110th Cascade Project

Seattle Public Utilities (SPU) replaced the existing ditch and culvert system along four blocks of NW 110th St, between Greenwood Ave N and 3rd Ave NW in the Piper's Creek Watershed with a “Cascade” model natural drainage system. View vicinity map (PDF).

Features and Benefits

The project is a series of stair-stepped natural pools that slow damaging stormwater flows, reduce flooding, and trap pollutants before they reach Pipers Creek. Stormwater flow from approximately 21 acres is managed through this natural infrastructure.

A "Cascade" prototype is a natural drainage design used on steep, residential streets. This design:

  • Manages high volumes of stormwater from many acres of watershed area (5 to 50 acres).
  • Provides excellent water quality benefits.
  • Slows stormwater velocity before reaching the creek.
  • Locates swales on one side of the roadway.
  • Locates a sidewalk on the opposite side of the roadway.
  • Adds extensive tree and shrub cover.

Construction Schedule

Construction was completed in December of 2002. The replanting and landscaping phase, which involved both sides of the street, took place between winter and spring of 2002-2003. Seattle Public Utilities is conducting ongoing monitoring of stormwater flow and velocity on the project.


The bioretention cells in the project are maintained by SPU Operations and Maintenance to ensure stormwater functionality at a service level B. Residents are welcome to provide additional maintenance to improve curb aesthetics.

Project Resources

Public Utilities

Andrew Lee, General Manager and CEO
Address: 700 5th Avenue, Suite 4900, Seattle, WA, 98104
Mailing Address: PO Box 34018, Seattle, WA, 98124-5177
Phone: (206) 684-3000

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Seattle Public Utilities (SPU) is comprised of three major direct-service providing utilities: the Water Utility, the Drainage and Wastewater Utility, and the Solid Waste Utility.