The Environmental Protection Agency (EPA) is finalizing an approval, a partial approval and partial disapproval, and a limited approval and limited disapproval of certain revisions to the Clark County portion of the Nevada State Implementation Plan (SIP). These revisions primarily concern the Clark County Department of Environment and Sustainability's ("DES" or "Department") general definitions rule and New Source Review (NSR) permitting program for new and modified sources of air pollution under the Clean Air Act (CAA or "Act").