In August 2007, the I-35W Mississippi River bridge spanning the Big River that links Minnesota to Wisconsin collapsed to the river and riverbanks beneath during the evening rush hour, killing 13 people and injuring 145.

Preliminarily blamed on design error, the eight-lane steel truss arch bridge, which was built in 1967, was regarded as Minnesota’s fifth-busiest, carrying 140,000 vehicles daily.

Those killed were remembered through many memorials, but the one tribute that might be the best of all was the replacement bridge—known as the St. Anthony Falls (35W) Bridge. The bridge was constructed with sustainable development practices in mind.

Opening on September 19, 2008, the $234 million St. Anthony Falls bridge is the first in the country to use LED lighting, which lasts longer and uses less energy. The bridge is illuminated with blue light-emitting diodes and is equipped with anti-icing sprayers and was constructed with high-strength concrete. Bridge conditions are monitored with 323 sensors that regularly measure bridge conditions, such as deck movement, stress and temperature. The new onramps are longer, to provide drivers a better sight line as they approach, and cut down on accidents.

Placed on the fast track under the state’s design-build procurement law, Longmont, Colo.-based Flatiron Constructors and Seattle-based Manson Construction Co. were awarded the contract in September 2007. Leading the design effort was Tallahassee, Fla.-based Figg Bridge Engineers Inc. Also on the team was Orlando-based Johnson Bros., in a support role.

With demolition of the old bridge, the total cost amounted to more than $400 million, with about three-quarters of the funding coming from the federal government. The state paid the remaining costs. The bridge was built using around-the-clock construction, in less than half the usual time it takes to build a project of this size.

Engineer Linda Figg, of Figg Bridge Engineers, said the bridge is built to last more than 100 years and handle double the weight of the vehicles expected to travel on it. “This is a modern concrete bridge for the future composed of high strength, high performance concrete with significant levels of redundancy,” Figg said. “That means that many of the elements all do the same job and in that way you have a lot of extra strength that is built into the structure.”

Minnesota’s Dept. of Transportation (MnDOT) maintained a project page that tracked all activities associated with the construction of the bridge, including weekly updates, traffic impacts, construction photos, animations, and virtual walking tours. On December 17, 2007, the first slab of concrete—200 feet long, 13.5 feet wide, and 4.5 feet thick—was poured off-site, which began to shape the bridge.

Participants agreed to allow the Visual Quality Advisory Team for the project to make a final decision on lighting after reviewing all of the completed design choices.