Designs unveiled for new I-5 bridge between Washington, Oregon

The first conceptual design drawings for a replacement Interstate 5 (I-5) bridge between Washington and Oregon were made public Monday.

The visualizations include examples of three different pedestrian viewpoints for the three configurations being studied. All images are from street level and do not represent the complete range of bridge types being considered.

“These are not the aesthetic design drawings that some folks are looking for. That will come a little bit later as we narrow down the scope of what we are proposing to build,” Interstate Bridge Replacement Program Administrator Greg Johnson said to a group of Washington and Oregon lawmakers tasked with overseeing the project.

Hayden Island, west side of bridge, looking north, double-deck bridge configuration. (Image courtesy of Interstate Bridge Replacement Program)

The three bridge types shown include a double-deck configuration called a Truss, a single-level span called an Extradose and a Steel Girder vertical lift bridge.

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Johnson presented an update on the project using the images to explain the trade-offs of each configuration.

He said his team has heard concerns from the biking community about the steepness of the double-deck and single-level span proposals.

“This is one of the issues, to make sure that we are creating something that is going to be safe, usable, and accessible to most levels of riders,” Johnson said.

He stated that his team is proposing safety shoulders that will be anywhere from 12 to 14 feet wide to accommodate a bus should it have to use the shoulder. The final width standard has not been set, but Johnson said the bridge will be wide enough to comfortably accommodate passing traffic, pedestrian, and biking traffic on each side.

Hayden Island, east side of bridge form the shared-use path, looking north, single-level movable span configuration. (Image courtesy of Interstate Bridge Replacement Program)

Retiring Republican State Senator Lynda Wilson asked if engineers are putting too much emphasis on a design that can accommodate bike and pedestrian traffic rather than the bridge’s main purpose of supporting commuter and freight traffic.

I-5 replacement bridge proposed width. (Image courtesy of the Interstate Bridge Replacement Program)

“We’re not neglecting any mode. We’re making sure that we’re building something that, if you choose not to be in a car, you can safely have an enjoyable trip across this bridge,” Johnson responded.

The two versions that do not include a lift bridge are designed to be 116 feet above the Columbia River. Johnson said they should be high enough to accommodate 95% of the bridge traffic that currently goes under the bridge.

I-5 replacement bridge proposed height. (Image courtesy of the Interstate Bridge Replacement Program)

He said the design relies on a new requirement that large ships must be able to lower movable parts that aren’t needed for navigation to pass under bridges at 116 feet tall.

“Those are some of the discussions that we’re having with the river users,” Johnson said. “We’re working diligently to not build a repeat of a stoplight for the next 100 years on the I-5.”

The project is expected to cost between $5 to $7 billion. So far, Washington has committed $45 million, Oregon $55 million, and $601 million from the federal government, leaving the remaining $4.3 to $6.3 billion to come from tolling, bonds based on toll revenues and other uncommitted funds.

Johnson did not provide a breakdown of the costs of protected bike lanes and pedestrian walkways on the bridge but said tolling bikers and walkers are not being considered.

“I’m unaware of situations across the country, or even across the world, where bicycling or walking is tolled,” Johnson said. “We’re trying to create options to decongest the freeway system. And that would be at odds with that purpose.”

The collapse of the Francis Scott Key Bridge in Baltimore has delivered an unexpected wrinkle in the design of the bridge.

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Johnson said million-pound cargo and container ships do not currently travel underneath the bridge because of tight turns and navigational hazards downstream.

The proposed bridge will have wider spans and fewer supports for a ship to crash into.

The Key Bridge accident has prompted some calls to revisit the possibility of building a tunnel underneath the Columbia River.

Johnson said engineers have looked at two tunnel possibilities: a bore tunnel similar to what was built along the Seattle waterfront and an immersed tube tunnel where a cut is opened in the middle of the river, and precast segments are placed and buried.

He said the team underestimated the original costs of building either tunnel, but even after revising construction estimates and combining operational costs, it would prove to be too costly.

The community will have an opportunity to review and provide input during an upcoming 60-day public comment period.

Matt Markovich often covers the state legislature and public policy for KIRO Newsradio. You can read more of Matt’s stories here. Follow him on X, or email him here.

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