IL 89 over the Illinois River

Built in 1937, the 1,775-foot-long IL 89 bridge over the Illinois River was deteriorated and needed replacement. Surrounding communities relied on this fracture critical, narrow structure for commerce, emergency response and general travel. However, the bridge did not meet modern roadway geometry standards and had already undergone numerous structural repairs.

Benesch developed a new bridge design option that limited impacts to the surrounding land uses, minimized environmental impacts and provided for an economical structure.

Since a detour route was not feasible during construction, Benesch developed and conducted an origin and destination study to document where trips across the bridge begin and end, as well as the trip’s purpose. Using information gathered from the study and public involvement, the selected alternative drew upon existing and innovative engineering techniques to build a new, nine-span steel plate girder on an offset alignment. A Traffic Management Plan (TMP) was developed that allowed the bridge to remain open during construction.

Developed by Benesch, the final design replaced the deteriorated truss and stringer spans; widened the roadway; added a pedestrian/bike lane; and maintained navigational span clearance for river traffic.

Since the existing bridge was eligible for the National Register of Historical Places, Benesch also prepared a Section 106/4(f) report to gain concurrence from the Federal Highway Administration and the State Historic Preservation Officer to demolish the existing bridge.