Swale on Yale

Seattle, Washington

  • Services Civil Engineering
  • Market(s) Civic
  • Awards Seattle Design Commission “On the Boards” Design Excellence Award


Acres Treating 190M Gallons/Year


LF Water Main
  • Owner Seattle Public Utilities
  • Architect ZGF Architects LLP
  • Contractor Vulcan
  • Team Seattle, WA
Swale on Yale

This unique green stormwater infrastructure project was designed to treat over 400 acres of stormwater runoff (roughly 190 million gallons per year) from the Capitol Hill neighborhood of Seattle prior to discharging into Lake Union. The multi-phase project is constructed and partially operational, with full operation anticipated in 2020. When complete, the system will consist of four biofiltration swales that are designed to remove sediment and pollutants from stormwater diverted from an existing 72-inch storm drain main. Stormwater runoff from the basin previously directly discharged to Lake Union without treatment. Each swale extends the length of one full block and has been constructed as part of private developments adjacent to the swales. A major component of the project provides a naturalistic water quality treatment system in an urban setting, while creating an amenity for the adjacent developments and the neighborhood as a whole. To accommodate the swales, the design required major street revisions, construction of a 12-inch water main, over 2,000 linear feet of stormwater conveyance piping, relocation of a gas main, and undergrounding of the overhead power, telephone, and cable in the area.

KPFF was hired by Seattle Public Utilities to take a concept design for the treatment system and develop the concepts into cost-efficient and constructible Street Improvement Permit (SIP) plans. KPFF met repeatedly with SDOT to ensure the format of the information being presented was acceptable and to work through a variety of design issues related to the street and pedestrian impacts. The project ran a parallel permitting timeline with the adjacent private development, whom KPFF also prepared SIP plans for. Through extensive experience in developing SIP plans, KPFF was able to approach the complex public-private project and use project phasing to streamline the design and construction of the conveyance system and the surrounding street improvements.

The project has been awarded an “In the Works Design Excellence Award” by the Seattle Design Commission. The project has been exemplary in terms of agency and consultant teams working together

Chris Woelfel quote marks

Here at Seattle Public Utilities, we are very pleased with your work on this project. I’d like to list several specifics qualities and traits your team demonstrates: Clear understanding of the design goals and challenges, sincere enthusiasm for the project and pride in your work, very competent engineering solutions to the hydraulic and water quality challenges, utilization of multiple team members ideas and skills to develop robust design options, tremendous flexibility with major scheduling and financial constraints, close and direct coordination with major stakeholders, as needed, which saves me considerable effort and understanding of the different needs that public sector and private sector clients have.

The various SPU design and planning staff, who have worked with your team, unanimously want to work with you on future projects. I’m appreciative of the designs services you’ve provided on the Swale-on-Yale project.

Chris Woelfel
Chris Woelfel
Project Manager, Seattle Public Utilities
Swale on Yale

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