Chicago Flood
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The Chicago Flood began on April 13, 1992, when a hole was punched through the bottom of the Chicago River into abandoned utility tunnels causing a leak which eventually flooded basements and underground facilities in much of the Chicago Loop.
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[edit] Cause
Rehabilitation work on the Kinzie Street bridge crossing the Chicago River required new pilings. Unknown to work crews aboard a barge operated by the Great Lakes Dredge and Dock Company, beneath the river was a Chicago Tunnel Company tunnel, used in the early twentieth century to transport coal and goods, and now abandoned. 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. After some weeks, all the soft mud had passed, opening a leak. To this day there remains contention as to whether the mistake was the fault of the workers on-site, their parent company, or the faulty maps provided by the city of Chicago which failed to accurately depict the old tunnel systems. In fact, the Kinzie St. river crossing did not descend as deeply under the river as any of the other crossings. When passing through any of the other crossings, the slope was quite unmistakable, whereas the Kinzie St. crossing offers no hint to a person inside the tunnel that they were passing under the river. So the stage was set for the disaster when the tunnels were originally constructed. Also, the other river crossing contained bulkheads while Kinzie St. did not -- although the bulkheads which would have been useless anyway due to the thinwall construction of the crossing. It was easy to mistake when one had crossed under the river at Kinzie for this reason as well.
Unauthorized tunnel explorers had discovered the leak in mid-January, and considered notifying the city, but the obvious liabilty of admitting illegal access kept them silent[citation needed].
A telecommunications worker inspecting a cable running through the tunnel discovered the leak and forwarded a videotape to the city, which did not see anything serious and began a bid process to repair the tunnels, which were never formally a public responsibility (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 was able to pour in unabated, creating an unmistakable emergency.
[edit] Effects
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 and the Chicago Mercantile Exchange ended in mid-morning as water seeped into their basements. At its height, some buildings had 40 feet (12 m) of water in their lower levels. When fish were found in the water, it became more clear what the problem was. Where the subways built in the 1940s had passed through areas with the freight tunnels, the freight tunnels were sealed off with concrete. At least one of these walls contained a one foot-by-two foot crack, and water began to fill the subways as well.
[edit] Repair and cleanup
Workers attempted to plug the car-sized hole with 65 truckloads of rocks and cement as well as mattresses. The Army Corps of Engineers flew up mine divers from Kentucky to work on sealing the hole. 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 a private contracting company Kenny Construction.
[edit] Aftermath
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.
