I-70 Fifth Street Reconstruction

St. Charles County Transportation Department


Horner & Shifrin led a design team in an effort to increase access along Interstate 70 from Fifth Street to Route 94 and improve traffic flow throughout the project area. Major responsibilities included conceptual design, extensive public involvement, a Design Report, Access Justification Report and final plans, specifications and estimates (PS&E) production for 1.5 miles of roadway in St. Charles County. The project was completed on an aggressive schedule to meet funding milestones.

The project included the conversion of Fifth Street under I-70 to a diverging diamond interchange (DDI) and creating a new interstate interchange at Fairgrounds Road. H&S designed a roundabout for the Fairgrounds/Veterans Memorial Parkway intersection and converted a portion of the two-way outer road to a one-way outer road south of I-70. Plans also included adding an additional lane along the interstate corridor at Route 94, designing two bridges, and improving pedestrian access in the area.

Horner & Shifrin continuously coordinated with the client, St. Charles County, as well as other state and local agencies throughout the conceptual design process. This coordination ensured the proposed concept was an agreeable design for all parties involved, while maximizing key factors like access and safety.



Project Components



Site Size

1.5 miles


St. Charles, Missouri

Year Completed


Innovation. Agility.
Reliability. Horner & Shifrin.