The illicit discharge detection and elimination (IDDE) minimum control measure consists of best management practices (BMPs) and program elements that focus on finding and addressing non-stormwater discharges and/or non-permitted discharges that may be entering the municipal separate storm sewer system (MS4).
Regulated MS4s are required to establish plans to detect and eliminate illicit discharges including discharges not composed entirely of stormwater. They must map all outfalls from the storm sewer system to surface waters (not only from pipes, but also from road ditches, swales and other stormwater carriers), and must inform public employees and the community about the hazards of illegal discharges and improper waste disposal. Further, illicit discharges to the storm sewer system must be prohibited by ordinance or regulation, and the prohibition must be enforced.
The MS4 is required to develop and maintain a map showing: the location of all outfalls and the names and location of all surface waters of the State that receive discharges from those outfalls. By March 9, 2010, the preliminary boundaries of the permittee's storm sewersheds should be determined using GIS or other tools, even if they extend outside of the urbanized area. This will help facilitate trackdown of illicit discharges. When grant funds are made available, a map of the sewer lines and storm sewer system should be completed.
The MS4 is required to field verify outfall locations and conduct an outfall reconnaissance inventory that addresses every outfall within the MS4 designated area at least once every five years.
An IDDE program should also address non-stormwater discharges, including illegal dumping. The program must include: procedures for identifying priority areas of concern (geographic, audiences, or otherwise); a description of priority areas of concern, available equipment, staff, funding, etc.; procedures for identifying and locating illicit discharges (trackdown); procedures for eliminating illicit discharges; and procedures for documenting actions.
In certain areas that have current Watershed Improvement Strategies and/or Total Maximum Daily Load (TMDL) requirements, the regulated community may also be required to undertake additional activities such as: completing entire system mapping by January 8, 2013; and developing an on-site wastewater system inspection, maintenance and rehabilitation program (including the necessary legal authority to enforce the program). The details associated with these additional requirements are further described, and should be referenced, in the SPDES General Permit for Stormwater Discharges from MS4s.