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Project Summary

The I-70 Cave Springs to Fairgrounds project is a Design-Build project that will make improvements to increase safety, make the interchanges smoother to move through and support local access.

Project Map

Click to enlarge map of I-70

Project Goals

  1. Maximize improvements within the program budget of $62 million.
  2. Improve safety and efficiency of the transportation network while supporting connectivity for the local community.
  3. Provide a durable and maintainable transportation infrastructure allowing for future expansion.
  4. Minimize impacts to the traveling public during construction while safely delivering the project by November 1, 2023.
  5. Deliver the project using a diverse workforce.

Corridor Issues

Infrastructure upgrades are needed because the population of St. Charles County is nearly three times what it was in 1980 when these interchanges were built.


The Cave Springs and Zumbehl interchanges often experience traffic jams making it tough for traffic to flow through the area. During the morning rush, vehicles crossing the interchange average a speed of 18 mph on Zumbehl Road and 7 mph on Cave Springs.


These delays cause traffic to back up onto I-70, creating a serious risk to safety. The interchanges have a higher than average crash rate. Between 2013 and 2017 the average crash rate in the area was more than 40% above the statewide average rate.


An interstate system includes outer roads, interchanges and the interstate. In this area, a section of the north outer road is missing, and Veterans Memorial Pkwy is disconnected by a large island at Cave Springs. This design makes it difficult to navigate the area.

Planning Vision

The need for this project came from the I-70 Planning and Environmental Linkage Study (I-70 PEL) completed in 2018. The PEL identified the following major strategies to address the issues in the area:

envision i70 logo
  • Upgrade infrastructure to better accommodate freight
  • Improve local/parallel road systems
  • Reduce/eliminate conflict points at interchanges
  • Improve interchange operations
  • Add/improve bicycle & pedestrian facilities

More information about the PEL, including the full report can be found here. The I-70 Cave Springs to Fairgrounds Project falls in Sections 2 and 3.

Possible Solutions to Fix Problems

Diverging Diamond Interchanges (DDI)

  • Handles heavy left turn movements efficiently
  • Reduces conflict points to improve safety
  • Uses current lanes without additional signals

Single-Point Urban Interchange (SPUI)

  • Fits within existing Right of Way
  • Reduces signals to improve traffic flow
  • Accommodates large trucks more easily

Flashing Yellow Left Turn Arrows

  • Reduces crashes
  • Increases opportunities to turn left
  • Handles more traffic safely


  • Moves traffic efficiently without signals
  • Reduces severity of crashes
  • Slows vehicles, improving safety

One-Way Outer Road

  • Improves safety by reducing congestion
  • Reduces travel time in congested areas
  • Moves traffic from interstate to outer roads

Two-Way Outer Roads

  • Allows for conventional traffic movement
  • Reduces travel distance
  • Decreases traffic on the outer roads

Project Schedule

Cave Springs and Zumbehl Interchange Study completed by City of St. Charles.

I-70 Planning and Environmental Linkages (PEL) Study from Wentzville to Mississippi River completed.

I-70 from Cave Springs to Fairgrounds identified as regional priority and MoDOT funds this project in the 2020-2024 Statewide Transportation Improvement Program (STIP).

Project designated as Design-Build and project team formed.

Winter 2021
MoDOT delays project to engage with the public.
To see the video of the virtual open house` held before the project was paused click here.

Fall 2021
Project awarded to the Best Value Proposer.

Spring 2022
Construction will begin.

Fall 2023
Project will be complete.

Funding Information

Total project cost is 62 million dollars. 52 million comes from MODOT at 85 percent. 10 million dollars comes from Saint charles county.

Diversity Goals

Disadvantaged Business Enterprise (DBE) Goals

14% for construction activities

20% for professional service activities

Federal Workforce Diversity Goals

14.7% Minority

6.9% Female