[Federal Register Volume 89, Number 89 (Tuesday, May 7, 2024)]
[Rules and Regulations]
[Pages 38508-38593]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-09148]



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Vol. 89

Tuesday,

No. 89

May 7, 2024

Part IV





Environmental Protection Agency





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40 CFR Part 63





National Emission Standards for Hazardous Air Pollutants: Coal- and 
Oil-Fired Electric Utility Steam Generating Units Review of the 
Residual Risk and Technology Review; Final Rule

  Federal Register / Vol. 89 , No. 89 / Tuesday, May 7, 2024 / Rules 
and Regulations  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2018-0794; FRL-6716.3-02-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: Final rule.

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SUMMARY: This action finalizes amendments to the national emission 
standards for hazardous air pollutants (NESHAP) for the Coal- and Oil-
Fired Electric Utility Steam Generating Units (EGUs) source category. 
These final amendments are the result of the EPA's review of the 2020 
Residual Risk and Technology Review (RTR). The changes, which were 
proposed under the technology review in April 2023, include amending 
the filterable particulate matter (fPM) surrogate emission standard for 
non-mercury metal hazardous air pollutants (HAP) for existing coal-
fired EGUs, the fPM emission standard compliance demonstration 
requirements, and the mercury (Hg) emission standard for lignite-fired 
EGUs. Additionally, the EPA is finalizing a change to the definition of 
``startup.'' The EPA did not propose, and is not finalizing, any 
changes to the 2020 Residual Risk Review.

DATES: This final rule is effective on July 8, 2024. The incorporation 
by reference of certain material listed in the rule was approved by the 
Director of the Federal Register as of April 16, 2012.

ADDRESSES: The U.S. Environmental Protection Agency (EPA) has 
established a docket for this action under Docket ID No. EPA-HQ-OAR-
2018-0794. All documents in the docket are listed on the https://www.regulations.gov website. Although listed, some information is not 
publicly available, e.g., Confidential Business Information or other 
information whose disclosure is restricted by statute. Certain other 
material, such as copyrighted material, is not placed on the internet 
and will be publicly available only in hard copy form. Publicly 
available docket materials are available either electronically through 
https://www.regulations.gov, or in hard copy at the EPA Docket Center, 
WJC West Building, Room Number 3334, 1301 Constitution Ave. NW, 
Washington, DC. The Public Reading Room hours of operation are 8:30 
a.m. to 4:30 p.m. Eastern Standard Time (EST), Monday through Friday. 
The telephone number for the Public Reading Room is (202) 566-1744, and 
the telephone number for the EPA Docket Center is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For questions about this final action 
contact Sarah Benish, Sector Policies and Programs Division (D243-01), 
Office of Air Quality Planning and Standards, U.S. Environmental 
Protection Agency, P.O. Box 12055, Research Triangle Park, North 
Carolina 27711; telephone number: (919) 541-5620; and email address: 
[email protected].

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

APH air preheater
Btu British Thermal Units
CAA Clean Air Act
CEMS continuous emission monitoring system
EGU electric utility steam generating unit
EIA Energy Information Administration
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
Hg\2+\ divalent Hg
HgCl2 mercuric chloride
Hgp particulate bound Hg
HQ hazard quotient
ICR Information Collection Request
IGCC integrated gasification combined cycle
IPM Integrated Planning Model
IRA Inflation Reduction Act
lb pounds
LEE low emitting EGU
MACT maximum achievable control technology
MATS Mercury and Air Toxics Standards
MMacf million actual cubic feet
MMBtu million British thermal units of heat input
MW megawatt
NAICS North American Industry Classification System
NESHAP national emission standards for hazardous air pollutants
NOX nitrogen oxides
NRECA National Rural Electric Cooperative Association
OMB Office of Management and Budget
PM particulate matter
PM2.5 fine particulate matter
PM CEMS particulate matter continuous emission monitoring systems
REL reference exposure level
RFA Regulatory Flexibility Act
RIA Regulatory Impact Analysis
RIN Regulatory Information Number
RTR residual risk and technology review
SC-CO2 social cost of carbon
SO2 sulfur dioxide
TBtu trillion British thermal units of heat input
tpy tons per year
UMRA Unfunded Mandates Reform Act
WebFIRE Web Factor Information Retrieval System

    Background information. On April 24, 2023, the EPA proposed 
revisions to the Coal- and Oil-Fired EGU NESHAP based on our review of 
the 2020 RTR. In this action, we are finalizing revisions to the rule, 
commonly known as the Mercury and Air Toxics Standards (MATS). We 
summarize some of the more significant comments regarding the proposed 
rule that were received during the public comment period and provide 
our responses in this preamble. A summary of all other public comments 
on the proposal and the EPA's responses to those comments is available 
in National Emission Standards for Hazardous Air Pollutants: Coal- and 
Oil-Fired Electric Utility Steam Generating Units Review of the 
Residual Risk and Technology Review Proposed Rule Response to Comments, 
Docket ID No. EPA-HQ-OAR-2018-0794. A ``track changes'' version of the 
regulatory language that incorporates the changes in this action is 
available in the docket.
    Organization of this document. The information in this preamble is 
organized as follows:

I. General Information
    A. Executive Summary
    B. Does this action apply to me?
    C. Where can I get a copy of this document and other related 
information?
    D. Judicial Review and Administrative Reconsideration
II. Background
    A. What is the authority for this action?
    B. What is the Coal- and Oil-Fired EGU source category and how 
does the NESHAP regulate HAP emissions from the source category?
    C. Summary of the 2020 Residual Risk Review
    D. Summary of the 2020 Technology Review
    E. Summary of the EPA's Review of the 2020 RTR and the 2023 
Proposed Revisions to the NESHAP
III. What is included in this final rule?
    A. What are the final rule amendments based on the technology 
review for the Coal- and Oil-Fired EGU source category?
    B. What other changes have been made to the NESHAP?
    C. What are the effective and compliance dates of the standards?

[[Page 38509]]

IV. What is the rationale for our final decisions and amendments to 
the filterable PM (as a surrogate for non-Hg HAP metals) standard 
and compliance options from the 2020 Technology Review?
    A. What did we propose pursuant to CAA Section 112(d)(6) for the 
Coal- and Oil-Fired EGU source category?
    B. How did the technology review change for the Coal- and Oil-
Fired EGU source category?
    C. What key comments did we receive on the filterable PM and 
compliance options, and what are our responses?
    D. What is the rationale for our final approach and decisions 
for the filterable PM (as a surrogate for non-Hg HAP metals) 
standard and compliance demonstration options?
V. What is the rationale for our final decisions and amendments to 
the Hg emission standard for lignite-fired EGUs from review of the 
2020 Technology Review?
    A. What did we propose pursuant to CAA section 112(d)(6) for the 
lignite-fired EGU subcategory?
    B. How did the technology review change for the lignite-fired 
EGU subcategory?
    C. What key comments did we receive on the Hg emission standard 
for lignite-fired EGUs, and what are our responses?
    D. What is the rationale for our final approach and decisions 
for the lignite-fired EGU Hg standard?
VI. What is the rationale for our other final decisions and 
amendments from review of the 2020 Technology Review?
    A. What did we propose pursuant to CAA section 112(d)(6) for the 
other NESHAP requirements?
    B. How did the technology review change for the other NESHAP 
requirements?
    C. What key comments did we receive on the other NESHAP 
requirements, and what are our responses?
    D. What is the rationale for our final approach and decisions 
regarding the other NESHAP requirements?
VII. Startup Definition for the Coal- and Oil-Fired EGU Source 
Category
    A. What did we propose for the Coal- and Oil-Fired EGU source 
category?
    B. How did the startup provisions change for the Coal- and Oil-
Fired EGU source category?
    C. What key comments did we receive on the startup provisions, 
and what are our responses?
    D. What is the rationale for our final approach and final 
decisions for the startup provisions?
VIII. What other key comments did we receive on the proposal?
IX. Summary of Cost, Environmental, and Economic Impacts and 
Additional Analyses Conducted
    A. What are the affected facilities?
    B. What are the air quality impacts?
    C. What are the cost impacts?
    D. What are the economic impacts?
    E. What are the benefits?
    F. What analysis of environmental justice did we conduct?
X. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 14094: Modernizing Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA) and 
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations and Executive Order 14096: Revitalizing Our Nation's 
Commitment to Environmental Justice for All
    K. Congressional Review Act (CRA)

I. General Information

A. Executive Summary

1. Background and Purpose of the Regulatory Action
    Exposure to hazardous air pollutants (``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. These 
adverse effects can be particularly acute for communities living near 
sources of HAP. 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 based on maximum achievable control 
technology (known as ``MACT'' standards) for major sources \1\ 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 
nonair quality health and environmental impacts and energy 
requirements, determines is achievable.'' 42 U.S.C. 7412(d)(2). The EPA 
is further required to ``review, and revise'' those standards every 8 
years ``as necessary (taking into account developments in practices, 
processes, and control technologies).'' Id. 7412(d)(6).
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    \1\ The term ``major source'' means any stationary source or 
group of stationary sources located within a contiguous area and 
under common control that emits or has the potential to emit 
considering controls, in the aggregate, 10 tons per year or more of 
any hazardous air pollutant or 25 tons per year or more of any 
combination of hazardous air pollutants. 42 U.S.C. 7412(a)(1).
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    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 two 
parts: (1) a finding that it is not appropriate and necessary to 
regulate coal- and oil-fired EGUs under CAA section 112; and (2) the 
RTR for the 2012 MATS Final Rule.
    The EPA reviewed both parts of the 2020 Final Action. The results 
of the EPA's review of the first part, finding it is appropriate and 
necessary to regulate EGUs under CAA section 112, were proposed on 
February 9, 2022 (87 FR 7624) (2022 Proposal) and finalized on March 6, 
2023 (88 FR 13956). In the 2022 Proposal, the EPA also solicited 
information on the performance and cost of new or improved technologies 
that control HAP emissions, improved methods of operation, and risk-
related information to further inform the EPA's review of the second 
part, the 2020 MATS RTR. The EPA proposed amendments to the RTR on 
April 24, 2023 (88 FR 24854) (2023 Proposal) and this action finalizes 
those amendments and presents the final results of the EPA's review of 
the MATS RTR.
2. Summary of Major Provisions of the Regulatory Action
    Coal- and oil-fired EGUs remain one of the largest domestic 
emitters of Hg and many other HAP, including many of the non-Hg HAP 
metals--including lead, arsenic, chromium, nickel, and cadmium--and 
hydrogen chloride (HCl). Exposure to these HAP, at certain levels and 
duration, is associated with a variety of adverse health effects. In 
the 2012 MATS Final Rule, the EPA established numerical standards for 
Hg, non-Hg HAP metals, and acid gas HAP emissions from coal- and oil-
fired EGUs. The EPA also established work practice standards for 
emissions of organic HAP. To address emissions of non-Hg HAP

[[Page 38510]]

metals, the EPA established individual emission limits for each of the 
10 non-Hg HAP metals \2\ emitted from coal- and oil- fired EGUs. 
Alternatively, affected sources could meet an emission standard for 
``total non-Hg HAP metals'' by summing the emission rates of each of 
the non-Hg HAP metals or meet a fPM emission standard as a surrogate 
for the non-Hg HAP metals. For existing coal-fired EGUs, almost every 
unit has chosen to demonstrate compliance with the non-Hg HAP metals 
surrogate fPM emission standard of 0.030 pounds (lb) of fPM per million 
British thermal units of heat input (lb/MMBtu).
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    \2\ The ten non-Hg HAP metals are antimony, arsenic, beryllium, 
cadmium, chromium, cobalt, lead, manganese, nickel, and selenium.
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    Pursuant to CAA section 112(d)(6), the EPA reviewed developments in 
the costs of control technologies, and the effectiveness of those 
technologies, as well as the costs of meeting a fPM emission standard 
that is more stringent than 0.030 lb/MMBtu and the other statutory 
factors. Based on that review, the EPA is finalizing, as proposed, a 
revised non-Hg HAP metal surrogate fPM emission standard for all 
existing coal-fired EGUs of 0.010 lb/MMBtu. This strengthened standard 
will ensure that the entire fleet of coal-fired EGUs is performing at 
the fPM pollution control levels currently achieved by the vast 
majority of regulated units. The EPA further concludes that it is the 
lowest level currently compatible with the use of PM CEMS for 
demonstrating compliance.
    Relatedly, the EPA is also finalizing a revision to the 
requirements for demonstrating compliance with the revised fPM emission 
standard. Currently, affected EGUs that do not qualify for the low 
emitting EGU (LEE) program for fPM \3\ can demonstrate compliance with 
the fPM standard either by conducting quarterly performance testing 
(i.e., quarterly stack testing) or by using particulate matter (PM) 
continuous emission monitoring systems (PM CEMS). PM CEMS confer 
significant benefits, including increased transparency regarding 
emissions performance for sources, regulators, and the surrounding 
communities; and real-time identification of when control technologies 
are not performing as expected, allowing for quicker repairs. After 
considering updated information on the costs for quarterly performance 
testing compared to the costs of PM CEMS and the measurement 
capabilities of PM CEMS, as well as the many benefits of using PM CEMS, 
the EPA is finalizing, as proposed, a requirement that all coal- and 
oil-fired EGUs demonstrate compliance with the revised fPM emission 
standard by using PM CEMS. As the EPA explained in the 2023 Proposal, 
by requiring facilities to use PM CEMS, the current compliance method 
for the LEE program becomes superfluous since LEE is an optional 
program in which stack testing occurs infrequently, and the revised fPM 
limit is below the current fPM LEE program limit. Therefore, the EPA is 
finalizing, as proposed, the removal of the fPM LEE program.
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    \3\ In order to qualify for fPM LEE status, an EGU must 
demonstrate that its fPM emission rate is below 50 percent of 
standard (or 0.015 lb/MMBtu) from quarterly stack tests for 3 
consecutive years. Once a source achieves LEE status for fPM, the 
source must conduct stack testing every 3 years to demonstrate that 
its emission rate remains below 50 percent of the standard.
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    Based on comments received during the public comment period, the 
EPA is not removing, but instead revising the alternative emission 
limits for the individual non-Hg HAP metals such as lead, arsenic, 
chromium, nickel, and cadmium and for the total non-Hg HAP metals 
proportional to the finalized fPM emission limit of 0.010 lb/MMBtu.\4\ 
Owners and operators of EGUs seeking to use these alternative standards 
must request and receive approval to use a HAP metal continuous 
monitoring system (CMS) as an alternative test method under 40 CFR 
63.7(f).
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    \4\ The emission limits for the individual non-Hg HAP metals and 
the total non-Hg HAP metals have been reduced by two-thirds, 
consistent with the revision of the fPM emission limit from 0.030 
lb/MMBtu to 0.010 lb/MMBtu.
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    The EPA is also finalizing, as proposed, a more protective Hg 
emission standard for existing lignite-fired EGUs, requiring that such 
lignite-fired EGUs meet the same Hg emission standard as EGUs firing 
other types of coal (i.e., bituminous and subbituminous), which is 1.2 
lb of Hg per trillion British thermal units of heat input (lb/TBtu) or 
an alternative output-based standard of 0.013 lb per gigawatt-hour (lb/
GWh). Finally, the EPA is finalizing, as proposed, the removal of the 
second option for defining the startup period for MATS-affected EGUs.
    The EPA did not propose and is not finalizing modifications to the 
HCl emission standard (nor the alternative sulfur dioxide 
(SO2) emission standard), which serves as a surrogate for 
all acid gas HAP (HCl, hydrogen fluoride (HF), selenium dioxide 
(SeO2)) for existing coal-fired EGUs. The EPA proposed to 
require PM CEMS for existing integrated gasification combined cycle 
(IGCC) EGUs but is not finalizing this requirement due to technical 
issues calibrating CEMS on these types of EGUs and the related fact 
that fPM emissions from IGCCs are very low.
    In establishing the final standards, as discussed in detail in 
sections IV., V., VI., and VII. of this preamble, the EPA considered 
the statutory direction and factors laid out by Congress in CAA section 
112. Separately, pursuant to Executive Order 12866 and Executive Order 
14904, the EPA prepared an analysis of the potential costs and benefits 
associated with this action. This analysis, Regulatory Impact Analysis 
for the Final 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-24-005), is 
available in the docket, and is briefly summarized in sections I.A.3. 
and IX. of this preamble.
3. Costs and Benefits
    In accordance with Executive Order 12866 and 14094, the EPA 
prepared a Regulatory Impact Analysis (RIA). The RIA presents estimates 
of the emission, cost, and benefit impacts of this final rulemaking for 
the 2028 to 2037 period; those estimates are summarized in this 
section.
    The power industry's compliance costs are represented in the RIA as 
the projected change in electric power generation costs between the 
baseline and final rule scenarios. The quantified emission estimates 
presented in the RIA include changes in pollutants directly covered by 
this rule, such as Hg and non-Hg HAP metals, and changes in other 
pollutants emitted from the power sector due to the compliance actions 
projected under this final rule. The cumulative projected national-
level emissions reductions over the 2028 to 2037 period under the 
finalized requirements are presented in table 1. The supporting details 
for these estimates can be found in the RIA.
BILLING CODE 6560-50-P

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[GRAPHIC] [TIFF OMITTED] TR07MY24.065

    The EPA expects that emission reductions under the final rulemaking 
will result in reduced exposure to Hg and non-Hg HAP metals. The EPA 
also projects health benefits due to improvements in particulate matter 
with a diameter of 2.5 micrometers or less (PM2.5) and ozone 
and climate benefits from reductions in carbon dioxide (CO2) 
emissions. The EPA also anticipates benefits from the increased 
transparency to the public, the assurance that standards are being met 
continuously, and the accelerated identification of anomalous emissions 
due to requiring PM CEMS in this final rule.
    The EPA estimates negative net monetized benefits of this rule (see 
table 2 below). However, the benefit estimates informing this result 
represent only a partial accounting of the potential benefits of this 
final rule. Several categories of human welfare and climate benefits 
are unmonetized and are thus not directly reflected in the quantified 
net benefit estimates (see section IX.B. in this preamble and section 4 
of the RIA for more details). In particular, estimating the economic 
benefits of reduced exposure to HAP generally has proven difficult for 
a number of reasons: it is difficult to undertake epidemiologic studies 
that have sufficient power to quantify the risks associated with HAP 
exposures experienced by U.S. populations on a daily basis; data used 
to estimate exposures in critical microenvironments are limited; and 
there remains insufficient economic research to support valuation of 
HAP benefits made even more challenging by the wide array of HAP and 
possible HAP effects.\5\ In addition, due to data limitations, the EPA 
is also unable to quantify potential emissions impacts or monetize 
potential benefits from continuous monitoring requirements.
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    \5\ See section II.B.2. for discussion of the public health and 
environmental hazards associated with HAP emissions from coal- and 
oil-fired EGUs and discussion on the limitations to monetizing and 
quantifying benefits from HAP reductions. See also National Emission 
Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric 
Utility Steam Generating Units--Revocation of the 2020 
Reconsideration and Affirmation of the Appropriate and Necessary 
Supplemental Finding, 88 FR 13956, 13970-73 (March 6, 2023).
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    The present value (PV) and equivalent annual value (EAV) of costs, 
benefits, and net benefits of this rulemaking over the 2028 to 2037 
period in 2019 dollars are shown in table 2. In this table, results are 
presented using a 2 percent discount rate. Results under other discount 
rates and supporting details for the estimates can be found in the RIA.

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[GRAPHIC] [TIFF OMITTED] TR07MY24.066

BILLING CODE 6560-50-C
    The EPA notes that analysis of such impacts is distinct from the 
determinations finalized in this action under CAA section 112, which 
are based on the statutory factors the EPA discusses in section II.A. 
and sections IV. through VII. below.

B. Does this action apply to me?

    Regulated entities. The source category that is the subject of this 
action is coal- and oil-fired EGUs regulated by NESHAP under 40 CFR 
part 63, subpart UUUUU, commonly known as MATS. The North American 
Industry Classification System (NAICS) codes for the coal- and oil-
fired EGU source category are 221112, 221122, and 921150. This list of 
NAICS codes is not intended to be exhaustive, but rather to provide a 
guide for readers regarding entities likely to be affected by the final 
action for the source category listed. To determine whether your 
facility is affected, you should examine the applicability criteria in 
the appropriate NESHAP. If you have any questions regarding the 
applicability of any aspect of this NESHAP, please contact the 
appropriate person listed in the preceding FOR FURTHER INFORMATION 
CONTACT section of this preamble.

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

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

D. Judicial Review and Administrative Reconsideration

    Under CAA section 307(b)(1), judicial review of this final action 
is available only by filing a petition for review in the United States 
Court of Appeals for the District of Columbia Circuit (the Court) by 
July 8, 2024. Under CAA section 307(b)(2), the requirements established 
by this final rule may not be challenged separately in any civil or 
criminal proceedings brought by the EPA to enforce the requirements.
    Section 307(d)(7)(B) of the CAA further provides that only an 
objection to a rule or procedure that was raised with reasonable 
specificity during the period for public comment (including any public 
hearing) may be raised during judicial review. This section also 
provides a mechanism for the EPA to reconsider the rule if the person 
raising an objection can demonstrate to the Administrator that it was 
impracticable to raise such objection within the period for public 
comment or if the grounds for such objection arose after the period for 
public comment (but within the time specified for judicial review) and 
if such objection is of central relevance to the outcome of the rule. 
Any person seeking to make such a demonstration should submit a 
Petition for Reconsideration to the Office of the Administrator, U.S. 
EPA, Room 3000, WJC South Building, 1200 Pennsylvania Ave., NW, 
Washington, DC 20460, with a copy to both the person(s) listed in the 
preceding FOR FURTHER INFORMATION CONTACT section, and the Associate

[[Page 38513]]

General Counsel for the Air and Radiation Law Office, Office of General 
Counsel (Mail Code 2344A), U.S. EPA, 1200 Pennsylvania Ave. NW, 
Washington, DC 20460.

II. Background

A. What is the statutory authority for this action?

1. Statutory Language
    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 major sources control HAP 
emissions at the level achieved by the best-performing sources, 
referred to as the 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 the emission standards should be revised 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, and control technologies.'' This review is commonly referred 
to as the ``technology review,'' and is the primary subject of this 
final rule. 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 
nonair quality health and environmental impacts and energy 
requirements, determines is achievable.'' (emphasis added). These 
standards are commonly referred to as MACT standards. CAA section 
112(d)(3) establishes a minimum control level for MACT standards, known 
as the MACT ``floor.'' \6\ 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.\7\
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    \6\ Specifically, for existing sources, the MACT ``floor'' shall 
not be less stringent than the average emission reduction achieved 
by the best performing 12 percent of existing sources. 42 U.S.C. 
7412(d)(3). For new sources MACT shall not be less stringent than 
the emission control that is achieved in practice by the best 
controlled similar source. Id.
    \7\ For categories of area sources subject to GACT standards, 
there is no requirement to address residual risk, but, similar to 
the major source categories, the technology review is required.
---------------------------------------------------------------------------

    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). The 
residual risk review and the technology review are distinct 
requirements and are both mandatory.
    In this action, the EPA is finalizing amendments to the MACT 
standards based on two independent sources of authority: (1) its review 
of the 2020 Final Action's risk and technology review pursuant to the 
EPA's statutory authority under CAA section 112, and (2) the EPA's 
inherent authority to reconsider previous decisions and to revise, 
replace, or repeal a decision to the extent permitted by law and 
supported by a reasoned explanation. FCC v. Fox Television Stations, 
Inc., 556 U.S. 502, 515 (2009); see also Motor Vehicle Mfrs. Ass'n v. 
State Farm Mutual Auto. Ins. Co., 463 U.S. 29, 42 (1983).
2. Statutory Structure and Legislative History
    In addition to the text of the specific subsections of CAA section 
112 discussed above, the statutory structure and legislative history of 
CAA section 112 further support the EPA's authority to take this 
action. Throughout CAA section 112 and its legislative history, 
Congress made clear its intent to quickly secure large reductions in 
the volume of HAP emissions from stationary sources based on 
technological developments in control technologies because of its 
recognition of the hazards to public health and the environment that 
result from exposure to such emissions. CAA section 112 and its 
legislative history also reveal Congress's understanding that fully 
characterizing the risks posed by HAP emissions was exceedingly 
difficult. Thus, Congress purposefully replaced a regime that required 
the EPA to make an assessment of risk in the first instance, with one 
in which Congress determined risk existed and directed the EPA to make 
swift and substantial reductions based upon the most stringent 
standards technology could achieve.
    Specifically, in 1990, Congress radically transformed section 112 
of the CAA and its treatment of HAP through the Clean Air Act 
Amendments, by

[[Page 38514]]

amending CAA section 112 to be a technology-driven standard setting 
provision as opposed to the risk-based one that Congress initially 
promulgated in the 1970 CAA. The legislative history of the 1990 
Amendments indicates Congress's dissatisfaction with the EPA's slow 
pace addressing HAP under the 1970 CAA: ``In theory, [hazardous air 
pollutants] were to be stringently controlled under the existing Clean 
Air Act section 112. However, . . . only 7 of the hundreds of 
potentially hazardous air pollutants have been regulated by EPA since 
section 112 was enacted in 1970.'' H.R. Rep. No. 101-490, at 315 
(1990); see also id. at 151 (noting that in 20 years, the EPA's 
establishment of standards for only seven HAP covered ``a small 
fraction of the many substances associated . . . with cancer, birth 
defects, neurological damage, or other serious health impacts.'').
    In enacting the 1990 Amendments with respect to the control of HAP, 
Congress noted that ``[p]ollutants controlled under [section 112] tend 
to be less widespread than those regulated [under other sections of the 
CAA], but are often associated with more serious health impacts, such 
as cancer, neurological disorders, and reproductive dysfunctions.'' Id. 
at 315. In its substantial 1990 Amendments, Congress itself listed 189 
HAP (CAA section 112(b)) and set forth a statutory structure that would 
ensure swift regulation of a significant majority of these HAP 
emissions from stationary sources. Specifically, after defining major 
and area sources and requiring the EPA to list all major sources and 
many area sources of the listed pollutants (CAA section 112(c)), the 
new CAA section 112 required the EPA to establish technology-based 
emission standards for listed source categories on a prompt schedule 
and to revisit those technology-based standards every 8 years on an 
ongoing basis (CAA section 112(d) (emission standards); CAA section 
112(e) (schedule for standards and review)). The 1990 Amendments also 
obligated the EPA to conduct a one-time evaluation of the residual risk 
within 8 years of promulgation of technology-based standards. CAA 
section 112(f)(2).
    In setting the standards, CAA section 112(d) requires the EPA to 
establish technology-based standards that achieve the ``maximum degree 
of reduction,'' ``including a prohibition on such emissions where 
achievable.'' CAA section 112(d)(2). Congress specified that the 
maximum degree of reduction must be at least as stringent as the 
average level of control achieved in practice by the best performing 
sources in the category or subcategory based on emissions data 
available to the EPA at the time of promulgation. This technology-based 
approach enabled the EPA to swiftly set standards for source categories 
without determining the risk or cost in each specific case, as the EPA 
had done prior to the 1990 Amendments. In other words, this approach to 
regulation quickly required that all major sources and many area 
sources of HAP meet an emission standard consistent with the top 
performers in each category, which had the effect of obtaining 
immediate reductions in the volume of HAP emissions from stationary 
sources. The statutory requirement that sources obtain levels of 
emission limitation that have actually been achieved by existing 
sources, instead of levels that could theoretically be achieved, 
inherently reflects a built-in cost consideration.\8\
---------------------------------------------------------------------------

    \8\ Congress recognized as much: ``The Administrator may take 
the cost of achieving the maximum emission reduction and any non-air 
quality health and environmental impacts and energy requirements 
into account when determining the emissions limitation which is 
achievable for the sources in the category or subcategory. Cost 
considerations are reflected in the selection of emissions 
limitations which have been achieved in practice (rather than those 
which are merely theoretical) by sources of a similar type or 
character.'' A Legislative History of the Clean Air Act Amendments 
of 1990 (CAA Legislative History), Vol 5, pp. 8508-8509 (CAA 
Amendments of 1989; p. 168-169; Report of the Committee on 
Environment and Public Works S. 1630).
---------------------------------------------------------------------------

    Further, after determining the minimum stringency level of control, 
or MACT floor, CAA section 112(d)(2) directs the EPA to ``require the 
maximum degree of reduction in emissions of the hazardous air 
pollutants subject to this section (including a prohibition on such 
emissions, where achievable)'' that the EPA determines are achievable 
after considering the cost of achieving such standards and any non-air-
quality health and environmental impacts and energy requirements of 
additional control. In doing so, the statute further specifies in CAA 
section 112(d)(2) that the EPA should consider requiring sources to 
apply measures that, among other things, ``reduce the volume of, or 
eliminate emissions of, such pollutants . . . '' (CAA section 
112(d)(2)(A)), ``enclose systems or processes to eliminate emissions'' 
(CAA section 112(d)(2)(B)), and ``collect, capture, or treat such 
pollutants when released . . . '' (CAA section 112(d)(2)(C)). The 1990 
Amendments also built in a regular review of new technologies and a 
one-time review of risks that remain after imposition of MACT 
standards. CAA section 112(d)(6) requires the EPA to evaluate every 
NESHAP no less often than every 8 years to determine whether additional 
control is necessary after taking into consideration ``developments in 
practices, processes, and control technologies,'' separate from its 
obligation to review residual risk. CAA section 112(f) requires the EPA 
to ensure within 8 years of promulgating a NESHAP that the risks are 
acceptable and that the MACT standards provide an ample margin of 
safety.
    The statutory requirement to establish technology-based standards 
under CAA section 112 eliminated the requirement for the EPA to 
identify hazards to public health and the environment in order to 
justify regulation of HAP emissions from stationary sources, reflecting 
Congress's judgment that such emissions are inherently dangerous. See 
S. Rep. No. 101-228, at 148 (``The MACT standards are based on the 
performance of technology, and not on the health and environmental 
effects of the [HAP].''). The technology review required in CAA section 
112(d)(6) further mandates that the EPA continually reassess standards 
to determine if additional reductions can be obtained, without 
evaluating the specific risk associated with the HAP emissions that 
would be reduced. Notably, Congress required the EPA to conduct the CAA 
section 112(d)(6) review of what additional reductions may be obtained 
based on new technology even after the EPA has conducted the one-time 
CAA section 112(f)(2) risk review and determined that the existing 
standard will protect the public with an ample margin of safety. The 
two requirements are distinct, and both are mandatory.

B. What is the Coal- and Oil-Fired EGU source category and how does the 
NESHAP regulate HAP emissions from the source category?

1. Summary of Coal- and Oil-Fired EGU Source Category and NESHAP 
Regulations
    The EPA promulgated the Coal- and Oil-Fired EGU NESHAP (commonly 
referred to as MATS) on February 16, 2012 (77 FR 9304) (2012 MATS Final 
Rule). The standards are codified at 40 CFR part 63, subpart UUUUU. The 
coal- and oil-fired electric utility industry consists of facilities 
that burn coal or oil 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

[[Page 38515]]

after May 3, 2011. An EGU is a 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 electric output to any utility power distribution 
system for sale is also considered an EGU. The 2012 MATS Final 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.'' In 2028, the EPA expects the source 
category covered by this MACT standard to include 314 coal-fired steam 
generating units (140 GW at 157 facilities), 58 oil-fired steam 
generating units (23 GW at 35 facilities), and 5 IGCC units (0.8 GW at 
2 facilities).
    For coal-fired EGUs, the 2012 MATS Final 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 flue gas desulfurization (FGD) systems and 
SO2 CEMS installed and operational. Standards for fPM serve 
as a surrogate for the non-Hg HAP metals. Work practice standards limit 
formation and emissions of organic HAP.
    For oil-fired EGUs, the 2012 MATS Final 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 also serve as a surrogate for total HAP metals, with standards 
for total and individual HAP metals provided as alternative equivalent 
standards. Work practice standards limit formation and emissions of 
organic HAP.
    MATS includes standards for existing and new EGUs for eight 
subcategories: three 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 seven of the subcategories are 
subject to numeric emission limits for all the pollutants described 
above except for organic HAP (limited-use liquid oil-fired EGUs are not 
subject to numeric emission limits). 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 and additional information of the history and other requirements 
of the 2012 MATS Final Rule are available in the 2023 Proposal preamble 
(88 FR 24854).
2. Public Health and Environmental Hazards Associated With Emissions 
From Coal- and Oil-Fired EGUs
    Coal- and oil-fired EGUs are a significant source of numerous HAP 
that are associated with adverse effects to human health and the 
environment, including Hg, HF, HCl, selenium, arsenic, chromium, 
cobalt, nickel, hydrogen cyanide, beryllium, and cadmium emissions. Hg 
is a persistent and bioaccumulative toxic metal that, once released 
from power plants into the ambient air, can be readily transported and 
deposited to soil and aquatic environments where it is transformed by 
microbial action into methylmercury.\9\ Methylmercury bioaccumulates in 
the aquatic food web eventually resulting in highly concentrated levels 
of methylmercury within the larger and longer-living fish (e.g., carp, 
catfish, trout, and perch), which can then be consumed by humans.
---------------------------------------------------------------------------

    \9\ U.S. EPA. 1997, Mercury Study Report to Congress, EPA-452/R-
97-003 (December 1997); see also 76 FR 24976 (May 3, 2011); 80 FR 
75029 (December 1, 2015).
---------------------------------------------------------------------------

    Of particular concern is chronic prenatal exposure via maternal 
consumption of foods containing methylmercury. Elevated exposure has 
been associated with developmental neurotoxicity and manifests as poor 
performance on neurobehavioral tests, particularly on tests of 
attention, fine motor function, language, verbal memory, and visual-
spatial ability. Evidence also suggests potential for adverse effects 
on the cardiovascular system, adult nervous system, and immune system, 
as well as potential for causing cancer. Because the impacts of the 
neurodevelopmental effects of methylmercury are greatest during periods 
of rapid brain development, developing fetuses, infants, and young 
children are particularly vulnerable. Children born to populations with 
high fish consumption (e.g., people consuming fish as a dietary staple) 
or impaired nutritional status may be especially susceptible to adverse 
neurodevelopmental outcomes. These dietary and nutritional risk factors 
are often particularly pronounced in vulnerable communities with people 
of color and low-income populations that have historically faced 
economic and environmental injustice and are overburdened by cumulative 
levels of pollution. In addition to adverse neurodevelopmental effects, 
there is evidence that exposure to methylmercury in humans and animals 
can have adverse effects on both the developing and adult 
cardiovascular system.
    Along with the human health hazards associated with methylmercury, 
it is well-established that birds and mammals are also exposed to 
methylmercury through fish consumption (Mercury Study). At higher 
levels of exposure, the harmful effects of methylmercury include slower 
growth and development, reduced reproduction, and premature mortality. 
The effects of methylmercury on wildlife are variable across species 
but have been observed in the environment for numerous avian species 
and mammals including polar bears, river otters, and panthers.
    EGUs are also the largest source of HCl, HF, and selenium 
emissions, and are a major source of metallic HAP emissions including 
arsenic, chromium, nickel, cobalt, and others. Exposure to these HAP, 
depending on exposure duration and levels of exposures, is associated 
with a variety of adverse health effects. These adverse health effects 
may include chronic health disorders (e.g., pneumonitis, decreased 
pulmonary function, pneumonia, or lung damage; detrimental effects on 
the central nervous system; damage to the kidneys) and alimentary 
effects (such as nausea and vomiting). As of 2021, three of the key 
metal HAP emitted by EGUs (arsenic, chromium, and nickel) have been 
classified as human carcinogens, while three others (cadmium, selenium, 
and lead) are classified as probable human carcinogens. Overall (metal 
and nonmetal), the EPA has classified four of the HAP emitted by EGUs 
as human carcinogens and five as probable human carcinogens.
    While exposure to HAP is associated with a variety of adverse 
effects, quantifying the economic value of these impacts remains 
challenging. Epidemiologic studies, which report a central estimate of 
population-level risk, are generally used in an air pollution benefits 
assessment to estimate the number of attributable cases of events. 
Exposure to HAP is typically more uneven and more highly concentrated 
among a smaller number of individuals than exposure to criteria 
pollutants.

[[Page 38516]]

Hence, conducting an epidemiologic study for HAP is inherently more 
challenging; for starters, the small population size means such studies 
often lack sufficient statistical power to detect effects (particularly 
outcomes like cancer, for which there can exist a multi-year time lag 
between exposure and the onset of the disease). By contrast, sufficient 
power generally exists to detect effects for criteria pollutants 
because exposures are ubiquitous and a variety of methods exist to 
characterize this exposure over space and time.
    For the reasons noted above, epidemiologic studies do not generally 
exist for HAP. Instead, the EPA tends to rely on experimental animal 
studies to identify the range of effects which may be associated with a 
particular HAP exposure. Human controlled clinical studies are often 
limited due to ethical barriers (e.g., knowingly exposing someone to a 
carcinogen). Generally, robust data are needed to quantify the 
magnitude of expected adverse impacts from varying exposures to a HAP. 
These data are necessary to provide a foundation for quantitative 
benefits analyses but are often lacking for HAP, made even more 
challenging by the wide array of HAP and possible noncancer HAP 
effects.
    Finally, estimating the economic value of HAP is made challenging 
by the human health endpoints affected. For example, though EPA can 
quantify the number and economic value of HAP-attributable deaths 
resulting from cancer, it is difficult to monetize the value of 
reducing an individual's potential cancer risk attributable to a 
lifetime of HAP exposure. An alternative approach of conducting 
willingness to pay studies specifically on risk reduction may be 
possible, but such studies have not yet been pursued.

C. Summary of the 2020 Residual Risk Review

    As required by CAA section 112(f)(2), the EPA conducted the 
residual risk review (2020 Residual Risk Review) in 2020, 8 years after 
promulgating the 2012 MATS Final Rule, and presented the results of the 
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 3 of this document, 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 (Document 
ID No. EPA-HQ-OAR-2018-0794-4553). The EPA summarized the results and 
findings of the 2020 Residual Risk Review in the preamble of the 2023 
Proposal (88 FR 24854), and additional information concerning the 
residual risk review can be found in our National-Scale Mercury Risk 
Estimates for Cardiovascular and Neurodevelopmental Outcomes for the 
National Emission Standards for Hazardous Air Pollutants: Coal- and 
Oil-Fired Electric Utility Steam Generating Units--Revocation of the 
2020 Reconsideration, and Affirmation of the Appropriate and Necessary 
Finding; Notice of Proposed Rulemaking memorandum (Document ID No. EPA-
HQ-OAR-2018-0794-4605).
BILLING CODE 6560-50-P

[[Page 38517]]

[GRAPHIC] [TIFF OMITTED] TR07MY24.067

BILLING CODE 6560-50-C

D. 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 2012 MATS Final Rule was promulgated. Control 
technologies typically used to minimize emissions of pollutants that 
have numeric emission limits under the 2012 MATS Final Rule include 
electrostatic precipitators (ESPs) and fabric filters (FFs) for control 
of fPM as a surrogate for non-Hg HAP metals; wet scrubbers, dry 
scrubbers, and dry sorbent injection for control of acid gases 
(SO2, HCl, and HF); and activated carbon injection (ACI) and 
other Hg-specific technologies for control of Hg. The EPA determined 
that the 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 2012 
MATS Final 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 2012 MATS Final 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

[[Page 38518]]

control technologies and, thus, did not propose changes to any 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 
(Document 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).

E. Summary of the EPA's Review of the 2020 RTR and the 2023 Proposed 
Revisions to the NESHAP

    Pursuant to CAA section 112(d)(6), the EPA conducted a review of 
the 2020 Technology Review and presented the results of this review, 
along with our proposed decisions, in the 2023 Proposal. The results of 
the technology review are presented briefly below in this preamble. 
More detail on the proposed technology review is in the memorandum 2023 
Technology Review for the Coal- and Oil-Fired EGU Source Category 
(``2023 Technical Memo'') (Document ID No. EPA-HQ-OAR-2018-0794-5789).
    Based on the results of the technology review, the EPA proposed to 
lower the fPM standard, the surrogate for non-Hg HAP metals, for coal-
fired EGUs from 0.030 lb/MMBtu to 0.010 lb/MMBtu. The Agency solicited 
comment on the control technology effectiveness and cost assumptions 
used in the proposed rule, as well as on a more stringent fPM limit of 
0.006 lb/MMBtu or lower. Additionally, the Agency proposed to require 
the use of PM CEMS for all coal-fired, oil-fired, and IGCC EGUs for 
demonstrating compliance with the fPM standard. As the Agency proposed 
to require PM CEMS for compliance demonstration, we also proposed to 
remove the LEE option, a program based on infrequent stack testing, for 
fPM and non-Hg HAP metals. As EGUs would be required to demonstrate 
compliance with PM CEMS, the Agency also proposed to remove the 
alternate emission standards for non-Hg HAP metals and total HAP 
metals, 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 solicited comment on 
prorated metal limits (adjusted proportionally according to the level 
of the final fPM standard), should the Agency not finalize the removal 
of the non-Hg HAP metals limits.
    The Agency also proposed to lower the Hg emission standard for 
lignite-fired EGUs from 4.0 lb/TBtu to 1.2 lb/TBtu and solicited 
comment on the performance of Hg controls and on cost and effectiveness 
of control strategies to meet more stringent Hg standards. Lastly, the 
EPA did not identify new developments in control technologies or 
improved methods of operation that would warrant revisions to the Hg 
emission standards for non-lignite EGUs, for the organic HAP work 
practice standards, for the acid gas standards, or for standards for 
oil-fired EGUs. Therefore, the Agency did not propose changes to these 
standards in the 2023 Proposal but did solicit comment on the EPA's 
proposed findings that no revisions were warranted and on the 
appropriateness of the existing standards.
    Additionally, the EPA proposed to remove one of the two options for 
defining the startup period for MATS-affected EGUs.
    In the 2023 Proposal, the EPA determined not to reopen the 2020 
Residual Risk Review, and accordingly did not propose any revisions to 
that review. As the EPA explained in the proposal, the EPA found in the 
2020 RTR that risks from the Coal- and Oil-Fired EGU source category 
due to emissions of air toxics are acceptable and that the existing 
NESHAP provides an ample margin of safety to protect public health. As 
noted in the proposal, the EPA also 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. The EPA granted in part the 
environmental organizations' petition which sought the EPA's review of 
startup and shutdown provisions in the 2023 Proposal, 88 FR 24885, and 
the EPA continues to review and will respond to other aspects of the 
petition in a separate action.\10\
---------------------------------------------------------------------------

    \10\ See Document ID No. EPA-HQ-OAR-2018-0794-4565 at https://www.regulations.gov.
---------------------------------------------------------------------------

III. What is included in this final rule?

    This action finalizes the EPA's determinations pursuant to the RTR 
provisions of CAA section 112 for the Coal- and Oil-Fired EGU source 
category and amends the Coal- and Oil-Fired EGU NESHAP based on those 
determinations. This action also finalizes changes to the definition of 
startup for this rule. This final rule includes changes to the 2023 
Proposal after consideration of comments received during the public 
comment period described in sections IV., V., VI., and VII. of this 
preamble.

A. What are the final rule amendments based on the technology review 
for the Coal- and Oil-Fired EGU source category?

    We determined that there are developments in practices, processes, 
and control technologies that warrant revisions to the MACT standards 
for this source category. Therefore, to satisfy the requirements of CAA 
section 112(d)(6), we are revising the MACT standards by revising the 
fPM limit for existing coal-fired EGUs from 0.030 lb/MMBtu to 0.010 lb/
MMBtu and requiring the use of PM CEMS for coal and oil-fired EGUs to 
demonstrate compliance with the revised fPM standard, as proposed. We 
are also finalizing, as proposed, a Hg limit for lignite-fired EGUs of 
1.2 lb/TBtu, which aligns with the existing Hg limit that has been in 
effect for other coal-fired EGUs since 2012. This revised Hg limit for 
lignite-fired EGUs is more stringent than the limit of 4.0 lb/TBtu that 
was finalized for such units in the 2012 MATS Final Rule. The rationale 
for these changes is discussed in more detail in sections IV. and V. 
below.
    Based on comments received during the public comment period, the 
EPA is not finalizing the proposed removal of the non-Hg HAP metals 
limits for existing coal-fired EGUs (see section V.). Additionally, 
this final rule is requiring the use of PM CEMS for compliance 
demonstration for coal- and oil-fired EGUs (excluding EGUs in the 
limited-use liquid oil-fired subcategory), but not for IGCC EGUs (see 
section VI.).
    Because this final rule includes revisions to the emissions 
standards for fPM as a surrogate for non-Hg HAP metals for existing 
coal-fired EGUs, the fPM emission standard compliance demonstration 
requirements, the Hg emission standard for lignite-fired EGUs, and the 
definition of ``startup,'' the EPA intends each portion of this rule to 
be severable from each other as it is multifaceted and addresses 
several distinct aspects of MATS for independent reasons. This includes 
the revised emission standard for fPM as a surrogate for non-Hg HAP 
metals and the fPM compliance demonstration requirement to utilize PM 
CEMS. While the EPA considered the technical feasibility of PM CEMS in 
establishing the revised fPM standard, the EPA finds there are 
independent reasons for adopting each revision to the standards, and 
that each would continue to be workable without the other in the place.

[[Page 38519]]

    The EPA intends that the various pieces of this package be 
considered independent of each other. For example, the EPA notes that 
our judgments regarding developments in fPM control technology for the 
revised fPM standard as a surrogate for non-Hg HAP metals largely 
reflect that the fleet was reporting fPM emission rates well below the 
current standard and with lower costs than estimated during 
promulgation of the 2012 MATS Final Rule; while our judgments regarding 
the ability for lignite-fired EGUs to meet the same standard for Hg 
emissions as other coal- and oil-fired EGUs rest on a separate analysis 
specific to lignite-fired units. Thus, the revised fPM surrogate 
emissions standard is feasible and appropriate even absent the revised 
Hg standard for lignite-fired units, and vice versa. Similarly, the EPA 
is finalizing changes to the fPM compliance demonstration requirement 
based on the technology's ability to provide increased transparency for 
owners and operators, regulators, and the public; and the EPA is 
finalizing changes to the startup definition based on considerations 
raised by environmental groups in petitions for reconsideration. Both 
of these actions are independent from the EPA's revisions to the fPM 
surrogate standard, and the Hg standard for lignite-fired units. 
Accordingly, the EPA finds that each set of standards is severable from 
each other set of standards.
    Finally, the EPA finds that implementation of each set of 
standards, compliance demonstration requirements, and revisions to the 
startup definition are independent. That is, a source can abide by any 
one of these individual requirements without abiding by any others. 
Thus, the EPA's overall approach to this source category continues to 
be fully implementable even in the absence of any one or more of the 
elements included in this final rule.
    Thus, the EPA has independently considered and adopted each portion 
of this final rule (including the revised fPM emission standard as a 
surrogate for non-Hg HAP metals, the fPM compliance demonstration 
requirement, the revised Hg emission standard for lignite-fired units, 
and the revised startup definition) and each is severable should there 
be judicial review. If a court were to invalidate any one of these 
elements of the final rule, the EPA intends the remainder of this 
action to remain effective. Importantly, the EPA designed the different 
elements of this final rule to function sensibly and independently. 
Further, the supporting bases for each element of the final rule 
reflect the Agency's judgment that the element is independently 
justified and appropriate, and that each element can function 
independently even if one or more other parts of the rule has been set 
aside.

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

    The EPA is finalizing, as proposed, the removal of the work 
practice standards of paragraph (2) of the definition of ``startup'' in 
40 CFR 63.10042. 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). 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 final rule requires that all EGUs use the work practice 
standards in paragraph (1) of the definition of ``startup,'' which is 
already being used by the majority of EGUs.

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

    The revisions to the MACT standards being promulgated in this 
action are effective on July 8, 2024. The compliance date for affected 
coal-fired sources to comply with the revised fPM limit of 0.010 lb/
MMBtu and for lignite-fired sources to meet the lower Hg limit of 1.2 
lb/TBtu is 3 years after the effective date of the final rule. The 
Agency believes this timeline is as expeditious as practicable 
considering the potential need for some sources to upgrade or replace 
pollution controls. As discussed elsewhere in this preamble, we are 
adding a requirement that compliance with the fPM limit be demonstrated 
using PM CEMS. Based on comments received during the comment period and 
our understanding of suppliers of PM CEMS, the EPA is finalizing the 
requirement that affected sources use PM CEMS for compliance 
demonstration by 3 years after the effective date of the final rule. 
The compliance date for existing affected sources to comply with 
amendments pertaining to the startup definition is 180 days after the 
effective date of the final rule, as few EGUs are affected, and changes 
needed to comply with paragraph (1) of startup are achievable by all 
EGUs at little to no additional expenditures. All affected facilities 
remain subject to the current requirements of 40 CFR part 63, subpart 
UUUUU, until the applicable compliance date of the amended rule.
    The EPA has considered the concerns raised by commenters that these 
compliance deadlines could affect electric reliability and concluded 
that given the flexibilities detailed further in this section, the 
requirements of the final rule for existing sources can be met without 
adversely impacting electric reliability. In particular, the EPA notes 
the flexibility of permitting authorities to allow, if warranted, a 
fourth year for compliance under CAA section 112(i)(3)(B). This 
flexibility, if needed, would address many of the concerns that 
commenters raised. Furthermore, in the event that an isolated, 
localized concern were to emerge that could not be addressed solely 
through the 1-year extension under CAA section 112(i)(3), the CAA 
provides additional flexibilities to bring sources into compliance 
while maintaining reliability.
    The EPA notes that similar concerns regarding reliability were 
raised about the 2012 MATS Final Rule--a rule that projected the need 
for significantly greater installation of controls and other capital 
investments than this current revision. In the 2012 MATS Final Rule, 
the EPA emphasized that most units should be able to comply with the 
requirements of the final rule within 3 years. However, the EPA also 
made it clear that permitting authorities have the authority to grant a 
1-year compliance extension where necessary, in a range of situations 
described in the 2012 MATS Final Rule preamble.\11\ The EPA's Office of 
Enforcement and Compliance Assurance (OECA) also issued the MATS 
Enforcement Response policy (Dec. 16, 2011) \12\ which described the 
approach regarding the issue of CAA section 113(a) administrative 
orders with respect to the sources that must operate in noncompliance 
with the MATS rule for up to 1 year to address specific documented 
reliability concerns. While several affected EGUs requested and were 
granted a 1-year CAA section 112(i)(3)(B) compliance extension by their 
permitting authority, OECA only issued five administrative orders in 
connection with the Enforcement Response policy. The 2012 MATS Final 
Rule was ultimately implemented over the 2015--2016 timeframe without 
challenges to grid reliability.
---------------------------------------------------------------------------

    \11\ 77 FR 9406.
    \12\ https://www.epa.gov/enforcement/enforcement-response-policy-mercury-and-air-toxics-standard-mats.

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[[Page 38520]]

IV. What is the rationale for our final decisions and amendments to the 
filterable PM (as a surrogate for non-Hg HAP metals) standard and 
compliance options from the 2020 Technology Review?

    In this section, the EPA provides descriptions of what we proposed, 
what we are finalizing, our rationale for the final decisions and 
amendments, and a summary of key comments and responses related to the 
emission standard for fPM, non-Hg HAP metals, and the compliance 
demonstration options. For all comments not discussed in this preamble, 
comment summaries and the EPA's responses can be found in the comment 
summary and response document National Emission Standards for Hazardous 
Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating 
Units Review of the Residual Risk and Technology Review Proposed Rule 
Response to Comments, available in the docket.
    Based on its review, the EPA is finalizing a revised non-Hg HAP 
metal surrogate fPM emission standard for all existing coal-fired EGUs 
of 0.010 lb/MMBtu and is requiring that all coal- and oil-fired EGUs 
demonstrate compliance with the revised fPM emission standard by using 
PM CEMS. The revised fPM standard will ensure that the entire fleet of 
coal-fired EGUs achieves performance levels that are consistent with 
those of the vast majority of regulated units operating today--i.e., 
that the small minority of units that currently emit significantly 
higher levels of HAP than their peers use proven technologies to reduce 
their HAP to the levels achieved by the rest of the fleet. Further, the 
EPA finds that a 0.010 lb/MMBtu fPM emission standard is the lowest 
level currently compatible with PM CEMS for demonstrating compliance, 
which the EPA finds provides significant benefits including increased 
transparency regarding emissions performance for sources, regulators, 
and the surrounding communities; and real-time identification of when 
control technologies are not performing as expected, allowing for 
quicker repairs. In addition, the rule's current requirement to shift 
electronic reporting of PM CEMS data to the Emissions Collection and 
Monitoring Plan System (ECMPS) will enable regulatory authorities, 
nearby citizens, and others, including members of the public and media, 
to quickly and easily locate, review, and download fPM emissions using 
simple, user-directed inquiries. An enhanced, web-based version of 
ECMPS (ECMPS 2.0) is currently being prepared that will ease data 
editing, importing, and exporting and is expected to be available prior 
to the date by which EGUs are required to use PM CEMS.

A. What did we propose pursuant to CAA section 112(d)(6) for the Coal- 
and Oil-Fired EGU source category?

1. Proposed Changes to the Filterable PM Standard
    The EPA proposed to lower the fPM limit, a surrogate for total non-
Hg HAP metals, for coal-fired EGUs from 0.030 lb/MMBtu to 0.010 lb/
MMBtu. The EPA further solicited comment on an emission standard of 
0.006 lb/MMBtu or lower. The EPA did not propose any changes to the fPM 
emission standard for oil-fired EGUs or for IGCC units. The EPA also 
proposed to remove the total and individual non-Hg HAP metals emission 
limits. The EPA also solicited comment on adjusting the total and 
individual non-Hg HAP metals emission limits proportionally to the 
revised fPM limit rather than eliminating the limits altogether.
2. Proposed Changes to the Requirements for Compliance Demonstration
    The EPA proposed to require that all coal- and oil-fired EGUs (IGCC 
units are discussed in section VI.) use PM CEMS to demonstrate 
compliance with the fPM emission limit. The EPA also proposed to remove 
the option of demonstrating compliance using infrequent stack testing 
and the LEE program (where stack testing occurs quarterly for 3 years, 
then every third year thereafter) for both PM and non-Hg HAP metals.

B. How did the technology review change for the Coal- and Oil-Fired EGU 
source category?

1. Filterable PM Emission Standard
    Commenters provided both supportive and opposing arguments for 
issues regarding the fPM limit that were presented in the proposed 
review of the 2020 Technology Review. Comments received on the proposed 
fPM limit for coal-fired EGUs, along with additional analyses, did not 
change the Agency's conclusions that were presented in the 2023 
Proposal, and, therefore, the Agency is finalizing the 0.010 lb/MMBtu 
fPM emission limit for existing coal-fired EGUs, as proposed.
    Additionally, commenters urged the Agency to retain the option of 
complying with individual non-Hg HAP metal (e.g., lead, arsenic, 
chromium, nickel, and cadmium) emission rates or with a total non-Hg 
HAP metal emission rate. After consideration of public comments, the 
Agency is finalizing updated limits for non-Hg HAP metals and total 
non-Hg HAP metals that have been reduced proportional to the reduction 
of the fPM emission limit from 0.030 lb/MMBtu to the new final fPM 
emission limit of 0.010 lb/MMBtu. EGU owners or operators who would 
choose to comply with the non-Hg HAP metals emission limits instead of 
the fPM limit must request and receive approval of a non-Hg HAP metal 
CMS as an alternative test method (e.g., multi-metal CMS) under the 
provisions of 40 CFR 63.7(f).
2. Compliance Demonstration Options
    Comments received on the compliance demonstration options for coal- 
and oil-fired EGUs also did not change the results of the technology 
review, therefore the Agency is finalizing the use of PM CEMS for 
compliance demonstration purposes and removing the fPM and non-Hg HAP 
metals LEE options for all coal-fired EGUs and for oil-fired EGUs 
(except those in the limited use liquid oil-fired EGU subcategory). The 
Agency received comments that some PM CEMS that are currently 
correlated for the 0.030 lb/MMBtu fPM emission limit may experience 
some difficulties should re-correlation be necessary at a lower fPM 
standard. Based on these comments and on additional review of PM CEMS 
test reports, as mentioned in sections IV.C.2. and IV.D.2., the Agency 
has made minor technical revisions to shift the basis of correlation 
testing from sampling a minimum volume per run to collecting a minimum 
mass or minimum sample volume per run and has adjusted the quality 
assurance (QA) criterion otherwise associated with the new emission 
limit. These changes will enable PM CEMS to be properly certified for 
use in demonstrating compliance with the lower fPM standard with a high 
degree of accuracy and reliability.

C. What key comments did we receive on the filterable PM and compliance 
options, and what are our responses?

1. Comments on the Filterable PM Emission Standard
    Comment: Some commenters supported the proposed fPM limit of 0.010 
lb/MMBtu as reasonable and achievable, noting that this limit is 
slightly greater than the fPM emission limit required for new and 
reconstructed units. Additionally, commenters stated CAA section 112 
was intended to improve the performance of lagging industrial sources 
and that a

[[Page 38521]]

standard that falls far behind what the vast majority of sources have 
already achieved, as the current standard does, is inadequate. Other 
commenters opposed the proposed fPM limit of 0.010 lb/MMBtu as too 
stringent. For instance, some commenters stated that the EPA did not 
provide adequate support for the proposed limit. Other commenters 
stated that the fact that the vast majority of units are achieving 
emission rates below the current limit does not constitute 
``developments in practices, processes, and control technologies.''
    Response: The EPA disagrees that the Agency has not adequately 
supported the proposed fPM limit. As described in the proposal 
preamble, the Agency conducted a review of the 2020 Technology Review 
pursuant to CAA section 112(d)(6), which focused on identifying and 
evaluating developments in practices, processes, and control 
technologies for the emission sources in the source category that 
occurred since promulgation of the 2012 MATS Final Rule. Based on that 
review, the EPA found that a majority of sources were not only 
reporting fPM emissions significantly below the current emission limit, 
but also that the fleet achieved lower fPM rates at lower costs than 
the EPA estimated when it promulgated the 2012 MATS Final Rule. The EPA 
explains these findings in more detail in section IV.D.1. of this 
preamble and elsewhere in the record. Further, the EPA finds that there 
are technological developments and improvements in PM control 
technology, which also controls non-Hg HAP metals, since the 2012 MATS 
Final Rule that informed the 2023 Proposal and this action, as 
discussed further in section IV.D.1. below. For example, industry has 
implemented ``best practices'' for monitoring ESP operation more 
carefully, and more durable materials have been adopted for FFs since 
the 2012 MATS Final Rule. The EPA also finds that these are cognizable 
developments for purposes of CAA section 112(d)(6). As other commenters 
noted, in National Association for Surface Finishing v. EPA, 795 F.3d 
1, 11 (D.C. Cir. 2015), the D.C. Circuit found that the EPA 
``permissibly identified and took into account cognizable 
developments'' based on the EPA's interpretation of the term as ``not 
only wholly new methods, but also technological improvements.'' 
Similarly, here the EPA identified a clear trend in control efficiency, 
costs, and technological improvements, which the EPA is accounting for 
in this action. Further, as discussed elsewhere in this section and in 
section IV.D.1. of this preamble, the EPA finds case law and 
substantial administrative precedent support the EPA's decision to 
update the fPM limit based upon these developments.
    Comment: Many commenters recommended that the EPA add a compliance 
margin in its achievability assumptions. These commenters conveyed that 
most EGUs typically operate well below the limit to allow for a 
compliance margin in the event of an equipment malfunction or failure, 
which they encouraged the EPA to consider when setting new limits. 
These commenters claimed that with a proposed fPM limit of 0.010 lb/
MMBtu, an appropriate design margin of 20 percent necessitates that 
control technologies must be able to achieve a limit of 0.008 lb/MMBtu 
or lower in practice. They also expressed concerns that the EPA did not 
take design margin into consideration in the cost analysis. They stated 
that by not including the need for a design margin, which the EPA has 
acknowledged the need for in at least two of the Agency's publications 
(NESHAP Analysis of Control Technology Needs for Revised Proposed 
Emission Standards for New Source Coal-fired EGUs, Document ID No. EPA-
HQ-OAR-2009-0234-20223 and PM CEMS Capabilities Summary for Performance 
Specification 11, NSPS, and MACT Rules, Document ID No. EPA-HQ-OAR-
2018-0794-5828), the EPA underpredicted the number of units that would 
require retrofits. These commenters stated that the combination of a 
very low fPM limit and having to account for the measurement 
uncertainty and correlation methodology of PM CEMS would likely 
necessitate an ``operational target limit'' of 50 percent of the 
applicable limit. Some commenters referenced the National Rural 
Electric Cooperative Association (NRECA) technical evaluation for the 
2023 Proposal titled Technical Comments on National Emissions Standard 
for Hazardous Air Pollutants: Coal- and Oil-fired Electric Utility 
Steam Generating Units Review of Residual Risk and Technology.\13\ They 
said that, even using the EPA's unrealistic ``baseline fPM rates'' and 
the lowest possible compliance margin of 20 percent, the NRECA 
technical evaluation estimated that 37 units--almost twice as many as 
the EPA's estimate--would be required to take substantial action to 
comply with the proposed limit.
---------------------------------------------------------------------------

    \13\ Technical Comments on National Emission Standards for 
Hazardous Air Pollutants: Coal- and Oil-fired Electric Utility Steam 
Generating Units Review of Residual Risk and Technology. 
Cichanowicz, et al. June 19, 2023. Attachment A to Document ID No. 
EPA-HQ-OAR-2018-0794-5994.
---------------------------------------------------------------------------

    Response: The EPA agrees that most facility operators normally 
target an emission level below the emission limit by incorporating a 
compliance margin or margin of error in case of equipment malfunctions 
or failures. As the commenters noted, the Agency has previously 
recognized that some operators target an emission level 20 to 50 
percent below the limit. However, no commenters provided data to 
suggest that ESPs or FF are unable to achieve a lower fPM limit. 
Furthermore, the Agency does not prescribe specifically how an EGU 
controls its emissions or how the unit operates. The choice to target a 
lower-level emission rate for a compliance margin is the sole decision 
of owners and operators. For facilities with more than one EGU in the 
same subcategory, owners or operators may find emissions averaging (40 
CFR 63.10009), coupled with or without a compliance margin, could help 
the facility attain and maintain emission limits as an effective, low-
cost approach. Additionally, no commenters provided data to indicate 
that every owner or operator aims to comply with the fPM limit with the 
same compliance margin. Because some operators might aim for a larger 
compliance margin than others, it would be difficult to select a 
particular assumption about compliance margin for the cost analysis. 
Every operator plans for compliance differently and the EPA cannot know 
every operator's plans for a compliance margin. Even if the EPA were to 
assume a 20 percent compliance margin in its evaluation of PM controls, 
the results of the analysis would not change the EPA's decision to 
adopt a lower fPM limit. Specifically, a 20 percent compliance margin 
assumption to a fPM limit of 0.010 lb/MMBtu would increase the number 
of affected EGUs from 33 to 53 (14.1 to 23.9 GW affected capacity) and 
the annual compliance costs from $87.2M to $147.7M. The number of EGUs 
that demonstrated an ability to meet the lower fPM limit, but do not do 
so on average and therefore would require O&M, would increase from 17 
to 27 (including the compliance margin). Similarly, the number of ESP 
upgrades (previously 11) and bag upgrades (previously 3) would also 
increase (to 20 and 4, respectively). There would be no change in the 
number of new FF installs. Therefore, cost-effectiveness values for fPM 
and individual and total non-Hg HAP metals would only increase 
slightly. Moreover, the 30-boiler operating day averaging period using 
PM CEMS for compliance

[[Page 38522]]

demonstration provides flexibility for owners and operators to account 
for equipment malfunctions, operational variability, and other issues. 
Lastly, as described in the 2023 Proposal, and updated here, the vast 
majority of coal-fired EGUs are reporting fPM emissions well below the 
revised fPM limit. For instance, the median fPM rate of the 296 coal-
fired EGUs assessed in the 2024 Technical Memo is 0.004 lb/MMBtu,\14\ 
or 60 percent below the revised fPM limit of 0.010 lb/MMBtu. The median 
fPM rate of a quarter of the best performing sources (N=74) is 0.002 
lb/MMBtu, about 80 percent below the revised fPM limit of 0.010 lb/
MMBtu. Therefore, for these reasons, the EPA disagrees with commenters 
that a compliance margin needs to be considered in the cost analysis.
---------------------------------------------------------------------------

    \14\ For the revised fPM analysis, the EPA uses two methods to 
assess the performance of the fleet: average and the 99th percentile 
of the lowest quarter of data. Values reported here use the average 
fPM rate for each EGU.
---------------------------------------------------------------------------

    The updated PM analysis, detailed in the memorandum 2024 Update to 
the 2023 Proposed Technology Review for the Coal- and Oil-Fired EGU 
Source Category (``2024 Technical Memo'') available in the docket, 
estimates that the number of EGUs that will need to improve their fPM 
emission rate to achieve a 0.010 lb/MMBtu limit has increased from the 
20 EGUs assumed in the 2023 Proposal to 33 EGUs, which is more 
consistent with the NRECA technical evaluation estimate of 37 EGUs. 
This increase is a result of updated methodology that utilizes both the 
lowest achieved fPM rate (i.e., the lowest quarter's 99th percentile) 
and the average fPM rate across all quarterly data when assessing PM 
upgrade and costs assumptions for the evaluated limits. The Agency 
disagrees with the commenters, however, that the 37 EGUs in the NRECA 
technical evaluation would require ``substantial action to comply with 
the proposed standard.'' In the Agency's revised analysis, only 13 EGUs 
would require capital investments to meet a fPM limit of 0.010 lb/
MMBtu. Of these, only two EGUs at one facility (Colstrip) currently 
without the most effective PM controls are projected to require 
installation of a FF, the costliest PM control upgrade option, to meet 
0.010 lb/MMBtu. The remaining nine EGUs projected by the EPA to require 
capital investments are estimated to require various levels of ESP 
upgrades. The EPA estimates that more than half (20 EGUs) would be able 
to comply without any capital investments and would instead require 
improvements to their existing FF or ESP as they have already 
demonstrated the ability to meet the limit, but do not do so on 
average.
    Comment: Some commenters stated that cost effectiveness is an 
important consideration in technology reviews under CAA section 
112(d)(6) and acknowledged that the EPA undertook cost-effectiveness 
analyses for the three fPM standards on which the Agency sought 
comment. However, the commenters stated, the NRECA technical evaluation 
found meaningful errors in the EPA's cost analysis, including 
unreasonably low capital cost estimates for ESP rebuilds and a failure 
to consider the variability of fPM due to changes in operation or 
facility design, by not utilizing a compliance margin. They asserted 
that these errors resulted in sizeable cost-effectiveness 
underestimates that eroded the EPA's overall determination that the 
proposed fPM limit is cost-effective. These commenters also asserted 
that the EPA's rationale was arbitrary on its face because it reversed, 
without explanation, the EPA's prior acknowledgements that a cost-
effectiveness analysis should account for the cost effectiveness of 
controls at each affected facility and not simply on an aggregate 
nationwide basis. They stated that facility-specific costs should 
factor into the EPA's assessment of what is ``necessary'' pursuant to 
the provisions of CAA section 112(d)(6) and CAA section 112(f)(2).
    Some commenters asserted that, even using the EPA's cost-
effectiveness figures, the proposed 0.010 lb/MMBtu limit is not cost-
effective. These commenters stated that the EPA's proposal to revise 
the fPM standard to 0.010 lb/MMBtu based on a cost-effectiveness 
estimate of up to $14.7 million per ton of total non-Hg HAP metals 
removed (equivalent to $44,900 per ton of fPM removed) is inconsistent 
with the EPA's prior actions because the cost-effectiveness estimate is 
substantially higher than estimates the Agency has previously found to 
be not cost-effective. They further said that, in the past, the EPA has 
decided against revising fPM standards based on cost-effectiveness 
estimates substantially lower than the cost-effectiveness estimates 
here. They said that the EPA should follow these precedents and 
acknowledge that $12.2 to $14.7 million per ton of non-Hg HAP metals 
reduced is not cost-effective. They argued that the Agency should not 
finalize the proposed standard of 0.010 lb/MMBtu for that reason. 
Further, these commenters argued that the alternative, more stringent 
limit of 0.006 lb/MMBtu is even less cost-effective at $25.6 million 
per ton of non-Hg HAP metals reduced, so it should not be considered 
either.
    The commenters provided the following examples of previous 
rulemakings where EPA found controls to not be cost-effective:
     In the Petroleum Refinery Sector technology review,\15\ 
the EPA declined to revise the fPM emission limit for existing fluid 
catalytic cracking units after finding that it would cost $10 million 
per ton of total non-Hg HAP metals reduced (in that case, equivalent to 
$23,000 per ton of fPM reduced), which was not cost-effective.
---------------------------------------------------------------------------

    \15\ Petroleum Refinery Sector Risk and Technology Review and 
New Source Performance Standards, 80 FR 75178, 75201 (December 1, 
2015).
---------------------------------------------------------------------------

     In the Iron Ore Processing technology review,\16\ the EPA 
declined to revise the non-Hg HAP metals limit after finding that 
installing wet scrubbers would cost $16 million per ton of non-Hg HAP 
metals reduced, which was not cost-effective.
---------------------------------------------------------------------------

    \16\ National Emission Standards for Hazardous Air Pollutants: 
Taconite Iron Ore Processing Residual Risk and Technology Review, 85 
FR 45476, 45483 (July 28, 2020).
---------------------------------------------------------------------------

     In the Integrated Iron and Steel Manufacturing Facilities 
technology review,\17\ the EPA declined to revise the non-Hg HAP metals 
limit after finding that upgrading all fume/flame suppressants at blast 
furnaces to baghouses would cost $7 million per ton of non-Hg HAP 
metals reduced, which was not cost-effective. The Agency made a similar 
finding for a proposed limit that would have cost $14,000 per ton of 
volatile HAP reduced.
---------------------------------------------------------------------------

    \17\ National Emission Standards for Hazardous Air Pollutants: 
Integrated Iron and Steel Manufacturing Facilities Residual Risk and 
Technology Review, 85 FR 42074, 42088 (July 13, 2020).
---------------------------------------------------------------------------

     In the Portland Cement Manufacturing beyond-the-floor 
analysis,\18\ the EPA declined to impose a more stringent non-Hg HAP 
metals limit because it resulted in ``significantly higher cost 
effectiveness for PM than EPA has accepted in other NESHAP.'' The EPA 
noted in that rulemaking that it had previously ``reject[ed] $48,501 
per ton of PM as not cost-effective for PM,'' and noted prior EPA 
statements in a subsequent rulemaking providing that $268,000 per ton 
of HAP removed was a higher cost-effectiveness estimate than the EPA 
had accepted in other NESHAP rulemakings.
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    \18\ National Emission Standards for Hazardous Air Pollutants 
for the Portland Cement Manufacturing Industry and Standards of 
Performance for Portland Cement Plants, 78 FR 10006, 10021 (February 
12, 2013).
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    In contrast, other commenters focused on the EPA's estimated cost-
effective estimates for fPM (which is a surrogate for non-Hg HAP 
metals) and argued that

[[Page 38523]]

those estimates were substantially lower than estimates that the EPA 
has considered to be cost-effective in other technology reviews. 
Therefore, these commenters concluded that the EPA should strengthen 
the limit to at least 0.010 lb/MMBtu. These commenters also pointed to 
a 2023 report by Andover Technology Partners \19\ that found that the 
cost to comply with an emission limit of 0.006 lb/MMBtu on a fleetwide 
basis was significantly less than the costs estimated by the EPA. 
Andover Technology Partners attributed this difference ``to the 
assumptions EPA made regarding the potential emission reductions from 
ESP upgrades, which result in a much higher estimate of baghouse 
retrofits in EPA's analysis for an emission rate of 0.006 lb/MMBtu.'' 
These commenters stated that meeting the lower emission limit of 0.006 
lb/MMBtu is technologically feasible using currently available 
controls, and they urged the EPA to adopt this limit. They stated that 
although cost effectiveness is less relevant in the CAA section 112 
context than for other CAA provisions, the $103,000 per ton of fPM and 
$209,000 per ton of filterable fine PM2.5 estimates that the 
EPA calculated for the 0.006 lb/MMBtu limit were reasonable and 
comparable to past practice in technology reviews under CAA section 
112(d)(6). They noted that the EPA has previously found a control 
measure that resulted in an inflation-adjusted cost of $185,000 per ton 
of PM2.5 reduced to be cost-effective for the ferroalloys 
production source category \20\ and proposed a limit for secondary lead 
smelting sources that cost an inflation-adjusted $114,000 per ton of 
fPM reduced.\21\ They argued that, using the Andover Technology 
Partners cost estimates, the 0.006 lb/MMBtu limit has even better cost-
effectiveness estimates at about $72,000 per ton of fPM reduced and 
$146,000 per ton of filterable PM2.5 reduced. These 
commenters noted that the EPA also calculated cost effectiveness based 
on allowable emissions (i.e., assuming emission reductions achieved if 
all evaluated EGUs emit at the maximum allowable amount of fPM, or 
0.030 lb/MMBtu) at $1,610,000 per ton, showing that a limit of 0.006 
lb/MMBtu allows far less pollution at low cost to the power sector. 
They concluded that all these metrics and approaches to considering 
costs show that a fPM limit of 0.006 lb/MMBtu would require cost-
effective reductions and can be achieved at a reasonable cost that 
would not jeopardize the power sector's function.
---------------------------------------------------------------------------

    \19\ Assessment of Potential Revisions to the Mercury and Air 
Toxics Standards. Andover Technology Partners. June 15, 2023. Docket 
ID No. EPA-HQ-OAR-2018-0794. Also available at https://www.andovertechnology.com/wp-content/uploads/2023/06/C_23_CAELP_Final.pdf.
    \20\ National Emission Standards for Hazardous Air Pollutants: 
Ferroalloys Production, 80 FR 37381 (June 30, 2015).
    \21\ National Emission Standards for Hazardous Air Pollutants: 
Secondary Lead Smelting, 76 FR 29032 (May 19, 2011).
---------------------------------------------------------------------------

    Additionally, some commenters cited Sierra Club v. Costle, 657 F.2d 
298, 330 (D.C. Cir. 1981), and said the case supports the EPA's 
discretion to weigh cost, energy, and environmental impacts, 
recognizing the Agency's authority to take these factors into account 
``in the broadest sense at the national and regional levels and over 
time as opposed to simply at the plant level in the immediate 
present.'' These commenters said that the EPA has the authority to 
require costs that are reasonable for the industry even if they are not 
reasonable for every facility. These commenters acknowledged that the 
EPA has discretion to consider cost effectiveness under CAA section 
112(d)(2), citing NRDC v. EPA, 749 F.3d 1055, 1060-61 (D.C. Cir. 2014), 
but argued that the dollar-per-ton cost-effectiveness metric is less 
relevant under CAA section 112 than under other CAA provisions because 
the Agency is not charged with equitably distributing the costs of 
emission reductions through a uniform compliance strategy, as the EPA 
has done in its transport rules. The commenters concluded that the 
Agency should require maximum reductions of HAP emissions from each 
regulated source category and has no authority to balance cost 
effectiveness across industries.
    Response: In this action, the EPA is acting under its authority in 
CAA section 112(d)(6) to ``review, and revise as necessary (taking into 
account developments in practices, processes, and control 
technologies), emission standards'' promulgated under CAA section 112. 
As the EPA explained in the 2023 Proposal, this technology review is 
separate and distinct from other standard-setting provisions under CAA 
section 112, such as establishing MACT floors, conducting the beyond-
the-floor analysis, and reviewing residual risk.
    Regarding the comments that the EPA underestimated costs to an 
extent that undermines the EPA's overall cost-effectiveness 
assumptions, the EPA disagrees that the Agency underestimated the 
typical costs of ESP rebuilds. The commenters provided cost examples 
from only two facilities to support their assertions regarding the 
costs of ESP rebuilds. The costs provided for one of those facilities, 
Labadie, were not the costs associated with an ESP rebuild, but instead 
were the costs associated with the full replacement of an ESP. The 
commenter stated that, ``Ameren retrofitted the entire ESP trains on 
two units in 2014/2015. On each of these units two of the three 
original existing ESPs had to be abandoned and one of the existing ESPs 
was retrofitted with new power supplies and flue gas flow 
modifications. A new state-of-the-art ESP was added to each unit to 
supplement the retrofitted ESPs.'' An ESP replacement is different from 
an ESP rebuild, and therefore the costs of an ESP replacement do not 
inform the costs of an ESP rebuild. The ESP rebuild cost provided for 
the other facility, Petersburg, was less than the EPA's final 
assumption regarding the typical cost of an ESP rebuild on a capacity-
weighted average basis. Neither of these examples provided by the 
commenter demonstrate that the EPA underestimated costs. For these 
reasons, the EPA disagrees with these commenters. Additionally, the EPA 
disagrees with these commenters that the Agency must add a compliance 
margin in its cost assumptions. As described above, the Agency does not 
prescribe specifically how an EGU must be controlled or how it must be 
operated, and the choice of overcompliance is at the sole discretion of 
the owners and operators.
    Generally, the EPA agrees with commenters that cost effectiveness, 
i.e., the costs per unit of emissions reduction, is a metric that the 
EPA consistently considers, often alongside other cost metrics, in CAA 
section 112 rulemakings where it can consider costs, e.g., beyond-the-
floor analyses and technology reviews, and agrees with commenters who 
recognize that the Agency has discretion in how it considers statutory 
factors under CAA section 112(d)(6), including costs. See e.g., 
Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 667, 673-74 
(D.C. Cir. 2013) (allowing that the EPA may consider costs in 
conducting technology reviews under CAA section 112(d)(6)); see also 
Nat'l Ass'n for Surface Finishing v. EPA, 795 F.3d 1, 11 (D.C. Cir. 
2015). The EPA acknowledges that the cost-effectiveness values for 
these standards are higher than cost-effectiveness values that the EPA 
concluded were not cost-effective and weighed against implementing more 
stringent standards for some prior rules. The EPA disagrees, however, 
that there is any particular threshold that renders

[[Page 38524]]

a rule cost-effective or not.\22\ The EPA's prior findings about cost 
effectiveness in other rules were specific to those rulemakings and the 
industries at issue in those rules. As commenters have pointed out, in 
considering cost effectiveness, the EPA will often consider what 
estimates it has deemed cost-effective in prior rulemakings. However, 
the EPA routinely views cost effectiveness in light of other factors, 
such as other relevant costs metrics (e.g., total costs, annual costs, 
and costs compared to revenues), impacts to the regulated industry, and 
industry-specific dynamics to determine whether there are 
``developments in practices, processes, and control technologies'' that 
warrant updates to emissions standards pursuant to CAA section 
112(d)(6). Some commenters, pointing to prior CAA section 112 
rulemakings where the EPA chose not to adopt more stringent controls, 
mischaracterized cost effectiveness as the sole criterion in those 
decisions. These commenters omitted any discussion of other relevant 
factors from those rulemakings that, in addition to cost effectiveness, 
counseled the EPA against adopting more stringent standards. For 
example, in the 2014 Ferroalloys rulemaking that commenters cited to, 
the EPA rejected a potential control option due to questions about 
technical feasibility and significant economic impacts the option would 
create for the industry, including potential facility closures that 
would impact significant portions of industry production.\23\ In 
contrast here, the controls at issue are technically feasible (they are 
used at facilities throughout the country) and will not have 
significant effects on the industry. Indeed, the EPA does not project 
that the final revisions to MATS will result in incremental changes in 
operational coal-fired capacity.
---------------------------------------------------------------------------

    \22\ See e.g., National Emissions Standards for Hazardous Air 
Pollutants: Ferroalloys Production, 80 FR 37366, 37381 (June 30, 
2015) (``[I]t is important to note that there is no bright line for 
determining acceptable cost effectiveness for HAP metals. Each 
rulemaking is different and various factors must be considered.'').
    \23\ National Emission Standards for Hazardous Air Pollutants: 
Ferroalloys Production, 79 FR 60238, 60273 (October 6, 2014).
---------------------------------------------------------------------------

    Similarly, in the other rulemakings these commenters pointed to, 
where the EPA found similar cost-effectiveness values to those that the 
EPA identified for the revised fPM standard here, there are distinct 
aspects of those rulemakings and industries that distinguish those 
prior actions from this rulemaking. In the 2015 Petroleum Refineries 
rulemaking, the EPA considered the cost effectiveness of developments 
at only two facilities to decide whether to deploy a standard across 
the much wider industry.\24\ Here in contrast, the EPA is basing 
updates to fPM standards for coal-fired EGUs on developments across the 
majority of the industry and the performance of the fleet as a whole, 
which has demonstrated the achievability of a more stringent standard. 
Additionally, there are inherent differences between the power sector 
and other industries that similarly distinguish prior actions from this 
rulemaking. For example, because of the size of the power sector (314 
coal-fired EGUs at 157 facilities), and because this source category is 
one of the largest stationary source emitters of Hg, arsenic, and HCl 
and is one of the largest regulated stationary source emitters of total 
HAP,\25\ even considering that this rule affects only a fraction of the 
sector, the estimated HAP reductions in this final rule (8.3 tpy) are 
higher than those in the prior rulemakings cited by the commenters (as 
are the estimated PM reductions (2,537 tpy) used as a surrogate for 
non-Hg HAP metals). In contrast, in the 2020 Integrated Iron and Steel 
Manufacturing rulemaking, the source category covered included only 11 
facilities, and the estimated reductions the EPA considered would have 
removed 3 tpy of HAP and 120 tpy of PM.\26\ Likewise, in the 2013 
Portland Cement rulemaking, the EPA determined not to pursue more 
stringent controls for the sector after finding the standard would only 
result in 138 tpy of nationwide PM reductions and that there was a high 
cost for such modest reductions.\27\ Here, the EPA estimates 
significantly greater HAP emission reductions, and fPM emission 
reductions that are orders of magnitude greater than both prior 
rulemakings.\28\
---------------------------------------------------------------------------

    \24\ Petroleum Refinery Sector Risk and Technology Review and 
New Source Performance Standards, 80 FR 75178, 75201 (December 1, 
2015).
    \25\ 2020 National Emissions Inventory (NEI) Data; https://www.epa.gov/air-emissions-inventories/2020-national-emissions-inventory-nei-data.
    \26\ National Emission Standards for Hazardous Air Pollutants: 
Integrated Iron and Steel Manufacturing Facilities Residual Risk and 
Technology Review, 85 FR 42074, 42088 (July 13, 2020).
    \27\ National Emission Standards for Hazardous Air Pollutants 
for the Portland Cement Manufacturing Industry and Standards of 
Performance for Portland Cement Plants, 78 FR 10006, 10020-10021 
(February 12, 2013).
    \28\ In addition, while commenters are correct that the EPA 
determined not to adopt more stringent controls under the iron ore 
processing technology review, the aspects of the rulemaking that the 
commenters cite to concerned whether additional controls were 
necessary to provide an ample margin of safety under a residual risk 
review. In that instance, the EPA determined not to implement more 
stringent standards under the risk review based on the installation 
of wet ESPs in addition to wet scrubbers, based on the EPA's 
determination that such improvements were not necessary to provide 
an ample margin of safety to protect public health. See National 
Emission Standards for Hazardous Air Pollutants: Taconite Iron Ore 
Processing Residual Risk and Technology Review, 84 FR 45476, 45483 
(July 28, 2020).
---------------------------------------------------------------------------

    There are also unique attributes of the power sector that the EPA 
finds support the finalization of revised standards for fPM and non-Hg 
HAP metals despite the relatively high cost-effectiveness values of 
this rulemaking as compared to other CAA section 112 rulemakings. As 
the EPA has demonstrated throughout this record, there are hundreds of 
EGUs regulated under MATS with well-performing control equipment that 
are already reporting emission rates below the revised standards, 
whereas only a handful of facilities with largely outdated or 
underperforming controls are emitting significantly more than their 
peers. That means that the communities located near these handful of 
facilities may experience exposure to higher levels of toxic metal 
emissions than communities located near similarly sized well-controlled 
plants. This is what the revised standards seek to remedy, and as 
discussed throughout this record, this goal is consistent with the 
EPA's authority under CAA section 112(d)(6) and the purpose of CAA 
section 112 more generally.
    U.S. EGUs are a major source of HAP metals emissions including 
arsenic, beryllium, cadmium, chromium, cobalt, lead, nickel, manganese, 
and selenium. Some HAP metals emitted by U.S. EGUs are known to be 
persistent and bioaccumulative and others have the potential to cause 
cancer. Exposure to these HAP metals, depending on exposure duration 
and levels of exposures, is associated with a variety of adverse health 
effects. These adverse health effects may include chronic health 
disorders (e.g., irritation of the lung, skin, and mucus membranes; 
decreased pulmonary function, pneumonia, or lung damage; detrimental 
effects on the central nervous system; damage to the kidneys; and 
alimentary effects such as nausea and vomiting). The emissions 
reductions projected under this final rule from the use of PM controls 
are expected to reduce exposure of individuals residing near these 
facilities to non-Hg HAP metals, including carcinogenic HAP.
    EGUs projected to be impacted by the revised fPM standards 
represent a small fraction of the total number of the coal-fired EGUs 
(11 percent for the 0.010 lb/MMBtu fPM limit). In addition, many 
regulated facilities are electing to retire

[[Page 38525]]

due to factors independent of the EPA's regulations, and the EPA 
typically has more information on plant retirements for this sector 
than other sectors regulated under CAA section 112. Both of these 
factors contribute to relatively higher cost-effectiveness estimates in 
this rulemaking as compared to other sectors where the EPA is not able 
to account for facility retirements and factor in shorter amortization 
periods for the price of controls.
    While some commenters stated that meeting an even lower emission 
limit of 0.006 lb/MMBtu is technologically feasible using currently 
available controls, the Agency declines to finalize this limit 
primarily due to the technological limitations of PM CEMS at this lower 
emission limit (as discussed in more detail in sections IV.C.2. and 
IV.D.2. below). Additionally, the EPA considered the higher costs 
associated with a more stringent standard as compared to the final 
standard presented in section IV.D.1.
    Finally, as mentioned in the Response to Comments document, the EPA 
finds that use of PM CEMS, which provide continuous feedback with 
respect to fPM variability, in lieu of quarterly fPM emissions testing, 
will render moot the commenter's suggestion that margin of compliance 
has not been taken into account.
    Comment: Some commenters argued that the low residual risks the EPA 
found in its review of the 2020 Residual Risk Review obviate the need 
for the EPA to revise the standards under the separate technology 
review, and that residual risk should be a relevant aspect of the EPA's 
technology review of coal- and oil-fired EGUs. These commenters argued 
that it is arbitrary and capricious for the EPA to impose high costs on 
facilities, which they claimed will only result in marginal emission 
reductions, when the EPA determined there is not an unreasonable risk 
to the environment or public health.
    Other commenters agreed with the EPA's ``two-pronged'' 
interpretation that CAA section 112(d)(6) provides authorities to the 
EPA that are distinct from the EPA's risk-based authorities under CAA 
section 112(f)(2). These commenters said that if the criteria under CAA 
section 112(d)(6) are met, the EPA must update the standards to reflect 
new developments independent of the risk assessment process under CAA 
section 112(f)(2). They said the technology-based review conducted 
under CAA section 112(d)(6) need not account for any information 
learned during the residual risk review under CAA section 112(f)(2) 
unless that information pertains to statutory factors under CAA section 
112(d)(6), such as costs. They concluded that CAA section 112(d)(6) 
requires the EPA to promulgate the maximum HAP reductions possible 
where achievable at reasonable cost and is separate from the EPA's 
residual risk analysis.
    Response: The EPA has an independent statutory authority and 
obligation to conduct the technology review separate from the EPA's 
authority to conduct a residual risk review, and the Agency agrees with 
commenters that recognized that the EPA is not required to account for 
information obtained during a residual risk review in conducting a 
technology review. The EPA's finding that there is an ample margin of 
safety under the residual risk review in no way interferes with the 
EPA's obligation to require more stringent standards under the 
technology review where developments warrant such standards. The D.C. 
Circuit has recognized the CAA section 112(d)(6) technology review and 
112(f)(2) residual review are ``distinct, parallel analyses'' that the 
EPA undertakes ``[s]eparately.'' Nat'l Ass'n for Surface Finishing v. 
EPA, 795 F.3d 1, 5 (D.C. Cir. 2015). In other recent residual risk and 
technology reviews, the EPA determined additional controls were 
warranted under technology reviews pursuant to CAA section 112(d)(6) 
although the Agency determined additional standards were not necessary 
to maintain an ample margin of safety under CAA section 112(f)(2).\29\ 
The EPA has also made clear that the Agency ``disagree[s] with the view 
that a determination under CAA section 112(f) of an ample margin of 
safety and no adverse environmental effects alone will, in all cases, 
cause us to determine that a revision is not necessary under CAA 
section 112(d)(6).'' \30\ While the EPA has considered risks as a 
factor in some previous technology reviews,\31\ that does not compel 
the Agency to do so in this rulemaking. Indeed, in other instances, the 
EPA has adopted the same standards under both CAA sections 112(f)(2) 
and 112(d)(6) based on independent rationales where necessary to 
provide an ample margin of safety and because it is technically 
appropriate and necessary to do so, emphasizing the independent 
authority of the two statutory provisions.\32\
---------------------------------------------------------------------------

    \29\ See, e.g., National Emission Standards for Hazardous Air 
Pollutants: Refractory Products Manufacturing Residual Risk and 
Technology Review, 86 FR 66045 (November 19, 2021); National 
Emission Standards for Hazardous Air Pollutants: Site Remediation 
Residual Risk and Technology Review, 85 FR 41680 (July 10, 2020); 
National Emission Standards for Hazardous Air Pollutants: Organic 
Liquids Distribution (Non-Gasoline) Residual Risk and Technology 
Review, 85 FR 40740, 40745 (July 7, 2020); National Emission 
Standards for Hazardous Air Pollutants: Generic Maximum Achievable 
Control Technology Standards Residual Risk and Technology Review for 
Ethylene Production, 85 FR 40386, 40389 (July 6, 2020); National 
Emission Standards for Hazardous Air Pollutants for Chemical 
Recovery Combustion Sources at Kraft, Soda, Sulfite, and Stand-Alone 
Semichemical Pulp Mills, 82 FR 47328 (October 11, 2017); National 
Emission Standards for Hazardous Air Pollutants: Generic Maximum 
Achievable Control Technology Standards; and Manufacture of Amino/
Phenolic Resins, 79 FR 60898, 60901 (October 8, 2014).
    \30\ National Emission Standards for Hazardous Air Pollutant 
Emissions: Group I Polymers and Resins; Marine Tank Vessel Loading 
Operations; Pharmaceuticals Production; and the Printing and 
Publishing Industry, 76 FR 22566, 22577 (April 21, 2011).
    \31\ See, e.g., National Emission Standards for Organic 
Hazardous Air Pollutants From the Synthetic Organic Chemical 
Manufacturing Industry, 71 FR 76603, 76606 (December 21, 2006); see 
also Proposed Rules: National Emission Standards for Halogenated 
Solvent Cleaning, 73 FR 62384, 62404 (October 20, 2008).
    \32\ National Emissions Standards for Hazardous Air Pollutants: 
Secondary Lead Smelting, 77 FR 556, 564 (January 5, 2012).
---------------------------------------------------------------------------

    The language and structure of CAA section 112, along with its 
legislative history, further underscores the independent nature of 
these two provisions.\33\ While the EPA is only required to undertake 
the risk review once (8 years after promulgation of the original MACT 
standards), it is required to undertake the technology review multiple 
times (at least every 8 years after promulgation of the original MACT 
standard). That Congress charged the EPA to ensure an ample margin of 
safety through the risk review, yet still required the technology 
review to be conducted on a periodic basis, demonstrates that Congress 
anticipated that the EPA would strengthen standards based on 
technological developments even after it had concluded there was an 
ample margin of safety. CAA section 112's overarching charge to the EPA 
to ``require the maximum degree of reduction in emissions of the 
hazardous air pollutants subject to this section (including a 
prohibition on such emissions)'' further demonstrates that Congress 
sought to minimize the emission of hazardous air pollution wherever 
feasible independent of a finding of risk. Moreover, as discussed 
supra, in enacting the 1990 CAA Amendments, Congress purposefully 
replaced the previous risk-based approach to establishing standards for 
HAP with a technology-driven approach. This technology-driven

[[Page 38526]]

approach recognizes the ability for the EPA to achieve substantial 
reductions in HAP based on technological improvements without the 
inherent difficulty in quantifying risk associated with HAP emission 
exposure given the complexities of the pathways through which HAP cause 
harm and insufficient availability of data to quantify their effects 
discussed in section II.B.2. Independent of risks, it would be 
inconsistent with the text, structure, and legislative history for the 
EPA to conclude that Congress intended the statute's technology-based 
approach to be sidelined after the EPA had concluded the risk review.
---------------------------------------------------------------------------

    \33\ See section II.A.2. above for further discussion of the 
statutory structure and legislative history of CAA section 112.
---------------------------------------------------------------------------

    Comment: Some commenters expressed concern that some portion of 
affected units could simply retire instead of coming into compliance 
with new requirements, potentially occurring before new generation 
could be built to replace the lost generation. During this period, a 
lack of dispatchable generation could significantly increase the 
likelihood of outages, particularly during periods of severe weather. 
In addition, some commenters argued that revising the fPM limit was 
unnecessary as there is a continuing downward trend in HAP emissions 
from early retirements of coal-fired EGUs, whereas accelerating this 
trend could have potential adverse effects on reliability. Some 
commenters also stated that as more capacity and generation is shifted 
away from coal-fired EGUs due to the Inflation Reduction Act (IRA) and 
other regulatory and economic factors, the total annual fPM and HAP 
emissions from industry will decline, regardless of whether the fPM 
limit is made more stringent.
    Response: The EPA disagrees that this rule would threaten resource 
adequacy or otherwise degrade electric system reliability. Commenters 
provided no credible information supporting the argument that this 
final rule would result in a significant number of retirements or a 
larger amount of capacity needing controls. The Agency estimates that 
this rule will require additional fPM control at less than 12 GW of 
operable capacity in 2028, which is about 11 percent of the total coal-
fired EGU capacity projected to operate in that year. The units 
requiring additional fPM controls are projected to generate less than 
1.5 percent of total generation in 2028. Moreover, the EPA does not 
project that any EGUs will retire in response to the standards 
promulgated in this final rule. Because the EPA projects no incremental 
changes in existing operational capacity to occur in response to the 
final rule, the EPA does not anticipate this rule will have any 
implications for resource adequacy.
    Nevertheless, it is possible that some EGU owners may conclude that 
retiring a particular EGU and replacing it with new capacity is a more 
economic option from the perspective of the unit's customers and/or 
owners than making investments in new emissions controls at the unit. 
The EPA understands that before implementing such a retirement 
decision, the unit's owner will follow the processes put in place by 
the relevant regional transmission organization (RTO), balancing 
authority, or state regulator to protect electric system reliability. 
These processes typically include analysis of the potential impacts of 
the proposed EGU retirement on electrical system reliability, 
identification of options for mitigating any identified adverse 
impacts, and, in some cases, temporary provision of additional revenues 
to support the EGU's continued operation until longer-term mitigation 
measures can be put in place. No commenter stated that this rule would 
somehow authorize any EGU owner to unilaterally retire a unit without 
following these processes, yet some commenters nevertheless assume 
without any rationale that is how multiple EGU owners would proceed, in 
violation of their obligations to RTOs, balancing authorities, or state 
regulators relating to the provision of reliable electric service.
    In addition, the Agency has granted the maximum time allowed for 
compliance under CAA section 112(i)(3) of 3 years, and individual 
facilities may seek, if warranted, an additional 1-year extension of 
the compliance date from their permitting authority pursuant to CAA 
section 112(i)(3)(B). The construction of any additional pollution 
control technology that EGUs might install for compliance with this 
rule can be completed within this time and will not require significant 
outages beyond what is regularly scheduled for typical maintenance. 
Facilities may also obtain, if warranted, an emergency order from the 
Department of Energy pursuant to section 202(c) of the Federal Power 
Act (16 U.S.C. 824a(c)) that would allow the facility to temporarily 
operate notwithstanding environmental limits when the Secretary of 
Energy determines doing so is necessary to address a shortage of 
electric energy or other electric reliability emergency.
    Further, despite the comments asserting concerns over electric 
system reliability, no commenter cited a single instance where 
implementation of an EPA program caused an adverse reliability impact. 
Indeed, similar claims made in the context of the EPA's prior CAA 
rulemakings have not been borne out in reality. For example, in the 
stay litigation over the Cross-State Air Pollution Rule (CSAPR), claims 
were made that allowing the rule to go into effect would compromise 
reliability. Yet in the 2012 ozone season starting just over 4 months 
after the rule was stayed, EGUs covered by CSAPR collectively emitted 
below the overall program budgets that the rule would have imposed in 
that year if the rule had been allowed to take effect, with most 
individual states emitting below their respective state budgets. 
Similarly, in the litigation over the 2015 Clean Power Plan, assertions 
that the rule would threaten electric system reliability were made by 
some utilities or their representatives, yet even though the Supreme 
Court stayed the rule in 2016, the industry achieved the rule's 
emission reduction targets years ahead of schedule without the rule 
ever going into effect. See West Virginia v. EPA, 142 S. Ct. 2587, 2638 
(2022) (Kagan, J., dissenting) (``[T]he industry didn't fall short of 
the [Clean Power] Plan's goal; rather, the industry exceeded that 
target, all on its own . . . . At the time of the repeal . . . `there 
[was] likely to be no difference between a world where the [Clean Power 
Plan was] implemented and one where it [was] not.' '') (quoting 84 FR 
32561). In other words, the claims that these rules would have had 
adverse reliability impacts proved to be groundless.
    The EPA notes that similar concerns regarding reliability were 
raised about the 2012 MATS Final Rule--a rule that projected the need 
for significantly greater installation of controls and other capital 
investments than this current revision.\34\ As with the current rule, 
the flexibility of permitting authorities to allow a fourth year for 
compliance was available in a broad range of situations, and in the 
event that an isolated, localized concern were to emerge that could not 
be addressed solely through the 1-year extension under CAA section 
112(i)(3), the CAA provides flexibilities to bring sources into 
compliance while maintaining reliability. We have seen no evidence in 
the last decade to suggest

[[Page 38527]]

that the implementation of MATS caused power sector adequacy and 
reliability problems, and only a handful of sources obtained 
administrative orders under the enforcement policy issued with MATS to 
provide relief to reliability critical units that could not comply with 
the rule by 2016.
---------------------------------------------------------------------------

    \34\ The EPA projected that the 2012 MATS Final Rule would drive 
the installation of an additional 20 GW of dry FGD (dry scrubbers), 
44 GW of DSI, 99 GW of additional ACI, 102 GW of additional FFs, 63 
GW of scrubber upgrades, and 34 GW of ESP upgrades. While a 
subsequent analysis found that the industry ultimately installed 
fewer controls than was projected, the control installations that 
occurred following the promulgation of the 2012 MATS Final Rule were 
still significantly greater than the installations that are 
estimated to occur as a result of this final rule (where, for 
example, the EPA estimates that less than 2 GW of capacity would 
install FF technology for compliance).
---------------------------------------------------------------------------

    Comment: Commenters suggested that the EPA use its authority to 
create subcategories of affected facilities that elect to permanently 
retire by the compliance date as the Agency has taken in similar 
proposed rulemakings affecting coal- and oil-fired EGUs. Commenters 
stated the EPA should subcategorize those sources that have adopted 
enforceable retirement dates and not subject those sources to any final 
rule requirements. They indicated that the EPA is fully authorized to 
subcategorize these units under CAA section 112(d)(1). Commenters asked 
that the EPA consider other simultaneous rulemakings, such as the 
proposed Greenhouse Gas Standards and Guidelines for Fossil Fuel Power 
Plants,\35\ where the EPA proposed that EGUs that elect to shut down by 
January 1, 2032, must maintain their recent historical carbon dioxide 
(CO2) emission rate via routine maintenance and operating 
procedures (i.e., no degradation of performance). Commenters also 
referenced the retirement date of December 31, 2032, in the EPA Office 
of Water's proposed Effluent Limitation Guidelines.\36\
---------------------------------------------------------------------------

    \35\ 88 FR 33245 (May 23, 2023).
    \36\ 88 FR 18824, 18837 (March 29, 2023).
---------------------------------------------------------------------------

    Commenters claimed that creating a subcategory for units facing 
near-term retirements that harmonizes the retirement dates with other 
rulemakings would greatly assist companies with moving forward on 
retirement plans without running the risk of being forced to retire 
early, which could create reliability concerns or, in the alternative, 
forced to deliberate whether to install controls and delaying 
retirement to recoup investments in the controls. Commenters also 
suggested that EGUs with limited continued operation be allowed to 
continue to perform quarterly stack testing to demonstrate compliance 
with the fPM limitations (rather than having to install PM CEMS). 
Commenters suggested that imposing different standards on these 
subcategories should continue the status quo for these units until 
retirement. Commenters claimed that it would make no sense for the EPA 
to require an EGU slated to retire in the near term to expend 
substantial resources on controls in the interim since these sources 
are very unlikely to find it viable to construct significant control 
upgrades for a revised standard that would become effective in mid-
2027, only 5 years before the unit's permanent retirement. Commenters 
further noted if the EPA does not establish such a subcategory or take 
other action to ensure these units are not negatively impacted by the 
rulemaking, the retirement of some units could be accelerated due to 
the costs of installing a PM CEMS and the need to rebuild or upgrade an 
existing ESP or install a FF to supplement an existing ESP. Commenters 
stated that the EPA cannot ignore the need for a coordinated retirement 
of thermal generating capacity while new generation sources come online 
to avoid detrimental impacts to grid reliability.
    Commenters suggested that if the EPA decides to proceed with 
finalizing the revised standards in the 2023 Proposal, the Agency 
should create a subcategory for coal-fired EGUs that elect by the 
compliance date of the revised standards (i.e., mid-2027) to retire the 
units by December 31, 2032, or January 1, 2032, if the EPA prefers to 
tie the 2023 Proposal to the proposed Emission Guidelines instead of 
the Effluent Limitation Guidelines, and maintain the current MATS 
standards for this subcategory of units. Commenters requested that the 
EPA coordinate the required retirement date for the 2023 Proposal with 
other rules so that all retirement dates align. Commenters reiterated 
that the EPA has multiple authorities with overlapping statutory 
timelines that affect commenters' plans regarding the orderly 
retirement of coal-fired EGUs and their ability to continue the 
industry's clean energy transformation while providing the reliability 
and affordability that their customers demand. Commenters suggested 
that EGUs that plan to retire by 2032 should have the opportunity to 
seek a waiver from PM CEMS installation altogether and continue 
quarterly stack testing during the remaining life of the unit. They 
also suggested that if a unit does not retire by the specified date, it 
should be required to immediately cease operation or meet the standards 
of the rule. Commenters stated that under this recommendation an EGU's 
failure to comply would then be a violation of the 2023 Proposal's 
final rule subject to enforcement.
    Response: In response to commenters' concerns, the EPA evaluated 
the feasibility of creating a subcategory for facilities with near-term 
retirements but disagrees with commenters that such a subcategory is 
appropriate for this rulemaking. In particular, the EPA found that, 
based on its own assessment and that of commenters, only a few 
facilities would likely be eligible for a near-term retirement 
subcategory and that it would not significantly reduce the costs of the 
revised standards. According to the EPA's assessment, 67 of the 296 
EGUs assessed \37\ have announced retirements between 2029 and 2032--
less than one-quarter of the fleet--and all but three of those EGUs (at 
two facilities) have already demonstrated the ability to comply with 
the 0.010 lb/MMBtu fPM standard on average. Additionally, these three 
EGUs already use PM CEMS to demonstrate compliance, therefore the 
comment requesting a waiver of PM CEMS installations for EGUs with 
near-term retirements is not relevant. Because the EPA's analysis led 
the Agency to conclude that there would be little utility to a near-
term retirement subcategory and it would not change the costs of the 
rule in a meaningful way, the EPA determined not to create a retirement 
subcategory for the fPM standard. In addition, the EPA notes that 
allowing units to operate without the best performing controls for an 
additional number of years would lead to higher levels of non-Hg HAP 
metals emissions and continued exposure to those emissions in the 
communities around these units during that timeframe. Regarding a fPM 
compliance requirement subcategory for EGUs with near-term retirements, 
the Agency estimates 26 of 67 EGUs are already using PM CEMS for 
compliance demonstration and finds that the costs to install PM CEMS 
for facilities with near-term retirements are reasonable. The Agency 
finds that the transparency provided by PM CEMS and the increased 
ability to quickly detect and correct potential control or operational 
problems using PM CEMS furthers Congress's goal to ensure that emission 
reductions are consistently maintained and makes PM CEMS the best 
choice for this rule's compliance monitoring for all EGUs.
---------------------------------------------------------------------------

    \37\ In this final rule, the EPA reviewed fPM compliance data 
for 296 coal-fired EGUs expected to be operational on January 1, 
2029. This review is explained in detail in the 2024 Technical Memo.
---------------------------------------------------------------------------

2. Comments on the Proposed Changes to the Compliance Demonstration 
Options
    Comment: The Agency received both supportive and opposing comments 
requiring the use of PM CEMS for compliance demonstration. Supportive 
commenters stated the EPA must require the use of PM CEMS to monitor 
their emissions of non-Hg HAP metals

[[Page 38528]]

as PM CEMS are now more widely deployed than when MATS was first 
promulgated, and experience with PM CEMS has enabled operators to more 
promptly detect and correct problems with pollution controls as 
compared to other monitoring and testing options allowed under MATS 
(i.e., periodic stack testing and parametric monitoring for PM), 
thereby lowering HAP emissions. They said that the fact that PM CEMS 
have been used to demonstrate compliance in a majority of units in the 
eight best performing deciles \38\ provides strong evidence that PM 
CEMS can be used effectively to measure low levels of PM emissions.
---------------------------------------------------------------------------

    \38\ Analysis of PM and Hg Emissions and Controls from Coal-
Fired Power Plants. Andover Technology Partners. August 19, 2021. 
Document ID No. EPA-HQ-OAR-2018-0794-4583.
---------------------------------------------------------------------------

    Opposing commenters urged the EPA to retain all current options for 
demonstrating compliance with non-Hg HAP metal standards, including 
quarterly PM and metals testing, LEE, and PM CPMS. These commenters 
said removing these compliance flexibility options goes beyond the 
scope of the RTR and does not address why the reasons these options 
were originally included in MATS are no longer valid. Commenters said 
they have previously raised concerns about PM CEMS that the EPA has 
avoided by stating that CEMS are not the only compliance method for PM. 
They stated that previously, the EPA has determined these compliance 
methods were both adequate and frequent enough to demonstrate 
compliance.
    Response: The Agency disagrees with commenters who suggests that 
the rule should retain all previous options for demonstrating 
compliance with either the individual metals, total metals, or fPM 
limits. Congress intended for CAA section 112 to achieve significant 
reductions of HAP, and the EPA agrees with other commenters that the 
use of CEMS in general and PM CEMS in particular enables owners or 
operators to detect and quickly correct control device or process 
issues in many cases before the issues become compliance problems. 
Consistent with the discussion contained in the 2023 Proposal (88 FR 
24872), the Agency finds the transparency and ability to quickly detect 
and correct potential control or operational problems furthers 
Congress's goal to ensure that emission reductions are consistently 
maintained and makes PM CEMS the best choice for this rule's compliance 
monitoring.
    Comment: Some commenters objected to the EPA's proposal to require 
the use of PM CEMS for purposes of demonstrating compliance with the 
revised fPM standard, stating that the requirements of Performance 
Specification 11 of 40 CFR part 60, appendix B (PS-11) will become 
extremely hard to satisfy at the low emission limits proposed. For PS-
11, relative correlation audit (RCA), and relative response audit 
(RRA), the tolerance interval and confidence interval requirements are 
expressed in terms of the emission standard that applies to the source. 
The commenters reviewed test data from operating units and found 
significantly higher PS-11 failure (>80 percent), RCA failure (>80 
percent), and RRA failure (60 percent) rates at the more stringent 
proposed emission limits. They stated that the cost, complexity, and 
failure rate of equipment calibration remains one of the biggest 
challenges with the use of PM CEMS and therefore other compliance 
demonstration methods should be retained. Commenters also noted that 
repeated tests due to failure could result in higher total emissions 
from the units.
    Response: The Agency is aware of concerns by some commenters that 
PM CEMS currently correlated for the 0.030 lb/MMBtu fPM emission limit 
may experience difficulties should re-correlation be necessary; and 
those concerns are also ascribed to yet-to-be installed PM CEMS. In 
response to those concerns, the Agency has shifted the basis of 
correlation testing from requiring only the collection of a minimum 
volume per run to also allowing the collection of a minimum mass per 
run and has adjusted the QA criterion otherwise associated with the new 
emission limit. These changes will ease the transition for coal- and 
oil-fired EGUs using only PM CEMS for compliance demonstration 
purposes. The first change, allowing the facility to choose either the 
collection of a minimum mass per run or a minimum volume per run, 
should reduce high-level correlation testing duration, addressing other 
concerns about extended runtimes with degraded emissions control or 
increased emissions, and should reduce correlation testing costs. The 
second change, adjusting the QA criteria, is consistent with other 
approaches the Agency has used when lower ranges of instrumentation or 
methods are employed. For example, in section 13.2 of Performance 
Specification 2 (40 CFR part 60, appendix B) the QA criteria for the 
relative accuracy test audit for SO2 and Nitrogen Oxide CEMS 
are relaxed as the emission limit decreases. This is accomplished at 
lower emissions by allowing a larger criterion or by modifying the 
calculation and allowing a less stringent number in the denominator. 
With these changes to the QA criteria and correlation procedures, the 
EPA believes EGUs will be able to use PM CEMS to demonstrate compliance 
at the revised level of the fPM standard.
    Comment: Some commenters asserted that if the EPA finalizes the 
requirement to demonstrate compliance using PM CEMS, EGUs will not be 
able to comply with a lower fPM limit on a continuous basis and that 
accompanying a lower limit with more restrictive monitoring 
requirements adds to the regulatory burden of affected sources and 
permitting authorities.
    Response: The EPA disagrees with commenters' claim that that EGUs 
will not be able to demonstrate compliance continuously with a fPM 
limit of 0.010 lb/MMBtu. The EPA believes that CEMS in general and PM 
CEMS in particular enable owners and operators to detect and quickly 
correct control device or process issues in many cases before the 
issues become compliance problems. Contrary to the commenter's 
assertion that EGUs will not be able to comply with a lower fPM limit 
on a continuous basis, as mentioned in the June 2023 Andover Technology 
Partners analysis,\39\ over 80 percent of EGUs using PM CEMS for 
compliance purposes have already been able to achieve and are reporting 
and certifying consistent achievement of fPM rates below 0.010 lb/
MMBtu.\40\ The EPA is unaware of any additional burden experienced by 
those EGU owners or operators or their regulatory authorities with 
regard to PM CEMS use at these lower emission levels, and does not 
expect additional burden to be placed on EGU owners or operators with 
regard to PM CEMS from application of the revised emission limit. 
However, this final rule incorporates approaches, such as switching 
from a minimum sample volume per run to collection of a

[[Page 38529]]

minimum mass sample or mass volume per run and adjusting the PM CEMS QA 
acceptability criteria, to reduce the challenges with using PM CEMS. 
Moreover, the 30-boiler-operating-day averaging period of the limit 
provides flexibility for owners and operators to account for equipment 
malfunctions and other issues. Consistent with the discussion in the 
2023 Proposal,\41\ the Agency finds that PM CEMS are the best choice 
for this rule's compliance monitoring as they provide increased 
emissions transparency, ability for EGU owner/operators to quickly 
detect and correct potential control or operational problems, and 
greater assurance of continuous compliance. While PM CEMS can produce 
values at lower levels provided correlations are developed 
appropriately, the Agency established the final fPM limit of 0.010 lb/
MMBtu after considering factors such as run times necessary to develop 
correlations, potential random error effects, and costs.
---------------------------------------------------------------------------

    \39\ Assessment of Potential Revisions to the Mercury and Air 
Toxics Standards. Andover Technology Partners. June 15, 2023. Docket 
ID No. EPA-HQ-OAR-2018-0794. June 2023. Also available at https://www.andovertechnology.com/wp-content/uploads/2023/06/C_23_CAELP_Final.pdf.
    \40\ See for example the PM CEMS Thirty Boiler Operating Day 
Rolling Average Reports for Duke's Roxboro Steam Electric Plant in 
North Carolina and at Minnesota Power's Boswell Energy Center in 
Minnesota. These reports and those from other EGUs reporting 
emission levels at or lower than 0.010 lb/MMBtu are available 
electronically by searching in the EPA's Web Factor Information 
Retrieval System (WebFIRE) Report Search and Retrieval portion of 
the Agency's WebFIRE internet website at https://cfpub.epa.gov/webfire/reports/esearch.cfm.
    \41\ See 88 FR 24872.
---------------------------------------------------------------------------

    Comment: Commenters stated that the EPA's cost estimates contradict 
the Agency's suggestion that the use of PM CEMS is a more cost-
effective monitoring approach than quarterly testing, especially for 
units that qualify as LEE. They said that the EPA used estimates from 
the Institute of Clean Air Companies (ICAC) or Envea/Altech which do 
not include numerous costs associated with PM CEMS that make them not 
cost-effective, such as the cost of intermittent stack testing 
associated with the PS-11 correlations and the ongoing costs of RCAs 
and RRA, which are a large part of the costs associated with PM CEMS 
and would rise substantially in conjunction with the proposed new PM 
limits. The commenters said that the ICAC estimated range of PM CEMS 
installation costs are particularly understated and outdated and should 
be ignored by the Agency. They said that the EPA estimates may also 
understate PM CEMS cost by assuming the most commonly used light 
scattering based PM CEMS will be used for all applications. The 
commenters said that while more expensive, a significant number of beta 
gauge PM CEMS are used for MATS compliance, especially where PM spiking 
is used for PS-11 correlation and RCA testing and that this higher 
degree of accuracy from beta gauge PM CEMS may be needed for sources 
without a margin of compliance under the new, more stringent emission 
limit.
    Response: The EPA disagrees with the commenters' suggestion that 
the Agency is required to select the most cost-effective approach for 
compliance monitoring. Rather, the Agency selects the approach that 
best provides assurance that emission limits are met. PM CEMS annual 
costs represent a very small fraction of a typical coal-fired EGU's 
operating costs and revenues. As described in the Ratio of Revised 
Estimated Non-Beta Gauge PM CEMS EUAC to 2022 Average Coal-Fired EGU 
Gross Profit memorandum, available in the docket, if all coal-fired 
EGUs were to purchase and install new PM CEMS, the Equivalent Uniform 
Annual Cost (EUAC) would represent less than four hundredths of a 
percent of the average annual operating expenses from coal-fired EGUs.
    Further, as described in the Revised Estimated Non-Beta Gauge PM 
CEMS and Filterable PM Testing Costs technical memorandum, available in 
the rulemaking docket, the EPA calculated average costs for PM CEMS and 
quarterly testing from values submitted by commenters in response to 
the proposal's solicitation, which are discussed in section IV.D. of 
the preamble. Based on the commenters' suggestions, these revised costs 
include the costs of intermittent stack testing associated with the PS-
11 correlations and ongoing costs of RCAs and RRAs. While the average 
EUAC for PM CEMS exceeds the average annual cost of quarterly stack 
emission testing, the cost for PM CEMS does not include important 
additional benefits associated with providing continuous emissions data 
to EGU owners or operators, regulators, nearby community members, or 
the general public. As a reminder, the EPA is not obligated to choose 
the most inexpensive approach for compliance demonstrations, 
particularly when all benefits are not monetized, even though costs can 
be an important consideration. Consistent with the discussion contained 
in the 2023 Proposal at 88 FR 24872, the Agency finds the increased 
transparency of EGU fPM emissions and the ability to quickly detect and 
correct potential control or operational problems, along with greater 
assurance of continuous compliance makes PM CEMS the best choice for 
this rule's compliance monitoring.
    The Agency acknowledges the commenters' suggestions that EGU owners 
or operators may find that using beta gauge PM CEMS is most appropriate 
for the lower fPM emission limit in the rule; such suggestions are 
consistent with the Agency's view, as expressed in 88 FR 24872. 
However, the Agency believes other approaches, including spiking, can 
also ease correlation testing for PM CEMS. Moreover, the Agency 
anticipates that the new fPM limit will increase demand for, and 
perhaps spur increased production of, beta gauge PM CEMS.

D. What is the rationale for our final approach and decisions for the 
filterable PM (as a surrogate for non-Hg HAP metals) standard and 
compliance demonstration options?

    The EPA is finalizing a lower fPM emission standard of 0.010 lb/
MMBtu for coal-fired EGUs, as a surrogate for non-Hg HAP metals, and 
the use of PM CEMS for compliance demonstration purposes for coal- and 
oil-fired EGUs (with the exception of limited-use liquid oil-fired 
EGUs) based on developments in the performance of sources within the 
category since the EPA finalized MATS and the advantages conferred by 
using CEMS for compliance. As described in the 2023 Proposal, non-Hg 
HAP metals are predominately a component of fPM, and control of fPM 
results in concomitant reduction of non-Hg HAP metals (with the 
exception of Se, which may be present in the filterable fraction or in 
the condensable fraction as the acid gas, SeO2). The EPA 
observes that since MATS was finalized, the vast majority of covered 
units have significantly outperformed the standard, with a small number 
of units lagging behind and emitting significantly higher levels of 
these HAP in communities surrounding those units. The EPA deems it 
appropriate to require these lagging units to bring their pollutant 
control performance up to that of their peers. Moreover, the EPA 
concludes that requiring use of PM CEMS for compliance yields manifold 
benefits, including increased emissions transparency and data 
availability for owners and operators and for nearby communities.
    The EPA's conclusions with regard to the fPM standard and 
requirement to use PM CEMS for compliance demonstration are closely 
related, both in terms of CAA section 112(d)(6)'s direction for the EPA 
to reduce HAP emissions based on developments in practices, processes, 
and control technologies, and in terms of technical compatibility.\42\ 
The EPA finds that the manifold benefits of PM CEMS render it 
appropriate to promulgate an updated fPM emission standard as a 
surrogate for non-Hg HAP metals for which PM CEMS can be used to 
monitor

[[Page 38530]]

compliance. However, as the fPM limit is lowered, operators may 
encounter difficulties establishing and maintaining existing 
correlations for the PM CEMS and may therefore be unable to provide 
accurate values necessary for compliance. The EPA has determined, based 
on comments and on the additional analysis described below, that the 
lowest possible fPM limit considering these challenges at this time is 
0.010 lb/MMBtu with adjusted QA criteria. Therefore, the EPA determined 
that this two-pronged approach--requiring PM CEMS in addition to a 
lower fPM limit--is the most stringent option that balances the 
benefits of using PM CEMS with the emission reductions associated with 
the tightened fPM emission standard. Further, the EPA finds that the 
more stringent limit of 0.006 lb/MMBtu fPM cannot be adequately 
monitored with PM CEMS at this time, because the random error component 
of measurement uncertainty from correlation stack testing is too large 
and the QA criteria passing rate for PM CEMS is too small to provide 
accurate (and therefore enforceable) compliance values. Below, we 
further describe our rationale for each change.
---------------------------------------------------------------------------

    \42\ As noted in section III.A. above, there are nonetheless 
independent reasons for adopting both the revision to the fPM 
standard and the PM CEMS compliance demonstration requirement and 
each of these changes would continue to be workable without the 
other in effect, such that the EPA finds the two revisions are 
severable from each other.
---------------------------------------------------------------------------

1. Rationale for the Final Filterable PM Emission Standard
    In the 2023 Proposal, the Agency proposed a lower fPM emission 
standard for coal-fired EGUs as a surrogate for non-Hg HAP metals based 
on developments in practices, processes, and control technologies 
pursuant to CAA section 112(d)(6), including the EPA's assessment of 
the differing performance of sources within the category and updated 
information about the cost of controls. As described in the 2023 
Proposal, non-Hg HAP metals are predominately a component of fPM, and 
control of fPM results in reduction of non-Hg HAP metals (with the 
exception of Se, which may be present in the filterable fraction or in 
the condensable fraction as the acid gas, SeO2).
    In conducting this technology review, the EPA found important 
developments that informed its proposal. First, from reviewing 
historical information contained in WebFIRE,\43\ the EPA observed that 
most EGUs were reporting fPM emission rates well below the 0.030 lb/
MMBtu standard. The fleet was achieving these performance levels at 
lower costs than estimated during promulgation of the 2012 MATS Final 
Rule. Second, there are technical developments and improvements in PM 
control technology since the 2012 MATS Final Rule that informed the 
2023 Proposal.\44\ For example, while ESP technology has not undergone 
fundamental changes since 2011, industry has learned and adopted ``best 
practices'' associated with monitoring ESP operation more carefully 
since the 2012 MATS Final Rule. For FFs, more durable materials have 
been developed since the 2012 MATS Final Rule, which are less likely to 
fail due to chemical, thermal, or abrasion failure and create risks of 
high PM emissions. For instance, fiberglass (once the most widely used 
material) has largely been replaced by more reliable and easier to 
clean materials, which are more costly. Coated fabrics, such as Teflon 
or P84 felt, also clean easier than other fabrics, which can result in 
less frequent cleaning, reducing the wear that could damage filter bags 
and reduce the effectiveness of PM capture.
---------------------------------------------------------------------------

    \43\ WebFIRE includes data submitted to the EPA from the 
Electronic Reporting Tool (ERT) and is searchable at https://cfpub.epa.gov/webfire/reports/esearch.cfm.
    \44\ Analysis of PM and Hg Emissions and Controls from Coal-
Fired Power Plants. Andover Technology Partners. August 19, 2021. 
Document ID No. EPA-HQ-OAR-2018-0794-4583.
---------------------------------------------------------------------------

    To examine potential revisions, the EPA evaluated fPM compliance 
data for the coal-fired fleet and evaluated the control efficiency and 
costs of PM controls to achieve a lower fPM standard. Based on comments 
received on the 2023 Proposal, the EPA reviewed additional fPM 
compliance data for 62 EGUs at 33 facilities (see 2024 Technical Memo 
and attachments for detailed information). The review of additional fPM 
compliance data showed that more EGUs had previously demonstrated an 
ability to meet a lower fPM rate, as shown in figure 4 of the 2024 
Technical Memo. Compared to the 2023 Proposal where 91 percent of 
existing capacity demonstrated an ability to meet 0.010 lb/MMBtu, the 
updated analysis showed that 93 percent are demonstrating the ability 
to meet 0.010 lb/MMBtu with existing controls. The EPA received 
comments on the cost assumptions for upgrading PM controls and found 
that the costs estimated at proposal were not only too high, but that 
the cost effectiveness of PM upgrades was also underestimated (i.e., 
the standard is more cost-effective than the EPA believed at proposal).
    The EPA is finalizing the fPM emission limit of 0.010 lb/MMBtu with 
adjusted QA criteria, based on developments since 2012, for the reasons 
described in this final rule and in the 2023 Proposal as the lowest 
achievable fPM limit that allows for the use of PM CEMS for compliance 
demonstration purposes. First, this level of control ensures that the 
highest emitters bring their performance to a level where the vast 
majority of the fleet is already performing. For example, as described 
above, the majority of the existing coal-fired fleet subject to this 
final rule has previously demonstrated an ability to comply with the 
lower 0.010 lb/MMBtu fPM limit at least 99 percent of the time during 
one quarter, in addition to meeting the lower fPM limit on average 
across all quarters assessed. The Agency estimates that only 33 EGUs 
are currently operating above this revised limit. Compared to some of 
the best performing EGUs, the 33 EGUs requiring additional PM control 
upgrades or maintenance are more likely to have an ESP instead of a FF 
and to demonstrate compliance using intermittent stack testing. In 
addition, most of these EGUs have operated at a higher level of 
utilization than the coal-fired fleet on average.
    Second, as discussed in section II.A.2. above, Congress updated CAA 
section 112 in the 1990 Clean Air Act Amendments to achieve significant 
reductions in HAP emissions, which it recognized are particularly 
harmful pollutants, and implemented a regime under which Congress 
directed the EPA to make swift and substantial reductions to HAP based 
upon the most stringent standards technology could achieve. This is 
evidenced by Congress's charge to the EPA to ``require the maximum 
degree of reduction in emissions of hazardous air pollutants (including 
a prohibition on such emissions),'' that is achievable accounting for 
``the cost of achieving such emission reduction, and any non-air 
quality health and environmental impacts and energy requirements. . . 
.'' CAA section 112(d)(2). Further, by creating separate and distinct 
requirements for the EPA to consider updates to CAA section 112 
pursuant to both technology review under CAA section 112(d)(6) and 
residual risk review under CAA section 112(f)(2), Congress anticipated 
that the EPA would strengthen standards pursuant to technology reviews 
``as necessary (taking into account developments in practices, 
processes, and control technologies),'' CAA section 112(d)(6), even 
after the EPA concluded there was an ample margin of safety based on 
the risks that the EPA can quantify.\45\ As the EPA explained in the

[[Page 38531]]

proposal, the EPA does consider costs, technical feasibility, and other 
factors when evaluating whether it is necessary to revise existing 
emission standards under CAA section 112(d)(6) to ensure the standards 
``require the maximum degree of emissions reductions . . . 
achievable.'' CAA section 112(d)(2). The text, structure, and history 
of this provision demonstrate Congress's direction to the EPA to 
require reduction in HAP where technology is available to do so and the 
EPA accounts for the other statutory factors.
---------------------------------------------------------------------------

    \45\ EPA's CAA section 112(f)(2) quantitative risk assessments 
evaluate cancer risk associated with a lifetime of exposure to HAP 
emissions from each source in the source category, the potential for 
HAP exposure to cause adverse chronic (or long-term) noncancer 
health effects, and the potential for HAP exposure to cause adverse 
acute (or short-term) noncancer health effects.
---------------------------------------------------------------------------

    Accordingly, the EPA finds that bringing this small number of units 
to the performance levels of the rest of the fleet serves Congress's 
mandate to the EPA in CAA section 112(d)(6) to continually consider 
developments ``that create opportunities to do even better.'' See LEAN, 
955 F.3d at 1093. As such, the EPA has a number of times in the past 
updated its MACT standards to reflect developments where the majority 
of sources were already outperforming the original MACT standards.\46\ 
Indeed, this final rule is consistent with the EPA's authority pursuant 
to CAA section 112(d)(6) to take developments in practices, processes, 
and control technologies into account to determine if more stringent 
standards are achievable than those initially set by the EPA in 
establishing MACT floors, based on developments that occurred in the 
interim. See LEAN v. EPA, 955 F.3d 1088, 1097-98 (D.C. Cir. 2020). 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, and those controls are of reasonable cost, sources should be 
required to use them.
---------------------------------------------------------------------------

    \46\ See, e.g., National Emission Standards for Hazardous Air 
Pollutants: Site Remediation Residual Risk and Technology Review, 85 
FR 41680, 41698 (July 10, 2020) (proposed 84 FR 46138, 46161; 
September 3, 2019)) (requiring compliance with more stringent 
equipment leak definitions under a technology review, which were 
widely adopted by industry); National Emissions Standards for 
Mineral Wool Production and Fiberglass Manufacturing, 80 FR 45280, 
45307 (July 29, 2015) (adopting more stringent limits for glass-
melting furnaces under a technology review where the EPA found that 
``all glass-melting furnaces were achieving emission reductions that 
were well below the existing MACT standards regardless of the 
control technology in use''); National Emissions Standards for 
Hazardous Air Pollutants From Secondary Lead Smelting, 77 FR 556, 
564 (January 5, 2012) (adopting more stringent stack lead emission 
limit under a technology review ``based on emissions data collected 
from industry, which indicated that well-performing baghouses 
currently used by much of the industry are capable of achieving 
outlet lead concentrations significantly lower than the [current] 
limit.'').
---------------------------------------------------------------------------

    The fleet has been able to ``over comply'' with the existing fPM 
standard due to the very high PM control effectiveness of well-
performing ESPs and FFs, often exceeding 99.9 percent. But the 
performance of a minority of units lags well behind the vast majority 
of the fleet. As indicated by the two highest fPM rates,\47\ EGUs 
without the most effective PM controls have not been able to 
demonstrate fPM rates comparable to the rest of the fleet. 
Specifically, the Colstrip facility, a 1,500 MW subbituminous-fired 
power plant located in Colstrip, Montana, operates the only two coal-
fired EGUs in the country without the most modern PM controls (i.e., 
ESP or FF). Instead, this facility utilizes venturi wet scrubbers as 
its primary PM control technology and has struggled to meet the 
original 0.030 lb/MMBtu fPM limit, even while employing emissions 
averaging across the operating EGUs at the facility. Colstrip is also 
the only facility where the EPA estimates the current controls would be 
unable to meet a lower fPM limit. Specifically, the 2018 second quarter 
compliance stack tests showed average fPM emission rates above the 
0.030 lb/MMBtu fPM limit, in violation of its Air Permit. Talen Energy, 
one of the owners of the facility, agreed to pay $450,000 to settle 
these air quality violations.\48\ As a result, the plant was offline 
for approximately 2.5 months while the plant's operator worked to 
correct the problem. Comments from Colstrip's majority owners discuss 
the efforts this facility has undergone to improve their wet PM 
scrubbers, which they state remove 99.7 percent of the fly ash 
particulate but agree with the EPA that additional controls would be 
needed to meet a 0.010 lb/MMBtu limit. However, as stated in 
NorthWestern Energy's Annual PCCAM Filing and Application of Tariff 
Changes,\49\ ``Colstrip has a history of operating very close to the 
upper end limit: for 43 percent of the 651 days of compliance preceding 
the forced outage its [Weighted Average Emission Rate or] WAER was 
within 0.03 lb/dekatherm \50\ of the limit [. . . to comply with the 
Air Permit and MATS, Colstrip's WAER must be equal to or less than 0.03 
lb/dekatherm].''
---------------------------------------------------------------------------

    \47\ See figure 4 of the 2024 Technical Memo.
    \48\ See Document CLT-1T Testimony, CLT-11, and CL-12 in Docket 
190882 at https://www.utc.wa.gov/documents-and-proceedings/dockets.
    \49\ See NorthWestern Energy's Annual PCCAM Filing and 
Application for Approval of Tariff Changes, Docket No. 2019.09.058, 
Final Order 7708f paragraph 21 (November 18, 2020) (noting that 
``Colstrip has a history of operating very close to the upper end 
limit''), available at https://reddi.mt.gov/prweb.
    \50\ For reference, a dekatherm is equivalent to one million 
Btus (MMBtu).
---------------------------------------------------------------------------

    The Northern Cheyenne Reservation is 20 miles from the Colstrip 
facility and the Tribe exercised its authority in 1977 to require 
additional air pollution controls on the new Colstrip units (Colstrip 3 
and 4, the same EGUs still operating today), recognizing the area as a 
Class I airshed under the CAA. According to comments submitted by the 
Northern Cheyenne Tribe, their tribal members--both those living on the 
Reservation and those living in the nearby community of Colstrip--have 
been disproportionally impacted by exposure to HAP emissions from the 
Colstrip facility.\51\
---------------------------------------------------------------------------

    \51\ See Document ID No. EPA-HQ-OAR-2018-5984 at https://www.regulations.gov.
---------------------------------------------------------------------------

    The EPA believes a fPM emission limit of 0.010 lb/MMBtu 
appropriately takes into consideration the costs of controls. The EPA 
evaluated the costs to improve current PM control systems and the cost 
to install better performing PM controls (i.e., a new FF) to achieve a 
more stringent emission limit. Costs of PM upgrades are much lower than 
the EPA estimated in 2012, and the Agency revised its costs assumptions 
as described in the 2024 Technical Memo, available in the docket. Table 
4 of this document summarizes the updated cost effectiveness of the 
three fPM emission limits considered in the 2023 Proposal for the 
existing coal-fired fleet. For the purpose of estimating cost 
effectiveness, the analysis presented in this table, described in 
detail in the 2023 and 2024 Technical Memos, is based on the observed 
emission rates of all existing coal-fired EGUs except for those that 
have announced plans to retire by the end of 2028. The analysis 
presented in table 4 estimated the costs associated for each unit to 
upgrade their existing PM controls to meet a lower fPM standard. In the 
cases where existing PM controls would not achieve the necessary 
reductions, unit-specific FF install costs were estimated. Unlike the 
cost and benefit projections presented in the RIA, the estimates in 
this table do not account for any future changes in the composition of 
the operational coal-fired EGU fleet that are likely to occur by 2028 
as a result of other factors affecting the power sector, such as the 
IRA, future regulatory actions, or changes in economic conditions. For 
example, of the more than 14 GW of coal-fired capacity that the EPA 
estimates would require control improvements to achieve the final fPM 
rate, less than 12 GW is projected to be

[[Page 38532]]

operational in 2028 (see section 3 of the RIA for this final rule).
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TR07MY24.068

BILLING CODE 6560-50-C
    The EPA has updated its costs analyses for this final rule based on 
comments received and additional data review, which is described in 
more detail in the 2024 Technical Memo available in the docket. In 
response to commenters stating that the use of the lowest quarter's 
99th percentile, or the lowest achievable fPM rate, is not indicative 
of overall EGU operation and emission performance, the EPA added a 
review of average fPM rates. In these updated analyses, both the lowest 
quarter's 99th percentile and the average fPM rate must be below the 
potential fPM limit for the EPA to assume no additional upgrades are 
needed to meet a revised limit. If an EGU has previously demonstrated 
an ability to meet a potential lower fPM limit, but the average fPM 
rate is greater than the potential limit, the analysis for the final 
rule has been updated to assume increased bag replacement frequency 
(for units with FFs) or operation and maintenance costing $100,000/year 
(2022$). This additional cost represents increased vigilance in 
maintaining ESP performance and includes technician labor to monitor 
performance of the ESP and to periodically make typical repairs (e.g., 
replacement of failed insulators, damaged electrodes or other internals 
that may fail, repairing leaks in the ESP casing, ductwork, or 
expansion joints, and periodic testing of ESP flow balance and any 
needed adjustments).
    Additionally, the Agency received comments that the PM upgrade 
costs estimated at proposal were too high on a dollar per ton basis and 
these costs have been updated and are provided in the 2024 Technical 
Memo. Specifically, commenters demonstrated that the observed percent 
reductions in fPM attributable to ESP upgrades were significantly 
greater than the percent reductions that the EPA had assumed for the 
proposed rule. Additionally, commenters demonstrated that ESP 
performance guarantees for coal-fired utility boilers were much lower 
than the EPA was aware of at proposal. These updates, as well as 
improving our methodology which increases the number of EGUs estimated 
to need PM upgrades, slightly lower the dollar per ton estimates from 
what was presented in the 2023 Proposal.
    The EPA considers costs in various ways, depending on the rule and 
affected sector. For example, the EPA has considered, in previous CAA 
section 112 rulemakings, cost effectiveness, the total capital costs of 
proposed measures, annual costs, and costs compared to total revenues 
(e.g., cost to revenue ratios).\52\ As much of the

[[Page 38533]]

fleet is already reporting fPM emission rates below 0.010 lb/MMBtu, 
both the total costs and non-Hg HAP metal reductions of the revised 
limit are modest in context of total PM upgrade control costs and 
emissions of the coal fleet. The cost-effectiveness estimate for EGUs 
reporting average fPM rates above the final fPM emission limit of 0.010 
lb/MMBtu is $10,500,000/ton of non-Hg HAP metals, slightly lower than 
the range presented in the 2023 Proposal.
---------------------------------------------------------------------------

    \52\ See, e.g., National Emission Standards for Hazardous Air 
Pollutants: Mercury Cell Chlor-Alkali Plants Residual Risk and 
Technology Review, 87 FR 27002, 27008 (May 6, 2022) (considered 
annual costs and average capital costs per facility in technology 
review and beyond-the-floor analysis); National Emission Standards 
for Hazardous Air Pollutants: Primary Copper Smelting Residual Risk 
and Technology Review and Primary Copper Smelting Area Source 
Technology Review, 87 FR 1616, 1635 (proposed January 11, 2022) 
(considered total annual costs and capital costs, annual costs, and 
costs compared to total revenues in proposed beyond-the-floor 
analysis); Phosphoric Acid Manufacturing and Phosphate Fertilizer 
Production RTR and Standards of Performance for Phosphate 
Processing, 80 FR 50386, 50398 (August 19, 2015) (considered total 
annual costs and capital costs compliance costs and annualized costs 
for technology review and beyond the floor analysis); National 
Emissions Standards for Hazardous Air Pollutants: Ferroalloys 
Production, 80 FR 37366, 37381 (June 30, 2015) (considered total 
annual costs and capital costs, annual costs, and costs compared to 
total revenues in technology review); National Emission Standards 
for Hazardous Air Pollutants: Off-Site Waste and Recovery 
Operations, 80 FR 14248, 14254 (March 18, 2015) (considered total 
annual costs and capital costs, and average annual costs and capital 
costs and annualized costs per facility in technology review); 
National Emission Standards for Hazardous Air Pollutant Emissions: 
Hard and Decorative Chromium Electroplating and Chromium Anodizing 
Tanks; and Steel Pickling-HCl Process Facilities and Hydrochloric 
Acid Regeneration Plants, 77 FR 58220, 58226 (September 19, 2012) 
(considered total annual costs and capital costs in technology 
review); Oil and Natural Gas Sector: New Source Performance 
Standards and National Emission Standards for Hazardous Air 
Pollutants Reviews, 77 FR 49490, 49523 (August 16, 2012) (considered 
total capital costs and annualized costs and capital costs in 
technology review). C.f. NRDC v. EPA, 749 F.3d 1055, 1060 (D.C. Cir. 
2014).
---------------------------------------------------------------------------

    Further, the EPA finds that costs for facilities to meet the 
revised fPM emission limit represent a small fraction of typical 
capital and total expenditures for the power sector. In the 2022 
Proposal (reaffirming the appropriate and necessary finding), the EPA 
evaluated the compliance costs that were projected in the 2012 MATS 
Final Rule relative to the typical annual revenues, capital 
expenditures, and total (capital and production) expenditures.\53\ 87 
FR 7648-7659 (February 9, 2022); 80 FR 37381 (June 30, 2015). Using 
electricity sales data from the U.S. Energy Information Administration 
(EIA), the EPA updated the analysis presented in the 2022 Proposal. We 
find revenues from retail electricity sales increased from $333.5 
billion in 2000 to a peak of $429.6 billion in 2008 (an increase of 
about 29 percent during this period) and slowly declined since to a 
post-2011 low of $388.6 billion in 2020 (a decrease of about 10 percent 
from its peak during this period) in 2019 dollars.\54\ Revenues 
increased in 2022 to nearly the same amount as the 2008 peak ($427.8 
billion). The annual control cost estimate for the final fPM standard 
based on the cost-effectiveness analysis in table 4 (see section 1c of 
the 2024 Technical Memo) of this document is a very small share of 
total power sector sales (about 0.03 percent of the lowest year over 
the 2000 to 2019 period). Making similar comparisons of the estimated 
capital and total compliance costs to historical trends in sector-level 
capital and production costs, respectively, would yield similarly small 
estimates. Therefore, as in previous CAA section 112 rulemakings, the 
EPA considered costs in many ways, including cost effectiveness, the 
total capital costs of proposed measures, annual costs, and costs 
compared to total revenues to determine the appropriateness of the 
revised fPM standard under the CAA section 112(d)(6) technology review, 
and determined the costs are reasonable.
---------------------------------------------------------------------------

    \53\ See Cost TSD for 2022 Proposal at Document ID No. EPA-HQ-
OAR-2018-0794-4620 at https://www.regulations.gov.
    \54\ 2019 dollars were used for consistency with the 2023 
Proposal.
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    In this final rule, the EPA finds that costs of the final fPM 
standard are reasonable, and that the revised fPM standard 
appropriately balances the EPA's obligation under CAA section 112 to 
achieve the maximum degree of emission reductions considering statutory 
factors, including costs. Further, the EPA finds that its consideration 
of costs is consistent with D.C. Circuit precedent, which has found 
that CAA section 112(d)(2) expressly authorizes cost consideration in 
other aspects of the standard-setting process, such as CAA section 
112(d)(6), see Association of Battery Recyclers, Inc. v. EPA, 716 F.3d 
667, 673-74 (D.C. Cir. 2013), and that CAA section 112 does not mandate 
a specific method of cost analysis in an analogous situation when 
considering the beyond-the-floor review. See NACWA v. EPA, 734 F.3d 
1115, 1157 (D.C. Cir. 2013) (finding the statute did not ``mandate a 
specific method of cost analysis''); see also NRDC v. EPA, 749 F.3d 
1055, 1060-61 (D.C. Cir. 2014).
    As discussed in section IV.C.1. in response to comments regarding 
the relatively higher dollar per ton cost effectiveness of the final 
fPM standard, the EPA finds that in the context of this industry and 
this rulemaking, the updated standards are an appropriate exercise of 
the EPA's standard setting authority pursuant to the CAA section 
112(d)(6) technology review. As commenters rightly note, the EPA 
routinely considers the cost effectiveness of potential standards where 
it can consider costs under CAA section 112, e.g., in conducting 
beyond-the-floor analyses and technology reviews, to determine the 
achievability of a potential control option. And the D.C. Circuit 
recognized that the EPA's interpretation of costs as ``allowing 
consideration of cost effectiveness was reasonable.'' NRDC v. EPA, 749 
F.3d 1055, 1060-61 (D.C. Cir. 2014) (discussing the EPA's consideration 
of cost effectiveness pursuant to a CAA section 112(d)(2) beyond-the-
floor analysis). However, cost effectiveness is not the sole factor 
that the EPA considers when determining the achievability of a 
potential standard in conducting a technology review, nor is cost 
effectiveness the only value that the EPA considers with respect to 
costs.\55\ Some commenters pointed to other rulemakings (which are 
discussed in section IV.C.1. above) where the EPA determined not to 
pursue potential control options with relatively higher cost-
effectiveness estimates as compared to prior CAA section 112 
rulemakings. However, there were other factors that the EPA considered, 
in addition to cost effectiveness, that counseled against pursuing such 
updates. In this rulemaking, the EPA finds that several factors 
discussed throughout this record make promulgation of the new fPM 
standard appropriate under CAA section 112(d)(6). First, a wide 
majority of units have invested in the most-effective PM controls and 
are already demonstrating compliance with the new fPM standard and at 
lower costs than assumed during promulgation of the original MATS fPM 
emission limit. Of the 33 EGUs that the EPA estimated would require 
control improvements to meet a 0.010 lb/MMBtu fPM standard, only two 
are not using the most effective PM control technologies available. The 
EPA assumed that these two units would need to install FFs to achieve 
the 0.010 lb/MMBtu emission standard, and the cost of those FF 
retrofits accounts for 42 percent of the total annualized costs 
presented in table 4. Further, 11 EGUs that the EPA assumed would 
require different levels of ESP upgrades to meet the 0.010 lb/MMBtu 
emission standard (all of which have announced retirement dates between 
2031 and 2042 resulting in shorter assumed amortization periods) 
account for about 57 percent of the total annualized costs. The 
remaining 1 percent of the total annualized costs are associated with 
10 EGUs with existing FFs that the EPA

[[Page 38534]]

assumes will require bag upgrades or increased bag changeouts and 10 
EGUs that are assumed to need additional operation and maintenance of 
existing ESPs, which is further explained in the 2024 Technical Memo. 
Since only a small handful of units emit significantly more than peer 
facilities, the Agency finds these upgrades appropriate. Additionally, 
the size and unique nature of the coal-fired power sector, and the 
emission reductions that will be achieved by the new standard, in 
addition to the costs, make promulgation of the new standard 
appropriate under CAA section 112(d)(6).
---------------------------------------------------------------------------

    \55\ See note 50, above, for examples of other costs metrics the 
EPA has considered in prior CAA section 112 rulemakings.
---------------------------------------------------------------------------

    The power sector also operates differently than other industries 
regulated under CAA section 112.\56\ For example, the power sector is 
publicly regulated, with long-term decision-making and reliability 
considerations made available to the public; it is a data-rich sector, 
which generally allows the EPA access to better information to inform 
its regulation; and the sector is in the midst of an energy generation 
transition leading to plant retirements that are independent of EPA 
regulation. Because of the relative size of the power sector, while 
cost effectiveness of the final standard is relatively high as compared 
to prior CAA section 112 rulemakings involving other industries, costs 
represent a much smaller fraction of industry revenue. In the likely 
case that the power sector's transition to lower-emitting generation is 
accelerated by the IRA, for example, the total costs and emission 
reductions achieved by each final fPM standard in table 4 of this 
document would also be an overestimate.
---------------------------------------------------------------------------

    \56\ This is a fact which Congress recognized in requiring the 
EPA to first determine whether regulation of coal-fired EGUs was 
``appropriate and necessary'' under CAA section 112(n)(1)(A) before 
proceeding to regulate such facilities under CAA section 112's 
regulatory scheme.
---------------------------------------------------------------------------

    As demonstrated in the proposal, the power sector, as a whole, is 
achieving fPM emission rates that are well below the 0.030 lb/MMBtu 
standard from the 2012 Final MATS Rule, with the exception of a few 
outlier facilities. The EPA estimates that only one facility (out of 
the 151 evaluated coal-fired facilities), which does not have the most 
modern PM pollution controls and has been unable to demonstrate an 
ability to meet a lower fPM limit, will be required to install the 
most-costly upgrade to meet the revised standards, which significantly 
drives up the cost of this final rule. However, the higher costs for 
one facility to install demonstrated improvements to its control 
technology should not prevent the EPA from establishing achievable 
standards for the sector under the EPA's CAA section 112(d)(6) 
authority. Instead, the EPA finds that it is consistent with its CAA 
section 112(d)(6) authority to consider the performance of the industry 
at large. The average fPM emissions of the industry demonstrate the 
technical feasibility of higher emitting facilities to meet the new 
standard and shows there are proven technologies that if installed at 
these units will allow them to significantly lower fPM and non-Hg HAP 
metals emissions.
    In this rulemaking, the EPA also determined not to finalize a more 
stringent standard for fPM emissions, such as a limit of 0.006 lb/MMBtu 
or lower, which the EPA took comment on in the 2023 Proposal. The EPA 
declines to finalize an emission standard of 0.006 lb/MMBtu or lower 
primarily due to technical limitations in using PM CEMS for compliance 
demonstration purposes described in the next section. The EPA has 
determined that a fPM emission standard of 0.010 lb/MMBtu is the lowest 
that would also allow the use of PM CEMS for compliance demonstration. 
Additionally, the EPA also considered the overall higher costs 
associated with a more stringent standard as compared to the final 
standard, which the EPA considered under the technology review.
    Additionally, compliance with a fPM emission limit of 0.006 lb/
MMBtu could only be demonstrated using periodic stack testing that 
would require test run durations longer than 4 hours \57\ and would not 
provide the source, the public, and regulatory authorities with 
continuous, transparent data for all periods of operation. Establishing 
a fPM limit of 0.006 lb/MMBtu while maintaining the current compliance 
demonstration flexibilities of quarterly ``snapshot'' stack testing 
would, theoretically, result in greater emission reductions; however, 
the measured emission rates are only representative of rates achieved 
at optimized conditions at full load. While coal-fired EGUs have 
historically provided baseload generation, they are being dispatched 
much more as load following generating sources due to the shift to more 
available and cheaper natural gas and renewable generation. As such, 
traditional generation assets--such as coal-fired EGUs--will likely 
continue to have more startup and shutdown periods, more periods of 
transient operation as load following units, and increased operation at 
minimum levels, all of which can produce higher PM emission rates. 
Maintaining the status quo with quarterly stack testing will likely 
mischaracterize emissions during these changing operating conditions. 
Thus, while a fPM emission limit of 0.006 lb/MMBtu paired with use of 
quarterly stack testing may appear to be more stringent than the 0.010 
lb/MMBtu standard paired with use of PM CEMS that the EPA is finalizing 
in this rule, there is no way to confirm emission reductions during 
periods in between quarterly tests when emission rates may be higher. 
Therefore, the Agency is finalizing a fPM limit of 0.010 lb/MMBtu with 
the use of PM CEMS as the only means of compliance demonstration. The 
EPA has determined that this combination of fPM limit and compliance 
demonstration represents the most stringent available option taking 
into account the statutory considerations.
---------------------------------------------------------------------------

    \57\ Run durations greater than 4 hours would ensure adequate 
sample collection and lower random error contributions to 
measurement uncertainty for a limit of 0.006 lb/MMBtu. The EPA aims 
to keep run durations as short as possible, generally at least one 
but no more than 4 hours in length, in order to minimize impacts to 
the facility (e.g., overall testing campaign testing costs, employee 
focused attention and safety).
---------------------------------------------------------------------------

    The EPA also determined not to finalize a fPM standard of 0.015 lb/
MMBtu, which the EPA took comment on in the 2023 Proposal, because the 
EPA determined that a standard of 0.010 lb/MMBtu is appropriate for the 
reasons discussed above.
    In this rule, the EPA is also reaching a different conclusion from 
the 2020 Technology Review with respect to the fPM emission standard 
and requirements to utilize PM CEMS. As discussed in section II.D. 
above, the 2020 Technology Review did not consider developments in the 
cost and effectiveness of proven technologies to control fPM as a 
surrogate for non-Hg HAP metals emissions, nor did the EPA evaluate the 
current performance of emission reduction control equipment and 
strategies at existing MATS-affected EGUs. In this rulemaking, in which 
the EPA reviewed the findings of the 2020 Technology Review, the Agency 
determined there are important developments regarding the emissions 
performance of the coal-fired EGU fleet, and the costs of achieving 
that performance that are appropriate for the EPA to consider under its 
CAA section 112(d)(6) authority, and which are the basis for the 
revised emissions standards the EPA is promulgating through this final 
rule.
    The 2012 MATS Final Rule contains emission limits for both 
individual and total non-Hg HAP metals (e.g., lead, arsenic, chromium, 
nickel, and cadmium), as well as emission limits for fPM. Those non-Hg 
HAP metals

[[Page 38535]]

emission limits serve as alternative emission limits because fPM was 
found to be a surrogate for either individual or total non-Hg HAP 
metals emissions. While EGU owners or operators may choose to 
demonstrate compliance with either the individual or total non-Hg HAP 
metals emission limits, the EPA is aware of just one owner or operator 
who has provided non-Hg HAP metals data--both individual and total--
along with fPM data, for compliance demonstration purposes. This is for 
a coal refuse-fired EGU with a generating capacity of 46.1 MW. Given 
that owners or operators of all the other EGUs that are subject to the 
requirements in MATS have chosen to demonstrate compliance with only 
the fPM emission limit, the EPA proposed to remove the total and 
individual non-Hg HAP metals emission limits from all existing MATS-
affected EGUs and solicited comment on our proposal. In the 
alternative, the EPA took comment on whether to retain total and/or 
individual non-Hg HAP metals emission limits that have been lowered 
proportionally to the revised fPM limit (i.e., revised lower by two-
thirds to be consistent with the revision of the fPM standard from 
0.030 lb/MMBtu to 0.010 lb/MMBtu).
    Commenters urged the EPA to retain the non-Hg HAP metals limits, 
arguing it is incongruous for the EPA to eliminate the measure for the 
pollutants that are the subject of regulation under CAA section 
112(d)(6), notwithstanding the fact that the fPM limit serves as a more 
easily measurable surrogate for these HAP metals. Additionally, some 
commenters stated that the inability to monitor HAP metals directly 
will significantly impair the EPA's ability to revise emission 
standards in the future.
    After considering comments, the EPA determined to promulgate 
revised total and individual non-Hg HAP metals emission limits for 
coal-fired EGUs that are lowered proportionally to the revised fPM 
standard. Just as this rule requires owners or operators to demonstrate 
continuous compliance with fPM limits, owners or operators who choose 
to demonstrate compliance with these alternative limits will need to 
utilize approaches that can measure non-Hg HAP metals on a continuous 
basis--meaning that intermittent emissions testing using Reference 
Method 29 will not be a suitable approach. Owners or operators may 
petition the Administrator to utilize an alternative test method that 
relies on continuous monitoring (e.g., multi-metal CMS) under the 
provisions of 40 CFR 63.7(f). The EPA disagrees with the suggestion 
that failure to monitor HAP metals directly could impair the ability to 
revise those standards in the future.
2. Rationale for the Final Compliance Demonstration Options
    In the 2023 Proposal, the EPA proposed to require that coal- and 
oil-fired EGUs utilize PM CEMS to demonstrate compliance with the fPM 
standard used as a surrogate for non-Hg HAP metals. The EPA proposed 
the requirement for PM CEMS based on its assessment of costs of PM CEMS 
versus stack testing, and the many other benefits of using PM CEMS 
including increased transparency and accelerated identification of 
anomalous emissions. In particular, the EPA noted the ability for PM 
CEMS to provide continuous feedback on control device and plant 
operations and to provide EGU owners and operators, regulatory 
authorities, and members of nearby communities with continuous 
assurance of compliance with emissions limits as an important benefit. 
Further, the EPA explained in the 2023 Proposal that PM CEMS are 
currently in use by approximately one-third of the coal-fired fleet, 
and that PM CEMS can provide low-level measurements of fPM from 
existing EGUs.
    After considering comments and conducting further analysis,\58\ the 
EPA is finalizing the use of PM CEMS for compliance demonstration 
purposes for coal- and oil-fired EGUs pursuant to its CAA section 
112(d)(6) authority. As discussed in section IV.D.1. above, Congress 
intended for CAA section 112 to achieve significant reductions in HAP, 
which it recognized as particularly harmful pollutants. The EPA finds 
that the benefits of PM CEMS to provide real-time information to owners 
and operators (who can promptly address any problems with emissions 
control equipment), to regulators, to adjacent communities, and to the 
general public, further Congress's goal to ensure that emission 
reductions are consistently maintained. The EPA determined not to 
require PM CEMS for existing IGCC EGUs, described in section VI.D., due 
to technical issues calibrating CEMS on these types of EGUs due to the 
difficulty in preparing a correlation range because these EGUs are 
unable to de-tune their fPM controls and their existing emissions are 
less than one-tenth of the final emission limit. Further, the EPA finds 
additional authority to require the use of PM CEMS under CAA section 
114(a)(1)(C), which allows that the EPA may require a facility that 
``may have information necessary for the purposes set forth in this 
subsection, or who is subject to any requirement of this chapter'' to 
``install, use, and maintain such monitoring equipment'' on a ``on a 
one-time, periodic or continuous basis.'' 114(a)(1)(C).
---------------------------------------------------------------------------

    \58\ The EPA explains additional analyses of PM CEMS in the 
memos titled Suitability of PM CEMS Use for Compliance Determination 
for Various Emissions Levels and Summary of Review of 36 PM CEMS 
Performance Test Reports versus PS11 and Procedure 2 of 40 CFR part 
60, appendices B and F, respectively, which are available in the 
docket.
---------------------------------------------------------------------------

    From the EPA's review of PM CEMS, the Agency determined that a fPM 
standard of 0.010 lb/MMBtu with adjusted QA criteria--used to verify 
consistent correlation of CEMS data initially and over time--is the 
lowest fPM emission limit possible at this time with use of PM 
CEMS.\59\ PM CEMS correlated using these values will ensure accurate 
measurements--either above, at, or below this emission limit. As 
discussed in section IV.D.1. above, one of the reasons the EPA 
determined not to finalize a more stringent standard for fPM is because 
it would prove challenging to verify accurate measurement of fPM using 
PM CEMS. Specifically, as mentioned in the Suitability of PM CEMS Use 
for Compliance Determination for Various Emission Levels, memorandum, 
available in the docket, no fPM standard more stringent than 0.010 lb/
MMBtu with adjusted QA criteria is expected to have acceptable passing 
rates for the QA checks or acceptable random error for reference method 
testing.
---------------------------------------------------------------------------

    \59\ The EPA notes that the fPM standard [0.010 lb/MMBtu] is 
based on hourly averages obtained from PM CEMS over 30 boiler 
operating days [see 40 CFR 63.10021(b)].
---------------------------------------------------------------------------

    At proposal, the EPA estimated that the EUAC of PM CEMS was $60,100 
(88 FR 24873). Based on comments the EPA received on the costs and 
capabilities of PM CEMS and additional analysis the EPA conducted, the 
EPA determined that the revised EUAC of PM CEMS is higher than 
estimated at proposal. The EPA now estimates that the EUAC of non-beta 
gauge PM CEMS is $72,325, which is 17 percent less than what was 
estimated for the 2012 MATS Final Rule. That amount is somewhat greater 
than the revised estimated costs of infrequent emission testing 
(generally quarterly)--the revised average estimated costs of such 
infrequent emissions testing using EPA Method 5I \60\ is $60,270.\61\
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    \60\ Method 5I is one of the EPA's reference test methods for 
PM. See 40 CFR part 60, appendix A.
    \61\ See Revised Estimated Non-Beta Gauge PM CEMS and Filterable 
PM Testing Costs memorandum, available in the docket.
---------------------------------------------------------------------------

    In choosing a compliance demonstration requirement, the EPA 
considers multiple factors, including

[[Page 38536]]

costs, benefits of the compliance technique, technical feasibility and 
commercial availability of the compliance method, ability of personnel 
to conduct the compliance method, and continuity of data used to assure 
compliance. PM CEMS are readily available and in widespread use by the 
electric utility industry, as evidenced by the fact that over 100 EGUs 
already utilize PM CEMS for compliance demonstration purposes. 
Moreover, the electric utility industry and its personnel have 
demonstrated the ability to install, operate, and maintain numerous 
types of CEMS--including PM CEMS. As mentioned earlier, EGU owners and/
or operators who chose PM CEMS for compliance demonstration have 
attested in their submitted reports to the suitability of their PM CEMS 
to measure at low emission levels, certifying fPM emissions lower than 
0.010 lb/MMBtu with their existing correlations developed using 
emission levels at 0.030 lb/MMBtu. The EPA conducted a review of eight 
EGUs with varying fPM control devices that rely on PM CEMS that showed 
certified emissions ranging from approximately 0.002 lb/MMBtu to 
approximately 0.007 lb/MMBtu. The EPA's review analyzed 30 boiler 
operating day rolling averages obtained from reports posted to WebFIRE 
for the third quarter of 2023 from these eight EGUs.\62\
---------------------------------------------------------------------------

    \62\ See Third Quarter 2023 p.m. CEMS Thirty Boiler Operating 
Day Rolling Average Reports for Iatan Generating Station units 1 and 
2, Missouri; Marshall Steam Station units 1 and 3, North Carolina; 
Kyger Creek Station unit 3, Ohio; Virginia City Hybrid Energy Center 
units 1 and 2, Virginia; and Ghent Generating Station unit 1, 
Kentucky. These reports are available electronically by searching in 
the WebFIRE Report Search and Retrieval portion of the Agency's 
WebFIRE internet website at https://cfpub.epa.gov/webfire/reports/esearch.cfm.
---------------------------------------------------------------------------

    As described in the Summary of Review of 36 PM CEMS Performance 
Test Reports versus PS11 and Procedure 2 of 40 CFR part 60, Appendices 
B and F memorandum, available in the docket, the EPA investigated how 
well a sample of EGUs using PM CEMS for compliance purposes would meet 
initial and ongoing QA requirements at various emission limit levels, 
even though no change in actual EGU operation occurred. As described in 
the aforementioned Suitability of PM CEMS Use for Compliance 
Determination for Various Emission Levels memorandum, as the emission 
limit is lowered, the ability to meet both components necessary to 
correlate PM CEMS--acceptable random error and QA passing rate 
percentages--becomes more difficult. Based on this additional analysis 
and review, the EPA determined to finalize requirements to use PM CEMS 
with adjusted QA criteria and a 0.010 lb/MMBtu fPM emission limit as 
the most stringent limit possible with PM CEMS.
    Use of PM CEMS can provide EGU owners or operators with an 
increased ability to detect and correct potential problems before 
degradation of emission control equipment, reduction or cessation of 
electricity production, or exceedances of regulatory emission 
standards. As mentioned in the Ratio of Revised Estimated Non-Beta 
Gauge PM CEMS EUAC to 2022 Average Coal-Fired EGU Gross Profit 
memorandum, using PM CEMS can be advantageous, particularly since their 
EUAC is offset if their use allows owners or operators to avoid 3 or 
more hours of generating downtime per year.
    In deciding whether to finalize the proposal to use PM CEMS as the 
only compliance demonstration method for non-IGCC coal- and oil-fired 
EGUs, the Agency assessed the costs and benefits afforded by requiring 
use of only PM CEMS as compared to continuing the current compliance 
demonstration flexibilities (i.e., allowing use of either PM CEMS or 
infrequent PM emissions stack testing). As mentioned above, the average 
annual cost for quarterly stack testing provided by commenters is about 
$12,000 less than the EUAC for PM CEMS. While no estimate of quantified 
benefits was provided by commenters, the EPA recognizes that the 35,040 
15-minute values provided by a PM CEMS used at an EGU operating during 
a 1-year period is over 243 times as much information as is provided by 
quarterly testing with three 3-hour run durations. This additional, 
timely information provided by PM CEMS affords the adjacent 
communities, the general public, and regulatory authorities with 
assurances that emission limits and operational processes remain in 
compliance with the rule requirements. It also provides EGU owners or 
operators with the ability to quickly detect, identify, and correct 
potential control device or operational problems before those problems 
become compliance issues. When establishing emission standards under 
CAA section 112, the EPA must select an approach to compliance 
demonstration that best assures compliance is being achieved.
    The continuous monitoring of fPM required in this rule provides 
several benefits which are not quantified in this rule, including 
greater certainty, accuracy, transparency, and granularity in fPM 
emissions information than exists today. Continuous measurement of 
emissions accounts for changes to processes and fuels, fluctuations in 
load, operations of pollution controls, and equipment malfunctions. By 
measuring emissions across all operations, power plant operators and 
regulators can use the data to ensure controls are operating properly 
and to assess compliance with relevant standards. Because CEMS enable 
power plant operators to quickly identify and correct problems with 
pollution control devices, it is possible that continuous monitoring 
could lead to lower fPM emissions for periods of time between otherwise 
required intermittent testing, currently up to 3 years for some units.
    To illustrate the potentially substantial differences in fPM 
emissions between intermittent and continuous monitoring, the EPA 
analyzed emissions at several EGUs for which both intermittent and 
continuous monitoring data are available. This analysis is provided in 
the 2024 Technical Memo, available in the rulemaking docket. For 
example, one 585-MW bituminous-fired EGU, with a cold-side ESP for PM 
control, has achieved LEE status for fPM and is currently required to 
demonstrate compliance with an emission standard of 0.015 lb/MMBtu 
using intermittent stack testing every 3 years. In the most recent LEE 
compliance report, submitted on February 25, 2021, the unit submitted 
the result of an intermittent stack test with an emission rate of 
0.0017 lb/MMBtu. In the subsequent 36 months over which this unit is 
currently not subject to any further compliance testing, continuous 
monitoring demonstrates that the fPM emission rate increased 
substantially. At one point, the continuously monitored 30-day rolling 
average emissions rate \63\ was nine times higher than the intermittent 
stack test average, reaching the fPM LEE limit of 0.015 lb/MMBtu. In 
this example, the actual continuously monitored daily average emissions 
rate over the February 2021 to April 2023 period ranged from near-zero 
to 0.100 lb/MMBtu. Emissions using either the stack test average or 
hourly PM CEMS data were calculated for 2022 for this unit. Both 
approaches indicate fPM emissions well below the allowable levels for a 
fPM limit of 0.010 lb/MMBtu, while estimates using PM CEMS are about 
2.5 times higher than the stack test estimate. Additional examples of 
differences between intermittent stack testing and continuous 
monitoring are provided in the 2024 Technical Memo, including for 
periods when PM CEMS data is lower

[[Page 38537]]

than the stack test averages,\64\ which further illustrate real-life 
scenarios in which fPM emissions for compliance methods may be 
substantially different.
---------------------------------------------------------------------------

    \63\ The 30-day rolling average emission rate was calculated by 
taking daily fPM rate averages over a 30-day operating period while 
filtering out hourly fPM data during periods of startup and 
shutdown.
    \64\ See Case Study 2 in the 2024 Technical Memo, which shows 
long time periods of PM CEMS data below the most recent RRA. Note 
this unit uses PM CEMS for compliance with the fPM standard, so the 
RRA is used as an indicator of stack test results.
---------------------------------------------------------------------------

    The potential reduction in fPM and non-Hg HAP metals emission 
resulting from the information provided by continuous monitoring 
coupled with corrective actions by plant operators could be sizeable 
over the total capacity that the EPA estimates would install PM CEMS 
under this rule (nearly 82 GW). Furthermore, the potential reduction in 
non-Hg HAP metal emissions would likely reduce exposures to people 
living in proximity to the coal-fired EGUs potentially impacted by the 
amended fPM standards. The EPA has found that populations living near 
coal-fired EGUs have a higher percentage of people living below two 
times the poverty level than the national average.
    In addition to significant value of further pollution abatement, 
the CEMS data are transparent and accessible to regulators, 
stakeholders, and the public, fostering greater accountability. 
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. This transparency is facilitated by a requirement for 
electronic reporting of fPM emissions data by the source to the EPA. 
This emissions data, once submitted, becomes accessible and 
downloadable--along with other operational and emissions data (e.g., 
for SO2, CO2, NOX, Hg, etc.) for each 
covered source.
    On balance, the Agency finds that the benefits of emissions 
transparency and the continuous information stream provided by PM CEMS 
coupled with the ability to quickly detect and correct problems 
outweigh the minor annual cost differential from quarterly stack 
testing. The EPA is finalizing, as proposed, the use of PM CEMS to 
demonstrate compliance with the fPM emission standards for coal- and 
oil-fired EGUs (excluding IGCC units and limited-use liquid-oil-fired 
EGUs).
    More information on the proposed technology review can be found in 
the 2023 Technical Memo (Document ID No. EPA-HQ-OAR-2018-0794-5789), in 
the preamble for the 2023 Proposal (88 FR 24854), and the 2024 
Technical Memo, available in the docket. For the reasons discussed 
above, pursuant to CAA section 112(d)(6), the EPA is finalizing, as 
proposed, the use of PM CEMS (with adjusted QA criteria as a result of 
review of comments) for the compliance demonstration of the fPM 
emission standard (as a surrogate for non-Hg HAP metal) for coal- and 
oil-fired EGUs, and the removal of the fPM and non-Hg HAP metals LEE 
provisions.

V. What is the rationale for our final decisions and amendments to the 
Hg emission standard for lignite-fired EGUs from review of the 2020 
Technology Review?

A. What did we propose pursuant to CAA section 112(d)(6) for the 
lignite-fired EGU subcategory?

    In the 2012 MATS Final Rule, the EPA finalized a Hg emission 
standard of 4.0E-06 lb/MMBtu (4.0 lb/TBtu) for a subcategory of 
existing lignite-fired EGUs.\65\ The EPA also finalized a Hg emission 
standard of 1.2E-06 lb/MMBtu (1.2 lb/TBtu) for coal-fired EGUs not 
firing lignite (i.e., for EGUs firing anthracite, bituminous coal, 
subbituminous coal, or coal refuse); and the EPA finalized a Hg 
emission output-based standard for new lignite-fired EGUs of 0.040 lb/
GWh and a Hg emission output-based standard for new non-lignite-fired 
EGUs of 2.0E-04 lb/GWh. In 2013, the EPA reconsidered the Hg emission 
standard for new non-lignite-fired EGUs and revised the output-based 
standard to 0.003 lb/GWh (see 78 FR 24075).
---------------------------------------------------------------------------

    \65\ The EPA referred to this subcategory in the final rule as 
``units designed for low rank virgin coal.'' The EPA went on to 
specify that such a unit is designed to burn and is burning non-
agglomerating virgin coal having a calorific value (moist, mineral 
matter-free basis) of less than 19,305 kJ/kg (8,300 Btu/lb) and that 
is constructed and operates at or near the mine that produces such 
coal. The EPA also finalized an alternative output-based emission 
standard of 0.040 lb/GWh. Currently, the approximately 22 units that 
are permitted as lignite-fired EGUs are located exclusively in North 
Dakota, Texas, and Mississippi.
---------------------------------------------------------------------------

    As explained in the 2023 Proposal, Hg emissions from the power 
sector have declined since promulgation of the 2012 MATS Final Rule 
with the installation of Hg-specific and other control technologies and 
as more coal-fired EGUs have retired or reduced utilization. The EPA 
estimated that 2021 Hg emissions from coal-fired EGUs were 3 tons (a 90 
percent decrease compared to pre-MATS levels). However, units burning 
lignite (or permitted to burn lignite) accounted for a disproportionate 
amount of the total Hg emissions in 2021. As shown in table 5 in the 
2023 Proposal (88 FR 24876), 16 of the top 20 Hg-emitting EGUs in 2021 
were lignite-fired EGUs. Overall, lignite-fired EGUs were responsible 
for almost 30 percent of all Hg emitted from coal-fired EGUs in 2021, 
while generating about 7 percent of total 2021 megawatt-hours. Lignite 
accounted for 8 percent of total U.S. coal production in 2021.
    Prior to the 2023 Proposal, the EPA assembled information on 
developments in Hg emission rates and installed controls at lignite-
fired EGUs from operational and emissions information that is provided 
routinely to the EPA for demonstration of compliance with MATS and from 
information provided to the EIA. In addition, the EPA's final decisions 
were informed by information that was submitted as part of a CAA 
section 114 information survey (2022 ICR). The EPA also revisited 
information that was used in establishing the emission standards in the 
2012 Final MATS Rule and considered information that was submitted 
during the public comment period for the 2023 Proposal. From that 
information, the EPA determined, as explained in the 2023 Proposal, 
that there are available cost-effective control technologies and 
improved methods of operation that would allow existing lignite-fired 
EGUs to achieve a more stringent Hg emission standard. As such, the EPA 
proposed a revised Hg emission standard for existing EGUs firing 
lignite (i.e., for those in the ``units designed for low rank virgin 
coal'' subcategory). Specifically, the EPA proposed that such lignite-
fired units must meet the same emission standard as existing EGUs 
firing other types of coal (e.g., anthracite, bituminous coal, 
subbituminous coal, and coal refuse), which is 1.2 lb/TBtu (or an 
alternative output-based standard of 0.013 lb/GWh). The EPA did not 
propose to revise the Hg emission standards either for existing EGUs 
firing non-lignite coal or for new non-lignite coal-fired EGUs.\66\
---------------------------------------------------------------------------

    \66\ As stated in the 2023 Proposal, when proposed revisions to 
existing source emission standards are more stringent than the 
corresponding new source emission standard, the EPA proposes to 
revise the corresponding new source standard to be at least as 
stringent as the proposed revision to the existing source standard. 
This is the case with the Hg emission standard for new lignite-fired 
sources, which will be adjusted to be as stringent as the existing 
source standard.
---------------------------------------------------------------------------

B. How did the technology review change for the lignite-fired EGU 
subcategory?

    The outcome of the technology review for the Hg standard for 
existing lignite-fired EGUs has not changed since the 2023 Proposal. 
However, in response to comments, the EPA expanded its review to 
consider additional coal compositional data and the impact of sulfur 
trioxide (SO3) in the flue gas.

[[Page 38538]]

C. What key comments did we receive on the Hg emission standard for 
lignite-fired EGUs, and what are our responses?

    The Agency received both supportive and critical comments on the 
proposed revision to the Hg emission standard for existing lignite-
fired EGUs. Some commenters agreed with the EPA's decision to not 
propose revisions to the Hg emission standards for non-lignite-fired 
EGUs, while others disagreed. Significant comments are summarized 
below, and the Agency's responses are provided.
    Comment: Several commenters stated that industry experience 
confirms that stringent limits on power plant Hg emissions can be 
readily achieved at lower-than-predicted costs and thus should be 
adopted nationally through CAA section 112(d)(6). They said that at 
least 14 states have, for years, enforced state-based limits on power 
plant Hg emissions, and nearly every one of those states has imposed 
more stringent emission limits than those proposed in this rulemaking 
or in the final 2012 MATS Final Rule. The commenters said that these 
lower emissions limits have resulted in significant and meaningful Hg 
emission reductions, which have proven to be both achievable and cost-
effective.
    Some commenters recommended that the EPA revise the Hg limits to 
levels that are much more stringent than existing or proposed standards 
for both EGUs firing non-lignite coals and those firing lignite. They 
claimed that more stringent Hg emission standards are supported by 
developments in practices, processes, and control technologies. They 
pointed to a 2021 report by Andover Technology Partners, which details 
advances in control technologies that support more stringent Hg 
standards for all coal-fired EGUs.\67\ These advances include advanced 
activated carbon sorbents with higher capture capacity at lower 
injection rates and carbon sorbents that are tolerant of flue gas 
species.
---------------------------------------------------------------------------

    \67\ Analysis of PM and Hg Emissions and Controls from Coal-
Fired Power Plants. Andover Technology Partners. August 19, 2021. 
Document ID No. EPA-HQ-OAR-2018-0794-4583.
---------------------------------------------------------------------------

    Response: The EPA has taken these comments and the referenced 
information into consideration when establishing the final emission 
standards. The EPA disagrees that the Agency should, in this final 
rule, revise the Hg limits for all coal-fired EGUs to levels more 
stringent than the current or proposed standards. The Agency did not 
propose in the 2023 Proposal to revise the Hg emission standard for 
``not-low-rank coal units'' (i.e., those EGUs that are firing on coals 
other than lignite) and did not suggest an emission standard for 
lignite-fired EGUs more stringent than the 1.2 lb/TBtu emission 
standard that was proposed. However, the EPA will continue to review 
emission standards and other rule requirements as part of routine CAA 
section 112(d)(6) technology reviews, which are required by statute to 
be conducted at least every 8 years. If we determine in subsequent CAA 
section 112(d)(6) technology reviews that further revisions to Hg 
emission standards (or to standards for other HAP or surrogate 
pollutants) are warranted, then we will propose revisions at that time. 
We discuss the rationale for the final emission standards in section 
V.D. of this preamble and in more detail in the 2024 Technical Memo.
    Comment: Several commenters challenged the data that the EPA used 
in the CAA 112(d)(6) technology review. Commenters stated that the 
information collected by the EPA via the CAA section 114 request 
consisted of 17 units each submitting two 1-week periods of data and 
associated operational data preselected by the EPA, and that only a 
limited number of the EGUs reported burning only lignite. Other EGUs 
reported burning primarily refined coal, co-firing with natural gas, 
and firing or co-firing with large amounts of subbituminous coal 
(referencing table 7 in the 2023 Proposal). Commenters stated that if 
the EPA's intent was to assess the Hg control performance of lignite-
fired EGUs, then the EGUs evaluated should have burned only lignite, 
not refined coal, subbituminous coal, or natural gas.
    Response: The EPA disagrees with the commenters' argument that the 
Agency should have only considered emissions and operational data from 
EGUs that were firing only lignite. The EPA's intent was to evaluate 
the Hg emission control performance of units that are permitted to burn 
lignite and are thus subject to a Hg emission standard of 4.0 lb/TBtu. 
According to fuel use information supplied to EIA on form 923,\68\ 13 
of 22 EGUs that were designed to burn lignite utilized ``refined coal'' 
to some extent in 2021, as summarized in table 7 in the 2023 Proposal 
preamble (88 FR 24878). EIA form 923 does not specify the type of coal 
that is ``refined'' when reporting boiler or generator fuel use. For 
the technology review, the EPA assumed that the facilities utilized 
``refined lignite,'' as reported in fuel receipts on EIA form 923. In 
any case, firing of refined lignite or subbituminous coal or co-firing 
with natural gas or fuel oil are considered to be Hg emission reduction 
strategies for a unit that is subject to an emission standard of 4.0 
lb/TBtu, which was based on the use of lignite as its fuel.
---------------------------------------------------------------------------

    \68\ https://www.eia.gov/electricity/data/eia923/.
---------------------------------------------------------------------------

    In a related context, in U.S. Sugar Corp. v. EPA, the D.C. Circuit 
held that the EPA could not exclude unusually high performing units 
within a subcategory from the Agency's determination of MACT floor 
standards for a subcategory pursuant to CAA section 112(d)(3). 830 F.3d 
579, 631-32 (D.C. Cir. 2016) (finding ``an unusually high-performing 
source should be considered[,]'' in determining MACT floors for a 
subcategory, and that ``its performance suggests that a more stringent 
MACT standard is appropriate.''). While the technology review at issue 
here is a separate and distinct analysis from the MACT floor setting 
requirements at issue in U.S. Sugar v. EPA, similarly here the EPA 
finds it is appropriate to consider emissions from all units that are 
permitted to burn lignite and are therefore subject to the prior Hg 
emission standard of 4.0 lb/TBtu and are part of the lignite-fired EGU 
subcategory, for the purposes of determining whether more stringent 
standards are appropriate under a technology review. However, while the 
EPA has considered the emissions performance of all units within the 
lignite-fired EGU subcategory, it is not the performance of units that 
are firing or co-firing with other non-lignite fuels that provide the 
strongest basis for the more stringent standard. Rather, the most 
convincing evidence to support the more stringent standard is that 
there are EGUs that are permitted to fire lignite--and are only firing 
lignite--that have demonstrated an ability to meet the more stringent 
standard of 1.2 lb/TBtu.
    Comment: Several commenters claimed that, rather than using actual 
measured Hg concentrations in lignite that had been provided in the CAA 
section 114 request responses (and elsewhere), the EPA used Integrated 
Planning Model (IPM) data to assign inlet Hg concentrations to various 
lignite-fired EGUs. Some commenters asserted that the actual 
concentration of Hg in lignite is higher than those assumed by the EPA 
and that there is considerable variability in the concentration of Hg 
in the lignite used in these plants. As a result, the commenters 
claimed, the percent Hg capture needed to achieve the proposed 1.2 lb/
TBtu emission standard would be higher than that assumed by the EPA in 
the 2023 Proposal.

[[Page 38539]]

    Response: In the 2023 Proposal, the EPA assumed a Hg inlet 
concentration (i.e., concentration of Hg in the fuel) that reflected 
the maximum Hg content of the range of feedstock coals that the EPA 
assumes is available to each of the plants in the IPM. In response to 
comments received on the proposal, the EPA has modified the Hg inlet 
concentration assumptions for each unit to reflect measured Hg 
concentrations in lignite using information provided by commenters and 
other sources, including measured Hg concentrations in fuel samples 
from the Agency's 1998 Information Collection Request (1998 ICR). This 
is explained in additional detail below in section V.D.1. and in a 
supporting technical memorandum titled 1998 ICR Coal Data Analysis 
Summary of Findings. However, this adjustment in the assumed 
concentration of Hg in the various fuels did not change the EPA's 
overall conclusion that there are available controls and improved 
methods of operation that will allow lignite-fired EGUs to meet a more 
stringent Hg emission standard of 1.2 lb/TBtu.
    Comment: Some commenters claimed that the Agency failed to account 
for compositional differences in lignite as compared to those of other 
types of coal--especially in comparison to subbituminous coal.
    Response: The EPA disagrees with these commenters. In the 2023 
Proposal, the EPA emphasized the similarities between lignite and 
subbituminous coal--especially regarding the fuel properties that most 
impact the control of Hg. The EPA noted that lignite and subbituminous 
coal are both low rank coals with low halogen content and explained 
that the halogen content of the coal--especially chlorine--strongly 
influences the oxidation state of Hg in the flue gas stream and, 
thereby, directly influences the ability to capture and contain the Hg 
before it is emitted into the atmosphere. The EPA further noted that 
the fly ashes from lignite and subbituminous coals tend to be more 
alkaline (relative to that from bituminous coal) due to the lower 
amounts of sulfur and halogen and to the presence of a more alkaline 
and reactive (non-glassy) form of calcium in the ash. Due to the 
natural alkalinity, subbituminous and lignite fly ashes can effectively 
neutralize the limited free halogen in the flue gas and prevent 
oxidation of gaseous elemental Hg vapor (Hg\0\). This lack of free 
halogen in the flue gas challenges the control of Hg from both 
subbituminous coal-fired EGUs and lignite-fired EGUs as compared to the 
Hg control of EGUs firing bituminous coal. The EPA noted in the 2023 
Proposal, however, that control strategies and control technologies 
have been developed and utilized to introduce halogens to the flue gas 
stream, and that EGUs firing subbituminous coals have been able to meet 
(and oftentimes emit at emission rates that are considerably lower 
than) the 1.2 lb/TBtu emission standard in the 2012 MATS Final Rule. 
Therefore, while the EPA acknowledges that there are differences in the 
composition of the various coal types, there are available control 
technologies that allow EGUs firing any of those coal types to achieve 
an emission standard of 1.2 lb/TBtu. The EPA further notes that North 
Dakota and Texas lignites are much more similar in composition and in 
other properties to Wyoming subbituminous coal than either coal type is 
to eastern bituminous coal. Both lignite and subbituminous coal are 
lower heating value fuels with high alkaline content and low natural 
halogen. In contrast, eastern bituminous coals are higher heating value 
fuels with high natural halogen content and low alkalinity. But while 
Wyoming subbituminous coal is much more similar to lignite than it is 
to eastern bituminous coals, EGUs firing subbituminous coal must meet 
the same Hg emission standard (1.2 lb/TBtu) as EGUs firing bituminous 
coal. The EPA further acknowledges the differences in sulfur content 
between subbituminous coal and lignite and its impact is discussed in 
the following comment summary and response.
    Comment: Some commenters claimed that the EPA did not account for 
the impacts of the higher sulfur content of lignite as compared to that 
of subbituminous coal, and that such higher sulfur content leads to the 
presence of additional SO3 in the flue gas stream. The 
commenters noted that the presence of SO3 is known to 
negatively impact the effectiveness of activated carbon for Hg control.
    Response: The EPA agrees with the commenters that the Agency did 
not fully address the potential impacts of SO3 on the 
control of Hg from lignite-fired EGUs in the 2023 Proposal. However, in 
response to these comments, the EPA conducted a more robust evaluation 
of the impact of SO3 in the flue gas of lignite-fired EGU 
and determined that it does not affect our previous determination that 
there are control technologies and methods of operation that are 
available to EGUs firing lignite that would allow them to meet a Hg 
emission standard of 1.2 lb/TBtu--the same emission standard that must 
be met by EGUs firing all other types of coal. As discussed in more 
detail below, the EPA determined that there are commercially available 
advanced ``SO3 tolerant'' Hg sorbents and other technologies 
that are specifically designed for Hg capture in high SO3 
flue gas environments. These advanced sorbents allow for capture of Hg 
in the presence of SO3 and other challenging flue gas 
environments at costs that are consistent with the use of conventional 
pre-treated activated carbon sorbents.\69\ The EPA has considered the 
additional information regarding the role of flue gas SO3 on 
Hg control and the information on the availability of advanced 
``SO3 tolerant'' Hg sorbents and other control technologies 
and finds that this new information does not change the Agency's 
determination that a Hg emission standard of 1.2 lb/TBtu is achievable 
for lignite-fired EGUs.
---------------------------------------------------------------------------

    \69\ See Tables 8 and 9 from ``Analysis of PM and Hg Emissions 
and Controls from Coal-Fired Power Plants'', Andover Technology 
Partners (August 2021); available in the rulemaking docket at Docket 
ID: EPA-HQ-OAR-2018-4583.
---------------------------------------------------------------------------

    Comment: Several commenters noted the EPA made improper assumptions 
to reach the conclusion that the revised Hg emissions limit is 
achievable and claimed that none of the 22 lignite-fired EGUs are 
currently in compliance with the proposed 1.2 lb/TBtu Hg emission 
standard and that the EPA has not shown that any EGU that is firing 
lignite has demonstrated that it can meet the proposed Hg emission 
standard.
    Response: The EPA disagrees with commenters' assertion and 
maintains that the Agency properly determined that the proposed, more 
stringent Hg emission standard can be achieved, cost-effectively, using 
available control technologies and improved methods of operation. 
Further, the EPA notes that, contrary to commenters' claim, there are, 
in fact, EGUs firing lignite that have demonstrated an ability to meet 
the more stringent 1.2 lb/TBtu Hg emission standard. Twin Oaks units 1 
and 2 are lignite-fired EGUs operated by Major Oak Power, LLC, and 
located in Robertson County, Texas. In the 2023 Proposal (see 88 FR 
24879 table 8), we showed that 2021 average Hg emission rates for Twin 
Oaks 1 and 2 (listed in the table as Major Oak #1 and Major Oak #2) 
were 1.24 lb/TBtu and 1.31 lb/TBtu, respectively, which are emission 
rates that are just slightly above the final emission limit. Both units 
at Major Oak have qualified for LEE status for Hg. To demonstrate LEE 
status for Hg an EGU owner/operator must conduct an initial EPA Method 
30B test over 30 days and follow the calculation procedures in the 
final rule to document a potential to emit (PTE) that is less than 10 
percent of the applicable Hg emissions limit (for

[[Page 38540]]

lignite-fired EGUs this would be a rate of 0.40 lb/TBtu) or less than 
29 lb of Hg per year. If an EGU qualifies as a LEE for Hg, then the 
owner/operator must conduct subsequent performance tests on an annual 
basis to demonstrate that the unit continues to qualify. In their most 
recent compliance reports \70\ (dated November 14, 2023), Major Oak 
Power, LLC, summarized the performance testing. Between August 1 and 
September 19, 2023, Major Oak Power, LLC, personnel performed a series 
of performance tests for Hg on Twin Oaks units 1 and 2. The average Hg 
emissions rate for the 30-boiler operating day performance tests was 
1.1 lb/TBtu for unit 1 and 0.91 lb/TBtu for unit 2. The EGUs 
demonstrated LEE status by showing that each of the units has a Hg PTE 
of less than 29 lb per year. Further, in LEE demonstration testing for 
the previous year (2022), Major Oak Power, LLC, found that the average 
Hg emissions rate for the 30-boiler operating day performance test was 
0.86 lb/TBtu for unit 1 and 0.63 lb/TBtu for unit 2.
---------------------------------------------------------------------------

    \70\ See page 1-1 of the 2023 Compliance Reports for Twin Oaks 1 
and 2 available in the rulemaking docket at EPA-HQ-OAR-2018-0794.
---------------------------------------------------------------------------

    In the 2023 LEE demonstration compliance report, Twin Oaks unit 1 
was described as a fluidized bed boiler that combusts lignite and is 
equipped with fluidized bed limestone (FBL) injection for 
SO2 control, selective non-catalytic reduction (SNCR) for 
control of nitrogen oxides (NOX), and a baghouse (FF) for PM 
control. In addition, unit 1 has an untreated activated carbon 
injection (UPAC) system as well as a brominated powdered activated 
carbon (BPAC) injection system for absorbing vapor phase Hg in the 
effluent upstream of the baghouse. Twin Oaks unit 2 is described in the 
same way.
    Similarly, Red Hills units 1 and 2, located in Choctaw County, 
Mississippi,\71\ also demonstrated 2021 annual emission rates while 
firing lignite from an adjacent mine of 1.33 lb/TBtu and 1.35 lb/TBtu, 
which are reasonably close to the proposed Hg emission standard of 1.2 
lb/TBtu to demonstrate achievability. In 2022, average Hg emission 
rates for Red Hills unit 1 and unit 2, again while firing Mississippi 
lignite, were 1.73 lb/TBtu and 1.75 lb/TBtu, respectively. The EPA also 
notes that, as shown below in table 5, lignite mined in Mississippi has 
the highest average Hg content--as compared to lignites mined in Texas 
and North Dakota.
---------------------------------------------------------------------------

    \71\ Choctaw Generation LP leases and operates the Red Hills 
Power Plant. The plant supplies electricity to the Tennessee Valley 
Authority (TVA) under a 30-year power purchase agreement. The 
lignite output from the adjacent mine is 100 percent dedicated to 
the power plant. https://www.purenergyllc.com/projects/choctaw-generation-lp-red-hills-power-plant/#page-content.
---------------------------------------------------------------------------

    The performance of Twin Oaks units 1 and 2 and Red Hills Generating 
Facility units 1 and 2 clearly demonstrate the achievability of the 
proposed 1.2 lb/TBtu emission standard by lignite-fired EGUs. However, 
even if there were no lignite-fired EGUs that are meeting (or have 
demonstrated an ability to meet) the more stringent Hg emission 
standard, that would not mean that the more stringent emission standard 
was not achievable. Most Hg control technologies are ``dial up'' 
technologies--for example, sorbents or chemical additives have 
injection rates that can be ``dialed'' up or down to achieve a desired 
Hg emission rate. In response to the EPA's 2022 CAA section 114 
information request, some responding owners/operators indicated that 
sorbent injection rates were set to maintain a Hg emission rate below 
the 4.0 lb/TBtu emission limit. In some instances, operators of EGUs 
reported that they were not injecting any Hg sorbent and were able to 
meet the less stringent emission standard. Most units that are 
permitted to meet a Hg emission standard of 4.0 lb/TBtu have no reason 
to ``over control'' since doing so by injecting more sorbent would 
increase their operating costs. So, it is unsurprising that many units 
that are permitted to fire lignite have reported Hg emission rates 
between 3.0 and 4.0 lb/TBtu.
    While most lignite-fired EGUs have no reason to ``over control'' 
beyond their permitted emission standard of 4.0 lb/TBtu, Twin Oaks 
units 1 and 2 do have such motivation. As mentioned earlier, those 
sources have achieved LEE status for Hg (by demonstrating a Hg PTE of 
less than 29 lb/yr) and they must conduct annual performance tests to 
show that the units continue to qualify. According to calculations 
provided in their annual LEE certification, to maintain LEE status, the 
units could emit no more than 1.79 lb/TBtu and maintain a PTE of less 
than 29 lb/TBtu. So, the facilities are motivated to over control 
beyond 1.79 lb/TBtu (which, as described earlier in this preamble, they 
have consistently done).
    Comment: To highlight the difference in the ability of lignite-
fired and subbituminous-fired EGUs to control Hg, one commenter created 
a table to show a comparison between the Big Stone Plant (an EGU 
located in South Dakota firing subbituminous coal) and Coyote Station 
(an EGU located in North Dakota firing lignite). Additionally, the 
commenter included figures showing rolling 30-boiler operating day 
average Hg emission rates and the daily average ACI feed rates for Big 
Stone and Coyote EGUs for years 2021-2022. Their table showed that Big 
Stone and Coyote are similarly configured plants that utilize the same 
halogenated ACI for Hg control. The commenters said, however, that 
Coyote Station's average sorbent feed rate on a lb per million actual 
cubic feet (lb/MMacf) basis is more than three times higher than that 
for Big Stone, yet Coyote Station's average Hg emissions on a lb/TBtu 
basis are more than five times higher than Big Stone.
    Response: The EPA agrees that the Big Stone and Coyote Station 
units referenced by the commenter are similarly sized and configured 
EGUs, with the Big Stone unit in South Dakota firing subbituminous coal 
and the Coyote Station unit in North Dakota firing lignite. However, 
there are several features of the respective units that can have an 
impact on the control of Hg. First, and perhaps the most significant, 
the Big Stone unit has a selective catalytic reduction (SCR) system 
installed for control of NOx. The presence of an SCR is known to 
enhance the control of Hg--especially in the presence of chemical 
additives. The Coyote Station EGU does not have an installed SCR. 
Further, both EGUs have a dry FGD scrubber and FF baghouse installed 
for SO2/acid gas and fPM control. The average sulfur content 
of North Dakota lignite is approximately 2.5 times greater than that of 
Wyoming subbituminous coal. However, the average SO2 
emissions from the Coyote Station EGU (0.89 lb/MMBtu) were 
approximately 10 times higher than the SO2 emissions from 
the Big Stone EGU (0.09 lb/MMBtu). The Big Stone dry scrubber/FF was 
installed in 2015; while the dry scrubber/FF at Coyote Station was 
installed in 1981--approximately 31 years earlier. So, considering the 
presence of an SCR--which is known to enhance Hg control--and newer and 
better performing downstream controls, it is unsurprising that there 
are differences in the control of Hg at the two EGUs. In addition, 
since the Coyote Station has been subject to a Hg emission standard of 
4.0 lb/TBtu, there would be no reason for the operators to further 
optimize its control system to achieve a lower emission rate. And, as 
numerous commenters noted, the Hg content of North Dakota is higher 
than that of Wyoming subbituminous coal.
    Comment: Some commenters claimed that the EPA has not adequately 
justified a reversal in the previous policy to establish a separate 
subcategory for lignite-fired EGUs.

[[Page 38541]]

    Response: In developing the 2012 Final MATS Rule, the EPA examined 
the EGUs in the top performing 12 percent of sources for which the 
Agency had Hg emissions data. In examining that data, the EPA observed 
that there were no lignite-fired EGUs among the top performing 12 
percent of sources for Hg emissions. The EPA then determined that this 
indicated that there is a difference in the Hg emissions from lignite-
fired EGUs when compared to the Hg emissions from EGUs firing other 
coal types (that were represented among the top performing 12 percent). 
That determination was not based on any unique property or 
characteristic of lignite--only on the observation that there were no 
lignite-fired EGUs among the best performing 12 percent of sources (for 
which the EPA had Hg emissions data). In fact, as noted in the preamble 
for the 2012 Final MATS Rule, the EPA ``believed at proposal that the 
boiler size was the cause of the different Hg emissions 
characteristics.'' See 77 FR 9378.
    The EPA ultimately concluded that it is appropriate to continue to 
base the subcategory definition, at least in part, on whether the EGUs 
were ``designed to burn and, in fact, did burn low rank-virgin coal'' 
(i.e., lignite), but that it is not appropriate to continue to use the 
boiler size criteria (i.e., the height-to-depth ratio). However, the 
EPA ultimately finalized the ``unit designed for low rank virgin coal'' 
subcategory based on the characteristics of the EGU--not on the 
properties of the fuel. ``We are finalizing that the EGU is considered 
to be in the ``unit designed for low rank virgin coal'' subcategory if 
the EGU: (1) meets the final definitions of ``fossil fuel-fired'' and 
``coal-fired electric utility steam generating unit;'' and (2) is 
designed to burn and is burning non-agglomerating virgin coal having a 
calorific value (moist, mineral matter-free basis) of less than 19,305 
kJ/kg (8,300 Btu/lb) and that is constructed and operates at or near 
the mine that produces such coal.'' See 77 FR 9369.
    While, in the 2012 MATS Final Rule, the EPA based the lignite-fired 
EGU subcategory on the design and operation of the EGUs, the EPA did 
not attribute the observed differences in Hg emissions to any unique 
characteristic(s) of lignite. As the EPA clearly noted in the 2023 
Proposal, there are, in fact, characteristics of lignite that make the 
control of Hg more challenging. These include the low natural halogen 
content, the high alkalinity of the fly ash, the sulfur content, the 
relatively higher Hg content, and the relatively higher variability of 
Hg content. However, as the EPA has explained, these characteristics 
that make the control of Hg more challenging are also found in non-
lignite fuels. Subbituminous coals also have low natural halogen 
content and high fly ash alkalinity. Eastern and central bituminous 
coals also have high sulfur content. Bituminous and anthracitic waste 
coals (coal refuse) have very high and variable Hg content. EGUs firing 
any of these non-lignite coals have been subject to--and have 
demonstrated compliance with--the more stringent Hg emission standard 
of 1.2 lb/TBtu.
    The EPA has found it appropriate to reverse the previous policy 
because the decision to subcategorize ``units designed for low rank 
virgin coal'' in the 2012 MATS Final Rule was based a determination 
that there were differences in Hg emissions from lignite-fired EGUs as 
compared to EGUs firing non-lignite coals. That perceived difference 
was based on an observation that there were no lignite-fired EGUs in 
the top performing 12 percent of EGUs for which the Agency had Hg 
emissions data and on an assumption that the perceived difference in 
emissions was somehow related to the design and operation of the EGU. 
The EPA is unaware of any distinguishing features of EGUs that were 
designed to burn lignite that would impact the emissions of Hg. 
Further, the EPA does not now view the fact that there were no lignite-
fired EGUs in the population of the best-performing 12 percent of EGUs 
for which the Agency had Hg emissions data to represent a ``difference 
in emissions.''
    But, on re-examination of the data, the EPA has concluded that the 
Hg emissions from the 2010 ICR for the lignite-fired EGUs were not 
clearly distinctive from the Hg emissions from EGUs firing non-lignite 
coal. In setting the emission standards for the 2012 MATS Final Rule, 
the EPA had available and useable Hg emissions data from nearly 400 
coal-fired EGUs (out of the 1,091 total coal-fired EGUs operating at 
that time). However, the EPA only had available and useable data from 
nine lignite-fired EGUs with reported floor Hg emissions ranging from 
1.0 to 10.9 lb/TBtu. But these were not outlier emission rates. EGUs 
firing bituminous coal reported Hg emissions as high as 30.0 lb/TBtu; 
and those firing subbituminous coal reported Hg emissions as high as 
9.2 lb/TBtu.

D. What is the rationale for our final approach and decisions for the 
lignite-fired EGU Hg standard?

    In the 2023 Proposal, the EPA proposed to determine that there are 
developments in available control technologies and methods of operation 
that would allow lignite-fired EGUs to meet a more stringent Hg 
emission standard of 1.2 lb/TBtu--the same Hg emission standard that 
must be met by coal-fired EGUs firing non-lignite coals (e.g., 
anthracite, bituminous coal, subbituminous coal, coal refuse, etc.). 
After consideration of public comments received on the proposed 
revision of the Hg emission standard, the EPA continues to find that 
the evidence supports that there are commercially available control 
technologies and improved methods of operation that allow lignite-fired 
EGUs to meet the more stringent Hg emission standard that the EPA 
proposed. As noted above, lignite-fired EGUs also comprise some of the 
largest sources of Hg emissions within this source category and are 
responsible for a disproportionate share of Hg emissions relative to 
their generation. While previous EPA assessments have shown that 
current modeled exposures [of Hg] are well below the reference dose 
(RfD), we conclude that further reductions of Hg emissions from 
lignite-fired EGUs covered in this final action should further reduce 
exposures including for the subsistence fisher sub-population. This 
anticipated exposure is of particular importance to children, infants, 
and the developing fetus given the developmental neurotoxicity of Hg. 
Therefore, in this final action, the EPA is revising the Hg emission 
standard for lignite-fired EGUs from the 4.0 lb/TBtu standard that was 
finalized in the 2012 MATS Final Rule to the more stringent emission 
standard of 1.2 lb/TBtu, as proposed. The rationale for the Agency's 
final determination is provided below.
    In this final rule, the EPA is also reaching a different conclusion 
from the 2020 Technology Review with respect to the Hg emission 
standard for lignite-fired EGUs. As discussed in section II.D. above, 
the 2020 Technology Review did not evaluate the current performance of 
emission reduction control equipment and strategies at existing 
lignite-fired EGUs. Nor did the 2020 Technology Review specifically 
address the discrepancy between Hg emitted from lignite-fired EGUs and 
non-lignite coal-fired EGUs or consider the improved performance of 
injected sorbents or chemical additives, or the development of 
SO3-tolerant sorbents. Based on the EPA's review in this 
rulemaking which considered such information, the Agency determined 
that there are available control technologies that allow EGUs firing 
lignite to achieve an emission standard of 1.2 lb/TBtu,

[[Page 38542]]

consistent with the Hg emission standard required for non-lignite coal-
fired EGUs, which the EPA is finalizing pursuant to its CAA section 
112(d)(6) authority.
1. Mercury Content of Lignite
    For analyses supporting the proposal, the EPA assumed ``Hg Inlet'' 
levels (i.e., Hg concentration in inlet fuel) that are consistent with 
those assumed in the Agency's power sector model (IPM) and then 
adjusted accordingly to reflect the 2021 fuel blend for each unit. 
Several commenters indicated that the Hg content of lignite fuels is 
much higher and has greater variability than the EPA assumed.
    To support the development of the NESHAP for the Coal- and Oil-
Fired EGU source category, the Agency conducted a 2-year data 
collection effort which was initiated in 1998 and completed in 2000 
(1998 ICR). The ICR had three main components: (1) identifying all 
coal-fired units owned and operated by publicly owned utility 
companies, federal power agencies, rural electric cooperatives, and 
investor-owned utility generating companies; (2) obtaining accurate 
information on the amount of Hg contained in the as-fired coal used by 
each electric utility steam generating unit with a capacity greater 
than 25 MW electric, as well as accurate information on the total 
amount of coal burned by each such unit; and (3) obtaining data by coal 
sampling and stack testing at selected units to characterize Hg 
reductions from representative unit configurations.
    The ICR captured the origin of the coal burned, and thus provided a 
pathway for linking emission properties to coal basins. The 1998-2000 
ICR resulted in more than 40,000 data points indicating the coal type, 
sulfur content, Hg content, ash content, chlorine content, and other 
characteristics of coal burned at coal-fired utility boilers greater 
than 25 MW.
    Annual fuel characteristics and delivery data reported on EIA form 
923 also provide continual data points on coal heat content, sulfur 
content, and geographic origin, which are used as a check against 
characteristics initially identified through the 1998 ICR.
    For this final rule, the EPA re-evaluated the 1998 ICR data.\72\ 
Specifically, the EPA evaluated the coal Hg data to characterize the Hg 
content of lignite, which is mined in North Dakota, Texas, and 
Mississippi, and to characterize by seam and by coal delivered to a 
specific plant.\73\ The results are presented as a range of Hg content 
of the lignites as well as the mean and median Hg content. The EPA also 
compared the fuel characteristics of lignites mined in North Dakota, 
Texas, and Mississippi against coals mined in Wyoming (subbituminous 
coal), Pennsylvania (mostly upper Appalachian bituminous coal), and 
Kentucky (mostly lower Appalachian bituminous coal). The Agency also 
included in the re-evaluation, coal analyses that were submitted in 
public comments by North American Coal (NA Coal). In addition to the Hg 
content, the analysis included the heating value and the sulfur, 
chlorine, and ash content for each coal that is characterized.
---------------------------------------------------------------------------

    \72\ Technical Support Document ``1998 ICR Coal Data Analysis 
Summary of Findings'' available in the rulemaking docket at EPA-HQ-
OAR-2018-0794.
    \73\ In 2022, over 99 percent of all lignite was mined in North 
Dakota (56.2 percent), Texas (35.9 percent), and Mississippi (7.1 
percent). Small amounts (less than 1 percent) of lignite were also 
mined in Louisiana and Montana. See Table 6. ``Coal Production and 
Number of Mines by State and Coal Rank'' from EIA Annual Coal 
Report, available at https://www.eia.gov/coal/annual/.
---------------------------------------------------------------------------

    The analysis showed that lignite mined in North Dakota had a mean 
Hg content of 9.7 lb/TBtu, a median Hg content of 8.5 lb/TBtu, and a Hg 
content range of 2.2 to 62.1 lb/TBtu. Other characteristics of North 
Dakota lignite include an average heating value (dry basis) of 10,573 
Btu/lb, an average sulfur content of 1.19 percent, an average ash 
content of 13.5 percent, and an average chlorine content of 133 parts 
per million (ppm). In response to comments on the 2023 Proposal, for 
analyses supporting this final action, the EPA has revised the assumed 
Hg content of lignite mined in North Dakota to 9.7 lb/TBtu versus the 
7.81 lb/TBtu assumed in the 2023 Proposal.
    Similarly, the analysis showed that lignite mined in Texas had a 
mean and median Hg content of 25.0 lb/TBtu and 23.8 lb/TBtu, 
respectively, and a Hg content range from 0.7 to 92.0 lb/TBtu. Other 
characteristics include an average heating value (dry basis) of 9,487 
Btu/lb, an average sulfur content of 1.42 percent, an average ash 
content of 24.6 percent, and an average chlorine content of 233 ppm. In 
response to comments on the 2023 Proposal, for analyses supporting this 
final action, the EPA has revised the assumed Hg content of lignite 
mined in Texas to 25.0 lb/TBtu versus the range of 14.65 to 14.88 lb/
TBtu that was assumed for the 2023 Proposal.
    Lignite mined in Mississippi had the highest mean Hg content at 
34.3 lb/TBtu and the second highest median Hg emissions rate, 30.1 lb/
TBtu. The Hg content ranged from 3.6 to 91.2 lb/TBtu. Lignite from 
Mississippi had an average heating value (dry basis) of 5,049 Btu/lb 
and a sulfur content of 0.58 percent. In response to comments submitted 
on the 2023 Proposal, for analyses supporting this final action, the 
EPA assumed a Hg content of 34.3 lb/TBtu for lignite mined in 
Mississippi versus the 12.44 lb/TBtu assumed for the proposal.
    The EPA 1998 ICR dataset did not contain information on lignite 
from Mississippi, which resulted in a smaller number of available data 
points (227 in Mississippi lignite versus 864 for North Dakota lignite 
and 943 for Texas lignite). Table 5 of this document more fully 
presents the characteristics of lignite from North Dakota, Texas, and 
Mississippi.

[[Page 38543]]

[GRAPHIC] [TIFF OMITTED] TR07MY24.069

    Coals mined in Kentucky, Pennsylvania, and Wyoming were also 
analyzed for comparison. The types of coal (all non-lignite) included 
bituminous, bituminous-high sulfur, bituminous-low sulfur, 
subbituminous, anthracite, waste anthracite, waste bituminous, and 
petroleum coke. Bituminous coal accounted for 92 percent of the data 
points from Kentucky and 75 percent of the data points from 
Pennsylvania. Subbituminous coal accounted for 96 percent of the data 
points from Wyoming.
    Bituminous coals from Kentucky had a mean Hg emissions content of 
7.2 lb/TBtu (ranging from 0.7 to 47.4 lb/TBtu), an average heating 
value (dry basis) of 13,216 Btu/lb, an average sulfur content of 1.43 
percent, an average ash content of 10.69 percent, and an average 
chlorine content of 1,086 ppm.
    Bituminous coals from Pennsylvania had a mean Hg emissions rate of 
14.5 lb/TBtu (ranging from 0.1 to 86.7 lb/TBtu), an average heating 
value (dry basis) of 13,635 Btu/lb, an average sulfur content of 1.88 
percent, an average ash content of 10.56 percent, and an average 
chlorine content of 1,050 ppm.
    Subbituminous coals from Wyoming had a mean Hg rate of 5.8 lb/TBtu, 
an average heating value (dry basis) of 12,008 Btu/lb, an average 
sulfur content of 0.44 percent, an average ash content of 7.19 percent, 
and an average chlorine content of 127 ppm. Table 6 of this document 
shows the characteristics of bituminous coal from Kentucky and 
Pennsylvania and subbituminous coal from Wyoming.
[GRAPHIC] [TIFF OMITTED] TR07MY24.070

    Several commenters claimed that one of the factors that contributes 
to the challenge of controlling Hg emissions from EGUs firing lignite 
is the variability of the Hg content in lignite. However, as can be 
seen in table 5 and table 6 of this document, all coal types examined 
by the EPA contain a variable content of Hg. The compliance 
demonstration requirements in the 2012 MATS Final Rule were designed to 
accommodate the variability of Hg in coal by requiring compliance with 
the respective Hg emission standards over a 30-operating-day rolling 
average period. When examining the Hg emissions for EGUs firing on the 
various coal types (including those firing Wyoming subbituminous coal, 
which has the lowest mean and median Hg content and the narrowest range 
of Hg content), daily emissions often exceed the applicable emission 
standard (sometimes considerably). However, averaging emissions over a 
rolling 30-operating-day period effectively dampens the impacts of fuel 
Hg content

[[Page 38544]]

variability. For example, in figure 1 (a graph) of this document, the 
2022 Hg emissions from Dave Johnston unit BW41, a unit firing 
subbituminous coal, are shown. The graph shows both the daily Hg 
emissions and the 30-operating-day rolling average Hg emissions. As can 
be seen in the graph, the daily Hg emissions very often exceed the 1.2 
lb/TBtu emission rate; however, the 30-operating-day rolling average is 
consistently below the emission limit (the annual average emission rate 
is 0.9 lb/TBtu).
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TR07MY24.071

    A similar effect can be seen with the 2022 daily and 30-operating-
day rolling average Hg emissions from Leland Olds unit 1, an EGU firing 
North Dakota lignite, shown in figure 2 of this document.

[[Page 38545]]

[GRAPHIC] [TIFF OMITTED] TR07MY24.072

BILLING CODE 6560-50-C
    As with the EGU firing subbituminous coal, the daily Hg emissions 
very often exceed the emission limit (in this case 4.0 lb/TBtu); 
however, the 30-operating-day rolling average is consistently below the 
applicable emission limit (the 2022 annual average emission rate for 
Leland Olds unit 1 is 2.3 lb/TBtu).
2. The Impact of Halogen Content of Lignite on Hg Control
    In the 2023 Proposal, the EPA explained that during combustion of 
coal, the Hg contained in the coal is volatilized and converted to 
Hg\0\ vapor in the high-temperature regions of the boiler. Hg\0\ vapor 
is difficult to capture because it is typically nonreactive and 
insoluble in aqueous solutions. However, under certain conditions, the 
Hg\0\ vapor in the flue gas can be oxidized to divalent Hg (Hg\2+\). 
The Hg\2+\ can bind to the surface of solid particles (e.g., fly ash, 
injected sorbents) in the flue gas stream, often referred to as 
``particulate bound Hg'' (Hgp) and be removed in a 
downstream PM control device. Certain oxidized Hg compounds that are 
water soluble may be further removed in a downstream wet scrubber. The 
presence of chlorine in gas-phase equilibrium favors the formation of 
mercuric chloride (HgCl2) at flue gas cleaning temperatures. 
However, Hg\0\ oxidation reactions are kinetically limited as the flue 
gas cools, and as a result Hg may enter the flue gas cleaning device(s) 
as a mixture of Hg\0\, Hg\2+\ compounds, and Hgp.
    This partitioning into various species of Hg has considerable 
influence on selection of Hg control approaches. In tables 5 and 6 of 
this document, the chlorine content of bituminous coals mined in 
Kentucky and Pennsylvania averaged 1,086 ppm and 1,050 ppm, 
respectively. In comparison, the average chlorine content of Wyoming 
subbituminous coal is 127 ppm; while the chlorine contents of lignite 
mined in North Dakota and Texas are 133 ppm and 232 ppm, respectively. 
In general, because of the presence of higher amounts of halogen 
(especially chlorine) in bituminous coals, most of the Hg in the flue 
gas from bituminous coal-fired boilers is in the form of Hg\2+\ 
compounds, typically HgCl2, and is more easily captured in 
downstream control equipment. Conversely, both subbituminous coal and 
lignite have lower natural halogen content compared to that of 
bituminous coals, and the Hg in the flue gas from boilers firing those 
fuels tends to be in the form of Hg\0\ and is more challenging to 
control in downstream control equipment.
    While some bituminous coal-fired EGUs require the use of additional 
Hg-specific control technology, such as injection of a sorbent or 
chemical additive, to supplement the control that these units already 
achieve from criteria pollutant control equipment, these Hg-specific 
control technologies are often required as part of the Hg emission 
reduction strategy at EGUs that are firing subbituminous coal or 
lignite. As described above, the Hg in the flue gas for EGUs firing 
subbituminous coal or lignite tends to be in the nonreactive Hg\0\ 
vapor phase due to lack of available free halogen to promote the 
oxidation reaction. To alleviate this challenge, activated carbon and 
other sorbent providers and control technology vendors have developed 
methods to introduce halogen into the flue gas to improve the control 
of Hg emissions from EGUs firing subbituminous coal and lignite. This 
is primarily through the injection of pre-halogenated (often pre-
brominated) activated carbon sorbents or through the injections of 
halogen-containing chemical additives along with conventional sorbents. 
In the

[[Page 38546]]

2022 CAA section 114 information collection, almost all the lignite-
fired units reported use of some sort of halogen additive or injection 
as part of their Hg control strategy by using refined coal (which 
typically has added halogen), bromide or chloride chemical additives, 
pre-halogenated sorbents, and/or oxidizing agents. Again, low chlorine 
content in the fuel is a challenge that is faced by EGUs firing either 
subbituminous coals or lignite, and EGUs firing subbituminous coal have 
been subject to a Hg emission standard of 1.2 lb/TBtu since the MATS 
rule was finalized in 2012.
3. The Impact of SO3 on Hg Control
    Some commenters noted that the EPA did not account for the impacts 
of the higher sulfur content of lignite as compared to that of 
subbituminous coal, and that such higher sulfur content leads to the 
presence of additional SO3 in the flue gas stream. As shown 
in table 5 and table 6 of this document, while the halogen content of 
subbituminous coal and lignite is similar, the average sulfur content 
of lignite is more like that of bituminous coal mined in Kentucky and 
Pennsylvania.
    During combustion, most of the sulfur in coal is oxidized into 
SO2, and only a small portion is further oxidized to 
SO3 in the boiler. In response to environmental 
requirements, many EGUs have installed SCR systems for NOX 
control and FGD systems for SO2 control. One potential 
consequence of an SCR retrofit is an increase in the amount of 
SO3 in the flue gas downstream of the SCR due to catalytic 
oxidation of SO2. Fly ash and condensed SO3 are 
the major components of flue gas that contribute to the opacity of a 
coal plant's stack emissions and the potential to create a visible 
sulfuric acid ``blue plume.'' In addition, higher SO3 levels 
can adversely affect many aspects of plant operation and performance, 
including corrosion of downstream equipment and fouling of the air 
preheater (APH). This is primarily an issue faced by EGUs firing 
bituminous coal. EGUs fueled by subbituminous coal and lignite do not 
typically have the same problem with blue plume formation. Of the EGUs 
that are designed to fire lignite, only Oak Grove units 1 and 2, 
located in Texas, have an installed SCR for NOX control. 
Several lignite-fired EGUs utilize SNCR systems for NOX 
control, which are less effective for NOX control as 
compared to SCR systems. Several commenters claimed that SCR is not a 
viable NOX control technology for EGUs firing North Dakota 
lignite because of catalyst fouling from the high sodium content of the 
fuel and resulting fly ash.
    Coal fly ash is typically classified as acidic (pH less than 7.0), 
mildly alkaline (pH greater than 7.0 to 9.0), or strongly alkaline (pH 
greater than 9.0). The pH of the fly ash is usually determined by the 
calcium/sulfur ratio and the amount of halogen. The ash from bituminous 
coals tends to be acidic due to the relatively higher sulfur and 
halogen content and the glassy (nonreactive) nature of the calcium 
present in the ash. Conversely, the ash from subbituminous coals and 
lignite tends to be more alkaline due to the lower amounts of sulfur 
and halogen and a more alkaline and reactive (non-glassy) form of 
calcium--and, as noted by commenters--the presence of sodium compounds 
in the ash. The natural alkalinity of the subbituminous and lignite fly 
ash may effectively neutralize the limited free halogen in the flue gas 
and prevent oxidation of the Hg\0\. However, the natural alkalinity 
also helps to minimize the impact of SO3, because a common 
control strategy for SO3 is the injection of alkaline 
sorbents (dry sorbent injection, DSI).
    Still, as commenters correctly noted, the presence of 
SO3 in the flue gas stream is also known to negatively 
impact the effectiveness of sorbent injection for Hg control. This 
impact has been known for some time, and control technology researchers 
and vendors have developed effective controls and strategies to 
minimize the impact of SO3.\74\ As noted above, coal-fired 
EGUs utilizing bituminous coal--which also experience significant rates 
of SO3 formation in the flue gas stream--have also 
successfully demonstrated the application of Hg control technologies to 
meet a standard of 1.2 lb/TBtu.
---------------------------------------------------------------------------

    \74\ The mention of specific products by name does not imply 
endorsement by the EPA. The EPA does not endorse or promote any 
particular control technology. The EPA mentions specific product 
names here to emphasize the broad range of products and vendors 
offering sulfur tolerant Hg control technologies.
---------------------------------------------------------------------------

    The AECOM patented SBS InjectionTM (``sodium-based 
solution'') technology has been developed for control of 
SO3, and co-control of Hg has also been demonstrated. A 
sodium-based solution is injected into the flue gas, typically ahead of 
the APH or, if present, the SCR. By removing SO3 prior to 
these devices, many of the adverse effects of SO3 can be 
successfully mitigated. AECOM has more recently introduced their 
patented HBS InjectionTM technology for effective Hg 
oxidation and control.\75\ This new process injects halogen salt 
solutions into the flue gas, which react in-situ to form halogen 
species that effectively oxidize Hg. The HBS InjectionTM can 
be co-injected with the SBS InjectionTM for effective 
SO3 control and Hg oxidation/control.
---------------------------------------------------------------------------

    \75\ https://www.aecom.com/wp-content/uploads/2019/07/10_EUEC_P_PT_Brochure_HBS_InjectionTechnology_20160226_singles.pdf.
---------------------------------------------------------------------------

    Other vendors also offer technologies to mitigate the impact of 
SO3 on Hg control from coal combustion flue gas streams. For 
example, Calgon Carbon offers their ``sulfur tolerant'' Fluepac ST, 
which is a brominated powdered activated carbon specially formulated to 
enhance Hg capture in flue gas treatment applications with elevated 
levels of SO3.\76\ In testing in a bituminous coal 
combustion flue gas stream containing greater than 10 ppm 
SO3, the Fluepac ST was able to achieve greater than 90 
percent Hg control at injection rates of a third or less as compared to 
injection rates using the standard brominated sorbent.
---------------------------------------------------------------------------

    \76\ https://www.calgoncarbon.com/app/uploads/DS-FLUEST15-EIN-E1.pdf.
---------------------------------------------------------------------------

    Babcock & Wilcox (B&W) offers dry sorbent injection systems that 
remove SO3 before the point of activated carbon sorbent 
injection to mitigate the impact of SO3.\77\ Midwest Energy 
Emissions Corporation (ME2C) offers ``high-grade sorbent 
enhancement additives--injected into the boiler in minimal amounts'' 
that work in conjunction with proprietary sorbent products to ensure 
maximum Hg capture. ME2C claims that their Hg control 
additives and proprietary sorbent products are ``high-sulfur-tolerant 
and SO3-tolerant sorbents.'' \78\
---------------------------------------------------------------------------

    \77\ https://www.babcock.com/assets/PDF-Downloads/Emissions-Control/E101-3200-Mercury-and-HAPs-Emissions-Control-Brochure-Babcock-Wilcox.pdf.
    \78\ ME2C 2016 Corporate Brochure, available in the rulemaking 
docket at EPA-HQ-OAR-2018-0794.
---------------------------------------------------------------------------

    Cabot Norit Activated Carbon is the largest producer of powdered 
activated carbon worldwide.\79\ Cabot Norit offers different grades of 
their DARCO[supreg] powdered activated carbon (PAC) for Hg removal at 
power plants. These grades include non-impregnated PAC which are ideal 
when most of the Hg is in the oxidized state; impregnated PAC for 
removing oxidized and Hg\0\ from flue gas; special impregnated PAC used 
in conjunction with DSI systems (for control of acid gases); and 
special impregnated ``sulfur resistant'' PAC for flue gases that 
contains higher concentrations of acidic gases like SO3.
---------------------------------------------------------------------------

    \79\ https://norit.com/application/power-steel-cement/power-plants.

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[[Page 38547]]

    Similarly, ADA-ES offers FastPACTM Platinum 80,\80\ an 
activated carbon sorbent that was specifically engineered for 
SO3 tolerance and for use in applications where 
SO3 levels are high. So, owner/operators of lignite-fired 
EGUs can choose from a range of technologies and technology providers 
that offer Hg control options in the presence of SO3. The 
EPA also notes that SO3 is more often an issue with EGUs 
firing eastern bituminous coal--as those coals typically have higher 
sulfur content and lower ash alkalinity. Those bituminous coal-fired 
EGUs are subject to--and have demonstrated compliance with--an emission 
standard of 1.2 lb/TBtu.
---------------------------------------------------------------------------

    \80\ https://www.advancedemissionssolutions.com/ADES-Investors/ada-products-and-services/default.aspx.
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4. Cost Considerations for the More Stringent Hg Emission Standard
    From the 2022 CAA section 114 information survey, most lignite-
fired EGUs utilized a control strategy that included sorbent injection 
coupled with chemical additives (usually halogens). In the beyond-the-
floor analysis in the 2012 MATS Final Rule, we noted that the results 
from various demonstration projects suggested that greater than 90 
percent Hg control can be achieved at lignite-fired units using 
brominated activated carbon sorbents at an injection rate of 2.0 lb/
MMacf (i.e., 2.0 pounds of sorbent injected per million actual cubic 
feet of flue gas) for units with installed FFs for PM control and at an 
injection rate of 3.0 lb/MMacf for units with installed ESPs for PM 
control. As shown in table 7 of this document, all units (in 2022) 
would have needed to control their Hg emissions to 95 percent or less 
to meet an emission standard of 1.2 lb/TBtu. Based on this, we expect 
that the units could meet the final, more stringent, emission standard 
of 1.2 lb/TBtu by utilizing brominated activated carbon at the 
injection rates suggested in the beyond-the-floor memorandum from the 
2012 MATS Final Rule.
BILLING CODE 6560-50-P

[[Page 38548]]

[GRAPHIC] [TIFF OMITTED] TR07MY24.073

BILLING CODE 6560-50-C
    To determine the cost effectiveness of that strategy, we calculated 
the cost per lb of Hg controlled for a model 800 MW lignite-fired EGU, 
as described in the 2024 Technical Memo. We calculated the cost of 
injecting brominated activated carbon sorbent at injection rates 
suggested in the beyond-the-floor memorandum from the 2012 MATS Final 
Rule (i.e., 2.0 lb/MMacf and 3.0 lb/MMacf) and at a larger injection 
rate of 5.0 lb/MMacf to achieve an emission rate of 1.2 lb/TBtu. We 
also calculated the incremental cost to meet the more stringent 
emission rate of 1.2 lb/TBtu versus the cost to meet an emission rate 
of 4.0 lb/TBtu using non-brominated activated carbon sorbent at an 
emission rate of 2.5 lb/MMacf. For an 800 MW lignite-fired EGU, the 
cost effectiveness of using the brominated carbon sorbent at an 
injection rate of 3.0 lb/MMacf was $3,050 per lb of Hg removed while 
the incremental cost effectiveness was $10,895 per incremental lb of Hg 
removed at a brominated activated carbon injection rate of 3.0 lb/
MMacf. The cost effectiveness of using the brominated carbon sorbent at 
an injection rate of 5.0 lb/MMacf was $5,083 per lb of Hg removed while 
the incremental cost effectiveness was $28,176 per incremental lb of Hg 
removed. The actual cost effectiveness is likely lower than either of 
these estimates as it is unlikely that sources will need to inject 
brominated activated carbon sorbent at rates as high as 5.0 lb/MMacf 
(from the 2022 CAA section 114 information collection, the Oak Grove 
units were injecting less than 0.5 lb/MMacf) and is either well below 
or reasonably consistent with the cost effectiveness that the EPA has 
found to

[[Page 38549]]

be acceptable in previous rulemakings for Hg controls.\82\
---------------------------------------------------------------------------

    \81\ Estimated Hg inlet values are based on fuel use data from 
EIA Form 923 and assumed Hg content of coals as shown in Table 5 and 
Table 6 in this preamble.
    \82\ For example, the EPA proposed that $27,500 per lb of Hg 
removed was cost-effective for the Primary Copper RTR (87 FR 1616); 
and approximately $27,000 per lb of Hg ($2021) was found to be cost-
effective in the beyond-the-floor analysis supporting the 2012 MATS 
Final Rule.
---------------------------------------------------------------------------

    In addition to cost effectiveness, the EPA finds that the revised 
Hg emission standard for lignite-fired units appropriately considers 
the costs of controls, both total costs and as a fraction of total 
revenues, along with other factors that the EPA analyzed pursuant to 
its CAA section 112(d)(6) authority. Similar to the revised fPM 
emission standard (as a surrogate for non-Hg HAP metals) discussed in 
section IV. of this preamble, the EPA anticipates that the total costs 
of controls (which consists of small annual incremental operating 
costs) to comply with the revised Hg emission standard will be a small 
fraction of the total revenues for the impacted lignite-fired units. 
The EPA expects that sources will be able to meet the revised emission 
standard using existing controls (e.g., using existing sorbent 
injection equipment), and that significant additional capital 
investment is unlikely. If site-specific conditions necessitate minor 
capital improvements to the ACI control technology, it is important to 
note that any incremental capital would be small relative to ongoing 
sorbent costs accounted for in this analysis. Further, in addition to 
the EPA finding that costs are reasonable for the revised Hg standard 
for lignite-fired EGUs, the revised standard will also bring these 
higher emitting sources of Hg emission in line with Hg emission rates 
that are achieved by non-lignite-fired EGUs. As mentioned earlier in 
this preamble, in 2021, lignite-fired EGUs were responsible for almost 
30 percent of all Hg emitted from coal-fired EGUs while generating 
about 7 percent of total megawatt-hours.
    Despite the known differences in the quality and composition of the 
various coal types, the EPA can find no compelling reasons why EGUs 
that are firing lignite cannot meet the same emission limit as EGUs 
that are firing other types of coal (e.g., eastern and western 
bituminous coal, subbituminous coal, and anthracitic and bituminous 
waste coal). Each of the coal types/ranks has unique compositions and 
properties. Low halogen content in coal is known to make Hg capture 
more challenging. But, both lignites and subbituminous coals have low 
halogen content with higher alkaline content. Lignites tend to have 
average higher Hg content than subbituminous and bituminous coals--
especially lignites mined in Mississippi and Texas. However, waste 
coals (anthracitic and bituminous coal refuse) tend to have the highest 
average Hg content. Lignites tend to have higher sulfur content than 
that of subbituminous coals and the sulfur in the coal can form 
SO3 in the flue gas. This SO3 is known to make Hg 
capture using sorbent injection more challenging. However, bituminous 
coals and waste coals have similar or higher levels of sulfur. The 
formation of SO3 is more significant with these coals. 
Despite all the obstacles and challenges presented to EGUs firing non-
lignite coals, all of those EGUs have been subject to the more 
stringent Hg emission limit of 1.2 lb/TBtu--and emit at or below that 
emission limit since the rule was fully implemented. Advanced, better 
performing Hg controls--including ``SO3 tolerant'' 
sorbents--are available to allow lignite-fired EGUs to also emit at or 
below the more stringent Hg emission limit of 1.2 lb/TBtu. As mentioned 
earlier in this preamble, in 2021, lignite-fired EGUs were responsible 
for almost 30 percent of all Hg emitted from coal-fired EGUs while 
generating about 7 percent of total megawatt-hours.

VI. What is the rationale for our other final decisions and amendments 
from review of the 2020 Technology Review?

A. What did we propose pursuant to CAA section 112(d)(6) for the other 
NESHAP requirements?

    The EPA did not propose any changes to the organic HAP work 
practice standards, acid gas standards, continental liquid oil-fired 
EGU standards, non-continental liquid oil-fired EGUs, limited-use oil-
fired EGU standards, or standards for IGCC EGUs. The EPA proposed to 
require that IGCC EGUs use PM CEMS for compliance demonstration with 
their fPM standard.
    The EPA did note in the 2023 Proposal that there have been several 
recent temporary and localized increases in oil combustion at 
continental liquid oil-fired EGUs during periods of extreme weather 
conditions, such as the 2023 polar vortex in New England. As such, the 
EPA solicited comment on whether the current definition of the limited-
use liquid oil-fired subcategory remains appropriate or if, given the 
increased reliance on oil-fired generation during periods of extreme 
weather, a period other than the current 24-month period or a different 
threshold would be more appropriate for the current definition. The EPA 
also solicited comment on the appropriateness of including new HAP 
standards for EGUs subject to the limited use liquid oil-fired 
subcategory, as well as on the means of demonstrating compliance with 
the new HAP standards.

B. How did the technology review change for the other NESHAP 
requirements?

    The technology review for the organic HAP work practice standards, 
acid gas standards, and standards for oil-fired EGUs has not changed 
from the proposal.
    The proposed technology review with respect to the use of PM CEMS 
for compliance demonstration by IGCC EGUs has changed due to comments 
received on the very low fPM emission rates and on technical challenges 
with certifying PM CEMS on IGCC EGUs. Therefore, the Agency is not 
finalizing the required use of PM CEMS for compliance demonstration 
with the fPM emission standard at IGCC EGUs.

C. What key comments did we receive on the other NESHAP requirements, 
and what are our responses?

    Comment: Commenters urged the EPA to retain the current definition 
of the limited-use liquid oil-fired subcategory and not to impose new 
HAP standards on EGUs in this subcategory, given that there are already 
limits on the amount of fuel oil that can be burned. Commenters noted 
that the Agency has not identified any justification for the costs 
required for implementation and compliance with new HAP standards for 
limited-use liquid oil-fired EGUs. Some commenters alleged that any 
changes to the existing HAP standards for EGUs in the limited-use 
liquid oil-fired subcategory may complicate reliability management 
during cold winter spells or other extreme weather events.
    Response: The Agency did not propose changes to the limited-use 
liquid oil-fired EGU subcategory or to the requirements for such units. 
To evaluate the potential HAP emission impact of liquid oil-fired EGUs 
\83\ during extreme weather events, the Agency reviewed the 2022 fPM 
emissions of 11 liquid oil-fired EGUs in the Northeast U.S. that were 
operated during December 2022 Winter Storm Elliot, as described in the 
2024 Technical Memo. The review found that total non-Hg HAP metal 
emissions during 2022 from the 11 oil-fired EGUs in New England were 
very small--approximately 70 times lower than the non-Hg HAP metal 
emissions estimated from oil-fired units

[[Page 38550]]

in Puerto Rico, which were among the facilities with the highest (but 
acceptable) residual risk in the 2020 Residual Risk Review.\84\ The EPA 
will continue to monitor the emissions from the dispatch of limited-use 
liquid oil-fired EGUs--especially during extreme weather events.
---------------------------------------------------------------------------

    \83\ Oil-fired EGUs burning residual fuel oil have generally 
higher emission rates of HAP compared to that from the use of other 
types of fuel.
    \84\ See Residual Risk Assessment for the Coal- and Oil-Fired 
EGU Source Category in Support of the 2019 Risk and Technology 
Review Proposed Rule (Docket ID No. EPA-HQ-OAR-2018-0794-0014).
---------------------------------------------------------------------------

    In addition, the Agency reviewed the performance of PM CEMS for 
compliance demonstration at oil-fired EGUs. Given the higher emission 
rates and limits from this subcategory of EGUs, the Agency did not find 
any of the correlation issues with the use of PM CEMS with oil-fired 
EGUs similar to those that were discussed earlier for coal-fired EGUs. 
Moreover, the benefits of PM CEMS use that were described earlier 
(i.e., emissions transparency, operational feedback, etc.) translate 
well to oil-fired EGUs; therefore, the EPA is finalizing the 
requirement for oil-fired EGUs (excluding limited-use liquid oil-fired 
EGUs) to use PM CEMS for compliance demonstration, as proposed.
    Comment: One commenter recommended that units involved with carbon 
capture and sequestration (CCS) projects retain the option to use stack 
testing for compliance demonstration. They said that PM emissions would 
be measured from the stack downstream of the carbon capture system 
(they specifically mentioned the carbon capture system being 
contemplated to be built to capture CO2 emission from the 
Milton R. Young Station facility in North Dakota). The commenters said 
that PM CEMS correlation testing will cause operational impacts on the 
CCS operations due to operational changes or reduced control 
efficiencies that temporarily increase PM emissions for long time 
periods, resulting in CCS operations being adversely affected or even 
shut down for long periods.
    Response: The Agency disagrees with the commenter's recommendation 
that units utilizing a carbon capture system should be able to continue 
to use periodic stack testing for compliance demonstration. At the 
present time, the many ways that CCS can be employed and deployed at 
coal-fired EGUs supports the use of PM CEMS for compliance purposes. 
For example, measures (such as a bypass stack) are available that would 
minimize the operational impacts on the carbon capture system and would 
allow for proper PM CEMS correlations. Furthermore, the Agency finds 
that the increased transparency and the improved ability to detect and 
correct potential control or operational problems offered by PM CEMS, 
as well as the greater assurance of continuous compliance, outweigh the 
minor operational impacts potentially experienced. To the extent that a 
specific coal- or oil-fired EGU utilizing CCS wishes to use an 
alternative test method for compliance demonstration purposes, its 
owner or operator may submit a request to the Administrator under the 
provisions of 40 CFR 63.7(f).

D. What is the rationale for our final approach and decisions regarding 
the other NESHAP requirements?

    The Agency did not receive comments that led to any changes in the 
outcome of the technology review for other NESHAP requirements as 
presented in the 2023 Proposal. The Agency did not propose any changes 
for the current requirements for organic HAP work practice standards, 
acid gas standards, or standards for oil-fired EGUs and therefore no 
changes are being finalized.
    The EPA is aware of two existing IGCC facilities that meet the 
definition of an IGCC EGU. The Edwardsport Power Station, located in 
Knox County, Indiana, includes two IGCC EGUs that had 2021 average 
capacity factors of approximately 85 percent and 67 percent. These EGUs 
have LEE qualification for PM, with most current test results of 0.0007 
and 0.0003 lb/MMBtu, respectively. The Polk Power Station, located in 
Polk County, Florida, had a 2021 average capacity factor of 
approximately 70 percent but burned only natural gas in 2021 (i.e., 
operating essentially as a natural gas combined cycle turbine EGU). 
Before this EGU switched to pipeline quality natural gas as a fuel, it 
qualified for PM LEE status in 2018; to the extent that the EGU again 
operates as an IGCC, it could continue to claim PM LEE status. While 
this subcategory has a less stringent fPM standard of 0.040 lb/MMBtu 
(as compared to that of coal-fired EGUs), recent compliance data 
indicate fPM emissions well below the most stringent standard option of 
0.006 lb/MMBtu that was evaluated for coal-fired EGUs.
    The EPA is not finalizing the required use of PM CEMS for 
compliance demonstration for IGCC EGUs due to technical limitations 
expressed by commenters. For example, commenters noted that due to 
differences in stack design, the only possible installation space for a 
PM CEMS on an IGCC facility is on a stack with elevated grating, 
exposing the instrument to the elements, which would impact the 
sensitivity and accuracy of a PM CEMS. Additionally, there are no PM 
control devices at an IGCC unit available for de-tuning, which is 
necessary for establishing a correlation curve under PS-11. The EPA has 
considered these comments and agrees with these noted challenges to the 
use of PM CEMS at IGCC EGUs and, for those reasons, the EPA is not 
finalizing the proposed requirement for IGCCs to use PM CEMS for 
compliance demonstration, thus IGCCs will continue to demonstrate 
compliance via fPM emissions testing. As a result of comments we 
received on coal-fired run durations and our consideration on those 
comments, along with the low levels of reported emissions, the EPA 
determined that owners or operators of IGCCs will need to ensure each 
run has a minimum sample volume of 2 dscm or a minimum mass collection 
of 3 milligrams. In addition, IGCC EGUs will continue to be able to 
obtain and maintain PM LEE status.

VII. Startup Definition for the Coal- and Oil-Fired EGU Source Category

A. What did we propose for the Coal- and Oil-Fired EGU source category?

    In the 2023 Proposal, the EPA proposed to remove the alternative 
work practice standards, i.e., those contained in paragraph (2) of the 
definition of ``startup'' in 40 CFR 63.10042 from the rule based on a 
petition for reconsideration from environmental groups that was 
remanded to the EPA in Chesapeake Climate Action Network v. EPA, 952 
F.3d 310 (D.C. Cir. 2020), and responding in part to a separate 
petition for reconsideration from environmental groups, that sought the 
EPA's reconsideration of certain aspects of the 2020 Residual Risk 
Review.\85\ The first option under paragraph (1) 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. 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 onsite 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

[[Page 38551]]

event. Startup ends 4 hours after the EGU generates electricity that is 
sold or used for any purpose (including onsite use), or 4 hours after 
the EGU makes useful thermal energy for industrial, commercial, 
heating, or cooling purposes, whichever is earlier.
---------------------------------------------------------------------------

    \85\ See Document ID No. EPA-HQ-OAR-2018-0794-4565 at https://www.regulations.gov.
---------------------------------------------------------------------------

    As described in the 2023 Proposal, the Agency proposed to remove 
paragraph (2) of the definition of ``startup'' as part of our 
obligation to address the remand on this issue. In addition, as the 
majority of EGUs currently rely on work practice standards under 
paragraph (1) of the definition of ``startup,'' we believe this change 
is achievable by all EGUs and would result in little to no additional 
expenditures, especially since the additional reporting and 
recordkeeping requirements associated with use of paragraph (2) would 
no longer apply. Lastly, the time period for engaging PM or non-Hg HAP 
metal controls after non-clean fuel use, as well as for full operation 
of PM or non-Hg HAP metal controls, is expected to be reduced when 
transitioning to paragraph (1), therefore increasing the duration in 
which pollution controls are employed and lowering emissions.

B. How did the startup provisions change for the Coal- and Oil-Fired 
EGU source category?

    The EPA is finalizing the amendment to remove paragraph (2) from 
the definition of ``startup'' as proposed.

C. What key comments did we receive on the startup provisions, and what 
are our responses?

    We received both supportive and adverse comments on the proposed 
removal of paragraph (2) of the definition of ``startup.'' The 
summarized comments and the EPA's responses are provided in the 
National Emission Standards for Hazardous Air Pollutants: Coal- and 
Oil-Fired Electric Utility Steam Generating Units Review of the 
Residual Risk and Technology Review Proposed Rule Response to Comments 
document. The most significant adverse comments and the EPA's responses 
are provided below.
    Comment: Commenters recommended that the 4-hour startup definition 
should continue to be allowed as removing it for simplicity is not an 
adequate justification. They said the EPA is conflating the MACT 
standard-setting process with this RTR process. Although the EPA notes 
that the best performing 12 percent of sources do not need this 
alternative startup definition, commenters stated that this change is 
beyond the scope of the technology review. Commenters asserted that the 
EPA's determination that only eight EGUs are currently using that 
option is insufficient justification for eliminating the definition. 
Given that the 2023 Proposal did not identify any flaws with the 
current definition, the commenters stated that the EPA should explain 
why elimination of the 4-hour definition from MATS is appropriate when 
there are units currently relying on it. Commenters also stated that 
the EPA should consider providing reasonable exemptions for the EGUs 
that currently use that definition, thus gradually phasing out the 
definition without imposing any additional compliance burdens. The 
commenters also argued that with potentially lower fPM standards, more 
facilities may need the additional flexibility allowed by this 
definition of startup as their margin of compliance is reduced. They 
noted that startup or non-steady state operation is not conducive to 
CEMS accuracy and that it may create false reporting of emissions data 
biased either high or low depending on the actual conditions.
    Commenters stated that several facilities are currently required to 
use the 4-hour startup definition per federal consent decrees or state 
agreements. They said such a scenario provides clear justification for 
a limited exemption, as MATS compliance should not result in an EGU 
violating its consent decree. Commenters noted other scenarios where 
state permits have special conditions with exemptions from emission 
limits during ramp-up or ramp-down periods. They said many facilities 
alleviate high initial emissions by using alternate fuels to begin the 
combustion process, which has been demonstrated as a Best Management 
Practice and to lower emissions. Commenters noted that the permit 
modification process, let alone any physical or operational 
modifications to the facility, could take significantly longer than the 
180-day compliance deadline, depending on public comments, meetings, or 
contested hearing requests made during the permit process.
    Commenters stated the startup definition paragraph (2) has seen 
limited use due to the additional reporting requirements that the EPA 
imposed on sources that chose to use the definition, which they believe 
are unnecessary and should be removed from the rule. The commenters 
said that the analysis the EPA conducted during the startup/shutdown 
reconsideration in response to Chesapeake Climate Action Network v. 
EPA, 952 F.3d 310 (D.C. Cir. 2020) showed that the definition was 
reasonable, and they argued that the definition may be needed if the 
EPA further reduces the limits, given the transitory nature of unit and 
control operation during these periods. Commenters also stated that the 
startup definition paragraph (2) is beneficial to units that require 
extended startups. They said including allowances for cold startup 
conditions could allow some EGUs to continue operation until more 
compliant generation is built, which would help facilitate a smooth 
transition to newer plants that meet the requirements without risking 
the reliability of the electric grid. Commenters also noted that some 
control devices, such as ESPs, may not be operating fully even when the 
plant begins producing electricity.
    Commenters stated that the EPA should consider allowing the use of 
diluent cap values from 40 CFR part 75. As these are limited under 
MATS, commenters noted that startup and shutdown variations are more 
pronounced than if diluent caps were to be allowed. They said that with 
a lower emissions limitation, the diluent cap would mathematically 
correct for calculation inaccuracies inherent in emission rate 
calculation immediately following startup. Commenters stated that 
relative accuracy test audits (RATA) must be conducted at greater than 
50 percent load under 40 CFR part 60 and at normal operating load under 
40 CFR part 75. They said that it is not reasonable to require 
facilities to certify their CEMS, including PM CEMS, at greater than 50 
percent capacity and use it for compliance at less than 50 percent 
capacity. Commenters stated that startups have constantly changing flow 
and temperatures that do not allow compliance tests to be conducted 
during these periods.
    Response: The Agency disagrees with the commenters who suggest that 
the 4-hour startup duration should be retained. As mentioned in the 
2023 Proposal (88 FR 24885), owners or operators of coal- and oil-fired 
EGUs that generated over 98 percent of electricity in 2022 have made 
the requisite adjustments, whether through greater clean fuel capacity, 
better tuned equipment, better trained staff, a more efficient and/or 
better design structure, or a combination of factors, to be able to 
meet the requirements of paragraph (1) of the startup definition. This 
ability points out an improvement in operation that all EGUs should be 
able to meet at little to no additional expenditure, since the 
additional recordkeeping and reporting provisions associated with the 
work practice standards of paragraph (2) of the startup definition were 
more expensive than the requirements of paragraph (1) of the 
definition. As mentioned with respect to gathering

[[Page 38552]]

experience with PM CEMS, the Agency believes owners or operators of the 
8 EGUs relying on the 4-hour startup period can build on their startup 
experience gained since finalization of the 2012 MATS Final Rule, along 
with the experience shared by some of the other EGUs that have been 
able to conform with startup definition paragraph (1), as well as the 
experience to be obtained in the period yet remaining before compliance 
is required; such experience could prove key to aiding source owners or 
operators in their shift from reliance on startup definition paragraph 
(2) to startup definition paragraph (1). Should EGU owners or operators 
find that their attempts to rely on startup definition (1) are 
unsuccessful after application of that experience, they may request of 
the Administrator the ability to use an alternate non-opacity standard, 
as described in the NESHAP general provisions at 40 CFR 63.6(g). Before 
the Administrator's approval can be granted, the EGU owner or 
operator's request must appear in the Federal Register for the 
opportunity for notice and comment by the public, as required in 40 CFR 
63.6(g)(1).
    Regarding consent decrees or state agreements for requirements 
other than those contained in this rule, while the rule lacks the 
ability to revise such agreements, the EPA recommends that EGU owners 
or operators contact the other parties to see what, if any, revisions 
could be made. Nonetheless, the Agency expects EGU source owners or 
operators to comply with the revised startup definition by the date 
specified in this rule. Given the concern expressed by the commenters 
for some sources, the Agency expects such source owners or operators to 
begin negotiations with other parties for other non-rule obligations to 
begin early enough to be completed prior to the compliance date 
specified in this rule.
    The Agency disagrees with the commenters' suggestions that startup 
definition paragraph (2)'s reporting requirements were too strict to be 
used. That suggestion is not consistent with the number of commenters 
who claimed to need to use paragraph (2) of the startup definition, 
even though only 2.5 percent of EGUs currently rely on this startup 
definition. The Agency's experience is that almost all EGU source 
owners or operators have been able to adjust their unit operation such 
that adherence to startup definition paragraph (1) reduced, if not 
eliminated, the concern by some about use of startup definition 
paragraph (1). As mentioned earlier in this document, the better 
performers in the coal-fired EGU source category no longer need to 
have, or use, paragraph (2) of the startup definition after gaining 
experience with using paragraph (1).
    The Agency disagrees with the commenter's suggestion that the 
diluent cap values allowed for use by 40 CFR part 75 be included in the 
rule, because diluent cap values are already allowed for use during 
startup and shutdown periods per 40 CFR 63.10007(f)(1). Note that while 
emission values are to be recorded and reported during startup and 
shutdown periods, they are not to be used in compliance calculations 
per 40 CFR 63.10020(e). In addition to diluent cap use during startup 
and shutdown periods, section 6.2.2.3 of appendix C to 40 CFR part 63, 
subpart UUUUU allows diluent cap use for PM CEMS during any periods 
when oxygen or CO2 values exceed or dip below, respectively, 
the cap levels. Diluent cap use for other periods from other 
regulations are not necessary for MATS. The Agency does not understand 
the commenter's suggestion concerning the load requirement for a RATA. 
The Agency believes the commenter may have mistaken HCl CEMS 
requirements, which use RATAs but were not proposed to be changed, with 
PM CEMS requirements, which do not use RATAs. Since PM CEMS are not 
subject to RATAs and the Agency did not propose changes to requirements 
for HCl CEMS, the comment on RATAs being conducted at greater than 50 
percent load is moot. The EPA is finalizing the removal of startup 
definition paragraph (2), as proposed.

D. What is the rationale for our final approach and final decisions for 
the startup provisions?

    The EPA is finalizing the removal of paragraph (2) of the 
definition of ``startup'' in 40 CFR 63.10042 consistent with reasons 
described in the 2023 Proposal. As the majority of EGUs are already 
relying on the work practice standards in paragraph (1) of the startup 
definition, the EPA finds that such a change is achievable within the 
180-day compliance timeline by all EGUs at little to no additional 
expenditure since the additional reporting and recordkeeping provisions 
under paragraph (2) were more expensive than paragraph (1). 
Additionally, the time period for engaging pollution controls for PM or 
non-Hg HAP metals is expected to be reduced when transitioning to 
paragraph (1), therefore increasing the duration in which pollution 
controls are employed and lowering emissions.

VIII. What other key comments did we receive on the proposal?

    Comment: Some commenters argued that it is well-established that 
cost is a major consideration in rulemakings reviewing existing NESHAP 
under CAA section 112(d)(6). In particular, commenters cited to 
Michigan v. EPA, 576 U.S. 743, 759 (2015), to support the argument that 
the EPA must consider the costs of the regulation in relation to the 
benefits intended by the statutory requirement mandating this 
regulation, that is, the benefits of the HAP reductions. Commenters 
stated that the EPA should not seek to impose the excessive costs 
associated with this action as there would be no benefit associated 
with reducing HAP. The commenters said that the EPA certainly should 
not do so for an industry that is rapidly reducing its emissions 
because it is on the way to retiring most, if not all, units in the 
source category in little over a decade. The commenters also claimed 
that as Michigan held that cost and benefits must be considered in 
determining whether it is ``appropriate'' to regulate EGUs under CAA 
section 112 in the first place, it necessarily follows that the same 
threshold must also apply when the EPA subsequently reviews the 
standards.
    Response: The EPA agrees that it is appropriate to take costs into 
consideration in deciding whether it is necessary to revise an existing 
NESHAP under CAA section 112(d)(6). As explained in the 2023 Proposal 
and this document, the EPA has carefully considered the costs of 
compliance and the effects of those costs on the industry. Although the 
commenters seem to suggest that the EPA should weigh the costs and 
benefits of the revisions to the standard, we do not interpret the 
comments as arguing that the EPA should undertake a formal benefit cost 
analysis but rather the commenters believe that the EPA should instead 
limit its analysis supporting the standard to HAP emission reductions. 
Our consideration of costs in this rulemaking is consistent with the 
Supreme Court's direction in Michigan where the Court noted that ``[i]t 
will be up to the Agency to decide (as always, within the limits of 
reasonable interpretation) how to account for cost,'' 576 U.S. 743, 759 
(2015), and with comments arguing that the EPA should focus its 
decision-making on the standard on the anticipated reductions in HAP.
    In Michigan, the Supreme Court concluded that the EPA erred when it 
concluded it could not consider costs when deciding as a threshold 
matter

[[Page 38553]]

whether it is ``appropriate and necessary'' under CAA section 
112(n)(1)(A) to regulate HAP from EGUs, despite the relevant statutory 
provision containing no specific reference to cost. 576 U.S. at 751. In 
doing so, the Court held that the EPA ``must consider cost--including, 
most importantly, cost of compliance--before deciding whether 
regulation is appropriate and necessary'' under CAA section 112. Id. at 
759. In examining the language of CAA section 112(n)(1)(A), the Court 
concluded that the phrase ``appropriate and necessary'' was 
``capacious'' and held that ``[r]ead naturally in the present context, 
the phrase `appropriate and necessary' requires at least some attention 
to cost.'' Id. at 752. As is clear from the record for this rulemaking, 
the EPA has carefully considered cost in reaching its decision to 
revise the NESHAP in this action.
    The EPA has also taken into account the numerous HAP-related 
benefits of the final rule in deciding to take this action. These 
benefits include not only the reduced exposure to Hg and non-Hg HAP 
metals, but also the additional transparency provided by PM CEMS for 
communities that live near sources of HAP, and the assurance PM CEMS 
will provide that the standards are being met on a continuous basis. As 
discussed in section II.B.2., and section IX.E. many of these important 
benefits are not able to be monetized. Although this rule will result 
in the reduction of HAP, including Hg, lead, arsenic, chromium, nickel, 
and cadmium, data limitations prevent the EPA from assigning monetary 
value to those reductions. In addition, there are several benefits 
associated with the use of PM CEMS which are not quantified in this 
rule.
    While the Court's examination of CAA section 112(n)(a)(1) in 
Michigan considered a different statutory provision than CAA section 
112(d)(6) under which the EPA is promulgating this rulemaking, the EPA 
has nonetheless satisfied the Court's directive to consider costs, both 
in the context of the individual revisions to MATS (as directed by the 
language of the statute) and in the context of the rulemaking as a 
whole. Moreover, while the EPA is not required to undertake a ``formal 
cost benefit analysis in which each advantage and disadvantage [of a 
regulation] is assigned a monetary value,'' Michigan, 576 U.S. at 759, 
the EPA has contemplated and carefully considered both the advantages 
and disadvantages of the revisions it is finalizing here, including 
qualitative and quantitative benefits of the regulation and the costs 
of compliance.

IX. Summary of Cost, Environmental, and Economic Impacts and Additional 
Analyses Conducted

    The following analyses of costs and benefits, and environmental, 
economic, and environmental justice impacts are presented for the 
purpose of providing the public with an understanding of the potential 
consequences of this final action. The EPA notes that analysis of such 
impacts is distinct from the determinations finalized in this action 
under CAA section 112, which are based on the statutory factors the EPA 
discussed in section II.A. and sections IV. through VII.
    The EPA's obligation to conduct an analysis of the potential costs 
and benefits under Executive Order 12866, discussed in this section and 
section X.A., is distinct from its obligation in setting standards 
under CAA section 112 to take costs into account. As explained above, 
the EPA considered costs in multiple ways in choosing appropriate 
standards consistent with the requirements of CAA section 112. The 
benefit-cost analysis is performed to comply with Executive Order 
12866. The EPA, however, did not rely on that analysis in choosing the 
appropriate standard here, consistent with the Agency's longstanding 
interpretation of the statute. As discussed at length in section 
II.B.2. above and in the EPA's 2023 final rulemaking finalizing the 
appropriate and necessary finding (88 FR 13956), historically there 
have been significant challenges in monetizing the benefits of HAP 
reduction. Important categories of benefits from reducing HAP cannot be 
monetized, making benefit-cost analysis ill-suited to the EPA's 
decision making on regulating HAP emissions under CAA section 112. 
Further, there are also unquantified emission reductions anticipated 
from installing PM CEMS, as discussed in section IX.E. For this reason, 
combined with Congress's recognition of the particular dangers posed by 
HAP and consequent direction to the EPA to reduce emissions of these 
pollutants to the ``maximum degree,'' the EPA does not at this time 
believe it is appropriate to rely on the results of the monetized 
benefit-cost analysis when setting the standards.
    As noted in section X.A. below, the EPA projects that the net 
monetized benefits of this rule are negative. Many of the benefits of 
this rule discussed at length in this section and elsewhere in this 
record, however, were not monetized. This rule will result in the 
reduction of HAP, including Hg, lead, arsenic, chromium, nickel, and 
cadmium,\86\ consistent with Congress's direction in CAA section 112 
discussed in section II.A. of this final rule. At this time, data 
limitations prevent the EPA from assigning monetary value to those 
reductions, as discussed in section II.B.2. above.\87\ In addition, the 
benefits of the additional transparency provided by the requirement to 
use PM CEMS for communities that live near sources of HAP, and the 
assurance PM CEMS provide that the standards are being met on a 
continuous basis were not monetized due to data limitations. While the 
EPA does not believe benefit-cost analysis is the right way to 
determine the appropriateness of a standard under CAA section 112, the 
EPA notes that when all of the costs and benefits are considered 
(including non-monetized benefits), this final rule is a worthwhile 
exercise of the EPA's CAA section 112(d)(6) authority.
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    \86\ As of 2023, three of the HAP metals or their compounds 
emitted by EGUs (arsenic, chromium, and nickel) are classified as 
carcinogenic to humans. More details are available in section 
II.B.2. and Chapter 4.2.2 of the RIA.
    \87\ See also National Emission Standards for Hazardous Air 
Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating 
Units--Revocation of the 2020 Reconsideration and Affirmation of the 
Appropriate and Necessary Supplemental Finding, 88 FR 13956, 13970-
73 (March 6, 2023) (for additional discussion regarding the 
limitations to monetizing and quantifying most benefits from HAP 
reductions in the 2023 rulemaking finalizing the appropriate and 
necessary finding).
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A. What are the affected facilities?

    The EPA estimates that there are 314 coal-fired EGUs \88\ and 58 
oil-fired EGUs that will be subject to this final rule by the 
compliance date.
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    \88\ The number of coal-fired affected EGUs is larger than the 
296 coal-fired EGUs assessed for the fPM standard in section IV. 
because it includes four EGUs that burn petroleum coke (which are a 
separate subcategory for MATS) and 14 EGUs without fPM compliance 
data available on the EPA's Compliance and Emissions Data Reporting 
Interface (CEDRI), https://www.epa.gov/electronic-reporting-air-emissions/cedri.
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B. What are the air quality impacts?

    The EPA estimated emission reductions under the final rule for the 
years 2028, 2030, and 2035 based upon IPM projections. The quantified 
emissions estimates were developed with the EPA's Power Sector Modeling 
Platform 2023 using IPM, a state-of-the-art, peer-reviewed dynamic, 
deterministic linear programming model of the contiguous U.S. electric 
power sector. IPM provides forecasts of least-cost capacity expansion, 
electricity dispatch, and emission control strategies while meeting 
electricity demand and various environmental, transmission, dispatch, 
and reliability constraints. IPM's least-cost dispatch

[[Page 38554]]

solution is designed to ensure generation resource adequacy, either by 
using existing resources or through the construction of new resources. 
IPM addresses reliable delivery of generation resources for the 
delivery of electricity between the 78 IPM regions, based on current 
and planned transmission capacity, by setting limits to the ability to 
transfer power between regions using the bulk power transmission 
system. The model includes state-of-the-art estimates of the cost and 
performance of air pollution control technologies with respect to Hg 
and other HAP controls.
    The quantified emission reduction estimates presented in the RIA 
include reductions in pollutants directly covered by this rule, such as 
Hg, and changes in other pollutants emitted from the power sector as a 
result of the compliance actions projected under this final rule. Table 
8 of this document presents the projected emissions under the final 
rule. Note that, unlike the cost-effectiveness analysis presented in 
sections IV. and V. of this preamble, the projections presented in 
table 8 are incremental to a projected baseline which reflects future 
changes in the composition of the operational coal-fired EGU fleet that 
are projected to occur by 2035 as a result of factors affecting the 
power sector, such as the IRA, promulgated regulatory actions, or 
changes in economic conditions.
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BILLING CODE 6560-50-C
    In addition to the projected emissions impacts presented in table 
8, we also estimate that the final rule will reduce at least 7 tons of 
non-Hg HAP metals in 2028, 5 tons of non-Hg HAP metals in 2030, and 4 
tons of non-Hg HAP metals in 2035. These reductions are composed of 
reductions in emissions of antimony, arsenic, beryllium, cadmium,

[[Page 38555]]

chromium, cobalt, lead, manganese, nickel, and selenium.\89\
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    \89\ Note that modeled projections include total PM10 
and total PM2.5. The EPA estimated non-Hg HAP metals 
reductions by multiplying the ratio of non-Hg HAP metals to fPM by 
modeled projections of total PM10 reductions under the 
rule. The ratios of non-Hg HAP metals to fPM were based on analysis 
of 2010 MATS Information Collection Request (ICR) data. As there may 
be substantially more fPM than PM10 reduced by the 
control techniques projected to be used under this rule, these 
estimates of non-Hg HAP metals reductions are likely underestimates. 
More detail on the estimated reduction in non-Hg HAP metals can be 
found in the docketed memorandum Estimating Non-Hg HAP Metals 
Reductions for the 2024 Technology Review for the Coal-Fired EGU 
Source Category.
---------------------------------------------------------------------------

    Importantly, the continuous monitoring of fPM required in this rule 
will likely induce additional emissions reductions that we are unable 
to quantify. Continuous measurements of emissions accounts for changes 
to processes and fuels, fluctuations in load, operations of pollution 
controls, and equipment malfunctions. By measuring emissions across all 
operations, power plant operators and regulators can use the data to 
ensure controls are operating properly and to assess compliance with 
relevant standards. Because CEMS enable power plant operators to 
quickly identify and correct problems with pollution control devices, 
it is possible that fPM emissions could be lower than they otherwise 
would have been for up to 3 months--or up to 3 years if testing less 
frequently under the LEE program--at a time. This potential reduction 
in fPM and non-Hg HAP metals emission resulting from the information 
provided by continuous monitoring coupled with corrective actions by 
plant operators could be sizeable over the existing coal-fired fleet 
and is not quantified in this rulemaking.
    Section 3 of the RIA presents a detailed discussion of the 
emissions projections under the regulatory options as described in the 
RIA. Section 3 also describes the compliance actions that are projected 
to produce the emission reductions in table 8 of this preamble. Please 
see section IX.E. of this preamble and section 4 of the RIA for 
detailed discussions of the projected health, welfare, and climate 
benefits of these emission reductions.

C. What are the cost impacts?

    The power industry's compliance costs are represented in this 
analysis as the change in electric power generation costs between the 
baseline and policy scenarios. In other words, these costs are an 
estimate of the increased power industry expenditures required to 
implement the final requirements of this rule. The compliance cost 
estimates were mainly developed using the EPA's Power Sector Modeling 
Platform 2023 using IPM. The incremental costs of the final rule's PM 
CEMS requirement were estimated outside of IPM and added to the IPM-
based cost estimate presented here and in section 3 of the RIA.
    We estimate the present value (PV) of the projected compliance 
costs over the 2028 to 2037 period, as well as estimate the equivalent 
annual value (EAV) of the flow of the compliance costs over this 
period. All dollars are in 2019 dollars. We estimate the PV and EAV 
using 2, 3, and 7 percent discount rates.\90\ Table 9 of this document 
presents the estimates of compliance costs for the final rule.
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    \90\ Results using the 2 percent discount rate were not included 
in the proposal for this action. The 2003 version of OMB's Circular 
A-4 had generally recommended 3 percent and 7 percent as default 
rates to discount social costs and benefits. The analysis of the 
proposed rule used these two recommended rates. In November 2023, 
OMB finalized an update to Circular A-4, in which it recommended the 
general application of a 2 percent rate to discount social costs and 
benefits (subject to regular updates). The Circular A-4 update also 
recommended consideration of the shadow price of capital when costs 
or benefits are likely to accrue to capital. As a result of the 
update to Circular A-4, we include cost and benefits results 
calculated using a 2 percent discount rate.
[GRAPHIC] [TIFF OMITTED] TR07MY24.075

    The PV of the compliance costs for the final rule, discounted at 
the 2 percent rate, is estimated to be about $860 million, with an EAV 
of about $96 million. At the 3 percent discount rate, the PV of the 
compliance costs of the final rule is estimated to be about $790 
million, with an EAV of about $92 million. At the 7 percent discount 
rate, the PV of the compliance costs of the rule is estimated to be 
about $560 million, with an EAV of about $80 million.
    We note that IPM provides the EPA's best estimate of the costs of 
the rules to the electricity sector and related energy sectors (i.e., 
natural gas, coal mining). These compliance cost estimates are used as 
a proxy for the social cost of the rule. For a detailed description of 
these compliance cost projections, please see section 3 of the RIA, 
which is available in the docket for this action.

D. What are the economic impacts?

    The Agency estimates that this rule will require additional fPM 
and/or Hg removal at less than 15 GW of operable capacity in 2028, 
which is about 14 percent of the total coal-fired EGU capacity 
projected to operate in that year. The units requiring additional fPM 
and/or Hg removal are projected to generate less than 2 percent of 
total generation in 2028. Moreover, the EPA does not project that any 
EGUs will retire in response to the standards promulgated in this final 
rule.
    Consistent with the small share of EGUs required to reduce fPM and/
or Hg emissions rates, this final action has limited energy market 
implications. There are limited impacts on energy prices projected to 
result from this final rule. On a national average basis,

[[Page 38556]]

delivered coal, natural gas, and retail electricity prices are not 
projected to change. The EPA does not project incremental changes in 
existing operational capacity to occur in response to the final rule. 
Coal production for use in the power sector is not projected to change 
significantly by 2028.
    The short-term estimates for employment needed to design, 
construct, and install the control equipment in the 3-year period 
before the compliance date are also provided using an approach that 
estimates employment impacts for the environmental protection sector 
based on projected changes from IPM on the number and scale of 
pollution controls and labor intensities in relevant sectors. Finally, 
some of the other types of employment impacts that will be ongoing are 
estimated using IPM outputs and labor intensities, as reported in 
section 5 of the RIA.

E. What are the benefits?

    The RIA for this action analyzes the benefits associated with the 
projected emission reductions under this rule. This final rule is 
projected to reduce emissions of Hg and non-Hg HAP metals, as well as 
PM2.5, SO2, NOX and CO2 
nationwide. The potential impacts of these emission reductions are 
discussed in detail in section 4 of the RIA. The EPA notes that the 
benefits analysis is distinct from the statutory determinations 
finalized herein, which are based on the statutory factors the EPA is 
required to consider under CAA section 112. The assessment of benefits 
described here and in the RIA is presented solely for the purposes of 
complying with Executive Order 12866, as amended by Executive Order 
14094, and providing the public with a complete depiction of the 
impacts of the rulemaking.
    Hg is a persistent, bioaccumulative toxic metal emitted from power 
plants that exists in three forms: gaseous elemental Hg, inorganic Hg 
compounds, and organic Hg compounds (e.g., methylmercury). Hg can also 
be emitted in a particle-bound form. Elemental Hg can exist as a shiny 
silver liquid, but readily vaporizes into air. Airborne elemental Hg 
does not quickly deposit or chemically react in the atmosphere, 
resulting in residence times that are long enough to contribute to 
global scale deposition. Oxidized Hg and particle-bound Hg deposit 
quickly from the atmosphere impacting local and regional areas in 
proximity to sources. Methylmercury is formed by microbial action in 
the top layers of sediment and soils, after Hg has precipitated from 
the air and deposited into waterbodies or land. Once formed, 
methylmercury is taken up by aquatic organisms and bioaccumulates up 
the aquatic food web. Larger predatory fish may have methylmercury 
concentrations many times that of the concentrations in the freshwater 
body in which they live.
    All forms of Hg are toxic, and each form exhibits different health 
effects. Acute (short-term) exposure to high levels of elemental Hg 
vapors results in central nervous system (CNS) effects such as tremors, 
mood changes, and slowed sensory and motor nerve function. Chronic 
(long-term) exposure to elemental Hg in humans also affects the CNS, 
with effects such as erethism (increased excitability), irritability, 
excessive shyness, and tremors. The major effect from chronic ingestion 
or inhalation of low levels of inorganic Hg is kidney damage.
    Methylmercury is the most common organic Hg compound in the 
environment. Acute exposure of humans to very high levels of 
methylmercury results in profound CNS effects such as blindness and 
spastic quadriparesis. Chronic exposure to methylmercury, most commonly 
by consumption of fish from Hg contaminated waters, also affects the 
CNS with symptoms such as paresthesia (a sensation of pricking on the 
skin), blurred vision, malaise, speech difficulties, and constriction 
of the visual field. Ingestion of methylmercury can lead to significant 
developmental effects, such as IQ loss measured by performance on 
neurobehavioral tests, particularly on tests of attention, fine motor-
function, language, and visual spatial ability. In addition, evidence 
in humans and animals suggests that methylmercury can have adverse 
effects on both the developing and the adult cardiovascular system, 
including fatal and non-fatal ischemic heart disease (IHD). Further, 
nephrotoxicity, immunotoxicity, reproductive effects (impaired 
fertility), and developmental effects have been observed with 
methylmercury exposure in animal studies.\91\ Methylmercury has some 
genotoxic activity and can cause chromosomal damage in several 
experimental systems. The EPA has concluded that mercuric chloride and 
methylmercury are possibly carcinogenic to humans.92 93
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    \91\ Agency for Toxic Substances and Disease Registry (ATSDR). 
Toxicological Profile for Mercury. Public Health Service, U.S. 
Department of Health and Human Services, Atlanta, GA. 2022.
    \92\ U.S. Environmental Protection Agency. Integrated Risk 
Information System (IRIS) on Methylmercury. National Center for 
Environmental Assessment, Office of Research and Development, 
Washington, DC. 2001.
    \93\ U.S. Environmental Protection Agency. Integrated Risk 
Information System (IRIS) on Mercuric Chloride. National Center for 
Environmental Assessment, Office of Research and Development, 
Washington, DC. 1995.
---------------------------------------------------------------------------

    The projected emissions reductions of Hg are expected to lower 
deposition of Hg into ecosystems and reduce U.S. EGU attributable 
bioaccumulation of methylmercury in wildlife, particularly for areas 
closer to the effected units subject to near-field deposition. 
Subsistence fishing is associated with vulnerable populations. 
Methylmercury exposure to subsistence fishers from lignite-fired units 
is below the current RfD for methylmercury neurodevelopmental toxicity. 
The EPA considers exposures at or below the RfD for methylmercury 
unlikely to be associated with appreciable risk of deleterious effects 
across the population. However, the RfD for methylmercury does not 
represent an exposure level corresponding to zero risk; moreover, the 
RfD does not represent a bright line above which individuals are at 
risk of adverse effects. Reductions in Hg emissions from lignite-fired 
facilities should further reduce exposure to methylmercury for 
subsistence fisher sub-populations located in the vicinity of these 
facilities, which are all located in North Dakota, Texas, and 
Mississippi.
    In addition, U.S. EGUs are a major source of HAP metals emissions 
including selenium, arsenic, chromium, nickel, and cobalt, cadmium, 
beryllium, lead, and manganese. Some HAP metals emitted by U.S. EGUs 
are known to be persistent and bioaccumulative and others have the 
potential to cause cancer. Exposure to these HAP metals, depending on 
exposure duration and levels of exposures, is associated with a variety 
of adverse health effects. The emissions reductions projected under 
this final rule are expected to reduce human exposure to non-Hg HAP 
metals, including carcinogens.
    Furthermore, there is the potential for reductions in Hg and non-Hg 
HAP metal emissions to enhance ecosystem services and improve 
ecological outcomes. The reductions will potentially lead to positive 
economic impacts although it is difficult to estimate these benefits 
and, consequently, they have not been included in the set of quantified 
benefits.
    As explained in section IX.B., the continuous monitoring of fPM 
required in this rule may induce further reductions of fPM and non-Hg 
HAP metals than we project in the RIA for

[[Page 38557]]

this action. As a result, there may be additional unquantified 
beneficial health impacts from these potential reductions. The 
continuous monitoring of fPM required in this rule is also likely to 
provide several additional benefits to the public which are not 
quantified in this rule, including greater certainty, accuracy, 
transparency, and granularity in fPM emissions information than exists 
today.
    The rule is also expected to reduce emissions of direct 
PM2.5, NOX, and SO2 nationally 
throughout the year. Because NOX and SO2 are also 
precursors to secondary formation of ambient PM2.5, reducing 
these emissions would reduce human exposure to ambient PM2.5 
throughout the year and would reduce the incidence of PM2.5-
attributable health effects. The rule is also expected to reduce ozone-
season NOX emissions nationally in most years of analysis. 
In the presence of sunlight, NOX, and volatile organic 
compounds (VOCs) can undergo a chemical reaction in the atmosphere to 
form ozone. Reducing NOX emissions in most locations reduces 
human exposure to ozone and reduces the incidence of ozone-related 
health effects, although the degree to which ozone is reduced will 
depend in part on local concentration levels of VOCs.
    The health effect endpoints, effect estimates, benefit unit values, 
and how they were selected, are described in the technical support 
document titled Estimating PM2.5\-\ and Ozone-Attributable 
Health Benefits (2023). This document describes our peer-reviewed 
approach for selecting and quantifying adverse effects attributable to 
air pollution, the demographic and health data used to perform these 
calculations, and our methodology for valuing these effects.
    Because of projected changes in dispatch under the final 
requirements, the rule is also projected to impact CO2 
emissions. The EPA estimates the climate benefits of CO2 
emission reductions expected from the final rule using estimates of the 
social cost of carbon (SC-CO2) that reflect recent advances 
in the scientific literature on climate change and its economic impacts 
and that incorporate recommendations made by the National Academies of 
Science, Engineering, and Medicine.\94\ The EPA published and used 
these estimates in the RIA for the December 2023 Natural Gas Sector 
final rule titled Standards of Performance for New, Reconstructed, and 
Modified Sources and Emissions Guidelines for Existing Sources: Oil and 
Natural Gas Sector Climate Review (2023 Oil and Natural Gas NSPS/
EG).\95\ The EPA solicited public comment on the methodology and use of 
these estimates in the RIA for the Agency's December 2022 Oil and 
Natural Gas Sector supplemental proposal \96\ that preceded the 2023 
Oil and Natural Gas NSPS/EG and has conducted an external peer review 
of these estimates. The response to public comments document and the 
response to peer reviewer recommendations can be found in the docket 
for the 2023 Oil and Natural Gas NSPS/EG action. Complete information 
about the peer review process is also available on the EPA's 
website.\97\
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    \94\ National Academies of Sciences, Engineering, and Medicine 
(National Academies). 2017. Valuing Climate Damages: Updating 
Estimation of the Social Cost of Carbon Dioxide. National Academies 
Press.
    \95\ Regulatory Impact Analysis of the Standards of Performance 
for New, Reconstructed, and Modified Sources and Emissions 
Guidelines for Existing Sources: Oil and Natural Gas Sector Climate 
Review, Docket ID No. EPA-HQ-OAR-2021-0317, December 2023.
    \96\ Supplemental Notice of Proposed Rulemaking for Standards of 
Performance for New, Reconstructed, and Modified Sources and 
Emissions Guidelines for Existing Sources: Oil and Natural Gas 
Sector Climate Review, 87 FR 74702 (December 6, 2022).
    \97\ https://www.epa.gov/environmental-economics/scghg-tsd-peer-review.
---------------------------------------------------------------------------

    Section 4.4 within the RIA for this final rulemaking provides an 
overview of the methodological updates incorporated into the SC-
CO2 estimates used in this final RIA.\98\ A more detailed 
explanation of each input and the modeling process is provided in the 
final technical report, EPA Report on the Social Cost of Greenhouse 
Gases: Estimates Incorporating Recent Scientific Advances.\99\
---------------------------------------------------------------------------

    \98\ Note that the RIA for the proposal of this rulemaking used 
the SC-CO2 estimates from the Interagency Working Group's 
(IWG) February 2021 Social Cost of Greenhouse Gases Technical 
Support Document (TSD) (IWG 2021) to estimate climate benefits. 
These SC-CO2 estimates were interim values recommended 
for use in benefit-cost analyses until updated estimates of the 
impacts of climate change could be developed. Estimated climate 
benefits using these interim SC-CO2 values (IWG 2021) are 
presented in Appendix B of the RIA for this final rulemaking for 
comparison purposes.
    \99\ Supplementary Material for the Regulatory Impact Analysis 
for the Final Rulemaking, ``Standards of Performance for New, 
Reconstructed, and Modified Sources and Emissions Guidelines for 
Existing Sources: Oil and Natural Gas Sector Climate Review,'' EPA 
Report on the Social Cost of Greenhouse Gases: Estimates 
Incorporating Recent Scientific Advances, Docket ID No. EPA-HQ-OAR-
2021-0317, November 2023.
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    The SC-CO2 is the monetary value of the net harm to 
society associated with a marginal increase in CO2 emissions 
in a given year, or the benefit of avoiding that increase. In 
principle, SC-CO2 includes the value of all climate change 
impacts both negative and positive, including, but not limited to, 
changes in net agricultural productivity, human health effects, 
property damage from increased flood risk and natural disasters, 
disruption of energy systems, risk of conflict, environmental 
migration, and the value of ecosystem services. The SC-CO2, 
therefore, reflects the societal value of reducing emissions of 
CO2 by one metric ton and is the theoretically appropriate 
value to use in conducting benefit-cost analyses of policies that 
affect CO2 emissions. In practice, data and modeling 
limitations restrain the ability of SC-CO2 estimates to 
include all physical, ecological, and economic impacts of climate 
change, implicitly assigning a value of zero to the omitted climate 
damages. The estimates are, therefore, a partial accounting of climate 
change impacts and likely underestimate the marginal benefits of 
abatement.
    Table 10 of this document presents the estimated PV and EAV of the 
projected health and climate benefits across the regulatory options 
examined in the RIA in 2019 dollars discounted to 2023.
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    This final rule is projected to reduce PM2.5 and ozone 
concentrations, producing a projected PV of monetized health benefits 
of about $300 million, with an EAV of about $33 million discounted at 2 
percent. The projected PV of monetized climate benefits of the final 
rule is estimated to be about $130 million, with an EAV of about $14 
million using the SC-CO2 discounted at 2 percent.\100\ Thus, 
this final rule would

[[Page 38559]]

generate a PV of monetized benefits of $420 million, with an EAV of $47 
million discounted at a 2 percent rate.
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    \100\ Monetized climate benefits are discounted using a 2 
percent discount rate, consistent with the EPA's updated estimates 
of the SC-CO2. The 2003 version of OMB's Circular A-4 had 
generally recommended 3 percent and 7 percent as default discount 
rates for costs and benefits, though as part of the Interagency 
Working Group on the Social Cost of Greenhouse Gases, OMB had also 
long recognized that climate effects should be discounted only at 
appropriate consumption-based discount rates. In November 2023, OMB 
finalized an update to Circular A-4, in which it recommended the 
general application of a 2 percent discount rate to costs and 
benefits (subject to regular updates), as well as the consideration 
of the shadow price of capital when costs or benefits are likely to 
accrue to capital (OMB 2023). Because the SC-CO2 
estimates reflect net climate change damages in terms of reduced 
consumption (or monetary consumption equivalents), the use of the 
social rate of return on capital (7 percent under OMB Circular A-4 
(2003)) to discount damages estimated in terms of reduced 
consumption would inappropriately underestimate the impacts of 
climate change for the purposes of estimating the SC-CO2. 
See Section 4.4 of the RIA for more discussion.
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    At a 3 percent discount rate, this final rule is expected to 
generate projected PV of monetized health benefits of $260 million, 
with an EAV of about $31 million discounted at 3 percent. Climate 
benefits remain discounted at 2 percent in this benefits analysis and 
are estimated to be about $130 million, with an EAV of about $14 
million using the SC-CO2. Thus, this final rule would 
generate a PV of monetized benefits of $390 million, with an EAV of $45 
million discounted at a 3 percent rate.
    At a 7 percent discount rate, this final rule is expected to 
generate projected PV of monetized health benefits of $180 million, 
with an EAV of about $25 million discounted at 7 percent. Climate 
benefits remain discounted at 2 percent in this benefits analysis and 
are estimated to be about $130 million, with an EAV of about $14 
million using the SC-CO2. Thus, this final rule would 
generate a PV of monetized benefits of $300 million, with an EAV of $39 
million discounted at a 7 percent rate.
    The benefits from reducing Hg and non-Hg HAP metals and from 
unquantified improvements in water quality were not monetized and are 
therefore not directly reflected in the monetized benefit-cost 
estimates associated with this rulemaking. Potential benefits from the 
increased transparency and accelerated identification of anomalous 
emission anticipated from requiring PM CEMS were also not monetized in 
this analysis and are therefore also not directly reflected in the 
monetized benefit-cost comparisons. We nonetheless consider these 
impacts in our evaluation of the net benefits of the rule and find 
that, if we were able to monetize these beneficial impacts, the final 
rule would have greater net benefits than shown in table 11 of this 
document.

F. What analysis of environmental justice did we conduct?

    For purposes of analyzing regulatory impacts, the EPA relies upon 
its June 2016 ``Technical Guidance for Assessing Environmental Justice 
in Regulatory Analysis,'' which provides recommendations that encourage 
analysts to conduct the highest quality analysis feasible, recognizing 
that data limitations, time, resource constraints, and analytical 
challenges will vary by media and circumstance. The Technical Guidance 
states that a regulatory action may involve potential EJ concerns if it 
could: (1) create new disproportionate impacts on communities with EJ 
concerns; (2) exacerbate existing disproportionate impacts on 
communities with EJ concerns; or (3) present opportunities to address 
existing disproportionate impacts on communities with EJ concerns 
through this action under development.
    The EPA's EJ technical guidance states that ``[t]he analysis of 
potential EJ concerns for regulatory actions should address three 
questions: (A) Are there potential EJ concerns associated with 
environmental stressors affected by the regulatory action for 
population groups of concern in the baseline? (B) Are there potential 
EJ concerns associated with environmental stressors affected by the 
regulatory action for population groups of concern for the regulatory 
option(s) under consideration? (C) For the regulatory option(s) under 
consideration, are potential EJ concerns created or mitigated compared 
to the baseline?'' \101\
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    \101\ See https://www.epa.gov/environmentaljustice/technical-guidance-assessing-environmental-justice-regulatory-analysis.
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    The environmental justice analysis is presented for the purpose of 
providing the public with as full as possible an understanding of the 
potential impacts of this final action. The EPA notes that analysis of 
such impacts is distinct from the determinations finalized in this 
action under CAA section 112, which are based solely on the statutory 
factors the EPA is required to consider under that section. To address 
these questions in the EPA's first quantitative EJ analysis in the 
context of a MATS rule, the EPA developed a unique analytical approach 
that considers the purpose and specifics of this rulemaking, as well as 
the nature of known and potential disproportionate and adverse 
exposures and impacts. However, due to data limitations, it is possible 
that our analysis failed to identify disparities that may exist, such 
as potential EJ characteristics (e.g., residence of historically red-
lined areas), environmental impacts (e.g., other ozone metrics), and 
more granular spatial resolutions (e.g., neighborhood scale) that were 
not evaluated. Also due to data and resource limitations, we discuss 
HAP and climate EJ impacts of this action qualitatively (section 6 of 
the RIA).
    For this rule, we employ two types of analysis to respond to the 
previous three questions: proximity analyses and exposure analyses. 
Both types of analysis can inform whether there are potential EJ 
concerns in the baseline (question 1).\102\ In contrast, only the 
exposure analyses, which are based on future air quality modeling, can 
inform whether there will be potential EJ concerns after implementation 
of the regulatory options under consideration (question 2) and whether 
potential EJ concerns will be created or mitigated compared to the 
baseline (question 3). While the exposure analysis can respond to all 
three questions, several caveats should be noted. For example, the air 
pollutant exposure metrics are limited to those used in the benefits 
assessment. For ozone, that is the maximum daily 8-hour average, 
averaged across the April through September warm season (AS-MO3) and 
for PM2.5 that is the annual average. This ozone metric 
likely smooths potential daily ozone gradients and is not directly 
relatable to the National Ambient Air Quality Standards (NAAQS), 
whereas the PM2.5 metric is more similar to the long-term 
PM2.5 standard. The air quality modeling estimates are also 
based on state and fuel level emission data paired with facility-level 
baseline emissions and provided at a resolution of 12 square 
kilometers. Additionally, here we focus on air quality changes due to 
this rulemaking and infer post-policy ozone and PM2.5 
exposure burden impacts. Note, we discuss HAP and climate EJ impacts of 
this action qualitatively (section 6 of the RIA).
---------------------------------------------------------------------------

    \102\ The baseline for proximity analyses is current population 
information, whereas the baseline for ozone exposure analyses are 
the future years in which the regulatory options will be implemented 
(e.g., 2023 and 2026).
---------------------------------------------------------------------------

    Exposure analysis results are provided in two formats: aggregated 
and distributional. The aggregated results provide an overview of 
potential ozone exposure differences across populations at the 
national- and state-levels, while the distributional results show 
detailed information about ozone concentration changes experienced by 
everyone within each population.
    In section 6 of the RIA, we utilize the two types of analysis to 
address the three EJ questions by quantitatively evaluating: (1) the 
proximity of affected facilities to various local populations with 
potential EJ concerns (section 6.4); and (2) the potential for 
disproportionate ozone and PM2.5 concentrations in the 
baseline and concentration changes after rule implementation across 
different demographic groups on the basis of race, ethnicity, poverty 
status, employment status, health insurance status, life expectancy, 
redlining, Tribal land, age, sex, educational attainment,

[[Page 38560]]

and degree of linguistic isolation (section 6.5). It is important to 
note that due to the small magnitude of underlying emissions changes, 
and the corresponding small magnitude of the ozone and PM2.5 
concentration changes, the rule is expected to have only a small impact 
on the distribution of exposures across each demographic group. Each of 
these analyses should be considered independently of each other, as 
each was performed to answer separate questions, and is associated with 
unique limitations and uncertainties.
    Baseline demographic proximity analyses can be relevant for 
identifying populations that may be exposed to local environmental 
stressors, such as local NO2 and SO2 emitted from 
affected sources in this final rule, traffic, or noise. The baseline 
analysis indicates that on average the populations living within 10 
kilometers of coal plants potentially impacted by the amended fPM 
standards have a higher percentage of people living below two times the 
poverty level than the national average. In addition, on average the 
percentage of the American Indian population living within 10 
kilometers of lignite plants potentially impacted by the amended Hg 
standard is higher than the national average. Assessing these results, 
we conclude that there may be potential EJ concerns associated with 
directly emitted pollutants that are affected by the regulatory action 
(e.g., SO2) for various population groups in the baseline 
(question 1). However, as proximity to affected facilities does not 
capture variation in baseline exposure across communities, nor does it 
indicate that any exposures or impacts will occur, these results should 
not be interpreted as a direct measure of exposure or impact.
    As HAP exposure results generated as part of the 2020 Residual Risk 
Review were below both the presumptive acceptable cancer risk threshold 
and noncancer health benchmarks and this regulation should further 
reduce exposure to HAP, there are no ``disproportionate and adverse 
effects'' of potential EJ concern. Therefore, we did not perform a 
quantitative EJ assessment of HAP risk. However, the potential 
reduction in non-Hg HAP metal emissions would likely reduce exposures 
to people living nearby coal plants potentially impacted by the amended 
fPM standards.
    This rule is also expected to reduce emissions of direct 
PM2.5, NOX, and SO2 nationally 
throughout the year. Because NOX and SO2 are also 
precursors to secondary formation of ambient PM2.5 and 
because NOX is a precursor to ozone formation, reducing 
these emissions would impact human exposure. Quantitative ozone and 
PM2.5 exposure analyses can provide insight into all three 
EJ questions, so they are performed to evaluate potential 
disproportionate impacts of this rulemaking. Even though both the 
proximity and exposure analyses can potentially improve understanding 
of baseline EJ concerns (question 1), the two should not be directly 
compared. This is because the demographic proximity analysis does not 
include air quality information and is based on current, not future, 
population information.
    The baseline analysis of ozone and PM2.5 concentration 
burden responds to question 1 from the EPA's EJ technical guidance more 
directly than the proximity analyses, as it evaluates a form of the 
environmental stressor targeted by the regulatory action. Baseline 
PM2.5 and ozone exposure analyses show that certain 
populations, such as residents of redlined census tracts, those 
linguistically isolated, Hispanic, Asian, those without a high school 
diploma, and the unemployed may experience higher ozone and 
PM2.5 exposures as compared to the national average. 
American Indian, residents of Tribal Lands, populations with higher 
life expectancy or with life expectancy data unavailable, children, and 
insured populations may also experience disproportionately higher ozone 
concentrations than the reference group. Hispanic, Black, below the 
poverty line, and uninsured populations may also experience 
disproportionately higher PM2.5 concentrations than the 
reference group. Therefore, also in response to question 1, there 
likely are potential EJ concerns associated with ozone and 
PM2.5 exposures affected by the regulatory action for 
population groups of concern in the baseline. However, these baseline 
exposure results have not been fully explored and additional analyses 
are likely needed to understand potential implications. Due to the 
small magnitude of the exposure changes across population demographics 
associated with the rulemaking relative to the magnitude of the 
baseline disparities, we infer that post-policy EJ ozone and 
PM2.5 concentration burdens are likely to remain after 
implementation of the regulatory action or alternative under 
consideration (question 2).
    Question 3 asks whether potential EJ concerns will be created or 
mitigated as compared to the baseline. Due to the very small magnitude 
of differences across demographic population post-policy ozone and 
PM2.5 exposure impacts, we do not find evidence that 
potential EJ concerns related to ozone and PM2.5 
concentrations will be created or mitigated as compared to the 
baseline.\103\
---------------------------------------------------------------------------

    \103\ Please note that results for ozone and PM2.5 
exposures should not be extrapolated to other air pollutants that 
were not included in the assessment, including HAP. Detailed EJ 
analytical results can be found in section 6 of the RIA.
---------------------------------------------------------------------------

X. Statutory and Executive Order Reviews

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

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

    This action is a ``significant regulatory action,'' as defined 
under section 3(f)(1) of Executive Order 12866, as amended by Executive 
Order 14094. Accordingly, the EPA submitted this action to the Office 
of Management and Budget (OMB) for Executive Order 12866 review. 
Documentation of any changes made in response to the Executive Order 
12866 review is available in the docket. The EPA prepared an analysis 
of the potential costs and benefits associated with this action. This 
analysis, Regulatory Impact Analysis for the Final 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-24-005), is briefly summarized in 
section IX. of this preamble and here. This analysis is also available 
in the docket.
    Table 11 of this document presents the estimated PV and EAV of the 
monetizable projected health benefits, climate benefits, compliance 
costs, and net benefits of the final rule in 2019 dollars discounted to 
2023. The estimated monetized net benefits are the projected monetized 
benefits minus the projected monetized costs of the final rule.
    Under Executive Order 12866, the EPA is directed to consider all of 
the costs and benefits of its actions, not just those that stem from 
the regulated pollutant. Accordingly, the projected monetized benefits 
of the final rule include health benefits associated with projected 
reductions in PM2.5 and ozone concentration. The projected 
monetized benefits also include climate benefits due to reductions in 
CO2 emissions. The projected health benefits are associated 
with several point estimates and are presented at real discount rates 
of 2, 3, and 7 percent. The projected climate

[[Page 38561]]

benefits in this table are based on estimates of the SC-CO2 
at a 2 percent near-term Ramsey discount rate and are discounted using 
a 2 percent discount rate to obtain the PV and EAV estimates in the 
table. The power industry's compliance costs are represented in this 
analysis as the change in electric power generation costs between the 
baseline and policy scenarios. In simple terms, these costs are an 
estimate of the increased power industry expenditures required to 
implement the finalized requirements and represent the EPA's best 
estimate of the social cost of the final rulemaking.
BILLING CODE 6560-50-P
[GRAPHIC] [TIFF OMITTED] TR07MY24.077

BILLING CODE 6560-50-C
    As shown in table 11 of this document, this rule is projected to 
reduce PM2.5 and ozone concentrations, producing a projected 
PV of monetized health benefits of about $300 million, with an EAV of 
about $33 million discounted at 2 percent. The rule is also projected 
to reduce greenhouse gas emissions in the form of CO2, 
producing

[[Page 38562]]

a projected PV of monetized climate benefits of about $130 million, 
with an EAV of about $14 million using the SC-CO2 discounted 
at 2 percent. Thus, this final rule would generate a PV of monetized 
benefits of $420 million, with an EAV of $47 million discounted at a 2 
percent rate. The PV of the projected compliance costs are $860 
million, with an EAV of about $96 million discounted at 2 percent. 
Combining the projected benefits with the projected compliance costs 
yields a net benefit PV estimate of -$440 million and EAV of -$49 
million.
    At a 3 percent discount rate, this rule is expected to generate 
projected PV of monetized health benefits of $260 million, with an EAV 
of about $31 million. Climate benefits remain discounted at 2 percent 
in this net benefits analysis. Thus, this final rule would generate a 
PV of monetized benefits of $390 million, with an EAV of $45 million 
discounted at a 3 percent rate. The PV of the projected compliance 
costs are $790 million, with an EAV of $92 million discounted at 3 
percent. Combining the projected benefits with the projected compliance 
costs yields a net benefit PV estimate of -$400 million and an EAV of -
$47 million.
    At a 7 percent discount rate, this rule is expected to generate 
projected PV of monetized health benefits of $160 million, with an EAV 
of about $23 million. Climate benefits remain discounted at 2 percent 
in this net benefits analysis. Thus, this final rule would generate a 
PV of monetized benefits of $300 million, with an EAV of $39 million 
discounted at a 3 percent rate. The PV of the projected compliance 
costs are $560 million, with an EAV of $80 million discounted at 7 
percent. Combining the projected benefits with the projected compliance 
costs yields a net benefit PV estimate of -$260 million and an EAV of -
$41 million.
    The potential benefits from reducing Hg and non-Hg HAP metals and 
potential improvements in water quality and availability were not 
monetized and are therefore not directly reflected in the monetized 
benefit-cost estimates associated with this final rule. Potential 
benefits from the increased transparency and accelerated identification 
of anomalous emission anticipated from requiring CEMS were also not 
monetized in this analysis and are therefore also not directly 
reflected in the monetized benefit-cost comparisons. We nonetheless 
consider these impacts in our evaluation of the net benefits of the 
rule and find, if we were able to quantify and monetize these 
beneficial impacts, the final rule would have greater net benefits than 
shown in table 11 of this preamble.

B. Paperwork Reduction Act (PRA)

    The information collection activities in this rule have been 
submitted for approval to the OMB under the PRA. The ICR document that 
the EPA prepared has been assigned EPA ICR number 2137-12. You can find 
a copy of the ICR in the docket for this rule, and it is briefly 
summarized here. The information collection requirements are not 
enforceable until OMB approves them. OMB has previously approved the 
information collection activities contained in the existing regulations 
and has assigned OMB control number 2060-0567.
    The information collection activities in this rule include 
continuous emission monitoring, performance testing, notifications and 
periodic reports, recording information, monitoring and the maintenance 
of records. The information generated by these activities will be used 
by the EPA to ensure that affected facilities comply with the emission 
limits and other requirements. Records and reports are necessary to 
enable delegated authorities to identify affected facilities that may 
not be in compliance with the requirements. Based on reported 
information, delegated authorities will decide which units and what 
records or processes should be inspected. The recordkeeping 
requirements require only the specific information needed to determine 
compliance. These recordkeeping and reporting requirements are 
specifically authorized by CAA section 114 (42 U.S.C. 7414). The burden 
and cost estimates below represent the total burden and cost for the 
information collection requirements of the NESHAP for Coal- and Oil-
Fired EGUs, not just the burden associated with the amendments in this 
final rule. The incremental cost associated with these amendments is 
$2.4 million per year.
    Respondents/affected entities: The respondents are owners or 
operators of coal- and oil-fired EGUs. The North American Industry 
Classification System (NAICS) codes for the coal- and oil-fired EGU 
industry are 221112, 221122, and 921150.
    Respondent's obligation to respond: Mandatory per 42 U.S.C. 7414 et 
seq.
    Estimated number of respondents: 192 per year.\104\
---------------------------------------------------------------------------

    \104\ Each facility is a respondent and some facilities have 
multiple EGUs.
---------------------------------------------------------------------------

    Frequency of response: The frequency of responses varies depending 
on the burden item. Responses include daily calibrations, monthly 
recordkeeping activities, semiannual compliance reports, and annual 
reports.
    Total estimated burden: 447,000 hours (per year). Burden is defined 
at 5 CFR part 1320.3(b).
    Total estimated cost: $106,600,000 (per year), includes $53,100,000 
in annual labor costs and $53,400,000 annualized capital and operation 
and maintenance costs.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for the 
EPA's regulations in 40 CFR are listed in 40 CFR part 9. When OMB 
approves this ICR, the Agency will announce that approval in the 
Federal Register and publish a technical amendment to 40 CFR part 9 to 
display the OMB control number for the approved information collection 
activities contained in this final rule.

C. Regulatory Flexibility Act (RFA)

    The EPA certifies that this action will not have a significant 
economic impact on a substantial number of small entities under the 
RFA. In the 2028 analysis year, the EPA identified 24 potentially 
affected small entities operating 45 units at 26 facilities, and of 
these 24, only one small entity may experience compliance cost 
increases greater than one percent of revenue under the final rule. 
Details of this analysis are presented in section 5 of the RIA, which 
is in the public docket.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain an unfunded mandate of $100 million or 
more (adjusted for inflation) as described in UMRA, 2 U.S.C. 1531-1538, 
and does not significantly or uniquely affect small governments. The 
costs involved in this action are estimated not to exceed $100 million 
or more (adjusted for inflation) in any one year.

E. Executive Order 13132: Federalism

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government.

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

    This action does not have tribal implications as specified in 
Executive

[[Page 38563]]

Order 13175. The Executive order defines tribal implications as 
``actions that have substantial direct effects on one or more Indian 
tribes, on the relationship between the Federal Government and Indian 
tribes.'' The amendments in this action would not have a substantial 
direct effect on one or more tribes, change the relationship between 
the Federal Government and tribes, or affect the distribution of power 
and responsibilities between the Federal Government and Indian tribes. 
Thus, Executive Order 13175 does not apply to this action.
    Although this action does not have tribal implications as specified 
in Executive Order 13175, the EPA consulted with tribal officials 
during the development of this action. On September 1, 2022, the EPA 
sent a letter to all federally recognized Indian tribes initiating 
consultation to obtain input on this action. The EPA did not receive 
any requests for consultation from Indian tribes. The EPA also 
participated in the September 2022 National Tribal Air Association EPA 
Air Policy Update Call to solicit input on this action.

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

    Executive Order 13045 directs Federal agencies to include an 
evaluation of the health and safety effects of the planned regulation 
on children in federal health and safety standards and explain why the 
regulation is preferable to potentially effective and reasonably 
feasible alternatives. This action is subject to Executive Order 13045 
because it is a significant regulatory action under section 3(f)(1) of 
Executive Order 12866. Accordingly, we have evaluated the potential for 
environmental health or safety effects from exposure to HAP, ozone, and 
PM2.5 on children. The EPA believes that, even though the 
2020 residual risk assessment showed all modeled exposures to HAP to be 
below thresholds for public health concern, the rule should reduce HAP 
exposure by reducing emissions of Hg and non-Hg HAP with the potential 
to reduce HAP exposure to vulnerable populations, including children. 
The action described in this rule is also expected to lower ozone and 
PM2.5 in many areas, including those areas that struggle to 
attain or maintain the NAAQS, and thus mitigate some pre-existing 
health risks across all populations evaluated, including children. The 
results of this evaluation are contained in the RIA and are available 
in the docket for this action.

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

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. For 2028, the compliance year for the 
standards, the EPA does not project a significant change in retail 
electricity prices on average across the contiguous U.S., coal-fired 
electricity generation, natural gas-fired electricity generation, or 
utility power sector delivered natural gas prices. Details of the 
projected energy effects are presented in section 3 of the RIA, which 
is in the public docket.

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

    The following standards appear in the amendatory text of this 
document and were previously approved for the locations in which they 
appear: ANSI/ASME PTC 19.10-1981, ASTM D6348-03(R2010), and ASTM D6784-
16.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations and 
Executive Order 14096: Revitalizing Our Nation's Commitment to 
Environmental Justice for All

    The EPA believes that the human health or environmental conditions 
that exist prior to this action result in or have the potential to 
result in disproportionate and adverse human health or environmental 
effects on communities with environmental justice concerns. For this 
rule, we employ the proximity demographic analysis and the 
PM2.5 and ozone exposure analyses to evaluate 
disproportionate and adverse human health and environmental effects on 
communities with EJ concerns that exist prior to the action. The 
proximity demographic analysis indicates that on average the population 
living within 10 kilometers of coal plants potentially impacted by the 
fPM standards have a higher percentage of people living below two times 
the poverty level than the national average. In addition, on average 
the percentage of the American Indian population living within 10 
kilometers of lignite-fired plants potentially impacted by the Hg 
standard is higher than the national average. Baseline PM2.5 
and ozone and exposure analyses show that certain populations, such as 
residents of redlined census tracts, those linguistically isolated, 
Hispanic, Asian, those without a high school diploma, and the 
unemployed may experience disproportionately higher ozone and 
PM2.5 exposures as compared to the national average. 
American Indian, residents of Tribal Lands, populations with higher 
life expectancy or with life expectancy data unavailable, children, and 
insured populations may also experience disproportionately higher ozone 
concentrations than the reference group. Hispanics, Blacks, those below 
the poverty line, and uninsured populations may also experience 
disproportionately higher PM2.5 concentrations than the 
reference group.
    The EPA believes that this action is not likely to change existing 
disproportionate and adverse effects on communities with environmental 
justice concerns. Only the exposure analyses, which are based on future 
air quality modeling, can inform whether there will be potential EJ 
concerns after implementation of the final rule, and whether potential 
EJ concerns will be created or mitigated. We infer that baseline 
disparities in ozone and PM2.5 concentration burdens are 
likely to remain after implementation of the final regulatory option 
due to the small magnitude of the exposure changes across population 
demographics associated with the rulemaking relative to the baseline 
disparities. We also do not find evidence that potential EJ concerns 
related to ozone or PM2.5 exposures will be exacerbated or 
mitigated in the final regulatory option, compared to the baseline due 
to the very small differences in the magnitude of post-policy ozone and 
PM2.5 exposure impacts across demographic populations. 
Additionally, the potential reduction in Hg and non-Hg HAP metal 
emissions would likely reduce exposures to people living nearby coal 
plants potentially impacted by the amended fPM standards.
    The information supporting this Executive Order review is contained 
in section IX.F. of this preamble and in section 6, Environmental 
Justice Impacts of the RIA, which is in the public docket (EPA-HQ-OAR-
2018-0794).

K. Congressional Review Act (CRA)

    This action is subject to the CRA, and the EPA will submit a rule 
report to each House of the Congress and to the Comptroller General of 
the United States. This action meets the criteria set forth in 5 U.S.C. 
804(2).

List of Subjects in 40 CFR Part 63

    Environmental protection, Administrative practice and procedures, 
Air pollution control, Hazardous

[[Page 38564]]

substances, Incorporation by reference, Intergovernmental relations, 
Reporting and recordkeeping requirements.

Michael S. Regan,
Administrator.

    For the reasons set forth in the preamble, 40 CFR part 63 is 
amended as follows:

PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS 
FOR SOURCE CATEGORIES

0
1. The authority citation for part 63 continues to read as follows:

    Authority: 42 U.S.C. 7401 et seq.

Subpart A--General Provisions

0
2. In Sec.  63.14, paragraph (f)(1) is amended by removing the text 
``tables 4 and 5 to subpart UUUUU'' and adding, in its place, the text 
``table 5 to subpart UUUUU''.

Subpart UUUUU--National Emission Standards for Hazardous Air 
Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating 
Units

0
3. Section 63.9991 is amended by revising paragraph (a)(2) to read as 
follows:


Sec.  63.9991  What emission limitations, work practice standards, and 
operating limits must I meet?

    (a) * * *
    (2) Before July 6, 2027, you must meet each operating limit in 
Table 4 to this subpart that applies to your EGU.
* * * * *

0
4. Amend Sec.  63.10000 by:
0
a. Revising paragraph (c)(1)(i) and paragraph (c)(1)(i)(A);
0
b. Redesignating paragraph (c)(1)(i)(C) as paragraph (c)(1)(i)(D);
0
c. Adding new paragraph (c)(1)(i)(C);
0
d. Revising paragraph (c)(1)(iv);
0
e. Adding new paragraphs (c)(1)(iv)(A) through (C);
0
f. Revising paragraphs (c)(2)(i) and (ii);
0
g. Revising paragraph (d)(5)(i); and
0
h. Revising paragraph (m) introductory text.
    The revisions and additions read as follows:


Sec.  63.10000  What are my general requirements for complying with 
this subpart?

* * * * *
    (c) * * *
    (1) * * *
    (i) For a coal-fired or solid oil-derived fuel-fired EGU or IGCC 
EGU, you may conduct initial performance testing in accordance with 
Sec.  63.10005(h), to determine whether the EGU qualifies as a low 
emitting EGU (LEE) for one or more applicable emission limits, except 
as otherwise provided in paragraphs (c)(1)(i)(A) through (C) of this 
section:
    (A) Except as provided in paragraph (c)(1)(i)(D) of this section, 
you may not pursue the LEE option if your coal-fired, IGCC, or solid 
oil-derived fuel-fired EGU is equipped with a main stack and a bypass 
stack or bypass duct configuration that allows the effluent to bypass 
any pollutant control device.
* * * * *
    (C) On or after July 6, 2027, you may not pursue the LEE option for 
filterable PM, total non-Hg HAP metals, or individual non-Hg HAP metals 
for coal-fired and solid oil-derived fuel-fired EGUs.
* * * * *
    (iv)(A) Before July 6, 2027, if your coal-fired or solid oil 
derived fuel-fired EGU does not qualify as a LEE for total non-mercury 
HAP metals, individual non-mercury HAP metals, or filterable 
particulate matter (PM), you must demonstrate compliance through an 
initial performance test and you must monitor continuous performance 
through either use of a particulate matter continuous parametric 
monitoring system (PM CPMS), a PM CEMS, or, for an existing EGU, 
compliance performance testing repeated quarterly.
    (B) On and after July 6, 2027, you may not pursue or continue to 
use the LEE option for your coal-fired or solid oil derived fuel-fired 
EGU for filterable PM or for non-mercury HAP metals. You must 
demonstrate compliance through an initial performance test, and you 
must monitor continuous performance with the applicable filterable PM 
emissions limit through the use of a PM CEMS or HAP metals CMS.
    (C) If your IGCC EGU does not qualify as a LEE for total non-
mercury HAP metals, individual non-mercury HAP metals, or filterable 
PM, you must demonstrate compliance through an initial performance test 
and you must monitor continuous performance through either use of a PM 
CPMS, a PM CEMS, or, for an existing EGU, compliance performance 
testing repeated quarterly.
* * * * *
    (2) * * *
    (i) For an existing liquid oil-fired unit, you may conduct the 
performance testing in accordance with Sec.  63.10005(h), to determine 
whether the unit qualifies as a LEE for one or more pollutants. For a 
qualifying LEE for Hg emissions limits, you must conduct a 30-day 
performance test using Method 30B at least once every 12 calendar 
months to demonstrate continued LEE status. For a qualifying LEE of any 
other applicable emissions limits, you must conduct a performance test 
at least once every 36 calendar months to demonstrate continued LEE 
status. On or after July 6, 2027, you may not pursue the LEE option for 
filterable PM, total non-Hg HAP metals, or individual non-Hg HAP 
metals.
    (ii) Before July 6, 2027, if your liquid oil-fired unit does not 
qualify as a LEE for total HAP metals (including mercury), individual 
metals (including mercury), or filterable PM you must demonstrate 
compliance through an initial performance test and you must monitor 
continuous performance through either use of a PM CPMS, a PM CEMS, or, 
for an existing EGU, performance testing conducted quarterly. On and 
after July 6, 2027, you may not pursue or continue to use the LEE 
option for your liquid oil-fired EGU for filterable PM or for non-
mercury HAP metals. You must demonstrate compliance through an initial 
performance test, and you must monitor continuous performance with the 
applicable filterable PM emissions limit through the use of a PM CEMS 
or HAP metals CMS.
    (d) * * *
    (5) * * *
    (i) Installation of the CMS or sorbent trap monitoring system 
sampling probe or other interface at a measurement location relative to 
each affected process unit such that the measurement is representative 
of control of the exhaust emissions (e.g., on or downstream of the last 
control device). See Sec.  63.10010(a) for further details. For PM CPMS 
installations (which with the exception of IGCC units, are only 
applicable before July 6, 2027), follow the procedures in Sec.  
63.10010(h).
* * * * *
    (m) Should you choose to rely on paragraph (2) of the definition of 
``startup'' in Sec.  63.10042 for your EGU (only allowed before January 
2, 2025), on or before the date your EGU is subject to this subpart, 
you must install, verify, operate, maintain, and quality assure each 
monitoring system necessary for demonstrating compliance with the work 
practice standards for PM or non-mercury HAP metals controls during 
startup periods and shutdown periods required to comply with Sec.  
63.10020(e). On and after January 2, 2025 you will no longer be able to 
choose paragraph (2) of the ``startup'' definition in Sec.  63.10042.
* * * * *

[[Page 38565]]


0
5. Amend Sec.  63.10005 by revising paragraphs (a)(1), (b) introductory 
text, (c), (d)(2) introductory text, (h) introductory text, and (h)(1) 
introductory text to read as follows:


Sec.  63.10005  What are my initial compliance requirements and by what 
date must I conduct them?

    (a) * * *
    (1) To demonstrate initial compliance with an applicable emissions 
limit in Table 1 or 2 to this subpart using stack testing, the initial 
performance test generally consists of three runs at specified process 
operating conditions using approved methods. Before July 6, 2027, if 
you are required to establish operating limits (see paragraph (d) of 
this section and Table 4 to this subpart), you must collect all 
applicable parametric data during the performance test period. On and 
after July 6, 2027, the requirements in Table 4 are not applicable, 
with the exception of IGCC units. Also, if you choose to comply with an 
electrical output-based emission limit, you must collect hourly 
electrical load data during the test period.
* * * * *
    (b) Performance testing requirements. If you choose to use 
performance testing to demonstrate initial compliance with the 
applicable emissions limits in Tables 1 and 2 to this subpart for your 
EGUs, you must conduct the tests according to 40 CFR 63.10007 and Table 
5 to this subpart. Notwithstanding these requirements, when Table 5 
specifies the use of isokinetic EPA test Method 5, 5I, 5D, 26A, or 29 
for a stack test, if concurrent measurement of the stack gas flow rate 
or moisture content is needed to convert the pollutant concentrations 
to units of the standard, separate determination of these parameters 
using EPA test Method 2 or EPA test Method 4 is not necessary. Instead, 
the stack gas flow rate and moisture content can be determined from 
data that are collected during the EPA test Method 5, 5I, 5D, 6, 26A, 
or 29 test (e.g., pitot tube (delta P) readings, moisture collected in 
the impingers, etc.). For the purposes of the initial compliance 
demonstration, you may use test data and results from a performance 
test conducted prior to the date on which compliance is required as 
specified in 40 CFR 63.9984, provided that the following conditions are 
fully met:
* * * * *
    (c) Operating limits. In accordance with Sec.  63.10010 and Table 4 
to this subpart, you may be required to establish operating limits 
using PM CPMS and using site-specific monitoring for certain liquid 
oil-fired units as part of your initial compliance demonstration. With 
the exception of IGCC units, on and after July 6, 2027, you may not 
demonstrate compliance with applicable filterable PM emissions limits 
with the use of PM CPMS or quarterly stack testing, you may only use PM 
CEMS.
* * * * *
    (d) * * *
    (2) For affected coal-fired or solid oil-derived fuel-fired EGUs 
that demonstrate compliance with the applicable emission limits for 
total non-mercury HAP metals, individual non-mercury HAP metals, total 
HAP metals, individual HAP metals, or filterable PM listed in Table 1 
or 2 to this subpart using initial performance testing and continuous 
monitoring with PM CPMS (with the exception of IGCC units, the use of 
PM CPMS is only allowed before July 6, 2027):
* * * * *
    (h) Low emitting EGUs. The provisions of this paragraph (h) apply 
to pollutants with emissions limits from new EGUs except Hg and to all 
pollutants with emissions limits from existing EGUs. With the exception 
of IGCC units, on or after July 6, 2027 you may not pursue the LEE 
option for filterable PM. You may pursue this compliance option unless 
prohibited pursuant to Sec.  63.10000(c)(1)(i).
    (1) An EGU may qualify for low emitting EGU (LEE) status for Hg, 
HCl, HF, filterable PM, total non-Hg HAP metals, or individual non-Hg 
HAP metals (or total HAP metals or individual HAP metals, for liquid 
oil-fired EGUs) if you collect performance test data that meet the 
requirements of this paragraph (h) with the exception that on or after 
July 6, 2027, you may not pursue the LEE option for filterable PM, 
total non-Hg HAP metals, or individual non-Hg HAP metals for any 
existing, new or reconstructed EGUs (this does not apply to IGCC 
units), and if those data demonstrate:
* * * * *

0
6. Amend Sec.  63.10006 by revising paragraph (a) to read as follows:


Sec.  63.10006  When must I conduct subsequent performance tests or 
tune-ups?

    (a) For liquid oil-fired, solid oil-derived fuel-fired and coal-
fired EGUs and IGCC units using PM CPMS before July 6, 2027 to monitor 
continuous performance with an applicable emission limit as provided 
for under Sec.  63.10000(c), you must conduct all applicable 
performance tests according to Table 5 to this subpart and Sec.  
63.10007 at least every year. On or after July 6, 2027 you may not use 
PM CPMS to demonstrate compliance for liquid oil-fired, solid oil-
derived fuel-fired and coal-fired EGUs. This prohibition against the 
use of PM CPMS does not apply to IGCC units.
* * * * *

0
7. Amend Sec.  63.1007 by revising paragraphs (a)(3) and (c) to read as 
follows:


Sec.  63.10007  What methods and other procedures must I use for the 
performance tests?

    (a) * * *
    (3) For establishing operating limits with particulate matter 
continuous parametric monitoring system (PM CPMS) to demonstrate 
compliance with a PM or non-Hg metals emissions limit (the use of PM 
CPMS is only allowed before July 6, 2027 with the exception of IGCC 
units), operate the unit at maximum normal operating load conditions 
during the performance test period. Maximum normal operating load will 
be generally between 90 and 110 percent of design capacity but should 
be representative of site specific normal operations during each test 
run.
* * * * *
    (c) If you choose the filterable PM method to comply with the PM 
emission limit and demonstrate continuous performance using a PM CPMS 
as provided for in Sec.  63.10000(c), you must also establish an 
operating limit according to Sec.  63.10011(b), Sec.  63.10023, and 
Tables 4 and 6 to this subpart. Should you desire to have operating 
limits that correspond to loads other than maximum normal operating 
load, you must conduct testing at those other loads to determine the 
additional operating limits. On and after July 6, 2027, you must 
demonstrate continuous compliance with the applicable filterable PM 
emission standard through the use of a PM CEMS (with the exception that 
IGCC units are not required to use PM CEMS and may continue to use PM 
CPMS). Alternatively, you may demonstrate continuous compliance with 
the non-Hg metals emission standard if you request and receive approval 
for the use of a HAP metals CMS under Sec.  63.7(f).
* * * * *

0
8. Amend Sec.  63.10010 by revising paragraphs (a) introductory text, 
(h) introductory text, (i) introductory text, (j), and (l) introductory 
text to read as follows:


Sec.  63.10010  What are my monitoring, installation, operation, and 
maintenance requirements?

    (a) Flue gases from the affected units under this subpart exhaust 
to the atmosphere through a variety of

[[Page 38566]]

different configurations, including but not limited to individual 
stacks, a common stack configuration or a main stack plus a bypass 
stack. For the CEMS, PM CPMS (which on or after July 6, 2027 you may 
not use PM CPMS for filterable PM compliance demonstrations unless it 
is for an IGCC unit), and sorbent trap monitoring systems used to 
provide data under this subpart, the continuous monitoring system 
installation requirements for these exhaust configurations are as 
follows:
* * * * *
    (h) If you use a PM CPMS to demonstrate continuous compliance with 
an operating limit (only applicable before July 6, 2027 unless it is 
for an IGCC unit), you must install, calibrate, maintain, and operate 
the PM CPMS and record the output of the system as specified in 
paragraphs (h)(1) through (5) of this section.
* * * * *
    (i) If you choose to comply with the PM filterable emissions limit 
in lieu of metal HAP limits (which on or after July 6, 2027 you may not 
use non-mercury metal HAP limits for compliance demonstrations for 
existing EGUs unless you request and receive approval for the use of a 
HAP metals CMS under Sec.  63.7(f)), you may choose to install, 
certify, operate, and maintain a PM CEMS and record and report the 
output of the PM CEMS as specified in paragraphs (i)(1) through (8) of 
this section. With the exception of IGCC units, on or after July 6, 
2027 owners/operators of existing EGUs must comply with filterable PM 
emissions limits in Table 2 of this subpart and demonstrate continuous 
compliance using a PM CEMS unless you request and receive approval for 
the use of a HAP metals CMS under Sec.  63.7(f). Compliance with the 
applicable PM emissions limit in Table 1 or 2 to this subpart is 
determined on a 30-boiler operating day rolling average basis.
* * * * *
    (j) You may choose to comply with the metal HAP emissions limits 
using CMS approved in accordance with Sec.  63.7(f) as an alternative 
to the performance test method specified in this rule. If approved to 
use a HAP metals CMS, the compliance limit will be expressed as a 30-
boiler operating day rolling average of the numerical emissions limit 
value applicable for your unit in tables 1 or 2. If approved, you may 
choose to install, certify, operate, and maintain a HAP metals CMS and 
record the output of the HAP metals CMS as specified in paragraphs 
(j)(1) through (5) of this section.
    (1)(i) Install, calibrate, operate, and maintain your HAP metals 
CMS according to your CMS quality control program, as described in 
Sec.  63.8(d)(2). The reportable measurement output from the HAP metals 
CMS must be expressed in units of the applicable emissions limit (e.g., 
lb/MMBtu, lb/MWh) and in the form of a 30-boiler operating day rolling 
average.
    (ii) Operate and maintain your HAP metals CMS according to the 
procedures and criteria in your site specific performance evaluation 
and quality control program plan required in Sec.  63.8(d).
    (2) Collect HAP metals CMS hourly average output data for all 
boiler operating hours except as indicated in section (j)(4) of this 
section.
    (3) Calculate the arithmetic 30-boiler operating day rolling 
average of all of the hourly average HAP metals CMS output data 
collected during all nonexempt boiler operating hours data.
    (4) You must collect data using the HAP metals CMS at all times the 
process unit is operating and at the intervals specified in paragraph 
(a) of this section, except for required monitoring system quality 
assurance or quality control activities, and any scheduled maintenance 
as defined in your site-specific monitoring plan.
    (i) You must use all the data collected during all boiler operating 
hours in assessing the compliance with your emission limit except:
    (A) Any data collected during periods of monitoring system 
malfunctions and repairs associated with monitoring system 
malfunctions. You must report any monitoring system malfunctions as 
deviations in your compliance reports under 40 CFR 63.10031(c) or (g) 
(as applicable);
    (B) Any data collected during periods when the monitoring system is 
out of control as specified in your site-specific monitoring plan, 
repairs associated with periods when the monitoring system is out of 
control, or required monitoring system quality assurance or quality 
control activities conducted during out-of-control periods. You must 
report any out of control periods as deviations in your compliance 
reports under 40 CFR 63.10031(c) or (g) (as applicable);
    (C) Any data recorded during required monitoring system quality 
assurance or quality control activities that temporarily interrupt the 
measurement of emissions (e.g., calibrations, certain audits, routine 
probe maintenance); and
    (D) Any data recorded during periods of startup or shutdown.
    (ii) You must record and report the results of HAP metals CMS 
system performance audits, in accordance with 40 CFR 63.10031(k). You 
must also record and make available upon request the dates and duration 
of periods when the HAP metals CMS is out of control to completion of 
the corrective actions necessary to return the HAP metals CMS to 
operation consistent with your site-specific performance evaluation and 
quality control program plan.
* * * * *
    (l) Should you choose to rely on paragraph (2) of the definition of 
``startup'' in Sec.  63.10042 for your EGU (only allowed before January 
2, 2025), you must install, verify, operate, maintain, and quality 
assure each monitoring system necessary for demonstrating compliance 
with the PM or non-mercury metals work practice standards required to 
comply with Sec.  63.10020(e). On and after January 2, 2025 you will no 
longer be able to choose paragraph (2) of the ``startup'' definition in 
Sec.  63.10042 for your EGU.
* * * * *

0
9. Amend Sec.  63.10011 by revising paragraphs (b), (g)(3), and (4) 
introductory text to read as follows:


Sec.  63.10011  How do I demonstrate initial compliance with the 
emissions limits and work practice standards?

* * * * *
    (b) If you are subject to an operating limit in Table 4 to this 
subpart, you demonstrate initial compliance with HAP metals or 
filterable PM emission limit(s) through performance stack tests and you 
elect to use a PM CPMS to demonstrate continuous performance (with the 
exception of existing IGCC units, on or after July 6, 2027 you may not 
use PM CPMS for compliance demonstrations with the applicable 
filterable PM limits and the Table 4 p.m. CPMS operating limits do not 
apply), or if, for an IGCC unit, and you use quarterly stack testing 
for HCl and HF plus site-specific parameter monitoring to demonstrate 
continuous performance, you must also establish a site-specific 
operating limit, in accordance with Sec.  63.10007 and Table 6 to this 
subpart. You may use only the parametric data recorded during 
successful performance tests (i.e., tests that demonstrate compliance 
with the applicable emissions limits) to establish an operating limit. 
On or after July 6, 2027 you may not use PM CPMS for compliance 
demonstrations with the applicable filterable PM limits and the Table 6 
procedures for establishing PM CPMS operating limits do not apply 
unless it is an IGCC unit.
* * * * *
    (g) * * *

[[Page 38567]]

    (3) You must report the emissions data recorded during startup and 
shutdown. If you are relying on paragraph (2) of the definition of 
startup in 40 CFR 63.10042 (only allowed before January 2, 2025), then 
for startup and shutdown incidents that occur on or prior to December 
31, 2023, you must also report the applicable supplementary information 
in 40 CFR 63.10031(c)(5) in the semiannual compliance report. For 
startup and shutdown incidents that occur on or after January 1, 2024, 
you must provide the applicable information in 40 CFR 
63.10031(c)(5)(ii) and 40 CFR 63.10020(e) quarterly, in PDF files, in 
accordance with 40 CFR 63.10031(i).
    (4) If you choose to use paragraph (2) of the definition of 
``startup'' in Sec.  63.10042 (only allowed before January 2, 2025), 
and you find that you are unable to safely engage and operate your 
particulate matter (PM) control(s) within 1 hour of first firing of 
coal, residual oil, or solid oil-derived fuel, you may choose to rely 
on paragraph (1) of definition of ``startup'' in Sec.  63.10042 or you 
may submit a request to use an alternative non-opacity emissions 
standard, as described below.
* * * * *

0
10. Section 63.10020 is amended by revising paragraphs (e) introductory 
text and (e)(3)(i) introductory text to read as follows:


Sec.  63.10020  How do I monitor and collect data to demonstrate 
continuous compliance?

* * * * *
    (e) Additional requirements during startup periods or shutdown 
periods if you choose to rely on paragraph (2) of the definition of 
``startup'' in Sec.  63.10042 for your EGU (only allowed before January 
2, 2025).
* * * * *
    (3) * * *
    (i) Except for an EGU that uses PM CEMS or PM CPMS to demonstrate 
compliance with the PM emissions limit, or that has LEE status for 
filterable PM or total non-Hg HAP metals for non- liquid oil-fired EGUs 
(or HAP metals emissions for liquid oil-fired EGUs), or individual non-
mercury metals CMS (except that unless it is for an IGCC unit, on or 
after July 6, 2027 you may not use PM CPMS for compliance 
demonstrations with the applicable filterable PM emissions limits, and 
you may not purse or continue to use the LEE option for filterable PM, 
total non-Hg HAP metals, or individual non-Hg HAP metals), you must:
* * * * *

0
11. Section 63.10021 is amended by revising paragraphs (c) introductory 
text and (i) to read as follows:


Sec.  63.10021  How do I demonstrate continuous compliance with the 
emission limitations, operating limits, and work practice standards?

* * * * *
    (c) If you use PM CPMS data (only allowed before July 6, 2027 
unless it is for an IGCC unit) to measure compliance with an operating 
limit in Table 4 to this subpart, you must record the PM CPMS output 
data for all periods when the process is operating and the PM CPMS is 
not out-of-control. You must demonstrate continuous compliance by using 
all quality-assured hourly average data collected by the PM CPMS for 
all operating hours to calculate the arithmetic average operating 
parameter in units of the operating limit (e.g., milliamps, PM 
concentration, raw data signal) on a 30 operating day rolling average 
basis, updated at the end of each new boiler operating day. Use 
Equation 9 to determine the 30 boiler operating day average. On or 
after July 6, 2027 you may not use PM CPMS for compliance 
demonstrations unless it is for an IGCC unit.
[GRAPHIC] [TIFF OMITTED] TR07MY24.079

Where:

    Hpvi is the hourly parameter value for hour i and n 
is the number of valid hourly parameter values collected over 30 
boiler operating days.
* * * * *
    (i) Before January 2, 2025, if you are relying on paragraph 2 of 
the definition of startup in 40 CFR 63.10042, you must provide reports 
concerning activities and periods of startup and shutdown that occur on 
or prior to January 1, 2024, in accordance with 40 CFR 63.10031(c)(5), 
in your semiannual compliance report. For startup and shutdown 
incidents that occur on and after January 1, 2024, you must provide the 
applicable information referenced in 40 CFR 63.10031(c)(5)(ii) and 40 
CFR 63.10020(e) quarterly, in PDF files, in accordance with 40 CFR 
63.10031(i). On or after January 2, 2025 you may not use paragraph 2 of 
the definition of startup in 40 CFR 63.10042.

0
12. Section 63.10022 is amended by revising paragraphs (a)(2) and (3) 
to read as follows:


Sec.  63.10022  How do I demonstrate continuous compliance under the 
emissions averaging provision?

    (a) * * *
    (2) For each existing unit participating in the emissions averaging 
option that is equipped with PM CPMS, maintain the average parameter 
value at or below the operating limit established during the most 
recent performance test. On or after July 6, 2027 you may not use PM 
CPMS for filterable PM compliance demonstrations unless it is for an 
IGCC unit;
    (3) For each existing unit participating in the emissions averaging 
option venting to a common stack configuration containing affected 
units from other subcategories, maintain the appropriate operating 
limit for each unit as specified in Table 4 to this subpart that 
applies. Since on or after July 6, 2027 you may not use PM CPMS, unless 
it is for an IGCC unit, for compliance demonstrations with the 
applicable filterable PM limits, the Table 4 p.m. CPMS operating limits 
do not apply.
* * * * *

0
13. Section 63.10023 is amended by adding introductory text to the 
section to read as follows:


Sec.  63.10023  How do I establish my PM CPMS operating limit and 
determine compliance with it?

    The provisions of this section Sec.  63.10023 are only applicable 
before July 6, 2027 unless it is for an IGCC unit. On or after July 6, 
2027 you may not use PM CPMS, unless it is an IGCC unit, for 
demonstrating compliance with the filterable PM emissions limits of 
this subpart.
* * * * *

0
14. Section 63.10030 is amended by revising paragraphs (e)(3), (8) 
introductory text, and (8)(i) introductory text to read as follows:

[[Page 38568]]

Sec.  63.10030  What notifications must I submit and when?

* * * * *
    (e) * * *
    (3) Identification of whether you plan to demonstrate compliance 
with each applicable emission limit through performance testing; fuel 
moisture analyses; performance testing with operating limits (e.g., use 
of PM CPMS--which on or after July 6, 2027--you may not use for 
filterable PM compliance demonstrations, unless it is for an IGCC 
unit); CEMS; or a sorbent trap monitoring system.
* * * * *
    (8) Identification of whether you plan to rely on paragraph (1) or 
(2) of the definition of ``startup'' in Sec.  63.10042. On or after 
January 2, 2025 you may not use paragraph (2) of the definition of 
startup in Sec.  63.10042.
    (i) Before January 2, 2025 should you choose to rely on paragraph 
(2) of the definition of ``startup'' in Sec.  63.10042 for your EGU, 
you shall include a report that identifies:
* * * * *

0
15. Section 63.10031 is amended by revising paragraphs (a)(4), (c)(5) 
introductory text, (f)(2), (i), and (k) to read as follows:


Sec.  63.10031  What reports must I submit and when?

    (a) * * *
    (4) Before July 6, 2027, if you elect to demonstrate continuous 
compliance using a PM CPMS, you must meet the electronic reporting 
requirements of appendix D to this subpart. Except for IGCC units, on 
or after July 6, 2027 you may not use PM CPMS for compliance 
demonstrations. Electronic reporting of the hourly PM CPMS output shall 
begin with the later of the first operating hour on or after January 1, 
2024; or the first operating hour after completion of the initial 
performance stack test that establishes the operating limit for the PM 
CPMS.
    (c) * * *
    (5) Should you choose to rely on paragraph (2) of the definition of 
``startup'' in Sec.  63.10042 for your EGU (only allowed before January 
2, 2025), for each instance of startup or shutdown you shall:
* * * * *
    (f) * * *
    (2) If, for a particular EGU or a group of EGUs serving a common 
stack, you have elected to demonstrate compliance using a PM CEMS, an 
approved HAP metals CMS, or a PM CPMS (on or after July 6, 2027 you may 
not use PM CPMS for compliance demonstrations, unless it is for an IGCC 
unit), you must submit quarterly PDF reports in accordance with 
paragraph (f)(6) of this section, which include all of the 30-boiler 
operating day rolling average emission rates derived from the CEMS data 
or the 30-boiler operating day rolling average responses derived from 
the PM CPMS data (as applicable). The quarterly reports are due within 
60 days after the reporting periods ending on March 31st, June 30th, 
September 30th, and December 31st. Submission of these quarterly 
reports in PDF files shall end with the report that covers the fourth 
calendar quarter of 2023. Beginning with the first calendar quarter of 
2024, the compliance averages shall no longer be reported separately, 
but shall be incorporated into the quarterly compliance reports 
described in paragraph (g) of this section. In addition to the 
compliance averages for PM CEMS, PM CPMS, and/or HAP metals CMS, the 
quarterly compliance reports described in paragraph (g) of this section 
must also include the 30- (or, if applicable 90-) boiler operating day 
rolling average emission rates for Hg, HCl, HF, and/or SO2, 
if you have elected to (or are required to) continuously monitor these 
pollutants. Further, if your EGU or common stack is in an averaging 
plan, your quarterly compliance reports must identify all of the EGUs 
or common stacks in the plan and must include all of the 30- (or 90-) 
group boiler operating day rolling weighted average emission rates 
(WAERs) for the averaging group.
* * * * *
    (i) If you have elected to use paragraph (2) of the definition of 
``startup'' in 40 CFR 63.10042 (only allowed before January 2, 2025), 
then, for startup and shutdown incidents that occur on or prior to 
December 31, 2023, you must include the information in 40 CFR 
63.10031(c)(5) in the semiannual compliance report, in a PDF file. If 
you have elected to use paragraph (2) of the definition of ``startup'' 
in 40 CFR 63.10042, then, for startup and shutdown event(s) that occur 
on or after January 1, 2024, you must use the ECMPS Client Tool to 
submit the information in 40 CFR 63.10031(c)(5) and 40 CFR 63.10020(e) 
along with each quarterly compliance report, in a PDF file, starting 
with a report for the first calendar quarter of 2024. The applicable 
data elements in paragraphs (f)(6)(i) through (xii) of this section 
must be entered into ECMPS with each startup and shutdown report.
* * * * *
    (k) If you elect to demonstrate compliance using a PM CPMS (on or 
after July 6, 2027 you may not demonstrate compliance with filterable 
PM emissions limits using a PM CPMS, unless it is for an IGCC unit) or 
an approved HAP metals CMS, you must submit quarterly reports of your 
QA/QC activities (e.g., calibration checks, performance audits), in a 
PDF file, beginning with a report for the first quarter of 2024, if the 
PM CPMS or HAP metals CMS is used for the compliance demonstration in 
that quarter. Otherwise, submit a report for the first calendar quarter 
in which the PM CPMS or HAP metals CMS is used to demonstrate 
compliance. These reports are due no later than 60 days after the end 
of each calendar quarter. The applicable data elements in paragraph 
(f)(6)(i) through (xii) of this section must be entered into ECMPS with 
the PDF report.

0
16. Section 63.10032 is amended by revising paragraphs (a) introductory 
text and (f)(2) introductory text to read as follows:


Sec.  63.10032  What records must I keep?

    (a) You must keep records according to paragraphs (a)(1) and (2) of 
this section. If you are required to (or elect to) continuously monitor 
Hg and/or HCl and/or HF and/or PM emissions, or if you elect to use a 
PM CPMS (unless it is for an IGCC unit, you may only use PM CPMS before 
July 6, 2027), you must keep the records required under appendix A and/
or appendix B and/or appendix C and/or appendix D to this subpart. If 
you elect to conduct periodic (e.g., quarterly or annual) performance 
stack tests, then, for each test completed on or after January 1, 2024, 
you must keep records of the applicable data elements under 40 CFR 
63.7(g). You must also keep records of all data elements and other 
information in appendix E to this subpart that apply to your compliance 
strategy.
* * * * *
    (f) * * *
    (2) Should you choose to rely on paragraph (2) of the definition of 
``startup'' in Sec.  63.10042 for your EGU (on or after January 2, 2025 
you may not use paragraph (2) of the definition of startup in Sec.  
63.10042), you must keep records of:
* * * * *

0
17. Section 63.10042 is amended by revising the definition ``Startup'' 
to read as follows:


Sec.  63.10042  What definitions apply to this subpart?

* * * * *
    Startup means:
    (1) The first-ever firing of fuel in a boiler for the purpose of 
producing

[[Page 38569]]

electricity, or the firing of fuel in a boiler after a shutdown event 
for any purpose. 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). Any fraction of an hour in which 
startup occurs constitutes a full hour of startup.
    (2) Alternatively, prior to January 2, 2025, the period in which 
operation of an EGU is initiated for any purpose. 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. 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 (16 U.S.C. 796(18)(A) and 18 
CFR 292.202(c)), whichever is earlier. Any fraction of an hour in which 
startup occurs constitutes a full hour of startup.
* * * * *

0
18. Revise table 1 to subpart UUUUU of part 63 to read as follows:

Table 1 to Subpart UUUUU of Part 63--Emission Limits for New or 
Reconstructed EGUs

    As stated in Sec.  63.9991, you must comply with the following 
applicable emission limits:

----------------------------------------------------------------------------------------------------------------
                                                                                 Using these requirements, as
                                                          You must meet the      appropriate (e.g., specified
      If your EGU is in this         For the following    following emission      sampling volume or test run
        subcategory . . .            pollutants . . .      limits and work    duration) and limitations with the
                                                          practice standards    test methods in Table 5 to this
                                                                . . .                    Subpart . . .
----------------------------------------------------------------------------------------------------------------
1. Coal-fired unit not low rank    a. Filterable         9.0E-2 lb/MWh \1\..  Collect a minimum catch of 6.0
 virgin coal.                       particulate matter                         milligrams or a minimum sample
                                    (PM).                                      volume of 4 dscm per run.
                                   OR                    OR
                                   Total non-Hg HAP      6.0E-2 lb/GWh......  Collect a minimum of 4 dscm per
                                    metals.                                    run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  8.0E-3 lb/GWh......
                                   Arsenic (As)........  3.0E-3 lb/GWh......
                                   Beryllium (Be)......  6.0E-4 lb/GWh......
                                   Cadmium (Cd)........  4.0E-4 lb/GWh......
                                   Chromium (Cr).......  7.0E-3 lb/GWh......
                                   Cobalt (Co).........  2.0E-3 lb/GWh......
                                   Lead (Pb)...........  2.0E-2 lb/GWh......
                                   Manganese (Mn)......  4.0E-3 lb/GWh......
                                   Nickel (Ni).........  4.0E-2 lb/GWh......
                                   Selenium (Se).......  5.0E-2 lb/GWh......
                                   b. Hydrogen chloride  1.0E-2 lb/MWh......  For Method 26A at appendix A-8 to
                                    (HCl).                                     part 60 of this chapter, collect
                                                                               a minimum of 3 dscm per run. For
                                                                               ASTM D6348-03(Reapproved 2010)
                                                                               \2\ or Method 320 at appendix A
                                                                               to part 63 of this chapter,
                                                                               sample for a minimum of 1 hour.
                                   OR
                                   Sulfur dioxide (SO2)  1.0 lb/MWh.........  SO2 CEMS.
                                    \3\.
                                   c. Mercury (Hg).....  3.0E-3 lb/GWh......  Hg CEMS or sorbent trap monitoring
                                                                               system only.
2. Coal-fired units low rank       a. Filterable         9.0E-2 lb/MWh \1\..  Collect a minimum catch of 6.0
 virgin coal.                       particulate matter                         milligrams or a minimum sample
                                    (PM).                                      volume of 4 dscm per run.
                                   OR                    OR
                                   Total non-Hg HAP      6.0E-2 lb/GWh......  Collect a minimum of 4 dscm per
                                    metals.                                    run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  8.0E-3 lb/GWh......
                                   Arsenic (As)........  3.0E-3 lb/GWh......
                                   Beryllium (Be)......  6.0E-4 lb/GWh......
                                   Cadmium (Cd)........  4.0E-4 lb/GWh......
                                   Chromium (Cr).......  7.0E-3 lb/GWh......
                                   Cobalt (Co).........  2.0E-3 lb/GWh......
                                   Lead (Pb)...........  2.0E-2 lb/GWh......
                                   Manganese (Mn)......  4.0E-3 lb/GWh......
                                   Nickel (Ni).........  4.0E-2 lb/GWh......
                                   Selenium (Se).......  5.0E-2 lb/GWh......
                                   b. Hydrogen chloride  1.0E-2 lb/MWh......  For Method 26A, collect a minimum
                                    (HCl).                                     of 3 dscm per run For ASTM D6348-
                                                                               03(Reapproved 2010) \2\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
                                   OR
                                   Sulfur dioxide (SO2)  1.0 lb/MWh.........  SO2 CEMS.
                                    \3\.

[[Page 38570]]

 
                                   c. Mercury (Hg).....  Before July 8,       Hg CEMS or sorbent trap monitoring
                                                          2024: 4.0E-2 lb/     system only.
                                                          GWh; On or after
                                                          July 8, 2024: 1.3E-
                                                          2 lb/GWh.
3. IGCC unit.....................  a. Filterable         7.0E-2 lb/MWh \4\    Collect a minimum catch of 3.0
                                    particulate matter    9.0E-2 lb/MWh \5\.   milligrams or a minimum sample
                                    (PM).                                      volume of 2 dscm per run.
                                   OR                    OR
                                   Total non-Hg HAP      4.0E-1 lb/GWh......  Collect a minimum of 1 dscm per
                                    metals.                                    run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 2 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  2.0E-2 lb/GWh......
                                   Arsenic (As)........  2.0E-2 lb/GWh......
                                   Beryllium (Be)......  1.0E-3 lb/GWh......
                                   Cadmium (Cd)........  2.0E-3 lb/GWh......
                                   Chromium (Cr).......  4.0E-2 lb/GWh......
                                   Cobalt (Co).........  4.0E-3 lb/GWh......
                                   Lead (Pb)...........  9.0E-3 lb/GWh......
                                   Manganese (Mn)......  2.0E-2 lb/GWh......
                                   Nickel (Ni).........  7.0E-2 lb/GWh......
                                   Selenium (Se).......  3.0E-1 lb/GWh......
                                   b. Hydrogen chloride  2.0E-3 lb/MWh......  For Method 26A, collect a minimum
                                    (HCl).                                     of 1 dscm per run; for Method 26
                                                                               at appendix A-8 to part 60 of
                                                                               this chapter, collect a minimum
                                                                               of 120 liters per run.
                                                                              For ASTM D6348-03(Reapproved 2010)
                                                                               \2\ or Method 320, sample for a
                                                                               minimum of 1 hour.
                                   OR
                                   Sulfur dioxide (SO2)  4.0E-1 lb/MWh......  SO2 CEMS.
                                    \3\.
                                   c. Mercury (Hg).....  3.0E-3 lb/GWh......  Hg CEMS or sorbent trap monitoring
                                                                               system only.
4. Liquid oil-fired unit--         a. Filterable         3.0E-1 lb/MWh \1\..  Collect a minimum of 1 dscm per
 continental (excluding limited-    particulate matter                         run.
 use liquid oil-fired subcategory   (PM).
 units).
                                   OR                    OR
                                   Total HAP metals....  2.0E-4 lb/MWh......  Collect a minimum of 2 dscm per
                                                                               run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 2 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  1.0E-2 lb/GWh......
                                   Arsenic (As)........  3.0E-3 lb/GWh......
                                   Beryllium (Be)......  5.0E-4 lb/GWh......
                                   Cadmium (Cd)........  2.0E-4 lb/GWh......
                                   Chromium (Cr).......  2.0E-2 lb/GWh......
                                   Cobalt (Co).........  3.0E-2 lb/GWh......
                                   Lead (Pb)...........  8.0E-3 lb/GWh......
                                   Manganese (Mn)......  2.0E-2 lb/GWh......
                                   Nickel (Ni).........  9.0E-2 lb/GWh......
                                   Selenium (Se).......  2.0E-2 lb/GWh......
                                   Mercury (Hg)........  1.0E-4 lb/GWh......  For Method 30B at appendix A-8 to
                                                                               part 60 of this chapter sample
                                                                               volume determination (Section
                                                                               8.2.4), the estimated Hg
                                                                               concentration should nominally be
                                                                               <\1/2\ the standard.
                                   b. Hydrogen chloride  4.0E-4 lb/MWh......  For Method 26A, collect a minimum
                                    (HCl).                                     of 3 dscm per run. For ASTM D6348-
                                                                               03(Reapproved 2010) \2\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
                                   c. Hydrogen fluoride  4.0E-4 lb/MWh......  For Method 26A, collect a minimum
                                    (HF).                                      of 3 dscm per run. For ASTM D6348-
                                                                               03 (Reapproved 2010) \2\ or
                                                                               Method 320, sample for a minimum
                                                                               of 1 hour.
5. Liquid oil-fired unit--non-     a. Filterable         2.0E-1 lb/MWh \1\..  Collect a minimum of 1 dscm per
 continental (excluding limited-    particulate matter                         run.
 use liquid oil-fired subcategory   (PM).
 units).
                                   OR                    OR
                                   Total HAP metals....  7.0E-3 lb/MWh......  Collect a minimum of 1 dscm per
                                                                               run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  8.0E-3 lb/GWh......

[[Page 38571]]

 
                                   Arsenic (As)........  6.0E-2 lb/GWh......
                                   Beryllium (Be)......  2.0E-3 lb/GWh......
                                   Cadmium (Cd)........  2.0E-3 lb/GWh......
                                   Chromium (Cr).......  2.0E-2 lb/GWh......
                                   Cobalt (Co).........  3.0E-1 lb/GWh......
                                   Lead (Pb)...........  3.0E-2 lb/GWh......
                                   Manganese (Mn)......  1.0E-1 lb/GWh......
                                   Nickel (Ni).........  4.1E0 lb/GWh.......
                                   Selenium (Se).......  2.0E-2 lb/GWh......
                                   Mercury (Hg)........  4.0E-4 lb/GWh......  For Method 30B sample volume
                                                                               determination (Section 8.2.4),
                                                                               the estimated Hg concentration
                                                                               should nominally be <\1/2\ the
                                                                               standard.
                                   b. Hydrogen chloride  2.0E-3 lb/MWh......  For Method 26A, collect a minimum
                                    (HCl).                                     of 1 dscm per run; for Method 26,
                                                                               collect a minimum of 120 liters
                                                                               per run. For ASTM D6348-03
                                                                               (Reapproved 2010) \2\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
                                   c. Hydrogen fluoride  5.0E-4 lb/MWh......  For Method 26A, collect a minimum
                                    (HF).                                      of 3 dscm per run. For ASTM D6348-
                                                                               03 (Reapproved 2010) \2\ or
                                                                               Method 320, sample for a minimum
                                                                               of 1 hour.
6. Solid oil-derived fuel-fired    a. Filterable         3.0E-2 lb/MWh \1\..  Collect a minimum of 1 dscm per
 unit.                              particulate matter                         run.
                                    (PM).
                                   OR                    OR
                                   Total non-Hg HAP      6.0E-1 lb/GWh......  Collect a minimum of 1 dscm per
                                    metals.                                    run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  8.0E-3 lb/GWh......
                                   Arsenic (As)........  3.0E-3 lb/GWh......
                                   Beryllium (Be)......  6.0E-4 lb/GWh......
                                   Cadmium (Cd)........  7.0E-4 lb/GWh......
                                   Chromium (Cr).......  6.0E-3 lb/GWh......
                                   Cobalt (Co).........  2.0E-3 lb/GWh......
                                   Lead (Pb)...........  2.0E-2 lb/GWh......
                                   Manganese (Mn)......  7.0E-3 lb/GWh......
                                   Nickel (Ni).........  4.0E-2 lb/GWh......
                                   Selenium (Se).......  6.0E-3 lb/GWh......
                                   b. Hydrogen chloride  4.0E-4 lb/MWh......  For Method 26A, collect a minimum
                                    (HCl).                                     of 3 dscm per run. For ASTM D6348-
                                                                               03 (Reapproved 2010) \2\ or
                                                                               Method 320, sample for a minimum
                                                                               of 1 hour.
                                   OR
                                   Sulfur dioxide (SO2)  1.0 lb/MWh.........  SO2 CEMS.
                                    \3\.
                                   c. Mercury (Hg).....  2.0E-3 lb/GWh......  Hg CEMS or Sorbent trap monitoring
                                                                               system only.
----------------------------------------------------------------------------------------------------------------
\1\ Gross output.
\2\ Incorporated by reference, see Sec.   63.14.
\3\ You may not use the alternate SO2 limit if your EGU does not have some form of FGD system (or, in the case
  of IGCC EGUs, some other acid gas removal system either upstream or downstream of the combined cycle block)
  and SO2 CEMS installed.
\4\ Duct burners on syngas; gross output.
\5\ Duct burners on natural gas; gross output.


0
19. Revise table 2 to subpart UUUUU of part 63 to read as follows:

Table 2 to Subpart UUUUU of Part 63--Emission Limits for Existing EGUs

    As stated in Sec.  63.9991, you must comply with the following 
applicable emission limits: \1\

----------------------------------------------------------------------------------------------------------------
                                                                                 Using these requirements, as
                                                          You must meet the      appropriate (e.g., specified
      If your EGU is in this         For the following    following emission      sampling volume or test run
        subcategory . . .            pollutants . . .      limits and work    duration) and limitations with the
                                                          practice standards    test methods in Table 5 to this
                                                                . . .                    Subpart . . .
----------------------------------------------------------------------------------------------------------------
1. Coal-fired unit not low rank    a. Filterable         Before July 6,       Before July 6, 2027: Collect a
 virgin coal.                       particulate matter    2027: 3.0E-2 lb/     minimum of 1 dscm per run.
                                    (PM).                 MMBtu or 3.0E-1 lb/
                                                          MWh \2\.

[[Page 38572]]

 
                                                         On or after July 6,  On or after July 6, 2027: Collect
                                                          2027: 1.0E-2 lb/     a minimum catch of 6.0 milligrams
                                                          MMBtu or 1.0E-1 lb/  or a minimum sample volume of 4
                                                          MWh \2\.             dscm per run.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following total non-Hg HAP
                                                                               metals emission limit if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Total non-Hg HAP      Before July 6,       Collect a minimum of 1 dscm per
                                    metals.               2027: 5.0E-5 lb/     run.
                                                          MMBtu or 5.0E-1 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.7E-5 lb/
                                                          MMBtu or 1.7E-1 lb/
                                                          GWh.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following individual HAP
                                                                               metals emissions limits if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  Before July 6,
                                                          2027: 8.0E-1 lb/
                                                          TBtu or 8.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 2.7E-1 lb/
                                                          TBtu or 2.7E-3 lb/
                                                          GWh.
                                   Arsenic (As)........  Before July 6,
                                                          2027: 1.1E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 3.7E-1 lb/
                                                          TBtu or 6.7E-3 lb/
                                                          GWh.
                                   Beryllium (Be)......  Before July 6,
                                                          2027: 2.0E-1 lb/
                                                          TBtu or 2.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 6.7E-2 lb/
                                                          TBtu or 6.7E-4 lb/
                                                          GWh.
                                   Cadmium (Cd)........  Before July 6,
                                                          2027: 3.0E-1 lb/
                                                          TBtu or 3.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.0E-1 lb/
                                                          TBtu or 1.0E-3 lb/
                                                          GWh.
                                   Chromium (Cr).......  Before July 6,
                                                          2027: 2.8E0 lb/
                                                          TBtu or 3.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 9.3E-1 lb/
                                                          TBtu or 1.0E-2 lb/
                                                          GWh.

[[Page 38573]]

 
                                   Cobalt (Co).........  Before July 6,
                                                          2027: 8.0E-1 lb/
                                                          TBtu or 8.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 2.7E-1 lb/
                                                          TBtu or 2.7E-3 lb/
                                                          GWh.
                                   Lead (Pb)...........  Before July 6,
                                                          2027: 1.2E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 4.0E-1 lb/
                                                          TBtu or 6.7E-3 lb/
                                                          GWh.
                                   Manganese (Mn)......  Before July 6,
                                                          2027: 4.0E0 lb/
                                                          TBtu or 5.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.3E0 lb/
                                                          TBtu or 1.7E-2 lb/
                                                          GWh.
                                   Nickel (Ni).........  Before July 6,
                                                          2027: 3.5E0 lb/
                                                          TBtu or 4.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.2E0 lb/
                                                          TBtu or 1.3E-2 lb/
                                                          GWh.
                                   Selenium (Se).......  Before July 6,
                                                          2027: 5.0E0 lb/
                                                          TBtu or 6.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.7E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                   b. Hydrogen chloride  2.0E-3 lb/MMBtu or   For Method 26A at appendix A-8 to
                                    (HCl).                2.0E-2 lb/MWh.       part 60 of this chapter, collect
                                                                               a minimum of 0.75 dscm per run;
                                                                               for Method 26, collect a minimum
                                                                               of 120 liters per run. For ASTM
                                                                               D6348-03 (Reapproved 2010) \3\ or
                                                                               Method 320 at appendix A to part
                                                                               63 of this chapter, sample for a
                                                                               minimum of 1 hour.
                                   OR
                                   Sulfur dioxide (SO2)  2.0E-1 lb/MMBtu or   SO2 CEMS.
                                    \4\.                  1.5E0 lb/MWh.
                                   c. Mercury (Hg).....  1.2E0 lb/TBtu or     LEE Testing for 30 days with a
                                                          1.3E-2 lb/GWh.       sampling period consistent with
                                                                               that given in section 5.2.1 of
                                                                               appendix A to this subpart per
                                                                               Method 30B at appendix A-8 to
                                                                               part 60 of this chapter run or Hg
                                                                               CEMS or sorbent trap monitoring
                                                                               system only.
                                                         OR
                                                         1.0E0 lb/TBtu or     LEE Testing for 90 days with a
                                                          1.1E-2 lb/GWh.       sampling period consistent with
                                                                               that given in section 5.2.1 of
                                                                               appendix A to this subpart per
                                                                               Method 30B run or Hg CEMS or
                                                                               sorbent trap monitoring system
                                                                               only.
2. Coal-fired unit low rank        a. Filterable         Before July 6,       Before July 6, 2027: Collect a
 virgin coal.                       particulate matter    2027: 3.0E-2 lb/     minimum of 1 dscm per run.
                                    (PM).                 MMBtu or 3.0E-1 lb/ On or after July 6, 2027: Collect
                                                          MWh \2\.             a minimum catch of 6.0 milligrams
                                                         On or after July 6,   or a minimum sample volume of 4
                                                          2027: 1.0E-2 lb/     dscm per run.
                                                          MMBtu or 1.0E-1 lb/
                                                          MWh \2\.

[[Page 38574]]

 
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following total non-Hg HAP
                                                                               metals emission limit if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Total non-Hg HAP      Before July 6,       Collect a minimum of 1 dscm per
                                    metals.               2027: 5.0E-5 lb/     run.
                                                          MMBtu or 5.0E-1 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.7E-5 lb/
                                                          MMBtu or 1.7E-1 lb/
                                                          GWh.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following individual HAP
                                                                               metals emissions limits if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  Before July 6,
                                                          2027: 8.0E-1 lb/
                                                          TBtu or 8.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 2.7E-1 lb/
                                                          TBtu or 2.7E-3 lb/
                                                          GWh.
                                   Arsenic (As)........  Before July 6,
                                                          2027: 1.1E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 3.7E-1 lb/
                                                          TBtu or 6.7E-3 lb/
                                                          GWh.
                                   Beryllium (Be)......  Before July 6,
                                                          2027: 2.0E-1 lb/
                                                          TBtu or 2.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 6.7E-2 lb/
                                                          TBtu or 6.7E-4 lb/
                                                          GWh.
                                   Cadmium (Cd)........  Before July 6,
                                                          2027: 3.0E-1 lb/
                                                          TBtu or 3.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.0E-1 lb/
                                                          TBtu or 1.0E-3 lb/
                                                          GWh.
                                   Chromium (Cr).......  Before July 6,
                                                          2027: 2.8E0 lb/
                                                          TBtu or 3.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 9.3E-1 lb/
                                                          TBtu or 1.0E-2 lb/
                                                          GWh.
                                   Cobalt (Co).........  Before July 6,
                                                          2027: 8.0E-1 lb/
                                                          TBtu or 8.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 2.7E-1 lb/
                                                          TBtu or 2.7E-3 lb/
                                                          GWh.

[[Page 38575]]

 
                                   Lead (Pb)...........  Before July 6,
                                                          2027: 1.2E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 4.0E-1 lb/
                                                          TBtu or 6.7E-3 lb/
                                                          GWh.
                                   Manganese (Mn)......  Before July 6,
                                                          2027: 4.0E0 lb/
                                                          TBtu or 5.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.3E0 lb/
                                                          TBtu or 1.7E-2 lb/
                                                          GWh.
                                   Nickel (Ni).........  Before July 6,
                                                          2027: 3.5E0 lb/
                                                          TBtu or 4.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.2E0 lb/
                                                          TBtu or 1.3E-2 lb/
                                                          GWh.
                                   Selenium (Se).......  Before July 6,
                                                          2027: 5.0E0 lb/
                                                          TBtu or 6.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.7E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                   b. Hydrogen chloride  2.0E-3 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HCl).                2.0E-2 lb/MWh.       of 0.75 dscm per run; for Method
                                                                               26 at appendix A-8 to part 60 of
                                                                               this chapter, collect a minimum
                                                                               of 120 liters per run. For ASTM
                                                                               D6348-03 (Reapproved 2010) \3\ or
                                                                               Method 320, sample for a minimum
                                                                               of 1 hour.
                                   OR                    OR
                                   Sulfur dioxide (SO2)  2.0E-1 lb/MMBtu or   SO2 CEMS.
                                    \4\.                  1.5E0 lb/MWh.
                                   c. Mercury (Hg).....  Before July 6,       LEE Testing for 30 days with a
                                                          2027: 4.0E0 lb/      sampling period consistent with
                                                          TBtu or 4.0E-2 lb/   that given in section 5.2.1 of
                                                          GWh.                 appendix A to this subpart per
                                                         On or after July 6,   Method 30B run or Hg CEMS or
                                                          2027: 1.2E0 lb/      sorbent trap monitoring system
                                                          TBtu or 1.3E-2 lb/   only.
                                                          GWh.
3. IGCC unit.....................  a. Filterable         4.0E-2 lb/MMBtu or   Before July 6, 2027: Collect a
                                    particulate matter    4.0E-1 lb/MWh \2\.   minimum of 1 dscm per run.
                                    (PM).                                     On or after July 6, 2027: Collect
                                                                               a minimum catch of 3.0 milligrams
                                                                               or a minimum sample volume of 2
                                                                               dscm per run.
                                   OR                    OR
                                   Total non-Hg HAP      6.0E-5 lb/MMBtu or   Collect a minimum of 1 dscm per
                                    metals.               5.0E-1 lb/GWh.       run.
                                   OR                    OR
                                   Individual HAP        ...................  Collect a minimum of 2 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  1.4E0 lb/TBtu or
                                                          2.0E-2 lb/GWh.
                                   Arsenic (As)........  1.5E0 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).......  2.9E0 lb/TBtu or
                                                          3.0E-2 lb/GWh.

[[Page 38576]]

 
                                   Cobalt (Co).........  1.2E0 lb/TBtu or
                                                          2.0E-2 lb/GWh.
                                   Lead (Pb)...........  1.9E+2 lb/TBtu or
                                                          1.8E0 lb/GWh.
                                   Manganese (Mn)......  2.5E0 lb/TBtu or
                                                          3.0E-2 lb/GWh.
                                   Nickel (Ni).........  6.5E0 lb/TBtu or
                                                          7.0E-2 lb/GWh.
                                   Selenium (Se).......  2.2E+1 lb/TBtu or
                                                          3.0E-1 lb/GWh.
                                   b. Hydrogen chloride  5.0E-4 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HCl).                5.0E-3 lb/MWh.       of 1 dscm per run; for Method 26,
                                                                               collect a minimum of 120 liters
                                                                               per run. For ASTM D6348-03
                                                                               (Reapproved 2010) \3\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
                                   c. Mercury (Hg).....  2.5E0 lb/TBtu or     LEE Testing for 30 days with a
                                                          3.0E-2 lb/GWh.       sampling period consistent with
                                                                               that given in section 5.2.1 of
                                                                               appendix A to this subpart per
                                                                               Method 30B run or Hg CEMS or
                                                                               sorbent trap monitoring system
                                                                               only.
4. Liquid oil-fired unit--         a. Filterable         3.0E-2 lb/MMBtu or   Collect a minimum of 1 dscm per
 continental (excluding limited-    particulate matter    3.0E-1 lb/MWh \2\.   run.
 use liquid oil-fired subcategory   (PM).
 units).
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following total non-Hg HAP
                                                                               metals emission limit if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Total HAP metals....  8.0E-4 lb/MMBtu or   Collect a minimum of 1 dscm per
                                                          8.0E-3 lb/MWh.       run.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following individual HAP
                                                                               metals emissions limits if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Individual HAP        ...................  Collect a minimum of 1 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  1.3E+1 lb/TBtu or
                                                          2.0E-1 lb/GWh.
                                   Arsenic (As)........  2.8E0 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).......  5.5E0 lb/TBtu or
                                                          6.0E-2 lb/GWh.
                                   Cobalt (Co).........  2.1E+1 lb/TBtu or
                                                          3.0E-1 lb/GWh.
                                   Lead (Pb)...........  8.1E0 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
                                                          1.1E0 lb/GWh.
                                   Selenium (Se).......  3.3E0 lb/TBtu or
                                                          4.0E-2 lb/GWh.
                                   Mercury (Hg)........  2.0E-1 lb/TBtu or    For Method 30B sample volume
                                                          2.0E-3 lb/GWh.       determination (Section 8.2.4),
                                                                               the estimated Hg concentration
                                                                               should nominally be <\1/2\ the
                                                                               standard.
                                   b. Hydrogen chloride  2.0E-3 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HCl).                1.0E-2 lb/MWh.       of 1 dscm per run; for Method 26,
                                                                               collect a minimum of 120 liters
                                                                               per run. For ASTM D6348-03
                                                                               (Reapproved 2010) \3\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
                                   c. Hydrogen fluoride  4.0E-4 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HF).                 4.0E-3 lb/MWh.       of 1 dscm per run; for Method 26,
                                                                               collect a minimum of 120 liters
                                                                               per run. For ASTM D6348-03
                                                                               (Reapproved 2010) \3\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
5. Liquid oil-fired unit--non-     a. Filterable         3.0E-2 lb/MMBtu or   Collect a minimum of 1 dscm per
 continental (excluding limited-    particulate matter    3.0E-1 lb/MWh \2\.   run.
 use liquid oil-fired subcategory   (PM).
 units).

[[Page 38577]]

 
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following total non-Hg HAP
                                                                               metals emission limit if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Total HAP metals....  6.0E-4 lb/MMBtu or   Collect a minimum of 1 dscm per
                                                          7.0E-3 lb/MWh.       run.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following individual HAP
                                                                               metals emissions limits if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Individual HAP        ...................  Collect a minimum of 2 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  2.2E0 lb/TBtu or
                                                          2.0E-2 lb/GWh.
                                   Arsenic (As)........  4.3E0 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
                                                          1.4E0 lb/GWh.
                                   Lead (Pb)...........  4.9E0 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
                                                          4.1E0 lb/GWh.
                                   Selenium (Se).......  9.8E0 lb/TBtu or
                                                          2.0E-1 lb/GWh.
                                   Mercury (Hg)........  4.0E-2 lb/TBtu or    For Method 30B sample volume
                                                          4.0E-4 lb/GWh.       determination (Section 8.2.4),
                                                                               the estimated Hg concentration
                                                                               should nominally be <\1/2\ the
                                                                               standard.
                                   b. Hydrogen chloride  2.0E-4 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HCl).                2.0E-3 lb/MWh.       of 1 dscm per run; for Method 26,
                                                                               collect a minimum of 120 liters
                                                                               per run. For ASTM D6348-03
                                                                               (Reapproved 2010) \3\ or Method
                                                                               320, sample for a minimum of 2
                                                                               hours.
                                   c. Hydrogen fluoride  6.0E-5 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HF).                 5.0E-4 lb/MWh.       of 3 dscm per run. For ASTM D6348-
                                                                               03 (Reapproved 2010) \3\ or
                                                                               Method 320, sample for a minimum
                                                                               of 2 hours.
6. Solid oil-derived fuel-fired    a. Filterable         8.0E-3 lb/MMBtu or   Before July 6, 2027: Collect a
 unit.                              particulate matter    9.0E-2 lb/MWh \2\.   minimum of 1 dscm per run.
                                    (PM).                                     On or after July 6, 2027: Collect
                                                                               a minimum catch of 6.0 milligrams
                                                                               or a minimum sample volume of 4
                                                                               dscm per run.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following total non-Hg HAP
                                                                               metals emission limit if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Total non-Hg HAP      4.0E-5 lb/MMBtu or   Collect a minimum of 1 dscm per
                                    metals.               6.0E-1 lb/GWh.       run.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following individual HAP
                                                                               metals emissions limits if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   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.

[[Page 38578]]

 
                                   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).........  1.1E0 lb/TBtu or
                                                          2.0E-2 lb/GWh.
                                   Lead (Pb)...........  8.0E-1 lb/TBtu or
                                                          2.0E-2 lb/GWh.
                                   Manganese (Mn)......  2.3E0 lb/TBtu or
                                                          4.0E-2 lb/GWh.
                                   Nickel (Ni).........  9.0E0 lb/TBtu or
                                                          2.0E-1 lb/GWh.
                                   Selenium (Se).......  1.2E0 lb/TBtu or
                                                          2.0E-2 lb/GWh.
                                   b. Hydrogen chloride  5.0E-3 lb/MMBtu or   For Method 26A, collect a minimum
                                    (HCl).                8.0E-2 lb/MWh.       of 0.75 dscm per run; for Method
                                                                               26, collect a minimum of 120
                                                                               liters per run. For ASTM D6348-03
                                                                               (Reapproved 2010) \3\ or Method
                                                                               320, sample for a minimum of 1
                                                                               hour.
                                   OR                    OR
                                   Sulfur dioxide (SO2)  3.0E-1 lb/MMBtu or   SO2 CEMS.
                                    \4\.                  2.0E0 lb/MWh.
                                   c. Mercury (Hg).....  2.0E-1 lb/TBtu or    LEE Testing for 30 days with a
                                                          2.0E-3 lb/GWh.       sampling period consistent with
                                                                               that given in section 5.2.1 of
                                                                               appendix A to this subpart per
                                                                               Method 30B run or Hg CEMS or
                                                                               sorbent trap monitoring system
                                                                               only.
7. Eastern Bituminous Coal Refuse  a. Filterable         Before July 6,       Before July 6, 2027: Collect a
 (EBCR)-fired unit.                 particulate matter    2027: 3.0E-2 lb/     minimum of 1 dscm per run.
                                    (PM).                 MMBtu or 3.0E-1 lb/ On or after July 6, 2027: Collect
                                                          MWh \2\.             a minimum catch of 6.0 milligrams
                                                         On or after July 6,   or a minimum sample volume of 4
                                                          2027: 1.0E-2 lb/     dscm per run.
                                                          MMBtu or 1.0E-1 lb/
                                                          MWh \2\.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following total non-Hg HAP
                                                                               metals emission limit if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Total non-Hg HAP      Before July 6,       Collect a minimum of 1 dscm per
                                    metals.               2027: 5.0E-5 lb/     run.
                                                          MMBtu or 5.0E-1 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.7E-5 lb/
                                                          MMBtu or 1.7E-1 lb/
                                                          GWh.
                                   OR                    OR                   On or after July 6, 2027 you may
                                                                               only demonstrate compliance with
                                                                               the following individual HAP
                                                                               metals emissions limits if you
                                                                               request and receive approval for
                                                                               the use of a non-Hg HAP metals
                                                                               CMS under 40 CFR 63.7(f).
                                   Individual HAP        ...................  Collect a minimum of 3 dscm per
                                    metals:.                                   run.
                                   Antimony (Sb).......  Before July 6,
                                                          2027: 8.0E-1 lb/
                                                          TBtu or 8.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 2.7E-1 lb/
                                                          TBtu or 2.7E-3 lb/
                                                          GWh.

[[Page 38579]]

 
                                   Arsenic (As)........  Before July 6,
                                                          2027: 1.1E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 3.7E-1 lb/
                                                          TBtu or 6.7E-3 lb/
                                                          GWh.
                                   Beryllium (Be)......  Before July 6,
                                                          2027: 2.0E-1 lb/
                                                          TBtu or 2.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 6.7E-2 lb/
                                                          TBtu or 6.7E-4 lb/
                                                          GWh.
                                   Cadmium (Cd)........  Before July 6,
                                                          2027: 3.0E-1 lb/
                                                          TBtu or 3.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.0E-1 lb/
                                                          TBtu or 1.0E-3 lb/
                                                          GWh.
                                   Chromium (Cr).......  Before July 6,
                                                          2027: 2.8E0 lb/
                                                          TBtu or 3.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 9.3E-1 lb/
                                                          TBtu or 1.0E-2 lb/
                                                          GWh.
                                   Cobalt (Co).........  Before July 6,
                                                          2027: 8.0E-1 lb/
                                                          TBtu or 8.0E-3 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 2.7E-1 lb/
                                                          TBtu or 2.7E-3 lb/
                                                          GWh.
                                   Lead (Pb)...........  Before July 6,
                                                          2027: 1.2E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 4.0E-1 lb/
                                                          TBtu or 6.7E-3 lb/
                                                          GWh.
                                   Manganese (Mn)......  Before July 6,
                                                          2027: 4.0E0 lb/
                                                          TBtu or 5.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.3E0 lb/
                                                          TBtu or 1.7E-2 lb/
                                                          GWh.
                                   Nickel (Ni).........  Before July 6,
                                                          2027: 3.5E0 lb/
                                                          TBtu or 4.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.2E0 lb/
                                                          TBtu or 1.3E-2 lb/
                                                          GWh.

[[Page 38580]]

 
                                   Selenium (Se).......  Before July 6,
                                                          2027: 5.0E0 lb/
                                                          TBtu or 6.0E-2 lb/
                                                          GWh.
                                                         On or after July 6,
                                                          2027: 1.7E0 lb/
                                                          TBtu or 2.0E-2 lb/
                                                          GWh.
                                   b. Hydrogen chloride  4.0E-2 lb/MMBtu or   For Method 26A at appendix A-8 to
                                    (HCl).                4.0E-1 lb/MWh.       part 60 of this chapter, collect
                                                                               a minimum of 0.75 dscm per run;
                                                                               for Method 26, collect a minimum
                                                                               of 120 liters per run. For ASTM
                                                                               D6348-03 (Reapproved 2010) \3\ or
                                                                               Method 320 at appendix A to part
                                                                               63 of this chapter, sample for a
                                                                               minimum of 1 hour.
                                   OR
                                   Sulfur dioxide (SO2)  6E-1 lb/MMBtu or     SO2 CEMS.
                                    \4\.                  9E0 lb/MWh.
                                   c. Mercury (Hg).....  1.2E0 lb/TBtu or     LEE Testing for 30 days with a
                                                          1.3E-2 lb/GWh.       sampling period consistent with
                                                                               that given in section 5.2.1 of
                                                                               appendix A to this subpart per
                                                                               Method 30B at appendix A-8 to
                                                                               part 60 of this chapter run or Hg
                                                                               CEMS or sorbent trap monitoring
                                                                               system only.
                                   OR
                                                         1.0E0 lb/TBtu or     LEE Testing for 90 days with a
                                                          1.1E-2 lb/GWh.       sampling period consistent with
                                                                               that given in section 5.2.1 of
                                                                               appendix A to this subpart per
                                                                               Method 30B run or Hg CEMS or
                                                                               sorbent trap monitoring system
                                                                               only.
----------------------------------------------------------------------------------------------------------------
\1\ For LEE emissions testing for total PM, total HAP metals, individual HAP metals, HCl, and HF, the required
  minimum sampling volume must be increased nominally by a factor of 2. With the exception of IGCC units, on or
  after July 6, 2027 you may not pursue the LEE option for filterable PM, total non-Hg metals, and individual
  HAP metals and you may not comply with the total non-Hg HAP metals or individual HAP metals emissions limits
  for all existing EGU subcategories unless you request and receive approval for the use of a HAP metals CMS
  under Sec.   63.7(f).
\2\ Gross output.
\3\ Incorporated by reference, see Sec.   63.14.
\4\ You may not use the alternate SO2 limit if your EGU does not have some form of FGD system and SO2 CEMS
  installed.


0
20. Revise table 3 to subpart UUUUU of part 63 to read as follows:

Table 3 to Subpart UUUUU of Part 63--Work Practice Standards

    As stated in Sec.  63.9991, you must comply with the following 
applicable work practice standards:

------------------------------------------------------------------------
     If your EGU is . . .          You must meet the following . . .
------------------------------------------------------------------------
1. An existing EGU...........  Conduct a tune-up of the EGU burner and
                                combustion controls at least each 36
                                calendar months, or each 48 calendar
                                months if neural network combustion
                                optimization software is employed, as
                                specified in Sec.   63.10021(e).
2. A new or reconstructed EGU  Conduct a tune-up of the EGU burner and
                                combustion controls at least each 36
                                calendar months, or each 48 calendar
                                months if neural network combustion
                                optimization software is employed, as
                                specified in Sec.   63.10021(e).
3. A coal-fired, liquid oil-   a. Before January 2, 2025 you have the
 fired (excluding limited-use   option of complying using either of the
 liquid oil-fired subcategory   following work practice standards in
 units), or solid oil-derived   paragraphs (1) and (2). On or after
 fuel-fired EGU during          January 2, 2025 you may not choose to
 startup.                       use paragraph (2) of the definition of
                                startup in Sec.   63.10042 and the
                                following associated work practice
                                standards in paragraph (2).

[[Page 38581]]

 
                               (1) If you choose to comply using
                                paragraph (1) of the definition of
                                ``startup'' in Sec.   63.10042, you must
                                operate all CMS during startup. Startup
                                means 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. 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). For startup of a unit, you
                                must use clean fuels as defined in Sec.
                                 63.10042 for ignition. Once you convert
                                to firing coal, residual oil, or solid
                                oil-derived fuel, you must engage all of
                                the applicable control technologies
                                except dry scrubber and SCR. You must
                                start your dry scrubber and SCR systems,
                                if present, appropriately to comply with
                                relevant standards applicable during
                                normal operation. You must comply with
                                all applicable emissions limits at all
                                times except for periods that meet the
                                applicable definitions of startup and
                                shutdown in this subpart. You must keep
                                records during startup periods. You must
                                provide reports concerning activities
                                and startup periods, as specified in
                                Sec.   63.10011(g) and Sec.
                                63.10021(h) and (i). If you elect to use
                                paragraph (2) of the definition of
                                startup in 40 CFR 63.10042, you must
                                report the applicable information in 40
                                CFR 63.10031(c)(5) concerning startup
                                periods as follows: For startup periods
                                that occur on or prior to December 31,
                                2023, in PDF files in the semiannual
                                compliance report; for startup periods
                                that occur on or after January 1, 2024,
                                quarterly, in PDF files, according to 40
                                CFR 63.10031(i).
                               (2) If you choose to comply using
                                paragraph (2) of the definition of
                                ``startup'' in Sec.   63.10042, you must
                                operate all CMS during startup. You must
                                also collect appropriate data, and you
                                must calculate the pollutant emission
                                rate for each hour of startup.
                               For startup of an EGU, you must use one
                                or a combination of the clean fuels
                                defined in Sec.   63.10042 to the
                                maximum extent possible, taking into
                                account considerations such as boiler or
                                control device integrity, throughout the
                                startup period. You must have sufficient
                                clean fuel capacity to engage and
                                operate your PM control device within
                                one hour of adding coal, residual oil,
                                or solid oil-derived fuel to the unit.
                                You must meet the startup period work
                                practice requirements as identified in
                                Sec.   63.10020(e).
                               Once you start firing coal, residual oil,
                                or solid oil-derived fuel, you must vent
                                emissions to the main stack(s). You must
                                comply with the applicable emission
                                limits beginning with the hour after
                                startup ends. You must engage and
                                operate your PM control(s) within 1 hour
                                of first firing of coal, residual oil,
                                or solid oil-derived fuel.
                               You must start all other applicable
                                control devices as expeditiously as
                                possible, considering safety and
                                manufacturer/supplier recommendations,
                                but, in any case, when necessary to
                                comply with other standards made
                                applicable to the EGU by a permit limit
                                or a rule other than this subpart that
                                require operation of the control
                                devices.
                               b. Relative to the syngas not fired in
                                the combustion turbine of an IGCC EGU
                                during startup, you must either: (1)
                                Flare the syngas, or (2) route the
                                syngas to duct burners, which may need
                                to be installed, and route the flue gas
                                from the duct burners to the heat
                                recovery steam generator.
                               c. If you choose to use just one set of
                                sorbent traps to demonstrate compliance
                                with the applicable Hg emission limit,
                                you must comply with the limit at all
                                times; otherwise, you must comply with
                                the applicable emission limit at all
                                times except for startup and shutdown
                                periods.
                               d. You must collect monitoring data
                                during startup periods, as specified in
                                Sec.   63.10020(a) and (e). You must
                                keep records during startup periods, as
                                provided in Sec.  Sec.   63.10021(h) and
                                63.10032. You must provide reports
                                concerning activities and startup
                                periods, as specified in Sec.  Sec.
                                63.10011(g), 63.10021(i), and 63.10031.
                                Before January 2, 2025, if you elect to
                                use paragraph (2) of the definition of
                                startup in 40 CFR 63.10042, you must
                                report the applicable information in 40
                                CFR 63.10031(c)(5) concerning startup
                                periods as follows: For startup periods
                                that occur on or prior to December 31,
                                2023, in PDF files in the semiannual
                                compliance report; for startup periods
                                that occur on or after January 1, 2024,
                                quarterly, in PDF files, according to 40
                                CFR 63.10031(i). On or after January 2,
                                2025 you may not use paragraph (2) of
                                the definition of startup in Sec.
                                63.10042.
4. A coal-fired, liquid oil-   You must operate all CMS during shutdown.
 fired (excluding limited-use   You must also collect appropriate data,
 liquid oil-fired subcategory   and you must calculate the pollutant
 units), or solid oil-derived   emission rate for each hour of shutdown
 fuel-fired EGU during          for those pollutants for which a CMS is
 shutdown.                      used.
                               While firing coal, residual oil, or solid
                                oil-derived fuel during shutdown, you
                                must vent emissions to the main stack(s)
                                and operate all applicable control
                                devices and continue to operate those
                                control devices after the cessation of
                                coal, residual oil, or solid oil-derived
                                fuel being fed into the EGU and for as
                                long as possible thereafter considering
                                operational and safety concerns. In any
                                case, you must operate your controls
                                when necessary to comply with other
                                standards made applicable to the EGU by
                                a permit limit or a rule other than this
                                subpart and that require operation of
                                the control devices.
                               If, in addition to the fuel used prior to
                                initiation of shutdown, another fuel
                                must be used to support the shutdown
                                process, that additional fuel must be
                                one or a combination of the clean fuels
                                defined in Sec.   63.10042 and must be
                                used to the maximum extent possible,
                                taking into account considerations such
                                as not compromising boiler or control
                                device integrity.
                               Relative to the syngas not fired in the
                                combustion turbine of an IGCC EGU during
                                shutdown, you must either: (1) Flare the
                                syngas, or (2) route the syngas to duct
                                burners, which may need to be installed,
                                and route the flue gas from the duct
                                burners to the heat recovery steam
                                generator.

[[Page 38582]]

 
                               You must comply with all applicable
                                emission limits at all times except
                                during startup periods and shutdown
                                periods at which time you must meet this
                                work practice. You must collect
                                monitoring data during shutdown periods,
                                as specified in Sec.   63.10020(a). You
                                must keep records during shutdown
                                periods, as provided in Sec.  Sec.
                                63.10032 and 63.10021(h). Any fraction
                                of an hour in which shutdown occurs
                                constitutes a full hour of shutdown. You
                                must provide reports concerning
                                activities and shutdown periods, as
                                specified in Sec.  Sec.   63.10011(g),
                                63.10021(i), and 63.10031. Before
                                January 2, 2025, if you elect to use
                                paragraph (2) of the definition of
                                startup in 40 CFR 63.10042, you must
                                report the applicable information in 40
                                CFR 63.10031(c)(5) concerning shutdown
                                periods as follows: For shutdown periods
                                that occur on or prior to December 31,
                                2023, in PDF files in the semiannual
                                compliance report; for shutdown periods
                                that occur on or after January 1, 2024,
                                quarterly, in PDF files, according to 40
                                CFR 63.10031(i). On or after January 2,
                                2025 you may not use paragraph (2) of
                                the definition of startup in Sec.
                                63.10042.
------------------------------------------------------------------------


0
21. Revise table 4 to subpart UUUUU of part 63 to read as follows:

Table 4 to Subpart UUUUU of Part 63--Operating Limits for EGUs

    Before July 6, 2027, as stated in Sec.  63.9991, you must comply 
with the applicable operating limits in table 4. However, on or after 
July 6, 2027 you may not use PM CPMS for compliance demonstrations, 
unless it is for an IGCC unit.

------------------------------------------------------------------------
If you demonstrate compliance   You must meet these operating limits . .
         using . . .                               .
------------------------------------------------------------------------
PM CPMS......................  Maintain the 30-boiler operating day
                                rolling average PM CPMS output
                                determined in accordance with the
                                requirements of Sec.   63.10023(b)(2)
                                and obtained during the most recent
                                performance test run demonstrating
                                compliance with the filterable PM, total
                                non-mercury HAP metals (total HAP
                                metals, for liquid oil-fired units), or
                                individual non-mercury HAP metals
                                (individual HAP metals including Hg, for
                                liquid oil-fired units) emissions
                                limitation(s).
------------------------------------------------------------------------


0
22. Revise table 5 to subpart UUUUU of part 63 to read as follows:

Table 5 to Subpart UUUUU of Part 63--Performance Testing Requirements

    As stated in Sec.  63.10007, you must comply with the following 
requirements for performance testing for existing, new or reconstructed 
affected sources:\1\
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    \1\ Regarding emissions data collected during periods of startup 
or shutdown, see Sec. Sec.  63.10020(b) and (c) and 63.10021(h). 
With the exception of IGCC units, on or after July 6, 2027: You may 
not use quarterly performance emissions testing to demonstrate 
compliance with the filterable PM emissions standards and for 
existing EGUs you may not choose to comply with the total or 
individual HAP metals emissions limits unless you request and 
receive approval for the use of a HAP metals CMS under Sec.  
63.7(f).
    \2\ See tables 1 and 2 to this subpart for required sample 
volumes and/or sampling run times.
    \3\ Incorporated by reference, see Sec.  63.14.

0
23. Revise table 6 to subpart UUUUU of part 63 to read as follows:

Table 6 to Subpart UUUUU of Part 63--Establishing PM CPMS Operating 
Limits

    Before July 6, 2027, as stated in Sec.  63.10007, you must comply 
with the following requirements for establishing operating limits in 
table 6. However, on or after July 6, 2027 you may not use PM CPMS for 
compliance demonstrations, unless it is for an IGCC unit.

----------------------------------------------------------------------------------------------------------------
                                 And you choose to
                                 establish PM CPMS                                           According to the
   If you have an applicable     operating limits,      And . . .         Using . . .     following procedures .
    emission limit for . . .       you must . . .                                                   . .
 
----------------------------------------------------------------------------------------------------------------
Filterable Particulate matter    Install, certify,  Establish a site-  Data from the PM   1. Collect PM CPMS
 (PM), total non-mercury HAP      maintain, and      specific           CPMS and the PM    output data during
 metals, individual non-mercury   operate a PM       operating limit    or HAP metals      the entire period of
 HAP metals, total HAP metals,    CPMS for           in units of PM     performance        the performance
 or individual HAP metals for     monitoring         CPMS output        tests.             tests.
 an EGU.                          emissions          signal (e.g.,                        2. Record the average
                                  discharged to      milliamps, mg/                        hourly PM CPMS output
                                  the atmosphere     acm, or other                         for each test run in
                                  according to       raw signal).                          the performance test.
                                  Sec.                                                    3. Determine the PM
                                  63.10010(h)(1).                                          CPMS operating limit
                                                                                           in accordance with
                                                                                           the requirements of
                                                                                           Sec.   63.10023(b)(2)
                                                                                           from data obtained
                                                                                           during the
                                                                                           performance test
                                                                                           demonstrating
                                                                                           compliance with the
                                                                                           filterable PM or HAP
                                                                                           metals emissions
                                                                                           limitations.
----------------------------------------------------------------------------------------------------------------


[[Page 38591]]


0
24. Revise table 7 to subpart UUUUU of part 63 to read as follows:

Table 7 to Subpart UUUUU of Part 63--Demonstrating Continuous 
Compliance

    As stated in Sec.  63.10021, you must show continuous compliance 
with the emission limitations for affected sources according to the 
following:

------------------------------------------------------------------------
If you use one of the following to meet
 applicable emissions limits, operating     You demonstrate continuous
 limits, or work practice standards . .        compliance by . . .
                   .
------------------------------------------------------------------------
1. CEMS to measure filterable PM, SO2,   Calculating the 30- (or 90-)
 HCl, HF, or Hg emissions, or using a     boiler operating day rolling
 sorbent trap monitoring system to        arithmetic average emissions
 measure Hg.                              rate in units of the
                                          applicable emissions standard
                                          basis at the end of each
                                          boiler operating day using all
                                          of the quality assured hourly
                                          average CEMS or sorbent trap
                                          data for the previous 30- (or
                                          90-) boiler operating days,
                                          excluding data recorded during
                                          periods of startup or
                                          shutdown.
2. PM CPMS to measure compliance with a  Calculating the 30- (or 90-)
 parametric operating limit. (On or       boiler operating day rolling
 after July 6, 2027 you may not use PM    arithmetic average of all of
 CPMS for compliance demonstrations,      the quality assured hourly
 unless it is for an IGCC unit.).         average PM CPMS output data
                                          (e.g., milliamps, PM
                                          concentration, raw data
                                          signal) collected for all
                                          operating hours for the
                                          previous 30- (or 90-) boiler
                                          operating days, excluding data
                                          recorded during periods of
                                          startup or shutdown.
3. Site-specific monitoring using CMS    If applicable, by conducting
 for liquid oil-fired EGUs for HCl and    the monitoring in accordance
 HF emission limit monitoring.            with an approved site-specific
                                          monitoring plan.
4. Quarterly performance testing for     Calculating the results of the
 coal-fired, solid oil derived fired,     testing in units of the
 or liquid oil-fired EGUs to measure      applicable emissions standard.
 compliance with one or more non-PM (or
 its alternative emission limits)
 applicable emissions limit in Table 1
 or 2, or PM (or its alternative
 emission limits) applicable emissions
 limit in Table 2. (On or after July 6,
 2027 you may not use quarterly
 performance testing for filterable PM
 compliance demonstrations, unless it
 is for an IGCC unit.).
5. Conducting periodic performance tune- Conducting periodic performance
 ups of your EGU(s).                      tune-ups of your EGU(s), as
                                          specified in Sec.
                                          63.10021(e).
6. Work practice standards for coal-     Operating in accordance with
 fired, liquid oil-fired, or solid oil-   Table 3.
 derived fuel-fired EGUs during startup.
7. Work practice standards for coal-     Operating in accordance with
 fired, liquid oil-fired, or solid oil-   Table 3.
 derived fuel-fired EGUs during
 shutdown.
------------------------------------------------------------------------


0
25. Revise table 8 to subpart UUUUU of part 63 to read as follows:

Table 8 to Subpart UUUUU of Part 63--Reporting Requirements

    [In accordance with 40 CFR 63.10031, you must meet the following 
reporting requirements, as they apply to your compliance strategy]

------------------------------------------------------------------------
               You must submit the following reports . . .
-------------------------------------------------------------------------
1. The electronic reports required under 40 CFR 63.10031 (a)(1), if you
 continuously monitor Hg emissions.
2. The electronic reports required under 40 CFR 63.10031 (a)(2), if you
 continuously monitor HCl and/or HF emissions.
    Where applicable, these reports are due no later than 30 days after
     the end of each calendar quarter.
3. The electronic reports required under 40 CFR 63.10031(a)(3), if you
 continuously monitor PM emissions.
    Reporting of hourly PM emissions data using ECMPS shall begin with
     the first operating hour after: January 1, 2024, or the hour of
     completion of the initial PM CEMS correlation test, whichever is
     later.
    Where applicable, these reports are due no later than 30 days after
     the end of each calendar quarter.
4. The electronic reports required under 40 CFR 63.10031(a)(4), if you
 elect to use a PM CPMS (on or after July 6, 2027 you may not use PM
 CPMS for compliance demonstrations, unless it is for an IGCC unit).
    Reporting of hourly PM CPMS response data using ECMPS shall begin
     with the first operating hour after January 1, 2024, or the first
     operating hour after completion of the initial performance stack
     test that establishes the operating limit for the PM CPMS,
     whichever is later.
    Where applicable, these reports are due no later than 30 days after
     the end of each calendar quarter.
5. The electronic reports required under 40 CFR 63.10031(a)(5), if you
 continuously monitor SO2 emissions.
    Where applicable, these reports are due no later than 30 days after
     the end of each calendar quarter.
6. PDF reports for all performance stack tests completed prior to
 January 1, 2024 (including 30- or 90-boiler operating day Hg LEE test
 reports and PM test reports to set operating limits for PM CPMS),
 according to the introductory text of 40 CFR 63.10031(f) and 40 CFR
 63.10031(f)(6).
    For each test, submit the PDF report no later than 60 days after the
     date on which testing is completed.
    For a PM test that is used to set an operating limit for a PM CPMS,
     the report must also include the information in 40 CFR
     63.10023(b)(2)(vi).
    For each performance stack test completed on or after January 1,
     2024, submit the test results in the relevant quarterly compliance
     report under 40 CFR 63.10031(g), together with the applicable
     reference method information in sections 17 through 31 of appendix
     E to this subpart.
7. PDF reports for all RATAs of Hg, HCl, HF, and/or SO2 monitoring
 systems completed prior to January 1, 2024, and for correlation tests,
 RRAs and/or RCAs of PM CEMS completed prior to January 1, 2024,
 according to 40 CFR 63.10031(f)(1) and (6).
    For each test, submit the PDF report no later than 60 days after the
     date on which testing is completed.
    For each SO2 or Hg system RATA completed on or after January 1,
     2024, submit the electronic test summary required by appendix A to
     this subpart or part 75 of this chapter (as applicable) together
     with the applicable reference method information in sections 17
     through 30 of appendix E to this subpart, either prior to or
     concurrent with the relevant quarterly emissions report.

[[Page 38592]]

 
    For each HCl or HF system RATA, and for each correlation test, RRA,
     and RCA of a PM CEMS completed on or after January 1, 2024, submit
     the electronic test summary in accordance with section 11.4 of
     appendix B to this subpart or section 7.2.4 of appendix C to this
     part, as applicable, together with the applicable reference method
     information in sections 17 through 30 of appendix E to this
     subpart.
8. Quarterly reports, in PDF files, that include all 30-boiler operating
 day rolling averages in the reporting period derived from your PM CEMS,
 approved HAP metals CMS, and/or PM CPMS (on or after July 6, 2027 you
 may not use PM CPMS, unless it is for an IGCC unit), according to 40
 CFR 63.10031(f)(2) and (6). These reports are due no later than 60 days
 after the end of each calendar quarter.
    The final quarterly rolling averages report in PDF files shall cover
     the fourth calendar quarter of 2023.
    Starting with the first quarter of 2024, you must report all 30-
     boiler operating day rolling averages for PM CEMS, approved HAP
     metals CMS, PM CPMS, Hg CEMS, Hg sorbent trap systems, HCl CEMS, HF
     CEMS, and/or SO2 CEMS (or 90-boiler operating day rolling averages
     for Hg systems), in XML format, in the quarterly compliance reports
     required under 40 CFR 63.10031(g).
    If your EGU or common stack is in an averaging plan, each quarterly
     compliance report must identify the EGUs in the plan and include
     all of the 30- or 90-group boiler operating day WAERs for the
     averaging group.
    The quarterly compliance reports must be submitted no later than 60
     days after the end of each calendar quarter.
9. The semiannual compliance reports described in 40 CFR 63.10031(c) and
 (d), in PDF files, according to 40 CFR 63.10031(f)(4) and (6). The due
 dates for these reports are specified in 40 CFR 63.10031(b).
    The final semiannual compliance report shall cover the period from
     July 1, 2023, through December 31, 2023.
10. Notifications of compliance status, in PDF files, according to 40
 CFR 63.10031(f)(4) and (6) until December 31, 2023, and according to 40
 CFR 63.10031(h) thereafter.
11. Quarterly electronic compliance reports, in accordance with 40 CFR
 63.10031(g), starting with a report for the first calendar quarter of
 2024. The reports must be in XML format and must include the applicable
 data elements in sections 2 through 13 of appendix E to this subpart.
    These reports are due no later than 60 days after the end of each
     calendar quarter.
12. Quarterly reports, in PDF files, that include the applicable
 information in 40 CFR 63.10031(c)(5)(ii) and 40 CFR 63.10020(e)
 pertaining to startup and shutdown events, starting with a report for
 the first calendar quarter of 2024, if you have elected to use
 paragraph 2 of the definition of startup in 40 CFR 63.10042 (see 40 CFR
 63.10031(i)). On or after January 2, 2025 you may not use paragraph 2
 of the definition of startup in 40 CFR 63.10042.
    These PDF reports shall be submitted no later than 60 days after the
     end of each calendar quarter, along with the quarterly compliance
     reports required under 40 CFR 63.10031(g).
13. A test report for the PS 11 correlation test of your PM CEMS, in
 accordance with 40 CFR 63.10031(j).
    If, prior to November 9, 2020, you have begun using a certified PM
     CEMS to demonstrate compliance with this subpart, use the ECMPS
     Client Tool to submit the report, in a PDF file, no later than 60
     days after that date.
    For correlation tests completed on or after November 9, 2020, but
     prior to January 1, 2024, submit the report, in a PDF file, no
     later than 60 days after the date on which the test is completed.
    For correlation tests completed on or after January 1, 2024, submit
     the test results electronically, according to section 7.2.4 of
     appendix C to this subpart, together with the applicable reference
     method data in sections 17 through 31 of appendix E to this
     subpart.
14. Quarterly reports that include the QA/QC activities for your PM CPMS
 (on or after July 6, 2027 you may not use PM CPMS, unless it is for an
 IGCC unit) or approved HAP metals CMS (as applicable), in PDF files,
 according to 40 CFR 63.10031(k).
    The first report shall cover the first calendar quarter of 2024, if
     the PM CPMS or HAP metals CMS is in use during that quarter.
     Otherwise, reporting begins with the first calendar quarter in
     which the PM CPMS or HAP metals CMS is used to demonstrate
     compliance.
    These reports are due no later than 60 days after the end of each
     calendar quarter.
------------------------------------------------------------------------


0
26. In appendix C to subpart UUUUU:
0
a. Revise sections 1.2, 1.3, 4.1, and 4.1.1.
0
b. Add sections 4.1.1.1 and 4.2.3.
0
c. Revise sections 5.1.1, 5.1.4, and the section heading for section 6.
    The revisions and additions read as follows:

Appendix C to Subpart UUUUU of Part 63--PM Monitoring Provisions

1. General Provisions

* * * * *
    1.2 Initial Certification and Recertification Procedures. You, 
as the owner or operator of an affected EGU that uses a PM CEMS to 
demonstrate compliance with a filterable PM emissions limit in Table 
1 or 2 to this subpart must certify and, if applicable, recertify 
the CEMS according to Performance Specification 11 (PS-11) in 
appendix B to part 60 of this chapter. Beginning on July 6, 2027, 
when determining if your PM CEMS meets the acceptance criteria in 
PS-11, the value of 0.015 lb/MMBtu is to be used in place of the 
applicable emission standard, or emission limit, in the 
calculations.
    1.3 Quality Assurance and Quality Control Requirements. You must 
meet the applicable quality assurance requirements of Procedure 2 in 
appendix F to part 60 of this chapter. Beginning on July 6, 2027, 
when determining if your PM CEMS meets the acceptance criteria in 
Procedure 2, the value of 0.015 lb/MMBtu is to be used in place of 
the applicable emission standard, or emission limit, in the 
calculations.
* * * * *

4. Certification and Recertification Requirements

    4.1 Certification Requirements. You must certify your PM CEMS 
and the other CMS used to determine compliance with the applicable 
emissions standard before the PM CEMS can be used to provide data 
under this subpart. However, if you have developed and are using a 
correlation curve, you may continue to use that curve, provided it 
continues to meet the acceptance criteria in PS-11 and Procedure 2 
as discussed below. Redundant backup monitoring systems (if used) 
are subject to the same certification requirements as the primary 
systems.
    4.1.1 PM CEMS. You must certify your PM CEMS according to PS-11 
in appendix B to part 60 of this chapter. A PM CEMS that has been 
installed and certified according to PS-11 as a result of another 
state or federal regulatory requirement or consent decree prior to 
the effective date of this subpart shall be considered certified for 
this subpart if you can demonstrate that your PM CEMS meets the 
acceptance criteria in PS-11 and Procedure 2 in appendix F to part 
60 of this chapter.
    4.1.1.1 Beginning on July 6, 2027, when determining if your PM 
CEMS meets the acceptance criteria in PS-11 and Procedure 2 the 
value of 0.015 lb/MMBtu is to be used in place of the applicable 
emission standard, or emission limit, in the calculations.
* * * * *
    4.2 Recertification.
* * * * *
    4.2.3 Beginning on July 6, 2027 you must use the value of 0.015 
lb/MMBtu in place of the applicable emission standard, or emission 
limit, in the calculations when determining if your PM CEMS meets 
the acceptance criteria in PS-11 and Procedure 2.
* * * * *

5. Ongoing Quality Assurance (QA) and Data Validation

* * * * *
    5.1.1 Required QA Tests. Following initial certification, you 
must conduct periodic QA testing of each primary and (if applicable) 
redundant backup PM CEMS. The required QA tests and the criteria 
that must be met are found in Procedure 2 of appendix F to part 60 
of this chapter

[[Page 38593]]

(Procedure 2). Except as otherwise provided in section 5.1.2 of this 
appendix, the QA tests shall be done at the frequency specified in 
Procedure 2.
* * * * *
    5.1.4 RCA and RRA Acceptability. The results of your RRA or RCA 
are considered acceptable provided that the criteria in section 
10.4(5) of Procedure 2 in appendix F to part 60 of this chapter are 
met for an RCA or section 10.4(6) of Procedure 2 in appendix F to 
part 60 of this chapter are met for an RRA. However, beginning on 
July 6, 2027 a value of 0.015 lb/MMBtu is to be used in place of the 
applicable emission standard, or emission limit, when determining 
whether the RCA and RRA are acceptable.
* * * * *

6. Data Reduction and Calculations

* * * * *

0
27. Appendix D to subpart UUUUU of part 63 is amended by adding 
introductory text to the appendix to read as follows:

Appendix D to Subpart UUUUU of Part 63--PM CPMS Monitoring Provisions

    On or after July 6, 2027 you may not use PM CPMS for compliance 
demonstrations with the applicable filterable PM emissions limits, 
unless it is for an IGCC unit.
* * * * *
[FR Doc. 2024-09148 Filed 5-6-24; 8:45 am]
BILLING CODE 6560-50-P