The Environmental Protection Agency (EPA) is approving portions and disapproving portions of a state implementation plan (SIP) revision submitted by the State of Colorado to meet Clean Air Act (CAA) requirements for the 2008 8-hour ozone national ambient air quality standards (NAAQS) in the Denver Metro/North Front Range nonattainment area (DMNFR Area). Specifically, the EPA is approving the submitted enhanced monitoring SIP element as meeting applicable Serious area requirements for the 2008 8-hour ozone NAAQS, and is disapproving the contingency measure element of the SIP submittal. The EPA is taking this action pursuant to the CAA.