Bridge Projects

New Viaduct Structure

Quincy Engineering Inc. provided a structural alternatives analysis and the final PS&E for this repair project on State Route 154 in Santa Barbara County that was part of the 1998 emergency storm damage repair work for Caltrans District 5. A geotechnical assessment of the project site concluded that an unstable segment of the roadway could collapse in a potentially catastrophic manner and was a potential threat to the highway and therefore public safety. The repairs for this two-phase project consisted of a 50’ high, 300’ long six-level tieback soldier pile wall ($2M) and a single-lane, three-span 300’ long post tensioned concrete box girder viaduct ($3M) constructed next to each other. The site was stabilized by first constructing the soldier pile wall and temporarily realigning the highway to be supported by this wall until the sidehill viaduct was completed the following year. Once the sidehill viaduct was constructed adjacent to the wall, traffic was shifted back to the final alignment, with eastbound traffic traveling on the viaduct and westbound traffic traveling on a roadbed supported by the retaining wall. Because of the potential threat to public safety, the project was completed on an extremely fast track schedule. The roadway also remained open the entire time while the project was being constructed.

The project also included realignment of the approach roadway while maintaining the existing profile, relocation of adjacent private driveways to improve sight distance, and widening the roadway to add turn lanes and to accommodate bicycle traffic. The horizontal alignment was improved to meet current design standards, the existing superelevation was corrected, and guard railing was constructed for the length of the project.

Client:  Caltrans District 5