Document ID: EPA-HQ-OAR-2020-0430-0140
Agency: epa
Document Type: Proposed Rule
Title: National Emission Standards for Hazardous Air Pollutants: Primary Copper Smelting
Posted Date: 2023-07-24T04:00Z

[Federal Register Volume 88, Number 140 (Monday, July 24, 2023)]
[Proposed Rules]
[Pages 47415-47437]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-15303]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0430; FRL-7522-04-OAR]
RIN 2060-AU63

National Emission Standards for Hazardous Air Pollutants: Primary 
Copper Smelting

AGENCY: Environmental Protection Agency (EPA).

ACTION: Supplemental notice of proposed rulemaking.

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SUMMARY: This action supplements our proposed amendments to the 
national emission standards for hazardous air pollutants (NESHAP) for 
the Primary Copper Smelting source category published in the Federal 
Register on January 11, 2022. In that action, the Environmental 
Protection Agency (EPA) proposed amendments based on the residual risk 
and technology review (RTR) for the major source category and the 
technology review for the area source category. Although the proposal 
included the technology review for the area source category, this 
supplemental proposal does not include any changes for the area source 
category. In order to complete the required technology review for the 
major source category, the EPA is proposing additional hazardous air 
pollutant (HAP) standards for the following pollutants: benzene, 
toluene, hydrogen chloride (HCl), chlorine, polycyclic aromatic 
hydrocarbons (PAH), naphthalene and dioxin/furans (D/F). The EPA also 
evaluated the potential for changes to the previously proposed residual 
risk assessment and the decisions related to risk. Furthermore, in this 
action the EPA is also proposing revised standards for certain 
provisions initially proposed in the January 11, 2022, RTR proposal 
based on additional information gathered since the publication of the 
2022 proposed rule.

DATES: Comments must be received on or before September 7, 2023. Under 
the Paperwork Reduction Act (PRA), comments on the information 
collection provisions are best assured of consideration if the Office 
of Management and Budget (OMB) receives a copy of your comments on or 
before August 23, 2023.
    Public hearing: If anyone contacts us requesting a public hearing 
on or before July 31, 2023, we will hold a virtual public hearing. See 
SUPPLEMENTARY INFORMATION for information on requesting and registering 
for a public hearing.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OAR-2020-0430, by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov/ 
(our preferred method). Follow the online instructions for submitting 
comments.
     Email: [email protected]. Include Docket ID No. EPA-
HQ-OAR-2020-0430 in the subject line of the message.
     Fax: (202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-
2020-0430.
     Mail: U.S. Environmental Protection Agency, EPA Docket 
Center, Docket ID No. EPA-HQ-OAR-2020-0430, Mail Code 28221T, 1200 
Pennsylvania Avenue NW, Washington, DC 20460.
     Hand/Courier Delivery: EPA Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. 
The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-
Friday (except Federal holidays).
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the SUPPLEMENTARY 
INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: For questions about this proposed 
action, contact Tonisha Dawson, Sector Policies and Programs Division 
(D243-02), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711; telephone number: (919) 541-1454; and email address: 
[email protected].

SUPPLEMENTARY INFORMATION: 

[[Page 47416]]

    Participation in virtual public hearing. To request a virtual 
public hearing, contact the public hearing team at (888) 372-8699 or by 
email at [email protected]. If requested, the hearing will be 
held via virtual platform on August 8, 2023. The hearing will convene 
at 11 a.m. Eastern Time (ET) and will conclude at 3 p.m. ET. The EPA 
may close a session 15 minutes after the last pre-registered speaker 
has testified if there are no additional speakers. The EPA will 
announce further details at https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air.
    If a public hearing is requested, the EPA will begin pre-
registering speakers for the hearing no later than 1 business day after 
a request has been received. To register to speak at the virtual 
hearing, please use the online registration form available at https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air or contact the public 
hearing team at (888) 372-8699 or by email at 
[email protected]. The last day to pre-register to speak at the 
hearing will be August 7, 2023. Prior to the hearing, the EPA will post 
a general agenda that will list pre-registered speakers in approximate 
order at: https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air.
    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 
hearings to run either ahead of schedule or behind schedule.
    Each commenter will have 4 minutes to provide oral testimony. The 
EPA encourages commenters to provide the EPA with a copy of their oral 
testimony electronically (via email) by emailing it to 
[email protected]. The EPA also recommends submitting the text of 
your oral testimony as written comments to the rulemaking docket.
    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 testimony and 
supporting information presented at the public hearing.
    Please note that any updates made to any aspect of the hearing will 
be posted online at https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air. While the EPA expects the hearing to go forward as set 
forth above, please monitor our website or contact the public hearing 
team at (888) 372-8699 or by email at [email protected] to 
determine if there are any updates. The EPA does not intend to publish 
a document in the Federal Register announcing updates.
    If you require the services of a translator or special 
accommodation such as audio description, please pre-register for the 
hearing with the public hearing team and describe your needs by July 
31, 2023. The EPA may not be able to arrange accommodations without 
advanced notice.
    Docket. The EPA has established a docket for this rulemaking under 
Docket ID No. EPA-HQ-OAR-2020-0430. All documents in the docket are 
listed in https://www.regulations.gov/. Although listed, some 
information is not publicly available, e.g., Confidential Business 
Information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the internet and will be publicly available only in hard 
copy. With the exception of such material, publicly available docket 
materials are available electronically in Regulations.gov.
    Instructions. Direct your comments to Docket ID No. EPA-HQ-OAR-
2020-0430. 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 CBI or other information whose disclosure is restricted by 
statute. Do not submit electronically to https://www.regulations.gov/ 
any information that you consider to be CBI or other information whose 
disclosure is restricted by statute. This type of information should be 
submitted as discussed below.
    The EPA may publish any comment received to its public docket. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. The EPA 
will generally not consider comments or comment contents located 
outside of the primary submission (i.e., on the Web, cloud, or other 
file sharing system). For additional submission methods, the full EPA 
public comment policy, information about CBI or multimedia submissions, 
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The https://www.regulations.gov/ website allows you to submit your 
comment anonymously, 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 
digital storage media 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.
    Submitting CBI. Do not submit information containing CBI to the EPA 
through https://www.regulations.gov/. Clearly mark the part or all of 
the information that you claim to be CBI. For CBI information on any 
digital storage media that you mail to the EPA, note the docket ID, 
mark the outside of the digital storage media as CBI, and identify 
electronically within the digital storage media 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 directly to the public docket through the procedures 
outlined in Instructions above. If you submit any digital storage media 
that does not contain CBI, mark the outside of the digital storage 
media clearly that it does not contain CBI and note the docket ID. 
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.
    Our preferred method to receive CBI is for it to be transmitted 
electronically using email attachments, File Transfer Protocol (FTP), 
or other online file sharing services (e.g., Dropbox, OneDrive, Google 
Drive). Electronic submissions must be transmitted

[[Page 47417]]

directly to the OAQPS CBI Office at the email address [email protected], 
and as described above, should include clear CBI markings and note the 
docket ID. If assistance is needed with submitting large electronic 
files that exceed the file size limit for email attachments, and if you 
do not have your own file sharing service, please email 
[email protected] to request a file transfer link. If sending CBI 
information through the postal service, please send it to the following 
address: OAQPS Document Control Officer (C404-02), OAQPS, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711, Attention Docket ID No. EPA-HQ-OAR-2020-0430. The mailed CBI 
material should be double wrapped and clearly marked. Any CBI markings 
should not show through the outer envelope.
    Preamble acronyms and abbreviations. Throughout this preamble the 
use of ``we,'' ``us,'' or ``our'' is intended to refer to the EPA. 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:

ACI activated carbon injection
ADEQ Arizona Department of Environmental Quality
ADL above detection limit
ANSI American National Standards Institute
BDL below detection limit
BTF beyond-the-floor
CAA Clean Air Act
CBI Confidential Business Information
CFR Code of Federal Regulations
D/F dioxins and furans
DLL detection level limited
DSI dry sorbent injection
EPA Environmental Protection Agency
GACT generally available control technology
HAP hazardous air pollutant(s)
HCl hydrogen chloride
ICR Information Collection Request
km kilometers
lbs pounds
lbs/hr pounds per hour
lb/ton pounds per ton
LEAN Louisiana Environmental Action Network
MACT maximum achievable control technology
MIR maximum individual risk
mg/dscm milligram per dry standard cubic meter
NAICS North American Industry Classification System
NESHAP national emission standards for hazardous air pollutants
ng TEQ/Mg nanograms Toxic Equivalent per megagrams
NTTAA National Technology Transfer and Advancement Act
OAQPS Office of Air Quality Planning and Standards
OMB Office of Management and Budget
PAH polycyclic aromatic hydrocarbons
PM particulate matter
PRA Paperwork Reduction Act
RDL representative detection level
RFA Regulatory Flexibility Act
RTR risk and technology review
SO2 sulfur dioxide
SO3 sulfur trioxide
SSM startup, shutdown, and malfunction
TEF toxicity equivalence factors
TEQ toxic equivalency
THC Total hydrocarbons
tpy tons per year
ug/m\3\ micrograms per cubic meter
UMRA Unfunded Mandates Reform Act
UOM unit of measure
UPL upper predictive level
VCS voluntary consensus standards
WESP wet electrostatic precipitator

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

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document and other related 
information?
II. Background
    A. What is the statutory authority for this action?
    B. What is this source category and how does the current NESHAP 
regulate its HAP emissions?
    C. What is the history of the Primary Copper Smelting Risk and 
Technology Review?
    D. What was included in the 2022 proposed RTR affecting major 
sources in the primary copper smelting source category?
    E. What data collection activities were conducted to support 
this action?
III. Analytical Results and Proposed Decisions
    A. What are the results of our analyses of unregulated 
pollutants and how did we establish the proposed MACT standards?
    B. What performance testing, monitoring, and recordkeeping and 
reporting are we proposing relative to the unregulated HAP emission 
limits?
    C. What revisions are we proposing specific to the emission 
limit for process fugitive emissions from roof vents at the anode 
refining operations from the 2022 proposed RTR?
    D. What revisions are we proposing specific to the emission 
limit for mercury from the 2022 proposed RTR?
    E. What emissions standards are we proposing for the Aisle 
Scrubber in this supplemental proposed rule that are different than 
decisions proposed in the 2022 proposed RTR?
    F. What are the results of risk analyses completed for this 
action?
    G. What other actions are we proposing, and what is the 
rationale for those actions?
    H. What compliance dates are we proposing and what is the 
rationale for the proposed compliance dates?
IV. Summary of Cost, Environmental, and Economic Impacts
    A. What are the affected sources?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
    F. What analysis of environmental justice did we conduct?
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 14094: Modernizing Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA) and 
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. General Information

A. Does this action apply to me?

    The source category that is the subject of this proposal is primary 
copper smelting major sources regulated under 40 CFR part 63, subpart 
QQQ. The North American Industry Classification System (NAICS) code for 
the primary copper smelting industry is 331410. This list of categories 
and NAICS codes is not intended to be exhaustive, but rather provides a 
guide for readers regarding the entities that this proposed action is 
likely to affect. The proposed standards, once promulgated, will be 
directly applicable to the affected sources. Federal, state, local, and 
tribal government entities would not be affected by this proposed 
action. As defined in the Initial List of Categories of Sources Under 
Section 112(c)(1) of the Clean Air Act Amendments of 1990 (see 57 FR 
31576; July 16, 1992) and Documentation for Developing the Initial 
Source Category List, Final Report (see EPA-450/3-91-030, July 1992), 
the primary copper smelting source category is any major source 
facility engaged in the pyrometallurgical process used for the 
extraction of copper from sulfur oxides, native ore concentrates, or 
other copper bearing minerals. As originally defined, the category 
includes, but is not limited to, the following smelting process units: 
roasters, smelting furnaces, and converters. Affected sources under the 
current major source NESHAP are

[[Page 47418]]

concentrate dryers, smelting furnaces, slag cleaning vessels, 
converters, and fugitive emission sources.

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. Following signature by the 
EPA Administrator, the EPA will post a copy of this proposed action at 
https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air. Following 
publication in the Federal Register, the EPA will post the Federal 
Register version of the proposal and key technical documents at this 
same website.
    A memorandum showing the rule edits that would be necessary to 
incorporate the changes to 40 CFR part 63, subpart QQQ proposed in this 
action is available in the docket (Docket ID No. EPA-HQ-OAR-2020-0430). 
The EPA also will post a copy of this document to https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air.

II. Background

A. What is the statutory authority for this action?

    The statutory authority for this action is provided by sections 112 
and 301 of the Clean Air Act (CAA), as amended (42 U.S.C. 7401 et 
seq.). Section 112 of the CAA establishes a two-stage regulatory 
process to develop standards for emissions of HAP from stationary 
sources. Generally, the first stage involves establishing technology-
based standards and the second stage involves evaluating those 
standards that are based on maximum achievable control technology 
(MACT) to determine whether additional standards are needed to address 
any remaining risk associated with HAP emissions. This second stage is 
commonly referred to as the ``residual risk review.'' In addition to 
the residual risk review, the CAA also requires the EPA to review 
standards set under CAA section 112 every 8 years and revise the 
standards as necessary taking into account any ``developments in 
practices, processes, or control technologies.'' This review is 
commonly referred to as the ``technology review.'' The discussion that 
follows identifies the most relevant statutory sections and briefly 
explains the contours of the methodology used to implement these 
statutory requirements. A more comprehensive discussion appears in the 
document titled CAA Section 112 Risk and Technology Reviews: Statutory 
Authority and Methodology, in the docket for this rulemaking.
    In the first stage of the CAA section 112 standard setting process, 
the EPA promulgates technology-based standards under CAA section 112(d) 
for categories of sources identified as emitting one or more of the HAP 
listed in CAA section 112(b). Sources of HAP emissions are either major 
sources or area sources, and CAA section 112 establishes different 
requirements for major source standards and area source standards. 
``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. All other sources are ``area sources.'' For major 
sources, CAA section 112(d)(2) provides that 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). These standards are commonly 
referred to as MACT standards. CAA section 112(d)(3) also establishes a 
minimum control level for MACT standards, known as the MACT ``floor.'' 
In certain instances, as provided in CAA section 112(h), the EPA may 
set work practice standards in lieu of numerical emission standards. 
The EPA must also consider control options that are more stringent than 
the floor. Standards more stringent than the floor are commonly 
referred to as beyond-the-floor (BTF) standards. For area sources, CAA 
section 112(d)(5) allows the EPA to set standards based on generally 
available control technologies or management practices (GACT standards) 
in lieu of MACT standards.
    The second stage in standard-setting focuses on identifying and 
addressing any remaining (i.e., ``residual'') risk pursuant to CAA 
section 112(f). For source categories subject to MACT standards, 
section 112(f)(2) of the CAA requires the EPA to determine whether 
promulgation of additional standards is needed to provide an ample 
margin of safety to protect public health or to prevent an adverse 
environmental effect. Section 112(d)(5) of the CAA provides that this 
residual risk review is not required for categories of area sources 
subject to GACT standards. Section 112(f)(2)(B) of the CAA further 
expressly preserves the EPA's use of the two-step approach 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 Residual 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 the United States Court of Appeals for the District of Columbia 
Circuit upheld the EPA's interpretation that CAA section 112(f)(2) 
incorporates the approach established in the Benzene NESHAP. See NRDC 
v. EPA, 529 F.3d 1077, 1083 (D.C. Cir. 2008).
    The approach incorporated into the CAA and used by the EPA to 
evaluate residual risk and to develop standards under CAA section 
112(f)(2) is a two-step approach. 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) 
\1\ of approximately 1-in-10 thousand.'' (54 FR at 38045). If risk is 
unacceptable, the EPA must determine the emissions standards necessary 
to reduce risks to an acceptable level without considering costs. In 
the second step of the approach, the EPA considers whether the 
emissions standards provide an ample margin of safety to protect public 
health ``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 to protect 
public health or determine that the standards being reviewed provide an 
ample margin of safety without any revisions. After conducting the 
ample margin of safety analysis, the Agency considers whether a more 
stringent standard is necessary to prevent, taking into consideration 
costs, energy, safety, and other relevant factors, an adverse 
environmental effect.
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    \1\ Although defined as ``maximum individual risk,'' MIR refers 
only to cancer risk. MIR, one metric for assessing cancer risk, is 
the estimated risk if an individual were exposed to the maximum 
level of a pollutant for a lifetime.
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    CAA section 112(d)(6) separately requires the EPA to review 
standards

[[Page 47419]]

promulgated under CAA section 112 and revise them ``as necessary 
(taking into account developments in practices, processes, and control 
technologies)'' no less often than every 8 years. While conducting this 
review, which we call the ``technology 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 EPA may consider cost in deciding whether to revise the 
standards pursuant to CAA section 112(d)(6). The EPA is also required 
to address regulatory gaps, such as missing standards for listed air 
toxics known to be emitted from the source category, and any new MACT 
standards must be established under CAA sections 112(d)(2) and (3), or, 
in specific circumstances, CAA sections 112(d)(4) or (h). Louisiana 
Environmental Action Network (LEAN) v. EPA, 955 F.3d 1088 (D.C. Cir. 
2020).
    As described in detail in section III of this preamble, pursuant to 
the authorities described above in this section, this supplemental 
proposed rule addresses additional currently unregulated emissions of 
HAP from the primary copper smelting major source category. In addition 
to the unregulated HAP addressed in the 2022 RTR proposed rule (87 FR 
1616; January 11, 2022), available data indicate the following 
unregulated pollutants are emitted from the source category: benzene, 
dioxins and furans, HCl, chlorine, PAH including naphthalene, and 
toluene. These pollutants are mainly emitted due to the combustion of 
natural gas and coke. Therefore, the EPA is proposing amendments 
establishing standards that reflect MACT for these pollutants emitted 
by the source category, pursuant to CAA sections 112(d)(2) and (3).

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

    Consistent with the description in section II.A. of this preamble, 
this supplemental proposal is applicable to major sources in the 
primary copper smelting major source category. There is one area source 
which is regulated by the primary copper smelting area source NESHAP 
(40 CFR part 63, subpart EEEEEE), but the following description is 
limited to the major source facilities consistent with this 
supplemental proposed rule. The primary copper smelting major source 
category includes any facility that is a major source of HAP and uses a 
pyrometallurgical process to produce anode copper from copper ore 
concentrates. Primary copper smelting begins with copper mines 
supplying the ore concentrate (typically 30 percent copper). In most 
cases, the moisture is reduced from the ore concentrate in dryers, and 
the concentrate is then fed through a smelting furnace where it is 
melted and reacts to produce copper matte. One existing smelter is able 
to feed its copper concentrate directly to the smelting furnace without 
prior drying. Copper matte is a molten solution of copper sulfide mixed 
with iron sulfide and is about 60 percent copper. The solution is 
further refined using converters to make blister copper, which is 
approximately 98 percent copper. Converters use oxidation to remove 
sulfide as sulfur dioxide (SO2) gas and the iron as a 
ferrous oxide slag. The majority of the SO2 gases are sent 
to a sulfuric acid plant. The slag is removed, cooled, and often 
processed again to remove any residual copper. The blister copper is 
reduced in the anode refining furnace to remove impurities and oxygen, 
typically by injecting natural gas and steam, to produce a high purity 
copper. The molten copper from the anode refining furnace is poured 
into molds and cooled to produce solid copper ingots called anodes. 
This process is known as casting. The anodes are sent to a copper 
refinery, either on-site or at an off-site location, for further 
purification using an electrolytic process to obtain high purity copper 
that is sold as a product. The processing units of interest at primary 
copper smelters, because of their potential to generate HAP emissions, 
are the following: dryers, smelting furnaces, copper converters, anode 
refining furnaces, and, if present, copper holding vessels, slag 
cleaning vessels, and matte drying and grinding plants. The smelting 
furnaces, converters and anode refining are sources of HAP emissions 
from point sources (i.e., stacks, control devices) and process fugitive 
emissions from roof vents. In addition, the transfers of matte, 
converter slag, and blister copper are sources of process fugitive 
emissions.
    There are two facilities (Asarco and Freeport--both located in 
Arizona) which are major sources of HAP emissions and are subject to 40 
CFR part 63, subpart QQQ, the major source NESHAP. The Asarco facility 
uses an INCO brand flash smelting furnace. Flash smelting furnaces 
consist of blowing fine, dried copper sulfide concentrate and silica 
flux with air, oxygen-enriched air or oxygen into a hot hearth-type 
furnace. The sulfide minerals in the concentrate react with oxygen 
resulting in oxidation of the iron and sulfur, which produces heat and 
therefore melting of the solids. The molten matte and slag are removed 
separately from the furnace as they accumulate, and the matte is 
transferred via ladles to the copper converters. The Freeport facility 
uses an ISASMELT smelting furnace. The ISASMELT process involves 
dropping wet feed through a feed port, such that dryers are not needed. 
A mixture of air, oxygen, and natural gas is blown through a vertical 
lance in the center of the furnace, generating heat and melting the 
feed. The molten metal is then tapped from the bottom and sent to an 
electric furnace to separate the matte from slag. The slag is removed 
from the electric furnace through tapholes and is transferred to slag 
pots via ladles. The matte is also removed from the electric furnace 
through tapholes and transferred to the converter via ladles.
    Molten blister copper is transferred from the converting vessel to 
an anode furnace for refining to further remove residual impurities and 
oxygen. The blister copper is reduced in the anode refining furnace to 
remove oxygen, typically by injecting natural gas and steam to produce 
a high purity copper. The molten copper from the anode refining furnace 
is poured into molds to produce solid copper ingots called anodes. The 
anode copper is sent to a copper refinery, either on-site or at another 
location, where it is further purified using an electrolytic process to 
obtain the high purity copper that is sold as a product. The copper 
refinery is not part of the primary copper smelting source category. 
The current NESHAP for major sources (40 CFR part 63, subpart QQQ) was 
proposed on April 20, 1998 (63 FR 19582), with a supplement to the 
proposed rulemaking published on June 26, 2000 (65 FR 39326). The final 
rule, promulgated on June 12, 2002 (67 FR 40478), established 
particulate matter (PM) standards as a surrogate for HAP metals for 
copper concentrate dryers, smelting furnaces, slag cleaning vessels, 
and existing converters. The major source NESHAP applies to major 
sources that use batch copper converters. Regarding new sources, the 
NESHAP prohibits batch converters for new sources, which indirectly 
means that any new source would need to install continuous converters 
or another technology. The reason for this prohibition for new sources 
is that continuous converters have lower process fugitive emissions 
than batch converters. Further explanation is provided in the 2002

[[Page 47420]]

NESHAP final rule preamble (67 FR 40478; June 12, 2002).
    The converter building is subject to an opacity limit in the NESHAP 
that only applies during performance testing. A fugitive dust plan is 
required to minimize fugitive dust emissions. Subpart QQQ also 
establishes requirements to demonstrate initial and continuous 
compliance with all applicable emission limitations, work practice 
standards, and operation and maintenance requirements. Annual 
performance testing is required to demonstrate compliance with the PM 
and opacity standards contained in the current NESHAP.

C. What is the history of the Primary Copper Smelting Risk and 
Technology Review?

    On January 11, 2022, the EPA proposed the risk and technology 
review required by CAA sections 112(d)(6) and 112(f)(2) for the NESHAP 
for Copper Smelting (hereafter referred to as the ``2022 proposed 
RTR'').\2\ Since the issuance of the 2022 proposed RTR, the EPA has 
obtained additional information that impacts the decisions made for 
certain amendments in the 2022 proposed RTR and that indicates there 
are additional unregulated HAP for the source category. Therefore, 
based on this new information, the EPA is proposing supplemental 
amendments to the NESHAP to ensure that all emissions of HAP from 
sources in the source category are regulated. Additionally, based on 
this new information and as described in more detail in section III of 
this preamble, we are proposing revised standards for certain 
amendments that were initially included in the 2022 proposed RTR for 
the copper smelting major source category.
---------------------------------------------------------------------------

    \2\ 87 FR 1616; January 11, 2022.
---------------------------------------------------------------------------

D. What was included in the 2022 proposed RTR affecting major sources 
in the primary copper smelting source category?

    Consistent with the statutory requirements described in section 
II.A of this preamble, the 2022 proposed RTR included a risk review 
pursuant to CAA section 112(f)(2) and a technology review pursuant to 
CAA section 112(d)(6) for the major source category. Additionally, the 
Agency reviewed available data to determine whether there were any 
unregulated emissions of HAP within the source category and evaluated 
the data for use in developing new emission standards.
    As described in the 2022 proposed RTR, as part of the technology 
review for the major source category, the EPA identified previously 
unregulated processes and pollutants and proposed to regulate them 
under CAA section 112(d)(2) and (3) for the major source NESHAP (40 CFR 
part 63, subpart QQQ), as follows:
     PM limits, as a surrogate for metal HAP, for anode 
refining point sources at existing and new sources.
     PM limits, as a surrogate for metal HAP, for process 
fugitive emissions from roofline vents of smelting furnaces at existing 
and new sources.
     PM limits, as a surrogate for metal HAP, for process 
fugitive emissions from converters at existing and new sources.
     PM limits, as a surrogate for metal HAP, for process 
fugitive emissions from roof vents at anode refining operations at 
existing and new sources.
     Mercury limits for any existing and new combination of 
stacks or other vents from the copper concentrate dryers, converting 
department, the anode refining department, and the smelting vessels 
affected sources.
     PM limits, as a surrogate for metal HAP, for new 
converters.
    The Agency also completed a review of residual risk for the source 
category consistent with CAA section 112(f). Based on the results of 
the risk review, the EPA proposed that risks from emissions of air 
toxics from the major source category were unacceptable due to HAP 
metal (primarily lead and arsenic) emissions. The largest contributor 
to risk was the process fugitive emissions from roof vents at anode 
refining operations (constituting about 71 percent of the MIR) followed 
by the aisle scrubber (constituting about 23 percent of the MIR) at the 
Freeport facility. In the 2022 proposed RTR, the EPA concluded that the 
emission limits proposed under CAA section 112(d)(2) and (3) for the 
process fugitive emissions from roof vents at anode refining operations 
will require additional controls that are expected to provide enough 
emissions reduction to reduce risks to an acceptable level; therefore, 
they were also proposed pursuant to CAA section 112(f)(2). The Agency 
also considered proposing additional control requirements for the aisle 
scrubber as part of the Agency's ample margin of safety analysis. The 
EPA did not propose any control requirements for the aisle scrubber in 
the 2022 proposed RTR but did seek comment on its analysis (including 
the costs, costs effectiveness, and risk reductions) and whether the 
EPA should establish more stringent standards to reduce HAP metal 
emissions from the aisle scrubber. Also, as part of the ample margin of 
safety analysis, the EPA evaluated additional work practices to reduce 
fugitive dust emissions, consistent with Asarco's current consent 
decree. The Agency found that the implementation of a more robust 
fugitive dust plan would result in an unquantified reduction of HAP, at 
minimal cost for implementation, and therefore proposed this 
requirement in the 2022 proposed RTR. In the 2022 proposed RTR, the EPA 
proposed that the combination of the standards for anode refining roof 
vents, fugitive dust plan and all other current standards in the NESHAP 
would ensure the NESHAP provides an ample margin of safety to protect 
public health.
    The EPA did not identify developments in practices, processes, or 
control technologies pursuant to CAA section 112(d)(6) to achieve 
further emissions reductions beyond the controls and reductions 
proposed under the risk review for major sources.
    The EPA also proposed to remove exemptions for periods of startup, 
shutdown, and malfunction (SSM) and specified that the emission 
standards apply at all times and proposed a requirement for electronic 
reporting of performance test results and notification of compliance 
reports.
    Of central relevance to this supplemental proposal are the proposed 
emission limits for the process fugitive emissions from roof vents at 
anode refining operations at new and existing sources; the mercury 
limits for any existing and new combination of stacks or other vents 
from the copper concentrate dryers, converting department, the anode 
refining department, and the smelting vessels affected sources; the 
potential control options for metal HAP at the aisle scrubber; and the 
proposed MACT limits for additional unregulated HAP. As detailed in the 
next section II.E of this preamble, the EPA has obtained additional 
information relative to these processes and pollutants. As a result of 
evaluating this new information, we are proposing both revised and new 
requirements in this supplemental proposed rulemaking (compared to the 
proposed requirements in the 2022 proposed RTR) for these processes and 
pollutants. A detailed discussion is provided in section III of this 
preamble, which covers what was proposed for these processes and 
pollutants in the 2022 proposed RTR, the evaluation of new information, 
and what we are proposing for these processes and pollutants in this 
supplemental proposed rulemaking.

[[Page 47421]]

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

    The 2022 proposed RTR was published in the Federal Register on 
January 11, 2022 (87 FR 1616). The initial 45-day comment period was 
extended by 60 days and ended on April 26, 2022. During the comment 
period, the EPA received public comments from industry, tribal nations, 
two environmental groups, Arizona Department of Environmental Quality 
(ADEQ), and private citizens. Some of the comments on the proposed 
rulemaking claimed that there are additional unregulated HAP from the 
source category beyond those the EPA addressed in the 2022 proposed 
RTR. In response to these public comments, the EPA issued a CAA section 
114 information request to collect further information. The section 114 
information request was sent to the Freeport facility only, as the 
Asarco facility has been idled since October 2019. The section 114 
information request was delivered to the Freeport facility on August 
31, 2022. The key components of the response to the request included 
the following:
     Results of performance testing which was required to be 
conducted in two phases. Initially, performance tests were conducted at 
the vent fume and aisle scrubber stacks of the Freeport facility for 
the following compounds: benzene, 1,4-dichlorobenzene, formaldehyde, 
hexane, hydrogen fluoride, hydrochloric acid, toluene, total 
hydrocarbons, polycyclic aromatic hydrocarbons including naphthalene, 
and dioxins and furans. For compounds that were detected at the vent 
fume and aisle scrubber, additional performance testing and reporting 
were required to be conducted at the acid plant tail gas stack. The 
Agency did not request chlorine testing; however, chlorine test results 
were included in respective test reports.
     Data regarding the costs and feasibility of installing 
additional controls for the aisle scrubber. This included the 
evaluation of two options: (1) installing a wet electrostatic 
precipitator (WESP) which would operate in series with the aisle 
scrubber to provide further emissions reductions, and (2) installing a 
baghouse which would control the secondary converter emissions before 
they enter the aisle scrubber.
     Detailed information regarding all input materials.
    In addition to the information collected through the section 114 
information request, the EPA also received information during and after 
the public comment period of the 2022 proposed RTR. This additional 
information included cost estimates for the control devices which would 
be required by the emission limits proposed in the 2022 proposed RTR 
(e.g., for mercury, lead and arsenic). It also included additional 
performance testing results for the roofline vents, vent fume, aisle 
scrubber, and acid plant. Finally, Freeport also voluntarily performed 
an additional performance test for mercury in 2022 and submitted those 
results to the EPA. The data collected and used in this action are 
provided in the docket for this action.
    Regarding the anode roofline vents, we received one additional 
stack test that resulted in a small increase to the annual emissions of 
lead, which we now estimate to be 4.47 tons/yr, relative to the 
estimate in the 2022 proposed rule, which was 4.09 tons/yr. For 
mercury, based on the additional mercury test, we now estimate mercury 
emissions from point and non-point sources at the Freeport facility to 
be 139 lb/yr, while the Asarco mercury emissions are unchanged from the 
2022 Proposed RTR (10 lb/yr). Finally, we received two new stack tests 
for the aisle scrubber at the Freeport facility, and based on these new 
test data, the estimates of PM metals emissions from the aisle scrubber 
are slightly lower compared to the 2022 proposed RTR, but only have a 
small effect on the overall risk assessment results. Nevertheless, we 
updated our risk analysis based on the additional data and concluded 
that the new data would not change our proposed determination that risk 
is unacceptable at baseline. We did not revise or redo the demographic 
analysis. The 2022 risk assessment and demographics analyses conducted 
for this action are available in the preamble of the 2022 proposed rule 
(87 FR 1616; January 11, 2022) and associated technical documents cited 
in that 2022 preamble. These documents can also be found in the docket 
of this supplemental proposal. Aspects of the updated risk review are 
summarized in sections III.C. and II.E of this preamble, and a more 
detailed discussion is provided in section III.F of this preamble.

III. Analytical Results and Proposed Decisions

    In this section, the EPA describes the analytical results and 
proposed decisions for addressing the additional unregulated HAP for 
the major source category. Additionally, this section discusses 
analytical results and revised decisions for certain provisions of the 
2022 proposed RTR. For more information regarding the types of 
analytical procedures used and the types of information the EPA 
evaluates for actions, see section III of the 2022 proposed rule (87 FR 
1616; January 11, 2022). These revised decisions affect the proposed 
emission limits for the process fugitive emissions from roof vents at 
anode refining operations at new and existing sources; the mercury 
limits for any existing and new combination of stacks or other vents 
from the copper concentrate dryers, converting department, the anode 
refining department, and the smelting vessels affected sources; and the 
proposed regulatory options for the particulate metal HAP (e.g., lead, 
arsenic) for the aisle scrubber at the Freeport facility. Finally, the 
EPA is proposing amendments to address the use of bypass stacks for 
major sources within the primary copper smelting category.

A. What are the results of our analyses of unregulated pollutants and 
how did we establish the proposed MACT standards?

    As mentioned in section II.E of this preamble, the EPA received 
comments on the 2022 proposed RTR concerning unregulated HAP from the 
major sources within the primary copper smelting category. In response, 
the EPA issued a CAA section 114 information request to the Freeport 
facility on August 31, 2022. The CAA section 114 information request 
required performance testing in two phases. Initially, performance 
testing was to be conducted for the required HAP at the vent fume and 
aisle scrubber. The acid plant stack was required to be tested for a 
required HAP only if the preliminary test results from the vent fume 
stack demonstrated that the pollutant is emitted above detection levels 
(ADL) for at least one sample run. Any pollutant that was not ADL at 
the vent fume stack was not required to be tested at the acid plant 
stack because it was assumed that the pollutant would not be detected 
at the acid plant stack as well. A summary of the HAP tested, the EPA 
test method, and the results by stack by detection classification 
(e.g., ADL; below detection levels (BDL); detection level limited 
(DLL)) are shown in Table 1. We note that while not required, the test 
report for the vent fume and aisle scrubber included results for 
chlorine. Complete copies of the stack test reports for the vent fume 
and aisle scrubber as well as the acid plant are available in the 
docket for this supplemental rule.\3\
---------------------------------------------------------------------------

    \3\ The vent fume and aisle scrubber test report was initially 
submitted to the EPA on November 25, 2022. The EPA sent Freeport 
several questions on the test report and Freeport submitted a 
revised version of the test report on February 10, 2023. All 
versions of the test report and related EPA correspondence are 
available in the docket EPA-HQ-OAR-2020-0430.

[[Page 47422]]

 Table 1--Summary of Unregulated HAP Performance Testing for the Major Source Copper Smelting Source Category in
                                                    2022-2023
----------------------------------------------------------------------------------------------------------------
                                                                    Vent fume/aisle
                 HAP                         Test method                scrubber                Acid plant
----------------------------------------------------------------------------------------------------------------
Benzene..............................  EPA Method 18..........  DLL....................  BDL.
1,4-dichlorobenzene..................  EPA Method 18..........  BDL....................  Not tested.
Hexane...............................  EPA Method 18..........  BDL....................  Not tested.
Toluene..............................  EPA Method 18..........  DLL....................  BDL.
Formaldehyde.........................  EPA Method 320.........  BDL....................  Not tested.
THC..................................  EPA Method 25A.........  N/A....................  N/A.
HCl..................................  EPA Method 26A.........  ADL....................  ADL.
Chlorine.............................  EPA Method 26A.........  ADL....................  Not tested.
Hydrogen Fluoride....................  EPA Method 26A.........  BDL....................  Not tested.
PAH (including Naphthalene)..........  EPA OTM 46.............  DLL....................  DLL.
Dioxins and Furans...................  EPA OTM 46.............  DLL....................  DLL.
----------------------------------------------------------------------------------------------------------------
* Revisions of Method 23 finalized March 20, 2023, is equivalent to OTM-46.

    As described in more detail in the following sections III.A.1 
through III.A.5 of this preamble, the EPA is proposing a source 
category MACT emission limit pursuant to CAA section 112(d)(2) and (3) 
for each unregulated HAP that was found to be emitted through these 
performance tests. The EPA contemplated using the total hydrocarbons 
(THC) results as a surrogate for some of the organics (e.g., benzene, 
toluene) but has decided to not propose THC as a surrogate, since the 
THC test was not conducted in accordance with all of the requirements 
of the EPA test method.
    The ``MACT floor'' for existing sources is calculated based on the 
average performance of the best-performing units in each category or 
subcategory and on a consideration of the variability of HAP emissions 
from these units. The MACT floor for new sources is based on the single 
best-performing source, with a similar consideration of variability. 
The MACT floor for new sources cannot be less stringent than the 
emissions performance that is achieved in practice by the best-
controlled similar source. Also as described in section II.E of this 
preamble, the section 114 request was issued to the only currently 
operating major source copper smelting facility, Freeport. Therefore, 
the proposed MACT floor for existing and new sources will be determined 
using these data (i.e., the proposed MACT emission limits are the same 
for existing and new sources). To account for variability in the copper 
smelting operations and resulting emissions, we calculated the MACT 
floors using the 99 percent Upper Predictive Limit (UPL) using all 
available stack test data.\4\ We are proposing MACT floor limits in 
units of mass of emissions allowed per mass of concentrate feed (for 
example, a proposed emissions limit of 0.0017 lbs of benzene per ton 
concentrated ore fed).
---------------------------------------------------------------------------

    \4\ For more information regarding the general use of the UPL 
and why it is appropriate for calculating MACT floors, see Use of 
Upper Prediction Limit for Calculating MACT Floors (UPL Memo), which 
is available in the docket for this action.
---------------------------------------------------------------------------

    The UPL approach addresses variability of emissions data from the 
best-performing source or sources in setting MACT standards. The UPL 
also accounts for uncertainty associated with emission values in a 
dataset, which can be influenced by components such as the number of 
samples available for developing MACT standards and the number of 
samples that will be collected to assess compliance with the emission 
limit. The UPL approach has been used in many environmental science 
applications. As explained in more detail in the UPL Memo cited above, 
the EPA uses the UPL approach to reasonably estimate the emissions 
performance of the best-performing source or sources to establish MACT 
floor standards.
    Additionally, we reviewed the December 13, 2011, memorandum from 
Peter Westlin and Ray Merrill titled Data and procedure for handling 
below detection level data in analyzing various pollutant emissions 
databases for MACT and RTR emissions limits (Docket ID No. EPA-HQ-OAR-
2017-0015), which describes the procedure for handling BDL data and 
developing representative detection level (RDL) data when setting MACT 
emission limits. In accordance with these guidance documents, the 
proposed new and existing UPL emission standards for each applicable 
compound (i.e., benzene, toluene, HCl, chlorine, PAH (excluding 
naphthalene), naphthalene, and D/F) were compared to the emission limit 
value determined to be equivalent to 3 times the RDL (3xRDL) \5\ of the 
test method. If the 3xRDL value was larger than the MACT Floor 99 
percent UPL value, then the proposed MACT floor limit is proposed as 
the 3xRDLvalue of the test method.
---------------------------------------------------------------------------

    \5\ The factor of three used in the 3xRDL calculation is based 
on a scientifically accepted definition of level of quantitation--
simply stated, the level where a test method performs with 
acceptable precision. The level of quantitation has been defined as 
ten times the standard deviation of seven replicate analyses of a 
sample at a concentration level close to the MDL units of the 
emission standard is then compared to the MACT floor value to ensure 
that the resulting emission limit is in a range that can be measured 
with reasonable precision. In other words, if the 3xRDL value were 
less than the calculated floor (e.g., calculated from the UPL), we 
would conclude that measurement variability has been adequately 
addressed; if it were greater than the calculated floor, we would 
adjust the emissions limit to comport with the 3xRDL value to 
address measurement variability.
---------------------------------------------------------------------------

    Further information on the development of the 99 percent UPL and 
3xRDL values for compounds for which emission standards are being 
proposed is included in a memorandum entitled, Proposed Maximum 
Achievable Control Technology (MACT) Floor Analysis for Unregulated HAP 
for the Primary Copper Smelting Major Source Category which is 
available in the docket for this rulemaking (Docket ID EPA-HQ-OAR-2020-
0430).
    In addition, the EPA must examine more stringent BTF regulatory 
options to determine MACT. Unlike the floor minimum stringency 
requirements, the EPA must consider various impacts (such as costs and 
cost effectiveness) of the more stringent regulatory options in 
determining whether MACT standards should reflect beyond-the-floor 
requirements. If the EPA concludes that the more stringent regulatory 
options have unreasonable impacts, the EPA

[[Page 47423]]

selects the MACT floor as MACT. However, if the EPA concludes that 
impacts associated with beyond-the-floor levels of control are 
reasonable in light of additional emissions reductions achieved, the 
EPA selects those BTF levels as MACT.
1. Benzene
    The performance testing conducted at Freeport included the results 
of stack testing for benzene using EPA Method 18. The proposed MACT 
floor emissions limit was calculated by summing the emission rates from 
the vent fume, aisle scrubber and acid plant combined, accounting for 
variability using the 99 percent UPL. Using this approach, we 
calculated a source category MACT floor emissions limit of 0.0017 lbs 
benzene/ton concentrated ore fed for new and existing sources. Based on 
the available data, the Agency concludes that both facilities in the 
major source copper smelting source category would be able to meet the 
MACT floor emissions limit with no additional controls.
    We then evaluated and considered a BTF option to further reduce 
emissions of benzene from new and existing sources. Based on the 
available test data, the Agency estimates that the aisle scrubber is 
the largest source of benzene emissions at Freeport, accounting for 87 
percent of the total, with an estimated 414 lbs/yr of benzene 
emissions. The BTF option for existing sources would require Freeport 
to install and operate an activated carbon injection (ACI) system with 
the existing air pollution control device (i.e., aisle scrubber). The 
Agency estimates the ACI system would achieve approximately 60 percent 
reduction of benzene from the aisle scrubber (i.e., 248 lbs/yr 
reduction of benzene). The EPA estimates $0.6 million for capital 
costs, and annualized costs are $2.7 million. This results in a cost 
effectiveness of approximately $22 million per ton of benzene reduced. 
We do not find costs associated with this BTF option to be reasonable 
and are therefore not proposing a BTF emission limit for benzene. 
Instead, we are proposing the source category MACT floor emissions 
limit of 0.0017 lbs benzene/ton concentrated ore fed for new and 
existing sources. A detailed description of the analysis of benzene 
emissions, the controls necessary to reduce benzene emissions, and the 
cost of these controls is included in the document, Estimated Cost for 
Beyond-the-floor Controls for HAP Emissions from Primary Copper 
Smelting Facilities, located in the docket (Docket ID No. EPA-HQ-OAR-
2020-0430).
2. Toluene
    The performance testing conducted at Freeport included the results 
of stack testing for toluene using EPA Method 18. The proposed MACT 
floor emissions limit was calculated by summing the emission rates from 
the vent fume, aisle scrubber and acid plant combined, accounting for 
variability using the 99 percent UPL. Using this approach, we 
calculated a source category MACT floor emissions limit of 0.00084 lbs 
toluene/ton concentrated ore fed for new and existing sources. Based on 
the available data, the Agency concludes that both facilities in the 
major source copper smelting source category would be able to meet the 
MACT floor emissions limit with no additional controls.
    We then evaluated and considered a BTF option to further reduce 
emissions of toluene from new and existing sources. Based on the 
available test data, the Agency estimates that the aisle scrubber is 
the largest source of toluene emissions at Freeport, accounting for 66 
percent of the total, with an estimated 187 lbs/yr of toluene 
emissions. The BTF option for existing sources would require Freeport 
to install and operate an ACI system with the existing air pollution 
control device (i.e., aisle scrubber). The Agency estimates the ACI 
system would achieve approximately 60 percent reduction of toluene from 
the aisle scrubber (i.e., 112 lbs/yr reduction of toluene). The EPA 
estimates $0.6 million for capital costs, and annualized costs are $2.7 
million. This results in a cost effectiveness of approximately $48 
million per ton of toluene reduced. We do not find costs associated 
with this BTF option to be reasonable and are therefore not proposing a 
BTF emission limit for toluene. Instead, we are proposing the source 
category MACT floor emissions limit of 0.00084 lbs toluene/ton 
concentrated ore fed for new and existing sources. A detailed 
description of the analysis of toluene emissions, the controls 
necessary to reduce toluene emissions, and the cost of these controls 
is included in the document, Estimated Cost for Beyond-the-floor 
Controls for HAP Emissions from Primary Copper Smelting Facilities, 
located in the docket (Docket ID No. EPA-HQ-OAR-2020-0430).
3. HCl
    The performance testing conducted at Freeport included the results 
of stack testing for HCl using EPA Method 26A. The proposed MACT floor 
emissions limit was calculated by summing the emission rates from the 
vent fume, aisle scrubber and acid plant combined, accounting for 
variability using the 99 percent UPL. The 99 percent UPL value HCl was 
0.0013. The 3xRDL was found to be slightly larger, 0.0015 pounds per 
ton (lb/ton) concentrated ore fed, so consistent with EPA guidelines, 
we have determined that the 3xRDL value (0.0015 lb/ton) represents the 
MACT floor emissions limit for new and existing sources. Based on the 
available data, the Agency concludes that both facilities in the major 
source copper smelting source category would be able to meet the 
emissions limit with no additional controls.
    We then evaluated and considered a BTF option to further reduce 
emissions of HCl from new and existing sources. Based on the available 
test data, the Agency estimates that the aisle scrubber is the largest 
source of HCl emissions at Freeport, accounting for 55 percent of the 
total, with an estimated 682 lbs/yr of HCl emissions. The BTF option 
for existing sources would require Freeport to install and operate a 
dry sorbent injection (DSI) system with the existing air pollution 
control device (i.e., aisle scrubber). The Agency estimates the DSI 
system would achieve approximately 98 percent reduction of HCl from the 
aisle scrubber (i.e., 668 lbs/yr reduction of HCl). The EPA estimates 
$0.6 million for capital costs, and annualized costs are $0.5 million. 
This results in a cost effectiveness of approximately $1.5 million per 
ton of HCl reduced. We do not find costs associated with this BTF 
option to be reasonable and are therefore not proposing a BTF emission 
limit for HCl. Instead, we are proposing the source category MACT floor 
emissions limit of 0.0015 lb/ton concentrated ore fed for HCl for new 
and existing sources. A detailed description of the analysis of HCl 
emissions, the controls necessary to reduce HCl emissions, and the cost 
of these controls is included in the document, Estimated Cost for 
Beyond-the-floor Controls for HAP Emissions from Primary Copper 
Smelting Facilities, located in the docket (Docket ID No. EPA-HQ-OAR-
2020-0430).
4. Chlorine
    The EPA did not require facilities to test for chlorine, however 
the performance testing conducted at Freeport included the results of 
stack testing for chlorine using EPA Method 26A. Because the acid plant 
had no data for chlorine, a percentage was calculated from the ratio of 
HCl to chlorine at the aisle scrubber and vent fume stack. The highest 
average ratio was used to estimate the chlorine emissions for the acid 
plant. The proposed MACT floor emissions limit was calculated by 
summing the

[[Page 47424]]

emission rates from the vent fume and aisle scrubber and the estimated 
emission rate from the acid plant, accounting for variability using the 
99 percent UPL. Using this approach, we calculated a source category 
MACT floor emissions limit of 0.0054 lbs chlorine/ton concentrated ore 
fed for new and existing sources. Based on the available data, the 
Agency concludes that both facilities in the major source copper 
smelting source category would be able to meet the emissions limit with 
no additional controls.
    We then evaluated and considered a BTF option to further reduce 
emissions of chlorine from new and existing sources. Based on the 
available test data, the Agency estimates that the aisle scrubber is 
the largest source of chlorine emissions at Freeport, accounting for 53 
percent of the total, with an estimated 2,490 lbs/yr of chlorine 
emissions. The BTF option for existing sources would require Freeport 
to install and operate a DSI system with the existing air pollution 
control device (i.e., aisle scrubber). The Agency estimates the DSI 
system would achieve approximately 98 percent reduction of chlorine 
from the aisle scrubber (i.e., 2,440 lbs/yr reduction of chlorine). The 
EPA estimates $0.6 million for capital costs, and annualized costs are 
$0.5 million. This results in a cost effectiveness of approximately 
$0.4 million per ton of chlorine reduced. We do not find costs 
associated with BTF options to be reasonable and are therefore not 
proposing a BTF emission limit for chlorine. Instead, we are proposing 
the source category MACT floor emissions limit of 0.0054 lbs chlorine/
ton concentrated ore fed for new and existing sources. A detailed 
description of the analysis of chlorine emissions, the controls 
necessary to reduce chlorine emissions, and the cost of these controls 
is included in the document, Estimated Cost for Beyond-the-floor 
Controls for HAP Emissions from Primary Copper Smelting Facilities, 
located in the docket (Docket ID No. EPA-HQ-OAR-2020-0430).
5. PAH
    The performance testing conducted at Freeport included the results 
of stack testing for PAH using EPA OTM-46. EPA OTM-46 is nearly 
identical to the updated EPA Method 23, for which revisions were 
promulgated on March 20, 2023 (88 FR 16732). In reviewing the test 
results, we found that approximately 70 percent of the PAH measured was 
naphthalene; therefore, we are proposing a PAH MACT floor emissions 
limit excluding naphthalene and a separate naphthalene MACT floor 
emissions limit. These proposed MACT floor emissions limits were 
calculated by summing the emission rates from the vent fume, aisle 
scrubber and acid plant combined, accounting for variability using the 
99 percent UPL. We are proposing a source category MACT floor emissions 
limit for PAH excluding naphthalene of 0.0001 lbs PAH excluding 
naphthalene/ton concentrated ore fed for new and existing sources. We 
are proposing a source category MACT floor emissions limit for 
naphthalene of 0.00028 lbs naphthalene/ton concentrated ore fed for new 
and existing sources. Based on the available data, the Agency concludes 
that both facilities in the major source copper smelting source 
category would be able to meet these MACT floor emissions limits with 
no additional controls.
    We also evaluated and considered a BTF option to further reduce 
emissions of PAH and naphthalene from new and existing sources. Based 
on the available test data, the Agency estimates that the aisle 
scrubber is the largest source of PAH and naphthalene emissions at 
Freeport, accounting for 77 percent of the total, with an estimated 97 
lbs/yr of PAH emissions. The BTF option for existing sources would 
require Freeport to install and operate an ACI system with the existing 
air pollution control device (i.e., aisle scrubber). The Agency 
estimates the ACI system would achieve approximately 60 percent 
reduction of PAH from the aisle scrubber (i.e., 58 lbs/yr reduction of 
PAH). The EPA estimates $0.6 million for capital costs, and annualized 
costs are $2.7 million. This results in a cost effectiveness of 
approximately $92 million per ton of PAH reduced. We do not find costs 
associated with BTF options to be reasonable and are therefore not 
proposing a BTF emission limit for PAH. Because it was not cost 
effective to propose further control of PAH, and since naphthalene is 
one compound in this group, we conclude it is also not cost effective 
to require BTF controls for naphthalene. Therefore, we are proposing 
the MACT floor limits for PAHs and naphthalene described previously in 
this section. A detailed description of the analysis of PAH emissions, 
the controls necessary to reduce PAH emissions, and the cost of these 
controls is included in the document, Estimated Cost for Beyond-the-
floor Controls for HAP Emissions from Primary Copper Smelting 
Facilities, located in the docket (Docket ID No. EPA-HQ-OAR-2020-0430).
6. D/F
    The performance testing conducted at Freeport included the results 
of stack testing for congeners of D/F using EPA OTM-46. The proposed 
MACT floor emissions limit was calculated by summing the emission rates 
from the vent fume, aisle scrubber and acid plant combined, accounting 
for variability using the 99 percent UPL. We are proposing a source 
category MACT floor emissions limit of 60 nanograms D/F Toxic 
Equivalent (TEQ)/Mg concentrated ore fed for new and existing sources. 
Based on the available data, the Agency concludes that both facilities 
in the major source copper smelting source category would be able to 
meet the MACT floor emissions limit with no additional controls.
    We also evaluated and considered a BTF option to further reduce 
emissions of D/F from new and existing sources. Based on the available 
test data, the Agency estimates that the aisle scrubber is the largest 
source of D/F emissions at Freeport, accounting for 83 percent of the 
total, with an estimated 0.04 grams/yr of D/F TEQ emissions. The BTF 
option for existing sources would require Freeport to install and 
operate an ACI system with the existing air pollution control device 
(i.e., aisle scrubber). The Agency estimates the ACI system would 
achieve approximately 85 percent reduction of D/F from the aisle 
scrubber (i.e., 0.03 grams/yr reduction of D/F TEQ). The EPA estimates 
$0.6 million for capital costs, and annualized costs are $2.7 million. 
This results in a cost effectiveness of approximately $83 million per 
gram of D/F TEQ reduced. We do not find costs associated with the BTF 
option to be reasonable and are therefore not proposing a BTF emission 
limit for D/F. Therefore, we are proposing the MACT floor limit 
described previously in this section. A detailed description of the 
analysis of D/F emissions, the controls necessary to reduce D/F 
emissions, and the cost of these controls is included in the document, 
Estimated Cost for Beyond-the-floor Controls for HAP Emissions from 
Primary Copper Smelting Facilities, located in the docket (Docket ID 
No. EPA-HQ-OAR-2020-0430).
7. Summary of Proposed New and Existing Source Limits for Copper 
Smelting
    The proposed emission limits for new and existing sources in the 
major source copper smelting source category are summarized in Table 2.

[[Page 47425]]

 Table 2--Summary of Proposed New and Existing Source MACT Emission Limits for the Major Source Copper Smelting
                                                 Source Category
----------------------------------------------------------------------------------------------------------------
                                               Existing source                           New source
                HAP                -----------------------------------------------------------------------------
                                         Limit      Unit of Measure (UOM)       Limit               UOM
----------------------------------------------------------------------------------------------------------------
Benzene...........................         1.7E-03  lb/ton concentrated           1.7E-03  lb/ton concentrated
                                                     ore fed.                               ore fed.
Toluene...........................         8.4E-04  lb/ton concentrated           8.4E-04  lb/ton concentrated
                                                     ore fed.                               ore fed.
HCl...............................         1.5E-03  lb/ton concentrated           1.5E-03  lb/ton concentrated
                                                     ore fed.                               ore fed.
Chlorine..........................         5.4E-03  lb/ton concentrated           5.4E-03  lb/ton concentrated
                                                     ore fed.                               ore fed.
PAH (excluding Naphthalene).......         1.0E-04  lb/ton concentrated           1.0E-04  lb/ton concentrated
                                                     ore fed.                               ore fed.
Naphthalene.......................         2.8E-04  lb/ton concentrated           2.8E-04  lb/ton concentrated
                                                     ore fed.                               ore fed.
Dioxins and Furans................              60  ng TEQ/Mg                          60  ng TEQ/Mg
                                                     concentrated ore fed.                  concentrated ore
                                                                                            fed.
----------------------------------------------------------------------------------------------------------------

B. What performance testing, monitoring, and recordkeeping and 
reporting are we proposing relative to the unregulated HAP emission 
limits?

    We are proposing, based on the new and existing source emissions 
limits for copper smelting, that new sources demonstrate initial 
compliance upon start-up, and existing sources demonstrate initial 
compliance within 1 year after the promulgation of the final rule. We 
are proposing that the initial performance tests to demonstrate 
compliance with the MACT standards of Table 2 of this preamble are 
conducted using the methods identified in Table 3.

                Table 3--Summary of Proposed Test Methods
------------------------------------------------------------------------
                 Pollutant                           EPA method
------------------------------------------------------------------------
Benzene...................................  EPA Method 18.
Toluene...................................  EPA Method 18.
HCl.......................................  EPA Method 26A.
Chlorine..................................  EPA Method 26A.
PAH (excluding Naphthalene)...............  EPA Method 23.
Naphthalene...............................  EPA Method 23.
Dioxins and Furans........................  EPA Method 23.
------------------------------------------------------------------------

    Additionally, we are proposing that subsequent performance testing 
will be required every five years, using the methods identified in 
Table 3.
    Under this proposal, and consistent with existing requirements in 
the Primary Copper Smelting NESHAP, a source owner will be required to 
submit semiannual compliance summary reports which document both 
compliance with the requirements of the Primary Copper Smelting NESHAP 
and any deviations from compliance with any of those requirements.
    Owners and operators would be required to maintain the records 
specified by 40 CFR 63.10 and, in addition, would be required to 
maintain records of all inspection and monitoring data, in accordance 
with the Primary Copper Smelting NESHAP (40 CFR 63.1456).
    We considered the possibility of proposing a fenceline monitoring 
requirement. However, we determined that fenceline monitoring is not 
appropriate for this source category primarily because the main 
emissions of interest for this source category are process fugitive 
emissions that are released from roofline vents that are at about 100 
feet elevation (i.e., not ``ground level'' like the source categories 
where we have required or proposed fenceline monitoring). Due to the 
elevation of the fugitive release points, the emissions would pass over 
the fenceline monitors and would not be effectively measured. In 
addition, EPA has determined that there are effective technologies for 
capturing these process fugitive emissions and routing them to control 
devices, and is proposing to require the use of such approaches in this 
rulemaking. Unlike many other source categories, it is also feasible to 
measure the process fugitive emissions at these facilities. These 
characteristics suggest that fenceline monitoring--which is typically 
used to detect emissions that can be difficult to control or measure at 
the points where they are emitted, and to identify the need for follow-
up investigation and corrective action--would have relatively limited 
value in the context of this source category.

C. What revisions are we proposing specific to the emission limit for 
process fugitive emissions from roof vents at the anode refining 
operations from the 2022 proposed RTR?

    As described in the 2022 proposed RTR, the current NESHAP does not 
include standards for process fugitive emissions from the rooflines of 
smelting furnaces, converters, or anode refining operations, except for 
an opacity limit for converter roof vents that applies during testing. 
During the development of the 2022 proposed RTR, the EPA determined 
that risk for the major source category was unacceptable. One of the 
main risk drivers was metal HAP emissions (mainly lead and arsenic) 
from the anode refining roofline at the Freeport facility, which 
comprised 71 percent of the MIR. Therefore, in the 2022 proposed RTR, 
pursuant to CAA sections 112(d)(2) and (3) for new and existing major 
sources, PM limits were proposed for process fugitive emissions from 
the rooflines of the converters and smelting furnaces. Pursuant to CAA 
sections 112(d)(2), (d)(3), and (f)(2) PM limits were proposed for 
process fugitive emissions for new and existing major sources' anode 
refining operations roofline vents.
    In the 2022 proposed RTR for converter and smelting furnace 
rooflines, we developed MACT floor emissions limits for PM, as a 
surrogate for particulate HAP metals, which include antimony, arsenic, 
beryllium, cadmium, chromium, cobalt, lead, manganese, nickel, and 
selenium compounds, based on the available test data. The use of PM as 
a surrogate for particulate metal HAP is consistent with the approach 
used to limit particulate metal HAP emissions from other copper 
smelting processes in the current NESHAP and for many other source 
categories (i.e., Ferroalloys Production, Integrated Iron and Steel 
Manufacturing, and Integrated Iron and Steel Foundries). The data used 
in the MACT floor emission limit development was from the Freeport 
facility. The Agency used the UPL methodology to develop the emission 
limits. The development of the MACT floor limits included in the 2022 
proposed RTR is described in detail in the memorandum entitled, Draft 
MACT Floor Analyses for the Primary Copper Smelting Source Category 
(Docket Item No. EPA-HQ-OAR-2020-0430-0055), which is available in the 
docket. Based on these analyses, the proposed MACT floor emission 
limits included in the 2022 proposed RTR were 1.7 pounds per hour (lbs/
hr) PM for process fugitive emissions for existing and new converter 
rooflines and 4.3 lbs/hr PM for existing and new smelting furnace 
rooflines. We also evaluated BTF PM limits for smelting furnace and

[[Page 47426]]

converter rooflines based on the potential addition of capture and 
control equipment designed to achieve approximately 90 percent 
reduction in process fugitive emissions. Based on the results of these 
analyses, the Agency did not propose BTF limits in the 2022 proposed 
RTR for converters or smelting furnaces because of the high costs and 
poor cost effectiveness and uncertainties in the estimates of 
emissions, emissions reductions and costs. Further details of these BTF 
analyses included in the 2022 proposed RTR are provided in the 
technical memo, Evaluation of Beyond-the-floor and Ample Margin of 
Safety Control Options and Costs for Process Fugitive Emissions from 
Smelting Furnaces and Converters, and for Point Source Emissions from 
Anode Refining Furnaces and for the Combined Emissions Stream Emitted 
from the Freeport Aisle Scrubber (Docket Item No. EPA-HQ-OAR-2020-0430-
0060).
    In the 2022 proposed RTR for the roofline vents of anode refining 
operations, we initially developed a MACT floor emissions PM limit of 
15.2 lbs/hr using the available test data and application of the UPL 
methodology. For this standard, PM also serves as a surrogate for 
particulate metal HAP similar to the other PM limits in the NESHAP. 
Subsequently, we evaluated a BTF emission limit for the anode refining 
operation roofline vents. The BTF emission limit was set at 90 percent 
lower than the MACT floor, or 1.6 lb PM/hr. As described in the 2022 
proposed RTR, in order to comply with the proposed anode refining 
operation BTF limit, the EPA expected that Freeport would need to 
install improved capture systems, including hoods, ductwork, and fans, 
and one additional baghouse. These improved capture systems would need 
to be applied to four units including the two-anode refining furnace 
pouring operations, the anode casting wheel, and the holding vessel. In 
the January 2022 proposed RTR, we estimated a total capital cost of 
$5,887,000 (2019 dollars), a total O&M cost of $1,002,000 (2019 
dollars) and total annualized costs of $1,558,000 (2019 dollars). The 
expected emission reductions were 4.25 tpy of lead and arsenic. The 
resulting cost effectiveness was $367,000/ton (2019 dollars). We 
concluded that this option was cost effective and proposed the BTF PM 
emission limit for the anode refining roofline vents. The same emission 
limit proposed pursuant to CAA 112(d)(2) and (3) for the anode refining 
operation roofline vent was also proposed to reduce risks to an 
acceptable level pursuant to CAA section 112(f)(2). Further information 
on the development of the proposed emission limit and the related cost 
estimates for control equipment are included in the record for the 2022 
proposed RTR in the memorandums entitled, Draft MACT Floor Analyses for 
the Primary Copper Smelting Source Category (Docket Item No. EPA-HQ-
OAR-2020-0430-0055) and Development of Estimated Costs for Enhanced 
Capture and Control of Process Fugitive Emissions form from Anode 
Refining Operations at Freeport (Docket Item No. EPA-HQ-OAR-2020-0430-
0061).
    During the public comment period for the 2022 proposed RTR, the EPA 
received comments from industry stakeholders that a combined limit 
would be preferred over individual limits. Commenters noted several 
reasons for this:
     Increased flexibility with respect to compliance options 
resulting in lower costs to comply;
     Lack of physical separation between departments and 
potential for emissions transfer; and
     Variability of department-specific emissions driven by the 
type of material being processed rather than by lack of emissions 
prevention measures.
    The Freeport facility also provided additional test data for the 
roofline vents for all three process areas in Appendices H1 and H2 of 
their public comment letter (Docket Item No. EPA-HQ-OAR-2020-0430-
0134). In reviewing these additional test data, we note that for 
completeness they should be included in the calculation of emission 
limits for these emission sources.
    In their comment letter, Freeport noted that the emission rates 
from the test data underlying the MACT floor emission limits from each 
smelter (electric and ISASMELT) should be added together rather than 
averaged since they are two distinct emission points. In reviewing the 
test data, we agree that the emission rates for the smelters should be 
added rather than averaged. This change is incorporated in our revised 
analyses included in this supplemental proposal for these emission 
sources.
    In response to the comments the EPA received on combining the three 
proposed roofline emission limits (i.e., from the smelters, converters, 
and anode refining rooflines) into a single combined emission limit, we 
performed an evaluation of the approach used in the 2022 proposed RTR 
and an evaluation of combining the emissions data to develop the 
emissions limit. The evaluations use all test data now available and 
incorporate the change to the processing of the smelter test data 
(i.e., adding the emission rates from each smelter rather than 
averaging them). Our evaluation of separate emission limits for 
filterable PM from the converter, smelter, and anode refining rooflines 
using the methodology in the 2022 proposed RTR, results in PM MACT 
floor emission limits of 2.4 lbs/hr for the converter roofline and 5.7 
lbs/hr for the smelting roofline, and a BTF emission limit (assuming 90 
percent control) of 1.6 lbs/hr for the anode refining roofline.
    We also evaluated the development of a combined emission limit for 
all the rooflines. This new emission limit is also calculated using the 
99 percent UPL methodology. Specifically, for calculating the combined 
emission limit, we first determined the 99 percent UPL of the combined 
emission rates based on all test data now available for filterable PM. 
We then determined the average fraction of emissions which are 
attributable to the anode refining roof vent (72 percent). Then we 
adjusted the anode refining roof vent's portion of the 99 percent UPL 
by reducing that portion of the value by 90 percent. This results in a 
combined filterable PM emission limit of 6.3 lbs/hr. We note that this 
emission limit is still expected to require 90 percent control of the 
anode refining roofline vent at the Freeport facility, and we expect 
the Freeport facility will still have to apply controls at this 
emission source. Therefore, despite the emission limit changing in 
format (i.e., becoming a single limit as opposed to three separate 
limits), we expect slightly higher emission reductions (i.e., 4.59 tpy 
of lead and arsenic). While we expect the Freeport facility will need 
to apply some control of the anode refining source, a combined limit 
would provide the facility with options to determine which source or 
combination of sources to control and to what level to achieve the 
overall needed emission reductions to comply with the combined emission 
limit. Because the option is expected to provide the same emission 
reductions as separate emission limits while also providing some 
flexibility for subject facilities, we are proposing a single combined 
emission limit for the converter, smelting, and anode refining roofline 
vents in this supplemental proposed rulemaking. Further information on 
our evaluation of separate and combined emission limits using all test 
data are available in the memorandum entitled Revised MACT Floor 
Analysis for the Fugitive Process Emission Sources in the docket for 
this

[[Page 47427]]

rulemaking (Docket ID EPA-HQ-OAR-2020-0430).
    The EPA also received comments from the Freeport facility 
concerning its cost estimates for the anode refining process fugitive 
roofline emissions controls. In their public comment letter on the 2022 
proposed RTR, the Freeport facility suggested that the EPA had 
underestimated costs for controlling the anode refining operations' 
process fugitive emissions. They provided their own cost assessment 
data in Attachment F of their comment letter (Docket Item No. EPA-HQ-
OAR-2020-0430-0134).
    After evaluating the comment letter and associated documents 
provided by Freeport, we determined that it is appropriate to update 
certain data input parameters in the cost estimates to reflect design 
requirements at the Freeport facility primarily by increasing the 
baghouse flowrate, lowering the air to cloth ratio, and adding a lime 
injection system to treat any acid gases in the exhaust stream. 
Additionally, the cost estimates have been updated to reflect 2022 
dollars and using an updated bank prime interest rate. The Agency now 
estimates that the BTF standard for the process fugitive emissions from 
the roofline at the Freeport facility would have capital costs of 
$10,239,666 and annualized costs of $2,143,972 and achieve about 4.59 
tpy reduction of lead and arsenic, with cost effectiveness of $467,000/
ton lead and arsenic, which is a level that, while higher than the cost 
effectiveness in the 2022 proposed RTR, we consider to be cost 
effective for these pollutants. Further information on our revised cost 
estimates can be found in the memorandum entitled, Cost Estimates for 
Enhanced Capture and Control of Process Fugitive Emissions from the 
Anode Refining Operations at Freeport in the docket for this rulemaking 
(Docket ID EPA-HQ-OAR-2020-0430). As described above, we are 
maintaining a proposed BTF emission limit for the roof vents in this 
supplemental proposal because it is cost effective and feasible to 
achieve. We also note that this BTF limit would ensure that risks are 
acceptable. We estimate that this BTF limit would reduce the cancer MIR 
near Freeport from 70-in-1 million to 20-in-1 million, ensure 3-month 
rolling average ambient lead concentrations remain well below the lead 
NAAQS near Freeport, and reduce the maximum noncancer acute HQ (for 
arsenic) from 7 to 2. Furthermore, this BTF limit would reduce the 
number of people with an estimated increased risk of cancer of greater 
than or equal to 1-in-1 million from 22,900 people (at baseline) to 
17,400 (post-control) and decrease the estimated cancer incidence from 
0.002 cases per year to 0.001 cases per year. The cancer MIR for Asarco 
would remain at 60-in-1 million.
    Consistent with the analysis provided in the 2022 proposed RTR, we 
expect the costs for the other major source copper smelting facility, 
Asarco, to be limited to emissions compliance testing and recordkeeping 
and reporting requirements. Also, consistent with the analysis provided 
in the 2022 proposed RTR, the EPA estimates the costs for the Asarco 
facility are $107,581 per year (after adjusting to 2022 dollars) to 
comply with the proposed testing and recordkeeping and reporting 
requirements for process fugitive lead emissions from its three 
roofline vents (i.e., for the anode, converter, and smelting furnace 
rooflines). While we are proposing a combined roofline emissions limit 
in this supplemental proposal, instead of separate limits for each 
department, we expect the testing costs to remain the same as those 
estimated in the 2022 proposed RTR since all three sources will have to 
be tested to compare to the proposed combined emission limit included 
in this supplemental proposal. This estimate is based on the EPA's 
experience and knowledge of typical costs associated with these types 
of testing requirements. We also note that the Freeport facility 
already performs the emissions testing that is required by the 
emissions limit in this supplemental proposal, thus this proposed rule 
does not impose any additional costs related to emissions testing and 
recordkeeping and reporting on the Freeport facility because these 
costs would be incurred in the absence of the supplemental proposed 
rule.
    We are proposing that existing facilities would need to comply 
within two years after promulgation of the final rule and that 
compliance would be demonstrated through an initial performance test 
followed by a compliance test once per year. Moreover, facilities would 
need to monitor control parameters (e.g., fan speed, amperage, pressure 
drops, and/or damper positioning), as applicable, on a continuous basis 
to ensure the control systems are working properly. All new or 
reconstructed facilities must comply with all requirements in the final 
rule upon startup.

D. What revisions are we proposing specific to the emission limit for 
mercury from the 2022 proposed RTR?

    As described in the 2022 proposed RTR, the current NESHAP does not 
include standards for mercury. Using the test data available during the 
development of the 2022 proposed RTR, the source category was estimated 
to emit 55 pounds per year of mercury with 45 pounds per year emitted 
from the Freeport facility. Because of the temperatures of the exhaust 
gas streams encountered at primary copper smelting operations, much of 
the mercury emitted is in vapor form, not in particulate form. The 
vapor form of mercury is not captured by the controls used to reduce PM 
emission. Therefore, the PM limits in the NESHAP do not serve as a 
surrogate for mercury. Therefore, in the 2022 proposed RTR, pursuant to 
CAA sections 112(d)(2) and (3) for new and existing major sources, 
mercury limits were proposed. In the 2022 proposed RTR, the Agency used 
the available test data from Asarco and Freeport to develop the mercury 
standards for new and existing sources (details can be found in Draft 
MACT Floor Analyses for the Primary Copper Smelting Source Category 
(Docket Item No. EPA-HQ-OAR-2020-0430-0055)).
    In the 2022 proposed RTR, the new source standard was based on the 
best performer, Asarco. The Agency evaluated proposing a BTF emission 
standard for new sources based on Asarco data in the 2022 proposed RTR 
but rejected this option based on the cost effectiveness, uncertainty 
in the quantity of emission reductions, and the fact that the new 
source MACT floor standard is significantly lower than the limit for 
existing sources. The proposed emission standard for new sources in the 
2022 proposed RTR was 0.00097 lbs/hr. The Agency has not received any 
new information relative to the new source standard included in the 
2022 proposed RTR and, therefore, maintains this proposed MACT floor 
emission limit for new sources.
    In the 2022 proposed RTR, the MACT floor emissions limit for 
existing sources was calculated based on the average of all the 
emissions tests from both facilities, accounting for variability using 
the 99 percent UPL. A MACT floor based on the 99 percent UPL for the 
combined facility-wide sources was 0.01 lbs/hr. The Agency also 
evaluated a BTF emission standard for existing sources, a value of 
0.0043 lbs/hr. The BTF standard was based on the addition of controls 
at the Freeport facility's acid plant which was identified as the 
largest source of mercury emissions at the Freeport facility using data 
available at the time. The additional controls were expected to include 
the installation of a polishing baghouse with activated carbon 
injection. The expected emission reductions were 26 lb/yr, based on 90 
percent control of the emissions from Freeport's acid plant. The 
estimated

[[Page 47428]]

capital costs for the polishing baghouse with activated carbon 
injection were $1.5 million (2019 dollars), and the estimated 
annualized costs were $714,000 (2019 dollars), for a cost effectiveness 
of $27,500 (2019 dollars) per pound of mercury reduced. In the 2022 
proposed RTR, the Agency proposed the BTF standard of 0.0043 lbs/hr for 
existing sources. The development of this beyond-the-floor limit is 
described in detail in the memorandum entitled, Estimated Costs for 
Beyond-the-floor Controls for Mercury Emissions from Primary Copper 
Smelting Facilities (Docket Item No. EPA-HQ-OAR-2020-0430-0059).
    Since the 2022 proposed RTR, the EPA received comments on the 
proposed existing source mercury standard and new information from the 
Freeport facility through the CAA section 114 information request 
described in II.E of this preamble. Freeport provided additional 
mercury performance test reports with results for the vent fume, aisle 
scrubber and acid plant covering calendar years 2019-2021. The Freeport 
facility noted that these test reports used a variation of EPA Method 
29 that may result in mercury emissions measurements that are biased 
low. These mercury tests conducted in 2019-21 were not done according 
to the EPA method. The facility voluntarily completed an additional 
mercury performance test at the vent fume, aisle scrubber, and acid 
plant in 2022 which fully followed EPA Method 29. These test reports 
are available in the docket for this rulemaking (Docket ID EPA-HQ-OAR-
2020-0430).
    In their public comment letter, Freeport provided comments 
specifically on controlling emissions from the acid plant. The facility 
questioned the technical feasibility of these controls, stating that 
they are unaware of a polishing baghouse with ACI operating downstream 
of a wet scrubber on an acid plant. They explained that the conditions 
of the acid plant exhaust streams are unsuited for ACI since the stream 
has a high moisture content, low mercury concentrations, and high 
concentrations of SO2/SO3 which inhibit mercury 
removal.
    Freeport argued that even if it was technically feasible, the EPA 
had underestimated costs and overstated reductions. Freeport submitted 
their own cost estimates for ACI plus a polishing baghouse on the acid 
plant as part of their comment letter on the 2022 proposed RTR (see 
Attachment I of Docket Item No. EPA-HQ-OAR-2020-0430-0134). The 
facility subsequently revised and resubmitted their evaluation of the 
baghouse with activated carbon injection control option for the acid 
plant to the EPA on March 12, 2023 (Docket ID EPA-HQ-OAR-2020-0430). In 
this evaluation, the Freeport facility estimated the emission 
reductions of mercury to be between 50 and 75 percent using a polishing 
baghouse with ACI, or about 15 to 22 lbs of mercury. The cost estimate 
from Freeport provided capital costs of $16.4M, annualized costs of 
$4.4 million and a cost effectiveness of about $169,000 per pound.
    The EPA has performed a review of all available mercury test data 
from Freeport and the cost estimate provided by Freeport. In reviewing 
the test data, we decided that only the test which was fully compliant 
with EPA Method 29 should be used to calculate emission limits and to 
estimate the quantity of potential emissions reductions. Using the data 
from this test report, the point and non-point source emissions from 
Freeport are estimated to be 139 lbs/yr which, when combined with the 
test report from Asarco which indicates that 10 lbs/yr are estimated to 
be emitted from that facility, results in an estimated total of 149 
lbs/yr mercury emitted from the source category. In Freeport's 2022 
mercury test which complied fully with EPA Method 29, the emissions 
were more evenly distributed between the three stacks at the facility 
with an estimated 45 lbs/yr from the vent fume stack, an estimated 49.3 
lbs/yr estimated from the aisle scrubber and an estimated 38.5 lbs/yr 
from the acid plant.
    Using the 2022 mercury test from Freeport and the performance test 
from Asarco, we calculated the MACT floor limit for existing sources by 
averaging all the test results from both facilities, accounting for 
variability using the 99 percent UPL. A MACT floor based on the 99 
percent UPL for the combined facility-wide limit for existing sources 
is 0.033 lbs/hr. Based on the available data, we conclude that both 
facilities would be able to meet the MACT floor limit with no 
additional controls. For new sources, we are maintaining the MACT floor 
limit of 0.00097 lbs/hr provided in the 2022 proposed RTR which was 
based on data from the best performer, Asarco. We have no new data with 
which to update this value. A detailed analysis and documentation of 
the revised MACT floor calculations for existing sources can be found 
in the technical document, Revised MACT Floor Analysis for Mercury, 
available in the docket (Docket ID EPA-HQ-2020-0430).
    As discussed previously, the Freeport facility submitted comments 
indicating several technical reasons that control of mercury from the 
acid plant would be difficult. In reviewing the 2022 mercury test from 
Freeport, we find that the mercury emissions were distributed more 
evenly among the facility's three stacks when compared to the other 
test reports which included mercury from 2018-2021. We have evaluated 
the technical aspects of Freeport's comment letter regarding mercury 
control from the acid plant and agree characteristics of the exhaust 
stream and equipment configuration may inhibit mercury control (e.g., 
moisture content, acid gas content, mercury concentration). Considering 
this, and the emissions distribution from the 2022 mercury test, we 
examined other control options to determine whether there is a more 
technically suitable and cost-effective option for controlling mercury 
emissions at Freeport. When reviewing the stack characteristics, we 
find that the aisle scrubber has a high flowrate, typically in excess 
of one million cubic feet per minute, and a very similar quantity of 
mercury emissions compared to the other two stacks based on the 2022 
test. The aisle scrubber also combines streams which are currently 
uncontrolled (i.e., secondary converter) with streams that are 
controlled (i.e., primary anode refining baghouse emissions). On the 
other hand, the vent fume stack handles emissions from the secondary 
capture system for the furnaces and has a lower flowrate than the aisle 
scrubber. Often, a higher flowrate and the complexity of combining 
multiple streams increase control costs. When evaluating beyond-the-
floor options for controlling mercury, we estimated costs and emissions 
reductions for controlling the vent fume exhaust stream because we 
expect the more simplistic exhaust stream configuration, lower 
flowrate, and similar quantity of expected reductions to be more 
favorable for controlling mercury than the aisle scrubber. For the BTF 
option, we estimated costs and emissions reductions associated with a 
baghouse with lime injection and activated carbon injection with an 
expected control efficiency of 90 percent for mercury from the vent 
fume. The estimated reduction would be 40.5 lbs of mercury from the 
vent fume stack. The overall reduction of mercury emissions that would 
occur from the Freeport facility with this BTF option is estimated to 
be 30 percent (i.e., the facility-wide total emissions of 139 lbs 
mercury would be reduced by 40.5 lbs mercury). The capital costs of the 
baghouse with lime injection and activated carbon injection

[[Page 47429]]

are estimated to be $6.04M, with annualized costs of $1.91M and a cost 
effectiveness of $47,000/lb mercury reduced. We do not find costs 
associated with the BTF option to be reasonable and are therefore not 
proposing a BTF emission limit for existing sources for mercury. We 
also considered other BTF options, but all other options were less cost 
effective than the option presented in this section. The EPA is 
requesting comment on the BTF options evaluated for mercury and whether 
the EPA should determine in this case that $47,000/lb mercury is cost-
effective for mercury control and include a BTF limit in the final 
rule. A detailed description of the BTF analysis of mercury emissions, 
the controls necessary to reduce mercury emissions, and the cost of 
these BTF controls are included in the document, Estimated Cost for 
Beyond-the-floor Controls for Mercury Emissions from Primary Copper 
Smelting Facilities, located in the docket (Docket ID No. EPA-HQ-OAR-
2020-0430). Since we have not identified a cost-effective BTF option, 
we are proposing the MACT floor limit for the combined facility-wide 
limit for mercury of 0.033 lbs/hr for existing sources.
    The EPA is proposing that compliance with the mercury emissions 
limits for existing sources will be demonstrated through an initial 
compliance test for each of the affected sources (e.g., furnaces, 
converters, anode refining) within 1 year of publication of the rule 
followed by a compliance test at least once every year. We estimate 
that Freeport and Asarco will incur performance testing costs for 
mercury of $49,940 per facility per year. For newly affected 
facilities, compliance is to be achieved no later than the effective 
date of the final rule or upon startup, whichever is later.

E. What emissions standards are we proposing for the Aisle Scrubber in 
this supplemental proposed rule that are different than decisions 
proposed in the 2022 proposed RTR?

    As discussed in the preamble of the 2022 proposed RTR, we proposed 
that the risks for the major source category were unacceptable. The EPA 
identified controls to reduce risk to an acceptable level, which were 
proposed to be achieved by controlling the anode refining roofline 
vents (as described in section III.C. of this preamble). Then, the EPA 
considered whether additional measures were required to provide an 
ample margin of safety to protect public health. An aisle scrubber 
located at one of the two major source facilities (Freeport) was 
estimated to emit 9.2 tpy metal HAP (mostly lead and arsenic) and was 
identified as an emission source that contributed significantly to risk 
at the Freeport facility (e.g., 23 percent of the cancer MIR). 
Therefore, the EPA evaluated the cost, the emissions reductions and 
risk reductions that could be achieved by additional controls for the 
aisle scrubber as part of the ample margin of safety analysis.
    Specifically. In the 2022 proposed RTR the EPA evaluated the cost 
and emission reductions of adding a WESP to the combined emissions 
stream from the aisle scrubber. The evaluation is described in the 
memorandum entitled Evaluation of Beyond-the-floor and Ample Margin of 
Safety Control Options and Costs for Process Fugitive Emissions from 
Smelting Furnaces and Converters, and for Point Source Emissions from 
Anode Refining Furnaces and for the Combined Emissions Stream Emitted 
from the Freeport Aisle Scrubber--REVISED (Docket Item No. EPA-HQ-OAR-
0430-0108). Based on the analysis included in the 2022 Proposed RTR, 
the estimated capital costs were $67 million (2019 dollars), and the 
estimated annualized costs were $17 million (2019 dollars). The 
associated emissions reduction achieved were estimated to be 8.7 tpy 
total metal HAP of which 7.6 tpy were estimated to be lead and arsenic 
resulting in a cost effectiveness of $2 million/ton (2019 dollars).
    The aisle scrubber at the Freeport facility is used to control the 
combined secondary emissions from the converter plus the emissions 
exiting the baghouse used to control primary anode refining point 
source emissions. Currently, there are emission limits for secondary 
capture systems from existing converter departments in 40 CFR 
63.1444(d)(6). Furthermore, the EPA proposed emissions limits for new 
and existing anode refining departments in the 2022 proposed RTR (i.e., 
proposed limits for 40 CFR 63.1444(i)(1)). In this supplemental 
proposal, the EPA is co-proposing regulatory options for additional 
control of either the secondary capture system for the converter 
department or additional control of the combined emissions stream of 
the secondary capture system for the converter department and the point 
source emissions from the anode refining department. These control 
options would result in more stringent emissions standards for these 
emission sources than what is currently required by the Primary Copper 
Smelting NESHAP as discussed more below. These standards are being 
proposed as technology developments pursuant to CAA section 112(d)(6) 
and to provide an ample margin of safety to protect public health 
pursuant to CAA section 112(f)(2).
    In order to best inform these options for additional controls, 
after the January 2022 proposal the EPA issued a CAA section 114 
information request to the Freeport facility as described in section 
II.E of this preamble. The CAA section 114 information request 
requested that Freeport perform a feasibility analysis of whether 
Freeport could further reduce the HAP metal emissions either from the 
secondary capture system for the converter department or from the 
combined emissions stream entering the aisle scrubber (i.e., the 
emissions stream from the secondary capture system for the converter 
department and the anode refining department).
    The Freeport facility subsequently provided the EPA with an 
evaluation of control options for the aisle scrubber, including:
     Option 1--Addition of a WESP downstream of the aisle 
scrubber to provide additional control of the combined emissions stream 
from the secondary capture system for the converter department and the 
anode refining department (i.e., the same option evaluated by the EPA 
in the ample margin of safety analysis included in the January 2022 
proposal);
     Option 2--Addition of a baghouse upstream of the aisle 
scrubber to provide additional control of the secondary capture system 
for the converter department.
    The Freeport facility regularly conducts performance testing of its 
aisle scrubber for filterable PM and metals. The EPA has obtained 
copies of the performance test results from 2018, 2019, 2020, 2021 and 
2022 for the aisle scrubber, which are available in the docket for this 
rulemaking (Docket ID No. EPA-HQ-OAR-2020-0430). We used these 
performance tests to estimate the baseline emissions and subsequently 
estimate the quantity of emissions reductions for the options for 
controlling the aisle scrubber at the Freeport facility. Using these 
test data, we now estimate the annual emissions of metal HAP to be 6.63 
tpy, of which more than 90 percent is lead and arsenic, on average. We 
also used the test reports to inform the development of potential 
emissions standards. Initially we developed a limit that represents 
current emissions from the aisle scrubber, accounting for variability 
using the 99 percent UPL. The resulting limit based on the 99 percent 
UPL for the combined emissions stream from the secondary capture system 
for the converter department and the anode refining department is 7.48 
milligram

[[Page 47430]]

per dry cubic standard meter (mg/dscm). This UPL served as the baseline 
for the development of the two control options described in this 
section. A detailed discussion of the option-specific control 
equipment, expected emission reductions, associated emissions standard, 
and control costs are described in the following paragraphs.
    For Option 1, as described previously, the WESP would be located 
downstream of the aisle scrubber and therefore further control the 
combined emissions stream from the secondary capture system for the 
converter department and the anode refining department. The expected 
control efficiency for the WESP is 95 percent, thus expected emission 
reductions from this option are 95 percent of the baseline emissions 
(6.63 tpy metal HAP) or 6.3 tpy metal HAP. The EPA updated the expected 
flowrate for the WESP in its cost estimates from the value used in the 
cost estimate we provided in the 2022 proposed RTR based on comments 
from Freeport. We also updated the cost estimate to reflect 2022 
dollars and updated the bank prime interest rate. Based on our 
analysis, the estimated capital costs for the WESP are $98.5 million, 
the annualized costs are $25.2 million, and estimated reductions are 
6.3 tpy reduction of metal HAP, with cost effectiveness of $4.0 
million/ton metal HAP. The emission limit for this option would be 
0.374 mg/dscm, which is based on applying the expected control of 95 
percent to the 99 percent UPL for the combined emissions stream from 
the secondary capture system for the converter department and the anode 
refining department.
    As described in the previous section III.C. of this preamble, we 
estimate the reductions of process fugitive emissions from the roof 
vents would reduce the MIR at Freeport from 70-in-1 million to 20-in-1 
million; reduce the number of people with cancer risk greater than 1-
in-1 million from 22,900 to 17,400; reduce ambient lead exposures below 
the lead NAAQS; and reduce the maximum HQ (due to arsenic emissions) 
from 7 to 2. We estimate that the proposed limit of 0.374 mg/dscm for 
the aisle scrubber (option 1) would reduce the incremental cancer risk 
of an additional 1,900 people below 1-in-1 million (from 17,400 to 
15,500). Furthermore, the maximum acute HQ due to arsenic emissions 
would be reduced from 2 to 1. Option 1 would result in a small 
additional reduction in the MIR at Freeport, but after rounding up (to 
1 significant figure) the MIR remains at 20-in-1 million. However, we 
note that the estimated cancer MIR for the source category would be 60-
in-1 million, which is the maximum cancer risk near the Asarco 
facility.
    Option 2, as described previously, would require a baghouse 
upstream of the aisle scrubber which would be designed to control the 
secondary capture system for the converter department. Currently, the 
uncontrolled emissions from the secondary capture system for the 
converter department combine with the baghouse-controlled primary anode 
refining point source emissions and route to the aisle scrubber. Unlike 
the aisle scrubber which is routinely tested for particulate matter and 
lead emissions, the secondary converter duct is not sampled at any 
regular frequency. However, in an engineering evaluation submitted by 
Freeport as part of the CAA section 114 information request in which 
the converter duct was sampled, the facility explained that 
approximately 75 percent of the emissions from the aisle scrubber are 
attributable to the secondary capture system for the converter 
department. Therefore, we estimate that average annual metal HAP 
emissions from the secondary capture system for the converter 
department are 4.97 tpy (75 percent of the estimated total average 
annual metal HAP emissions from the aisle scrubber, which is 6.63 tpy). 
To estimate the expected reductions from this option, we applied the 
expected control efficiency of the baghouse (90 percent) to the 
emissions which are estimated to be from the secondary capture system 
for the converter department (4.97 tpy). This results in an estimated 
emissions reduction of 4.5 tpy metal HAP from the aisle scrubber, which 
is about a 68 percent reduction of emissions from the aisle scrubber. 
We estimate these controls (i.e., baghouse) will have capital costs of 
$37M, annualized costs of $6.2 million and achieve about a 4.5 tpy 
reduction in metal HAP with cost effectiveness of $1.38 million/ton 
metal HAP. The emission standard for this option was calculated by 
first determining the fraction of the 99 percent UPL that is estimated 
to be from the secondary capture system for the converter department, 
5.61 mg/dscm, and then applying the expected control efficiency of the 
baghouse (i.e., 90 percent) to determine the reduction in the emission 
limit (5.09 mg/dscm). The resulting emissions limit under option 2 
would be 2.43 mg/dscm for additional controls on the secondary capture 
system for the converter department.
    As described in the previous section III.C. of this preamble, we 
estimate the reductions of process fugitive emissions from the roof 
vents would reduce the MIR at Freeport from 70-in-1 million to 20-in-1 
million; reduce the number of people with cancer risk greater than 1-
in-1 million from 22,900 to 17,400; reduce ambient lead exposures below 
the lead NAAQS; and reduce the maximum HQ (due to arsenic emissions) 
from 7 to 2. We estimate that the proposed limit of 2.43 mg/dscm (based 
on addition of a baghouse on the secondary capture system for the 
converter department--option 2) would reduce the incremental cancer 
risk of an additional 700 people to below 1-in-1 million (from 17,400 
to 16,700). Furthermore, the maximum acute HQ due to arsenic emissions 
would be reduced from 2 to 1. Option 2 would also result in a small 
additional reduction in the maximum cancer risk at Freeport, but after 
rounding up (to 1 significant figure) the maximum risk would remain at 
20-in-1 million. The estimated cancer MIR for the source category would 
be 60-in-1 million, which is the maximum cancer risk near the Asarco 
facility.
    As discussed below, based on consideration and evaluation of both 
options, the EPA is proposing both options pursuant to CAA section 
112(d)(6) and CAA section 112(f). We propose that both options are 
feasible, achieve significant reductions of the HAP metals and risk 
reduction, and that the cost impacts are reasonable. Therefore, both 
options represent cost-effective developments in control technology 
pursuant to CAA section 112(d)(6) and ensure the NESHAP will provide an 
ample margin of safety to protect public health pursuant to CAA section 
112(f). We expect that the Asarco facility can comply with either 
option without the need to install additional controls. We are 
proposing that facilities would need to comply within two years after 
promulgation of the final rule and that compliance would be 
demonstrated through an initial performance test followed by a 
compliance test once per year. Moreover, facilities would need to 
monitor control parameters (e.g., fan speed, amperage, pressure drops, 
and/or damper positioning), as applicable, on a continuous basis to 
ensure the control systems are working properly.
    Further information regarding our estimated control costs, 
associated emission reductions, and estimated cost effectiveness can be 
found in the memorandum entitled, Cost Estimates for Additional 
Controls of Freeport's Aisle Scrubber which is available in the docket 
for this rulemaking (Docket ID No. EPA-HQ-OAR-2020-0430). Further 
information regarding the development of the proposed emission 
standards for

[[Page 47431]]

each option can be found in the memorandum entitled, Emission Standard 
Development for the Options to Provide Additional Controls for the 
Secondary Capture System for the Converter Department and Anode 
Refining Department which is available in the docket for this 
rulemaking (Docket ID No. EPA-HQ-OAR-2020-0430).
    The EPA is presenting both options (described in this section) in 
this supplemental proposal as potential regulatory options that we may 
finalize for this source category under CAA section 112(d)(6) and/or 
CAA section 112(f) after consideration of public comments. Under CAA 
section 112(d)(6) we propose that both options represent cost-effective 
developments in control technology and that it is necessary to revise 
the standards to reduce emissions from the aisle scrubber. In addition 
to the controls described above, we note that in the 2022 RTR Proposed 
Rule we also proposed a requirement that facilities develop and operate 
according to a fugitive dust minimization plan, which would provide 
some additional unquantified health protection. We are not proposing 
any changes to that proposed fugitive dust minimization requirement in 
this action.
    Noting that in setting standards to provide ample margin of safety 
to protect public health EPA strives to provide protection to the 
greatest number of persons possible to an individual lifetime risk 
level no higher than approximately 1-in-1 million (54 FR 38044; 
September 14, 1989), and after considering the risk reduction achieved 
under both options as well as the cost and feasibility of controls, 
along with the fugitive dust plan, we propose that either option 
provides an ample margin of safety to protect public health under CAA 
section 112(f). We are seeking comments on the technical feasibility, 
costs, expected emission reductions, and risk reductions achieved and 
whether one option is preferable over the other and why.

F. What are the results of risk analyses completed for this action?

    In the January 11, 2022, proposed amendments to the Primary Copper 
Smelting RTR rule (87 FR 1616; January 11, 2022), the EPA conducted a 
residual risk assessment and determined that risks from the primary 
copper smelting source category were unacceptable due to HAP metal 
(primarily lead and arsenic) emissions and proposed standards to reduce 
risk to an acceptable level and provide an ample margin of safety to 
protect public health. The risk analysis supporting the proposed rule 
indicated exceedances of the lead NAAQS at the baseline (i.e., based on 
current HAP emissions). That risk analysis also indicated that the 
cancer risk for the individual most exposed could be up to 80-in-1 
million based on actual emissions and up to 90-in-1 million based on 
allowable emissions. In addition to the noncancer risk from lead, the 
analysis also indicated a chronic HI of 1 due to arsenic and a maximum 
acute HQ of 7 for arsenic (see Docket No. EPA-HQ-OAR-2020-0430). Since 
issuance of the proposal, the EPA has received new facility operation 
and HAP emissions data from the Freeport facility through the public 
comments and issuance of a 2022 CAA section 114 information request. 
Detailed information on the new data is provided in the memorandum 
Updated Stack/Emissions Data Collected for 2023 Primary Copper Smelting 
Risk Review, which is available in the docket for this action (Docket 
ID No. EPA-HQ-OAR-2020-0430).
    Based on the updated stack and performance tests submitted by 
Freeport as part of the section 114 request, we updated the baseline 
risk assessment for this supplemental proposal. The new assessment 
reflects emissions changes to the known risk drivers (arsenic and lead) 
and a potential risk driver (mercury) at Freeport. Since this 
supplemental proposal only reflects emissions changes for the Freeport 
facility, we only updated the risk assessment for this facility.
    Also, this supplemental proposal includes an updated control option 
1 and a new control option 2 that affect the Freeport facility only, as 
described in Table 4. Because of these changes, we conducted for this 
supplemental proposal an updated assessment of post-control risk for 
both of these emission control scenarios for Freeport. The risk results 
for the Asarco facility have not changed since the 2022 proposal. The 
details of the risk assessment for Asarco are described in the 2022 
proposal Federal Register publication (87 FR 1616; January 11, 2022) 
for details and the 2022 risk report, which is available in the docket 
for this proposed rule.

  Table 4--Comparison of the Primary Copper Smelting Baseline Inhalation Risk Assessment Results for Freeport With Post-Control Risk Estimates for Two
                                                       2023 Proposed Supplemental Control Options
                                                       [Estimated risks based on actual emissions]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Population at                                      Maximum      Max predicted
                                              Maximum     increased risk   Annual cancer      Maximum       residential       3-month
      Risk assessment scenario \1\          individual       of cancer       incidence        chronic        annual Pb      modeled Pb    Acute HQ (REL)
                                            cancer risk   [gteqt]  1-in-    (cases per       noncancer      conc. (ug/      conc. (ug/          \5\
                                          (in-1 million)     1 million         year)         TOSHI \2\       m\3\) \3\       m\3\)\4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Proposed Rule (original baseline).......         80 (As)          24,400           0.002          1 (As)            0.12       0.17 (Pb)          7 (As)
Supplemental Proposal (revised baseline)         70 (As)          22,900           0.002          1 (As)            0.12       0.17 (Pb)          7 (As)
Supplemental Proposal Post-Control for           20 (As)          17,400           0.001        0.3 (As)           0.041       0.06 (Pb)          2 (As)
 Anode Roofline.........................
Supplemental Proposal Post-Control               20 (As)          15,500          0.0006        0.3 (As)           0.026       0.04 (Pb)          1 (As)
 Option 1 for Aisle Scrubber \6\........
Supplemental Proposal Post-Control               20 (As)          16,700          0.0006        0.3 (As)           0.028       0.04 (Pb)          1 (As)
 Option 2 for Aisle Scrubber \7\........
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ All values provided in this table are based upon only arsenic and lead emissions from Freeport (Miami, AZ).
\2\ TOSHI value for developmental effects does not include contribution from lead.
\3\ The maximum annual concentration for lead is based upon the MIR location which is also the maximum off-site exposure location for Freeport.
\4\ The maximum predicted 3-month Pb (lead) conc based on actual emissions at the time of proposal was based on AERMOD modeling with LEAD_POST, while
  the maximum predicted 3-month Pb conc for the supplemental proposal are based upon extrapolations of the HEM-4 annual Pb concentrations using the
  annual and 3-month modeled results from proposal.
\5\ The HQ values are based upon the lowest 1-hour acute health benchmark, the reference exposure level (REL) for arsenic. Arsenic also has an AEGL-2
  value (irreversible or escape-impairing effects) which resulted in a maximum HQ value of 0.0006 based upon actual emissions estimated in this
  supplemental proposal.
\6\ Option 1 represents controls on anode roofline (described in section III.C of this preamble) +WESP on aisle scrubber (described in section III.E of
  this preamble).
\7\ Option 2 represents controls on anode roofline (described in section III.C of this preamble) + baghouse upstream of aisle scrubber (described in
  section III.E of this preamble).

[[Page 47432]]

    The methodologies used for the updated baseline risk analysis are 
described in section III.C. of the preamble to the January 11, 2022, 
proposed rule National Emission Standards for Hazardous Air Pollutants: 
Primary Copper Smelting Residual Risk and Technology Review (87 FR 
1616; January 11, 2022). We present the results of the updated baseline 
risk analysis for Freeport and the analysis of the proposed control 
options in Table 4 of this preamble (rows labeled ``Supplemental 
Proposal Post-Control Option 1'' and ``Supplemental Proposal Post-
Control Option 2'') and in more detail in the document: Revised 
Residual Risk Assessment for the Freeport Smelter (Miami, AZ) in 
Support of the 2023 Supplemental Proposal for the Primary Copper 
Smelting Source Category, available in the docket for this action 
(Docket No. EPA-HQ-OAR-2020-0430). For more detail on the proposed 
control options, refer to sections III.C and III.E. of this preamble.
    The updated baseline risk assessment did not result in a 
significant change to the estimated cancer or non-cancer impacts at the 
Freeport facility. The updated cancer MIR for Freeport changed from 80-
in-1 million to 70-in-1 million with cancer incidence remaining the 
same at 0.002 excess cancer cases per year, or one excess case every 
500 years. These results are summarized in Table 4 of this preamble. 
The maximum individual cancer risk at Freeport is driven mostly by 
process fugitive emissions of arsenic from the anode refining roofline 
(about 70% of the MIR), and to a lesser degree the anode furnaces and 
secondary converter point source emissions that are emitted through the 
aisle scrubber (about 20% of the MIR). The arsenic emissions represent 
more than 97 percent of the cancer risk at the MIR location for the 
Freeport facility. The population exposed to excess cancer risks 
greater than or equal to 1-in-1 million are approximately 23,000 people 
for the baseline scenario. The chronic non-cancer risk remained the 
same with an HI equal to 1, driven by arsenic exposure. The acute 
noncancer risks from arsenic emissions remained the same with an HQ 
(based on the Reference Exposure Level) of 7. More detail is provided 
in the revised risk assessment document cited previously in this 
section. When applying the acute exposure guideline levels-2 (AEGL-2) 
value for arsenic for the supplemental proposal, the acute HQ results 
in a HQ (AEGL-2) less than 1 (0.0006).
    There was no change to the risk results for lead. The emissions 
update resulted in the same estimated ambient annual concentration of 
0.12 ug/m\3\. This concentration results in a maximum ambient 
concentration of lead for 3-month intervals of 0.17 ug/m\3\ based on 
actual emissions, which is the same result as in the 2022 proposal and 
which still exceeds the lead NAAQS of 0.15 ug/m\3\.
    Regarding multipathway risk, in the Primary Copper Smelting RTR 
proposed rule (87 FR 1616; January 11, 2022), we concluded that there 
was ``no significant potential for multipathway health effects.'' This 
determination was based on applying site-specific multipathway 
assessments conducted for other source categories with multipathway 
Tier 2 and Tier 3 screening estimates for the Freeport facility. The 
multipathway risk screening results for arsenic are now estimated to be 
lower than presented in the 2022 proposal based upon the reduced 
arsenic emissions in the revised baseline (described previously in this 
section). The new stack test data for mercury provided by Freeport 
resulted in an increase in emissions by a factor of 3, with annual 
emissions increasing to 139 pounds per year. This increase in baseline 
emissions would still result in an estimated mercury HQ less than 1 
(0.2) for the fisher scenario.
    Based on the results of the Updated Stack/Emissions Data Collected 
for 2023 Primary Copper Smelting Risk Review, the EPA proposes that the 
risks for this source category under the current MACT provisions remain 
unacceptable. The updated risk analysis still indicates exceedances of 
the lead NAAQS and a HI of 1 based on exposure to arsenic. The 
noncancer risk from lead is not included in the cumulative noncancer HI 
calculation. However, the health benchmarks for lead and arsenic are 
based on adverse neurocognitive effects, and the two chemicals may have 
combined effects on neurodevelopment. In addition, the updated risk 
analysis indicates a maximum acute HQ of 7 for arsenic for the baseline 
scenario. The risk analysis also indicates that the estimated 
inhalation cancer risk to the individual most exposed is 70-in-1 
million based on actual emissions, which is approaching the presumptive 
level of unacceptability of 100-in-1 million.
    The details of the risk assessment for allowable emissions for the 
baseline have not changed since the 2022 proposed rule. The estimated 
risks based on allowable emissions are described in the 2022 proposal 
Federal Register publication (87 FR 1616; January 11, 2022), and the 
2022 risk report, which is available in the docket for this proposed 
rule.
    With regard to the risk assessment we conducted for the updated 
control option 1 (i.e., the BTF limit for process fugitive emissions 
from roof vents discussed in section III.C of this preamble, plus a 
WESP on the aisle scrubber described in section III.E of this preamble) 
and the new control option 2 (i.e., the BTF limit for roof vents 
discussed in section III.C of this preamble, plus a baghouse upstream 
of the aisle scrubber described in section III.E of this preamble), we 
estimate the controls from option 1 would reduce the maximum risk at 
Freeport from 70-in-1 million to 20-in-1 million and would also reduce 
the population with cancer risks greater than or equal to 1-in-1 
million from 22,900 to 15,500 people. Cancer incidence would also 
decrease from 0.002 to 0.0006, or from 1 excess cancer case every 500 
years to every 1,600 years with additional reductions in potential 
noncancer developmental risks from arsenic and lead emissions. The 
maximum acute risk at public locations from arsenic emissions would 
also be reduced from an HQ of 7 to 1. Both control options 1 and 2 (as 
described in this section) would reduce the estimated maximum 3-month 
lead concentration from 0.17 ug/m\3\ to 0.04 ug/m\3\. The expected 
controls for option 2 (shown in Table 4 of this preamble) provide 
almost the same level of risk reduction as option 1, except the post-
control population with cancer risks greater than or equal to 1-in-1 
million is slightly higher at 16,700 people.
    Refer to the document titled: Revised Residual Risk Assessment for 
the Freeport Smelter (Miami, AZ) in Support of the 2023 Supplemental 
Proposal for the Primary Copper Smelting Source Category, in the docket 
for this rulemaking for more details regarding the updated risk 
assessment.

G. What other actions are we proposing, and what is the rationale for 
those actions?

    In addition to the proposed actions described above, we are 
proposing an additional revision to the NESHAP. We are proposing 
revisions to the startup, shutdown, and malfunction (SSM) provisions of 
the NESHAP in order to ensure that they are consistent with the 
decision in Sierra Club v. EPA, 551 F. 3d 1019 (D.C. Cir. 2008), in 
which the court vacated two provisions that exempted sources from the 
requirement to comply with otherwise applicable CAA section 112(d) 
emission standards during periods of SSM. Specifically, we are 
proposing to prohibit the use of a bypass stack. We are proposing to 
define the term ``bypass stack'' in 40 CFR 63.1459 and are also 
proposing that use

[[Page 47433]]

of a bypass stack will result in a violation of the numerical emission 
standards contained in the Primary Copper Smelting NESHAP in 40 CFR 
63.1448. We are also proposing that the use of a bypass stack during a 
performance test will invalidate the test. These proposed conditions 
are consistent with the EPA's interpretation of the application of the 
court's decision in Sierra Club v. EPA, 551 F. 3d 1019 (D.C. Cir. 2008) 
and consistent with the treatment of bypass stacks other rules (e.g., 
40 CFR part 60 subpart Ec).

H. What compliance dates are we proposing and what is the rationale for 
the proposed compliance dates?

    For the additional MACT floor emission limits (mercury, HCl, 
chlorine, D/F, benzene, toluene, PAHs excluding naphthalene, and 
naphthalene), the EPA proposes that existing facilities must comply 
with MACT floor limits within 1 year after promulgation of the final 
rule, because the EPA estimated that both facilities can meet MACT 
floor limits without having to install new controls. For affected 
facilities that commence construction or reconstruction after July 24, 
2023, owners or operators must comply with all requirements of the 
subpart, including all the amendments being proposed, no later than the 
effective date of the final rule or upon startup, whichever is later.
    The EPA is proposing a single combined PM roofline emissions limit 
for converters, anode refining and smelting furnace roof vents due to 
plant configurations and comingling of process fugitive emissions. The 
Agency maintains the proposed requirement that existing facilities must 
comply with the limit within 2 years after promulgation of the final 
rule.
    The EPA is also proposing that existing facilities must comply with 
the applicable emissions limit that the EPA promulgates for secondary 
converter emissions and anode baghouse emissions, which will apply to 
the emissions from the aisle scrubber at Freeport, as described in 
section III.E of this preamble, within 2 years after promulgation of 
the final rule.
    The EPA is proposing that facilities must comply with the PM 
roofline emissions limit and the PM limit that applies to the aisle 
scrubber within 2 years after promulgation of the final rule because we 
expect the facility will need up to 2 years to design, construct and 
operate the necessary capture and control equipment to meet these 
limits. The reason the Agency is not proposing to allow more than 2 
years for compliance is because the controls on the roofline are 
required to achieve acceptable risk pursuant to CAA section 112(f), the 
additional controls on the aisle scrubber are required to provide an 
ample margin of safety to protect public health pursuant to CAA section 
112(f), and section 112(f) only allows up to 2 years to comply with 
standards promulgated pursuant section 112(f). For affected facilities 
that commence construction or reconstruction after July 24, 2023, 
owners or operators must comply with all requirements of the subpart, 
including all the amendments being proposed, no later than the 
effective date of the final rule or upon startup, whichever is later.

IV. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

    The Primary Copper Smelting major source category includes any 
major source facility that uses a pyrometallurgical process to extract 
copper from copper sulfide ore concentrates, native ore concentrates, 
or other copper bearing minerals. There are currently two major source 
copper smelting facilities in the United States. No new copper smelting 
facilities are currently being constructed or are planned in the near 
future.
    The affected sources subject to 40 CFR part 63, subpart QQQ, the 
major source NESHAP, are copper concentrate dryers, smelting furnaces, 
slag cleaning vessels, copper converter departments, and fugitive 
emission sources.

B. What are the air quality impacts?

    The proposed amendments in this action would achieve estimated 
emissions reductions of 4.59 tpy of HAP metals (primarily lead, arsenic 
and cadmium) from the roof vents at the anode refining operations. 
Additionally, depending on the option chosen for additional controls of 
either: the secondary capture system for the converter department; or 
the combined emissions stream of the secondary capture system for the 
converter department and the point source emissions from the anode 
refining department, as described in section III.E of this preamble, 
additional emission reductions from the updated baseline of 4.5 or 6.3 
tpy of metal HAP are expected. Therefore, the total expected estimated 
reductions from the updated baseline are either 9.1 tpy or 11.1 tpy of 
metal HAP (primarily lead and arsenic) for the source category. The 
proposed amendments also include removal of the SSM exemptions relative 
to the use of a bypass stack which will result in an unquantified 
reduction of episodic emissions.

C. What are the cost impacts?

    As described above, the proposed BTF standard for the combined 
emissions from roofline vents, which we expect will mainly require 
reductions from the anode refining process fugitive emissions roof 
vents, would require estimated capital costs of $10.2 million and 
annualized costs of $2.1 million for the Freeport facility (2022 
dollars). Additionally, depending on the option chosen for additional 
controls of either: (1) the secondary capture system for the converter 
department; or (2) the combined emissions stream of the secondary 
capture system for the converter department and the point source 
emissions from the anode refining department, as described in section 
III.E. of this preamble, the estimated capital costs are $37 million or 
$98 million, respectively, and the estimated annualized costs are $6.2 
million or $25.2 million, respectively, for the Freeport facility (2022 
dollars). The total estimated capital costs are $47.2 million or $108.7 
million. The Asarco facility is not expected to require controls for 
any standard in this supplemental proposal, so no capital costs or 
annualized costs related to control options are included for Asarco.
    This supplemental proposal also includes performance testing 
requirements for unregulated HAP which are expected to be incurred by 
both facilities, including testing requirements for benzene, toluene, 
chlorine, HCl, PAH excluding naphthalene, naphthalene, D/F, and 
mercury. The Freeport facility has three units (vent fume, aisle 
scrubber, acid plant) which will require testing, and the Asarco 
facility has five units (vent gas baghouse, secondary hood baghouse, 
tertiary hoods, anode baghouse, and acid plant). The estimated costs 
for performance testing of these unregulated HAP are $240,140 (2022 
dollars) for the Freeport facility and $366,940 (2022 dollars) for the 
Asarco facility on each occurrence (once every five years). The 
annualized testing costs for unregulated HAP (assuming mercury testing 
is performed annually, and all other performance testing related to the 
new standards occurs once every five years) are $87,980 for Freeport 
and $113,340 for Asarco. Additionally, the Asarco facility will incur 
estimated costs of about $107,581 (2022 dollars) per year to complete 
compliance testing for the process fugitive rooflines emission 
standards. Freeport already conducts annual testing of these roofline 
vents pursuant to state ADEQ

[[Page 47434]]

requirements; therefore, the Agency does not expect Freeport to incur 
new testing costs related to the BTF standard.
    The total annual costs of the requirements in the supplemental 
proposal (i.e., annualized capital, annual operating and maintenance, 
and annual emissions testing costs) are estimated to be about $9 
million if the baghouse regulatory control option is applied to the 
Freeport aisle scrubber and about $28 million if the WESP regulatory 
control option is applied to the aisle scrubber.

D. What are the economic impacts?

    The net present value (NPV) of the estimated cost impacts of this 
proposed rule, discounted at a 7 percent rate over an eight-year period 
from 2024 to 2031, is $75 million in 2022 dollars for the baghouse 
upstream of the aisle scrubber option. The equivalent annualized value 
(EAV) is $13 million at a 7 percent discount rate. At a 3 percent 
discount rate, the NPV and EAV of the cost impacts (baghouse upstream 
of aisle scrubber) are estimated to be $78 million and $11.8 million, 
respectively. When applying the WESP controls for the aisle scrubber, 
the NPV of the estimated cost impacts of this proposed rule, discounted 
at a 7 percent rate over the 2024 to 2031 period, is $219 million in 
2022 dollars. The EAV is $37 million at a 7 percent discount rate. At a 
3 percent discount rate, the NPV and EAV of the cost impacts (WESP for 
aisle scrubber) are estimated to be $233 million and $33 million, 
respectively.
    This proposed rule does not affect any small businesses. 
Nonetheless, neither of the ultimate owners of the two affected 
facilities are expected to incur annualized costs greater than one 
percent of company-wide annual revenues. This supplemental proposal is 
not expected to have market impacts, so the EPA does not expect effects 
on primary copper smelter production or prices.

E. What are the benefits?

    As described above, the supplemental proposed amendments would 
result in reductions in emissions of HAP metals, especially lead and 
arsenic, with corresponding reductions in human health risk. The 
proposed amendments also revise the standards such that they apply at 
all times and prohibit the use of a bypass stack.

F. What analysis of environmental justice did we conduct?

    Executive Order 12898 directs the EPA to identify the populations 
of concern who are most likely to experience unequal burdens from 
environmental harms, which are specifically minority populations 
(people of color), low-income populations, and Indigenous peoples (59 
FR 7629, February 16, 1994). Additionally, Executive Order 13985 is 
intended to advance racial equity and support underserved communities 
through Federal Government actions (86 FR 7009, January 20, 2021). The 
EPA defines EJ as ``the fair treatment and meaningful involvement of 
all people regardless of race, color, national origin, or income, with 
respect to the development, implementation, and enforcement of 
environmental laws, regulations, and policies.'' \6\ The EPA further 
defines fair treatment to mean that ``no group of people should bear a 
disproportionate burden of environmental harms and risks, including 
those resulting from the negative environmental consequences of 
industrial, governmental, and commercial operations or programs and 
policies.'' In recognizing that people of color and low-income 
populations often bear an unequal burden of environmental harms and 
risks, the EPA continues to consider ways of protecting them from 
adverse public health and environmental effects of air pollution. For 
purposes of analyzing regulatory impacts, the EPA relies upon its June 
2016 ``Technical Guidance for Assessing Environmental Justice in 
Regulatory Analysis,'' \7\ which provides recommendations that 
encourage analysts to conduct the highest quality analysis feasible, 
recognizing that data limitations, time, resource constraints, and 
analytical challenges will vary by media and circumstance. The 
Technical Guidance states that a regulatory action may involve 
potential EJ concerns if it could: (1) create new disproportionate 
impacts on minority populations, low-income populations, and/or 
Indigenous peoples; (2) exacerbate existing disproportionate impacts on 
minority populations, low-income populations, and/or Indigenous 
peoples; or (3) present opportunities to address existing 
disproportionate impacts on minority populations, low-income 
populations, and/or Indigenous peoples through the promulgation of 
these actions.
---------------------------------------------------------------------------

    \6\ https://www.epa.gov/environmentaljustice.
    \7\ See https://www.epa.gov/environmentaljustice/technical-guidance-assessing-environmental-justice-regulatory-analysis.
---------------------------------------------------------------------------

    We did not conduct any additional demographics analyses for this 
supplemental proposed rule. EPA performed a risk-based demographic 
analysis for the 2022 proposed rule to identify the demographics of the 
populations with cancer risks greater than or equal to 1-in-1 million 
living within 5 kilometers (km) and within 50 km of the two major 
source primary copper facilities. The estimated baseline population 
with cancer risks greater than or equal to 1-in-1 million due to 
emissions from primary copper major sources has not changed 
significantly since proposal.
    In the 2022 proposal, the EPA determined that elevated cancer risks 
associated with emissions from the major source facilities 
disproportionately affect Native Americans, Hispanics, those living 
Below the Poverty Level and those Over 25 without High School Diploma 
living near primary copper major sources. For one facility, Asarco, the 
proposed baseline demographic analysis indicated that of the population 
with risks at or above 1-in-1 million, 73 percent are Hispanic, which 
is significantly greater than the nationwide percentage, 19 percent,
    As indicated in Section III.F. of this preamble, this proposed 
action is projected to reduce the number of individuals with cancer 
risks equal to or greater than 1-in-1 million associated with emissions 
from the Freeport facility. See Section III.F. of this preamble for 
more details.
    The methodology and the results of the demographic analysis 
presented in the 2022 proposal are presented in the preamble of the 
2022 proposed rule (87 FR 1616; January 11, 2022) and in the technical 
report, Risk and Technology Review--Analysis of Demographic Factors for 
Populations Living Near Primary Copper Smelting Source Category 
Operations (Docket Item No. EPA-HQ-OAR-2020-0430-0052).

V. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at https://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 14094: Modernizing Regulatory Review

    This action is not a significant regulatory action as defined in 
Executive Order 12866, as amended by Executive Order 14094, and was 
therefore not subject to a requirement for Executive Order 12866 
review.
    The EPA prepared an economic analysis of the proposed action. This 
analysis, Economic Impact Analysis for the Supplemental Proposed 
Residual Risk and Technology Review of the

[[Page 47435]]

National Emission Standards for Hazardous Air Pollutants for Primary 
Copper Smelting Sources, Residual Risk and Technology Review, is 
available in the docket EPA-HQ-OAR-2020-0430.

B. Paperwork Reduction Act (PRA)

    The information collection activities in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the PRA. The Information Collection Request (ICR) document 
that the EPA prepared has been assigned EPA ICR number 1850.10. You can 
find a copy of the ICR in the docket for this rule, and it is briefly 
summarized here.
    The EPA is proposing amendments that affect reporting and 
recordkeeping requirements for primary copper smelting facilities, such 
as requirements to submit new performance test reports and to maintain 
new operating parameter records to demonstrate compliance with new 
standards. This information would be collected to assure compliance 
with 40 CFR part 63, subpart QQQ.
    Respondents/affected entities: Owners or operators of primary 
copper smelting facilities.
    Respondent's obligation to respond: Mandatory (40 CFR part 63, 
subpart QQQ).
    Estimated number of respondents: Two (total).
    Frequency of response: The frequency of responses varies depending 
on the burden item.
    Total estimated burden: The annual recordkeeping and reporting 
burden for facilities from the proposed recordkeeping and reporting 
requirements is estimated to be 5,500 hours (per year). Burden is 
defined at 5 CFR 1320.3(b).
    Total estimated cost: The annual recordkeeping and reporting burden 
for facilities to comply with all of the requirements in the NESHAP is 
estimated to be $1,020,000 (per year), of which $331,000 is for this 
rule, and $685,000 is for the other costs related to continued 
compliance with the NESHAP. There are no annualized capital or 
operation & maintenance costs.
    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.
    Submit your comments on the Agency's need for this information, the 
accuracy of the provided burden estimates and any suggested methods for 
minimizing respondent burden to the EPA using the docket identified at 
the beginning of this rule. The EPA will respond to any ICR-related 
comments in the final rule. You may also send your ICR-related comments 
to OMB's Office of Information and Regulatory Affairs using the 
interface at www.reginfo.gov/public/do/PRAMain. Find this particular 
information collection by selecting ``Currently under Review--Open for 
Public Comments'' or by using the search function. OMB must receive 
comments no later than August 23, 2023.

C. Regulatory Flexibility Act (RFA)

    We certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. Based on the 
Small Business Administration size category for this source category, 
no small entities are subject to this action.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. The action imposes no enforceable duty on any state, 
local, or tribal governments or the private sector.

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.

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

    This action does not have tribal implications as specified in 
Executive Order 13175. Thus, Executive Order 13175 does not apply to 
this action. However, consistent with the EPA policy on coordination 
and consultation with Indian tribes, the EPA will offer government-to-
government consultation with tribes as requested.

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

    Executive Order 13045 (62 FR 19885, April 23, 1997) directs Federal 
agencies to include an evaluation of the health and safety effects of 
the planned regulation on children in Federal health and safety 
standards and explain why the regulation is preferable to potentially 
effective and reasonably feasible alternatives. This action is not 
subject to Executive Order 13045 because the EPA does not believe the 
environmental health or safety risks addressed by this action present a 
disproportionate risk to children. This action proposes emission 
standards for six previously unregulated pollutants and emissions 
limits for the anode refining process fugitive emissions and the aisle 
scrubber, which will achieve reductions of HAP metals (as described 
previously in section III of this preamble); therefore, the proposed 
rule would provide health benefits to children by reducing the level of 
HAP emissions (e.g., lead and arsenic) emitted from the copper smelting 
process. This action's health and risk assessments are contained in 
sections III and IV of the 2022 RTR proposed rule (87 FR 1616; January 
11, 2022), and in section III.F of this preamble, and also in the 
document titled Residual Risk Assessment for the Primary Copper 
Smelting Major Source Category in Support of the 2021 Risk and 
Technology Review Proposed Rule, which is available in the docket for 
this proposed rule (Docket ID No. EPA-HQ-OAR-2020-0430-0051).

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

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action as defined in Executive Order 12866 
and as amended by Executive Order 14094.

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR 
Part 51

    This action involves technical standards. Therefore, the EPA 
conducted searches for the Primary Copper Smelting NESHAP through the 
Enhanced National Standards Systems Network (NSSN) Database managed by 
the American National Standards Institute (ANSI). We also conducted a 
review of voluntary consensus standards (VCS) organizations and 
accessed and searched their databases. Searches were conducted for EPA 
Methods 1, 1A, 2, 2A, 2C, 2D, 2F, 2G, 3, 3A, 3B, 4, 5, 5B, 5D, 9, 17, 
18, 22, 23, 26A, 29, 30A, 30B of 40 CFR part 60, appendix A. During the 
EPA's VCS search, if the title or abstract (if provided) of the VCS 
described technical sampling and analytical procedures that are similar 
to the EPA's referenced method, the EPA ordered a copy of the standard 
and reviewed it as a potential equivalent method. We

[[Page 47436]]

reviewed all potential standards to determine the practicality of the 
VCS for this rule. No applicable voluntary consensus standards were 
identified for EPA Methods 1A, 2A, 2D, 2F, 2G, 5B, 5D, 22, 30A and 30B.
    Four voluntary consensus standards were identified as an acceptable 
alternative to EPA test methods for the purposes of this rule.
    The EPA proposes to incorporate by reference the VCS ANSI/ASME PTC 
19-10-1981 Part 10 (2010), ``Flue and Exhaust Gas Analyses'' as an 
acceptable alternative to EPA Methods 3B, manual portion only and not 
the instrumental portion. This standard is acceptable as an alternative 
to EPA Method 3B and is available from ASME at http://www.asme.org; by 
mail at Three Park Avenue, New York, NY 10016-5990; or by telephone at 
(800) 843-2763. This method determines quantitatively the gaseous 
constituents of exhausts resulting from stationary combustion sources. 
The gases covered in ANSI/ASME PTC 19.10-1981 are oxygen, carbon 
dioxide, carbon monoxide, nitrogen, sulfur dioxide, sulfur trioxide, 
nitric oxide, nitrogen dioxide, hydrogen sulfide, and hydrocarbons; 
however, the use in this rule is only applicable to oxygen and carbon 
dioxide.
    The EPA proposes to incorporate by reference the VCS ASTM D7520-16, 
``Standard Test Method for Determining the Opacity of a Plume in the 
Outdoor Ambient Atmosphere'' as an acceptable alternative to EPA Method 
9 only if the following conditions are followed:
     During the digital camera opacity technique (DCOT) 
certification procedure outlined in Section 9.2 of ASTM D7520-16, you 
or the DCOT vendor must present the plumes in front of various 
backgrounds of color and contrast representing conditions anticipated 
during field use such as blue sky, trees, and mixed backgrounds (clouds 
and/or a sparse tree stand).
     You must also have standard operating procedures in place 
including daily or other frequency quality checks to ensure the 
equipment is within manufacturing specifications as outlined in Section 
8.1 of ASTM D7520-16.
     You must follow the record keeping procedures outlined in 
40 CFR 63.10(b)(1) for the DCOT certification, compliance report, data 
sheets, and all raw unaltered JPEGs used for opacity and certification 
determination.
     You or the DCOT vendor must have a minimum of four (4) 
independent technology users apply the software to determine the 
visible opacity of the 300 certification plumes. For each set of 25 
plumes, the user may not exceed 15 percent opacity of anyone reading 
and the average error must not exceed 7.5 percent opacity.)
    This approval does not provide or imply a certification or 
validation of any vendor's hardware or software. The onus to maintain 
and verify the certification and/or training of the DCOT camera, 
software and operator in accordance with ASTM D7520-16 and this letter 
is on the facility, DCOT operator, and DCOT vendor. The EPA proposes to 
incorporate by reference the VCS ASTM D6420-99 (2010), ``Test Method 
for Determination of Gaseous Organic Compounds by Direct Interface Gas 
Chromatography/Mass Spectrometry.'' This ASTM procedure has been 
approved by the EPA as an alternative to EPA Method 18 only when the 
target compounds are all known and the target compounds are all listed 
in ASTM D6420 as measurable. This alternative should not be used for 
methane and ethane because atomic mass is less than 35. ASTM D6420 
should never be specified as a total VOC method.
    The EPA proposes to incorporate by reference the VCS ASTM D6784-16, 
``Standard Test Method for Elemental, Oxidized, Particle-Bound and 
Total Mercury Gas Generated from Coal-Fired Stationary Sources (Ontario 
Hydro Method)'' (D6784-16 was reapproved in 2016 to include better 
quality control than earlier 2008 version) as an acceptable alternative 
to EPA Method 29 (portion for mercury only) as a method for measuring 
mercury. [Note: Applies to concentrations approximately 0.5-100 [mu]g/
Nm\3\].
    The ASTM D7520-16; D6420-99 (2010); and D6784-16 documents are 
available from ASTM at https://www.astm.org or 100 Barr Harbor Drive, 
West Conshohocken, PA 19428-2959, telephone number: (610) 832-9500, fax 
number: (610) 8329555 at [email protected].
    The EPA proposes to incorporate by reference ``Recommended Toxicity 
Equivalence Factors (TEFs) for Human Health Risk Assessments of 2, 3, 
7, 8-Tetrachlorodibenzo-p-dioxin and Dioxin-Like Compounds'' (EPA/100/
R-10/005 December 2010), which is the source of the toxicity equivalent 
factors for dioxins and furans used in calculating the toxic 
equivalence quotient of the proposed dioxin and furan standard. This 
document can be found at https://www.epa.gov/risk/documents-recommended-toxicity-equivalency-factors-human-health-risk-assessments-dioxin-and.
    Detailed information on the VCS search and determination can be 
found in the memorandum, Voluntary Consensus Standard Results for 
National Emission Standards for Hazardous Air Pollutants: Copper 
Smelting Supplemental Proposal, which is available in the docket for 
this action (Docket ID No. EPA-HQ-OAR-2020-0430).

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) 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 (people of color and/or Indigenous 
peoples) and low-income populations.
    The EPA believes that the human health or environmental conditions 
that exist prior to this action result in or have the potential to 
result in disproportionate and adverse human health or environmental 
effects on people of color, low-income populations and/or Indigenous 
peoples. In In the 2022 proposal, the evaluated the demographic 
characteristics of communities located near the major source facilities 
and determined that elevated cancer risks associated with emissions 
from these facilities disproportionately affect Native American, 
Hispanic, Below Poverty Level and Over 25 without High School Diploma 
individuals living nearby.
    The EPA believes that this action is likely to reduce existing 
disproportionate and adverse effects on people of color, low-income 
populations and/or Indigenous peoples living near the Freeport 
facility. To support the 2022 proposal, EPA determined that the 
population living within 5 km of the Freeport facility is 1.5 percent 
Native American (versus 0.7 percent nationwide); 45 percent Hispanic or 
Latino (versus 19 percent nationwide); 23 percent Below Poverty Level 
(versus 13 percent nationwide); and 23 percent Over 25 without a High 
School Diploma (versus 12 percent nationwide). The standards proposed 
in this supplemental proposal are estimated to reduce metal HAP 
emissions, primarily lead and arsenic, from the Freeport facility by 
either 9.1 tpy or 11.1 tpy and are projected to reduce the number of 
individuals with cancer risks equal to or greater than 1-in-1 million 
associated with emissions from the Freeport facility. EPA does not 
anticipate that

[[Page 47437]]

this action will reduce emissions from the Asarco facility.
    The methodology and the results of the demographic analysis are 
presented in the preamble of the 2022 proposed rule (87 FR 1616; 
January 11, 2022) and in the technical report, Risk and Technology 
Review--Analysis of Demographic Factors for Populations Living Near 
Primary Copper Smelting Source Category Operations (Docket Item No. 
EPA-HQ-OAR-2020-0430-0052). The information supporting this Executive 
Order review is contained in section V.E. of the 2022 proposed RTR 
preamble (87 FR 1616; January 11, 2022). We did not conduct any 
additional demographics analyses for this supplemental proposed rule.

List of Subjects in 40 CFR Part 63

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

Michael S. Regan,
Administrator.
[FR Doc. 2023-15303 Filed 7-21-23; 8:45 am]
BILLING CODE 6560-50-P