I-5 near SeaTac closing this weekend at South 216th Street Bridge

The South 216th Street Bridge in SeaTac has nearly completed the installation of its concrete girders — a heavy beam to support the deck of a bridge. It is a significant milestone in the construction project that started in early 2022.

The south portion of the bridge opened to traffic last fall as work shifts to the north end of the bridge as crews install the girders.

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How big are the bridge girders?

The Washington State Department of Transportation (WSDOT) claimed if someone were to stack 10 girders vertically on top of each other, they would be as tall as the Columbia Center and Space Needle combined.

“Each girder is 168 feet long and weighs 191,000 pounds,” Kris Olsen, a communications manager with WSDOT, told KIRO Newsradio. “They’re big. After we placed the girders and we start building the bridge deck and adding the rebar that’s needed, we expect the bridge should be open and operational by the end of the summer.”

The project was initially set to be completed by the middle of 2023 before delays occurred, according to WSDOT.

But this milestone marks the final stretch of construction on the new bridge, which will be longer than the previous bridge while allowing plenty of room below for future collector-distributor lanes. The construction project will also widen sidewalks, add bike lanes and create a center turn lane.

I-5 shutdown for South 216th Street Bridge construction

“This requires Interstate 5 (I-5) to be shut down this weekend,” Olsen said. “We need to put two big cranes on the lanes to set these girders. So on Friday night, we’ll close the southbound lanes and we’ll lift five girders into place. Then on Saturday night, we’ll close the northbound lanes and we’ll set those five girders into place.”

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Friday night the southbound lanes close at South 200 Street, including the on-ramp. Saturday night work shifts to the northbound lanes closing at State Route 516. Both nights, I-5 will close at 10 and all lanes and ramps reopen the following morning by 6 a.m.

“What people need to remember however, and this is really important, is our lane closures start at 8 p.m.,” Olsen added. “You’re just going to start seeing those backups and they will persist. The best advice that I have is to take alternate routes. Consider 167 or take 99.”

Drivers can still commute I-5 both nights through a detour. Travelers should just be prepared for heavy congestion.

You can read more of Nate Connors’ stories here. Follow Nate on X, formerly known as Twitter, here and the KIRO Newsradio traffic team here for more traffic updates.

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