U.S. EPA Region 5 issued an Administrative Consent Order (ACO) to Duke Energy Indiana, Inc., Gibson Station to resolve violations of the Clean Air Act (CAA). EPA alleged that Duke exceeded opacity limits for all 5 fossil fueled steam generating units at it's Gibson Station in violation of it's Title V permit, New Source Performance Standards for Fossil-Fuel-Fired Steam Generators at 40 C.F.R. Part 60, Subpart D (for Unit 5 only), and the Indiana State Implementation Plan provisions. EPA issued a NOV/FOV to Duke on June 23, 2011 and July 16, 2013. The ACO requires Duke to install PM CEMS at each of the fossil fueled steam generating units at Gibson Stations (Units 1 thru 5) on or before December 31, 2014. The installation of PM CEMS cost Duke $2 million. Additionally, Duke completed upgrades to their EPS at a cost of $10 million.