Over the course of this coming Friday, March 1 and Saturday, March 2, a whopping 1.9 million pounds worth of concrete will be hoisted over I-5 as contractor crews build a new bridge in SeaTac as part of the State Route 509 Completion Project.

Travelers will want to plan ahead for this work.

On Friday, March 1 and Saturday, March 2, crews will set 10 girders for the northern portion of the new South 216th Street bridge. Setting the girders is another milestone in construction of the bridge.

To complete this work, construction crews working for the Washington State Department of Transportation must close one direction of I-5 each night to safely lift the girders into place.

“Closing I-5 is not something we take lightly,” said Project Engineer Ward Anderson. “But it’s necessary to ensure we have the room needed to bring in the girders, lift them into the air and secure them to new bridge piers while keeping both our crews and travelers safe.”

Southbound I-5 closures (all lanes and ramps) – Friday, March 1 to the morning of Saturday, March 2:

  • 8 p.m. – Southbound I-5 lanes begin closing.
  • 10 p.m. – All southbound lanes close at South 200th Street. The South 200th Street on-ramp to southbound I-5 also closes.
  • 6 a.m. – All southbound lanes and the ramp reopen.

Northbound I-5 closures (all lanes and ramps) – Saturday, March 2 to the morning of Sunday, March 3:

  • 8 p.m. – Northbound I-5 lanes begin closing.
  • 10 p.m. – All lanes close at SR 516 and the SR 516 ramps to northbound I-5 also close.
  • 6 a.m. – All I-5 lanes and the ramps reopen.

South 216th Street overnight closure – nightly, Friday, March 1 to Sunday, March 3:

  • South 216th Street between Military Road South and 31st Avenue South closes nightly from 9 p.m. to 6 a.m.

During the closures, travelers will follow signed detours via SR 99. Travelers whose destinations are not within the local area should consider using SR 167 or other alternate routes to bypass the freeway closure and local SR 99 detour. Work may be rescheduled due to snow, ice, high winds or lightning.

Know before you go

Even with detour and bypass routes available, drivers should plan for heavy congestion on the interstate each night approaching the closure point. SR 167 may also experience heavier-than-normal traffic. Nearby surface streets are also likely to be congested. Drivers are urged to:

  • Delay or reschedule discretionary trips.
  • Allow extra time and prepare for delays.
  • Use the WSDOT app and check the real-time traffic map for updated travel information.

About the new South 216th Street bridge

The new bridge is needed to span new collector-distributor lanes on I-5 that will accommodate drivers entering or exiting the new SR 509 Expressway. The new bridge will have one lane in each direction, an eastbound center left turn lane, ADA-accessible sidewalks and bike lanes on both sides.

The southern portion of the bridge opened to westbound traffic in fall 2023. Eastbound drivers on South 216th Street will continue to use detour routes to cross I-5 until the northern portion of the bridge is complete in summer 2024.

About the girders

Each girder weighs 191,400 pounds and is 168 feet long. If stacked end to end, the 10 new girders would be approximately 700 feet taller than Seattle’s Columbia Center. Five girders will be transported each night into the construction zone where two large cranes will lift them into place. The girders were cast in Tacoma by Concrete Technology Corporation.

SR 509 Completion Project information

The SR 509 Completion Project builds 3 miles of new tolled highway between I-5 and South 188th Street near the south end of Seattle-Tacoma International Airport. The expressway and its features can be viewed in an interactive map. The new highway will be completed in stages. The portion currently under construction between I-5 and 24th Avenue South is scheduled to open in 2025. The final stage will build the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street. The entire project is scheduled for completion in 2028.

Puget Sound Gateway Program overview

The SR 509 Completion Project is part of WSDOT’s Puget Sound Gateway Program, which also includes the SR 167 Completion Project in Pierce County. Combined, the two completion projects finish critical missing links in Washington’s highway and freight network.