Michigan's St. Clair Gets EPA Nod for Cleaner SO2 Air
Published Date: 4/10/2026
Proposed Rule
Summary
Good news for folks in southeast Michigan! The EPA wants to officially say the St. Clair area now meets clean air standards for sulfur dioxide (SO2) and approve Michigan’s plan to keep it that way. This means cleaner air near the DTE Belle River Power Plant, with rules to limit pollution and a chance for the community to weigh in by May 11, 2026.
Analyzed Economic Effects
6 provisions identified: 4 benefits, 1 costs, 1 mixed.
Belle River Planned Gas Conversion by 2027
The Belle River facility plans to convert from coal to natural gas by 2027; Michigan's permit shows baseline actual emissions of 21,470 tons per year and projects actual emissions will decline to 24 tons per year after conversion.
St. Clair Area Proposed Attainment
The EPA is proposing to redesignate the Partial St. Clair nonattainment area in southeast Michigan to attainment for the 2010 1-hour sulfur dioxide (SO2) National Ambient Air Quality Standard (75 ppb). Michigan submitted the redesignation request on December 15, 2023, supplemented July 24, 2025, and the EPA is taking public comments through May 11, 2026.
Belle River Emissions Limits Made Enforceable
The EPA is proposing to incorporate Michigan Permit to Install 51-22 into the State Implementation Plan, making federally enforceable the Belle River Power Plant SO2 limits of 0.680 lbs/MMBtu as a 30-day rolling average and 1.2 lbs/MMBtu based on any 3-hour average. Permit 51-22 was approved April 26, 2022 and revised May 25, 2023.
St. Clair Plant Shutdown Cuts Emissions
The St. Clair Power Plant shut down in 2022, and Michigan's modeling shows area-wide modeled hourly SO2 emissions declined from pre-2022 modeled allowable emissions of 38,798 lbs/hour to 9,268 lbs/hour after the permanent reductions. The modeling yields a maximum SO2 concentration of 62.8 ppb, below the 2010 NAAQS of 75 ppb.
PSD Permitting Will Apply After Redesignation
If the St. Clair area is redesignated to attainment, Prevention of Significant Deterioration (PSD) permitting requirements under the Clean Air Act will apply to any new major sources or major modifications in the area.
Maintenance Plan, Monitoring, and Contingencies
Michigan's maintenance plan demonstrates continued attainment for at least 10 years after redesignation, commits to annual emissions reporting for the Belle River Power Plant per the EPA SO2 Data Requirements Rule, and identifies potential contingency measures (for example: requiring alternative fuel, add-on SO2 controls, reduced operating hours, or SO2 offsets for new/modified sources) to address any future NAAQS violations.
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