I-5 – Mounts Road to Steilacoom-DuPont Road Corridor Improvements

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Background

The Washington State Department of Transportation is in the third phase of a series of projects that widen Interstate 5 from Mounts Road near DuPont to Gravelly Lake Drive in Lakewood. Southbound I-5 currently narrows down from four lanes to three, just past 41st Division Drive. This project extends the existing southbound I-5 HOV lane to Steilacoom-DuPont Road. The northbound HOV lane will extend from Mounts Road to the existing HOV lane at 41st Division Drive.

At the Steilacoom-DuPont Road interchange (exit 119), a new overpass will be constructed. The new overpass creates enough space to extend the I-5 HOV lanes further south into DuPont and provides increased vertical clearance over the interstate to meet current standards.

Aerial photo of southbound I-5, Mounts Rd. to Steilacoom-DuPont Road

The aerial shows where southbound I-5 narrows down from four lanes to three, just past 41st Division Drive.

Current traffic flow in the area is constrained by the proximity of the I-5 ramp intersections, Joint Base Lewis-McChord’s DuPont Gate, the railroad, and the intersection of Wilmington Drive and Barksdale Avenue. Building a new Steilacoom-DuPont Road interchange will provide increased distance between the intersections while maintaining access to neighboring communities and JBLM. Once the new interchange is constructed, the existing bridge at exit 119 will be removed.

Design changes and benefits

Aerial photo showing lextended HOV lane in both directions of I-5

Improvements include an extended HOV lane in both directions of I-5. Crews will build a partial diverging diamond interchange at the new Steilacoom-DuPont overpass and a roundabout. There also will be improved access to and from JBLM.

This project features a number of design changes around the Steilacoom-DuPont Road interchange that will result in improved access and reduced traffic congestion. The changes and benefits include:

Extending the HOV lanes in both directions of I-5. The northbound HOV lane will start at Mounts Road. The southbound HOV lane will be extended from 41st Division Drive south into DuPont.
- Increases capacity in this section of I-5 and reduces chronic traffic congestion.
A new Steilacoom-DuPont Road overpass and a partial Diverging Diamond Interchange (DDI).
- The new overpass will cross over the railroad, eliminating the current at-grade crossing. The DDI will reduce vehicle conflict points and improve efficiency with fewer traffic signals.
Barrier-separated shared-use path on the new Steilacoom-DuPont Road overpass spanning I-5.
- Improves pedestrian access by connecting JBLM to communities west of I-5 for people who walk, bike, or roll.
Roundabout connecting the new overpass and Steilacoom-Dupont Road.
- Improves efficiency for all users on the west side of I-5.
Dedicated lanes at the reconstructed interchange that separate traffic traveling to either the JBLM DuPont Gate or the communities on the west side of I-5.
- Improves efficiency through the interchange.
- Check out the video below for a detailed look at improvements happening east of I-5 near JBLM.

What to expect

Construction will require lane shifts on I-5, overnight lane reductions and overnight and weekend ramp closures. Drivers, pedestrians and bicyclists should expect detours in the vicinity of Steilacoom-DuPont Road at various points of the project. All detours will be clearly signed.

Bicycles are not permitted on I-5 between 41st Division Drive and Center Drive. Travelers should be aware that access is restricted to JBLM property bordering the route.

Construction along this stretch of I-5 began in early August 2023 and will continue through 2026. The completed project will improve mobility along I-5 in the vicinity of Joint Base Lewis-McChord.

Construction

Keeping you moving throughout construction

Construction crews will keep people moving as the project reaches new stages. People will notice temporary changes to traffic patterns. The temporary changes will last at least several months.

The changes allow workers to continue building the new overpass and ramps while making space to finish the extended HOV lanes.

At the Steilacoom-DuPont Interchange, people will continue to see three travel lanes on both directions of I-5.

The new overpass is not yet open to people who are walking. There is a pedestrian route on the existing Steilacoom-DuPont Road overpass.

December 2025 – February 2026 recap

The fourth of six construction stages began in late January 2026. Stage 4 is expected to be completed in late March 2026.

The new southbound I-5 off-ramp to Steilacoom-DuPont Road (exit 119) is now open. The ramp connects to the new Steilacoom-DuPont Road overpass.

An aerial photo showing I-5 and the new southbound I-5 off-ramp and overpass.

This aerial photo, from late January 2026, shows the new southbound I-5 off-ramp connecting to the overpass (middle of the image).

The new roundabout on Steilacoom-DuPont Road is now open to all traffic, connecting JBLM, DuPont and Steilacoom.

An aerial photo showing the new Steilacoom-DuPont Road roundabout.

The new Steilacoom-DuPont Road is open to traffic. A final layer of asphalt will be applied in spring 2026.

March - April 2026: New interchange fully opens and bridge demolition

If weather allows, the interchange traffic flow in DuPont will change again on Saturday morning, March 21. The new Steilacoom-DuPont Road on-ramp to southbound I-5 will open. Traffic will shift from the existing overpass to the new Steilacoom-DuPont Road overpass. At that time, crews will close the old overpass to all traffic.

An aerial photo showing the new on-ramp to southbound I-5 under construction.

This aerial photo, taken in January 2026, shows the new on-ramp to southbound I-5 under construction. The on-ramp will connect to southbound I-5 from the new overpass.

The new overpass will open as a diverging diamond interchange, similar to the one on Marvin Road in Lacey. Driving through a diverging diamond is as easy as following the signs and lane lines.

To learn more about how to navigate a diverging diamond interchange, watch the video below and review WSDOT’s online resources.

How to get around, March 2026 – summer 2026

Beginning as early as March 21, the new Steilacoom-DuPont Road overpass will be fully open to two-way traffic. The old Steilacoom-DuPont Road bridge will be removed on the weekend of April 3-4. Here’s how to get around the area:

DuPont or Steilacoom to southbound I-5, northbound I-5 and JBLM

If leaving DuPont or Steilacoom for southbound I-5, travel through the roundabout toward the new overpass. Before crossing the overpass, turn right onto the southbound I-5 on-ramp.

To access northbound I-5, travel around the new Steilacoom-DuPont Road roundabout and head across the new overpass. At the end of the overpass, keep left to use the on-ramp.

To reach JBLM, travel around the new Steilacoom-DuPont Road roundabout, over the new overpass, and keep right toward the base.

A map showing how someone would get from DuPont or Steilacoom to I-5 or JBLM.

JBLM to I-5 and DuPont or Steilacoom

If leaving the JBLM DuPont Gate for northbound I-5, take a right from the gate and continue straight onto the on-ramp.

If leaving JBLM for southbound I-5, go straight from the gate and follow the lane lines as they guide you across the new overpass. At the end of the overpass, turn left to reach the new southbound on-ramp.

To reach DuPont or Steilacoom, go straight from the gate to the new overpass. Follow the signs to the new roundabout.

A map showing how someone would get from JBLM to DuPont, Steilacoom or I-5.

Southbound I-5 to DuPont, Steilacoom or JBLM

The new southbound I-5 exit to DuPont, Steilacoom and JBLM opened late-January 2026.

People heading to DuPont or Steilacoom use the right exit lane to travel toward the new roundabout.

People heading to the JBLM DuPont Gate will turn left onto the overpass and continue toward the gate.

A map showing how someone would get from southbound I-5 to DuPont, Steilacoom or JBLM.

Northbound I-5 to DuPont, Steilacoom or JBLM

If heading on northbound I-5 to DuPont or Steilacoom, keep left after the exit and continue straight to the new bridge. From there, follow the lane lines and traffic lights to continue across the bridge to the new roundabout.

To reach the JBLM DuPont Gate, keep right at the ramp and continue into the base.

A map showing how someone would get from northbound I-5 to DuPont or JBLM.

Overnight bridge demolition planned

Shortly after the new on-ramp to southbound I-5 is opened, crews will remove the old overpass. Both directions of I-5 will be detoured through exit 119 Steilacoom-DuPont Road.

10 p.m. Friday and Saturday, April 3-4 to 6 a.m. each following day.

People should add at least 30 minutes of travel time to help prevent delays. WSDOT encourages people to carpool or reschedule trips to travel before or after the work hours. Travelers should allow plenty of extra time to reach their destination.

During overnight demolition, I-5 traffic will detour over the on- and off-ramps.

Northbound travelers will use the on- and off-ramps to continue northbound.
Southbound travelers will exit, go around the roundabout, then travel back to southbound I-5 using the new on-ramp.
Uniformed police officers will help direct traffic while the detour is in place.

A map showing the detour with I-5 closed for bridge demolition.

Northbound I-5 traffic will be detoured up and over the Steilacoom-DuPont Road on- and off-ramps. Southbound traffic will exit, travel around the new roundabout, then return to southbound I-5 using the new on-ramp.

For the latest updates to scheduled work, check the project page on WSDOT’s website.

Safety and mobility improvements

The permanent closure of the 1950s era overpass is a significant safety improvement. Moving traffic to the new interchange will eliminate an at-grade railroad crossing.

People who walk, bicycle or roll will use a barrier-separated shared-use path on the new overpass. This path will connect JBLM to DuPont and Steilacoom.

Pedestrian and bicycle access

When the old overpass closes, people will begin using the pathway across the new overpass. The 12-foot wide shared-use path will provide a place for people who walk, bike or roll between JBLM and DuPont.

A rendering of the final diverging diamond interchange showing the new pedestrian path across the overpass.

When the old overpass closes, pedestrians and bicyclists will begin using new multimodal path on the new Steilacoom-DuPont Road overpass.

Changes to Wilmington Drive and Barksdale Avenue intersection

When the former Steilacoom-DuPont Road overpass closes, crews will create a three-way intersection north of the old railroad crossing.

The traffic lights will be removed. Travelers will see three new stop signs at the Wilmington Drive and Barksdale Avenue 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 can expect to see flaggers occasionally alternate traffic during daytime hours at this intersection.

Crews will work overnight this spring to pave the new three-way intersection. They will also repave the road up to the new Steilacoom-DuPont Road roundabout.

What's next

As the project progresses, we will share updates about upcoming work and milestones, including:

Full closure of Pendleton Avenue under I-5 (JBLM-use only) in late spring 2026.
Finalized dates for the demolition of the existing Steilacoom-DuPont Bridge at Clark Road.
Opening of extended HOV lanes.

Please help keep road workers safe. When approaching a work zone, remember to:

Slow down – drive the posted speeds for worker and traveler safety.
Be kind – workers are out there helping to keep people safe and improve the roadways.
Pay attention – both to workers directing travelers and surrounding traffic.
Stay calm – expect delays, leave early or take alternate routes if possible; no meeting or appointment is worth risking someone’s life.

Stay connected

Travel conditions change quickly, we strongly encourage travelers to use the tools below to stay informed.

View updates and upcoming closures on the project webpage
Check real time travel conditions, view cameras and travel times
Download WSDOT’s free smartphone app
Sign up for email updates using GovDelivery