We know the earthquake is coming and we know the damage will be bad. A seismic vulnerability report published last fall by the Oregon Department of Transportation provides a typically gloomy assessment, stating: “The effects of this (9.0 Cascadia) earthquake would be widespread across the most dynamic portion of the transportation network.” The report describes, among the carnage, an impassable Highway 101, closure of all state routes between 101 and I-5, 400 collapsed bridges, 600 damaged bridges and widespread damage to I-5.
“You know how a report usually says: ‘A portion of the highway will remain closed?’” asks Kent Yu, a structural engineer with Degenkolb Engineers and an OSSPAC member. “Well, this one says: ‘A portion of I-5 will remain open.’ That’s how grave the situation is.”
The energy situation is equally dire. Oregon imports 90% of its fuel from Washington, most of which is stored in tank farms along the Willamette River. But the majority of those storage facilities do not meet seismic standards and sit on soil that will liquefy during a major quake, says Deanna Henry, emergency preparedness manager for the Oregon Department of Energy. “These are old, old, old tanks on bad, bad, bad soil,” she says. The pipelines were not built to seismic standards either, she says.
Fuel is the linchpin of the recovery system — without it, efforts to restore the electrical grid in the aftermath of a seismic event will be severely compromised. “Maintenance trucks cannot do grid backup without fuel, and if I can’t get fuel out to maintenance trucks — it’s a vicious cycle,” Henry says.
Henry adds that a Cascadia quake would “most likely devastate” terminals at the Port of Portland, which also sit on liquefiable soils.
The condition of Portland’s older commercial buildings adds to the litany of woes. Of greatest concern are the 1,700 unreinforced masonry structures deemed at high risk of collapse in a major quake. Under Oregon code, property owners are required to complete seismic retrofits only when there is a change in use or major renovation. “But because of the costs involved, many property owners try to avoid triggering those thresholds,” says Mark Chubb, operations manager for the city of Portland Office of Emergency Management.
Even new buildings are vulnerable. Oregon’s earthquake construction standards, which were implemented in 1994, do not take into account the extended duration associated with subduction zone quakes, about 4 to 5 minutes of continuous shaking, says Stacy Bartoletti, president of Degenkolb. “We are not designing our buildings any differently than in California, where the earthquakes have a shorter duration,” he says. The ground motions produced by subduction zone quakes are particularly hazardous for mid- to high-rise towers, Bartoletti adds.