[Federal Register Volume 88, Number 86 (Thursday, May 4, 2023)]
[Proposed Rules]
[Pages 28918-28984]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-08732]



[[Page 28917]]

Vol. 88

Thursday,

No. 86

May 4, 2023

Part V





Environmental Protection Agency





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40 CFR Parts 52, 78, and 97





Revision and Promulgation of Air Quality Implementation Plans; Texas; 
Regional Haze Federal Implementation Plan; Disapproval and Need for 
Error Correction; Denial of Reconsideration of Provisions Governing 
Alternative to Source-Specific Best Available Retrofit Technology 
(BART) Determinations; Proposed Rule

  Federal Register / Vol. 88, No. 86 / Thursday, May 4, 2023 / Proposed 
Rules  

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 ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52, 78, and 97

[EPA-R06-OAR-2016-0611; EPA-HQ-OAR-2016-0598; FRL-9771-01-R6]


Revision and Promulgation of Air Quality Implementation Plans; 
Texas; Regional Haze Federal Implementation Plan; Disapproval and Need 
for Error Correction; Denial of Reconsideration of Provisions Governing 
Alternative to Source-Specific Best Available Retrofit Technology 
(BART) Determinations

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or Act), the 
Environmental Protection Agency (EPA) is proposing to withdraw the 
existing Texas Sulfur Dioxide (SO2) Trading Program 
provisions, which constitute the Federal implementation plan (FIP) the 
EPA previously promulgated to address SO2 Best Available 
Retrofit Technology (BART) requirements for EGUs in Texas that are not 
adequately satisfied by the Texas Regional Haze State implementation 
plan (SIP). In its place, the EPA proposes a FIP that establishes 
SO2 limits on 12 Electric Generating Units (EGUs) located at 
six Texas facilities to fulfill requirements of the Regional Haze Rule 
for the installation and operation of BART for SO2. Based on 
these proposed changes, we also propose to affirm the continued 
validity of participation in the Cross-State Air Pollution Rule (CSAPR) 
trading programs as a BART alternative. Therefore, the EPA is proposing 
to deny a petition for reconsideration of our 2017 determination that 
States that are participating in CSAPR can continue to rely on CSAPR 
participation as a BART alternative. Finally, we are proposing to find 
that our prior approval of the portion of the Texas Regional Haze SIP 
that addresses the BART requirement for EGUs for Particulate Matter 
(PM) was made in error and are proposing to correct that error by 
proposing to disapprove that portion of the Texas Regional Haze SIP 
through our authority under the CAA section 110(k)(6), and, as part of 
a FIP, we are proposing PM BART limits for 12 EGUs located at six Texas 
facilities.

DATES: 
    Comments: Comments must be received on or before July 3, 2023.
    Virtual Public Hearing: The EPA will hold a virtual public hearing 
to solicit comments on May 19, 2023. The last day to pre-register to 
speak at the hearing will be on May 17, 2023. On May 18, 2023, the EPA 
will post a general agenda for the hearing that will list pre-
registered speakers in approximate order at https://www.epa.gov/tx/texas-regional-haze-best-available-retrofit-technology-federal-implementation-plan-and-cross. If you require the services of a 
translator or a special accommodation such as audio description/closed 
captioning, please pre-register for the hearing and describe your needs 
by May 11, 2023.
    For more information on the virtual public hearing, see 
SUPPLEMENTARY INFORMATION.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R06-
OAR-2016-0611 to the Federal eRulemaking Portal: https://www.regulations.gov/ (our preferred method). For additional submission 
methods, please contact the person identified in the FOR FURTHER 
INFORMATION CONTACT section.
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided.
    Docket: The docket for this action is available electronically at 
https://www.regulations.gov. Some information in the docket may not be 
publicly available via the online docket due to docket file size 
restrictions, such as certain modeling files, or content (e.g., CBI). 
To request a copy of the modeling files, please send a request via 
email to [email protected]">R6[email protected]. For questions about a 
document in the docket please contact individual listed in the FOR 
FURTHER INFORMATION CONTACT section.
    CBI: Do not submit information containing CBI to the EPA through 
https://www.regulations.gov. To submit information claimed as CBI, 
please contact the individual listed in the FOR FURTHER INFORMATION 
CONTACT section. Clearly mark the part or all of the information that 
you claim to be CBI. In addition to one complete version of the 
comments that includes information claimed as CBI, you must submit a 
copy of the comments that does not contain the information claimed as 
CBI directly to the public docket through the procedures outlined in 
Instructions earlier. Information not marked as CBI will be included in 
the public docket and the EPA's electronic public docket without prior 
notice. Information marked as CBI will not be disclosed except in 
accordance with procedures set forth in 40 Code of Federal Regulations 
(CFR) part 2. For the full EPA public comment policy, information about 
CBI or multimedia submissions, and general guidance on making effective 
comments, please visit https://www2.epa.gov/dockets/commenting-epa-dockets.
    To pre-register to attend or speak at the virtual public hearing, 
please use the online registration form available at https://www.epa.gov/tx/texas-regional-haze-best-available-retrofit-technology-federal-implementation-plan-and-cross or contact us via email at 
[email protected]. For more information on the virtual 
public hearing, see SUPPLEMENTARY INFORMATION.

FOR FURTHER INFORMATION CONTACT: Michael Feldman, Air and Radiation 
Division, SO2 and Regional Haze Section (ARSH), 
Environmental Protection Agency, 1201 Elm St., Suite 500 Dallas, TX 
75270; telephone number: 214-665-9793; or via email: 
[email protected].

SUPPLEMENTARY INFORMATION: Throughout this document wherever ``we,'' 
``us,'' or ``our'' is used, we mean the EPA.
    There are two dockets supporting this action, EPA-R06-OAR-2016-0611 
and EPA-HQ-OAR- EPA-HQ-OAR-2016-0598. Docket No. EPA-R06-OAR-2016-0611 
contains information specific to BART requirements for Texas, including 
this notice of proposed rulemaking and prior rulemakings related to 
Texas BART, previous submittals from the State, and the Technical 
Support Documents for this action. Docket No. EPA-HQ-OAR-2016-0598 
contains previous actions and information related to CSAPR as a BART 
alternative. All comments regarding this proposed action should be made 
in Docket No. EPA-R06-OAR-2016-0611. For additional submission methods, 
please email [email protected].

Virtual Public Hearing

    The EPA is holding a virtual public hearing to provide interested 
parties the opportunity to present data, views, or arguments concerning 
the proposal. The EPA will hold a virtual public hearing to solicit 
comments on May 19, 2023. The hearing will convene in two sessions. 
Session 1 will convene at 1 p.m. Central Time (CT) and will conclude at 
3 p.m. CT, or 15 minutes after the last pre-registered presenter in 
attendance has presented if there are no additional presenters. Session 
2 will convene at 4 p.m. Central Time (CT) and will conclude at 7 p.m. 
CT, or 15 minutes after the last pre-registered presenter in attendance 
has presented if

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there are no additional presenters. The EPA will announce further 
details, including information on how to register for the virtual 
public hearing, on the virtual public hearing website at https://www.epa.gov/tx/texas-regional-haze-best-available-retrofit-technology-federal-implementation-plan-and-cross. The EPA will begin pre-
registering speakers and attendees for the hearing upon publication of 
this document in the Federal Register. To pre-register to attend or 
speak at the virtual public hearing, please use the online registration 
form available at https://www.epa.gov/tx/texas-regional-haze-best-available-retrofit-technology-federal-implementation-plan-and-cross or 
contact us via email at [email protected]. The last day to 
pre-register to speak at the hearing will be on May 17, 2023. On May 
18, 2023, the EPA will post a general agenda for the hearing that will 
list pre-registered speakers in approximate order at https://www.epa.gov/tx/texas-regional-haze-best-available-retrofit-technology-federal-implementation-plan-and-cross. Additionally, requests to speak 
will be taken on the day of the hearing as time allows.
    The EPA will make every effort to follow the schedule as closely as 
possible on the day of the hearing; however, please plan for the 
hearing to run either ahead of schedule or behind schedule. Each 
commenter will have approximately 3 to 5 minutes to provide oral 
testimony. The EPA encourages commenters to provide the EPA with a copy 
of their oral testimony electronically by including it in the 
registration form or emailing it to [email protected]. The 
EPA may ask clarifying questions during the oral presentations but will 
not respond to the presentations at that time. Written statements and 
supporting information submitted during the comment period will be 
considered with the same weight as oral comments and supporting 
information presented at the virtual public hearing. A transcript of 
the virtual public hearing, as well as copies of oral presentations 
submitted to the EPA, will be included in the docket for this action.
    The EPA is asking all hearing attendees to pre-register, even those 
who do not intend to speak. The EPA will send information on how to 
join the public hearing to pre-registered attendees and speakers.
    Please note that any updates made to any aspect of the hearing will 
be posted online at https://www.epa.gov/tx/texas-regional-haze-best-available-retrofit-technology-federal-implementation-plan-and-cross. 
While the EPA expects the hearing to go forward as set forth above, 
please monitor our website or contact us via email at 
[email protected] to determine if there are any updates. 
The EPA does not intend to publish a document in the Federal Register 
announcing updates.
    If you require the services of a translator or a special 
accommodation such as audio description/closed captioning, please pre-
register for the hearing and describe your needs by May 11, 2023. The 
EPA may not be able to arrange accommodations without advance notice.

Table of Contents

I. Executive Summary
II. Background
    A. Regional Haze
    B. BART
    C. Previous Actions Related to Texas BART and ``CSAPR Better-
Than-BART''
    D. Consultation With Federal Land Managers (FLMs)
III. Overview of Proposed Action
IV. Withdrawal of the Texas SO2 Trading Program as a BART 
Alternative for SO2
    A. Legal Authority To Withdraw the Texas SO2 Trading 
Program
    B. Basis for Withdrawing the Texas SO2 Trading 
Program
V. CSAPR Participation as a BART Alternative
    A. Introduction
    B. Background
    C. Summary of the 2020 Petition for Reconsideration and 
Associated Litigation
    D. Criteria for Granting a Mandatory Petition for 
Reconsideration
    E. The EPA's Evaluation of the Petition for Reconsideration
VI. The EPA's Authority To Promulgate a FIP Addressing 
SO2 and PM BART
    A. CAA Authority To Promulgate a FIP for SO2 BART
    B. Error Correction and CAA Authority To Promulgate a FIP--PM 
BART
VII. BART Analysis for SO2 and PM
    A. Identification of Sources Subject to BART
    B. BART Five Factor Analysis
VIII. Weighing of the Five BART Factors and Proposed BART 
Determinations
    A. SO2 BART for Coal-Fired Units With no 
SO2 Controls
    B. SO2 BART for Coal-Fired Units With Existing 
Scrubbers
    C. PM BART
IX. Proposed Action
    A. Regional Haze
    B. CSAPR Better-Than-BART
X. Environmental Justice Considerations
XI. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Overview
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    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 That Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Determinations Under CAA Section 307(b)(1) and (d)

I. Executive Summary

    The CAA's visibility protection program was created in response to 
a national goal set by Congress in 1977 to remedy and prevent 
visibility impairment in certain national parks, such as Grand Canyon 
National Park, and national wilderness areas, such as the Okefenokee 
National Wildlife Refuge. Vistas in these areas are often obscured by 
visibility impairment such as regional haze, which is caused by 
emissions from numerous sources located over a wide geographic area.
    In response to this Congressional directive, the EPA promulgated 
regulations to address visibility impairment in 1999. These 
regulations, which are commonly referred to as the Regional Haze Rule, 
established an iterative process for achieving Congress's national goal 
by providing for multiple, approximately 10-year ``planning periods'' 
in which State air agencies must submit to EPA plans that address 
sources of visibility-impairing pollution in their States. The first 
State plans were due in 2007 for the planning period that ended in 
2018. The second State plans were due in 2021 for the period that ends 
in 2028. This proposal focuses on obligations from the first planning 
period of the regional haze program.
    A central element of these first planning period State plans was 
the requirement for certain older stationary sources to install the 
Best Available Retrofit Technology (BART) for the purpose of making 
reasonable progress towards Congress's national goal of eliminating 
visibility impairment within our nation's most treasured lands. The 
Regional Haze Rule provided two approaches a State could take to 
fulfill its BART obligations: (1) conduct source-by-source evaluations 
for covered sources, or (2) implement an alternative program, such as 
an emissions trading program, that achieves greater reasonable progress 
than source-by-source BART.

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    One such BART alternative that 19 States have relied on for over a 
decade to fulfill some or all of their BART obligations with respect to 
visibility-impairing pollution from power plants is participation in 
the EPA's Cross-State Air Pollution Rule (CSAPR), an emissions trading 
program that was promulgated in 2011. Changes to the CSAPR program over 
the years, particularly with respect to the status of the State of 
Texas, have required the EPA to reexamine on several occasions whether 
the program continues to achieve greater reasonable progress than 
source-by-source BART for participating States. Most recently, after 
removing Texas from certain aspects of the CSAPR program, the EPA 
reaffirmed the viability of the CSAPR program as a BART alternative in 
2017 and then again in 2020 when the EPA denied a petition for 
reconsideration of the 2017 reaffirmation.
    Texas submitted its first State plan to address regional haze in 
2009, relying at that time on the now-defunct predecessor program to 
CSAPR to satisfy the BART requirement for its power plants.\1\ The EPA 
disapproved this portion of Texas's plan in 2012. Texas is home to 
numerous power plants, many of which operate without modern pollution 
controls. As a result, several of these plants are among the highest 
emitters of visibility-impairing pollutants, such as sulfur dioxide 
(SO2), in the nation. These emissions cause or contribute to 
visibility impairment in such iconic places as Big Bend National Park 
and Guadalupe Mountains National Park in Texas, Salt Creek Wilderness 
Area in New Mexico, Caney Creek Wilderness Area in Arkansas, and 
Wichita Mountains Wilderness Area in Oklahoma. In 2017, the EPA 
proposed to address the gap in Texas's plan by, among other things, 
requiring source-by-source BART controls for SO2 emissions 
from covered sources that would have significantly reduced these 
emissions. The EPA never finalized this proposal, however. Instead, in 
2017 (and again in 2020), the EPA promulgated an intrastate trading 
program to govern SO2 emissions from Texas power plants, 
based on a finding that the program would achieve greater reasonable 
progress than source-by-source BART even though the program would allow 
for increases in SO2 emissions (and thus increased 
visibility impairment) instead of emission reductions.
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    \1\ https://www.tceq.texas.gov/airquality/sip/bart/haze_sip.html.
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    This proposal seeks to address both the BART requirements for 
Texas's power plants and an outstanding petition that once again calls 
into question the continued viability of the CSAPAR program as a BART 
alternative for participating States due to the status of Texas, and 
the complicated interactions between these two regulatory regimes. 
Specifically, the EPA is proposing to withdraw the intrastate trading 
program on the basis that it does not achieve greater reasonable 
progress than source-by-source BART. In its place, the EPA is proposing 
to promulgate source-by-source BART emission limits for covered sources 
in Texas. If finalized, these emission limits would reduce emissions 
from these sources by more than 80,000 tons of SO2 
emissions, improving visibility across a wide range of the nation's 
most scenic vistas. In addition, the EPA is proposing that these 
changes to the Texas plan, if finalized, would allow the EPA to once 
again reaffirm that the CSAPR program remains a viable BART alternative 
for the 19 participating States. On that basis, the EPA is proposing to 
deny the outstanding petition seeking to end these States' longstanding 
reliance on the CSAPR program to satisfy their BART obligations for 
power plants.

II. Background

A. Regional Haze

    Regional haze is visibility impairment that is produced by a 
multitude of sources and activities which are located across a broad 
geographic area. These sources and activities emit fine particulate 
matter (PM2.5) (e.g., sulfates, nitrates, organic carbon, 
elemental carbon, and soil dust) and its precursors (e.g., sulfur 
dioxide (SO2), nitrogen oxides (NOX), and, in 
some cases, ammonia (NH3) and volatile organic compounds 
(VOCs)). Fine particle precursors react in the atmosphere to form 
PM2.5, which, in addition to direct sources of PM 
2.5, impairs visibility by scattering and absorbing light. 
Visibility impairment (i.e., light scattering) reduces the clarity, 
color, and visible distance that one can see. PM2.5 can also 
cause serious health effects (including premature death, heart attacks, 
irregular heartbeat, aggravated asthma, decreased lung function, and 
increased respiratory symptoms) and mortality in humans, and 
contributes to environmental effects such as acid deposition and 
eutrophication.
    In section 169A of the 1977 Amendments to the Clean Air Act (CAA), 
Congress created a program for protecting visibility in the nation's 
national parks and wilderness areas. This section of the CAA 
establishes as a national goal the prevention of any future, and the 
remedying of any existing, anthropogenic impairment of visibility in 
156 national parks and wilderness areas designated as mandatory Class I 
areas.\2\ Congress added section 169B to the CAA in 1990 to address 
regional haze issues, and the EPA promulgated the Regional Haze Rule 
(RHR), codified at 40 CFR 51.308,\3\ on July 1, 1999.\4\ The RHR 
established a requirement to submit a regional haze SIP, which applies 
to all 50 States, the District of Columbia, and the Virgin Islands.\5\
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    \2\ Areas designated as mandatory Class I areas consist of 
National Parks exceeding 6,000 acres, wilderness areas and national 
memorial parks exceeding 5,000 acres, and all international parks 
that were in existence on August 7, 1977. 42 U.S.C. 7472(a). In 
accordance with section 169A of the CAA, the EPA, in consultation 
with the Department of Interior, promulgated a list of 156 areas 
where visibility is identified as an important value. 44 FR 69122 
(November 30, 1979). The extent of a mandatory Class I area includes 
subsequent changes in boundaries, such as park expansions. 42 U.S.C. 
7472(a). Although States and Tribes may designate as Class I 
additional areas which they consider to have visibility as an 
important value, the requirements of the visibility program set 
forth in section 169A of the CAA apply only to ``mandatory Class I 
Federal areas.'' Each mandatory Class I Federal area is the 
responsibility of a ``Federal Land Manager.'' 42 U.S.C. 7602(i). 
When we use the term ``Class I area'' in this action, we mean a 
``mandatory Class I Federal area.''
    \3\ In addition to the generally applicable regional haze 
provisions at 40 CFR 51.308, the EPA also promulgated regulations 
specific to addressing regional haze visibility impairment in Class 
I areas on the Colorado Plateau at 40 CFR 51.309. The latter 
regulations are not relevant here.
    \4\ See 64 FR 35714 (July 1, 1999). On January 10, 2017, the EPA 
promulgated revisions to the RHR that apply for the second and 
subsequent implementation periods. See 82 FR 3078 (Jan. 10, 2017).
    \5\ 40 CFR 51.300(b).
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    To address regional haze visibility impairment, the RHR established 
an iterative planning process that requires States in which Class I 
areas are located and States from which emissions may reasonably be 
anticipated to cause or contribute to any impairment of visibility in a 
Class I area to periodically submit SIP revisions to address regional 
haze visibility impairment.\6\ Under the CAA, each SIP submission must 
contain ``a long-term (ten to fifteen years) strategy for making 
reasonable progress toward meeting the national goal,'' and the initial 
round of SIP submissions also had to address the statutory requirement

[[Page 28921]]

that certain older, larger sources of visibility-impairing pollutants 
install and operate the Best Available Retrofit Technology (BART), as 
discussed further in Section II.B.\7\ States' first regional haze SIPs 
were due by December 17, 2007, with subsequent SIP submissions 
containing revised long-term strategies originally due July 31, 2018, 
and every ten years thereafter.\8\
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    \6\ See 42 U.S.C. 7491(b)(2); 40 CFR 51.308(b) and (f); see also 
64 FR 35768 (July 1, 1999). The EPA established in the RHR that all 
States either have Class I areas within their borders or ``contain 
sources whose emissions are reasonably anticipated to contribute to 
regional haze in a Class I area;'' therefore, all States must submit 
regional haze SIPs. See 64 FR 35721. In addition to each of the 50 
States, the EPA also concluded that the Virgin Islands and District 
of Columbia contain a Class I area and/or contain sources whose 
emissions are reasonably anticipated to contribute regional haze in 
a Class I area. See 40 CFR 51.300(b) and (d)(3).
    \7\ See 42 U.S.C. 7491(b)(2)(A); 40 CFR 51.308(d) and (e).
    \8\ See 40 CFR 51.308(b). The 2017 RHR revisions changed the 
second period SIP due date from July 31, 2018, to July 31, 2021, and 
maintained the existing schedules for the subsequent implementation 
periods. See 40 CFR 51.308(f).
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B. BART

    Section 169A of the CAA directs States to evaluate the use of 
retrofit controls at certain larger, older stationary sources to 
address visibility impacts from these sources, whose emissions are 
often uncontrolled or poorly controlled. Specifically, section 
169A(b)(2) of the CAA requires States to revise their SIPs to contain 
such measures as may be necessary to make reasonable progress towards 
the national visibility goal, including a requirement that certain 
categories of existing major stationary sources built between 1962 and 
1977 procure, install, and operate BART as determined by the State 
applying five statutory factors. On July 6, 2005, the EPA published the 
Guidelines for BART Determinations Under the Regional Haze Rule at 
Appendix Y to 40 CFR part 51 (BART Guidelines) to assist States in the 
BART evaluation process. Under the RHR and the BART Guidelines, the 
BART evaluation process consists of three steps: (1) An identification 
of all BART-eligible sources in the State, (2) an assessment of whether 
the BART-eligible sources are subject to BART (based on a determination 
that each source or sources may reasonably be anticipated to cause or 
contribute to any visibility impairment in a Class I area), and (3) a 
determination of an emission limit reflecting BART after applying the 
five statutory BART factors.\9\ In applying the BART factors for a 
fossil fuel-fired electric generating plant with a total generating 
capacity in excess of 750 megawatts, a State must use the approach set 
forth in the BART Guidelines.\10\ A State is generally encouraged, but 
not required, to follow the BART Guidelines for other types of 
sources.\11\
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    \9\ See generally 40 CFR 51.308(e)(1); 40 CFR part 51, Appendix 
Y.
    \10\ 42 U.S.C. 7491(b); 40 CFR 51.308(e)(1)(ii)(B).
    \11\ See 40 CFR part 51, Appendix Y. For additional details 
regarding the three steps of the BART evaluation process, see, e.g., 
85 FR 47134, 47136-37 (August 4, 2020).
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    States must make source-specific BART determinations for all 
``BART-eligible'' sources determined to be subject to BART. However, as 
an alternative to making these ``source-specific'' BART determinations, 
States may adopt an emissions trading program or other alternative 
program for all or a portion of their BART-eligible sources, so long as 
the alternative achieves greater reasonable progress towards improving 
visibility than BART would for those sources, and the alternative meets 
certain other requirements. Several options are available for making 
BART-alternative demonstrations, and these are discussed in greater 
detail in Section IV.B and Section V.\12\
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    \12\ See generally 40 CFR 51.308(e)(2)-(4).
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    States generally undertook the BART determination process during 
the regional haze program's first implementation period. While the BART 
requirement is considered a one-time requirement, BART-eligible 
sources, including sources found subject to BART and for which a BART 
emission limit was established, may need to be re-assessed for 
additional controls in future implementation periods under the CAA's 
reasonable progress provisions. Thus, the EPA has stated that States 
should treat BART-eligible sources the same as other reasonable 
progress sources going forward.\13\
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    \13\ See 81 FR 26942, 26947 (May 4, 2016).
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C. Previous Actions Related to Texas BART and ``CSAPR Better-Than-
BART''

    The procedural history leading up to this proposed action is set 
forth in detail in this section. On March 31, 2009, Texas submitted a 
regional haze SIP (the 2009 Regional Haze SIP) to the EPA that included 
reliance on Texas's participation in trading programs under the Clean 
Air Interstate Rule (CAIR) as an alternative to BART for SO2 
and NOX emissions from Electric Generating Units (EGUs).\14\ 
This reliance was consistent with the EPA's regulations at the time 
that Texas developed its 2009 Regional Haze SIP.\15\ However, at the 
time Texas submitted its SIP to the EPA, the D.C. Circuit had remanded 
CAIR (without vacatur).\16\ The court left CAIR and our CAIR FIPs in 
place in order to ``temporarily preserve the environmental values 
covered by CAIR'' until we could, by rulemaking, replace CAIR 
consistent with the court's opinion. The EPA promulgated the Cross-
State Air Pollution Rule (CSAPR) to replace CAIR in 2011 \17\ (and 
revised it in 2012).\18\ CSAPR established FIP requirements for sources 
in a number of States, including Texas, to address the States' 
interstate transport obligation under CAA section 110(a)(2)(D)(i)(I). 
CSAPR addresses interstate transport of PM2.5 and ozone by 
requiring affected EGUs in these States to participate in one or more 
of the CSAPR trading programs, which establish emissions budgets that 
apply to the EGUs' collective annual emissions of SO2 and 
NOX, as well as emissions of NOX during ozone 
season.\19\
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    \14\ CAIR required certain States, including Texas, to reduce 
emissions of SO2 and NOX that contribute 
significantly to downwind nonattainment of the 1997 NAAQS for fine 
particulate matter and ozone. See 70 FR 25152 (May 12, 2005).
    \15\ See 70 FR 39104 (July 6, 2005).
    \16\ See North Carolina v. EPA, 531 F.3d 896 (D.C. Cir. 2008), 
as modified, 550 F.3d 1176 (D.C. Cir. 2008).
    \17\ Federal Implementation Plans; Interstate Transport of Fine 
Particulate Matter and Ozone and Correction of SIP Approvals, 76 FR 
48208 (Aug. 8, 2011).
    \18\ CSAPR was amended three times in 2011 and 2012 to add five 
States to the seasonal NOX program and to increase 
certain State budgets. 76 FR 80760 (December 27, 2011); 77 FR 10324 
(February 21, 2012); 77 FR 34830 (June 12, 2012).
    \19\ Ozone season for CSAPR purposes is May 1 through September 
30.
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    Following the issuance of CSAPR, the EPA determined that CSAPR 
would achieve greater reasonable progress towards improving visibility 
than would source-specific BART in CSAPR States (a determination often 
referred to as ``CSAPR Better-than-BART'').\20\ In the EPA's 2012 
action promulgating CSAPR-Better-than-BART, the EPA used air quality 
modeling to show that CSAPR met the two-pronged numerical test for a 
BART alternative under 40 CFR 51.308(e)(3).\21\ In the same action, we 
revised the Regional Haze Rule to allow States whose sources 
participate in the CSAPR trading programs to rely on such participation 
in lieu of requiring BART-eligible EGUs in the State to meet source-
specific emission limits reflective of BART controls as to the relevant 
pollutant. In addition to allowing States to rely on CSAPR to address 
BART requirements, the EPA issued limited disapprovals of a number of 
States' regional haze SIPs, including the 2009 Regional Haze SIP 
submittal from Texas, due to the States' reliance on CAIR, which had 
been replaced by CSAPR.\22\ The EPA did not immediately promulgate a 
FIP to address those aspects of the 2009 Regional Haze SIP submittal 
from Texas subject to the

[[Page 28922]]

limited disapproval in order to allow more time for the EPA to assess 
the remaining elements of the SIP.
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    \20\ 77 FR 33642 (June 7, 2012). This determination was upheld 
by the D.C. Circuit. See Util. Air Regulatory Grp. v. EPA, 885 F.3d 
714 (D.C. Cir. 2018).
    \21\ See generally 77 FR 33642 (June 7, 2012).
    \22\ Id.
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    In December 2014, we proposed an action to address the remaining 
regional haze obligations for Texas.\23\ In that action, we proposed, 
among other things, to rely on our CSAPR FIP requiring Texas sources' 
participation in the CSAPR trading programs to satisfy the 
NOX and SO2 BART requirements for Texas's BART-
eligible EGUs consistent with the 2012 revisions to the Regional Haze 
Rule. We also proposed to approve the portions of the 2009 Texas 
Regional Haze SIP addressing PM BART requirements for the State's BART-
eligible EGUs. Before that proposed rule was finalized, however, the 
D.C. Circuit issued a decision on a number of challenges to CSAPR, 
denying most claims, but remanding the CSAPR SO2 and/or 
seasonal NOX emissions budgets of several States to the EPA 
for reconsideration, including the Phase 2 SO2 and seasonal 
NOX budgets for Texas.\24\ Due to the uncertainty arising 
from the remand of Texas's CSAPR budgets, we did not finalize our 
December 2014 proposal to rely on CSAPR to satisfy the SO2 
and NOX BART requirements for Texas EGUs.\25\ Additionally, 
because our proposed action on the PM BART provisions for EGUs was 
dependent on how SO2 and NOX BART were satisfied, 
we did not take final action on the PM BART elements of the 2009 Texas 
Regional Haze SIP.\26\
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    \23\ 79 FR 74818 (Dec. 16, 2014).
    \24\ EME Homer City Generation, L.P. v. EPA (EME Homer City II), 
795 F.3d 118, 132 (D.C. Cir. 2015). In 2012, several State, 
industry, and other petitioners challenged CSAPR in the D.C. 
Circuit, which stayed and then vacated the rule, ruling on only a 
subset of petitioners' claims. See EME Homer City Generation, L.P. 
v. EPA, 696 F.3d 7 (D.C. Cir. 2012). However, in April 2014 the 
Supreme Court reversed the vacatur and remanded to the D.C. Circuit 
for resolution of petitioners' remaining claims. See EPA v. EME 
Homer City Generation, L.P., 572 U.S. 489 (2014). Following the 
Supreme Court remand, the D.C. Circuit conducted further proceedings 
to address petitioners' remaining claims. In July 2015, the court 
issued a decision denying most of the claims but remanding the Phase 
2 SO2 emissions budgets for Alabama, Georgia, South 
Carolina, and Texas and the Phase 2 ozone-season NOX 
budgets for eleven States to the EPA for reconsideration.
    \25\ 81 FR 296 (Jan. 5, 2016).
    \26\ In January 2016, we finalized action on the remaining 
aspects of the December 2014 proposal. This final action 
disapproved, among other things Texas's reasonable progress analysis 
and Texas's long-term strategy. The EPA promulgated a FIP 
establishing a new long-term strategy that consisted of 
SO2 emission limits for 15 coal-fired EGUs at eight power 
plants. 81 FR 296, 302 (Jan. 5, 2016). That rulemaking was 
judicially challenged, however, and in July 2016, the Fifth Circuit 
granted the petitioners' motion to stay the rule pending review. 
Texas v. EPA, 829 F.3d 405 (5th Cir. 2016). On March 22, 2017, 
following the submittal of a request by the EPA for a voluntary 
remand of the parts of the rule under challenge, the Fifth Circuit 
Court of Appeals remanded the rule in its entirety. (In this 
rulemaking, we are not addressing those remanded requirements.) 
March 22, 2017, Order, Texas v. EPA, 829 F.3d 405 (5th Cir. 2016) 
(No. 16-60118).
---------------------------------------------------------------------------

    On October 26, 2016, the EPA finalized an update to CSAPR to 
address the interstate transport requirements of CAA section 
110(a)(2)(D)(i)(I) with respect to the 2008 ozone NAAQS (CSAPR 
Update).\27\ The EPA also responded to the D.C. Circuit's remand in EME 
Homer City II of certain CSAPR seasonal NOX budgets in that 
action.\28\ As to Texas, the EPA withdrew Texas's seasonal 
NOX budget finalized in CSAPR to address the 1997 ozone 
NAAQS. However, in that same action, the EPA promulgated a FIP with a 
revised seasonal NOX budget for Texas to address the 2008 
ozone NAAQS.\29\ Accordingly, Texas sources remain subject to CSAPR 
seasonal NOX requirements.
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    \27\ 81 FR 74504 (Oct. 26, 2016).
    \28\ See generally EME Homer City II, 795 F.3d 118, (D.C. Cir. 
2015).
    \29\ 81 FR 74504, 74524-25.
---------------------------------------------------------------------------

    On November 10, 2016, in response to the D.C. Circuit's remand in 
EME Homer II of Texas's CSAPR SO2 budget, we proposed to 
withdraw the FIP provisions that required EGUs in Texas to participate 
in the CSAPR trading programs for annual emissions of SO2 
and NOX.\30\ The EPA indicated that if the withdrawal was 
finalized, Texas would no longer be eligible under 40 CFR 51.308(e)(4) 
to rely on participation of its EGUs in a CSAPR trading program as an 
alternative to source-specific SO2 BART determinations.\31\ 
We also proposed to reaffirm the EPA's 2012 analytical demonstration 
that CSAPR provides greater reasonable progress than BART despite the 
changes in CSAPR's geographic scope to address the EME Homer City II 
remand, including removal of Texas's EGUs from the CSAPR trading 
program for SO2 emissions.\32\ On September 29, 2017, we 
finalized the withdrawal of the FIP provisions for annual emissions of 
SO2 and NOX for EGUs in Texas \33\ and affirmed 
our proposed finding that the EPA's 2012 analytical demonstration 
remains valid and that participation in the CSAPR trading programs as 
amended continues to meet the Regional Haze Rule's criteria for an 
alternative to BART.\34\ (We refer to this as the ``2017 Affirmation of 
CSAPR Better-than-BART'' throughout this notice.) In the September 29, 
2017, final rule we evaluated the potential emissions shifting that 
could occur due to the withdrawal of Texas from the CSAPR trading 
program for SO2 emissions. Based on this evaluation, we 
determined that an increase in emissions in the remaining CSAPR States 
participating in the SO2 trading program would be more than 
offset by the favorable visibility impacts brought about by the reduced 
emissions in Texas under presumptive source-specific SO2 
BART for the State's BART-eligible EGUs.\35\ As discussed later in this 
section, certain environmental organizations filed a petition for 
reconsideration of this affirmation in November 2017.
---------------------------------------------------------------------------

    \30\ 81 FR 78954 (Nov. 10, 2016).
    \31\ Id. at 78956. The EPA also noted that because Texas EGUs 
would continue to participate in a CSAPR trading program for ozone-
season NOX emissions, Texas would still be eligible under 
40 CFR 51.308(e)(4) to rely on CSAPR participation as an alternative 
to source-specific NOX BART determinations for the 
covered sources. 81 FR at 78962.
    \32\ Id.
    \33\ Texas continues to participate in CSAPR for ozone season 
NOX. See final action signed September 21, 2017, 
available at regulations.gov in Docket No. EPA-HQ-OAR-2016-0598.
    \34\ 82 FR 45481 (September 29, 2017).
    \35\ Id. at 45493-94.
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    On January 4, 2017, we proposed a FIP to address the BART 
requirements for Texas's BART-eligible EGUs. With respect to 
NOX, we proposed to replace the 2009 Regional Haze SIP's 
reliance on CAIR with reliance on our CSAPR FIP to address the 
NOX BART requirements for EGUs.\36\ This portion of our 
proposal was based on the CSAPR Update and our separate November 10, 
2016, proposed finding that the EPA's actions in response to the D.C. 
Circuit's remand would not adversely impact our 2012 demonstration that 
participation in the CSAPR trading programs meets the Regional Haze 
Rule's criteria for alternatives to BART.\37\ We noted that we could 
not finalize this portion of our proposed FIP to address the 
NOX BART requirements for EGUs unless and until we finalized 
our proposed finding that CSAPR was still better than BART.\38\ (This 
predicate finding was finalized on September 29, 2017.)
---------------------------------------------------------------------------

    \36\ 82 FR 912, 914-15 (Jan. 4, 2017).
    \37\ 81 FR 74504 (Nov. 10, 2016).
    \38\ 82 FR 912, 915 (Jan. 4, 2017).
---------------------------------------------------------------------------

    The January 4, 2017, proposed action addressing the SO2 
BART requirements for Texas EGUs acknowledged that Texas sources would 
no longer be participating in the CSAPR program for SO2, and 
therefore, the remaining unfulfilled BART requirements for Texas's 
BART-eligible EGUs would need to be fulfilled by either an approved SIP 
or an EPA-issued FIP. The EPA proposed to satisfy these requirements 
through a BART FIP,

[[Page 28923]]

which addressed the identification of BART-eligible EGU sources, 
screening to identify which BART-eligible sources are ``subject-to-
BART'' (i.e., may reasonably be anticipated to cause or contribute to 
any impairment of visibility in any Class I area), and source-by-source 
determinations of SO2 BART controls as appropriate. We 
proposed SO2 emission limits on 29 EGUs located at 14 
facilities.
    In the January 2017 proposal, we also proposed to disapprove the 
portion of the 2009 Texas Regional Haze SIP that made BART 
determinations for PM from EGUs, on the grounds that the demonstration 
in the 2009 Texas Regional Haze SIP relied on underlying assumptions as 
to how the SO2 and NOX BART requirements for EGUs 
were being met that were no longer valid with the proposed source-
specific SO2 requirements.\39\ The 2009 Texas Regional Haze 
SIP included a pollutant-specific screening analysis for PM to 
demonstrate that Texas EGUs were not subject to BART for PM. In a 2006 
guidance document,\40\ the EPA stated that pollutant-specific screening 
can be appropriate where a State is relying on a BART alternative to 
address both NOX and SO2 BART. While we 
previously proposed to approve the EGU BART determinations for PM in 
the 2009 Texas Regional Haze SIP back in 2014, at that time, CSAPR was 
an appropriate alternative for SO2 and NOX BART 
requirements for EGUs. With the proposal to promulgate source-specific 
SO2 BART requirements, however, SO2 BART would no 
longer be addressed by a BART alternative. Thus, pollutant-specific 
screening for PM was no longer appropriate. To address PM BART 
requirements, we proposed to promulgate source-specific PM BART 
requirements, which generally were based on existing practices and 
control capabilities for those EGUs that we proposed to find subject to 
BART. For coal-fired units, we proposed PM BART limits consistent with 
PM emission limits in the Mercury and Air Toxics Standards (MATS) rule; 
for gas-fired units, we proposed PM BART would be satisfied by making 
the burning of pipeline-quality gas federally enforceable; and for oil-
fired units, we proposed that fuel-content requirements for 
SO2 BART would also satisfy PM BART.\41\
---------------------------------------------------------------------------

    \39\ In the 2009 Regional Haze Texas SIP, emissions of both 
SO2 and NOX from Texas's BART-eligible EGUs 
were covered by participation in trading programs, which allowed 
Texas to conduct a screening analysis of the visibility impacts from 
PM emissions from such units in isolation. However, modeling on a 
pollutant specific basis for PM is appropriate only in the narrow 
circumstance of reliance on BART alternatives to satisfy both 
NOX and SO2 BART. Due to the complexity and 
nonlinear nature of atmospheric chemistry and chemical 
transformation among pollutants, the EPA has not recommended 
performing modeling on a pollutant-specific basis to determine 
whether a source is subject to BART, except in the unique situation 
described above. See discussion in Memorandum from Joseph Paisie to 
Kay Prince, ``Regional Haze Regulations and Guidelines for Best 
Available Retrofit Technology (BART) Determinations,'' July 19, 
2006.
    \40\ See discussion in Memorandum from Joseph Paisie to Kay 
Prince, ``Regional Haze Regulations and Guidelines for Best 
Available Retrofit Technology (BART) Determinations,'' July 19, 
2006.
    \41\ 82 FR at 936.
---------------------------------------------------------------------------

    The EPA received public comments on this 2017 proposal encouraging 
the agency to consider other potentially viable methods of implementing 
a BART alternative for SO2 in Texas, rather than finalizing 
source-specific BART limits. Specifically, some commenters suggested to 
the EPA the concept of a trading program as a BART alternative to 
satisfy SO2 BART requirements. After considering these and 
other public comments, rather than finalizing source-specific BART 
limits for subject-to-BART EGUs in Texas, we issued a final action on 
October 17, 2017, that addressed SO2 BART requirements for 
all BART-eligible coal-fired units and a number of BART-eligible gas- 
or gas/fuel oil-fired units through a BART alternative for 
SO2--specifically, a new intrastate trading program (Texas 
SO2 Trading Program). The remaining BART-eligible EGUs not 
covered by the Texas SO2 Trading Program were determined to 
be not subject to BART based on screening methods as described in our 
January 2017 proposed rule and the associated BART Screening technical 
support document (BART Screening TSD) for that action.\42\
---------------------------------------------------------------------------

    \42\ See document in regulations.gov at docket identification 
number EPA-R06-OAR-2016-0611-0005.
---------------------------------------------------------------------------

    At the time, the EPA modeled the Texas SO2 Trading 
Program after the CSAPR SO2 trading program. We determined 
that the Texas SO2 Trading Program would achieve similar 
emission reductions to CSAPR had the State continued to be subject to 
the CSAPR trading program through a FIP or SIP. As such, we concluded 
that the Texas program satisfied the clear-weight-of-evidence test 
requirements for a BART alternative under 40 CFR 51.308(e)(2).\43\ As 
finalized in October 2017, the Texas SO2 Trading Program 
established an annual trading program budget of 238,393 tons allocated 
to the covered units, as well as a Supplemental Allowance Pool budget 
of 10,000 tons, for a total of up to 248,393 allowances potentially 
available in each year on average.\44\ The Texas SO2 Trading 
Program allowed ``banking'' of allowances for use in future years, 
similar to the CSAPR trading programs, but unlike the CSAPR programs, 
did not impose an ``assurance level'' above which annual emissions 
would be penalized via a higher allowance-surrender ratio. The Texas 
SO2 Trading Program did not include all EGUs that would have 
been subject to CSAPR, but the EPA concluded that potential annual 
emissions from the excluded units were relatively small (i.e., less 
than 27,500 tons) and would not undermine its overall conclusion that 
the Texas SO2 Trading Program was essentially equivalent in 
design and stringency to the CSAPR program.\45\ In reaching that 
conclusion, the EPA compared the annual average emission limit of 
248,393 tons under the Texas SO2 Trading Program (combined 
with estimated emissions for the non-covered EGUs) to a benchmark 
figure of 317,100 tons of annual SO2 emissions evaluated for 
EGUs in Texas in the 2012 CSAPR Better-Than-BART analysis.\46\
---------------------------------------------------------------------------

    \43\ 82 FR 48324, 48329-30, 48357 (Oct. 17, 2017). The EPA 
initially determined that the Texas SO2 Trading Program 
achieved greater reasonable progress than source-specific BART under 
the clear-weight-of-evidence test in 40 CFR 51.308(e)(2), relying on 
the EPA's national finding that CSAPR provides for greater 
reasonable progress than BART and the fact that the Texas 
SO2 Trading Program would achieve similar emission 
reductions to CSAPR in Texas. See 82 FR at 48329-30.
    \44\ Id. at 48358.
    \45\ Id.
    \46\ Id. at 48359-60.
---------------------------------------------------------------------------

    In our final action on October 17, 2017, we also finalized our 
January 2017 proposed determination that Texas's participation in 
CSAPR's trading program for ozone-season NOX qualifies as an 
alternative to source-specific NOX BART. Because Texas 
continues to participate in CSAPR's trading program for ozone-season 
NOX, we are not reopening this determination in this action. 
Finally, because both NOX and SO2 were now once 
again addressed by a BART alternative, we approved Texas's 2009 
Regional Haze SIP's determination, based on a pollutant-specific 
screening analysis, that Texas's EGUs are not subject to BART for PM.
    On November 28, 2017, Sierra Club and the National Parks 
Conservation Association (NPCA) submitted a petition for partial 
reconsideration of our September 2017 finding affirming that CSAPR 
continues to satisfy requirements as a BART alternative.\47\

[[Page 28924]]

Among other things, the petitioners alleged that it was impracticable, 
and indeed impossible, to comment on the relationship between the Texas 
SO2 Trading Program and the CSAPR Better-than-BART analysis 
in the final rule because the EPA did not finalize the Texas 
SO2 Trading Program until after the final rule was signed 
and the EPA had assumed presumptive source-specific SO2 BART 
controls in the rulemaking record for the final rule.\48\ Petitioners 
alleged, in particular, that the EPA's emissions shifting analysis 
accounted for potential increases in emissions in remaining CSAPR 
States of between 22,300 to 53,000 tons by assuming these emissions 
would be offset by an estimated 127,300 tons of SO2 emission 
reductions in Texas due to presumptive source-specific BART 
controls.\49\ However, these petitioners alleged that this assumption 
was proven false when the EPA promulgated the Texas SO2 
Trading Program rather than source-specific BART.\50\ On this basis, 
among other things, petitioners sought mandatory reconsideration of the 
September 29, 2017 action under CAA section 307(d)(7)(B).
---------------------------------------------------------------------------

    \47\ Sierra Club and National Parks Conservation Association, 
Petition for Partial Reconsideration of Interstate Transport of Fine 
Particulate Matter: Revision of Federal Implementation Plan 
Requirements for Texas; Final Rule; 82 FR 45481 (Sept. 29, 2017); 
EPA-HQ-OAR-2016-0598; FRL-9968-46-OAR (submitted Nov. 28, 2017).
    \48\ Id. at 8-9.
    \49\ Id. at 13-14.
    \50\ Id.
---------------------------------------------------------------------------

    On December 15, 2017, the EPA received a separate petition from 
Sierra Club, NPCA, and the Environmental Defense Fund (EDF) requesting 
reconsideration of certain aspects of the October 2017 final rule 
focused mainly on issues related to the Texas SO2 Trading 
Program promulgated to address the SO2 BART requirement for 
Texas EGUs.\51\ In response to the December 15, 2017, petition for 
reconsideration and in light of the change in direction between the 
EPA's proposed and final actions for SO2 BART in Texas, we 
stated that we believed that certain aspects of the October 2017 final 
rule could benefit from further public comment. Accordingly, on August 
27, 2018, the EPA proposed to affirm in most respects the October 2017 
final rule, including the Texas SO2 Trading Program, but 
solicited public comment on certain issues including whether the Texas 
SO2 Trading Program for certain EGUs in Texas met the 
requirements for an alternative to BART for SO2 and our 
approval of Texas's SIP determination that no sources are subject to 
BART for PM.\52\
---------------------------------------------------------------------------

    \51\ Sierra Club, National Parks Conservation Association, and 
Environmental Defense Fund Petition for Reconsideration of 
Promulgation of Air Quality Implementation Plans; State of Texas; 
Regional Haze and Interstate Visibility Transport Federal 
Implementation Plan (Oct. 17, 2017) EPA-R06-OAR-2016-0611; FRL-9969-
07-Region 6 (submitted Dec. 15, 2017).
    \52\ 83 FR 43586, 43587.
---------------------------------------------------------------------------

    On November 14, 2019, partly in response to comments received on 
its 2018 proposed affirmation, the EPA issued a supplemental proposal 
to amend certain parts of the Texas SO2 Trading Program.\53\ 
The supplemental proposal included additional measures such as an 
assurance level and penalty provisions. Specifically, these provisions 
imposed a penalty surrender ratio of three-to-one on SO2 
emissions exceeding a specified ``assurance level.'' \54\ The notice 
also proposed a variability limit set at 7 percent of the trading 
program budget (or 16,668 tons) and a resulting assurance level of 107 
percent of the trading program budget (or 255,081 tons \55\) based on 
the CSAPR methodology establishing such amounts for CSAPR States but 
applied to Texas-specific data.\56\ The supplemental proposal also 
included other minor changes with the goal of strengthening the overall 
stringency of the program.\57\
---------------------------------------------------------------------------

    \53\ 84 FR 61850 (Nov. 14, 2019).
    \54\ Id. at 61853.
    \55\ In the final rule signed on June 29, 2020, we adjusted the 
assurance level to 255,083 tons rather than the 255,081-ton 
assurance level we proposed in the November 2019 supplemental 
proposal. 85 FR 49170, 49183 (Aug. 12, 2020).
    \56\ The increment between a State's emissions budget and its 
corresponding assurance level is referred to as a ``variability 
limit,'' because the increment is designed to account for year-to-
year variability in electricity generation and associated emissions.
    \57\ 84 FR at 61855-56.
---------------------------------------------------------------------------

    On June 29, 2020, in two separate but concurrent actions, former 
EPA Administrator Andrew Wheeler signed a final rule affirming, with 
the proposed modifications from the supplemental proposal described 
above, the Texas SO2 Trading Program as an alternative to 
BART for SO2 for certain sources in Texas and signed a 
letter denying the petition for reconsideration of the 2017 affirmation 
of CSAPR Better-than-BART.\58\ Along with the denial of the petition, 
the EPA also published in the docket the ``Cross-State Air Pollution 
Rule (CSAPR) Better Than Best Available Retrofit Technology (BART) 
Petition for Reconsideration Sensitivity Calculations'' \59\ to 
demonstrate that, even accounting for the reduced stringency of the 
Texas SO2 Trading Program as compared to source-specific 
BART in Texas, and assuming a concomitant shift in SO2 
emissions to remaining CSAPR States in the southeastern United States, 
CSAPR remained a valid BART alternative.
---------------------------------------------------------------------------

    \58\ See 85 FR 49170 (Aug. 12, 2020) (affirming the Texas 
SO2 Trading Program as an alternative to BART for certain 
EGU sources in Texas). 85 FR 40286 (July 6, 2020) (providing notice 
that the agency responded to a petition for partial reconsideration 
of the 2017 affirmation of CSAPR better than BART).
    \59\ Docket document ID EPA-HQ-OAR-2016-0598-0034 available at 
https://www.regulations.gov/docket/EPA-HQ-OAR-2016-0598.
---------------------------------------------------------------------------

    On August 28, 2020, the Sierra Club, NPCA, and Earthjustice 
submitted a petition for partial reconsideration under CAA section 
307(d)(7)(B) of the EPA's 2020 Denial of their November 2017 petition 
for reconsideration (August 2020 petition).\60\ The petitioners alleged 
that because the EPA presented the updated CSAPR Better-than-BART 
sensitivity calculations for the first time in its 2020 denial of the 
2017 Petition (and thus they were not afforded an opportunity to 
comment), and because that updated analysis is of central relevance to 
the September 2017 Final Rule, the EPA must reconsider both actions 
under CAA section 307(d)(7)(B).\61\ The petitioners alleged that, 
contrary to the EPA's conclusions in its 2020 Denial, the updated CSAPR 
Better-than-BART analysis demonstrates that visibility improvement 
under CSAPR is not equal to or greater than visibility improvement 
under source-specific BART averaged over all 140 Class I areas, or the 
60 eastern Class I areas covered by CSAPR.\62\ The August 2020 petition 
will be discussed in further detail in Section V.
---------------------------------------------------------------------------

    \60\ Petition for Partial Reconsideration of Denial of Petition 
for Reconsideration and Petition for Reconsideration of the 
Interstate Transport of Fine Particulate Matter: Revision of Federal 
Implementation Plan Requirements for Texas (Aug. 28, 2020), Docket 
document ID EPA-HQ-OAR-2016-0598-0041, available in 
www.regulations.gov.
    \61\ 2020 Pet. at 8.
    \62\ 2020 Pet. at 9.
---------------------------------------------------------------------------

    On October 13, 2020, we received a separate petition for partial 
reconsideration from NPCA, Sierra Club, and Earthjustice, on our 2020 
final rule affirming that the Texas SO2 Trading Program is a 
valid alternative to SO2 BART requirements for Texas 
EGUs.\63\ In the petition, Petitioner's allege that the EPA presented a 
corrected sensitivity analysis for the first time on July 6, 2020, the 
day the EPA published notice of its denial of the 2017 administrative 
petition for reconsideration of the CSAPR Better-than-BART affirmation 
and after the EPA signed the final rule affirming the Texas Regional 
Haze BART FIP.

[[Page 28925]]

Specifically, the Petitioners alleged that the corrected sensitivity 
analysis is the ``primary evidence'' for the EPA's conclusion that the 
Texas SO2 Trading Program is a lawful and valid BART 
alternative for SO2 under the Regional Haze Rule, and that 
contrary to the EPA's assertions, the ``corrected'' analysis reveals 
that the Texas SO2 Trading Program does not achieve greater 
reasonable progress than source-specific BART, and therefore, is 
arbitrary and contrary to the Clean Air Act and Regional Haze Rule. 
Moreover, Petitioners contended that the corrected sensitivity analysis 
demonstrates that visibility improvement under CSAPR, including the 
Texas SO2 Trading Program, is not equal to or greater than 
visibility improvement under source-specific BART averaged over all 140 
Class I areas or the 60 eastern Class I areas generally within the 
States covered under CSAPR. Because the EPA disclosed the updated 
analysis for the first time on July 6, 2020, the Petitioners argued 
that the grounds for the objections raised in this petition arose after 
the period for public comment, which ended on January 13, 2020, for the 
EPA's supplemental notice of proposed rulemaking (84 FR 61,850 (Nov. 
14, 2019)). Thus, Petitioners alleged the petition met the requirements 
for mandatory reconsideration under CAA section 307(d)(7)(B).
---------------------------------------------------------------------------

    \63\ Sierra Club, National Parks Conservation Association, and 
Earthjustice Petition for Partial Reconsideration of Promulgation of 
Air Quality Implementation Plans; State of Texas; Regional Haze and 
Interstate Visibility Transport Federal Implementation Plan EPA-R06-
OAR-2016-0611 (dated Oct. 13, 2020).
---------------------------------------------------------------------------

    By letter dated June 22, 2021, the EPA acknowledged receipt of the 
petition for partial reconsideration and, without conceding that the 
conditions for mandatory reconsideration were necessarily met pursuant 
to CAA section 307(d)(7)(B), the agency recognized that aspects of this 
action warrant careful review, and potential modification, to ensure 
our actions are fully consistent with the requirements of the Clean Air 
Act and the Regional Haze Rule.\64\ The letter stated the EPA's intent 
to reconsider certain aspects of the Texas Regional Haze BART action, 
which we are proposing in this action.
---------------------------------------------------------------------------

    \64\ Letter from Joseph Goffman, Acting Assistant Administrator 
Office of Air and Radiation, Re: Sierra Club and National Parks 
Conservation Association, Petition for Partial Reconsideration of 
Promulgation of Air Quality Implementation Plans; State of Texas; 
Regional Haze and Interstate Visibility Transport Federal 
Implementation Plan EPA-R06-OAR-2016-0611 (June 22, 2021) available 
in Docket ID No. EPA-R06-OAR-2016-0611 or at https://www.epa.gov/system/files/documents/2021-07/tx-rh-bart-fip-response-signed_1.pdf.
---------------------------------------------------------------------------

D. Consultation With Federal Land Managers (FLMs)

    The Regional Haze Rule requires that a State, or the EPA if 
promulgating a FIP, consult with FLMs before adopting and submitting a 
required SIP or SIP revision or a required FIP or FIP revision. Under 
40 CFR 51.308(i)(2), a State, or the EPA if promulgating a FIP, must 
provide an opportunity for consultation no less than 60 days prior to 
holding any public hearing or other public comment opportunity on a SIP 
or SIP revision, or FIP or FIP revision, for regional haze. The EPA 
must include a description of how it addressed comments provided by the 
FLMs when considering a FIP or FIP revision. We consulted with the FLMs 
(specifically, U.S. Fish and Wildlife Service, U.S. Forest Service, and 
the National Park Service) on December 6, 2022. During the consultation 
we provided an overview of our proposed actions. The FLMs signaled 
support for our proposed action.\65\
---------------------------------------------------------------------------

    \65\ See ``Texas Regional Haze FLM Consultation 12-6-2022.xls'' 
in the docket for this action.
---------------------------------------------------------------------------

III. Overview of Proposed Action

    In this notice of proposed rulemaking, the EPA proposes an action 
with several interrelated components. As more fully explained in the 
following sections, on reconsideration, and due to concerns that our 
justification for the Texas SO2 Trading Program rested on an 
erroneous interpretation of our BART alternative regulations, we are 
proposing to withdraw the Texas SO2 Trading Program and 
instead propose source-specific BART limits for certain EGUs in Texas. 
We are proposing to satisfy the Regional Haze Rule's SO2 
BART requirements through conducting a source-specific BART analysis 
for certain BART-eligible EGU sources identified in this action. 
Additionally, based on our assessment of the effect of this proposed 
action with regard to Texas BART (if finalized), we are proposing to 
re-affirm our 2017 analytical demonstration that CSAPR remains a valid 
BART alternative. Thus, in this action we propose to deny the 2020 
petition for partial reconsideration of our 2020 denial of a petition 
for reconsideration of that 2017 determination. Finally, we are 
proposing to make an error correction under CAA section 110(k)(6) with 
respect to our prior approval of the portion of the 2009 Texas Regional 
Haze SIP that found that Texas's EGUs are not subject to BART for PM on 
the grounds that our approval relied on underlying assumptions as to 
how the SO2 and NOX BART requirements for EGUs 
were being met that are no longer valid with the proposed withdrawal of 
the Texas SO2 Trading Program. As such, we propose to 
correct the error by disapproving Texas's 2009 Regional Haze SIP 
submission related to PM BART and propose to satisfy PM BART by also 
conducting a source-specific BART analysis for certain BART-eligible 
EGU sources identified in this action. Unless expressly reopened in 
this notice, the EPA is not reopening any other prior determinations 
related to regional haze requirements in the State of Texas.

IV. Withdrawal of the Texas SO2 Trading Program as a BART Alternative 
for SO2

    As previously stated, on August 12, 2020, the EPA published a final 
rule affirming our 2017 final rule that the Texas SO2 
Trading Program, with amendments, satisfied the requirements for a BART 
alternative for SO2 under 40 CFR 51.308(e)(2).\66\ In this 
action, we are proposing to find that the basis for the Texas 
SO2 Trading Program as a BART alternative rested on an 
erroneous interpretation of our BART alternative regulations. That 
interpretation in turn produced an analytical basis for the BART 
alternative that we now propose to find insufficient and in error. We 
are proposing to withdraw the Texas SO2 Trading Program 
under CAA section 110(k)(6) and our inherent authority to reconsider 
prior actions.
---------------------------------------------------------------------------

    \66\ See generally 85 FR 49170.
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A. Legal Authority To Withdraw the Texas SO2 Trading Program

1. The EPA's Error Correction Authority Under CAA 110(k)(6)
    The EPA proposes to correct its Texas Regional Haze BART FIP by 
proposing to withdraw the Texas SO2 Trading Program and 
proposing to instead conduct a source-specific BART analysis for the 
BART-eligible EGUs included in the Texas SO2 Trading 
Program. In this action, we are proposing to find that the Texas 
SO2 Trading Program was promulgated on an erroneous basis, 
constituting an error under CAA section 110(k)(6).
    Section 110(k)(6) of the CAA provides the EPA with the authority to 
make corrections to actions on CAA implementation plans that are 
subsequently found to be in error. Ass'n of Irritated Residents v. EPA, 
790 F.3d 934, 948 (9th Cir. 2015) (110(k)(6) is a ``broad provision'' 
enacted to provide the EPA with an avenue to correct errors). The key 
provisions of section 110(k)(6) are that the Administrator has the 
authority to ``determine'' that the promulgation of a plan was ``in 
error,'' and when the Administrator does so, may then revise the action 
``as

[[Page 28926]]

appropriate,'' in the same manner as the prior action.\67\ Moreover, 
CAA section 110(k)(6) ``confers discretion on the EPA to decide if and 
when it will invoke the statute to revise a prior action.'' 790 F.3d at 
948 (section 110(k)(6) grants the ``EPA the discretion to decide when 
to act pursuant to that provision'').
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    \67\ See 85 FR 73636, 73637 (Nov. 19, 2020).
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    While CAA section 110(k)(6) provides the EPA with the authority to 
correct its own ``error,'' nowhere does this provision or any other 
provision in the CAA define what qualifies as ``error.'' Thus, the EPA 
believes that the term should be given its plain language, everyday 
meaning, which includes all unintentional, incorrect, or wrong actions 
or mistakes.\68\ Under CAA section 110(k)(6), the EPA must make an 
error determination and provide the ``the basis thereof.'' There is no 
indication that this is a substantial burden for the Agency to meet. To 
the contrary, the requirement is met if the EPA clearly articulates the 
error and basis thereof. Ass'n of Irritated Residents v. EPA, 790 F.3d 
at 948; see also 85 FR 73636, 73638.
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    \68\ See 85 FR at 73637-38.
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2. The EPA's Inherent Authority To Reconsider Its Prior Action
    In addition to the error correction provision of CAA section 
110(k)(6), the EPA also has the inherent administrative authority to 
withdraw the Texas SO2 Trading Program and propose in its 
place to conduct a source-specific BART analysis for the BART-eligible 
EGUs included in the Texas SO2 Trading Program. This 
authority lies in CAA section 301(a), read in conjunction with CAA 
section 110 and case law holding that an agency has inherent authority 
to reconsider its prior actions.\69\ Section 301(a) authorizes the EPA 
``to prescribe such regulations as are necessary to carry out the 
[EPA's] functions'' under the CAA. Reconsidering prior rulemakings, 
when necessary, is part of the ``[EPA's] functions'' under the CAA--
considering the EPA's inherent authority as recognized under the case 
law to do so--and as a result, CAA section 301(a) confers authority 
upon the EPA to undertake this rulemaking. Moreover, CAA section 
110(c)(1) provides the EPA with the authority to promulgate a FIP where 
``the Administrator . . . disapproves a State implementation plan 
submission in whole or in part.'' As such, the EPA's authority to 
promulgate FIPs under the CAA necessarily provides it the inherent 
authority to amend/withdraw FIPs.\70\
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    \69\ Trujillo v. General Electric Co., 621 F.2d 1084, 1086 (10th 
Cir. 1980) (``Administrative agencies have an inherent authority to 
reconsider their own decisions, since the power to decide in the 
first instance carries with it the power to reconsider.'')
    \70\ See 76 FR 25177, 25181 (May 2011).
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    Additionally, it is well-established that the EPA has discretion to 
revisit existing regulations. Specifically, agencies have inherent 
authority to reconsider past 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) (``Fox''); Motor Vehicle Manufacturers Ass'n of the 
United States, Inc. v. State Farm Mutual Automobile Insurance Co., 463 
U.S. 29, 42 (1983) (``State Farm''); see also Encino Motorcars, LLC v. 
Navarro, 579 U.S. 211, 221-22 (2016).
    As such, we find that our inherent ability to reconsider past 
actions also provides us the authority to withdraw the Texas 
SO2 Trading Program for the same reasons as under CAA 
section 110(k)(6), as described in Section IV.B. That is, because the 
Texas SO2 Trading Program rested on what we find to be an 
improper interpretation of our BART alternative regulations, we are 
proposing to withdraw the program and to conduct a source-specific BART 
analysis for those EGUs currently participating in the program.
    The EPA acknowledges the potential for reliance interests to be 
affected by our reconsideration of a prior rule. However, the EPA is 
not aware of any substantial commitment of resources or capital, or 
that the EGUs covered by the Texas SO2 Trading Program 
undertook any significant decisions in reliance on participation in the 
trading program. The Texas SO2 Trading Program established 
an emissions budget that the covered sources were already operating 
well below. Therefore, the requirements of the Texas SO2 
Trading Program did not cause any sources to invest in new pollution 
control technology or to undertake any other significant investments. 
Further, because the Texas SO2 Trading Program rested on an 
improper interpretation of our BART alternative regulations, we do not 
think a reliance interest alone (even if there were such interests) 
would be sufficient to overcome the need to return to a proper 
interpretation of our BART regulations and proper implementation of the 
BART program.

B. Basis for Withdrawing the Texas SO2 Trading Program

    We propose that, in attempting to demonstrate that the Texas 
SO2 Trading Program satisfied the BART alternative 
requirements in 40 CFR 51.308(e)(2), the EPA erroneously relied on its 
previous determination that the CSAPR trading program is better-than-
BART nationwide, when in fact the Texas SO2 Trading Program 
was a separate BART alternative program that was not a part of the 
CSAPR program.\71\ Because the Texas SO2 Trading Program was 
and is separate and distinct from CSAPR and functioned as an 
independent BART alternative disconnected from any other BART 
alternative, we propose that in conducting the comparative analysis 
required by 51.308(e)(2)(i), the EPA should have compared the 
visibility benefits of the Texas SO2 Trading Program in 
isolation with the visibility benefits of source-specific BART controls 
for the particular subject-to-BART sources that would have been 
required in the absence of the BART alternative. We conducted no such 
comparison in either the 2017 rule originally promulgating the Texas 
SO2 Trading Program, nor in the 2020 action affirming the 
Texas SO2 Trading Program with certain, minor amendments. 
For purposes of determining whether it is appropriate to now withdraw 
the Texas SO2 Trading Program as a BART alternative, we have 
conducted an analysis comparing the Texas SO2 Trading 
Program to source-specific BART for the relevant EGU BART sources. We 
propose to find that source-specific BART controls substantially 
outperform the Texas SO2 Trading Program in terms of 
emission reductions and visibility improvement at the Class I areas 
that are affected by the sources in Texas. As a result of this finding 
of error, we are proposing to withdraw the Texas SO2 Trading 
Program as a BART alternative for SO2 and propose in its 
place to conduct a source-specific BART analysis for those BART-
eligible EGUs included in the Texas SO2 Trading Program.
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    \71\ See 82 FR 48324, 48330 (Oct. 17, 2017).
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1. BART Alternative Requirements
    The Regional Haze Rule's BART provisions generally direct States to 
identify all BART-eligible sources; determine which of those BART-
eligible sources are subject to BART requirements based on whether the 
sources emit air pollutants that may reasonably be anticipated to cause 
or contribute to visibility impairment in a Class I area; determine 
source-specific BART for each source that is subject to BART 
requirements, based on an analysis taking specified factors into 
consideration; and include emission limitations reflecting those BART 
determinations in their SIPs. However, the Regional Haze Rule also 
provides

[[Page 28927]]

each State with the flexibility to adopt an allowance trading program 
or other alternative measure instead of requiring source-specific BART 
controls, so long as the alternative measure is demonstrated to achieve 
greater reasonable progress than BART toward the national goal of 
achieving natural visibility conditions in Class I areas.
    States, or the EPA if promulgating a FIP, that opt to rely on an 
alternative program in lieu of source-specific BART, must meet the 
requirements under 40 CFR 51.308(e)(2) and, if applicable, (e)(3). 
These requirements for alternative programs establish the criteria for 
demonstrating that the alternative program will achieve greater 
reasonable progress than would be achieved through the installation and 
operation of BART (i.e., they establish the ``better-than-BART'' tests) 
and are fundamental elements of any alternative program. To demonstrate 
that the alternative program achieves greater reasonable progress than 
source-specific BART, States, or the EPA if developing a FIP, must 
demonstrate that the alternative meets the requirements, as applicable, 
in 40 CFR 51.308(e)(2)(i) through (vi). Separately, under 40 CFR 
51.308(e)(4), States whose sources participate in the CSAPR trading 
program(s) may rely on such programs to satisfy BART as to the relevant 
pollutants and sources without the need for any additional analysis 
(discussed in more detail in Section V).
    Under 40 CFR 51.308(e)(2), the State, or the EPA, must conduct an 
analysis of the best system of continuous emission control technology 
available and the associated emission reductions achievable for each 
source subject to BART covered by the alternative program, termed a 
``BART benchmark.'' \72\ Where the alternative program has been 
designed to meet requirements other than BART, simplifying assumptions 
may be used to establish a BART benchmark.\73\ The BART benchmark is 
the basis for comparison in the better-than-BART test for BART 
alternatives. Under 40 CFR 51.308(e)(2)(i)(E), the State or the EPA 
must provide a determination that the alternative program achieves 
greater reasonable progress than BART under 40 CFR 51.308(e)(3). 40 CFR 
51.308(e)(3), in turn, provides two different avenues, applicable under 
specific circumstances, for determining whether the BART alternative 
achieves greater reasonable progress than BART. If the distribution of 
emissions under the alternative program is not substantially different 
than under BART, and the alternative program results in greater 
emissions reductions of each relevant pollutant than BART, then the 
alternative program may be deemed to achieve greater reasonable 
progress. On the other hand, if the distribution of emissions is 
significantly different, the differences in visibility improvement 
between BART and the alternative program must be determined by 
conducting dispersion modeling for each impacted Class I area for the 
best and worst 20 percent of days. This modeling demonstrates ``greater 
reasonable progress'' if both of the following criteria are met: (1) 
Visibility does not decline in any Class I area; and (2) there is 
overall improvement in visibility when comparing the average 
differences in visibility conditions between BART and the alternative 
program across all the affected Class I areas.\74\
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    \72\ 40 CFR 51.308(e)(2)(i)(C).
    \73\ 40 CFR 51.308(e)(2)(i)(C).
    \74\ 40 CFR 51.308(e)(3).
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    Alternatively, pursuant to 40 CFR 51.308(e)(2)(i)(E), a third test 
is available under which States may show that the BART alternative 
achieves greater reasonable progress than BART ``based on the clear 
weight of evidence.'' As stated in the EPA's revisions to the Regional 
Haze Rule governing alternatives to source-specific BART 
determinations, such demonstrations attempt to make use of all 
available information and data which can inform a decision while 
recognizing the relative strengths and weaknesses of that information 
in arriving at the soundest decision possible.\75\ Factors which can be 
used in a weight of evidence determination in this context may include, 
but are not limited to, future projected emissions levels under the 
program as compared to under BART, future projected visibility 
conditions under the two scenarios, the geographic distribution of 
sources likely to reduce or increase emissions under the program as 
compared to BART sources, monitoring data and emissions inventories, 
and sensitivity analyses of any models used. This array of information 
and other relevant data may be of sufficient quality to inform the 
comparison of visibility impacts between BART and the alternative 
program. In showing that an alternative program is better than BART and 
when there is confidence that the difference in visibility impacts 
between BART and the alternative scenarios are expected to be large 
enough, a weight of evidence comparison may be warranted in making the 
comparison.
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    \75\ 71 FR 60612, 60622 (Oct. 13, 2006).
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    Under 40 CFR 51.308(e)(2)(iii) and (iv), all emission reductions 
for the alternative program must take place during the period of the 
first long-term strategy (i.e., the first planning period) for regional 
haze and all the emission reductions resulting from the alternative 
program must be surplus to those reductions resulting from measures 
adopted to meet requirements of the CAA as of the baseline date of the 
SIP.
2. The EPA Inappropriately Relied on CSAPR When Promulgating and 
Affirming the Texas SO2 Trading Program in 2017 and 2020
    The EPA has long maintained that the CSAPR trading programs can 
function as a BART alternative for the relevant covered visibility 
pollutants for the EGU BART sources that are covered by the relevant 
CSAPR trading program. The EPA promulgated CSAPR, a revised multistate 
trading program to replace CAIR, in 2011 (and revised it in 2012).\76\ 
CSAPR established FIP requirements for several States, including Texas, 
to address the States' interstate transport obligation under CAA 
section 110(a)(2)(D)(i)(I). The EPA made the original CSAPR better-
than-BART determination in a 2012 rulemaking, codified at 40 CFR 
51.308(e)(4), and subsequently reaffirmed that determination in a 2017 
rulemaking.\77\ At the time of the 2012 rulemaking, Texas was part of 
the CSAPR annual NOX and SO2 trading programs to 
address interstate transport of PM2.5. Therefore, Texas was 
among the States who could choose to meet BART obligations for their 
EGUs through participation in the relevant CSAPR trading program. The 
EPA subsequently withdrew Texas from CSAPR for purposes of addressing 
interstate transport requirements for the PM2.5 NAAQS (i.e., 
Texas was withdrawn from the annual NOX and SO2 
trading programs) in response to the D.C. Circuit Court's decision in 
EME Homer City Generation, L.P. v. EPA.\78\ However, when the EPA 
promulgated the Texas SO2 Trading Program, the Agency 
reasoned that it could nonetheless

[[Page 28928]]

satisfy the Regional Haze Rule's BART alternative requirements by 
demonstrating that SO2 emissions under the Texas 
SO2 Trading Program were comparable to SO2 
emissions anticipated from Texas had Texas remained in CSAPR.\79\
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    \76\ Federal Implementation Plans; Interstate Transport of Fine 
Particulate Matter and Ozone and Correction of SIP Approvals, 76 FR 
48208 (Aug. 8, 2011).
    \77\ 77 FR 33642 (June 7, 2012) (codified at 40 CFR 
51.308(e)(4)). The final rule amended the Regional Haze Rule to 
allow States whose EGUs participate in one of the CSAPR trading 
programs for a given pollutant to rely on that participation as an 
alternative to source-specific BART requirements); see also 82 FR 
45481 (Sep 29, 2017) (affirming that CSAPR remained better than BART 
nationwide after Texas and other States were removed from CSAPR for 
PM).
    \78\ EME Homer City Generation, L.P. v. EPA, 795 F. 3d 118, 138 
(D.C. Cir. 2015).
    \79\ 82 FR 48324, 48336 (Oct. 17, 2017).
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    As we explained in our June 2020 affirmation of the Texas 
SO2 Trading Program, annual SO2 emissions for 
sources covered by the Texas SO2 Trading Program are 
constrained by the annual budgets and an assurance level of 255,083 
tons. The EPA then added to this amount an estimated 35,000 tons per 
year of emissions from units not covered by the Texas SO2 
Trading Program, but which would have been covered by the CSAPR 
program. This yielded 290,083 tons of SO2, which was below 
the 317,100-tons per year emissions level assumed for Texas sources 
under CSAPR.\80\ Thus, rather than considering the Texas SO2 
Trading Program in isolation as a BART alternative and comparing the 
effects of that program to the effects of source-specific BART for the 
relevant EGUs in Texas to determine whether it made ``greater 
reasonable progress,'' the EPA instead relied on the CSAPR Better-than-
BART analysis as the basis for concluding that the Texas SO2 
Trading Program provided greater reasonable progress than BART--even 
though the Texas SO2 Trading Program was not connected in 
any way to CSAPR and functioned as its own, independent BART 
alternative.
---------------------------------------------------------------------------

    \80\ Promulgation of Air Quality Implementation Plans; State of 
Texas; Regional Haze and Interstate Visibility Transport Federal 
Implementation Plan 85 FR 49170, 49183 (Aug. 12, 2020).
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    Such reliance is inconsistent with the requirements of the Regional 
Haze Rule's requirements for a BART alternative in 40 CFR 51.308(e)(2), 
which requires a comparison between the BART alternative and the BART 
benchmark for the relevant sources.\81\ Because the Texas 
SO2 Trading Program is an intrastate program, the effects of 
that program should have been considered independently of CSAPR. 
Indeed, participation in the CSAPR program in lieu of implementing BART 
requirements is provided for under a separate provision of the Regional 
Haze Rule, 40 CFR 51.308(e)(4). Thus, the EPA could only rely on the 
analytical demonstrations made in the CSAPR better-than-BART 
rulemakings had Texas remained in CSAPR.\82\ Once Texas was withdrawn 
from CSAPR, the EPA could not rely on that provision as justification 
that the Texas SO2 Trading Program made ``greater reasonable 
progress'' than BART at Texas EGUs. Thus, whether the Texas 
SO2 Trading Program provided similar or more reductions than 
anticipated had Texas remained in CSAPR is irrelevant and fails to 
demonstrate that it achieves greater reasonable progress than BART as 
required by 40 CFR 51.308(e)(2).
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    \81\ 40 CFR 51.308(e)(2).
    \82\ Even after the removal of Texas (and other States) from 
CSAPR following the remand of certain CSAPR budgets in EME Homer 
City Generation, Texas (and other States) had the option to 
voluntarily participate in CSAPR to gain the benefit of addressing 
BART obligations. Texas declined to adopt this approach.
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    Furthermore, although the Texas SO2 Trading Program was 
modeled after CSAPR in its design and operation, the two programs are 
distinct. First, the sources covered under the Texas SO2 
Trading Program do not include all the sources in Texas that were part 
of the CSAPR trading program.\83\ Thus, the EPA had to rely on an 
unenforceable emissions assumption of 35,000 tons per year from the 
non-covered sources to allow for an apples-to-apples comparison between 
the Texas program and the CSAPR program in terms of the universe of 
sources analyzed.\84\ However, there was no obligation that the non-
covered sources would emit below that assumed level in perpetuity.
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    \83\ See 85 FR 49170, 49184.
    \84\ 85 FR 49170, 49184.
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    Second, CSAPR was designed as a regional trading program that 
involved the participation of sources from many States over a wide 
geographic area, as compared to the Texas SO2 Trading 
Program, which is an intrastate trading program. As such, the Texas 
SO2 Trading Program is limited to sources in Texas which 
cannot trade allowances with sources in other States as is permitted 
under CSAPR. Because of the scope of participation in CSAPR, in 
demonstrating that CSAPR was Better-than-BART, the EPA was not required 
by the rule to demonstrate that CSAPR achieves greater reasonable 
progress than BART at every Class I area or in every State.\85\ Rather, 
the EPA demonstrated that CSAPR achieved greater visibility improvement 
than BART when visibility was averaged across all Class I areas.\86\ In 
averaging visibility improvement from CSAPR across all the affected 
Class I areas, the 2012 demonstration properly relied on the 
substantial emission reductions anticipated to occur in the eastern 
half of the country for which other States, which included Texas at the 
time, could take advantage of without having to apply source-specific 
BART.\87\ For example, SO2 emissions in Tennessee were 
anticipated to be approximately 321,300 in a nationwide BART 
scenario,\88\ but only approximately 66,700 under CSAPR.\89\ Similar 
situations were also anticipated in several other States including Ohio 
(546,700 tons of SO2 under a nationwide BART scenario 
compared to only 190,000 tons under CSAPR); Indiana (454,500 tons of 
SO2 under a nationwide BART scenario compared to only 
202,900 tons under CSAPR); and Pennsylvania (222,600 tons of 
SO2 under a BART scenario compared to only 134,500 tons 
under CSAPR).\90\
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    \85\ See 77 FR at 33650.
    \86\ See e.g., 77 FR at 33650.
    \87\ Specifically, in the 2017 affirmation that CSAPR remains 
better than BART after withdrawal of multiple States from CSAPR, 
including Texas, we stated that the 2012 analytic demonstration 
showed that the difference in emissions between the CSAPR scenario 
plus BART elsewhere would lead to an overall reduction in 
SO2 emission reductions for the overall modeled region of 
773,000 tons as compared to application of source specific BART 
nationwide. See memo entitled ``Sensitivity Analysis Accounting for 
Increases in Texas and Georgia Transport Rule State Emissions 
Budgets,'' Docket document ID No. EPA-HQ-OAR-2011-0729-0323 (May 29, 
2012) (2012 CSAPR/BART sensitivity analysis memo), at 1-2, available 
in the docket for this proposed action.
    \88\ For all BART-eligible EGUs in the Nationwide BART scenario 
and for BART-eligible EGUs not subject to CSAPR for a particular 
pollutant in the CSAPR + BART-elsewhere scenario, the modeled 
emission rates were the presumptive EGU BART limits for 
SO2 and NOX as specified in the BART 
Guidelines (Appendix Y to 40 CFR part 51--Guidelines for BART 
Determinations under the Regional Haze Rule), unless an actual 
emission rate at a given unit with existing controls was lower, in 
which case the lower emission rate was modeled. (For additional 
details see Technical Support Document for Demonstration of the 
Transport Rule as a BART Alternative, Docket document ID No. EPA-HQ-
OAR-2011-0729-0014 (December 2011) (2011 CSAPR/BART Technical 
Support Document EPA-HQ-OAR-2011-0729-0014) in www.regulations.gov.
    \89\ See Technical Support Document for Demonstration of the 
Transport Rule as a BART Alternative, Docket document ID No. EPA-HQ-
OAR-2011-0729-0014 (December 2011) (2011 CSAPR/BART Technical 
Support Document EPA-HQ-OAR-2011-0729-0014), at table 2-4, also 
available in the docket for this action at document ID EPA-R06-OAR-
2016-0611-0119.
    \90\ See Technical Support Document for Demonstration of the 
Transport Rule as a BART Alternative, Docket ID No. EPA-HQ-OAR-2011-
0729-0014 (December 2011) (2011 CSAPR/BART Technical Support 
Document), at table 2-4, available in www.regulations.gov, document 
ID EPA-R06-OAR-2016-0611-0119.
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    However, while CSAPR leads to greater emissions reductions overall 
over the modeled region, we explained that for certain CSAPR States, 
application of source-specific BART was projected to lead to greater 
emission reductions than through participation in CSAPR. We explained 
that this could occur in CSAPR States that have numerous BART-eligible 
EGUs.\91\ One

[[Page 28929]]

such State where this was anticipated to occur was Texas. In the case 
of Texas, the projected SO2 emissions from affected EGUs in 
the modeled nationwide-BART scenario (139,300 tons per year) are 
considerably lower than the projected SO2 emissions from the 
affected EGUs in the CSAPR scenario (266,600 tons per year as modeled, 
and up to approximately 317,100 tons, as addressed in the 2012 CSAPR/
BART sensitivity analysis memo).\92\ Thus, the application of 
presumptive source-specific BART, instead of participation in the CSAPR 
SO2 trading program, would have resulted in projected 
emissions of 139,300 tons per year, a reduction in projected 
SO2 emissions by between approximately 127,300 tons and 
177,800 tons from the CSAPR SO2 trading program 
emissions.\93\ As a result, a demonstration that the Texas 
SO2 Trading Program achieves equivalent emissions reductions 
as anticipated had Texas remained in CSAPR fails to demonstrate that 
the Texas SO2 Trading Program achieves greater reasonable 
progress than BART for the BART sources in Texas participating in the 
Texas SO2 Trading Program. The comparison in estimated 
emissions above strongly indicates this not to be the case.
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    \91\ 81 FR 78954, 78962-63 (Nov. 10, 2016).
    \92\ 81 FR 78954, 78962-63 (Nov. 10, 2016).
    \93\ 81 FR 78954, 78962-63 (Nov. 10, 2016). As stated in both 
the proposal and final rule withdrawing Texas from CSAPR 
SO2 trading program, the 127,300-ton amount was described 
as the minimum reduction in projected Texas SO2 emissions 
because it did not reflect a 50,500-ton increase in the Texas 
SO2 budget that occurred after the original CSAPR 
scenario was modeled. If that budget increase had been reflected in 
the original CSAPR scenario, modeled Texas EGU SO2 
emissions in that scenario would likely have been higher, 
potentially by the full 50,500-ton amount. The CSAPR budget increase 
would have had no effect on Texas EGUs' modeled SO2 
emissions under BART. Therefore, the 127,300-ton minimum estimate of 
the reduction in projected Texas SO2 emissions caused by 
removing Texas EGUs from CSAPR for SO2, which are 
computed as the difference between Texas EGUs' collective emissions 
in the original CSAPR scenario and the BART scenario, may be 
understated by as much as 50,500 tons. See 82 FR at 45492; 81 FR at 
78962-63.
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    Thus, we propose that it was an error to allow the Texas 
SO2 Trading Program to rely on a demonstration made for a 
different and unconnected BART alternative (i.e., CSAPR) because it 
failed to comport with the requirements in 40 CFR 51.308(e)(2). 
Instead, the EPA should have assessed whether the Texas SO2 
Trading Program provides for greater reasonable progress than BART for 
those BART sources in Texas covered by the Texas SO2 Trading 
Program.\94\
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    \94\ See 40 CFR 51.308(e)(2), (e)(3).
---------------------------------------------------------------------------

3. The Texas SO2 Trading Program Does Not Achieve Greater 
Reasonable Progress Than BART
    Because the 2017 Texas BART FIP and subsequent affirmation 
improperly relied on CSAPR to support the validity of the Texas 
SO2 Trading Program, there is no evidence in the record to 
support a finding that the Texas SO2 Trading Program 
provides for greater reasonable progress than BART when compared to the 
proper BART benchmark (i.e., source specific BART for the sources in 
Texas covered by the Texas SO2 Trading Program). Rather, the 
relevant information indicates that had the Texas SO2 
Trading Program been compared to the appropriate Texas-specific BART 
benchmark, the analysis would have found that the Texas SO2 
Trading Program does not provide for greater reasonable progress than 
BART at the Class I areas affected by those sources.
    For purposes of determining whether it is appropriate to now 
withdraw the Texas SO2 Trading Program as a BART 
alternative, we have conducted an analysis comparing the effects of the 
Texas SO2 Trading Program to source-specific BART for the 
relevant EGU BART sources. The purpose of this analysis is not to 
conduct a full re-evaluation of the Texas SO2 Trading 
Program under each of the requirements of the BART-alternative 
regulations of 40 CFR 51.308(e)(2). Rather, this analysis evaluates the 
question of whether, even under conservative assumptions, the Texas 
SO2 Trading Program, when compared to the proper BART 
benchmark (source-specific BART for the relevant sources in Texas), 
could possibly achieve greater reasonable progress. The analysis 
confirms a stark disparity in outcomes, with the Texas SO2 
Trading Program not securing any additional emission reductions and 
even allowing for substantial SO2 emissions increases from 
baseline levels while source-specific BART would achieve substantial 
SO2 emissions decreases. We propose to find that the 
installation and operation of source-specific BART controls 
substantially outperform the Texas SO2 Trading Program in 
terms of emission reductions and resulting visibility improvement at 
the Class I areas that are affected by the sources in Texas, and that 
the Texas SO2 Trading Program does not achieves greater 
reasonable progress than BART as required by 40 CFR 51.308(e)(2).
    As we explained earlier in Section II and in our June 2020 
affirmation of the Texas SO2 Trading Program as an 
alternative to BART for SO2, annual SO2 emissions 
for sources covered by the Texas SO2 Trading Program are 
constrained by the annual budgets and an assurance level of 255,083 
tons.\95\ The Texas SO2 Trading Program imposes a penalty 
surrender ratio of three allowances for each ton of emissions in any 
year in excess of the assurance level, which provides a disincentive 
against emissions exceeding the assurance level. Added to this amount 
is an estimated 35,000 tons per year of emissions from units not 
covered by the Texas SO2 Trading Program, but which would 
have been covered by the CSAPR program. This yields an estimated 
290,083 tons of SO2 from all Texas EGUs. This is 
significantly higher than the 139,300 tons per year estimated in the 
nationwide BART only scenario for Texas EGUs in the 2012 CSAPR better 
than BART demonstration. In other words, the presumptive BART scenario 
developed for the 2012 demonstration would result in approximately 
150,000 tons per year less SO2 emissions than the Texas 
SO2 Trading Program scenario.
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    \95\ 85 FR 49170, 49183 (Aug. 12, 2020).
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    We note, however, that this comparison of emissions of the Texas 
SO2 Trading Program and presumptive BART from the 2012 CSAPR 
analysis does not account for recent facility shutdowns. Sandow,\96\ 
Big Brown,\97\ and Monticello \98\ retired in 2018. Welsh Unit 2 
retired in 2016,\99\ and the J. T. Deely units retired at the end of 
2018.\100\ While these retirements have resulted in overall emission 
reductions, they have also resulted in a surplus of allowances that 
serve to decrease or eliminate any
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    \96\ See letter dated February 14, 2018, from Kim Mireles of 
Luminant to the TCEQ requesting to cancel certain air permits and 
registrations for Sandow Steam Electric Station available in the 
docket for this action at document ID EPA-R06-OAR-2016-0611-0143 for 
Sandow Unit 4 and document ID EPA-R06-OAR-2016-0611-0134 for Sandow 
Unit 5.
    \97\ See letter dated March 27, 2018, from Kim Mireles of 
Luminant to the TCEQ requesting to cancel certain air permits and 
registrations for Big Brown available in the docket for this action 
at document ID EPA-R06-OAR-2016-0611-0130.
    \98\ See letter dated February 8, 2018, from Kim Mireles of 
Luminant to the TCEQ requesting to cancel certain air permits and 
registrations for Monticello available in the docket for this action 
at document ID EPA-R06-OAR-2016-0611-0132.
    \99\ Welsh Unit 2 was retired on April 16, 2016, pursuant to a 
Consent Decree (No. 4:10-cv-04017-RGK) and subsequently removed from 
the Title V permit (permit no. O26). See ``TX197.183 Turk (Welsh) 
Consent Decree 12.22.11'' (document ID EPA-R06-OAR-2016-0611-0138) 
and ``TX187.129 AIR OP_O26-13404_Permits_Public_20160919_Project 
File Folder_1410429 (document ID EPA-R06-OAR-2016-0611-0129) in the 
docket for this action.
    \100\ See letters dated December 2021 from the TCEQ to Danielle 
Frerich regarding the cancellation of air quality permits for the J. 
T. Deely Units available in the docket for this action.

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[[Page 28930]]

regulatory pressure from the Texas SO2 Trading Program to 
further decrease emissions from current levels. Under the Texas 
SO2 Trading Program, retired units continue to be allocated 
allowances for a period of five years.\101\ After that period, those 
allowances are still allocated but to the supplemental allowance 
pool.\102\ Sources participating in the Texas SO2 Trading 
Program have flexibility to transfer allowances among multiple 
participating units under the same owner/operator when planning 
operations, and unused allowances can be banked for use in future 
years.\103\ Furthermore, allowances are allocated from the supplemental 
allowance pool each year if the reported emissions for an ownership 
group exceeds the amount of allowances allocated to that group, with a 
limit on these allocations in any year of 16,688 tons plus any 
allowances added to the pool in that year from retired units. The 
combination of allocations to retired units, banking of allowances, and 
allocations from the supplemental allowance pool results in an excess 
availability in allowances to cover the sources' emissions with the 
only limitation being the assurance level.
---------------------------------------------------------------------------

    \101\ 40 CFR 97.911(a)(2).
    \102\ 40 CFR 97.911(a)(2).
    \103\ See 45 FR at 49208.
---------------------------------------------------------------------------

    Because the Texas SO2 Trading Program contains both BART 
and non-BART EGUs, we must establish emission estimates for both types 
of units to compare the installation and operation of source-specific 
BART for SO2 to the Texas SO2 Trading Program. 
For the purposes of comparing the Texas SO2 Trading Program 
to source-specific BART, we assume that all BART-eligible coal-fired 
sources are subject to BART \104\ and that source-specific BART results 
in emission reductions greater than or equal to those reductions 
estimated based on a presumptive BART level of 0.15 lb/MMBtu.\105\ 
\106\ For the gas fired sources included in the Texas SO2 
Trading Program, we assume that they are not subject to BART for 
purposes of this analysis and thus treat them as non-BART sources.\107\ 
We note that an assumption of 95 percent control would result in lower 
emissions than the 0.15 lb/MMBtu rate for all BART units, however, for 
the purpose of this comparison, we are selecting a conservative (high) 
estimate for presumptive BART limits to illustrate the large emission 
reductions available through the installation and operation of BART 
even at this conservatively high emission rate. We also note that the 
assumption of 0.15 lb/MMBtu is more conservative than what was used for 
these units in the 2012 CSAPR Better-than-BART analysis.
---------------------------------------------------------------------------

    \104\ This is consistent with our subject to BART screening 
analysis below in Section VII.
    \105\ BART Guidelines, 70 FR 39104, 39131 (July 6, 2005). ``. . 
., we are establishing a BART presumptive emission limit for coal-
fired EGUs greater than 200 MW in size without existing 
SO2 control. These EGUs should achieve either 95 percent 
SO2 removal, or an emission rate of 0.15 lb 
SO2/MMBtu, unless a State determines that an alternative 
control level is justified based on a careful consideration of the 
statutory factors.''
    \106\ In Section VII of this proposed action, we evaluate and 
identify which of the BART-eligible EGUs currently in the Texas 
SO2 Trading Program are subject to BART sources as well 
as the analysis of the five factors that inform the BART 
determination for subject to BART sources. In Section VIII, we 
provide our weighing of the factors and proposed determination on 
source-specific BART requirements for these sources.
    \107\ We note that in Section VII we determined that W. A. 
Parish Unit WAP4, which is gas fired, is subject to BART because it 
is co-located with two other coal-fired BART units (Units WAP5 & 
WAP6). Thus, in evaluating whether the BART-eligible units at W. A. 
Parish were subject to BART we evaluated emissions from Units WAP4 
with WAP5 & WAP6, which is consistent with the subject to BART 
evaluation process as explained in Section VII. For Unit WAP4, we 
are not assuming any further reductions due to application of BART 
because of the inherently low levels of SO2 from firing 
natural gas.
---------------------------------------------------------------------------

    To estimate emissions for BART sources, we multiplied the average 
heat input from 2016-2020 by a presumptive BART emission rate of 0.15 
lb/MMBtu.\108\ To obtain a conservative estimate for non-BART units, we 
used the maximum annual emissions from the 2016-2020 period for each 
unit. The use of the maximum annual emissions from the 2016-2020 period 
for each non-BART unit provides a conservative assumption of emissions 
anticipated from these units to represent a scenario in which they are 
not participating in the Texas SO2 Trading Program. We then 
added the estimated emissions from the BART units together with the 
estimated emissions from the non-BART units to compare emissions 
between the Texas SO2 Trading Program and BART. Sources that 
have recently shutdown were not included in the analysis. In addition 
to comparing emission levels under source-specific BART to the 
assurance level of the Texas SO2 Trading Program, we also 
consider the impact of source-specific BART on current emissions levels 
under the program.
---------------------------------------------------------------------------

    \108\ The Fayette BART units (Units 1 and 2) are currently 
operating well below 0.15 lb/MMBtu. For these units, the maximum 
annual emissions from 2016-2020 were used in this comparison.
---------------------------------------------------------------------------

    Table 1 shows 2021 annual emissions in one column, and the other 
column shows estimated emissions under the presumptive BART assumptions 
plus the maximum annual emissions from the 2016-2020 period for those 
non-BART units as described in the paragraph above. The 2021 emissions 
are the most recent annual emissions available at the time of this 
action and represent emissions under the Texas SO2 Trading 
Program regulations, including the amended provisions in the 2020 final 
action. Under these conservative assumptions, presumptive BART for 
those BART-eligible units plus the maximum annual emissions from the 
2016-2020 period for those non-BART units still results in an 
approximately 32 percent reduction in total estimated emissions as 
compared to actual emissions for these same sources as provided for 
under the Texas SO2 Trading Program. This is a significant 
reduction compared to actual emissions and far below the assurance 
level of 255,083 tons per year. Additionally, in looking at only 
subject-to-BART units, presumptive BART reduces emissions by more than 
70,000 tons as compared to what those units are emitting under the 
Texas SO2 Trading Program. The estimated emissions for the 
BART sources under presumptive BART of 24,108 tons is also far below 
the allowance allocations to these units of 96,487 tons of allowances 
per year. As detailed in Section VIII, our determinations of source-
specific BART result in even larger emission reductions than what was 
calculated here under these presumptive BART assumptions.

[[Page 28931]]



   Table 1--Comparison of Actual Emissions Under the Texas SO2 Trading
                   Program and Presumptive BART \109\
------------------------------------------------------------------------
                                                        Presumptive BART
                                                         emissions plus
                                       2021 Actual       max. emissions
                                     emissions (tons)     for non-BART
                                                             (tons)
------------------------------------------------------------------------
Total (SO2 Trading Program Units).            129,790             88,023
Total (Subject-to-BART units only)             96,601             24,108
------------------------------------------------------------------------

    Because the alternative program under review, the Texas 
SO2 Trading Program, results in much higher emissions than 
source-specific BART, we are proposing to find that the Texas 
SO2 Trading Program does not meet the requirements of a BART 
alternative under 40 CFR 51.308(e)(2). As discussed earlier, if the 
distribution of emissions under the alternative program is not 
substantially different than under BART, and the alternative program 
results in greater emissions reductions of each relevant pollutant than 
under BART, then the alternative program may be deemed to achieve 
greater reasonable progress.\110\ The Texas SO2 Trading 
Program under review does not result in greater emission reductions 
than under BART. Rather, compared to the presumptive BART scenario, 
emissions from sources covered by the Texas SO2 Trading 
Program are similar or higher. Furthermore, the Texas SO2 
Trading Program does not secure emission reductions at non-BART sources 
in Texas to compensate for the higher than BART emissions at the Texas 
BART sources. In these situations, a BART alternative program can only 
achieve greater reasonable progress than BART when emission reductions 
from non-BART sources are large enough (or the resulting visibility 
benefits from those reductions are large enough) to compensate for 
smaller emission reductions at BART sources than would be achieved 
under source-specific BART.
---------------------------------------------------------------------------

    \109\ See ``Annual EI Texas thru 2021.xlsx'' available in the 
docket for this action.
    \110\ 40 CFR 51.308(e)(2)(E), (e)(3).
---------------------------------------------------------------------------

    This finding that the Texas SO2 Trading Program, which 
was designed to achieve a stringency level on par with CSAPR, does not 
achieve greater reasonable progress than BART, when isolated to the 
units in Texas, is not surprising, and it does not undermine the 
continued validity of CSAPR as a BART-alternative in other States. As 
discussed earlier in Section IV.B.2, the CSAPR program resulted in 
large emission reductions anticipated to occur in the eastern half of 
the country due to its coverage of both many BART sources and many non-
BART sources. However, this was not true for every State. Texas, for 
instance, generally had higher emissions under the CSAPR BART 
alternative compared to source-specific BART, since it had relatively 
more BART-eligible sources compared to many other States in the eastern 
United States. As discussed, Texas was removed from the CSAPR 
SO2 trading program in September 2017, and therefore, cannot 
rely on the reductions in the eastern half of the country brought about 
by CSAPR because the Texas SO2 Trading Program is 
independent of CSAPR. As an independent BART alternative, the Texas 
SO2 Trading Program is deficient because it secures no 
additional emission reductions from any non-BART sources and, as 
demonstrated, the BART emission reductions that would need to be offset 
are very large. Because the Texas SO2 Trading Program 
secures no reductions (and in fact would have permitted significant 
growth in emissions from current levels), the establishment of source-
specific BART emission limits would result in large additional emission 
reductions by comparison that would result in comparatively greater 
visibility benefits. Accordingly, the Texas SO2 Trading 
Program does not provide for greater reasonable progress than the 
installation and operation of BART, and therefore, fails to meet the 
requirements for a BART alternative under the Regional Haze Rule. Thus, 
we are proposing to withdraw the Texas SO2 Trading Program 
and instead propose to satisfy the Regional Haze Rule's SO2 
BART requirements through conducting a source-specific BART analysis 
for certain BART-eligible EGU sources identified in Sections VII and 
VIII of this action.

V. CSAPR Participation as a BART Alternative

A. Introduction

    If the proposed source-specific BART requirements in Texas are 
finalized, the analytical basis within the EPA's withdrawal of Texas 
from the CSAPR trading programs for annual NOX and 
SO2 in September of 2017 will be restored (82 FR 45481). 
Therefore, the EPA is proposing to find that, if this proposal to 
implement source-specific BART requirements at certain EGUs in Texas is 
finalized, the analytical basis for concluding that the implementation 
of CSAPR in the remaining covered States will continue to meet the 
criteria for a BART alternative for those States remains valid. Related 
to this finding, the EPA is also proposing to deny a 2020 
administrative petition for partial reconsideration brought by Sierra 
Club, National Parks Conservation Association (NPCA), and Earthjustice 
of the EPA's June 2020 denial of a 2017 petition to reconsider the 
EPA's original September 2017 finding, the details of which are 
provided in the next sections. Based on this analysis, the EPA is 
affirming the current Regional Haze Rule provision allowing States 
whose EGUs continue to participate in a CSAPR trading program for a 
given pollutant to continue to rely on CSAPR participation as a BART 
alternative for its BART-eligible EGUs for that pollutant. The public 
is invited to comment on this proposed basis for denying the 2020 
petition for partial reconsideration.

B. Background

1. CSAPR Better-Than-BART
a. General Background
    CSAPR (76 FR 48208; Aug. 8, 2011) implements a series of emissions 
trading programs for sulfur dioxide (SO2) and nitrogen 
oxides (NOX) across the eastern United States to address 
interstate ozone and fine particulate (PM2.5) pollution 
under CAA section 110(a)(2)(D)(i)(I) (the ``good neighbor 
provision'').\111\ The EPA has issued regulations allowing the CSAPR 
States to rely on participation in these trading programs in lieu of 
requiring source-specific BART controls at their BART-eligible EGUs 
covered by one or more of the CSAPR trading programs with respect to 
the visibility pollutant at issue (i.e., NOX or 
SO2). See

[[Page 28932]]

40 CFR 51.308(e)(4).\112\ This determination authorizing reliance on 
CSAPR participation as a BART alternative is often referred to as 
``CSAPR Better-Than-BART.'' \113\
---------------------------------------------------------------------------

    \111\ 42 U.S.C. 7410(a)(2)(D)(i)(I).
    \112\ The EPA had previously made a similar finding for the 
predecessor to CSAPR, the Clean Air Interstate Rule (CAIR), and this 
determination was upheld in UARG v. EPA, 471 F.3d 1333 (D.C. Cir. 
2006) (UARG I).
    \113\ 77 FR 33642 (June 7, 2012).
---------------------------------------------------------------------------

    In the EPA's 2012 action promulgating CSAPR Better-Than-BART, the 
EPA used air quality modeling to show CSAPR met the two-pronged 
numerical test for a BART alternative.\114\ To account for certain 
CSAPR State-budget increases that were made after the initial modeling 
was conducted, the 2012 CSAPR Better-Than-BART determination also 
included a sensitivity analysis (2012 sensitivity analysis) that 
examined the effect of those budget increases on the modeled visibility 
impacts for the CSAPR scenario.\115\ In the 2012 action, the EPA found 
that under a scenario analyzing the visibility benefits of CSAPR 
(referred to as the ``CSAPR + BART-Elsewhere'' scenario), visibility 
would not decline in any Class I area compared to a baseline scenario, 
satisfying the first prong of the two-pronged BART-alternative test. 
The EPA also found that the CSAPR + BART-Elsewhere scenario would 
result in an overall improvement in visibility on average across 
affected Class I areas, as compared to a scenario analyzing visibility 
benefits resulting from ``presumptive'' BART limits at all BART-
eligible sources (referred to as the ``nationwide BART'' scenario), 
satisfying the second prong of the two-pronged BART-alternative test. 
The EPA's findings held true whether looking at the 60 Class I areas in 
the eastern U.S. most heavily impacted by the sources subject to CSAPR 
or looking at all 140 Class I areas in the continental United States. 
The United States Court of Appeals for the D.C. Circuit (D.C. Circuit) 
upheld this action in UARG v. EPA, 885 F.3d 714 (D.C. Cir. 2018) (UARG 
II).
---------------------------------------------------------------------------

    \114\ 40 CFR 51.308(e)(3); See generally 77 FR 33642 (June 7, 
2012).
    \115\ See 77 FR 33642, 33651-52; This sensitivity analysis was 
included in a technical memo accompanying the 2012 action. See 
``Sensitivity Analysis Accounting for Increases in Texas and Georgia 
Transport Rule State Budgets,'' Docket ID No. EPA-HQ-OAR-2011-0729 
and in the docket for this action at document ID EPA-R06-OAR-2016-
0611-0113.
---------------------------------------------------------------------------

    To account for certain CSAPR State-budget increases that were made 
after the initial modeling was conducted, the 2012 CSAPR Better-Than-
BART determination also included a sensitivity analysis (2012 
sensitivity analysis) that examined the effect of those budget 
increases on the modeled visibility impacts for the CSAPR + BART-
Elsewhere scenario.\116\ The EPA determined that the increases in 
SO2 and NOX budgets were small enough that they 
did not require a comprehensive set of new power sector and air quality 
modeling. Instead, the 2012 sensitivity analysis applied a simple, but 
very conservative adjustment factor to the existing quantitative air 
quality modeling results to show that, even with the higher emissions 
budgets, the CSAPR + BART-Elsewhere scenario was still projected to 
show greater reasonable progress toward natural visibility than the 
Nationwide BART scenario. Specifically, the 2012 sensitivity analysis 
applied adjustments to visibility impacts in the CSAPR + BART-Elsewhere 
scenario to account for increases in the SO2 budgets for 
Texas and Georgia, since SO2-driven impacts were the most 
important impacts in the analysis and Texas and Georgia had the largest 
SO2 budget increases.
---------------------------------------------------------------------------

    \116\ See 77 FR 33642, 33651-52; This sensitivity analysis was 
included in a technical memo accompanying the 2012 action. See 
``Sensitivity Analysis Accounting for Increases in Texas and Georgia 
Transport Rule State Budgets,'' Docket ID No. EPA-HQ-OAR-2011-0729 
and in the docket for this action at document ID EPA-R06-OAR-2016-
0611-0113.
---------------------------------------------------------------------------

    The 2012 sensitivity analysis identified sets of Class I areas that 
are most impacted by emissions in Texas (9 areas) and Georgia (7 areas) 
and assumed that all of the modeled visibility improvement in those 
sets of Class I areas is due to SO2 emissions reductions 
from either Texas or Georgia, respectively. This methodology is highly 
conservative because the projected SO2 emissions reductions 
in Texas and Georgia represented only 4.4 percent and 1.8 percent, 
respectively, of the total projected regional emissions reductions in 
the CSAPR + BART-Elsewhere scenario, and the Class I areas most 
impacted by Texas and Georgia emissions are also affected by the very 
large emissions reductions projected from other States in the regional 
CSAPR + BART-Elsewhere scenario. By assuming a linear relationship 
between emissions increases in Texas and Georgia and visibility 
degradation in those Class I areas, the EPA very conservatively 
determined that even with the budget increases, the CSAPR + BART-
Elsewhere scenario was projected to achieve greater visibility 
improvement than the Nationwide BART scenario on average across all 60 
eastern Class I areas and all 140 nationwide Class I areas, thereby 
satisfying the second prong of the two-pronged test under 40 CFR 
51.308(e)(3). The sensitivity analysis also showed no visibility 
degradation in the CSAPR + BART-Elsewhere scenario relative to the 
baseline scenario at any Class I area, thereby satisfying the first 
prong of the test.
b. The CSAPR Remand and the EPA's 2017 Affirmation of CSAPR Better-
Than-BART
    The original 2011 CSAPR action was largely upheld by the Supreme 
Court in 2014.\117\ However, the case was remanded to the D.C. Circuit 
to assess whether the EPA may have ``over-controlled'' certain States 
for purposes of implementing the good neighbor provision. In EME Homer 
City Generation, L.P. v. EPA, 795 F.3d 118 (D.C. Cir. 2015), based on 
this potential for overcontrol, the court remanded certain State 
budgets to the EPA, including Texas' SO2 budget, which the 
EPA had established to address PM2.5 transport.
---------------------------------------------------------------------------

    \117\ EPA v. EME Homer City Generation, L.P., 572 U.S. 489 
(2014).
---------------------------------------------------------------------------

    To address the remand, in November 2016, the EPA proposed to remove 
Texas EGUs from the CSAPR SO2 Group 2 Trading Program as 
well as the CSAPR NOX Annual Trading Program, which 
similarly addressed PM2.5 transport.\118\ The EPA indicated 
that if the withdrawal was finalized, Texas would no longer be eligible 
under 40 CFR 51.308(e)(4) to rely on participation of its EGUs in a 
CSAPR trading program as an alternative to source-specific 
SO2 BART determinations.\119\ The EPA also provided a 
proposed analysis (2016 proposed analysis) showing that the changes in 
the geographic scope of CSAPR coverage since the EPA's original 2012 
CSAPR Better-Than-BART determination, including the proposed withdrawal 
of Texas EGUs from the CSAPR SO2 and annual NOX 
trading programs, would not have altered the 2012 determination because 
the changes would not have altered the EPA's analytical findings that 
both prongs of the two-pronged test for a BART alternative under 40 CFR 
51.308(e)(3) were satisfied.\120\
---------------------------------------------------------------------------

    \118\ See 81 FR 78954 (Nov. 10, 2016).
    \119\ Id. at 78956; the EPA also noted that because Texas EGUs 
would continue to participate in a CSAPR trading program for ozone-
season NOX emissions, Texas would still be eligible under 
40 CFR 51.308(e)(4) to rely on CSAPR participation as an alternative 
to source-specific NOX BART determinations for the 
covered sources. 81 FR at 78962.
    \120\ See id. at 78961-64.
---------------------------------------------------------------------------

    In September 2017, the EPA finalized the withdrawal of Texas EGUs 
from the

[[Page 28933]]

CSAPR SO2 and annual NOX programs.\121\ In the 
same action, the EPA also issued its final analysis (2017 final 
analysis) showing that, even with Texas EGUs no longer participating in 
these programs (and other changes in the geographic coverage of CSAPR), 
the EPA's original 2012 analytical finding that CSAPR is better than 
BART remained valid.\122\ In response to comments received on the 2016 
proposed analysis, the EPA's 2017 final analysis included an evaluation 
of the potential impact of emissions shifting under both prongs of the 
two-pronged test for a BART alternative under 40 CFR 51.308(e)(3). This 
analysis focused on the fact that if Texas sources were withdrawn from 
the CSAPR SO2 Group 2 Trading Program, they would no longer 
purchase up to 22,300 SO2 allowances from sources in other 
Group 2 States, as had been projected in the CSAPR + BART-Elsewhere 
scenario used in the 2012 CSAPR Better-Than-BART determination. As to 
the first prong, the EPA explained that, relative to a baseline 
scenario without CSAPR or BART, a revised CSAPR + BART-Elsewhere 
scenario with an increased quantity of SO2 allowances 
available for use by units in other Group 2 States would still show no 
visibility degradation at any Class I area because, absent unusual 
circumstances that the EPA showed were not expected to occur in this 
case, all units in the remaining Group 2 States would still have 
stronger incentives to control their SO2 emissions in the 
revised CSAPR + BART-Elsewhere scenario (with some positive allowance 
price) than in the baseline scenario (without any allowance 
price).\123\
---------------------------------------------------------------------------

    \121\ See 82 FR 45481 (September 29, 2017).
    \122\ See id. at 45490-94.
    \123\ Id. at 45493.
---------------------------------------------------------------------------

    As to the second prong, the EPA assumed that the availability of 
22,300 additional allowances would result in a 22,300-ton increase in 
emissions in the remaining Group 2 States, but observed that the 
potential adverse visibility impacts of those emissions would be more 
than offset by the favorable visibility impacts of at least 127,300 
tons of reduced emissions in Texas under presumptive source-specific 
SO2 BART for the State's BART-eligible EGUs.\124\ In other 
words, under the methodological framework the EPA devised in 2012 to 
compare CSAPR with BART, see 77 FR 33648-49, the EPA concluded that the 
``Transport Rule [CSAPR] + BART Elsewhere'' scenario would still 
outperform the ``Nationwide BART'' scenario, even if Texas's EGU BART 
sources fell under the ``BART Elsewhere'' category rather than the 
CSAPR category. Thus, the EPA's conclusion that CSAPR satisfied the 
second prong of the two-pronged test rested in part on assuming net 
SO2 reductions of approximately 105,000 tons from 
presumptive source-specific BART in Texas, after accounting for the 
potential for shifting of 22,300 tons of emissions from Texas to the 
remaining Group 2 States.\125\
---------------------------------------------------------------------------

    \124\ Id. at 45493-94.
    \125\ 82 FR 45493-94.
---------------------------------------------------------------------------

2. Promulgation and Affirmation of the Texas SO2 Trading 
Program as a BART Alternative
    As explained in Section II.C, rather than finalize source-specific 
BART SO2 emission limits for subject-to-BART EGUs in Texas 
(as had been assumed in the September 2017 finding affirming CSAPR as 
better than BART), the EPA took final action in October 2017 
establishing an intrastate trading program for SO2 for 
certain Texas EGUs as an alternative to BART.\126\ On June 29, 2020, 
after completing rulemaking proceedings on reconsideration, the EPA 
affirmed the Texas SO2 Trading program as a BART 
alternative, with certain amendments as proposed in November 2019.\127\ 
This rulemaking, its rationale, and subsequent reconsideration and 
affirmation in June 2020 are summarized in Section II.C and are not 
repeated here.
---------------------------------------------------------------------------

    \126\ See 82 FR 48324 (October 17, 2017); In the same January 
2017 and October 2017 notices, the EPA also proposed and finalized 
action to rely on CSAPR participation as a NOX BART 
alternative for Texas EGUs, see 82 FR at 946; 82 FR at 48361.
    \127\ 85 FR 49170 (Aug. 12, 2020).
---------------------------------------------------------------------------

3. The EPA's Denial of Petition for Reconsideration of the 2017 
Affirmation of CSAPR As a BART Alternative
    On November 28, 2017, the Sierra Club and NPCA submitted a petition 
for partial reconsideration (2017 petition) under CAA section 
307(d)(7)(B) of our September 29, 2017 action withdrawing Texas from 
the CSAPR trading programs for SO2 and annual NOX 
and affirming that CSAPR participation continues to satisfy 
requirements as a BART alternative (September 2017 Final Rule).\128\ 
The petitioners alleged that it was impracticable, and indeed 
impossible, to comment on the relationship between the Texas 
SO2 Trading Program and the CSAPR Better-Than-BART analysis 
in the final rule because the EPA did not finalize the Texas 
SO2 Trading Program until after the final rule was signed 
and the EPA had assumed presumptive source-specific SO2 BART 
controls in the rulemaking record for the final rule.\129\ The 
petitioners also alleged it was impracticable to comment on other 
aspects of the EPA's geographic emissions shifting analysis, which was 
not presented until the final rule.\130\ The petitioners argued that 
both sets of issues are of central relevance to the September 2017 
Final Rule.
---------------------------------------------------------------------------

    \128\ The Sierra Club and National Parks Conservation 
Association, Petition for Partial Reconsideration of Interstate 
Transport of Fine Particulate Matter: Revision of Federal 
Implementation Plan Requirements for Texas; Final Rule; 82 FR 45,481 
(September 29, 2017); EPA-HQ-OAR-2016-0598; FRL-9968-46-OAR 
(November 28, 2017).
    \129\ Id. at 8-9.
    \130\ Id. at 9.
---------------------------------------------------------------------------

    With respect to the BART requirements in Texas, the petitioners 
argued that the final rule was ``impermissibly based upon a factual 
predicate that no longer exists--namely, that sulfur dioxide emission 
reductions associated with the installation of presumptive source-
specific BART would be install [sic] at Texas EGUs.'' \131\ The 
petitioners went on to purportedly demonstrate, using the 2012 
sensitivity analysis methodology developed by the EPA, that source-
specific BART in Texas would improve visibility in Class I areas in or 
affected by Texas more than CSAPR or the Texas SO2 Trading 
Program.\132\
---------------------------------------------------------------------------

    \131\ Id. at 10.
    \132\ Id. at 11-13.
---------------------------------------------------------------------------

    Concurrently with the affirmation of the Texas SO2 
Trading Program on June 29, 2020, the EPA issued a denial of the 2017 
petition (2020 Denial).\133\ In addition to addressing the other 
objections raised in the 2017 petition,\134\

[[Page 28934]]

the EPA included an updated sensitivity analysis (2020 sensitivity 
analysis) assessing whether CSAPR would remain a valid BART alternative 
based on assumptions regarding emissions performance under the Texas 
SO2 Trading Program rather than source-specific BART.\135\ 
The EPA used the same methodology it had used in its 2012 CSAPR Better-
Than-BART determination and applied an emissions assumption for the 
Texas SO2 Trading Program used by Petitioners in their 2017 
petition of 320,600 tons of SO2 per year. The EPA also used 
an assumption that there would be a 22,300-ton increase in emissions in 
a single State in the Group 2 trading program, Georgia.\136\ The EPA 
presented the results of this analysis in Table 3 of the 2020 Denial, 
and we asserted that for purposes of the ``prong 2'' portion of the 
BART analysis, that CSAPR continued to perform equal to or better than 
BART.\137\ Based on this analysis, the EPA reaffirmed the 2012 CSAPR 
Better-Than-BART determination, albeit now on the assumption of the 
Texas SO2 Trading Program operating in Texas rather than 
CSAPR or presumptive source-specific BART.\138\
---------------------------------------------------------------------------

    \133\ 85 FR 40286 (July 6, 2020) (``2020 Denial''); See, e.g., 
Letter from U.S. EPA Administrator Andrew Wheeler to Joshua Smith, 
Sierra Club, denying petition for reconsideration (June 29, 2020), 
Docket ID EPA-HQ-OAR-2016-0598-0036. The EPA concurrently sent 
identical letters to other petitioners. This letter, rather than the 
Federal Register notice, is what we refer to when citing specific 
pages in the ``2020 Denial.''
    \134\ In their 2020 petition for partial reconsideration 
summarized below, Petitioners did not renew their objections as to 
other aspects of the EPA's analysis in the 2020 Denial and therefore 
these issues will not be summarized here. As to the issues not 
raised in their 2020 petition, but addressed in denying their 2017 
petition, the EPA is not reopening the bases for denial of these 
objections set forth in its 2020 Denial letter. We note that in 
their 2020 petition for partial reconsideration, Petitioners noted 
that they ``continue to object'' to the EPA's use of ``presumptive'' 
BART limits in its CSAPR better than BART analysis. See 2020 
Petition at 5 n.10. The EPA is not revisiting this issue here. The 
EPA explained in its 2020 Denial why this objection did not meet 
either prong of the CAA section 307(d)(7)(B) test for mandatory 
reconsideration, including that petitioners could have, but did not, 
comment on this issue in the original 2017 affirmation rulemaking 
proceeding. See 2020 Denial at 19-20.
    \135\ 2020 Denial at 13-16.
    \136\ Id. at 14-15.
    \137\ Id. at 16.
    \138\ Note that neither in the 2020 Denial or in this present 
proposal are we reopening our determination in the September 2017 
Final Rule that withdrawal of Texas from the annual NOX 
trading program would have caused sufficient changes in modeled 
NOX emissions in a revised CSAPR scenario to materially 
alter the visibility impacts comparison. See 82 FR 45492 n.82. As 
detailed in the November 2016 proposal, projected annual 
NOX emissions from Texas EGUs were only 2,600 tons higher 
than the annual NOX emissions projected for the CSAPR + 
BART-Elsewhere case, in which it was assumed that the EGUs were 
subject to CSAPR requirements for both ozone-season and annual 
NOX emissions. The EPA determined that this relatively 
small increase in NOX emissions in the CSAPR + BART-
Elsewhere case would have been too small to cause any change in the 
results of either prong of the two-pronged CSAPR-Better-Than-BART 
test.
---------------------------------------------------------------------------

C. Summary of the 2020 Petition for Reconsideration and Associated 
Litigation

    On August 28, 2020, the Sierra Club, NPCA, and Earthjustice 
submitted a petition for partial reconsideration under CAA section 
307(d)(7)(B) of the EPA's 2020 Denial of their November 2017 petition 
for reconsideration (2020 petition).\139\ The petitioners alleged that 
because the EPA presented the updated CSAPR Better-than-BART 
sensitivity calculations for the first time in its 2020 Denial of the 
2017 Petition (and thus they were not afforded an opportunity to 
comment), and because that updated analysis is of central relevance to 
the September 2017 Final Rule, the EPA must reconsider both actions 
under CAA section 307(d)(7)(B). The petitioners alleged that, contrary 
to the EPA's conclusions in its 2020 Denial, the updated CSAPR Better-
Than-BART analysis demonstrates that visibility improvement under CSAPR 
is not equal to or greater than visibility improvement under source-
specific BART averaged over all 140 Class I areas, or the 60 eastern 
Class I areas covered by CSAPR.\140\
---------------------------------------------------------------------------

    \139\ Petition for Partial Reconsideration of Denial of Petition 
for Reconsideration and Petition for Reconsideration of the 
Interstate Transport of Fine Particulate Matter: Revision of Federal 
Implementation Plan Requirements for Texas (Aug. 28, 2020), Docket 
ID EPA-HQ-OAR-2016-0598-0041.
    \140\ Id. at 9.
---------------------------------------------------------------------------

    Specifically, Petitioners note that had the EPA's results been 
reformatted to display two decimal places instead of one, the average 
visibility improvement for the CSAPR + BART-Elsewhere scenario would 
have been less than that of the Nationwide BART scenario on two of the 
four metrics used.\141\ Thus, Petitioners concluded that the EPA's 2020 
sensitivity analysis proves that the visibility improvement in the 
CSAPR + BART-Elsewhere scenario, with the adjustments made to Texas's 
and Georgia's emissions, is not equal to or greater than the visibility 
improvement in the Nationwide BART scenario. Moreover, Petitioners also 
argue that it was impracticable for them to raise these issues 
concerning the sensitivity analysis during the comment period for the 
September 2017 Final Rule because the sensitivity calculations were 
presented for the first time in the 2020 Denial.\142\ The Petitioners 
claim that the data within the 2020 sensitivity analysis addresses an 
issue of central relevance to the September 2017 Final Rule, i.e., 
whether CSAPR results in an overall improvement in visibility compared 
to source-specific BART. Moreover, because Petitioners claim that the 
EPA's sensitivity analysis showed that source-specific BART would 
result in greater visibility improvement than CSAPR, they argue that 
the EPA's continued reliance on CSAPR as a BART alternative is 
arbitrary, capricious, and contrary to law.\143\
---------------------------------------------------------------------------

    \141\ Id. at 11.
    \142\ Id. at 12.
    \143\ Id. at 13.
---------------------------------------------------------------------------

    Sierra Club, NPCA, and Earthjustice also filed a petition for 
judicial review of the 2020 Denial in the U.S. Court of Appeals for the 
District of Columbia.\144\ On November 3, 2020, this challenge and the 
Petitioners' preexisting challenge to the September 2017 final analysis 
(No. 17-1253 (D.C. Cir.)) were consolidated. On January 13, 2021, the 
court placed the petitions for review in abeyance pending further order 
of the court, and the court directed the parties to file motions to 
govern following the EPA's action on the 2020 petition.
---------------------------------------------------------------------------

    \144\ National Parks Conservation Association et al. v. EPA, No. 
20-1341 (D.C. Cir. filed Sept. 4, 2020).
---------------------------------------------------------------------------

    The EPA is now proposing to deny the 2020 petition in this action.

D. Criteria for Granting a Mandatory Petition for Reconsideration

    Under section 307(d)(7)(B) of the Act, ``[o]nly an objection to a 
rule or procedure which was raised with reasonable specificity during 
the period for public comment . . . may be raised during judicial 
review.'' \145\ However, ``[i]f a person raising an objection can 
demonstrate . . . that it was impracticable to raise such objection 
within such time or if the grounds for such objection arose after the 
period for public comment . . . and if such objection is of central 
relevance to the outcome of the rule, the Administrator shall convene a 
proceeding for reconsideration of the rule.'' \146\ The EPA considers 
an objection to be of ``central relevance'' to the outcome of a rule 
``if it provides substantial support for the argument that the 
regulation should be revised.'' \147\
---------------------------------------------------------------------------

    \145\ 42 U.S.C. 7607(d)(7)(B).
    \146\ Id.
    \147\ See Coal. For Responsible Regulation, Inc. v. EPA, 684 
F.3d 102, 125 (D.C. Cir. 2012) (internal citation and quotation 
omitted).
---------------------------------------------------------------------------

E. The EPA's Evaluation of the Petition for Reconsideration

    The EPA proposes to deny the 2020 petition because the objections 
raised to the 2020 Denial are not ``centrally relevant'' under a 
scenario in which the EPA finalizes the proposal to withdraw the 
present BART-alternative intrastate trading FIP for Texas EGUs and 
replaces those requirements with source-specific SO2 BART 
requirements. Under this scenario, the findings made in the September 
2017 Final Rule (i.e., the EPA's finding that CSAPR remains better than 
BART) can be affirmed. The Agency acknowledges that the petitioners 
raised legitimate questions in the 2020 petition concerning the 2020 
sensitivity analysis and the conclusion that CSAPR remains better than 
BART in a scenario in which the Texas SO2 Trading Program is 
implemented. However, with this proposal and the return to source-
specific BART requirements in Texas, this issue is effectively 
resolved. The 2020 petition can therefore be denied since the

[[Page 28935]]

objection raised is no longer centrally relevant.
    For purposes of the 2012 analytic demonstration that CSAPR provides 
for greater reasonable progress than BART, the EPA treated Texas EGUs 
as subject to CSAPR for SO2 and annual NOX (as 
well as ozone-season NOX). In the September 2017 Final Rule, 
the EPA recognized that the treatment of Texas EGUs in the 2012 
analysis would have been different if those sources were not in the 
CSAPR SO2 and annual NOX programs. To address 
potential concerns about continuing to rely on CSAPR participation as a 
BART alternative for EGUs in the remaining CSAPR States, the EPA 
provided an analysis explicitly addressing the potential effect on the 
2012 analytic demonstration if the treatment of Texas (and several 
other States') EGUs had been consistent with the updated scope of CSAPR 
coverage following the D.C. Circuit's remand of CSAPR in EME Homer 
City. In particular, in its September 2017 Final Rule, the EPA assumed 
that, as for all other non-CSAPR States, Texas EGUs would be subject to 
presumptive, source-specific SO2 BART limits.
    As discussed below, if the EPA's proposal in this action to 
implement source-specific BART requirements at certain EGUs in Texas is 
finalized, the analytical basis for the EPA's September 2017 
conclusions will be restored, and that analysis will continue to 
support the conclusion that CSAPR participation would achieve greater 
reasonable progress than BART, despite the change in the treatment of 
Texas EGUs. Consequently, by virtue of this proposed action that 
relates to Texas, the EPA is also able to propose to reaffirm the 
continued validity of the CSAPR better-than-BART provision, 40 CFR 
51.308(e)(4), which authorizes the use of CSAPR participation as a BART 
alternative for BART-eligible EGUs for a given pollutant in States 
whose EGUs continue to participate in a CSAPR trading program for that 
pollutant. In the September 2017 Final Rule, the EPA evaluated whether 
a revised CSAPR scenario reflecting the removal of Texas EGUs from the 
CSAPR SO2 program (and other changes in CSAPR's geographic 
scope) would continue to satisfy the two-pronged test under 40 CFR 
51.308(e)(3). Regarding the changes in CSAPR requirements for Texas 
EGUs, the EPA determined that the changes would have no adverse impact 
on the 2012 analytic demonstration. Finalization of this proposal would 
restore the analytical bases for the EPA's conclusions in the September 
2017 Final Rule. We discuss that analysis in the following paragraphs 
and explain how it would be restored if this action is finalized as 
proposed.
    As the EPA concluded in the September 2017 Final Rule, Texas EGUs 
are ineligible to rely on CSAPR as an SO2 BART alternative. 
In this proposal, we are affirming this position and rejecting the 
contrary arguments that the Agency previously put forward in support of 
the Texas BART-alternative FIP, as explained above in Section IV. As 
explained in the November 2016 proposal,\148\ if this information had 
been available at the time of the 2012 CSAPR Better-than-BART 
demonstration, the treatment of Texas EGUs in the baseline case and in 
the Nationwide BART case would not have changed, but in the CSAPR + 
BART-Elsewhere case, Texas EGUs would have been treated as subject to 
source-specific SO2 BART instead of being treated as subject 
to CSAPR SO2 requirements. In the case of Texas, the 
projected SO2 emissions from affected EGUs in the modeled 
Nationwide BART scenario (139,300 tons per year) are considerably lower 
than the projected SO2 emissions from the affected EGUs in 
the CSAPR + BART-Elsewhere scenario (266,600 tons per year as modeled, 
and up to approximately 317,100 tons, as addressed in the 2012 
sensitivity analysis).
---------------------------------------------------------------------------

    \148\ See 81 FR 78954 (Nov. 10, 2016).
---------------------------------------------------------------------------

    As modeled, treating Texas EGUs in the CSAPR + BART-Elsewhere 
scenario as subject to source-specific SO2 BART instead of 
CSAPR SO2 requirements would therefore have reduced 
projected SO2 emissions by between 127,300 tons and 
approximately 177,800 tons in this scenario, thereby improving 
projected air quality in this scenario relative to projected air 
quality in both the Nationwide BART scenario and the baseline 
scenario.\149\ At the lower end of this range, a reduction in 
SO2 emissions of 127,300 tons would represent a reduction of 
over four percent of the total SO2 emissions from EGUs in 
all modeled States in the CSAPR + BART-elsewhere scenario. The EPA has 
previously observed that the visibility improvements from CSAPR 
relative to BART are primarily attributable to the greater reductions 
in SO2 emissions from CSAPR across the overall modeled 
region in the CSAPR + BART-Elsewhere scenario relative to the 
Nationwide BART scenario.
---------------------------------------------------------------------------

    \149\ As explained in greater detail in Section IV, while many 
States participating in CSAPR were projected to have substantially 
lower SO2 emissions under CSAPR as compared to 
implementing BART requirements, this was not the case for Texas's 
EGUs.
---------------------------------------------------------------------------

    With a return to source-specific SO2 BART requirements 
at the relevant Texas EGUs, this analysis will continue to (or, once 
again will) be valid. Further, we propose to find that the conclusions 
reached in the September 2017 Final Rule regarding ``emissions 
shifting'' from Texas back into the remaining CSAPR region would remain 
valid if source-specific BART requirements are implemented at the 
relevant Texas EGUs. The September 2017 Final Rule responded to a 
comment regarding potential ``emissions shifting'' when Texas was 
removed from the CSAPR SO2 trading program. For purposes of 
the second prong, to account for the effect of potential emissions 
shifting caused by the fact that Texas sources would no longer purchase 
SO2 allowances from sources in other CSAPR Group 2 States, 
the EPA assumed that SO2 emissions in Georgia could increase 
by up to 22,300 tons, the quantity of allowances that Texas had been 
projected to purchase from the other Group 2 States in the original 
CSAPR scenario. However, as detailed above, the EPA showed in 2017 that 
a potential shift of up to 22,300 SO2 tons to Georgia (or 
other CSAPR States) would be dwarfed by the lower SO2 tons 
emitted in Texas under a source-specific BART scenario (127,300 tons or 
more). Therefore, the EPA proposes that the September 2017 Final Rule's 
conclusion that CSAPR would continue to pass both prongs of the better-
than-BART test, even accounting for emissions shifting, remains valid 
(or will once again be valid) if this proposal is finalized and source-
specific BART is implemented in Texas.
    In summary, the EPA proposes to affirm that if the information 
regarding the proposed withdrawal of CSAPR FIP requirements for 
SO2 for Texas EGUs had been available at the time of the 
2012 CSAPR Better-than-BART analytic demonstration, the CSAPR + BART-
Elsewhere scenario would have reflected SO2 emissions from 
Texas EGUs under presumptive source-specific BART. This would have been 
127,300 or more tons per year lower than the emissions projections 
under CSAPR and remains a valid assumption so long as the presumed 
source-specific SO2 BART reductions are in fact required in 
Texas. Under this assumption--which is, again, made possible by 
withdrawing the current BART-alternative FIP and implementing source-
specific BART in Texas as outlined in this proposal--emissions would 
not have changed in the Nationwide BART or baseline scenarios. Instead, 
modeled visibility improvement in the CSAPR + BART-Elsewhere scenario 
would have been

[[Page 28936]]

even larger relative to the other scenarios than what was modeled in 
the 2012 analytic demonstration.
    Lower SO2 emissions in Texas (after implementation of 
source-specific BART) would clearly lead to more visibility improvement 
on the best and worst visibility days in the nearby Class I areas. 
Since the ``original'' CSAPR + BART-Elsewhere scenario passed both 
prongs of the better-than-BART test (compared to the Nationwide BART 
scenario and the baseline scenario), a modified CSAPR + BART-Elsewhere 
scenario without Texas in the CSAPR region would without question also 
have passed both prongs of the better-than-BART test. The EPA therefore 
further proposes that there is no need to do any new modeling or more 
complicated sensitivity analysis to affirm the findings of the 
September 2017 Final Rule. And for the same reason, there is no need to 
do any additional modeling or analysis to support this finding under 
the current Texas BART proposal in this action (i.e., to withdraw the 
Texas SO2 Trading Program and replace the FIP with source-
specific BART for Texas EGUs), assuming this proposal is finalized.
    Therefore, the EPA proposes to deny the 2020 petition for partial 
reconsideration and proposes to again affirm the use of CSAPR as a BART 
alternative for all States whose EGUs continue to participate in the 
CSAPR trading programs as to the relevant pollutants. Specifically, the 
EPA proposes to conclude that, if the present proposal and the 
restoration of the analytical premise for the findings of the September 
2017 Final Rule are finalized, the objections that the 2020 petition 
for partial reconsideration raised as to the analysis the EPA presented 
in the 2020 Denial will be resolved and are therefore not of ``central 
relevance'' to the September 2017 Final Rule. We are providing the 
opportunity for, and invite, public comment on this proposed denial of 
the petition for partial reconsideration.

VI. The EPA's Authority To Promulgate a FIP Addressing SO2 
and PM BART

A. CAA Authority To Promulgate a FIP for SO2 BART

    Under section 110(c) of the CAA, whenever the EPA disapproves a 
mandatory SIP submission in whole or in part, the EPA is required to 
promulgate a FIP within 2 years unless we approve a SIP revision 
correcting the deficiencies before promulgating a FIP. The term 
``Federal implementation plan'' is defined in Section 302(y) of the CAA 
in pertinent part as a plan promulgated by the Administrator to correct 
an inadequacy in a SIP.
    Beginning in 2012, following the limited disapproval of the Texas 
Regional Haze SIP, the EPA has had the authority and obligation to 
promulgate a FIP to address BART for Texas EGUs for SO2. As 
discussed in Section II, we exercised this FIP authority in October 
2017 to promulgate a BART alternative (the Texas SO2 Trading 
Program) to address the inadequacy of Texas's SIP as it pertained to 
BART requirements for Texas EGUs for SO2. Because we are now 
proposing that the basis for the Texas SO2 Trading Program 
as a BART alternative rested on an erroneous interpretation of our BART 
alternative regulations, and thus proposing to withdraw the program for 
the reasons explained throughout Section IV, we have an obligation 
under the CAA to promulgate a FIP in its place. We propose to exercise 
this FIP authority through conducting a source-specific BART analysis 
for those BART-eligible EGU sources participating in the Texas 
SO2 Trading Program and, as appropriate, establish source-
specific BART emission limits and associated compliance requirements, 
as identified in Sections VII and VIII of this action.

B. Error Correction and CAA Authority To Promulgate a FIP--PM BART

    The EPA proposes that its prior approval of a portion of Texas's 
2009 Regional Haze SIP related to its finding that no EGUs were subject 
to BART requirements for PM (PM BART) was in error under CAA section 
110(k)(6). Section 110(k)(6) of the CAA provides the EPA with the 
authority to make corrections to actions that are subsequently found to 
be in error. Ass'n of Irritated Residents v. EPA, 790 F.3d 934, 948 
(9th Cir. 2015) (explaining that 110(k)(6) is a ``broad provision'' 
enacted to provide the EPA with an avenue to correct errors). The EPA 
proposes that its approval of the portion of Texas's Regional Haze SIP 
addressing PM BART for EGUs was in error, as the approval was based on 
the Texas SO2 Trading Program that was promulgated in error. 
Under CAA section 110(k)(6), once the EPA determines that its previous 
action approving a SIP revision was in error, the EPA may revise such 
action as appropriate without requiring any further submission from the 
State. To correct the error here, the EPA proposes to revise its 
previous approval of the portion of Texas's 2009 Regional Haze SIP 
addressing PM BART for EGUs and proposes to instead disapprove this 
portion of Texas's SIP.
    In the 2009 Texas Regional Haze SIP, Texas conducted a screening 
analysis of the visibility impacts from PM emissions in isolation and 
determined that no EGUs were subject to BART for PM based on an 
assumption that BART requirements for EGUs for both SO2 and 
NOX were covered by participation in an earlier trading 
program (CAIR). This decision was consistent with a 2006 EPA memorandum 
titled ``Regional Haze Regulations and Guidelines for Best Available 
Retrofit Technology (BART) Determinations''; however, that memorandum 
stated that pollutant-specific screening is only appropriate in the 
limited situation where a State is relying on a BART alternative, such 
as a trading program, to address both NOX and SO2 
BART.\150\
---------------------------------------------------------------------------

    \150\ Memorandum from Joseph Paisie to Kay Prince, ``Regional 
Haze Regulations and Guidelines for Best Available Retrofit 
Technology (BART) Determinations,'' July 19, 2006, available in the 
docket for this action.
---------------------------------------------------------------------------

    In our 2017 Texas BART FIP, we created the Texas SO2 
Trading Program as a BART alternative to satisfy SO2 BART 
requirements for EGUs. As a result, the Texas BART FIP created a 
scenario in which Texas EGUs were again subject to trading programs to 
address both NOX and SO2 BART, and therefore, the 
EPA approved the pollutant-specific screening for PM as performed by 
Texas in its 2009 Regional Haze SIP submittal. Upon further 
consideration, and as described in more detail above in Section IV, we 
have determined that the Texas SO2 Trading Program as 
promulgated in 2017, and affirmed in 2020, was based on an erroneous 
interpretation of our BART alternative regulations. As such, it failed 
to meet the requirements for a valid BART alternative and thus we are 
proposing to withdraw the Texas SO2 Trading Program and to 
satisfy SO2 BART requirements through conducting a source-
specific BART analysis. The basis for approval of Texas's SIP related 
to the BART requirements for PM for EGUs rested on our creation of a 
BART alternative for SO2, and we are proposing in this 
action to determine that the Texas SO2 Trading Program is 
not a valid BART alternative. Consistent with our proposal regarding 
the Texas SO2 Trading Program, we are also proposing that 
our approval of the portion of the 2009 Texas Regional Haze SIP related 
to PM BART requirements for EGUs was in error.
    Accordingly, the EPA is proposing to correct its previous approval 
of the Texas 2009 Regional Haze SIP submittal related to PM BART for 
EGUs by proposing to disapprove Texas's pollutant-specific PM screening 
analysis and determination that PM BART emission limits are not 
required for any

[[Page 28937]]

Texas EGUs. The EPA is proposing this action through an error 
correction under CAA section 110(k)(6). If the EPA finalizes this 
disapproval, the EPA will have the authority and obligation under CAA 
section 110(c)(1)(B), to promulgate a FIP within 2 years. As part of 
this rulemaking, the EPA proposes to promulgate a FIP addressing PM 
BART requirements and satisfying that FIP obligation. As discussed 
further in Section VII and Section VIII, the EPA is proposing source-
specific PM BART requirements for those EGUs that we propose to find 
subject to BART.

VII. BART Analysis for SO2 and PM

    As discussed in Section IV of this action, we are proposing to 
withdraw the Texas SO2 Trading Program previously 
established as an alternative to SO2 BART for Texas EGUs. 
Thus, to satisfy SO2 BART requirements for Texas, we are 
proposing to conduct a source-specific BART evaluation consistent with 
the BART Guidelines for appropriate EGU sources. Specifically, we must 
evaluate EGUs that were previously identified as BART-eligible, but for 
which no subject-to-BART determinations were made because they were 
included in the Texas SO2 Trading Program. Additionally, 
because our approval of the portion of the Texas Regional Haze SIP 
related to PM BART for EGUs was in error, we are now proposing an error 
correction to disapprove that portion of the Texas SIP. We propose to 
address the deficiency through a source-specific BART evaluation 
consistent with the BART Guidelines for PM BART for the EGU sources 
that were previously identified as BART-eligible, but for which no 
subject-to-BART determinations were made because they were included in 
the Texas SO2 Trading Program.

A. Identification of Sources Subject to BART

    In January 2016, we approved Texas's determination of which non-EGU 
sources in the State are BART-eligible and the determination that none 
of the State's BART-eligible non-EGU sources are subject to BART 
because they are not reasonably anticipated to cause or contribute to 
visibility impairment at any Class I areas.\151\ In our October 2017 
Texas BART FIP,\152\ and subsequent affirmation in 2020, addressing 
BART requirements for Texas EGUs, we noted that all BART-eligible EGUs 
in Texas are either covered by a BART alternative or have screened out 
of being subject to BART. Our October 2017 FIP lists the units covered 
by the BART alternative for SO2 (i.e., the Texas 
SO2 Trading Program) and identifies which of those units are 
BART-eligible.\153\ For those BART-eligible EGUs that were not covered 
by the Texas SO2 Trading Program, we finalized 
determinations that those EGUs are not subject-to-BART for 
NOX, SO2, and PM based on screening methods as 
described in our 2017 proposed rule and BART Screening TSD.\154\
---------------------------------------------------------------------------

    \151\ See 81 FR 296, 301 (Jan. 5, 2016).
    \152\ See 82 FR at 48328 (Oct. 17, 2017).
    \153\ 82 FR at 48329 (Oct.17, 2017).
    \154\ See 82 FR at 48328-29 (Oct.17, 2017). Table 2 in the 
October 2017 notice lists the EGUs that we finalized as being BART-
eligible, but for which we determined were not be subject-to-BART 
based on various screening analysis as more fully described in the 
2017 proposal (82 FR at 918-21). We are not reopening that 
determination in this action.
---------------------------------------------------------------------------

    Because we are now proposing to withdraw the Texas SO2 
Trading Program, we must evaluate the EGU sources that were previously 
identified as BART-eligible, but for which no subject-to-BART 
determinations were made because they were included in the Texas 
SO2 Trading Program. The sources included in the Texas 
SO2 Trading Program are identified in Table 2.

                           Table 2--Sources Included in the Texas SO2 Trading Program
----------------------------------------------------------------------------------------------------------------
              Owner/operator                             Units                          BART-eligible
----------------------------------------------------------------------------------------------------------------
AEP......................................  Welsh Power Plant Unit 1........  Yes.
                                           Welsh Power Plant Unit 2........  Yes.
                                           Welsh Power Plant Unit 3........  No.
                                           H W Pirkey Power Plant Unit 1...  No.
                                           Wilkes Unit 1 [dagger]..........  Yes.
                                           Wilkes Unit 2 [dagger]..........  Yes.
                                           Wilkes Unit 3 [dagger]..........  Yes.
CPS Energy...............................  J. T. Deely Unit 1..............  Yes.
                                           J. T. Deely Unit 2..............  Yes.
                                           O. W. Sommers Unit 1 [dagger]...  Yes.
                                           O. W. Sommers Unit 2 [dagger]...  Yes.
LCRA.....................................  Fayette/Sam Seymour Unit 1......  Yes.
                                           Fayette/Sam Seymour Unit 2......  Yes.
Luminant.................................  Big Brown Unit 1................  Yes.
                                           Big Brown Unit 2................  Yes.
                                           Martin Lake Unit 1..............  Yes.
                                           Martin Lake Unit 2..............  Yes.
                                           Martin Lake Unit 3..............  Yes.
                                           Monticello Unit 1...............  Yes.
                                           Monticello Unit 2...............  Yes.
                                           Monticello Unit 3...............  Yes.
                                           Sandow Unit 4...................  No.
                                           Stryker ST2 [dagger]............  Yes.
                                           Graham Unit 2 [dagger]..........  Yes.
                                           Coleto Creek Unit 1.............  Yes.
NRG......................................  Limestone Unit 1................  No.
                                           Limestone Unit 2................  No.
                                           W. A. Parish Unit WAP4 [dagger].  Yes.
                                           W. A. Parish Unit WAP5..........  Yes.
                                           W. A. Parish Unit WAP6..........  Yes.
                                           W. A. Parish Unit WAP7..........  No.
Xcel.....................................  Tolk Station Unit 171B..........  No.
                                           Tolk Station Unit 172B..........  No.

[[Page 28938]]

 
                                           Harrington Unit 061B............  Yes.
                                           Harrington Unit 062B............  Yes.
                                           Harrington Unit 063B............  No.
El Paso Electric.........................  Newman Unit 2 [dagger]..........  Yes.
                                           Newman Unit 3 [dagger]..........  Yes.
                                           Newman Unit **4 [dagger]........  Yes.
                                           Newman Unit **5[dagger].........  Yes.
----------------------------------------------------------------------------------------------------------------
[dagger] Gas-fired or gas/fuel oil-fired units.

    Some of the BART-eligible sources that were included in the Texas 
SO2 Trading Program have retired. Welsh Unit 2 retired in 
2016 \155\ and Big Brown,\156\ Monticello,\157\ and the J.T. Deely 
units retired at the end of 2018.\158\ These shutdowns are permanent 
and enforceable because the CAA permits for these units have been 
cancelled or the units have been withdrawn from the facilities' Title V 
operating permits. These units may not return to operation without 
going through CAA new source permitting and Title V operating 
permitting requirements. Therefore, because the units are permanently 
retired, it is not necessary to include these units in our screening 
analysis to determine whether these sources are subject to BART.
---------------------------------------------------------------------------

    \155\ Welsh Unit 2 was retired on April 16, 2016, pursuant to a 
Consent Decree (No. 4:10-cv-04017-RGK) and subsequently removed from 
the Title V permit (permit no. O26). We have included the Consent 
Decree, permitting notes, and new Title V permit showing that the 
Unit is removed in the docket for this action.
    \156\ See letter dated March 27, 2018, from Kim Mireles of 
Luminant to the TCEQ requesting to cancel certain air permits and 
registrations for Big Brown available in the docket (EPA-R06-OAR-
2016-0611-0132) for this action.
    \157\ See letter dated February 8, 2018, from Kim Mireles of 
Luminant to the TCEQ requesting to cancel certain air permits and 
registrations for Monticello available in the docket (EPA-R06-OAR-
2016-0611-0130) for this action.
    \158\ See letter dated December 15, 2021, from Johnny Bowers, 
Team Leader Air Permits Division at TCEQ to Danielle Frerich 
regarding the cancellation of air quality permits for the J.T. Deely 
units available in the docket for this action.
---------------------------------------------------------------------------

    To determine which of those remaining BART-eligible sources listed 
in Table 2 are anticipated to cause or contribute to visibility 
impairment in any Class I area (subject-to-BART),\159\ the BART 
Guidelines state that CALPUFF or another appropriate model can be used 
to predict the visibility impacts from a single source at a Class I 
area. The BART source is the collection of BART-eligible emission units 
at a facility. A detailed discussion of the subject-to-BART screening 
analysis is provided in the 2023 BART Modeling TSD.\160\ We summarize 
the methodology and results of this analysis here.
---------------------------------------------------------------------------

    \159\ See 40 CFR part 51, Appendix Y, III, How to Identify 
Sources ``Subject to BART.''
    \160\ See our 2023 BART Modeling TSD in our docket.
---------------------------------------------------------------------------

1. Modeling Approach
    For States (or the EPA in the case of a FIP) using modeling to 
determine the applicability of BART to single sources, the first step 
in the BART Guidelines is to set a contribution threshold to assess 
whether the impact of a single source (collectively the BART-eligible 
units at a specific facility) is sufficient to cause or contribute to 
visibility impairment at a Class I area. The BART Guidelines preamble 
advises that, ``for purposes of determining which sources are subject 
to BART, States should consider a 1.0 deciview (dv) change or more from 
an individual source to `cause' visibility impairment, and a change of 
0.5 dv to `contribute' to impairment.'' \161\ The BART Guidelines 
further advise that ``States should have discretion to set an 
appropriate threshold depending on the facts of the situation,'' but 
``[a]s a general matter, any threshold that you use for determining 
whether a source `contributes' to visibility impairment should not be 
higher than 0.5 dv,'' and describe situations in which States may wish 
to exercise their discretion to set lower thresholds, mainly in 
situations in which a large number of BART-eligible sources within the 
State and in proximity to a Class I area justify this approach.\162\ We 
do not believe that the sources under consideration in this rule, most 
of which are not in close proximity to a Class I area, merit the 
consideration of a lower contribution threshold. Therefore, our 
analysis employs a contribution threshold of 0.5 dv.
---------------------------------------------------------------------------

    \161\ 70 FR at 39118.
    \162\ 70 FR at 39118.
---------------------------------------------------------------------------

    In this action we conducted modeling using both CALPUFF \163\ and 
CAMx.\164\ In the 2005 BART Guidelines, CALPUFF was in part chosen 
because it is much less resource intensive with respect to required 
computing power, run time, and development of model inputs than 
chemical transport models such as CAMx. Additionally, CAMx tools for 
assessing single source impacts were still undergoing development at 
that time. CAMx tools have advanced since 2005, and while still 
resource intensive, for this action we were able to conduct CAMx 
modeling using TCEQ's modeling platform as a starting point for this 
assessment. We discuss details of the CALPUFF and CAMx modeling systems 
throughout this section and in the 2023 BART Modeling TSD.
---------------------------------------------------------------------------

    \163\ EPA used the version of CALPUFF approved previously for 
regulatory modeling (CALPUFF version 5.8.5, level 15214) as 
discussed on EPA's website (https://www.epa.gov/scram/air-quality-dispersion-modeling-alternative-models) and this CALPUFF version is 
available for download from Exponent at https://www.src.com/.
    \164\ CAMx is available for download at https://www.camx.com/.
---------------------------------------------------------------------------

    As recommended in the BART Guidelines, we performed stand-alone, 
source-specific CALPUFF modeling on several of the remaining BART-
eligible sources included in Table 2 to determine which of the BART-
eligible sources in Table 2 cause or contribute to visibility 
impairment in nearby Class I areas. CALPUFF is a multi-species non-
steady-state puff dispersion model that simulates the effects of 
pollution transport, dispersion, transformation, and removal of 
emissions from modeled sources for transport distances beyond 50 km 
using general background concentrations to represent air pollution 
levels that the modeled sources emissions interact. Relevant guidance 
\165\ States that the CALPUFF

[[Page 28939]]

model is generally applicable at distances from 50 km to at least 300 
km downwind of a source. However, previous Regional Haze BART SIP 
modeling conducted by consultants and the States extended beyond 300km 
for numerous BART analyses.\166\ In fact, in evaluating the Texas 2009 
Regional Haze SIP, the EPA, FLM representatives, and TCEQ agreed with 
using CALPUFF for Texas sources for distances out to 614 km.\167\ 
Initially, CALPUFF results beyond 300 km were thought to be potentially 
conservative (overestimate impacts); however subsequent analysis of 
CALPUFF indicates that it can also underpredict impacts at ranges 
greater than 300km.\168\ For this particular BART analysis, we chose to 
evaluate CALPUFF results out to approximately 450 km due to these 
potential uncertainties that seem to be larger at ranges greater than 
450 km.\169\ All BART-eligible sources that we modeled with CALPUFF in 
this action have at least one Class I area within the more typical 
CALPUFF range of 300km (see Table 3 for distance to most impacted Class 
I areas for each modeled source). This use of CALPUFF is consistent 
with the EPA's recommendation in the 2005 BART Guidelines \170\ to 
determine whether a source is subject to BART and in conducting the 
BART analysis for those sources determined to be subject to BART.\171\ 
We also have CAMx modeling results for all coal-fired BART-eligible 
sources and as such we have both CALPUFF and CAMx modeling results for 
the coal-fired sources within 450 km of Class I area(s). For those 
sources beyond 450 km, we only used CAMx modeling results as discussed 
in more detail later in this section.
---------------------------------------------------------------------------

    \165\ Interagency Workgroup on Air Quality Modeling (IWAQM) 
Phase 2 Summary Report and Recommendations for Modeling Long-Range 
Transport and Impacts on Regional Visibility, EPA- 454/R-98-019, 
IWAQM, 1998; ``Federal Land Managers' Air Quality Related Values 
Workgroup (FLAG)'': Phase I Report, FLAG, USDI--National Park 
Service, Air Resources Division, Denver, CO., 2000. https://www.nature.nps.gov/air/Pubs/pdf/flag/FlagFinal.pdf; Revisions to the 
Guideline on Air Quality Models: Adoption of a Preferred Long Range 
Transport Model and Other Resources, 72 FR 18440 (Apr. 15, 2003).
    \166\ Historically, the EPA has indicated that use of CALPUFF 
was generally acceptable at 300 km and for larger emissions sources 
with elevated stacks, such as coal-fired power plants, we and FLM 
representatives have also allowed or supported the use of CALPUFF 
results at larger distances, beyond 400 km in some cases. For 
example, South Dakota used CALPUFF for Big Stone's BART 
determination, including its impact on multiple Class I areas 
further than 400 km away. See 76 FR 76646, 76654 (Dec. 8, 2011), 77 
FR 24845 (Apr.26, 2012). Nebraska relied on CALPUFF modeling to 
evaluate whether numerous power plants were subject to BART where 
the ``Class I areas [were] located at distances of 300 to 600 
kilometers or more from'' the sources. See Best Available Retrofit 
Technology Dispersion Modeling Protocol for Selected Nebraska 
Utilities, p. 3, EPA Docket ID No. EPA-R07-OAR-2012-0158-0008.
    \167\ In our 2014 proposed action and the 2016 final action on 
the 2009 Texas Regional Haze SIP, we approved the use of CALPUFF to 
screen BART-eligible non-EGU sources at distances of 400 to 614 km 
for some sources. 79 FR 74818 (Dec. 16, 2014), 81 FR 296 (Jan. 5, 
2016).
    \168\ ``Documentation of the Evaluation of CALPUFF and Other 
Long Range Transport Models using Tracer Field Experiment Data'' 
(PDF)(247 pp, 8 MB, 05-01-2012, 454-R-12-003). Prepared for the U.S. 
Environmental Protection Agency by the ENVIRON International 
Corporation. (EPA Contract No: EP-D-07-102, Work Assignment No: 4-
06); ``Evaluation of Chemical Dispersion Models using Atmospheric 
Plume Measurements from Field Experiments'' (PDF)(127 pp, 3 MB, 09-
01-2012). Prepared for the U.S. Environmental Protection Agency by 
the ENVIRON International Corporation. (EPA Contract No: EP-D-07-
102, Work Assignment No: 4-06 and 5-08); and ``Comparison of Single-
Source Air Quality Assessment Techniques for Ozone, 
PM2.5, other Criteria Pollutants and AQRVs'' (PDF)(143 
pp, 19 MB, 09-01-2012). Prepared for the U.S. Environmental 
Protection Agency by the ENVIRON International Corporation. (EPA 
Contract No: EP-D-07-102, Work Assignment No: 4-06 and 5-08); 
https://www.epa.gov/scram/air-modeling-reports-and-journal-articles. 
See 2023 BART Modeling TSD for further discussion on this topic.
    \169\ We discuss the choice of using CALPUFF model results in 
the 300-450 km range in more detail in the 2023 BART Modeling TSD.
    \170\ See 70 FR 39104, 39122-23 (July 6, 2005).
    \171\ 70 FR at 39122.
---------------------------------------------------------------------------

    Consistent with the BART Guidelines, for those sources modeled with 
CALPUFF, we compared the 98th percentile (equivalent to the 8th highest 
daily value in each year modeled) impact from the three modeled years 
to the 0.5 dv screening threshold following the modeling protocol 
described in the 2023 BART Modeling TSD.\172\ The BART Guidelines 
recommend that States (or the EPA in the case of a FIP) use the 24-hour 
average actual emission rate from the highest emitting day of the 
meteorological period modeled, unless this rate reflects periods of 
start-up, shutdown, or malfunction. Consistent with this 
recommendation, in this action, we used the 24-hour average actual 
emission rate from the highest emitting day during the baseline period.
---------------------------------------------------------------------------

    \172\ In the 2005 BART Guidelines the selection of the 98th 
percentile value rather than the maximum value was made to address 
concerns with CALPUFF's limitations that could result in the maximum 
from CALPUFF modeling being overly conservative. We state that, 
``Most important, the simplified chemistry in the model tends to 
magnify the actual visibility effects of that source. Because of 
these features and the uncertainties associated with the model, we 
believe it is appropriate to use the 98th percentile--a more robust 
approach that does not give undue weight to the extreme tail of the 
distribution.'' 70 FR at 39121.
---------------------------------------------------------------------------

    For this proposed action, we conducted modeling using a baseline 
period of emissions data of 2016-2020 and used meteorological data for 
2016-2018 to evaluate source visibility impacts to Class I areas. Our 
selection of this baseline period for subject-to-BART screening 
modeling was made based on consideration of a number of factors. We 
note that most BART screening analyses, including the BART screening in 
the 2009 Texas Regional Haze SIP, were based on a 2000-2004 baseline 
period, used 2001-2003 meteorological data, and used 2002 in the 
baseline modeling to project 2018 visibility conditions for the first 
planning period SIPs. Our 2017 proposed rule also used this 
period.\173\
---------------------------------------------------------------------------

    \173\ See generally 82 FR 912 (January 4, 2017).
---------------------------------------------------------------------------

    We selected the 2016-2020 emissions baseline period for subject-to-
BART screening in this instance because recent actual emissions more 
accurately reflect future anticipated emissions which is required in 
evaluating controls. In addition, this emissions baseline period is 
consistent with the 2016-2018 meteorological period modeled. In this 
manner, the screening, visibility benefit analysis, cost analysis, and 
consideration of existing controls are all based on consideration of 
the same baseline meteorological time period, operating conditions, and 
emissions. The 2000-2004 baseline period is no longer representative of 
anticipated future emissions or current operations because more recent 
regulatory actions, such as the MATS rule, and market pressures have 
impacted how these units now operate. We also note that our previous 
use of baseline emissions data from 2000-2004 reflected steady-state 
operating conditions during periods of high-capacity utilization and 
was appropriate for the screening nature of the analysis rather than 
any specific federally enforceable limit in effect at that time. We 
believe this same approach, updated for 2016-2020, continues to serve 
the same function and provides a suitable estimate of emissions during 
high utilization for each of these sources. Additionally, it also 
allows the screening, visibility benefit analysis, cost analysis, and 
consideration of existing controls to all be based on the same baseline 
period for meteorological data, operating conditions, and emissions. 
Using an appropriate, updated baseline is also the foundation for 
evaluating control costs once a source is determined to be subject to 
BART. The BART determination includes consideration of past practices, 
existing controls, and anticipated future operation. The BART 
Guidelines state that in evaluating the costs of controls as part of 
the five-factor analysis for sources determined to be subject to BART, 
baseline annual emissions utilized for control cost analyses should be 
a realistic depiction of anticipated annual emissions for the source 
and calculated based upon continuation of past practice \174\ in the 
absence of enforceable limitations.
---------------------------------------------------------------------------

    \174\ Past practices can include a broad consideration of 
operations, changes in market conditions, and unique situations that 
can impact emissions.

---------------------------------------------------------------------------

[[Page 28940]]

    For both the CALPUFF and CAMx modeling, the maximum 24-hour 
emission rate (lb/hr) for NOX and SO2 from the 
2016-2020 baseline period for each source was identified through a 
review of the daily emission data obtained from the EPA's Clean Air 
Markets Program Data \175\ for each of the BART-eligible units included 
in Table 2. Because daily emissions are not available for PM, we used 
data from EPA's Air Markets Program Data and TCEQ's Central Registry EI 
information to obtain PM10 and PM2.5 tpy emission 
rates for each year (2016-2020) on a unit basis. We used the annual 
average lb/MMBtu and the maximum daily heat input to calculate the 
maximum daily PM10 and PM2.5 emissions rates that 
were used in the subject to BART modeling and were also used in the 
control cases. For the gas and gas/fuel oil facilities,\176\ we 
utilized the heat input data from the EPA Clean Air Markets Division 
(CAMD) coupled with the EPA's AP-42 emission factors to estimate 
maximum PM10 and PM2.5 emissions. The 2023 BART 
Modeling TSD includes additional discussion and source-specific 
information used in the CALPUFF modeling for this portion of the 
screening analysis.
---------------------------------------------------------------------------

    \175\ https://campd.epa.gov/. See ``2016-2020 CAMD Data 
Evaluation.xlsx'' in the docket for this action.
    \176\ When we use the term ``gas,'' we mean ``pipeline natural 
gas.''
---------------------------------------------------------------------------

    As previously discussed, while the BART Guidelines recommend the 
use of CALPUFF to determine which sources are anticipated to contribute 
to visibility impairment, the Guidelines also allow the use of another 
``appropriate model'' to predict the visibility impacts from a single 
source at a Class I area. Because some of these BART-eligible sources 
(included in Table 2) are beyond the distance to Class I areas for 
which CALPUFF modeling is typically used, we used photochemical grid 
modeling (CAMx) to evaluate the visibility impacts of those sources. In 
addition, we also used CAMx to evaluate the other BART-eligible coal-
fired EGUs with SO2 emissions located within the typical 
CALPUFF modeling range. The CAMx modeling includes all of these 
emission sources to provide a consistent approach to compare the 
modeling results across all these sources. CAMx is a photochemical grid 
model that is formulated to assess the long-range transport of 
emissions from sources up to distances of several thousand miles 
including emissions from sources outside the range that CALPUFF is 
typically utilized. CAMx allows modeling of impacts from individual 
sources and assessment of their impacts on Class I areas at distances 
much greater than the limited CALPUFF model system and accounts for all 
the other known emissions sources in the modeling domain that results 
in varying background pollution levels temporally and spatially that 
individual source emissions interact. Furthermore, CAMx is also more 
suited than other possible modeling approaches for evaluating the 
visibility impacts of SO2, NOX, VOC, and PM 
emissions, as it has a more robust chemistry mechanism that is 
continually updated as the scientific community of peers agree on 
chemistry, physics, and structural upgrades. As such, CAMx provides a 
scientifically defensible platform for the assessment of visibility 
impacts over a wide range of source-to-receptor distances that has been 
used by a number of States in development of their Regional Haze SIPs, 
including Texas.
    Since CAMx modeling differs in several ways from CALPUFF modeling, 
we are using different metrics to evaluate BART visibility impacts from 
CAMx. For CAMx modeling, we utilize the maximum daily impact as the 
primary metric for BART screening and assessment of visibility impacts 
as compared to the use of the 98th percentile metric with CALPUFF. As 
explained in the 2023 BART Modeling TSD, this approach recognizes 
differences in the models and model inputs and their application in 
determining whether the source is anticipated to cause or contribute to 
visibility impairment. For example, one difference is that compared to 
CALPUFF, CAMx utilizes a more robust chemistry mechanism, thus the 
primary concern that drove the selection of the 98th percentile value 
for CALPUFF based modeling are not applicable. Furthermore, because the 
CAMx modeling uses a more limited meteorological data period (one year 
of meteorology instead of three years used for CALPUFF modeling), and 
CAMx modeling also uses only one receptor for the Class I area \177\ 
versus the many receptors covering the entire area of the Class I area 
that are used in CALPUFF modeling, the maximum of the daily impacts at 
a Class I area is appropriate for determining if a source is subject to 
BART. The use of the maximum value from CAMx also comports with TCEQ's 
use of the maximum value from CAMx modeling for BART screening that 
TCEQ included in the 2009 Texas Regional Haze SIP.178 179 
See the 2023 BART Modeling TSD for further discussion of the CALPUFF 
and CAMx modeling systems, the metrics evaluated, and the limitations 
and strengths of each modeling system.
---------------------------------------------------------------------------

    \177\ For CAMx, we used the location coordinates of the 13 
IMPROVE monitors that represent the 15 Class I areas, as was done in 
previous modeling. IMPROVE monitor GUMO1 represents both the 
Guadalupe Mountains NP and the Carlsbad Caverns NP Class I areas, 
and IMPROVE monitor WHPE1 represents both Wheeler Peak and Pecos 
Wilderness Areas Class I areas. IMPROVE monitors are part of a 
nationwide visibility monitoring network. The IMPROVE program 
establishes current visibility and aerosol conditions in mandatory 
Class I areas; identifies chemical species and emission sources 
responsible for existing man-made visibility impairment; documents 
long-term trends in visibility; and provides regional haze 
monitoring representing all visibility-protected Federal Class I 
areas, where practical.
    \178\ See 2009 Texas Regional Haze SIP Appendix 9-5, ``Screening 
Analysis of Potential BART-Eligible Sources in Texas''; Revised 
Draft Final Modeling Protocol Screening Analysis of Potentially 
BART-Eligible Sources in Texas, Environ Sept. 27, 2006; and Guidance 
for the Application of the CAMx Hybrid Photochemical Grid Model to 
Assess Visibility Impacts of Texas BART Sources at Class I Areas, 
Environ December 13, 2007 all available in the docket for this 
action. The EPA, the Texas Commission on Environmental Quality 
(TCEQ), and FLM representatives verbally approved the approach in 
2006 and in email exchange with TCEQ representatives in February 
2007 (see email from Erik Snyder (EPA) to Greg Nudd of TCEQ Feb. 13, 
2007 and response email from Greg Nudd to Erik Snyder Feb. 15, 2007, 
available in the docket for this action).
    \179\ We approved Texas's subject-to-BART analysis for non-EGU 
sources which relied on this CAMx modeling in our January 5, 2016, 
rulemaking (81 FR 296).
---------------------------------------------------------------------------

    For this proposed action, our CAMx modeling platform began with 
TCEQ's 2016 Modeling Platform,\180\ namely TCEQ's 2016 emissions data, 
2016 meteorological data, and other modeling files utilized in their 
CAMx modeling for TCEQ's Second Planning Period Texas Regional Haze 
SIP. We are using this updated modeling platform to reflect more recent 
meteorology and emissions inventories and have identified it to be the 
best available platform for modeling these sources in Texas.\181\ We 
upgraded this modeling platform to the newest version of the CAMx 
model, adjusted emissions for BART-eligible units, and utilized

[[Page 28941]]

different/new Particulate Matter Source Apportionment Technology (PSAT) 
\182\ categories (individual EGU units and facilities) to track source 
contributions for BART-eligible units. These adjustments are explained 
in more detail in the 2023 BART Modeling TSD.
---------------------------------------------------------------------------

    \180\ For this action, we used TCEQ's 2016 modeling platform 
from its Second Planning Period Regional Haze SIP revision. TCEQ 
submitted this Second Planning Period Regional Haze SIP revision to 
the EPA on July 20, 2021. The EPA has not reviewed this SIP nor 
proposed action on this SIP, but we are utilizing the modeling 
platform developed by TCEQ for this SIP to perform our modeling 
analyses to determine whether a source is subject to BART and in 
conducting the BART analysis for those sources determined to be 
subject to BART. The EPA will evaluate the Second Planning Period 
Regional Haze SIP submitted by TCEQ in a separate action. The SIP is 
available at https://www.tceq.texas.gov/airquality/sip/bart/haze_sip.html and in the docket for this action.
    \181\ Consequently, a 2016-2018 period for CALPUFF modeling and 
2016-2020 emissions would be consistent with this choice.
    \182\ CAMx includes an advanced mechanism that allows tracking 
the contributions of individual sources and pollutants within the 
grid model. For purposes of tracking particulate matter formation, 
we employed the CAMx PSAT for the BART-eligible sources included in 
the Texas SO2 Trading Program, including the three coal-
fired EGU sources that did not screen out with the CALPUFF modeling 
(Harrington, Martin Lake, and Welsh).
---------------------------------------------------------------------------

    Using the BART Guidelines recommended maximum daily emissions and 
post-processing approach, if the source (which is the aggregate of all 
BART-eligible units at a specific facility) is shown to contribute less 
than 0.5 dv to visibility impairment at all modeled Class I areas on 
all modeled days, then it is said to be ``not subject to BART'' and may 
be excluded from further steps in the BART process. The maximum modeled 
impact for each source, taking into account the annual average natural 
background conditions at the Class I areas, was compared to the 0.5 dv 
contribution threshold. See the 2023 BART Modeling TSD for additional 
details on the CAMx modeling.
2. Subject to BART Determinations Based on CALPUFF and CAMx Modeling 
Results
    Table 3 shows the CALPUFF modeling results for the screening 
analysis. The Graham, Newman, Stryker Creek, and Wilkes BART-eligible 
units (all gas-fired or gas/fuel oil-fired BART-eligible units) that 
were included in the Texas SO2 Trading Program can be 
exempted from further analysis because they all have modeled maximum 
98th percentile annual impacts at all Class I areas of less than the 
0.5 dv threshold. When considering impacts modeled using CALPUFF, a 
source is considered subject to BART if any of the three annual 98th 
percentile values are 0.5 dv or greater. As Table 3 shows, the coal-
fired BART-eligible units at Martin Lake, Harrington, and Welsh did not 
screen out based on the CALPUFF modeling and thus are considered to 
cause or contribute to visibility impairment at Class I areas. See the 
2023 BART Modeling TSD for this action for more details on the CALPUFF 
modeling and the modeling results.

                                                        Table 3--CALPUFF BART Screening Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                    Maximum delta deciviews
          Plant name             Operator name     Boiler ID(s)    Most impacted class ------------------------------------------------ Less than 0.5 dv
                                                                    I area (distance)        2016            2017            2018
--------------------------------------------------------------------------------------------------------------------------------------------------------
Graham.......................  Luminant........  2..............  Wichita Mountains              0.297           0.203           0.423  Yes.
                                                                   (174 km).
Newman.......................  El Paso Electric  2, 3, **4, **5.  Guadalupe Mountain             0.342           0.368           0.354  Yes.
                                                                   (133 km).
Stryker Creek................  Luminant........  ST2............  Caney Creek (283 km)           0.054           0.059           0.064  Yes.
Wilkes Power Plant...........  AEP.............  1, 2, 3........  Caney Creek (174 km)           0.380           0.373           0.442  Yes.
Martin Lake..................  Luminant........  1,2,3..........  Caney Creek (238 km)            3.28            3.60            3.35  No.
Harrington...................  Xcel............  061B, 062B.....  Salt Creek (305 km).            0.49            0.59            0.54  No.
Harrington...................  Xcel............  061B, 062B.....  Wichita Mountains               0.54            0.45            0.58  No.
                                                                   (278 km).
Welsh........................  AEP.............  1..............  Caney Creek (161 km)             0.7            0.94            0.96  No.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Table 4 summarizes the results of the CAMx screening analysis. 
These results also establish the baseline impacts for further modeling 
analyses of potential visibility benefits of controls. We note that all 
six sources analyzed with CAMx PSAT modeling had impacts greater than 
0.5 dv at one or more Class I areas. Table 4 also shows that the CAMx-
predicted visibility impacts range from 0.52 dv to 6.69 dv for these 
six sources at individual Class I areas on their maximum impact day. 
Additionally, Table 4 shows the number of days impacted over 0.5 dv and 
1.0 dv at the maximum impacted Class I areas for each source. We note 
that maximum impacts from Fayette \183\ are just above the 0.5 dv 
threshold and only exceed the threshold on one day. However, because 
the intent of the screening analysis is to be inclusive, we therefore 
consider Fayette subject to BART. The relatively lower visibility 
impacts and potential benefits from controls will be considered as part 
of the five-factor analysis when determining the potential availability 
of cost-effective emission reductions. With the exception of Fayette, 
the BART-eligible sources modeled using CAMx had maximum impacts well 
over the 0.5 dv threshold on multiple modeled days (ranging from 8 to 
150 days).
---------------------------------------------------------------------------

    \183\ Fayette Power Project is also known as Sam Seymour. We 
refer to it as Fayette throughout this document.

                                                  Table 4--CAMx BART Screening Source Analysis Summary
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                             Number of       Number of
       BART-eligible source                 Units           Most impacted class  Maximum delta-     Less than 0.5 dv?      modeled days    modeled days
                                                                  I area               dv                                  >=0.5 dv \1\    >=1.0 dv \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coleto Creek......................  1....................  Caney Creek.........            1.55  No.....................              18               2
Fayette Power.....................  1 & 2................  Caney Creek.........            0.52  No.....................               1               0
Harrington........................  061B & 062B..........  White Mountain......            2.64  No.....................               8               3
Martin Lake.......................  1, 2, & 3............  Caney Creek.........            6.69  No.....................             150             101
W. A. Parish......................  WAP4, WAP5, & WAP6...  Wichita Mountains...            3.97  No.....................              35              12
Welsh.............................  1....................  Caney Creek.........            1.58  No.....................              27               6
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Number of days over 0.5 or 1.0 dv at the most impacted Class I area. See Table 12 for cumulative results at the 15 Class I areas analyzed.


[[Page 28942]]

    Based on the modeling analysis, the BART-eligible sources in Table 
5 have been determined to cause or contribute to visibility impairment 
at a nearby Class I area; therefore, we propose to find the six sources 
are subject to BART. We must establish emission limits for visibility 
impairing pollutants SO2 and PM through further evaluation 
using the BART five factor analysis.\184\
---------------------------------------------------------------------------

    \184\ The NOX BART requirement for these EGU sources 
is not addressed by source-specific limits in this proposal. The 
EPA's determination that Texas' participation in CSAPR for ozone-
season NOX satisfies NOX BART for EGUs was 
finalized in our October 17, 2017 final rule (82 FR 48324), thus 
dispensing with the need for source-specific BART determinations and 
requirements for NOX. We did not reopen that 
determination in our August 2018 proposal, November 2019 
supplemental proposal, or August 2020 final rule, and are not 
reopening it in this proposal.

                Table 5--Sources That Are Subject-to-BART
------------------------------------------------------------------------
                 Facility                               Units
------------------------------------------------------------------------
Coleto Creek..............................  1.
Fayette Power.............................  1 & 2.
Harrington................................  061B & 062B.
Martin Lake...............................  1, 2 & 3.
W. A. Parish..............................  WAP4, WAP5 & WAP6.
Welsh.....................................  1.
------------------------------------------------------------------------

3. Subject to BART Determination for O.W. Sommers Units 1 and 2
    CPS Energy operates the Calaveras Power Station which is comprised 
of O. W. Sommers Units 1 and 2, J. T. Deely Units 1 and 2,\185\ and J. 
K. Spruce Units 1 and 2. In our 2017 Texas BART proposal, we identified 
O. W. Sommers Units 1 and 2 and J. T. Deely Units 1 and 2 as BART-
eligible and conducted CAMx modeling to determine their visibility 
impacts. Because J. T. Deely Units 1 and 2 subsequently ceased 
operation and shut down, our analysis in this action is limited to the 
two gas-fired units at O. W. Sommers. Given the retirement of the two 
coal-fired units at J. T. Deely and the low SO2 emissions 
from the O. W. Sommers gas-fired EGUs, rather than conducting new CAMx 
modeling, we updated our analysis of O. W. Sommers Units 1 and 2 
relying on the CAMx modeling from our 2017 Texas BART proposal (further 
referred to as 2017 Proposal). In that analysis, we conducted CAMx 
modeling using the combined maximum 24-hour emissions from both J. T. 
Deely Units 1 and 2 and O. W. Sommers Units 1 and 2 to determine if the 
aggregate BART-eligible source (all four BART-eligible units at 
Calaveras Power Station) was subject to BART. The maximum modeled 
impact from the Calaveras Power Station was 1.513 dv. As documented in 
the BART Screening TSD and associated supporting documents for the 2017 
BART FIP,\186\ the impacts of the two O. W. Sommers BART-eligible units 
were previously estimated to have a maximum visibility impact of 0.286 
dv at the Caney Creek Class I area, which is below the 0.5 dv 
threshold.\187\
---------------------------------------------------------------------------

    \185\ Acosta, Sarah (January 3, 2019). ``CPS Energy closes coal-
fired Deely plant in operation since `70s to focus on cleaner energy 
sources''. KSAT-TV. Retrieved January 4, 2019.
    \186\ ``Technical Support Document Our Strategy for Assessing 
which Units are Subject to BART for the Texas Regional Haze BART 
Federal Implementation Plan (BART Screening TSD), pdf page 72 and 
Appendix E, available in the docket EPA-R06-OAR-2016-0611 (at EPA-
R06-OAR-2016-0611-0005).
    \187\ Id. pdf page 72 and Appendix E. CAMx Maximum Impact at 
each Class Area; The O. W. Sommers BART-eligible units were modeled 
individually, the sum (maximum dv impacts) of which is 0.286 dv. 
Adding the maximum impacts of each unit results in a slight 
overestimation of the visibility impacts, since we did not first 
calculate total extinction and then dv, which is a natural 
logarithmic function. Therefore 0.286 dv is conservative (higher 
than if modeled).
---------------------------------------------------------------------------

    To bolster our current analysis, we also compared the modeled 
SO2 and NOx emission rates from the O. W. Sommers 
units with the recent maximum daily emissions from 2016-2020. Sulfate 
and nitrate made up almost all of the extinction value on the maximum 
impact day at Caney Creek Class I area, with approximately 89 percent 
of the total extinction from nitrates and 9 percent from sulfates on 
the maximum impact day due to emissions from O. W. Sommers. Because the 
two O. W. Sommers BART-eligible units are located near each other and 
have similar stack parameters, we used a linear adjustment comparing 
emissions modeled previously to more recent emissions (2016-2020) to 
provide an estimate of current visibility impact. While linear scaling 
does not result in the same values as modeling, it is a reasonable 
methodology to conservatively approximate the visibility impact from a 
source.
    Table 6 compares the NOX and SO2 emission 
rates modeled in the 2017 Proposal to the maximum daily emission rates 
of NOX and SO2 from the 2016-2020 
period.188 189 We did not compare PM10 or 
PM2.5 as they were less than 3 percent of the total light 
extinction on the maximum impact day. SO2 emissions from the 
2016-2020 period were less than 3 percent of what was previously 
modeled, and NOX emissions were 13.71 percent higher than 
what was modeled for our 2017 Proposal for these two units. 
Acknowledging that the reduction in SO2 emissions will 
result in lower visibility impact, we choose to not adjust for the 
lower SO2 emissions in an effort to be conservative in our 
analysis. Scaling the 2017 visibility impact (0.286 dv at Caney Creek 
Class I area) linearly to account for the 13.71 percent total increase 
in NOX emissions, we estimate a maximum visibility impact of 
0.325 dv at the Caney Creek Class I area, which is well below the 0.5 
dv threshold. Based on this analysis, it is reasonable to conclude that 
if emissions from the two O. W. Sommers BART-eligible units were 
remodeled using recent emissions, it would result in a maximum 
visibility impact less than 0.5 dv and would screen out of further 
analysis. Therefore, the EPA proposes that O. W. Sommers Units 1 and 2 
are not subject to BART.
---------------------------------------------------------------------------

    \188\ Id. Appendix A. Modeled parameters: Stack and emissions 
for CAMx modeled sources for modeled emissions in 2017 proposal.
    \189\ https://campd.epa.gov/.

                           Table 6--O. W. Sommers BART-Eligible Units Emissions Modeled in 2017 vs. Recent 2016-2020 Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                         O. W. Sommers modeled in 2017 proposal (TPD)     O. W. Sommers max daily emissions 2016-2020
                                       ------------------------------------------------                      (TPD)                       2016-2020 Total
                                                                                       ------------------------------------------------ as percentage of
                                            Unit 1          Unit 2           Total          Unit 1          Unit 2           Total      2017 modeled (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2...................................            2.01           10.92           12.93           0.167           0.147            0.31              2.43
NOX...................................            5.96            8.04           14.00            9.32             6.6           15.92            113.71
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 28943]]

B. BART Five Factor Analysis

    The purpose of the BART analysis is to identify and evaluate the 
best system of continuous emission reduction based on the BART 
Guidelines.\190\ In determining BART, a State, or the EPA when 
promulgating a FIP, must consider the five statutory factors in section 
169A of the CAA: (1) The costs of compliance; (2) the energy and non-
air quality environmental impacts of compliance; (3) any existing 
pollution control technology in use at the source; (4) the remaining 
useful life of the source; and (5) the degree of improvement in 
visibility which may reasonably be anticipated to result from the use 
of such technology. See also 40 CFR 51.308(e)(1)(ii)(A). This is 
commonly referred to as the ``BART five factor analysis.'' The BART 
Guidelines break the analyses of these requirements into five steps: 
\191\
---------------------------------------------------------------------------

    \190\ See July 6, 2005 BART Guidelines, 40 CFR part 51, Regional 
Haze Regulations and Guidelines for Best Available Retrofit 
Technology Determinations.
    \191\ 70 FR 39104, 39164 (July 6, 2005) [40 CFR part 51, App. 
Y].
---------------------------------------------------------------------------

    STEP 1--Identify All Available Retrofit Control Technologies,
    STEP 2--Eliminate Technically Infeasible Options,
    STEP 3--Evaluate Control Effectiveness of Remaining Control 
Technologies,
    STEP 4--Evaluate Impacts and Document the Results, and
    STEP 5--Evaluate Visibility Impacts.
    The following sections treat these steps individually for 
SO2. We are combining these steps into one section in our 
assessment of PM BART that follows the SO2 sections.
1. Step 1 and 2: Technically Feasible SO2 Retrofit Controls
    The BART Guidelines state that in identifying all available 
retrofit control options,

    [Y]ou must identify the most stringent option and a reasonable 
set of options for analysis that reflects a comprehensive list of 
available technologies. It is not necessary to list all permutations 
of available control levels that exist for a given technology--the 
list is complete if it includes the maximum level of control each 
technology is capable of achieving.\192\
---------------------------------------------------------------------------

    \192\ 70 FR at 39164, fn 12 [40 CFR part 51, App. Y].

    Adhering to this, we will identify a reasonable set of 
SO2 control options, including those that cover the maximum 
level of control each technology is capable of achieving. We will also 
note whether any of these technologies are technically infeasible.
    The subject-to-BART units identified in Table 5 can be organized 
into three broad categories, based on their fuel type and the potential 
types of SO2 control options that could be available: (1) 
coal-fired EGUs with no SO2 scrubber, (2) coal-fired EGUs 
with existing SO2 scrubbers, and (3) gas-fired EGUs that do 
not burn oil. This classification is represented in Table 7.

                             Table 7--Fuel/Control Types for Subject-to-BART Sources
----------------------------------------------------------------------------------------------------------------
                                                                            Coal (existing
              Facility                     Unit       Coal (no scrubber)       scrubber)              Gas
----------------------------------------------------------------------------------------------------------------
Coleto Creek (Dynegy)...............               1                  X
Fayette (LCRA)......................               1                                      X
Fayette (LCRA)......................               2                                      X
Harrington Station (Xcel)...........            061B                  X
Harrington Station (Xcel)...........            062B                  X
Martin Lake (Luminant)..............               1                                      X
Martin Lake (Luminant)..............               2                                      X
Martin Lake (Luminant)..............               3                                      X
W. A. Parish (NRG)..................            WAP4                                                          X
W. A. Parish (NRG)..................            WAP5                  X
W. A. Parish (NRG)..................            WAP6                  X
Welsh Power Plant (AEP).............               1                  X
----------------------------------------------------------------------------------------------------------------

    For the coal-fired EGUs without an existing scrubber, we have 
identified four potential control technologies: (1) coal pretreatment, 
(2) Dry Sorbent Injection (DSI), (3) dry Flue Gas Desulfurization 
(FGD), and (4) wet FGD. For the coal-fired EGUs with existing 
scrubbers, we will examine whether those scrubbers can be upgraded.
    Gas-fired EGUs that do not burn oil (W. A. Parish Unit WAP4) have 
inherently very low SO2 emissions and there are no known 
SO2 controls that can be evaluated.
a. Identification of Technically Feasible SO2 Retrofit 
Control Technologies for Coal-Fired Units
    Available SO2 control technologies for coal-fired EGUs 
consist of either pretreating the coal in order to improve its 
qualities or by treating the flue gas through the installation of 
either DSI or some type of scrubbing technology.
Coal Pretreatment
    Coal pretreatment, or coal upgrading, has the potential to reduce 
emissions by reducing the amount of coal that must be burned in order 
to result in the same heat input to the boiler. Coal pretreatment 
broadly falls into two categories: coal washing and coal drying.
    Coal washing is often described as preparation (for particular 
markets) or cleaning (by reducing the amount of mineral matter and/or 
sulfur in the product coal).\193\ Washing operations are carried out 
mainly on bituminous and anthracitic coals, as the characteristics of 
subbituminous coals and lignite (brown coals) do not lend themselves to 
separation of mineral matter by this means, except in a few cases.\194\ 
Coal is mechanically sized, then various washing techniques are 
employed, depending on the particle size, type of coal, and the desired 
level of preparation.\195\ Following the coal washing, the coal is 
dewatered, and the waste streams are disposed.
---------------------------------------------------------------------------

    \193\ Couch, G. R., ``Coal Upgrading to Reduce CO2 
emissions,'' CCC/67, October 2002, IEA Clean Coal Centre.
    \194\ Id.
    \195\ Various coal washing techniques are treated in detail in 
Chapter 4 of Meeting Projected Coal Production Demands In The USA, 
Upstream Issues, Challenges, and Strategies, The Virginia Center for 
Coal and Energy Research, Virginia Polytechnic Institute and State 
University, contracted for by the National Commission on Energy 
Policy, 2008.
---------------------------------------------------------------------------

    Coal washing takes place offsite at large dedicated coal washing 
facilities, typically located near where the coal is mined. Coal 
washing carries with it a number of problems:
     Coal washing is not typically performed on the types of 
coals used in

[[Page 28944]]

the power plants under consideration, Powder River Basin (PRB) 
subbituminous and Texas lignites.
     Coal washing poses significant energy and non-air quality 
considerations under section 51.308(e)(1)(ii)(A). For instance, it 
results in the use of large quantities of water,\196\ and coal washing 
slurries are typically stored in impoundments, which can, and have, 
leaked.\197\
---------------------------------------------------------------------------

    \196\ ``Water requirements for coal washing are quite variable, 
with estimates of roughly 20 to 40 gallons per ton of coal washed (1 
to 2 gal per MMBtu) (Gleick, 1994; Lancet, 1993).'' Energy Demands 
on Water Resources, Report to Congress on the Interdependency of 
Energy and Water, U.S. Department of Energy, December 2006.
    \197\ Committee on Coal Waste Impoundments, Committee on Earth 
Resources, Board on Earth Sciences and Resources, Division on Earth 
and Life Studies; Coal Waste Impoundments, Risks, Responses, and 
Alternatives; National Research Council; National Academy Press, 
2002.
---------------------------------------------------------------------------

    Because of these issues, we do not consider coal washing as a part 
of our reasonable set of options for analysis as BART SO2 
control technology.
    In general, coal drying consists of reducing the moisture content 
of lower rank coals, thereby improving the heating value of the coal 
and so reducing the amount of coal that has to be combusted to achieve 
the same power, thus improving the efficiency of the boiler. In the 
process, certain pollutants are reduced as a result of (1) mechanical 
separation of mineralized sulfur (e.g., iron pyrite) and rocks, and (2) 
the unit burning less coal to make the same amount of power.
    Coal drying could be considered a potential BART control. Great 
River Energy has developed a patented process which is being 
successfully utilized at the Coal Creek facility in North Dakota and is 
potentially available for installation at other facilities.\198\ This 
process utilizes excess waste heat to run trains of moving fluidized 
bed dryers. The process offers a number of co-benefits, such as general 
savings due to lower coal usage (e.g., coal cost, ash disposal), less 
power required to run mills and ID fans, and lower maintenance on coal 
handling equipment air preheaters, etc. Coal Creek units also utilize 
wet FGD to reduce SO2 emissions. Therefore, the observed 
additional SO2 emission reductions are due to the 
combination of a higher percentage of flue gas being scrubbed 
(decreased bypass of the wet FGD) in combination with a decrease in 
coal usage and any removal of sulfur in the drying process. We are not 
aware of any other EGUs in the United States that utilize coal drying 
for the purpose of reducing SO2 emissions. Therefore, we 
believe coal drying has limited application at EGUs in the United 
States.
---------------------------------------------------------------------------

    \198\ DryFining\TM\ is the company's name for the process. It is 
described here: https://www.powermag.com/improve-plant-efficiency-and-reduce-co2-emissions-when-firing-high-moisture-coals/.
---------------------------------------------------------------------------

    Although coal drying may be a potential option for generally 
improving boiler efficiency and obtaining some reduction in 
SO2, its analysis presents a number of difficulties. For 
instance, the degree of reduction in SO2 is dependent on 
several factors. These include (1) the quality and quantity of the 
waste heat available at the unit, (2) the type of coal being dried 
(amount of bound sulfur, i.e., pyrites, moisture content), and (3) the 
design of the boiler (e.g., limits to steam temperatures, which can 
decrease due to the reduced flue gas flow through the convective pass 
of the boiler). As a result of these issues, we do not further assess 
coal drying as part of our reasonable set of options for BART analysis.
DSI
    DSI is not a stand-alone, add-on air pollution control system but a 
modification to the combustion unit or ductwork. DSI is performed by 
injecting a dry reagent into the hot flue gas, which chemically reacts 
with SO2 and other gases to form a solid product that is 
subsequently captured by the particulate control device. A blower 
delivers the sorbent from its storage silos through piping directly to 
the flue gas ducting via injection lances. In general, there are many 
types of sorbent materials, but their efficacy is variable and 
dependent on operating conditions. Trona is currently the most commonly 
used sorbent for SO2 removal and is a naturally occurring 
mineral primarily mined from the Green River Formation in Wyoming. 
Trona can also be processed into sodium bicarbonate, which is more 
reactive with SO2 than trona, but more expensive. Hydrated 
lime is another potential sorbent that is more frequently used for acid 
gas control.199 200
---------------------------------------------------------------------------

    \199\ See Documentation for the EPA's Power Sector Modeling 
Platform v6 Using the Integrated Planning Model, dated September 
2021, page 5-19. Documentation for v.6 downloaded from https://www.epa.gov/power-sector-modeling/documentation-epas-power-sector-modeling-platform-v6-summer-2021-reference.
    \200\ ``Dry Sorbent Injection of Sodium Sorbents,'' presented at 
the LADCO Lake Michigan Air Directors Consortium, Emission Control 
and Measurement Technology for Industrial Sources Workshop, March 
24, 2010. A copy of the presentation is located in the docket at 
EPA-R06-OAR-2016-0611-0043.
---------------------------------------------------------------------------

    There are many examples of DSI being used on coal-fired EGUs. 
However, DSI may not be technically feasible at every coal-fired EGU. 
For example, DSI technology is not a technically feasible control 
option for boilers that burn fuels with sulfur content greater than 2 
lb SO2/MMBtu.\201\ Although individual installations may 
present technical difficulties or poor performance due to the 
suboptimization of operational factors, we believe that DSI may be a 
particularly appropriate SO2 control option for boilers that 
burn low-sulfur coal or lignite, as such boilers typically do not need 
SO2 controls with very high control efficiencies (i.e., 
greater than 95 percent) to achieve low emission rates. Because the 
Texas coal-fired EGUs we are evaluating in this proposal burn low-
sulfur coal, we find that they are well suited for consideration of DSI 
for SO2 control. Additionally, boilers that operate DSI and 
burn low-sulfur coal require much less sorbent than boilers burning 
high-sulfur coal to achieve similar control efficiencies. We also note 
that DSI is a common control technology that has been widely installed 
for compliance with the acid gas control requirements in the Mercury 
and Air Toxics Standards (MATS).\202\ For these reasons, we find that 
DSI is technically feasible and should be considered as a potential 
BART control.
---------------------------------------------------------------------------

    \201\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy, page 3. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.
    \202\ The MATS rule was finalized by the EPA in December 2011, 
and compliance with the standard was required by 2015. The MATS rule 
requires that plants greater than 25 megawatts meet the maximum 
achievable control technology for mercury, hydrochloric acid, and 
filterable particulate matter (note the MATS rule does not require 
controls for SO2). See https://www.epa.gov/mats/regulatory-actions-final-mercury-and-air-toxics-standards-mats-power-plants.
---------------------------------------------------------------------------

SO2 Scrubbing Systems
    In contrast to DSI, SO2 scrubbing techniques utilize a 
large, dedicated vessel in which the chemical reaction between the 
sorbent (typically lime or limestone) and SO2 takes place 
either completely or in large part. Also, in contrast to DSI systems, 
SO2 scrubbers add water to the sorbent when introduced to 
the flue gas. The two predominant types of SO2 scrubbing 
employed at coal-fired EGUs are wet FGD and dry FGD. The U.S. Energy 
Information Administration (EIA) reports \203\ the following types of 
flue

[[Page 28945]]

gas desulfurization systems as being operational in the U.S. for 2020:
---------------------------------------------------------------------------

    \203\ See EIA-860 data available here: https://www.eia.gov/electricity/data/eia860/.

          Table 8--EIA Reported Desulfurization Systems in 2020
------------------------------------------------------------------------
                                                             Number of
                          Type                             installations
------------------------------------------------------------------------
Wet spray tower scrubber................................             288
Spray dryer absorber....................................             256
Circulating dry scrubber................................              41
Packed tower wet scrubber...............................               4
Venturi wet scrubber....................................              58
Jet bubbling reactor....................................              23
Tray tower wet scrubber.................................              63
Mechanically aided wet scrubber.........................               4
DSI.....................................................             149
Other...................................................              36
Unspecified.............................................               0
                                                         ---------------
  Total.................................................             922
------------------------------------------------------------------------

    Excluding the DSI installations,\204\ EIA lists 773 SO2 
scrubber installations in operation in 2020. Of these, 288 are listed 
as being spray type wet scrubbers, with an additional 63 listed as 
being tray type wet scrubbers.\205\ An additional 256 are listed as 
being spray dry absorber (SDA) scrubbers, which are a type of dry FGD. 
Consequently, spray type or tray type wet scrubbers (wet FGD) account 
for approximately 45 percent of all scrubber systems, and SDA accounts 
for approximately 33 percent of all scrubber systems that were 
operational in the U.S. in 2020.
---------------------------------------------------------------------------

    \204\ As discussed in this section, DSI is more commonly 
installed for compliance with the acid gas control requirements for 
MATS, not for meeting SO reduction requirements.
    \205\ Trays are often employed in spray type wet scrubbers and 
EIA lists some of the wet spray tower systems as secondarily 
including trays.
---------------------------------------------------------------------------

    We consider some of the other scrubber system types (e.g., venturi 
and packed wet scrubber types) to be older, outdated technologies (that 
are not existing controls or factor into considerations regarding 
existing controls) and therefore will not be considered in our BART 
analysis. Circulating dry scrubbers (CDS) is another type of dry 
scrubbing system that can achieve high removal efficiencies but has 
seen more limited use in the United States compared to SDA.\206\ Based 
on available data, CDS systems have installed costs that are comparable 
to SDA systems even though there are differences in design.\207\ CDS 
systems may be capable of achieving a slightly higher control 
efficiency than SDA, but based on 2019 data for coal-fired units at 
power plants, the 12-month average emission rate for the top performing 
50 percent FGD systems is 0.06 lb/MMBtu for SDA systems and 0.12 lb/
MMBtu for CDS systems.\208\
---------------------------------------------------------------------------

    \206\ See the EPA Air Pollution Control Cost Manual, Seventh 
Edition (April 2021), Section 5, Chapter 1, page 1-44. The EPA Air 
Pollution Control Cost Manual is available at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual. The EPA is currently in 
the process of updating the Control Cost Manual and this update will 
be the Seventh Edition. Although updates are not yet complete for 
all sections the EPA intends to update in the Seventh Edition, 
updated Section 5, Chapter 1, which is titled ``Wet and Dry 
Scrubbers for Acid Gas Control,'' is now available and is part of 
the Seventh Edition of the Control Cost Manual.
    \207\ See Control Cost Manual, Wet and Dry Scrubbers for Acid 
Gas Control Response to Comment Document, pg 32. Available at 
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.epa.gov/sites/default/files/2021-05/documents/rtcdocument_wet_and_dry_scrubbers_controlcostmanual_7thedition.pdf 
and in the docket for this action.
    \208\ The EPA Air Pollution Control Cost Manual (the Control 
Cost Manual, or Manual), Seventh Edition (April 2021), Section 5, 
Chapter 1 titled ``Wet and Dry Scrubbers for Acid Gas Control,'' 
page 1-12. The Control Cost Manual can be found at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual.
---------------------------------------------------------------------------

    The BART Guidelines explain that:
    A possible outcome of the BART procedures discussed in these 
guidelines is the evaluation of multiple control technology 
alternatives which result in essentially equivalent emissions. It is 
not our intent to encourage evaluation of unnecessarily large numbers 
of control alternatives for every emissions unit. Consequently, you 
should use judgment in deciding on those alternatives for which you 
will conduct the detailed impacts analysis (Step 4 below).\209\
---------------------------------------------------------------------------

    \209\ See 40 CFR part 51, Appendix Y--Guidelines For BART 
Determinations Under the Regional Haze Rule, Section IV.D.2.
---------------------------------------------------------------------------

    We believe that evaluation of SDA and wet FGD covers a reasonable 
range of control efficiencies offered by available SO2 
scrubbing technologies and includes the most stringent control option 
available.\210\ CDS will not be further considered as part of our 
reasonable set of options for analysis for BART controls given the 
similarity in cost and removal efficiencies with SDA. However, CDS 
could potentially be considered as an alternative dry scrubber control 
to SDA. We therefore solicit comment regarding costs and control 
efficiency of CDS, including comments from the facilities we evaluated 
for SO2 scrubbers on whether they have conducted analysis of 
CDS, the level of SO2 control efficiency that could be 
achieved with installation of CDS at the unit, and the estimated cost 
of that control technology at the unit.
---------------------------------------------------------------------------

    \210\ The EPA Air Pollution Control Cost Manual (the Control 
Cost Manual, or Manual), Seventh Edition (April 2021), Section 5, 
Chapter 1 titled ``Wet and Dry Scrubbers for Acid Gas Control'' 
provides data summarizing the efficiency and SO2 emission 
rates for SO2 scrubbers based on 2019 data for coal-fired 
units at power plants. The 12-month average emission rate for the 
top performing 50 percent FGD systems is 0.04 lb/MMBtu for limestone 
wet FGD systems, 0.06 lb/MMBtu for SDA systems, and 0.12 lb/MMBtu 
for CDS systems. (See page 1-12). The Control Cost Manual can be 
found at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual.
---------------------------------------------------------------------------

    Wet FGD and SDA installations account for approximately 79 percent 
of all scrubber installations in the U.S. and as such constitute a 
reasonable set of SO2 scrubber control options. The vast 
majority of the wet FGD and SDA installations utilize limestone and 
lime, respectively as reagents. In addition, these technologies cover 
the maximum level of SO2 control available. As described 
above, these controls are in wide use and have been retrofitted to a 
variety of boiler types and plant configurations. Based on typical SDA 
performance, SDA scrubbers should not be applied to boilers that burn 
fuels with more than 3 lb SO2/MMBtu.\211\ Typically, SDA 
technology has been applied to boilers that burn fuels with less than 2 
lb/MMBtu. The Texas coal-fired EGUs we are evaluating in our BART 
analyses burn low sulfur coal and are suitable for evaluation of both 
SDA and wet FGD. We see no technical infeasibility issues and believe 
that limestone wet FGD and lime SDA should be considered as potential 
BART controls for all unscrubbed coal-fired subject to BART units. 
However, due to potential non-air quality concerns associated with 
water availability, we limit our SO2 control analysis for 
Harrington Units 061B and 062B to DSI and SDA. This is discussed in 
more detail in Section VII.B.3.
---------------------------------------------------------------------------

    \211\ IPM Model--Updates to Cost and Performance for APC 
Technologies, SDA FGD Cost Development Methodology, Final January 
2017, Project 13527-001, Eastern Research Group, Inc., Prepared by 
Sargent & Lundy, p. 2.
---------------------------------------------------------------------------

b. Identification of Technically Feasible SO2 Control 
Technologies for Scrubber Upgrades
    In our 2016 Texas-Oklahoma FIP,\212\ we presented a great deal of 
information on which we reached a conclusion that the existing 
scrubbers for a number of facilities could be very cost-effectively 
upgraded.\213\ While that action was stayed by the Fifth Circuit, the 
basis for the stay was not related to that technical analysis. This 
information remains valid and can be used to inform our BART analysis 
in this proposal. Therefore, we have included this information in the 
record for this proposal in Appendix A

[[Page 28946]]

of the 2023 BART FIP TSD in the docket.\214\ Appendix A also contains a 
comprehensive survey we prepared as part of our 2016 Texas-Oklahoma FIP 
of available literature concerning the kinds of upgrades that have been 
performed by industry on scrubber systems similar to the ones installed 
on the units included in this proposal. We then reviewed all 
information we had at our disposal regarding the status of the existing 
scrubbers for each unit, including any upgrades the facility may have 
already installed. We finished by calculating the cost-effectiveness of 
scrubber upgrades, using the facility's own information, obtained as a 
result of our previous CAA section 114 collection efforts. The 
companies that supplied this information have asserted a Confidential 
Business Information (CBI) claim for much of it, as provided in 40 CFR 
2.203(b). We therefore redacted any CBI information we utilized in our 
analyses, or otherwise disguised it so that it cannot be traced back to 
its specific source. Based on our review of this information, we find 
that upgrades to the existing scrubbers should be considered as 
potential BART controls for the three subject-to-BART units at the 
Martin Lake facility.
---------------------------------------------------------------------------

    \212\ 81 FR 296, 321 (Jan. 5, 2016).
    \213\ See information presented in Sections 6 and 7 of the 2016 
Texas-Oklahoma FIP Cost TSD, Document No. EPA-R06-OAR-2014-0754-
0008, available at www.regulations.gov.
    \214\ See our 2023 BART FIP TSD, Appendix A, ``Wet FGD Scrubber 
Upgrade Control Analysis as used in the Texas-Oklahoma FIP.''
---------------------------------------------------------------------------

    The Fayette Units 1 and 2 are currently equipped with high 
performing wet FGDs. Both units have demonstrated the ability to 
maintain a SO2 30 Boiler Operating Day (BOD) average below 
0.04 lb/MMBtu for years at a time.\215\ As we discuss in Section 
VII.B.2.a, we state that retrofit wet FGDs should be evaluated at 98 
percent control not to go below 0.04 lb/MMBtu. Because the Fayette 
units are already performing at this level, we do not evaluate any 
additional scrubber upgrades for these two units. Thus, our 
SO2 BART analysis in this proposed rulemaking evaluates 
scrubber upgrades as potential BART controls only for Martin Lake Units 
1, 2, and 3.
---------------------------------------------------------------------------

    \215\ See our 2023 BART FIP TSD for additional information and 
graphs of this data.
---------------------------------------------------------------------------

c. Identification of Technically Feasible SO2 Control 
Technologies for Gas Fired Units
    Based on our subject to BART screening analysis, W. A. Parish Unit 
WAP4 is the only gas-fired unit we determined to be subject to BART. 
Because the BART screening analysis is done on a facility-wide basis, 
Unit WAP4 is only subject to BART because it is collocated with two 
BART-eligible coal-fired units. Gas-fired EGUs have inherently low 
SO2 emissions \216\ and there are no known SO2 
controls that can be evaluated. While we must assign SO2 
BART determinations to the gas-fired unit, there are no practical add-
on controls to consider for setting a more stringent BART emission 
limit. The Guidelines state that if the most stringent controls are 
made federally enforceable for BART, then the otherwise required 
analyses leading up to the BART determination can be skipped.\217\ As 
there are no appropriate add-on controls and the status quo reflects 
the most stringent control level, we are proposing that SO2 
BART for W. A. Parish Unit WAP4 is to limit fuel to pipeline natural 
gas, as defined at 40 CFR 72.2.\218\
---------------------------------------------------------------------------

    \216\ AP 42, Fifth Edition, Volume 1, Chapter 1: External 
Sources, Section 1.4, Natural Gas Combustion, available here: 
https://www3.epa.gov/ttn/chief/ap42/ch01/final/c01s04.pdf.
    \217\ 70 FR at 39165 (``. . . you may skip the remaining 
analyses in this section, including the visibility analysis . . 
.'').
    \218\ As provided for in 40 CFR 72.2, pipeline natural gas 
contains 0.5 grains or less of total sulfur per 100 standard cubic 
feet. This is equivalent to an SO2 emission rate of 
0.0006 lb/MMBtu.
---------------------------------------------------------------------------

2. Step 3: Evaluation of Control Effectiveness
    In the following subsections, we evaluate the control levels each 
technically feasible technology can achieve for the coal units. In so 
doing, we consider the maximum level of control each technology is 
capable of delivering based on a 30 BOD period. As the BART Guidelines 
direct, ``[y]ou should consider a boiler operating day to be any 24-
hour period between 12:00 midnight and the following midnight during 
which any fuel is combusted at any time at the steam generating unit.'' 
\219\ To calculate a 30-day rolling average based on BOD, the average 
of the last 30 ``boiler operating days'' is used. In other words, days 
are skipped when the unit is down, as for maintenance.
---------------------------------------------------------------------------

    \219\ 70 FR 39103, 39172 (July 6, 2005), [40 CFR part 51, App. 
Y].
---------------------------------------------------------------------------

a. Evaluation of SO2 Control Effectiveness for Coal-Fired 
Units Without an Existing Scrubber
Control Effectiveness of DSI
    DSI involves pneumatically injecting a sorbent either directly into 
a coal-fired boiler or into ducting downstream of where the coal is 
combusted. The sorbent interacts with various pollutants in the flue 
gas, including SO2 and acid gases such as hydrochloric acid 
(HCl), such that a fraction of these pollutants are removed from the 
gas stream. After the appropriate chemical interactions between the 
sorbent and the pollutants in the flue gas, the dry waste product of 
the reaction is removed using a particulate control device, typically a 
fabric filter baghouse or electrostatic precipitator (ESP). The 
SO2 removal efficiency of DSI varies greatly but is highly 
dependent on the following factors: the type of sorbent used; the 
careful balancing of the stoichiometry of the molecules in the sorbent 
(sodium in the case of trona or sodium bicarbonate, or calcium in the 
case of hydrated lime) and SO2 molecules in the flue gas; 
and the type of particulate capture device used in conjunction with the 
sorbent injection. Removal efficiency can also be improved by 
increasing the surface area of the sorbent to increase reactivity with 
the SO2 gas. This can be achieved by crushing or ``milling'' 
the sorbent and also by applying heat. Both the application of heat and 
milling the sorbent increase the efficiency of the DSI system, but also 
increase the cost.\220\
---------------------------------------------------------------------------

    \220\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy.
---------------------------------------------------------------------------

    The most common sodium-based sorbents used in DSI systems are trona 
and sodium bicarbonate. Sodium bicarbonate is more effective in 
removing SO2 emissions than trona,\221\ and therefore, less 
sodium bicarbonate is needed for an equivalent amount of SO2 
removal compared to trona. However, sodium bicarbonate is more 
expensive than trona on a per ton basis. Hydrated lime is a calcium-
based sorbent that is also used in DSI systems. DSI using hydrated lime 
typically achieves a lower SO2 removal efficiency compared 
to DSI using trona. Aside from the lower SO2 removal 
efficiency typically seen with hydrated lime, we also note that DSI 
using hydrated lime as the sorbent may necessitate the use of a 
baghouse rather than an ESP as the particulate capture device, which 
would increase costs if a unit does not already have an existing 
baghouse. Because trona is generally considered the most cost-effective 
of the DSI sorbents for SO2 removal and considering the 
limitations associated with hydrated lime for SO2 removal, 
our DSI analysis is based on using milled trona as the sorbent.\222\
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    \221\ Sodium bicarbonate may be able to achieve even higher 
SO2 removal efficiencies compared to trona. However, the 
April 2017 IPM DSI documentation and associated 2019 Retrofit Cost 
Analyzer (RCA) tool cost spreadsheet do not include information on 
sodium bicarbonate costs and removal efficiencies.
    \222\ As discussed in the preceding paragraph, the removal 
efficiency of trona can be improved by crushing or ``milling'' the 
sorbent, which increases the reactivity with the SO2 gas. 
The control efficiencies we evaluate for DSI and our cost analysis 
is based on the use of milled trona.

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[[Page 28947]]

    In developing our BART analysis for DSI, we relied on the EPA's 
April 2017 version of the Integrated Planning Model (IPM) DSI 
documentation 223 224 and the 2019 version of the EPA's 
Retrofit Cost Analyzer (RCA), which is an Excel-based tool that can be 
used to estimate the cost of building and operating air pollution 
controls and also employs version 6 of our IPM model.\225\ We expect 
that by the time this proposal is published in the Federal Register, or 
shortly thereafter, the EPA will have issued an updated version of the 
IPM DSI documentation and an accompanying updated version of the RCA 
tool for calculating the cost of DSI. The updated IPM DSI documentation 
and updated RCA tool for DSI include a number of updates to the cost 
algorithms and updated estimates for sorbent costs. Initial review of 
the updated DSI documentation indicates the maximum potential 
SO2 control efficiencies of DSI may be higher than indicated 
in the April 2017 version of the IPM DSI documentation. The updated DSI 
documentation and RCA tool also include updated cost algorithms 
predicting the amount of sorbent required to achieve certain control 
efficiencies that generally result in similar cost effectiveness values 
($/ton) for DSI using milled trona compared to the cost algorithms used 
in the April 2017 version of the IPM DSI documentation and the 2019 
version of the RCA tool. This is the result of the updated efficiency 
curves estimating lower sorbent use and updated higher costs for milled 
trona. The updated RCA tool contains cost information for sodium 
bicarbonate and the capability to estimate the cost of DSI using sodium 
bicarbonate as the sorbent. In general, the cost-effectiveness values 
for DSI using milled trona and sodium bicarbonate appear to be very 
similar. Less sodium bicarbonate is needed than milled trona to achieve 
a given control efficiency but the cost per ton of sodium bicarbonate 
is higher compared to milled trona, thereby resulting in similar cost-
effectiveness values. However, the updated IPM DSI documentation 
indicates that sodium bicarbonate may be able to achieve higher control 
efficiencies compared to milled trona. We will include these documents 
in the docket once they are finalized and made publicly available. As 
these updated documents were not available at the time we developed our 
cost analysis, we did not rely on this updated information in our DSI 
cost analysis presented in this proposal. In general, the updated IPM 
DSI documentation and updated RCA tool for DSI suggest that DSI could 
potentially achieve higher SO2 control efficiencies at a 
similar cost per SO2 tons removed. However, as described in 
further detail below, absent site-specific information from the 
facilities that we evaluated for DSI, we believe there is uncertainty 
whether these units are capable of achieving the assumed maximum DSI 
performance levels specified in either the April 2017 IPM DSI 
documentation or the updated version of the IPM DSI documentation. 
Similarly, we believe that our concern regarding the uncertainty in the 
cost estimates for DSI at high SO2 removal levels would 
still exist even if we were to rely on the updated versions of the IPM 
DSI documentation and the RCA tool.\226\ However, as we discuss later 
in this subsection, we solicit comment on the range and maximum control 
efficiency that can be achieved with DSI at the evaluated units and 
estimates of the range of associated costs. We are especially 
interested in any site-specific analysis of DSI for the units we 
evaluated, the level of SO2 control efficiency that could be 
achieved with installation of DSI at these units, and the estimated 
cost of that control technology at these units.
---------------------------------------------------------------------------

    \223\ See Documentation for the EPA's Power Sector Modeling 
Platform v6 Using the Integrated Planning Model, dated September 
2021. Documentation for v.6 downloaded from https://www.epa.gov/power-sector-modeling/documentation-epas-power-sector-modeling-platform-v6-summer-2021-reference.
    \224\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent &Lundy. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.
    \225\ Retrofit Cost Analyzer, rev: 06-04-2019, downloaded from 
https://www.epa.gov/power-sector-modeling/retrofit-cost-analyzer.
    \226\ We discuss these issues in more detail in Sections 
VII.B.3.a and VIII.A.
---------------------------------------------------------------------------

    According to the April 2017 IPM DSI documentation, the assumed 
maximum DSI performance level using milled trona is 80 percent 
SO2 removal for an Electrostatic Precipitator (ESP) 
installation and 90 percent SO2 removal for a baghouse 
installation.\227\ The BART Guidelines state the following regarding 
selection of an emissions performance level or levels to evaluate in a 
BART analysis for a control option with a wide range of emission 
performance levels:
---------------------------------------------------------------------------

    \227\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.

    It is not our intent to require analysis of each possible level 
of efficiency for a control technique as such an analysis would 
result in a large number of options. It is important, however, that 
in analyzing the technology you take into account the most stringent 
emission control level that the technology is capable of achieving. 
You should consider recent regulatory decisions and performance data 
(e.g., manufacturer's data, engineering estimates and the experience 
of other sources) when identifying an emissions performance level or 
levels to evaluate.\228\
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    \228\ See 40 CFR Part 51, Appendix Y--Guidelines For BART 
Determinations Under the Regional Haze Rule, Section IV.D.3.

    Adhering to this, we are evaluating each unit at its assumed 
maximum achievable DSI performance level according to the April 2017 
IPM DSI documentation. All the units we are evaluating for DSI controls 
have existing baghouses with the exception of Harrington Unit 061B, 
which has an ESP. For Coleto Creek Unit 1 and W. A. Parish Units WAP5 
and WAP6, we are evaluating DSI at 90 percent SO2 removal. 
For Welsh Unit 1 and Harrington Unit 062B, we are limiting the upper 
DSI control to their equivalent SDA control efficiencies of 87 percent 
and 89 percent, respectively. For Harrington Unit 061B, the only unit 
with an existing ESP, we are evaluating DSI at 80 percent 
SO2 removal.
    We recognize that there is some variation based on facility-
specific circumstances which could affect whether a given unit is 
actually capable of achieving these assumed maximum performance levels. 
There is typically a direct correlation with DSI between the targeted 
SO2 removal efficiency and the amount of sorbent needed; 
therefore, more sorbent is needed to reach higher SO2 
removal efficiencies. However, the reaction between the sorbent and the 
various pollutants in the flue gas results in a dry waste product that 
must be removed using a particulate control device. As additional 
sorbent is added to achieve higher SO2 removal efficiencies, 
the increased dry waste product can impact the performance of the 
particulate control device. For instance, DSI using trona and an ESP 
for capture of the dry waste product typically can achieve 40-50 
percent SO2 removal efficiency without an increase in 
particulate emissions.\229\ At higher

[[Page 28948]]

SO2 removal efficiencies, however, depending on the 
throughput capacity, an ESP may not be able to handle the increased dry 
waste product. Similar issues exist where DSI is used with a fabric 
filter for capture of the dry waste product. The increased dry waste 
product produced in trying to achieve high SO2 removal 
efficiencies would result in the more rapid formation of baghouse 
filter cake, which is the mixture of fly ash and sorbent-SO2 
reaction product. This would result in the need for more frequent 
cleaning, more rapid filter bag wear, and more frequent replacement of 
filter bags. The frequent need to clean and replace the filter bags may 
become impractical and additional fabric filter compartments may need 
to be added to handle the high loading that occurs at high 
SO2 removal efficiencies. The exact SO2 removal 
efficiency at which these secondary impacts would become significant is 
typically site-specific. As we discuss in Section VII.B.3.a, these 
secondary impacts associated with trying to achieve higher 
SO2 removal efficiencies also lead to some uncertainty in 
our cost estimates for DSI at high SO2 removal efficiencies.
---------------------------------------------------------------------------

    \229\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, p. 3; downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.
---------------------------------------------------------------------------

    Site-specific information based on individual performance testing 
is typically needed to be able to accurately determine the maximum DSI 
SO2 removal efficiency for a particular unit. We do not have 
this site-specific information and testing for the individual units 
that we are evaluating for DSI. Instead, we analyzed publicly available 
2017-2021 data for coal-fired EGUs with existing DSI systems and 
estimated the monthly average SO2 removal efficiency of 
existing DSI systems by utilizing the reported sulfur content and 
tonnages of the fuels burned and reported to EIA \230\ and the 
monitored SO2 outlet emissions reported to the EPA.\231\ 
Based on our analysis, we found that there is a large range of 
SO2 removal efficiency at the coal-fired EGUs with existing 
DSI for which there is publicly available data. However, unless there 
is a specific regulatory requirement to meet a low SO2 
emissions rate, DSI installations are often not optimized to achieve 
the highest possible SO2 control efficiency. Of particular 
interest for this BART analysis, there are existing coal-fired DSI 
units that are consistently achieving high monthly average 
SO2 removal efficiencies in the 70-90 percent range. We 
discuss this analysis in further detail in our 2023 BART FIP TSD in the 
docket. However, because we could only identify a few cases where units 
are consistently achieving greater than 70 percent SO2 
control efficiency and, most importantly, because we do not have the 
site-specific information and individual performance testing needed to 
accurately determine the maximum DSI SO2 removal efficiency 
for a particular unit, we do not know whether the EGUs we are 
evaluating in this proposal are capable of achieving the assumed 
maximum DSI performance levels specified in the April 2017 IPM DSI 
documentation or what level of control should be considered the maximum 
achievable level for these units.
---------------------------------------------------------------------------

    \230\ EIA Form 923. Available at https://www.eia.gov/electricity/data/eia923/.
    \231\ EPA Air Markets and Programs Data. Available at https://campd.epa.gov/.
---------------------------------------------------------------------------

    Recognizing that DSI has a wide range of SO2 removal 
efficiencies, that there is some variation based on facility-specific 
circumstances which could affect whether a given unit is actually 
capable of achieving the assumed maximum achievable control levels 
outlined in the April 2017 IPM DSI documentation, and because we 
believe it is useful to evaluate lesser levels of DSI control to 
provide a range of costs, we will also evaluate these units at a DSI 
SO2 control level that can likely be achieved by most coal-
fired units. DSI using trona and an ESP for particulate capture can 
typically remove 40-50 percent of SO2 without affecting the 
performance of the particulate control device.\232\ Therefore, we 
believe 50 percent SO2 removal is a conservatively low DSI 
control efficiency that any given coal-fired EGU is likely capable of 
achieving without requiring high sorbent injection rates that may 
negatively impact the particulate control. This approach is consistent 
with the BART Guidelines, which state the following:
---------------------------------------------------------------------------

    \232\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, p. 3; downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.

    You may encounter cases where you may wish to evaluate other 
levels of control in addition to the most stringent level for a 
given device. While you must consider the most stringent level as 
one of the control options, you may consider less stringent levels 
of control as additional options. This would be useful, particularly 
in cases where the selection of additional options would have widely 
varying costs and other impacts.\233\
---------------------------------------------------------------------------

    \233\ See 40 CFR part 51, appendix Y--Guidelines For BART 
Determinations Under the Regional Haze Rule, Section IV.D.3.

    We invite comments on the range and maximum control efficiency that 
can be achieved with DSI at the evaluated units. We are especially 
interested in any site-specific DSI testing for the units we evaluated 
to determine the range and maximum control efficiency that can be 
achieved at those units. Any data to support the range and maximum 
control efficiency for a particular unit should be submitted along with 
those comments. We will further consider DSI site-specific information 
provided to us during the public comment period in making our final 
decision and potentially re-evaluate DSI and the control efficiency for 
one or more particular units.
Control Effectiveness of Wet FGD and SDA
    We have assumed a wet FGD level of control to be a maximum of 98 
percent not to go below 0.04 lb/MMBtu, in which case, we assume the 
percentage of control equal to 0.04 lb/MMBtu. As we discuss later in 
this proposal, we conducted our wet FGD control cost analysis using the 
EPA's ``Air Pollution Control Cost Estimation Spreadsheet For Wet and 
Dry Scrubbers for Acid Gas Control,'' \234\ which employs version 6 of 
our IPM model.\235\ The IPM wet FGD

[[Page 28949]]

Documentation states: ``The least-squares curve fit of the data was 
defined as a ``typical'' wet FGD retrofit for removal of 98 percent of 
the inlet sulfur. It should be noted that the lowest available 
SO2 emission guarantees, from the original equipment 
manufacturers of wet FGD systems, are 0.04 lb/MMBtu.'' \236\ The most 
recent version of the EPA Air Pollution Control Cost Manual (the 
Control Cost Manual, or Manual) section on Wet and Dry Scrubbers for 
Acid Gas Control \237\ provides data summarizing the efficiency and 
SO2 emission rates for SO2 scrubbers based on 
2019 data for coal-fired units at power plants. The 12-month average 
emission rate for the top performing 50 percent of wet limestone FGD 
systems is 0.04 lb/MMBtu.\238\
---------------------------------------------------------------------------

    \234\ Air Pollution Control Cost Estimation Spreadsheet For Wet 
and Dry Scrubbers for Acid Gas Control, U.S. Environmental 
Protection Agency, Air Economics Group, Health and Environmental 
Impacts Division, Office of Air Quality Planning and Standards 
(January 2023), downloaded from https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.
    \235\ See Documentation for the EPA's Power Sector Modeling 
Platform v6 Using the Integrated Planning Model, dated September 
2021. Documentation for v.6 downloaded from https://www.epa.gov/power-sector-modeling/documentation-epas-power-sector-modeling-platform-v6-summer-2021-reference.
    IPM Model--Updates to Cost and Performance for APC Technologies, 
Dry Sorbent Injection for SO2/HCl Control Cost 
Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.
    IPM Model--Updates to Cost and Performance for APC Technologies, 
SDA FGD Cost Development Methodology, Final January 2017, Project 
13527-001, Eastern Research Group, Inc., Prepared by Sargent & 
Lundy. Documentation for v.6: Chapter 5: Emission Control 
Technologies, Attachment 5-2: SDA FGD Cost Methodology, downloaded 
from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-2_sda_fgd_cost_development_methodology.pdf.
    IPM Model--Updates to Cost and Performance for APC Technologies, 
Wet FGD Cost Development Methodology, Final January 2017, Project 
13527-001, Eastern Research Group, Inc., Prepared by Sargent & 
Lundy. Documentation for v.6: Chapter 5: Emission Control 
Technologies, Attachment 5-1: Wet FGD Cost Methodology, downloaded 
from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-1_wet_fgd_cost_development_methodology.pdf.
    \236\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Wet FGD Cost Development Methodology, Final January 
2017, Project 13527-001, Eastern Research Group, Inc., Prepared by 
Sargent & Lundy, p. 2.
    \237\ EPA Air Pollution Control Cost Manual, Seventh Edition, 
April 2021 available at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual. The EPA is currently in the process of 
updating the Control Cost Manual and this update will be the Seventh 
Edition. Although updates are not yet complete for all sections the 
EPA intends to update in the Seventh Edition, updated Section 5, 
Chapter 1, which is titled ``Wet and Dry Scrubbers for Acid Gas 
Control,'' is now available and is part of the Seventh Edition of 
the Control Cost Manual.
    \238\ These observed overall SO2 emission rates are 
likely attributable to a variety of factors including improvements 
in the design and operation of FGD systems and operational changes 
at some utilities from switching to lower sulfur coal and operating 
at less than full capacity. EPA Air Pollution Control Cost Manual, 
Seventh Edition, April 2021, Section 5, Chapter 1, p 1-12.
---------------------------------------------------------------------------

    Assuming a wet FGD level of control to be a maximum of 98 percent 
not to go below 0.04 lb/MMBtu is also consistent with our determination 
in the 2011 Oklahoma FIP.\239\ Issues that have been raised in the past 
concerning these conclusions are discussed further in Appendix A of the 
2023 BART FIP TSD in the docket. Elsewhere in this notice and in the 
2023 BART FIP TSD, we discuss the performance of the wet FGD on Fayette 
Units 1 and 2 as an example of units with emission rates consistent 
with our assumption of 0.04 lb/MMBtu with this control technology. We 
propose that this level of control for wet FGD is reasonable.
---------------------------------------------------------------------------

    \239\ As discussed previously in our TSD for that action, 
control efficiencies reasonably achievable by dry scrubbing and wet 
scrubbing were determined to be 95 percent and 98 percent 
respectively. 76 FR 81728, 81742 (2011); Oklahoma v. EPA, 723 F.3d 
1201 (July 19, 2013), cert. denied (U.S. May 27, 2014). This level 
of control was also employed in our Texas-Oklahoma FIP. See 81 FR at 
321.
---------------------------------------------------------------------------

    In evaluating the control effectiveness for SDA, the Control Cost 
Manual identifies the 12-month average emission rate for the top 
performing 50 percent of SDA systems as 0.06 lb/MMBtu.\240\ As with our 
Oklahoma FIP, we have assumed an SDA level of control equal to 95 
percent, unless that level of control would fall below an outlet 
SO2 level of 0.06 lb/MMBtu, in which case, we assume the 
percentage of control equal to 0.06 lb/MMBtu.\241\ In that Oklahoma 
FIP, we finalized the same emission limit of 0.06 lb/MMBtu on a 30 BOD 
average for six coal-fired EGUs in Oklahoma. We justified those limits 
based on the same SDA technology, using a combination of industry 
publications and real-world monitoring data. Much of the information in 
support of our position that an emission limit of 0.06 lb/MMBtu on a 30 
BOD average is within the demonstrated capabilities of SDA retrofits is 
summarized in our response to comments document for the Oklahoma FIP 
\242\ and in our 2023 BART FIP TSD. We propose that this level of 
control for SDA is reasonable.
---------------------------------------------------------------------------

    \240\ These observed overall SO2 emission rates are 
likely attributable to a variety of factors including improvements 
in the design and operation of FGD systems and operational changes 
at some utilities from switching to lower sulfur coal and operating 
at less than full capacity. EPA Air Pollution Control Cost Manual, 
Seventh Edition, April 2021, Section 5, Chapter 1, p 1-12.
    \241\ See 76 FR 81728 (December 28, 2011).
    \242\ Response to Technical Comments for Sections E through H of 
the Federal Register Notice for the Oklahoma Regional Haze and 
Visibility Transport Federal Implementation Plan, Docket No. EPA-
R06-OAR-2010-0190, 12/13/2011. See comment and response beginning on 
page 91.
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b. Evaluation of SO2 Control Effectiveness for Coal-fired 
Units With Existing Scrubbers
Control Effectiveness of Upgrades to Existing Scrubbers
    Of the units we are proposing to determine are subject to BART, 
Martin Lake Units 1, 2, and 3 are currently equipped with wet FGDs that 
are not high-performing. Based on information we received from the 
facility, which we obtained in response to our previous CAA Section 
114(a) information collection request, we find that upgrades to the 
existing scrubbers should be considered as potential BART controls for 
these Martin Lake units. Because the company asserted a CBI claim for 
much of the information supplied to us, as provided in 40 CFR 2.203(b), 
we are limited in what information we can include in this section. The 
following summary is based on information not claimed as CBI.
     The absorber system could be upgraded to perform at an 
SO2 removal efficiency of at least 95 percent using proven 
equipment and techniques.
     The SO2 scrubber bypass could be eliminated, 
and the additional flue gas could be treated by the absorber system 
with at least a 95 percent removal efficiency.
     Additional modifications necessary to eliminate the bypass 
could be performed using proven equipment and techniques.
     The additional SO2 emission reductions 
resulting from the scrubber upgrade would be substantial.
    Given that we lack Continuous Emissions Monitoring Systems (CEMS) 
data for the inlet of the scrubbers and only have CEMS data for the 
outlet of the scrubbers, we calculated the current removal efficiency 
of each scrubber by utilizing the reported sulfur content and tonnages 
of the fuels burned and reported to EIA \243\ and the monitored 
SO2 scrubber outlet emissions reported to the EPA.\244\ Our 
approach for estimating the current removal efficiency of the existing 
scrubbers is discussed in greater detail in our 2023 BART FIP TSD in 
the docket. Based on emissions rate data and reported sulfur content 
and tonnages of the fuels burned in 2016--2020, we have estimated that 
the current removal efficiency of the existing scrubbers at the Martin 
Lake units is approximately 64 percent at Unit 1, 66 percent at Unit 2, 
and 64 percent at Unit 3.\245\ We find that an assumption that upgrades 
to the existing scrubbers can increase their control efficiency to 95 
percent at Martin Lake Units 1, 2, and 3 is reasonable. This is below 
the upper end of what an upgraded wet SO2 scrubber can 
achieve, which is 98-99 percent, as we have noted in the 2023 BART FIP 
TSD in the docket. We believe that a 95 percent control assumption 
provides an adequate margin of error, such that the Martin Lake units 
would be able to comfortably achieve this removal efficiency. Based on 
the reported sulfur content and tonnages of the fuels

[[Page 28950]]

burned in 2016-2020, 95 percent control would equate to an emission 
rate of 0.08 lb/MMBtu for each unit.
---------------------------------------------------------------------------

    \243\ EIA Form 923. Available at https://www.eia.gov/electricity/data/eia923/.
    \244\ EPA Air Markets and Programs Data. Available at https://campd.epa.gov/.
    \245\ See ``Coal vs CEM data 2016-2020_ML.xlsx,'' tab 
``charts,'' cell H12. This Excel spreadsheet is located in the 
docket associated with this proposed rule.
---------------------------------------------------------------------------

3. Step 4: Evaluate Impacts and Document the Results for SO2
    The BART Guidelines offer the following with regard to how Step 4 
should be conducted: \246\
---------------------------------------------------------------------------

    \246\ 70 FR at 39166.

    After you identify the available and technically feasible 
control technology options, you are expected to conduct the 
following analyses when you make a BART determination:
    Impact analysis part 1: Costs of compliance,
    Impact analysis part 2: Energy impacts, and
    Impact analysis part 3: Non-air quality environmental impacts.
    Impact analysis part 4: Remaining useful life.

    We evaluate the cost of compliance on a unit by unit basis because 
control cost analysis depends on specific factors that can vary from 
unit to unit. However, we generally evaluate the energy impacts, non-
air quality impacts, and the remaining useful life for all the units in 
question together because there are usually no appreciable differences 
in these factors from unit to unit.\247\ In developing our cost 
estimates for the units in Table 7, we rely on the methods and 
principles contained within the EPA Air Pollution Control Cost Manual 
(the Control Cost Manual, or Manual).\248\ We proceed in our 
SO2 cost analyses by examining the current SO2 
emissions and the level of SO2 control, if any, for each of 
the coal-fired units listed in Table 7.\249\
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    \247\ To the extent these factors inform the cost of controls, 
consistent with the BART Guidelines, they do inform our 
considerations on a unit-by-unit basis.
    \248\ EPA Air Pollution Control Cost Manual, Seventh Edition, 
April 2021 available at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual. The EPA is currently in the process of 
updating the Control Cost Manual and this update will be the Seventh 
Edition. Although updates are not yet complete for all sections the 
EPA intends to update in the Seventh Edition, updated Section 5, 
Chapter 1, which is titled ``Wet and Dry Scrubbers for Acid Gas 
Control,'' is now available and is part of the Seventh Edition of 
the Control Cost Manual.
    \249\ W.A. Parish WAP4 is the only gas-fired unit we determined 
to be subject to BART. As we discussed in Section VII.B.1.c, gas-
fired EGUs have inherently low SO2 emissions and there 
are no known SO2 controls that can be evaluated. 
Therefore, our cost analysis does not include WAP4.
---------------------------------------------------------------------------

a. Impact Analysis Part 1: Cost of Compliance for DSI, SDA, and Wet FGD
    As we discuss in Section VII.B.2. and in our 2023 BART FIP TSD 
associated with this notice, we evaluated each unit at the assumed 
maximum SO2 performance levels, considering the type of 
SO2 control device. For DSI, in addition to evaluating each 
unit at the assumed maximum achievable level of SO2 control, 
we also evaluated each unit at 50 percent control efficiency. In Table 
9 we present a summary of our DSI, SDA, and wet FGD cost analysis.\250\
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    \250\ In this table, the annualized cost is the sum of the 
annualized capital cost and the annualized operational cost. See our 
TSD for more information on how these costs were calculated.

                                                 Table 9--Summary of DSI, SDA, and Wet FGD Cost Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                       SO2 reduction                        Cost        Incremental Cost-
           Facility                 Unit              Control          Control level       (tpy)        Annualized    effectiveness (/   effectiveness(/
                                                                            (%)                            cost           ton) \1\        ton) \2\ \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Coleto Creek.................  1.............  DSI..................              50           6,680     $15,016,712            $2,249  ................
                                               DSI..................              90          12,024      29,320,229             2,439             2,677
                                               SDA..................              91          12,035      32,400,831             2,692             3,246
                                               Wet FGD..............              94          12,448      36,238,608             2,911             9,292
Harrington...................  061B..........  DSI..................              50           1,892       7,075,817             3,740  ................
                                               DSI..................              80           3,027      11,596,018             3,830             3,983
                                               SDA..................              89           3,327      21,967,236             6,603            10,377
                               062B..........  DSI..................              50           2,703       7,408,200             2,742  ................
                                               DSI..................              89           4,794      13,104,954             2,734             2,724
                                               SDA..................              89           4,812      23,369,564             4,857             7,568
Welsh........................  1.............  DSI..................              50           3,959      10,952,162             2,766  ................
                                               DSI..................              87           6,885      18,562,875             2,696             2,601
                                               SDA..................              87           6,878      30,056,814             4,370             6,545
                                               Wet FGD..............              91           7,219      32,464,043             4,497             7,059
W.A. Parish..................  WAP5..........  DSI..................              50           6,689      15,125,672             2,262  ................
                                               DSI..................              90          12,039      29,457,805             2,447             2,679
                                               SDA..................              91          12,139      36,957,568             3,044             4,006
                                               Wet FGD..............              94          12,560      38,607,330             3,074             3,919
                               WAP6..........  DSI..................              50           6,902      15,489,974             2,244  ................
                                               DSI..................              90          12,423      30,246,942             2,435             2,673
                                               SDA..................              91          12,475      33,070,310             2,651             3,155
                                               Wet FGD..............              94          12,908      35,073,781             2,717             4,627
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ We evaluated DSI both at the assumed maximum DSI performance levels of 80/90 percent specified in the April 2017 IPM DSI documentation and at 50
  percent control efficiency. However, we note there is uncertainty that the units we are evaluating for DSI are actually capable of achieving the
  assumed maximum DSI performance levels specified in the April 2017 IPM DSI documentation and there is also potential uncertainty in the DSI cost
  estimates at these high DSI performance levels.
\2\ The incremental cost effectiveness calculation compares the costs and performance level of a control option to those of the next most stringent
  option, as shown in the following formula (with respect to cost per emissions reduction): Incremental Cost Effectiveness (dollars per incremental ton
  removed) = (Total annualized costs of control option)-(Total annualized costs of next control option) / (Control option annual emissions)-(Next
  control option annual emissions). See Section IV.D.4.e of Appendix Y to Part 51--Guidelines for BART Determinations Under the Regional Haze Rule.
\3\ We calculated the incremental cost-effectiveness of SDA by comparing it to DSI at 50 percent control efficiency rather than to DSI at 80/87/89/90
  percent control efficiency. We took this approach given the following considerations: (1) the control efficiencies of SDA and DSI at the assumed
  maximum DSI performance level for units with fabric filters specified in the April 2017 IPM DSI documentation are assumed to be identical; (2) there
  is uncertainty that the units we are evaluating for DSI are actually capable of achieving the assumed maximum DSI performance levels specified in the
  April 2017 IPM DSI documentation; and (3) there is potential uncertainty in the cost estimates for DSI at these high DSI performance levels, as
  discussed later in this subsection.


[[Page 28951]]

    For the coal units without any SO2 control, we 
calculated the cost of installing DSI, an SDA scrubber, and a wet FGD 
scrubber. In order to estimate the costs for SDA scrubbers and wet FGD 
scrubbers, we used the ``Air Pollution Control Cost Estimation 
Spreadsheet For Wet and Dry Scrubbers for Acid Gas Control,'' which is 
an Excel-based tool that can be used to estimate the costs for 
installing and operating scrubbers for reducing sulfur dioxide and 
acidic gas emissions from fossil fuel-fired combustion units and other 
industrial sources of acid gases.\251\ The methodologies for wet FGD 
scrubbers and SDA scrubbers are based on those from version 6 of our 
IPM model.\252\ The size and costs of a wet FGD scrubber and SDA 
scrubber are based primarily on the size of the combustion unit and the 
sulfur content of the coal burned. The wet FGD scrubber methodology 
includes cost algorithms for capital and operating cost for wastewater 
treatment consisting of chemical pretreatment, low hydraulic residence 
time biological reduction, and ultrafiltration to treat wastewater 
generated by the wet FGD system. The calculation methodologies used in 
the ``Air Pollution Control Cost Estimation Spreadsheet For Wet and Dry 
Scrubbers for Acid Gas Control,'' are those presented in the U.S. EPA's 
Air Pollution Control Cost Manual.
---------------------------------------------------------------------------

    \251\ Air Pollution Control Cost Estimation Spreadsheet For Wet 
and Dry Scrubbers for Acid Gas Control, U.S. Environmental 
Protection Agency, Air Economics Group, Health and Environmental 
Impacts Division, Office of Air Quality Planning and Standards 
(January 2023), downloaded from https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution.
    \252\ See Documentation for EPA's Power Sector Modeling Platform 
v6 Using the Integrated Planning Model, dated September 2021. 
Documentation for v.6 downloaded from https://www.epa.gov/power-sector-modeling/documentation-epas-power-sector-modeling-platform-v6-summer-2021-reference.
---------------------------------------------------------------------------

    The cost algorithm used in the ``Air Pollution Control Cost 
Estimation Spreadsheet For Wet and Dry Scrubbers for Acid Gas Control'' 
calculates the Total Capital Investment, Direct Annual Cost, and 
Indirect Annual Cost. The Total Capital Investment for wet FGD is a 
function of the absorber island capital costs, reagent preparation 
equipment costs, waste handling equipment costs, balance of plant 
costs, and wastewater treatment facility costs. For SDA, the Total 
Capital Investment is a function of the absorber island capital costs 
that include both an absorber and a baghouse, reagent preparation and 
waste recycling/handling costs, and balance of plant costs. The Direct 
Annual Costs consist of annual maintenance cost, annual operator cost, 
annual reagent cost, annual make-up water cost, annual waste disposal 
cost, and annual auxiliary power cost. Additionally, the Direct Annual 
Costs for wet FGD also include annual wastewater treatment cost and the 
replacement cost of a mercury monitor (replaced once every 6 years). 
The Indirect Annual Cost consists of administrative charges and capital 
recovery costs.
    To estimate the costs for DSI, we relied on the EPA's April 2017 
IPM DSI documentation \253\ and the 2019 version of the EPA's RCA tool, 
which employs version 6 of our IPM model.\254\ The cost algorithm used 
in the RCA tool calculates the Total Project Cost (TPC), Fixed 
Operating and Maintenance (Fixed O&M) costs, and Variable Operating and 
Maintenance (Variable O&M) costs. As we discuss in Section VII.B.2.a., 
for DSI systems using a fabric filter for particulate control and 
operating at high SO2 removal efficiency, it is expected 
that filter bag wear would occur more rapidly and that filter bags 
would need to be replaced more frequently due to the increased dry 
waste product. The frequent need to clean and replace the filter bags 
may become impractical and additional fabric filter compartments may 
need to be added to handle the high loading that occurs at high 
SO2 removal efficiencies. This impacts the cost and leads to 
some uncertainty in our cost estimates for DSI at high SO2 
removal efficiencies given that we do not have site-specific 
information and performance testing to determine how frequently filter 
bags would need to be replaced or whether additional fabric filter 
compartments are necessary. Similarly, DSI systems with an ESP for 
particulate control may not be capable of handling the higher loadings 
at high SO2 removal efficiencies and would require 
consideration of additional costs for a new ESP or fabric filter to 
handle the load at these high sorbent injection rates. This impacts the 
cost and leads to some uncertainty in our cost estimates for DSI with 
an existing ESP (for Harrington Unit 061B) given that our cost 
estimates do not reflect the cost of a new ESP or fabric filter even 
though we do not know with certainty whether the existing ESP can 
handle the high sorbent injection rates needed at high SO2 
removal efficiency.
---------------------------------------------------------------------------

    \253\ See Documentation for EPA's Power Sector Modeling Platform 
v6 Using the Integrated Planning Model, dated September 2021. 
Documentation for v.6 downloaded from https://www.epa.gov/power-sector-modeling/documentation-epas-power-sector-modeling-platform-v6-summer-2021-reference.
    IPM Model--Updates to Cost and Performance for APC Technologies, 
Dry Sorbent Injection for SO2/HCl Control Cost 
Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy. 
Documentation for v.6: Chapter 5: Emission Control Technologies, 
Attachment 5-5: DSI Cost Methodology, downloaded from https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-5_dsi_cost_development_methodology.pdf.
    \254\ Retrofit Cost Analyzer, rev: 06-04-2019, downloaded from 
https://www.epa.gov/power-sector-modeling/retrofit-cost-analyzer.
---------------------------------------------------------------------------

    As we discuss in Section VII.B.2.a, we expect that by the time this 
proposal is published in the Federal Register, or shortly thereafter, 
the EPA will have issued an updated version of the IPM DSI 
documentation and an updated version of the RCA tool for calculating 
the cost of DSI. We will include these documents in the docket once 
they are finalized and made publicly available. As these updated 
documents were not available at the time we developed our cost 
analysis, we did not rely on this information in our DSI cost analysis 
presented in this proposal. In general, the updated IPM DSI 
documentation and updated RCA tool for DSI suggest that DSI could 
potentially achieve higher SO2 control efficiencies and at a 
similar cost per SO2 tons removed. Absent site-specific 
information from the facilities that we evaluated for DSI, we believe 
that our concerns regarding the uncertainty of whether these units are 
actually capable of achieving the assumed maximum DSI performance 
levels and the uncertainty in the cost estimates for DSI at high 
SO2 removal efficiencies would still exist even if we were 
to rely on the updated versions of the IPM DSI documentation and the 
RCA tool. However, we invite comments on the range and maximum control 
efficiency that can be achieved with DSI at the evaluated units and 
estimates of the range of associated costs. We are especially 
interested in any site-specific DSI testing for the units we evaluated 
to determine the range and maximum control efficiency that can be 
achieved at those units and any other unit-specific information that 
would help provide better insight into the unit-specific DSI costs. Any 
data to support the control efficiency range, maximum control 
efficiency, and cost of DSI for a particular unit should be submitted 
along with those comments. We will further consider DSI site-specific 
information provided to us during the public comment period in our 
final decision and potentially re-evaluate DSI for those particular 
units.
    The cost models used in IPM version 6 were based on 2016 dollars. 
Thus, in

[[Page 28952]]

performing the cost calculations \255\ for each unit listed in Table 9 
we have escalated the costs to 2020 dollars. For DSI, we accomplished 
this escalation using the annual Chemical Engineering Plant Cost 
Indices (CEPCI). For the SDA and wet FGD scrubbers, the ``Air Pollution 
Control Cost Estimation Spreadsheet For Wet and Dry Scrubbers for Acid 
Gas Control'' allows the user to enter a different dollar-year for 
costs and the corresponding cost index if a different dollar-year is 
desired. Using this capability, we entered the 2020 CEPCI index into 
the spreadsheet to estimate the cost of wet FGD scrubbers and SDA 
scrubbers in 2020 dollars. For a more detailed discussion of the inputs 
and cost calculations, see our 2023 BART FIP TSD in the docket.
---------------------------------------------------------------------------

    \255\ The cost calculation spreadsheets can be found in the 
docket for this action under the heading ``Cost Calculations''.
---------------------------------------------------------------------------

b. Impact Analysis Part 1: Cost of Compliance for Scrubber Upgrades
    In our 2023 BART FIP TSD associated with this proposed rulemaking, 
we analyze those units listed in Table 7 of this notice that have an 
existing SO2 scrubber in order to determine if cost-
effective scrubber upgrades are available. Of our subject-to-BART 
units, Martin Lake Units 1, 2, 3; and Fayette Units 1 and 2 are 
currently equipped with wet FGDs. As discussed in Section VII.B.1.b, 
because the Fayette units are already performing at the maximum level 
of control we considered for wet FGD, we will not evaluate any 
additional scrubber upgrades for these two units.
    Martin Lake was the highest emitting EGU facility for 
SO2 in the United States for the past four years (2018-
2021). On an individual unit basis, Martin Lake Units 1, 2, and 3 were 
the top three emitting units in the country in 2018 and among the top 
four emitting units in 2019 and 2021.\256\ In general, given the very 
large emissions, potential for large emission reductions, and the lower 
costs associated with upgrading existing controls compared to a new 
scrubber retrofit, it is reasonable to expect scrubber upgrades at 
Martin Lake to be very cost-effective in terms of cost per ton removed. 
A review of emissions data for these units shows significant 
variability and demonstrates the ability of these units to be operated 
with higher removal efficiency to maintain lower emission levels for 
periods of time depending on the mixture of coals, the operation of the 
scrubbers, and the amount of scrubber bypass. For example, in 2016, the 
annual average emission rate for the three units ranged from 0.3 to 
0.43 lb/MMBtu, but in 2020, the annual average emission rate ranged 
from 0.55 to 0.73 lb/MMBtu.\257\ At the same time, the amount of higher 
sulfur lignite burned in 2016 was higher than in 2020 \258\ (61 to 71 
percent of heat input came from lignite in 2016 for the three units 
compared to 14 to 32 percent in 2020), meaning that the scrubbers and 
amount bypassed were operated in a manner that achieved a significantly 
higher overall removal efficiency in 2016 than in 2020. Table 10 
summarizes the annual emission rate and the estimated annual scrubber 
removal efficiency. Given the variability in demonstrated scrubber 
efficiency, higher removal efficiency can be and has been achieved with 
optimized operation, reduced bypass, and increased reagent use with the 
current configuration of the scrubbers. As discussed earlier in this 
section, additional remaining cost-effective physical modifications to 
the scrubbers can further improve scrubber removal efficiency. This 
further supports our assessment that increased scrubber efficiency is 
cost-effective.
---------------------------------------------------------------------------

    \256\ In 2019 and 2021, a unit at the Gavin Facility in Ohio was 
the third highest emitting unit in the country. In 2020, the three 
Martin Lake units fell within the top 6 units. See 
``Largest_units_SO2_annual emissions 2016-2021.xlsx'' 
available in the docket for this action.
    \257\ See ``Largest_units_SO2_annual emissions 2016-
2021.xlsx'' available in the docket for this action.
    \258\ See ``Coal vs CEM data 2016-2020_ML.xlsx'' available in 
the docket for this action.

           Table 10--Martin Lake Annual Emission Rate and Estimated Annual Scrubber Removal Efficiency
----------------------------------------------------------------------------------------------------------------
                                         Annual emission rate (lb/MMBtu)    Estimated overall removal efficiency
                                     --------------------------------------                  (%)
             Martin Lake                                                   -------------------------------------
                                             2016               2020               2016               2020
----------------------------------------------------------------------------------------------------------------
Unit 1..............................               0.42               0.73               78.2               52.8
Unit 2..............................               0.30               0.60               84.5               62.8
Unit 3..............................               0.43               0.55               78.0               62.8
----------------------------------------------------------------------------------------------------------------

    The cost of scrubber upgrades at coal-fired power plants has been 
evaluated in many other instances in both the context of BART and 
reasonable progress for both the first and second planning periods for 
regional haze. Based on what we have seen in other regional haze 
actions, upgrading an underperforming SO2 scrubber is 
generally very cost-effective.\259\ In our TSD, we provide further 
discussion of other regional haze actions where scrubber upgrades have 
been found to be very cost-effective.
---------------------------------------------------------------------------

    \259\ See for instance, the North Dakota Regional Haze SIP: 
scrubber upgrades for the Milton R. Young Station Unit 2 were 
evaluated under BART and were found to cost $522/ton and scrubber 
upgrades with coal drying for the Coal Creek Station Units 1 and 2 
were evaluated under BART and found to cost $555/ton at each unit. 
See the EPA's final action approving the SO2 BART 
determinations for the Coal Creek Station Units 1 and 2 and for the 
Milton R. Young Station Unit 2 at 77 FR 20894 (April 6, 2012). See 
also the Wyoming Regional Haze SIP: scrubber upgrades for Wyodak 
Unit 1 were evaluated to address the regional haze rule requirements 
under 40 CFR 51.309 and found to cost $1,167/ton. The EPA approved 
this portion of the Wyoming Regional Haze SIP at 77 FR 73926 
(December 12, 2012).
---------------------------------------------------------------------------

    In the Texas Regional Haze SIP for the Second Planning Period 
recently submitted to us by TCEQ, the State evaluated Martin Lake Units 
1, 2, and 3 for controls under the reasonable progress requirements for 
the regional haze second planning period.\260\ Specifically, TCEQ 
evaluated scrubber upgrades for the Martin Lake units, the same 
SO2 control type we have evaluated for those units in this 
proposal. In that SIP submittal, TCEQ took an approach in its cost 
analysis of scrubber upgrades different from ours in this proposal and 
they did not rely on cost information from the facility. As they did 
not rely on cost information claimed to be CBI by the facility, TCEQ 
was able to present estimated cost-effectiveness numbers for scrubber 
upgrades for the Martin Lake units in their SIP submittal. TCEQ 
estimated the cost-effectiveness of scrubber upgrades at Martin Lake to 
be $907/ton for Unit

[[Page 28953]]

1; $1,040/ton for Unit 2; and $891/ton for Unit 3. Since we have not 
completed our review of the Texas Regional Haze SIP for the Second 
Planning Period and have not yet proposed action on it, we are not at 
this time taking a position on the approvability or appropriateness of 
TCEQ's cost analyses and determinations in the Texas Regional Haze SIP 
for the Second Planning Period. We merely present TCEQ's cost-
effectiveness estimates here to illustrate that they are comparable to 
our own cost-effectiveness estimates in this notice.
---------------------------------------------------------------------------

    \260\ The Texas Regional Haze SIP for the Second Planning Period 
was submitted to the EPA by TCEQ on July 20, 2021. A copy of this 
submission is available at https://www.tceq.texas.gov/airquality/sip/bart/haze_sip.html and in the docket for this action.
---------------------------------------------------------------------------

    In our cost analysis of scrubber upgrades for the Martin Lake 
units, we are using information we received from the facility in 
response to our previous CAA Section 114(a) information collection 
request. We are limited in what information we can include in this 
section because the facility claimed this information as CBI. We can 
disclose that we previously used this information claimed as CBI by the 
facility to calculate the total annualized costs for the Martin Lake 
units in our 2016 Texas-Oklahoma FIP.\261\ We have escalated those 
total annualized costs to 2020 dollars and are using this to estimate 
the cost-effectiveness of scrubber upgrades at these units. As we 
discuss in Section VII.B.2.b, we believe that modifications necessary 
to eliminate the bypass could be performed using proven equipment and 
techniques to increase the control efficiency of the scrubbers to 95 
percent and substantially reduce SO2 emissions at these 
units. Our estimates of the baseline emissions and the annual 
SO2 emissions reductions anticipated from upgrading the 
scrubbers at Martin Lake Units 1, 2, and 3 are presented in Table 11. 
Using the anticipated annual SO2 emissions reductions 
presented in Table 11, we have estimated the cost-effectiveness of 
scrubber upgrades at these units. Because those calculations depended 
on cost information claimed by the facility as CBI, we cannot present 
them here except to note that for each unit, the cost-effectiveness was 
less than $1,200/ton.
---------------------------------------------------------------------------

    \261\ See generally, 81 FR 296 (Jan 5, 2016).

     Table 11--Martin Lake Updated Baseline Emissions and SO2 Emissions Reductions Due to Scrubber Upgrades
----------------------------------------------------------------------------------------------------------------
                                                                                Annual SO2
                                        2016-2020 avg     SO2 emissions at      emissions      SO2 emission rate
                Unit                   annual emissions     95% control      reduction due to    at 95% control
                                            (tons)             (tons)        crubber upgrade       (lb/MMBtu)
                                                                                  (tons)
----------------------------------------------------------------------------------------------------------------
Martin Lake 1.......................             14,885              2,047             12,838               0.08
Martin Lake 2.......................             11,909              1,769             10,140               0.08
Martin Lake 3.......................             14,121              1,941             12,180               0.08
                                     ---------------------------------------------------------------------------
    Total SO2 Removed...............  .................  .................             35,158  .................
----------------------------------------------------------------------------------------------------------------

    We recognize that the information we used in our cost analysis on 
scrubber upgrades was provided by the facility several years ago and 
that our escalation of the total annualized costs from 2013 to 2020 
dollars introduces some level of uncertainty in our cost estimates. We 
acknowledge that it is reasonable to assume that the cost information 
we received from the facility may have changed in the interim, due to 
changes in the costs of various materials and services, as well as 
possible recent upgrades to the scrubbers that may have already been 
implemented at these units that would no longer need to be considered 
in our cost analysis. However, based on the information presented in 
this subsection, we find that the cost of scrubber upgrades at the 
Martin Lake units is so low in terms of dollars per ton reduced such 
that even if we had updated cost information, we expect that scrubber 
upgrades would continue to be very cost-effective. Accordingly, we 
would still propose to require upgrades to these SO2 
scrubbers in light of the significant visibility benefits, as discussed 
later in our weighing of the factors in Section VIII. Nevertheless, we 
invite comment on any additional analysis on the cost of scrubber 
upgrades at the Martin Lake units that may have been conducted in the 
interim period following Luminant's response to our request for cost 
information. We also invite comments regarding documentation on any 
upgrades or optimization that may have been made to the scrubbers at 
the Martin Lake units in the interim period. Finally, we invite comment 
on whether a lower emission limit of 0.04 lb/MMBtu should be required 
that would be consistent with 95 percent control efficiency and the 
burning of only subbituminous coal.\262\
---------------------------------------------------------------------------

    \262\ In the Matter of an Agreed order Concerning Luminant 
Generation Company, LLC, Martin Lake Steam Electric Station, Docket 
No. 2021-0508-MIS includes a requirement to burn only subbituminous 
coal.
---------------------------------------------------------------------------

    The Fayette Units 1 and 2 are currently equipped with high 
performing wet FGDs. Both units have demonstrated the ability to 
maintain a SO2 30 BOD average below 0.04 lb/MMBtu for years 
at a time.\263\ As we discuss in Section VII.B.2, we evaluate BART 
demonstrating that retrofit wet FGDs should be evaluated at 98 percent 
control not to go below 0.04 lb/MMBtu. Because the Fayette units are 
already performing below this level, we propose that no scrubber 
upgrades are necessary and there are no additional costs associated 
with maintaining the current levels of operation.
---------------------------------------------------------------------------

    \263\ See our 2023 BART FIP TSD for graphs of this data.
---------------------------------------------------------------------------

c. Impact Analysis Parts 2, 3, and 4: Energy and Non-Air Quality 
Environmental Impacts, and Remaining Useful Life
i. Energy and Non-Air Quality Environmental Impacts
    Regarding the analysis of energy impacts, the BART Guidelines 
advise, ``You should examine the energy requirements of the control 
technology and determine whether the use of that technology results in 
energy penalties or benefits.'' \264\ The key part of this analysis is 
the energy requirements of the ``control technology.'' As such, this 
part of the analysis is focused on considering the various energy 
impacts of the control technologies identified earlier in the BART 
analysis as technologically feasible and determining whether there are 
energy penalties or benefits associated that may factor into the 
overall decision to select

[[Page 28954]]

a certain control technology over another. Such considerations would 
include extra fuel or electricity to power a control device or the 
availability of potentially scarce fuels.\265\ As discussed in our 2023 
BART FIP TSD, in our cost analyses for DSI, SDA, and wet FGD, our cost 
model allows for the inclusion or exclusion of the cost of the 
additional auxiliary power required for the pollution controls we 
considered to be included in the variable operating costs. We chose to 
include this additional auxiliary power in all cases. Consequently, we 
believe that any energy impacts of compliance have been adequately 
considered in our analyses through the inclusion of related costs of 
electricity to operate the controls.
---------------------------------------------------------------------------

    \264\ 70 FR 39103, 39168 (July 6, 2005), [40 CFR part 51, App. 
Y.].
    \265\ 70 FR at 39168-69.
---------------------------------------------------------------------------

    Neither the CAA nor the BART Guidelines specifically require the 
examination of grid reliability considerations because utilities may 
shut down or retire a unit rather than comply with a more stringent 
emission limit or limits. However, the Guidelines recognize there may 
be cases where the installation of controls, even when cost-effective, 
would ``affect the viability of continued plant operations.'' \266\ 
Under the Guidelines, where there are ``unusual circumstances,'' we are 
permitted to take into consideration ``the conditions of the plant and 
the economic effects of requiring the use of a control technology.'' 
\267\ If the effects are judged to have a ``severe impact,'' those 
effects can be considered in the selection process. In such cases, the 
Guidelines counsel that any determinations be made with an economic 
analysis with sufficient detail for public review on the ``specific 
economic effects, parameters, and reasoning.'' \268\ It is recognized, 
by the language of the Guidelines, that any such review process may 
entail the use of sensitive business information that may be 
confidential.\269\ As suggested by the Guidelines, the information 
necessary to inform our judgment with respect to the viability of 
continued operations for a source would likely entail source-specific 
information on ``product prices, the market share, and the 
profitability of the source.'' All of that said, the Guidelines also 
advise that we may ``consider whether other competing plants in the 
same industry have been required to install BART controls if this 
information is available.'' \270\ Because Texas EGUs are among the last 
to have SO2 BART determinations, this information is 
available. It is indeed the case that other similar EGUs have been 
required to install the same types of SO2 BART controls that 
we are proposing as cost effective. The emission limits that we propose 
for these sources are based on conventional, proven, at-the-source 
pollution control technology that is in place across a vast portion of 
the existing EGU fleet in the United States.\271\ In general these 
pollution controls are cost-effective and can be implemented while the 
EGU continues in large part to operate as it had before.
---------------------------------------------------------------------------

    \266\ 70 FR 39103, 39171 (July 6, 2005), [40 CFR part 51, App. 
Y].
    \267\ Id.
    \268\ 70 FR at 39171.
    \269\ The FOR FURTHER INFORMATION section of this proposal 
explains how to submit confidential information with comments, and 
when claims of confidential business information, or CBI, are 
asserted with respect to any information that is submitted, the EPA 
regulations at 40 CFR part 2, subpart B-Confidentiality Business 
Information apply to protect it.
    \270\ 70 FR at 39171.
    \271\ See EIA Reported Desulfurization Systems in 2020 data in 
Table 8 of this notice showing the hundreds of scrubber 
installations that have been performed on similar EGUs.
---------------------------------------------------------------------------

    Should any of the units faced with a final BART emission limit 
choose instead to explore retirement, such a decision would presumably 
be made on the basis of a determination that the retirement of the unit 
would be the more economical choice, taking into account any and all 
regulatory requirements impacting the source and market conditions. 
Further, the relevant grid operator would follow their planning 
requirements to ensure that sufficient reserve capacity is available.
    We have also reviewed available information regarding the grids 
operating in Texas to provide data on these generation units and 
reserve capacity. The Welsh and Harrington facilities operate as part 
of the Southwest Power Pool (SPP).\272\ The owners of these facilities 
have announced plans to convert to natural gas in the near future so it 
is unlikely that these sources would now choose to shut down as a 
result of the proposed BART requirements, which could be met by burning 
natural gas instead of coal.\273\ The Electric Reliability Council of 
Texas (ERCOT) operates Texas's electrical grid which represents 90 
percent of the State's electric load. Coleto Creek, Fayette, Martin 
Lake, and W. A. Parish facilities produce power for the ERCOT grid. As 
discussed elsewhere, we are not proposing to require additional 
reductions from the Fayette units due to their high efficiency 
scrubbers. For that reason, we do not anticipate any impact to 
operations of this source. Further, the owners of Coleto Creek already 
have announced their intentions to shut down the unit in 2027,\274\ 
citing costs imposed by Federal regulations for coal ash disposal and 
wastewater treatment, and market pressures. Therefore, we focus the 
remainder of this section on the Martin Lake and W. A. Parish BART 
units.
---------------------------------------------------------------------------

    \272\ SPP oversees the bulk electric grid and wholesale power 
market in the central United States for utilities and transmission 
companies in 17 States.
    \273\ See Section VII.B.3.c.ii for more information regarding 
Harrington's conversion to natural gas.
    \274\ Rosenberg, Mike. ``Coleto Creek Power Plant shutting down 
by 2027.'' Victoria Advocate, December 1, 2020, https://www.victoriaadvocate.com/counties/goliad/coleto-creek-power-plant-shutting-down-by-2027/article_261596c8-342b-11eb-92e8-0f9c2d927a2b.html. Last Accessed February 1, 2023.
---------------------------------------------------------------------------

    One way to evaluate potential changes to the grid is to examine 
forecasted peak demand and generation capacity for summer and winter. 
These five coal-fired units represent 3,737 MW of summer capacity.\275\ 
ERCOT's November 2022 Report on the Capacity, Demand and Reserves \276\ 
estimates that 2023 operational generation capacity for summer peak 
demand will be 92,792 MW with additional planned resource capacity 
expected for the 2023 summer peak demand of 4,400 MW. This includes 
1,254 MW of summer-rated gas-fired resources, and the remainder in 
additional wind and solar resources becoming available by next summer. 
Summer peak demand is estimated to be 80,218 MW for 2023, resulting in 
an estimated reserve margin of 22.2 percent for 2023, with capacity 
outpacing demand by approximately 18,000 MW. That reserve margin is 
projected to increase to 39.9 percent for summer 2024, as planned 
generation increases to almost 21,400 MW, largely reflecting solar 
capacity additions for 2024 and increasing total estimated capacity to 
115,000 MW. The current minimum target reserve margin established by 
ERCOT is 13.75 percent. Projections through 2027 include additional 
planned generation for a total estimated capacity of 121,000 MW and an 
estimated reserve margin of 40.1 percent in 2027. Projections for 2028 
through 2032 hold generation capacity at 2027 levels (no additional 
planned capacity) but continue to project increased demand each year 
resulting in a

[[Page 28955]]

decreasing reserve margin each year with 2032 estimated at 36.3 
percent.
---------------------------------------------------------------------------

    \275\ Report on the Capacity, Demand, and Reserves (CDR) in the 
ERCOT Region, 2023-2032. November 29, 2022. Available at https://www.ercot.com/files/docs/2022/11/29/CapacityDemandandReservesReport_Nov2022.pdf and in the docket for 
this action.
    \276\ Report on the Capacity, Demand, and Reserves (CDR) in the 
ERCOT Region, 2023-2032. November 29, 2022. Available at https://www.ercot.com/files/docs/2022/11/29/CapacityDemandandReservesReport_Nov2022.pdf and in the docket for 
this action.
---------------------------------------------------------------------------

    ERCOT's November 2022 Report on the Capacity, Demand and Reserves 
\277\ estimates that 2023/2024 operational generation capacity for 
winter peak demand will be 90,599 MW with additional planned resource 
capacity expected for the 2023 summer peak demand of 2,893 MW. This 
includes 1,323 MW of winter-rated gas-fired resources, and the 
remainder in additional wind and solar resources becoming available by 
next winter. Winter peak demand is estimated to be 66,645 MW for 2023/
2024, resulting in an estimated reserve margin of 35.9 percent for 
Winter 2023/2024. That reserve margin is projected to increase to 36.2 
percent for winter 2024/2025, and then decrease to 28.7 percent for 
winter 2027/2028 as projected peak demand increases.
---------------------------------------------------------------------------

    \277\ Report on the Capacity, Demand, and Reserves (CDR) in the 
ERCOT Region, 2023-2032. November 29, 2022. Available at https://www.ercot.com/files/docs/2022/11/29/CapacityDemandandReservesReport_Nov2022.pdf and in the docket for 
this action.
---------------------------------------------------------------------------

    The SO2 BART emission limits for these EGUs are proposed 
to take effect no later than five years from the effective date of a 
final rule (Martin Lake's scrubber upgrades would be required within 
three years).\278\ Thus, even if all five of these units chose to 
retire instead of complying with the BART emission limits, the removal 
of 3,737 MW of summer capacity (3,782 MW winter capacity) would 
decrease the estimated summer reserve margin to 35.8 percent in 2027 
(estimated winter 2027/2028 reserve margin decreases to 23.6 percent). 
Even if we also account for the additional 655 MW loss of generation 
from Coleto Creek in 2027, the summer reserve margin would be estimated 
to be 35.1 percent with estimated summer generating capacity of 116,706 
MW, about 30,000 MW more than the projected summer peak demand. The 
winter 2027/2028 reserve margin would be 22.7 percent, with generating 
capacity about 16,500 MW higher than peak demand when including the 
loss of Coleto Creek generation. Further, this level of reserve 
generating capacity is already projected to be available without 
considering whether the owners or operators of the affected EGUs would 
continue to invest and pursue additional replacement generation 
projects. Based on this analysis, there will be more than sufficient 
existing and planned capacity in the ERCOT grid to provide for 
substitute generation and reserve capacity by the time the BART 
emission limits would take effect to meet the projected demand.
---------------------------------------------------------------------------

    \278\ See 76 FR 81729, 81758 (December 28, 2011) and 81 FR 
66332, 66416 (September 27, 2016), where we promulgated regional 
haze FIPs for Oklahoma and Arkansas, respectively. These FIPs 
required BART SO2 emission limits on coal-fired EGUs 
based on new scrubber retrofits with a compliance date of no later 
than five years from the effective date of the final rule.
---------------------------------------------------------------------------

    To further evaluate the potential changes to the grid due to 
retirements, we also examined ERCOT's December 2017 Report on the 
Capacity, Demand and Reserves,\279\ the first report issued after the 
announced retirement of 4,273 MW of generating capacity from the 
Luminant facilities (Monticello, Big Brown, and Sandow) in early 2018. 
Due to the retirements, the reserve margin was projected to decrease to 
9.3 percent for summer 2018 and 9.0 percent in summer 2022. In response 
to requests from Luminant to retire these units, ERCOT issued 
determinations that these resources were not required to support ERCOT 
transmission system reliability in early 2018 and allowed to 
permanently retire. Additional gas, solar and wind resources have come 
online since that time to increase the generation capacity and provide 
for a much larger reserve margin. And again, this rule, if finalized, 
only establishes an emission limit for each EGU that could be met with 
proven, conventional, at the source control technologies already in use 
across a broad swath of the U.S. EGU fleet; thus retirements, if they 
should occur, are at the discretion of the sources and subject to the 
reliability authority and planning requirements that would be overseen 
by the grid operator, ERCOT.
---------------------------------------------------------------------------

    \279\ Report on the Capacity, Demand, and Reserves (CDR) in the 
ERCOT Region, 2018-2027. December 18, 2017. Available at https://www.ercot.com/files/docs/2018/01/03/CapacityDemandandReserveReport-Dec2017.pdf and in the docket for this action.
---------------------------------------------------------------------------

    Regarding the analysis of non-air quality environmental impacts, 
the BART Guidelines advise: \280\
---------------------------------------------------------------------------

    \280\ 70 FR at 39169 (July 6, 2005), [40 CFR part 51, App. Y.].

    Such environmental impacts include solid or hazardous waste 
generation and discharges of polluted water from a control device. 
You should identify any significant or unusual environmental impacts 
associated with a control alternative that have the potential to 
affect the selection or elimination of a control alternative. Some 
control technologies may have potentially significant secondary 
environmental impacts. Scrubber effluent, for example, may affect 
water quality and land use. Alternatively, water availability may 
affect the feasibility and costs of wet scrubbers. Other examples of 
secondary environmental impacts could include hazardous waste 
discharges, such as spent catalysts or contaminated carbon. 
Generally, these types of environmental concerns become important 
when sensitive site-specific receptors exist or when the incremental 
emissions reductions potential of the more stringent control is only 
marginally greater than the next most-effective option. However, the 
fact that a control device creates liquid and solid waste that must 
be disposed of does not necessarily argue against selection of that 
technology as BART, particularly if the control device has been 
applied to similar facilities elsewhere and the solid or liquid 
waste is similar to those other applications. On the other hand, 
where you or the source owner can show that unusual circumstances at 
the proposed facility create greater problems than experienced 
elsewhere, this may provide a basis for the elimination of that 
---------------------------------------------------------------------------
control alternative as BART.

    The SO2 control technologies we considered in our 
analysis--DSI and scrubbers--are in wide use in the coal-fired 
electricity generation industry. Both technologies add spent reagent to 
the waste stream already generated by the facilities we analyzed. As 
discussed in our cost analyses for DSI and scrubbers, our cost model 
includes estimated waste disposal costs in the variable operating 
costs. With DSI, when sodium-based sorbents such as trona are captured 
in the same particulate control device as the fly ash, the resulting 
waste must be landfilled.\281\ We are aware that some facilities may 
sell their fly ash, and that the addition of trona may render that fly 
ash unsellable. We included the fly ash disposal costs in the variable 
operation and maintenance costs for DSI in all cases, but our cost 
analysis did not account for any potential lost revenue resulting from 
being unable to sell the fly ash. We invite comments on the assumptions 
we have made regarding fly ash disposal costs and on any unforeseen 
waste disposal costs associated with DSI when using trona or sodium 
bicarbonate.
---------------------------------------------------------------------------

    \281\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy, p.6.
---------------------------------------------------------------------------

    Regarding water related impacts, we recognize that wet FGD requires 
additional amounts of water as compared to SDA and DSI. Furthermore, 
based on recent Effluent Limitation Guidelines (ELG), it is expected 
that all future wet FGD installations will require the facility to 
incorporate a wastewater treatment facility.\282\ While this cost is 
factored into our cost analysis, it also

[[Page 28956]]

highlights water quality concerns associated with the waste stream for 
wet FGD as compared to the installation of dry scrubbers and DSI. 
Additionally, we are aware of water availability concerns in the area 
surrounding the Harrington facility. As such, the Harrington facility 
has instituted a water recycling program and obtains some of its water 
from the City of Amarillo.\283\ Because of the increased water required 
for wet FGD as compared to dry scrubbers and DSI, we limit our 
SO2 control analysis for Harrington to DSI and dry 
scrubbers. For the other facilities where we consider wet FGD as a 
potential control option, we weigh the additional water usage and 
wastewater treatment requirements associated with wet FGD in comparison 
to other control options.
---------------------------------------------------------------------------

    \282\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Wet FGD Cost Development Methodology, Final January 
2017, Project 13527-001, Eastern Research Group, Inc., Prepared by 
Sargent & Lundy, p. 1.
    \283\ https://www.powermag.com/xcel-energys-harrington-generating-station-earns-powder-river-basin-coal-users-group-award/.
---------------------------------------------------------------------------

ii. Remaining Useful Life
    Regarding the remaining useful life, the BART Guidelines advise: 
\284\
---------------------------------------------------------------------------

    \284\ 70 FR 39103, 39169, [40 CFR part 51, App. Y].

    You may decide to treat the requirement to consider the source's 
``remaining useful life'' of the source for BART determinations as 
one element of the overall cost analysis. The ``remaining useful 
life'' of a source, if it represents a relatively short time period, 
may affect the annualized costs of retrofit controls. For example, 
the methods for calculating annualized costs in EPA's OAQPS Control 
Cost Manual require the use of a specified time period for 
amortization that varies based upon the type of control. If the 
remaining useful life will clearly exceed this time period, the 
remaining useful life has essentially no effect on control costs and 
on the BART determination process. Where the remaining useful life 
is less than the time period for amortizing costs, you should use 
---------------------------------------------------------------------------
this shorter time period in your cost calculations.

    We have no reason to conclude that the remaining useful life of any 
SO2 control options we are evaluating would be any less than 
the thirty years recommended by the Control Cost Manual.\285\ As we 
stated in our Oklahoma FIP,\286\ the scrubber vendors indicated that 
the lifetime of a scrubber is equal to the lifetime of the boiler, 
which might easily be well over 60 years. We identified specific 
scrubbers installed between 1975 and 1985 that are still in operation, 
such as the scrubbers at Martin Lake. These scrubbers were installed in 
the early 1970s, and, while they may be inefficient for a modern 
scrubber, they are still operational.
---------------------------------------------------------------------------

    \285\ EPA Air Pollution Control Cost Manual, Seventh Edition, 
April 2021, Section 5 ``SO2 and Acid Gas Controls,'' 
Chapter 1 ``Wet and Dry Scrubbers for Acid Gas Control,'' see 
Section 1.1.6, p. 1-8, available at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual.
    \286\ Response to Technical Comments for Sections E. through H. 
of the Federal Register Notice for the Oklahoma Regional Haze and 
Visibility Transport Federal Implementation Plan, Docket No. EPA-
R06-OAR-2010-0190, 12/13/2011. See discussion beginning on page 36.
---------------------------------------------------------------------------

    Some of the facilities we have analyzed for BART in this action 
have announced plans to retire or refuel to natural gas within the next 
several years.\287\ For example, we are aware that Xcel Energy has 
signed an Administrative Order with TCEQ to refuel Harrington Units 
061B and 062B to natural gas by January 1, 2025.\288\ We discuss this 
change in future operating conditions in our weighing of the factors. 
However, the BART Guidelines state that in situations where a future 
operating parameter will differ from past or current practices, and if 
such future operating parameters will have a deciding effect in the 
BART determination, then the future operating parameters need to be 
made federally enforceable and permanent to consider them in the BART 
determination.\289\
---------------------------------------------------------------------------

    \287\ We received a November 21, 2016, letter from the source 
owner regarding W.A. Parish Units WAP5 & WAP6. The letter available 
in the docket, explains the units have natural gas firing 
capabilities and expresses interest in obtaining flexibility to 
avoid BART or obtaining multiple options for complying with BART. We 
are not aware of any more recent commitments to change operations at 
these units that would impact our BART analysis at this time. 
Rosenberg, Mike. ``Coleto Creek Power Plant shutting down by 2027.'' 
Victoria Advocate, December 1, 2020, https://www.victoriaadvocate.com/counties/goliad/coleto-creek-power-plant-shutting-down-by-2027/article_261596c8-342b-11eb-92e8-0f9c2d927a2b.html. Last Accessed February 1, 2023. ``SWEPCO to End 
Coal Operations at Two Plants, Upgrade a Third''.'' Southwestern 
Electric Power Co.'s News Release, November 5, 2020, https://www.swepco.com/company/news/view?releaseID=5847. Last Accessed 
February 2, 2023.
    \288\ In the Matter of an Agreed Order Concerning Southwestern 
Public Service Company, dba Xcel Energy, Harrington Station Power 
Plant, TCEQ Docket No. 2020-0982-MIS (Adopted Oct. 21, 2020). A copy 
of the Order is available in the docket for this action.
    \289\ 70 FR at 39167.
---------------------------------------------------------------------------

    If a facility owner were to enter into a federally enforceable 
commitment to shut down or refuel by a date certain, that date would be 
used to revise the remaining useful life and the annualized costs 
weighed in making the BART determination. Whether that adjustment in 
analysis would ultimately alter our final BART determinations from this 
proposal would depend on the outcome of an updated BART analysis with 
the inclusion of the shutdown or refuel date. Should an owner decide to 
shut down or refuel a unit before the compliance date set out for the 
proposed BART controls, the shutdown or refueling to natural gas would 
also achieve the required SO2 emission limits.
4. Step 5: Evaluate Visibility Impacts
    The 2023 BART Modeling TSD describes in detail the modeling runs we 
conducted, our methodology and selection of emission rates, modeling 
results, and final modeling analyses that we used to evaluate the 
benefits of the proposed controls and their associated emission 
decreases on visibility impairment values. In this section, we present 
a summary of our analyses and our proposed findings regarding the 
estimated visibility benefits of emission reductions based on the 
CALPUFF and/or CAMx modeling results. For those sources that are within 
450 km of a Class I area (Martin Lake, Harrington, and Welsh), we 
utilized both CALPUFF and CAMx modeling results to assess the 
visibility benefits of potential controls. For the remaining coal-fired 
sources (Coleto Creek, Fayette, and W. A. Parish), only CAMx modeling 
was utilized, as these sources are located at greater distances from 
the nearest Class I areas than typically modeled with the CALPUFF model 
for BART analyses. The CAMx modeling provides unit specific impacts and 
also total facility impacts where the CALPUFF modeling was performed 
such that only total facility impacts were generated. Therefore, we do 
not have unit specific CALPUFF results. Additional details regarding 
our approach to using CAMx and CALPUFF modeling are within Section 
VII.A.1 and the 2023 BART Modeling TSD.
    To assess the visibility benefits of controls, we modeled the 
sources with emissions reflecting a low control level and a high 
control level.290 291 For the low control level, we 
evaluated the visibility benefits of DSI for all the subject to BART 
units at each facility identified in Tables 12 and 13 that currently 
have no SO2 control. For these low control levels, we 
modeled these units at a DSI SO2 control level of 50 
percent, which we believe is achievable for any unit. At this assumed 
control

[[Page 28957]]

level, we expect that the corresponding visibility benefits from DSI in 
most cases would be close to half of the benefits from scrubbers, which 
are generally at a control level of 90 percent or greater from the 
baseline. For the high control level, we evaluated the visibility 
benefits for scrubber retrofits (wet FGD or SDA) for these same units, 
assuming the same control levels corresponding to SDA (for Harrington 
BART units) and wet FGD (for all other unscrubbed BART units) that we 
used in our control cost analyses. NOX and PM10 
and PM2.5 emissions were held constant for the control case.
---------------------------------------------------------------------------

    \290\ As discussed in Section VIII.A and in the 2023 BART 
Modeling TSD, we completed some additional CALPUFF modeling for 
Welsh and Harrington units in addition to the low and high control 
scenarios. We also extrapolated CAMx results to estimate visibility 
benefits for SDA for units at Coleto Creek, W.A. Parish, and Welsh, 
and extrapolated CAMx results for Harrington Unit 61B for additional 
levels of control. See the 2023 BART Modeling TSD for discussion of 
all modeled and extrapolated visibility modeling.
    \291\ NOX and PM10/PM2.5 
emissions were held constant at baseline emission levels for all 
emission units in order to isolate visibility improvements due to 
SO2 reductions from any visibility benefits that would 
result from reductions in NOX emissions.
---------------------------------------------------------------------------

    We also modeled the visibility benefits of improved efficiency on 
the existing scrubbers at Martin Lake. We assumed the same 95 percent 
control level represented by an emission limit of 0.08 lb/MMBtu used in 
our control cost analyses for the high control level. We also modeled a 
lower control level based on an emission rate of 0.32 lb/MMBtu. This 
emission rate is consistent with the limit included in an Agreed Order 
\292\ between TCEQ and Luminant for purposes of addressing 
SO2 NAAQS nonattainment requirements.\293\
---------------------------------------------------------------------------

    \292\ Agreed Order 2021-0508-MIS, signed February 22, 2022, 
available in the docket for this action.
    \293\ The agreed order and accompanying SIP submittal remain 
before the EPA for review. In this action we are not taking a 
position on the approvability or appropriateness of the limits in 
the agreed order for purposes of addressing SO2 NAAQS 
nonattainment requirements.
---------------------------------------------------------------------------

    As discussed in Section VII.B.1.b, Fayette Units 1 and 2 have 
scrubbers that are operating consistently at a high control level. 
Accordingly, we modeled both units at an emission rate of 0.04 lb/MMBtu 
for the high control level, which is consistent with emission rates 
from the past several years. For the low control scenario, we evaluated 
the visibility impacts at the current permitted emission rates, which 
is higher than the current actual emissions. These model runs do not 
correspond to ``low control'' and ``high control'' specifically. We 
discuss the model results for Fayette further in Section VIII.B. As 
discussed elsewhere, we found that for these units no additional 
controls or upgrades were necessary.
    Tables 12 and 13 present a summary of the modeled visibility 
impacts for the baseline at the Class I areas most impacted by each 
source, and the visibility benefits from the low and high control 
scenarios, as predicted by CAMx \294\ and CALPUFF. In evaluating the 
impacts and benefits of control options, we utilized a number of 
metrics, including change in deciviews on the maximum impacted day for 
CAMx results and annual 98th percentile for CALPUFF results, and also 
number of days impacted over 0.5 dv and 1.0 dv. In Section VIII, we 
provide some additional discussion of model results and additional 
metrics in weighing the visibility benefits of controls. Consistent 
with the BART Guidelines, the visibility impacts and benefits modeled 
in CALPUFF and CAMx are calculated as the change in deciviews compared 
against natural visibility conditions.\295\ For a more detailed 
discussion of our review of all the modeling results and factors that 
we considered in evaluating and weighing results, including scrubber 
upgrades, see our 2023 BART FIP TSD and 2023 BART Modeling TSD.
---------------------------------------------------------------------------

    \294\ For the CAMx modeling, visibility was assessed using the 
grid cell containing the monitor representative of the Class I area. 
In 2016, Carlsbad Caverns shared a monitor with the Guadalupe 
Mountains and Pecos Wilderness shared a monitor with Wheeler Peak. 
Therefore, the modeled impacts and benefits at these receptors/
monitors were applied to both Class I areas represented by that 
monitor site.
    \295\ 40 CFR 51 Appendix Y, IV.D.5: ``Calculate the model 
results for each receptor as the change in deciviews compared 
against natural visibility conditions.'' For the specific 
calculations, see 2023 BART Modeling TSD for this action.

[[Page 28958]]



                                           Table 12--CAMx Modeling of Baseline Impacts and Visibility Benefits of Controls for Subject-to-BART Sources
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               2016 Baseline impacts                           Low control scenario                            High control scenario
                                                 -----------------------------------------------------------------------------------------------------------------------------------------------
        BART source & top 3 Class I areas            Impact at                                      Benefit at    Number of days  Number of days    Benefit at    Number of days  Number of days
                                                   class I area   Number of days  Number of days   class I area   impacted >=0.5  impacted >=1.0   class I area   impacted >=0.5   impacted>=1.0
                                                       (dv)          >=0.5 dv        >=1.0 dv          (dv)             dv              dv             (dv)             dv              dv
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Martin Lake, Units 1, 2, and 3                                    (0.32 lb/MMBtu)
                                                                  (0.08 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Caney Creek.................................            6.69             150             101            3.28              97              46            5.00              32               7
    Wichita Mountains...........................            5.49              51              27            2.87              21               7            4.57               3               0
    Upper Buffalo...............................            5.16             111              70            2.78              61              25            4.39               7               0
    Cumulative (all 15 Class I areas)...........           33.79             521             301           18.29             259              91           27.91              47               7
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
W.A. Parish, Units WAP4, WAP5, and WAP6                             (DSI @50%)
                                                             (wet FGD @0.04 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Wichita Mountains...........................            3.97              35              12            1.73              15               1            3.61               0               0
    Caney Creek.................................            3.13              86              38            1.31              48              11            2.59               1               0
    Breton......................................            2.21              12               4            0.85               4               2            1.89               0               0
    Cumulative (all 15 Class I areas)...........           17.96             269              91            7.76             119              18           15.66               1               0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Harrington Station, Units 061B and 062B                             (DSI @50%)
                                                               (SDA @0.06 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    White Mountain..............................            2.64               8               3            0.96               4               1            1.78               1               0
    Bandelier...................................            1.60               4               1            0.65               1               0            1.23               0               0
    Salt Creek..................................            1.52              13               6            0.49               7               1            0.97               1               0
    Cumulative (all 15 Class I areas)...........           12.77              44              10            5.01              13               2            9.08               2               0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Coleto Creek, Unit 1                                                (DSI @50%)
                                                             (wet FGD @0.04 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Caney Creek.................................            1.55              18               2            0.67               2               0            1.38               0               0
    Breton......................................            1.19               4               1            0.50               1               0            1.08               0               0
    Wichita Mountains...........................            1.13              23               3            0.54               4               0            1.00               0               0
    Cumulative (all 15 Class I areas)...........            8.54              69               6            3.92               9               0            7.75               0               0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Welsh, Unit 1                                                       (DSI @50%)
                                                             (wet FGD @0.04 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Caney Creek.................................            1.58              27               6            0.48               8               1            1.08               0               0
    Wichita Mountains...........................            1.54               6               2            0.69               2               0            1.34               0               0
    Upper Buffalo...............................            1.12               8               1            0.40               2               0            0.83               0               0
    Cumulative (all 15 Class I areas)...........            6.67              46               9            2.60              13               1            5.27               0               0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 28959]]

    To further illustrate the CAMx modeled visibility benefits provided 
by both the low and high control levels, we compared the visibility 
benefits of the low and high control levels to the baseline impacts in 
terms of percent reduction in visibility impacts. To make this 
comparison, we used the maximum impact for each Class I area and 
compared these values for the low control and high control with the 
baseline impacts, looking at the values for the highest impacted Class 
I area and the average of the 15 Class I areas from the baseline 
modeling to show the benefit for the control levels. For Martin Lake, 
low and high control resulted in a reduction of visibility impacts at 
Caney Creek by 49 percent and 75 percent, respectively, and an average 
reduction of visibility impacts at the 15 Class I areas of 54 percent 
and 83 percent, respectively. For W.A. Parish, low and high control 
resulted in a reduction of visibility impacts at Wichita Mountains by 
44 percent and 91 percent, respectively, and an average reduction of 
visibility impacts at the 15 Class I areas of 43 percent and 87 
percent, respectively. For Harrington, low and high control resulted in 
a reduction of visibility impacts by 36 percent and 67 percent, 
respectively, and an average reduction of visibility impacts at the 15 
Class I areas of 39 percent and 71 percent, respectively. For Coleto 
Creek, low and high control resulted in a reduction of visibility 
impacts by at Caney Creek 43 percent and 89 percent, respectively, and 
an average reduction of visibility impacts at the 15 Class I areas of 
46 percent and 91 percent, respectively. For Welsh, low and high 
control resulted in a reduction of visibility impacts at Caney Creek by 
30 percent and 68 percent, respectively, and an average reduction of 
visibility impacts at the 15 Class I areas of 39 percent and 79 
percent, respectively. For Fayette, high control resulted in a 
reduction of visibility impacts at Caney Creek by 0 percent and an 
average reduction of visibility impacts at the 15 Class I areas of 5 
percent. We provide additional analysis of the visibility benefits of 
the different control levels in Section VIII and in the 2023 BART FIP 
TSD and 2023 BART Modeling TSD.
    For each of the facilities, CAMx predicted a large decrease in the 
number of days with visibility impacts greater than 0.5 dv with the 
high level of controls. Aside from impacts on the Caney Creek Class I 
area, CAMx predicted zero days over 1.0 dv with the high level of 
controls on the Martin Lake facility. Additional unit-specific 
information for these sources can be found in the 2023 BART Modeling 
TSD.

[[Page 28960]]



                                           Table 13--CALPUFF Modeling Baseline Impact and Visibility Benefit of Controls for Subject-to-BART Sources *
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                       2016-18 Baseline                                  Low control scenario                                High control scenario
                                     -----------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Cumulative       Benefit at class I area (dv)       Cumulative       Benefit at class I area (dv)       Cumulative
                                                                              2016-18 #  ---------------------------------------  2016-18 #  ---------------------------------------  2016-18 #
     BART source & class I area                                                of days                                             of days                                             of days
                                        2016 dv      2017 dv      2018 dv        with                                                with                                                with
                                                                               impacts      2016 dv      2017 dv      2018 dv      impacts      2016 dv      2017 dv      2018 dv      impacts
                                                                              >=0.5 dv/                                           >=0.5 dv/                                           >=0.5 dv/
                                                                               >=1.0 dv                                            >=1.0 dv                                            >=1.0 dv
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Martin Lake, Units 1, 2, and 3                          (0.32 lb/MMBtu)
                                                        (0.08 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Caney Creek.....................         3.28         3.60         3.35      338/215         1.62         1.78         1.75       222/95         2.12         2.36         2.16       133/44
    Upper Buffalo...................         2.12         2.54         2.27      212/115         1.12         1.39         1.10       100/29         1.58         1.90         1.72         33/8
    Wichita Mountains...............         1.45         1.07         1.15        79/36         0.80         0.58         0.65         25/4         1.21         0.89         0.91          5/2
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Welsh, Unit 1                                             (DSI @50%)
                                                   (wet FGD @0.04 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Caney Creek.....................         0.70         0.94         0.96        77/13         0.17         0.30         0.32         41/3         0.28         0.37         0.53         18/1
    Upper Buffalo...................         0.36         0.49         0.60         16/0         0.14         0.17         0.22          3/0         0.25         0.33         0.42          0/0
    Wichita Mountains...............         0.25         0.35         0.24          3/0         0.09         0.17         0.08          1/0         0.17         0.28         0.16          0/0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Harrington Station, Units 061B and 062B                   (DSI @50%)
                                                     (SDA @0.06 lb/MMBtu)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
    Carlsbad Caverns................         0.39         0.41         0.56         16/5         0.12         0.16         0.15          7/1         0.24         0.27         0.31          1/1
    Bandelier.......................         0.17         0.12         0.14          2/0         0.06         0.04         0.05          0/0         0.12         0.09         0.11          0/0
    Pecos...........................         0.22         0.28         0.24          9/0         0.08         0.09         0.09          3/0         0.15         0.17         0.16          0/0
    Salt Creek......................         0.49         0.59         0.54         27/3         0.13         0.22         0.19         14/1         0.23         0.39         0.32          2/0
    Wheeler Peak....................         0.12         0.15         0.16          2/0         0.03         0.05         0.06          0/0         0.07         0.10         0.11          0/0
    White Mountain..................         0.26         0.43         0.33          7/0         0.09         0.15         0.13          1/0         0.17         0.26         0.24          0/0
    Wichita Mountains...............         0.54         0.45         0.58         24/8         0.19         0.16         0.18         12/0         0.35         0.23         0.33          3/0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* Benefit of control values are the decrease in deciview between baseline and the control scenario. Number of days is the number of days that are equal or greater than 0.5 and 1.0 dv after
  controls.


[[Page 28961]]

    As discussed in prior sections, when using CALPUFF, the visibility 
benefit (dv) is derived from the 98th percentile (eighth highest day 
for each year) for each Class I area. We provide additional analysis of 
the benefits of the different control levels in Section VIII and in the 
2023 BART FIP TSD and 2023 BART Modeling TSD. As shown in Table 13, 
CALPUFF predicted large reductions in the number of days over the 1.0 
dv threshold under the high control level for all three facilities. For 
Harrington, CALPUFF results predicted one day with visibility impacts 
over 1.0 dv compared to baseline impacts of 16 days. For Welsh, CALPUFF 
results predicted only one day over 1.0 dv compared to baseline impacts 
of 16 days. For Martin Lake, CALPUFF results predicted 54 days over 1.0 
dv compared to baseline impacts of 366 days.
    To further illustrate the CALPUFF modeled visibility benefits 
provided by both the low and high control levels, we also compared the 
visibility benefits of the low and high control levels to the baseline 
impacts in terms of percent reduction in visibility impacts as we did 
in analyzing CAMx benefits. To make this comparison, we first 
calculated the average of the 98th percentile for the three years 
modeled for each Class I area. We then compared these values for the 
low control and high control with the baseline impacts, looking at the 
values for the highest impacted Class I area and the average of the 
Class I areas from the baseline modeling to show the benefit for the 
control levels. For Harrington, Salt Creek was the highest impacted of 
the seven Class I areas and low and high control resulted in a 
reduction of visibility impacts by 33 percent and 58 percent, 
respectively, and an average reduction of visibility impacts at the 
seven Class I areas of 34 percent and 61 percent, respectively. For 
Martin Lake, Caney Creek was the highest impacted of the three Class I 
areas and low and high control resulted in a reduction of visibility 
impacts by 50 percent and 65 percent, respectively, and an average 
reduction of visibility impacts at the three Class I areas of 52 
percent and 71 percent, respectively. For Welsh, Caney Creek was the 
highest impacted of the three Class I areas and low and high control 
resulted in a reduction of visibility impacts by 30 percent and 45 
percent, respectively and an average reduction of visibility impacts at 
the three Class I areas of 34 percent and 57 percent, respectively. As 
further discussed in the 2023 BART Modeling TSD, CALPUFF model results 
are not directly comparable to CAMx results due to difference in the 
modeling analysis as discussed elsewhere (years modeled, receptor(s) 
modeled, etc.) and difference in the model including the simplified 
chemistry in CALPUFF. The potential to overestimate nitrate impacts in 
the CALPUFF model may limit (resulting in an underestimation) the 
amount of modeled visibility benefits (improvement) on both the 98th 
percentile days and the number of days above a threshold that result 
from decreases in SO2 emissions.
5. BART Five Factor Analysis for PM
    In our 2017 Texas BART FIP, we approved Texas's determination in 
its 2009 Regional Haze SIP that no PM BART controls were appropriate 
for its EGUs, based on a screening analysis of the visibility impacts 
from just PM emissions and the premise that EGU SO2 
emissions were covered by the Texas SO2 Trading Program and 
NOX emissions were covered by participation in CSAPR 
(allowing consideration of PM emissions in isolation). For reasons 
provided for in Section VI, we are now proposing that our approval was 
in error and are correcting that error by disapproving the portion of 
the SIP regarding PM BART for EGUs. Based on this proposed disapproval, 
the FIP we are proposing to address BART requirements for those Texas 
EGUs that are subject to BART will cover PM BART.
    The BART Guidelines permit us to conduct a streamlined analysis of 
PM BART for PM sources subject to MACT standards. Unless there are new 
technologies subsequent to the MACT standards which would lead to cost-
effective increases in the level of control, the Guidelines state it is 
permissible to rely on MACT standards for purposes of BART.\296\ With 
this background, we are providing our evaluation, along with some 
supplementary information, on the BART sources as divided into two 
categories: coal-fired EGUs and gas-fired EGUs.
---------------------------------------------------------------------------

    \296\ 70 FR at 39163-64.
---------------------------------------------------------------------------

BART Analysis for PM for Coal-Fired Units
    All coal-fired EGUs that are subject to BART are currently equipped 
with either Electrostatic Precipitators (ESPs) or baghouses, or both, 
as illustrated in Table 14:

                    Table 14--Current PM Controls for Coal-Fired Units Subject to BART \297\
----------------------------------------------------------------------------------------------------------------
          Facility name             Unit ID   Fuel type (primary)     SO2 control(s)          PM control(s)
----------------------------------------------------------------------------------------------------------------
Coleto Creek.....................          1  Coal...............  ...................  Baghouse.
Harrington Station...............       061B  Coal...............  ...................  Electrostatic
                                                                                         Precipitator.
Harrington Station...............       062B  Coal...............  ...................  Baghouse.
Martin Lake......................          1  Coal...............  Wet Limestone......  Electrostatic
                                                                                         Precipitator.
Martin Lake......................          2  Coal...............  Wet Limestone......  Electrostatic
                                                                                         Precipitator.
Martin Lake......................          3  Coal...............  Wet Limestone......  Electrostatic
                                                                                         Precipitator.
Fayette..........................          1  Coal...............  Wet Limestone......  Electrostatic
                                                                                         Precipitator.
Fayette..........................          2  Coal...............  Wet Limestone......  Electrostatic
                                                                                         Precipitator.
W. A. Parish.....................       WAP5  Coal...............  ...................  Baghouse.
W. A. Parish.....................       WAP6  Coal...............  ...................  Baghouse.
Welsh Power Plant................          1  Coal...............  ...................  Baghouse (Began Nov 15,
                                                                                         2015) + Electrostatic
                                                                                         Precipitator.
----------------------------------------------------------------------------------------------------------------

    We began our analysis by examining the control efficiencies of both 
baghouses and ESPs. When considering the units controlled by a 
baghouse, they were widely reported to be capable of achieving 99.9 
percent control of PM, which is the maximum level of control for PM. 
Therefore, the units equipped with a baghouse will not be further 
analyzed for PM BART. The remaining units are fitted with ESPs.
---------------------------------------------------------------------------

    \297\ www.eia.gov/electricity/data/eia860/.
---------------------------------------------------------------------------

    The particulate matter control efficiency of ESPs varies somewhat 
with design, resistivity of the particulate

[[Page 28962]]

matter, and maintenance of the ESP. We do not have information 
specifically on the control level efficiency of any of the ESPs for the 
units in question. However, reported control efficiencies for well-
maintained ESPs typically range from greater than 99 percent to 99.9 
percent.\298\ We therefore consider this pertinent when concluding that 
the potential additional particulate control that a baghouse can offer 
over an ESP is relatively minimal.\299\ Accordingly, even if we did 
obtain additional control information specific to the ESP units in 
question, we do not expect the additional information would result in a 
different conclusion.
---------------------------------------------------------------------------

    \298\ EPA, ``Air Pollution Control Technology Fact Sheet: Dry 
Electrostatic Precipitator (ESP)--Wire Plate Type,'' EPA-452/F-03-
028. Grieco, G., ``Particulate Matter Control for Coal-fired 
Generating Units: Separating Perception from Fact,'' apcmag.net, 
February, 2012. Moretti, A.L.; Jones, C.S., ``Advanced Emissions 
Control Technologies for Coal-Fired Power Plants, Babcox and Wilcox 
Technical Paper BR-1886, Presented at Power-Gen Asia, Bangkok, 
Thailand, October 3-5, 2012.
    \299\ We do not discount the potential health benefits this 
additional control can have for ambient PM. However, the regional 
haze program is only concerned with improving the visibility at 
Class I areas.
---------------------------------------------------------------------------

    Nevertheless, we will examine the potential cost of retrofitting a 
typical 500 MW coal- fired unit with a baghouse. Using our baghouse 
cost algorithms as employed in version 6 of our IPM model,\300\ and 
assuming a conservative air to cloth ratio of 6.0, the results for 
capital engineering and construction costs are $84,770,000.\301\ For 
the purposes of analyzing the subject units, this cost assumes a 
retrofit factor of 1.0, and does not consider the demolition of the 
existing ESP, should it be required in order to make space for the 
baghouse.
---------------------------------------------------------------------------

    \300\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Particulate Control Cost Development Methodology, 
Final April 2017, Project 13527-001, Eastern Research Group, Inc., 
Prepared by Sargent & Lundy. Documentation for v.6: Chapter 5: 
Emission Control Technologies, Attachment 5-7: PM Cost Methodology, 
downloaded from: https://www.epa.gov/sites/default/files/2018-05/documents/attachment_5-7_pm_control_cost_development_methodology.pdf.
    \301\ Id. See page 11.
---------------------------------------------------------------------------

    We did not calculate the cost-effectiveness resulting from 
replacing an ESP with a baghouse because we expect that the tons of 
additional PM removed by a baghouse over an ESP to be very small, which 
would result in a very high cost-effectiveness figure. For this reason, 
we did not model the visibility benefit of replacing an ESP with a 
baghouse. As noted previously, our visibility impact modeling indicates 
that the contributions to visibility impairment from the baseline PM 
emissions of these units are very small, and thus we expect the 
visibility improvement from replacing an ESP with a baghouse to be 
minimal. For instance, our CAMx baseline modeling shows that on a 
source-wide level, impacts from PM emissions on the maximum impacted 
days was at most 7 percent in the case of Fayette, a few were near 1 
percent, and others were less than 1 percent of the total visibility 
impairment, as calculated as the percent of total extinction due to the 
source(s) at each subject to BART facility. Similarly, our CALPUFF 
modeling indicates that visibility impairment from PM is also a small 
fraction (at most 3 percent for Harrington) of the total visibility 
impairment due to each source. Therefore, additional PM controls are 
anticipated to result in very little visibility benefit on the maximum 
impacted days.
    Accordingly, we believe an appropriately stringent PM BART control 
level that would be met with existing, or otherwise-required, controls 
is a filterable PM limit of 0.030 lb/MMBtu for each of the coal-fired 
units subject to BART. This limit is consistent with the Mercury and 
Air Toxics (MATS) Rule, which establishes an emission standard of 0.030 
lb/MMBtu filterable PM (as a surrogate for toxic non-mercury metals) as 
representing Maximum Achievable Control Technology (MACT) for coal-
fired EGUs.\302\ This standard derives from the average emission 
limitation achieved by the best performing 12 percent of existing coal-
fired EGUs, as based upon test data used in developing the MATS Rule. 
Thus, consistent with the BART Guidelines, we are proposing to rely on 
this limit for purposes of PM BART for all of the coal-fired units as 
part of our FIP.\303\ We understand the coal-fired units covered by 
this proposal to be subject to MATS, but to the extent the units may be 
following alternate limits that differ from the surrogate PM limits 
found in MATS, we welcome comments on different, appropriately 
stringent limits reflective of current control capabilities.\304\ 
Because we anticipate any limit we assign should be achieved by current 
control capabilities, we propose that compliance can be met at the 
effective date of the rule. To address periods of startups and 
shutdowns, we are further proposing that PM BART for these units will 
additionally be met by following the work practice standards specified 
in 40 CFR part 63, subpart UUUUU, Table 3, and using the relevant 
definitions in 63.10042. We are proposing that the demonstration of 
compliance can be satisfied by the methods for demonstrating compliance 
with filterable PM limits that are specified in 40 CFR part 63, subpart 
UUUUU, Table 7. However, we invite comment on alternate or additional 
methods of demonstrating compliance.
---------------------------------------------------------------------------

    \302\ 77 FR 9304, 9450, 9458 (February 16, 2012) (codified at 40 
CFR 60.42 Da(a), 60.50 Da(b)(1)); 40 CFR part 63 Subpart UUUUU--
National Emission Standards for Hazardous Air Pollutants: Coal- and 
Oil-Fired Electric Utility Steam Generating Units.
    \303\ 70 FR at 39163-64.
    \304\ The various limits are provided at 40 CFR part 63, subpart 
UUUUU, Table 2 (``Emission Limits for Existing EGUs'').
---------------------------------------------------------------------------

BART Analysis for PM for Gas-Fired Units
    As explained in Section VII.A, W. A. Parish Unit WAP4 is the only 
gas fired unit that we are proposing to find subject to BART. With 
respect to gas-fired units, which have inherently low emissions of PM 
(as well as SO2),\305\ the RHR did not specifically envision 
new or additional controls or emissions reductions from the PM BART 
requirement.\306\ The BART Guidelines preclude us from stating that PM 
emissions are de minimis when plant-wide emissions exceed 15 tons per 
years.\307\ In assigning a PM BART determination to the W. A. Parish 
Unit WAP4, there are no practical add-on controls to consider for 
setting a more stringent PM BART emission limit than what is already 
required of the unit, and therefore, the status quo reflects the most 
stringent controls. The Guidelines state that if the most stringent 
controls are made federally enforceable for BART, then the otherwise 
required analyses leading up to the BART determination can be 
skipped.\308\ Thus, we are proposing that PM BART for W. A. Parish Unit 
WAP4 is to limit fuel to pipeline natural gas, as defined at 40 CFR 
72.2.
---------------------------------------------------------------------------

    \305\ AP 42, Fifth Edition, Volume 1, Chapter 1: External 
Sources, Section 1.4, Natural Gas Combustion, available here: 
https://www3.epa.gov/ttn/chief/ap42/ch01/final/c01s04.pdf.
    \306\ See 70 FR at 39165.
    \307\ 70 FR at 39116-17.
    \308\ 70 FR at 39165 (``. . . you may skip the remaining 
analyses in this section, including the visibility analysis . . 
.'').
---------------------------------------------------------------------------

VIII. Weighing of the Five BART Factors and Proposed BART 
Determinations

    In this section, we present our reasoning for our proposed BART 
determinations for 12 EGUs in Texas, based on our analysis and weighing 
of the five statutory BART factors for the following unit types: (1) 
proposed SO2 and PM BART determinations for 6 coal-fired 
units with no SO2 controls, and (2) proposed SO2 
and PM BART determinations for 5 coal-fired units

[[Page 28963]]

with existing scrubbers, and (3) proposed SO2 and PM BART 
determination for the gas-fired unit (W. A. Parish Unit WAP4).
    In previous sections of this proposal, we have described how we 
assessed the five BART factors. We will now discuss how we weigh these 
factors in our BART determinations. As a general matter, cost 
effectiveness and visibility benefits are the driving factors for most 
of our BART determinations. However, site specific considerations can 
impact the evaluation of control options and establishing an 
appropriate BART limit. As defined in the BART Guidelines, ``BART means 
an emission limitation based on the degree of reduction achievable 
through the application of the best system of continuous emission 
reduction for each pollutant which is emitted by . . . [a BART-eligible 
source].'' Through this process, we will establish emission limits that 
represent a system of continuous emission reduction for specific 
pollutants based on consideration of the technology available, the 
costs of compliance, the energy and non-air quality environmental 
impacts of compliance, any pollution control equipment in use or in 
existence at the source, the remaining useful life of the source, and 
the degree of improvement in visibility which may reasonably be 
anticipated to result from the use of such technology.
    In considering cost-effectiveness and visibility benefit, we do not 
eliminate any controls based solely on the magnitude of the cost-
effectiveness value, nor do we use cost-effectiveness as the primary 
determining factor. Rather, we compare the cost-effectiveness to the 
anticipated visibility benefit, and we take note of any additional 
considerations. Also, in judging the visibility benefit we do not 
simply examine the highest value for a given Class I area, or a group 
of Class I areas, but we also consider the cumulative visibility 
benefit for all affected Class I areas, the number of days in a 
calendar year in which we see significant improvements, and other 
factors.\309\ We consider visibility improvement in a holistic manner, 
taking into account all reasonably anticipated improvements in 
visibility expected to result at all impacted Class I areas. As 
explained in Section VII.A, and in accordance with the BART Guidelines, 
a source with a modeled 0.5 dv impact at a single Class I area 
``contributes'' to visibility impairment and must be analyzed for BART 
controls. Controlling individual units to reduce emissions of a 
visibility impairing pollutant, such as SO2, at such a 
source will address only a fraction of the total visibility impairment 
and will not result in perceptible improvements (~1 dv improvement) or 
visibility improvements greater than 0.5 dv. However, when considered 
in the aggregate, small improvements from controls on multiple sources 
will lead to visibility progress.
---------------------------------------------------------------------------

    \309\ See 70 FR at 39130: ``comparison thresholds can be used in 
a number of ways in evaluating visibility improvement (e.g., the 
number of days or hours that the threshold was exceeded, a single 
threshold for determining whether a change in impacts is 
significant, a threshold representing an x percent change in 
improvement, etc.).''
---------------------------------------------------------------------------

    The visibility benefits and cost-effectiveness of all of the 
controls that form the basis of our proposed BART determinations are 
within a range found to be acceptable in other BART actions nationwide, 
with the exception of SDA on Harrington Unit 061B which is discussed in 
further detail in Section VIII.A.2.a.\310\ As we stated in the BART 
Rule, a reasonable range would be a range that is consistent with cost 
effectiveness values used in other similar decisions over a period of 
time.\311\ We looked at past BART actions to assess the upper range of 
cost effectiveness values that have previously been found to be 
acceptable. In past BART decisions, several controls were required by 
either EPA or States as BART with average cost-effectiveness values in 
the $4,200 to $5,100/ton range (escalated to 2020 dollars) and 
visibility benefits of 0.26 to 0.83 dv. For instance, the EPA 
promulgated a FIP for Arkansas where we made the determination that 
SO2 BART for Flint Creek Unit 1 is an SO2 
emission limit based on dry scrubbers at a cost of $3,845/ton, which is 
$4,232/ton escalated to 2020 dollars using the CEPCI, and estimated to 
result in visibility benefit of 0.615 dv at the Class I area with the 
greatest visibility benefit.312 313 The EPA also promulgated 
a FIP for Wyoming where we made the determination that NOX 
BART for Laramie River Units 1, 2, and 3 is a NOX emission 
limit based on LNB with SOFA and Selective Catalytic Reduction (SCR) at 
a cost per unit ranging from $4,375 to $4,461/ton, which is $4,599 to 
$4,689/ton escalated to 2020 dollars, and estimated to result in 
visibility benefit ranging from 0.52 to 0.57 dv per unit at the Class I 
area with the greatest visibility benefit.314 315 In that 
Wyoming Regional Haze FIP, we explained the following:
---------------------------------------------------------------------------

    \310\ See for instance 77 FR 18070 (March 26, 2012): the EPA 
proposed approval of Colorado's NOX BART determination of 
SCR for Hayden Unit 2, later finalized at 77 FR 76871 (December 31, 
2012). The estimated cost of SCR at Hayden Unit 2 is $4,064/ton 
($4,211/ton when escalated from 2008 dollars to 2020 dollars) and 
anticipated to result in visibility benefit of 0.85 dv at the Class 
I area with greatest visibility benefit. We escalated this cost-
effectiveness value using the following equation: Cost-effectiveness 
escalated to 2020 dollars = Cost-effectiveness in 2008 dollars x 
(2020 CEPCI/2008 CEPCI).
    \311\ 70 FR at 39168 (July 6, 2005).
    \312\ See the EPA's proposed Arkansas Regional Haze FIP at 80 FR 
18944 (April 8, 2015), later finalized at 81 FR 66332 (September 27, 
2016). The Arkansas Regional Haze FIP was later replaced with a SIP 
revision submitted by Arkansas that included the same SO2 
BART determination for Flint Creek Unit 1. See the EPA's approval of 
Arkansas Regional Haze SIP Revision at 84 FR 51033 (September 27, 
2019).
    \313\ The year basis for the EPA's cost-effectiveness 
calculation is 2016. We escalated the cost-effectiveness value from 
2016 dollars to 2020 dollars using CEPCI and the following equation: 
Cost-effectiveness escalated to 2020 dollars = Cost-effectiveness in 
2016 dollars x (2020 CEPCI/2016 CEPCI); 2016 CEPCI = 541.7, 2020 
CEPCI = 596.2.
    \314\ See the EPA's Wyoming Regional Haze FIP at 79 FR 5032 
(January 30, 2014).
    \315\ The year basis for the EPA's cost-effectiveness 
calculations is 2013. We escalated the cost-effectiveness value from 
2013 dollars to 2020 dollars using the CEPCI and the following 
equation: Cost-effectiveness escalated to 2020 dollars = Cost-
effectiveness in 2013 dollars x (2020 CEPCI/2013 CEPCI); 2013 CEPCI 
= 567.2, 2020 CEPCI = 596.2.

    In regards to the costs of compliance, we found that the revised 
average and incremental cost-effectiveness of LNB/SOFA + SCR is in 
line with what we have found to be acceptable in our other FIPs. The 
average cost-effectiveness per unit ranges from $4,375 to $4,461/
ton, while the incremental cost-effectiveness ranges from $5,449 to 
$5,871/ton. We believe that these costs are reasonable, especially 
in light of the significant visibility improvement associated with 
LNB/SOFA + SCR. As a result, we are finalizing our proposed 
disapproval of the State's NOX BART determination for 
Laramie River Station and finalizing our proposed FIP that includes 
a NOX BART determination of LNB/SOFA + SCR, with an 
emission limit of 0.07 lb/MMBtu (30-day rolling average).\316\
---------------------------------------------------------------------------

    \316\ See 79 FR at 5047-48.

    In addition, the EPA approved several BART SIP decisions that 
required controls with similar cost-effectiveness values. For example, 
the EPA approved Colorado's determination that NOX BART for 
the Colorado Energy Nations Company Unit 5 is a NOX emission 
limit based on Low NOX burners (LNB) with Separated Overfire 
Air (SOFA) and Selective Non-Catalytic Reduction (SNCR) at a cost of 
$4,918/ton, which is $5,096/ton escalated to 2020 dollars, and 
estimated to result in visibility benefit of 0.26 dv at the Class I 
area with the greatest visibility benefit.317 318 The

[[Page 28964]]

EPA also approved Colorado's determination that NOX BART for 
Tri-State Craig Unit 1 is a NOX emission limit based on SNCR 
at a cost of $4,877/ton, which is $5,053/ton escalated to 2020 dollars, 
and estimated to result in visibility benefit of 0.31 dv at the Class I 
area with the greatest visibility benefit.319 320 The EPA 
approved Kentucky's determination that PM BART for Mill Creek Station 
Units 3 and 4 is an emission limit based on sorbent injection at a cost 
of $4,293/ton for Unit 3 and $4,443/ton for Unit 4, which is $4,872/ton 
and $5,042/ton escalated to 2020 dollars (respectively), and estimated 
to result in visibility benefit of 0.83 dv for both units combined at 
the Class I area with the greatest visibility 
benefit.321 322 In these BART determinations, the EPA and 
States found that the evaluated controls were reasonable based on the 
weighing of the five factors (including cost-effectiveness and 
visibility benefits).
---------------------------------------------------------------------------

    \317\ See the EPA's proposed approval of Colorado Regional Haze 
SIP at 77 FR 18052, later finalized at 77 FR 76871.
    \318\ The year basis for Colorado's cost-effectiveness 
calculation is 2008. We escalated the cost-effectiveness value from 
2008 dollars to 2020 dollars using the CEPCI and the following 
equation: Cost-effectiveness escalated to 2020 dollars = Cost-
effectiveness in 2008 dollars x (2020 CEPCI/2008 CEPCI); 2008 CEPCI 
= 575.4, 2020 CEPCI = 596.2.
    \319\ See the EPA's proposed approval of Colorado Regional Haze 
SIP at 77 FR 18052, later finalized at 77 FR 76871.
    \320\ The year basis for Colorado's cost-effectiveness 
calculation is 2008. We escalated the cost-effectiveness value from 
2008 dollars to 2020 dollars using the CEPCI and the following 
equation: Cost-effectiveness escalated to 2020 dollars = Cost-
effectiveness in 2008 dollars x (2020 CEPCI/2008 CEPCI); 2008 CEPCI 
= 575.4, 2020 CEPCI = 596.2.
    \321\ See the EPA's proposed approval of Kentucky Regional Haze 
SIP at 76 FR 78194 (December 16, 2011), later finalized at 77 FR 
19098 (March 30, 2012).
    \322\ The year basis for Kentucky's cost-effectiveness 
calculations is 2007. We escalated the cost-effectiveness value from 
2007 dollars to 2020 dollars using the CEPCI and the following 
equation: Cost-effectiveness escalated to 2020 dollars = Cost-
effectiveness in 2007 dollars x (2020 CEPCI/2007 CEPCI); 2007 CEPCI 
= 525.4, 2020 CEPCI = 596.2.
---------------------------------------------------------------------------

A. SO2 BART for Coal-Fired Units With No SO2 Controls

    In this section, we compare DSI, SDA, and wet FGD using the five 
BART factors for the six coal-fired units with no SO2 
controls. As discussed in Section VII.B.2 and in our TSD, we evaluated 
each unit at its assumed maximum achievable DSI performance level using 
milled trona according to the April 2017 IPM DSI documentation, which 
corresponds to 90 percent for units with an existing fabric filter 
baghouse and 80 percent for units with an ESP.323 324 All 
units we evaluated for DSI have an existing baghouse, with the 
exception of Harrington Unit 061B, which has an ESP. Since we do not 
have site-specific information and individual DSI performance testing, 
we do not know with certainty whether the EGUs we are evaluating in 
this proposal are capable of achieving the assumed maximum DSI 
performance levels specified in the April 2017 IPM DSI documentation. 
Taking this into account, and recognizing that DSI has a wide range of 
SO2 removal efficiencies, we also evaluated all units at a 
DSI SO2 control level of 50 percent, which we believe is a 
conservatively low DSI control efficiency that any given coal-fired EGU 
is likely capable of achieving without requiring high sorbent injection 
rates that may negatively impact the performance of the particulate 
control device. Evaluating a range of control levels better informs our 
analysis of control options by providing a range of costs. 
Additionally, this approach addresses the BART Guidelines directive 
that in evaluating technically feasible alternatives we ``(1) [ensure 
we] express the degree of control using a metric that ensures an 
`apples to apples' comparison of emissions performance levels among 
options, and (2) [give] appropriate treatment and consideration of 
control techniques that can operate over a wide range of emission 
performance levels.'' \325\
---------------------------------------------------------------------------

    \323\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Dry Sorbent Injection for SO2/HCl Control 
Cost Development Methodology, Final April 2017, Project 13527-001, 
Eastern Research Group, Inc., Prepared by Sargent & Lundy.
    \324\ Note for Harrington Unit 062B and Welsh Unit 1, we further 
limited the maximum DSI control level to that of our calculated SDA 
control level of 89 percent and 87 percent, respectively.
    \325\ 70 FR 39166 (July 6, 2005).
---------------------------------------------------------------------------

    For the units with existing baghouses where we evaluated DSI at 50 
percent and 90 percent control, in comparing the 50 percent control 
level to the higher control level, we found DSI to have similar or 
slightly higher (up to around 10 percent higher) $/ton average cost-
effectiveness at 90 percent control compared to 50 percent 
control.\326\ This is due to higher annual operation and maintenance 
costs associated with increased sorbent usage, as well as higher 
capital costs. Similarly, for Harrington Unit 061B, which is the only 
unit we evaluated that has an existing ESP rather than a baghouse, we 
found DSI to have a slightly higher $/ton on average at 80 percent 
control compared to 50 percent control. While the cost-effectiveness of 
DSI in certain cases had a slightly higher $/ton, when going from 50 
percent to 80/90 percent control efficiency, DSI at 80/90 percent 
control efficiency offered much greater SO2 reductions and 
higher resulting visibility benefits compared to 50 percent control 
efficiency. For all units evaluated, DSI at both 50 percent and 80/90 
percent control efficiency has a lower cost-effectiveness ($/ton) than 
SDA and wet FGD. However, because of the lack of site-specific 
information and related uncertainty over whether the specific units we 
are evaluating can achieve these assumed maximum achievable DSI 
performance levels, which we discuss in Section VII.B.2.a, we place 
much greater weight on our evaluation of DSI at 50 percent control 
efficiency compared to 80/90 percent control efficiency. There is also 
additional potential uncertainty in our cost estimates for DSI at these 
high performance levels. For the units with existing fabric filters, we 
do not know how frequently fabric filter bags would need to be cleaned 
and replaced or whether additional fabric filter compartments are 
necessary at these high DSI performance levels and so our cost 
estimates do not include these potential additional costs. For 
Harrington Unit 061B (the only unit with an existing ESP), our cost 
estimate for DSI at 80 percent control efficiency does not include the 
cost of a new ESP or fabric filter even though we do not know with 
certainty whether the existing ESP would be able to handle the high 
sorbent injection rates needed at high SO2 removal 
efficiency. Therefore, without additional site-specific information 
regarding the range of maximum control efficiency achievable and 
associated costs needed to consider DSI at higher control levels, we 
are not further considering DSI at 80/90 percent control efficiency in 
our weighing of the factors. We welcome site-specific information and 
comments on the potential for these units to consistently achieve DSI 
SO2 control efficiencies much higher than 50 percent (which 
may be as high as 80 to 90 percent).
---------------------------------------------------------------------------

    \326\ Harrington Unit 062B and Welsh Unit 1 show small 
improvement in cost effectiveness at the higher level of DSI 
control.
---------------------------------------------------------------------------

    In comparing DSI at 50 percent control level with SDA and wet FGD, 
we found that DSI at the 50 percent control level was more cost-
effective than either SDA or wet FGD. In general, DSI systems have low 
capital costs in comparison to SDA or wet FGD. At 50 percent control 
level, the ongoing annual operation and maintenance costs of DSI are 
comparable to those of SDA and wet FGD. Given the relatively low 
initial capital costs of DSI as compared to the installation of SDA or 
wet FGD, DSI may be a more favorable control option from a cost 
perspective for a coal-fired EGU that may have plans to retire in the 
next several years. However, we are not aware of any federally 
enforceable and permanent commitment to cease operations for these 
sources that would impact the remaining useful life of controls.

[[Page 28965]]

Therefore, we do not place extra weight on the capital cost benefit of 
DSI at 50 percent control over the visibility benefit gained by SDA. In 
considering CAMx modeled visibility benefits, wet FGD and SDA provide 
approximately twice the amount of visibility benefits as DSI at 50 
percent control level. Additionally, for all units, with the exception 
of Harrington Unit 061B, we conclude that scrubbers are approximately 
$4,900/ton or less, and thus within the range we regularly find to be 
cost-effective. We are proposing to find that, with the possible 
exception of Harrington Unit 061B, the resulting visibility benefit 
offered by scrubbers outweighs any possible advantage DSI at 50 percent 
control may hold in terms of cost-effectiveness. At higher control 
efficiencies, DSI may become more favorable as the difference in 
visibility benefits between DSI and SDA or wet FGD decreases and 
estimated cost-effectiveness for DSI even at higher control is 
estimated to be less than that for SDA or wet FGD, resulting in 
increasing incremental costs between DSI and scrubbers. However, as 
noted elsewhere, there is uncertainty as to what DSI control 
efficiencies are achievable for these particular units and the 
associated costs at these higher control efficiencies. We will further 
consider site-specific information provided to us during the public 
comment period in making our final decision on SO2 BART and 
potentially re-evaluate DSI for one or more particular units.
    As we indicate elsewhere in our proposal, both SDA and wet FGD are 
mature technologies that are in wide use throughout the United States. 
In comparing wet FGD versus SDA, wet FGD is slightly less cost-
effective than SDA in all cases evaluated for this proposed action. Wet 
FGD has slightly higher SO2 removal efficiency than SDA and 
generally requires lower reagent usage and has lower associated reagent 
costs than a comparable dry scrubber. However, as the Control Cost 
Manual explains, ``In general, dry scrubbers have lower capital and 
operating costs than wet scrubbers because dry scrubbers are generally 
simpler, consume less water and require less waste processing.'' \327\ 
The Control Cost Manual also notes that SDA has lower auxiliary power 
usage and lower water usage than wet FGD and does not require any 
wastewater treatment, unlike a wet FGD.\328\ These factors all 
contribute to the generally lower capital and operating costs of SDA 
compared to wet FGD. Further, the wet FGD cost algorithms were updated 
in version 6 of our IPM model to incorporate the capital and operating 
costs of a wastewater treatment facility for all wet FGDs. The IPM wet 
FGD Documentation states:
---------------------------------------------------------------------------

    \327\ EPA Air Pollution Control Cost Manual, Seventh Edition, 
April 2021, Section 5, Chapter 1, titled ``Wet and Dry Scrubbers for 
Acid Gas Control,'' page 1-11. The EPA Air Pollution Control Cost 
Manual is available at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual.
    \328\ Id. At 1-3 and 1-4.

    Industry data from ``Current Capital Cost and Cost-effectiveness 
of Power Plant Emissions Control Technologies'' prepared by J. E. 
Cichanowicz for the Utility Air Regulatory Group (UARG) in 2012 to 
2014 were used by Sargent & Lundy LLC (S&L) to update the wet FGD 
cost algorithms from 2013. The published data were significantly 
augmented by the S&L in-house database of recent wet FGD and wet FGD 
wastewater treatment system projects. Due to recently published 
Effluent Limitation Guidelines (ELG), it is expected that all future 
wet FGDs will have to incorporate a wastewater treatment 
facility.\329\
---------------------------------------------------------------------------

    \329\ IPM Model--Updates to Cost and Performance for APC 
Technologies, Wet FGD Cost Development Methodology, Final January 
2017, Project 13527-001, Eastern Research Group, Inc., Prepared by 
Sargent & Lundy, p. 1.

    The anticipated need for a wastewater treatment facility for all 
future wet FGDs also contributes to the higher capital and operating 
costs of wet FGD compared to SDA. We discuss the cost differences and 
the factors that result in wet FGD being slightly less cost-effective 
than SDA for the evaluated units in greater detail in our 2023 BART FIP 
TSD. We solicit comment on any additional factors or information that 
may affect the costs of wet FGD and/or SDA for the evaluated units and 
weigh in favor of one control option or the other. Although wet FGD 
would offer slightly greater SO2 emission reductions 
compared to SDA, that the estimated visibility benefits of the two 
control options are very similar in all cases. In consideration of the 
additional costs and non-air environmental impacts associated with wet 
FGD, we propose to conclude that, based on a weighing of these factors, 
the selection of SDA is appropriate for Coleto Creek Unit 1, W. A. 
Parish Units WAP5 and WAP6, Welsh Unit 1, and Harrington Unit 062B. We 
propose that SO2 BART should be based on the emission limit 
associated with SDA control levels. For those units with existing 
fabric filters, DSI could potentially meet the same emission 
limitations as SDA but this would need to be confirmed with site-
specific performance testing. For Harrington Unit 061B, as discussed in 
Section VIII.A.2., there are unique circumstances that impact the 
evaluation of controls. For this unit, we propose that SO2 
BART should be an emission limit based on SDA and we propose in the 
alternative an emission limit based on DSI at 50 percent control level.
    We discuss in further detail our consideration of the cost-
effectiveness and anticipated visibility benefits of controls for each 
of the facilities. Tables 15 thru 17 and 19 thru 26 provide summary 
CAMx and CALPUFF model results of the benefits from the recommended 
BART controls. The CAMx model results shown in the following tables for 
each evaluated BART source summarize the benefits from the recommended 
controls at the three Class I areas most impacted by the source or unit 
in the baseline modeling. The benefit is calculated as the difference 
between the maximum impact modeled for the baseline and the maximum 
impact level modeled under the control scenario. Also summarized are 
the cumulative benefit and the number of days impacted over 0.5 and 1.0 
dv. Cumulative benefit is calculated as the difference in the maximum 
visibility impacts from the baseline and control scenario summed across 
the 15 Class I areas included in the CAMx modeling. The baseline total 
cumulative number of days over 0.5 (1.0) dv is calculated as the sum of 
the number of modeled days at each of the 15 Class I area impacted over 
the threshold in the baseline modeling. The reduction in number of days 
is calculated as the sum of the number of days over the chosen 
threshold across the 15 Class I areas included in the CAMx modeling for 
the baseline scenario subtracted by the number of days over the 
threshold for the control scenario.
    In addition to these metrics, to further inform the impacts and 
potential benefits of emission reductions, we also provide the average 
of modeled potential impacts from CAMx on a broader set of high impact 
days. The CAMx model results tables include the average impact across 
the top ten highest impacted days at the most impacted class I areas 
(and cumulative across all Class I areas) for the baseline and the 
recommended control scenario, as well as the calculated visibility 
benefits, to assess the potential visibility benefits that could be 
anticipated due to

[[Page 28966]]

controls during the ten days with meteorological/transport conditions 
that result in the largest visibility impacts. These varying conditions 
affect the reaction rates and transport of pollutants which can be 
simulated within the photochemical grid model. While the BART analysis 
is focused on examination of the maximum potential visibility 
impairment and benefits, these additional metrics provide a sense for 
the potential benefit across days other than just the maximum impact 
day.
    For Coleto Creek, Parish and Welsh units, we also present the 
benefits of SDA control levels for comparison with wet FGD, though 
these SDA control levels were not directly modeled in CAMx. To evaluate 
SDA control levels using the available CAMx model results, we 
calculated an estimate of the visibility benefits using a mathematical 
extrapolation method, which is further discussed in the 2023 BART 
Modeling TSD.
    The CALPUFF model results in the following tables for the evaluated 
BART sources include the 98th percentile modeled impact and the number 
of days impacted over 0.5 and 1.0 dv for those Class I areas within the 
range of CALPUFF typically used for BART. See the 2023 BART Modeling 
TSD for a complete summary of our visibility benefit analysis of 
controls, including modeled benefits and impacts at all Class I areas 
included in the modeling analyses, plus additional metrics considered 
in the assessment of visibility benefits.
1. Coleto Creek Unit 1
    In reviewing Coleto Creek Unit 1, we conclude that the installation 
of SDA or wet FGD results in significant visibility benefits. We 
summarize some of these visibility benefits in Table 15 and discuss 
them after the table.

                Table 15--CAMx-Predicted Wet FGD (SDA) Visibility Benefits at Coleto Creek Unit 1
----------------------------------------------------------------------------------------------------------------
     Coleto Creek Unit 1                     Baseline                                 Controlled
----------------------------------------------------------------------------------------------------------------
                                                                       Visibility
                              Impact (dv)   Avg impact   Number of     improvement   Avg visibility    Impacted
        Class I area             on the      (dv) for   days >=0.5/    (dv) on the     improvement    number of
                                maximum     the top 10    >=1.0 dv       maximum      (dv) for the   days >=0.5/
                               impact day      days                   impact day *    top 10 days *    >=1.0 dv
----------------------------------------------------------------------------------------------------------------
Caney Creek.................         1.55         0.89         18/2     1.38 (1.34)     0.80 (0.78)          0/0
Breton......................         1.19         0.47          4/1     1.08 (1.05)     0.43 (0.42)          0/0
Wichita Mountains...........         1.13         0.86         23/3     1.00 (0.98)     0.79 (0.76)          0/0
Cumulative (all Class I              8.54         5.14         69/6            7.75            4.71          0/0
 areas).....................
----------------------------------------------------------------------------------------------------------------
* Secondary values in parentheses indicate estimated visibility benefits for SDA.

    The visibility benefits predicted by CAMx with wet FGD control 
levels applied to Coleto Creek Unit 1 are summarized in Table 15. We 
also present the estimated benefits of SDA (shown in parentheses) for 
the visibility improvement at the top three impacted Class I areas. The 
small difference in visibility benefits between SDA and wet FGD is 
consistent with the relatively small difference in control efficacy, 
with an estimated difference between wet FGD and SDA on the maximum 
impacted day of 0.04 dv at Caney Creek and an average top 10 days 
difference of 0.02 dv at Caney Creek and Wichita Mountains.
    CAMx modeling results indicate that wet FGD will 
eliminate all 69 days impacted over 0.5 dv across all Class I areas. At 
each of the three most impacted Class I areas (Caney Creek, Breton, and 
Wichita Mountains), wet FGD will result in visibility improvements of 
more than 1.0 dv on the maximum impacted days at each Class I area, and 
for the average of the top 10 most impacted days, CAMx 
predicts an average improvement of 0.43 to 0.80 dv at those same three 
Class I areas. Overall, there is a cumulative improvement to the 
average of the top 10 impacted days of approximately 4.7 dv with wet 
FGD across all impacted Class I areas and 7.7 dv cumulative improvement 
on the maximum impacted day. When compared to wet FGD, we estimate that 
SDA will result in very similar visibility benefits, ranging from 0.98 
to 1.34 dv at the three most impacted Class I areas on the maximum 
impacted days and an average improvement of 0.42 to 0.78 dv at those 
same three Class I areas for the average of the top 10 most impacted 
days. See the 2023 BART Modeling TSD for more information on our 
estimation of the visibility benefits of SDA. Additional evaluation of 
the visibility benefits of DSI are presented in the 2023 BART Modeling 
TSD, but in summary, we find that DSI averaged 46 percent reduction in 
cumulative visibility impacts at the Class I areas, while wet FGD 
averaged 91 percent reduction in cumulative visibility impacts overall 
on the most impacted days. At Caney Creek (highest baseline maximum 
impact of 1.55 dv), DSI results in improvement on the maximum impacted 
day of 0.66 dv compared to 1.38 dv for wet FGD and 1.34 dv for SDA. 
Thus, we conclude that the resulting visibility benefit offered by 
scrubbers outweighs the possible advantage DSI at 50 percent control 
may hold in cost-effectiveness.
    We also conclude that both SDA and wet FGD are cost-effective at 
$2,692/ton and $2,911/ton (respectively) and, as discussed in Section 
VIII, well within a range that we have previously found to be 
acceptable. Wet FGD is less cost-effective than SDA and we estimate 
that it would have only a slight additional visibility benefit over 
SDA. As discussed earlier, in weighing the factors between SDA and wet 
FGD, we determined the additional visibility benefits did not outweigh 
the additional cost, water requirements, and wastewater treatment 
requirements associated with wet FGD. We consider the significant 
visibility benefits that will result as justification for the cost of 
SDA at the Coleto Creek Unit 1. We therefore propose that 
SO2 BART for Coleto Creek Unit 1 is an emission limit of 
0.06 lbs/MMBtu on a 30 BOD rolling average based on the installation of 
SDA.
2. Harrington Units 061B & 062B
    From our identification of available controls, we conclude that 
both DSI and SDA are technically feasible on both Harrington units. 
Harrington Unit 061B is distinct from the other coal-fired units we 
evaluated in that it has an existing ESP rather than a fabric filter. 
Additionally, this unit had relatively low utilization at times during 
the 2016-2020 baseline we used in our BART analysis, which has resulted 
in a cost per SO2 tons removed for SDA that is relatively 
high compared to the other units evaluated for SDA. Based on these 
facts, we are proposing and taking comment on two alternative BART

[[Page 28967]]

determinations. We are proposing BART is an emission limit reflective 
of the installation and operation of SDA on both Unit 061B and 062B. In 
the alternative, we are proposing BART to be an emission limit 
reflective of the installation and operation of DSI at 50 percent 
control for Unit 061B and SDA on 062B. We provide the reasoning for 
each determination in detail in the following paragraphs and solicit 
comment on both approaches.
    In order to evaluate visibility benefits of control options for the 
Harrington units, we performed modeling using both CALPUFF and 
CAMx. As discussed in Section VII, and in more detail in our 
2023 BART Modeling TSD, there are a number of differences between CAMx 
and CALPUFF with one of the concerns being CALPUFF's simpler chemistry 
mechanism that may underestimate the benefit of SO2 
reductions versus CAMx generated values using more state of 
the science chemistry.
a. Control Scenario 1: SDA on Unit 061B and Unit 062B

                                    Table 16--CALPUFF Predicted Visibility Benefits of SDA on Both Harrington Units.*
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Harrington                                   2016-2018 baseline impact              Modeled Benefit of SDA on both
--------------------------------------------------------------------------------------------------------              units                 Cumulative
                                                                                           Cumulative   --------------------------------- 2016-2018 # of
                                                                                         2016-2018 # of                                      days with
                     Class I Area                        2016 dv    2017 dv    2018 dv      days with                                      impacts >=0.5
                                                                                          impacts >=0.5   2016 dv    2017 dv    2018 dv     dv/>=1.0 dv
                                                                                           dv/>=1.0 dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
Carlsbad Caverns......................................       0.39       0.41       0.56            16/5       0.24       0.27       0.31             1/1
Bandelier.............................................       0.17       0.12       0.14             2/0       0.12       0.09       0.11             0/0
Pecos.................................................       0.22       0.28       0.24             9/0       0.15       0.17       0.16             0/0
Salt Creek............................................       0.49       0.59       0.54            27/3       0.23       0.39       0.32             2/0
Wheeler Peak..........................................       0.12       0.15       0.16             2/0       0.07       0.10       0.11             0/0
White Mountain........................................       0.26       0.43       0.33             7/0       0.17       0.26       0.24             0/0
Wichita Mountains.....................................       0.54       0.45       0.58            24/8       0.35       0.23       0.33             3/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Benefit of control values are the decrease in deciview between baseline and the control scenario. Number of days is the number of days that are equal
  or greater than 0.5 and 1.0 dv after controls.

    As in Section VII, we compared the visibility benefits (as 
predicted by CALPUFF) of the SDA control levels on both units to the 
baseline impacts in terms of percent reduction in visibility impacts. 
To make this comparison, we first calculated the average of the 98th 
percentile (8th highest value) for the three years modeled for each 
Class I area and the average for the seven Class I areas. For 
Harrington, Salt Creek was the highest impacted of the seven Class I 
areas and SDA control on both units compared to baseline resulted in a 
reduction of visibility impacts by 58 percent, from 0.54 dv to 0.23 dv. 
At the second highest impacted Class I area, Wichita Mountains, SDA on 
both units result in a reduction of visibility impacts by 58 percent, 
from 0.52 dv to 0.22 dv. SDA on both units also resulted in an average 
reduction of visibility impacts across the seven Class I areas combined 
of 61 percent. Using the CALPUFF modeling results from the baseline, we 
determined the total number of days when facility impacts were greater 
than 0.5 dv and 1.0 dv. Harrington had a total of 87 days with 
visibility impacts above 0.5 dv and 16 days above 1.0 dv at the seven 
Class I areas modeled with CALPUFF. In comparison, SDA on both units 
results in a large reduction in impacted days with only six days still 
above 0.5 dv and one day above 1.0 dv at the same seven Class I areas. 
In conclusion, the CALPUFF modeling results show that SDA on both units 
would provide notable visibility improvements.

                                       Table 17--CAMx-Predicted Visibility Impact and Benefit of Controls for SDA
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       Harrington                                            Baseline                                       Controlled
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Visibility
                                                          Impact (dv) on    Avg impact    Number of days    improvement   Avg visibility     Impacted
                      Class I area                          the maximum    (dv) for the    >=0.5/ >=1.0     (dv) on the     improvement   number of days
                                                            impact day      top 10 days         dv        maximum impact   (dv) for the   >=0.5/>=1.0 dv
                                                                                                                day         top 10 days
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Harrington Unit 061B
--------------------------------------------------------------------------------------------------------------------------------------------------------
White Mountain..........................................            1.43            0.48             3/1            0.96            0.35             0/0
Bandelier...............................................            0.83            0.28             1/0            0.64            0.23             0/0
Salt Creek..............................................            0.79            0.55             6/0            0.50            0.43             0/0
Cumulative (all Class I areas)..........................            6.59            3.15            10/1            4.61            2.48             0/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                  Harrington Unit 062B
--------------------------------------------------------------------------------------------------------------------------------------------------------
White Mountain..........................................            1.36            0.48             3/1            0.95            0.36             0/0
Bandelier...............................................            0.82            0.29             1/0            0.65            0.23             0/0
Salt Creek..............................................            0.79            0.56             6/0            0.52            0.45             0/0
Cumulative (all Class I areas)..........................            6.55            3.17            10/1            4.79            2.56             0/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                             Harrington Units 061B and 062B
--------------------------------------------------------------------------------------------------------------------------------------------------------
White Mountain..........................................            2.64            0.93             8/3            1.78            0.70             1/0
Bandelier...............................................            1.60            0.56             4/1            1.24            0.45             0/0
Salt Creek..............................................            1.52            1.08            13/6            0.97            0.86             1/0

[[Page 28968]]

 
Cumulative (all Class I areas)..........................           12.77            6.23           44/10            9.08            5.00             2/0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The CAMx results reinforce that installation of SDA at the 
Harrington units would provide significant visibility benefits. CAMx 
modeling results indicate SDA on the individual Harrington units will 
eliminate all days impacted over 0.5 dv at all Class I areas. When 
considering the combined impacts of the two units, visibility benefits 
from SDA installed on both units predicts only one day to exceed the 
0.5 dv threshold at each of the White Mountain and Salt Creek Class I 
areas. This is an overall (cumulative Class I areas) reduction from 44 
days over 0.5 dv in the baseline to a total of only two days with SDA. 
The overall cumulative visibility improvement is 9.08 dv on the maximum 
impacted days and 5.0 dv improvement when considering the average of 
the top ten days across all 15 Class I areas.
    For Harrington Unit 061B, the CAMx results show that SDA would 
eliminate all days impacted over 0.5 dv for that unit. On the maximum 
impacted day at White Mountain, SDA results in 0.96 dv improvement over 
baseline (1.43 dv), an additional 0.44 dv improvement over DSI at 50 
percent control (from Table 12). On the maximum impacted day at 
Bandelier, SDA results in 0.64 dv improvement over the baseline (0.83 
dv), an additional 0.3 dv improvement over DSI at 50 percent control. 
Furthermore, the CAMx results predict that the cumulative visibility 
benefit provided by SDA on just Unit 061B is 4.6 dv, with eight Class I 
areas seeing improvements of 0.25 dv or more.\330\ SDA control on both 
units resulted in a reduction of maximum visibility impacts by 67 
percent at White Mountain and an average reduction of maximum 
visibility impacts across all 15 Class I areas of 71 percent. This 
highlights that emissions and reductions from Harrington impact 
visibility conditions at several Class I areas. Visibility benefits for 
SDA on Unit 062B are very similar to Unit 061B.
---------------------------------------------------------------------------

    \330\ Bandelier, Guadalupe Mountains, Carlsbad Caverns, Salt 
Creek, Upper Buffalo, White Mountain, Wheeler Peak, and Pecos 
visibility improvements with SDA on Harrington Unit 061B ranging 
from 0.25 dv to 0.96 dv.

                                                 Table 18--Cost Analysis Summary for Units 061B and 062B
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                               2020
                                                                                        SO2 reduction                       2020 Cost-      Incremental
                   Facility                                    Control                      (tpy)       2020 Annualized    effectiveness       cost-
                                                                                                              cost            ($/ton)      effectiveness
                                                                                                                                              ($/ton)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Harrington 061B...............................  DSI w/ESP--50% control efficiency....           1,892         $7,075,817          $3,740  ..............
Harrington 061B...............................  SDA..................................           3,327        $21,967,236          $6,603         $10,377
Harrington 062B...............................  DSI w/BGH--50% control efficiency....           2,703         $7,408,200          $2,742  ..............
Harrington 062B...............................  SDA..................................           4,812        $23,369,564          $4,857          $7,568
--------------------------------------------------------------------------------------------------------------------------------------------------------

    A summary of our cost analyses from Section VII.B.3. are presented 
in Table 18. In our analysis, we find SDA to have a cost of $6,603/ton 
for Harrington Unit 061B, which is above the range for controls that we 
have previously found to be cost-effective. It is reasonable to expect 
that similar controls installed on units that are designed for similar 
capacity would result in similar tons reduced and cost effectiveness. 
Units 061B and 062B are designed to produce 360 MW of electricity but 
based on a review of heat input data from 2010 to 2021, differences in 
utilization or heat input have resulted in different estimates of tons 
reduced and cost effectiveness.\331\ The resulting control cost 
effectiveness for Harrington Unit 061B ($6,603/ton) is higher than at 
the similarly designed and sized Unit 062B ($4,857/ton) because of a 
lower utilization rate.
---------------------------------------------------------------------------

    \331\ See ``CAMD Heat Input Data for Harrington Station.xlsx'' 
available in the docket for this action.

---------------------------------------------------------------------------

[[Page 28969]]

[GRAPHIC] [TIFF OMITTED] TP04MY23.115

    As shown in Figure 1, the utilization rate of Unit 061B was much 
lower than Unit 062B during the 2016-2020 baseline period we evaluated 
for this proposed action. However, utilization rates both before and 
after the baseline period have been more consistent between the two 
units, and the utilization rate at Unit 061B has at times exceeded the 
annual utilization at Unit 062B. The difference in utilization during 
the baseline period used for the BART analysis results in a relatively 
smaller estimated reduction of SO2 emissions (3,327 tons per 
year with SDA for Unit 061B compared to 4,812 tons per year reduced 
with SDA for Unit 062B) used to calculate the cost-effectiveness in $/
ton removed.
    Further examination of the historical heat input for these units 
shows that Unit 061B annual heat input for 2015 and for 2021 are higher 
than during the 2016-2020 period, and for both 2015 and 2021, heat 
input for Units 061B and 062B are similar. During Fall of 2016 through 
spring of 2017, Unit 061B was utilized less than the other two units at 
the facility.\332\ This pattern continued for 2017/2018 and 2018/2019, 
resulting in lower overall heat input for the unit during those years. 
Starting in Fall of 2019, utilization of the BART units at the facility 
became roughly similar again, except during periods where a unit at the 
facility was down. We also note that July 2022 heat input for Unit 061B 
is higher than in any other single month from 2015-2022. These changes 
in utilization in the more recent period may suggest that the 
historical pattern of lower utilization of Unit 061B compared to Unit 
062B that was observed in the majority of the 2016-2020 period may not 
continue in the future, which could result in more favorable (lower $/
ton) cost-effectiveness for SDA and other controls at Harrington Unit 
061B. Furthermore, because there are no enforceable limitations on 
utilization for these units, there is no assurance that Unit 061B will 
operate in the future at the lower utilization rates seen between 2016 
and 2020.
---------------------------------------------------------------------------

    \332\ The Harrington facility has three EGUs. The third unit, 
Unit 063B, is not BART-eligible.
---------------------------------------------------------------------------

    We find that SDA on Units 061B and 062B provides significant 
visibility benefits. For Unit 062B we find SDA at $4,857/ton within the 
range we have previously found to be cost effective for BART. While 
above the range we have previously found to be cost effective, we still 
find SDA at $6,603/ton for Unit 061B to be reasonable based on the 
visibility benefits. Additionally, the estimated higher cost-
effectiveness associated with SDA is driven by past lower utilization 
of Unit 061B during the baseline period. We propose and are taking 
comment on our determination that BART for Units 061B and 062B is an 
emission limit of 0.06 lb/MMBtu consistent with the installation and 
operation of SDA.
b. Control Scenario 2: DSI on Unit 061B and SDA on Unit 062B
    Because we recognize the cost effectiveness of SDA at Harrington 
Unit 061B is above a range of costs we have previously required for 
BART, we are proposing in the alternative to determine that BART is DSI 
at a control level of 50 percent, with a requirement to conduct a DSI 
performance evaluation.

[[Page 28970]]



                     Table 19--CALPUFF Predicted Visibility Benefit of DSI (50 Percent) on Harrington Unit 061B and SDA on Unit 062B
--------------------------------------------------------------------------------------------------------------------------------------------------------
                   Harrington                                     2016-2018 Baseline                   Benefit of DSI--50% at Unit 061B and
-----------------------------------------------------------------------------------------------------            SDA at Unit 062B             Cumulative
                                                                                          Cumulative --------------------------------------- 2016-2018 #
                                                                                          # of days                                            of days
                                                                                             with                                                with
                  Class I area                      2016 dv      2017 dv      2018 dv      impacts      2016 dv      2017 dv      2018 dv      impacts
                                                                                          >=0.5 dv/                                           >=0.5 dv/
                                                                                           >=1.0 dv                                            >=1.0 dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
Carlsbad Caverns................................         0.39         0.41         0.56         16/5         0.18         0.21         0.23          5/1
Bandelier.......................................         0.17         0.12         0.14          2/0         0.09         0.06         0.08          0/0
Pecos...........................................         0.22         0.28         0.24          9/0         0.11         0.13         0.12          0/0
Salt Creek......................................         0.49         0.59         0.54         27/3         0.16         0.30         0.25         11/1
Wheeler Peak....................................         0.12         0.15         0.16          2/0         0.05         0.08         0.08          0/0
White Mountain..................................         0.26         0.43         0.33          7/0         0.14         0.20         0.19          0/0
Wichita Mountains...............................         0.54         0.45         0.58         24/8         0.27         0.20         0.25          8/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Benefit of control values are the decrease in deciview between baseline and the control scenario. Number of days is the number of days that are equal
  or greater than 0.5 and 1.0 dv after controls.

    For Harrington, CALPUFF results show installation of DSI at a 50 
percent control level on Unit 061B and SDA on Unit 062B resulted in a 
reduction of visibility impacts by 44 percent from the baseline at the 
highest impacted Class I area (Salt Creek) from 0.54 dv to 0.31 dv, and 
an average reduction of visibility impacts across seven Class I areas 
of 47 percent. For the 2016-2018 modeled years (baseline period), 
Harrington baseline had a total of 87 days with visibility impacts 
above 0.5 dv and 16 days above 1.0 dv at the seven Class I areas 
modeled with CALPUFF. DSI at 50 percent on Unit 061B and SDA on Unit 
062B resulted in 24 days above 0.5 dv and two days above 1.0 dv. The 
incremental visibility benefit between DSI and SDA is larger with the 
CAMx modeling than with the CALPUFF modeling.\333\
---------------------------------------------------------------------------

    \333\ See the 2023 BART Modeling TSD for detailed discussion of 
differences between CAMx and CALPUFF models and modeling results.

                            Table 20--CAMx Predicted Visibility Benefit of DSI (50 Percent) on Unit 061B and SDA on Unit 062B
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       Harrington                                            Baseline                                       Controlled
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Visibility
                                                          Impact (dv) on    Avg impact    Number of days    improvement   Avg visibility     Impacted
                      Class I area                          the maximum    (dv) for the    >=0.5/ >=1.0     (dv) on the     improvement   number of days
                                                            impact day      top 10 days         dv        maximum impact   (dv) for the    >=0.5/ >=1.0
                                                                                                                day         top 10 days         dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                   Harrington Unit 061B with DSI (50 percent) control
--------------------------------------------------------------------------------------------------------------------------------------------------------
White Mountain..........................................            1.43            0.48             3/1            0.52            0.19             1/0
Bandelier...............................................            0.83            0.28             1/0            0.34            0.12             0/0
Salt Creek..............................................            0.79            0.55             6/0            0.26            0.23             1/0
Cumulative (all Class I areas)..........................            6.59            3.15            10/1            2.56            1.34             2/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Harrington Unit 062B with SDA control
--------------------------------------------------------------------------------------------------------------------------------------------------------
White Mountain..........................................            1.36            0.48             3/1            0.95            0.36             0/0
Bandelier...............................................            0.82            0.29             1/0            0.65            0.23             0/0
Salt Creek..............................................            0.79            0.56             6/0            0.52            0.45             0/0
Cumulative (all Class I areas)..........................            6.55            3.17            10/1            4.79            2.56             0/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Harrington Unit 061B with DSI (50 percent) and 062B with SDA controls
--------------------------------------------------------------------------------------------------------------------------------------------------------
White Mountain..........................................            2.64            0.93             8/3          * 1.34          * 0.54          ** 1/1
Bandelier...............................................            1.60            0.56             4/1          * 0.94          * 0.34          ** 1/0
Salt Creek..............................................            1.52            1.08            13/6          * 0.73          * 0.66          ** 3/0
Cumulative (all Class I areas)..........................           12.77            6.23           44/10          * 7.03          * 3.86          ** 5/1
--------------------------------------------------------------------------------------------------------------------------------------------------------
* We did not model this combination (50 percent DSI on 061B and SDA on 062B) directly, so we estimated these values by subtracting the difference
  between the 50 percent DSI (Low Control) and SDA for 061B improvement values from the combined units SDA-only values in the previous table.
** Again, we did not model this combination directly, so we estimated the number of days based on the High (SDA) and Low (50 percent DSI) control number
  of days.

    The CAMx results for Harrington for this second control scenario 
show that White Mountain was the most impacted of the 15 Class I areas, 
the same as in the first control scenario, which had SDA on both units. 
From Table 17 of the first control scenario, we calculate that SDA 
control on both units compared to baseline resulted in a reduction of 
visibility impacts at White Mountain by 67 percent and an average 
reduction of visibility impacts across the 15 Class I areas of 71 
percent; whereas, from Table 20 we calculate that the 50% DSI on Unit 
061B and SDA on Unit 062B

[[Page 28971]]

compared to the baseline resulted in a reduction of visibility impacts 
at White Mountain by 51 percent and an average reduction of visibility 
impacts across the 15 Class I areas of 55 percent.
    For Unit 061B, by itself, DSI at 50 percent control results in 
visibility benefits approximately one half of those achieved through 
SDA. On the maximum impacted day at White Mountain, DSI at 50 percent 
on Unit 061B results in 0.52 dv improvement compared to 0.96 dv with 
SDA on that unit; at Bandelier, DSI at 50 percent results in 0.34 dv 
improvement compared to 0.64 dv with SDA on that unit. The cumulative 
visibility benefit across all Class I areas on the maximum impacted 
days for Unit 61B with DSI at 50 percent is 2.56 dv compared to 4.61 dv 
with SDA. For the average of the top 10 most impacted days, SDA 
provides for a 0.43 dv benefit at Salt Creek compared to 0.23 dv for 
DSI at 50 percent control, and SDA provides for 0.35 dv benefit at 
White Mountain compared to 0.19 dv for DSI at 50 percent control--
almost twice the improvement with SDA over DSI at 50% on Unit 061B.
    When considering the combined benefits of DSI for Unit 061B and SDA 
for Unit 062B, the visibility improvement at White Mountain Class I 
area is estimated to be more than 1.3 (1.78 minus 0.44) dv on the 
highest impact day, while the average of the top 10 most impacted days 
visibility improvement is approximately 0.6 (0.86 minus 0.20) dv at 
Salt Creek. Overall, for the visibility improvement at the cumulative 
Class I areas from the Harrington facility, CAMx predicts an average 
improvement of almost 4.0 (5.00 minus 1.14) dv across all the Class I 
areas evaluated on the top 10 days and an improvement on the maximum 
impacted days of approximately 7.0 (9.08 minus 2.05) dv with SDA 
controls on Unit 062B and DSI at 50 percent on Unit 061B. Thus, we find 
that SDA on Unit 062B and DSI at 50 percent control on Unit 061B 
results in a significant reduction in visibility impacts from these 
units and that the benefits are spread across a number of Class I areas 
in New Mexico, Texas, and Oklahoma. As previously discussed, SDA on 
both units provides an additional cumulative visibility benefit (the 
difference between DSI at 50 percent control and SDA on Unit 061B) on 
the average of the top 10 days from the Harrington facility of 1.14 dv 
across all the Class I areas evaluated and an additional improvement on 
the maximum impacted days of 2.05 dv. However, DSI at 50 percent 
control for Harrington is more cost-effective ($2,742/ton for Unit 062B 
and $3,740/ton for Unit 061B) than SDA ($4,857/ton for Unit 062B and 
$6,603/ton for Unit 061B) and is well within the range of what we have 
previously found to be acceptable in other BART actions. For Harrington 
Unit 062B, we consider SDA to also be cost-effective and within the 
range of what we have previously found to be acceptable in other BART 
actions. As discussed earlier, the cost of SDA at Unit 061B is above 
the range we have previously found to be cost-effective, and the 
incremental cost-effectiveness of SDA (going from DSI at 50 percent 
control efficiency to SDA) is $10,377, which we consider to be 
relatively high. The cost of SDA at Unit 061B is relatively high, but 
we still find SDA to be reasonable based on the important visibility 
benefits of SDA on this unit. However, given the relatively high cost 
of SDA at Unit 061B, we propose in the alternative that BART for this 
unit is based on DSI. While the visibility benefits of DSI are 
approximately half those from SDA on Unit 061B using the CAMx results, 
installation of DSI is significantly less costly than SDA. Therefore, 
we are proposing in the alternative that BART for Unit 061B is 0.27 lb/
MMBtu based on DSI at 50 percent, with a compliance period of no later 
than two (2) years from the effective date of the final rule.\334\
---------------------------------------------------------------------------

    \334\ The proposed regulatory language for this rulemaking only 
covers our first proposed approach (SDA on Harrington Units 061B and 
062B). If the EPA finalizes an action consistent with our 
alternative proposed approach (DSI at 50% control on Unit 061B and 
SDA on Unit 062B), we will revise the regulatory language 
accordingly.
---------------------------------------------------------------------------

    We believe Unit 061B is likely capable of achieving an 
SO2 emission limit of 0.27 lb/MMBtu with DSI but are not 
certain whether the unit could achieve a lower emission limit on a 30 
BOD or what the potential impacts to PM emissions could be at higher 
injections rates necessary for higher control efficiencies using the 
existing ESP. We evaluated DSI at a 50 percent control level as a 
conservative representative of what DSI can achieve on average. Because 
the control efficiency of DSI is dependent on several operational 
variables, we also propose to require a performance evaluation (as 
provided for in Section IX.A.3) to determine the maximum control 
efficiency of DSI for Harrington Unit 061B specifically along with an 
estimate of the cost to operate DSI at this control level.\335\ Based 
on available information, on a unit-specific basis, using sodium-based 
sorbents, we believe DSI could potentially achieve up to 80 percent or 
higher SO2 control, even with an ESP. However, as noted 
earlier, because of unit-specific uncertainty we are proposing an 
emissions limit of 0.27 lb/MMBtu based on DSI at 50 percent. If a DSI 
performance evaluation finds that Unit 061B can meet a lower rate, we 
will propose to adjust this limit in a future notice to reflect the 
maximum control efficiency that the unit can consistently meet. As 
discussed in Sections VII.B.2.a and VII.B.3.a, we are also soliciting 
comments on the range and maximum control efficiency that can be 
achieved with DSI at the evaluated units, including Harrington Unit 
061B, and estimates of the range of associated costs. We are especially 
interested in comments on any site-specific DSI testing for Unit 061B 
to determine the range and maximum control efficiency that can be 
achieved with DSI at the unit. Any data to support the control 
efficiency range, maximum control efficiency, and cost of DSI for the 
unit should be submitted along with those comments. We will further 
consider DSI site-specific information provided to us during the public 
comment period in our final decision and potentially re-evaluate DSI 
for this particular unit.
---------------------------------------------------------------------------

    \335\ The purpose of the DSI performance evaluation is to 
determine the lowest SO2 emission rate Unit 061B would be 
able to sustainably achieve on a 30 BOD with DSI under three 
different scenarios for particulate removal ((1) using the existing 
ESP; (2) with a new ESP installation; and (3) with a new fabric 
filter installation) and to determine how compliance with such an 
emission rate would impact our cost estimates for DSI. The proposed 
DSI performance evaluation requirements are discussed in greater 
detail in Section IX.A.3.
---------------------------------------------------------------------------

c. Option To Convert to Natural Gas
    Additionally, we recognize that Xcel Energy has announced its 
intent to convert Harrington Station to natural gas by January 1, 2025. 
We understand this has been formalized further in an Agreed Order with 
TCEQ,\336\ a PSD permit revision,\337\ and approval from the Texas 
Public Utility Commission (PUC).\338\ The BART Guidelines state in 
situations where a future operating parameter will differ from past or 
current practices, and if such future operating parameters will have a 
deciding effect in the BART determination, then the future operating 
parameters need to be made federally enforceable and permanent in order 
to consider them in the BART

[[Page 28972]]

determination.\339\ Thus, we are providing Xcel Energy the option to 
make this conversion to natural gas a permanent and federally 
enforceable commitment by incorporating it into this FIP. We are 
proposing that should Xcel Energy agree to these future operating 
parameters (i.e., operating as a natural gas source no later than 
January 1, 2025), then for purposes of this analysis we will consider 
Harrington to be a natural gas source. We noted earlier that for 
natural gas units, there are no practical add-on controls to consider 
for setting a more stringent SO2 BART emission limit. 
Therefore, under this option, we propose that BART for both Harrington 
units is the burning of pipeline natural gas, as defined at 40 CFR 
72.2.\340\ Because the conversion to natural gas no later than January 
1, 2025, would occur before the deadline to comply with a BART emission 
limit reflective of the installation of DSI or scrubbers, there is no 
need to evaluate whether an interim SO2 emission limit is 
necessary prior to the conversion to natural gas. Additionally, the 
visibility benefits of a conversion to natural gas would be greater 
than with the limits we are proposing based on either SDA or DSI. We 
are interested in comments on this option and specifically invite 
Harrington to provide comments as to their interest in this option.
---------------------------------------------------------------------------

    \336\ In the Matter of an Agreed Order Concerning Southwestern 
Public Service Company, dba cel Energy, Harrington Station Power 
Plant, TCEQ Docket No. 2020-0982-MIS (Adopted Oct. 21, 2020). A copy 
of the Order is available in the docket for this action.
    \337\ See Harrington's revised PSD permits (NSR1529 and NSR1388) 
located in the docket for this action.
    \338\ See the Texas PUC Order, Docket No. 52485-201, located in 
the docket for this action.
    \339\ 70 FR at 39167.
    \340\ ``Pipeline natural gas'' means a naturally occurring fluid 
mixture of hydrocarbons (e.g., methane, ethane, or propane) produced 
in geological formations beneath the Earth's surface that maintains 
a gaseous state at standard atmospheric temperature and pressure 
under ordinary conditions, and which is provided by a supplier 
through a pipeline. Pipeline natural gas contains 0.5 grains or less 
of total sulfur per 100 standard cubic feet. This is equivalent to 
an SO2 emission rate of 0.0006 lb/MMBtu. Additionally, 
pipeline natural gas must either be composed of at least 70 percent 
methane by volume or have a gross calorific value between 950 and 
1100 Btu per standard cubic foot. 40 CFR 72.2.
---------------------------------------------------------------------------

3. Welsh Unit 1
    In reviewing the modeling results for Welsh Unit 1, we conclude 
that the installation of a wet FGD or SDA will provide significant 
visibility benefits. As discussed in Section VII.A.1, we modeled Welsh 
Unit 1 with both CALPUFF and CAMx. The visibility benefits for Welsh 
are summarized in Tables 21 and 22.

                                    Table 21--CALPUFF-Predicted Wet FGD and SDA Visibility Benefits at Welsh Unit 1 *
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                        2016-18 baseline                                High control scenarios (WFGD/SDA)
                                       -----------------------------------------------------------------------------------------------------------------
                                                                           Cumulative      Visibility benefit at Class I area    Cumulative 2016-2018 #
             Class I area                                                 2016-18 # of       (dv) from baseline (WFGD/SDA)        of days with  impacts
                                         2016 dv    2017 dv    2018 dv      days with   ---------------------------------------      >=0.5 />=1.0 dv
                                                                          impacts >=0.5                                        -------------------------
                                                                           dv/>=1.0 dv     2016 dv      2017 dv      2018 dv        WFGD         SDA
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek...........................       0.70       0.94       0.96           77/13    0.28/0.27    0.37/0.35    0.53/0.53         18/1         18/1
Upper Buffalo.........................       0.36       0.49       0.60            16/0    0.25/0.24    0.33/0.32    0.42/0.40          0/0          1/0
Wichita Mountains.....................       0.25       0.35       0.24             3/0    0.17/0.16    0.28/0.26    0.16/0.16          0/0          1/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Benefit of control values are the decrease in deciview between baseline and the control scenario. Number of days is the number of days that are equal
  or greater than 0.5 and 1.0 dv after controls.

    The Welsh facility is within 450 km of three Class I areas (Caney 
Creek, Wichita Mountains, and Upper Buffalo), and therefore, within the 
range that the CALPUFF model has been used for assessing visibility 
impacts in BART analyses. CALPUFF results for Welsh indicate that 
installation of wet FGD or SDA resulted in a reduction of visibility 
impacts by 45 percent (0.39 dv average visibility benefit) and 44 
percent (0.38 dv average visibility benefit), respectively from the 
baseline (0.86 dv) at the highest impacted Class I area (Caney Creek), 
and an average reduction of visibility impacts across the three Class I 
areas of 57 percent and 55 percent respectively.
    Using three years (2016-2018) CALPUFF modeling results, we assessed 
the annual number of days when the facility impacts were greater than 
the 0.5 dv and 1.0 dv threshold at each of the Class I areas and then 
summed this value for all Class I areas to determine the total number 
of days in the 2016-2018 modeled period where visibility impacts were 
above 0.5 dv and 1.0 dv. These results indicate that the installation 
of wet FGD or SDA will eliminate 78 days (81 percent decrease) and 76 
days (79 percent decrease) respectively where visibility is greater 
than 0.5 dv and 12 days (92 percent decrease) where visibility is 
greater than 1.0 dv over the three modeled years for these three Class 
I areas. Comparing the CALPUFF modeled improvement with the 
installation of wet FGD versus SDA on Unit 1 indicates the visibility 
benefits are very similar (within 1.3-5.4 percent of each other).

                                       Table 22--CAMx-Predicted Wet FGD (SDA) Visibility Benefits at Welsh Unit 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      Welsh Unit 1                                           Baseline                                       Controlled
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Visibility
                                                          Impact (dv) on    Avg impact    Number of days    improvement   Avg visibility     Impacted
                      Class I area                          the maximum    (dv) for the    >=0.5/ >=1.0     (dv) on the     improvement   number of days
                                                            impact day      top 10 days         dv        maximum impact   (dv) for the   >=0.5/>=1.0 dv
                                                                                                               day *       top 10 days *
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.............................................            1.58            1.11            27/6     1.08 (1.02)     0.83 (0.79)             0/0
Wichita Mountains.......................................            1.54            0.71             6/2     1.34 (1.29)     0.60 (0.57)             0/0
Upper Buffalo...........................................            1.12            0.68             8/1     0.83 (0.79)     0.53 (0.50)             0/0
Cumulative (all Class I areas)..........................            6.67            3.97            46/9            5.27            3.21             0/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Secondary values in parentheses indicate estimated visibility benefits for SDA.


[[Page 28973]]

    Table 22 displays the visibility benefits predicted by CAMx with 
wet FGD control levels applied to Welsh Unit 1. We also present the 
estimated benefits of SDA (shown in parentheses). Since SDA is slightly 
less effective at reducing SO2 emissions than wet FGD, the 
comparative results between SDA and wet FGD are consistent with the 
difference in control efficacy, with a difference between wet FGD and 
SDA on the maximum impacted day of 0.06 dv at Caney Creek and 0.05 dv 
at Wichita Mountains and an average top 10 days difference of 0.03-0.04 
dv at each of the top three Class I areas.
    CAMx modeling results indicate that wet FGD on Welsh Unit 1 will 
eliminate all days impacted by the unit over 0.5 dv at all Class I 
areas, from 46 days in the baseline to zero with wet FGD, and SDA 
controls eliminate all but one day with impacts over 0.5 dv. At the 
most impacted Class I areas, wet FGD control results in visibility 
improvements of up to 1.35 dv on the maximum impacted day at Wichita 
Mountains and 1.29 dv with SDA control compared to the baseline maximum 
impact of 1.54 dv. Similarly, wet FGD control results in visibility 
improvements of up to 1.08 dv on the maximum impacted day at Caney 
Creek and 1.02 dv with SDA control compared to the baseline maximum 
impact of 1.58 dv. For the average of the top 10 most impacted days, 
wet FGD control results in 0.82 dv, while SDA results in 0.79 dv 
visibility improvements at Caney Creek (baseline impact 1.11 dv). For 
the average of the top 10 most impacted days, wet FGD control results 
in 0.60 dv, while SDA results in 0.57 dv visibility improvements at 
Wichita Mountains (baseline impact 0.71 dv).
    Overall, there is a cumulative improvement to the average of the 
top 10 days of approximately 3.2 dv with wet FGD across all impacted 
Class I areas and approximately 5.3 dv cumulative improvement on the 
maximum impacted day. The 2023 BART Modeling TSD shows that DSI control 
achieved approximately 39 percent average improvement in visibility, 
while wet FGD averaged 79 percent overall visibility improvement. At 
Caney Creek, DSI results in improvement on the maximum impacted day of 
0.48 dv compared to 1.08 dv for wet FGD and 1.02 dv for SDA. At Wichita 
Mountains, DSI results in improvement on the maximum impacted day of 
0.69 dv compared to 1.35 dv for wet FGD and 1.29 dv for SDA. At Caney 
Creek, the baseline had 27 days over 0.5 dv and 6 days over 1.0 dv, but 
with DSI these number of days were reduced to 8 and 1, respectively, 
and further reduced with wet FGD to zero days over 0.5 dv and zero days 
over 1.0 dv. At Wichita Mountains, the baseline had 6 days over 0.5 dv 
and 2 days over 1.0 dv, but with DSI these number of days were reduced 
to 2 and zero, respectively, and further reduced with wet FGD to zero 
days over 0.5 dv and zero days over 1.0 dv.
    We conclude that both SDA and wet FGD are cost-effective at $4,370/
ton and $4,497/ton (respectively) and remain within a range that we 
have previously found to be acceptable. Wet FGD is less cost-effective 
than SDA and as discussed in the preceding paragraphs, it would have 
only a slight additional visibility benefit over SDA. As discussed 
earlier, in weighing the factors between SDA and wet FGD, we determined 
the additional visibility benefits did not outweigh the additional 
cost, water requirements, and wastewater treatment requirements 
associated with wet FGD. DSI at 50 percent control is more cost-
effective but results in much less visibility benefit. We consider the 
significant visibility benefits that will result from the installation 
of SDA at Welsh Unit 1 to justify the cost, and therefore, we propose 
that SO2 BART for Welsh Unit 1 should be based on the 
installation of SDA at an emission limit of 0.06 lb/MMBtu based on a 30 
BOD.
    We recognize that at $4,370/ton, the cost of SDA for Welsh Unit 1 
is in the upper range of cost-effectiveness of controls found to be 
acceptable in other BART actions nationwide. Nevertheless, we consider 
it to be cost-effective and provides for significant visibility 
benefit. Since BART is defined as an emission limitation,\341\ sources 
have the flexibility to decide what controls to install and implement 
so long as they comply with the BART emission limitations and 
associated requirements that are promulgated. As discussed in Section 
VIII.A, based on available DSI cost information, some EGUs with an 
installed baghouse may be able to achieve 90+ percent SO2 
control efficiency using DSI with sodium-based sorbents. Therefore, 
Welsh Unit 1 could potentially comply with our proposed SO2 
emission limit of 0.06 lb/MMBtu with DSI operated at a high 
SO2 control level, but this would need to be confirmed with 
site-specific performance testing. If the unit is capable of meeting 
this SO2 emission limit with DSI, this control technology is 
likely to be even more cost-effective than SDA.
---------------------------------------------------------------------------

    \341\ See 40 CFR part 51, Appendix Y--Guidelines For BART 
Determinations Under the Regional Haze Rule, section IV.A.
---------------------------------------------------------------------------

    As discussed in Sections VII.B.2.a and VII.B.3.a, we also invite 
comments on the range and maximum control efficiency that can be 
achieved with DSI at Welsh Unit 1 and estimates of the range of 
associated costs. We are especially interested in any site-specific DSI 
testing for Welsh Unit 1 to determine the range and maximum control 
efficiency that can be achieved with DSI at this unit. Any data to 
support the control efficiency range, maximum control efficiency, and 
cost of DSI for the unit should be submitted along with those comments. 
We will further consider site-specific information provided to us 
during the public comment period in making our final decision on 
SO2 BART and potentially re-evaluate DSI for this particular 
unit.
4. W. A. Parish Units WAP4, WAP5 & WAP6
    W. A. Parish Unit WAP4 is the only gas-fired unit we determined to 
be subject to BART. Gas-fired EGUs have inherently low SO2 
emissions and there are no known SO2 controls that can be 
evaluated. While we must assign SO2 BART determinations to 
the gas-fired unit, there are no practical add-on controls to consider 
for setting a more stringent BART emission limit. As explained earlier 
in Section VII.B.1.c, the BART Guidelines state that if the most 
stringent controls are made federally enforceable for BART, then the 
otherwise required analyses leading up to the BART determination can be 
skipped. As there are no appropriate add-on controls and the status quo 
reflects the most stringent control level, we are proposing that 
SO2 BART for W. A. Parish Unit WAP4 is to limit fuel to 
pipeline natural gas, as defined at 40 CFR 72.2.\342\
---------------------------------------------------------------------------

    \342\ As provided for in 40 CFR 72.2, pipeline natural gas 
contains 0.5 grains or less of total sulfur per 100 standard cubic 
feet. This is equivalent to an SO2 emission rate of 
0.0006 lb/MMBtu.
---------------------------------------------------------------------------

    In evaluating W. A. Parish Units WAP5 and WAP6, we conclude that 
the installation of wet FGD or SDA will result in significant 
visibility benefits. We summarize some of these visibility benefits in 
Table 23.

[[Page 28974]]



                                      Table 23--CAMx Predicted Visibility Benefit of Wet FGD (SDA) at W. A. Parish
--------------------------------------------------------------------------------------------------------------------------------------------------------
                      W. A. Parish                                           Baseline                                       Controlled
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Visibility
                                                          Impact (dv) on    Avg impact                      improvement   Avg visibility     Impacted
                      Class I area                          the maximum    (dv) for the   Number of days    (dv) on the     improvement   number of days
                                                            impact day      top 10 days   >=0.5/>=1.0 dv  maximum impact   (dv) for the   >=0.5/>=1.0 dv
                                                                                                               day *       top 10 days *
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    W. A. Parish WAP5
--------------------------------------------------------------------------------------------------------------------------------------------------------
Wichita Mountains.......................................            2.01            0.83            12/1     1.86 (1.80)     0.77 (0.75)             0/0
Caney Creek.............................................            1.57            1.09            36/6     1.38 (1.36)     0.97 (0.94)             0/0
Breton..................................................            1.08            0.52             4/1     0.94 (0.92)     0.47 (0.45)             0/0
Cumulative (all Class I areas)..........................            8.82            5.18           86/10            7.93            4.71             0/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    W. A. Parish WAP6
--------------------------------------------------------------------------------------------------------------------------------------------------------
Wichita Mountains.......................................            2.24            0.93            15/1     2.07 (2.01)     0.86 (0.84)             0/0
Caney Creek.............................................            1.75            1.22            47/9     1.52 (1.50)     1.08 (1.05)             0/0
Breton..................................................            1.21            0.58             4/2     1.05 (1.02)     0.52 (0.50)             0/0
Cumulative (all Class I areas)..........................            9.86            5.80          119/15            8.81            5.27             0/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               W. A. Parish WAP5 and WAP6
--------------------------------------------------------------------------------------------------------------------------------------------------------
Wichita Mountains.......................................            3.97            1.71           35/12            3.61            1.56             0/0
Caney Creek.............................................            3.13            2.22           86/38            2.59            1.91             1/0
Breton..................................................            2.21            1.08            12/4            1.89            0.96             0/0
Cumulative (all Class I areas)..........................           17.96           10.72          269/91           15.66            9.56             1/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Secondary values in parentheses indicate estimated visibility benefits for SDA

    Table 23 displays the visibility benefits predicted by CAMx 
modeling with wet FGD control levels applied to Units WAP5 and WAP6. We 
also present the estimated benefits of SDA (shown in parentheses) for 
each unit individually. Since SDA is slightly less effective at 
reducing SO2 emissions than wet FGD, the comparative results 
between SDA and wet FGD are consistent with the difference in control 
efficacy, with a maximum difference between wet FGD and SDA on the 
maximum impacted day of 0.06 dv at Wichita Mountains for each unit 
(0.02-0.03 dv for Caney Creek and Breton) and an average top 10 days 
difference of 0.03 dv at Caney Creek (0.02 dv at Wichita Mountains and 
Breton) for each unit, with SDA always showing marginally less 
improvement from the baseline. These values indicate that SDA per unit 
results in approximately 2-4 percent less benefit than wet FGD on a per 
unit basis.
    CAMx modeling results indicate that wet FGD installed on each of 
Units WAP5 and WAP6 will eliminate all days impacted by each unit over 
0.5 dv at all Class I areas, and our estimates for SDA control also 
show no days over 0.5 dv at any Class I areas. When considering the 
combined impacts from all three units taken together with wet FGD on 
WAP5 and WAP6, the CAMx results predict one day to exceed the 0.5 dv 
threshold (at Caney Creek).\343\ We would expect similar results in 
looking at SDA for Units WAP5 and WAP6 as the visibility differences 
for SDA and wet FGD are small. Overall, there is a cumulative reduction 
from 269 days over 0.5 dv in the baseline to a total of just one day 
over the threshold with wet FGD across all impacted Class I areas.
---------------------------------------------------------------------------

    \343\ W. A. Parish Unit WAP4 is a gas-fired unit for which we 
are locking in the requirement to burn pipeline quality natural gas.
---------------------------------------------------------------------------

    Installation of wet FGD on both units results in 3.61 dv 
improvement (91 percent reduction of 3.97 dv baseline) on the maximum 
impact day at Wichita Mountains and a 1.56 dv improvement (91 percent 
reduction of 1.71 dv baseline) on the top 10 average days at Wichita 
Mountains. Installation of wet FGD on both units results in 2.59 dv 
improvement (83 percent reduction of 3.13 dv baseline) on the maximum 
impact day at Caney Creek and a 1.91 dv improvement (86 percent 
reduction of 2.22 dv baseline) on the top 10 average days at Caney 
Creek. SDA visibility benefits on a unit basis result in 95 percent or 
more of the visibility benefit of wet FGD on a unit basis. At the most 
impacted Class I areas, either wet FGD or SDA on each unit will each 
result in visibility improvements of more than 1.8 dv per unit at 
Wichita Mountains, and the top 10 days average visibility improvement 
for the individual units are more than 0.9 dv at Caney Creek for each 
unit with wet FGD or SDA. Across all impacted Class I areas, the top 10 
days average improvement from all three units combined is predicted to 
be approximately 9.5 dv, or approximately 89 percent reduction in 
visibility impairment due to wet FGD controls or SDA. As provided in 
Section VII.B.4, DSI operated at 50 percent control (``low control 
scenario'') results in 43 percent visibility improvement for the 
overall three units, whereas wet FGD visibility benefits result in 87 
percent improvement at the most impacted Class I areas for the three 
units and the cumulative 15 Class I areas included in the modeling.
    We conclude that both SDA and wet FGD are cost-effective at $3,044/
ton and $3,074/ton (respectively) for Unit WAP5 and $2,651/ton and 
$2,717/ton (respectively) for Unit WAP6 and remain well within a range 
that we have previously found to be acceptable. While DSI at 50 percent 
control is more cost-effective at $2,262/ton for Unit WAP5 and $2,244/
ton for Unit WAP6, it results in less visibility benefit. The 
incremental cost-effectiveness of SDA (going from DSI at 50 percent 
control efficiency to SDA) is $4,006/ton for Unit WAP5 and $3,155/ton 
for Unit WAP6, which we consider to be reasonable. Thus, we conclude 
that the resulting visibility benefit offered by scrubbers outweighs 
the possible advantage DSI at 50 percent control may hold in cost-
effectiveness.

[[Page 28975]]

    Wet FGD is slightly less cost-effective than SDA and we estimate 
based on scaling of our CAMx modeling results that it would have only a 
slight additional visibility benefit over SDA. As discussed earlier, in 
weighing the factors between SDA and wet FGD, we determined the 
additional visibility benefits did not outweigh the additional cost, 
water requirements and wastewater treatment requirements associated 
with wet FGD. We consider the cost of SDA at the two W. A. Parish units 
to be justified by the significant visibility benefits that will 
result. We therefore propose that SO2 BART for W. A. Parish 
Units WAP5 and WAP6 should be based on the installation of SDA at an 
emission limit of 0.06 lb/MMBtu based on a 30 BOD.

B. SO2 BART for Coal-Fired Units With Existing Scrubbers

1. Martin Lake Units 1, 2, and 3
    The BART Guidelines state that underperforming scrubber systems 
should be evaluated for upgrades.\344\ Other than upgrading the 
existing scrubbers, all of which are wet FGDs, there are no competing 
control technologies that could be considered for these units at Martin 
Lake. These units were modeled with both CALPUFF and CAMx. We summarize 
some of these visibility benefits from upgrading Martin Lake's existing 
scrubbers in Tables 24 and 25.
---------------------------------------------------------------------------

    \344\ 70 FR 39171 (July 6, 2005).

                                     Table 24--CALPUFF-Predicted Scrubber Upgrade Visibility Benefits at Martin Lake
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        2016-18 Baseline impacts                          Scrubber upgrades
                                                             -------------------------------------------------------------------------------------------
                                                                                                Cumulative   Visibility benefit at class I    Cumulative
                                                                                               2016-2018 #      area (dv) from baseline      2016-2018 #
                        Class I area                                                             of days   ---------------------------------   of days
                                                               2016 dv    2017 dv    2018 dv       with                                          with
                                                                                                 impacts                                       impacts
                                                                                                >=0.5 dv/    2016 dv    2017 dv    2018 dv    >=0.5 dv/
                                                                                                 >=1.0 dv                                      >=1.0 dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.................................................       3.28       3.60       3.35      338/215       2.12       2.36       2.16       133/44
Upper Buffalo...............................................       2.12       2.54       2.27      212/115       1.58       1.90       1.72         33/8
Wichita Mountains...........................................       1.45       1.07       1.15        79/36       1.21       0.89       0.91          5/2
Cumulative..................................................       6.84       7.21       6.78      629/366       4.90       5.15       4.79       171/54
--------------------------------------------------------------------------------------------------------------------------------------------------------

    In evaluating Martin Lake, there are three Class I areas (Caney 
Creek, Upper Buffalo, and Wichita Mountains) within the typical 450 km 
range that CALPUFF has been used for assessing visibility impacts. The 
modeled scrubber upgrades result in large visibility improvements of 
over 2.2 dv at Caney Creek and 1.7 dv at Upper Buffalo. Visibility 
benefits at Wichita Mountains also exceed 1.0 dv. CALPUFF results for 
Martin Lake indicate that upgrading the scrubbers resulted in a 
reduction of visibility impacts by 65 percent from the baseline at the 
highest impacted Class I area (Caney Creek), and an average reduction 
of visibility impacts at the three Class I areas of 71 percent. Using 
the three years (2016-2018) of CALPUFF modeling results, we assessed 
the annual average number of days, averaged across the three years, 
when the facility impacts were greater than 0.5 dv at each Class I 
area; we also looked at the cumulative number of days summed across the 
three years at all the Class I areas (three in this case). The 
reduction in the number of days (annual average) was calculated using 
the cumulative value of the number of days (three-year total) over the 
0.5 dv threshold across the three Class I areas for the baseline 
scenario minus the cumulative number of days (three-year total) over 
the threshold for the control scenario. For the three Class I areas, 
2016-2018 CALPUFF modeling results indicate that upgraded scrubbers on 
the three units will eliminate 152 days annually (3-year average), or 
458 days cumulatively across the 3 years, when the facility has impacts 
greater than 0.5 dv in the baseline. The same analysis for the 1.0 dv 
threshold, as reported in Table 24, has 104 days (312 days total) 
reduced on annual average. CALPUFF modeling results indicate large 
improvements at the individual Class I areas and the cumulative 
improvement of almost 5 dv; these scrubber upgrades markedly improve 
the overall cumulative predicted visibility by approximately 71 percent 
from the baseline.
    Table 25 includes each affected Martin Lake unit and the combined 
facility along with the resulting CAMx-modeled visibility benefits from 
upgrading Martin Lake's existing scrubbers.

                                    Table 25--CAMx Predicted Visibility Benefit of Scrubber Upgrades for Martin Lake
--------------------------------------------------------------------------------------------------------------------------------------------------------
                       Martin Lake                                           Baseline                                       Controlled
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                            Visibility
                                                          Impact (dv) on    Avg impact                      improvement   Avg visibility     Impacted
                      Class I area                          the maximum    (dv) for the   Number of days    (dv) on the     improvement   number of days
                                                            impact day      top 10 days   >=0.5/>=1.0 dv      maximum      (dv) for the   >=0.5/>=1.0 dv
                                                                                                            impact day      top 10 days
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Martin Lake Unit 1
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.............................................            2.60            1.98           74/22            2.00            1.56             2/0
Wichita Mountains.......................................            2.08            1.01            17/3            1.76            0.85             0/0
Upper Buffalo...........................................            1.93            1.39            48/8            1.66            1.18             0/0
Cumulative (all Class I areas)..........................           12.39            7.90          197/38           10.36            6.64             2/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Martin Lake Unit 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.............................................            2.54            1.94           72/22            1.94            1.52             2/0

[[Page 28976]]

 
Wichita Mountains.......................................            2.03            0.99            17/3            1.71            0.82             0/0
Upper Buffalo...........................................            1.89            1.36            44/8            1.62            1.14             0/0
Cumulative (all Class I areas)..........................           12.09            7.71          188/38           10.06            6.44             2/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Martin Lake Unit 3
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.............................................            2.81            2.14           85/24            2.23            1.73             2/0
Wichita Mountains.......................................            2.24            1.09            18/3            1.93            0.93             0/0
Upper Buffalo...........................................            2.09            1.51           51/12            1.84            1.30             0/0
Cumulative (all Class I areas)..........................           13.44            8.59          223/48           11.45            7.34             2/0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              Martin Lake Units 1, 2, and 3
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.............................................            6.69            5.27         150/101            5.00            4.07            32/7
Wichita Mountains.......................................            5.49            2.83           51/27            4.57            2.35             3/0
Upper Buffalo...........................................            5.16            3.83          111/70            4.39            3.21             7/0
Cumulative (all Class I areas)..........................           33.79           22.16         521/301           27.91           18.44            47/7
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Table 25 shows that the Martin Lake units individually cause or 
contribute to visibility impairment at Wichita Mountains, Caney Creek, 
and Upper Buffalo on a large number of days. CAMx predicts baseline 
impacts for these combined three units to be more than the 0.5 dv 
visibility threshold 150 days of the year at Caney Creek, 111 days of 
the year at Upper Buffalo, 51 days of the year at Wichita Mountains, 
and in total for 209 days per year for the other 12 Class I areas 
modeled. The average visibility impact across the top 10 days for the 
combined units is more than 5.2 dv at Caney Creek and more than 3.8 dv 
at Upper Buffalo. CAMx modeling results indicate that upgrades to 
Martin Lake's wet FGD scrubbers to 95 percent control efficiency 
installed on each of the units will eliminate all but two days impacted 
by each individual unit over 0.5 dv at all Class I areas. When 
considering the combined impacts from all three units, the modeling 
results show an overall (across all impacted Class I areas) reduction 
from 521 days over 0.5 dv in the baseline to a total of 47 days over 
the threshold after the scrubber upgrades are installed, for an overall 
reduction of more than 90 percent in the number of days over the 
threshold. With the modeled scrubber upgrades, the number of days 
impacted over 1.0 dv are reduced from 101 days to 7 days at Caney 
Creek. Days over the 1.0 dv threshold at all other Class I areas are 
eliminated, decreasing from 200 in the baseline to zero with the 
scrubber upgrades. At the most impacted Class I Areas, the scrubber 
upgrades on each unit will each result in visibility improvements of 
approximately 2.0 dv on the most impacted days at Caney Creek, and the 
top 10 days average visibility improvement for the individual units is 
more than 1.5 dv at Caney Creek. Across all 15 Class I areas, the top 
10 days average impact from all three units combined dropped from 
baseline of 22.2 dv to 3.7 dv after control upgrades, for an overall 
cumulative improvement of approximately 83 percent reduction due to 
improved scrubber efficiency. Similarly, across all 15 Class I areas, 
the maximum daily impact from scrubber upgrades results in a visibility 
improvement of 27.91 dv compared to the 33.79 dv baseline total, which 
is a reduction of 83 percent.
    As we state elsewhere in this proposal, we estimate scrubber 
upgrades at the Martin Lake units to be very cost-effective and less 
than $1,200/ton. We conclude that these scrubber upgrades are very 
cost-effective and result in very significant visibility benefits, 
significantly reducing the impacts from these units and reducing the 
number of days that Class I areas are impacted over 1.0 dv and 0.5 dv. 
We propose SO2 BART for each Martin Lake unit should be to 
upgrade the wet FGD scrubbers to a control efficiency of 95 percent, 
with an emission limit of 0.08 lb/MMBtu on a 30 BOD basis. This cost 
analysis, the reasons set forth in previous sections regarding the 
overall SO2 emissions impact of these units, and the modeled 
benefits, support this proposed BART determination.
2. Fayette Units 1 and 2
    Fayette Units 1 and 2 are currently equipped with high performing 
wet FGDs. Both units have demonstrated the ability to maintain a 
SO2 30 Boiler Operating Day (BOD) average below 0.04 lb/
MMBtu for years at a time.\345\ As discussed in Section VII.B.2.a, 
retrofit wet FGDs should be evaluated at 98 percent control or no less 
than 0.04 lb/MMBtu. Table 26 shows the visibility impacts for the 
baseline emissions, the current permitted emission limit (which is 
greater than the baseline emission rate), and an emission limit of 0.04 
lb/MMBtu (which is representative of controlled emissions with wet 
FGD).
---------------------------------------------------------------------------

    \345\ See our 2023 BART FIP TSD for additional information and 
graphs of this data.

[[Page 28977]]



          Table 26--CAMx-Predicted Visibility Impacts of Baseline, Permit Limits, and Wet FGD Limit of 0.04 lb/MMBtu for Fayette Units 1 and 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                  Fayette Units 1 and 2                        2016 Baseline impacts      Permitted limit (0.2 lb/MMBtu)      Wet FGD (0.04 lb/MMBtu)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                          Number of days
                                                             Impact at    Number of days     Impact at    >0.5 dv/number     Impact at    Number of days
                      Class I area                         Class I area   >=0.5 dv/>=1.0   Class I area    of days >1.0    Class I area   >=0.5 dv/>=1.0
                                                               (dv)             dv             (dv)             dv             (dv)             dv
--------------------------------------------------------------------------------------------------------------------------------------------------------
Caney Creek.............................................            0.52             1/0            1.04            11/1            0.52             1/0
Wichita Mountains.......................................            0.34             0/0            1.02             3/1            0.31             0/0
Upper Buffalo...........................................            0.33             0/0            0.73             5/0            0.34             0/0
Cumulative (all 15 Class I areas).......................            2.24             1/0            5.31            21/2            2.12             1/0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    Fayette modeling shows increased visibility impacts when modeling 
the existing permit limit (Title V permit level of 0.2 lb/MMBtu to meet 
NSPS UUUUU). At this higher permitted rate, the Fayette source would 
have visibility impacts greater than 1 dv at Caney Creek and Wichita 
Mountains. However, Fayette routinely emits at rates less than this 
permit limit. We also modeled wet FGD at 0.04 lb/MMBtu, which these 
units already consistently meet on a 30-day BOD basis. The results are 
very similar to baseline modeling results reflecting the maximum 24-hr 
emissions from 2016-2020, but did result in a slight overall benefit 
from baseline conditions. Therefore, we propose that additional 
scrubber upgrades for Fayette are not necessary and that Fayette Units 
1 and 2 maintain a 30 BOD rolling average SO2 emission rate 
of 0.04 lb/MMBtu. We believe that based on their demonstrated ability 
to maintain an emission rate below this value on a 30 BOD basis, these 
units can consistently achieve this emission level.

C. PM BART

    As discussed in Section VI.B, we propose to disapprove the portion 
of the Texas Regional Haze SIP that sought to address the BART 
requirement for EGUs for PM. We present our analysis of the BART 
factors and the potential costs and visibility benefits of PM controls 
in Section VII.B.5. All the coal-fired units are either currently 
fitted with a baghouse, an ESP and a polishing baghouse, or an ESP. As 
part of our BART determination, we propose to conclude that the cost of 
retrofitting the subject units (Harrington Unit 061B, Martin Lake 
Units, and Fayette Units) with a baghouse would be extremely high 
compared to the visibility benefit for any of the units currently 
fitted with an ESP. The BART Guidelines state it is permissible to rely 
on MACT standards for purposes of BART unless there are new 
technologies subsequent to the MACT standards which would lead to cost-
effective increases in the level of control. Because the costs of 
installing a baghouse would be extremely high, we propose that PM BART 
for the coal-fired units is an emission limit of 0.030 lb/MMBtu along 
with work practice standards. This limit is consistent with the MATS 
Rule, which establishes an emission standard of 0.030 lb/MMBtu 
filterable PM (as a surrogate for toxic non-mercury metals) as 
representing MACT for coal-fired EGUs.
    For the gas-fired BART unit, W. A. Parish Unit WAP4, there are no 
appropriate add-on controls and the status quo reflects the most 
stringent controls. We are proposing to make the requirement to burn 
pipeline natural gas federally enforceable. We are proposing that PM 
BART for W. A. Parish Unit WAP4 is to limit fuel to pipeline natural 
gas, as defined at 40 CFR 72.2.

IX. Proposed Action

A. Regional Haze

    We are proposing to withdraw the Texas SO2 Trading 
Program set forth in 40 CFR part 97 Subpart FFFFF, which constitutes 
the FIP provisions the EPA previously promulgated to address 
SO2 BART obligations for EGUs in Texas. In its place, we are 
proposing to promulgate a FIP as described in this notice and 
summarized in this section to address the SO2 BART 
requirements for those BART-eligible sources participating in the Texas 
SO2 Trading Program. Additionally, as described in Section 
VI, we are proposing that our prior approval of the portion of the 
Texas Regional Haze SIP related to PM BART for EGUs was in error and 
are correcting that through disapproving that portion of the SIP and 
promulgating source specific BART requirements to address the 
deficiency. Our proposed FIP includes SO2 and PM BART 
emission limits for 12 EGUs located at 6 different facilities.
1. SO2 BART
    We propose that SO2 BART for the subject-to-BART units 
is the following SO2 emission limits to be met on a 30 BOD 
period:

               Table 27--Proposed SO2 BART Emission Limits
------------------------------------------------------------------------
                                                           Proposed SO2
                          Unit                            emission limit
                                                            (lb/MMBtu)
------------------------------------------------------------------------
                    Scrubber Upgrades
Martin Lake Unit 1......................................            0.08
Martin Lake Unit 2......................................            0.08
Martin Lake Unit 3......................................            0.08
                 Emission Limit as BART
Fayette Unit 1..........................................            0.04
Fayette Unit 2..........................................            0.04
W A. Parish Unit WAP4 *.................................  ..............
                   Scrubber Retrofits
Harrington 061B.........................................            0.06
Harrington 062B.........................................            0.06
Coleto Creek Unit 1.....................................            0.06
W. A. Parish WAP5.......................................            0.06
W. A. Parish WAP6.......................................            0.06
Welsh Unit 1............................................            0.06
                           DSI
Harrington 061B.........................................    0.27 (in the
                                                            alternative)
------------------------------------------------------------------------
* For Unit WAP4, BART is to limit fuel use to pipeline natural gas, as
  defined at 40 CFR 72.2. As provided for in 40 CFR 72.2, pipeline
  natural gas contains 0.5 grains or less of total sulfur per 100
  standard cubic feet. This is equivalent to an SO2 emission rate of
  0.0006 lb/MMBtu.

    We propose that the following sources comply with these limits 
within five years of the effective date of our final rule: Coleto Creek 
Unit 1; Harrington Units 061B (for a limit consistent with scrubber 
retrofit) and 062B; W. A. Parish Units WAP5 and WAP6; and Welsh Unit 1. 
This is the maximum amount of time allowed under the Regional Haze Rule 
for BART compliance. We based our cost analysis on the installation of 
wet FGD and SDA scrubbers for these units, and in past actions we have 
typically required that scrubber retrofits under BART be operational 
within five years.\346\
---------------------------------------------------------------------------

    \346\ See 76 FR 81729, 81758 (December 28, 2011) and 81 FR 
66332, 66416 (September 27, 2016), where we promulgated regional 
haze FIPs for Oklahoma and Arkansas, respectively. These FIPs 
required BART SO2 emission limits on coal-fired EGUs 
based on new scrubber retrofits with a compliance date of no later 
than five years from the effective date of the final rule.

---------------------------------------------------------------------------

[[Page 28978]]

    We are proposing an alternative BART limit based on DSI at 50 
percent for Harrington Unit 061B with a proposed compliance date within 
two years of the effective date of our final rule. We believe that two 
years is appropriate as the installation of DSI systems is less complex 
and time consuming than the construction of a scrubber. We also propose 
to require a DSI performance evaluation, as more fully described in 
Section IX.A.3, within one year of the effective date of our final 
rule. In Section VIII.A.2 we also provide an option for Harrington to 
agree as part of this FIP to convert to natural gas by no later than 
January 1, 2025.
    For Martin Lake Units 1, 2, and 3, we propose that compliance with 
these limits be within three years of the effective date of our final 
rule. We believe that three years is appropriate for these units, as we 
based our cost analysis on upgrading the existing wet FGD scrubbers of 
these units, which we believe to be less complex and time consuming 
than the construction of a new scrubber.
    For Fayette Units 1 and 2, we propose that compliance with these 
limits be within one year. We believe that one year is appropriate for 
these units because the Fayette units have already demonstrated their 
ability to meet these emission limits.
2. Potential Process for Alternative Scrubber Upgrade Emission Limits
    In our 2023 BART FIP TSD, we discuss how we calculated the 
SO2 removal efficiency of the units we analyzed for scrubber 
upgrades. Since we do not have CEMS data for the inlet of the scrubbers 
(we only have CEMS data for the outlet of the scrubbers) and we do not 
have recent site-specific testing from the facility to more accurately 
determine the current control efficiency of the scrubbers, we estimated 
the current removal efficiency of each scrubber using formulas. These 
formulas utilize the reported sulfur content and tonnages of the fuels 
burned at each unit to calculate the theoretical uncontrolled 
SO2 emissions. The calculated theoretical uncontrolled 
SO2 emissions and CEMS data for the scrubber outlet 
SO2 emissions are then used to calculate scrubber 
efficiency. Given a lack of updated source-specific information 
resulting in an estimated control efficiency based on available fuel 
usage and SO2 emissions data, we cannot assure accuracy in 
our quantification of scrubber efficiency. However, despite the 
potential for inaccurate information regarding scrubber efficiency, 
based on the results of our scrubber upgrade cost analysis, we do not 
believe that any such error in calculating the true tons of 
SO2 removed affects our proposed determination that scrubber 
upgrades are cost-effective. Even if we were to make reasonable 
adjustments in the tons removed to account for any potential error in 
our scrubber efficiency calculation, we would still propose to upgrade 
these SO2 scrubbers. We believe we have demonstrated that 
upgrading an underperforming SO2 scrubber is one of the most 
cost-effective pollution control upgrades a coal-fired power plant can 
implement to improve the visibility at Class I areas. However, our 
proposed FIP does specify an SO2 emission limit that is 
based on 95 percent removal. This is below the upper end of what an 
upgraded wet SO2 scrubber can achieve, which is 98-99 
percent, as we have noted in our 2023 BART FIP TSD. We believe that a 
95 percent control assumption provides an adequate margin of error for 
the units for which we have proposed scrubber upgrades, such that they 
should be able to comfortably attain the emission limits we have 
proposed. However, for the owner of any unit that disagrees with us on 
this point, we propose the following:

    (1) The affected unit should comment why it believes it cannot 
attain the SO2 emission limit we have proposed, based on 
a scrubber upgrade that includes the kinds of improvements (e.g., 
elimination of bypass, wet stack conversion, installation of trays 
or rings, upgraded spray headers, upgraded ID fans, using all 
recycle pumps, etc.) typically included in a scrubber upgrade.
    (2) After considering those comments, and responding to all 
relevant comments in a final rulemaking action, should we still 
require a scrubber upgrade in our final FIP we will provide the 
company the following option in the FIP to seek a revised emission 
limit after taking the following steps:
    (a) Install a CEMS at the inlet to the scrubber.
    (b) Pre-approval of a scrubber upgrade plan conducted by a third 
party engineering firm that considers the kinds of improvements 
(e.g., elimination of bypass, wet stack conversion, installation of 
trays or rings, upgraded spray headers, upgraded ID fans, using all 
recycle pumps, etc.) typically performed during a scrubber upgrade. 
The goal of this plan will be to maximize the unit's overall 
SO2 removal efficiency.
    (c) Installation of the scrubber upgrades.
    (d) Pre-approval of a performance testing plan, followed by the 
performance testing itself.
    (e) A pre-approved schedule for 2.a through 2.d.
    (f) Should we determine that a revision of the SO2 
emission limit is appropriate, we will have to propose a 
modification to the BART FIP after it has been promulgated. It 
should be noted that any proposal to modify the SO2 
emission limit will be based largely on the performance testing and 
may result in a proposed increase or decrease of that value.
3. DSI Performance Evaluation for Harrington Unit 061B
    We are proposing that SO2 BART for Harrington Unit 061B 
should be based on the installation of SDA at an emission limit of 0.06 
lb/MMBtu based on a 30 BOD and in the alternative, we are proposing 
that SO2 BART should be based on DSI at 50 percent control 
efficiency at an emission limit of 0.27 lb/MMBtu based on a 30 BOD with 
the requirement to conduct a DSI performance evaluation and submit to 
the EPA no later than one (1) year from the effective date of our final 
rule. We believe Unit 061B is likely capable of achieving an 
SO2 emission limit of 0.27 lb/MMBtu with DSI, but are not 
certain whether the unit could achieve a lower emission limit on a 30 
BOD or what the potential impacts to PM emissions could be at higher 
injections rates necessary for higher control efficiencies using the 
existing ESP. The purpose of the DSI performance evaluation is to 
determine the lowest SO2 emission rate Unit 061B would be 
able to sustainably achieve on a 30 BOD with DSI as well as the 
potential control efficiencies achievable with upgraded particulate 
removal and to determine how compliance with such an emission rate 
would impact our cost estimates for DSI. Therefore, as part of the 
performance evaluation, we are also proposing to require an estimate of 
the costs of DSI for each of the three control scenarios specified in 
1.a through 1.c.
    Should we require an SO2 emission limit based on DSI for 
Harrington Unit 061B in our final FIP, we are proposing the following 
requirements for a DSI performance evaluation:
    (1) The performance evaluation must be conducted by a third-party 
engineering firm and must determine the potential lowest sustainable 
SO2 emission rate on a 30 BOD with DSI for each of the 
following control scenarios:
    (a) DSI with the existing ESP for particulate removal;
    (b) DSI with a new ESP installation for particulate removal;
    (c) DSI with a new fabric filter installation for particulate 
removal.
    (2) The performance evaluation must include an estimate of the 
costs for each of the three control scenarios specified in 1.a through 
1.c. The cost estimates must include a detailed breakdown of the 
capital costs and annual operation and maintenance costs for each 
control scenario as well as an estimate of the annual SO2 
emissions reductions under each control scenario. The cost estimates 
should adhere to the costing methodologies recommended in the

[[Page 28979]]

EPA Air Pollution Control Cost Manual.\347\
---------------------------------------------------------------------------

    \347\ EPA Air Pollution Control Cost Manual, Seventh Edition, 
April 2021 available at https://www.epa.gov/economic-and-cost-analysis-air-pollution-regulations/cost-reports-and-guidance-air-pollution#cost%20manual.
---------------------------------------------------------------------------

    (3) The facility must submit a detailed report of the performance 
evaluation and all supporting documentation to the EPA no later than 
one year from the effective date of our final BART FIP.
    Based on the DSI performance evaluation, we will determine whether 
a revision of the SO2 emission limit for Harrington Unit 
061B is appropriate. Should we determine that a revision of the 
SO2 emission limit is appropriate, we will propose a 
modification to the BART FIP after it has been promulgated.
4. PM BART
    We propose that PM BART limits for the coal-fired units, Martin 
Lake Units 1, 2, and 3; Coleto Creek Unit 1; W. A. Parish Units WAP5 
and WAP6; Welsh Unit 1; Harrington Units 061B and 062B; and Fayette 
Units 1 and 2 are 0.030 lb/MMBtu and work practice standards, shown in 
Table 28.

    Table 28--PM BART Emissions Standards and Work Practice Standards
------------------------------------------------------------------------
                 Unit type                        PM BART proposal
------------------------------------------------------------------------
Coal-Fired BART Units.....................  0.030 lb/MMBtu filterable PM
                                            Table 3 to Subpart UUUUU
Gas-Fired Only BART Units.................  Pipeline quality natural gas
------------------------------------------------------------------------

    We propose that compliance with these emissions standards and work 
practice standards be the effective date of our final rule, as the 
affected facilities should already be meeting them.
    We propose that PM BART for W. A. Parish WAP4 is to limit fuel to 
pipeline natural gas, as defined at 40 CFR 72.2.

B. CSAPR Better-Than-BART

    We propose that, if this proposal to implement source-specific BART 
requirements at certain EGUs in Texas is finalized, the EPA's 
analytical basis for our 2017 CSAPR Better-than-BART determination will 
be restored,\348\ which concluded that implementation of CSAPR in the 
remaining covered States will continue to meet the criteria for a BART 
alternative. This will also resolve the claims in the 2017 and 2020 
petitions for consideration. We are therefore proposing to deny the 
2020 petition for partial reconsideration of our September 2017 Final 
Rule affirming 40 CFR 51.308(e)(4) and our subsequent 2020 denial of a 
2017 petition for reconsideration of that rule. This proposed 
reaffirmation will allow the continued reliance on CSAPR participation 
as a BART alternative for BART-eligible EGUs for a given pollutant in 
States whose EGUs continue to participate in a CSAPR trading program 
for that pollutant.
---------------------------------------------------------------------------

    \348\ 82 FR 45481.
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X. Environmental Justice Considerations

    The EPA defines environmental justice (EJ) as ``the fair treatment 
and meaningful involvement of all people regardless of race, color, 
national origin, or income with respect to the development, 
implementation, and enforcement of environmental laws, regulations, and 
policies.'' The EPA further defines the term fair treatment to mean 
that ``no group of people should bear a disproportionate burden of 
environmental harms and risks, including those resulting from the 
negative environmental consequences of industrial, governmental, and 
commercial operations or programs and policies.'' \349\ Recognizing the 
importance of these considerations to local communities, the EPA 
conducted an environmental justice screening analysis around the 
location of the facilities associated with this action to identify 
potential environmental stressors on these communities and the 
potential impacts of this action. However, the EPA is providing the 
information associated with this analysis for informational purposes 
only. The information provided herein is not a basis of the proposed 
action.
---------------------------------------------------------------------------

    \349\ See https://www.epa.gov/environmentaljustice/learn-about-environmental-justice.
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    The EPA conducted the screening analyses using EJScreen, an EJ 
mapping and screening tool that provides the EPA with a nationally 
consistent dataset and approach for combining various environmental and 
demographic indicators.\350\ The EJScreen tool presents these 
indicators at a Census block group (CBG) level or a larger user-
specified ``buffer'' area that covers multiple CBGs.\351\ An individual 
CBG is a cluster of contiguous blocks within the same census tract and 
generally contains between 600 and 3,000 people. EJScreen is not a tool 
for performing in-depth risk analysis, but is instead a screening tool 
that provides an initial representation of indicators related to EJ and 
is subject to uncertainty in some underlying data (e.g., some 
environmental indicators are based on monitoring data which are not 
uniformly available; others are based on self-reported data).\352\ For 
informational purposes, we have summarized EJScreen data within larger 
``buffer'' areas covering multiple block groups and representing the 
average resident within the buffer areas surrounding the BART 
facilities. EJScreen environmental indicators help screen for locations 
where residents may experience a higher overall pollution burden than 
would be expected for a block group with the same total population in 
the U.S. These indicators of overall pollution burden include estimates 
of ambient particulate matter (PM2.5) and ozone 
concentration, a score for traffic proximity and volume, percentage of 
pre-1960 housing units (lead paint indicator), and scores for proximity 
to Superfund sites, risk management plan (RMP) sites, and hazardous 
waste facilities.\353\ EJScreen also provides information on 
demographic indicators, including percent low-income, communities of 
color, linguistic isolation, and less than high school education.
---------------------------------------------------------------------------

    \350\ The EJSCREEN tool is available at https://www.epa.gov/ejscreen.
    \351\ See https://www.census.gov/programs-surveys/geography/about/glossary.html.
    \352\ In addition, EJSCREEN relies on the five-year block group 
estimates from the U.S. Census American Community Survey. The 
advantage of using five-year over single-year estimates is increased 
statistical reliability of the data (i.e., lower sampling error), 
particularly for small geographic areas and population groups. For 
more information, see https://www.census.gov/content/dam/Census/library/publications/2020/acs/acs_general_handbook_2020.pdf.
    \353\ For additional information on environmental indicators and 
proximity scores in EJSCREEN, see ``EJSCREEN Environmental Justice 
Mapping and Screening Tool: EJSCREEN Technical Documentation,'' 
Chapter 3 and Appendix C (September 2019) at https://www.epa.gov/sites/default/files/2021-04/documents/ejscreen_technical_document.pdf.
---------------------------------------------------------------------------

    The EPA prepared EJScreen reports covering buffer areas of 
approximately 6-mile radii around the BART facilities. From those 
reports, one BART facility, Harrington Station, showed EJ indices 
greater than the 80th national percentiles,\354\ which were for ozone, 
lead paint, and RMP facility proximity, none of which are regulated by 
this proposed action. No BART facility showed an EJ index greater than 
80th national percentile for PM2.5, diesel particulate 
matter, air toxics cancer risk, air toxics respiratory hazard index, 
traffic proximity, hazardous waste site proximity, underground storage 
tanks,

[[Page 28980]]

or wastewater discharge. The full, detailed EJScreen reports are 
provided in the docket for this rulemaking.
---------------------------------------------------------------------------

    \354\ For a place at the 80th percentile nationwide, that means 
20% of the U.S. population has a higher value. EPA identified the 
80th percentile filter as an initial starting point for interpreting 
EJScreen results. The use of an initial filter promotes consistency 
for EPA programs and regions when interpreting screening results.
---------------------------------------------------------------------------

    This action is proposing to promulgate a FIP to address BART 
requirements that are not adequately satisfied by the Texas Regional 
Haze SIP. The proposed rule is proposing SO2 and PM BART 
limits on EGUs in Texas to fulfill regional haze program requirements 
and additionally disapproving portions of the Texas Regional Haze SIP 
related to PM BART. Exposure to PM and SO2 is associated 
with significant public health effects. Short-term exposures to 
SO2 can harm the human respiratory system and make breathing 
difficult. People with asthma, particularly children, are sensitive to 
these effects of SO2.\355\ Exposure to PM can affect both 
the lungs and heart and is associated with: premature death in people 
with heart or lung disease, nonfatal heart attacks, irregular 
heartbeat, aggravated asthma, decreased lung function, and increased 
respiratory symptoms, such as irritation of the airways, coughing or 
difficulty breathing. People with heart or lung diseases or conditions, 
children, and older adults are the most likely to be affected by PM 
exposure.\356\ Therefore, we expect that these requirements for EGUs in 
Texas, if finalized, and resulting emissions reductions will contribute 
to reduced environmental and health impacts on all populations impacted 
by emissions from these sources, including populations experiencing a 
higher overall pollution burden, people of color and low-income 
populations. There is nothing in the record which indicates that this 
proposed action, if finalized, would have disproportionately high or 
adverse human health or environmental effects on communities with 
environmental justice concerns.
---------------------------------------------------------------------------

    \355\ See https://www.epa.gov/so2-pollution/sulfur-dioxide-basics#effects.
    \356\ See https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm.
---------------------------------------------------------------------------

XI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Overview

    This action is exempt from review by the Office of Management and 
Budget (OMB) because the proposed FIP, if finalized, would not 
constitute a rule of general applicability, as it proposes source 
specific requirements for electric generating units at six different 
facilities located in Texas.

B. Paperwork Reduction Act

    This action does not impose any new information collection burden 
under the PRA. OMB has previously approved the information collection 
activities contained in the existing regulations and has assigned OMB 
control number 2060-0667. Because the proposed source specific BART 
emission limits apply to only six different facilities, the Paperwork 
Reduction Act does not apply. See 5 CFR 1320.3(c).
    Additionally, the proposed withdrawal of the Texas SO2 
Trading Program does not impose any new or revised information 
collection burden under the provisions of the Paperwork Reduction Act 
(PRA), 44 U.S.C. 3501 et seq. OMB has previously approved the 
information collection activities for the Texas SO2 Trading 
Program as part of the most recent information collection request 
renewal for the CSAPR trading programs, which was assigned OMB control 
number 2060-0667. The withdrawal of the Texas SO2 Trading 
Program does not change any collection requests required as part of the 
CSAPR trading programs. Furthermore, the withdrawal of the Texas 
SO2 Trading Program will cause no change in information 
collection burden related to SO2 requirements because the 
sources that are currently participating in the Texas SO2 
Trading Program have the same SO2 monitoring and reporting 
requirements under the Acid Rain Program. Thus, the withdrawal of the 
Texas SO2 Trading Program proposed in this action will not 
change any collection burden that these sources are subject to under 
either the CSAPR trading programs or the Acid Rain Program.

C. Regulatory Flexibility Act

    I certify that this action will not have a significant impact on a 
substantial number of small entities under the RFA. This action will 
not impose any requirements on small entities. The proposed FIP action, 
if finalized, will apply to EGUs at six facilities, none of which are 
small entities as defined by the RFA.

D. Unfunded Mandates Reform Act

    The EPA has determined that Title II of UMRA does not apply to this 
proposed rule. In 2 U.S.C. 1502(1) all terms in Title II of UMRA have 
the meanings set forth in 2 U.S.C. 658, which further provides that the 
terms ``regulation'' and ``rule'' have the meanings set forth in 5 
U.S.C. 601(2). Under 5 U.S.C. 601(2), ``the term `rule' does not 
include a rule of particular applicability relating to . . . 
facilities.'' Because this proposed rule is a rule of particular 
applicability relating to specific EGUs located at six named 
facilities, the EPA has determined that it is not a ``rule'' for the 
purposes of Title II of UMRA.

E. Executive Order 13132: Federalism

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

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

    This proposed rule does not have tribal implications, as specified 
in Executive Order 13175. It will not have substantial direct effects 
on tribal governments. Thus, Executive Order 13175 does not apply to 
this rule.

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

    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that EPA has reason to believe may disproportionately affect children, 
per the definition of ``covered regulatory action'' in section 2-202 of 
the Executive Order. Therefore, this action is not subject to Executive 
Order 13045 because it does not concern an environmental health risk or 
safety risk. Since this action does not concern human health, EPA's 
Policy on Children's Health also does not apply.

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

    This proposed action is not subject to Executive Order 13211 (66 FR 
28355 (May 22, 2001)), because it is not a significant regulatory 
action under Executive Order 12866.

I. National Technology Transfer and Advancement Act

    Section 12 of the National Technology Transfer and Advancement Act 
(NTTAA) of 1995 requires Federal agencies to evaluate existing 
technical standards when developing a new regulation. To comply with 
NTTAA, the EPA must consider and use ``voluntary consensus standards'' 
(VCS) if available and applicable when developing programs and policies 
unless doing so would be inconsistent with applicable law or otherwise 
impractical. The EPA

[[Page 28981]]

believes that VCS are inapplicable to this action. This action does not 
require the public to perform activities conducive to the use of VCS.

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

    Executive Order 12898 (59 FR 7629, February 16, 1994) directs 
Federal agencies, to the greatest extent practicable and permitted by 
law, to make environmental justice part of their mission by identifying 
and addressing, as appropriate, disproportionately high and adverse 
human health or environmental effects of their programs, policies, and 
activities on minority populations (people of color and/or Indigenous 
peoples) and low-income populations.
    The EPA believes that the human health or environmental conditions 
that exist prior to this action have the potential to result in 
disproportionate and adverse human health or environmental effects on 
people of color, low-income populations and/or Indigenous peoples. As 
explained further in Section X, the EPA's screening analysis provides 
an assessment of indicators related to environmental justice and 
overall pollution burden and demonstrates the potential for 
disproportionate and adverse effects on the areas located near at least 
one of the facilities subject to this action.
    The EPA believes that this action, if finalized, is not likely to 
change the human health or environmental conditions, unrelated to 
SO2 emissions, that exist prior to this action and that have 
the potential to result in disproportionate and adverse human health or 
environmental effects on people of color, low-income populations and/or 
Indigenous peoples. For example, this action is not expected to reduce 
potential community impacts associated with ozone, lead paint, or RMP 
facility status. However, the action, if finalized, is expected to 
reduce any potential existing disproportionate and adverse effects 
associated with SO2 emissions from the sources covered by 
this action. This action, if finalized, will significantly reduce 
SO2 emissions in the State of Texas, which is anticipated to 
improve air quality. The analyses and proposed requirements included in 
this proposed rulemaking are consistent with and commensurate with the 
Regional Haze Rule and how that rule functions. As discussed in Section 
X, exposure to SO2 is associated with significant public 
health effects.
    For informational purposes in a manner consistent with both the CAA 
and E.O. 12898, the EPA conducted an EJScreen analysis, considered a 
large radius around the BART facilities as well as environmental 
indicators beyond the scope of this action, as discussed in Section X. 
The EPA intends to promote fair treatment and provide meaningful 
involvement in developing the final action through the public notice 
and comment process. This will include a virtual public hearing and 
public comment period, as well as additional outreach to promote public 
engagement. Information related to this action will be available on the 
EPA's website as well as in the docket for this action.
    The information supporting this Executive Order review is contained 
in Section X of this Preamble as well as throughout the Preamble, and 
all supporting documents have been placed in the public docket for this 
action.

K. Determinations Under CAA Section 307(b)(1) and (d)

    Section 307(b)(1) of the CAA governs judicial review of final 
actions by the EPA. This section provides, in part, that petitions for 
review must be filed in the U.S. Court of Appeals for the D.C. Circuit: 
(i) when the agency action consists of ``nationally applicable 
regulations promulgated, or final actions taken, by the 
Administrator,'' or (ii) when such action is locally or regionally 
applicable, but ``such action is based on a determination of nationwide 
scope or effect and if in taking such action the Administrator finds 
and publishes that such action is based on such a determination.'' For 
locally or regionally applicable final actions, the CAA reserves to the 
Administrator complete discretion whether to invoke the exception in 
(ii).
    This proposed action, if finalized, will be ``nationally 
applicable'' within the meaning of CAA section 307(b)(1). As set forth 
in Section V, the EPA proposes to deny the 2020 petition for partial 
reconsideration of our September 2017 Final Rule affirming 40 CFR 
51.308(e)(4) and our subsequent 2020 denial of a 2017 petition for 
reconsideration of that rule. This denial, if finalized, will once 
again reaffirm the continued validity of the CSAPR better-than-BART 
provision at 40 CFR 51.308(e)(4), which is a nationally applicable 
regulation. The EPA's proposed denial of the 2020 petition for partial 
reconsideration is dependent on the EPA's promulgation of source-
specific BART emissions limits in Texas. As explained in Section IV, 
the proposed withdrawal of the Texas SO2 Trading Program and 
proposed adoption of source-specific BART limits for EGUs in Texas 
allows the EPA to restore the analytical basis for 40 CFR 51.308(e)(4), 
as set forth in our September 2017 Final Rule affirming the 2012 CSAPR 
better-than-BART determination. The CSAPR better-than-BART provision at 
40 CFR 51.308(e)(4) allows States covered by a CSAPR trading program in 
40 CFR 52.38 or 52.39 (or a SIP-approved trading program meeting these 
requirements) to implement those trading programs in lieu of source-
specific BART limits for BART-eligible EGU sources. Currently, 19 
States located across five of the ten EPA regions and in seven judicial 
circuits are included in at least one of the CSAPR trading programs and 
rely on these programs in lieu of source-specific BART, pursuant to 40 
CFR 51.308(e)(4). The EPA's restoration of the analytical basis for 40 
CFR 51.308(e)(4) would thus affect all of these States and BART-
eligible EGU sources located in these States.
    In the alternative, to the extent a court finds this proposal, if 
finalized, to be locally or regionally applicable, the Administrator 
intends to exercise the complete discretion afforded to him under the 
CAA to make and publish a finding that this action is based on a 
determination of ``nationwide scope or effect'' within the meaning of 
CAA section 307(b)(1).\357\ First, this proposed action, if finalized, 
would be based on a determination of nationwide scope or effect for the 
same reasons identified above with respect to this action being 
``nationally applicable''--namely, because it would reaffirm the 
validity of 40 CFR 51.308(e)(4). Currently, 19 States would be directly 
affected by our decision to reaffirm the continued validity of the 
CSAPR better-than-BART provision at 40 CFR 51.308(e)(4), and these 
States represent a wide geographic area falling within nine different 
judicial circuits.\358\ Second, underlying the EPA's decision to 
reaffirm the validity of 40 CFR 51.308(e)(4) is our proposed action to 
withdraw the Texas SO2 Trading Program and instead to

[[Page 28982]]

adopt source-specific BART limits for SO2 at the relevant 
Texas EGU sources, together with PM BART limits as part of a complete 
BART analysis that is required by the withdrawal of the Texas 
SO2 Trading Program as a BART alternative, as explained in 
Section IV. Thus, the source-specific BART control program for Texas is 
a necessary component of the proposed action because it provides the 
basis for the reaffirmation of our conclusion that CSAPR serves as an 
alternative to BART for EGU sources located in over half the States in 
the country. As explained in Section V, our proposed reaffirmation of 
the CSAPR better-than-BART provision depends on our finalization and 
implementation of source-specific BART emissions limits for BART-
eligible EGUs in Texas, thus achieving (among other things) 
SO2 emissions reductions comparable to the assumptions used 
in the September 2017 Final Rule affirming the 2012 CSAPR better-than-
BART determination.
---------------------------------------------------------------------------

    \357\ In deciding whether to invoke the exception by making and 
publishing a finding that an action is based on a determination of 
nationwide scope or effect, the Administrator takes into account a 
number of policy considerations, including his judgment balancing 
the benefit of obtaining the D.C. Circuit's authoritative 
centralized review versus allowing development of the issue in other 
contexts and the best use of agency resources.
    \358\ In the report on the 1977 Amendments that revised CAA 
section 307(b)(1), Congress noted that the Administrator's 
determination that the ``nationwide scope or effect'' exception 
applies would be appropriate for any action that has a scope or 
effect beyond a single judicial circuit. See H.R. Rep. No. 95-294 at 
323-24, reprinted in 1977 U.S.C.C.A.N. 1402-03.
---------------------------------------------------------------------------

    The Administrator intends to find that this is a matter on which 
national uniformity is desirable, to take advantage of the D.C. 
Circuit's administrative law expertise, and to facilitate the orderly 
development of the basic law under the Act. The Administrator also 
intends to find that consolidated review of this action in the D.C. 
Circuit will avoid piecemeal litigation in the regional circuits, 
further judicial economy, and eliminate the risk of inconsistent 
results for different States, and that a nationally consistent approach 
to implementation of CSAPR trading programs at EGUs nationwide to 
satisfy BART requirements constitutes the best use of agency resources.
    For these reasons, this action, if finalized, will be nationally 
applicable or, alternatively, the Administrator intends to exercise the 
complete discretion afforded to him under the CAA to make and publish a 
finding that this action is based on a determination of nationwide 
scope or effect for purposes of CAA section 307(b)(1).
    This proposed action is subject to the provisions of section 
307(d). CAA section 307(d)(1)(B) provides that section 307(d) applies 
to, among other things, ``the promulgation or revision of an 
implementation plan by the Administrator under [CAA section 110(c)].'' 
42 U.S.C. 7407(d)(1)(B). This action, if finalized, among other things, 
promulgates a Federal implementation plan pursuant to the authority of 
section 110(c). To the extent any portion of this proposed action is 
not expressly identified under section 307(d)(1)(B), the Administrator 
determines that the provisions of section 307(d) apply to this proposed 
action. See CAA section 307(d)(1)(V) (the provisions of section 307(d) 
apply to ``such other actions as the Administrator may determine'').

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Nitrogen dioxide, Particulate 
matter, Reporting and recordkeeping requirements, Sulfur dioxides, 
Visibility, Interstate transport of pollution, Regional haze, Best 
available retrofit technology.

40 CFR Part 78

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Reporting and recordkeeping requirements, Sulfur 
dioxides.

40 CFR Part 97

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Intergovernmental relations, Nitrogen dioxide, 
Reporting and recordkeeping requirements, Sulfur dioxides.

Michael S. Regan,
Administrator.

    For the reasons stated in the preamble, the EPA proposes to amend 
40 CFR parts 52, 78 and 97 as follows:

PART 52--APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS

0
1. The authority citation for part 52 continues to read as follows:

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

Subpart SS--Texas


Sec.  52.2270  [Amended]

0
2. Section 52.2270 is amended in the second table in paragraph (e), 
titled ``EPA Approved Nonregulatory Provisions and Quasi-Regulatory 
Measures in the Texas SIP,'' by removing the entry ``Texas Regional 
Haze BART Requirement for EGUs for PM''.
0
3. Section 52.2287 is added to subpart SS to read as follows:


Sec.  52.2287  Best Available Retrofit Requirements (BART) for 
SO2 and Particulate Matter; What are the FIP requirements 
for visibility protection?

    (a) Applicability. The provisions of this section shall apply to 
each owner or operator, or successive owners or operators, of the coal 
or natural gas burning equipment designated below.
    (b) Definitions. All terms used in this part but not defined herein 
shall have the meaning given them in the CAA and in parts 51 and 60 of 
this subchapter. For the purposes of this section:24-hour period means 
the period of time between 12:01 a.m. and 12 midnight.
    Air pollution control equipment includes selective catalytic 
control units, baghouses, particulate or gaseous scrubbers, and any 
other apparatus utilized to control emissions of regulated air 
contaminants that would be emitted to the atmosphere.
    Boiler-operating-day means any 24-hour period between 12 midnight 
and the following midnight during which any fuel is combusted at any 
time at the steam generating unit.
    Daily average means the arithmetic average of the hourly values 
measured in a 24-hour period.
    Heat input means heat derived from combustion of fuel in a unit and 
does not include the heat input from preheated combustion air, 
recirculated flue gases, or exhaust gases from other sources. Heat 
input shall be calculated in accordance with 40 CFR part 75.
    Owner or Operator means any person who owns, leases, operates, 
controls, or supervises any of the coal or natural gas burning 
equipment designated below.
    PM means particulate matter.
    Regional Administrator means the Regional Administrator of EPA 
Region 6 or his/her authorized representative.
    Unit means one of the natural gas or coal-fired units covered in 
this section.
    (c) Emissions Limitations and Compliance Dates for SO2. 
The owner/operator of the units listed in table 1 to paragraph (c)(1) 
of this section shall not emit or cause to be emitted pollutants in 
excess of the following limitations from the subject unit. Compliance 
with the requirements of this section is required as listed below 
unless otherwise indicated by compliance dates contained in specific 
provisions.
    (1) Coal-Fired Units:

                       Table 1 to Paragraph (c)(1)
------------------------------------------------------------------------
                                       Proposed
                                         SO2      Compliance date  (from
                Unit                   emission    the effective date of
                                     limit  (lb/      the final rule)
                                        MMBtu)
------------------------------------------------------------------------
Martin Lake 1......................         0.08  3 years.
Martin Lake 2......................         0.08  3 years.
Martin Lake 3......................         0.08  3 years.
Coleto Creek 1.....................         0.06  5 years.
Fayette 1..........................         0.04  1 year.
Fayette 2..........................         0.04  1 year.
Harrington 061B....................         0.06  5 years.
Harrington 062B....................         0.06  5 years.
W. A. Parish WAP5..................         0.06  5 years.
W. A. Parish WAP6..................         0.06  5 years.
Welsh 1............................         0.06  5 years.
------------------------------------------------------------------------


[[Page 28983]]

    (2) W. A. Parish WAP4 shall burn only pipeline natural gas, as 
defined in 40 CFR 72.2. Compliance for this unit shall be as of 
[EFFECTIVE DATE OF FINAL RULE].
    (d) Emissions Limitations and Compliance Dates for PM. The owner/
operator of the units listed below shall not emit or cause to be 
emitted pollutants in excess of the following limitations from the 
subject unit. Compliance with the requirements of this section is 
required as listed below unless otherwise indicated by compliance dates 
contained in specific provisions.
    (1) Coal-Fired Units at Martin Lake Units 1, 2, and 3; Coleto Creek 
Unit 1; W. A. Parish WAP5 and WAP6; Welsh Unit 1; Harrington Units 061B 
and 062B; and Fayette Units 1 and 2.
    (i) Normal operations: Filterable PM limit of 0.030 lb/MMBtu.
    (ii) Work practice standards specified in 40 CFR part 63, subpart 
UUUUU, Table 3, and using the relevant definitions in 63.10042.
    (2) W. A. Parish WAP4 shall burn only pipeline natural gas, as 
defined in 40 CFR 72.2.
    (3) Compliance for the units included in paragraph (d) of this 
section shall be as of [EFFECTIVE DATE OF FINAL RULE].
    (e) Testing and monitoring. (1) No later than the compliance date 
of this regulation, the owner or operator shall install, calibrate, 
maintain and operate Continuous Emissions Monitoring Systems (CEMS) for 
SO2 on the units covered under paragraph (c)(1) of this 
section. Compliance with the emission limits for SO2 for 
those units covered under paragraph (c)(1) shall be determined by using 
data from a CEMS.
    (2) Continuous emissions monitoring shall apply during all periods 
of operation of the units covered under paragraph (c)(1) of this 
section, including periods of startup, shutdown, and malfunction, 
except for CEMS breakdowns, repairs, calibration checks, and zero and 
span adjustments. Continuous monitoring systems for measuring 
SO2 and diluent gas shall complete a minimum of one cycle of 
operation (sampling, analyzing, and data recording) for each successive 
15-minute period. Hourly averages shall be computed using at least one 
data point in each fifteen minute quadrant of an hour. Notwithstanding 
this requirement, an hourly average may be computed from at least two 
data points separated by a minimum of 15 minutes (where the unit 
operates for more than one quadrant in an hour) if data are unavailable 
as a result of performance of calibration, quality assurance, 
preventive maintenance activities, or backups of data from data 
acquisition and handling system, and recertification events. When valid 
SO2 pounds per hour, or SO2 pounds per million 
Btu emission data are not obtained because of continuous monitoring 
system breakdowns, repairs, calibration checks, or zero and span 
adjustments, emission data must be obtained by using other monitoring 
systems approved by the EPA to provide emission data for a minimum of 
18 hours in each 24-hour period and at least 22 out of 30 successive 
boiler operating days.
    (3) Compliance with the requirement for the unit covered under 
paragraphs (c)(2) and (d)(2) of this section shall be determined from 
documentation demonstrating the use of pipeline natural gas as defined 
in 40 CFR 72.2.
    (4) Compliance with the PM emission limits for units in paragraph 
(d)(1) of this section shall be demonstrated by the filterable PM 
methods specified in 40 CFR part 63, subpart UUUUU, table 7.
    (f) Reporting and Recordkeeping Requirements. Unless otherwise 
stated all requests, reports, submittals, notifications, and other 
communications to the Regional Administrator required by this section 
shall be submitted, unless instructed otherwise, to the Director, Air 
and Radiation Division, U.S. Environmental Protection Agency, Region 6, 
to the attention of Mail Code: ARD, at 1201 Elm Street, Suite 500, 
Dallas, Texas 75270. For each unit subject to the emissions limitation 
in this section and upon completion of the installation of CEMS as 
required in this section, the owner or operator shall comply with the 
following requirements:
    (1) For each SO2 emission limit in paragraph (c)(1) of 
this section, comply with the notification, reporting, and 
recordkeeping requirements for CEMS compliance monitoring in 40 CFR 
60.7(c) and (d).
    (2) For each day, provide the total SO2 emitted that day 
by each emission unit covered under paragraph (c)(1) of this section. 
For any hours on any unit where data for hourly pounds or heat input is 
missing, identify the unit number and monitoring device that did not 
produce valid data that caused the missing hour.
    (3) For the unit covered under paragraphs (c)(2) and (d)(2) of this 
section, records sufficient to demonstrate that the fuel for the unit 
is pipeline natural gas.
    (4) Records for demonstrating compliance with the SO2 
and PM emission limitations in this section shall be maintained for at 
least five years.
    (g) Equipment operations. At all times, including periods of 
startup, shutdown, and malfunction, the owner or operator shall, to the 
extent practicable, maintain and operate the unit including associated 
air pollution control equipment in a manner consistent with good air 
pollution control practices for minimizing emissions. Determination of 
whether acceptable operating and maintenance procedures are being used 
will be based on information available to the Regional Administrator 
which may include, but is not limited to, monitoring results, review of 
operating and maintenance procedures, and inspection of the unit.
    (h) Enforcement. (1) Notwithstanding any other provision in this 
implementation plan, any credible evidence or information relevant as 
to whether the unit would have been in compliance with applicable 
requirements if the appropriate performance or compliance test had been 
performed, can be used to establish whether or not the owner or 
operator has violated or is in violation of any standard or applicable 
emission limit in the plan.
    (2) Emissions in excess of the level of the applicable emission 
limit or requirement that occur due to a malfunction shall constitute a 
violation of the applicable emission limit.
0
4. Section 52.2304 is amended by revising the paragraph (f) heading and 
adding paragraph (f)(3) to read as follows:


Sec.  52.2304  Visibility protection.

* * * * *
    (f) Measures Addressing Disapproval Associated with NOX, SO2, and 
PM. * * *
    (3) The deficiencies associated with PM with respect to best 
available retrofit technology under section 169A of the Clean Air Act, 
as identified in EPA's disapproval of the regional haze plan submitted 
by Texas on March 31, 2009, are satisfied by Sec.  52.2287.
0
5. Section 52.2312 is amended by revising paragraph (a) and removing 
and reserving paragraph (b).
    The revision reads as follows:


Sec.  52.2312  Requirements for the control of SO2 emissions to address 
in full or in part requirements related to BART, reasonable progress, 
and interstate visibility transport.

    (a) The Texas source-specific BART limits set forth in Sec.  
52.2287 constitute the Federal Implementation Plan provisions fully 
addressing Texas' obligations with respect to best available retrofit 
technology under section 169A of the Act and the deficiencies 
associated with EPA's disapprovals in

[[Page 28984]]

Sec.  52.2304(d) and partially addressing Texas' obligations with 
respect to reasonable progress under section 169A of the Act, as those 
obligations relate to emissions of sulfur dioxide (SO2) from 
electric generating units (EGUs).
* * * * *

PART 78--APPEAL PROCEDURES

0
6. The authority citation for part 78 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.


Sec.  78.1   [Amended]

0
7. Section 78.1 is amended in paragraph (a)(1)(i)(D) by removing 
``FFFFF,'' and by removing and reserving paragraph (b)(18).


Sec.  78.3   [Amended]

0
8. Section 78.3 is amended in paragraphs (a)(4), (c)(7)(iv), and 
(d)(2)(iv) by removing ``FFFFF,'' and in paragraph (d)(6) by removing 
``FFFFF,'' and ``Sec.  97.906,''.


Sec.  78.4  [Amended]

0
9. Section 78.4 is amended:
0
a. In paragraph (a)(1)(iv)(A), by removing ``CSAPR SO2 Group 
2 unit or CSAPR SO2 Group 2 source, or Texas SO2 
Trading Program unit or Texas SO2 Trading Program source'' 
and adding in its place ``or CSAPR SO2 Group 2 unit or CSAPR 
SO2 Group 2 source''; and
0
b. In paragraph (a)(1)(iv)(B), by removing ``CSAPR SO2 Group 
2 allowances, or Texas SO2 Trading Program allowances'' and 
adding in its place ``or CSAPR SO2 Group 2 allowances''.

PART 97--FEDERAL NOX BUDGET TRADING PROGRAM, CAIR NOX AND SO2 
TRADING PROGRAMS, AND CSAPR NOX AND SO2 TRADING PROGRAMS

0
10. The authority citation for part 97 is revised to read as follows:

    Authority: 42 U.S.C. 7401, 7403, 7410, 7426, 7601, and 7651, et 
seq.

0
11. Revise the heading for part 97 to read as set forth above.

Subpart FFFFF--[Removed and Reserved]

0
12. Remove and reserve subpart FFFFF, consisting of Sec. Sec.  97.901 
through 97.935.

[FR Doc. 2023-08732 Filed 5-2-23; 8:45 am]
BILLING CODE 6560-50-P