The document discusses the Regional Haze Rule and EPA's regulatory responsibilities regarding Best Available Retrofit Technology (BART) Federal Implementation Plans (FIPs) for power plants on Navajo lands. Specifically: 1) The Regional Haze Rule aims to achieve natural visibility levels in protected areas by 2064 by limiting pollutants like sulfur dioxide, nitrogen oxides, and particulate matter from large sources. 2) EPA is responsible for promulgating FIPs with emission limits for sources like the Navajo Generating Station and Four Corners Power Plant as tribal plans were not submitted. 3) Additional controls on nitrogen oxides and particulate matter from these plants may improve visibility and provide ancillary