Missouri Department of Transportation (MoDOT) St. Louis, Missouri, United States
Delivering an iconic bridge for millions less than original estimates
Landmark bridge across the Mississippi
An Alberici joint venture constructed a new cable-stayed bridge across the Mississippi River between downtown St. Louis and St. Clair County, Illinois. The new bridge was a central piece of MoDOT and IDOT’s joint Interstate 70 relocation plan, which relieved traffic congestion and reduced accident frequency along one of the busiest commuter corridors in the region.
Super-sized structure
The $230 million bridge features a main span of 1,500 feet and two back spans of 635 feet. With a total length of 2,770 feet, it is the third longest cable-stayed bridge in the United States and among the top 50 in the world.
Added value through innovation
During the bid phase, the Alberici team submitted an Alternative Technical Concept (ATC) that allowed for the use specialized equipment to drill fewer shafts with larger diameters. This innovation saved taxpayers more than $12 million in total project costs.
Built to last
Designed to exceed 100 years of service life, the new bridge is held in place by more than 3.4 million feet of stay-cable strand secured to two 405-foot-tall A-shaped towers. To support the expansive superstructure, footings comprised of six drilled-pier shafts are embedded deep into bedrock. Each shaft is reinforced with 42 #18 vertical bars. The bridge’s shafts set a world record during load testing, registering a remarkable 36,000 tons of resistance without failure.
Extensive materials and quantities
Notable construction quantities include placement of more than 45,000 cubic yards of concrete for the foundations, deck slab, and towers. In addition, nearly 10,000 tons of structural steel and 8,600 tons of reinforcing steel were installed as part of the footings and towers.