Major Changes Coming to I-70, Mid Rivers Mall Drive Intersection as Construction Begins

Construction on the diverging diamond intersection upgrade at Interstate 70 and Mid Rivers Mall Drive started Monday in St. Peters and is expected to be completed by Oct. 31.

Crews will build a diverging diamond interchange and add an additional lane to westbound Interstate 70. The $13 million project is being paid for with federal, regional and local money. 

This week, crews will build a temporary slip ramp from westbound Interstate 70 to the North Outer Road, which will go to one-way traffic between the slip ramp and Mid Rivers Mall Drive. 

Starting the week of March 18, the loop ramps will be closed, which means drivers exiting from westbound I-70 to Mid Rivers Mall will have to use the slip ramp.

Several additional changes will also go into effect.

Drivers heading northbound on Mid Rivers Mall trying to go westbound on I-70 will be detoured to Highway 79 and then to I-70. 

Drivers heading southbound on Mid Rivers Mall Drive hoping to get on eastbound I-70 will need to be in the left-hand lane instead of the right-hand lane because the loop ramp will be closed. Those drivers would take the South I-70 Outer Road to the slip ramp onto the highway. 

In addition, the exit from Route 370 to Mid Rivers Mall Drive will drop from two lanes to one lane, which could lead to a bottleneck of traffic around rush hour, said Jim Wright, MoDOT engineer for St. Charles County. 

An option would be to take 370 to the Salt River Road to Route 79, he said. 

"During any traffic change there's always about a one- to two-week period of adjustment," Wright said.  

This spring, crews will also widen the bridge and may have to shift lanes around to build support columns in the center of the highway, he said. During the day, a minimum of three lanes will remain open. More lanes may be closed at night. 

Read our earlier story about the project here, or check out the project page from the Missouri Department of Transportation.