Dolores River Bridge—Bedrock, CO: Remote Site Solution for Deep Scour

The Dolores River Bridge in Bedrock, Colorado carries SH-90 over the Dolores River. The bridge is in a remote location and crosses a channel that has the potential for deep scour during the extreme flooding event. The structure was designed with a combined focus on cost, constructability, and hydraulic performance during both the design and extreme events. The superstructure consists of concrete bulb tee girders and precast deck panels and the substructure consists of steel H-piles with precast concrete abutment caps. All bridge components except the barrier curb were designed using precast concrete elements because the site location is far from ready-mix concrete plants. The precast elements were designed and detailed to connect using high strength threaded rods and tolerances were established to allow for field adjustment and avoid lengthy delays during construction. The 100-year flood event has the potential to lower the channel grade by nearly 17 feet. To mitigate this, the abutment walls and wing walls were designed using driven sheet piles with rip rap protection. For the 500-year extreme event, the abutment was designed to remain stable and allow the roadway embankment to be replaced, providing a much faster and more economical repair than a complete structural replacement. This paper presents the unique design challenges of this structure and the solutions that were developed and implemented to meet the challenges while providing a cost effective product. This paper will provide an understanding of bridge abutment design that combines deep foundations for structural stability during the extreme scour event and sheet pile wing walls for stability during the intermediate scour event. The paper will also provide an understanding of the design and detailing considerations for a bridge structure using entirely precast components.