Approval of Air Quality Implementation Plans; California; Regional Haze State Implementation Plan for the Second Implementation Period

ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R09-OAR-2025-0203; FRL-12755-01-R9]</DEPDOC> <SUBJECT>Approval of Air Quality Implementation Plans; California; Regional Haze State Implementation Plan for the Second Implementation Period</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) revision submitted by California on August 9, 2022 (hereinafter the “2022 California Regional Haze Plan” or “the Plan”), under the Clean Air Act (CAA) and the EPA's Regional Haze Rule for the program's second implementation period. California's SIP submission addresses the requirement that states must periodically revise their long-term strategies for making 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. The SIP submission also addresses other applicable requirements for the second implementation period of the regional haze program. The EPA is proposing this action pursuant to CAA sections 110 and 169A. The EPA is also withdrawing its previous proposed rule to partially approve and partially disapprove California's regional haze SIP revision as published in the <E T="04">Federal Register</E> on December 19, 2024. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Written comments must be received on or before July 18, 2025. As of June 18, 2025, the proposed rule published on December 19, 2024, at 89 FR 103737, is withdrawn. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> Submit your comments, identified by Docket ID No. EPA-R09-OAR-2025-0203 at <E T="03">https://www.regulations.gov.</E> For comments submitted at <E T="03">Regulations.gov</E> , follow the online instructions for submitting comments. Once submitted, comments cannot be edited or removed from <E T="03">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, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. For 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> If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Emily Millar, Geographic Strategies and Modeling Section (ARD-2-2), Planning & Analysis Branch, EPA Region IX, 75 Hawthorne Street, San Francisco, CA 94105, 213-244-1882, or by email at <E T="03">millar.emily@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document, “we,” “us,” and “our” refer to 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 Background</FP> <FP SOURCE="FP1-2">B. Roles of Agencies in Addressing Regional Haze</FP> <FP SOURCE="FP-2">III. Requirements for Regional Haze Plans for the Second Implementation Period</FP> <FP SOURCE="FP1-2">A. Long-Term Strategy for Regional Haze</FP> <FP SOURCE="FP1-2">B. Reasonable Progress Goals</FP> <FP SOURCE="FP1-2">C. Monitoring Strategy and Other State Implementation Plan Requirements</FP> <FP SOURCE="FP1-2">D. Requirements for Periodic Reports Describing Progress Towards the Reasonable Progress Goals</FP> <FP SOURCE="FP1-2">E. Requirements for State and Federal Land Manager Coordination</FP> <FP SOURCE="FP-2">IV. Withdrawal of Prior Proposed Disapproval</FP> <FP SOURCE="FP-2">V. The EPA's Rationale for Proposing Approval</FP> <FP SOURCE="FP-2">VI. The EPA's Evaluation of California's Regional Haze Submission for the Second Implementation Period</FP> <FP SOURCE="FP1-2">A. Identification of Class I Areas</FP> <FP SOURCE="FP1-2">B. Calculations of Baseline, Current, and Natural Visibility Conditions; Progress to Date; and the Uniform Rate of Progress</FP> <FP SOURCE="FP1-2">C. Long-Term Strategy for Regional Haze</FP> <FP SOURCE="FP1-2">D. Reasonable Progress Goals</FP> <FP SOURCE="FP1-2">E. Monitoring Strategy and Other Implementation Plan Requirements</FP> <FP SOURCE="FP1-2">F. Requirements for Periodic Reports Describing Progress Towards the Reasonable Progress Goals</FP> <FP SOURCE="FP1-2">G. Requirements for State and Federal Land Manager Coordination</FP> <FP SOURCE="FP-2">VII. Proposed Action</FP> <FP SOURCE="FP-2">VIII. Statutory and Executive Order Reviews</FP> </EXTRACT> <HD SOURCE="HD1">I. What action is the EPA proposing?</HD> On August 9, 2022, the California Air Resources Board (CARB) submitted the 2022 California Regional Haze Plan to address the requirements of the CAA's regional haze program pursuant to CAA sections 169A and 169B and 40 CFR 51.308. On December 19, 2024, the EPA proposed to approve the elements of the Plan related to requirements contained in 40 CFR 51.308(f)(1), 40 CFR 51.308(f)(4)-(6), and 40 CFR 51.308 (g)(1)-(5) and to disapprove the elements of the Plan related to requirements contained in 40 CFR 51.308(f)(2), 40 CFR 51.308(f)(3), and 40 CFR 51.308(i)(2)-(4). <SU>1</SU> <FTREF/> The EPA is now withdrawing that proposal and is proposing to fully approve the Plan for the reasons described in this document. <FTNT> <SU>1</SU>  89 FR 103737. </FTNT> <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>2</SU> <FTREF/> For additional background on the 2017 Regional Haze Rule (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>3</SU> <FTREF/> The following is an abbreviated history and background of the regional haze program and 2017 RHR as it applies to the current action. <FTNT> <SU>2</SU>  See 90 FR 13516 (March 24, 2025). </FTNT> <FTNT> <SU>3</SU>  See 82 FR 3078 (January 10, 2017). </FTNT> <HD SOURCE="HD2">A. Regional Haze Background</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>4</SU> <FTREF/> 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.”  <SU>5</SU> <FTREF/> <FTNT> <SU>4</SU>  CAA 169A. 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 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> <FTNT> <SU>5</SU>  CAA 169A(a)(1). </FTNT> Regional haze is visibility impairment that is produced by a multitude of anthropogenic sources and activities which 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 matter (PM <E T="52">2.5</E> ), which impairs visibility by scattering and absorbing light. Visibility impairment reduces the perception of clarity and color, as well as visible distance. <SU>6</SU> <FTREF/> <FTNT> <SU>6</SU>  There are several ways to measure the amount of visibility impairment, <E T="03">i.e.,</E> haze. One such measurement is the deciview, which is the principal metric used by the RHR. Under many circumstances, a change in one deciview will be perceived by the human eye to be the same on both clear and hazy days. The deciview is unitless. It is proportional to the logarithm of the atmospheric extinction of light, which is the perceived dimming of light due to its being scattered and absorbed as it passes through the atmosphere. Atmospheric light extinction (b <SU>ext</SU> ) is a metric used for expressing visibility and is measured in inverse megameters (Mm-1). The formula for the deciview is 10 ln (b <SU>ext</SU> )/10 Mm <E ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 121k characters. 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