Three lanes of the freeway were closed near South Holgate Street after the metal plate covering an expansion joint buckled at about 6:10 a.m. State Department of Transportation officials later said it appeared the plate was pulled up by the chains from a large truck.
DOT crews initially thought they could make an emergency repair to the damaged plate in about a half-hour, but it ended up taking nearly five hours to complete.
At its peak, the backup extended over 11 miles. By 10 a.m. it had shrunk to about 8 miles and the estimated travel time from Alderwood to Southcenter was about 90 minutes.
Officials said the backup took some time to clear after the freeway was reopened, but traffic had mostly returned to normal by 1 p.m.
At least three cars were damaged when they ran over the buckled joint cover, and tires on several other vehicles were flattened, the Washington State Patrol reports.
Ironically, state DOT officials scheduled a 10 a.m. news conference to discuss upcoming construction for this weekend and next weekend, but it had to be postponed to a later time after officials got stuck in traffic and couldn't make it there on schedule.
Officials said the expansion joint cover that failed is an old one and not one of the new expansion joints that have recently been installed along some stretches of the freeway.
Department of Transportation officials are also cautioning drivers about summer highway work, which begins this weekend with the closure of the 520 Bridge. From 11 p.m. on Friday to 5 a.m. On Monday, the bridge will be closed in both directions.
"It does require closures, so it is painful for drivers. But then the overall impact and benefit is we don't have joints popping up randomly during the morning commutes," said WSDOT's Lorena Eng.