The Seawall Project is replacing the aging seawall along Seattle’s central waterfront. A guiding principle for the project is to put the shoreline and innovative, sustainable design at the forefront. The goals are to bring people to the water’s edge to experience the water and ecology of Elliott Bay, to improve shoreline ecology while preserving and enhancing maritime activities, and to reflect Seattle’s commitment to sustainability and innovation. An important part of this project is replacing the central waterfront’s utilities making this one of the city’s largest utility projects.
75 years’ worth of utilities to replace and update
The central waterfront is home to many critical utilities, not only to serve the piers but to reach a broad local and regional network. Large stormwater and combined sewer overflow systems, high voltage electrical systems, steam and high capacity natural gas lines, water and sewer mains, as well as several telecommunications providers’ networks all create a complex network of utilities under the street and below the piers. Nearly 75 years of additions and changes have resulted in crisscrossed utility services, and the passage of time means that some of these utilities were not always well documented. When designing the new seawall, it has been critically important to locate and identify all of these utilities to ensure that critical services were not impacted by seawall construction.
Bridging the work zone – Temporary utilities
Many of the existing utilities were unavoidable in the path of construction and needed to be temporarily relocated to keep the lights on a water running. At several locations along the construction zone, the project built several utility “bridges,” to allow temporary utility connections to span the large excavation pit. These bridges help ensure the project not only maintains utility service, but also simplifies the amount of obstructions the project must work around during construction.
This temporarily utility bridge near Pier 56 supports several utility services that cross the work zone to reach the piers (Photo left top). Pipes and conduits fan out from the utility bridge to serve the piers (Photo top right). A temporary sewage pump station is suspended from a pier, and designed to work while completely submerged in water (Photo bottom left).
After construction – installing final utilities
Once seawall construction is complete, temporary utilities will be disconnected and reconnected to permanent services. The new seawall was designed with over 100 utility “knock-outs”, or built-in holes, that allow permanent pipes and conduit to pass through the wall to reach the piers.
Each face panel also includes at least two knockout locations for any unplanned future utilities. When the work is complete, the new design will accommodate the existing and future utility service needs, providing another critical foundation for the future waterfront.