Emergency Application — Westmoreland Mining Holdings LLC, et al., Applicants v. Environmental Protection Agency, et al.

TABLE OF CONTENTS

APPENDIX A

Order Denying Stay, State of North Dakota v. EPA,

No. 24-1119 (D.C. Circuit, August 6, 2024) ………………………………… App.1

APPENDIX B

42 U.S.C. § 7412 ………………………………………………………………… App.3

APPENDIX C

National Emission Standards for Hazardous Air Pollutants:

Coal- and Oil-Fired Electric Utility Steam Generating Units

Review of the Residual Risk and Technology Review,

89 Fed. Reg. 38508 (May 7, 2024) ……………………………………….…..App.34

APPENDIX D

Comments of Westmoreland Mining Holdings LLC,

EPA-HQ-OAR-2018-0794-5935………………………………………..…… App.120

APPENDIX E

Comments of Northwestern Energy,

EPA-HQ-OAR-2018-0794-5980……………………………………………...App.226

APPENDIX F

Comments of National Mining Association,

EPA-HQ-OAR-2009-0234-20531…………………………………………….App.251

APPENDIX G

Comments of Talen Montana,

EPA-HQ-OAR-2018-0794-5987……………………………………………...App.443

APPENDIX H

Declarations:

Exhibit 1 – Declaration of Patrick Barkey ………………………. App.484

Exhibit 2 – Declaration of Jeremy Cottrell …………………...…. App.518

APPENDIX C

APPENDIX

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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

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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: benish.sarah@epa.gov.

SUPPLEMENTARY INFORMATION:

Preamble acronyms and

abbreviations. We use multiple

acronyms and terms in this preamble.

While this list may not be exhaustive, to

ease the reading of this preamble and for

reference purposes, the EPA defines the

following terms and acronyms here:

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

Hg0 elemental Hg vapor

Hg2+ 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

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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?

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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 OilFired 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 lignitefired 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 OilFired 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

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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

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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revise’’ those standards every 8 years

‘‘as necessary (taking into account

developments in practices, processes,

and control technologies).’’ Id.

7412(d)(6).

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

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metals, the EPA established individual

emission limits for each of the 10 nonHg 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 coalfired 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).

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

2 The ten non-Hg HAP metals are antimony,

arsenic, beryllium, cadmium, chromium, cobalt,

lead, manganese, nickel, and selenium.

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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the surrounding communities; and realtime 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.

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).

The EPA is also finalizing, as

proposed, a more protective Hg

emission standard for existing lignitefired EGUs, requiring that such lignitefired 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 outputbased standard of 0.013 lb per gigawatthour (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

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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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.

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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

5 See section II.B.2. for discussion of the public

health and environmental hazards associated with

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limitations, the EPA is also unable to

quantify potential emissions impacts or

monetize potential benefits from

continuous monitoring requirements.

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.

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 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

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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.

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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.

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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-airpollution/mercury-and-air-toxicsstandards. 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-airpollution/risk-and-technology-reviewnational-emissions-standardshazardous. 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

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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

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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

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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

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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

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,

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.

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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

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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 onetime 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

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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

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 onetime review of risks that remain after

imposition of MACT standards. CAA

section 112(d)(6) requires the EPA to

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).

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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 coaland 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 oilfired 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

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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 onethird 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 fuelfired 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

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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.

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

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).

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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.

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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

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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 HAPattributable 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

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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 NationalScale 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

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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

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that the existing air pollution control

technologies that were in use were wellestablished 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

PO 00000

Frm 00011

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

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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 coalfired, 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

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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 lignitefired 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 MATSaffected 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 OilFired 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

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

10 See Document ID No. EPA–HQ–OAR–2018–

0794–4565 at https://www.regulations.gov.

PO 00000

Frm 00012

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 coalfired 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 limiteduse 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.

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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

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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 lignitefired 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

PO 00000

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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-airtoxics-standard-mats.

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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 coaland 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

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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

PO 00000

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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 recorrelation 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

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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

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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

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.

PO 00000

Frm 00015

substantial action to comply with the

proposed limit.

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 30boiler operating day averaging period

using PM CEMS for compliance

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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 coalfired 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.

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

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.

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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 costeffectiveness 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 costeffectiveness 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 costeffectiveness 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

PO 00000

Frm 00016

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.

• 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.

• 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.

• 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 costeffectiveness estimate than the EPA had

accepted in other NESHAP rulemakings.

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

15 Petroleum Refinery Sector Risk and Technology

Review and New Source Performance Standards, 80

FR 75178, 75201 (December 1, 2015).

16 National Emission Standards for Hazardous

Air Pollutants: Taconite Iron Ore Processing

Residual Risk and Technology Review, 85 FR

45476, 45483 (July 28, 2020).

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).

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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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 inflationadjusted $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

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).

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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.

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 costeffectiveness 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 beyondthe-floor analysis, and reviewing

residual risk.

Regarding the comments that the EPA

underestimated costs to an extent that

undermines the EPA’s overall costeffectiveness 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,

PO 00000

Frm 00017

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 costeffectiveness 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

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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 industryspecific 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.

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

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).

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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 coalfired 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 nonHg 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

PO 00000

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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 wellperforming 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 coalfired EGUs (11 percent for the 0.010 lb/

MMBtu fPM limit). In addition, many

regulated facilities are electing to retire

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).

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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 coaland 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

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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

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).

PO 00000

Frm 00019

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

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

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).

33 See section II.A.2. above for further discussion

of the statutory structure and legislative history of

CAA section 112.

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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.

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

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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

PO 00000

Frm 00020

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

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).

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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.

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

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

35 88 FR 33245 (May 23, 2023).

36 88 FR 18824, 18837 (March 29, 2023).

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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 coalfired 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

PO 00000

Frm 00021

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.

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

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.

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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.

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

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.

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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 recorrelation 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 highlevel 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

PO 00000

Frm 00022

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

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.

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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.

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

41 See 88 FR 24872.

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is required to select the most costeffective 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 coalfired 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.

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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

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.

App.55

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

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.

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

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.

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.

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1. Rationale for the Final Filterable PM

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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 t

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