The Fishing Wars Memorial Bridge in Tacoma, Washington won a 2020 Project of the Year Award from the American Public Works Association (APWA) in the $25-$75 million structures category. GeoEngineers Inc. provided geotechnical services for a partial replacement of this heavily trafficked bridge over the Puyallup River.
The bridge had been carrying traffic over the Puyallup River from Tacoma toward the suburb of Fife for nearly a century, and it needed to be replaced. In 2017 GeoEngineers began geotechnical services for the first phase of bridge replacement as a member of a design-build team led by Atkinson Construction and Jacobs Engineering. Together, the team successfully replaced the western-most portion of the bridge, extending from Portland Avenue to the Puyallup River.
As the geotechnical subconsultant on the project, GeoEngineers also investigated soil conditions and gave recommendations for embankment construction, the drilled shaft deep foundation design and seismic slope stability. The geotechnical team, led by Dave Phelps, PE and Morgan McArthur, PE investigated the site and found that soft clays and liquefiable deposits meant large seismic downdrag loads. The engineers recommended using large (8-9-foot diameter) deep drilled shafts that would go beyond the soft clay and liquefiable alluvial deposits and bear on deeper glacially consolidated soils.
GeoEngineers’ analysis also found a potential issue with a new structural earth wall abutment at Portland Avenue. Calculations showed that the existing embankment intended to support the new abutment would not be able to handle seismic stress in the event of an earthquake. To manage this risk, King Chin, PE and GeoEngineers’ PBE-RA Group performed seismic slope deformation analysis to model the extent of lateral deformation and the resulting lateral loads on the shaft foundations. The design team decided to leave extra space between the wall and the first bridge pier and designed the structural earth wall to intentionally deform laterally under stress.
The project began construction in 2018 and completed in Summer 2019. The remaining portion of the bridge, extending from the west side of the Puyallup River into Fife, still needs to be replaced, and the City of Tacoma hopes to finish it once funding is secured.