SEATTLE — A string of failures caused the SR 99 tunnel to shut down for hours Thursday morning, leading to gridlock across the city, said the Washington State Department of Transportation (WSDOT). They say the traffic was caused by a broken piece of equipment miles away and a failsafe that did not work.
“Normally it would take me about 10 minutes to get to my building,” Youn Coy, who works in Sodo, said. “It took me about 45 minutes.”
Coy doesn’t even take the tunnel to work, but its closure still messed up her morning. When she got to work, she found the rest of her day was also messed up; half her building had power, and the other half didn’t.
She had no idea that both problems were connected.
“I was completely shocked to hear that it was related and that the tunnel being out was from this line right behind me,” she said.
Neighbors told KIRO 7 the power lines on Fourth Avenue popped three times and shot off a series of beachball-sized fireballs before the power went out in the area. That outage caused the ventilation system in the tunnel to quit working, leading to its closure.
WSDOT says the tunnel is supposed to have a failsafe. A device called a switchgear is designed to pull power from a different part of the grid should an outage affect its systems.
The failsafe failed. The tunnel was closed for hours, and WSDOT is working with the manufacturer to figure out why.
“We were just waiting for the power to be turned back on,” RB McKeon with WSDOT said. “As soon as it was, our crews went through and did their systems check, and then we were able to reopen the tunnel.”
Seattle City Light said the power line broke because of regular deterioration. According to a spokesperson, a small connector went bad, and there are simply too many miles of powerlines to thoroughly check and maintain each part ahead of a failure like Thursday’s.
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