Tolerable Risk Vs. Terrible Catastrophe: Dams And The Big One

The Bureau of Reclamation is analyzing the economics and the options for reinforcing Scoggins Dam, 25 miles west of Portland. Photo by US Bureau of Reclamation

It's a question all of us face sooner or later: whether to spend a good chunk of money to protect against a catastrophe that has a very low chance of occurring. A workshop that just wrapped up in Corvallis considered that dilemma in the context of Northwest dams and a magnitude 9 earthquake.

Oregon, Washington and the federal Bureau of Reclamation have prioritized which dams they're most concerned about in case the Big One hits. For the feds, it's Scoggins Dam, 25 miles west of Portland. Brian Becker is chief of Reclamation's dam safety program. He's concerned the earthen dam could fail in a megaquake.

"We're in the range where the probability of failure is around one in 1,000 to one in 10,000 in any given year," Becker says. "It does sound like a very low risk, but..."

But Becker says if the dam gave way, it would have life-threatening consequences for people downstream. So Becker's division is currently analyzing the economics and the options for reinforcing this dam.

A handful of municipal and private dam owners on the Oregon Coast, in Western Washington and British Columbia are beginning similar investigations.

On the Web:

Scoggins Dam overview:

http://www.usbr.gov/projects/Facility.jsp?fac_Name=Scoggins+Dam

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