The Chicago River Flood of 1992.

On April 13, 1992, the Chicago River mysteriously sprung an underground leak that flooded subways and basements across the Chicago Loop with up to 40 feet of fishy water. People were evacuated, and the power went off while a mass of debris quietly began swirling in the river, directly above a breach in Chicago’s historic underground freight railway network.

Lying 40 feet underground, the railway network once linked four public stations and many large businesses in The Loop. Over the years, the tunnels supplied telecommunications, delivered coal, transported mail, and took excavation debris to the shore of Lake Michigan, where it was used to create the land under Grant Park, Soldier Field and McCormick Place.

In the early twentieth century, buildings were constructed with deep foundations to access these handy waterproofed tunnels directly (and possibly illegally).

Unfortunately, after the tunnels were abandoned in 1959, the redundant access shafts were mostly bricked up and forgotten about. At least, this was the case until the early hours of the 13th when the basements of City Hall, The Merchandise Mart, Chicago Hilton and Towers, the Federal Reserve Bank, and many other business district buildings and subways began to flood.

It was decided that the breached section of the tunnel underneath the river had been slowly deteriorating under pressure created by a piling being driven too close to the tunnel wall during remedial work on the Kinzie Street Bridge back in 1991. 

Pumping dirty river water from Marshall Field's flooded basement.

Allegedly, urban explorers had noticed what was initially a small leak inside the tunnel, which had been reported during a cable inspection. There was a delay in deciding who would fix it.

Chicago’s resulting flood (or ‘leak‘ as it was called for insurance purposes) caused around $1.9 billion worth of damage. After attempting to close the breach by dropping rocks from above, the tunnels were drained, drilled, and plugged. To prevent further problems, the section underneath the river was eventually sealed off from the rest of the network, and the tunnels have since been secured after a terrorist threat.

Compiled by Dr. Neil Gale, Ph.D.