and successful fight to prevent disaster. In 1992, a cable television employee in the tunnel underneath the Chicago River videotaped mud and water oozing in where the bottom of the wooden pilings had cracked the tunnel wall. The pilings making up the dolphin had been driven only a few feet from the side of the tunnel, and the wooden pilings were visible through the collapsed tunnel wall where wet clay had slumped away from the wood into the tunnel. Official response to the reported leak was slow; no emergency measures were deemed necessary, and a formal bidding process began for the contract to repair the damage. On April 13, some six months later, the slow oozing of wet clay opened a clear passage from the riverbed, allowing the river to pour directly into the tunnel. In what became known as the Chicago Flood, the entire system was quickly flooded. The Merchandise Mart was the first victim, declaring a water emergency at 5:57 am. City Hall began to flood by 6:02 am, the Federal Reserve Bank at 8:29 am, finally, the Chicago and Hilton Towers at 12:08 pm. The long delay before some buildings were flooded was the result of closure of some sections of the tunnel system in 1942 when the passenger subways were built. Many businesses had not realized that they were still connected to the tunnel complex, as the openings were boarded up, bricked up, or otherwise closed off—but not made watertight. At that point, government agencies belatedly responded. The leak was stopped and the tunnels were emptied within days at great cost. The tunnels are still used for power and communication cables. They have been popular with urban exploration groups who would sometimes sneak in to have a look around, but after a terrorism scare in the early 2000s, all access to the tunnels has been secured. The accident shut down the entire downtown area for days, causing considerable economic losses. 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 some have called it the "Great Chicago Leak." Recent incidents On October 14, 2009, workers pumping concrete into the tunnel under the Kennedy Expressway caused the roadway to buckle, shutting down all but one lane