The EPA is promulgating the third step (Step 3) of our phase- in approach to permitting sources of greenhouse gas (GHG) emissions that we committed to do in the GHG Tailoring Rule. This rule completes Step 3 by determining not to lower the current Prevention of Significant Deterioration (PSD) and title V applicability thresholds for GHG-emitting sources established in the Tailoring Rule for Steps 1 and 2. We are also promulgating regulatory revisions for better implementation of the federal program for establishing plantwide applicability limitations (PALs) for GHG emissions, which will improve the administration of the GHG PSD permitting programs.