Illicit Discharge Detection and Elimination is a Key Component of a Stormwater Management Program

A Municipal Separate Storm Sewer System (MS4) is made up of a series of stormwater management facilities, inlets, pipes, swales, and outfalls that collect and convey stormwater. Ultimately, many of these discharges end up in local waterways, where water quality must be monitored to ensure health and safety. Part of an MS4 community’s permit requires the creation and implementation of an Illicit Discharge & Elimination (IDD&E) plan/program under Minimum Control Measure (MCM) 3, which outlines cost-effective strategies to locate, correct, and prevent illegal discharges to the MS4 that contain pollutants such as sediment, nutrients, pathogens/bacteria, and toxic chemicals.

These discharges pose numerous threats to the waterways within a community, including:

  • Increased cost to treat drinking water
  • Unsanitary or hazardous conditions to residents (bacteria, odors, etc.)
  • Trash and other debris clogging the system, causing flooding
  • Harm, including death, to wildlife
  • Expensive fines from the DEP and the EPA to fix the problems


What is Required of an MS4 Community for Illicit Discharges?

The PA Department of Environmental Protection (DEP) and the Environmental Protection Agency (EPA) require the following for each MS4 community under MCM 3:

  • Develop, implement, and enforce a written program to detect and eliminate illicit discharges into the MS4.
  • Develop and maintain a storm sewer system map, showing the location of all outfalls and the names and locations of all surface waters of the Commonwealth that receive discharges from those outfalls.
  • Develop and implement a plan to screen/detect and address non-stormwater discharges, including illegal dumping, to the borough’s system.
  • Effectively prohibit, through an ordinance, non-stormwater discharges into the borough’s storm sewer system and implement appropriate enforcement procedures and actions.
  • Provide educational outreach to public employees, businesses, and the general public about the program and the hazards associated with illegal discharges and improper disposal of waste.


Are any Discharges Allowed?

Depending on your MS4 community there may be any number of authorized discharges to waterways, including:

  • Discharges from fire-fighting activities
  • Potable water, including waterline flushing
  • Irrigation drainage
  • Air-conditioning condensate
  • Pavement wash waters where spills or leaks of toxic or hazardous materials have not occurred (unless spill material was removed) and where detergents were not used
  • Uncontaminated water from foundations or from footing drains
  • Lawn watering
  • Dechlorinated swimming pool discharges
  • Water from residential car washing
  • Routine external building wash down (without use of detergents or similar)

What Happens if an Illicit Discharge is Suspected?

An MS4 community cannot realistically inspect every property’s runoff into the MS4 every day, so they rely on property owners and other residents to notice any telltale signs of illicit discharges into waterways, especially during dry weather (non-rainy) conditions. If you see something suspicious (soapy suds or unusually colored water flowing into or within a local waterway, someone dumping material like leaves, grass clippings, trash, or liquids into a local waterway, etc.), contact your municipal public works department and have as much information ready as possible, including the location, description of the dumping activity or other discharge, what you saw being discharged, and when this occurred. The municipality will respond to potential illicit discharges using progressive enforcement actions, which may focus initially on education to promote voluntary compliance, followed by a written warning and then penalties if voluntary compliance is not obtained.


You can assist your MS4 community by keeping a watchful eye for illicit discharges, keeping your property clean, and reporting any suspicious runoff to municipal staff. This will help keep all our waterways as clean as possible.

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