Seattle City Light south service center, 1998. Spokane Street Viaduct at right leads to West Seattle Bridge at upper center.
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Seattle City Light south service center, 1998. Spokane Street Viaduct at right leads to West Seattle Bridge at upper center.

Seattle pole collapse: Decayed wood and beetles to blame

Investigators now know what caused two-dozen electrical poles to collapse in Tukwila: beetles, rotting wood and wind

Two people were injured when 26 poles fell in April 2019 near the Museum of Flight. As they came down, they hit one car and taking out power for 16,000 homes and businesses for several hours.

Seattle City Light had already flagged at least 10 of the poles as needing to be replaced, but had not set a deadline to do so.

That's according to a new engineering report by Nelson Research, which was released by Seattle City Light today.

A group of poles was decaying or infested by beetles, and with strong gusts of wind they toppled, pulling down surrounding lines. It happened during a wind and rain storm, with winds up to 26 miles per hour that were bolstered by their surroundings to gust at 50 mph.

City Light CEO Debra Smith said they're taking action to try to prevent another similar incident.

"We replace poles all the time," she said. "So far in 2019 we've replaced about 1,400 poles but we know we need to tighten those timelines."

She said that could require City Light to redirect money from other projects in progress.

The utility has 6,000 power poles that are marked for replacement because they are no longer up to national standards. Smith said they'll prioritize 360 that are thought to be vulnerable to beetle infestation.

A second report about the Tukwila power pole collapse is expected in several months and will include recommendations from engineers and scientists.