Many NW bridges at risk for tremors, need retrofit

Several of Portland's older bridges spanning the Willamette could collapse in an earthquakeHundreds of bridges around Washington and Oregon could fail in an earthquake, and although many have been retrofitted, 591 in Washington alone remain vulnerable.

Highway officials are aware and continue to work on the backlog. Residents can help themselves by stocking food, water, and earthquake kits at home, where they could find themselves hemmed in if a big shaker leaves Northwest roadways impassable.

The Oregon Department of Transportation (ODOT) believes the I-5 Columbia River bridge would fail in a large Cascadia Subduction Zone quake. In Portland alone, several older Willamette River spans likely would collapse – the Ross Island, Hawthorne, Steel, and Broadway bridges.

Statewide, ODOT found in late 2015 that nearly 60% of Oregon's "lifeline" bridges would likely collapse or be impassable after a quake. The Oregon Legislature provides enough funding to replace just one to three bridges a year.

The Deception Pass Bridge, connecting Whidbey Island with the mainland, is a lifeline roadway for manyWashington has been retrofitting its vulnerable bridges since the 1990s. KING-5 reported on Feb. 27 that 317 spans (like Seattle's Aurora Bridge) have been fixed, while 591 need retrofitting, and that doesn't include bridges owned by cities or counties. Most of the vulnerable spans are in Western Washington.

Of particular concern are older bridges and overpasses built with hollow concrete columns. Retrofitters can wrap solid concrete columns in steel; if the concrete crumbles in an earthquake, it's contained and continues supporting the roadway. In contrast, hollow concrete columns can collapse within themselves, removing support.

An interactive map of state-owned bridges shows you which ones need retrofitting, and which ones already have been fixed. Vulnerable spans familiar to many motorists include:

  • Deception Pass Bridge on Whidbey Island

  • Stillaguamish River I-5 bridges near Smokey Point

  • Sultan, Skykomish, Tye, and Wenatchee River bridges on U.S. 2

  • I-5 over Northgate Way and Ravenna Blvd.

  • More than 15 elevated I-5 Seattle spans between SR 520 and I-90

  • Canyon Park I-405 overpass

  • Agate Pass Bridge on Bainbridge Island

  • The Denny Creek Viaduct, an I-90 bridge spanning nearly .7 miles, needs earthquake retrofittingFort Lewis I-5 overpass

  • Cowlitz River and Lewis River I-5 bridges

  • Auburn's SR 167 – SR 18 interchange

  • I-90's .7-mile long Denny Creek Viaduct

  • Yakima River bridges on I-90

Aside from preparing your home, you can limit your risk in a car. Learn what to do if you're driving when an earthquake hits.

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