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News / Clark County News

Video shows what earthquake would do to Interstate 5 Bridge

Group releases animated depiction of 8-plus temblor

By Will Campbell, Columbian Associate Editor
Published: November 9, 2021, 6:04am

The group tasked with building a new Interstate 5 Bridge has created an animated video of the current bridge collapsing in an earthquake. It hopes the video, which it has shared on social media, will bring awareness to the need for a new bridge.

The video shows digital piers rotating in the sand, road sections collapsing like dominos, towers with counterweights buckling and collapsing, and a wave of water radiating from the wreckage. Program team members from the Interstate Bridge Replacement Program created the video, said Kelliann Amico, program spokeswoman. As of Monday evening, the video, posted on the program’s YouTube channel, had 1,125 views.

“The IBR is bringing awareness to how the bridge will react in a seismic event and why replacement is essential and how to anchorage preparedness by sharing an animation of what could happen to the interstate bridge area during a magnitude 8-plus Cascadia Zone earthquake,” said Ray Mabey, assistant program administrator.

The current bridge’s foundations “are set in sandy soil on timber piles. The shaking from an earthquake is likely to cause the soil to liquefy, resulting in movement of the entire structure and loss of support,” Mabey said in the video.

Other bridges with similar foundations have failed during earthquakes, including California’s Oakland Bay Bridge in 1989, he said.

Should the bridge fail, it would likely be loaded with cars and trucks.

In 2020, about 120,361 vehicles crossed the I-5 Bridge daily; even during a pandemic, it’s a lot more than in 1982, when 109,786 cars passed over the bridge. That year, the Interstate 205 bridge opened to ease the congestion. At the peak in 2019, about 138,530 vehicles crossed the I-5 Bridge on an average weekday, according to the Southwest Washington Regional Transportation Council.

“This bridge, spanning a federal waterway between two cities in two different states, is a vital link for both commuters and commercial truck freight. I-5 is a vital trade route not just for our local and regional economies, but also for national and international economies,” wrote Vancouver Mayor Anne McEnerny-Ogle. “The video clearly shows the potentially horrifying consequences of a significant seismic event, and the crippling disruption effect it could have. It visually underscores the urgency for addressing the replacement of the current 100-year-old Interstate Bridge.”

The bridge replacement program is considering a few options for a bridge that will be built to the west of the current I-5 Bridge.

Some residents are pushing other options, including multiple other bridges between Clark County and Oregon.

What about tunnel?

One of the more vocal opponents of the current options is Bob Ortblad, a retired professional civil engineer and certified public accountant. He claims a tunnel will be less expensive, have a positive environmental impact, and be safer for both traffic and in the case of an earthquake.

“The IBR program’s three current options are steel truss designs similar to the 100-year-old bridge. However, these designs will have trusses that are 10 times heavier … These designs will be very complex to engineer and expensive to build if they are to withstand an 8- or 9-Richter-scale earthquake,” he wrote in an email to The Columbian.

In late August, project engineers determined that a tunnel would not be a viable option, according to a seven-page memo.

According to Greg Johnson, bridge program administrator, a tunnel would create “significant out-of-direction travel for drivers, freight, transit users, bicyclists, and pedestrians; the inability to tie in to existing connections such as Highway 14, Vancouver city center, and Hayden Island; safety concerns for bicyclists and pedestrians; and significant archaeological, cultural, and environmental impacts. Additionally, cost estimates for the (tunnel) would be approximately two times higher than cost estimates for a replacement bridge and approaches,” he stated in an email to The Columbian.