Illinois Route 23 Interchange on I-90

Firm: H.R. Green, Inc. & Stantec Consulting Services Inc.

Other Consultants: Strand Associates, McCleary Engineering, inVISION Studios, Gonzalez Companies, LLC, DB Sterlin Consultants Inc., J.A. Watts, Inc., Gulaid Consulting Engineers, P.C., Material Solutions Laboratory Corp., Bravo Company Engineering

Owner: Illinois Tollway

Description:In December 2019, the Illinois Tollway delivered a long-awaited interchange in McHenry County at Illinois Route 23 on the Jane Addams Memorial Tollway (I-90) featuring roundabouts and all-electronic tolling at the I-90 exit and entrance ramps to improve safety and mobility.

I-90 is the only interstate that cuts through McHenry County and the new interchange at Illinois Route 23 is the county’s first. The interchange gives the City of Marengo, a rural community 60 miles west of Chicago, and surrounding communities direct access to I-90, which has the potential to stimulate economic growth along the Illinois Route 23 corridor. This strategic location provides much-needed access in the middle of what was a 17-mile gap between the two closest interchanges on I-90.

The Illinois Route 23 Interchange on I-90 is the result of years of planning, study, and cooperation through a partnership among the Illinois Tollway, the Illinois Department of Transportation, the McHenry County Division of Transportation and Marengo. After multiple studies, the Illinois Tollway and its agency partners moved forward with a partial cloverleaf interchange, a standard interchange layout. What makes this interchange unique are the roundabouts at the ramp termini. Roundabouts are in use throughout Illinois, but this is the first use of roundabouts at an interstate interchange in Illinois.

HR Green and its team assisted with the planning stages and provided the Phase I and Phase II engineering services. The Phase II engineering services included contract plans, cost estimates and specifications to meet not only Illinois Tollway requirements, but those of partner agencies, as well. This included developing a robust public involvement program, using 3D video to educate customers and showing how oversized, overweight trucks would navigate the roundabouts.

Stantec’s contribution consisted of the Phase III construction management services as the Illinois Tollway’s representative during the construction of the interchange and roundabouts. Stantec’s responsibilities included contract administration, establishing controls, engineering and inspection, monitoring costs and schedule, measuring and documenting pay quantities, layout verification, monitoring staging and maintenance of traffic, on-site material and quality assurance testing, utility coordination, project documentation and close-out. Stantec was able to accommodate various Phase III challenges, including the management of a large amount of excavated material with unsuitable soils in the infield. Additionally, the roundabouts were redesigned during construction to accommodate the movement of larger-than-anticipated trucks, specifically those used to transport wind turbine blades.

Illinois Tollway

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