Project overview
The Seattle multimodal ferry terminal at Colman Dock provides the main cross-sound connection, with auto ferry routes to Bremerton and Bainbridge Island and passenger-only ferry routes to the Kitsap Peninsula, Vashon Island and West Seattle.
Steel pilings that support some areas of the terminal are corroding rapidly and require intervention to retain the facility’s structural capacity. This project will clean, wrap and jacket 165 36-inch diameter steel pilings and will add a cathodic protection system. The work will be performed by dive teams working on pilings beneath the terminal. The terminal will be fully operational during construction.
What to expect
During in-water work windows, multiple dive teams are expected to be in the water.
Work will include:
- Excavating around the base of each piling
- Pressure washing each from the bottom of the excavation to the bottom of the pile caps
- Coating and wrapping the piling from two feet below the sediment surface to the bottom of the pile caps
- Installing HDPE jackets around the piling to protect the wrapping system, again from two feet below the sediment surface to the bottom of the pile caps
- Backfilling the excavations at the base of the piling
- Constructing (aluminum) anode sleds and installing them on the bottom under the ferry terminal
- Wiring the anode sleds to the piling and to testing stations on the terminal
Pressure washing will be used to remove marine growth and loose corrosion products. There is no paint on the piling. Excavation at the base of the piling can be performed by hand or with diver-operated hand dredges. There is a sediment cap under the trestle. When the sediment cap material is excavated it will be used to backfill around other completed piling or stockpiled and reused to backfill the excavation after the pile is wrapped and jacketed. When the excavation encounters native material beneath the sediment cap, it will be captured, removed and tested and then disposed of at an accepted disposal facility. Clean material will be imported and used to backfill any excavations that can not be appropriately backfilled with stockpiled materials.
Project Benefits
This project will arrest severe ongoing corrosion on 165 36-inch diameter steel pilings. These pilings provide critical structural support for:
- WSF’s new terminal building
- The King County Metropolitan Water Taxi Passenger-Only Ferry Facility
- The Yesler vehicle exit lanes, as well as the southern edge of the trestle
Aerial View of the Seattle multimodal ferry terminal on the Seattle waterfront.
Steel pilings supporting the terminal are rapidly corroding and require intervention to retain the facility’s structural capacity.
