The Environmental Protection Agency (EPA) is proposing to approve revisions to the Washington State Implementation Plan (SIP) that were submitted on June 22, 2023, by the Department of Ecology (Ecology) in coordination with the Southwest Clean Air Agency (SWCAA). In 2017, the EPA approved a comprehensive update to SWCAA 400 General Regulations for Air Pollution Sources in the SIP, which includes new source review permitting requirements as well as other general requirements for sources regulated under SWCAA's jurisdiction. In this action, the EPA proposes to approve minor updates to SWCAA 400 promulgated since our comprehensive approval in 2017.