Understanding Illicit Discharge
An illicit discharge is defined in the federal regulations as:
"...any discharge to an Municipal Separate Storm Sewer Systems (MS4) that is not composed entirely of storm water..."
There are two modes of entry: direct and indirect.
Direct:
Flows in the storm drains created by illicit/improper connections between sanitary sewer and storm drain system.
Indirect:
Flows in the storm drains created by pollutants that enter the storm drain system through an inlet or through the joints of the pipe (infiltration).
Examples of Illicit Discharge
Direct
- Sewage cross-connections with storm drains
- Straight pipe connections
- Industrial and commercial cross-connections with storm drains
Indirect
- Groundwater seepage into the storm drain pipe
- Spills that enter the storm drain system at an inlet
- Dumping liquid into a storm drain inlet
- Outdoor washing activities that create flow to a storm drain inlet
- Non-target irrigation from landscaping or lawns that reaches the storm drain system
