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

Federal RegisterJan 11, 2022

Ask Donna

What actually matters in this document.

Text

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2020-0430; FRL-7522-01-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:

Proposed rule.

SUMMARY:

This proposal presents the results of the U.S. Environmental Protection Agency's (EPA's) 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. The EPA is proposing new emissions standards in the major source NESHAP. The EPA is also proposing to remove exemptions for periods of startup, shutdown, and malfunction (SSM) and specify that the emission standards apply at all times and require electronic reporting of performance test results and notification of compliance reports.

DATES:

Comments.

Comments must be received on or before February 25, 2022. Under the Paperwork Reduction Act (PRA), comments on the information collection provisions are best assured of consideration if the Office of Management and Budget (OMB) receives a copy of your comments on or before February 10, 2022.

Public hearing.

If anyone contacts us requesting a public hearing on or before January 18, 2022, the EPA will hold a virtual public hearing. See

SUPPLEMENTARY INFORMATION

for information on requesting and registering for a public hearing.

ADDRESSES:

You may send comments, identified by Docket ID No. EPA-HQ-OAR-2020-0430, by any of the following methods:

•

Federal eRulemaking Portal: https://www.regulations.gov/

(our preferred method). Follow the online instructions for submitting comments.

•

Email: a-and-r-docket@epa.gov.

Include Docket ID No. EPA-HQ-OAR-2020-0430 in the subject line of the message.

•

Fax:

(202) 566-9744. Attention Docket ID No. EPA-HQ-OAR-2020-0430.

•

Mail:

U.S. Environmental Protection Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2020-0430, Mail Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.

•

Hand/Courier Delivery:

EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. The Docket Center's hours of operation are 8:30 a.m.-4:30 p.m., Monday-Friday (except federal holidays).

Instructions:

All submissions received must include the Docket ID No. for this rulemaking. Comments received may be posted without change to

https://www.regulations.gov/,

including any personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the

SUPPLEMENTARY INFORMATION

section of this document. Out of an abundance of caution for members of the public and our staff, the EPA Docket Center and Reading Room are closed to the public, with limited exceptions, to reduce the risk of transmitting COVID-19. Our Docket Center staff will continue to provide remote customer service via email, phone, and webform. The EPA encourages the public to submit comments via

https://www.regulations.gov/

or email, as there may be a delay in processing mail and faxes. Hand deliveries and couriers may be received by scheduled appointment only. For further information on EPA Docket Center services and the current status, please visit us online at

https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT:

For questions about this proposed action, contact Tonisha Dawson, Sector Policies and Programs Division (D243-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-1454; fax number: (919) 541-4991; and email address:

dawson.tonisha@epa.gov.

For specific information regarding the risk modeling methodology, contact James Hirtz, Health and Environmental Impacts Division (C539-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-0881; fax number: (919) 541-4991; and email address:

hirtz.james@epa.gov.

SUPPLEMENTARY INFORMATION:

Executive Summary.

This proposal presents the results of the EPA's residual risk and technology review (RTR) for the NESHAP for major source Primary Copper Smelters as required under the 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 proposing that risks from emissions of air toxics from this major source category are unacceptable. The EPA also completed a demographic analysis which indicates that elevated cancer risks associated with emissions from the major source category disproportionately affect communities with environmental justice concerns, including low-income residents, Native Americans, and Hispanics living near these facilities. To address these risks, the EPA is proposing new emissions standards in the major source NESHAP, which will reduce risks to an acceptable level, and is also proposing work practice standards to provide an ample margin of safety to protect public health.

The EPA is also proposing new emissions standards for the major source NESHAP to address currently unregulated emissions of hazardous air pollutants (HAP), as follows: Particulate matter (PM), as a surrogate for particulate HAP metals, for anode refining furnace point source emissions; and PM for roofline emissions from anode refining furnaces, smelting furnaces, and converters. EPA is also proposing new emission standards for mercury emissions from any combination of stacks from dryers, converters, anode refining furnaces, and smelting furnaces. The EPA is proposing test methods for roofline PM emissions and amending the test methods to incorporate by reference three voluntary consensus standards (VCS).

Under the technology review, the EPA identified no developments in practices, processes, or control technologies to achieve further emissions reductions beyond the controls and reductions proposed under the risk review for major sources. With regard to primary copper smelting area sources, the Agency did not identify any developments in practices, processes, or control technologies.

The EPA is also proposing to remove exemptions for periods of startup, shutdown, and malfunction (SSM) and specify that the emission standards apply at all times and require electronic reporting of performance test results and notification of compliance reports. Implementation of these proposed rules is expected to reduce HAP metal emissions from primary copper

smelters, improve human health, and reduce environmental impacts associated with those emissions.

Participation in virtual public hearing.

Please note that the EPA is deviating from its typical approach for public hearings because the President has declared a national emergency. Due to the current Centers for Disease Control and Prevention (CDC) recommendations, as well as state and local orders for social distancing to limit the spread of COVID-19, the EPA cannot hold in-person public meetings at this time.

To request a virtual public hearing, contact the public hearing team at (888) 372-8699 or by email at

SPPDpublichearing@epa.gov

. If requested, the virtual hearing will be held on January 26, 2022. The hearing will convene at 9:00 a.m. Eastern Time (ET) and will conclude at 3:00 p.m. ET. The EPA may close a session 15 minutes after the last pre-registered speaker has testified if there are no additional speakers. The EPA will announce further details at

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

The EPA will begin pre-registering speakers for the hearing upon publication of this document in the

Federal Register

. To register to speak at the virtual hearing, please use the online registration form available at

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

or contact the public hearing team at (888) 372-8699 or by email at

SPPDpublichearing@epa.gov

. The last day to pre-register to speak at the hearing will be January 24, 2022. Prior to the hearing, the EPA will post a general agenda that will list pre-registered speakers in approximate order at:

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

The EPA will make every effort to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearings to run either ahead of schedule or behind schedule.

Each commenter will have 5 minutes to provide oral testimony. The EPA encourages commenters to provide the EPA with a copy of their oral testimony electronically (via email) by emailing it to

dawson.tonisha@epa.gov

. The EPA also recommends submitting the text of your oral testimony as written comments to the rulemaking docket.

The EPA may ask clarifying questions during the oral presentations but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral testimony and supporting information presented at the public hearing.

Please note that any updates made to any aspect of the hearing will be posted online at

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

. While the EPA expects the hearing to go forward as set forth above, please monitor our website or contact the public hearing team at (888) 372-8699 or by email at

SPPDpublichearing@epa.gov

to determine if there are any updates. The EPA does not intend to publish a document in the

Federal Register

announcing updates.

If you require the services of a translator or a special accommodation such as audio description, please pre-register for the hearing with the public hearing team and describe your needs by January 18, 2022. The EPA may not be able to arrange accommodations without advanced notice.

Docket.

The EPA has established a docket for this rulemaking under Docket ID No. EPA-HQ-OAR-2020-0430. All documents in the docket are listed in

https://www.regulations.gov/

. Although listed, some information is not publicly available,

e.g.,

Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy. With the exception of such material, publicly available docket materials are available electronically in

Regulations.gov

Instructions.

Direct your comments to Docket ID No. EPA-HQ-OAR-2020-0430. The EPA's policy is that all comments received will be included in the public docket without change and may be made available online at

https://www.regulations.gov/,

including any personal information provided, unless the comment includes information claimed to be CBI or other information whose disclosure is restricted by statute. Do not submit electronically any information that you consider to be CBI or other information whose disclosure is restricted by statute. This type of information should be submitted by mail as discussed below.

The EPA may publish any comment received to its public docket. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (

i.e.,

on the Web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit

https://www.epa.gov/dockets/commenting-epa-dockets

The

https://www.regulations.gov/

website allows you to submit your comment anonymously, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through

https://www.regulations.gov/,

your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the internet. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any digital storage media you submit. If the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should not include special characters or any form of encryption and be free of any defects or viruses. For additional information about the EPA's public docket, visit the EPA Docket Center homepage at

https://www.epa.gov/dockets

The EPA is temporarily suspending its Docket Center and Reading Room for public visitors, with limited exceptions, to reduce the risk of transmitting COVID-19. Our Docket Center staff will continue to provide remote customer service via email, phone, and webform. The EPA encourages the public to submit comments via

https://www.regulations.gov/

as there may be a delay in processing mail and faxes. Hand deliveries or couriers will be received by scheduled appointment only. For further information and updates on EPA Docket Center services, please visit us online at

https://www.epa.gov/dockets

The EPA continues to carefully and continuously monitor information from the CDC, local area health departments, and our Federal partners so that the Agency can respond rapidly as conditions change regarding COVID-19.

Submitting CBI.

Do not submit information containing CBI to the EPA through

https://www.regulations.gov/

or email. Clearly mark all of the

information that you claim to be CBI. For CBI information on any digital storage media that you mail to the EPA, mark the outside of the digital storage media as CBI and then identify electronically within the digital storage media the specific information that is claimed as CBI. In addition to one complete version of the comments that includes information claimed as CBI, you must submit a copy of the comments that does not contain the information claimed as CBI directly to the public docket through the procedures outlined in

Instructions

above. If you submit any digital storage media that does not contain CBI, mark the outside of the digital storage media clearly that it does not contain CBI. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 Code of Federal Regulations (CFR) part 2. Send or deliver information identified as CBI only to the following address: Office of Air Quality Planning and Standards Document Control Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2020-0430. Note that written comments containing CBI and submitted by mail may be delayed and no hand deliveries will be accepted.

Preamble acronyms and abbreviations.

The Agency uses 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

AEGL acute exposure guideline level

AERMOD air dispersion model used by the HEM-4 model

BTF beyond-the-floor

CAA Clean Air Act

CalEPA California EPA

CBI Confidential Business Information

CFR Code of Federal Regulations

mg/dscm milligrams per dry standard cubic meter

ECHO Enforcement and Compliance History Online

EPA Environmental Protection Agency

ERPG emergency response planning guideline

ERT Electronic Reporting Tool

GACT generally available control technology

HAP hazardous air pollutant(s)

HCl hydrochloric acid

HEM-4 Human Exposure Model, Version 1.5.5

HF hydrogen fluoride

HI hazard index

HQ hazard quotient

ICR Information Collection Request

IRIS Integrated Risk Information System

km kilometer

MACT maximum achievable control technology

mg/kg-day milligrams per kilogram per day

mg/m

milligrams per cubic meter

MIR maximum individual risk

NAAQS National Ambient Air Quality Standards

NAICS North American Industry Classification System

NEI National Emissions Inventory

NESHAP national emission standards for hazardous air pollutants

NTTAA National Technology Transfer and Advancement Act

OAQPS Office of Air Quality Planning and Standards

OMB Office of Management and Budget

PB-HAP hazardous air pollutants known to be persistent and bio-accumulative in the environment

PM particulate matter

POM polycyclic organic matter

ppm parts per million

RBLC Reasonably Available Control Technology, Best Available Control Technology, and Lowest Achievable Emission Rate Clearinghouse

RfC reference concentration

RTR residual risk and technology review

SAB Science Advisory Board

SV screening value

SSM startup, shutdown, and malfunction

TOSHI target organ-specific hazard index

tpy tons per year

TRIM.FaTE Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure model

UF uncertainty factor

µg/m

microgram per cubic meter

URE unit risk estimate

USGS U.S. Geological Survey

VCS voluntary consensus standards

Organization of this document.

The information in this preamble is organized as follows:

I. General Information

A. Does this action apply to me?

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

II. Background

A. What is the statutory authority for this action?

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

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

D. What other relevant background information and data are available?

III. Analytical Procedures and Decision-Making

A. How do we consider risk in our decision-making?

B. How do we perform the technology review?

C. How do we estimate post-MACT risk posed by the source category?

IV. Analytical Results and Proposed Decisions

A. What actions are we taking pursuant to CAA sections 112(d)(2) and 112(d)(3)?

B. What are the results of the risk assessment and analyses?

C. What are our proposed decisions regarding risk acceptability, ample margin of safety, and adverse environmental effect?

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

E. What other actions are we proposing?

F. What compliance dates are we proposing?

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

VI. Request for Comments

VII. Submitting Data Corrections

VIII. Incorporation by Reference

IX. Statutory and Executive Order Reviews

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

B. Paperwork Reduction Act (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 and 1 CFR part 51

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

I. National Technology Transfer and Advancement Act (NTTAA)

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

I. General Information

A. Does this action apply to me?

The source categories that are the subject of this proposal 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 proposed action is likely to affect. The proposed standards, once promulgated, will be directly applicable to the affected sources. State, local, and tribal governments would not be directly affected by this proposed action. As defined in the

Initial List of Categories of Sources Under Section 112(c)(1) of

the Clean Air Act Amendments of 1990

(see 57 FR 31576, July 16, 1992) and

Documentation for Developing the Initial Source Category List, Final Report

(

see

EPA-450/3-91-030, July 1992), the Primary Copper Smelting major source category was defined as 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.

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

In addition to being available in the docket, an electronic copy of this action is available on the internet. Following signature by the EPA Administrator, the EPA will post a copy of this proposed action at

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

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 of the proposal and key technical documents at these same websites. Information on the overall RTR program is available at

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

The proposed changes to the CFR that would be necessary to incorporate the changes proposed in this action are presented in attachments to the two memoranda titled:

Proposed Regulation Edits for 40 CFR part 63, subpart QQQ: Primary Copper Smelting NESHAP Risk and Technology Review Proposal

; and

Proposed Regulatory Edits for 40 CFR part 63 Subpart EEEEEE: Primary Copper Smelting Area Sources NESHAP Technology Review Proposal,

both of which are available in the docket for this action (Docket ID No. EPA-HQ-OAR-2020-0430). These documents include redline versions of the two regulations. Following signature by the EPA Administrator, the EPA will also post a copy of these two memoranda and the attachments to

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

and to

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

II. Background

A. What is the statutory authority for this action?

The statutory authority for this action is provided by sections 112 and 301 of the CAA, as amended (42 U.S.C. 7401

et seq.

). Section 112 of the CAA establishes a two-stage regulatory process to develop standards for emissions of HAP from stationary sources. Generally, the first stage involves establishing technology-based standards and the second stage involves evaluating those standards that are based on maximum achievable control technology (MACT) to determine whether additional standards are needed to address any remaining risk associated with HAP emissions. This second stage is required under CAA section 112(f) and is commonly referred to as the “residual risk review.” In addition to the residual risk review, section 112(d)(6) of the CAA requires the EPA to review standards set under CAA section 112 every 8 years and revise the standards as necessary taking into account any “developments in practices, processes, or control technologies.” This review is commonly referred to as the “technology review.” When the two reviews are combined into a single rulemaking, it is commonly referred to as the “risk and technology review.” The discussion that follows identifies the most relevant statutory sections and briefly explains the contours of the methodology used to implement these statutory requirements. A more comprehensive discussion appears in the document titled

CAA Section 112 Risk and Technology Reviews: Statutory Authority and Methodology,

in the docket for this rulemaking.

In the first stage of the CAA section 112 standard setting process, the EPA promulgates technology-based standards under CAA section 112(d) for categories of sources identified as emitting one or more of the HAP listed in CAA section 112(b). Sources of HAP emissions are either major sources or area sources, and CAA section 112 establishes different requirements for major source standards and area source standards. “Major sources” are those that emit or have the potential to emit 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of HAP. All other sources are “area sources.” For major sources, CAA section 112(d)(2) provides that the technology-based NESHAP must reflect the maximum degree of emission reductions of HAP achievable (after considering cost, energy requirements, and non-air quality health and environmental impacts). These standards are commonly referred to as MACT standards. CAA section 112(d)(3) also establishes a minimum control level for MACT standards, known as the MACT “floor.” In certain instances, as provided in CAA section 112(h), the EPA may set work practice standards in lieu of numerical emission standards. The EPA must also consider control options that are more stringent than the floor. Standards more stringent than the floor are commonly referred to as beyond-the-floor (BTF) standards. For area sources, CAA section 112(d)(5) gives the EPA discretion to set standards based on generally available control technologies or management practices (GACT standards) in lieu of MACT standards.

The second stage in standard-setting focuses on identifying and addressing any remaining (

i.e.,

“residual”) risk pursuant to CAA section 112(f). For source categories subject to MACT standards, section 112(f)(2) of the CAA requires the EPA to determine whether promulgation of additional standards is needed to provide an ample margin of safety to protect public health or to prevent an adverse environmental effect. Section 112(d)(5) of the CAA provides that this residual risk review is not required for categories of area sources subject to GACT standards. Section 112(f)(2)(B) of the CAA further expressly preserves the EPA's use of the two-step approach for developing standards to address any residual risk and the Agency's interpretation of “ample margin of safety” developed in the National Emissions Standards for Hazardous Air Pollutants: Benzene Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants (Benzene NESHAP) (54 FR 38044, September 14, 1989). The EPA notified Congress in the Residual Risk Report that the Agency intended to use the Benzene NESHAP approach in making CAA section 112(f) residual risk

determinations (EPA-453/R-99-001, p. ES-11). The EPA subsequently adopted this approach in its residual risk determinations and the United States Court of Appeals for the District of Columbia Circuit upheld the EPA's interpretation that CAA section 112(f)(2) incorporates the approach established in the Benzene NESHAP. See

NRDC

EPA,

529 F.3d 1077, 1083 (D.C. Cir. 2008).

The approach incorporated into the CAA and used by the EPA to evaluate residual risk and to develop standards under CAA section 112(f)(2) is a two-step approach. In the first step, the EPA determines whether risks are acceptable. This determination “considers all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR)

of approximately 1 in 10 thousand.” (54 FR at 38045). If risks are unacceptable, the EPA must determine the emissions standards necessary to reduce risk to an acceptable level without considering costs. In the second step of the approach, the EPA considers whether the emissions standards provide an ample margin of safety to protect public health “in consideration of all health information, including the number of persons at risk levels higher than approximately 1 in 1 million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.”

Id.

The EPA must promulgate emission standards necessary to provide an ample margin of safety to protect public health or determine that the standards being reviewed provide an ample margin of safety without any revisions. After conducting the ample margin of safety analysis, the Agency considers whether a more stringent standard is necessary to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect.

Although defined as “maximum individual risk,” MIR refers only to cancer risk. MIR, one metric for assessing cancer risk, is the estimated risk if an individual were exposed to the maximum level of a pollutant for a lifetime.

CAA section 112(d)(6) separately requires the EPA to review standards promulgated under CAA section 112 and revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less often than every 8 years. While conducting the technology review, the EPA is not required to recalculate the MACT floor.

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.

Louisiana Environmental Action Network (LEAN)

EPA,

955 F.3d 1088 (D.C. Cir. 2020).

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

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 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—both located in Arizona) are major sources of HAP emissions and are subject to subpart QQQ, the major source NESHAP; the third facility (Kennecott—located in Utah) is an area source and 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 ISA smelting furnace. The ISA smelt® 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.

Molten blister copper is transferred from the converting vessel to an anode furnace for refining to further remove residual impurities and oxygen. The blister copper is reduced in the anode refining furnace to remove oxygen, typically by injecting natural gas and steam to produce a high purity copper. The molten copper from the anode refining furnace is poured into molds to produce solid copper ingots called anodes. The anode copper is sent to a copper refinery, either on-site or at another location, where it is further purified using an electrolytic process to obtain the high purity copper that is sold as a product. The copper refinery is not part of the primary copper smelting source category.

The current NESHAP for major sources (40 CFR part 63, subpart QQQ) was proposed on April 20, 1998 (63 FR 19582), with a supplement to the proposed 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 must be demonstrated by performance tests conducted every 2.5 years.

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

For the Primary Copper Smelting source category, the EPA used the best available data. Initially, emissions and supporting data from the 2017 National Emissions Inventory (NEI) were gathered to develop the initial draft model input file for the residual risk assessments for major source primary copper smelters. The NEI is a database that contains information about sources that emit criteria air pollutants, their precursors, and HAP. The database includes estimates of annual air pollutant emission from point, nonpoint, and mobile sources in the 50 states, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands. The EPA collects this information and releases an updated version of the NEI database every 3 years. The NEI includes data necessary for conducting risk modeling, including annual HAP emissions estimates from individual emission sources at facilities and the related emissions release parameters.

The Arizona Department of Environmental Quality (ADEQ) provided 2018 emissions test data for both major source primary copper smelters located in that state, which allowed the EPA to use more current metal HAP emissions data than what was available in the 2017 NEI in some cases. The data from ADEQ and the NEI were used to develop an initial draft risk model input file. This initial draft model file was posted to the EPA's Primary Copper website on February 26, 2020, and stakeholders were provided an opportunity to voluntarily review and provide input regarding the sources of emissions and release parameters that were reported in the NEI. The Asarco and Freeport facilities provided input, and the modeling file was finalized. The data include multiple emissions test reports for PM and HAP metals for point source emissions from both facilities and seven test reports for emissions tests conducted in 2018, 2019 and 2020 for process fugitive emissions for anode refining, smelting furnaces and converters at Freeport. However, we have no test data for Asarco process fugitive emissions. The process fugitive emissions estimates for Asarco are based on emissions factors and process information. Therefore, we have higher confidence and less uncertainty with our emissions estimates for Freeport as compared to Asarco. We made an adjustment to the lead emissions estimates from the anode refining roofline at Freeport by applying a weighting factor to one of the 2018 test results. This factor is based on information in the document titled:

Technical Report on Test Method for Roofline Lead Emissions, Operational Influences During Testing, And Effect of Smelter Reconfiguration,

by Trinity Consultants, December 2018, which is available in the docket for this action. The data and data sources used to support this action and additional information on the development of the modeling file are described in Appendix 1 to the

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the 2021 Risk and Technology Review Proposed Rule,

which is available in the docket for this proposed rule (Docket ID No. EPA-HQ-OAR-2020-0430). Additional information is provided in section II.D below.

D. What other relevant background information and data are available?

The EPA used multiple sources of information to support this proposed action. Before developing the final list of affected facilities described in section II.B of this preamble, the EPA's Enforcement and Compliance History Online (ECHO) database was used as a tool to identify potentially affected facilities with primary copper smelting operations that are subject to the NESHAPs. The ECHO database provides integrated compliance and enforcement information for approximately 800,000 regulated facilities nationwide. The EPA also reviewed the compliance history on the ADEQ website, active consent decrees, and consent orders to verify that the facilities were accurately classified as major sources.

During the technology review, the EPA examined information in the Reasonably Available Control Technology (RACT)/Best Available Control Technology (BACT)/Lowest Achievable Emission Rate (LAER) Clearinghouse (RBLC) to identify technologies in use and determine whether there have been relevant developments in practices, processes, or control technologies. The RBLC is a database that contains case specific information on air pollution technologies that have been required to reduce the emissions of air pollutants from stationary sources. Under the EPA's New Source Review (NSR) program, if a facility is planning new construction or a modification that will significantly increase air emissions, an NSR permit must be obtained. This central database promotes the sharing of information among permitting agencies and aids in case-by-case determinations for NSR permits. The EPA also reviewed subsequent air toxics regulatory actions for other source categories and

information from a virtual site visit at the Freeport plant to determine whether there have been developments in practices, processes, or control technologies in the Primary Copper Smelting source category. The docket for this rulemaking contains the following document which provides more information on the technology review:

Final Technology Review for the Primary Copper Smelting Source Category

III. Analytical Procedures and Decision-Making

In this section, the Agency describes the analyses performed to support the proposed decisions for the RTR and other issues addressed in this proposal. In this proposed action, pursuant to CAA section 112(f), the EPA conducted a risk review for the major sources in the primary copper smelting source category. Consistent with CAA section 112(f)(5), the risk review did not cover the area source category. Therefore, the discussions of risk assessment procedures described in the following paragraphs apply only to the major source category. However, pursuant to CAA section 112(d)(6), the EPA conducted a technology review for the NESHAPs covering both the major source category and the area source category (40 CFR part 63, subpart EEEEEE). Therefore, the following discussions of the technology reviews apply to both major sources and area sources.

A. How do we consider risk in our decision-making?

As discussed in section II.A of this preamble and in the Benzene NESHAP, in evaluating and developing standards under CAA section 112(f)(2), the Agency applies a two-step approach to determine whether or not risks are acceptable and to determine if the standards provide an ample margin of safety to protect public health. As explained in the Benzene NESHAP, “the first step judgment on acceptability cannot be reduced to any single factor” and, thus, “[t]he Administrator believes that the acceptability of risk under section 112 is best judged on the basis of a broad set of health risk measures and information.” (54 FR at 38046). Similarly, with regard to the ample margin of safety determination, “the Agency again considers all of the health risk and other health information considered in the first step. Beyond that information, additional factors relating to the appropriate level of control will also be considered, including cost and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors.”

Id.

The Benzene NESHAP approach provides flexibility regarding factors the EPA may consider in making determinations and how the EPA may weigh those factors for each source category. 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 hazard index (HI) for chronic exposures to HAP with the potential to cause noncancer health effects, and the hazard quotient (HQ) for acute exposures to HAP with the potential to cause noncancer health effects.

The assessment also provides estimates of the distribution of cancer risk within the exposed populations, cancer incidence, and an evaluation of the potential for an adverse environmental effect. 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:

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.

The policy chosen by the Administrator permits consideration of multiple measures of health risk. Not only can the MIR figure be considered, but also incidence, the presence of noncancer health effects, and the uncertainties of the risk estimates. In this way, the effect on the most exposed individuals can be reviewed as well as the impact on the general public. These factors can then be weighed in each individual case. This approach complies with the

Vinyl Chloride

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

(54 FR at 38057). 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. Similarly, with regard to the ample margin of safety analysis, the EPA stated in the Benzene NESHAP that: “EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category.”

Id.

at 38061. The Agency also considers the uncertainties associated with the various risk analyses, as discussed earlier in this preamble, in our determinations of acceptability and ample margin of safety.

The EPA notes that it has not considered certain health information to date in making residual risk determinations. At this time, the Agency does not attempt to quantify the HAP risk that may be associated with emissions from other facilities that do not include the source category under review, mobile source emissions, natural source emissions, persistent environmental pollution, or atmospheric transformation in the vicinity of the sources in the category.

The EPA understands the potential importance of considering an individual's total exposure to HAP in addition to considering exposure to HAP emissions from the source category and facility. The Agency recognizes that such consideration may be particularly important when assessing noncancer risk, where pollutant-specific exposure health reference levels (

e.g.,

reference concentrations (RfCs)) are based on the assumption that thresholds exist for adverse health effects. For example, the EPA recognizes that, although exposures attributable to emissions from a source category or facility alone may not indicate the potential for increased risk of adverse noncancer health effects in a population, the exposures resulting from emissions from the facility in combination with emissions from all of the other sources (

e.g.,

other facilities) to which an individual is exposed may be sufficient to result in an increased risk of adverse noncancer health effects. In May 2010, the Science Advisory Board

(SAB) advised the EPA “that RTR assessments will be most useful to decision makers and communities if results are presented in the broader context of aggregate and cumulative risks, including background concentrations and contributions from other sources in the area.”

Recommendations of the SAB Risk and Technology Review Methods Panel are provided in their report, which is available at:

https://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf

In response to the SAB recommendations, the EPA incorporates cumulative risk analyses into its RTR risk assessments. The Agency (1) conducts facility-wide assessments, which include source category emission points, as well as other emission points within the facilities; (2) combines exposures from multiple sources in the same category that could affect the same individuals; and (3) for some persistent and bioaccumulative pollutants, analyzes the ingestion route of exposure. In addition, the RTR risk assessments consider aggregate cancer risk from all carcinogens and aggregated noncancer HQs for all noncarcinogens affecting the same target organ or target organ system.

Although the EPA is interested in placing source category and facility-wide HAP risk in the context of total HAP risk from all sources combined in the vicinity of each source, the EPA is also concerned about the uncertainties of doing so. Estimates of total HAP risk from emission sources other than those that the Agency has studied in depth during this RTR review would have significantly greater associated uncertainties than the source category or facility-wide estimates. Such aggregate or cumulative assessments would compound those uncertainties, making the assessments too unreliable.

B. How do we perform the technology review?

Our technology review primarily focuses on the identification and evaluation of developments in practices, processes, and control technologies that have occurred since the MACT standards were promulgated. Where we identify such developments, we analyze their technical feasibility, estimated costs, energy implications, and non-air environmental impacts. The EPA also considers the emission reductions associated with applying each development. This analysis informs our decision of whether it is “necessary” to revise the emissions standards. In addition, the Agency considers the appropriateness of applying controls to new sources versus retrofitting existing sources. For this exercise, the EPA considers any of the following to be a “development”:

• Any add-on control technology or other equipment that was not identified and considered during development of the original MACT standards;

• Any improvements in add-on control technology or other equipment (that were identified and considered during development of the original MACT standards) that could result in additional emissions reduction;

• Any work practice or operational procedure that was not identified or considered during development of the original MACT standards;

• Any process change or pollution prevention alternative that could be broadly applied to the industry and that was not identified or considered during development of the original MACT standards; and

• Any significant changes in the cost (including cost effectiveness) of applying controls (including controls the EPA considered during the development of the original MACT standards).

In addition to reviewing the practices, processes, and control technologies that were considered at the time the EPA originally developed the NESHAP, we review a variety of data sources in our investigation of potential practices, processes, or controls to consider. The EPA also reviews the NESHAP and the available data to determine if there are any unregulated emissions of HAP within the source category, and evaluate the data for use in developing new emission standards. See sections II.C and II.D of this preamble for information on the specific data sources that were reviewed as part of the technology review.

C. How do we estimate post-MACT risk posed by the source category?

In this section, the EPA provides a complete description of the types of analyses that we generally perform during the risk assessment process. In some cases, the Agency does not perform a specific analysis because it is not relevant. For example, in the absence of emissions of hazardous air pollutants known to be persistent and bioaccumulative in the environment (PB-HAP), the Agency would not perform a multipathway exposure assessment. If an analysis is not performed, the Agency will provide the reason. While we present all of our risk assessment methods, the Agency only presents risk assessment results for the analyses actually conducted (see section IV.B of this preamble).

The EPA conducts a risk assessment that provides estimates of the MIR for cancer posed by the HAP emissions from each source in the source category, the HI for chronic exposures to HAP with the potential to cause noncancer health effects, and the HQ for acute exposures to HAP with the potential to cause noncancer health effects. 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. The eight sections that follow this paragraph describe how the Agency estimated emissions and conducted the risk assessment. The docket for this rulemaking contains the following document which provides more information on the risk assessment inputs and models:

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the 2021 Risk and Technology Review Proposed Rule

. The methods used to assess risk (as described in the eight primary steps below) are consistent with those described by the EPA in the document reviewed by a panel of the EPA's SAB in 2009

and described in the SAB review report issued in 2010. They are also consistent with the key recommendations contained in that report.

U.S. EPA.

Risk and Technology Review (RTR) Risk Assessment Methodologies: For Review by the EPA's Science Advisory Board with Case Studies—MACT I Petroleum Refining Sources and Portland Cement Manufacturing,

June 2009. EPA-452/R-09-006.

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

1. How did we estimate actual emissions and identify the emissions release characteristics?

To create the initial modeling input file, the Agency gathered actual HAP emissions data from the 2017 NEI and 2018 emissions estimates provided by ADEQ. The 2019 emissions data for Asarco and Freeport were not available when the initial modeling input file was developed. The Asarco plant's smelting operation was shut down for a significant portion of 2018 due to equipment upgrades. Since the 2019 emissions data for Asarco were not available, the 2017 NEI data were used for the initial modeling input file. The Freeport plant made significant upgrades in 2017, so the 2018 emissions data were used for the initial modeling input file as the best representation of the current plant configuration. The modeling input file was posted on the EPA website on February 26, 2020, for

public review. Asarco and Freeport provided comments, revisions to the initial modeling file, and supporting documents, which consisted of 2019 emissions data and various performance test reports. The data provided by both facilities were used to develop the final modeling input file.

For each NEI record, the EPA reviewed the standard classification code (SCC) and emission unit and process descriptions, and assigned the record to one of the emission process groups (

i.e.,

Anode Furnaces; Anode Refining Roofline; Combustion; Converters; Anode Furnaces and Converters; Converters Roofline; Dryers, Furnaces, Converters and Acid Plant; Non-process Fugitives; Rod Plant; Smelting Furnace Roofline; Smelting Furnace Secondary; Smelting Furnaces and Converters).

If the SCC and emission unit and process descriptions were ambiguous for a specific NEI record, the Agency used the facility air permits and flow diagrams to help us assign the appropriate emission process group. Both facilities have many combined gas streams that vent to a common control system and/or stack. In those cases, there may be multiple emissions sources included in the Emission Process Group Description. For example, at Asarco, the exhaust gases from the two dryers and flash furnace are vented to the same baghouse. The facility has a sampling port at the exhaust of the baghouse to measure emissions during performance testing. The emission sources associated with this example are represented by “Dryers and Flash Furnace” under the Emission Process Group Description.

The EPA did not conduct a risk review pursuant to section 112(f) of the CAA for Kennecott since it is an area source subject to GACT standards (not MACT standards). However, we did obtain emissions estimates and evaluated some information on ambient monitoring data near the facility.

Based on reported 2017 estimates to the NEI, Kennecott emits an estimated 5.6 tpy of lead and 1.6 tpy of arsenic. However, we do not have any HAP metals emissions test data for Kennecott. Therefore, we consider these estimates uncertain and we are soliciting comments, data and additional information regarding these emissions estimates.

With regard to ambient monitoring data, Utah Division of Air Quality (DAQ) conducted lead monitoring at the Magna station near the Kennecott copper smelter from January 2010 through June 2017 (see Figure 18 of the memorandum titled

Emissions Data Used for Primary Copper Smelting Risk and Technology Review (RTR) Modeling Files

). At that time Utah DAQ was able to demonstrate that the likelihood of violating the National Ambient Air Quality Standard (NAAQS) for lead was so low, it would no longer be necessary to run the monitor. With EPA's concurrence, the Magna lead monitor was shut down in June 2017. Utah DAQ and the EPA continue to evaluate the development of requirements, such as source emission thresholds, population, and NAAQS revisions, that may trigger the necessity to resume monitoring lead in Utah.

Nevertheless, the Agency solicits comments, data and additional information regarding these ambient monitoring data and how they should be considered in the context of the EPA's technology review of the Primary Copper Smelting area source NESHAP.

Utah Division of Air Quality 2019 Annual Report

. 2019. Utah Department of Environmental Quality—Air Quality. Available at:

https://deq.utah.gov/air-quality/annual-reports-division-of-air-quality

2. How did we estimate MACT-allowable emissions?

The available emissions data in the RTR emissions dataset include estimates of the mass of HAP emitted during a specified annual time period. These “actual” emission levels are often lower than the emission levels allowed under the requirements of the current MACT standards. The emissions allowed under the MACT standards are referred to as the “MACT-allowable” emissions. The Agency discussed the consideration of both MACT-allowable and actual emissions in the final Coke Oven Batteries RTR (70 FR 19992, 19998-19999, April 15, 2005) and in the proposed and final Hazardous Organic NESHAP RTR (71 FR 34421, 34428, June 14, 2006, and 71 FR 76603, 76609, December 21, 2006, respectively). In those actions, the Agency noted that assessing the risk at the MACT-allowable level is inherently reasonable since that risk reflects the maximum level facilities could emit and still comply with national emission standards. The EPA also explained that it is reasonable to consider actual emissions, where such data are available, in both steps of the risk analysis, in accordance with the Benzene NESHAP approach. (54 FR 38044.)

The current Primary Copper Smelting NESHAP specifies numerical emission standards for each copper concentrate dryer, smelting vessel, and slag cleaning vessel. Consequently, the MACT-allowable emissions for each of these emission sources are assumed to be equal to the numerical emission standard. The NESHAP specifies work practice standards for fugitive dust sources. Therefore, the Agency believes that the actual fugitive dust sources emission levels are a reasonable estimation of the MACT-allowable emissions levels. The current NESHAP does not include standards for anode refining departments, anode refining rooflines, converter rooflines and smelting furnace rooflines. However, the EPA has determined that these sources are part of the source category and plans to propose MACT standards with this RTR. The MACT-allowable emissions for our baseline risk assessment for the anode refining departments, anode refining rooflines, converter rooflines and smelting furnace rooflines are assumed to be equal to the actual emissions, which are the estimated emissions prior to implementation of the proposed MACT standards.

For further details on the assumptions and methodologies used to estimate MACT-allowable emissions, see Appendix X of the document titled

Emissions Data Used for Primary Copper Smelting Risk and Technology Review (RTR) Modeling Files,

which is available in the docket for this rulemaking.

3. How do we conduct dispersion modeling, determine inhalation exposures, and estimate individual and population inhalation risk?

Both long-term and short-term inhalation exposure concentrations and health risk from the source category addressed in this proposal were estimated using the Human Exposure Model, Version 1.5.5(HEM-4).

The HEM-4 performs three primary risk assessment activities: (1) Conducting dispersion modeling to estimate the concentrations of HAP in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 kilometers (km) of the modeled sources, and (3) estimating individual and population-level inhalation risk using the exposure estimates and quantitative dose-response information.

For more information about HEM-4, go to

https://www.epa.gov/fera/risk-assessment-and-modeling-human-exposure-model-hem

a. Dispersion Modeling

The air dispersion model AERMOD, used by the HEM-4 model, is one of the EPA's preferred models for assessing air pollutant concentrations from industrial facilities.

To perform the dispersion

modeling and to develop the preliminary risk estimates, HEM-4 draws on three data libraries. The first is a library of meteorological data, which is used for dispersion calculations. This library includes 1 year (2016) of hourly surface and upper air observations from 840 meteorological stations. These stations may include multiple years other than meteorological data from 2016. These meteorological stations provide coverage of the United States and Puerto Rico. However, for this source category, the EPA utilized on-site meteorological data (2012-2013) from non-attainment modeling conducted by ADEQ. A second library of United States Census Bureau census block

internal point locations and populations provides the basis of human exposure calculations (U.S. Census, 2010). In addition, for each census block, the census library includes the elevation and controlling hill height, which are also used in dispersion calculations. A third library of pollutant-specific dose-response values is used to estimate health risk. These are discussed below.

U.S. EPA. Revision to the

Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex Terrain) Dispersion

Model and Other Revisions

(70 FR 68218, November 9, 2005).

A census block is the smallest geographic area for which census statistics are tabulated.

b. Risk From Chronic Exposure to HAP

In developing the risk assessment for chronic exposures, the EPA uses the estimated annual average ambient air concentrations of each HAP emitted by each source in the source category. The HAP air concentrations at each nearby census block centroid located within 50 km of the facility are a surrogate for the chronic inhalation exposure concentration for all the people who reside in that census block. A distance of 50 km is consistent with both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the limitations of Gaussian dispersion models, including AERMOD.

For each facility, the Agency calculates the MIR as the cancer risk associated with a continuous lifetime (24 hours per day, 7 days per week, 52 weeks per year, 70 years) exposure to the maximum concentration at the centroid of each inhabited census block. The EPA calculates individual cancer risk by multiplying the estimated lifetime exposure to the ambient concentration of each HAP (in micrograms per cubic meter (μg/m

)) by its unit risk estimate (URE). The URE is an upper-bound estimate of an individual's incremental risk of contracting cancer over a lifetime of exposure to a concentration of 1 microgram of the pollutant per cubic meter of air. For residual risk assessments, the EPA generally uses UREs from the EPA's Integrated Risk Information System (IRIS). For carcinogenic pollutants without IRIS values, the EPA looks to other reputable sources of cancer dose-response values, often using California EPA (CalEPA) UREs, where available. In cases where new, scientifically credible dose-response values have been developed in a manner consistent with the EPA's guidelines and have undergone a similar peer review process, the Agency may use such dose-response values in place of, or in addition to, other values, if appropriate. The pollutant-specific dose-response values used to estimate health risk are available at

https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants

Arsenic emissions from this source category are driving cancer risks. Inhalation cancer risks are based on an association between cumulative arsenic exposure and an increase in lung cancer mortality in two distinct smelter worker populations.

US EPA IRIS;

Chemical Assessment Summary for Arsenic (inorganic) https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0278_summary.pdf#nameddest=cancerinhal

Arsenic is also evaluated for multipathway risks as a PB-HAP based upon conservative food ingestions rates (

i.e.,

ingestion of fish and produce) and ingestion of contaminated soil.

To estimate individual lifetime cancer risks associated with exposure to HAP emissions from each facility in the source category, the Agency sums the risks for each of the carcinogenic HAP

emitted by the modeled facility. We estimate cancer risk at every census block within 50 km of every facility in the source category. The MIR is the highest individual lifetime cancer risk estimated for any of those census blocks. In addition to calculating the MIR, we estimate the distribution of individual cancer risks for the source category by summing the number of individuals within 50 km of the sources whose estimated risk falls within a specified risk range. We also estimate annual cancer incidence by multiplying the estimated lifetime cancer risk at each census block by the number of people residing in that block, summing results for all of the census blocks, and then dividing this result by a 70-year lifetime.

The EPA's 2005

Guidelines for Carcinogen Risk Assessment

classifies carcinogens as: “carcinogenic to humans,” “likely to be carcinogenic to humans,” and “suggestive evidence of carcinogenic potential.” These classifications also coincide with the terms “known carcinogen, probable carcinogen, and possible carcinogen,” respectively, which are the terms advocated in the EPA's

Guidelines for Carcinogen Risk Assessment,

published in 1986 (51 FR 33992, September 24, 1986). In August 2000, the document,

Supplemental Guidance for Conducting Health Risk Assessment of Chemical Mixtures

(EPA/630/R-00/002), was published as a supplement to the 1986 document. Copies of both documents can be obtained from

https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=20533&CFID=70315376&CFTOKEN=71597944

. Summing the risk of these individual compounds to obtain the cumulative cancer risk is an approach that was recommended by the EPA's SAB in their 2002 peer review of the EPA's National Air Toxics Assessment (NATA) titled

NATA—Evaluating the National-scale Air Toxics Assessment 1996 Data—an SAB Advisory,

available at

https://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf

To assess the risk of noncancer health effects from chronic exposure to HAP, we calculate either an HQ or a target organ-specific hazard index (TOSHI). We calculate an HQ when a single noncancer HAP is emitted. Where more than one noncancer HAP is emitted, we sum the HQ for each of the HAP that affects a common target organ or target organ system to obtain a TOSHI. The HQ is the estimated exposure divided by the chronic noncancer dose-response value, which is a value selected from one of several sources. The preferred chronic noncancer dose-response value is the EPA RfC, defined as “an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime” (

https://iaspub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&vocabName=IRIS%20Glossary

). In cases where an RfC from the EPA's IRIS is not available or where the EPA determines that using a value other than the RfC is appropriate, sometimes the EPA uses such an alternative value to assess risks. An example of such an alternative value is the use of the primary NAAQS for lead. The lead NAAQS is based upon a maximum 3-month average ambient concentration of 0.15 ug/m3. Additional chronic noncancer dose-response values can be a value from the following prioritized sources, which define their dose-response values similarly to the EPA: (1) The Agency for Toxic Substances and Disease Registry (ATSDR) Minimum Risk Level (

https://www.atsdr.cdc.gov/mrls/index.asp

); (2) the CalEPA Chronic Reference Exposure Level (

https://oehha.ca.gov/air/crnr/notice-adoption-air-toxics-hot-spots-program-guidance-manual-preparation-

health-risk-0

); or (3) as noted above, a scientifically credible dose-response value that has been developed in a manner consistent with the EPA guidelines and has undergone a peer review process similar to that used by the EPA. The pollutant-specific dose-response values used to estimate health risks are available at

https://www.epa.gov/fera/dose-response-assessment-assessing-health-risks-associated-exposure-hazardous-air-pollutants

This assessment identified emissions of arsenic and lead as a chronic noncancer hazard concern for children. Both pollutants impact brain development. The chronic, noncancer health effect benchmark for arsenic exposure is based on a decrease in intellectual function and adverse effects on neurobehavioral development in 10-yr-old children exposed through drinking water from birth.

Wasserman et al. (2004) and Tsai et al. (2003).

For lead, the NAAQS of 0.15 µg/m

specifies a level of air quality that protects the most sensitive subpopulation, children, from adverse effects, such as IQ loss, with an adequate margin of safety following exposure through inhalation or ingestion of lead previously emitted into the air.

Several studies were used as the basis for the standard, including an international pooled analysis of seven prospective cohort studies (n = 1,333).

EPA Final Rule (National Ambient Air Quality Standards for Lead;

November 12, 2008);

https://www.govinfo.gov/content/pkg/FR-2008-11-12/pdf/E8-25654.pdf

Lanphear et al. (2005).

A review of the health effect benchmarks for arsenic and lead determined that, although the target organ is the same for these two pollutants, a TOSHI should not be calculated based upon the difference in exposure duration for the two benchmarks. The chronic REL for arsenic is an airborne concentration of inorganic arsenic at or below which no adverse noncancer health effects are anticipated in individuals indefinitely exposed to that concentration, while the lead standard is applied to a maximum 3-month rolling average of monitored lead concentrations.

c. Risk From Acute Exposure to HAP That May Cause Health Effects Other Than Cancer

For each HAP for which appropriate acute inhalation dose-response values are available, the EPA also assesses the potential health risks due to acute exposure. For these assessments, the EPA makes conservative assumptions about emission rates, meteorology, and exposure location. As part of our efforts to continually improve our methodologies to evaluate the risks that HAP emitted from categories of industrial sources pose to human health and the environment,

the EPA revised our treatment of meteorological data to use reasonable worst-case air dispersion conditions in our acute risk screening assessments instead of worst-case air dispersion conditions. This revised treatment of meteorological data and the supporting rationale are described in more detail in

Residual Risk Assessment for Primary Copper Smelting Major Source Category in Support of the 2021 Risk and Technology Review Proposed Rule

and in Appendix 5 of the report:

Technical Support Document for Acute Risk Screening Assessment

. This revised approach has been used in this proposed rule and in all other RTR rulemakings proposed on or after June 3, 2019.

See,

e.g.,

U.S. EPA.

Screening Methodologies to Support Risk and Technology Reviews (RTR): A Case Study Analysis

(Draft Report, May 2017.

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

To assess the potential acute risk to the maximally exposed individual, we use the peak hourly emission rate for each emission point,

reasonable worst-case air dispersion conditions (

i.e.,

99th percentile), and the point of highest off-site exposure. Specifically, we assume that peak emissions from the source category and reasonable worst-case air dispersion conditions co-occur and that a person is present at the point of maximum exposure.

In the absence of hourly emission data, the EPA develops estimates of maximum hourly emission rates by multiplying the average actual annual emissions rates by a factor (either a category-specific factor or a default factor of 10) to account for variability. This is documented in

Residual Risk Assessment for Primary Copper Smelting Major Source Category in Support of the 2020 Risk and Technology Review Proposed Rule

and in Appendix 5 of the report:

Technical Support Document for Acute Risk Screening Assessment

. Both are available in the docket for this rulemaking.

To characterize the potential health risks associated with estimated acute inhalation exposures to a HAP, we generally use multiple acute dose-response values, including acute RELs, acute exposure guideline levels (AEGLs), and emergency response planning guidelines (ERPG) for 1-hour exposure durations, if available, to calculate acute HQs. The acute HQ is calculated by dividing the estimated acute exposure concentration by the acute dose-response value. For each HAP for which acute dose-response values are available, the EPA calculates acute HQs. For this source category, acute risks from arsenic were a concern based upon the 1-hour REL of 0.2 μg/m

. The acute REL is based on developmental effects in mice (decreased fetal weight, growth retardation, skeletal defects).

Nagymajtenyi et al. 1985.

An acute REL is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration.”

Acute RELs are based on the most sensitive, relevant, adverse health effect reported in the peer-reviewed medical and toxicological literature. They are designed to protect the most sensitive individuals in the population through the inclusion of margins of safety. Because margins of safety are incorporated to address data gaps and uncertainties, exceeding the REL does not automatically indicate an adverse health impact. AEGLs represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to 8 hours.

They are guideline levels for “once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals.”

Id.

at 21. The AEGL-1 is specifically defined as “the airborne concentration (expressed as ppm (parts per million) or mg/m

(milligrams per cubic meter)) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.”

Id.

at 3. The document also notes that “Airborne concentrations below AEGL-1 represent exposure levels that can produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects.”

Id.

AEGL-2 are defined as “the airborne concentration (expressed as parts per million or

milligrams per cubic meter) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.”

Id.

CalEPA issues acute RELs as part of its Air Toxics Hot Spots Program, and the 1-hour and 8-hour values are documented in

Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The Determination of Acute Reference Exposure Levels for Airborne Toxicants,

which is available at

https://oehha.ca.gov/air/general-info/oehha-acute-8-hour-and-chronic-reference-exposure-level-rel-summary

National Academy of Sciences, 2001.

Standing Operating Procedures for Developing Acute Exposure Levels for Hazardous Chemicals,

page 2. Available at

https://www.epa.gov/sites/production/files/2015-09/documents/sop_final_standing_operating_procedures_2001.pdf

. Note that the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances ended in October 2011, but the AEGL program continues to operate at the EPA and works with the National Academies to publish final AEGLs (

https://www.epa.gov/aegl

ERPGs are “developed for emergency planning and are intended as health-based guideline concentrations for single exposures to chemicals.”

Id.

at 1. The ERPG-1 is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or without perceiving a clearly defined, objectionable odor.”

Id.

at 2. Similarly, the ERPG-2 is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.”

Id.

at 1.

ERPGS Procedures and Responsibilities

. March 2014. American Industrial Hygiene Association. Available at:

https://www.aiha.org/get-involved/AIHAGuidelineFoundation/EmergencyResponsePlanningGuidelines/Documents/ERPG%20Committee%20Standard%20Operating%20Procedures%20%20-%20March%202014%20Revision%20%28Updated%2010-2-2014%29.pdf

An acute REL for 1-hour exposure durations is typically lower than its corresponding AEGL-1 and ERPG-1. Even though their definitions are slightly different, AEGL-1s are often the same as the corresponding ERPG-1s, and AEGL-2s are often equal to ERPG-2s. The maximum HQs from our acute inhalation screening risk assessment typically result when we use the acute REL for a HAP. In cases where the maximum acute HQ exceeds 1, we also report the HQ based on the next highest acute dose-response value (usually the AEGL-1 and/or the ERPG-1).

For this source category, we developed source category-specific acute factors ranging from 3 to 10 to estimate peak hourly emissions from annual emissions estimates for the input to the acute risk assessment modeling analysis. In general, hourly emissions estimates were based on batch cycle times for smelting and anode furnaces with an emission hourly multiplier of 3 applied while road fugitive emissions were modeled with a default hourly multiplier of 10 times the annual average. A further discussion of these factors and why they were chosen can be found in the memorandum,

Emissions Data Used for Primary Copper Smelting Risk and Technology Review (RTR) Modeling Files,

available in the docket for this rulemaking.

In our acute inhalation screening risk assessment, acute impacts are deemed negligible for HAP for which acute HQs are less than or equal to 1, and no further analysis is performed for these HAP. In cases where an acute HQ from the screening step is greater than 1, we assess the site-specific data to ensure that the acute HQ is at an off-site location. For this source category, the data refinements employed consisted of overlaying satellite imagery with off-site polar receptors to estimate off-site acute impacts. These refinements are discussed more fully in the

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the 2021 Risk and Technology Review Proposed Rule,

which is available in the docket for this source category.

4. How do we conduct the multipathway exposure and risk screening assessment?

The EPA conducts a tiered screening assessment examining the potential for significant human health risks due to exposures via routes other than inhalation (

i.e.,

ingestion). We first determine whether any sources in the source category emit any HAP known to be persistent and bioaccumulative in the environment, as identified in the EPA's Air Toxics Risk Assessment Library (see Volume 1, Appendix D, at

https://www.epa.gov/fera/risk-assessment-and-modeling-air-toxics-risk-assessment-reference-library

For the Primary Copper Smelting source category, we identified PB-HAP emissions of lead, arsenic, mercury and cadmium, so we proceeded to the next step of the evaluation. Except for lead, the human health risk screening assessment for PB-HAP consists of three progressive tiers. In a Tier 1 screening assessment, we determine whether the magnitude of the facility-specific emissions of PB-HAP warrants further evaluation to characterize human health risk through upper-end ingestion rates of (meat, produce, fruits, fish, etc.) based upon a combined farmer and fisher scenario. To facilitate this step, we evaluate emissions against previously developed screening threshold emission rates for several PB-HAP that are based on a hypothetical upper-end screening exposure scenario developed for use in conjunction with the EPA's Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure (TRIM.FaTE) model. The PB-HAP with screening threshold emission rates are arsenic compounds, cadmium compounds, chlorinated dibenzodioxins and furans, mercury compounds, and polycyclic organic matter (POM). Based on the EPA estimates of toxicity and bioaccumulation potential, these pollutants represent a conservative list for inclusion in multipathway risk assessments for RTR rules. (For more details see the risk assessment report cited above and Volume 1, Appendix D at

https://www.epa.gov/sites/production/files/2013-08/documents/volume_1_reflibrary.pdf

.). In this assessment, we compare the facility-specific emission rates of these PB-HAP to the screening threshold emission rates for each PB-HAP to assess the potential for significant human health risks via the ingestion pathway. We call this application of the TRIM.FaTE model the Tier 1 screening assessment. The ratio of a facility's actual emission rate to the Tier 1 screening threshold emission rate is a screening value (SV).

We derive the Tier 1 screening threshold emission rates for these PB-HAP (other than lead compounds) to correspond to a maximum excess lifetime cancer risk of 1-in-1 million (

i.e.,

for arsenic compounds, polychlorinated dibenzodioxins and furans, and POM) or, for HAP that cause noncancer health effects (

i.e.,

cadmium compounds and mercury compounds), a maximum HQ of 1. If the emission rate of any one PB-HAP or combination of carcinogenic PB-HAP in the Tier 1 screening assessment exceeds the Tier 1 screening threshold emission rate for any facility (

i.e.,

the SV is greater than 1), we conduct a second screening assessment, which we call the Tier 2 screening assessment. The Tier 2 screening assessment separates the Tier 1 combined fisher and farmer exposure scenario into fisher, farmer, and gardener scenarios that retain upper-bound ingestion rates.

In the Tier 2 screening assessment, the location of each facility that exceeds a Tier 1 screening threshold emission rate is used to refine the assumptions associated with the Tier 1 fisher and farmer exposure scenarios at that facility. A key assumption in the Tier 1 screening assessment is that a lake and/or farm is located near the facility. As part of the Tier 2 screening assessment, we use a U.S. Geological Survey (USGS) database to identify actual waterbodies within 50 km of each facility and assume the fisher only consumes fish from lakes within that 50 km zone. We also examine the differences between local meteorology near the facility and the meteorology used in the Tier 1 screening assessment. We then adjust the previously developed Tier 1

screening threshold emission rates for each PB-HAP for each facility based on an understanding of how exposure concentrations estimated for the screening scenario change with the use of local meteorology and the USGS lakes database.

In the Tier 2 farmer scenario, we maintain an assumption that the farm is located within 0.5 km of the facility and that the farmer consumes meat, eggs, dairy, vegetables, and fruit produced near the facility. We may further refine the Tier 2 screening analysis by assessing a gardener scenario to characterize a range of exposures, with the gardener scenario being more plausible in RTR evaluations. Under the gardener scenario, we assume the gardener consumes home-produced eggs, vegetables, and fruit products at the same ingestion rate as the farmer. The Tier 2 screen continues to rely on the high-end food intake assumptions that were applied in Tier 1 for local fish (adult female angler at 99th percentile fish consumption

) and locally grown or raised foods (90th percentile consumption of locally grown or raised foods for the farmer and gardener scenarios

). If PB-HAP emission rates do not result in a Tier 2 SV greater than 1, we consider those PB-HAP emissions to pose risks below a level of concern. If the PB-HAP emission rates for a facility exceed the Tier 2 screening threshold emission rates, we may conduct a Tier 3 screening assessment.

Burger, J. 2002.

Daily consumption of wild fish and game: Exposures of high end recreationists. International Journal of Environmental Health Research,

12:343-354.

U.S. EPA.

Exposure Factors Handbook 2011 Edition (Final)

. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-09/052F, 2011.

There are several analyses that can be included in a Tier 3 screening assessment, depending upon the extent of refinement warranted, including validating that the lakes are fishable, locating residential/garden locations for urban and/or rural settings, considering plume-rise to estimate emissions lost above the mixing layer, and considering hourly effects of meteorology and plume-rise on chemical fate and transport (a time-series analysis). If necessary, the EPA may further refine the screening assessment through a site-specific assessment.

In evaluating the potential multipathway risk from emissions of lead compounds, rather than developing a screening threshold emission rate, the Agency compares maximum estimated chronic inhalation exposure concentrations to the level of the current NAAQS for lead.

Values below the level of the primary (health-based) lead NAAQS are considered to have a low potential for multipathway risk. For this source category based upon high modeled annual concentrations of lead from HEM-4, a refined assessment was conducted to estimate the maximum 3-month average concentration for lead over multiple years. These refinements included the use of a post-processer (Lead-POST) in AERMOD to calculate the maximum 3-month lead concentration for each off-site receptor to directly compare to the current lead NAAQS standard.

In doing so, the EPA notes that the legal standard for a primary NAAQS—that a standard is requisite to protect public health and provide an adequate margin of safety (CAA section 109(b))—differs from the CAA section 112(f) standard (requiring, among other things, that the standard provide an “ample margin of safety to protect public health”). However, the primary lead NAAQS is a reasonable measure of determining risk acceptability (

i.e.,

the first step of the Benzene NESHAP analysis) since it is designed to protect the most susceptible group in the human population—children, including children living near major lead emitting sources. 73 FR 67002/3; 73 FR 67000/3; 73 FR 67005/1. In addition, applying the level of the primary lead NAAQS at the risk acceptability step is conservative since that primary lead NAAQS reflects an adequate margin of safety.

EPA Support Center for Regulatory Atmospheric Modeling site to access LEADPOST utilized in the Pb NAAQS program:

https://www.epa.gov/scram/air-quality-dispersion-modeling-preferred-and-recommended-models

For further information on the multipathway assessment approach, see the

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the Risk and Technology Review 2021 Proposed Rule,

which is available in the docket for this action.

5. How do we assess risks considering emissions control options?

In addition to assessing baseline inhalation risks and screening for potential multipathway risks, the EPA also estimates risks considering the potential emission reductions that would be achieved by the control options under consideration. In these cases, the expected emission reductions are applied to the specific HAP and emission points in the RTR emissions dataset to develop corresponding estimates of risk and incremental risk reductions.

6. How do we conduct the environmental risk screening assessment?

a. Adverse Environmental Effect, Environmental HAP, and Ecological Benchmarks

The EPA conducts a screening assessment to examine the potential for an adverse environmental effect as required under section 112(f)(2)(A) of the CAA. Section 112(a)(7) of the CAA defines “adverse environmental effect” as “any significant and widespread adverse effect, which may reasonably be anticipated, to wildlife, aquatic life, or other natural resources, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental quality over broad areas.”

The EPA focuses on eight HAP, which are referred to as “environmental HAP,” in its screening assessment: Six PB-HAP and two acid gases. The PB-HAP included in the screening assessment are arsenic compounds, cadmium compounds, dioxins/furans, POM, mercury (both inorganic mercury and methyl mercury), and lead compounds. The acid gases included in the screening assessment are hydrochloric acid (HCl) and hydrogen fluoride (HF).

HAP that persist and bioaccumulate are of particular environmental concern because they accumulate in the soil, sediment, and water. The acid gases, HCl and HF, are included due to their well-documented potential to cause direct damage to terrestrial plants. In the environmental risk screening assessment, the EPA evaluates the following four exposure media: terrestrial soils, surface water bodies (includes water-column and benthic sediments), fish consumed by wildlife, and air. Within these four exposure media, the Agency evaluates nine ecological assessment endpoints, which are defined by the ecological entity and its attributes. For PB-HAP (other than lead), both community-level and population-level endpoints are included. For acid gases, the ecological assessment endpoint evaluated is terrestrial plant communities.

An ecological benchmark represents a concentration of HAP that has been linked to a particular environmental effect level. For each environmental HAP, the Agency identified the available ecological benchmarks for each assessment endpoint and where possible, the ecological benchmarks at the following effect levels: probable effect levels, lowest-observed-adverse-effect level, and no-observed-adverse-effect level. In cases where multiple effect levels were available for a particular PB-HAP and assessment endpoint, the EPA uses all of the available effect levels to help us to determine whether ecological risks exist and, if so, whether the risks could be considered significant and widespread.

For further information on how the environmental risk screening

assessment was conducted, including a discussion of the risk metrics used, how the environmental HAP were identified, and how the ecological benchmarks were selected, see Appendix 9 of the

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the Risk and Technology Review 2021 Proposed Rule,

which is available in the docket for this action.

b. Environmental Risk Screening Methodology

For the environmental risk screening assessment, the EPA first determined whether any facilities in the Primary Copper Smelting source category emitted any of the environmental HAP. For the Primary Copper Smelting source category, the Agency identified emissions of arsenic, mercury, cadmium and lead. Because one or more of the environmental HAP evaluated are emitted by at least one facility in the source category, the Agency proceeded to the second step of the evaluation.

c. PB-HAP Methodology for Environmental Risk Screening

The environmental risk screening assessment includes six PB-HAP: Arsenic compounds, cadmium compounds, dioxins/furans, POM, mercury (both inorganic mercury and methyl mercury), and lead compounds. With the exception of lead, the environmental risk screening assessment for PB-HAP consists of three tiers. The first tier of the environmental risk screening assessment uses the same health-protective conceptual model that is used for the Tier 1 human health screening assessment. TRIM.FaTE model simulations were used to back-calculate Tier 1 screening threshold emission rates. The screening threshold emission rates represent the emission rate in tons of pollutant per year that results in media concentrations at the facility that equal the relevant ecological benchmark. To assess emissions from each facility in the category, the reported emission rate for each PB-HAP was compared to the Tier 1 screening threshold emission rate for that PB-HAP for each assessment endpoint and effect level. If emissions from a facility do not exceed the Tier 1 screening threshold emission rate, the facility “passes” the screening assessment, and, therefore, is not evaluated further under the screening approach. If emissions from a facility exceed the Tier 1 screening threshold emission rate, the EPA evaluates the facility further in Tier 2.

In Tier 2 of the environmental risk screening assessment, the screening threshold emission rates are adjusted to account for local meteorology and the actual location of lakes in the vicinity of facilities that did not pass the Tier 1 screening assessment. For soils, the EPA evaluates the average soil concentration for all soil parcels within a 7.5-km radius for each facility and PB-HAP. For the water, sediment, and fish tissue concentrations, the highest value for each facility for each pollutant is used. If emission concentrations from a facility do not exceed the Tier 2 screening threshold emission rate, the facility “passes” the screening assessment and typically is not evaluated further. If emissions from a facility exceed the Tier 2 screening threshold emission rate, the EPA evaluates the facility further in Tier 3.

As in the multipathway human health risk assessment, in Tier 3 of the environmental risk screening assessment, the Agency examines the suitability of the lakes around the facilities to support life and remove those that are not suitable (

e.g.,

lakes that have been filled in or are industrial ponds), adjust emissions for plume-rise, and conduct hour-by-hour time-series assessments. If these Tier 3 adjustments to the screening threshold emission rates still indicate the potential for an adverse environmental effect (

i.e.,

facility emission rate exceeds the screening threshold emission rate), the Agency may elect to conduct a more refined assessment using more site-specific information. If, after additional refinement, the facility emission rate still exceeds the screening threshold emission rate, the facility may have the potential to cause an adverse environmental effect.

To evaluate the potential for an adverse environmental effect from lead, we compared the average modeled air concentrations (from HEM-4) of lead around each facility in the source category to the level of the secondary NAAQS for lead. The secondary lead NAAQS is a reasonable means of evaluating environmental risk because it is set to provide substantial protection against adverse welfare effects which can include “effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate, damage to and deterioration of property, and hazards to transportation, as well as effects on economic values and on personal comfort and well-being.”

d. Acid Gas Environmental Risk Methodology

The environmental risk screening assessment for acid gases evaluates the potential phytotoxicity and reduced productivity of plants due to chronic exposure to HF and HCl. The environmental risk screening methodology for acid gases is a single-tier screening assessment that compares modeled ambient air concentrations (from AERMOD) to the ecological benchmarks for each acid gas. To identify a potential adverse environmental effect (as defined in section 112(a)(7) of the CAA) from emissions of HF and HCl, the Agency evaluates the following metrics: the size of the modeled area around each facility that exceeds the ecological benchmark for each acid gas, in acres and square kilometers; the percentage of the modeled area around each facility that exceeds the ecological benchmark for each acid gas; and the area-weighted average SV around each facility (calculated by dividing the area-weighted average concentration over the 50-km modeling domain by the ecological benchmark for each acid gas). For further information on the environmental screening assessment approach, see Appendix 9 of the

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the Risk and Technology Review 20201 Proposed Rule,

which is available in the docket for this action.

7. How do we conduct facility-wide assessments?

To put the source category risks in context, the EPA typically examines the risks from the entire “facility,” where the facility includes all HAP-emitting operations within a contiguous area and under common control. In other words, the Agency examines the HAP emissions not only from the source category emission points of interest, but also emissions of HAP from all other emission sources at the facility for which we have data. For this source category, we conducted the facility-wide assessment using a dataset compiled from the 2017 NEI and 2018 actual emissions provided by ADEQ. The source category records of that 2017 and 2018 actual emissions dataset were removed, evaluated, and updated as described in section II.C of this preamble: What data collection activities were conducted to support this action? Once a quality assured source category dataset was available, it was placed back with the remaining records from the NEI for that facility. The facility-wide file was then used to analyze risks due to the inhalation of HAP that are emitted “facility-wide” for the populations residing within 50 km of each facility, consistent with the methods used for the source category analysis described above. For these

facility-wide risk analyses, the modeled source category risks were compared to the facility-wide risks to determine the portion of the facility-wide risks that could be attributed to the source category addressed in this proposal. The EPA also specifically examined the facility that was associated with the highest estimate of risk and determined the percentage of that risk attributable to the source category of interest. The

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the Risk and Technology Review 20201 Proposed Rule,

available through the docket for this action, provides the methodology and results of the facility-wide analyses, including all facility-wide risks and the percentage of source category contribution to facility-wide risks.

8. How do we consider uncertainties in risk assessment?

Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for this proposal. Although uncertainty exists, we believe that our approach, which used conservative tools and assumptions, ensures that our decisions are health and environmentally protective. A brief discussion of the uncertainties in the RTR emissions dataset, dispersion modeling, inhalation exposure estimates, and dose-response relationships follows below. Also included are those uncertainties specific to our acute screening assessments, multipathway screening assessments, and our environmental risk screening assessments. A more thorough discussion of these uncertainties is included in the

Residual Risk Assessment for the Primary Copper Smelting Major Source Category in Support of the Risk and Technology Review 2021 Proposed Rule,

which is available in the docket for this action. If a multipathway site-specific assessment was performed for this source category, a full discussion of the uncertainties associated with that assessment can be found in Appendix 11 of that document,

Site-Specific Human Health Multipathway Residual Risk Assessment Report

a. Uncertainties in the RTR Emissions Dataset

Although the development of the RTR emissions dataset involved quality assurance/quality control processes, the accuracy of emissions values will vary depending on the source of the data, the degree to which data are incomplete or missing, the degree to which assumptions made to complete the datasets are accurate, errors in emission estimates, and other factors. The emission estimates considered in this analysis generally are annual totals for certain years, and they generally do not reflect short-term fluctuations during the course of a year or variations from year to year except in potentially a few cases, such as the May/June 2018 lead test data for anode refining roof vent fugitive emissions from the Freeport facility. Nevertheless, the estimates of peak hourly emission rates for the acute effects screening assessment were based on emission adjustment factors applied to the average annual hourly emission rates, which are intended to account for emission fluctuations due to normal facility operations.

b. Uncertainties in Dispersion Modeling

The EPA recognizes there is uncertainty in ambient concentration estimates associated with any model, including the EPA's recommended regulatory dispersion model, AERMOD. In using a model to estimate ambient pollutant concentrations, the user chooses certain options to apply. For RTR assessments, we select some model options that have the potential to overestimate ambient air concentrations (

e.g.,

not including plume depletion or pollutant transformation). We select other model options that have the potential to underestimate ambient impacts (

e.g.,

not including building downwash). Other options that we select have the potential to either under- or overestimate ambient levels (

e.g.,

location and year of meteorology data and receptor locations). On balance, considering the directional nature of the uncertainties commonly present in ambient concentrations estimated by dispersion models, the approach we apply in the RTR assessments should yield unbiased estimates of ambient HAP concentrations. The uncertainties attributed to dispersion modeling in RTR assessments were assessed by EPA's Science Advisory Board (SAB) and deemed suitable and appropriate.

We also note that the selection of meteorology dataset location could have an impact on the risk estimates. For this source category, the two facilities being modeled have ambient air toxics monitors and on-site meteorological stations in place that can be used to help characterize the uncertainty of the emissions modeling. For the Freeport facility, we were unable to collect on-site meteorological data for the 2019 monitor to model comparison; therefore, the model to monitor evaluation was based upon on-site 2011-2012 meteorological data with the 2019 monitoring data. This was not an uncertainty for the Asarco facility, since both model and monitoring comparisons were for 2019. A review of the model to monitor comparisons between the two site(s) can be found in Appendix 1 of the

Residual Risk Assessment for the Primary Copper Smelting Source Category in Support of the Risk and Technology Review 2021 Proposed Rule,

report which is available in the docket for this action and Section IV; B-6 of this proposal. As we continue to update and expand our library of meteorological station data used in our risk assessments, we expect to reduce this variability.

USEPA, 2009a.

Risk and Technology Review (RTR) Risk Assessment Methodologies: For Review by the EPA's Science Advisory Board with Case Studies—MACT I Petroleum Refining Sources and Portland Cement Manufacturing

. EPA-452/R-09-006.

https://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf

c. Uncertainties in Inhalation Exposure Assessment

Although every effort is made to identify all of the relevant facilities and emission points, as well as to develop accurate estimates of the annual emission rates for all relevant HAP, the uncertainties in our emission inventory likely dominate the uncertainties in the exposure assessment. Some uncertainties in our exposure assessment include human mobility, using the centroid of each census block, assuming lifetime exposure, and assuming only outdoor exposures. For most of these factors, there is neither an under nor overestimate when looking at the maximum individual risk or the incidence, but the shape of the distribution of risks may be affected. With respect to outdoor exposures, actual exposures may not be as high if people spend time indoors, especially for very reactive pollutants or larger particles. For all factors, we reduce uncertainty when possible. For example, with respect to census-block centroids, we analyze large blocks using aerial imagery and adjust locations of the block centroids to better represent the population in the blocks. We also add additional receptor locations where the population of a block is not well represented by a single location.

d. Uncertainties in Dose-Response Relationships

There are uncertainties inherent in the development of the dose-response values used in our risk assessments for cancer effects from chronic exposures and noncancer effects from both chronic and acute exposures. Some uncertainties are generally expressed quantitatively, and others are generally

expressed in qualitative terms. We note, as a preface to this discussion, a point on dose-response uncertainty that is stated in the EPA's

2005 Guidelines for Carcinogen Risk Assessment

; namely, that “the primary goal of EPA actions is protection of human health; accordingly, as an Agency policy, risk assessment procedures, including default options that are used in the absence of scientific data to the contrary, should be health protective” (the EPA's

2005 Guidelines for Carcinogen Risk Assessment,

page 1-7). This is the approach followed here as summarized in the next paragraphs.

Cancer UREs used in our risk assessments are those that have been developed to generally provide an upper bound estimate of risk.

That is, they represent a “plausible upper limit to the true value of a quantity” (although this is usually not a true statistical confidence limit). In some circumstances, the true risk could be as low as zero; however, in other circumstances the risk could be greater.

Chronic noncancer RfC and reference dose values represent chronic exposure levels that are intended to be health-protective levels. To derive dose-response values that are intended to be “without appreciable risk,” the methodology relies upon an uncertainty factor (UF) approach,

which considers uncertainty, variability, and gaps in the available data. The UFs are applied to derive dose-response values that are intended to protect against appreciable risk of deleterious effects.

IRIS glossary (

https://ofmpub.epa.gov/sor_internet/registry/termreg/searchandretrieve/glossariesandkeywordlists/search.do?details=&glossaryName=IRIS%20Glossary

An exception to this is the URE for benzene, which is considered to cover a range of values, each end of which is considered to be equally plausible, and which is based on maximum likelihood estimates.

See

A Review of the Reference Dose and Reference Concentration Processes,

U.S. EPA, December 2002, and

Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry,

U.S. EPA, 1994.

Many of the UFs used to account for variability and uncertainty in the development of acute dose-response values are quite similar to those developed for chronic durations. Additional adjustments are often applied to account for uncertainty in extrapolation from observations at one exposure duration (

e.g.,

4 hours) to derive an acute dose-response value at another exposure duration (

e.g.,

1 hour). Not all acute dose-response values are developed for the same purpose, and care must be taken when interpreting the results of an acute assessment of human health effects relative to the dose-response value or values being exceeded. Where relevant to the estimated exposures, the lack of acute dose-response values at different levels of severity should be factored into the risk characterization as potential uncertainties.

Uncertainty also exists in the selection of ecological benchmarks for the environmental risk screening assessment. The EPA established a hierarchy of preferred benchmark sources to allow selection of benchmarks for each environmental HAP at each ecological assessment endpoint. We searched for benchmarks for three effect levels (

i.e.,

no-effects level, threshold-effect level, and probable effect level), but not all combinations of ecological assessment/environmental HAP had benchmarks for all three effect levels. Where multiple effect levels were available for a particular HAP and assessment endpoint, we used all of the available effect levels to help us determine whether risk exists and whether the risk could be considered significant and widespread.

For a group of compounds that are unspeciated (

e.g.,

glycol ethers), we conservatively use the most protective dose-response value of an individual compound in that group to estimate risk. Similarly, for an individual compound in a group (

e.g.,

ethylene glycol diethyl ether) that does not have a specified dose-response value, we also apply the most protective dose-response value from the other compounds in the group to estimate risk.

e. Uncertainties in Acute Inhalation Screening Assessments

In addition to the uncertainties highlighted above, there are several factors specific to the acute exposure assessment that the EPA conducts as part of the risk review under section 112 of the CAA. The accuracy of an acute inhalation exposure assessment depends on the simultaneous occurrence of independent factors that may vary greatly, such as hourly emissions rates, meteorology, and the presence of a person. In the acute screening assessment that we conduct under the RTR program, we assume that peak emissions from the source category and reasonable worst-case air dispersion conditions (

i.e.,

99th percentile) co-occur. We then include the additional assumption that a person is located at this point at the same time. Together, these assumptions represent a reasonable worst-case actual exposure scenario. In most cases, it is unlikely that a person would be located at the point of maximum exposure during the time when peak emissions and reasonable worst-case air dispersion conditions occur simultaneously.

f. Uncertainties in the Multipathway and Environmental Risk Screening Assessments

For each source category, the Agency generally relies on site-specific levels of PB-HAP or environmental HAP emissions to determine whether a refined assessment of the impacts from multipathway exposures is necessary or whether it is necessary to perform an environmental screening assessment. This determination is based on the results of a three-tiered screening assessment that relies on the outputs from models—TRIM.FaTE and AERMOD—that estimate environmental pollutant concentrations and human exposures for five PB-HAP (dioxins, POM, mercury, cadmium, and arsenic) and two acid gases (HF and HCl). For lead, the Agency uses AERMOD to determine ambient air concentrations, which are then compared to the secondary NAAQS standard for lead. Two important types of uncertainty associated with the use of these models in RTR risk assessments and inherent to any assessment that relies on environmental modeling are model uncertainty and input uncertainty.

In the context of this discussion, the term “uncertainty” as it pertains to exposure and risk encompasses both

variability

in the range of expected inputs and screening results due to existing spatial, temporal, and other factors, as well as

uncertainty

in being able to accurately estimate the true result.

Model uncertainty concerns whether the model adequately represents the actual processes (

e.g.,

movement and accumulation) that might occur in the environment. For example, does the model adequately describe the movement of a pollutant through the soil? This type of uncertainty is difficult to quantify. However, based on feedback received from previous EPA SAB reviews and other reviews, we are confident that the models used in the screening assessments are appropriate and state-of-the-art for the multipathway and environmental screening risk assessments conducted in support of RTRs. For example, the SAB found that the general methodology of the tiered screening approach and the use of TRIM.FaTE and AERMOD are appropriate for both multipathway and ecological screening tools. The SAB noted the simplicity of the air dispersion treatment in TRIM.FaTE and encouraged the advancement of

incorporating AERMOD analysis within the TRIM.FaTE framework.

USEPA, 2018. Review of EPA's draft technical report entitle Screening Methodologies to Support Risk and Technology Review (RTR): A Case Study Analysis; EPA-SAB-18-004.

https://yosemite.epa.gov/sab/sabproduct.nsf/LookupWebReportsLastMonthBOARD/7A84AADF3F2FE04A85258307005F7D70/$File/EPA-SAB-18-004+.pdf.

Input uncertainty is concerned with how accurately the models have been configured and parameterized for the assessment at hand. For Tier 1 of the multipathway and environmental screening assessments, the EPA configured the models to avoid underestimating exposure and risk. This was accomplished by selecting upper-end values from nationally representative datasets for the more influential parameters in the environmental model, including selection and spatial configuration of the area of interest, lake location and size, meteorology, surface water, soil characteristics, and structure of the aquatic food web. The EPA also assumes an ingestion exposure scenario and values for human exposure factors that represent reasonable maximum exposures.

In Tier 2 of the multipathway and environmental screening assessments, we refine the model inputs to account for meteorological patterns in the vicinity of the facility versus using upper-end national values, and we identify the actual location of lakes near the facility rather than the default lake location that we apply in Tier 1. By refining the screening approach in Tier 2 to account for local geographical and meteorological data, we decrease the likelihood that concentrations in environmental media are overestimated, thereby increasing the usefulness of the screening assessment. In Tier 3 of the screening assessments, we refine the model inputs again to account for hour-by-hour plume-rise and the height of the mixing layer. The EPA can also use those hour-by-hour meteorological data in a TRIM.FaTE run using the screening configuration corresponding to the lake location. These refinements produce a more accurate estimate of chemical concentrations in the media of interest, thereby reducing the uncertainty with those estimates. The assumptions and the associated uncertainties regarding the selected ingestion exposure scenario are the same for all three tiers.

For the environmental screening assessment for acid gases, we employ a single-tiered approach. We use the modeled air concentrations and compare those with ecological benchmarks.

For all tiers of the multipathway and environmental screening assessments, our approach to addressing model input uncertainty is generally cautious. We choose model inputs from the upper end of the range of possible values for the influential parameters used in the models, and we assume that the exposed individual exhibits ingestion behavior that would lead to a high total exposure. This approach reduces the likelihood of not identifying high risks for adverse impacts.

Despite the uncertainties, when individual pollutants or facilities do not exceed screening threshold emission rates (

i.e.,

screen out), we are confident that the potential for adverse multipathway impacts on human health is very low. On the other hand, when individual pollutants or facilities do exceed screening threshold emission rates, it does not mean that impacts are significant, only that the Agency cannot rule out that possibility and that a refined assessment for the site might be necessary to obtain a more accurate risk characterization for the source category.

The EPA evaluates the following HAP in the multipathway and/or environmental risk screening assessments, where applicable: Arsenic, cadmium, dioxins/furans, lead, mercury (both inorganic and methyl mercury), POM, HCl, and HF. These HAP represent pollutants that can cause adverse impacts either through direct exposure to HAP in the air or through exposure to HAP that are deposited from the air onto soils and surface waters and then through the environment into the food web. These HAP represent those HAP for which the Agency can conduct a meaningful multipathway or environmental screening risk assessment. For other HAP not included in our screening assessments, the model has not been parameterized such that it can be used for that purpose. In some cases, depending on the HAP, the Agency may not have appropriate multipathway models that allow us to predict the concentration of that pollutant. The EPA acknowledges that other HAP beyond these that we are evaluating may have the potential to cause adverse effects and, therefore, the EPA may evaluate other relevant HAP in the future, as modeling science and resources allow.

IV. Analytical Results and Proposed Decisions

A. What actions are we taking pursuant to CAA sections 112(d)(2) and 112(d)(3)?

In this proposal, the EPA is proposing the following standards pursuant to CAA section 112(d)(2) and (3) for the major source NESHAP (40 CFR part 63, subpart QQQ):

• PM limits for anode refining point sources at existing and new sources.

• PM limits for process fugitive emissions from rooflines of smelting furnaces at existing and new sources.

• PM limits for process fugitive emissions from converters at existing and new sources.

• PM limits for process fugitive emissions from roof vents at anode refining operations at existing and new sources.

• Mercury limits for any existing and new combination of stacks or other vents from the copper concentrate dryers, converting department, the anode refining department, and the smelting vessels affected sources.

• PM limits for new converters.

The results and proposed decisions based on the analyses performed pursuant to CAA section 112(d)(2) and (3) are presented below. When addressing previously unregulated HAP emission sources or unregulated HAP from previously regulated sources in the proposed rule, we apply the MACT methodology, as described in section II.A above.

1. Anode Refining Point Source Emissions

The 1998 proposal for primary copper smelting identified anode refining in the definition of primary copper smelters. However, at that time, the EPA said there were insufficient data to set an emission limit for anode refining. Therefore, the Agency did not propose specific emission standards for anode copper refining operations in the major source NESHAP at that time. In contrast, the 2007 area source NESHAP for primary copper smelting (subpart EEEEEE) does include emissions standards for anode refining. We conclude that anode refining is part of the source category and emits HAP emissions. Therefore, pursuant to CAA section 112(d)(2) and (3), the Agency is proposing to revise the 2002 major source NESHAP to include emission limits for new and existing anode refining point sources. We have anode refining point source test data from only one source, and because there are less than 30 sources in the category, the MACT floor is based on the average performance of the best 5 sources (in this case, the upper predictive limit (UPL) for the best single source because the Agency only has test data from one source). Using available test data, we are proposing a MACT floor PM limit as a surrogate for particulate metal HAP, which includes, but is not limited to,

antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, nickel, and selenium compounds. This approach is consistent with the approach used to limit metal HAP emissions from the other copper smelting processes. A detailed analysis and documentation of the MACT floor calculations can be found in the technical document,

Draft MACT Floor Analyses for the Primary Copper Smelting Source Category.

The MACT floor emissions limit was calculated based on the average of the emissions tests, accounting for variability using the 99 percent UPL. The MACT floor limit for the anode refining point source emissions for existing and new sources is 5.8 milligrams per dry standard cubic meter (mg/dscm).

We identified one BTF option to further reduce PM emissions from anode refining furnaces point sources. The BTF option would require the two facilities to each install and operate a wet electrostatic precipitator (ESP) in addition to their existing controls (baghouses). We estimated that emissions of lead would be reduced by about 0.8 tpy and arsenic emissions would be reduced by about 0.3 tpy. For the 2 existing facilities to comply with this BTF standard, we estimated capital costs of $72 million and annualized costs of $9.6 million for a cost effectiveness of $8.7 million per ton of HAP metal reduced. Regarding new sources, the MACT floor control technology would be a baghouse since the current best performing source is controlled with a baghouse, and the BTF control option for new sources would also be the same as existing (

i.e.,

new source BTF option is based on the addition of a Wet ESP on top of the baghouse). Therefore, we assume the costs for a new source would also be about the same (

i.e.,

$38 million capital, with annualized costs of $4.8 million). The Agency cannot estimate a precise cost effectiveness number because it would depend on unknown factors (such as concentration of HAP metals in the ore and/or other input materials used by a new source). Therefore, the Agency assumes the cost effectiveness for new sources would be roughly the same as for existing sources described above. Based on this analysis, the Agency is not proposing this BTF option for existing or new sources because of the relatively high costs and poor cost effectiveness.

Based on the analyses described above, the Agency is proposing to revise the 2002 NESHAP to include the following MACT floor-based emission limits for anode refining point sources:

• For existing anode refining point sources located at primary copper smelting facilities, we are proposing a PM emissions limit of 5.8 mg/dscm.

• For new anode refining point sources located at primary copper smelting facilities, we are proposing a PM emissions limit of 5.8 mg/dscm.

We propose that compliance with the PM emissions limit for anode refining will be demonstrated through an initial compliance test followed by a compliance test at least once every year.

2. Process Fugitive Roof Vents

The major source NESHAP currently does not include standards for process fugitive emissions from the rooflines of smelting furnaces, converters, or anode refining operations, with the exception of an opacity limit for converter roof vents that applies during testing. We note that some of these rooflines are among the main sources driving risks as described in the discussion of the risk results in section IV.B. Pursuant to CAA section 112(d)(2) and (3), the EPA is proposing to revise the 2002 NESHAP to include emission limits for rooflines for smelting furnaces, converters, and anode refining at existing and new sources.

For smelting furnace and converter rooflines, we evaluated the potential to establish MACT floor emissions limits for PM, as a surrogate for HAP metals, which includes, but is not limited to, antimony, arsenic, beryllium, cadmium, chromium, cobalt, lead, manganese, nickel, and selenium compounds, based on available test data. While the Agency only had test data for one of the two facilities (

i.e.,

Freeport), the Agency used those data for calculating MACT floor PM limits for converters and smelting furnaces using the UPL methodology. Establishing PM as a surrogate for HAP metals is consistent with the approach used to limit metal HAP emissions from the other copper smelting processes in the current NESHAP and for many other source categories (

i.e.,

Ferroalloys Production, Integrated Iron and Steel Manufacturing, Iron and Steel Foundries). Based on our analyses, we calculated a MACT floor emissions limit of 1.7 lbs/hr PM for process fugitive emissions for existing and new converter rooflines and a MACT floor limit of 4.3 lbs/hr PM for existing and new smelting furnaces rooflines.

The EPA also evaluated BTF PM limits for smelting furnace and converter rooflines based on the potential addition of capture and control equipment designed to achieve approximately 90 percent reduction in process fugitive emissions. With regard to smelting furnaces, based on available information, we estimate that 1.2 tpy year of HAP metals are emitted from the smelting flash furnace at Asarco. Freeport has two smelting furnaces. Freeport already has primary and secondary capture systems that capture and control process fugitives, resulting in total estimated HAP metal emissions from both furnaces of 0.626 tpy based on available test data, or about half of the emissions from Asarco's furnace. Asarco has primary capture and control and some secondary capture and control, but based on available reported emission estimates, Asarco emits significantly more HAP metals than Freeport. For the BTF option, we evaluated the potential to add enhanced, improved capture and control equipment to achieve about 90 percent reduction of HAP metal emissions from the Asarco smelting flash furnace (

i.e.,

reduce estimated HAP metal emissions from 1.2 tpy to about 0.12 tpy). To achieve 90 percent reduction of process fugitives from the rooflines, the Agency assumes additional secondary capture and/or enhanced capture (

e.g.,

hooding, duct work, fans, etc.) would be needed for at least one operation (

i.e.,

matte tapping/pouring). We think another significant source of fugitives is the material transfer operation, which includes movement of a large ladle containing very hot liquid matte from the flash furnace tapping/pouring operation by an overhead crane to the converters after each tapping/pouring operation. To capture these fugitive emissions from the material transfer operations, we assume a roof ventilation capture system would be needed. We also assume a new baghouse (or other PM collection control device) would be needed to handle these additional exhaust gases. Another potential source of fugitives is the pouring/tapping of slag, but we are assuming 90 percent reduction could be achieved by adding a secondary capture and/or enhanced capture system to reduce fugitive emissions from at least one operation, such as the matte tapping/pouring, without adding capture and control equipment to the slag operation. Therefore, no costs are estimated for capturing fugitives from the slag pouring process.

Furthermore, to comply with this BTF option for smelting furnaces, we estimate Freeport would also need to reduce HAP emissions. If the standard was based on total emissions from smelting furnaces, we estimate Freeport would need to achieve 80 percent reduction (

e.g.,

from 0.626 to 0.12 tpy,

which is the target level described above for the Asarco smelting furnace). To achieve this level of additional reductions of process fugitive emissions, we assume Freeport would need to install two roof ventilation capture systems, one for each of its two furnaces. Further details of this beyond the floor analysis are provided in the technical memo

Evaluation of Beyond-the-floor and Ample Margin of Safety Control Options and Costs for Process Fugitive Emissions from Smelting Furnaces and Converters, and for Point Source Emissions from Anode Refining Furnaces and for the Combined Emissions Stream Emitted from the Freeport Aisle Scrubber,

which is available in the docket for this action.

Based on this analysis, the Agency estimates the BTF PM limit of 0.12 tpy for existing sources would have total capital costs of $26,501,600 and annualized costs of $5,443,937 and would achieve about 1.53 tpy reduction of HAP metals, with cost effectiveness of $3,445,529 per ton of HAP metal reduction. With regard to new sources (

i.e.,

new furnaces), since the MACT Floor limit is based on test data from Freeport, the Agency assumes the BTF controls for a new furnace would be similar to the BTF controls described above for Freeport (

i.e.,

need to install a roof ventilation capture system on top of whatever controls they need to meet the MACT Floor level of control for each new furnace). Based on costs estimated for Freeport, and applying this to a potential new source, the estimated costs for BTF option for a new furnace would be $3,700,000 capital and annualized costs of $600,000 and achieve about 0.25 tpy metal HAP reduction, with cost effectiveness of $2,400,000 per ton of HAP. Further information and details regarding the MACT floor and BTF analyses are provided in the memorandum titled

Draft MACT Floor Analyses for the Primary Copper Smelting Source Category,

and in the costs memo cited above, which are available in the docket for this proposed action.

With regard to converters, Asarco has three converters and Freeport has four converters. Asarco already has primary, secondary and tertiary capture and controls, and the reported total estimated HAP emissions are 0.0000022 tpy. On the other hand, Freeport has primary and secondary capture and controls, but no tertiary controls, and the total estimated HAP emissions from Freeport converters are 0.115 tpy. Therefore, we considered proposing a BTF option for existing converters for the source category that would require reductions at Freeport based on installation of tertiary controls which would be similar to the tertiary capture and controls on the converters at Asarco or the roof ventilation capture system described in the BTF analysis above for Freeport smelting furnaces. Given that all four converters at Freeport are in the same building, we assume that one such system would be sufficient to achieve about 80 percent reduction of fugitives. We assume Freeport could route these additional emissions to current control devices, since they already have two such control systems (

i.e.,

scrubbers). Therefore, we are not including an additional baghouse for this potential BTF control option. Based on the analysis described above, the Agency estimates this potential BTF standard for existing converters would have total capital costs of $3,697,200 and annualized costs of $599,663, and achieve about 0.09 tpy reduction of HAP metals, with cost effectiveness of $6,662,928 per ton of HAP metal reduction.

With regard to potential BTF standards for process fugitive emissions from roof vents for new converters, it is difficult to determine the appropriate standard because of a number of issues and uncertainties. First, based on reported emissions described above, Asarco has substantially lower HAP metal emissions as compared to Freeport. However, we have no test data for Asarco, so we have low confidence in these reported emissions estimates. Second, as described above, the current NESHAP prohibits new sources from using batch converters. Therefore, we assume any new converter would be a continuous converter, and we have no test data or even estimates of process fugitive emissions from continuous converter building roof vents. Based on this lack of information, we assume the BTF limit and associated costs for process fugitives for new sources would be the same as the BTF limit and associated costs for existing sources described in the paragraph above.

The EPA also evaluated the potential to establish MACT floor limits, or BTF limits, for HAP metals based on establishing additional opacity limits in the NESHAP for each affected source. For example, we considered proposing opacity limits consistent with the state air permits and opacity limits in the Consent Decree (CD) for Asarco as potential MACT standards in addition to, or instead of, the MACT floor PM limits. The opacity limits are not expected to result in emission reductions. Instead, the opacity would be monitored to ensure that the process equipment and control devices are operating properly. Furthermore, there would be no additional costs associated with establishing these opacity limits, since the limits would be consistent with what the facilities are already complying with under the state air permits or a CD. There is variability in opacity limits in the state air permits and CD and uncertainty as to what specific opacity limits represent MACT floor and BTF for each of the processes. These opacity limits are described in detail in the memorandum titled

Opacity Standards for Major Primary Copper Smelting Facilities,

which is available in the docket.

Based on the above analyses, we are proposing the MACT floor PM emissions limits as a surrogate for metal HAP for converter and smelting furnace roof vents. The Agency is not proposing the BTF limits for converters or smelting furnaces because of the high costs and poor cost effectiveness and uncertainties in the estimates of emissions, emissions reductions and costs. Furthermore, the Agency is not proposing the opacity limits at this time due to variability in opacity limits in the state air permits and CD and uncertainty as to what specific opacity limits represent MACT floor and BTF for each of the processes. Nevertheless, the EPA solicits comments regarding the opacity limits, including whether it would be appropriate to establish opacity limits (such as the opacity limits in the state air permits and CD) in the NESHAP in addition to, or instead of, the numeric PM MACT floor emissions limits described above, and, if so, an explanation as to how or why these opacity limits reflect MACT floor, or BTF, levels of control. The Agency also solicits comments, data and other information regarding the MACT Floor analyses and BTF analyses, and our proposed determinations described above.

With regard to process fugitive emissions from anode refining roof vents, we estimate that Freeport emits 5.22 tpy of total metal HAP, comprised mainly of lead (4.09 tpy) and arsenic (0.622 tpy), and that Asarco emits 0.1076 tpy of total metal HAP. To develop a proposed standard for this source, we initially calculated a MACT floor emissions limit for PM of 15.2 lbs/hr based on available test data and application of the UPL methodology. For this standard, PM serves as a surrogate for all particulate HAP metals, similar to the other PM limits in the NESHAP.

Subsequently, we evaluated a potential BTF PM emissions limit for the anode refining roof vents, which would be set at a level approximately 90 percent lower than the MACT floor

limit. Based on these analyses, which are described in detail in the

Draft MACT Floor Analyses for the Primary Copper Smelting Source Category

memorandum, which is available in the docket, the BTF emissions limit for PM is 1.6 lbs/hr. Based on available data, to comply with this BTF limit, we expect the Freeport facility would need to install improved capture systems, including hoods, ductwork, and fans, and one additional baghouse to reduce process fugitive emissions from anode refining roof vents. We anticipate the improved capture systems would need to be applied to four units, including the two anode refining furnace pouring operations, the anode casting wheel, and the holding vessel. However, the facility might identify other methods or approaches to reduce these emissions, such as applying these equipment to only a subset of the four units, limiting the input of certain raw materials that have relatively high HAP metal content (such as acid plant sludge) into the process, and/or converting their holding vessel into an enclosed, controlled anode refining furnace. The Agency expects that the capture, control and/or other measures the facility adopts to reduce metal HAP emissions from roof vents on anode refining buildings to meet the BTF limit will also significantly reduce human health risks (

e.g.,

due to lead and arsenic emissions) as discussed below in section IV.C.2.

The Agency estimates that total costs for Freeport to comply with this BTF PM emissions limit would be capital costs of $5,887,000 and annualized costs of $1,558,000, and would achieve about 4.25 tpy reduction of lead and arsenic emissions, with cost effectiveness of $367,000 per ton of lead and arsenic reduction. Lead and arsenic account for more than 90 percent of the HAP metal emissions from the roof vents on the anode refining building at Freeport. This cost effectiveness estimate is within the range of cost effectiveness values that EPA has historically considered acceptable for lead when compared to similar prior rulemakings. For example, in the 2012 Secondary Lead Smelting RTR, EPA accepted a cost effectiveness up to about $1.3M/ton for metal HAP (mainly Pb, based on 2009 dollars). The EPA's consideration of the cost effectiveness estimate of $367,000 per ton of lead and arsenic (noted above) also reflects fact-specific circumstances for addressing lead and arsenic emissions from the Primary Copper Smelting source category. For example, in other instances when the focus is on controlling other pollutants, such as PM, the agency would compare to other cost-effectiveness values. It is also important to note that cost effectiveness is but one factor we consider in assessing the cost of the emission reduction at issue here. See

NRDC

EPA,

749 F.3d 1055, 1060 (D.C. Cir. April 18, 2014) (“Section 112 does not command EPA to use a particular form of cost analysis.”). We also consider other factors in assessing the cost of the emission reduction as part of our BTF analysis, including, but not limited to, total capital costs, annual costs and costs compared to total revenues (

e.g.,

costs to revenue ratios). As explained in section V.D., the estimated total annualized costs for Freeport are about 0.016 percent of the annual revenue of the facility's ultimate parent company in 2019. Furthermore, based on Freeport's existing permit, background information in a consent order with the state of Arizona (which are available in the docket), and discussions with facility representatives, improvements to their anode refining capture and control systems are already being considered. Because estimated HAP metals emissions from Asarco are much lower, they would not be expected to incur additional control costs to meet the BTF limit. However, Asarco would have new costs for compliance testing and recordkeeping and reporting, as described below. Overall, the EPA concludes that these costs are not economically significant and the cost effectiveness is within the range accepted in other NESHAP for these types of HAP metals (

e.g.,

Secondary Lead RTR Proposed Rule, 76 FR 99, 29032, May 19, 2011, and the Final rule, 77 FR 3, 556, January 5, 2012).

The Agency also considered proposing a BTF lead emissions limit in addition to, or instead of, the PM limit since lead is the primary HAP metal emitted from the anode refining roof vents. For example, the Agency considered a possible lead limit of approximately 0.26 lbs/hr as a potential BTF MACT limit for anode refining process fugitive emissions, which is described in the MACT Floor memo cited above. However, there is some uncertainty with this analysis. It was not clear how best to apply the EPA's UPL methodology to the available lead emissions data to appropriately account for variability and determine a lead UPL limit that would reflect the MACT floor level of control, and to then subsequently determine what lead limit would represent a 90 percent reduction from the lead MACT Floor. The EPA expects the costs and reductions for such a lead BTF limit would be the same as the costs and reductions for the BTF option for PM described in the above paragraph. If the Agency was to establish such a lead limit instead of a PM limit, it would also serve as a surrogate for all HAP metals, similar to the Secondary Lead Smelting NESHAP, which established emissions limits for lead that serve as surrogates for all particulate HAP metals. Due to the uncertainties with the analysis of lead emissions and methodology used to develop the lead UPL limit, the Agency is not proposing this lead limit at this time. However, the EPA solicits comments regarding this potential lead limit and whether it would be appropriate to establish such a lead limit in addition to, or instead of, the PM limit, and if so, why?

Further information and details regarding the derivation of the MACT floor and BTF limits are provided in the memorandum titled

Draft MACT Floor Analyses for the Primary Copper Smelting Source Category.

Further information and details regarding the cost estimates for Freeport to comply with the BTF limits for the anode refining process fugitives roof vents are described in the memorandum

Development of Estimated Costs for Enhanced Capture and Control of Process Fugitive Emissions from Anode Refining Operations at Freeport,

which is available in the docket for this proposed action.

Based on the analyses described above, the Agency is proposing a BTF emissions limit for PM of 1.6 lbs/hr for anode refining process fugitive emissions at existing and new sources.

In summary, based on the analyses described above, the Agency is proposing to revise the 2002 NESHAP to include the following emission limits for process fugitive HAP metal emissions from roof vents of smelting furnaces, converters, and anode refining processes located at primary copper smelting facilities, as follows:

• For existing and new converter operations located at primary copper smelting facilities, the Agency is proposing a PM emissions limit of 1.7 lbs/hr for process fugitive roof vents.

• For existing and new smelting furnaces located at primary copper smelting facilities, the Agency is proposing a PM emissions limit of 4.3 lbs/hr for process fugitive roof vents.

• For existing and new anode refining operations located at primary copper smelting facilities, the Agency is proposing a PM emissions limit of 1.6 lbs/hr for process fugitive roof vents.

The Agency is proposing that compliance with these emissions limits for smelting furnaces, converters and

anode refining will be demonstrated through an initial compliance test followed by a compliance test at least once every year. Moreover, facilities will need to monitor various control parameters (

e.g.,

fan speed, amperage, pressure drops, and/or damper positioning) on a continuous basis to ensure the fugitive capture system and controls are working properly.

With regard to testing and recordkeeping costs, the Agency estimates Asarco will have total costs of about $95,000 per year for all the testing and recordkeeping and reporting to demonstrate compliance with these proposed three new standards for the process fugitive emissions roof vents for the converters, smelting furnaces and anode refining processes. As mentioned above, Freeport will have no new testing costs since they already conduct this testing per ADEQ requirements.

3. Mercury

As mentioned above, the 2002 NESHAP does not include emission limits for mercury. The source category emits an estimated 55 pounds of mercury annually with 45 pounds per year emitted from the Freeport facility. Because of the temperatures of exhaust gas streams encountered at primary copper smelting operations, much of the mercury emitted is in vapor form, not in a particulate form. The vapor form of mercury is not captured by the controls used to reduce PM emissions. Therefore, the PM limits do not serve as a surrogate for mercury. Pursuant to CAA section 112(d)(2) and (3), the Agency is proposing to revise the 2002 NESHAP to include emission limits for mercury.

Initially the Agency calculated MACT floor limits based on test data from both of the primary copper smelting facilities. A detailed analysis and documentation of the MACT floor calculations can be found in the technical document,

Draft MACT Floor Analyses for the Primary Copper Smelting Source Category,

available in the docket.

The MACT floor emissions limit for existing sources was calculated based on the average of all the emissions tests from both facilities, accounting for variability using the 99 percent UPL. A MACT floor based on the 99 percent UPL for the combined facility-wide limit for existing sources is 0.01 lbs/hr. Based on available data, the Agency concludes that both facilities would be able to meet the MACT floor limit with no additional controls.

For new sources, the Agency calculated a MACT floor limit of 0.00097 lbs/hr based on emissions data from the best performing (or lowest emitting) facility, which is Asarco.

We then evaluated and considered a BTF option to further reduce emissions of mercury from existing furnaces and converters. Based on available test data, the Agency estimates that the acid plant is by far the largest source of mercury emissions at Freeport, accounting for about 64 percent of the total, with an estimated 29 lbs/yr of mercury emissions. The BTF option for existing sources would require the Freeport facility to install and operate an activated carbon injection (ACI) system and a polishing baghouse on the combined stack emissions release point, the acid plant. The Agency estimates the ACI system would achieve approximately 90 percent reduction of mercury from the acid plant stack (

i.e.,

26 lbs/yr reduction of mercury). Therefore, the BTF emissions limit would be 0.0043 lbs/hr, which reflects a 90 percent reduction from the acid plant portion of the UPL MACT floor level of 0.01 lbs//hr described above.

The EPA estimates that these controls would achieve 26 pounds of mercury reductions per year (

i.e.,

90 percent reduction of emissions from the acid plant), at a capital cost of $1.5 million and annualized costs of $714,000 (in 2019 dollars) for a cost effectiveness of $27,500 per pound of mercury reduced. After considering both the MACT floor and BTF options for existing sources, the EPA is proposing the BTF facility-wide emissions limit for mercury of 0.0043 lbs/hr for existing sources. The EPA is proposing this BTF limit for mercury because mercury is a highly toxic, persistent and bioaccumulative HAP and the estimated cost effectiveness is within the range of cost effectiveness values the EPA has previously considered acceptable for this HAP after correcting to dollar year values. For example, in the 2012 Mercury and Air Toxics (MATS) final rule, EPA finalized a BTF standard for mercury that had cost effectiveness of $22,496 per pound (based on 2007 dollars), which would be about $27,500 per pound based on 2019 dollars (see

Regulatory Impact Analysis for the Final Mercury and Air Toxics Standards,

December 2011, on pages 1-9 and 1-10, available at:

https://www.epa.gov/mats/epa-announces-mercury-and-air-toxics-standards-mats-power-plants-technical-information

A detailed analysis and documentation of the BTF option for the Primary Copper Smelting major source NESHAP and cost calculations can be found in the technical document,

Estimated Costs for Beyond-the-floor Controls for Mercury Emissions from Primary Copper Smelting Facilities,

available in the docket for this action.

With regard to new sources, as described above, the MACT floor for new sources (

i.e.,

0.00097 lbs/hr) is already significantly lower than the BTF limit for existing sources (

i.e.,

0.0043 lbs/hr). The EPA evaluated a potential BTF option to further reduce emissions of mercury from new furnaces and converters. This analysis is very similar to that described above for existing furnaces and converters, which would require the installation and operation of at least one ACI system plus a polishing baghouse on a combined emissions stream from the converter and furnace. Therefore, the EPA assumes the costs for a beyond the floor option for a new source could be the same as shown above for Freeport. With regard to numerical emissions limit, if the Agency assumes the same percentage reduction from the new source MACT floor (

i.e.,

0.00097 lbs/hr) that the Agency described above for existing sources, that would result in a BTF limit for new sources of 0.00042 lbs/hr.

However, with regard to reductions, it is impossible to accurately estimate potential reductions in mercury from a new source without knowing more information regarding a potential new source. For example, mercury emissions are highly dependent on the concentration of mercury in the ore and mercury concentrations can vary significantly across different ore bodies. If the EPA assumes a new source would have similar ore as Asarco, which has much lower mercury emissions compared to Freeport, the costs for controls could be similar to those estimated for Freeport above. However, the emissions reductions would be far lower, and therefore the controls would probably not be cost effective. If, on the other hand, the ore was similar to Freeport's, it may not be feasible for such a facility to achieve a limit of 0.00042 lbs/hr) with these types of controls. For example, if such a facility had characteristics similar to Freeport, they would likely need to achieve far greater reductions than 90 percent from the acid plant to achieve a limit of 0.00042 lbs/hr, which would require additional controls beyond the ACI system and polishing baghouse described above.

Given these uncertainties described above, and the fact that the new source MACT floor limit (

i.e.,

0.00097 lbs/hr) is already significantly lower than the BTF limit for existing sources of 0.0043 lbs/hr, the Agency is proposing a MACT floor limit for mercury for new sources of 0.00097 lbs/hr. More details are provided in the memorandums titled

Draft MACT Floor Analyses for the Primary Copper Smelting Source Category

and

Estimated Costs for Beyond-the-floor Controls for Mercury Emissions from Primary Copper Smelting Facilities,

which are available in the docket for this action.

Based on the analysis described above, the Agency is proposing to revise the 2002 NESHAP to include the following emission limits for mercury:

• For existing primary copper smelting facilities, the Agency is proposing a facility-wide BTF emissions limit for mercury of 0.0043 lbs/hr.

• For new primary copper smelting facilities, the Agency is proposing a facility-wide MACT Floor emissions limit for mercury of 0.00097 lbs/hr.

The EPA is proposing that compliance with the mercury emissions limits for existing sources will be demonstrated through an initial compliance test for each of the affected sources (

e.g.,

furnaces, converters, anode refining) within 3 years of publication of the final rule followed by a compliance test at least once every year. The actual number of tests required will depend on the specific configurations of the emissions capture and control equipment and number of release points at each facility. For affected facilities that commence construction or reconstruction after January 11, 2022, owners or operators must comply with all requirements of the subpart, including all the amendments being proposed, no later than the effective date of the final rule or upon startup, whichever is later.

The EPA solicit comments, information and data regarding the proposed standards for mercury, and the relevant technical analyses described above, as well as the proposed compliance dates and testing requirements.

4. New Source Limits for Converters in the Major Source NESHAP

The current requirement for new copper converters is that the NESHAP prohibits the use of batch copper converters. By default, new copper converters covered by the NESHAP would need to be continuous converters, or some other

This text is long and has been trimmed here. Open the source document for the complete record.

This is a copy of a public record, reproduced as it was published. It is not legal advice, and it may not be the version a court would rely on. Check the official source before you cite it.