Chicago Flood of 1992 - Chicago River Breached

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 gallons of water. Rehabilitation work on the Kinzie Street Bridge crossing the Chicago River required new pilings. 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 twentieth 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. After some weeks, all the soft mud had passed, opening a 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 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 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.

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. The public notification of the source of the leak also makes for an interesting story. One of the all-news radio stations had the information before the city could pinpoint the source. At about dawn, WMAQ radio began reporting that crews were being dispatched to some downtown buildings on reports of flooding.

WMAQ reporter Larry Langford, who was that station's overnight crime reporter and was known to cover all overnight police and fire activity for that station, headed downtown and with his bank of scanner radios, starting monitoring various conversations. He reported that several of the buildings affected were along State Street. He reported that City crews were searching for the leak and were in the process of shutting down large water mains to see if the flow could be stopped. One such main was a 42-inch (1,100 mm) pipe under LaSalle Street.

At about the same time Langford heard 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. Langford drove to the Merchandise Mart which is located near the Kinzie Street Bridge. He looked at the deserted area near the bridge and reported on WMAQ that he saw a water swirl near a piling that resembled the pattern of 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 on WMAQ, a battery of city trucks, police and fire vehicles converged on what had been the empty parking areas near the bridge. Langford was the first to figure out the source of the leak. Langford retired from WMAQ in 2000 after that station converted to sports radio station WSCR and became the director of Media Affairs for the Chicago Fire Department.

Workers attempted to plug the hole, by then about 20 feet (6.1 m) wide, with 65 truckloads of rocks and cement as well as 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 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 the faulty maps provided by the city of Chicago which failed to accurately depict the old tunnel systems. In fact, the Kinzie Street river crossing did not descend as deeply under the river as any of the other crossings.

On April 13, 1992, adjacent construction tore a 20-foot-long hole through the wall of a tunnel 20 feet beneath the bed of the Chicago River, some 50 feet beneath downtown Chicago. Over 200 million gallons of water surged through an extensive series of underground tunnels, affecting more than 30 major buildings, including City Hall and the financial markets. Lower levels of major office high-rises held up to 40 feet of water, and the city center was evacuated out of fear that electrical or utility connection failures could endanger lives.

Exponent geotechnical, structural and materials engineers performed an investigation to help determine the cause of the accident. It was determined that, in 1991, workers were replacing wooden pile clusters at a bridge pier and apparently had no knowledge of the existing tunnel system beneath them. Pressure from soil displaced by pile driving collapsed the concrete tunnel wall inwards, exposing clay and new wood piles and allowing mud and water to seep slowly into the tunnel. Many months after the initial damage, the breach abruptly destabilized, allowing the river to flood downtown Chicago and causing estimated damages of $2 billion.

On April 13, 1992, basements and other underground facilities throughout Chicago were flooded with more than 250 million gallons of water from the Chicago River when workers who were driving in pilings in the river near Kinzie Street, punctured a century-old freight tunnel which was connected to dozens of underground areas downtown.