Petitioners, the City of Port St. Joe and the Florida Coast Paper Company, petitioned for review of a National Pollutant Discharge Elimination System (“NPDES”) permit that was issued by EPA Region IV (the “Region”) to the City for the Port St. Joe Industrial Wastewater Treatment Plant (the “IWTP” or the “plant”). Under the NPDES permit program, dischargers are subject to different statutory and regulatory requirements depending on whether they are categorized as a “publicly owned treatment works” (“POTW”) or “other than publicly owned treatment works” (“non-POTW”).