The Environmental Protection Agency (EPA) is taking final action to approve changes to the North Carolina State Implementation Plan (SIP) submitted by the State of North Carolina, through the North Carolina Department of Environmental Quality (NCDEQ), through letters dated April 4, 2017, August 22, 2017, and September 28, 2018. These SIP revisions make amendments, most of which are structural and minor, to North Carolina's source testing rules. This action is being taken pursuant to the Clean Air Act (CAA or Act).