HNTB was selected by the Iowa Department of Transportation to perform construction engineering and inspection services for the new I-74 Mississippi River Bridge including the new EB and WB viaducts in Iowa, and reconstruction of the approach roadways leading to the Iowa viaducts.  Each new twin river bridge features a 72-foot roadway, a 795-foot basket handle true arch span over the navigation channel and includes 14  parallel flange welded plate girder spans for total bridge length of 3,440 feet from the Illinois abutment to the transition pier on the Iowa bank. The EB bridge includes a separate 14-foot bike path.  The EB and WB viaducts each contain 16 parallel flange welded plate girder spans for a total length of 2272’.  Viaduct roadway widths vary with converging and diverging ramps and a typical width of 60-feet.  The program included approximately one mile of roadway improvements beyond the end of the viaducts adding one traffic lane in each direction (total 3 lanes EB and WB) and full width concrete pavement reconstruction.

The I-74 Mississippi River crossing is a vital interstate connection facilitating the movement of people, goods and services across a major waterway between Iowa and Illinois.  The new signature arch bridge will replace the existing, obsolete suspension bridges which carry an estimated 80,000 vehicles per day.

The project is in response to the projected traffic demands of the community providing increased access across the river. Entities involved in the success of the project include the Iowa DOT, Illinois DOT, FHWA, USACE, USCG, the Cities of Bettendorf, IA and Moline, Illinois and many others.

HNTB is providing much of the Construction, Engineering and Inspection (CE&I) for the Iowa DOT.  At the peak of construction efforts included 25 full time HNTB employees from offices around the country, four full time subconsultant employees on-site plus part time subconsultant materials testers and surveyors.

Location: Mississippi River between Bettendorf, IA and Moline, IL

Client: Iowa Department of Transportation

Read More: Enhancing Mobility over the Mississippi, Designer article