EPA is taking final action in making a finding, under the Clean Air Act (CAA or Act), that Nevada failed to make a carbon monoxide (CO) nonattainment area state implementation plan (SIP) submittal required for the Las Vegas Valley under the Act. Under certain provisions of the Act, states are required to submit SIPs providing for, among other things, reasonable further progress and attainment of the CO national ambient air quality standards (NAAQS) in areas classified as serious. The deadline for submittal of this plan for the Las Vegas Valley was May 3, 1999. This action triggers the 18-month time clock for mandatory application of sanctions and 2-year time clock for a federal implementation plan (FIP) under the Act. This action is consistent with the CAA mechanism for assuring SIP submissions.