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Spills and Illicit Discharge Detection and Elimination (IDDE)

Warning signs of illicit discharges
or connections

Illicit Discharge photo of turbid water
Murky, turbid waters flow
out of a culvert
An illicit discharge into a storm drain
Suds flow into a storm drain
A pipe slope drain illicit connection
A pipe on top of a storm drain
A trenched illicit connection
Ditch water is directed into a
roadside drainage system

Though WSDOT does its best to treat stormwater running off of its highways and properties, stormwater often times flows untreated from storm drainage systems into local waterways.  It is illegal to discharge (dump) anything other than stormwater into a storm drainage system (illicit discharge) or to connect any unauthorized pipe, ditch, or other manmade structure to a storm drainage system (illicit connection). Report spills, illicit discharges or connection to the appropriate authorities listed below.

Report spills, illicit discharges or connections on state highways

To report a hazardous spill on state highways:

  • Call 911 for spills on state highways that may impact the safety of the traveling public or the environment, such as spills related to: vehicle accidents, fires, unknown chemicals, or an explosion hazard.

For non-emergency spills or illicit discharges that have a potential to reach WSDOT stormwater drainage system:

  • Call the closest Department of Ecology office for spills or discharges along state highways or WSDOT properties that are not comprised entirely of stormwater and reach, or have the potential to reach, WSDOT's stormwater drainage system (storm drains, culverts, ditches, etc.):

Central Region: (509) 575 -2490
(Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan and Yakima counties)

Eastern Region: (509) 329-3400
(Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, and Whitman counties)

Northwest Region: (425) 649-7000
(Island, King, Kitsap, San Juan, Skagit, Snohomish, and Whatcom counties)

Southwest Region: (360) 407-6300
(Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Mason, Lewis, Pacific, Pierce, Skamania, Thurston, and Wahkiakum counties)

For non-emergency spills or illicit discharges that do not reach WSDOT stormwater drainage system or illicit connections:

  • Contact the appropriate WSDOT Region IDDE contact for all other spills and illicit discharges that occur along state highways or WSDOT properties but do not reach, or have the potential to reach, WSDOT's stormwater drainage system; or for illicit connections to WSDOT's stormwater drainage system or property.  Contacts are available during normal business hours only. Leave a message if contacting outside of business hours.

Map of IDDE Contacts by WSDOT Region

WSDOT's Illicit Discharge Detection and Elimination (IDDE) Program

As required by WSDOT's National Pollution Discharge Elimination System (NPDES) Municipal Stormwater permit, WSDOT's IDDE Program trains applicable WSDOT personnel to recognize illicit discharges and connections along with how to report spills on state highways to the appropriate entity.  The permit requires WSDOT to track all spills/discharges that affect state highways or WSDOT property and seek remediation where necessary.


Illicit Discharge is any discharge to WSDOT property or drainage system that is not comprised entirely of stormwater. Signs of an illicit discharge (pdf 200kb) can include:

  • staining
  • residues
  • oily substances
  • odors
  • abnormal flow during dry weather periods
  • turbid waters
  • suds

Illicit Connection is any unauthorized pipe, ditch, or other manmade structure that is physically connected to WSDOT's property or drainage system.

Spill is an unintentional release of a non-stormwater substance to WSDOT's stormwater drainage system or property related to a single event. Many times they are associated with emergency situations such as an automobile accident spilling oil or other automotive fluids onto the highway surface and potentially flowing into the stormwater drainage system.

For all other questions, please contact the WSDOT Environmental Services Office at (360) 709-8058 or email the WSDOT IDDE Program at