One Mile Bridge replacement
Engineer: Muth Engineers
Owner: City of Tacoma
ABC members: H2 Environmental
Pivetta Brothers Construction removed the 106-year-old One Mile Bridge in the Tacoma watershed and built a new bridge foundation and structure in six weeks.
The team's first task was to demolish the existing bridge without dropping any bridge components or sections of peeling lead paint into the Green River. With the site located just 300 feet upstream of the main intake for Tacoma's water supply, water safety was a priority. Pivetta first cleaned the lead paint from all the areas on the truss that were going to be cut. By installing pipe supports at three strategic locations, workers were able to cut the bridge into manageable sections for crane hoisting.
After the truss span was fully deconstructed, Pivetta removed the independent approach structures and the existing decking, bull rail and remains of the bridge. More than 263,000 pounds of steel were removed and recycled.
With a very short timeline for bridge construction, Pivetta precast the concrete bridge foundation assemblies at its headquarters while the bridge structure was prefabricated by a specialty subcontractor. After closing the road to traffic, the crew removed the overhead power and widened the west approach. Workers brought eight loads of bridge components, staged at the entrance to the water shed, to the east side of the bridge and assembled the welded plate girders.
After modifying the east pier support with a precast 27.5-ton bench, a precast 17.5-ton bench was anchored on the west side. The team also installed inserts and modifications to existing abutments and assembled and installed the approach spans. Because the existing abutment on the west approach had never contained a headwall, the new span fell two feet short of the roadway. To fix that problem, Pivetta designed and poured a structural slab without impacting the schedule.
The completed two center span beams consisted of two welded plate girders. Each 150-foot assembly weighed 198,000 pounds. To set the girders, a crane launched each assembly approximately 50 feet over open water. Finally, the team placed the deck plating, poured concrete, and installed the asphalt overlay and remaining appurtenances.
The project was completed eight days ahead of schedule, on budget and with no injuries during the 1,256 hours worked.