Illicit Discharges


What is an Illicit Discharge


An illicit discharge is any discharge into a storm drain system that is not composed entirely of stormwater. An illicit discharge could be the result of someone dumping a pollutant (automobile fluids, paint, etc.) into the conveyance system; the result of an illicit connection into the conveyance system, such as a sewer pipe connected to the stormwater conveyance system; or a pipe that bypasses the connection or septic drain field, producing a direct discharge into open channels or streams. The exceptions include water from firefighting activities and discharges from facilities already under a National Pollutant Discharge Elimination Systems (NPDES) permit.


Why Protecting Stormwater from Illicit Discharges is Important


Stormwater flows to waterways without any additional treatment. Illicit discharges can contribute high levels of pollutants to water bodies. Pollutants commonly found in illicit discharges include raw sewage (viruses and bacteria), heavy metals, toxics, oil and grease, solvents, and nutrients. Pollutant levels from these illicit discharges have been shown in EPA studies to be high enough to significantly degrade water quality, close beaches, and threaten aquatic, wildlife, and human health.


Difference Between Stormwater Discharge and an Illicit Discharge


Dry weather flow is the best indication that water coming from an outfall pipe is from an illicit connection. If it has not rained in at least three days and there is water coming from a stormwater pipe, chances are that water is from an illegal source. Although it is a good indication, dry weather flow is not always from an illicit source. Sometimes groundwater seeps into the stormwater conveyance system and is discharged through the outfall pipe. This is a natural source and not illicit.



When to Report Dry Weather Flow


The best way to tell if the dry weather flow is an illicit discharge, and should be reported, is by examining the characteristics of the water being discharged.


  1. Does the discharge have a distinct odor? Some smells coming from an outfall pipe are an immediate indicator of an illicit discharge, for example, sewage, gasoline, or chemical smell should be reported.

  2. Is the water cloudy or full of sediment? Gray water that should be treated at a sewage treatment plant may cause a cloudy appearance in the discharged water. A construction site without proper stormwater best management practices could be discharging sediment to a storm drain. These conditions should be reported.

  3. Is there anything floating in the discharge? Soap suds or oil sheens are examples of floatables that may be found in an illicit discharge. These conditions should be reported.

  4. What color is the discharge? An abnormally colored discharge is a good indication that there is an illicit connection to the stormwater conveyance system. However sometimes an abnormal color may have a natural cause. For instance, an orange discharge could be naturally occurring from groundwater that is high in iron. However if an abnormal color is coupled with another one of the characteristics listed here (odor, floatables, cloudiness, vegetative growth), it should be reported.

  5. Is there excessive vegetation around the outfall pipe? Excessive vegetation around the outfall pipe as opposed to the surrounding area is an indication of increased nutrients in the stormwater discharge; this could be from fertilizers or sewage in the discharge and should be reported.



Allowable Discharges by Our MS4 Permit


  • Water line flushing (excluding discharges of hyper-chlorinated water, unless the water is first de-chlorinated and discharges are not expected to adversely affect aquatic life) 
  • Runoff or return flow from landscape irrigation, lawn irrigation, and other irrigation utilizing potable water, groundwater, or surface water sources 
  • Discharges from potable water sources
  • Diverted stream flows
  • Rising groundwater and springs
  • Uncontaminated groundwater infiltration 
  • Uncontaminated pumped groundwater 
  • Foundation and foot drains
  • Air conditioning condensation 
  • Water from crawl space pumps 
  • Individual residential vehicle washing 
  • Flows from wetlands and riparian habitats 
  • De-chlorinated swimming pool discharges 
  • Street wash water
  • Discharges or flows from firefighting activities (firefighting activities do not include washing of trucks, run-off water from training activities, test water from fire suppression systems, and similar activities)


Reporting Illicit Discharges


If someone is dumping liquids or trash into a storm drain or if you see an illicit discharge, please contact the City of Manor Public Works Department at 512-272-5555 ext. 3.


Reporting Illegal Dumping


Illegal dumping can also affect our stormwater. Please report any illegal dumping to the City of Manor Police Department at 512-272-8177


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