Proposed Rule2025-11250
Air Plan Approval; Utah; Interstate Transport of Air Pollution for the 2008 8-Hour Ozone National Ambient Air Quality Standard
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
June 18, 2025
Issuing agencies
Environmental Protection Agency
Abstract
Pursuant to the Federal Clean Air Act (CAA or the Act), the Environmental Protection Agency (EPA) is proposing to approve a portion of a Utah State Implementation Plan (SIP) submission addressing interstate transport for the 2008 8-hour ozone national ambient air quality standard (NAAQS). The "interstate transport" provision requires that each state's SIP contain adequate provisions to prohibit emissions from within the state from significantly contributing to nonattainment or interfering with maintenance of the NAAQS in other states. In this action, EPA is only addressing the requirement prohibiting interference with maintenance, referred to as "prong 2," for the 2008 ozone NAAQS.
Full Text
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<title>Federal Register, Volume 90 Issue 116 (Wednesday, June 18, 2025)</title>
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[Federal Register Volume 90, Number 116 (Wednesday, June 18, 2025)]
[Proposed Rules]
[Pages 25918-25923]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-11250]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 52
[EPA-R08-OAR-2025-0054; FRL-12595-01-R8]
Air Plan Approval; Utah; Interstate Transport of Air Pollution
for the 2008 8-Hour Ozone National Ambient Air Quality Standard
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed rule.
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SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the
Environmental Protection Agency (EPA) is proposing to approve a portion
of a Utah State Implementation Plan (SIP) submission addressing
interstate transport for the 2008 8-hour ozone national ambient air
quality standard (NAAQS). The ``interstate transport'' provision
requires that each state's SIP contain adequate provisions to prohibit
emissions from within the state from significantly contributing to
nonattainment or interfering with maintenance of the NAAQS in other
states. In this action, EPA is only addressing the requirement
prohibiting interference with maintenance, referred to as ``prong 2,''
for the 2008 ozone NAAQS.
DATES: Written comments must be received on or before July 18, 2025.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R08-
OAR-2025-0054, to the Federal Rulemaking Portal: <a href="https://www.regulations.gov">https://www.regulations.gov</a>. Follow the online instructions for submitting
comments. Once submitted, comments cannot be edited or removed from
<a href="https://www.regulations.gov">https://www.regulations.gov</a>. EPA may publish any comment received to
its public
[[Page 25919]]
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 EPA public comment policy,
information about CBI or multimedia submissions, and general guidance
on making effective comments, please visit <a href="https://www.epa.gov/dockets/commenting-epa-dockets">https://www.epa.gov/dockets/commenting-epa-dockets</a>.
Docket: All documents in the docket are listed in the <a href="https://www.regulations.gov">https://www.regulations.gov</a> index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available electronically in
<a href="https://www.regulations.gov">https://www.regulations.gov</a>. Please email or call the person listed in
the FOR FURTHER INFORMATION CONTACT section if you need to make
alternative arrangements for access to the docket.
FOR FURTHER INFORMATION CONTACT: Adam Clark, Air and Radiation
Division, EPA, Region 8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver,
Colorado 80202-1129, telephone number: (303) 312-7104, email address:
<a href="/cdn-cgi/l/email-protection#3f5c535e4d54115e5b5e527f5a4f5e11585049"><span class="__cf_email__" data-cfemail="c5a6a9a4b7aeeba4a1a4a885a0b5a4eba2aab3">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: Throughout this document whenever ``we,''
``us,'' or ``our'' is used, we mean EPA.
Table of Contents
I. Background
II. EPA's Ozone Transport Modeling Information
III. Selection of Analytic Year
IV. Summary of Utah's Submission
V. EPA's Evaluation
VI. Proposed Action
VII. Statutory and Executive Order Reviews
I. Background
On March 12, 2008, EPA strengthened the NAAQS for ozone. (73 FR
16436; March 27, 2008). EPA revised the level of the 8-hour ozone NAAQS
from 80 parts per billion (ppb) to 75 ppb. EPA also revised the
secondary 8-hour standard to the level of 75 ppb making it identical to
the revised primary standard.
Section 110(a)(1) of the CAA imposes an obligation upon states to
submit SIP submissions that provide for the implementation,
maintenance, and enforcement of a new or revised NAAQS within 3 years
following the promulgation of that NAAQS. Section 110(a)(2) lists
specific requirements that states must meet in these SIP submissions,
as applicable. EPA refers to this type of SIP submission as the
``infrastructure'' SIP because the SIP ensures that states can
implement, maintain, and enforce the air quality standards. Within
these requirements, CAA section 110(a)(2)(D)(i)(I) contains
requirements to address interstate transport of NAAQS pollutants or
their precursors. CAA section 110(a)(2)(D)(i)(I), which is also known
as the ``interstate transport'' provision, requires SIPs to contain
provisions prohibiting any source or other type of emissions activity
within the State from emitting any air pollutant in amounts that will
contribute significantly to nonattainment of the NAAQS in any other
state (commonly referred to as prong 1) or interfere with maintenance
of the NAAQS in any other state (prong 2). A SIP addressing this
provision is often referred to as an ``interstate transport SIP.''
Through the development and implementation of several previous
rulemakings,\1\ EPA, working in partnership with states, established
the following 4-step framework to address the requirements of the
interstate transport provision for ground-level ozone NAAQS: (1)
identifying downwind ozone air quality monitors, termed ``receptors,''
that are expected to have problems attaining or maintaining the NAAQS;
(2) determining which upwind states contribute to these identified
problems in amounts sufficient to ``link'' them to downwind air quality
problems; (3) for states linked to downwind air quality problems,
identifying upwind emissions that significantly contribute to downwind
nonattainment or interfere with downwind maintenance of the NAAQS; and
(4) for states that are found to have emissions that significantly
contribute to downwind nonattainment or interfere with maintenance of
the NAAQS downwind, implementing the necessary emissions reductions
through enforceable measures.
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\1\ See, e.g., the Cross-State Air Pollution Rule (CSAPR) at 76
FR 48208 (August 8, 2011), the CSAPR Update at 81 FR 74504 (October
26, 2016), and the Revised CSAPR Update at 86 FR 23054 (April 30,
2021).
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On August 4, 2015, EPA issued a Notice of Data Availability (NODA)
containing air quality modeling to assist states with meeting section
110(a)(2)(D)(i)(I) requirements for the 2008 ozone NAAQS within the
context of the 4-step framework.\2\ Specifically, the air quality
modeling helped states address steps 1 and 2 of the framework by (1)
identifying locations in the United States where EPA anticipated
nonattainment or maintenance issues in 2017 for the 2008 ozone NAAQS,
and (2) quantifying the projected contributions from emissions from
upwind states to downwind ozone concentrations at the receptors in
2017. EPA used this modeling to support the Cross-State Air Pollution
Rule Update for the 2008 Ozone NAAQS (``CSAPR Update'') proposed rule
(80 FR 75706; December 3, 2015), and updated this modeling in 2016 to
support the CSAPR Update final rule (81 FR 74504; October 26, 2016).
The 2017 projections in this updated version of the modeling (hereon
referred to as the ``CSAPR Update modeling'') were part of the
technical record for EPA's final action disapproving the prong 2
portion of the Utah 2008 Ozone Infrastructure SIP (81 FR 71991; October
19, 2016), which is discussed in more detail later in this document.
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\2\ See Notice of Availability of the Environmental Protection
Agency's Updated Ozone Transport Modeling Data for the 2008 Ozone
National Ambient Air Quality Standard (NAAQS), 80 FR 46271 (August
4, 2015); see also ``Updated Air Quality Modeling Technical Support
Document for the 2008 Ozone NAAQS Transport Assessment,'' August
2015 (included in the docket to the NODA).
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In the CSAPR Update, EPA used the CSAPR Update modeling to identify
downwind nonattainment and maintenance receptors at step 1 of the 4-
step framework (see 81 FR 74530-74532; October 26, 2016). Specifically,
EPA identified nonattainment receptors as those monitoring sites with
current measured design values exceeding the NAAQS that also have
projected (i.e., in 2017) average design values exceeding the NAAQS.\3\
EPA identified maintenance receptors as those monitoring sites with
projected maximum design values exceeding the NAAQS. EPA considered all
nonattainment receptors to also be maintenance receptors because a
monitoring site with a projected average design value above the
standard necessarily also has a projected maximum design value above
the standard. Monitoring sites with
[[Page 25920]]
projected maximum design values that exceed the standard and which are
not also nonattainment receptors were thus referred to as maintenance-
only receptors.
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\3\ For the 2008 ozone NAAQS, the air quality design value for a
monitoring site is the 3-year average annual fourth-highest daily
maximum 8-hour average ozone concentration. See 73 FR 16513 (March
27, 2008).
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At step 2 of the 4-step framework in the CSAPR Update, EPA used the
CSAPR Update modeling to determine whether states' impact on each
projected downwind air quality problem would be considered significant
(see 80 FR 75713-75714; December 3, 2015). EPA's modeling projected
ozone concentrations and contributions in 2017, which would be the last
ozone season before the then-upcoming July 2018 attainment date for
nonattainment areas classified as Moderate for the 2008 ozone NAAQS.
Consistent with the original CSAPR rulemaking (76 FR 48208; August 8,
2011), EPA identified linkages between upwind states and downwind
nonattainment and maintenance receptors in the CSAPR Update. See 81 FR
74518 (October 26, 2016).
In its January 31, 2013 infrastructure-SIP submission to address
the 2008 ozone NAAQS, the Utah Division of Air Quality (UDAQ) addressed
110(a)(2)(D)(i)(I) by citing EPA Administrator Gina McCarthy's November
19, 2012 memo \4\ which outlined EPA's intention to abide by the
decision of the United States Court of Appeals for the District of
Columbia Circuit (D.C. Circuit) in EME Homer City Generation, L.P. v.
E.P.A., 696 F.3d 7 (D.C. Cir. 2012)). The EME Homer City decision
addressed the original CSAPR rulemaking promulgated by EPA to address
the interstate transport requirements under section 110(a)(2)(D)(i)(I)
with respect to the 1997 ozone NAAQS, the 1997 fine particulate matter
(PM<INF>2.5</INF>) NAAQS, and the 2006 PM<INF>2.5</INF> NAAQS. Among
other things, the D.C. Circuit held that states did not have an
obligation to submit SIPs addressing section 110(a)(2)(D)(i)(I)
interstate transport requirements as to any NAAQS until EPA first
quantified each state's emissions reduction obligation. Id. at 30-31.
In its submission, UDAQ noted that EPA had not quantified Utah's
transport obligation as to the 2008 ozone NAAQS and that Utah's
infrastructure SIP was therefore adequate with regard to CAA section
110(a)(2)(D)(i)(I).
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\4\ Memorandum from Gina McCarthy to Air Division Directors,
Regions 1-10 re: Next Steps for Pending Redesignation Requests and
State Implementation Plan Actions Affected by the Recent Court
Decision Vacating the 2011 Cross-State Air Pollution Rule (Nov. 19,
2012).
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Subsequent to the UDAQ submission, on April 29, 2014, the U.S.
Supreme Court reversed and remanded the D.C. Circuit's EME Homer City
decision on CSAPR and held, among other things, that under the plain
language of the CAA, states must submit SIPs addressing interstate
transport requirements of CAA section 110(a)(2)(D)(i)(I) within three
years of the promulgation of a new or revised NAAQS, regardless of
whether EPA first provides guidance, technical data or rulemaking to
quantify the state's obligation. See EPA v. EME Homer City Generation,
L.P., 134 S. Ct. 1584, 1601 (2014). UDAQ therefore additionally
addressed 110(a)(2)(D)(i)(I) prongs 1 and 2 for the 2008 ozone NAAQS as
part of its December 22, 2015 infrastructure submission that otherwise
addressed the 2012 PM<INF>2.5</INF> NAAQS.
In its December 22, 2015 infrastructure submission, UDAQ
acknowledged the changed legal landscape, and asserted that emissions
from the State did not significantly contribute to nonattainment or
interfere with maintenance of the 2008 ozone NAAQS in any other state.
UDAQ cited air quality modeling assessing interstate transport of ozone
that was released as part of EPA's August 4, 2015 NODA, and explained
that it did not consider Utah's modeled contribution levels to
nonattainment and maintenance receptors in the Denver, Colorado area
and in southern California to be significant.
On October 19, 2016, EPA took a final action disapproving the prong
2 portion of both submissions for the 2008 ozone NAAQS. See 81 FR
71991.\5\ This disapproval was largely based on the 2016 air quality
modeling included with the final CSAPR Update, which projected that
contributions from Utah would interfere with maintenance with respect
to three maintenance receptors in the Denver, Colorado area in 2017.
Id. at 71992. This disapproval established a 2-year deadline, under CAA
section 110(c), for EPA to promulgate a federal implementation plan
(FIP) or approve a SIP that meets the requirements of prong 2 of the
interstate transport provision for the 2008 ozone NAAQS for Utah.\6\
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\5\ EPA separately approved Utah's interstate transport SIP for
the 2008 ozone NAAQS as to prong 1. 82 FR 9155 (Feb. 3, 2017).
\6\ EPA has not promulgated a FIP for Utah for the 2008 ozone
NAAQS and is under a consent decree deadline to take final action on
the SIP by December 15, 2025. See Our Children's Earth Foundation v.
EPA, No. 23-cv-04955 (N.D. Cal.).
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On January 29, 2020, Utah submitted an infrastructure SIP
submission (``2020 submission'') to address the deficiencies identified
in EPA's October 19, 2016, disapproval. Specifically, the 2020
submission addressed prong 2 for the 2008 ozone NAAQS as part of an
infrastructure SIP that otherwise addressed the 2015 ozone NAAQS. In
this proposed action, EPA is only addressing the 2008 ozone NAAQS prong
2 portion of the 2020 submission.\7\ In the 2020 submission, UDAQ
relied, in part, on updated EPA air quality modeling. Below, EPA
provides further detail on the updated air quality modeling used by
UDAQ and subsequent iterations that were developed following the
State's 2020 submission.
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\7\ EPA addressed most other parts of the January 29, 2020
submission regarding the 2015 ozone NAAQS. See 85 FR 57731
(September 15, 2020).
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II. EPA's Ozone Transport Modeling Information
In general, EPA has performed nationwide air quality modeling to
project ozone design values which are used in combination with measured
data to identify nonattainment and maintenance receptors at step 1. To
quantify the contribution of emissions from individual upwind states on
2023 and 2026 ozone design values for the identified downwind
nonattainment and maintenance receptors at step 2, EPA has performed
multiple iterations of nationwide, state-level ozone source
apportionment modeling for 2023 and 2026. The source apportionment
modeling projected contributions to ozone at receptors from precursor
emissions of anthropogenic nitrogen oxides (NO<INF>X</INF>) and
volatile organic compounds (VOCs) in individual upwind states.
EPA has released several documents containing projected ozone
design values, contributions, and information relevant to air agencies
for evaluation of interstate transport with respect to the ozone NAAQS.
First, on January 6, 2017, EPA published a NODA in which the Agency
requested comment on preliminary interstate ozone transport data
including projected ozone design values and interstate contributions
for 2023 using a 2011 base year platform.\8\ In the 2017 NODA, EPA used
the year 2023 as the analytic year for this preliminary modeling
because this year aligns with the expected attainment year for Moderate
ozone nonattainment areas for the 2015 8-hour ozone NAAQS.\9\ On
October 27, 2017, EPA released a memorandum (October 2017 memorandum)
containing updated modeling data on receptors for 2023,
[[Page 25921]]
which incorporated changes made in response to comments on the 2017
NODA, and was intended to provide information to assist states' efforts
to develop SIP submissions to address interstate transport obligations
for the 2008 ozone NAAQS.\10\ EPA notes that UDAQ relied upon 2023
modeling receptor data released with October 2017 memorandum in
developing its 2020 SIP submission.
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\8\ See Notice of Availability of the Environmental Protection
Agency's Preliminary Interstate Ozone Transport Modeling Data for
the 2015 8-hour Ozone National Ambient Air Quality Standard (NAAQS),
82 FR 1733 (January 6, 2017).
\9\ Id. at 1735.
\10\ See Information on the Interstate Transport State
Implementation Plan Submissions for the 2008 Ozone National Ambient
Air Quality Standards under Clean Air Act Section
110(a)(2)(D)(i)(I), October 27, 2017, available in the docket for
this action.
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On March 27, 2018, EPA issued a memorandum (March 2018 memorandum)
noting that the same 2023 modeling data released in the October 2017
memorandum could also be useful for identifying potential downwind air
quality problems with respect to the 2015 ozone NAAQS at step 1 of the
4-step interstate transport framework.\11\ The March 2018 memorandum
also included the then newly available contribution modeling data for
2023 to assist states in evaluating their impact on potential downwind
air quality problems for the 2015 8-hour ozone NAAQS under step 2 of
the 4-step interstate transport framework.\12\ Utah did not reference
the modeling data shared in the March 2018 memorandum within the 2008
ozone NAAQS interstate transport prong 2 portion of their January 29,
2020 submission.
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\11\ See Information on the Interstate Transport State
Implementation Plan Submissions for the 2015 Ozone National Ambient
Air Quality Standards under Clean Air Act Section
110(a)(2)(D)(i)(I), March 27, 2018 (``March 2018 memorandum''),
available in the docket for this action.
\12\ The March 2018 memorandum, however, provided, ``While the
information in this memorandum and the associated air quality
analysis data could be used to inform the development of these SIPs,
the information is not a final determination regarding states'
obligations under the good neighbor provision. Any such
determination would be made through notice-and-comment rulemaking.''
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Following the release of the modeling data shared in the March 2018
memorandum, EPA performed updated modeling using a 2016-based emissions
modeling platform (i.e. 2016 Version 1 Emissions Platform Modeling, or
``2016v1''). This emissions platform was developed under the EPA/Multi-
Jurisdictional Organization (MJO)/state collaborative project.\13\ This
collaborative project was a multi-year joint effort by EPA, MJOs, and
states to develop a new, more recent emissions platform as an
improvement over the dated 2011-based platform that EPA had used to
project ozone design values and contribution data provided in the 2017
and 2018 memoranda.\14\ \15\
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\13\ The results of this modeling, as well as the underlying
modeling files, are included in Docket ID No. EPA-HQ-OAR-2021-0663.
The 2016v1 emissions modeling technical support document is
available in Docket ID No. EPA-HQ-OAR-2020-0272-0187. Both dockets
are available at <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
\14\ See 85 FR 68964, 68981.
\15\ See Air Quality Modeling Technical Support Document for the
Final Revised Cross-State Air Pollution Rule Update, in Docket ID
No. EPA-HQ-OAR-2021-0663.
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Following the final Revised CSAPR Update, EPA made further updates
to the 2016-based emissions platform to include updated onroad mobile
emissions and updated emissions for electric generating units (EGUs)
that reflect the reductions from the Revised CSAPR Update, and other
inventory-data improvements.\16\ \17\ EPA performed air quality
modeling using the 2016v2 emissions to provide projections of ozone
design values and contributions in 2023 and 2026 that reflect the
effects on air quality of the 2016v2 emissions platform.
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\16\ <a href="https://www.epa.gov/air-emissions-modeling/2016v2-platform">https://www.epa.gov/air-emissions-modeling/2016v2-platform</a>.
\17\ See Technical Support Document (TSD): Preparation of
Emissions Inventories for the 2016v2 North American Emissions
Modeling Platform, in Docket ID No. EPA-HQ-OAR-2021-0663 for
information on the construct of the updated emissions platform,
2016v2.
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In response to comments on the 2016v2 emissions inventories, EPA
made a number of updates to the 2016v2 inventories and model design to
construct another emissions platform, 2016v3, which was used to update
the air quality modeling. EPA used this 2016v3 updated modeling to
inform a rulemaking taking final action on 21 interstate transport SIP
submissions for the 2015 ozone NAAQS and to inform EPA's FIP addressing
those disapprovals.\18\ \19\ Additional details related to the updated
2016v3 emissions platform are located in the Technical Support Document
(TSD) titled ``Preparation of Emissions Inventories for the 2016v3
North American Emissions Modeling Platform.'' \20\
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\18\ See 88 FR 9336 (February 13, 2023), and 88 FR 36654 (June
5, 2023).
\19\ See Docket ID No. EPA-HQ-OAR-2021-0668-1157 on <a href="https://www.regulations.gov">https://www.regulations.gov</a> for details on the air quality modeling and
methods for projecting design values and determining contributions
in 2023 and 2026.
\20\ See Preparation of Emissions Inventories for the 2016v3
North American Emissions Modeling Platform, in Docket ID No. EPA-HQ-
OAR-2021-0663.
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In this proposed action, in addition to considering the modeling
and other information submitted by Utah, EPA relies on the modeling for
2026 using the updated 2016v3 emissions platform, which will generally
be referenced within this action as the ``2016v3 modeling.'' In using
these modeling results, EPA is taking into account the most current and
technically appropriate information for this proposed rulemaking. In
this proposed action, EPA is accepting public comment on the
application of the 2016v3 modeling solely as it relates to Utah's
interstate transport obligations for the 2008 ozone NAAQS. EPA is not
reopening for comment any other aspects of the 2016v3 modeling or the
use of this modeling in relation to any other state or regulatory
action. Any comments received on the modeling that are not relevant to
the evaluation of Utah's interstate transport obligations will be
treated as beyond the scope of this action.
III. Selection of Analytic Year
States and EPA must implement the interstate transport provision in
a manner ``consistent with the provisions of [title I of the CAA.]''
See CAA section 110(a)(2)(D)(i)(I). This requires, among other things,
that these obligations are addressed consistently with the timeframes
for downwind areas to meet their CAA obligations. With respect to ozone
NAAQS, under CAA section 181(a), this means obligations must be
addressed ``as expeditiously as practicable'' and no later than the
schedule of attainment dates provided in CAA section 181(a)(1). Several
D.C. Circuit court decisions address the issue of the relevant analytic
year for the purposes of evaluating ozone transport air-quality
problems. On September 13, 2019, the D.C. Circuit issued a decision in
Wisconsin vs EPA, remanding the CSAPR Update to the extent that it
failed to require upwind states to eliminate their significant
contribution by the next applicable attainment date by which downwind
states must come into compliance with the NAAQS, as established under
CAA section 181(a). See Wisconsin v. EPA, 938 F.3d 303, 313 (D.C. Cir.
2019).
On May 19, 2020, the D.C. Circuit issued a decision in Maryland v.
EPA that cited the Wisconsin decision in holding that EPA must assess
the impact of interstate transport on air quality at the next downwind
attainment date, including Marginal area attainment dates, in
evaluating the basis for EPA's denial of a petition under CAA section
126(b) Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020)
(Maryland). The court noted that ``section 126(b) incorporates the Good
Neighbor Provision,'' and, therefore, ``EPA must find a violation [of
section 126] if an upwind source will significantly contribute to
downwind nonattainment
[[Page 25922]]
at the next downwind attainment deadline. Therefore, the agency must
evaluate downwind air quality at that deadline, not at some later
date.'' Id. at 1204 (emphasis added). EPA interprets the court's
holding in Maryland as requiring the states and the Agency to assess
downwind air quality as expeditiously as practicable and no later than
the next applicable attainment date,\21\ which is currently the 2008
ozone NAAQS Severe area attainment date of July 20, 2027 under CAA
section 181.\22\ Thus, 2026 is currently the appropriate year for
analysis of interstate transport obligations for the 2008 ozone NAAQS
because the 2026 ozone season is the last relevant ozone season during
which achieved emission reductions in linked upwind states could assist
downwind states with meeting the July 20, 2027 Severe area attainment
date.
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\21\ We note that the court in Maryland did not have occasion to
evaluate circumstances in which EPA may determine that an upwind
linkage to a downwind air quality problem exists at steps 1 and 2 of
the interstate transport framework by a particular attainment date,
but for reasons of impossibility or profound uncertainty the Agency
is unable to mandate upwind pollution controls by that date. See
Wisconsin, 938 F.3d at 320. The D.C. Circuit noted in Wisconsin that
upon a sufficient showing, these circumstances may warrant
flexibility in effectuating the purpose of the interstate transport
provision.
\22\ See CAA section 181(a); 40 CFR 51.1103; ``Implementation of
the 2008 National Ambient Air Quality Standards for Ozone:
Nonattainment Area Classifications Approach, Attainment Deadlines
and Revocation of the 1997 Ozone Standards for Transportation
Conformity Purposes,'' 77 FR 30170 (May 21, 2012, effective July 20,
2012).
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IV. Summary of Utah's Submission
UDAQ submitted an infrastructure SIP submission to EPA addressing
the CAA section 110(a)(2)(D)(i)(I) prong 2 interstate transport
requirement for the 2008 8-hour ozone NAAQS on January 29, 2020.\23\ In
this submission, UDAQ concluded it will not interfere with maintenance
of the 2008 ozone NAAQS in any other state.\24\ To support this
conclusion, UDAQ used EPA's 4-step framework. For steps 1 and 2, Utah
specifically noted three Denver-area ozone monitors (site IDs 80590006,
80590011, and 80350004) that were projected by the CSAPR Update
modeling to be maintenance receptors for the 2008 ozone NAAQS (in
2017), and to which Utah interfered with maintenance,\25\ were all
projected to attain the 2008 ozone NAAQS in 2023 in the October 2017
memorandum modeling.\26\ The State asserted that, because they did not
contribute to any downwind air quality problem at step 2 of the 4-step
framework, they were not required to complete steps 3 or 4.
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\23\ State of Utah 110(a)(2) SIP Infrastructure Elements for
Ozone: Section 110(a)(2)(D)(i)(I): Interstate Transport Provisions
Prong II: Interfere with Maintenance, hereon ``Utah 2020 SIP
Submission,'' located in the docket for this rulemaking at <a href="https://regulations.gov">https://regulations.gov</a>, Docket ID No. EPA-R08-OAR-2025-0054. Although
portions of the submission shared to EPA by Utah include a watermark
indicating they are a draft, this was an inadvertent clerical error
and is treating the document as the final version of Utah's
submission.
\24\ Id. at 14.
\25\ See 81 FR 71992 (October 19, 2016).
\26\ See Utah 2020 SIP Submission at 11-12. See also October
2017 memorandum, attachment A.
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UDAQ also referenced EPA's July 3, 2018 approval of the State of
Colorado's attainment demonstration for the 2008 8-Hour Ozone Standard
for the Denver Metro/North Front Range Moderate nonattainment area
(hereon ``DMNFR attainment demonstration'').\27\ Utah cited language
from EPA's proposed approval of Colorado's DMNFR attainment
demonstration, in which EPA acknowledged that certain high ozone days
from 2009 to 2013 that were likely influenced by atypical activities
such as wildfire or stratospheric intrusion ``do affect the baseline
design values and thus affect the model projected future design value
for 2017'' and that ``all future [2017] design values are below the
0.75 ppb NAAQS . . . when data possibly influenced by atypical
activities are excluded in the calculation of the 2011 design values.''
\28\ Utah asserted that, based on EPA's approval of the DMNFR
attainment demonstration, it would be appropriate to consider the three
Denver-area receptors to which Utah was linked in the CSAPR Update
modeling to be ``attainment receptors,'' rather than maintenance
receptors.\29\ Utah asserted that Colorado's attainment demonstration
shows that Utah would not interfere with maintenance of the 2008 ozone
NAAQS at the three monitors.\30\
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\27\ Utah 2020 SIP Submission at 12 (citing 83 FR 31068, July 3,
2018).
\28\ Id. (quoting 83 FR 14807, April 6, 2018, at 14812-14813).
\29\ Id. at 12.
\30\ Id. at 12-13.
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Lastly, UDAQ notes that they have benefited from, but does not rely
on or seek adoption into their SIP, actions resulting in reductions in
ozone precursor pollutants (NO<INF>X</INF> and VOC) in the state.\31\
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\31\ Id. at 13-14.
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UDAQ concluded, based on the above, that Utah does not interfere
with maintenance of the 2008 ozone NAAQS in any downwind state.\32\
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\32\ Id. at 14.
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V. EPA's Evaluation
EPA is proposing to find that Utah's SIP meets the State's
obligations with respect to prohibiting emissions that interfere with
maintenance of the 2008 8-hour ozone NAAQS in any other state. EPA's
decision to propose approval of this portion of Utah's January 29, 2020
SIP submission is based on our evaluation of the SIP using the 4-step
interstate transport framework, which is the same framework Utah used
(Utah 2020 SIP Submission at 11-12).
At step 1 and step 2 of the 4-step interstate transport framework,
UDAQ relied on EPA modeling released with the CSAPR Update, and in the
October 2017 memorandum, to identify nonattainment and maintenance
receptors and upwind state linkages to those receptors in 2023. In this
proposal, EPA has also considered the Agency's most recently available
modeling (2016v3) to identify upwind contributions and linkages to
downwind air quality problems in 2026, which serves to verify Utah's
conclusion in its submission.
As described in section II. of this proposal, EPA performed air
quality modeling to project ozone design values and contributions for
2023 and 2026 using the 2016v3 emissions platform. EPA proposes to rely
on this modeling in evaluating Utah's transport SIP submission, and
specifically the 2026 projections given that year's relevance to 2008
ozone attainment planning as discussed in section III. The design
values and contributions from the updated modeling were examined to
determine if Utah interferes with maintenance at any downwind
nonattainment or maintenance receptor. The data \33\ indicates that the
highest contributions from Utah to downwind nonattainment or
maintenance-only receptors for the 2008 ozone NAAQS, all of which are
located in the state of California, are 0.13 ppb and 0.07 ppb,
respectively, in 2026.\34\
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\33\ Design values and contributions at individual monitoring
sites nationwide are provided in Docket ID No. EPA-HQ-OAR-2021-0668-
1130 on <a href="https://www.regulations.gov">https://www.regulations.gov</a>.
\34\ EPA's analysis indicates that in 2026 Utah will have a 0.13
ppb impact at the projected nonattainment receptor in San Bernadino,
California (site ID 60710005), and a 0.07 ppb impact at the
projected maintenance-only receptors in Madera County, California
(site IDs 60392010, 60390004).
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EPA's evaluation of 2026 projections indicates that the
contribution to ozone concentrations in other states from emissions
from sources in Utah will not interfere with maintenance of the 2008
ozone NAAQS. Thus, EPA proposes to find that the State does not impact
downwind air quality problems at step 2 of the 4-step framework, and
therefore does not warrant further review and analysis at steps 3 and
4. The results of
[[Page 25923]]
EPA's evaluation are consistent with the conclusion drawn by UDAQ in
its 2020 SIP submission that emissions from sources in Utah will not
interfere with maintenance of the 2008 ozone NAAQS in any other state.
For these reasons, EPA is proposing to approve the 2008 ozone portion
of Utah's 2020 SIP submission with regard to the interstate transport
prong 2 requirement of CAA section 110(a)(2)(D)(i)(I).
VI. Proposed Action
Based on EPA's evaluation of the impact of air emissions from Utah
to downwind states using 2026 analytic year modeling as described in
this document, EPA is proposing to approve Utah's January 29, 2020 SIP
submission as meeting the prong 2 interstate transport requirement of
CAA section 110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS.
VII. 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, EPA's role is to approve state choices,
provided that they meet the criteria of the CAA. Accordingly, this
action merely proposes to approve state law as meeting Federal
requirements and does not impose additional requirements beyond those
imposed by state law. For that reason, this action:
<bullet> 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);
<bullet> Is not subject to Executive Order 14192 (90 FR 9065,
February 6, 2025) because SIP actions are exempt from review under
Executive Order 12866;
<bullet> Does not impose an information collection burden under the
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
<bullet> 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.);
<bullet> 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);
<bullet> Does not have federalism implications as specified in
Executive Order 13132 (64 FR 43255, August 10, 1999);
<bullet> Is not subject to Executive Order 13045 (62 FR 19885,
April 23, 1997) because it approves a state program;
<bullet> Is not a significant regulatory action subject to
Executive Order 13211 (66 FR 28355, May 22, 2001);
<bullet> 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 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).
List of Subjects in 40 CFR Part 52
Environmental protection, Air pollution control, Incorporation by
reference, Ozone.
Authority: 42 U.S.C. 7401 et seq.
Dated: June 2, 2025.
Cyrus M. Western,
Regional Administrator, Region 8.
[FR Doc. 2025-11250 Filed 6-17-25; 8:45 am]
BILLING CODE 6560-50-P
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