Wahoo South Bridge

Wahoo’s Highway 77 bypass route required an 1,800-foot long bridge to span a valley containing two creeks and a railroad line. In 2003, Terracon was retained to evaluate shoring and dewatering requirements for the project. Due to the low strength of the upper cohesive soils and shallow groundwater conditions, excavations for pile driving and pile cap construction would have required installation of sheet pile shoring and dewatering systems for each of the 66 column locations.  The deepened pile caps next to the creek channels would have required relatively deep and internally braced sheet pile shoring and large capacity dewatering wells.

Terracon suggested that slurry-drilled shafts be considered as a value-engineering alternative to the driven piles and pile caps to eliminate the extensive shoring and dewatering from the project. Terracon also provided supplemental geotechnical subsurface exploration and the drilled shaft design and load testing services. The resulting redesign saved $385,000 and accelerated the foundation installation by 10 months. As a result of this project, the NDOR now accepts the use of slurry-drilled shafts and has successfully applied the technology on several of their subsequent bridge projects. The project won a 2004 ACEC Nebraska Engineering Excellence Honor Award.