Rising from the Ashes

09/25/2006 |

Grand Prize Winner in Buildings’ New Construction Awards 2006: 7 World Trade Center, New York, NY, submitted by Tishman Construction Corp.

 

Like the mythical Phoenix born anew and rising from its own ashes, the new 7 World Trade Center (WTC) embodies the beginning of a new downtown New York City.

On 9/11, the facility was badly damaged from falling parts of the Twin Towers. In the evening - long after its evacuation - the building, which was engulfed in flames most of the day, fell. Just 5 years later, a new 7 WTC has risen in its place.

The design of this 1.7-million-square-foot tower was influenced by a rethinking of the area street grid. Greenwich Street, which previously dead-ended at 7 WTC, was reopened - a decision that dramatically changed the shape of the new tower (from a trapezoid to a parallelogram). The result was a 36,000-square-foot footprint and 52 stories rather than an earlier-designed, 2 million-square-foot building with a 40,000-square-foot footprint and only 47 stories.

Another influential factor in the building’s design was the replacement of a Con Edison substation in the first 80 feet of the tower. The transformer vaults located at 7 WTC mandated that the podium wrapper on the building façade provide ample airflow. “The first floors on the north and south side are open to air to keep the transformers cool,” explains Michael Mennella, executive vice president, Tishman Construction Corp., New York City. A stainless-steel screen comprising two layers of steel separated by an 8-inch cavity is a breathing surface that, when lit at night by blue and white LED sources, becomes not only practical, but visually exciting. This study in reflected color and light was a collaboration with artist James Carpenter. The result is a façade that is animated with light, evolving naturally by day and changing at night due to programmed LED projection sequences.

As you approach the building, it’s impossible for your gaze not to fall upon Jeff Koons’ mirror-polished, red stainless-steel Balloon Flower, a sculpture of substantial size that was installed in the fountain at the on-site public park. Before entering the street-level lobby, passersby are greeted once again by fine art - this time thanks to the work of Jenny Holzer (it’s located in the lobby, but visible though the glass façade). The 65-foot-wide, 14-foot-high wall sculpture provides traveling text about New York. This integration of art and architecture was the brainchild of the developer (Silverstein Properties) and architect (Skidmore, Owings & Merrill). With so much attention paid to the community, the city infrastructure, and the cultural arts, there is no doubt that 7 WTC is more than mere real estate - it’s an experience.

Following 9/11, life-safety and security measures in high-rises were immediately scrutinized. Developing a property that would address heightened concerns presented a unique opportunity to raise the bar. No decision was made without thinking about protecting 7 WTC’s building occupants. The building’s safety enhancements exceed minimum New York City building codes and Port Authority requirements. The tower has a reinforced concrete core and a steel superstructure. “We’ve built concrete cores in New York City before, but, in the past, it’s been more for structural economy. This time, it was done not just for structural purposes, but also to encapsulate the vertical systems and the vertical circulation,” explains Mennella. “In emergencies, [occupants] would come down in a building that is basically a 2-foot-thick, concrete-encased stairwell.”

Each stairwell is 20-percent wider than required by code to facilitate rapid evacuation and easier access by emergency responders. The two stairways from the tower are joined by a connecting fire-rated corridor at a lower floor leading to four fire stairs that provide exiting occupants with options in the event that one or two exits are blocked. Additionally, the stairs exit directly to the exterior (as opposed to exiting through the lobby, which could be confusing during an emergency).

Other safety enhancements include:

  • Water-storage capacity for building sprinklers that is twice what is required by code.
  • An internal antenna system to improve communication among emergency responders.
  • A fresh-air system with multiple levels of high-performance filters (located on top of the tower) to reduce the possibility of contaminants entering occupied spaces from the exterior.
  • Emergency generators on top of the building to maximize distance from potential threats and to provide greater reliability. Fuel tanks are buried in the ground outside the building footprint.

Even the lobby’s glass façade was not overlooked; it was designed to meet the U.S. General Services Administration’s Class C blast-resistance standard. “It is a wall of glass that is suspended by point supports at the corners and is suspended by a cable system as opposed to a mullion system,” Mennella explains. He likens it to a trampoline; because of its uniquely designed suspension, it is better equipped to absorb shock from a blast.

In addition to its safety-conscious design, 7 WTC is also green. U.S. Green Building Council President, CEO, and Founding Chair Rick Fedrizzi; Developer Larry A. Silverstein; Governor Pataki’s Chief of Staff John Cahill; and Tishman Chairman Daniel R. Tishman gathered on March 8, 2006, to announce the project’s LEED Gold certification. 7 WTC is the first certified green building in New York City and provides ample natural light, superior indoor air quality, and excellent energy and water conservation.

With so many aspects of the building being hailed a success, it’s hard to believe that the project underwent an extremely accelerated construction schedule. Construction of 7 WTC was a priority because of the need to replace the Con Edison substation. “When 9/11 happened, Con Edison, as well as other utilities in the area, were now struggling with less than the necessary capacity to run the facilities in Lower Manhattan and were anxious to reinstall their equipment to meet demand,” says Mennella. Despite having to build the tower while city infrastructure was rebuilt around the site, Tishman Construction Corp. devised and implemented a method to fast-track the construction by building the tower’s steel frame ahead of its structural concrete core. By means of reusable, self-climbing forms used to construct the core, workers were able to build a floor in half the time it would have taken using a hand-set system. “We delivered a floor every 4 days,” Mennella says.

Meanwhile, all of this work was going on while the lower floors were completed and the Con Edison substation was operating. There were two separate contracts for the construction project. “We were building the Con Edison space for Con Edison and the development space [above it] for Silverstein Properties,” Mennella says.

As the last building to fall and the first to rise on the World Trade Center site, it took incredible dedication and ingenuity to overcome so many challenges and give New York City a building worthy of its downtown address. Today, it is a symbol of rejuvenation, a model of safe and environmental architecture, and a sign of things to come.

Jana J. Madsen (jana.madsen@buildings.com) is managing editor at Buildings magazine.

JUDGES’ COMMENTS: “Congratulations should be given to the building owners for having the courage to push the envelope and challenging the complete team to find a solution that reflects new trends in the marketplace, incorporates new technologies, uses artists in imaginative ways, provides a basis for revitalizing building codes, and provides the nation with a glimpse of things to come.”


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