90 FR 116 pgs. 25918-25923 - Air Plan Approval; Utah; Interstate Transport of Air Pollution for the 2008 8-Hour Ozone National Ambient Air Quality Standard
Type: PRORULEVolume: 90Number: 116Pages: 25918 - 25923
Pages: 25918, 25919, 25920, 25921, 25922, 25923Docket number: [EPA-R08-OAR-2025-0054; FRL-12595-01-R8]
FR document: [FR Doc. 2025-11250 Filed 6-17-25; 8:45 am]
Agency: Environmental Protection Agency
Official PDF Version: PDF Version
[top]
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.
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:
[top] Submit your comments, identified by Docket ID No. EPA-R08-OAR-2025-0054, to the Federal Rulemaking Portal: https://www.regulations.gov. Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from https://www.regulations.gov. EPA may publish any comment received to its public
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:
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: clark.adam@epa.gov.
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.
Footnotes:
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).
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.
Footnotes:
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).
[top] 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
Footnotes:
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).
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 2.5 ) NAAQS, and the 2006 PM 2.5 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).
Footnotes:
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).
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 2.5 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
Footnotes:
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.).
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.
Footnotes:
7 ?EPA addressed most other parts of the January 29, 2020 submission regarding the 2015 ozone NAAQS. See 85 FR 57731 (September 15, 2020).
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 X ) and volatile organic compounds (VOCs) in individual upwind states.
[top] 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,
Footnotes:
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.
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.
Footnotes:
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."
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
Footnotes:
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 https://www.regulations.gov.
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.
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.
Footnotes:
16 ? https://www.epa.gov/air-emissions-modeling/2016v2-platform.
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.
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
Footnotes:
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 https://www.regulations.gov 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.
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).
[top] 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
Footnotes:
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).
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.
Footnotes:
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 https://regulations.gov , 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.
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
Footnotes:
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.
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 X and VOC) in the state. 31
Footnotes:
31 ? Id. at 13-14.
UDAQ concluded, based on the above, that Utah does not interfere with maintenance of the 2008 ozone NAAQS in any downwind state. 32
Footnotes:
32 ? Id. at 14.
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
Footnotes:
33 ?Design values and contributions at individual monitoring sites nationwide are provided in Docket ID No. EPA-HQ-OAR-2021-0668-1130 on https://www.regulations.gov.
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).
[top] 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
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:
• 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);
• Is not subject to Executive Order 14192 (90 FR 9065, February 6, 2025) because SIP actions are exempt from review under Executive Order 12866;
• 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 subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a state program;
• 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 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]
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