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| Dangers to underground infrastructure London has responded effectively to the disruption of services following terrorist bombings July 7, but the event underscores the need for a careful examination of the vulnerabilities of the underground infrastructure of our cities, says a Cornell University engineer Thomas O'Rourke. O'Rourke described the lessons of 9/11, based on his own research at the site. Communications in New York City were widely disrupted, largely because of damage to the underground infrastructure near the collapsed towers. Broken water mains poured 35, 000 gallons of water per minute into a seven-story underground space, filling it "like a big bathtub" and flooding transportation tunnels all the way to New Jersey. Falling debris smashed into a vault beside the Verizon building just north of the Twin Towers, cutting cables. "What wasn't severed was flooded by millions of gallons of water from the broken water mains, " O'Rourke told his London audience. He predicted that in a major disaster, cell phones would not be helpful for emergency communications because of the overload on the system. The prediction was borne out after the London bombings, he found. What does work besides two-way radio communication, he said, is wireless e-mail through portable devices like the Blackberry. Because e-mail is not a continuous flow of data like voice communication, mail routing is more flexible and able to accommodate heavy traffic more easily.Fortunately, the London bombings did not attack underground infrastructure directly. They were aimed at destroying transit vehicles and tying up the transportation system. But the underground utility systems of large cities remain highly vulnerable to damage. In the Winter Structures Laboratory at Cornell, O'Rourke and Harry Stewart, Cornell professor of computer and electrical engineering, work with lab manager Tim Bond, research associate Mike Palmer, information technology specialist Dave Ash and civil engineering students with massive, computer-controlled hydraulic rams to simulate the effect of earth movements on pipelines and other utility conduits. The lab is part of a chain of testing and research sites called the George E. Brown Jr. Network for Earthquake Engineering Simulation, funded by the National Science Foundation. O'Rourke also is working with Stephen Wicker, Cornell professor of electrical and computer engineering, on ways to distribute remote sensors throughout utility networks to monitor their behavior. Much underground infrastructure is aging and was not designed to handle extreme stress, he has found. For example, he said, about 75 percent of water mains in New York City and Los Angeles are made of brittle cast iron. Newer mains use ductile metals and plastics that have more flexibility. Another problem, O'Rourke said, is that different utilities are often in close proximity. "You can have a major telecommunications line next to a water main next to a high-voltage electric cable, " he said. In 1983, he recalled, a water main broke in the Garment District in New York City, flooding an adjacent electric substation, starting transformer fires that released toxic chemicals. Electricity service in midtown Manhattan was shut down, and along with it the track signaling systems of the subway, paralyzing transit. And all during that week, garment buyers came to town to place their orders for the year. "It cost scores of millions of dollars, all from one 12-inch water line, " O'Rourke said. The problem is aggravated, he said, by the fact that utility companies often don't talk to each another, so workers are not able to locate these dangerous proximities. "We can make them strong where they cross, " he said. "Somebody has to know where they are, but organizations are reluctant to disclose this information." In August, O'Rourke will be off to a conference on resilient infrastructure in New Zealand, where it turns out people do tell each other. "They have evolved to have a more open and communicative arrangement among service providers, " he explained. "They feel a threat from natural hazards, like earthquakes, volcanic action and windstorms. New Zealand is a living laboratory that is scalable to systems here." write your comments about the article :: © 2005 Construction News :: home page |