Interstate 5 (I-5) — which runs along the West Coast from the Canadian border to the Mexican border — is currently under construction in DuPont, Washington. The Washington State Department of Transportation (WSDOT) and design-build partners Guy F. Atkinson Construction (Atkinson) and Jacobs Engineering Group (Jacobs) are working on this section of I-5, which is near the Joint Base Lewis-McChord (JBLM) military base. The area has been a pinch-point in the busy Puget Sound area for many years.
The United States Army website describes Joint Base Lewis-McChord as “the Department of Defense's premier military installation on the West Coast.” Fort Lewis, an Army base, was established in 1917. Thirty years later, the military established the McChord Air Force Base.
"The joint base ... began operation in October 2010 from the consolidation of Fort Lewis and McChord Air Force Base," according to the website. The base is 142 square miles. It is home to 40,000 active-duty members, 60,000 family members, and 15,000 civilian and contract employees.
"JBLM is one of the top employers in the state, and its presence has a great impact on the economy," said Doug Adamson, Assistant Communications Manager for the Olympic Region at WSDOT.
The base is a magnet for traffic. "The area around JBLM is virtually landlocked," Adamson said. "With Puget Sound to the north and JBLM to the south, there's no viable travel alternative in the area."
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Traffic to the base comes primarily from Olympia, Washington, in the south and Tacoma, Washington, in the north. Other I-5 users include tourists, through traffic, and freight. There are also several warehouses and fulfillment centers in the vicinity.
In 2023, the average daily traffic was 134,000 (northbound and southbound), representing a 2 percent increase from the previous year.
The focus of the I-5 - Mounts Road to Steilacoom-DuPont Road project is to improve mobility along I-5 in the vicinity of JBLM. This project is the third one that WSDOT has taken on to widen I-5 and create new high-occupancy vehicle (HOV) lanes. More projects are scheduled.
The scope includes the following:
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- Extending an HOV lane on southbound I-5 for 1.7 miles
- Extending an HOV lane on northbound I-5 for 3.5 miles
- Replacing an aging overpass
- Adding a roundabout on a local road adjacent to I-5
- Improving access to JBLM's DuPont gate
- Installing a new traffic signal on southbound I-5 at an exit
According to WSDOT’s website, the overpass being replaced was built in 1957 and is "classified as poor condition. It does not meet current vertical clearance standards from I-5." Periodically, vehicles have hit the overpass, which leads to lengthy backups.
The new overpass will be a partial diverging diamond interchange (DDI) and have a traffic signal. A blog on the WSDOT website said that "adding a DDI here improves mobility and safety between I-5, DuPont, and JBLM.”
The existing interchange included an at-grade railroad crossing. The Amtrak Cascades route, which runs between Seattle, Washington, and Portland, Oregon, has 12 daily trains passing through the crossing.
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The new bridge over I-5 will span the railroad tracks, eliminating the need for DuPont travelers to stop for passing trains. Therefore, it will reduce travel times.
"Removing the at-grade railroad crossing will significantly enhance the safety of both vehicular and non-motorized traffic in this busy area," Adamson said. "The new overpass will greatly increase traffic operational capacity of the surrounding roadways."
The rebuilding of a JBLM gate provides those entering the base with a secure access point. The gate will improve traffic flow for people entering and leaving JBLM.
"Rebuilding the gate required a weeklong closure of the secure access point," Adamson said. "The work required a lot of coordination with JBLM to help ensure users were aware of the closure."
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"Performing construction on I-5 while a minimum of three lanes remain open in each direction is like building an airplane while you are trying to fly it," Adamson said.
This is the challenge that Atkinson is under, as WSDOT requires the design-build contractor to keep at minimum three lanes open in each direction of I-5 during daytime hours. Atkinson can only close lanes or ramps at night when traffic volumes are much lower.
Meeting this challenge required the design-builder to develop and implement traffic staging that shifts travel lanes as new work zones are created.
"Atkinson and Jacobs have successfully developed and implemented a staging plan that has kept the project moving forward efficiently," Adamson said.
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Originally, WSDOT proposed two bridges over I-5. However, the design-build team altered the plan, which has many benefits.
"Our design-build team developed an innovative design that uses one new bridge over Interstate 5 in lieu of WSDOT's initial concept, which had two bridges," said Mannie Barnes, a Construction Project Manager for Atkinson.
"This solution meets all of the performance criteria, while providing a more efficient schedule at a lower cost of construction, that is safer to build," Barnes added.
It also means significant coordination and communication with all the major stakeholders.
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"Now that we are in construction, we have been working closely with Joint Base Lewis McChord, City of DuPont, and WSDOT to coordinate the delivery of this project," Barnes said. Other partners include Sound Transit.
"Keeping all of our partners in the loop on the status of construction is critical in keeping a project of this size moving forward while meeting their needs," Adamson said.
The design-build team of Atkinson and Jacobs has performed other I-5 projects in the area. Their experience gives them an understanding of the area, stakeholders, and WSDOT procedures and expectations.
Despite the past work, WSDOT judged Atkinson and Jacobs like the other teams. WSDOT selected them as the winning team based on their design and value. Adamson and WSDOT have been pleased with the selection.
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"The contractor has also been very engaged with JBLM and Department of Defense staff to keep them informed and to mitigate impacts to base traffic and operations, which has ensured there would be no delays to project completion," Adamson said.
The design-build team has also worked with WSDOT to make enhancements to the traffic staging and maintenance of traffic plans as the project has progressed.
"They developed an additional stage, Stage 3A, that allowed the team to advance work on the footing and abutment construction ahead of their original schedule for the new I-5 overcrossing," Adamson said. “This proactive approach of continuing to seek out innovation and efficiencies as the project has progressed has helped to ensure the project timelines are achieved.”
Construction began in summer 2023, and completion is expected in late fall of 2026, a few months ahead of schedule. This can be attributed to multiple reasons:
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- Cooperative weather
- Good project management and planning
- Open communication and a partnering mindset by all involved
The team meets frequently in person to discuss the project schedule, upcoming traffic impacts, risks, and project issues that may affect the schedule and quality. The meetings empower them to address the problems quickly.
The construction budget for the project is approximately $227.5 million. The state is funding the project via the Connecting Washington transportation package. The WSDOT website says that the package, which the state legislature passed in 2015, is "a $16 billion investment that enhances the statewide transportation system and maintains critical infrastructure.”
The 16-year program received funding primarily via an 11.9-cent gas tax increase that was fully phased in on July 1, 2016.
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Upon completion of the project, it is anticipated that there will be a significant decrease in congestion in the area, as was experienced when the previous stage was opened to traffic. Those who use this roadway as an access point to JBLM and regional traffic can expect more reliable drive times. The corridor will also be safer due to the removal of the at-grade railroad crossing and revised intersection control.
Finally, pedestrians and bicyclists will also have improved access. Paths and bike lanes will be part of the new overpass and other additions.
- Owner: Washington State Department of Transportation; Project Engineer, Barsha Pradhan
- General Contractor: Guy F. Atkinson, Golden, Colorado
- Designer: Jacobs Engineering Group, Dallas, Texas Photos courtesy of WSDOT
