Section 60.28a - Plan revisions by the State(a) Any significant revision to a State plan shall be adopted by such State after reasonable notice, public hearing, and meaningful engagement. For plan revisions required in response to a revised emission guideline, such plan revisions shall be submitted to the Administrator within fifteen months, or as determined by the Administrator, after publication in the FEDERAL REGISTER of a final revised emission guideline under § 60.22a . All plan revisions must be submitted in accordance with the procedures and requirements applicable to development and submission of the original plan.(b) A revision of a plan, or any portion thereof, shall not be considered part of an applicable plan until approved by the Administrator in accordance with this subpart. 84 FR 32575 , July 8, 2019, as amended at 88 FR 80545 , Nov. 17, 2023 84 FR 32575 , 9/6/2019; 88 FR 80545 , 12/18/2023