Illicit Discharge

An illicit discharge is defined as any discharge to a Municipal Separate Stormsewer System (MS4) that is not composed entirely of stormwater. Illicit discharges enter the system through either direct connections (e.g. wastewater piping either mistakenly or deliberately connected to the storm drains) or indirect connections (e.g., infiltration into the MS4 from cracked sanitary systems, spills collected by drain outlets, or paint or used oil dumped directly into a drain). The result is untreated discharges. Illicit discharges may be continuous or intermittent. Intermittent discharges tend to be discharged only when carried by a storm event while continuous illicit discharges often flow during dry weather.