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Delridge Basin


Natural drainage prevents polluted runoff from harming the fish and other wildlife that call Longfellow Creek home.

Seattle Public Utilities (SPU) is responsible for managing stormwater throughout the city and right now is working in the Delridge neighborhood.

  • Fix It First—retrofit existing storage tanks to control up to 100 percent of the total volume.
  • Keep the Stormwater Out—add Green Stormwater Infrastructure (GSI), such as natural drainage, to protect Longfellow Creek from polluted runoff.
  • Store What’s Left—if the retrofit and GSI projects are as successful as expected, a new storage tank would not be needed.

Delridge Natural Drainage System Project

SPU is planning to construct a natural drainage project along several blocks of 17th Avenue SW in Delridge. The rain gardens will be located within the Seattle Department of Transportation (SDOT) proposed neighborhood greenway to create a street that not only manages stormwater but also provides safe and comfortable features for people of all ages and abilities to walk and ride bikes. Please see Project Updates for more information.

Delridge Retrofit Project

We will replace the existing control systems at two existing storage tanks in the Delridge area. The tanks — one at the corner of Delridge and Orchard and the other at the corner of 22nd and Henderson — were built in the 1980s and do not operate as designed. Fixing these facilities will:

  • improve the ability to monitor and control the amount of flow allowed into the sewer system
  • reduce the frequency and volumes of sewage overflows into Longfellow Creek
  • reduce maintenance costs

Retrofit Project Schedule

Design and pre-construction planning is happening through May 2014. Construction is expected to begin in June 2014 and be completed by November 2015.

Environmental Analysis Documents

The Washington State Environmental Policy Act (SEPA) Checklist and Determination of Non-Significance were published on September 16, 2013. These documents detail the regulatory compliance efforts for the retrofit project.

Retrofit Project Contact

Tara Wong-Esteban
(206) 684-5903