SR 16 Westbound Nalley Valley Interchange
The Westbound SR-16 Nalley Valley project improved the westbound connection between I-5 and SR 16 by constructing new westbound bridges over Nalley Valley and eliminating traffic weaves with a new direct connection from southbound I-5 to Sprague Avenue and westbound SR 16. Improvements also included building a new Sprague Avenue on-ramp to westbound SR 16, a new eastbound SR 16 off-ramp to Sprague Avenue, and a new flyover ramp from northbound I-5 to westbound SR 16 and Sprague Avenue.
The project also improved safety with full-width shoulders and new lighting. Construction also included adding traffic cameras, electronic signs for traveler notification, highway advisory radio transmitters, and traffic data collectors to provide real-time traffic information for the web and 5-1-1.
Due to high steel prices, Atkinson proposed a 43-foot-wide, 1,061-foot-long pre-cast concrete segmental bridge—a first for WSDOT—in lieu of the planned steel tub girder bridge. Atkinson self-performed the segment precasting operations utilizing a long-line casting bed that defined the profile geometry. Atkinson erected segments at night to minimize impacts to drivers. We also created and engineered a method to remove 430 LF of barrier from the existing viaduct to complete the Temporary Eastbound Detour tie-in—the first time an operation like this had been performed in Washington.
This project included the deconstruction of seven bridges, totaling 6,900 cubic yards of concrete, 80-foot columns, and massive girders. Deconstruction of the 16/6S-N bridge over SR 16 was executed flawlessly and met strict SR-16 weekend closure restrictions of WSDOT and City of Tacoma. Deconstruction also included the post-tensioned tetrapod columns supporting the existing viaduct. These columns were especially challenging as they leaned 20 to 35 degrees from vertical.
This project received several awards including the 2012 AGC Build Washington Award for Construction Excellence (Highway & Transportation Division) and the 2012 Engineering News Record NW Region Best Transportation Project.