I-5 - SR 510 Interchange - Reconstruct Interchange

Project news

Why is WSDOT reconstructing the I-5 and 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.

WSDOT is accommodating planned regional growth adjacent to the interchange. 

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 this 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.
  • 2020 – Complete construction.


Financial Data for PIN BL1100110

  • Pre-Existing Funds (PEF) - $267,554
  • CWA - $47,728,025
  • Total - $47,995,579


Doug Adamson
Olympic Region Communications 

I-5 - SR 510 Interchange locational map