On August 24, 2012, EPA took final action to promulgate a Federal Implementation Plan (FIP) to implement the Best Available Retrofit Technology (BART) requirement of the Regional Haze Rule for the Four Corners Power Plant (FCPP), located on the Navajo Nation. EPA's final action required the owners of FCPP to choose between two strategies for compliance: compliance with the emission limits in EPA's final BART determination; or compliance with an alternative to BART, originally put forth by the owners of FCPP, that included closure of Units 1, 2, and 3 at FCPP and installation of new air pollution controls to meet BART limits on Units 4 and 5. EPA's final action required the owners of FCPP to provide notification to EPA by July 1, 2013, of its selection of which BART compliance strategy it would implement at FCPP. On June 19, 2013, Arizona Public Service (APS), the operator and a co-owner of FCPP, requested that EPA extend the notification date from July 1 to December 31, 2013, due to new uncertainties that complicate its decision related to BART compliance. These uncertainties result from a recent decision by the Arizona Corporation Commission to explore retail competition of the electricity market in Arizona. Because the basis provided by APS for an extended notification date is reasonable and justified given the uncertainties in the electrical market in Arizona, EPA is proposing to extend the date by which APS must notify EPA of its BART compliance strategy, from July 1, 2013 to December 31, 2013. EPA is not proposing to amend any other requirements in the FIP for FCPP.