SUPPLEMENTARY INFORMATION:

Throughout this document, the use of “we,” “us,” or “our” is intended to refer to the EPA. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here:

CAA—Clean Air Act

CBI—Confidential Business Information

CT—Central Time

DIG—Dearborn Industrial Generation

EPA—Environmental Protection Agency

FIP—Federal Implementation Plan

NAAQS—National Ambient Air Quality Standard

NSR—New Source Review

OMB—Office of Management and Budget

PBI—Proprietary Business Information

PRA—Paperwork Reduction Act

RACM—Reasonably Available Control Measures

RACT—Reasonably Available Control Technology

RFA—Regulatory Flexibility Act

RFP—Reasonable Further Progress

SIP—State Implementation Plan

SO₂ —Sulfur Dioxide

UMRA—Unfunded Mandates Reform Act

Organization of this document. The information presented in this preamble is organized as follows:

I. Background

II. Detroit SO₂ FIP

III. Michigan's Revised SIP for the Detroit SO₂ Area

IV. FIP Withdrawal

V. What action is the EPA taking?

VI. Statutory and Executive Order Reviews

I. Background

On August 5, 2013, the EPA designated the Detroit area, a portion of Wayne County, Michigan, as nonattainment for the 2010 1-hour primary SO₂ NAAQS based on ambient air quality data collected at the Detroit SW monitoring site (AQS ID 26-163-0015) from 2009 to 2011.^[1] The nonattainment area designation became effective on October 4, 2013. CAA section 191 directs States to submit a SIP for an area designated as nonattainment for the 2010 1-hour primary SO₂ NAAQS to the EPA within 18 months of the effective date of the designation, i.e., in this case, by no later than April 4, 2015. Under CAA section 192, the SIP must demonstrate attainment of the NAAQS as expeditiously as practicable, but no later than five years from the effective date of designation, which was October 4, 2018, for the Detroit nonattainment area.

On March 18, 2016, the EPA published an action finding that Michigan had failed to submit the required SO₂ attainment plan by the submittal deadline.^[2] Under CAA section 110(c), the finding triggered a requirement that the EPA promulgate a FIP within two years of the finding unless, by that time, (a) the State had made the necessary complete submittal, and (b) the Agency had fully approved the submittal as meeting all applicable requirements.

On May 31, 2016, and June 30, 2016, Michigan submitted a Detroit SO₂ attainment plan and associated final enforceable measures, respectively. Michigan's submission of a complete attainment plan terminated the deadlines for imposing sanctions, pursuant to 40 CFR 52.31(d)(5), but it did not terminate the EPA's FIP obligation. On March 19, 2021, the EPA partially approved and partially disapproved Michigan's SO₂ plan as submitted in 2016 (the “March 2021 ( printed page 72840) Action”).^[3] The March 2021 Action approved the enforceable control measures for two facilities, approved the base-year emissions inventory, and affirmed that the New Source Review (NSR) requirements for the area had previously been met in the SIP. In the same March 2021 Action, the EPA disapproved the SIP attainment demonstration, as well as the requirements for meeting reasonable further progress (RFP) toward attainment of the NAAQS, reasonably available control measures/reasonably available control technology (RACM/RACT), contingency measures, and control measures for two facilities. The partial disapproval started a new sanctions clock under CAA section 179(a), but it did not have any impact on the FIP clock.

II. Detroit SO 2 FIP

On October 12, 2022, the EPA promulgated the 2022 FIP for the Detroit SO₂ nonattainment area.^[4] In accordance with CAA section 172, the 2022 FIP includes an attainment demonstration for the Detroit area and addresses requirements for RFP, RACM/RACT, enforceable emission limitations and control measures, and contingency measures. The 2022 FIP did not address emissions inventory or NSR requirements, as they had already been approved in the SIP as part of the March 2021 Action.

The 2022 FIP, codified at 40 CFR 52.1189, includes emission limits and associated requirements for United States Steel Corporation (“U.S. Steel”), EES Coke Battery (“EES Coke”), Cleveland-Cliffs Steel Corporation, and Dearborn Industrial Generation (DIG). The 2022 FIP also relies upon emission limits for Carmeuse Lime and DTE Trenton Channel, which had already been incorporated into Michigan's SIP at the time the 2022 FIP was promulgated.

The 2022 FIP satisfied the Agency's duty to promulgate a FIP for the area under CAA section 110(c) that resulted from the previous finding of failure to submit. However, the 2022 FIP did not affect the sanctions clock started under CAA section 179 resulting from the EPA's partial disapproval of the prior SIP, which would be terminated by an EPA rulemaking approving a revised SIP.

III. Michigan's Revised SIP for the Detroit SO 2 Area

On December 20, 2022, Michigan submitted a revised attainment plan for the Detroit SO₂ nonattainment area mirroring the 2022 FIP. Michigan's submittal relied in part upon permits that had not yet been issued but would include limits and associated requirements for U.S. Steel, EES Coke, and DIG facilities no less stringent than those set forth in the 2022 FIP. On February 21, 2023, Michigan submitted a clarification letter committing to submit the necessary permits by April 30, 2024. On March 23, 2023, the EPA proposed to conditionally approve Michigan's plan, conditioned upon the issuance, and submission for incorporation into the SIP, of the applicable permits for the U.S. Steel, EES Coke, and DIG facilities.^[5]

On December 14, 2023, Michigan submitted three applicable permits for the U.S. Steel, EES Coke, and DIG facilities. On April 2, 2024, Michigan submitted the final applicable permit for the DIG facility, along with a request that the EPA approve the State's revised plan. On May 19, 2025, the EPA fully approved Michigan's revised SIP submission, which the State submitted to the Agency on December 20, 2022, and supplemented on February 21, 2023, December 14, 2023, and April 2, 2024, for attaining the 2010 1-hour primary SO₂ NAAQS for the Detroit area and for meeting other nonattainment area planning requirements of CAA sections 110, 172, 179, and 192.^[6] The EPA approved Michigan's demonstration that these requirements provide for attainment of the 2010 1-hour primary SO₂ NAAQS in Detroit and concluded that Michigan had satisfied the other applicable requirements for nonattainment areas.

On May 5, 2025, Michigan submitted a redesignation request and maintenance plan for the Detroit nonattainment area for the 2010 1-hour primary SO₂ NAAQS, which relies on the State's approved attainment plan for the area. On April 2, 2026, the EPA determined that the Detroit, Michigan area is attaining the 2010 1-hour primary SO₂ NAAQS and took action in accordance with Michigan's request to redesignate the area to attainment of the 2010 1-hour primary SO₂ NAAQS and approve the State's maintenance plan for the area.^[7] The maintenance plan, designed to ensure the area will continue to maintain attainment of the 2010 1-hour primary SO₂ NAAQS, does not rely on the 2022 FIP and instead relies on the permanent and enforceable SO₂ emission limits and associated requirements in Michigan's SIP.

IV. FIP Withdrawal

The EPA is now proposing to withdraw the 2022 FIP because the Agency has since taken subsequent SIP actions such that Michigan's SIP for the Detroit SO₂ area now satisfies the requirements of the March 2021 Action. As is explained in section III of this preamble, the EPA approved Michigan's complete submittal into the State's SIP, rendering it federally enforceable. As a result, the 2022 FIP is no longer necessary for attainment of the 2010 1-hour primary SO₂ NAAQS in the Detroit area.

Under CAA section 110(l), the EPA cannot approve a plan revision if the revision would interfere with any applicable requirement concerning attainment and maintenance of the NAAQS, RFP, or any other applicable requirement of the CAA. Michigan's SIP for the Detroit SO₂ area mirrors the 2022 FIP and contains SO₂ emission limits and associated requirements that are equally as stringent as those set forth in the 2022 FIP. Therefore, the withdrawal of the 2022 FIP will not interfere with attainment or maintenance of the NAAQS, RFP, or any applicable requirements under the CAA, and the EPA proposes to find that the withdrawal of the 2022 FIP is consistent with CAA section 110(l).

V. What action is the EPA taking?

The EPA is proposing to withdraw the 2022 Detroit SO₂ FIP by removing 40 CFR 52.1189 and all provisions therein because Michigan's SIP for attaining the 2010 1-hour primary SO₂ NAAQS in the Detroit area, which the Agency approved on May 19, 2025, satisfied the requirements of the March 2021 Action. The maintenance plan for the Detroit area, designed to ensure the area will continue to maintain attainment of the 2010 1-hour primary SO₂ NAAQS, does not rely on the 2022 FIP and instead relies on the permanent and enforceable SO₂ emission limits and associated requirements in Michigan's SIP. The EPA is proposing this action pursuant to CAA section 110.

VI. Statutory and Executive Order Reviews

Additional information about these statutes and Executive Orders can be found at www.epa.gov/​laws-regulations/​laws-and-executive-orders. ( printed page 72841)

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review

This action is exempt from review by the Office of Management and Budget (OMB) for review because it is deemed to be a rule of particular applicability. This action affects and is limited to four specific facilities in the Detroit area.

B. Executive Order 14192: Unleashing Prosperity Through Deregulation

Executive Order 14192 does not apply because rules of particular applicability are exempted from review under Executive Order 12866.

C. Paperwork Reduction Act (PRA)

This rule does not impose an information collection burden under the provisions of the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.). This action does not contain any information collection activities.

D. Regulatory Flexibility Act (RFA)

I certify that this action will not have a significant economic impact on a substantial number of small entities under the RFA (5 U.S.C. 601 et seq.). This action will not impose any requirements on small entities. This action merely proposes to remove duplicative requirements and imposes no new requirements.

E. Unfunded Mandates Reform Act (UMRA)

This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 1531 through 1538, and does not significantly or uniquely affect small governments. The action imposes no enforceable duty on any State, local, or Tribal governments or the private sector.

F. Executive Order 13132: Federalism

This action does not have federalism implications. It would not have substantial direct effects 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.

G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

This rule does not have Tribal implications, as specified in Executive Order 13175. It would not have substantial direct effects on Tribal governments. Thus, Executive Order 13175 does not apply to this rule.

H. Executive Order 13045: Protection of Children From Environmental Health and Safety Risks

The EPA interprets Executive Order 13045 as applying only to those regulatory actions that concern environmental health or safety risks that the Agency has reason to believe may disproportionately affect children, per the definition of “covered regulatory action” in section 2-202 of the Executive Order.

Therefore, this action is not subject to Executive Order 13045 because it proposes to withdraw a previously promulgated FIP.

Furthermore, the EPA's Policy on Children's Health does not apply to this action.

I. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

This action is not subject to Executive Order 13211 because it is not a significant regulatory action under Executive Order 12866.

J. National Technology Transfer Advancement Act

This rulemaking does not involve technical standards.

For the reasons stated in the preamble, the EPA proposes to amend 40 CFR part 52 as follows:

1. The authority citation for part 52 continues to read as follows:

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

2. Remove and reserve § 52.1189.

91 FR 72838