en.Wedoany.com Reported - The Washington State Department of Transportation (WSDOT) is partnering with contractor Atkinson Construction on a $240 million design-build project between DuPont and Joint Base Lewis-McChord (JBLM), which is approximately 85% complete, aimed at reducing congestion and introducing new safety measures.
Officially named the "I-5 - Mounts Road to Steilacoom-DuPont Road Corridor Improvement Project," the work primarily extends high-occupancy vehicle lanes on I-5 in both directions, improving access between DuPont and the military base. The project also includes constructing a more efficient interchange, enhancing connectivity for pedestrians, cyclists, and users of other wheeled modes between the city and the base, while increasing vertical clearance on the Pendleton Avenue bridge over I-5, a key road within the base.
Joint Base Lewis-McChord, operated jointly by the Army and Air Force, combines Fort Lewis and McChord Air Force Base and is home to the 62nd Airlift Wing, facilitating rapid deployment of military equipment to deep-water ports.
Construction Equipment Guide interviewed Atkinson Construction Manager Mannie Barnes about the project. A key phase involved setting 17 precast concrete girders over railroad tracks, ranging from 148 to 156 feet in length and weighing up to 171,000 pounds. Barnes stated that the team executed a precise relay-style lift using two 330-ton crawler cranes, operating on an hourly schedule to safely hoist and transfer the large girders of varying lengths over the tracks. During deck pours, the irregular shape required 1,200 linear feet of screed rails to control the Bidwell screed.
Workers will remove an at-grade railroad crossing to enhance safety. Road capacity in the surrounding area will increase, allowing drivers to enter DuPont and merge onto I-5 without waiting for trains to pass. The new diverging diamond interchange will feature a protected shared-use path, providing safe passage for non-motorized users between the two communities. WSDOT Spokesperson Doug Adamson told Construction Equipment Guide that the design-build team developed an innovative solution, consolidating two planned I-5 intersections into a single bridge over I-5 by creating a unique intersection at the JBLM gate and the new interchange.
The Atkinson team and subcontractors placed over 100,000 tons of asphalt, used 3.2 million pounds of rebar, and completed 450,000 cubic yards of embankment and 120,000 square feet of retaining wall. The team collaborated with JBLM to transport old materials such as timber, wood chips, and brush to the base to support landscaping activities, reducing disposal costs. Adamson said the construction of the new Steilacoom-DuPont Road bridge over the railroad tracks was a major achievement, with the construction team completing a complex three-stage abutment pour while avoiding conflicts with underground utilities. Concrete placement was a significant challenge, testing the ability to construct a bridge deck with trapezoidal geometry and flared wing walls. The 80-foot elevation difference between the piers required close coordination among crews to complete the final 750-cubic-yard deck pour, which is approximately 3 inches thicker than a standard bridge deck.
Regarding safety, Atkinson stated its commitment to an "innovation-first" safety culture. By using advanced portable traffic signals instead of traditional flaggers, workers are removed from lanes most vulnerable to inattentive drivers. Site supervisors monitor complex work zones via high-definition cameras and sensors without needing to remain on the shoulder or median. The project has already positively impacted motorists traveling on and off I-5, as well as personnel entering and exiting the military base. Workers are reconstructing a major gate at JBLM to reduce congestion for service members, contractors, and civilians. Adamson concluded that the gate reconstruction builds upon the opening of the new I-5 interchange, and the new interchange, new railroad bridge, and gate reconstruction will significantly improve traffic flow for both military and civilian vehicles.
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