A semi-truck hauling hydrochloric acid rolled over on westbound I-90 near Harmony just after midnight Friday, blocking all lanes of the interstate in McHenry County and triggering a hazmat cleanup that stretched into the morning commute. No injuries were reported, and an investigation into the crash was underway.
The crash happened around 12:10 a.m. near milepost 36, according to ABC7 Chicago, which reported that Illinois State Police confirmed the westbound lanes were shut down in the immediate aftermath. The overturned trailer left the interstate completely impassable for travelers heading west through the county overnight, as NBC Chicago reported.
The truck's trailer was carrying hydrochloric acid, prompting hazmat crews to respond to the scene, the station's report notes. CBS News Chicago also covered the overnight rollover and the hazmat response it set off on I-90.
Westbound Drivers Rerouted at IL-23
By 7 a.m., westbound traffic was still being diverted off the interstate at IL-23, per the same account from NBC Chicago. ABC7 Chicago reported that drivers exiting at IL-23 were able to reenter I-90 at the entrance ramp once past the closure, offering commuters a workaround during the morning rush.
No confirmed time for reopening the westbound lanes was available as crews worked to clear the scene. The cause of the rollover had not been determined as the investigation continued.
How Hazmat Spills Are Tracked and Reported
Illinois residents can look up hazardous-material incidents statewide through a system run by the Illinois Emergency Management Agency, according to Illinois.gov, which notes that reports can be searched by incident number, city, county, street address or date. Nationally, the Pipeline and Hazardous Materials Safety Administration compiles statistics on hazmat incidents by type, year and location using data drawn from federal incident report forms, with the dataset updated nightly.
Overturned trucks carrying hazardous chemicals have forced similar highway shutdowns elsewhere in the past year. In Colorado, a leaking semitrailer spilled hydrochloric acid after a commercial vehicle fire on I-70 near Morrison in August 2025, closing parts of that interstate and U.S. 40 in Jefferson County for more than six hours, according to the Denver Post. The Colorado State Patrol reported no crash or injuries in that initial fire and spill, though a second semitrailer later overturned on a nearby road as drivers tried to bypass the closure, spilling fuel and setting off another hazmat response. All lanes on I-70 and U.S. 40 were reopened by 2:30 p.m. that day.
Back in McHenry County, officials had not identified the hazmat agencies or cleanup contractors working the Harmony scene as of the latest reports. Drivers planning westbound trips on I-90 through the area were advised to expect lingering delays while cleanup and the investigation continued.
