The Washington State Department of Transportation (WSDOT) reports that lifting and carefully placing long pieces of concrete weighing roughly 200,000 pounds is no easy feat, but that is about to happen on Interstate 5 in the SeaTac/Des Moines area.
Starting the week of June 26, contractor crews from Atkinson Construction will begin to lift, position and secure 30 girders for two new bridges over I-5 just north of the interchange with State Route 516. The overnight girder setting is scheduled to begin Monday, June 26 and last about a month. This work is part of the Washington State Department of Transportation’s SR 509 Completion Project in south King County and will require evening traffic shifts to complete the work.
The girders are massive – ranging from 65 feet to nearly 200 feet long and weighing between 191,400 and 252,100 pounds (or 95 to 126 tons). Their size means setting the girders requires careful coordination between two massive cranes hoisting them into place. The girders form the backbones of the new South 216 Street bridge across I-5, and the northbound I-5 flyover ramp that will eventually connect to the SR 509 Expressway, which is also under construction.
I-5 Cross-over lane for nighttime drivers
When the girders are lifted into place, one direction of I-5 will be reduced to a single lane overnight and routed to the opposite side of the freeway. The work – and closures – will not take place during the day or on weekends.
“We need drivers to be prepared for this cross-over lane because we don’t use it often on I-5,” said Project Engineer Ward Anderson. “But it means we can keep I-5 open and drivers safe while we set the girders.”
As drivers approach the work zone in the one open lane, they’ll cross over the median and into the high occupancy vehicle lane on the other side. Concrete barriers will help protect those drivers from oncoming traffic while they use the HOV lane to safely get past the work zone.
Once beyond the work zone, drivers will cross over the median again to return to normal travel lanes. The concrete barriers protecting the HOV lane have sections at both ends that can be moved, allowing crews to adjust them depending on whether northbound or southbound traffic is using the HOV lane during the girder setting. The HOV lane in each direction will only be used for cross-over traffic during the overnight construction work and will convert back to normal use each morning. The concrete barriers will remain in place around the clock for up to eight months.
Crews will set girders over northbound I-5 lanes first, followed by the southbound lanes.
Weeknight I-5 lane closure hours beginning Monday, June 26
- Northbound lanes begin closing as early as 7:00 p.m.
- Southbound lanes begin closing as early as 8:00 p.m.
- 11:59 p.m. to 4:00 a.m.: One direction of I-5 will be reduced to a single lane of travel using the cross-over lane.
Please plan ahead and stay alert in this and any work zone to protect both the workers making these traffic improvements and everyone else on the roadway.
New South 216th Street bridge
A new and wider South 216th Street bridge will be built in the same location as the existing bridge. Six of the 16 girders for the bridge will be set this summer, followed by the remaining 10 in 2024. The six girders set this summer will form the southern half of the new bridge. After the southern half is completed in fall 2023, westbound traffic will begin using it. Eastbound traffic will be detoured while the existing bridge is demolished, and the northern half of the new bridge is built.
The new South 216th Street bridge is scheduled for completion in summer 2024. It will include a new center turn lane, bike lanes, and wider ADA-accessible sidewalks. The existing bridge is tentatively scheduled for demolition in fall 2023.
Northbound I-5 flyover ramp
Of the 30 girders being set this summer, 24 of them are for the northbound I-5 flyover ramp. The flyover ramp will provide direct access to the new SR 509 Expressway. Crews are currently building the first mile of the expressway between I-5 and 24th Avenue South.
Construction of the remaining 2 miles of the expressway between 24th Avenue South and South 188th Street in SeaTac, where SR 509 currently ends, is scheduled to begin in 2024.
For Real-Time I-5 Traffic and Construction information, visit I-5 Traffic.
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