By Roland Li
After the towers fell, one of the largest clean-ups in history began. Because the damage was so massive, officials divided the site – referred to as “the pile” – into five zones. Specialists around the country flew in to assist in the efforts, which quickly moved from search-and-rescue to the complete clearing and removal of the debris. For 99 days, fires continue to burn underground, creating noxious fumes and a reminder of the destruction that had occurred.
For many construction workers, it was an unexpected return to a site that they had built decades before.
Arie Moshe, a foreman at WDF, Inc., had worked at the original 7 World Trade Center in 1984, and was at the Related Companies’ Time Warner Center at the time of the attacks. The day after, he and a group of plumbers from WDF began volunteering after work from 3 p.m. until 11 p.m., filling buckets with debris.
“I never thought that I was giving anything, only that so many had lost so much,” he said.
Skansa, the original erectors of the steel beams, began removing the ghostly skin of the Trade Center over two weeks.
“Given Skanska’s history of working at the World Trade Center, we also helped officials leading the clean-up effort by showing them where existing mechanical, electrical and plumbing lines were, and how utility lines interacted with the subway lines,” said Gary Winsper, senior vice president of Skanska USA Civil Northeast.
In May 2002, the last steel beam was removed, three months ahead of schedule and without any serious injuries, although questions have been raised over workers being exposed to toxic chemicals. In 2007, the column returned to the site, and it will be part of the 9/11 Memorial and Museum’s permanent collection.
By then, rebuilding had begun to accelerate, and the past few years have made the new World Trade Center the busiest, most complex construction site in the country. A partnership of Tishman Construction, an AECOM Company, and Turner Construction is the construction manager overseeing all work.
Skansha is a contractor for the Santiago Calatrava-design transit hub, which will connect to the PATH train, 13 subway lines and the site’s five office towers. During construction, an active subway line and PATH train is operation, adding additional complexity to the project. Furthermore, the hub is being construction from the top down, rather than from the bottom, allowing the Port Authority to simultaneous construct other projects, such as the 9/11 Memorial.
“We coordinate job site logistics, work with and around other contractors on the site and then plan phases of our own portion of this massive project,” said Skanska’s Winsper. “Coordination is paramount.”
Tishman Construction, an AECOM company, is the construction manager for the site’s most visible structure, One World Trade Center. The core team drew on its experiences in building Larry Silverstein’s adjacent 7 World Trade Center, and has adopted some of the same techniques of building a concrete core.
The organization of the project is critical for maintaining the speed of construction and strength of the building. “The success of a project is based on the effort that’s put in before you put a shovel into the ground,” said Mel Ruffini of Tishman Construction, One World Trade Center’s project executive.
Each day, a fleet of trucks brings concrete, which arrives at a centralized pumping area. Because the core of the building is so large, due to security concerts, 50 to 60 trucks can arrive in 12 hours, and concrete moves through three separate risers, which can be moved and turned off as needed. The concrete is 14,000 pounds per square inch (psi), a strength that has never been used in New York.
“The pace is extremely challenging,” said Ruffini. “It’s a vertical freight train.”
An entire floor of steel is built within a week, followed by concrete, fireproofing and the curtain wall. The concrete base of the skyscraper, built to withstand a truck bomb, will be encased in glass – bids from manufacturers were due last week. Plumbing, electricity and mechanical systems are also being constructed, along with the bathrooms and elevators. Tenants will finish building out their own spaces.
The vertical delivery system has been built alongside the tower, and Tishman must also ensure that contractors are paid by the Port on time and equipment flows efficiently to the site.
The steel of the 105-story tower will top out in March 2012, followed by a 400-foot spire of steel and radon, which will be preassembled and delivered in 20 separate sections by barge. The tower will be completely finished by the end of 2013.
“Building One World Trade Center is just an unbelievable experience. I can’t say how proud we are as a team,” said Ruffini. “All the men and women, from the executive team to project team to the trade workers on site, truly feel that this is a special project.”
“And the willingness to get this done as quickly as possible and safely as possible – I’ve never seen it work so well,” he added, “It’s almost flawless.”
