How to drive on a (very) low rated bridge

HOOD RIVER — Seven out of 100 is not a high score. That’s the current “sufficiency rating” for the Hood River-White Salmon Interstate Bridge — but engineers assured Hood River Port commissioners that doesn’t mean the bridge is unsafe.

“The sufficiency rating incorporates four factors,” Mikal Mitchell with the engineering firm HDR told Hood River Port commissioners at their Sept. 16 meeting. “Each one of those is informed by multiple aspects of the bridge inspection as well.”

The four factors are structural adequacy, serviceability, how essential the bridge is to the public, and other special factors. So what seems like a very straightforward — and unsettling — number, is instead, quite complex. For example, to figure out the structural adequacy, engineers look at the load the bridge can handle and the condition of the structure.

Still, Commissioner Ben Sheppard said the most common question he gets about the bridge is whether it is safe to drive on. Mitchell had an answer: yes. And it might help to drive slowly — especially if you’re driving a truck.

“Every time [a truck] hits a bump, it bounces up and creates an additional load when it comes back down,” he told commissioners. “So yes, going slower is in fact one of the ways load ratings can be addressed.”

A bridge inspection scheduled for 2026 will look at load ratings, among many other things.

Commissioners also got a look at the bridge’s foundation plans from 1923. Back then, engineers couldn’t ensure a bridge was truly anchored in bedrock. And it turns out, the Hood River-White Salmon bridge is not.

“Is that concerning?” Mitchell asked commissioners, rhetorically. “The answer is really no, it’s not concerning for everyday use of the bridge.”

But if there’s a significant earthquake, don’t head over the bridge. “If there’s a seismic event, liquefaction of those soils may not provide the same resistance as they would in everyday life,” Mitchell cautioned.

His advice?

“Get a new bridge before that happens.”

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Find more Uplift Local stories at upliftlocal.news/columbia-gorge. See Documenter Jinlu Yuan’s full notes at columbia-gorge.documenters.org.