EPA is approving a State Implementation Plan (SIP) revisions submitted by the Connecticut Department of Environmental Protection (DEP). The revisions include new provisions that implement the core requirements of 1990 Clean Air Act Amendments (CAAA) regarding nonattainment New Source Review (NSR) in areas that have not attained the National Ambient Air Quality Standards (NAAQS). In addition, the changes amend the applicability requirements and certain other requirements of the Prevention of Significant Protection (PSD) program and NSR rules. Finally, the changes provide a definition for "Practicably Enforceable" that would allow sources a streamlined approach to limit potential to emit for PSD/NSR applicability purposes. In aggregate, these revisions will substantially strengthen the DEP's air permitting rules. This action is to approve the revisions to section 22a-174-1, "Definitions," section 22a-174-2a, "Procedural Requirements for New Source Review and Title V Permitting," and section 22a-174-3a, "Permit to Construct and Operate Stationary Sources." This action is being taken in accordance with the Clean Air Act (CAA or Act).