The Environmental Protection Agency (EPA) is disapproving certain portions of a state implementation plan (SIP) revision submitted by the State of Delaware, through the Delaware Department of Natural Resources and Environmental Control (DNREC), on November 22, 2016. The revision was submitted by Delaware in response to a national finding of substantial inadequacy and SIP call published on June 12, 2015, which included certain provisions in the Delaware SIP related to excess emissions during startup, shutdown, and malfunction (SSM) events. EPA is disapproving certain portions of the SIP revision and determining that such SIP revision does not correct the remaining deficiencies in Delaware's SIP identified in the June 12, 2015, SIP call in accordance with the requirements for SIP provisions under the Clean Air Act (CAA or Act). This action addresses the remaining deficiencies identified in EPA's June 2015 SIP call that have not yet been addressed by prior EPA actions on Delaware's November 2016 SIP submission.