On February 5, 2013, the Environmental Protection Agency (EPA) proposed a source-specific federal implementation plan (FIP) requiring the Navajo Generating Station (NGS), located on the Navajo Nation, to reduce emissions of oxides of nitrogen (NO X) under the Best Available Retrofit Technology (BART) provision of the Clean Air Act (CAA or Act) in order to reduce visibility impairment resulting from NGS at 11 National Parks and Wilderness Areas. EPA provided a 90-day public comment period for the proposed rule that is scheduled to close on May 6, 2013. The Navajo Nation and other stakeholders have submitted requests to extend the comment period an additional 90 days to allow time for interested parties to explore alternatives to BART that provide additional flexibility and also ensure greater reasonable progress than would be achieved under BART. In today's action, EPA is extending the comment period an additional 90 days.