Columbia River Skywalk

As part of the City of Trail’s Downtown Revitalization Plan, and in conjunction with the Regional District of Kootenay Boundary’s need to address the sewer pipe bridge, the Columbia River Skywalk serves an aesthetic and functional role. The landmark bridge connects cycling and walking routes, while also providing a vital utility corridor over the Columbia River. At a span of over 295 meters, this is one of the longest pedestrian suspension bridges in North America.

The Graham team developed comprehensive temporary work plans for foundation construction, erection of the towers, and installation of cable, structural steel, pipework, and fiber-reinforced polymer deck. Graham’s installation strategy was focused on worker safety, equipment and material access, environmental management and minimizing impact to stakeholders.

Working with Graham and the client’s design team, Graham’s chosen cable supplier designed the cable clamps. As a result, Graham eliminated costly and time consuming cast clamps and manufactured the clamps out of high strength plate steel. Rigorous material testing including low temperature Charpy V-notch testing, X-ray testing, Mag particle testing, and standard tensile testing were completed on clamp and socket components to confirm long term performance including in cold weather. The strands were manufactured by an international cable manufacturer that pre-stretched and spooled them. Special spools were designed by Graham in order to accommodate the strand pay-out system. All the bridge components were galvanized, including each individual strand piece before a strand assembly was turned together.

Graham designed and built a highline crane system that attached to the piers on either side of the river and used cable winch drives to propel up, down and back and forth. In order to install the 2.5in main cable strands across the 225m main span, Graham designed and built a cable pay-out system using custom cable spools and cable breaks anchored to the ground. In order to install the wind cables which pull the structure down and provide the lateral stability for the bridge, Graham designed a cable pulley system using 35 ton four-part cable blocks and various cable winches to pull the 2.75in wind strand position at a final developed load of 1280KN.

The main purpose for this bridge and a source of 40% of the funding was the construction of a 16” HDPE force sewer main and insulated 12” HDPE water main. The City of Trail was in a phase of revitalization and a big part of their plan was to have a new landmark in the town. This tall galvanized structure will be seen through most of the City.

The challenge for the project was the temporary engineering, including: bridge modeling and engineered erection sequence (by All-Span), the highline crane system, cable pay-out system, and wind cable tensioning system. The friction pile and soil anchor restrained concrete foundations, the structural steel frame and, the pre-formed deck panels were items well practiced at Graham.

As the structure was loaded with components, the geometry of the bridge structure changed. Graham regularly monitored the geometry of the structure and compared it to the model to ensure predictable movement and performance of the structure as it was being constructed. Graham’s engineered erection procedure detailed the hold points where the tension in backstay cables must be adjusted and the towers pulled back towards shore in preparation for the next phase of components. Eight centerless hydraulic rams were used simultaneously to adjust the open-ended bridge sockets and ultimately adjust the tension in the cables and shape of the bridge.