City Light still unsure of reason behind Friday collapse of 26 light poles

The reason behind the collapse of over two-dozen light poles on Friday near Tukwila’s Museum of Flight largely remains a mystery.

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Seattle City Light CEO Debra Smith told The Seattle Times that the poles were last inspected three years ago. Some were replaced in 2016, and others were reportedly due for replacement within five years. None had outlived their purported lifespans.

On Friday, 26 light poles collapsed in a domino-like sequence in Tukwila. One pole came down on a car, live wires were scattered across the museum’s pedestrian bridge, and thousands lost power in the ensuing hours. No life-threatening injuries were reported.

At this point, engineers don’t have an explanation for how it happened. Wind and rain at the time weren’t outside the ordinary levels for the area.

“The winds at nearby sites don’t seem strong enough to take down properly maintained poles,” UW climate scientist Cliff Mass said in a recent blog post. Winds in the area at the time of the collapse were just over 30 miles per hour.

Mass went on to theorize that one of two possibilities were likely: That “one pole (or several) … were rotted or weakened,” or that “winds were stronger in the location of the Museum of Flight” than in the rest of the surrounding area.

That latter theory would require a “localized microburst” to have occurred, something that Mass noted “does not seem probable.”

Mass’s prevailing theory is that the wind’s interaction with the terrain of the valley Boeing Field sits in could have been a factor, paired with “sharp spikes in pressure” at the time of the collapse.

Q13 reports that surveillance video will be reviewed Monday, in hopes of shedding more light on the incident.

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