Built in 1962, the 240th Street SE Bridge over North Creek had a high propensity for flooding and displayed many signs of wear. Part way through the process of designing a replacement bridge, further inspection revealed advanced deterioration of the bridge’s timber foundation. Along with the ongoing scour action of the creek water further compromising the integrity of the structure, the City of Bothell was forced to immediately close the bridge to traffic.
With the emergency closure of 240th Street, the City faced the daunting challenge of reconfiguring the project, finalizing the bridge design, and selecting a contractor. Adding to these challenges were construction restrictions to protect the salmon and other fish populations in North Creek.
WSP met these challenges by installing a sheet pile wall system with deadman anchor tiebacks to enable the contractor to separate bridge construction from in-water work. The channel-shaped, cast-in-place, post-tensioned concrete replacement structure placed the girders/main structural elements above the roadway surface to add clearance below for the 100-year flood level.