New Mid Rivers Mall/I-70 bridge coming by Thanksgiving

A new design for the Mid Rivers Mall Drive bridge at I-70 will add a sixth lane and permanently move traffic to the “wrong” side, according to plans unveiled recently by the Missouri Department of Transportation (MoDOT).

The bridge will remain open during the change to a Diverging Diamond Interchange, which shifts traffic to the left lanes as it crosses the bridge then back to the right at the far side.

St. Charles County roads Director John Greifzu said at a MoDOT presentation on Jan. 31, “The goal of the project is have this project open before Thanksgiving. It’s a very quick construction.” MoDOT expects construction to begin in March.

The unique interchange is the first in St. Charles County but the second in the greater St. Louis area, Greifzu said.  The intersection at I-270 and Dorsett Road in St. Louis County also uses the design.

Westbound I-70 traffic exiting onto southbound Mid Rivers Mall Drive will continue onto and across the bridge in the left lanes then cross to the right lanes at the far side.

Similarly, northbound Mid Rivers Mall Drive drivers heading to westbound I-70 will move to the left lanes, cross the bridge, and then take a “free flowing lane” without a traffic light onto the interstate ramp.

All north and southbound Mid Rivers Mall Drive traffic going straight across the bridge will shift left then right.

Greifzu said that with fewer signals and the free flowing lanes, “You reduce the amount of time vehicles are stopped at the intersections.”

I-70 will also get an additional westbound lane from Mid Rivers Mall Drive to Hwy. 79.  The eastbound side gets a new ramp onto Veterans Memorial Parkway just past the Mid Rivers Mall Drive bridge.

Greifzu said the overall project “will help relieve that backup at Mid Rivers Mall Drive that we see every night from 370 and 70 merging together.”

The project will cost an estimated $13 million, which will be shared by MoDOT, St. Charles County, and St. Peters.