40 CFR §51.908

1. (a)What is the attainment demonstration requirement for an area classified as moderate or higher under subpart 2 pursuant to § 51.903? An area classified as moderate or higher under § 51.903 shall be subject to the attainment demonstration requirement applicable for that classification under section 182 of the Act, except such demonstration is due no later than 3 years after the area's designation for the 8-hour NAAQS.
2. (b)What is the attainment demonstration requirement for an area subject only to subpart 1 in accordance with § 51.902(b)? An area subject to § 51.902(b) shall be subject to the attainment demonstration under section 172(c)(1) of the Act and shall submit an attainment demonstration no later than 3 years after the area's designation for the 8-hour NAAQS.
3. (c)What criteria must the attainment demonstration meet? An attainment demonstration due pursuant to paragraph (a) or (b) of this section must meet the requirements of § 51.112; the adequacy of an attainment demonstration shall be demonstrated by means of a photochemical grid model or any other analytical method determined by the Administrator, in the Administrator's discretion, to be at least as effective.
4. (d)For each nonattainment area, the State must provide for implementation of all control measures needed for attainment no later than the beginning of the attainment year ozone season.