Willamette Valley Dams Deemed Safe After Saturday's Earthquake

Jul 6, 2015

The Army Corps of Engineers sent inspectors to 13 Willamette Valley dams following Saturday’s magnitude 4.2 earthquake. All of them were judged to be safe.

The Fern Ridge Dam (pictured here) was built in 1941.
Credit US Army Corps of Engineers

Protocol requires dams within 75 miles of a magnitude 4.0 or greater earthquake be inspected within 24 hours.

Clemans: “I guess if I could summarize it in a word, we’re looking for change.”

Scott Clemans is with the Army Corps of Engineers. He says there may be change in the shape or performance of a facility. Clemans says the dams are fine this time. But they are looking at the risks of a larger event:

Clemans: “When our dams were built, you know in the 1940s to the 1970s primarily, nobody had ever heard of a Cascadia earthquake.”

He says the scale of a Cascadia-level quake has only been understood in the last 10-15 years. The results of the seismic studies will indicate whether upgrades should be made.

Clemans says dams perform better than most people think. For example, there were 270 dams in the area of the 9.0 Japan earthquake in 2011, and only one failed.