The system violated the requirements of the Surface Water Treatment Rule (SWTR), 40 C.F.R. Part 141, Subpart H, by exceeding New York StateÂs alternative Maximum Contaminant Level (MCL) for entry-point turbidity in unfiltered systems that must install filtration, as specified in 10 NYCRR §5-1.52, for source water obtained from New York CityÂs Delaware Aqueduct. The AO requires the system to submit a written plan detailing the corrective actions that will be taken to return to and maintain compliance with the MCL.