Illicit discharges are the introduction of non-stormwater runoff, sewage, or hazardous materials into the public stormwater system. Studies have shown that pollutant discharge from stormwater systems in dry weather due to illicit discharges can exceed the total pollutant flow from storm event flows. Stormwater systems typically flow untreated to water bodies thus the Department of Ecology places a significant emphasis on illicit discharge detection to protect water quality.

Illicit Discharge Requirements & Conditions
Illicit discharges are:

• Hazardous waste
• Liquid or solid wastes
• Operational wash water
• Septic or sewer connections

With certain conditions, the following are not illicit discharges:

• Dust control water
• Lawn water
• Permitted discharges covered under another permit
• Street/sidewalk wash water
• Swimming pool discharge
• Water line or hydrant flush water

Illicit discharges are not:

• Air conditioning condensate
• Uncontaminated crawl space pump discharge
• Footing drains
• Foundation drains
• Ground water
• Irrigation water from agricultural sources

An ordinance prohibiting illicit discharges has been adopted by the regional co-permittees in accordance with permit requirements. The following table links the ordinances to the specific jurisdictions.