Outfalls

The stormwater problem for Puget Sound is immense and must be addressed if we are to restore the health of the Sound by 2020.

People For Puget Sound collaborated with a team of students in the University of Washington Geographic Information Systems (GIS) Certificate Program to produce the first comprehensive map of existing public stormdrains into Puget Sound. To date, such a map has not been created due to the challenges of the large number of jurisdictions each with different data management programs.

By contacting agencies, we identified and mapped the following features:

• 4,529 known public Manmade Outfalls
• 2,123 Natural Outfalls
• 93 Combined Sewer Overflow (CSO) Outfalls
• 297 WSDOT Outfalls
• 70 WSDOT Bridges

These features convey stormwater to the tidally influenced area of Puget Sound, that is, to the Sound itself and the channels and rivers that are low elevation. The project did not include private and industrial stormdrains.

These public manmade drains primarily carry stormwater from paved surfaces.  Stormwater-related pollutants and stressors have been identified by scientists as the most important water quality problem of the Puget Sound Basin.  Recent toxics loading assessments by WA Department of Ecology found that metals such as copper and zinc, as well as polycyclic aromatic hydrocarbons (PAHs), and 52,300 metric tons (57,651 US tons) per year total petroleum hydrocarbons (largely oil and petroleum from vehicles) flow in these drains to Puget Sound.

Recommendations:  The Problem is Immense

Our project is the first to compile all of the known municipal or equivalent public stormdrain outfalls to Puget Sound.  This project demonstrates that there are a larger number of municipal outfalls to Puget Sound than had been earlier understood, further underscoring the importance of moving forward to address stormwater pollution:

• As has now been documented by Ecology, toxic chemicals in stormwater pollution represent a major threat to the health of Puget Sound.
• The largest source of toxic pollutions to Puget Sound is from paved surfaces, especially from residential areas -  i.e., the developed area of the Puget Sound basin.
• In addition to 2,123 natural drainage, 4,529 manmade outfalls, 93 combined sewer overflow (CSO) outfalls, 297 mapped WSDOT outfalls and 70 WSDOT bridges convey polluted stormwater to Puget Sound.
• We need to step up our efforts to address stormwater pollution by low impact development (LID) retrofit programs, pollution prevention, and treatment.
• A sustainable source of new funding is needed to address the stormwater carried pollution to the Puget Sound basin.

The report was completed by University of Washington Geographic Information System students:  Robyn Carmichael, Liz Green, Collin O'Meara, and Matt Yarrow.  In addition to the GIS maps, the team also produced a report that details how the project was completed, including a table of contacts for each jurisdiction.

Contact: Heather Trim | Urban Bays and Toxics Program Manager | 206.382.7007 x215