The person who supervised the massive and complex cleanup at the World Trade Center following the terrorist attacks was—what else? An engineer.

- By Warren Cohen

Peter Rinaldi nods to the guards in front of the tall, chain-link fence. They allow him to pass through the gate. Inside, a huge canyon stretches for blocks and American flags hang everywhere. On Sept. 11, 2001, when terrorists flew two commercial jetliners into the twin towers of New York's World Trade Center and obliterated them, Rinaldi was on vacation. That holiday break probably saved his life. Rinaldi, 54, is an engineer for the Port Authority of New York and New Jersey. His offices were on the 72nd floor of the North Tower.

Rinaldi had precious little time to reflect on his fate. He was named lead engineer and oversaw the recovery and cleanup of the WTC, managing a team of some 100 engineers and demolition experts. Rescuers were still frantic that survivors might be buried in the ruins, and the police and fire departments wanted to recover their dead comrades. But the dangerous conditions threatened to take more lives. “It was unprecedented complexity,” Rinaldi says. “We were learning as we went.”

The rubble resembled a giant game of pick-up sticks, Rinaldi says, with debris and steel building walls tangled up to 250 feet in the air across a length equivalent to three and a half football fields. Rinaldi and other engineers risked their lives while tunneling beneath the surface through smoldering, partially collapsed basement floors, and floating through flooded train tunnels on rubber rafts. He recalls seeing five stories of the North Tower, with layers of floor, rug, cement, and steel compressed into 2 feet, looking like soil stratum. But the forays underground were necessary to diagram maps of the disaster to indicate dangerous zones.

Those maps helped identify dangers that could have thwarted the cleanup, such as a potential collapse of the 70-foot-deep concrete walls that held back groundwater. Nearly nine months and 108,342 truckloads of debris later, a final steel column was removed from ground zero, completing the cleanup phase. But there is still much to do. Now Rinaldi is helping solidify the foundation that will house the new buildings that will rise from the ashes of the twin towers.

The Bronx native majored in civil engineering at Manhattan College. He later earned a graduate degree at Polytechnic Institute in Brooklyn, where he specialized in geotechnical engineering, which has to do with foundations, soil mechanics, and earthworks. His interest stemmed from the fact that soil, rock, and water don't have the same predictable behaviors as manufactured materials like concrete and steel. “There was room for judgment and creativity,” he says.

After graduating, Rinaldi served as an adjunct professor for many years at Manhattan College, teaching soil mechanics and fluids as well as classes in earth pressures and retaining structures. But the demands of his job with the Port Authority became too much and he gave up teaching about 15 years ago.

The trade center site was too dangerous to allow engineering students to view the cleanup efforts until most of the debris was removed. But now classes are starting to come. Since buildings are rarely “unbuilt” in such a violent manner, Rinaldi says the disaster is unlikely to ever make a university case study, but there are lessons for students to learn from the experience. “It's probably unique in terms of the circumstances,” he says, “but not so unique in the skills and experiences you need to have.”

Firefighters and police have been widely hailed for their bravery during the response to the disaster, but engineers played a crucial role, too. Unlike precise, methodical desk-bound engineering, this job required engineering in action. “What we had to do was not found in engineering books,” says Rinaldi. “We needed experience, intuition, and analysis, and a lot of professional judgment.” Thanks to his experience and training, no lives were lost during the recovery efforts.

 

Warren Cohen is a freelance writer based in New York City.
He can be reached at wcohen@asee.org.