Federal Register, Volume 76 Issue 234 (Tuesday, December 6, 2011)

[Federal Register Volume 76, Number 234 (Tuesday, December 6, 2011)]
[Proposed Rules]
[Pages 76259-76291]
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:

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