PORTLAND, Ore. – On the same day that a new study found a Cascadia Subduction Zone earthquake could displace 85,000 Portland metro residents and injure 27,000 people, Multnomah County announced it is one step closer to figuring out how to prepare the Burnside Bridge for an earthquake.

In the fall of 2016, Multnomah County started a process to figure out what to do about the Burnside Bridge, which serves as a critical lifeline between Portland’s east and west sides.

The Burnside Bridge is 92 years old and would suffer extensive damage in a Cascadia Subduction Zone earthquake.

There is a 40 percent chance of a Cascadia quake in the next 50 years, Oregon State University found.

Simulation shows the Burnside Bridge collapsing during a major earthquake
Simulation shows the Burnside Bridge collapsing during a major earthquake

On Thursday, Multnomah County released a digital presentation outlining its progress on the bridge project.

So far, the project ruled out three of five bridge replacement options. The bridge will not be left as-is, and the county won’t fix a different bridge instead of the Burnside Bridge. The county will also not fund a full retrofit, since it would greatly impact Interstate 5 during construction.

The county decided to move forward with two options: The bridge will either be fully replaced, or mostly retrofitted and sections replaced over I-5 and the Union Pacific rail line so the freeway isn’t as disrupted.

Now, the county is judging the two options to see how well they fit six categories, including how well the bridge would function in an earthquake and support bicyclists, pedestrians and people with disabilities.

The winning option will be picked by the fall of 2018, Multnomah County said. Then a handful of concepts will be considered, such as whether the bridge will stay low and moveable or be higher and not open for ships, like the St. Johns Bridge.

Multnomah County spokesman Mike Pullen explained that the drawn-out process is necessary due to federal regulations.

"There's a federal law that says you need to study every option and look at the best option and study their impacts ... it's there to protect the environment and people from bad decisions," he said.

The county is hoping to secure $80 million in funding for the bridge design and $415 million for the project itself. Construction is projected to start at the end of 2023 and end by 2028.

The county is funding the current study period but hopes to get local, state and federal support for the bridge design and construction.

The Burnside Bridge is currently undergoing a maintenance project, which does not include seismic upgrades that would protect it during an earthquake. The maintenance project will cost between $18 and $22 million and is expected to keep the bridge in working order for another 15 to 20 years.

Burnside Bridge project timeline
Burnside Bridge project timeline
Multnomah County

More: Simulation shows Burnside Bridge collapsing during earthquake

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