EPA Greenlights North Carolina's Ozone Air Plan
Published Date: 9/23/2026
Proposed Rule
Summary
North Carolina wants to keep the air clean in the Charlotte-Rock Hill area by following a plan that controls ozone pollution through 2035. This plan, approved by the EPA, sets limits on car emissions to keep the air safe and healthy. People living or working in this area will benefit from cleaner air, and the public can comment on the plan until October 23, 2026.
Analyzed Economic Effects
10 provisions identified: 6 benefits, 3 costs, 1 mixed.
EPA proposes approval of Charlotte maintenance plan
The EPA is proposing to approve North Carolina's second 10-year maintenance plan that is designed to maintain the 2008 8-hour ozone standard in the North Carolina portion of the bi-state Charlotte-Rock Hill Area through 2035. The proposed action would incorporate the plan into North Carolina's State Implementation Plan (SIP). You can comment on the proposal by October 23, 2026.
Motor-vehicle NOX and VOC budgets adopted
The plan establishes and the EPA is proposing to approve motor vehicle emissions sub-area budgets for nitrogen oxides (NOX) and volatile organic compounds (VOC) for 2018 and 2035 for the Charlotte Area (e.g., total NOX: 2018 = 92.76 tons/summer day; 2035 = 42.71 tons/summer day; total VOC: 2018 = 104.96 tons/summer day; 2035 = 100.92 tons/summer day). These budgets would be incorporated into the SIP and used for transportation conformity determinations.
Transportation projects must 'conform' to SIP budgets
Under the Clean Air Act and existing EPA rules, transportation plans, programs, and projects in the area must conform to the SIP's motor vehicle emissions budgets. If a transportation plan does not conform, most new projects that would expand roadway capacity cannot go forward.
Possible NOX RACT on small stationary sources (<100 tpy)
If a primary or secondary contingency trigger activates, the State may consider adopting NOX Reasonably Available Control Technology (RACT) requirements on stationary sources with a potential to emit less than 100 tons per year within the Charlotte Area.
Reinstatement of vehicle emissions I/M could be considered
If the contingency plan's primary or secondary triggers occur, the State may consider reinstating the on-road light-duty gasoline vehicle emissions inspection and maintenance (I/M) program in the counties subject to the maintenance plan. Note: North Carolina previously submitted a SIP revision on October 1, 2024, to remove the I/M program and EPA intends to act on that I/M SIP revision before finalizing the maintenance plan.
Contingency triggers set at 0.076 ppm
The maintenance plan sets three contingency triggers tied to ozone monitor readings: (1) tertiary trigger — a single monitor 4th-highest daily value of 0.076 ppm or greater (trigger date 60 days after that reading); (2) secondary trigger — two consecutive ozone seasons with the 4th-highest value at a single monitor of 0.076 ppm or greater (trigger date 60 days after the qualifying reading); and (3) primary trigger — a violation or a 3-year average of the 4th-highest values equal to or greater than 0.076 ppm (trigger date 60 days). When triggered, NCDAQ will analyze causes and consider control actions.
Diesel retrofit programs (with incentives) may be implemented
As a contingency if triggered, North Carolina may implement diesel retrofit programs for vehicles, including incentives to perform retrofits. These programs would be considered after analyses following a trigger.
Timeline for contingency action after triggers
If a primary or secondary trigger is activated, North Carolina will complete sufficient analyses by May 1 of the year following the ozone season in which the trigger occurred to begin adopting necessary rules. Adopted rules would become effective by the following March 1 unless legislative review is required, and the State commits to begin implementing at least one control measure no later than 24 months after the primary or secondary trigger.
State commits to continue ozone monitoring (funding permitting)
North Carolina committed to continue operating the five ozone monitors in the bi-state Charlotte Area in compliance with 40 CFR part 58, provided sufficient funding is available. The EPA approved North Carolina's 2025-2026 Ambient Air Monitoring Network Plan on October 29, 2025.
Public comment deadline on proposed rule
The EPA is accepting public comments on this proposed approval; comments must be received on or before October 23, 2026. Comments should be submitted at Regulations.gov under Docket ID EPA-R04-OAR-2025-0223.
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