I-5 - Steilacoom-DuPont Rd. to Thorne Lane - Corridor Improvements

Project news

  • COVID-19 construction effects
  • The new Berkeley Street overpass and associated I-5 ramps are open. The old overpass was removed during the overnight hours of March 6 and 7.
  • Starting Monday, March 16, a one-block section of Union Avenue is closed between Spruce Street and Thorne Lane. The around-the-clock closure will be in place until late spring while crews raise the profile of Union Avenue over 23 feet so the street can connect with the new Thorne Lane overpass. During the closure, drives will detour using Thorne Lane, Portland Avenue and Berkeley Street. The WSDOT blog has more information about the I-5/Thorne Lane interchange.
  • 146th Street Southwest at Murray Road will close starting 9 p.m. Saturday, March 14 while crews build the curbs and sidewalks on the new alignment of Murray Road as it leads to I-5. During the closure, a signed detour will be in place. Two-way traffic will be maintained on Murray Road.
  • View the latest ramp and lane closure schedule on the Pierce County construction webpage.
  • View the latest project photos on the WSDOT Flickr account.

Needs & benefits

Why is WSDOT rebuilding the Berkeley Street and Thorne Lane interchanges and adding a lane in each direction on Interstate 5 between DuPont and Lakewood?
To relieve chronic traffic congestion and improve mobility along I-5 in the vicinity of Joint Base Lewis-McChord, WSDOT is rebuilding the interchanges at Thorne Lane and Berkeley Street and adding lanes to I-5.

The End Result
The changes would reduce chronic traffic congestion through the JBLM corridor. New interchanges that incorporate roundabouts and grade separation from the rail line improves traffic flow and reduces the potential for collisions.

Project Benefits
Congestion Relief:

  • Adding one lane in each direction of I-5 between Steilacoom-DuPont Road in DuPont and Thorne Lane in Lakewood will add additional capacity and improve traffic flow.
  • Auxiliary lanes are being added on northbound I-5 between Berkeley Street and Gravelly Lake Drive, and on southbound I-5 from Gravelly Lake Drive to Thorne Lane, and from Berkeley Street to JBLM Main Gate, providing a supplemental lane for vehicles entering and exiting I-5.
  • Benefit-Cost Analysis Report (pdf 695 kb)

Safety:

  • The new interchanges are grade-separated from the existing rail line, reducing conflicts with trains.
  • Builds roundabouts at Thorne Lane interchange. Roundabouts are shown to reduce injury crashes by 75 percent at intersections where stop signs or signals were previously used for traffic control.

What to Expect

  • Narrowed and shifted lanes on I-5 and ramps in the project limits.
  • Overnight ramp and lane closures with signed detours.
  • Occasional weekend ramp closures and one extended closure of the Berkeley Street on-ramp to northbound I-5. 
  • Extended closure of Union Avenue at Thorne Lane starting mid-March 2020.
  • Access to Joint Base Lewis-McChord and Madigan Army Medical Center will be maintained.
     

Timeline

  • The Interchange Justification Report was published September 2016.
  • On May 23, 2017, 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 Environmental Assessment.
  • Design-Build contract awarded to Guy F. Atkinson Construction, LLC on May 17, 2018.
  • Design-Build contract began mid-2018.
  • October 2018 - construction began at the Berkeley Street interchange.
  • February 2019 - construction begins at the Thorne Lane interchange.
  • April 2019 - widening of Interstate 5 begins.
  • Winter 2020 - new Berkeley Street interchange opens.
  • Summer 2020 - new Thorne Lane interchange opens.
  • Fall 2020 - traffic in final configuration
  • Summer 2021 - final paving and striping, and construction ends.

Funding

Financial Data for PIN 300503T
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $0
CWA $243,098
Total $243,098

In July 2015, the Washington State Legislature included $495 million to fund the I-5 Mounts Road to Thorne Lane Interchange - Corridor Improvements project, as part of the Connecting Washington transportation revenue package. The project is funded through a 10 year period, from 2015-2025.

Contact

Brian Whitehouse,
WSDOT Project Engineer
360-412-3420

Cara Mitchell
Media Relations
WSDOT Olympic Region
360-357-2703

Small map for I-5 Steilacoom-DuPont Road to Thorne Lane project.