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Water: Best Management Practices

Illicit Discharge Detection and Elimination

Wash water from a commercial car wash discharging down a storm drain is an example of an illicit discharge

Illicit discharges are generally any discharge into a storm drain system this is not composed entirely of stormwater. The exceptions include water from fire fighting activities and discharges from facilities already under an NPDES permit. Illicit discharges are a problem because, unlike wastewater which 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.

Phase II MS4s are required to develop a program to detect and eliminate these illicit discharges. This primarily includes developing: 

  • a storm sewer system map,
  • an ordinance prohibiting illicit discharges,
  • a plan to detect and address these illicit discharges, and
  • an education program on the hazards associated with illicit discharges.

An effective illicit discharge program needs to be both reactive and proactive. The program is reactive in addressing spills and other illicit discharges to the storm drain system that are found. The program must also be proactive in preventing and eliminating illicit discharges through education, training and enforcement.

Additional information on this minimum measure, including the stormwater Phase II regulatory requirements for IDDE and a fact sheet on the IDDE minimum measure [PDF - 262 KB - 4 pp], is also available.

Key BMPs and Resources:

MS4s addressing the IDDE minimum measure should begin with the IDDE program development BMP fact sheet. The additional BMPs listed below can be used to help implement an IDDE program. A key reference for IDDE is the IDDE Guidance developed by the Center for Watershed Protection and Dr. Robert Pitt, listed below.

  • Illicit Discharge Detection and Elimination: A Guidance Manual for Program Development and Technical Assessments - Center for Watershed Protection's comprehensive manual that outlines practical, low cost, and effective techniques for stormwater program managers and practitioners. The guidelines include details on creating and managing an IDDE program, timelines that estimate how long program implementation will take, information on estimating program costs in terms of capital and personnel expenses, and types of testing used to detect stormwater illicit discharges. This manual provides valuable guidance for communities and others seeking to establish IDDE programs. 
BMP Fact Sheets:

The fact sheets in this section describe BMPs and how to use them to help municipal stormwater programs and construction site operators comply with the stormwater Phase II requirements.
EPA has started updating these fact sheets to include new practices and technologies. Several of these updated fact sheets are now available in PDF format.

Developing an IDDE Program

Illicit Discharge Detection and Elimination Program Development
Reducing the Occurrence of SSOs

Trash and Illegal Dumping

Developing a Used Oil Recycling Program
Illegal Dumping Control

Trash and Debris Management

Decentralized Wastewater

Preventing Septic System Failure
Sewage from Recreational Activities

Public Reporting

Community Hotlines

EPA Internet Resources:
Other Internet Resources:   

Note: If you are referencing this page, please use this alias web address: http://www.epa.gov/npdes/stormwater/menuofbmps/illicitdischarge

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