EPA Reclassifies Tribal Connecticut Areas as Serious Ozone Violators
Published Date: 11/20/2025
Proposed Rule
Summary
The EPA found that parts of the Greater Connecticut area run by the Mashantucket Pequot and Mohegan Tribes didn’t meet clean air standards for ozone by the deadline. So, these tribal areas will be officially bumped up to a more serious pollution status, meaning stricter rules to clean the air. People have until December 22, 2025, to share their thoughts, and this could affect local air quality plans and funding.
Analyzed Economic Effects
5 provisions identified: 4 benefits, 0 costs, 1 mixed.
Tribal Areas Reclassified to Serious
The EPA proposes that the Mashantucket Pequot Tribal Nation and the Mohegan Indian Tribe portions of the Greater Connecticut ozone nonattainment area failed to meet the 2015 ozone standard by the Moderate attainment date of August 3, 2024. The EPA calculated a 2021–2023 design value of 0.072 ppm (with a 2023 fourth-highest daily maximum of 0.071 ppm) and proposes to reclassify those tribal portions to Serious for the 2015 ozone NAAQS.
State Must Submit Serious-Area SIPs by 2027
If finalized, the tribal portions will be reclassified to Serious and the state must submit State Implementation Plan (SIP) revisions showing how the area will attain the 2015 ozone NAAQS no later than August 3, 2027. EPA has stated it may adjust certain deadlines other than the attainment date, but the Serious area attainment date remains August 3, 2027.
NNSR Permit Thresholds Change for Reclassified Areas
EPA notes that for areas newly reclassified to Serious, the nonattainment New Source Review (NNSR) major source thresholds and offset requirements change for stationary sources seeking preconstruction permits. However, EPA also states that the Mashantucket Pequot Tribal Nation and Mohegan Indian Tribe lands were already subject to Serious-area NNSR requirements under a prior ozone standard, so this reclassification would have no effect on NNSR permitting requirements for those tribal lands.
Exceptional Events Decision and Comment Period
The EPA has concurred with CT DEEP to exclude event-influenced monitoring data for June 30 and July 1, 2023 at the Groton site and July 1, 2023 at the East Hartford and Cornwall sites, but did not concur with excluding April 13-14 or July 12, 2023 at Groton. The EPA is soliciting public comment on its July 22, 2024 exceptional events decisions and related supporting documents, and written comments must be received by December 22, 2025.
Tribes Not Required to Submit TIP Revisions
Under the Clean Air Act and the Tribal Authority Rule, Tribes may but are not required to submit Tribal Implementation Plans (TIPs) to EPA. The EPA states that the Mashantucket Pequot Tribal Nation and the Mohegan Indian Tribe would not be required to submit TIP revisions applicable to the Serious area requirements for the 2015 ozone NAAQS.
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