Illicit Discharge Detection and Elimination (IDDE)


"Only Rain in the Storm drain"

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What is an Illicit Discharge?

An illicit discharge is any disposal of any substance other than stormwater into the stormwater system.  Illicit discharges involve materials like used oil, trash juice from dumpsters, chemicals, or other hazardous materials being discharged, intentionally or unintentionally, into the stormwater system.

The stormwater system collects all the rainwater that runs over hard surfaces, like pavement and rooftops.  This stormwater runs along the curb and gutter and then drains into a basin or an inlet.  The stormwater and any pollutants it has picked up go to the nearest body of water. Anything that enters the stormwater system besides rainfall is considered an illicit discharge. Water pollution can damage fish and wildlife.  It can also make activities such as swimming and fishing unsafe.  Keeping pollution out of stormwater protects public health and the environment.

In the event of an illicit discharge into the stormwater system, the City of Annapolis will investigate and then notify the parties performing such activities, and will order such activities be stopped or conducted in such a manner as to avoid the discharge into the stormwater system.  The City’s regulations regarding Illicit Discharge are located in Chapter 17.07.

Examples of Illicit Discharges

  • Paint Spills
  • Soapy Wash Water
  • Gasoline or Oil Spills
  • Sewage
  • Food Grease
  • Sediment
  • Yard Waste
  • Chlorinated Pool Water
Tackling Stormwater Management: Keeping Clean Water in Focus

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IDDE Program

The City is required to identify outfalls, or the opening of the end of pipes within a storm drain system, that have flowing water when it has not rained within the last 48 hours.  This is considered dry-weather flow, and is indicative of a potential illicit discharge.  Once identified, the water is tested for a variety of chemicals in order to isolate a source.  Once the source is documented, whether a business or a homeowner, the appropriate actions are taken to cease the discharge and ensure proper clean up.

Stop illicit discharges
Do your part to help! 
  • The City of Annapolis relies on you to help us identify any illicit discharges, dumping, or spills. 
  • Outfalls or the opening of the end of pipes within the stormwater system should not be flowing water when it has not rained within the last 48 hours.

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