The Town of Paradise Valley (Town) is regulated under the Arizona Pollutant Discharge Elimination System (AZPDES) permitting program because it owns and operates a small MS4 (municipal separate storm sewer system). MS4s (as defined in 40 Code of Federal Regulations [CFR] §122.26[b]) include any publicly owned conveyance or system of conveyances used for collecting and conveying stormwater that discharges to “waters of the United States” (WUS).
Illicit discharge – What is it?
Illicit discharges are generally any discharges into a storm drain system that are not composed entirely of stormwater, and are restricted by Federal, State, and local laws. Examples of illicit discharge include water from swimming pools or the runoff from washing down a driveway or spill. Illicit discharges are a problem because unlike wastewater that flows to a wastewater treatment plant, stormwater generally flows to waterways without any additional treatment. Illicit discharges often include pathogens, nutrients, surfactants, and various toxic pollutants.