Prairie State Wire

The Illinois Department of Transportation (IDOT) has undertaken an innovative approach to replacing the two aging bridges that carry Illinois 2 over the Rock River in Rockton. The project began with an unusual method: moving the entire southbound bridge more than 40 feet closer to its northbound counterpart.

This move created a temporary workstation, or tramway, enabling contractors to demolish and replace both structures with increased safety and efficiency. Typically, such projects require building a temporary structure in the river, which can be time-consuming and susceptible to flooding.

IDOT is monitoring this new method for its potential time and cost savings as it manages a record level of construction activity across the state. Traditionally, temporary tramways and causeways are constructed from scratch and later dismantled, a process vulnerable to changes in river levels.

District 2 Construction Engineer Matt Hardt explained, “These temporary tramways and causeways would have been susceptible to river level fluctuations with potential for lost time if they were overtopped by flooding. The use of an elevated tramway allowed both structures to be built from a single tramway and was not susceptible to river level fluctuations.”

The bridges, originally built in 1965, accommodate about 8,550 vehicles each day between Rockford, Rockton, South Beloit, and Beloit, Wisconsin. They had surpassed their design lifespan, with posted weight limits of 26 tons for single vehicles and 40 tons for combination vehicles. Helm Civil secured the contract for the replacement with a $25.3 million bid.

Work began in early 2024 to shift the 3-million-pound, 588-foot-long southbound span into its new position. Temporary supports were constructed in the river between the bridges, followed by installation of slide rail columns to guide the bridge toward the center. Hydraulic rams then moved the structure in increments of 8-10 inches every 30 seconds until it reached its new location. This process established the elevated tramway, after which demolition and replacement of the old southbound bridge commenced.

Mahmoud Etemadi, Illinois Highways and Roads Construction Leader for Bloom Companies—which provided engineering services for the project—said this effort marked a first for Illinois and much of the United States. “It’s innovative and something they have never tried before,” Etemadi said about Helm Civil. “There have been structures smaller than this that were done, but this was a big, big thing.”

The new southbound bridge opened to traffic in June. Work on replacing the northbound bridge is ongoing and is expected to conclude by year’s end. The last pieces of the old southbound bridge will be removed after serving as a temporary structure during construction.