This action responds to a petition submitted by the Sierra Club on June 30, 2011, concerning how state air agency rules in EPA-approved State Implementation Plans (SIPs) treat excess emissions during periods of startup, shutdown or malfunction (SSM).The Petitioner requested the EPA to issue a SIP Call pursuant to the Clean Air Act (CAA) to require each state to revise its SIP to remedy the identified deficiencies In a February 22, 2013 NPRM, the EPA proposed its response to all issues identified in the Petition, granting it in part and denying it in part, as well as proposing a SIP Call for 36 states. Subsequent to that proposal, a federal court ruled that the CAA precludes the authority of the EPA to create affirmative defense provisions applicable to private civil suits. As a result, on September 17, 2014, the EPA issued a Supplemental NPRM addressing its revised interpretation of the CAA, but only with respect to affirmative defense provisions in SIPs, as well issuing a new or revised SIP Call to affected jurisdictions.