Illicit Discharge

Understanding Illicit Discharge

An illicit discharge is defined in the federal regulations as:

"...any discharge to an Municipal Separate Storm Sewer Systems (MS4) that is not composed entirely of storm water..."

There are two modes of entry: direct and indirect.


Flows in the storm drains created by illicit/improper connections between sanitary sewer and storm drain system.


Flows in the storm drains created by pollutants that enter the storm drain system through an inlet or through the joints of the pipe (infiltration).

Examples of Illicit Discharge


  • Sewage cross-connections with storm drains
  • Straight pipe connections
  • Industrial and commercial cross-connections with storm drains


  • Groundwater seepage into the storm drain pipe
  • Spills that enter the storm drain system at an inlet
  • Dumping liquid into a storm drain inlet
  • Outdoor washing activities that create flow to a storm drain inlet
  • Non-target irrigation from landscaping or lawns that reaches the storm drain system

Contact Us

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    3826 Amherst

    West University Place, TX  77005 

    Public Works Customer Service
    Phone: 713.662.5839

    After-Hours Emergency
    Phone: 713.668.0330


    Monday - Friday

    7:30 a.m. - 5:30 p.m.

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