Air Plan Approval; Montana; Regional Haze Plan for the Second Implementation Period; Prong 4 (Visibility) for the 2015 8-Hour Ozone National Ambient Air Quality Standard

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R08-OAR-2024-0608; FRL-12597-01-R8]</DEPDOC> <SUBJECT>Air Plan Approval; Montana; Regional Haze Plan for the Second Implementation Period; Prong 4 (Visibility) for the 2015 8-Hour Ozone National Ambient Air Quality Standard</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Proposed rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is proposing to approve the regional haze state implementation plan (SIP) submission submitted by the State of Montana on August 10, 2022, under the Clean Air Act (CAA) and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. Montana's 2022 SIP submission addresses the requirement that states revise their long-term strategies every implementation period to make reasonable progress towards the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility, including regional haze, in mandatory Class I Federal areas. Montana's 2022 SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. The EPA is also proposing to approve the prong 4 visibility portion of Montana's October 1, 2018 Infrastructure SIP submission for the 2015 ozone National Ambient Air Quality Standards (NAAQS). The EPA is taking these actions pursuant to the CAA. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Written comments must be received on or before October 14, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R08-OAR-2024-0608, to the Federal Rulemaking Portal: <E T="03">https://www.regulations.gov.</E> Follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">https://www.regulations.gov.</E> The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission ( <E T="03">i.e.,</E> on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit <E T="03">https://www.epa.gov/dockets/commenting-epa-dockets.</E> <E T="03">Docket:</E> All documents in the docket are listed in the <E T="03">https://www.regulations.gov</E> index. Although listed in the index, some information is not publicly available, <E T="03">e.g.,</E> CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available electronically in <E T="03">https://www.regulations.gov.</E> Please email or call the person listed in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section if you need to make alternative arrangements for access to the docket. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Jaslyn Dobrahner, Air and Radiation Division, EPA, Region 8, Mailcode 8ARD-IO, 1595 Wynkoop Street, Denver, Colorado 80202-1129, telephone number: (303) 312-6252; email address: <E T="03">dobrahner.jaslyn@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA. <HD SOURCE="HD1">Table of Contents</HD> <EXTRACT> <FP SOURCE="FP-2">I. What action is the EPA proposing?</FP> <FP SOURCE="FP-2">II. Background and Requirements for Regional Haze Plans</FP> <FP SOURCE="FP1-2">A. Regional Haze</FP> <FP SOURCE="FP1-2">B. Roles of Agencies in Addressing Regional Haze</FP> <FP SOURCE="FP1-2">C. Status of Montana's Regional Haze Plan for the First Implementation Period</FP> <FP SOURCE="FP1-2">D. Montana's Regional Haze Plan for the Second Implementation Period</FP> <FP SOURCE="FP-2">III. Requirements for Regional Haze Plans for the Second Implementation Period</FP> <FP SOURCE="FP-2">IV. The EPA's Evaluation of Montana's Regional Haze Plan for the Second Implementation Period</FP> <FP SOURCE="FP1-2">A. Identification of Class I Areas</FP> <FP SOURCE="FP1-2">B. Calculation of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and Uniform Rate of Progress for Class I Areas Within the State</FP> <FP SOURCE="FP1-2">C. Long-Term Strategy</FP> <FP SOURCE="FP1-2">1. Montana's Long-Term Strategy Four-Factor Analysis</FP> <FP SOURCE="FP1-2">a. Summary of Montana's Long-Term Strategy Four-Factor Analysis</FP> <FP SOURCE="FP1-2">b. The EPA's Evaluation of Montana's Long-Term Strategy Four-Factor Analysis</FP> <FP SOURCE="FP1-2">2. Other Long-Term Strategy Requirements</FP> <FP SOURCE="FP1-2">D. Reasonable Progress Goals</FP> <FP SOURCE="FP1-2">E. Reasonably Attributable Visibility Impairment (RAVI)</FP> <FP SOURCE="FP1-2">F. Monitoring Strategy and Other State Implementation Plan Requirements</FP> <FP SOURCE="FP1-2">G. Requirements for Periodic Reports Describing Progress Towards the Reasonable Progress Goals</FP> <FP SOURCE="FP1-2">H. Requirements for State and Federal Land Manager Coordination</FP> <FP SOURCE="FP-2">V. Interstate Transport Prong 4 (Visibility) for the 2015 Ozone NAAQS Infrastructure SIP</FP> <FP SOURCE="FP1-2">A. Background on Infrastructure SIPs</FP> <FP SOURCE="FP1-2">B. Prong 4 Requirements</FP> <FP SOURCE="FP1-2">C. Montana's Infrastructure SIP Submission</FP> <FP SOURCE="FP1-2">D. The EPA's Evaluation of Montana's Infrastructure SIP Submission</FP> <FP SOURCE="FP-2">VI. Proposed Action</FP> <FP SOURCE="FP-2">VII. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. What action is the EPA proposing?</HD> The EPA is proposing to approve a SIP submission submitted by the State of Montana to the EPA on August 10, 2022, addressing the requirements of the second implementation period of the RHR. Specifically, the EPA is proposing approval for the portions of Montana's 2022 SIP submission relating to 40 CFR 51.308(f)(1): calculations of baseline, current, and natural visibility conditions, progress to date, and the uniform rate of progress; 40 CFR 51.308(f)(2): long-term strategy; 40 CFR 51.308(f)(3): reasonable progress goals; 40 CFR 51.308(f)(4): reasonably attributable visibility impairment; 40 CFR 51.308(f)(5) and 40 CFR 51.308(g): progress report requirements; 40 CFR 51.308(f)(6): monitoring strategy and other implementation plan requirements; and 40 CFR 51.308(i): Federal Land Manager (FLM) consultation. The EPA is also proposing to approve the CAA section 110(a)(2)(D)(i) prong 4 (visibility) portion of Montana's October 1, 2018 Infrastructure SIP submission addressing the 2015 ozone NAAQS. <HD SOURCE="HD1">II. Background and Requirements for Regional Haze Plans</HD> A detailed history and background of the regional haze program is provided in multiple prior EPA proposal actions. <SU>1</SU> <FTREF/> For additional background on the 2017 RHR revisions, please refer to section III. Overview of Visibility Protection Statutory Authority, Regulation, and Implementation of “Protection of Visibility: Amendments to Requirements for State Plans” of the 2017 RHR. <SU>2</SU> <FTREF/> The following is an abbreviated history and background of the regional haze program and 2017 Regional Haze Rule as it applies to the current action. <FTNT> <SU>1</SU>   <E T="03">See</E> 90 FR 13516 (March 24, 2025). </FTNT> <FTNT> <SU>2</SU>   <E T="03">See</E> 82 FR 3078 (January 10, 2017, located at <E T="03">https://www.federalregister.gov/documents/2017/01/10/2017-00268/protection-of-visibility-amendments-to-requirements-for-State-plans#h-16</E> ). </FTNT> <HD SOURCE="HD2">A. Regional Haze</HD> In the 1977 CAA amendments, Congress created a program for protecting visibility in the nation's mandatory Class I Federal areas, which include certain national parks and wilderness areas. <SU>3</SU> <FTREF/> CAA section 169A. The CAA establishes as a national goal the “prevention of any future, and the remedying of any existing, impairment of visibility in mandatory Class I Federal areas which impairment results from manmade air pollution.” CAA section 169A(a)(1). <FTNT> <SU>3</SU>  Areas statutorily designated as mandatory Class I Federal areas consist of national parks exceeding 6,000 acres, wilderness areas and national memorial parks exceeding 5,000 acres, and all international parks that were in existence on August 7, 1977. CAA section 162(a). There are 156 mandatory Class I areas. The list of areas to which the requirements of the visibility protection program apply is in 40 CFR part 81, subpart D. </FTNT> Regional haze is visibility impairment that is produced by a multitude of anthropogenic sources and activities that are located across a broad geographic area and that emit pollutants that impair visibility. Visibility impairing pollutants include fine and coarse particulate matter (PM) ( <E T="03">e.g.,</E> sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( <E T="03">e.g.,</E> sulfur dioxide (SO <E T="52">2</E> ), nitrogen oxides (NO <E T="52">X</E> ), and, in some cases, volatile organic compounds (VOC) and ammonia (NH <E T="52">3</E> )). Fine particle precursors react in the atmosphere to form fine particulate ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 105k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━