Seattle Digs Deep for Sustainability with the Ship Canal Water Quality Project

Many cities are facing combined sewer overflow (CSO) challenges due to intensifying federal and state regulations and increased attention on public health impacts. Municipalities across the country are exploring multiple alternatives to improve their CSO outcomes and, while there is no one-solution-fits-all approach, the complexities of the Ship Canal Water Quality Project offer insights into planning, design, and implementation. Additionally, there is an added twist of improving sustainability across social, economic, and environmental aspects, as evidenced by the project’s use of Envision. This paper will describe the process for implementing this large-scale CSO tunnel solution, from alternatives analysis through preparation for construction. It will focus on sustainable components-some related directly to the CSO tunnel and others planned as a result of community input or intended for community improvement. Although this is a CSO solution on a grand scale, the decision-making process and sustainability-driven conversations are applicable and transferable to projects of various sizes and locations. The paper will: communicate the importance of integrated agency and community planning-level considerations; illustrate how a CSO project can integrate with and support surrounding infrastructure, above and below ground; highlight innovative practices designed to improve sustainable performance; explain the influence of the Envision sustainable infrastructure on project design, implementation, and policy.