The ACO requires DPL to retire two of its coal-fired boilers identified as Unit 1 and Unit 2. The ACO requires DPL to repower, refuel or retire the remaining four coal-fired boilers (Units 3-6) within one year of the effective date of the ACO. DPL may repower or refuel these boilers to natural gas or another non-fossil fuel. The ACO also requires DPL spend no less than $200,000 on environmentally beneficial projects which mitigate past harm caused by the excess opacity and PM emissions. The requirements of the ACO will help ensure continuous compliance with the Ohio SIP and, even with an option to repower or refuel four of the six units, will achieve significant reductions in NOx, SO2, and PM emissions.