The HNTB-designed bridge is one of only two entrances into the small town of Index. The only other access is a 25-mi.-long primitive gravel road — not suitable for emergency services or school bus travel. The original bridge was rehabilitated in 1980, but was later classified as structurally deficient and functionally obsolete.

Some of the key innovative concepts of the Wes Smith Index Bridge include:

1. The existing truss served as a temporary detour bridge. The truss was relocated upstream using two cranes to move the bridge to the new location. The total roadway closure was six hours, and no supports were required in the river to accomplish truss relocation.

2. Construction sequence was identified in the plans that allowed erection to take place without impacting the environmentally-sensitive North Fork of the Skykomish River.

3. A full moment connection was designed for the end floorbeam to stabilize the arch for seismic and wind loading. This connection also reduced the effective length factor to allow a reduction in the number of vierendeel struts required.

4. The continuous cast-in-place concrete slab was designed to eliminate the need for lateral bracing of the floorbeams and tie girder.

5. A modified bearing was designed to allow movement during construction, with the bearings fixed at the end of construction to reduce loads to the foundation. The fixed bearings provided for the longitudinal seismic force to be resisted by the soil at each abutment.

6. A combination pedestrian/traffic barrier was placed at the edge of the structure to provide a pedestrian-friendly facility with good views up and down the river.