The Environmental Protection Agency (EPA) is taking final action to approve portions of the Kentucky infrastructure State Implementation Plan (SIP) submission for the 2015 8-hour ozone National Ambient Air Quality Standards (NAAQS) submitted to EPA in a letter dated January 11, 2019. Whenever EPA promulgates a new or revised NAAQS, the Clean Air Act (CAA or Act) requires that each state adopt and submit a SIP submission to establish that the state's SIP meets infrastructure requirements for the implementation, maintenance, and enforcement of each such NAAQS. Specifically, EPA is taking final action to approve portions of the Kentucky infrastructure SIP submission that address the prevention of significant deterioration (PSD) and modeling requirements for the 2015 8-hour ozone NAAQS.