Washington’s third diverging diamond interchange opening soon over I-5 in DuPont

DUPONT – On the heels of opening the new southbound Interstate 5 exit 119 to Steilacoom-DuPont Road, crews are making final preparations to fully open the state’s third diverging diamond interchange. The new I-5 overpass will provide access between DuPont and Joint Base Lewis-McChord in Pierce County. Demolition of the old overpass is currently scheduled for April 3-4, and will require two overnight full closures of both north and southbound I-5.

What to expect

At 8 p.m. Friday, March 20, the southbound I-5 exit to Steilacoom-DuPont Road will close. At 6 a.m. Saturday, March 21, the new Steilacoom-DuPont Road on-ramp to southbound I-5 will open. At that time, crews will close the 1957 overpass to all traffic. Northbound I-5 travelers using exit 119 will begin using the new interchange.

Additional information is available via the Washington State Department of Transportation online open house.

Some of the work needed to fully open the new diverging diamond interchange could be delayed due to rain, snow or cold weather. WSDOT will update travelers of any changes.

Safety and mobility improvements

The permanent closure of the 1957 overpass is a significant safety improvement. Moving traffic to the new interchange will eliminate an at-grade railroad crossing. The new overpass is built to modern design standards, reducing the potential for overhead bridge strikes.

People who walk, bicycle or roll will use a barrier-separated shared-use path on the new overpass. This 12-foot-wide path connects JBLM to DuPont.

Overnight bridge demolition planned April 3-4

Overnight Friday and Saturday, April 3-4, both directions of I-5 will detour through exit 119 at Steilacoom-DuPont Road.

• Travelers will see lane closures on I-5 each night from 10 p.m. to 6 a.m. the following day.
• To keep travelers moving, law enforcement will direct traffic through the interchange.
• Travelers should allow at least 30 minutes of extra time to reach their destination. WSDOT encourages people to carpool or reschedule trips before or after work hours.

Once the original overpass is removed, crews can finish widening I-5 to extend the high occupancy vehicle (HOV) lanes.

Those HOV lanes will open this summer as part of the I-5 Mounts Road to Steilacoom-DuPont Road Corridor Improvements project.