Air Plan Approval; ID; Regional Haze Plan for the Second Implementation Period

<RULE> ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 52</CFR> <DEPDOC>[EPA-R10-OAR-2024-0545; FRL-11879-02-R10]</DEPDOC> <SUBJECT>Air Plan Approval; ID; Regional Haze Plan for the Second Implementation Period</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The Environmental Protection Agency (EPA) is approving the Idaho regional haze State Implementation Plan (SIP) revision submitted on August 5, 2022, supplemented on September 27, 2024, and clarified on August 12, 2025, as satisfying applicable requirements under the Clean Air Act and the EPA's Regional Haze Rule (RHR) for the program's second implementation period. The Idaho SIP revision addressed the requirement to make reasonable progress toward the national goal of preventing any future, and remedying any existing, anthropogenic impairment of visibility in certain national parks and wilderness areas. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This final rule is effective October 6, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> The EPA has established a docket for this action under Docket ID No. EPA-R10-OAR-2024-0545 at <E T="03">https://www.regulations.gov.</E> Although listed in the index, some information is not publicly available, <E T="03">e.g.,</E> Confidential Business Information or other information the disclosure of which 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 at <E T="03">https://www.regulations.gov,</E> or please contact the person listed in the <E T="02">FOR FURTHER INFORMATION CONTACT</E> section for additional availability information. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> John Chi, EPA Region 10, 1200 Sixth Avenue, Suite 155, Seattle, WA 98101, at (206) 553-1185 or <E T="03">chi.john@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> Throughout this document, the use of “we” and “our” means “the EPA.” <HD SOURCE="HD1">Table of Contents</HD> <EXTRACT> <FP SOURCE="FP-2">I. Background</FP> <FP SOURCE="FP-2">II. EPA Responses to Comments Received</FP> <FP SOURCE="FP1-2">A. The National Parks Conservation Association, the Coalition To Protect America's National Parks, and the Sierra Club</FP> <FP SOURCE="FP1-2">1. Additional Facilities Considered</FP> <FP SOURCE="FP1-2">2. Low Cost-Effectiveness Threshold</FP> <FP SOURCE="FP1-2">3. Clearwater Paper Corporation</FP> <FP SOURCE="FP1-2">4. ITAFOS Conda LLC</FP> <FP SOURCE="FP1-2">5. J.R. Simplot—Don Siding Pocatello</FP> <FP SOURCE="FP1-2">6. TASCO Paul</FP> <FP SOURCE="FP1-2">7. Clearwater Paper Corporation Low Sulfur Fuel Oil Requirement</FP> <FP SOURCE="FP1-2">B. The Amalgamated Sugar Company</FP> <FP SOURCE="FP1-2">1. Inclusion of Site-Specific Permit Conditions</FP> <FP SOURCE="FP1-2">2. Condition 4.6 Is Redundant in Permit T1-2019-0020</FP> <FP SOURCE="FP1-2">C. The Idaho Association of Commerce and Industry</FP> <FP SOURCE="FP-2">III. Final Action</FP> <FP SOURCE="FP-2">IV. Incorporation by Reference</FP> <FP SOURCE="FP-2">V. Statutory and Executive Order Reviews </FP> </EXTRACT> <HD SOURCE="HD1">I. Background</HD> On March 24, 2025, the EPA proposed to approve the regional haze State Implementation Plan (SIP) revision submitted by Idaho on August 5, 2022, supplemented on September 27, 2024, and clarified on August 12, 2025, as satisfying applicable requirements under the Clean Air Act and the EPA's Regional Haze Rule (RHR) for the program's second implementation period (90 FR 13516). The public comment period for our notice of proposed rulemaking (NPRM) closed on April 23, 2025. We received six comments. We determined two of the comments were not germane to our action. One commenter requested that, “the EPA and the Idaho Department of Environmental Quality [“IDEQ” or “DEQ”] consider a program to install supplemental catalytic converters on older gasoline cars to reduce NO <E T="52">X</E> , VOCs, and CO emissions.” The commenter further stated that the commenter's company has developed supplemental catalytic converters to reduce tailpipe emissions. This comment is outside the scope of this action. The revisions to Idaho's SIP addressed in this action do not relate to control of motor vehicle emissions in general, or the control of tailpipe emissions using supplemental catalytic converters. Rather, this action primarily addresses stationary source industrial emissions that may impact visibility in Class I areas in Idaho. In addition, the commenter did not indicate that the EPA approval of the Idaho regional haze plan submission is inconsistent with the Clean Air Act. A second commenter recommended not approving the plan until Idaho attains clean air standards. The commenter also stated that “Idaho will need to degrowth, contract and regulate more to provide clean air for Idahoans health and safety.” This action addresses the Clean Air Act visibility protection requirements of sections 169A and 169B, not the Clean Air Act's health-based air quality standards, such as the national ambient air quality standards. Therefore, this comment is outside the scope of this action. We also received one comment in support of this action. The commenter conveyed overall support for our NPRM, stating, “I am very happy and proud of the EPA for proposing this influential rule that will help in Idaho. However, seeing that Idaho has an average AQI of 62 which many other states are well above 70 I think similar rules to these should be implemented in other areas of our nation.” The EPA acknowledges the commenter's support. We received germane, adverse comments from a coalition of conservation groups (the National Parks Conservation Association, the Coalition to Protect America's National Parks, and the Sierra Club), the Amalgamated Sugar Company (TASCO), and the Idaho Association of Commerce and Industry (IACI). The full text of the comments may be found in the docket for this action. We have reprinted in relevant part or summarized the comments and provided our responses in section II of this preamble. <HD SOURCE="HD1">II. EPA Responses to Comments Received</HD> <HD SOURCE="HD2">A. The National Parks Conservation Association, the Coalition To Protect America's National Parks, and the Sierra Club</HD> <HD SOURCE="HD3">1. Additional Facilities Considered</HD> <E T="03">Comment:</E> “[W]e believe DEQ should have considered additional facilities to strengthen their SIP Revision Package.” <E T="03">Response:</E> The RHR does not require a State to evaluate all sources of emissions, nor does it list factors that a State must or may consider when selecting sources. Rather, the RHR requires that a State's submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.”  <SU>1</SU> <FTREF/> The State must also appropriately document the technical basis for source selection, which may include methods for quantifying potential visibility impacts such as emissions divided by distance metrics, trajectory analyses, residence time analyses, and/or photochemical modeling. <FTNT> <SU>1</SU>  40 CFR 51.308(f)(2)(i). </FTNT> As detailed in the submission and described in our NPRM, Idaho used the source selection methodology developed by the Western Regional Air Partnership (WRAP) for western States. <SU>2</SU> <FTREF/> The WRAP's approach used the Q/d method, where Q is the sum of visibility impairing pollutants (NO <E T="52">X</E> , SO <E T="52">2</E> and PM <E T="52">10</E> ), and d is the distance (kilometers) to the boundary of the nearest Class I area. The Idaho DEQ screened sources as described in the following steps:  <SU>3</SU> <FTREF/> <FTNT> <SU>2</SU>   <E T="03">See</E> the WRAP Technical Support System (TSS) at <E T="03">www.wrapair2.org.</E> </FTNT> <FTNT> <SU>3</SU>  Idaho 2022 plan submission, page 54. </FTNT> 1. Identify those facilities with total facility-wide emissions of visibility impairing pollutants (NO <E T="52">X</E> , SO <E T="52">2</E> and PM <E T="52">10</E> ) greater than 25 tons per year (tpy) based on 2014 National Emissions Inventory (NEI) data. 2. Calculate the distance from each facility identified in Step 1 to the nearest Class I area boundary (including those in other States) in kilometers (km). Facilities greater than 400 km from the nearest Class I area were considered to have minimal impact on visibility and were excluded. 3. Identify those facilities with a Q/d greater than the State-defined threshold. Idaho used a relatively low Q/d threshold of 2.0 because the State estimated that the threshold captured 70% to 80% of emissions from Idaho facilities. 4. Refine the Q/d analysis using more recent 2017 NEI data to screen out sources that have a Q/d less than the State-defined threshold for 2017 emissions. Idaho's initial source screening used 2014 emissions inventory data to identify 14 facilities in Idaho with Q/d greater than 2.0. <SU>4</SU> <FTREF/> Idaho refined the Q/d analysis using 2017 emissions inventory data and screened out three additional facilities from the original 14 (Idaho Forest Group LLC-Riley Creek-Moyie Springs, Plummer Forest Group, Inc-Post Falls, and Rexburg Facility of Basic American Foods). <SU>5</SU> <FTREF/> Idaho also screened out a facility outside of the State's regulatory purview (Boise Airport), as well as a facility near Sawtooth Wilderness Area (Northwest Pipeline—Mountain Home) because the facility primarily emitted NO <E T="52">X</E> and WRAP modeling found anthropogenic contributions to NO <E T="52">X</E> at SAWT1 were negligible. <SU>6</SU> <FTREF/> ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 54k characters. 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