Oregon and Washington officials have identified hundreds of bridges that still need to be replaced or retrofitted to withstand a magnitude 9 earthquake from the offshore Cascadia fault zone.
But the pace of highway reinforcements is picking up.
The legislatures in both states included money for additional seismic improvements to highways and bridges in big transportation packages—passed last summer in Oregon and in 2015 in Washington.
With the new money, the Oregon Department of Transportation and Washington Department of Transportation are focusing on what they call "seismic lifelines."
WSDOT Deputy Secretary Keith Metcalf told a state Senate panel on Wednesday that these reinforced highway corridors would carry emergency relief and recovery supplies into population centers.
"Really, what it is is the ability to restore essential services within three to seven days,” he said. "That's our goal."
Metcalf said Washington's priority is to establish a lifeline from Everett to Joint Base Lewis McChord south of Tacoma, skirting around the east side of Seattle on I-405 because I-5 through Seattle has too many vulnerable bridge columns to tackle initially.
With its new money, ODOT is focusing on replacing or retrofitting bridges on I-5 between Eugene and Portland and on I-84 through the Columbia River Gorge. ODOT previously upgraded bridges along U.S. 97 in Central Oregon between the towns of Madras and Chemult. Upgrades to OR 58 also received funding and are now underway to ensure a corridor across the Cascades into the Willamette Valley for relief supplies.
"Redmond (Oregon) is considered the go-to airport for receiving aid from out of state and then the lifelines radiate out from there," explained ODOT State Bridge Engineer Bruce Johnson.
ODOT's entire seismic lifelines plan carries an estimated $1.5 billion price tag and will take 20 to 30 years to complete. For his part, Metcalf also quoted a $1.5 billion figure to fully address all of Washington's seismically-deficient bridges and crossings.
Nearly 50 percent of ODOT's bridges were built more than half a century ago, the agency said in its 2017 Bridge Condition Report.
Metcalf said WSDOT and the state Emergency Management Division are eager to secure funds to expand the central Puget Sound seismic lifeline corridor east to Moses Lake via I-90. The military has identified the airport in Moses Lake as a good staging area for relief in the event of a catastrophic earthquake and tsunami.
He said other lifeline extensions west to the Pacific Coast, north to Canada and south to Oregon would be desirable.