The I.B. Perrine Bridge is a 1500-foot-long steel arch structure carrying US 93 over the Snake River Canyon near Twin Falls, Idaho. This landmark structure is among the highest bridges in the United States, with the top of the deck 486 feet above the Snake River. The Idaho Transportation Department (ITD) retained Burgess and Niple (B&N) to develop a comprehensive, long-range Asset Management Plan (AMP) for the bridge. The AMP provides ITD with a bridge-specific plan to extend the service life, avoid future load restrictions, maintain safety, and minimize maintenance costs.
Components of the AMP included: 1) A review of existing data, including construction plans, shop drawings, repair plans, and inspection reports. 2) A bridge condition assessment, including visual inspection and testing. 3) A risk assessment consisting of a workshop to identify risks and prepare a risk register. 4) An analysis of alternatives consisting of a high-level comparison of maintenance and rehabilitation options. 5) Preparation of a maintenance and monitoring manual, providing recommendations and cost estimates for future preservation actions. The information collected was compiled into a single guidance document to provide ITD with a reference when performing future maintenance on the bridge.
Partially due to the condition assessment associated with the AMP, B&N prepared bridge repair plans to be performed in 2023. These repairs include the replacement of corroded bolts in the arch end posts, protective coating installation in corrosion-prone areas, repairs to the inspection access system, repairs to the concrete substructures, and repairs to the sidewalk joints. Construction access for repairs will be difficult due to the type of work and the position of the bridge. Bolt replacements in the end-posts will require workers to enter confined chambers through small openings to reach the repair location. In addition, the extreme height of the structure makes accessing any of the below-deck repairs a challenge.
The presentation will discuss the preparation and content of the AMP and the forthcoming repair project. Presenters will include ITD and B&N representatives.