I-5 - SR 510 Interchange - Reconstruct Interchange

Project news​

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

Crews have reconfigured the Marvin Road overpass to create a diverging diamond interchange. The rebuilt interchange is intended to help ease congestion and reduce the potential for crashes. The project was 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 built a 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. Access will remain closed until the City of Lacey builds local connecting streets.

The End Result
This project will benefit all users of the I-5/Marvin Road interchange and all modes of transportation. Pedestrians use a network of crosswalks and a barrier separated walkway to cross the overpass. Bicyclists can also use the pedestrian path to cross the overpass or use dedicated bike lanes. The improvements help accommodate economic development for the Hawks Prairie community and 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.
  • Aug. 2, 2020 - Marvin Road overpass opened as a diverging diamond interchange.
  • Summer 2021 – 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 $46,205
Total $46,472


Brian Whitehouse 
Project Office 

Doug Adamson
Media Relations  

I-5 - SR 510 Interchange locational map