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A Multnomah County task force has endorsed construction of a replacement for the Burnside Bridge.

The vote Monday was in favor of a 鈥渓ong span,鈥� which supporters said would offer better seismic performance and fewer columns and other impediments than would a short span.

The task force also rejected construction of a temporary bridge that would cost approximately $90 million. A temporary bridge would shave only 3-4 minutes from an average vehicle trip and lengthen construction by 18 months to two years, county staff said.

The long span would result in a very different Burnside Bridge. The current bridge, which opened in 1926, has no superstructure. The long span would require a superstructure 鈥� perhaps not unlike the cable-stayed Tilikum Crossing.

An early rendering shows two tied arches sandwiching a middle drawbridge section that would allow boats to pass underneath. Two massive columns would anchor the bridge into the Willamette River.

The conceptual illustration is not final. The bridge type 鈥� likely tied arches or cable stays 鈥� will be selected next summer.

The new bridge would also be wider by about 20 feet to provide more space to serve bus drivers, bicyclists and pedestrians. The existing bridge narrows in the middle.

Some task force members expressed aesthetic reservations, but said the advantages of a long span outweighed any drawbacks.

鈥淚t has to be done elegantly, if you can do that,鈥� said Bill Burgel, who represents the Portland Freight Advisory Committee. 鈥淚 don’t want the final result to be chaotic with the built environment.鈥�

The task force recommendation is nonbinding. A policy group of elected leaders and agency officials will meet Oct. 2 to adopt or reject the task force’s recommendation.

Supporters said the long span would avoid unstable soils 鈥� 鈥渨iggly earth close to the river,鈥� as described by task force member Susan Lindsay of the Buckman Community Association.

Seismic resiliency is the driving force behind the project. The existing bridge is at risk of collapse during a sizable earthquake, according to county officials and consultants. In recent years, seismologists have warned the Cascadia subduction zone could rupture, causing a devastating tremor.

The task force roundly rejected construction of a temporary bridge to serve during the main project. A temporary span was used during construction of the Sellwood Bridge replacement, but the Burnside Bridge is much more centrally located. Without a temporary bridge, traffic would be diverted to other downtown bridges during the Burnside Bridge replacement project.

Construction is expected to take 4.5 to 5.5 years.

Traffic impacts downtown could cause consternation, said Fred Cooper, a representative of the Laurelhurst Neighborhood Association.

鈥淚 see a public nightmare here if we tear down the bridge and tell them to go another route,鈥� he said.

Another task force member said building a temporary bridge would also risk controversy.

鈥淭here’s going to be a whole lot of public backlash if we spend $90 million on a temporary bridge,鈥� said Cameron Hunt, captain of the Portland Spirit fleet.

Some task force members expressed concern about the impacts to homeless pedestrians who must cross the river on foot.

鈥淭hat will be a burden,鈥� said Timothy Desper, director of Burnside shelter services for the Portland Rescue Mission.

A Burnside Bridge replacement project will need to undergo an environmental impact statement and win various federal approvals, including from the Coast Guard. County leaders expect to pursue Federal Highway Administration funds to help pay for the $825 million project. In November, county commissioners voted to nearly triple vehicle license fees to raise local funding for the project.

The Portland office of聽HDR, an Omaha, Nebraska-based engineering company, is engaged in the bridge planning effort.