Home/Federal/Federal Register/2026-11436

Proposed Rule2026-11436

Approval and Promulgation of Air Quality Implementation Plans; Wyoming; Regional Haze Federal Implementation Plan

Primary source

Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.

Published

June 8, 2026

Issuing agencies

Environmental Protection Agency

Abstract

The U.S. Environmental Protection Agency (EPA) is proposing revisions to the Federal Implementation Plan (FIP) addressing regional haze in the State of Wyoming. The EPA is proposing revisions to the FIP's nitrogen oxides (NO<INF>X</INF>) best available retrofit technology (BART) requirements for the PacifiCorp Dave Johnston Power Plant Unit 3. In response to PacifiCorp's letter no longer consenting to closure of Dave Johnston Unit 3, the EPA is proposing to withdraw the NO<INF>X</INF> BART determination containing the closure requirement. Additionally, in response to a request from PacifiCorp, and in light of new information that was not available at the time the EPA originally promulgated the FIP in 2014, the Agency is also proposing to revise the other NO<INF>X</INF> BART determination for Dave Johnston Unit 3.

Full Text

<html>
<head>
<title>Federal Register, Volume 91 Issue 109 (Monday, June 8, 2026)</title>
</head>
<body><pre>
[Federal Register Volume 91, Number 109 (Monday, June 8, 2026)]
[Proposed Rules]
[Pages 34589-34597]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2026-11436]

=======================================================================
-----------------------------------------------------------------------

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2026-1651; FRL-13299-01-R8]

Approval and Promulgation of Air Quality Implementation Plans;
Wyoming; Regional Haze Federal Implementation Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: The U.S. Environmental Protection Agency (EPA) is proposing
revisions to the Federal Implementation Plan (FIP) addressing regional
haze in the State of Wyoming. The EPA is proposing revisions to the
FIP's nitrogen oxides (NO<INF>X</INF>) best available retrofit
technology (BART) requirements for the PacifiCorp Dave Johnston Power
Plant Unit 3. In response to PacifiCorp's letter no longer consenting
to closure of Dave Johnston Unit 3, the EPA is proposing to withdraw
the NO<INF>X</INF> BART determination containing the closure
requirement. Additionally, in response to a request from PacifiCorp,
and in light of new information that was not available at the time the
EPA originally promulgated the FIP in 2014, the Agency is also
proposing to revise the other NO<INF>X</INF> BART determination for
Dave Johnston Unit 3.

DATES:
Comments: Written comments must be received on or before July 23,
2026 unless a public hearing is held. If a public hearing is held,
comments on this notice of proposed rulemaking must be received on or
before date 30 days after date of public hearing.
Public Hearing: Any party requesting a public hearing must notify
the contact listed in the FOR FURTHER INFORMATION CONTACT section by 5
p.m. Mountain Daylight Time on or before June 15, 2026. If a public
hearing is held, it will take place on or around June 23, 2026.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2026-1651, to the Federal Rulemaking Portal: <a href="https://www.regulations.gov">https://www.regulations.gov</a>. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
<a href="http://www.regulations.gov">www.regulations.gov</a>. The EPA may publish any comment received to the
Agency's public docket. Do not submit electronically any information
you consider to be Confidential Business Information (CBI) or other
information the disclosure of which is restricted by statute.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
If a public hearing is requested on or before June 15, 2026, the
EPA will post an update at <a href="https://www.epa.gov/wy/wyoming-events-and-public-notices">https://www.epa.gov/wy/wyoming-events-and-public-notices</a>. The EPA does not intend to publish a document in the
Federal Register (FR) announcing updates. The public hearing will be
held on or around June 23, 2026. Information on the hearing including
the time and URL will be posted at <a href="https://www.epa.gov/wy/wyoming-events-and-public-notices">https://www.epa.gov/wy/wyoming-events-and-public-notices</a>.
Docket: All documents in the docket are listed in the <a href="https://www.regulations.gov">https://www.regulations.gov</a> index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
the disclosure of which is restricted by statute. Certain other
material, such as copyrighted material, will be publicly available only
in hard copy. Publicly available docket materials are available
electronically in <a href="https://www.regulations.gov">https://www.regulations.gov</a>. Please email or call the
person listed in the FOR FURTHER INFORMATION CONTACT section if you
need to make alternative arrangements for access to the docket.

FOR FURTHER INFORMATION CONTACT: For information about this proposed
rule, contact Jaslyn Dobrahner, Air and Radiation Division, EPA, Region
8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver, Colorado 80202-1129,
telephone number: (303) 312-6252, email address:
<a href="/cdn-cgi/l/email-protection#ceaaa1acbcafa6a0abbce0a4afbda2b7a08eabbeafe0a9a1b8">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION: Throughout this document, the use of ``we,''
``us,'' or ``our'' is intended to refer to the EPA. We use multiple
acronyms and terms in this preamble. While this list may not be
exhaustive, to ease the reading of this preamble and for reference
purposes, the EPA defines the following terms and acronyms here:

BART Best Available Retrofit Technology
CAA Clean Air Act
CAMPD Clean Air Markets Program Data
CBI Confidential Business Information
CFR Code of Federal Regulations
EGU Electric Generating Unit
EPA U.S. Environmental Protection Agency
FGD Flue Gas Desulfurization
FIP Federal Implementation Plan
FLM Federal Land Manager
FR Federal Register
IRP Integrated Resource Plan
LB Pound
LNB/OFA Low-NO<INF>X</INF> Burners With Overfire Air
MMBtu Million British Thermal Units
MW Megawatt
NAAQS National Ambient Air Quality Standards
NERC North American Electric Reliability Corporation
NO<INF>X</INF> Nitrogen Oxides
OMB Office of Management and Budget
PM Particulate Matter
PRA Paperwork Reduction Act
RFA Regulatory Flexibility Act
RHR Regional Haze Rule
RTC Response to Comments
SCR Selective Catalytic Reduction
SIP State Implementation Plan
SNCR Selective Non-Catalytic Reduction
SO<INF>2</INF> Sulfur Dioxide
TPY Tons Per Year

[[Page 34590]]

UMRA Unfunded Mandates Reform Act
USFS United States Forest Service

Table of Contents

I. What action is the EPA proposing?
II. Background
A. Dave Johnston Power Plant
B. Legal Authority and Requirements
C. Regulatory History
III. NO<INF>X</INF> BART Determination for Dave Johnston Unit 3
A. Costs of Compliance
B. Energy and Non-Air Quality Environmental Impacts of
Compliance
C. Pollution Control Equipment in Use at the Source
D. Remaining Useful Life of the Source
E. Degree of Improvement in Visibility
F. Conclusion
IV. Coordination With FLMs
V. Clean Air Act Section 110(l)
VI. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

The EPA is proposing to revise the Wyoming regional haze FIP to
amend the NO<INF>X</INF> BART determination for Dave Johnston Unit 3.
Specifically, the EPA is proposing to: (1) remove the NO<INF>X</INF>
BART requirement of 0.28 pounds per million British thermal units (lb/
MMBtu) (30-day rolling average) interim emission limit and permanent
cessation of operations at Dave Johnston Unit 3 on or before December
31, 2027; and (2) revise the other NO<INF>X</INF> BART requirement of
0.07 lb/MMBtu (30-day rolling average).\1\ Specifically, the EPA is
proposing to revise the NO<INF>X</INF> BART determination and establish
a new NO<INF>X</INF> BART requirement of 0.23 lb/MMBtu (30-day rolling
average) and associated compliance date for Dave Johnston Unit 3.
Although the EPA is proposing to revise the Wyoming regional haze FIP
NO<INF>X</INF> BART determination for Dave Johnston Unit 3, the Agency
invites Wyoming to submit a new regional haze State Implementation Plan
(SIP) NO<INF>X</INF> BART determination in the future for Dave Johnston
Unit 3 to the Agency in an effort to replace this FIP with a SIP.
---------------------------------------------------------------------------

\1\ 40 CFR 52.2636(c)(1) Table 2 and 40 CFR 52.2636(d)(4).
---------------------------------------------------------------------------

II. Background

A. Dave Johnston Power Plant

The Dave Johnston power plant is located in Converse County,
Wyoming and is comprised of four coal-fired units, but only Units 3 and
4 are subject to BART requirements.\2\
---------------------------------------------------------------------------

\2\ Dave Johnston Units 1 and 2 began operation in 1958 and
1960, respectively. BART applies to sources built between 1962 and
1977.
---------------------------------------------------------------------------

Dave Johnston Unit 3 is a 230 megawatt (MW) coal-fired boiler that
commenced service in 1964. The coal is currently sourced from the Dry
Fork Mine, Caballo Mine, and Coal Creek Mine in the Powder River Basin
in Wyoming.\3\ In June 2008, Wyoming issued a construction permit
approving PacifiCorp's construction permit application request to
install new emission controls at Dave Johnston Units 3 and 4.\4\ In
December 2009, Wyoming issued a BART permit with emission limits to
meet BART requirements for Dave Johnston Unit 3.\5\ In 2010, PacifiCorp
completed emissions controls upgrades on Unit 3, including installation
of Flue Gas Desulfurization (FGD) sulfur dioxide (SO<INF>2</INF>)
emission controls, upgrades to the existing electrostatic precipitator
to a baghouse for particulate matter (PM) emission controls, and
installation of low-NO<INF>X</INF> burners with overfire air (LNB/OFA)
for NO<INF>X</INF> emission controls. Additionally, Dave Johnston Unit
3 was originally equipped with burners in a cell configuration until
the 2010 upgrades when it was converted to a dry bottom wall-fired
boiler to enable the installation of the LNB/OFA combustion controls.
---------------------------------------------------------------------------

\3\ Email communication between the EPA and PacifiCorp. May 28,
2026. Available in the docket for this rulemaking at Docket ID No.
EPA-R08-OAR-2026-1651.
\4\ Wyoming permit number MD-5098. (June 27, 2008).
\5\ Wyoming permit number MD-6041. (December 31, 2009).
---------------------------------------------------------------------------

B. Legal Authority and Requirements

Clean Air Act (CAA) section 169A sets forth the regional haze
program for protecting visibility in certain national parks and
wilderness areas, establishing ``as a national goal the prevention of
any future, and the remedying of any existing, impairment of visibility
in mandatory Class I Federal areas which impairment results from
manmade air pollution.'' \6\ The EPA promulgated the Regional Haze Rule
(RHR) to address regional haze on July 1, 1999,\7\ and published a
revision to the RHR on January 10, 2017.\8\
---------------------------------------------------------------------------

\6\ 42 U.S.C. 7491(a).
\7\ 64 FR 35714 (July 1, 1999).
\8\ 82 FR 3078 (January 10, 2017).
---------------------------------------------------------------------------

The CAA requires each State to develop a SIP to meet various air
quality requirements, including protection of visibility.\9\ Regional
haze SIPs must ensure reasonable progress toward the national goal of
achieving natural visibility conditions in Class I areas. A State must
submit its SIP and SIP revisions to the EPA for approval.\10\ If a
State elects not to make a required SIP submittal, fails to make a
required SIP submittal, or if the EPA finds that a State's required
submittal is incomplete or not approvable, then CAA section 110(c)(1)
requires the EPA to promulgate a FIP.\11\
---------------------------------------------------------------------------

\9\ 42 U.S.C. 7410(a), 7491, and 7492(a); CAA sections 110(a),
169A, and 169B.
\10\ Regional haze SIPs for the first implementation period were
due on December 17, 2007.
\11\ 42 U.S.C. 7410(c)(1).
---------------------------------------------------------------------------

Under the CAA, even if the EPA establishes a FIP, a State may
submit a SIP that, if approved by the Agency, would replace the FIP.
1. Best Available Retrofit Technology (BART)
CAA section 169A directs States, or the EPA if developing a FIP, to
evaluate the use of retrofit controls at certain larger stationary
sources built between 1962 and 1977 to address visibility impacts from
these sources.\12\ Specifically, CAA section 169A(b)(2) requires SIPs
to contain such measures as may be necessary to make reasonable
progress toward the natural visibility goal.\13\ This includes a
requirement that existing major stationary sources built between 1962
and 1977 that emit air pollutants which may reasonably be anticipated
to cause or contribute to any impairment in a Class I area shall
procure, install, and operate, as expeditiously as practicable, BART
for controlling emissions from such sources for the purpose of
eliminating or reducing any such impairment. BART is determined by the
States through their SIPs, or by the EPA in a FIP.\14\ For fossil fuel-
fired generating powerplants having a total generating capacity in
excess of 750 megawatts, the emission limitations required shall be
determined pursuant to guidelines promulgated by the Administrator.\15\
---------------------------------------------------------------------------

\12\ 42 U.S.C. 7491.
\13\ 42 U.S.C. 7491(b)(2).
\14\ Id.
\15\ Id.
---------------------------------------------------------------------------

CAA section 169A(g)(2) requires that States, or the EPA if
developing a FIP, must consider the following five factors in making
BART determinations: (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. Under the RHR, States (or the EPA) are directed to
conduct BART determinations for such ``BART-eligible'' sources that may
reasonably be anticipated to cause or contribute to any visibility
impairment in a Class I area.\16\
---------------------------------------------------------------------------

\16\ 40 CFR 51.308(e).
---------------------------------------------------------------------------

On July 6, 2005, the EPA published the Guidelines for BART
Determinations under the RHR at appendix Y to 40

[[Page 34591]]

Code of Federal Regulations (CFR) part 51 (the ``BART Guidelines'') to
assist States and the Agency in determining which sources should be
subject to the BART requirements and the appropriate emission limits
for each applicable source.17 18 Under the BART Guidelines
promulgated per CAA 169A(b)(2), ``States must follow the guidelines in
making BART determinations on a source-by-source basis for 750 megawatt
power plants but are not required to use the process under the
guidelines when making BART determinations for other type of sources.''
In addition to what is required by the RHR, general SIP requirements
mandate that the SIP or FIP include all regulatory requirements related
to monitoring, recordkeeping, and reporting for the BART emission
limitations.\19\
---------------------------------------------------------------------------

\17\ 70 FR 39104 (July 6, 2005).
\18\ In making a BART determination for a fossil fuel-fired
electric generating plant with a total generating capacity in excess
of 750 MW, a State must use the approach set forth in the BART
Guidelines.
\19\ See CAA section 110(a); 40 CFR part 51, subpart K.
---------------------------------------------------------------------------

2. Consultation With Federal Land Managers
The RHR requires that a State, or the EPA if promulgating a FIP,
consult with the Federal land managers (FLMs) before adopting and
submitting a required SIP or SIP revision, or a required FIP or FIP
revision.\20\ Further, a State, or the EPA if considering a FIP
revision, must include in its notice to the public a summary of the
conclusions and recommendations of the FLMs.\21\
---------------------------------------------------------------------------

\20\ CAA section 169A(d), 40 CFR 51.308(i).
\21\ CAA section 169A(d).
---------------------------------------------------------------------------

3. BART Guidelines Definition of Baseline Emissions
On January 30, 2014, the EPA partially approved and partially
disapproved a regional haze SIP revision submitted by the State of
Wyoming on January 12, 2011 (the ``2014 Final Rule'').\22\ In the 2014
Final Rule, the EPA limited the adjustment of baseline emissions for
recently installed controls and stated that the baseline should only be
adjusted in cases in which controls were installed to meet other CAA
requirements. However, the BART Guidelines gives discretion to States
and the EPA in setting baseline emissions and defines baseline
emissions as a ``realistic depiction of anticipated emissions.''
23 24 Additionally, the third BART statutory factor requires
consideration of ``existing pollution control technology in use at the
source.'' \25\ Therefore, given the language in both the statute and
the BART Guidelines, the EPA is proposing to determine that inclusion
of existing controls in the baseline emissions, regardless of purpose,
is both permissible and reasonable.
---------------------------------------------------------------------------

\22\ 79 FR 5032 (January 30, 2014).
\23\ Since the Dave Johnston power plant is larger than 750
megawatts, the BART Guidelines apply.
\24\ BART Guidelines, 40 CFR part 51, appendix Y section
IV.D.4.d.1.
\25\ CAA section 169A(g)(2).
---------------------------------------------------------------------------

According to the BART Guidelines, for purposes of calculating the
costs of compliance, ``the baseline emissions rate should represent a
realistic depiction of anticipated annual emissions for the source.''
\26\ The BART Guidelines allow States and the EPA to adjust baseline
emissions to take into account projections of ``future operating
parameters'' by making such assumptions into enforceable limits.\27\ In
previous regional haze first planning period actions, the EPA confirmed
that neither the RHR nor the BART Guidelines require a particular
timeframe be used as the baseline for BART determinations at individual
sources.\28\ Consequently, States and the EPA have considerable
discretion in how they consider existing controls in use at a source,
so long as that consideration is explained and reasonable.
---------------------------------------------------------------------------

\26\ BART Guidelines, 40 CFR part 51, appendix Y section
IV.D.4.d.1.
\27\ BART Guidelines, 40 CFR part 51, appendix Y section
IV.D.4.d.2.
\28\ 77 FR 72526 (December 5, 2012); 79 FR 5104 (January 30,
2014).
---------------------------------------------------------------------------

In the 2014 Final Rule, the EPA did not update the baseline
NO<INF>X</INF> emissions to account for the newly installed LNB/OFA
combustion controls. In the EPA's responses to comments, the Agency
explained that it would have been inappropriate for the Agency to take
LNB/OFA into consideration, because it appeared the controls on certain
sources in Wyoming had been installed early to avoid a more stringent
BART determination as opposed to comply with other CAA
requirements.\29\ Allowing for inclusion of existing controls in the
baseline emissions, regardless of purpose, more closely aligns with the
``consideration of any existing pollution control technology'' CAA
requirement and the BART Guidelines requirement that the baseline
emissions rate should represent a ``realistic depiction of annual
emissions'' and ``in general, for the existing source subject to BART,
you will estimate the anticipated annual emissions based upon actual
emissions from a baseline period.'' \30\ Therefore, given the language
in both the statute and the BART Guidelines, the EPA believes it is
permissible and appropriate to adjust the baseline emissions rate to
reflect existing controls at the source, regardless of purpose, despite
the EPA declining to do so in the 2014 Final Rule.
---------------------------------------------------------------------------

\29\ 79 FR 5105 (January 30, 2014).
\30\ BART Guidelines, 40 CFR part 51 appendix Y section
IV.D.4.d.
---------------------------------------------------------------------------

In the 2014 Final Rule, the EPA also stated that the Agency's
action would not be inconsistent with the Eighth Circuit's decision in
North Dakota.31 32 In the EPA's responses to comments, the
Agency stated that the Eighth Circuit rejected the Agency's position to
not consider the Dry Fining\TM\ control technology in use at Coal Creek
Station in the BART evaluation (either in the cost of control options
or adjustment to the baseline), holding that the ``EPA's refusal to
consider Dry Fining\TM\ as an existing pollution control technology in
use at the Coal Creek Station because it had been voluntarily installed
was arbitrary and capricious.'' \33\ The Eighth Circuit explained that
``any existing pollution control technology'' also included voluntarily
installed controls.\34\ The Eighth Circuit did not opine as to how
``existing'' must be considered and, thus, North Dakota did not
specifically require the EPA to ``take into consideration'' the
existing controls by adjusting the baseline emissions.\35\ However, the
Eighth Circuit recognized that the relevance of the plain language
requirement of the CAA to ``take into consideration'' existing
pollution control technology in use at the source can include adjusting
the baseline emissions to reflect existing controls.\36\
---------------------------------------------------------------------------

\31\ 79 FR 5032 at 5103 through 5105 (January 30, 2014).
\32\ North Dakota v. EPA, 730 F.3d 750 (8th Cir. 2013), cert.
denied (2014).
\33\ 79 FR 5032 at 5103 through -5105 (January 30, 2014).
\34\ Id.
\35\ Id.
\36\ North Dakota v. EPA, 730 F.3d 750 (8th Cir. 2013), cert.
denied (2014).
---------------------------------------------------------------------------

Subsequent to the EPA's 2014 NO<INF>X</INF> BART determination for
Dave Johnston Unit 3, the Ninth Circuit upheld the Agency's selection
of a 2008-2010 baseline period representing the 2009 installation of
combustion controls for a source subject-to-BART in the Agency's 2012
FIP for Montana.\37\ Conservation organizations argued that the EPA
should have chosen earlier periods between 2000-2004 because the source
was not required to maintain the rate of emissions achieved between
2008-2010, describing the changes at the source as ``unenforceable.''
The Ninth Circuit found that the EPA offered a reasoned response to the
comment. Specifically,

[[Page 34592]]

the Ninth Circuit agreed with the EPA on the following: (1) the
Agency's decision to adjust the baseline to include recently installed
controls to meet CAA Acid Rain Program emission limits; (2) that the
source had achieved reduced emissions using technology it has no plans
to deactivate; and (3) that conservation organizations suggested no
reason to believe that the source would change course and remove the
additional combustion controls it had already installed.\38\ While the
EPA updated the baseline in the 2012 FIP for Montana to reflect
currently installed controls for Colstrip due to CAA acid rain
requirements, as described above, the CAA and the BART Guidelines allow
for adjustment of baseline to account for installed controls,
regardless of purpose.
---------------------------------------------------------------------------

\37\ 77 FR 57864 (September 18, 2012).
\38\ NPCA v. EPA, 788 F.3d 1134, 1143 (9th Cir. 2015).
---------------------------------------------------------------------------

In summary, the EPA considered the following when determining the
baseline emissions rate for Dave Johnston Unit 3: (1) BART requires the
consideration of any pollution control equipment in use at the source;
\39\ (2) the BART Guidelines provide that, for purposes of calculating
the costs of compliance, the baseline emissions rate should represent a
realistic depiction of the anticipated annual emissions for the source;
\40\ (3) neither the RHR nor the BART Guidelines require a particular
timeframe be used as the baseline for BART determinations at individual
sources; and (4) updating the baseline to reflect installation of
additional combustion controls is consistent with case law. Thus, it is
reasonable to interpret the BART Guidelines to allow for NO<INF>X</INF>
emission controls that are currently in place at Dave Johnston Unit 3
to represent the baseline emissions rate when calculating the costs of
compliance, particularly given the fact that Dave Johnston Unit 3 has
maintained that rate for 15 years and the emissions represent a
realistic depiction of anticipated annual emissions.\41\
---------------------------------------------------------------------------

\39\ CAA section 169A(g)(2); 40 CFR 51.308(e)(1)(ii)(A).
\40\ BART Guidelines, 40 CFR part 51 appendix Y section
IV.D.4.d.
\41\ 2010-2025 Dave Johnston Emissions. Clean Air Markets
Program Data (CAMPD). (April 17, 2026).
---------------------------------------------------------------------------

C. Regulatory History

In the 2014 Final Rule, the EPA partially disapproved the Wyoming
regional haze SIP, including the NO<INF>X</INF> BART emission limit of
0.28 lb/MMBtu (30-day rolling average) reflecting LNB/OFA at Dave
Johnston Unit 3, among other actions. Within the same action, the EPA
promulgated a FIP that required a NO<INF>X</INF> BART emission limit of
0.07 lb/MMBtu (30-day rolling average) to be implemented by March 4,
2019 (five years from the effective date of the FIP). At PacifiCorp's
request, the EPA also included an alternative NO<INF>X</INF> BART
requirement of 0.28 lb/MMBtu (30-day rolling average) interim emission
limit and permanent cessation of operations at Dave Johnston Unit 3 by
December 31, 2027. PacifiCorp is currently operating within the
NO<INF>X</INF> BART requirement of 0.28 lb/MMBtu interim emission limit
and permanent cessation of operations at Dave Johnston Unit 3 on or
before December 31, 2027.42 43
---------------------------------------------------------------------------

\42\ 2020 to 2025 Dave Johnston Emissions. EPA Clean Air Markets
Program Data (CAMPD). (March 13, 2026).
\43\ 40 CFR 52.2636(c) and (d)(4).
---------------------------------------------------------------------------

On March 4, 2026, PacifiCorp informed the EPA that it withdrew its
consent to the closure of Dave Johnston Unit 3 by December 31,
2027.\44\ In its letter, PacifiCorp explained that due to projected
``[d]ramatic increases in electricity demand'' associated with the
``resurgence of domestic manufacturing and the construction of
artificial intelligence data processing centers,'' PacifiCorp's 2025
Integrated Resource Plan (IRP) projects a need for an additional 1,000
MW more generating capacity in the next eight years than had been
projected in the 2019 IRP for the same time period. Accordingly,
PacifiCorp states that it ``no longer consents to closure of [Dave
Johnston Unit 3] and has retracted its prior request to the EPA to
include the retirement option in the FIP.'' \45\
---------------------------------------------------------------------------

\44\ Letter from Jayson Branch, Senior Vice President, Power
Supply, PacifiCorp, to Cyrus Western, U.S. EPA Regional
Administrator. (March 4, 2026).
\45\ Id. at 3. See also comment requesting addition of
NO<INF>X</INF> BART shutdown option with interim limit in the 2014
Final Rule. 79 FR 5032, and 5045 (January 30, 2014).
---------------------------------------------------------------------------

III. NOX BART Determination for Dave Johnston Unit 3

A. Costs of Compliance

In the 2014 Final Rule, the EPA relied on a number of emissions and
control cost assumptions for Dave Johnston Unit 3. To provide cost
information that is consistent with the original FIP, the EPA generally
relied on the same control costs assumptions used in the 2014 Final
Rule to re-analyze the prior control scenarios at Dave Johnston Unit 3.
This allows for a direct comparison between the current cost
assumptions and other BART analyses from that same time period.
In the 2014 Final Rule, the EPA relied on baseline pre-combustion
control NO<INF>X</INF> emissions of 4,913 tons per year (tpy), based on
the actual annual average of NO<INF>X</INF> emissions for the years
2001-2003, as the baseline emissions.\46\ However, for this current
analysis, and as previously described, the EPA is reconsidering the
baseline emissions assumptions. As noted earlier, in 2010, PacifiCorp
installed LNB/OFA combustion controls on Dave Johnston Unit 3, and
those controls are permanent and have now been operating for over 15
years. Therefore, based on the third BART statutory factor, ``pollution
equipment in use at the source,'' \47\ the EPA is adjusting the
baseline to reflect the pollution equipment installed at Dave Johnston
Unit 3. Additionally, in selecting a baseline emissions period, the
BART Guidelines state that the baseline should ``represent(s) a
realistic depiction of anticipated emissions for the source.'' \48\
Therefore, in selecting baseline emissions for this revised BART
analysis, a baseline that includes operation of LNB/OFA combustion
controls represents both ``pollution equipment in use at the source''
and ``represent(s) a realistic depiction of anticipated emissions for
the source.'' \49\
---------------------------------------------------------------------------

\46\ Wyoming EGU BART and Reasonable Progress Costs (79 FR 5039;
October 28, 2013).
\47\ CAA section 169A(g)(2).
\48\ BART Guidelines, 40 CFR part 51 appendix Y section
IV.D.4.d.1.
\49\ CAA section 169A(g)(2); BART Guidelines, 40 CFR part 51
appendix Y section IV.D.4.d.1.
---------------------------------------------------------------------------

Since LNB/OFA was installed in 2010, the EPA is using the period of
operation immediately following the LNB/OFA installation as the updated
baseline period for the revised BART analysis. Dave Johnston Unit 3
achieved an actual NO<INF>X</INF> emission rate of 0.22 lb/MMBtu
(annual average) for the years 2011, 2012, and the first two quarters
of 2013,\50\ which reduced NO<INF>X</INF> emissions by 2,837 tpy and
resulted in post-combustion control baseline NO<INF>X</INF> emissions
of 2,076 tpy.\51\ Based on the current boiler configuration, PacifiCorp
provided information that LNB/OFA has consistently achieved an emission
limit of 0.23 lb/MMBtu (30-day rolling average) since installation in
2010.\52\ Therefore, for purposes of calculating the costs of
compliance, the EPA's revised NO<INF>X</INF> BART determination for
Dave Johnston Unit 3 uses the post-combustion control baseline of 2,076
tpy. As explained above, this baseline is

[[Page 34593]]

consistent with the demonstrated actual NO<INF>X</INF> emissions from
the installation of LNB/OFA in 2010 continuing through present day
(over a 15-year period) and is consistent with both the CAA statutory
factor(s) and the BART Guidelines.
---------------------------------------------------------------------------

\50\ These time periods reflect the emission data available
following the installation of LNB/OFA and prior to the finalization
of the 2014 Final Rule in January 2014.
\51\ Wyoming EGU BART and Reasonable Progress Costs. `Emissions'
worksheet (79 FR 5039; October 28, 2013).
\52\ Letter from Jayson Branch, Senior Vice President, Power
Supply, PacifiCorp, to Cyrus Western, U.S. EPA Regional
Administrator at 12. (March 4, 2026).
---------------------------------------------------------------------------

The next step in determining BART is to identify all available
retrofit control technologies and eliminate technically infeasible
options. As determined in the 2014 Final Rule, selective non-catalytic
reduction (SNCR) and selective catalytic reduction (SCR) are the
primary available post-combustion retrofit technologies for the Dave
Johnston Unit 3 boiler, and both technologies were determined to be
feasible, which are not being challenged currently. The next step is to
evaluate the control effectiveness of the feasible control
technologies. To calculate the potential NO<INF>X</INF> emissions
reductions for the SNCR and SCR scenarios, the EPA used a
NO<INF>X</INF> emission rate assumption of 0.16 lb/MMBtu (annual
average) for SNCR and 0.05 lb/MMBtu (annual average) for SCR.\53\ The
emission reductions associated with the installation of SNCR reflect a
control efficiency of 25 percent and would potentially reduce
NO<INF>X</INF> emissions by only 519 tpy compared to the post-
combustion control baseline NO<INF>X</INF> emissions of 2,076 tpy. The
emission reductions associated with the installation of SCR reflect a
control efficiency of 77 percent and would potentially reduce
NO<INF>X</INF> emissions by 1,597 tpy compared to the post-control
baseline NO<INF>X</INF> emissions of 2,076 tpy. Based on these
assumptions, the annualized costs to install SNCR and SCR using a 20-
year equipment life were found to be $1,810,782 per year and $9,980,337
per year, respectively, as compared to the pre-combustion control
annualized costs of $3,510,589 per year and $11,680,144 per year to
install LNB/OFA + SNCR and LNB/OFA + SCR, respectively.\54\ The current
version of the EPA's Control Cost Manual (revised in 2014) includes a
30-year equipment life for SCR.\55\ Therefore, the EPA also calculated
the annualized costs to install SCR using a 30-year equipment life to
be $8,862,953 per year. Thus, the average cost-effectiveness for SNCR,
SCR (20-year life), and SCR (30-year life) are $3,488 per ton, $6,251
per ton, and $5,551 per ton, respectively. The incremental cost-
effectiveness \56\ of installing SCR compared to an SNCR is $7,583 per
ton for SCR (20-year life) and $6,602 per ton for SCR (30-year life).
Costs of compliance for Dave Johnston Unit 3 NO<INF>X</INF> BART are
summarized in table 1.\57\
---------------------------------------------------------------------------

\53\ In the 2014 Final Rule, the EPA estimated the
NO<INF>X</INF> reduction from SNCR for Dave Johnston to be
approximately 25 percent of the initial NO<INF>X</INF> rate of 0.22
lb/MMBtu (annual average) based on review of similar units (78 FR
34748). Per the EPA's Control Cost Manual, a 0.05 lb/MMBtu (annual
average) should be obtainable by a power plant boiler with an SCR
system. (EPA, Cost Control Manual. Section 4, Chapter 2, June 2019,
page 57, available at <a href="https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf">https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf</a>.
\54\ Wyoming EGU BART and Reasonable Progress Costs. (79 FR
5039; October 28, 2013).
\55\ U.S. Environmental Protection Agency. Cost Control Manual.
Section 4, Chapter 2, June 2019, page 80, available at <a href="https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf">https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf</a>.
\56\ The incremental cost effectiveness calculation compares the
costs and performance level of a control option to the costs and
performance level of the next most stringent option. BART
Guidelines, 40 CFR part 51 appendix Y.
\57\ Wyoming EGU BART and Reasonable Progress Costs. (79 FR
5039; October 28, 2013).

Table 1--Summary of Dave Johnston Unit 3 NOX BART Cost Analysis
----------------------------------------------------------------------------------------------------------------
Emission rate (lb/ Emission Average cost- Incremental cost-
Control technology MMBtu; annual reduction Annualized effectiveness ($/ effectiveness ($/
average) (tons/year) costs ton) ton)
----------------------------------------------------------------------------------------------------------------
Baseline (LNB/OFA).......... 0.22 N/A N/A N/A N/A
SNCR........................ 0.16 519 $1,810,782 $3,488 .................
SCR (20-year life).......... 0.05 1,597 9,980,337 6,251 $7,583
SCR (30-year life).......... 0.05 1,597 8,862,953 5,551 6,602
----------------------------------------------------------------------------------------------------------------

Notably, the EPA's NO<INF>X</INF> BART determination relies on the
baseline NO<INF>X</INF> rate of 0.22 lb/MMBtu (annual average)
contained in the 2014 Final Rule as opposed to the proposed 0.23 lb/
MMBtu (30-day rolling average) NO<INF>X</INF> emission limit.
Generally, the NO<INF>X</INF> annual average emission rate is based on
the expected annual emission performance under a 30-day rolling average
emission rate. The latter value will be higher than the former because
of the shorter averaging period and a margin for compliance. For
example, Dave Johnston Unit 3 is generally able to achieve a 30-day
rolling average NO<INF>X</INF> emission rate of 0.23 lb/MMBtu and an
annual average emission rate of between 0.20 to 0.21 lb/MMBtu.\58\
Thus, the proposed 0.23 lb/MMBtu (30-day rolling average) reflects a
more conservative annual NO<INF>X</INF> emission rate than the 0.22 lb/
MMBtu (annual average) that was used in the 2014 Final Rule and in this
proposed revision for purposes of calculating the costs of compliance
contained in table 1.
---------------------------------------------------------------------------

\58\ 2020-2025 Dave Johnston Emissions, Clean Air Markets
Program Data (CAMPD) (March 13, 2026).
---------------------------------------------------------------------------

As described in section III.E of this preamble and consistent with
other BART actions, the EPA proposes to find that neither SNCR nor SCR
are cost effective when compared to the associated visibility
improvement.

B. Energy and Non-Air Quality Environmental Impacts of Compliance

In its March 2026 letter to the EPA withdrawing its consent to the
closure of Dave Johnston Unit 3, PacifiCorp noted the recent increase
in energy demand. Specifically, PacifiCorp noted that the North
American Electric Reliability Corporation's (NERC) 2024 Long-Term
Reliability Assessment, which includes Wyoming and other western
States, describes the need for replacement of five gigawatts of
baseload resource retirements, anticipated between 2024 and 2028 in the
region.\59\
---------------------------------------------------------------------------

\59\ North American Electric Reliability Corporation. 2024 Long-
Term Reliability Assessment at 128. (December 2024).
---------------------------------------------------------------------------

PacifiCorp's 2025 IRP projects increasing system-wide retail sales
with a compounded annual growth rate of 2.17 percent between 2024 and
2033 and a compounded annual growth rate of 1.35 percent between 2024
and 2042, which reflects a noticeable increase in forecasted growth
from previous forecasts.60 61 According to PacifiCorp's 2025
IRP, growth is driven, in part, by ``significant new data center loads

[[Page 34594]]

coming online in the 2027-2033 timeframe.'' \62\
---------------------------------------------------------------------------

\60\ PacifiCorp 2025 Integrated Resource Plan, Appendix A.
(January 30, 2026).
\61\ Letter from Jayson Branch, Senior Vice President, Power
Supply, PacifiCorp, to Cyrus Western, U.S. EPA Regional
Administrator at 8. (March 4, 2026).
\62\ PacifiCorp 2025 Integrated Resource Plan at 6. (March 31,
2025).
---------------------------------------------------------------------------

PacifiCorp states that Dave Johnston Unit 3 is ``uniquely poised to
respond to these growing demand needs'' because, in part, it has an
operating range of 90-220 MW of dispatchable generation that allows
Unit 3 to generate more or less power to respond to changes in energy
demand, including accommodating intermittent wind generation.\63\
Additionally, Dave Johnston Unit 3 also provides frequency response--an
automatic, rapid adjustment of power output to stabilize grid
frequency--making it ``uniquely capable of offsetting unanticipated
reductions in wind generation,'' according to PacifiCorp.\64\
---------------------------------------------------------------------------

\63\ Letter from Jayson Branch, Senior Vice President, Power
Supply, PacifiCorp, to Cyrus Western, U.S. EPA Regional
Administrator at 9. (March 4, 2026).
\64\ Id.
---------------------------------------------------------------------------

The EPA recognizes that any source that previously decided to close
could determine in the future that closure is no longer appropriate. As
PacifiCorp notes in its March 2026 letter to the EPA, the demand for
electricity is rising. Executive Order 14261, Reinvigorating America's
Beautiful Clean Coal Industry and Amending Executive Order 14241,
states that ``[o]ur Nations' beautiful clean coal resources will be
critical to meeting the rise in electricity demand due to the
resurgence of domestic manufacturing and the construction of artificial
intelligence data processing centers'' and power generated from coal
resources is critical to addressing this surging demand and a matter of
national interest, national security, and energy policy.\65\
---------------------------------------------------------------------------

\65\ Executive Order 14261, Reinvigorating America's Beautiful
Clean Coal Industry and Amending Executive Order 14241, 90 FR 15517
(April 14, 2025). <a href="https://www.whitehouse.gov/presidential-actions/2025/04/reinvigorating-americas-beautiful-clean-coal-industry-and-amending-executive-order-14241/">https://www.whitehouse.gov/presidential-actions/2025/04/reinvigorating-americas-beautiful-clean-coal-industry-and-amending-executive-order-14241/</a>.
---------------------------------------------------------------------------

The EPA does not encourage electric generating facilities to close
in the face of this energy demand. Moreover, the EPA does not expect an
electrical generating facility to close in order to comply with the
CAA's regional haze requirements. Voluntary source retirement and
replacement is much different from enforceable, unconsented closures,
which neither the RHR nor the CAA's regional haze provisions reference
or contemplate in any manner. Furthermore, the EPA is unaware of any
instance where the Agency has approved a SIP revision containing a
forced, unconsented closure. Finally, although there are identified
energy impacts from potential emission controls (e.g., parasitic energy
requirements to operate SCR), the EPA did not identify any ``energy and
non-air quality environmental impacts of compliance'' that would
preclude the selection of any of the emission controls evaluated.

C. Pollution Control Equipment in Use at the Source

Dave Johnston Unit 3 currently employs LNB/OFA for control of
NO<INF>X</INF> emissions, which was installed in 2010. As part of the
installation of LNB/OFA, PacifiCorp converted the boiler configuration
from a cell boiler to a dry-bottom wall-fired configuration.\66\ Based
on the current boiler configuration, PacifiCorp provided information
from the EPA's Clean Air Markets Program Data (CAMPD) that LNB/OFA has
consistently achieved an emission limit of 0.23 lb/MMBtu (30-day
rolling average) since installation in 2010.\67\
---------------------------------------------------------------------------

\66\ Id.
\67\ Id.
---------------------------------------------------------------------------

As previously stated, the EPA accounted for the ``pollution
equipment in use at the source'' in the Agency's adjustment of the
baseline to reflect the pollution equipment currently installed. In
doing so, the EPA finds that the Agency's proposed BART determination
for Dave Johnston Unit 3, as described in section III of this preamble,
is consistent with the Ninth Circuit's decision. Dave Johnston Unit 3
has achieved NO<INF>X</INF> emission reductions using technology (LNB/
OFA) that it has no plans to deactivate. Additionally, there is no
reason to believe that PacifiCorp would remove the combustion controls
it has already installed, given that PacifiCorp received a Wyoming 2008
construction permit to construct those control technologies.\68\ This
is further demonstrated by Dave Johnston Unit 3 maintaining its
existing NO<INF>X</INF> emissions close to 0.23 lb/MMBtu (30-day
rolling average) for the last 15 years since its installation of LNB/
OFA.\69\ If this proposed rule is finalized as proposed, Dave Johnston
Unit 3 would be required to continue to meet a 0.23 lb/MMBtu (30-day
rolling average) NO<INF>X</INF> emission limit by the compliance date.
---------------------------------------------------------------------------

\68\ Wyoming permit number MD-5098. (June 27, 2008).
\69\ 2010-2025 Dave Johnston Emissions. CAMPD. (April 17, 2026).
---------------------------------------------------------------------------

D. Remaining Useful Life of the Source

With this proposed action, the EPA is proposing to withdraw the
requirement to permanently close Dave Johnston Unit 3 by December 31,
2027, because the source no longer consents to closure.\70\ As
previously stated in section III.B of this preamble, the EPA does not
expect an electrical generating facility to close in order to comply
with the CAA's regional haze requirements. Thus, because the proposal
removes the enforceable closure for Dave Johnston Unit 3, the remaining
useful life is based on the useful life of the control equipment.\71\
Therefore, for the remaining useful life for evaluation of controls
consistent with the Control Cost Manual, the BART Guidelines, and the
2014 Final Rule, the EPA evaluated both 20-years (for SNCR and SCR) and
30-years (for SCR).\72\ Those 20-year and/or 30-year lifetime of the
emission controls assumptions are accounted for in the cost
calculations for both SNCR and SCR controls.
---------------------------------------------------------------------------

\70\ See section II.C of this preamble.
\71\ BART Guidelines, 40 CFR part 51 appendix Y section
IV.D.4.k.
\72\ U.S. Environmental Protection Agency. Control Cost Manual.
Available at <a href="https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf">https://www.epa.gov/sites/default/files/2017-12/documents/scrcostmanualchapter7thedition_2016revisions2017.pdf</a>; BART
Guidelines, 40 CFR part 51 appendix Y; 79 FR 5032 (January 30,
2014).
---------------------------------------------------------------------------

E. Degree of Improvement in Visibility

The EPA relied on CALPUFF \73\ used in the 2014 Final Rule \74\ and
adjusted the baseline to reflect the inclusion of the pollution control
equipment in use at the source (LNB/OFA) when determining visibility
improvement. The 2014 model included visibility impacts from Dave
Johnston Unit 3 to Badlands National Park, Wind Cave National Park,
Mount Zirkel Wilderness Area, Rawah Wilderness Area, and Rocky Mountain
National Park. The modeling indicated that visibility impact was
greatest at Wind Cave National Park. The visibility improvement (delta
deciviews) for Dave Johnston Unit 3 with LNB/OFA as baseline controls
is summarized in table 2.\75\
---------------------------------------------------------------------------

\73\ CALPUFF is a multi-layer, multi-species non-steady state
puff dispersion model that simulates the effects of time and space
varying meteorological conditions on pollution transport,
transformation, and removal. <a href="https://www.epa.gov/scram/air-quality-dispersion-modeling-alternative-models">https://www.epa.gov/scram/air-quality-dispersion-modeling-alternative-models</a>.
\74\ Modeling in the 2014 Final Rule predicted visibility
improvement for each emissions control technology at each of the
Class I areas that the EPA modeled in the Agency's analysis of the
Dave Johnston power plant.
\75\ Air Quality Modeling Protocol. Wyoming Regional Haze
Federal Implementation Plan. (79 FR 5039; January 2014).

[[Page 34595]]

Table 2--Summary of Dave Johnston Unit 3 NOX BART Visibility Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
Wind Cave Badlands Rocky Mountain Rawah Wilderness Mount Zirkel
Control technology National Park National Park National Park Area Wilderness Area
--------------------------------------------------------------------------------------------------------------------------------------------------------
Visibility improvement (delta deciview for the maximum 98th percentile impact)
--------------------------------------------------------------------------------------------------------------------------------------------------------
SNCR.......................................................... 0.06 0.06 0.03 0.05 0.02
SCR........................................................... 0.18 0.17 0.10 0.14 0.06
--------------------------------------------------------------------------------------------------------------------------------------------------------

While all five BART statutory factors must be considered when
determining BART, the average cost-effectiveness value is weighed
against the expected visibility improvement from the controls to
determine if the potential control is overall ``cost-effective.''
Additionally, to promote consistency, the facts of each BART decision
can be compared to previous BART decisions by both States and the EPA.
As shown in table 1, the EPA evaluated NO<INF>X</INF> emission
controls, SNCR and SCR, from the baseline reflecting the currently
installed LNB/OFA emission controls.
First, the EPA evaluated SNCR as a potential BART control. For Dave
Johnston Unit 3, the average cost-effectiveness associated with the
installation of SNCR is $3,488 per ton with an associated visibility
improvement of only 0.06 deciviews. This is similar to the installation
of SNCR on Colorado's Comanche Unit 1 for which the average cost-
effectiveness was $3,644 per ton with an associated visibility
improvement of 0.11 deciviews. In 2012, the EPA agreed with Colorado
that based on its consideration of the five factors, the NO<INF>X</INF>
BART emission limit for Comanche Unit 1, a tangentially fired
boiler,\76\ is 0.20 lb/MMBtu (30-day rolling average)--and not SNCR--
which can be achieved through the operation of existing LNBs.\77\
Although other alternatives, including SNCR, achieve more emission
reductions, Colorado determined, and the EPA agreed, that the added
expense of achieving lower limits through different controls was not
reasonable based on the ``high cost effectiveness coupled with the low-
visibility (under 0.20 deciview) afforded.'' \78\ Here, the average
cost-effectiveness value is similar, but the visibility benefit from
the addition of SNCR is half as much, at only 0.06 deciviews.
Similarly, in the 2014 Final Rule, the EPA found it unreasonable to
require SNCR on Naughton Units 1 and 2 due to the ``very low''
incremental visibility improvement of 0.10 deciviews across both units
(0.04 deciviews for Unit 1; 0.06 deciviews for Unit 2).\79\ Therefore,
this proposed action is consistent with historical BART decisions on
sources for which controls were found not to be BART due to the very
small visibility benefits of installing controls.
---------------------------------------------------------------------------

\76\ 77 FR 18065 (March 26, 2012).
\77\ 77 FR 76871 (December 31, 2012).
\78\ 77 FR 18066 (March 26, 2012).
\79\ 79 FR 5050 (January 30, 2014).
---------------------------------------------------------------------------

Next, the EPA evaluated SCR as a potential control. For Dave
Johnston Unit 3, the installation of SCR would result in a modest
increase in visibility improvement of 0.12 deciviews compared to SNCR
and 0.18 deciviews compared to the LNB/OFA baseline with an average
cost-effectiveness of $6,251 per ton (20-year life) and $5,551 per ton
(30-year life). In this case, the cost-effectiveness of SCR is similar
to the installation of SCR on Colorado's Martin Drake Units 5, 6, and 7
of $7,314 per ton, $5,395 per ton, and $4,981 per ton, respectively. In
2012, the EPA agreed with Colorado that SCR was not cost effective on
Martin Drake Units 5, 6, and 7 when compared with the associated
visibility improvement of 0.12 deciviews, 0.27 deciviews, and 0.37
deciviews, respectively.\80\ Similarly, the EPA also determined that
Colorado reasonably considered the five BART statutory factors when
Colorado determined SCR was not reasonable at Craig Units 1 and 2 due
to the ``high cost-effectiveness value[s]'' of $6,432 per ton and
$6,299 per ton, respectively, despite an associated visibility
improvement of 1.01 deciviews for each unit.\81\ The cost-effectiveness
values at Craig Units 1 and 2 are almost identical to the cost-
effectiveness of the installation of SCR at Dave Johnston Unit 3 at
$6,251 per ton (using the same 20-year amortization period as
Colorado), while the associated visibility improvement is significantly
less at Dave Johnston Unit 3 at only 0.18 deciviews. Again, the average
cost-effectiveness of SCR for Dave Johnston Unit 3 is similar to the
average cost-effectiveness at other BART sources for which the EPA
determined SCR was not cost effective, and the potential visibility
benefit from SCR at Dave Johnston Unit 3 is considerably smaller than
at these same BART sources. In conclusion, based on considering the
average cost-effectiveness and expected visibility improvement, the EPA
finds that neither SNCR nor SCR are reasonable.
---------------------------------------------------------------------------

\80\ 77 FR 76871 (December 31, 2012).
\81\ 77 FR 18068 (March 26, 2012).
---------------------------------------------------------------------------

F. Conclusion

Based on the EPA's consideration of the CAA and BART Guidelines and
evaluation of the five BART factors (cost of controls, predicted
visibility improvement, energy and non-air quality environmental
impacts of compliance, pollution control currently in use, and
remaining useful life), the Agency proposes to find that a
NO<INF>X</INF> emission limit of 0.23 lb/MMBtu (30-day rolling
average), consistent with the continued operation of LNB/OFA combustion
controls, is NO<INF>X</INF> BART for Dave Johnston Unit 3. The proposed
emission limit is consistent with a rate that Dave Johnston Unit 3 has
consistently achieved since installation of the LNB/OFA and is equal to
the presumptive NO<INF>X</INF> BART limit for a dry-bottom, wall-fired
boiler burning sub-bituminous coal in the BART Guidelines.\82\
Additionally, PacifiCorp recently submitted a permit application to
Wyoming requesting a revised NO<INF>X</INF> emission limit for Dave
Johnston Unit 3 of 0.23 lb/MMBtu based on a 30-day rolling average.\83\
To ensure uninterrupted implementation of NO<INF>X</INF> BART at Dave
Johnston Unit 3, and because Unit 3 can already meet the proposed limit
without any upgrades or changes in operation, the EPA proposes to
require compliance upon the effective date of the final rule.\84\
---------------------------------------------------------------------------

\82\ BART Guidelines, 40 CFR part 51 appendix Y, table 1.
Presumptive NO<INF>X</INF> Emission Limits for BART-Eligible Coal-
Fired Units.
\83\ Letter from Jayson Branch, Senior Vice President, Power
Supply, PacifiCorp, to Cyrus Western, U.S. EPA Regional
Administrator, Attachment 2 at 15. (March 4, 2026).
\84\ The effective date of the final rule will be 30 days after
publication in the Federal Register.
---------------------------------------------------------------------------

IV. Coordination With FLMs

There are seven Class I areas in the State of Wyoming. The U.S.
Forest Service (USFS) manages the Bridger Wilderness, Fitzpatrick
Wilderness, North Absaroka Wilderness, Teton Wilderness, and the
Washakie Wilderness. The U.S. National Park

[[Page 34596]]

Service manages the Grand Teton National Park and Yellowstone National
Park.
There are obligations to consult on the plan revisions under CAA
section 169A(d) and associated regulations found at 40 CFR 51.308(i).
Thus, the EPA consulted with the USFS, the U.S. Fish and Wildlife
Service, and the U.S. National Park Service on the proposed FIP
revision. The EPA described the proposed revisions with the USFS, the
Fish and Wildlife Service, and the National Park Service on April 13,
2026, and provided a summary of the conclusions and recommendations of
the FLMs along with a description of how the Agency addressed the
comments in the docket for this action.\85\ Therefore, the EPA met the
obligations under 40 CFR 51.308(i)(2) and (3) and CAA 169A(d).
---------------------------------------------------------------------------

\85\ Summary of FLM Conclusions and Recommendations and How the
EPA Addressed the Comments. (May 2026). Available in the docket for
this rulemaking at Docket ID No. EPA-R08-OAR-2026-1651.
---------------------------------------------------------------------------

V. Clean Air Act Section 110(l)

Under CAA section 110(l), the EPA cannot approve a plan revision
``if the revision would interfere with any applicable requirement
concerning attainment and reasonable further progress (as defined in
section 7501 of this title), or any other appliable requirement of this
chapter.'' \86\ The EPA proposes to find that these revisions satisfy
section 110(l). The previous section of this preamble explains how the
proposed FIP revision will comply with applicable regional haze
requirements and general implementation plan requirements such as
enforceability. With respect to requirements concerning attainment and
reasonable further progress, the FIP, as revised by this action, will
not result in an increase in emissions compared to historical levels.
In addition, the area where the Dave Johnston power plant is located is
in attainment for all National Ambient Air Quality Standards (NAAQS).
Thus, the revision will ensure no increases in NO<INF>X</INF> emissions
compared to historical levels in an area that has not been designated
nonattainment for any NAAQS.
---------------------------------------------------------------------------

\86\ Note that ``reasonable further progress'' as used in CAA
section 110(l) is a reference to that term as defined in section
301(a) (i.e., 42 U.S.C. 7501(a)), and as such means reductions
required to attain the National Ambient Air Quality Standards
(NAAQS) set for criteria pollutants under CAA section 109. This term
as used in CAA section 110(l) (and defined in CAA section 301(a)) is
not synonymous with ``reasonable progress'' as that term is used in
the regional haze program. Instead, CAA section 110(l) provides that
the EPA cannot approve plan revisions that interfere with regional
haze requirements (including reasonable progress requirements)
insofar as they are ``other applicable requirement[s]'' of the CAA.
---------------------------------------------------------------------------

VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

This action is not a significant regulatory action and was
therefore not submitted to the Office of Management and Budget (OMB)
for review.

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

This action is expected to be an Executive Order 14192 deregulatory
action. This proposed rule is expected to provide burden reduction by
revising the NO<INF>X</INF> BART determination for, and not requiring
the contested closure of, Dave Johnston Unit 3.

C. Paperwork Reduction Act (PRA)

This proposed rule does not impose an information collection burden
under the provisions of the Paperwork Reduction Act of 1995 (44 U.S.C.
3501 et seq.).

D. Regulatory Flexibility Act (RFA)

I certify that this action will not have a significant economic
impact on a substantial number of small entities under the RFA (5
U.S.C. 601 et seq.). This action will not impose any requirements on
small entities. This action will establish an emission limit for one
electric generating unit. This unit is not owned by a small entity, and
therefore, there are no impacts on small entities.

E. Unfunded Mandates Reform Act (UMRA)

This action does not contain any unfunded mandate as described in
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect
small governments. The action imposes no enforceable duty on any State,
local, or Tribal governments or the private sector.

F. Executive Order 13132: Federalism

This action does not have federalism implications as it revises an
already existing FIP. 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.

G. 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 proposed rule.

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

This action is not subject to Executive Order 13045 because it is
not 3(f)(1) significant as defined in Executive Order 12866, and
because the EPA does not believe the environmental health or safety
risks addressed by this action present a disproportionate risk to
children.

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

This action is not subject to Executive Order 13211 because it is
not a significant regulatory action under Executive Order 12866. This
action will not have a significant adverse effect on the supply,
distribution, or use of energy as, if finalized, it would result in
additional electricity generation remaining on the grid.

J. National Technology Transfer Advancement Act

This rulemaking does not involve technical standards.

List of Subjects in 40 CFR Part 52

Environmental protection, Air pollution control, Ammonia, Carbon
oxides, Incorporation by reference, Intergovernmental relations, Lead,
Nitrogen oxides, Ozone, Particulate matter, Reporting and recordkeeping
requirements, Sulfur oxides, Volatile organic compounds.

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

Lee Zeldin,
EPA Administrator.

For the reasons stated in the preamble, the Environmental
Protection Agency is proposing to amend 40 CFR part 52 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 ZZ--Wyoming

0
2. In Sec. 52.2636:
0
a. Table 2 in paragraph (c)(1) is amended by:
0
i. Revising the entry ``PacifiCorp Dave Johnston Unit 3'';
0
ii. Adding footnote ``5'' in numerical order; and

[[Page 34597]]

0
iii. Removing footnote ``*''; and
0
b. Removing paragraph (d)(4).
The revisions and additions read as follows:

Sec. 52.2636 Implementation plan for regional haze.

* * * * *
(c) * * *

Table 2 to Sec. 52.2636 [Emission Limits and Required Control Technologies for BART Units for Which the EPA Disapproved the State's BART Determination
and Implemented a FIP]
--------------------------------------------------------------------------------------------------------------------------------------------------------
SO2 emission limit--lb/MMBtu
Source name/BART unit NOX required control NOX emission limit--lb/MMBtu (30- (averaged annually across Units
technology day rolling average) 1 and 2)
--------------------------------------------------------------------------------------------------------------------------------------------------------

* * * * * * *
PacifiCorp Dave Johnston Unit 3.............................. N/A 0.23 \5\ N/A

* * * * * * *
--------------------------------------------------------------------------------------------------------------------------------------------------------
\5\ By [DATE 30 DAYS AFTER DATE OF PUBLICATION OF FINAL RULE].

* * * * *
[FR Doc. 2026-11436 Filed 6-5-26; 8:45 am]
BILLING CODE 6560-50-P

</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>

View on FederalRegister.gov →Plain-text source

Indexed from Federal Register on June 8, 2026.

This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.