The US 20 bridge is a 460-meter (1510-foot) steel I-girder structure, consisting of five 92-meter (302-foot) spans supported on four concrete piers and two end abutments. Two 20-meter (66-foot) precast concrete spans connect the bridge to the roadway approaches.
The two central piers are supported on 8-foot diameter concrete drill shafts extending some 25 to 28 meters (82 to 91 feet) to bedrock.
The two outer piers and two end abutments are supported by 100-ton piles driven to bedrock.
The deck of the bridge carries traffic approximately 42 meters (137 feet) above the Iowa River. To minimize the impact of construction on the floor of the Greenbelt valley, engineers used a construction technique called Launching. This technique has been used widely in Europe with concrete box structures. It is not commonly used for the erection of steel I-girder bridges, and it has never been used on a project of this magnitude in the United States