Slurry Wall Guru
By Christine McKenna
Foundation engineering is more an art form than a science, explains George Tamaro, 64, a partner at Mueser Rutledge Consulting Engineers (MRCE.) Unlike the superstructure engineer who works with one-eighths of an inch, the foundation engineer the "below-grade guy" may work with inches and feet, allowing for the uncertainties of the geological conditions below ground.
Denied the luxury of such precise calculations, the below-grade guy must sometimes rely more heavily on experience and intuition. This "tolerance for not knowing" served Tamaro well in the unpredictable underground of the World Trade Center after September 11 so much of the recovery and clean-up hinged on the sub-grade conditions. After years stuck in the basement, attention was turned to the below-grade guys to explain the nuances of this tangled, ever-changing terrain.
Tamaro was suddenly in the spotlight.
He laughs at a description of him in a recent article, "Balding and avuncular! Uncle-like!" For the purpose of this profile, he suggests, "I'd prefer Valentino-like." In fact, it is Tamaro's Italian roots and an assignment in Italy that cemented his career as a foundation engineer. A New Jersey native, Tamaro's first language was Italian, learned from his father at the kitchen table. "Otherwise I would have starved to death."
Tamaro took his first trip to Italy in the 1960s, when, as a staff engineer for the Port Authority of New York and New Jersey, he was sent to Rome to study reinforced concrete design with well-known architect Pier Luigi Nervi. There, he was introduced to the slurry wall, "la diaframma," a foundation technology that would figure prominently in his future role at the WTC complex.
In April of 1967, the Port Authority asked Tamaro to be a resident engineer on the World Trade Center, supervising ICOS Corporation of America, an Italian company working on the site's deep basement. The foundations themselves were relatively straightforward, says Tamaro. The towers were to be anchored on Manhattan bedrock, roughly 70 feet down. The tricky part was preventing soil and water from the nearby Hudson from seeping into the eight-block area (four blocks north-south by two blocks east-west.)
"What people don't realize is that the towers were built on an area that was once beneath the Hudson River," says Tamaro. Over centuries, the water line expanded westward, as the river was filled with assorted garbage and debris demolished buildings, vessels parts, and piers. In 1967, the soil surrounding the site was old soft river bottom covered by fill, saturated with water. The slurry wall a three-foot thick, concrete perimeter wall functioned like a "bathtub" except it kept the water out of the 70-feet deep basement beneath the Towers, the Marriott Hotel and the U.S. Customs House.
Sitting in his MRCE office on 34th Street, Tamaro points out artifacts pulled from various New York construction sites: cannon balls, wine bottles, a pulley from a sailing vessel. Tamaro spent a year working at the WTC site and later went to work for ICOS as a Chief Engineer with offices on the 15th floor of the North Tower. "Initially it was the 15th floor but I got nose bleeds so we moved to the 11th," says Tamaro. "I joke around I say I do foundations because I get vertigo if I get above the second floor."
Tamaro became a well-regarded expert in foundations, and a specialist in slurry walls with several patents on the technology. Though he had once aspired to be an architect, decades experience doing "belows" had now sealed his fate as a "mole." A mole, explains Tamaro, is "a subterranean animal that doesn't have eyes and does tunneling." He and about 800 other below-grade guys are members of an association called the Moles; Tamaro was their president in 2001. "I don't know if that implies that I am more blind than the rest," he says.