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

Federal RegisterMay 13, 2024

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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.

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

https://www.regulations.gov/

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

https://www.regulations.gov/

, 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:

hansen.amanda@epa.gov.

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:

hirtz.james@epa.gov.

SUPPLEMENTARY INFORMATION:

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

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

sulfur dioxide

SSM startup, shutdown, and malfunction

TEQ toxic equivalency quotient

TOSHI target organ-specific hazard index

tpy ton per year

ug/m

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.

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

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

based on 2019 actual emissions and 0.24 ug/m

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

, while the modeled Pb concentration based upon actual emissions for this site was 0.045 ug/m

. 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

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

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

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

https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-national-emissions-standards-hazardous-air

and at

https://www.epa.gov/stationary-sources-air-pollution/primary-copper-smelting-area-sources-national-emissions-standards

. 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

https://www.epa.gov/stationary-sources-air-pollution/risk-and-technology-review-national-emissions-standards-hazardous

. 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

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)

EPA

, 529 F.3d 1077, 1084 (D.C. Cir. 2008).

Association of Battery Recyclers, Inc.

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)

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).

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.

The Court has affirmed this approach of implementing CAA section 112(f)(2)(A):

NRDC

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.”).

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

) gas and the iron as a ferrous oxide slag. The majority of the SO

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

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®, 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® 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:

• PM limits based on the MACT floor for anode refining point sources at new and existing major sources;

• PM limits based on the MACT floor for process fugitive emissions from roofline vents of smelting furnaces at new and existing major sources;

• PM limits based on the MACT floor for process fugitive emissions from roofline vents of converters at new and existing major sources;

• 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;

• PM limits based on the MACT floor for new converters at major sources;

• 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;

• Facility-wide mercury limit based on the MACT floor for new major sources;

• 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;

• Removal of SSM exemptions and associated provisions and specify that emissions standards apply at all times for both area sources and major sources; and

• 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:

• 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;

• 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;

• 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

• 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:

• 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

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);

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.

• 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

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.

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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

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

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

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.

https://www.epa.gov/electronic-reporting-air-emissions/electronic-reporting-tool-ert.

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 § 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,

revisions to the wording in § 63.1450 clarifying that facilities must test for filterable particulate, not total particulate. The test methods in § 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

, 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 § 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 §§ 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

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).

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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

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

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.

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-

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

ER13MY24.104

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

, 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

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.

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

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,

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.

1-in-10 thousand is equivalent to 100-in-1 million. The EPA currently describes cancer risks as ‘n-in-1 million.’

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 µg/m3, which is below the NAAQS of 0.15 µg/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

this final rule) that will reduce their process fugitive emissions of metal HAP as well as SO

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

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

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

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:

•

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.

•

Fuming Ladle Capture System:

This project involves the construction of a hood and retaining walls to improve capture of process fugitives from fuming ladles.

• 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.

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/m

) 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

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

) 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

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

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.

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

), 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

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

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

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

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

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

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

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 requiremen

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