On September 31, 2021, the United States Environmental Protection Agency (U.S. EPA) issued a policy memorandum withdrawing the Agency’s October 9, 2020 policy memorandum which provided guidance on when a state may include provisions in its State Implementation Plan (SIP) exempting and/or providing an affirmative defense for sources violating air emission limits during startup, shutdown and malfunction (SSM) periods. U.S. EPA also reinstated its 2015 policy that SSM exemption and affirmative defense provisions in SIPs will generally be viewed as inconsistent with Clean Air Act (CAA) requirements. The September 31, 2021 memorandum explains U.S. EPA's decision to withdraw its 2020 SSM policy and reinstate the 2015 SSM policy, noting that 2020 SSM policy "does not adequately address CAA requirements other than NAAQS attainment and maintenance", whereas the 2015 SSM policy "analyzes how CAA requirements affect the permissibility of SSM exemptions and meaningfully applies relevant D.C. Circuit case law."
The September 31, 2021 policy memorandum is available on U.S. EPA’s website here.