Project overview
This project is intended to help relieve chronic traffic congestion and improve mobility along Interstate 5 near Joint Base Lewis-McChord. Crews will rebuild the Steilacoom-DuPont Road (Exit 119) interchange and extend I-5 HOV lanes to Mounts Road.
What to expect
Remaining paving closures
Travelers should expect increased travel times during the paving closures and consider altering plans or adding extra time for trips.
Northbound I-5 ramps at Steilacoom-DuPont Road
From 9 p.m. Friday, June 26 to 6 a.m. Saturday, June 27:
- The northbound I-5 on- and off-ramps will close.
- Travelers will detour via the 41st Division Drive exit.
Southbound I-5 ramps at Steilacoom-DuPont Road
From 10 p.m. Friday, July 10 to 6:30 a.m. Monday, July 13:
- The southbound I-5 on- and off-ramps will close.
- Travelers will detour via the Center Drive exit.
- Southbound I-5 travel lanes will shift towards the median during the closures.
Southbound I-5 Center Drive off-ramp
From 10 p.m. Sunday, July 12 to 6:30 a.m. Monday, July 13:
- The southbound I-5 off-ramp to Center Drive off-ramp will close.
- Travelers will detour via the Mounts Road exit.
If it rains, the work may be rescheduled. Real-time travel information is available on the statewide travel map and WSDOT app. Travelers are encouraged to sign up for project email updates.
New HOV lanes
Travelers will see crews working in the median along I-5, approaching Steilacoom-DuPont Road. They are finishing new high-impact median barriers and paving the new HOV lanes. If the weather cooperates, crews will open sections of the new HOV lanes in late June/early July.
I-5 mainline will shift into the final configuration once the lanes are open to traffic.
Project overview
The I-5 Mounts Road to Steilacoom-DuPont Road Corridor Improvements project is expected to be complete late 2026.
The $240 million project is part of a suite of improvements as part of the I-5 Mounts Road to Thorne Lake Corridor Improvements project. The previous improvements:
- Rebuilt the Berkeley Street and Thorne Lane interchanges, which include improved access for people who walk, bike and roll.
- Added new HOV lanes and auxiliary lanes in both directions of I-5.
The project will add HOV lanes to both directions of I-5 and rebuild the Steilacoom-DuPont Road interchange.
New Steilacoom-DuPont Road interchange opened March 22, 2026
Crews have opened the state’s third diverging diamond interchange. The new bridge eliminates an at-grade railroad intersection and includes a barrier-protected shared-use path connecting JBLM to DuPont.
The original bridge was demolished and removed the nights of April 3-4.
Final paving work
Crews finished paving the northbound I-5 ramps at Steilacoom-DuPont Road during overnight closures the week of June 1. Some work is remaining for permanent markings on the ramps.
I-5 corridor improvements
This project is the third in a series of projects that widen I-5. The work creates new HOV lanes. After this project is complete, both directions of I-5 will have HOV lanes between Mounts Road and Gravelly Lake Drive.
New overpasses are necessary to add lanes. This is the case for the original overpass at the Steilacoom-DuPont Road interchange.
The existing overpass was built in 1957. It is classified as "poor condition". It did not meet current vertical clearance standards from I-5.
A new interchange was built to current design standards and allows for new HOV lanes in both directions of I-5.
Traffic flow was slowed in the prior configuration due to the distance between each interchange. Other factors included JBLM’s DuPont Gate, the railroad, and the intersection of Wilmington Drive and Barksdale Avenue.
JBLM DuPont Gate
Crews finished construction and final paving in front of JBLM's DuPont Gate. The gate reopened June 8 after a two-week closure.
Steilacoom-DuPont Road updates
Crews finished final paving and striping along Steilacoom-DuPont Road, the new roundabout and the section between the roundabout and Barksdale Avenue.
Changes to Wilmington Drive and Barksdale Avenue intersection
Crews built a three-way intersection at Wilmington Drive and Barksdale Avenue. Travelers will see three new stop signs at the intersection.
Other changes include:
- A new sidewalk that connects Wilmington Drive to Steilacoom-DuPont Road for people walking or rolling to or from Barksdale Station.
- The addition of a left turn lane into Barksdale Station, and the removal of the existing concrete median curb.
- Dedicated left turn lanes to and from the Historic Village.
Travelers may continue to see flaggers occasionally alternate traffic during daytime hours at this intersection.
Crews worked overnight during June 2026 to pave the new three-way intersection. They also repaved the new Steilacoom-DuPont Road roundabout.
Environment
On June 30, 2021, the U.S. Department of Transportation Federal Highway Administration issued a Finding Of No Significant Impact (FONSI) for the Interstate 5 JBLM Congestion Relief Project Revised Environmental Assessment (PDF 31MB).
WSDOT has published the I-5 JBLM Vicinity Congestion Relief - South Study Area Supplemental Environmental Assessment (PDF 61.84MB).
This document was prepared as a supplement to the 2017 Environmental Assessment (EA) for the project's North Study Area. The Supplemental Environmental Assessment (SEA) describes the South Study Area and cover the potential environmental effects related to transportation, noise, natural resources, parks and recreation, community resources, and other resources.
The South Study area is located between the vicinity of the Mounts Road (116) and Main Gate (120) exits.
For links to the 2017 EA, please refer to the Environment tab on the I-5 - Mounts Road to Thorne Lane I/C - Corridor Improvements webpage.
