SUPPLEMENTARY INFORMATION:

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

I. What action is the EPA proposing?

The EPA is proposing to approve a revision to the Oklahoma SIP for the regional haze first implementation period that revises source-specific requirements for the American Electric Power/Public Service of Oklahoma (AEP/PSO) ^[1] Northeastern Power Station that are part of the State's long-term strategy. Specifically, this action proposes to remove the requirement that PSO Northeastern Unit 3 cease operations by December 31, 2026, and allow the unit to continue operations as a natural gas-fired unit. In addition, consistent with the requirements of Clean Air Act Section 110(l) this action proposes to approve reductions in nitrogen oxides (NO_X ) emissions at Unit 2. The EPA is proposing to find that Oklahoma's 2026 SIP submission, with the accompanying revised regional haze agreement for PSO Northeastern, satisfies the long-term strategy regulatory requirements from the first planning period under the regional haze program.^[2]

II. Background and Requirements for Regional Haze First Planning Period Plans

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. The CAA under section 169A 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.” ^[3]

Regional haze is visibility impairment that is produced by a multitude of anthropogenic sources and activities that are located across a broad geographic area and that emit pollutants that impair visibility. Visibility impairing pollutants include fine and coarse particulate matter (PM) ( e.g., sulfates, nitrates, organic carbon, elemental carbon, and soil dust) and their precursors ( e.g., sulfur dioxide (SO₂), nitrogen oxides (NO_X), and, in some cases, volatile organic compounds (VOC) and ammonia (NH₃)). 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 ( printed page 55288) perception of clarity and color, as well as visible distance.^[4]

To address regional haze visibility impairment, the 1999 Regional Haze Rule (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 section 169A(b)(2); ^[5] see also 40 CFR 51.308(b) and (f) (establishing submission dates for iterative regional haze SIP revisions); 64 FR 35714 at 64 FR 35768 (July 1, 1999)).

Much of the focus in the first implementation period of the regional haze program, which ran from 2007 through 2018, was on satisfying States' Best Available Retrofit Technology (BART) obligations.^[6] First implementation period SIPs were additionally required to contain long-term strategies for making reasonable progress toward the national visibility goal, of which BART is one component. The long-term strategy is the compilation of “enforceable emissions limitations, compliance schedules, and other measures as necessary to achieve the [reasonable progress goals (RPGs)],” ^[7] and is the means through which the State ensures that its RPG will be met. The core required elements for the first implementation period SIPs (other than BART) are laid out in 40 CFR 51.308(d). The RHR gives States wide latitude to determine the set of source categories and control measures for the long-term strategy and the related reasonable progress goals (RPGs). Those provisions required that States containing Class I areas establish RPGs that are measured in deciviews and reflect the anticipated visibility conditions at the end of the implementation period including from implementation of States' long-term strategies. The first planning period RPGs were required to provide for an improvement in visibility for the most impaired days over the period of the implementation plan and ensure no degradation in visibility for the least impaired days over the same period. In establishing the RPGs for any Class I area in a State, the State was required to consider four statutory factors: the costs of compliance, the time necessary for compliance, the energy and nonair quality environmental impacts of compliance, and the remaining useful life of any potentially affected sources.^[8]

States were also required to calculate baseline (using the five year period of 2000 through 2004) and natural visibility conditions ( i.e., visibility conditions without anthropogenic visibility impairment) for each Class I area, and to calculate 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 known as the uniform rate of progress (URP) and 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.^[9] The 1999 RHR also provided that States' long-term strategies must include the “enforceable emissions limitations, compliance, schedules, and other measures as necessary to achieve the reasonable progress goals.” ^[10] In establishing their long-term strategies, States are required to consult with other States that also contribute to visibility impairment in a given Class I area and include all measures necessary to obtain their shares of the emission reductions needed to meet the RPGs.^[11] Section 51.308(d) also contains seven additional factors States must consider in formulating their long-term strategies, 40 CFR 51.308(d)(3)(v), as well as provisions governing monitoring and other implementation plan requirements.^[12]

Finally, the 1999 RHR required States to consult with the Federal Land Manager(s) ^[13] (FLMs) responsible for each Class I area according to the requirements in CAA section 169A(d) and 40 CFR 51.308(i).

III. Rulemaking History on Oklahoma's Regional Haze Plans for the AEP PSO Northeastern Facility

A. Oklahoma's Regional Haze Plan for the First Implementation Period

Oklahoma submitted its regional haze SIP for the first implementation period to the EPA on February 19, 2010. On December 28, 2011 (76 FR 81728), the EPA partially approved certain requirements for the PSO Northeastern facility as provided in the 2010 Oklahoma regional haze SIP. As part of that action, we approved Oklahoma's SO₂, NO_X, and PM BART determinations for PSO Northeastern Unit 2, and the NO_X and PM BART determinations for PSO Northeastern Units 3 and 4. Specifically, we approved Oklahoma's determination that for Unit 2, the NO_X BART emission limit is 0.28 pounds per million British thermal units (lbs/MMBtu) on a 30-day rolling average. As Unit 2 is gas fired, the Oklahoma Department of Environmental Quality (ODEQ) determined that no additional controls were necessary for SO₂ and PM BART. For Units 3 and 4, we approved Oklahoma's determination that the NO_X BART emission limit is 0.15 lbs/MMBtu on a 30-day rolling average. In that same 2011 action, we disapproved Oklahoma's SO₂ BART determination for PSO Northeastern Units 3 and 4 and promulgated a Federal implementation plan (FIP) that imposed SO₂ BART emission limits for these units.

The State of Oklahoma and AEP/PSO filed Petitions for Review ^[14] of the FIP, ( printed page 55289) and both parties separately entered into a settlement agreement with the EPA and Sierra Club (“2013 PSO Settlement Agreement,” formalized February 8, 2013), which included a timeline for preparing and processing a SIP that would implement a comprehensive strategy for PSO and Oklahoma to comply with its obligations with respect to visibility and interstate transport provisions of the CAA.^[15] On March 7, 2014 (79 FR 12944), the EPA approved the 2013 Oklahoma regional haze SIP ^[16] that replaced and approved SO₂ BART requirements for the PSO Northeastern Units 3 and 4 and concurrently withdrew the FIP's applicability to these two units. In that same 2014 action (79 FR 12944, March 7, 2014), the EPA approved revised NO_X BART compliance schedules for these two units as well as requirements providing for further reductions for NO_X and SO₂ through reductions in maximum utilization. Specifically, the approved Oklahoma revised SO₂ BART determination included interim SO₂ emission limits for Units 3 and 4 of 0.60 lbs/MMBtu (with additional caps on combined annual SO₂ emissions) until 2016 when AEP/PSO would retire one of the two units. The unit remaining in operation had an SO₂ emission limit of 0.40 lbs/MMBtu on a 30-day rolling average basis through December 31, 2026, when the remaining unit would cease operation. Currently, Oklahoma has SIP-approved regional haze first planning period requirements that provide for emission controls and compliance schedules for PSO Northeastern Units 2, 3, and 4.

As part of the approval of Oklahoma's regional haze SIP submissions, the EPA approved Oklahoma's BART determinations for PSO Northeastern facility, which included provisions contained in the “PSO Regional Haze Agreement, DEQ Case No. 10-025 (February 10, 2010)” (“2010 PSO Regional Haze Agreement”), as amended by the “First Amended Regional Haze Agreement, DEQ Case No. 10-025 (March 26, 2013)” (“2013 PSO Regional Haze Agreement”).^[17]

In sum, the NO_X requirements for PSO Northeastern Unit 2 and initial NO_X requirements for Units 3 and 4 are contained in the 2010 PSO Regional Haze Agreement. The SO₂ requirements and revised NO_X compliance schedules for Units 3 and 4, including requirements for reduced utilization and cessation of operation of these units, are contained in the 2013 PSO Regional Haze Agreement.^[18]

B. Oklahoma's 2026 SIP Submission for the Regional Haze First Implementation Period

On March 12, 2026, the Oklahoma Department of Environmental Quality (ODEQ) ^[19] submitted a SIP revision to amend certain source-specific requirements for the PSO Northeastern facility and included a revised agreement as the enforceable mechanism. Our evaluation of this SIP submission is provided in the following section.

IV. The EPA's Evaluation of Oklahoma's 2026 SIP Submission

A. Background for the Revised PSO Northeastern Facility's Source-Specific Requirements

AEP/PSO Northeastern Power Station is an electric utility located in Rogers County, Oklahoma. PSO Northeastern Units 2, 3, and 4 were BART-eligible sources under the regional haze program first planning period.^[20] Unit 2 is a gas-fired boiler with a gross output of 495 MW. Units 3 and 4 are or were coal-fired boilers, permitted to fire coal and/or natural gas, with gross outputs of 490 MW each. Consistent with Oklahoma regional haze SIP requirements for the first planning period, AEP/PSO elected to retire Unit 4 on April 16, 2016, and only Units 2 and 3 are currently in operation.

More information and our evaluation of the proposed changes to the regional haze SIP requirements for PSO Northeastern Units 2 and 3 are provided in sections IV.A.1 and IV.A.2. of this document.

1. Oklahoma's Revisions to Requirements for AEP/PSO Northeastern Units 2 and 3

In 2024, AEP/PSO notified ODEQ that they would not be able to comply with the Southwest Power Pool's (SPP) increasing electric generation demands if Northeastern Unit 3 is required to cease operation on December 31, 2026, as stipulated in the 2013 settlement agreement and SIP. Therefore, to ensure reliable power in Oklahoma, AEP/PSO requested that Unit 3 be allowed to continue operating past this deadline as a natural gas-fired unit. Operating on natural gas will limit Unit 3's SO₂ emissions to a negligible 2.34 tons per year (TPY). In addition, AEP/PSO committed to an annual NO_X emission limit of 300 TPY on Unit 3 and lowering the allowable NO_X emissions of Unit 2 by 300 TPY to address CAA section 110(l) requirements with respect to the NO_X emissions from the continued operation of Unit 3.

On August 2, 2024, the Sierra Club and PSO executed a new settlement agreement based on these terms. The agreement provides for Northeastern Unit 3 continuing to operate as a natural gas-fired power plant, contingent upon ODEQ developing and EPA approving a SIP revision.^[21] On May 14, 2025, ODEQ and PSO executed the “Second Amended Regional Haze Agreement, DEQ Case No. 10-025” (“2025 PSO Regional Haze Agreement”), which amends portions of the 2010 and 2013 PSO Regional Haze Agreements from Case No. 10-025 and allows for the continued operation of Northeastern Unit 3 as a natural gas-fired unit, while also limiting the NO_X emissions at Unit 2, contingent upon an EPA-approved SIP revision.

The revised NO_X and SO₂ emission limits for PSO Northeastern Units 2 and 3 are provided as follows in table 1 of this document.^[22]

( printed page 55290)

Certain requirements for PSO Northeastern Units 2 and 3 remain unchanged from the previous PSO regional haze agreements. Unit 2 will still be subject to the NO_X emission limits from the 2010 PSO Regional Haze Agreement. For Unit 3, until January 1, 2026, or the EPA's approval of the 2026 SIP submission, PSO will continue to meet the utilization and emission limits that were required under the 2013 PSO Regional Haze Agreement as approved by the EPA.

The 2025 PSO Regional Haze Agreement provides new and revised requirements for PSO Northeastern Units 2 and 3, by providing (1) new, lower NO_X emission limits for Unit 2 by January 1, 2027 to offset the increase in NO_X emissions at Unit 3; and (2) revised requirements for Unit 3, including annual emission limits and a utilization rate of no more than 20% in addition to limiting operation to burning only pipeline-grade natural gas by the date of the EPA's approval of the agreement. In addition, and as discussed further in section IV.C of this document, the 2025 PSO Regional Haze Agreement also contains testing, monitoring, recordkeeping and reporting requirements for PSO Northeastern Units 2 and 3 to ensure compliance with the revised emission limits. Applicable requirements for Units 2 and 3 will also be incorporated into their corresponding Oklahoma air quality permits upon final EPA approval of Oklahoma's 2026 SIP submission incorporating the requirements of the 2025 PSO Regional Haze Agreement.

2. Evaluation of PSO Northeastern Facility's Source-Specific Requirements in Oklahoma's 2026 SIP Submission

Oklahoma's 2026 SIP submission revises or adds to those portions of Oklahoma's regional haze SIP that relate to the SO₂ and NO_X regional haze requirements for AEP/PSO's Northeastern Units 2 and 3. Oklahoma's SIP revision does not revise the previously approved BART determinations for the PSO Northeastern facility. As discussed further in section III.A of this document, the NO_X limits approved in 2011 for Units 2 and 3 are 0.28 and 0.15 lbs/MMBtu respectively. The NO_X emission limit for Unit 3 will continue to be 0.15 lbs/MMBtu, and as discussed further in sections IV.A.1 and IV.F of this document, the NO_X limit for Unit 2 will be reduced to 0.22 lbs/MMBtu and lowered by 300 tons annually. Unit 3 will continue to meet an SO₂ emission limit of 0.4 lbs/MMBtu, as required by the 2013 PSO Regional Haze agreement, until the unit only burns pipeline-grade natural gas. After January 1, 2026, or upon EPA approval of the 2026 SIP submission, the SO₂ emission limit will be a nominal 2.34 TPY based on an SO₂ emission rate of 0.0006 lbs/MMBtu from burning pipeline-grade natural gas.^[25] Gas-fired EGUs have inherently low SO₂ emissions ^[26] and there are no known SO₂ controls that can be evaluated. Oklahoma states in the SIP submission that these emission limitations effectively equal the SO₂ and NO_X emission reductions in the approved Oklahoma SIP as part of the long-term strategy.

A comparison of the requirements for PSO Northeastern Units 2 and 3 between the 2010, 2013, and 2025 PSO Regional Haze Agreements are provided in table 2 of this document.

( printed page 55291)

When comparing the current and proposed NO_X requirements for Units 2 and 3, the total amount of annual NO_X emissions between the two units is equivalent to the previous requirement to retire Unit 3 because the 300 TPY NO_X emissions from the burning of natural gas at Unit 3 is offset by a commensurate reduction of 300 TPY NO_X at Unit 2. Oklahoma's 2026 SIP submission revises, and we propose to approve, the NO_X annual limit for Unit 2 to decrease by 300 tons and limit Unit 3 to 300 tons annually; the NO_X annual emissions would continue to be limited to 5,830 TPY combined for these units. In addition, we propose to approve the revised requirement that Unit 2 will be subject to a NO_X emission rate limit of 0.22 lbs/MMBtu on a 30-day rolling average, compared to the 0.28 lbs/MMBtu under the current requirements, which represents a 20 percent reduction in the permitted emission rate.

SO₂ emissions under the existing and revised requirements are anticipated to provide for the same visibility benefits. The combustion of natural gas results in minimal SO₂ emissions, typically at a rate of 0.6 pounds per million standard cubic feet (MMscf).^[28] Consistent with the 2010 approval of Oklahoma's regional haze SIP, Unit 2 continues to operate as a natural gas-fired unit. For Unit 3, the requirement to retire by December 31, 2026, is revised to allow for continued operation using only natural gas with a nominal limit of 2.34 TPY for SO₂. As discussed in Oklahoma's 2026 SIP submission, Unit 3 is limited to burning pipeline-grade natural gas as defined in 40 CFR 72.2, with an equivalent SO₂ emission rate of 0.0006 lbs/MMBtu.^[29]

The EPA is proposing to find that the revised requirements for PSO Northeastern Units 2 and 3 provide for equivalent emission reductions compared to the existing EPA-approved requirements for the PSO Northeastern facility.

B. Amended Long-Term Strategy

Under 40 CFR 308(d)(3), a State's “long-term strategy must include enforceable emissions limitations, compliance schedules, and other measures as necessary to achieve the reasonable progress goals established by States having mandatory Class I Federal areas.” Oklahoma submitted its 2026 SIP submission to revise the currently approved source-specific requirements for PSO Northeastern Unit 3 under its long-term strategy with equivalent emission reductions and reasonable progress. As described in more detail in section IV.A of this document, we are proposing to find that limiting Unit 3 operations to only pipeline-grade natural gas in combination with a new NO_X limit for Unit 2 results in equivalent NO_X and SO₂ emissions reductions that would be achieved through the shutdown of PSO Northeastern Unit 3.

Since reasonable progress is a subset of the requirements for the long-term strategy, adoption of the emission reductions under reasonable progress for Oklahoma PSO Northeastern Unit 3 will also ensure that the long-term strategy requirements will continue to be met. Because Oklahoma has demonstrated that the proposed control measures and emissions reductions for PSO Northeastern Units 2 and 3 are equivalent to the current SIP-approved control measures, we are proposing to approve Oklahoma's amended long-term strategy as provided in its 2026 SIP submission. This includes Oklahoma's revised NO_X and SO₂ requirements for PSO Northeastern Units 2 and 3 as provided in Oklahoma's 2026 SIP submission and accompanying 2025 PSO Regional Haze Agreement.

C. Testing, Monitoring, Recordkeeping, and Reporting Requirements

We are proposing to approve the testing, monitoring, recordkeeping, and reporting requirements as provided Oklahoma's 2026 SIP submission, and as detailed in the 2025 PSO Regional Haze Agreement, paragraphs 26.E and 26.F, for the PSO Northeastern facility Units 2 and 3 that are associated with Unit 3 burning only natural gas and the revised emission limits for these two units. Specifically, the 2025 PSO Regional Haze Agreement contains provisions for testing and continuous monitoring requirements in accordance with 40 CFR 60.8, 60.13(e) through (h), appendix B of 40 CFR part 60, as well 40 CFR part 75, with further requirements detailed in paragraph 26.E of the agreement. The 2025 PSO Regional Haze Agreement also includes reporting and recordkeeping requirements for continuous monitoring compliance in accordance with 40 CFR 60.7(c) and (d) and 40 CFR part 75, as well as compliance with the Unit 2 SO₂ emission rate through fuel records. These testing, monitoring, recordkeeping, and reporting would provide for enforceability of the new emission limits for PSO Northeastern Units 2 and 3.

D. Consultation With States

States must meet the additional requirements when developing their long-term strategies. 40 CFR 51.308(d)(3)(i) requires States to consult with other States that have emissions that are reasonably anticipated to contribute to visibility impairment in Class I areas to develop coordinated emission management strategies. In section V.C of its 2026 SIP submission, Oklahoma describes how it consulted with other States on its draft SIP in accordance with 40 CFR 51.308(d)(3)(i). Oklahoma stated that it consulted with States that have Class I areas whose visibility is potentially affected by Oklahoma emissions during its original first planning period regional haze SIP development. On December 18, 2025, Oklahoma notified electronically the appropriate clean air agency staff for bordering and potentially affected States that were previously consulted on its proposed 2026 SIP submission and provided them with electronic access to the revision and related documents. These States include Arkansas, Iowa, Kansas, Louisiana, Minnesota, Missouri, Nebraska, New Mexico, and Texas, and the appropriate agency staff for each State is included in appendix VII of its SIP submission. Oklahoma also notified the State agency staff of the public hearing scheduled for January 22, 2026. Oklahoma did not receive any comments from other States on its draft SIP.

We are proposing to find that Oklahoma met applicable State to State consultation requirements under 40 CFR 51.308(d)(3)(i) in its 2026 SIP submission.

E. Consultation With Federal Land Managers

Oklahoma has one mandatory Class I Federal area within its borders, the Wichita Mountains Wilderness, located in the Wichita Mountains National Wildlife Refuge in Comanche County, in the southwest part of Oklahoma. Wichita Mountains Wilderness is managed by the US Fish and Wildlife Service (FWS). As provided in this section and in section II.D of this document, the RHR grants the FLMs, ( printed page 55292) regardless of whether an FLM manages a Class I area within the State, a special role in the review of regional haze implementation plans.

Section 169A(d) of the CAA 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. Under the RHR, 40 CFR 51.308(i)(2)'s FLM consultation provision requires a State to provide FLMs with an opportunity for consultation at least sixty days before a public hearing or public comment period at the State level. 40 CFR 51.308(i)(3) requires States, in developing their implementation plans, to include a description of how they addressed FLMs' comments.

In section V.B of its 2026 SIP submission, Oklahoma describes how it consulted with FLMs on its draft SIP in accordance with 40 CFR 51.308(i)(2). Oklahoma provided the FLMs a draft copy of its proposed 2026 SIP submission via email on November 13, 2025, and a consultation meeting was held virtually on December 16, 2025, between ODEQ and the U.S. Department of Agriculture Forest Service (FS) and the National Park Service (NPS). Oklahoma held a separate consultation phone call with the FWS on December 16, 2025. Oklahoma stated in it SIP that none of the agencies had any comments on the revision or requested further consultation. Oklahoma provided documentation of the virtual meeting and phone record in appendix II of its 2026 SIP submission. Oklahoma also provided the FLMs with notice of the opening of the public comment period on December 18, 2025, and the public hearing scheduled for January 22, 2026. FLMs did not provide any comments during the public comment period or during the public hearing. Oklahoma provided FLMs an opportunity for consultation in accordance with 40 CFR 51.308(i)(2). No comments were provided by FLMs, and thus no comments needed to be addressed in accordance with 40 CFR 51.308(i)(3).

We are proposing to find that Oklahoma met applicable FLM consultation requirements under CAA section 169A(d) and 40 CFR 51.308(i) in its 2026 SIP submission.

F. CAA Section 110(l)

Under CAA section 110( l ), the EPA cannot approve a plan revision “if the revision would interfere with any applicable requirement concerning attainment and reasonable further progress (as defined in section 7501 of this title), or any other applicable requirement of this chapter.” ^[30]

The previous sections of this rulemaking explain how Oklahoma's 2026 SIP submission will comply with applicable regional haze requirements and general implementation plan requirements, such as compliance and enforceability through testing, monitoring, recordkeeping, and reporting requirements, and that annual NO_X and SO₂ emissions are not greater than what is currently allowed in the SIP. Additionally, there are no National Ambient Air Quality Standard (NAAQS) nonattainment areas in Oklahoma for nitrogen dioxide (NO₂), SO₂, ozone, or PM. ODEQ provided a CAA section 110( l ) demonstration to show that the substitute measures provided in this SIP revision are quantifiable and represent a surplus from current allowable emission levels.^[31] As discussed in section IV.C of this document, testing, monitoring, recordkeeping, and reporting requirements in Oklahoma's 2026 SIP submission provide for enforceability of the new requirements.

In Oklahoma's 2026 SIP submission, allowing for the continued operation of Unit 3 will result in an increase in NO_X emissions of 300 TPY, as compared to the existing requirement to retire Unit 3. To demonstrate that this change in emissions will not interfere with any applicable requirements, specifically the regional haze requirements, ODEQ's 2026 SIP submission includes a commensurate 300 TPY reduction in NO_X emissions from Unit 2. Therefore, emission limits for the PSO Northeastern Units 2 and 3 will provide for equivalent emissions reductions when compared to the existing requirements for Unit 3.^[32] Under these existing requirements, PSO Northeastern Unit 3 is required to cease operation by December 31, 2026. Under Oklahoma's 2026 SIP submission and accompanying 2025 PSO Regional Haze Agreement requirements, PSO Northeastern Unit 3 will burn only natural gas, and Units 2 and 3 will be subject to additional emission limits.

In the 2025 PSO Regional Haze Agreement, PSO committed to only use natural gas as fuel in Northeastern Unit 3 no later than the EPA's approval of Oklahoma's 2026 SIP submission. The use of pipeline-grade natural gas at Unit 3 will provide for negligible annual SO₂ emissions (2.34 TPY). Under the agreement, Unit 3 will also be subject to a 300 TPY NO_X limit. As stated in the SIP, effective January 1, 2027, PSO Northeastern Unit 2 will be subject to a NO_X emission rate limit of 0.22 lbs/MMBtu (compared to the current limit of 0.28 lbs/MMBtu), which is included in the agreement and will also be incorporated into and made enforceable through the facility's New Source Review (NSR) construction permit.^[33] This emission rate limit represents a 20 percent reduction in allowable NO_X emissions at full load and will result in a reduction in allowable NO_X emissions of at least 300 tons per 12-month period to offset the continuing NO_X emissions from Unit 3. The 2025 PSO Regional Haze Agreement includes an annual limit for Unit 2 of 5,530 TPY of NO_X on a 12-month rolling basis, which is a 300 TPY decrease from PSO Northeastern's current permit limit of 5,830 TPY of NO_X as provided in the original February 17, 2010, Regional Haze Agreement between PSO and ODEQ.

Because the proposed emission limits for the PSO Northeastern Units 2 and 3 will provide for quantifiable and enforceable emission limits that provide for equivalent emissions when compared to the existing SIP requirements for the PSO Northeastern facility, we propose to find that Oklahoma's 2026 SIP submission is not anticipated to interfere with applicable requirements of the CAA, including requirements concerning attainment and reasonable further progress.

G. Summary of the EPA's Evaluation

We are proposing to approve Oklahoma's 2026 SIP submission as it meets the following requirements as provided under sections IV.A through F of this document:

(1) Long-term strategy requirements under 40 CFR 51.308(d)(3) as applied to the revision of the PSO Northeastern facility control measures as well as enforceability of those controls through testing, monitoring, recordkeeping, and reporting requirements; ( printed page 55293)

(2) FLM consultation requirements under CAA section 169A(d) and 40 CFR 51.308(i); and,

(3) CAA section 110( l) requirements.

V. Proposed Action

The EPA is proposing to approve Oklahoma's SIP submission submitted on March 12, 2026, that revises source-specific requirements for the PSO Northeastern facility and amends the State's long-term strategy for the first implementation period of the regional haze program as meeting applicable Federal requirements under CAA section 110( l), section 169A, and 40 CFR 51.308. The EPA is proposing to find that Oklahoma's 2026 SIP submission satisfies the long-term strategy regulatory requirements from the first planning period under the regional haze program.^[34]

The EPA is proposing to approve as part of Oklahoma's 2026 SIP submission source-specific requirements for the AEP/PSO Northeastern Power Station as described in the accompanying Seconded Amended Regional Haze Agreement between PSO and ODEQ, Case No. 10-025, dated May 14, 2025 (“2025 PSO Regional Haze Agreement”), which amends portions of the 2010 and 2013 PSO Regional Haze Agreements from Case No. 10-025. The 2025 PSO Regional Haze Agreement is the enforceable mechanism for the revised control measures for the PSO Northeastern facility. The EPA is proposing to approve all requirements set forth in the 2025 PSO Regional Haze Agreement as source-specific revisions to be incorporated into the Oklahoma SIP.

VI. Impact on Areas of Indian Country

Following the U.S. Supreme Court decision in McGirt v. Oklahoma, 140 S. Ct. 2452 (2020), the Governor of the State of Oklahoma requested approval under Section 10211(a) of the Safe, Accountable, Flexible, Efficient Transportation Equity Act of 2005: A Legacy for Users, Public Law 109-59, 119 Stat. 1144, 1937 (August 10, 2005) (“SAFETEA”), to administer in certain areas of Indian country (as defined at 18 U.S.C. 1151) the State's environmental regulatory programs that were previously approved by the EPA outside of Indian country. The State's request excluded certain areas of Indian country further described below. In addition, the State only sought approval to the extent that such approval was necessary for the State to administer a program in light of Oklahoma Dept. of Environmental Quality v. EPA, 740 F.3d 185 (D.C. Cir. 2014).^[35]

The EPA has approved Oklahoma's SAFETEA request to administer all of the State's EPA-approved environmental regulatory programs in the requested areas of Indian country. As requested by Oklahoma, the EPA's approval under SAFETEA does not include Indian country lands, including rights-of-way running through the same, that: (1) qualify as Indian allotments, the Indian titles to which have not been extinguished, under 18 U.S.C. 1151(c); (2) are held in trust by the United States on behalf of an individual Indian or Tribe; or (3) are owned in fee by a Tribe, if the Tribe (a) acquired that fee title to such land, or an area that included such land, in accordance with a treaty with the United States to which such Tribe was a party, and (b) never allotted the land to a member or citizen of the Tribe (collectively “excluded Indian country lands”).

The EPA's approval under SAFETEA expressly provided that to the extent the EPA's prior approvals of Oklahoma's environmental programs excluded Indian country, any such exclusions are superseded for the geographic areas of Indian country covered by the EPA's approval of Oklahoma's SAFETEA request.^[36] The approval also provided that future revisions or amendments to Oklahoma's approved environmental regulatory programs would extend to the covered areas of Indian country (without any further need for additional requests under SAFETEA).

As explained above, the EPA is proposing to approve Oklahoma's 2026 Regional Haze SIP for meeting applicable CAA requirements. This SIP submission revises a portion of Oklahoma's previously approved regional haze SIP for the first planning period for the PSO Northeastern facility located in Rogers County. If this proposed approval is finalized, this revision will become a part of the overall approved Oklahoma regional haze SIP, which applies statewide. Consistent with the D.C. Circuit's decision in ODEQ v. EPA and with the EPA's SAFETEA approval, these SIP revisions will apply to areas of Indian country as follows: (1) pursuant to the SAFETEA approval, the SIP revisions will apply to all Indian country in the State of Oklahoma other than the excluded Indian country lands as described above; and (2) pursuant to the D.C. Circuit's decision in ODEQ v. EPA, the SIP revisions will also apply to any Indian allotments or dependent Indian communities that are located outside of any Indian reservation over which there has been no demonstration of Tribal authority.

VII. Incorporation by Reference

In this proposed action, we are proposing to include in a final rule regulatory text that includes incorporation by reference. In accordance with the requirements of 1 CFR 51.5, we are proposing to incorporate by reference revisions to the Oklahoma source specific requirements as described in section V of this preamble. We have made, and will continue to make, these documents generally available electronically through www.regulations.gov (please contact the persons identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information).

VIII. Statutory and Executive Order Reviews

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, the 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 underExecutive Order 12866 (58 FR 51735, October 4, 1993);
• Is not anExecutive Order 14192 (90 FR 9065, February 6, 2025) regulatory action because this action is not significant 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 ( printed page 55294) 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 inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not subject toExecutive Order 13045 (62 FR 19885, April 23, 1997) because it approves a State program;
• Is not a significant regulatory action subject toExecutive 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 Clean Air Act.

This proposed approval of Oklahoma's 2026 Regional Haze SIP that contains revisions to Oklahoma's first planning period regional haze source-specific requirements will apply, if finalized as proposed, to certain areas of Indian country throughout Oklahoma as discussed in the preamble, and therefore has Tribal implications as specified in E.O. 13175 (65 FR 67249, November 9, 2000). However, this action will neither impose substantial direct compliance costs on federally recognized Tribal governments, nor preempt Tribal law. This action will not impose substantial direct compliance costs on federally recognized Tribal governments because no actions will be required of Tribal governments. This action will also not preempt Tribal law as no Oklahoma Tribe implements a regulatory program under the CAA, and thus does not have applicable or related Tribal laws. Consistent with the EPA Policy on Consultation and Coordination with Indian Tribes (December 7, 2023), the EPA has offered consultation to Tribal governments that may be affected by this action and provided information about this action.

Authority: 42 U.S.C. 7401 et seq.

91 FR 55287