Crews working on the Colman Dock replacement project in Seattle have now shifted focus with the closing of the fish window on Feb. 15. From now until Aug. 1, when the window again opens for in-water work, the main thrust of the project moves away from driving steel piles to support the future passenger-only dock and toward construction of a new ferry terminal, the largest in the state.

The $350 million project reconstructs the Colman Dock while building a new passenger-only ferry facility on the southern edge of the dock and reconstructing a new terminal building. With 9 million passengers using the Colman Dock ferry facilities annually—and 5.5 million of those foot passengers—not only will the project deal with seismic concerns of the aging dock, but also recreate the layout of the facility to address safety concerns and operational inefficienes due to conflicts between vehicles, bicycles and pedestrian traffic. A new elevated walkway will help with that interaction.

In water, the project will remove 7,400 tons of creosote-treated timber piles from Seattle’s Elliott Bay, open up an area of shoreline and near-shore habitat while using concrete and steel to recreate the Colman Dock. The bulk of the dock and passenger ferry work will wrap up in fall 2018, while main terminal work will continue into 2023.

Exterior demolition of the existing terminal building will kick off in late spring, clearing the way to install new steel support piles on the north side of the dock once the fish window opens in August. Outside the water this February through April, crews will block off sections of vehicle holding lanes under the terminal building and on the southern trestle to start work on reinforcing the terminal building support columns and create space for future utility infrastructure needs.

Over the last six months, crews installed 167 new steel piles to support the future passenger-only dock and one-third of the trestle to support the new ferry terminal building. A total of 500 steel piles will eventually serve as the foundation for the new terminal.

The fish window in Elliott Bay serves to protect migrating salmon—work stops no matter the date when protected species, such as southern resident orcas are in sight. Washington State Dept. of Transportation biologists work with regulatory agencies to study salmon migration patterns and determine the best window to work in, as the impact hammer used to drive the last 10 to 15 ft of each steel pile creates underwater shockwaves capable of harming the fish.

Crews must also perform sediment capping only during the in-water work window, as the sand and gravel designed to cap off hazardous materials hits the bottom of the bay when dropped onto the piles, creating a hazy mix considered dangerous for fish.

Follow Tim Newcomb on Twitter at @tdnewcomb.