Missouri's Plan to Tame Sulfur Dioxide in New Madrid Approved
Published Date: 5/7/2026
Proposed Rule
Summary
The EPA is proposing to approve Missouri’s plan to clean up sulfur dioxide pollution in the New Madrid area. This plan shows how Missouri will reduce harmful emissions to meet air quality standards, protecting local communities and the environment. People and businesses in New Madrid should expect cleaner air soon, with progress tracked and rules in place to keep improvements on schedule.
Analyzed Economic Effects
6 provisions identified: 2 benefits, 0 costs, 4 mixed.
EPA proposes to make Missouri limits federally enforceable
The EPA is proposing to approve Missouri's May 3, 2023 State Implementation Plan for the New Madrid SO2 nonattainment area and to incorporate the state consent agreements for Magnitude 7 Metals and AECI New Madrid into the federally enforceable SIP. If approved, the emission limits and requirements in those consent agreements would become federally enforceable and would be used to track progress toward attaining the 2010 1-hour SO2 standard.
M7M must stop low-level SO2 emissions unless rerouted
The Magnitude 7 Metals (M7M) consent agreement prohibits any SO2 emissions from existing low-level carbon bake furnace stacks unless those emissions are rerouted to a new taller stack by December 31, 2023 (the State allowed extension up to January 1, 2025 and extended once to January 28, 2024). M7M curtailed operations on January 28, 2024, has not built the new stack, but retains permits and would have to comply if it restarts.
AECI New Madrid limits effective January 1, 2023
The State established new SO2 emission limitations and monitoring requirements for the AECI New Madrid Power Plant that were applicable beginning on January 1, 2023, as set out in the AECI New Madrid consent agreement incorporated in the state's attainment plan.
New 30‑day rolling SO2 limits require EPA SIP revision
EPA is approving the process in the M7M consent agreement for developing a replacement 30-day rolling average emission limit (based on CEMS data), but EPA is not approving any specific 30-day limit itself. Any new 30-day rolling average emission limit that would replace an hourly limit must undergo public notice and comment and then be submitted to and approved by EPA as a SIP revision before it can take effect.
Relocating monitors can trigger SIP revision requirement
The M7M consent agreement allows requests to relocate any of the three SO2 monitors, but EPA says moving monitors in a way that changes their scale of representation or prevents them from capturing maximum impacts would materially change the attainment plan. Such relocations would require EPA review and, if they alter the plan's reliance on the monitors, a SIP revision before taking effect.
Force majeure clauses approved as affirmative defense
Both consent agreements include force majeure provisions (covering events like natural disasters, pandemics, labor disputes, etc.) that reschedule obligations rather than cancel them. EPA interprets these as a 'complete' affirmative defense and proposes to approve them into the SIP, meaning sources may avoid liability for violations during qualifying force majeure events if they meet the agreement's criteria and notice requirements.
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