The Environmental Protection Agency (EPA) is approving most of the elements of a State Implementation Plan (SIP) revision submitted by the State of Connecticut that addresses the infrastructure requirements of the Clean Air Act (CAA or Act), excluding the interstate transport provisions, for the 2015 ozone National Ambient Air Quality Standards (NAAQS). We are conditionally approving several elements of Connecticut's SIP revision regarding air quality modeling requirements. The infrastructure requirements are designed to ensure that the structural components of each state's air-quality management program, including provisions prohibiting emissions that will have certain adverse air- quality effects in other states, are adequate to meet the state's responsibilities under the CAA. This action is being taken in accordance with the Clean Air Act.