[Federal Register Volume 80, Number 199 (Thursday, October 15, 2015)]
[Rules and Regulations]
[Pages 62389-62427]
[FR Doc No: 2015-25137]

Vol. 80

Thursday,

No. 199

October 15, 2015

Part IV

Environmental Protection Agency

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40 CFR Part 63

 National Emission Standards for Hazardous Air Pollutants for Primary
Aluminum Reduction Plants; Final Rule

Federal Register / Vol. 80 , No. 199 / Thursday, October 15, 2015 /
Rules and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2011-0797; FRL-9934-16-OAR]
RIN 2060-AQ92

National Emission Standards for Hazardous Air Pollutants for
Primary Aluminum Reduction Plants

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action finalizes the residual risk and technology review
(RTR) conducted for the Primary Aluminum Production source category
regulated under national emission standards for hazardous air
pollutants (NESHAP). In addition, we are taking final action regarding
new and revised emission standards for various hazardous air pollutants
(HAP) emitted by this source category based on the RTR, newly obtained
emissions test data, and comments we received in response to the 2011
proposal and 2014 supplemental proposal.
    These final amendments include technology-based standards and work
practice standards reflecting performance of maximum achievable control
technology (MACT), and related monitoring, reporting, and testing
requirements, for several previously unregulated HAP from various
emissions sources. Furthermore, based on our risk review, we are
finalizing new and revised emission standards for certain HAP emissions
from potlines using the Soderberg technology to address risk. We are
also adding a requirement for electronic reporting of compliance data,
eliminating the exemptions for periods of startup, shutdown, and
malfunctions (SSM), and not adopting the affirmative defense provisions
proposed in 2011, consistent with a recent court decision vacating the
affirmative defense provisions. This action will provide improved
environmental protection regarding potential emissions of HAP emissions
from primary aluminum reduction facilities.

DATES: This final action is effective on October 15, 2015. The
incorporation by reference of certain publications listed in the rule
is approved by the Director of the Federal Register as of October 15,
2015.

ADDRESSES: The Environmental Protection Agency (EPA) has established a
docket for this action under Docket ID No. EPA-HQ-OAR-2011-0797. All
documents in the docket are listed on the www.regulations.gov Web site.
Although listed in the index, some information is not publicly
available, e.g., confidential business information (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 form. Publicly
available docket materials are available either electronically through
http://www.regulations.gov, or in hard copy at the EPA Docket Center,
EPA WJC West Building, Room Number 3334, 1301 Constitution Ave. NW.,
Washington, DC. The Public Reading Room hours of operation are 8:30
a.m. to 4:30 p.m. Eastern Standard Time (EST), Monday through Friday.
The telephone number for the Public Reading Room is<PHONE_NUMBER>, and
the telephone number for the EPA Docket Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For questions about this final action,
contact Mr. David Putney, Sector Policies and Programs Division (D243-
02), Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina, 27711;
telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; and email
address<EMAIL_ADDRESS>For specific information regarding the
risk modeling methodology, contact Mr. Jim Hirtz, Health and
Environmental Impacts Division (C539-02), Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina 27711; telephone number:<PHONE_NUMBER>;
fax number:<PHONE_NUMBER>; and email address<EMAIL_ADDRESS>For
information about the applicability of the NESHAP to a particular
entity, contact Mr. Patrick Yellin, Office of Enforcement and
Compliance Assurance, U.S. Environmental Protection Agency, EPA WJC
South Building, 1200 Pennsylvania Ave. NW., Washington, DC 20460;
telephone number:<PHONE_NUMBER>; and email address:
<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:
    Preamble Acronyms and Abbreviations. We use multiple acronyms and
terms in this preamble. While this list may not be exhaustive, to ease
the reading of this preamble and for reference purposes, the EPA
defines the following terms and acronyms here:

AERMET AERMOD Meteorological Preprocessor
AERMOD American Meteorological Society and EPA Regulatory Model
As arsenic
BLDS bag leak detection systems
BLP Buoyant Line and Point source model
CAA Clean Air Act
CBI confidential business information
CDX Central Data Exchange
CEMS continuous emission monitoring system
CFR Code of Federal Regulations
CRA Congressional Review Act
CWPB1 center-worked prebake one
CWPB2 center-worked prebake two
CWPB3 center-worked prebake three
D/F dioxins and furans
dscm dry standard cubic meter
ERT Electronic Reporting Tool
FR Federal Register
HAP hazardous air pollutant(s)
HEM3 Human Exposure Model version 3
Hg mercury
HQ hazard quotient
IBR incorporation by reference
ICR information collection request
lb pound(s)
lb/ton pound(s) per ton
lb/yr pound(s) per year
MACT maximum achievable control technology
MIR maximum individual risk
NESHAP National Emission Standards for Hazardous Air Pollutants
Ni nickel
NTTAA National Technology Transfer and Advancement Act
PCB polychlorinated biphenyls
PM particulate matter
PM2.5 p.m. with diameter of 2.5 microns and less
POM polycyclic organic matter
PRA Paperwork Reduction Act
RDL representative detection limit
REL reference exposure level
RFA Regulatory Flexibility Act
RIA Regulatory Impact Analysis
RIN Regulatory Information Number
RTR Residual Risk and Technology Review
SSM startup, shutdown, and malfunction
SWPB side-worked prebake
TEQ toxicity equivalence
TOSHI target organ-specific hazard index
TTN Technology Transfer Network
[micro]g microgram(s)
[micro]g/dscm microgram(s) per dry standard cubic meter
UMRA Unfunded Mandates Reform Act
UPL upper prediction limit
VE visible emissions
VSS2 vertical stud Soderberg two

    Background Information. On December 6, 2011, and December 8, 2014,
the EPA proposed revisions to the Primary Aluminum Reduction Plants
NESHAP based on our RTR and MACT review. After considering public
comments, in this action, we are finalizing decisions and revisions for
the rule. We summarize some of the more significant comments we timely
received regarding the 2011 and 2014 proposed rules and provide our
responses in this preamble. A summary of all other public comments on
the proposals and the EPA's responses to those comments is available in
the National Emission Standards for

Hazardous Air Pollutants: Primary Aluminum Reduction Plants Summary of
Public Comments and Responses document, which is available in the
docket for this action (Docket ID No. EPA-HQ-OAR-2011-0797). A ``track
changes'' version of the regulatory language that incorporates the
changes in this action is also available in the docket for this action.
    Organization of this Document. The information in this preamble is
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related
information?
    C. Judicial Review and Administrative Reconsideration
II. Background
    A. What is the statutory authority for this action?
    B. What is the Primary Aluminum Production source category and
how does the NESHAP regulate HAP emissions from the source category?
    C. What changes did we propose for the Primary Aluminum
Production source category in our December 6, 2011, proposal and
December 8, 2014, proposal?
III. What is included in this final rule?
    A. What are the final rule amendments based on the risk review
for the Primary Aluminum Production source category?
    B. What are the final rule amendments based on the technology
review for the Primary Aluminum Production source category?
    C. What are the final rule amendments pursuant to Clean Air Act
sections 112(d)(2) and (3) for the Primary Aluminum Production
source category?
    D. What are the final rule amendments addressing emissions
during periods of SSM?
    E. What other changes have been made to the Primary Aluminum
Reduction Plants NESHAP?
    F. What are the effective and compliance dates of the standards?
    G. What are the requirements for submission of performance test
data to the EPA?
    H. What materials are being incorporated by reference?
IV. What is the rationale for our final decisions and amendments for
the Primary Aluminum Production source category?
    A. Residual Risk Review for the Primary Aluminum Production
Source Category
    B. CAA Sections 112(d)(2) and (3) Revisions for the Primary
Aluminum Production Source Category
    C. Revisions to the Work Practice Standards for the Primary
Aluminum Production Source Category
    D. What changes did we make to the control device monitoring
requirements for the Primary Aluminum Production source category?
    E. What changes did we make to compliance dates for the Primary
Aluminum Production source category?
V. Summary of Cost, Environmental, and Economic Impacts and
Additional Analyses Conducted
    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?
    F. What analysis of environmental justice did we conduct?
    G. What analysis of children's environmental health did we
conduct?
VI. Statutory and Executive Order Reviews
    A. Executive Orders 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    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 (NTTAA) and
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act (CRA)

I. General Information

A. Does this action apply to me?

    Regulated Entities. Categories and entities potentially regulated
by this action are shown in Table 1 of this preamble.

 Table 1--NESHAP and Industrial Source Categories Affected by This Final
                                 Action
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                                                                NAICS a
                  NESHAP and source category                      code
------------------------------------------------------------------------
Primary Aluminum Reduction Plants............................     331312
------------------------------------------------------------------------
a North American Industry Classification System.

    Table 1 of this preamble is not intended to be exhaustive, but
rather to provide a guide for readers regarding entities likely to be
affected by the final action for the source category listed. To
determine whether your facility is affected, you should examine the
applicability criteria in the appropriate NESHAP. If you have any
questions regarding the applicability of any aspect of this NESHAP,
please contact the appropriate person listed in the preceding FOR
FURTHER INFORMATION CONTACT section of this preamble.

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

    In addition to being available in the docket, an electronic copy of
this final action will also be available on the Internet through the
Technology Transfer Network (TTN) Web site, a forum for information and
technology exchange in various areas of air pollution control.
Following signature by the EPA Administrator, the EPA will post a copy
of this final action at http://www.epa.gov/ttn/atw/alum/alumpg.html.
Following publication in the Federal Register, the EPA will post the
Federal Register version and key technical documents at this same Web
site.
    Additional information is available on the RTR Web site at http://www.epa.gov/ttn/atw/rrisk/rtrpg.html. This information includes an
overview of the RTR program, links to project Web sites for the RTR
source categories and detailed emissions and other data we used as
inputs to the risk assessments.

C. Judicial Review and Administrative Reconsideration

    Under Clean Air Act (CAA) section 307(b)(1), judicial review of
this final action is available only by filing a petition for review in
the United States Court of Appeals for the District of Columbia Circuit
by December 14, 2015. Under CAA section 307(b)(2), the requirements
established by this final rule may not be challenged separately in any
civil or criminal proceedings brought by the EPA to enforce the
requirements.
    Section 307(d)(7)(B) of the CAA further provides that ``[o]nly an
objection to a rule or procedure which was raised with reasonable
specificity during the period for public comment (including any public
hearing) may be raised during judicial review.'' This section also
provides a mechanism for the EPA to reconsider the rule ``[i]f the
person raising an objection can demonstrate to the Administrator that
it was impracticable to raise such objection within [the period for
public comment] or if the grounds for such objection arose after the
period for public comment (but within the time specified for judicial
review) and if such objection is of central relevance to the outcome of
the rule.'' Any person seeking to make such a demonstration should
submit a Petition for Reconsideration to the Office of the
Administrator, U.S. EPA, Room 3000,

EPA WJC North Building, 1200 Pennsylvania Ave. NW., Washington, DC
20460, with a copy to both the person(s) listed in the preceding FOR
FURTHER INFORMATION CONTACT section, and the Associate General Counsel
for the Air and Radiation Law Office, Office of General Counsel (Mail
Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW., Washington, DC
20460.

II. Background

A. What is the statutory authority for this action?

    Section 112 of the CAA establishes a two-stage regulatory process
to address emissions of HAP from stationary sources. In the first
stage, we must identify categories of sources emitting one or more of
the HAP listed in CAA section 112(b) and then promulgate technology-
based NESHAP for those sources. ``Major sources'' are those that emit,
or have the potential to emit, any single HAP at a rate of 10 tons per
year (tpy) or more, or 25 tpy or more of any combination of HAP. For
major sources, these standards are commonly referred to as MACT
standards and must reflect the maximum degree of emission reductions of
HAP achievable (after considering cost, energy requirements, and non-
air quality health and environmental impacts). In developing MACT
standards, CAA section 112(d)(2) directs the EPA to consider the
application of measures, processes, methods, systems, or techniques,
including, but not limited to, those that reduce the volume of or
eliminate HAP emissions through process changes, substitution of
materials, or other modifications; enclose systems or processes to
eliminate emissions; collect, capture, or treat HAP when released from
a process, stack, storage, or fugitive emissions point; are design,
equipment, work practice, or operational standards; or any combination
of the above.
    For these MACT standards, the statute specifies certain minimum
stringency requirements, which are referred to as MACT floor
requirements and which may not be based on cost considerations. See CAA
section 112(d)(3). For new sources, the MACT floor cannot be less
stringent than the emission control achieved in practice by the best-
controlled similar source. The MACT standards 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 under CAA section 112(d)(2). We may establish
standards more stringent than the floor, based on the consideration of
the cost of achieving the emissions reductions, any non-air quality
health and environmental impacts, and energy requirements.
    In the second stage of the regulatory process, the CAA requires the
EPA to undertake two different analyses, which we refer to as the
technology review and the residual risk review. Under the technology
review, we must review the technology-based standards and revise them
``as necessary (taking into account developments in practices,
processes, and control technologies)'' no less frequently than every 8
years, pursuant to CAA section 112(d)(6). Under the residual risk
review, we must evaluate the risk to public health remaining after
application of the technology-based standards and revise the standards,
if necessary, to provide an ample margin of safety to protect public
health or to prevent, taking into consideration costs, energy, safety,
and other relevant factors, an adverse environmental effect. The
residual risk review is required within 8 years after promulgation of
the technology-based standards, pursuant to CAA section 112(f). In
conducting the residual risk review, if the EPA determines that the
current standards provide an ample margin of safety to protect public
health, it is not necessary to revise the MACT standards pursuant to
CAA section 112(f).\1\ For more information on the statutory authority
for this rule, see 76 FR 76259 and 79 FR 72914.
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    \1\ The U.S. Court of Appeals has affirmed this approach of
implementing CAA section 112(f)(2)(A). See 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.'').
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    Today's amendments involve rule changes pursuant to these
authorities. Specifically, pursuant to CAA sections 112(d)(2) and (3),
and 112(h), the EPA is amending the NESHAP to add standards for HAP not
previously addressed. In addition, pursuant to CAA section 112(f), the
EPA is amending certain MACT standards already promulgated to address
risk. The EPA also conducted a technology review and determined that no
further changes to the rule are necessary (within the meaning of CAA
section 112(d)(6)) to reflect developments in practices, processes, and
control technologies other than the work practices for anode bake
furnaces and paste plants during startup periods, and work practices
for potlines during normal operations (to help minimize POM, TF, and PM
emissions), described in the 2011 and 2014 proposals.

B. What is the Primary Aluminum Production source category and how does
the NESHAP regulate HAP emissions from the source category?

    The EPA promulgated the Primary Aluminum Reduction Plants NESHAP,
which apply to the Primary Aluminum Production source category, on
October 7, 1997 (62 FR 52407). The rule was amended on November 2, 2005
(70 FR 66280). The associated standards are codified at 40 CFR part 63,
subpart LL.
    The Primary Aluminum Production source category consists of
facilities that produce aluminum from refined bauxite ore (also known
as alumina), using an electrolytic reduction process in a series of
cells called a ``potline.'' The two main potline types are prebake (a
newer, higher-efficiency, lower-emitting technology) and Soderberg (an
older, lower-efficiency, higher-emitting technology). The raw materials
include alumina, petroleum coke, pitch, and fluoride salts. According
to information available on the Web site of The Aluminum Association,
Inc. (http://www.aluminum.org), approximately 40 percent of the
aluminum produced in the U.S. comes from primary aluminum facilities.
The other 60 percent either comes from Secondary Aluminum Production
facilities or is imported.
    Primary aluminum reduction facilities emit HAP from four basic
processes: Pitch storage tanks, paste production plants, anode bake
furnaces, and potlines. Operators form anode paste in the paste
production plant from a mixture of petroleum coke and pitch. In a
prebake facility, this anode paste is then formed into anodes and baked
in an anode bake furnace. Operators subsequently place these
``prebaked'' anodes into a prebake potline where they are consumed via
the electrolytic reduction process. Soderberg facilities do not have
anode bake furnaces. Instead, the anode paste is fed directly into the
Soderberg potlines and baked in place to form anodes, which again are
consumed via the electrolytic reduction process.
    There are currently 11 facilities located in the United States that
are subject to the requirements of this NESHAP: 10 primary aluminum
reduction plants and one carbon-only prebake anode production facility.
These 10 primary aluminum reduction

plants have approximately 35 potlines that produce aluminum. Each of
the 10 primary aluminum reduction plants has a paste production plant
and at least one anode bake furnace (for a total of about 22 existing
anode bake furnaces). However, not all existing paste production plants
and anode bake furnaces are currently operating, as some facilities
obtain their prebaked anodes from the carbon-only prebake anode
production facility. All currently operating primary aluminum
facilities use prebake potlines.
    At the time of the 2011 proposal, there were two facilities in the
U.S. that used Soderberg potlines. One of those facilities (Massena
East) was operating at that time, and the other (Columbia Falls) was
idle. However, in 2014, before publication of the supplemental
proposal, the Massena East facility was permanently shut down.
Therefore, at the time we published the supplemental proposal, there
was only one Soderberg facility (Columbia Falls) in the U.S., which was
idle. After publication of the 2014 supplemental proposal, we learned
that the one remaining idle Soderberg facility located in Columbia
Falls was permanently shut down. We also learned that one prebake
facility (run by Ormet Primary Aluminum Corporation) was shut down.
Therefore, currently there are 10 existing facilities with potlines
(all prebake facilities) in the source category plus the one facility
without potlines that only produces anodes.
    The major HAP emitted by these facilities are carbonyl sulfide
(COS), hydrogen fluoride (HF), particulate HAP metals and polycyclic
organic matter (POM), specifically polycyclic aromatic hydrocarbons
(PAH).
    The current Primary Aluminum Reduction Plants NESHAP (as they
existed before today's final action) included MACT standards
(promulgated in 1997 and 2005) for emissions of total fluorides (TF)
(as a surrogate for HF) from anode bake furnaces and potlines and for
emissions of POM from paste production plants, anode bake furnaces,
Soderberg potlines, and new pitch storage tanks.

C. What changes did we propose for the Primary Aluminum Production
source category in our December 6, 2011, proposal and our December 8,
2014, proposal?

    On December 6, 2011, and December 8, 2014, the EPA published
proposed rules in the Federal Register for the Primary Aluminum
Reduction Plants NESHAP, 40 CFR part 63, subpart LL, that took into
consideration the RTR analyses and other reviews of the rule. In the
proposed rules, we proposed several minor clarifications and
corrections, and the items summarized in Table 2, below.

  Table 2--Summary of Changes Proposed Pursuant to Analyses Associated
                            With This Action
------------------------------------------------------------------------
                                                         As a result of
            Action                     Proposal          which analysis
------------------------------------------------------------------------
2011 proposal (76 FR 76259)...  COS emission limits     CAA section
                                 for new and existing    112(d)(2) and
                                 potlines.               (3).
                                POM emission limits
                                 for new and existing
                                 prebake potlines and
                                 existing pitch
                                 storage tanks.
                                Work practices for      CAA section
                                 anode bake furnaces     112(d)(6)
                                 during startup          Technology
                                 periods.                review.
                                Work practices for      CAA section
                                 potlines during         112(h).
                                 startup periods.
                                Revised POM emission    CAA section
                                 limits for Soderberg    112(f) Risk
                                 potlines.               Review.
2014 proposal (79 FR 72914)...  Revised POM emission    CAA section
                                 limits for new and      112(d)(2) and
                                 existing prebake        (3).
                                 potlines.
                                Emission limits for
                                 particulate matter
                                 (PM) for new and
                                 existing potlines,
                                 anode bake furnaces
                                 and paste production
                                 plants.
                                Revised work practice
                                 standards for
                                 potlines.
                                Reduced testing         CAA section
                                 frequencies for         112(d)(2) and
                                 potlines.               (3).
                                Work practices for      CAA section
                                 paste production        112(d)(6)
                                 plants during startup   Technology
                                 periods.                Review.
                                Nickel (Ni), arsenic    CAA section
                                 (As) and revised POM    112(f) Risk
                                 emission limits for     Review.
                                 Soderberg potlines.
------------------------------------------------------------------------

III. What is included in this final rule?

    This action finalizes the EPA's determinations pursuant to the RTR
provisions of CAA section 112 for the Primary Aluminum Production
source category, finalizes our reviews of other aspects of the rule,
and amends the Primary Aluminum Reduction Plants NESHAP based on those
determinations and reviews. The changes being finalized in this action
include the following: The promulgation of MACT floor-based limits for
previously unregulated HAP (e.g., COS and PM); emissions limits for
POM, As, and Ni from Soderberg potlines to address risk; the addition
of work practice standards for paste production plants, potlines and
anode bake furnaces; and the removal of SSM exemptions. This final
action includes several changes to the proposed requirements in the
December 2011 and December 2014 proposals based on consideration of
comments and information received during the public comment periods as
described in section IV of this preamble.

A. What are the final rule amendments based on the risk review for the
Primary Aluminum Production source category?

    This section provides a summary of the final amendments to the
Primary Aluminum Reduction Plants NESHAP being promulgated in this
action pursuant to CAA section 112(f).
    To address risk, we are promulgating emission limits for POM, As,
and Ni from existing vertical stud Soderberg two (VSS2) potlines at the
following levels: 1.9 pounds (lb) POM/ton of aluminum produced, 0.006
lb As/ton of aluminum produced, and 0.07 lb Ni/ton of aluminum
produced.
    To address risk, we are promulgating As and Ni emission limits for
new Soderberg potlines at the following levels: 0.006 lb As/ton of
aluminum produced and 0.07 lb Ni/ton of aluminum produced. New or
reconstructed Soderberg potlines would also be subject to the POM limit
of 0.77 lb per ton of aluminum produced that we are promulgating for
all new potlines. These emission limits for POM, Ni, and As for new and
existing Soderberg plants being promulgated in this rule are the same
as the limits proposed in the 2014 supplemental proposal. Additional
information regarding the limits addressing risk is available in the
Development of Emissions Standards to Address Risks for the Primary
Aluminum Production Source Category Pursuant to Section 112(f) of the
Clean Air Act, which is

available in the docket for this rulemaking (Docket ID No. EPA-HQ-OAR-
2011-0797). As noted earlier, the last remaining Soderberg primary
aluminum facility in the U.S. announced the permanent closure of that
facility after publication of the supplemental proposal in 2014.
Notwithstanding our well-supported expectation that this facility will
not reopen and that no new Soderberg facilities will be constructed due
to the less efficient and higher emitting nature of the Soderberg
technology, we are finalizing, as proposed, the standards for POM, As,
and Ni associated with Soderberg facilities in the final rule to
address the risk from existing potlines at the Columbia Falls facility
that have not yet been demolished and to ensure that risks would be
acceptable and to provide an ample margin of safety in the very
unlikely event that a new Soderberg facility is ever built.

B. What are the final rule amendments based on the technology review
for the Primary Aluminum Production source category?

    Based on our analyses of the data and information collected and our
general understanding of the industry and other available information
on potential controls for this industry, we have determined that there
are no developments in practices, processes, and control technologies
that warrant revisions to the MACT standards for this source category,
other than the work practices for anode bake furnaces during startup
periods (described in the December 2011 proposal), the work practices
for paste plants during startup (described in the 2014 proposal) and
work practices for potlines (to minimize emissions of PM, TF and POM)
during normal operations (described in the 2014 supplemental proposal).
We are promulgating these work practices as proposed for anode bake
furnaces and paste plants during startup periods, and for potlines
during normal operations, under section 112(d)(6) of the CAA. These
standards apply to both new and existing sources using either of the
production technologies.
    In summary, we are not revising the MACT standards under CAA
section 112(d)(6) other than the startup work practices for anode bake
furnaces and paste plants described in the 2011 and 2014 proposals, and
the work practices for potlines during normal operations described in
the 2014 supplemental proposal. Additional information is available in
the Final Technology Review for the Primary Aluminum Production Source
Category document, which can be found in the docket for this rulemaking
(Docket ID No. EPA-HQ-OAR-2011-0797).

C. What are the final rule amendments pursuant to Clean Air Act
sections 112(d)(2) and (3) for the Primary Aluminum Production source
category?

    We are promulgating MACT emission limits for COS, PM (as a
surrogate for HAP metals other than mercury (Hg)), Hg, and
polychlorinated biphenyls (PCB),\2\ all of which were previously
unregulated HAP, pursuant to CAA sections 112(d)(2) and (3). In
addition, we are promulgating MACT limits for emissions of POM from new
and existing prebake potlines and existing pitch storage tanks, which
were previously unregulated sources of POM. A summary of the
promulgated MACT standards is provided in Table 3, below, and
additional information is available in the Final MACT Floor Analysis
for the Primary Aluminum Production Source Category document, which is
available in the docket for this action (Docket ID No. EPA-HQ-OAR-2011-
0797). For more information on the MACT standards that the EPA
promulgated and how they are different from those the EPA proposed, see
section VI.B of this preamble.
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    \2\ From Soderberg potlines only.

             Table 3--Summary of Promulgated MACT Standards
------------------------------------------------------------------------
                                                      Promulgated MACT
             HAP                     Source               standard
------------------------------------------------------------------------
COS.........................  New potlines........  3.1 lb/ton aluminum
                                                     produced.
                              Existing potlines...  3.9 lb/ton aluminum
                                                     produced.
POM.........................  New potlines........  0.77 lb/ton aluminum
                                                     produced.
                              Existing potlines:
                                 CWPB1............  1.1 lb/ton aluminum
                                                     produced.
                                 CWPB2............  12 lb/ton aluminum
                                                     produced.
                                 CWPB3............  2.7 lb/ton aluminum
                                                     produced.
                                 SWPB.............  17 lb/ton aluminum
                                                     produced.
                              Existing pitch        Minimum 95-percent
                               storage tanks.        reduction of inlet
                                                     POM emissions.
PM..........................  New potlines........  4.9 lb/ton aluminum
                                                     produced.
                              Existing potlines:
                                 CWPB1............  7.4 lb/ton aluminum
                                                     produced.
                                 CWPB2............  11 lb/ton aluminum
                                                     produced.
                                 CWPB3............  20 lb/ton aluminum
                                                     produced.
                                 SWPB.............  4.9 lb/ton aluminum
                                                     produced.
                                 VSS2.............  26 lb/ton aluminum
                                                     produced.
                              New anode bake        0.07 lb/ton of green
                               furnace.              anode produced.
                              Existing anode bake   0.20 lb/ton of green
                               furnace.              anode produced.
                              New paste production  0.0056 lb/ton of
                               plant.                paste produced.
                              Existing paste        0.082 lb/ton of
                               production plant.     paste produced.
PCB.........................  New and existing      2.0 micrograms
                               Soderberg potlines.   ([micro]g) toxicity
                                                     equivalence (TEQ)
                                                     per ton of aluminum
                                                     produced.
Hg..........................  New and existing      1.7 [mu]g per dry
                               anode bake furnaces.  standard cubic
                                                     meter (dscm).
------------------------------------------------------------------------
CWPB1 = Center-worked prebake one.
CWPB2 = Center-worked prebake two.
CWPB3 = Center-worked prebake three.
SWPB = Side-worked prebake.
VSS2 = Vertical stud Soderberg two.

D. What are the final rule amendments addressing emissions during
periods of SSM?

    We are finalizing, as proposed in the 2014 proposal, changes to the
Primary Aluminum Reduction Plants NESHAP to eliminate the exemption in
the present rules for emissions occurring during SSM operations.
Consistent with Sierra Club v. EPA, 551 F. 3d 1019 (D.C. Cir. 2008),
the EPA is establishing standards in this rule that apply at all times.
Appendix A to subpart LL of 40 CFR part 63 (General Provisions
applicability table) is being revised to change several references
related to requirements that apply during periods of SSM. We are also
eliminating or revising certain recordkeeping and reporting
requirements related to the eliminated SSM exemption. The EPA also made
changes to the rule to remove or modify inappropriate, unnecessary, or
redundant language in the absence of the SSM exemption. We are also not
adopting the affirmative defense provisions proposed in 2011,
consistent with a recent court decision vacating the affirmative
defense provisions in one of the EPA's CAA section 112(d) regulations.
NRDC v. EPA, 749 F. 3d 1055 (D.C. Cir. 2014).
    In addition, we are finalizing work practices for potlines, paste
production plants, and anode bake furnaces during startup periods that
will ensure improved capture and control of emissions from those
sources.

E. What other changes have been made to the Primary Aluminum Reduction
Plants NESHAP?

    This rule also finalizes revisions to several other Primary
Aluminum Reduction Plants NESHAP requirements as proposed, or in some
cases with some modification, which are summarized in this section.
1. Electronic Reporting Tool
    To increase the ease and efficiency of data submittal and data
accessibility, we are finalizing, as proposed, a requirement that
owners and operators of sources subject to the Primary Aluminum
Reduction Plants NESHAP submit electronic copies of certain required
performance test reports through an electronic performance test report
tool called the Electronic Reporting Tool (ERT). This requirement to
submit performance test data electronically to the EPA does not require
any additional performance testing and applies only to those
performance tests conducted using test methods that are supported by
the ERT. A listing of the pollutants and test methods supported by the
ERT is available at the ERT Web site.
2. Work Practice Standards
    We are finalizing work practice standards for all potlines (i.e.
both prebake and Soderberg) and for anode bake furnaces that will
ensure improved capture and control of TF, POM, and PM emissions from
those sources. These work practice standards also address Hg emissions
from all potlines, PCB emissions from prebake potlines and anode bake
furnaces, and dioxins and furan (D/F) emissions from Soderberg potlines
(see section IV.C of this preamble for additional discussion of these
work practice standards).
3. Control Device and Emissions Monitoring
    We are finalizing new twice-daily visible emissions (VE) monitoring
requirements as an alternative to bag leak detection systems (BLDS) or
PM continuous emissions monitoring systems (CEMS) for control devices
installed on existing sources (see section IV.D of this preamble for
additional discussion of these monitoring changes).
    We are finalizing the inclusion of PM for the potline similarity
option found in the current subpart LL at 40 CFR 63.848(d). This
section allows an owner or operator to use the monitoring of secondary
TF and/or POM emissions from one potline to represent the performance
of other ``similar'' potlines. Potlines are similar ``if the owner or
operator demonstrates that their structure, operability, type of
emissions, volume of emissions and concentration of emissions are
substantially equivalent.'' Based on consideration of comments and
information received in responses to the 2014 proposal, the EPA is
amending the existing rule to allow potline owners or operators this
same option for PM. That is, potline owners and operators now will have
the option to establish ``similarity of potlines'' with respect to PM
emissions. ``Similarity'' would be established based on the criteria
already applicable with respect to TF and POM. See subpart LL at 40 CFR
63.848(d). As with TF and POM, an owner or operator would have to make
this demonstration to the applicable regulatory authority and obtain
approval from that authority.
4. Emission Averaging
    We are modifying 40 CFR 63.846 to allow emission averaging in the
case of PM from potlines and anode bake furnaces. That section
currently allows emission averaging in the cases of POM and TF from
these process units with certain prohibitions (e.g., averaging between
different pollutants or process units is not allowed). We are only
adding PM to these existing provisions, and not reopening the core
concept of allowing emission averaging.
5. Alternative Emissions Limits for Co-Controlled New and Existing
Anode Bake Furnaces
    We are also finalizing the alternative emissions limits for co-
controlled new and existing anode bake furances as proposed in the 2014
supplemental proposal (79 FR 72949).
6. Minor Technical and Editorial Revisions
    We are also finalizing other minor technical and editorial changes
to the NESHAP in response to comments received during the public
comment period for the proposal and supplemental proposal, as described
in this preamble.

F. What are the effective and compliance dates of the standards?

    The revisions to the MACT standards being promulgated in this
action are effective on October 15, 2015.
    The compliance dates for existing sources are:
    October 15, 2015 for the malfunction provisions and the electronic
reporting provisions;
    October 17, 2016 for potline work practice standards and COS
emission limits, for Soderberg potline PM and PCB emission limits, and
for anode bake furnace and paste production plant work practices and PM
emission limits; and
    October 16, 2017 for prebake potline POM and PM emission limits;
for Soderberg potline revised POM emission limits and emission limits
for Ni and As; for anode bake furnace Hg emission limits; and for pitch
storage tank POM equipment standards.
    For more information on how we selected compliance dates for
existing sources, refer to section IV.E of this preamble and the Final
Rationale for Selection of Compliance Dates for the Primary Aluminum
Production Source Category document, which can be found in the docket
for this rulemaking (Docket ID No. EPA-HQ-OAR-2011-0797).
    New sources must typically comply with all of the standards
immediately upon the effective date of the standard, or upon startup,
whichever is later. CAA section 112(i)(1).\3\ CAA section 112(a)(4)

indicates that a new source is one which commenced construction (or
reconstruction) after the Administrator first proposes regulations
under CAA section 112 for the source category. We have interpreted this
date to be the date of the December 2014 proposal given the
substantially new record set forth in that proposal. Consequently, for
the purposes of compliance with the emission standards for PM, a new
affected potline, anode bake furnace, or paste production plant is one
for which construction or reconstruction commenced after December 8,
2014, the date on which the EPA first proposed the amendments finalized
here. For the purposes of compliance with the emission standards for
POM and COS, a new affected potline is one for which construction or
reconstruction commenced after December 8, 2014. For the purposes of
compliance with the emission standards for Hg or PCB, a new affected
anode bake furnace or Soderberg potline is one for which construction
or reconstruction commenced after December 8, 2014, although the
compliance dates for these standards are October 16, 2017 for anode
bake furnaces and October 17, 2016 for Soderberg potlines, since these
standards differ from the proposal (see CAA section 112(i)(2)).
---------------------------------------------------------------------------

    \3\ If a new source standard is more stringent than the standard
proposed, a new source may have three years to comply, provided it
complies with the proposed standard during that 3-year period. CAA
section 112(i)(2).
---------------------------------------------------------------------------

G. What are the requirements for submission of performance test data to
the EPA?

    The EPA is requiring owners and operators of sources subject to the
Primary Aluminum Reduction Plants NESHAP facilities to submit
electronic copies of certain required performance test reports [and any
other reports, e.g. performance evaluation reports] through the EPA's
Central Data Exchange (CDX) using the Compliance and Emissions Data
Reporting Interface (CEDRI). As stated in the 2011 proposal preamble,
the EPA believes that the electronic submittal of the reports addressed
in this rulemaking will increase the usefulness of the data contained
in those reports, is in keeping with current trends in data
availability, will further assist in the protection of public health
and the environment and will ultimately result in less burden on the
regulated community. Electronic reporting can also eliminate paper-
based, manual processes, thereby saving time and resources, simplifying
data entry, eliminating redundancies, minimizing data reporting errors
and providing data quickly and accurately to the affected facilities,
air agencies, the EPA and the public.
    As mentioned in the preamble of the 2011 proposal, the EPA Web site
that stores the submitted electronic data, WebFIRE, will be easily
accessible to everyone and will provide a user-friendly interface that
any stakeholder could access. By making the records, data and reports
addressed in this rulemaking readily available, the EPA, the regulated
community and the public will benefit when the EPA conducts its CAA-
required technology and risk-based reviews. As a result of having
reports readily accessible, our ability to carry out comprehensive
reviews will be increased and achieved within a shorter period of time.
    We anticipate fewer or less substantial information collection
requests (ICRs) in conjunction with prospective CAA-required technology
and risk-based reviews may be needed. We expect this to result in a
decrease in time spent by industry to respond to data collection
requests. We also expect the ICRs to contain less extensive stack
testing provisions, as we will already have stack test data
electronically. Reduced testing requirements would be a cost savings to
industry. The EPA should also be able to conduct these required reviews
more quickly. While the regulated community may benefit from a reduced
burden of ICRs, the general public benefits from the agency's ability
to provide these required reviews more quickly, resulting in increased
public health and environmental protection.
    Air agencies could benefit from more streamlined and automated
review of the electronically submitted data. Having reports and
associated data in electronic format will facilitate review through the
use of software ``search'' options, as well as the downloading and
analyzing of data in spreadsheet format. The ability to access and
review air emission report information electronically will assist air
agencies to more quickly and accurately determine compliance with the
applicable regulations, potentially allowing a faster response to
violations which could minimize harmful air emissions. This benefits
both air agencies and the general public.
    For a more thorough discussion of electronic reporting required by
this rule, see the discussion in the preamble of the 2011 proposal (see
76 FR 76280). 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 will save industry, air agencies, and the EPA
significant time, money, and effort while improving the quality of
emission inventories, air quality regulations, and enhancing the
public's access to this important information.

H. What materials are being incorporated by reference?

    In this final rule, the EPA is including regulatory text that
includes incorporation by reference (IBR). In accordance with
requirements of 1 CFR 51.5, the EPA is incorporating by reference the
following documents described in the amendments to 40 CFR 63.14:
     ASTM D4239-14e1, ``Standard Test Method for Sulfur in the
Analysis Sample of Coal and Coke Using High-Temperature Tube Furnace
Combustion,'' approved March 1, 2014;
     ASTM D6376-10, ``Standard Test Method for Determination of
Trace Metals in Petroleum Coke by Wavelength Dispersive X-Ray
Fluorescence Spectroscopy,'' approved July 1, 2010; and
     Method 428, ``Determination Of Polychlorinated Dibenzo-P-
Dioxin (PCDD), Polychlorinated Dibenzofuran (PCDF), and Polychlorinated
Biphenyle Emissions from Stationary Sources,'' amended September 12,
1990.
    The following material will be referenced in 40 CFR 63.14 and as
noted below. This material has already received IBR approval for
subpart LL of 40 CFR part 63. We are moving it from an IBR section
established earlier within subpart LL to the centralized IBR section in
Sec.  63.14.
     Industrial Ventilation: A Manual of Recommended Practice,
22nd Edition, 1995, Chapter 3, ``Local Exhaust Hoods'' and Chapter 5,
``Exhaust System Design Procedure.'' IBR approved for Sec. Sec.
63.843(b) and 63.844(b).
     ASTM D2986-95A, ``Standard Practice for Evaluation of Air
Assay Media by the Monodisperse DOP (Dioctyl Phthalate) Smoke Test,''
approved September 10, 1995, IBR approved for section 7.1.1 of Method
315 in appendix A to 40 CFR part 63.
    The EPA has made, and will continue to make, these documents
generally available electronically through www.regulations.gov and/or
in hard copy at the appropriate EPA office (see the ADDRESSES section
of this preamble for more information).

IV. What is the rationale for our final decisions and amendments for
the Primary Aluminum Production source category?

    This section provides a description of what we proposed and what we
are finalizing for several issues, the EPA's rationale for the final
decisions and

amendments, and a summary of key comments and responses. For all
comments not discussed in this preamble, comment summaries and the
EPA's responses can be found in the National Emission Standards for
Hazardous Air Pollutants: Primary Aluminum Reduction Plants Summary of
Public Comments and Responses document, which is available in the
docket for this action (Docket ID No. EPA-HQ-OAR-2011-0797).

A. Residual Risk Review for the Primary Aluminum Production Source
Category

1. What did we propose pursuant to CAA section 112(f) for the Primary
Aluminum Production source category?
    Pursuant to CAA section 112(f), we conducted a residual risk review
and presented the results of this review, along with our proposed
decisions regarding risk acceptability and ample margin of safety, in
the December 2014 supplemental proposal for the Primary Aluminum
Reduction Plants NESHAP. The EPA views the residual risk review
associated with the 2011 proposal as superseded by the residual risk
review associated with the 2014 supplemental proposal, and so is
referring only to that later risk assessment. The results of the risk
assessment for the 2014 supplemental proposal are summarized in the
preamble for that proposal and presented in more detail in the residual
risk document, Residual Risk Assessment for the Primary Aluminum
Production Source Category in Support of the 2014 Supplemental
Proposal, which is available in the docket for this rulemaking. Table 4
below provides the estimated inhalation health risks from the
supplemental proposal.

    Table 4--Primary Aluminum Production Source Category Inhalation Risk Assessment Results From Supplemental
                                                    Proposal
----------------------------------------------------------------------------------------------------------------
                                                        Estimated
                                                          annual
  Maximum  individual  cancer    Estimated population     cancer     Maximum chronic non-  Refined maximum acute
   risk (-in-1 million) \a\       at increased risk     incidence     cancer  TOSHI \b\       non-cancer HQ \c\
                                   levels of cancer     (cases per
                                                          year)
----------------------------------------------------------------------------------------------------------------
                                                Actual Emissions
----------------------------------------------------------------------------------------------------------------
70............................  >=1-in-1 million:             0.06  1 Cadmium and Nickel   HQREL = 10 (Arsenic
                                 881,000.                            Compounds.             Compounds).
                                >=10-in-1 million:
                                 65,000.
                                >=100-in-1 million: 0  ...........  .....................  Residential.
----------------------------------------------------------------------------------------------------------------
                                             Allowable Emissions \d\
----------------------------------------------------------------------------------------------------------------
300...........................  >=1-in-1 million:             0.06  2 Nickel and Arsenic
                                 950,000.                            Compounds.
                                >=10-in-1 million:
                                 76,000.
                                >=100-in-1 million:
                                 200.
----------------------------------------------------------------------------------------------------------------
\a\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\b\ Maximum TOSHI. The target organ with the highest TOSHI for the Primary Aluminum Production source category
  for actual emissions is the kidney and respiratory system and for allowable emissions is the respiratory,
  immunological, and developmental systems.
\c\ The maximum off-site HQ acute value of 10 at a residential location for actuals is driven by emissions of As
  from the potline roof vents. See section III.A.3 of the December 8, 2014 supplemental proposal for explanation
  of acute dose-response values. Acute assessments are not performed on allowable emissions.
\d\ The development of allowable emission estimates can be found in the memorandum titled Development of the RTR
  Revised Risk Modeling Dataset for the Primary Aluminum Production Source Category (Docket item number EPA-HQ-
  OAR-2011-0797-0346).

    Based on actual emissions estimates for the Primary Aluminum
Production source category supplemental proposal, the maximum
individual risk (MIR) for cancer was estimated to be up to 70-in-1
million driven by emissions of As and Ni compounds. The maximum chronic
non-cancer target organ-specific hazard index (TOSHI) value was
estimated to be up to 1 driven by Ni emissions. The maximum off-site
acute hazard quotient (HQ) value was estimated to be 10 for As
compounds and 2 for HF. The total estimated national cancer incidence
from this source category, based on actual emission levels, was 0.06
excess cancer cases per year, or one case in every 17 years.
    Based on MACT-allowable emissions, in the supplemental proposal,
the MIR was estimated by the EPA to be up to 300-in-1 million, driven
by potential emissions of As, Ni, and POM from the one idle Soderberg
facility (Columbia Falls), which is now permanently closed. The maximum
chronic non-cancer TOSHI value was estimated to be up to 2, driven by
Ni. The MIR due to allowable emissions from prebake facilities was
estimated by the EPA to be up to 70-in-1 million, driven by As and Ni.
    The EPA also assessed the risks due to multipathway exposures to
HAP emissions from the primary aluminum reduction plants. The
assessment included tier 1 and tier 2 screening analyses and a refined
analysis for the one Soderberg facility which was operational at the
time recent emissions data for this source category were collected and
this analysis was commenced, but which subsequently announced its
permanent shut down in March 2014.
    The multipathway screens rely on health-protective assumptions
about consumption of local fish and locally grown or raised foods
(adult female angler at 99th percentile consumption of fish \4\ for the
subsistence fisherman scenario and 90th percentile for consumption of
locally grown or raised foods \5\ for the farmer scenario) which may
not occur for this source category. The tier 2 assessment is less
conservative than the tier 1 analysis. However, it is important to note
that, even with the inclusion of some site-specific information in the
tier 2 analysis, the multipathway screening analysis is still a very
conservative health-protective assessment, and, in all likelihood, will
yield results that serve

as an upper-bound multipathway risk associated with any facility in the
Primary Aluminum Production source category.
---------------------------------------------------------------------------

    \4\ Burger, J. 2002. Daily consumption of wild fish and game:
Exposures of high end recreationists. International Journal of
Environmental Health Research 12:343-354.
    \5\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final).
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
---------------------------------------------------------------------------

    The highest cancer exceedance in the tier 2 analyses for dioxins
was 40 times and 7 times for PAH for the subsistence fisherman scenario
(total cancer screen value of 50 for the MIR site). Thus, these results
indicate that the maximum cancer risks due to multipathway exposures to
D/F and PAH emissions for the subsistence fisher scenario are less than
50-in-1 million under these highly conservative screening
assumptions.\6\ The multipathway analysis for chronic non-cancer
effects did not identify any persistent and bioaccumulative hazardous
air pollutants (PB-HAP) that exceeded an HQ value of 1. For more
information on the risk results, please refer to the residual risk
document, Residual Risk Assessment for the Primary Aluminum Production
Source Category in Support of the 2014 Supplemental Proposal, which is
available in the docket for this rulemaking.
---------------------------------------------------------------------------

    \6\ D/F emissions used in this analysis are likely to be
overstated because the EPA imputed values for D/F congeners even
from facilities and process units where those D/F congeners were not
detected in the emissions tests.
---------------------------------------------------------------------------

    For the supplemental proposal, we weighed all health risk factors
in our risk acceptability determination, and we proposed that the risks
due to potential HAP emissions at baseline from the Soderberg
subcategory were unacceptable due mainly to the estimated cancer risks
of 300-in-1 million based on potential emissions from the one idle
Soderberg facility were it to operate.
    Regarding the prebake subcategories, as explained in the
supplemental proposal, the EPA had concerns regarding the potential
acute risks due to As emissions (with a maximum acute HQ of 10). See 79
FR 72947. However, given the conservative nature of the EPA's analysis
of acute effects, and the facts that: (a) The inhalation cancer MIR was
well below 100-in-1 million (MIR = 70-in-1 million); (b) the chronic
non-cancer risks were low (e.g., hazard index (HI) = 1); and (c) given
further that the multipathway assessment indicated the maximum cancer
risk due to multipathway exposures to HAP emissions from prebake
facilities was no higher than 50-in-1 million, we proposed that the
risks due to emissions from the prebake subcategories are acceptable.
See 79 FR 72947.
2. How did the risk review change for the Primary Aluminum Production
source category?
    The EPA carefully considered public comments regarding the
supplemental proposal (and original proposal), but did not find any
comments that resulted in a change in analysis. Thus, the EPA did not
change the risk assessment due to actual emissions for the source
category and made no changes in the overall results for prebake
facilities from the December 2014 supplemental proposal. However, the
estimated risks due to allowable emissions for the source category
decreased significantly due to the permanent closure of the one idle
Soderberg facility. For the supplemental proposal, we included the one
idle Soderberg facility in our assessment of allowable risks because,
at that time, the facility still had a permit to operate, had not
formally announced plans to close, and, therefore, could have reopened.
However, that facility is now permanently closed, and the EPA is no
longer including it in the risk assessment. Therefore, the final rule
considers only risks from prebake facilities. Nevertheless, as
discussed in section III.A. of this preamble, we are promulgating the
As, Ni and POM standards proposed in the supplemental proposal to
address risk from Soderberg facilities in the very unlikely event that
either this idle Soderberg facility is reopened or a new Soderberg
facility is constructed. A summary of the risk assessment results for
the final rule is provided in Table 5 below. The documentation and
details for the final rule risk assessment can be found in the document
titled, Residual Risk Assessment for the Primary Aluminum Production
Source Category in Support of the September 2015 Risk and Technology
Review Final Rule, which is available in the docket for this action
(Docket ID No. EPA-HQ-OAR-2011-0797).

   Table 5--Primary Aluminum Production Source Category Inhalation Risk Assessment Results for the Final Rule
                                                    [Prebake]
----------------------------------------------------------------------------------------------------------------
                                                         Estimated
                                                           annual
  Maximum  individual  cancer    Estimated population      cancer    Maximum chronic non-  Refined maximum acute
   risk (-in-1 million) \a\        at increased risk     incidence     cancer TOSHI \b\      non-cancer HQ \c\
                                   levels of cancer      (cases per
                                                           year)
----------------------------------------------------------------------------------------------------------------
                                                Actual Emissions
----------------------------------------------------------------------------------------------------------------
70............................  >=1-in-1 million:              0.06  1 Nickel Compounds..  HQREL = 10 (Arsenic
                                 881,000.                                                   Compounds)
                                >=10-in-1 million:      ...........  ....................  Residential
                                 65,000.
----------------------------------------------------------------------------------------------------------------
                                             Allowable Emissions \d\
----------------------------------------------------------------------------------------------------------------
70............................  >=1-in-1 million:              0.06  1 Nickel Compounds..
                                 950,000.
                                >=10-in-1 million:
                                 76,000.
----------------------------------------------------------------------------------------------------------------
\a\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\b\ Maximum TOSHI. The target organ with the highest TOSHI for the Primary Aluminum Production source category
  for actual emissions is the kidney and respiratory system and for allowable emissions is the respiratory,
  immunological, and developmental systems.
\c\ The maximum off-site HQ acute value of 10 at a residential location for actuals is driven by emissions of As
  from the potline roof vents. See section III.A.3 of the December 8, 2014, supplemental proposal for
  explanation of acute dose-response values. Acute assessments are not performed on allowable emissions.
\d\ The development of allowable emission estimates can be found in the memorandum titled, Development of the
  RTR Revised Risk Modeling Dataset for the Primary Aluminum Production Source Category (Docket item number EPA-
  HQ-OAR-2011-0797-0346).

    For the final rule, we again weighed all health risk factors in our
risk acceptability determination. The EPA had concerns regarding the
potential acute risks due to As emissions (with a maximum acute HQ of
10). See 79 FR 72947. However, given the conservative nature of the
EPA's analysis of acute effects, and the facts that: (a) The inhalation
cancer MIR was well below 100-in-1 million (MIR = 70-in-1 million); (b)
the chronic non-cancer risks were low (e.g., HI = 1); and (c) given
further that the multipathway assessment indicated the maximum cancer
risk due to multipathway exposures to HAP emissions from prebake
facilities was no higher than 50-in-1 million, we have determined that
the risks due to emissions from the source category are acceptable. See
79 FR 72947.
    We also conducted an ample margin of safety analysis. As we
described in the supplemental proposal, for prebake facilities we
considered what further reductions might be obtained from technically
feasible controls, further considering the cost of such controls and
their cost-effectiveness. We identified no cost-effective controls
under the ample margin of safety analysis to further reduce risks or
environmental effects due to HAP emissions from prebake facilities. 79
FR 72947-48. Therefore, we indicated in the supplemental proposal, and
conclude again in this final rule, that the NESHAP for prebake
facilities provides an ample margin of safety to protect public health
and prevent an adverse environmental effect.
    With regard to Soderberg facilities, as mentioned in section III
above, we proposed more stringent emission limits for Ni, As, and POM
under CAA section 112(f) to ensure that the cancer MIR would remain
below 100-in-1 million, the level of risk we defined as acceptable for
purposes of this rule. We did not propose more stringent standards
under the ample margin of safety analysis since we identified no
feasible controls that would yield risk reductions at reasonable cost.
Id at 72948. In this final action, we are promulgating these standards
as proposed. Although these standards may not apply to any facilities,
we are still promulgating the As, Ni and POM emissions limits for
Soderberg facilities under CAA section 112(f) to address the shut down,
but not yet demolished, existing Soderberg potlines, and the very
unlikely scenario of construction of new Soderberg potlines.
3. What key comments did we receive on the risk review, and what are
our responses?
    The EPA received several comments regarding the revised risk
assessment for the Primary Aluminum Production source category. The
following is a summary of some key comments and our responses to those
comments. Other comments received and our responses to those comments
can be found in the document titled, National Emission Standards for
Hazardous Air Pollutants: Primary Aluminum Reduction Plants Summary of
Public Comments and Responses, which is available in the docket for
this action (Docket ID No. EPA-HQ-OAR-2011-0797).
    Comment: One commenter stated that the EPA's determination of the
emissions reduction required to reduce health risks to an acceptable
level violates CAA section 112(f)(2) and is arbitrary. The commenter
believed that the EPA's acceptability determination for prebake
facilities is flawed for the following reasons:
     The EPA's acceptability determination is unlawful and
arbitrary because its risk assessment is incomplete and fails to follow
the up-to-date science to assess health risk;
     The EPA's acceptability determination fails to consider or
prevent unacceptable levels of cumulative impacts;
     Socioeconomic disparity in health risk from this source
category makes the risk the EPA has found unacceptable, and the EPA
must finalize a rule that is consistent with the principle of
environmental justice (EJ);
     The EPA has failed to provide a reasoned explanation for
why the lifetime cancer risk of 1-in-1 million or more based on
inhalation alone from this sector is acceptable;
     After finding a level of acute risk that is 10 times the
EPA's safety threshold, the agency has failed to justify not requiring
the reduction of acute health risk below 1; and
     The EPA has failed to justify finding chronic non-cancer
health risk to be acceptable.
    Response: We disagree with the commenter that the assessment is
incomplete and fails to use up-to-date science. The dose-response
values used in the risk assessment are based on the current peer
reviewed Integrated Risk Information System (IRIS) values, as well as
other similarly peer-reviewed values. Our approach, which uses
conservative tools and assumptions, ensures that our decisions are
appropriately health protective and environmentally protective. The
approach for selecting appropriate health benchmark values, in general,
places greater weight on the EPA derived health benchmarks than those
from other agencies (see http://www.epa.gov/ttn/atw/nata1999/99pdfs/healtheffectsinfo.pdf). This approach has been endorsed by the Science
Advisory Board (SAB).\7\ The SAB further recommended that the EPA
scrutinize values that emerge as drivers of risk assessment results,
and the Agency has incorporated this recommendation into the risk
assessment process. This may result in the EPA determining that it is
more appropriate to use a peer-reviewed dose-response value from
another agency even if an IRIS value exists.
---------------------------------------------------------------------------

    \7\ Refer to the May 2010, SAB response to the EPA Administrator
(EPA-SAB-10-007); http://www.regulations.gov/#!documentDetail;D=EPA-
HQ-OAR-2011-0797-0075.
---------------------------------------------------------------------------

    With regard to the comment that the EPA failed to consider
cumulative impacts, we note that while the incorporation of additional
background concentrations from the environment in our risk assessments
(including those from mobile sources and other industrial and area
sources) could be technically challenging, they are neither mandated
nor barred from our analysis. In developing the decision framework in
the Benzene NESHAP used for making residual risk decisions, and now
codified in CAA section 112(f)(2)(B), the EPA rejected approaches that
would have mandated consideration of background levels of pollution in
assessing the acceptability of risk, concluding that comparison of
acceptable risk should not be associated with levels in polluted urban
air (54 FR 38044, 38061, September 14, 1989). Background levels
(including natural background) are not barred from the EPA's ample
margin of safety analysis, and the EPA may consider them, as
appropriate and as available, along with other factors, such as cost
and technical feasibility, in the second step of its CAA section 112(f)
analysis. As discussed in the 2014 supplemental proposal, the risk
assessment for this source category did not include background
contributions (that may reflect emissions that are from outside the
source category and from other than co-located sources) because the
available data are of insufficient quality upon which to base a
meaningful analysis.\8\
---------------------------------------------------------------------------

    \8\ Note that this question is distinct from the issue of
consideration of emissions from co-located facilities, which
emissions are fully reflected in the EPA's analysis. See discussion
in section IV.A.3 of this preamble, below, and 79 FR 72929/1
(emissions estimated for all emitting sources in a contiguous area
under common control).

---------------------------------------------------------------------------

    This rule has been finalized consistent with agency EJ principles
and analyses. To examine the potential for any EJ issues that might be
associated with the Primary Aluminum Production source category, we
performed a demographic analysis, which is an assessment of risks to
individual demographic groups, of the population close to the
facilities. In this analysis, we evaluated the distribution of HAP-
related cancer risks and non-cancer hazards from this source category
across different social, demographic, and economic groups within the
populations living near facilities identified as having the highest
risks. The results of the demographic analysis are summarized in Table
6 below and indicate that there are no significant disproportionate
risks to any particular minority, low income, or indigenous population.
The methodology and the results of the demographic analyses are
included in a technical report, Analysis of Socio-Economic Factors for
Populations Living Near Primary Aluminum Facilities, which is available
in the docket for this rulemaking (Docket item number EPA-HQ-OAR-2011-
0797-0360).

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

    With regard to the comments that the EPA did not justify the
determination that risks are acceptable, we generally draw no bright
lines of acceptability regarding cancer or non-cancer risks from source
category HAP emissions. This is a core feature of the Benzene NESHAP
approach, now codified in CAA section 112(f)(2)(B). See 54 FR at 38046,
38057; see also 79 FR 72933-34. It is always important to consider the
specific uncertainties of the emissions and health effects information
regarding the source category or subcategory in question when deciding
exactly what level of cancer and non-cancer risk should be considered
acceptable. In addition, the source category-specific or subcategory-
specific decision of what constitutes an acceptable level of risk
should be a holistic one; that is, it should simultaneously consider
all potential health impacts--chronic and acute, cancer and non-cancer,
and multipathway--along with their uncertainties, when determining the
acceptable level of source category risk. Today, such flexibility is
even more imperative, because new information relevant to the question
of risk acceptability is being developed all the time, and the accuracy
and uncertainty of each piece of information must be considered in a
weight-of-evidence approach for each decision. This relevant body of
information is growing fast (and will likely continue to grow even
faster), necessitating a flexible weight-of-evidence approach that
acknowledges both complexity and uncertainty in the simplest and most
transparent way possible. While this challenge is formidable, it is
nonetheless the goal of the EPA's RTR decision-making, and it is the
goal of the risk assessment to provide the information to support the
decision-making process.
    Our acceptability decisions for the prebake subcategory presented
in the supplemental proposal, and again in this final rule, are
appropriate. The rationale for our acceptability decision for the
prebake subcategory was clearly explained in the supplemental proposal
and was based on full consideration of the health risk information and
associated uncertainties, and we summarize it here:
    Regarding the prebake subcategories, as explained in the
supplemental proposal, the EPA had concerns regarding the potential
acute risks due to As emissions (with a maximum acute HQ of 10). See 79
FR 72947. However, given the conservative nature of the EPA's analysis
of acute effects--among them, an assumption of the unlikely confluence
of peak emissions, worst-

case-meteorology, and an exposed individual present at the precise
point this occurs (see 79 FR 72943/1), and the facts that: (a) The
inhalation cancer MIR was well below 100-in-1 million (MIR = 70-in-1
million); (b) the chronic non-cancer risks were low (e.g., HI = 1); and
(c) given further that the multipathway assessment indicated the
maximum cancer risk due to multipathway exposures to HAP emissions from
prebake facilities was no higher than 50-in-1 million, we have
determined that the risks due to emissions from the prebake
subcategories are acceptable.
    Comment: A commenter stated support for the EPA's risk assessment
conclusion that the risk due to actual emissions from the prebake
aluminum smelting subcategory is acceptable. The commenter stated that
the modeled ambient concentrations that were used in the risk
assessment likely overpredict actual concentrations since the Human
Exposure Model version 3 (HEM3) uses the American Meteorological
Society and EPA Regulatory Model (AERMOD) for air dispersion modeling
to determine ambient concentrations. The commenter stated that the use
of AERMOD is inappropriate for modeling stationary line sources like
the potroom roof monitors of the facilities and overpredicts ambient
concentrations from roof monitor emissions by a factor of about 30
times. The commenter recommended that the EPA use the Buoyant Line and
Point source (BLP) dispersion model to correctly model the potline roof
monitors.
    Response: The EPA disagrees that the BLP model needs to be used to
correctly model potline roof monitors. An analysis performed by the EPA
to compare the modeled estimates from AERMOD and the BLP model for a
typical primary aluminum facility indicated that the maximum modeled
concentrations from the BLP model were only 20 percent higher than
those from AERMOD. Considering the uncertainties in release
characteristics and emission rates--both inputs into the models--the
results estimated by both HEM3 and BLP are the same within that range
of uncertainty.\9\ The EPA concluded that this difference was not
significant enough to warrant changing the RTR modeling methodology it
uses for all source categories, which includes the use of AERMOD and
meteorological data generated by the AERMOD Meteorological Preprocessor
(AERMET). In addition, the 20 percent increase in maximum modeled
concentrations would translate into an increase in the risk from 70-in-
1 million to 80-in-1 million. This level would still be within the
range of acceptability and, if the EPA had determined that it was
necessary to use the BLP, the Agency would have reaffirmed that risks
are acceptable.
---------------------------------------------------------------------------

    \9\ September 27, 2010, Memo to the EPA from EC/R Incorporated;
``Draft Modeling Comparison of BLP and AERMOD for Primary Aluminum''
available in the docket at http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OAR-2011-0797-0175.
---------------------------------------------------------------------------

    Comment: One commenter stated that the EPA must strengthen the risk
assessment and proposed risk action in order to meet its
responsibilities under CAA section 112(f)(2) to provide the requisite
``ample margin of safety to protect public health.'' The EPA also
should find risk from the prebake subcategories to be unacceptable,
instead of acceptable. The commenter stated that the combined health
risks for these sources are substantial and stated that the EPA found
that the allowable emissions-based cancer risk from inhalation exposure
is 70-in-1 million, plus another 70-in-1 million from multipathway
exposure (50-in-1 million for the ``fisher'' scenario, or fish-based
exposure; and 20-in-1 million for the ``farmer'' scenario, or farm-
based exposure). The commenter stated that the 70-in-1 million
inhalation risk, combined with the high acute and chronic risks the EPA
found, is enough alone to find risk unacceptable.
    The commenter stated that in view of the EPA's scientific policy of
summing cancer risks, it should recognize that the most-exposed
person's combined multipathway and inhalation cancer risk is 70 + 70 or
140-in-1 million. The commenter stated that this is well above the
EPA's presumptive acceptability benchmark (which itself is
insufficiently stringent, as explained in their 2012 comments,
incorporated by reference). The commenter also stated that the EPA
should find the current cancer risk from inhalation and multipathway
exposure, due to a combination of As, Ni, PAH, and dioxins, is
unacceptable. The commenter stated that if viewed together with the
high acute and chronic non-cancer risks the EPA found, as a result of
As and Ni in particular, the data the EPA has compiled on risk show
that the current health risks are unacceptable.
    The commenter stated that the EPA has not assessed the additional
multipathway risk from risk-driver pollutants, such as As and Ni. The
commenter stated that, as discussed in their 2012 comments (to EPA's
original proposal), this is inconsistent with the scientific evidence
showing these are persistent bioaccumulative toxics [PBTs], and it is,
thus, unlawful and arbitrary and capricious for the EPA not to assess
and address the multipathway risks they create.
    Response: We disagree with the commenter's arguments for finding
risks to be unacceptable. The thrust of the comment is that the risk
analysis failed to combine risks from various scenarios and pathways,
and that, added together, these risks are unacceptable. In fact, the
analysis combines risk estimates to the extent that it is
scientifically appropriate to do so. We consider the effect of mixtures
of carcinogens consistent with the EPA guidelines and use a TOSHI
approach for our chronic non-cancer assessments. We do not use a TOSHI
approach for acute analyses, nor do we combine the results of our
inhalation and multipathway assessments. (See the Residual Risk
Assessment for the Primary Aluminum Production Source Category in
Support of the September 2015 Risk and Technology Review Final Rule,
which is available in the docket for this action (Docket ID No. EPA-HQ-
OAR-2011-0797)).
    In the multipathway screening assessment, we did not sum the risk
results of the fisher and farmer scenarios. The modeling approach used
for this analysis constructs two different exposure scenarios, which
serves as a conservative estimate of potential risks to the most-
exposed receptor in each scenario. Given that it is highly unlikely
that the most-exposed farmer is the same person as the most-exposed
fisher, it is not reasonable to add risk results from these two
exposure scenarios (see Appendix 5 and Section 2.5 of the Residual Risk
Assessment for the Primary Aluminum Production Source Category in
Support of the September 2015 Risk and Technology Review Final Rule).
    We do not find it reasonable to combine the results of our
inhalation and multipathway assessments for this source category. The
multipathway risk assessment for prebake facilities was a screening-
level assessment. The screening assessment used highly conservative
assumptions designed to ensure that sources with results below the
screening threshold values did not have the potential for multipathway
impacts of concern. The screening scenario is a hypothetical scenario,
and, due to the theoretical construct of the screening model,
exceedances of the thresholds are not directly translatable into
estimates of risk or HQs for these facilities. Rather, it represents a
high-end estimate of what the risk or hazard may be. For example, an
exceedance of 2 for a non-carcinogen can be interpreted to mean that we
have high confidence that the HQ or HI would be

less than 2. Similarly, an exceedance of 30 for a carcinogen means that
we have high confidence that the risk is lower than 30-in-1 million.
Our confidence comes from the health-protective assumptions that are in
the screens: We choose inputs from the upper end of the range of
possible values for the influential parameters used in the screens, and
we assume that the exposed individual exhibits ingestion behavior that
would lead to a high total multipathway exposure. It would be
inappropriate to sum the risk results from the chronic inhalation
assessment and the screening multipathway assessment. In addition to
the constraints in the screening-level multipathway assessment
described above, it is highly unlikely that the same receptor has the
maximum results in both assessments. In other words, it is unlikely
that the person with the highest chronic inhalation cancer risk is also
the same person with the highest individual multipathway cancer risk.
We agree with the commenter that we ``should look at the whole picture
of cancer risk,'' but we do so by assessing cancer and chronic non-
cancer inhalation risk, acute risk, multipathway risk, and combining
risk results where it is scientifically appropriate to do so, not by
arbitrarily and indiscriminately summing risk measures in the absence
of a valid technical basis.
    We currently do not have screening values for some PB-HAP, but we
disagree that the multipathway assessment is inadequate because it did
not include ``all HAP metals emitted (such as arsenic and nickel).'' We
developed the current PB-HAP list considering all available information
on persistence and bioaccumulation (see http://www2.epa.gov/fera/air-toxics-risk-assessment-reference-library-volumes-1-3, specifically
Volume 1, Appendix D). (The Air Toxics Risk Assessment Reference
Library presents the decision process by which the PB-HAP were selected
and provides information on the fundamental principles of risk-based
assessment for air toxics and how to apply those principles.) In
developing the list, we considered HAP identified as PB-HAP by other
EPA program offices (e.g., the Great Waters Program), as well as
information from the PBT profiler (see http://www.pbtprofiler.net/).
Considering this list was peer-reviewed by the SAB and found to be
acceptable,\10\ we believe it to be reasonable for use in risk
assessments for the RTR program.
---------------------------------------------------------------------------

    \10\ 10 Refer to the May 2010, SAB response to the EPA
Administrator (EPA-SAB-10-007); http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OAR-2011-0797-0075
---------------------------------------------------------------------------

    Regarding the commenter's assertion that we did not base the
multipathway risk assessment on allowable emissions, we believe it is
reasonable for the multipathway risk assessment to be based on actual
emissions for this source category, and not the allowable level of
emissions--i.e. the level that facilities are permitted to emit. The
potline fugitive emissions, which drive the risks associated with this
source category, vary in magnitude and location along the roofline due
to normal operations, including, among others, replacement of anodes.
We exacerbate the uncertainty associated with these variations in
fugitive emissions when we scale up actual emissions to estimate
allowable emissions. Also, there is considerable uncertainty associated
with estimated allowable emissions from batch operations, such as pitch
storage tank and pitch production, due to the nature of batch
operations (e.g., estimating the number of batch operations possible or
necessary during a period of time). Further uncertainty results when we
consider that, in order to comply with the emission limits at all
times, a source's allowable emissions would need to be below the
associated standard by an indeterminate amount during normal
operations. Therefore, we conclude that the uncertainties associated
with the multipathway screen along with uncertainties in the allowable
emissions estimates would make a multipathway risk assessment based on
allowable emissions highly uncertain and, thereby, not appropriate for
use in making this regulatory decision.
    The commenter also argued for summing acute HQs from different HAP
to assess acute non-cancer risk. We do not sum results of the acute
non-cancer inhalation assessment to create a combined acute risk number
that would represent the total acute risk for all pollutants that act
in a similar way on the same organ system or systems (similar to the
chronic TOSHI). The worst-case acute screen is already a conservative
scenario. That is, the acute screening scenario assumes worst-case
meteorology, peak emissions for all emission points occurring
concurrently and an individual being located at the site of maximum
concentration for an hour. Thus, as noted in the Residual Risk
Assessment for the Primary Aluminum Production Source Category in
Support of the September 2015 Risk and Technology Review Final Rule,
page 31, which is available in the docket for this action (Docket ID
No. EPA-HQ-OAR-2011-0797), ``because of the conservative nature of the
acute inhalation screening and the variable nature of emissions and
potential exposures, acute impacts were screened on an individual
pollutant basis, not using the TOSHI approach.'' The EPA may conduct a
reasoned screening assessment without having to adopt the most
conceivably conservative assumption for each and every part of the
analysis.
    Comment: One commenter stated that, as the EPA recognized in the
secondary aluminum proposal, at least nine secondary aluminum
facilities have co-located primary aluminum operations. The commenter
stated that for both source categories, the EPA found that the
facility-wide MIR is 70-in-1 million, driven by As, Ni, and hexavalent
chromium, and that the TOSHI (chronic non-cancer risk) is 1, driven by
cadmium. The commenter stated that the TOSHI number appears to consider
only inhalation risk and stated that the TOSHI number must be viewed in
context, as the EPA is aware that scientists have directed the EPA to
do (and as previously explained and cited to the EPA in comments). The
commenter stated that if considered in combination with the high
secondary aluminum multipathway risk, and with the high inhalation and
multipathway risks for primary aluminum, the facility-wide cancer risk
provides additional evidence that risks from both source categories are
unacceptable. The commenter asserts this is the case because the most-
exposed person's full amount of risk is the combined amount from the
co-located primary and secondary aluminum, not just each source
category separately. The commenter stated that it would be unlawful and
arbitrary to consider each type of risk separately, when people near
both sources are exposed to both kinds of risk at the same time and,
thus, face a higher overall amount of risk.
    The commenter stated that the EPA has not offered and can not offer
a valid justification for not finding risk from both source categories
(including primary aluminum prebake and secondary aluminum) to be
unacceptable based on the co-located and combined risks. The commenter
stated that the EPA has collected data from both source categories and
is evaluating that data in rulemakings for both source categories. The
commenter stated that the EPA may not lawfully ignore the full picture
of risk that its combined rulemakings show is present

for people exposed simultaneously to both source categories at the same
facility.
    The commenter stated that the EPA only assessed facility-wide risks
based on so-called ``actual'' emissions, so the facility-wide risk
number could be at least 1.5 to 3 times higher, based on the EPA's
recognition that allowable emissions from primary aluminum facilities
are about 1.5 to 1.9 times higher and the fact that allowable emissions
from secondary aluminum are at least 3 times higher.
    The commenter stated that it is important that the EPA is
evaluating facility-wide risk from sources in multiple categories that
are co-located.
    The commenter stated that the EPA may not reasonably or lawfully
then decide not to use the results of that assessment to set stronger
standards for these sources. The commenter stated that this rulemaking
is an important opportunity for the EPA to recognize the need to act
based on data showing significant combined and cumulative risks and
impacts at the facility-wide level. The commenter stated that the EPA
is also required to do so to meet its CAA section 112(f)(2) duties, as
explained in the 2012 comments and reincorporated by reference here.
    Response: We agree with the commenter that facility-wide risk
assessment is appropriately considered in putting the source category
risks in context. However, we disagree with the comment that we failed
to appropriately consider or account for cumulative risk.
    We conducted facility-wide risk assessments for all major sources
in the source category that were operating in 2014, including the nine
secondary aluminum production facilities co-located with primary
aluminum reduction plants. See 79 FR 72929 (emissions estimated for all
emitting sources in a contiguous area under common control).
    The commenter stated that the EPA must find the risks unacceptable
based on the whole-facility risks from co-located primary and secondary
aluminum operations. The EPA does not typically include whole-facility
assessments in the CAA section 112(f) acceptability determination for a
source category. Reasons for this include the fact that emissions and
source characterization data are usually not of the same vintage and
quality for all source categories that are on the same site, and, thus,
the results of the whole-facility assessment are generally not
appropriate to include in the regulatory decisions regarding
acceptability. However, in this case, we are developing the risk
assessments for primary and secondary aluminum production at the same
time. The data are generally of the same vintage and we have actual
emissions data and source characterization data for both source
categories. In response to the comment, we refer to the facility-wide
risk assessment, which included the nine facilities with co-located
primary and secondary aluminum operations. As discussed above and shown
in Table 6, for the facility with the highest risk from inhalation, the
facility-wide MIR for cancer from actual emissions is 70-in-1 million.
The facility-wide non-cancer hazard is 1. The highest facility-wide
exceedance of the multipathway screen is 70. There was no facility-wide
exceedance of a noncancer threshold in the multipathway screen.
Considering these facility-wide results as part of the acceptability
determination is thus corroborative of our determination that the risks
are acceptable for the Secondary Aluminum Production source category.
    The commenter is correct that we based our facility-wide risk
assessment on actual emissions rather than on estimated allowable
emissions. Because the facility-wide allowable emissions estimates have
not been subjected to the same level of scrutiny, quality assurance,
and technical evaluation as the actual emissions estimates from the
source category, and because of the larger inherent uncertainty
associated with allowable emissions discussed above, facility-wide risk
results based on allowable emissions would be too uncertain to support
a regulatory decision, but they could remain important for providing
context as long as their uncertainty is taken into consideration.
    The distinct issue of whether background emissions not associated
with co-located emitting sources at the facility is discussed above. We
reiterate that while the incorporation of additional background
concentrations from the environment in our risk assessments (including
those from mobile sources and other industrial and area sources) could
be technically challenging, they are neither mandated nor barred from
our analysis. In developing the decision framework in the Benzene
NESHAP used for making residual risk decisions, the EPA rejected
approaches that would have mandated consideration of background levels
of pollution in assessing the acceptability of risk, concluding that
comparison of acceptable risk should not be associated with levels in
polluted urban air (54 FR 38044, 38061, September 14, 1989).
    Background levels (including natural background) are not barred
from the EPA's ample margin of safety analysis, and the EPA may
consider them, as appropriate and as available, along with other
factors, such as cost and technical feasibility, in the second step of
its CAA section 112(f) analysis. As discussed in the 2014 supplemental
proposal, the risk assessment for this source category did not include
background contributions (that may reflect emissions that are from
outside the source category and from other than co-located sources)
because the available data are of insufficient quality upon which to
base a meaningful analysis.
    Comment: Some commenters recommended that the EPA should proceed
with the required full multipathway risk assessment, as the data showed
that the persistent and bioaccumulation screening emission rates were
exceeded for POM. The commenters do not believe the risk analysis for
this source category is final until this step is complete and disagree
with the EPA's explanation that the results are biased high and subject
to significant uncertainties, arguing that the EPA cannot ignore the
implications of this screening assessment. The commenter recommended
that the EPA perform a full multipathway assessment to find a number it
believes fully represents this risk, or use the number it has created
as the best available number, without discounting the impact of that
number.
    One commenter recommended conducting a full multipathway risk
assessment for this source category that includes consideration of a
child's multipathway exposure in urban and rural residential scenarios.
The commenter further stated that the failure of the EPA to assess an
exposed child scenario as part of the cumulative risk assessment
ignores the exposures that may pose the most significant risk from this
source category. The commenter highlighted the risk to children from
contaminated soils, noting that past risk assessments have relied on
outdated estimates of incidental soil ingestion exposures and stated
that the EPA must update these values. The commenter cited two EPA
exposures factors handbooks and a journal article as resources to use
for assessing risks.
    Response: We disagree with the comment that our multipathway risk
assessment does not consider children. The multipathway screening
scenario is intended to represent a high-end exposure for children via
incidental soil ingestion. The 2011 Exposure Factors Handbook
recommended ``upper-percentile'' soil ingestion rate (numeric
percentile not specified) for children aged 3 to 6 years is 200
milligrams per

day (mg/d). The EPA also published the Child-Specific Exposure Factors
Handbook (2008). No additional data or recommendations for child soil
ingestion are presented in this source, and, in fact, an ``upper
percentile'' value for this parameter is not provided. Based on these
sources, a value of 200 mg/d is used in the current RTR multipathway
screening scenario for the child incidental soil ingestion rate.
    The multipathway risk assessment conducted for the proposal was a
screening-level assessment. The screening assessment used highly
conservative assumptions designed to ensure that facilities with
results below the screening threshold values did not have the potential
for multipathway impacts of concern. The screening scenario is a
hypothetical scenario, and, due to the theoretical construct of the
screening model, exceedances of the thresholds are not directly
translatable into estimates of risk or HQs for these facilities. The
scope of the assessment did not change across the tiers in the
multipathway screening assessment and is described in the risk
assessment documents (and related appendices) available in the docket
for this rulemaking (Docket ID No. EPA-HQ-OAR-2011-0797).
4. What is the rationale for our final approach and final decisions for
the risk review?
    As discussed above and in the preamble of the 2014 supplemental
proposal, after considering health risk information and other factors,
including uncertainties, we have determined that the risks from primary
aluminum production prebake facilities are acceptable and that the
current NESHAP provides an ample margin of safety to protect public
health for prebake facilities given that the inhalation cancer MIR was
well below 100-in-1 million, the chronic non-cancer risks were low, and
the multipathway assessment indicated the maximum cancer risk due to
multipathway exposures to HAP emissions from prebake facilities was no
higher than 50-in-1 million. In summary, our revised risk assessment
indicates that cancer risks due to actual and allowable emissions from
prebake facilities are below the presumptive limit of acceptability,
and that non-cancer results indicate minimal likelihood of adverse
health effects. We evaluated potential risk reductions as well as the
cost of control options, but did not identify any control technologies
or other measures that would be cost-effective in further reducing
risks (or potential risks) for prebake facilities. In particular, we
did not identify any cost-effective approaches to further reduce As,
Ni, and PAH emissions and risks beyond what is already being achieved
by the current NESHAP.
    Regarding the Soderberg facilities, as discussed above, since all
existing Soderberg facilities are permanently shut down, we necessarily
conclude the risks due to emissions from Soderberg facilities are
currently acceptable. However, under our ample margin of safety
analysis, we have determined that it is appropriate to promulgate
standards for Ni, As, and PAH under CAA section 112(f) for the
Soderberg subcategory potlines to ensure that excess cancer risk due to
HAP emissions from any possible future primary aluminum reduction plant
would remain below 100-in-1 million. We estimate the costs to comply
with these standards for Soderberg facilities would be zero since there
are no existing operating Soderberg facilities in the U.S. Furthermore,
we expect any future new primary aluminum reduction plant would use
prebake potlines since prebake potlines are more energy efficient (and
lower-emitting) than Soderberg potlines. Therefore, we also estimate
that these standards would pose no cost for any future new primary
aluminum reduction plant.

B. CAA Sections 112(d)(2) and (3) Revisions for the Primary Aluminum
Production Source Category

1. What did we propose pursuant to CAA sections 112(d)(2) and (3) for
the Primary Aluminum Production source category?
    We proposed several MACT standards in the December 2011 proposal
pursuant to CAA sections 112(d)(2) and (3), which are summarized in
Table 7, below.
    We received significant comments on the 2011 proposal from industry
representatives, environmental organizations, and state regulatory
agencies. After reviewing the comments, and after consideration of
additional data and information received since the 2011 proposal, the
EPA determined it was appropriate to gather additional data, revise
some of the analyses associated with that proposal, and to publish a
supplemental proposal.
    In support of the supplemental proposal, the EPA sent an
information request to owners of currently operating primary aluminum
reduction plants in March of 2013. The EPA received associated
responses in May through August 2013. As part of this data collection
effort, we received emissions data for PM, HAP metals (including
antimony, As, beryllium, cobalt, manganese, selenium, Ni, cadmium,
chromium, lead, and Hg), PCB, and D/F from potlines, anode bake
furnaces, and/or paste production plants from every primary aluminum
reduction plant that was operational at that time, including nine
prebake-type facilities and one Soderberg-type facility.
    Based on evaluation of all the data, we proposed several revised
and new MACT standards in the December 2014 proposal pursuant to CAA
sections 112(d)(2) and (3), which are summarized in Table 7, below.

                                   Table 7--Summary of Proposed MACT Standards
----------------------------------------------------------------------------------------------------------------
                                                                                Promulgated MACT
              Proposal                           HAP                      Source                 standard
----------------------------------------------------------------------------------------------------------------
2011 proposal (76 FR 76259)........  COS........................  New potlines..........  3.1 lb/ton aluminum
                                                                  Existing potlines.....   produced.
                                                                                3.9 lb/ton aluminum
                                                                                produced.
                                     POM........................  New potlines..........  0.62 lb/ton aluminum
                                                                                produced.
                                                                  Existing potlines.....
                                                                  CWPB1.................  0.62 lb/ton aluminum
                                                                                produced.
                                                                  CWPB2.................  1.3 lb/ton aluminum
                                                                                produced.
                                                                  CWPB3.................  1.26 lb/ton aluminum
                                                                                produced.
                                                                  SWPB..................  0.65 lb/ton aluminum
                                                                                produced.
                                                                  VSS2..................  3.8 lb/ton aluminum
                                                                                produced.
                                                                  HSS...................  3.0 lb/ton aluminum
                                                                                produced.
                                                                  Existing pitch storage  Minimum 95-percent
                                                                   tanks.                  reduction of inlet
                                                                                POM emissions.
2014 proposal (79 FR 72914)........  POM........................  New potlines..........  0.77 lb/ton aluminum
                                                                                produced.
                                                                  Existing potlines.

                                                                  CWPB1.................  1.1 lb/ton aluminum
                                                                                produced.
                                                                  CWPB2.................  12 lb/ton aluminum
                                                                                produced.
                                                                  CWPB3.................  2.7 lb/ton aluminum
                                                                                produced.
                                                                  SWPB..................  19 lb/ton aluminum
                                                                                produced.
                                     PM.........................  New potlines..........  4.6 lb/ton aluminum
                                                                                produced.
                                                                  Existing potlines.
                                                                  CWPB1.................  7.2 lb/ton aluminum
                                                                                produced.
                                                                  CWPB2.................  11 lb/ton aluminum
                                                                                produced.
                                                                  CWPB3.................  20 lb/ton aluminum
                                                                                produced.
                                                                  SWPB..................  4.6 lb/ton aluminum
                                                                                produced.
                                                                  VSS2..................  26 lb/ton aluminum
                                                                                produced.
                                                                  New anode bake furnace  0.036 lb/ton of green
                                                                                anode produced.
                                                                  Existing anode bake     0.068 lb/ton of green
                                                                   furnace.                anode produced.
                                                                  New paste production    0.0056 lb/ton of paste
                                                                   plant.                  produced.
                                                                  Existing paste          0.082 lb/ton of paste
                                                                   production plant.       produced.
----------------------------------------------------------------------------------------------------------------
HSS = horizontal stud Soderberg.

2. How did the proposed CAA sections 112(d)(2) and (3) standards change
for the Primary Aluminum Production source category?
    Commenters provided additional emissions data for POM from SWPB
potlines and for PM from CWPB1 potlines and anode bake furnaces, and
identified areas where we had misinterpreted data used for the proposed
PM and POM standards.
    Based on these comments and additional PM and POM emissions data,
we re-evaluated the proposed PM and POM MACT standards and revised the
following MACT limits:
     POM emission limit of 19 lb/ton aluminum for existing SWPB
potlines changed to 17 lb/ton aluminum;
     PM emission limit of 7.2 lb/ton aluminum for existing
CWPB1 potlines changed to 7.4 lb/ton aluminum;
     PM emission limit of 4.6 lb/ton aluminum for existing SWPB
potlines changed to 4.9 lb/ton aluminum;
     PM emission limit of 4.6 lb/ton aluminum for new potlines
changed to 4.9 lb/ton aluminum;
     PM emission limit of 0.068 lb/ton green anode for existing
anode bake furnaces changed to 0.2 lb/ton green anode; and
     PM emission limit of 0.036 lb/ton green anode for new
anode bake furnaces changed to 0.07 lb/ton green anode.
    The EPA discussed at proposal whether to promulgate MACT standards
at this time for HAP where much, most, or virtually all of the data
showed levels below detection limits. See 79 FR 72936. We received
comments claiming that, in addition to the standards listed above, the
EPA must promulgate standards for these HAP: Hg, D/F, and PCB. Based on
these comments, and considering further reply comments from industry
addressing this issue (see email, dated July 1, 2015, from Mr. Curt
Wells of The Aluminum Association, which is available in the docket for
this rulemaking (Docket ID No. EPA-HQ-OAR-2011-0797)), we re-evaluated
the data we had for PCB, D/F, and Hg to determine whether it would be
appropriate to establish emissions limits for these HAP. Based on that
evaluation, we determined that the emissions data for PCB from VSS2
Soderberg potlines are above detection limits and that numerical limits
reflecting MACT can be set for these sources. Therefore, we are
finalizing a MACT limit for PCB of 2.0 [micro]g TEQ/ton for existing
Soderberg VSS2 potlines and new Soderberg potlines. These standards
were developed based on the 99-percent upper prediction limit (UPL) for
PCB emissions from the available emissions data and represent the MACT
floor level of control. We also considered beyond-the-floor options,
but did not identify any feasible or cost-effective beyond-the-floor
options.
    Furthermore, we determined that the emissions data for Hg from
anode bake furnaces are above detection limits and that MACT limits can
be set for these sources. Therefore, we are finalizing a MACT limit for
Hg of 1.7 [mu]g/dscm for new and existing anode bake furnaces. These
standards are equal to 3 times the representative detection limit (RDL)
value for Hg. The RDL is the average method detection level (MDL)
achieved in practice by laboratories whose data support the best
performing 12 percent of a MACT category (or categories). We use an
average value for the RDL because a decision for a new source floor may
be based upon a test report where the laboratory chosen has better
equipment and/or practices than other laboratories and, therefore,
reported a lower MDL. Using that data to set the floor would result in
requiring all new sources to choose that laboratory in order to
demonstrate compliance with the new limit. We recognize the need to
allow sources to conduct business with their local laboratories, or a
laboratory of their preference; however, we limit the RDL to the best
laboratory performers because we do not want to incentivize the use of
the worst performing laboratories. The EPA policy is to set MACT
standards for a pollutant at a level of 3 times the RDL level for that
pollutant when the 99-percent UPL value for the available emissions
data results in a value that is less than 3 times the RDL level for
that pollutant, which is the case for Hg emissions from anode bake
furnaces. See, e.g., docket item number EPA-HQ-OAR-2009-0559-0157.
    We use the multiplication factor of 3 to approximately reduce the
imprecision of the analytical method until the imprecision in the field
sampling reflects the relative method precision as estimated by the
American Society of Mechanical Engineers (ASME) study \11\ that also
indicates that such relative imprecision, from 10 to 20 percent,
remains constant over the range of the methods. For comparing to the
floor, if 3 times the RDL were less than the calculated floor or
emissions limit (e.g., calculated from the UPL), we would conclude that
measurement variability was adequately addressed. The calculated floor
or emissions limit would need no adjustment. If, on the other hand, the
value equal to 3 times the RDL were greater than the UPL, we would
conclude that the calculated floor or emissions limit does not account
entirely for measurement variability.

Therefore, we substituted the value equal to 3 times the RDL for the
calculated floor or emissions limit which results in a concentration
where the method would produce measurement accuracy on the order of 10
to 20 percent similar to other EPA test methods and the results found
in the ASME study.
---------------------------------------------------------------------------

    \11\ Reference Method Accuracy and Precision (ReMAP): PHASE 1,
Precision of Manual Stack Emission Measurements; American Society of
Mechanical Engineers, Research Committee on Industrial and Municipal
Waste, February 2001.
---------------------------------------------------------------------------

    Please refer to the Final MACT Floor Analysis for the Primary
Aluminum Production Source Category, which is available in the docket
for this rulemaking (Docket ID No. EPA-HQ-OAR-2011-0797), for more
information regarding the new standards.
    Regarding the Hg and PCB emissions from the other process units
(such as potlines and paste production plants), and D/F from all the
process units, most (or all) of the emissions tests were below the
detection limit. Therefore, we conclude it is not feasible to prescribe
or enforce a numerical emission standard for these HAP emissions,
within the meaning of CAA section 112(h)(1) and (2). Specifically,
measured values for these HAP would be neither duplicable nor
replicable and would not give reliable indication of what (if anything)
the source was emitting. Under CAA section 112(h)(2), the EPA may adopt
work practice standards when ``the application of measurement
methodology to a particular class of sources is not practicable due to
technological and economic limitations.'' As discussed more fully in
section IV.C below, the EPA does not regard measurements which are
unreliable, non-duplicable, and non-replicable to be practicable.
Simply put, the CAA simply does not compel promulgation of numerical
emission standards that are too unreliable to be meaningful. Therefore,
as discussed in section IV.C of this preamble, we are promulgating work
practice standards for these HAP under section 112(h) of the CAA for
various process units.
3. What key comments did we receive on the CAA sections 112(d)(2) and
(3) proposed revisions, and what are our responses?
    Comment: Commenters identified POM and PM emissions data from
prebake potlines and PM emissions data from anode bake furnaces that
were incorrectly represented in the data sets used for MACT limit
determinations. Commenters also provided additional PM data for prebake
potlines and anode bake furnaces. Commenters requested the EPA to re-
evaluate MACT floors and recalculate MACT limits for PM and POM based
on the corrected and additional data.
    Response: We agree with commenters that the EPA misinterpreted
certain data in the supplemental proposal. For example, we
misinterpreted the PM and POM emissions from a single exhaust stack of
a control device with multiple exhaust stacks to be the total PM and
POM emissions from that source and misinterpreted the primary POM
emissions from a potline to be total POM emissions from that potline
(see pages 5 through 8 of the public comments provided by The Aluminum
Association, which are available in the docket for this rulemaking
(Docket ID No. EPA-HQ-OAR-2011-0797). The final rule reflects
appropriate data corrections, and the additional data provided have
been incorporated in the final limits promulgated for POM and PM from
prebake potlines and PM from anode bake furnaces. Further information
regarding the development of the final emission limits can be found in
the document titled, Final MACT Floor Analysis for the Primary Aluminum
Production Source Category, which is available in the docket for this
action.
    Comment: One commenter stated that the EPA must set standards for
all HAP emitted by primary aluminum reduction plants. The commenter
explained that the EPA's data collection found that primary aluminum
reduction plants emit D/F, Hg, and PCB. Nevertheless, the EPA proposed
not to set standards to limit these pollutants at all because ``many of
the emissions tests were below detection limit'' even though there are
emissions data in the record above the detection limits for these
pollutants for some sources. The commenter continued their argument by
stating that the CAA and D.C. Circuit case law require the EPA to set
limits for all emitted pollutants. As the D.C. Circuit has held, the
EPA has a ``clear statutory obligation to set emissions standards for
each listed HAP [i.e., hazardous air pollutant]'' under CAA section
112.
    Response: As explained above, based on consideration of this
comment, industry comment, and re-evaluation of the data, we are
promulgating numerical emissions limits for Hg from anode bake furnaces
and PCB for Soderberg potlines because the data we have support the
development of such numerical limits. Furthermore, regarding Hg, D/F,