The Bureau is proposing to revise its 2013 rule articulating procedures for allocations from the Civil Penalty Fund to rescind procedures related to allocations for consumer education and financial literacy programs. The Bureau now believes that the procedures outlined in the rule provide neither adequate guardrails for the agency's exercise of its discretion nor adequate transparency to the public regarding a potentially significant expenditure.

The CFPA established the Bureau with a mandate to regulate the offering and provision of consumer financial products and services under the Federal consumer financial laws. Public Law 111-203, sec. 1011(a) (2010), codified at 12 U.S.C. 5491(a). The CFPA authorizes the Bureau, among other things, to enforce Federal consumer financial law through judicial actions and administrative adjudication proceedings. 12 U.S.C. 5563, 5564. In those actions and proceedings, a court or the Bureau may require a party that has violated the law to pay a civil penalty. See, e.g., 12 U.S.C. 5565.

Section 1017(d)(1) of the CFPA establishes a separate fund in the Federal Reserve, the “Consumer Financial Civil Penalty Fund” (Civil Penalty Fund), into which the Bureau must deposit civil penalties it collects from any person in any judicial or administrative action under Federal consumer financial laws. 12 U.S.C. 5497(d)(1). Under the Act, amounts in the Fund may be used “for payments to the victims of activities for which civil penalties have been imposed under the Federal consumer financial laws.” 12 U.S.C. 5497(d)(2). In addition, “[t]o the extent that such victims cannot be located or such payments are otherwise not practicable,” the Bureau may use amounts in the Fund for consumer education and financial literacy programs. Id.

The Bureau is issuing this rule pursuant to its authority under section 1022(b)(1) of the CFPA, which authorizes the Bureau to prescribe rules as may be necessary or appropriate to enable the Bureau to administer and carry out the purposes and objectives of Federal consumer financial law, 12 U.S.C. 5512(b)(1); and under section 1017(d) of the CFPA, which establishes the Civil Penalty Fund and authorizes the Bureau to use amounts in that Fund for payments to victims and for consumer education and financial literacy programs.

On May 7, 2013, the Bureau published a rule (2013 Rule) that stated its interpretation of what kinds of payments to victims are appropriate and established procedures for allocating such funds to both victims and to consumer education and financial literacy programs. First, it described the roles of Bureau officials involved in managing the Civil Penalty Fund, including by establishing the position of Civil Penalty Fund Administrator (Fund Administrator) and providing that the Civil Penalty Fund Governance Board—the body comprised of senior Bureau officials established by the Director to advise on matters relating to the Civil Penalty Fund—may advise or direct the Fund Administrator on the administration of the Civil Penalty Fund. Second, the 2013 Rule identified the category of victims who may receive payments from the Civil Penalty Fund and set forth the amounts they may receive. Third, the 2013 Rule established a two-stage procedure for expending money in the Civil Penalty Fund, pursuant to which, based on six-month periods, the Fund Administrator will first allocate funds for payments to classes of victims and, if appropriate, for consumer education and financial literacy programs, then designate a payments administrator to distribute allocated funds to individual victims in the classes to which funds have been allocated. Fourth, the 2013 Rule set forth several circumstances in which it will be deemed impracticable to make payments to victims or to classes of victims. Finally, the 2013 Rule required the Fund Administrator to issue regular reports on the disposition of funds in the Civil Penalty Fund. 1

The 2013 Rule provided limited information on how the Bureau was to exercise its discretion to use funds in the Civil Penalty Fund for the purpose of consumer education and financial literacy programs, should such funds remain available after allocations to victims. The preamble stated only that “the Bureau has adopted criteria—not contained in this rule—for selecting the particular consumer education or financial literacy programs to be funded” and referred to a page on the Bureau's website. The regulatory text's discussion of funding consumer education or financial literacy programs consisted, in its entirety, of two bare recitations of the phrase “allocating funds to consumer education and financial literacy programs,”  2 one provision parroting the statutory grant of discretionary authority to make allocations, 3 and two provisions clarifying the authority of the Fund Administrator with respect to such allocations. 4

Simultaneously with the issuance of the 2013 Rule, the Bureau also issued a notice of proposed rulemaking seeking comment on, inter alia, the provisions of the 2013 Rule governing allocations to consumer education and financial literacy programs, including whether the rule should limit the amount of remaining funds that the Fund Administrator may allocate to consumer education and financial literacy programs. 5 The Bureau received four comments addressing allocations of remaining funds for consumer education and financial literacy programs. Comments from three consumer advocacy groups encouraged the Bureau not to place limits on these allocations. One individual commenter opposed the use of funds for any purpose other than repayment to individuals who have been harmed. The Bureau did not subsequently modify the 2013 Rule.

In the twelve years since the 2013 Rule, the Bureau has allocated $3,641,510,398 from the Civil Penalty Fund for payments to victims of activities for which civil penalties have been imposed under Federal consumer financial laws. 6 The Bureau has exercised its discretion to allocate funds to consumer education and financial literacy programs with respect to a single program; allocations for that program, amounting to $28,812,809, were made from fiscal years 2013-2016. 7

The Bureau now believes that the 2013 Rule provides neither adequate guardrails for the agency's exercise of its discretion nor adequate transparency to the public regarding a potentially significant expenditure. In the absence of adequate guardrails, there could be incentives to bring enforcement actions for the purpose of aggrandizing the operational scope of the agency. Accordingly, the Bureau proposes to rescind those aspects of the 2013 Rule that reference the Bureau's use of amounts in the Fund for consumer education and financial literacy programs. The Bureau does not intend to exercise its discretionary authority to allocate funds to consumer education and financial literacy programs, but it does intend to consider whether revised procedures would be appropriate to address these concerns with respect to any future exercises of this discretionary authority.

While this proposal is exempt from the notice-and-comment rulemaking requirements of the Administrative Procedure Act—both because it relates to benefits, 5 U.S.C. 553(a)(2), and because it concerns matters of agency organization, procedure, and practice, 5 U.S.C. 553(b)—the Bureau nevertheless invites interested parties to comment.

The CFPB proposes that, once issued, the final rule for this proposed rule would be effective upon publication in the Federal Register . The rule is procedural and not substantive and, thus, is not subject to the 30-day delay in effective date required by 5 U.S.C. 553(d).

In developing this proposal to amend the 2013 Rule implementing the provision of the CFPA that establishes a Civil Penalty Fund, the Bureau has considered the potential benefits, costs, and impacts of doing so. This proposed rule would remove references to allocating funds for consumer education and financial literacy programs.

The CFPB is proposing this revision because it now believes that the procedures outlined in the rule provide neither adequate guardrails for the agency's exercise of its discretion nor adequate transparency to the public regarding a potentially significant expenditure. In the absence of adequate guardrails, there could be incentives to bring enforcement actions for the purpose of aggrandizing the operational scope of the agency.

Section 1017(d)(2) of the CFPA, implemented by the 2013 Rule, provides that the Bureau may, at its own discretion, allocate to consumer education and financial literacy programs any funds from the Civil Penalty Fund that remain after the Fund Administrator allocates funds to payments to victims of activities subject to civil penalties.

This proposed rule would rescind those aspects of the 2013 Rule that reference this discretion. The Bureau does not intend to exercise its discretionary authority to allocate funds to consumer education and financial literacy programs, but it does intend to consider whether revised procedures would be appropriate to address the above enumerated concerns for any future exercise of this discretionary authority.

The Bureau has limited information with which to precisely quantify the costs and benefits of the proposed rule. Thus, the discussion considers a qualitative analysis of the likely effects of the proposed rule. The Bureau does not anticipate that this proposal would result in any significant costs or benefits for consumers or covered persons. The proposed rule does not impose or remove any binding legal requirements on the public. We note also that historically, the Bureau has allocated relatively little of the Civil Penalty Fund to consumer education and financial literacy programs.

The Bureau seeks specific comment on the extent to which this proposed rule would result in benefits or costs. The Bureau is specifically interested in any comments that could model such impacts in a quantitative and methodologically rigorous manner.

The proposed revision would not impose any obligations on depository institutions or credit unions. Moreover, the Bureau does not expect the proposed revision to affect Bureau behavior related to depository institutions or credit unions, including examination and enforcement work. Therefore, the Bureau expects this proposal would not have specific impacts on insured depository institutions and insured credit unions with $10 billion or less in total assets. The Bureau seeks specific comment on the accuracy of this expectation.

The proposed revision would not impose new costs on providers of financial products and services. Accordingly, the Bureau does not expect the proposed revision would impact consumer access to financial products and services.

Similarly, the proposed revision would neither impose costs on providers of financial products and services in rural areas nor impose costs on consumers in rural areas. Therefore, the Bureau does not expect the proposed revision would impact consumers in rural areas.

The Bureau seeks specific comment on the accuracy of these expectations.

The Regulatory Flexibility Act (RFA) generally requires an agency to conduct an initial regulatory flexibility analysis (IRFA) and a final regulatory flexibility analysis (FRFA) of any rule subject to notice-and-comment rulemaking requirements, unless the agency certifies that the rule will not have a significant economic impact on a substantial number of small entities. 5 The Bureau also is subject to certain additional procedures under the RFA involving the convening of a panel to consult with small business representatives before proposing a rule for which an IRFA is required. 6

The Final Rule concerns benefits and relates solely to agency procedure and practice and, thus, is not subject to the notice and comment requirements of the Administrative Procedure Act. 5 U.S.C. 553(a)(2), (b). Because no notice of proposed rulemaking is required, this rule does not require an IRFA or a FRFA pursuant to the RFA, 5 U.S.C. 601 et seq.

The Office of Information and Regulatory Affairs has determined that this action is not a “significant regulatory action” under Executive Order 12866, as amended by Executive Order 14215.

E.O. 12866 states that “Federal agencies should promulgate only such regulations as are required by law, are necessary to interpret the law, or are made necessary by compelling public need, such as material failures of private markets. . . .” The Bureau seeks specific comment regarding whether there is any data, and in particular methodologically rigorous research, to indicate the existence of a market failure or other compelling public need that would justify the retention of the references in the 2013 Rule to allocating funds for consumer education and financial literacy programs.

For the reasons set forth in the preamble, the Bureau proposes to amend 12 CFR part 1075 as set forth below:

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2025-1102; Project Identifier MCAI-2024-00183-R” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to George Weir, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

The European Union Aviation Safety Agency (EASA), which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2024-0071, dated March 14, 2024 (EASA AD 2024-0071) (also referred to as “the MCAI”), to correct an unsafe condition on HG Model Cabri G2 helicopters, all serial numbers. The MCAI states that occurrences were reported where, during maintenance, cracks were found on the rotating and non-rotating part of the swashplates of two HG Model Cabri G2 helicopters. HG concluded that the cracks were likely caused by aging and corrosion.

The MCAI states that this condition, if not detected and corrected, could lead to failure of the swashplate, which could result in loss of control of the helicopter. The MCAI requires inspecting each swashplate and, if there are any cracks, replacing each cracked swashplate before the next flight. The MCAI allows installing an affected swashplate on a helicopter provided that, before installation, it is inspected and no cracks are found.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-1102.

The FAA reviewed Guimbal Mandatory Service Bulletin SB 24-001, Revision C, dated March 20, 2024 (Guimbal SB 24-001 C), which specifies procedures for performing repetitive inspections of the six arms from both the rotating and non-rotating swashplate part number G41-00-000 for cracks, replacing any cracked swashplate, and contacting HG support. If there is doubt about the existence of a crack or if there is paint damage or peeling, Guimbal SB 24-001 C specifies removing the paint and further inspecting for cracks. If no crack is found, Guimbal SB 24-001 C specifies touching up the paint in areas where paint was removed before approving the helicopter for return to service.

This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

These products have been approved by the aviation authority of another country and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, it has notified the FAA of the unsafe condition described in the MCAI and material referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

This proposed AD would require removing the paint on each swashplate and performing repetitive visual inspections of the six arms of the rotating and non-rotating swashplates for a crack. Depending on the results, this proposed AD would require removing any cracked swashplate from service and replacing the swashplate with an airworthy part, or repainting the swashplate. This proposed AD would also prohibit installing an affected swashplate unless the part is inspected prior to installation and thereafter as identified in the proposed AD.

The material referenced in the MCAI specifies removing paint if there is doubt regarding if there is a crack or if there is paint damage, and this proposed AD requires removing the paint before performing each inspection.

The material referenced in the MCAI specifies contacting HG support after replacing the swashplate, whereas this proposed AD would not require that action.

The FAA estimates that this AD, if adopted as proposed, would affect 59 helicopters of U.S. registry. Labor rates are estimated at $85 per hour. The FAA estimates the following costs to comply with this proposed AD.

Inspecting a swashplate would take .25 work-hour for an estimated cost of $22 per helicopter and $1,298 for the U.S. fleet, per inspection cycle. Removing the paint and repainting the swashplate would take .5 work-hour for an estimated cost of $43 per helicopter and $2,537 for the U.S. fleet, per inspection cycle. If required, replacing a swashplate would take 6 work-hours and parts would cost about $7,066 for an estimated cost of $7,576 per helicopter.

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under ADDRESSES . Include “Docket No. FAA-2025-0917; Project Identifier MCAI-2024-00740-A” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov , including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Doug Rudolph, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2024-0240, dated December 10, 2024 (EASA AD 2024-0240) (also referred to as the MCAI), to correct an unsafe condition on Pilatus Model PC-24 airplanes, all manufacturer serial numbers. The MCAI states there was a report of inaccurate flight director calculation on approach with APEX Build 5.3 and below software installed. Further investigation revealed that heading splits can cause errors in the flight director calculation resulting in lateral offsets to the desired approach course. The MCAI also states that the AD is considered an interim action and further AD action may follow. This condition, if not addressed, could result in increased pilot workload, resulting in a reduction of the safety margins. The FAA is proposing this AD to address the unsafe condition on these products.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-0917.

The FAA reviewed EASA AD 2024-0240, which specifies procedures for incorporating Pilatus PC-24 AFM Temporary Revision 02371-075 (also referred to as AFM-TR) into the AFM, which revises the Abnormal Procedures Section. EASA AD 2024-0240 also specifies informing all flight crews of the change, and, thereafter, operating the airplane accordingly, and allows for the incorporation of a later AFM revision that includes the same AFM amendment content. This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

These products have been approved by the aviation authority of another country and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

This proposed AD would require accomplishing the actions specified in the MCAI described previously, except for any differences identified as exceptions in the regulatory text of this proposed AD. See “Differences Between this AD and the MCAI” for a discussion of the general differences included in this AD. The owner/operator (pilot) holding at least a private pilot certificate may revise the existing AFM for your airplane and must enter compliance with the applicable paragraph of this proposed AD into the airplane maintenance records in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The pilot may perform this action because it only involves revising the AFM. This action could be performed equally well by a pilot or a mechanic. This is an exception to the FAA's standard maintenance regulations.

In the FAA's ongoing efforts to improve the efficiency of the AD process, the FAA developed a process to use some civil aviation authority (CAA) ADs as the primary source of information for compliance with requirements for corresponding FAA ADs. The FAA has since coordinated with other manufacturers and CAAs to use this process. As a result, the FAA proposes to incorporate by reference EASA AD 2024-0240 in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 2024-0240 in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD. Using common terms that are the same as the heading of a particular section in the EASA AD does not mean that operators need comply only with that section. For example, where the AD requirement refers to “all required actions and compliance times,” compliance with this AD requirement is not limited to the section titled “Required Action(s) and Compliance Time(s)” in EASA AD 2024-0240. Service information required by the EASA AD for compliance will be available at regulations.gov under Docket No. FAA-2025-0917 after the FAA final rule is published.

EASA AD 2024-0240 includes requirements to “inform all flight crews and, thereafter, operate the [airplane] accordingly”, and this proposed AD would not specifically require those actions because those actions are already required by FAA regulations.

The FAA considers that this proposed AD would be an interim action. This unsafe condition is still under investigation by the manufacturer and, depending on the results of that investigation, the FAA may consider further rulemaking action.

The FAA estimates that this AD, if adopted as proposed, would affect 150 airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD:

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2025-1106; Project Identifier MCAI-2023-01052-R” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may amend this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov , including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Aryanna Sanchez, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

EASA, which is the Technical Agent for the Member States of the European Union, has issued EASA AD 2023-0175, dated October 5, 2023 (EASA AD 2023-0175) (also referred to as “the MCAI”), to correct an unsafe condition on Airbus Helicopters Deutschland GmbH Model MBB-BK 117 D-2, MBB-BK 117 D-2m, MBB-BK 117 D-3, and MBB-BK 117 D-3m helicopters. The MCAI states that there have been reports of airspeed and altitude indication errors. Subsequent investigation revealed that the ACS condenser outlets are in close proximity to the static ports, and air from the outlets affects the static ports during flight. The static ports and pitot tubes measure different pressures, which are then used to calculate airspeed, altitude, and vertical speed. Incorrect readings can then occur. This condition, if not corrected, could result in a significant increase in crew workload and reduced situational awareness. The FAA is proposing this AD to address the unsafe condition on these products.

You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2025-1106.

The FAA reviewed EASA AD 2023-0175, which specifies procedures for amending the applicable RFMS by incorporating new altitude corrections if the helicopter has ACS condenser outlet grids, and not covers, installed. EASA AD 2023-0175 also specifies procedures for replacing the ACS condenser outlet grid part number (P/N) D211M1821302 or P/N D211M1822302 with ACS condenser outlet cover P/N D211M1821402 or P/N D211M1822402 and prohibits installing ACS condenser outlet grids on any helicopter. This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

These products have been approved by the aviation authority of another country and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

This proposed AD would require accomplishing the actions specified in the material already described, except for any differences identified as exceptions in the regulatory text of this AD. See “Differences Between this Proposed AD and the MCAI” for a discussion of those differences.

This proposed AD would require revising the RFMS for the helicopter. This proposed action may be performed by the owner/operator (pilot) holding at least a private pilot certificate and compliance with the applicable paragraphs of this proposed AD must be entered into the helicopter maintenance records in accordance with 14 CFR 43.9(a) and 91.417(a)(2)(v). The pilot may perform this action because it only involves revising the existing RFMS by inserting pages, which is not considered a maintenance action.

In the FAA's ongoing efforts to improve the efficiency of the AD process, the FAA developed a process to use some civil aviation authority (CAA) ADs as the primary source of information for compliance with requirements for corresponding FAA ADs. The FAA has been coordinating this process with manufacturers and CAAs. As a result, the FAA proposes to incorporate EASA AD 2023-0175 by reference in the FAA final rule. This proposed AD would, therefore, require compliance with EASA AD 2023-0175 in its entirety through that incorporation, except for any differences identified as exceptions in the regulatory text of this proposed AD. Using common terms that are the same as the heading of a particular section in EASA AD 2023-0175 does not mean that operators need comply only with that section. For example, where the AD requirement refers to “all required actions and compliance times,” compliance with this AD requirement is not limited to the section titled “Required Action(s) and Compliance Time(s)” in EASA AD 2023-0175. Material referenced in EASA AD 2023-0175 for compliance will be available at regulations.gov under Docket No. FAA-2025-1106 after the FAA final rule is published.

EASA AD 2023-0175 applies to Model MBB-BK117 D-2m and MBB-BK117 D-3m helicopters, whereas this AD would not because those models do not have an FAA type certificate.

EASA AD 2023-0175 requires operators to “inform all flight crews” of the revisions to the RFMS, and thereafter to “operate the helicopter accordingly.” However, this proposed AD would not require those actions as those actions are already required by FAA regulations. FAA regulations require operators furnish to pilots any changes to the RFM (for example, 14 CFR 135.21) and that pilots are familiar with the RFM (for example, 14 CFR 91.505). As with any other flight crew training requirement, training on the updated RFM content is tracked by the operators and recorded in each pilot's training record, which is available for the FAA to review. FAA regulations also require pilots to follow the procedures in the existing RFM including all updates. Section 91.9 requires that any person operating a civil aircraft must comply with the operating limitations specified in the RFM. Therefore, including a requirement in this proposed AD to operate the helicopter according to the revised RFM would be redundant and unnecessary.

EASA AD 2023-0175 does not have any flight restrictions, whereas this proposed AD would require a revision to the RFMS restricting helicopters to operation under visual flight rules (VFR) until the helicopter is modified with ACS condenser outlet covers.

EASA AD 2023-0175 specifies amending the applicable RFMS, whereas this proposed AD would specifically require amending the Limitations Section of the applicable RFMS.

The FAA considers that this proposed AD would be an interim action. The manufacturer is currently developing a modification that will address the unsafe condition identified in this AD. Once this modification is developed, approved, and available, the FAA might consider additional rulemaking.

The FAA estimates that this AD, if adopted as proposed, would affect 71 helicopters of U.S. registry. Labor costs are estimated at $85 per hour. Based on these numbers, the FAA estimates the following costs to comply with this proposed AD.

Replacing the ACS condenser outlet grids would take 20 work-hours and parts would cost $970, for an estimated cost of $2,670 per helicopter and $189,570 for the U.S. fleet. Revising the existing RFM for the helicopter would take 1 work-hour for an estimated cost of $85 per helicopter and $6,035 for the U.S. fleet.

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.

The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify this proposed regulation:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Would not affect intrastate aviation in Alaska, and

(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

The FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. Subtitle I, Section 106 describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the agency's authority. This rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart I, Section 40103. Under that section, the FAA is charged with prescribing regulations to assign the use of airspace necessary to ensure the safety of aircraft and the efficient use of airspace. This regulation is within the scope of that authority as it would amend the Class E airspace extending upward from 700 feet above the surface at Marshall County Airport, Lacon, IL, to support IFR operations at this airport.

The FAA invites interested persons to participate in this rulemaking by submitting written comments, data, or views. Comments are specifically invited on the overall regulatory, aeronautical, economic, environmental, and energy-related aspects of the proposal. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. To ensure the docket does not contain duplicate comments, commenters should submit only one time if comments are filed electronically, or commenters should send only one copy of written comments if comments are filed in writing.

The FAA will file in the docket all comments it receives, as well as a report summarizing each substantive public contact with FAA personnel concerning this proposed rulemaking. Before acting on this proposal, the FAA will consider all comments it received on or before the closing date for comments. The FAA will consider comments filed after the comment period has closed if it is possible to do so without incurring expense or delay. The FAA may change this proposal in light of the comments it receives.

Privacy: In accordance with 5 U.S.C. 553(c), DOT solicits comments from the public to better inform its rulemaking process. DOT posts these comments, without edit, including any personal information the commenter provides, to www.regulations.gov as described in the system of records notice (DOT/ALL-14FDMS), which can be reviewed at www.dot.gov/privacy.

An electronic copy of this document may be downloaded through the internet at www.regulations.gov. Recently published rulemaking documents can also be accessed through the FAA's web page at www.faa.gov/air_traffic/publications/airspace_amendments/.

You may review the public docket containing the proposal, any comments received, and any final disposition in person in the Dockets Office (see the ADDRESSES section for the address, phone number, and hours of operations). An informal docket may also be examined during normal business hours at the Federal Aviation Administration, Air Traffic Organization, Central Service Center, Operations Support Group, 10101 Hillwood Parkway, Fort Worth, TX 76177.

Class E airspace is published in paragraph 6005 of FAA Order JO 7400.11, Airspace Designations and Reporting Points, which is incorporated by reference in 14 CFR 71.1 on an annual basis. This document proposes to amend the current version of that order, FAA Order JO 7400.11J, dated July 31, 2024, and effective September 15, 2024. These updates would be published subsequently in the next update to FAA Order JO 7400.11. FAA Order JO 7400.11J, which lists Class A, B, C, D, and E airspace areas, air traffic service routes, and reporting points, is publicly available as listed in the ADDRESSES section of this document.

The FAA is proposing an amendment to 14 CFR part 71 by modifying the Class E airspace extending upward from 700 ft above the surface: (1) to within a 7-mile (increased from a 6.3-mile) radius of the Marshall County Airport, Lacon, IL; (2) updating the geographic coordinates of the airport to coincide with the FAA's aeronautical database; and (3) removing the city associated with the airport in the airspace legal description to comply with changes to FAA Order JO 7400.2P, Procedures for Handling Airspace Matters.

This action is the result of airspace reviews conducted as part of the decommissioning of the Bradford VOR as part of the VOR MON Program.

The FAA has determined that this proposed regulation only involves an established body of technical regulations for which frequent and routine amendments are necessary to keep them operationally current. It, therefore: (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory evaluation as the anticipated impact is so minimal. Since this is a routine matter that will only affect air traffic procedures and air navigation, it is certified that this proposed rule, when promulgated, will not have a significant economic impact on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

This proposal will be subject to an environmental analysis in accordance with FAA Order 1050.1F, “Environmental Impacts: Policies and Procedures” prior to any FAA final regulatory action.

In consideration of the foregoing, the Federal Aviation Administration proposes to amend 14 CFR part 71 as follows:

The FAA's authority to issue rules regarding aviation safety is found in Title 49 of the United States Code. Subtitle I, Section 106 describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the agency's authority. This rulemaking is promulgated under the authority described in Subtitle VII, Part A, Subpart I, Section 40103. Under that section, the FAA is charged with prescribing regulations to assign the use of the airspace necessary to ensure the safety of aircraft and the efficient use of airspace. This regulation is within the scope of that authority as it establishes restricted area airspace at Camp Lejeune, NC and Cherry Point, NC, to enhance aviation safety and accommodate essential United States (U.S.) Marine Corps training activities.

The FAA invites interested persons to participate in this rulemaking by submitting written comments, data, or views. Comments are specifically invited on the overall regulatory, aeronautical, economic, environmental, and energy-related aspects of the proposal. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. To ensure the docket does not contain duplicate comments, commenters should submit only one time if comments are filed electronically, or commenters should send only one copy of written comments if comments are filed in writing. There is no need to re-post comments already submitted to this docket in connection with the earlier NPRM.

The FAA will file in the docket all comments it receives, as well as a report summarizing each substantive public contact with FAA personnel concerning this proposed rulemaking. Before acting on this proposal, the FAA will consider all comments it receives on or before the closing date for comments. The FAA will consider comments filed after the comment period has closed if it is possible to do so without incurring expense or delay. The FAA may change this proposal in light of the comments it receives.

Privacy: In accordance with 5 U.S.C. 553(c), DOT solicits comments from the public to better inform its rulemaking process. DOT posts these comments, without edit, including any personal information the commenter provides, to www.regulations.gov, as described in the system of records notice (DOT/ALL-14 FDMS), which can be reviewed at www.dot.gov/privacy.

An electronic copy of this document may be downloaded through the internet at www.regulations.gov. Recently published rulemaking documents can also be accessed through the FAA's web page at www.faa.gov/air_traffic/publications/airspace_amendments/.

You may review the public docket containing the proposal, any comments received and any final disposition in person in the Dockets Office (see ADDRESSES section for address, phone number, and hours of operation). An informal docket may also be examined during normal business hours at the office of the Eastern Service Center, Federal Aviation Administration, Room 210, 1701 Columbia Avenue, College Park, GA 30337.

On March 20, 2025, the FAA issued an NPRM (90 FR 13112) in this docket. Subsequent to publication of the NPRM, the FAA identified that it incorrectly stated a geographic coordinate due to a rounding error. This geographic coordinate partially defines the northern boundary of restricted areas R-5305A, R-5305B, and R-5305C. As restricted areas R-5305A, R-5305B, and R-5305C are proposed to share the same lateral boundaries, updating this coordinate moves the northern boundary approximately 1 nautical mile north of the position listed in the NPRM. The point “lat. 34°41′00″ N, long. 077°24′59″ W” is changed to “lat. 34°42′00″ N, long. 077°24′59″ W” as originally intended. Additionally, the supporting graphic depicting the boundary of restricted area R-5305A, R-5305B, and R-5305C, overlaid on a sectional chart, correctly depicts the intended boundary.

Other components of the proposal from the original NPRM remain unchanged.

The FAA is proposing an amendment to 14 CFR part 73 to establish restricted areas R-5305A, R-5305B, and R-5305C; Camp Lejeune, NC. This additional restricted area airspace, combined with the existing restricted area R-5003, R-5004, and R-5306 complexes, would support USMC training and readiness requirements and would provide the contiguous restricted area airspace required to contain hazardous activities such as weapon deployment, non-eye safe lasers, and artillery necessary to conduct complex training scenarios required to realistically train to accomplish mission essential tasks.

Proposed restricted areas R-5305A, R-5305B, and R-5305C would share the same lateral boundaries. Restricted area R-5305A would be from the surface to but not including 7,000 feet MSL, excluding the airspace from the surface to 200 feet above ground level (AGL) within 200 feet either side of U.S. Highway 17. Published times of use would be Monday through Friday, 0600 to 2359 local time, other times of use would be published in a Notice to Airmen (NOTAM) at least 24 hours in advance. Restricted area R-5305A would be expected to be activated 8 hours per day, 150 days per year. Approximately 25 percent of the activation time would be during the hours of darkness, and approximately 5 percent of all activation would include fixed-wing operations.

Restricted area R-5305B would be from 7,000 feet (mean sea level) MSL to but not including 10,000 feet MSL. A NOTAM would publish the intermittent times of use of restricted area R-5305B. Restricted area R-5305B is expected to be activated 4 hours per day, 30 days per year. Approximately 25 percent of the activation time would be during the hours of darkness, and approximately 50 percent of the activation time would include fixed-wing operations.

Restricted area R-5305C would be from 10,000 feet MSL to but not including FL 180. A NOTAM would publish intermittent times of use of restricted area R-5305C. It is expected to be activated 4 hours per day, 30 days per year. Approximately 25 percent of the activation time would be during the hours of darkness, and approximately 50 percent of the activation time would include fixed-wing operations.

The full descriptions of the above restricted areas are set forth below in the proposed amendments to part 73. This action continues to propose restricted areas R-5307A, R-5307B, and R-5307C; Cherry Point, NC.

The FAA has determined that this proposed regulation only involves an established body of technical regulations for which frequent and routine amendments are necessary to keep them operationally current. It, therefore: (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034; February 26, 1979); and (3) does not warrant preparation of a regulatory evaluation as the anticipated impact is so minimal. Since this is a routine matter that will only affect air traffic procedures and air navigation, it is certified that this proposed rule, when promulgated, will not have a significant economic impact on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

This proposal will be subject to an environmental analysis in accordance with FAA Order 1050.1F, “Environmental Impacts: Policies and Procedures” prior to any FAA final regulatory action.

In consideration of the foregoing, the Federal Aviation Administration proposes to amend 14 CFR part 73 as follows:

Pursuant to section 18(a)(1)(B) of the Federal Trade Commission Act, 15 U.S.C. 57a(1)(B), and FTC Rule 1.31(f), 16 CFR 1.31(f), notice is hereby given that the above-captioned petition has been filed with the Secretary of the Commission and has been placed on the public record for a period of 30 days. Any person may submit comments in support of or in opposition to the petition. All timely and responsive comments submitted in connection with this petition will become part of the public record.

This petition requests to reform FTC procedures and practices affecting the issuance of civil investigative demands; FTC burdens of proof and pleading requirements in hearings; and FTC procedures and practices affecting appeals from Initial Decisions of Administrative Law Judges in health-related product advertising cases under Sections 5 and 12 of the Federal Trade Commission Act. The Commission will not consider the petition's merits until after the comment period closes. It may grant or deny the petition in whole or in part, and it may deem the petition insufficient to warrant commencement of a rulemaking proceeding. The purpose of this document is to facilitate public comment on the petition to aid the Commission in determining what, if any, action to take regarding the request contained in the petition. This document is not intended to start, stop, cancel, or otherwise affect rulemaking proceedings in any way.

Because your comment will be placed on the publicly accessible website at https://www.regulations.gov, you are solely responsible for making sure your comment does not include any sensitive or confidential information. In particular, your comment should not include any sensitive personal information, such as your or anyone else's Social Security number; date of birth; driver's license number or other state identification number, or foreign country equivalent; passport number; financial account number; or credit or debit card number. You are also solely responsible for making sure your comment does not include any sensitive health information, such as medical records or other individually identifiable health information. In addition, your comment should not include any “trade secret or any commercial or financial information which . . . is privileged or confidential”—as provided by section 6(f) of the FTC Act, 15 U.S.C. 46(f), and FTC Rule 4.10(a)(2), 16 CFR 4.10(a)(2).

Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA.

On March 12, 2008, EPA strengthened the NAAQS for ozone. (73 FR 16436; March 27, 2008). EPA revised the level of the 8-hour ozone NAAQS from 80 parts per billion (ppb) to 75 ppb. EPA also revised the secondary 8-hour standard to the level of 75 ppb making it identical to the revised primary standard.

Section 110(a)(1) of the CAA imposes an obligation upon states to submit SIP submissions that provide for the implementation, maintenance, and enforcement of a new or revised NAAQS within 3 years following the promulgation of that NAAQS. Section 110(a)(2) lists specific requirements that states must meet in these SIP submissions, as applicable. EPA refers to this type of SIP submission as the “infrastructure” SIP because the SIP ensures that states can implement, maintain, and enforce the air quality standards. Within these requirements, CAA section 110(a)(2)(D)(i)(I) contains requirements to address interstate transport of NAAQS pollutants or their precursors. CAA section 110(a)(2)(D)(i)(I), which is also known as the “interstate transport” provision, requires SIPs to contain provisions prohibiting any source or other type of emissions activity within the State from emitting any air pollutant in amounts that will contribute significantly to nonattainment of the NAAQS in any other state (commonly referred to as prong 1) or interfere with maintenance of the NAAQS in any other state (prong 2). A SIP addressing this provision is often referred to as an “interstate transport SIP.”

Through the development and implementation of several previous rulemakings, 1 EPA, working in partnership with states, established the following 4-step framework to address the requirements of the interstate transport provision for ground-level ozone NAAQS: (1) identifying downwind ozone air quality monitors, termed “receptors,” that are expected to have problems attaining or maintaining the NAAQS; (2) determining which upwind states contribute to these identified problems in amounts sufficient to “link” them to downwind air quality problems; (3) for states linked to downwind air quality problems, identifying upwind emissions that significantly contribute to downwind nonattainment or interfere with downwind maintenance of the NAAQS; and (4) for states that are found to have emissions that significantly contribute to downwind nonattainment or interfere with maintenance of the NAAQS downwind, implementing the necessary emissions reductions through enforceable measures.

On August 4, 2015, EPA issued a Notice of Data Availability (NODA) containing air quality modeling to assist states with meeting section 110(a)(2)(D)(i)(I) requirements for the 2008 ozone NAAQS within the context of the 4-step framework. 2 Specifically, the air quality modeling helped states address steps 1 and 2 of the framework by (1) identifying locations in the United States where EPA anticipated nonattainment or maintenance issues in 2017 for the 2008 ozone NAAQS, and (2) quantifying the projected contributions from emissions from upwind states to downwind ozone concentrations at the receptors in 2017. EPA used this modeling to support the Cross-State Air Pollution Rule Update for the 2008 Ozone NAAQS (“CSAPR Update”) proposed rule (80 FR 75706; December 3, 2015), and updated this modeling in 2016 to support the CSAPR Update final rule (81 FR 74504; October 26, 2016). The 2017 projections in this updated version of the modeling (hereon referred to as the “CSAPR Update modeling”) were part of the technical record for EPA's final action disapproving the prong 2 portion of the Utah 2008 Ozone Infrastructure SIP (81 FR 71991; October 19, 2016), which is discussed in more detail later in this document.

In the CSAPR Update, EPA used the CSAPR Update modeling to identify downwind nonattainment and maintenance receptors at step 1 of the 4-step framework ( see 81 FR 74530-74532; October 26, 2016). Specifically, EPA identified nonattainment receptors as those monitoring sites with current measured design values exceeding the NAAQS that also have projected ( i.e., in 2017) average design values exceeding the NAAQS. 3 EPA identified maintenance receptors as those monitoring sites with projected maximum design values exceeding the NAAQS. EPA considered all nonattainment receptors to also be maintenance receptors because a monitoring site with a projected average design value above the standard necessarily also has a projected maximum design value above the standard. Monitoring sites with projected maximum design values that exceed the standard and which are not also nonattainment receptors were thus referred to as maintenance-only receptors.

At step 2 of the 4-step framework in the CSAPR Update, EPA used the CSAPR Update modeling to determine whether states' impact on each projected downwind air quality problem would be considered significant ( see 80 FR 75713-75714; December 3, 2015). EPA's modeling projected ozone concentrations and contributions in 2017, which would be the last ozone season before the then-upcoming July 2018 attainment date for nonattainment areas classified as Moderate for the 2008 ozone NAAQS. Consistent with the original CSAPR rulemaking (76 FR 48208; August 8, 2011), EPA identified linkages between upwind states and downwind nonattainment and maintenance receptors in the CSAPR Update. See 81 FR 74518 (October 26, 2016).

In its January 31, 2013 infrastructure-SIP submission to address the 2008 ozone NAAQS, the Utah Division of Air Quality (UDAQ) addressed 110(a)(2)(D)(i)(I) by citing EPA Administrator Gina McCarthy's November 19, 2012 memo  4 which outlined EPA's intention to abide by the decision of the United States Court of Appeals for the District of Columbia Circuit (D.C. Circuit) in EME Homer City Generation, L.P. v. E.P.A., 696 F.3d 7 (D.C. Cir. 2012)). The EME Homer City decision addressed the original CSAPR rulemaking promulgated by EPA to address the interstate transport requirements under section 110(a)(2)(D)(i)(I) with respect to the 1997 ozone NAAQS, the 1997 fine particulate matter (PM 2.5 ) NAAQS, and the 2006 PM 2.5 NAAQS. Among other things, the D.C. Circuit held that states did not have an obligation to submit SIPs addressing section 110(a)(2)(D)(i)(I) interstate transport requirements as to any NAAQS until EPA first quantified each state's emissions reduction obligation. Id. at 30-31. In its submission, UDAQ noted that EPA had not quantified Utah's transport obligation as to the 2008 ozone NAAQS and that Utah's infrastructure SIP was therefore adequate with regard to CAA section 110(a)(2)(D)(i)(I).

Subsequent to the UDAQ submission, on April 29, 2014, the U.S. Supreme Court reversed and remanded the D.C. Circuit's EME Homer City decision on CSAPR and held, among other things, that under the plain language of the CAA, states must submit SIPs addressing interstate transport requirements of CAA section 110(a)(2)(D)(i)(I) within three years of the promulgation of a new or revised NAAQS, regardless of whether EPA first provides guidance, technical data or rulemaking to quantify the state's obligation. See EPA v. EME Homer City Generation, L.P., 134 S. Ct. 1584, 1601 (2014). UDAQ therefore additionally addressed 110(a)(2)(D)(i)(I) prongs 1 and 2 for the 2008 ozone NAAQS as part of its December 22, 2015 infrastructure submission that otherwise addressed the 2012 PM 2.5 NAAQS.

In its December 22, 2015 infrastructure submission, UDAQ acknowledged the changed legal landscape, and asserted that emissions from the State did not significantly contribute to nonattainment or interfere with maintenance of the 2008 ozone NAAQS in any other state. UDAQ cited air quality modeling assessing interstate transport of ozone that was released as part of EPA's August 4, 2015 NODA, and explained that it did not consider Utah's modeled contribution levels to nonattainment and maintenance receptors in the Denver, Colorado area and in southern California to be significant.

On October 19, 2016, EPA took a final action disapproving the prong 2 portion of both submissions for the 2008 ozone NAAQS. See 81 FR 71991. 5 This disapproval was largely based on the 2016 air quality modeling included with the final CSAPR Update, which projected that contributions from Utah would interfere with maintenance with respect to three maintenance receptors in the Denver, Colorado area in 2017. Id. at 71992. This disapproval established a 2-year deadline, under CAA section 110(c), for EPA to promulgate a federal implementation plan (FIP) or approve a SIP that meets the requirements of prong 2 of the interstate transport provision for the 2008 ozone NAAQS for Utah. 6

On January 29, 2020, Utah submitted an infrastructure SIP submission (“2020 submission”) to address the deficiencies identified in EPA's October 19, 2016, disapproval. Specifically, the 2020 submission addressed prong 2 for the 2008 ozone NAAQS as part of an infrastructure SIP that otherwise addressed the 2015 ozone NAAQS. In this proposed action, EPA is only addressing the 2008 ozone NAAQS prong 2 portion of the 2020 submission. 7 In the 2020 submission, UDAQ relied, in part, on updated EPA air quality modeling. Below, EPA provides further detail on the updated air quality modeling used by UDAQ and subsequent iterations that were developed following the State's 2020 submission.

In general, EPA has performed nationwide air quality modeling to project ozone design values which are used in combination with measured data to identify nonattainment and maintenance receptors at step 1. To quantify the contribution of emissions from individual upwind states on 2023 and 2026 ozone design values for the identified downwind nonattainment and maintenance receptors at step 2, EPA has performed multiple iterations of nationwide, state-level ozone source apportionment modeling for 2023 and 2026. The source apportionment modeling projected contributions to ozone at receptors from precursor emissions of anthropogenic nitrogen oxides (NO X ) and volatile organic compounds (VOCs) in individual upwind states.

EPA has released several documents containing projected ozone design values, contributions, and information relevant to air agencies for evaluation of interstate transport with respect to the ozone NAAQS. First, on January 6, 2017, EPA published a NODA in which the Agency requested comment on preliminary interstate ozone transport data including projected ozone design values and interstate contributions for 2023 using a 2011 base year platform. 8 In the 2017 NODA, EPA used the year 2023 as the analytic year for this preliminary modeling because this year aligns with the expected attainment year for Moderate ozone nonattainment areas for the 2015 8-hour ozone NAAQS. 9 On October 27, 2017, EPA released a memorandum (October 2017 memorandum) containing updated modeling data on receptors for 2023, which incorporated changes made in response to comments on the 2017 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. 10 EPA notes that UDAQ relied upon 2023 modeling receptor data released with October 2017 memorandum in developing its 2020 SIP submission.

On March 27, 2018, EPA issued a memorandum (March 2018 memorandum) noting that the same 2023 modeling data released in the October 2017 memorandum could also be useful for identifying potential downwind air quality problems with respect to the 2015 ozone NAAQS at step 1 of the 4-step interstate transport framework. 11 The March 2018 memorandum also included the then newly available contribution modeling data for 2023 to assist states in evaluating their impact on potential downwind air quality problems for the 2015 8-hour ozone NAAQS under step 2 of the 4-step interstate transport framework. 12 Utah did not reference the modeling data shared in the March 2018 memorandum within the 2008 ozone NAAQS interstate transport prong 2 portion of their January 29, 2020 submission.

Following the release of the modeling data shared in the March 2018 memorandum, EPA performed updated modeling using a 2016-based emissions modeling platform ( i.e. 2016 Version 1 Emissions Platform Modeling, or “2016v1”). This emissions platform was developed under the EPA/Multi-Jurisdictional Organization (MJO)/state collaborative project. 13 This collaborative project was a multi-year joint effort by EPA, MJOs, and states to develop a new, more recent emissions platform as an improvement over the dated 2011-based platform that EPA had used to project ozone design values and contribution data provided in the 2017 and 2018 memoranda. 14   15

Following the final Revised CSAPR Update, EPA made further updates to the 2016-based emissions platform to include updated onroad mobile emissions and updated emissions for electric generating units (EGUs) that reflect the reductions from the Revised CSAPR Update, and other inventory-data improvements. 16   17 EPA performed air quality modeling using the 2016v2 emissions to provide projections of ozone design values and contributions in 2023 and 2026 that reflect the effects on air quality of the 2016v2 emissions platform.

In response to comments on the 2016v2 emissions inventories, EPA made a number of updates to the 2016v2 inventories and model design to construct another emissions platform, 2016v3, which was used to update the air quality modeling. EPA used this 2016v3 updated modeling to inform a rulemaking taking final action on 21 interstate transport SIP submissions for the 2015 ozone NAAQS and to inform EPA's FIP addressing those disapprovals. 18   19 Additional details related to the updated 2016v3 emissions platform are located in the Technical Support Document (TSD) titled “Preparation of Emissions Inventories for the 2016v3 North American Emissions Modeling Platform.”  20

In this proposed action, in addition to considering the modeling and other information submitted by Utah, EPA relies on the modeling for 2026 using the updated 2016v3 emissions platform, which will generally be referenced within this action as the “2016v3 modeling.” In using these modeling results, EPA is taking into account the most current and technically appropriate information for this proposed rulemaking. In this proposed action, EPA is accepting public comment on the application of the 2016v3 modeling solely as it relates to Utah's interstate transport obligations for the 2008 ozone NAAQS. EPA is not reopening for comment any other aspects of the 2016v3 modeling or the use of this modeling in relation to any other state or regulatory action. Any comments received on the modeling that are not relevant to the evaluation of Utah's interstate transport obligations will be treated as beyond the scope of this action.

States and EPA must implement the interstate transport provision in a manner “consistent with the provisions of [title I of the CAA.]” See CAA section 110(a)(2)(D)(i)(I). This requires, among other things, that these obligations are addressed consistently with the timeframes for downwind areas to meet their CAA obligations. With respect to ozone NAAQS, under CAA section 181(a), this means obligations must be addressed “as expeditiously as practicable” and no later than the schedule of attainment dates provided in CAA section 181(a)(1). Several D.C. Circuit court decisions address the issue of the relevant analytic year for the purposes of evaluating ozone transport air-quality problems. On September 13, 2019, the D.C. Circuit issued a decision in Wisconsin vs EPA, remanding the CSAPR Update to the extent that it failed to require upwind states to eliminate their significant contribution by the next applicable attainment date by which downwind states must come into compliance with the NAAQS, as established under CAA section 181(a). See Wisconsin v. EPA, 938 F.3d 303, 313 (D.C. Cir. 2019).

On May 19, 2020, the D.C. Circuit issued a decision in Maryland v. EPA that cited the Wisconsin decision in holding that EPA must assess the impact of interstate transport on air quality at the next downwind attainment date, including Marginal area attainment dates, in evaluating the basis for EPA's denial of a petition under CAA section 126(b) Maryland v. EPA, 958 F.3d 1185, 1203-04 (D.C. Cir. 2020) ( Maryland ). The court noted that “section 126(b) incorporates the Good Neighbor Provision,” and, therefore, “EPA must find a violation [of section 126] if an upwind source will significantly contribute to downwind nonattainment 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). EPA interprets the court's holding in Maryland as requiring the states and the Agency to assess downwind air quality as expeditiously as practicable and no later than the next applicable attainment date, 21 which is currently the 2008 ozone NAAQS Severe area attainment date of July 20, 2027 under CAA section 181. 22 Thus, 2026 is currently the appropriate year for analysis of interstate transport obligations for the 2008 ozone NAAQS because the 2026 ozone season is the last relevant ozone season during which achieved emission reductions in linked upwind states could assist downwind states with meeting the July 20, 2027 Severe area attainment date.

UDAQ submitted an infrastructure SIP submission to EPA addressing the CAA section 110(a)(2)(D)(i)(I) prong 2 interstate transport requirement for the 2008 8-hour ozone NAAQS on January 29, 2020. 23 In this submission, UDAQ concluded it will not interfere with maintenance of the 2008 ozone NAAQS in any other state. 24 To support this conclusion, UDAQ used EPA's 4-step framework. For steps 1 and 2, Utah specifically noted three Denver-area ozone monitors (site IDs 80590006, 80590011, and 80350004) that were projected by the CSAPR Update modeling to be maintenance receptors for the 2008 ozone NAAQS (in 2017), and to which Utah interfered with maintenance, 25 were all projected to attain the 2008 ozone NAAQS in 2023 in the October 2017 memorandum modeling. 26 The State asserted that, because they did not contribute to any downwind air quality problem at step 2 of the 4-step framework, they were not required to complete steps 3 or 4.

UDAQ also referenced EPA's July 3, 2018 approval of the State of Colorado's attainment demonstration for the 2008 8-Hour Ozone Standard for the Denver Metro/North Front Range Moderate nonattainment area (hereon “DMNFR attainment demonstration”). 27 Utah cited language from EPA's proposed approval of Colorado's DMNFR attainment demonstration, in which EPA acknowledged that certain high ozone days from 2009 to 2013 that were likely influenced by atypical activities such as wildfire or stratospheric intrusion “do affect the baseline design values and thus affect the model projected future design value for 2017” and that “all future [2017] design values are below the 0.75 ppb NAAQS . . . when data possibly influenced by atypical activities are excluded in the calculation of the 2011 design values.”  28 Utah asserted that, based on EPA's approval of the DMNFR attainment demonstration, it would be appropriate to consider the three Denver-area receptors to which Utah was linked in the CSAPR Update modeling to be “attainment receptors,” rather than maintenance receptors. 29 Utah asserted that Colorado's attainment demonstration shows that Utah would not interfere with maintenance of the 2008 ozone NAAQS at the three monitors. 30

Lastly, UDAQ notes that they have benefited from, but does not rely on or seek adoption into their SIP, actions resulting in reductions in ozone precursor pollutants (NO X and VOC) in the state. 31

UDAQ concluded, based on the above, that Utah does not interfere with maintenance of the 2008 ozone NAAQS in any downwind state. 32

EPA is proposing to find that Utah's SIP meets the State's obligations with respect to prohibiting emissions that interfere with maintenance of the 2008 8-hour ozone NAAQS in any other state. EPA's decision to propose approval of this portion of Utah's January 29, 2020 SIP submission is based on our evaluation of the SIP using the 4-step interstate transport framework, which is the same framework Utah used (Utah 2020 SIP Submission at 11-12).

At step 1 and step 2 of the 4-step interstate transport framework, UDAQ relied on EPA modeling released with the CSAPR Update, and in the October 2017 memorandum, to identify nonattainment and maintenance receptors and upwind state linkages to those receptors in 2023. In this proposal, EPA has also considered the Agency's most recently available modeling (2016v3) to identify upwind contributions and linkages to downwind air quality problems in 2026, which serves to verify Utah's conclusion in its submission.

As described in section II. of this proposal, EPA performed air quality modeling to project ozone design values and contributions for 2023 and 2026 using the 2016v3 emissions platform. EPA proposes to rely on this modeling in evaluating Utah's transport SIP submission, and specifically the 2026 projections given that year's relevance to 2008 ozone attainment planning as discussed in section III. The design values and contributions from the updated modeling were examined to determine if Utah interferes with maintenance at any downwind nonattainment or maintenance receptor. The data  33 indicates that the highest contributions from Utah to downwind nonattainment or maintenance-only receptors for the 2008 ozone NAAQS, all of which are located in the state of California, are 0.13 ppb and 0.07 ppb, respectively, in 2026. 34

EPA's evaluation of 2026 projections indicates that the contribution to ozone concentrations in other states from emissions from sources in Utah will not interfere with maintenance of the 2008 ozone NAAQS. Thus, EPA proposes to find that the State does not impact downwind air quality problems at step 2 of the 4-step framework, and therefore does not warrant further review and analysis at steps 3 and 4. The results of EPA's evaluation are consistent with the conclusion drawn by UDAQ in its 2020 SIP submission that emissions from sources in Utah will not interfere with maintenance of the 2008 ozone NAAQS in any other state. For these reasons, EPA is proposing to approve the 2008 ozone portion of Utah's 2020 SIP submission with regard to the interstate transport prong 2 requirement of CAA section 110(a)(2)(D)(i)(I).

Based on EPA's evaluation of the impact of air emissions from Utah to downwind states using 2026 analytic year modeling as described in this document, EPA is proposing to approve Utah's January 29, 2020 SIP submission as meeting the prong 2 interstate transport requirement of CAA section 110(a)(2)(D)(i)(I) for the 2008 ozone NAAQS.

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve state choices, provided that they meet the criteria of the CAA. Accordingly, this action merely proposes to approve state law as meeting Federal requirements and does not impose additional requirements beyond those imposed by state law. For that reason, this action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Orders 12866 (58 FR 51735, October 4, 1993);

• Is not subject to Executive Order 14192 (90 FR 9065, February 6, 2025) because SIP actions are exempt from review under Executive Order 12866;

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Public Law 104-4);

• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);

• Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a state program;

• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001);

• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA; and

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the proposed rule does not have Tribal implications and will not impose substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

Throughout this document wherever “we,” “us,” or “our” is used, we mean the EPA.

On June 2, 2010, the EPA established a revised primary 1-hour SO 2 NAAQS with a level of 75 parts per billion (ppb), based on a 3-year average of the annual 99th percentile of daily maximum 1-hour average concentrations. 1 CAA section 110(a)(1) requires all states to submit, within three years after promulgation of a new or revised NAAQS, SIP submissions to provide for the implementation, maintenance, and enforcement of the NAAQS. 2 The EPA has historically referred to these SIPs as “infrastructure SIPs.” Specifically, section 110(a)(1) provides the procedural and timing requirements for SIP submissions. Section 110(a)(2) lists specific elements that all states must meet related to a newly established or revised NAAQS, such as requirements for monitoring, basic program requirements, and legal authority that are designed to assure attainment and maintenance of the NAAQS.

Section 110(a)(2)(D)(i)(I) of the CAA requires a state's SIP to include provisions prohibiting any source or other type of emissions activity in the state from emitting any air pollutant in amounts that will contribute significantly to nonattainment, or interfere with maintenance, of the NAAQS in any other state. The EPA has long interpreted this language to enact a “functional prohibition” on certain emissions from upwind states, necessitating the EPA's independent assessment of whether those emissions will occur or have been adequately controlled in the state where they originate. 3 The EPA often refers to these requirements as Prong 1 (significant contribution to nonattainment of the NAAQS) and Prong 2 (interference with maintenance of the NAAQS). We are addressing Prongs 1 and 2 in this action. All other applicable infrastructure SIP requirements of the Texas SIP submission are addressed in separate rulemakings.

In this proposed action, the EPA has considered information from the 2010 1-hour SO 2 NAAQS designations process which is discussed in more detail in section III.C. of this document. For this reason, a brief summary of the EPA's designations process for the 2010 1-hour SO 2 NAAQS is included here. 4

After the promulgation of a new or revised NAAQS, the EPA is required to designate areas as “nonattainment,” “attainment,” or “unclassifiable” pursuant to section 107(d)(1)-(2) of the CAA. The process for designating areas following promulgation of a new or revised NAAQS is contained in section 107(d) of the CAA. The CAA requires the EPA to complete the initial designations process within two years of promulgating a new or revised standard. If the Administrator has insufficient information to make these designations by that deadline, the EPA has the authority to extend the deadline for completing designations by up to one year.

The EPA promulgated the 2010 1-hour SO 2 NAAQS on June 2, 2010. See 75 FR 35520 (June 22, 2010). The EPA Administrator signed the first round  5 of designations (“Round 1”)  6 for the 2010 1-hour SO 2 NAAQS on July 25, 2013, designating 29 areas in 16 States as nonattainment for the 2010 1-hour SO 2 NAAQS. See 78 FR 47191 (August 5, 2013). The EPA Administrator signed Federal Register documents for Round 2 designations  7 on June 30, 2016 (81 FR 45039 (July 12, 2016)) and on November 29, 2016 (81 FR 89870 (December 13, 2016)). Round 3 designations  8 were signed on December 21, 2017 (83 FR 1098 (January 9, 2018)) and March 28, 2018 (83 FR 14597(April 5, 2018)). Round 4 designations  9 were signed on December 21, 2020 (86 FR 16055 (March 26, 2021))  10 and April 8, 2021 (86 FR 19576 (April 14, 2021)). 11

For Texas, the EPA designated Atascosa, Fort Bend, Goliad, Lamb, Limestone, McLennan, and Robertson Counties as unclassifiable/attainment and Potter County as unclassifiable in Round 2. Designations for Freestone, Anderson, Milam, Rusk, Gregg, Panola, and Titus counties were delayed. Final designations for these counties were published on December 13, 2016 (81 FR 89870). Nonattainment designations were promulgated for three areas: (1) portions of Freestone and Anderson Counties; (2) portions of Rusk and Panola Counties;  12 and (3) a portion of Titus County. An unclassifiable designation was promulgated for Milam County. After these designations were promulgated, the EPA underwent additional actions related to the area designations in TX. By the time Round 2 was completed, Milam County had been redesignated as attainment/unclassifiable.

In Round 4 the EPA designated the remaining counties—Bexar, Jefferson Robertson, and Titus as attainment/unclassifiable; Harrison and Orange as unclassifiable; and Howard, Hutchinson, and Navarro as nonattainment.

Although SO 2 is emitted from a similar universe of point and nonpoint sources as directly emitted fine particulate matter (PM 2.5 ) and the precursors to ozone and PM 2.5 , interstate transport of SO 2 is unlike the transport of PM 2.5 or ozone, which disperse over a wide area and can contribute to nonattainment or maintenance issues hundreds of miles from precursor-emitting sources or activities. SO 2 emissions usually do not undergo long-range transport in the atmosphere. The transport of SO 2 relative to the 2010 1-hour SO 2 NAAQS is more analogous to the transport of lead (Pb) relative to the Pb NAAQS in that emissions of SO 2 typically result in 1-hour pollutant impacts of greatest concern near the emissions source. However, ambient 1-hour concentrations of SO 2 do not decrease as quickly with distance from the source as do 3-month average concentrations of Pb, because SO 2 gas is not removed by deposition as rapidly as are Pb particles. Emitted SO 2 has wider-ranging impacts than emitted Pb, but it does not have such wide-ranging (far downwind) impacts that treatment in a manner similar to ozone or PM 2.5 would be appropriate. Accordingly, the approaches that EPA has adopted for ozone or PM 2.5 transport are too regionally focused, and the approach for Pb transport is too tightly circumscribed to the source, to be appropriate for assessing SO 2 transport. SO 2 transport is therefore a unique case and necessitates an analytical approach that examines potential impacts that are further from the source than would be examined for Pb transport but less regional in scope than ozone or PM transport.

In this proposed rulemaking, and consistent with prior SO 2 transport analyses, the EPA focused on a 50 kilometer (km)-wide zone around sources of interest because the physical properties of SO 2 result in relatively localized pollutant impacts near an emissions source that drop off with distance. Given the properties of SO 2 , the EPA believes that significant impacts in a downwind state are unlikely at distances greater than 50 km from a source and thus, we are focusing our review on areas within 50 km of the state lines. This scale of analysis is consistent with the “urban scale” which is the largest appropriate spatial scale for SO 2 monitors and is useful for assessing SO 2 transport and trends in area-wide air quality. 13

As discussed in section III, and in further detail in the Technical Support Document (TSD) for this action, the EPA reviewed Texas' SO 2 SIP submittal, and the particular HYSPLIT back trajectories Texas relied upon in its SIP. The State's submission did not have sufficient information to fully assess whether Texas was meeting its CAA good neighbor requirements for the 2010 SO 2 NAAQS. Therefore, we elected to review and assess other available information regarding SO 2 emissions and air quality in Texas to assist in our own evaluation. We independently analyzed such information to determine whether Texas meets the interstate transport requirements described in the CAA. 14

Consistent with our prior evaluations of other states' SO 2 transport obligations, we conducted a weight of evidence (WOE) analysis evaluating several sources of information, including current air quality data from monitors as well as available emissions and/or source modeling for sources in Texas and in neighboring states within 50 km of the Texas border. A WOE approach can be appropriate in instances, such as this case, to determine whether SO 2 emissions from Texas contribute to nonattainment or maintenance issues in adjoining states. A WOE analysis that is based solely on available data may not be sufficient in all instances for evaluating interstate SO 2 transport, and additional analysis may be necessary. Further, the term “WOE” does not establish the legal or technical meaning for what constitutes significant contribution to nonattainment or interference with maintenance for the 2010 SO 2 NAAQS. Rather, the term refers to the gathering and consideration of a wide range of information, on a case-by-case basis, to make a determination regarding whether a statutory or regulatory requirement is met.

In other SO 2 transport actions, the EPA has typically been able to use a WOE analysis to reach a conclusion that there are no SO 2 nonattainment or maintenance issues in the relevant areas of other states, or that no sources in the upwind state are contributing to those issues. If the available evidence indicated, however, that an upwind source, sources, or emissions activities were contributing to an out-of-state SO 2 nonattainment or maintenance problem, then further analysis and a regulatory determination would be necessary concerning what amount of those emissions, if any, constituted “significant contribution” under Prong 1 or Prong 2 of the good neighbor provision.

We find that there is sufficient information to support the EPA's proposed determination that, under baseline conditions and likely future emissions scenarios, no Texas sources are contributing or will contribute to any out-of-state SO 2 nonattainment or maintenance concerns, and therefore it is not necessary for the purposes of this action to render a determination concerning what amount of emissions would be “significant” and therefore subject to prohibition under the good neighbor provision. 15

On April 23, 2013, the Texas Commission on Environmental Quality (TCEQ) submitted to the EPA a SIP revision to address the requirements of CAA section 110(a)(1) and (2), including section 110(a)(2)(D)(i)(I), that addresses 2010 SO 2 interstate transport requirements Prongs 1 and 2.

On January 11, 2016 (81 FR 1127), the EPA approved most elements of the Texas infrastructure SIP submittal, but we took no action on the interstate transport provisions of section 110(a)(2)(D)(i)(I) pertaining to Texas' significant contribution to nonattainment (Prong 1) and interference with maintenance (Prong 2) of the NAAQS in other states or the portion of 110(a)(2)(D)(i)(II) regarding visibility protection (Prong 4).

In the portions of Texas' 2013 submittal addressing interstate transport (for section 110(a)(2)(D)(i)(I)), the State relied on the back trajectory analysis  16 to assess the impacts of SO 2 emissions emitted in Texas and transported to neighboring states. Texas used the HYSPLIT  17 model version 4 (2012) developed by the National Oceanic and Atmospheric Administration (NOAA) to construct back trajectories, where ambient air network monitors with the highest observed SO 2 values were chosen as receptor sites for the back trajectory analysis. The receptor sites that Texas chose for this analysis were a single monitor in each of the surrounding states, sites which were not necessarily sited to characterize high or maximum SO 2 concentrations (especially from large emitting SO 2 sources) reaching into other states to determine whether Texas meets the interstate transport requirement described in the CAA. Texas chose receptor locations for the HYSPLIT modeling that were very distant from Texas and the SO 2 sources within Texas.

In the submittal, Texas acknowledged that the back trajectory analysis does not (and cannot) assume a link between a mean-trajectory path and an SO 2 concentration. A mean-trajectory-path provides only an indication/prediction of the direction (and locations over which) a parcel of air might have traveled and that more analysis would be needed to determine the sources and levels of contribution of air pollutants to a particular location. Texas also stated that the back trajectory HYSPLIT method quantifies the directions and frequency of air traveling to the monitor but cannot identify the precise routes of pollutant particle travel or its concentrations in the air parcels. 18

While HYSPLIT can be informative for evaluating air quality issues, the utility and accuracy of back trajectory analysis depends on the quality and resolution of the meteorological data used and should be coupled with other information on emissions data sources and ambient pollution levels near borders or across borders. Texas' submission neither evaluated SO 2 emissions levels or likely levels of contribution from Texas sources to the receptor locations it used for its HYSPLIT analysis, nor established that those receptor locations were adequate to ensure SO 2 nonattainment and maintenance issues in other states were properly identified. Therefore, the EPA elected to review and assess other available information, as described below and in more detail in the TSD for this action, regarding SO 2 emissions and air quality for sources in Texas to assist in our evaluation and to fully assess whether Texas was meeting its CAA good neighbor obligations for the 2010 SO 2 NAAQS.

For this CAA section 110 (a)(2)(D)(i)(I) evaluation of the 2010 SO 2 NAAQS, the EPA conducted a WOE analysis for Prong 1 and Prong 2 separately, 19 evaluating available information such as air quality, emission sources, modeling, and emission trends in Texas and the states that border Texas. To identify which sources and emissions activities in Texas could potentially impact downwind air quality in other states with respect to the 2010 1-hour SO 2 NAAQS, the EPA used information in the EPA's National Emissions Inventory (NEI)  20 and Emissions Inventory System (EIS). 21 The NEI is a comprehensive and detailed estimate of air emissions for criteria pollutants, criteria pollutant precursors, and hazardous air pollutants from air emissions sources, updated every three years using information provided by the states and other information available to the EPA. For analyses, we largely relied on data from the 2020 NEI, because it is the most recently available, complete, and quality assured dataset. However, in evaluating emissions trends, both state-wide and at the facility level, the EPA also considered data from prior NEI reports and EIS queries, as part of the overall WOE analysis.

As shown in table 1, the majority of SO 2 emissions in Texas originate from point sources. In 2020, total SO 2 emissions from point sources in Texas comprised approximately 77 percent of the total SO 2 emissions in the State. Non-point sources, on road, and non-road emissions sources contribute to a much smaller portion of total SO 2 emissions; these emissions are also more dispersed throughout the State and are therefore unlikely to contribute to high ambient concentrations of SO 2 when compared to point source contributions. Further analysis  22 shows that facilities with reported emissions greater than 100 tons per year (tpy) represent approximately 4 percent of the total number of Texas SO 2 point sources but are responsible for 184,480 tons of SO 2 or 96 percent of the total 2020 SO 2 emissions.23 Based on this analysis, the EPA focused our WOE analysis on SO 2 emissions from Texas' larger point sources ( i.e. point sources emitting over 100 tpy of SO 2 ) that are located within 50 km of one or more state borders.

Throughout this document, “we,” “us,” and “our” refer to the EPA.

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). 1 The EPA is now withdrawing that proposal and is proposing to fully approve the Plan for the reasons described in this document.

A detailed history and background of the regional haze program is provided in multiple prior EPA proposal actions. 2 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. 3 The following is an abbreviated history and background of the regional haze program and 2017 RHR as it applies to the current action.

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. 4 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.”  5

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.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., sulfur dioxide (SO 2 ), nitrogen oxides (NO X ), and, in some cases, volatile organic compounds (VOC) and ammonia (NH 3 )). Fine particle precursors react in the atmosphere to form fine particulate matter (PM 2.5 ), which impairs visibility by scattering and absorbing light. Visibility impairment reduces the perception of clarity and color, as well as visible distance. 6

To address regional haze visibility impairment, the 1999 RHR established an iterative planning process that requires both states in which Class I areas are located and states “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to periodically submit SIP revisions to address such impairment. 7

On January 10, 2017, the EPA promulgated revisions to the RHR, that apply for the second and subsequent implementation periods. 8

Because the air pollutants and pollution affecting visibility in Class I areas can be transported over long distances, successful implementation of the regional haze program requires long-term, regional coordination among multiple jurisdictions and agencies that have responsibility for Class I areas and the emissions that impact visibility in those areas. To address regional haze, states need to develop strategies in coordination with one another, considering the effect of emissions from one jurisdiction on the air quality in another. Five regional planning organizations (RPOs), 9 which include representation from state and tribal governments, the EPA, and Federal Land Managers (FLMs), were developed in the lead-up to the first implementation period to address regional haze. RPOs evaluate technical information to better understand how emissions from State and Tribal land impact Class I areas across the country, pursue the development of regional strategies to reduce emissions of particulate matter and other pollutants leading to regional haze, and help states meet the consultation requirements of the RHR. California is a member of the Western Regional Air Partnership (WRAP)  10 RPO, which is a collaborative effort of state governments, Tribal governments, and various Federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the western corridor of the United States.

Under the CAA and the EPA's regulations, all 50 states, the District of Columbia, and the U.S. Virgin Islands were required to submit regional haze SIP revisions satisfying the applicable requirements for the second implementation period of the regional haze program by July 31, 2021. Each state's SIP must contain a long-term strategy for making reasonable progress toward meeting the national goal of remedying any existing and preventing any future anthropogenic visibility impairment in Class I areas. 11 To this end, 40 CFR 51.308(f) lays out the process by which states determine what constitutes their long-term strategies, with the order of the requirements in 40 CFR 51.308(f)(1) through (3) generally mirroring the order of the steps in the reasonable progress analysis  12 and (f)(4) through (6) containing additional, related requirements. Broadly speaking, a state first must identify the Class I areas within the state and determine the Class I areas outside the state in which visibility may be affected by emissions from the state. These are the Class I areas that must be addressed in the state's long-term strategy. 13 For each Class I area within its borders, a state must then calculate the baseline (five-year average period of 2000-2004), current, and natural visibility conditions ( i.e., visibility conditions without anthropogenic visibility impairment) for that area, as well as the visibility improvement made to date and the “uniform rate of progress” (URP). The URP is the linear rate of progress needed to attain natural visibility conditions, assuming a starting point of baseline visibility conditions in 2004 and ending with natural conditions in 2064. This linear interpolation is used as a tracking metric to help states assess the amount of progress they are making towards the national visibility goal over time in each Class I area. 14 Each state having a Class I area and/or emissions that may affect visibility in a Class I area must then develop a long-term strategy that includes the enforceable emissions limitations, compliance schedules, and other measures that are necessary to make reasonable progress in such areas. A reasonable progress determination is based on applying the four factors in CAA section 169A(g)(1) to sources of visibility-impairing pollutants that the state has selected to assess for controls for the second implementation period. Additionally, as further explained below, the RHR at 40 CFR 51.308(f)(2)(iv) separately provides five “additional factors”  15 that states must consider in developing their long-term strategies. 16 A state evaluates potential emissions reduction measures for those selected sources and determines which are necessary to make reasonable progress. Those measures are then incorporated into the state's long-term strategy. After a state has developed its long-term strategy, it then establishes Reasonable Progress Goals (RPGs) for each Class I area within its borders by modeling the visibility impacts of all reasonable progress controls at the end of the second implementation period, i.e., in 2028, as well as the impacts of other requirements of the CAA. The RPGs include reasonable progress controls not only for sources in the state in which the Class I area is located, but also for sources in other states that contribute to visibility impairment in that area. The RPGs are then compared to the baseline visibility conditions and the URP to ensure that progress is being made towards the statutory goal of preventing any future and remedying any existing anthropogenic visibility impairment in Class I areas. 17 There are additional requirements in the rule, including FLM consultation, that apply to all visibility protection SIPs and SIP revisions. 18

While states have discretion to choose any source selection methodology that is reasonable, whatever choices they make should be reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that a state's SIP submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.” 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, must also be appropriately documented, as required by 40 CFR 51.308(f)(2)(iii).

Once a state has selected the set of sources, the next step is to determine the emissions reduction measures for those sources that are necessary to make reasonable progress for the second implementation period. 19 This is accomplished by considering the four factors—“the costs of compliance, the time necessary for compliance, and the energy and nonair quality environmental impacts of compliance, and the remaining useful life of any existing source subject to such requirements.”  20 The EPA has explained that the four-factor analysis is an assessment of potential emissions reduction measures ( i.e., control options) for sources; “use of the terms `compliance' and `subject to such requirements' in section 169A(g)(1) can be read that Congress intended the relevant determination to be the requirements with which sources would have to comply to satisfy the CAA's reasonable progress mandate.”  21 Thus, for each source it has selected for four-factor analysis, 22 a state must consider a “meaningful set” of technically feasible control options for reducing emissions of visibility impairing pollutants. 23

The EPA has also explained that, in addition to the four statutory factors, states have flexibility under the CAA and RHR to reasonably consider visibility benefits as an additional factor alongside the four statutory factors. 24 Ultimately, while states have discretion to reasonably weigh the factors and to determine what level of control is needed, 40 CFR 51.308(f)(2)(i) provides that a state “must include in its implementation plan a description of . . . how the four factors were taken into consideration in selecting the measure for inclusion in its long-term strategy.”

As explained above, 40 CFR 51.308(f)(2)(i) requires states to determine the emissions reduction measures for sources that are necessary to make reasonable progress by considering the four factors. Pursuant to 40 CFR 51.308(f)(2), measures that are necessary to make reasonable progress towards the national visibility goal must be included in a state's long-term strategy and in its SIP. If the outcome of a four-factor analysis is that an emissions reduction measure is necessary to make reasonable progress towards remedying existing or preventing future anthropogenic visibility impairment, that measure must be included in the SIP.

The characterization of information on each of the factors is also subject to the documentation requirement in section 51.308(f)(2)(iii). The reasonable progress analysis is a technically complex exercise, and also a flexible one that provides states with bounded discretion to design and implement approaches appropriate to their circumstances. Given this flexibility, 40 CFR 51.308(f)(2)(iii) plays an important function in requiring a state to document the technical basis for its decision making so that the public and the EPA can comprehend and evaluate the information and analysis the state relied upon to determine what emissions reduction measures must be in place to make reasonable progress. The technical documentation must include the modeling, monitoring, cost, engineering, and emissions information on which the state relied to determine the measures necessary to make reasonable progress.

Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors”  25 that states must consider in developing their long-term strategies: (1) Emissions reductions due to ongoing air pollution control programs, including measures to address reasonably attributable visibility impairment; (2) measures to reduce the impacts of construction activities; (3) source retirement and replacement schedules; (4) basic smoke management practices for prescribed fire used for agricultural and wildland vegetation management purposes and smoke management programs; and (5) the anticipated net effect on visibility due to projected changes in point, area, and mobile source emissions over the period addressed by the long-term strategy.

Because the air pollution that causes regional haze crosses state boundaries, 40 CFR 51.308(f)(2)(ii) requires a state to consult with other states that also have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area. If a state, pursuant to consultation, agrees that certain measures ( e.g., a certain emissions limitations) are necessary to make reasonable progress at a Class I area, it must include those measures in its SIP. 26 Additionally, the RHR requires that states that contribute to visibility impairment at the same Class I area consider the emissions reduction measures the other contributing states have identified as being necessary to make reasonable progress for their own sources. 27 If a state has been asked to consider or adopt certain emissions reduction measures, but ultimately determines those measures are not necessary to make reasonable progress, that state must document in its SIP the actions taken to resolve the disagreement. 28

Reasonable progress goals “measure the progress that is projected to be achieved by the control measures states have determined are necessary to make reasonable progress based on a four-factor analysis.”  29

For the second implementation period, the RPGs are set for 2028. Reasonable progress goals are not enforceable targets. 30 While states are not legally obligated to achieve the visibility conditions described in their RPGs, 40 CFR 51.308(f)(3)(i) requires that “[t]he long-term strategy and the reasonable progress goals must provide for an improvement in visibility for the most impaired days since the baseline period and ensure no degradation in visibility for the clearest days since the baseline period.”

RPGs may also serve as a metric for assessing the amount of progress a state is making towards the national visibility goal. To support this approach, the RHR requires states with Class I areas to compare the 2028 RPG for the most impaired days to the corresponding point on the URP line (representing visibility conditions in 2028 if visibility were to improve at a linear rate from conditions in the baseline period of 2000-2004 to natural visibility conditions in 2064). If the most impaired days RPG in 2028 is above the URP ( i.e., if visibility conditions are improving more slowly than the rate described by the URP), each state that contributes to visibility impairment in the Class I area must demonstrate, based on the four-factor analysis required under 40 CFR 51.308(f)(2)(i), that no additional emissions reduction measures would be reasonable to include in its long-term strategy. 31 To this end, 40 CFR 51.308(f)(3)(ii) requires that each state contributing to visibility impairment in a Class I area that is projected to improve more slowly than the URP provide “a robust demonstration, including documenting the criteria used to determine which sources or groups [of] sources were evaluated and how the four factors required by paragraph (f)(2)(i) were taken into consideration in selecting the measures for inclusion in its long-term strategy.”

Section 51.308(f)(6) requires states to have certain strategies and elements in place for assessing and reporting on visibility. Individual requirements under this subsection apply either to states with Class I areas within their borders, states with no Class I areas but that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area, or both. Compliance with the monitoring strategy requirement may be met through a state's participation in the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network, which is used to measure visibility impairment caused by air pollution at the 156 Class I areas covered by the visibility program. 32

All states' SIPs must provide for procedures by which monitoring data and other information are used to determine the contribution of emissions from within the state to regional haze visibility impairment in affected Class I areas, as well as a statewide inventory documenting such emissions. 33 All states' SIPs must also provide for any other elements, including reporting, recordkeeping, and other measures, that are necessary for states to assess and report on visibility. 34

Section 51.308(f)(5) requires a state's regional haze SIP revision to address the requirements of paragraphs 40 CFR 51.308(g)(1) through (5) so that the plan revision due in 2021 will serve also as a progress report addressing the period since submission of the progress report for the first implementation period. The regional haze progress report requirement is designed to inform the public and the EPA about a state's implementation of its existing long-term strategy and whether such implementation is in fact resulting in the expected visibility improvement. 35 To this end, every state's SIP revision for the second implementation period is required to assess changes in visibility conditions and describe the status of implementation of all measures included in the state's long-term strategy, including BART and reasonable progress emissions reduction measures from the first implementation period, and the resulting emissions reductions. 36

Clean Air Act section 169A(d) requires that before a state holds a public hearing on a proposed regional haze SIP revision, it must consult with the appropriate FLM or FLMs; pursuant to that consultation, the state must include a summary of the FLMs' conclusions and recommendations in the notice to the public. Consistent with this statutory requirement, the RHR also requires that states “provide the [FLM] with an opportunity for consultation, in person and at a point early enough in the State's policy analyses of its long-term strategy emissions reduction obligation so that information and recommendations provided by the [FLM] can meaningfully inform the State's decisions on the long-term strategy.”  37 For the EPA to evaluate whether FLM consultation meeting the requirements of the RHR has occurred, the SIP submission should include documentation of the timing and content of such consultation. The SIP revision submitted to the EPA must also describe how the state addressed any comments provided by the FLMs. 38 Finally, a SIP revision must provide procedures for continuing consultation between the state and FLMs regarding the state's visibility protection program, including development and review of SIP revisions, five-year progress reports, and the implementation of other programs having the potential to contribute to impairment of visibility in Class I areas. 39

On December 19, 2024, the EPA published a notice of proposed rulemaking proposing partial approval and partial disapproval of the 2022 California Regional Haze Plan. 40 During the 45-day comment period, we received one comment letter opposing disapproval and five comment letters in support of disapproval. In this document, we are withdrawing our December 19, 2024 proposed disapproval. We are now reproposing the action as an approval based on a change in policy, as discussed in Section V of this document. Commenters who would like the EPA to consider any comments submitted on the December 19, 2024 proposal that are relevant to this proposed action must resubmit those comments during the comment period for this proposed action.

The EPA is now proposing to approve the 2022 California Regional Haze Plan because we have determined that it meets the applicable statutory and regulatory requirements. The Plan included evaluations, including information on the four CAA section 169(g)(1) factors as applied to mobile sources, and a four-factor analysis for a stationary source. California also considered historical emissions data, existing control technologies on major sources, and the large NO X reductions and visibility improvements that have already occurred in California and nearby Class I areas during the first and second planning periods. Because the State assessed the potential for additional measures, considered the four statutory factors, and the projected that 2028 visibility conditions for the most impaired days at all Class I areas influenced by emissions from California sources are below the URP, with one exception as discussed in section VI.C.4 below, the EPA proposes to find that the Plan meets the statutory and regulatory requirement to make reasonable progress towards the national visibility goal.

In this proposed action, the EPA notes that it is the Agency's policy, as announced in the EPA's recent proposed approval of the West Virginia Regional Haze SIP, that where visibility conditions for a Class I area impacted by a State for the most impaired days, are projected to be below the URP in 2028, and the State has considered the four statutory factors, the State has presumptively demonstrated reasonable progress for the second implementation period for that area. 41 The EPA acknowledges that this proposed action reflects a change in policy as to how the URP should be used in the evaluation of regional haze second planning period SIP revisions. However, the EPA finds that this policy aligns with the purpose of the statute and RHR, which is achieving “reasonable” progress, not maximal progress, toward Congress' natural visibility goal. In addition, this policy aligns with comments submitted by CARB during the public comment period on our initial proposal. 42

In developing the regulations required by CAA section 169A(b), the EPA established the concept of the URP, for each Class I area. The URP is determined by drawing a straight line from the measured 2000-2004 baseline conditions (in deciviews) for the 20 percent most impaired days at each Class I area to the estimated 20 percent most impaired days natural conditions (in deciviews) in 2064. From this linear regression, a URP value can be calculated for each year between 2004 and 2064. For each Class I area, there is a regulatory requirement to compare the projected visibility impairment represented by the RPG for the most impaired days at the end of each planning period to the URP ( e.g., in 2028 for the second planning period). 43 If the projected RPG is above the URP—that is, if visibility improvements are not tracking toward natural visibility conditions by 2064—then an additional “robust demonstration” requirement is triggered for each state that contributes to that Class I area. 44

In comments on the EPA's initial proposal, California stated that:

In this proposed action, the EPA is proposing to approve the 2022 California Regional Haze Plan because the State evaluated potential additional measures, considered the four statutory factors, and the projected 2028 visibility conditions on the most impaired days at the affected Class I areas are below the URP, with one exception as discussed in section VI.C.4 below, thus supporting the State's decision regarding reasonable progress for the second planning period.

The EPA has the discretion and authority to change policy. In FCC v. Fox Television Stations, Inc., the U.S. Supreme Court plainly stated that an agency is free to change a prior policy and “need not demonstrate . . . that the reasons for the new policy are better than the reasons for the old one; it suffices that the new policy is permissible under the statute, that there are good reasons for it, and that the agency believes it to be better.”  46 The EPA's new policy is that so long as projected 2028 visibility conditions for most impaired days at a Class I area impacted by a state are below the URP and the State considers the four factors, the State will have presumptively demonstrated reasonable progress for the second planning period for that area. As stated above, the EPA believes that this new policy aligns with the purpose of the statute and RHR, which is achieving “reasonable” progress, not maximal progress, toward Congress' natural visibility goal.

In the 2017 RHR Revisions, the EPA addressed the role of the URP as it relates to a State's development of its second planning period SIP revision. 47 Specifically, in response to comments suggesting that the URP should be considered a “safe harbor” and relieve States of any obligation to consider the four statutory factors, the EPA explained that the URP was not intended to be such a safe harbor. 48 Some commenters stated a desire for corresponding rule text dealing with situations where RPGs are equal to (“on”) or better than (“below”) the URP or glidepath. Several commenters stated that the URP or glidepath should be a “safe harbor,” opining that states should be permitted to analyze whether projected visibility conditions for the end of the implementation period will be on or below the glidepath based on on-the-books or on-the-way control measures, and that in such cases a four-factor analysis should not be required. 49 Other 2017 RHR comments indicated a similar approach, such as “a somewhat narrower entrance to a `safe harbor,' ” by suggesting that if current visibility conditions are already below the end-of-planning-period point on the URP line, a four-factor analysis should not be required. 50 In response, the EPA stated that we did not agree with either of these recommendations because “[t]he CAA requires that each SIP revision contain long-term strategies for making reasonable progress, and that in determining reasonable progress states must consider the four statutory factors.”  51 We concluded that, “[t]reating the URP as a safe harbor would be inconsistent with the statutory requirement that states assess the potential to make further reasonable progress towards natural visibility goal in every implementation period.”  52 However, so long as a State considers the four factors, the presumption that a Class I area for which projected 2028 visibility conditions on the most impaired days are below the URP is achieving reasonable progress is consistent with the CAA and RHR. Indeed, we believe this policy also recognizes the considerable improvements in visibility impairment that have been made by a wide variety of State and Federal programs in recent decades. The EPA invites comments on this proposed policy.

In sum, California selected a number of sources, evaluated emissions control measures, and considered the four statutory factors. In addition, with one exception, as discussed in section VI.C.4 of this document, visibility conditions on the most impaired days at all Class I areas to which California contributes are projected to be below the URP in 2028. In light of these facts, the EPA is proposing to approve the 2022 California Regional Haze Plan. The EPA's determinations are described in more detail in section VI of this document.

The EPA invites comments on the following subsections that contain our evaluation of the Plan with respect to the requirements of the CAA and RHR for the second planning period of the regional haze program.

Section 169A(b)(2) of the CAA requires each state in which any Class I area is located or “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to have a plan for making reasonable progress toward the national visibility goal. The RHR implements this statutory requirement at 40 CFR 51.308(f), which provides that each state's plan “must address regional haze in each mandatory Class I Federal area located within the State and in each mandatory Class I Federal area located outside the State that may be affected by emissions from within the State,” and (f)(2), which requires each state's plan to include a long-term strategy that addresses regional haze in such Class I areas.

The EPA concluded in the 1999 RHR that “all [s]tates contain sources whose emissions are reasonably anticipated to contribute to regional haze in a Class I area,”  53 and this determination was not changed in the 2017 RHR. Critically, the statute and regulation both require that the cause-or-contribute assessment consider all emissions of visibility impairing pollutants from a state, as opposed to emissions of a particular pollutant or emissions from a certain set of sources.

California has 29 Class I areas within its borders: Redwood National Park; Marble Mountain Wilderness; Lava Beds National Monument; South Warner Wilderness; Thousand Lakes Wilderness; Lassen Volcanic National Park; Caribou Wilderness; Yolla Bolly-Middle Eel Wilderness (includes land managed by USBLM); Point Reyes National Seashore; Ventana Wilderness; Pinnacles National Monument; Desolation Wilderness; Mokelumne Wilderness; Emigrant Wilderness; Hoover Wilderness; Yosemite National Park; Ansel Adams Wilderness; Kaiser Wilderness; John Muir Wilderness; Kings Canyon National Park; Sequoia National Park; Dome Lands Wilderness; San Rafael Wilderness; San Gabriel Wilderness; Cucamonga Wilderness; San Gorgonio Wilderness; San Jacinto Wilderness; Agua Tibia Wilderness; and Joshua Tree National Park.

In its submission, CARB also assessed the contribution of emissions from California to visibility impairment at Class I areas in three neighboring states: Oregon, Nevada, and Arizona. 54 CARB noted that the projected share of ammonium nitrate and ammonium sulfate attributable to California sources ranges from 0.1 to 1.7 percent and 0.1 to 1.0 percent, respectively, of the total light extinction budgets at Class I areas in neighboring states. 55

As discussed in further detail below, the EPA is proposing to find that the 2022 California Regional Haze Plan meets the requirements of 40 CFR 51.308(f)(2) related to the development of a long-term strategy and the requirements of 40 CFR 51.308(f)(3) related to reasonable progress goals. Thus, we propose to find that California has satisfied the applicable requirements for making reasonable progress towards natural visibility conditions in Class I areas that may be affected be emissions from the state.

Section 51.308(f)(1) requires states to determine the following for “each mandatory Class I Federal area located within the State”: baseline visibility conditions for the most impaired and clearest days, natural visibility conditions for the most impaired and clearest days, progress to date for the most impaired and clearest days, the differences between current visibility conditions and natural visibility conditions, and the URP. This section also provides the option for states to propose adjustments to the URP line for a Class I area to account for visibility impacts from anthropogenic sources outside the United States and/or the impacts from wildland prescribed fires that were conducted for certain, specified objectives. 56

In the 2022 California Regional Haze Plan, CARB used visibility data from IMPROVE monitoring sites for 2000-2004 for baseline visibility. 57 CARB also obtained visibility data from IMPROVE monitoring data for 2014-2018, which it used to represent current visibility conditions. CARB determined natural visibility by estimating the natural concentrations of visibility-impairing pollutants and then calculating the resultant total light extinction with the IMPROVE algorithm. Comparison of baseline conditions to natural visibility conditions shows the improvement necessary to attain natural visibility by 2064, measured in deciviews of improvement per year, that represents the URP. The calculations of baseline, current, and natural visibility conditions, as well as progress to date and progress remaining to achieve natural visibility conditions (“Difference”) can be found in Chapter 2 of the 2022 California Regional Haze Plan and are summarized in Tables 1 and 2 of this document.

Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA.

On December 29, 2021, IDEM submitted a SIP revision to address regional haze requirements for the second implementation period. IDEM submitted this SIP revision to satisfy the requirements pursuant to CAA sections 169A and 169B and 40 CFR 51.308(f) related to the regional haze program. EPA proposes to find that Indiana's regional haze SIP submission for the second implementation period meets the applicable statutory and regulatory requirements and thus proposes to approve Indiana's submission into its SIP.

A detailed history and background of the regional haze program is provided in multiple prior EPA proposal actions. 1 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. 2 The following is an abbreviated history and background of the regional haze program and 2017 RHR as it applies to the current action.

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. 3 CAA 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 169A(a)(1).

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.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., sulfur dioxide (SO 2 ), nitrogen oxides (NO X ), and, in some cases, volatile organic compounds (VOC) and ammonia (NH 3 )). Fine particle precursors react in the atmosphere to form fine particulate matter (PM 2.5 ), which impairs visibility by scattering and absorbing light. Visibility impairment reduces the perception of clarity and color, as well as visible distance. 4

To address regional haze visibility impairment, the 1999 RHR established an iterative planning process that requires both States in which Class I areas are located and States “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to periodically submit SIP revisions to address such impairment. CAA 169A(b)(2);  5 see also 40 CFR 51.308(b), (f) (establishing submission dates for iterative regional haze SIP revisions); (64 FR 35714 at 35768, July 1, 1999).

On January 10, 2017 (82 FR 3078), EPA promulgated revisions to the RHR, that apply for the second and subsequent implementation periods. The reasonable progress requirements as revised in the 2017 rulemaking (referred to here as the 2017 RHR Revisions) are codified at 40 CFR 51.308(f).

Because the air pollutants and pollution affecting visibility in Class I areas can be transported over long distances, successful implementation of the regional haze program requires long-term, regional coordination among multiple jurisdictions and agencies that have responsibility for Class I areas and the emissions that impact visibility in those areas. To address regional haze, States need to develop strategies in coordination with one another, considering the effect of emissions from one jurisdiction on the air quality in another. Five regional planning organizations (RPOs), 6 which include representation from State and Tribal governments, EPA, and FLMs, were developed in the lead-up to the first implementation period to address regional haze. RPOs evaluate technical information to better understand how emissions from State and Tribal lands impact Class I areas across the country, pursue the development of regional strategies to reduce emissions of particulate matter and other pollutants leading to regional haze, and help States meet the consultation requirements of the RHR.

The Lake Michigan Air Directors Consortium (LADCO) is an RPO that includes the States of Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin. LADCO's work is a collaborative effort of State governments, Tribal governments, and various Federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the Midwest. Along with the six LADCO States, participants in LADCO's Regional Haze Technical Workgroup include EPA, the U.S. National Park Service (NPS), the U.S. Fish and Wildlife Service (FWS), and the U.S. Forest Service (USFS).

Under the CAA and EPA's regulations, all 50 States, the District of Columbia, and the U.S. Virgin Islands are required to submit regional haze SIPs satisfying the applicable requirements for the second implementation period of the regional haze program by July 31, 2021. Each State's SIP must contain a long-term strategy for making reasonable progress toward meeting the national goal of remedying any existing and preventing any future anthropogenic visibility impairment in Class I areas. CAA 169A(b)(2)(B). To this end, 40 CFR 51.308(f) lays out the process by which States determine what constitutes their long-term strategies, with the order of the requirements in 40 CFR 51.308(f)(1) through (3) generally mirroring the order of the steps in the reasonable progress analysis  7 and (f)(4) through (6) containing additional, related requirements. Broadly speaking, a State first must identify the Class I areas within the State and determine the Class I areas outside the State in which visibility may be affected by emissions from the State. These are the Class I areas that must be addressed in the State's long-term strategy. See 40 CFR 51.308(f), (f)(2). For each Class I area within its borders, a State must then calculate the baseline (five-year average period of 2000-2004), current, and natural visibility conditions ( i.e., visibility conditions without anthropogenic visibility impairment) for that area, as well as the visibility improvement made to date and the “uniform rate of progress” (URP). The URP is the linear rate of progress needed to attain natural visibility conditions, assuming a starting point of baseline visibility conditions in 2004 and ending with natural conditions in 2064. This linear interpolation is used as a tracking metric to help States assess the amount of progress they are making towards the national visibility goal over time in each Class I area. See 40 CFR 51.308(f)(1). Each State having a Class I area and/or emissions that may affect visibility in a Class I area must then develop a long-term strategy that includes the enforceable emission limitations, compliance schedules, and other measures that are necessary to make reasonable progress in such areas. A reasonable progress determination is based on applying the four factors in CAA section 169A(g)(1) to sources of visibility-impairing pollutants that the State has selected to assess for controls for the second implementation period. Additionally, as further explained below, the RHR at 40 CFR 51.308(f)(2)(iv) separately provides five “additional factors”  8 that States must consider in developing their long-term strategies. See 40 CFR 51.308(f)(2). A State evaluates potential emission reduction measures for those selected sources and determines which are necessary to make reasonable progress. Those measures are then incorporated into the State's long-term strategy. After a State has developed its long-term strategy, it then establishes RPGs for each Class I area within its borders by modeling the visibility impacts of all reasonable progress controls at the end of the second implementation period, i.e., in 2028, as well as the impacts of other requirements of the CAA. The RPGs include reasonable progress controls not only for sources in the State in which the Class I area is located, but also for sources in other States that contribute to visibility impairment in that area. The RPGs are then compared to the baseline visibility conditions and the URP to ensure that progress is being made towards the statutory goal of preventing any future and remedying any existing anthropogenic visibility impairment in Class I areas. 40 CFR 51.308(f)(2)-(3). There are additional requirements in the rule, including FLM consultation, that apply to all visibility protection SIPs and SIP revisions. See e.g., 40 CFR 51.308(i).

While States have discretion to choose any source selection methodology that is reasonable, whatever choices they make should be reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that a State's SIP submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.” 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, must also be appropriately documented, as required by 40 CFR 51.308(f)(2)(iii).

Once a State has selected the set of sources, the next step is to determine the emissions reduction measures for those sources that are necessary to make reasonable progress for the second implementation period. 9 This is accomplished by considering the four factors—“the costs of compliance, the time necessary for compliance, and the energy and non-air quality environmental impacts of compliance, and the remaining useful life of any existing source subject to such requirements.” CAA 169A(g)(1). EPA has explained that the four-factor analysis is an assessment of potential emission reduction measures ( i.e., control options) for sources; “use of the terms `compliance' and `subject to such requirements' in section 169A(g)(1) strongly indicates that Congress intended the relevant determination to be the requirements with which sources would have to comply to satisfy the CAA's reasonable progress mandate.” 82 FR 3078 at 3091, January 10, 2017. Thus, for each source it has selected for four-factor analysis, 10 a State must consider a “meaningful set” of technically feasible control options for reducing emissions of visibility impairing pollutants. Id. at 3088.

EPA has also explained that, in addition to the four statutory factors, States have flexibility under the CAA and RHR to reasonably consider visibility benefits as an additional factor alongside the four statutory factors. 11 Ultimately, while States have discretion to reasonably weigh the factors and to determine what level of control is needed, 40 CFR 51.308(f)(2)(i) provides that a State “must include in its implementation plan a description of . . . how the four factors were taken into consideration in selecting the measure for inclusion in its long-term strategy.”

As explained above, 40 CFR 51.308(f)(2)(i) requires States to determine the emission reduction measures for sources that are necessary to make reasonable progress by considering the four factors. Pursuant to 40 CFR 51.308(f)(2), measures that are necessary to make reasonable progress towards the national visibility goal must be included in a State's long-term strategy and in its SIP. 12 If the outcome of a four-factor analysis is that an emissions reduction measure is necessary to make reasonable progress towards remedying existing or preventing future anthropogenic visibility impairment, that measure must be included in the SIP.

The characterization of information on each of the factors is also subject to the documentation requirement in 40 CFR 51.308(f)(2)(iii). The reasonable progress analysis is a technically complex exercise, and also a flexible one that provides States with bounded discretion to design and implement approaches appropriate to their circumstances. Given this flexibility, 40 CFR 51.308(f)(2)(iii) plays an important function in requiring a State to document the technical basis for its decision making so that the public and EPA can comprehend and evaluate the information and analysis the State relied upon to determine what emission reduction measures must be in place to make reasonable progress. The technical documentation must include the modeling, monitoring, cost, engineering, and emissions information on which the State relied to determine the measures necessary to make reasonable progress.

Additionally, the RHR at 40 CFR 51.308(f)(2)(iv) separately provides five “additional factors”  13 that States must consider in developing their long-term strategies: (1) Emission reductions due to ongoing air pollution control programs, including measures to address reasonably attributable visibility impairment; (2) measures to reduce the impacts of construction activities; (3) source retirement and replacement schedules; (4) basic smoke management practices for prescribed fire used for agricultural and wildland vegetation management purposes and smoke management programs; and (5) the anticipated net effect on visibility due to projected changes in point, area, and mobile source emissions over the period addressed by the long-term strategy.

Because the air pollution that causes regional haze crosses State boundaries, 40 CFR 51.308(f)(2)(ii) requires a State to consult with other States that also have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area. If a State, pursuant to consultation, agrees that certain measures ( e.g., a certain emission limitation) are necessary to make reasonable progress at a Class I area, it must include those measures in its SIP. 40 CFR 51.308(f)(2)(ii)(A). Additionally, the RHR requires that States that contribute to visibility impairment at the same Class I area consider the emission reduction measures the other contributing States have identified as being necessary to make reasonable progress for their own sources. 40 CFR 51.308(f)(2)(ii)(B). If a State has been asked to consider or adopt certain emission reduction measures, but ultimately determines those measures are not necessary to make reasonable progress, that State must document in its SIP the actions taken to resolve the disagreement. 40 CFR 51.308(f)(2)(ii)(C). Under all circumstances, a State must document in its SIP submission all substantive consultations with other contributing States. 40 CFR 51.308(f)(2)(ii)(C).

RPGs “measure the progress that is projected to be achieved by the control measures States have determined are necessary to make reasonable progress based on a four-factor analysis.” 82 FR 3078 at 3091, January 10, 2017.

For the second implementation period, the RPGs are set for 2028. RPGs are not enforceable targets, 40 CFR 51.308(f)(3)(iii). While States are not legally obligated to achieve the visibility conditions described in their RPGs, 40 CFR 51.308(f)(3)(i) requires that “[t]he long-term strategy and the RPGs must provide for an improvement in visibility for the most impaired days since the baseline period and ensure no degradation in visibility for the clearest days since the baseline period.”

RPGs may also serve as a metric for assessing the amount of progress a State is making towards the national visibility goal. To support this approach, the RHR requires States with Class I areas to compare the 2028 RPG for the most impaired days to the corresponding point on the URP line (representing visibility conditions in 2028 if visibility were to improve at a linear rate from conditions in the baseline period of 2000-2004 to natural visibility conditions in 2064). If the most impaired days RPG in 2028 is above the URP ( i.e., if visibility conditions are improving more slowly than the rate described by the URP), each State that contributes to visibility impairment in the Class I area must demonstrate, based on the four-factor analysis required under 40 CFR 51.308(f)(2)(i), that no additional emission reduction measures would be reasonable to include in its long-term strategy. 40 CFR 51.308(f)(3)(ii). To this end, 40 CFR 51.308(f)(3)(ii) requires that each State contributing to visibility impairment in a Class I area that is projected to improve more slowly than the URP provide “a robust demonstration, including documenting the criteria used to determine which sources or groups [of] sources were evaluated and how the four factors required by paragraph (f)(2)(i) were taken into consideration in selecting the measures for inclusion in its long-term strategy.”

The provisions of 40 CFR 51.308(f)(6) require States to have certain strategies and elements in place for assessing and reporting on visibility. Individual requirements under this section apply either to States with Class I areas within their borders, States with no Class I areas but that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area, or both. Compliance with the monitoring strategy requirement may be met through a State's participation in the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network, which is used to measure visibility impairment caused by air pollution at the 156 Class I areas covered by the visibility program. 40 CFR 51.308(f)(6), (f)(6)(i), (f)(6)(iv).

All States' SIPs must provide for procedures by which monitoring data and other information are used to determine the contribution of emissions from within the State to regional haze visibility impairment in affected Class I areas, as well as a statewide inventory documenting such emissions. 40 CFR 51.308(f)(6)(ii), (iii), (v). All States' SIPs must also provide for any other elements, including reporting, recordkeeping, and other measures, that are necessary for States to assess and report on visibility. 40 CFR 51.308(f)(6)(vi).

The provisions of 40 CFR 51.308(f)(5) require a State's regional haze SIP revision to address the requirements of paragraphs 40 CFR 51.308(g)(1) through (5) so that the plan revision due in 2021 will serve also as a progress report addressing the period since submission of the progress report for the first implementation period. The regional haze progress report requirement is designed to inform the public and EPA about a State's implementation of its existing long-term strategy and whether such implementation is in fact resulting in the expected visibility improvement. See 81 FR 26942, 26950, May 4, 2016, (82 FR 3078 at 3119, January 10, 2017). To this end, every State's SIP revision for the second implementation period is required to assess changes in visibility conditions and describe the status of implementation of all measures included in the State's long-term strategy, including Best Available Retrofit Technology (BART) and reasonable progress emission reduction measures from the first implementation period, and the resulting emissions reductions. 40 CFR 51.308(g)(1) and (2).

CAA section 169A(d) requires that before a State holds a public hearing on a proposed regional haze SIP revision, it must consult with the appropriate FLM or FLMs; pursuant to that consultation, the State must include a summary of the FLMs' conclusions and recommendations in the notice to the public. Consistent with this statutory requirement, the RHR also requires that States “provide the [FLM] with an opportunity for consultation, in person and at a point early enough in the State's policy analyses of its long-term strategy emission reduction obligation so that information and recommendations provided by the [FLM] can meaningfully inform the State's decisions on the long-term strategy.” 40 CFR 51.308(i)(2). For EPA to evaluate whether FLM consultation meeting the requirements of the RHR has occurred, the SIP submission should include documentation of the timing and content of such consultation. The SIP revision submitted to EPA must also describe how the State addressed any comments provided by the FLMs. 40 CFR 51.308(i)(3). Finally, a SIP revision must provide procedures for continuing consultation between the State and FLMs regarding the State's visibility protection program, including development and review of SIP revisions, five-year progress reports, and the implementation of other programs having the potential to contribute to impairment of visibility in Class I areas. 40 CFR 51.308(i)(4).

Indiana submitted its regional haze SIP to EPA for the first implementation period, 2007-2018, on January 14, 2011, and supplemented it on March 10, 2011. The requirements for regional haze SIPs for the first implementation period are contained in 40 CFR 51.308(d) and (e). See 40 CFR 51.308(b).

On May 29, 2012, EPA finalized a limited approval of Indiana's 2011 SIP submission as satisfying the requirements for BART in 40 CFR 51.308(e) for non-electric generating units (EGUs) and for PM from EGUs. EPA also approved the submission's BART limits for the Alcoa Warrick facility, its identification of Class I areas that the State's emissions affect, its demonstration that the State had consulted with other States in establishing RPGs, and identification of emissions reductions needed in Indiana to meet those goals. 77 FR 34218, June 11, 2012. On May 30, 2012, EPA issued a limited disapproval of Indiana's 2011 SIP submission because of deficiencies arising from the remand of the Clean Air Interstate Rule (CAIR). In the same rulemaking, EPA promulgated a Federal Implementation Plan (FIP) to replace Indiana's reliance on CAIR with the Cross-State Air Pollution Rule (CSAPR). 77 FR 33642, June 7, 2012.

Pursuant to 40 CFR 51.308(g), Indiana was also responsible for submitting a five-year progress report as a SIP revision for the first implementation period, which it did on March 30, 2016. EPA approved this five-year progress report as a revision to the Indiana SIP at 40 CFR 52.770(e) on January 23, 2018 (83 FR 4847, February 2, 2018).

On November 27, 2017, Indiana submitted a revision to its 2011 Regional Haze SIP submission to change reliance on CAIR to reliance on CSAPR, which EPA approved on August 28, 2019, converting EPA's limited approval/limited disapproval to a full approval and withdrawing the FIP provisions that addressed the limited disapproval. 84 FR 46889, September 6, 2019.

In accordance with CAA sections 169A and the RHR at 40 CFR 51.308(f), Indiana submitted a SIP revision on December 29, 2021, to address its regional haze obligations for the second implementation period, which runs through 2028. Indiana provided a draft of its regional haze SIP to the FLMs for consultation on May 18, 2021. Indiana then provided a public comment period before submitting its SIP revision to EPA. 14

The following sections describe Indiana's SIP submission, including Indiana's assessment of progress made since the first implementation period, in reducing emissions of visibility impairing pollutants, and the visibility improvement progress at nearby Class I areas. These sections also contain EPA's evaluation of Indiana's submission against the requirements of the CAA and the RHR for the second implementation period of the regional haze program.

The provisions of section 169A(b)(2) of the CAA require each State in which any Class I area is located or “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to have a plan for making reasonable progress toward the national visibility goal. The RHR implements this statutory requirement at 40 CFR 51.308(f), which provides that each State's plan “must address regional haze in each mandatory Class I Federal area located within the State and in each mandatory Class I Federal area located outside the State that may be affected by emissions from within the State,” and (f)(2), which requires each State's plan to include a long-term strategy that addresses regional haze in such Class I areas.

Indiana has no Class I areas within its borders that are among the 156 mandatory Class I Federal areas where EPA deemed visibility to be an important value. See 40 CFR part 81, subpart D. Thus, IDEM only considered out-of-state mandatory Class I Federal areas.

Indiana is a member of LADCO and participated in its regional approach for developing a strategy for making reasonable progress towards the national visibility goal in the northern Midwest Class I areas. IDEM reviewed technical analyses conducted by LADCO to determine which Class I areas outside the State are affected by Indiana emission sources. For the second regional haze implementation period, to determine LADCO member State contributions to impaired visibility in all Class I areas, LADCO used the Comprehensive Air Quality Model with extensions applying Particulate Matter Source Apportionment Tool. LADCO tagged emissions from individual States and several multi-state regions as well as individual point sources and inventory source groups to apportion emissions to States and regions. This included 27 tagged source categories, nine of which were source categories or individual sources in Indiana: (1) Indiana non-point sources, (2) Rockport EGUs, (3) Gibson EGUs, (4) all other Indiana EGUs, (5) Indiana cement manufacturing facilities, (6) Indiana iron and steel facilities, (7) Indiana plastics and resin manufacturing facilities, (8) Indiana aluminum production facilities, and (9) all other Indiana point sources. LADCO assessed relative visibility impacts in 2028 by projecting representative emissions inventories and known emission controls from 2016. 15 A group of RPOs, States, and EPA established 2016 as the base year for a national air quality modeling platform for future ozone, PM 2.5 , and regional haze SIP development because of fairly typical ozone conditions and wildfire conditions. 16 LADCO relied upon EPA's inventory estimates for 2016 and 2028 for most emission sectors as described in EPA's September 19, 2019, “Availability of Modeling Data and Associated Technical Support Document for the EPA's Updated 2028 Visibility Air Quality Modeling,” (EPA's Updated 2028 Visibility Air Quality Modeling). 17 For EGUs, LADCO used forecasts from the Eastern Regional Technical Advisory Committee (ERTAC) based on continuous emissions monitoring data from 2016 instead of the Integrated Planning Model used in EPA's 2016 modeling platform. LADCO also incorporated state-reported changes to EGUs received through September 2020 to estimate 2028 EGU emissions, which was considered by LADCO to be the best available information on EGU forecasts for the Midwest and Eastern U.S. available at the time.

Based on LADCO's source apportionment modeling results for 2028, IDEM identified 17 out-of-state Class I areas where Indiana's contribution to the total light extinction was 1.5 percent or greater. IDEM also included three additional Class I areas below the 1.5 percent threshold: Boundary Waters Canoe Area Wilderness (Minnesota) and Voyageurs National Park (Minnesota) since they are part of the LADCO region, as well as Caney Creek (Arkansas) based on a request for inter-state consultation from Arkansas. IDEM found that the 1.5 percent threshold provided adequate geographic coverage of potential visibility impacts from Indiana on surrounding Class I areas and that the modeling of those areas would be representative of Class I areas further from the State. These Class I areas, along with Indiana's 2028 projected contributions to the total light extinction, are: Mammoth Cave National Park in Kentucky (11.2 percent); Sipsey Wilderness Area in Alabama (5.90 percent); Dolly Sods and Otter Creek Wilderness Areas in West Virginia (5.56 percent); Great Smoky Mountains National Park and Joyce-Kilmer-Slickrock Wilderness Area in Tennessee (5.29 percent); Shenandoah National Park in Virginia (5.14 percent); Cohutta Wilderness Area in Georgia (4.83 percent); Mingo Wilderness Area in Missouri (4.16 percent); Seney Wilderness Area in Michigan (4.01 percent); James River Face Wilderness Area in Virginia (3.75 percent); Linville Gorge Wilderness Area in North Carolina (2.84 percent); Lye Brook Wilderness Area in Vermont (2.33 percent); Brigantine Wilderness Area in New Jersey (2.30 percent); Shining Rock Wilderness Area in North Carolina (2.17 percent); Upper Buffalo Wilderness Area in Arkansas (2.02 percent); Hercules-Glades Wilderness Area in Missouri (2.01 percent); Swanquarter National Wildlife Refuge in North Carolina (1.85 percent); Isle Royale National Park in Michigan (1.85 percent); Caney Creek Wilderness Area in Arkansas (1.10 percent); Boundary Waters Canoe Area Wilderness in Minnesota (0.74 percent); and Voyageurs National Park in Minnesota (0.49 percent). 18 At each of these Class I areas, EPA notes that the visibility conditions in LADCO's modeling as well as EPA's Updated 2028 Visibility Air Quality Modeling are projected to be below their respective glidepaths in 2028 as depicted in Section 23 of Indiana's 2021 Regional Haze SIP submission. Visibility conditions at the Class I areas most impacted by Indiana are projected to be below their respective glidepaths in 2028 at Mammoth Cave National Park by 2.16 deciviews (dv), Sipsey Wilderness Area by 2.44 dv, Dolly Sods and Otter Creek Wilderness Areas by 4.33 dv, Great Smoky Mountains National Park and Joyce-Kilmer-Slickrock Wilderness Area by 5.43 dv, and Shenandoah National Park by 4.98 dv. IDEM addressed each of these Class I areas as well as requests from their host RPOs and States in Indiana's 2021 Regional Haze SIP Sections 22-25 and appendix AA.

The provisions of 40 CFR 51.308(f)(1) require States to determine the following for “each mandatory Class I Federal area located within the State”: baseline visibility conditions for the most impaired and clearest days, natural visibility conditions for the most impaired and clearest days, progress to date for the most impaired and clearest days, the differences between current visibility conditions and natural visibility conditions, and the URP. This section also provides the option for States to propose adjustments to the URP line for a Class I area to account for visibility impacts from anthropogenic sources outside the United States and/or the impacts from wildland prescribed fires that were conducted for certain, specified objectives. 40 CFR 51.308(f)(1)(vi)(B).

Indiana has no mandatory Class I areas within its borders to which the requirements of the visibility protection program apply in 40 CFR part 81, subpart D, and therefore, 40 CFR 51.308(f)(1) and its requirements do not apply.

Each State having a Class I area within its borders or emissions that may affect visibility in a Class I area must develop a long-term strategy for making reasonable progress towards the national visibility goal. CAA 169A(b)(2)(B). After considering the four statutory factors, all measures that are determined to be necessary to make reasonable progress must be in the long-term strategy. In developing its long-term strategies, a State must also consider the five additional factors in 40 CFR 51.308(f)(2)(iv). As part of its reasonable progress determinations, the State must describe the criteria used to determine which sources or group of sources were evaluated ( i.e., subjected to four-factor analysis) for the second implementation period and how the four factors were taken into consideration in selecting the emission reduction measures for inclusion in the long-term strategy. 40 CFR 51.308(f)(2)(iii).

States may rely on technical information developed by the RPOs of which they are members to select sources for four-factor analysis and to conduct that analysis, as well as to satisfy the documentation requirements under 40 CFR 51.308(f). States may also satisfy the requirement of 40 CFR 51.308(f)(2)(ii) to engage in interstate consultation with other States that have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area under the auspices of intra- and inter-RPO engagement.

In developing a process for selecting sources for possible additional control measures during the second planning period, IDEM considered NO X , SO 2 , and NH 3 emissions as precursors to the formation of ammonium sulfate, ammonium nitrate, and organic carbon that can impair visibility. Of these precursors, LADCO's June 17, 2021, Technical Support Document “Modeling and Analysis for Demonstrating Reasonable Progress for the Regional Haze Rule 2018-2028 Planning Period,” (LADCO's 2021 TSD)  19 provided an analysis of the IMPROVE monitoring data. The analysis demonstrated that NO X and SO 2 emissions lead to the formation of the particulate species of nitrate and sulfate that currently contribute more to visibility impairment in the LADCO Class I Areas than PM 2.5 , NH 3 , and VOC. The LADCO Class I Areas consist of Boundary Waters Canoe Area Wilderness and Voyageurs National Park in Minnesota, as well as Isle Royale National Park and Seney Wilderness Area in Michigan. For this reason, Indiana chose to focus on potential reductions in emissions of NO X and SO 2, which Indiana found would be a reasonable approach for the second implementation period as noted in the “Guidance on Regional Haze State Implementation Plans for the Second Implementation Period,” EPA Office of Air Quality Planning and Standards, Research Triangle Park, August 20, 2019 (“2019 Guidance”) at page 12. 20

In selecting sources for a potential four-factor analysis, IDEM followed the methodology in LADCO's October 14, 2020, technical memorandum “Description of the Sources and Methods Used to Support Q/d Analysis for the 2nd Regional Haze Planning Period”  21 and section 5 of the LADCO's 2021 TSD. IDEM generated a list of sources based on total process-level emissions (Q) divided by distance (d) to the nearest Class I area, where Q/d was used as a surrogate quantitative metric of visibility impact in lieu of air quality modeling results. For Q, total emissions refer to the sum of NO X and SO 2 , and IDEM chose to use data from the National Emissions Inventory, EPA's Emissions Inventory System  22 for 2016-2018, and Clean Air Markets Program Data (CAMPD)  23 for 2018 to represent the most current operations at the time as a reflection of decreasing emissions overall. For Q/d, the distance to the closest Class I area for all selected sources was Mammoth Cave. IDEM chose a Q/d threshold of five to capture a variety of higher emitting sources that were representative of 85 percent of SO 2 and 77 percent of NO X emissions from Indiana sources and to screen out sources with either lower emissions or located at farther distances from the Class I areas with lower visibility impacts. 24 This process identified 20 sources for a possible four-factor analysis: 11 power generating stations and nine non-EGUs (such as steel mills, cement kilns, a plastics manufacturer, an aluminum smelter, and electric services operations).

IDEM's source selection approach identified the following 36 EGUs units at the 11 power generating stations: Indiana Michigan Power Company, dba American Electric Power—Rockport Plant (AEP—Rockport), Boilers MB1 and MB2; Duke Energy, Inc.—Gibson Generating Station (Duke—Gibson), Units 1, 2, 3, 4, and 5; AES Indiana—Petersburg Generating Station (AES—Petersburg), Units 1, 2, 3, and 4; Indiana-Kentucky Electric Corporation (IKEC) and Ohio Valley Electric Corporation—Clifty Creek Station (IKEC—Clifty Creek), Units 1, 2, 3, 4, 5, and 6; Duke Energy Indiana, LLC—Cayuga Generating Station (Duke—Cayuga), Units 1 and 2; Southern Indiana Gas and Electric Company (SIGECO)—A.B. Brown Generating Station (SIGECO—A.B. Brown), Units 1 and 2; Alcoa Power Generating, Inc.—Warrick Power Plant (Alcoa—Warrick Power Plant), Unit 4; SIGECO—F.B. Culley Generating Station (SIGECO—F.B. Culley), Units 2 and 3; Hoosier Energy REC, Inc.—Merom Generating Station (Hoosier Energy—Merom), Units 1SG1, 2SG1; Northern Indiana Public Service Company, LLC (NIPSCO)—R.M. Schahfer Generating Station (NIPSCO—R.M. Schahfer), Units 14, 15, 16A, 16B, 17, and 18; and Duke Energy Indiana, LLC—R. Gallagher Generating Station (Duke—Gallagher), Units 2 and 4.

The nine non-EGU facilities are: Warrick Newco LLC (Alcoa—Warrick Operations); Cleveland-Cliffs Steel, LLC—Burns Harbor, LLC (Burns Harbor); Lehigh Cement Company, LLC—Mitchell Plant, Lawrence County (Lehigh Cement—Mitchell Plant); Cokenergy LLC; Cleveland-Cliffs Steel, LLC—Indiana Harbor East (Indiana Harbor East); Lone Star Industries, Inc. dba Buzzi Unicem USA—Greencastle Plant (Lone Star Industries—Greencastle); United States Steel Corporation—Gary Works (U.S. Steel—Gary Works); Cleveland-Cliffs Steel, LLC—Indiana Harbor West (Indiana Harbor West); and SABIC Innovative Plastics—Mt. Vernon LLC. 25

During the FLM consultation process, NPS and USFS provided IDEM with their lists of sources for potential four-factor analyses based on Q/d; however, none of the additional sources identified by NPS or USFS met IDEM's threshold of Q/d greater than five. 26 NPS later agreed that the units IDEM identified represented a reasonable group of sources for potential four-factor analyses. The FLM consultation on source selection is further discussed in Section 2.2 of EPA's April 22, 2025 Technical Support Document (TSD) for this proposed rulemaking, which is included in the docket.

IDEM further refined the list of selected sources by considering whether units would continue to operate or whether they had existing effective controls such that a full four-factor analysis would likely result in a conclusion that no further controls are necessary. Applying these criteria, IDEM determined a full four-factor analysis was not necessary for the 36 EGUs identified. IDEM selected the remaining nine non-EGU facilities for a four-factor analysis as described below. Of the emission units that met Indiana's Q/d source selection criteria, eight EGUs and one non-EGU facility are no longer operating: Duke—Gallagher Units 2 and 4 ; NIPSCO—R.M. Schahfer Units 14 and 15 ; AES—Petersburg Unit 1 (2021) and Unit 2 ; SIGECO—A.B. Brown Units 1 and 2, and Lehigh Cement—Mitchell Kilns 1, 2, and 3.

For the units that are no longer operating, permitting changes, 27 Unit Exemption forms, 28 and verification from the regional transmission organization  29 are included in the docket. 30 Any major stationary source upon restart is subject to permitting as a new source and must comply with requirements pertaining to Federal New Source Review and Prevention of Significant Deterioration requirements as well as Indiana Administrative Code (IAC), Title 326, Article 2. 31

For the remaining EGUs continuing to operate, IDEM examined the facilities for existing effective controls in determining that a full four-factor analysis would likely result in the conclusion that no further controls are necessary for reasonable progress in the second implementation period as described in Section 2 of EPA's April 22, 2025, TSD.

Citing to the flexibility allowed under the RHR, Indiana plans to reexamine the EGUs in the third planning period because the State has found that the landscape for the EGU sector has changed dramatically since the last planning period and is continuing to change in the second implementation period. In addition, IDEM states, “fuel costs have upended the order in which resources are dispatched by [MISO] to meet the region's power generation needs and maintain adequate power grid management in the future. Coal fired units that were previously dispatched first are now dispatched last. This change in economic driven dispatching is expected to result in less reliance on the remaining coal fired EGUs and accelerated retirement. As such, Indiana believes that conducting four-factor analyses for EGUs during the next planning period would result in a better use of resources because much of what the State would require based on four-factor analyses conducted for the EGUs would become moot as the EGU sector remains in flux as sources continue to shutdown units, convert to natural gas, and rely more on renewable energy.” See responses 2 and 3, appendix V of Indiana's 2021 Regional Haze SIP submission.

EPA has provided clarification regarding when it is appropriate to forgo a four-factor analysis for sources with existing effective control measures. As explained in the 2019 Guidance, Section 3(f), “A source may already have effective controls in place as a result of a previous regional haze SIP or to meet another CAA requirement.” Section 3(f) goes on to provide “examples, which are intended to illustrate (in a non-exhaustive fashion) scenarios in which EPA believes it may be reasonable for a State not to select a particular source for further analysis.”

As discussed below, IDEM provided information to demonstrate that the EGUs have existing effective control measures as described in the examples in the 2019 Regional Haze Guidance, Section 3(f). 32 In addition to IDEM's analysis of emissions from 2007 to 2019, EPA also considered limits contained in existing permits  33 and 2018 to 2023 CAMPD information showing that each unit has consistently implemented their existing measures and have achieved, using those measures, a reasonably consistent emission rate. With emission limits in the title V permits, provisions in Federal consent decrees, historical data showing relatively consistent or declining NO X and SO 2 annual emissions and emission rates, as well as 2028 projections, the overall emissions are not expected to increase in the future. As such, IDEM determined that the existing control measures are not necessary to prevent future emission increases and thus not necessary to make reasonable progress in the second implementation period and that pursuing additional emission reductions through the addition of new emission control equipment or emissions limitations is not reasonable as a cost-effective method. Section 2.4 of EPA's April 22, 2025, TSD provides a detailed summary of IDEM's assessment of the EGUs continuing to operate.

After addressing the EGUs as described above and in EPA's April 22, 2025 TSD, Indiana provided site-specific four-factor analyses for the remaining nine non-EGU facilities identified by IDEM's Q/d source selection threshold: Alcoa—Warrick Operations; Burns Harbor; Lehigh Cement—Mitchell; Cokenergy LLC; Indiana Harbor East; Lone Star Industries—Greencastle; U.S. Steel—Gary Works; Indiana Harbor West; and SABIC Innovative Plastics—Mt. Vernon LLC. The background and four-factor analysis for each of the nine units is described below.

The provisions of 40 CFR 51.308(f)(2)(i) require States to evaluate and determine the emission reduction measures that are necessary to make reasonable progress by applying the four statutory factors to sources in a control analysis. The emission reduction measures that are necessary to make reasonable progress must be included in the long-term strategy. 40 CFR 51.308(f)(2).

IDEM's evaluation of each of the nine non-EGU facilities identified through its Q/d source selection process is described in Section 2.5 and 3 of EPA's April 22, 2025 TSD. Each of the four-factor analyses provided for these facilities considered all four statutory factors and appropriately followed the methods in the EPA Air Pollution Control Cost Manual. 34

In addition to the four-factor analyses and evaluations provided by IDEM, EPA also considered limits contained in existing permits and information from Indiana's Emissions Summary Data  35 showing that each unit has consistently implemented their existing measures and have achieved, using those measures, reasonably consistent emission rates. With limits in the title V permits, provisions in Federal consent decrees, historical data showing relatively consistent or declining NO X and SO 2 annual emissions, and emission rates as well as 2028 projections of overall emissions not expected to increase in the future, IDEM determined that the existing emission control measures for each of the non-EGUs are not necessary to prevent future emission increase in the second implementation period and thus not necessary for reasonable progress. As such, IDEM determined that additional control measures are not necessary to make reasonable progress in the second implementation period and that pursuing additional emission reductions through the addition of new emission control equipment or emissions limitations is not cost effective.

Each State's long-term strategy must include the enforceable emission limitations, compliance schedules, and other measures that are necessary to make reasonable progress. 40 CFR 51.308(f)(2). After considering information regarding existing effective controls, analyses under the four statutory factors in 40 CFR 51.308(f)(2)(i), and the five additional factors in 40 CFR 51.308(f)(2)(iv) in addition to other requirements in 40 CFR 51.308(f)(2)(ii) described below, Indiana developed the State's long-term strategy for the second implementation planning period. The measures below represent reductions beyond those planned in the first implementation planning period, as well as emission reductions due to ongoing air pollution control programs, including those that were factored into LADCO's 2028 modeling. The following measures are already permanent and federally enforceable.

On-the-books controls in the second implementation period include:

• Tier 2 Motor Vehicle Emissions and Gasoline Standards Rule (40 CFR 80, 85, and 86)

• Tier 3 Motor Vehicle Emission and Fuel Standards (40 CFR 79, 80, 85, 86, 600, 1036, 1037, 1039, 1042, 1048, 1054, 1065, 1066)

• Tier 4 Non-road Engines and Diesel Fuel Rule (40 CFR 9, 69, 80 86, 89, 94, 1039, 1048, 1051, 1065, 1068)

• Heavy-Duty Diesel Engine and Highway Diesel Fuel Rule (40 CFR 69, 80, 86)

• Data Requirements Rule for the 2010 SO 2 NAAQS (40 CFR 51, Subpart BB)

• Mercury and Air Toxics Standards (MATS) (40 CFR 63, subpart UUUUU)

• Boiler Maximum Achievable Control Technology (MACT) (40 CFR 63, Subpart DDDDD

On-the-way controls that reflect additional emission reductions expected by 2028 include:

• Revised CSAPR Update (40 CFR 97, subpart GGGGG)

EPA proposes to find that Indiana has satisfied the requirements of 40 CFR 51.308(f)(2)(i) related to evaluating sources and determining the emission reduction measures that are necessary to make reasonable progress by considering the four statutory factors. Indiana's selection of sources and evaluation of control measures was reasonable and consistent with the requirements of 40 CFR 51.308(f)(2)(i). Considering the four statutory factors, the projected 2028 visibility conditions for Class I areas influenced by emissions from Indiana sources all being below the URP in 2028, the historical emissions data, the emissions reductions, and the current control technologies, EPA also finds Indiana reasonably concluded that no additional measures are necessary to make reasonable progress in the second planning period. As detailed further below, EPA proposes to approve Indiana's long-term strategy under 40 CFR 51.308(f)(2).

In line with recent proposals from EPA, 36 it is the Agency's policy that, where visibility conditions for a Class I area impacted by a State are below the URP and the State has considered the four statutory factors, the State will have presumptively demonstrated reasonable progress for the second planning period for that area. In developing the regulations required by CAA section 169A(b), EPA established the concept of the URP for each Class I area. As discussed above, for each Class I area, there is a regulatory requirement to compare the projected visibility impairment (represented by the reasonable progress goal, or “RPG”) at the end of each planning period to the URP ( e.g., in 2028 for the second planning period). 37

EPA's new policy is that so long as the Class I areas impacted by a State are below the URP in 2028 and the State considers the four factors, the State will have presumptively demonstrated it has already made reasonable progress for the second planning period for that area. Indeed, we believe this policy also recognizes the considerable improvements in visibility impairment that have been made by a wide variety of State and federal programs in recent decades.

Applying this new policy in our evaluation of Indiana's SIP and as further detailed in the paragraphs that follow, EPA agrees with Indiana's determination that, for the second planning period, no additional measures are necessary to achieve reasonable progress towards natural visibility at Class I areas impacted by emissions from Indiana sources.

The SIP submittal included evaluations for 20 emissions sources, including consideration of the four statutory factors for nine non-EGU facilities and consideration of existing measures at a further 11 power generating stations. Based on these evaluations and analyses, the State determined that no additional measures were necessary for reasonable progress. In reaching this determination, Indiana also considered the emissions reductions and visibility improvements that have already occurred in the second planning period in nearby Class I areas.

For Indiana's source selection methodology, IDEM targeted the sources with the highest potential to impair visibility at mandatory Class I areas. IDEM included a thorough description of its source selection methodology. Starting with LADCO's Q/d methodology and focusing on SO 2 and NO X as the predominant species contributing to visibility impairment in the LADCO Class I areas, IDEM queried data for all sources reporting to the National Emissions Inventory, EPA's Emissions Inventory System for 2016—2018, and CAMPD  38 for 2018 to represent the most current operations at the time. IDEM appropriately chose a Q/d threshold of 5 to capture a variety of higher emitting sources and to screen out sources with either lower emissions or located at farther distances from the Class I areas. As noted in section IV.E.1, above, this process identified 20 sources for a possible four-factor analysis. Overall, the sources selected by IDEM for potential four-factor analysis accounted for 81 percent of the total emissions for SO 2 and NO X for all sources reporting under Indiana's Emission Reporting Rule at Title 326, Article 2, Rule 6 of the Indiana Administrative Code (326 IAC 2-6) in 2018, including 85 percent of SO 2 and 77 percent of NO X .

In determining which facilities to evaluate through a four-factor analysis, IDEM refined the list of sources selected using its Q/d threshold by providing adequate justification for no further analysis where sources had existing effective controls. For EGUs that are now no longer operating, IDEM provided information on emissions from 2009 to 2019 and results of source apportionment modeling to demonstrate statewide emission reductions and projections for SO 2 and NO X . Compared to the 2018 inventories used in IDEM's source selection process, 39 the emissions reductions from the sources no longer operating represent decreases of SO 2 by over 7,000 tons per year (tpy) and NO X by over 9,000 tpy from all the sources IDEM selected with Q/d greater than five. These include: Duke—Gallagher Units 2 and 4 (1,149 ton SO 2 and 535 tons NO X ); NIPSCO—R.M. Schahfer Units 14 and 15 (375 tons SO 2 and 2,429 tons NO X ); AES—Petersburg Unit 1 and 2 (1,412 tons SO 2 and 2,773 tons NO X ); SIGECO—A.B. Brown Units 1 and 2 (3,527 tons SO 2 and 2,112 tons NO X ); and Lehigh Cement—Mitchell Kilns 1, 2, and 3 (700 tons SO 2 and 1,800 tons NO X ).

For the selected EGUs continuing to operate, IDEM appropriately examined the facilities for existing effective controls, trends in SO 2 and NO X emissions, and LADCO's 2028 projected emissions in determining that a four-factor analysis would not likely result in the conclusion that further controls are necessary for reasonable progress. In evaluating IDEM's reasoning, EPA also considered trends in annual emissions and emission rates from 2018—2023 CAMPD, emission limits in current title V permits, and the fact that the projected 2028 visibility conditions for Class I areas influenced by emissions from Indiana sources are below the URP in 2028. The EGUs continuing to operate include: AEP—Rockport Boiler MB1 and MB2; Duke—Gibson Units 1, 2, 3, 4, 5; AES—Petersburg Units 3, 4; IKEC—Clifty Creek Units 1, 2, 3, 4, 5, 6; Duke—Cayuga Units 1, 2; Alcoa—Warrick Power Plant Unit 4; SIGECO—F.B. Culley Units 2, 3; Hoosier Energy—Merom Units 1SG1, 2SG1; and NIPSCO—R.M. Schahfer Units 16A, 16B, 17, 18. As summarized below, IDEM adequately documented that these EGUs are effectively controlled for SO 2 and NO X for the second implementation period in determining that a full four-factor analysis would likely result in the conclusion that no further controls are necessary for reasonable progress.

• AEP—Rockport Boiler MB1 and MB2: The SO 2 and NO X emission limits and plant-wide tonnage caps are in a Federal consent decree, 40 SO 2 emission rates are below the 0.2 pounds per million British thermal units (lbs/MMBtu) for coal-fired EGUs in MATS, and NO X emission rates are below the 0.08 lbs/MMBtu level for units with selective catalytic reduction (SCR) under the Federal “Good Neighbor Plan”. 41

• Duke—Gibson Units 1, 2, 3, 4, and 5: The SO 2 emission rates for all units are below the MATS, NO X emission rates are below the 0.08 lbs/MMBtu level for units with SCR under the Good Neighbor Plan, and the flue gas desulfurization (FGD) and SCR systems achieve high control efficiencies.

• AES—Petersburg Units 3 and 4: The FGD systems achieve high percentages of SO 2 control efficiency, actual SO 2 emission rates for both units are below the MATS, and SO 2 and NO X emission caps and limits are in place under a 2020 Federal consent decree.

• IKEC—Clifty Creek Units 1, 2, 3, 4, 5, and 6: The FGD systems achieve 98 percent control efficiency, the SCR and OFA systems achieve 70-90 percent control efficiency on an annual basis, SO 2 limits are contained Indiana's SIP at 40 CFR 52.770(d), actual SO 2 emission rates for all six units are below MATS, and NO X emissions are progressively constrained on an annual basis under the Revised CSAPR Update Rule. While NPS provided an estimate for cost effectiveness of the addition of SCR to Unit 6 at $6,100/ton of NO X removed, IDEM determined that additional emission reductions through the addition of new emission control equipment would not be cost-effective.

• Duke—Cayuga Units 1 and 2: The SO 2 emission rates are below the MATS, and the FGD and SCR systems achieve control efficiencies near 90 percent or more.

• Alcoa—Warrick Power Plant: Unit 4 is subject to BART emission limitations from the first implementation period on a pollutant specific basis and is currently operating controls to meet those BART emission limits, SO 2 and NO X controls are in place, and actual SO 2 emission rates are below MATS.

• SIGECO—F.B. Culley Units 2 and 3: Federally enforceable SO 2 and NO X emission limits and conditions regarding operation of the FGD and SCR control systems are contained in the Federal consent decree and in Indiana's SIP at 52.770(c)(190), SO 2 emission rates are below the MATS, and the FGD system achieves a control efficiency of 99 percent.

• Hoosier Energy—Merom Units 1SG1 and 2SG1: The FGD and SCR control systems achieve greater than 90 percent control efficiency, SO 2 emission rates are below MATS, and NO X emission rates are below the 0.08 lbs/MMBtu level for units with SCR under the Good Neighbor Plan.

• NIPSCO—R.M. Schahfer: Units 16A and 16B are natural gas turbines emitting less than 1 tpy SO 2 and 17 tpy NO X . For Units 17 and 18, FGD systems achieve 99 percent control efficiency, SO 2 emission rates are below MATS, and NO X emission rates are below 0.199 lbs/MMBtu for units with low NO X burners (LNB) under the Good Neighbor Plan.

In addition to demonstrating that these EGUs are effectively controlled for the second implementation period, Indiana's analysis of emissions from 2007 to 2019 and projected emissions from 2028 projections, in addition to the CAMPD information from 2018 to 2023 that EPA considered along with control measures in Federal consent decrees and title V permits, showed each unit had consistently implemented their existing measures, had demonstrated declining trends in total annual emissions at each facility, and emissions were not projected to increase through 2028. Additionally, the projected 2028 visibility conditions for Class I areas influenced by emissions from Indiana sources are below the URP in 2028. 42 As such, IDEM adequately demonstrated that additional measures for these units are not necessary to make reasonable progress during the second implementation period.

Indiana's long-term strategy included Federal on-the-books and on-the-way controls. Indiana did not rely on additional measures as part of the long-term strategy to make reasonable progress in the second planning period for the units that IDEM identified through its Q/d source selection process. For the units no longer operating, emission reductions have already taken place during the second implementation period. For the EGUs continuing to operate, IDEM sufficiently demonstrated that existing effective controls are in place as described in the 2019 Guidance, section 3(f) in determining that a full four-factor analysis would likely result in the conclusion that no further controls are necessary for reasonable progress. IDEM's analysis of emissions from 2007 to 2019 and 2028 projections, CAMPD information from 2018 to 2023, limits contained in existing permits and Federal consent decrees, and the fact that projected 2028 visibility conditions for Class I areas influenced by emissions from Indiana sources are below the URP in 2028 support IDEM's determination that additional measures at these EGUs are not necessary to make reasonable progress for the second implementation period.

For the nine non-EGU facilities, Indiana provided a thorough analysis of existing measures or a full four-factor analysis that appropriately followed the methods in the EPA Air Pollution Control Cost Manual. 43 IDEM documented the range of cost effectiveness for control options considered technically feasible in the four-factor analyses.

For the other units evaluated at the non-EGU facilities, the analyses thoroughly demonstrated that no reasonable set of SO 2 or NO X control measures were identified beyond what is currently installed and operated as described in Section 3 of EPA's April 22, 2025 TSD.

The emission reductions that have already occurred during the second implementation period at Duke—Gallagher, NIPSCO—R.M. Schahfer, AES—Petersburg, SIGECO—A.B. Brown, and Lehigh Cement—Mitchell represent permanent reductions in SO 2 and NO X from Indiana sources that have reduced visibility impairment at impacted Class I areas. These decreases in emissions represent over 7,000 tpy SO 2 and over 9,000 tpy NO X from all the sources IDEM selected with Q/d greater than five based on 2018 emissions. With a relatively small potential for additional emission reductions identified in the four-factor analyses compared to emission reductions that have already taken place, IDEM provided a reasoned basis for its conclusions that pursuing additional emission reductions through the addition of new emission control measures or emissions limitations is not cost-effective for the second implementation period. The trends in NO X and SO 2 emissions noted in IDEM's progress report discussed below and its analysis of emissions from 2007 to 2019 and 2028 projections, along with the 2018 to 2023 emissions data considered by EPA demonstrate how Indiana's long-term strategy will continue to make significant emissions reductions during the second implementation period. Indiana's SIP revision shows that these measures will achieve substantial SO 2 and NO X emission reductions beyond those included in its first implementation period. The reductions in emissions that have already occurred during the second implementation period, along with on-the-books and on-the-way control measures, contribute to Indiana's emission reductions and the associated visibility improvements at the affected Class I areas for the second implementation planning period.

EPA proposes to find that Indiana has satisfied the requirements of 40 CFR 51.308(f)(2)(i) related to evaluating sources and determining the emission reduction measures that are necessary to make reasonable progress by applying the four statutory factors to sources in a control analysis. Indiana's SIP submission reasonably applied the Q/d source selection process in relying on the closest Class I area and the emissions of SO 2 and NO X . IDEM examined a reasonable set of sources, including sources identified by FLMs. In addition, IDEM adequately explained its decision to focus on the two pollutants—SO 2 and NO X —that currently drive visibility impairment within the LADCO region. EPA proposes to find that Indiana adequately supported its conclusions for its top-impacting sources in determining that no additional controls are necessary for reasonable progress in the second implementation period. EPA is basing this proposed finding on the State's examination of its largest operating EGU and non-EGU sources, particularly the State's consideration of the four statutory factors, the projected 2028 visibility conditions for Class I areas influenced by emissions from Indiana sources all being below the URP in 2028, the historical emissions data, the emission reductions that have already taken place during the second implementation period, and the current control technologies.

The consultation requirements of 40 CFR 51.308(f)(2)(ii), provide that States must consult with other States that are reasonably anticipated to contribute to visibility impairment in a Class I area to develop coordinated emission management strategies containing the emission reductions measures that are necessary to make reasonable progress. The provisions of 40 CFR 51.308(f)(2)(ii)(A) and (B) require States to consider the emission reduction measures identified by other States as necessary for reasonable progress and to include agreed upon measures in their SIPs, respectively. The provisions of 40 CFR 51.308(f)(2)(ii)(C) speak to what happens if States cannot agree on what measures are necessary to make reasonable progress. States may satisfy the requirement of 40 CFR 51.308(f)(2)(ii) to engage in interstate consultation with other States that have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area under the auspices of intra- and inter-RPO engagement.

Although Indiana has no mandatory Class I Federal areas within its borders, Indiana has previously been shown to have sources with emissions that impact visibility at downwind Class I Federal areas. Indiana consulted with other States to develop a coordinated emission management approach to its regional haze SIP and to address Indiana's impact on nearby Class I areas. IDEM participated in the LADCO and inter-RPO processes which developed the technical information needed for such coordinated strategies.

Indiana participated in the LADCO Regional Haze Technical Workgroup meetings with other LADCO States, FLMs, and EPA Region 5. Indiana also consulted with other States and Tribes, receiving and responding to letters  44 from Arkansas, Missouri, Metro 4/SESARM/VISTAS, 45 MANE-VU, 46 Arkansas, Missouri. IDEM replied with emissions analysis and modeling results to demonstrate Indiana is meeting the State's regional haze obligations to the surrounding States with Class I areas and that no further analysis is necessary for the sources identified by the States and RPOs. IDEM did not receive any replies disagreeing with their responses. Section 4 of EPA's April 22, 2025 TSD provides a detailed summary of Indiana's consultation with States.

EPA proposes to find that Indiana has satisfied the consultation requirements of 40 CFR 51.308(f)(2)(ii). Indiana has met the requirements of 40 CFR 51.308(f)(2)(ii)(A) and (B) with its participation in the LADCO consultation process plus its individual consultation meetings with contributing States. There were no disagreements with another State; therefore, 40 CFR 51.308(f)(2)(ii)(C) does not apply to Indiana.

The requirements of 40 CFR 51.308(f)(2)(iii) provide that a State must document the technical basis for its decision making to determine the emission reductions measures that are necessary to make reasonable progress. The documentation requirement of 40 CFR 51.308(f)(2)(iii) provides that States may meet their obligations to document the technical bases on which they are relying to determine the emission reductions measures that are necessary to make reasonable progress through an RPO, as long as the process has been “approved by all State participants.” Indiana adequately documented the technical basis, including the modeling, monitoring, engineering, costs, and emissions information that was relied on in determining the emission reduction measures that are necessary to make reasonable progress.

For modeling, IDEM documented the modeling done by LADCO to determine visibility projections and contributions to impairment at the Class I areas. Indiana included justification for the 2016 base year selection and the 2028 emission projections based on ERTAC forecasts and state-reported changes.

For monitoring, IDEM described how ambient air quality monitoring data were analyzed to produce a conceptual understanding of the air quality problems contributing to haze as well as to project visibility conditions in 2028 through LADCO's modeling and EPA's Updated 2028 Visibility Air Quality Modeling. IDEM noted that LADCO relied upon the IMPROVE monitoring data to track the chemical composition of PM 2.5 in haze at Class I areas in the LADCO region, which included ammonium nitrate, ammonium sulfate, elemental carbon, organic carbon, sea salt, and inorganic soil. IDEM also documented IMPROVE monitoring data for several Class I areas from the 2000-2004, 2009-2013, 2014-2018 monitored baselines along with graphs depicting their respective glidepaths and monitored visibility for the 20 percent most impaired days on an annual basis over the same time period.

For emissions information, IDEM provided data for 2007 through 2019, the most recent data years available at the time, from various sources for each unit screened in using Indiana's Q/d source selection threshold. Emissions data were obtained from EPA's Emissions Inventory System, CAMPD, and the National Emissions Inventory (NEI). Additionally, EPA considered 2011-2022 information from Indiana's Emissions Summary Data and 2018-2022 emissions from CAMPD. Data from 2016 for annual emissions of NO X , SO 2 , PM 2.5 , and NH 3 that was used in LADCO's modeling relied upon the 2016 inventory developed by the National Emissions Inventory Collaborative described above as well as forecasts from ERTAC with state-reported changes to EGUs through 2020. The pollutants inventoried by Indiana for the photochemical modeling included NO X , SO 2 , VOCs, PM 2.5 , and PM 10 data collected through Indiana's emissions reporting rules. Since ammonia emissions are not reported to Indiana, modeled estimates were provided by LADCO.

For engineering and costs, Indiana provided site-specific four-factor analyses that evaluated potential engineering designs and costs for various NO X and SO 2 emission control systems for the nine non-EGU facilities as previously mentioned.

EPA proposes to find that such documentation of the technical basis of the long-term strategy, including the modeling, monitoring, engineering, costs, and emissions information discussed above, satisfies the requirements of 40 CFR 51.308(f)(2)(iii).

The provisions of 40 CFR 51.308(f)(2)(iii) require that the emissions information considered to determine the measures that are necessary to make reasonable progress include information on emissions for the most recent year for which the State has submitted triennial emissions data to EPA (or a more recent year), with a 12-month exemption period for newly submitted data. As previously mentioned above, IDEM participated in the development of technical analyses, including emission inventory information, by LADCO and its member States, and is relying in part on those analyses to satisfy the emission inventory requirements. Emissions for the 2016 base year and the 2028 projected year used in LADCO's modeling address elements of 40 CFR 51.308(f)(6)(v) of the Regional Haze Rule, which requires that States provide recent and future year emissions inventories of pollutants anticipated to contribute to visibility impairment in any Class I areas. Indiana's 2021 Regional Haze SIP revision for the second implementation period also included 2017 NEI emission data, which corresponds to the year of the most recent triennial NEI at the time of Indiana's 2021 Regional Haze SIP submission, as required under 40 CFR 51.308(f)(2)(iii) of the Regional Haze Rule. Based on IDEM's consideration and analysis of the 2017 emission data in its SIP submission, EPA proposes to find that Indiana has satisfied the emissions information requirement in 40 CFR 51.308(f)(2)(iii).

In addition to the four statutory factors, States must also consider the five additional factors listed in 40 CFR 51.308(f)(2)(iv) in developing their long-term strategies. EPA proposes to find that Indiana adequately considered those factors in developing this submission.

As required by 40 CFR 51.308(f)(2)(iv)(A), Indiana considered emission reductions due to ongoing air pollution control programs. IDEM documented significant emission reductions based on current emission control strategies at its sources that have reduced visibility impairment at all surrounding Class I areas. IDEM noted ongoing Federal emission control programs that have reduced and will continue to reduce visibility-impairing pollutants from Indiana point sources, as well as on-road and non-road mobile sources, in the second implementation period. For point sources, these programs included Federal provisions for title V permitting actions; Boiler MACT; Mercury and Air Toxics Standards for power plants; Data Requirements Rule for the 2010 SO 2 NAAQS; and Revised CSAPR Update. For on-road mobile sources, Indiana cited to Federal regulations for the Tier 2 Motor Vehicle Emissions and Gasoline Standards Rule, Tier 3 Motor Vehicle Emission and Fuel Standards, and Heavy-Duty Diesel Engine and Highway Diesel Fuel Rule. For non-road mobile sources, IDEM cited to Federal regulations for the Tier 4 Nonroad Engines and Diesel Fuel Rule.

As required by 40 CFR 51.308(f)(2)(iv)(B), Indiana's consideration of measures to mitigate the impacts of construction activities in its SIP submission referred to the State's title V permit program as well as LADCO's inclusion of building construction, road construction, agricultural dust, and road dust in the modeling, which identified contributions to visibility impairment for consideration by the States.

Pursuant to 40 CFR 51.308(f)(2)(iv)(C), Indiana's SIP submission addressed schedules for source retirements and replacements.

In considering smoke management for prescribed burns as required in 40 CFR 51.308(f)(2)(iv)(D), Indiana's Open Burning Rule at 326 IAC 4-1 addresses open burning, including prescribed burns used for agricultural and wildland vegetation management purposes. Under 326 IAC 4-1-3, burning of vegetation for agricultural maintenance purposes is exempt from the open burning rules on agricultural land, farms, orchards, nursery, tree farms, cemeteries, and drainage ditches. Burning of natural growth for the purpose of land management, such as wildlife habitat maintenance, forestry purposes, natural area management, and ecosystem management generally requires IDEM approval. The exceptions are for burning conducted on properties owned by the Indiana Department of Natural Resources, municipal or county governments, the US Department of Interior, the US Department of Agriculture, or USFS. Indiana's rules provide that such prescribed burns are not allowed during unfavorable meteorological conditions, including high winds, temperature inversions, air stagnation, or when a pollution alert or ozone action day has been declared. To ensure smoke from such activities is accounted for in the visibility projections, IDEM noted that LADCO's modeling included a sector for wild and prescribed fires.

As required by 40 CFR 51.308(f)(2)(iv)(E), Indiana considered the anticipated net effect on visibility improvements due to projected changes in emissions from point, area, and mobile sources during the second implementation period addressed by the long-term strategy. The visibility improvement expected during the second implementation period was estimated using LADCO's 2016 base year and 2028 future year inventory components to simulate 2016 and 2028 air quality. As described above, for EGUs, projected changes for 2028 emissions in LADCO's modeling platform were based on ERTAC forecasts and state-reported changes. For most other emission sectors, LADCO relied upon EPA's 2016 and 2028 inventory estimates for projected changes in sectors such as agriculture, on-road and non-road mobile, rail, commercial marine, point and nonpoint oil and gas, residential wood combustion, wild and prescribed fires, and Mexico and Canada anthropogenic emissions. The projected changes in EPA's 2016 and 2028 inventory estimates take into account Federal on-the-books controls such as those listed in Indiana's long-term strategy, above.

IDEM also demonstrated that visibility conditions in the LADCO Class I Areas have shown continued improvement relative to baseline conditions. As depicted in LADCO's 2021 TSD, 2016 visibility impairment conditions at the LADCO Class I Areas on the 20 percent most impaired days as well as the 20 percent clearest days were below their respective glidepaths. By the end of the second implementation period in 2028, both LADCO's projections and EPA's Updated 2028 Visibility Air Quality Modeling show 2028 visibility conditions will remain below the URP glidepaths for the LADCO Class I Areas.

After weighing the four-factor analyses and the five additional required factors, Indiana determined that the existing emission controls for the sources identified above IDEM's Q/d threshold are effective for the second implementation period and that additional measures are not necessary to meet second implementation period regional haze SIP requirements. IDEM's process for selecting sources for four-factor analyses represented 81 percent of the total SO 2 and NO X emissions for all sources reporting under 326 IAC 2-6, including 85 percent of SO 2 and 77 percent of NO X . IDEM provided an analytical means for refining the list of sources selected by evaluating EGUs and non-EGUs for demonstration of existing effective controls or four-factor analysis. For the add-on controls evaluated for the units selected for four-factor analyses, Indiana determined that the controls evaluated were not cost effective to achieve emission reductions during the second implementation period. IDEM reflected upon the steady and significant improvement in visibility at each of the Class I areas impacted by sources in Indiana and noted that LADCO's modeling shows continued improvement with 2028 projections below their URP glidepaths in 2028. As discussed under the progress report elements below, from 2007 to 2019, SO 2 emissions from all Indiana EGUs decreased by 210,180 tons or 81 percent while NO X emissions decreased by 46,360 tons or 50 percent. The decreasing trend continues with the permanent emission reductions that have already occurred during the second implementation period, representing over 7,000 tpy of SO 2 and over 9,000 tpy of NO X from all the sources identified by IDEM's Q/d selection process based on 2018 emissions.

Given all these factors, Indiana demonstrated that Federal on-the-books and on-the-way controls are sufficient to make reasonable progress in the second implementation period. EPA proposes to find that Indiana reasonably considered and satisfied the requirements for each of the five additional factors in 40 CFR 51.308(f)(2)(iv) in developing its long-term strategy.

The provisions of 40 CFR 51.308(f)(3) contain the requirements pertaining to RPGs for each Class I area. Under 40 CFR 51.308(f)(3)(i), a State, in which a mandatory Class I area is located, is required to establish RPGs—one each for the most impaired and clearest days—reflecting the visibility conditions that will be achieved at the end of the implementation period as a result of the emission limitations, compliance schedules and other measures required under paragraph (f)(2) to be in States' long-term strategies, as well as implementation of other CAA requirements. The long-term strategies as reflected by the RPGs must provide for an improvement in visibility on the most impaired days relative to the baseline period and ensure no degradation on the clearest days relative to the baseline period. The provisions of 40 CFR 51.308(f)(3)(ii) apply in circumstances in which a Class I area's RPG for the most impaired days represents a slower rate of visibility improvement than the uniform rate of progress calculated under 40 CFR 51.308(f)(1)(vi). Under 40 CFR 51.308(f)(3)(ii)(A), if the State in which a mandatory Class I area is located establishes an RPG for the most impaired days that provides for a slower rate of visibility improvement than the URP, the State must demonstrate that there are no additional emission reduction measures for anthropogenic sources or groups of sources in the State that would be reasonable to include in its long-term strategy. The provisions of 40 CFR 51.308(f)(3)(ii)(B) requires that if a State contains sources that are reasonably anticipated to contribute to visibility impairment in a Class I area in another State, and the RPG for the most impaired days in that Class I area is above the URP, the upwind State must provide the same demonstration. Because Indiana has no Class I areas within its borders to which the requirements of the visibility protection program apply in 40 CFR part 81, subpart D, Indiana is subject only to 40 CFR 51.308(f)(3)(ii)(B), but not 40 CFR 51.308(f)(3)(i) or (f)(3)(ii)(A).

Under 40 CFR 51.308(f)(3)(ii)(B), a State that contains sources that are reasonably anticipated to contribute to visibility impairment in a Class I area in another State for which a demonstration by the other State is required under 40 CFR 51.308(f)(3)(ii)(B) must demonstrate that there are no additional emission reduction measures that would be reasonable to include in its long-term strategy. Section 23 of Indiana's SIP submission shows that at the Class I areas impacted by emissions from Indiana, the 2028 projected visibility impairment is not above the adjusted URP glidepaths for the 20 percent most impaired days and ensures no degradation on the 20 percent clearest days. Therefore, EPA proposes that the demonstration requirement under 40 CFR 51.308(f)(3)(ii)(B) as it pertains to these areas is not triggered.

EPA proposes to determine that Indiana has satisfied the applicable requirements of 40 CFR 51.308(f)(3) relating to RPGs.

The requirements of 40 CFR 51.308(f)(6) specify that each comprehensive revision of a State's regional haze SIP must contain or provide for certain elements, including monitoring strategies, emissions inventories, and any reporting, recordkeeping and other measures needed to assess and report on visibility. A main requirement of this subsection is for States with Class I areas to submit monitoring strategies for measuring, characterizing, and reporting on visibility impairment. Compliance with this requirement may be met through participation in the IMPROVE network.

As noted above, Indiana does not have any mandatory Class I Federal areas located within its borders to which the requirements of the visibility protection program apply in 40 CFR part 81, subpart D. Therefore, 40 CFR 51.308(f)(6)(i), (ii), and (iv) do not apply.

The provisions of 40 CFR 51.308(f)(6)(iii) require States with no Class I areas to include procedures by which monitoring data and other information are used in determining the contribution of emissions from within the State to regional haze visibility impairment at Class I areas in other States. States with Class I areas must establish a monitoring program and report data to EPA that is representative of visibility at the Class I Federal areas. The IMPROVE network meets this requirement. Indiana stated that, as a participant in LADCO, it reviewed information about the chemical composition of baseline monitoring data at Class I Federal areas in the LADCO region to understand the sources of haze causing pollutants. IDEM does not operate any monitoring sites under the Federal IMPROVE program and, therefore, does not require approval of its monitoring network under the Regional Haze Rule. IDEM relies upon participation in the IMPROVE network as part of the State's monitoring strategy for regional haze to review progress and trends in visibility at Class I areas that may be affected by emissions from Indiana, for comprehensive periodic revisions of this implementation plan, and for periodic reports describing progress towards the RPGs for those areas.

The provisions of 40 CFR 51.308(f)(6)(v) require SIPs to provide for a statewide inventory of emissions of pollutants that are reasonably anticipated to cause or contribute to visibility impairment, including emissions for the most recent year for which data are available. In appendix O of its SIP submission, Indiana provided statewide emission inventories for 2016-2018 in EPA's Emissions Inventory System, as the most recent years available at the time of the State's SIP submission. EPA's Emissions Inventory System is used to develop the NEI, which provides for, among other things, a triennial state-wide inventory of pollutants that are reasonably anticipated to cause or contribute to visibility impairment. Indiana's SIP submission at Section 5.13 and 5.15 also provided a summary of SO 2 , NO X , PM 2.5 , VOCs, and NH 3 emissions for 2016 that LADCO used in developing Q/d metrics and the 2016 base year emissions inventory to project emissions to year 2028. Additionally, as described in further detail under the progress report elements, IDEM provided more recent data through 2019 from CAMPD to depict trends in EGU emissions, which demonstrated an 81 percent decrease in SO 2 emissions and a 50 percent decrease in NO X emissions from 2007 to 2019.

The provisions of 40 CFR 51.308(f)(6)(v) also require States to include estimates of future projected emissions and include a commitment to update the inventory periodically. For future projected emissions, Indiana relied on the LADCO modeling and analysis, which estimated 2028 projected emissions of SO 2 and NO X for specific facilities and emission groups in the LADCO States to provide an assessment of expected future year air quality based on 2016 emissions as well as ERTAC and State forecasts. In addition, Indiana annually updates its Emissions Summary Data for pollutants anticipated to cause or contribute to visibility impairment in Class I areas to support future regional haze progress reports and SIP revisions.

EPA proposes to find that Indiana has met the requirements of 40 CFR 51.308(f)(6) as described above, including through its continued participation in LADCO, its own statewide Emissions Summary Data, and its emissions reporting to EPA's Emissions Inventory System.

The provisions of 40 CFR 51.308(f)(5) require that periodic comprehensive revisions of States' regional haze plans also address the progress report requirements of 40 CFR 51.308(g)(1) through (5). The purpose of these requirements is to evaluate progress towards the applicable RPGs for each Class I area within the State and each Class I area outside the State that may be affected by emissions from within that State. The provisions of 40 CFR 51.308(g)(1) and (2) apply to all States and require a description of the status of implementation of all measures included in a State's first implementation period regional haze plan and a summary of the emission reductions achieved through implementation of those measures. The provisions of 40 CFR 51.308(g)(3) apply only to States with Class I areas within their borders and requires such States to assess current visibility conditions, changes in visibility relative to baseline (2000-2004) visibility conditions, and changes in visibility conditions relative to the period addressed in the first implementation period progress report. The provisions of 51.308(g)(4) apply to all States and requires an analysis tracking changes in emissions of pollutants contributing to visibility impairment from all sources and sectors since the period addressed by the first implementation period progress report. This provision further specifies the year or years through which the analysis must extend depending on the type of source and the platform through which its emission information is reported. Finally, 40 CFR 51.308(g)(5), which also applies to all States, requires an assessment of any significant changes in anthropogenic emissions within or outside the State have occurred since the period addressed by the first implementation period progress report, including whether such changes were anticipated and whether they have limited or impeded expected progress towards reducing emissions and improving visibility.

Indiana's previous progress report, which was a 5-year progress report submitted as a SIP revision for the first implementation period on March 30, 2016, 47 included NO X and SO 2 emission inventories from CAMPD for 2005, 2009, 2013 for EGUs, Indiana's Emissions Summary Data from 2005—2014 for contributing sources, as well as inventories from 2005 and 2011 with 2018 projections for the sources categories of point, mobile, non-road, EGU, and area sources. Based on Indiana's Emissions Summary Data covering the period 2010 to 2014 for contributing sources, Indiana's 2016 5-year progress report showed a decrease in SO 2 emissions by 28 percent and a decrease in NO X emissions by 12 percent. Over the longer period from 2005 to 2014, IDEM documented a decrease in SO 2 emissions by 64 percent and NO X emissions by 42 percent. See 82 FR 57694, December 7, 2017, and 83 FR 4847, February 2, 2018.

For the second implementation period SIP submission, the 2019 Guidance recommends the progress report cover the first full year that was not incorporated into the previous progress report through a year that is as close as possible to the submission date of the SIP. 2019 Guidance at 55. Indiana's 2021 progress report covered the measures and emissions reductions achieved from 2007 through 2019 in Indiana's Emissions Summary Data, from 2016-2018 in EPA's Emissions Inventory System for 2016-2018, and from 2007-2019 in CAMPD.

To address the progress report elements of 51.308(g)(1), Indiana described the status of implementation of all measures in the long-term strategy under its first implementation period regional haze plan. These measures included several Federal measures, including CAIR and its successor CSAPR, to which Indiana attributed the majority of reductions in visibility-impairing emissions from the largest point-source sector, EGUs, during the first implementation period. Federal measures for point sources also included BART, MATS, Boiler MACT, and the Data Requirements Rule for the 2010 SO 2 NAAQS. Additional on-the-books control measures that generated further emission reductions addressed mobile sources, such as Federal on-road provisions under the Tier 2 Motor Vehicle Emissions and Gasoline Standards Rule, Tier 3 Motor Vehicle Emissions and Fuel Standards, and Heavy-Duty Diesel Engine and Highway Diesel Fuel Rule. Non-road Federal measures for mobile sources included the Tier 4 Non-road Engines and Diesel Fuel Rule.

As required by 40 CFR 51.308(g)(2), Indiana provided a summary of the emission reductions achieved through the measures outlined above from the first implementation period. As a result of these measures, Indiana's Emissions Summary Data from 2007 to 2019 from across all emission categories for all contributing sources, discussed more fully below, show that Indiana's SO 2 emissions decreased by 90 percent from 836,260 to 82,677 tons, and NO X emissions decreased by 65 percent from 271,556 to 94,002 tons. The most significant emissions reductions from Indiana's SIP strategies resulted from CAIR and CSAPR, MATS, and the Data Requirements Rule for the 2010 SO 2 NAAQS. CAMPD information shows that the EGU sector experienced an 82 percent reduction in SO 2 from 263,766 tons in 2014 to 47,834 tons in 2019, and a 50 percent reduction in NO X from 95,284 tons in 2014 to 47,219 tons in 2019. Over the longer period from 2007 to 2019, the EGUs reporting to CAMPD achieved a 93 percent decrease in SO 2 from 655,139 to 47,834 tons as well as a 72 percent decrease in NO X from 168,916 to 47,219 tons. EPA proposes to find that Indiana has met the requirements of 40 CFR 51.308(g)(1) and (2) because its SIP submission describes the measures included in the long-term strategy from the first implementation period, as well as the status of their implementation and the emission reductions achieved through such implementation.

The provisions of 40 CFR 51.308(g)(3) do not apply because Indiana has no mandatory Class I Federal areas within its borders as described above.

To address 40 CFR 51.308(g)(4), Indiana documented the change in emissions of SO 2 and NO X from all sources and activities in the State. Graph 26-1 and appendix E of Indiana's SIP submission documents changes in emissions of each of these pollutants for biogenics, fires, non-point, non-road, on-road, and point source categories for each year from 2007 through 2019, the most recent data year available at the time for category level emissions in Indiana's Emissions Summary Data. Indiana's tracking showed an overall decline in emission reductions from 2007 to 2019, with a 90 percent reduction in SO 2 and 65 percent reduction in NO X . IDEM also provided data in appendix E of its SIP submission, as noted earlier, with respect to EGUs that report to CAMPD from 2007 to 2019, the most recent year available at the time, tracking the change in emissions and chronicling the decrease in SO 2 by 93 percent from 655,139 to 47,834 tons as well as the decrease in NO X by 72 percent from 168,916 to 47,219 tons. EPA proposes to find that Indiana has satisfied the requirements of 40 CFR 51.308(g)(4) by tracking the change in emissions of SO 2 and NO X from all contributing sources since the first progress report.

To address 40 CFR 51.308(g)(5), Indiana documented significant changes in anthropogenic emissions since the first implementation period plan, within and outside of the State through LADCO and the interstate consultation process, as an indicator of whether they were anticipated and whether they limited or impeded progress in improving visibility. Within the State, Indiana compared emissions from all contributing sources in the State for each year from 2007 to 2019 to identify changes in anthropogenic emissions, finding that overall emissions significantly decreased for NO X and SO 2 . As previously mentioned, these changes were anticipated and attributed to CSAPR as it replaced CAIR, MATS, and the Data Requirements Rule for the 2010 SO 2 NAAQS. With the significant decreases in anthropogenic emissions of SO 2 and NO X across all source categories, Indiana did not find any changes in anthropogenic emissions within or outside the State that occurred from 2007 to 2019 that would limit or impede progress in reducing pollutant emissions and improving visibility. Indiana noted that further improvements in visibility are anticipated with the emission reductions to be realized from the Revised CSAPR Update along with the emission reductions occuring during the second implementation period as mentioned previously. The emissions trend data in Indiana's SIP submission support an assessment that anthropogenic haze-causing pollutant emissions in Indiana have decreased during the reporting period and that changes in emissions have not limited or impeded progress in reducing pollutant emissions and improving visibility. EPA proposes to find that Indiana has met the requirements of 40 CFR 51.308(g)(5).

In section 28.1 of its SIP submission, Indiana committed to submit a 5-year progress report for the second implementation period to evaluate progress towards the reasonable progress goal for each mandatory Class I Federal area located within and outside the State that may be affected by emissions from within the State as required by 40 CFR 51.308(g). Indiana also committed to revising its regional haze SIP and submitting it to EPA on schedule as required by 40 CFR 51.308(f).

CAA section 169A(d) requires States to consult with FLMs before holding the public hearing on a proposed regional haze SIP and to include a summary of the FLMs' conclusions and recommendations in the notice to the public. In addition, 40 CFR 51.308(i)(2)'s FLM consultation provision requires a State to provide FLMs with an opportunity for consultation that is early enough in the State's policy analyses of its emission reduction obligation so that information and recommendations provided by the FLMs' can meaningfully inform the State's decisions on its long-term strategy. If the consultation has taken place at least 120 days before a public hearing or public comment period, the opportunity for consultation will be deemed early enough. Regardless, the opportunity for consultation must be provided at least 60 days before a public hearing or public comment period at the State level. The requirements of 40 CFR 51.308(i)(2) also provide two substantive topics on which FLMs must be provided an opportunity to discuss with States: assessment of visibility impairment in any Class I area and recommendations on the development and implementation of strategies to address visibility impairment. In 40 CFR 51.308(i)(3), States, in developing their implementation plans, are required to include a description of how they addressed FLMs' comments.

In developing its SIP submission, IDEM participated with the FLMs in an early consultation process regarding source selection as well as a formal consultation process on a full draft regional haze SIP. Additionally, through LADCO, IDEM consulted directly and indirectly with the FLMs through emails, webinars, and conference calls early in the SIP planning and development process. 48 On June 16, 2020, IDEM began the early consultation process on the State's source selection process and selection of sources for four-factor analyses. On May 18, 2021, Indiana initiated a formal consultation process with the FLMs, providing a full draft of its Regional Haze SIP and offering an opportunity for consultation in person. IDEM initiated the early consultation process more than 120 days before the first public comment period on Indiana's plan and began the formal consultation process at least 60 days prior to the first public comment period on Indiana's plan, as required by 40 CFR 51.308(i)(2). IDEM's response to the FLMs' comments from are included as appendix U of Indiana's SIP submission as required by 40 CFR 51.308(i)(3). Section 2.2 of EPA's April 22, 2025 TSD provides more information on the FLM consultation.

On September 28, 2021, Indiana announced the opportunity for public comment and public hearing regarding the State's proposed SIP submission for the second implementation period on IDEM's website for public notices and for regional haze. 49 The public notice included the FLMs' comments in the proposed SIP submission. An in-person and virtual public hearing was held on October 28, 2021. 50 The public comment period ended November 15, 2021. Following the public comment period, Indiana submitted its SIP revision to EPA on December 29, 2021.

IDEM considered input from the FLMs and the public that were provided during the FLM consultation period and public notice period when finalizing this SIP revision.

As required by 40 CFR 51.308(i)(4), Indiana committed to continue consultation with States and FLMs on the development and review of any future plan revisions and progress reports, as well as other programs having the potential to contribute to visibility impairment in the mandatory Class I areas. Given IDEM's actions recounted above and in EPA's April 22, 2025, TSD, EPA proposes to find that Indiana has satisfied the requirements of 40 CFR 51.308(i) to consult with the FLMs on its regional haze SIP for the second implementation period.

EPA proposes to approve Indiana's December 29, 2021, SIP submission as satisfying the regional haze requirements for the second implementation period contained in 40 CFR 51.308(f).

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve State choices, provided that they meet the criteria of the CAA. Accordingly, this action merely approves State law as meeting Federal requirements and does not impose additional requirements beyond those imposed by State law. For that reason, this action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);

• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);

• Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;

• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001); and

• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA.

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the rule does not have Tribal implications and will not impose substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

In this document “we,” “us,” and “our” refer to the EPA.

As explained below, the EPA is proposing to approve Colorado SIP revisions stemming from four submittals related to Serious ozone nonattainment area RACT requirements for the DMNFR area. These submittals also include organizational SIP revisions affecting the submitted regulations, including the relocation of existing portions of Colorado's Regulation Number 7 (“Reg. 7”) into new standalone regulations. The four submittals that are the subject of this action are described below.

First, on June 26, 2023, Colorado submitted SIP revisions related to the Moderate and Severe nonattainment requirements for the 2015 and 2008 ozone NAAQS, respectively, which included revisions to Reg. 7. 1 The June 26, 2023 revisions to Reg. 7 do not specifically address Serious ozone nonattainment area RACT requirements. Because the June 2023 submittal included revisions to Reg. 7, parts A and E that were further revised by the subsequent three submittals by Colorado described below (that are specific to Serious ozone nonattainment area RACT requirements), the EPA is acting on all these revisions collectively. Second, on May 23, 2024, Colorado submitted revisions to Reg. 7 that separate out Part E of that state regulation into a new Regulation 26 (“Reg. 26”). 2 Third, on May 30, 2024, Colorado submitted revisions to Reg. 26 concerning landfill/biogas fired Reciprocating Internal Combustion Engines (RICE), as well as other revisions related to Moderate and Severe ozone nonattainment requirements for the 2015 and 2008 ozone NAAQS, respectively. 3 Fourth, on April 2, 2025, Colorado submitted SIP revisions to address outstanding RACT requirements for Serious ozone nonattainment areas under the 2008 ozone NAAQS, which includes associated revisions to Reg.7 and Reg. 26. 4

The EPA had previously finalized disapprovals with respect to SIP revisions related to RACT requirements for refinery fuel process heaters, a cold rolling mill, and landfill/biogas fired RICE. 5 In this action, and as detailed in this preamble, we are proposing to approve the portions of the June 26, 2023, May 23, 2024, May 30, 2024, and April 2, 2025 submittals related to the previously disapproved state RACT regulations.

The EPA is proposing to approve the May 30, 2024 revisions establishing a revised RACT emission limitation for landfill/biogas fired RICE. The EPA is acting on this change as a superseding revision in recognizing that Colorado's intent is for the landfill/biogas fired RICE regulatory provision, that was previously disapproved by the EPA, to now be incorporated into the SIP with subsequent changes that were made to address the disapproval. Therefore, the EPA is proposing to approve all of Reg. 26, Part B, section II.A.4.f., including the revised emission limitation, into the SIP. The EPA is also proposing to approve the April 2, 2025 revisions with respect to the RACT determinations for refinery fuel process heaters and a cold rolling mill. We are also proposing approval of organizational SIP revisions from the June 26, 2023 and May 23, 2024 submittals to Reg. 7 and Reg. 26 that are unrelated to the substance of Colorado's RACT determinations, but which facilitate efficient reorganization of Reg. 7, Part E into Reg. 26 and/or that are clerical or clarifying in nature. The portions of the four SIP submittals that the EPA is proposing approval of in this action are summarized in table 1 of this preamble. The remaining revisions from the June 26, 2023, May 23, 2024, May 30, 2024 and April 2, 2025 submittals will be addressed in future rulemakings.

If the EPA finalizes this rulemaking as proposed, Colorado will have corrected the deficiencies identified in the EPA's December 8, 2023 disapproval with respect to the Serious area RACT requirement for the 2008 ozone NAAQS. Consistent with applicable regulations, 6 the EPA is concurrently making an interim final determination, which also appears in this issue of the Federal Register , to defer application of the CAA emission offset sanction for permitting of new or modified major sources as well as highway sanctions associated with the December 8, 2023 disapproval. The deferral is based on this proposal to approve SIP revisions from Colorado to resolve the RACT requirement deficiencies that were the basis for the December 8, 2023 disapproval. If the EPA does not finalize this approval as proposed and instead disapproves or proposes to disapprove these SIP revisions, then the offset sanction under CAA section 179(b)(2) for permitting new or modified major sources would apply in the DMNFR area on the later of: (1) the date the EPA issues such a proposed or final disapproval; or (2) July 8, 2025 ( i.e., 18 months from the effective date of the finding that started the original sanctions clock). 7 Subsequently, highway sanctions under section 179(b)(1) would apply in the DMNFR area six months after the date the offset sanction is applied. 8

The basis for our proposed action is discussed in more detail below. The State's submittals, including technical information that we are relying on, is in the docket, available at https://www.regulations.gov, Docket ID No. EPA-R08-OAR-2025-0233.

On March 12, 2008, the EPA revised both the primary and secondary NAAQS for ozone to a level of 0.075 parts per million (ppm) (based on the annual fourth-highest daily maximum 8-hour average concentration, averaged over 3 years). 9 The 2008 ozone NAAQS retains the same general form and averaging time as the 0.08 ppm NAAQS set in 1997, but is set at a more protective level. Specifically, the 2008 8-hour ozone NAAQS is met when the 3-year average of the annual fourth-highest daily maximum 8-hour average ambient air quality ozone concentrations is less than or equal to 0.075 ppm. 10 Effective July 20, 2012, the EPA designated any area as nonattainment that was violating the 2008 8-hour ozone NAAQS based on the three most recent years (2008-2010) of air monitoring data. 11

Ozone nonattainment areas are classified based on the severity of their ambient ozone levels, as determined using the area's design value. The design value is the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration at a monitoring site. 12 In our July 20, 2012 action, the EPA designated the DMNFR area as nonattainment and classified the area as Marginal. 13 The DMNFR area did not attain the 2008 8-hour ozone NAAQS by the applicable Marginal area attainment deadline, and accordingly was reclassified as Moderate. 14 After not attaining the 2008 ozone NAAQS for subsequent attainment dates, the area was reclassified to Serious, and then to Severe nonattainment status. 15

Although the area is currently classified as Severe nonattainment for the 2008 ozone NAAQS, the present action pertains only to outstanding requirements from the prior Serious nonattainment classification. Among the requirements for Serious nonattainment areas, states must submit SIP provisions to impose RACT-level emission limitations on relevant emission sources in the nonattainment area. As described above, on December 8, 2023, the EPA disapproved Colorado's RACT determinations for refinery fuel process heaters, landfill/biogas fired RICE, and a cold rolling mill. The EPA has taken action to approve or conditionally approve other SIP revisions related to Serious ozone nonattainment requirements. 16

CAA sections 172(c)(1) and 182(b)(2) require states to include provisions in the SIP providing for the implementation of RACT in areas classified as Moderate nonattainment or higher for an ozone NAAQS. The EPA has defined RACT as “[t]he lowest emission limitation that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility.”  17 For a given category of sources, or emission units, RACT may be determined to be work practices, rather than the application of add-on controls and/or numerical emission limitations. 18 The RACT requirement applies to sources of volatile organic compound (VOC) emissions that are covered by an EPA Control Techniques Guideline (CTG), as well as to all major stationary sources of VOC or nitrogen oxides (NO X ) emissions within a nonattainment area. 19 For nonattainment areas classified as Moderate, Serious, or Severe under an ozone NAAQS, a major stationary source that is subject to RACT is one that emits, or has the potential to emit, 100, 50, or 25 tpy or more, respectively, of VOCs or NO X . 20 Therefore, under the DMNFR area's Serious nonattainment classification for the 2008 ozone NAAQS, Colorado was required to submit SIP revisions providing for the implementation of RACT at stationary sources subject to an EPA CTG and at major stationary sources emitting 50 tpy or more of VOC or NO X .

Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA.

On June 22, 2010 (75 FR 35520), EPA published a revised primary SO 2 NAAQS, establishing a new one-hour standard of 75 parts per billion (ppb). On August 21, 2015 (80 FR 51052), EPA issued the Data Requirements Rule (DRR), which required State air agencies to characterize air quality around sources that emitted 2,000 tons per year (tpy) or more of SO 2 .

EPA has identified the U.S. Mineral Wool facility, also known as “Isolatek,” as an emissions source that may have been contributing to violations of the 2010 SO 2 NAAQS based on air quality modeling conducted by EPA and used in support of the DRR. Isolatek is located in the Huntington County, Indiana nonattainment area for the 2010 SO 2 NAAQS. EPA's air quality modeling, conducted in 2015 using estimated actual emissions from the Isolatek facility, found that the 3-year average of the annual 99th percentile of daily maximum one-hour average SO 2 concentrations exceeded the 75 ppb level of the NAAQS. EPA's March 15, 2016, response to the initial submittal of DRR sources from the Indiana Department of Environmental Management (IDEM) is included in the docket for this rulemaking. Evidence of IDEM's selection of the modeling pathway to characterize air quality in the area surrounding the Isolatek facility on June 30, 2016, is also included in the docket for this rulemaking.

The Isolatek facility is the only listed DRR source in the Huntington area and there is no approved SO 2 monitoring network to characterize air quality in its vicinity. IDEM did not include updated air quality information for the Huntington area in its letter of designations recommendations for the 2010 SO 2 NAAQS. Therefore, during the initial area designations process, EPA relied on the prior EPA air quality modeling, which indicated that the Huntington area may have been violating the 2010 SO 2 NAAQS, and which led EPA to include Isolatek on the list of sources subject to DRR requirements. On August 22, 2017, EPA notified IDEM that we intended to designate the Huntington area as nonattainment, based on the best information available to EPA at the time of designation, which was EPA's air quality modeling indicating that the area may have been violating the 2010 SO 2 NAAQS.

On January 9, 2018, EPA finalized the third round of initial area designations for the 2010 SO 2 NAAQS. Based on prior air quality modeling information, EPA designated Huntington Township, a partial area of Huntington County, Indiana, which includes the Isolatek facility, as nonattainment for the 2010 SO 2 NAAQS with an effective date of April 9, 2018 (83 FR 1098). Pursuant to CAA section 192(a), 42 U.S.C. 7514a(a), EPA established an attainment date of no later than five years after the effective date of the nonattainment area designation, which was April 9, 2023.

CAA section 179(c)(1) requires EPA to determine whether a nonattainment area attained an ambient air quality standard by the applicable attainment date based on the area's air quality as of the attainment date. As stated in EPA's April 23, 2014, “Guidance for 1-Hour SO 2 Nonattainment Area SIP Submissions” (“April 2014 SO 2 guidance”), EPA may consider ambient monitoring data, air quality dispersion modeling, and/or a demonstration that the control strategy in the SIP has been fully implemented when determining the attainment status of SO 2 nonattainment areas.

Under EPA regulations in 40 CFR 50.17, the 2010 SO 2 standard is met at a monitoring site (or in the case of dispersion modeling, at an ambient air quality receptor location) when the three-year average of the annual 99th percentile of daily maximum one-hour average concentrations is less than or equal to 75 ppb, as determined in accordance with appendix T of 40 CFR part 50 (40 CFR 50.17(a)-(b)). Design values are calculated by computing the three-year average of the annual 99th percentile daily maximum one-hour average concentrations. When calculating one-hour primary standard design values based on modeling, the modeled concentration is compared to the one-hour SO 2 NAAQS of 196.4 micrograms per cubic meter. An SO 2 one-hour primary standard design value is valid if it encompasses three consecutive calendar years of complete monitoring data or modeling data. See appendix T of 40 CFR part 50.

As of this action, and as of the statutory attainment date of April 9, 2023, there is no approved SO 2 monitoring network in the Huntington area. The best air quality information available to EPA to characterize air quality in the area on the attainment date was the air quality modeling that was used to support the DRR. As part of the State's SO 2 attainment plan for this area, IDEM submitted control measures on November 6, 2023, that included enforceable allowable emissions limits for the Isolatek facility (see Section III, “Proposed Approval of Indiana's SIP Submittal,” of this preamble for discussion of the control strategy). On February 12, 2024, IDEM supplemented the November 6, 2023, SIP submittal with Commissioner's Order 2023-Air-02, which revised Commissioner's Order 2023-Air-01, which had been included in the November 6, 2023, submittal. In this notice of proposed rulemaking, we are referring to the updated Order 2023-Air-02 as the “Commissioner's Order,” which established compliance requirements for the one-hour SO 2 emissions limits, which were effective on March 1, 2024. In other words, the control measures that EPA is proposing to approve in the following section of this action were not in place as of the statutory attainment date of April 9, 2023. Therefore, based on EPA's air quality modeling used to support the DRR, EPA has determined that the area may have been violating the 2010 SO 2 NAAQS prior to full implementation of the control strategy. EPA is proposing to find that, as of the applicable attainment date of April 9, 2023, the Huntington area failed to attain the 2010 SO 2 NAAQS by the attainment date.

The consequences for an SO 2 nonattainment area that fails to attain a NAAQS by the applicable attainment date are set forth in CAA section 179(d). Under section 179(d), a State must submit a SIP revision for the area meeting the requirements of CAA sections 110 and 172, the latter of which requires, among other elements, a demonstration of attainment and reasonable further progress and contingency measures. In addition, under CAA section 179(d)(2), the SIP revision must include such additional measures as EPA may reasonably prescribe, including all measures that can be feasibly implemented in the area in light of technological achievability, costs, and any non-air quality and other air quality-related health and environmental impacts. The State is required to submit the SIP revision within one year after EPA publishes a final action in the Federal Register determining that the nonattainment area failed to attain the SO 2 NAAQS.

In section III. of this preamble, EPA is proposing to approve IDEM's revised SO 2 attainment plan for the Huntington area, which was submitted to EPA on November 6, 2023, and supplemented on February 15, 2024. (Both submittals occurred after the statutory attainment date of April 9, 2023). The proposed approval is based on air quality modeling demonstrating that the area is currently attaining the NAAQS as a result of the implemented control measures in the State's SIP and the compliance requirements established in the Commissioner's Order. If EPA subsequently takes final action to approve the subject SIP submittals, EPA is proposing to find that these SIP revisions, as approved, satisfy the State's obligation under CAA section 179(d) to submit a SIP revision to address the proposed finding that the area failed to timely attain the 2010 SO 2 NAAQS.

Under CAA sections 172(a)(2), 179(d)(3), the new attainment date for each primary NAAQS nonattainment area is the date by which attainment can be achieved as expeditiously as practicable, but no later than five years after EPA publishes a final action in the Federal Register determining that the nonattainment area failed to attain the SO 2 NAAQS. In this action, we are proposing to approve IDEM's SIP revision and proposing to find that the control measures identified in IDEM's November 6, 2023, and February 15, 2024, SIP revisions satisfy the CAA requirement to achieve attainment of the 2010 SO 2 NAAQS as expeditiously as practicable (see Section III). Therefore, if the proposed Finding of Failure to Attain (FFA) is finalized, this will establish a new attainment date for the Huntington, IN area of no later than five years after the effective date of the final FFA. However, in the following section, EPA is proposing to approve Indiana's SIP and, if finalized, the approved SIP would fulfill the new SIP submission requirement triggered by the finalization of this FFA. We are proposing that the new SIP submission requirement will be met by the SIP we are acting on below in this unique circumstance because control measures are now in place and effective, the area is attaining the 2010 primary SO 2 NAAQS, and the State has submitted a complete and approvable attainment plan with all required planning elements. The new attainment date established 5 years after the date of the effective date of the final FFA also requires contingency measures under CAA section 172(c)(9). EPA is proposing to find that IDEM's comprehensive SO 2 enforcement program, as described in Section III.D.5 of this preamble, satisfies the CAA section 172(c) requirements for contingency measures.

On November 3, 2020 (85 FR 69504), EPA issued a finding that Indiana had failed to submit a SIP provision to satisfy certain nonattainment area planning requirements of the CAA for the 2010 SO 2 NAAQS. The effective date of the Finding of Failure to Submit was December 3, 2020. Indiana was required to submit a SIP provision in response to the Finding of Failure to Submit under CAA section 179(a). This finding started a sanctions clock for EPA to issue Nonattainment New Source Review (NNSR) sanctions and highway sanctions for Huntington Township under CAA section 179(b). EPA imposed NNSR offset sanctions that were effective on June 3, 2022, and imposed highway sanctions that were effective on December 3, 2022. This action also started a Federal Implementation Plan (FIP) clock for EPA to fully approve an SO 2 attainment SIP, or issue a FIP, for the Huntington, Indiana area within two years, by December 3, 2022, under CAA section 110(c).

On November 6, 2023, IDEM submitted State rules for EPA approval as revisions to the Indiana SIP intended to provide for attainment of the 2010 SO 2 NAAQS in the Huntington area. The revisions included an Attainment Demonstration, Reasonably Available Control Measures/Reasonably Available Control Technology (RACM/RACT) requirements, Reasonable Further Progress (RFP) provisions, Contingency Measures, Emissions Inventories for 2017 Base Year and 2023 Attainment Year, and NNSR Certification. On November 27, 2023, EPA issued a completeness determination for the November 6, 2023, SIP submittal, which terminated all sanctions for this area and which is available in the docket for this rulemaking. On February 15, 2024, IDEM submitted a supplemental SIP revision including updated compliance methods (contained in the revised Commissioner's Order 2023-Air-02, as previously described in this action) for the Attainment Demonstration for the Huntington, Indiana SO 2 nonattainment area. In this notice of proposed rulemaking, EPA is proposing to find that this supplement satisfies the CAA sections 110(a)(2)(A) and 172(c)(6) requirements to provide enforceable emissions limitations and control measures as part of an attainment demonstration. As mentioned in the previous section, under CAA section 179(d), States must submit a SIP provision within one year of EPA publishing a finding of failure to attain by the attainment date for any nonattainment area. The submission must include a demonstration of attainment, reasonable further progress and contingency measures, and other measures EPA may reasonably prescribe. Assuming EPA finalizes the proposed finding of failure to attain and the proposed approval of Indiana's SIP submissions, EPA is also proposing to find that IDEM's November 6, 2023, and February 15, 2024, SIP submissions fully satisfy the State's obligation under CAA section 179(d). Lastly, EPA is proposing to terminate the FIP clock that was triggered by EPA's November 3, 2020, Finding of Failure to Submit for Huntington County.

Nonattainment area SO 2 SIPs must meet the applicable requirements of the CAA, and specifically CAA sections 110, 172, 191 and 192. EPA's regulations governing nonattainment area SIPs are set forth at 40 CFR part 51, with specific procedural requirements and control strategy requirements contained in subparts F and G, respectively. Soon after Congress enacted the 1990 amendments to the CAA, EPA issued comprehensive guidance on SIPs in a document entitled the “General Preamble for the Implementation of Title I of the Clean Air Act Amendments of 1990,” published at 57 FR 13498 (April 16, 1992) (General Preamble). Among other things, the General Preamble addressed SO 2 SIPs and fundamental principles for SIP control strategies. Id. at 13545-49, 13567-68.

In the April 2014 SO 2 guidance, EPA described the statutory requirements for a complete nonattainment area SIP, which include: an accurate emissions inventory of current emissions for all sources of SO 2 within the nonattainment area; an attainment demonstration; enforceable emissions limitations and control measures; demonstration of RFP; implementation of RACM (including RACT); NNSR provisions; and adequate contingency measures for the affected area.

In order for EPA to fully approve a SIP as meeting the requirements of CAA sections 110, 172 and 191-192 and EPA's regulations at 40 CFR part 51, the SIP for the affected area needs to demonstrate to EPA's satisfaction that each of the aforementioned requirements have been met. Under CAA section 110(l) EPA may not approve a SIP that would interfere with any applicable requirement concerning NAAQS attainment and RFP, or any other applicable requirement; and, under section 193, no control requirement in effect (or required to be adopted by an order, settlement, agreement, or plan in effect before November 15, 1990), in any area which is a nonattainment area for any air pollutant, may be modified in any manner unless the modification ensures equivalent or greater emission reductions of such air pollutant.

This section describes EPA's evaluation of the air quality dispersion modeling IDEM provided as part of its SIP submission. EPA is proposing to approve Indiana's attainment plan on the basis that this modeling is technically sound and appropriate and provides for attainment of the 2010 SO 2 NAAQS.

IDEM followed EPA guidance at 40 CFR part 51, appendix W, and selected EPA's regulatory dispersion model, AERMOD, to model SO 2 emissions impacts in the Huntington, Indiana nonattainment area. IDEM used the set of regulatory default options in AERMOD version 22112 to develop the attainment demonstration discussed in this section. Version 22112 was the current version of AERMOD at the time the air quality modeling report was submitted (October 6, 2023) as part of the attainment demonstration (see section 5.0 and appendix A1 of the attainment demonstration) and the most recent update to AERMOD since then did not include any bug fixes or other model code changes that would impact the modeled concentrations in the modeled attainment. AERMOD was conducted with the use of rural dispersion coefficients, based on a land use analysis of a 3-kilometer radius from the Isolatek facility showing that only 17.2% of the nearby land was classified as urban. IDEM used an appropriate downwash algorithm for stacks that did not meet EPA's Good Engineering Practice (GEP) stack height policy, which is further described in this section. This is consistent with established practice for use of AERMOD in determining NAAQS compliance for SIP revisions. EPA proposes to find that selection of the default AERMOD options and use of the rural dispersion coefficient are both technically appropriate.

IDEM's attainment demonstration uses a modeling domain reflecting the geographic extent of the Huntington nonattainment area. The Thermafiber, Paperworks, and Real Alloy facilities in Wabash County, the Steel Dynamics facility in Whitely County, the FXI facility in Allen County, and the Teijin Automotive Technologies facility within the Huntington nonattainment area were explicitly modeled as nearby sources in the modeling demonstration. The Teijin Automotive Technologies facility is located 5.6 kilometers from Isolatek. The rest of the nearby sources explicitly modeled in the attainment demonstration are located 27-37 kilometers away from the Isolatek facility. Nearby sources, though not evaluated for an emission limit, are those sources in the vicinity of the source(s) under consideration for emissions limits that are not adequately represented by ambient monitoring data. Consistent with EPA's DRR modeling for the Huntington area, IDEM determined that the primary source of SO 2 emissions in the area is the Isolatek facility, which is the primary source of violations of the 2010 SO 2 NAAQS in the nonattainment area. EPA's evaluation of IDEM's modeling of the Isolatek source is discussed further in Section III.C.3-4 of this preamble.

The receptor network fully encompasses the Huntington nonattainment area. IDEM used four nested receptor grids with different densities and included a fenceline receptor grid with 50-meter spacing. The fine Cartesian grid contains receptors spaced at 100-meter intervals extending to approximately three kilometers away from the center of the facility. The extended fine Cartesian grid contains receptors spaced at 250-meter intervals starting approximately three kilometers away from the center of the facility and extend to five kilometers away from the center of the facility. The medium Cartesian grid contains receptors spaced at 500-meter intervals starting approximately five kilometers away from the center of the facility and extend to ten kilometers away from the center of the facility. The coarse Cartesian grid contains receptors spaced at 750-meter intervals starting approximately ten kilometers away from the center of the facility and extend to twenty kilometers away from the center of the facility. The receptors projected to have maximum modeled concentrations were all contained within the 100-meter spacing fine receptor grid. EPA proposes to find that the receptor density is consistent with standard modeling guidance for adequately capturing and resolving SO 2 concentration maxima.

IDEM's selection of terrain data corresponds to the geographic area represented by the Huntington Township nonattainment area, as well as the locations of nearby facilities influencing SO 2 concentrations in the area. U.S. Geological Survey (USGS) National Elevation Dataset (NED) data were obtained in an appropriate format for use in AERMAP (version 18081) and used for generating the necessary terrain inputs. Elevations from the NED data were determined for all sources and structures, and both elevations and representative hill heights were determined for receptors. EPA proposes to find that these selections are technically appropriate and consistent with established practice in determining NAAQS compliance for SIP revisions.

EPA's appendix W guidance requires States to evaluate whether physical structures may affect the dispersion of emissions from stack sources. Stacks that are constructed to heights lower than specified GEP height and within the “zone of influence” of a nearby structure have plumes that are potentially subject to the effects of downwash which would affect dispersion and modeled concentrations in the building wake, near to the source. IDEM used EPA's Building Profile Input Program with PRIME algorithm (BPIPPRM) to generate direction-specific building parameters for modeling building wake effects. The location and height of each stack and flare to be evaluated, and the locations and heights of nearby structures, were processed in BPIPPRM (version 04274) to produce the building downwash parameters required by AERMOD. The actual release heights of all stacks were less than the calculated GEP value. Therefore, all stacks at the Isolatek facility were modeled at their actual release heights and were subject to downwash effects. EPA is proposing to determine that IDEM's application of the modeling guidance is appropriate for addressing stacks subject to downwash effects.

Procedures for selecting and developing meteorological data have been provided in appendix W, as well as in the document “Regional Meteorological Data Processing Protocol, EPA Region 5 and States,” which is available in the docket for this action. These documents describe selection criteria for surface meteorological data that address the representativeness of the meteorological data collection site to the emission source/receptor impact area. There are two specific criteria to be considered: (1) the suitability of meteorological data for the study area, and (2) the similarity of surface conditions and surroundings at the emission source/receptor impact area compared to surface characteristics at the location of the meteorological instrumentation tower.

IDEM used five years of surface meteorological data from the Fort Wayne National Weather Service (NWS) and upper air meteorological data from Wilmington, Ohio for the period of 2017-2021. This data set was determined to be representative of the nonattainment area's airshed and was the most current data set available when the modeling analysis was conducted. IDEM pre-processes meteorological data and provides the datasets for modeling applicants on their website. 1 AERMINUTE (version 15272) was used to process two-minute averaged ASOS (Automated Surface Observing System) wind data (reported every minute) from Fort Wayne and used the EPA recommended 0.5 meters per second calm wind threshold. Surface characteristic data such as albedo, Bowen ratio, and surface roughness were calculated using the non-regulatory surface characteristics preprocessor AERSURFACE. The one-minute ASOS wind data and surface characteristics were processed together with the surface and upper air meteorological data using AERMET (version 19191 for the years 2017-2020 and version 21112 for the year 2021) to prepare the meteorological data for input into AERMOD. Two different versions of AERMET were used as the 2017-2020 data set was previously processed by IDEM when the year 2021 was processed and the differences between AERMET versions 19191 and 21112 would not have resulted in significant changes in meteorological parameters. The Fort Wayne NWS wind rose shows the frequency of the wind direction every ten degrees for each of the wind speed ranges for the five-year modeled period and demonstrates that the prevailing winds are from the southwest and west-southwest at the Fort Wayne NWS station. EPA proposes to find that the meteorological data set IDEM selected for the air quality modeling to support its SIP submission was technically appropriate.

As EPA identified at the time of promulgating the DRR, the primary source affecting nonattainment and contributing to violations of the 2010 SO 2 NAAQS in Huntington County was the Isolatek facility. EPA has not identified any other sources in the area that may have been contributing to violations of the 2010 SO 2 NAAQS. IDEM's SIP submission establishes permanent and enforceable emissions limits for this facility through a Commissioner's Order. IDEM reviewed detailed engineering analyses for multiple control options at the Isolatek facility, as described in section 5.8 of the SIP submittal. Construction for the control measures selected at the facility, including increasing the cupola stack height, enclosing screenhouses, and building a new elevated stack, was completed in November 2022. Data from stack testing conducted in December 2022 and January 2023 were used to establish the emission limits necessary to provide for attainment of the 2010 one-hour SO 2 NAAQS. The attainment demonstration incorporates hourly modeled emission rate limits, contained in the Commissioner's Order, of 160.0 pounds per hour (lbs/hr) for Cupola units EU #1 and EU #2, exhausting to shared Stack #1, and 20.0 lbs/hr for blow chambers EU #3 and EU #4, exhausting to Screen Houses CE #3 and CE #4, which exhaust to Stack #3 at the Isolatek facility.

IDEM's modeled demonstration of attainment of the 2010 SO 2 NAAQS relies on Isolatek meeting the one-hour SO 2 emissions limit established in the Commissioner's Order. For EPA to approve an attainment plan that relies on establishing emissions limits, EPA must determine that the limits are quantifiable, fully enforceable, replicable, and accountable. See General Preamble at 13567-68. IDEM's February 6, 2024, SIP submission includes an IDEM Commissioner's Order that establishes a compliance date of March 1, 2024, for the emissions limits included in the revised SIP. In addition to requiring compliance with the hourly SO 2 emissions limits and defining stack testing parameters, this order also specifies that Isolatek must incorporate reporting and recordkeeping requirements into its part 70 Operating Permit within 90 days of EPA's approval of the SIP submission. Isolatek must report monthly average hourly SO 2 emissions from Cupola #1 and Cupola #2 and monthly average hourly SO 2 emissions from Blow Chamber #3 and Blow Chamber #4 on a quarterly basis to IDEM and must report any exceedances of the SO 2 emissions limits. Based on these requirements, EPA is proposing to find that the emissions limits in IDEM's SIP revision will become permanent and enforceable upon EPA's approval of the SIP submission.

Using the source-specific one-hour average emissions rates for Isolatek that are established in the SIP submission, IDEM demonstrated that the highest 4th high one-hour maximum daily SO 2 concentration, averaged across five years for the entire area defined by the receptor grid, is 195.9 micrograms per cubic meter and occurred approximately 175 meters northeast of the fenceline receptor grid. As the maximum modeled concentrations occurred within a one kilometer radius of Isolatek, receptors were not placed inside the fencelines of the other explicitly modeled nearby sources to determine the ambient impacts from Isolatek. Based on this modeling, EPA proposes to conclude that the permanent and enforceable emission limits for Isolatek provide for attainment of the 2010 SO 2 NAAQS of 75 ppb (or 196.4 micrograms per cubic meter) in the Huntington nonattainment area.

IDEM's demonstration providing for modeled attainment of the 2010 SO 2 NAAQS is based on a combination of facility-specific emission rates and monitored background concentrations. Regional sources not explicitly modeled in AERMOD, but which contribute to ambient SO 2 loadings within the nonattainment area, are represented via background monitoring data. IDEM identified background concentration estimates from the Lima, Ohio monitor as the most representative site in the vicinity of the modeling domain. The Lima, OH SO 2 monitor is located approximately 74 miles east-southeast of Isolatek and is the closest monitor within the region. The hour-by-season averaged SO 2 background values for 2019-2021 at this monitor range from 0.33 ppb to 1.33 ppb. EPA proposes to conclude that the background concentrations used in IDEM's modeled attainment demonstration are appropriate and consistent with EPA modeling guidance.

EPA's DRR modeling indicated that the Isolatek facility was contributing to violations of the 2010 SO 2 NAAQS in the Huntington area. IDEM evaluated control options for the nonattainment area and established emissions limits for the Isolatek facility. Construction of the relevant control projects was completed in November 2022, with a compliance date to codify the emissions limits as permanent and enforceable on March 1, 2024. IDEM's modeling demonstrated that the one-hour average hourly SO 2 emissions limits contained in the SIP revision yielded a highest 4th high one-hour daily maximum SO 2 concentration of 195.9 micrograms per cubic meter which is below the 2010 SO 2 NAAQS level of 196.4 micrograms per cubic meter.

EPA is proposing to conclude that IDEM's modeling is a technically sound demonstration that the Isolatek facility, as the primary source contributing to violations of the 2010 SO 2 NAAQS, has been properly addressed in the State's attainment plan. EPA proposes to find that IDEM's modeling appropriately provides for attainment of the 2010 SO 2 NAAQS.

CAA section 172(c)(3) requires States to provide a comprehensive, accurate, and current inventory of actual emissions from all sources of SO 2 in the nonattainment area, as well as any sources located outside the nonattainment area which may affect attainment in the area. The emissions inventory and source emission rate data for an area serve as the foundation for air quality modeling and other analyses that enable States to: (1) estimate the degree to which different sources within a nonattainment area contribute to violations within the affected area; and (2) assess the prospects for attaining the standard based on alternative control measures. EPA's April 2014 SO 2 Guidance includes requirements for submitting emissions inventories that are representative of base year conditions and a projection to the attainment year.

IDEM provided a comprehensive, accurate, and current inventory of emissions of SO 2 in Huntington County. The 2017 base year inventory was developed using data from the National Emissions Inventory (NEI) and included point sources, nonpoint sources, non-road mobile sources, and on-road mobile sources. County level emissions data are summarized in Table 1 for the 2017 base year. The data indicate the largest contribution to SO 2 emissions in the nonattainment area is from non-EGU point sources. IDEM compiled actual SO 2 emissions, as reported, shown in Table 2, from the two non-EGU point sources in Huntington County. Isolatek reports annual emissions to IDEM; Teijin Automotive Technologies reports to IDEM on a triennial basis. IDEM did not find evidence of any other large sources near the nonattainment area that may have been impacting air quality in the Huntington area. EPA is proposing to determine that IDEM's list of sources with potential to cause nonattainment of the NAAQS is thorough and complete.

IDEM's projected emissions for the 2023 attainment year are based on the attainment modeling described previously in this notice in Section III.C. As noted in EPA's evaluation of the attainment modeling demonstration, the source emission rate data for Isolatek is calculated by the maximum allowable hourly emissions limit established in the SIP revision. Projected county level emissions data by sector are summarized in Table 3 for the 2023 attainment year.

Section 172(c)(1) of the CAA requires States to adopt and submit all RACM, including RACT, as needed to attain the standards as expeditiously as practicable. Section 172(c)(6) requires the SIP to contain enforceable emission limits and control measures necessary to provide for timely attainment of the standard.

The Isolatek facility, identified by EPA as the largest source of SO 2 emissions contributing to violations of the 2010 SO 2 NAAQS in Huntington, Indiana, was required by the State to increase the height of its stack, enclose screenhouses, and build a new elevated stack. These emissions control projects were completed in November 2022. Together with the permanent and enforceable hourly average emissions limits in IDEM's Commissioner's Order, EPA is proposing to find that the control measures implemented at the Isolatek facility provide for attainment of the 2010 SO 2 NAAQS. Because CAA section 172(c) does not require the State to impose emissions control measures for SO 2 nonattainment areas beyond the emissions reductions necessary to provide for attainment, EPA is proposing to find that the control measures implemented at the Isolatek facility satisfy the requirements of CAA section 172(c)(1) to reduce emissions from existing sources in the area as expeditiously as practicable. EPA is proposing to determine that the State's plan satisfies the applicable CAA requirements for RACM and RACT.

EPA approved Indiana's NNSR rules on October 7, 1994 (94 FR 24837). These rules, which are contained in the SIP, provide for review of SO 2 sources undergoing construction or major modification in nonattainment areas such as the Huntington Township area. Although these rules predated promulgation of the 2010 SO 2 standard, they are written in a manner such that new sources within areas that become designated nonattainment for the new standard, such as the Huntington Township area, become subject to these nonattainment new source review requirements. Therefore, EPA is proposing to determine that this CAA requirement has been met for this area.

CAA section 172(c)(2) requires Indiana's SO 2 Attainment Plan SIP for Huntington, Indiana to provide for reasonable further progress toward attainment. For SO 2 SIPs, which address a small number of affected sources, requiring expeditious compliance with attainment emission limits can address the RFP requirement. Isolatek completed construction of the new stack and other emissions control projects by November 2022. Furthermore, Isolatek was required by the Commissioner's Order to comply with enforceable and permanent control measures by March 1, 2024.

In this action, EPA is proposing to approve the hourly average SO 2 emissions limits that Isolatek was required to comply with, per the Commissioner's Order, into Indiana's SIP as permanent and enforceable. EPA is proposing to conclude that the requirements in the State's plan, including establishing hourly SO 2 emission limits for the Isolatek facility, represent implementation of control measures as expeditiously as practicable. This plan provides for attainment of the 2010 SO 2 NAAQS. Accordingly, EPA proposes to find that IDEM's plan provides for RFP.

Section 172(c)(9) of the CAA requires that nonattainment plans include additional measures which will take effect if an area fails to meet RFP or fails to attain the standard by the attainment date. As noted previously, EPA guidance describes special features of SO 2 planning that influence the suitability of alternative means of addressing the requirement in CAA section 172(c)(9) for contingency measures for SO 2 . An appropriate means of satisfying this requirement for SO 2 nonattainment area planning is for the State to have a comprehensive SO 2 enforcement program that identifies sources of violations of the SO 2 NAAQS and for the State to undertake aggressive follow-up for compliance and enforcement. IDEM's plan provides for satisfying the contingency measure requirement in this manner for sources in the State. IDEM provided example measures that may be considered if enforcement of violations of the NAAQS is required, such as requiring alternative fuels, requiring installation of additional control technologies, or requiring the source to reduce operating hours. EPA is proposing to concur with this approach and proposes to approve IDEM's plan for meeting the contingency measures requirement in this manner.

EPA is proposing to find, under section 179 of the CAA, that the Huntington County, Indiana nonattainment area failed to attain the 2010 SO 2 NAAQS by the applicable attainment date of April 9, 2023, and that Indiana is therefore subject to the requirement under section 179 to submit a revision to its SIP to provide for attainment in that area no later than five years from the date of any final determination that the area failed to attain. See section 179(c)-(d). EPA is also proposing to approve Indiana's November 6, 2023, SIP attainment plan submittal and February 15, 2024, supplemental SIP revision for the Huntington County SO 2 nonattainment area as fulfilling this requirement to provide for attainment of the 2010 SO 2 NAAQS by the attainment date, in this unique circumstance because control measures are now in place and effective, the area is attaining the 2010 SO 2 NAAQS, and the State has submitted a complete and approvable attainment plan with all required planning elements. EPA is proposing to determine that IDEM has appropriately demonstrated that the plan provides for attainment of the 2010 SO 2 NAAQS in the Huntington County, Indiana nonattainment area and that the plan meets the other applicable requirements under CAA sections 172, 191, and 192. The proposed approval of IDEM's SO 2 attainment plan, if finalized, would also terminate the FIP clock that was triggered by EPA's November 3, 2020, Finding of Failure to Submit for the Huntington County area. EPA is soliciting public comments for 30 days following the publication of this proposed action in the Federal Register and will take these comments into consideration in our final action.

Under the CAA, the Administrator is required to approve a SIP submission that complies with the provisions of the CAA and applicable Federal regulations. 42 U.S.C. 7410(k); 40 CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to approve State choices, provided that they meet the criteria of the CAA. Accordingly, this action merely approves State law as meeting Federal requirements and does not impose additional requirements beyond those imposed by State law.

For that reason, this action:

• Is not a significant regulatory action subject to review by the Office of Management and Budget under Executive Order 12866 (58 FR 51735, October 4, 1993);

• Is not subject to Executive Order 14192 (90 FR 9065, February 6, 2025) because SIP actions are exempt from review under Executive Order 12866;

• Does not impose an information collection burden under the provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq. );

• Is certified as not having a significant economic impact on a substantial number of small entities under the Regulatory Flexibility Act (5 U.S.C. 601 et seq. );

• Does not contain any unfunded mandate or significantly or uniquely affect small governments, as described in the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4);

• Does not have federalism implications as specified in Executive Order 13132 (64 FR 43255, August 10, 1999);

• Is not subject to Executive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;

• Is not a significant regulatory action subject to Executive Order 13211 (66 FR 28355, May 22, 2001); and

• Is not subject to requirements of section 12(d) of the National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) because application of those requirements would be inconsistent with the CAA.

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where EPA or an Indian Tribe has demonstrated that a Tribe has jurisdiction. In those areas of Indian country, the rulemaking does not have Tribal implications and will not impose substantial direct costs on Tribal governments or preempt Tribal law as specified by Executive Order 13175 (65 FR 67249, November 9, 2000).

Throughout this document whenever “we,” “us,” or “our” is used, we mean EPA.

On August 23, 2021, EGLE submitted a revision to its SIP to address regional haze requirements for the second implementation period. On April 3, 2025, EGLE submitted a supplement in draft for parallel processing. EGLE made this SIP submission to satisfy the requirements of the CAA's regional haze program pursuant to CAA sections 169A and 169B and 40 CFR 51.308. EPA proposes to find that the Michigan Regional Haze SIP submission for the second implementation period meets the applicable statutory and regulatory requirements. Thus, EPA proposes to approve EGLE's submission into its SIP.

Consistent with EPA regulations found at 40 CFR part 51, appendix V, section 2.3.1, for purposes of expediting review of a SIP submission, parallel processing allows a State to submit a plan to EPA prior to final adoption by the State.

Generally, the State submits a copy of the proposed regulation or other revisions to EPA before conducting its public hearing. EPA reviews this proposed State action and prepares a notice of proposed rulemaking. EPA's notice of proposed rulemaking is published in the Federal Register during the same time frame that the State is holding its public process. The State and EPA then provide for concurrent public comment periods on both the State action and Federal action.

If the revision that is finally adopted and submitted by EGLE is changed in aspects other than those identified in the proposed rulemaking on the parallel process submission, EPA will evaluate those changes and if necessary and appropriate, issue another notice of proposed rulemaking. The final rulemaking action by EPA will occur only after the SIP revision has been adopted by the State and submitted formally to EPA for incorporation into the SIP.

On April 3, 2025, EGLE submitted a request for parallel processing of a draft SIP supplement that it has taken to public comment on March 10, 2025. EGLE requested parallel processing so that EPA can act on its Regional Haze SIP revision in advance of EGLE's submission of a SIP supplement. As stated previously, the final rulemaking action by EPA will occur only after the SIP supplement has been: (1) submitted formally to EPA for incorporation into the SIP and (2) evaluated by EPA, including any changes made by EGLE after the April 3, 2025, draft SIP supplement was submitted to EPA.

A detailed history and background of the regional haze program is provided in prior EPA proposal action. 1 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. 2 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.

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. 3 CAA 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 169A(a)(1).

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.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., sulfur dioxide (SO 2 ), nitrogen oxides (NO X ), and, in some cases, volatile organic compounds (VOC) and ammonia (NH 3 )). Fine particle precursors react in the atmosphere to form fine particulate matter (PM 2.5 ), which impairs visibility by scattering and absorbing light. Visibility impairment reduces the perception of clarity and color, as well as visible distance. 4

To address regional haze visibility impairment, the 1999 RHR established an iterative planning process that requires both States in which Class I areas are located and States “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to periodically submit SIP revisions to address such impairment. CAA 169A(b)(2);  5 see also 40 CFR 51.308(b), (f) (establishing submission dates for iterative regional haze SIP revisions); (64 FR at 35768, July 1, 1999).

On January 10, 2017 (82 FR 3078), EPA promulgated revisions to the RHR, that apply for the second and subsequent implementation periods. The reasonable progress requirements as revised in the 2017 rulemaking (referred to here as the 2017 RHR Revisions) are codified at 40 CFR 51.308(f).

Five regional planning organizations (RPOs) were developed in the lead-up to the first implementation period to address regional haze. The Lake Michigan Air Directors Consortium (LADCO), one of the five RPOs, is a collaborative effort of State governments, Tribal governments, and various Federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the Midwest. LADCO member States are Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin. The LADCO Regional Haze Technical Workgroup also includes Tribes, Iowa, EPA, U.S. National Park Service (NPS), U.S. Fish and Wildlife Service (FWS), and U.S. Forest Service (USFS).

Under the CAA and EPA's regulations, all 50 States, the District of Columbia, and the U.S. Virgin Islands are required to submit regional haze SIPs satisfying the applicable requirements for the second implementation period of the regional haze program by July 31, 2021. Each State's SIP must contain a long-term strategy for making reasonable progress toward meeting the national goal of remedying any existing and preventing any future anthropogenic visibility impairment in Class I areas. CAA 169A(b)(2)(B). To this end, 40 CFR 51.308(f) lays out the process by which States determine what constitutes their long-term strategies, with the order of the requirements in 40 CFR 51.308(f)(1) through (3) generally mirroring the order of the steps in the reasonable progress analysis  6 and (f)(4) through (6) containing additional, related requirements. Broadly speaking, a State first must identify the Class I areas within the State and determine the Class I areas outside the State in which visibility may be affected by emissions from the State. These are the Class I areas that must be addressed in the State's long-term strategy. See 40 CFR 51.308(f), (f)(2). For each Class I area within its borders, a State must then calculate the baseline (five-year average period of 2000-2004), current, and natural visibility conditions ( i.e., visibility conditions without anthropogenic visibility impairment) for that area, as well as the visibility improvement made to date and the “uniform rate of progress” (URP). The URP is the linear rate of progress needed to attain natural visibility conditions, assuming a starting point of baseline visibility conditions in 2004 and ending with natural conditions in 2064. This linear interpolation is used as a tracking metric to help States assess the amount of progress they are making towards the national visibility goal over time in each Class I area. See 40 CFR 51.308(f)(1). Each State having a Class I area and/or emissions that may affect visibility in a Class I area must then develop a long-term strategy that includes the enforceable emission limitations, compliance schedules, and other measures that are necessary to make reasonable progress in such areas. A reasonable progress determination is based on applying the four factors in CAA section 169A(g)(1) to sources of visibility impairing pollutants that the State has selected to assess for controls for the second implementation period. Additionally, as further explained below, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors”  7 that States must consider in developing their long-term strategies. See 40 CFR 51.308(f)(2). A State evaluates potential emission reduction measures for those selected sources and determines which are necessary to make reasonable progress. Those measures are then incorporated into the State's long-term strategy. After a State has developed its long-term strategy, it then establishes RPGs for each Class I area within its borders by modeling the visibility impacts of all reasonable progress controls at the end of the second implementation period, i.e., in 2028, as well as the impacts of other requirements of the CAA. The RPGs include reasonable progress controls not only for sources in the State in which the Class I area is located, but also for sources in other States that contribute to visibility impairment in that area. The RPGs are then compared to the baseline visibility conditions and the URP to ensure that progress is being made towards the statutory goal of preventing any future and remedying any existing anthropogenic visibility impairment in Class I areas. 40 CFR 51.308(f)(2)-(3). There are additional requirements in the rule, including FLM consultation, that apply to all visibility protection SIPs and SIP revisions. See e.g., 40 CFR 51.308(i).

While States have discretion to choose any source selection methodology that is reasonable, whatever choices they make should be reasonably explained. To this end, 40 CFR 51.308(f)(2)(i) requires that a State's SIP submission include “a description of the criteria it used to determine which sources or groups of sources it evaluated.” 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, must also be appropriately documented, as required by 40 CFR 51.308(f)(2)(iii).

Once a State has selected the set of sources, the next step is to determine the emissions reduction measures for those sources that are necessary to make reasonable progress for the second implementation period. 8 This is accomplished by considering the four factors—“the costs of compliance, the time necessary for compliance, and the energy and non-air quality environmental impacts of compliance, and the remaining useful life of any existing source subject to such requirements.” CAA 169A(g)(1). EPA has explained that the four-factor analysis is an assessment of potential emission reduction measures ( i.e., control options) for sources; “use of the terms `compliance' and `subject to such requirements' in section 169A(g)(1) strongly indicates that Congress intended the relevant determination to be the requirements with which sources would have to comply to satisfy the CAA's reasonable progress mandate.” 82 FR 3091. Thus, for each source it has selected for four-factor analysis, 9 a State must consider a “meaningful set” of technically feasible control options for reducing emissions of visibility impairing pollutants. Id. at 3088.

EPA has also explained that, in addition to the four statutory factors, States have flexibility under the CAA and RHR to reasonably consider visibility benefits as an additional factor alongside the four statutory factors. 10 Ultimately, while States have discretion to reasonably weigh the factors and to determine what level of control is needed, 40 CFR 51.308(f)(2)(i) provides that a State “must include in its implementation plan a description of . . . how the four factors were taken into consideration in selecting the measure for inclusion in its long-term strategy.”

As explained above, 40 CFR 51.308(f)(2)(i) requires States to determine the emission reduction measures for sources that are necessary to make reasonable progress by considering the four factors. Pursuant to 40 CFR 51.308(f)(2), measures that are necessary to make reasonable progress towards the national visibility goal must be included in a State's long-term strategy and in its SIP. If the outcome of a four-factor analysis is that an emissions reduction measure is necessary to make reasonable progress towards remedying existing or preventing future anthropogenic visibility impairment, that measure must be included in the SIP.

The characterization of information on each of the factors is also subject to the documentation requirement in 40 CFR 51.308(f)(2)(iii). The reasonable progress analysis is a technically complex exercise, and also a flexible one that provides States with bounded discretion to design and implement approaches appropriate to their circumstances. Given this flexibility, 40 CFR 51.308(f)(2)(iii) plays an important function in requiring a State to document the technical basis for its decision making so that the public and EPA can comprehend and evaluate the information and analysis the State relied upon to determine what emission reduction measures must be in place to make reasonable progress. The technical documentation must include the modeling, monitoring, cost, engineering, and emissions information on which the State relied to determine the measures necessary to make reasonable progress. Additionally, the RHR at 40 CFR 51.3108(f)(2)(iv) separately provides five “additional factors”  11 that States must consider in developing their long-term strategies: (1) Emission reductions due to ongoing air pollution control programs, including measures to address reasonably attributable visibility impairment; (2) measures to reduce the impacts of construction activities; (3) source retirement and replacement schedules; (4) basic smoke management practices for prescribed fire used for agricultural and wildland vegetation management purposes and smoke management programs; and (5) the anticipated net effect on visibility due to projected changes in point, area, and mobile source emissions over the period addressed by the long-term strategy.

Because the air pollution that causes regional haze crosses State boundaries, 40 CFR 51.308(f)(2)(ii) requires a State to consult with other States that also have emissions that are reasonably anticipated to contribute to visibility impairment in a given Class I area. If a State, pursuant to consultation, agrees that certain measures ( e.g., a certain emission limitation) are necessary to make reasonable progress at a Class I area, it must include those measures in its SIP. 40 CFR 51.308(f)(2)(ii)(A). Additionally, the RHR requires that States that contribute to visibility impairment at the same Class I area consider the emission reduction measures the other contributing States have identified as being necessary to make reasonable progress for their own sources. 40 CFR 51.308(f)(2)(ii)(B). If a State has been asked to consider or adopt certain emission reduction measures, but ultimately determines those measures are not necessary to make reasonable progress, that State must document in its SIP the actions taken to resolve the disagreement. 40 CFR 51.308(f)(2)(ii)(C). Under all circumstances, a State must document in its SIP submission all substantive consultations with other contributing States. 40 CFR 51.308(f)(2)(ii)(C).

RPGs “measure the progress that is projected to be achieved by the control measures States have determined are necessary to make reasonable progress based on a four-factor analysis.” 82 FR 3091.

For the second implementation period, the RPGs are set for 2028. RPGs are not enforceable targets, 40 CFR 51.308(f)(3)(iii). While States are not legally obligated to achieve the visibility conditions described in their RPGs, 40 CFR 51.308(f)(3)(i) requires that “[t]he long-term strategy and the reasonable progress goals must provide for an improvement in visibility for the most impaired days since the baseline period and ensure no degradation in visibility for the clearest days since the baseline period.”

RPGs may also serve as a metric for assessing the amount of progress a State is making towards the national visibility goal. To support this approach, the RHR requires States with Class I areas to compare the 2028 RPG for the most impaired days to the corresponding point on the URP line (representing visibility conditions in 2028 if visibility were to improve at a linear rate from conditions in the baseline period of 2000-2004 to natural visibility conditions in 2064). If the most impaired days RPG in 2028 is above the URP ( i.e., if visibility conditions are improving more slowly than the rate described by the URP), each State that contributes to visibility impairment in the Class I area must demonstrate, based on the four-factor analysis required under 40 CFR 51.308(f)(2)(i), that no additional emission reduction measures would be reasonable to include in its long-term strategy. 40 CFR 51.308(f)(3)(ii). To this end, 40 CFR 51.308(f)(3)(ii) requires that each State contributing to visibility impairment in a Class I area that is projected to improve more slowly than the URP provide “a robust demonstration, including documenting the criteria used to determine which sources or groups [of] sources were evaluated and how the four factors required by paragraph (f)(2)(i) were taken into consideration in selecting the measures for inclusion in its long-term strategy.”

Section 51.308(f)(6) requires States to have certain strategies and elements in place for assessing and reporting on visibility. Individual requirements under this section apply either to States with Class I areas within their borders, States with no Class I areas but that are reasonably anticipated to cause or contribute to visibility impairment in any Class I area, or both. Compliance with the monitoring strategy requirement may be met through a State's participation in the Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring network, which is used to measure visibility impairment caused by air pollution at the 156 Class I areas covered by the visibility program. 40 CFR 51.308(f)(6), (f)(6)(i), (f)(6)(iv).

All States' SIPs must provide for procedures by which monitoring data and other information are used to determine the contribution of emissions from within the State to regional haze visibility impairment in affected Class I areas, as well as a statewide inventory documenting such emissions. 40 CFR 51.308(f)(6)(ii), (iii), (v). All States' SIPs must also provide for any other elements, including reporting, recordkeeping, and other measures, that are necessary for States to assess and report on visibility. 40 CFR 51.308(f)(6)(vi).

Section 51.308(f)(5) requires a State's regional haze SIP revision to address the requirements of paragraphs 40 CFR 51.308(g)(1) through (5) so that the plan revision due in 2021 will serve also as a progress report addressing the period since submission of the progress report for the first implementation period. The regional haze progress report requirement is designed to inform the public and EPA about a State's implementation of its existing long-term strategy and whether such implementation is in fact resulting in the expected visibility improvement. See 81 FR 26942, 26950 (May 4, 2016), (82 FR 3119, January 10, 2017). To this end, every State's SIP revision for the second implementation period is required to assess changes in visibility conditions and describe the status of implementation of all measures included in the State's long-term strategy, including BART and reasonable progress emission reduction measures from the first implementation period, and the resulting emissions reductions. 40 CFR 51.308(g)(1) and (2).

CAA section 169A(d) requires that before a State holds a public hearing on a proposed regional haze SIP revision, it must consult with the appropriate FLM or FLMs; pursuant to that consultation, the State must include a summary of the FLMs' conclusions and recommendations in the notice to the public. Consistent with this statutory requirement, the RHR also requires that States “provide the [FLM] with an opportunity for consultation, in person and at a point early enough in the State's policy analyses of its long-term strategy emission reduction obligation so that information and recommendations provided by the [FLM] can meaningfully inform the State's decisions on the long-term strategy.” 40 CFR 51.308(i)(2). For EPA to evaluate whether FLM consultation meeting the requirements of the RHR has occurred, the SIP submission should include documentation of the timing and content of such consultation. The SIP revision submitted to EPA must also describe how the State addressed any comments provided by the FLMs. 40 CFR 51.308(i)(3). Finally, a SIP revision must provide procedures for continuing consultation between the State and FLMs regarding the State's visibility protection program, including development and review of SIP revisions, five-year progress reports, and the implementation of other programs having the potential to contribute to impairment of visibility in Class I areas. 40 CFR 51.308(i)(4).

Please see section 2 of the May 22, 2025, technical support document (TSD) accompanying this rule for background on EGLE's first implementation period plan.

In accordance with CAA section 169A and the RHR at 40 CFR 51.308(f), on August 23, 2021, and supplemented on April 3, 2025, EGLE submitted a revision to the Michigan SIP to address its regional haze obligations for the second implementation period that runs through 2028.

The following sections describe EGLE's SIP submission, including analyses conducted by LADCO and EGLE's determinations based on those analyses, EGLE's assessment of progress made since the first implementation period in reducing emissions of visibility impairing pollutants, and the visibility improvement progress at its Class I areas and nearby Class I areas. This proposed rulemaking and the accompanying May 22, 2025, TSD also contain EPA's evaluation of EGLE's submission against the requirements of the CAA and RHR for the second implementation period of the regional haze program.

Section 169A(b)(2) of the CAA requires each State in which any Class I area is located or “the emissions from which may reasonably be anticipated to cause or contribute to any impairment of visibility” in a Class I area to have a plan for making reasonable progress toward the national visibility goal. The RHR implements this statutory requirement at 40 CFR 51.308(f), which provides that each State's plan “must address regional haze in each mandatory Class I Federal area located within the State and in each mandatory Class I Federal area located outside the State that may be affected by emissions from within the State,” and paragraph (f)(2), which requires each State's plan to include a long-term strategy that addresses regional haze in such Class I areas.

Michigan has two mandatory Class I Federal areas: Isle Royale National Park (Isle Royale) and Seney National Wildlife Refuge (Seney). LADCO performed a technical analysis to help assess state-level contributions to visibility impairment at Class I areas for the second implementation period. EGLE provided the analysis in section 2.1, Tables 6 and 7 of its supplement.

Based on LADCO's source apportionment modeling results for 2028, Michigan was projected to have the greatest visibility impact on the Class I areas within the State, Seney and Isle Royale, contributing an estimated 3.4 Mm −1 and 1.7 Mm −1 of visibility impairment, respectively. This represents about 6.0 percent of the total light extinction at Seney and 3.5 percent at Isle Royale. Michigan also identified 13 out-of-state Class I areas where Michigan's contribution to the total light extinction was 1 percent or greater. In addition, Michigan identified the two Class I areas in Minnesota since they are also located within LADCO, although the projected impacts to these out-of-state areas are less than 1 percent at both Voyageurs National Park and Boundary Waters Canoe Area Wilderness (0.2 Mm −1 and 0.3 Mm −1 impairment, respectively).

The regulation at 40 CFR 51.308(f)(1) requires States to determine the following for “each mandatory Class I Federal area located within the State”: baseline visibility conditions for the most impaired and clearest days, natural visibility conditions for the most impaired and clearest days, progress to date for the most impaired and clearest days, the differences between current visibility conditions and natural visibility conditions, and the URP. This section also provides the option for States to propose adjustments to the URP line for a Class I area to account for visibility impacts from anthropogenic sources outside the United States and/or the impacts from wildland prescribed fires that were conducted for certain, specified objectives. 40 CFR 51.308(f)(1)(vi)(B).

EGLE provided this analysis for Isle Royale and Seney in section 2 of its 2021 submission with updates in section 6 of its supplement. The 2002 to 2004 observed baseline visibility conditions for Isle Royale are 6.77 deciviews (dv) on the 20 percent clearest days and 19.63 dv on the 20 percent most impaired days. For Seney, the baseline visibility is 7.14 dv on the 20 percent clearest days and 23.58 dv on the 20 percent most impaired days. The natural conditions at Isle Royale are 3.72 dv on the 20 percent clearest days and 10.17 dv on the 20 percent most impaired days. Natural conditions at Seney are 3.74 dv on the 20 percent clearest days and 11.11 dv on the 20 percent most impaired days. Current conditions, based on 2014 to 2018 monitoring data, at Isle Royale are 15.54 dv on the 20 percent most impaired days and 5.30 dv on the 20 percent clearest days. At Seney, the current conditions, based on 2014 to 2018 monitoring data, are 17.57 dv on the 20 percent most impaired days and 5.27 dv on the 20 percent clearest days. Based on the ambient data trends, steady progress towards natural conditions is being made at both Isle Royale and Seney.

EGLE calculated the URP for the Class I areas for 2028 using LADCO's 2016 base year modeling. The 2028 URP is 15.85 dv at Isle Royale and 18.59 dv at Seney on the most impaired days. EGLE projects 14.83 dv impairment at Isle Royale and 16.67 dv at Seney on the most impaired days, which are 1.02 dv and 1.92 dv below the URP, respectively.

EPA proposes to find that EGLE has submitted a regional haze plan that meets the requirements of 40 CFR 51.308(f)(1) related to the calculations of baseline, current, and natural visibility conditions; progress to date; and the URP for the second implementation period.

Each State having a Class I area within its borders or emissions that may affect visibility in a Class I area must develop a long-term strategy for making reasonable progress towards the national visibility goal. CAA 169A(b)(2)(B). After considering the four statutory factors, all measures that are determined to be necessary to make reasonable progress must be in the long- term strategy. In developing its long-term strategies, a State must also consider the five additional factors in 40 CFR 51.308(f)(2)(iv). As part of its reasonable progress determinations, the State must describe the criteria used to determine which sources or group of sources were evaluated ( i.e., subjected to four-factor analysis) for the second implementation period and how the four factors were taken into consideration in selecting the emission reduction measures for inclusion in the long-term strategy. 40 CFR 51.308(f)(2)(iii).

EGLE details its measures necessary to make reasonable progress in section 5.2 of its supplement. EGLE's long-term strategy includes VOC Control Techniques, National Emission Standards for Hazardous Air Pollutants for some source categories, New Source Performance Standards for solid waste incinerators and for residential wood heaters, Federal onroad mobile sources rules, and several Federal non-road mobile sources rules among other Federal measures.