An illicit discharge is anything that goes "down the drain" (curb inlet, drainage ditch, directly discharged to a stream, etc.) that's not composed entirely of stormwater. When source pollutants are introduced and mix with the stormwater, you then have an illicit discharge to the storm sewer system - which drains directly to our surface waters without treatment.
Examples of source pollutants that could cause an illicit discharge:
Automotive fluids (oil, fuel, antifreeze)
Landscape waste (grass clippings, etc.)
Cooking oil and grease
Improperly applied fertilizer
Vehicle wash water
Chemical cleansers (detergents, soaps)
Sanitary sewer wastewaters
Improperly applied pesticides/herbicides
Improperly managed salts
Discharging any of these things into the City of Salem storm sewer system is a violation and you will be penalized. Any person found to be knowingly causing illicit discharges shall be guilty of a Class 1 misdemeanor, liable for all costs of cleanup and disposal, and shall be subject to a civil penalty up to $1,000 per day.
The regulations do have some exemptions, however. Examples of sources that are not an illicit discharge: