2025 Mountain States Best Projects
Best Highway/Bridge: US 50 Blue Mesa Bridge Emergency Repair
US 50 Blue Mesa Bridge Emergency Repair
Gunnison County, Colo.
BEST PROJECT
Submitted by Michael Baker International
Owner Colorado Dept. of Transportation
Lead Design Firm Michael Baker International
General Contractor Kiewit
Two long-span steel structures—the Lake Fork Bridge and the Blue Mesa Middle Bridge—each carry two lanes of US 50 traffic over the Blue Mesa Reservoir, but each structure had three fracture critical spans consisting of two continuous welded steel plate girders. In April 2024, inspectors identified a 2.5-in. crack and a weld defect indication on the Blue Mesa Bridge, noting internal defects within the weld. The project team immediately moved to identify the type and severity of issues, model bridge capacity and formulate a plan for interim and permanent fixes. The emergency nature of the project required preconstruction and design phases to run concurrently with construction.
To reopen US-50 to one-way traffic by July 4, the team utilized a 3-in. by 30-in. underslung grade 50 plating repair. This allowed the contractor to rapidly fabricate four plate assemblies, procure A325 fasteners and install only one assembly at each repair location.
Photo courtesy Michael Baker International
For the permanent repairs, the team developed a strategy to protect against future cracks in web-to-flange welds. The “plinko plate” strategy consisted of a closely spaced pattern of offset crack arrest holes and an overlying plate to contain any future cracks before they could become a safety concern. However, underslung repairs require a fastener swapping program, under which permanent repair plates were temporarily positioned and each existing fastener was swapped out one by one to maintain force transfer through the splice. The piles through this section were in excess of 11-in., so crews installed high strength threaded rods using a double-nut method. Cheese plates allowed for the new structural plates to be set into final position while still providing access to remove each bolt one at a time. The cheese plates were sized to match the thicknesses of either a bolt head or nut. Given the bridge’s issues and the fact that Lake Fork Bridge was built at the same time by the same contractor, the team applied the same continuous global plating solution to Lake Fork Bridge with minimal testing. After 20,000 design hours, installation of 410 tons of steel plate and more than 50,000 bolts, repairs were completed and both bridges reopened before Thanksgiving 2024.
