HEAVY HIGHWAY CONSTRUCTION

I-57 / I-64 AT
ILLINOIS 15

Rebuilding one of Mt. Vernon’s key interchanges with a new diverging diamond design, replacement overpass and upgraded ramps built to improve safety and traffic flow.

Location

Mt. Vernon, Illinois

Division

Heavy Highway Construction

Size

Approx. 0.55 Miles

Completion

Expected 2027

Project Overview

The I-57/I-64 interchange at Illinois 15 is a major connection point on the west side of Mt. Vernon, bringing together two interstate corridors and one of the city’s primary east-west routes. Years of planning identified the need to improve capacity, traffic flow and safety at the existing interchange as travel demands continued to grow.

E.T. Simonds Construction is reconstructing the existing interchange into a diverging diamond interchange, replacing the Illinois 15 bridge over I-57/I-64 and rebuilding the associated approaches and ramps. The project also includes improvements along Illinois 15 from Potomac Boulevard/45th Street to 44th Street.

The broader work includes concrete pavement and shoulders, curb and gutter, medians, sidewalk, storm sewer, culverts, grading, pavement markings, sign structures and landscaping.

PROJECT SNAPSHOT

Reconstructing the existing interchange as a diverging diamond

Replacing the Illinois 15 overpass structure

Reconstructing interchange ramps and roadway approaches

Improving intersections along Illinois 15

Upgrading pavement, drainage, signals, lighting and signage

Adding pedestrian and bicycle accommodations

BUILT TO SOLVE THE
PROBLEM AT ITS SOURCE

Our Approach

The challenge goes beyond replacing a bridge. Crews are rebuilding an active interchange at the intersection of I-57, I-64 and Illinois 15 while maintaining access through one of Mt. Vernon’s most important transportation corridors.

Construction is being completed in stages so the interstate ramps and Illinois 15 can remain open through most of the project. Traffic patterns shift as work progresses, with shorter overnight closures scheduled when operations cannot safely take place above live interstate traffic. IDOT planned the project specifically around staged construction and limited short-term or overnight closures.

One of the project’s major milestones came during structural steel placement for the new Illinois 15 overpass in June 2026. Interstate traffic was diverted overnight through the interchange ramps while crews worked above I-57. The E.T. Simonds project draft describes the bridge operation as a coordinated multi-night effort involving up to five cranes, with the new structure constructed alongside the existing bridge to help maintain traffic during construction.

The new diverging diamond configuration is designed to reduce the number of conflict points at the interchange ramps, improve traffic flow and provide safer movement through the Illinois 15 corridor.

PROJECT GALLERY

BUILDING THE NEW INTERCHANGE

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OUTCOME

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When complete, the reconstructed interchange will replace the existing configuration with a diverging diamond designed to improve traffic flow, increase capacity and reduce conflict points where vehicles enter and exit the interstate.

The project will also deliver a new Illinois 15 overpass, reconstructed ramps and approaches, updated traffic signals and lighting, improved drainage and accommodations for pedestrians and bicycles. Together, those improvements are designed to create a safer and more efficient connection between Illinois 15, I-57 and I-64.

WHAT WE DELIVERED

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New Illinois 15 overpass

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Diverging diamond interchange

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Reconstructed interstate ramps and approaches

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New pavement and drainage infrastructure

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Updated traffic signals, lighting and signage

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Improved pedestrian and bicycle access

“This is the kind of project where every phase has to work together. We’re rebuilding a major regional connection while keeping traffic moving, and that takes a lot of coordination from the crews in the field.”

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Beck Simonds

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President, E.T. Simonds Construction