On August 24, 2012, EPA promulgated 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), which is located on the Navajo Nation Indian Reservation. Included in the FIP was a requirement that by July 1, 2013, Arizona Public Service (APS), co-owner and operator of FCPP must notify EPA of its selected BART compliance strategy. On June 19, 2013, APS requested that EPA extend the notification date from July 1 to December 31, 2013, due to new uncertainties related to the potential deregulation of the retail electricity market in Arizona that complicate its decision for selecting a BART compliance option. In response to this request, on July 11, 2013, EPA proposed to extend the notification date, from July 1, 2013 to December 31, 2013. EPA did not receive any comments during the 30-day public comment period for the proposed action. EPA received one comment that was emailed to EPA on August 13, 2013, one day after the close of the comment period. We are providing a response to the late comment, however the information in the late comment did not change the basis or justification for our proposal to extend the notification date. Therefore, EPA is taking final action to extend the notification date in the FIP from July 1, 2013 to December 31, 2013.