Illicit Discharge Elimination Program

Illicit Discharge Elimination Program Outfall MapsAs part of MDOT's Illicit Discharge Elimination Program (IDEP), employees are trained and educated to identify illicit connections or discharges to department's drainage system. The most common warning signs of illicit discharges are dry weather flow, suds, sewage, oil and gas. In addition, MDOT field crews investigate point source discharges (PSDs) as part of their dry weather screening component of IDEP. A PSD is an outfall from a drainage system to waters of the state, or a point where a storm water drainage system discharges into a system operated by another public body. MDOT maps the locations of their known PSDs. These maps can be viewed by clicking on the 'Outfall Maps' graphic below.


Illicit discharge is any discharge (or seepage) to the separate storm water drainage system that is not composed entirely of storm water or uncontaminated groundwater.

Illicit connection is a phyical connection to a separate storm water drainage system that primarily conveys illicit discharges into the system and/or is not authorized or permitted by the local authority (where a local authority requires such).

Illicit Discharge Reporting

 Anonymously report sources of pollution along roadsides and at rest areas/roadside parks to the Pollution Emergency Alerting System (PEAS) hotline at 800-292-4706. This includes dumping of waste/oil or other vehicle fluids and suspicious pipes outletting to ditches. Protect the quality of streams and public health, report illicit discharges.

Illicit Discharge Warning Signs


Dry Weather Flow


Sanitary Sewage


Dry Weather Flow is noted when it has not rained for at least 72 hours and the storm drain has flow or the drain shows signs of intermittent flow (staining, odor).


Sanitary Sewage may be present if there is black staining inside the drainage pipe; visible evidence of sanitary waste, such as toilet paper; or opaque or gray water.  Sewage may originate from septic tank overflow pipes or improperly dumped travel trailer waste. 




Oil Gas


Suds may be harmful to fish because suds deplete oxygen levels in the water.  Suds often enter lakes and streams as a result of improperly connected car washes or  washing machines. 


Oil/Gas is recognized as a sheen on the water. Natural sheens may be differentiated from an oil/gas sheen by swirling the sheen around in the water. If it re-attaches, the sheen is oil/gas. Natural sheens will remain separated. Oil/Gas enters waterbodies via storm water runoff (spills while topping off at gas stations, oil leaks on pavement, etc.) and illegal dumping.



Illicit Discharge Interactive Demonstration Click one of the buttons below to view an interactive illicit discharge demonstration.

Demo of what to do Demo of what NOT to do

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