Construction Starts on New I-270 Mississippi River Bridge

Work has begun on building a new Interstate 70 bridge over the Mississippi River between Missouri and Illinois.

The new Chain of Rocks Bridge will be built beside the existing bridge, which opened in 1966 between St. Louis and Madison County, Illinois.

Walsh Construction is the contractor on the project and has been preparing for construction on the new bridge’s substructure, according to the Illinois Department of Transportation.

The project also involves the construction of a new diverging diamond interchange at the I-270 Riverview Drive intersection in St. Louis. The interchange ramp has been closed for the work and is not scheduled to be reopened until July 2024, according to the Missouri Department of Transportation. IDOT and MoDOT are collaborating on the projects.

The existing four-lane I-270 Chain of Rocks Bridge will be demolished after a new span built south of the bridge opens. After the old bridge is demolished, the next span will be built in its place. The bridge, when completed, will initially open as four lanes but eventually will have six lanes after I-270 east and west of the Riverview Drive interchange is widened to six lanes, according to IDOT. The Riverview Drive interchange will also be built to six lanes but initially will be striped for four until the other sections are widened, MoDOT says.

Construction on the bridge is expected to conclude at the end of 2026 at a cost of about $500 million. 

The existing 5,400-foot-long Chain of Rocks Bridge consists of twin bridges with 43 spans. It handles about 51,000 vehicles a day with 17% of them trucks, according to IDOT. The bridge is nearing the end of its design life and has undergone numerous repairs, including to its structural steel and substructure, the agency says.