Manning Crevice Bridge Replacement Project Awarded ACEC & ASCE Idaho Awards

On Monday, April 8, Horrocks Engineers was awarded the ACEC Idaho 2019 1st place Engineering Excellence Award for our work on the Manning Crevice Bridge Replacement project. This project also received 1st place in Projects Under $10M at the ASCE awards banquet for the Southern Idaho Section.

Horrocks was hired as a sub consultant to Atkins to serve as roadway and retaining wall designer, local project liaison, and Construction Manager/General Contractor (CM/GC) adviser for the project. Drawing on prior experience with the CM/GC delivery method, Horrocks successfully assisted Western Federal Lands Highway Division and Idaho County in executing their first CM/GC project.

The original Manning Crevice Bridge was built in the 1930s as a Civilian Conservation Corps project. After nearly 80 years of use, this bridge secured its place as an iconic representation of connectivity and recreational opportunities for the local community and visitors to the scenic Salmon River. However, the aging bridge’s ability to sustain loads became an increasing concern.

The Manning Crevice Bridge, located along the Salmon River near Riggins, Idaho

To replace the aging structure, a new one-lane asymmetrical suspension bridge was constructed, spanning over 300 feet with a 75-foot tall tower on the north end. The new structure has an increased deck width, greater load capacity, new pullouts, and information kiosks displaying the history of the area and the original structure.

The project is located in a very steep, rocky, v-shaped canyon of the Salmon River. Working in this setting presented many significant challenges such as mitigating potential rock fall and positioning cranes for construction on the narrow roadway.

Due to the significant constructability issues associated with this remote project, Horrocks recommended that the project utilize the CM/GC delivery method. The goal of using the CM/GC method was to facilitate innovation, risk management, and problem solving with the design team and contractor working together to develop the design and construction plans.

As the local liaison, Horrocks led meetings with stakeholders to discuss the preservation of historical and environmental resources. Horrocks also developed 3D and 4D models (the fourth dimension being time) showing construction of the project step-by-step for easy visualization of the bridge construction.

Over the life of the project, the Horrocks team contributed approximately seven years of service. Effective collaboration between the owner, designer, and contractor led to the successful planning, design, and construction of the project.