Readying a Vulnerable Region for Recovery

The Burnside Bridge in Portland, Oregon, straddles the Willamette River in one of the world’s most powerful earthquake zones. HDR was hired to lead a study of the bridge’s seismic vulnerabilities, develop a range of replacement or rehabilitation alternatives, conduct the environmental review process to select a preferred alternative, and then conduct the Type, Size and Location study.

Oregon sits in the Cascadia Subduction Zone, making it subject to some of the world’s largest earthquakes. Since being identified in the 1980s as an active fault, scientists have documented a long history of earthquakes and tsunamis in the zone, regularly doing catastrophic damage in the region.

Developing Resilient Bridge Alternatives

In a major earthquake, Portland’s downtown bridges are all expected to suffer moderate to significant damage. If not collapsing, all are expected to at least be rendered unusable, threatening critical emergency response, evacuation and recovery efforts.

To help address that threat, Burnside Street and the associated Burnside Bridge, built in 1926, were identified as a critical “lifeline” route that should be able to withstand the next earthquake and either remain open or reopen quickly after a major earthquake event.

Our services included identifying the bridge’s vulnerabilities; public involvement and stakeholder outreach; exploration of funding options; civil engineering (including traffic, roadway, structural, geotechnical, hydraulic and seismic); movable bridge engineering (mechanical, electrical and seismic); geo-environmental and cultural resources; NEPA documentation; and developing the TS&L study. 

High-Tech Public Outreach

An important part of our public outreach was helping Multnomah County build support through a public outreach campaign that drove home the need for action. Animators based in our Boise, Idaho, office created a true-to-life video of how the bridge would shake, sway and eventually crumble onto nearby interstates and into the water during a major earthquake.

The video, a vivid illustration of the need for the project, was released publicly in 2017 and quickly received coverage in local media. Since its release, the animation has been seen in nearly 100 countries and received more than 80,000 views.

Bridge Design Expertise at Work

After considering more than 100 options for the bridge, four alternatives (three replacement and one retrofit) were identified. In the process, a set of unique seismic design criteria was developed in conjunction with leading industry experts. The project is now in the environmental review phase, with experts studying and documenting the effects of the remaining bridge alternatives, as well as a no-build option. After public comment, a preferred alternative is expected to be chosen by fall of 2021, with design work and construction to begin in 2022, depending on funding.

Concurrent to the earthquake resiliency study, we also led rehabilitation work on the current, aging bridge. As the prime consultant for our seven-firm delivery team, we led the preliminary conceptual design and final plan, specification and estimate to extend the Burnside Bridge’s service life. Our bridge engineering experts provided structural, mechanical/electrical, and roadway rehabilitation improvements to ensure the safety of the current bridge, as well as its load carrying capacity and reliability through 2035.