The Environmental Protection Agency (EPA) is conditionally approving portions of the Tennessee infrastructure State Implementation Plan (SIP) submission for the 2015 8-hour ozone National Ambient Air Quality Standards (NAAQS) provided to EPA on September 13, 2018. Whenever EPA promulgates a new or revised NAAQS, the Clean Air Act (CAA or Act) requires that states 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 conditionally approve the portions of the Tennessee infrastructure SIP submission related to the prevention of significant deterioration (PSD) infrastructure elements for the 2015 8-hour ozone NAAQS.