How good are Seattle's dams? City council briefed on safety

Seattle's utility conducted a major review of its dams in the wake of the troubles at California's Oroville dam last month.

Seattle's city owned electric utility says it's conducted a major safety review of six major dams in the wake of the Oroville, Calif. dam overtopping and eroding spillways in February. 

"I just try to challenge ourselves to make sure we're asking the right questions, and Oroville highlights the need to be aware of those questions," said Michael Haynes, officer for generation operations and engineering for Seattle City Light. 

A Seattle City Council committee was briefed Tuesday on the safety of its dams.

You won't find a dam anywhere in the city of Seattle between Puget Sound and Lake Washington. Yet, the city is responsible for very large dams,  dams are outside the city, and in one case way outside, in northeastern Washington. 

Most city owned dams are operated by Seattle City Light, the electric utility that controls multiple dams high in the Cascade Mountains on the Skagit River. It also controls Boundary Dam on the Pend Oreille River in northeastern Washington.    

Some, like the earthen Tolt River Dam in eastern King County, are there primarily to supply drinking water, and they generate a limited amount of power. 

"We have a dedicated dam safety group, part of our engineering group that reports directly to me," said Haynes, "Which caused us to take a pause as we're in the middle of inspection cycles right now." 

Haynes said each dam is inspected annually, with major inspections every five years.  A five-year inspection is now going on for the Skagit River complex, including the oldest dam in the city's inventory.  

The committee hearing is prompted by the troubles at California's Oroville dam, which in February used its emergency spillways because of massive rains in that state. Parts of the spillways were severely eroded because of the large amounts of water flushed out of Oroville Lake. That damage currently being repaired. At one point, tens of thousands of residents down stream on the Feather River had to be evacuated as a precaution. 

California's Department of Water Resources said the lake is filling up again, much of it snow melt driving the level of the large lake up eight inches in the last 24 hours.  

Copyright 2017 KING


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