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

Project news

  • Sign up for project updates.
  • Overnight single lane closures are scheduled for both directions of I-5 within the project limits Monday through Friday between the hours of 8:30 p.m. to 4:30 a.m. each following day.
  • The northbound I-5 exit 122 to Berkeley Street and the Berkeley Street on-ramp to northbound I-5 will close from 10:30 p.m. Saturday, Oct. 20 to 8:30 a.m. Sunday, Oct. 21.
  • Learn about construction timeline and impacts at a Community Open House (pdf 419 kb) scheduled Thursday, Oct. 25 at the Tillicum Elementary School, 8514 Maple Street SW, Lakewood, WA 98498, from 4:30 to 7 p.m.
  • Read the news release announcing the start of construction on this project. 
  • Guy F. Atkinson Construction, LLC was awarded the contract on May 17, 2018.
  • Design-Build contract will start mid-2018.
  • This project funded in the 2015 Connecting Washington transportation revenue package.
     

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 new interchanges are also grade-separated from the existing rail line, eliminating conflicts with trains. The new Thorne Lane interchange will incorporate roundabouts instead of signals which improve traffic flow and reduce the potential for collisions. 

Freeway capacity will increase with the addition of a lane in each direction between Steilacoom-DuPont Road in DuPont to Thorne Lane is Lakewood.

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. These lanes are frequently used between closely spaced interchanges to allow for maneuvering of entering and exiting traffic, speed changes, weaving and truck climbing.

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:

  • Additional capacity will 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:

  • Grade separation from rail line
  • 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.
     

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 will start mid-2018
  • Construction ends 2021

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 $242,945
Total $242,945

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

Chuck Meade, WSDOT Project Engineer
360-412-3420

Cara Mitchell
WSDOT Olympic Region Communications
360-357-2703

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