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Proposed Rule2024-18462

Air Plan Partial Approval and Partial Disapproval; Utah; Regional Haze State Implementation Plan for the Second Implementation Period; Air Plan Disapproval; Utah; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards

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Published

August 19, 2024

Issuing agencies

Environmental Protection Agency

Abstract

In this notice of proposed rulemaking, the Environmental Protection Agency (EPA) is proposing to act on two Utah State implementation plan (SIP) submissions related to visibility protection. First, we are proposing to partially approve and partially disapprove a regional haze SIP submission for the second implementation period that Utah submitted on August 2, 2022. The regional haze SIP submission addresses the requirement that states revise their long-term strategies every implementation period to make reasonable progress towards the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility, including regional haze, in mandatory Class I Federal areas. Utah's regional haze SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. The EPA is taking this action on Utah's regional haze SIP submission pursuant to the Clean Air Act (CAA or the Act). Second, the EPA is proposing to disapprove a portion of Utah's infrastructure SIP submission submitted on January 9, 2020, to address the applicable requirements of CAA section 110(a)(2) for the 2015 Ozone National Ambient Air Quality Standards (NAAQS). Our proposed disapproval is based on CAA section 110(a)(2)(D)(i)(II)'s requirement that a state's SIP contain adequate provisions prohibiting emissions that will interfere with measures to protect visibility required to be included in any other state's SIP (known as interstate transport "prong 4"). The EPA is taking this action on Utah's infrastructure SIP submission pursuant to section 110 of the CAA.

Full Text

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<title>Federal Register, Volume 89 Issue 160 (Monday, August 19, 2024)</title>
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[Federal Register Volume 89, Number 160 (Monday, August 19, 2024)]
[Proposed Rules]
[Pages 67208-67255]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-18462]

[[Page 67207]]

Vol. 89

Monday,

No. 160

August 19, 2024

Part III

Environmental Protection Agency

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40 CFR Part 52

Air Plan Partial Approval and Partial Disapproval; Utah; Regional Haze
State Implementation Plan for the Second Implementation Period; Air
Plan Disapproval; Utah; Interstate Transport of Air Pollution for the
2015 8-Hour Ozone National Ambient Air Quality Standards; Proposed Rule

Federal Register / Vol. 89, No. 160 / Monday, August 19, 2024 /
Proposed Rules

[[Page 67208]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R08-OAR-2024-0389; FRL-12173-01-R8]

Air Plan Partial Approval and Partial Disapproval; Utah; Regional
Haze State Implementation Plan for the Second Implementation Period;
Air Plan Disapproval; Utah; Interstate Transport of Air Pollution for
the 2015 8-Hour Ozone National Ambient Air Quality Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: In this notice of proposed rulemaking, the Environmental
Protection Agency (EPA) is proposing to act on two Utah State
implementation plan (SIP) submissions related to visibility protection.
First, we are proposing to partially approve and partially disapprove a
regional haze SIP submission for the second implementation period that
Utah submitted on August 2, 2022. The regional haze SIP submission
addresses the requirement that states revise their long-term strategies
every implementation period to make reasonable progress towards the
national goal of preventing any future, and remedying any existing,
anthropogenic impairment of visibility, including regional haze, in
mandatory Class I Federal areas. Utah's regional haze SIP submission
also addresses other applicable requirements for the second
implementation period of the regional haze program. The EPA is taking
this action on Utah's regional haze SIP submission pursuant to the
Clean Air Act (CAA or the Act). Second, the EPA is proposing to
disapprove a portion of Utah's infrastructure SIP submission submitted
on January 9, 2020, to address the applicable requirements of CAA
section 110(a)(2) for the 2015 Ozone National Ambient Air Quality
Standards (NAAQS). Our proposed disapproval is based on CAA section
110(a)(2)(D)(i)(II)'s requirement that a state's SIP contain adequate
provisions prohibiting emissions that will interfere with measures to
protect visibility required to be included in any other state's SIP
(known as interstate transport ``prong 4''). The EPA is taking this
action on Utah's infrastructure SIP submission pursuant to section 110
of the CAA.

DATES: Written comments must be received on or before September 18,
2024.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2024-0389 at <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="https://www.regulations.gov">https://www.regulations.gov</a>. The EPA may
publish any comment received to its public docket. Do not submit
electronically any information you consider to be Confidential Business
Information (CBI) or other information whose disclosure 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 public comment policy of the EPA, 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>.
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
whose disclosure 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: Clayton Bean, U.S. Environmental
Protection Agency, Region 8, Air and Radiation Division; 1595 Wynkoop
Street, Denver, Colorado 80202-1129; telephone: (303) 312-6143; email
address: <a href="/cdn-cgi/l/email-protection#4b292e2a256528272a323f24250b2e3b2a652c243d">[email&#160;protected]</a>.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. What action is the EPA proposing?
II. Background and Requirements for Regional Haze Plans
A. Regional Haze Background
B. Roles of Agencies in Addressing Regional Haze
C. Background on Utah's First Implementation Period SIP
D. Utah's Second Implementation Period SIP Submission
III. Requirements for Regional Haze Plans for the Second
Implementation Period
A. Identification of Class I Areas
B. Calculations of Baseline, Current, and Natural Visibility
Conditions; Progress to Date; and the Uniform Rate of Progress
C. Long-Term Strategy for Regional Haze
D. Reasonable Progress Goals
E. Monitoring Strategy and Other State Implementation Plan
Requirements
F. Requirements for Periodic Reports Describing Progress Towards
the Reasonable Progress Goals
G. Requirements for State and Federal Land Manager Coordination
IV. The EPA's Evaluation of Utah's Regional Haze Submission for the
Second Implementation Period
A. Identification of Class I Areas
B. Calculations of Baseline, Current, and Natural Visibility
Conditions; Progress to Date; and the Uniform Rate of Progress
C. Long-Term Strategy
D. Reasonable Progress Goals
E. Reasonably Attributable Visibility Impairment
F. Monitoring Strategy and Other State Implementation Plan
Requirements
G. Requirements for Periodic Reports Describing Progress Towards
the Reasonable Progress Goals
H. Requirements for State and Federal Land Manager Coordination
V. Interstate Transport Prong 4 (Visibility) for the 2015 Ozone
NAAQS Infrastructure SIP
A. Infrastructure SIPs
B. Prong 4 Requirements
C. Utah's Prong 4 Elements
D. The EPA's Evaluation of Utah's Submittal
VI. Proposed Action
VII. Environmental Justice
VIII. Statutory and Executive Order Reviews

I. What action is the EPA proposing?

In this notice of proposed rulemaking, the EPA is proposing to take
action on two Utah SIP submissions related to visibility protection.
First, as detailed in section IV., the EPA's Evaluation of Utah's
Regional Haze Submission for the Second Implementation Period, we are
proposing to partially approve and partially disapprove Utah's regional
haze second implementation period SIP submission. Second, as a
consequence of our proposed partial disapproval of the regional haze
SIP submission and as detailed in section V. of this document, we are
proposing to disapprove a portion of Utah's infrastructure SIP for the
2015 ozone NAAQS.
On August 2, 2022, the Utah Department of Environmental Quality's
Division of Air Quality (DAQ) submitted a SIP submission to the EPA to
address regional haze for the second implementation period. Utah made
this SIP submission to satisfy the requirements of the CAA's regional
haze program pursuant to CAA sections 169A and 169B and 40 CFR
51.308(f). The EPA is proposing to approve the portions of Utah's
Regional Haze SIP

[[Page 67209]]

submission relating to 40 CFR 51.308(f)(1): calculations of baseline,
current, and natural visibility conditions, progress to date, and the
uniform rate of progress; (f)(4): reasonably attributable visibility
impairment; (f)(5) and (g): progress report requirements; and (f)(6):
monitoring strategy and other implementation plan requirements. The EPA
is proposing disapproval for the portions of Utah's regional haze SIP
submission relating to 40 CFR 51.308(f)(2): long-term strategy; (f)(3):
reasonable progress goals; and (i): FLM consultation. Consistent with
section 110(k)(3) of the CAA, the EPA may partially approve portions of
a SIP submittal if those elements meet all applicable requirements and
may disapprove the remainder so long as the elements are fully
separable.
Additionally, the EPA proposes to disapprove a portion of Utah's
January 9, 2020 infrastructure SIP submission for the 2015 ozone NAAQS
that addresses interstate transport of visibility impairing pollutants.
Utah submitted this SIP submission to address the applicable
requirements of CAA section 110(a)(2) for the 2015 ozone NAAQS. We
propose to disapprove the portion of the infrastructure SIP submission
addressing interstate transport of visibility impairing pollutants for
not meeting the requirements of CAA section 110(a)(2)(D)(i)(II).

II. Background and Requirements for Regional Haze Plans

A. Regional Haze Background

In the 1977 CAA amendments, Congress created a program for
protecting visibility in the nation's mandatory Class I Federal areas,
which include certain national parks and wilderness areas.\1\ CAA
section 169A. The CAA establishes 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.'' CAA section 169A(a)(1). The CAA further
directs the EPA to promulgate regulations to assure reasonable progress
toward meeting this national goal. CAA section 169A(a)(4). On December
2, 1980, the EPA promulgated regulations to address visibility
impairment in mandatory Class I Federal areas (hereinafter referred to
as ``Class I areas'') that is ``reasonably attributable'' to a single
source or small group of sources. (45 FR 80084, December 2, 1980).
These regulations, codified at 40 CFR 51.300 through 51.307,
represented the first phase of the EPA's efforts to address visibility
impairment. In 1990, Congress added section 169B to the CAA to further
address visibility impairment, specifically, impairment from regional
haze. CAA section 169B. The EPA promulgated the Regional Haze Rule
(RHR), codified at 40 CFR 51.308 and 51.309,\2\ on July 1, 1999 (64 FR
35714, July 1, 1999). On January 10, 2017, the EPA promulgated
additional regulations that address visibility impairment for the
second and subsequent implementation periods (82 FR 3078, January 10,
2017). These regional haze regulations are a central component of the
EPA's comprehensive visibility protection program for Class I areas.
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\1\ Areas statutorily designated as mandatory Class I Federal
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. CAA
section 162(a). There are 156 mandatory Class I areas. The list of
areas to which the requirements of the visibility protection program
apply is in 40 CFR part 81, subpart D.
\2\ 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 requirements
under 40 CFR 51.309(d)(4) contain general requirements pertaining to
stationary sources and market trading and allow states to adopt
alternatives to the point source application of BART.
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Regional haze is visibility impairment that is produced by a
multitude of anthropogenic sources and activities that are located
across a broad geographic area and that emit pollutants that impair
visibility. Visibility impairing pollutants include fine and coarse
particulate matter (PM) (e.g., sulfates, nitrates, organic carbon,
elemental carbon, and soil dust) and their precursors (e.g., sulfur
dioxide (SO<INF>2</INF>), nitrogen oxides (NO<INF>X</INF>), and, in
some cases, volatile organic compounds (VOC) and ammonia
(NH<INF>3</INF>)). Fine particle precursors react in the atmosphere to
form fine particulate matter (PM<INF>2.5</INF>), which impairs
visibility by scattering and absorbing light. Visibility impairment
reduces the perception of clarity and color, as well as visible
distance.\3\
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\3\ There are several ways to measure the amount of visibility
impairment, i.e., haze. One such measurement is the deciview, which
is the principal metric used by the RHR. Under many circumstances, a
change in one deciview will be perceived by the human eye to be the
same on both clear and hazy days. The deciview is unitless. It is
proportional to the logarithm of the atmospheric extinction of
light, which is the perceived dimming of light due to its being
scattered and absorbed as it passes through the atmosphere.
Atmospheric light extinction (bext) is a metric used for
expressing visibility and is measured in inverse megameters
(Mm-1). The EPA's Guidance on Regional Haze State
Implementation Plans for the Second Implementation Period (``2019
Guidance'') offers the flexibility for the use of light extinction
in certain cases. Light extinction can be simpler to use in
calculations than deciviews, since it is not a logarithmic function.
See, e.g., 2019 Guidance at 16, 19, <a href="https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period">https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period</a>, The EPA Office of Air Quality Planning and
Standards, Research Triangle Park (August 20, 2019). The formula for
the deciview is 10 ln (bext)/10 Mm-1). 40 CFR
51.301.
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To address regional haze visibility impairment, the 1999 RHR
established an iterative planning process that requires both states in
which Class I areas are located and states ``the emissions from which
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 such impairment. CAA section 169A(b)(2); \4\ see also 40 CFR
51.308(b), (f) (establishing submission dates for iterative regional
haze SIP revisions) (64 FR 35768, July 1, 1999). 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,'' CAA section 169A(b)(2)(B); the initial round of SIP submissions
also had to address the statutory requirement that certain older,
larger sources of visibility impairing pollutants install and operate
the best available retrofit technology (BART). CAA section
169A(b)(2)(A); 40 CFR 51.308(d), (e). States' first regional haze SIPs
were due by December 17, 2007, 40 CFR 51.308(b), with subsequent SIP
submissions containing updated long-term strategies originally due July
31, 2018, and every ten years thereafter. (64 FR 35768, July 1, 1999)
The EPA established in the 1999 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.\5\ Id. at
35721.
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\4\ The RHR expresses the statutory requirement for states to
submit plans addressing out-of-state Class I areas by providing that
states must address visibility impairment ``in each mandatory Class
I Federal area located outside the State that may be affected by
emissions from within the State.'' 40 CFR 51.308(d), (f).
\5\ In addition to each of the fifty states, the EPA also
concluded that the Virgin Islands and District of Columbia must also
submit regional haze SIPs because they either contain a Class I area
or contain sources whose emissions are reasonably anticipated to
contribute regional haze in a Class I area. See 40 CFR 51.300(b),
(d)(3).
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Much of the focus in the first implementation period of the
regional haze program, which ran from 2007 through 2018, was on
satisfying states' BART obligations. First implementation period SIPs
were additionally required to contain long-term strategies for

[[Page 67210]]

making reasonable progress toward the national visibility goal, of
which BART is one component. The core required elements for the first
implementation period SIPs (other than BART) are laid out in 40 CFR
51.308(d). Those provisions required that states containing Class I
areas establish reasonable progress goals (RPGs) that are measured in
deciviews and reflect the anticipated visibility conditions at the end
of the implementation period including from implementation of states'
long-term strategies. The first implementation period \6\ RPGs were
required to provide for an improvement in visibility for the most
impaired days over the period of the implementation plan and ensure no
degradation in visibility for the least impaired days over the same
period. In establishing the RPGs for any Class I area in a state, the
state was required to consider four statutory factors: the costs of
compliance, the time necessary for compliance, the energy and non-air
quality environmental impacts of compliance, and the remaining useful
life of any potentially affected sources. CAA section 169A(g)(1); 40
CFR 51.308(d)(1).
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\6\ The EPA uses the terms ``implementation period'' and
``planning period'' interchangeably.
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States were also required to calculate baseline (using the five-
year period of 2000-2004) and natural visibility conditions (i.e.,
visibility conditions without anthropogenic visibility impairment) for
each Class I area, and to calculate the linear rate of progress needed
to attain natural visibility conditions, assuming a starting point of
baseline visibility conditions in 2004 and ending with natural
conditions in 2064. This linear interpolation is known as the uniform
rate of progress (URP) and is used as a tracking metric to help states
assess the amount of progress they are making towards the national
visibility goal over time in each Class I area.\7\ 40 CFR
51.308(d)(1)(i)(B), (d)(2). The 1999 RHR also provided that states'
long-term strategies must include the ``enforceable emissions
limitations, compliance schedules, and other measures as necessary to
achieve the reasonable progress goals.'' 40 CFR 51.308(d)(3). In
establishing their long-term strategies, states are required to consult
with other states that also contribute to visibility impairment in a
given Class I area and include all measures necessary to obtain their
shares of the emission reductions needed to meet the RPGs. 40 CFR
51.308(d)(3)(i), (ii). Section 51.308(d) also contains seven additional
factors states must consider in formulating their long-term strategies
(see 40 CFR 51.308(d)(3)(v)), as well as provisions governing
monitoring and other implementation plan requirements. 40 CFR
51.308(d)(4). Finally, the 1999 RHR required states to submit periodic
progress reports--SIP revisions due every five years that contain
information on states' implementation of their regional haze plans and
an assessment of whether anything additional is needed to make
reasonable progress, see 40 CFR 51.308(g), (h)--and to consult with the
Federal Land Manager(s) \8\ (FLMs) responsible for each Class I area
according to the requirements in CAA section 169A(d) and 40 CFR
51.308(i).
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\7\ The EPA established the URP framework in the 1999 RHR to
provide ``an equitable analytical approach'' to assessing the rate
of visibility improvement at Class I areas across the country. The
starting point for the URP analysis is 2004 and the endpoint was
calculated based on the amount of visibility improvement that was
anticipated to result from implementation of existing CAA programs
over the period from the mid-1990s to approximately 2005. Assuming
this rate of progress would continue into the future, the EPA
determined that natural visibility conditions would be reached in 60
years, or 2064 (60 years from the baseline starting point of 2004).
However, the EPA did not establish 2064 as the year by which the
national goal must be reached. 64 FR 35731-32. That is, the URP and
the 2064 date are not enforceable targets but are rather tools that
``allow for analytical comparisons between the rate of progress that
would be achieved by the state's chosen set of control measures and
the URP. (82 FR 3078, 3084, January 10, 2017).
\8\ The EPA's regulations define ``Federal Land Manager'' as
``the Secretary of the department with authority over the Federal
Class I area (or the Secretary's designee) or, with respect to
Roosevelt-Campobello International Park, the Chairman of the
Roosevelt-Campobello International Park Commission.'' 40 CFR 51.301.
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On January 10, 2017, the EPA promulgated revisions to the RHR (82
FR 3078, January 10, 2017) that apply for the second and subsequent
implementation periods. The 2017 rulemaking made several changes to the
requirements for regional haze SIPs to clarify states' obligations and
streamline certain regional haze requirements. The revisions to the
regional haze program for the second and subsequent implementation
periods focused on the requirement that states' SIPs contain long-term
strategies for making reasonable progress towards the national
visibility goal. The reasonable progress requirements as revised in the
2017 rulemaking (referred to here as the 2017 RHR Revisions) are
codified at 40 CFR 51.308(f). Among other changes, the 2017 RHR
Revisions adjusted the deadline for states to submit their second
implementation period SIPs from July 31, 2018, to July 31, 2021,
clarified the order of analysis and the relationship between RPGs and
the long-term strategy, and focused on making visibility improvements
on the days with the most anthropogenic visibility impairment, as
opposed to the days with the most visibility impairment overall. The
EPA also revised requirements of the visibility protection program
related to periodic progress reports and FLM consultation. The specific
requirements applicable to second implementation period regional haze
SIP submissions are addressed in detail below.
The EPA provided guidance to the states for their second
implementation period SIP submissions in the preamble to the 2017 RHR
Revisions as well as in subsequent, stand-alone guidance documents. In
August 2019, the EPA issued ``Guidance on Regional Haze State
Implementation Plans for the Second Implementation Period'' (``2019
Guidance'').\9\ On July 8, 2021, the EPA issued a memorandum containing
``Clarifications Regarding Regional Haze State Implementation Plans for
the Second Implementation Period'' (``2021 Clarifications Memo'').\10\
Additionally, the EPA further clarified the recommended procedures for
processing ambient visibility data and optionally adjusting the URP to
account for international anthropogenic and prescribed fire impacts in
two technical guidance documents: the December 2018 ``Technical
Guidance on Tracking Visibility Progress for the Second Implementation
Period of the Regional Haze Program'' (``2018 Visibility Tracking
Guidance''),\11\ and the June 2020 ``Recommendation for the Use of
Patched and Substituted Data and Clarification of Data Completeness for
Tracking Visibility Progress for the Second Implementation Period of
the Regional Haze Program'' and associated

[[Page 67211]]

Technical Addendum (``2020 Data Completeness Memo'').\12\
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\9\ Guidance on Regional Haze State Implementation Plans for the
Second Implementation Period. <a href="https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period">https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period</a>. The EPA Office of Air Quality Planning and
Standards, Research Triangle Park (August 20, 2019).
\10\ Clarifications Regarding Regional Haze State Implementation
Plans for the Second Implementation Period. <a href="https://www.epa.gov/system/files/documents/2021-07/clarifications-regarding-regional-haze-state-implementation-plans-for-the-second-implementation-period.pdf">https://www.epa.gov/system/files/documents/2021-07/clarifications-regarding-regional-haze-state-implementation-plans-for-the-second-implementation-period.pdf</a>. The EPA Office of Air Quality Planning and Standards,
Research Triangle Park (July 8, 2021).
\11\ Technical Guidance on Tracking Visibility Progress for the
Second Implementation Period of the Regional Haze Program. <a href="https://www.epa.gov/visibility/technical-guidance-tracking-visibility-progress-second-implementation-period-regional">https://www.epa.gov/visibility/technical-guidance-tracking-visibility-progress-second-implementation-period-regional</a>. The EPA Office of
Air Quality Planning and Standards, Research Triangle Park (December
20, 2018).
\12\ Recommendation for the Use of Patched and Substituted Data
and Clarification of Data Completeness for Tracking Visibility
Progress for the Second Implementation Period of the Regional Haze
Program. <a href="https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program">https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program</a>. The EPA
Office of Air Quality Planning and Standards, Research Triangle Park
(June 3, 2020).
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As explained in the 2021 Clarifications Memo, the EPA intends the
second implementation period of the regional haze program to secure
meaningful reductions in visibility impairing pollutants that build on
the significant progress states have achieved to date. The Agency also
recognizes that analyses regarding reasonable progress are state-
specific and that, based on states' and sources' individual
circumstances, what constitutes reasonable reductions in visibility
impairing pollutants will vary from state-to-state. While there exist
many opportunities for states to leverage both ongoing and upcoming
emission reductions under other CAA programs, the Agency expects states
to undertake rigorous reasonable progress analyses that identify
further opportunities to advance the national visibility goal
consistent with the statutory and regulatory requirements. See
generally 2021 Clarifications Memo. This is consistent with Congress's
determination that a visibility protection program is needed in
addition to the CAA's National Ambient Air Quality Standards and
Prevention of Significant Deterioration programs, as further emission
reductions may be necessary to adequately protect visibility in Class I
areas throughout the country.\13\
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\13\ See, e.g., H.R. Rep. No. 95-294 at 205 (``In determining
how to best remedy the growing visibility problem in these areas of
great scenic importance, the committee realizes that as a matter of
equity, the national ambient air quality standards cannot be revised
to adequately protect visibility in all areas of the country.'')
(``the mandatory Class I increments of [the PSD program] do not
adequately protect visibility in Class I areas'').
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B. Roles of Agencies in Addressing Regional Haze

Because the air pollutants and pollution affecting visibility in
Class I areas can be transported over long distances, successful
implementation of the regional haze program requires long-term,
regional coordination among multiple jurisdictions and agencies that
have responsibility for Class I areas and the emissions that impact
visibility in those areas. To address regional haze, states need to
develop strategies in coordination with one another, considering the
effect of emissions from one jurisdiction on the air quality in
another. Five regional planning organizations (RPOs),\14\ which include
representation from state and Tribal governments, the EPA, and FLMs,
were developed in the lead-up to the first implementation period to
address regional haze. RPOs evaluate technical information to better
understand how emissions from state and tribal land impact Class I
areas across the country, pursue the development of regional strategies
to reduce emissions of particulate matter and other pollutants leading
to regional haze, and help states meet the consultation requirements of
the RHR.
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\14\ RPOs are sometimes also referred to as ``multi-
jurisdictional organizations,'' or MJOs. For the purposes of this
document, the terms RPO and MJO are synonymous.
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The Western Regional Air Partnership (WRAP), one of the five RPOs
described in the previous paragraph, is a collaborative effort of State
governments, local air agencies, Tribal governments, and various
Federal agencies established to initiate and coordinate activities
associated with the management of regional haze, visibility, and other
air quality issues in the western United States. Members include the
States of Alaska, Arizona, California, Colorado, Hawaii, Idaho,
Montana, Nevada, New Mexico, North Dakota, Oregon, South Dakota, Utah,
Washington, Wyoming, and 28 Tribal governments.\15\ The Federal partner
members of WRAP are the EPA, U.S. National Parks Service (NPS), U.S.
Fish and Wildlife Service (USFWS), U.S. Forest Service (USFS), and the
U.S. Bureau of Land Management (BLM).
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\15\ A full list of WRAP members is available at <a href="https://www.westar.org/wrap-council-members/">https://www.westar.org/wrap-council-members/</a>.
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The WRAP membership formed a workgroup to develop a planning
framework for state regional haze second implementation period SIPs.
Based on emissions inventories and monitoring data supplied by its
membership, WRAP produced a technical system to support regional
modeling of visibility impacts at Class I areas across the West. The
WRAP Technical Support System (TSS) consolidated air quality monitoring
data, meteorological and receptor modeling data analyses, emissions
inventories and projections, and gridded air quality/visibility
regional modeling results. The WRAP TSS is accessible by member States
and allows for the creation of maps, figures, and tables to export and
use in SIP development. WRAP TSS also maintains the original source
data for verification and further analysis. Utah relied on the WRAP TSS
products and Interagency Monitoring of Protected Visual Environments
(IMPROVE) data to determine visibility conditions and impacts at in-
state and out-of-state Class I areas.

C. Background on Utah's First Implementation Period SIP

The CAA required that regional haze plans for the first
implementation period include both a long-term strategy for making
reasonable progress and BART requirements for certain older stationary
sources, where applicable.\16\ Utah submitted SIP revisions addressing
regional haze for the first implementation period in September 2008 and
May 2011. In 2012, the EPA partially approved and partially disapproved
Utah's 2008 and 2011 SIP submissions, which included disapproval of
NO<INF>X</INF> and PM BART for subject-to-BART sources.\17\
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\16\ Requirements for regional haze SIPs for the first
implementation period are contained in Clean Air Act section
169A(b)(2). The RHR provided two paths for states to address
regional haze in the first implementation period. Most states must
follow 40 CFR 51.308(d) and (e), which require states to perform
individual point source BART determinations and evaluate the need
for other control strategies. The requirements for addressing
regional haze visibility impairment in the sixteen Class I areas
covered by the Grand Canyon Visibility Transport Commission are
found in 40 CFR 51.309(d)(4), which contains general requirements
pertaining to stationary sources and market trading and allows
states to adopt alternatives to the point source application of
BART. See also 40 CFR 51.308(b). States with Class I areas covered
by the Grand Canyon Visibility Transport Commission could choose to
submit a regional haze SIP under 40 CFR 51.308 or 51.309.
\17\ 77 FR 74355, 74357 (Dec. 14, 2012).
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In June 2015, Utah submitted a SIP revision to address the
NO<INF>X</INF> and PM BART determinations we had previously
disapproved. In 2016, the EPA partially approved and partially
disapproved the June 2015 SIP submission and promulgated a Federal
implementation plan (FIP) for NO<INF>X</INF> BART at Hunter Units 1, 2,
and 3, and Huntington Units 1 and 2.\18\
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\18\ 81 FR 43894, 43896, 43907 (July 5, 2016).
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In 2019, Utah submitted a new SIP revision for NO<INF>X</INF>
BART.\19\ In November 2020, the EPA approved Utah's 2019 SIP submission
and concurrently withdrew the 2016 FIP.\20\
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\19\ On December 3, 2019, Utah submitted a supplement to the
July 3, 2019 SIP submission that included an amendment to the
monitoring, recordkeeping, and reporting requirements.
\20\ 85 FR 75860 (Nov. 27, 2020).
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Utah submitted its first implementation period progress report in
2016 to meet the requirements of 40 CFR 51.308(g) and (h). The progress
report described progress toward the reasonable progress goals and
contained a determination of adequacy of Utah's regional haze SIP to
achieve established goals for visibility improvement and

[[Page 67212]]

emissions reductions. The EPA approved the progress report in 2020.\21\
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\21\ 85 FR 64050 (Oct. 9, 2020).
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D. Utah's Second Implementation Period SIP Submission

In accordance with CAA section 169A and the RHR at 40 CFR
51.308(f), on August 2, 2022, Utah made a SIP submission to the EPA to
address the State's regional haze obligations for the second
implementation period.\22\ Prior to submission, Utah made its draft
regional haze SIP available for public comment from May 1, 2022, to May
31, 2022, and held a public hearing on May 26, 2022. The public
comments and Utah's responses are contained in the State's regional
haze SIP submission and are available in the docket for this action.
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\22\ Utah's regional haze SIP submission comprises several
documents that are available in the docket for this action. The
document titled ``Utah Regional Haze SIP Submittal 2022 v2'' is a
PDF totaling 491 pages that Utah submitted to the EPA on August 2,
2022. This document includes both Utah's final regional haze SIP
narrative (titled ``Utah State Implementation Plan, Regional Haze
Second Implementation Period, Section XX.A'' and dated August 1,
2022) and the draft regional haze SIP that Utah proposed for public
comment in May 2022 during its State public comment process. The EPA
is not evaluating Utah's draft public comment version of the
regional haze SIP. Therefore, for the reader's convenience, we have
included a standalone document in the docket for this action titled
``Final SIP Only--Utah Regional Haze SIP Submittal 2022 v2.'' This
document contains only the submittal letter, Legal Authority, Public
Comments, Final Effective Rule, Final Effective Plans, and
Certification portions of Utah's August 2, 2022 SIP submission. We
created this document to help the public avoid confusion between the
State's public comment draft SIP and final SIP. In this notice of
proposed rulemaking, our references to page numbers in Utah's
regional haze SIP submission are based on the internal pagination of
the ``Utah State Implementation Plan, Regional Haze Second
Implementation Period, Section XX.A'' dated August 1, 2022.
As part of its SIP submission, Utah also submitted a 704-page
PDF titled ``Utah State Implementation Plan Appendices,'' which
contains a collection of technical documents and communications.
This PDF is also available in the docket for this action. Because
many portions of the PDF are illegible due to poor quality, we have
included a legible version of each individual document contained
within the larger ``Utah State Implementation Plan Appendices'' PDF
in the docket for this action. In this notice of proposed
rulemaking, our references to page numbers in appendices to Utah's
regional haze SIP submission are based on the internal pagination of
the legible individual documents.
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Section IV of this document describes Utah's regional haze SIP
submission, including the four-factor analyses conducted by certain
sources that Utah identified as potential contributors to visibility
impairment, and Utah's determinations of the emissions reduction
measures necessary to make reasonable progress based on those analyses.
The regional haze SIP submission also includes Utah's assessment of
progress made since the first implementation period in reducing
emissions of visibility impairing pollutants, as well as visibility
progress at in-state and out-of-state Class I areas. Section IV also
contains the EPA's evaluation of Utah's SIP submission against the
requirements of the CAA and RHR (as described in section III. of this
document). The entirety of Utah's regional haze SIP submission is
included in the docket for this action.
We have also included a Technical Support Document (TSD) in the
docket to provide technical information and analysis supporting our
proposed action on the Utah regional haze SIP submission. The TSD
includes our review of the WRAP analyses that Utah relied on during the
State's regional haze second implementation period SIP development
process.

III. Requirements for Regional Haze Plans for the Second Implementation
Period

Under the CAA and the EPA's regulations, all 50 states, the
District of Columbia, and the U.S. Virgin Islands are required to
submit regional haze SIPs satisfying the applicable requirements for
the second implementation period of the regional haze program by July
31, 2021. Each state's SIP must contain a long-term strategy for making
reasonable progress toward meeting the national goal of remedying any
existing and preventing any future anthropogenic visibility impairment
in Class I areas. CAA section 169A(b)(2)(B). To this end, 40 CFR
51.308(f) lays out the process by which states determine what
constitutes their long-term strategies, with the order of the
requirements in Sec. 51.308(f)(1) through (3) generally mirroring the
order of the steps in the reasonable progress analysis \23\ and (f)(4)
through (6) containing additional, related requirements. Broadly
speaking, a state first must identify the Class I areas within the
state and determine the Class I areas outside the state in which
visibility may be affected by emissions from the state. These are the
Class I areas that must be addressed in the state's long-term strategy.
See 40 CFR 51.308(f) introductory text, (f)(2). For each Class I area
within its borders, a state must then calculate the baseline, current,
and natural visibility conditions for that area, as well as the
visibility improvement made to date and the URP. See 40 CFR
51.308(f)(1). Each state having a Class I area and/or emissions that
may affect visibility in a Class I area must then develop a long-term
strategy that includes the enforceable emission limitations, compliance
schedules, and other measures that are necessary to make reasonable
progress in such areas. A reasonable progress determination is based on
applying the four factors in CAA section 169A(g)(1) to sources of
visibility impairing pollutants that the state has selected to assess
for controls for the second implementation period. Additionally, as
further explained below, the RHR at 40 CFR 51.3108(f)(2)(iv) separately
provides five ``additional factors'' \24\ that states must consider in
developing their long-term strategies. See 40 CFR 51.308(f)(2). A state
evaluates potential emission reduction measures for those selected
sources and determines which are necessary to make reasonable progress.
Those measures are then incorporated into the state's long-term
strategy. After a state has developed its long-term strategy, it then
establishes RPGs for each Class I area within its borders by modeling
the visibility impacts of all reasonable progress controls at the end
of the second implementation period, i.e., in 2028, as well as the
impacts of other requirements of the CAA. The RPGs include reasonable
progress controls not only for sources in the state in which the Class
I area is located, but also for sources in other states that contribute
to visibility impairment in that area. The RPGs are then compared to
the baseline visibility conditions and the URP to ensure that progress
is being made towards the statutory goal of preventing any future and
remedying any existing anthropogenic visibility impairment in Class I
areas. 40 CFR 51.308(f)(2) and (3).
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\23\ The EPA explained in the 2017 RHR Revisions that we were
adopting new regulatory language in 40 CFR 51.308(f) that, unlike
the structure in Sec. 51.308(d), ``tracked the actual planning
sequence.'' 82 FR 3091.
\24\ The five ``additional factors'' for consideration in Sec.
51.308(f)(2)(iv) are distinct from the four factors listed in CAA
section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states must
consider and apply to sources in determining reasonable progress.
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In addition to satisfying the requirements at 40 CFR 51.308(f)
related to reasonable progress, the regional haze SIP revisions for the
second implementation period must address the requirements in Sec.
51.308(g)(1) through (5) pertaining to periodic reports describing
progress towards the RPGs, 40 CFR 51.308(f)(5), as well as requirements
for FLM consultation that apply to all visibility protection SIPs and
SIP revisions. 40 CFR 51.308(i).
A state must submit its regional haze SIP and subsequent SIP
revisions to the EPA according to the requirements applicable to all
SIP revisions under the CAA and the EPA's regulations. See

[[Page 67213]]

CAA section 169A(b)(2); CAA section 110(a). Upon approval by the EPA, a
SIP is enforceable by the Agency and the public under the CAA. If the
EPA finds that a state fails to make a required SIP revision, or if the
EPA finds that a state's SIP is incomplete or if it disapproves the
SIP, the Agency must promulgate a FIP that satisfies the applicable
requirements. CAA section 110(c)(1).

A. Identification of Class I Areas

The first step in developing a regional haze SIP is for a state to
determine which Class I areas, in addition to those within its borders,
``may be affected'' by emissions from within the state. In the 1999
RHR, the EPA determined that all states contribute to visibility
impairment in at least one Class I area (see 64 FR 35720-22), and
explained that the statute and regulations lay out an ``extremely low
triggering threshold'' for determining ``whether States should be
required to engage in air quality planning and analysis as a
prerequisite to determining the need for control of emissions from
sources within their State.'' Id. at 35721.
A state must determine which Class I areas must be addressed by its
SIP by evaluating the total emissions of visibility impairing
pollutants from all sources within the state. While the RHR does not
require this evaluation to be conducted in any particular manner, the
EPA's 2019 Guidance provides recommendations for how such an assessment
might be accomplished, including by, where appropriate, using the
determinations previously made for the first implementation period.
2019 Guidance at 8-9. In addition, the determination of which Class I
areas may be affected by a state's emissions is subject to the
requirement in 40 CFR 51.308(f)(2)(iii) to ``document the technical
basis, including modeling, monitoring, cost, engineering, and emissions
information, on which the State is relying to determine the emission
reduction measures that are necessary to make reasonable progress in
each mandatory Class I Federal area it affects.''

B. Calculations of Baseline, Current, and Natural Visibility
Conditions; Progress to Date; and the Uniform Rate of Progress

As part of assessing whether a SIP submission for the second
implementation period is providing for reasonable progress towards the
national visibility goal, the RHR contains requirements in Sec.
51.308(f)(1) related to tracking visibility improvement over time. The
requirements of this section apply only to states having Class I areas
within their borders; the required calculations must be made for each
such Class I area. The EPA's 2018 Visibility Tracking Guidance \25\
provides recommendations to assist states in satisfying their
obligations under Sec. 51.308(f)(1); specifically, in developing
information on baseline, current, and natural visibility conditions,
and in making optional adjustments to the URP to account for the
impacts of international anthropogenic emissions and prescribed fires.
See 82 FR 3103-05.
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\25\ The 2018 Visibility Tracking Guidance references and relies
on parts of the 2003 Tracking Guidance: ``Guidance for Tracking
Progress Under the Regional Haze Rule,'' which can be found at
<a href="https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf">https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf</a>.
---------------------------------------------------------------------------

The RHR requires tracking of visibility conditions on two sets of
days: the clearest and the most impaired days. Visibility conditions
for both sets of days are expressed as the average deciview index for
the relevant five-year period (the period representing baseline or
current visibility conditions). The RHR provides that the relevant sets
of days for visibility tracking purposes are the 20% clearest (the 20%
of monitored days in a calendar year with the lowest values of the
deciview index) and 20% most impaired days (the 20% of monitored days
in a calendar year with the highest amounts of anthropogenic visibility
impairment).\26\ 40 CFR 51.301. A state must calculate visibility
conditions for both the 20% clearest and 20% most impaired days for the
baseline period of 2000-2004 and the most recent five-year period for
which visibility monitoring data are available (representing current
visibility conditions). 40 CFR 51.308(f)(1)(i), (iii). States must also
calculate natural visibility conditions for the clearest and most
impaired days,\27\ by estimating the conditions that would exist on
those two sets of days absent anthropogenic visibility impairment. 40
CFR 51.308(f)(1)(ii). Using all these data, states must then calculate,
for each Class I area, the amount of progress made since the baseline
period (2000-2004) and how much improvement is left to achieve to reach
natural visibility conditions.
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\26\ This document also refers to the 20% clearest and 20% most
anthropogenically impaired days as the ``clearest'' and ``most
impaired'' or ``most anthropogenically impaired'' days,
respectively.
\27\ The RHR at 40 CFR 51.308(f)(1)(ii) contains an error
related to the requirement for calculating two sets of natural
conditions values. The rule says ``most impaired days or the
clearest days'' where it should say ``most impaired days and
clearest days.'' This is an error that was intended to be corrected
in the 2017 RHR Revisions but did not get corrected in the final
rule language. This is supported by the preamble text at 82 FR 3098:
``In the final version of 40 CFR 51.308(f)(1)(ii), an occurrence of
``or'' has been corrected to ``and'' to indicate that natural
visibility conditions for both the most impaired days and the
clearest days must be based on available monitoring information.''
---------------------------------------------------------------------------

Using the data for the set of most impaired days only, states must
plot a line between visibility conditions in the baseline period and
natural visibility conditions for each Class I area to determine the
URP--the amount of visibility improvement, measured in deciviews, that
would need to be achieved during each implementation period to achieve
natural visibility conditions by the end of 2064. The URP is used in
later steps of the reasonable progress analysis for informational
purposes and to provide a non-enforceable benchmark against which to
assess a Class I area's rate of visibility improvement.\28\
Additionally, in the 2017 RHR Revisions, the EPA provided states the
option of proposing to adjust the endpoint of the URP to account for
impacts of anthropogenic sources outside the United States and/or
impacts of certain types of wildland prescribed fires. These
adjustments, which must be approved by the EPA, are intended to avoid
any perception that states should compensate for impacts from
international anthropogenic sources and to give states the flexibility
to determine that limiting the use of wildland-prescribed fire is not
necessary for reasonable progress. 82 FR 3107, footnote 116.
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\28\ Being on or below the URP is not a ``safe harbor''; i.e.,
achieving the URP does not mean that a Class I area is making
``reasonable progress'' and does not relieve a state from using the
four statutory factors to determine what level of control is needed
to achieve such progress. See, e.g., 82 FR 3093.
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The EPA's 2018 Visibility Tracking Guidance can be used to help
satisfy the 40 CFR 51.308(f)(1) requirements, including in developing
information on baseline, current, and natural visibility conditions,
and in making optional adjustments to the URP. In addition, the 2020
Data Completeness Memo provides recommendations on the data
completeness language referenced in Sec. 51.308(f)(1)(i) and provides
updated natural conditions estimates for each Class I area.

C. Long-Term Strategy for Regional Haze

The core component of a regional haze SIP submission is a long-term
strategy that addresses regional haze in each Class I area within a
state's borders and each Class I area outside the state that may be
affected by emissions from the state. The long-term strategy ``must
include the enforceable emissions limitations, compliance schedules,
and

[[Page 67214]]

other measures that are necessary to make reasonable progress, as
determined pursuant to (f)(2)(i) through (iv).'' 40 CFR 51.308(f)(2).
The amount of progress that is ``reasonable progress'' is based on
applying the four statutory factors in CAA section 169A(g)(1) in an
evaluation of potential control options for sources of visibility
impairing pollutants, which is referred to as a ``four-factor''
analysis. The outcome of that analysis is the emission reduction
measures that a particular source or group of sources needs to
implement to make reasonable progress towards the national visibility
goal. See 40 CFR 51.308(f)(2)(i). Emission reduction measures that are
necessary to make reasonable progress may be either new, additional
control measures for a source, or they may be the existing emission
reduction measures that a source is already implementing. See 2019
Guidance at 43; 2021 Clarifications Memo at 8-10. Such measures must be
represented by ``enforceable emissions limitations, compliance
schedules, and other measures'' (i.e., any additional compliance tools)
in a state's long-term strategy in its SIP. 40 CFR 51.308(f)(2).
Section 51.308(f)(2)(i) provides the requirements for the four-
factor analysis. The first step of this analysis entails selecting the
sources to be evaluated for emission reduction measures; to this end,
the RHR requires states to consider ``major and minor stationary
sources or groups of sources, mobile sources, and area sources'' of
visibility impairing pollutants for potential four-factor control
analysis. 40 CFR 51.308(f)(2)(i). A threshold question at this step is
which visibility impairing pollutants will be analyzed. As the EPA
previously explained, consistent with the first implementation period,
the EPA generally expects that each state will analyze at least
SO<INF>2</INF> and NO<INF>X</INF> in selecting sources and determining
control measures. See 2019 Guidance at 12; 2021 Clarifications Memo at
4. A state that chooses not to consider at least these two pollutants
should demonstrate why such consideration would be unreasonable. 2021
Clarifications Memo at 4.
While states have the option to analyze all sources, the 2019
Guidance explains that ``an analysis of control measures is not
required for every source in each implementation period,'' and that
``[s]electing a set of sources for analysis of control measures in each
implementation period is . . . consistent with the Regional Haze Rule,
which sets up an iterative planning process and anticipates that a
state may not need to analyze control measures for all its sources in a
given SIP revision.'' 2019 Guidance at 9. However, given that source
selection is the basis of all subsequent control determinations, a
reasonable source selection process ``should be designed and conducted
to ensure that source selection results in a set of pollutants and
sources the evaluation of which has the potential to meaningfully
reduce their contributions to visibility impairment.'' 2021
Clarifications Memo at 3.
The EPA explained in the 2021 Clarifications Memo that each state
has an obligation to submit a long-term strategy that addresses the
regional haze visibility impairment that results from emissions from
within that state. Thus, source selection should focus on the in-state
contribution to visibility impairment and be designed to capture a
meaningful portion of the state's total contribution to visibility
impairment in Class I areas. A state should not decline to select its
largest in-state sources on the basis that there are even larger out-
of-state contributors. 2021 Clarifications Memo at 4.\29\
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\29\ Similarly, in responding to comments on the 2017 RHR
Revisions, the EPA explained that ``[a] state should not fail to
address its many relatively low-impact sources merely because it
only has such sources and another state has even more low-impact
sources and/or some high impact sources.'' Responses to Comments on
Protection of Visibility: Amendments to Requirements for State
Plans; Proposed Rule (81 FR 26942, May 4, 2016) at 87-88.
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Thus, while states have discretion to choose any source selection
methodology that is reasonable, whatever choices they make should be
reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that
a state's SIP submission include ``a description of the criteria it
used to determine which sources or groups of sources it evaluated.''
The technical basis for source selection, which may include methods for
quantifying potential visibility impacts such as emissions divided by
distance metrics, trajectory analyses, residence time analyses, and/or
photochemical modeling, must also be appropriately documented, as
required by 40 CFR 51.308(f)(2)(iii).
Once a state has selected the set of sources, the next step is to
determine the emissions reduction measures for those sources that are
necessary to make reasonable progress for the second implementation
period.\30\ This is accomplished by considering the four factors--``the
costs of compliance, the time necessary for compliance, and the energy
and nonair quality environmental impacts of compliance, and the
remaining useful life of any existing source subject to such
requirements.'' CAA section 169A(g)(1). The EPA has explained that the
four-factor analysis is an assessment of potential emission reduction
measures (i.e., control options) for sources; ``use of the terms
`compliance' and `subject to such requirements' in section 169A(g)(1)
strongly indicates that Congress intended the relevant determination to
be the requirements with which sources would have to comply to satisfy
the CAA's reasonable progress mandate.'' 82 FR 3091. Thus, for each
source it has selected for four-factor analysis,\31\ a state must
consider a ``meaningful set'' of technically feasible control options
for reducing emissions of visibility impairing pollutants. Id. at 3088.
The 2019 Guidance provides that ``[a] state must reasonably pick and
justify the measures that it will consider, recognizing that there is
no statutory or regulatory requirement to consider all technically
feasible measures or any particular measures. A range of technically
feasible measures available to reduce emissions would be one way to
justify a reasonable set.'' 2019 Guidance at 29.
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\30\ The CAA provides that ``[i]n determining reasonable
progress there shall be taken into consideration'' the four
statutory factors. CAA section 169A(g)(1). However, in addition to
four-factor analyses for selected sources, groups of sources, or
source categories, a state may also consider additional emission
reduction measures for inclusion in its long-term strategy, e.g.,
from other newly adopted, on-the-books, or on-the-way rules and
measures for sources not selected for four-factor analysis for the
second implementation period.
\31\ ``Each source'' or ``particular source'' is used here as
shorthand. While a source-specific analysis is one way of applying
the four factors, neither the statute nor the RHR requires states to
evaluate individual sources. Rather, states have ``the flexibility
to conduct four-factor analyses for specific sources, groups of
sources or even entire source categories, depending on state policy
preferences and the specific circumstances of each state.'' 82 FR
3088. However, not all approaches to grouping sources for four-
factor analysis are necessarily reasonable; the reasonableness of
grouping sources in any particular instance will depend on the
circumstances and the manner in which grouping is conducted. If it
is feasible to establish and enforce different requirements for
sources or subgroups of sources, and if relevant factors can be
quantified for those sources or subgroups, then states should make a
separate reasonable progress determination for each source or
subgroup. 2021 Clarifications Memo at 7-8.
---------------------------------------------------------------------------

The EPA's 2021 Clarifications Memo provides further guidance on
what constitutes a reasonable set of control options for consideration:
``A reasonable four-factor analysis will consider the full range of
potentially reasonable options for reducing emissions.'' 2021
Clarifications Memo at 7. In addition to add-on controls and other
retrofits (i.e., new emissions reduction measures for sources), the EPA
explained that states should generally analyze efficiency improvements
for sources' existing

[[Page 67215]]

measures as control options in their four-factor analyses, as in many
cases such improvements are reasonable given that they typically
involve only additional operation and maintenance costs. Additionally,
the 2021 Clarifications Memo provides that states that have assumed a
higher emissions rate than a source has achieved or could potentially
achieve using its existing measures should also consider lower
emissions rates as potential control options. That is, a state should
consider a source's recent actual and projected emission rates to
determine if it could reasonably attain lower emission rates with its
existing measures. If so, the state should analyze the lower emission
rate as a control option for reducing emissions. 2021 Clarifications
Memo at 7. The EPA's recommendations to analyze potential efficiency
improvements and achievable lower emission rates apply to both sources
that have been selected for four-factor analysis and those that have
forgone a four-factor analysis on the basis of existing ``effective
controls.'' See 2021 Clarifications Memo at 5, 10.
After identifying a reasonable set of potential control options for
the sources it has selected, a state then collects information on the
four factors with regard to each option identified. The EPA has also
explained that, in addition to the four statutory factors, states have
flexibility under the CAA and RHR to reasonably consider visibility
benefits as an additional factor alongside the four statutory
factors.\32\ The 2019 Guidance provides recommendations for the types
of information that can be used to characterize the four factors (with
or without visibility), as well as ways in which states might
reasonably consider and balance that information to determine which of
the potential control options is necessary to make reasonable progress.
See 2019 Guidance at 30-36. The 2021 Clarifications Memo contains
further guidance on how states can reasonably consider modeled
visibility impacts or benefits in the context of a four-factor
analysis. 2021 Clarifications Memo at 12-13, 14-15. Specifically, the
EPA explained that while visibility can reasonably be used when
comparing and choosing between multiple reasonable control options, it
should not be used to summarily reject controls that are reasonable
given the four statutory factors. 2021 Clarifications Memo at 13.
Ultimately, while states have discretion to reasonably weigh the
factors and to determine what level of control is needed, Sec.
51.308(f)(2)(i) provides that a state ``must include in its
implementation plan a description of . . . how the four factors were
taken into consideration in selecting the measure for inclusion in its
long-term strategy.''
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\32\ See, e.g., Responses to Comments on Protection of
Visibility: Amendments to Requirements for State Plans; Proposed
Rule (81 FR 26942, May 4, 2016), Docket ID No. EPA-HQ-OAR-2015-0531,
U.S. Environmental Protection Agency at 186; 2019 Guidance at 36-37.
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As explained above, Sec. 51.308(f)(2)(i) requires states to
determine the emission reduction measures for sources that are
necessary to make reasonable progress by considering the four factors.
Pursuant to Sec. 51.308(f)(2), measures that are necessary to make
reasonable progress towards the national visibility goal must be
included in a state's long-term strategy and in its SIP.\33\ If the
outcome of a four-factor analysis is a new, additional emission
reduction measure for a source, that new measure is necessary to make
reasonable progress towards remedying existing anthropogenic visibility
impairment and must be included in the SIP. If the outcome of a four-
factor analysis is that no new measures are reasonable for a source,
continued implementation of the source's existing measures is generally
necessary to prevent future emission increases and thus to make
reasonable progress towards the second part of the national visibility
goal: preventing future anthropogenic visibility impairment. See CAA
section 169A(a)(1). That is, when the result of a four-factor analysis
is that no new measures are necessary to make reasonable progress, the
source's existing measures are generally necessary to make reasonable
progress and must be included in the SIP. However, there may be
circumstances in which a state can demonstrate that a source's existing
measures are not necessary to make reasonable progress. Specifically,
if a state can demonstrate that a source will continue to implement its
existing measures and will not increase its emissions rate, it may not
be necessary to have those measures in the long-term strategy to
prevent future emissions increases and future visibility impairment.
The EPA's 2021 Clarifications Memo provides further explanation and
guidance on how states may demonstrate that a source's existing
measures are not necessary to make reasonable progress. See 2021
Clarifications Memo at 8-10. If the state can make such a
demonstration, it need not include a source's existing measures in the
long-term strategy or its SIP.
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\33\ States may choose to, but are not required to, include
measures in their long-term strategies beyond just the emission
reduction measures that are necessary for reasonable progress. See
2021 Clarifications Memo at 16. For example, states with smoke
management programs may choose to submit their smoke management
plans to the EPA for inclusion in their SIPs but are not required to
do so. See, e.g., 82 FR 3108-09 (requirement to consider smoke
management practices and smoke management programs under 40 CFR
51.308(f)(2)(iv) does not require states to adopt such practices or
programs into their SIPs, although they may elect to do so).
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As with source selection, the characterization of information on
each of the factors is also subject to the documentation requirement in
Sec. 51.308(f)(2)(iii). The reasonable progress analysis, including
source selection, information gathering, characterization of the four
statutory factors (and potentially visibility), balancing of the four
factors, and selection of the emission reduction measures that
represent reasonable progress, is a technically complex exercise, but
also a flexible one that provides states with bounded discretion to
design and implement approaches appropriate to their circumstances.
Given this flexibility, Sec. 51.308(f)(2)(iii) plays an important
function in requiring a state to document the technical basis for its
decision making so that the public and the EPA can comprehend and
evaluate the information and analysis the state relied upon to
determine what emission reduction measures must be in place to make
reasonable progress. The technical documentation must include the
modeling, monitoring, cost, engineering, and emissions information on
which the state relied to determine the measures necessary to make
reasonable progress. This documentation requirement can be met through
the provision of and reliance on technical analyses developed through a
regional planning process, so long as that process and its output has
been approved by all state participants. In addition to the explicit
regulatory requirement to document the technical basis of their
reasonable progress determinations, states are also subject to the
general principle that those determinations must be reasonably moored
to the statute.\34\ That is, a state's decisions about the emission
reduction measures that are necessary to make reasonable progress must
be consistent with the statutory goal of remedying existing and
preventing future visibility impairment.
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\34\ See Arizona ex rel. Darwin v. U.S. EPA, 815 F.3d 519, 531
(9th Cir. 2016); Nebraska v. EPA, 812 F.3d 662, 668 (8th Cir. 2016);
North Dakota v. EPA, 730 F.3d 750, 761 (8th Cir. 2013); Oklahoma v.
EPA, 723 F.3d 1201, 1206, 1208-10 (10th Cir. 2013); cf. Nat'l Parks
Conservation Ass'n v. EPA, 803 F.3d 151, 165 (3d Cir. 2015); Alaska
Dep't of Envtl. Conservation v. EPA, 540 U.S. 461, 485, 490 (2004).

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[[Page 67216]]

The four statutory factors (and potentially visibility) are used to
determine what emission reduction measures for selected sources must be
included in a state's long-term strategy for making reasonable
progress. Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately
provides five ``additional factors'' \35\ that states must consider in
developing their long-term strategies: (1) Emission reductions due to
ongoing air pollution control programs, including measures to address
reasonably attributable visibility impairment; (2) measures to reduce
the impacts of construction activities; (3) source retirement and
replacement schedules; (4) basic smoke management practices for
prescribed fire used for agricultural and wildland vegetation
management purposes and smoke management programs; and (5) the
anticipated net effect on visibility due to projected changes in point,
area, and mobile source emissions over the period addressed by the
long-term strategy. The 2019 Guidance provides that a state may satisfy
this requirement by considering these additional factors in the process
of selecting sources for four-factor analysis, when performing that
analysis, or both, and that not every one of the additional factors
needs to be considered at the same stage of the process. See 2019
Guidance at 21. The EPA provided further guidance on the five
additional factors in the 2021 Clarifications Memo, explaining that a
state should generally not reject cost-effective and otherwise
reasonable controls merely because there have been emission reductions
since the first implementation period owing to other ongoing air
pollution control programs or merely because visibility is otherwise
projected to improve at Class I areas. Additionally, states generally
should not rely on these additional factors to summarily assert that
the state has already made sufficient progress and, therefore, no
sources need to be selected or no new controls are needed regardless of
the outcome of four-factor analyses. 2021 Clarifications Memo at 13.
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\35\ The five ``additional factors'' for consideration in Sec.
51.308(f)(2)(iv) are distinct from the four factors listed in CAA
section 169A(g)(1) and 40 CFR 51.308(f)(2)(i) that states must
consider and apply to sources in determining reasonable progress.
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Because the air pollution that causes regional haze crosses state
boundaries, Sec. 51.308(f)(2)(ii) requires a state to consult with
other states that also have emissions that are reasonably anticipated
to contribute to visibility impairment in a given Class I area.
Consultation allows for each state that impacts visibility in an area
to share whatever technical information, analyses, and control
determinations may be necessary to develop coordinated emission
management strategies. This coordination may be managed through inter-
and intra-RPO consultation and the development of regional emissions
strategies; additional consultations between states outside of RPO
processes may also occur. If a state, pursuant to consultation, agrees
that certain measures (e.g., a certain emission limitation) are
necessary to make reasonable progress at a Class I area, it must
include those measures in its SIP. 40 CFR 51.308(f)(2)(ii)(A).
Additionally, the RHR requires that states that contribute to
visibility impairment at the same Class I area consider the emission
reduction measures the other contributing states have identified as
being necessary to make reasonable progress for their own sources. 40
CFR 51.308(f)(2)(ii)(B). If a state has been asked to consider or adopt
certain emission reduction measures, but ultimately determines those
measures are not necessary to make reasonable progress, that state must
document in its SIP the actions taken to resolve the disagreement. 40
CFR 51.308(f)(2)(ii)(C). The EPA will consider the technical
information and explanations presented by the submitting state and the
state with which it disagrees when considering whether to approve the
state's SIP. See id.; 2019 Guidance at 53. Under all circumstances, a
state must document in its SIP submission all substantive consultations
with other contributing states. 40 CFR 51.308(f)(2)(ii)(C).

D. Reasonable Progress Goals

Reasonable progress goals ``measure the progress that is projected
to be achieved by the control measures states have determined are
necessary to make reasonable progress based on a four-factor
analysis.'' 82 FR 3091. Their primary purpose is to assist the public
and the EPA in assessing the reasonableness of states' long-term
strategies for making reasonable progress towards the national
visibility goal for Class I areas within the state. See 40 CFR
51.308(f)(3)(iii) and (iv). States in which Class I areas are located
must establish two RPGs, both in deciviews--one representing visibility
conditions on the clearest days and one representing visibility on the
most anthropogenically impaired days--for each area within their
borders. 40 CFR 51.308(f)(3)(i). The two RPGs are intended to reflect
the projected impacts, on the two sets of days, of the emission
reduction measures the state with the Class I area, as well as all
other contributing states, have included in their long-term strategies
for the second implementation period.\36\ The RPGs also account for the
projected impacts of implementing other CAA requirements, including
non-SIP based requirements. Because RPGs are the modeled result of the
measures in states' long-term strategies (as well as other measures
required under the CAA), they cannot be determined before states have
conducted their four-factor analyses and determined the control
measures that are necessary to make reasonable progress. See 2021
Clarifications Memo at 6.
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\36\ RPGs are intended to reflect the projected impacts of the
measures all contributing states include in their long-term
strategies. However, due to the timing of analyses, control
determinations by other states, and other on-going emissions
changes, a particular state's RPGs may not reflect all control
measures and emissions reductions that are expected to occur by the
end of the implementation period. The 2019 Guidance provides
recommendations for addressing the timing of RPG calculations when
states are developing their long-term strategies on disparate
schedules, as well as for adjusting RPGs using a post-modeling
approach. 2019 Guidance at 47-48.
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For the second implementation period, the RPGs are set for 2028.
Reasonable progress goals are not enforceable targets, 40 CFR
51.308(f)(3)(iii); rather, they ``provide a way for the states to check
the projected outcome of the [long-term strategy] against the goals for
visibility improvement.'' 2019 Guidance at 46. While states are not
legally obligated to achieve the visibility conditions described in
their RPGs, Sec. 51.308(f)(3)(i) requires that ``[t]he long-term
strategy and the reasonable progress goals must provide for an
improvement in visibility for the most impaired days since the baseline
period and ensure no degradation in visibility for the clearest days
since the baseline period.'' Thus, states are required to have emission
reduction measures in their long-term strategies that are projected to
achieve visibility conditions on the most impaired days that are better
than the baseline period and that show no degradation on the clearest
days compared to the clearest days from the baseline period. The
baseline period for the purpose of this comparison is the baseline
visibility condition--the annual average visibility condition for the
period 2000-2004. See 40 CFR 51.308(f)(1)(i), 82 FR 3097-98.
So that RPGs may also serve as a metric for assessing the amount of
progress a state is making towards the national visibility goal, the
RHR requires states with Class I areas to compare the 2028 RPG for the
most

[[Page 67217]]

impaired days to the corresponding point on the URP line (representing
visibility conditions in 2028 if visibility were to improve at a linear
rate from conditions in the baseline period of 2000-2004 to natural
visibility conditions in 2064). If the most impaired days RPG in 2028
is above the URP (i.e., if visibility conditions are improving more
slowly than the rate described by the URP), each state that contributes
to visibility impairment in the Class I area must demonstrate, based on
the four-factor analysis required under 40 CFR 51.308(f)(2)(i), that no
additional emission reduction measures would be reasonable to include
in its long-term strategy. 40 CFR 51.308(f)(3)(ii). To this end, 40 CFR
51.308(f)(3)(ii) requires that each state contributing to visibility
impairment in a Class I area that is projected to improve more slowly
than the URP provide ``a robust demonstration, including documenting
the criteria used to determine which sources or groups [of] sources
were evaluated and how the four factors required by paragraph (f)(2)(i)
were taken into consideration in selecting the measures for inclusion
in its long-term strategy.'' The 2019 Guidance provides suggestions
about how such a ``robust demonstration'' might be conducted. See 2019
Guidance at 50-51.
The 2017 RHR, 2019 Guidance, and 2021 Clarifications Memo also
explain that projecting an RPG that is on or below the URP based on
only on-the-books and/or on-the-way control measures (i.e., control
measures already required or anticipated before the four-factor
analysis is conducted) is not a ``safe harbor'' from the CAA's and
RHR's requirement that all states must conduct a four-factor analysis
to determine what emission reduction measures constitute reasonable
progress. The URP is a planning metric used to gauge the amount of
progress made thus far and the amount left before reaching natural
visibility conditions. However, the URP is not based on consideration
of the four statutory factors and therefore cannot answer the question
of whether the amount of progress being made in any particular
implementation period is ``reasonable progress.'' See 82 FR 3093, 3099-
3100; 2019 Guidance at 22; 2021 Clarifications Memo at 15-16.

E. Monitoring Strategy and Other State Implementation Plan Requirements

Section 51.308(f)(6) requires states to have certain strategies and
elements in place for assessing and reporting on visibility. Individual
requirements under this section apply either to states with Class I
areas within their borders, states with no Class I areas but that are
reasonably anticipated to cause or contribute to visibility impairment
in any Class I area, or both. A state with Class I areas within its
borders must submit with its SIP revision a monitoring strategy for
measuring, characterizing, and reporting regional haze visibility
impairment that is representative of all Class I areas within the
state. SIP revisions for such states must also provide for the
establishment of any additional monitoring sites or equipment needed to
assess visibility conditions in Class I areas, as well as reporting of
all visibility monitoring data to the EPA at least annually. Compliance
with the monitoring strategy requirement may be met through a state's
participation in the Interagency Monitoring of Protected Visual
Environments (IMPROVE) monitoring network, which is used to measure
visibility impairment caused by air pollution at the 156 Class I areas
covered by the visibility program. 40 CFR 51.308(f)(6) introductory
text and (f)(6)(i) and (iv). The IMPROVE monitoring data is used to
determine the 20% most anthropogenically impaired and 20% clearest sets
of days every year at each Class I area and tracks visibility
impairment over time.
All states' SIPs must provide for procedures by which monitoring
data and other information are used to determine the contribution of
emissions from within the state to regional haze visibility impairment
in affected Class I areas. 40 CFR 51.308(f)(6)(ii) and (iii). Section
51.308(f)(6)(v) further requires that all states' SIPs provide for a
statewide inventory of emissions of pollutants that are reasonably
anticipated to cause or contribute to visibility impairment in any
Class I area; the inventory must include emissions for the most recent
year for which data are available and estimates of future projected
emissions. States must also include commitments to update their
inventories periodically. The inventories themselves do not need to be
included as elements in the SIP and are not subject to the EPA's review
as part of the Agency's evaluation of a SIP revision.\37\ All states'
SIPs must also provide for any other elements, including reporting,
recordkeeping, and other measures, that are necessary for states to
assess and report on visibility. 40 CFR 51.308(f)(6)(vi). Per the 2019
Guidance, a state may note in its regional haze SIP that its compliance
with the Air Emissions Reporting Rule (AERR) in 40 CFR part 51, subpart
A, satisfies the requirement to provide for an emissions inventory for
the most recent year for which data are available. To satisfy the
requirement to provide estimates of future projected emissions, a state
may explain in its SIP how projected emissions were developed for use
in establishing RPGs for its own and nearby Class I areas.\38\
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\37\ See ``Step 8: Additional requirements for regional haze
SIPs'' in the 2019 Guidance at 55.
\38\ Id.
---------------------------------------------------------------------------

Separate from the requirements related to monitoring for regional
haze purposes under 40 CFR 51.308(f)(6), the RHR also contains a
requirement at Sec. 51.308(f)(4) related to any additional monitoring
that may be needed to address visibility impairment in Class I areas
from a single source or a small group of sources. This is called
``reasonably attributable visibility impairment.'' \39\ Under this
provision, if the EPA or the FLM of an affected Class I area has
advised a state that additional monitoring is needed to assess
reasonably attributable visibility impairment, the state must include
in its SIP revision for the second implementation period an appropriate
strategy for evaluating such impairment.
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\39\ The EPA's visibility protection regulations define
``reasonably attributable visibility impairment'' as ``visibility
impairment that is caused by the emission of air pollutants from
one, or a small number of sources.'' 40 CFR 51.301.
---------------------------------------------------------------------------

F. Requirements for Periodic Reports Describing Progress Towards the
Reasonable Progress Goals

Section 51.308(f)(5) requires a state's regional haze SIP revision
to address the requirements of 40 CFR 51.308(g)(1) through (5) so that
the plan revision due in 2021 will serve also as a progress report
addressing the period since submission of the progress report for the
first implementation period. The regional haze progress report
requirement is designed to inform the public and the EPA about a
state's implementation of its existing long-term strategy and whether
such implementation is in fact resulting in the expected visibility
improvement. See 81 FR 26942, 26950 (May 4, 2016); 82 FR 3119 (January
10, 2017). To this end, every state's SIP revision for the second
implementation period is required to describe the status of
implementation of all measures included in the state's long-term
strategy, including BART and reasonable progress emission reduction
measures from the first implementation period, and the resulting
emissions reductions. 40 CFR 51.308(g)(1) and (2).
A core component of the progress report requirements is an
assessment of changes in visibility conditions on the clearest and most
impaired days. For

[[Page 67218]]

second implementation period progress reports, Sec. 51.308(g)(3)
requires states with Class I areas within their borders to first
determine current visibility conditions for each area on the most
impaired and clearest days, 40 CFR 51.308(g)(3)(i), and then to
calculate the difference between those current conditions and baseline
(2000-2004) visibility conditions to assess progress made to date. See
40 CFR 51.308(g)(3)(ii). States must also assess the changes in
visibility impairment for the most impaired and clearest days since
they submitted their first implementation period progress reports. See
40 CFR 51.308(g)(3)(iii), (f)(5). Since different states submitted
their first implementation period progress reports at different times,
the starting point for this assessment will vary state by state.
Similarly, states must provide analyses tracking the change in
emissions of pollutants contributing to visibility impairment from all
sources and activities within the state over the period since they
submitted their first implementation period progress reports. See 40
CFR 51.308(g)(4), (f)(5). Changes in emissions should be identified by
the type of source or activity. Section 51.308(g)(5) also addresses
changes in emissions since the period addressed by the previous
progress report and requires states' SIP revisions to include an
assessment of any significant changes in anthropogenic emissions within
or outside the state. This assessment must explain whether these
changes in emissions were anticipated and whether they have limited or
impeded progress in reducing emissions and improving visibility
relative to what the state projected based on its long-term strategy
for the first implementation period.

G. Requirements for State and Federal Land Manager Coordination

CAA section 169A(d) requires that before a state holds a public
hearing on a proposed regional haze SIP revision, it must consult with
the appropriate FLM or FLMs; pursuant to that consultation, the state
must include a summary of the FLMs' conclusions and recommendations in
the notice to the public. Consistent with this statutory requirement,
the RHR also requires that states ``provide the [FLM] with an
opportunity for consultation, in person and at a point early enough in
the State's policy analyses of its long-term strategy emission
reduction obligation so that information and recommendations provided
by the [FLM] can meaningfully inform the State's decisions on the long-
term strategy.'' 40 CFR 51.308(i)(2). Consultation that occurs 120 days
prior to any public hearing or public comment opportunity will be
deemed ``early enough,'' but the RHR provides that in any event the
opportunity for consultation must be provided at least 60 days before a
public hearing or comment opportunity. This consultation must include
the opportunity for the FLMs to discuss their assessment of visibility
impairment in any Class I area and their recommendations on the
development and implementation of strategies to address such
impairment. 40 CFR 51.308(i)(2). For the EPA to evaluate whether FLM
consultation meeting the requirements of the RHR has occurred, the SIP
submission should include documentation of the timing and content of
such consultation. The SIP revision submitted to the EPA must also
describe how the state addressed any comments provided by the FLMs. 40
CFR 51.308(i)(3). Finally, a SIP revision must provide procedures for
continuing consultation between the state and FLMs regarding the
state's visibility protection program, including development and review
of SIP revisions, five-year progress reports, and the implementation of
other programs having the potential to contribute to impairment of
visibility in Class I areas. 40 CFR 51.308(i)(4).

IV. The EPA's Evaluation of Utah's Regional Haze SIP Submission for the
Second Implementation Period

In section IV of this document, we summarize Utah's regional haze
SIP submission and evaluate it against the requirements of the CAA and
RHR for the second implementation period of the regional haze program.

A. Identification of Class I Areas

Section 169A(b)(2) of the CAA requires each state in which any
Class I area is located or ``the emissions from which may reasonably be
anticipated to cause or contribute to any impairment of visibility'' in
a Class I area to have a plan for making reasonable progress toward the
national visibility goal. The RHR implements this statutory requirement
at 40 CFR 51.308(f) introductory text, which provides that each state's
plan ``must address regional haze in each mandatory Class I Federal
area located within the State and in each mandatory Class I Federal
area located outside the State that may be affected by emissions from
within the State,'' and paragraph (f)(2), which requires each state's
plan to include a long-term strategy that addresses regional haze in
such Class I areas.
The EPA explained in the 1999 RHR preamble that the CAA section
169A(b)(2) requirement that states submit SIPs to address visibility
impairment establishes ``an `extremely low triggering threshold' in
determining which States should submit SIPs for regional haze.'' 64 FR
35721. In concluding that each of the contiguous 48 states and the
District of Columbia meet this threshold,\40\ the EPA relied on ``a
large body of evidence demonstrat[ing] that long-range transport of
fine PM contributes to regional haze,'' Id., including modeling studies
that ``preliminarily demonstrated that each State not having a Class I
area had emissions contributing to impairment in at least one downwind
Class I area.'' Id. at 35722. In addition to the technical evidence
supporting a conclusion that each state contributes to existing
visibility impairment, the EPA also explained that the second half of
the national visibility goal--preventing future visibility impairment--
requires having a framework in place to address future growth in
visibility impairing emissions and makes it inappropriate to
``establish criteria for excluding States or geographic areas from
consideration as potential contributors to regional haze visibility
impairment.'' Id. at 35721. Thus, the EPA concluded that the agency's
``statutory authority and the scientific evidence are sufficient to
require all States to develop regional haze SIPs to ensure the
prevention of any future impairment of visibility, and to conduct
further analyses to determine whether additional control measures are
needed to ensure reasonable progress in remedying existing impairment
in downwind Class I areas.'' Id. at 35722. The EPA's 2017 revisions to
the RHR did not disturb this conclusion. See 82 FR 3094.
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\40\ The EPA determined that ``there is more than sufficient
evidence to support our conclusion that emissions from each of the
48 contiguous states and the District of Columba may reasonably be
anticipated to cause or contribute to visibility impairment in a
Class I area.'' 64 FR 35721. Hawaii, Alaska, and the U.S. Virgin
Islands must also submit regional haze SIPs because they contain
Class I areas.
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Utah has five mandatory Federal Class I Federal areas within its
borders: Arches National Park, Bryce Canyon National Park, Canyonlands
National Park, Capitol Reef National Park, and Zion National Park.
These five mandatory Class I areas are located within the physiographic
region known as the Colorado Plateau.\41\
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\41\ National Park Service, ``Colorado Plateaus Province,''
<a href="https://www.nps.gov/articles/coloradoplateaus.htm">https://www.nps.gov/articles/coloradoplateaus.htm</a> (last accessed
July 24, 2024); National Park Service, ``Colorado Plateaus Province:
U.S. Physiographic Province Map,'' <a href="https://www.nps.gov/common/uploads/photogallery/nri/park/geology/49177B13-1DD8-B71B-0BF120CC77B24F45/49177B13-1DD8-B71B-0BF120CC77B24F45-large.jpg">https://www.nps.gov/common/uploads/photogallery/nri/park/geology/49177B13-1DD8-B71B-0BF120CC77B24F45/49177B13-1DD8-B71B-0BF120CC77B24F45-large.jpg</a> (last
accessed July 24, 2024).

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[[Page 67219]]

Additionally, based on its review of WRAP's source apportionment
modeling \42\ and weighted emission potential (WEP) analysis,\43\ Utah
identified at least 45 Class I areas outside the State where visibility
may be affected by Utah sources.\44\ Those Class I areas are listed in
tables 26 and 30 of the TSD for this action.
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\42\ For its source apportionment modeling, WRAP used its
emissions inventories, including projections of future emissions, as
inputs to a photochemical model that assesses light extinction
(i.e., visibility impairment) at each Class I area. More detail on
source apportionment modeling is provided in the EPA's TSD for this
action.
\43\ WEP is a quantitative method of analyzing how pollutants
from particular sources may be transported to Class I areas. More
detail on WRAP's WEP analysis is provided in the EPA's TSD for this
action.
\44\ Utah tabulated 30 IMPROVE receptor sites located in
adjacent neighboring states in tables 21-22 of the Utah regional
haze SIP submission at 77-78. These sites represent 45 Class I
areas. We have identified numerous other Class I areas, beyond
Utah's neighboring states, that are impacted by light extinction
originating from the NO<INF>X</INF> and SO<INF>2</INF> emissions of
Utah's sources. The forty-five out-of-state Class I areas identified
for sulfate light extinction impacts represent 29% of all mandatory
Class I areas, and the 45 out-of-state Class I areas identified for
nitrate impacts also represent 29% of all mandatory Class I areas.
At a minimum, the emissions sources identified by Utah impact
visibility in more than a quarter of the 156 mandatory Class I areas
nationwide.
---------------------------------------------------------------------------

B. Calculations of Baseline, Current, and Natural Visibility
Conditions; Progress to Date; and the Uniform Rate of Progress

Section 51.308(f)(1) requires states to determine the following for
``each mandatory Class I Federal area located within the State'':
baseline visibility conditions for the most impaired and clearest days,
natural visibility conditions for the most impaired and clearest days,
progress to date for the most impaired and clearest days, the
differences between current visibility conditions and natural
visibility conditions, and the URP. This section also provides the
option for states to propose adjustments to the URP line for a Class I
area to account for visibility impacts from anthropogenic sources
outside the United States and/or the impacts from wildland prescribed
fires that were conducted for certain, specified objectives. 40 CFR
51.308(f)(1)(vi)(B).
Utah relied on WRAP TSS products and IMPROVE data to determine
visibility conditions at its five in-state Class I areas.\45\ Utah
elected not to adjust the URP for those Class I areas for this
implementation period.
---------------------------------------------------------------------------

\45\ Utah regional haze SIP submission, chapter 4 and section
8.C.
---------------------------------------------------------------------------

Visibility impairing particulate species at Class I areas are
measured and analyzed through the IMPROVE network. The IMPROVE network
uses identical sampling equipment and analysis protocols to ensure that
IMPROVE sites and their respective data are directly comparable.
Samples collected from IMPROVE monitors provide estimations of light
extinction \46\ to monitor visibility conditions and compare long-term
visibility trends at Class I areas. IMPROVE monitoring data is also
used to determine the 20% most anthropogenically impaired days (most
impaired days) and the 20% clearest days every year at each Class I
area and to track visibility impairment over time, as required by the
RHR.
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\46\ The primary cause of regional haze is light extinction by
particulate matter (PM). For purposes of regional haze, light
extinction is estimated from measurements of PM and its chemical
components (sulfate, nitrate, organic mass by carbon (OMC), light
absorbing carbon, fine soil, sea salt, and coarse material),
assumptions about relative humidity at the monitoring site, and the
use of a commonly accepted algorithm. These estimates of light
extinction are logarithmically transformed to deciviews (dv). The PM
measurements used in the regional haze program are collected by the
IMPROVE monitoring network.
---------------------------------------------------------------------------

Due to their remote nature and/or close proximity to each other,
several Class I areas throughout the United States share a common
IMPROVE monitoring station.\47\ Four IMPROVE monitors measure
visibility conditions at the five Class I areas in Utah. The IMPROVE
monitor at Canyonlands National Park has been determined to also be
representative of the visibility conditions at Arches National Park.
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\47\ Utah identified several Class I areas where visibility is
affected by emissions from Utah sources, some of which share a
single IMPROVE monitoring station. The IMPROVE Site IDs for these
Class I areas are: BRID1 for Bridger Wilderness and Fitzpatrick
Wilderness; CANY1 for Arches National Park and Canyonlands National
Park; GUMO1 for Carlsbad Caverns National Park and Guadalupe
Mountains National Park; NOAB1 for North Absaroka Wilderness and
Washakie Wilderness; SULA1 for Anaconda-Pintler Wilderness and
Selway-Bitterroot Wilderness; WEMI1 for Black Canyon of the Gunnison
National Monument, La Garita Wilderness, and Weminuche Wilderness;
WHPE1 for Pecos Wilderness and Wheeler Peak Wilderness; and WHRI1
for Eagles Nest Wilderness, Flat Tops Wilderness, Maroon Bells-
Snowmass Wilderness, and West Elk Wilderness.
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Utah determined that Arches National Park and Canyonlands National
Park (CANY1) have 2000-2004 baseline visibility conditions of 3.75
deciviews on the 20% clearest days and 8.79 deciviews on the 20% most
impaired days. Utah calculated an estimated natural background
visibility of 1.05 deciviews on the 20% clearest days and 4.13
deciviews on the 20% most impaired days. The current visibility
conditions, which are based on 2014-2018 monitoring data, were 2.20
deciviews on the clearest days and 6.76 deciviews on the most impaired
days, which are 1.15 deciviews and 2.63 deciviews greater than natural
conditions on the respective sets of days. The five-year rolling
average IMPROVE data from 2014-2018 indicate that Arches National Park
and Canyonlands National Park are 0.9 deciviews below the 2018 URP of
7.7 deciviews.\48\
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\48\ Utah regional haze SIP submission at 175 (figure 66).
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Utah determined that Bryce Canyon National Park (BRCA1) has 2000-
2004 baseline visibility conditions of 2.77 deciviews on the 20%
clearest days and 8.42 deciviews on the 20% most impaired days. Utah
calculated an estimated natural background visibility of 0.57 deciviews
on the 20% clearest days and 4.08 deciviews on the 20% most impaired
days. The current visibility conditions, which are based on 2014-2018
monitoring data, were 1.46 deciviews on the clearest days and 6.60
deciviews on the most impaired days, which are 0.89 deciviews and 2.52
deciviews greater than natural conditions on the respective sets of
days. The five-year rolling average IMPROVE data from 2014-2018
indicates that Bryce Canyon National Park is 0.8 deciviews below the
2018 URP of 7.4 deciviews.\49\
---------------------------------------------------------------------------

\49\ Id. at 174 (figure 65).
---------------------------------------------------------------------------

Utah determined that Capitol Reef National Park (CAPI1) has 2000-
2004 baseline visibility conditions of 4.10 deciviews on the 20%
clearest days and 8.78 deciviews on the 20% most impaired days. Utah
calculated an estimated natural background visibility of 1.28 deciviews
on the 20% clearest days and 4.00 deciviews on the 20% most impaired
days. The current visibility conditions, which are based on 2014-2018
monitoring data, were 2.38 deciviews on the clearest days and 7.18
deciviews on the most impaired days, which are 1.10 deciviews and 3.18
deciviews greater than natural conditions on the respective sets of
days. The five-year rolling average IMPROVE data from 2014-2018
indicate that Capitol Reef National Park is 0.5 deciviews below the
2018 URP of 7.7 deciviews.\50\
---------------------------------------------------------------------------

\50\ Id. at 176 (figure 67).
---------------------------------------------------------------------------

Utah determined that Zion National Park (ZICA1) has 2000-2004
baseline visibility conditions of 4.48 deciviews on the 20% clearest
days and 10.40 deciviews on the 20% most impaired days. Utah calculated
an estimated natural background visibility of 1.83 deciviews on the 20%
clearest days and 5.26 deciviews on the 20% most

[[Page 67220]]

impaired days. The current visibility conditions, which are based on
2014-2018 monitoring data, were 3.86 deciviews on the clearest days and
8.75 deciviews on the most impaired days, which are 2.03 deciviews and
3.49 deciviews greater than natural conditions on the respective sets
of days. The five-year rolling average IMPROVE data from 2014-2018
indicate that Zion National Park is 0.5 deciviews below the 2018 URP of
9.2 deciviews.\51\
---------------------------------------------------------------------------

\51\ Id. at 177 (figure 68).
---------------------------------------------------------------------------

Based on this information, which is provided in chapter 4 and
section 8.C. of Utah's regional haze SIP submission, the EPA finds that
the visibility condition calculations for all five Utah Class I areas
meet the requirements of 40 CFR 51.308(f)(1). For this reason, we
propose to approve the portions of Utah's regional haze SIP submission
relating to 40 CFR 51.308(f)(1): calculations of baseline, current, and
natural visibility conditions; progress to date; and the URP.

C. Long-Term Strategy

Each state having a Class I area within its borders or emissions
that may affect visibility in any Class I area outside the state must
develop a long-term strategy for making reasonable progress towards the
national visibility goal for each impacted Class I area. CAA section
169A(b)(2)(B). As explained in the Background section of this document,
reasonable progress is achieved when all states contributing to
visibility impairment in a Class I area are implementing the measures
determined--through application of the four statutory factors to
sources of visibility impairing pollutants--to be necessary to make
reasonable progress. 40 CFR 51.308(f)(2)(i). Each state's long-term
strategy must include the enforceable emission limitations, compliance
schedules, and other measures that are necessary to make reasonable
progress. 40 CFR 51.308(f)(2). All new (i.e., additional) measures that
are the outcome of four-factor analyses are necessary to make
reasonable progress and must be in the long-term strategy. If the
outcome of a four-factor analysis and other measures necessary to make
reasonable progress is that no new measures are reasonable for a
source, that source's existing measures are necessary to make
reasonable progress, unless the state can demonstrate that the source
will continue to implement those measures and will not increase its
emission rate. Existing measures that are necessary to make reasonable
progress must also be in the long-term strategy. In developing its
long-term strategies, a state must also consider the five additional
factors in 40 CFR 51.308(f)(2)(iv). As part of its reasonable progress
determinations, the state must describe the criteria used to determine
which sources or group of sources were evaluated (i.e., subjected to
four-factor analysis) for the second implementation period and how the
four factors were taken into consideration in selecting the emission
reduction measures for inclusion in the long-term strategy. 40 CFR
51.308(f)(2)(iii).
1. Summary of Utah's Four-Factor Analyses and Long-Term Strategy to
Make Reasonable Progress
a. Selection of Sources for Four-Factor Analysis
Utah relied on Q/d analysis to identify sources for consideration
of the four statutory factors.\52\ Q/d analysis results in a value that
represents the ratio of an individual source's annual emissions of
light-impairing emission precursors (NO<INF>X</INF>, SO<INF>2</INF>,
and PM<INF>10</INF>) in combined tons (``Q'') divided by the distance
in kilometers (``d'') between the source and the nearest Class I area.
The larger the Q/d value, the greater the source's expected effect on
visibility impairment in each associated Class I area. Utah chose a Q/d
source selection threshold of >= 6, meaning that any source with a Q/d
value greater than or equal to 6 was ``screened in'' to the pool of
sources Utah believed were appropriate for consideration of the four
factors.\53\ Following Q/d analysis, Utah then conducted a ``secondary
screening to review the initial pool of Q/d-qualifying sources to
account for factors such as recent emissions controls required by other
air quality programs, facility closures, federal preemptions on state
controls, etc.'' \54\
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\52\ Utah regional haze SIP submission at 14, 99.
\53\ Utah used 2014 NEI emissions data to select sources for
four-factor analysis. Utah performed an additional analysis using
2017 NEI emissions data at the EPA's request; no additional sources
were captured.
\54\ Utah regional haze SIP submission at 77.
---------------------------------------------------------------------------

Utah's Q/d analysis initially screened in ten sources: Ash Grove
Leamington Cement Plant, CCI Paradox Lisbon Natural Gas Plant, Graymont
Cricket Mountain Plant, Intermountain Power Authority Intermountain
Power Plant,\55\ Kennecott Utah Copper Mine & Copperton Concentrator,
Kennecott Utah Copper Power Plant Lab Tailings Impoundment, PacifiCorp
Hunter Power Plant, PacifiCorp Huntington Power Plant, Sunnyside
Cogeneration Facility, and US Magnesium Rowley Plant. Utah determined
that four of those sources, Intermountain Power Authority Intermountain
Power Plant; CCI Paradox Lisbon Natural Gas Plant; Kennecott Utah
Copper Mine & Copperton Concentrator; and Kennecott Utah Copper Power
Plant Lab Tailings Impoundment, were not required to perform four-
factor analyses based on current emissions, 2028 projected emissions,
or plant closures or emission control measures that were put in place
after the 2014 base year inventory (which was used to determine
sources' Q in the Q/d analysis).\56\ Table 1 lists Utah's reasoning for
not requiring four-factor analyses for the four sources.
---------------------------------------------------------------------------

\55\ Intermountain Power Plant is also referred to as
Intermountain Generation Station or Intermountain.
\56\ Utah regional haze SIP submission at 100, 102.
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BILLING CODE 6560-50-P

[[Page 67221]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.000

Figure 1 below shows the six sources Utah selected for four-factor
analysis and their proximity to the State's Class I areas. We have also
included CCI Paradox Lisbon Natural Gas Plant in figure 1 because, as
detailed in section IV.C.2.b. of this document, we find that Utah
unreasonably excluded this source from four-factor analysis.
---------------------------------------------------------------------------

\57\ Utah initially selected Intermountain power plant to
perform a four-factor analysis based on the plant's combined Q/d
value of 193.6 (based on 2014 NO<INF>X</INF>, SO<INF>2</INF>, and
PM<INF>10</INF> emissions totaling 28,946 tpy). Utah regional haze
SIP submission 100. However, due to the source's planned retirement,
Intermountain power plant's emissions were not included in the
2028OTBa2 emissions inventory projection or in WRAP's source
apportionment modeling. Intermountain power plant's combined
NO<INF>X</INF>, SO<INF>2</INF>, and PM<INF>10</INF> emissions, in
2022, were 10,174 tpy. 2022 EPA Emission Inventory System. By
magnitude of emissions, in 2022, Intermountain power plant was the
sixth highest emitter of NO<INF>X</INF>(behind Hunter power plant,
the fifth highest emitter) and the 127th highest emitter of
SO<INF>2</INF> in the United States. EPA Clean Air Markets Program
Data; TSD at 11-12, Table 7. Intermountain power plant is further
discussed in sections IV.C.2.c and IV.C.2.f. of this document.
\58\ Utah regional haze SIP submission at 104-05 and appendix G.
---------------------------------------------------------------------------

Figure 1. Sources Required to Perform Four-Factor Analysis and CCI
Paradox Lisbon Natural Gas Plant

[[Page 67222]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.001

Table 2 tabulates the Q/d values associated with each source that
Utah selected for four-factor analysis, as well as CCI Paradox Lisbon
Natural Gas Plant. Q/d values were calculated by Utah and WRAP.\59\ Q/d
values are not listed for out-of-state Class I areas located more than
400 kilometers from a selected source, as those Class I areas fell
outside WRAP's and Utah's analysis threshold.\60\
---------------------------------------------------------------------------

\59\ See WRAP_Threshold_Analysis.xlsm in the docket.
\60\ The WRAP and Utah Q/d methodology did not calculate Q/d
values for any source located at a distance greater than 400
kilometers from a Class I area.

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[[Page 67223]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.002

[[Page 67224]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.003

BILLING CODE 6560-50-C
Utah also compared the sources it selected through Q/d analysis to
WRAP's Weighted Emissions Potential (WEP) analysis, which was released
after Utah selected its sources. WEP is a quantitative method of
analyzing the contribution of visibility impairing pollutants from
individual sources to visibility impairment at individual Class I
areas. WEP values are calculated by overlaying extinction weighted
residence time with the future projected emissions of light extinction
precursors to predict which sources may have the highest contribution
potential to affect visibility at Class I areas on the 20% most
impaired days. In other words, WEP is an analytical method that can
identify significant emission sources that are upwind from a particular
Class I area.\61\ Based on its review of WEP results, Utah determined
that its selection of sources for four-factor analysis sufficiently
captured point sources that have the potential to affect visibility at
in-state and out-of-state Class I areas.\62\
---------------------------------------------------------------------------

\61\ WEP is calculated by overlaying extinction weighted
residence time results with 2028OTBa2 emissions of light extinction
precursors (i.e., NO<INF>X</INF> emissions for ammonium nitrate
light extinction and SO<INF>2</INF> emissions for ammonium sulfate
light extinction). Extinction weighted residence time is calculated
by weighting Hybrid Single-Particle Lagrangian Integrated Trajectory
(HYSPLIT) back trajectories by the actual observed light extinction
at IMPROVE sites on each Most Impaired Day. The results are then
normalized by the sum of the WEP for the total anthropogenic
emissions. WEP results include percentages of the total for nitrates
and sulfates and the rankings by Class I areas. WRAP, ``WEP/AOI
Analysis for western U.S. Class I Areas,'' <a href="https://views.cira.colostate.edu/tssv2/WEP-AOI/">https://views.cira.colostate.edu/tssv2/WEP-AOI/</a> (last accessed July 24,
2024).
\62\ Utah regional haze SIP submission at 108.
---------------------------------------------------------------------------

b. Four-Factor Analyses
Each of the six sources that Utah selected through Q/d analysis
prepared and submitted a four-factor analysis to the State. Utah
provided each source with the State's evaluation of its four-factor
analysis and received responses and other information submittals from
each source.\63\ Chapter 7.C of Utah's regional haze SIP submission
describes

[[Page 67225]]

the sources' four-factor analyses, Utah's evaluations, the sources'
responses and corrections, and Utah's conclusions.
---------------------------------------------------------------------------

\63\ Id. at 14.
---------------------------------------------------------------------------

i. Ash Grove Leamington Cement Plant \64\
---------------------------------------------------------------------------

\64\ The four-factor analyses for this facility are contained in
the Utah regional haze SIP submission at 132-34 and appendix C.1.A.
---------------------------------------------------------------------------

Ash Grove Leamington Cement Plant is a cement manufacturing plant
in Leamington, Utah. The facility has a combined Q/d value of 6.9; the
nearest Class I area is Capitol Reef National Park at 134 kilometers
away. Existing controls at the Leamington Cement Plant are low-
NO<INF>X</INF> burners (LNB), selective non-catalytic reduction (SNCR),
and a federally enforceable NO<INF>X</INF> emission rate of 2.8 lbs/ton
clinker (30-day rolling average). Ash Grove identified six potential
emission control technologies. It determined four of them to be
technically infeasible; the remaining two are already installed at the
plant. The results of Ash Grove's analysis are shown in table 3.
[GRAPHIC] [TIFF OMITTED] TP19AU24.004

In its review of Ash Grove's submission, Utah noted that Ash Grove
could have evaluated more efficient or upgraded versions of LNB or
SNCR.\65\ Ash Grove responded that it was ``not aware of any changes
that could be made to achieve a higher level of control with the
system.'' \66\
---------------------------------------------------------------------------

\65\ Utah regional haze SIP submission, appendix C.1.B. at 7.
\66\ Utah regional haze SIP submission, appendix C.1.C at 2.
---------------------------------------------------------------------------

Utah concluded that the Leamington Cement Plant is adequately
controlled and that no additional emission reduction measures are
required in the regional haze second implementation period. The State
determined that the source's existing SNCR controls and emissions
limits are necessary for reasonable progress.\67\
---------------------------------------------------------------------------

\67\ Utah regional haze SIP submission at 178.
---------------------------------------------------------------------------

ii. Graymont Cricket Mountain Plant \68\
---------------------------------------------------------------------------

\68\ The four-factor analyses for this facility are contained in
the Utah regional haze SIP submission at 134-138, 179, and
appendices C.2.A and C.2.C.
---------------------------------------------------------------------------

The Graymont Cricket Mountain Plant is a lime processing plant with
five rotary lime kilns located in rural Millard County, Utah. The
facility has a combined Q/d value of 9; the nearest Class I area is
Capitol Reef National Park at 130.8 kilometers away. Existing controls
at the Cricket Mountain Plant are low-NO<INF>X</INF> burners and
baghouses at each kiln.
Given Cricket Mountain's low SO<INF>2</INF> emissions, Utah did not
require Graymont to conduct a four-factor analysis for SO<INF>2</INF>
controls. The facility's SO<INF>2</INF> Q/d values at Capitol Reef
National Park and SO<INF>2</INF> emissions data are shown in table 4.

[[Page 67226]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.005

Graymont identified several potential NO<INF>X</INF> control
technologies for the Cricket Mountain Plant. It conducted a four-factor
analysis for SNCR, although it considered that technology to be
infeasible at the facility. Utah requested that Graymont also consider
two additional control options: fuel switching (use of alternative
fuels instead of coal) and alternative production techniques (use of
vertical lime kilns instead of long horizontal kilns). The results of
Graymont's analysis are shown in table 5.

[[Page 67227]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.006

Utah identified several errors with Graymont's analysis and
requested that it further evaluate SNCR. Graymont submitted additional
analyses to support its contention that SNCR is not cost-effective or
technically feasible due to potential proprietary costs and associated
cost per ton.\69\ Graymont also found that fuel switching to natural
gas would not be feasible, as natural gas with the Btu values required
for lime production is not currently available to the facility and
would require construction of extensive infrastructure and process
modifications to connect to the nearest natural gas pipeline. Finally,
Graymont found replacement of its existing kilns with vertical lime
kilns to be infeasible because it would require demolition of the
existing kilns and plant infrastructure and construction of a new
plant.
---------------------------------------------------------------------------

\69\ Utah regional haze SIP submission at 137-48 and appendix
C.2.C.
---------------------------------------------------------------------------

Utah ultimately concluded that additional controls are not required
for reasonable progress at the Cricket Mountain Plant based on their
cost/ton and the potential proprietary costs of SNCR technology for the
kilns. The State determined that the facility's existing control
measures and emissions limits are necessary for reasonable progress
during the second implementation period.\70\
---------------------------------------------------------------------------

\70\ Utah regional haze SIP submission at 179.
---------------------------------------------------------------------------

iii. PacifiCorp Hunter and PacifiCorp Huntington \71\
---------------------------------------------------------------------------

\71\ The four-factor analyses for these facilities are contained
in the Utah regional haze SIP submission at 138-164, 179, and
appendices C.3.A, C.3.C, and C.3.D.
---------------------------------------------------------------------------

Utah selected two electric generating units (EGUs) operated by
PacifiCorp for four-factor analysis: PacifiCorp Hunter and PacifiCorp
Huntington. Hunter is a 1,455 megawatt (MW) coal-fired steam EGU
consisting of three units. It is located near Castle Dale in Emery
County, Utah. Hunter has a combined Q/d value of 216.1, and the nearest
Class I area is Capitol Reef National Park at 74.9 kilometers away.
Huntington is a 960 MW coal-fired steam EGU consisting of two units. It
is located in

[[Page 67228]]

Huntington, Utah. Huntington has a combined Q/d value of 105.5, and the
nearest Class I area is Capitol Reef National Park at 95.8 kilometers
away. Although Hunter and Huntington are entirely separate facilities,
Utah's regional haze SIP submission and PacifiCorp's supporting
documentation analyzed Hunter and Huntington alongside each other.
Therefore, we address these two facilities together in this document.
Both Hunter and Huntington operate existing emissions controls,
although neither have post-combustion NO<INF>X</INF> controls. Hunter
Units 1 and 2 are equipped with LNB/separated overfire air (SOFA) for
NO<INF>X</INF> control, baghouses for PM control, and wet flue-gas
desulfurization (FGD) scrubbers for SO<INF>2</INF> control. Hunter Unit
3 has LNB/SOFA for NO<INF>X</INF> control, baghouse for PM control, and
FGD scrubber for SO<INF>2</INF> control. Huntington Units 1 and 2 have
LNB/SOFA for NO<INF>X</INF> control, fabric filter baghouses for PM
control, and FGD scrubbers for SO<INF>2</INF> control.
In its four-factor analyses for NO<INF>X</INF> controls \72\ at the
two facilities, PacifiCorp evaluated three options: SCR, SNCR, and
``Reasonable Progress Emission Limits'' (RPELs). PacifiCorp's proposed
RPELs were plantwide (i.e., not unit-specific) combined
(NO<INF>X</INF>+SO<INF>2</INF>) annual emission limits that PacifiCorp
proposed to replace the facilities' permitted existing plantwide
applicability limits (PALs), which feature separate PALs for
NO<INF>X</INF> and SO<INF>2</INF>. PacifiCorp proposed an RPEL of
17,773 tpy for Hunter and an RPEL of 10,491 tpy for Huntington. It
asserted that these RPELs would reduce emissions compared to the
plants' most restrictive existing permits.
---------------------------------------------------------------------------

\72\ Aside from the RPELs, PacifiCorp did not evaluate any
additional SO<INF>2</INF> controls on the basis that the units are
already effectively controlled. Utah ultimately agreed with that
conclusion.
---------------------------------------------------------------------------

Based on its calculated cost/ton values for all three control
options, PacifiCorp argued that SCR and SNCR at Hunter and Huntington
were not cost-effective. It urged Utah to select the RPELs for
inclusion in the State's long-term strategy based on a balance of the
four statutory factors.
Utah identified several deficiencies in PacifiCorp's cost
calculations and requested that PacifiCorp ``expand its analysis of
mitigating factors, excessive capital costs, alternative solutions, and
other costs in order to justify the removal of either SNCR and/or SCR
as viable control options.'' \73\ Utah also determined that
PacifiCorp's proposed RPELs were ``lacking'' because they would not
achieve any actual reductions in emissions given that the facilities
have consistently operated well below their permitted PALs.\74\
Following PacifiCorp's submission of additional information, Utah
rejected the proposed RPELs, concluding they could not be effectively
compared against the cost/ton values for physical controls (SNCR and
SCR).
---------------------------------------------------------------------------

\73\ Utah regional haze SIP submission, appendix C.3.B. at 8.
\74\ Id. at 9.
---------------------------------------------------------------------------

PacifiCorp provided updated cost/ton values for SCR and SNCR at
Hunter and Huntington, which Utah accepted. Depending on the unit,
those values ranged from $5,417/ton to $6,579/ton for SNCR and $4,401/
ton to $6,533/ton for SCR,\75\ as shown in tables 6 and 7. PacifiCorp's
cost/ton calculations were based on the plants' average utilization
levels (in the form of the units' heat input, expressed as million
British thermal units (MMBtu)/year) during the 2015-2019 period.\76\ To
determine cost/ton values for SNCR and SCR, PacifiCorp first multiplied
heat inputs for each unit by an emission rate (which varied based on
the SCR, SNCR, and ``no additional controls'' scenarios) to calculate
each unit's emission levels under the three control scenarios. Each
control scenario yielded a different level of NO<INF>X</INF> emissions.
The total annual cost of each control was then divided by its
associated emission reductions (in tons/year) to arrive at a cost-
effectiveness metric of dollars per ton of NO<INF>X</INF> emissions
reduced for each unit at the plants. Tables 6 and 7 also show the
NO<INF>X</INF> emissions reductions that SNCR and SCR post-combustion
controls would achieve relative to the plants' average actual emissions
during the 2015-2019 period.\77\
---------------------------------------------------------------------------

\75\ Utah regional haze SIP submission at 147; appendix C.3.C.,
attachment B.
\76\ Utah regional haze SIP submission at 147.
\77\ To calculate the NO<INF>X</INF> emissions reductions, we
consulted appendix C.3.C. of Utah's regional haze SIP submission. We
determined the tons of NO<INF>X</INF> removed shown in tables 6 and
7 by subtracting each unit's NO<INF>X</INF> emissions (in tons per
year) listed in the ``SNCR Emissions'' and ``SCR Emissions'' tables
in Attachment B in appendix C.3.C. from the corresponding units'
NO<INF>X</INF> emissions (in tons per year) listed in the ``SNCR and
SCR Baseline Emissions'' table in Attachment B.
[GRAPHIC] [TIFF OMITTED] TP19AU24.007

[[Page 67229]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.008

Although it accepted PacifiCorp's updated cost/ton calculations,
Utah did not proceed to evaluate SCR and SNCR with reference to those
costs of compliance and the other three statutory factors. Rather, Utah
elected to further analyze the cost/ton values by predicting how
changes in future plant utilization at Hunter and Huntington might
affect the cost-effectiveness of SCR.\78\ Utah developed a sensitivity
analysis to assess cost/ton values under three alternative plant
utilization scenarios relative to utilization during the baseline
period of 2015-2019: 50%, 75%, and 125% of baseline utilization. The
cost/ton values were calculated by scaling 2015-2019 average heat input
by those percentages. Utah's analysis showed that, all else equal,
higher plant utilization produced lower cost/ton values (meaning that
SCR was relatively more cost-effective), while lower utilization
produced higher cost/ton values (meaning that SCR was relatively less
cost-effective).
---------------------------------------------------------------------------

\78\ Utah focused its analysis on SCR and did not analyze SNCR
in detail. SCR would achieve greater emissions reductions at a lower
cost/ton value compared to SNCR.
---------------------------------------------------------------------------

Utah observed that its sensitivity analysis ``raises the question
of how the units at both plants are likely to be utilized throughout
the second regional haze planning period.'' \79\ To try to address that
question, Utah consulted WRAP's projections of 2028 emissions for
Hunter and Huntington that were developed through the WRAP planning
process.\80\ WRAP's projections of the plants' 2028 emissions were very
similar to the 2015-2019 average actual emissions that PacifiCorp used
in its cost/ton calculations.\81\ WRAP's projections were based on
2016-2018 plant utilization levels.
---------------------------------------------------------------------------

\79\ Utah regional haze SIP submission at 149.
\80\ Id. at 149-50. WRAP relied on the Center for the New Energy
Economy (CNEE) at Colorado State University to project 2028
emissions for coal- and gas-fired EGUs in Western states.
Projections for coal-fired EGUs such as Hunter and Huntington were
based on 2016-2018 plant utilization (in the form of gross load),
heat rates, and emission rates; they also incorporated ``on-the-
books'' controls such as the installation of emissions controls or
plant closures. CNEE's analysis is contained in the docket for this
action. CNEE, ``Project Report for WESTAR-WRAP: Analysis of EGU
Emissions for Regional Haze Planning and Ozone Transport
Contribution'' (June 14, 2019).
\81\ Using the methodology developed by CNEE, WRAP projected
2028 NO<INF>X</INF> emissions for Hunter (10,001 tpy) and Huntington
(6,091 tpy). Utah explained that these emission projections are
``similar though not identical to PacifiCorp's recent actual
emissions used in its four-factor analyses, with the differences
stemming from the use of different averaging periods and
methodologies.'' Utah regional haze SIP submission at 150.
---------------------------------------------------------------------------

After considering WRAP's 2028 emissions projections, Utah asserted
that the electrical generating sector ``is experiencing significant
change'' due to increases in natural gas and renewable energy
generation, enhanced grid coordination, greater transmission capacity
and planning efforts, improvements in equipment efficiency, uncertainty
regarding climate regulation, and customer preferences for renewable
energy.\82\ The State turned to PacifiCorp's 2021 Integrated Resource
Plan (IRP) \83\ to assess potential future operations at Hunter and
Huntington. The IRP contains PacifiCorp's assessment of the ``least-
cost, least-risk portfolio'' of resources while accounting for
compliance with regulatory requirements and customer demand for clean
energy. PacifiCorp completes the full IRP planning process every two
years and reviews and updates it in the in-between years. While the IRP
does not project future utilization at Hunter and Huntington (which
PacifiCorp considers confidential information), Utah cited PacifiCorp's
long-term (2021-2040) plans to increase renewable energy generation and
energy storage capacity, retire certain coal-fired units or convert
them to natural gas, and utilize remaining coal-fired units to support
growth in renewable energy generation by providing power when renewable
generation is not available. Utah concluded there would be a ``likely
reduction in utilization of Hunter and Huntington in future years,''
which would reduce the cost-effectiveness of SCR.\84\
---------------------------------------------------------------------------

\82\ Utah regional haze SIP submission at 150.
\83\ PacifiCorp, ``2021 Integrated Resource Plan'' Vol. I (Sept.
1, 2021), available in the docket for this action (hereinafter
``PacifiCorp 2021 IRP'').
\84\ Utah regional haze SIP submission at 156.
---------------------------------------------------------------------------

Utah also highlighted several ``affordability'' considerations
regarding the installation of SCR at Hunter and Huntington.\85\ It
cited PacifiCorp's concerns about supply chain constraints, inflation,
competition from renewable and storage resources, and the potential for
public utility commissions to reject a future request by PacifiCorp to
recover the costs of SCR. Utah maintained that a requirement to install
SCR could create the potential for involuntary closure of Hunter and
Huntington units, pointing to other coal-fired plants that PacifiCorp
asserted had either retired or switched to a different fuel rather than
installing SCR to control NO<INF>X</INF> pollution. Finally, Utah noted
that Deseret Power, a part-owner of Hunter Unit 2, had raised concerns
about its ability to finance its portion of SCR costs under the terms
of a debt forbearance agreement that restricts Deseret's ability to
take on new debt. Utah concluded that ``[t]hese affordability concerns
and the potential for forced unit closures weigh in favor of
considering reasonable alternatives to requiring the installation of
physical controls.'' \86\
---------------------------------------------------------------------------

\85\ Id. at 154-56.
\86\ Id. at 156.
---------------------------------------------------------------------------

As a result of these potential affordability issues and its
concerns that reduced future utilization of Hunter and Huntington would
erode the cost-

[[Page 67230]]

effectiveness of SCR, Utah rejected SCR in favor of establishing mass-
based annual emission limits for Hunter and Huntington. To provide
compliance flexibility to PacifiCorp, Utah decided to apply these
emission limits at a plantwide level, rather than a unit-by-unit level.
Utah's mass-based emission limits are shown in table 8 below and are
similar in concept to the RPELs that were originally proposed by
PacifiCorp. To set the limits, Utah calculated the plant utilization
and resulting emissions levels that would be associated with the
installation of SCR at $5,750/ton NO<INF>X</INF> removed at all units
of the plants; it then summed the unit-level allowable emissions for
the three units at Hunter and the two units at Huntington to establish
plantwide emissions limits for each plant. Although Utah stated that it
was not establishing a bright-line cost-effectiveness threshold, it
chose the $5,750/ton level based on its determination that $5,750/ton
for physical controls is not cost-effective when balancing all four
statutory factors.\87\ Utah stated that the plantwide mass-based
emission limits will prevent Hunter and Huntington from operating at
levels above which SCR would have been cost-effective. Finally, to
provide additional compliance flexibility, Utah established initial,
interim, and final limits that become more stringent over time, as
shown in table 8.
---------------------------------------------------------------------------

\87\ Id. at 157, 160-61.
[GRAPHIC] [TIFF OMITTED] TP19AU24.009

Although the mass-based emission limits do not require any
reductions in NO<INF>X</INF> emissions from Hunter and Huntington
compared to their recent actual (2014-2019) emissions, Utah noted that
they would prevent the plants from ``backsliding.'' \88\ Utah also
stated that the limits would result in emissions levels that are
``generally consistent'' with those that WRAP used in its 2028
modeling.\89\
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\88\ Id. at 163, appendix H at 656.
\89\ Utah regional haze SIP submission at 162-63.
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The mass-based emission limits apply on an annual basis (12-month
rolling total),\90\ meaning that Hunter and Huntington may vary their
plantwide emissions over the course of a 12-month period so long as
they do not emit more than the total allowable amount of
NO<INF>X</INF>. Utah acknowledged that the variations allowed under
annual limits could potentially exacerbate visibility impairment on the
most impaired days at Class I areas. Utah observed that the worst
nitrate impairment at Class I areas in Utah occurs during the winter.
Hunter and Huntington have two operating peaks (with associated peaks
in NO<INF>X</INF> emissions) each year: a summer peak and a winter
peak. Utah concluded that the plants were unlikely to consume the
majority of their annual NO<INF>X</INF> emissions limit in the winter
because they must preserve their ability to operate at peak loads in
the summer. Thus, Utah concluded that annual limits were ``sufficient
to reduce the likelihood of excess emissions impact [at Class I areas]
during periods of high electricity demand.'' \91\
---------------------------------------------------------------------------

\90\ Utah regional haze SIP submission, appendix A, part
H.23.d.-e.
\91\ Utah regional haze SIP submission at 162.
---------------------------------------------------------------------------

Utah also explained that the other three statutory factors
supported its decision to adopt the mass-based emission limits instead
of an SCR-based requirement. As to the time necessary for compliance,
Utah stated that SCR likely could not be installed during the time
remaining in the second implementation period, while the mass-based
emission limits could be implemented immediately after approval of the
SIP submission. For energy and non-air quality environmental impacts of
SCR, Utah pointed to potential increases in water and coal consumption,
increased generation of coal combustion residuals and other waste
products, and increased greenhouse gas emissions from the additional
energy needed to operate SCR. Utah also noted that because Hunter and
Huntington are ``projected to assist in the transition towards
intermittent renewable resources,'' early plant closures would require
the provision of alternative resources.\92\ As to remaining useful
life, Utah pointed to the then-planned (but not federally enforceable)
closure of Hunter by 2042 and Huntington by 2036, which would occur
before the expiration of the 30-year useful life of SCR. Utah noted
that reduced amortization periods for SCR would reduce its cost-
effectiveness.
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\92\ Id. at 157.
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In sum, Utah determined that physical controls to reduce
NO<INF>X</INF> (i.e., SCR) at Hunter and Huntington are not necessary
to make reasonable progress in the second implementation period.\93\ It
concluded that the enforceable mass-based annual emission limits, as
well as Hunter and Huntington's existing control measures and emission
limits (namely, SO<INF>2</INF> emission limits in the plants' title V
permits), are necessary to make reasonable progress.\94\
---------------------------------------------------------------------------

\93\ Id.
\94\ Id. at 179.
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iv. Sunnyside Cogeneration \95\
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\95\ The four-factor analysis for this facility is contained in
the Utah regional haze SIP submission at 164-69, 179, and appendices
C.4.A. and C.4.C. Additional submissions from Sunnyside that relate
to Utah's determination of the measures necessary to make reasonable
progress are also contained in the docket for this action.
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The Sunnyside Cogeneration Facility is a single unit 58 MW waste-
coal combustion boiler located in Sunnyside, Utah. The facility has a
combined Q/d value of 15.2; the nearest Class I area is Arches National
Park at 97 kilometers away. Sunnyside utilizes a circulating fluidized
bed (CFB) boiler that injects limestone in situ with the fuel stock, so
that combustion of the fluidized fuel achieves some reduction in
SO<INF>2</INF> emissions. A baghouse controls for flue gas
particulates.
Sunnyside identified several potential add-on NO<INF>X</INF> and
SO<INF>2</INF> control technologies for the boiler unit and performed a
four-factor analysis for the technologies it determined to be
technically feasible.\96\ Utah identified multiple errors related to
Sunnyside's

[[Page 67231]]

evaluation of technical feasibility and costs of compliance and
requested that Sunnyside resubmit a corrected four-factor analysis.\97\
Sunnyside submitted an updated four-factor analysis in October 2021,
followed by several submissions in 2022 to respond to issues raised by
the FLMs and public commenters. The results of Sunnyside's analyses are
shown in table 9.
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\96\ Utah regional haze SIP submission, appendix C.4.A.
\97\ Utah regional haze SIP submission, appendix C.4.B at 15-19.
[GRAPHIC] [TIFF OMITTED] TP19AU24.010

Utah ultimately concurred with Sunnyside's conclusion, based on the
costs of compliance and effectiveness of existing controls, that
additional NO<INF>X</INF> or SO<INF>2</INF> controls are not necessary
to make reasonable progress. Utah determined that the existing control
measures and emissions limits for Sunnyside are necessary for
reasonable progress during the second implementation period.\98\
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\98\ Utah regional haze SIP submission at 179.
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v. US Magnesium \99\
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\99\ The four-factor analyses for this facility are contained in
the Utah regional haze SIP submission at 169-72, 179-80, and
appendices C.5.A. and C.5.C.
---------------------------------------------------------------------------

US Magnesium LLC's Rowley Plant is a magnesium production facility
located in Rowley, Utah, west of Salt Lake City. The facility has a
combined Q/d value of 7.4; the nearest Class I area is Capitol Reef
National Park at 288.7 kilometers away. US Magnesium has multiple units
that emit NO<INF>X</INF> as a result of fuel combustion. Existing
controls at US Magnesium are primarily related to the chlorine
reduction burner and associated acid gas scrubbing.
Given the facility's low SO<INF>2</INF> emissions, US Magnesium did
not conduct a four-factor analysis for SO<INF>2</INF> controls. The
facility's SO<INF>2</INF> specific Q/d values for Capitol Reef National
Park and emissions data are shown in table 10.
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[[Page 67232]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.011

US Magnesium identified several potential NO<INF>X</INF> control
technologies for the facility and conducted a four-factor analysis for
each control that it found to be technically feasible. The results of
these analyses are shown in table 11.

[[Page 67233]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.012

[[Page 67234]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.013

BILLING CODE 6560-50-C
Utah identified multiple errors related to US Magnesium's cost
calculations, particularly for the Riley boiler, and requested a
corrected analysis. US Magnesium responded that it had conducted a
reevaluation of the Riley boiler and believed that the cost/ton numbers
for FGR and SNCR were higher than the values Utah had calculated,
pointing to (1) overestimated NO<INF>X</INF> emissions and (2) the
presence of an existing low-NO<INF>X</INF> burner on the boiler.
However, US Magnesium did not submit supporting information on the low-
NO<INF>X</INF> burner or its NO<INF>X</INF> removal efficacy, and Utah
had no record of its existence. Thus, Utah concluded that FGR was a
cost-effective and viable control for the Riley boiler. Utah also
determined that the existing control measures and emissions limits for
US Magnesium are necessary for reasonable progress during the second
implementation period.
2. The EPA's Evaluation of Utah's Long-Term Strategy
The EPA must exercise its independent technical judgment in
evaluating the adequacy of Utah's long-term strategy, including the
sufficiency of the underlying methodology and documentation; we may not
approve a SIP that is based on unreasoned analysis or that lacks
foundation in the CAA's requirements.\100\ As detailed in sections
IV.C.2.a-d. of this document, we find that Utah's long-term strategy
does not satisfy the requirements of CAA section 169A and 40 CFR
51.308(f)(2) on four separate grounds: (1) Utah unreasonably rejected
NO<INF>X</INF> emission reduction measures at Hunter and Huntington
power plants; (2) Utah did not evaluate whether emission reduction
measures at CCI Paradox Lisbon Natural Gas Plant are necessary for
reasonable progress; (3) Utah improperly included automatic exemptions
for startup, shutdown, and malfunction (SSM) in the emission
limitations for Intermountain power plant; and (4) Utah unreasonably
rejected SO<INF>2</INF> emission reduction measures and incorporated an
unsupported emission limitation into its SIP for Sunnyside
Cogeneration. For these reasons, we find that Utah did not adequately
``evaluate and determine the emission reduction measures that are
necessary to make reasonable progress'' by considering the four
statutory factors, as required by CAA section 169A(g)(1) and 40 CFR
51.308(f)(2)(i), and did not adequately ``document the technical basis,
including modeling, monitoring, cost, engineering, and emissions
information, on which the State is relying to determine the emission
reduction measures that are necessary to make reasonable progress,'' as
required by 40 CFR 51.308(f)(2)(iii). Therefore, we are proposing to
disapprove Utah's long-term strategy for the second implementation
period under CAA section 169A and 40 CFR 51.308(f)(2) because it does
not include the enforceable emissions limitations, compliance
schedules, and other measures that are necessary to make reasonable
progress.\101\
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\100\ See Wyoming v. EPA, 78 F.4th 1171, 1180-81 (10th Cir.
2023); Oklahoma v. EPA, 723 F.3d 1201 (10th Cir. 2013); Arizona v.
EPA, 815 F.3d 519, 530-32 (9th Cir. 2016); North Dakota v. EPA, 730
F.3d 750, 760-61 (8th Cir. 2013).
\101\ See also CAA section 169A(b)(2), section 169(b)(2)(B) (the
CAA requires that each implementation plan for a State in which the
emissions from may reasonably be anticipated to cause or contribute
to visibility impairment in a Class I area ``contain such emision
limits, schedules of compliance and other measures as may be
necessary to make reasonable progress toward meeting the national
goal, . . . including . . . a long-term . . . strategy for making
reasonable progress[.]'').
---------------------------------------------------------------------------

a. Unreasonable Rejection of NO<INF>X</INF> Emission Reduction Measures
at Hunter and Huntington
Based on its evaluation of the four statutory factors, Utah
concluded that SCR or other physical NO<INF>X</INF> pollution controls
at Hunter and Huntington are not necessary to achieve reasonable
progress toward Congress's national visibility goal.\102\ Instead, Utah
chose to establish plantwide annual mass-based NO<INF>X</INF> emission
limits for inclusion in its long-term strategy.\103\ To provide a
``compliance glidepath,'' Utah established initial limits of 11,041 tpy
of NO<INF>X</INF> at Hunter and 6,604 tpy of NO<INF>X</INF> at
Huntington for 2022, interim limits of 10,442 tpy of NO<INF>X</INF> at
Hunter and 6,422 tpy of NO<INF>X</INF> at Huntington for 2025, and
final limits of 9,843 tpy of NO<INF>X</INF> at Hunter and 6,240 tpy of
NO<INF>X</INF> at Huntington for 2028.\104\
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\102\ Utah regional haze SIP submission at 157.
\103\ Utah proposed to include these limits in its SIP at
section IX, part H.23.d.-e.
\104\ Utah regional haze SIP submission at 158.
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Utah's determination to impose plantwide annual mass-based emission
limits will not secure any reduction in NO<INF>X</INF> emissions from
Hunter and Huntington.\105\ Tables 12-13 and figures 2-3 of this
document compare annual emissions levels allowed under the plantwide
annual mass-based emission limits to Hunter and Huntington's recent
actual (2014-2021) emissions and to WRAP's projections of the plants'

[[Page 67235]]

2028 emissions under the 2028OTBa2 ``on-the-books'' (no additional
controls) scenario. Table 12 shows that Utah's most stringent mass-
based emission limits (the 2028 final limits) will result in a net
increase in NO<INF>X</INF> emissions of 8 tpy from Hunter and
Huntington combined, compared to WRAP's projected 2028 emissions.\106\
Table 13 and figures 2-3 show that both power plants' recent actual
(2014-2021) NO<INF>X</INF> emissions were, in many years, lower than
the initial, interim, and/or final mass-based emission limits. In stark
contrast to the mass-based emission limits, installation of SCR would
reduce annual NO<INF>X</INF> emissions by 7,858 tpy across all three
units at Hunter and 4,412 tpy across the two units at Huntington
(compared to 2015-2019 average actual emissions),\107\ as shown in
tables 6-7 of this document.
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\105\ Utah regional haze SIP submission at 163 (noting that the
limits are generally consistent with WRAP's projections of 2028
emissions for the ``on-the-books'' scenario and will prevent the
plants from ``backsliding'').
\106\ WRAP's 2028OTBa2 emissions inventory includes emissions
from the ``EGU'' and ``non-EGU'' components at Hunter and
Huntington. Utah did not specify whether the mass-based emission
limits contained in appendix A, part H.23.d.-e. include non-EGU
emissions from the power plants; based on our interpretation of part
H.23.d.-e., we understand them not to incorporate non-EGU emissions.
Therefore, our calculation of the net increase in emissions of 8 tpy
accounts for only the ``EGU'' component emissions in WRAP's
2028OTBa2 inventory.
WRAP projected 2028 non-EGU emissions of 9 tpy for Hunter and 8
tpy for Huntington. See
WRAP_2028OTBa2_and_RepBase2_Point_Emissions_after_states_review_17Aug
2021.xlsx in the docket for this action. If we accounted for the
non-EGU emissions in our comparison of the mass-based emission
limits to WRAP's 2028OTBa2 projected inventory, the mass-based
emission limits would result in a net 9 tpy decrease in emissions
from Hunter and Huntington combined. Given the similarity between +8
tpy and -9 tpy, and the fact that a decrease of just 9 tpy (0.06% of
the power plants' projected 2028 emissions) would not represent any
real reduction in emissions, the inclusion of non-EGU emissions in
our calculations would not affect the analysis or conclusions
contained in this notice of proposed rulemaking.
\107\ The record does not contain information on the exact
amount of NO<INF>X</INF> emissions reductions that installation of
SCR at Hunter and Huntington would achieve relative to WRAP's
projected 2028 emissions for those plants. However, Hunter and
Huntington's 2015-2019 average actual emissions and WRAP's projected
2028 emissions are very similar, as shown in table 13. Therefore, we
can reasonably conclude that the relative emissions reductions would
be comparable in magnitude.
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BILLING CODE 6560-50-P

[[Page 67236]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.014

[GRAPHIC] [TIFF OMITTED] TP19AU24.015

Figure 2. Annual Actual NO<INF>X</INF> Emissions at Hunter Compared
to Utah's Plantwide Mass-Based Emission Limits and 2028OTBa2 Projected
Emissions \108\
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\108\ Data source: EPA CAMPD as reported by Utah and PacifiCorp,
available in the docket for this action.

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[[Page 67237]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.016

Figure 3. Annual Actual NO<INF>X</INF> emissions at Huntington
Compared to Utah's Plantwide Mass-Based Emission Limits and 2028OTBa2
Projected Emissions \109\
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\109\ Id.
[GRAPHIC] [TIFF OMITTED] TP19AU24.017

BILLING CODE 6560-50-C
The Technical Support Document (TSD) for this action contains
detailed information on the effect of emissions from EGUs in Utah, and
Hunter and

[[Page 67238]]

Huntington in particular, on visibility impairment at all five of
Utah's Class I areas and at numerous out-of-state Class I areas. In the
following paragraphs of this document, we summarize key points that are
further detailed in the TSD.
Utah relied on and referenced data from WRAP's TSS, which includes
analytical tools and products that WRAP developed to assist WRAP member
states in developing their regional haze SIPs.\110\ Among other
analyses, WRAP performed photochemical source apportionment modeling
for 2028 using the Comprehensive Air Quality Model with extensions
(CAMx) model to estimate the statewide visibility impacts for each WRAP
state to Class I areas on the 20% most impaired days. This modeling
also included a more detailed breakout of state-by-state sulfate and
nitrate contributions for five separate emissions source categories
(EGUs, mobile sources, non-EGU point sources, oil and gas, and all
other remaining anthropogenic sources combined). As part of our
evaluation of Utah's regional haze SIP submission, the EPA examined the
results of the WRAP products, including the emissions inventories, Q/d
analyses, weighted emissions potential (WEP) analyses, and source
apportionment modeling. This data provides quantitative results of the
sulfate and nitrate Class I area visibility impacts from EGUs in Utah.
We also used this data to estimate the visibility impairment impacts at
Class I areas from Hunter power plant, Huntington power plant, and both
plants combined.
---------------------------------------------------------------------------

\110\ Utah regional haze SIP submission at 34-35 (stating that
the WRAP TSS ``is the source of the key summary analytical results
and methods for the required technical elements of the [Regional
Haze Rule] contained within this SIP''). See also id. at 61-71, 73-
81, 97-102, and 108-120.
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The WRAP 2028 projected emissions inventories show that Utah
NO<INF>X</INF> and SO<INF>2</INF> emissions are highly influenced by
Hunter and Huntington power plants.\111\ Of all 2028 projected
statewide anthropogenic NO<INF>X</INF> and SO<INF>2</INF> emissions,
from every anthropogenic source in Utah, Hunter is projected to account
for 11.41% of NO<INF>X</INF> and 25.56% of SO<INF>2</INF> emissions;
Huntington is projected to account for 6.94% of NO<INF>X</INF> and
17.89% of SO<INF>2</INF> emissions; and Hunter and Huntington combined
are projected to account for 18.35% of NO<INF>X</INF> and 43.45% of
SO<INF>2</INF> emissions.
---------------------------------------------------------------------------

\111\ See the TSD at section II, Emissions Inventories, for
detailed information.
---------------------------------------------------------------------------

Comparing the NO<INF>X</INF> and SO<INF>2</INF> emission
contributions of Hunter and Huntington to just the Utah EGU source
category shows even higher projected contributions. Of all statewide
EGU NO<INF>X</INF> and SO<INF>2</INF> emissions from every EGU source
located in Utah for 2028,\112\ Hunter is projected to account for 41.9%
of NO<INF>X</INF> and 35.45% of SO<INF>2</INF> emissions; Huntington is
projected to account for 25.51% of NO<INF>X</INF> and 24.81% of
SO<INF>2</INF> emissions; and Hunter and Huntington combined are
projected to account for 67.41% of NO<INF>X</INF> and 60.26% of
SO<INF>2</INF> emissions.
---------------------------------------------------------------------------

\112\ Section II of the TSD contains detailed information on
emissions from EGU sources in Utah. WRAP's 2028OTBa2 projected
emissions inventory indicates that of the 16 currently operating EGU
sources that are subject to Utah's regulatory jurisdiction, Hunter
and Huntington power plants' combined NO<INF>X</INF> emissions of
16,075 tpy far exceed the total combined NO<INF>X</INF> emissions of
894 tpy from the 14 other EGU sources.
---------------------------------------------------------------------------

WRAP's 2028 projected emissions inventories include emissions from
Bonanza power plant, which is on Tribal land and is not subject to
Utah's regulatory jurisdiction, and Kennecott power plant, which has
been retired. Removing Bonanza and Kennecott's NO<INF>X</INF> and
SO<INF>2</INF> emissions contributions from the 2028 projected
statewide totals of anthropogenic NO<INF>X</INF> and SO<INF>2</INF>
emissions indicates even higher contributions from Hunter and
Huntington. Hunter is projected to account for 58.87% of all EGU source
category NO<INF>X</INF> and 54.37% of all EGU source category
SO<INF>2</INF> emissions; Huntington is projected to account for 35.84%
of all EGU source category NO<INF>X</INF> and 38.06% of all EGU source
category SO<INF>2</INF> emissions; and Hunter and Huntington combined
are projected to account for 94.7% of all EGU source category
NO<INF>X</INF> emissions and 92.43% of all EGU source category
SO<INF>2</INF> emissions. In other words, Hunter and Huntington account
for more than 90% of the EGU source category emissions that are subject
to Utah's regulatory jurisdiction under the regional haze program.
Hunter and Huntington's NO<INF>X</INF> emissions are significant on
a national scale. Hunter ranked as the third highest emitter of
NO<INF>X</INF> for all EGUs within the United States in 2021 and as the
fifth highest emitter of NO<INF>X</INF> for all EGUs within the United
States in 2022. Huntington ranked 20th in 2021 and 29th in 2022 for
NO<INF>X</INF> emissions among all EGUs in the United States.
WRAP's Q/d analyses \113\ show that Hunter and Huntington have, by
far, the highest Q/d values for Utah's five Class I areas of all the
sources that Utah selected for four-factor analysis.\114\ Specifically,
Hunter has the highest Q/d values and Huntington has the second-highest
Q/d values for all Utah Class I areas. For out-of-state Class I areas,
Hunter and Huntington also have the highest Q/d values among the
sources Utah selected for four-factor analysis.
---------------------------------------------------------------------------

\113\ Utah employed Q/d analysis to ``[determine] which sources
have the highest potential impact on Utah's [Class I areas].'' Utah
regional haze SIP submission at 81.
\114\ See the TSD at section IV, Q/d Analysis of Utah Sources,
for detailed information.
---------------------------------------------------------------------------

In addition, due to source decommissionings, enforceable
retirements, and requirements to install NO<INF>X</INF> post-combustion
controls, many of the in-state and out-of-state sources that had the
highest Q/d values for Utah's five Class I areas (based on 2014
emissions data, which WRAP used to calculate Q/d values in its
analysis) will no longer be major contributors to visibility impairment
in the second implementation period. If the Q/d values were updated to
reflect these sources' resulting lower emissions, Hunter and Huntington
would rank even higher among all sources nationwide with the highest
potential impact (in terms of Q/d value) on Utah's Class I areas.
In addition, WRAP's nitrate and sulfate WEP analyses identified
Hunter and Huntington as significant emissions sources located upwind
of several in-state and out-of-state Class I areas.115 116
Among all in-state and out-of-state point sources, WRAP's nitrate WEP
results classify Hunter as the top-ranked source for Arches National
Park, Bryce Canyon National Park, Canyonlands National Park, and
Capitol Reef National Park; and the second-ranked source for Zion
National Park. Similarly, WRAP's nitrate WEP results classify
Huntington as the second-ranked source for Arches National Park, Bryce
Canyon National Park, Canyonlands National Park, and Capitol Reef
National Park; and the eighth-ranked source for Zion National Park.
Considering only the sources that Utah selected for four-factor
analysis, Hunter and Huntington have the highest nitrate WEP values for
each of Utah's five Class I areas. Furthermore, WRAP's sulfate WEP
results for Utah's five Class I areas show that Hunter and Huntington
are the top two ranked sources for many of Utah's Class I areas; they
also have the highest sulfate WEP values among all sources that Utah
selected for four-factor analysis.
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\115\ Utah regional haze SIP submission at 37 (``[WEP] analyses
can identify what significant emission sources are upwind from a
Class I area'').
\116\ See the TSD at section V, Weighted Emission Potential
(WEP) Analysis, for detailed information.
---------------------------------------------------------------------------

WRAP's 2028 source apportionment modeling also shows that Utah
NO<INF>X</INF> and SO<INF>2</INF> emission sources are by far the
largest sources of anthropogenic nitrate and sulfate visibility
impairment at

[[Page 67239]]

Arches National Park, Canyonlands National Park, and Capitol Reef
National Park. For example, at Arches and Canyonlands National Parks
(CANY1 \117\ site), 60.37% of the total modeled anthropogenic nitrate
(from all anthropogenic emissions sources in the country) and 40.34% of
the total modeled anthropogenic sulfate are attributed to Utah
anthropogenic emissions. The modeling shows that a large percentage of
these total anthropogenic emissions originate specifically from Utah
EGUs. At Arches and Canyonlands National Parks, 82.26% of the total
modeled anthropogenic nitrate and 48.49% of the total modeled
anthropogenic sulfate visibility impairment from all EGU sources
nationwide is attributed to Utah EGU emissions. The modeled visibility
impacts at Arches and Canyonlands National Parks from Utah EGUs to
nitrate light extinction are higher than any other anthropogenic source
category contribution in the entire continental United States.\118\ And
the modeled visibility impacts at Arches and Canyonlands National Parks
from Utah EGUs to sulfate light extinction are also by far the largest
among any other state or source category.\119\ Furthermore, the WRAP
modeling results indicate that Utah's EGU source category has the
highest contributions to nitrate and sulfate visibility impairment of
all EGU sources nationwide at all Utah Class I areas (except Zion
National Park for sulfate, where Utah has the third-highest
contribution).
---------------------------------------------------------------------------

\117\ The CANY1 IMPROVE monitoring site represents both
Canyonlands and Arches National Parks.
\118\ Utah regional haze SIP submission at 74, figure 36.
\119\ Utah regional haze SIP submission at 74, figure 35.
---------------------------------------------------------------------------

The EPA further evaluated WRAP's source apportionment modeling for
the EGU source category to estimate contributions attributable to
Hunter and Huntington.\120\ WRAP's 2028 emissions inventory projects
that Hunter and Huntington will account for 67.41% of NO<INF>X</INF>
emissions and 60.26% of SO<INF>2</INF> emissions from the Utah EGU
source category.\121\ Therefore, we assumed that these power plants
would contribute an equivalent percentage of the total modeled
contribution from the Utah EGU source category for nitrate and sulfate
light extinction at Class I areas.\122\ Using this approach, we
estimated Hunter and Huntington's contribution to total (nationwide)
anthropogenic visibility impairment at Arches and Canyonlands National
Park to be 14.39% of the total (nationwide) modeled 2028 anthropogenic
nitrate light extinction and 14.92% of the total (nationwide) modeled
2028 anthropogenic sulfate light extinction. This represents a
substantial contribution to both nitrate and sulfate visibility
impairment at these Class I areas, and is by far the largest modeled
contribution among all anthropogenic sources within and outside Utah.
For Capitol Reef National Park, Hunter and Huntington's estimated
contributions to total (nationwide) modeled 2028 anthropogenic nitrate
light extinction is 7.51% and 7.42% for sulfate light extinction among
all source categories.
---------------------------------------------------------------------------

\120\ See the TSD at section III, Source Apportionment Modeling,
for detailed information.
\121\ In the WRAP 2028OTBa2 emissions inventory, Intermountain
was assumed to be retired and therefore had no modeled emissions. In
addition to Hunter and Huntington, the vast majority of the rest of
the modeled Utah NO<INF>X</INF> and SO<INF>2</INF> EGU emissions
were from the Bonanza power plant, a Tribal source in northeast
Utah.
\122\ Because the source apportionment modeling was performed at
the state level, apportioning the Class I area EGU visibility
impacts to the facility level is an approximation. However, since
the majority of the statewide modeled 2028 NO<INF>X</INF> and
SO<INF>2</INF> EGU source category emissions are from Hunter and
Huntington, and those power plants are in closer proximity to
Canyonlands National Park and Arches National Park than the only
other modeled major source of EGU NO<INF>X</INF> and SO<INF>2</INF>
emissions (Bonanza power plant), our estimates are reasonable
assumptions. In fact, since Hunter and Huntington are closer to
Canyonlands National Park and Arches National Park than the Bonanza
power plant, the calculations likely underestimate Hunter and
Huntington's combined anthropogenic nitrate and sulfate visibility
impacts. Furthermore, WRAP's modeling does not account for the
closure of Kennecott power plant or for retirements and pollution
control installations at certain other sources, further underscoring
the likelihood that our calculation underestimates the relative
importance of Hunter and Huntington's modeled visibility impacts to
Class I areas compared to other sources.
---------------------------------------------------------------------------

Using the same assumptions as detailed in the paragraph above, the
EPA estimated that of the modeled Utah EGU source category
contributions to light extinction at Arches and Canyonlands National
Parks, 55.45% of nitrate light extinction and 29.22% of sulfate light
extinction is attributable to Hunter and Huntington. Of the modeled
Utah EGU source category contributions to light extinction at Capitol
Reef National Park, 42.19% of nitrate light extinction and 17.81% of
sulfate light extinction is attributable to Hunter and Huntington.
Aside from Arches, Canyonlands, and Capitol Reef National Parks,
Utah EGUs also heavily influence visibility impairment at other Class I
areas within and outside of Utah. For example, Utah EGUs have the
highest modeled contribution to nitrate and sulfate light extinction at
Maroon Bells-Snowmass Wilderness, CO, Eagles Nest Wilderness, CO, Flat
Tops Wilderness, CO, and West Elk Wilderness, CO (WHRI1 \123\), among
all EGU sources nationwide. As shown in table 14, the estimated
contribution from Hunter and Huntington to these four Class I areas is
3.46% (nitrate) and 13.77% (sulfate) of all total modeled anthropogenic
light extinction.
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\123\ The WHRI1 IMPROVE site represents Maroon Bells-Snowmass
Wilderness, Eagles Nest Wilderness, Flat Tops Wilderness, and West
Elk Wilderness.

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[[Page 67240]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.018

In sum, WRAP and other available data show that Utah EGUs, and
Hunter and Huntington in particular, make substantial contributions to
anthropogenic visibility impairment at numerous Class I areas. Because
Utah's plantwide mass-based emission limits for Hunter and Huntington
do not require emissions reductions compared to the plants' recent
actual emissions and 2028 projected emissions, the mass-based emission
limits will not mitigate the plants' major effects on anthropogenic
visibility impairment at Class I areas.
For the reasons explained in section IV.C.2.a.i.-iv. of this
document, we find that Utah's determination that the plantwide mass-
based NO<INF>X</INF> emission limits for Hunter and Huntington are all
that is necessary to make reasonable progress is not grounded in a
reasoned evaluation of the four statutory factors or a defensible
technical analysis. Therefore, we propose to disapprove Utah's long-
term strategy because it does not satisfy the requirements of CAA
section 169A(b)(2)(b) and (g)(1) and 40 CFR 51.308(f)(2).
i. Evaluation of Costs of Compliance
Utah's evaluation of the costs of compliance was influenced by its
finding that physical controls that cost more than $5,750/ton are not
cost-effective; its determination that likely reductions in the future
utilization of Hunter and Huntington would reduce the cost-
effectiveness of SCR and other physical controls; and its concern about
various ``affordability'' considerations associated with physical
controls, including the potential for involuntary plant closures. Based
on our evaluation of the SIP submission and supporting materials in the
record, we find that Utah's analysis of and conclusions regarding the
costs of compliance lack support. Therefore, we find that Utah did not
reasonably consider the costs of compliance in evaluating emission
reduction measures for Hunter and Huntington, as required by CAA
section 169A(g)(1) and 40 CFR 51.308(f)(2).

A. Determination That Physical Controls Above $5,750/ton Are Not Cost-
Effective

Utah determined that physical controls that cost more than $5,750/
ton are not cost-effective for Hunter and Huntington. It then set the
plantwide mass-based emission limits at the amount of annual
NO<INF>X</INF> emissions corresponding to the plant utilization and
associated emissions levels at which SCR would have cost $5,750/ton. As
explained below, we find that Utah did not adequately justify its
determination of the measures necessary to make reasonable progress at
Hunter and Huntington based on its chosen cost-effectiveness level.
First, regardless of the appropriateness of the $5,750/ton level,
Utah did not specifically address whether SCR at Hunter Unit 3 (at the
lower cost of $4,401/ton NO<INF>X</INF> removed) is necessary for
reasonable progress. Hunter Unit 3 has the highest emissions among the
five units at Hunter and Huntington; installing SCR at that unit alone
would reduce NO<INF>X</INF> by 3,579 tons per year, a >80% reduction in
emissions compared to recent levels. See tables 6-7. In its draft
regional haze SIP, Utah acknowledged that ``the relatively lower
estimated $/ton for SCR for Hunter 3 merits further evaluation of
whether this control could be cost-effective.'' \124\ However, Utah did
not include that evaluation in its final SIP submission, which is
silent on whether SCR at Hunter Unit 3 specifically is cost-effective.
Since installing SCR at Hunter Unit 3 would achieve significant
emissions reductions at a cost of $4,401/ton (below Utah's $5,750/ton
cost-effectiveness level) and the State did not address this issue in
its SIP submission, we find that Utah unreasonably rejected SCR for
this unit.
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\124\ Draft Utah Regional Haze SIP at 127 (contained within
``Utah Regional Haze SIP Submittal 2022 v2,'' available in the
docket for this action).
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Second, Utah did not adequately justify its conclusion that
physical controls above $5,750/ton are not cost-effective. Utah noted
that this level is ``in line with the range considered by other
states,'' which it identified as $1,000/ton at the low end to $18,000/
ton at the high end.\125\ However, Utah

[[Page 67241]]

did not adequately explain why it selected $5,750/ton as the
appropriate amount, the factors it considered in doing so, or how this
cost/ton level relates to the State's obligation to make reasonable
progress toward the national visibility goal. While Utah asserted that
$5,750/ton is not cost-effective ``when balanced against the remaining
three statutory factors,'' \126\ the State's evaluation of those
factors evinces no connection to its chosen cost/ton level. Since Utah
did not sufficiently explain the basis for its determination and did
not provide adequate underlying technical documentation, we cannot
conclude that Utah's selection of a $5,750/ton cost-effectiveness level
was based on reasoned analysis.
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\125\ Utah regional haze SIP submission at 160-61.
\126\ Id. at 157-58.
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The information in the record indicates that installation of SCR,
at an estimated cost of $5,979-$6,533/ton NO<INF>X</INF> reduced, may
well be cost-effective for Hunter Units 1 and 2 and Huntington Units 1
and 2 (or some subset of these units). These values are on the higher
end of emission reduction measures found to be cost-effective in
previous regional haze actions,\127\ but they may be cost-effective
here in light of the magnitude of Hunter and Huntington's contributions
to anthropogenic visibility impairment at several Class I areas. Based
on the information provided by Utah, installation of SCR at all five
units at Hunter and Huntington would reduce NO<INF>X</INF> emissions by
over 12,000 tons per year compared to both the baseline emissions
assumed in the four-factor analysis and the 2028 mass-based emission
limits that Utah determined to be necessary for reasonable progress
(see tables 6, 7, and 8 above). Utah explained that in making its
source-specific reasonable progress determinations, it evaluated the
four statutory factors ``as well as the [visibility] modeling results
provided by the WRAP.'' \128\ The State also concluded that its
determinations of the measures necessary to make reasonable progress
``will help protect . . . visibility in Utah.'' \129\ At the same time,
Utah did not evaluate the appropriateness of the $5,750/ton cost-
effectiveness level in light of these visibility considerations. As
explained above in this document and in the TSD for this action, the
WRAP modeling shows that Utah EGUs, and Hunter and Huntington in
particular, have large impacts on both anthropogenic nitrate and
sulfate impairment at several Class I areas in Utah and outside the
State. SCR would achieve substantial reductions in NO<INF>X</INF>
emissions from these plants, mitigating their contributions to
anthropogenic nitrate visibility impairment in numerous Class I
areas.\130\ See tables 6-7. As we noted in the 2017 RHR Revisions, if a
state arbitrarily excludes ``cost-effective controls at sources with
significant visibility impacts, then the EPA has the authority to
disapprove the state's unreasoned analysis.'' \131\
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\127\ The EPA recently proposed a BART FIP for Texas that
references first implementation period BART decisions and notes that
the EPA and states required several BART controls with average cost-
effectiveness values in the $4,200/ton to $5,100/ton range
(escalated to 2020 dollars). 88 FR 28918, 28963 (May 4, 2024). Other
states have found higher control costs to be reasonable, as Utah
acknowledged in figure 61 of its regional haze SIP submission. For
example, Oregon selected a $10,000/ton cost-effectiveness threshold
for the second implementation period. 89 FR 13622, 13638 (Feb. 23,
2024). PacifiCorp submitted its updated cost analysis in August 2021
(appendix C.3.C. to Utah's regional haze SIP submission), though it
is not clear what cost year was assumed for the cost/ton values.
Even if the cost/ton values for SCR at Hunter and Huntington are
somewhat higher than those referenced in the Texas BART FIP and
other actions, they may still be cost-effective for purposes of
reasonable progress in the second implementation period. Most of the
least expensive available emission reduction measures were already
required and implemented during the first implementation period. As
we move forward to subsequent implementation periods, source
emissions will become smaller and potential controls will become
more expensive on a cost per ton basis. However, the statute and
regulations still require states to continue to make reasonable
progress towards the national visibility goal. See generally CAA
section 169A(b)(2)(B); 40 CFR 51.308(f)(2); 40 CFR 51.308(e)(5); 82
FR 3080.
\128\ Utah regional haze SIP submission at 14.
\129\ Id. at 178.
\130\ The mass-based emission limits are very similar to the
RPELs that PacifiCorp initially proposed, which Utah found to be
``lacking'' because they would ``not represent a reduction in actual
emissions.'' Utah regional haze SIP submission, appendix C.3.B. at
9. But Utah did not acknowledge or address this issue when it
adopted the mass-based emission limits.
\131\ 82 FR 3088.
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For these reasons, we find that Utah unreasonably relied on a
$5,750 cost-effectiveness level in determining that the mass-based
emission limits at Hunter and Huntington are all that is necessary for
reasonable progress.

B. Consideration of Future Plant Utilization

In its evaluation of the costs of compliance, Utah also determined
that likely reductions in the future utilization of Hunter and
Huntington would erode the cost-effectiveness of SCR. Consequently, the
State concluded that this factor weighed in favor of the mass-based
emission limits over SCR.\132\ As detailed in this section
IV.C.2.b.i.B., we find that Utah's decision-making based on projected
changes in future plant utilization was not based on reasoned analysis.
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\132\ Utah regional haze SIP submission at 156-57, appendix H at
672.
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Utah did not employ the plant utilization assumptions that WRAP
used in its 2028 emissions projection (based on 2016-2018 utilization
levels) and that PacifiCorp used in its cost/ton analysis (based on
2015-2019 utilization levels). Utah instead utilized PacifiCorp's 2021
IRP to predict future operations at Hunter and Huntington.\133\ The
IRP, however, does not provide plant- or unit-specific projections of
utilization.\134\ More importantly, IRPs are neither permanent nor
enforceable at the state or Federal levels and are subject to change at
any time.\135\ Instead, PacifiCorp's IRP outlines the company's
``preferred portfolio'': the ``least-cost, least-risk'' portfolio of
company-wide resources at the time the IRP was published.\136\ Utah
reviewed the IRP preferred portfolio's projections of new renewable
resource and storage capacity, coal unit retirements or conversions to
natural gas, and coal generation and capacity compared to total energy
generation and capacity.\137\ Based on its interpretation of the 2021
IRP, Utah concluded that utilization of Hunter and Huntington is likely
to decline.\138\
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\133\ Utah regional haze SIP submission at 152.
\134\ PacifiCorp's Public Comment on Utah's Regional Haze Second
Implementation Period SIP (May 31, 2022) at 18 n.39 (hereinafter
``PacifiCorp Public Comment''); PacifiCorp 2021 IRP at 21
(``PacifiCorp's portfolio development process is based on achieving
reliable system operation using the aggregate contributions of each
resource in the portfolio, rather than focusing on an individual
estimate.'').
\135\ PacifiCorp 2021 IRP at 7. The page following the cover
page states: ``This 2021 Integrated Resource Plan Report is based
upon the best available information at the time of preparation. The
IRP . . . is subject to change as new information becomes available
or as circumstances change. It is PacifiCorp's intention to revisit
and refresh the IRP action plan no less frequently than annually.''
\136\ Id. at 7.
\137\ Utah regional haze SIP submission at 152-54.
\138\ Id. at 153-54.
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As the 2021 IRP itself cautions, ``these plans, particularly the
longer-range elements, can and do change over time.'' \139\ While the
2021 IRP projected retirement dates of 2036 for Huntington and 2042 for
Hunter under the company's then-preferred portfolio,\140\ the 2023 IRP
moved those projections up to 2031-2032.\141\ Just one year later, as a
result of regulatory developments leading to ``fewer restrictions on
coal-fired operation than were assumed,'' the

[[Page 67242]]

2023 IRP Update (released in April 2024) returned the plants' projected
retirement dates to 2036 and 2042.\142\ As these changes demonstrate,
PacifiCorp's preferred portfolio frequently evolves in response to
changing costs, consumer demand for clean energy, and risks, including
changes to the company's regional haze and other environmental
compliance obligations.\143\
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\139\ PacifiCorp 2021 IRP at 7.
\140\ Id. at 136-37; Utah regional haze SIP submission at 153,
158.
\141\ PacifiCorp, ``2023 Integrated Resource Plan'' Vol. I (Mar.
31, 2023) at 146, available in the docket for this action.
\142\ PacifiCorp, ``2023 Integrated Resource Plan Update''
(April 1, 2024) at 12, available in the docket for this action.
\143\ PacifiCorp 2021 IRP at 7, 24, 53-56.
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Notably, PacifiCorp did not provide evidence regarding changes in
plant utilization during the SIP development process. In its
submissions to the State, the company noted overall changes in the
electricity generation sector and ``uncertainty regarding medium to
long-term operations of Hunter and Huntington,'' but it never once
stated that it expected the plants' utilization to decline.\144\ For
the reasons explained in this section IV.C.2.a.i.B., we disagree with
Utah's assertion that its SIP submission includes ``strong evidence
that utilization of these facilities is likely to decrease in the
future.'' \145\ Consequently, the information in the record does not
support Utah's conclusion as to the likely ``erosion'' of the cost-
effectiveness of SCR at Hunter and Huntington ($4,401/ton to $6,533/
ton).\146\
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\144\ PacifiCorp Public Comment at 18. PacifiCorp declined to
provide its projected capacity factors for Hunter and Huntington,
citing their proprietary and commercially sensitive nature. Utah and
EPA regulations provide for the confidential treatment of qualifying
business information. See generally 40 CFR 2.201 through 2.311; Utah
Admin. Code 307-102-2.
\145\ Utah regional haze SIP submission, appendix H at 672.
\146\ Utah regional haze SIP submission at 156.
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Furthermore, the mass-based emission limits that Utah established
bear no relationship to the State's judgment that utilization of Hunter
and Huntington is likely to decline. Table 59 in Utah's regional haze
SIP submission shows the inputs Utah used to calculate the emission
limits, including each unit's 2028 utilization (in the form of heat
input). As shown in table 15, Utah's projected 2028 heat input levels
are slightly higher than 2015-2019 average heat input for all Hunter
and Huntington units except Hunter Unit 3. Plantwide, the 2028
utilization levels Utah used in calculating the mass-based emission
limits represent a 7.75% increase in utilization across the two units
at Huntington and a 0.94% increase across the three units at Hunter,
compared to their average actual 2015-2019 utilization. In other words,
Utah set its mass-based emission limits at levels premised on an
increased plant utilization scenario. The State did not acknowledge or
reconcile this conflict within its SIP submission.
[GRAPHIC] [TIFF OMITTED] TP19AU24.019

Because the mass-based emission limits are predicated on increased
plant utilization, Utah's citation to the 2019 Guidance and 2021
Clarifications Memo \147\ lends no support to its position. The 2019
Guidance states that ``[g]enerally, the estimate of a source's 2028
emissions is based at least in part on information on the source's
operation and emissions during a representative historical period.''
\148\ However, both the 2019 Guidance and 2021 Clarifications Memo
provide examples of situations where it may be reasonable to conclude
that a source's 2028 operations will differ from its historical
operations, such as the addition of enforceable requirements or
expected changes in utilization due to documented and verifiable
renewable energy or energy efficiency programs.\149\ The 2021
Clarifications Memo notes that when a state relies on an assumption of
reduced utilization to reject emission control measures, it may
incorporate a utilization or production limit corresponding to that
assumption into its SIP.\150\ Utah projected that utilization of Hunter
and Huntington would decline compared to recent historical utilization
levels. In alignment with the 2021 Clarifications Memo, Utah could have
proposed enforceable utilization limits and/or mass-based emission
limits based upon the decreasing utilization assumptions. However, Utah
set the mass-based emission limits at levels premised on increased,
rather than decreased, plant utilization, which does not align with the
2019 Guidance or 2021 Clarifications Memo.
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\147\ Utah regional haze SIP submission at 147-48.
\148\ 2019 Guidance at 29.
\149\ Id.; 2021 Clarifications Memo at 12.
\150\ 2021 Clarifications Memo at 12.

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[[Page 67243]]

In sum, Utah's reliance on an unsubstantiated and unenforceable
projected reduction in future plant utilization does not justify its
conclusion that installing SCR at Hunter and Huntington, at an
estimated cost of $4,401/ton to $6,533/ton depending on the unit, is
not cost-effective and is not necessary for reasonable progress.\151\
Furthermore, the specific levels at which Utah established the mass-
based emission limits are not grounded in reasoned analysis. For the
reasons explained in this section, we find that Utah has not justified
its reliance on changes in plant utilization to determine that the
mass-based emission limits at Hunter and Huntington are all that is
necessary for reasonable progress.
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\151\ Utah also highlighted the ``regulatory flexibility'' that
mass-based limits provide, noting that PacifiCorp can meet them by
``modifying operation, installing controls, switching fuels, closing
units, or some combination of these options.'' Utah regional haze
SIP submission at 164. Given that Utah's mass-based limits are
predicated on increased plant utilization, we do not see the logic
in Utah's assumption that PacifiCorp must make any changes to comply
with them. In any event, SCR-based numeric emission limits would
provide that same flexibility, as sources can generally choose to
comply with those limits in any manner they choose.
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C. Evaluation of Affordability Considerations

In its evaluation of the costs of compliance, Utah also considered
several ``affordability'' arguments presented by PacifiCorp and Deseret
Power, a part owner of Hunter Unit 2. These included the potential for
involuntary plant closures or conversions to natural gas, difficulties
in recovering the costs of SCR installation, and Deseret's contention
that it could not finance its share of SCR costs at Hunter Unit 2.\152\
Utah concluded that ``these affordability concerns and the potential
for forced unit closures weigh in favor of'' the mass-based emission
limits over SCR.\153\
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\152\ Utah regional haze SIP submission at 154-156.
\153\ Id. at 156.
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To support its affordability arguments, PacifiCorp relied on the
BART Guidelines,\154\ which the EPA promulgated to address BART, a
separate statutory and regulatory requirement from the requirement to
make reasonable progress toward the national visibility goal. While we
may consider affordability under the costs of compliance factor for
reasonable progress, affordability is not an overriding element of the
costs of compliance analysis and cannot be considered in isolation to
determine whether emission reduction measures are necessary to make
reasonable progress. As explained in the paragraphs that follow, Utah's
conclusion regarding affordability was not based on adequate analysis
or supporting documentation. Therefore, as with plant utilization, we
find Utah's reliance on affordability considerations to be unjustified.
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\154\ 40 CFR part 51, appendix Y, section IV.E.3.
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First, the record does not substantiate Utah's concerns that Hunter
and Huntington may be effectively forced to cease operations if the
State required emission reductions based on SCR. While Utah listed
several coal-fired power plants regionally and nationwide that
PacifiCorp alleged have either ``retired or powered [to natural gas]
rather than installing SCR,'' \155\ the record contains no details
about those closures or conversions.\156\ Without that information, it
is impossible to conclude whether they resulted from market forces,
regulatory requirements, other factors, or some combination of causes.
Utah also cited an ``Affordability Analysis'' that PacifiCorp prepared
for its Wyodak power plant in Wyoming.\157\ That document presented an
economic analysis of SCR installation at Wyodak using system modeling
analysis and a plant-specific market-based dispatch analysis.\158\
PacifiCorp acknowledged that ``the outcome of the Affordability
Analysis does not directly translate'' to Hunter and Huntington,\159\
and it did not submit a similar plant-specific analysis for those
facilities. Utah did not address the Affordability Analysis'
applicability to Hunter and Huntington, conduct its own economic
analysis, or make any determination as to the likelihood (versus the
potential) of plant closures. Without such a determination grounded in
adequate documentation and supporting analysis, Utah's stated concerns
about involuntary plant closures cannot be substantiated.\160\
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\155\ Utah regional haze SIP submission at 154.
\156\ PacifiCorp Public Comment at 13-14 (listing sources but
providing no details on the factors that led to the decision).
PacifiCorp also conceded that ``some coal-fueled units have elected
to install SCR.'' Id. at 14.
\157\ Utah regional haze SIP submission at 154-55.
\158\ PacifiCorp Public Comment, appendix A--``Wyodak Facility
SCR Affordability Analysis, August 25, 2020.'' The EPA is not
expressing any opinion on the content of the Affordability Analysis
or its accuracy.
\159\ PacifiCorp Public Comment at 10.
\160\ Only once has the EPA agreed with a facility's position
that regional haze emissions controls would be unaffordable, and
that evaluation was pursuant to the BART Guidelines. In that case,
the company provided the EPA with data substantiating its assertion
that it would likely not be able to operate profitably if it
installed the required control technology, and that the plant would
likely close rather than install and operate the BART-required
controls. The EPA relied on its own affordability analysis and
detailed financial records submitted by the company demonstrating
that the facility and the company were in a strained financial
position that would have been exacerbated by the installation of the
BART controls. 78 FR 79344, 79353-54 (Dec. 30, 2013) (proposed
rule); 79 FR 33438, 33442-42 (June 11, 2014) (final rule).
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Second, PacifiCorp's broad assertions about affordability do not
justify Utah's concern that SCR could be deemed an ``imprudent
investment'' by state public service commissions.\161\ PacifiCorp (a
regulated public utility) highlighted the ``likely inability to recover
the costs of SCR,'' citing out-of-state laws and prior difficulties in
recovering the costs of pollution control equipment in Oregon,
California, and Washington, but not in Utah.\162\ Utah lent credence to
these concerns without evaluating the likelihood that PacifiCorp would
be unable to recover the costs of SCR installation at Hunter and
Huntington or addressing which states would have jurisdiction over such
a request.\163\ Therefore, we find that Utah's concerns about potential
scrutiny of investments in SCR are unsubstantiated and lack a
sufficient connection to the sources at issue.
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\161\ Utah regional haze SIP submission at 154-55, 158.
\162\ PacifiCorp Public Comment at 14-15.
\163\ Utah regional haze SIP submission at 154-55.
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Third, Utah gave unreasonable weight to assertions by Deseret Power
(which owns a 25% share in Hunter Unit 2) that it may be unable to
finance its portion of SCR installation costs for that unit.\164\
Deseret stated in a short comment letter that under the terms of a debt
forbearance with its principal creditor, it cannot take on new debt
without the creditor's consent.\165\ Deseret did not attach any
supporting documentation (e.g., a debt forbearance agreement) and did
not opine on the likelihood that its creditor would withhold consent.
We find that Utah did not have a sufficient basis for taking Deseret's
unsubstantiated concerns into account in its evaluation of the costs of
compliance.\166\
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\164\ Utah regional haze SIP submission at 155-56, appendix H at
674-75.
\165\ Deseret Generation & Transmission Co-operative Public
Comment (May 31, 2022) at 2.
\166\ See generally 78 FR 79344, 79353 (in proposing to find
that BART controls were unaffordable, relying on detailed financial
information submitted by the company and the EPA's affordability
analysis addressing ``the long-term power supply contract, cost/
sales ratio, ability to borrow funds, the price of electricity,
updated investment ratings, aluminum market conditions and other
factors relevant to the affordability determination'').
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For these reasons, we find that Utah unreasonably relied on
affordability c

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