Section 51.1108 - Modeling and attainment demonstration requirements(a) An area classified as Moderate under § 51.1103(a) shall be subject to the attainment demonstration requirement applicable for that classification under CAA section 182(b), and such demonstration is due no later than 36 months after the effective date of the area's designation for the 2008 ozone NAAQS.(b) An area classified as Serious or higher under § 51.1103(a) shall be subject to the attainment demonstration requirement applicable for that classification under CAA section 182(c), and such demonstration is due no later than 48 months after the effective date of the area's designation for the 2008 ozone NAAQS.(c) Attainment demonstration criteria. 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.(d) Implementation of control measures. 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. 80 FR 12314 , Mar. 6, 2015