The Environmental Protection Agency (EPA) is proposing action on four permitting rules submitted as a revision to the Mendocino County Air Quality Management District (“MCAQMD” or “the District”) portion of the applicable state implementation plan (SIP) for the State of California pursuant to requirements under the Clean Air Act (CAA or Act). We are proposing a limited approval and limited disapproval of one rule and we are proposing to approve the remaining three permitting rules. The submitted revisions include amended rules governing the issuance of permits for stationary sources, including review and permitting of minor sources, and major sources and major modifications under part C of title I of the Act. The intended effect of these proposed actions is to update the applicable SIP with current MCAQMD permitting rules and to set the stage for remedying certain deficiencies in these rules. If finalized as proposed, the limited disapproval actions would trigger an obligation for EPA to promulgate a Federal Implementation Plan (FIP) for the specific New Source Review (NSR) program deficiencies unless California submits and we approve SIP revisions that correct the deficiencies within two years of the final action.