This story was originally posted to MyNorthwest.com

Washington’s newest freeway overpass is being born in Pierce County. But before this baby is delivered, contractors will need to close some lanes.

Nightly lane and ramp closures will begin on and around I-5 at the Steilacoom-DuPont Road on Monday. They will last through next weekend, including several overnight hours when southbound I-5 will be down to just one lane.

The Washington Department of Transportation (WSDOT) is building a new freeway interchange there. You might remember that the freeway was almost entirely closed for a weekend in April when the girders were put up over I-5.

More girders to be added for Washington interchange

This weekend, the contractor is adding the rest of the girders, taking the overpass over the railroad tracks just west of the freeway.

“Previously, people in the area saw us put down the backbone, or the girders for the overpass, and now we’ve reached the point where we’re going to be extending the overpass by placing the girders over the Sound Transit line,” WSDOT spokesperson Doug Adamson said.

As you might imagine, moving these girders will not be easy.

“Will be bringing in 17 long pieces of steel and concrete, and they’re more than 150 feet long,” Adamson said. “It’s quite the process to get them there to the construction zone, and each one of them weighs about 170,000 pounds.”

The contractor will be moving these girders through DuPont, so drivers can expect some intermittent traffic holds early in the week during those overnight hours.

“This work will have substantial effects for people who use I-5, so expect a number of lane closures in the area,” Adamson said. “We’re going to have to route those girders in through town. We’ll have some ramp closures there at the Steilacoom-DuPont Road, so a large ‘pardon our dust’ as we reach this key staging construction.”

Planning your trip

You can find the current schedule here so you can plan your trips.

This is another spot where trains can impact backups on the freeway. The tracks are just west of the off-ramps. This new interchange will go over the tracks to eliminate that problem.

“When we open this early next year, we will have a new overpass which will remove that at-grade conflict and give people the ability to drive over there and not have to stop for the trains,” Adamson said.

This project not only includes this new overpass, but it will also extend the HOV lane from where it ends at the Joint Base Lewis-McChord main gate through DuPont.

Completion is expected next spring.

Chris Sullivan is a traffic reporter for KIRO Newsradio. Read more of his stories here. Follow KIRO Newsradio traffic on X.