On 13 April 1992, a hole opened under the Kinzie Street Bridge and drowned Chicago's Loop:
During the Great Chicago Flood of 1992, 250,000 gallons of water had the city drowning by the hour.
The leak that sprung in the old freight tunnels under the city quickly turned into a major flood often referred to as the "unseen catastrophe.”
It was a calamity that filled the basements of buildings on State Street, LaSalle Street and even the Merchandise Mart. Water rose to 7 feet, then 10 feet and up. It cut power and evacuated trading floors at the Board of Trade and the Mercantile Exchange. It closed major retails stores like Marshall Fields and even left the Merchandise Mart wet and flooded.
Water poured in from the bottom up. But where was it coming from?
Back in September of 1991, wood pilings were driven into the Chicago River to act as bumpers for the Kinzie bridge house so passing boats wouldn't knock it over. Story has it, the contractor hired to install the pilings hit an underground freight tunnel in the process creating a slow leak that got bigger and bigger with time until the tunnel gave way seven months later: April 13th, 1992.
Historian J.R. Schmidt has more:
It was an odd disaster. At street level, everything looked as it always had. Officials assured the public that the situation was under control. Governor Jim Edgar met with Mayor Richard M. Daley at City Hall. Afterward the governor told reporters there was no need to call out the National Guard.
About 11 a.m. the river locks were opened. That let the Chicago River resume its natural course into Lake Michigan. The water in the tunnels continued to rise, but more slowly.
By evening the water level had finally stabilized. Now the cleaning up and pumping out began. It would take weeks. A private contractor finally had to be brought in to seal the original leak at Kinzie Street.
The water emergency was expensive. Some estimates place the price tag for damaged goods, repair costs, and lost business at over $100,000,000. For insurance reasons, the event is officially classified as a “leak.” But no matter what name is used, those who experienced it firsthand often echo the reaction of their mayor—“What a day!”
Public transit services shined that day, evacuating about a million people from downtown in only a few hours with no injuries or crime.