National Emissions Standards for Hazardous Air Pollutants: Secondary Aluminum Production, 72873-72912 [2014-27497]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 79, Number 235 (Monday, December 8, 2014)]
[Proposed Rules]
[Pages 72873-72912]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-27497]



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Vol. 79

Monday,

No. 235

December 8, 2014

Part III





Environmental Protection Agency





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40 CFR Part 63





 National Emissions Standards for Hazardous Air Pollutants: Secondary 
Aluminum Production; Proposed Rule

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

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2010-0544; FRL-9919-33-OAR]
RIN 2060-AQ40


National Emissions Standards for Hazardous Air Pollutants: 
Secondary Aluminum Production

AGENCY: Environmental Protection Agency.

ACTION: Supplemental notice of proposed rulemaking.

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SUMMARY: This action supplements our notice of proposed rulemaking for 
the national emissions standards for hazardous air pollutants (NESHAP) 
for secondary aluminum production, which was published in the Federal 
Register on February 14, 2012. In that action, the Environmental 
Protection Agency (EPA) proposed decisions concerning the residual risk 
and technology review for the Secondary Aluminum Production source 
category and proposed amendments to correct and clarify rule 
requirements. This supplemental proposal presents a revised risk review 
(including a revised inhalation risk assessment, a refined multipathway 
risk assessment, and an updated ample margin of safety analysis) and a 
revised technology review for the Secondary Aluminum Production source 
category. Similar to the 2012 proposal, we found risks due to emissions 
of air toxics to be acceptable from this source category and we 
identified no cost effective controls under the updated ample margin of 
safety analysis or the technology review to achieve further emissions 
reductions. Therefore, we are proposing no revisions to the numeric 
emission standards based on these revised analyses. However, this 
supplemental proposal supplements and modifies several of the proposed 
technical corrections and rule clarifications that were originally 
presented in the February 14, 2012 proposal; withdraws our previous 
proposal to include affirmative defense provisions in the regulation; 
proposes alternative compliance options for the operating and 
monitoring requirements for sweat furnaces; and provides a revised cost 
analysis for compliance testing. This action, if finalized, would 
result in improved monitoring, compliance and implementation of the 
rule.

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

ADDRESSES: Comments. Submit your comments, identified by Docket ID No. 
EPA-HQ-OAR-2010-0544, by one of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov. 
Follow the online instructions for submitting comments.
     Email: A-and-R-docket@epa.gov. Include Attention Docket ID 
No. EPA-HQ-OAR-2010-0544 in the subject line of the message.
     Fax: (202) 566-9744, Attention Docket ID No. EPA-HQ-OAR-
2010-0544.
     Mail: Environmental Protection Agency, EPA Docket Center 
(EPA/DC), Mail Code 28221T, Attention Docket ID No. EPA-HQ-OAR-2010-
0544, 1200 Pennsylvania Avenue NW., Washington, DC 20460. Please mail a 
copy of your comments on the information collection provisions to the 
Office of Information and Regulatory Affairs, Office of Management and 
Budget (OMB), Attn: Desk Officer for EPA, 725 17th Street NW., 
Washington, DC 20503.
     Hand/Courier Delivery: EPA Docket Center, Room 3334, EPA 
WJC West Building, 1301 Constitution Avenue NW., Washington, DC 20004, 
Attention Docket ID No. EPA-HQ-OAR-2010-0544. Such deliveries are only 
accepted during the Docket's normal hours of operation, and special 
arrangements should be made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2010-0544. The EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at https://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be confidential business information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through https://www.regulations.gov or email. The https://www.regulations.gov Web site 
is an ``anonymous access'' system, which means the EPA will not know 
your identity or contact information unless you provide it in the body 
of your comment. If you send an email comment directly to the EPA 
without going through https://www.regulations.gov, your email address 
will be automatically captured and included as part of the comment that 
is placed in the public docket and made available on the Internet. If 
you submit an electronic comment, the EPA recommends that you include 
your name and other contact information in the body of your comment and 
with any disk or CD-ROM you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should not include special characters or any form of encryption and be 
free of any defects or viruses. For additional information about the 
EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
    Docket: The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2010-0544. All documents in the docket are 
listed in the www.regulations.gov index. Although listed in the index, 
some information is not publicly available, e.g., CBI or other 
information whose disclosure is restricted by statute. Certain other 
material, such as copyrighted material, is not placed on the Internet 
and will be publicly available only in hard copy. Publicly available 
docket materials are available either electronically in https://www.regulations.gov or in hard copy at the EPA Docket Center, Room 
3334, EPA WJC West Building, 1301 Constitution Avenue NW., Washington, 
DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
EPA Docket Center is (202) 566-1742.
    Public Hearing: If anyone contacts the EPA requesting a public 
hearing by December 15, 2014, the public hearing will be held on 
December 23, 2014 at the EPA's campus at 109 T.W. Alexander Drive, 
Research Triangle Park, North Carolina. The hearing will begin at 1:00 
p.m. (Eastern Standard Time) and conclude at 5:00 p.m. (Eastern 
Standard Time). Please contact

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Ms. Virginia Hunt at 919-541-0832 or at hunt.virginia@epa.gov to 
register to speak at the hearing or to inquire as to whether or not a 
hearing will be held. The last day to pre-register in advance to speak 
at the hearing will be December 22, 2014. Additionally, requests to 
speak will be taken the day of the hearing at the hearing registration 
desk, although preferences on speaking times may not be able to be 
accommodated. If you require the service of a translator or special 
accommodations such as audio description, please let us know at the 
time of registration. If you require an accommodation, we ask that you 
pre-register for the hearing, as we may not be able to arrange such 
accommodations without advance notice.
    If no one contacts the EPA requesting a public hearing to be held 
concerning this proposed rule by December 15, 2014, a public hearing 
will not take place. If a hearing is held, it will provide interested 
parties the opportunity to present data, views or arguments concerning 
the supplemental notice of proposed rulemaking. The EPA will make every 
effort to accommodate all speakers who arrive and register. Because the 
hearing will be held at a U.S. government facility, individuals 
planning to attend the hearing should be prepared to show valid picture 
identification to the security staff in order to gain access to the 
meeting room. Please note that the REAL ID Act, passed by Congress in 
2005, established new requirements for entering federal facilities. If 
your driver's license is issued by Alaska, American Samoa, Arizona, 
Kentucky, Louisiana, Maine, Massachusetts, Minnesota, Montana, New 
York, Oklahoma or the state of Washington, you must present an 
additional form of identification to enter the federal building. 
Acceptable alternative forms of identification include: Federal 
employee badges, passports, enhanced driver's licenses and military 
identification cards. In addition, you will need to obtain a property 
pass for any personal belongings you bring with you. Upon leaving the 
building, you will be required to return this property pass to the 
security desk. No large signs will be allowed in the building, cameras 
may only be used outside of the building and demonstrations will not be 
allowed on federal property for security reasons.
    The EPA may ask clarifying questions during the oral presentations, 
but will not respond to the presentations at that time. Written 
statements and supporting information submitted during the comment 
period will be considered with the same weight as oral comments and 
supporting information presented at the public hearing. Commenters 
should notify Ms. Hunt if they will need specific equipment, or if 
there are other special needs related to providing comments at the 
hearings. Verbatim transcripts of the hearing and written statements 
will be included in the docket for the rulemaking. The EPA will make 
every effort to follow the schedule as closely as possible on the day 
of the hearing; however, please plan for the hearing to run either 
ahead of schedule or behind schedule. Again, a hearing will not be held 
unless requested. Please contact Ms. Virginia Hunt at (919) 541-0832 or 
at hunt.virginia@epa.gov to request or register to speak at the hearing 
or to inquire as to whether or not a hearing will be held.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Ms. Rochelle Boyd, Sector Policies and Programs 
Division (D243-02), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711, telephone (919) 541-1390; fax number: (919) 541-3207; and email 
address: boyd.rochelle@epa.gov. For specific information regarding the 
risk modeling methodology, contact James Hirtz, Health and 
Environmental Impacts Division, (C539-02), Office of Air Quality 
Planning and Standards, U.S. Environmental Protection Agency, Research 
Triangle Park, NC 27711; telephone number: (919) 541-0881; fax number: 
(919) 541-0840; and email address: hirtz.james@epa.gov. For information 
about the applicability of the NESHAP to a particular entity, contact 
Scott Throwe, Office of Enforcement and Compliance Assurance (OECA), 
telephone number (202) 564-7013; and email address: 
throwe.scott@epa.gov.

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:
ACGIH American Conference of Government Industrial Hygienists
AEGL acute exposure guideline levels
AERMOD air dispersion model used by the HEM-3 model
AMOS ample margin of safety
ATSDR Agency for Toxic Substances and Disease Registry
BACT best available control technology
CAA Clean Air Act
CalEPA California Environmental Protection Agency
CBI confidential business information
CFR Code of Federal Regulations
D/F dioxins and furans
EJ environmental justice
EPA United States Environmental Protection Agency
ERPG Emergency Response Planning Guidelines
ERT Electronic Reporting Tool
HAP hazardous air pollutants
HCl hydrogen chloride
HEM-3 Human Exposure Model, Version 3
HF hydrogen fluoride
HI hazard index
HQ hazard quotient
ICR information collection request
IRIS Integrated Risk Information System
km kilometer
lb/yr pounds per year
LOAEL lowest-observed-adverse-effect level
MACT maximum achievable control technology
mg/m\3\ milligrams per cubic meter
MIR maximum individual risk
NAAQS National Ambient Air Quality Standard
NAICS North American Industry Classification System
NAS National Academy of Sciences
NATA National Air Toxics Assessment
NEI National Emissions Inventory
NESHAP National Emissions Standards for Hazardous Air Pollutants
NOAEL no observed adverse effects level
NRC National Research Council
NTTAA National Technology Transfer and Advancement Act
O&M operation and maintenance
OAQPS Office of Air Quality Planning and Standards
OECA Office of Enforcement and Compliance Assurance
OMB Office of Management and Budget
OM&M operation, maintenance and monitoring
PAH polycyclic aromatic hydrocarbons
PB-HAP hazardous air pollutants known to be persistent and bio-
accumulative in the environment
PEL probable effect levels
PM particulate matter
POM polycyclic organic matter
REL reference exposure level
RFA Regulatory Flexibility Act
RfC reference concentration
RfD reference dose
RTR residual risk and technology review
SAB Science Advisory Board
SAPU secondary aluminum processing unit
SBA Small Business Administration
SOP standard operating procedures
SSM startup, shutdown, and malfunction
TEQ toxic equivalents
THC total hydrocarbons
TOSHI target organ-specific hazard index
tpy tons per year
TRIM.FaTE Total Risk Integrated Methodology Fate, Transport and 
Ecological Exposure model
TTN Technology Transfer Network
UBC used beverage containers
UF uncertainty factor
[micro]g/m\3\ microgram per cubic meter
UMRA Unfunded Mandates Reform Act
URE unit risk estimate
WHO World Health Organization
    Organization of this Document. The information in this preamble is 
organized as follows:


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I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related 
information?
    C. What should I consider as I prepare my comments for the EPA?
II. Background Information
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP 
regulate its HAP emissions?
    C. What is the history of the Secondary Aluminum Risk and 
Technology Review?
    D. What data collection activities were conducted to support 
this action?
III. Analytical Procedures
    A. How did we evaluate the post-MACT risks posed by the 
Secondary Aluminum Production source category in the risk assessment 
developed for this supplemental proposal?
    B. How did we consider the risk results in making decisions for 
this supplemental proposal?
    C. How did we perform the technology review?
IV. Revised Analytical Results and Proposed Decisions for the 
Secondary Aluminum Production Source Category
    A. What are the results of the risk assessment and analysis?
    B. What are our proposed decisions regarding risk acceptability, 
ample margin of safety and adverse environmental effects based on 
our revised analyses?
    C. What are the results and proposed decisions based on our 
technology review?
    D. What other actions are we proposing?
    E. What compliance dates are we proposing?
V. Summary of the Revised Cost, Environmental and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
VI. Request for Comments
VII. Submitting Data Corrections
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination with 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Does this action apply to me?

    The regulated industrial source category that is the subject of 
this supplemental proposal is listed in Table 1 of this preamble. Table 
1 of this preamble is not intended to be exhaustive, but rather 
provides a guide for readers regarding the entities likely to be 
affected by this proposed action. These standards, once finalized, will 
be directly applicable to affected sources. Federal, state, local and 
tribal government entities are not affected by this proposed action. To 
determine whether your facility would be affected, you should examine 
the applicability criteria in the NESHAP. The Secondary Aluminum 
Production source category includes any facility using clean charge, 
aluminum scrap or dross from aluminum production, as the raw material 
and performing one or more of the following processes: scrap shredding, 
scrap drying/delacquering/decoating, thermal chip drying, furnace 
operations (i.e., melting, holding, sweating, refining, fluxing or 
alloying), recovery of aluminum from dross, in-line fluxing or dross 
cooling.

    Table 1--NESHAP and Industrial Source Categories Affected by This
                             Proposed Action
------------------------------------------------------------------------
                                                                 NAICS
        Industrial source category                NESHAP        Code \a\
------------------------------------------------------------------------
Secondary Aluminum Production.............  Secondary........     331314
Primary Aluminum Production Facilities....  Aluminum.........     331312
Aluminum Sheet, Plate, and Foil             Production.......     331315
 Manufacturing Facilities.
Aluminum Extruded Product Manufacturing     .................     331316
 Facilities.
Other Aluminum Rolling and Drawing          .................     331319
 Facilities.
Aluminum Die Casting Facilities...........  .................     331521
Aluminum Foundry Facilities...............  .................     331524
------------------------------------------------------------------------
\a\ North American Industry Classification System.

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

    In addition to being available in the docket, an electronic copy of 
this action is available on the Internet through EPA's Technology 
Transfer Network (TTN) Web site, a forum for information and technology 
exchange in various areas of air pollution control. Following signature 
by the EPA Administrator, the EPA will post a copy of this supplemental 
proposal at: https://www.epa.gov/ttn/atw/alum2nd/alum2pg.html. Following 
publication in the Federal Register, the EPA will post the Federal 
Register version of the proposal and key technical documents at this 
same Web site. Information on the overall residual risk and technology 
review program is available at the following Web site: https://www.epa.gov/ttn/atw/rrisk/rtrpg.html.

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

    Submitting CBI. Do not submit information containing CBI to the EPA 
through https://www.regulations.gov or email. Clearly mark the part or 
all of the information that you claim to be CBI. For CBI information on 
a disk or CD-ROM that you mail to the EPA, mark the outside of the disk 
or CD-ROM as CBI and then identify electronically within the disk or 
CD-ROM the specific information that is claimed as CBI. In addition to 
one complete version of the comments that includes information claimed 
as CBI, you must submit a copy of the comments that does not contain 
the information claimed as CBI for inclusion in the public docket. If 
you submit a CD-ROM or disk that does not contain CBI, mark the outside 
of the disk or CD-ROM clearly that it does not contain CBI. Information 
not marked as CBI will be included in the public docket and the EPA's 
electronic public docket without prior notice. Information marked as 
CBI will not be disclosed except in accordance with procedures set 
forth in 40 Code of Federal Regulations (CFR) part 2. Send or deliver 
information identified as CBI only to the following address: Roberto 
Morales, OAQPS Document Control

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Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, 
Research Triangle Park, North Carolina 27711, Attention Docket ID No. 
EPA-HQ-OAR-2010-0544.

II. Background Information

A. What is the statutory authority for this action?

    Section 112 of the Clean Air Act (CAA) establishes a two-stage 
regulatory process to address emissions of hazardous air pollutants 
(HAP) from stationary sources. In the first stage, after the EPA has 
identified categories of sources emitting one or more of the HAP listed 
in CAA section 112(b), CAA section 112(d) requires us to promulgate 
technology-based NESHAP for those sources. ``Major sources'' are those 
that emit or have the potential to emit 10 tons per year (tpy) or more 
of a single HAP or 25 tpy or more of any combination of HAP. For major 
sources, the technology-based NESHAP must reflect the maximum degree of 
emission reductions of HAP achievable (after considering cost, energy 
requirements and non-air quality health and environmental impacts) and 
are commonly referred to as maximum achievable control technology 
(MACT) standards.
    MACT standards must reflect the maximum degree of emission 
reduction achievable through the application of measures, processes, 
methods, systems or techniques, including, but not limited to, measures 
that (1) reduce the volume of or eliminate pollutants through process 
changes, substitution of materials or other modifications; (2) enclose 
systems or processes to eliminate emissions; (3) capture or treat 
pollutants when released from a process, stack, storage or fugitive 
emissions point; (4) are design, equipment, work practice or 
operational standards (including requirements for operator training or 
certification); or (5) are a combination of the above. CAA section 
112(d)(2)(A) through (E). The MACT standards may take the form of 
design, equipment, work practice or operational standards where the EPA 
first determines either that (1) a pollutant cannot be emitted through 
a conveyance designed and constructed to emit or capture the pollutant, 
or that any requirement for, or use of, such a conveyance would be 
inconsistent with law; or (2) the application of measurement 
methodology to a particular class of sources is not practicable due to 
technological and economic limitations. CAA section 112(h)(1) and (2).
    The MACT ``floor'' is the minimum control level allowed for MACT 
standards promulgated under CAA section 112(d)(3) and may not be based 
on cost considerations. For new sources, the MACT floor cannot be less 
stringent than the emissions control that is achieved in practice by 
the best-controlled similar source. The MACT floor for existing sources 
can be less stringent than floors for new sources but not less 
stringent than the average emissions limitation achieved by the best-
performing 12 percent of existing sources in the category or 
subcategory (or the best-performing five sources for categories or 
subcategories with fewer than 30 sources). In developing MACT 
standards, the EPA must also consider control options that are more 
stringent than the floor. We may establish standards more stringent 
than the floor based on considerations of the cost of achieving the 
emission reductions, any non-air quality health and environmental 
impacts and energy requirements.
    The EPA is then required to review these technology-based standards 
and revise them ``as necessary (taking into account developments in 
practices, processes, and control technologies)'' no less frequently 
than every eight years. CAA section 112(d)(6). In conducting this 
review, the EPA is not required to recalculate the MACT floor. Natural 
Resources Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 
2008). Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 
(D.C. Cir. 2013).
    The second stage in standard-setting focuses on reducing any 
remaining (i.e., ``residual'') risk according to CAA section 112(f). 
Section 112(f)(1) required that the EPA prepare a report to Congress 
discussing (among other things) methods of calculating the risks posed 
(or potentially posed) by sources after implementation of the MACT 
standards, the public health significance of those risks and the EPA's 
recommendations as to legislation regarding such remaining risk. The 
EPA prepared and submitted the Residual Risk Report to Congress, EPA-
453/R-99-001 (Risk Report) in March 1999. CAA section 112(f)(2) then 
provides that if Congress does not act on any recommendation in the 
Risk Report, the EPA must analyze and address residual risk for each 
category or subcategory of sources 8 years after promulgation of such 
standards pursuant to CAA section 112(d).
    Section 112(f)(2) of the CAA requires the EPA to determine for 
source categories subject to MACT standards whether the emission 
standards provide an ample margin of safety to protect public health. 
Section 112(f)(2)(B) of the CAA expressly preserves the EPA's use of 
the two-step process for developing standards to address any residual 
risk and the agency's interpretation of ``ample margin of safety'' 
developed in the National Emissions Standards for Hazardous Air 
Pollutants: Benzene Emissions from Maleic Anhydride Plants, 
Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment 
Leaks, and Coke By-Product Recovery Plants (Benzene NESHAP) (54 FR 
38044, September 14, 1989). The EPA notified Congress in the Risk 
Report that the agency intended to use the Benzene NESHAP approach in 
making CAA section 112(f) residual risk determinations (EPA-453/R-99-
001, p. ES-11). The EPA subsequently adopted this approach in its 
residual risk determinations and in a challenge to the risk review for 
the Synthetic Organic Chemical Manufacturing source category, the 
United States Court of Appeals for the District of Columbia Circuit 
upheld as reasonable the EPA's interpretation that subsection 112(f)(2) 
incorporates the approach established in the Benzene NESHAP. See NRDC 
v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008)(``[S]ubsection 
112(f)(2)(B) expressly incorporates the EPA's interpretation of the 
Clean Air Act from the Benzene standard, complete with a citation to 
the Federal Register.''); see also A Legislative History of the Clean 
Air Act Amendments of 1990, vol. 1, p. 877 (Senate debate on Conference 
Report).
    The first step in the process of evaluating residual risk is the 
determination of acceptable risk. If risks are unacceptable, the EPA 
cannot consider cost in identifying the emissions standards necessary 
to bring risks to an acceptable level. The second step is the 
determination of whether standards must be further revised in order to 
provide an ample margin of safety to protect public health. The ample 
margin of safety is the level at which the standards must be set, 
unless an even more stringent standard is necessary to prevent, taking 
into consideration costs, energy, safety and other relevant factors, an 
adverse environmental effect.
1. Step 1--Determination of Acceptability
    The agency in the Benzene NESHAP concluded that ``the acceptability 
of risk under section 112 is best judged on the basis of a broad set of 
health risk measures and information'' and that the ``judgment on 
acceptability cannot be reduced to any single factor.'' Benzene

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NESHAP at 38046. The determination of what represents an ``acceptable'' 
risk is based on a judgment of ``what risks are acceptable in the world 
in which we live'' (Risk Report at 178, quoting NRDC v. EPA, 824 F. 2d 
1146, 1165 (D.C. Cir. 1987) (en banc) (``Vinyl Chloride''), recognizing 
that our world is not risk-free.
    In the Benzene NESHAP, we stated that ``EPA will generally presume 
that if the risk to [the maximum exposed] individual is no higher than 
approximately one in 10 thousand, that risk level is considered 
acceptable.'' 54 FR at 38045. We discussed the maximum individual 
lifetime cancer risk (or maximum individual risk (MIR)) as being ``the 
estimated risk that a person living near a plant would have if he or 
she were exposed to the maximum pollutant concentrations for 70 
years.'' Id. We explained that this measure of risk ``is an estimate of 
the upper bound of risk based on conservative assumptions, such as 
continuous exposure for 24 hours per day for 70 years.'' Id. We 
explained that this measure of risk ``is an estimate of the upper bound 
of risk based on conservative assumptions, such as continuous exposure 
for 24 hours per day for 70 years.'' Id. We acknowledged that maximum 
individual lifetime cancer risk ``does not necessarily reflect the true 
risk, but displays a conservative risk level which is an upper-bound 
that is unlikely to be exceeded.'' Id.
    Understanding that there are both benefits and limitations to using 
the MIR as a metric for determining acceptability, we acknowledged in 
the Benzene NESHAP that ``consideration of maximum individual risk . . 
. must take into account the strengths and weaknesses of this measure 
of risk.'' Id. Consequently, the presumptive risk level of 100-in-1 
million (1-in-10 thousand) provides a benchmark for judging the 
acceptability of maximum individual lifetime cancer risk, but does not 
constitute a rigid line for making that determination. Further, in the 
Benzene NESHAP, we noted that:

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

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

``[i]n establishing a presumption for MIR, rather than a rigid line 
for acceptability, the Agency intends to weigh it with a series of 
other health measures and factors. These include the overall 
incidence of cancer or other serious health effects within the 
exposed population, the numbers of persons exposed within each 
individual lifetime risk range and associated incidence within, 
typically, a 50 km exposure radius around facilities, the science 
policy assumptions and estimation uncertainties associated with the 
risk measures, weight of the scientific evidence for human health 
effects, other quantified or unquantified health effects, effects 
due to co-location of facilities, and co-emission of pollutants.''

Id. at 38045. In some cases, these health measures and factors taken 
together may provide a more realistic description of the magnitude of 
risk in the exposed population than that provided by maximum individual 
lifetime cancer risk alone.

    As noted earlier, in NRDC v. EPA, the court held that section 
112(f)(2) ``incorporates the EPA's interpretation of the Clean Air Act 
from the Benzene Standard.'' The court further held that Congress' 
incorporation of the Benzene standard applies equally to carcinogens 
and non-carcinogens. 529 F.3d at 1081-82. Accordingly, we also consider 
non-cancer risk metrics in our determination of risk acceptability and 
ample margin of safety.
2. Step 2--Determination of Ample Margin of Safety
    CAA section 112(f)(2) requires the EPA to determine, for source 
categories subject to MACT standards, whether those standards provide 
an ample margin of safety to protect public health. As explained in the 
Benzene NESHAP, ``the second step of the inquiry, determining an `ample 
margin of safety,' again includes consideration of all of the health 
factors, and whether to reduce the risks even further. . . . Beyond 
that information, additional factors relating to the appropriate level 
of control will also be considered, including costs and economic 
impacts of controls, technological feasibility, uncertainties and any 
other relevant factors. Considering all of these factors, the agency 
will establish the standard at a level that provides an ample margin of 
safety to protect the public health, as required by section 112.'' 54 
FR at 38046, September 14, 1989.
    According to CAA section 112(f)(2)(A), if the MACT standards for 
HAP ``classified as a known, probable, or possible human carcinogen do 
not reduce lifetime excess cancer risks to the individual most exposed 
to emissions from a source in the category or subcategory to less than 
one in one million,'' the EPA must promulgate residual risk standards 
for the source category (or subcategory), as necessary to provide an 
ample margin of safety to protect public health. In doing so, the EPA 
may adopt standards equal to existing MACT standards if the EPA 
determines that the existing standards (i.e., the MACT standards) are 
sufficiently protective. NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 
2008) (``If EPA determines that the existing technology-based standards 
provide an `ample margin of safety,' then the Agency is free to readopt 
those standards during the residual risk rulemaking.'') The EPA must 
also adopt more stringent standards, if necessary, to prevent an 
adverse environmental effect,\1\ but must consider cost, energy, safety 
and other relevant factors in doing so.
---------------------------------------------------------------------------

    \1\ ``Adverse environmental effect'' is defined as any 
significant and widespread adverse effect, which may be reasonably 
anticipated to wildlife, aquatic life or natural resources, 
including adverse impacts on populations of endangered or threatened 
species or significant degradation of environmental qualities over 
broad areas. CAA section 112(a)(7).
---------------------------------------------------------------------------

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

In protecting public health with an ample margin of safety under 
section 112, EPA strives to provide maximum feasible protection 
against risks to health from hazardous air pollutants by (1) 
protecting the greatest number of persons possible to an individual 
lifetime risk level no higher than approximately 1-in-1 million and 
(2) limiting to no higher than approximately 1-in-10 thousand [i.e., 
100-in-1 million] the estimated risk that a person living near a 
plant would have if he or she were exposed to the maximum pollutant 
concentrations for 70 years.

    The agency further stated that ``[t]he EPA also considers incidence 
(the number of persons estimated to suffer cancer or other serious 
health effects as a result of exposure to a pollutant) to be an 
important measure of the health risk to the exposed population. 
Incidence measures the extent of health risks to the exposed population 
as a whole, by providing an estimate of the occurrence of cancer or 
other serious health effects in the exposed population.'' Id. at 38045.
    In the ample margin of safety decision process, the agency again 
considers all of the health risks and other health information 
considered in the first step, including the incremental risk reduction

[[Page 72879]]

associated with standards more stringent than the MACT standard or a 
more stringent standard that the EPA has determined is necessary to 
ensure risk is acceptable. In the ample margin of safety analysis, the 
agency considers additional factors, including costs and economic 
impacts of controls, technological feasibility, uncertainties and any 
other relevant factors. Considering all of these factors, the agency 
will establish the standard at a level that provides an ample margin of 
safety to protect the public health, as required by CAA section 112(f). 
54 FR 38046, September 14, 1989.

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

    The Secondary Aluminum Production source category includes 
facilities that produce aluminum from scrap aluminum material and 
consists of the following operations: (1) Preprocessing of scrap 
aluminum, including size reduction and removal of oils, coatings and 
other contaminants; (2) furnace operations, including melting, in-
furnace refining, fluxing and tapping; (3) additional refining, by 
means of in-line fluxing; and (4) cooling of dross. The following 
sections include descriptions of the affected sources in the Secondary 
Aluminum Production source category, the origin of HAP emissions from 
these affected sources and factors affecting the emissions.
    Scrap aluminum is often preprocessed prior to melting. 
Preprocessing steps may include shredding to reduce the size of 
aluminum scrap; drying of oily scrap such as machine turnings and 
borings; and/or heating in a scrap dryer, delacquering kiln or 
decoating kiln to remove coatings or other contaminants that may be 
present on the scrap. Heating of high iron content scrap in a sweat 
furnace to reclaim the aluminum content is also a preprocessing 
operation.
    Crushing, shredding and grinding operations are used to reduce the 
size of scrap aluminum. Particulate matter (PM) and HAP metals 
emissions are generated as dust from coatings and other contaminants 
contained in the scrap aluminum.
    A chip dryer is used to evaporate oil and/or moisture from uncoated 
aluminum chips and borings. Chip dryers typically operate at 
temperatures ranging between 150 [deg]C to 400 [deg]C (300 [deg]F to 
750 [deg]F). An uncontrolled chip dryer may emit dioxins and furans (D/
F) and total hydrocarbons (THC), of which some fraction is organic HAP.
    Painted and/or coated materials are processed in a scrap dryer/
delacquering kiln/decoating kiln to remove coatings and other 
contaminants that may be present in the scrap prior to melting. 
Coatings, oils, grease and lubricants represent up to 20 percent of the 
total weight of these materials. Organic HAP, D/F and inorganic HAP 
including particulate metal HAP are emitted during the drying/
delacquering/decoating process.
    Used beverage containers (UBC) comprise a major portion of the 
recycled aluminum scrap used as feedstock by the industry. In scrap 
drying/delacquering/decoating operations, UBC and other post-consumer 
coated products (e.g., aluminum siding) are heated to an exit 
temperature of up to 540 [deg]C (1,000 [deg]F) to volatilize and remove 
various organic contaminants such as paints, oils, lacquers, rubber and 
plastic laminates prior to melting. An uncontrolled scrap dryer/
delacquering kiln/decoating kiln emits PM (of which some fraction is 
particulate metal HAP), hydrogen chloride (HCl), THC (of which some 
fraction is organic HAP) and D/F.
    A sweat furnace is typically used to reclaim (or ``sweat'') the 
aluminum from scrap with high levels of iron. These furnaces operate in 
batch mode at a temperature that is high enough to melt the aluminum, 
but not high enough to melt the iron. The aluminum melts and flows out 
of the furnace while the iron remains in the furnace in solid form. The 
molten aluminum can be cast into sows, ingots or T-bars that are used 
as feedstock for aluminum melting and refining furnaces. Alternately, 
molten aluminum can be fed directly to a melting or refining furnace. 
An uncontrolled sweat furnace may emit D/F.
    Process (i.e., melting, holding or refining) furnaces are 
refractory-lined metal vessels heated by an oil or gas burner to 
achieve a metal temperature of about 760 [deg]C (1,400 [deg]F). The 
melting process begins with the charging of scrap into the furnace. A 
gaseous (typically, chlorine) or salt flux may be added to remove 
impurities and reduce aluminum oxidation. Once molten, the chemistry of 
the bath is adjusted by adding selected scrap or alloying agents, such 
as silicon. Salt and other fluxes contain chloride and fluoride 
compounds that may be released when introduced to the bath. HCl may 
also be released when chlorine-containing contaminants (such as 
polyvinyl chloride coatings) present in some types of scrap are 
introduced to the bath. Argon and nitrogen fluxes are not reactive and 
do not produce HAP. In a sidewell melting furnace, fluxing is performed 
in the sidewell, and fluxing emissions from the sidewell are 
controlled. In this type of furnace, fluxing is not typically done in 
the hearth, and hearth emissions (which include products of combustion 
from the oil and gas-fired furnaces) are typically uncontrolled.
    Process furnaces may process contaminated scrap which can result in 
HAP emissions. In addition, fluxing agents may contain compounds 
capable of producing HAP, some fraction of which is emitted from the 
furnace. Process furnaces are significant sources of HAP emissions in 
the secondary aluminum industry. An uncontrolled melting furnace which 
processes contaminated scrap and uses reactive fluxes emits PM (of 
which some fraction is particulate metal HAP), HCl and D/F.
    Process furnaces are divided into group 1 and group 2 furnaces. 
Group 1 furnaces are unrestricted in the type of scrap they process and 
the type of fluxes they can use. Group 2 furnaces process only clean 
charge and conduct no reactive fluxing.
    Dross-only furnaces are furnaces dedicated to reclamation of 
aluminum from drosses formed during the melting/holding/alloying 
operations carried out in other furnaces. Exposure to the atmosphere 
causes the molten aluminum to oxidize, and the flotation of the 
impurities to the surface along with any salt flux creates ``dross.'' 
Prior to tapping, the dross is periodically skimmed from the surface of 
the aluminum bath and cooled. Dross-only furnaces are typically rotary 
barrel furnaces (also known as salt furnaces). A dross-only furnace 
emits PM (of which some fraction is particulate metal HAP).
    Rotary dross coolers are devices used to cool dross in a rotating, 
water-cooled drum. A rotary dross cooler emits PM (of which some 
fraction is particulate metal HAP).
    In-line fluxers are devices used for aluminum refining, including 
degassing, outside the furnace. The process involves the injection of 
chlorine, argon, nitrogen or other gases to achieve the desired metal 
purity. In-line fluxers are found primarily at facilities that 
manufacture very high quality aluminum or in facilities with no other 
means of degassing. An in-line fluxer operating without emission 
controls emits HCl and PM.
    A summary description of requirements in the existing subpart RRR 
NESHAP is provided below for the convenience of the reader. The 
inclusion of this description, however, does not reopen the existing 
rule requirements and we are neither reconsidering nor soliciting 
public comment on the requirements

[[Page 72880]]

described. In addition, this summary description should not be relied 
on to determine applicability of the regulatory provisions or 
compliance obligations. The proposed decisions and rule amendments 
addressed in section IV below are the only provisions on which we are 
taking comment.
    The NESHAP for the Secondary Aluminum Production source category 
were promulgated on March 23, 2000 (65 FR 15690) and codified at 40 CFR 
part 63, subpart RRR (referred to from here on as subpart RRR in the 
remainder of this document). The rule was amended at 67 FR 79808, 
December 30, 2002; 69 FR 53980, September 3, 2004; 70 FR 57513, October 
3, 2005 and 70 FR 75320, December 19, 2005. The existing subpart RRR 
NESHAP regulates HAP emissions from secondary aluminum production 
facilities that are major sources of HAP that operate aluminum scrap 
shredders, thermal chip dryers, scrap dryers/delacquering kilns/
decoating kilns, group 1 furnaces, group 2 furnaces, sweat furnaces, 
dross-only furnaces, rotary dross coolers and secondary aluminum 
processing units (SAPUs). The SAPUs include group 1 furnaces and in-
line fluxers. The subpart RRR NESHAP regulates HAP emissions from 
secondary aluminum production facilities that are area sources of HAP 
only with respect to emissions of D/F from thermal chip dryers, scrap 
dryers/delacquering kilns/decoating kilns, group 1 furnaces, sweat 
furnaces and SAPUs.
    The secondary aluminum industry consists of approximately 161 
secondary aluminum production facilities, of which the EPA estimates 53 
to be major sources of HAP. The HAP emitted by these facilities are 
metals, organic HAP, D/F, HCl and hydrogen fluoride (HF).
    Several of the secondary aluminum facilities are co-located with 
primary aluminum, coil coating and possibly other source category 
facilities. Natural gas boilers or process heaters may also be co-
located at a few secondary aluminum facilities.
    The standards promulgated in 2000 established emission limits for 
PM as a surrogate for metal HAP, THC as a surrogate for organic HAP 
other than D/F, D/F expressed as toxic equivalents and HCl as a 
surrogate for acid gases including HF, chlorine and fluorine. HAP are 
emitted from the following affected sources: Aluminum scrap shredders 
(subject to PM standards), thermal chip dryers (subject to standards 
for THC and D/F), scrap dryers/delacquering kilns/decoating kilns 
(subject to standards for PM, D/F, HCl and THC), sweat furnaces 
(subject to D/F standards), dross-only furnaces (subject to PM 
standards), rotary dross coolers (subject to PM standards), group 1 
furnaces (subject to standards for PM, HCl and D/F) and in-line fluxers 
(subject to standards for PM and HCl). Group 2 furnaces and certain in-
line fluxers are subject to work practice standards. Table 2 provides a 
summary of the current MACT emissions limits for existing and new 
sources under the subpart RRR NESHAP.

[[Page 72881]]

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[[Page 72882]]


[GRAPHIC] [TIFF OMITTED] TP08DE14.501


[[Page 72883]]


[GRAPHIC] [TIFF OMITTED] TP08DE14.502

    Control devices currently in use to reduce emissions from affected 
sources subject to the subpart RRR NESHAP include fabric filters for 
control of PM from aluminum scrap shredders; afterburners for control 
of THC and D/F from thermal chip dryers; afterburners plus lime-
injected fabric filters for control of PM, HCl, THC and D/F from scrap 
dryers/delacquering kilns/decoating kilns; afterburners for control of 
D/F from sweat furnaces; fabric filters for control of PM from dross-
only furnaces and rotary dross coolers; lime-injected fabric filters 
for control of PM and HCl from in-line fluxers; and lime-injected 
fabric filters for control of PM, HCl and D/F from group 1 furnaces. 
All affected sources with add-on controls are also subject to design 
requirements and operating limits to limit fugitive emissions.
    Compliance with the emission limits in the current rule is 
demonstrated by an initial performance test for each affected source. 
Repeat performance tests are required every 5 years. Area sources are 
only subject to one-time performance tests for D/F. After the 
compliance tests, facilities are required to monitor various control 
parameters or conduct other types of monitoring to ensure continuous 
compliance with the MACT standards. Owners or operators of sweat 
furnaces that operate an afterburner that meets temperature and 
residence time requirements are not required to conduct performance 
tests.

C. What is the history of the Secondary Aluminum Risk and Technology 
Review?

    On February 14, 2012 (77 FR 8576), we proposed that no amendments 
to subpart RRR were necessary as a result of the residual risk and 
technology review (RTR) conducted for the Secondary Aluminum Production 
source category. In the same notice (77 FR 8576, which is referred to 
as the 2012 proposal in the remainder of this Federal Register 
document), we proposed amendments to correct and clarify existing 
requirements in subpart RRR. In this supplemental proposal, we are 
soliciting comment on modified proposed amendments to the subpart RRR 
rule requirements and on alternative compliance options related to 
sweat furnaces. The proposed revisions and alternative compliance 
options, described in more detail later in this document, on which we 
are soliciting comment are:
     Revised proposed limit on number of allowed furnace 
operating mode changes per year (i.e., frequency) in proposed section 
63.1514(e) of four times in any 6-month period, with the ability of 
sources to apply to the appropriate authority for additional furnace 
operating mode changes;
     Revised wording in proposed section 63.1511(b)(1) related 
to testing under worst-case scenario clarifying under what conditions 
the performance tests are to be conducted;
     Revised proposed requirements to account for fugitive 
emissions during performance testing of uncontrolled furnaces, 
including: (1) Installation of hooding according to American Conference 
of Government Industrial Hygienists (ACGIH) guidelines; (2) application 
of an assumption of 67 percent capture/control efficiency when 
calculating emissions; or (3) in certain cases where installing ACGIH 
hooding is impractical, allowing the facility to petition the 
permitting authority for major sources or the Administrator for area 
sources, for approval to use alternative testing procedures that will 
minimize fugitive emissions;
     Revised proposed requirement that emission sources comply 
with the emissions limits at all times including periods of startup and 
shutdown. Definitions of startup and shutdown are

[[Page 72884]]

being proposed as well as an alternative method for demonstrating 
compliance with emission limits;
     Revised proposed monitoring requirements in section 
63.1510(d)(2) that require annual inspection of capture/collection 
systems;
     Revised proposed compliance dates of 180 days for certain 
requirements and 2 years for other requirements; and
     Revised operating and monitoring requirements for 
demonstrating compliance for sweat furnaces.
    In addition, we are withdrawing our 2012 proposal to include 
provisions establishing an affirmative defense in light of a recent 
court decision vacating an affirmative defense in one of the EPA's 
section 112(d) regulations. NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014) 
(vacating affirmative defense provisions in Section 112(d) rule 
establishing emission standards for Portland cement kilns).
    After reviewing the comments, data and other information received 
after the 2012 proposal, we determined it is appropriate to present 
certain revised analyses and revised proposed amendments in this 
supplemental proposal to allow the public an opportunity to review and 
comment on these revised analyses and revised proposed amendments.
    The 2012 proposal also contained other proposed requirements 
(topics listed below) for which we have not made any changes to the 
analyses, and, therefore, on which we are not seeking public comment in 
this document. Other amendments or requirements that we proposed in 
2012, which we are not re-opening for comment, are the following:
     Electronic reporting.
     ACGIH Guidelines.
     Lime injection rate.
     Flux monitoring.
     Cover flux.
     Bale breakers.
     Bag Leak Detection Systems (BLDS).
     Sidewell furnaces.
     Testing representative units.
     Initial performance tests.
     Scrap dryer/delacquering/decoating kiln definition.
     Group 2 furnace definition.
     HF emissions compliance.
     SAPU definition.
     Clean charge definition.
     Residence time definition.
     SAPU feed/charge rate.
     Dross-only versus dross/scrap furnaces.
     Applicability of rule to area sources.
     Altering parameters during testing with new scrap streams.
     Controlled furnaces that are temporarily idled for 24 
hours or longer.
     Annual compliance certification for area sources.
    The comment period for the February 2012 proposal ended on April 
13, 2012. We will address the comments we received during the public 
comment period for the 2012 proposal, as well as comments received 
during the comment period for this supplemental proposal, at the time 
we take final action.
    Subpart RRR inadvertently uses several different terms for the 
agency that has primary responsibility for implementation of certain 
subpart RRR provisions. The terms used include ``responsible permitting 
authority,'' ``permitting authority,'' ``applicable permitting 
authority'' and ``delegated authority.'' Depending on the particular 
state and whether the facility is a major or area source, the 
permitting authority and the delegated authority for purposes of 
subpart RRR may be the same or may differ. Therefore, the EPA deems it 
appropriate to clarify for purposes of these specific subpart RRR 
provisions that the ``permitting authority'' (defined in the General 
Provisions as the Title V permitting authority) is the primary 
implementing authority for major sources, and the Administrator is the 
primary implementing authority for area sources. The General Provisions 
define ``Administrator'' to mean the EPA Administrator or his or her 
authorized representative (e.g., a state that has been delegated 
authority to implement Subpart RRR).
    Where these terms for the implementing authority appear in this 
supplemental proposal, we have made the necessary corrections. We plan 
to correct the remainder of these references when we issue the final 
rule.

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

    For the risk analysis performed for the 2012 proposal, we compiled 
a dataset from two primary sources: (1) A nine-company testing 
information collection request (ICR) sent in May 2010, and (2) an all-
company ICR sent to companies in February 2011. These data collection 
efforts are described in the 2012 proposal, and a comprehensive 
description of the emissions data, calculations and risk assessment 
inputs are in the memorandum, Development of the RTR Risk Modeling 
Dataset for the Secondary Aluminum Production Source Category (Docket 
item EPA-HQ-OAR-2010-0544-0149).
    For the revised risk analysis conducted for this supplemental 
proposal, changes were made in the methodology used to calculate 
allowable emissions. Generally, allowable emissions were calculated for 
the 2012 proposal as the product of the emissions limit for the 
secondary aluminum emissions unit and the maximum production capacity 
of the unit. For the revised emissions modeling for this supplemental 
proposal, the amount of charge to the unit from the all-company ICR was 
used in the allowable emissions calculation, rather than the maximum 
production capacity of the unit. Uniformly assuming that every piece of 
equipment is being used at maximum capacity results in an overestimate 
of total aluminum throughput that is much larger than the actual 
throughput for the facility as a whole. Moreover, if we assume maximum 
production capacity coupled with the assumption that all HAP are being 
emitted at the highest level allowed by the MACT rule (i.e., at the 
level of the emissions limit), this results in an overly conservative 
estimate of emissions. This overestimation is magnified for large 
facilities, with multiple pieces of equipment. Therefore, for this 
supplemental proposal, the amount of charge to the unit from the all-
company ICR was used in the allowable emissions calculation, rather 
than the maximum production capacity of the unit. Furthermore, this 
revised methodology is consistent with EPA's risk assessment 
methodology performed in other RTR modeling projects. See National 
Emission Standards for Hazardous Air Pollutants: Primary Lead Smelting; 
proposed rule (76 FR 9410, February 17, 2011), National Emissions 
Standards for Hazardous Air Pollutants: Secondary Lead Smelting; 
proposed rule (76 FR 29032, May 19, 2011) and National Emissions 
Standards for Hazardous Air Pollutants: Ferroalloys Production (76 FR 
72508, November 23, 2011). For an in-depth description of the revised 
risk modeling dataset, including changes in methodologies between the 
emissions modeling for the 2012 proposal and the emissions modeling for 
this supplemental proposal, see the memorandum, Development of the RTR 
Supplemental Proposal Risk Modeling Dataset for the Secondary Aluminum 
Production Source Category, available in this rulemaking docket.
    As part of the revised risk analysis, process equipment and unit 
emissions data used in the emissions modeling for the 2012 proposal 
were also reviewed. Since cancer risks were driven by D/F emissions in 
the modeling done for the 2012 proposal, we focused our refined 
assessment on the D/F emissions data. The other modeled pollutants had 
considerably lower estimated risks (compared to D/F) and the estimated

[[Page 72885]]

risks for all these HAP were well below the presumptive acceptable risk 
levels.
    For almost all facilities, the D/F emissions reported in the 2011 
ICR responses were used for the revised modeling. However, for the 
companies operating the 10 facilities that had the highest modeled risk 
from actual emissions in the modeling for the 2012 proposal, we 
requested and received results from additional compliance D/F testing 
that was conducted since the 2011 ICR. The results for all test runs 
associated with 2011 ICR responses and all test runs received as part 
of the request for additional test data were averaged together for each 
facility to provide more accurate estimates of the D/F emissions and 
resulting risks for these facilities. A memorandum comparing the 2011 
emissions data with the revised emissions data used for this 
supplemental proposal and the reasons for differences is available in 
the docket for this rulemaking. See Modeling Input Revisions for the 
RTR Risk Modeling Dataset for the Secondary Aluminum Production Source 
Category.
    We also revised emissions data for primary aluminum operations at 
primary aluminum facilities that were co-located at secondary aluminum 
facilities. The revised primary aluminum emissions data were based on 
recent test data used in the supplemental proposed rulemaking for the 
Primary Aluminum Production source category. These data included the 
following:
     Additional emission test data for polycyclic organic 
matter (POM) emissions from prebake potlines;
     Additional emission test data for PM emissions from 
prebake and Soderberg potlines, anode bake furnaces and paste plants;
     Additional emission test data for speciated polycyclic 
aromatic hydrocarbons (PAHs), speciated HAP metals, speciated 
polychlorinated biphenyls (PCBs) and speciated D/Fs from potlines, 
anode bake furnaces and paste plants.

III. Analytical Procedures

A. How did we evaluate the post-MACT risks posed by the Secondary 
Aluminum Production source category in the risk assessment developed 
for this supplemental proposal?

    The EPA conducted a risk assessment that provides estimates of the 
MIR posed by the HAP emissions from each source in the source category, 
the hazard index (HI) for chronic exposures to HAP with the potential 
to cause noncancer health effects and the hazard quotient (HQ) for 
acute exposures to HAP with the potential to cause noncancer health 
effects. The assessment also provides estimates of the distribution of 
cancer risks within the exposed populations, cancer incidence and an 
evaluation of the potential for adverse environmental effects. The 
seven sections that follow this paragraph describe how we estimated 
emissions and conducted the risk assessment. The docket for this 
rulemaking contains the following document which provides more 
information on the risk assessment inputs and models used for this 
revised assessment: Residual Risk Assessment for the Secondary Aluminum 
Production Source Category in Support of the 2014 Supplemental 
Proposal. The methods used to assess risks (as described in the seven 
primary steps below) are consistent with those peer-reviewed by a panel 
of the EPA's Science Advisory Board (SAB) in 2009 and described in 
their peer review report issued in 2010; \3\ they are also consistent 
with the key recommendations contained in that report.
---------------------------------------------------------------------------

    \3\ U.S. EPA SAB. Risk and Technology Review (RTR) Risk 
Assessment Methodologies: For Review by the EPA's Science Advisory 
Board with Case Studies--MACT I Petroleum Refining Sources and 
Portland Cement Manufacturing, May 2010.
---------------------------------------------------------------------------

1. How did we estimate actual emissions and identify the emissions 
release characteristics?
    As explained in section II.D above, the revised RTR emissions 
dataset for the Secondary Aluminum Production source category 
constitutes the basis for the revised risk assessment. This includes 
recent test data received from the primary aluminum facilities that 
were co-located at secondary aluminum production facilities. We 
estimated the magnitude of emissions using emissions test data 
collected through ICRs along with more recent data submitted by 
companies with facilities identified as the highest risk facilities for 
D/F emissions in the 2012 risk analysis. We also reviewed the 
information regarding emissions release characteristics such as stack 
heights, stack gas exit velocities, stack temperatures and source 
locations. In addition to the data quality checks performed on the 
source data for the facilities contained in the dataset, we also 
verified the coordinates of every emission source in the dataset 
through visual observations using Google Earth. We also performed data 
quality checks on the emissions data and release characteristics. The 
revised emissions data, the data quality checks and the methods used to 
estimate emissions from all the various emissions sources, are 
described in more detail in the technical documents: Development of the 
RTR Supplemental Proposal Risk Modeling Dataset for the Secondary 
Aluminum Production Source Category and Modeling Input Revisions for 
the RTR Risk Modeling Dataset for the Secondary Aluminum Production 
Source Category, which are available in the docket for this action.
2. How did we estimate MACT-allowable emissions?
    The available emissions data in the RTR emissions dataset include 
estimates of the mass of HAP emitted during the specified annual time 
period. In some cases, these ``actual'' emission levels are lower than 
the emission levels required to comply with the MACT standards. The 
emissions level allowed to be emitted by the MACT standards is referred 
to as the ``MACT-allowable'' emissions level. We discussed the use of 
both MACT-allowable and actual emissions in the final Coke Oven 
Batteries residual risk rule (70 FR 19998-19999, April 15, 2005) and in 
the proposed and final Hazardous Organic NESHAP residual risk rules (71 
FR 34428, June 14, 2006 and 71 FR 76609, December 21, 2006, 
respectively). In those previous actions, we noted that assessing the 
risks at the MACT-allowable level is inherently reasonable since these 
risks reflect the maximum level facilities could emit and still comply 
with national emission standards. We also explained that it is 
reasonable to consider actual emissions, where such data are available, 
in both steps of the risk analysis, in accordance with the Benzene 
NESHAP approach (54 FR 38044, September 14, 1989).
    For this supplemental proposal, we evaluated allowable stack 
emissions based on the level of control required by the subpart RRR 
MACT standards. As described in section II.D above, changes were made 
in the methodology used to calculate the allowable emissions for the 
revised risk analysis conducted for this supplemental proposal. In the 
2012 proposal, allowable emissions were calculated using the emissions 
limits for the 67 secondary aluminum emissions units and the maximum 
production capacity of each unit. For the revised emissions modeling, 
the actual amount of charge to the unit from the all-company ICR was 
used in the allowable emissions calculation, rather than the maximum 
production capacity of the unit. The methodology used to calculate 
allowable emissions is explained in more detail in the technical 
documents: Development of the RTR Supplemental Proposal Risk Modeling 
Dataset for the Secondary Aluminum Production

[[Page 72886]]

Source Category and Modeling Input Revisions for the RTR Risk Modeling 
Dataset for the Secondary Aluminum Production Source Category, which 
are available in the docket for this action.
3. How did we conduct dispersion modeling, determine inhalation 
exposures and estimate individual and population inhalation risks?
    Both long-term and short-term inhalation exposure concentrations 
and health risks from the source category addressed in this proposal 
were estimated using the Human Exposure Model (Community and Sector 
HEM-3 version 1.1.0). The HEM-3 performs three primary risk assessment 
activities: (1) Conducting dispersion modeling to estimate the 
concentrations of HAP in ambient air, (2) estimating long-term and 
short-term inhalation exposures to individuals residing within 50 
kilometers (km) of the modeled sources \4\, and (3) estimating 
individual and population-level inhalation risks using the exposure 
estimates and quantitative dose-response information.
---------------------------------------------------------------------------

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

    The air dispersion model used by the HEM-3 model (AERMOD) is one of 
the EPA's preferred models for assessing pollutant concentrations from 
industrial facilities.\5\ To perform the dispersion modeling and to 
develop the preliminary risk estimates, HEM-3 draws on three data 
libraries. The first is a library of meteorological data, which is used 
for dispersion calculations. This library includes 1 year (2011) of 
hourly surface and upper air observations for more than 800 
meteorological stations, selected to provide coverage of the United 
States and Puerto Rico. A second library of United States Census Bureau 
census block \6\ internal point locations and populations provides the 
basis of human exposure calculations (U.S. Census, 2010). In addition, 
for each census block, the census library includes the elevation and 
controlling hill height, which are also used in dispersion 
calculations. A third library of pollutant unit risk factors and other 
health benchmarks is used to estimate health risks. These risk factors 
and health benchmarks are the latest values recommended by the EPA for 
HAP and other toxic air pollutants. These values are available at 
https://www.epa.gov/ttn/atw/toxsource/summary.html and are discussed in 
more detail later in this section.
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    \5\ U.S. EPA. Revision to the Guideline on Air Quality Models: 
Adoption of a Preferred General Purpose (Flat and Complex Terrain) 
Dispersion Model and Other Revisions (70 FR 68218, November 9, 
2005).
    \6\ A census block is the smallest geographic area for which 
census statistics are tabulated.
---------------------------------------------------------------------------

    In developing the risk assessment for chronic exposures, we used 
the estimated annual average ambient air concentrations of each HAP 
emitted by each major source and D/F emissions from each area source 
for which we have emissions data in the source category. The air 
concentrations at each nearby census block centroid were used as a 
surrogate for the chronic inhalation exposure concentration for all the 
people who reside in that census block. We calculated the MIR for each 
facility as the cancer risk associated with a continuous lifetime (24 
hours per day, 7 days per week and 52 weeks per year for a 70-year 
period) exposure to the maximum concentration at the centroid of 
inhabited census blocks. Individual cancer risks were calculated by 
multiplying the estimated lifetime exposure to the ambient 
concentration of each of the HAP (in micrograms per cubic meter ([mu]g/
m\3\)) by its unit risk estimate (URE). The URE is an upper bound 
estimate of an individual's probability of contracting cancer over a 
lifetime of exposure to a concentration of 1 microgram of the pollutant 
per cubic meter of air. For residual risk assessments, we generally use 
URE values from the EPA's Integrated Risk Information System (IRIS). 
For carcinogenic pollutants without EPA IRIS values, we look to other 
reputable sources of cancer dose-response values, often using 
California EPA (CalEPA) URE values, where available. In cases where 
new, scientifically credible dose response values have been developed 
in a manner consistent with the EPA guidelines and have undergone a 
peer review process similar to that used by the EPA, we may use such 
dose-response values in place of, or in addition to, other values, if 
appropriate.
    The EPA estimated incremental individual lifetime cancer risks 
associated with emissions from the facilities in the source category as 
the sum of the risks for each of the carcinogenic HAP (including those 
classified as carcinogenic to humans, likely to be carcinogenic to 
humans and suggestive evidence of carcinogenic potential \7\) emitted 
by the modeled sources. Cancer incidence and the distribution of 
individual cancer risks for the population within 50 km of the sources 
were also estimated for the source category as part of this assessment 
by summing individual risks. A distance of 50 km is consistent with 
both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044, 
September 14, 1989) and the limitations of Gaussian dispersion models, 
including AERMOD.
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    \7\ These classifications also coincide with the terms ``known 
carcinogen, probable carcinogen, and possible carcinogen,'' 
respectively, which are the terms advocated in the EPA's previous 
Guidelines for Carcinogen Risk Assessment, published in 1986 (51 FR 
33992, September 24, 1986). Summing the risks of these individual 
compounds to obtain the cumulative cancer risks is an approach that 
was recommended by the EPA's SAB in their 2002 peer review of the 
EPA's National Air Toxics Assessment (NATA) titled, NATA--Evaluating 
the National-scale Air Toxics Assessment 1996 Data--an SAB Advisory, 
available at: https://yosemite.epa.gov/sab/sabproduct.nsf/
214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.
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    To assess the risk of non-cancer health effects from chronic 
exposures, we summed the HQ for each of the HAP that affects a common 
target organ system to obtain the HI for that target organ system (or 
target organ-specific HI, TOSHI). The HQ is the estimated exposure 
divided by the chronic reference value, which is a value selected from 
one of several sources. First, the chronic reference level can be the 
EPA reference concentration (RfC) (https://www.epa.gov/riskassessment/glossary.htm), defined as ``an estimate (with uncertainty spanning 
perhaps an order of magnitude) of a continuous inhalation exposure to 
the human population (including sensitive subgroups) that is likely to 
be without an appreciable risk of deleterious effects during a 
lifetime.'' Alternatively, in cases where an RfC from the EPA's IRIS 
database is not available or where the EPA determines that using a 
value other than the RfC is appropriate, the chronic reference level 
can be a value from the following prioritized sources: (1) The Agency 
for Toxic Substances and Disease Registry (ATSDR) Minimum Risk Level 
(https://www.atsdr.cdc.gov/mrls/index.asp), which is defined as ``an 
estimate of daily human exposure to a hazardous substance that is 
likely to be without an appreciable risk of adverse non-cancer health 
effects (other than cancer) over a specified duration of exposure''; 
(2) the CalEPA Chronic Reference Exposure Level (REL) (https://www.oehha.ca.gov/air/hot_spots/pdf/HRAguidefinal.pdf), which is defined 
as ``the concentration level (that is expressed in units of micrograms 
per cubic meter ([mu]g/m\3\) for inhalation exposure and in a dose 
expressed in units of milligram per kilogram-day (mg/kg-day) for oral 
exposures), at or below which no adverse health effects are anticipated 
for a specified exposure duration''; or (3), as noted above, a 
scientifically credible dose-response value that has been developed in 
a

[[Page 72887]]

manner consistent with the EPA guidelines and has undergone a peer 
review process similar to that used by the EPA, in place of or in 
concert with other values.
    The EPA also evaluated screening estimates of acute exposures and 
risks for each of the HAP at the point of highest potential off-site 
exposure for each facility. To do this, the EPA estimated the risks 
when both the peak hourly emissions rate and worst-case dispersion 
conditions occur. We also assume that a person is located at the point 
of highest impact during that same time. In accordance with our mandate 
in section 112 of the CAA, we use the point of highest off-site 
exposure to assess the potential risk to the maximally exposed 
individual. In some cases, the agency may choose to refine the acute 
screen by also assessing the exposure that may occur at a centroid of a 
census block. The acute HQ is the estimated acute exposure divided by 
the acute dose-response value. In each case, the EPA calculated acute 
HQ values using best available, short-term dose-response values. These 
acute dose-response values, which are described below, include the 
acute REL, acute exposure guideline levels (AEGL) and emergency 
response planning guidelines (ERPG) for 1-hour exposure durations. As 
discussed below, we used conservative assumptions for emissions rates, 
meteorology and exposure location for our acute analysis.
    As described in the CalEPA's Air Toxics Hot Spots Program Risk 
Assessment Guidelines, Part I, The Determination of Acute Reference 
Exposure Levels for Airborne Toxicants, an acute REL value (https://www.oehha.ca.gov/air/pdf/acuterel.pdf) is defined as ``the 
concentration level at or below which no adverse health effects are 
anticipated for a specified exposure duration.'' Id. at page 2. Acute 
REL values are based on the most sensitive, relevant, adverse health 
effect reported in the peer-reviewed medical and toxicological 
literature. Acute REL values are designed to protect the most sensitive 
individuals in the population through the inclusion of margins of 
safety. Because margins of safety are incorporated to address data gaps 
and uncertainties, exceeding the REL does not automatically indicate an 
adverse health impact.
    As we state above, in assessing the potential risks associated with 
acute exposures to HAP, we do not follow a prioritization scheme and, 
therefore, we consider available dose-response values from multiple 
authoritative sources. In the RTR program, the EPA assesses acute risk 
using toxicity values derived from one hour exposures.
    AEGL values were derived in response to recommendations from the 
National Research Council (NRC). As described in Standing Operating 
Procedures (SOP) of the National Advisory Committee on Acute Exposure 
Guideline Levels for Hazardous Substances (https://www.epa.gov/oppt/aegl/pubs/sop.pdf),\8\ ``the NRC's previous name for acute exposure 
levels--community emergency exposure levels--was replaced by the term 
AEGL to reflect the broad application of these values to planning, 
response, and prevention in the community, the workplace, 
transportation, the military, and the remediation of Superfund sites.'' 
Id. at 2. This document also states that AEGL values ``represent 
threshold exposure limits for the general public and are applicable to 
emergency exposures ranging from 10 minutes to eight hours.'' Id. at 2.
---------------------------------------------------------------------------

    \8\ National Academy of Sciences (NAS), 2001. Standing Operating 
Procedures for Developing Acute Exposure Levels for Hazardous 
Chemicals, page 2.
---------------------------------------------------------------------------

    The document lays out the purpose and objectives of AEGL by stating 
that ``the primary purpose of the AEGL program and the National 
Advisory Committee for Acute Exposure Guideline Levels for Hazardous 
Substances is to develop guideline levels for once-in-a-lifetime, 
short-term exposures to airborne concentrations of acutely toxic, high-
priority chemicals.'' Id. at 21. In detailing the intended application 
of AEGL values, the document states that ``[i]t is anticipated that the 
AEGL values will be used for regulatory and nonregulatory purposes by 
U.S. Federal and state agencies and possibly the international 
community in conjunction with chemical emergency response, planning, 
and prevention programs. More specifically, the AEGL values will be 
used for conducting various risk assessments to aid in the development 
of emergency preparedness and prevention plans, as well as real-time 
emergency response actions, for accidental chemical releases at fixed 
facilities and from transport carriers.'' Id. at 31.
    The AEGL-1 value is then specifically defined as ``the airborne 
concentration (expressed as ppm (parts per million) or mg/m\3\ 
(milligrams per cubic meter)) of a substance above which it is 
predicted that the general population, including susceptible 
individuals, could experience notable discomfort, irritation, or 
certain asymptomatic nonsensory effects. However, the effects are not 
disabling and are transient and reversible upon cessation of 
exposure.'' Id. at 3. The document also notes that, ``Airborne 
concentrations below AEGL-1 represent exposure levels that can produce 
mild and progressively increasing but transient and nondisabling odor, 
taste, and sensory irritation or certain asymptomatic, nonsensory 
effects.'' Id. Similarly, the document defines AEGL-2 values as ``the 
airborne concentration (expressed as parts per million or milligrams 
per cubic meter) of a substance above which it is predicted that the 
general population, including susceptible individuals, could experience 
irreversible or other serious, long-lasting adverse health effects or 
an impaired ability to escape.'' Id.
    ERPG values are derived for use in emergency response, as described 
in the American Industrial Hygiene Association's Emergency Response 
Planning (ERP) Committee document titled, ERPGS Procedures and 
Responsibilities (https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERP-SOPs2006.pdf), which states that, ``Emergency Response Planning 
Guidelines were developed for emergency planning and are intended as 
health based guideline concentrations for single exposures to 
chemicals.'' \9\ Id. at 1. The ERPG-1 value is defined as ``the maximum 
airborne concentration below which it is believed that nearly all 
individuals could be exposed for up to 1 hour without experiencing 
other than mild transient adverse health effects or without perceiving 
a clearly defined, objectionable odor.'' Id. at 2. Similarly, the ERPG-
2 value is defined as ``the maximum airborne concentration below which 
it is believed that nearly all individuals could be exposed for up to 
one hour without experiencing or developing irreversible or other 
serious health effects or symptoms which could impair an individual's 
ability to take protective action.'' Id. at 1.
---------------------------------------------------------------------------

    \9\ ERP Committee Procedures and Responsibilities. November 1, 
2006. American Industrial Hygiene Association.
---------------------------------------------------------------------------

    As can be seen from the definitions above, the AEGL and ERPG values 
include the similarly-defined severity levels 1 and 2. For many 
chemicals, a severity level 1 value AEGL or ERPG has not been developed 
because the types of effects for these chemicals are not consistent 
with the AEGL-1/ERPG-1 definitions; in these instances, we compare 
higher severity level AEGL-2 or ERPG-2 values to our modeled exposure 
levels to screen for potential

[[Page 72888]]

acute concerns. When AEGL-1/ERPG-1 values are available, they are used 
in our acute risk assessments.
    Acute REL values for 1-hour exposure durations are typically lower 
than their corresponding AEGL-1 and ERPG-1 values. Even though their 
definitions are slightly different, AEGL-1 values are often the same as 
the corresponding ERPG-1 values and AEGL-2 values are often equal to 
ERPG-2 values. Maximum HQ values from our acute screening risk 
assessments typically result when basing them on the acute REL value 
for a particular pollutant. In cases where our maximum acute HQ value 
exceeds 1, we also report the HQ value based on the next highest acute 
dose-response value (usually the AEGL-1 and/or the ERPG-1 value).
    To develop screening estimates of acute exposures in the absence of 
hourly emissions data, generally we first develop estimates of maximum 
hourly emissions rates by multiplying the average actual annual hourly 
emissions rates by a default factor to cover routinely variable 
emissions. We choose the factor to use partially based on process 
knowledge and engineering judgment. The factor chosen also reflects a 
Texas study of short-term emissions variability, which showed that most 
peak emission events in a heavily-industrialized four-county area 
(Harris, Galveston, Chambers and Brazoria Counties, Texas) were less 
than twice the annual average hourly emissions rate. The highest peak 
emissions event was 74 times the annual average hourly emissions rate 
and the 99th percentile ratio of peak hourly emissions rate to the 
annual average hourly emissions rate was 9.\10\ Considering this 
analysis, to account for more than 99 percent of the peak hourly 
emissions, we apply a conservative screening multiplication factor of 
10 to the average annual hourly emissions rate in our acute exposure 
screening assessments as our default approach. However, we use a factor 
other than 10 if we have information that indicates that a different 
factor is appropriate for a particular source category. For this source 
category, there was no such information available and the default 
factor of 10 was used in the acute screening process.
---------------------------------------------------------------------------

    \10\ See https://www.tceq.state.tx.us/compliance/field_ops/eer/ or docket to access the source of these data.
---------------------------------------------------------------------------

    Ideally, we would prefer to have continuous measurements over time 
to see how the emissions vary by each hour over an entire year. Having 
a frequency distribution of hourly emissions rates over a year would 
allow us to perform a probabilistic analysis to estimate potential 
threshold exceedances and their frequency of occurrence. Such an 
evaluation could include a more complete statistical treatment of the 
key parameters and elements adopted in this screening analysis. 
Recognizing that this level of data is rarely available, we instead 
rely on the multiplier approach.
    As part of our acute risk assessment process, for cases where acute 
HQ values from the screening step are less than or equal to 1 (even 
under the conservative assumptions of the screening analysis), acute 
impacts are deemed negligible and no further analysis is performed. In 
cases where an acute HQ from the screening step are greater than 1, 
additional site-specific data would be considered to develop a more 
refined estimate of the potential for acute impacts of concern. 
However, for this source category, no acute values were greater than 1. 
Therefore, further refinement was not performed.
    To better characterize the potential health risks associated with 
estimated acute exposures to HAP, and in response to a key 
recommendation from the SAB's peer review of the EPA's RTR risk 
assessment methodologies,\11\ we generally examine a wider range of 
available acute health metrics (e.g., RELs, AEGLs) than we do for our 
chronic risk assessments. This is in response to the SAB's 
acknowledgement that there are generally more data gaps and 
inconsistencies in acute reference values than there are in chronic 
reference values. In some cases, when Reference Value Arrays \12\ for 
HAP have been developed, we consider additional acute values (i.e., 
occupational and international values) to provide a more complete risk 
characterization.
---------------------------------------------------------------------------

    \11\ The SAB peer review of RTR Risk Assessment Methodologies is 
available at: https://yosemite.epa.gov/sab/sabproduct.nsf/
4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.
    \12\ U.S. EPA. (2009) Chapter 2.9 Chemical Specific Reference 
Values for Formaldehyde in Graphical Arrays of Chemical-Specific 
Health Effect Reference Values for Inhalation Exposures (Final 
Report). U.S. Environmental Protection Agency, Washington, DC, EPA/
600/R-09/061 and available online at https://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=211003.
---------------------------------------------------------------------------

4. How did we conduct the multipathway exposure and risk screening?
    The EPA conducted a screening analysis examining the potential for 
significant human health risks due to exposures via routes other than 
inhalation (i.e., ingestion). We first determined whether any major 
sources in the source category emitted any HAP known to be persistent 
and bioaccumulative in the environment (PB-HAP). The PB-HAP compounds 
or compound classes are identified for the screening from the EPA's Air 
Toxics Risk Assessment Library (available at: https://www2.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library). Since D/F is the only pollutant for which subpart RRR area 
sources are regulated under CAA section 112(d), this was the only PB-
HAP evaluated in this screening analysis for area sources.
    For major sources in the Secondary Aluminum Production source 
category, we identified emissions of cadmium compounds, D/F, lead 
compounds, mercury compounds and POM. Because one or more of these PB-
HAP are emitted by at least one facility in the Secondary Aluminum 
Production source category, we proceeded to the next step of the 
evaluation. In this step, we determined whether the facility-specific 
emissions rates of the emitted PB-HAP were large enough to create the 
potential for significant non-inhalation human health risks under 
reasonable worst-case conditions. To facilitate this step, we developed 
emissions rate screening levels for several PB-HAP using a hypothetical 
upper-end screening exposure scenario developed for use in conjunction 
with the EPA's Total Risk Integrated Methodology.Fate, Transport and 
Ecological Exposure (TRIM.FaTE) model. The PB-HAP with emissions rate 
screening levels are: lead, cadmium, D/F, mercury compounds and POM. We 
conducted a sensitivity analysis on the screening scenario to ensure 
that its key design parameters would represent the upper end of the 
range of possible values, such that it would represent a conservative 
but not impossible scenario. The facility-specific emissions rates of 
these PB-HAP were compared to the emission rate screening levels for 
these PB-HAP to assess the potential for significant human health risks 
via non-inhalation pathways. We call this application of the TRIM.FaTE 
model the Tier 1 TRIM-screen or Tier 1 screen.
    For the purpose of developing emissions rates for our Tier 1 TRIM-
screen, we derived emission levels for these PB-HAP (other than lead 
compounds) at which the maximum excess lifetime cancer risk would be 1-
in-1 million (i.e., for D/F and POM) or, for HAP that cause non-cancer 
health effects (i.e., cadmium compounds and mercury compounds), the 
maximum HQ would be 1. If the emissions rate of any PB-HAP included in 
the Tier 1 screen exceeds the Tier 1 screening emissions rate for any 
facility, we conduct a

[[Page 72889]]

second screen, which we call the Tier 2 TRIM-screen or Tier 2 screen.
    In the Tier 2 screen, the location of each facility that exceeded 
the Tier 1 emission rate is used to refine the assumptions associated 
with the environmental scenario while maintaining the exposure scenario 
assumptions. A key assumption that is part of the Tier 1 screen is that 
a lake is located near the facility; we confirm the existence of lakes 
near the facility as part of the Tier 2 screen. We then adjust the 
risk-based Tier 1 screening level for each PB-HAP for each facility 
based on an understanding of how exposure concentrations estimated for 
the screening scenarios for the subsistence fisher and the subsistence 
farmer change with meteorology and environmental assumptions. PB-HAP 
emissions that do not exceed these new Tier 2 screening levels are 
considered to pose no unacceptable risks. If the PB-HAP emissions for a 
facility exceed the Tier 2 screening emissions rate and data are 
available, we may decide to conduct a more refined Tier 3 multipathway 
screening analysis. There are several analyses that can be included in 
a Tier 3 screen depending upon the extent of refinement warranted, 
including validating that the lake is fishable and considering plume-
rise to estimate emissions lost above the mixing layer. If the Tier 3 
screen is exceeded, the EPA may further refine the assessment.
    For this source category, we conducted a Tier 3 screening analysis 
for six major sources with Tier 2 cancer screen values greater than or 
equal to 50 times the Tier 2 threshold for the subsistence fisher 
scenario. The major sources represented the highest screened cancer 
risk for multipathway impacts. Therefore, further screening analyses 
were not performed on the area sources. A detailed discussion of the 
approach for this risk assessment can be found in Appendix 8 of the 
Residual Risk Assessment for the Secondary Aluminum Production Source 
Category in Support of the 2014 Supplemental Proposal.
    In evaluating the potential multipathway risk from emissions of 
lead compounds, rather than developing a screening emissions rate for 
them, we compared maximum estimated chronic inhalation exposures with 
the level of the current National Ambient Air Quality Standard (NAAQS) 
for lead.\13\ Values below the level of the primary (health-based) lead 
NAAQS were considered to have a low potential for multipathway risk.
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    \13\ In doing so, the EPA notes that the legal standard for a 
primary NAAQS--that a standard is requisite to protect public health 
and provide an adequate margin of safety (CAA section 109(b))--
differs from the CAA section 112(f) standard (requiring among other 
things that the standard provide an ``ample margin of safety''). 
However, the lead NAAQS is a reasonable measure of determining risk 
acceptability (i.e., the first step of the Benzene NESHAP analysis) 
since it is designed to protect the most susceptible group in the 
human population--children, including children living near major 
lead emitting sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. 
In addition, applying the level of the primary lead NAAQS at the 
risk acceptability step is conservative, since that primary lead 
NAAQS reflects an adequate margin of safety.
---------------------------------------------------------------------------

    For further information on the multipathway analysis approach, see 
the Residual Risk Assessment for the Secondary Aluminum Production 
Source Category in Support of the 2014 Supplemental Proposal, which is 
available in the docket for this action.
5. How did we conduct the environmental risk screening assessment?
a. Adverse Environmental Effect
    The EPA conducts a screening assessment to examine the potential 
for adverse environmental effects as required under section 
112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines ``adverse 
environmental effect'' as ``any significant and widespread adverse 
effect, which may reasonably be anticipated, to wildlife, aquatic life, 
or other natural resources, including adverse impacts on populations of 
endangered or threatened species or significant degradation of 
environmental quality over broad areas.''
b. Environmental HAP
    The EPA focuses on seven HAP, which we refer to as ``environmental 
HAP,'' in its screening analysis: Five PB-HAP and two acid gases. The 
five PB-HAP are cadmium, D/F, POM, mercury (both inorganic mercury and 
methyl mercury) and lead compounds. The two acid gases are HCl and HF. 
The rationale for including these seven HAP in the environmental risk 
screening analysis is presented below.
    The HAP that persist and bioaccumulate are of particular 
environmental concern because they accumulate in the soil, sediment and 
water. The PB-HAP are taken up, through sediment, soil, water and/or 
ingestion of other organisms, by plants or animals (e.g., small fish) 
at the bottom of the food chain. As larger and larger predators consume 
these organisms, concentrations of the PB-HAP in the animal tissues 
increase as does the potential for adverse effects. The five PB-HAP we 
evaluate as part of our screening analysis account for 99.8 percent of 
all PB-HAP emissions nationally from stationary sources (on a mass 
basis from the 2005 National Emissions Inventory (NEI)).
    In addition to accounting for almost all of the mass of PB-HAP 
emitted, we note that the TRIM.FaTE model that we use to evaluate 
multipathway risk allows us to estimate concentrations of cadmium 
compounds, D/F, POM and mercury in soil, sediment and water. For lead 
compounds, we currently do not have the ability to calculate these 
concentrations using the TRIM.FaTE model. Therefore, to evaluate the 
potential for adverse environmental effects from lead compounds, we 
compare the estimated HEM-modeled exposures from the source category 
emissions of lead with the level of the secondary NAAQS for lead.\14\ 
We consider values below the level of the secondary lead NAAQS as 
unlikely to cause adverse environmental effects.
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    \14\ The secondary lead NAAQS is a reasonable measure of 
determining whether there is an adverse environmental effect since 
it was established considering ``effects on soils, water, crops, 
vegetation, man-made materials, animals, wildlife, weather, 
visibility and climate, damage to and deterioration of property, and 
hazards to transportation, as well as effects on economic values and 
on personal comfort and well-being.''
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    Due to their well-documented potential to cause direct damage to 
terrestrial plants, we include two acid gases, HCl and HF, in the 
environmental screening analysis. According to the 2005 NEI, HCl and HF 
account for about 99 percent (on a mass basis) of the total acid gas 
HAP emitted by stationary sources in the U.S. In addition to the 
potential to cause direct damage to plants, high concentrations of HF 
in the air have been linked to fluorosis in livestock. Air 
concentrations of these HAP are already calculated as part of the human 
multipathway exposure and risk screening analysis using the HEM3-AERMOD 
air dispersion model, and we are able to use the air dispersion 
modeling results to estimate the potential for an adverse environmental 
effect.
    The EPA acknowledges that other HAP beyond the seven HAP discussed 
above may have the potential to cause adverse environmental effects. 
Therefore, the EPA may include other relevant HAP in its environmental 
risk screening in the future, as modeling science and resources allow. 
The EPA invites comment on the extent to which other HAP emitted by the 
source category may cause adverse environmental effects. Such 
information should include references to peer-reviewed ecological 
effects benchmarks that are of sufficient quality for making

[[Page 72890]]

regulatory decisions, as well as information on the presence of 
organisms located near facilities within the source category that such 
benchmarks indicate could be adversely affected.
c. Ecological Assessment Endpoints and Benchmarks for PB-HAP
    An important consideration in the development of the EPA's 
screening methodology is the selection of ecological assessment 
endpoints and benchmarks. Ecological assessment endpoints are defined 
by the ecological entity (e.g., aquatic communities including fish and 
plankton) and its attributes (e.g., frequency of mortality). Ecological 
assessment endpoints can be established for organisms, populations, 
communities or assemblages and ecosystems.
    For PB-HAP (other than lead compounds), we evaluated the following 
community-level ecological assessment endpoints to screen for organisms 
directly exposed to HAP in soils, sediment and water:
     Local terrestrial communities (i.e., soil invertebrates, 
plants) and populations of small birds and mammals that consume soil 
invertebrates exposed to PB-HAP in the surface soil;
     Local benthic (i.e., bottom sediment dwelling insects, 
amphipods, isopods and crayfish) communities exposed to PB-HAP in 
sediment in nearby water bodies; and
     Local aquatic (water-column) communities (including fish 
and plankton) exposed to PB-HAP in nearby surface waters.
    For PB-HAP (other than lead compounds), we also evaluated the 
following population-level ecological assessment endpoint to screen for 
indirect HAP exposures of top consumers via the bioaccumulation of HAP 
in food chains;
     Piscivorous (i.e., fish-eating) wildlife consuming PB-HAP-
contaminated fish from nearby water bodies.
    For cadmium compounds, D/F, POM and mercury, we identified the 
available ecological benchmarks for each assessment endpoint. An 
ecological benchmark represents a concentration of HAP (e.g., 0.77 
[mu]g of HAP per liter of water) that has been linked to a particular 
environmental effect level through scientific study. For PB-HAP we 
identified, where possible, ecological benchmarks at the following 
effect levels:
     Probable effect levels (PEL): Level above which adverse 
effects are expected to occur frequently;
     Lowest-observed-adverse-effect level (LOAEL): The lowest 
exposure level tested at which there are biologically significant 
increases in frequency or severity of adverse effects; and
     No-observed-adverse-effect levels (NOAEL): The highest 
exposure level tested at which there are no biologically significant 
increases in the frequency or severity of adverse effect.
    We established a hierarchy of preferred benchmark sources to allow 
selection of benchmarks for each environmental HAP at each ecological 
assessment endpoint. In general, the EPA sources that are used at a 
programmatic level (e.g., Office of Water, Superfund Program) were used 
in the analysis, if available. If not, the EPA benchmarks used in 
regional programs (e.g., Superfund) were used. If benchmarks were not 
available at a programmatic or regional level, we used benchmarks 
developed by other federal agencies (e.g., National Oceanic and 
Atmospheric Administration (NOAA)) or state agencies.
    Benchmarks for all effect levels are not available for all PB-HAP 
and assessment endpoints. In cases where multiple effect levels were 
available for a particular PB-HAP and assessment endpoint, we use all 
of the available effect levels to help us to determine whether 
ecological risks exist and, if so, whether the risks could be 
considered significant and widespread.
d. Ecological Assessment Endpoints and Benchmarks for Acid Gases
    The environmental screening analysis also evaluated potential 
damage and reduced productivity of plants due to direct exposure to 
acid gases in the air. For acid gases, we evaluated the following 
ecological assessment endpoint:
     Local terrestrial plant communities with foliage exposed 
to acidic gaseous HAP in the air.
    The selection of ecological benchmarks for the effects of acid 
gases on plants followed the same approach as for PB-HAP (i.e., we 
examine all of the available benchmarks). For HCl, the EPA identified 
chronic benchmark concentrations. We note that the benchmark for 
chronic HCl exposure to plants is greater than the reference 
concentration for chronic inhalation exposure for human health. This 
means that where the EPA includes regulatory requirements to prevent an 
exceedance of the reference concentration for human health, additional 
analyses for adverse environmental effects of HCl would not be 
necessary.
    For HF, the EPA identified chronic benchmark concentrations for 
plants and evaluated chronic exposures to plants in the screening 
analysis. High concentrations of HF in the air have also been linked to 
fluorosis in livestock. However, the HF concentrations at which 
fluorosis in livestock occur are higher than those at which plant 
damage begins. Therefore, the benchmarks for plants are protective of 
both plants and livestock.
e. Screening Methodology
    For the environmental risk screening analysis, the EPA first 
determined whether any of the major source facilities in the Secondary 
Aluminum Production source category emitted any of the seven 
environmental HAP. We identified emissions of five of the PB-HAP 
(cadmium, mercury, lead, D/F, PAHs) and two acid gases (HCl and HF). 
Because one or more of the seven environmental HAP evaluated were 
emitted by facilities in the source category, we proceeded to the 
second step of the evaluation. Since D/F is the only pollutant for 
which subpart RRR area sources are regulated under CAA section 112(d), 
this was the only PB-HAP evaluated in this screening analysis.
f. PB-HAP Methodology
    For cadmium, mercury, POM and D/F, the environmental screening 
analysis consists of two tiers, while lead compounds are analyzed 
differently as discussed earlier. In the first tier, we determined 
whether the maximum facility-specific emission rates of each of the 
emitted environmental HAP for the major sources were large enough to 
create the potential for adverse environmental effects under reasonable 
worst-case environmental conditions. This same assessment was done for 
area sources for D/F because this is the only pollutant for which 
subpart RRR area sources are regulated under CAA section 112(d). These 
are the same environmental conditions used in the human multipathway 
exposure and risk screening analysis.
    To facilitate this step, TRIM.FaTE was run for each PB-HAP under 
hypothetical environmental conditions designed to provide 
conservatively high HAP concentrations. The model was set to maximize 
runoff from terrestrial parcels into the modeled lake, which in turn, 
maximized the chemical concentrations in the water, the sediments and 
the fish. The resulting media concentrations were then used to back-
calculate a screening level emission rate that corresponded to the 
relevant exposure benchmark

[[Page 72891]]

concentration value for each assessment endpoint. To assess emissions 
from a facility, the reported emission rate for each PB-HAP was 
compared to the screening level emission rate for that PB-HAP for each 
assessment endpoint. If emissions from a facility do not exceed the 
Tier 1 screening level, the facility ``passes'' the screen, and, 
therefore, is not evaluated further under the screening approach. If 
emissions from a facility exceed the Tier 1 screening level, we 
evaluate the facility further in Tier 2.
    In Tier 2 of the environmental screening analysis, the emission 
rate screening levels are adjusted to account for local meteorology and 
the actual location of lakes in the vicinity of facilities that did not 
pass the Tier 1 screen. The modeling domain for each facility in the 
Tier 2 analysis consists of eight octants. Each octant contains 5 
modeled soil concentrations at various distances from the facility (5 
soil concentrations x 8 octants = total of 40 soil concentrations per 
facility) and one lake with modeled concentrations for water, sediment 
and fish tissue. In the Tier 2 environmental risk screening analysis, 
the 40 soil concentration points are averaged to obtain an average soil 
concentration for each facility for each PB-HAP. For the water, 
sediment and fish tissue concentrations, the highest value for each 
facility for each pollutant is used. If emission concentrations from a 
facility do not exceed the Tier 2 screening level, the facility passes 
the screen, and is typically not evaluated further. If emissions from a 
facility exceed the Tier 2 screening level, the facility does not pass 
the screen and, therefore, may have the potential to cause adverse 
environmental effects. Such facilities are evaluated further to 
investigate factors such as the magnitude and characteristics of the 
area of exceedance.
g. Acid Gas Methodology
    The environmental screening analysis evaluates the potential 
phytotoxicity and reduced productivity of plants due to chronic 
exposure to acid gases. The environmental risk screening methodology 
for acid gases is a single-tier screen that compares the average off-
site ambient air concentration over the modeling domain to ecological 
benchmarks for each of the acid gases. Because air concentrations are 
compared directly to the ecological benchmarks, emission-based 
screening levels are not calculated for acid gases as they are in the 
ecological risk screening methodology for PB-HAP.
    For purposes of ecological risk screening, the EPA identifies a 
potential for adverse environmental effects to plant communities from 
exposure to acid gases when the average concentration of the HAP around 
a facility exceeds the LOAEL ecological benchmark. In such cases, we 
further investigate factors such as the magnitude and characteristics 
of the area of exceedance (e.g., land use of exceedance area, size of 
exceedance area) to determine if there is an adverse environmental 
effect. For further information on the environmental screening analysis 
approach, see the Residual Risk Assessment for the Secondary Aluminum 
Production Source Category in Support of the 2014 Supplemental 
Proposal, which is available in the docket for this action.
6. How did we conduct facility-wide assessments?
    To put the source category risks in context, we typically examine 
the risks from the entire ``facility,'' where the facility includes all 
HAP-emitting operations within a contiguous area and under common 
control. In other words, we examine the HAP emissions not only from the 
source category of interest, but also emissions of HAP from all other 
emissions sources at the facility for which we have data. For the 
Secondary Aluminum Production source category, we had nine facilities 
that were co-located with primary aluminum reduction plants.
7. How did we consider uncertainties in risk assessment?
    In the Benzene NESHAP, we concluded that risk estimation 
uncertainty should be considered in our decision-making under the ample 
margin of safety framework. Uncertainty and the potential for bias are 
inherent in all risk assessments, including those performed for this 
proposal. Although uncertainty exists, we believe that our approach, 
which used conservative tools and assumptions, ensures that our 
decisions are health protective and environmentally protective. A brief 
discussion of the uncertainties in the RTR emissions dataset, 
dispersion modeling, inhalation exposure estimates and dose-response 
relationships follows below. A more thorough discussion of these 
uncertainties is included in the Development of the RTR Supplemental 
Proposal Risk Modeling Dataset for the Secondary Aluminum Production 
Source Category and Modeling Input Revisions for the RTR Risk Modeling 
Dataset for the Secondary Aluminum Production Source Category, which 
are available in the docket for this action. The other uncertainties 
are described in more detail in the Residual Risk Assessment for the 
Secondary Aluminum Production Source Category in Support of the 2014 
Supplemental Proposal, which is available in the docket for this 
action.
a. Uncertainties in the RTR Emissions Dataset
    Although the development of the RTR emissions dataset involved 
quality assurance/quality control processes, the accuracy of emissions 
values will vary depending on the source of the data, the degree to 
which data are incomplete or missing, the degree to which assumptions 
made to complete the datasets are accurate, errors in emission 
estimates and other factors. The emission estimates considered in this 
analysis generally are annual totals for certain years, and they do not 
reflect short-term fluctuations during the course of a year or 
variations from year to year. The estimates of peak hourly emission 
rates for the acute effects screening assessment were based on an 
emission adjustment factor of 10 applied to the average annual hourly 
emission rates for all emission process groups, which are intended to 
account for emission fluctuations due to normal facility operations. A 
description of the development of the emissions dataset is in section 
II.D of this preamble and in the documents, Development of the RTR 
Supplemental Proposal Risk Modeling Dataset for the Secondary Aluminum 
Production Source Category and Modeling Input Revisions for the RTR 
Risk Modeling Dataset for the Secondary Aluminum Production Source 
Category, which are in the docket for this rulemaking.
b. Uncertainties in Dispersion Modeling
    We recognize there is uncertainty in ambient concentration 
estimates associated with any model, including the EPA's recommended 
regulatory dispersion model, AERMOD. In using a model to estimate 
ambient pollutant concentrations, the user chooses certain options to 
apply. For RTR assessments, we select some model options that have the 
potential to overestimate ambient air concentrations (e.g., not 
including plume depletion or pollutant transformation). We select other 
model options that have the potential to underestimate ambient impacts 
(e.g., not including building downwash). Other options that we select 
have the potential to either under- or overestimate ambient levels 
(e.g., meteorology and receptor locations). On balance, considering the 
directional nature of the uncertainties commonly present in ambient 
concentrations estimated by dispersion models, the approach we apply in 
the

[[Page 72892]]

RTR assessments should yield unbiased estimates of ambient HAP 
concentrations.
c. Uncertainties in Inhalation Exposure
    The EPA did not include the effects of human mobility on exposures 
in the assessment. Specifically, short-term mobility and long-term 
mobility between census blocks in the modeling domain were not 
considered.\15\ The approach of not considering short or long-term 
population mobility does not bias the estimate of the theoretical MIR 
(by definition), nor does it affect the estimate of cancer incidence 
because the total population number remains the same. It does, however, 
affect the shape of the distribution of individual risks across the 
affected population, shifting it toward higher estimated individual 
risks at the upper end and reducing the number of people estimated to 
be at lower risks, thereby increasing the estimated number of people at 
specific high risk levels (e.g., 1-in-10 thousand or 1-in-1 million).
---------------------------------------------------------------------------

    \15\ Short-term mobility is movement from one micro-environment 
to another over the course of hours or days. Long-term mobility is 
movement from one residence to another over the course of a 
lifetime.
---------------------------------------------------------------------------

    In addition, the assessment predicted the chronic exposures at the 
centroid of each populated census block as surrogates for the exposure 
concentrations for all people living in that block. Using the census 
block centroid to predict chronic exposures tends to over-predict 
exposures for people in the census block who live farther from the 
facility and under-predict exposures for people in the census block who 
live closer to the facility. Thus, using the census block centroid to 
predict chronic exposures may lead to a potential understatement or 
overstatement of the true maximum impact, but is an unbiased estimate 
of average risk and incidence. We reduce this uncertainty by analyzing 
large census blocks near facilities using aerial imagery and adjusting 
the location of the block centroid to better represent the population 
in the block, as well as adding additional receptor locations where the 
block population is not well represented by a single location.
    The assessment evaluates the cancer inhalation risks associated 
with pollutant exposures over a 70-year period, which is the assumed 
lifetime of an individual. In reality, both the length of time that 
modeled emission sources at facilities actually operate (i.e., more or 
less than 70 years) and the domestic growth or decline of the modeled 
industry (i.e., the increase or decrease in the number or size of 
domestic facilities) will influence the future risks posed by a given 
source or source category. Depending on the characteristics of the 
industry, these factors will, in most cases, result in an overestimate 
both in individual risk levels and in the total estimated number of 
cancer cases. However, in the unlikely scenario where a facility 
maintains, or even increases, its emissions levels over a period of 
more than 70 years, residents live beyond 70 years at the same 
location, and the residents spend most of their days at that location, 
then the cancer inhalation risks could potentially be underestimated. 
However, annual cancer incidence estimates from exposures to emissions 
from these sources would not be affected by the length of time an 
emissions source operates.
    The exposure estimates used in these analyses assume chronic 
exposures to ambient (outdoor) levels of pollutants. Because most 
people spend the majority of their time indoors, actual exposures may 
not be as high, depending on the characteristics of the pollutants 
modeled. For many of the HAP, indoor levels are roughly equivalent to 
ambient levels, but for very reactive pollutants or larger particles, 
indoor levels are typically lower. This factor has the potential to 
result in an overestimate of 25 to 30 percent of exposures.\16\
---------------------------------------------------------------------------

    \16\ U.S. EPA. National-Scale Air Toxics Assessment for 1996. 
(EPA 453/R-01-003; January 2001; page 85.)
---------------------------------------------------------------------------

    In addition to the uncertainties highlighted above, there are 
several factors specific to the acute exposure assessment that the EPA 
conducts as part of the risk review under section 112 of the CAA that 
should be highlighted. The accuracy of an acute inhalation exposure 
assessment depends on the simultaneous occurrence of independent 
factors that may vary greatly, such as hourly emissions rates, 
meteorology and the presence of humans at the location of the maximum 
concentration. In the acute screening assessment that we conduct under 
the RTR program, we assume that peak emissions from the source category 
and worst-case meteorological conditions co-occur, thus, resulting in 
maximum ambient concentrations. These two events are unlikely to occur 
at the same time, making these assumptions conservative. We then 
include the additional assumption that a person is located at this 
point during this same time period. For this source category, these 
assumptions would tend to be worst-case actual exposures as it is 
unlikely that a person would be located at the point of maximum 
exposure during the time when peak emissions and worst-case 
meteorological conditions occur simultaneously.
d. Uncertainties in Dose-Response Relationships
    There are uncertainties inherent in the development of the dose-
response values used in our risk assessments for cancer effects from 
chronic exposures and non-cancer effects from both chronic and acute 
exposures. Some uncertainties may be considered quantitatively, and 
others generally are expressed in qualitative terms. We note as a 
preface to this discussion a point on dose-response uncertainty that is 
brought out in the EPA's 2005 Cancer Guidelines; namely, that ``the 
primary goal of EPA actions is protection of human health; accordingly, 
as an Agency policy, risk assessment procedures, including default 
options that are used in the absence of scientific data to the 
contrary, should be health protective'' (EPA 2005 Cancer Guidelines, 
pages 1-7). This is the approach followed here as summarized in the 
next several paragraphs. A complete detailed discussion of 
uncertainties and variability in dose-response relationships is given 
in the Residual Risk Assessment for the Secondary Aluminum Production 
Source Category in Support of the 2014 Supplemental Proposal, which is 
available in the docket for this action.
    Cancer URE values used in our risk assessments are those that have 
been developed to generally provide an upper bound estimate of risk. 
That is, they represent a ``plausible upper limit to the true value of 
a quantity'' (although this is usually not a true statistical 
confidence limit).\17\ In some circumstances, the true risk could be as 
low as zero; however, in other circumstances the risk could be 
greater.\18\ When developing an upper bound estimate of risk and to 
provide risk values that do not underestimate risk, health-protective 
default approaches are generally used. To err on the side of ensuring 
adequate health protection, the EPA typically uses the upper bound 
estimates rather than lower bound or central tendency estimates in our 
risk assessments, an approach that may have limitations for

[[Page 72893]]

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

    \17\ IRIS glossary (https://www.epa.gov/NCEA/iris/help_gloss.htm).
    \18\ An exception to this is the URE for benzene, which is 
considered to cover a range of values, each end of which is 
considered to be equally plausible, and which is based on maximum 
likelihood estimates.
---------------------------------------------------------------------------

    Chronic non-cancer RfC and reference dose (RfD) values represent 
chronic exposure levels that are intended to be health-protective 
levels. Specifically, these values provide an estimate (with 
uncertainty spanning perhaps an order of magnitude) of a continuous 
inhalation exposure (RfC) or a daily oral exposure (RfD) to the human 
population (including sensitive subgroups) that is likely to be without 
an appreciable risk of deleterious effects during a lifetime. To derive 
values that are intended to be ``without appreciable risk,'' the 
methodology relies upon an uncertainty factor (UF) approach (U.S. EPA, 
1993, 1994) which considers uncertainty, variability and gaps in the 
available data. The UF are applied to derive reference values that are 
intended to protect against appreciable risk of deleterious effects. 
The UF are commonly default values,\19\ e.g., factors of 10 or 3, used 
in the absence of compound-specific data; where data are available, UF 
may also be developed using compound-specific information. When data 
are limited, more assumptions are needed and more UF are used. Thus, 
there may be a greater tendency to overestimate risk in the sense that 
further study might support development of reference values that are 
higher (i.e., less potent) because fewer default assumptions are 
needed. However, for some pollutants, it is possible that risks may be 
underestimated.
---------------------------------------------------------------------------

    \19\ According to the NRC report, Science and Judgment in Risk 
Assessment (NRC, 1994) ``[Default] options are generic approaches, 
based on general scientific knowledge and policy judgment, that are 
applied to various elements of the risk assessment process when the 
correct scientific model is unknown or uncertain.'' The 1983 NRC 
report, Risk Assessment in the Federal Government: Managing the 
Process, defined default option as ``the option chosen on the basis 
of risk assessment policy that appears to be the best choice in the 
absence of data to the contrary'' (NRC, 1983a, p. 63). Therefore, 
default options are not rules that bind the agency; rather, the 
agency may depart from them in evaluating the risks posed by a 
specific substance when it believes this to be appropriate. In 
keeping with the EPA's goal of protecting public health and the 
environment, default assumptions are used to ensure that risk to 
chemicals is not underestimated (although defaults are not intended 
to overtly overestimate risk). See EPA, 2004, An Examination of EPA 
Risk Assessment Principles and Practices, EPA/100/B-04/001 available 
at: https://www.epa.gov/osa/pdfs/ratf-final.pdf.
---------------------------------------------------------------------------

    While collectively termed ``UF,'' these factors account for a 
number of different quantitative considerations when using observed 
animal (usually rodent) or human toxicity data in the development of 
the RfC. The UF are intended to account for: (1) Variation in 
susceptibility among the members of the human population (i.e., inter-
individual variability); (2) uncertainty in extrapolating from 
experimental animal data to humans (i.e., interspecies differences); 
(3) uncertainty in extrapolating from data obtained in a study with 
less-than-lifetime exposure (i.e., extrapolating from sub-chronic to 
chronic exposure); (4) uncertainty in extrapolating the observed data 
to obtain an estimate of the exposure associated with no adverse 
effects; and (5) uncertainty when the database is incomplete or there 
are problems with the applicability of available studies.
    Many of the UF used to account for variability and uncertainty in 
the development of acute reference values are quite similar to those 
developed for chronic durations, but they more often use individual UF 
values that may be less than 10. The UF are applied based on chemical-
specific or health effect-specific information (e.g., simple irritation 
effects do not vary appreciably between human individuals, hence a 
value of 3 is typically used), or based on the purpose for the 
reference value (see the following paragraph). The UF applied in acute 
reference value derivation include: (1) Heterogeneity among humans; (2) 
uncertainty in extrapolating from animals to humans; (3) uncertainty in 
lowest observed adverse effect (exposure) level to no observed adverse 
effect (exposure) level adjustments; and (4) uncertainty in accounting 
for an incomplete database on toxic effects of potential concern. 
Additional adjustments are often applied to account for uncertainty in 
extrapolation from observations at one exposure duration (e.g., 4 
hours) to derive an acute reference value at another exposure duration 
(e.g., 1 hour).
    Not all acute reference values are developed for the same purpose 
and care must be taken when interpreting the results of an acute 
assessment of human health effects relative to the reference value or 
values being exceeded. Where relevant to the estimated exposures, the 
lack of short-term dose-response values at different levels of severity 
should be factored into the risk characterization as potential 
uncertainties.
    Although every effort is made to identify appropriate human health 
effect dose-response assessment values for all pollutants emitted by 
the sources in this risk assessment, some HAP emitted by this source 
category are lacking dose-response assessments. Accordingly, these 
pollutants cannot be included in the quantitative risk assessment, 
which could result in quantitative estimates understating HAP risk. To 
help to alleviate this potential underestimate, where we conclude 
similarity with a HAP for which a dose-response assessment value is 
available, we use that value as a surrogate for the assessment of the 
HAP for which no value is available. To the extent use of surrogates 
indicates appreciable risk, we may identify a need to increase priority 
for new IRIS assessment of that substance. We additionally note that, 
generally speaking, HAP of greatest concern due to environmental 
exposures and hazard are those for which dose-response assessments have 
been performed, reducing the likelihood of understating risk.
    For a group of compounds that are unspeciated (e.g., glycol 
ethers), we conservatively use the most protective reference value of 
an individual compound in that group to estimate risk. Similarly, for 
an individual compound in a group (e.g., ethylene glycol diethyl ether) 
that does not have a specified reference value, we also apply the most 
protective reference value from the other compounds in the group to 
estimate risk.
e. Uncertainties in the Multipathway Assessment
    For each source category, we generally rely on site-specific levels 
of PB-HAP emissions to determine whether a refined assessment of the 
impacts from multipathway exposures is necessary. This determination is 
based on the results of a tiered screening analysis that relies on the 
outputs from models that estimate environmental pollutant 
concentrations and human exposures for four PB-HAP. Two important types 
of uncertainty associated with the use of these models in RTR risk 
assessments and inherent to any assessment that relies on environmental 
modeling are model uncertainty and input uncertainty.\20\
---------------------------------------------------------------------------

    \20\ In the context of this discussion, the term ``uncertainty'' 
as it pertains to exposure and risk encompasses both variability in 
the range of expected inputs and screening results due to existing 
spatial, temporal, and other factors, as well as uncertainty in 
being able to accurately estimate the true result.
---------------------------------------------------------------------------

    Model uncertainty concerns whether the selected models are 
appropriate for the assessment being conducted and whether they 
adequately represent the actual processes that might occur for that 
situation. An example of model uncertainty is the question of whether 
the model adequately describes the movement of a pollutant through the 
soil. This type of uncertainty is difficult to quantify. However, based 
on feedback received from previous SAB reviews and other reviews, we 
are confident that the models used in the screen are

[[Page 72894]]

appropriate and state-of-the-art for the multipathway risk assessments 
conducted in support of RTR.
    Input uncertainty is concerned with how accurately the models have 
been configured and parameterized for the assessment at hand. For Tier 
1 of the multipathway screen, we configured the models to avoid 
underestimating exposure and risk. This was accomplished by selecting 
upper-end values from nationally-representative datasets for the more 
influential parameters in the environmental model, including selection 
and spatial configuration of the area of interest, lake location and 
size, meteorology, surface water and soil characteristics and structure 
of the aquatic food web. We also assume an ingestion exposure scenario 
and values for human exposure factors that represent reasonable maximum 
exposures. The multipathway screens include some hypothetical elements, 
namely the hypothetical farmer and fisher scenarios. It is important to 
note that even though the multipathway assessment has been conducted, 
no data exist to verify the existence of either the farmer or fisher 
scenario outlined above.
    In Tier 2 of the multipathway assessment, we refine the model 
inputs to account for meteorological patterns in the vicinity of the 
facility versus using upper-end national values and we identify the 
actual location of lakes near the facility rather than the default lake 
location that we apply in Tier 1. By refining the screening approach in 
Tier 2 to account for local geographical and meteorological data, we 
decrease the likelihood that concentrations in environmental media are 
overestimated, thereby increasing the usefulness of the screen. The 
assumptions and the associated uncertainties regarding the selected 
ingestion exposure scenario are the same for all the Tiers.
    For both Tiers 1 and 2 of the multipathway assessment, our approach 
to addressing model input uncertainty is generally cautious. We choose 
model inputs from the upper end of the range of possible values for the 
influential parameters used in the models, and we assume that the 
exposed individual exhibits ingestion behavior that would lead to a 
high total exposure. This approach reduces the likelihood of not 
identifying high risks for adverse impacts.
    Despite the uncertainties, when individual pollutants or facilities 
do screen out, we are confident that the potential for adverse 
multipathway impacts on human health is very low. On the other hand, 
when individual pollutants or facilities do not screen out, it does not 
mean that multipathway impacts are significant, only that we cannot 
rule out that possibility and that a refined multipathway screening 
analysis for the site might be necessary to obtain a more accurate risk 
characterization for the source category.
    For further information on uncertainties and the multipathway 
screening methods, refer to the Appendix 5 of the Residual Risk 
Assessment for the Secondary Aluminum Production Source Category in 
Support of the 2014 Supplemental Proposal.
    We completed a Tier 3 refined multipathway screening analysis for 
this supplemental proposal for assessing multipathway risks. This 
assessment contains less uncertainty compared to the Tier 1 and Tier 2 
screens. The Tier 3 screen reduces uncertainty through improved lake 
evaluations used in the Tier 2 screen and by calculating the amount of 
mass lost to the upper air sink through plume rise. Nevertheless, some 
uncertainties also exist with these refined assessments. The Tier 3 
multipathway screen and related uncertainties are described in detail 
in the Residual Risk Assessment for the Secondary Aluminum Production 
Source Category in Support of the 2014 Supplemental Proposal, which is 
available in the docket for this action.
f. Uncertainties in the Environmental Risk Screening Assessment
    For each source category, we generally rely on site-specific levels 
of environmental HAP emissions to perform an environmental screening 
assessment. The environmental screening assessment is based on the 
outputs from models that estimate environmental HAP concentrations. The 
same models, specifically the TRIM.FaTE multipathway model and the 
AERMOD air dispersion model, are used to estimate environmental HAP 
concentrations for both the human multipathway screening analysis and 
for the environmental screening analysis. Therefore, both screening 
assessments have similar modeling uncertainties.
    Two important types of uncertainty associated with the use of these 
models in RTR environmental screening assessments--and inherent to any 
assessment that relies on environmental modeling--are model uncertainty 
and input uncertainty.\21\
---------------------------------------------------------------------------

    \21\ In the context of this discussion, the term 
``uncertainty,'' as it pertains to exposure and risk assessment, 
encompasses both variability in the range of expected inputs and 
screening results due to existing spatial, temporal and other 
factors, as well as uncertainty in being able to accurately estimate 
the true result.
---------------------------------------------------------------------------

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

[[Page 72895]]

highest value for each facility for each pollutant is used.
    For the environmental screening assessment for acid gases, we 
employ a single-tiered approach. We use the modeled air concentrations 
and compare those with ecological benchmarks.
    For both Tiers 1 and 2 of the environmental screening assessment, 
our approach to addressing model input uncertainty is generally 
cautious. We choose model inputs from the upper end of the range of 
possible values for the influential parameters used in the models, and 
we assume that the exposed individual exhibits ingestion behavior that 
would lead to a high total exposure. This approach reduces the 
likelihood of not identifying potential risks for adverse environmental 
impacts.
    Uncertainty also exists in the ecological benchmarks for the 
environmental risk screening analysis. We established a hierarchy of 
preferred benchmark sources to allow selection of benchmarks for each 
environmental HAP at each ecological assessment endpoint. In general, 
EPA benchmarks used at a programmatic level (e.g., Office of Water, 
Superfund Program) were used, if available. If not, we used EPA 
benchmarks used in regional programs (e.g., Superfund Program). If 
benchmarks were not available at a programmatic or regional level, we 
used benchmarks developed by other agencies (e.g., NOAA) or by state 
agencies.
    In all cases (except for lead compounds, which were evaluated 
through a comparison to the NAAQS), we searched for benchmarks at the 
following three effect levels, as described in section III.A.6 of this 
preamble:
    1. A no-effect level (i.e., NOAEL).
    2. Threshold-effect level (i.e., LOAEL).
    3. Probable effect level (i.e., PEL).
    For some ecological assessment endpoint/environmental HAP 
combinations, we could identify benchmarks for all three effect levels, 
but for most, we could not. In one case, where different agencies 
derived significantly different numbers to represent a threshold for 
effect, we included both. In several cases, only a single benchmark was 
available. In cases where multiple effect levels were available for a 
particular PB-HAP and assessment endpoint, we used all of the available 
effect levels to help us to determine whether risk exists and if the 
risks could be considered significant and widespread.
    The EPA evaluates the following seven HAP in the environmental risk 
screening assessment: cadmium, D/F, POM, mercury (both inorganic 
mercury and methyl mercury), lead compounds, HCl and HF, where 
applicable. These seven HAP represent pollutants that can cause adverse 
impacts for plants and animals either through direct exposure to HAP in 
the air or through exposure to HAP that is deposited from the air onto 
soils and surface waters. These seven HAP also represent those HAP for 
which we can conduct a meaningful environmental risk screening 
assessment. For other HAP not included in our screening assessment, the 
model has not been parameterized such that it can be used for that 
purpose. In some cases, depending on the HAP, we may not have 
appropriate multipathway models that allow us to predict the 
concentration of that pollutant. The EPA acknowledges that other HAP 
beyond the seven HAP that we are evaluating may have the potential to 
cause adverse environmental effects and, therefore, the EPA may 
evaluate other relevant HAP in the future, as modeling science and 
resources allow.
    Further information on uncertainties and the Tier 1 and 2 screening 
methods is provided in Appendix 5 of the Residual Risk Assessment for 
the Secondary Aluminum Production Source Category in Support of the 
2014 Supplemental Proposal, available in the docket for this action.

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

    As discussed in section II.A of this preamble, in evaluating and 
developing standards under CAA section 112(f)(2), we apply a two-step 
process to address residual risk. In the first step, the EPA determines 
whether risks are acceptable. This determination ``considers all health 
information, including risk estimation uncertainty, and includes a 
presumptive limit on maximum individual lifetime [cancer] risk (MIR) of 
approximately [1-in-10 thousand] [i.e., 100-in-1 million].'' 54 FR 
38045, September 14, 1989. If risks are unacceptable, the EPA must 
determine the emissions standards necessary to bring risks to an 
acceptable level without considering costs. In the second step of the 
process, the EPA considers whether the emissions standards provide an 
ample margin of safety ``in consideration of all health information, 
including the number of persons at risk levels higher than 
approximately 1-in-1 million, as well as other relevant factors, 
including costs and economic impacts, technological feasibility, and 
other factors relevant to each particular decision.'' Id. The EPA must 
promulgate emission standards necessary to provide an ample margin of 
safety.
    In past residual risk actions, the EPA considered a number of human 
health risk metrics associated with emissions from the categories under 
review, including the MIR, the number of persons in various risk 
ranges, cancer incidence, the maximum non-cancer HI and the maximum 
acute non-cancer hazard. See, e.g., 72 FR 25138, May 3, 2007; 71 FR 
42724, July 27, 2006. The EPA considered this health information for 
both actual and allowable emissions. See, e.g., 75 FR 65068, October 
21, 2010; 75 FR 80220, December 21, 2010; 76 FR 29032, May 19, 2011. 
The EPA also discussed risk estimation uncertainties and considered the 
uncertainties in the determination of acceptable risk and ample margin 
of safety in these past actions. The EPA considered this same type of 
information in support of this action.
    The agency is considering these various measures of health 
information to inform our determinations of risk acceptability and 
ample margin of safety under CAA section 112(f). As explained in the 
Benzene NESHAP, ``the first step judgment on acceptability cannot be 
reduced to any single factor'' and, thus, ``[t]he Administrator 
believes that the acceptability of risk under [previous] section 112 is 
best judged on the basis of a broad set of health risk measures and 
information.'' 54 FR 38046, September 14, 1989. Similarly, with regard 
to the ample margin of safety determination, ``the Agency again 
considers all of the health risk and other health information 
considered in the first step. Beyond that information, additional 
factors relating to the appropriate level of control will also be 
considered, including cost and economic impacts of controls, 
technological feasibility, uncertainties, and any other relevant 
factors.'' Id.
    The Benzene NESHAP approach provides flexibility regarding factors 
the EPA may consider in making determinations and how the EPA may weigh 
those factors for each source category. In responding to comment on our 
policy under the Benzene NESHAP, the EPA explained that:

``[t]he policy chosen by the Administrator permits consideration of 
multiple measures of health risk. Not only can the MIR figure be 
considered, but also incidence, the presence of non-cancer health 
effects, and the uncertainties of the risk estimates. In this way, 
the effect on the most exposed individuals can be reviewed as well 
as the impact on the general public. These factors can then be 
weighed in each individual case. This approach complies with the 
Vinyl Chloride mandate that the Administrator

[[Page 72896]]

ascertain an acceptable level of risk to the public by employing 
[her] expertise to assess available data. It also complies with the 
Congressional intent behind the CAA, which did not exclude the use 
of any particular measure of public health risk from the EPA's 
consideration with respect to CAA section 112 regulations, and 
thereby implicitly permits consideration of any and all measures of 
health risk which the Administrator, in [her] judgment, believes are 
appropriate to determining what will `protect the public health'.''

    See 54 FR at 38057, September 14, 1989. Thus, the level of the MIR 
is only one factor to be weighed in determining acceptability of risks. 
The Benzene NESHAP explained that ``an MIR of approximately one in 10 
thousand should ordinarily be the upper end of the range of 
acceptability. As risks increase above this benchmark, they become 
presumptively less acceptable under CAA section 112, and would be 
weighed with the other health risk measures and information in making 
an overall judgment on acceptability. Or, the Agency may find, in a 
particular case, that a risk that includes MIR less than the 
presumptively acceptable level is unacceptable in the light of other 
health risk factors.'' Id. at 38045. Similarly, with regard to the 
ample margin of safety analysis, the EPA stated in the Benzene NESHAP 
that: ``EPA believes the relative weight of the many factors that can 
be considered in selecting an ample margin of safety can only be 
determined for each specific source category. This occurs mainly 
because technological and economic factors (along with the health-
related factors) vary from source category to source category.'' Id. at 
38061. We also consider the uncertainties associated with the various 
risk analyses, as discussed earlier in this preamble, in our 
determinations of acceptability and ample margin of safety.
    The EPA notes that it has not considered certain health information 
to date in making residual risk determinations. At this time, we do not 
attempt to quantify those HAP risks that may be associated with 
emissions from other facilities that do not include the source 
categories in question, mobile source emissions, natural source 
emissions, persistent environmental pollution or atmospheric 
transformation in the vicinity of the sources in these categories.
    The agency understands the potential importance of considering an 
individual's total exposure to HAP in addition to considering exposure 
to HAP emissions from the source category and facility. We recognize 
that such consideration may be particularly important when assessing 
non-cancer risks, where pollutant-specific exposure health reference 
levels (e.g., RfCs) are based on the assumption that thresholds exist 
for adverse health effects. For example, the agency recognizes that, 
although exposures attributable to emissions from a source category or 
facility alone may not indicate the potential for increased risk of 
adverse non-cancer health effects in a population, the exposures 
resulting from emissions from the facility in combination with 
emissions from all of the other sources (e.g., other facilities) to 
which an individual is exposed may be sufficient to result in increased 
risk of adverse non-cancer health effects. In May 2010, the SAB advised 
the EPA ``that RTR assessments will be most useful to decision makers 
and communities if results are presented in the broader context of 
aggregate and cumulative risks, including background concentrations and 
contributions from other sources in the area.'' \22\
---------------------------------------------------------------------------

    \22\ The EPA's responses to this and all other key 
recommendations of the SAB's advisory on RTR risk assessment 
methodologies (which is available at: https://yosemite.epa.gov/sab/
sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-
007-unsigned.pdf) are outlined in a memo to this rulemaking docket 
from David Guinnup titled, EPA's Actions in Response to the Key 
Recommendations of the SAB Review of RTR Risk Assessment 
Methodologies.
---------------------------------------------------------------------------

    In response to the SAB recommendations, the EPA is incorporating 
cumulative risk analyses into its RTR risk assessments, including those 
reflected in this proposal. The agency is: (1) Conducting facility-wide 
assessments, which include source category emission points as well as 
other emission points within the facilities; (2) considering sources in 
the same category whose emissions result in exposures to the same 
individuals; and (3) for some persistent and bioaccumulative 
pollutants, analyzing the ingestion route of exposure. In addition, the 
RTR risk assessments have always considered aggregate cancer risk from 
all carcinogens and aggregate non-cancer hazard indices from all non-
carcinogens affecting the same target organ system.
    Although we are interested in placing source category and facility-
wide HAP risks in the context of total HAP risks from all sources 
combined in the vicinity of each source, we are concerned about the 
uncertainties of doing so. Because of the contribution to total HAP 
risk from emission sources other than those that we have studied in 
depth during this RTR review, such estimates of total HAP risks would 
have significantly greater associated uncertainties than the source 
category or facility-wide estimates. Such aggregate or cumulative 
assessments would compound those uncertainties, making the assessments 
too unreliable.

C. How did we perform the technology review?

    Our technology review focused on the identification and evaluation 
of developments in practices, processes and control technologies that 
have occurred since the MACT standards were promulgated. Where we 
identified such developments, in order to inform our decision of 
whether it is ``necessary'' to revise the emissions standards, we 
analyzed the technical feasibility of applying these developments and 
the estimated costs, energy implications, non-air environmental 
impacts, as well as considering the emission reductions. We also 
considered the appropriateness of applying controls to new sources 
versus retrofitting existing sources.
    Based on our analyses of the available data and information, we 
identified potential developments in practices, processes and control 
technologies. For this exercise, we considered any of the following to 
be a ``development'':
     Any add-on control technology or other equipment that was 
not identified and considered during development of the original MACT 
standards.
     Any improvements in add-on control technology or other 
equipment (that were identified and considered during development of 
the original MACT standards) that could result in additional emission 
reduction.
     Any work practice or operational procedure that was not 
identified or considered during development of the original MACT 
standards.
     Any process change or pollution prevention alternative 
that could be broadly applied to the industry and that was not 
identified or considered during development of the original MACT 
standards.
     Any significant changes in the cost (including cost 
effectiveness) of applying controls (including controls the EPA 
considered during the development of the original MACT standards).
    We reviewed a variety of data sources in our investigation of 
potential practices, processes or controls to consider. Among the 
sources we reviewed were the NESHAP for various industries that were 
promulgated since the MACT standards being reviewed in this action. We 
reviewed the regulatory requirements and/or technical analyses 
associated with these regulatory actions to identify any practices, 
processes and control technologies considered in these efforts that 
could be applied to emission

[[Page 72897]]

sources in the Secondary Aluminum Production source category, as well 
as the costs, non-air impacts and energy implications associated with 
the use of these technologies. Additionally, we requested information 
from facilities regarding developments in practices, processes or 
control technology. Finally, we reviewed information from other 
sources, such as state and/or local permitting agency databases and 
industry-supported databases.

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

A. What are the results of the risk assessment and analysis?

1. Inhalation Risk Assessment Results
    Table 3 provides an overall summary of the results of the 
inhalation risk assessment.

                                Table 3--Secondary Aluminum Production Source Category Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                     Maximum individual cancer                 Estimated   Maximum chronic non-cancer
                                      risk (in 1-million) \a\     Estimated    population           TOSHI \b\
                                    ---------------------------    annual          at     ----------------------------
                                                                   cancer      increased                                  Worst-case maximum screening
    Number of facilities modeled       Based on      Based on     incidence     risk of      Based on      Based on         acute non-cancer HQ \c\
                                        actual      allowable    (cases/yr)   cancer  >=1-    actual       allowable
                                       emissions    emissions        \d\          in-1       emissions     emissions
                                                                              million \d\      level         level
--------------------------------------------------------------------------------------------------------------------------------------------------------
Major Sources (52).................           0.6            4        0.0007            0        0.04           0.1    HQ(REL) = 0.7 (HF).
                                                                                                                       HQ(AEGL1) = 0.4 (HCl).
Area Sources (103).................           0.3            1        0.001             0        0.0003         0.001  NA.
Facility-wide (52 Major Sources)...          70             NA        0.05        760,000        1             NA      NA.
--------------------------------------------------------------------------------------------------------------------------------------------------------
 \a\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category for major sources and for D/F emissions from
  the area sources.
 \b\ Maximum TOSHI. The target organ with the highest TOSHI for the Secondary Aluminum Production source category for both actual and allowable
  emissions is the respiratory system.
 \c\ There is no acute dose-response value for D/F. Thus an acute HQ value for area sources was not calculated. The maximum off-site HQ acute value of
  0.7 for actuals is driven by emissions of hydrofluoric acid. See section III.A.3 of this document for explanation of acute dose-response values. Acute
  assessments are not performed on allowable emissions.
 \d\ These estimates are based upon actual emissions.

    The inhalation risk modeling performed to estimate risks based on 
actual and allowable emissions relied primarily on emissions data from 
the ICRs. The results of the chronic baseline inhalation cancer risk 
assessment indicate that, based on estimates of current actual 
emissions, the MIR posed by the Secondary Aluminum Production source 
category from major sources and from area sources was less than 1-in-1 
million. The estimated cancer incidence is slightly higher for area 
sources compared to the major sources due to the larger number of area 
sources nationwide. The total estimated cancer incidence from secondary 
aluminum production sources from both major and area sources based on 
actual emission levels is 0.002 excess cancer cases per year, with 
emissions of D/F, naphthalene and PAH contributing 48 percent, 31 
percent and 11 percent, respectively, to this cancer incidence. In 
addition, we note that there are no excess cancer risks greater than or 
equal to 1-in-1 million as a result of actual emissions from this 
source category over a lifetime. The maximum modeled chronic non-cancer 
HI (TOSHI) value for the source category for both major and area 
sources based on actual emissions was estimated to be 0.04, with HCl 
emissions from group 1 furnaces accounting for 99 percent of the HI.
    When considering MACT-allowable emissions, the MIR is estimated to 
be up to 4-in-1 million, driven by emissions of D/F compounds, 
naphthalene and PAHs from the scrap dryer/delacquering/decoating kiln. 
The estimated potential cancer incidence considering allowable 
emissions for both major and area sources is estimated to be 0.014 
excess cancer cases per year, or 1 case every 70 years. Approximately 
3,400 people were estimated to have cancer risks greater than or equal 
to 1-in-1 million considering allowable emissions from secondary 
aluminum plants. When considering MACT-allowable emissions, the maximum 
chronic non-cancer TOSHI value was estimated to be 0.1, driven by 
allowable emissions of HCl from the group 1 furnaces.
2. Acute Risk Results
    Our screening analysis for worst-case acute impacts based on actual 
emissions indicates no pollutants exceeding an HQ value of 1 based upon 
the REL.
3. Multipathway Risk Screening Results
    Results of the worst-case Tier 1 screening analysis indicate that 
36 of the 52 major sources exceeded the PB-HAP emission cancer 
screening rates (based on estimates of actual emissions) for D/F, and 3 
of the 52 major sources exceeded the Tier 1 screen value for PAHs. 
Regarding area sources, 60 of the 103 area sources exceeded the PB-HAP 
emission cancer screening rates (based on estimates of actual 
emissions) for D/F. For the compounds and facilities that did not 
screen out at Tier 1, we conducted a Tier 2 screen. The Tier 2 screen 
replaces some of the assumptions used in Tier 1 with site-specific 
data, including the location of fishable lakes and local precipitation, 
wind direction and speed. The Tier 2 screen continues to rely on high-
end assumptions about consumption of local fish and locally grown or 
raised foods (adult female angler at 99th percentile consumption for 
fish \23\ for the subsistence fisherman scenario and 90th percentile 
consumption for locally grown or raised foods \24\ for the farmer 
scenario). It is important to note that, even with the inclusion of 
some site-specific information in the Tier 2 analysis, the multipathway 
screening analysis is still a very conservative, health-protective 
assessment (e.g., upper-bound consumption of local fish and locally 
grown and/or raised foods) and in all likelihood will yield results 
that serve as an upper-bound multipathway risk associated with a 
facility.
---------------------------------------------------------------------------

    \23\ Burger, J. 2002. Daily Consumption of Wild Fish and Game: 
Exposures of High End Recreationists. International Journal of 
Environmental Health Research 12:343-354.
    \24\ U.S. EPA. Exposure Factors Handbook 2011 Edition (Final). 
U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/
052F, 2011.
---------------------------------------------------------------------------

    While the screening analysis is not designed to produce a 
quantitative risk result, the factor by which the emissions exceed the 
threshold serves as a rough gauge of the ``upper-limit'' risks we would 
expect from a facility. Thus, for

[[Page 72898]]

example, if a facility emitted a PB-HAP carcinogen at a level 2 times 
the screening threshold, we can say with a high degree of confidence 
that the actual maximum cancer risks will be less than 2-in-1 million. 
Likewise, if a facility emitted a noncancer PB-HAP at a level 2 times 
the screening threshold, the maximum noncancer hazard would represent 
an HQ less than 2. The high degree of confidence comes from the fact 
that the screens are developed using the very conservative (health-
protective) assumptions that we describe above.
    Based on the Tier 2 cancer screening analysis, 25 of the 52 major 
sources and 34 of the 103 area sources emit D/F above the Tier 2 cancer 
screening thresholds for the subsistence fisher and farmer scenarios. 
The individual D/F emissions are all scaled based on their toxicity to 
2,3,7,8-tetrachlorodibenzo-p-dioxin and reported as toxic equivalents 
(TEQs). The subsistence fisher scenario for the highest risk facilities 
exceeds the D/F cancer threshold by a factor of 80 for the major 
sources and by a factor of 70 for the area sources. The Tier 2 analysis 
also identifies 23 of the 52 major sources and 26 of the 103 area 
sources emitting D/F above the Tier 2 cancer screening thresholds for 
the subsistence farmer scenario. The highest exceedance of the Tier 2 
screen value is 40 for the major sources and 20 for the area sources 
for the farmer scenario.
    We have only one major source emitting PAHs above the Tier 2 cancer 
screen value with an exceedance of 2 for the farmer scenario. All PAH 
emissions are scaled based on their toxicity to benzo(a)pyrene and 
reported as TEQs.
    A more refined Tier 3 multipathway screening analysis was conducted 
for six Tier 2 major source facilities. The six facilities were 
selected because the Tier 2 cancer screening assessments for these 
facilities had exceedances greater than or equal to 50 times the screen 
value for the subsistence fisher scenario. The major sources 
represented the highest screened cancer risk for multipathway impacts. 
Therefore, further screening analyses were not performed on the area 
sources. The Tier 3 screen examined the set of lakes from which the 
fisher might ingest fish. Any lakes that appeared to not be fishable or 
not publicly accessible were removed from the assessment, and the 
screening assessment was repeated. After we made the determination the 
critical lakes were fishable, we analyzed plume rise data for each of 
the sites. The Tier 3 screen was conducted only on those HAP that 
exceeded the Tier 2 screening threshold, which for this assessment were 
D/F and PAHs. Both of these PB-HAP are carcinogenic. The Tier 3 screen 
resulted in lowering the maximum exceedance of the screen value for the 
highest site from 80 to 70. Results for the other sites were all less 
than 70. The highest exceedance of the Tier 2 cancer screen value of 40 
for the farmer scenario was also reduced in the Tier 3 screening 
assessment to a value of 30 for the major sources within this source 
category.
    Overall, the refined multipathway screening analysis for D/F and 
PAHs utilizing the Tier 3 screen predicts a potential lifetime cancer 
risk of 70-in-1 million or lower to the most exposed individual, with 
D/F emissions from group 1 furnaces handling other than clean charge 
driving the risk. Cancer risks due to PAH emissions for the maximum 
exposed individual were less than 1-in-1 million.
    The chronic non-cancer HQ is predicted to be below 1 for cadmium 
compounds and 1 for mercury compounds. For lead, we did not estimate 
any exceedances of the primary lead NAAQS.
    Further details on the refined multipathway screening analysis can 
be found in Appendix 8 of the Residual Risk Assessment for the 
Secondary Aluminum Production Source Category in Support of the 2014 
Supplemental Proposal, which is available in the docket.
4. Environmental Risk Screening Results
    As described in section III.A of this document, we conducted an 
environmental risk screening assessment for the Secondary Aluminum 
Production source category for the following seven pollutants: PAHs, 
mercury (methyl mercury and mercuric chloride), cadmium, lead, D/F, HCl 
and HF.
    Of the seven pollutants included in the environmental risk screen, 
major sources in this source category emit PAHs, mercuric chloride, 
cadmium, lead, D/F, HCl and HF. In the Tier 1 screening analysis for 
PB-HAP, none of the individual modeled concentrations for any facility 
in the source category exceeded any of the ecological benchmarks 
(either the LOAEL or NOAEL) for PAHs, mercuric chloride, cadmium and D/
F. For lead, we did not estimate any exceedances of the secondary lead 
NAAQS. For HCl and HF, the average modeled concentration around each 
facility (i.e., the average concentration of all off-site data points 
in the modeling domain) did not exceed any ecological benchmark. In 
addition, each individual modeled concentration of HCl and HF (i.e., 
each off-site data point in the modeling domain) was below the 
ecological benchmarks for all facilities.
    Of the seven pollutants included in the environmental risk screen, 
area sources in this source category are regulated only for D/F. In the 
Tier 1 screening analysis for D/F, none of the individual modeled 
concentrations for any facility in the source category exceeded any of 
the ecological benchmarks (either the LOAEL or NOAEL) for D/F.
5. Facility-Wide Risk Assessment Results
    Considering facility-wide emissions at the 52 major sources, the 
MIR is estimated to be 70-in-1 million driven by arsenic and Ni 
emissions, and the chronic non-cancer TOSHI value is calculated to be 1 
driven by emissions of cadmium compounds. The above risks are driven by 
emissions from the potline roof vents at the co-located primary 
aluminum production operations. The Secondary Aluminum Production 
source category represents less than 1 percent of the inhalation risks 
from the facility-wide assessment based upon actual emissions. 
Emissions from primary aluminum sources are being addressed in a 
separate action. Details regarding primary aluminum sources are 
available at https://www.epa.gov/ttn/atw/alum/alumpg.html.
6. What demographic groups might benefit from this regulation?
    To determine whether or not to conduct a demographics analysis, 
which is an assessment of risks to individual demographic groups, we 
look at a combination of factors including the MIR, non-cancer TOSHI, 
population around the facilities in the source category and other 
relevant factors. For the Secondary Aluminum Production source 
category, inhalation risks were low with excess cancer risks being less 
than 1-in-1 million and non-cancer hazards being less than 1. 
Therefore, we did not conduct an assessment of risks to individual 
demographic groups for this rulemaking. However, we did conduct a 
proximity analysis for both area and major sources, which identifies 
any overrepresentation of minority, low income or indigenous 
populations near facilities in the source category. The results of the 
proximity analyses suggest there are a higher percent of minorities, 
people with low income, and people without a high school diploma living 
near these facilities (i.e., within 3 miles) compared to the national 
averages for these subpopulations. However, as explained above, the 
risks due to HAP emissions from this source category are low for all 
populations (e.g., inhalation cancer risks are less than 1-in-1 million

[[Page 72899]]

for all populations and non-cancer hazard indices are less than 1). 
Furthermore, we do not expect this supplemental proposal to achieve 
reductions in HAP emissions. Therefore, we conclude that this 
supplemental proposal will not have disproportionately high and adverse 
human health or environmental effects on minority or low-income 
populations because it does not affect the level of protection provided 
to human health or the environment. However, this supplemental 
proposal, if finalized, will provide additional benefits to these 
demographic groups by improving the compliance, monitoring and 
implementation of the NESHAP.
    The detailed results of the proximity analyses can be found in the 
EJ Screening Report for Secondary Aluminum Area Sources and the EJ 
Screening Report for Secondary Aluminum Major Sources, which are 
available in the docket for this rulemaking.

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

1. Risk Acceptability
    As noted in section II.A.1 of this preamble, the EPA sets standards 
under CAA section 112(f)(2) using ``a two-step standard-setting 
approach, with an analytical first step to determine an `acceptable 
risk' that considers all health information, including risk estimation 
uncertainty, and includes a presumptive limit on MIR of approximately 1 
in 10 thousand 25.'' (54 FR 38045, September 14, 1989).
---------------------------------------------------------------------------

    \25\ 1-in-10 thousand is equivalent to 100-in-1 million. The EPA 
currently describes cancer risks as ``n-in-1 million.''
---------------------------------------------------------------------------

    In this proposal, the EPA estimated risks based on both actual and 
allowable emissions from secondary aluminum facilities. As discussed 
above, in determining acceptability, we considered risks based on both 
actual and allowable emissions.
a. Estimated Risks From Actual Emissions
    The baseline inhalation cancer risk to the individual most exposed 
to emissions from the Secondary Aluminum Production source category is 
from major sources with cancer risks less than 1-in-1 million based on 
actual emissions. The total estimated incidence of cancer for this 
source category from both major and area sources due to inhalation 
exposures is 0.002 excess cancer cases per year, or 1 case in 500 
years. The agency estimates that the maximum chronic non-cancer TOSHI 
from inhalation exposure for this source category is from major sources 
with an HI of 0.04 based on actual emissions, with HCl emissions from 
group 1 furnaces accounting for a large portion (99 percent) of the HI.
    The multipathway screening analysis, based upon actual emissions, 
indicates the excess cancer risk from this source category is lower 
than 70-in-1 million with D/F emissions representing 99 percent of 
these potential risks based on the fisher scenario. The multipathway 
MIR cancer risks are the same for both the major and area sources 
within this source category for the fisher scenario. For the farmer 
scenario, the excess cancer risk is lower than 30-in-1 million for the 
major sources and 20-in-1 million for the area sources. There were no 
facilities within this source category having a multipathway non-cancer 
screen value greater than 1 for cadmium or mercury. In evaluating the 
potential for multipathway effects from emissions of lead, modeled 
maximum annual lead concentrations were compared to the secondary NAAQS 
for lead (0.15 [mu]g/m\3\). Results of this analysis estimate that the 
NAAQS for lead would not be exceeded at any off-site locations.
    As noted above, the multipathway screens are conservative and 
incorporate many health-protective assumptions. For example, the EPA 
chooses inputs from the upper end of the range of possible values for 
the influential parameters used in the Tier 2 screen and assumes that 
the exposed individual for each scenario exhibits ingestion behavior 
that would lead to a high total exposure. A Tier 2 or 3 exceedance of a 
cancer or non-cancer screen value cannot be equated with an actual risk 
value or a HQ or HI. Rather, it represents a high-end estimate of what 
the risk or hazard may be. For example, a non-cancer screen value of 2 
can be interpreted to mean that we have high confidence that the HI is 
lower than 2. Similarly, a cancer screen value of 30 for a carcinogen 
means that we have high confidence that the risk is lower than 30-in-1-
million. Confidence comes from the conservative, or health-protective, 
assumptions that are used in the Tier 2 and Tier 3 screens. The Tier 3 
screen improves the accuracy of the Tier 2 screen through validation of 
impacted lakes assessed and accounting for mass lost to the upper air 
sink, which reduces the uncertainty in the screen. The maximum Tier 3 
exceedance of the cancer screen values for the secondary aluminum 
source category are 70 for the sustainable fisher scenario and 30 for 
the farmer scenario, both driven by D/F emissions from major sources.
    The screening assessment of worst-case acute inhalation impacts 
from baseline actual emissions indicates no pollutants exceeding an HQ 
value of 1 based on the REL, with an estimated worst-case maximum acute 
HQ of 0.7 for HF based on the 1-hour REL.
b. Estimated Risks From Allowable Emissions
    The EPA estimates that the inhalation cancer risk to the individual 
most exposed to emissions from the Secondary Aluminum Production source 
category is up to 4-in-1 million based on allowable emissions from 
major sources, with D/F, naphthalene and PAH emissions driving the 
risks. The EPA estimates that the incidence of cancer due to inhalation 
for the entire source category based on allowable emissions could be up 
to 0.014 excess cancer cases per year, or 1 case approximately every 70 
years. About 3,400 people face an estimated increased cancer risk 
greater than or equal to 1-in-1 million due to inhalation exposure to 
allowable HAP emissions from this source category.
    The risk assessment estimates that the maximum chronic non-cancer 
TOSHI from inhalation exposure values for the source category is up to 
0.1 based on allowable emissions, driven by HCl emissions from major 
sources.
c. Acceptability Determination
    In determining whether risks are acceptable for this source 
category, the EPA considered all available health information and risk 
estimation uncertainty as described above. As noted above, the agency 
estimated risk from actual and allowable emissions. While there are 
uncertainties associated with both the actual and allowable emissions, 
we consider the allowable emissions to be an upper bound, based on the 
conservative methods we used to calculate allowable emissions.
    The risk results indicate that both the actual and allowable 
inhalation cancer risks to the individual most exposed are up to but no 
greater than approximately 4-in-1 million, based on allowable emissions 
which is considerably less than 100-in-1 million, the presumptive limit 
of acceptability. The MIR based on actual emissions is 0.6-in-1 
million, well below the presumptive limit as well. The maximum chronic 
non-cancer hazard indices for both the actual and allowable inhalation 
non-cancer risks to the individual most exposed are less than 1. The 
maximum individual non-cancer HI is 0.04 based on actual

[[Page 72900]]

emissions and 0.1 based on allowable emissions.
    The maximum acute non-cancer HQ for all pollutants was below 1, 
with a maximum value of 0.7 based on the REL for hydrofluoric acid. The 
excess cancer risks from the multipathway screen from actual D/F and 
PAH emissions from major and area sources indicate that the risk to the 
individual most exposed could be up to, but no greater than, 70-in-1 
million for the fisher scenario and 30-in-1 million for the farmer 
scenario. These results are less than 100-in-1 million, which is the 
presumptive limit of acceptability. The multipathway Tier 2 screen for 
non-cancer is at 1 for mercury and cadmium.
    The multipathway screens are based on model runs that use upper end 
values for influential parameters and we assume that the exposed 
individual exhibits ingestion behavior that would lead to a high total 
exposure. The multipathway screens also include some hypothetical 
elements, namely the existence and location of the hypothetical farmer 
and fisher.
    Considering all of the health risk information and factors 
discussed above, including the uncertainties discussed in section 
III.A.8 of this preamble, the EPA proposes that the risks at baseline 
are acceptable since the cancer risks are below the presumptive limit 
of acceptability and the non-cancer results indicate there is minimal 
likelihood of adverse non-cancer health effects due to HAP emissions 
from this source category.
2. Ample Margin of Safety Analysis
    Under the ample margin of safety analysis, we evaluated the cost 
and feasibility of available control technologies and other measures 
(including the controls, measures and costs reviewed under the 
technology review) that could be applied in this source category to 
further reduce the risks (or potential risks) due to emissions of HAP 
identified in our risk assessment, along with all of the health risks 
and other health information considered in the risk acceptability 
determination described above. In this analysis, we considered the 
results of the technology review, risk assessment and other aspects of 
our MACT rule review to determine whether there are any cost-effective 
controls or other measures that would reduce emissions further to 
provide an ample margin of safety with respect to the risks associated 
with these emissions.
    Our inhalation risk analysis indicated very low potential for risk 
from the facilities in the source category, and, therefore, very little 
inhalation risk reductions could be realized regardless of the 
availability of control options. Our technology review, which was 
conducted for the 2012 proposal and is in large part applicable to this 
supplemental proposal (see section IV.C below for more discussion of 
the technology review), did not identify any new practices, controls or 
process options that are being used in this industry or in other 
industries that would be cost effective for further reduction of these 
emissions and risks.
    Our multipathway screening analysis results for the 2012 proposal 
indicated exceedances of the worst-case screening levels which did not 
necessarily indicate any risks. However, they did suggest a potential 
for risks. For this supplemental proposal, a more refined multipathway 
screening analysis was conducted, including a Tier 3 screen for the top 
six major source facilities for cancer. The more refined screening 
analysis was conducted only on those PB-HAP that exceeded the screening 
threshold, which for this assessment were PAHs and D/F. The refined 
multipathway screening analysis showed that the earlier screening 
analysis for the 2012 proposal over-predicted the potential cancer risk 
when compared to the refined analysis for three of the six facilities 
assessed, with emissions of D/F driving these cancer risks. The 
remaining facilities had the same cancer screen value in the refined 
analysis as in the earlier screening results when rounded to 1 
significant figure. The cancer risks due to PAH emissions were less 
than 1-in-1 million based on the refined analysis.
    To evaluate the potential to reduce D/F emissions and risks, as 
part of our revised ample margin of safety analysis, we used the same 
analysis that we conducted for the 2012 proposal except that we 
incorporated more recent D/F emissions data and control cost 
information. As in the analysis conducted for the 2012 proposal, we 
evaluated two control options. Option 1 considered lowering the 
existing D/F emissions limit from 15 to 10 [mu]g TEQ/Mg feed for all 
group 1 furnaces processing other than clean charge. Option 2 
considered lowering the existing D/F limit for group 1 furnaces 
processing other than clean charge after applying a subcategorization 
based on facility production capacity. An emission reduction to 10 
[mu]g TEQ/Mg represents a level that could potentially be met with an 
activated carbon injection system. With regard to the option of 
lowering the D/F emission limit to 10 [mu]g TEQ/Mg feed for group 1 
furnaces handling other than clean charge, we estimate that about 12 
furnaces at eight facilities would need to reduce their D/F emissions 
and that the total capital costs would be $390,000 with total 
annualized costs of $1.4 million. This option would achieve an 
estimated 0.49 grams TEQ reduction of D/F emissions with an overall 
cost effectiveness of about $2.9 million per gram D/F TEQ. For the 
second option, facilities with group 1 furnace production capacity 
greater than 200,000 tpy (melting other than clean charge) would be 
required to meet a limit of 10 [mu]g TEQ/Mg limit. For this option, we 
estimate that 4 furnaces at two facilities would be required to reduce 
their D/F emissions. We estimate that the total capital costs would be 
$130,000 with total annualized costs of $460,000. This option would 
achieve an estimated 0.12 grams TEQ reduction of D/F emissions with an 
overall cost-effectiveness of about $3.8 million per gram D/F TEQ. As 
we concluded in the ample margin of safety analysis for the 2012 
proposal, our analysis indicates that these options would result in 
very little emission reductions (0.49 grams TEQ of D/F for Option 1 and 
0.12 grams TEQ of D/F reductions for Option 2) and, therefore, would 
result in little or no changes to the potential risk levels. After 
considering the costs and the level of reductions that would be 
achieved, we have decided, as we did in the 2012 proposal, not to 
propose any of these options. For more information on this analysis, 
see the Supplemental Proposal Technical Support Document for the 
Secondary Aluminum Production Source Category, which is available in 
the public docket for this proposed rulemaking.
    In the 2012 proposal, we also evaluated possible options based on 
work practices to achieve further emission reductions. The current 
subpart RRR NESHAP includes work practices to minimize D/F emissions 
which include scrap inspection, limitations on materials processed by 
group 2 furnaces, temperature and residence time requirements for 
afterburners controlling sweat furnaces, labeling requirements, 
capture/collection requirements and requirements for an operations, 
maintenance and monitoring plan that contains details on the proper 
operation and maintenance of processes and control equipment. For the 
2012 proposal, we searched for and evaluated other possible work 
practices such as good combustion practices, better scrap inspection 
and cleaning, and process monitoring. However, none of these potential 
work practices were determined to be feasible and effective

[[Page 72901]]

in further reducing D/F emissions for this source category. Thus, we 
did not identify any feasible or applicable work practices for this 
industry beyond those that are currently in the MACT rule. Therefore, 
in the 2012 proposal we did not propose any additional work practices. 
Since the 2012 proposal, we have not identified any changes in the 
sources of emissions, the types of pollutants emitted or the work 
practices available to be used in the secondary aluminum production 
industry. Therefore, as in the 2012 proposal, we are not proposing any 
revisions to subpart RRR based on work practices. Further details on 
work practices and control options are provided in the Supplemental 
Proposal Technology Review for the Secondary Aluminum Production Source 
Category, which is available in the public docket for this rulemaking.
    In accordance with the approach established in the Benzene NESHAP, 
we weighed all health risk information and factors considered in the 
risk acceptability determination, including uncertainties, along with 
the cost and feasibility of control technologies and other measures 
that could be applied in this source category, in making our ample 
margin of safety determination. In summary, our risk analysis indicated 
very low potential for risk, and we identified no developments in 
technology that would be cost effective in reducing HAP emissions 
relative to reductions already being achieved. We also did not identify 
any cost effective approaches to further reduce D/F emissions and 
multipathway risk beyond what is already being achieved by the current 
NESHAP.
    Because of the high cost associated with the use of activated 
carbon injection systems and because work practices are already 
required to help ensure low emissions, and in light of the 
considerations discussed above, we propose that the existing MACT 
standards provide an ample margin of safety to protect public health.
3. Adverse Environmental Effects
    Based on the results of our environmental risk screening 
assessment, we conclude that there is not an adverse environmental 
effect as a result of HAP emissions from the Secondary Aluminum 
Production source category. We are proposing that it is not necessary 
to set a more stringent standard to prevent, taking into consideration 
costs, energy, safety and other relevant factors, an adverse 
environmental effect.

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

    A technology review was conducted for the Secondary Aluminum 
Production source category and is described in the 2012 proposal at 77 
FR 8596, February 14, 2012. Details of the technology review and its 
findings are available in the memorandum, Draft Technology Review for 
the Secondary Aluminum Production Source Category (Docket item EPA-HQ-
OAR-2010-0544-0144). The typical controls used to minimize emissions at 
secondary aluminum facilities include fabric filters for control of PM 
from aluminum scrap shredders; afterburners for control of THC and D/F 
from thermal chip dryers; afterburners plus lime-injected fabric 
filters for control of PM, HCl, THC and D/F from scrap dryers/
delacquering kilns/decoating kilns; afterburners for control of D/F 
from sweat furnaces; fabric filters for control of PM from dross-only 
furnaces and rotary dross coolers; lime-injected fabric filters for 
control of PM and HCl from in-line fluxers; and lime-injected fabric 
filters for control of PM, HCl and D/F from group 1 furnaces. In our 
review of technology, we determined that there have been some 
developments in practices, processes or control technologies that have 
been implemented in this source category since promulgation of the 
current NESHAP. We stated in the 2012 proposal that these findings did 
not warrant any changes to subpart RRR. Following the 2012 proposal, no 
public comments were received that would alter the conclusions of our 
technology review for the Secondary Aluminum Production source 
category. Therefore, for this supplemental proposal, we are proposing 
that the technology review findings are still valid. The EPA is not 
aware of any changes in technology development since the 2012 proposal.
    As part of the technology review for the 2012 proposal, we also 
evaluated other technologies that have the potential to reduce HAP 
emissions, in particular emissions of D/F. See Draft Technical Support 
Document for the Secondary Aluminum Production Source Category, Docket 
item EPA-HQ-OAR-2010-0544-0152. We have updated that analysis for this 
supplemental proposal. See Supplemental Proposal Technical Support 
Document for the Secondary Aluminum Production Source Category and the 
Supplemental Proposal Technology Review for the Secondary Aluminum 
Production Source Category, which are available in the public docket 
for this rulemaking. Under this analysis, we evaluated the same 
approaches that were evaluated under the ample margin of safety 
analysis described in section IV.B of this document. We evaluated the 
option of lowering the existing D/F limit from 15 to 10 [mu]g TEQ/Mg 
feed for group 1 furnaces processing other than clean charge either at 
all secondary aluminum facilities or only at larger secondary aluminum 
facilities based on facility production capacity. The lower D/F 
emissions limits potentially could be met by using an activated carbon 
injection system. Using updated information on emissions and control 
costs, we estimate that about 12 furnaces at eight facilities would 
need to reduce their D/F emissions to meet the 10 [mu]g TEQ/Mg feed for 
group 1 furnaces and that the total capital costs would be $390,000 
with total annualized costs of $1.4 million. This option would achieve 
an estimated 0.49 grams TEQ reduction of D/F emissions with an overall 
cost effectiveness of about $2.9 million per gram D/F TEQ. For the 
second option, only facilities with group 1 furnace production capacity 
greater than 200,000 tpy (melting other than clean charge) would be 
required to meet the lower 10 [mu]g TEQ/Mg limit. For this option, we 
estimate that four furnaces at two facilities would be required to 
reduce their D/F emissions. We estimate that the total capital cost 
would be $130,000 with total annualized costs of $460,000. This option 
would achieve an estimated 0.12 grams TEQ reduction of D/F emissions 
with an estimated overall cost effectiveness of $3.8 million per gram 
D/F TEQ. (The details of this analysis are in the Supplemental Proposal 
Technical Support Document for the Secondary Aluminum Production Source 
Category, which is available in the public docket for this rulemaking. 
After considering the costs and the small emission reductions that 
would be achieved, we have decided not to propose any of these options.

D. What other actions are we proposing?

    In the 2012 proposal, we proposed amendments to correct and clarify 
existing requirements in subpart RRR. In this supplemental proposal, we 
are proposing revisions to certain rule corrections and clarifications 
that were in the 2012 proposal as well as proposing alternative 
compliance options to the operating and monitoring requirements for 
sweat furnaces. On these limited revisions, we are soliciting comment. 
As discussed above, the 2012 proposal also contained other proposed 
rule corrections and clarifications for which we are not proposing any 
changes in this document, and,

[[Page 72902]]

therefore, for which we are not seeking public comment (if EPA 
nonetheless were to receive any such comments, the comments would be 
outside the scope of this supplemental proposal and would not be 
considered).
1. Changing Furnace Classification
    In the 2012 proposal, we proposed to address an area of uncertainty 
under subpart RRR by specifying in 40 CFR 63.1514 rule provisions 
expressly allowing changes in furnace classification, subject to 
procedural and testing requirements, operating requirements and 
recordkeeping requirements. We proposed a frequency limit of no more 
than one change in classification (and associated reversion) every six 
months, with an exception for planned control device maintenance 
activities requiring shutdown. We received comments on the 2012 
proposal requesting additional or unlimited changes in furnace 
classification. Based on the information received, we reevaluated the 
appropriate limit on frequency of furnace classification changes. The 
EPA received from one commenter an inventory of the number of 
classification changes that occurred each year at a specific subpart 
RRR furnace over a nearly 10-year period (available in the docket for 
this rulemaking). The highest number of furnace classification changes 
in one year, including both planned and unplanned changes, was nine.
    Based on the comments and information received and because of the 
potential difficulty in distinguishing between a planned and unplanned 
change in classification, we are proposing and requesting comments on a 
revised limit on the frequency of changes in furnace classification of 
four (including the four associated reversions) in any 6-month period, 
including both planned and unplanned changes in classification, with a 
provision allowing additional changes by petitioning the permitting 
authority for major sources, or the Administrator for area sources. 
These revisions in proposed 40 CFR 63.1514(e) would balance the 
interest in allowing industry to make furnace classification changes 
while preserving the EPA's and delegated authorities' practical and 
effective enforcement of the emission limitations, work practice 
standards and other requirements of subpart RRR. We request that any 
commenter who would like the EPA to consider a different limit on 
frequency to include a specific rationale and factual basis for why a 
different frequency would be appropriate as well as any data on 
historical frequencies of furnace classification changes under subpart 
RRR.
    We are specifically requesting comments on the revised proposed 
provisions in 40 CFR 63.1514(e), which addresses the frequency of 
changing furnace classification. No substantive changes have been made 
to the other proposed provisions in 40 CFR 63.1514, and we are not 
requesting comments on any other aspect of the proposed provisions for 
furnace classification changes. We will address the comments previously 
received on the 2012 proposal, as well as comments that are received in 
response to the revised proposed frequency limit in this document, when 
we take final rulemaking action.
2. Worst Case Scenario Testing
    In the 2012 proposal, we proposed amendments to clarify that 
performance tests under multiple scenarios may be required in order to 
reflect the emissions ranges for each regulated pollutant. We received 
comments on the 2012 proposal that the worst case charge materials, and 
blends of these, have differing process rates and, therefore, the 
charge rate from the stack tests is not representative of the charge 
rate that will be achieved during normal operations. Based on the 
comments received and recognizing that it may be necessary to conduct 
performance tests under one or multiple scenarios to be representative 
of the range of normal operating conditions, we are proposing revised 
language in 40 CFR 63.1511(b)(1) to clarify the conditions under which 
subpart RRR performance tests must be conducted. The intention in the 
subpart RRR rule is to require testing under ``worst case'' conditions 
from the standpoint of emissions and to establish parameters based on 
such testing that ensure compliance under all operating conditions. For 
example, in a response to comments on the original proposed subpart RRR 
rule regarding the inlet temperature requirement for fabric filters, 
the EPA stated that testing under worst case conditions, such as higher 
than normal fabric filter inlet temperatures, could provide a larger 
temperature operating range, which would be used to monitor and ensure 
continuous compliance between periodic performance tests (65 FR 15699, 
March 23, 2000). In the EPA response-to-comments document (Summary of 
Public Comments and Responses on Secondary Aluminum NESHAP, December 
14, 1999, Docket No. A-92-61, item V-C-1, comment 4.1.47), the EPA 
explained that requiring multiple tests over a range of different 
furnace operating conditions will show that the selected monitoring 
parameters are valid indicators of emissions and that it may not be 
possible for a single test to be representative of worst case 
conditions and that more than a single test may be required. It is not 
permissible, for example, to demonstrate compliance while processing 
relatively uncontaminated scrap, and then at a later time, when the 
supply of this scrap is constrained, process more heavily contaminated 
scrap, without demonstrating compliance under these conditions based on 
previous emissions testing or on new emissions testing if previous 
tests would not be representative of the emissions from the processing 
of the more heavily contaminated scrap.
    To clarify the requirements for testing, we are proposing that 
performance tests be conducted under representative (normal) conditions 
expected to produce the highest level of HAP emissions expressed in the 
units of the emission standards for the HAP (considering the extent of 
scrap contamination, reactive flux addition rate and feed/charge rate). 
If a single test condition is not expected to produce the highest level 
of emissions for all HAP, testing under two or more sets of conditions 
(for example high contamination at low feed/charge rate and low 
contamination at high feed/charge rate) may be required. Any subsequent 
performance tests for the purposes of establishing new or revised 
parametric limits shall be allowed upon pre-approval from the 
permitting authority for major sources or the Administrator for area 
sources. These new parametric settings shall be used to demonstrate 
compliance for the period being tested. We solicit comment on whether 
the proposed amendment adequately addresses and clarifies the 
requirement that multiple tests may be necessary to represent different 
operational conditions.
3. Testing of Uncontrolled Furnaces
    As explained in the 2012 proposal, while subpart RRR specifies 
capture and collection requirements for emission units that are 
equipped with add-on air pollution control devices, there are no such 
requirements for furnaces that are not equipped with an add-on air 
pollution control device. To clarify how uncontrolled sources are to be 
tested for compliance, in 2012 we proposed compliance alternatives for 
uncontrolled affected sources. Specifically, in 2012 we proposed either 
the installation of ACGIH hooding or an assumption of 67-percent 
capture

[[Page 72903]]

efficiency for furnace exhaust (i.e., multiply emissions measured at 
the furnace exhaust outlet by 1.5 to calculate the total estimated 
emissions from the furnace). Under the 2012 proposed provisions, if the 
source fails to demonstrate compliance using the 67-percent capture 
efficiency assumption, the source would have to retest using hooding 
that meets ACGIH guidelines or petition the permitting authority for 
major sources, or the Administrator for area sources, that such hoods 
are impractical and propose alternative testing procedures that will 
minimize unmeasured fugitive emissions. In the 2012 proposal, we 
proposed that the retesting would need to occur within 90 days.
    We received comments that the EPA was proposing to mandate ACGIH 
hooding during performance testing for uncontrolled furnaces. 
Commenters also provided information that ACGIH-compliant hoods are not 
possible to install on round top furnaces.
    Based on the comments received and our consideration of specific 
testing scenarios and types of uncontrolled furnaces, we are proposing 
revised requirements for the testing of uncontrolled furnaces. In this 
supplemental proposal, we are proposing that if the source fails to 
demonstrate compliance by the uncontrolled furnace using the 67-percent 
capture efficiency assumption proposed in the 2012 proposal, then they 
must retest using ACGIH hooding within 180 days (rather than the 90 
days specified in the 2012 proposal), or the source can petition the 
appropriate authority within 180 days that such hoods are impracticable 
and propose alternative testing procedures to minimize emissions. No 
time constraints on petitioning the appropriate authority were 
specified in the 2012 proposal. In this supplemental proposal, we are 
also proposing to clarify situations and circumstances whereby 
installation of hooding according to ACGIH guidelines would be 
considered impractical and are adding examples of procedures for 
minimizing fugitive emissions during testing for such situations and 
circumstances. The EPA is proposing conditions that would be considered 
impractical to install hooding according to ACGIH guidelines. The EPA 
is also proposing alternative procedures to minimize fugitive emissions 
in the event that ACGIH-compliant hooding cannot be installed. These 
alternative procedures are described in more detail below.
    Comments on the 2012 proposal also contained information regarding 
the feasibility of installing ACGIH-compliant hooding on certain 
furnace types in preparation for testing. Based on our review of the 
information submitted by the commenters, we agree that it is not 
possible to install ACGIH-compliant hoods on round top furnaces for 
testing because the top of the furnace would have to be removed by a 
crane operating above the furnace. We also agree that case-by-case 
impracticability determinations are not necessary for round top 
furnaces. Consequently, we are proposing that existing round top 
furnaces be excluded from the proposed requirement either to install 
ACGIH-compliant hooding or to use a 67-percent capture efficiency, as 
well as from the proposed requirement that a petition of impracticality 
be submitted to the appropriate authority. Instead, we propose that 
round top furnaces must be operated to minimize fugitive emissions 
during testing. We have not received any documentation to support 
requests by commenters to exclude other types of furnaces such as box 
reverberatory furnaces and box reverberatory furnaces with a side door. 
Therefore, we have not proposed to exclude them, but we are prepared to 
evaluate any comments submitted regarding impracticality and other 
types of furnaces and, most importantly, supporting documentation that 
we may receive from commenters.
    Under this supplemental proposal, owners or operators of 
uncontrolled furnaces, including round top furnaces, who petition the 
appropriate authority that it is impractical to install ACGIH-compliant 
hooding would be required to minimize fugitive emissions from such 
furnaces during testing. In response to commenters' requests, we are 
proposing example procedures that can be used to minimize unmeasured 
fugitive emissions during testing. These procedures may include, if 
practical, one or more of the following, but are not limited to:
     Installing a hood that does not entirely meet ACGIH 
guidelines;
     Using the building as an enclosure and measuring emissions 
exhausted from the building if there are no other furnaces or other 
significant sources in the building of the pollutants to be measured;
     Installing temporary baffles on the sides or top of the 
furnace opening, if it is practical to do so where they will not 
interfere with material handling or with the furnace door opening and 
closing;
     Increasing the exhaust rate from the furnace from furnaces 
with draft fans, so as to capture emissions that might otherwise escape 
into the building;
     Minimizing the time the furnace doors are open or the top 
is off;
     Delaying gaseous reactive fluxing until charging doors are 
closed or the top is on;
     Agitating or stirring molten metal as soon as practicable 
after salt flux addition and closing doors as soon as possible after 
solid fluxing operations, including mixing and dross removal;
     Keeping building doors and other openings closed to the 
greatest extent possible to minimize drafts that would divert emissions 
from being drawn into the furnace; and
     Maintaining burners on low-fire or pilot operation while 
the doors are open or the top is off.
    We are also proposing revised amendments to clarify in what 
circumstances installation of temporary capture hoods for testing would 
be considered impractical. We are proposing that temporary capture 
hooding installation would be considered impractical if:
     Building or equipment obstructions (for example, wall, 
ceiling, roof, structural beams, utilities, overhead crane or other) 
are present such that the temporary hood cannot be located consistent 
with acceptable hood design and installation practices;
     Space limitations or work area constraints exist such that 
the temporary hood cannot be supported or located to prevent 
interference with normal furnace operations or avoid unsafe working 
conditions for the furnace operator; or
     Other obstructions and limitations subject to agreement by 
the permitting authority for major sources, or the Administrator for 
area sources.
    We invite comments and solicit information on certain aspects of 
the proposed compliance provisions for testing of uncontrolled 
furnaces. Specifically, we are soliciting comments and information on 
the requirements in this supplemental proposal that specify the types 
of obstacles and limitations that can be used to show that testing 
using ACGIH-compliant hooding is impractical, the procedures that can 
be implemented to minimize unmeasured fugitive emissions during 
testing, and the exemption of existing round top furnaces from the 
requirements to test using ACGIH-compliant hooding or apply the 67-
percent capture efficiency assumption. We are not soliciting comment on 
any other element of the provisions proposed in the 2012 proposal 
regarding testing of uncontrolled furnaces.

[[Page 72904]]

4. Annual Inspections of Capture/Collection Systems
    In the 2012 proposal, we proposed codifying in subpart RRR our 
existing interpretation that annual hood inspections include flow rate 
measurements using EPA Reference Methods 1 and 2 in Appendix A to 40 
CFR part 60. These flow rate measurements supplement the effectiveness 
of the required visual inspection for leaks, to reveal the presence of 
obstructions in the ductwork, confirm that fan efficiency has not 
declined and provide a measured value for air flow. Commenters 
requested that the EPA allow flexibility in the methods used to 
complete the annual inspections of capture/collection systems stating 
that the use of volumetric flow measurement was often not necessary and 
Method 1 and 2 tests could be a cost burden for some facilities. 
Comments also indicated that routine, but less frequent, flow rate 
measurements could ensure that capture/collection systems are operated 
properly and suggested alternative methods of ensuring the efficiency 
of capture/collection systems.
    Based on the comments received and our consideration of inspection 
needs, the EPA is proposing additional options that provide more 
flexibility in how affected sources can verify the efficiency of their 
capture/collection system. Instead of annual Methods 1 and 2 testing, 
we propose that sources may choose to perform flow rate measurements 
using EPA Methods 1 and 2 once every 5 years provided that a flow rate 
indicator consisting of a pitot tube and differential pressure gauge is 
installed and used to record daily the differential pressure and to 
ensure that the differential pressure is maintained at or above 90 
percent of the pressure differential measured during the most recent 
Method 2 performance test series, and that the flow rate indicator is 
inspected annually. As another option to annual flow rate measurements 
using Methods 1 and 2, the EPA is proposing to allow Methods 1 and 2 
testing to be performed every 5 years provided that daily measurements 
of the revolutions per minute (RPM) of the capture and collection 
system's fan are taken, the readings are recorded daily and the fan RPM 
is maintained at or above 90 percent of the RPM measured during the 
most recent Method 2 performance test. Further, we are proposing that 
as an alternative to the flow rate measurements using Methods 1 and 2, 
the annual hood inspection requirements can be satisfied by conducting 
annual verification of a permanent total enclosure using EPA Method 
204. We are further proposing that as an alternative to the annual 
verification of a permanent total enclosure using EPA Method 204, 
verification can be performed once every 5 years if negative pressure 
in the enclosure is directly monitored by a pressure indicator and 
readings are recorded daily or the system is interlocked to halt 
material feed should the system not operate under negative pressure. In 
this supplemental proposal, we are also proposing that readings outside 
a specified range would need to be investigated and steps taken to 
restore normal operation, and that pressure indicators would need to be 
inspected annually for damage and operability.
5. Sweat Furnace Operating and Monitoring Requirements
    We are also proposing to amend 40 CFR 63.1506(c) and 63.1510(d) to 
provide sweat furnaces with alternative compliance options to the ACGIH 
Guidelines and the required annual flow rate measurements using EPA 
Methods 1 and 2. We are proposing that in lieu of meeting the ACGIH 
guidelines for capture and collection and the annual flow rate 
measurements using Methods 1 and 2, sweat furnaces may comply by 
demonstrating negative air flow into or towards the sweat furnace 
opening as well as operating and maintaining the sweat furnace in such 
a way that minimizes fugitive emissions.
6. Startup, Shutdown, Malfunction and the Malfunction Affirmative 
Defense
    In the 2012 proposal, we proposed to eliminate provisions that 
exempt sources from the requirement to comply with the otherwise 
applicable CAA section 112(d) emission standards during periods of 
Startup, Shutdown and Malfunction (SSM). We explained in the 2012 
proposal that because the scrap processed at secondary aluminum 
production facilities is the source of emissions, we expect emissions 
during startup and shutdown would be no higher, and most likely would 
be significantly lower, than emissions during normal operations since 
no scrap is processed during those periods. We stated that we knew of 
no reason why the existing standards should not apply at all times. For 
production processes in the Secondary Aluminum Production source 
category where the standards are expressed in units of pounds per ton 
of feed or similar units (i.e., thermal chip dyers, scrap dryer/
delacquering kiln/decoating kilns, dross-only furnaces, in-line fluxers 
using reactive flux and group 1 furnaces), the 2012 proposal included a 
method for demonstrating compliance with those limits based on 
emissions measured during startup and shutdown.
    Because conducting meaningful testing during periods of startup and 
shutdown can be problematic, in this supplemental proposal we are 
proposing an additional method that can be used to demonstrate 
compliance with production based emission limits during periods of 
startup and shutdown. Together, these proposed compliance provisions 
for periods of startup and shutdown better reflect the MACT requirement 
for those periods. Recognizing that the source of HAP emissions is the 
processing of scrap and the use of fluxes during processing and that 
the heat for processing in the Secondary Aluminum Production source 
category is generated exclusively by use of clean fuels--natural gas, 
propane or electricity--we are proposing that compliance with emission 
standards during startup and shutdown can be demonstrated by keeping 
records that show that the feed/charge rate was zero, the flux rate was 
zero and the affected source or emission unit either was heated with 
electricity, propane or natural gas as the sole sources of heat or was 
not heated (see proposed section 63.1513(f)). We are also proposing 
that the following records be kept: The date and time of each startup 
and shutdown, the quantity of feed/charge and flux introduced during 
each startup and shutdown and the types of fuel used to heat the unit 
during startup and shutdown.
    We are also proposing to define periods of startup and shutdown. 
For the purposes of subpart RRR, startup means ``the period of 
operation for thermal chip dryers, scrap dryers/delacquering kilns, 
decoating kilns, dross-only furnaces, group 1 furnaces, in-line 
fluxers, sweat furnaces and group 2 furnaces that begins with equipment 
warming from a cold start or a complete shutdown. Startup ends at the 
point that feed/charge is introduced.'' Shutdown means the period of 
operation for thermal chip dryers, scrap dryers/delacquering kilns, 
decoating kilns, dross-only furnaces, group 1 furnaces, in-line 
fluxers, sweat furnaces and group 2 furnaces that begins when the 
introduction of feed/charge is halted and all product has been removed 
from the emission unit (e.g., by tapping a furnace).''
    We solicit comments and additional information related to the 
proposed definitions of startup and shutdown, as well as the additional 
option proposed in this supplemental proposal for demonstrating 
compliance during

[[Page 72905]]

periods of startup and shutdown based on the presence (or absence) in 
the furnace of feed/charge or fluxing, and the type of combustion fuels 
or the absence of combustion fuels. We are also proposing to move the 
requirements for compliance demonstration during startup and shutdown 
from the emission standards section (section 63.1505), where they were 
in the 2012 proposal, to the more appropriate compliance demonstration 
section (section 63.1513). However, we are not soliciting comments on 
the compliance demonstration method for periods of startup and shutdown 
that was presented in the 2012 proposal.
    In the 2012 proposal, we proposed to eliminate provisions that 
exempt sources from the requirement to comply with the otherwise 
applicable CAA section 112(d) emission standards during periods of SSM. 
We also included provisions for affirmative defense to civil penalties 
for violations of emission standards caused by malfunctions. Periods of 
startup, normal operations and shutdown are all predictable and routine 
aspects of a source's operations. Malfunctions, in contrast, are 
neither predictable nor routine. Instead they are, by definition 
sudden, infrequent and not reasonably preventable failures of emissions 
control, process or monitoring equipment. As explained in the 2012 
proposal (77 FR 8598), the EPA interprets CAA section 112 as not 
requiring emissions that occur during periods of malfunction to be 
factored into development of CAA section 112 standards. Under section 
112, emissions standards for new sources must be no less stringent than 
the level ``achieved'' by the best controlled similar source and for 
existing sources generally must be no less stringent than the average 
emission limitation ``achieved'' by the best performing 12 percent of 
sources in the category. There is nothing in section 112 that directs 
the agency to consider malfunctions in determining the level 
``achieved'' by the best performing sources when setting emission 
standards. As the United States Court of Appeals for the District of 
Columbia Circuit has recognized, the phrase ``average emissions 
limitation achieved by the best performing 12 percent of'' sources 
``says nothing about how the performance of the best units is to be 
calculated.'' Nat'l Ass'n of Clean Water Agencies v. EPA, 734 F.3d 
1115, 1141 (D.C. Cir. 2013). While the EPA accounts for variability in 
setting emissions standards, nothing in section 112 requires the agency 
to consider malfunctions as part of that analysis. A malfunction should 
not be treated in the same manner as the type of variation in 
performance that occurs during routine operations of a source. A 
malfunction is a failure of the source to perform in a ``normal or 
usual manner'' and no statutory language compels the EPA to consider 
such events in setting section 112 standards.
    Further, accounting for malfunctions in setting emission standards 
would be difficult, if not impossible, given the myriad different types 
of malfunctions that can occur across all sources in the category and 
given the difficulties associated with predicting or accounting for the 
frequency, degree and duration of various malfunctions that might 
occur. As a result, the performance of units that are malfunctioning is 
not ``reasonably'' foreseeable. See, e.g., Sierra Club v. EPA, 167 F.3d 
658, 662 (D.C. Cir. 1999) (``The EPA typically has wide latitude in 
determining the extent of data-gathering necessary to solve a problem. 
We generally defer to an agency's decision to proceed on the basis of 
imperfect scientific information, rather than to `invest the resources 
to conduct the perfect study.' '') See also, Weyerhaeuser v. Costle, 
590 F.2d 1011, 1058 (D.C. Cir. 1978) (``In the nature of things, no 
general limit, individual permit, or even any upset provision can 
anticipate all upset situations. After a certain point, the 
transgression of regulatory limits caused by `uncontrollable acts of 
third parties,' such as strikes, sabotage, operator intoxication or 
insanity and a variety of other eventualities, must be a matter for the 
administrative exercise of case-by-case enforcement discretion, not for 
specification in advance by regulation.''). In addition, emissions 
during a malfunction event can be significantly higher than emissions 
at any other time of source operation. For example, if an air pollution 
control device with 99 percent removal goes off-line as a result of a 
malfunction (as might happen if, for example, the bags in a baghouse 
catch fire) and the emission unit is a steady state type unit that 
would take days to shut down, the source would go from 99 percent 
control to zero control until the control device was repaired. The 
source's emissions during the malfunction would be 100 times higher 
than during normal operations. As such, the emissions over a 4-day 
malfunction period would exceed the annual emissions of the source 
during normal operations. As this example illustrates, accounting for 
malfunctions could lead to standards that are not reflective of (and 
significantly less stringent than) levels that are achieved by a well-
performing non-malfunctioning source. It is reasonable to interpret 
section 112 to avoid such a result. The EPA's approach to malfunctions 
is consistent with section 112 and is a reasonable interpretation of 
the statute.
    In the event that a source fails to comply with the applicable CAA 
section 112(d) standards as a result of a malfunction event, the EPA 
would determine an appropriate response based on, among other things, 
the good faith efforts of the source to minimize emissions during 
malfunction periods, including preventative and corrective actions, as 
well as root cause analyses to ascertain and rectify excess emissions. 
The EPA would also consider whether the source's failure to comply with 
the CAA section 112(d) standard was, in fact, sudden, infrequent, not 
reasonably preventable and was not instead caused in part by poor 
maintenance or careless operation.
    If the EPA determines in a particular case that enforcement action 
against a source for violation of an emission standard is warranted, 
the source can raise any and all defenses in that enforcement action 
and the federal district court will determine what, if any, relief is 
appropriate. The same is true for citizen enforcement actions. 
Similarly, the presiding officer in an administrative proceeding can 
consider any defense raised and determine whether administrative 
penalties are appropriate.
    In summary, the EPA interpretation of the CAA and, in particular, 
section 112 is reasonable and encourages practices that will avoid 
malfunctions. Administrative and judicial procedures for addressing 
exceedances of the standards fully recognize that violations may occur 
despite good faith efforts to comply and can accommodate those 
situations.
    As noted above, the 2012 proposal included an affirmative defense 
to civil penalties for violations caused by malfunctions. The EPA 
included the affirmative defense in the 2012 proposal as it had in 
several prior rules in an effort to create a system that incorporates 
some flexibility, recognizing that there is a tension, inherent in many 
types of air regulation, to ensure adequate compliance while 
simultaneously recognizing that despite the most diligent of efforts, 
emission standards may be violated under circumstances entirely beyond 
the control of the source. Although the EPA recognized that its case-
by-case enforcement discretion provides sufficient flexibility in these 
circumstances, it included the

[[Page 72906]]

affirmative defense in the 2012 proposal and in several prior rules to 
provide a more formalized approach and more regulatory clarity. See 
Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58 (D.C. Cir. 1978) 
(holding that an informal case-by-case enforcement discretion approach 
is adequate); but see Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 
(9th Cir. 1977) (requiring a more formalized approach to consideration 
of ``upsets beyond the control of the permit holder.''). Under the 
EPA's regulatory affirmative defense provisions, if a source could 
demonstrate in a judicial or administrative proceeding that it had met 
the requirements of the affirmative defense in the regulation, civil 
penalties would not be assessed. The United States Court of Appeals for 
the District of Columbia Circuit vacated an affirmative defense in one 
of the EPA's section 112(d) regulations. NRDC v. EPA, 749 F.3d 1055 
(D.C. Cir. 2014) (vacating affirmative defense provisions in section 
112 rule establishing emission standards for Portland cement kilns). 
The court found that the EPA lacked authority to establish an 
affirmative defense for private civil suits and held that under the 
CAA, the authority to determine civil penalty amounts in such cases 
lies exclusively with the courts, not the EPA. Specifically, the court 
found: ``As the language of the statute makes clear, the courts 
determine, on a case-by-case basis, whether civil penalties are 
`appropriate.' '' See NRDC v. EPA, 749 F.3d 1055, 1063 (D.C. Cir. 2014) 
(``[U]nder this statute, deciding whether penalties are `appropriate' 
in a given private civil suit is a job for the courts, not for EPA.''). 
In light of NRDC, the EPA is withdrawing its proposal to include a 
regulatory affirmative defense provision in this rulemaking and in this 
supplementary proposal has eliminated section 63.1520 (the provision 
that established the affirmative defense in the proposed rule published 
in the Federal Register on February 14, 2012 (77 FR 8576)). As 
explained above, if a source is unable to comply with emissions 
standards as a result of a malfunction, the EPA may use its case-by-
case enforcement discretion to provide flexibility, as appropriate. 
Further, as the D.C. Circuit recognized, in an EPA or citizen 
enforcement action, the court has the discretion to consider any 
defense raised and determine whether penalties are appropriate. Cf. 
NRDC v. EPA, 749 F.3d 1055, 1064 (D.C. Cir. 2014) (arguments that 
violation were caused by unavoidable technology failure can be made to 
the courts in future civil cases when the issue arises). The same logic 
applies to EPA administrative enforcement actions.

E. What compliance dates are we proposing?

    In the 2012 proposal, the EPA proposed that owners or operators of 
existing affected sources comply with the proposed amendments within 90 
days of the publication of the final rule in the Federal Register. 
Commenters stated that the proposed 90 day compliance deadline was 
insufficient for sources to comply with certain provisions of the final 
rule. They maintained that the rule changes would require operational 
planning, maintenance planning, reprogramming of data acquisition 
systems, design and installation of hooding equipment and/or 
negotiations with permitting authorities to gain performance test plan 
approvals (with provisions to minimize fugitive emissions during 
testing in place of capture hoods). They pointed out that facilities 
that choose to design and install capture hoods for performance testing 
will need time to design and complete these installations, conduct 
initial performance testing and modify their operations, charge 
materials and/or products to ensure compliance. Some rule changes, 
furnace switching, HF testing and testing uncontrolled furnaces for 
example, would require revisions to operation, maintenance and 
monitoring (OM&M) plans as well as to permits to include newly 
established operating parameters in cases where changes to furnace 
classifications are made. Commenters stated that compliance with HF 
emission standards that may affect choice of flux materials, daily 
calculation of HF emissions and compliance with SAPU limit that will 
require reprogramming of data systems to include HF and/or fluoride 
containing flux composition data would also require time to be 
researched, selected, purchased, financed and installed. Commenters 
suggested compliance deadlines ranging from 2 to 3 years.
    The EPA agrees with commenters that the proposed 90-day compliance 
deadline is insufficient for sources to comply with certain provisions 
of the final rule and is proposing extended compliance periods. The EPA 
is proposing a 180-day compliance period for the revisions listed in 
section 63.1501(d). For the amendments to include HF emissions (in 
section 63.1505(i)(4) and (k)(2)), the testing of existing uncontrolled 
furnaces (sections 63.1512(e)(4), (e)(5), (e)(6) and (e)(7)), and 
changing furnace classification (section 63.1514), the EPA agrees that 
a longer compliance period is required and is proposing a compliance 
date of 2 years after promulgation.

V. Summary of the Revised Cost, Environmental and Economic Impacts

A. What are the affected sources?

    We estimate that there are 161 secondary aluminum production 
facilities that will be affected by this proposed rule. We performed 
risk modeling for 155 of these sources (52 of the 53 major sources and 
103 of the 108 area sources). There were six facilities that are 
subject to the Secondary Aluminum NESHAP that were not included in the 
risk assessment input modeling files. The facilities that were not 
included in the risk assessment input files included one major HAP 
source and five area HAP sources. The major HAP source was not included 
because the secondary aluminum equipment at the source consists of 
group 2 furnaces, for which the EPA did not have HAP emissions 
estimates. The five area sources were not included because they had no 
equipment subject to D/F emission standards, which are the only 
standards in the NESHAP applicable to area sources. We estimate that 
nine secondary aluminum facilities have co-located primary aluminum 
operations. The affected sources at secondary aluminum production 
facilities include new and existing scrap shredders, thermal chip 
dryers, scrap dryer/delacquering kiln/decoating kilns, group 2 
furnaces, sweat furnaces, dross-only furnaces, rotary dross cooler and 
secondary aluminum processing units containing group 1 furnaces and in-
line fluxers.

B. What are the air quality impacts?

    No changes are being proposed to numerical emissions limits. This 
supplemental proposal affects the number of times that a furnace can 
switch operating modes, clarifies how uncontrolled furnaces are to 
conduct emissions testing, extends the compliance deadline, revises the 
monitoring requirements for annual inspection of capture/collection 
systems, clarifies the requirements for conducting performance testing 
under worst case conditions and provides monitoring alternatives for 
sweat furnaces. These proposed amendments would not have any 
appreciable effect on emissions or result in emission reductions, 
although the proposed requirements for testing uncontrolled furnaces 
could result in some unquantifiable emission reduction. Therefore, no 
quantifiable air quality impacts are expected. However, these

[[Page 72907]]

proposed amendments will help to improve compliance, monitoring and 
implementation of the rule.

C. What are the cost impacts?

    We conservatively estimate the total cost of the proposed 
amendments to be $1,711,000 per year (in 2011 dollars). However, 
depending on assumptions used for the costs for installing temporary 
hooding for uncontrolled furnaces, the estimate of total annualized 
costs could range from $611,000 to $2,871,000 per year.
    Our estimate for the source category includes an annualized cost of 
$1,200,000 to $3,460,000 for installing hooding that meets ACGIH 
guidelines for testing uncontrolled furnaces, assuming that 107 
furnaces choose that option (rather than assuming a 67-percent capture 
efficiency for their existing furnace exhaust system). We believe that 
a number of these 107 furnaces will choose to apply the 67-percent 
assumption rather than install hooding. Therefore, these total cost 
estimates are considered conservative (more likely to be overestimates 
rather than underestimates) of the total costs to the industry. Our 
estimates of total costs also include an annualized cost of $11,000 for 
testing for HF on uncontrolled furnaces that are already testing for 
HCl. Finally, we estimate cost savings of $600,000 per year for 
furnaces that change furnace operating modes and turn off their control 
devices. Our estimate of savings is based on 50 furnaces turning off 
their controls for approximately 6 months every year. This savings 
reflects the cost of testing (to demonstrate these furnaces remain in 
compliance with emission limits) minus the savings realized from 
operating with the control devices turned off.
    We estimate that 57 facilities will be affected and that the cost 
per facility ranges from negative $36,000 (a cost savings) per year for 
a facility changing furnace operating modes to $216,500 per year for a 
facility installing hooding for testing.
    The estimated costs are explained further in the document titled 
Updated Cost Estimates for the Proposed Rule Changes to Secondary 
Aluminum NESHAP, which is available in the docket for this action.

D. What are the economic impacts?

    We performed an economic impact analysis for the proposed revisions 
and amendments in this supplemental proposed rulemaking. This analysis 
estimates impacts based on using annualized cost-to-sales ratios for 
affected firms. For the 28 parent firms affected by this proposed rule, 
the cost-to-sales estimate for each parent firm is less than 0.1 
percent. For more information, please refer to the document titled 
Economic Impact Analysis for the Secondary Aluminum Supplemental 
Proposal, which is available in the docket.

E. What are the benefits?

    We do not anticipate any significant reductions in HAP emissions as 
a result of these proposed amendments. However, we think that the 
proposed amendments will help to improve the clarity of the rule, which 
can improve compliance and minimize emissions. Certain provisions also 
provide operational flexibility with no increase in HAP emissions.

VI. Request for Comments

    As discussed in detail above, we solicit comments on the revised 
risk assessment and proposed changes presented in this supplemental 
proposal. We are not re-opening comment on any other elements of the 
2012 proposal (77 FR 8576, February 14, 2012). Comments previously 
received on the 2012 proposal, along with comments received on and 
within the scope of this supplemental proposal, will be addressed in 
the final rulemaking action.
    We are also interested in any additional data that may help to 
reduce the uncertainties inherent in the risk assessments and other 
analyses. We are specifically interested in receiving corrections to 
the site-specific emissions profiles used for risk modeling. Such data 
should include supporting documentation in sufficient detail to allow 
characterization of the quality and representativeness of the data or 
information. Section VII of this preamble provides more information on 
submitting data.

VII. Submitting Data Corrections

    The site-specific emissions profiles used in the source category 
risk and demographic analyses and instructions are available on the RTR 
Web page at https://www.epa.gov/ttn/atw/rrisk/rtrpg.html. The data files 
include detailed information for each HAP emissions release point for 
the facilities in the source category.
    If you believe that the data are not representative or are 
inaccurate, please identify the data in question, provide your reason 
for concern and provide any ``improved'' data that you have, if 
available. When you submit data, we request that you provide 
documentation of the basis for the revised values to support your 
suggested changes. To submit comments on the data downloaded from the 
RTR page, complete the following steps:
    1. Within this downloaded file, enter suggested revisions to the 
data fields appropriate for that information.
    2. Fill in the commenter information fields for each suggested 
revision (i.e., commenter name, commenter organization, commenter email 
address, commenter phone number and revision comments).
    3. Gather documentation for any suggested emissions revisions 
(e.g., performance test reports, material balance calculations, etc.).
    4. Send the entire downloaded file with suggested revisions in 
Microsoft[supreg] Access format and all accompanying documentation to 
Docket ID No. EPA-HQ-OAR-2010-0544 (through one of the methods 
described in the ADDRESSES section of this preamble).
    5. If you are providing comments on a single facility or multiple 
facilities, you need only submit one file for all facilities. The file 
should contain all suggested changes for all sources at that facility. 
We request that all data revision comments be submitted in the form of 
updated Microsoft[supreg] Excel files that are generated by the 
Microsoft[supreg] Access file. These files are provided on the RTR Web 
page at https://www.epa.gov/ttn/atw/rrisk/rtrpg.html.

VIII. Statutory and Executive Order Reviews

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

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

B. Paperwork Reduction Act

    The information collection requirements in this proposed action 
have been submitted for approval to OMB under the Paperwork Reduction 
Act, 44 U.S.C. 3501 et seq. The ICR document prepared by the EPA has 
been assigned the EPA ICR number 2453.01.
    We are proposing changes to the paperwork requirements to the 
Secondary Aluminum Production source category that were proposed in 
2012.
    In addition, in the 2012 proposal, we included an estimate of the 
burden associated with the affirmative defense in the ICR. However, as 
explained above, we are withdrawing our proposal

[[Page 72908]]

to include affirmative defense provisions, and the burden estimate has 
been revised accordingly.
    We estimate 161 regulated entities are currently subject to subpart 
RRR. The annual monitoring, reporting and recordkeeping burden for this 
collection (averaged over the first 3 years after the effective date of 
the standards) for these amendments to subpart RRR is estimated to be 
$2,990,000 per year. This includes 1,694 labor hours per year at a 
total labor cost of $162,000 per year, and total non-labor capital and 
operation and maintenance (O&M) costs of $2,828,000 per year. The total 
burden for the federal government (averaged over the first 3 years 
after the effective date of the standard) is estimated to be 271 labor 
hours per year at an annual cost of $12,231. Burden is defined at 5 CFR 
1320.3(b).
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9.
    To comment on the agency's need for this information, the accuracy 
of the provided burden estimates and any suggested methods for 
minimizing respondent burden, the EPA has established a public docket 
for this rule, which includes this ICR, under Docket ID No. EPA-HQ-OAR-
2010-0544. Submit any comments related to the ICR to the EPA and OMB. 
See the ADDRESSES section at the beginning of this document for where 
to submit comments to the EPA. Send comments to OMB at the Office of 
Information and Regulatory Affairs, Office of Management and Budget, 
725 17th Street NW., Washington, DC 20503, Attention: Desk Office for 
the EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after December 8, 2014, a comment to OMB is best 
assured of having its full effect if OMB receives it by January 7, 
2015. The final rule will respond to any OMB or public comments on the 
information collection requirements contained in this proposal.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act, or any other statute, unless the agency certifies that 
the rule will not have a significant economic impact on a substantial 
number of small entities. Small entities include small businesses, 
small organizations and small governmental jurisdictions.
    For purposes of assessing the impacts of this action on small 
entities, small entity is defined as: (1) A small business as defined 
by the Small Business Administration's (SBA) regulations at 13 CFR 
121.201; (2) a small governmental jurisdiction that is a government of 
a city, county, town, school district or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise that is independently owned and operated 
and is not dominant in its field. For this source category, which has 
the NAICS code 331314 (i.e., Secondary Smelting and Alloying of 
Aluminum), the SBA small business size standard is 750 employees 
according to the SBA small business standards definitions.
    After considering the economic impacts of these proposed changes on 
small entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. We 
determined in the economic and small business analysis that, using the 
results from the cost memorandum, 28 entities will incur costs 
associated with the proposed rule. Of these 28 entities, nine of them 
are small. Of these nine, all of them are estimated to experience a 
negative cost (i.e., a cost savings) as a result of the proposed action 
according to our analysis. For more information, please refer to the 
Economic Impact Analysis for the Secondary Aluminum Supplemental 
Proposal, which is available in the docket.

D. Unfunded Mandates Reform Act

    This action does not contain a Federal mandate that may result in 
expenditures of $100 million or more for state, local and tribal 
governments, in the aggregate, or the private sector in any one year. 
Thus, this action is not subject to the requirements of section 202 or 
205 of the Unfunded Mandates Reform Act (UMRA).
    This action is also not subject to the requirements of section 203 
of UMRA because it contains no regulatory requirements that might 
significantly or uniquely affect small governments as it contains no 
requirements that apply to such governments nor does it impose 
obligations upon them.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states or on the distribution of power 
and responsibilities among the various levels of government, as 
specified in Executive Order 13132. None of the facilities subject to 
this proposed action are owned or operated by state governments. Thus, 
Executive Order 13132 does not apply to this proposed action.
    In the spirit of Executive Order 13132, and consistent with the EPA 
policy to promote communications between the EPA and State and local 
governments, the EPA specifically solicits comment on this proposed 
rule from state and local officials.

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

    This action does not have tribal implications, as specified in 
Executive Order 13175 (65 FR 67249, November 9, 2000). There are no 
secondary aluminum production facilities that are owned or operated by 
tribal governments. Thus, Executive Order 13175 does not apply to this 
action. The EPA specifically solicits additional comments on this 
proposed action from tribal officials.

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

    This action is not subject to Executive Order 13045 (62 FR 19885, 
April 23, 1997) because it is not economically significant as defined 
in Executive Order 12866 and because the agency does not believe the 
environmental health or safety risks addressed by this action present a 
disproportionate risk to children. This action's health and risk 
assessments are contained in sections III and IV of this document. The 
public is invited to submit comments or identify peer-reviewed studies 
and data that assess effects of early life exposures to the pollutants 
emitted by this source category.

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

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

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Public Law 104-113 (15 U.S.C. 272 note), 
directs the EPA to use voluntary consensus standards (VCS) in its 
regulatory

[[Page 72909]]

activities unless to do so would be inconsistent with applicable law or 
otherwise impractical. VCS are technical standards (e.g., materials 
specifications, test methods, sampling procedures and business 
practices) that are developed or adopted by VCS bodies. NTTAA directs 
the EPA to provide Congress, through OMB, explanations when the agency 
decides not to use available and applicable VCS.
    This proposed action involves technical standards. Therefore, the 
agency conducted a search to identify potentially applicable VCS. The 
VCS ASTM D7520-09, ``Standard Test Method for Determining the Opacity 
of a Plume in the Outdoor Ambient Atmosphere'' was identified as an 
acceptable alternative to EPA Method 9. The standard was developed and 
is published by the American Society for Testing and Materials (ASTM). 
The standard can be obtained by contacting ASTM at 100 Barr Harbor 
Drive, Post Office Box C700, West Conshohocken, PA 19428-2959 or at 
their Web site, https://www.astm.org.
    In addition, as a result of comments received on the 2012 proposal, 
EPA Method 26 was identified as a reasonable alternative to EPA Method 
26A and EPA Method 204 was identified as a reasonable alternative 
method for EPA Methods 1 and 2. The EPA agrees that EPA Methods 26 and 
204 are acceptable alternatives for use in this rule. Therefore, the 
EPA has proposed adding ASTM D7520-09, ``Standard Test Method for 
Determining the Opacity of a Plume in the Outdoor Ambient Atmosphere,'' 
as an alternative method for the currently required EPA Method 9; EPA 
Method 26 as an alternative for the currently required EPA Method 26A; 
and EPA Method 204 as an alternative to the currently required EPA 
Methods 1 and 2.
    The EPA welcomes comments on this aspect of the proposed rulemaking 
and, specifically, invites the public to identify potentially-
applicable VCS and to explain why such standards should be used in this 
regulation.

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

    Executive Order 12898 (59 FR 7629, February 16, 1994) establishes 
federal executive policy on environmental justice. Its main provision 
directs federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies and activities on minority populations and low-income 
populations in the United States.
    The EPA has determined that this proposed rule will not have 
disproportionately high and adverse human health or environmental 
effects on minority or low-income populations because it does not 
affect the level of protection provided to human health or the 
environment. This proposed rule will not relax the emission limits on 
regulated sources and will not result in emissions increases.
    Because our residual risk assessment determined that there was 
minimal residual risk associated with the emissions from facilities in 
this source category, a demographic risk analysis was not necessary for 
this category. However, the EPA did conduct a proximity analysis for 
both area and major sources. The results of these analyses are 
summarized in section IV.A.6 of this notice and in more detail in the 
EJ Screening Report for Area Sources and the EJ Screening Report for 
Major Sources, which are available in the docket for this rulemaking.

List of Subjects in 40 CFR Part 63

    Environmental protection, Air pollution control, Reporting and 
recordkeeping requirements.

    Dated: November 13, 2014.
Gina McCarthy,
Administrator.
    For the reasons stated in the preamble, part 63 of title 40, 
chapter I, of the Code of Federal Regulations is proposed to be amended 
as follows:

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

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

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

Subpart RRR--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR 
POLLUTANTS FOR SECONDARY ALUMINUM PRODUCTION

0
2. Section 63.1501 is amended by adding paragraphs (d), (e), and (f) to 
read as follows:


Sec.  63.1501  Dates.

* * * * *
    (d) The owner or operator of an existing affected source must 
comply with the following requirements of this subpart by [DATE 180 
DAYS FROM PUBLICATION OF THE FINAL RULE IN THE Federal Register]: Sec.  
63.1505 (k) introductory text, (k)(1) through (k)(5), other than the 
emission standards for HF in (k)(2); Sec.  63.1506 (a)(1), (c)(1), 
(g)(5), (k)(3), (m)(4), (n)(1); Sec.  63.1510, (b)(5), (b)(9), (d)(2), 
(d)(3), (f)(1)(ii), (i)(4), (j)(4), (n)(1), (o)(1), (o)(1)(ii), 
(s)(2)(iv), (t) introductory text, (t)(2)(i), (t)(2)(ii), (t)(4), 
(t)(5); Sec.  63.1511(a) introductory text, (b) introductory text, 
(b)(1), (b)(6), (c)(9), (f)(6), (g)(5); Sec.  63.1512(e)(1), (e)(2), 
(e)(3), (h)(2), (j), (j)(1)(i), (j)(2)(i), (o)(1), (p)(2); Sec.  
63.1513(b) introductory text, (b)(1), (e)(1), (e)(2), (e)(3), (f); 
Sec.  63.1516 (b) introductory text, (b)(2)(iii), (b)(3), (d); Sec.  
63.1517(b)(16)(i), (b)(18), (b)(19), (c).
    (e) The owner or operator of an existing affected source must 
comply with the following requirements of this subpart by [DATE 2 YEARS 
FROM PUBLICATION OF THE FINAL RULE IN THE Federal Register]: Sec.  
63.1505(i)(4) and (k)(2) emission standards for HF; Sec.  63.1512(e)(4) 
through (7) requirements for testing existing uncontrolled group 1 
furnaces; and Sec.  63.1514 requirements for change of furnace 
classification.
    (f) The owner or operator of a new affected source that commences 
construction or reconstruction after February 14, 2012 must comply with 
all of the requirements listed in paragraphs (d) and (e) of this 
section by [DATE OF PUBLICATION OF THE FINAL RULE IN THE Federal 
Register] or upon startup, whichever is later.
0
3. Section 63.1503 is amended by adding in alphabetical order 
definitions for ``round top furnace,'' ``shutdown,'' and ``startup'' to 
read as follows:


Sec.  63.1503  Definitions.

* * * * *
    Round top furnace means a cylindrically-shaped reverberatory 
furnace that has a top that is removed for charging and other furnace 
operations.
* * * * *
    Shutdown means the period of operation for thermal chip dryers, 
scrap dryers/delacquering kilns, decoating kilns, dross-only furnaces, 
group 1 furnaces, in-line fluxers, sweat furnaces and group 2 furnaces 
that begins when the introduction of feed/charge is halted and all 
product has been removed from the emission unit (e.g., by tapping a 
furnace).
* * * * *
    Startup means the period of operation for thermal chip dryers, 
scrap dryers/delacquering kilns, decoating kilns, dross-only furnaces, 
group 1 furnaces, in-line fluxers, sweat furnaces and group 2 furnaces 
that begins with equipment warming from a cold start or

[[Page 72910]]

a complete shutdown. Startup ends at the point that feed/charge is 
introduced.
* * * * *
0
4. Section 63.1506 is amended by adding paragraph (c)(4) to read as 
follows:


Sec.  63.1506  Operating requirements.

* * * * *
    (c) * * *
    (4) In lieu of paragraph (c)(1) of this section, the owner or 
operator of a sweat furnace may design, install and operate each sweat 
furnace in accordance with paragraphs (c)(4)(i) through (iii) of this 
section.
    (i) As demonstrated by an annual negative air flow test conducted 
in accordance with Sec.  63.1510(d)(3), air flow must be into the sweat 
furnace or towards the plane of the sweat furnace opening.
    (ii) The owner or operator must maintain and operate the sweat 
furnace in a manner consistent with the good practices requirements for 
minimizing emissions, including fugitive emissions, in paragraph (a)(5) 
of this section. Procedures that will minimize fugitive emissions may 
include, but are not limited to the following:
    (A) Increasing the exhaust rate from the furnace with draft fans, 
so as to capture emissions that might otherwise escape from the sweat 
furnace opening;
    (B) Minimizing the time the sweat furnace doors are open;
    (C) Keeping building doors and other openings closed to the 
greatest extent possible to minimize drafts that would divert emissions 
from being drawn into the sweat furnace;
    (D) Maintaining burners on low-fire or pilot operation while the 
doors are open;
    (E) Conducting periodic inspections and maintenance of sweat 
furnace components to ensure their proper operation and performance 
including but not limited to, door assemblies, seals, combustion 
chamber refractory material, afterburner and stack refractory, blowers, 
fans, dampers, burner tubes, door raise cables, pilot light assemblies, 
baffles, sweat furnace and afterburner shells and other internal 
structures.
    (iii) The owner or operator must document in their OM&M plan the 
procedures to be used to minimize emissions, including fugitive 
emissions, in addition to the procedures to ensure the proper operation 
and maintenance of the sweat furnace.
* * * * *
0
5. Section 63.1510 is amended by revising paragraph (d)(2) and adding 
paragraph (d)(3) to read as follows:


Sec.  63.1510  Monitoring requirements.

* * * * *
    (d) * * *
    (2) Inspect each capture/collection and closed vent system at least 
once each calendar year to ensure that each system is operating in 
accordance with the operating requirements in Sec.  63.1506(c) and 
record the results of each inspection. This inspection shall include a 
volumetric flow rate measurement taken at a location in the ductwork 
downstream of the hoods that is representative of the actual volumetric 
flow rate without interference due to leaks, ambient air added for 
cooling or ducts from other hoods. The flow rate measurement must be 
performed in accordance with paragraphs (d)(2)(i), (ii), or (iii) of 
this section. As an alternative to the flow rate measurement specified 
in this paragraph, the inspection may satisfy the requirements of this 
paragraph, including the operating requirements in Sec.  63.1506(c), by 
including permanent total enclosure verification in accordance with 
(d)(2)(i) or (iv) of this section.
    (i) Conduct annual flow rate measurements using EPA Methods 1 and 2 
in Appendix A to 40 CFR part 60, or conduct annual verification of a 
permanent total enclosure using EPA Method 204; or
    (ii) As an alternative to annual flow rate measurements using EPA 
Methods 1 and 2, measurement with EPA Methods 1 and 2 can be performed 
once every 5 years, provided that:
    (A) A flow rate indicator consisting of a pitot tube and 
differential pressure gauge (Magnehelic[supreg], manometer or other 
differential pressure gauge) is installed with the pitot tube tip 
located at a representative point of the duct proximate to the location 
of the Methods 1 and 2 measurement site; and
    (B) The flow rate indicator is installed and operated in accordance 
with the manufacturer's specifications; and
    (C) The differential pressure is recorded during the Method 2 
performance test series; and
    (D) Differential pressure readings are recorded daily, and 
maintained at or above 90 percent of the pressure differential 
indicated by the flow rate indicator during the most recent Method 2 
performance test series; and
    (E) An inspection of the pitot tube and associated lines for 
damage, plugging, leakage and operational integrity is conducted at 
least once per year; or
    (iii) As an alternative to annual flow rate measurements using EPA 
Methods 1 and 2, measurement with EPA Methods 1 and 2 can be performed 
once every 5 years, provided that:
    (A) Daily measurements of the capture and collection system's fan 
revolutions per minute (RPM) are made by taking three measurements with 
at least 5 minutes between each measurement, and averaging the three 
measurements; and
    (B) Readings are recorded daily and maintained at or above 90 
percent of the RPM measured during the most recent Method 2 performance 
test series.
    (iv) As an alternative to the annual verification of a permanent 
total enclosure using EPA Method 204, verification can be performed 
once every 5 years, provided that:
    (A) Negative pressure in the enclosure is directly monitored by a 
pressure indicator installed at a representative location;
    (B) Pressure readings are recorded daily or the system is 
interlocked to halt material feed should the system not operate under 
negative pressure;
    (C) When there are readings outside the range specified in the OM&M 
plan, the facility investigates and takes steps to restore normal 
operation, which may include initial inspection and evaluation, 
recording that operations returned to normal without operator action or 
other applicable actions; and
    (D) An inspection of the pressure indicator for damage and 
operational integrity is conducted at least once per calendar year.
    (3) In lieu of paragraph (d)(2) of this section, the owner or 
operator of a sweat furnace may inspect each sweat furnace at least 
once each calendar year to ensure that they are being operated in 
accordance with the negative air flow requirements in Sec.  
63.1506(c)(4). The owner or operator of a sweat furnace must 
demonstrate negative air flow into the sweat furnace in accordance with 
paragraphs (d)(3)(i) through (iii) of this section.
    (i) Perform an annual visual smoke test to demonstrate airflow into 
the sweat furnace or towards the plane of the sweat furnace opening;
    (ii) Perform the smoke test using a smoke source, such as a smoke 
tube, smoke stick, smoke cartridge, smoke candle or other smoke source 
that produces a persistent and neutral buoyancy aerosol; and
    (iii) Perform the visual smoke test at a safe distance from and 
near the center of the sweat furnace opening.
* * * * *
0
6. Section 63.1511 is amended by revising paragraph (b)(1) to read as 
follows:


Sec.  63.1511  Performance test/compliance demonstration general 
requirements.

* * * * *

[[Page 72911]]

    (b) * * *
    (1) The performance tests must be conducted under representative 
(normal) conditions expected to produce the highest level of HAP 
emissions expressed in the units of the emission standards for the HAP 
(considering the extent of scrap contamination, reactive flux addition 
rate and feed/charge rate). If a single test condition is not expected 
to produce the highest level of emissions for all HAP, testing under 
two or more sets of conditions (for example high contamination at low 
feed/charge rate, and low contamination at high feed/charge rate) may 
be required. Any subsequent performance tests for the purposes of 
establishing new or revised parametric limits shall be allowed upon 
pre-approval from the permitting authority for major sources, or the 
Administrator for area sources. These new parametric settings shall be 
used to demonstrate compliance for the period being tested.
* * * * *
0
7. Section 63.1512 is amended by adding paragraphs (e)(4) through (7) 
to read as follows:


Sec.  63.1512  Performance test/compliance demonstration requirements 
and procedures.

* * * * *
    (e) * * *
    (4) When testing an existing uncontrolled furnace, the owner or 
operator must comply with the requirements of either paragraphs 
(e)(4)(i) or (ii) of this section at the next required performance 
test.
    (i) Install hooding that meets ACGIH Guidelines, or
    (ii) Assume a 67-percent capture efficiency for the furnace exhaust 
(i.e., multiply emissions measured at the furnace exhaust outlet by 
1.5). If the source fails to demonstrate compliance using the 67-
percent capture efficiency assumption, the owner or operator must re-
test with a hood that meets the ACGIH Guidelines within 180 days, or 
petition the permitting authority for major sources, or the 
Administrator for area sources, within 180 days that such hoods are 
impractical under the provisions of paragraph (e)(6) of this section 
and propose testing procedures that will minimize fugitive emissions 
during the performance test according to paragraph (e)(7) of this 
section.
    (iii) Existing round top furnaces are exempt from the requirements 
of paragraphs (e)(4)(i) and (ii) of this section. Round top furnaces 
must be operated to minimize fugitive emissions according to paragraph 
(e)(7) of this section.
    (5) When testing a new uncontrolled furnace the owner or operator 
must:
    (i) Install hooding that meets ACGIH Guidelines or petition the 
permitting authority for major sources, or the Administrator for area 
sources, that such hoods are impracticable under the provisions of 
paragraph (e)(6) of this section and propose testing procedures that 
will minimize fugitive emissions during the performance test according 
to the provisions of paragraph (e)(7); and
    (ii) Subsequent testing must be conducted in accordance with 
paragraphs (e)(4)(i) and (ii) of this section.
    (6) The installation of hooding that meets ACGIH Guidelines is 
considered impractical if any of the following conditions exist:
    (i) Building or equipment obstructions (for example, wall, ceiling, 
roof, structural beams, utilities, overhead crane or other 
obstructions) are present such that the temporary hood cannot be 
located consistent with acceptable hood design and installation 
practices;
    (ii) Space limitations or work area constraints exist such that the 
temporary hood cannot be supported or located to prevent interference 
with normal furnace operations or avoid unsafe working conditions for 
the furnace operator; or
    (iii) Other obstructions and limitations subject to agreement of 
the permitting authority for major sources, or the Administrator for 
area sources.
    (7) Testing procedures that will minimize fugitive emissions may 
include, but are not limited to the following:
    (i) Installing a hood that does not entirely meet ACGIH guidelines;
    (ii) Using the building as an enclosure, and measuring emissions 
exhausted from the building if there are no other furnaces or other 
significant sources in the building of the pollutants to be measured;
    (iii) Installing temporary baffles on those sides or top of furnace 
opening if it is practical to do so where they will not interfere with 
material handling or with the furnace door opening and closing;
    (iv) Increasing the exhaust rate from the furnace with draft fans, 
so as to capture emissions that might otherwise escape into the 
building if it can be done without increasing furnace emissions in a 
way that make the test non-representative;
    (v) Minimizing the time the furnace doors are open or the top is 
off;
    (vi) Delaying gaseous reactive fluxing until charging doors are 
closed and, for round top furnaces, until the top is on;
    (vii) Agitating or stirring molten metal as soon as practicable 
after salt flux addition and closing doors as soon as possible after 
solid fluxing operations, including mixing and dross removal;
    (viii) Keeping building doors and other openings closed to the 
greatest extent possible to minimize drafts that would divert emissions 
from being drawn into the furnace; or
    (ix) Maintaining burners on low-fire or pilot operation while the 
doors are open or the top is off.
* * * * *
0
8. Section 63.1513 is amended by adding paragraph (f) to read as 
follows:


Sec.  63.1513  Equations for determining compliance.

* * * * *
    (f) Periods of startup and shutdown. For a new or existing affected 
source, or a new or existing emission unit subject to an emissions 
limit in paragraphs Sec.  63.1505(b) through (j) expressed in units of 
pounds per ton of feed/charge, or [mu]g TEQ or ng TEQ per Mg of feed/
charge, demonstrate compliance during periods of startup and shutdown 
in accordance with paragraph (f)(1) of this section or determine your 
emissions per unit of feed/charge during periods of startup and 
shutdown in accordance with paragraph (f)(2) of this section. Startup 
and shutdown emissions for group 1 furnaces and in-line fluxers must be 
calculated individually, and not on the basis of a SAPU. Periods of 
startup and shutdown are excluded from the calculation of SAPU emission 
limits in Sec.  63.1505(k), the SAPU monitoring requirements in Sec.  
63.1510(t) and the SAPU emissions calculations in Sec.  63.1513(e).
    (1) For periods of startup and shutdown, records establishing a 
feed/charge rate of zero, a flux rate of zero, and that the affected 
source or emission unit was either heated with electricity, propane or 
natural gas as the sole sources of heat or was not heated, may be used 
to demonstrate compliance with the emission limit, or
    (2) For periods of startup and shutdown, divide your measured 
emissions in lb/hr or [mu]g/hr or ng/hr by the feed/charge rate in 
tons/hr or Mg/hr from your most recent performance test associated with 
a production rate greater than zero, or the rated capacity of the 
affected source if no prior performance test data is available.
0
9. Amend section 63.1514, as proposed to be added at 77 FR 8576 
(February 14, 2012), by revising paragraph (e) to read as follows:


Sec.  63.1514  Change of furnace classification.

* * * * *

[[Page 72912]]

    (e) Limit on Frequency of changing furnace operating mode.
    (1) Changing furnace operating mode including reversion to the 
previous mode, as provided in paragraphs (a) through (d) of this 
section, may not be done more frequently than 4 times in any 6-month 
period.
    (2) If additional changes are needed, the owner or operator must 
apply in advance to the permitting authority, for major sources, or the 
Administrator, for area sources, for approval.
0
10. Section 63.1517 is amended by adding paragraphs (b)(18) and (19) to 
read as follows:


Sec.  63.1517  Records.

* * * * *
    (b) * * *
    (18) For each period of startup or shutdown for which the owner or 
operator chooses to demonstrate compliance for an affected source based 
on a feed/charge rate of zero, a flux rate of zero and the use of 
electricity, propane or natural gas as the sole sources of heating or 
the lack of heating, the owner or operator must maintain the following 
records:
    (i) The date and time of each startup and shutdown,
    (ii) The quantities of feed/charge and flux introduced during each 
startup and shutdown, and
    (iii) The types of fuel used to heat the unit, or that no fuel was 
used, during startup and shutdown.
    (19) For owners or operators that choose to change furnace 
operating modes, the following records must be maintained:
    (i) The date and time of each change in furnace operating mode, and
    (ii) The nature of the change in operating mode (for example, group 
1 controlled furnace processing other than clean charge to group 2).
0
11. Table 2 to subpart RRR of part 63 is amended by revising the entry 
for ``All affected sources and emission units with an add-on air 
pollution control device'' to read as follows:

Table 2 to Subpart RRR of Part 63--Summary of Operating Requirements for
          New and Existing Affected Sources and Emission Units
------------------------------------------------------------------------
                                     Monitor type/         Operating
  Affected source/emission unit    operation/process     requirements
------------------------------------------------------------------------
All affected sources and          Emission capture    Design and install
 emission units with an add-on     and collection      in accordance
 air pollution control device.     system.             with ACGIH
                                                       Guidelines;
                                                       operate in
                                                       accordance with
                                                       OM&M plan (sweat
                                                       furnaces may be
                                                       operated
                                                       according to
                                                       63.1506(c)(4)).\b
                                                       \
 
                              * * * * * * *
------------------------------------------------------------------------
* * * * *
\b\ OM&M plan_Operation, maintenance, and monitoring plan.

* * * * *
0
12. Table 3 to subpart RRR of part 63 is amended by revising the entry 
for ``All affected sources and emission units with an add-on air 
pollution control device'' and revising footnote d to Table 3 to read 
as follows:

  Table 3 to Subpart RRR of Part 63--Summary of Monitoring Requirements
        for New and Existing Affected Sources and Emission Units
------------------------------------------------------------------------
                                     Monitor type/        Monitoring
  Affected source/emission unit    operation/process     requirements
------------------------------------------------------------------------
All affected sources and          Emission capture    Annual inspection
 emission units with an add-on     and collection      of all emission
 air pollution control device.     system.             capture,
                                                       collection, and
                                                       transport systems
                                                       to ensure that
                                                       systems continue
                                                       to operate in
                                                       accordance with
                                                       ACGIH Guidelines.
                                                       Inspection
                                                       includes
                                                       volumetric flow
                                                       rate measurements
                                                       or verification
                                                       of a permanent
                                                       total enclosure
                                                       using EPA Method
                                                       204.\d\
 
                              * * * * * * *
------------------------------------------------------------------------
\d\ The frequency of volumetric flow rate measurements may be decreased
  to once every 5 years if daily differential pressure measures or daily
  fan RPM measurements are made in accordance with Sec.   63.1510(d)(ii)
  and (iii). The frequency of annual verification of a permanent total
  enclosure may be decreased to once every 5 years if negative pressure
  measurements in the enclosure are made daily in accordance with Sec.
  63.1510(d)(iv). In lieu of volumetric flow rate measurements or
  verification of permanent total enclosure, sweat furnaces may
  demonstrate annually negative air flow into the sweat furnace opening
  in accordance with Sec.   63.1510(d)(3).

[FR Doc. 2014-27497 Filed 12-5-14; 8:45 am]
BILLING CODE 6560-50-P