I-5 - SR 510 Interchange - Reconstruct Interchange

Project news

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  • WSDOT will build a Diverging Diamond Interchange at I-5 and SR 510 in Lacey. It will be the first Diverging Diamond Interchange, also called a DDI, built in the state of Washington. 
  • Learn more on the linked YouTube video.

Why is WSDOT reconstructing the I-5 and SR 510 interchange in Lacey?
WSDOT is accommodating planned regional growth adjacent to the interchange. Traffic modeling shows that a Diverging Diamond Interchange, the first of its kind in the state, will accommodate future growth in the area.

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

DDIs are 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.
  • Fall 2018 – Begin construction.
  • 2020 – Complete construction.


Financial Data for PIN BL1100110
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $0
CWA $72,000
Total $72,000


Doug Adamson
Olympic Region Communications 

I-5 - SR 510 Interchange locational map