SUPPLEMENTARY INFORMATION:

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

Table of Contents

I. Background

II. Rationale for This Final Action

III. Public Comments and EPA Responses

IV. Final Action

V. Incorporation by Reference

VI. Statutory and Executive Order Reviews

I. Background

The background for this action is discussed in detail in our September 5, 2025, proposed action (90 FR 43030). In that document, we proposed approval of the 2022 Arkansas Regional Haze Planning Period II SIP revision (2022 Planning Period II SIP), submitted August 8, 2022, and clarified on July 29, 2025, as meeting the applicable regional haze program requirements for the second implementation period contained in 40 CFR 51.308(f), (g)(1) through (5), and (i).

On May 4, 2026, DEQ submitted a supplemental package to the EPA to finalize the 2022 Planning Period II SIP and address any concerns with Arkansas' SIP revision and its July 29, 2025, clarification letter regarding opportunity for public comment and FLM consultation. The supplemental package contained the July 2025 letter, as well as required documentation of FLM consultation and public notice with opportunity to comment. The State did not receive any public comments nor comments from FLMs or State agencies through this process.

We find that the 2022 Planning Period II SIP revision meets the statutory and specific regulatory requirements of the regional haze second planning period as discussed in the preamble of this final action ( see sections II and III), the accompanying response-to-comments document (RTC Document), and in our September 2025 proposed action.^[1]

II. Rationale for This Final Action

In this final action, we are approving the 2022 Planning Period II SIP and affirming that it is now the Agency's policy that, where visibility conditions for a Class I Federal area impacted by a State are below the uniform rate of progress (URP) and that State has considered the four statutory factors, then that State will have presumptively demonstrated reasonable progress for the second planning period for that area. We acknowledge that this final action reflects a change in policy as to how the URP should be used in the evaluation of regional haze second planning period SIPs but believe that this policy better aligns with the purpose of the statute and the RHR for achieving “reasonable” progress toward natural visibility. As described in the September 2025 proposed action,^[2] we have discretion and authority to change our policy.^[3]

In developing the regulations required by CAA section 169A(b), we established the concept of the URP for each Class I area. The URP is determined by drawing a straight line from the measured 2000 through 2004 baseline conditions (in deciviews) for the 20 percent most impaired days at each Class I area to the estimated natural conditions (in deciviews) for the 20 percent most impaired days in 2064. From this calculation, a URP value can be calculated for each year between 2004 and 2064. We developed the URP to address the diverse concerns of Eastern and Western States and account for the varying levels of visibility impairment in Class I areas around the Country while ensuring an equitable approach nationwide. For each Class I area, States must calculate the URP for the end of each planning period ( e.g., in 2028 for the second planning period). ⁴ See40 CFR 51.308(f)(1)(vi)(A). States may also adjust the URP to account for impacts from anthropogenic sources outside the United States and/or impacts from certain wildland prescribed fires. See40 CFR 51.308(f)(1)(vi)(B). Then, for each Class I area, States must compare the RPG for the 20 percent most impaired days to the URP for the end of the planning period. If the RPG is above the URP, then an additional “robust demonstration” requirement is triggered for each State that contributes to that Class I area. See40 CFR 51.308(f)(3)(ii)(B).

In the 2017 RHR revisions,^[5] we addressed the role of the URP as it relates to the development of a State's second planning period SIP. Specifically, in response to comments suggesting that the URP should be considered a “safe harbor” that relieves States of any obligation to consider the four statutory factors, we explained that the URP was not intended to be such a safe harbor.^[6] “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 ( printed page 55270) 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.” ^[7] Other 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.^[8] We stated in our response that we did not agree with either of these recommendations. “The CAA requires that each SIP revision contains long-term strategies for making reasonable progress, and that in determining reasonable progress States must consider the four statutory factors. Treating the URP as a safe harbor would be inconsistent with the statutory requirement that States assess the potential to make further reasonable progress toward natural visibility goal in every implementation period.” ^[9]

Importantly, our recently adopted policy does not make the URP a safe harbor. The policy merely creates a presumption that a State's second planning period SIP is making reasonable progress for a Class I area if a State has taken into consideration the four statutory factors of CAA section 169A(g)(1) and that area is below the URP. This is consistent with the CAA and RHR.

The Class I areas impacted by emissions from Arkansas are all below their 2028 URP values, and Arkansas' SIP submittal demonstrated that the State took into consideration the four reasonable progress factors ^[10] listed in CAA section 169A(g)(1) with respect to an adequate number of emissions sources selected for analysis. Thus, we have determined that 2022 Planning Period II SIP revision is fully approvable under the Agency's new policy. Indeed, we think this policy better aligns with the statutory goal because it recognizes the considerable improvements in visibility impairment made by a wide variety of State and Federal programs in recent decades.

III. Public Comments and EPA Responses

The public comment period for our proposed approval ^[11] of the 2022 Planning Period II SIP revision expired on October 6, 2025. We received four total sets of comments. We received two adverse comment letters submitted on October 6, 2025—one collectively from Conservation Organizations (Sierra Club, National Parks Conservation Association (NPCA), and the Coalition to Protect America's National Parks), and another from the Mid-Atlantic/Northeast Visibility Union (MANEVU). Both adverse commenters asserted that the new URP policy violates the plain language of the CAA and RHR; that it violates the procedural requirements of the CAA when announcing and applying it in State-specific regional actions; that it is inconsistent with different aspects of the RHR; and that the 2022 Planning Period II SIP does not meet the new URP policy for presumptive approval. The Conservation Groups also specifically asserted that removal of the Independence retirement order was arbitrary, capricious, and contrary to law; that DEQ's cost effectiveness thresholds were based on incomplete data; that Flint Creek's reasonable progress determination was arbitrary, capricious, and contrary to law; and that the EPA should have analyzed impacts of Arkansas pollution on local communities.

We also acknowledge two other comment letters received on October 6, 2025, from Entergy Services LLS on behalf of Entergy Arkansas, LLC; and Hunton Andrews Kurth LLP on behalf of Ameren Missouri, American Electric Power, Inc. and its operating companies, and Nebraska Public Power District (collectively referred to as “the utilities”) that were largely in support of our proposed action. Specifically, Entergy supported the determinations that Arkansas made in its second implementation period regional haze SIP and that EPA proposed to approve. The utilities specifically supported EPA's new URP policy stating that the policy implements EPA's original understanding of the regional haze program and its fundamental purpose; that it implements the Congressional design of cooperative federalism; and that it implements the plain text of the CAA and the RHR.

We evaluated the 2022 Planning Period II SIP submission against the statutory and regulatory regional haze requirements and determined that it satisfies those requirements. As detailed at length in the RTC document associated with this rulemaking, we explained that our new policy is consistent with the CAA and RHR, and the 2022 Planning Period II SIP met the applicable statutory and regulatory requirements in accordance with the new policy. In addition, we detailed that the 2022 Planning Period II SIP without the Independence Administrative Order (LIS No. 22-085) demonstrates reasonable progress under the RHR and the CAA and addresses all required elements of 40 CFR 51.308(f). We explained that the May 4, 2026, supplement addressed any concerns with the 2022 Planning Period II SIP regarding opportunity for public comment and FLM consultation. We further explained in the RTC document that the State reasonably considered the cost effectiveness for the different equipment types and analyzed the four factors based on complete cost data that was appropriate for the second planning period. We also detailed that DEQ adequately considered the four statutory factors in its assessment of potential additional controls for the Flint Creek Power Plant and demonstrated reasonable progress toward the national visibility goal for the second planning period. We clarified that the State reasonably documented all cost calculations and provided appropriate assumptions and parameters in its analyses for Flint Creek. Lastly, regarding analyzing impacts to local communities, we explained that neither the CAA nor the RHR requires States or the EPA to consider the impact of pollution on communities near potentially affected facilities when developing or reviewing a regional haze SIP.

We provide the complete comments with our detailed responses to the full range of significant issues raised in the associated RTC document included in the docket of this action. After careful consideration of the public comments received, we are finalizing our action as proposed.

IV. Final Action

We are finalizing approval of the Arkansas 2022 Regional Haze Planning Period II SIP revision submitted August 8, 2022, clarified on July 29, 2025, and further supplemented on May 4, 2026, as meeting the applicable regional haze program requirements for the second implementation period contained in 40 CFR 51.308(f), (g)(1) through (5), and (i).

We are finalizing approval of the State's determination for FutureFuel Chemical Company to require a fuel switch from coal with 3 percent sulfur ( printed page 55271) content by weight to a low sulfur coal that has 1.5 percent sulfur content (equating to 2.93 lb/MMBtu SO₂) for its three coal-fired boilers (SN:6M01-01). This requirement has been made enforceable by the State through an Administrative Order (LIS No. 22-085) dated August 3, 2022, and is included as part of the 2022 Planning Period II SIP submittal. We are finalizing approval of all requirements set forth in this Administrative Order for FutureFuel Chemical Company included as part of the 2022 Planning Period II SIP submittal as a source specific revision to be incorporated into the Arkansas SIP.

V. Incorporation by Reference

In this rule, we are finalizing regulatory text that includes incorporation by reference. In accordance with requirements of 1 CFR 51.5, we are finalizing the incorporation by reference of the revisions to the Arkansas source specific requirements described in section IV of the preamble of this final action. We have made, and will continue to make, these materials generally available through www.regulations.gov (please contact the person identified in the FOR FURTHER INFORMATION CONTACT section of this preamble for more information). Therefore, these materials are approved by the EPA for inclusion in the SIP, and have been incorporated by reference by the EPA into the plan, are fully federally enforceable under CAA sections 110 and 113 as of the effective date of our approval of this final rulemaking, and will be incorporated by reference into the next update to the SIP compilation.

VI. Statutory and Executive Order Reviews

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, 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 under Executive Orders 12866 (58 FR 51735, October 4, 1993);
• Is not subject toExecutive Order 14192 (90 FR 9065, February 6, 2025) because State Implementation Plan approvals under the CAA 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 inExecutive Order 13132 (64 FR 43255, August 10, 1999);
• Is not an economically significant regulatory action based on health or safety risks subject toExecutive Order 13045 (62 FR 19885, April 23, 1997);
• Is not a significant regulatory action subject toExecutive 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 Clean Air Act.

In addition, the SIP is not approved to apply on any Indian reservation land or in any other area where the 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).

For the reasons stated in the preamble, the EPA amends 40 CFR part 52 as follows:

91 FR 55268