ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 63
[EPA-HQ-OAR-2018-0794; FRL-6716.3-01-OAR]
RIN 2060-AV53
National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units Review of the Residual Risk and Technology Review
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
SUMMARY: The EPA is proposing to amend the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Coal- and Oil-Fired Electric Utility Steam Generating Units (EGUs), commonly known as the Mercury and Air Toxics Standards (MATS). Specifically, the EPA is proposing to amend: the surrogate standard for non-mercury (Hg) metal HAP (filterable particulate matter (fPM)) for existing coal-fired EGUs; the fPM compliance demonstration requirements; the Hg standard for lignite-fired EGUs; and the definition of startup. These proposed amendments are the result of the EPA's review of the May 22, 2020 residual risk and technology review (RTR) of MATS.
DATES: Comments: Comments must be received on or before [INSERT DATE 46 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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 [INSERT DATE 30 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER].
Public hearing: The EPA will hold a virtual public hearing on [INSERT DATE 15 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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-2018-0794, by any of the following methods:
 Federal eRulemaking Portal: https://www.regulations.gov/ (our preferred method). Follow the online instructions for submitting comments.
 Email<EMAIL_ADDRESS>Include Docket ID No. EPA-HQ-OAR-2018-0794 in the subject line of the message.
 Fax:<PHONE_NUMBER>. Attention Docket ID No. EPA-HQ-OAR-2018-0794.
 Mail: U.S. Environmental Protection Agency, EPA Docket Center, Docket ID No. EPA-HQ-OAR-2018-0794, Mail Code 28221T, 1200 Pennsylvania Avenue, NW, Washington, DC 20460.
 Hand/Courier Delivery: EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue, NW, Washington, DC 20004. The Docket Center's hours of operation are 8:30 a.m.  -  4:30 p.m., Monday  -  Friday (except federal holidays).
Instructions: All submissions received must include the Docket ID No. for this rulemaking. Comments received may be posted without change to https://www.regulations.gov/, including any personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the SUPPLEMENTARY INFORMATION section of this document.
FOR FURTHER INFORMATION CONTACT: For questions about this proposed action, contact Sarah Benish, Sector Policies and Programs Division (D243-01), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number:<PHONE_NUMBER>; and email address<EMAIL_ADDRESS>SUPPLEMENTARY INFORMATION:
Participation in virtual public hearing. The public hearing will be held via virtual platform on [INSERT DATE 15 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER] and will convene at 11 a.m. Eastern Time (ET) and conclude at 7 p.m. ET. If the EPA receives a high volume of registrations for the public hearing, we may continue the public hearing on [INSERT DATE 16 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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/mercury-and-air-toxics-standards.
The EPA will begin pre-registering speakers for the hearing no later than 1 business day following publication of this document in the Federal Register. The EPA will accept registrations on an individual basis. To register to speak at the virtual hearing, please use the online registration form available at https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards or contact the public hearing team at<PHONE_NUMBER> or by email at<EMAIL_ADDRESS>The last day to pre-register to speak at the hearing will be [INSERT DATE 12 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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/mercury-and-air-toxics-standards.
The EPA will make every effort to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearings to run either ahead of schedule or behind schedule.
Each commenter will have 4 minutes to provide oral testimony. The EPA encourages commenters to provide the EPA with a copy of their oral testimony by 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/mercury-and-air-toxics-standards. While the EPA expects the hearing to go forward as described in this section, please monitor our website or contact the public hearing team at<PHONE_NUMBER> or by email at<EMAIL_ADDRESS>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 an interpreter or special accommodation such as audio description, please pre-register for the hearing with the public hearing team and describe your needs by [INSERT DATE 7 DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 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-2018-0794. 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-2018-0794. The EPA's policy is that all comments received will be included in the public docket without change and may be made available online at https://www.regulations.gov/, including any personal information provided, unless the comment includes information claimed to be CBI or other information whose disclosure is restricted by statute. Do not submit electronically to https://www.regulations.gov/ any information that you consider to be CBI or other information whose disclosure is restricted by statute. This type of information should be submitted as discussed in the Submitting CBI section of this document.
The EPA may publish any comment received to its public docket. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (i.e., on the Web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
The https://www.regulations.gov/ website allows you to submit your comment anonymously, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through https://www.regulations.gov/, your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, the EPA recommends that you include your name and other contact information in the body of your comment and with any digital storage media you submit. If the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should not include special characters or any form of encryption and be free of any defects or viruses. For additional information about the EPA's public docket, visit the EPA Docket Center homepage at https://www.epa.gov/dockets.
Submitting CBI. Do not submit information containing CBI to the EPA through https://www.regulations.gov/. Clearly mark the part or all of the information that you claim to be CBI. For CBI information on any digital storage media that you mail to the EPA, note the Docket ID No., mark the outside of the digital storage media as CBI, and identify electronically within the digital storage media the specific information that is claimed as CBI. In addition to one complete version of the comments that includes information claimed as CBI, you must submit a copy of the comments that does not contain the information claimed as CBI directly to the public docket through the procedures outlined in Instructions section of this document. If you submit any digital storage media that does not contain CBI, mark the outside of the digital storage media clearly that it does not contain CBI and note the Docket ID No. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 Code of Federal Regulations (CFR) part 2.
Our preferred method to receive CBI is for it to be transmitted electronically using email attachments, File Transfer Protocol (FTP), or other online file sharing services (e.g., Dropbox, OneDrive, Google Drive). Electronic submissions must be transmitted directly to the OAQPS CBI Office at the email address<EMAIL_ADDRESS>and as described above, should include clear CBI markings and note the Docket ID No. If assistance is needed with submitting large electronic files that exceed the file size limit for email attachments, or if you do not have your own file sharing service, please email<EMAIL_ADDRESS>to request a file transfer link. If sending CBI information through the postal service, please send it to the following address: OAQPS Document Control Officer (C404-02), OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID No. EPA-HQ-OAR-2018-0794. The mailed CBI material should be double wrapped and clearly marked. Any CBI markings should not show through the outer envelope.
Preamble acronyms and abbreviations. Throughout this document the use of "we," "us," or "our" is intended to refer to the EPA. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:
Btu		British Thermal Units
CAA          			Clean Air Act
CBI          	Confidential Business Information
CEMS	continuous emissions monitoring systems
CFR          	Code of Federal Regulations
CO2	carbon dioxide
CPMS	continuous parameter monitoring system
EAV	equivalent annualized value
ECMPS	Emissions Collection and Monitoring Plan System
EGU	electric utility steam generating unit
EIA	Energy Information Administration
EJ	environmental justice
EPA          	Environmental Protection Agency
ESP	electrostatic precipitator
FF	fabric filter
FGD	flue gas desulfurization
fPM                       filterable particulate matter
GWh	gigawatt-hour
HAP          	hazardous air pollutant(s)
HCl	hydrogen chloride
HF             	hydrogen fluoride
Hg	mercury
Hg[0]	elemental Hg vapor
HQ	hazard quotient
IGCC	integrated gasification combined cycle
IPM	Integrated Planning Model
lb	Pounds
LEE	low emitting EGU
MACT         	maximum achievable control technology
MATS	Mercury and Air Toxics Standards
MM	million
MW	megawatt
NAICS        	North American Industry Classification System
NEEDS	National Electric Energy Data System
NESHAP         	National Emission Standards for Hazardous Air Pollutants
OAQPS        	Office of Air Quality Planning and Standards
OMB          	Office of Management and Budget
PDF	Portable Document Format
PM           	particulate matter
ppm          	parts per million
PV	present value
RIA	regulatory impact analysis
RTR	residual risk and technology review
SBA          	Small Business Administration
SC-CO2	social cost of carbon
SO2	sulfur dioxide
tpy                         tons per year
TBtu	trillion British thermal units
WebFIRE	Web Factor Information Retrieval System

Organization of this document. The information in this preamble is organized as follows:
I. Executive Summary
A. Background and Purpose of the Regulatory Action
B. Summary of the Major Provisions of the Regulatory Action
II. General Information
A. Does this action apply to me?
B. Where can I get a copy of this document and other related information?
III. Background
A. What is the 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?
E. How does the EPA perform the technology review?
IV. Review of 2020 Residual Risk and Technology Review
A. Summary of the 2020 Residual Risk Review
B. Summary of the 2020 Technology Review
V. Analytical Results and Proposed Decisions
A. Review of the 2020 Residual Risk Review
B. Review of the 2020 Technology Review
C. What are the results and proposed decisions based on our technology review, and what is the rationale for those decisions?
D. What other actions are we proposing, and what is the rationale for those actions?
E. What compliance dates are we proposing, and what is the rationale for the proposed compliance dates?
VI. Summary of Cost, Environmental, and Economic Impacts
A. What are the affected sources?
B. What are the air quality impacts?
C. What are the cost impacts?
D. What are the economic impacts?
E. What are the benefits?
F. What analysis of environmental justice did we conduct?
VII. Request for Comments
VIII. Statutory and Executive Order Reviews
A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review
B. Paperwork Reduction Act (PRA)
C. Regulatory Flexibility Act (RFA)
D. Unfunded Mandates Reform Act (UMRA)
E. Executive Order 13132: Federalism
F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments
G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks
H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use
I. National Technology Transfer and Advancement Act (NTTAA)
J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations

 Executive Summary
 A. Background and Purpose of the Regulatory Action
Exposure to hazardous air pollution ("HAP," sometimes known as toxic air pollution, including Hg, chromium, arsenic, and lead) can cause a range of adverse health effects including harming people's central nervous system; damage to their kidneys; and cancer. Recognizing the dangers posed by HAP, Congress enacted Clean Air Act (CAA) section 112. Under CAA section 112, the EPA is required to set standards (known as "MACT" (maximum achievable control technology) standards) for major sources of HAP that "require the maximum degree of reduction in emissions of the hazardous air pollutants ... (including a prohibition on such emissions, where achievable) that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements, determines is achievable." To ensure a minimum level (or "floor") of emissions reductions, Congress required that MACT standards for existing sources "shall not be less stringent than the emission control than ... the average emission limitation achieved by the best performing 12 percent of existing sources"; and MACT standards for new sources "shall not be less stringent than the emission control that is achieved in practice by the best controlled similar source[.]" 42 U.S.C. § 7412(d)(3). These requirements effectively obligated all sources to reduce emissions as well as the best sources in their category. Congress did not stop there, however. First, 8 years after setting the standard, it required the EPA to address any residual risks posed by the source category (called the "residual risk review"). Second, and as explained in more detail below, it required the EPA, at least every 8 years on an ongoing basis, to review and revise as necessary the MACT standard taking into account developments in practices, processes and control technologies (called the "technology review"). For EGUs, Congress also required the EPA to make a one-time determination of whether it is "appropriate and necessary" to regulate this source category under CAA section 112. The EPA found regulation of EGUs "appropriate and necessary" in 2000 and reaffirmed that finding in 2012 and 2016. MACT standards were originally set for EGUs in 2012, and those standards remain in place today. In 2020, the EPA conducted the 8-year residual risk and technology review and determined not to update the MACT standard.
On January 20, 2021, President Biden signed Executive Order 13990, "Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis" (86 FR 7037; January 25, 2021). The Executive Order, among other things, instructed the EPA to review the 2020 final rule titled, "National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units - Reconsideration of Supplemental Finding and Residual Risk and Technology Review" (85 FR 31286; May 22, 2020) (2020 Final Action) and to consider publishing a notice of proposed rulemaking suspending, revising, or rescinding that action. The 2020 Final Action included a finding that it is not appropriate and necessary to regulate coal- and oil-fired EGUs under CAA section 112 as well as the RTR for the MATS rule. The results of the EPA's review of the 2020 appropriate and necessary finding were proposed on February 9, 2022 (87 FR 7624) (2022 Proposal). In that proposal, the EPA also solicited information on the performance and cost of new or improved technologies that control hazardous air pollutant (HAP) emissions, improved methods of operation, and risk-related information to further inform the EPA's review of the MATS RTR. This action presents the proposed results of the EPA's review of the MATS RTR, as directed by Executive Order 13990.
In particular, with respect to the standard for fPM (as a surrogate for non-Hg metals), and the standard for Hg from EGUs that burn lignite coal, the EPA proposes to conclude that developments since 2012 -- and in particular the fact that the majority of sources are vastly outperforming the MACT standards with control technologies that are cheaper and more effective than the EPA forecast while a smaller number of sources' performance lags behind -- warrant strengthening these standards. While the 2012 MATS drove critical HAP reductions at much lower cost than estimated, coal-fired EGUs still emit a substantial amount of HAP and developments since 2012 provide opportunities to address these emissions and ensure that all coal-fired EGUs are performing at levels achieved by the vast majority of the fleet. These proposed revisions would ensure that the EPA's standards continue to fulfill Congress's direction to require the maximum degree of reduction of HAP while taking into account the statutory factors.
 B. Summary of the Major Provisions of the Regulatory Action
The 2012 MATS Final Rule established emission standards to limit emissions of HAP from coal- and oil-fired EGUs. The rule required that affected sources limit emissions of Hg, of non-Hg metal HAP (e.g., chromium, nickel, arsenic, lead), acid gas HAP (e.g., hydrogen chloride (HCl), hydrogen fluoride (HF), selenium dioxide (SeO2)), and organic HAP (e.g., formaldehyde, dioxins/furans). Since MATS was promulgated in 2012, power sector emissions of mercury, acid gas HAP, and non-mercury metal HAP have decreased by about 86 percent, 96 percent, and 81 percent, respectively, as compared to 2010 emissions levels (See Table 4 at 84 FR 2689, February 7, 2019). Still, coal- and oil-fired EGUs remain the largest domestic emitter of mercury and many other HAP, including many of the non-Hg HAP metals and HCl. Exposure to these HAP, at certain levels and duration, is associated with a variety of adverse health effects. These adverse health effects may include irritation of the lung, skin, and mucus membranes; detrimental effects on the central nervous system; damage to the kidneys; alimentary effects such as nausea and vomiting; and cancer. See 77 FR 9310 for a fuller discussion of the health effects associated with these pollutants. Three of the key metal HAP emitted by EGUs (inorganic arsenic (As), hexavalent chromium (Cr), and nickel compounds (Ni)) have been classified as human carcinogens, while two others (cadmium (Cd) and selenium (Se)) are classified as probable human carcinogens.
To address emissions of these non-Hg metal HAP, MATS sets individual emission limits for each of the 10 non-Hg metals emitted from coal- and oil-fired EGUs. Alternatively, affected sources may meet an emission standard for "total non-Hg metals" by summing the emission rates of each of the non-Hg metals. The MATS rule also allows affected sources to meet a filterable PM (fPM) emission standard as a surrogate for the non-Hg metals. For existing coal-fired EGUs, most units have chosen to demonstrate compliance with the non-Hg metal HAP surrogate fPM emission standard of 3.0E-02 pounds of fPM per million British thermal units of heat input (lb/MMBtu).
CAA section 112(d)(2) directs the EPA to require the maximum degree of HAP emission reductions achievable, taking into account certain considerations, and CAA section 111(d)(3) sets the floor for emission standards based on the reductions achieve by the best performing sources. The MATS was based upon the EPA's analysis under CAA sections 112(d)(2) and (d)(3) in 2012. CAA section 112(d)(6) further requires the EPA, every 8 years, to review and revise standards taking into account developments in practices, processes and control technologies. After reviewing developments in the current emission levels of fPM from existing coal-fired EGUs, the costs of control technologies, and the effectiveness of those technologies, as well as the costs of meeting a standard that is more stringent than 3.0E-02 lb/MMBtu and the other statutory factors, the EPA is proposing to revise the non-Hg metal surrogate fPM emission standard for all existing coal-fired EGUs to a more stringent fPM emission standard of 1.0E-02 lb/MMBtu, which is comparable to the MATS new source standard for fPM. The EPA is also soliciting comment on opportunities to revise the MATS fPM emission standard to an even more stringent level of 6.0E-03 lb/MMBtu.
The EPA is also proposing a revision to the requirements for demonstrating compliance with the fPM emission standard. Currently, EGUs that do not qualify for the low emitting EGU (LEE) program can demonstrate compliance with the fPM standard either by conducting quarterly performance testing (i.e., quarterly stack testing) or by using PM continuous emission monitoring systems (PM CEMS). After considering updated information on the costs for quarterly performance testing compared to the costs of PM CEMS and on the measurement capabilities of PM CEMS, as well as other benefits of using PM CEMS, which include increased transparency and accelerated identification of anomalous emissions, the EPA is proposing to require that all MATS-affected EGUs demonstrate compliance with the fPM emission standard by using PM CEMS. Accordingly, because almost all regulated sources have chosen to demonstrate compliance with the non-Hg HAP metal standards by demonstrating compliance with the surrogate fPM standard and because of the benefits of PM CEMS use for demonstrating compliance, the EPA is proposing to remove the total and individual non-Hg metals emission limits from MATS. Requiring the use of PM CEMS, if finalized, would also render the current compliance method for the LEE program superfluous, since LEE is an optional stack testing program and the considered fPM limits are both below the current fPM LEE program limit of 1.5E-02 lb/MMBtu (i.e., 50 percent of the current fPM standard). Therefore, the EPA also proposes to remove fPM, as well as the total and individual non-Hg HAP metals, from the LEE program.
The EPA is also proposing to establish a more protective Hg emission standard for existing lignite-fired EGUs. Currently, existing lignite-fired EGUs must meet a Hg emission standard of 4.0E-06 lb/MMBtu or an alternative output-based emission standard of 4.0E-02 pounds of Hg per gigawatt-hour output (lb/GWh). The EPA recently collected information on current Hg emission levels and controls for lignite-fired EGUs from information provided routinely to the EPA and to the Energy Information Administration (EIA) and by using the information collection authority provided under CAA section 114. That information showed developments that demonstrate that lignite-fired EGUs can achieve a Hg emission rate that is much lower than the current standard, and that there are cost-effective control technologies and methods of operation that are available to achieve a more stringent standard. Accordingly, the EPA is proposing that lignite-fired EGUs must meet the same Hg emission standard as EGUs firing other types of coal (i.e., bituminous, and subbituminous) which is 1.2 lb/TBtu or an alternative output-based standard of 1.3E-02 lb/GWh. The EPA is not proposing to revise the current Hg emission standard for existing EGUs firing non-lignite coal.
Finally, the EPA is proposing to remove one of the two options for defining the startup period for MATS-affected EGUs. The first option defines startup as either the first-ever firing of fuel in a boiler for the purpose of producing electricity, or the firing of fuel in a boiler after a shutdown event for any purpose. Under the first option, startup ends when any of the steam from the boiler is used to generate electricity for sale over the grid or for any other purpose (including on-site use). In the second option, startup is defined as the period in which operation of an EGU is initiated for any purpose, and startup begins with either the firing of any fuel in an EGU for the purpose of producing electricity or useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes (other than the first-ever firing of fuel in a boiler following construction of the boiler) or for any other purpose after a shutdown event. Under the second option, startup ends 4 hours after the EGU generates electricity that is sold or used for any other purpose (including on-site use), or 4 hours after the EGU makes useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes, whichever is earlier. The EPA is proposing to remove the second option, which is currently being used by fewer than 10 EGUs as discussed in section V.D.1 of this preamble.
The EPA is not proposing to modify the HCl emission standard (nor the alternative sulfur dioxide (SO2) emission standard), which serves as a surrogate for all acid gas HAP (HCl, HF, SeO2) for existing coal-fired EGUs. An evaluation of recent compliance data for HCl and/or SO2 emissions revealed that approximately two-thirds of coal-fired EGUs operate at or below the alternative SO2 emission standard of 2.0E-01 lb SO2/MMBtu (SO2 may be used as an alternative surrogate for acid gas HAP at coal-fired EGUs with operational flue gas desulfurization (FGD) systems and SO2 CEMS). Approximately one-third of coal-fired EGUs have a SO2 emission rate above the current SO2 standard, but instead operate in compliance with the primary acid gas HAP limit for HCl of 2.0E-03 lb HCl/MMBtu, with most using an FGD system and/or by firing coal with low chlorine content and high alkalinity. The EPA did not identify any new technologies or developments in existing technologies that would achieve additional emission reductions. Based on this review, the EPA is not proposing revisions to the acid gas HAP emission standards for coal-fired EGUs.
The EPA is unaware of any new coal- or oil-fired EGUs in development and has not projected any new coal- or oil-fired EGUs in EPA modeling to support various power sector-related rulemakings. For that reason, the EPA has not reviewed and is not proposing any revisions to the MATS new source emission standards. In some cases, however, proposed revisions to existing source emission standards may be more stringent than the corresponding new source emission standard. In those instances, the EPA has addressed that illogical outcome by proposing to revise the corresponding new source standard to be at least as stringent as the proposed revision to the existing source standard.
The EPA is also not proposing to revise MATS emission standards for existing Integrated Gasification Combined Cycle (IGCC) EGUs, nor to the MATS emission standards for any of the subcategories of existing oil-fired EGUs.
In addition to generally soliciting comments on all aspects of this proposed action, the EPA has identified several aspects of the proposal on which comments are specifically requested.
In selecting a standard, as discussed in detail below, the EPA considered the statutory direction and factors laid out by Congress in CAA section 112. Separately, pursuant to EO 12866, the EPA prepared an analysis of the potential costs and benefits associated with this action. This analysis, "Regulatory Impact Analysis for the Proposed National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units Review of the Residual Risk and Technology Review" (Ref. EPA-452/R-23-002), is available in the docket, and is briefly summarized here and in section VI of this preamble.
 General Information
  Does this action apply to me?
The source category that is the subject of this proposal is Coal- and Oil-Fired EGUs regulated under 40 CFR 63, subpart UUUUU. The North American Industry Classification System (NAICS) codes for the Coal- and Oil-fired EGU industry are 221112, 221122, and 921150. This list of categories and NAICS codes is not intended to be exhaustive, but rather provides a guide for readers regarding the entities that this proposed action is likely to affect. The proposed standards, once promulgated, will be directly applicable to the affected sources. Federal, state, local, and tribal government entities that own and/or operate EGUs subject to 40 CFR part 63, subpart UUUUU would be affected by this proposed action. The Coal- and Oil-Fired EGU source category was added to the list of categories of major and area sources of HAP published under section 112(c) of the CAA on December 20, 2000 (65 FR 79825). CAA section 112(a)(8) defines an EGU as any fossil fuel-fired combustion unit of more than 25 megawatts (MW) that serves a generator that produces electricity for sale. A unit that cogenerates steam and electricity and supplies more than one-third of its potential electric output capacity and more than 25 MW electrical output to any utility power distribution system for sale is also considered an EGU.
 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/mercury-and-air-toxics-standards. Following publication in the Federal Register, the EPA will post the Federal Register version of the proposal and key technical documents at this same website.
      A memorandum showing the rule edits that would be necessary to incorporate the changes proposed in this action to 40 CFR part 63, subpart UUUUU is available in the docket for this action (Docket ID No. EPA-HQ-OAR-2018-0794). Following signature by the EPA Administrator, the EPA also will post a copy of this document to https://www.epa.gov/stationary-sources-air-pollution/mercury-and-air-toxics-standards.
 Background
  What is the authority for this action?
  Statutory Authority
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 multi-stage regulatory process to develop standards for emissions of HAP from stationary sources. Generally, during the first stage Congress directed the EPA to establish technology-based standards to ensure that all sources control pollution at the level achieved by the best-performing sources, referred to as the maximum achievable control technology (MACT). After the first stage, Congress directed the EPA to review those standards periodically to determine whether they should be strengthened. Within 8 years after promulgation of the standards, the EPA must evaluate the MACT standards to determine whether additional standards are needed to address any remaining risk associated with HAP emissions. This second stage is commonly referred to as the "residual risk review." In addition, the CAA also requires the EPA to review standards set under CAA section 112 on an ongoing basis no less than 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," and is the subject of this proposal. The discussion that follows identifies the most relevant statutory sections and briefly explains the contours of the methodology used to implement these statutory requirements.
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 reduction in emissions of the [HAP] subject to this section (including a prohibition on such emissions, where achievable) that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements, determines is achievable." 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" standards. For area sources, CAA section 112(d)(5) allows the EPA to set standards based on generally available control technologies or management practices (GACT standards) in lieu of MACT standards.
For categories of major sources and any area source categories subject to MACT standards, the next stage in standard-setting focuses on identifying and addressing any remaining (i.e., "residual") risk pursuant to CAA section 112(f)(2). The residual risk review requires the EPA to update standards if needed to provide an ample margin of safety to protect public health.
Concurrent with that review, and then at least every 8 years thereafter, CAA section 112(d)(6) 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)." See Portland Cement Ass'n v. EPA, 665 F.3d 177, 189 (D.C. Cir. 2011) ("Though EPA must review and revise standards `no less often than every eight years,' 42 U.S.C. § 7412(d)(6), nothing prohibits EPA from reassessing its standards more often."). In conducting this review, which we call the "technology review," the EPA is not required to recalculate the MACT floors that were established in earlier rulemakings. Natural Resources Defense Council (NRDC) v. EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008); Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667 (D.C. Cir. 2013). The EPA may consider cost in deciding whether to revise the standards pursuant to CAA section 112(d)(6). See e.g., Nat'l Ass'n for Surface Finishing v. EPA, 795 F.3d 1, 11 (D.C. Cir. 2015). The EPA is required to address regulatory gaps, such as missing MACT standards for listed air toxics known to be emitted from the source category. Louisiana Environmental Action Network (LEAN) v. EPA, 955 F.3d 1088 (D.C. Cir. 2020).
  EGU Regulation Under CAA Section 112
Congress enacted a special provision concerning coal- and oil-fired EGU HAP emission regulations in the 1990 CAA Amendments under section 112(n)(1)(a) of the CAA that is not applicable to other source categories. This provision required the EPA to conduct a study to evaluate the hazards to public health that are reasonably anticipated to occur as a result of HAP emissions from EGUs, and to make a one-time finding of whether to regulate EGUs under CAA section 112 if the EPA found that doing so was "appropriate and necessary." 42 U.S.C. § 7412(n)(1)(A) (the "appropriate and necessary finding"). Once this one-time finding was made, if the decision was to regulate, Congress subjected EGUs to the same standards and procedures as other source categories. Id. ("The Administrator shall regulate electric utility steam generating units under this section" if he finds doing so is "appropriate and necessary."); see also New Jersey v. EPA, 517 F.3d 574 (D.C. Cir. 2008) (establishing that coal- and oil-fired EGUs are treated similarly as other CAA section 112 regulated sources once listed under CAA section 112(c)).
The EPA originally made the appropriate and necessary finding in 2000. This was followed by a series of affirmations and reversals of this finding, as well as a Supreme Court decision that required the EPA to consider the costs of regulation in making this finding, see Michigan v. EPA, 576 U.S. 743 (2015). On February 9, 2022, the EPA published a notice of proposed rulemaking reaffirming that it remains appropriate and necessary to regulate HAP, including Hg, from coal- and oil-fired EGUs after considering cost. The EPA's consideration of costs in its decision to reaffirm the appropriate and necessary finding was based on estimated and realized costs from the first stage of CAA section 112 regulation, i.e., establishing MACT-based standards and determining whether additional "beyond-the-floor" standards are needed to address remaining risk.
Consistent with Congress's direction, after making the appropriate and necessary finding, the EPA treated EGUs like all other source categories. As required by CAA section 112(d)(2), the EPA first set a floor based on the best 12 percent of performers, and then conducted a beyond-the-floor analysis. That inquiry led to the current MATS, established in 2012. As explained above, the CAA then required the EPA, within 8 years of promulgating the standards, to conduct the residual risk and technology reviews. Congress thus contemplated that well after the EPA determined the regulation of EGUs was appropriate and necessary and well after the EPA set initial standards in accordance with the floor and beyond-the-floor requirements in CAA section 112(d)(2), that at least every 8 years thereafter on a continuing basis, the EPA would review and revise those standards as necessary taking into account developments in practices, processes, and control technologies. The EPA has conducted over 100 technology reviews and has regularly updated emissions standards for HAP based upon the technology review.
 Executive Order 13990
On January 20, 2021, President Biden signed Executive Order 13990, "Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis." The Executive Order, among other things, instructs the EPA to review the 2020 Final Action titled, "National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units  -  Reconsideration of Supplemental Finding and Residual Risk and Technology Review" (85 FR 31286; May 22, 2020) and consider publishing a notice of proposed rulemaking suspending, revising, or rescinding that action.
 What is this source category and how does the current NESHAP regulate its HAP emissions?
The NESHAP for the Coal- and Oil-Fired EGU source category (commonly referred to as MATS) were initially promulgated on February 16, 2012 (77 FR 9304) (2012 MATS Final Rule), under title 40 part 63, subpart UUUUU. The MATS rule was amended on April 19, 2012 (77 FR 23399), to correct typographical errors and certain preamble text that was inconsistent with regulatory text; on April 24, 2013 (78 FR 24073), to update certain emission limits and monitoring and testing requirements applicable to new sources; on November 19, 2014 (79 FR 68777), to revise definitions for startup and shutdown and to finalize work practice standards and certain monitoring and testing requirements applicable during periods of startup and shutdown; and on April 6, 2016 (81 FR 20172), to correct conflicts between preamble and regulatory text and to clarify regulatory text. In addition, the electronic reporting requirements of the rule were amended on March 24, 2015 (80 FR 15510), to allow for the electronic submission of Portable Document Format (PDF) versions of certain reports until April 16, 2017, while the EPA's Emissions Collection and Monitoring Plan System (ECMPS) is revised to accept all reporting that is required by the rule, and on April 6, 2017 (82 FR 16736), and on July 2, 2018 (83 FR 30879), to extend the interim submission of PDF versions of reports through June 30, 2018, and July 1, 2020, respectively.
The MATS rule applies to coal- and oil-fired EGUs located at both major and area sources of HAP emissions. An existing affected source is the collection of coal- or oil-fired EGUs in a subcategory within a single contiguous area and under common control. A new affected source is each coal- or oil-fired EGU for which construction or reconstruction began after May 3, 2011. As previously stated in section II of this preamble, an EGU is a fossil fuel-fired combustion unit of more than 25 MW that serves a generator that produces electricity for sale. A unit that cogenerates steam and electricity and supplies more than one-third of its potential electric output capacity and more than 25 MW electric output to any utility power distribution system for sale is also considered an EGU. The MATS rule defines additional terms for determining rule applicability, including, but not limited to, definitions for "coal-fired electric utility steam generating unit," "oil-fired electric utility steam generating unit," and "fossil fuel-fired." Certain types of electric generating units are not subject to 40 CFR part 63, subpart UUUUU: any unit designated as a major source stationary combustion turbine subject to subpart YYYY of 40 CFR part 63 and any unit designated as an area source stationary combustion turbine, other than an IGCC unit; any EGU that is not a coal- or oil-fired EGU and that meets the definition of a natural gas-fired EGU in 40 CFR 63.10042; any EGU greater than 25 MW that has the capability of combusting either coal or oil, but does not meet the definition of a coal- or oil-fired EGU because it did not fire sufficient coal or oil to satisfy the average annual heat input requirement set forth in the definitions for coal-fired and oil-fired EGUs in 40 CFR 63.10042; and any electric steam generating unit combusting solid waste (i.e., a solid waste incineration unit) subject to standards established under sections 129 and 111 of the CAA.
For coal-fired EGUs, the rule established standards to limit emissions of Hg, acid gas HAP (e.g., HCl, HF), non-Hg HAP metals (e.g., nickel, lead, chromium), and organic HAP (e.g., formaldehyde, dioxin/furan). Emission standards for HCl serve as a surrogate for the acid gas HAP, with an alternate standard for SO2 that may be used as a surrogate for acid gas HAP for those coal-fired EGUs with FGD systems and SO2 CEMS installed and operational. Standards for fPM serve as a surrogate for the non-Hg HAP metals, with standards for total non-Hg HAP metals and individual non-Hg HAP metals provided as alternative equivalent standards. Work practice standards limit formation and emissions of organic HAP.
For oil-fired EGUs, the rule established standards to limit emissions of HCl and HF, total HAP metals (e.g., Hg, nickel, lead), and organic HAP (e.g., formaldehyde, dioxin/furan). Standards for fPM serve as a surrogate for total HAP metals, with standards for total HAP metals and individual HAP metals provided as alternative equivalent standards. Work practice standards limit formation and emissions of organic HAP.
The MATS rule includes standards for existing and new EGUs for seven subcategories: two for coal-fired EGUs, one for IGCC EGUs, one for solid oil-derived fuel-fired EGUs (i.e., petroleum coke-fired), and three for liquid oil-fired EGUs. EGUs in six of the subcategories are subject to numeric emission limits for all the pollutants described above except for organic HAP. Emissions of organic HAP are regulated by a work practice standard that requires periodic combustion process tune-ups. EGUs in the subcategory of limited-use liquid oil-fired EGUs with an annual capacity factor of less than 8 percent of its maximum or nameplate heat input are also subject to a work practice standard consisting of periodic combustion process tune-ups but are not subject to any numeric emission limits. Emission limits for existing EGUs are summarized in Table 1.
            Table 1  --  Emission Limits for Existing Affected EGUs
Subcategory
Pollutant
Emission Limit[1]
Any coal-fired unit firing any rank of coal
a. fPM
 3.0E-2 lb/MMBtu or 3.0E-1 lb/MWh

OR
OR

Total non-Hg HAP metals
 5.0E-5 lb/MMBtu or 5.0E-1 lb/GWh

OR
OR

Individual HAP metals:

Antimony, Sb
 8.0E-1 lb/TBtu or 8.0E-3 lb/GWh

Arsenic, As
 1.1 lb/TBtu or 2.0E-2 lb/GWh

Beryllium, Be
 2.0E-1 lb/TBtu or 2.0E-3 lb/GWh

Cadmium, Cd
 3.0E-1 lb/TBtu or 3.0E-3 lb/GWh

Chromium, Cr
 2.8 lb/TBtu or 3.0E-2 lb/GWh

Cobalt, Co
 8.0E-1 lb/TBtu or 8.0E-3 lb/GWh

Lead, Pb
 1.2 lb/TBtu or 2.0E-2 lb/GWh

Manganese, Mn
 4.0 lb/TBtu or 5.0E-2 lb/GWh

Nickel, Ni
 3.5 lb/TBtu or 4.0E-2 lb/GWh

Selenium, Se
 5.0 lb/TBtu or 6.0E-2 lb/GWh

b. HCl
 2.0E-3 lb/MMBtu or 2.0E-2 lb/MWh

OR
OR

SO2[2]
 2.0E-1 lb/MMBtu or 1.5 lb/MWh
Coal-fired unit low rank virgin coal.
c. Hg
 1.2 lb/TBtu or 1.3E-2 lb/GWh
Coal-fired unit low rank virgin coal.
c. Hg
 4.0 lb/TBtu or 4.0E-2 lb/GWh
IGCC unit.
a. fPM
 4.0E-2 lb/MMBtu or 4.0E-1 lb/MWh

OR
OR

Total non-Hg HAP metals
 6.0E-5 lb/MMBtu or 5.0E-1 lb/GWh

OR
OR

Individual HAP metals:

Antimony, Sb
 1.4 lb/TBtu or 2.0E-2 lb/GWh

Arsenic, As
 1.5 lb/TBtu or 2.0E-2 lb/GWh

Beryllium, Be
 1.0E-1 lb/TBtu or 1.0E-3 lb/GWh

Cadmium, Cd
 1.5E-1 lb/TBtu or 2.0E-3 lb/GWh

Chromium, Cr
 2.9 lb/TBtu or 3.0E-2 lb/GWh

Cobalt, Co
 1.2 lb/TBtu or 2.0E-2 lb/GWh

Lead, Pb
 1.9E+2 lb/MMBtu or 1.8 lb/MWh

Manganese, Mn
 2.5 lb/TBtu or 3.0E-2 lb/GWh

Nickel, Ni
 6.5 lb/TBtu or 7.0E-2 lb/GWh

Selenium, Se
 2.2E+1 lb/TBtu or 3.0E-1 lb/GWh

b. HCl
 5.0E-4 lb/MMBtu or 5.0E-3 lb/MWh

c. Hg
 2.5 lb/TBtu or 3.0E-2 lb/GWh
Liquid oil-fired unit  -  continental (excluding limited-use liquid oil-fired subcategory units).
a. fPM
 3.0E-2 lb/MMBtu or 3.0E-1 lb/MWh

OR
OR

Total HAP metals
 8.0E-4 lb/MMBtu or 8.0E-3 lb/MWh

OR
OR

Individual HAP metals:

Antimony, Sb
 1.3E+1 lb/TBtu or 2.0E-1 lb/GWh

Arsenic, As
 2.8 lb/TBtu or 3.0E-2 lb/GWh

Beryllium, Be
 2.0E-1 lb/TBtu or 2.0E-3 lb/GWh

Cadmium, Cd
 3.0E-1 lb/TBtu or 2.0E-3 lb/GWh

Chromium, Cr
 5.5 lb/TBtu or 6.0E-2 lb/GWh

Cobalt, Co
 2.1E+1 lb/TBtu or 3.0E-1 lb/GWh

Lead, Pb
 8.1 lb/TBtu or 8.0E-2 lb/GWh

Manganese, Mn
 2.2E+1 lb/TBtu or 3.0E-1 lb/GWh

Nickel, Ni
 1.1E+2 lb/TBtu or 1.1 lb/GWh

Selenium, Se
 3.3 lb/TBtu or 4.0E-2 lb/GWh

Hg
 2.0E-1 lb/TBtu or 2.0E-3 lb/GWh

b. HCl
 2.0E-3 lb/MMBtu or 1.0E-2 lb/MWh

c. HF
 4.0E-4 lb/MMBtu or 4.0E-3 lb/MWh
Liquid oil-fired unit  -  non-continental (excluding limited-use liquid oil-fired subcategory units).
a. fPM
 3.0E-2 lb/MMBtu or 3.0E-1 lb/MWh

OR
OR

Total HAP metals
 6.0E-4 lb/MMBtu or 7.0E-3 lb/MWh

OR
OR

Individual HAP metals:

Antimony, Sb
 2.2 lb/TBtu or 2.0E-2 lb/GWh

Arsenic, As
 4.3 lb/TBtu or 8.0E-2 lb/GWh

Beryllium, Be
 6.0E-1 lb/TBtu or 3.0E-3 lb/GWh

Cadmium, Cd
 3.0E-1 lb/TBtu or 3.0E-3 lb/GWh

Chromium, Cr
 3.1E+1 lb/TBtu or 3.0E-1 lb/GWh

Cobalt, Co
 1.1E+2 lb/TBtu or 1.4 lb/GWh

Lead, Pb
 4.9 lb/TBtu or 8.0E-2 lb/GWh

Manganese, Mn
 2.0E+1 lb/TBtu or 3.0E-1 lb/GWh

Nickel, Ni
 4.7E+2 lb/TBtu or 4.1 lb/GWh

Selenium, Se
 9.8 lb/TBtu or 2.0E-1 lb/GWh

Hg
 4.0E-2 lb/TBtu or 4.0E-4 lb/GWh

b. HCl
 2.0E-4 lb/MMBtu or 2.0E-3 lb/MWh

c. HF
 6.0E-5 lb/MMBtu or 5.0E-4 lb/MWh
Solid oil-derived fuel-fired unit.
a. fPM
 8.0E-3 lb/MMBtu or 9.0E-2 lb/MWh

OR
OR

Total non-Hg HAP metals
 4.0E-5 lb/MMBtu or 6.0E-1 lb/GWh

OR
OR

Individual HAP metals

Antimony, Sb
 8.0E-1 lb/TBtu or 7.0E-3 lb/GWh

Arsenic, As
 3.0E-1 lb/TBtu or 5.0E-3 lb/GWh

Beryllium, Be
 6.0E-2 lb/TBtu or 5.0E-4 lb/GWh

Cadmium, Cd
 3.0E-1 lb/TBtu or 4.0E-3 lb/GWh

Chromium, Cr
 8.0E-1 lb/TBtu or 2.0E-2 lb/GWh

Cobalt, Co
 1.1 lb/TBtu or 2.0E-2 lb/GWh

Lead, Pb
 8.0E-1 lb/TBtu or 2.0E-2 lb/GWh

Manganese, Mn
 2.3 lb/TBtu or 4.0E-2 lb/GWh

Nickel, Ni
 9.0 lb/TBtu or 2.0E-1 lb/GWh

Selenium, Se
 1.2 lb/Tbtu 2.0E-2 lb/GWh

b. HCl
 5.0E-3 lb/MMBtu or 8.0E-2 lb/MWh

OR
OR

SO2[2]
 3.0E-1 lb/MMBtu or 2.0 lb/MWh

c. Hg
 2.0E-1 lb/TBtu or 2.0E-3 lb/GWh
  [1] Units of emission limits:
  	lb/MMBtu = pounds pollutant per million British thermal units fuel input;
  	lb/TBtu = pounds pollutant per trillion British thermal units fuel input;
  	lb/MWh = pounds pollutant per megawatt-hour electric output (gross); and
  	lb/GWh = pounds pollutant per gigawatt-hour electric output (gross).
  [2] Alternate SO2 limit may be used if the EGU has some form of FGD system and SO2 CEMS installed.

 What data collection activities were conducted to support this action?
On February 9, 2022, the EPA published a notice of proposed rulemaking reaffirming that it remains appropriate and necessary to regulate coal- and oil-fired EGUs under CAA section 112 after considering the cost of regulation. In that same action, the EPA solicitated information on the cost and performance of new or improved technologies that control HAP emissions, on improved methods of operation, and on risk-related information to further inform the EPA's assessment of the MATS RTR. Generally, commenters were unaware of new technologies, but indicated that current technologies are more widely used, more effective, and cheaper than at the time of the adoption of MATS. Specific data or information used to support this action are discussed in more detail in section V of this preamble.
      The EPA also issued a limited request for information pursuant to section 114 of the CAA to obtain information related to HAP emissions from coal- and oil-fired EGUs to inform the technology review under CAA section 112(d)(6). Specifically, the EPA collected information and data related to Hg emissions and control technologies for lignite-fired EGUs. The CAA section 114 survey and responses are available in the docket for this action.
 What other relevant background information and data are available?
      The EPA used multiple sources of information to support this proposed action. A comprehensive list of facilities and EGUs that are subject to the MATS rule was compiled primarily using the list from the 2020 Final Action and publicly available information reported to the EPA and information contained in the EPA's National Electric Energy Data System (NEEDS) database. Affected sources are required to use the 40 CFR part 75-based ECMPS for reporting emissions and related data either directly for EGUs that use Hg, HCl, HF, or SO2 CEMS or Hg sorbent traps for compliance purposes or indirectly as PDF files for EGUs that use performance test results, PM continuous parameter monitoring system (CPMS) data, or PM CEMS for compliance purposes. Directly submitted data are maintained in ECMPS; indirectly submitted data are maintained in Web Factor Information Retrieval System (WebFIRE). The NEEDS database contains generation unit information used in the EPA's power sector modeling. Other sources used include the U.S. Department of Energy's EIA list of fuel consumption reported for 2021 under Form EIA-923 and emissions test data collected in an ICR in 2010 (2010 ICR) when promulgating the 2011 Proposal.
      In conducting the technology review, the EPA examined information submitted to the EPA's ECMPS as well as information that supports previous 40 CFR part 63, subpart UUUUU actions to identify technologies currently being used by affected EGUs and to determine if there have been developments in practices, processes, or control technologies. In addition to the ECMPS data, we reviewed regulatory actions for similar combustion sources and conducted a review of literature published by industry organizations, technical journals, and government organizations.
 How does the EPA 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 the technical feasibility, estimated costs, energy implications, non-air environmental impacts, and potential emissions reductions of more stringent standards, to ensure that the MACT standards continue to fulfill Congress's direction to require the maximum degree of reduction of HAP taking into account the statutory factors. This analysis informs our decision of whether it is "necessary" to revise the emissions standards. In addition, we typically consider the appropriateness of applying controls to new sources versus retrofitting existing sources. For this exercise, we consider any of the following to be a "development":
Any add-on control technology or other equipment that was not identified and considered during development of the original MACT standards;
Any improvements in add-on control technology or other equipment (that were identified and considered during development of the original MACT standards) that could result in additional emission reductions;
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 we originally developed (or last updated) the NESHAP, we review a variety of data sources in our investigation of potential practices, processes, or controls to consider. We also review the NESHAP and the available data to determine if there are any unregulated emissions of HAP within the source category and evaluate this data for use in developing new emission standards. When reviewing MACT standards, the EPA is required to address regulatory gaps, such as missing standards for listed air toxics known to be emitted from the source category, and any new MACT standards must be established under CAA sections 112(d)(2) and (3), or, in specific circumstances, CAA sections 112(d)(4) or (h). Louisiana Environmental Action Network (LEAN) v. EPA, 955 F.3d 1088 (D.C. Cir. 2020). See sections III.C and III.D of this preamble for information on the specific data sources that were reviewed as part of the technology review.
 Review of 2020 Residual Risk and Technology Review
  Summary of the 2020 Residual Risk Review
Pursuant to CAA section 112(f)(2), the EPA conducted a residual risk review (2020 Residual Risk Review) and presented the results of this review, along with our decisions regarding risk acceptability, ample margin of safety, and adverse environmental effects, in the 2020 Final Action. The results of the risk assessment are presented briefly in Table 2, and in more detail in the document titled Residual Risk Assessment for the Coal- and Oil-Fired EGU Source Category in Support of the 2020 Risk and Technology Review Final Rule (risk document for the final rule), available in the docket (Docket ID No. EPA-HQ-OAR-2018-0794-4553).
Table 2  --  Coal- and Oil-Fired EGU Inhalation Risk Assessment Results in the 2020 Final Action (85 FR 31286; May 22, 2020)
                            Number of Facilities[1]
               Maximum Individual Cancer Risk (in 1 million)[2]
           Population at Increased Risk of Cancer >= 1-in-1 million
                   Annual Cancer Incidence (cases per year)
                      Maximum Chronic Noncancer TOSHI[3]
                    Maximum Screening Acute Noncancer HQ[4]
                                      322
                                Based on . . .
                                Based on . . .
                                Based on . . .
                                Based on . . .
                        Based on Actual Emissions Level

                            Actual Emissions Level
                           Allowable Emissions Level
                            Actual Emissions Level
                           Allowable Emissions Level
                            Actual Emissions Level
                           Allowable Emissions Level
                            Actual Emissions Level
                           Allowable Emissions Level

                                       9
                                      10
                                    193,000
                                    636,000
                                     0.04
                                      0.1
                                      0.2
                                      0.4
                                 HQREL = 0.09
                                   (arsenic)
[1] Number of facilities evaluated in the risk analysis. At the time of the risk analysis there were an estimated 323 facilities in the Coal- and Oil-Fired EGU source category; however, one facility is located in Guam, which was beyond the geographic range of the model used to estimate risks. Therefore, the Guam facility was not modeled and the emissions for that facility were not included in the assessment.
[2] Maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
[3] Maximum target organ-specific hazard index (TOSHI). The target organ systems with the highest TOSHI for the source category are neurological and reproductive.
[4] The maximum estimated acute exposure concentration was divided by available short-term threshold values to develop an array of hazard quotient (HQ) values. HQ values shown use the lowest available acute threshold value, which in most cases is the reference exposure level (REL). When an HQ exceeds 1, we also show the HQ using the next lowest available acute dose-response value.
  Chronic Inhalation Risk Assessment Results
The results of the chronic inhalation cancer risk assessment based on actual emissions, as shown in Table 2 of this preamble, indicated that the estimated maximum individual lifetime cancer risk (cancer MIR) was 9-in-1 million, with nickel emissions from certain oil-fired EGUs as the major contributor to the risk. The total estimated cancer incidence from this source category was 0.04 excess cancer cases per year, or one excess case in every 25 years. Approximately 193,000 people were estimated to have cancer risks at or above 1-in-1 million from HAP emitted from the facilities in this source category. The estimated maximum chronic noncancer TOSHI for the source category was 0.2 (respiratory), which was driven by emissions of nickel and cobalt from oil-fired EGUs. No one was exposed to TOSHI levels above 1 based on actual emissions from sources regulated under this source category.
The EPA also evaluated the cancer risk at the maximum emissions allowed by the MACT standard (i.e., "allowable emissions"). As shown in Table 2 of this preamble, based on allowable emissions, the estimated cancer MIR was 10-in-1 million, and, as before, nickel emissions from oil-fired EGUs were the major contributor to the risk. The total estimated cancer incidence from this source category, considering allowable emissions, was 0.1 excess cancer cases per year, or one excess case in every 10 years. Based on allowable emissions, approximately 636,000 people were estimated to have cancer risks at or above 1-in-1 million from HAP emitted from the facilities in this source category. The estimated maximum chronic noncancer TOSHI for the source category was 0.4 (respiratory) based on allowable emissions, driven by emissions of nickel and cobalt from oil-fired EGUs. No one was exposed to TOSHI levels above 1 based on allowable emissions.
 Screening Level Acute Risk Assessment Results
Table 2 of this preamble provides the worst-case acute HQ (based on the REL) of 0.09, driven by emissions of arsenic. There were no facilities that have acute HQs (based on the REL or any other reference values) greater than 1. For more detailed acute risk results, refer to the risk document available in the docket (Docket ID No. EPA-HQ-OAR-2018-0794-4553).
 Multipathway Risk Screening and Site-Specific Assessment Results
Potential multipathway health risks under a fisher and gardener scenario were identified using a three-tier screening assessment of the HAP known to be persistent and bio-accumulative in the environment (PB-HAP) emitted by facilities in the Coal- and Oil-Fired EGU source category, and a site-specific assessment of Hg using the EPA's Total Risk Integrated Methodology.Fate, Transport, and Ecological Exposure (TRIM.FaTE) for one location (three facilities located in North Dakota) as further described below. Of the 322 MATS-affected facilities modeled, 307 facilities had reported emissions of carcinogenic PB-HAP (arsenic, dioxins, and polycyclic organic matter (POM)) that exceeded a Tier 1 cancer screening value of 1, and 235 facilities had reported emissions of non-carcinogenic PB-HAP (lead, Hg, and cadmium) that exceeded a Tier 1 noncancer screening value of 1. For facilities that exceeded a Tier 1 multipathway screening value of 1, we used additional facility site-specific information to perform an assessment through Tiers 2 and 3, as necessary, to determine the maximum chronic cancer and noncancer impacts for the source category. For cancer, the highest Tier 2 screening value was 200. This screening value was reduced to 50 after the plume rise stage of Tier 3. Because this screening value was much lower than 100-in-1 million, and because we expected the actual risk to be lower than the screening value (site-specific assessments typically lower estimates by an order of magnitude), we did not perform further assessment for cancer. For noncancer, the highest Tier 2 screening value was 30 (for Hg), with four facilities having screening values greater than 20. These screening values were reduced to 9 or lower after the plume rise stage of Tier 3.
Because the final stage of Tier 3 (time-series) was unlikely to reduce the highest Hg screening values to 1, we conducted a site-specific multipathway assessment of Hg emissions for this source category. Analysis of the facilities with the highest Tier 2 and Tier 3 screening values helped identify the location for the site-specific assessment and the facilities to model with TRIM.FaTE. The assessment considered the effect that multiple facilities within the source category may have on common lakes. The three facilities selected were located near Underwood, North Dakota. All three facilities had Tier 2 screening values greater than or equal to 20. Two of the facilities were near each other (16 kilometers (km) apart). The third facility was more distant, about 20 to 30 km from the other facilities, but it was included in the analysis because it is within the 50-km modeling domain of the other facilities and because it had an elevated Tier 2 screening value. We expected that the exposure scenarios we assessed for these facilities are among the highest, if not the highest, that might be encountered for other facilities in this source category. The refined multipathway assessment estimated an HQ of 0.06 for Hg for the three facilities assessed. We believed the assessment represented the highest potential for Hg hazards through fish consumption for the source category.
In evaluating the potential multipathway risk from emissions of lead compounds, rather than developing a screening threshold emission rate, we compared maximum estimated chronic inhalation exposure concentrations to the level of the current National Ambient Air Quality Standards (NAAQS) for lead (0.15 micrograms per cubic meter). Values below the level of the primary (health-based) lead NAAQS were considered to have a low potential for multipathway risk. We did not estimate any exceedances of the lead NAAQS in this source category.
 Environmental Risk Screening Results
An environmental risk screening assessment for the Coal- and Oil-Fired EGU source category was conducted for the following pollutants: arsenic, cadmium, dioxins/furans, HCl, HF, lead, Hg (methylmercury and mercuric chloride), and POMs. In the Tier 1 screening analysis for PB-HAP (other than lead, which was evaluated differently), POM emissions had no exceedances of any of the ecological benchmarks evaluated. Arsenic and dioxin/furan emissions had Tier 1 exceedances for surface soil benchmarks. Cadmium and methylmercury emissions had Tier 1 exceedances for surface soil and fish benchmarks. Divalent Hg emissions had Tier 1 exceedances for sediment and surface soil benchmarks.
A Tier 2 screening analysis was performed for arsenic, cadmium, dioxins/furans, divalent Hg, and methylmercury emissions. In the Tier 2 screening analysis, arsenic, cadmium, and dioxin/furan emissions had no exceedances of any of the ecological benchmarks evaluated. Divalent Hg emissions from two facilities exceeded the Tier 2 screen for a sediment threshold level benchmark by a maximum screening value of 2. Methylmercury emissions from the same two facilities exceeded the Tier 2 screen for a fish (avian/piscivores) no-observed-adverse-effect-level (NOAEL) (merganser) benchmark by a maximum screening value of 2. A Tier 3 screening assessment was performed to verify the existence of the lake associated with these screening values, and it was found to be located on-site and is a man-made industrial pond, and, therefore, was removed from the assessment.
Methylmercury emissions from two facilities exceeded the Tier 2 screen for a surface soil NOAEL for avian ground insectivores (woodcock) benchmark by a maximum screening value of 2. Other surface soil benchmarks for methylmercury, such as the NOAEL for mammalian insectivores and the threshold level for the invertebrate community, were not exceeded. Given the low Tier 2 maximum screening value of 2 for methylmercury, and the fact that only the most protective benchmark was exceeded, a Tier 3 environmental risk screen was not conducted for methylmercury.
For lead, we did not estimate any exceedances of the secondary lead NAAQS. For HCl and HF, the average modeled concentration around each facility (i.e., the average concentration of all off-site data points in the modeling domain) did not exceed any ecological benchmark. In addition, each individual modeled concentration of HCl and HF (i.e., each off-site data point in the modeling domain) was below the ecological benchmarks for all facilities.
Based on the results of the environmental risk screening analysis, we did not expect an adverse environmental effect as a result of HAP emissions from the Coal- and Oil-Fired EGU source category.
 Facility-Wide Risk Results
An assessment of risk from facility-wide emissions was performed to provide context for the source category risks. Based on facility-wide emissions estimates developed using the same estimates of actual emissions for emissions sources in the source category, and emissions data from the 2014 National Emissions Inventory (NEI) (version 2) for the sources outside the source category, the estimated cancer MIR was 9-in-1 million, and nickel emissions from oil-fired EGUs were the major contributor to the risk. The total estimated cancer incidence based on facility-wide emissions was 0.04 excess cancer cases per year, or one excess case in every 25 years. Approximately 203,000 people were estimated to have cancer risks at or above 1-in-1 million from HAP emitted from all sources at the facilities in this source category. The estimated maximum chronic noncancer TOSHI posed by facility-wide emissions was 0.2 (respiratory), driven by emissions of nickel and cobalt from oil-fired EGUs. No one was exposed to TOSHI levels above 1 based on facility-wide emissions. These results were very similar to those based on actual emissions from the source category because there was not significant collocation of other sources with EGUs.
 Decisions Regarding Risk Acceptability, Ample Margin of Safety, and Adverse Environmental Effect
In determining whether residual risks are acceptable for this source category in accordance with CAA section 112, the EPA considered all available health information and risk estimation uncertainty. The results of the risk analysis indicated that both the actual and allowable inhalation cancer risks to the individual most exposed were below 100-in-1 million, which is the presumptive limit of acceptability. Also, the highest chronic noncancer TOSHI, and the highest acute noncancer HQ, were below 1, indicating low likelihood of adverse noncancer effects from inhalation exposures. There were also low risks associated with ingestion, with the highest cancer risk being less than 50-in-1 million based on a conservative screening assessment, and the highest noncancer hazard being less than 1 based on a site-specific multipathway assessment. Considering this information, the EPA determined that the residual risks of HAP emissions from the Coal- and Oil-Fired EGU source category were acceptable.
We then considered whether the current standards provided an ample margin of safety to protect public health and whether more stringent standards were necessary to prevent an adverse environmental effect by taking into consideration costs, energy, safety, and other relevant factors. In determining whether the standards provided an ample margin of safety to protect public health, we examined the same risk factors that we investigated for our acceptability determination and we also considered the costs, technological feasibility, and other relevant factors related to emissions control options that might reduce risk associated with emissions from the source category. In our analysis, we considered the results of the technology review, risk assessment, and other aspects of our MACT rule review to determine whether there were any cost-effective controls or other measures that would reduce emissions further to provide an ample margin of safety. The risk analysis indicated that the risks from the source category are low for both cancer and noncancer health effects. Thus, we determined that the current MATS requirements provided an ample margin of safety to protect public health in accordance with CAA section 112.
Based on the results of our environmental risk screening assessment, we also determined that more stringent standards were not necessary to prevent an adverse environmental effect.
 Summary of the 2020 Technology Review
Pursuant to CAA section 112(d)(6), the EPA conducted a technology review (2020 Technology Review) in the 2020 Final Action, which focused on identifying and evaluating developments in practices, processes, and control technologies for the emission sources in the source category that occurred since the MATS rule was promulgated. Control technologies typically used to minimize emissions of pollutants that have numeric emission limits under the MATS rule include electrostatic precipitators (ESPs) and fabric filters (FFs) for control of non-Hg HAP metals; wet scrubbers and dry scrubbers for control of acid gases (SO2, HCl, and HF); and activated carbon injection (ACI) for control of Hg. The EPA determined that existing air pollution control technologies that were in use were well-established and provided the capture efficiencies necessary for compliance with the MATS emission limits. Based on the effectiveness and proven reliability of these control technologies, and the relatively short period of time since the promulgation of the MATS rule, the EPA did not identify any developments in practices, processes, or control technologies, nor any new technologies or practices, for the control of non-Hg HAP metals, acid gas HAP, or Hg. However, in the 2020 Technology Review, the EPA did not consider developments in the cost and effectiveness of these proven technologies, nor did the EPA evaluate the current performance of emission reduction control equipment and strategies at existing MATS-affected EGUs, to determine whether revising the standards was warranted. Organic HAP, including emissions of dioxins and furans, are regulated by a work practice standard that requires periodic burner tune-ups to ensure good combustion. The EPA found that this work practice continued to be a practical approach to ensuring that combustion equipment was maintained and optimized to run to reduce emissions of organic HAP and continued to be more effective than establishing a numeric standard that cannot reliably be measured or monitored. Based on the effectiveness and proven reliability of the work practice standard, and the relatively short amount of time since the promulgation of the MATS rule, the EPA did not identify any developments in work practices nor any new work practices or operational procedures for this source category regarding the additional control of organic HAP.
After conducting the 2020 Technology Review, the EPA did not identify developments in practices, processes, or control technologies and, thus, did not propose changes to emission standards or other requirements. More information concerning that technology review is in the memorandum titled Technology Review for the Coal- and Oil-Fired EGU Source Category, available in the docket (Docket ID No. EPA-HQ-OAR-2018-0794-0015), and in the February 7, 2019, proposed rule. 84 FR 2700. On May 20, 2020, the EPA finalized the first technology review required by CAA section 112(d)(6) for the Coal- and Oil-Fired EGU source category regulated under MATS. Based on the results of that technology review, the EPA found that no revisions to MATS were warranted. See 85 FR 31314 (May 22, 2020).
   Analytical Results and Proposed Decisions
As described in section IV, the EPA conducted a residual risk review under CAA section 112(f) and presented results of the review in the 2020 Final Action. Executive Order 13990, "Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis" required the EPA to review the 2020 Final Action and consider publishing a notice of proposed rulemaking suspending, revising, or rescinding the 2020 Final Action. As part of this effort, the EPA solicited information to inform a review of the MATS RTR in the 2022 Proposal affirming it is appropriate and necessary finding to regulate coal- and oil-fired EGUs under CAA section 112. The EPA summarizes the results of the review of the RTR and proposed decisions consequent of the review below and requests comment on specific considerations. In addition to generally soliciting comments on all aspects of this proposed action, the EPA is requesting public comment on specific issues as described below. In addition, the EPA is granting in part certain petitions for reconsideration on the Agency's prior rulemakings, which are discussed in further detail below.
 Review of the 2020 Residual Risk Review
The EPA has reviewed the 2020 Residual Risk Review as directed by EO 13990. This included a review of the 2020 residual risk assessment described in Docket ID No. EPA-HQ-OAR-2018-0794-0014 and consideration of comments received in response to the 2022 Proposal. The EPA did not receive any new information in response to the 2022 Proposal that would affect the EPA's 2020 residual risk analysis or the decisions emanating from that analysis. In reviewing the 2020 residual risk analysis, the EPA has determined that the risk analysis was a rigorous and robust analytical review using approaches and methodologies that are consistent with those that have been utilized in residual risk analyses and reviews for other industrial sectors. In addition, the results of the 2020 residual risk assessment, as summarized in section IV.A of this preamble, indicated low residual risk from the Coal- and Oil-fired EGU source category. For these reasons, we are not proposing any revisions to the 2020 Residual Risk Review. The EPA acknowledges that it received a petition for reconsideration from environmental organizations that, in relevant part, sought the EPA's reconsideration of certain aspects of the 2020 Residual Risk Review, which the EPA continues to review and will respond to in a separate action.
 Review of the 2020 Technology Review
The EPA's review of the 2020 Technology Review included evaluating the technology review described in Docket ID No. EPA-HQ-OAR-2018-0794-0015 and comments related to potential practices, processes, or controls received as part of the 2022 Proposal. The review also focused on the identification and evaluation of any developments in practices, processes, and control technologies that have occurred since finalization of the MATS rule in 2012 and since publishing the 2020 Technology Review. As explained in detail herein, based on this information, the EPA now concludes that developments in the costs and effectiveness of control technologies and the related fact that the vast majority of sources are far outperforming the MACT standards while a smaller number of sources lag behind, warrant revising certain MACT standards.
Technology reviews can, and often do, include obtaining better information about the performance of a control technology (e.g., emissions data from affected sources) showing that an add-on technology that was identified and considered during the development of the original MACT standards works better (e.g., gets more emissions reductions or costs less) than anticipated. In fact, considering data on outperforming sources and cost and effectiveness of existing controls is well established. See, e.g., Coke Oven Batteries, 69 FR 48338, 48351 (August 9, 2014) ("[A]lthough no new control technologies have been developed since the original standards were promulgated, our review of emissions data revealed that existing MACT track batteries can achieve a level of control for door leaks and topside leaks more stringent than that required by the 1993 national emission standards ... through diligent work practices to identify and stop leaks."); Site Remediation, 85 FR 41680, 41690 (July 10, 2020) (noting that commenters had not identified developments like a reduction in costs); Petroleum Refineries, 80 FR 75178, 75201 (December 1, 2015); Mineral Wood Production and Fiberglass Manufacturing, 80 FR 45280, 45284-85 (July 29, 2015); see also Nat'l Ass'n for Surface Finishing v. EPA, 795 F3d 1, 11-12 (D.C. Cir 2015).
For example, in the 2014 technology review for Ferroalloys Production, the EPA found that PM emission levels were well below the MACT standards established in the original 1999 NESHAP. These findings "demonstrate[d] that the add-on emission control technology (venturi scrubber, positive pressure FF, negative pressure FF) used to control emissions from the furnaces are quite effective in reducing PM (used as a surrogate for metal HAP) and that all of the facilities have emissions well below the current limits." See 79 FR 60271 (October 6, 2014). Therefore, the EPA determined that it was appropriate to revise the PM limits for furnaces. Similarly, in the 2017 technology review for Wool Fiberglass Manufacturing, the EPA found that formaldehyde emissions had decreased by approximately 95 percent since promulgation of the MACT Standards in the original 1999 NESHAP due to "(1) Improvements in control technology (e.g., improved bag materials, replacement of older baghouses) and (2) the use of electrostatic precipitators," as well as upgraded pollution prevention practices (i.e., development and use non-phenol-formaldehyde binders). See 82 FR 40975 (August 29, 2017). Although the EPA declined to lower the formaldehyde limit in this case, it was only because the source category had already upgraded the technology (i.e., non-phenol-formaldehyde binders), resulting in major sources becoming area sources that were no longer subject to the NESHAP.
As in those cases, here many commenters provided data showing that control technologies are more widely used, more effective, and cheaper than at the time EPA promulgated MATS. For example, commenters explained that, due to the many options that are available to control Hg emissions (e.g., equipment, activated carbon, reagents and sorbents, as well as fuel blending, non-carbon or improvements to carbon-based solvents, wet and dry scrubber additives, oxidizing coal additives, and existing control optimization) and a "robust industry of technology suppliers that drive innovation through internal research and development," the costs of compliance for end users has decreased over time (Docket ID No. EPA-HQ-OAR-2018-0794-4940). Similarly, commenters noted that the large number of EGUs that are outperforming the current Hg and fPM standards would support a decision to revise the standards (Docket ID No. EPA-HQ-OAR-2018-0794-4962). Specific comments leading to our proposed decisions are detailed below, and a summary of this technology review is provided in the memorandum "2023 Technology Review for the Coal- and Oil-Fired EGU Source Category," which can be found in Docket ID No. EPA-HQ-OAR-2018-0794. Based on our review of the 2020 Technology Review, the EPA is proposing to revise the current standards as discussed below.
 What are the results and proposed decisions based on our technology review, and what is the rationale for those decisions?
This section summarizes the EPA's proposed decisions concerning the technology review. Where the EPA has identified developments in practices, processes, or controls, we analyzed the technical feasibility, estimated costs, energy implications, and non-air environmental impacts, as well as the potential emission reductions associated with each development. In addition, we reviewed a variety of data sources in our investigation of developments in practices, processes, or controls. See section III of this preamble for information on the specific data sources that were reviewed as part of the technology review.
  Filterable Particulate Matter (fPM) Emission Limit (as a Surrogate for non-Hg HAP Metals)
As described in section III of this preamble, EGUs in six subcategories are subject to numeric emission limits for each of the individual non-Hg metal HAP. Alternatively, certain affected EGUs can choose to demonstrate compliance with an alternative total non-Hg metal HAP emission limit. Finally, affected EGUs can demonstrate compliance with an alternative fPM emission limit that serves as a surrogate for total non-Hg metal HAP. The EPA chose fPM as a surrogate for non-Hg metal HAP in the original MATS rulemaking because non-Hg metal HAP are predominantly a component of the filterable fraction of total PM (which is comprised of a filterable fraction and a condensable fraction), and control of fPM results in co-reduction of non-Hg metal HAP (with the exception of Se, which may be present in the filterable fraction or in the condensable fraction as the acid gas, SeO2). Additionally, not all fuels emit the same type and amount of non-Hg metal HAP, but most generally emit fPM that includes some amount and combination of all the non-Hg metal HAP. Lastly, the use of fPM as a surrogate eliminates the cost of performance testing to demonstrate compliance with numerous standards for individual non-Hg metal HAP (Docket ID No. EPA-HQ-OAR-2009-0234). For these reasons, the EPA focused its review on the fPM emissions of coal-fired EGUs as a surrogate for non-Hg metal HAP.
In the 2020 Technology Review, the EPA did not identify any developments in practices, processes, or control technologies for non-Hg metal HAP or fPM. The assessment of implementation and developments in non-Hg metal HAP metal is summarized in the memorandum, "Technology Review for the Coal- and Oil-Fired EGU Source Category," which is included in Docket ID No. EPA-HQ-OAR-2018-0794-0015. The 2020 review simply presented a list of PM control technologies used by coal-fired EGUs in operation, finding that the units primarily employ ESPs and FFs, and did not identify any new control technologies to reduce non-Hg metal HAP. That review did not consider or discuss the costs or performance of already-installed controls nor discuss or analyze opportunities for improved performance. In the 2020 Technology Review, the EPA concluded that "[t]he PM air pollution control device technologies that are currently in use are well-established and provide the capture efficiencies necessary for compliance with the subpart UUUUU [MATS] filterable PM limits." In the 2022 Proposal, the EPA solicited information on the cost and performance of new or improved control technologies that control HAP emissions and improved methods of operation.
In this review of the RTR, the EPA expanded upon the 2020 Technology Review to also assess the fPM emission performance of the fleet. This review included evaluating the control efficiency and costs of common control systems used for fPM control, primarily ESPs and FFs, detailed in the memorandum, "2023 Technology Review for the Coal- and Oil-Fired EGU Source Category," which is included in Docket ID No. EPA-HQ-OAR-2018-0794. As part of this effort, the EPA reviewed more recent fPM compliance data that was not available during the 2020 Final Action. Our review of fPM compliance data for coal-fired EGUs indicated no new practices, processes, or control technologies for non-Hg metal HAP, but revealed two important developments that inform the EPA's decision to propose revisions to the standard. First, it revealed that most existing coal-fired EGUs are performing well below the current fPM emission limit of 3.0E-02 lb/MMBtu. Information we received in response to the 2022 Proposal similarly noted that the fleet is achieving much lower fPM rates than what is currently allowed. Second, it revealed that the fleet is achieving these performance levels at lower costs than assumed during promulgation of the original MATS fPM emission limit. More specifically, one commenter presented its fleetwide evaluation using data from 100 coal units in the PJM Interconnection and in the Electric Reliability Council of Texas (ERCOT) markets. The commenter's analysis suggested that only 42 EGUs would require additional capital or operating costs to meet a more stringent fPM limit of 7.0E-03 lb/MMBtu, while 79 EGUs would incur those costs to meet a limit of 3.75E-03 lb/MMBtu. The commenter's analysis suggested that a majority of units would incur costs in the range of $0/kW to $75/kW (Docket ID No. EPA-HQ-OAR-2018-0794-5121). Additional commenters pointed to an independent report finding that units are doing "just enough" to satisfy the MATS limits and that EGUs can achieve fPM emission rates at or below 7.0E-03 lb/MMBtu with relatively low capital cost upgrades to pollution control systems. Commenters also cited studies finding the actual costs of complying with air pollution regulations are often substantially lower than pre-compliance estimates assumed in the 2012 MATS Final Rule.
Figure 1 shows that all coal-fired EGUs are performing well below the current MATS fPM limit of 0.030 lbs/MMBtu, and that 91 percent of EGUs are reducing emissions to levels lower than a third of the current limit. In fact, the average fPM rate of the EGUs assessed in Figure 1 is 4.8E-03 lb/MMBtu, which is 84 percent below the MATS current limit. Even the top emitting units, with rates above the current fPM LEE standard, are performing 30 percent to 43 percent below the current standard. Even so, the handful of the worst performing EGUs are emitting fPM at rates approximately three to four times as the fleet average.
Because an evaluation of compliance data showed that a significant portion of coal-fired EGUs are performing well below the allowed emission limit (Figure 1), and because the EPA obtained information indicating lower costs to improve controls to achieve additional fPM emission reductions than assumed during promulgation of the original MATS fPM emission limit, the EPA concluded that there were developments that warranted an examination of whether to revise the standard in light of these developments.
To examine potential revisions, the EPA used representative fPM emissions as a surrogate for total non-Hg metal HAP to evaluate three more stringent emission limits. The fPM emission limits that were evaluated are (1) 1.5E-02 lb/MMBtu, which is 50 percent of the current limit and the qualifying emission rate for the LEE program EGUs (2) 1.0E-02 lb/MMBtu, which is comparable to the MATS new source fPM emission limit; and (3) 6.0E-03 lb/MMBtu, which is the average fPM emission rate from the 2010 ICR. Currently, 96 percent of existing coal-fired capacity without known retirement plans before the proposed compliance period already have demonstrated an emission rate of 1.5E-02 lb/MMBtu or lower, 91 percent of existing coal-fired capacity have demonstrated an emission rate of 1.0E-02 lb/MMBtu or lower, and 72 percent of existing coal-fired capacity have demonstrated an emission rate of 6.0E-03 lb/MMBtu or lower. The EPA evaluated reductions of the 10 individual non-Hg metal HAP, total non-Hg metal HAP, and fPM and the associated costs for each unit to achieve each of the three fPM emission limits listed above.

Figure 1 -- fPM rate distribution for affected coal-fired EGUs in the continental U.S. in reference to the three considered fPM limit (horizontal dashed lines): 1.5E-02 lb/MMBtu, 1.0E-02 lb/MMBtu, and 6.0E-03 lb/MMBtu. More information available in the technical memo supporting this action.

The EPA discussed the opportunity for improved performance of existing fPM control technologies in the 2012 MATS Final Rule. In the Regulatory Impact Analysis (RIA) supporting the 2012 MATS Final Rule, the EPA estimated that 34 gigawatts (GW) of coal-fired EGU capacity would perform ESP upgrades as part of their fPM emission limit compliance strategy. EPA's methodology was based on historic PM emission rates and reported control efficiencies and is explained in the IPM 4.10 Supplemental Documentation for MATS. Depending on the incremental fPM reduction needed to bring a unit into compliance, units with existing ESPs for PM control were assigned either a FF retrofit or one of three tiered ESP upgrades to bring them into compliance. In response to the solicitation in the 2022 Proposal, commenters provided detailed information on updated costs for similar upgrades for improved ESP performance. Using that data and additional information from one of the EPA's engineering consultants, the EPA evaluated revised costs to upgrade existing PM controls. The cost effectiveness estimates presented in this section are based on an assumption that eight units would need to upgrade existing ESPs to comply with a revised fPM emission standard of 1.5E-02 lb/MMBtu, that 20 units would need to implement similar ESP upgrades to comply with a revised fPM emission standard of 1.0E-02 lb/MMBtu, and that 65 units would need to install a new FF or modify an existing FF to meet a revised fPM emission limit of 6.0E-03 lb/MMBtu.
In this proposal, the EPA proposes to set an fPM emission limit of 1.0E-02 lb/MMBtu (0.010 lb/MMBtu) and seeks comment on whether its control technology effectiveness and cost assumptions are correct, and whether it should finalize a more stringent standard. The EPA's decision to propose a standard of 1.0E-02 lb/MMBtu is based on several factors. First, this level of control would ensure that the very worst performers bring their performance level up to where the vast majority of the fleet is performing. The EPA notes that Figure 1 shows a "knee in the curve" around 1.0E-02 lb/MMBtu, with coal-fired EGUs above that rate emitting substantially more pollution than those below it. Bringing this small number of sources (9 percent of coal-fired EGU capacity) to the performance of the rest of the fleet serves Congress's mandate to the EPA to continually consider developments and to ensure that standards account for developments "that create opportunities to do even better." See LEAN, 955 F.3d at 1093. As discussed above in section V.B. of this notice, the EPA has a number of times in the past updated its MACT standards to reflect developments where the majority of sources is vastly outperforming the original MACT standards.
According to comments received in response to the solicitation in the 2022 Proposal, since the MATS Final Rule was promulgated in 2012, improvements to existing PM controls to comply with the MATS fPM standard were achieved at lower costs than had been projected by the EPA. The commenter also noted that industry installed far fewer FFs than EPA projected and that there were a smaller number of ESP upgrades than projected. The 2012 MATS Final Rule used the Upper Predictive Limit (UPL) to establish the fPM emission limit of 3.0E-02 lb/MMBtu for existing coal-fired EGUs. The UPL considers the average of the best performing EGUs, but also includes an allowance for variation that is determined by a confidence level that the UPL will not be exceeded. Using 2019 fPM compliance data compiled by Natural Resources Defense Council (NRDC), an independent report submitted to the EPA in response to the 2020 Proposal found an updated UPL (using 2019 data) to be 5.0E-03 lb/MMBtu, about one-sixth of the EPA's 2011 estimate of 3.0E-02 lb/MMBtu. The updated 5.0E-03 lb/MMBtu UPL value was attributed to updated fPM rates that were lower on average and reflected less variability in emissions for each individual EGU. More specifically, according to the commenter, the lower fPM emissions and thus lower UPL were attributed to: (1) greater attention to fPM emissions due to the monitoring and reporting requirements of MATS; (2) efforts to restore ESPs and other equipment to original designed performance levels; (3) modest improvements to ESPs when needed, such as addition of high frequency transformer rectifier (TR) sets; and (4) efforts to minimize the wear and tear on filter bags and increased attention to FF operation. Developments in the technology, including better performance at lower costs, combined with improved variability assumptions updated since promulgation of the 2012 MATS Final Rule, presents an opportunity to strengthen the MACT standard for fPM.
Second, the EPA believes that a level of 1.0E-02 lb/MMBtu appropriately takes into account the costs of control. The EPA evaluated the costs to improve current PM control systems and the cost to install better performing PM controls (a new FF) to achieve a more stringent emission limit. As noted above, data received since 2012 demonstrates that the costs of PM control upgrades are likely much lower than the EPA estimated in 2012. Table 3 summarizes the estimated costs and fPM reductions directly attributable to the three emission limits evaluated for the existing fleet. This table reflects all coal-fired EGUs in the existing fleet except for those that have announced plans to retire by the end of 2028, the year the proposed standards are expected to take effect. The cost estimates presented in this table could be overestimated for a number of reasons, and the EPA seeks comment on these cost and cost-effectiveness estimates. The estimates in this table do not account for any future changes in the composition of the operational coal fleet that are likely to occur by 2028 as a result of other factors affecting the power sector, such as the Inflation Reduction Act (IRA), future regulatory actions, or changes in economic conditions. Of the over 9 GW of coal-fired capacity that the EPA estimates would require control improvements to achieve the proposed fPM rate, less than 5 GW is projected to be operational in 2028 (see Section 3 of the Regulatory Impact Analysis (RIA) for this proposal). Additionally, it is possible that some EGUs may be able to achieve a lower fPM rate at significantly lower cost than assumed here, and possibly without any additional capital investments. The large percentage of existing units meeting each of the three emission limits with existing technology demonstrates that coal-fired EGUs can meet and have met these limits with existing control technology. While such factors could likely lower the overall cost estimates and improve cost-effectiveness, this table presents conservative estimates based on the best information available to the EPA at this time.
Because much of the fleet is already reporting fPM rates below 6.0E-03 lb/MMBtu, both the total costs and the total fPM and non-Hg metal HAP reductions for the three potential emission limits are modest in the context of the total control costs and emissions of the coal fleet. The cost-effectiveness estimates for EGUs reporting fPM rates above 6.0E-03 lb/MMBtu to achieve similar performance as the rest of the fleet range from $4.9k per lb of non-Hg metal HAP to $12.8k per lb of non-Hg metal HAP for the three potential emission limits. These cost-effectiveness numbers are larger than those we have found to be cost-effective in previous rulemakings. However, the EPA has never determined that cost-effectiveness values in the range described above are unreasonable for non-Hg metal HAP and recognizes that other means of evaluating cost may be considered depending on the rule and affected sector. See NRDC v. EPA, 749 F.3d 1055, 1060 (D.C. Cir. 2014) ("Section 112 does not command EPA to use a particular form of cost analysis"). The EPA also considers other factors in assessing the reasonableness of the costs of emission reduction, including, but not limited to, total capital costs, annual costs, and costs compared to total revenues (e.g., cost to revenue ratios). See 87 FR 1635 (January 11, 2022); 80 FR 37381 (June 30, 2015).
Table 3  --  Emission Reductions and Cost of Three Potential fPM Emission Limits[1]

Potential fPM Emission Limit (lb/MMBtu)

1.5E-02
1.0E-02
6.0E-03
Affected Units (Capacity, GW)
8 (4.02)
20 (9.34)
65 (32.9)
Annual Cost ($M)
13.9 - 19.3
77.3 - 93.2
633
fPM Reductions (tons/year)
463
1,631
6,163
Total non-Hg metal HAP Reductions (tons/year)
1.41
5.34
24.7
Total non-Hg metal HAP Cost Effectiveness ($k/lb)
4.93 - 6.84
7.23 - 8.74
12.8
Total non-Hg metal HAP Cost Effectiveness -- Allowable ($/lb)
17.7 - 24.6
98.5 - 118.7
806.3
1 Note that these values represent annual cost and projected emission reductions assuming the affected coal-fired EGUs operate consistent with their operation in their lowest quarter (see technical memo accompanying this action for more information).

Because this cost-effectiveness evaluation only considers improved fPM control needed at a few units and not the entire fleet, we also evaluated an alternative cost-effectiveness approach that considers allowable emissions, assuming all evaluated EGUs emit fPM at the current standard of 3.0E-02 lb/MMBtu. Using this approach, the EPA estimates the allowable cost-effectiveness of non-Hg HAP metals of $17.7/lb to $24.6/lb for a 1.5E-02 lb/MMBtu emission limit, $98.5/lb to $118.7/lb for a 1.0E-02 lb/MMBtu emission limit, and $806.3/lb for a 6.0E-03 lb/MMBtu emission limit.
Taking all of these cost metrics into account, the EPA believes that the middle option, a limit of 1.0E-02 lb/MMBtu best balances the critical importance of reducing hazardous emissions pursuant to the EPA's statutory obligations under CAA section 112(d)(6) and ensuring that the worst performers are required to perform at the level of the remainder of the fleet with the costs of doing so in the context of this industry. Based on the foregoing discussion and these analyses, the EPA is proposing to lower the fPM emission limit, as a surrogate for the total non-Hg metal HAP, to 1.0E-02 lb/MMBtu as supported by our analyses of technical feasibility, control costs, cost-effectiveness, and economics. The EPA believes this standard appropriately balances CAA section 112's direction to achieve the maximum degree of emissions reductions while taking into account the statutory factors, including cost. This proposed emission limit is comparable to the new source standard for fPM in MATS. This proposed emission limit is estimated to reduce non-Hg metal HAP by 5.34 tons per year (and fPM emissions by 1,631 tons/year) at annual costs between $77.3 and $93.2 million. While the 2020 Residual Risk Review concluded that the residual risks are an acceptable level, Congress required the EPA to conduct technology reviews on an ongoing basis, at least every 8 years, independent of the residual risk review. Moreover, Congress required the EPA to set the standards at the maximum degree of emissions reductions (including prohibition on emissions) that is achievable taking into account the statutory factors. The technological standard approach of CAA section 112 is based on the premise that, to the extent there are controls available to reduce HAP emissions, sources should be required to use them. Since 91 percent of the anticipated capacity of the fleet is already achieving a limit below 1.0E-02 lb/MMBtu, the EPA proposes that this emissions limit level is technologically feasible and demonstrated for a range of control configurations. Additionally, this revised limit would result in significantly lower allowable PM emissions from the source category compared to the level of emissions allowed by the 2012 MATS Final Rule and help prevent any emissions increases. The EPA does not anticipate any significant non-air health, environmental, or energy impacts as a result of these proposed amendments. Our assessment of control options, costs, and emission reductions is summarized in the memorandum "2023 Technology Review for the Coal- and Oil-Fired EGU Source Category" in Docket ID No. EPA-HQ-OAR-2018-0794.
The EPA is not proposing the highest limit examined (1.5E-02 lb/MMBtu) because it would largely leave in place the status quo, in which despite the proven feasibility and effectiveness of control technologies, a number of sources are lagging far behind. The EPA does not consider this standard consistent with its statutory charge.
While the EPA is not proposing the lowest limit examined (6.0E-03 lb/MMBtu), the EPA is taking comment on whether it should consider finalizing such a standard. Such a standard would achieve far more emissions reductions than the standards the EPA is proposing in this action. It would also ensure that the bottom quarter of the fleet performs at the level of the remaining three-quarters of the fleet. The EPA declined to propose this standard here because both the total cost and cost effectiveness of meeting such a standard was estimated to be much higher for the more stringent limit than for the proposed 1.0E-02 lb/MMBtu limit, when considering the current fleet. These cost estimates are based on the assumption that existing ESP-controlled units would need to install a FF in order to meet the lower limit, or if existing FF-controlled units do not meet the more stringent limit, those units would upgrade their FF bags. If this assumption is unnecessarily conservative, total costs and cost-effectiveness may be considerably lower than estimated. The EPA takes comment on whether there are lower cost compliance options for units with existing ESPs.
An additional factor affecting the total estimated compliance cost is the size and composition of the generating fleet. As noted above, the cost estimates in Table 3 do not account for market and policy developments that are likely to further change the universe of regulated sources and reduce the expected costs of meeting more protective fPM standards. In the likely case that the power sector's transition to lower-emitting generation is accelerated by the IRA, for example, the total costs shown in Table 3 would also be an overestimate.
Additionally, the EPA notes that other future state and federal policies could affect the size, composition, and fPM emissions rate of the future coal-fired EGU fleet. The EPA seeks comment on the extent to which, and how, to take these future policies into account when considering the total cost and cost effectiveness of a more stringent fPM emission limit.
The EPA requests public comment on all aspects of this proposed rule, including our evaluation of the costs and efficacy of control option assumptions. Among other issues, the EPA requests comment on whether we have accurately assessed the variability of fPM emissions and requests information on the costs, pollution reduction benefits, and cost-effectiveness of applying lower emission limits to sources subject to MATS; and whether there are other factors the EPA should consider that would support a lower emission limit, including the contribution that HAP from these sources make to the overall pollution burden in communities with environmental justice concerns. The EPA seeks comment on requiring existing coal-fired EGUs to meet a fPM standard of 6.0E-03 lb/MMBtu at costs above levels the EPA typically considers to be cost effective for these types of HAP to inform our consideration of whether a more stringent standard would reduce the overall pollution burden in these communities. The EPA also seeks comment on whether there are any areas where EPA has overestimated costs, including some of the generation and storage technologies discussed above as well as the cost of PM controls themselves.
 PM Emission Monitoring
Under the current rule, EGU owners or operators may choose among quarterly testing, PM CEMS, and PM CPMS to demonstrate compliance with the alternate fPM emission limit in MATS. The initial MATS ICR, available at www.reginfo.gov, anticipated that all EGU owners or operators would use PM CEMS for compliance purposes and estimated Equivalent Uniform Annual Cost (EUAC) for the beta gauge PM CEMS to be $65,388. As mentioned in the 2012 proposed Portland Cement NESHAP, beta gauge technology, also referred to as beta attenuation, allows PM CEMS to be much less sensitive to changes in particle characteristics than light-based PM CEMS technologies such as light-scatter or scintillation. Beta attenuation PM CEMS extracts a sample from the stack gas and collects the fPM on filter tape. The device periodically advances the tape from the sampling mode to an area where the sample is exposed to beta radiation. The detector measures the amount of beta radiation emitted by the sample and that amount can be directly related to the mass of the filter. The unannualized purchase cost for a beta gauge PM CEMS and its installation were estimated to be $115,267 in the initial MATS ICR; and the EUAC for beta gauge PM CEMS was estimated to be less expensive than quarterly EPA Method 5 (M5) testing for fPM. Even so, not all EGU owners or operators chose the most cost-effective means of demonstrating compliance with the fPM emission limits. Review of reports submitted to WebFIRE and ongoing ICR renewals shows PM CEMS are used for compliance purposes by about one-third of EGU owners or operators. 		 In addition to being more cost-effective for compliance purposes, PM CEMS provide regulators and the public, as well as the EGU owners or operators, direct and continuous measurement of the pollutant of concern. Such data supply real-time, quality-assured feedback that can lead to improved control device and power plant operation, which, in turn, can lead to fPM emission reductions. Moreover, quick detection of potential problems with PM emissions as provided by PM CEMS, coupled with appropriate corrective measures, can prevent instances of non-compliance, which otherwise could go undetected (or corrected) until the next quarterly PM test. This quicker identification and correction of high emitting EGUs will lead to less pollution emitted and lower pollutant exposure for local communities. Transparency of EGU emissions as provided by PM CEMS, along with real-time assurance of compliance has intrinsic value to the public and communities as well as instrumental value in holding sources accountable.
Since promulgation of MATS, two important developments in the PM CEMS industry have occurred, which the EPA identified as part of this technology review: cessation of beta gauge PM CEMS manufacturing and reduced overall costs for non-beta gauge PM CEMS instruments and installation. These two occurrences have reduced the current one-time costs for PM CEMS, making their use even more cost-effective. As shown in Table 4 below, average non-beta gauge instrument and installation costs obtained from representatives of the Institute of Clean Air Companies (ICAC), a trade association consisting of air pollution control and measurement and monitoring system manufacturers and of environmental equipment and service providers, and from Envea / Altech, a PM CEMS manufacturer and vendor, show about a 48 percent reduction (from $109,420 to $57,095) from average comparable costs determined from the EPA's CEMS Cost Model and Monitoring Cost / Benefit Analysis Tool (MCAT).
     Table 4  --  Non-Beta Gauge PM CEMS Cost Estimates Using M5I for PS 11

                                  Data Source

                                 PM CEMS type
                               One Time Costs, $
                                Annual Costs, $

                                    EUAC, $

                          Instrument and Installation
                              Other Initial Costs
                               Capital Recovery
                           Operation and Maintenance

                                    Audits
                              Other Annual Costs

                                   EPA MCAT
                                    In situ
                                    119,295
                                    81,220
                                    22,016
                                     1,558
                                    54,877
                                    11,219
                                    89,670

                                  Extractive
                                    152,850
                                    81,220
                                    25,700
                                     2,579
                                    54,877
                                    12,241
                                    95,397
                              EPA CEMS Cost Model
                                    In situ
                                    65,107
                                    79,813
                                    15,912
                                     2,689
                                    54,392
                                     6,525
                                    79,518

                                  Extractive
                                    100,427
                                    84,458
                                    20,300
                                     3,689
                                    54,392
                                     7,525
                                    85,906
                                    Average
                                    109,420
                                    81,678
                                    20,982
                                     2,629
                                    54,635
                                     9,378
                                    87,623

                                     ICAC
                                      Low
                                    35,000

                                     3,843
                                    12,000
                                    14,290

                                    30,133

                                     High
                                    40,000

                                     4,392
                                    12,000
                                    14,290

                                    30,682

                                Envea / Altech
                                      Dry
                                    34,743

                                     3,821

                                    14,290

                                    18,111

                                      Wet
                                    118,585

                                    13,020

                                    14,290

                                    27,310
                                    Average
                                    57,095

                                     6,269
                                    12,000
                                    14,290

                                    32,559

Generally, EPA models include other initial costs associated with PM CEMS installation, including those associated with planning, selecting equipment, and conducting correlation testing, in its models; such one-time costs are annualized along with instrument and installation costs. The proposed lower fPM emission limit will require longer duration runs for M5 testing and may require the use of M5I, which was designed for PM CEMS correlation testing at low fPM levels. Initial costs in Table 4 for M5I emission testing are $58,000; such testing includes 18 runs of 3-hour duration spread over 9 total days. PM CEMS correlation testing for the proposed lower fPM levels using M5 is estimated to be $41,000. Of course, the quarterly testing run durations would need to increase if PM CEMS were not used; annual cost for M5 testing with 3 hour run duration is estimated to be $85,127 ($82,000 for testing, and $3,127 for 24 hours of site technical support); quarterly testing using M5I with runs of similar duration is estimated to be $107,127. However, neither ICAC nor Envea / Altech explicitly included those costs as line items in their estimates. This does not necessarily mean that such costs have been excluded. Their average capital recovery cost, determined from the sum of the instrument, installation, and other initial costs amortized over 15 years at a 7 percent interest rate, is about 70 percent lower than that obtained from the average capital recovery cost obtained from the EPA models. As shown in the table, EPA models also include annual costs for operation and maintenance, relative response and correlation audits, and other items such as reporting and recordkeeping. The sum of those items plus the capital recovery cost yields EUAC of PM CEMS. ICAC includes operation and maintenance as a line item in its annual costs, but neither ICAC nor Envea / Altech include audits or other items in their annual costs estimates. Because EPA believes some EGUs may require PM spiking  --  an approach that involves introducing known amounts of fPM to increase fPM concentration without altering control device equipment --  the EPA added $14,290 (the annualized cost of conducting $35,000 PM spiking every 3 years at an interest rate of 7 percent) to the audit portion of all entries. As mentioned earlier, omission of specifically named costs does not necessarily mean that those costs have been excluded; rather these costs may be included in other listed costs. Using the data provided and explained above, the average EUAC for PM CEMS that rely on M5I correlation testing is about 63 percent lower than the average EUAC from EPA models (from $87,623 to $32,559). Given that the annual cost of quarterly M5 testing for fPM is now estimated to be $85,127, annualized other one-time costs and operation and maintenance, audits, and other annualized costs  --  if omitted by the manufacturers  --  would have to be more than $52,568 for PM CEMS to be less cost-effective than quarterly testing.
As mentioned in the proposed Portland Cement NESHAP from 10 years ago (see 77 FR 42374, July 18, 2012), the EPA was aware of the potential difficulty use of PM CEMS might have created in determining compliance for that rulemaking due to the low end of emission limits (0.04 lb/ton clinker, which translates to a range of about 5 to 8 mg/dscm, depending on particle characteristics) and to the short duration of emission test runs. The EPA addressed those concerns for that rulemaking by proposing to raise the emission limit to 0.07 lb/ton clinker, which translated to a range of about 7 to 14 mg/dscm, and to no longer require PM CEMS use; instead, owners or operators would use their PM CEMS as PM CPMS. Even so, the durations of test runs used to develop the correlation of the instrument with the emissions limit remained unchanged, at about 1 hour per run. Such short run durations led to inherent measurement uncertainty accounting for more than half the emission limit at the expected portland cement plant operating condition, leading some to question whether values provided by instrumentation were appropriately related to emissions.
The conditions experienced by portland cement facilities that required revisions to emission limits and compliance determination method are not similar to those expected to be faced by EGU owners or operators subject to MATS. First, the fuel used by coal-fired EGUs is more uniform and its characteristics are more consistent than those of the fuel and additive mixtures used by portland cement kilns. Such fuel combustion particle consistency allows technologies such as light scattering and scintillation, in addition to beta gauges, to be used by PM CEMS for compliance determination purposes. Moreover, consistent fPM particle characteristics for EGUs provide stable correlations for those EGUs with existing PM CEMS; while the fPM particle characteristics provide correlations that remain within specifications, as evidenced by ongoing relative correlation audits, the existing correlations do not change and can continue to be used now and in the future without having to develop a new correlation. Second, the proposed MATS emission limit of 1.0E-02 lb/MMBtu, which translates to about 7.3 mg/dscm, coupled with a minimum sampling collection time of 3 hours per run, based on a typical sampling rate of (3/4) cubic feet per minute, avoids the measurement problems described by the Portland Cement NESHAP by reducing the average inherent measurement uncertainty for half of the proposed emission limit (where the EGU is expected to operate) from more than 50 to 80 percent. In addition, use of 3 hour run durations would allow for a 6.0E-03 lb/MMBtu (or about 4.4 mg/dscm) MATS emission limit, which the EPA is seeking comment on, to have an average inherent measurement uncertainty of 14 percent at 3.0E-03 lb/MMBtu. As shown, inherent measurement uncertainty does not appear to be problematic for the proposed emission limits. Note that the proposed MATS emission limit is just above the fPM limit for new EGUs, as 9.0E-02 lb/MWh on an electrical output basis translates to about 9.0E-03 lb/MMBtu on a heat input basis; MATS now requires use of PM CEMS for new EGUs, along with minimum sampling collection time of 3 hours per run. Proposed use of runs of at least 3 hour durations and emission limits of 1.0E-02 lb/MMBtu would be consistent with run durations and limits already in MATS. Third, Performance Specification 11 (PS 11), which provides procedures and acceptance criteria for validating PM CEMS technologies, already anticipates and includes approaches for developing low-level emission correlations for PM CEMS. Those techniques include varying process operations; varying fPM control device conditions; PM spiking zero point methods when the previous techniques aren't able to provide the 3 distinct fPM concentration levels. As mentioned earlier, average costs for fPM spiking are about $35,000 every 3 years, or $14,290 annually at an interest rate of 7 percent, and not every EGU will need to adjust its existing correlation in order to continue to use its existing PM CEMS to demonstrate compliance with the proposed limits; however, for purposes of this proposal, costs for spiking will be included in annual PM CEMS cost estimates. In addition to these techniques to aid PM CEMS use for rules with low level emissions, the EPA is aware that the Electric Power Research Institute (EPRI) began working with an instrument manufacturer in 2009, prior to MATS promulgation, to develop a National Institute of Standards and Technology (NIST) traceable aerosol generator that injects known particle size distribution and mass into PM CEMS. Such an instrument, known as a Quantitative Aerosol Generator (QAG), would allow direct PM CEMS calibration, as opposed to the development of a curve that provides a correlation for the PM CEMS. That study relied on six emission rates, four of which were at or under 5 mg/dscm, and reported successful sample collection and transport. EPRI continued this work and provided a technical update in 2014, but the EPA is unaware of specific recommendations or suggestions regarding QAG application to PM CEMS. While we believe the use of the QAG could lower fPM monitoring costs for PM CEMS use, we seek more information on its application for lower fPM limits as measured by PM CEMS; specifically, we solicit comment on whether implementation of the QAG is another reason that PM CEMS costs have decreased.
For these reasons, we propose to require the use of PM CEMS as the method to demonstrate compliance with the fPM emissions limit pursuant to the EPA's authority under CAA section 112(d)(6). Were our proposal finalized, EGU owners or operators currently relying on quarterly PM emissions testing would need to install, operate, and maintain PM CEMS; such a switch is projected to be more cost-effective, more informative, and more effective in assuring compliance than use of quarterly testing. Those EGU owners or operators already using PM CEMS as their means of compliance determination would maintain their current approach; while some may have no need for additional expenditures, the proposal includes the costs associated with revised and ongoing correlation testing and spiking for all EGUs. Since a proposed requirement for use PM CEMS renders the current compliance option for the LEE program superfluous, the EPA proposes to remove the individual and total non-Hg metal HAP and the surrogate fPM from the LEE program for all MATS-affected EGUs and solicits comments on removing these limits.
The EPA seeks comment on distinctions between portland cement plants and EGUs that would facilitate PM CEMS use at EGUs. Specifically, the EPA seeks comment on the ability, type, and capabilities of PM CEMS to accurately measure fPM emissions at the levels proposed in this rule. Moreover, the EPA seeks comment on additional or other approaches that could be employed to facilitate PM CEMS use for the proposed emission levels. Specific comments on direct PM CEMS calibration methods, such as the QAG, as well as limitations, are welcome.