Peter Courtney Minto Island Bicycle & Pedestrian Bridge
Owner: City of Salem, Public Works
Lead Design Firm/ Structural Engineer: OBEC Consulting Engineers
General Contractor: Legacy Contracting Inc.
At nearly 500 ft long, the new steel arch bridge spanning the Willamette Slough connects downtown Salem, Ore., to Minto-Brown Island. The design of the $12.5-million Peter Courtney Minto Island Bicycle and Pedestrian Bridge included a main tied-arch span of 304.5 ft and four approach spans, three at 50 ft and one at 35 ft.
“During construction, challenges arose during work on the six drilled shafts and fabrication of the arches,” says Aaron Kimsey, program manager for the City of Salem’s Public Works Dept.
Riverfront Park on the Salem side of the bridge was built over a former industrial site that processed wood pulp. During construction of the drilled shafts, the crew encountered large woody debris that the drilling equipment was not designed to penetrate. Unusually cold weather also threatened to delay portions of the approach span superstructure casting and deck casting over the main span. The crews erected tents to enclose the space and used kerosene heaters to warm forms before and after casting.
Challenges continued with the installation of precast panels, which provided counterweight for the arches to remain suspended. As the panels were set, the arches wanted to move, says Todd Ross, project manager for contractor Legacy Contracting Inc.
To ensure stability, a revision to the erection sequence was required. “Before we could go to the next sequence, we would have to get up there and adjust the falsework towers,” Ross says. “Then we would have to go back and terminate those connections or even perform additional adjustments.”
The project team created a system that allowed for vertical and horizontal movements on the tower support and its 12 connection points, Ross says, permitting the continued installation of precast panels.