By Rachel Terry
Advocate News Staff
The I-270 construction project is intended to replace the Chain of Rocks Bridge that carries the interstate over the Mississippi River, connecting Madison County with St. Louis. According to IDOT, Phase II of the project, consisting of preparing contract plans and acquiring right-of-way, is underway. Construction will be the third and final phase of the project.
The current Chain of Rocks Bridge was constructed in 1966, is composed of 43 spans, and has a total length of over 5,400 feet. The bridge carries 4 lanes of traffic, 2 in each direction. In addition to previous repairs, IDOT reports, the bridge has seen a significant increase in traffic. In 1975, there was a projected average daily traffic of 19,800 vehicles, but the bridge now sees over 51,000 vehicles a day now. Approximately 17 percent of those vehicles are trucks.
IDOT reports that the selected alternative is to build two new twin bridges, “one on the same alignment as the existing Chain of Rocks bridge, and one directly south of the existing Chain of Rocks bridge. The new bridges will provide inside and outside shoulders that will be wide enough to accommodate a stalled vehicle or emergency responders responding to an accident. These will be much wider compared to the 1-foot shoulders that exist today.” The bridges will also reportedly be wide enough to accommodate future expansion of I-270. According to IDOT, “While I-270 is currently four lanes, MoDOT has completed a study for I-270 in Missouri that proposed expanding I-270 to six lanes up to Riverview Drive in Missouri. Similarly, IDOT has recently initiated a study to potentially expand I-270 to six lanes from Missouri to Illinois Route 157.”
The project may result in “occasional short-term off-peak lane closures”, but IDOT says their goal is to keep 4 lanes of traffic open to the public during all stages of construction. The southern bridge is scheduled to be built first. “Traffic will be shifted to the southern bridge before removing the existing Chain of Rocks bridge,” IDOT reports, “Once the bridge is demolished, the construction of the northern bridge will begin and be constructed in the same location as the current bridge.”