The decision to switch to low-sulfur Power River Basin (PRB) coal allowed TMPA to shut down the FGD system on its 570 MW unit and it remained dormant for about 15 years. TMPA hired AECOM Process Technologies (legacy URS) in 2007 to refurbish and restart the FGD system. AECOM Process Technologies converted the absorbers to the forced oxidation process that included retrofitting the absorber spray towers with a tray, new recycle pump direct drive motors, new alloy spray headers, and new mist eliminators. Balance-of-plant upgrades included refurbishment of the existing limestone handling and grinding systems and installation of a new dewatering and wastewater system to remove selenium and mercury. AECOM Process Technologies modified the existing chimney for wet operation, including installation of a liner on top of the existing brick flue. AECOM Process Technologies provided engineering and construction management services.