing, we 
could reasonably expect emissions of approximately 23 POM specific POM 
compounds from primary aluminum production facilities. The allocation 
incorporated POM emissions at 50 percent of the detection limit for 
those compounds ``reported as below detection limit.'' The use of 50 
percent of the detection limit is more conservative than assuming that 
these compounds were not present; an assumption that the compounds were 
present at the detection limit would be an overestimation. The 
assumption that these compounds were present at 50 percent of the 
detection limit represented the midpoint of two extreme options. For 
Soderberg potline stacks, six out of 38 measurements were below the 
detection limit. For Soderberg potroom roof vents, 10 out of 38 
measurements were below the detection limit. For prebake potline 
stacks, 21 out of 38 measurements were below the detection limit. For 
prebake potroom roof vents, 25 out of 38 measurements were below the 
detection limit.
    To estimate allowable emissions, we analyzed the emissions data 
gathered from the 2002 NEI, the 2005 NEI and responses to the ICR 
described above. Based on that analysis, we estimated that allowable 
emissions were generally about 1.5 times higher than actual emissions. 
Therefore, to calculate allowable emissions we assumed that allowable 
emissions were 1.5 times greater than actual emissions for all 
facilities except for one idle Soderberg facility (Columbia Falls). For 
Columbia Falls, which has the highest potential for emissions of all 
the facilities, we evaluated site-specific data and estimated that 
allowable emissions were about 1.9 times higher than actual emissions.
    Actual emissions of COS for the industry are estimated to be about 
4,400 tons per year (tpy), with an average of about 330 tons per 
facility. Actual emissions of HF are estimated to be about 1,900 tpy 
with an average of about 160 tpy per facility. Estimated emissions of 
speciated compounds of POM were much lower. Estimated actual emissions 
of identified POM species totaled approximately 180 tpy for the 
industry. Moreover, POM emissions are much higher from Soderberg 
facilities compared to prebake facilities. The average POM emissions 
from prebake facilities are about 4.5 tpy per facility, and the average 
POM emissions for Soderberg facilities are about 60 tpy per facility. 
We estimate that approximately one-third of the emissions of POM for 
both types of potrooms come from the control device stack, and the 
remainder are secondary emissions emitted from potroom vents. This 
estimate is based on a summary of emissions derived from reports of 
emission testing conducted at two prebake facilities and two Soderberg 
facilities (``Industry Review of Draft POM Speciation and Emissions 
Data,'' December 19, 2007).
    The emissions data, calculations and risk assessment inputs for the 
Primary Aluminum Reduction Plant source category are described further 
in Draft Development of the RTR Emissions Dataset for the Primary 
Aluminum Production Source Category which is available in the docket 
for this proposed rulemaking.

III. Analyses Performed

    In this section we describe the analyses performed to support the 
proposed decisions for the RTR for this source category.

A. How did we address unregulated emissions sources?

    In the course of evaluating the Primary Aluminum Reduction Plant 
source category, we identified certain HAP for which we failed to 
establish emission standards in the original MACT. See National Lime v. 
EPA, 233 F. 3d 625, 634 (DC Cir. 2000) (the EPA has ``clear statutory 
obligation to set emissions standards for each listed HAP'').
    We evaluated establishing emissions limits for COS for the source 
category and for POM for various emissions points that had not been 
regulated in the 1997 MACT rule or in the 2005

[[Page 76267]]

amendments. Section 112(d)(3)(B) of the CAA requires that the MACT 
standards for existing sources be at least as stringent as the average 
emissions limitation achieved by the best performing five sources (for 
which the Administrator has or could reasonably obtain emissions 
information) in a category with fewer than 30 sources. The Primary 
Aluminum source category consists of fewer than 30 sources.
    The EPA must exercise its judgment, based on an evaluation of the 
relevant factors and available data, to determine the level of 
emissions control that has been achieved by the best performing sources 
under variable conditions. It is recognized in the case law that the 
EPA may consider variability in estimating the degree of emissions 
reduction achieved by best-performing sources and in setting MACT 
floors. See Mossville Envt'l Action Now v. EPA, 370 F.3d 1232, 1241-42 
(DC Cir 2004) (holding that the EPA may consider emissions variability 
in estimating performance achieved by best-performing sources and may 
set the floor at a level that a best-performing source can expect to 
meet ``every day and under all operating conditions''). More details on 
how we calculate MACT floors and how we account for variability are 
described in the Draft MACT Floor Analysis for the Primary Aluminum 
Source Category which is available in the docket for this proposed 
action.
    Carbonyl sulfide (COS) was not regulated in the 1997 NESHAP or in 
the 2005 amendments for Primary Aluminum Reduction Plants. In this 
action we analyzed the available data and evaluated options for 
developing MACT standards for this HAP. Based on all our analyses, 
which are described in section IV.A of this preamble, we concluded that 
establishing a standard based on a mass balance equation would be the 
most appropriate approach. Therefore, we are proposing MACT standards 
for COS in today's action based on use of a mass balance equation to 
derive COS emissions based on data on anode coke sulfur content, anode 
consumption and aluminum production.
    Polycyclic organic matter (POM) emissions from prebake potlines 
were also not regulated in the 1997 NESHAP or in the 2005 amendments. 
We are proposing MACT limits for new and existing prebake potlines in 
today's action based on available data. Finally, the 1997 NESHAP 
included MACT standards for new pitch storage tanks, which required a 
95 percent reduction in emissions. However, the rule had no limits for 
existing storage tanks. We are proposing that existing tanks will be 
subject to the same standard (i.e., minimum of 95 percent reduction of 
POM emissions). At least three facilities are currently achieving this 
level of control on existing tanks.
    Further details about the analyses, the results and proposed 
decisions regarding the proposed MACT limits pursuant to CAA section 
112(d)(2) and 112(d)(3) are presented in section IV.A of this preamble.

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

    The EPA conducted risk assessments that provided estimates of the 
MIR posed by the HAP emissions for each source in the category, the HI 
for chronic exposures to HAP with the potential to cause noncancer 
health effects, and the hazard quotient (HQ) for acute exposures to HAP 
with the potential to cause noncancer health effects. The assessments 
also provided estimates of the distribution of cancer risks within the 
exposed populations, cancer incidence and an evaluation of the 
potential for adverse environmental effects for each source category. 
The risk assessments consisted of seven primary steps, as discussed 
below. The docket for this rulemaking contains the following document 
which provides more information on the risk assessment inputs and 
models: Draft Residual Risk Assessment for the Primary Aluminum 
Reduction Plant Source Category. The methods used to assess risks (as 
described in the seven primary steps below) are consistent with those 
peer-reviewed by a panel of the EPA's Science Advisory Board (SAB) in 
2009 and described in their peer review report issued in 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. Establishing the Nature and Magnitude of Actual Emissions and 
Identifying the Emissions Release Characteristics
    As discussed in section II.B of this preamble, we used a dataset 
consisting of the estimated actual and allowable emissions as the basis 
for the risk assessment. In addition to the quality assurance (QA) of 
the emissions and associated parameters contained in the dataset, we 
also checked the coordinates of every facility in the dataset through 
visual observations using tools such as Google Earth and ArcView. Where 
coordinates were found to be incorrect, we identified and corrected 
them to the extent possible. We also performed QA of the emissions data 
and release characteristics to ensure there were no outliers.
2. Establishing the Relationship Between Actual Emissions and MACT-
Allowable Emissions Levels
    The available emissions data in the MACT dataset include estimates 
of the mass of HAP actually emitted during the specified annual time 
period. These ``actual'' emission levels are often lower than the 
emission levels that a facility might be allowed to emit and still 
comply with the MACT standards. The emissions level allowed to be 
emitted by the MACT standards is referred to as the ``MACT-allowable'' 
emissions level. This represents the highest emissions level that could 
be emitted by the facility without violating the MACT standards.
    We discussed the use of both MACT-allowable and actual emissions in 
the final Coke Oven Batteries residual risk rule (70 FR 19998-19999, 
April 15, 2005) and in the proposed and final Hazardous Organic NESHAP 
residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609, 
December 21, 2006, respectively). In those previous actions, we noted 
that assessing the risks at the MACT-allowable level is inherently 
reasonable since these risks reflect the maximum level sources could 
emit and still comply with national emission standards. But we also 
explained that it is reasonable to consider actual emissions, where 
such data are available, in both steps of the risk analysis, in 
accordance with the Benzene NESHAP. (54 FR 38044, September 14, 1989.)
    Further explanation is provided in the document Draft Development 
of the RTR Emissions Dataset for the Primary Aluminum Production Source 
Category which is available in the docket for this proposed rulemaking.
3. Conducting Dispersion Modeling, Determining Inhalation Exposures and 
Estimating Individual and Population Inhalation Risks
    Both long-term and short-term inhalation exposure concentrations 
and health risks from each facility in the source category addressed in 
this proposal were estimated using the Human Exposure Model (HEM) 
(Community and Sector HEM-3 version 1.1.0). The HEM-3 performs three 
primary risk assessment activities: (1) Conducting dispersion modeling 
to estimate the concentrations of HAP in ambient air, (2) estimating 
long-term

[[Page 76268]]

and short-term inhalation exposures to individuals residing within 50 
km of the modeled sources and (3) estimating individual and population-
level inhalation risks using the exposure estimates and quantitative 
dose-response information.
    The dispersion model used by HEM-3 is AERMOD, which is one of the 
EPA's preferred models for assessing pollutant concentrations from 
industrial facilities.\4\ To perform the dispersion modeling and to 
develop the preliminary risk estimates, HEM-3 draws on three data 
libraries. The first is a library of meteorological data, which is used 
for dispersion calculations. This library includes 1 year (1991) of 
hourly surface and upper air observations for more than 158 
meteorological stations, selected to provide coverage of the United 
States and Puerto Rico. A second library of United States Census Bureau 
census block \5\ internal point locations and populations provides the 
basis of human exposure calculations (Census, 2000). In addition, for 
each census block, the census library includes the elevation and 
controlling hill height, which are also used in dispersion 
calculations. A third library of pollutant unit risk factors and other 
health benchmarks is used to estimate health risks. These risk factors 
and health benchmarks are the latest values recommended by the EPA for 
HAP and other toxic air pollutants. These values are available at 
http://www.epa.gov/ttn/atw/toxsource/summary.html and are discussed in 
more detail later in this section.
---------------------------------------------------------------------------

    \4\ U.S. EPA. Revision to the Guideline on Air Quality Models: 
Adoption of a Preferred General Purpose (Flat and Complex Terrain) 
Dispersion Model and Other Revisions (70 FR 68218, November 9, 
2005).
    \5\ A census block is generally the smallest geographic area for 
which census statistics are tabulated.
---------------------------------------------------------------------------

    In developing the risk assessment for chronic exposures, we used 
the estimated annual average ambient air concentration of each of the 
HAP emitted by each source for which we have emissions data in the 
source category. The air concentrations at each nearby census block 
centroid were used as a surrogate for the chronic inhalation exposure 
concentration for all the people who reside in that census block. We 
calculated the MIR for each facility as the cancer risk associated with 
a continuous lifetime (24 hours per day, 7 days per week, and 52 weeks 
per year for a 70-year period) exposure to the maximum concentration at 
the centroid of an inhabited census block. Individual cancer risks were 
calculated by multiplying the estimated lifetime exposure to the 
ambient concentration of each of the HAP (in micrograms per cubic 
meter) by its unit risk estimate (URE), which is an upper bound 
estimate of an individual's probability of contracting cancer over a 
lifetime of exposure to a concentration of 1 microgram of the pollutant 
per cubic meter of air. For residual risk assessments, we generally use 
URE values from the EPA's Integrated Risk Information System (IRIS). 
For carcinogenic pollutants without the EPA IRIS values, we look to 
other reputable sources of cancer dose-response values, often using 
California EPA (CalEPA) URE values, where available. In cases where 
new, scientifically credible 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.
    Polycyclic organic matter (POM), a carcinogenic HAP with a 
mutagenic mode of action, is emitted by the facilities in this source 
category.\6\ For this compound group,\7\ the age-dependent adjustment 
factors (ADAF) described in the EPA's Supplemental Guidance for 
Assessing Susceptibility from Early-Life Exposure to Carcinogens \8\ 
were applied. This adjustment has the effect of increasing the 
estimated lifetime risks for POM by a factor of 1.6. In addition, 
although only a small fraction of the total POM emissions were not 
reported as individual compounds, the EPA expresses carcinogenic 
potency for compounds in this group in terms of benzo[a]pyrene 
equivalence, based on evidence that carcinogenic POM has the same 
mutagenic mechanism of action as benzo[a]pyrene. For this reason, the 
EPA's Science Policy Council \9\ recommends applying the Supplemental 
Guidance to all carcinogenic polycyclic aromatic hydrocarbons for which 
risk estimates are based on relative potency. Accordingly, we have 
applied the ADAF to the benzo[a]pyrene equivalent portion of all POM 
mixtures.
---------------------------------------------------------------------------

    \6\ U.S. EPA. Performing risk assessments that include 
carcinogens described in the Supplemental Guidance as having a 
mutagenic mode of action. Science Policy Council Cancer Guidelines 
Implementation Work Group Communication II: Memo from W.H. Farland, 
dated October 4, 2005.
    \7\ See the Risk Assessment for Source Categories document 
available in the docket for a list of HAP with a mutagenic mode of 
action.
    \8\ U.S. EPA. Supplemental Guidance for Assessing Early-Life 
Exposure to Carcinogens. EPA/630/R-03/003F, 2005. http://www.epa.gov/ttn/atw/childrens_supplement_final.pdf.
    \9\ U.S. EPA. Science Policy Council Cancer Guidelines 
Implementation Workgroup Communication II: Memo from W.H. Farland, 
dated June 14, 2006.
---------------------------------------------------------------------------

    Incremental individual lifetime cancer risks associated with 
emissions from the source category were estimated 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 \10\) emitted by the 
modeled source. Cancer incidence and the distribution of individual 
cancer risks for the population within 50 km of any source were also 
estimated for the source category as part of these assessments by 
summing individual risks. A distance of 50 km is consistent with both 
the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the 
limitations of Gaussian dispersion models, including AERMOD.
---------------------------------------------------------------------------

    \10\ These classifications also coincide with the terms ``known 
carcinogen, probable carcinogen and possible carcinogen,'' 
respectively, which are the terms advocated in the EPA's previous 
Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR 
33992, September 24, 1986). Summing the risks of these individual 
compounds to obtain the cumulative cancer risks is an approach that 
was recommended by the EPA's SAB in their 2002 peer review of EPA's 
NATA entitled, NATA--Evaluating the National-scale Air Toxics 
Assessment 1996 Data--an SAB Advisory, available at: http://
yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
---------------------------------------------------------------------------

    To assess risk of noncancer health effects from chronic exposures, 
we summed the HQ for each of the HAP that affects a common target organ 
system to obtain the HI for that target organ system (or target organ-
specific HI, TOSHI). The HQ for chronic exposures is the estimated 
chronic exposure divided by the chronic reference level, which is 
either the EPA reference concentration (RfC), defined as ``an estimate 
(with uncertainty spanning perhaps an order of magnitude) of a 
continuous inhalation exposure to the human population (including 
sensitive subgroups) that is likely to be without an appreciable risk 
of deleterious effects during a lifetime,'' or, in cases where an RfC 
from the EPA's IRIS database is not available, a value from the 
following prioritized sources: (1) The agency for Toxic Substances and 
Disease Registry Minimum Risk Level, which is defined as ``an estimate 
of daily human exposure to a substance that is likely to be without an 
appreciable risk of adverse effects (other than cancer) over a 
specified duration of exposure''; (2) the CalEPA Chronic Reference 
Exposure Level (REL), which is defined as ``the concentration level at 
or below which no adverse health effects are anticipated for a 
specified exposure duration;'' or

[[Page 76269]]

(3) as noted above, a scientifically credible dose-response value that 
has been developed in a manner consistent with the EPA guidelines and 
has undergone a peer review process similar to that used by the EPA, in 
place of or in concert with other values.
    Screening estimates of acute exposures and risks were also 
evaluated for each of the HAP at the point of highest off-site exposure 
for each facility (i.e., not just the census block centroids), assuming 
that a person is located at this spot at a time when both the peak 
(hourly) emission rates from each emission point at the facility and 
worst-case dispersion conditions occur. The acute HQ is the estimated 
acute exposure divided by the acute dose-response value. In each case, 
acute HQ values were calculated using best available, short-term dose-
response values. These acute dose-response values, which are described 
below, include the acute REL, acute exposure guideline levels (AEGL) 
and emergency response planning guidelines (ERPG) for 1-hour exposure 
durations. As discussed below, we used conservative assumptions for 
emission rates, meteorology and exposure location for our acute 
analysis.
    As described in the CalEPA's Air Toxics Hot Spots Program Risk 
Assessment Guidelines, Part I, The Determination of Acute Reference 
Exposure Levels for Airborne Toxicants, an acute REL value (http://www.oehha.ca.gov/air/pdf/acuterel.pdf) is defined as ``the 
concentration level at or below which no adverse health effects are 
anticipated for a specified exposure duration.'' Acute REL values are 
based on the most sensitive, relevant, adverse health effect reported 
in the medical and toxicological literature. Acute REL values are 
designed to protect the most sensitive sub-populations (e.g., 
asthmatics) by the inclusion of margins of safety. Since margins of 
safety are incorporated to address data gaps and uncertainties, 
exceeding the acute REL does not automatically indicate an adverse 
health impact.
    AEGL values were derived in response to recommendations from the 
National Research Council (NRC). As described in Standing Operating 
Procedures (SOP) of the National Advisory Committee on Acute Exposure 
Guideline Levels for Hazardous Substances (http://www.epa.gov/opptintr/aegl/pubs/sop.pdf),\11\ ``the NRC's previous name for acute exposure 
levels--community emergency exposure levels--was replaced by the term 
AEGL to reflect the broad application of these values to planning, 
response, and prevention in the community, the workplace, 
transportation, the military, and the remediation of Superfund sites.'' 
This document also states that AEGL values ``represent threshold 
exposure limits for the general public and are applicable to emergency 
exposures ranging from 10 minutes to eight hours.'' The document lays 
out the purpose and objectives of AEGL by stating (page 21) that ``the 
primary purpose of the AEGL program and the National Advisory Committee 
for Acute Exposure Guideline Levels for Hazardous Substances is to 
develop guideline levels for once-in-a-lifetime, short-term exposures 
to airborne concentrations of acutely toxic, high-priority chemicals.'' 
In detailing the intended application of AEGL values, the document 
states (page 31) that ``[i]t is anticipated that the AEGL values will 
be used for regulatory and nonregulatory purposes by U.S. Federal and 
state agencies and possibly the international community in conjunction 
with chemical emergency response, planning, and prevention programs. 
More specifically, the AEGL values will be used for conducting various 
risk assessments to aid in the development of emergency preparedness 
and prevention plans, as well as real-time emergency response actions, 
for accidental chemical releases at fixed facilities and from transport 
carriers.''
---------------------------------------------------------------------------

    \11\ NAS, 2001. Standing Operating Procedures for Developing 
Acute Exposure Levels for Hazardous Chemicals, page 2.
---------------------------------------------------------------------------

    The AEGL-1 value is then specifically defined as ``the airborne 
concentration of a substance above which it is predicted that the 
general population, including susceptible individuals, could experience 
notable discomfort, irritation, or certain asymptomatic nonsensory 
effects. However, the effects are not disabling and are transient and 
reversible upon cessation of exposure.'' The document also notes (page 
3) that, ``Airborne concentrations below AEGL-1 represent exposure 
levels that can produce mild and progressively increasing but transient 
and nondisabling odor, taste, and sensory irritation or certain 
asymptomatic, nonsensory effects.'' Similarly, the document defines 
AEGL-2 values as ``the airborne concentration (expressed as ppm or mg/
m\3\) 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.''
    ERPG values are derived for use in emergency response, as described 
in the American Industrial Hygiene Association's document entitled, 
Emergency Response Planning Guidelines (ERPG) Procedures and 
Responsibilities (http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf) which states that, ``Emergency Response Planning 
Guidelines were developed for emergency planning and are intended as 
health based guideline concentrations for single exposures to 
chemicals.'' \12\ The ERPG-1 value is defined as ``the maximum airborne 
concentration below which it is believed that nearly all individuals 
could be exposed for up to 1 hour without experiencing other than mild 
transient adverse health effects or without perceiving a clearly 
defined, objectionable odor.'' Similarly, the ERPG-2 value is defined 
as ``the maximum airborne concentration below which it is believed that 
nearly all individuals could be exposed for up to 1 hour without 
experiencing or developing irreversible or other serious health effects 
or symptoms which could impair an individual's ability to take 
protective action.''
---------------------------------------------------------------------------

    \12\ 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; in these instances, higher severity level AEGL-2 or ERPG-2 
values are compared to our modeled exposure levels to assess potential 
for acute concerns.
    Acute REL values for 1-hour exposure durations are typically lower 
than their corresponding AEGL-1 and ERPG-1 values. Even though their 
definitions are slightly different, AEGL-1 values are often similar to 
the corresponding ERPG-1 values, and AEGL-2 values are often similar to 
ERPG-2 values. Maximum HQ values from our acute screening risk 
assessments typically result when basing them on the acute REL value 
for a particular pollutant. In cases where our maximum acute HQ value 
exceeds 1, we also report the HQ value based on the next highest acute 
dose-response value (usually the AEGL-1 and/or the ERPG-1 value).
    To develop screening estimates of acute exposures, we developed 
estimates of maximum hourly emission rates by multiplying the average 
actual annual hourly emission rates by a factor to cover routinely 
variable emissions. Acute risk modeling is conducted under the 
assumption that peak emissions are ten times greater than long term 
average

[[Page 76270]]

emissions, in the absence of information regarding the variability of 
the emissions.
    With respect to routine variable emissions, primary aluminum 
potlines have a more consistent emissions profile than many other 
sources because these emissions actually reflect the average of the 
emissions from approximately 100 individual pots which operate in 
cycles that are not in phase with each other. Thus any variability 
associated with aluminum levels or electrode replacement for a 
particular pot may be damped out by the other pots at different stages. 
Alcoa provided to EPA a series of hourly hydrogen fluoride 
concentration data for two potlines at their Wenatchee facility. 
Approximately 2,075 consecutive hourly readings were provided based on 
Fourier Transform Infrared measurements at the roof vents. Alcoa found 
that the ratio of the maximum HAP emission rate to the average HAP 
emission rate for these two potlines were 2.7 and 5.6. Only one value 
out 2,075 consecutive hour samples (0.05 percent) was more than 5 times 
the average (i.e., 99.95 percent of values were less than 5 times the 
average).
    This dataset was then combined and subjected to two statistical 
analysis techniques: The upper prediction limit (UPL) calculated 
assuming a log-normal distribution after adjusting for temporal 
correction and extreme value theory. The average of the concentration 
values is 514 [micro]g/m\3\. The 99 percent UPL was calculated at 2,215 
[micro]g/m, which corresponds to 4.3 times the mean.
    Using the extreme value theory, the 99.9 percentile estimate of the 
generalized extreme value distribution (corresponding to 1 observation 
in 1000) was 2,306 [micro]g/m\3\, which corresponds to 4.5 times the 
mean. Based on these data, a source category factor of 5 times the 
average hourly emissions rate, rather than the default factor of 10, 
was used in the acute screening assessment.
    When worst-case HQ values from the initial acute screen step were 
less than 1, acute impacts were deemed negligible and no further 
analysis was performed. In cases where an acute HQ value from the 
screening step indicated the potential for acute risk, we further 
analyzed these values by considering additional site-specific data to 
develop a relatively more refined estimate of the potential for acute 
impacts of concern. This site-specific data includes the facility 
layout that was used to distinguish facility property from an area 
where the public could be exposed. These refinements are discussed in 
the Draft Residual Risk Assessment for the Primary Aluminum Production 
Source Category document, which is available in the docket for this 
proposed rulemaking.
    Ideally, we would prefer to have continuous measurements over time 
to see how the emissions vary by each hour over an entire year. Having 
a frequency distribution of hourly emission rates over a year would 
allow us to perform a probabilistic analysis to estimate potential 
threshold exceedances and their frequency of occurrence. Such an 
evaluation could include a more complete statistical treatment of the 
key parameters and elements adopted in this screening analysis. 
However, we recognize that having this level of data is rare, hence our 
use of the multiplier approach.
    To better characterize the potential health risks associated with 
estimated acute exposures to HAP, and in response to a key 
recommendation from the SAB's peer review of the EPA's RTR risk 
assessment methodologies,\13\ we generally examine a wider range of 
available acute health metrics than we do for our chronic risk 
assessments. This is in response to the SAB's acknowledgement that 
there are generally more data gaps and inconsistencies in acute 
reference values than there are in chronic reference values. 
Comparisons of the estimated maximum off-site 1-hour exposure levels 
are not typically made to occupational levels for the purpose of 
characterizing public health risks in RTR assessments. This is because 
they are developed for working-age adults and are not generally 
considered protective for the general public. We note that occupational 
ceiling values are, for most chemicals, set at levels higher than a 1-
hour AEGL-1.
---------------------------------------------------------------------------

    \13\ The SAB peer review of RTR Risk Assessment Methodologies is 
available at: http://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
---------------------------------------------------------------------------

4. Conducting Multi-Pathway Exposure and Risk Screening
    The potential for significant human health risks due to exposures 
via routes other than inhalation (i.e., multi-pathway exposures) and 
the potential for adverse environmental impacts were evaluated in a 
three-step process. In the first step, we determined whether any 
facilities emitted any PB-HAP (HAP known to be persistent and bio-
accumulative in the environment). There are 14 PB-HAP compounds or 
compound classes identified for this screening in the EPA's Air Toxics 
Risk Assessment Library (available at http://www.epa.gov/ttn/fera/risk_atra_vol1.html). They are cadmium compounds, chlordane, 
chlorinated dibenzodioxins and furans, 
dichlorodiphenyldichloroethylene, heptachlor, hexachlorobenzene, 
hexachlorocyclohexane, lead compounds, mercury compounds, methoxychlor, 
polychlorinated biphenyls, POM, toxaphene and trifluralin.
    Since POM is a PB-HAP and is emitted by all facilities in this 
source category, we proceeded to the second step of the evaluation to 
screen for potentially significant multi-pathway risks due to POM 
emissions. In this step, we determined whether the facility-specific 
emission rates of POM were large enough to create the potential for 
significant non-inhalation human or environmental risks under 
reasonable worst-case conditions. To facilitate this step, we have 
developed emission rate thresholds for each PB-HAP using a hypothetical 
worst-case screening exposure scenario developed for use in conjunction 
with the EPA's TRIM.FaTE model. The hypothetical screening scenario was 
subjected to a sensitivity analysis to ensure that its key design 
parameters were established such that environmental media 
concentrations were not underestimated (i.e., to minimize the 
occurrence of false negatives or results that suggest that risks might 
be acceptable when, in fact, actual risks are high) and to also 
minimize the occurrence of false positives for human health endpoints. 
We call this application of the TRIM.FaTE model TRIM-Screen. The 
facility-specific emission rates of POM were compared to the TRIM-
Screen emission threshold values for POM to assess the potential for 
significant human health risks or environmental risks via non-
inhalation pathways.
5. Assessing Risks Considering Emissions Control Options
    In addition to assessing baseline inhalation risks and screening 
for potential multi-pathway risks, where appropriate, we also estimated 
risks considering the potential emission reductions that would be 
achieved by the particular control options under consideration. In 
these cases, the expected emissions reductions were applied to the 
specific HAP and emissions sources in the source category dataset to 
develop corresponding estimates of risk reductions.
6. Conducting Other Risk-Related Analyses: Facility Wide Assessments
    To put the source category risks in context, for our residual risk 
reviews, we also typically examine the risks from the entire 
``facility,'' where the facility

[[Page 76271]]

includes all HAP-emitting operations within a contiguous area and under 
common control. In these facility wide assessments we examine the HAP 
emissions not only from the source category of interest, but also 
emissions of HAP from all other emissions sources at the facility. 
Eleven of the primary aluminum reduction plants are collocated with 
secondary aluminum production operations. Based on a general knowledge 
of these facilities, we believe that the Primary Aluminum sources are 
the largest sources of HAP emissions at each of them. Moreover, we plan 
to do a facility wide assessment for each of these eleven facilities in 
an upcoming RTR rulemaking for the Secondary Aluminum source category. 
Therefore, we did not perform a facility wide risk assessment for these 
eleven facilities as part of today's action. For the four primary 
aluminum facilities that are not collocated with secondary aluminum 
production operations, the risk assessment performed as part of today's 
action is a facility wide risk assessment.
7. Considering Uncertainties in Risk Assessment
    Uncertainty and the potential for bias are inherent in all risk 
assessments, including those performed for the Primary Aluminum source 
category addressed in this proposal. Although uncertainty exists, we 
believe that our approach, which used conservative tools and 
assumptions, ensures that our decisions are health-protective. A brief 
discussion of the uncertainties in the emissions datasets, dispersion 
modeling, inhalation exposure estimates and dose-response relationships 
follows below. A more thorough discussion of these uncertainties is 
included in the risk assessment documentation (referenced earlier) 
available in the docket for this action.
a. Uncertainties in the Emissions Datasets
    Although the development of the MACT dataset involved QA/quality 
control processes, the accuracy of emissions values will vary depending 
on the source of the data, the degree to which data are incomplete or 
missing, the degree to which assumptions made to complete the datasets 
are inaccurate, errors in estimating emissions values and other 
factors. The emission estimates considered in this analysis generally 
are annual totals for certain years that do not reflect short-term 
fluctuations during the course of a year or variations from year to 
year.
    The estimates of peak hourly emission rates for the acute effects 
screening assessment were based on a multiplication factor of 5 applied 
to the average annual hourly emission rate, which is intended to 
account for emission fluctuations due to normal facility operations.
b. Uncertainties in Dispersion Modeling
    While the analysis employed the EPA's recommended regulatory 
dispersion model, AERMOD, we recognize that there is uncertainty in 
ambient concentration estimates associated with any model, including 
AERMOD. In circumstances where we had to choose between various model 
options, where possible, model options (e.g., rural/urban, plume 
depletion, chemistry) were selected to provide an overestimate of 
ambient air concentrations of the HAP rather than underestimates. 
However, because of practicality and data limitation reasons, some 
factors (e.g., meteorology, building downwash) have the potential in 
some situations to overestimate or underestimate ambient impacts. For 
example, meteorological data were taken from a single year (1991), and 
facility locations can be a significant distance from the sites where 
these data were taken. Despite these uncertainties, we believe that at 
off-site locations and census block centroids, the approach considered 
in the dispersion modeling analysis should generally yield 
overestimates of ambient HAP concentrations.
c. Uncertainties in Inhalation Exposure
    The effects of human mobility on exposures were not included in the 
assessment. Specifically, short-term mobility and long-term mobility 
between census blocks in the modeling domain were not considered.\14\ 
The assumption of not considering short or long-term population 
mobility does not bias the estimate of the theoretical MIR, nor does it 
affect the estimate of cancer incidence since the total population 
number remains the same. It does, however, affect the shape of the 
distribution of individual risks across the affected population, 
shifting it toward higher estimated individual risks at the upper end 
and reducing the number of people estimated to be at lower risks, 
thereby increasing the estimated number of people at specific risk 
levels.
---------------------------------------------------------------------------

    \14\ Short-term mobility is movement from one micro-environment 
to another over the course of hours or days. Long-term mobility is 
movement from one residence to another over the course of a 
lifetime.
---------------------------------------------------------------------------

    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 further from the 
facility, and under-predict exposures for people in the census block 
who live closer to the facility. Thus, using the census block centroid 
to predict chronic exposures may lead to a potential understatement or 
overstatement of the true maximum impact, but it is an unbiased 
estimate of average risk and incidence.
    The assessments evaluate the cancer inhalation risks associated 
with continuous pollutant exposures over a 70-year period, which is the 
assumed lifetime of an individual. In reality, both the length of time 
that modeled emissions sources at facilities actually operate (i.e., 
more or less than 70 years) and the domestic growth or decline of the 
modeled industry (i.e., the increase or decrease in the number or size 
of United States facilities) will influence the risks posed by a given 
source category. Depending on the characteristics of the industry, 
these factors will, in most cases, result in an overestimate both in 
individual risk levels and in the total estimated number of cancer 
cases. However, in rare cases, where a facility maintains or increases 
its emission levels beyond 70 years, residents live beyond 70 years at 
the same location, and the residents spend most of their days at that 
location, then the risks could potentially be underestimated. Annual 
cancer incidence estimates from exposures to emissions from these 
sources would not be affected by uncertainty in the length of time 
emissions sources operate.
    The exposure estimates used in these analyses assume chronic 
exposures to ambient levels of pollutants. Because most people spend 
the majority of their time indoors, actual exposures may not be as 
high, depending on the characteristics of the pollutants modeled. For 
many of the HAP, indoor levels are roughly equivalent to ambient 
levels, but for very reactive pollutants or larger particles, these 
levels are typically lower. This factor has the potential to result in 
an overstatement of 25 to 30 percent of exposures.\15\
---------------------------------------------------------------------------

    \15\ 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 other factors specific to the acute exposure assessment. The 
accuracy of an acute inhalation exposure assessment depends on the 
simultaneous

[[Page 76272]]

occurrence of independent factors that may vary greatly, such as hourly 
emissions rates, meteorology, and human activity patterns. In this 
assessment, we assume that individuals remain for 1 hour at the point 
of maximum ambient concentration as determined by the co-occurrence of 
peak emissions and worst-case meteorological conditions. These 
assumptions would tend to overestimate actual exposures since it is 
unlikely that a person would be located at the point of maximum 
exposure during the time of worst-case impact.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and noncancer effects from both chronic and acute 
exposures. Some uncertainties may be considered quantitatively, and 
others generally are expressed in qualitative terms. We note as a 
preface to this discussion a point on dose-response uncertainty that is 
brought out in the EPA 2005 Cancer Guidelines; namely, that ``the 
primary goal of the EPA actions is protection of human health; 
accordingly, as an agency policy, risk assessment procedures, including 
default options that are used in the absence of scientific data to the 
contrary, should be health protective.'' (EPA 2005 Cancer Guidelines, 
pages 1-7.) This is the approach followed here as summarized in the 
next several paragraphs. A complete detailed discussion of 
uncertainties and variability in dose-response relationships is given 
in the residual risk documentation, which is available in the docket 
for this action.
    Cancer URE values used in our risk assessments are those that have 
been developed to generally provide an upper bound estimate of risk. 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit).\16\ In some circumstances, the true risk could be as 
low as zero; however, in other circumstances, the risk could also be 
greater.\17\ When developing an upper bound estimate of risk and to 
provide risk values that do not underestimate risk, health-protective 
default approaches are generally used. To err on the side of ensuring 
adequate health-protection, the EPA typically uses the upper bound 
estimates rather than lower bound or central tendency estimates in our 
risk assessments, an approach that may have limitations for other uses 
(e.g., priority-setting or expected benefits analysis).
---------------------------------------------------------------------------

    \16\ IRIS glossary (http://www.epa.gov/NCEA/iris/help_gloss.htm).
    \17\ An exception to this is the URE for benzene, which is 
considered to cover a range of values, each end of which is 
considered to be equally plausible and which is based on maximum 
likelihood estimates.
---------------------------------------------------------------------------

    Chronic noncancer reference (RfC and reference dose (RfD)) values 
represent chronic exposure levels that are intended to be health-
protective levels. Specifically, these values provide an estimate (with 
uncertainty spanning perhaps an order of magnitude) of daily oral 
exposure (RfD) or of a continuous inhalation exposure (RfC) to the 
human population (including sensitive subgroups) that is likely to be 
without an appreciable risk of deleterious effects during a lifetime. 
To derive values that are intended to be ``without appreciable risk,'' 
the methodology relies upon an uncertainty factor (UF) approach (U.S. 
EPA, 1993, 1994) which includes consideration of both uncertainty and 
variability. When there are gaps in the available information, UF are 
applied to derive reference values that are intended to protect against 
appreciable risk of deleterious effects. The UF are commonly default 
values,\18\ e.g., factors of 10 or 3, used in the absence of compound-
specific data; where data are available, UF may also be developed using 
compound-specific information. When data are limited, more assumptions 
are needed and more UF are used. Thus, there may be a greater tendency 
to overestimate risk in the sense that further study might support 
development of reference values that are higher (i.e., less potent) 
because fewer default assumptions are needed. However, for some 
pollutants, it is possible that risks may be underestimated. While 
collectively termed ``uncertainty factor,'' these factors account for a 
number of different quantitative considerations when using observed 
animal (usually rodent) or human toxicity data in the development of 
the RfC. The UF are intended to account for: (1) Variation in 
susceptibility among the members of the human population (i.e., inter-
individual variability); (2) uncertainty in extrapolating from 
experimental animal data to humans (i.e., interspecies differences); 
(3) uncertainty in extrapolating from data obtained in a study with 
less-than-lifetime exposure (i.e., extrapolating from sub-chronic to 
chronic exposure); (4) uncertainty in extrapolating the observed data 
to obtain an estimate of the exposure associated with no adverse 
effects; and (5) uncertainty when the database is incomplete or there 
are problems with the applicability of available studies. Many of the 
UF used to account for variability and uncertainty in the development 
of acute reference values are quite similar to those developed for 
chronic durations, but they more often use individual UF values that 
may be less than 10. UF are applied based on chemical-specific or 
health effect-specific information (e.g., simple irritation effects do 
not vary appreciably between human individuals, hence a value of 3 is 
typically used), or based on the purpose for the reference value (see 
the following paragraph). The UF applied in acute reference value 
derivation include: (1) Heterogeneity among humans; (2) uncertainty in 
extrapolating from animals to humans; (3) uncertainty 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).
---------------------------------------------------------------------------

    \18\ According to the NRC report, Science and Judgment in Risk 
Assessment (NRC, 1994) ``[Default] options are generic approaches, 
based on general scientific knowledge and policy judgment, that are 
applied to various elements of the risk assessment process when the 
correct scientific model is unknown or uncertain.'' The 1983 NRC 
report, Risk Assessment in the Federal Government: Managing the 
Process, defined default option as ``the option chosen on the basis 
of risk assessment policy that appears to be the best choice in the 
absence of data to the contrary'' (NRC, 1983a, p. 63). Therefore, 
default options are not rules that bind the Agency; rather, the 
Agency may depart from them in evaluating the risks posed by a 
specific substance when it believes this to be appropriate. In 
keeping with EPA's goal of protecting public health and the 
environment, default assumptions are used to ensure that risk to 
chemicals is not underestimated (although defaults are not intended 
to overtly overestimate risk). See EPA, 2004, An Examination of EPA 
Risk Assessment Principles and Practices, EPA/100/B-04/001 available 
at: http://www.epa.gov/osa/pdfs/ratf-final.pdf.
---------------------------------------------------------------------------

    Not all acute reference values are developed for the same purpose, 
and care must be taken when interpreting the results of an acute 
assessment of human health effects relative to the reference value or 
values being exceeded. Where relevant to the estimated exposures, the 
lack of short-term dose-response values at different levels of severity 
should be factored into the risk characterization as potential 
uncertainties.
    Although every effort is made to identify peer-reviewed reference 
values for cancer and noncancer effects for all pollutants emitted by 
the sources included in this assessment, some HAP

[[Page 76273]]

continue to have no reference values for cancer or chronic noncancer or 
acute effects. Since exposures to these pollutants cannot be included 
in a quantitative risk estimate, an understatement of risk for these 
pollutants at environmental exposure levels is possible. For a group of 
compounds that are either unspeciated or do not have reference values 
for every individual compound (e.g., glycol ethers), we conservatively 
use the most protective reference value to estimate risk from 
individual compounds in the group of compounds.
    Additionally, chronic reference values for several of the compounds 
included in this assessment are currently under the EPA IRIS review, 
and revised assessments may determine that these pollutants are more or 
less potent than the current value. We may re-evaluate residual risks 
for the final rulemaking if these reviews are completed prior to our 
taking final action for this source category and a dose-response metric 
changes enough to indicate that the risk assessment supporting this 
notice may significantly understate human health risk.
e. Uncertainties in the Multi-Pathway and Environmental Effects 
Screening Assessment
    We generally assume that when exposure levels are not anticipated 
to adversely affect human health, they also are not anticipated to 
adversely affect the environment. For each source category, we 
generally rely on the site-specific levels of PB-HAP emissions to 
determine whether a full assessment of the multi-pathway and 
environmental effects is necessary. For this source category, we only 
performed a multi-pathway screening assessment for PB-HAP. Thus, it is 
important to note that potential PB-HAP multi-pathway risks are biased 
high.

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

    In evaluating and developing standards under section 112(f)(2), as 
discussed in section I.A of this preamble, we apply a two-step process 
to address residual risk. In the first step, the EPA determines whether 
risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) 
\19\ of approximately 1-in-10 thousand [i.e., 100-in-1 million]'' (54 
FR 38045). In the second step of the process, the EPA sets the standard 
at a level that provides an ample margin of safety ``in consideration 
of all health information, including the number of persons at risk 
levels higher than approximately 1-in-1 million, as well as other 
relevant factors, including costs and economic impacts, technological 
feasibility, and other factors relevant to each particular decision'' 
(Id.)
---------------------------------------------------------------------------

    \19\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk were an individual exposed to the maximum level 
of a pollutant for a lifetime.
---------------------------------------------------------------------------

    In past residual risk actions, the EPA has presented and considered 
a number of human health risk metrics associated with emissions from 
the category under review, including: The MIR; the numbers of persons 
in various risk ranges; cancer incidence; the maximum non-cancer hazard 
index (HI); and the maximum acute non-cancer hazard (72 FR 25138, May 
3, 2007; 71 FR 42724, July 27, 2006). In more recent proposals (75 FR 
65068, October 21, 2010, and 75 FR 80220, December 21, 2010), the EPA 
also presented and considered additional measures of health 
information, such as estimates of the risks associated with the maximum 
level of emissions which might be allowed by the current MACT standards 
(see, e.g., 75 FR 65068, October 21, 2010, and 75 FR 80220, December 
21, 2010). The EPA also discussed and considered risk estimation 
uncertainties. The EPA is providing this same type of information in 
support of the proposed actions described in this Federal Register 
notice.
    The agency is considering all available health information to 
inform our determinations of risk acceptability and ample margin of 
safety under CAA section 112(f). Specifically, as explained in the 
Benzene NESHAP, ``the first step judgment on acceptability cannot be 
reduced to any single factor'' and thus ``[t]he Administrator believes 
that the acceptability of risk under [previous] section 112 is best 
judged on the basis of a broad set of health risk measures and 
information'' (54 FR 38046). Similarly, with regard to making the ample 
margin of safety determination, as stated in the Benzene NESHAP ``[in 
the ample margin decision, the agency again considers all of the health 
risk and other health information considered in the first step. Beyond 
that information, additional factors relating to the appropriate level 
of control will also be considered, including cost and economic impacts 
of controls, technological feasibility, uncertainties, and any other 
relevant factors.'' Id.
    The agency acknowledges that the Benzene NESHAP provides 
flexibility regarding what factors the EPA might consider in making 
determinations and how these factors might be weighed for each source 
category. In responding to comment on our policy under the Benzene 
NESHAP, the EPA explained that: ``The policy chosen by the 
Administrator permits consideration of multiple measures of health 
risk. Not only can the MIR figure be considered, but also incidence, 
the presence of non-cancer health effects, and the uncertainties of the 
risk estimates. In this way, the effect on the most exposed individuals 
can be reviewed as well as the impact on the general public. These 
factors can then be weighed in each individual case. This approach 
complies with the Vinyl Chloride mandate that the Administrator 
ascertain an acceptable level of risk to the public by employing [her] 
expertise to assess available data. It also complies with the 
Congressional intent behind the CAA, which did not exclude the use of 
any particular measure of public health risk from the EPA's 
consideration with respect to CAA section 112 regulations, and, 
thereby, implicitly permits consideration of any and all measures of 
health risk which the Administrator, in [her] judgment, believes are 
appropriate to determining what will `protect the public health' '' (54 
FR 38057).
    Thus, the level of the MIR is only one factor to be weighed in 
determining acceptability of risks. The Benzene NESHAP explained that 
``an MIR of approximately 1-in-10 thousand should ordinarily be the 
upper end of the range of acceptability. As risks increase above this 
benchmark, they become presumptively less acceptable under CAA section 
112, and would be weighed with the other health risk measures and 
information in making an overall judgment on acceptability. Or, the 
agency may find, in a particular case, that a risk that includes MIR 
less than the presumptively acceptable level is unacceptable in the 
light of other health risk factors'' (Id. at 38045). Similarly, with 
regard to the ample margin of safety analysis, the EPA stated in the 
Benzene NESHAP that: ``* * * the EPA believes the relative weight of 
the many factors that can be considered in selecting an ample margin of 
safety can only be determined for each specific source category. This 
occurs mainly because technological and economic factors (along with 
the health-related factors) vary from source category to source 
category'' (Id. at 38061).

D. How did we perform the technology review?

    Our technology review focused on the identification and evaluation 
of developments in practices, processes, and control technologies that 
have

[[Page 76274]]

occurred since the Primary Aluminum Reduction Plant NESHAP was 
promulgated.
    Based on our analyses of the data and information collected from 
industry and the trade organization representing all facilities subject 
to the NESHAP, our general understanding of the industry, and other 
available information in the literature on potential controls for this 
industry, we identified no new developments in practices, processes, 
and control technologies. For the purpose of this exercise, we 
considered any of the following to be a ``development'':
     Any add-on control technology or other equipment that was 
not identified and considered during development of the 1997 Primary 
Aluminum Reduction Plant NESHAP.
     Any improvements in add-on control technology or other 
equipment (that were identified and considered during development of 
the 1997 Primary Aluminum Reduction Plant NESHAP) that could result in 
significant additional emissions reduction.
     Any work practice or operational procedure that was not 
identified or considered during development of the 1997 Primary 
Aluminum Reduction Plant NESHAP.
     Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during development of the 1997 Primary 
Aluminum Reduction Plant NESHAP.
    We also consulted the EPA's RACT/BACT/LAER Clearinghouse (RBLC) to 
identify potential technology advances. Control technologies classified 
as RACT (Reasonably Available Control Technology), BACT (Best Available 
Control Technology), or LAER (Lowest Achievable Emissions Rate) apply 
to stationary sources depending on whether the sources exist or new and 
on the size, age, and location of the facility. BACT and LAER (and 
sometimes RACT) are determined on a case-by-case basis, usually by 
State or local permitting agencies. The EPA established the RBLC to 
provide a central database of air pollution technology information 
(including technologies required in source-specific permits) to promote 
the sharing of information among permitting agencies and to aid in 
identifying future possible control technology options that might apply 
broadly to numerous sources within a category or apply only on a 
source-by-source basis. The RBLC contains over 5,000 air pollution 
control permit determinations that can help identify appropriate 
technologies to mitigate many air pollutant emissions streams. We 
searched this database to determine whether it contained any practices, 
processes, or control technologies for the types of processes covered 
by the Primary Aluminum Reduction Plant NESHAP. No such practices, 
processes, or control technologies were identified in this database.

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

    In addition to the analyses described above, we also reviewed other 
aspects of the MACT standards for possible revision as appropriate and 
necessary. Based on this review we have identified aspects of the MACT 
standards that we believe need revision.
    This includes proposing revisions to the startup, shutdown and 
malfunction (SSM) provisions of the MACT rule in order to ensure that 
they are consistent with a recent court decision in Sierra Club v. EPA, 
551 F. 3d 1019 (DC Cir. 2008). In addition, we are proposing other 
changes to the rule which are not based on residual risk. These include 
establishing MACT floor-based standards for POM emissions from prebake 
potlines, COS emissions from all potlines, and design standards for 
control of POM emissions from existing pitch storage tanks. We are also 
proposing changes to the rule related to affirmative defense for 
exceedance of an emission limit during a malfunction. The analyses and 
proposed decisions for these actions are presented in section IV of 
this preamble.

IV. Analytical Results and Proposed Decisions

    This section of the preamble provides the results of our RTR for 
the Primary Aluminum Reduction Plant source category and our proposed 
decisions concerning changes to the Primary Aluminum Reduction Plant 
NESHAP.

A. What are the results of our analyses and proposed decisions 
regarding unregulated emissions sources?

    The current MACT rule has no standards for POM from prebake 
potlines. Prebake facilities have significantly lower POM emissions 
compared to Soderberg facilities. Nevertheless, these emissions are not 
negligible. We are proposing to establish MACT emission limits for POM 
from prebake potlines in this action. The typical controls used on 
these prebake potlines to limit the primary (i.e., stack) emissions, 
and which reflect the MACT floor level of control, are dry alumina 
scrubbers (with a baghouse). We calculated MACT floor limits for these 
potlines based on the limited available data. We also considered 
possible controls beyond the MACT floor, such as wet roof scrubbers, 
but we estimated that these beyond-the-floor controls would only 
achieve approximately an additional 30 percent reduction in secondary 
(i.e., roof vent) emissions and that the costs of these additional 
controls would be quite high (e.g., well over $100 million in capital 
costs for the industry). We estimate that the cost of controlling POM 
from prebake potroom secondary emissions would be approximately 
$800,000 per ton. Therefore, we are proposing emission limits for POM 
from prebake potlines, after considering variability in emissions using 
a 99% upper prediction level approach, based on the MACT floor. We are 
proposing a POM emission limit for new prebake potlines equal to the 
lowest limit for existing prebake potlines (developed from data 
obtained from the best performing sources (center-worked prebake one) 
facilities). More details about the data and analyses used to derive 
the MACT limits, and explanation of the beyond-the-floor analyses, are 
provided in the technical document Draft MACT Floor Analysis for the 
Primary Aluminum Production Source Category which is available in the 
docket for this proposed action. The proposed limits for prebake 
potlines are shown in Table 5.

 Table 5--Proposed Emission Limits for New and Existing Prebake Potlines
------------------------------------------------------------------------
            Source                  Pollutant          Emission limit
------------------------------------------------------------------------
Existing Prebake:
    CWPB1 potlines............  POM..............  0.31 kg/Mg (0.62 lb/
                                                    ton) of aluminum
                                                    produced.
    CWPB2 potlines............  POM..............  0.65 kg/Mg (1.3 lb/
                                                    ton) of aluminum
                                                    produced.
    CWPB3 potlines............  POM..............  0.63 kg/Mg (1.26 lb/
                                                    ton) of aluminum
                                                    produced.
    SWPB potlines:............  POM..............  0.33 kg/Mg (0.65 lb/
                                                    ton) of aluminum
                                                    produced.
New Prebake:

[[Page 76275]]

 
    All prebake potline types.  POM..............  0.31 kg/Mg (0.62 lb/
                                                    ton) of aluminum
                                                    produced.
------------------------------------------------------------------------

    As mentioned above, the current MACT rule has no standards for COS. 
It is very difficult and quite expensive to measure total COS emissions 
because the concentrations of secondary emissions are below the 
detection limit of the EPA reference method. However, stack tests are 
feasible and have been completed. Moreover, emissions studies have been 
completed using an experimental test method to estimate COS emissions 
from these secondary emissions sources (Determination of COS to 
SO2 Ratio in Smelting Process Emissions at the Alcoa Warrick 
Operations, 4 August 1995). We have been able to use the experimental 
test results along with stack test data and data on sulfur content of 
input materials to estimate total COS emissions. We have determined 
that there is a direct relationship between the COS emissions and the 
sulfur content of raw materials. The results of these studies indicate 
that an estimated 8 percent of the sulfur present in the coke (used to 
make anodes) is converted to COS emissions.
    Given the technical difficulties of measuring secondary COS 
emissions directly, and given that there is a direct relationship 
between sulfur content of input materials and COS emissions, we 
developed a mass balance equation for calculating COS emissions. Using 
this approach, we developed a proposed MACT standard for COS using the 
mass balance equation. The equation derives monthly COS emission rates 
based on anode coke sulfur content, anode consumption and aluminum 
production, as follows:
[GRAPHIC] [TIFF OMITTED] TP06DE11.005

Where:

ECOS = the facility wide emission rate of COS during the 
calendar month in pounds per ton of aluminum produced;
K = factor accounting for molecular weights and conversion of sulfur 
to carbonyl sulfide = 234;
Y = the tons of anode used at the facility during the calendar 
month;
Z = the tons of aluminum produced at the facility during the 
calendar month; and
%S = the weighted average sulfur content of the anode coke utilized 
in the production of aluminum during the calendar month (e.g., if 
the weighted average sulfur content of the anode coke utilized 
during the calendar month was 2.5%, then %S = 0.025).

    Using this method, we are proposing a MACT floor limit for COS for 
existing facilities at 3.9 pounds of COS per ton of aluminum produced 
(lb/ton Al), based on data obtained from the five facilities with the 
lowest calculated COS emissions and adjustment to account for 
variability using a 99% upper prediction limit approach. With regard to 
costs for this standard, we estimate that all facilities will be able 
to meet this limit with minimal additional costs (e.g., calculating COS 
emissions and the associated monitoring, recordkeeping and reporting). 
With regard to new sources, the MACT floor limit for COS for new 
facilities is proposed at 3.1 lb COS/ton Al, based on data obtained 
from the facility with the lowest calculated COS emissions and 
adjustment to account for variability.
    We also considered beyond-the-floor options for COS. For example, 
we assessed the feasibility and costs of proposing that all existing 
facilities meet a limit of 3.1 lb COS/ton Al. We estimate that a limit 
at this level would impact 5 facilities, result in 220 tpy reductions 
of COS emissions, at a total cost of $13,000,000 (or $2.6 million per 
facility) per year. However, there are significant uncertainties 
regarding the future availability and costs of the associated lower-
sulfur anode coke. The Primary Aluminum industry obtains most of their 
coke as a by-product from the gas and oil refinery industry. It is our 
understanding that currently available coke with low sulfur contents 
could be very hard to obtain in the future and will likely be much more 
expensive. This situation is expected due to the following: (1) The 
type of crude oil input at refineries in the future is generally 
expected to be heavier and, therefore, less likely to result in ``anode 
grade coke'' that has the structure necessary for use in anode 
production; (2) the type of crude oil input at refineries in the future 
is generally expected to have higher sulfur content because the per 
barrel cost of heavy sour (i.e., high-sulfur) crude oil is so much 
lower than light sweet (i.e., low-sulfur) crude oil; (3) refineries 
initially designed to process light sweet crude oil are being converted 
to process heavy sour crude oil at a rapid pace worldwide due to 
refinery economics; (4) refineries are designed to desulfurize the 
product streams (gasoline, diesel, etc.), not the crude oil input, and 
the sulfur in the crude oil tends to concentrate in the petroleum coke 
(i.e., the ``bottoms''); (5) unwillingness of refineries to 
preferentially process light sweet crude oil in place of heavy sour 
crude oil due to unfavorable economics (i.e., refineries will not 
modify their operations to change the quality of a by-product such as 
petroleum coke); and (6) the lack of leverage that primary aluminum 
companies have over the quality of this by-product, as coke is a very 
low profit item for refineries and anode grade coke represents less 
than 20% of all the petroleum coke produced worldwide. Thus, based on 
future availability of low-sulfur coke, the true long term costs could 
exceed the present estimated cost of $13,000,000 per year.
    We also evaluated the feasibility and costs of another beyond-the-
floor option of requiring that all existing facilities meet a limit of 
3.5 lb COS/ton Al. We estimate that a limit at this level would impact 
2 facilities, result in 52 tpy reductions of COS emissions, at a total 
cost of $2,000,000 (or $1 million per facility) per year. Once again, 
these estimated costs could be significant underestimates of the true 
long-term costs. The uncertainties and concerns about the future 
availability and costs of the required low-sulfur content coke that are 
described above for the 3.1 lb COS/ton Al option are also a concern for 
this 3.5 lb COS/ton Al option.
    We also considered control options including incineration and 
scrubbing of COS. The cost of incineration would be quite high due to 
the volume (typically millions of cubic feet per minute) and the 
relatively low temperature of the exhaust stream (typically less than 
200 [deg]F). Incineration also involves the disadvantage of the 
generation of sulfur dioxide and other pollutants. Similarly, the cost 
of scrubbers would be quite high and involve the disadvantage of 
generating a waste sludge stream.
    Given the analyses and conclusions described above, we are 
proposing a MACT standard for COS for existing facilities based on the 
MACT floor analysis, which is a limit of 3.9 lb COS/ton Al. With regard 
to new sources, we are proposing a MACT standard for COS based on the 
MACT floor analysis, which is a limit of 3.1 lb COS/ton Al.
    With regard to POM emissions from pitch storage tanks, the 1997 
NESHAP included MACT standards for new pitch

[[Page 76276]]

storage tanks, which required a 95 percent reduction in POM emissions. 
However, the 1997 NESHAP had no limits for existing storage tanks. We 
are proposing in today's action that existing tanks will be subject to 
the same standard (i.e., minimum of 95 percent reduction of POM 
emissions). At least three facilities are currently achieving this 
level of control. We estimate that eight facilities would be affected 
by this standard and would need to add controls, at a total annualized 
cost of about $21,000 per facility. We also estimate that this would 
achieve 1.6 tons reductions in POM emissions per year.
    A non-contact single stage, refrigerated, water cooled condenser 
system was considered as a beyond the floor option for POM from pitch 
storage tanks. However, we believe the associated cost (estimated at 
$184,000 per year, per facility) is not justified by the incremental 
control of HAP (estimated at 0.081 tons per year for the industry).

B. What are the results of the risk assessments?

    For the Primary Aluminum source category, we conducted an 
inhalation risk assessment for all HAP emitted. We also conducted 
multi-pathway screening analyses for PB-HAP emitted (i.e., POM). 
Results of the risk assessment are presented briefly below and in more 
detail in the residual risk documentation referenced in section III of 
this preamble, which is available in the docket for this action.
    Table 6 of this preamble provides an overall summary of the results 
of the inhalation risk assessment.

                                      Table 6--Primary Aluminum Reduction Plant Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Maximum individual cancer risk (in 1 million) \1\        Estimated                 Maximum chronic non-cancer
----------------------------------------------------------  population     Estimated            TOSHI \2\
                                                           at increased     annual    ----------------------------
                                               Based on       risk of       cancer       Based on      Based on         Worst-case  maximum refined
      Based on actual emissions level          allowable   cancer  >=1-    incidence      actual       allowable     screening acute non-cancer HQ \3\
                                               emissions       in-1       (cases per     emissions     emissions
                                               level 4 5      million        year)         level         level
--------------------------------------------------------------------------------------------------------------------------------------------------------
30.........................................          100        41,000         0.005           0.4           0.6   HQREL 10 (HF)
                                                                                                                   HQAEGL-1
                                                                                                                   4 (HF)
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\2\ Maximum TOSHI. The target organ with the highest TOSHI for the primary aluminum source category is the skeletal system.
\3\ See section III.B of this preamble for explanations of acute dose-response values.
\4\ The facility with the highest MIR based on allowable emissions is the Columbia Falls facility. Notably, this facility has not operated in
  approximately 2 years and therefore, the EPA did not generate risk estimates (i.e., MIR, TOSHI, and acute screening values) based on actual emissions
  for this facility.
\5\ The highest MIR based on allowable emissions from an operating facility is estimated to be up to 50 in one million, for the operating Soderberg
  facility.

    The results of the chronic inhalation cancer risk assessment 
indicate that, based on estimates of current actual emissions, the 
maximum individual lifetime cancer risk (MIR) could be up to 30 in one 
million, with emissions of POM \20\ primarily from potline roof vents 
(secondary emissions) and anode bake furnaces driving these risks. The 
highest MIR of up to 30 in one million based on actual emissions is due 
to POM emissions from the one currently operating Soderberg facility. 
The highest MIR due to actual emissions from prebake facilities was 
estimated to be up to 20 in one million; the next highest MIR for an 
operating prebake facility is estimated to be up to 6 in one million. 
The total estimated cancer incidence from this source category based on 
actual emission levels is 0.005 excess cancer cases per year or one 
case in every 200 years, with emissions of POM contributing 
approximately 99 percent to this cancer incidence. In addition, we note 
that approximately 41,000 people are estimated to have cancer risks 
greater than 1 in one million, and approximately 900 people are 
estimated to have risks greater than 10 in one million. When 
considering the risks associated with MACT-allowable emissions, the MIR 
could be up to 100 in one million if the Columbia Falls facility (a 
Soderberg type facility) were to resume its primary aluminum operations 
(see note 4 on Table 6). The MIR based on allowable emissions from the 
one currently operating Soderberg facility (Massena East facility) was 
up to 50 in one million. The highest MIR based on allowable emissions 
from any of the prebake facilities was up to 30 in one million.
---------------------------------------------------------------------------

    \20\ Most all POM emitted by this source category are PAHs.
---------------------------------------------------------------------------

    The maximum modeled chronic non-cancer TOSHI value is 0.4 based on 
actual emissions, driven primarily by HF emissions. When considering 
MACT allowable emissions, the maximum chronic non-cancer TOSHI value 
could be up to 0.6. For this source category, there were two HAP that 
had relevant acute health effect screening values: Carbonyl sulfide 
(COS) and hydrofluoric acid (HF). Acute health effect screening is 
performed using actual emissions data. The Columbia Falls facility has 
not operated in about 2 years and has not operated at capacity since 
about 1999. Therefore, suitable actual emission data was not available 
for this facility and its acute health effects are not included in this 
discussion. Further, the carbon-only prebake anode production facility 
does not emit COS or HF. Therefore, this discussion addresses the acute 
health effects of only the 13 remaining facilities subject to this 
NESHAP. With respect to COS, we did not find any potential for acute 
health concerns for the 13 facilities based on their actual emissions. 
However, HF emissions did not screen out with respect to potential 
acute health effects. The highest refined worst-case HQ for HF based on 
a REL is 10, based on an AEGL-1 is 4, and based on an ERPG-1 is 2. 
Moreover, 8 of the 13 facilities show the potential for worst-case 
acute HQ values greater than 1 based on the REL, 4 of the 13 facilities 
show the potential for worst-case acute HQ values greater than 1 based 
on the AEGL-1 and 4 of the 13 facilities show the potential for worst-
case acute HQ values greater than or equal to 1 based on the ERPG-
1.\21\ Nevertheless, it is

[[Page 76277]]

important to note that all the worst-case acute HQs are based on 
conservative assumptions (e.g., worst-case meteorology coinciding with 
peak short-term one-hour emissions from each emission point, with a 
person located at the point of maximum concentration during that hour).
---------------------------------------------------------------------------

    \21\ Individual facility acute HQ values for all facilities can 
be found in Appendix 5, Table 4, of the risk assessment document 
that is included in the docket for this proposed rulemaking. Acute 
HQ values exceeding a value of 1 based on the REL were as follows: 
10, 10, 9, 9, 5, 3, 2 and 2. Acute HQ values greater than a value of 
1 based on the AEGL-1 were as follows: 4, 4, 3 and 3. Acute HQ 
values greater than or equal to a value of 1 based on the ERPG-1 
were as follows: 2, 2, 1 and 1.
---------------------------------------------------------------------------

    In addition to the analyses presented above, to screen for 
potential multi-pathway effects from emissions of POM, we compared the 
estimated actual PAH emission rates from 14 facilities in this source 
category to the multi-pathway screening rate for PAHs described in 
section III.B. Results of this worst-case screen estimate that actual 
PAH emissions from all 14 facilities exceed the PAH multi-pathway 
screening rate. With respect to these exceedances of the worst-case 
multi-pathway screening rate for PAHs, we note that this only indicates 
the potential for multi-pathway-related cancer risks of concern from 
PAHs. Moreover, due to data limitations, we were not able to refine our 
multi-pathway analysis beyond the screening assessment. Thus, we note 
that these results are biased high for purposes of screening and are 
subject to significant uncertainties. As such, they do not necessarily 
indicate that multi-pathway risks from POM are significant, only that 
we cannot rule out the possibility that they might be significant.

C. What are our proposed decisions regarding risk acceptability and 
ample margin of safety?

1. Risk Acceptability
    As noted in section III.C of this preamble, we weigh all health 
risk factors in our risk acceptability determination, including the 
MIR, the numbers of persons in various risk ranges, cancer incidence, 
the maximum noncancer HI, the maximum acute noncancer hazard, the 
extent of noncancer risks, the potential for adverse environmental 
effects, distribution of risks in the exposed population, and risk 
estimation uncertainties (54 FR 38044, September 14, 1989).
    For the Primary Aluminum Reduction source category, the risk 
analysis we performed indicates that the cancer risk to the individual 
most exposed due to actual emissions is well below 100 in one million, 
and the cancer incidence is low (1 case in every 200 years). The 
potential risks due to allowable emissions are higher with an estimated 
MIR of up to 100 in one million which is the presumptive upper limit of 
acceptable risk.
    With regard to noncancer risks, the analysis indicates that chronic 
noncancer health risks are negligible due to both actual and allowable 
emissions. The assessment of potential acute noncancer effects 
(described in the previous section) suggests that there may be 
potential for some acute risks due to HF emissions with worst-case HQs 
up to 10 (based on the REL). In characterizing the potential for acute 
noncancer impacts of concern, it is important to remember the upward 
bias of these worst-case exposure estimates and to consider the results 
along with the rather large uncertainties related to the emissions 
estimates and screening methodology.
    With regard to multi-pathway exposures and risks, results of the 
screening analysis indicate that actual PAH emissions from all the 
facilities exceed the worst-case multi-pathway screening rate for PAHs, 
indicating the potential for possible multi-pathway-related cancer 
risks of concern from PAHs. We note that these screening results do not 
necessarily indicate that significant multi-pathway risks actually 
exist at primary aluminum facilities, only that we cannot rule them out 
as a possibility.
    Overall, in determining whether risk is acceptable, we considered 
all the available health risk information, as described above. In this 
case, because the MIRs due to actual emissions are well below 100-in-1 
million risk, and since the one facility that could pose possible risks 
due to allowable emissions of up to 100 in one million is not 
operating, and because a number of other factors indicate relatively 
low risk concern (e.g., low cancer incidence and low potential for 
chronic noncancer risks), and given the conservative, worst-case 
screening level characteristics of the acute and multi-pathway 
assessments, and various uncertainties, we are proposing to determine 
that the risks due to HAP emissions from this source category are 
acceptable.
2. Ample Margin of Safety Analysis
    We next considered whether the existing MACT standard provides an 
ample margin of safety (AMOS). Under the ample margin of safety 
analysis, we evaluate the cost and feasibility of available control 
technologies and other measures (including the controls, measures and 
costs reviewed under the technology review) that could be applied in 
this source category to further reduce the risks (or potential risks) 
due to emissions of HAP identified in our risk assessment, along with 
all of the health risks and other health information considered in the 
risk acceptability determination described above.
    First, we evaluated the feasibility to reduce the potential risks 
due to allowable POM emissions from Soderberg facilities. As described 
above, the potential cancer MIR from Soderberg facilities is estimated 
to be up to 100 in one million due to allowable emissions. These risks 
are driven by POM emissions from a Soderberg facility within the 
vertical stud Soderberg (VSS2) subcategory. The current emissions limit 
(from the 2005 NESHAP amendments) for POM from potlines in this VSS2 
subcategory is 2.85 kg of POM per Mg of Aluminum produced (2.85 kg/Mg, 
or 5.7 lbs/ton). Based on site-specific emissions data submitted by the 
company in early 2008 for this facility, the estimated actual emissions 
from this facility were about 2 lbs/ton during the most recent years of 
operation (see Document EPA-HQ-OAR-2002-0031-0029, which is available 
in the docket for this rulemaking).
    After considering variability in emissions, which is appropriate 
for establishing MACT limits (as described in section III.A above), we 
calculated, using a 99% upper prediction level approach, that an 
emissions limit of 3.8 lbs/ton could be achieved by this facility 
without any additional controls and therefore no additional costs. This 
would result in a reduction of approximately 33 percent for the 
allowable emissions from VSS2 potlines, and would reduce the potential 
cancer MIR due to allowable emissions to about 70 in one million. We 
also evaluated potential controls to reduce these risks further (such 
as requiring wet roof scrubbers). We determined that these controls 
would be quite costly (approximately $4 million per ton of organic 
HAP), with estimated capital costs of about $40 million for this 
facility, and would only achieve about an additional 9.6 tons of HAP 
per year (30 percent) reduction in POM emissions. These controls and 
costs are described in more detail below.
    We also evaluated the POM emissions from the one operating 
Soderberg facility (which is in the HSS subcategory) as part of our 
AMOS analyses. Based on the risk assessment, we estimated that this 
facility posed a cancer MIR of up to 30 in one million based on actual 
emissions and an MIR of up to 50 in one million based on allowable 
emissions. The current

[[Page 76278]]

emissions limit for POM from potlines for this HSS subcategory is 2.35 
kg/Mg (or 4.7 lbs/ton). Based on site specific emissions data for this 
facility, the actual emissions from this facility are estimated to be 
about 1.5 lbs/ton. After considering variability in emissions, we 
determined that an emissions limit of 3.0 lbs/ton could be achieved by 
this facility with no additional controls and, therefore, no additional 
costs. This would result in a reduction of approximately 36 percent for 
the allowable emissions from these HSS potlines, and would reduce the 
potential cancer MIR due to allowable emissions from this facility to 
about 30 in one million.
    We identified wet roof scrubbers as one possible control technology 
that could be applied to further reduce allowable and actual emissions 
of POM from potlines, to reduce the cancer risks due to actual and 
allowable POM emissions, and to reduce the potential risks due to 
multi-pathway exposures to POM. One facility in the source category 
currently has this type of scrubber. These controls can also be used to 
reduce HF emissions and, thus, would reduce the potential for acute 
noncancer risks. However, the costs for these controls are high. For 
example, we estimate that the capital costs for the typical facility 
would be more than $40 million, with annualized costs of $13 million. 
Industry wide this would result in total capital costs of over $400 
million, with estimated annualized costs of over $150 million. These 
controls would achieve reductions of secondary emissions of about 30 to 
50 percent. Given the high costs (estimated at approximately $140,000 
per ton of HAP) and relatively low emissions and risk reductions, we 
propose that it is not appropriate or necessary to establish these 
additional controls under 112(f)(2). Therefore, based our AMOS 
analysis, we are proposing under section 112(f)(2) of the CAA to lower 
the POM emissions limit for VSS2 potlines from 5.7 to 3.8 lbs/ton and 
to lower the POM limit for HSS potlines from 4.7 to 3.0 lbs/ton. 
Pursuant to CAA section 112(f)(4), we are proposing that these changes 
apply 90 days after the effective date of this rulemaking. We did not 
identify any other cost-effective controls to further reduce HAP 
emissions for this source category under the AMOS analyses.
    In accordance with the approach established in the Benzene NESHAP, 
the EPA weighed all health risk measures and information considered in 
the risk acceptability determination, along with the costs and economic 
impacts of emissions controls, technological feasibility, uncertainties 
and other relevant factors in proposing our ample margin of safety 
determination. Considering the health risk information and the costs of 
the options identified, we propose that the existing MACT standards, 
along with the proposed lower POM limits for potlines at Soderberg 
facilities (VSS2 and HSS subcategories) described above, will provide 
an ample margin of safety to protect public health.
    Pursuant to CAA section 112(f)(4), we are proposing that these 
changes (i.e., lower emission limits for potlines at Soderberg 
facilities) apply 90 days after the effective date of this rulemaking. 
See CAA section 112(f)(4)(A).
    Nevertheless, we solicit comment and information on the 
feasibility, costs and appropriateness of any additional controls or 
options to further reduce the potential risks due to emissions of HAP, 
especially POM and HF.

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

    As described above, dry alumina scrubbers (with baghouses) are the 
typical controls used to minimize primary emissions of HF and POM from 
the potlines. However, some facilities use wet scrubbers and ESPs to 
control these emissions. The MACT control technology typically used for 
anode bake furnaces is also a dry alumina scrubber, and a capture 
system vented to a dry coke scrubber is used for control of paste 
production plants. These facilities further reduce HAP emissions from 
anode bake furnaces by implementation of certain practices during 
periods of startup (e.g., development of an anode bake furnace startup 
schedule, operation of the associated control system(s) within normal 
parametric limits prior to the startup of the anode bake furnace). To 
further control potline secondary emissions, one facility has wet roof 
scrubbers to get additional control of HF and POM. As described in the 
AMOS section above, it would be quite costly to require wet roof 
scrubbers on other facilities.
    Overall, based on our technology review, we determined that there 
have been no developments in practices, processes, and control 
technologies that would be considered feasible and cost-effective to 
apply to this source category since promulgation of the Primary 
Aluminum Reduction Plant NESHAP, other than the anode bake furnace 
startup practices mentioned above. We propose to modify the MACT 
requirements for anode bake furnaces to include implementation of the 
startup practices mentioned above. Further, based on an analysis of 
recent emissions data, we believe that the practices, processes and 
control technologies currently in use by this source category allow for 
a reduction in the POM emission limits for Soderberg potlines (please 
refer to the ample margin of safety analysis in section IV.C.2 of this 
preamble).
    Additional details regarding these analyses can be found in the 
following technical document for this action which is available in the 
docket: Draft Technology Review for the Primary Aluminum Reduction 
Plant Source Category.

E. What other actions are we proposing?

1. Startup, Shutdown and Malfunctions
    The United States Court of Appeals for the District of Columbia 
Circuit vacated portions of two provisions in the EPA's CAA section 112 
regulations governing the emissions of HAP during periods of startup, 
shutdown and malfunction (SSM). Sierra Club v. EPA, 551 F.3d 1019 (DC 
Cir. 2008), cert. denied, 130 S. Ct. 1735 (U.S. 2010). Specifically, 
the Court vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and 
40 CFR 63.6(h)(1), that are part of a regulation, commonly referred to 
as the ``General Provisions Rule,'' that the EPA promulgated under CAA 
section 112. When incorporated into CAA section 112(d) regulations for 
specific source categories, these two provisions exempt sources from 
the requirement to comply with the otherwise applicable CAA section 
112(d) emissions standard during periods of SSM.
    We are proposing the elimination of the SSM exemption in this rule. 
Consistent with Sierra Club v. EPA, the EPA is proposing standards in 
this rule that apply at all times. We are also proposing several 
revisions to Appendix A to subpart LL of part 63 (the General 
Provisions Applicability table). For example, we are proposing to 
eliminate the incorporation of the General Provisions' requirement that 
the source develop an SSM plan. We also are proposing to eliminate or 
revise certain recordkeeping and reporting requirements related to the 
SSM exemption. The EPA has attempted to ensure that we have not 
included in the proposed regulatory language any provisions that are 
inappropriate, unnecessary, or redundant in the absence of the SSM 
exemption. We are specifically seeking comment on whether there are any 
such provisions that we have inadvertently incorporated or overlooked.

[[Page 76279]]

    In proposing the standards in this rule, the EPA has taken into 
account startup and shutdown periods and, for the reasons explained 
below, the EPA is proposing in some cases different standards for 
startup periods.
    The 1997 MACT rule allowed for periods of up to six months for 
startup of existing potlines that had been previously shutdown. These 
long startup periods for potlines are recognized as part of the normal 
operations during which emissions testing is not feasible. The current 
MACT emission limits are not applicable during these startup periods. 
Thus, we are proposing MACT standards for these periods in today's 
action. Given that it is economically and technically infeasible to 
measure emissions during these startup periods, we are proposing 
detailed work practice standards that will minimize HAP emissions and 
ensure proper operation of the processes and control equipment during 
startup periods. The proposed work practices include bringing the 
potline scrubbers and exhaust fans on line prior to energizing the 
first cell being restarted, ensuring that the primary capture and 
control system is operating at all times during startup, and keeping 
pots covered during startup as much as practicable to include, but not 
limited to, minimizing the removal of covers or panels of the pots on 
which work is being performed. Moreover, facilities must inspect 
potlines daily during startup and perform additional work practices, 
including resealing pot crust as often and as soon as practicable, 
reducing cell temperatures to as low as practicable, and adjusting pot 
parameters to their optimum levels to include, but not limited to, the 
following parameters: Alumina addition rate, exhaust air flow, cell 
voltage, feeding level, anode current, and liquid and solid bath 
levels.
    The 1997 MACT rule allowed for startup periods for new or 
reconstructed anode bake furnaces and pitch storage tanks and for anode 
bake furnaces that had been previously shutdown. Based on information 
received from industry, we believe that these sources can comply with 
their MACT standards during startup periods. Therefore, we are removing 
the provisions for startup of anode bake furnaces and pitch storage 
tanks. However, we have added startup practices for anode bake furnace 
startup periods to help ensure that the standards will be met. These 
startup practices will minimize HAP emissions and ensure proper 
operation of the processes and control equipment during startup periods 
(please refer to the discussion of the technology review in section 
IV.D of this preamble).
    Shutdown emissions are not expected to be different from those 
during normal operation; therefore, no separate standard or work 
practice is warranted. We propose that the numerical MACT limits 
described in previous sections of this preamble (established for normal 
operations) will apply during shutdown periods. We also propose that 
the MACT limits for all other affected units besides potlines (bake 
furnaces, pitch tanks, and paste production plants) apply at all times, 
including during startups and shutdowns.
    Information on periods of startup and shutdown received from the 
industry indicate that emissions during startup (except for potlines) 
and shutdown periods are no greater than emissions during normal 
operations. Therefore, the continued operation of the existing control 
devices and emission capture systems will, in conjunction with the 
detailed proposed startup practices and work practices described above, 
be consistent with maximum achievable control technology and will be 
adequate, along with all the other standards described above, to ensure 
that risks will be acceptable and the rule will provide an ample margin 
of safety.
    Periods of startup, normal operations, and shutdown are all 
predictable and routine aspects of a source's operations. However, by 
contrast, malfunction is defined as a ``sudden, infrequent, and not 
reasonably preventable failure of air pollution control and monitoring 
equipment, process equipment or a process to operate in a normal or 
usual manner * * *'' (40 CFR 63.2). The EPA has determined that CAA 
section 112 does not require that emissions that occur during periods 
of malfunction be factored into development of CAA section 112 
standards. Under CAA section 112, emissions standards for new sources 
must be no less stringent than the level ``achieved'' by the best 
controlled similar source and for existing sources generally must be no 
less stringent than the average emissions limitation ``achieved'' by 
the best performing 12 percent of sources in the category. There is 
nothing in CAA section 112 that directs the agency to consider 
malfunctions in determining the level ``achieved'' by the best 
performing or best controlled sources when setting emissions standards. 
Moreover, while the EPA accounts for variability in setting emissions 
standards consistent with the CAA section 112 case law, nothing in that 
case law requires the agency to consider malfunctions as part of that 
analysis. Section 112 of the CAA uses the concept of ``best 
controlled'' and ``best performing'' unit in defining the level of 
stringency that CAA section 112 performance standards must meet. 
Applying the concept of ``best controlled'' or ``best performing'' to a 
unit that is malfunctioning presents significant difficulties, as 
malfunctions are sudden and unexpected events.
    Further, accounting for malfunctions would be difficult, if not 
impossible, given the myriad different types of malfunctions that can 
occur across all sources in the category and given the difficulties 
associated with predicting or accounting for the frequency, degree, and 
duration of various malfunctions that might occur. As such, the 
performance of units that are malfunctioning is not ``reasonably'' 
foreseeable. See, e.g., Sierra Club v. EPA, 167 F.3d 658, 662 (DC Cir. 
1999) (EPA typically has wide latitude in determining the extent of 
data-gathering necessary to solve a problem. We generally defer to an 
agency's decision to proceed on the basis of imperfect scientific 
information, rather than to ``invest the resources to conduct the 
perfect study.''). See also, Weyerhaeuser v. Costle, 590 F.2d 1011, 
1058 (DC 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, the goal of a best controlled or 
best performing source is to operate in such a way as to avoid 
malfunctions of the source, and accounting for malfunctions could lead 
to standards that are significantly less stringent than levels that are 
achieved by a well-performing non-malfunctioning source. The EPA's 
approach to malfunctions is consistent with CAA section 112 and is a 
reasonable interpretation of the statute.
    In the event that a source fails to comply with the applicable CAA 
section 112(d) standards as a result of a malfunction event, the EPA 
would determine an appropriate response based on, among other things, 
the good faith efforts of the source to minimize emissions during 
malfunction periods, including preventative and corrective actions, as 
well as root cause analyses to ascertain and rectify excess emissions. 
The EPA would also consider whether the source's failure to comply with 
the CAA section 112(d)

[[Page 76280]]

standard was, in fact, ``sudden, infrequent, not reasonably 
preventable'' and was not instead ``caused in part by poor maintenance 
or careless operation'' 40 CFR 63.2 (definition of malfunction).
    Finally, the EPA recognizes that even equipment that is properly 
designed and maintained can sometimes fail and that such failure can 
sometimes cause an exceedance of the relevant emissions standard. (See, 
e.g., State Implementation Plans: Policy Regarding Excessive Emissions 
During Malfunctions, Startup, and Shutdown (Sept. 20, 1999); Policy on 
Excess Emissions During Startup, Shutdown, Maintenance, and 
Malfunctions (Feb. 15, 1983).). The EPA is therefore proposing to add 
to the final rule an affirmative defense to civil penalties for 
exceedances of emissions limits that are caused by malfunctions. See 40 
CFR 63.842 (defining ``affirmative defense'' to mean, in the context of 
an enforcement proceeding, a response or defense put forward by a 
defendant, regarding which the defendant has the burden of proof, and 
the merits of which are independently and objectively evaluated in a 
judicial or administrative proceeding). We also are proposing other 
regulatory provisions to specify the elements that are necessary to 
establish this affirmative defense; the source must prove by a 
preponderance of the evidence that it has met all of the elements set 
forth in 40 CFR 63.855 (see also 40 CFR 22.24). The criteria ensure 
that the affirmative defense is available only where the event that 
causes an exceedance of the emissions limit meets the narrow definition 
of malfunction in 40 CFR 63.2 (sudden, infrequent, not reasonably 
preventable and not caused by poor maintenance and or careless 
operation). For example, to successfully assert the affirmative 
defense, the source must prove by a preponderance of the evidence that 
excess emissions ``[w]ere caused by a sudden, infrequent, and 
unavoidable failure of air pollution control and monitoring equipment, 
process equipment, or a process to operate in a normal or usual manner 
* * *.'' The criteria also are designed to ensure that steps are taken 
to correct the malfunction, to minimize emissions in accordance with 40 
CFR sections 63.843(f) and 63.844(f) to prevent future malfunctions. 
For example, the source must prove by a preponderance of the evidence 
that ``[r]epairs were made as expeditiously as possible when the 
applicable emissions limitations were being exceeded * * *'' and that 
``[a]ll possible steps were taken to minimize the impact of the excess 
emissions on ambient air quality, the environment and human health * * 
*.'' In any judicial or administrative proceeding, the Administrator 
may challenge the assertion of the affirmative defense and, if the 
respondent has not met its burden of proving all of the requirements in 
the affirmative defense, appropriate penalties may be assessed in 
accordance with CAA section 113 (see also 40 CFR 22.27).
    The EPA included an affirmative defense in the proposed rule in an 
attempt to balance a tension, inherent in many types of air regulation, 
to ensure adequate compliance while simultaneously recognizing that 
despite the most diligent of efforts, emission limits may be exceeded 
under circumstances beyond the control of the source. The EPA must 
establish emission standards that ``limit the quantity, rate, or 
concentration of emissions of air pollutants on a continuous basis.'' 
42 U.S.C. 7602(k) (defining ``emission limitation and emission 
standard''). See generally Sierra Club v. EPA, 551 F.3d 1019, 1021 (DC 
Cir. 2008). Thus, the EPA is required to ensure that section 112 
emissions limitations are continuous. The affirmative defense for 
malfunction events meets this requirement by ensuring that even where 
there is a malfunction, the emission limitation is still enforceable 
through injunctive relief. While ``continuous'' limitations, on the one 
hand, are required, there is also case law indicating that in many 
situations it is appropriate for EPA to account for the practical 
realities of technology. For example, in Essex Chemical v. Ruckelshaus, 
486 F.2d 427, 433 (DC Cir. 1973), the DC Circuit acknowledged that in 
setting standards under CAA section 111 ``variant provisions'' such as 
provisions allowing for upsets during startup, shutdown and equipment 
malfunction ``appear necessary to preserve the reasonableness of the 
standards as a whole and that the record does not support the `never to 
be exceeded' standard currently in force.'' See also, Portland Cement 
Association v. Ruckelshaus, 486 F.2d 375 (DC Cir. 1973). Though 
intervening case law such as Sierra Club v. EPA and the CAA 1977 
amendments undermine the relevance of these cases today, they support 
the EPA's view that a system that incorporates some level of 
flexibility is reasonable. The affirmative defense simply provides for 
a defense to civil penalties for excess emissions that are proven to be 
beyond the control of the source. By incorporating an affirmative 
defense, the EPA has formalized its approach to upset events. In a 
Clean Water Act setting, the Ninth Circuit required this type of 
formalized approach when regulating ``upsets beyond the control of the 
permit holder.'' Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 (9th 
Cir. 1977). But see, Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58 
(DC Cir. 1978) (holding that an informal approach is adequate). The 
affirmative defense provisions give the EPA the flexibility to both 
ensure that its emission limitations are ``continuous'' as required by 
42 U.S.C. 7602(k), and account for unplanned upsets and thus support 
the reasonableness of the standard as a whole.
    Specifically, we are proposing the following rule changes:
     Add general duty requirements in 40 CFR sections 63.843 
and 63.844 to replace General Provision requirements that reference 
vacated SSM provisions.
     Add replacement language that eliminates the reference to 
SSM exemptions applicable to performance tests in 40 CFR section 
63.847(d).
     Add paragraphs in 40 CFR section 63.850(d) requiring the 
reporting of malfunctions as part of the affirmative defense 
provisions.
     Add paragraphs in 40 CFR section 63.850(e) requiring the 
keeping of certain records during malfunctions as part of the 
affirmative defense provisions.
     Revise Appendix A to subpart LL of part 63 to reflect 
changes in the applicability of the General Provisions to this subpart 
resulting from a court vacatur of certain SSM requirements in the 
General Provisions.
2. Electronic Reporting
    The EPA must have performance test data to conduct effective 
reviews of CAA sections 112 and 129 standards, as well as for many 
other purposes including compliance determinations, emissions factor 
development, and annual emissions rate determinations. In conducting 
these required reviews, the EPA has found it ineffective and time 
consuming, not only for us, but also for regulatory agencies and source 
owners and operators, to locate, collect, and submit performance test 
data because of varied locations for data storage and varied data 
storage methods. In recent years, though, stack testing firms have 
typically collected performance test data in electronic format, making 
it possible to move to an electronic data submittal system that would 
increase the ease and efficiency of data submittal and improve data 
accessibility.
    Through this proposal the EPA is presenting a step to increase the 
ease and efficiency of data submittal and

[[Page 76281]]

improve data accessibility. Specifically, the EPA is proposing that 
owners and operators of Primary Aluminum Reduction Plant facilities 
submit electronic copies of required performance test reports to the 
EPA's WebFIRE database. The WebFIRE database was constructed to store 
performance test data for use in developing emissions factors. A 
description of the WebFIRE database is available at http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main.
    As proposed above, data entry would be through an electronic 
emissions test report structure called the Electronic Reporting Tool. 
The ERT would be able to transmit the electronic report through the 
EPA's Central Data Exchange network for storage in the WebFIRE database 
making submittal of data very straightforward and easy. A description 
of the ERT can be found at http://www.epa.gov/ttn/chief/ert/ert_tool.html.
    The proposal to submit performance test data electronically to the 
EPA would apply only to those performance tests conducted using test 
methods that will be supported by the ERT. The ERT contains a specific 
electronic data entry form for most of the commonly used EPA reference 
methods. A listing of the pollutants and test methods supported by the 
ERT is available at http://www.epa.gov/ttn/chief/ert/ert_tool.html. We 
believe that industry would benefit from this proposed approach to 
electronic data submittal. Having these data, the EPA would be able to 
develop improved emissions factors, make fewer information requests, 
and promulgate better informed regulations.
    One major advantage of the proposed submittal of performance test 
data through the ERT is a standardized method to compile and store much 
of the documentation required to be reported by this rule. Another 
advantage is that the ERT clearly states what testing information would 
be required. Another important proposed benefit of submitting these 
data to the EPA at the time the source test is conducted is that it 
should substantially reduce the effort involved in data collection 
activities in the future. When the EPA has performance test data in 
hand, there will likely be fewer or less substantial data collection 
requests in conjunction with prospective required residual risk 
assessments or technology reviews. This would result in a reduced 
burden on both affected facilities (in terms of reduced manpower to 
respond to data collection requests) and the EPA (in terms of preparing 
and distributing data collection requests and assessing the results).
    State, local, and Tribal agencies could also benefit from more 
streamlined and accurate review of electronic data submitted to them. 
The ERT would allow for an electronic review process rather than a 
manual data assessment making review and evaluation of the source 
provided data and calculations easier and more efficient. Finally, 
another benefit of the proposed data submittal to WebFIRE 
electronically is that these data would greatly improve the overall 
quality of existing and new emissions factors by supplementing the pool 
of emissions test data for establishing emissions factors and by 
ensuring that the factors are more representative of current industry 
operational procedures. A common complaint heard from industry and 
regulators is that emissions factors are outdated or not representative 
of a particular source category. With timely receipt and incorporation 
of data from most performance tests, the EPA would be able to ensure 
that emissions factors, when updated, represent the most current range 
of operational practices. In summary, in addition to supporting 
regulation development, control strategy development, and other air 
pollution control activities, having an electronic database populated 
with performance test data would save industry, state, local, Tribal 
agencies, and the EPA significant time, money, and effort while also 
improving the quality of emissions inventories and, as a result, air 
quality regulations.
    Records must be maintained in a form suitable and readily available 
for expeditious review, according to 63.10(b)(1). Electronic 
recordkeeping and reporting is available for many records, and is the 
form considered most suitable for expeditious review if available. 
Electronic recordkeeping and reporting is encouraged in this proposal 
and some records and reports are required to be kept in electronic 
format.

F. Compliance Dates

    We are proposing that existing facilities must comply with the 
proposed revised emissions limits for Soderberg potlines (which are 
being proposed under CAA sections 112(f)(2) for all affected sources), 
no later than 90 days after the date of publication of the final rule. 
We are proposing that existing facilities must comply with all other 
changes proposed in this action (other than affirmative defense 
provisions and electronic reporting which are effective upon 
promulgation of the final rule) no later than 3 years after the date of 
publication of the final rule. All new or reconstructed facilities must 
comply with all requirements in this rule upon startup.

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    The affected sources are new and existing potlines, new and 
existing pitch storage tanks, new and existing anode bake furnaces 
(except for one that is located at a facility that only produces anodes 
for use off-site), and new and existing paste production plants.

B. What are the air quality impacts?

    The proposed rule will require the POM emissions from existing 
uncontrolled pitch storage tanks to be reduced by a minimum of 95 
percent. This is estimated to result in a reduction of 1.6 tons per 
year (tpy) of POM. In addition, the proposed lower Soderberg potline 
POM limits would reduce POM emissions from the two Soderberg 
facilities, assuming production at plant capacity, by approximately 300 
tpy, combined.

C. What are the cost impacts?

    Under the proposed amendments, 8 facilities would be required to 
install or upgrade, and operate emissions control systems (such as 
activated carbon adsorbers or condensers) to control emissions of HAP 
from pitch storage tanks at total estimated cost of $167,832 per year, 
or $20,979 per facility. In addition, 12 facilities will have to 
conduct periodic performance tests for POM emissions from 45 prebake 
potlines at an estimated total cost of $90,000 per year for the source 
category, or $7,500 per year per facility. The total estimated cost of 
the rule is $258,000 per year.

D. What are the economic impacts?

    We performed an economic impact analysis for the proposed 
modifications in this rulemaking. That analysis estimates total 
annualized costs of approximately $257,832 at 13 facilities and cost to 
revenue of less than 0.02% for the Primary Aluminum Production source 
category. For more information, please refer to the Draft Economic 
Impact Analysis for this proposed rulemaking that is available in the 
public docket for this proposed rulemaking.

E. What are the benefits?

    This proposed rule will achieve about 1.6 tons per year reductions 
in POM emissions, which may result in a slight health benefit. The 
proposed limits of 3.9 pounds of COS per ton of aluminum produced (lb 
COS/ton Al) for existing facilities and 3.1 lb COS/ton Al for new

[[Page 76282]]

facilities will prevent increases in COS emissions and prevent 
increases in SO2 emissions as a co-benefit. The proposed COS 
standard will likely result in the use of lower sulfur content coke in 
the anode production processes. This reduction in anode coke sulfur 
content would result in decreases in emissions of both COS and sulfur 
dioxide (SO2). We estimate that SO2 emissions 
will decrease by 12 tons for each ton of COS reduction.

VI. Request for Comments

    We are soliciting comments on all aspects of this proposed action. 
In addition to general comments on this proposed action, we are also 
interested in any additional data that may help to reduce the 
uncertainties inherent in the risk assessments and other analyses. We 
are specifically interested in receiving corrections to the site-
specific emissions profiles used for risk modeling. Such data should 
include supporting documentation in sufficient detail to allow 
characterization of the quality and representativeness of the data or 
information. Section VII of this preamble provides more information on 
submitting data.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses are available for download on the RTR Web 
page at: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The data files 
include detailed information for each HAP emissions release point for 
the facility included in the source category.
    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern, and provide any ``improved'' data that you have, if 
available. When you submit data, we request that you provide 
documentation of the basis for the revised values to support your 
suggested changes. To submit comments on the data downloaded from the 
RTR Web page, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information. The data fields that may 
be revised include the following:

------------------------------------------------------------------------
           Data element                          Definition
------------------------------------------------------------------------
Control Measure...................  Are control measures in place? (yes
                                     or no)
Control Measure Comment...........  Select control measure from list
                                     provided, and briefly describe the
                                     control measure.
Delete............................  Indicate here if the facility or
                                     record should be deleted.
Delete Comment....................  Describes the reason for deletion.
Emissions Calculation Method Code   Code description of the method used
 for Revised Emissions.              to derive emissions. For example,
                                     CEM, material balance, stack test,
                                     etc.
Emissions Process Group...........  Enter the general type of emissions
                                     process associated with the
                                     specified emissions point.
Fugitive Angle....................  Enter release angle (clockwise from
                                     true North); orientation of the y-
                                     dimension relative to true North,
                                     measured positive for clockwise
                                     starting at 0 degrees (maximum 89
                                     degrees).
Fugitive Length...................  Enter dimension of the source in the
                                     east-west (x-) direction, commonly
                                     referred to as length (ft).
Fugitive Width....................  Enter dimension of the source in the
                                     north-south (y-) direction,
                                     commonly referred to as width (ft).
Malfunction Emissions.............  Enter total annual emissions due to
                                     malfunctions (tpy).
Malfunction Emissions Max Hourly..  Enter maximum hourly malfunction
                                     emissions here (lb/hr).
North American Datum..............  Enter datum for latitude/longitude
                                     coordinates (NAD27 or NAD83); if
                                     left blank, NAD83 is assumed.
Process Comment...................  Enter general comments about process
                                     sources of emissions.
REVISED Address...................  Enter revised physical street
                                     address for MACT facility here.
REVISED City......................  Enter revised city name here.
REVISED County Name...............  Enter revised county name here.
REVISED Emissions Release Point     Enter revised Emissions Release
 Type.                               Point Type here.
REVISED End Date..................  Enter revised End Date here.
REVISED Exit Gas Flow Rate........  Enter revised Exit Gas Flowrate here
                                     (ft\3\/sec).
REVISED Exit Gas Temperature......  Enter revised Exit Gas Temperature
                                     here (F).
REVISED Exit Gas Velocity.........  Enter revised Exit Gas Velocity here
                                     (ft/sec).
REVISED Facility Category Code....  Enter revised Facility Category Code
                                     here, which indicates whether
                                     facility is a major or area source.
REVISED Facility Name.............  Enter revised Facility Name here.
REVISED Facility Registry           Enter revised Facility Registry
 Identifier.                         Identifier here, which is an ID
                                     assigned by the EPA Facility
                                     Registry System.
REVISED HAP Emissions Performance   Enter revised HAP Emissions
 Level Code.                         Performance Level here.
REVISED Latitude..................  Enter revised Latitude here (decimal
                                     degrees).
REVISED Longitude.................  Enter revised Longitude here
                                     (decimal degrees).
REVISED MACT Code.................  Enter revised MACT Code here.
REVISED Pollutant Code............  Enter revised Pollutant Code here.
REVISED Routine Emissions.........  Enter revised routine emissions
                                     value here (tpy).
REVISED SCC Code..................  Enter revised SCC Code here.
REVISED Stack Diameter............  Enter revised Stack Diameter here
                                     (ft).
REVISED Stack Height..............  Enter revised Stack Height here
                                     (ft).
REVISED Start Date................  Enter revised Start Date here.
REVISED State.....................  Enter revised State here.
REVISED Tribal Code...............  Enter revised Tribal Code here.
REVISED Zip Code..................  Enter revised Zip Code here.
Shutdown Emissions................  Enter total annual emissions due to
                                     shutdown events (tpy).
Shutdown Emissions Max Hourly.....  Enter maximum hourly shutdown
                                     emissions here (lb/hr).
Stack Comment.....................  Enter general comments about
                                     emissions release points.
Startup Emissions.................  Enter total annual emissions due to
                                     startup events (tpy).
Startup Emissions Max Hourly......  Enter maximum hourly startup
                                     emissions here (lb/hr).

[[Page 76283]]

 
Year Closed.......................  Enter date facility stopped
                                     operations.
------------------------------------------------------------------------

    2. Fill in the commenter information fields for each suggested 
revision (i.e., commenter name, commenter organization, commenter email 
address, commenter phone number, and revision comments).
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft[reg] Access format and all accompanying documentation to 
Docket ID Number EPA-HQ-OAR-2011-0797 (through one of the methods 
described in the ADDRESSES section of this preamble). To expedite 
review of the revisions, it would also be helpful if you submitted a 
copy of your revisions to the EPA directly at RTR@epa.gov in addition 
to submitting them to the docket.
    5. If you are providing comments on a facility, you need only 
submit one file for that facility, which should contain all suggested 
changes for all sources at that facility. We request that all data 
revision comments be submitted in the form of updated Microsoft[supreg] 
Access files, which are provided on the RTR Web Page at: http://www.epa.gov/ttn/atw/rrisk/rtrpg.html.

VIII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this 
action is a significant regulatory action because it raises novel legal 
and policy issues. Accordingly, the EPA submitted this action to the 
Office of Management and Budget (OMB) for review under Executive Orders 
12866 and 13563 (76 FR 3821, January 21, 2011) and any changes made in 
response to OMB recommendations have been documented in the docket for 
this action.

B. Paperwork Reduction Act

    The information collection requirements in this rule have been 
submitted for approval to the Office of Management and Budget (OMB) 
under the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. The 
Information Collection Request (ICR) document prepared by the EPA has 
been assigned the EPA ICR number 2447.01. The information collection 
requirements are not enforceable until OMB approves them. The 
information requirements are based on notification, recordkeeping, and 
reporting requirements in the NESHAP General Provisions (40 CFR part 
63, subpart A), which are mandatory for all operators subject to 
national emissions standards. These recordkeeping and reporting 
requirements are specifically authorized by CAA section 114 (42 U.S.C. 
7414). All information submitted to the EPA pursuant to the 
recordkeeping and reporting requirements for which a claim of 
confidentiality is made is safeguarded according to agency policies set 
forth in 40 CFR part 2, subpart B.
    We are proposing new paperwork requirements for the Primary 
Aluminum Reduction Plant source category in the form of a one-time 
requirement to prepare design specifications for existing pitch storage 
tank controls, and submissions of test reports and calculations for 
demonstration of compliance with prebake potline POM limits.
    For this proposed rule, the EPA is adding affirmative defense to 
the estimate of burden in the ICR. To provide the public with an 
estimate of the relative magnitude of the burden associated with an 
assertion of the affirmative defense position adopted by a source, the 
EPA has provided administrative adjustments to this ICR to show what 
the notification, recordkeeping and reporting requirements associated 
with the assertion of the affirmative defense might entail. The EPA's 
estimate for the required notification, reports and records for any 
individual incident, including the root cause analysis, totals $3,141 
and is based on the time and effort required of a source to review 
relevant data, interview plant employees, and document the events 
surrounding a malfunction that has caused an exceedance of an emissions 
limit. The estimate also includes time to produce and retain the record 
and reports for submission to the EPA. The EPA provides this 
illustrative estimate of this burden because these costs are only 
incurred if there has been a violation and a source chooses to take 
advantage of the affirmative defense.
    Given the variety of circumstances under which malfunctions could 
occur, as well as differences among sources' operation and maintenance 
practices, we cannot reliably predict the severity and frequency of 
malfunction-related excess emissions events for a particular source. It 
is important to note that the EPA has no basis currently for estimating 
the number of malfunctions that would qualify for an affirmative 
defense. Current historical records would be an inappropriate basis, as 
source owners or operators previously operated their facilities in 
recognition that they were exempt from the requirement to comply with 
emissions standards during malfunctions. Of the number of excess 
emissions events reported by source operators, only a small number 
would be expected to result from a malfunction (based on the definition 
above), and only a subset of excess emissions caused by malfunctions 
would result in the source choosing to assert the affirmative defense. 
Thus we believe the number of instances in which source operators might 
be expected to avail themselves of the affirmative defense will be 
extremely small.
    With respect to the Primary Aluminum Production source category, 
the emissions controls are operational before the associated emission 
source(s) commence operation and remain operational until after the 
associated emission source(s) cease operation. Also, production 
operations would not proceed or continue if there is a malfunction of a 
control device and the time required to shut down production operations 
(i.e., on the order of a day) is small compared to the averaging time 
of the emission standards (i.e., monthly, quarterly and annual 
averages). Thus, we believe it is unlikely that a control device 
malfunction would cause an exceedance of any emission limit. Therefore, 
sources within this source category are not expected to have any need 
or use for the affirmative defense and we believe that there is no 
burden to the industry for the affirmative defense provisions in the 
proposed rule.
    We expect to gather information on such events in the future and 
will revise this estimate as better information becomes available. We 
estimate 15 regulated entities are currently subject to subpart LL and 
will be subject to all proposed standards. The annual monitoring, 
reporting, and recordkeeping burden for this collection (averaged over 
the first 3 years after the effective date of the standards) for these 
amendments to subpart LL is estimated

[[Page 76284]]

to be $148,000 per year. This includes 1,558 labor hours per year at a 
total labor cost of $148,000 per year, and total non-labor capital and 
operation and maintenance (O&M) costs of $500 per year. This estimate 
includes performance tests, notifications, reporting, and recordkeeping 
associated with the new requirements for existing pitch storage tanks 
and new and existing potlines. The total burden for the Federal 
government (averaged over the first 3 years after the effective date of 
the standard) is estimated to be 120 hours per year at a total labor 
cost of $11,400 per year. Burden is defined at 5 CFR 1320.3(b).
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9. When these 
ICRs are approved by OMB, the agency will publish a technical amendment 
to 40 CFR part 9 in the Federal Register to display the OMB control 
numbers for the approved information collection requirements contained 
in the final rules.
    To comment on the agency's need for this information, the accuracy 
of the provided burden estimates, and any suggested methods for 
minimizing respondent burden, the EPA has established a public docket 
for this rule, which includes this ICR, under Docket ID number EPA-HQ-
OAR-2011-0797. Submit any comments related to the ICR to the EPA and 
OMB. See the ADDRESSES section at the beginning of this notice for 
where to submit comments to the EPA. Send comments to OMB at the Office 
of Information and Regulatory Affairs, Office of Management and Budget, 
725 17th Street, NW., Washington, DC 20503, Attention: Desk Office for 
the EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after December 6, 2011, a comment to OMB is best 
assured of having its full effect if OMB receives it by January 5, 
2012. The final rule will respond to any OMB or public comments on the 
information collection requirements contained in this proposal.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of this proposed rule on 
small entities, small entity is defined as: (1) A small business as 
defined by the Small Business Administration's (SBA) regulations at 13 
CFR 121.201; (2) a small governmental jurisdiction that is a government 
of a city, county, town, school district or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise that is independently owned and operated 
and is not dominant in its field. For this source category, which has 
the NAICS code 331312, the SBA small business size standard is 1,000 
employees according to the SBA small business standards definitions. 
There are no small entities subject to subpart LL.
    After considering the economic impacts of today's proposed rule on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. This 
proposed rule will not impose any requirements on small entities. We 
continue to be interested in the potential impacts of the proposed rule 
on small entities and welcome comment on issues related to such 
impacts.

D. Unfunded Mandates Reform Act

    This proposed rule does not contain a Federal mandate under the 
provisions of Title II of the Unfunded Mandates Reform Act of 1995 
(UMRA), 2 U.S.C. 1531-1538 for State, local, or Tribal governments or 
the private sector. The proposed rule would not result in expenditures 
of $100 million or more for State, local, and Tribal governments, in 
aggregate, or the private sector in any 1 year. The proposed rule 
imposes no enforceable duties on any State, local or Tribal governments 
or the private sector. Thus, this proposed rule is not subject to the 
requirements of sections 202 or 205 of the UMRA.
    This proposed rule is also not subject to the requirements of 
section 203 of UMRA because it contains no regulatory requirements that 
might significantly or uniquely affect small governments because it 
contains no requirements that apply to such governments nor does it 
impose obligations upon them.

E. Executive Order 13132: Federalism

    This proposed rule does not have federalism implications. It will 
not have substantial direct effects on the States, on the relationship 
between the national government and the States, or on the distribution 
of power and responsibilities among the various levels of government, 
as specified in Executive Order 13132. None of the facilities subject 
to this action are owned or operated by State governments, and, because 
no new requirements are being promulgated, nothing in this proposed 
rule will supersede State regulations. Thus, Executive Order 13132 does 
not apply to this proposed rule.
    In the spirit of Executive Order 13132, and consistent with the EPA 
policy to promote communications between the EPA and State and local 
governments, the EPA specifically solicits comment on this proposed 
rule from State and local officials.

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

    This proposed rule does not have Tribal implications, as specified 
in Executive Order 13175 (65 FR 67249, November 9, 2000). None of the 
provisions of this proposed rule will result in increased emissions of 
any hazardous air pollutant from any facility. The more stringent 
limitations of POM emissions from horizontal stud Soderberg potlines 
may result in decreased risk to Indian Tribal populations. Thus, 
Executive Order 13175 does not apply to this action.
    The EPA specifically solicits additional comment on this proposed 
action from Tribal officials.

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

    This proposed rule is not subject to Executive Order 13045 (62 FR 
19885, April 23, 1997) because it is not economically significant as 
defined in Executive Order 12866. Moreover, the agency does not believe 
the environmental health risks or safety risks addressed by this action 
present a disproportionate risk to children. Nevertheless, the public 
is invited to submit comments or identify studies and data that assess 
effects of early life exposure to HAP from Primary Aluminum sources. 
The EPA will typically accord greater weight to studies and data that 
have been peer reviewed.

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

    This action is not a ``significant energy action'' as defined under 
Executive Order 13211, ``Actions Concerning Regulations That

[[Page 76285]]

Significantly Affect Energy Supply, Distribution, or Use'' (66 FR 
28355, May 22, 2001), because it is not likely to have significant 
adverse effect on the supply, distribution, or use of energy. This 
action will not create any new requirements and therefore no additional 
costs for sources in the energy supply, distribution, or use sectors.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Public Law 104-113 (15 U.S.C. 272 note), 
directs the EPA to use voluntary consensus standards (VCS) in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. VCS are technical standards 
(e.g., materials specifications, test methods, sampling procedures, and 
business practices) that are developed or adopted by voluntary 
consensus standards bodies. NTTAA directs the EPA to provide Congress, 
through OMB, explanations when the agency decides not to use available 
and applicable VCS.
    This proposed rulemaking involves technical standards. The EPA 
proposes to use ASTM D3177-02 (2007) Standard Test Methods for Total 
Sulfur in the Analysis Sample of Coal and Coke. This is a voluntary 
consensus method. This method can be obtained from the American Society 
for Testing and Materials, 100 Bar Harbor Drive, West Conshohocken, 
Pennsylvania 19428 (telephone number (610) 832-9500). This method was 
proposed because it is commonly used by primary aluminum reduction 
facilities to demonstrate compliance with sulfur dioxide emission 
limitations imposed in their current Title V permits. The EPA welcomes 
comments on this aspect of this proposed rulemaking and, specifically, 
invites the public to identify potentially-applicable voluntary 
consensus standards and to explain why such standards should be used in 
this regulation.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (59 FR 7629, February 16, 1994) establishes 
Federal executive policy on environmental justice. Its main provision 
directs Federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States.
    For the primary aluminum source category, EPA has determined that 
the current health risks posed to anyone by actual emissions from this 
source category are within the acceptable range, and that the proposed 
rulemaking will not appreciably reduce these risks further. As a 
result, this proposed rule will not have disproportionately high and 
adverse human health or environmental effects on minority or low-income 
populations.
    To examine the potential for any environmental justice issues that 
might be associated with each source category, we evaluated the 
distributions of HAP-related cancer and non-cancer risks across 
different social, demographic, and economic groups within the 
populations living near the facilities where this source category is 
located. The methods used to conduct demographic analyses for this rule 
are described in the document Draft Residual Risk Assessment for the 
Primary Aluminum Reduction Plant Source Category which may be found in 
the docket for this rulemaking. The development of demographic analyses 
to inform the consideration of environmental justice issues in the EPA 
rulemakings is an evolving science. The EPA offers the demographic 
analyses in today's proposed rulemaking as examples of how such 
analyses might be developed to inform such consideration, and invites 
public comment on the approaches used and the interpretations made from 
the results, with the hope that this will support the refinement and 
improve utility of such analyses.
    In the demographics analysis, we focused on populations within 50 
km of the facilities in this source category with emissions sources 
subject to the MACT standard. More specifically, for these populations 
we evaluated exposures to HAP that could result in cancer risks of 1 in 
one million or greater. We compared the percentages of particular 
demographic groups within the focused populations to the total 
percentages of those demographic groups nationwide. The results of this 
analysis are documented in the document Draft Residual Risk Assessment 
for the Primary Aluminum Reduction Plant Source Category in the docket 
for this proposed rulemaking.

List of Subjects in 40 CFR Part 63

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

    Dated: November 4, 2011.
Lisa P. Jackson,
Administrator.

    For the reasons stated in the preamble, part 63 of title 40, 
chapter I, of the Code of Federal Regulations is proposed to be amended 
as follows:

PART 63--[AMENDED]

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

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

Subpart LL--[AMENDED]

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

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.
* * * * *
    3. Section 63.841 is amended by adding paragraph (a)(3) to read as 
follows:

Sec.  63.841  Incorporation by reference.

    (a) * * *
    (3) ASTM D3177-02 (2007) Standard Test Methods for Total Sulfur in 
the Analysis Sample of Coal and Coke.
* * * * *
    4. Section 63.842 is amended to read as follows:
    a. Removing the definition for ``Vertical stud Soderberg one 
(VSS1)'' and
    b. Adding, in alphabetical order, definitions for ``Affirmative 
defense'' and ``Startup of an anode bake furnace''

Sec.  63.842  Definitions.

* * * * *
    Affirmative defense means, in the context of an enforcement 
proceeding, a response or defense put forward by a defendant, regarding 
which the defendant has the burden of proof, and the merits of which 
are independently and objectively evaluated in a judicial or 
administrative proceeding.
* * * * *
    Startup of an anode bake furnace means the process of initiating 
heating to the anode baking furnace where all sections of the furnace 
have previously been at ambient temperature. The startup or re-start of 
the furnace begins when the heating begins. The startup or

[[Page 76286]]

re-start concludes at the start of the second anode bake cycle.
* * * * *
    5. Section 63.843 is amended to read as follows:
    a. Revising paragraph (a)(1)introductory text;
    b. Removing and reserving paragraph (a)(1)(v);
    c. Revising paragraph (a)(2)introductory text, and (a)(2)(i);
    d. Removing and reserving paragraph (a)(2)(ii);
    e. Revising paragraph (a)(2)(iii); and
    f. Adding paragraphs (a)(2)(iv) through (a)(2)(vii), (d), (e), and 
(f)

Sec.  63.843  Emission limits for existing sources.

    (a) * * *
    (1) Emissions of TF must not exceed:
* * * * *
    (v) [Reserved]
* * * * *
    (2) Emissions of POM must not exceed:
    (i) 1.5 kg/Mg (3.0 lb/ton) of aluminum produced for each HSS 
potline;
    (ii) [Reserved;]
    (iii) 1.9 kg/Mg (3.8 lb/ton) of aluminum produced for each VSS2 
potline;
    (iv) 0.31 kg/Mg (0.62 lb/ton) of aluminum produced for each 
existing CWPB1 prebake potline;
    (v) 0.65 kg/Mg (1.3 lb/ton) of aluminum produced for each existing 
CWPB2 prebake potline;
    (vi) 0.63 kg/Mg (1.26 lb/ton) of aluminum produced for each 
existing CWPB3 prebake potline;
    (vii) 0.33 kg/Mg (0.65 lb/ton) of aluminum produced for each 
existing SWPB prebake potline;
* * * * *
    (d) Pitch storage tanks. Each pitch storage tank shall be equipped 
with an emission control system designed and operated to reduce inlet 
emissions of POM by 95 percent or greater.
    (e) COS limit. Emissions of COS must not exceed 3.9 lb/ton of 
aluminum produced.
    (f) At all times, the owner or operator must operate and maintain 
any affected source, including associated air pollution control 
equipment and monitoring equipment, in a manner consistent with safety 
and good air pollution control practices for minimizing emissions. 
Determination of whether such operation and maintenance procedures are 
being used will be based on information available to the Administrator 
which may include, but is not limited to, monitoring results, review of 
operation and maintenance procedures, review of operation and 
maintenance records, and inspection of the source.
    6. Section 63.844 is amended to read as follows:
    a. Adding paragraph (a)(3);
    b. Adding paragraph (e); and
    c. Adding paragraph (f)

Sec.  63.844  Emission limits for new or reconstructed sources.

    (a) * * *
    (3) POM limit. Emissions of POM from prebake potlines must not 
exceed 0.31 kg/Mg (0.62 lb/ton) of aluminum produced.
* * * * *
    (e) COS limit. Emissions of COS must not exceed 3.1 lb/ton of 
aluminum produced.
    (f) At all times, the owner or operator must operate and maintain 
any affected source, including associated air pollution control 
equipment and monitoring equipment, in a manner consistent with safety 
and good air pollution control practices for minimizing emissions. 
Determination of whether such operation and maintenance procedures are 
being used will be based on information available to the Administrator 
which may include, but is not limited to, monitoring results, review of 
operation and maintenance procedures, review of operation and 
maintenance records, and inspection of the source.
    7. Section 63.846 is amended to read as follows:
    a. Revising paragraph (b);
    b. Revising paragraph (d)(2)(iv);
    c. Revising paragraphs (d)(4)(ii) and (iii);
    d. Removing and reserving paragraph (d)(4)(iv); and
    e. Adding paragraphs (e) and (f)

Sec.  63.846  Emission averaging.

* * * * *
    (b) Soderberg Potlines. The owner or operator may average TF 
emissions from potlines and demonstrate compliance with the limits in 
Table 1 of this subpart using the procedures in paragraphs (b)(1) and 
(b)(2) of this section. The owner or operator also may average POM 
emissions from potlines and demonstrate compliance with the limits in 
Table 2 of this subpart using the procedures in paragraphs (b)(1) and 
(b)(3) of this section.
* * * * *
    (d) * * *
    (2) * * *
    (iv) The test plan for the measurement of TF or POM emissions in 
accordance with the requirements in Sec. Sec.  63.847(b) and (k);
* * * * *
    (4) * * *
    (ii) The inclusion of any emission source other than an existing 
potline or existing anode bake furnace subject to the same operating 
permit; or
    (iii) The inclusion of any potline or anode bake furnace while it 
is shut down, in the emission calculations.
    (iv) [Reserved]
* * * * *
    (e) TF emissions from Prebake Potlines. The owner or operator may 
average TF emissions from potlines and demonstrate compliance with the 
limits in Table 1 of this subpart using the procedures in paragraphs 
(e)(1) and (e)(2) of this section.
    (1) Monthly average emissions of TF must not exceed the applicable 
emission limit in Table 1 of this subpart. The emission rate must be 
calculated based on the total emissions from all potlines over the 
period divided by the quantity of aluminum produced during the period, 
from all potlines comprising the averaging group.
    (2) To determine compliance with the applicable emission limit in 
Table 1 of this subpart for TF emissions, the owner or operator must 
determine the monthly average emissions (in lb/ton) from each potline 
from at least three runs per potline each month for TF secondary 
emissions using the procedures and methods in Sec. Sec.  63.847 and 
63.849. The owner or operator must combine the results of secondary TF 
monthly average emissions with the TF results for the primary control 
system and divide total emissions by total aluminum production.
    (f) POM Emissions from Prebake Potlines. The owner or operator also 
may average POM emissions from potlines and demonstrate compliance with 
the limits in Table 2 of this subpart using the procedures in 
paragraphs (f)(1) and (f)(2) of this section.
    (1) Average emissions of POM for each compliance demonstration 
period, must not exceed the applicable emission limit in Table 2 of 
this subpart. The emission rate must be calculated based on the total 
emissions from all potlines divided by the quantity of aluminum 
produced during the period, from all potlines comprising the averaging 
group.
    (2) To determine compliance with the applicable emission limit in 
Table 2 of this subpart for POM emissions, the owner or operator must 
determine the emissions (in lb/ton) from each potline using the 
procedures and methods in Sec. Sec.  63.847 and 63.849. The owner or 
operator must combine the results of measured or calculated secondary 
POM emissions with the POM emissions from the primary control system 
and divide

[[Page 76287]]

total emissions by total aluminum production.
    8. Section 63.847 is amended to read as follows:
    a. Revising paragraph (a)
    b. Removing and reserving paragraph (a)(3);
    c. Revising paragraph (b) introductory text;
    d. Removing and reserving paragraph (b)(6);
    e. Revising paragraphs (c)(1); (c)(2); and (c)(3);
    f. Removing paragraphs (c)(2)(i) through (iii);
    g. Revising paragraph (c)(3);
    h. Revising paragraphs (d) introductory text and (d)(2);
    i. Adding paragraph (d)(5);
    j. Revising paragraph (e)(2);
    k. Adding paragraph (e)(8);
    l. Revising paragraph (g) introductory text;
    m. Adding and reserving paragraph (i); and
    n. 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 
reduction plant must comply with the requirements of this subpart by 
the applicable compliance date in paragraph (a)(1), (a)(2) or (a)(3) of 
this section:
    (1) Except as noted in paragraph (a)(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 90 days after date of publication of final rule] for 
Soderberg potlines subject to emission limits in Sec. Sec.  
63.843(a)(2)(i) and (iii) which became effective [Date of publication 
of final rule].
    (ii) [Date 3 years after date of publication of final rule] for 
prebake potlines subject to emission limits in Sec. Sec.  
63.843(a)(2)(iv) through (vii) and Sec.  63.848(n) which became 
effective [Date of publication of final rule].
    (iii) [Date 3 years after date of publication of final rule] for 
potlines subject to the work practice standards in Sec.  63.854 which 
became effective [insert date of publication of final rule].
    (iv) [Date 3 years after date of publication of final rule] for 
anode bake furnaces subject to the startup practices in Sec.  63.847(m) 
which became effective [insert date of publication of final rule].
    (v) [Date 3 years after date of publication of final rule] for 
compliance with the pitch storage tank POM limit provisions of Sec.  
63.843(d) and the COS emission limit provisions of Sec. Sec.  63.843(e) 
and 63.844(e).
    (vi) [Date of publication of final rule] for the malfunction 
provisions of Sec. Sec.  63.850(d)(2) and (e)(4)(xvi) and (xvii), the 
affirmative defense provisions of Sec.  63.855, and the electronic 
reporting provisions of Sec. Sec.  63.850(c) and (f).
    (3) [Reserved]
* * * * *
    (b) Test plan for TF from all anode bake furnaces and potlines and 
POM from Soderberg potlines. The owner or operator shall prepare a 
site-specific test plan prior to the initial performance test according 
to the requirements of Sec.  63.7(c) of this part. The test plan must 
include procedures for conducting the initial performance test and for 
subsequent performance tests required in Sec.  63.848 for emission 
monitoring. In addition to the information required by Sec.  63.7, the 
test plan shall include:
* * * * *
    (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.
* * * * *
    (2) POM emissions from Soderberg potlines. For each Soderberg (HSS 
and VSS2) potline, the owner or operator must measure and record the 
emission rate of POM exiting the primary emission control system and 
the rate of secondary emissions exiting through each roof monitor, or 
for a plant with roof scrubbers, exiting through the scrubbers. Using 
the equation in paragraph (e)(2) of this section, the owner or operator 
must compute and record the average of at least three runs each quarter 
(one run per month) for secondary emissions and at least three runs 
each year for the primary control system to determine compliance with 
the applicable emission limit. Compliance is demonstrated when the 
emission rate of POM is equal to or less than the applicable emission 
limit in Sec. Sec.  63.843, 63.844 or 63.846.
* * * * *
    (5) POM emissions from prebake potlines. For each prebake potline, 
the owner or operator shall measure and record the emission rate of POM 
exiting the primary emission control system. The owner or operator 
shall compute and record the average of at least three runs every five 
years. For each prebake potline for which the owner or operator chooses 
to demonstrate compliance using the provisions of Sec.  63.847(e)(2), 
the owner or operator shall measure and record the emission rate of 
secondary emissions exiting through each roof monitor, or for a plant 
with roof scrubbers, exiting through the scrubbers. The owner or 
operator shall compute and record the average of at least three runs 
every five years for secondary emissions. The owner or operator shall 
calculate POM emissions in accordance with Sec. Sec.  63.847(e)(2) or 
(8). Compliance is demonstrated when the emission rate of POM is equal 
to or less than the applicable emission limit in Sec. Sec.  63.843, 
63.844 or 63.846.
    (e) * * *
    (2) Compute the emission rate of POM from each Soderberg potline, 
and from those prebake potlines for which the owner or operator chooses 
to measure secondary emissions, using Equation 1,

Where:

Ep = emission rate of POM from the potline, kg/mg (lb/
ton); and
Cs = concentration of POM, mg/dscm (mg/dscf). POM 
emission data collected during the installation and startup of a 
cathode must not be included in Cs.
* * * * *
    (8) Compute the rate of POM from each prebake potline for which the 
owner or operator does not choose to determine the measure the 
secondary emissions using Equation 3:

[[Page 76288]]

[GRAPHIC] [TIFF OMITTED] TP06DE11.006

Where:

Epp = emission rate of POM from a potline, kg/Mg (lb/
ton);
Cpp1 = concentration of POM from the primary control 
system, mg/dscm (mg/dscf);
Q1 = volumetric flow rate of effluent gas from the 
primary control system dscm/hr (dscf/hr);
CpF2 = concentration of TF from the secondary control 
system or roof monitor, mg/dscm (mg/dscf);
CpF1 = concentration of TF from the primary control 
system, mg/dscm (mg/dscf); and
Q2 = volumetric flow rate of effluent gas from the 
secondary control system or roof monitor, dscm/hr (dscf/hr).
* * * * *
    (g) Pitch storage tanks. The owner or operator must demonstrate 
initial compliance with the standard for pitch storage tanks in 
Sec. Sec.  63.843(d) and 63.844(d) by preparing a design evaluation or 
by conducting a performance test. The owner or operator shall submit 
for approval by the regulatory authority the information specified in 
paragraph (g)(1) of this section, along with the information specified 
in paragraph (g)(2) of this section where a design evaluation is 
performed or the information specified in paragraph (g)(3) of this 
section where a performance test is conducted.
* * * * *
    (i) [Reserved]
    (j) COS Emissions. The owner operator of each plant must calculate 
the facility wide emission rate of COS for each calendar month of 
operation using the following equation:
[GRAPHIC] [TIFF OMITTED] TP06DE11.007

Where:

ECOS = the facility wide emission rate of COS during the 
calendar month in pounds per ton of aluminum produced;
K = factor accounting for molecular weights and conversion of sulfur 
to carbonyl sulfide = 234;
Y = the tons of anode used at the facility during the calendar 
month;
Z = the tons of aluminum produced at the facility during the 
calendar month; and
%S = the weighted average sulfur content of the anode coke utilized 
in the production of aluminum during the calendar month (e.g., if 
the weighted average sulfur content of the anode coke utilized 
during the calendar month was 2.5%, then %S = 0.025).

    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) Test plan POM from prebake potlines. The owner or operator must 
prepare a site-specific test plan prior to the initial performance test 
according to the requirements of Sec.  63.7(c) of this part. The test 
plan must include procedures for conducting the initial performance 
test and for subsequent performance tests required in Sec.  63.848 for 
emission monitoring. In addition to the information required by Sec.  
63.7 the test plan shall include:
    (1) Procedures to ensure a minimum of three runs are performed for 
the primary control system for each source;
    (2) For a source with a single control device exhausted through 
multiple stacks, procedures to ensure that at least three runs are 
performed by a representative sample of the stacks satisfactory to the 
applicable regulatory authority;
    (3) For multiple control devices on a single source, procedures to 
ensure that at least one run is performed for each control device by a 
representative sample of the stacks satisfactory to the applicable 
regulatory authority;
    (4) For plants with roof scrubbers, procedures for rotating 
sampling among the scrubbers or other procedures to obtain 
representative samples as approved by the applicable regulatory 
authority.
    (l) Potlines. The owner or operator shall 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 applicable regulatory 
authority.
    (m) Anode bake furnaces. If you own or operate a new or existing 
primary aluminum reduction affected source, you must develop a written 
startup plan as described in paragraphs (m)(1) through (4) of this 
section. Compliance with the startup plan will be demonstrated through 
site inspection(s) and review of site records by the applicable 
regulatory authority. The written startup plan must contain specific 
procedures to be followed during startup periods of anode bake 
furnaces, including the following:
    (1) A requirement to develop an anode bake furnace startup schedule 
prior to startup of the first anode bake furnace.
    (2) Records of time, date, duration and any nonroutine actions 
taken during startup of the furnaces.
    (3) A requirement that the associated emission control system 
should be operating within normal parametric limits prior to startup of 
the first anode bake furnace.
    (4) A requirement to shut down the anode bake furnaces immediately 
if the associated emission control system is off line at any time 
during startup.
    9. Section 63.848 is amended by revising paragraph (b) and adding 
paragraph (n) to read as follows:

Sec.  63.848  Emission monitoring requirements.

* * * * *
    (b) POM emissions from Soderberg potlines. Using the procedures in 
Sec.  63.847 and in the approved test plan, the owner or operator shall 
monitor emissions of POM from each Soderberg (HSS and VSS2) potline 
every three months. The owner or operator shall compute and record the 
quarterly (3-month) average from at least one run per month for 
secondary emissions and the previous 12-month average of all runs for 
the primary control systems to determine compliance with the applicable 
emission limit. The owner or operator must include all valid runs in 
the quarterly (3-month) average. The duration of each run for secondary 
emissions must represent a complete operating cycle. The primary 
control system must be sampled over an 8-hour period, unless site-
specific factors dictate an alternative sampling time subject to the 
approval of the regulatory authority.
* * * * *
    (n) POM emissions from prebake potlines. Using the procedures in 
Sec.  63.847 and in the approved test plan, the owner or operator must 
monitor emissions of POM from each prebake potline every five years. 
The owner or operator must compute and record the sum of the average 
primary and secondary emissions using the procedures of Sec. Sec.  
63.847(e)(2) or (e)(8).
    10. Section 63.849 is amended by adding paragraph (f) to read as 
follows:

Sec.  63.849  Test methods and procedures.

* * * * *
    (f) The owner or operator must use ASTM Method D3177--02 (2007) for 
determination of the sulfur content in anode coke shipments to 
determine

[[Page 76289]]

compliance with the applicable facility wide emission limit for COS 
emissions.
    11. Section 63.850 is amended to read as follows:
    a. Revising paragraphs (c) and (d);
    b. Removing and reserving paragraph (e)(4)(iii); and
    c. Adding paragraphs (e)(4)(xvi), (e)(4)(xvii) and (f).
    The revisions and additions read as follows:

Sec.  63.850  Notification, reporting and recordkeeping requirements.

* * * * *
    (c) As of January 1, 2012, and within 60 days after the date of 
completing each performance test, as defined in Sec.  63.2, and as 
required in this subpart, the owner or operator must submit performance 
test data, except opacity data, electronically to the EPA's Central 
Data Exchange by using the ERT (see http://www.epa.gov/ttn/chief/ert/erttool.html/) or other compatible electronic spreadsheet. Only data 
collected using test methods compatible with ERT are subject to this 
requirement to be submitted electronically into the EPA's WebFIRE 
database.
    (d) Reporting. In addition to the information required under Sec.  
63.10 of the General Provisions, the owner or operator must provide 
semi-annual reports containing the information specified in paragraphs 
(d)(1) through (d)(2) of this section to the Administrator or 
designated authority.
    (1) Excess emissions report. As required by 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]
* * * * *
    (xvi) Records of the occurrence and duration of each malfunction of 
operation (i.e., process equipment) or the air pollution control 
equipment and monitoring equipment.
    (xvii) Records of actions taken during periods of malfunction to 
minimize emissions in accordance with 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.
    12. Section 63.854 is added to read as follows:

Sec.  63.854  Work Practice Standards for Periods of Startup.

    (a) Startup of potlines. If you own or operate a new or existing 
primary aluminum reduction affected source, you must comply with the 
requirements of paragraphs (a)(1) through (7) of this section during 
startup for each affected potline.
    (1) Develop a potline startup schedule before starting up the 
potline.
    (2) Keep records of number of pots started per day.
    (3) Bring the potline scrubbers and exhaust fans on line prior to 
energizing the first cell being restarted.
    (4) Ensure that the primary capture and control system is operating 
at all times during startup.
    (5) Keep pots covered during startup as much as practicable to 
include but not limited to minimizing the removal of covers or panels 
of the pots on which work is being performed.
    (6) Inspect potlines daily during startup and perform the following 
work practices as specified in paragraphs (a)(6)(i) through (iv) of 
this section.
    (i) Identify unstable pots as soon as practicable but in no case 
more than 12 hours from the time the pot became unstable;
    (ii) Reduce cell temperatures to as low as practicable, but no 
higher than the maximum temperature specified in the operating plan 
described in paragraph (a)(7) of this section;
    (iii) Reseal pot crusts that have been broken as often and as soon 
as practicable but in no case more than 24 hours from the time the 
crust was broken; and
    (iv) Adjust pot parameters to their optimum levels, as specified in 
the operating plan described in paragraph (a)(7) of this section, 
including, but not limited to, the following parameters: Alumina 
addition rate, exhaust air flow, cell voltage, feeding level, anode 
current and liquid and solid bath levels.
    (7) Prepare a written operating plan to minimize emissions during 
startup to include, but not limited to, the requirements in (a)(1) 
through (6) of this section.
    13. Section 63.855 is added to read as follows:

Sec.  63.855  Affirmative defense for exceedance of emission limit 
during malfunction.

    In response to an action to enforce the standards set forth in this 
subpart, you may assert an affirmative defense to a claim for civil 
penalties for exceedances of such standards that are caused by 
malfunction, as defined at Sec.  63.2. Appropriate penalties may be 
assessed, however, if you fail to meet your burden of proving all of 
the requirements in the affirmative defense. The affirmative defense 
shall not be available for claims for injunctive relief.
    (a) To establish the affirmative defense in any action to enforce 
such a limit, you must timely meet the notification requirements in 
Sec.  63.850, and must prove by a preponderance of evidence that:
    (1) The excess emissions:
    (i) Were caused by a sudden, infrequent, and unavoidable failure of 
air pollution control and monitoring equipment, process equipment, or a 
process to operate in a normal or usual manner; and
    (ii) Could not have been prevented through careful planning, proper 
design or better operation and maintenance practices; and
    (iii) Did not stem from any activity or event that could have been 
foreseen and avoided, or planned for.
    (iv) Were not part of a recurring pattern indicative of inadequate 
design, operation, or maintenance; and
    (2) Repairs were made as expeditiously as possible when the 
applicable emissions limitations were being exceeded. Off-shift and 
overtime labor were used, to the extent practicable to make these 
repairs; and
    (3) The frequency, amount and duration of the excess emissions 
(including any bypass) were minimized to the maximum extent practicable 
during periods of such emissions; and
    (4) If the excess emissions resulted from a bypass of control 
equipment or a process, then the bypass was unavoidable to prevent loss 
of life,

[[Page 76290]]

personal injury, or severe property damage; and
    (5) All possible steps were taken to minimize the impact of the 
excess emissions on ambient air quality, the environment and human 
health; and
    (6) All emissions monitoring and control systems were kept in 
operation if at all possible, consistent with safety and good air 
pollution control practices; and
    (7) All of the actions in response to the excess emissions were 
documented by properly signed, contemporaneous operating logs; and
    (8) At all times, the affected source was operated in a manner 
consistent with good practices for minimizing emissions; and
    (9) A written root cause analysis has been prepared, the purpose of 
which is to determine, correct, and eliminate the primary causes of the 
malfunction and the excess emissions resulting from the malfunction 
event at issue. The analysis shall also specify, using best monitoring 
methods and engineering judgment, the amount of excess emissions that 
were the result of the malfunction.
    (b) Notification. The owner or operator of the affected source 
experiencing an exceedance of its emissions limit(s) during a 
malfunction, shall notify the Administrator by telephone or facsimile 
transmission as soon as possible, but no later than two business days 
after the initial occurrence of the malfunction, if it wishes to avail 
itself of an affirmative defense to civil penalties for that 
malfunction. The owner or operator seeking to assert an affirmative 
defense, shall also submit a written report to the Administrator within 
45 days of the initial occurrence of the exceedance of the standards in 
this subpart to demonstrate, with all necessary supporting 
documentation, that it has met the requirements set forth in paragraph 
(e) of this section. The owner or operator may seek an extension of 
this deadline for up to 30 additional days by submitting a written 
request to the Administrator before the expiration of the 45 day 
period. Until a request for an extension has been approved by the 
Administrator, the owner or operator is subject to the requirement to 
submit such report within 45 days of the initial occurrence of the 
exceedance.
    14. Table 1 to Subpart LL of Part 63 is revised to read as follows:

                   Table 1 to Subpart LL of Part 63--Potline TF Limits for Emission Averaging
----------------------------------------------------------------------------------------------------------------
                                    Monthly TF limit (1b/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
     VSS2              2.6            2.5           2.5           2.4           2.4           2.4           2.4
      HSS              2.5            2.4           2.4           2.3           2.3           2.3           2.3
     SWPB              1.4            1.3           1.3           1.2           1.2           1.2           1.2
----------------------------------------------------------------------------------------------------------------

    15. Table 2 to Subpart LL of Part 63 is revised to read as follows:

                   Table 2 to Subpart LL of Part 63--Potline POM Limits for Emission Averaging
----------------------------------------------------------------------------------------------------------------
                                       POM limit (lb/ton) (for given number of potlines)
     Type     --------------------------------------------------------------------------------------------------
                  2 lines        3 lines       4 lines       5 lines       6 lines       7 lines       8 lines
----------------------------------------------------------------------------------------------------------------
      HSS              3.5            3.2           3.1           3.0           3.0           2.9           2.8
     VSS2              3.5            3.3           3.2           3.1           3.0           2.9           2.9
    CWPB1              0.63           0.56          0.52          0.52          0.48          0.48          0.48
    CWBP2              1.4            1.35          1.31          1.31          1.26          1.26          1.26
    CWBP3              1.33           1.28          1.28          1.26          1.26          1.26          1.26
     SWPB              0.63           0.56          0.52          0.52          0.48          0.48          0.48
----------------------------------------------------------------------------------------------------------------

    16. Appendix A to Subpart LL of Part 63 is revised to read as 
follows:

Appendix A to Subpart LL of Part 63--Applicability of General 
Provisions (40 CFR Part 63, Subpart A)

------------------------------------------------------------------------
                               Applies to  subpart
 Reference Section(s) * * *            LL                  Comment
------------------------------------------------------------------------
63.1........................  Yes.                  ....................
63.2........................  Yes.                  ....................
63.3........................  Yes.                  ....................
63.4........................  Yes.                  ....................
63.5........................  Yes.                  ....................
63.6(a), (b), (c)...........  Yes.                  ....................
63.6(d).....................  No..................  Section reserved.
63.6(e)(1)(i)...............  No..................  See 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.                  ....................

[[Page 76291]]

 
63.6(e)(2)..................  No..................  Section reserved.
63.6(e)(3)..................  No.                   ....................
63.6(f)(1)..................  No.                   ....................
63.6(g).....................  Yes.                  ....................
63.6(h).....................  No..................  No opacity limits in
                                                     rule.
63.6(i).....................  Yes.                  ....................
63.6(j).....................  Yes.                  ....................
63.7(a) through (d).........  Yes.                  ....................
63.7(e)(1)..................  No..................  See Sec.
                                                     63.847(d).
63.7(e)(2) through (e)(4)...  Yes.                  ....................
63.7(f), (g), (h)...........  Yes.                  ....................
63.8(a) and (b).............  Yes.                  ....................
63.8(c)(1)(i)...............  No..................  See 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),  Yes.                  ....................
 (h)(1) through (3), (h)(5)
 and (6), (i) and (j).
63.9(f).....................  No.                   ....................
63.9(h)(4)..................  No..................  Section reserved.
63.10(a)....................  Yes.                  ....................
63.10(b)(1).................  Yes.                  ....................
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           No.                   ....................
 (b)(2)(v).
63.10(b)(2)(vi) through       Yes.                  ....................
 (b)(2)(xiv).
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 (c)(14)  Yes.                  ....................
63.10(c)(15)................  No.                   ....................
63.10(d)(1) through (4).....  Yes.                  ....................
63.10(d)(5).................  No..................  See Sec.
                                                     63.850(d)(2) for
                                                     reporting of
                                                     malfunctions.
63.10(e) and (f)............  Yes.                  ....................
63.11.......................  No..................  Flares will not be
                                                     used to comply with
                                                     the emission
                                                     limits.
63.12 through 63.15.........  Yes.                  ....................
------------------------------------------------------------------------

[FR Doc. 2011-29881 Filed 12-5-11; 8:45 am]
BILLING CODE 6560-50-P