Southbound Interstate 5 travelers in Lacey are encouraged to prepare for a detour or alternative route as crews transform the existing State Route 510/Marvin Road overpass into a diverging diamond interchange. The Marvin Road overpass itself also will see an around-the-clock lane reduction. These changes could occur as soon as the evening of Monday, April 1.

Southbound I-5 drivers who want to turn left onto Marvin Road will instead turn right and follow a detour via Hogum Bay Road Northeast, Willamette Drive Northeast and back to Marvin Road. Southbound I-5 drivers heading towards Hawks Prairie also can take Nisqually exit 114 as an alternate route.

Marvin Road
Drivers also can expect the Marvin Road overpass, which typically sees 34,000 vehicles per day, reduced to one lane in each direction.

Travelers should expect heavier-than-normal traffic along the routes, alternate routes and across the Marvin Road overpass during the work.

To help avoid congestion and keep traffic flowing travelers can:

  • Allow extra time or take alternate routes.
  • Reschedule discretionary trips.
  • Travel early in the morning or later in the evening.

The temporary detour and Marvin Road lane reduction, which will continue for at least two months, will allow crews to rebuild the I-5 southbound off-ramp to accommodate the future diverging diamond interchange.

Additional information about this project available at

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.

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 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.