The Navajo Nation Environmental Protection Agency (NNEPA), acting with authority delegated by the U.S. Environmental Protection Agency (EPA) in 2004 pursuant to EPA regulations at 40 C.F.R. part 71, issued a federal Clean Air Act Title V operating permit to Peabody Western Coal Company (Peabody) governing air emissions from Peabody's mining operation at the Kayenta Complex in Arizona. Peabody appealed NNEPA's issuance of that permit to the Environmental Appeals Board. The petition for review was denied on March 13, 2012, and the permit became final.