The new fourth street bridge is two separate parallel 1,137- foot structures spanning a river, a rail yard and a city street in Pueblo, Colorado. At 377 feet, the bridge’s main span is the longest concrete in Colorado at the time of construction. Each bridge consists of two 12-foot travel lanes, six-foot inside shoulders, 10-foot outside shoulders and 10-foot sidewalks.

Fourth Street is a major east-west route through Pueblo, Colo. connecting Interstate 25, downtown Pueblo, and western residential neighborhoods. The 4th Street Bridge carries State Highway 96A across a city street, the Arkansas River, and the Union Pacific and Burlington Northern Santa Fe railroad yards (the Pueblo Yard). The bridge provides improved safety and an increased load capacity.

The project’s location, across the 36-track Pueblo Yard, posed unique challenges. With access into and out of the railroad yard limited, Flatiron constructed the bridge using cast-in-place balanced cantilever segmental construction. Flatiron also used tower cranes to minimize the footprint in the railroad yard and unloaded all materials from an existing nearby bridge. In addition, Flatiron pumped concrete and provided access for personnel from this existing bridge.

In addition to the cast-in-place cantilever method, use of a wetland pad, river barrier, bridge removal decking over the river, on-site dewatering and other innovative methods were used to avoid or minimize impacts to the surrounding environment, including wetlands, water quality, historic resources, and migratory birds.