I-5 - SR 510 Interchange - Reconstruct Interchange

Project news

  • Crews have reopened the Marvin Road on-ramp to southbound I-5 and all lanes on the Marvin Road overpass. On Monday, May 18, lanes on the overpass were reduced and the on-ramp was closed allowing crews to rebuild the ramp to southbound I-5. WSDOT would like to thank travelers for their patience and cooperation during the extended ramp closure.
  • ​All users of this overpass are encouraged to check the Thurston County construction and travel updates web page and sign up for project updates

Why is WSDOT reconstructing the I-5 and Marvin Road (SR 510) interchange in Lacey?

Crews will reconfigure the interchange to create a diverging diamond interchange. The rebuilt interchange is intended to help ease congestion and reduce the potential for crashes. The project will be constructed ahead of planned major development in Lacey north of I-5.

A diverging diamond interchange improves traffic flow by allowing drivers to make a free left turn onto the highway without stopping at a traffic signal.

The project also includes a new frontage road and extended Marvin Road on-ramp to southbound I-5. The frontage road will provide access into and out of planned development in the area adjacent to southbound I-5. 

WSDOT is committed to keeping people moving during construction. Crews will do as much work as possible to minimize effects. At the same time, there will be traffic shifts, lane reductions and detours during construction. WSDOT will announce these changes as they are scheduled. 

The End Result
This project will benefit all users of the I-5/Marvin Road interchange and all modes of transportation. In addition to helping drivers, pedestrians and cyclists will also see improvements. The improvements will also help accommodate economic development for the Hawks Prairie community. This project will expand on previous improvements that have been implemented by the City of Lacey and WSDOT.

Needs & benefits

A diverging diamond interchange is a proven way to move more people and reduce the potential for collisions by reducing conflict points.


  • Late 2015 – Finalize project scope and determine project delivery method.
  • 2016 – Acquire right-of-way and environmental permits.
  • Early 2016 – Begin preliminary design.
  • Early 2017 – Begin final design.
  • July 9, 2018 - Project advertised for competitive bidding
  • Sept. 6, 2018 - Project awarded to Scarsella Bros, Inc.
  • Oct. 2018 – Begin construction.
  • Later winter 2020 – Complete construction.


Financial Data for PIN 300502C
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $268
CWA $45,605
Total $45,872


Brian Whitehouse 
Project Office 

Doug Adamson
Olympic Region Communications  

I-5 - SR 510 Interchange locational map