A Task Force Has Recommended a Design to Replace the Burnside Bridge to Make It Earthquake Ready

The model would have the fewest number of columns to prevent shaking and preserve the Burnside Skatepark.

Protesters march across the Burnside Bridge on June 1, 2020. (Mick Hangland-Skill)

By now, you've probably seen the animated rendering of Portland's Burnside Bridge crumbling into the Willamette River during a powerful earthquake.

In an effort to prevent such a scenario, a task force has now recommended a specific model to take its place—and it might look a lot like another iconic bridge.

The group working on the Earthquake Ready Burnside Bridge project proposed June 15 to choose a long-span bridge design. That means a bridge that stretches farther into the Central Eastside, has fewer support columns, and requires an above-deck structure to support its weight.

That structure is the part that looks familiar. The group recommended one of three superstructure options: a tied arch, like that on the Fremont Bridge; cable-stayed supports, like atop Tilikum Crossing; or supports extending the length of the span, as seen on the Broadway Bridge. What won't be built is a flat bridge like the current Burnside design.

That decision follows 18 months of research and discussions.

Task force members cite benefits associated with the long-span bridge, including the fewest support columns of the four options that were studied. That would mean a reduced risk of bridge movement should soil liquefaction occur during an earthquake.

Another big advantage: This style of bridge could preserve the Burnside Skatepark.

Additionally, the bridge has the lowest price tag, $825 million, compared to alternatives that could have cost as much as $950 million. The long span would replace the existing bridge in the same location and alignment, but offer additional deck width for bicyclists and pedestrians.

Construction on the proposed design would mean Portland has one less span crossing the river for several years. The task force recommended that the project should not include a temporary bridge to divert drivers while the old structure is removed and replaced. Members felt that a stand-in that could only carry a third to a half of existing traffic did not warrant the $90 million cost and extra two years of construction it would require.

The public will have a chance to weigh in on these ideas in August through an online open house and survey. That input is scheduled to be presented to the projects policy group Oct. 2, when a preferred alternative will be selected by vote. The Multnomah County Board of Commissioners will also vote on the matter.

Construction is slated to start in 2024 and should wrap up in about four and a half years.

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