MoDOT’s overhaul of section of I-70 in St. Charles County underway, Wentzville ‘S Curve’ slated for 2025

ST. LOUIS, Mo. (KMOV) - Several state road projects are in motion in St. Charles County after an increase in the gas tax in 2021 helped pave the way for additional funding.

In St. Charles, crews are currently working on the Cave Springs to Fairgrounds project, a $62 million project made up of state, federal and local funding. The four-mile stretch from just west of the Blanchette Bridge to Cave Springs Road includes the rebuilding of the Zumbehl Road and Cave Springs Road interchanges.

“These are fun projects, you know, but for the last decade or so, we’ve been in maintenance mode,” said Andy Tuerck, a MoDOT Engineer for St. Charles County projects. “The tipping point was the passing of the additional gas tax in 2021 as a major funding source.”

As part of the project, the 40-year-old Cave Springs bridge over I-70 will be replaced with a wider bridge offering a single-point urban interchange, similar to the traffic flow of the interchange at I-70 and Highway 94. Crews are nearing completion of the west side of the new bridge, at which point traffic will be diverted onto the new piece while crews demolish the existing old bridge before beginning work on the final piece of the new bridge.

Additionally, part of the plan calls for a new overpass to be built to allow traffic on Veterans Memorial Parkway to go under Cave Springs Road without stopping at a traffic signal.

“Again, very similar to the interchange at I-70 and Highway 94,” Tuerck said.

The Zumbehl Road bridge over I-70 will also be replaced to accommodate a single-point urban interchange. It will also boast longer exit and on ramps to allow for easier merging.

The two interchanges are slated to be complete by the end of the year. Then, crews will move on to building a new section of the north outer road. The road will end where the existing westbound I-70 westbound off-ramp intersects with Route 94. The intersection will then be widened to accommodate three left turn lanes to southbound 94 and two right lanes to northbound 94, according to MODOT.

Early on in the project, several local business owners along the north outer road between Cave Springs and Zumbehl roads expressed concern at public input sessions about the potential of turning the two-way roads into one-way roads. According to MODOT, all existing outer roads will remain two-way. The project does call for the construction of the new one-way north outer road between Convention Center Blvd. and Route 94.

Tuerck said MoDOT is also eyeing improvements to I-70 near Wentzville, which it hopes to begin the bid process for in the fall. MoDOT hopes to widen I-70 within the “S Curve” stretch between Route Z and Wentzville Parkway.

“The curve itself is not defective,” said Tuerck. “But, the horizontal and vertical clearance as you go under the railroad bridge combined with the fact that it’s only two lanes in both directions just can’t accommodate the traffic congestion we’re seeing.”

The existing railroad bridge has been a major hurdle the department is working to clear. However, Tuerck said MODOT plans to build a new, wider bridge for the railway, allowing for four lanes of traffic in both directions to pass underneath it, with room for more expansion in the future.

“We’ve talked about this being a 150-year project,” he said. “We don’t want people to have to come back and be forced to make more changes, so we want to do this in a way that accounts for future growth.”

To learn more about the Cave Springs to Fairgrounds project, along with future road closure plans, click here.

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