Seattle Multimodal Terminal / Colman Dock

Client Washington State Ferries
Location Seattle, WA
Scope Of Work Demolition and Construction
Schedule 10-2017 to 2-2023

Project Detail

Colman Dock is Washington State Ferries largest and busiest ferry terminal. Key elements of the project included replacement of the timber trestle with a new concrete and steel trestle, reconfiguring the dock layout, replacing the vehicle transfer span, and the overhead loading structures of the northernmost Slip 3, and mitigation for an additional 5,200 SF of overwater coverage. The updated layout is designed to address safety concerns and operational inefficiencies and preserve Colman Dock as a safe and reliable transportation hub. The new structure is designed for 1,000 year seismic event.

Construction  was performed in stages. The dock is an occupied facility that had to continue operations during construction involving complex scheduling, phasing, and coordination. During Phase 1, a temporary trestle was installed at the North Pier in stages. The North Trestle East was 35-ft x 126-ft (4,410 SF). The North Trestle West was 35-ft x 86-ft (3,010 SF). Piling includes (473) 36-in diameter steel pile including (18) 112-ft long pile for Slip 2 and Slip 3 bridge seats totaling more than 46,500 LF, (22) 30-in diameter steel pile including 94-ft pedestrian overpass pile, and (236) 24-in steel pile for templating and falsework. 495 new steel piles, cast-in-place, and precast concrete will be installed utilizing two Demag CC 2500 Crawler Cranes with 550-ton lifting capacity.

An estimated 7,400 tons of creosote-treated timber piles will be removed from Elliott Bay and open up an area of shoreline and near-shore habitat. 50,000 tons of open water and under dock aggregate sediment capping was placed over the existing subgrade. Other environmental considerations include stormwater treatment for all new and replaced areas of the trestle and remediation of contaminated sediments.