What is an illicit discharge?

Stormwater regulations define an "illicit discharge" as "any discharge to a municipal separate storm sewer that is not composed entirely of stormwater" (except discharges resulting from fire fighting activities and a few other categories). 

Common sources of non-stormwater dry weather discharges in urban areas include:

  • Airports
  • Apartments and homes
  • Car washes
  • Gas stations
  • Landfills
  • Restaurants

These so called "generating sites" and include, among other substances:

  • Antifreeze
  • Discharge sanitary wastewater
  • Gasoline and fuel spills
  • Motor oil
  • Septic system effluent
  • Vehicle wash water
  • Washdown from grease traps

Although these illicit discharges can enter the storm drain system in various ways, they generally result from either direct connections (e.g, wastewater piping either mistakenly or deliberately connected to the storm drains) or indirect connections (e.g, infiltration into the storm drain system, spills, or "midnight dumping"). Illicit discharges can be further divided into those discharging continuously and those discharging intermittently.

Report an illicit discharge online

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Show All Answers

1. What is stormwater runoff?
2. What is allowed in storm drains?
3. What are catch basins?
4. What is an illicit discharge?
5. How can I report a spill?
6. What can I do to prevent stormwater pollution?
7. How can I help?
8. Why manage stormwater?
9. Do catch basins and storm drains get cleaned out?
10. Why doesn’t the City clean out all of the storm drains before a storm?
11. What are the metal buttons that are above catch basins around Aberdeen?
12. What discharges are allowed in catch basins?
13. What is the Stormwater Rate?