Long-Span Option Selected for Portland’s Burnside Bridge Replacement
New crossing will be a long-span structure. Rendering courtesy of Multnomah County
The Earthquake Ready Burnside Bridge project task force has recommended a new, $825-million long-span bridge to replace the Multnomah County-owned structure that crosses Portland’s Willamette River.
The task force studied over 100 options, including tunnels, ferries and bridges, during the 18-month process to quell seismic concerns issues on the 94-year-old, 1,382-ft-long bascule bridge. The other three final options included an enhanced seismic retrofit and two short-span alternatives. All bridge options include movable components.
“Several task force members said they preferred the long span alternative because it avoided the liquefiable soils near the river and had the lowest cost and seismic risk as a result,” says Mike Pullen, Multnomah County spokesperson.
The long-span alternative would replace the existing bridge in the same location and alignment. The $825-million price tag was the cheapest of the four options and includes reduced columns in Waterfront Park, wide deck capacity and reduced impacts to natural resources.
Structure scale questions will be addressed during the Bridge Type Selection phase, beginning this fall with final approval in 2021. A public comment period this summer precedes an Oct. 2 vote from leaders on the preferred alternative. If selected, the long span will require superstructure above the bridge deck, likely either a tied-arch or cable-stayed structure. Bridge design is expected to run from 2021 to 2024; a four-plus-year construction phase starts in 2024.
The task force recommended nixing a proposed $90-million temporary bridge that would have added two years to the project’s timeline.
