The Environmental Protection Agency (EPA) is taking final action to approve elements of state implementation plan (SIP) submissions by Michigan regarding the infrastructure requirements of section 110 of the Clean Air Act (CAA) for the 2008 ozone, 2010 nitrogen dioxide (NO<INF>2</INF>), 2010 sulfur dioxide (SO<INF>2</INF>), and 2012 fine particulate (PM<INF>2.5</INF>) 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 requirements of the CAA. The proposed rulemaking associated with this final action was published on June 24, 2015, and EPA received one comment letter during the comment period, which ended on July 24, 2015. The concerns raised in this letter, as well as EPA's responses, are addressed in this final action.