A steel plate that failed "is over 50 years old," said a spokesman for the Washington State Department of Transportation.

Share story

Three lanes of northbound Interstate 5 near the Duwamish River in Tukwila were reopened shortly before 2:30 p.m., following emergency repairs Tuesday to a broken expansion joint — in a place where the state carried out major repaving and weekend lane closures this spring.

The joint failure caused traffic jams for about two hours, stretching back to the I-405 junction for about a mile.

The steel plate that failed was more than 50 years old,  said spokesman Tom Pearce of the Washington State Department of Transportation (WSDOT).

Traffic Lab is a Seattle Times project that digs into the region’s thorny transportation issues, spotlights promising approaches to easing gridlock, and helps readers find the best ways to get around. It is funded with the help of community sponsors Alaska Airlines, CenturyLink, Kemper Development Co., NHL Seattle, PEMCO Mutual Insurance Company and Seattle Children’s hospital. Seattle Times editors and reporters operate independently of our funders and maintain editorial control over Traffic Lab content.

Learn more about Traffic Lab » | Follow us on Twitter »

Contractors were on-site as recently as early June, as part of the $51 million “Revive I-5” program to fix or replace road decks and expansion joints from Tukwila to downtown Seattle, which required weekend shutdowns and congestion.

But WSDOT didn’t completely replace the 1960s-vintage expansion joint with new-generation epoxy joints, as the agency has done since the late ’00s in Sodo.

“Cost and time” are why the state didn’t make epoxy replacements this spring for the Tukwila joint, in which steel plates wrap around the corners of each road deck, Pearce said.

“The vertical plates were in good enough condition, we felt we can re-use them,” he said.

Still, they can wear out with more than 100,000 vehicles a day passing through, he said. “The metal just finally flexed to the point where it couldn’t hold up anymore.”

WSDOT will probably review the situation and its strategy for expansion joint replacements, he said. “Where we feel it’s necessary, we’ll make adjustments.”