Are King County’s dams safe? Officials plan to launch review

The crisis at a California dam has raised concerns about evacuation plans and risks from quakes and overflows in the Puget Sound area.

The unfolding crisis at California’s Oroville Dam is prompting local officials to take a closer look at dams in King County.

King County Councilmember Reagan Dunn is calling for a detailed analysis of existing evacuation plans, as well as a review of the risks of dam failure caused by heavy storms and earthquakes.

“On virtually every major river system in King County, you’ve got a dam, most of them built in the 1960s,” Dunn said. ”There’s a lot of people who live in those valleys … all of which are potentially at risk.”

According to King County’s Regional Hazard Mitigation Plan, there are 122 dams in the county that hold at least 10 acre-feet of water. The four with the potential to cause countywide emergencies if they fail are: Howard Hanson Dam on the Green River; Tolt River Dam, above Carnation; Masonry Dam on the Cedar River; and Mud Mountain Dam on the White River.

With 200,000 people presently evacuated downstream of the Oroville Dam in California, King County Flood Control District members plan to reevaluate and improve existing evacuation plans here. King County is home to four major dams. (Courtesy video)

Other dams that could cause significant damage include Lake Youngs Outlet Dam, near Covington and Culmback Dam. The latter, on the Sultan River, mostly poses a hazard to Snohomish County communities like Sultan and Monroe, but could also flood Duvall and a swath of unincorporated King County that’s home to more than 3,000 people.

All of the major dams in the county have emergency plans and are inspected regularly, officials said. The county-mitigation plan ranks the risk from dam failure as “low.”

“I don’t think there’s any significant danger in the near future,” Dunn said, “But that’s what they thought in Oroville. We need to be…

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