Design & Build Case Study:
Seattle, WA
How a Public/Private Partnership Between Seattle Public Utilities and Vulcan Inc. in Seattle, Washington Led to Innovations and Community Benefits
| Region | Northwest | Principle | Establish Design Standards |
| City | Seattle, WA | Best Practice | Build in flexibility for innovation |
| Population | 755,000 | ||
| Partners | Seattle Public Utilities, Vulcan Inc., Stormwater Retrofit and LID Grant (WA Department of Ecology), and State Water Pollution Control Revolving Fund Ecology Loan (WA Department of Ecology) | ||
“The Swale on Yale project gave us the opportunity to build flexibility into the design process—testing new ideas, learning from phase one, and applying those lessons in real time.”
– Kelly Castillo, Seattle Public Utilities
Project Description
In Seattle’s rapidly developing South Lake Union neighborhood, Seattle Public Utilities (SPU) forged an innovative partnership with Vulcan Inc. on a green infrastructure project. Vulcan Inc., a private developer, shared an interest in being a sustainable partner and implementing green technologies. While private development is required to provide 91 percent treatment of the average annual runoff volume, this project was entirely voluntary and not required by code. Working together with SPU, the guidelines were to treat as much stormwater and provide the highest level of treatment possible.
In 2012, SPU and Vulcan Inc. initiated the Swale on Yale Project. As part of the planning process, the project team conducted outreach to the local community, held design charrettes with municipal agencies and consultant firms, presented to the Seattle Design Commission, and collaborated with local businesses like REI and churches. Now in its second phase, the Swale on Yale project provides a natural drainage system to remove pollutants from stormwater coming from Capitol Hill before it enters Lake Union. Each of the project’s four bioswales can treat an average of 190 million gallons of stormwater each year.
The Swale on Yale project, located in Seattle’s South Lake Union neighborhood, provides a natural drainage system to remove pollutants from stormwater.
Best Practices in Action
By aligning around similar values, the partnership between SPU and Vulcan Inc. prioritized best practices in green technologies and innovation, while delivering a project that reflected the vision and feel of the South Lake Union neighborhood. The project applied new approaches including using a stormwater treatment device, the Vortechs Swirl Separator, to trap large solids and trash in the water. Additional methods included spreading stormwater across the swale through inflow trench drains with raised gates and implementing a polishing layer in the south swales. Although not required by code, polishing layers are now used on SPU capital projects in certain scenarios.
The Swale on Yale project allowed for flexibility through a phased approach to test certain technologies and methodologies in the first phase and make changes as needed in the second phase. As an example, SPU tested two methods for swale plantings. For the first method, plantings were grown in bioretention soil at a nursery then installed in swales. The second method used plantings grown in soil at the nursery that were then planted bare-root in the swales. SPU also found ongoing maintenance was a challenge and it was critical to maintain ongoing points of contact with maintenance crews. To keep plants healthy and thriving, the team has since installed an irrigation system.
The Swale on Yale project illustrates thoughtful design solutions that respond to the surrounding environment. To create a visual and physical cue to pedestrians of the vertical drop created by the swales, the team installed custom handrails and physical barriers between the swale and sidewalk. As a way to create a visual connection with the surrounding area, the project team coordinated with the Berger Partnership to integrate steel from adjacent buildings into bridge installations.
Key Learnings
Test and confirm new approaches
A phased implementation allowed for opportunities to pilot and learn from what worked and address any challenges in the second phase. Applying a polishing layer is now a practice SPU uses for other green infrastructure projects, while also now proactively planning for ongoing maintenance of the swales.
Establish feedback loops with maintenance crews
Through this process, feedback loops for SPU projects are now in development. SPU found that coordinating ongoing touchpoints with maintenance crews are critical to project success.
Enhance community benefits with public/private partnerships
When values and goals are aligned, partnering with a private developer can lead to high-impact environmental and community benefits. Vulcan Inc. supported advancing ambitious green infrastructure goals and helped build a connection between public and private spaces.