Major interchange project moves forward
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MOUNT VERNON — Work is already ongoing for the State of Illinois’ massive reconstruction project at the I-57/64 interchange at Illinois 15 in Mount Vernon, but motorists shouldn’t notice any significant closures or traffic disruptions until next summer.
Carrie Nelsen, P.E., program development engineer for District 9 of the Illinois Department of Transportation, was the guest speaker at Tuesday’s Mount Vernon Rotary Club meeting at Joe’s Pizza. During her presentation, she provided updates on the timeline of the I-57/64 project, and also discussed upcoming ramp closures and other aspects of the interchange reconstruction.
The poor condition of the current Illinois 15 bridge at that site prompted the state to pursue a major multi-year project to transform it into a “Diverging Diamond Interchange.” This is a traffic interchange design that moves the traffic on a local road to the opposite side of the road at the on- and off-ramps, online sources state. This gets rid of left turns across oncoming traffic, which increases safety by reducing conflict points and improves efficiency by reducing traffic delay, online sources state. A similar type of interchange was done in Marion.
“When it’s complete, Illinois 15 will have three lanes in each direction and will have a shared-use path,” Nelsen said, later adding, “It’s a modern interchange type. (The department) is building quite a few of these.”
For the first year of the project, 2025, there has been very little impact to traffic because Illinois 15 is still being used and the ramps are still being utilized. The proposed new Illinois 15 bridge over I-57/64 and the embankment can be built while traffic is fully using the existing Illinois 15 bridge.
“So our new bridge is going to be just south of the old bridge,” Nelsen said. “That way, we can maintain two lanes of traffic on Illinois 15 while we’re in construction.”
Illinois 15 is currently open to traffic but may see some nighttime lane closures starting soon. The first major closure, though, will likely occur in the summer of 2026 when the north leg of Potomac Boulevard is partially closed for 21 days while the intersection is rebuilt. Traffic will still be able to get into Potomac during that time but motorists will have to use a marked detour to get back out, Nelsen said.
Furthermore, in the summer of 2026, there will also be a 21-day closure at 45th Street to rebuild that intersection. Similarly, traffic will be able to enter the road from Illinois 15 but will have to use a detour to get back out.
Then in the fall of 2026, there will start to be ramp closures so the ramps can be tied into the new interchange. The ramps on the south side of the interchange will be done first and each will have a four-week closure, Nelsen said. Once those ramps are done, half of the new bridge will be put in place, with two lanes open in each direction.
In 2027, the two north ramps will have to be closed for four-week periods and new bridge construction will continue. The tentative completion date for the project is Nov. 15, 2027, Nelsen said.
Nelsen’s presentation Tuesday also included information on other significant IDOT projects in Jefferson County. She works out of the Carbondale IDOT office and her district, District 9, takes care of state roadways in the southern 16 counties, a total of 1,462 miles of roadway.
In 2023, 2024, and 2025, the state had a total of about $1 billion worth of road construction going on in the southern 16 counties, Nelsen said.
“And that’s a really good thing for our infrastructure in our region,” Nelsen said.
Brandon Bullard, president of the Mount Vernon Rotary Club, said his club was happy to bring Nelsen to town once again to discuss this major project. The public is invited to come to the Rotary Club’s weekly Tuesday meetings at noon at Joe’s Pizza. Next Tuesday will feature a speaker from the new Sugar Camp Trade School in Mount Vernon.
“It’s our pleasure to bring her to our community to discuss this, and really this is kind of what we do each week,” Bullard said, later adding, “So I would encourage any readers that want to take part in our group – it’s a fun group, we have lunch, we have guest speakers each week, and it’s at noon on Tuesday at Joe’s Pizza. We’d love to have you.”
