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Rule2024-09883

National Emission Standards for Hazardous Air Pollutants: Primary Copper Smelting Residual Risk and Technology Review and Primary Copper Smelting Area Source Technology Review

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Published

May 13, 2024

Effective

May 13, 2024

Issuing agencies

Environmental Protection Agency

Abstract

This action finalizes the residual risk and technology review (RTR) conducted for the Primary Copper Smelting major source category regulated under national emission standards for hazardous air pollutants (NESHAP). This action also finalizes the technology review for the Primary Copper Smelting area source NESHAP. The final amendments for the major source NESHAP include particulate matter (PM) emission standards as a surrogate for metal hazardous air pollutants (HAP) other than mercury (primarily lead and arsenic) for anode refining point sources, process fugitive emissions from roofline vents, Hoboken converter process fugitive capture systems where they combine with anode refining point sources, and new converters. We are also finalizing emission standards for previously unregulated HAP including mercury, benzene, toluene, hydrogen chloride (HCl), chlorine, polycyclic aromatic hydrocarbons (PAH), and dioxins and furans (D/F). In addition, we are taking final action in the major source NESHAP to establish work practice standards for bypass stacks, and add a new emissions limit for lead and emissions control design standards to minimize process fugitive emissions at facilities with flash furnaces and Peirce-Smith converters. Final amendments for both the major source NESHAP and the area source NESHAP include removing exemptions and associated provisions for periods of startup, shutdown, and malfunction (SSM), specifying that the emission standards apply at all times, and requiring electronic reporting of performance test results and notification of compliance reports.

Full Text

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[Federal Register Volume 89, Number 93 (Monday, May 13, 2024)]
[Rules and Regulations]
[Pages 41648-41724]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-09883]

[[Page 41647]]

Vol. 89

Monday,

No. 93

May 13, 2024

Part V

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants: Primary
Copper Smelting Residual Risk and Technology Review and Primary Copper
Smelting Area Source Technology Review; Final Rule

Federal Register / Vol. 89, No. 93 / Monday, May 13, 2024 / Rules and
Regulations

[[Page 41648]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0430; FRL-7522-02-OAR]
RIN 2060-AU63

National Emission Standards for Hazardous Air Pollutants: Primary
Copper Smelting Residual Risk and Technology Review and Primary Copper
Smelting Area Source Technology Review

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action finalizes the residual risk and technology review
(RTR) conducted for the Primary Copper Smelting major source category
regulated under national emission standards for hazardous air
pollutants (NESHAP). This action also finalizes the technology review
for the Primary Copper Smelting area source NESHAP. The final
amendments for the major source NESHAP include particulate matter (PM)
emission standards as a surrogate for metal hazardous air pollutants
(HAP) other than mercury (primarily lead and arsenic) for anode
refining point sources, process fugitive emissions from roofline vents,
Hoboken converter process fugitive capture systems where they combine
with anode refining point sources, and new converters. We are also
finalizing emission standards for previously unregulated HAP including
mercury, benzene, toluene, hydrogen chloride (HCl), chlorine,
polycyclic aromatic hydrocarbons (PAH), and dioxins and furans (D/F).
In addition, we are taking final action in the major source NESHAP to
establish work practice standards for bypass stacks, and add a new
emissions limit for lead and emissions control design standards to
minimize process fugitive emissions at facilities with flash furnaces
and Peirce-Smith converters. Final amendments for both the major source
NESHAP and the area source NESHAP include removing exemptions and
associated provisions for periods of startup, shutdown, and malfunction
(SSM), specifying that the emission standards apply at all times, and
requiring electronic reporting of performance test results and
notification of compliance reports.

DATES: This final rule is effective May 13, 2024, except for amendatory
instruction 3, which is effective July 15, 2024. The incorporation by
reference (IBR) of certain publications listed in the rule is approved
by the Director of the Federal Register as of May 13, 2024.

ADDRESSES: The U.S. Environmental Protection Agency (EPA) has
established a docket for this action under Docket ID No. EPA-HQ-OAR-
2020-0430. All documents in the docket are listed on the <a href="https://www.regulations.gov/">https://www.regulations.gov/</a>website. Although listed, some information is not
publicly available, e.g., Confidential Business Information or other
information whose disclosure is restricted by statute. Certain other
material, such as copyrighted material, is not placed on the internet
and will be publicly available only in hard copy form. Publicly
available docket materials are available either electronically through
<a href="https://www.regulations.gov/">https://www.regulations.gov/</a>, or in hard copy at the EPA Docket Center,
WJC West Building, Room Number 3334, 1301 Constitution Ave. NW,
Washington, DC. The Public Reading Room hours of operation are 8:30
a.m. to 4:30 p.m. Eastern Standard Time (EST), Monday through Friday.
The telephone number for the Public Reading Room is (202) 566-1744, and
the telephone number for the EPA Docket Center is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For questions about this final action,
contact U.S. EPA, Attn: Amanda Hansen, Mail Drop: D243-04, 109 T.W.
Alexander Drive, P.O. Box 12055, RTP, North Carolina 27711; telephone
number: (919) 541-3165; email address: <a href="/cdn-cgi/l/email-protection#e98188879a8c87c7888488878d88a98c9988c78e869f">[email&#160;protected]</a>. For
specific information regarding the risk modeling methodology, contact
U.S. EPA, Attn: James Hirtz, Mail Drop: C539-02, 109 T.W. Alexander
Drive, P.O. Box 12055, RTP, North Carolina 27711; telephone number:
(919) 541-0881; email address: <a href="/cdn-cgi/l/email-protection#b3dbdac1c7c99dd9d2ded6c0f3d6c3d29dd4dcc5">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION: Preamble acronyms and abbreviations. We use
multiple acronyms and terms in this preamble. While this list may not
be exhaustive, to ease the reading of this preamble and for reference
purposes, the EPA defines the following terms and acronyms here:

ACI activated carbon injection
ADEQ Arizona Department of Environmental Quality
ANSI American National Standards Institute
BTF beyond-the-floor
CAA Clean Air Act
CEDRI Compliance and Emissions Data Reporting Interface
CEMS continuous emissions monitoring system
CFR Code of Federal Regulations
CRA Congressional Review Act
CMS continuous monitoring systems
DCOT digital camera opacity technique
D/F dioxins and furans
DSI dry sorbent injection
EAF electric arc furnaces
EJ Environmental Justice
EPA Environmental Protection Agency
ERT Electronic Reporting Tool
FEM Federal equivalent method
FR Federal Register
FRM Federal reference method
GACT generally available control technology
gr/dscf grains per dry standard cubic feet
HAP hazardous air pollutants
HCl hydrogen chloride
HEM-4 Human Exposure Model, Version 1.5.5
HI hazard index
HQ hazard quotient
ICR information collection request
lbs pounds
lb/hr pounds per hour
LEAN Louisiana Environmental Action Network
MACT maximum achievable control technology
mg/dscm milligrams per dry standard cubic meter
MIR maximum individual risk
MTG Measurement Technology Group
NAAQS National Ambient Air Quality Standards
NAICS North American Industry Classification System
NESHAP National Emission Standards for Hazardous Air Pollutants
NTTAA National Technology Transfer and Advancement Act
OAR Office of Air and Radiation
OMB Office of Management and Budget
PAH polycyclic aromatic hydrocarbons
Pb lead
PDF portable document format
PM particulate matter
PRA Paperwork Reduction Act
RATA Relative Accuracy Test Audit
REL reference exposure level
RFA Regulatory Flexibility Act
RIN Regulatory Information Number
RTR risk and technology review
SIP state implementation plan
SO<INF>2</INF> sulfur dioxide
SSM startup, shutdown, and malfunction
TEQ toxic equivalency quotient
TOSHI target organ-specific hazard index
tpy ton per year
ug/m\3\ micrograms per cubic meter
UMRA Unfunded Mandates Reform Act
UPL upper prediction limit
VCS voluntary consensus standards
WESP wet electrostatic precipitator

Background information. On January 11, 2022 (87 FR 1616), and July
24, 2023 (88 FR 47415), the EPA proposed revisions to the Primary
Copper Smelting major source NESHAP based on our RTR. In this action,
we are finalizing decisions and revisions for the major source rule. On
January 11, 2022 (87 FR 1616), the EPA also proposed revisions to the
Primary Copper Smelting area source NESHAP based on our technology
review. In this action, we are also finalizing decisions and revisions
for the area source rule.

[[Page 41649]]

We summarize some of the more significant comments we timely received
regarding the proposed rules and provide our responses in this
preamble. A summary of all other public comments on the proposals and
the EPA's responses to those comments is available in National Emission
Standards for Hazardous Air Pollutant Emissions: Primary Copper
Smelting Residual Risk and Technology Review and Primary Copper
Smelting Area Source Technology Review: Summary of Public Comments and
Responses, Docket ID No. EPA-HQ-OAR-2020-0430. ``Track changes''
versions of the regulatory language that incorporate the changes to the
two rules in this action are available in the docket.
Organization of this document. The information in this preamble is
organized as follows:

I. General Information
A. Executive Summary
B. Does this action apply to me?
C. Where can I get a copy of this document and other related
information?
D. Judicial Review and Administrative Reconsideration
II. Background
A. What is the statutory authority for this action?
B. What is the Primary Copper Smelting source category and how
does the NESHAP regulate HAP emissions from the source category?
C. What changes did we propose for the Primary Copper Smelting
source category in our January 11, 2022, proposal and in our July
24, 2023, supplemental proposal?
III. What is included in this final rule?
A. What are the final rule amendments based on the risk review
for the Primary Copper Smelting source category?
B. What are the final rule amendments based on the technology
review for the Primary Copper Smelting source category?
C. What are the final rule amendments pursuant to CAA sections
112(d)(2) and (3) for the Primary Copper Smelting source category?
D. What are the final rule amendments addressing emissions
during periods of startup, shutdown, and malfunction?
E. What other changes have been made to the NESHAP?
F. What are the effective and compliance dates of the standards?
IV. What is the rationale for our final decisions and amendments for
the Primary Copper Smelting source category?
A. Residual Risk Review for the Primary Copper Smelting Source
Category
B. Technology Review for the Primary Copper Smelting Source
Category
C. CAA Sections 112(d)(2) and (3) Revisions for the Primary
Copper Smelting Source Category
D. Final Rule Amendments Addressing Bypass Stack Emissions
E. Final Rule Amendments Addressing Compliance Dates
F. Other Major Comments
V. Summary of Cost, Environmental, and Economic Impacts and
Additional Analyses Conducted
A. What are the affected facilities?
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?
VI. Statutory and Executive Order Reviews
A. Executive Orders 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
B. Paperwork Reduction Act (PRA)
C. Regulatory Flexibility Act (RFA)
D. Unfunded Mandates Reform Act (UMRA)
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act (NTTAA) and
1 CFR Part 51
J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations and Executive Order 14096: Revitalizing Our Nation's
Commitment to Environmental Justice for All
K. Congressional Review Act (CRA)

I. General Information

A. Executive Summary

This action presents the results of the U.S. Environmental
Protection Agency (EPA or the Agency) residual risk and technology
review (RTR) for the National Emission Standards for Hazardous Air
Pollutants (NESHAP) for major source Primary Copper Smelters as
required under the Clean Air Act (CAA). Pursuant to the CAA, this
action also presents the results of the technology review for the
Primary Copper Smelting area source NESHAP.
Based on the results of the risk review, the EPA is finalizing a
determination that risks from emissions of air toxics from this major
source category are currently unacceptable. This unacceptable risk
determination considers all health information, including the EPA's
analysis of health risks associated with emissions of lead and arsenic
from these facilities. The modeled exceedance of the lead National
Ambient Air Quality Standard (NAAQS) of 0.15 ug/m\3\ at Freeport
represents an important health metric in EPA's unacceptability
determination for the Primary Copper source category. The EPA estimated
that the highest modeled rolling 3-month concentration of lead at a
residential location is 0.17 ug/m\3\ based on 2019 actual emissions and
0.24 ug/m\3\ based on allowable emissions, at the Freeport facility,
refer to appendix 1; section 9 of the Residual Risk Assessment for the
Primary Copper Smelting Source Category in Support of the 2021 Risk and
Technology Review Proposed Rule for additional details of the monitor
to model comparison for this rule. The NAAQS off-site lead (Pb) monitor
(at Miami Golf Course) recorded Pb levels for 2019 were below the NAAQS
with a maximum 3-month Pb concentration at the monitor of 0.038 ug/
m\3\, while the modeled Pb concentration based upon actual emissions
for this site was 0.045 ug/m\3\. This close alignment of the monitor
with model results for the Miami Golf Course site provides us with
additional confidence in our maximum off-site model concentration of
0.17 ug/m\3\ at a residential location. The EPA also found that the
maximum individual risk (MIR) of cancer was estimated to be 70-in-1
million based on actual emissions and 90-in-1 million based on
allowable emissions (driven by arsenic emissions), which is approaching
the presumptive level of unacceptability of 100-in-1 million. In
addition, the EPA found that the maximum acute hazard quotient (HQ) was
7 (also driven by arsenic emissions). Considering all of the health
risk information and factors discussed above, along with the risk
information and uncertainties discussed in the 2022 proposed rule
preamble (87 FR 1616), the EPA has determined that the current risks
for this source category are unacceptable.
To reduce risks to an acceptable level, the EPA is finalizing a new
emission limit for particulate matter (PM) as a surrogate for
particulate hazardous air pollutant (HAP) metals (such as lead and
arsenic) in the major source NESHAP for a combination of process
fugitive roofline emissions from the anode refining department, copper
converter departments, slag cleaning vessels and smelting vessels (also
known as smelting furnaces). This standard will achieve significant
reductions of lead and arsenic emissions and their associated health
risks (as described in section IV.A. of this preamble).
Pursuant to the LEAN decision (which is described further in
section II.A. of this preamble), the EPA is also finalizing new
emissions standards based on maximum achievable control technology
(MACT) for the major source NESHAP to address currently

[[Page 41650]]

unregulated emissions of HAP, as follows: PM, as a surrogate for
particulate HAP metals, for (1) anode refining furnace point source
emissions; (2) new converters; and (3) the combination of process
fugitive roofline emissions from the anode refining department, copper
converter departments, slag cleaning vessels and smelting vessels (also
known as smelting furnaces). The EPA is also finalizing new pollutant-
specific emissions limits based on MACT for the following HAP: mercury,
lead, benzene, toluene, hydrogen chloride (HCl), chlorine, polycyclic
aromatic hydrocarbons (PAH), naphthalene and dioxins and furans (D/F).
Furthermore, in this final action, after reviewing and considering
public comments, the EPA is finalizing work practice standards
according to CAA 112(h) for bypass stacks which were previously an
unregulated emissions source.
Pursuant to the CAA mandated technology review, we are finalizing a
PM limit (as a surrogate for nonmercury metal HAP) for the combined
emissions from the Hoboken converter process fugitive capture systems
where they combine with anode refining point source emissions. This
standard will achieve significant reductions of lead and arsenic
emissions (as described in sections III.B. and IV.B. of this preamble).
Furthermore, we are finalizing emissions control design standards to
minimize process fugitive HAP metals emissions from roof vents at
facilities with flash furnaces and Peirce-Smith converters. In
addition, under the technology review the EPA is finalizing work
practice standards to minimize fugitive dust emissions which will
achieve further emissions reductions beyond the reductions that will be
achieved from the rooflines under the risk review for major sources
(described above).
With regard to primary copper smelting area sources, the Agency did
not identify any developments in practices, processes, or control
technologies. Therefore, the EPA is not finalizing any new or revised
standards pursuant to the CAA technology review for the area source
NESHAP.
In addition to the new and revised standards described in the
previous paragraphs, consistent with Sierra Club v. EPA (which is
described further in section III.D. of this preamble), the EPA is also
finalizing rule changes to remove exemptions and associated provisions
for periods of startup, shutdown, and malfunction (SSM) and to specify
that the emission standards apply at all times. The EPA is also
finalizing rule changes to require electronic reporting of performance
test results and notification of compliance reports for both area and
major sources. Implementation of the rules is expected to reduce HAP
metal emissions from primary copper smelters, improve human health, and
reduce environmental impacts associated with those emissions. This
final action will also result in improved monitoring, compliance, and
implementation of the existing standards.
During development of these proposed and final rules, the EPA also
completed a demographic analysis which indicates that cancer risks
associated with emissions from the major source category
disproportionately affect communities with environmental justice
concerns, including low-income residents, American Indians, and
Hispanics living near these facilities. Once the new and revised
standards (described in this preamble) are implemented, risks in nearby
communities due to HAP emissions will be reduced to acceptable levels
and the NESHAP will provide an ample margin of safety to protect public
health.

B. Does this action apply to me?

The source categories that are the subject of this action are
Primary Copper Smelting Major Sources regulated under 40 CFR part 63,
subpart QQQ, and Primary Copper Smelting Area Sources, regulated under
40 CFR part 63, subpart EEEEEE. 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 final action is likely to affect. The
final standards will be directly applicable to the affected sources.
State, local, and Tribal governments would not be directly affected by
this final 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 major source category addresses 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 concentrate dryers, smelting furnaces,
slag cleaning vessels, converters, and fugitive emission sources. The
area source category was added to the source category list in 2002 (67
FR 70427, 70428). Affected sources under the area source NESHAP are
concentrate dryers, smelting vessels (e.g., furnaces), converting
vessels, matte drying and grinding plants, secondary gas systems, and
anode refining operations.

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

In addition to being available in the docket, an electronic copy of
this final action will also be available on the internet. Following
signature by the EPA Administrator, the EPA will post a copy of this
final action at <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air</a> and
at <a href="https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards">https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards</a>. Following
publication in the Federal Register, the EPA will post the Federal
Register version and key technical documents at this same website.
Additional information is available on the RTR website at <a href="https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous">https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous</a>. This information
includes an overview of the RTR program and links to project websites
for the RTR source categories.

D. Judicial Review and Administrative Reconsideration

Under Clean Air Act (CAA) section 307(b)(1), judicial review of
this final action is available only by filing a petition for review in
the United States Court of Appeals for the District of Columbia Circuit
(the Court) by July 12, 2024. Under CAA section 307(b)(2), the
requirements established by this final rule may not be challenged
separately in any civil or criminal proceedings brought by the EPA to
enforce the requirements.
Section 307(d)(7)(B) of the CAA further provides that only an
objection to a rule or procedure which was raised with reasonable
specificity during the period for public comment (including any public
hearing) may be raised during judicial review. This section also
provides a mechanism for the EPA to reconsider the rule if the person
raising an objection can demonstrate to the Administrator that it was
impracticable

[[Page 41651]]

to raise such objection within the period for public comment or if the
grounds for such objection arose after the period for public comment
(but within the time specified for judicial review) and if such
objection is of central relevance to the outcome of the rule. Any
person seeking to make such a demonstration should submit a Petition
for Reconsideration to the Office of the Administrator, U.S. EPA, Room
3000, WJC South Building, 1200 Pennsylvania Ave. NW, Washington, DC
20460, with a copy to both the person(s) listed in the preceding FOR
FURTHER INFORMATION CONTACT section, and the Associate General Counsel
for the Air and Radiation Law Office, Office of General Counsel (Mail
Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW, Washington, DC 20460.

II. Background

A. What is the statutory authority for this action?

Section 112 of the CAA establishes a two-stage regulatory process
to address emissions of HAP from stationary sources. In the first
stage, we must identify categories of sources emitting one or more of
the HAP listed in CAA section 112(b) and then promulgate technology-
based NESHAP for those sources. ``Major sources'' are those that emit,
or have the potential to emit, any single HAP at a rate of 10 tons per
year (tpy) or more, or 25 tpy or more of any combination of HAP. For
major sources, these standards are commonly referred to as MACT
standards and must reflect the maximum degree of emission reductions of
HAP achievable (after considering cost, energy requirements, and non-
air quality health and environmental impacts). In developing MACT
standards, CAA section 112(d)(2) directs the EPA to consider the
application of measures, processes, methods, systems, or techniques,
including, but not limited to, those that reduce the volume of or
eliminate HAP emissions through process changes, substitution of
materials, or other modifications; enclose systems or processes to
eliminate emissions; collect, capture, or treat HAP when released from
a process, stack, storage, or fugitive emissions point; are design,
equipment, work practice, or operational standards; or any combination
of the above.
For these MACT standards, the statute specifies certain minimum
stringency requirements, which are referred to as MACT floor
requirements, and which may not be based on cost considerations. See
CAA section 112(d)(3). For new sources, the MACT floor cannot be less
stringent than the emission control achieved in practice by the best-
controlled similar source. The MACT standards for existing sources can
be less stringent than floors for new sources, but they cannot be less
stringent than the average emission limitation achieved by the best-
performing 12 percent of existing sources in the category or
subcategory (or the best-performing five sources for categories or
subcategories with fewer than 30 sources). In developing MACT
standards, we must also consider control options that are more
stringent than the floor under CAA section 112(d)(2). We may establish
standards more stringent than the floor, based on the consideration of
the cost of achieving the emissions reductions, any non-air quality
health and environmental impacts, and energy requirements. Standards
more stringent than the floor are commonly referred to as beyond-the-
floor (BTF) standards. In certain instances, as provided in CAA section
112(h), the EPA may set work practice standards in lieu of numerical
emission standards. For area sources, CAA section 112(d)(5) gives the
EPA discretion to set standards based on generally available control
technologies or management practices (Generally Available Control
Technology (GACT) standards) in lieu of MACT standards.
In the second stage of the regulatory process, the CAA requires the
EPA to undertake two different analyses, which we refer to as the
technology review and the residual risk review. Under the technology
review, we must review the technology-based standards and revise them
``as necessary (taking into account developments in practices,
processes, and control technologies)'' no less frequently than every 8
years, pursuant to CAA section 112(d)(6). In conducting this review,
the EPA is not required to recalculate the MACT floors that were
established in earlier rulemakings. 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 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). Under the
residual risk review, we must evaluate the risk to public health
remaining after application of the technology-based standards and
revise the standards, if necessary, to provide an ample margin of
safety to protect public health or to prevent, taking into
consideration costs, energy, safety, and other relevant factors, an
adverse environmental effect. The residual risk review is required
within 8 years after promulgation of the technology-based standards,
pursuant to CAA section 112(f). In conducting the residual risk review,
if the EPA determines that the current standards provide an ample
margin of safety to protect public health, it is not necessary to
revise the MACT standards pursuant to CAA section 112(f).\1\ 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. For
more information on the statutory authority for this rule, see 87 FR
1616 and 88 FR 47415.
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\1\ The Court has affirmed this approach of implementing CAA
section 112(f)(2)(A): NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. Cir.
2008) (``If EPA determines that the existing technology-based
standards provide an `ample margin of safety,' then the Agency is
free to readopt those standards during the residual risk
rulemaking.'').
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B. What is the Primary Copper Smelting source category and how does the
NESHAP regulate HAP emissions from the source category?

The primary copper smelting source category includes any facility
that 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 then the ore concentrate is 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 (SO<INF>2</INF>) gas and the iron as a
ferrous oxide slag. The majority of the SO<INF>2</INF> 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 furnace to remove impurities and oxygen, typically
by injecting natural gas and steam, to produce a high purity

[[Page 41652]]

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. In addition, fugitive
emissions are sources of HAP at primary copper smelters. The transfer
of matte, converter slag, and blister copper is the primary source of
fugitive emissions.
There are three primary copper smelting facilities in the U.S. that
are subject to the NESHAPs in this review. Two of the facilities,
Asarco and Freeport (also referred to as FMMI), are both located in
Arizona and are major sources of HAP emissions that are subject to
subpart QQQ, the major source NESHAP. The third facility, Kennecott, is
located in Utah and is an area source subject to subpart EEEEEE, the
area source NESHAP.
Two of the facilities (Asarco and Kennecott) use flash smelting
furnaces (the INCO smelting furnace and the Outotec[supreg],
respectively). 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 at the facility using the INCO furnace, the matte
is transferred via ladles to the copper converters. The Freeport
facility uses an ISASMELT 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.
At the area source primary copper smelter, molten copper matte
tapped from the Outotec[supreg] smelting furnace is not transferred as
molten material directly to the converting vessel as is performed at
the two major source smelters. Instead, the matte is first quenched
with water to form solid granules of copper matte. These matte granules
are then ground to a finer texture and fed to the flash converting
furnace for the continuous converting of copper. The continuous copper
converter differs significantly in design and operation from the
cylindrical batch converters operated at the other U.S. smelters.
Because there are no transfers of molten material between the smelting
furnace and the continuous copper converter, this technology has
inherently lower potential HAP emissions than a smelter using batch
copper converting technology.
In either a facility using batch copper converting or a facility
using continuous copper converting, and as discussed above in this
section, molten blister copper is next transferred from the converting
vessel to an anode furnace for refining to further remove residual
impurities and oxygen, and then 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 rule published on June 26, 2000 (65 FR 39326). The final rule,
promulgated on June 12, 2002 (67 FR 40478), established 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 have continuous converters, similar to the area source
(Kennecott), or another technology. The converter building is subject
to an opacity limit 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.
The NESHAP for area sources (40 CFR part 63, subpart EEEEEE)
establishes GACT standards for primary copper smelting area sources and
was proposed on October 6, 2006 (71 FR 59302) and finalized on January
23, 2007 (72 FR 2930). Technical corrections were then published on
July 3, 2007, via direct final rule (72 FR 36363). The affected sources
(i.e., copper concentrate dryers, smelting vessels, converting vessels,
matte drying and grinding plants, secondary gas systems and anode
refining departments) are subject to PM limits as a surrogate for HAP
metals. Compliance is demonstrated by either continuously measuring PM,
conducting a performance test every 2.5 years, or operating a PM
continuous emission monitoring system (CEMS).

C. What changes did we propose for the Primary Copper Smelting source
category in our January 11, 2022, proposal and in our July 24, 2023,
supplemental proposal?

On January 11, 2022, the EPA published a proposed rule in the
Federal Register (87 FR 1616) for the NESHAP for Primary Copper
Smelting, 40 CFR part 63, subpart QQQ, that took into consideration the
RTR analyses and for the NESHAP for Primary Copper Smelting Area
Sources, 40 CF part 63, subpart EEEEEE, that took into consideration
the technology review. In the 2022 proposed rule, we proposed:
<bullet> PM limits based on the MACT floor for anode refining point
sources at new and existing major sources;
<bullet> PM limits based on the MACT floor for process fugitive
emissions from roofline vents of smelting furnaces at new and existing
major sources;
<bullet> PM limits based on the MACT floor for process fugitive
emissions from roofline vents of converters at new and existing major
sources;
<bullet> PM limits based on beyond-the-floor (BTF) for process
fugitive emissions from roofline vents at anode refining operations at
new and existing major sources;
<bullet> PM limits based on the MACT floor for new converters at
major sources;
<bullet> Facility-wide mercury limit based on BTF for any
combination of stacks or other vents from the copper concentrate
dryers, copper converter department, the anode refining department, and
the smelting vessels at existing major sources;
<bullet> Facility-wide mercury limit based on the MACT floor for
new major sources;

[[Page 41653]]

<bullet> Revisions to the existing fugitive dust control work
practice standards to make them more robust than what is currently
required by the major source NESHAP;
<bullet> Removal of SSM exemptions and associated provisions and
specify that emissions standards apply at all times for both area
sources and major sources; and
<bullet> Requirements for electronic reporting of performance test
reports and notification of compliance reports for both area sources
and major sources.
During the comment period for the 2022 proposal, the EPA received
public comments from industry, Tribal nations, environmental groups,
Arizona Department of Environmental Quality (ADEQ), and private
citizens. After reviewing the comments, and after consideration of
additional data and information received since the 2022 proposal, the
EPA determined it was appropriate to gather additional data, revise
some of the analyses associated with that proposal, and to publish a
supplemental proposal for the major source NESHAP.
In support of the supplemental proposal, the EPA sent a section 114
information request 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. In
response to this section 114 information request, the EPA received
performance test results for the Freeport facility containing emission
rates of benzene, 1,4-dichlorobenzene, chlorine, formaldehyde, hexane,
hydrogen fluoride, hydrogen chloride, toluene, total hydrocarbons, PAH
including naphthalene, and dioxins and furans. The section 114
information request response from Freeport also provided data regarding
costs and feasibility of installing additional controls for the aisle
scrubber including a wet electrostatic precipitator (WESP) and a
baghouse to control emissions from the Hoboken converter process
fugitive capture system. Finally, the section 114 information request
response from Freeport provided detailed information for input
materials, emission sources, and process information.
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 we
expect would be needed to comply with the emission limits proposed in
the 2022 proposal (e.g., for mercury, lead and arsenic). It also
included additional performance testing results for the roofline vents,
vent fume stack, aisle scrubber, and acid plant stack. Finally,
Freeport also voluntarily performed an additional performance test for
mercury in 2022 and submitted those results to the EPA.
Based on evaluation of all the data, we proposed several revised
and new MACT standards in a supplemental proposal published in the
Federal Register (88 FR 47415) on July 24, 2023, pursuant to CAA
sections 112(d)(2), (d)(3), (d)(6), and (f). For the supplemental
proposal, which addressed only the major source NESHAP, we proposed:
<bullet> Benzene, toluene, HCl, chlorine, PAH, naphthalene and D/F
limits based on the MACT floor for any new and existing combination of
stacks or other vents from the copper concentrate dryers, copper
converter department, the anode refining department, and the smelting
vessels at major sources based on test data submitted by the only
operating major source;
<bullet> Revisions to the proposed PM limits for process fugitive
emissions from roofline vents of smelting vessels, converters, and
anode refining operations at new and existing sources to provide a
combined emission limit for all roofline vents based on additional test
data and comments submitted by affected facilities;
<bullet> Revisions to the proposed mercury limits for any new and
existing combination of stacks or other vents from the copper
concentrate dryers, converting department, the anode refining
department, and the smelting vessels to provide a limit based on the
MACT floor after considering additional test data and comments
submitted by affected facilities; and
<bullet> Prohibition of the use of bypass stacks for major sources.
We also co-proposed two options for further controlling HAP metals
at the aisle scrubber source at Freeport as follows:
<bullet> Option 1--PM limits based on the 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 \2\ 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);
---------------------------------------------------------------------------

\2\ Based on comments on the supplemental proposal, this system
should be referred to as a process fugitive capture system for the
Hoboken converters; we are clarifying this terminology in the final
rule.
---------------------------------------------------------------------------

<bullet> Option 2--PM limits based on the addition of a baghouse
upstream of the aisle scrubber to provide additional control of the
secondary capture system for the converter department.

III. What is included in this final rule?

This action finalizes the EPA's determinations pursuant to the RTR
provisions of CAA section 112 for the Primary Copper Smelting major
source category and amends the Primary Copper Smelting major source
NESHAP, 40 CFR part 63, subpart QQQ, based on those determinations. The
changes being finalized for the major sources in this action include
promulgation of MACT floor-based PM limits for the anode refining
department point source emissions; BTF PM limits to address process
fugitive emissions from the smelting vessels, copper converter
department, and anode refining roofline vents combined; MACT floor-
based PM limits for new copper converter departments; MACT floor-based
emission standards for previously unregulated HAP (e.g., mercury,
benzene, toluene, HCl, chlorine, PAH, naphthalene and D/F); and PM
limits for the combined anode refining department and Hoboken converter
process fugitive capture systems. This action also finalizes design
standards to limit HAP metals and a BTF lead emissions limit to
minimize process fugitive emissions from roofline vents for certain
processes. In addition, this action finalizes work practice standards
for the use of bypass stacks and revisions to the fugitive dust control
plan requirements. This action also finalizes other changes to the
major source NESHAP including electronic reporting requirements and the
removal of SSM exemptions. This final action includes several changes
to the proposed requirements in the 2022 proposal and 2023 supplemental
proposal based on consideration of comments and information received
during the public comment periods as described in section IV. of this
preamble.
This action also finalizes the EPA's determination pursuant to the
technology review provisions of CAA section 112 for the Primary Copper
Smelting area source category. We determined that there are no
developments in practices, processes, and control technologies that
warrant revisions to the NESHAP for Primary Copper Smelting Area
Sources, 40 CFR part 63, subpart EEEEEE, pursuant to CAA section
112(d)(6). However, this action finalizes amendments to the area

[[Page 41654]]

source NESHAP to remove SSM exemptions and associated provisions and
provide electronic reporting requirements.

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

This section introduces the final amendments to the Primary Copper
Smelting NESHAP, 40 CFR part 63, subpart QQQ, being promulgated
pursuant to CAA section 112(f). The EPA is promulgating a PM emission
limit (as a surrogate for HAP metals other than mercury) of 6.3 pounds
per hour (lb/hour) for process fugitive emissions from roofline vents
of the smelting vessels, copper converter departments, slag cleaning
vessels and anode refining departments combined, at new and existing
sources. This emission limit is the same as proposed in the 2023
supplemental proposal. This combined PM emission limit for process
fugitive emissions from roofline vents is also being promulgated under
CAA section 112(d)(2) and (d)(3) as described in section III.C. of this
preamble.

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

We determined that there are developments in practices, processes,
and control technologies that warrant revisions to the MACT standards
for this source category. Therefore, to satisfy the requirements of CAA
section 112(d)(6), we are revising the MACT standards to include a
combined emission standard for the anode refining department point
source emissions and Hoboken converter process fugitive capture system
of 4.1 milligrams per dry standard cubic meter (mg/dscm). The
promulgated standard was co-proposed in the 2023 supplemental proposal
as one of the two options expected to require additional controls of
the combined emission streams. The promulgated standard is expected to
require the installation of PM controls (such as a baghouse) to control
the emissions from the Hoboken converter process fugitive capture
system before this emission stream combines with the anode refining
department point source exhaust in the aisle scrubber.
We are also promulgating, as proposed in the 2022 proposal,
amendments to the existing requirements for facilities to develop and
implement a fugitive dust control plan pursuant to CAA section
112(d)(6) as part of technology review.
In addition, the EPA is promulgating a lead emission limit of 0.326
lb/hour under CAA section 112(d)(2) and (3) and design standards under
CAA section 112(d)(6) for minimizing process fugitive emissions from
any combination of roofline vents associated with the Peirce-Smith
copper converter department, Inco flash furnace and the anode refining
department, at new and existing sources. The design standards are being
promulgated for the flash furnace area capture system, fuming ladle
capture system, and the anode furnace secondary hood capture and
control system to further reduce process fugitive HAP metals at
facilities with a combination of the Peirce-Smith copper converter
department, Inco flash furnace and the anode refining department. We
note that the combined lead emission limit for reducing process
fugitive emissions from roofline vents is being promulgated under CAA
section 112(d)(2) and (d)(3) as described in section III.C. of this
preamble. However, the design standards are being promulgated under CAA
section 112(d)(6).
As part of the technology review for the major source NESHAP, we
also identified regulatory gaps (previously unregulated processes or
pollutants) and are establishing new standards to fill those gaps as
described in section III.C. of this preamble.

C. What are the final rule amendments pursuant to CAA sections
112(d)(2) and (3) for the Primary Copper Smelting source category?

Pursuant to CAA sections 112(d)(2) and (3), we are promulgating
MACT floor limits for emissions of PM (as a surrogate for HAP metals
other than mercury) from new and existing anode refining departments
and new copper converter departments, which were previously unregulated
sources of HAP metals. We are also promulgating, pursuant to CAA
sections 112(d)(2) and (3), a BTF limit for emissions of PM (as a
surrogate for HAP metals other than mercury) from new and existing
sources of process fugitive emissions from the roofline vents from the
smelting vessels, slag cleaning vessels, the copper converter
department, and the anode refining department combined, which were
previously unregulated sources of HAP metals. As described in section
III.A. of this preamble, the emissions standard for new and existing
sources of process fugitive gases from the roofline vents from the
smelting vessels, slag cleaning vessels, the converter department, and
the anode refining department is also being finalized pursuant to CAA
section 112(f)(2) to address the source category unacceptable risk
determination. In addition, we are also promulgating, pursuant to CAA
sections 112(d)(2) and (3), a BTF lead emission limit to minimize
process fugitive emissions from any combination of roofline vents
associated with the Peirce-Smith copper converter department, Inco
flash furnace and the anode refining department. Lastly, we are
promulgating, pursuant to CAA sections 112(d)(2) and (3), MACT emission
limits for mercury, benzene, toluene, HCl, chlorine, PAH excluding
naphthalene, naphthalene, and D/F, all of which were previously
unregulated HAP. A summary of the MACT standards promulgated pursuant
to CAA sections 112(d)(2) and (3) is provided in table 1 below. For
more information on these standards, including their rationale, see
section IV.C. of this preamble.
BILLING CODE 6560-50-P

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[[Page 41656]]

[GRAPHIC] [TIFF OMITTED] TR13MY24.102

BILLING CODE 6560-50-C

D. What are the final rule amendments addressing emissions during
periods of startup, shutdown, and malfunction?

We are finalizing the elimination of SSM exemptions and associated
provisions in the Primary Copper Smelting NESHAPs (40 CFR part 63,
subparts QQQ and EEEEEE) as proposed in the 2022 proposal, other than
clarifications and other non-substantive updates in SSM exemption
removal explanation and provisions. In its 2008 decision in Sierra Club
v. EPA, 551 F.3d 1019 (D.C. Cir. 2008), the court vacated portions of
two provisions in the EPA's CAA section 112 regulations governing the
emissions of HAP during periods of SSM. Specifically, the court vacated
the SSM exemption contained in 40 CFR 63.6(f)(1) and (h)(1), holding
that under section 302(k) of the CAA, emissions standards or
limitations must be continuous in nature and that the SSM exemption
violates the CAA's requirement that some section 112 standards apply
continuously. Consistent with Sierra Club v. EPA, the EPA is
establishing standards in these rules that apply at all times. We have
revised table 1 (the General Provisions Applicability Table) in both
rules in several respects related to SSM. For example, we have
eliminated the incorporation of the General Provisions requirement that
the sources develop an SSM plan, changed several references related to
requirements that apply during periods of SSM, and eliminated or
revised certain recordkeeping and reporting requirements related to the
eliminated SSM exemption. The EPA also made changes to the rules to
remove or modify inappropriate, unnecessary, or redundant language in
the absence of the SSM exemption. See the 2022 proposed rule for
additional information on removal of SSM exemptions. In addition, for
40 CFR part 63, subpart QQQ, we are finalizing a work practice standard
allowing the venting of process gases through a bypass stack during
planned maintenance events under limited conditions as described in
section IV.D.

E. What other changes have been made to the NESHAP?

1. Electronic Reporting
To increase the ease and efficiency of data submittal and data
accessibility, the EPA is finalizing, as proposed in the 2022 proposal,
a requirement that owners and operators of sources subject to the
Primary Copper Smelting NESHAP for major sources (subpart QQQ) submit
electronic copies of required performance test reports and performance
evaluations of continuous monitoring systems (CMS) measuring relative
accuracy test audit (RATA) pollutants (being finalized at 40 CFR
63.1455) through the EPA's Central Data Exchange (CDX) using the
Compliance and Emissions Data Reporting Interface (CEDRI). A
description of the electronic data submission process is provided in
the memorandum Electronic Reporting Requirements for New Source
Performance Standards (NSPS) and National Emission Standards for
Hazardous Air Pollutants (NESHAP) Rules, available in the docket for
this action (Docket ID No. EPA-HQ-OAR-2020-0430-0031). The final rule
requires that performance test results or performance evaluation of CMS
measuring RATA pollutants collected using test methods that are
supported by the EPA's Electronic Reporting Tool (ERT) as listed on the
ERT website \3\ at the time of the test be submitted in the format
generated through the use of the ERT; or alternatively, owners or
operators may submit an electronic file consistent with the extensible
markup language (XML) schema listed on the EPA's ERT website. Other
performance tests or performance evaluations of CMS measuring RATA
pollutants collected using test methods that are not supported by the
EPA's ERT as listed on the EPA's ERT website at the time of the test
must be included as an attachment in the ERT or an alternate electronic
file consistent with the XML schema listed on the EPA's ERT website.
The final rule also requires that notification of compliance reports be
submitted as a portable document format (PDF) upload in CEDRI.
---------------------------------------------------------------------------

\3\ <a href="https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert">https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert</a>.
---------------------------------------------------------------------------

We are finalizing the electronic reporting requirements for the
Primary Copper Smelting NESHAP for area sources (40 CFR part 63,
subpart EEEEEE) as proposed in the 2022 proposal. The electronic
reporting requirements are in 40 CFR 63.11147, 63.11148, and 63.11149
of the rule, and include electronic reporting requirements for monthly
emissions reports, emergency notifications, notifications of a
deviation, semi-annual monitoring reports; and performance tests, where
applicable.
2. Other Changes
The EPA is finalizing, as proposed in the 2022 proposal, the
revision to the applicability description under Sec. 63.1441 to
clarify that the NESHAP applies to major source smelting facilities
that use any type of converter, not just batch converters because the
current definition limits applicability to only major sources that use
batch converters. The major source NESHAP should apply to any Primary
Copper major source regardless of what type of converter they use.
Therefore, we are finalizing this change.
Regarding revisions to testing requirements, the Agency is
finalizing, as proposed in the 2022 proposal,

[[Page 41657]]

revisions to the wording in Sec. 63.1450 clarifying that facilities
must test for filterable particulate, not total particulate. The test
methods in Sec. 63.1450(a) have not changed for PM from the existing
regulation. The methods in the existing regulation (Methods 5, 5D, and
17) are methods for filterable PM. Total PM includes filterable PM and
condensable PM. The condensable PM test method (Method 202) is not
included in the existing regulation for the emission standards set in
2002. In conjunction with clarifying that facilities must test for
filterable particulate, not total particulate, we are changing all
instances of the wording ``total particulate matter'' in the current
rule to ``filterable particulate matter.''
The Agency is finalizing, as proposed in the 2022 proposal and 2023
supplemental proposal, the addition of appropriate test methods for
PM<INF>10</INF>, fugitive PM, mercury, benzene, toluene, chlorine,
hydrogen chloride, PAH excluding naphthalene, naphthalene, and dioxins/
furans, as well as updating test methods that are incorporated by
reference because the affected facilities will need to know what test
methods they need to use to demonstrate compliance with the new
standards.
Finally, the EPA is finalizing, as proposed in the 2022 proposal,
to revise the definitions under Sec. 63.1459 by changing the term
``smelting furnace'' to ``smelting vessel'' to be consistent with the
definition in the area source rule, 40 CFR part 63, subpart EEEEEE,
because we find it is appropriate that both rules include the broader
definition of smelting vessel, which is already in the area source
rule. The specific definition is as follows: Smelting vessel means a
furnace, reactor, or other type of vessel in which copper ore
concentrate and fluxes are smelted to form a molten mass of material
containing copper matte and slag. Other copper-bearing materials may
also be charged to the smelting vessel.

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

For the additional MACT floor emission limits (mercury, HCl,
chlorine, D/F, benzene, toluene, PAHs excluding naphthalene, and
naphthalene) in 40 CFR part 63, subpart QQQ, the EPA is finalizing, as
proposed in the 2023 supplemental proposal, the requirement that
existing facilities must comply with these limits within 1 year after
promulgation because we estimated both facilities can meet these MACT
floor limits without having to install new controls. Similarly, for the
new PM emission standard for anode refining point sources where the
anode emissions are not combined with Hoboken converter process
fugitive capture system emissions in an aisle scrubber, the Agency is
finalizing, as proposed in the 2022 proposal, the proposed requirement
that existing facilities must comply within 1 year after promulgation
of the final rule as major source facilities that do not combine their
anode point source emissions are expected to meet the limit without
additional controls. For anode refining point sources that combine
their anode emissions with Hoboken converter process fugitive capture
system emissions in an aisle scrubber, compliance with the anode
refining point source limit will be demonstrated through compliance
with the combined PM limit at the aisle scrubber outlet and its
associated compliance date.
For the combined PM limit at the aisle scrubber outlet, which
treats combined emissions from the Hoboken converter process fugitive
capture system and anode refining point source, the EPA is finalizing
that facilities must comply with this limit within 3 years after
promulgation of the final rule. We are allowing up to 3 years to meet
this limit as we expect facilities will need up to 3 years to design,
construct and operate the necessary capture and control equipment to
meet the limit.
For the combined process fugitive PM roofline emissions limit for
copper converter departments, anode refining departments, slag cleaning
vessels and smelting vessel roofline vents, the EPA is finalizing, as
proposed in the 2023 supplemental proposal, the requirement that
existing facilities comply with this limit within 2 years after
promulgation of the final rule. We are allowing up to two years to meet
this limit as we expect facilities will need up to 2 years to design,
construct and operate the necessary capture and control equipment to
meet the limit.
For the combined process fugitive lead roofline emissions limit for
Peirce-Smith copper converter department, Inco flash furnace and the
anode refining department roofline vents, the EPA is finalizing that
facilities must comply with this limit within 3 years after
promulgation of the final rule. We are allowing up to 3 years to meet
this limit as we expect facilities will need up to 3 years to design,
construct and operate the necessary capture and control equipment to
meet the limit.
For all other changes in this action we are finalizing, as
proposed, that existing facilities must comply within 180 days after
promulgation of the final rule.
New sources must comply with all of the standards immediately upon
the effective date of the standard, May 13, 2024, or upon startup,
whichever is later.
We are also finalizing amendments to Sec. Sec. 63.1442 and 63.1443
and adding a new table (table 4 to 40 CFR part 63, subpart QQQ) which
provides the applicability dates for previously unregulated affected
sources (e.g., anode refining department, bypass stack), as well as the
effective dates and compliance dates for the emission standards
proposed in the 2022 proposal and 2023 supplemental proposal which are
being promulgated in this final action.

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

For each issue, this section provides a description of what we
proposed and what we are finalizing for the issue, the EPA's rationale
for the final decisions and amendments, and a summary of key comments
and responses. For all comments not discussed in this preamble, comment
summaries and the EPA's responses can be found in the National Emission
Standards for Hazardous Air Pollutant Emissions: Primary Copper
Smelting Residual Risk and Technology Review and Primary Copper
Smelting Area Source Technology Review: Summary of Public Comments and
Responses document, available in the docket for this action (Docket ID
No. EPA-HQ-OAR-2020-0430).

A. Residual Risk Review for the Primary Copper Smelting Source Category

1. What did we propose pursuant to CAA section 112(f) for the Primary
Copper Smelting source category?
Pursuant to CAA section 112(f), the EPA conducted a residual risk
review and presented the results of this review, along with the
proposed decisions regarding risk acceptability and ample margin of
safety, in the January 11, 2022, proposed rule (87 FR 1616). In the
2022 proposed rule, the EPA determined that risks from the primary
copper smelting source category were unacceptable due to HAP metal
(primarily lead and arsenic) emissions. Based on new information and
data received after the 2022 proposal through the comment period and
issuance of a 2022 CAA section 114 information request from the
Freeport facility, the EPA updated the baseline risk assessment,
updated control Option 1, and added a new control Option 2 that
affected the Freeport facility only. The Asarco facility has been idle
since October 2019, and therefore, a section

[[Page 41658]]

114 information request was not issued to them. The risk results for
the Asarco facility did not change in the 2023 supplemental proposal
because we did not receive any new data or information after the 2022
proposal was published and before the supplemental proposal was
published.
The results of the risk assessment for the 2022 proposal are
described in more detail in the Residual Risk Assessment for the
Primary Copper Smelting Major Source Category in Support of the 2021
Risk and Technology Review Proposed Rule document, which is available
in the docket (Docket ID No. EPA-HQ-OAR-2020-0430-0051). The results of
the baseline risk assessment for the 2023 supplemental proposal are
presented in table 2 and in more detail in the residual risk 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, which is available in the Docket for this
action (Docket ID No. EPA-HQ-OAR-2020-0430-0187).
[GRAPHIC] [TIFF OMITTED] TR13MY24.103

A refined modeling analysis for the 2022 proposal was conducted at
the facility with the highest annual concentration of lead, Freeport,
to characterize ambient concentrations of lead for 3-month intervals.
The maximum 3-month concentration was predicted for each off-site
receptor. The concentrations were then compared to the Pb NAAQS of 0.15
micrograms per cubic meter (ug/m3). The maximum 3-month off-site
modeled concentration was 0.17 ug/m3 for actual emissions and 0.24 ug/
m3 for allowable emissions, and these results occurred near the
Freeport facility. These results did not change in the 2023
supplemental proposal.
The inhalation risk assessment in the 2023 supplemental proposal
estimated that the baseline cancer maximum individual risk (MIR) was
70-in-1 million for the source category based on actual emissions. The
total estimated cancer incidence from the source category was 0.002
excess cancer cases per year, or one excess case every 500 years, with
arsenic compounds contributing 97 percent of the cancer incidence for
the source category in the 2023 supplemental proposal. Approximately
22,900 people of the 46,460 people within 50 km of the facility were
estimated to have cancer risks above 1-in-1 million from HAP emitted
from the source category. The HEM-4 model predicted the maximum chronic
noncancer hazard index (HI) value for the source category was 1
(developmental), with an acute non-cancer HQ value equal to 7 driven by
emissions of arsenic from the anode refining roofline at Freeport and,
to a lesser degree, the anode furnace point source and Hoboken
converter process fugitive capture system emissions emitted through the
aisle scrubber at Freeport.
The inhalation risk assessment based on MACT-allowable emissions
did not change from the 2022 proposal and indicated that the cancer MIR
was 90-in-1 million. The total estimated cancer incidence from the
source category was

[[Page 41659]]

0.003 excess cancer cases per year, or one excess case every 333 years,
with arsenic contributing 90 percent and cadmium contributing 8 percent
of the cancer incidence for the source category. Approximately 29,001
people were estimated to have cancer risks above 1-in-1 million from
exposure to HAP emissions if HAP were emitted at the levels allowed
under the NESHAP as it existed prior to finalization of this regulatory
action. The chronic non-cancer risks remained the same as actuals, with
acute non-cancer hazards not being modeled due to the uncertainty of
estimating acute impacts based upon hourly allowable emission
estimates.
Regarding multipathway risk, we concluded in the 2022 proposal that
there was no significant potential for multipathway health effects
based upon EPA's Tier 3 screening analysis. Due to the conservative
nature of the screens and the level of additional refinements that
would go into a site-specific multipathway assessment, were one to be
conducted, we are confident that the
HQ for ingestion exposure, specifically cadmium and mercury through
fish ingestion, is less than 1. For arsenic, maximum cancer risk posed
by fish ingestion would also be reduced to levels below 1-in-1 million,
and maximum cancer risk under the rural gardener scenario would
decrease to 20-in-1 million or less. The estimated risks for the garden
scenario seem unlikely due to the arid climate of the area and the
hypothetical nature of the scenario. Further details on the Tier 3
screening assessment can be found in Appendix 10-11 of Residual Risk
Assessment for the Primary Copper Smelting Major Source Category in
Support of the Risk and Technology Review 2021 Proposed Rule.
In the 2023 supplemental proposal, we estimated that the
multipathway and inhalation risk results would be reduced further due
to baseline arsenic emissions at proposal (2022) being lowered based
upon additional data being received. We also estimated in the 2023
supplemental proposal that, although the mercury emissions increased
from the 2022 proposal baseline, the mercury HQ would still be less
than 1 (0.2) for the fisher scenario.
For the 2023 supplemental proposal, the Agency weighed all the
health risk factors in the risk acceptability determination and
proposed that the risks from the Primary Copper Smelting source
category are unacceptable at baseline. To address the unacceptable
risks, in the supplemental proposal, we proposed a combined PM emission
limit for process fugitive emissions from roofline vents of smelting
furnaces, converters, and anode refining operations, which would
significantly reduce risks. We estimated in the supplemental proposal
that this combined PM limit would reduce emissions of HAP metal
(primarily lead and arsenic) by 4.59 tpy. To be able to comply with the
limit, we estimated that the Freeport facility would need to install
controls (e.g., improved capture system, including hoods, ductwork, and
fans, and one additional baghouse) to reduce process fugitive roofline
emissions from the anode refining source, the main risk driver. As
described in the supplemental proposal, we estimated that these
controls would reduce the MIR at Freeport from 70-in-1 million to an
estimated 20-in-1 million and that the acute noncancer HQ (for arsenic)
would be reduced from 7 to 2 (based on actual emissions). In addition,
the modeled lead concentrations would be reduced below the NAAQS. We
estimated that the MIR for Asarco would remain at 60-in-1 million and
would be the source category MIR after the proposed controls are
applied at Freeport. In the supplemental proposal, we concluded that
these risks, after implementation of proposed controls, were
acceptable. We also proposed that existing facilities would need to
comply within two years after promulgation of the final rule and new
facilities must comply with all requirements in the final rule upon
start up. We proposed that compliance would be demonstrated through an
initial performance test followed by a compliance test once per year.
We then considered whether the Primary Copper Smelting NESHAP
provides an ample margin of safety to protect public health and whether
more stringent standards are necessary to prevent an adverse
environmental effect, taking into consideration costs, energy, safety,
and other relevant factors. In considering whether the standards should
be tightened to provide an ample margin of safety to protect public
health, we considered the same risk factors that we considered for our
acceptability determination and also considered the costs,
technological feasibility, and other relevant factors related to
emissions control options that might reduce risks associated with
emissions from the source category.
As discussed in the 2023 supplemental proposal, 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), the EPA co-proposed
two regulatory options for additional control of either the secondary
capture system for the converter department \4\ 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. For Option 1, a WESP would be located downstream
of the aisle scrubber and therefore further control the combined
emissions stream of the secondary capture system for the converter
department and the point source emissions from the anode refining
department. Under Option 2, a baghouse would be installed upstream of
the aisle scrubber to provide additional control of the secondary
capture system for the converter department. The EPA proposed that
these control options would result in more stringent emission standards
for these emission sources than were currently required in 40 CFR part
63, subpart QQQ.
---------------------------------------------------------------------------

\4\ Based on cmments on the supplement proposal, this system
should be referred to as a roofline capture sysem for the Hoboken
converters; we are claarifying this termionlogy in the final rule.
---------------------------------------------------------------------------

In the 2022 proposal, the EPA evaluated additional work practices
to reduce fugitive dust emissions, and the Agency found that the
implementation of a more robust fugitive dust plan would result in an
unquantified reduction of HAP, and we therefore proposed this
requirement in the 2022 proposal. In the 2022 proposal, 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.
2. How did the risk review change for the Primary Copper Smelting
source category?
While reviewing the information provided during the 2023
supplemental proposal public comment period and reviewing the data
provided during the section 114 process, a correction was made to the
spreadsheet used to calculate the average emissions from the aisle
scrubber based on stack tests provided by Freeport. The correction
resulted in a slightly lower average arsenic emission rate for this
source (from 0.626 tpy in the supplemental proposal to 0.563 tpy in the
final rule), and therefore we re-modeled the baseline and roofline vent
control scenarios as well as the two control options for the aisle
scrubber. In addition to the corrected emission rate for the aisle
scrubber, the EPA re-evaluated the estimated control efficiencies of
the control options co-

[[Page 41660]]

proposed for the aisle scrubber source at Freeport based on the
comments and information received on the supplemental proposal. These
comments and our responses are discussed further in section IV.A.3. of
this preamble.
As discussed in the memorandum Cost Estimates for Additional
Controls of Freeport's Aisle Scrubber--REVISED, which is available in
the docket for this action, and as further discussed in section IV.B.
of this preamble, we updated the control efficiency estimates for the
aisle scrubber control options. In the 2023 supplemental proposal, we
estimated that under Option 1, installing a WESP downstream of the
aisle scrubber would achieve 95 percent control efficiency, and we
estimated 6.3 tpy metal HAP reductions. Based on the comments received
from Freeport regarding the technical feasibility of controlling the
high-volume aisle scrubber exhaust stream using a WESP and our
evaluation of those comments, we updated the estimated control
efficiency for the WESP option to 73 percent, and we now estimate 4.9
tpy metal HAP reduced. In the 2023 supplemental proposal, we estimated
that under Option 2 (Baghouse option), installing a baghouse upstream
of the aisle scrubber to control the Hoboken converter process fugitive
capture system gas stream for the copper converter department would
reduce metal HAP emissions by 4.5 tpy. Note that in the supplemental
proposal, we referred to the process fugitive capture system as a
``secondary'' capture system. However, Freeport commented that the
capture system is better characterized as a tertiary capture system.
Therefore, for the remainder of this preamble, we refer to this capture
system as the Hoboken converter process fugitive capture system.
Furthermore, based on comments received from Freeport in response to
the 2023 supplemental proposal regarding the technical feasibility of
controlling the high-volume Hoboken converter process fugitive capture
system using a baghouse and our evaluation of those comments, we now
estimate the baghouse will achieve 61 percent control efficiency of the
Hoboken converter process fugitive capture system gas stream, and using
the same assumption that this gas stream contributes 75 percent to the
aisle scrubber, we estimate that HAP metals will be reduced under this
option by 3.0 tpy (which represents an overall control efficiency of 46
percent for the aisle scrubber). Therefore, the modeling conducted in
support of the final rule was updated to reflect these new control
efficiencies. The results of the updated modeling for the aisle
scrubber control options, in addition to our consideration of public
comment on this issue, resulted in a change to what we proposed for
ample margin of safety. The details of what we are finalizing for the
ample margin of safety analysis are in section IV.A.3. of this
preamble. The details of what we are promulgating for the aisle
scrubber source are in section IV.B.3.
With the exception of the revised emissions described above, the
risk assessment supporting the final rule was conducted in the same
manner, using the same models and methods, as that conducted for the
supplemental proposal. The documentation for the final rule risk
assessment can be found in the memorandum titled Freeport Baseline and
Control Options Re-model Risk Analysis Memo, which is available in the
docket for this rulemaking.
Inhalation Risk Assessment Results.
Table 3 presents the updated summary of the inhalation risk
assessment results based on the updated modeling supporting the final
rule. The results are very similar to those of the 2023 supplemental
proposal. The only changes are to the number of people at increased
risk of cancer greater than or equal to 1-in-1 million.
BILLING CODE 6560-50-P

[[Page 41661]]

[GRAPHIC] [TIFF OMITTED] TR13MY24.104

3. What key comments did we receive on the risk review, and what are
our responses?
We received comments regarding the risk assessment for the Primary
Copper Smelting source category. The following is a summary of some of
the more significant comments and our responses to those comments.
Other comments received and our responses to those comments can be
found in the document titled National Emission Standards for Hazardous
Air Pollutant Emissions: Primary Copper Smelting Residual Risk and
Technology Review and Primary Copper Smelting Area Source Technology
Review: Summary of Public Comments and Responses, available in the
docket for this action (Docket ID No. EPA-HQ-OAR-2020-0430).
Comment: In response to the EPA's request for comment on our ample
margin of safety analysis in the 2022 proposal, in which we discussed
and sought comment on but decided not to propose additional controls
for the aisle scrubber, specifically a WESP, one commenter stated that
they agreed with our decision. The commenter suggested that the aisle
scrubber should be subject to a concentration-based filterable
particulate matter (fPM) limit of 23 mg/dscm similar to other vents
processing emissions from the vessels managing

[[Page 41662]]

molten material, and that the existing MACT floor emissions from the
aisle scrubber do not significantly contribute to the estimated risks
from metal HAP. Other commenters supported our consideration of
additional controls for the aisle scrubber. In the 2023 supplemental
proposal, we discussed another ample margin of safety analysis in which
we co-proposed two possible control options for the aisle scrubber, a
WESP downstream of the aisle scrubber or a baghouse upstream of the
aisle scrubber. One commenter expressed support for the additional
controls on the aisle scrubber and for the associated reduction to
risk. Several commenters stated the proposed options do not meet the
requirements for ample margin of safety, which according to the
commenters must be cost effective, feasible, and provide meaningful
improvement in risk to public health. One of the commenters explained
that the two metrics for evaluating risk reduction are based on the MIR
cancer risk and the noncancer HQ. Concerning these control options, the
commenters asserted the MIR is unchanged when reducing to significant
digits and that it remains at 20-in-1 million after accounting for the
associated reductions. One commenter noted that these MIR values
consider expected reductions from other risk-based standards in the
2022 proposal and 2023 supplemental proposal (e.g., the process
fugitive roofline vent standard). One of the commenters took issue with
the standard being applied only to the Freeport facility. The commenter
contended that the roofline controls to achieve acceptable risk leave
the MIR for the other major source copper smelter (Asarco)
``untouched'' at 60-in-1 million, asserting that this is ``unfair,
arbitrary and capricious, and unsupported by the record.'' While the
EPA estimated the HQ would drop from 2 to 1 for both options in the
2023 proposed rule, the commenter argued that the acute arsenic HQ
value is based on a poorly documented and outdated study, and that more
recent studies have failed to demonstrate the developmental impact
which is at the foundation of the EPA's HQ assessment. The commenters
added that the EPA has accepted much higher HQ values for arsenic in
other rules (e.g., Integrated Iron and Steel Manufacturing NESHAP 85 FR
42074, 42083; Primary Aluminum Reduction Plants NESHAP 80 FR 62390,
62398). The commenters also noted that emission reductions were
overestimated by the EPA and resulted in overstated reductions to risk.
Response: The finding of unacceptable risks is not based on any one
risk metric (e.g., acute hazard quotients), but rather considering all
health information available and the degree of uncertainty associated
with that information. In the 2015 final rule for Primary Aluminum
(Docket ID No. EPA-HQ-OAR-2011-0797), EPA weighed all health risk
factors and uncertainties in the risk acceptability determination for
the Prebake ovens subcategory. The current acute methodology, while
similar between the two rules, is still considered a screening
assessment. While the chronic cancer risks for both source categories
were comparable, the acute screening methodologies differ and must be
weighted in regard to the accuracy and uncertainty of each piece of
information in a weight-of-evidence approach for each decision. This
relevant body of information is growing fast (and will likely continue
to grow even faster), necessitating a flexible weight-of-evidence
approach that acknowledges both complexity and uncertainty in the
simplest and most transparent way possible. The acute screening risks
posed by arsenic are based upon the most up to date review of the REL
by EPA and considered the best available benchmark for assessing
current risks posed by this pollutant. The application of the acute
benchmarks when paired with our acute methodology to assess
``reasonable worst-case one-hour concentrations (i.e., 99th
percentile)'' for off-site locations where people maybe present
provides a realistic estimate or screen for short-term exposures while
we consider EPA's chronic assessment for this source category to be a
refined site-specific assessment.
Based on comments and information provided during the comment
period, we have updated the estimated control efficiency for both
options co-proposed in the 2023 supplemental proposal, and therefore
the final rule expected emission reductions are less than those
proposed in the 2023 supplemental proposal. We have taken this and all
comments into consideration and determined that it is necessary to
promulgate a PM emission limit for the combined emissions from the
anode refining point source and the Hoboken converter process fugitive
capture system pursuant to CAA section 112(d)(6) but not pursuant to
CAA section 112(f)(2) because after further consideration and
comparison to other source categories, in this specific case, we agree
with the commenter that the risk reductions are minimal and that these
controls are not necessary to ensure the NESHAP provides an ample
margin of safety pursuant to CAA section 112(f). Given the space and
infrastructure issues and challenges and effort needed to construct and
operate such a new control system at Freeport, we conclude that the
facility will likely need up to 3 years to demonstrate compliance with
the new standards, which are described in more detail in section IV.B.
of this preamble. Given the factors described above, we are finalizing
Option 2, with a revised PM emission standard of 4.1 mg/dscm, under the
CAA section 112(d)(6) technology review because we conclude that this
option represents a development in technologies, processes or practices
pursuant to section 112(d)(6). As described in more detail in section
IV.B. of this preamble, the baghouse technology to reduce metal HAP
emissions at the aisle scrubber identified in the 2023 supplemental
proposal is feasible, readily available and already in use at primary
copper smelting facilities (including Freeport) as well as in use at
facilities in other source categories. We are allowing up to 3 years to
comply with this standard because we conclude the facility will need up
to 3 years to plan, design, install and operate new controls to reduce
emissions from the aisle scrubber. The rationale for our decision to
promulgate a standard under CAA 112(d)(6) is described further in
section IV.B. of this preamble.
4. What is the rationale for our final approach and final decisions for
the risk review?
The EPA sets standards under CAA section 112(f)(2) using ``a two-
step standard-setting approach, with an analytical first step to
determine an `acceptable risk' that considers all health information,
including risk estimation uncertainty and includes a presumptive limit
on MIR of approximately 1-in-10 thousand.\5\ If risks are unacceptable,
the EPA must determine the emissions standards necessary to reduce risk
to an acceptable level without considering costs. A second step follows
in which the actual standard is set at a level that provides `an ample
margin of safety' in consideration of all health information, including
the number of persons at risk levels higher than approximately 1-in-1
million, as well as other relevant factors including costs and economic
impacts, technological feasibility, and other

[[Page 41663]]

factors relevant to each particular decision.'' As discussed in more
detail in the 2022 proposal and in the Benzene NESHAP, there is
flexibility regarding factors the EPA may consider in making
determinations and how the EPA may weigh those factors for each source
category. The EPA conducts a risk assessment that provides estimates of
the MIR posed by emissions of HAP that are carcinogens from each source
in the source category, the HI for chronic exposures to HAP with the
potential to cause noncancer health effects, the HQ for acute exposures
to HAP with the potential to cause noncancer health effects,\6\ and to
assess risks for lead, the EPA compares ambient air concentrations with
the lead NAAQS, which is 0.15 ug/m3 based on 3-month rolling averages.
The assessment also provides estimates of the distribution of cancer
risk within the exposed populations, cancer incidence, and an
evaluation of the potential for an adverse environmental effect. (54 FR
38045, September 14, 1989) As discussed in the 2022 proposed rule, the
scope of the EPA's risk analysis is consistent with the explanation in
EPA's response to comments on our policy under the Benzene NESHAP (54
FR 38057) summarized hereafter: In summary, the EPA's policy permits
consideration of multiple measures of health risk including, but not
limited to, the MIR, the presence of non-cancer health effects, and the
uncertainties of the risk estimates such that these factors can then be
weighed in each individual case. The EPA's policy, as discussed in the
Benzene NESHAP response to comments, also complies with the
Congressional intent behind the CAA.
---------------------------------------------------------------------------

\5\ 1-in-10 thousand is equivalent to 100-in-1 million. The EPA
currently describes cancer risks as `n-in-1 million.'
\6\ The MIR is defined as the cancer risk associated with a
lifetime of exposure at the highest concentration of HAP where
people are likely to live. The HQ is the ratio of the potential HAP
exposure concentration to the noncancer dose-response value; the HI
is the sum of HQs for HAP that affect the same target organ or organ
system.
---------------------------------------------------------------------------

Thus, the level of the MIR is only one factor to be weighed in
determining acceptability of risk. The Benzene NESHAP explained that
``an MIR of approximately one in 10 thousand should ordinarily be the
upper end of the range of acceptability. As risks increase above this
benchmark, they become presumptively less acceptable under CAA section
112, and would be weighed with the other health risk measures and
information in making an overall judgment on acceptability. Or, the
Agency may find, in a particular case, that a risk that includes an MIR
less than the presumptively acceptable level is unacceptable in the
light of other health risk factors.'' Id. at 38045. In other words,
risks that include an MIR above 100-in-1 million may be determined to
be acceptable, and risks with an MIR below that level may be determined
to be unacceptable, depending on all of the available health
information.
a. Acceptability Determination
In this final rule, as in the 2023 supplemental proposal and in the
2022 proposal, the EPA concludes that the baseline risks are
unacceptable. This determination, as described in the 2022 proposal and
the 2023 supplemental proposal, is largely based on the estimated
exceedance of the lead NAAQS, along with the maximum acute HQ of 7 for
arsenic, which indicate there are significant risks of acute noncancer
health effects--especially for children, infants, and developing
fetuses, all of whom are particularly vulnerable to chemical exposures
as they undergo key developmental processes. Also contributing to this
determination, although to a lesser extent, are the inhalation cancer
MIRs due to arsenic, with an estimated MIR of 70-in-1 million for
actual emissions and 90-in-1 million for allowable emissions, which are
approaching the presumptive level of unacceptability of 100-in-1
million.
b. What is EPA requiring in the final rule to address the unacceptable
risk?
To address the unacceptable risk, the Agency is promulgating a
combined PM emission limit (as a surrogate for HAP metals other than
mercury) for process fugitive emissions from roofline vents of a
combination of smelting vessels, copper converter departments, slag
cleaning vessels and anode refining departments at new and existing
sources as proposed in the 2023 supplemental proposal. We are also
finalizing the PM emission standard pursuant to CAA section 112(d)(2)
and (d)(3) as discussed further in section IV.C. of this preamble. We
are also finalizing, as proposed, that compliance would be demonstrated
through an initial performance test followed by a compliance test once
per year.
c. Remaining Risks After Implementation of the Requirements To Address
Unacceptable Risk
To determine the remaining risks after implementation of the new
combined PM emission limit to control process fugitive emissions from
the roofline vents, we conducted a post-control risk assessment. As
described in section IV.A.2., the baseline emissions for the aisle
scrubber source at Freeport were corrected and the baseline modeling
was conducted again for the final rule along with the roofline vents
control option. The revised baseline modeling results, as discussed in
section IV.A.2., did not result in any change to the acceptability
determination or to the main risk driver under section 112(f) of the
CAA. More details on the modeling for the final rule are in the
memorandum Freeport Baseline and Control Options Re-model Risk Analysis
Memo, found in the docket for this action. More details on the modeling
analysis for the 2023 supplemental proposal are described 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 ID No. EPA-HQ-OAR-2020-0430-0187).
The post-control modeled risks were updated as described in the
memorandum Freeport Baseline and Control Options Re-model Risk Analysis
Memo, available in the docket for this rule (Docket ID No. EPA-HQ-OAR-
2020-0430). The risk assessment after implementing the PM limit for
process fugitive emission from roof vents as discussed in this section
of this preamble indicates that the modeled lead concentrations would
be reduced to 0.06 [micro]g/m3, which is below the NAAQS of 0.15
[micro]g/m3. The MIR at Freeport is reduced from 70-in-1 million to 20-
in-1 million and the population with cancer risks greater than or equal
to 1-in-1 million is reduced from 21,875 to 16,035. We estimate that at
Freeport the maximum chronic noncancer inhalation TOSHI will be reduced
from 1 to less than 1 (0.3), and the acute HQ will be reduced from a
value of 7 to 2. We estimate that the source category MIR after
implementation of the PM limit for process fugitive emissions from
roofline vents will be 60-in-1 million, which is the maximum baseline
cancer risk near the Asarco facility. We expect that Asarco can comply
with the PM standard for process fugitive emissions from roofline vents
without additional controls, and therefore it will not achieve emission
reductions at Asarco as a result of this PM limit. However, as
described in sections III.B. and III.C., and IV.B. and IV.C. of this
preamble, we are finalizing a lead limit under CAA sections 112(d)(2)
and (3) and design standards under our CAA section 112(d)(6) technology
review, respectively, that will achieve reductions of HAP metal
emissions at Asarco. We note that the facility already has plans to
implement improvements (consistent with the design standards in

[[Page 41664]]

this final rule) that will reduce their process fugitive emissions of
metal HAP as well as SO<INF>2</INF> emissions. In fact, these
improvements have been adopted into their most recent state operating
permit (finalized in October 2023). As mentioned elsewhere in this
preamble, Asarco is currently not operating. However, we expect that
these improvement projects will likely reduce the MIR when Asarco
returns to operating status.
Based on the post-control risk assessment, we conclude that, after
the requirements described in this preamble to address unacceptable
risk are implemented, the risks to public health will be reduced to an
acceptable level.
d. Ample Margin of Safety Analysis
Under the ample margin of safety analysis, we again considered all
of the health factors evaluated in the acceptability determination and
evaluated the cost and feasibility of available control technologies
and other measures (including the controls, measures, and costs
reviewed under the technology review) that could be applied to further
reduce the risks due to emission of HAP identified in our risk
assessment.
While the additional controls for the combined gas stream from the
anode refining department and the Hoboken converter process fugitive
capture system identified under the technology review will provide some
additional risk reduction, in this case the additional risk reduction
is minimal (for example, no change in the cancer MIR of 20-in-1
million), and therefore we are not finalizing this emission standard to
provide an ample margin of safety. We conclude that the standards we
are finalizing to achieve acceptable risk will also provide an ample
margin of safety to protect public health and that, as proposed, a more
stringent standard is not necessary to prevent an adverse environmental
effect in accordance with CAA section 112(f)(2).

B. Technology Review for the Primary Copper Smelting Source Category

1. What did we propose pursuant to CAA section 112(d)(6) for the
Primary Copper Smelting source category?
In the 2022 proposal, as part of our ample margin of safety
analysis and technology review, we considered additional controls for
the Freeport aisle scrubber which was the second highest contributor to
the baseline risks, estimated to represent 23 percent of the MIR. We
estimated emission reductions and costs for controlling the combined
emissions stream of the anode refining department and Hoboken converter
process fugitive capture system (i.e., the aisle scrubber) with a WESP.
We also estimated the impacts on risk reductions of these additional
controls. The Agency sought comment on this control option but did not
propose it in the 2022 proposal. We received comments on the control
option for the aisle scrubber as well as additional information from
the Freeport facility in response to the EPA's 2022 section 114
information request.
Subsequently, in the 2023 supplemental proposal, based on the
comments on the 2022 proposal and the new information from the section
114 information request, the EPA co-proposed regulatory options for
additional control of either the Hoboken converter process fugitive
capture system or additional control of the combined emissions stream
of the Hoboken converter process fugitive capture system and the anode
refining department (i.e., aisle scrubber). These standards were
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). As described in the 2023
supplemental proposal, the first option (hereafter referred to as
Option 1) was the addition of a WESP downstream of the aisle scrubber
providing additional control of the combined emissions stream from the
Hoboken converter process fugitive capture system and the anode
refining department point source (i.e., the same option evaluated by
the EPA in our ample margin of safety analysis included in the 2022
proposal). The second option (hereafter referred to as Option 2) was
the addition of a baghouse upstream of the aisle scrubber providing
additional control of the Hoboken converter process fugitive capture
system. As noted in the 2023 supplemental proposal, using performance
test data from Freeport we estimated the baseline emissions for the
aisle scrubber to be 6.63 tpy metal HAP. We also used these test data
as the basis to establish an emissions limit along with an estimate of
the expected reductions that would be achieved with the additional
controls (i.e., a new baghouse up-stream of current Aisle scrubber or a
WESP after the Aisle scrubber). To do this, we first used the data to
develop the 99 percent upper prediction limit (UPL). The 99 percent UPL
for the combined emissions stream from the anode refining department
and the Hoboken converter process fugitive capture system is 7.48 mg/
dscm. This UPL served as the baseline for the development of the
potential emission standards for each option. Secondly, the UPL value
was adjusted (decreased) based on the expected percent reduction that
would be achieved by each option. Finally, we estimated costs and risk
reductions for each control option. A summary of the options as
presented in the 2023 supplemental proposal is included here for
reference. Because we proposed these standards under both the
technology review authority of CAA section 112(d)(6) and the risk
review authority of CAA section 112(f)(2), we estimated risk reductions
associated with each of the options consistent with a CAA section
112(f)(2) ample margin of safety analysis and our summary that follows
includes those results even though the risk results would not typically
be part of the analysis to support a CAA section 112(d)(6) technology
review. The summary of the risk reductions presented are the
incremental changes attributed to the control option after considering
the effects of the implementation of the other risk-based standards in
this rulemaking (i.e., the process fugitive roofline vent standards).
For Option 1, we estimated that the control technology could
achieve 95 percent emissions reduction which was estimated to be 6.3
tpy metal HAP. The emission limit for this option was 0.374 mg/dscm.
The estimated costs were $98.5 million capital costs, $25.2 million
total annualized costs, and a cost effectiveness of $4.0 million/ton
metal HAP. Risks would be reduced below 1-in-1 million for an
additional 1,900 people (the number of people with risk greater than 1-
in-1 million would be reduced from 17,400 to 15,500). The maximum acute
HQ due to arsenic emissions would be reduced from 2 to 1. The MIR at
Freeport (20-in-1 million) and for the source category (60-in-1
million) would be unchanged by this control option.
For Option 2, we estimated that the control technology could
achieve 90 percent reduction of the Hoboken converter process fugitive
capture system emissions (or 68 percent reduction of the aisle scrubber
emissions overall) which was estimated to be 4.5 tpy metal HAP. The
emission limit for this option was 2.43 mg/dscm. The estimated costs
were $37 million capital costs, $6.2 million total annualized costs,
and a cost effectiveness of $1.38 million/ton metal HAP. Risks would be
reduced below 1-in-1 million for an additional 700 people (the number
of people with risk greater than 1-in-1 million would be reduced from
17,400 to 16,700). The maximum acute HQ due to arsenic

[[Page 41665]]

emissions would be reduced from 2 to 1. The MIR at Freeport (20-in-1
million) and for the source category (60-in-1 million) would be
unchanged by this control option.
The Agency also proposed, in the 2022 proposal, additional work
practices to reduce fugitive dust emissions and development of a
fugitive dust control plan that must be reviewed, updated (if
necessary), and approved by the Administrator or delegated permitting
authority. We proposed these requirements in order to provide an ample
margin of safety under CAA section 112(f)(2) and as a development in
practices pursuant to CAA section 112(d)(6).
With regard to the emission sources at the area source primary
copper smelting facility, including sources of fugitive dust emissions,
the Agency did not identify any developments in practices, processes,
or control technologies. For more details, refer to the document
Technology Review for the Primary Copper Smelting Source Category,
which is available in Docket ID No. EPA-HQ-OAR-2020-0430.
2. How did the technology review change for the Primary Copper Smelting
major source category?
Based on comments received during the comment period for the 2023
supplemental proposal, as discussed in more detail in section IV.B.3.
of this preamble, we revised our expected emission reductions and
control costs for the aisle scrubber control options. A detailed
description of the emission reduction estimates and cost estimates
associated with these options is provided in the memorandum Cost
Estimates for Additional Controls of Freeport's Aisle Scrubber--
REVISED, which is available in the docket for this rulemaking.
Specifically, for Option 1, we now estimate the control efficiency
as 73 percent and estimate emissions reductions of 4.9 tpy metal HAP.
We did not amend our cost estimates for this option from those
presented in the 2023 supplemental proposal. So, combining our revision
to the estimated emission reductions with the costs presented in the
2023 supplemental proposal yields a revised cost effectiveness value of
$5.2 million/ton HAP metal. We received additional information from
Freeport regarding the costs for site preparation well after the close
of the public comment period in a letter dated January 29, 2024, which
is available in the docket. In this letter, Freeport estimated costs to
demolish and relocate part of the aisle scrubber motor control center
(MCC) room, a parking and storage area, and part of the converter
maintenance building in order to install a WESP. They estimated these
site preparation costs to be $9.2M in capital. As noted above, we
received this information about four months after the close of the
comment period. Furthermore, the letter did not provide sufficient
details to determine the validity of the estimate. Therefore we have
not included it in our cost estimates. However, we note that if we did
include these costs, the total capital costs would be $108M, the
annualized costs would be $26M, and the cost effectiveness would be
slightly higher at $5.4M/ton of HAP metal reduced.
For Option 2, we now estimate the baghouse will achieve 61 percent
control efficiency of the Hoboken converter process fugitive capture
system gas stream and estimate emissions reductions of 3.0 tpy metal
HAP (which represents an overall control efficiency of 46 percent for
the aisle scrubber). We also revised our cost estimates for Option 2.
The revised cost estimates provide a total capital investment of $59.5
million, total annualized costs of $10.8 million and a cost
effectiveness of $3.6 million/ton HAP metal. As noted above under
Option 1, we received additional information from Freeport, well after
the close of the comment period, regarding costs for site preparation
in the area where a baghouse would be installed. They estimated it
would cost $5.2M to demolish and relocate the anode baghouse MCC room,
storage bunkers, and demolition and rerouting of the aisle scrubber
piping that is currently located in the area where they estimate the
baghouse would be installed. As stated under Option 1, we have not
included this cost in our estimates because we received this
information well after the close of the comment period and we have
insufficient details to evaluate its validity. However, we note that if
we did include their estimate for site preparation, the total capital
investment would increase to $64.8M, with total annualized costs of
$11.5M and a slightly higher cost effectiveness of $3.8M/ton HAP metal
reduced.
In addition, we received new information regarding the Asarco
facility since publication of the 2023 supplemental proposal. Asarco is
located in the Hayden area of Gila and Pinal Counties in Arizona and is
the primary source of lead emissions in this area. As discussed in the
2022 proposed rule, the Hayden area is currently designated as
nonattainment for the 2010, 1-hour primary SO<INF>2</INF> NAAQS and
2008 lead NAAQS. There have been various regulatory actions to reduce
emissions in this area and at the Asarco facility including, but not
limited to, a consent decree between EPA and Asarco to bring the
facility into compliance with the NESHAP by December 2018 and revisions
to the state implementation plan (SIP) to help achieve attainment of
the lead NAAQS by October 2019. However, effective March 2, 2022, the
EPA determined that the Hayden lead nonattainment area failed to attain
the 2008 lead primary and secondary lead NAAQS and the 2010 1-hour
primary SO<INF>2</INF> NAAQS (87 FR 4805, January 31, 2022) by the
applicable date of October 3, 2019. As a result, the State of Arizona
is required to submit revisions of the SIP to EPA. As part of this
process, EPA Region 9 staff informed the EPA Office of Air Quality
Planning and Standards staff in October 2023 of several projects that
Asarco has planned as part of the most recent SIP revisions and that
ADEQ has adopted into Appendix A of Asarco's operating permit (October
3, 2023), which is available in the docket for this action. The
projects include engineering controls and work practices which Asarco
estimates will reduce fugitive metal HAP emissions at the facility. The
projects that are in Asarco's operating permit include the following:
<bullet> Flash Furnace Control System: This project involves
installing and ventilating a partial enclosure around the Inco flash
furnace uptake shaft to improve the capture of process fugitives.
<bullet> Fuming Ladle Capture System: This project involves the
construction of a hood and retaining walls to improve capture of
process fugitives from fuming ladles.
<bullet> Anode Furnace Secondary Hood Capture and Control System:
This project involves the construction of secondary hoods to improve
capture and then ducts the emissions to a planned new anode secondary
hood baghouse.
These projects will help ensure that process fugitive metal HAP
roofline emissions would be reduced and will ensure that the roofline
emissions at Asarco can meet a lead limit of 0.326 lb/hour, which is
based on modeling demonstration submitted by the facility to the state
in support of a revision to the lead SIP. We expect no additional costs
to comply with the lead limit other than compliance testing costs. The
lead limit is further discussed in section IV.C.2.

[[Page 41666]]

3. What key comments did we receive on the technology review, and what
are our responses?
Comment: Commenters objected to the EPA's change in position in the
supplemental proposal about using a WESP to control aisle scrubber
emissions. The commenters stated that the EPA rejected the technology
in the 2022 proposal yet co-proposed it as an option in the 2023
supplemental proposal. Commenters stated that in the 2022 proposal, the
EPA concluded with regards to using a WESP to control aisle scrubber
emissions that ``[g]iven the relatively high estimated capital costs,
uncertainties, and moderate risk reductions . . . the Agency is not
proposing these additional controls'' under the ample margin of safety
analysis. Yet in the supplemental proposal the EPA stated the ``cost
impacts'' of $4.0 million/ton metal HAP for a WESP are ``reasonable.''
The commenters point out the new cost effectiveness in the supplemental
is more than 2 times the cost effectiveness that the EPA considered
excessive for a WESP in the 2022 proposal, and that it far exceeds the
precedent set in the recent Coke Oven proposed NESHAP revisions, where
the agency found that $1.3 million/ton is the reasonable upper
threshold of cost effectiveness for nonmercury metal HAP.
In addition to objecting to the EPA's change of position on using a
WESP, another commenter stated that the EPA overestimated the
achievable removal efficiency for a WESP in the dilute, high volume gas
stream at the aisle scrubber. The commenter asserted that the actual
removal efficiency would be 60 percent, rather than the 95 percent
estimated by the EPA. The commenter performed their own estimate of
emission reductions and cost and estimated a cost effectiveness of $6.3
million/ton HAP metal. Other commenters expressed support for using a
WESP to control aisle scrubber emissions as it would reduce metal
emissions from the converter department and the anode refining
department. The commenter stated that while the EPA does not express a
preference for either the WESP or baghouse option, the WESP-based limit
is consistent with the Clean Air Act, while the baghouse-based limit is
not. Clean Air Act section 112(d)(2) expressly provides that the EPA's
air toxics standards must require the ``maximum'' reduction that is
``achievable'' considering cost and other statutory factors. As such,
both proposed limits are achievable considering cost and other
statutory factors, however, the ``maximum'' degree of reduction that is
achievable is the one provided by the WESP-based limit. The commenter
also noted the WESP-based limit would yield substantially greater
reductions in metal HAP emissions (6.3 tpy as opposed to 4.5 tpy from
the baghouse-based limit) and would reduce cancer risk below 1-in-1
million for 1,900 people, whereas the baghouse-based limit would reduce
cancer risk below 1-in-1 million for only 700 people. Another commenter
added that emissions from smelters are virtually certain to increase in
the future as the demand for copper increases, which means that the
difference in reductions in using a WESP versus a baghouse will also
increase. The commenter stated that the cost effectiveness ``of the
WESP option will increase relative to the baghouse option, therefore,
the EPA should issue a strong limit based on the reductions that are
achievable with a WESP.'' Several commenters stated that the San Carlos
Apache Tribe is directly impacted by both major source smelters, and
emissions of lead and arsenic are of particular concern due to their
persistent and bioaccumulative nature. The same commenters stated their
support for the WESP option to achieve maximum emission reductions.
These commenters also claimed that EPA underestimated the emissions of
lead and other pollutants from the copper smelters based on a
comparison to Toxics Release Inventory (TRI) data. One commenter
provided TRI estimates for lead from the Freeport smelter, stating ``In
2020, for example, the Freeport smelter alone reported emitting more
than 14 tons of lead. In 2019, it reported emitting 21 tons of lead
and, in 2018, it reported emitting more than 29 tons of lead . . .''.
Response: In the 2022 proposal, we stated that we were not
proposing the WESP control option at that time, however we solicited
comments regarding our analysis and whether we should establish more
stringent standards to reduce HAP metal emissions from the aisle
scrubber. We also subsequently requested in a 2022 section 114
information request that the Freeport facility perform feasibility
analyses for additional control of the aisle scrubber. In response to
the 2022 proposal, we received comment that we should establish more
stringent standards to reduce HAP metal from the aisle scrubber.
Therefore, we used the new information collected during the comment
period and from Freeport's response to the CAA section 114 information
request to develop the WESP and baghouse options presented in the 2023
supplemental proposal.
Based on comments we received on the 2023 supplemental proposal, we
also revised our emission reductions estimates for the WESP. As
described in the 2023 supplemental proposal, the expected control
efficiency for the WESP was 95 percent, however, we acknowledge that a
number of factors can affect control efficiency, including the
particulate concentration of the inlet stream to the control device.
The aisle scrubber handles a high volume of gas (flowrate of
approximately 1 million actual cubic feet per minute) and low
particulate loading relative to the flowrate. We agree with commenters
that the low concentration of particulate in the exhaust stream of the
aisle scrubber, which would be the inlet to the WESP, may present
technical feasibility issues in achieving a 95 percent reduction.
Therefore, we updated our estimates of emission reductions. As detailed
in the technical memorandum Cost Estimates for Additional Controls of
Freeport's Aisle Scrubber--REVISED, which is available in the docket
for this rulemaking, we back-calculated the control efficiency of the
WESP by assuming the aisle scrubber exhaust particulate would be
reduced to 1 milligram per cubic meter (mg/m3) by the WESP,
which is an assumed minimum outlet concentration for this control
technology. Based on this back-calculation, the resulting control
efficiency of the WESP is 73 percent. Applying this revised control
efficiency to the baseline emissions for the aisle scrubber (6.63 tpy
metal HAP) yields an estimated reduction of 4.9 tpy metal HAP. We did
not receive information during the 2023 supplemental proposal comment
period on our total annualized costs for the WESP option. Therefore,
when we combine the revised emission reductions (4.9 tpy metal HAP)
with the total annualized costs ($25.2 million) presented in the 2023
supplemental proposal for the WESP option, the cost effectiveness is
$5.2 million/ton HAP metal.
As described in this final rule preamble, we have concluded that,
after taking public comment into consideration and making the
appropriate revisions to our estimates, the costs for Option 1 are not
reasonable. For this reason and others discussed in this preamble, we
are not promulgating the WESP option.
In regard to comments on Tribal impacts and their concerns about
lead and arsenic, the EPA recognizes the concerns of Tribal commenters
and their representatives and we have taken their

[[Page 41667]]

comments into consideration in this action. With regard to impacts,
although the EPA determined that risks due to HAP emissions are
unacceptable at baseline for populations living close to the Freeport
facility, the EPA's risk assessment completed for this source category
indicates that health risks due to HAP emissions from primary copper
smelting sources on Tribal lands, which are further away (about 10
miles from the facility) are well within acceptability at baseline.
After the amendments in this final rule are implemented, the NESHAP
will provide an ample margin of safety for all populations, including
the San Carlos Apache Tribe. More information regarding the estimated
health risks due to lead and arsenic emissions to humans at baseline
(due to current emissions) and post-control (due to emissions after the
amendments in this action are implemented) are described in sections
III.A. and IV.A. of this preamble, and the estimated impacts to various
demographic groups are described in section V.F. of this preamble. More
details of the risk assessment are available 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.
Regarding the comments supporting the addition of WESP to control
HAP metal emissions, for the reasons described elsewhere in this
preamble, we are not promulgating the WESP option and are promulgating
the baghouse option for the aisle scrubber. We estimate that the
amendments in the final rule will reduce total metal HAP emissions
(primarily lead and arsenic) by 8 tpy for the major source category.
Regarding the TRI emissions estimates provided by the commenter
compared to our estimates, we estimate that the two major source
facilities currently emit a total of 16.7 tpy of metal HAP (the
majority of these emissions are from Freeport). We estimated these
emissions primarily using test data provided by the facility for the
sources subject to the Primary Copper Smelting major source NESHAP. The
TRI is a ``whole facility'' inventory, which means that it includes
estimates of stack and fugitive air emissions for all HAPs that are
emitted at the facility which also include emissions from non-source
category processes. Our emission estimates include those applicable to
the primary copper smelting source category only. However, as noted in
previous paragraph, this final rule will achieve an estimated reduction
of 8 tpy of HAP metals, therefore after these amendments to the NESHAP
are implemented, total estimated emissions will be about 8.7 tpy for
the major source category.
Comment: Commenters stated that the EPA erroneously describes their
facility's converters as having ``primary and secondary capture systems
and controls, but no tertiary controls.'' According to the commenter,
Hoboken converters use a side-flue intake capture system, and the
roofline canopy system (installed in 2017 as part of facility-wide
improvements to ensure the Miami area's compliance with revised
standards for SO<INF>2</INF>) is properly described as a tertiary
capture system. Therefore, the commenter noted that the proposed
standards would not appropriately apply to the converters at their
facility as they do not have ``secondary capture systems.''
Response: We have corrected the characterization of the capture and
control systems for converters at the Freeport facility in the preamble
and regulatory text associated with the final rule.
Comment: Several commenters asserted that the aisle scrubber
standards are not justified pursuant to section 112(d)(6). The
commenters argued that the EPA has not identified any ``developments in
practice, processes or control technologies'' since the original
publication of the Primary Copper Smelting NESHAP that would justify
additional controls on the aisle scrubber. Commenters noted that the
EPA cites section 112(d)(6) to claim that ``developments'' warrant the
imposition of new controls, but the EPA fails to recognize that section
112(d)(6) only authorizes revisions that are ``necessary.'' The
commenter asserted the word ``necessary'' cannot be ignored, and that
it clearly requires some showing of necessity beyond the identification
of ``developments'' because the mere existence of a development does
not make it ``necessary.'' According to commenters, the fact that the
term ``developments'' is found only in a parenthetical confirms it is
merely one component of the analysis that ultimately must conclude a
revision to a standard is ``necessary,'' a showing that the EPA has not
made here.
Response: We disagree that, in this case, additional controls to
reduce emissions at the aisle scrubber are not necessary. The aisle
scrubber stack was identified in the 2022 proposal as one of the
largest sources of metal HAP emissions at Freeport. We currently
estimate it emits 6.63 tpy of HAP metals (primarily lead and arsenic).
The aisle scrubber is a control device that is mainly used to control
SO<INF>2</INF> emissions. This device controls emissions from the anode
refining point source and emissions from the Hoboken converter process
fugitive capture system. The anode refining point source gas stream
passes through a PM control device (i.e., a baghouse) before entering
the aisle scrubber for SO<INF>2</INF> control, but the converter
process fugitive capture system is ducted directly to the aisle
scrubber without PM control prior to the aisle scrubber. We identified
and proposed in the 2023 supplemental proposal 2 options to reduce
metal HAP emissions from the aisle scrubber stack at Freeport. Our
analysis shows that the technologies to reduce metal HAP emissions at
the aisle scrubber identified in the 2023 supplemental proposal are
readily available and already in use at primary copper smelting
facilities (including Freeport) as well as in use at facilities in
other source categories. This is especially true for baghouses.
Regarding the WESP, although this technology has been applied at some
emissions points at these facilities and other metals sectors (e.g.,
Secondary Lead Smelters), we are not aware of the WESP being
successfully applied to emissions sources similar to the aisle
scrubber. Specifically, the aisle scrubber has a very high flow rate
and low concentration of PM compared to other point source emissions
sources where the WESP has been applied.
Another factor we considered in our decision is that the Asarco
facility has a secondary hood capture system to collect secondary
emissions from their Peirce-Smith converters and that secondary hood
capture system is vented to a baghouse for PM control (which also
controls metal HAP emissions). We find these PM controls are especially
important for lead and arsenic because these two pollutants are
persistent, bioaccumulative and highly toxic HAPs.
Given all of this information, we conclude that additional PM
controls are necessary to further reduce metal HAP at the aisle
scrubber source, and that the baghouse technology that we proposed in
the 2023 supplemental proposal (i.e., Option 2 in the supplemental
proposed rule) represents a development that will further reduce metal
HAP emissions at Freeport. The baghouse is a common, well demonstrated
technology used to control PM emissions from various industrial
emissions sources.
Comment: One commenter was supportive of the baghouse option
despite expressing a preference for the WESP option.

[[Page 41668]]

Other commenters were opposed to the baghouse option. These
commenters noted that the cost effectiveness of this option exceeds the
threshold for cost effectiveness for nonmercury metal HAP despite being
underestimated. Commenters stated that the EPA overstated emission
reductions and underestimated costs by about a factor of 2.
Commenters asserted that the EPA overstated the emission reductions
from this option. One commenter explained that due to the high volume
of the exhaust stream and the low particulate concentration in the
exhaust stream (estimated to be on the order of 0.001 gr/ft\3\),
control efficiency is expected to be closer to 50 percent, rather than
the 90 percent used by the EPA. The commenter explained this is because
they are not aware of any vendor guarantee of a minimum exhaust
concentration of 0.0001 gr/ft\3\ which would be required to achieve 90
percent control.
Commenters provided their own estimate of the baghouse costs of
$70-88 million and noted that the discrepancy between their estimate
and the EPA's estimate in the supplemental proposal (which differed by
about a factor of 2) can be attributed to: under sizing and, thus,
underestimating costs for ductwork; using a shaker instead of more
modern pulse jet style baghouse; using too small of a scaling factor to
size the baghouse; underestimating the cost of the lime injection
system; omitting indirect costs (e.g., freight, spare parts,
engineering procurement and construction management services, equipment
rental); and omitting contingency which the commenter included at a
value of 25 percent. Using their own emission reduction estimates of
2.5 tpy HAP metal and total annualized cost estimates ranging from
$12.7M to $14.5M (with 25 percent contingency included), commenters
estimated the cost effectiveness value for this option as being between
$4.8 to $5.8 million/ton HAP.
Response: As described in the previous comment response, we
conclude that additional PM controls are necessary to further reduce
metal HAP at the aisle scrubber source, and that the baghouse
technology represents a development that will further reduce metal HAP
emissions at Freeport. To inform our decision under the technology
review, we evaluated the types of technology used in the industry and
other source categories. We found that baghouse technology is readily
available, feasible, well demonstrated and is being used to control a
similar source at the other major source primary copper smelter in this
source category. However, we have revised our emission reductions
estimates and our cost estimates for this option after considering the
comments.
As described in the 2023 supplemental proposal, for a baghouse we
generally expect achievable control efficiencies to be at least 90
percent. We acknowledge that a number of factors can affect the control
efficiency, including the particulate concentration of the inlet stream
to the control device. Based on the engineering evaluation provided by
Freeport in their 2022 section 114 information collection request
response, the Hoboken converter process fugitive capture system has a
high flowrate and low particulate loading relative to the flowrate. We
agree with commenters that the expected concentration of particulate in
the inlet stream may present technical feasibility issues achieving a
90 percent reduction. Therefore, we updated our estimates of emission
reductions.
First, we note that through CAA section 114 information requests
for other EPA rules (e.g., electric arc furnaces (EAF), foundries), we
have collected data demonstrating that baghouses achieve average
particulate outlet concentrations below 0.001 grains per dry standard
cubic feet (gr/dscf). We found that baghouses with similar flowrates to
those expected for the Hoboken process fugitive capture system in the
EAF source category achieve, on average, outlet concentrations of
filterable particulate of 0.0006 gr/dscf with a range of 0.0001 to
0.0017 gr/dscf. For foundries, there were 2 facilities that were used
to set the new source standard which had average PM emissions of 0.0002
gr/dscf and a high value of 0.0004 gr/dscf. The other had an average of
0.0008 gr/dscf and a high value of 0.00086 gr/dscf. Considering this
information and the information provided in Freeport's engineering
evaluation for the Hoboken converter process fugitive capture system,
we back-calculated the control efficiency of the baghouse assuming that
the Hoboken converter process fugitive capture system particulate would
be reduced to 0.0005 gr/dscf which is an assumed achievable outlet
concentration for this control option when estimating the control
efficiency. The expected baghouse flowrate was taken from the Freeport
engineering analysis, and the particulate loading was assumed to be 75
percent of the aisle scrubber outlet. The resulting control efficiency
is 61 percent. Applying this revised control efficiency to the baseline
emissions for the Hoboken converter process fugitive capture system
(assumed to be 75 percent of the aisle scrubber or 4.97 tpy metal HAP)
yields an estimated reduction of 3.0 tpy metal HAP. The expected
reduction is 46 percent of the aisle scrubber emissions overall, after
the Hoboken converter process fugitive capture system baghouse stream
combines with the controlled anode refining department stream in the
aisle scrubber.
Next, concerning costs, we have updated our cost estimates after
considering the comments. We revised the estimated costs for total
capital investment to include those costs provided by the commenter for
equipment supply. We utilized the EPA cost control manual to estimate
all indirect costs including contingency in accordance with section 6,
Chapter 1--Baghouses and Filters. The revised cost estimates provide a
total capital investment of $59.5 million and total annualized costs of
$10.8 million. Using our emission reduction estimate and the total
annualized cost estimate, the cost effectiveness is $3.6 million/ton
metal HAP reduced.
While this cost effectiveness is higher than we have accepted in
the past for reducing metal HAP in some standards, there are other
relevant factors that EPA can consider, and has considered. The highest
cost effectiveness accepted in the past was $1.5M/ton of metal HAP in
2009 dollars (which is about $2M/ton of metal HAP in 2022 dollars) in
the Secondary Lead Smelting NESHAP (77 FR 556, January 5, 2012).
However, it is important to note that EPA considers other factors
besides cost-effectiveness when considering requirements under the
technology reviews, such as feasibility of controls, how well certain
controls have been demonstrated, and overall economic impacts. In this
case, as described previously in this section, we determined that
baghouse technology is readily available, feasible, well demonstrated
and is being used to control a similar source at the other major source
primary copper smelter in this source category. Furthermore, in this
specific case, we have collectively considered the significant emission
reductions of persistent, bioaccumulative, and toxic (PBT) HAPs
(primarily lead and arsenic, which are both PBT HAPs), non-air
environmental impacts, feasibility concerns, and the costs of each of
the options. We note that lead and arsenic are known developmental
toxicants that can cause particular harm to infants, children, and the
developing fetus. Furthermore, arsenic is classified as a human
carcinogen by the EPA and the World Health Organization. In addition,
we do

[[Page 41669]]

not expect that the overall economic impacts of this rule will lead to
significant changes in domestic copper production; the market price for
commercial grade copper or any products comprised of copper inputs; or
employment, as described in section V.D. of this preamble. This
rationale and these considerations are discussed in more detail in
section IV.B.4. of this preamble.
The details of our emission reduction estimates and cost estimates
have been provided in the technical memorandum Cost Estimates for
Additional Controls of Freeport's Aisle Scrubber--REVISED, which is
available in the docket for this rulemaking.
4. What is the rationale for our final approach for the technology
review?
As noted in section IV.A. of this preamble, we updated our risk
modeling based on the revisions to the expected emission reductions for
each of the options proposed in the 2023 supplemental proposal. We
conclude that, in this case, the risk reductions achieved are not
sufficient to promulgate this standard (i.e., the PM limit for the
Aisle scrubber described previously in this section) pursuant to CAA
section 112(f); however, we continue to maintain that baghouses are
proven technologies for achieving high degrees of particulate control.
We also find that additional controls on similar exhaust streams are
used in the source category. As discussed in section IV.B.3. of this
preamble, the aisle scrubber stack is one of the largest sources of
metal HAP emissions at Freeport. We estimate it emits 6.63 tpy of HAP
metals (primarily lead and arsenic). The aisle scrubber is a control
device that is mainly used to control SO<INF>2</INF> emissions from the
anode refining point source and from the Hoboken converter process
fugitive capture system. While the anode refining point source gases
are vented to a PM control device before entering the aisle scrubber,
the gas stream from the Hoboken converter process fugitive capture
system vents directly to the aisle scrubber without prior PM control.
We conclude that further reduction of metal HAP emissions from the
aisle scrubber are necessary and that there are developments in
practices, processes, or control technologies that will achieve further
reductions of metal HAP emissions at Freeport. The PM controls on this
source are especially important for reducing lead and arsenic because
these two pollutants are PBT HAPs.
To inform our decision under the technology review, we evaluated
the types of technology used in the industry and in other source
categories to control PM emissions. As discussed in this preamble, we
proposed two options in the 2023 supplemental proposal: Option 1
evaluated a tighter PM limit based on the application of a WESP
downstream of the aisle scrubber and Option 2 evaluated a tighter PM
limit based on using baghouse technology upstream of the aisle
scrubber. We next analyzed the technical feasibility, estimated costs,
and non-air environmental impacts for each option. As described in
section IV.B.3. of this preamble, we are not aware of a WESP (Option 1)
being successfully applied to emissions sources similar to the aisle
scrubber, which has a very high flow rate and low concentration of PM
compared to other point source emissions sources where the WESP has
been applied. As described previously in this preamble, we determined
that baghouse technology (Option 2) is readily available, feasible, and
is being used to control a similar source at the other major source
copper smelter in this source category.
With regard to feasibility, the Freeport facility property does not
extend far beyond its core manufacturing operations and is bordered on
one side by a railroad track; therefore, space to install large
equipment such as that required in either option is limited. In their
feasibility analysis for these control options, Freeport explained that
Option 1 requires a larger footprint than Option 2. We also considered
the secondary impacts of the two control options and found that Option
1 would require the use of significant amounts of water, which is of
particular concern because the facility is located in an arid climate
where water resources are limited.
As is permitted under CAA section 112(d)(6), we also considered the
costs of each option. The cost estimates for the WESP option include a
total capital investment of $98.5M and total annualized costs of
$25.2M. With an estimated reduction of 4.9 tpy of total metal HAP
emissions, we estimate the cost effectiveness of installing a WESP is
$5.2M/ton of HAP metal reduced. We have updated our cost and emission
reduction estimates for the baghouse option after considering the
comments as described in section IV.B.3. The revised cost estimates
include a total capital investment of $59.5 million and total
annualized costs of $10.8 million. Using our emission reduction
estimate of 3.0 tpy and the total annualized cost estimate, the cost
effectiveness is $3.6 million/ton metal HAP reduced for the baghouse
option (Option 2).
In collectively considering the emission reductions, secondary
impacts, feasibility concerns, and the costs of each of the options, we
find that Option 2 provides sizeable reductions of HAP metals,
including two highly toxic persistent bioaccumulative HAPs (i.e., lead
and arsenic) at reasonable costs while minimizing secondary impacts and
feasibility concerns. Therefore, taking into consideration the comments
and other information and data as well as the other factors discussed
in this preamble, we are promulgating a PM standard of 4.1 mg/dscm for
the combined emissions stream from the Hoboken converter process
fugitive capture system and the anode refining department (i.e., the
aisle scrubber) pursuant to CAA section 112(d)(6). We estimate this
will reduce HAP metal emissions by 3.0 tpy.
A detailed description on the development of this emission standard
is provided in the memorandum Final Emission Standard Development for
the Aisle Scrubber, which is available in the docket for this
rulemaking.
In the 2022 proposal, additional work practice standards to
minimize fugitive dust and development of a fugitive dust control plan
that must be reviewed, updated (if necessary), and approved by the
Administrator or delegated permitting authority were proposed. These
standards were proposed in order to provide an ample margin of safety
to protect public health and pursuant to CAA section 112(d)(6). In this
specific case, for the Primary Copper Smelting source category, we have
decided to promulgate the additional work practices to minimize
fugitive dust and the development of a fugitive dust control plan under
only the technology review. The work practices and dust plan
requirements are the same as proposed in the 2022 proposal. The
fugitive dust plan and work practices are appropriate under CAA section
112(d)(6) because they are practices that will ensure emissions will be
minimized. It is our understanding that the facilities are already
doing these types of practices so, although these measures are
anticipated to further address fugitive emissions and advance the goal
of minimizing HAP metal emissions, we are unable to quantify and assure
significant enough reductions in actual emissions that would
significantly reduce health risk; therefore, we are not promulgating
under CAA 112(f) in this particular case. We expect that since
facilities are already implementing most of the additional work
practices as part of requirements in the facility's operating permit or
to comply with consent

[[Page 41670]]

decree, there will be minimal additional costs to comply with the final
rule work practices and fugitive dust plan requirements. The only
additional costs would be a slight increase related to recordkeeping
and reporting requirements. For details on the work practices see the
2022 proposal preamble (87 FR 1616).
As noted in section IV.A.3., one of the commenters took issue with
the aisle scrubber standard being applied only to the Freeport facility
when their post-roofline control MIR is 20-in-1 million. They stated
that roofline controls to achieve acceptable risk leave the MIR for the
other major source copper smelter (Asarco) ``untouched'' at 60-in-1
million, asserting this is ``unfair, arbitrary and capricious, and
unsupported by the record.'' After considering this comment, our prior
proposals, and the information in the record, we evaluated options
under CAA section 112(d)(6) and 112(d)(2) and (3) to reduce process
fugitive emissions from Asarco. In the 2022 proposal, we solicited
comment on a BTF limit to control process fugitives from the flash
furnace roofline vent to reduce risk at Asarco. We estimated that to
comply with a BTF limit, the facility would need to install improved
capture and control of the flash furnaces as well as the large ladle
containing hot liquid matte from the flash furnace taping/pouring
operations, called the fuming ladle. In our cost estimates, we assumed
a new baghouse would be needed as well as a roofline ventilation
capture system. We did not receive comments on this specific BTF
standard or our cost estimation. However, as noted above in this
paragraph, we did receive the general comment that said our proposal
would do nothing to reduce the MIR of 60-in-1 million at Asarco.
Nevertheless, as described in section IV.B.2., we received new
information regarding developments in technology (3 projects to reduce
process fugitive emissions from roof vents) currently planned for the
Asarco facility (and have been incorporated into their state permit and
draft SIP), which are estimated to achieve a 30 percent reduction in
process fugitive metal HAP emissions from the roofline vents. We have
reviewed this information and agree that these developments will reduce
fugitive metal HAP emissions. We estimate, based on the roofline vent
metal HAP emissions estimates we had for the 2022 proposal and applying
a 30 percent reduction, that the total process fugitive metal HAP
emissions (including lead and arsenic, which are persistent,
bioaccumulative HAPs) from the roofline will be reduced by 0.39 tpy.
These estimates are available in the docket for this action (see
memorandum Cost Estimates for Enhanced Capture and Control of Process
Fugitive Emissions at Asarco). We expect that the reductions in process
fugitive metal HAP emissions will also reduce risk; however, we have
not yet quantified this risk reduction because the facility is not
currently operating and their future operational emission profile may
be different than what we have modeled in support of the 2022 proposed
rule. Furthermore, we received this information regarding the three
projects well after the end of the comment period and therefore we did
not have sufficient time to remodel and calculate the risk reductions
that will be achieved.
With regard to cost impacts, we estimate that for the facility to
comply with these design standards (and comply with the lead limit,
promulgated under CAA section 112(d)(2) and (3), which is discussed in
section IV.C.2. of this preamble), the facility will need to install
improved capture and control consistent with what is expected under the
state permit and SIP. As mentioned in section IV.B. of this preamble,
the improvements needed to comply with the design standards and
emissions limit are already adopted into the facility's operating
permit and therefore costs impacts are already expected regardless of
the requirements we are including in this final rule. However, since
the facility has not yet begun construction for these improvements, we
estimated costs for these projects as part of this action. We estimate
that the total costs for complying with the design standards and lead
emission limit are $15.4M in capital costs and $3.9M in annualized
costs. Asarco provided estimated costs for these projects in a letter
provided on February 26, 2024, which is available in the docket for
this action. They estimate total capital costs of $22.4M and $5.8M in
annualized costs for all three projects. Given the late submittal and
the court-ordered promulgation deadline of May 2, 2024, we did not have
sufficient time to review these estimates and determine their validity.
However, we note again that the projects are already requirements in
their operating permit and the facility is already expecting to incur
these costs unrelated to the NESHAP. More details on the estimated
costs are found in the memorandum Cost Estimates for Enhanced Capture
and Control of Process Fugitive Emissions at Asarco, which is available
in the docket for this action. To achieve reduction of HAP metals at
Asarco, we are finalizing design standards consistent with their 2023
operating permit which include improved capture and control of the
Peirce-Smith flash furnaces, fuming ladles, and anode furnaces.

C. CAA Sections 112(d)(2) and (3) Revisions for the Primary Copper
Smelting Source Category

1. Anode Refining Point Source Emissions
a. What did we propose for the anode refining point source pursuant to
CAA section 112(d)(2) and (d)(3)?
We proposed a MACT floor PM limit as a surrogate for metal HAP in
40 CFR 63.1444(i) (finalized at 40 CFR 63.1444(f)) for new and existing
anode refining departments in the 2022 proposal. The MACT floor
emissions standard for new and existing sources, 5.78 mg/dscm, was
developed based on the 99 percent UPL for PM emissions from the
available emissions data (which was from Asarco) and represents the
MACT floor level of control. We considered beyond-the-floor options for
the standard, but we did not identify any feasible, cost-effective
beyond-the-floor options. It should be noted that at the Freeport
facility, the anode refining department gas stream and the Hoboken
converter process fugitive capture system exhaust stream are both
routed to and combined in the aisle scrubber from which they are
emitted to the atmosphere. The facility conducts performance tests
after the anode refining department stream is combined with the Hoboken
converter process fugitive capture system exhaust stream (i.e., at the
aisle scrubber outlet). Therefore, the EPA also proposed amendments to
the existing alternative emission limit in 40 CFR 63.1446 to include
the anode refining department stream, as we expected Freeport would be
able to use this option to demonstrate compliance with the anode
refining department emission limit at the aisle scrubber outlet.
Lastly, we proposed in 40 CFR 63.1451(a) and 63.1453(a), respectively,
that compliance with the PM emissions limit for the anode refining
department will be demonstrated through an initial performance test
followed by a compliance test at least once per year.
b. How did the anode refining point source revisions made pursuant to
CAA section 112(d)(2) and (3) change since proposal?
There are no changes to the emission standard for the anode
refining point source since the proposals, except that we rounded the
5.78 mg/dscm to 2

[[Page 41671]]

significant figures (i.e., 5.8 mg/dscm). We are promulgating the MACT
floor-based PM emission standard of 5.8 mg/dscm for the anode refining
department point source emissions (i.e., emissions exiting the anode
baghouse) and related compliance requirements, as proposed in the 2022
proposal. However, because Freeport combines their anode refining point
source emissions with the fugitive capture system from the Hoboken
converters, we are also finalizing, as proposed, to include the anode
refining department point source emissions as an emission source to be
included in the alternative emission limit calculation for the combined
stream.
Additionally, in the final rule based on comments, we are also
providing that facilities that combine the anode refining department
and Hoboken converter process fugitive capture system streams must
comply with the combined stream PM limit of 4.1 mg/dscm and related
compliance requirements to demonstrate compliance with the anode
refining department emission standard and related compliance
requirements. As discussed in section IV.B. of this preamble and
pursuant to CAA section 112 (d)(6), we are finalizing a PM emission
standard of 4.1 mg/dscm for the combined stream of the anode refining
department and Hoboken converter process fugitive capture system and an
annual compliance testing requirement.
c. What key comments did we receive on the proposed anode refining
point source revisions made pursuant to CAA section 112(d)(2) and (3)
and what are our responses?
Comment: One commenter stated that the EPA should set the PM MACT
floor based on a concentration limit of 23 mg/dscm, which is an
existing technology-based limit for similar emission points in the
current NESHAP rather than the 99 percent UPL emission standard
developed using only data from Asarco. The commenter explained that
this limit should be applied at their aisle scrubber stack, which is
the emission point for emissions from their Hoboken converter process
fugitive capture system and their anode refining department, thus each
affected source would be subject to the same 23 mg/dscm limit. The
commenter added that the EPA does not have sufficient data to set a
mass rate for the anode refining department MACT floor since the only
data used to set the limit are from Asarco, which does not reflect the
operating performance of their anode refining department and does not
reflect the best 5 sources as is required by the EPA's procedure for
source categories with less than 30 sources. The commenter explained
that they cannot provide performance tests of their anode refining
department emissions using EPA methods because of the duct
configuration of the baghouse controlling these emissions. However, in
their comment letter they submitted an engineering evaluation which
characterized the flowrate and particulate emissions for the anode
refining department's baghouse. The engineering evaluation was not
conducted following EPA methods. The commenter used the data from the
engineering evaluation with the data the EPA used in the development of
the 99 percent UPL (i.e., Asarco's data) to estimate a revised MACT
standard, 7.3 mg/dscm. The commenter stated that the purpose of the
recalculation of the MACT standard was to demonstrate their argument
that more data collection is necessary to support the development of a
representative MACT standard for the anode refining department.
Response: First, as described in the preamble of the 2022 proposal,
the emission standard for the anode refining point source was proposed
pursuant to CAA section 112(d)(2) and (3). This standard is not being
proposed pursuant to CAA section 112(d)(6). The 1998 proposal for
primary copper smelting identified the anode refining department in the
definition of primary copper smelters; however, the EPA did not have
sufficient data at the time to set a standard for this emission source.
In contrast, in the 2007 area source NESHAP for primary copper
smelting, data were available to set an emissions standard for the
anode refining department. With the recently acquired Asarco data, we
now have sufficient data to develop a MACT floor emission standard for
the anode refining point source at major sources. The Asarco data
includes 9 data points, which exceeds the minimum sample size of 3 data
points necessary to develop a MACT floor. Therefore, we disagree that
we have insufficient data to develop the emission standard. We also do
not find the data included in Freeport's engineering evaluation
appropriate to include in the MACT floor dataset since these data were
not collected following EPA methods. In regard to the comment that the
MACT floor limit does not reflect the best 5 sources, there are only
two major sources in this category, and as stated, only one of these
major sources had valid data from an anode refining department. We used
all available valid data from the best performing sources for which the
EPA could reasonably obtain emissions information in the category,
which is in accordance with CAA section 112 (d)(3)(B).
Comment: One commenter explained that the configuration of their
anode refining department baghouse makes the proposed test methods
infeasible. The commenter stated that the anode refining department
exhaust at their facility is controlled by a baghouse, which is ducted
to the aisle scrubber where it combines with exhaust from the
facility's Hoboken converter process fugitive capture system. The point
of emission for their anode refining department exhaust is the outlet
of the aisle scrubber. The commenter stated implementing the
alternative emission limit option to comply with the anode refining
limit (as proposed by the EPA) is not feasible due to the inability to
measure flowrate using EPA Method 1 in the duct between the baghouse
outlet and aisle scrubber inlet. The commenter explained the ductwork
does not have enough straight passes to measure flowrate according to
EPA Method 1.
Response: Based on reviewing information submitted by the commenter
and observations made by the EPA during a November 7, 2023, site visit
to the facility, the EPA agrees that there is currently no viable
testing location for flowrates using EPA Method 1 from the anode
refining department baghouse to the aisle scrubber. In light of this
new information, we agree that the use of the alternative emission
limit is not an option for demonstrating compliance with the anode
refining department for this facility. However, this alternative
emission limit procedure may be appropriate at a new facility; thus, we
are finalizing the proposed amendment to add the anode refining
department to the list of emission sources which could be included in
the emission alternative limit calculation option. However, as
discussed elsewhere, we are promulgating a limit for the combined
stream of the anode refining department and Hoboken converter process
fugitive capture system (i.e., the Freeport aisle scrubber). Based on
the data provided by the Freeport facility in their section 114
information request response, an estimated 75 percent of the
particulate emissions emitted from the aisle scrubber are from the
Hoboken converter process fugitive capture system while the remaining
25 percent are from the anode refining baghouse. The emission standard
for the combined stream of the anode refining department and Hoboken
converter process fugitive capture system based on 61 percent control
of the emissions by a baghouse controlling the emissions from the

[[Page 41672]]

Hoboken converter process fugitive capture system is 4.1 mg/dscm. The
emission standard for the combined stream of the anode refining
department and Hoboken converter process fugitive capture system is
more stringent than the anode refining department emission standard
alone (5.8 mg/dscm). Therefore, we are finalizing that compliance with
the emission standard for the combined stream of the anode refining
department and Hoboken converter process fugitive capture system
demonstrates compliance with the anode refining department emission
standard.
Comment: One commenter stated that in the 2022 proposal the EPA
proposed a new MACT floor limit for the anode refining department. The
commenter requested clarification if the PM limits for the aisle
scrubber in the 2023 supplemental proposal replace the anode refining
department limit in the 2022 proposal (because their anode refining
department baghouse vents to the aisle scrubber), or if the EPA intends
to retain the separate anode baghouse requirement.
Response: As described in section IV.B. of this preamble, we are
promulgating a particulate emission limit for the combined stream of
the anode refining department and the Hoboken converter process
fugitive capture system (i.e., aisle scrubber) as proposed in the 2023
supplemental proposal, as well as an independent anode refining
department emission limit as proposed in the 2022 proposal. Compliance
with the anode refining department emission limit will be demonstrated
by complying with the appropriate limit, i.e., if there is a combined
emission stream then the affected source will comply with the combined
emission standard, or if the anode refining department is independent
(i.e., not combined with other emission streams), then the affected
source will comply with the independent limit for anode refining
department.
d. What is the rationale for our final approach and final decisions for
the anode refining point source revisions made pursuant to CAA section
112(d)(2) and (3)?
As discussed in the 2022 proposal preamble, the 1998 proposal for
primary copper smelting major sources identified anode refining in the
definition of primary copper smelters. However, at that time, the EPA
did not have sufficient data to set an emission limit for anode
refining, and therefore did not propose specific emission standards for
anode refining operations in the major source NESHAP. The 2007 area
source NESHAP includes emission standards for anode refining operations
at area sources. Therefore, in the 2022 proposal, we concluded that
anode refining is part of the source category and emits HAP emissions.
In the 2022 proposal, we considered a BTF option, but did not consider
going BTF in this case due to cost effectiveness. Pursuant to section
112(d)(2) and (3), we are finalizing, as proposed in the 2022 proposal,
a MACT floor PM limit of 5.8 mg/dscm as a surrogate for metal HAP for
new and existing anode refining departments. We are finalizing, as
proposed, that compliance with the PM emissions limit for the anode
refining department will be demonstrated through an initial performance
test followed by a compliance test at least once per year. We are also
finalizing to include the anode refining department as an emission
source to be included in the alternative emission limit calculation for
new facilities.
Based on the comments received on the 2022 proposal and the 2023
supplemental proposal and on information collected during a November 7,
2023, site visit to the Freeport facility, we are promulgating that
compliance with the combined emission standard of 4.1 mg/dscm, for the
combination of anode refining department emissions and Hoboken
converter process fugitive capture system emissions (being promulgated
under CAA section 112(d)(6) as described in section IV.B. of this
preamble) will demonstrate compliance with the anode refining MACT
floor PM limit. Under section 112(d)(6), we are finalizing initial and
continuous compliance requirements for the combined emission standard
including initial and subsequent annual performance testing. The
combined standard and associated compliance requirements will ensure
that affected sources can demonstrate compliance with the rule
requirements.
2. Process Fugitive Emissions From Roofline Vents
a. What did we propose for process fugitive emissions from roofline
vents pursuant to CAA section 112(d)(2) and (d)(3)?
As noted previously in the preamble for this final rule, the
standards and associated compliance requirements for the process
fugitive emissions from roofline vents source are being finalized
pursuant CAA section 112(f)(2) to address unacceptable risk for the
source category as well as pursuant to CAA section 112(d)(2) and (3).
As proposed in the 2022 proposal and the 2023 supplemental proposal, we
are promulgating the same emission standard to reduce risk to a level
that would be considered acceptable and to satisfy the requirements of
CAA section 112(d)(2) and (3). As discussed in the context of risk in
section IV.A. of the preamble for this final rule, we proposed emission
standards for the process fugitive emissions from roofline vents. In
the 2022 proposal, we proposed separate standards for each roofline
vent (i.e., smelting vessels, copper converter department, and anode
refining department) based on emissions data received from the Freeport
facility. We performed a BTF analysis for additional controls of each
roofline vent and concluded in the 2022 proposal that a BTF standard
was appropriate for the anode refining process fugitive roofline vent
while MACT floor standards were appropriate for the smelting and copper
converter roofline vents.
During the comment period for the 2022 proposal, we received
additional test data of the roofline vents from the Freeport facility.
We received comments from both facilities in the major source category
requesting that the roofline vent be a combined limit because there is
comingling of emissions in the building where the processes are
located. We received significant comment regarding the proposed test
methods for demonstrating compliance with the roofline vent emission
standards. We also received comments on our cost estimates for the BTF
control option of the anode refining roofline vent.
In the 2023 supplemental proposal, we proposed a combined limit.
The combined limit was 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. We also adjusted our costs in response to
public comments on the proposed option to reflect the design
requirements at the Freeport facility primarily by increasing the
baghouse flowrate, lowering the air to cloth ratio and adding a lime
injection system. The revised capital costs were $10.2 million and
annualized costs were $2.14 million. The baghouse is expected to
achieve 4.59 tpy reduction of lead and arsenic with a cost

[[Page 41673]]

effectiveness of $467,000/ton metal HAP.
In addition, in the 2022 proposal we solicited comment on a lead
limit for the roofline vents in addition to, or instead of, the PM
limit for the anode refining roof vents. The agency considered a
possible lead limit of 0.26 lb/hr as a potential BTF MACT limit for
anode refining process fugitive emissions.
b. How did the requirements for process fugitive emissions from
roofline vents proposed pursuant to CAA section 112(d)(2) and (3)
change since proposal?
As discussed in this preamble, we are promulgating the combined BTF
PM limit of 6.3 lb/hour for the roofline vents as proposed in the 2023
supplemental proposal. The BTF control cost estimates were updated to
incorporate the most current bank prime interest rate resulting in a
small increase in total annualized costs which are now estimated as
$2.30 million with a resulting cost effectiveness of $500,000/ton metal
HAP with 4.6 tpy (rounded from 4.59 tpy) reduction of lead and arsenic.
The revised cost estimates are documented in the memorandum Cost
Estimates for Enhanced Capture and Control of Process Fugitive
Emissions from the Anode Refining Operations at Freeport--REVISED,
which is available in the docket for this rulemaking. The cost
estimates were otherwise unchanged and the adjustments do not change
our conclusions about the necessity of promulgating the BTF standard.
However, we received significant comment on the proposed compliance
test methods. To address some of the concerns raised by the commenters,
we are promulgating revised methods and allowing the use of Federal
reference method (FRM) and Federal equivalent method (FEM) monitors as
discussed in section IV.C.2.c.
We are promulgating a lead emission limit of 0.326 lb/hour for
minimizing process fugitive emissions from any combination of roofline
vents associated with the Peirce-Smith copper converter department,
Inco flash furnace and the anode refining department, at existing
sources. This emissions limit reflects the estimated reductions that
will be achieved by the design standards described in section IV.B. We
are also finalizing that facilities must demonstrate compliance with
this emission limit once per year. We note that Peirce-Smith converters
are batch converters and the NESHAP prohibits the use of batch
converters for new sources. Therefore, this lead limit is not relevant
for new sources.
c. What key comments did we receive on the proposed requirements for
process fugitive emissions from roofline vents pursuant to CAA section
112(d)(2) and (3) and what are our responses?
Comment: Numerous comments were received on the proposed test
methods for measuring PM at roof vents, which include EPA Test Methods
1, 2/2F/2G, 3/3A/3B, 4, 5D and Oregon Method 8. Most comments were that
the proposed test methods are not suited for testing PM from roof
vents; that MiniVol portable samplers should be used for sampling PM at
the roof vents instead of the proposed test methods; and that the
proposed test methods are unsafe to conduct at rooflines.
Commenters discussed the lack of isokinetic conditions at the
roofline, which they stated inhibits the use of Method 1. For example,
a commenter explained that Method 1 provides two alternative
procedures: a ``simplified procedure,'' and an ``alternative
procedure.'' Citing section 1.2 of the method, the commenter stated the
simplified procedure ``cannot be used when the measurement site is less
than 2 stack or duct diameters or less than a half diameter upstream
from a flow disturbance.'' The commenter stated that neither stack
diameters nor duct diameters can be defined for the smelter facilities'
roofline vents, within the meaning and purposes of section 1.2. With
regards to the alternative procedure, the commenter stated this
procedure depends on the ability to develop representative pitch and
yaw angles of the gas flow to be sampled, based on directional flow-
sensing probe measurements of pitch and yaw angles at forty or more
traverse points within the flow. The commenter stated this procedure is
not possible to perform at the smelter facilities' roofline vents
because fugitive emissions at the vents occur at a variety of angles
that are constantly changing due to ambient winds.
Another commenter discussed the lack of isokinetic conditions at
the roofline and referenced a feasibility study (EPA-HQ-OAR-2020-0430-
0062) that concluded that the roofline vents at the Miami smelter
cannot meet the minimum methods of Method 1, including either the
simplified procedure or alternative procedure. The commenter stated
that if Method 1 cannot be utilized effectively at the 2 facilities
subject to the major source rule, the rule is not practical to
implement or enforce.
A commenter discussed in depth the limitations of Method 5D,
stating that, unlike a positive pressure baghouse for which Method 5D
was designed, the roofline vent air flow is induced by natural buoyance
of the warmer gas inside the smelter building and by outside air wind
pressures--not by use of a forced air blower like those used in a
baghouse. The commenter referenced an illustration in a technical
analysis of the proposed vent test methods, which shows that the flow
rate varies significantly over short periods of time and occasionally
is negative (i.e., air flows into the vent). Another commenter stated,
``FMMI identified the incompatibility of Method 5D to the roofline vent
configurations as part of its original comments on April 26, 2022 . . .
Nevertheless, the EPA left the issue unaddressed in the supplemental
rule proposal, and the agency has not provided any guidance or
technical analysis explaining how Method 5D could be adapted to the
distinctly different conditions presented by the roofline vents.'' A
commenter stated because EPA Method 5D is not compatible with the low,
variable air velocities and physical configuration of the roofline
vents, FMMI has utilized a sampling methodology and test protocol
negotiated with the ADEQ (the ``ADEQ test method'').
Commenters advocated using MiniVol portable air samplers as an
alternative to the proposed test methods for measuring PM from roof
vents. They stated that using MiniVol portable air samplers is the most
representative sampling method for the roofline emissions application,
and while not a FRM sampler, they provide results that closely
approximate data from FRM samplers to obtain representative
concentrations of PM without the need for isokinetic sampling. The
commenter noted that the portable air samplers can be run concurrently
at several locations along the roofline, which the commenter notes
offers several benefits: (1) fluctuations in flows and emissions along
the roofline are better managed, (2) sampling is not dependent on
linear air flow, so constant adjustments are not required, and (3)
sampling can occur for longer periods of time, which provides a more
representative sample of the process operations occurring in the
smelter buildings. The commenter noted use of this sampling protocol
will require the collection of velocity and temperature measurements
using the existing roofline monitoring system equipment. As an added
benefit, the portable air samplers also are capable of speciating
samples of PM, PM<INF>10</INF>, and PM<INF>2.5</INF>.
A commenter noted that Asarco's 2015 consent decree with ADEQ,
which governs the operation of their Hayden

[[Page 41674]]

smelter, requires process fugitive emissions studies (FES) pursuant to
a protocol (``FES Protocol'' or ``Protocol'') approved by the EPA on
May 24, 2017. Within the FES Protocol is a determination that process
fugitive PM emissions at the roofline shall be quantified via a
sampling methodology that centers on the use of MiniVol portable air
samplers at the roofline vents. The commenter stated that the EPA's
approval of the Protocol constitutes a determination by the EPA that
this sampling method is appropriate for determining the rate of
fugitive PM emissions at the roofline. The MiniVol sampler, in
particular, is a low-flow sampler, which is well-suited to low,
variable air flows at the roofline--unlike the iso-kinetic sampling
methods specified in paragraph (e)(1) of proposed 40 CFR 63.1450. The
commenter attached copies of the Protocol and the EPA's approval of the
Protocol to their comment letters submitted on the 2022 proposed RTR
and on the 2023 supplemental proposal (Docket ID Nos. EPA-HQ-OAR-2020-
0430-0135 and EPA-HQ-OAR-2020-0430-0204, respectively).
A commenter stated the final rulemaking should include a provision
that explicitly authorizes the use of MiniVol portable air samplers,
together with appropriate temperature and flow sensors to determine PM
emissions at the roofline. The commenter advocated the use of a
fugitive emissions monitoring protocol specific to the relevant smelter
and approved by the EPA's Office of Air Quality Planning and Standards,
Measurement Technology Group (MTG) or other reviewing body such as ADEQ
and believes (a) 6 months after the date of the final rulemaking's
publication in the Federal Register would be an appropriate deadline
for submittal of the protocol for agency approval; and (b) 2 years
after agency approval of the protocol would be an appropriate deadline
for commencing measurements of the rate of fugitive PM emissions at the
roofline to determine whether they exceed the fugitive PM emissions-
rate limit. Correspondingly, the commenter noted the final rulemaking
should provide that, during the pendency of the protocol's
implementation, only the work practice standards and operation and
maintenance requirements of the revised subpart QQQ rules shall apply
to the process fugitive PM emissions. This would be consistent with 42
U.S.C. 7412(h)(1)-(2)(B) and the approach the EPA took in the Mercury
and Air Toxics Standards (MATS) and Industrial Boilers rulemakings.
The commenter stated that the ADEQ test method was utilized to
collect all of the emission data that the EPA relied on for the UPL
calculation that is the sole basis for the combined roofline PM
emission limit in the supplemental proposed rule. According to the
commenter, it is not appropriate for the EPA to set emission limits
based upon the ADEQ test method and then prohibit the use of that very
same method to demonstrate compliance. If the ADEQ test method was good
enough to set enforceable emission limits, it should also be good
enough to demonstrate compliance. The commenter stated that if the ADEQ
test method (or some reasonable modification of that method) does not
meet the EPA's requirements, then no limit should be established at
this time because that approach necessarily means that a valid data
basis for a limit does not yet exist. If that is indeed the EPA's
position FMMI and the EPA can work together to develop an acceptable
test method, FMMI can collect the necessary data to support the
calculation of a UPL based on that agreed method, and the agency can
set emission limits based on that data set.
In a related point, a commenter stated that they are concerned that
the proposed roofline lead limit is based on data collected using
samplers that are not designated as an FRM. Use of non-FRM sampler data
could create a standard that is not achievable if tested using an FRM.
It is unclear from the EPA's proposed rule how to address a potential
discrepancy between a standard based on non-FRM and testing using an
FRM. The commenter goes on to say that the EPA's proposed PM limit was
established using data that were collected using a method other than
EPA Method 5. Another commenter has similar concerns with the EPA's
rule in regard to the proposed limit being based on data collected
using samplers that are not designated as an FRM: First, they state it
is not clear from the EPA's rule that a Method 5 test conducted at the
same time would have produced the same result as the alternative method
used to obtain the data the rule is based on. Second, they state it is
unknown whether this standard is achievable, as determined by the
proposed test methodology.
Lastly, commenters had concerns about the safety of the personnel
conducting testing at the roofline. The commenter stated it would be
unsafe, due to the elevated temperature environment and other
conditions at the roofline, for humans to perform roofline activities
required by paragraph (e) of proposed 40 CFR 63.1450. Many areas of the
roofline are currently only accessible by narrow catwalks that do not
currently have approved tie-off points or sufficient space to
accommodate the personnel and the required sampling equipment. Some
roofline areas require respirators or other personal protective
equipment, and the EPA's proposed testing methods would require
continuous presence of multiple personnel working directly in the
pathway of exiting fumes for 3, 12-hour test runs. The commenter stated
the Method 5 sampling protocol requires adequate sample locations to
account for variations in the flows along the roofline, which then
necessitates a large number of sampling staff to be located in a
dangerous, high temperature environment for extended periods of 12
hours or more. The commenter noted the temperatures at the roofline can
reach 140 degrees Fahrenheit and pose a significant safety concern for
the testing personnel.
Response: In reviewing the comments and as a result of a site
visit, the EPA is revising the methods for the roof-vent testing. For
sample location determination, if EPA method 1 is inappropriate, the
facilities need to use method 5D, section 8.1.3, Roof Monitor or
Monovent, and also use section 8.2 to determine how many traverse
points should be sampled or have proposed sampling locations approved
by EPA Office of Air and Radiation (OAR), Office of Air Quality
Planning and Standards, MTG or the delegated authority. Due to the
variability in the flow rates, an anemometer may be used to determine
the flow. For the PM concentration measurements, a constant sample flow
rate and mass volume is required due to the highly variable process
flow rate. EPA method 17 may be used for this constant flow rate
sampling. EPA Method 17 particulate matter samples will be collected at
the roofline vent temperatures to maintain the same temperature basis
as the samples used in setting the standard. EPA Methods 5 and 5D have
been removed since these methods require heating the filter to 248
<plus-minus> 25 Fahrenheit, which would not be representative of the
roofline temperatures. It is understood that isokinetics may not be met
with this sampling and this calculation is waived for this sampling.
The MiniVol samplers are not EPA- approved samplers. There is a
concern because these are battery operated and may not provide a
constant rate of sampling. As an alternative, an approved FRM or FEM
ambient PM monitor may be used, which will also address the commenter's
safety

[[Page 41675]]

concerns. A list of designated reference and equivalent methods is
provided here: <a href="https://www.epa.gov/amtic/air-monitoring-methods-criteria-pollutants">https://www.epa.gov/amtic/air-monitoring-methods-criteria-pollutants</a>. However, tapered oscillating microbalances are not
appropriate for this sampling. The FRM or FEM ambient PM monitor must
be able to tolerate temperatures up to 150 degrees Fahrenheit.
The commenter has raised concerns on the use of the MiniVol sampler
to set the standard while different methods are used for determining
compliance. The EPA has mitigated these issues through the adaptations
to the methodology finalized, the use of calibrated anemometer for low
and variable process flow rates, fixed rate sampling and the allowance
for in stack filter methodology (EPA Method 17). The primary sampling
difference between the methods now is the more stable operation of the
EPA Method 17 sampling system or an FRM/FEM, ensuring that the sampled
flow rate is consistent.
The EPA alternative methods approval is conducted by the
Measurement Technology Group (MTG). The MiniVol roof-vent sampling
protocols/sampling methods have not been submitted or approved by MTG.
The Asarco protocol included FRM sampling side-by-side with the MiniVol
sampling. This side-by-side sampling could use Method 301 to validate
the MiniVol samplers, but the proposed sampling has not yet occurred.
This Method 301 validation could still occur, and the data could be
used to support an alternative method approval from MTG. If these
revised methods are not appropriate or the tester/facility wants to use
alternative methods, the tester/facility can apply for an alternative
test method approval through MTG. A Method 301 study should be
conducted to verify that the selected monitors used provide equivalent
data to the EPA methods.
Comment: A commenter agreed with the EPA's reasoning and
determination not to propose a BTF lead emissions limit in addition to,
or instead of, the fugitive PM emissions limit in proposed 40 CFR
63.1444(i)(3). Similarly, another commenter stated that, in response to
EPA's request for comments, an additional lead limit on the roofline
vents is not necessary. They explained that they agreed with the EPA's
conclusion that PM is the most appropriate surrogate for metal HAPs.
Response: While we agree that PM is an appropriate surrogate for
metal HAP, we are also finalizing a process fugitive lead limit for
facilities using flash furnaces and associated with the Peirce-Smith
converters of 0.326 lb/hr for a combination of roof vents associated
with Peirce-Smith copper converter department, Inco flash furnace and
the anode refining department. We estimate that this final standard
will reduce lead emissions by 0.39 tpy.
Comment: Commenters requested that the EPA establish direct lead
limits, either in addition to or instead of the PM limit because it is
one of the risk drivers for this source category and would be
appropriate to control for it directly.
Response: We have determined that filterable particulate is an
adequate surrogate for lead and other HAP metals for this source
category. 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). Therefore, providing PM emission standards which require
reductions as a surrogate for metal HAPs is expected to result in
commensurate reductions of metal HAP. We are also finalizing a process
fugitive lead limit for facilities using Inco flash furnaces and
Peirce-Smith converters of 0.326 lb/hr for a combination of roof vents
associated with the Peirce-Smith copper converter department, Inco
flash furnace and the anode refining department which we estimate will
reduce lead emissions by 0.39 tpy.
d. What is the rationale for our final approach and final decisions for
the process fugitive emissions from roofline vents revisions made
pursuant to CAA section 112(d)(2) and (3)?
As described in the 2022 proposal and in the 2023 supplemental
proposal, the 2002 major source NESHAP does not include standards for
process fugitive emissions from the rooflines of smelting vessels,
converters, or anode refining operations, except for an opacity limit
for converter roof vents that applies during testing. Therefore, we are
finalizing, as proposed in the 2023 supplemental proposal, a BTF
combined PM limit of 6.3 lb/hr as a surrogate for metal HAP for new and
existing process fugitive emissions from roofline vents pursuant to CAA
section 112(d)(2) and (3). As described in section IV.A., we are also
finalizing this combined roofline PM limit under CAA section 112(f) to
reduce emissions of HAP metals (especially lead and arsenic, which are
two persistent, bioaccumulative and highly toxic HAPs), and their
associated risks, to achieve acceptable risks levels. We are
finalizing, as proposed, that compliance with the PM emissions limit
for the process fugitive emissions from roofline vents will be
demonstrated through an initial performance test followed by a
compliance test at least once per year. Based on comments we received
on the 2022 proposal and the 2023 supplemental proposal, we are
finalizing adaptations to the test methods by which compliance with
this limit can be demonstrated including the use of fixed rate sampling
and the allowance for in stack filter methodology (EPA Method 17). The
costs for Freeport to comply with this combined PM limit are described
in section IV.C.2.b., and we estimate that Asarco can already comply
with this limit and therefore will not incur costs to comply with the
combine PM roofline limit except testing costs. We estimate that both
facilities will incur testing costs of $107,000 per year to comply with
the performance test requirements.
In addition, we are finalizing a lead emission limit of 0.326 lb/
hour to minimize process fugitive lead emissions from any combination
of roofline vents associated with Peirce-Smith copper converter
departments, Inco flash furnaces and the anode refining departments, at
existing sources. This limit will only apply to the Asarco facility
(since they are the only existing major source with Peirce-Smith copper
converter departments and Inco flash furnaces), and we estimate this
will reduce metal HAP by 0.39 tpy and ensure that future violations of
the lead NAAQS will not occur. As mentioned in section IV.B.2. of this
preamble, Asarco has been a major contributer to the Hayden Arizona
lead NAAQS non-attainment status. This limit is consistent with the
modeling demonstration submitted by the facility to the state in
support of a revision to the lead SIP. This document is available in
the docket for this action (Docket ID No. EPA-HQ-OAQ-2020-0430). As
discussed in section IV.B., we are also promulgating design standards
under CAA section 112 (d)(6) that will ensure this limit is met. As
discussed in section IV.B., the costs to comply with the design
standards are already expected to be incurred by the facility. We are
finalizing, that compliance with the lead emissions limit for the
process fugitive emissions from roofline vents will be demonstrated
through an initial performance test followed by a compliance test at
least once per year. The facility can test for lead at the same time as
the performance test for PM; however, they will have some

[[Page 41676]]

additional costs for the laboratory analysis that we estimate to be
$18,000 per year.
3. Mercury
a. What did we propose for mercury emissions pursuant to CAA section
112(d)(2) and (3)?
In the 2022 proposal, the EPA proposed a BTF mercury limit of
0.0043 lb/hr for existing sources, based on emissions data from
Freeport and Asarco, and a MACT floor mercury limit of 0.00097 lb/hr
for new sources, based on emissions data from Asarco. As noted in the
preamble of the 2022 proposal, in order to comply with the proposed
emission limit for existing sources, the EPA expected that the Freeport
facility would have to install and operate an activated carbon
injection (ACI) system and a polishing baghouse on the stack emissions
release point, the acid plant. The EPA expected the installation of
these additional controls would result in a 90 percent reduction of
mercury emissions from the acid plant source and that the cost-
effectiveness of mercury control would be $27,500 per pound (in 2019
dollars).
During and after public comment period of the 2022 proposal, the
EPA received a number of comments and additional data concerning the
BTF limit for existing sources including:
<bullet> Mercury testing results obtained in 2018-2021 by the
Freeport facility which did not fully follow EPA Method 29;
<bullet> Additional mercury testing results collected at the
Freeport facility in 2022 which fully followed EPA Method 29; and
<bullet> Comments regarding the technical infeasibility of adding
mercury controls (e.g., polishing baghouse with ACI) at the acid plant,
including explanations that the conditions of the acid plant exhaust
streams are unsuited for the control option since the stream has a high
moisture content, low mercury concentrations, and high concentrations
of SO<INF>2</INF>/SO<INF>3</INF> which inhibit mercury removal.
As discussed in the 2023 supplemental proposal, the EPA evaluated
the emissions data from all of Freeport's performance tests (i.e.,
2018-2022) and concluded that only the test conducted in 2022 which
fully followed Method 29 should be used in the MACT floor emission
limit development. The EPA also agreed that characteristics of the
exhaust stream from the acid plant stack and equipment configuration at
the acid plant may inhibit mercury control (e.g., moisture content,
acid gas content, mercury concentration) which could result in
diminished emission reductions. Therefore, we evaluated controlling
mercury from the aisle scrubber stack and the vent fume stack and
determined the latter was best suited for mercury control (see
discussion in the 2023 supplemental proposal). Based on a new stack
location and a new emissions data set, which includes the original
Asarco data and data from Freeport's 2022 test, the revised mercury
limit for existing sources in the 2023 supplemental proposal, as
determined using the 99 percent UPL approach, is a MACT floor limit of
0.033 lb/hr for combined facility wide emissions. We also evaluated BTF
control options in the 2023 supplemental proposal and concluded that
the costs were unreasonable, and we proposed the MACT floor emission
standard. We proposed that compliance with the mercury emissions limit
for new and existing sources would be demonstrated through an initial
compliance test for each of the affected sources (e.g., furnaces,
converters, anode refining) followed by a compliance test at least once
every year.
b. How did the mercury emissions standard made pursuant to CAA section
112(d)(2) and (3) change since proposal?
The mercury emission standard for new sources, 0.00097 lb/hr, is
being promulgated as proposed in 2022. In the 2023 supplemental
proposal, we proposed a revised mercury emission standard of 0.033 lb/
hr for existing sources and are finalizing that standard as proposed.
Both emission standards are based on the MACT floor.
c. What key comments did we receive on the mercury revisions made
pursuant to CAA section 112(d)(2) and (3) and what are our responses?
Comment: Commenters contend that the EPA does not have sufficient
data to develop a MACT floor for mercury. They stated that they do not
believe the single 3-run test results are sufficient to establish the
proposed MACT floor emission standard for existing sources. The
commenter noted there was significant run-to-run variability which the
commenter stated can be attributed to the profile of the process feed
and the nature of a batch process. Commenters noted that additional
performance testing of mercury will be conducted at the Freeport
facility in the fourth quarter of 2023, and first quarter of 2024 using
EPA Method 29, and they asked that the EPA allow for submittal and
consideration of these data (which they say they will be able to
provide at least several weeks prior to the May 2, 2024, deadline for
final rule publication) when establishing limits in the final rule. In
the absence of additional data, commenters believe that a
representative MACT floor cannot be established, and any regulatory
action should be postponed or limited to workplace standards. They
rationalized this comment by citing the NESHAP for Secondary Lead
Smelting (77 FR 570) where the EPA did not promulgate standards because
of incomplete testing and lack of testing data for furnaces that burn
varying types of fuel.
Response: As described in the 2023 supplemental proposal, the EPA
revised its calculations by only using the stack test data that
followed EPA Method 29. The proposed mercury standard was developed
based on the 99 percent UPL of the available emissions data for this
source category, which included data collected from Freeport through
the 2022 section 114 information request from Freeport as well as test
data from Asarco, yielding a sample size of 5 data points. The test
report associated with Freeport's section 114 information request
response was conducted using EPA test Method 29 and was reviewed by EPA
measurement experts upon submission. A dataset of more than 3 data
points meets the sample size necessary to use the 99 percent UPL
approach to develop a MACT standard. We acknowledge that a sample size
of 5 is considered a limited dataset; however, we have followed our
documented approach for MACT floor development for limited datasets
included in Appendix B of the aforementioned memorandum (Docket ID No.
EPA-HQ-OAR-2020-0430-0153). Therefore, we disagree that we have
insufficient data to develop a numerical emission standard based on the
MACT floor.
We note that we received two additional test reports from Freeport;
one on January 29, 2024 (non-metal HAPs) and one on February 16, 2024
(mercury), well after close of the public comment period (i.e.,
September 22, 2023) and have been notified that Freeport plans to send
a third test report in mid-April 2024. Based on a preliminary review of
the new test data, we determined that some tests were not valid due to
deviation from the EPA method and that incorporation of the valid tests
would not result in significant changes to the proposed emission
limits. We did not incorporate these late-submitted data for two timing
related reasons. First, other stakeholders would not have an
opportunity to review and comment on these new data; and second, given
the court-ordered promulgation deadline of May 2, 2024, we had
insufficient time to complete the

[[Page 41677]]

necessary quality control and assurance of the data, and to perform new
calculations and analyses to establish revised limits before the May 2,
2024, deadline. Thus, we are promulgating the existing source MACT
floor emission standards for mercury, as well as for the other non-
metal HAP, as proposed in the 2023 supplemental proposal and as
discussed in sections IV.C.3. and IV.C.4. of this preamble.
Comment: Some commenters expressed support for the decision in the
2023 supplemental proposal not to move forward with a BTF standard for
mercury, while other commenters suggested that the EPA adopt the BTF
standard for mercury. Commenters stated that indirect costs including
engineering, procurement, and construction management, as well as
startup costs had not been included in our estimates. Specifically
concerning costs for baghouses, commenters stated that most modern
baghouses are of the pulse jet, rather than shaker style,
configuration.
Response: As described in the 2023 supplemental proposal, the EPA
re-proposed a MACT floor standard for mercury after considering the
technical feasibility and costs of BTF control options. In
consideration of the comments regarding costs, we performed a holistic
review of the cost estimates for controls included in this rulemaking.
As described in the 2023 supplemental proposal, we estimated costs for
controlling mercury at the vent fume stack using a polishing baghouse
with ACI. We found that our BTF cost estimates for mercury controls
omitted indirect costs and assumed costs for a shaker style baghouse.
In response to the comments received on the 2023 supplemental proposal,
we have revised our BTF cost estimates for mercury control of the vent
fume stack at the Freeport facility to include indirect costs and to
more appropriately assume a pulse jet configuration baghouse. The
details of these revisions can be found in the memorandum Estimated
Cost for Beyond-the-floor Controls for Mercury Emissions from Primary
Copper Smelting Facilities--REVISED, available in the docket for this
rulemaking. Our revised estimates of the cost of BTF mercury are
capital costs of $10.7 million and total annualized costs of $3.0
million. We did not receive additional test data or other information
that would result in revisions to the expected emission reductions we
presented in the 2023 supplemental proposal. Using the expected
reductions, 40.5 lb/yr, the resulting cost effectiveness is $73,300/lb
mercury. We continue to maintain, as proposed in the 2023 supplemental
proposal, that the cost effectiveness for the BTF control of mercury is
unreasonable and are promulgating the MACT floor emission standard for
existing sources.
d. What is the rationale for our final approach and final decisions for
the mercury revisions made pursuant to CAA section 112(d)(2) and (3)?
As described in the 2022 proposal and the 2023 supplemental
proposal, the 2002 major source NESHAP does not include standards for
mercury. We are finalizing, as proposed in the 2022 proposal, the new
source MACT floor mercury limit of 0.00097 lb/hr mercury. As stated in
the 2022 proposal, the new source MACT floor mercury limit was
calculated based on emissions data from the best performing facility,
which is Asarco in this case. We are finalizing, as proposed in the
2023 supplemental proposal, the existing source MACT floor mercury
limit of 0.033 lb/hr mercury. As discussed in section IV.C.3.c. of this
preamble, we made some revisions to the cost of mercury controls that
were included in the 2023 supplemental proposal. These revisions
improved the completeness of our estimates but did not change our
conclusion that the costs of the BTF option for controlling mercury
with a polishing baghouse and ACI at the vent fume stack are
unreasonable ($73,000/lb mercury reduced). We also considered other BTF
options, but all other options were less cost-effective than additional
controls of the vent fume stack using the baghouse/ACI option. We note
the BTF options we considered are higher than historic acceptable cost
effectiveness values for mercury. The highest historic acceptable cost-
effective values in the 2011 final MATS rule were up to $22,400 per
pound of mercury reduced in 2007 dollars (which equates to about
$32,000 per pound in current dollars). We are finalizing, as proposed,
that compliance with the mercury emissions limit for new and existing
sources will be demonstrated through an initial compliance test for
each of the affected sources (e.g., furnaces, converters, anode
refining) followed by

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