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1,500-ft-long cable-stayed bridge
MoDOT
New Mississippi River crossing planned

The Missouri and Illinois departments of transportation have chosen HNTB Corp., Kansas City, to design a planned new 1,500-ft-long cable-stayed bridge to carry Interstate 70 over the Mississippi River between St. Louis and suburbs. Once negotiations over fee are finished by mid-May, design work will begin on the $306-million bridge and $334-million new roadway connections, with construction possible in 2010.

The bridge, in planning for two decades, finally received a federal earmark in 2005 of $239 million, combined with $88 million from MoDOT and $313 million from Illinois. Illinois will spend $264 million on interchanges with I-55 and I-64. The bridge itself will cost about $303 million, says Greg Horn, MoDOT project manager. HNTB must finish design by July 9, 2009, says Steve Hague, HNTB project manager.

The four-lane bridge, with room for two more lanes, is expected to carry 40,000 vehicles a day and relieve traffic on the Poplar Street Bridge when opened as early as 2014. Hague says the plan is to stay faithful to the conceptual rendering by the state DOTs, with a delta configuration on the tower. Design challenges will include 100-year-old utilities, navigation on the Mississippi, seismic issues, dealing with five railroads, and soft soils on the Illinois side of the river, he adds. HNTB's designers will be co-located in a St. Louis office with decision-making state transportation staffers, says Horn.

Funding issues delayed the project, which received a Record of Decision in 2001. "In 1990 we decided we had a traffic problem," recalls Horn. "We did an Environmental Impact Statement in 1991 and selected the location in 1997." With projected cost up to $1.6 billion, the DOTs discussed potential public-private partnerships, tolls and alternative locations. Finally, they opted to build the project in phases, building one bridge now and anticipating building another twin crossing some 20 years in the future, says Horn.

HNTB edged out other big-name competitors such as HDR Inc./T.Y. Lin International, Parsons Brinckerhoff, URS Corp., Figg Engineering Group and Jacobs Engineering.