# Air Plan Disapprovals; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2023-02407 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** February 13, 2023 - **Citation:** 88 FR 9336 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-HQ-OAR-2021-0663; EPA-R02-OAR-2021-0673; EPA-R03-OAR-2021-0872; EPA-R03-OAR-2021-0873; EPA-R04-OAR-2021-0841; EPA-R05-OAR-2022-0006; EPA-R06-OAR-2021-0801; EPA-R07-OAR-2021-0851; EPA-R08-OAR-2022-0315; EPA-R09-OAR-2022-0394; EPA-R09-OAR-2022-0138; FRL-10209-01-OAR] Air Plan Disapprovals; Interstate Transport of Air Pollution for the 2015 8-Hour Ozone National Ambient Air Quality Standards AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule; final agency action. SUMMARY: Pursuant to the Federal Clean Air Act (CAA or the Act), the Environmental Protection Agency (EPA or the Agency) is finalizing the disapproval of State Implementation Plan (SIP) submissions for 19 states regarding interstate transport and finalizing a partial approval and partial disapproval of elements of the SIP submission for two states for the 2015 8-hour ozone national ambient air quality standards (NAAQS). The “good neighbor” or “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. This requirement is part of the broader set of “infrastructure” requirements, which are designed to ensure that the structural components of each state's air quality management program are adequate to meet the state's responsibilities under the CAA. Disapproving a SIP submission establishes a 2-year deadline for the EPA to promulgate Federal Implementation Plans (FIPs) to address the relevant requirements, unless the EPA approves a subsequent SIP submission that meets these requirements. Disapproval does not start a mandatory sanctions clock. The EPA is deferring final action at this time on the disapprovals it proposed for Tennessee and Wyoming. DATES: The effective date of this final rule is March 15, 2023. ADDRESSES: The EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2021-0663. Additional supporting materials associated with this final action are included in certain regional dockets. See the memo “Regional Dockets Containing Additional Supporting Materials for Final Action on 2015 Ozone NAAQS Good Neighbor SIP Submissions” in the docket for this action. All documents in the dockets are listed on the https://www.regulations.gov website. Although listed in the index, some information is not publicly available, i.e., confidential business information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available through https://www.regulations.gov or please contact the person identified in the FOR FURTHER INFORMATION CONTACT section for additional information. FOR FURTHER INFORMATION CONTACT: General questions concerning this document should be addressed to Mr. Thomas Uher, Office of Air Quality Planning and Standards, Air Quality Policy Division, Mail Code C539-04, 109 TW Alexander Drive, Research Triangle Park, NC 27711; telephone number: (919) 541-5534; email address: uher.thomas@epa.gov. SUPPLEMENTARY INFORMATION: Throughout this document “we,” “us,” and “our” refer to the EPA. References to section numbers in roman numeral refer to sections of this preamble unless otherwise specified. I. General Information A. How can I get copies of this document and other related information? The EPA established a Headquarters docket for this action under Docket ID No. EPA-HQ-OAR-2021-0663 and several regional dockets. All documents in the docket are listed in the electronic indexes, which, along with publicly available documents, are available at https://www.regulations.gov. Publicly available docket materials are also available in hard copy at the Air and Radiation Docket and Information Center, EPA/DC, William Jefferson Clinton West Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC. Some information in the docket may not be publicly available via the online docket due to docket file size restrictions, such as certain modeling files, or content ( e.g., CBI). For further information on the EPA Docket Center services and the current status, please visit us online at https://www.epa.gov/dockets. The EPA also established dockets in each of the EPA Regional offices to help support the proposals that are now being finalized in this national action. These include all public comments, technical support materials, and other files associated with this final action. Each regional docket contains a memorandum directing the public to the headquarters docket for this final action. While all documents in regional dockets are listed in the electronic indexes at https://www.regulations.gov, some information may not be publicly available via the online dockets due to docket file size restrictions, such as certain modeling files, or content ( e.g., CBI). Please contact the EPA Docket Center Services for further information. B. How is the preamble organized? Table of Contents I. General Information A. How can I get copies of this document and other related information? B. How is the preamble organized? C. Where do I go if I have state-specific questions? II. Background and Overview A. Description of Statutory Background B. Description of the EPA's 4-Step Interstate Transport Framework C. Background on the EPA's Ozone Transport Modeling Information D. The EPA's Approach to Evaluating Interstate Transport SIPs for the 2015 8-Hour Ozone NAAQS III. The EPA's Updated Air Quality and Contribution Analysis A. Description of Air Quality Modeling for the Final Action B. Air Quality Modeling To Identify Nonattainment and Maintenance Receptors C. Air Quality Modeling To Quantify Upwind State Contributions IV. Summary of Bases for Disapproval A. Alabama B. Arkansas C. California D. Illinois E. Indiana F. Kentucky G. Louisiana H. Maryland I. Michigan J. Minnesota K. Mississippi L. Missouri M. Nevada N. New Jersey O. New York P. Ohio Q. Oklahoma R. Texas S. Utah T. West Virginia U. Wisconsin V. Response to Key Comments A. SIP Evaluation Process B. Application of the 4-Step Interstate Transport Framework C. Good Neighbor Provision Policy VI. Statutory and Executive Orders Reviews A. Executive Orders 12866: Regulatory Planning and Executive Order 13563: Improving Regulation and Regulatory Review B. Paperwork Reduction Act (PRA) C. Regulatory Flexibility Act (RFA) D. Unfunded Mandates Reform Act of 1995 (UMRA) E. Executive Order 13132: Federalism F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments G. Executive Order 13045: Protection of Children From Environmental Health and Safety Risks H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution or Use I. National Technology Transfer and Advancement Act (NTTAA) J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations K. Congressional Review Act (CRA) L. Judicial Review C. Where do I go if I have state-specific questions? The following table identifies the states covered by this final action along with an EPA Regional office contact who can respond to questions about specific SIP submissions. Regional offices States EPA Region 2: Kenneth Fradkin, Air and Radiation Division/Air Programs Branch, EPA Region 2, 290 Broadway, 25th Floor, New York, NY 10007 New Jersey, New York. EPA Region 3: Mike Gordon, Planning and Implementation Branch, EPA Region III, 1600 JFK Boulevard, Philadelphia, Pennsylvania 19103 Maryland, West Virginia. EPA Region 4: Evan Adams, Air and Radiation Division/Air Planning and Implementation Branch, EPA Region IV, 61 Forsyth Street SW, Atlanta, Georgia 30303 Alabama, Kentucky, Mississippi. EPA Region 5: Olivia Davidson, Air & Radiation Division/Air Programs Branch, EPA Region V, 77 W. Jackson Boulevard, Chicago, Illinois 60604-3511 Indiana, Illinois, Michigan, Minnesota, Ohio, Wisconsin. EPA Region 6: Sherry Fuerst, Air and Radiation Division, EPA Region 6, 1201 Elm Street, Suite 500, Dallas, Texas 75270 Arkansas, Louisiana, Oklahoma, Texas. EPA Region 7: William Stone, Air and Radiation Division, Air Quality Planning Branch, EPA Region VII, 11201 Renner Boulevard, Lenexa, Kansas 66219 Missouri. EPA Region 8: Adam Clark, Air and Radiation Division, EPA, Region VIII, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver, Colorado 80202 Utah. EPA Region 9: Tom Kelly, Air and Radiation Division, EPA Region IX, 75 Hawthorne St., San Francisco, California 94105 California, Nevada. II. Background and Overview The following provides background for the EPA's final action on these SIP submissions related to the interstate transport requirements for the 2015 8-hour ozone NAAQS (2015 ozone NAAQS). A. Description of Statutory Background On October 1, 2015, the EPA promulgated a revision to the ozone NAAQS (2015 ozone NAAQS), lowering the level of both the primary and secondary standards to 0.070 parts per million (ppm) for the 8-hour standard. 1 Section 110(a)(1) of the CAA requires states to submit, within 3 years after promulgation of a new or revised standard, SIP submissions 2 meeting the applicable requirements of section 110(a)(2). 3 One of these applicable requirements is found in CAA section 110(a)(2)(D)(i)(I), otherwise known as the “good neighbor” or “interstate transport” provision, which generally requires SIPs to contain adequate provisions to prohibit in-state emissions activities from having certain adverse air quality effects on other states due to interstate transport of pollution. There are two so-called “prongs” within CAA section 110(a)(2)(D)(i)(I). A SIP for a new or revised NAAQS must contain adequate provisions prohibiting any source or other type of emissions activity within the state from emitting air pollutants in amounts that will significantly contribute to nonattainment of the NAAQS in another state (prong 1) or interfere with maintenance of the NAAQS in another state (prong 2). The EPA and states must give independent significance to prong 1 and prong 2 when evaluating downwind air quality problems under CAA section 110(a)(2)(D)(i)(I). 4 1 National Ambient Air Quality Standards for Ozone, Final Rule, 80 FR 65292 (October 26, 2015). Although the level of the standard is specified in the units of ppm, ozone concentrations are also described in parts per billion (ppb). For example, 0.070 ppm is equivalent to 70 ppb. 2 The terms “submission,” “revision,” and “submittal” are used interchangeably in this document. 3 SIP revisions that are intended to meet the applicable requirements of section 110(a)(1) and (2) of the CAA are often referred to as infrastructure SIPs and the applicable elements under CAA section 110(a)(2) are referred to as infrastructure requirements. 4 See North Carolina v. EPA, 531 F.3d 896, 909-11 (D.C. Cir. 2008) ( North Carolina ). On February 22, 2022, the EPA proposed to disapprove 19 good neighbor SIP submissions from the States of Alabama, Arkansas, Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Missouri, New Jersey, New York, Ohio, Oklahoma, Tennessee, Texas, West Virginia, and Wisconsin. 5 On May 24, 2022, the EPA proposed to disapprove four additional good neighbor SIP submissions from the States of California, Nevada, Utah, and Wyoming. 6 On October 25, 2022, the EPA proposed to disapprove a new good neighbor SIP submission from Alabama submitted on June 21, 2022. 7 The EPA is deferring action on the proposals related to the good neighbor SIP submissions from Tennessee and Wyoming at this time. As explained in the notifications of proposed disapproval, the EPA's justification for each of these proposals applies uniform, nationwide analytical methods, policy judgments, and interpretation with respect to the same CAA obligations, i.e., implementation of good neighbor requirements under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS for states across the country. The EPA's final action is likewise based on this common core of determinations. As indicated at proposal, the EPA is taking a consolidated, single final action on the proposed SIP disapprovals. 8 Included in this document is final action on 2015 ozone NAAQS interstate transport SIPs addressing CAA section 110(a)(2)(D)(i)(I) for Alabama, Arkansas, California, Illinois, Indiana, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Mississippi, Missouri, Nevada, New Jersey, New York, Ohio, Oklahoma, Texas, Utah, West Virginia, and Wisconsin. The 2015 ozone NAAQS interstate transport SIP submissions addressing CAA section 110(a)(2)(D)(i)(I) for Tennessee and Wyoming will be addressed in a separate action. 5 87 FR 9545 (February 22, 2022) (Alabama, Mississippi, Tennessee); 87 FR 9798 (February 22, 2022) (Arkansas, Louisiana, Oklahoma, Texas); 87 FR 9838 (February 22, 2022) (Illinois, Indiana, Michigan, Minnesota, Ohio, Wisconsin); 87 FR 9498 (February 22, 2022) (Kentucky); 87 FR 9484 (February 22, 2022) (New Jersey, New York); 87 FR 9463 (February 22, 2022) (Maryland); 87 FR 9533 (February 22, 2022) (Missouri); 87 FR 9516 (February 22, 2022) (West Virginia). 6 87 FR 31443 (May 24, 2022) (California); 87 FR 31485 (May 24, 2022) (Nevada); 87 FR 31470 (May 24, 2022) (Utah); 87 FR 31495 (May 24, 2022) (Wyoming). 7 87 FR 64412 (October 25, 2022) (Alabama). Alabama withdrew its original good neighbor SIP submission on April 21, 2022. Id. at 64419. 8 In its proposals, the EPA stated “The EPA may take a consolidated, single final action on all the proposed SIP disapproval actions with respect to obligations under CAA section 110(a)(2)(D)(i)(I) for the 2015 ozone NAAQS. Should EPA take a single final action on all such disapprovals, this action would be nationally applicable, and the EPA would also anticipate, in the alternative, making and publishing a finding that such final action is based on a determination of nationwide scope or effect.” E.g., 87 FR 9463, 9475 n.51. B. Description of the EPA's 4-Step Interstate Transport Framework The EPA used a 4-step interstate transport framework (or 4-step framework) to evaluate each state's implementation plan submission addressing the interstate transport provision for the 2015 ozone NAAQS. The EPA has addressed the interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) with respect to prior NAAQS in several regulatory actions, including the Cross-State Air Pollution Rule (CSAPR), which addressed interstate transport with respect to the 1997 ozone NAAQS as well as the 1997 and 2006 fine particulate matter standards, 9 the Cross-State Air Pollution Rule Update (CSAPR Update) 10 and the Revised CSAPR Update, both of which addressed the 2008 ozone NAAQS. 11 9 See Federal Implementation Plans: Interstate Transport of Fine Particulate Matter and Ozone and Correction of SIP Approvals, 76 FR 48208 (August 8, 2011). 10 Cross-State Air Pollution Rule Update for the 2008 Ozone NAAQS, 81 FR 74504 (October 26, 2016). 11 In 2019, the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit) remanded CSAPR Update to the extent 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). Wisconsin v. EPA, 938 F.3d 303, 313 (D.C. Cir. 2019) ( Wisconsin ). The Revised CSAPR Update for the 2008 Ozone NAAQS, 86 FR 23054 (April 30, 2021), responded to the remand of CSAPR Update in Wisconsin and the vacatur of a separate rule, the “CSAPR Close-Out,” 83 FR 65878 (December 21, 2018), in New York v. EPA, 781 F. App'x. 4 (D.C. Cir. 2019). Shaped through the years by input from state air agencies 12 and other stakeholders on EPA's prior interstate transport rulemakings and SIP actions, 13 as well as a number of court decisions, the EPA has developed and used the following 4-step interstate transport framework to evaluate a state's obligations to eliminate interstate transport emissions under the interstate transport provision for the ozone NAAQS: (1) Identify monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS ( i.e., nonattainment and/or maintenance receptors); (2) identify states that impact those air quality problems in other ( i.e., downwind) states sufficiently such that the states are considered “linked” and therefore warrant further review and analysis; (3) identify the emissions reductions necessary (if any), applying a multifactor analysis, to eliminate each linked upwind state's significant contribution to nonattainment or interference with maintenance of the NAAQS at the locations identified in Step 1; and (4) adopt permanent and enforceable measures needed to achieve those emissions reductions. 12 See 63 FR 57356, 57361 (October 27, 1998). 13 In addition to CSAPR rulemakings, other regional rulemakings addressing ozone transport include the “NO X SIP Call,” 63 FR 57356 (October 27, 1998), and the “Clean Air Interstate Rule” (CAIR), 70 FR 25162 (May 12, 2005). The general steps of this framework allow for some methodological variation, and this can be seen in the evolution of the EPA's analytical process across its prior rulemakings. This also means states have some flexibility in developing analytical methods within this framework (and may also attempt to justify an alternative framework altogether). The four steps of the framework simply provide a reasonable organization to the analysis of the complex air quality challenge of interstate ozone transport. As discussed further throughout this document, the EPA has organized its evaluation of the states' SIP submissions around this analytical framework (including the specific methodologies within each step as evolved over the course of the CSAPR rulemakings since 2011), but where states presented alternative approaches either to the EPA's methodological approaches within the framework, or organized their analysis in some manner that differed from it entirely, we have evaluated those analyses on their merits or, in some cases, identified why even if those approaches were acceptable, the state still does not have an approvable SIP submission as a whole. C. Background on the EPA's Ozone Transport Modeling Information In general, the 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 specific upwind states on 2023 ozone design values for the identified downwind nonattainment and maintenance receptors at Step 2, the EPA performed nationwide, state-level ozone source apportionment modeling for 2023. 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. The EPA has released several documents containing projected design values, contributions, and information relevant to air agencies for evaluating interstate transport with respect to the 2015 ozone NAAQS. First, on January 6, 2017, the EPA published a notice of data availability (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. 14 In the NODA, the EPA used the year 2023 as the analytic year for this preliminary modeling because that year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 ozone NAAQS. 15 On October 27, 2017, the EPA released a memorandum (October 2017 memorandum) containing updated modeling data for 2023, which incorporated changes made in response to comments on the 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. 16 On March 27, 2018, the 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. 17 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 ozone NAAQS under Step 2 of the 4-step interstate transport framework. 18 The EPA subsequently issued two more memoranda in August and October 2018, providing additional information to states developing interstate transport SIP submissions for the 2015 ozone NAAQS concerning, respectively, potential contribution thresholds that may be appropriate to apply in Step 2 of the 4-step interstate transport framework, and considerations for identifying downwind areas that may have problems maintaining the standard at Step 1 of the 4-step interstate transport framework. 19 14 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). 15 See 82 FR 1733, 1735 (January 6, 2017). 16 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 (“October 2017 memorandum”), available in Docket No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices. 17 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 Docket No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/interstate-air-pollution-transport/interstate-air-pollution-transport-memos-and-notices. 18 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.” March 2018 memorandum at 2. 19 See Analysis of Contribution Thresholds for Use in Clean Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State Implementation Plan Submissions for the 2015 Ozone National Ambient Air Quality Standards, August 31, 2018) (“August 2018 memorandum”); Considerations for Identifying Maintenance Receptors for Use in Clean Air Act Section 110(a)(2)(D)(i)(I) Interstate Transport State Implementation Plan Submissions for the 2015 Ozone National Ambient Air Quality Standards, October 19, 2018 (“October 2018 memorandum”), available in Docket No. EPA-HQ-OAR-2021-0663 or at https://www.epa.gov/airmarkets/memo-and-supplemental-information-regarding-interstate-transport-sips-2015-ozone-naaqs. Following the release of the modeling data shared in the March 2018 memorandum, the EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e., 2016v1). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 20 This collaborative project was a multi-year joint effort by the EPA, MJOs, and states to develop a new, more recent emissions platform for use by the EPA and states in regulatory modeling as an improvement over the dated, 2011-based platform that the EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. The EPA used the 2016v1 emissions to project ozone design values and contributions for 2023. On October 30, 2020, in the notice of proposed rulemaking for the Revised CSAPR Update, the EPA released and accepted public comment on 2023 modeling that used the 2016v1 emissions platform. 21 Although the Revised CSAPR Update addressed transport for the 2008 ozone NAAQS, the projected design values and contributions from the 2016v1 platform were also useful for identifying downwind ozone problems and linkages with respect to the 2015 ozone NAAQS. 22 20 The results of this modeling, as well as the underlying modeling files, are included in Docket No. EPA-HQ-OAR-2021-0663. 21 See 85 FR 68964, 68981 (October 30, 2020). 22 See the Air Quality Modeling Technical Support Document for the Final Revised Cross-State Air Pollution Rule Update, included in Docket No. EPA-HQ-OAR-2021-0663. Following the final Revised CSAPR Update, the EPA made further updates to the 2016-based emissions platform to include updated onroad mobile emissions from Version 3 of the EPA's Motor Vehicle Emission Simulator (MOVES) model (MOVES3) 23 and updated emissions projections for electric generating units (EGUs) that reflect the emissions reductions from the Revised CSAPR Update, recent information on plant closures, and other inventory improvements. The construct of the updated emissions platform, 2016v2, is described in the “Technical Support Document (TSD): Preparation of Emissions Inventories for the 2016v2 North American Emissions Modeling Platform,” hereafter known as the 2016v2 Emissions Modeling TSD, and is included in Docket No. EPA-HQ-OAR-2021-0663. The EPA performed air quality modeling using the 2016v2 emissions to provide projections of ozone design values and contributions in 2023 that reflect the effects on air quality of the 2016v2 emissions platform. The results of the 2016v2 modeling were used by the EPA as part of the Agency's evaluation of state SIP submissions with respect to Steps 1 and 2 of the 4-step interstate transport framework at the proposal stage of this action. By using the 2016v2 modeling results, the EPA used the most current and technically appropriate information for the proposed rulemakings that were issued earlier in 2022. 23 86 FR 1106. Additional details and documentation related to the MOVES3 model can be found at https://www.epa.gov/moves/latest-version-motor-vehicle-emission-simulator-moves. The EPA invited and received comments on the 2016v2 emissions inventories and modeling that were used to support proposals related to 2015 ozone NAAQS interstate transport. (The EPA had earlier published the emissions inventories on its website in September of 2021 and invited initial feedback from states and other interested stakeholders. 24 ) In response to these comments, the EPA made a number of updates to the 2016v2 inventories and model design to construct a 2016v3 emissions platform which was used to update the air quality modeling. The EPA made additional updates to its modeling in response to comments as well. The EPA is now using this updated modeling to inform its final action on these SIP submissions. Details on the air quality modeling and the methods for projecting design values and determining contributions in 2023 are described in Section III and in the TSD titled “Air Quality Modeling TSD for the 2015 8-hour ozone NAAQS Transport SIP Final Actions”, hereafter known as the Final Action AQM TSD. 25 26 Additional details related to the updated 2016v3 emissions platform are located in the TSD titled “Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform,” hereafter known as the 2016v3 Emissions Modeling TSD, included in Docket ID No. EPA-HQ-OAR-2021-0663. 27 24 https://www.epa.gov/air-emissions-modeling/2016v2-platform. 25 See Final Action AQM TSD in Docket ID No. EPA-HQ-OAR-2021-0663 26 References to section numbers in roman numeral refer to sections of this preamble unless otherwise specified, and references to section numbers in numeric form refer to the Response to Comments document for this final action included in the docket. 27 See 2016v3 Emissions Modeling TSD in Docket ID No. EPA-HQ-OAR-2021-0663. D. The EPA's Approach To Evaluating Interstate Transport SIPs for the 2015 Ozone NAAQS The EPA is applying a consistent set of policy judgments across all states for purposes of evaluating interstate transport obligations and the approvability of interstate transport SIP submissions for the 2015 ozone NAAQS under CAA section 110(a)(2)(D)(i)(I). These policy judgments conform with relevant case law and past agency practice as reflected in CSAPR and related rulemakings. Employing a nationally consistent approach is particularly important in the context of interstate ozone transport, which is a regional-scale pollution problem involving many smaller contributors. Effective policy solutions to the problem of interstate ozone transport going back to the NO X SIP Call have necessitated the application of a uniform framework of policy judgments to ensure an “efficient and equitable” approach. See EPA v. EME Homer City Generation, LP, 572 U.S. 489, 519 (2014) ( EME Homer City ). Some comments on EPA's proposed SIP disapprovals claim the EPA is imposing non-statutory requirements onto SIPs or that the EPA must allow states to take inconsistent approaches to implementing good neighbor requirements. Both views are incorrect; the EPA's use of its longstanding framework to evaluate these SIP submissions reflects a reasonable and consistent approach to implementing the requirements of CAA section 110(a)(2)(D)(i)(I), while remaining open to alternative approaches states may present. These comments are further addressed in Section V and the Response to Comment (RTC) document contained in the docket for this action, Docket ID No. EPA-HQ-OAR-2021-0663. In the March, August, and October 2018 memoranda, the EPA recognized that states may be able to establish alternative approaches to addressing their interstate transport obligations for the 2015 ozone NAAQS that vary from a nationally uniform framework. The EPA emphasized in these memoranda, however, that such alternative approaches must be technically justified and appropriate in light of the facts and circumstances of each particular state's submission. 28 In general, the EPA continues to believe that deviation from a nationally consistent approach to ozone transport must be substantially justified and have a well-documented technical basis that is consistent with CAA obligations and relevant case law. Where states submitted SIP submissions that rely on any such potential concepts as the EPA or others may have identified or suggested in the past, the EPA evaluated whether the state adequately justified the technical and legal basis for doing so. For example, the EPA has considered the arguments put forward by Alabama, Missouri, Ohio, Oklahoma, Texas, and Utah related to alternative methods of identifying receptors. 29 The EPA also has considered the arguments attempting to justify an alternative contribution threshold at Step 2 pursuant to the August 2018 memorandum made by Alabama, Arkansas, Illinois, Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Oklahoma, and Utah, 30 as well as criticisms of the 1 percent of the NAAQS contribution threshold made by Nevada and Ohio. 31 These topics are further addressed in Section V.B as well as the RTC document. 28 March 2018 memorandum at 3 (“EPA also notes that, in developing their own rules, states have flexibility to follow the familiar four-step transport framework (using EPA's analytical approach or somewhat different analytical approaches within this steps) or alternative framework, so long as their chosen approach has adequate technical justification and is consistent with the requirements of the CAA.”); August 2018 memorandum at 1 (“The EPA and air agencies should consider whether the recommendations in this guidance are appropriate for each situation.”); October 2018 memorandum at 1 (“Following the recommendations in this guidance does not ensure that EPA will approve a SIP revision in all instances where the recommendations are followed, as the guidance may not apply to the facts and circumstances underlying a particular SIP.”). 29 87 FR 64421-64422 (Alabama); 87 FR 9540-9541 (Missouri); 87 FR 9869-9870 (Ohio); 87 FR 9820-9822 (Oklahoma); 87 FR 9826-9829 (Texas); and 87 FR 31480-31481 (Utah). 30 87 FR 64423-64424 (Alabama); 87 FR 9806-9807 (Arkansas); 87 FR 9852-9853 (Illinois); 87 FR 9855-9856 (Indiana); 87 FR 9509-9510 (Kentucky); 87 FR 9815-9816 (Louisiana); 87 FR 9861-9862 (Michigan); 87 FR 9557 (Mississippi); 87 FR 9541-9544 (Missouri); 87 FR 9819 (Oklahoma); 87 FR 31478 (Utah). 31 87 FR 31492 (Nevada); 87 FR 9871 (Ohio). The EPA notes that certain potential concepts included in an attachment to the March 2018 memorandum require unique consideration, and these ideas do not constitute agency guidance with respect to interstate transport obligations for the 2015 ozone NAAQS. Attachment A to the March 2018 memorandum identified a “Preliminary List of Potential Flexibilities” that could potentially inform SIP development. However, the EPA made clear in both the March 2018 memorandum 32 and in Attachment A that the list of ideas was not endorsed by the Agency but rather “comments provided in various forums” on which the EPA sought “feedback from interested stakeholders.” 33 Further, Attachment A stated, “EPA is not at this time making any determination that the ideas discussed below are consistent with the requirements of the CAA, nor are we specifically recommending that states use these approaches.” 34 Attachment A to the March 2018 memorandum, therefore, does not constitute agency guidance, but was intended to generate further discussion around potential approaches to addressing ozone transport among interested stakeholders. To the extent states sought to develop or rely on one or more of these ideas in support of their SIP submissions, the EPA reviewed their technical and legal justifications for doing so. 35 32 “In addition, the memorandum is accompanied by Attachment A, which provides a preliminary list of potential flexibilities in analytical approaches for developing a good neighbor SIP that may warrant further discussion between EPA and states.” March 2018 memorandum at 1. 33 March 2018 memorandum, Attachment A at A-1. 34 Id. 35 E.g., 87 FR 64423-64425 (Alabama); 87 FR 31453-31454 (California); 87 FR 9852-9854 (Illinois); 87 FR 9859-9860 (Indiana); 87 FR 9508, 9515 (Kentucky); 87 FR 9861-9862 (Michigan); 87 FR 9869-9870 (Ohio); 87 FR 9798, 9818-9820 (Oklahoma); 87 FR 31477-31481 (Utah); 87 FR 9526-9527 (West Virginia). The remainder of this section describes the EPA's analytical framework with respect to analytic year, definition of nonattainment and maintenance receptors, selection of contribution threshold, and multifactor control strategy assessment. 1. Selection of Analytic Year In general, the states and the 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). 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). 36 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, 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 938 F.3d 303, 313. 36 For attainment dates for the 2015 ozone NAAQS, refer to CAA section 181(a), 40 CFR 51.1303, and Additional Air Quality Designations for the 2015 Ozone National Ambient Air Quality Standards, 83 FR 25776 (June 4, 2018, effective August 3, 2018). On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that the 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 the 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 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). The EPA interprets the court's holding in Maryland as requiring the states and the Agency, under the good neighbor provision, to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 37 which at the time of EPA's proposed and final actions on the SIPs addressed in this action is the Moderate area attainment date under CAA section 181 for ozone nonattainment. The Moderate area attainment date for the 2015 ozone NAAQS is August 3, 2024. 38 Thus, 2023 is now the appropriate year for analysis of interstate transport obligations for the 2015 ozone NAAQS, because the 2023 ozone season is the last relevant ozone season during which achieved emissions reductions in linked upwind states could assist downwind states with meeting the August 3, 2024, Moderate area attainment date for the 2015 ozone NAAQS. 37 The EPA notes that the court in Maryland did not have occasion to evaluate circumstances in which the 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. 38 See CAA section 181(a); 40 CFR 51.1303; Additional Air Quality Designations for the 2015 Ozone National Ambient Air Quality Standards, 83 FR 25776 (June 4, 2018, effective August 3, 2018). The EPA recognizes that the attainment date for nonattainment areas classified as Marginal for the 2015 ozone NAAQS was August 3, 2021. Under the Maryland holding, any necessary emissions reductions to satisfy interstate transport obligations should have been implemented by no later than this date. At the time of the statutory deadline to submit interstate transport SIPs (October 1, 2018), many states relied upon the EPA's modeling of the year 2023, and no state provided an alternative analysis using a 2021 analytic year (or the prior 2020 ozone season). However, the EPA must act on SIP submissions using the information available at the time it takes such action, and it is now past 2021. In this circumstance, the EPA does not believe it would be appropriate to evaluate states' obligations under CAA section 110(a)(2)(D)(i)(I) as of an attainment date that is wholly in the past, because the Agency interprets the interstate transport provision as forward looking. See 86 FR 23054, 23074; see also Wisconsin, 938 F.3d at 322 (rejecting Delaware's argument that the EPA should have used an analytic year of 2011 instead of 2017). Consequently, in this proposal the EPA will use the analytical year of 2023 to evaluate each state's CAA section 110(a)(2)(D)(i)(I) SIP submission with respect to the 2015 ozone NAAQS. 2. Step 1 of the 4-Step Interstate Transport Framework In Step 1, the EPA identifies monitoring sites that are projected to have problems attaining and/or maintaining the NAAQS in the 2023 analytic year. Where the EPA's analysis shows that a site does not fall under the definition of a nonattainment or maintenance receptor, that site is excluded from further analysis under the EPA's 4-step interstate transport framework. For sites that are identified as a nonattainment or maintenance receptor in 2023, the EPA proceeds to the next step of the 4-step interstate transport framework by identifying which upwind states contribute to those receptors above the contribution threshold. The EPA's approach to identifying ozone nonattainment and maintenance receptors in this action gives independent consideration to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of CAA section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina. 39 39 See North Carolina, 531 F.3d at 910-11 (holding that the EPA must give “independent significance” to each prong of CAA section 110(a)(2)(D)(i)(I)). The EPA identifies nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the CSAPR Update, where the EPA defined nonattainment receptors as those areas that both currently measure nonattainment and that the EPA projects will be in nonattainment in the analytic year ( i.e., 2023). 40 40 See 81 FR 74504 (October 26, 2016). This same concept, relying on both current monitoring data and modeling to define nonattainment receptor, was also applied in CAIR. See 70 FR 25241, 25249 (January 14, 2005); see also North Carolina, 531 F.3d at 913-14 (affirming as reasonable the EPA's approach to defining nonattainment in CAIR). In addition, the EPA identifies a receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in CSAPR and upheld by the D.C. Circuit in EME Homer City Generation, L.P. v. EPA, 795 F.3d 118, 136 (D.C. Cir. 2015) ( EME Homer City II ). 41 Specifically, the EPA identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that takes into account historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. The EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). The EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS. 41 See 76 FR 48208 (August 8, 2011). The CSAPR Update and Revised CSAPR Update also used this approach. See 81 FR 74504 (October 26, 2016) and 86 FR 23054 (April 30, 2021). Recognizing that nonattainment receptors are also, by definition, maintenance receptors, the EPA often uses the term “maintenance-only” to refer to those receptors that are not nonattainment receptors. Consistent with the concepts for maintenance receptors, as described earlier, the EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance-only” receptors, even if they are currently measuring nonattainment based on the most recent official design values. As discussed further in Section III.B., in response to comments, the Agency has also taken a closer look at measured ozone levels at monitoring sites in 2021 and 2022 for the purposes of informing the identification of additional receptors in 2023. We find there is a basis to consider certain sites with elevated ozone levels that are not otherwise identified as receptors to be an additional type of maintenance-only receptor given the likelihood that ozone levels above the NAAQS could persist at those locations through at least 2023. We refer to these as violating-monitor maintenance-only receptors (“violating monitors”). For purposes of this action, we use this information only in a confirmatory way for states that are otherwise found to be linked using the modeling-based methodology. The EPA intends to take separate action to address states that are linked only to one or more violating-monitor receptors. 3. Step 2 of the 4-Step Interstate Transport Framework In Step 2, the EPA quantifies the contribution of each upwind state to each receptor in the 2023 analytic year. The contribution metric used in Step 2 is defined as the average impact from each state to each receptor on the days with the highest ozone concentrations at the receptor based on the 2023 modeling. If a state's contribution value does not equal or exceed the threshold of 1 percent of the NAAQS ( i.e., 0.70 ppb for the 2015 ozone NAAQS), the upwind state is not “linked” to a downwind air quality problem, and the EPA, therefore, concludes that the state does not contribute significantly to nonattainment or interfere with maintenance of the NAAQS in the downwind states. However, if a state's contribution equals or exceeds the 1 percent threshold, the state's emissions are further evaluated in Step 3, considering both air quality and cost as part of a multi-factor analysis, to determine what, if any, emissions might be deemed “significant” and, thus, must be eliminated pursuant to the requirements of CAA section 110(a)(2)(D)(i)(I). In this final action, the EPA relies in the first instance on the 1 percent threshold for the purpose of evaluating a state's contribution to nonattainment or maintenance of the 2015 ozone NAAQS ( i.e., 0.70 ppb) at downwind receptors. This is consistent with the Step 2 approach that the EPA applied in CSAPR for the 1997 ozone NAAQS, which has subsequently been applied in the CSAPR Update and Revised CSAPR Update when evaluating interstate transport obligations for the 2008 ozone NAAQS, and in the EPA's proposals for this action. The EPA continues to find 1 percent to be an appropriate threshold. For ozone, as the EPA found in the CAIR, CSAPR, and CSAPR Update, a portion of the nonattainment problems from anthropogenic sources in the U.S. result from the combined impact of relatively small contributions, typically from multiple upwind states and, in some cases, substantially larger contributions from a subset of particular upwind states, along with contributions from in-state sources. The EPA's analysis shows that much of the ozone transport problem being analyzed in this action is still the result of the collective impacts of contributions from upwind states. Therefore, application of a consistent contribution threshold is necessary to identify those upwind states that should have responsibility for addressing their contribution to the downwind nonattainment and maintenance problems to which they collectively contribute. Continuing to use 1 percent of the NAAQS as the screening metric to evaluate collective contribution from many upwind states also allows the EPA (and states) to apply a consistent framework to evaluate interstate emissions transport under the interstate transport provision from one NAAQS to the next. See 81 FR 74518; see also 86 FR 23085 (reviewing and explaining rationale from CSAPR, 76 FR 48237-38, for selection of 1 percent threshold). The EPA's August 2018 memorandum recognizes that in certain circumstances, a state may be able to establish that an alternative contribution threshold of 1 ppb is justifiable. Where a state relies on this alternative threshold in their SIP submission, and where that state determined that it was not linked at Step 2 using the alternative threshold, the EPA evaluated whether the state provided a technically sound assessment of the appropriateness of using this alternative threshold based on the facts and circumstances underlying its application in the particular SIP submission. The states covered by this action that rely on a contribution threshold other than 1 percent of the NAAQS in their 2015 ozone NAAQS good neighbor SIP submission are Alabama, Arkansas, Illinois, Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Oklahoma, and Utah. Ohio also criticized the 1 percent of the NAAQS threshold, though it acknowledged it was linked above either a 1 percent of the NAAQS or 1 ppb contribution threshold. Nevada also criticized the 1 percent of the NAAQS contribution threshold, but ultimately relied on it to support its submission. In the proposals for this action, the EPA evaluated each states' support for the use of an alternative threshold at Step 2 ( e.g., 1 ppb), and additionally shared its experience since the issuance of the August 2018 memorandum regarding use of alternative thresholds at Step 2. The EPA solicited comment on the subject as it considered the appropriateness of rescinding the memorandum. 42 The EPA received numerous comments related to both the EPA's evaluation of SIP submissions relying on an alternative threshold, and the EPA's experience with alternative thresholds. The EPA is not, at this time rescinding the August 2018 memorandum; however, for purposes of evaluating contribution thresholds for the 2015 ozone NAAQS, the EPA continues to find the use of an alternative threshold problematic for the reasons stated at proposal. Regardless of the EPA's position on the August 2018 memorandum, the EPA continues to find that the arguments put forth in the SIP submissions of by Alabama, Arkansas, Illinois, Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Oklahoma, and Utah, as well as arguments in comments received on these actions, to be inadequate. See Section V.B.7 and the RTC Document for additional detail. 42 See, e.g., 87 FR 9551. 4. Step 3 of the 4-Step Interstate Transport Framework Consistent with the EPA's longstanding approach to eliminating significant contribution and interference with maintenance, at Step 3, a multifactor assessment of potential emissions controls is conducted for states linked at Steps 1 and 2. The EPA's analysis at Step 3 in prior Federal actions addressing interstate transport requirements has primarily focused on an evaluation of cost-effectiveness of potential emissions controls (on a marginal cost-per-ton basis), the total emissions reductions that may be achieved by requiring such controls (if applied across all linked upwind states), and an evaluation of the air quality impacts such emissions reductions would have on the downwind receptors to which a state is linked; other factors may potentially be relevant if adequately supported. In general, where the EPA's or state-provided alternative air quality and contribution modeling establishes that a state is linked at Steps 1 and 2, it will be insufficient at Step 3 for a state merely to point to its existing rules requiring control measures as a basis for SIP approval. In general, the emissions-reducing effects of all existing emissions control requirements are already reflected in the future year projected air quality results of the modeling for Steps 1 and 2. If the state is shown to still be linked to one or more downwind receptor(s) despite these existing controls, but that state believes it has no outstanding good neighbor obligations, the EPA expects the state to provide sufficient justification to support a conclusion by the EPA that the state has adequate provisions prohibiting “any source or other type of emissions activity within the State from emitting any air pollutant in amounts which will” “contribute significantly to nonattainment in, or interfere with maintenance by,” any other State with respect to the NAAQS. See CAA section 110(a)(2)(D)(i)(I). While the EPA has not prescribed a particular method for this assessment, as many commenters note, the EPA expects states at a minimum to present a sufficient technical evaluation. This would typically include information on emissions sources, applicable control technologies, emissions reductions, costs, cost effectiveness, and downwind air quality impacts of the estimated reductions, before concluding that no additional emissions controls should be required. 43 The EPA responds to comment on issues related to Step 3 in Section V.B.8. and in the RTC document. 43 Because no state included new enforceable emissions control measures in the submissions under review here, we focus our analysis on whether states justified that no additional controls were required. As examples of general approaches for how a Step 3 analysis could be conducted for their sources, states could look to the CSAPR Update, 81 FR 74504, 74539-51; CSAPR, 76 FR 48208, 48246-63; CAIR, 70 FR 25162, 25195-229; or the NO X SIP Call, 63 FR 57356, 57399-405. See also Revised CSAPR Update, 86 FR 23054, 23086-23116. Consistently across these rulemakings, the EPA has developed emissions inventories, analyzed different levels of control stringency at different cost thresholds, and assessed resulting downwind air quality improvements. 5. Step 4 of the 4-Step Interstate Transport Framework At Step 4, states (or the EPA) develop permanent and federally-enforceable control strategies to achieve the emissions reductions determined to be necessary at Step 3 to eliminate significant contribution to nonattainment or interference with maintenance of the NAAQS. 44 For a state linked at Steps 1 and 2 to rely on an emissions control measure at Step 3 to address its interstate transport obligations, that measure must be included in the state's SIP so that it is permanent and federally enforceable. See CAA section 110(a)(2)(D) (“Each such [SIP] shall . . . contain adequate provisions. . . .”). See also CAA section 110(a)(2)(A); Committee for a Better Arvin v. EPA, 786 F.3d 1169, 1175-76 (9th Cir. 2015) (holding that measures relied on by a state to meet CAA requirements must be included in the SIP). 44 The EPA notes that any controls included in an approved SIP are federally-enforceable. III. The EPA's Updated Air Quality and Contribution Analysis As noted in Section II, the EPA relied in part on its 2016v2 emissions platform-based air quality modeling to support its proposed interstate transport actions taken in 2022. Following receipt of comments, the EPA updated this modeling, incorporating new information received to create the 2016v3 emissions inventory and making additional updates to improve model performance. Using the 2016v3 emissions inventory, the EPA evaluated modeling projections for air quality monitoring sites and considered current ozone monitoring data at these sites to identify receptors that are anticipated to have problems attaining or maintaining the 2015 ozone NAAQS. This section presents a summary of the methodology and results of the 2016v3 modeling of 2023, along with the application of the EPA's Step 1 and Step 2 methodology for identifying receptors and upwind states that contribute to those receptors. We also explain that current measured ozone levels based on data for 2021 and preliminary data for 2022 at other monitoring sites ( i.e., monitoring sites that are not projected to be receptors in 2023 based on air quality modeling) confirm the likely continuation of elevated ozone levels in 2023 at these locations and confirm that nearly all upwind states in this action are also linked above 1 percent of the NAAQS to one or more of these monitors. While all of this information compiled by the EPA (both the modeling and monitoring data) plays a critical role in the basis for this final action, the EPA has also thoroughly evaluated the modeling information and other analyses and arguments presented by the upwind states in their SIP submittals. Our evaluation of the states' analyses was generally set forth in the proposals, and the EPA in this final action has responded to comments on our evaluation of the various information and arguments made by states. The EPA's final decision to disapprove these states' SIP submittals is based on our evaluation of the entire record, recognizing that states possess the authority in the first instance to propose how they would address their significant contribution to air quality problems in other states. Nonetheless, as explained in the proposals, and in this document and supporting materials in the docket, we conclude that no state included in this action effectively demonstrated that it will not be linked to at least one air quality receptor in 2023, and none of these states' various arguments for alternative approaches ultimately present a satisfactory basis for the EPA to approve these states' SIP submissions. A. Description of Air Quality Modeling for the Final Action In this section, the Agency describes the air quality modeling performed consistent with Steps 1 and 2 of the 4-step interstate transport framework to (1) Identify locations where it expects nonattainment or maintenance problems with respect to the 2015 ozone NAAQS for the 2023 analytic year, and (2) quantify the contributions from anthropogenic emissions from upwind states to downwind ozone concentrations at monitoring sites projected to be in nonattainment or have maintenance problems for the 2015 ozone NAAQS in 2023. This section includes information on the air quality modeling platform used in support of the final SIP disapproval action with a focus on the base year and future base case emissions inventories. The EPA also provides the projection of 2023 ozone concentrations and the interstate contributions for 8-hour ozone. The Final Action AQM TSD in Docket ID No. EPA-HQ-OAR-2021-0663 contains more detailed information on the air quality modeling aspects supporting our final action on these SIP submissions. 1. Public Review of Air Quality Modeling Information for the Proposed Action The EPA provided several opportunities to comment on the emissions modeling platform and air quality modeling results that were used for the proposed SIP submission actions. On September 20, 2021, the EPA publicly released via our web page updated emissions inventories (2016v2) and requested comment from states and MJOs on these data. 45 In January 2022, the EPA released air quality modeling results including projected ozone design values and contributions from 2023 based on the 2016v2 emissions. At that time the EPA indicated its intent to use these data to support upcoming transport rulemakings. Then, on February 22, 2022, the EPA published proposed disapprovals for 19 interstate transport SIP submissions using the modeling data released in January 2022 and the emissions inventories shared in September 2021. 46 The EPA provided a 60-day comment period on these proposals. On May 24, 2022, the EPA proposed disapprovals for an additional four states' interstate transport SIP submissions using the same modeling platform, and provided a 62-day comment period. 47 The EPA provided a 30-day comment period beginning on October 25, 2022, on the proposed disapproval of Alabama's June 21, 2022, SIP submission, which relied on the same modeling platform as the other noted proposals. 48 In addition to its proposed disapprovals, the EPA also proposed approval of Iowa's, Arizona's, and Colorado's SIP submissions using the 2016v2 modeling and provided 30-day comment periods. 87 FR 9477 (February 22, 2022) (Iowa); 87 FR 37776 (June 24, 2022) (Arizona); and 87 FR 27050 (May 6, 2022) (Colorado). 45 https://www.epa.gov/air-emissions-modeling/2016v2-platform. 46 These proposals are listed in footnote 5 of this action. 47 The EPA also relied on this same modeling data to support proposed Federal Implementation Plans (FIPs) resolving interstate transport obligations for 27 states for the 2015 ozone NAAQS. 87 FR 20036 (April 6, 2022). The EPA allowed 60 days to receive comments on the proposed FIP rule, including acceptance of comment on the 2016v2 emissions inventory-based modeling platform. The EPA then allowed for an additional 15 days via an extension of the comment period. 87 FR 29108 (May 12, 2022). 48 87 FR 64412, 64413. 2. Overview of Air Quality Modeling Platform The EPA used version 3 of the 2016-based modeling platform ( i.e., 2016v3) for the air quality modeling for this final SIP disapproval action. This modeling platform includes 2016 base year emissions from anthropogenic and natural sources and future year projected anthropogenic emissions for 2023. 49 The emissions data contained in the 2016v3 platform represent an update to the 2016 version 2 inventories used for the proposal modeling. 49 The 2016v3 platform also includes projected emissions for 2026. However, the 2026 data are not applicable and were not used in this final action. The air quality modeling for this final disapproval action was performed for a modeling region ( i.e., modeling domain) that covers the contiguous 48 states using a horizontal resolution of 12 x 12 km. The EPA used the CAMx version 7.10 for air quality modeling which is the same model that the EPA used for the proposed rule air quality modeling. 50 Additional information on the 2016-based air quality modeling platform can be found in the Final Action AQM TSD. 50 Ramboll Environment and Health, January 2021, https://www.camx.com. Comments: Commenters noted that the 2016 base year summer maximum daily average 8-hour (MDA8) ozone predictions from the proposal modeling were biased low compared to the corresponding measured concentrations in certain locations. In this regard, commenters said that model performance statistics for a number of monitoring sites, particularly those in portions of the West and in the area around Lake Michigan, were outside the range of published performance criteria for normalized mean bias (NMB) and normalized mean error (NME) of less than plus or minus 15 percent and less than 25 percent, respectively. 51 Comments say the EPA must investigate the factors contributing to low bias and make necessary corrections to improve model performance in the modeling supporting final SIP actions. Some commenters said that the EPA should include NO X emissions from lightning strikes and assess the treatment of other background sources of ozone to improve model performance for the final action. Additional information on the comments on model performance can be found in the RTC document for this final SIP disapproval action. 51 Christopher Emery, Zhen Liu, Armistead G. Russell, M. Talat Odman, Greg Yarwood & Naresh Kumar (2017) Recommendations on statistics and benchmarks to assess photochemical model performance, Journal of the Air & Waste Management Association, 67:5, 582-598, DOI: 10.1080/10962247.1265027. EPA Response: In response to these comments the EPA examined the temporal and spatial characteristics of model under prediction to investigate the possible causes of under prediction of MDA8 ozone concentrations in different regions of the U.S. in the proposal modeling. The EPA's analysis indicates that the under prediction was most extensive during May and June with less bias during July and August in most regions of the U.S. For example, in the Upper Midwest region model under prediction was larger in May and June compared to July through September. Specifically, the normalized mean bias for days with measured concentrations greater than or equal to 60 ppb improved from a 21.4 percent under prediction for May and June to a 12.6 percent under prediction in the period July through September. As described in the AQM TSD, the seasonal pattern in bias in the Upper Midwest region improves somewhat gradually with time from the middle of May to the latter part of June. In view of the seasonal pattern in bias in the Upper Midwest and in other regions of the U.S., the EPA focused its investigation of model performance on model inputs that, by their nature, have the largest temporal variation within the ozone season. These inputs include emissions from biogenic sources and lightning NO X , and contributions from transport of international anthropogenic emissions and natural sources into the U.S. Both biogenic and lightning NO X emissions in the U.S. dramatically increase from spring to summer. 52 53 In contrast, ozone transported into the U.S. from international anthropogenic and natural sources peaks during the period March through June, with lower contributions during July through September. 54 55 To investigate the impacts of the sources, the EPA conducted sensitivity model runs which focused on the effects on model performance of adding NO X emissions from lightning strikes, using updated biogenic emissions, and using an alternative approach (described in more detail later in this section) for quantifying transport of ozone and precursor pollutants into the U.S. from international anthropogenic and natural sources. In the air quality modeling for proposal, the amount of transport from international sources was based on a simulation of the hemispheric version of the Community Multi-scale Air Quality Model (H-CMAQ) 56 for 2016. The outputs from this hemispheric modeling were then used to provide boundary conditions for the national scale air quality modeling at proposal. 57 Overall, H-CMAQ tends to under predict daytime ozone concentrations at rural and remote monitoring sites across the U.S. during the spring of 2016 whereas the predictions from the GEOS-Chem global model 58 were generally less biased. 59 During the summer of 2016 both models showed varying degrees of over prediction with GEOS-Chem showing somewhat greater over prediction, compared to H-CMAQ. In view of those results, the EPA examined the impacts of using GEOS-Chem as an alternative to H-CMAQ for providing boundary conditions for the modeling supporting this final action. 52 Guenther, A.B., 1997. Seasonal and spatial variations in natural volatile organic compound emissions. Ecol. Appl. 7, 34-45. http://dx.doi.org/10.1890/1051-0761(1997 ) 007[0034:SASVIN]2.0.CO;2. Guenther, A., Hewitt, C.N., Erickson, D., Fall, R. 53 Kang D, Mathur R, Pouliot GA, Gilliam RC, Wong DC. Significant ground-level ozone attributed to lightning-induced nitrogen oxides during summertime over the Mountain West States. NPJ Clim Atmos Sci. 2020 Jan 30;3:6. doi: 10.1038/s41612-020-0108-2. PMID: 32181370; PMCID: PMC7075249. 54 Jaffe DA, Cooper OR, Fiore AM, Henderson BH, Tonnesen GS, Russell AG, Henze DK, Langford AO, Lin M, Moore T. Scientific assessment of background ozone over the U.S.: Implications for air quality management. Elementa (Wash DC). 2018;6(1):56. doi: 10.1525/elementa.309. PMID: 30364819; PMCID: PMC6198683. 55 Henderson, B.H., P. Dolwick, C. Jang, A., Eyth, J. Vukovich, R. Mathur, C. Hogrefe, N. Possiel, G. Pouliot, B. Timin, K.W. Appel, 2019. Global Sources of North American Ozone. Presented at the 18th Annual Conference of the UNC Institute for the Environment Community Modeling and Analysis System (CMAS) Center, October 21-23, 2019. 56 Mathur, R., Gilliam, R., Bullock, O.R., Roselle, S., Pleim, J., Wong, D., Binkowski, F., and 1 Streets, D.: Extending the applicability of the community multiscale air quality model to 2 hemispheric scales: motivation, challenges, and progress. In: Steyn DG, Trini S (eds) Air 3 pollution modeling and its applications, XXI. Springer, Dordrecht, pp 175-179, 2012. 57 Boundary conditions are the concentrations of pollutants along the north, east, south, and west boundaries of the air quality modeling domain. Boundary conditions vary in space and time and are typically obtained from predictions of global or hemispheric models. Information on how boundary conditions were developed for modeling supporting EPA's final SIP actions can be found in the AQM TSD. 58 I. Bey, D.J. Jacob, R.M. Yantosca, J.A. Logan, B.D. Field, A.M. Fiore, Q. Li, H.Y. Liu, L.J. Mickley, M.G. Schultz. Global modeling of tropospheric chemistry with assimilated meteorology: model description and evaluation. J. Geophys. Res. Atmos., 106 (2001), pp. 23073-23095, 10.1029/2001jd000807. 59 Henderson, B.H., P. Dolwick, C. Jang, A., Eyth, J. Vukovich, R. Mathur, C. Hogrefe, G. Pouliot, N. Possiel, B. Timin, K.W. Appel, 2022. Meteorological and Emission Sensitivity of Hemispheric Ozone and PM 2.5 . Presented at the 21st Annual Conference of the UNC Institute for the Environment Community Modeling and Analysis System (CMAS) Center, October 17-19, 2022. For the lightning NO X , biogenics, and GEOS-Chem sensitivity runs, the EPA reran the proposal modeling using each of these inputs, individually. Results from these sensitivity runs indicate that each of the three updates provides an improvement in model performance. However, by far the greatest improvement in modeling performance is attributable to the use of GEOS-Chem. In view of these results the EPA has included lightning NO X emissions, updated biogenic emissions, and international transport from GEOS-Chem in the air quality modeling supporting final SIP actions. Details on the results of the individual sensitivity runs can be found in the AQM TSD. For the air quality modeling supporting final SIP actions, model performance based on days in 2016 with measured MDA8 ozone greater than or equal to 60 ppb is considerably improved ( i.e., less bias and error) compared to the proposal modeling in nearly all regions. For example, in the Upper Midwest, which includes monitoring sites along Lake Michigan, the normalized mean bias improved from a 19 percent under prediction to a 6.9 percent under prediction and in the Southwest region, which includes monitoring sites in Denver, Las Cruces, El Paso, and Salt Lake City, normalized mean bias improved from a 13.6 percent under prediction to a 4.8 percent under prediction. 60 In all regions, the normalized mean bias and normalized mean error statistics for high ozone days based on the modeling supporting final SIP actions are within the range of performance criteria benchmarks ( i.e., less than plus or minus 15 percent for normalized mean bias and less than 25 percent for normalized mean error). 61 Additional information on model performance information is provided in the AQM TSD. In summary, the EPA included emissions of lightning NO X , as requested by commenters, and investigated and addressed concerns about model performance for the modeling supporting final SIP actions. 60 A comparison of model performance from the proposal modeling to the final modeling for individual monitoring sites can be found in the docket for this final action. 61 Christopher Emery, Zhen Liu, Armistead G. Russell, M. Talat Odman, Greg Yarwood & Naresh Kumar (2017) Recommendations on statistics and benchmarks to assess photochemical model performance, Journal of the Air & Waste Management Association, 67:5, 582-598, DOI: 10.1080/10962247.1265027. 3. Emissions Inventories The EPA developed emissions inventories to support air quality modeling for this final action, including emissions estimates for EGUs, non-EGU point sources ( i.e., stationary point sources), stationary nonpoint sources, onroad mobile sources, nonroad mobile sources, other mobile sources, wildfires, prescribed fires, and biogenic emissions that are not the direct result of human activities. The EPA's air quality modeling relies on this comprehensive set of emissions inventories because emissions from multiple source categories are needed to model ambient air quality and to facilitate comparison of model outputs with ambient measurements. Prior to the modeling of air quality, the emissions inventories must be processed into a format that is appropriate for the air quality model to use. To prepare the emissions inventories for air quality modeling, the EPA processed the emissions inventories using the Sparse Matrix Operator Kernel Emissions (SMOKE) Modeling System version 4.9 to produce the gridded, hourly, speciated, model-ready emissions for input to the air quality model. Additional information on the development of the emissions inventories and on data sets used during the emissions modeling process are provided in the document titled “Technical Support Document (TSD): Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform,” hereafter known as the “2016v3 Emissions Modeling TSD.” This TSD is available in the docket for this action. 62 62 See Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform TSD, also available at https://www.epa.gov/air-emissions-modeling/2016v3-platform . 4. Foundation Emissions Inventory The 2016v3 emissions platform is comprised of data from various sources including data developed using models, methods, and source datasets that became available in calendar years 2020 through 2022, in addition to data retained from the Inventory Collaborative 2016 version 1 (2016v1) Emissions Modeling Platform, released in October 2019. The 2016v1 platform was developed through a national collaborative effort between the EPA and state and local agencies along with MJOs. The 2016v2 platform used to support the proposed action included updated data, models and methods as compared to 2016v1. The 2016v3 platform includes updates implemented in response to comments along with other updates to the 2016v2 platform such as corrections and the incorporation of updated data sources that became available prior to the 2016v3 inventories being developed. Several commenters noted that the 2016v2 platform did not include NO X emissions that resulted from lightning strikes. To address this, lightning NO X emissions were computed and included in the 2016v3 platform. For this final action, the EPA developed emissions inventories for the base year of 2016 and the projected year of 2023. The 2023 inventories represent changes in activity data and of predicted emissions reductions from on-the-books actions, planned emissions control installations, and promulgated Federal measures that affect anthropogenic emissions. The 2016 emissions inventories for the U.S. primarily include data derived from the 2017 National Emissions Inventory (2017 NEI) 63 and data specific to the year of 2016. The following sections provide an overview of the construct of the 2016v3 emissions and projections. The fire emissions were unchanged between the 2016v2 and 2016v3 emissions platforms. For the 2016v3 platform, the biogenic emissions were updated to use the latest available versions of the Biogenic Emissions Inventory System and associated land use data to help address comments related to a degradation in model performance in the 2016v2 platform as compared to the 2016v1 platform. Details on the construction of the inventories are available in the 2016v3 Emissions Modeling TSD. Details on how the EPA responded to comments related to emissions inventories are available in the RTC document for this action. 63 https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-technical-support-document-tsd . Development of emissions inventories for annual NO X and sulfur dioxide (SO 2 ) emissions for EGUs in the 2016 base year inventory are based primarily on data from continuous emissions monitoring systems (CEMS) and other monitoring systems allowed for use by qualifying units under 40 CFR part 75, with other EGU pollutants estimated using emissions factors and annual heat input data reported to the EPA. For EGUs not reporting under part 75, the EPA used data submitted to the NEI by state, local, and tribal agencies. The final action inventories include updates made in response to comments on the proposed actions including the proposed SIP submission disapprovals and the proposed FIP. The Air Emissions Reporting Rule, (80 FR 8787; February 19, 2015), requires that Type A point sources large enough to meet or exceed specific thresholds for emissions be reported to the EPA via the NEI every year, while the smaller Type B point sources must only be reported to EPA every 3 years. In response to comments, emissions data for EGUs that did not have data submitted to the NEI specific to the year 2016 were filled in with data from the 2017 NEI. For more information on the details of how the 2016 EGU emissions were developed and prepared for air quality modeling, see the 2016v3 Emissions Modeling TSD. The EPA projected 2023 baseline EGU emissions using version 6 of the Integrated Planning Model (IPM) ( www.epa.gov/airmarkets/powersector-modeling ). IPM, developed by ICF Consulting, is a state-of-the-art, peer-reviewed, multi-regional, dynamic, deterministic linear programming model of the contiguous U.S. electric power sector. It provides forecasts of least cost capacity expansion, electricity dispatch, and emissions control strategies while meeting energy demand and environmental, transmission, dispatch, and reliability constraints. The EPA has used IPM for over two decades to better understand power sector behavior under future business-as-usual conditions and to evaluate the economic and emissions impacts of prospective environmental policies. The model is designed to reflect electricity markets as accurately as possible. The EPA uses the best available information from utilities, industry experts, gas and coal market experts, financial institutions, and government statistics as the basis for the detailed power sector modeling in IPM. The model documentation provides additional information on the assumptions discussed here as well as all other model assumptions and inputs. 64 The EPA relied on the same model platform as in the proposals but made substantial updates to reflect public comments on near-term fossil fuel market price volatility and updated fleet information reflecting Summer 2022 U.S. Energy Information Agency (EIA) 860 data, unit-level comments, and additional updates to the National Electric Energy Data System (NEEDS) inventory. 64 Detailed information and documentation of the EPA's Base Case, including all the underlying assumptions, data sources, and architecture parameters can be found on the EPA's website at: https://www.epa.gov/airmarkets/power-sector-modeling . The IPM version 6—Updated Summer 2021 Reference Case incorporated recent updates through the summer 2022 to account for updated Federal and state environmental regulations (including Renewable Portfolio Standards (RPS), Clean Energy Standards (CES) and other state mandates), fleet changes (committed EGU retirements and new builds), electricity demand, technology cost and performance assumptions from recent data for renewables adopting from National Renewable Energy Lab (NREL's) Annual Technology Baseline 2020 and for fossil sources from the EIA's Annual Energy Outlook (AEO) 2020. Natural gas and coal price projections reflect data developed in fall 2020 but updated in summer 2022 to capture near-term price volatility and current market conditions. The inventory of EGUs provided as an input to the model was the NEEDS fall 2022 version and is available on the EPA's website. 65 This version of NEEDS reflects announced retirements and under construction new builds known as of early summer 2022. This projected base case accounts for the effects of the final Mercury and Air Toxics Standards rule, CSAPR, the CSAPR Update, the Revised CSAPR Update, New Source Review enforcement settlements, the final Effluent Limitation Guidelines (ELG) Rule, the Coal Combustion Residual (CCR) Rule, and other on-the-books Federal and state rules (including renewable energy tax credit extensions from the Consolidated Appropriations Act of 2021) through early 2021 impacting emissions of SO 2 , NO X , directly emitted particulate matter, carbon dioxide (CO 2 ), and power plant operations. It also includes final actions, up through the Summer 2022, the EPA has taken to implement the Regional Haze Rule and best available retrofit technology (BART) requirements. Documentation of IPM version 6 and NEEDS, along with updates, is in Docket ID No. EPA-HQ-OAR-2021-0663 and available online at https://www.epa.gov/airmarkets/power-sector-modeling . 65 Available at https://www.epa.gov/airmarkets/national-electric-energy-data-system-needs-v6 . Non-EGU point source emissions are mostly consistent with those in the proposal modeling except where they were updated in response to comments. Several commenters mentioned that point source emissions carried forward from 2014 NEI were not the best estimates of 2017 emissions. Thus, emissions sources in 2016v2 that had been projected from the 2014 NEI in the proposal were replaced with emissions based on the 2017 NEI. Point source emissions submitted to the 2016 NEI or to the 2016v1 platform development process specifically for the year 2016 were retained in 2016v3. The 2023 non-EGU point source emissions were grown from 2016 to 2023 using factors based on AEO 2022 and reflect emissions reductions due to known national and local rules, control programs, plant closures, consent decrees, and settlements that could be computed as reductions to specific units by July 2022. Aircraft emissions and ground support equipment at airports are represented as point sources and are based on adjustments to emissions in the January 2021 version of the 2017 NEI. The EPA developed and applied factors to adjust the 2017 airport emissions to 2016 and 2023 based on activity growth projected by the Federal Aviation Administration Terminal Area Forecast 2021, 66 the latest available version at the time the factors were developed. 66 https://www.faa.gov/data_research/aviation/taf/ . Emissions at rail yards were represented as point sources. The 2016 rail yard emissions are largely consistent with the 2017 NEI rail yard emissions. The 2016 and 2023 rail yard emissions were developed through the 2016v1 Inventory Collaborative process. Class I rail yard emissions were projected based on the AEO freight rail energy use growth rate projections for 2023 with the fleet mix assumed to be constant throughout the period. The EPA made multiple updates to point source oil and gas emissions in response to comments. For the 2016v3 modeling, the point source oil and gas emissions for 2016 were based on the 2016v2 point inventory except that most 2014 NEI-based emissions were replaced with 2017 NEI emissions. Additionally, in response to comments, state-provided emissions equivalent to those in the 2016v1 platform were used for Colorado, and some New Mexico emissions were replaced with data backcast from 2020 to 2016. To develop inventories for 2023 for the 2016v3 platform, the year 2016 oil and gas point source inventories were first projected to 2021 values based on actual historical production data, then those 2021 emissions were projected to 2023 using regional projection factors based on AEO 2022 projections. This was an update from the 2016v2 approach in which actual data were used only through the year 2019, because 2021 data were not yet available. NO X and VOC reductions resulting from co-benefits to New Source Performance Standards (NSPS) for Stationary Reciprocating Internal Combustion Engines (RICE) are reflected, along with Natural Gas Turbine and Process Heater NSPS NO X controls and Oil and Gas NSPS VOC controls. In some cases, year 2019 point source inventory data were used instead of the projected future year emissions except for the Western Regional Air Partnership (WRAP) states of Colorado, New Mexico, Montana, Wyoming, Utah, North Dakota, and South Dakota. The WRAP future year inventory 67 was used in these WRAP states in all future years except in New Mexico where the WRAP base year emissions were projected using the EIA historical and AEO forecasted production data. Estimated impacts from the recent oil and gas rule in the New Mexico Administrative code 20.2.50 68 were also included. Details on the development of the projected point and nonpoint oil and gas emissions inventories are available in the 2016v3 Emissions Modeling TSD in Docket ID No. EPA-HQ-OAR-2021-0663. 67 http://www.wrapair2.org/pdf/WRAP_OGWG_2028_OTB_RevFinalReport_05March2020.pdf . 68 https://www.env.nm.gov/air-quality/ozone-draft-rule/ and https://www.srca.nm.gov/parts/title20/20.002.0050.html . Onroad mobile sources include exhaust, evaporative, and brake and tire wear emissions from vehicles that drive on roads, parked vehicles, and vehicle refueling. Emissions from vehicles using regular gasoline, high ethanol gasoline, diesel fuel, and electric vehicles were represented, along with buses that used compressed natural gas. The EPA developed the onroad mobile source emissions for states other than California using the EPA's Motor Vehicle Emissions Simulator (MOVES). MOVES3 was released in November 2020 and has been followed by some minor releases that improved the usage of the model but that do not have substantive impacts on the emissions estimates. For 2016v2, MOVES3 was run using inputs provided by state and local agencies through the 2017 NEI where available, in combination with nationally available data sets to develop a complete inventory. Onroad emissions were developed based on emissions factors output from MOVES3 run for the year 2016, coupled with activity data ( e.g., vehicle miles traveled and vehicle populations) representing the year 2016. The 2016 activity data were provided by some state and local agencies through the 2016v1 process, and the remaining activity data were derived from those used to develop the 2017 NEI. The onroad emissions were computed within SMOKE by multiplying emissions factors developed using MOVES with the appropriate activity data. Prior to computing the final action emissions for 2016, updates to some onroad inputs were made in response to comments and to implement corrections. Onroad mobile source emissions for California were consistent with the updated emissions data provided by the state for the final action. The 2023 onroad emissions reflect projected changes to fuel properties and usage, along with the impact of the rules included in MOVES3 for each of those years. MOVES emissions factors for the year 2023 were used. A comprehensive list of control programs included for onroad mobile sources is available in the 2016v3 Emissions Modeling TSD. Year 2023 activity data for onroad mobile sources were provided by some state and local agencies, and otherwise were projected to 2023 by first projecting the 2016 activity to year 2019 based on county level vehicle miles traveled (VMT) from the Federal Highway Administration. The VMT were held flat from 2019 to 2021 to account for pandemic impacts, and then projected from 2021 to 2023 using AEO 2022-based factors. 69 Recent updates to inspection and maintenance programs in North Carolina and Tennessee were reflected in the MOVES inputs for the modeling supporting this final action. The 2023 onroad mobile emissions were computed within SMOKE by multiplying the respective emissions factors developed using MOVES with the year-specific activity data. Prior to computing the final action emissions for 2023, the EPA made updates to some onroad inputs in response to comments and to implement corrections. 69 VMT data for 2020 were the latest available at the time of final rule data development but were heavily impacted by the pandemic and unusable to project to 2023; in addition, it was determined that chaining factors based on AEO 2020 and AEO2021 obtain the needed factors led to unrealistic artifacts, thus only AEO 2022 data were used. The commercial marine vessel (CMV) emissions in the 2016 base case emissions inventory for this action were based on those in the 2017 NEI. Factors were applied to adjust the 2017 NEI emissions backward to represent emissions for the year 2016. The CMV emissions are consistent with the emissions for the 2016v1 platform CMV emissions released in February 2020 although, in response to comments, the EPA implemented an improved process for spatially allocating CMV emissions along state and county boundaries for the modeling supporting this final action. The EPA developed nonroad mobile source emissions inventories (other than CMV, locomotive, and aircraft emissions) for 2016 and 2023 from monthly, county, and process level emissions output from MOVES3. Types of nonroad equipment include recreational vehicles, pleasure craft, and construction, agricultural, mining, and lawn and garden equipment. 70 The nonroad emissions for the final action were unchanged from those at the proposal. The nonroad mobile emissions control programs include reductions to locomotives, diesel engines, and recreational marine engines, along with standards for fuel sulfur content and evaporative emissions. A comprehensive list of control programs included for mobile sources is available in the 2016v3 Emissions Modeling TSD. 70 Line haul locomotives are also considered a type of nonroad mobile source but the emissions inventories for locomotives were not developed using MOVES3. Year 2016 and 2023 locomotive emissions were developed through the 2016v1 process, and the year 2016 emissions are mostly consistent with those in the 2017 NEI. The projected locomotive emissions for 2023 were developed by applying factors to the base year emissions using activity data based on AEO freight rail energy use growth rate projections along with emissions rates adjusted to account for recent historical trends. For stationary nonpoint sources, some emissions in the 2016 base case emissions inventory come directly from the 2017 NEI, others were adjusted from the 2017 NEI to represent 2016 levels, and the remaining emissions including those from oil and gas, fertilizer, and solvents were computed specifically to represent 2016. Stationary nonpoint sources include evaporative sources, consumer products, fuel combustion that is not captured by point sources, agricultural livestock, agricultural fertilizer, residential wood combustion, fugitive dust, and oil and gas sources. The emissions sources derived from the 2017 NEI include agricultural livestock, fugitive dust, residential wood combustion, waste disposal (including composting), bulk gasoline terminals, and miscellaneous non-industrial sources such as cremation, hospitals, lamp breakage, and automotive repair shops. A recent method to compute solvent VOC emissions was used. 71 71 https://doi.org/10.5194/acp-21-5079-2021 . Where comments were provided about projected control measures or changes in nonpoint source emissions, those inputs were first reviewed by the EPA. Those found to be based on reasonable data for affected emissions sources were incorporated into the projected inventories for 2023 to the extent possible. Where possible, projection factors based on the AEO used data from AEO 2022, the most recent AEO at the time available at the time the inventories were developed. Federal regulations that impact the nonpoint sources were reflected in the inventories. Adjustments for state fuel sulfur content rules for fuel oil in the Northeast were included along with solvent controls applicable within the northeast ozone transport region (OTR) states. Details are available in the 2016v3 Emissions Modeling TSD. Nonpoint oil and gas emissions inventories for many states were developed based on outputs from the 2017 NEI version of the EPA Oil and Gas Tool using activity data for year 2016. Production-related emissions data from the 2017 NEI were used for Oklahoma, 2016v1 emissions were used for Colorado and Texas production-related sources to respond to comments. Data for production-related nonpoint oil and gas emissions in the States of Colorado, Montana, New Mexico, North Dakota, South Dakota, Utah, and Wyoming were obtained from the WRAP baseline inventory. 72 A California Air Resources Board-provided inventory was used for 2016 oil and gas emissions in California. Nonpoint oil and gas inventories for 2023 were developed by first projecting the 2016 oil and gas inventories to 2021 values based on actual production data. Next, those 2021 emissions were projected to 2023 using regional projection factors by product type based on AEO 2022 projections. A 2017-2019 average inventory was used for oil and natural gas exploration emissions in 2023 everywhere except for California and in the WRAP states in which data from the WRAP future year inventory 73 were used. NO X and VOC reductions that are co-benefits to the NSPS for RICE are reflected, along with Natural Gas Turbines and Process Heaters NSPS NO X controls and NSPS Oil and Gas VOC controls. The WRAP future year inventory was used for oil and natural gas production sources in 2023 except in New Mexico where the WRAP Base year emissions were projected using the EIA historical and AEO forecasted production data. Estimated impacts from the New Mexico Administrative Code 20.2.50 were included. 72 http://www.wrapair2.org/pdf/WRAP_OGWG_Report_Baseline_17Sep2019.pdf . 73 http://www.wrapair2.org/pdf/WRAP_OGWG_2028_OTB_RevFinalReport_05March2020.pdf . B. Air Quality Modeling To Identify Nonattainment and Maintenance Receptors This section describes the air quality modeling and analyses that the EPA performed in Step 1 to identify locations where the Agency expects there to be nonattainment or maintenance receptors for the 2015 ozone NAAQS in 2023. Where the EPA's analysis shows that an area or site does not fall under the definition of a nonattainment or maintenance receptor in 2023, that site is excluded from further analysis under the EPA's good neighbor framework. 1. Approach for Identifying Receptors In the proposed actions, the EPA applied the same approach used in the CSAPR Update and the Revised CSAPR Update to identify nonattainment and maintenance receptors for the 2008 ozone NAAQS. 74 The EPA's approach gives independent effect to both the “contribute significantly to nonattainment” and the “interfere with maintenance” prongs of section 110(a)(2)(D)(i)(I), consistent with the D.C. Circuit's direction in North Carolina . Further, in its decision on the remand of CSAPR from the Supreme Court in the EME Homer City II case, the D.C. Circuit confirmed that the EPA's approach to identifying maintenance receptors in CSAPR comported with the court's prior instruction to give independent meaning to the “interfere with maintenance” prong in the good neighbor provision. 75 74 See 86 FR 23078-79. 75 EME Homer City II, 795 F.3d at 136. In the CSAPR Update and the Revised CSAPR Update, the EPA identified nonattainment receptors as those monitoring sites that are projected to have average design values that exceed the NAAQS and that are also measuring nonattainment based on the most recent monitored design values. This approach is consistent with prior transport rulemakings, such as the NO X SIP Call and CAIR, where the EPA defined nonattainment receptors as those areas that both currently monitor nonattainment and that the EPA projects will be in nonattainment in the future compliance year. The Agency explained in the NO X SIP Call and CAIR and then reaffirmed in the CSAPR Update that the EPA has the most confidence in our projections of nonattainment for those counties that also measure nonattainment for the most recent period of available ambient data. The EPA separately identified maintenance receptors as those receptors that would have difficulty maintaining the relevant NAAQS in a scenario that accounts for historical variability in air quality at that receptor. The variability in air quality was determined by evaluating the “maximum” future design value at each receptor based on a projection of the maximum measured design value over the relevant period. The EPA interprets the projected maximum future design value to be a potential future air quality outcome consistent with the meteorology that yielded maximum measured concentrations in the ambient data set analyzed for that receptor ( i.e., ozone conducive meteorology). The EPA also recognizes that previously experienced meteorological conditions ( e.g., dominant wind direction, temperatures, and air mass patterns) promoting ozone formation that led to maximum concentrations in the measured data may reoccur in the future. The maximum design value gives a reasonable projection of future air quality at the receptor under a scenario in which such conditions do, in fact, reoccur. The projected maximum design value is used to identify upwind emissions that, under those circumstances, could interfere with the downwind area's ability to maintain the NAAQS. Therefore, applying this methodology for this action, the EPA assessed the magnitude of the maximum projected design values for 2023 at each receptor in relation to the 2015 ozone NAAQS and, where such a value exceeds the NAAQS, the EPA determined that receptor to be a “maintenance” receptor for purposes of defining interference with maintenance, consistent with the method used in CSAPR and upheld by the D.C. Circuit in EME Homer City II . 76 That is, monitoring sites with a maximum design value that exceeds the NAAQS are projected to have maintenance problems in the future analytic years. 76 EME Homer City II, 795 F.3d at 136. Recognizing that nonattainment receptors are also, by definition, maintenance receptors, the EPA often uses the term “maintenance-only” to refer to receptors that are not also nonattainment receptors. Consistent with the concepts for maintenance receptors, as described earlier, the EPA identifies “maintenance-only” receptors as those monitoring sites that have projected average design values above the level of the applicable NAAQS, but that are not currently measuring nonattainment based on the most recent official design values. In addition, those monitoring sites with projected average design values below the NAAQS, but with projected maximum design values above the NAAQS are also identified as “maintenance only” receptors, even if they are currently measuring nonattainment based on the most recent official certified design values. 77 77 See https://www.epa.gov/air-trends/air-quality-design-values for design value reports. At the time of this action, the most recent reports of certified design values available are for the calendar year 2021. The 2022 values are considered “preliminary” and therefore subject to change before certification. Comment: The EPA received comments claiming that the projected design values for 2023 were biased low compared to recent measured data. Commenters noted that a number of monitoring sites that are projected to be below the NAAQS in 2023 based on the EPA's modeling for the proposed action are currently measuring nonattainment based on data from 2020 and 2021. One commenter requested that the EPA determine whether its past modeling tends to overestimate or underestimate actual observed design values. If EPA finds that the agency's model tends to underestimate future year design values, the commenter requests that EPA re-run its ozone modeling, incorporating parameters that account for this tendency. EPA Response: In response to comments, the EPA compared the projected 2023 design values based on the proposal modeling to recent trends in measured data. As a result of this analysis, the EPA agrees that current data indicate that there are monitoring sites at risk of continued nonattainment in 2023 even though the model projected average and maximum design values at these sites are below the NAAQS ( i.e., these sites would not be modeling-based receptors at Step 1). While the EPA has confidence in the reliability of the modeling for projecting air quality conditions and contributions in future years, it would not be reasonable to ignore recent measured ozone levels in many areas that are clearly not fully consistent with certain concentrations in the Step 1 analysis for 2023. Therefore, the EPA has developed an additional maintenance-only receptor category, which includes what we refer to as “violating monitor” receptors, based on current ozone concentrations measured by regulatory ambient air quality monitoring sites. Specifically, the EPA has identified monitoring sites with measured 2021 and preliminary 2022 design values and 4th high maximum daily 8-hour average (MDA8) ozone in both 2021 and 2022 (preliminary data) that exceed the NAAQS as having the greatest risk of continuing to have a problem attaining the standard in 2023. These criteria sufficiently consider measured air quality data so as to avoid including monitoring sites that have measured nonattainment data in recent years but could reasonably be anticipated to not have a nonattainment or maintenance problem in 2023, in line with our modeling results. Our methodology is intended only to identify those sites that have sufficiently poor ozone levels that there is clearly a reasonable expectation that an ozone nonattainment or maintenance problem will persist in the 2023 ozone season. Moreover, the 2023 ozone season is so near in time that recent measured ozone levels can be used to reasonably project whether an air quality problem is likely to persist. We view this approach to identifying additional receptors in 2023 as the best means of responding to the comments on this issue in this action, while also identifying all transport receptors. For purposes of this action, we will treat these violating monitors as an additional type of maintenance-only receptor. We acknowledge that the traditional modeling plus monitoring methodology we used at proposal and in prior ozone transport rules would otherwise have identified such sites as being in attainment in 2023. Because our modeling did not identify these sites as receptors, we do not believe it is sufficiently certain that these sites will be in nonattainment that they should be considered nonattainment receptors. In the face of this uncertainty in the record, we regard our ability to consider such sites as receptors for purposes of good neighbor analysis under CAA section 110(a)(2)(D)(i)(I) to be a function of the requirement to prohibit emissions that interfere with maintenance of the NAAQS; even if an area may be projected to be in attainment, we have reliable information indicating that there is a clear risk that attainment will not in fact be achieved in 2023. Thus, our authority for treating these sites as receptors at Step 1 in 2023 flows from the responsibility in CAA section 110(a)(2)(i)(I) to prohibit emissions that interfere with maintenance of the NAAQS. See, e.g., North Carolina, 531 F.3d at 910-11 (failing to give effect to the interfere with maintenance clause “provides no protection for downwind areas that, despite EPA's predictions, still find themselves struggling to meet NAAQS due to upwind interference . . . .”) (emphasis added). Recognizing that no modeling can perfectly forecast the future, and “a degree of imprecision is inevitable in tackling the problem of interstate air pollution,” this approach in the Agency's judgement best balances the need to avoid both “under-control” and “overcontrol,” EME Homer City, 572 U.S. at 523. The EPA's analysis of these additional receptors further is explained in Section III.C. However, because we did not propose to apply this expansion of the basis for regulation under the good neighbor provision receptor-identification methodology as the sole basis for finding an upwind state linked, in this action we are only using this receptor category on a confirmatory basis. That is, for states that we find linked based on our traditional modeling-based methodology in 2023, we find in this final analysis that the linkage at Step 2 is strengthened and confirmed if that state is also linked to one or more “violating-monitor” receptors. If a state is only linked to a violating-monitor receptor in this final analysis, we are deferring taking final action on that state's SIP submittal. This is the case for the State of Tennessee. Among the states that previously had their transport SIPs approved for the 2015 ozone NAAQS, the EPA has also identified a linkage to violating-monitor receptors for the State of Kansas. The EPA intends to further review its air quality modeling results and recent measured ozone levels, and we intend to address these states' good neighbor obligations as expeditiously as practicable in a future action. 2. Methodology for Projecting Future Year Ozone Design Values Consistent with the EPA's modeling guidance, the 2016 base year and future year air quality modeling results were used in a relative sense to project design values for 2023. 78 That is, the ratios of future year model predictions to base year model predictions are used to adjust ambient ozone design values up or down depending on the relative (percent) change in model predictions for each location. The EPA's modeling guidance recommends using measured ozone concentrations for the 5-year period centered on the base year as the air quality data starting point for future year projections. This average design value is used to dampen the effects of inter-annual variability in meteorology on ozone concentrations and to provide a reasonable projection of future air quality at the receptor under average conditions. In addition, the Agency calculated maximum design values from within the 5-year base period to represent conditions when meteorology is more favorable than average for ozone formation. Because the base year for the air quality modeling used in this final action is 2016, measured data for 2014-2018 ( i.e., design values for 2016, 2017, and 2018) were used to project average and maximum design values in 2023. 78 U.S. Environmental Protection Agency, 2018. Modeling Guidance for Demonstrating Attainment of Air Quality Goals for Ozone, PM 2.5 , and Regional Haze, Research Triangle Park, NC. https://www.epa.gov/scram/state-implementation-plan-sip-attainment-demonstration-guidance . The ozone predictions from the 2016 and future year air quality model simulations were used to project 2016-2018 average and maximum ozone design values to 2023 using an approach similar to the approach in the EPA's guidance for attainment demonstration modeling. This guidance recommends using model predictions from the 3 x 3 array of grid cells surrounding the location of the monitoring site to calculate a Relative Response Factor (RRF) for that site. However, the guidance also notes that an alternative array of grid cells may be used in certain situations where local topographic or geographical feature ( e.g., a large water body or a significant elevation change) may influence model response. The 2016-2018 base period average and maximum design values were multiplied by the RRF to project each of these design values to 2023. In this manner, the projected design values are grounded in monitored data, and not the absolute model-predicted future year concentrations. Following the approach in the CSAPR Update and the Revised CSAPR Update, the EPA also projected future year design values based on a modified version of the “3 x 3” approach for those monitoring sites located in coastal areas. In this alternative approach, the EPA eliminated from the RRF calculations the modeling data in those grid cells that are dominated by water ( i.e., more than 50 percent of the area in the grid cell is water) and that do not contain a monitoring site ( i.e., if a grid cell is more than 50 percent water but contains an air quality monitor, that cell would remain in the calculation). The choice of more than 50 percent of the grid cell area as water as the criteria for identifying overwater grid cells is based on the treatment of land use in the Weather Research and Forecasting model (WRF). Specifically, in the WRF meteorological model those grid cells that are greater than 50% overwater are treated as being 100 percent overwater. In such cases the meteorological conditions in the entire grid cell reflect the vertical mixing and winds over water, even if part of the grid cell also happens to be over land with land-based emissions, as can often be the case for coastal areas. Overlaying land-based emissions with overwater meteorology may be representative of conditions at coastal monitors during times of on-shore flow associated with synoptic conditions or sea-breeze or lake-breeze wind flows. But there may be other times, particularly with off-shore wind flow, when vertical mixing of land-based emissions may be too limited due to the presence of overwater meteorology. Thus, for our modeling the EPA projected average and maximum design values at individual monitoring sites based on both the “3 x 3” approach as well as the alternative approach that eliminates overwater cells in the RRF calculation for near-coastal areas ( i.e., “no water” approach). The projected 2023 design values using both the “3 x 3” and “no-water” approaches are provided in the docket for this final action. Both approaches result in the same set of receptors in 2023. That is, monitoring sites that are identified as receptors in 2023 based on the “3 x 3” approach are also receptors based on the “no water” approach. Consistent with the truncation and rounding procedures for the 8-hour ozone NAAQS, the projected design values are evaluated after truncation to integers in units of ppb. Therefore, projected design values that are greater than or equal to 71 ppb are considered to be violating the 2015 ozone NAAQS. For those sites that are projected to be violating the NAAQS based on the average design values in 2023, the Agency examined the measured design values for 2021, which are the most recent official measured design values at the time of this final action. As noted earlier, the Agency proposes to identify nonattainment receptors in this rulemaking as those sites that are violating the NAAQS based on current measured air quality through 2021 and have projected average design values of 71 ppb or greater. Maintenance-only receptors include both: (1) Those sites with projected average design values above the NAAQS that are currently measuring clean data ( i.e., ozone design values below the level of the 2015 ozone NAAQS in 2021) and (2) those sites with projected average design values below the level of the NAAQS, but with projected maximum design values of 71 ppb or greater. In addition to the maintenance-only receptors, ozone nonattainment receptors are also maintenance receptors because the projected maximum design values for each of these sites is always greater than or equal to the average design value. Further, as explained previously in this section, the EPA identifies certain monitoring sites as “violating monitor” maintenance-only receptors based on 2021 and 2022 measured ozone levels. The monitoring sites that the Agency projects to be nonattainment and maintenance receptors for the ozone NAAQS in the 2023 base case are used for assessing the contribution of emissions in upwind states to downwind nonattainment and maintenance of the 2015 ozone NAAQS as part of this final action. 3. 2023 Nonattainment and Maintenance-Only Receptors for the Final Action In this section we provide information on modeling-based design values and measured data for monitoring sites identified as nonattainment or maintenance-only receptors in 2023 for this final action. Table III.B-1 of this action contains the 2016-centered base period average and maximum 8-hour ozone design values, the 2023 projected average and maximum design values and the measured 2021 design values for monitoring sites that are projected to be nonattainment receptors in 2023. Table III.B-2 of this action contains this same information for monitoring sites that are projected to be maintenance-only receptors in 2023, based on air quality modeling. Table III.B-3 of this action contains the 2023 projected average and maximum design values and 2021 design values and 4th high MDA8 ozone concentrations and preliminary 2020 design values and 4th high MDA8 ozone concentrations for monitoring sites identified as violating monitor maintenance-only receptors. The design values for all monitoring sites in the U.S. are provided in the docket for this action. Additional details on the approach for projecting average and maximum design values are provided in the AQM TSD. Table III.B-1—Average and Maximum 2016-Centered and 2023 Base Case 8-Hour Ozone Design Values and 2021 Design Values (ppb) at Projected Nonattainment Receptors a Monitor ID State County 2016 centered average 2016 centered maximum 2023 average 2023 maximum 2021 060650016 CA Riverside 79.0 80.0 72.2 73.1 78 060651016 CA Riverside 99.7 101 91.0 92.2 95 080350004 CO Douglas 77.3 78 71.3 71.9 83 080590006 CO Jefferson 77.3 78 72.8 73.5 81 080590011 CO Jefferson 79.3 80 73.5 74.1 83 090010017 CT Fairfield 79.3 80 71.6 72.2 79 090013007 CT Fairfield 82.0 83 72.9 73.8 81 090019003 CT Fairfield 82.7 83 73.3 73.6 80 481671034 TX Galveston 75.7 77 71.5 72.8 72 482010024 TX Harris 79.3 81 75.1 76.7 74 490110004 UT Davis 75.7 78 72.0 74.2 78 490353006 UT Salt Lake 76.3 78 72.6 74.2 76 490353013 UT Salt Lake 76.5 77 73.3 73.8 76 551170006 WI Sheboygan 80.0 81 72.7 73.6 72 a 2016-centered base period average design values and projected average and maximum design values are reported with 1 digit to the right of the decimal, as recommended in the EPA's modeling guidance. The 2016 maximum design values and 2021 design values are truncated to integer values consistent with ozone design value reporting convention in appendix U of 40 CFR part 50. Table III.B-2—Average and Maximum 2016-Centered and 2023 Base Case 8-Hour Ozone Design Values and 2021 Design Values (ppb) at Projected Maintenance-Only Receptors Monitor ID State County 2016 centered average 2016 centered maximum 2023 average 2023 maximum 2021 040278011 AZ Yuma 72.3 74 70.4 72.1 67 080690011 CO Larimer 75.7 77 70.9 72.1 77 090099002 CT New Haven 79.7 82 70.5 72.6 82 170310001 IL Cook 73.0 77 68.2 71.9 71 170314201 IL Cook 73.3 77 68.0 71.5 74 170317002 IL Cook 74.0 77 68.5 71.3 73 350130021 NM Dona Ana 72.7 74 70.8 72.1 80 350130022 NM Dona Ana 71.3 74 69.7 72.4 75 350151005 NM Eddy 69.7 74 69.7 74.1 77 350250008 NM Lea 67.7 70 69.8 72.2 66 480391004 TX Brazoria 74.7 77 70.4 72.5 75 481210034 TX Denton 78.0 80 69.8 71.6 74 481410037 TX El Paso 71.3 73 69.8 71.4 75 482010055 TX Harris 76.0 77 70.9 71.9 77 482011034 TX Harris 73.7 75 70.1 71.3 71 482011035 TX Harris 71.3 75 67.8 71.3 71 530330023 WA King 73.3 77 67.6 71.0 64 550590019 WI Kenosha 78.0 79 70.8 71.7 74 551010020 WI Racine 76.0 78 69.7 71.5 73 In total, in 2023 there are a total of projected 33 modeling-based receptors nationwide including 14 nonattainment receptors in 9 different counties and 19 maintenance-only receptors in 13 additional counties (Harris County, TX, has both nonattainment and maintenance-only receptors). As shown in Table III.B-3 of this action, there are 49 monitoring sites that are identified as “violating-monitor” maintenance-only receptors in 2023.As noted earlier in this section, the EPA uses the approach of considering “violating-monitor” maintenance-only receptors as confirmatory of the proposal's identification of receptors and does not implicate additional linked states in this final action, Rather, using this approach serves to strengthen the analytical basis for our Step 2 findings by establishing that many upwind states covered in this action are also projected to contribute above 1 percent of the NAAQS to these additional “violating monitor” maintenance-only receptors. Table III.B-3—Average and Maximum 2023 Base Case 8-Hour Ozone, and 2021 and Preliminary 2022 Design Values (ppb) and 4th High Concentrations at Violating Monitors a Monitor ID State County 2023 average 2023 maximum 2021 2022 P 2021 4th high 2022 P 4th high 40070010 AZ Gila 67.9 69.5 77 76 75 74 40130019 AZ Maricopa 69.8 70.0 75 77 78 76 40131003 AZ Maricopa 70.1 70.7 80 80 83 78 40131004 AZ Maricopa 70.2 70.8 80 81 81 77 40131010 AZ Maricopa 68.3 69.2 79 80 80 78 40132001 AZ Maricopa 63.8 64.1 74 78 79 81 40132005 AZ Maricopa 69.6 70.5 78 79 79 77 40133002 AZ Maricopa 65.8 65.8 75 75 81 72 40134004 AZ Maricopa 65.7 66.6 73 73 73 71 40134005 AZ Maricopa 62.3 62.3 73 75 79 73 40134008 AZ Maricopa 65.6 66.5 74 74 74 71 40134010 AZ Maricopa 63.8 66.9 74 76 77 75 40137020 AZ Maricopa 67.0 67.0 76 77 77 75 40137021 AZ Maricopa 69.8 70.1 77 77 78 75 40137022 AZ Maricopa 68.2 69.1 76 78 76 79 40137024 AZ Maricopa 67.0 67.9 74 76 74 77 40139702 AZ Maricopa 66.9 68.1 75 77 72 77 40139704 AZ Maricopa 65.3 66.2 74 77 76 76 40139997 AZ Maricopa 70.5 70.5 76 79 82 76 40218001 AZ Pinal 67.8 69.0 75 76 73 77 80013001 CO Adams 63.0 63.0 72 77 79 75 80050002 CO Arapahoe 68.0 68.0 80 80 84 73 80310002 CO Denver 63.6 64.8 72 74 77 71 80310026 CO Denver 64.5 64.8 75 77 83 72 90079007 CT Middlesex 68.7 69.0 74 73 78 73 90110124 CT New London 65.5 67.0 73 72 75 71 170310032 IL Cook 67.3 69.8 75 75 77 72 170311601 IL Cook 63.8 64.5 72 73 72 71 181270024 IN Porter 63.4 64.6 72 73 72 73 260050003 MI Allegan 66.2 67.4 75 75 78 73 261210039 MI Muskegon 67.5 68.4 74 79 75 82 320030043 NV Clark 68.4 69.4 73 75 74 74 350011012 NM Bernalillo 63.8 66.0 72 73 76 74 350130008 NM Dona Ana 65.6 66.3 72 76 79 78 361030002 NY Suffolk 66.2 68.0 73 74 79 74 390850003 OH Lake 64.3 64.6 72 74 72 76 480290052 TX Bexar 67.1 67.8 73 74 78 72 480850005 TX Collin 65.4 66.0 75 74 81 73 481130075 TX Dallas 65.3 66.5 71 71 73 72 481211032 TX Denton 65.9 67.7 76 77 85 77 482010051 TX Harris 65.3 66.3 74 73 83 72 482010416 TX Harris 68.8 70.4 73 73 78 71 484390075 TX Tarrant 63.8 64.7 75 76 76 77 484391002 TX Tarrant 64.1 65.7 72 77 76 80 484392003 TX Tarrant 65.2 65.9 72 72 74 72 484393009 TX Tarrant 67.5 68.1 74 75 75 75 490571003 UT Weber 69.3 70.3 71 74 77 71 550590025 WI Kenosha 67.6 70.7 72 73 72 71 550890008 WI Ozaukee 65.2 65.8 71 72 72 72 a 2022 preliminary design values are based on 2022 measured MDA8 concentrations provided by state air agencies to the EPA's Air Quality System (AQS), as of January 3, 2023. C. Air Quality Modeling To Quantify Upwind State Contributions This section documents the procedures the EPA used to [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2023-02407. Public record. Not legal advice.