The Environmental Protection Agency (EPA) is approving elements of a State Implementation Plan (SIP) submission from Ohio regarding the infrastructure requirements of section 110 of the Clean Air Act (CAA) for the 2015 Ozone National Ambient Air Quality Standards (NAAQS). The infrastructure requirements are designed to ensure that the structural components of each state's air quality management program are adequate to meet the state's responsibilities under the CAA. EPA proposed to approve this action on March 9, 2021, and received no adverse comments.