I-70 New Mississippi River Bridge

Summary

Engineering studies began in 1992 for a new Mississippi River crossing between Illinois and St. Louis, Missouri. The Illinois Department of Transportation (IDOT) and the Missouri Department of Transportation (MoDOT) are the sponsoring agencies for the New Mississippi River Bridge (MRB) project. The states received approval from the Federal Highway Administration for the Ultimate Project Concept in 2001.

The ultimate concept includes an 8-lane bridge located north of the current I-70 crossing. In July 2009, the Missouri and Illinois Departments of Transportation made a determination that the new bridge would be designed and constructed as a 4-lane structure based on the combined value of funds available between both states to meet the Financial Plan requirements.  The additional four lanes will be designed and constructed in the future when traffic volumes justify the additional lanes.

Project

The MRB Design Team consisted of engineers and designers from, IDOT, MoDOT, HNTB, CMT, Kaskaskia Engineering Group, LLC (KEG), and EFK Moen.  KEG performed the structural design and plan preparation for the Illinois approach to the main river span of I-70 over the Mississippi River.  The Illinois approach is a 2,500-foot-long viaduct carrying four lanes of traffic over property owned by four different railroad companies.  The bridge superstructure consists of a cast-in-place concrete deck on stay-in-place precast deck forms supported by 112-inch deep hybrid plate girders.  The superstructure is supported by concrete piers with 8- foot deep pier caps and 6-foot diameter columns on 6.5-foot diameter drilled shafts.  The drilled shafts were designed to withstand liquefaction during a seismic event.  KEG engineers also provided utility coordination for both the Missouri and Illinois approach spans.

The structure was designed for a 2500-year seismic event. A site-specific analysis was performed to determine accurate soil-structure interaction for an economical substructure design.

The construction contracts for the new bridge and approaches were awarded using the design-bid-build process. Contractors for the main span were prequalified to assure that they had the technical expertise and resources to handle this project. The project also used the Alternate Technical Concept Process (ATC).  This process allowed contractors to provide design and constructability input in the early stages of design. The process saved money by taking the risk away from the contractor since their ideas were analyzed and approved or rejected before bidding. This allowed contractors to be innovative so that the best value for the client was achieved.