What is Illicit Discharge Detection and Elimination (IDDE)?

An illicit discharge is defined by the US EPA as “any discharge into a separate storm sewer system that is not composed entirely of storm water…” with some exemptions. These exceptions include discharges from NPDES permitted industrial sources and discharges from fire-fighting activities. Illicit discharges are considered “illicit” because MS4s are not designed to accept, process, or discharge such non-stormwater wastes.  

Typically, illicit discharges enter a storm sewer either through direct connection, such as sanitary sewer piping, or indirectly through cracked sanitary sewer conveyance systems, spills collected by storm drains or from contaminants dumped directly into a storm drain inlet. In many instances, the MS4 is directly connected to a water body and does not receive any type of treatment prior to its discharge to receiving water bodies of the state. These untreated discharges have the potential to cause significant degradation to receiving water bodies. As result of this non-treatment, it is vital that only stormwater is discharged from these MS4s to prevent contamination of water bodies. ​

One element of the NPDES Storm Water Phase II MS4 regulation is Minimum Control Measure 3 (MCM #3) – Illicit Discharge Detection and Elimination, which requires permittees to develop a strategic plan to detect and eliminate illicit discharge into the public storm sewer system from entering the waters of the states and prevent pollution.

Warren County IDDE Program

Warren County SWCD works in partnership with Warren County Engineer's Office, Warren County Health District and Warren County Prosecutors to form the Warren Co IDDE Advisory Committee.  This committee is working to formulate the management document which details the Warren Co IDDE Program.

Warren Co SWCD plays and inportant role in this advisory committee, but also in yearly inspections of outfalls.  Warren SWCD inspects stormwater outfalls in most MS4s in the County, maps and then resports findings in an annual report to the Ohio EPA.