Illicit Discharge

What is an illicit discharge?

An illicit discharge is defined as any discharge to the municipal separate storm sewer system (MS4) that is not composed entirely of stormwater, except for discharges allowed under a TPDES permit. Non-stormwater discharges can originate from direct connections to the storm drain system from business or commercial establishments (illicit connections), or indirectly as improper surface discharges to the storm drain system.

What types of discharges to the storm drain system are prohibited?

The following table lists some of the prohibited and allowed discharges to the storm drain system.

Prohibited Discharges Allowed Discharges
Industrial process water Water utility line flushing
Commercial car wash wastewater Runoff from firefighting
Sanitary sewer flows Landscape irrigation
Wash-down of loading areas Uncontaminated ground water infiltration
Wastewater treatment plant effluent Discharges from potable water sources
Dumping of liquid waste Dechlorinated pool water
Chlorinated pool water Street wash water from cleaning/maintenance (excluding street sweeper water waste)
Water softener brine backwash Residential car washing
Used oil Air conditioning condensation

 

What are indications of illegal/illicit discharges to the storm drain system?

The following table lists some of the physical indicators that may signal an illicit discharge; physical indicators are those that can be observed or sensed during dry weather field screening and routine inspections.

Unusual color or cloudiness
Strong pungent or musty odor
Floating debris
Surface scum or foam
Oil sheen
Algae
Dead vegetation or inhibited growth
Dead animals
Stains on channel bottom or sides
Pipe corrosion

 

Workshops

Thu, Aug 6, 2020
Workshop

Presentations included an introduction to dry weather field screening, Outfall Reconnaissance Inventory, monitoring procedures, case studies and a field screening demonstration.

Tue, Jul 27, 2021
Workshop

Presentations included Expanding on the Basics of IDDE, advanced source detection methods, the Stormwater/Wastewater Nexus, sanitary sewer maintenance programs, and case studies from the City of Irving.

Wed, Oct 27, 2021
Workshop

Presentations included a Phase I MS4 Industrial Program example, an overview of the TPDES Industrial Program, and a mock inspection of the Peterbilt manufacturing facility.

Thu, May 5, 2022
Workshop

Presentations included an introduction to and demonstration of dry weather field screening, monitoring procedures, and case studies led by instructors from the cities of Carrollton, Cedar Hill, Dallas and Grand Prairie.

Tue, Sep 20, 2022
Workshop

Presentations included an overview of the TPDES Industrial Program, an example of the Phase I MS4 Industrial Program, and a mock inspection of the Bud Ervin Water Treatment Plant.

Fri, Jun 16, 2023
Workshop

Presentations  included an introduction to dry weather field screening, information on Optical Brightener Monitoring (OBM), IDDE Source Tracking, and an Industrial Illicit Discharge Case Study.

Tue, Apr 30, 2024
Workshop

Presentations included an overview on SIC/NAICS Code, an Industrial Inspection Program Example, a Tour of Owens Corning Plant, and a Mock Inspection.

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