Illicit Discharge

Illicit Discharge Detection and Elimination

What is an illicit discharge?
According 327 IAC 15-13-5 (28), an illicit discharge means any discharge to an MS4 conveyance that is not composed entirely of storm water, except naturally occurring floatables, such as leaves or tree limbs. Sources of illicit discharges include sanitary wastewater, septic tank effluent, car wash wastewater, oil disposal, radiator flushing disposal, laundry wastewater, roadway accident spillage, and household hazardous wastes.

Why Is It a Problem?
Illicit discharges are a problem because unlike wastewater which will be treated at a wastewater treatment facility before it is discharged back into waterways, storm water does not go to a treatment facility.  As a result, as the storm water flows across developed and undeveloped land, it picks up pollutants and carries those pollutants to the nearest storm sewer or ditch.  When these storm sewers and ditches outlet into creeks and waterways, the pollutants are also discharged into the creeks and waterways.

What Are Vanderburgh County’s Requirements and Obligations?
In order to comply with the requirements of 327 IAC 15-13, Vanderburgh County had to develop an Illicit Discharge Detection and Elimination Plan to detect and eliminate illicit discharges into the municipal separate storm sewer conveyance system.  Vanderburgh County also had to develop an ordinance that prohibits illicit discharges into the MS4 system.  The ordinance can be viewed at this link.

The regulations contained in 327 IAC 15-13 also require the county to prepare a storm sewer system map for the entire county.  This map must show where storm sewers and ditches outlet into creeks and streams, which are know as “outfalls”.  The county is then required to inspect these outfalls during dry weather conditions to determine if there are any illicit discharges coming out of the outfalls.  In the event that illicit discharges are found, the county must then try to determine the source of the illicit discharge, and then attempt to implement an appropriate remedy to prevent further discharges.

What Can You Do To Help?
Citizens may report complaints of storm water pollution or dumping of pollutants into storm drainage systems by calling 812-435-5773 or by email at

Residents can also help by properly disposing of all automotive fluids, household wastes, etc.  Never dump any of these materials into any ditches or storm sewers!  In order to prevent improper dumping of these items, numerous recycling opportunities are provided throughout the county every year.  For more information on the availability of recycling, please visit the Vanderburgh County Solid Waste District website by clicking here.