The existing seven-span 4th Street Bridge opened in 1958 and carried two lanes of traffic in both directions, linking the historic downtown with the western residential neighborhoods of Pueblo. Options to replace and repair the existing bridge were evaluated prior to design, but the condition of the aging substructure drove the decision to replace the existing bridge. This project replaces the existing bridge which carries SH 96A over a city street, the Arkansas River, a floodwall, the Union Pacific Railroad’s river trail and railroad yards, and the Burlington Northern Santa Fe Railroad. The new bridge passes over 30 railroad tracks, including one mainline track for the BNSF Railroad and two mainline tracks for the Union Pacific Railroad.
The new bridges are twin cast-in-place segmental concrete box girder bridge with a six foot separation between the bridges. The new bridge span lengths are 151’, 235’, 377’, 229’ and 145’. The average length of the bridges is 1,137 feet. The superstructure cross section for each bridge provides for two twelve foot travel lanes, a six foot inside shoulder, a ten foot outside shoulder, and a ten foot sidewalk. The superstructure was built utilizing the balanced cantilever method of construction for interior piers 3 and 4 as well as cast-in-place construction on falsework for the end spans over piers 2 and 5. The box girder varies in depth from 8’ to 18’.