The Washington State Department of Transportation is beginning a massive repaving project of 22 miles of northbound Interstate 5 in and around Seattle.

Share story

Northbound Interstate 5 in and around Seattle will see nighttime and weekend lane closures over the next three years as the state’s most heavily trafficked stretch of freeway gets its first repaving in half a century.

The work, on 22 miles of highway from Kent to Ravenna, will begin this week and is expected to last through late 2019, the Washington State Department of Transportation (WSDOT) said.

That stretch of I-5 has not been repaved since it was built in the 1960s, and its concrete pavement has been in place twice as long as its expected 25-year life span, WSDOT said.

“You can repaint sections of your house as needed, but one day you’ll need to repaint the whole thing. That’s where we stand with I-5,” Justin Fujioka, a WSDOT spokesman, wrote. “More than half a century of heavy traffic and Pacific Northwest weather have taken their toll.”

The repaving project follows similar efforts on 13 miles of southbound I-5, from Tukwila to Federal Way, which is scheduled to be completed this summer.

The northbound paving will proceed in two parts; the first, on the more southern stretch of freeway, will begin this week.

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 »

On four miles of lanes between South 216th Street in SeaTac and South 178th Street in Tukwila, crews will overlay the current road surface of concrete panels with a ribbon of asphalt highway.

Because the 12- by 15-foot concrete panels can shift underneath the asphalt pavement, crews use a process called “crack, seat and overlay” to do the work.

First, a machine with a 12,000-pound guillotine-like blade will travel the lanes, cracking the concrete pavement into smaller pieces. Then, a 35-ton roller depresses the cracked concrete, ensuring that large sections won’t shift. Finally, crews lay asphalt over the cracked but stabilized roadway.

In other places, where it is more efficient to do so, crews will replace more than 400 broken concrete panels of roadway, rather than paving over them.

Crews also will replace eight expansion joints, which connect roadways to bridges.

The work will cut I-5 down to two lanes on 10 different weekends, mostly this summer and next summer.

“We want to thank commuters in advance for adjusting around what we know will be some rough commutes,” Fujioka said.

This first part of the repaving project is expected to cost about $31 million.

The second portion of repaving will begin later this year and cover 13 miles of I-5 in Seattle, between Martin Luther King Jr. Way in Rainier Beach and Northeast Ravenna Boulevard in Ravenna.

Crews will replace 37 expansion joints that connect sections of elevated freeway. They’ll replace hundreds of broken concrete roadway panels and will repave 24 on- and offramps.

Work on these projects will initially be done only at night, but will also expand to as many as 16 weekend lane closures in 2018 and 2019.

This second phase of the project is expected to cost $36 million.