The Environmental Protection Agency (EPA) is partially approving portions of State Implementation Plan (SIP) revisions submitted by the State of Michigan on December 18, 2020. Specifically, EPA is approving the 2015 ozone National Ambient Air Quality Standards (NAAQS) base-year emissions inventory for Detroit area as meeting the requirements of the Clean Air Act (CAA). EPA is also approving revisions to Michigan's emissions statement program as meeting the requirements of the CAA.

The Environmental Protection Agency (EPA) is taking final action to approve revisions to the San Diego Air Pollution Control District (SDAPCD or ``District'') portion of the California State Implementation Plan (SIP). These revisions concern SDAPCD's negative declarations for certain Control Techniques Guidelines (CTGs) as they apply to the 2008 and 2015 ozone national ambient air quality standards (NAAQS or ``standards'') reasonably available control technology (RACT) SIP. We are approving revisions that regulate these emission sources under the Clean Air Act (CAA or the Act).

The Environmental Protection Agency (EPA) is taking final action to approve revisions to the State Implementation Plan (SIP) for the State of Missouri. This final action will amend the SIP to incorporate revisions to a state regulation related to the reporting of start-up, shutdown, and malfunction (SSM) events in Missouri. The revisions to this rule include adding incorporations by reference to other state rules, including definitions specific to the rule and making administrative wording changes.

The Environmental Protection Agency (EPA) is finalizing approval of a North Carolina State Implementation Plan (SIP) revision, submitted through a letter dated April 13, 2021. The SIP revision includes changes to North Carolina's SIP-approved rule addressing best available retrofit technology (BART) for regional haze. EPA is approving North Carolina's SIP revision because the changes are consistent with Clean Air Act (CAA or Act) requirements.