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Area Designations for 1997 Ground-level Ozone Standards

Redesignation Requests


On April 15, 2004, EPA designated a total of 126 nonattainment areas for the 8-hour ozone standard. EPA identified 13 areas as Early Action Compact (EAC) areas and 3 areas were designated as unclassifiable pending a review of further air quality data. Since that time, EPA has reclassified 9 of the 126 original nonattainment areas to the next lower classification. Section 107(d)(3)(E) of the 1990 CAA allows states to request nonattainment areas be redesignated to attainment providing certain criteria are met. EPA is beginning to receive redesignation requests. The following are the criteria that must be met in order for an area to be redesignated from nonattainment to attainment:

  • EPA has determined NAAQS has been attained. The level of the national 8-hour ozone primary standard is 0.08 parts per million (ppm), daily maximum 8-hour average. The 8-hour ozone design value is based on the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration.

  • Applicable State Implementation Plan (SIP) has been fully approved by the EPA under section 110(k).

  • EPA has determined that the improvement in air quality is due to permanent and enforceable reductions in emissions.

  • State has met all applicable requirements for the area under section 110 and part D.

  • EPA has fully approved a maintenance plan, including a contingency plan, for the area under section 175A.

This section focuses on the last condition concerning the maintenance plan and the respective contingency measures. In addition, total VOC and NOx emission reductions planned to occur during the 10-year maintenance period for each area are examined. The CAA requires a demonstration of maintenance for ten years after redesignation. However, in some cases, modeling can be used to allow for increase/growth in emissions during the maintenance period so long as the NAAQS is not violated. This plan will therefore set a base year of attainment and project maintenance for at least that 10-year period. The maintenance plan specifies techniques used by the area in order to continue maintenance and compliance with the NAAQS, as well as the controls the area will use to ensure these levels of emissions.

The maintenance plan also includes contingency measures to ensure prompt and effective correction of any violation of the NAAQS that may occur after redesignation, despite the State's best efforts to demonstrate continued compliance. The events that would trigger such measures to be implemented should be clearly identified, as well as an adequate description of the measures to be adopted, a schedule and procedure for implementation, and a specific time limit for action to be taken by the State. At a minimum, the contingency measures must include a requirement that the State will implement measures contained in the nonattainment SIP prior to redesignation. For the purposes of 175A, the State is not required to fully adopt contingency measures prior to redesignation. This contingency plan is, however, considered an enforceable part of the SIP and must ensure that the measures will be adopted and implemented promptly after they are triggered.

Redesignation Guidance

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