[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 [www.gpo.gov]
[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 https://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from https://www.regulations.gov. 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 https://www.epa.gov/dockets/commenting-epa-dockets.
    Docket: All documents in the docket are listed in the https://www.regulations.gov 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 
https://www.regulations.gov. 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: [email protected].

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

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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 (SO2), nitrogen oxides (NOX), and, in 
some cases, volatile organic compounds (VOC) and ammonia 
(NH3)). Fine particle precursors react in the atmosphere to 
form fine particulate matter (PM2.5), 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, https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period, 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. https://www.epa.gov/visibility/guidance-regional-haze-state-implementation-plans-second-implementation-period. 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. https://www.epa.gov/system/files/documents/2021-07/clarifications-regarding-regional-haze-state-implementation-plans-for-the-second-implementation-period.pdf. 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. https://www.epa.gov/visibility/technical-guidance-tracking-visibility-progress-second-implementation-period-regional. 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. https://www.epa.gov/visibility/memo-and-technical-addendum-ambient-data-usage-and-completeness-regional-haze-program. 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 https://www.westar.org/wrap-council-members/.
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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 
NOX 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 
NOX 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 NOX 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 NOX 
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 
https://www.epa.gov/sites/default/files/2021-03/documents/tracking.pdf.
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    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 
SO2 and NOX 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.
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    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.
---------------------------------------------------------------------------

    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).
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \41\ National Park Service, ``Colorado Plateaus Province,'' 
https://www.nps.gov/articles/coloradoplateaus.htm (last accessed 
July 24, 2024); National Park Service, ``Colorado Plateaus Province: 
U.S. Physiographic Province Map,'' https://www.nps.gov/common/uploads/photogallery/nri/park/geology/49177B13-1DD8-B71B-0BF120CC77B24F45/49177B13-1DD8-B71B-0BF120CC77B24F45-large.jpg (last 
accessed July 24, 2024).

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

[[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.
---------------------------------------------------------------------------

    \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 NOX and SO2 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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \48\ Utah regional haze SIP submission at 175 (figure 66).
---------------------------------------------------------------------------

    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 (NOX, SO2, 
and PM10) 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.
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    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.
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    \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 NOX, SO2, and 
PM10 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 
NOX, SO2, and PM10 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 NOX(behind Hunter power plant, 
the fifth highest emitter) and the 127th highest emitter of 
SO2 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.
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    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\
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    \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\
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    \61\ WEP is calculated by overlaying extinction weighted 
residence time results with 2028OTBa2 emissions of light extinction 
precursors (i.e., NOX emissions for ammonium nitrate 
light extinction and SO2 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,'' https://views.cira.colostate.edu/tssv2/WEP-AOI/ (last accessed July 24, 
2024).
    \62\ Utah regional haze SIP submission at 108.
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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.
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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-
NOX burners (LNB), selective non-catalytic reduction (SNCR), 
and a federally enforceable NOX 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\
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    \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\
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    \67\ Utah regional haze SIP submission at 178.
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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-NOX burners and 
baghouses at each kiln.
    Given Cricket Mountain's low SO2 emissions, Utah did not 
require Graymont to conduct a four-factor analysis for SO2 
controls. The facility's SO2 Q/d values at Capitol Reef 
National Park and SO2 emissions data are shown in table 4.

[[Page 67226]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.005

    Graymont identified several potential NOX 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 NOX controls. Hunter 
Units 1 and 2 are equipped with LNB/separated overfire air (SOFA) for 
NOX control, baghouses for PM control, and wet flue-gas 
desulfurization (FGD) scrubbers for SO2 control. Hunter Unit 
3 has LNB/SOFA for NOX control, baghouse for PM control, and 
FGD scrubber for SO2 control. Huntington Units 1 and 2 have 
LNB/SOFA for NOX control, fabric filter baghouses for PM 
control, and FGD scrubbers for SO2 control.
    In its four-factor analyses for NOX 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 
(NOX+SO2) annual emission limits that PacifiCorp 
proposed to replace the facilities' permitted existing plantwide 
applicability limits (PALs), which feature separate PALs for 
NOX and SO2. 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 SO2 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 NOX 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 NOX emissions 
reduced for each unit at the plants. Tables 6 and 7 also show the 
NOX 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 NOX emissions reductions, we 
consulted appendix C.3.C. of Utah's regional haze SIP submission. We 
determined the tons of NOX removed shown in tables 6 and 
7 by subtracting each unit's NOX 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' 
NOX 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 NOX 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 NOX 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 NOX 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 NOX 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\
---------------------------------------------------------------------------

    \88\ Id. at 163, appendix H at 656.
    \89\ Utah regional haze SIP submission at 162-63.
---------------------------------------------------------------------------

    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 
NOX. 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 NOX emissions) each year: a summer peak and a winter 
peak. Utah concluded that the plants were unlikely to consume the 
majority of their annual NOX 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.
---------------------------------------------------------------------------

    \92\ Id. at 157.
---------------------------------------------------------------------------

    In sum, Utah determined that physical controls to reduce 
NOX (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, SO2 emission limits in the plants' title V 
permits), are necessary to make reasonable progress.\94\
---------------------------------------------------------------------------

    \93\ Id.
    \94\ Id. at 179.
---------------------------------------------------------------------------

iv. Sunnyside Cogeneration \95\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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 
SO2 emissions. A baghouse controls for flue gas 
particulates.
    Sunnyside identified several potential add-on NOX and 
SO2 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.
---------------------------------------------------------------------------

    \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 NOX or SO2 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 NOX 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 SO2 emissions, US Magnesium did 
not conduct a four-factor analysis for SO2 controls. The 
facility's SO2 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 NOX 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 NOX emissions and (2) the 
presence of an existing low-NOX burner on the boiler. 
However, US Magnesium did not submit supporting information on the low-
NOX burner or its NOX 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 
NOX 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 SO2 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[.]'').
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a. Unreasonable Rejection of NOX Emission Reduction Measures 
at Hunter and Huntington
    Based on its evaluation of the four statutory factors, Utah 
concluded that SCR or other physical NOX 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 NOX emission 
limits for inclusion in its long-term strategy.\103\ To provide a 
``compliance glidepath,'' Utah established initial limits of 11,041 tpy 
of NOX at Hunter and 6,604 tpy of NOX at 
Huntington for 2022, interim limits of 10,442 tpy of NOX at 
Hunter and 6,422 tpy of NOX at Huntington for 2025, and 
final limits of 9,843 tpy of NOX at Hunter and 6,240 tpy of 
NOX 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 NOX 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 NOX 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) NOX 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 NOX 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 NOX 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 NOX 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 NOX 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 
NOX and SO2 emissions are highly influenced by 
Hunter and Huntington power plants.\111\ Of all 2028 projected 
statewide anthropogenic NOX and SO2 emissions, 
from every anthropogenic source in Utah, Hunter is projected to account 
for 11.41% of NOX and 25.56% of SO2 emissions; 
Huntington is projected to account for 6.94% of NOX and 
17.89% of SO2 emissions; and Hunter and Huntington combined 
are projected to account for 18.35% of NOX and 43.45% of 
SO2 emissions.
---------------------------------------------------------------------------

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

    Comparing the NOX and SO2 emission 
contributions of Hunter and Huntington to just the Utah EGU source 
category shows even higher projected contributions. Of all statewide 
EGU NOX and SO2 emissions from every EGU source 
located in Utah for 2028,\112\ Hunter is projected to account for 41.9% 
of NOX and 35.45% of SO2 emissions; Huntington is 
projected to account for 25.51% of NOX and 24.81% of 
SO2 emissions; and Hunter and Huntington combined are 
projected to account for 67.41% of NOX and 60.26% of 
SO2 emissions.
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    \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 NOX emissions of 
16,075 tpy far exceed the total combined NOX 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 NOX and 
SO2 emissions contributions from the 2028 projected 
statewide totals of anthropogenic NOX and SO2 
emissions indicates even higher contributions from Hunter and 
Huntington. Hunter is projected to account for 58.87% of all EGU source 
category NOX and 54.37% of all EGU source category 
SO2 emissions; Huntington is projected to account for 35.84% 
of all EGU source category NOX and 38.06% of all EGU source 
category SO2 emissions; and Hunter and Huntington combined 
are projected to account for 94.7% of all EGU source category 
NOX emissions and 92.43% of all EGU source category 
SO2 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 NOX emissions are significant on 
a national scale. Hunter ranked as the third highest emitter of 
NOX for all EGUs within the United States in 2021 and as the 
fifth highest emitter of NOX for all EGUs within the United 
States in 2022. Huntington ranked 20th in 2021 and 29th in 2022 for 
NOX 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.
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    In addition, due to source decommissionings, enforceable 
retirements, and requirements to install NOX 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.
---------------------------------------------------------------------------

    \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 
NOX and SO2 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.
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    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 NOX 
emissions and 60.26% of SO2 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 NOX and SO2 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 NOX and 
SO2 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 NOX and SO2 
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.
---------------------------------------------------------------------------

    \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 NOX 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 
NOX 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 NOX 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 NOX 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.
---------------------------------------------------------------------------

    \124\ Draft Utah Regional Haze SIP at 127 (contained within 
``Utah Regional Haze SIP Submittal 2022 v2,'' available in the 
docket for this action).
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    The information in the record indicates that installation of SCR, 
at an estimated cost of $5,979-$6,533/ton NOX 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 NOX 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 NOX 
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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    \154\ 40 CFR part 51, appendix Y, section IV.E.3.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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).
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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'').
---------------------------------------------------------------------------

    For these reasons, we find that Utah unreasonably relied on 
affordability considerations to conclude that the costs of compliance 
factor favors mass-based emission limits over SCR.

[[Page 67244]]

ii. Evaluation of Time Necessary for Compliance, Energy and Non-air 
Quality Impacts of Compliance, and Remaining Useful Life
    Utah also concluded that the three other statutory factors 
supported its determination that the plantwide mass-based emission 
limits are all that is necessary to demonstrate reasonable 
progress.\167\ As explained in the paragraphs below, we find that Utah 
did not reasonably evaluate these three statutory factors.
---------------------------------------------------------------------------

    \167\ Utah regional haze SIP submission at 157.
---------------------------------------------------------------------------

    In considering the time necessary for compliance, Utah pointed out 
the ``short window available'' for installation of physical controls 
during the time remaining in the second implementation period 
(``approximately five years, depending [on] the final approval 
date'').\168\ Utah concluded this was likely not enough time for 
installation of SCR, while mass-based emission limits could be 
implemented immediately upon SIP approval.\169\ Utah's analysis 
contravenes the plain text of 40 CFR 51.308(f)(2)(i), which states: 
``In considering the time necessary for compliance, if the State 
concludes that a control measure cannot reasonably be installed and 
become operational until after the end of the implementation period, 
the State may not consider this fact in determining whether the measure 
is necessary to make reasonable progress.'' \170\ But even if that 
consideration were permissible, PacifiCorp expressly stated in a 
submission to Utah that SCR could be installed at all units of Hunter 
and Huntington by the end of the second implementation period in 
2028.\171\ Utah provided no explanation for its contrary assessment.
---------------------------------------------------------------------------

    \168\ Id.
    \169\ Id.
    \170\ 40 CFR 51.308(f)(2)(i) (emphasis added).
    \171\ Utah regional haze SIP submission, appendix C.3.A at 12, 
24.
---------------------------------------------------------------------------

    In its analysis of the energy and non-air quality impacts of 
compliance, Utah stated that because Hunter and Huntington are 
``projected to assist in the transition towards intermittent renewable 
resources, alternative resources will be required to provide such 
support'' if an SCR-based requirement leads to early plant 
closures.\172\ As explained in section IV.C.2.a.i.C. of this document, 
Utah did not substantiate its concern that Hunter and Huntington would 
cease operations rather than install SCR. But even it if it had, Utah 
provided no analysis or documentation of how the plants' closure would 
affect renewable energy deployment or the sufficiency of ``alternative 
resources'' to assume their role. Without any supporting documentation 
or analysis, Utah's reliance on this issue in its consideration of 
energy and non-air quality impacts cannot be substantiated.
---------------------------------------------------------------------------

    \172\ Utah regional haze SIP submission at 157.
---------------------------------------------------------------------------

    Finally, in its consideration of Hunter and Huntington's remaining 
useful lives, Utah stated that the expected closure dates of 2042 for 
Hunter and 2036 for Huntington both involve shorter time periods than 
the 30-year economic life of SCR. Utah asserted that closure of the 
plants at or before these planned retirement dates ``would further 
erode the cost-effectiveness of physical controls by shortening the 
amortization period for control costs.'' \173\ It also stated that 
``[o]ngoing scrutiny of expenditures associated with coal-fired power 
plants by state public service commissions and the establishment of 
clean energy requirements in California, Oregon, and Washington 
increase the risk that these facilities may face early closure.'' \174\ 
Utah did not substantiate its concerns about early plant closures; it 
also conceded that the planned retirement dates of 2036 and 2042, which 
were sourced from the 2021 IRP, are not enforceable.\175\ Therefore, we 
find that Utah did not accurately or reasonably consider Hunter and 
Huntington's remaining useful lives.
---------------------------------------------------------------------------

    \173\ Id. at 158.
    \174\ Id.
    \175\ Id. 40 CFR 51.308(f)(2) requires SIPs to include 
enforceable measures. Therefore, as we explained in the 2019 
Guidance at 34, a state should rely on a facility's planned closure 
date in its evaluation of remaining useful life only if the closure 
is enforceable.
---------------------------------------------------------------------------

    In sum, Utah unreasonably concluded that the remaining three 
statutory factors support its determination that plantwide mass-based 
emission limits for Hunter and Huntington, instead of SCR, are all that 
is necessary to make reasonable progress toward the national visibility 
goal.
iii. Establishment of Annual Limits
    Apart from its unreasonable evaluation of the four statutory 
factors, we find that Utah did not adequately support its determination 
that mass-based emission limits that apply on an annual basis, as 
opposed to a shorter time period such as monthly or seasonally, are 
sufficient to make reasonable progress. As the State recognized, 
nitrate visibility impairment at Utah's Class I areas (i.e., impairment 
caused by NOX emissions) is ``largely seasonal'' and peaks 
in the winter.\176\ The EPA commented that short-term limits may better 
protect visibility on the most impaired days in Class I areas.\177\ In 
response, Utah asserted that Hunter and Huntington, whose operational 
peaks have historically occurred in both summertime and wintertime (in 
response to electricity demand), are unlikely to consume the majority 
of their annual NOX limit in the winter because they must 
preserve enough of their emissions budgets for the summertime peak. 
Utah also noted that short-term limits ``may limit flexibility to 
provide support for PacifiCorp's energy transition to intermittent non-
emitting resources like renewables.'' \178\
---------------------------------------------------------------------------

    \176\ Utah regional haze SIP submission at 161-62.
    \177\ Utah regional haze SIP submission, appendix H at 693-94.
    \178\ Id. at 693-94.
---------------------------------------------------------------------------

    We find that Utah did not provide adequate technical documentation 
to support its conclusion that short-term limits are ``unnecessary.'' 
\179\ Utah did not explain why it is reasonable to assume the plants' 
historical operational patterns (e.g., summer and winter seasonal 
peaks) are likely to persist in the future despite the ``significant 
change[s]'' the State predicted for the electricity generation industry 
in general and Hunter and Huntington's operations in particular.\180\ 
Nor did Utah provide any data or analysis examining how short-term 
limits could impair Hunter and Huntington's ability to produce 
sufficient electricity during times of low renewable energy generation. 
For example, Utah provided no information on the anticipated times of 
year or expected frequencies that Hunter and Huntington may be required 
to provide support to renewable generation. Therefore, Utah has not 
shown that annual limits are sufficient to ensure reasonable progress 
toward the national goal of preventing any future and remedying any 
existing anthropogenic visibility impairment at Class I areas.
---------------------------------------------------------------------------

    \179\ Id. at 694.
    \180\ Utah regional haze SIP submission at 150-54.
---------------------------------------------------------------------------

    In conclusion, for the reasons explained above in sections 
IV.C.2.a.i.-iv. of this document, we propose to disapprove Utah's long-
term strategy for failing to reasonably evaluate the NOX 
emission reduction measures for Hunter and Huntington that are 
necessary to make reasonable progress toward Congress's national 
visibility goal.
iv. SO2 Emissions at Hunter and Huntington
    Utah did not conduct a four-factor evaluation of SO2 
emission reduction measures for Hunter and Huntington, concluding that 
the plants are already

[[Page 67245]]

well-controlled based on their current permitted SO2 limits 
(0.12 lb/MMBtu 30-day rolling average).\181\ As detailed in the TSD for 
this action, Hunter and Huntington make substantial contributions to 
sulfate light extinction at several Class I areas. We are seeking 
comment on whether SO2 emission reduction measures (such as 
installation of new controls, efficiency improvements to the plants' 
existing scrubber systems, operational changes, or other measures) and/
or emission limit tightening to align with the plants' recent actual 
operation \182\ are necessary to make reasonable progress under CAA 
section 169A and 40 CFR 51.308(f)(2).
---------------------------------------------------------------------------

    \181\ Id. at 145-46.
    \182\ Since 2011, all five units at Hunter and Huntington have 
consistently operated at levels below their permitted SO2 
limits, achieving SO2 emission rates between 0.06 and 
0.10 lb/MMBtu. Utah regional haze SIP submission at 145.
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    Utah determined that continued operation of the plants' existing 
SO2 controls is necessary for reasonable progress. The State 
incorporated the SO2 emission limits in the plants' title V 
permits into the regulatory language of its SIP at parts H.23.d.vi-vii 
(Hunter) and H.23.e.vi-vii (Huntington). For Hunter Unit 3, however, 
the limit specified in part H.23.d.vii (1.2 lb/MMBtu heat input for any 
3-hour period) does not match the more stringent title V permitted 
limit of 0.12 lb/MMBtu heat input based on a 30-day rolling 
average.\183\ Utah did not address this discrepancy in its regional 
haze SIP submission. We invite comment on this issue.
---------------------------------------------------------------------------

    \183\ Title V Operating Permit for PacifiCorp--Hunter Power 
Plant (Permit No. 1500101004, last revised Nov. 19, 2021), section 
II.B.3.b., available in the docket for this action.
---------------------------------------------------------------------------

b. Failure To Evaluate Whether Emission Reduction Measures at CCI 
Paradox Lisbon Natural Gas Plant Are Necessary for Reasonable Progress
    In developing its long-term strategy, Utah chose not to evaluate 
the four statutory factors to determine whether emission reduction 
measures at CCI Paradox Lisbon Natural Gas Plant are necessary to make 
reasonable progress. For the reasons explained in this section 
IV.C.2.b., we find Utah's decision to be unjustified. Therefore, we 
propose to disapprove Utah's long-term strategy because the State did 
not consider the emission reduction measures at Lisbon Natural Gas 
Plant that are necessary to make reasonable progress toward the 
national visibility goal, as required by 40 CFR 51.308(f)(2).
    The Lisbon Natural Gas Plant is a natural gas processing plant in 
an area known as the Lisbon Valley in southeastern Utah. As explained 
in section IV.C.1.a. of this document, Utah used a Q/d screening 
process to identify potential sources for four-factor analysis. The 
facility fell within Utah's Q/d screening due to its combined Q/d value 
of 20.9 for Canyonlands National Park (based on 2014 actual 
emissions).\184\ It is located 35.8 kilometers (approximately 22 miles) 
from Canyonlands and 54.6 kilometers (approximately 33 miles) from 
Arches, closer to Class I areas than any other source Utah 
analyzed.\185\
---------------------------------------------------------------------------

    \184\ Utah regional haze SIP submission at 100.
    \185\ Id. at 100, 103.
---------------------------------------------------------------------------

    During its ``secondary'' review of sources, Utah eliminated the 
Lisbon Natural Gas Plant from further evaluation. Utah elected not to 
require four-factor analysis for the facility due to its ``anomalously 
high SO2 emissions in 2014 (and 2015),'' a Q/d recalculation 
for years 2017-2021 indicating that the source was below Utah's Q/d 
threshold of 6, and the facility's recent actual SO2 
emissions dropping to a small fraction of the 2014 emissions used in 
the original Q/d calculation.\186\ As detailed below, these reasons do 
not justify Utah's decision not to consider the four factors and 
determine the emission reduction measures at Lisbon Natural Gas Plant 
that are necessary to make reasonable progress.
---------------------------------------------------------------------------

    \186\ Id. at 102-103.
---------------------------------------------------------------------------

    To evaluate the State's discussion of Lisbon Natural Gas Plant's Q/
d values, the EPA calculated the facility's combined (SO2, 
NOX, and PM10) Q/d values for Canyonlands 
National Park using emissions data the source provided to Utah.\187\ 
Our results are listed in table 16 of this document; the State's Q/d 
calculations are reported in table 29 (Q/d values based on 2014 
emissions) and table 31 (Q/d values for 2017-2021) of its regional haze 
SIP submission. Table 16 shows Lisbon Natural Gas Plant's actual 
emissions from 2008-2021 and the Q/d values we calculated for 
Canyonlands National Park based on those actual emissions. Given Utah's 
reference to ``anomalously high'' SO2 emissions in 2014 and 
2015, we also included a scenario calculating the facility's Q/d value 
had it emitted zero SO2 (i.e., the Q/d value reflects only 
NOX and PM10 emissions) in the years when its 
actual SO2 emissions caused the Q/d value to exceed 6.
---------------------------------------------------------------------------

    \187\ See CCI Paradox emissions data.xlsx, available in the 
docket for this action.
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BILLING CODE 6560-50-P

[[Page 67246]]

[GRAPHIC] [TIFF OMITTED] TP19AU24.020

BILLING CODE 6560-50-C
    For 2020, we calculated a combined Q/d value of 6.96, compared to 
the State's value of 5.3. This discrepancy appears to have resulted 
from Utah's use of a NOX emission value of 126.0 tpy for 
2020, rather than the 186.53 tpy reported in the EPA's Emissions

[[Page 67247]]

Inventory System (EIS).\188\ Thus, we disagree with the State's 
determination that Lisbon Natural Gas Plant's Q/d values based on 2017-
2021 emissions ``all . . . fall below'' its Q/d threshold of 6.\189\
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    \188\ Utah regional haze SIP submission at 103. The EIS data for 
Lisbon Natural Gas Plant is included in the docket for this action.
    \189\ Utah regional haze SIP submission at 102.
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    The data in table 16 do not support the State's assessment that 
anomalously high SO2 emissions in 2014 and 2015 were largely 
responsible for Lisbon Natural Gas Plant's Q/d values. For every year 
between 2008 and 2021 where the source exceeded Utah's combined Q/d 
threshold of 6, table 16 shows that would still hold true even when all 
SO2 emissions are eliminated from the ``Q.'' \190\ In other 
words, the source's anomalous SO2 emissions in 2014 and 2015 
(and its SO2 emissions in any other year) did not cause it 
to exceed the Q/d threshold. It would have surpassed that threshold 
based on NOX and PM10 emissions alone. For that 
same reason, Utah's statement that the source's SO2 
emissions in 2017-2021 dropped to ``0.01 and 0.13 percent of the 2014 
levels used in the original screening'' \191\ do not justify the 
State's decision not to evaluate the four statutory factors for Lisbon 
Natural Gas Plant. Moreover, even if the State had properly excluded 
SO2 emissions from consideration, a four-factor analysis may 
still have been warranted for NOX and PM emission reduction 
measures because those emissions caused the source to exceed Utah's Q/d 
threshold.
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    \190\ See the ``No SO2 Emissions Scenario'' for 2008, 
2009, 2013, 2014, 2015, 2016, and 2020 in table 16.
    \191\ Utah regional haze SIP submission at 102.
---------------------------------------------------------------------------

    The WEP values for Lisbon Natural Gas Plant, which Utah considered 
when evaluating the appropriateness of its source selections,\192\ show 
that the facility is a top ten contributor to nitrate visibility 
impairment at Arches National Park and Canyonlands National Park. 
Considering all in-state and all out-of-state point sources, Lisbon 
Natural Gas Plant ranks ninth for nitrate WEP value, indicating that 
its NOX emissions are expected to affect visibility even 
without considering SO2.
---------------------------------------------------------------------------

    \192\ Id. at 108.
---------------------------------------------------------------------------

    Furthermore, other sources that Utah selected for four-factor 
analysis (namely Ash Grove Leamington Cement Plant, Graymont Cricket 
Mountain Plant, and US Magnesium Rowley Plant) all have similar Q/d 
values as the Lisbon Natural Gas Plant. See table 17. Utah's regional 
haze SIP submission does not adequately justify the State's decision to 
evaluate the four statutory factors for all of these other sources but 
not for Lisbon Natural Gas Plant.
[GRAPHIC] [TIFF OMITTED] TP19AU24.021

    The regulations at 40 CFR 51.308(f)(2)(i) requires a state's SIP 
submission to include ``a description of the criteria it used to 
determine which sources or groups of sources it evaluated.'' In 
addition, the state must adequately document the technical basis for 
source selection, as required by 40 CFR 51.308(f)(2)(iii). As explained 
in this section, Utah did not adequately justify its decision not to 
evaluate the four statutory factors for Lisbon Natural

[[Page 67248]]

Gas Plant to determine the emission reduction measures necessary to 
make reasonable progress. Consequently, we find that Utah's long-term 
strategy does not satisfy the requirements of 40 CFR 51.308(f)(2).
c. Improper Inclusion of Automatic Exemption for Startup, Shutdown, and 
Malfunction Events in Emission Limitations for Intermountain Power 
Plant
    We are also proposing to disapprove Utah's long-term strategy for 
the improper inclusion of an automatic exemption for SSM events in the 
emission limitations for Intermountain power plant. As detailed in this 
section, these automatic exemptions violate CAA requirements.
    The CAA, RHR, and 2017 RHR Revisions establish the requirements 
states must meet in developing SIPs to address visibility 
impairment.\193\ CAA section 110(a)(2)(A) requires that each SIP 
submitted by a state under the CAA ``shall include enforceable emission 
limitations and other control measures, means, or techniques . . ., as 
well as schedules and timetables for compliance, as may be necessary or 
appropriate to meet the applicable requirements of this chapter.'' 
Under the CAA's visibility provisions, CAA section 169A(b)(2) requires 
states' SIPs to ``contain such emission limits, schedules of compliance 
and other measures as may be necessary to make reasonable progress 
toward meeting the national goal.'' In addition, CAA section 169B(e)(2) 
directs the Administrator to promulgate regulations under section 169A 
requiring states to revise their SIPs under CAA section 110, specifying 
that those SIPs must contain such emission limits, schedules of 
compliance, and other measures as may be necessary to carry out the 
regulations promulgated pursuant to the CAA's visibility provisions.
---------------------------------------------------------------------------

    \193\ 42 U.S.C. 7410(a)(2)(B), 7491(b)(2), 7492(e)(2). 1999 RHR, 
64 FR 35714, 35743 (Jul. 1, 1999), and 2017 RHR revisions, 82 FR 
3078 (Jan. 10, 2017).
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    Pursuant to this statutory directive, the EPA promulgated the RHR 
and its subsequent 2017 revisions,\194\ which require states' long-term 
strategies to ``include the enforceable emissions limitations, 
compliance schedules, and other measures that are necessary to make 
reasonable progress'' towards remedying and preventing anthropogenic 
visibility impairment in Class I areas.\195\ Under CAA section 302(k), 
``emission limitation'' is defined as ``a requirement established by 
the State or the Administrator which limits the quantity, rate, or 
concentration of emissions of air pollutants on a continuous basis, 
including any requirement relating to the operation or maintenance of a 
source to assure continuous emission reduction, and any design, 
equipment, work practice or operational standard promulgated under this 
chapter.'' \196\
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    \194\ 1999 RHR, 64 FR 35714 (Jul. 1, 1999), and 2017 RHR 
Revisions, 82 FR 3078 (Jan. 10, 2017).
    \195\ 40 CFR 51.308(f)(2).
    \196\ CAA section 302(k).
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    When states are developing SIPs to address regional haze, they may 
exercise discretion, consistent with the statutory and regulatory 
requirements, to determine what emission limitations are necessary to 
make reasonable progress. If a state determines that emission 
limitations are necessary, it must incorporate those emission 
limitations into its SIP pursuant to CAA section 110(a)(2)(A).
    In 2015, the EPA issued a SIP call that laid out our policy with 
respect to SSM provisions in SIPs.\197\ Specifically, the EPA 
determined that SIP provisions that create or authorize exemptions from 
SIP emission limitations during SSM events are inconsistent with the 
CAA. This is because excess emissions during SSM events result in 
higher emissions that are not considered a violation under the CAA, 
even though the source exceeds the otherwise applicable emission 
limitation.\198\
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    \197\ 80 FR 33840 (June 12, 2015).
    \198\ Id. at 33842, 33874. This type of exemption from a SIP 
emission limitation is referred to as an automatic exemption under 
the SSM policy, since the SSM provision in a SIP emission limitation 
automatically exempts excess emissions from the SIP emission 
limitation.
---------------------------------------------------------------------------

    In Environmental Committee of the Florida Electric Power 
Coordination Group, Inc. v. EPA,\199\ petitioners challenged the EPA's 
2015 SIP call for four categories of SIP provisions that provide full 
or limited exemptions for SSM events: (1) automatic exemptions; (2) 
director's discretion provisions; (3) overbroad enforcement discretion 
provisions; and (4) affirmative defense provisions. The D.C. Circuit 
held that the EPA impermissibly issued a SIP call for automatic and 
director's discretion exemptions, because the EPA was required to 
determine under CAA section 110(a)(2)(A) whether it was ``necessary or 
appropriate'' for the emissions restrictions at issue in the 2015 SIP 
call to qualify as emission limitations as defined by CAA section 
302(k).\200\
---------------------------------------------------------------------------

    \199\ 94 F.4th 77 (D.C. Cir. 2024).
    \200\ See 94 F.4th at 100.
---------------------------------------------------------------------------

    Based on Environmental Committee of the Florida Electric Power 
Coordination Group, Inc. v. EPA, the EPA's evaluation of Utah's 
regional haze SIP submission hinges on whether the emission 
restrictions contained in the SSM provision included in the regulatory 
portion of Utah's regional haze SIP submission are ``emissions 
limitations . . . that are necessary to make reasonable progress'' 
\201\ toward the national goal of remedying and preventing 
anthropogenic visibility impairment at Class I areas. As explained 
below, the State has concluded that these provisions are emission 
limitations necessary to make reasonable progress under CAA sections 
169A(b)(2) and 110(a)(2) and 40 CFR 51.308(f)(2); thus, CAA section 
302(k) requires that they be continuous.
---------------------------------------------------------------------------

    \201\ 40 CFR 51.308(f)(2). In addition, CAA section 169B(e)(2) 
authorized the EPA to promulgate the RHR (40 CFR 51.308) requiring 
states to revise their SIPs under CAA section 110, specifying that 
those SIPs must contain such emission limits, schedules of 
compliance, and other measures as may be necessary to carry out 
these regulations.
---------------------------------------------------------------------------

    In its regional haze SIP submission, Utah, under CAA section 
169A(b)(2) and 40 CFR 51.308(f)(2), selected seven sources, including 
Intermountain power plant, as sources whose emission limitations are 
measures necessary for reasonable progress.\202\ For Intermountain 
power plant, the State is requiring existing emission limitations until 
the coal-fired units cease operations by December 31, 2027. In chapter 
8.d (Reasonable Progress Determinations), Utah determined, and the EPA 
agrees, that it is necessary for Intermountain power plant to implement 
emission controls in the form of existing emission limitations to 
guarantee that Intermountain power plant will continue to implement 
existing measures and will not increase its emission rate before the 
scheduled shutdown of the coal-fired units.\203\ This is supported by 
chapter 6 (Long-Term Strategy for Second Planning Period of Utah's 
regional haze SIP submission).\204\ Chapter 6.A provides the long-term 
strategy requirements under 40 CFR 51.308(f)(2), including 
incorporation of emission limitations and schedules for compliance for 
Intermountain power plant and six other sources to achieve the 
reasonable progress goals.\205\ In addition, chapter 6.A.8 (Emissions 
Limitations and Schedules for Compliance to Achieve the RPG) states 
that ``emissions limitations and schedules for compliance for the 
second planning period may be found in SIP subsection IX.H.23.'' \206\ 
Section IX.H.23 is titled ``Emission Limitations: Regional

[[Page 67249]]

Haze Requirement, Reasonable Progress Control Measures'' and provides 
the emission reduction measures, including emission limitations, for 
Intermountain power plant and other sources that are necessary to make 
reasonable progress for the second implementation period.\207\ While 
not all control measures qualify as emission limitations, in this 
instance, the EPA agrees with the State's determination that these 
provisions are ``emission limitations'' that the State has concluded 
are necessary to make reasonable progress toward the national 
goal.\208\
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    \202\ Utah regional haze SIP submission at 180.
    \203\ Id. at 180.
    \204\ Id. at 72.
    \205\ Id.
    \206\ Id. at 88.
    \207\ Utah regional haze SIP submission, appendix A, part H.23.
    \208\ Utah regional haze SIP submission at 180.
---------------------------------------------------------------------------

    When a state relies on an emission limitation as part of its SIP 
submission, the emission limitation must limit the quantity, rate, or 
concentration of emissions of air pollutants on a continuous basis, as 
required under CAA section 302(k).\209\ The goal that Congress 
established for the visibility protection program is to prevent future 
and remedy existing anthropogenic visibility impairment in Class I 
areas.\210\ When a state submits a SIP with an emission limitation to 
meet the CAA's visibility requirements, the emission limitation needs 
to be continuous to ensure that visibility conditions at Class I areas 
are improving uninterrupted.\211\ Relying on an emission limitation 
that allows for uncontrolled excess emissions during SSM events could 
negatively impact a state's ability to make reasonable progress toward 
meeting the national goal.
---------------------------------------------------------------------------

    \209\ CAA section 110(a)(2)(A), section 302(k).
    \210\ CAA section 169A(a)(1).
    \211\ CAA sections 110(a)(2)(A), 169A, 169B(e)(2), and 302(k); 
40 CFR 51.308(f).
---------------------------------------------------------------------------

    The Intermountain power plant emission limitations contained in SIP 
subsection IX, part H.23., ``Source Specific Emission Limitations: 
Regional Haze Requirements, Reasonable Progress Controls,'' include an 
automatic exemption for SSM events that occur when Intermountain power 
plant is operating prior to its closure.\212\ Parts H.23.c.i.B.I-III 
establish PM10, NOX, and SO2 emission 
limitations for Intermountain power plant, while part H.23.c.i.B.IV 
provides that these emission limitations ``apply at all times except 
for periods of startup, shutdown, malfunction (NOX or 
PM10 only), or emergency conditions (SO2 only).'' 
\213\ This exemption means that emissions exceeding the normal 
operational limits under periods of SSM or emergency conditions would 
not be considered to violate the emission limitations. The emission 
limitations for all of the other sources that Utah determined are 
necessary to make reasonable progress are continuous.\214\ However, the 
SSM provision that is part of the Intermountain power plant emission 
limitations at H.23.c.i.B.IV has no defined parameters for the excess 
emissions that will occur during periods of SSM or emergency 
conditions,\215\ making these emission limitations less than 
continuous. Because Utah has determined that the emission limitations 
for Intermountain power plant are measures necessary for reasonable 
progress, the emission limitations must be continuous at all times. 
Therefore, the emission limitations are inconsistent with the CAA and 
are not approvable for inclusion into the Utah SIP.
---------------------------------------------------------------------------

    \212\ Utah regional haze SIP submission, appendix A, part H.23.
    \213\ Id.
    \214\ Id.
    \215\ Id.
---------------------------------------------------------------------------

d. Unreasonable Rejection of Technically Feasible SO2 
Emissions Reduction Measures and Establishment of Unsupported Emission 
Limitations for Sunnyside Cogeneration Facility
    As detailed in sections IV.C.d.i.-ii. of this document, we also 
propose to disapprove Utah's long-term strategy based on problems with 
the State's evaluation of the measures necessary to make reasonable 
progress for Sunnyside Cogeneration Facility. First, the State 
unreasonably rejected dry scrubbing (also known as dry sorbent 
injection, or DSI),\216\ a technically feasible SO2 control, 
without providing adequate technical documentation. Second, the State 
did not provide adequate technical documentation to support the 
emission limitations for Sunnyside that it incorporated into its SIP.
---------------------------------------------------------------------------

    \216\ The documents in the record use several terms to refer to 
this control technology, including dry scrubbing, dry scrubbers, dry 
sorbent injection (DSI), and dry injection.
---------------------------------------------------------------------------

i. Unreasonable Rejection of Technically Feasible SO2 
Emissions Reduction Measures
    Sunnyside conducted an initial evaluation of additional 
SO2 controls for its facility and eliminated spray dry 
absorbers, wet scrubbing, and hydrated ash reinjection as technically 
infeasible. Sunnyside found that dry scrubbing/DSI, an add-on retrofit 
control, was technically feasible. Dry scrubbing/DSI systems operate 
through the injection of a powdered sorbent, such as lime, into the 
flue gas downstream of the boiler.\217\ Sunnyside noted the mechanical 
simplicity, ease of installation, limited water use, and simplicity of 
waste disposal associated with dry scrubbing/DSI systems.\218\ 
Sunnyside conducted a four-factor analysis for dry scrubbing/DSI and 
calculated a cost/ton value of just over $10,000/ton.\219\
---------------------------------------------------------------------------

    \217\ Sunnyside clarified that dry scrubbing is an add-on 
technology that is separate from its existing practice of injecting 
limestone directly into the circulating fluidized bed boiler. Utah 
regional haze SIP submission, appendix C.4.C at 5-6.
    \218\ Utah regional haze SIP submission, appendix C.4.A at 5-2--
5-4.
    \219\ Id. at 5-5.
---------------------------------------------------------------------------

    Utah identified multiple problems with Sunnyside's cost analysis, 
which it found ``improperly inflated the costs of a dry scrubber.'' 
\220\ Among other issues, the State pointed out that Sunnyside did not 
adequately justify its application of a retrofit factor of 1.3 (which 
resulted in a 30% inflation of costs),\221\ its use of a 20-year 
instead of a 30-year amortization period, and its inclusion of the 
costs of a new baghouse, which Sunnyside maintained would be necessary 
for a dry scrubbing/DSI system.\222\
---------------------------------------------------------------------------

    \220\ Utah regional haze SIP submission, appendix C.4.B at 15.
    \221\ Retrofit factors are used to quantify the additional costs 
of installation not directly related to the capital costs of the 
controls themselves, such as the unexpected magnitude of anticipated 
cost elements, the costs of unexpected delays, the cost of re-
engineering and re-fabrication, and the cost of correcting design 
errors. EPA, Control Cost Manual, Chapter 2: Cost Estimation: 
Concepts and Methodology (Nov. 2017), at 27, available in the docket 
for this action.
    \222\ Utah regional haze SIP submission, appendix C.4.B at 15-
19.
---------------------------------------------------------------------------

    In its October 2021 response to the State, Sunnyside abandoned its 
consideration of dry scrubbing/DSI, asserting that ``[a]fter further 
evaluation, a dry scrubbing unit cannot be retrofitted between the 
[circulating fluidized bed] boiler and the existing baghouse due to 
space limitations requiring significant reconfiguration of existing 
equipment.'' \223\ It concluded that a circulating dry scrubber/
circulating fluidized bed scrubber (CDS/CFBS) was the only add-on 
SO2 control technology that is potentially technically 
feasible.\224\ Sunnyside provided a new cost analysis for CDS/CFBS to 
replace its previous dry scrubbing/DSI analysis, calculating cost/ton 
values that ranged between $27,890-$118,553/ton based on minimum, 
average, and maximum cost scenarios.\225\ Those cost/ton values 
significantly exceeded that of the dry scrubbing/DSI system (just over 
$10,000/ton), which Utah had already

[[Page 67250]]

determined was likely overestimated. Utah ultimately accepted 
Sunnyside's analyses and concluded that CDS/CFBS was not necessary for 
reasonable progress.
---------------------------------------------------------------------------

    \223\ Utah regional haze SIP submission, appendix C.4.C at 7.
    \224\ Id.
    \225\ Utah regional haze SIP submission, appendix D.2.I at 2-3 
(section titled ``Total Installed Cost for Circulating Dry Scrubber 
(CDS)'').
---------------------------------------------------------------------------

    Sunnyside did not submit any documentation to substantiate the 
space constraints that led it to exclude dry scrubbing/DSI from further 
consideration as an emission reduction measure necessary to make 
reasonable progress. Its appeal to space limitations consisted of a 
single conclusory sentence with no supporting details or 
explanation.\226\ The National Park Service commented that Sunnyside 
had not adequately explained why there would be insufficient space for 
a dry scrubbing/DSI system but not for a CDS/CFBS system.\227\ 
Conservation organizations presented a similar criticism, pointing out 
that DSI involves injecting sorbent into the flue gas ductwork between 
the air preheater and the baghouse, which should not present any space 
limitations.\228\ Although Sunnyside submitted two letters to the State 
responding specifically to comments raised by the National Park Service 
and the conservation organizations, it did not address their points 
about its failure to substantiate the purported space constraints on a 
dry scrubber/DSI system.\229\ While Utah responded that Sunnyside had 
adequately demonstrated infeasibility based on the lack of physical 
space and air flow mechanics described in the facility's May 27, 2022 
submission,\230\ the information in that submission pertains to CDS/
CFBS and not to the dry scrubber/DSI system that Sunnyside rejected in 
its October 2021 submission.\231\
---------------------------------------------------------------------------

    \226\ Utah regional haze SIP submission, appendix C.4.C at 7.
    \227\ Utah regional haze SIP submission, appendix D.I at 34. The 
National Park Service referred to dry scrubbing as a dry sorbent 
injection (DSI) system.
    \228\ National Parks Conservation Association et al., ``Comments 
on Utah's Proposed Regional Haze State Implementation Plan for the 
2nd Implementation Period'' (May 31, 2022) at 36; exhibit A at 43.
    \229\ Utah regional haze SIP submission, appendices D.2.G and 
D.2.I.
    \230\ Utah regional haze SIP submission, appendix H at 668.
    \231\ Utah regional haze SIP submission, appendix D.2.G at 5-7.
---------------------------------------------------------------------------

    Based on our review of the materials in the record, we find that 
Utah has not provided adequate technical documentation justifying the 
exclusion of a dry scrubber/DSI system from further consideration based 
on space constraints. And because Sunnyside abandoned its evaluation of 
the dry scrubber/DSI system in favor of CDS/CFBS, it never prepared a 
revised cost analysis remedying the shortcomings Utah had initially 
identified. As a result, Utah did not satisfy 40 CFR 
51.308(f)(2)(iii)'s requirement to document the technical basis, 
including modeling, monitoring, cost, engineering, and emissions 
information on which it is relying. For these reasons, we propose to 
disapprove Utah's long-term strategy because the State did not 
reasonably evaluate and determine the emission reduction measures for 
Sunnyside that are necessary to make reasonable progress, as required 
by CAA section 169A and 40 CFR 51.308(f)(2).
ii. Unsupported Emission Limitations for Making Reasonable Progress
    We are also proposing to disapprove Utah's long-term strategy 
because the State did not provide adequate technical documentation to 
support the emission limitations it incorporated into its SIP for 
Sunnyside Cogeneration Facility. In its regional haze SIP submission, 
Utah determined that the existing control measures and emission 
limitations at Sunnyside are necessary to achieve reasonable progress 
in the second implementation period and incorporated those limitations 
into its SIP.\232\ However, the SIP incorporates two separate emission 
limitations for both NOX and SO2: one that 
applies during normal boiler operation and one that applies during SSM 
events.\233\
---------------------------------------------------------------------------

    \232\ Utah regional haze SIP submission at 179.
    \233\ Part H.23(f) states: ``i. Emissions of NOX 
(during normal boiler operation not including startup, shutdown and 
malfunction) shall not exceed 0.25 lb per MMBtu heat input on a 30-
day rolling average. ii. Emissions of NOX (including 
startup, shutdown and malfunction) shall not exceed 0.6 lb per 10-6 
BTU heat input on a 30-day rolling average. iii. Emissions of 
SO2 (during normal boiler operation not including 
startup, shutdown and malfunction) shall not exceed 0.42 lb per 
MMBtu heat input on a 30-day rolling average and 462 lb per hour on 
a 3-hour block average. Emissions of SO2 (including 
startup, shutdown and malfunction) shall not exceed 1.2 lb per 10-6 
BTU heat input on a 30-day rolling average.'' Utah regional haze SIP 
submission, appendix A, section IX, part H.23(f).
---------------------------------------------------------------------------

    Utah neither included a definition of the term ``normal boiler 
operations'' nor provided any documentation of the frequency of normal 
boiler operations versus SSM events, making it difficult to determine 
what combination of emission limitations under normal boiler operations 
and SSM events Utah has determined are necessary to make reasonable 
progress. Based on the analysis that Utah submitted for Sunnyside, we 
cannot determine whether the State concluded that the ``existing 
controls and emissions limits for the Sunnyside Cogeneration Facility. 
. . necessary for reasonable progress'' \234\ are based on Sunnyside 
operating continuously at the higher SSM emission limitation or on some 
other operational scenario. Because Utah did not provide adequate 
technical documentation explaining how the alternative SSM emission 
limitation relates to the State's obligation to make reasonable 
progress, we propose to disapprove Utah's long-term strategy under CAA 
section 169A and 40 CFR 51.308(f)(2).
---------------------------------------------------------------------------

    \234\ Utah regional haze SIP submission at 179.
---------------------------------------------------------------------------

e. Other Long-Term Strategy Requirements Under 40 CFR 51.308(f)(2)(ii) 
Through (iv)
    States must also meet the requirements specified in 40 CFR 
51.308(f)(2)(ii) through (iv) when developing their long-term 
strategies. 40 CFR 51.308(f)(2)(ii) requires states to consult with 
other states (states that have emissions that are reasonably 
anticipated to contribute to visibility impairment in Class I areas) to 
develop coordinated emission management strategies. Utah engaged with 
other states throughout the development of its regional haze SIP 
submission by participating in WRAP regional haze workgroup meetings. 
Additionally, Utah directly communicated with other states about the 
SIP submittal, including Arizona, Colorado, Idaho, New Mexico, Nevada, 
and Wyoming.\235\
---------------------------------------------------------------------------

    \235\ Id. at 181-83 and appendix B.
---------------------------------------------------------------------------

    The regulation at 40 CFR 51.308(f)(2)(iii) requires states to 
document the technical basis, including modeling, monitoring, costs, 
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 area it impacts. Utah 
relied on WRAP technical information, modeling, and analysis to support 
the development of its long-term strategy.
    The regulation at 40 CFR 51.308(f)(2)(iv) specifies five additional 
factors states must consider in developing their long-term strategies. 
The five additional factors are: emission reductions due to ongoing air 
pollution control programs, including measures to address reasonably 
attributable visibility impairment; measures to mitigate the impacts of 
construction activities; source retirement and replacement schedules; 
basic smoke management practices for prescribed fire used for 
agricultural and wildland vegetation management purposes and smoke 
management programs; and the anticipated net effect on visibility due 
to projected changes in point, area, and

[[Page 67251]]

mobile source emissions over the period addressed by the long-term 
strategy. Utah described each of the five additional factors in 
sections 6.A.5. through 6.A.10. of its regional haze SIP submission.
    Regardless, as explained in the preceding sections of this 
document, due to flaws and omissions in its four-factor analyses and 
the resulting control determinations, the EPA finds that Utah did not 
submit a long-term strategy that includes ``the enforceable emissions 
limitations, compliance schedules, and other measures that are 
necessary to make reasonable progress'' as required by 40 CFR 
51.308(f)(2).\236\ Consequently, we find that Utah's regional haze SIP 
submission does not satisfy the long-term strategy requirements of 40 
CFR 51.308(f)(2). Therefore, the EPA proposes to disapprove all 
elements of Utah's regional haze SIP submission that relate to Sec.  
51.308(f)(2)'s long-term strategy requirements.
---------------------------------------------------------------------------

    \236\ See also CAA section 169A(b)(2), section 169A(b)(2)(B) 
(requiring regional haze SIPs to ``contain such emission 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[.]'').
---------------------------------------------------------------------------

f. Implications of Senate Bill 161
    On March 21, 2024, the Governor of Utah signed legislation titled 
``Senate Bill 161'' (SB 161),\237\ which includes a provision that 
requires entities that own coal-fired electric generating facilities 
that are slated to be decommissioned, such as Intermountain power 
plant, to continue operations through the establishment of a 
transitional and alternative permit process. SB 161 also prescribes the 
authority and process for the State of Utah to purchase these 
facilities and auction them to continue operations. On June 21, 2024, 
the Governor of Utah signed House Bill 3004, which revises SB 161.\238\ 
Specifically, House Bill 3004 revises the alternative permitting 
process for electric generating facilities that are slated for 
decommissioning. As submitted, Utah's regional haze SIP submission 
incorporates the retirement of two coal-fired units at Intermountain 
power plant with a closure date of no later than December 31, 2027. We 
recognize there is uncertainty related to the legislation, alternative 
permitting process, and potential changes in ownership, as well as any 
ensuing litigation that could potentially occur during and after the 
EPA's rulemaking on Utah's regional haze SIP submission. We are seeking 
comment on the potential impact of the existing language in SB 161 and 
HB 3004 on Utah's regional haze SIP provision incorporating the two 
coal-fired unit retirements at Intermountain power plant, including any 
implications related to compliance with CAA section 110(a)(2)(E).
---------------------------------------------------------------------------

    \237\ The enrolled copy of SB 161 is available in the docket for 
this action. Additional information on SB 161 can be found on the 
Utah State Legislature's website: https://le.utah.gov/~2024/bills/
static/SB0161.html (last accessed July 24, 2024).
    \238\ The enrolled copy of House Bill 3004 is available in the 
docket for this action. Additional information on House Bill 3004 
can be found on the Utah State Legislature's website: https://
le.utah.gov/~2024S3/bills/static/HB3004.html (last accessed July 24, 
2024).
---------------------------------------------------------------------------

D. Reasonable Progress Goals

    The EPA proposes to find that Utah did not meet the reasonable 
progress goal requirements under 40 CFR 51.308(f)(3). Section 
51.308(f)(3)(i) requires a state in which a Class I area is located to 
establish RPGs--one each for the most impaired and clearest days--
reflecting the visibility conditions that will be achieved at the end 
of the implementation period as a result of the emission limitations, 
compliance schedules and other measures required under paragraph (f)(2) 
in states' long-term strategies, as well as implementation of other CAA 
requirements.
    After establishing its long-term strategy, Utah developed 
reasonable progress goals for each Class I area for the 20% most 
impaired days and 20% clearest days based on the results of 2028 WRAP 
modeling.\239\ The reasonable progress goals are based on Utah's long-
term strategy, the long-term strategy of other states that may affect 
Class I areas in Utah, and other CAA requirements.
---------------------------------------------------------------------------

    \239\ Utah regional haze SIP submission at 172-180.
---------------------------------------------------------------------------

    Per 40 CFR 51.308(f)(3)(iv), the EPA must evaluate the 
demonstrations the State developed pursuant to 40 CFR 51.308(f)(2) to 
determine whether the State's reasonable progress goals for visibility 
improvement provide for reasonable progress towards natural visibility 
conditions. As previously explained in section IV.C.2. of this 
document, we are proposing to disapprove Utah's long-term strategy for 
not meeting the requirements of 40 CFR 51.308(f)(2). Therefore, we also 
propose to disapprove Utah's reasonable progress goals under 40 CFR 
51.308(f)(3) because compliance with that requirement is dependent on 
compliance with 40 CFR 51.308(f)(2).

E. Reasonably Attributable Visibility Impairment (RAVI)

    The RHR contains a requirement at 40 CFR 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,'' \240\ also known as RAVI. 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 RAVI, the state must include 
in its SIP revision for the second implementation period an appropriate 
strategy for evaluating such impairment. The EPA has not advised Utah 
to that effect, and the FLMs for the Class I areas that Utah 
contributes to have not identified any RAVI from sources located in 
Utah.\241\ Accordingly, the EPA proposes to approve the portions of 
Utah's regional haze SIP submission relating to 40 CFR 51.308(f)(4).
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    \240\ 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.
    \241\ Utah regional haze SIP submission at 81.
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F. Monitoring Strategy and Other State Implementation Plan Requirements

    Section 51.308(f)(6) specifies that each comprehensive revision of 
a state's regional haze SIP must contain or provide for certain 
elements, including monitoring strategies, emissions inventories, and 
any reporting, recordkeeping and other measures needed to assess and 
report on visibility. A main requirement of this section is for states 
with Class I areas to submit monitoring strategies for measuring, 
characterizing, and reporting on visibility impairment. Compliance with 
this requirement may be met through participation in the IMPROVE 
network. Utah participates in the IMPROVE monitoring network.
    Section 51.308(f)(6)(i) requires SIPs to provide for the 
establishment of any additional monitoring sites or equipment needed to 
assess whether reasonable progress goals to address regional haze for 
all mandatory Class I Federal areas within the state are being 
achieved. As we stated in the 2017 RHR Revisions, ``neither the EPA nor 
any state has concluded that the IMPROVE network is not sufficient in 
this way.'' \242\ The EPA is not aware of information suggesting that 
the IMPROVE monitors within Utah Class I areas are no longer sufficient 
to assess

[[Page 67252]]

the status of reasonable progress goals. Therefore, the EPA finds that 
Utah has satisfied 40 CFR 51.308(f)(6)(i).
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    \242\ 82 FR 3085.
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    Section 51.308(f)(6)(ii) requires SIPs to provide for procedures by 
which monitoring data and other information are used in determining the 
contribution of emissions from within the state to regional haze 
visibility impairment at mandatory Class I Federal areas both within 
and outside the state. Chapters 4, 5, 6, 7, and 8 of the Utah regional 
haze SIP submission describe various analytical methods and tools the 
State relied on to assess the quantitative impact of Utah emissions on 
in-state and out-of-state Class I areas. IMPROVE monitoring data and 
the State's emissions inventory data were used, in many instances, as 
inputs to the tools and products available in WRAP's TSS, such as the 
CAMx Particle Source Apportionment tool (PSAT) photochemical model used 
to assess Utah's contributions to light extinction at Class I areas. 
Due to the State's reliance on the WRAP TSS products and other 
analytical methods and tools, as described in chapters 4, 5, 6, 7, and 
8 of the Utah regional haze SIP submission, we determine that Utah has 
satisfied 40 CFR 51.308(f)(6)(ii).
    Section 51.308(f)(6)(iii) does not apply to Utah, as it has Class I 
areas.
    Section 51.308(f)(6)(iv) requires the SIP to provide for the 
reporting of all visibility monitoring data to the Administrator at 
least annually for each Class I area in the state. Utah's monitoring 
strategy relies on the IMPROVE network, whose monitors at Utah's Class 
I areas are operated and maintained by the National Park Service. The 
IMPROVE Steering committee and Data Analysis and Reporting subcommittee 
develop policies to generate and distribute IMPROVE data, metadata, and 
data products. That data is made available on IMPROVE, FLM, and the EPA 
Air Quality System databases. We find that Utah has satisfied 40 CFR 
51.308(f)(6)(iv).
    Section 51.308(f)(6)(v) requires SIPs to provide for a statewide 
inventory of emissions of pollutants that are reasonably anticipated to 
cause or contribute to visibility impairment, including emissions for 
the most recent year for which data are available and estimates of 
future projected emissions. It also requires a commitment to update the 
inventory periodically. Utah provides for emissions inventories and 
estimates of future projected emissions by participating in WRAP and 
complying with the EPA's AERR. In 40 CFR part 51, subpart A, the AERR 
requires states to submit updated emissions inventories for criteria 
pollutants to the EPA's EIS annually or triennially depending on the 
source type. The EPA uses the inventory data from the EIS to develop 
the National Emissions Inventory (NEI), which is a comprehensive 
estimate of air emissions of criteria pollutants, criteria precursors, 
and hazardous air pollutants from air emissions sources. The EPA 
releases an NEI every three years. Section 5.E of the Utah regional 
haze SIP submission includes tables of statewide NEI data.\243\ 
Anthropogenic emissions and natural emissions are tabulated under 
various source categories. The inventories account for emissions of 
SO2, NOX, VOC, PM2.5, PM10, 
and NH3. Utah also relied on WRAP's projected future 
inventories of emissions under different modeling scenarios for 
2028.244 245 The EPA finds that Utah has met the 
requirements of 40 CFR 51.308(f)(6)(v) through its ongoing compliance 
with the AERR, its compilation of a statewide emissions inventory based 
on NEI data, its use of WRAP modeling to project future emissions, and 
its commitment to update its inventory periodically.
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    \243\ Utah regional haze SIP submission at 66-70 (tables 15-20).
    \244\ WRAP's modeling methodology used to develop the projected 
emissions inventories is described in ``WRAP Technical Support 
System for Regional Haze Planning: Modeling Methods, Results, and 
References'' (Sept. 30, 2021), available in the docket for this 
action.
    \245\ Utah regional haze SIP submission at 66-70 (tables 15-20).
---------------------------------------------------------------------------

    Finally, 40 CFR 51.308(f)(6)(vi) requires the SIP to provide for 
any other elements, including reporting, recordkeeping, and other 
measures, that are necessary for states to assess and report on 
visibility. Utah assesses and reports on visibility through 
participation in the IMPROVE network. The EPA finds that Utah has 
satisfied the requirements of 40 CFR 51.308(f)(6)(vi) and that no 
further elements are necessary at this time for Utah to assess and 
report on visibility.
    In sum, for all the reasons discussed in this section IV.F., the 
EPA is proposing to approve Utah's Regional Haze SIP submission as 
meeting the applicable requirements of 40 CFR 51.308(f)(6).

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

    The regulation at 40 CFR 51.308(f)(5) requires that periodic 
comprehensive revisions of states' regional haze plans also address the 
progress report requirements of 40 CFR 51.308(g)(1) through (5). The 
purpose of these requirements is to evaluate progress towards the 
applicable RPGs for each Class I area within the state and each Class I 
area outside the state that may be affected by emissions from within 
that state. Section 51.308(g)(1) and (2) apply to all states and 
require a description of the status of implementation of all measures 
included in a state's first implementation period regional haze plan 
and a summary of the emission reductions achieved through 
implementation of those measures. Section 51.308(g)(3) applies only to 
states with Class I areas within their borders and requires such states 
to assess current visibility conditions, changes in visibility relative 
to baseline (2000-2004) visibility conditions, and changes in 
visibility conditions relative to the period addressed in the first 
implementation period progress report. Section 51.308(g)(4) applies to 
all states and requires an analysis tracking changes in emissions of 
pollutants contributing to visibility impairment from all sources and 
sectors since the period addressed by the first implementation period 
progress report. This provision further specifies the year or years 
through which the analysis must extend depending on the type of source 
and the platform through which its emission information is reported. 
Finally, Sec.  51.308(g)(5), which also applies to all states, requires 
an assessment of any significant changes in anthropogenic emissions 
within or outside the state that have occurred since the period 
addressed by the first implementation period progress report, including 
whether such changes were anticipated and whether they have limited or 
impeded expected progress towards reducing emissions and improving 
visibility.
    Utah included the progress report required by 40 CFR 51.308(f)(5) 
in its regional haze SIP submission. Utah addresses each of the 
elements specified in 40 CFR 51.308(g)(1) through (5) in chapter 3 of 
the state's SIP.
    To address 40 CFR 51.308(g)(1), Utah details the status of all 
control measures implemented during the first implementation period, 
including emission reduction measures at Hunter, Huntington, and 
Carbon. To address 40 CFR 51.308(g)(2), Utah indicates that the 
retirement of Carbon Units 1 and 2 resulted in total SO2 
reductions of 8,005 tpy; unit level reductions were 3,388 tpy of 
SO2 at Unit 1 and 4,617 tpy of SO2 at Unit 2. 
Other reductions are detailed in chapter 5.
    To address 40 CFR 51.308(g)(3), Utah refers to chapter 4 of the 
SIP, which contains its Utah Visibility Analysis. Table 9 within 
chapter 4 tabulates the

[[Page 67253]]

progress in visibility conditions for the clearest and most impaired 
days at Utah's Class I areas over the baseline period (2000-2004), 
first implementation period (2008-2012), and current period (2014-
2018).
    To address 40 CFR 51.308(g)(4), Utah provides an emissions trend 
analysis of visibility-impairing pollutants from all emissions sources 
within the State. It also refers to section 5.E of its SIP submission, 
which compares historical and recent emissions to future projected 
emissions of visibility-impairing pollutants at Utah's Class I areas.
    To address 40 CFR 51.308(g)(5), Utah provides a Western states EGU 
emissions trend analysis for NOX and SO2, which 
indicates an overall downward trend due to EGU retirements and new 
pollution controls. Table 3 tabulates changes in emissions over years 
1996, 2002, and 2018 for the nine member states of the Grand Canyon 
Visibility Transport Commission. The table shows that emissions of VOC, 
NOX, SO2, and PM2.5 declined, while 
emissions of coarse material increased.
    In sum, because Utah addressed the requirements of 40 CFR 
51.308(g)(1) through (5), the EPA is proposing to approve chapter 3 of 
Utah's Regional Haze SIP as meeting the requirements of 40 CFR 
51.308(f)(5) and (g) for periodic progress reports.

H. Requirements for State and Federal Land Manager Coordination

    Section 169A(d) of the Clean Air Act requires states to consult 
with FLMs before holding the public hearing on a proposed regional haze 
SIP, and to include a summary of the FLMs' conclusions and 
recommendations in the notice to the public. In addition, Sec.  
51.308(i)(2)'s FLM consultation provision requires a state to provide 
FLMs with an opportunity for consultation that is early enough in the 
state's policy analyses of its emission reduction obligation so that 
information and recommendations provided by the FLMs' can meaningfully 
inform the state's decisions on its long-term strategy. If the 
consultation has taken place at least 120 days before a public hearing 
or public comment period, the opportunity for consultation will be 
deemed early enough. Regardless, the opportunity for consultation must 
be provided at least sixty days before a public hearing or public 
comment period at the state level. Section 51.308(i)(2) also provides 
two substantive topics on which FLMs must be provided an opportunity to 
discuss with states: assessment of visibility impairment in any Class I 
area and recommendations on the development and implementation of 
strategies to address visibility impairment. Section 51.308(i)(3) 
requires states, in developing their implementation plans, to include a 
description of how they addressed FLMs' comments.
    Utah DAQ met with the FLMs (the National Park Service and the U.S. 
Forest Service) throughout the second implementation period planning 
process.\246\ Utah provided its draft SIP to the FLMs in December 2021. 
In February 2022, the FLMs provided detailed comment letters to Utah 
DAQ on the draft SIP \247\ and met with Utah DAQ to present their 
feedback. Utah DAQ responded to the FLM comments and included the 
responses in its SIP submission.\248\
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    \246\ Utah regional haze SIP submission at 186.
    \247\ Utah regional haze SIP submission, appendices D.I and D.3.
    \248\ Utah regional haze SIP submission at 187-194.
---------------------------------------------------------------------------

    Compliance with 40 CFR 51.308(i) is dependent on compliance with 40 
CFR 51.308(f)(2)'s long-term strategy provisions and paragraph (f)(3)'s 
reasonable progress goals provisions. Because the EPA is proposing to 
disapprove Utah's long-term strategy under 40 CFR 51.308(f)(2) and the 
reasonable progress goals under 40 CFR 51.308(f)(3), the EPA is also 
proposing to disapprove the State's FLM consultation under 40 CFR 
51.308(i). While Utah did take administrative steps to provide the FLMs 
the opportunity to review and provide feedback on the State's initial 
draft regional haze SIP, the EPA cannot approve that consultation 
because it was based on a plan that does not meet the statutory and 
regulatory requirements of the CAA and the RHR, as described in this 
notice of proposed rulemaking. In addition, if the EPA finalizes our 
proposed partial approval and partial disapproval of Utah's regional 
haze SIP submission, the State (or the EPA in the potential case of a 
FIP) will be required to again complete the FLM consultation 
requirements under 40 CFR 51.308(i). Therefore, the EPA proposes to 
disapprove the FLM consultation component of Utah's regional haze SIP 
submission for failure to meet the requirements of 40 CFR 51.308(i), as 
outlined in this section.

V. Interstate Transport Prong 4 (Visibility) for the 2015 Ozone NAAQS 
Infrastructure SIP

A. Background on Infrastructure SIPs

    Under CAA sections 110(a)(1) and 110(a)(2), each state is required 
to submit a SIP that provides for the implementation, maintenance, and 
enforcement of each primary or secondary NAAQS. Moreover, CAA sections 
110(a)(1) and 110(a)(2) require each state to make this new SIP 
submission within three years (or less, if the Administrator so 
prescribes) after promulgation of a new or revised NAAQS. This type of 
SIP submission is commonly referred to as an ``infrastructure SIP.'' 
The overall purpose of the infrastructure SIP requirements is to ensure 
that the necessary structural components of each state's air quality 
management program are adequate to meet the state's responsibilities 
for the new or revised NAAQS. Overall, the infrastructure SIP 
submission process provides an opportunity for the responsible air 
agency, the public, and the EPA to review the basic structural 
requirements of the air agency's air quality management program in 
light of each new or revised NAAQS.
    CAA section 110(a)(2)(D) has two components: 110(a)(2)(D)(i) and 
110(a)(2)(D)(ii). CAA section 110(a)(2)(D)(i) includes four distinct 
components, commonly referred to as ``prongs,'' that must be addressed 
in infrastructure SIP submissions. The first two prongs, which are 
codified in CAA section 110(a)(2)(D)(i)(I), prohibit any source or 
other type of emissions activity in one state from contributing 
significantly to nonattainment of the NAAQS in another state (prong 1) 
and from interfering with maintenance of the NAAQS in another state 
(prong 2). The third and fourth prongs, which are codified in CAA 
section 110(a)(2)(D)(i)(II), prohibit emissions activity in one state 
from interfering with measures required to prevent significant 
deterioration of air quality in another state (prong 3) or from 
interfering with measures to protect visibility in another state (prong 
4).

B. Prong 4 Requirements

    CAA section 110(a)(2)(D)(i)(II) requires SIPs to contain provisions 
prohibiting sources in a state from emitting pollutants in amounts that 
interfere with any other state's efforts to protect visibility under 
part C of the CAA (which includes sections 169A and 169B). The EPA 
issued guidance on infrastructure SIPs in a September 13, 2013 
memorandum from Stephen D. Page titled ``Guidance on Infrastructure 
State Implementation Plan (SIP) Elements under Clean Air Act Sections 
110(a)(1) and 110(a)(2)'' (``2013 Guidance''). The 2013 Guidance states 
that these prong 4 requirements can be satisfied by approved SIP 
provisions that the EPA has found to adequately address any 
contribution of that state's sources that impact the visibility

[[Page 67254]]

program requirements in other states.\249\ The 2013 Guidance also 
states that ``[t]he EPA interprets this prong to be pollutant-specific, 
such that the infrastructure SIP submission need only address the 
potential for interference with protection of visibility caused by the 
pollutant (including precursors) to which the new or revised NAAQS 
applies.'' \250\
---------------------------------------------------------------------------

    \249\ 2013 Guidance at 32-33.
    \250\ Id. at 33.
---------------------------------------------------------------------------

    The 2013 Guidance lays out how a state's infrastructure SIP may 
satisfy prong 4. In the second implementation period, confirmation that 
the state has a fully approved regional haze SIP that fully meets the 
requirements of 40 CFR 51.308 or 51.309 will satisfy the requirements 
of prong 4.\251\ The regulations at 40 CFR 51.308 and 51.309 
``specifically require that a state participating in a regional 
planning process include all measures needed to achieve its 
apportionment of emission reduction obligations agreed upon through 
that process.'' \252\ A fully approved regional haze SIP \253\ will 
ensure that emissions from sources under an air agency's jurisdiction 
are not interfering with measures required to be included in other air 
agencies' plans to protect visibility.
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    \251\ The EPA acknowledges that in the 2013 Guidance, we 
indicated that the EPA may find it appropriate to supplement the 
guidance regarding the relationship between regional haze SIPs and 
prong 4 after second implementation period SIPs become due, which 
occurred on July 31, 2021. After a review of the 2013 Guidance and 
the second implementation period regional haze requirements, the EPA 
maintains the interpretation that a fully approved regional haze SIP 
satisfies prong 4 requirements in the second implementation period.
    \252\ 2013 Guidance at 33.
    \253\ Since second implementation period SIPs became due, a 
``fully approved regional haze SIP'' would necessarily include fully 
approved first and second implementation period regional haze SIPs.
---------------------------------------------------------------------------

    Through this action, the EPA is proposing to disapprove the prong 4 
portion of Utah's 2020 ozone infrastructure SIP submittal. All other 
applicable infrastructure SIP requirements for that SIP submission have 
been addressed in separate rulemakings.\254\
---------------------------------------------------------------------------

    \254\ See 85 FR 57731 (Sept. 16, 2020) and 88 FR 9336 (Feb. 13, 
2023).
---------------------------------------------------------------------------

    On October 26, 2015, the EPA revised the 8-hour ozone NAAQS to 70 
parts per billion.\255\ States were required to submit infrastructure 
SIPs within three years of promulgation of the revised NAAQS. On 
October 24, 2019, the State of Utah submitted a SIP revision to the EPA 
addressing the CAA sections 110(a)(1) and (2) infrastructure 
requirements for the 2015 ozone NAAQS, including CAA section 
110(a)(2)(D)(i)(II) prong 4. The EPA evaluated this submission for 
completeness pursuant to the criteria in 40 CFR part 51, appendix V, 
and concluded that it was incomplete because Utah had not provided the 
necessary certification under section 2.1(g) of appendix V that a 
public hearing was held or provided the opportunity for the public to 
request a public hearing in accordance with 40 CFR 51.102(a). On 
November 21, 2019, the EPA sent a letter to Utah explaining our 
incompleteness determination.\256\ On January 29, 2020, Utah submitted 
a new SIP revision addressing the infrastructure requirements for the 
2015 ozone NAAQS (``2020 ozone infrastructure SIP submittal''), 
including CAA section 110(a)(2)(D)(i)(II) prong 4.\257\ This proposed 
rulemaking only addresses the prong 4 element of the 2020 Ozone 
infrastructure SIP submittal.
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    \255\ 80 FR 65292 (Oct. 26, 2015).
    \256\ The EPA's November 21, 2019 letter to the State of Utah is 
included in the docket for this action.
    \257\ The EPA is not proposing any action on the 2008 ozone 
portion of Utah's January 29, 2020 submittal, or on any of the other 
infrastructure elements apart from those portions submitted to meet 
the requirements of CAA section 110(a)(2)(D)(i)(I) for the 2015 
ozone NAAQS.
---------------------------------------------------------------------------

C. Utah's Prong 4 Elements

    To satisfy the prong 4 requirements for the 2015 ozone NAAQS, 
Utah's 2020 ozone infrastructure SIP submittal points to the EPA's 
initial disapproval action, subsequent litigation, and the State's 
then-forthcoming submission to meet the requirements of the first 
regional haze implementation period. This history, including the final 
approval action the EPA ultimately took on November 27, 2020,\258\ is 
discussed in section II.C. of this document.
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    \258\ 85 FR 75860.
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D. The EPA's Evaluation of Utah's Submittal

    The EPA acknowledges that Utah has a fully approved regional haze 
SIP for the first implementation period, which the State relied on to 
satisfy prong 4 in the 2020 ozone infrastructure SIP submittal. 
However, the EPA is proposing to partially disapprove Utah's regional 
haze SIP submission for the second implementation period, as discussed 
in section IV. of this document. Therefore, Utah cannot rely on a fully 
approved regional haze SIP to fulfill the prong 4 requirements for the 
2015 ozone NAAQS. Consequently, the EPA is proposing to disapprove the 
prong 4 portion of Utah's 2020 ozone infrastructure SIP submittal.

VI. Proposed Action

    For the reasons discussed in this document, the EPA is proposing to 
partially approve and partially disapprove Utah's regional haze SIP 
submission for the second implementation period. We are proposing to 
approve the portions of the SIP 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): progress report 
requirements; and (f)(6): monitoring strategy and other implementation 
plan requirements. The EPA is proposing to disapprove the remainder of 
the SIP submission, which addresses 40 CFR 51.308(f)(2): long-term 
strategy; (f)(3): reasonable progress goals; and (i): FLM consultation.
    Additionally, as consequence of our proposed partial disapproval of 
Utah's regional haze SIP submission, the EPA is proposing to disapprove 
the prong 4 portion of Utah's infrastructure SIP for the 2015 ozone 
NAAQS, pursuant to CAA section 110(a)(2)(D)(i)(II).

VII. Environmental Justice

    As explained in EPA Legal Tools to Advance Environmental Justice 
and the 2021 Clarifications Memo, CAA section 169A and the RHR provide 
states with discretion to consider environmental justice (EJ) in 
developing rules and measures related to regional haze.\259\ Utah 
exercised this discretion, as described in this document. In section 
7.A.5 of its regional haze SIP submission, Utah explained that it 
considered EJ during source screening ``to ensure sources within 
disproportionately affected areas are included in the four-factor 
analysis process.'' \260\ Utah used EJScreen, an EPA-developed EJ 
mapping and screening tool that provides a nationally consistent 
dataset and approach for combining various environmental and 
demographic indicators.\261\ Utah prepared EJScreen reports covering 
buffer areas of 20 miles around the ten facilities initially screened 
in for four-factor analysis. The results of Utah's EJScreen analysis 
are set forth in section 7.A.5 of the SIP submission. The analysis 
showed environmental and socioeconomic indicators at or above

[[Page 67255]]

the 80% percentile at the state level (meaning that 20% of Utah's 
population has a higher value) for Ash Grove Leamington Cement Plant, 
Graymont Western Cricket Mountain, PacifiCorp Hunter, PacifiCorp 
Huntington, Sunnyside Cogeneration, US Magnesium Rowley Plant, 
Intermountain power plant, Kennecott Power Plant, Kennecott Mine and 
Copperton Concentrator, and CCI Paradox Lisbon Natural Gas Plant. Utah 
stated that it ``was not able to draw significant conclusions from this 
analysis affecting the reasonable progress determinations made in this 
SIP revision.'' \262\
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    \259\ EPA Legal Tools to Advance Environmental Justice (May 
2022) is available at: https://www.epa.gov/system/files/documents/2022-05/EJ%20Legal%20Tools%20May%202022%20FINAL.pdf; 2021 
Clarifications Memo at 16.
    \260\ Utah regional haze SIP submission at 122.
    \261\ The EJSCREEN tool is available at https://www.epa.gov/ejscreen.
    \262\ Utah regional haze SIP submission at 122.
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    The EPA also conducted an EJ screening analysis using the latest 
version of EJScreen (Version 2.3) around the coordinate locations of 
the facilities associated with Utah's regional haze SIP submission to 
identify potential environmental stressors on communities. The EPA is 
providing the information associated with this analysis for 
informational purposes only; it does not form any part of the basis of 
this proposed action. Consistent with our notices of proposed 
rulemaking on regional haze SIP submissions by other states within EPA 
Region 8, the EPA prepared EJScreen reports covering buffer areas of 
approximately six miles around the ten facilities included in Utah's EJ 
analysis. The following facilities showed EJ indicators greater than 
the 80th national percentiles (meaning that 20 percent of the U.S. 
population has a higher value): Ash Grove Leamington Cement Plant 
(drinking water non-compliance); Kennecott Power Plant (ozone, toxic 
releases to air, Superfund proximity, wastewater discharge); and 
Sunnyside Cogeneration (ozone, lead paint, drinking water non-
compliance).\263\ The full, detailed EJScreen reports are provided in 
the docket for this rulemaking. There is nothing in the record 
indicating that this proposed action, if finalized, would have 
disproportionately high or adverse human health or environmental 
effects on communities with EJ concerns. EJ is further discussed in 
section VIII. of this document.
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    \263\ The EPA identified the 80th percentile filter as an 
initial starting point for interpreting EJScreen results. The use of 
an initial filter promotes consistency for the EPA's programs and 
regions when interpreting screening results.
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VIII. Statutory and Executive Order Reviews

    Under the CAA, the Administrator is required to approve a SIP 
submission that complies with the provisions of the Act and applicable 
Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in 
reviewing SIP submissions, the EPA's role is to approve state choices, 
provided that they meet the criteria of the CAA. Accordingly, this 
action merely proposes to partially approve and partially disapprove 
the state's SIP submission as meeting Federal requirements and does not 
impose additional requirements beyond those imposed by state law. For 
that reason, this action:
     Is not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Orders 
12866 (58 FR 51735, October 4, 1993) and 13563 (76 FR 3821, January 21, 
2011);
     Does not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Is certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Does not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Public Law 104-4);
     Does not have federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Is not an economically significant regulatory action based 
on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Is not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Is not subject to requirements of section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA; and
    In addition, the SIP is not approved to apply on any Indian 
reservation land or in any other area where the EPA or an Indian Tribe 
has demonstrated that a Tribe has jurisdiction. In those areas of 
Indian country, the proposed rule does not have Tribal implications and 
will not impose substantial direct costs on Tribal governments or 
preempt Tribal law as specified by Executive Order 13175 (65 FR 67249, 
November 9, 2000).
    Executive Order 12898 (Federal Actions to Address Environmental 
Justice in Minority Populations and Low-Income Populations, 59 FR 7629, 
Feb. 16, 1994) directs Federal agencies to identify and address 
disproportionately high and adverse human health or environmental 
effects of their actions on minority populations and low-income 
populations to the greatest extent practicable and permitted by law. 
The EPA defines EJ as the fair treatment and meaningful involvement of 
all people regardless of race, color, national origin, or income with 
respect to the development, implementation, and enforcement of 
environmental laws, regulations, and policies. The EPA further defines 
the term fair treatment to mean that no group of people should bear a 
disproportionate burden of environmental harms and risks, including 
those resulting from the negative environmental consequences of 
industrial, governmental, and commercial operations or programs and 
policies.
    Utah evaluated EJ considerations as part of its SIP submittal even 
though the CAA and applicable implementing regulations neither prohibit 
nor require an evaluation. A summary of Utah's EJ considerations is 
contained in section VII. of this document. The EPA also performed an 
EJ analysis, as described above in section VII. of this document. Both 
Utah's and the EPA's analyses were done for the purpose of providing 
additional context and information about this rulemaking to the public, 
not as a basis of the action. The EPA is taking action under the CAA on 
bases independent of Utah's evaluation of EJ. In addition, there is no 
information in the record upon which this decision is based that is 
inconsistent with the stated goal of E.O. 12898 of achieving EJ for 
people of color, low-income populations, and Indigenous peoples.

List of Subjects in 40 CFR Part 52

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

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

    Dated: August 13, 2024.
KC Becker,
Regional Administrator, Region 8.
[FR Doc. 2024-18462 Filed 8-16-24; 8:45 am]
BILLING CODE 6560-50-P