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The Chicago flood occurred on April 13, 1992, when the damaged wall of a utility tunnel beneath the Chicago River opened into a breach which flooded basements and underground facilities throughout the Chicago Loop with an estimated 250 million US gallons (950,000 m3) of water.
Rehabilitation work on the Kinzie Street Bridge crossing the Chicago River required new pilings.[clarification needed] Unbeknownst to work crews aboard a barge operated by the Great Lakes Dredge and Dock Company, beneath the river was an abandoned Chicago Tunnel Company tunnel that had been used in the early 20th century to transport coal and goods. One of the pilings on the east bank was driven into the bottom of the river alongside the north wall of the old tunnel. Although the piling did not actually punch through the tunnel wall, it caused pressure that cracked the wall, and mud began to ooze in.[clarification needed] After some weeks, all the soft mud had passed, opening a leak. The situation was very serious because the flood doors had been removed from the old tunnels after they fell into disuse.
Discovery of the leak 
A telecommunications worker inspecting a cable running through the tunnel discovered the leak while it was still passing mud and forwarded a videotape to the city, which did not see anything serious and began a bid process to repair the tunnel. The CTC tunnels were never formally a public responsibility, as most of them had been dug clandestinely, many violated private property, and the collapse of the operator had failed to resolve ownership and maintenance responsibilities. Meanwhile the mud continued to push through until the river water was able to pour in unabated, creating an unmistakable emergency.
The water flooded into the basements of several Loop office buildings and retail stores and an underground shopping district. The city quickly evacuated the Loop and financial district in fear that electrical wires could short out. Electrical power and natural gas went down or were shut off as a precaution in much of the area. Trading at both the Chicago Board of Trade Building and the Chicago Mercantile Exchange ended in mid-morning, having a global effect, as water seeped into their basements. At its height, some buildings had 40 feet (12 m) of water in their lower levels. However, at the street level there was no water to be seen, as it was all underground.
At first, the source of the water was unclear. WMAQ radio reporter Larry Langford reported that city crews were in the process of shutting down large water mains to see if the water flow could be stopped.
Langford was monitoring police scanners and overheard security crews from Chicago's Merchandise Mart report that they had several feet of water in the basement and were seeing fish in the water that was in the basements. Langford drove to the Merchandise Mart, which is located near the Kinzie Street Bridge, and reported on WMAQ that he saw water swirling near a piling in a manner that resembled water going down the drain of a bathtub. The swirl had a generous amount of small debris spinning in it. His exact words on WMAQ were:
- "I have found something very interesting in the Chicago River on the east side of the Kinzie Bridge. I see swirling water that looks like a giant drain ... I would say it looks like the source of the water could be the river itself, and I am hearing reports that fish are swimming in the basement of the Mart just feet from the swirl! I do not see any emergency crews near this spinning swirl, but I think they may want to take a look. In fact, I think someone should wake up the mayor!" Within minutes of that report hitting the airwaves, a battery of city trucks, police, and fire vehicles converged on the bridge.
Repair and cleanup 
Workers attempted to plug the hole, by then about 20 feet (6.1 m) wide, with 65 truckloads of rocks, cement and old mattresses. In an attempt to slow the leak, the level of the Chicago River was lowered by closing the locks at Lake Michigan and opening them downstream of Chicago, and the freight tunnels were drained into the Chicago Deep Tunnel system. The leak was eventually stopped by Kenny Construction, a private contracting company, by drilling shafts into the flooded tunnel near Kinzie Street and placing emergency plugs in it.
It took three days before the flood was cleaned up enough to allow business to begin to resume and cost the city an estimated $1.95 billion. Some buildings remained closed for a few weeks. Parking was banned downtown during the cleanup and some subway routes were temporarily closed or rerouted. Since it occurred near Tax Day, the IRS granted natural disaster extensions to those affected.
Eventually, the city assumed maintenance responsibility for the tunnels, and watertight hatches were installed at the river crossings.
Insurance battles lasted for years, the central point being the definition of the accident, i.e., whether it was a "flood" or a "leak." Leaks were covered by insurance, while floods were not. Eventually it was classified as a leak, which is why many residents still call it the "Great Chicago Leak."
Today, there remains contention as to whether the mistake was the fault of the workers on-site, their parent company, or even the claim that maps provided by the city of Chicago failed to accurately depict the old tunnel systems. In fact, the Kinzie Street river crossing was clearly delineated on the city maps: the typical tunnel ran down the center of the old streets. At Kinzie Street, like some of the other river crossings, veered off to the side as the historic Kinzie bridge (at the time of the tunnel construction) was a pivoting bridge with a central pivot in the middle of the street. Thus the original tunnels were moved to the side, as were several other bridges across the Chicago River - shown in detail on the city maps.
Court cases 
In the lawsuits that followed Great Lakes was initially found liable but was later cleared after it was revealed that the city was aware the tunnel was leaking before the flood and the city had also not properly maintained the tunnel.
In addition the case went the United States Supreme Court in Jerome B. Grubart, Inc. v. Great Lakes Dredge & Dock Co. - 513 U.S. 527 (1994) which ruled that since the work was being done by a vessel in navigable waters of the Chicago River, Admiralty law applied and Great Lakes liability was greatly limited.
- "1992 Loop Flood Brings Chaos, Billions In Losses". CBS2 Chicago. 2007-04-14. Archived from the original on 2007-09-27. Retrieved 2008-01-11.
- "Great Chicago Flood of 1992". Kenny Construction Company. Archived from the original on 2008-01-01. Retrieved 2008-01-11.
- "The Mix". Chicago Sun Times. October 9, 1992. Retrieved 12 July 2012.
- Powers, Richard (2009). "Soaked". Granta 108. Granta.
- Bullett, Karla (1992-04-14). "US Army Corps of Engineers responds to strange flood". Chicago District. Archived from the original on 2008-06-07.