SR 16 Westbound Nalley Valley Interchange
The SR 16 Westbound Nalley Valley Interchange project provides new westbound bridges over Nalley Valley to improve the westbound connection between Interstate 5 and SR 16. The project eliminates traffic weave with a new direct connection from southbound I-5 to Sprague Avenue and westbound SR 16 and improves safety on the heavily-traveled roadway.
On the SR 16 Westbound Nalley Valley Interchange project, Atkinson constructed a series of ramps and overpasses to help improve traffic flow, including the 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. In addition, the project team added full-width shoulders, new lighting, additional traffic cameras, electronic signs for traveler notification, and highway advisory radio transmitters and traffic data collectors to provide real-time traffic information online.
Atkinson proposed to change a 1,061-foot-long ramp from one with steel tub girders to a precast segmental structure — a first for the Washington State Deptartment of Transportation. Atkinson and value engineer McNary Bergeron and Associates also redesigned and built, in less than a year, a critical-path temporary bridge with bulb-tee girders rather than steel girders. The redesigned flyover ramp used a long-line casting bed, allowing crews to start match-casting segments from the pier segment toward the middle on concrete slabs that defined the profile geometry. Using the balanced cantilever method to erect the 70-ton segments minimized falsework and traffic delays on a congested I-5.
Rigorous and extensive safety training resulted in zero lost-time hours over three years and 458,700 manhours.