CDOT said a weekend inspection determined an immediate need for the repair of part of the steel structure. The double-leaf bascule bridge was originally built in 1913, and was rehabbed in 1974.
The bridge will be closed until October 7.
Automobile, bicycle and pedestrian traffic will detoured around the bridge via Halsted Street, Chicago Avenue and LaSalle Street.
The Chicago Transit Authority #65 bus route will be detoured around the bridge via Halsted, Chicago and Kingsbury Street.