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After years of hoping and planning, construction begins on new Interstate 270 bridge

An aerial view of the Chain Rocks Bridge and the Mississippi River.
Illinois Department of Transportation
Construction is beginning on “twin” bridges that will replace the existing Chain of Rocks Bridge (Interstate 270) over the Mississippi River between Madison County, Illinois, and St. Louis, Missouri.

Editor's note: This story was originally published in the Belleville News-Democrat.

This week is a milestone for transportation in the St. Louis metropolitan area.

The Missouri Department of Transportation (MoDOT) blocked off the ramp from Riverview Drive in St. Louis to eastbound Interstate 270 to build a new interchange. The ramp will remain closed for more than a year.

Why is that so significant?

It signals that construction is beginning in earnest on a new Chain of Rocks Bridge over the Mississippi River. Missouri and Illinois, which jointly own the existing bridge, have been planning a replacement for years and hoping that funding would become available.

“The first substructures (for the bridge) are expected to be poured later in February,” MoDOT officials stated last week when announcing the ramp closure.

The contractor is Walsh Construction, headquartered in Chicago with regional offices throughout the United States, which already has been making construction preparations on the river’s bank.

The new bridge will actually be “twin” bridges, one on the same alignment as the existing bridge and one directly south of it, according to an overview on the Illinois Department of Transportation website.

A longstanding complaint about the existing bridge is that its 1-foot-wide shoulders keep first responders from quickly reaching accidents and motorists from pulling over with mechanical problems.

Plans call for wide shoulders on either side of the new bridge’s four lanes.

“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,” according to an overview on the Illinois Department of Transportation’s website.

“Similarly, IDOT has recently initiated a study to potentially expand I-270 to six lanes from Missouri to Illinois Route 157. The Chain of Rocks bridge, as currently proposed, will be wide enough to accommodate the future six lanes when they are needed.”

Interstate 270 is not only a highway for passenger vehicles, it’s a major freight-hauling route in a region that has evolved into a key distribution hub for Amazon and other companies.

The existing Chain of Rocks Bridge was built in 1966. It’s a little more than a mile long.

By 2018, IDOT was reporting that an average 51,000 vehicles were crossing the bridge each day (up from 19,800 in 1975), many more than it was designed to handle.

IDOT is the lead agency in construction of the new bridge. In 2020, officials estimated the cost at $246 million with a completion date of 2025.

“While there may be occasional short term off peak lane closures, IDOT’s goal is to keep four lanes of traffic open to the public during all stages of construction,” according to the overview.

“The southern bridge will be constructed first. Traffic will be shifted to the southern bridge before removing the existing Chain of Rocks bridge. Once the bridge is demolished, the construction of the northern bridge will begin and be constructed in the same location as the current bridge.”

MoBot closed the eastbound ramp from Riverview Drive at 7 a.m. Tuesday.

Motorists heading to Illinois now have to go west on Interstate 270, exit at Lilac Avenue, cross the Lilac Avenue bridge and take the eastbound ramp onto 270 at that point. The detour is about 2 miles.

Teri Maddox is a reporter with the Belleville News-Democrat, a news partner of St. Louis Public Radio.

Teri Maddox is a reporter with the Belleville News Democrat, a news partner of St. Louis Public Radio.

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