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Preserving Washington State’s Largest Ferry Terminal

Rendering of the new Colman Dock, courtesy of NBBJ.

Construction is well underway at the largest and busiest ferry terminal within the Washington State Ferries (WSF) system. The Colman Dock terminal in Seattle provides a critical link for commuters, bicyclists, and pedestrians across the Puget Sound. In 2017, more than 10 million people traveled through Colman Dock, including more than 5 million foot passengers.

Originally constructed in 1964, using many of the piles from the 1938 structure it replaced, Colman Dock’s timber piles and key structural components were aging and seismically vulnerable despite aggressive and frequent inspection and maintenance repair. As part of WSF’s long-range planning, the rehabilitation of Colman Dock focuses on its preservation while encouraging multimodal ridership without expanding the size of the facility.

WSF selected BergerABAM to replace the structurally deficient components at Colman Dock in order to continue to provide safe and reliable ferry service at the busy terminal. The project replaces the dock’s aging timber trestle with a new concrete trestle, as well as the main terminal building; north slip (Slip 3) transfer span and overhead loading structures; and the south edge passenger-only ferry facility that is being funded by King County. The south edge of the project is located at the original “skid row”— named such because it is where they would skid logs to the water to then be loaded onto ships.

The design for the passenger-only facility was modified with significant input from bicycle advocacy organizations. For most efficient access, the facility will have a second dedicated bicycle entry point. An elevated walkway between the terminal building and passenger-only facility provides a safer pedestrian connection between the two facilities. The project also addresses safety concerns related to the immersion of vehicles and pedestrian traffic around the terminal by reconfiguring the dock layout to provide safer and more efficient multimodal infrastructure. Accessibility will be further enhanced with the addition of a tactile wayfinding path and tactile maps, which will be coordinated with the new Waterfront Seattle promenade that will be constructed next to the Colman Dock terminal.

Technical complexities, particularly relating to seismic design, were complicated by the presence of liquefiable soils and environmental constraints. Environmental benefits include removal of 7,400 tons of creosote-treated timber piles from Elliott Bay, contaminated sediment remediation, a new stormwater treatment system, and opening an area for new shoreline and nearshore habitat.

Construction of the Colman Dock terminal requires complex phasing in order to maintain daily operations. Only one slip of the three total can be taken out of service at any given time. Construction is phased over five years and will continue until 2023, with the terminal remaining open throughout construction. As WSF comments, “We’re building our house while living in it.”

An extensive community engagement process exposed the importance of Colman Dock throughout the Puget Sound region. It is not only the largest and busiest ferry terminal but is considered an iconic facility rooted in the history of Puget Sound and an integral part of people’s lives. With the enhanced multimodal features, the new facility will be able to accommodate pedestrian and bicycle ridership that is expected to increase by more than 40 percent by 2040.

During the Statewide Project Engineer’s Conference held in November, the Colman Dock project was awarded the 2018 Washington State Department of Transportation Excellence in Design Award for preservation projects. Projects were considered based on the following criteria: integration of public and community outreach, quality assurance/quality control, practical design solutions, effective change management, innovation, external partnerships, involvement with other disciplines, basis of design, multimodal integration, and lessons learned.