Council on Tall Buildings and Urban Habitat
World Trade Center Tour

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Almost ten years after the destruction of the twin towers, we can now see that the reconstruction of the 65,000 square meters (16 acres) of the World Trade Center site is in full swing. Due to be finished by September 11, 2011, the National September 11 Memorial was clearly nearing completion. It is occupied by a forest of trees with two square pools in the center where the twin towers once stood. Simultaneously, much construction work is being done on the memorial museum and visitor center adjacent to the memorial.

Map showing the planned development on and along the World Trade Center site. Source:Skidmore, Owings & Merrill LLP

Also under construction on the site is a new transport hub between the anticipated Two WTC and Three WTC, replacing the temporary station currently in use. This will connect the stations for the PATH and subway line #1 to the ferry terminal, the World Financial Center and One World Trade Center on the west, and 11 other lines of the New York City Transit Authority subway trains through the Fulton Street Transit Center on the east.

Along the northern and eastern perimeter of the original site, four skyscrapers have been planned, of which towers One and Four are currently under construction. Although the foundations of towers Two and Three are part of the current construction work, the development of these buildings has been pushed back to await better economic times. 

Construction works on the foundation of Two World Trade Center, transport hub and Three World Trade Center
National September 11 Memorial under construction

Located to the north from the World Trade Center site, 7 World Trade Center was completed in 2006 on the site of the original 7 World Trade Center Tower. To the south of the original site and on the location of the recently demolished Deutsche Bank Building, Five World Trade Center has been planned for future development.

One World Trade Center
Naturally, the centerpiece of the whole development is One World Trade Center Tower. America’s tallest-to-be is a product of much debate and involves many, many stakeholders. One of the involved parties mentioned that the construction of the tower is probably the most relaxed part of the whole project, which indicates how hectic the design phase must have been. A view from above the World Trade Center site allows one to understand the massive scale and complexity of the development.

One World Trade Center going up! Bottom section Scale model of One World Trade Center

With curtain wall enclosure currently reaching to the 39th floor and steel installed to the 60th floor, the tower is well on its way up to the 105th and highest floor. A 124 meter tall spire will be placed on top of the tower, which is a number that does not mean much using the metric system, but in feet it represents the difference between the full height of the building at 1,776 feet (a reference to 1776, the year of the United States’ Declaration of Independence) and the rooftop height of 1,368 feet, which is the same height as the old 1 World Trade Center tower. In metric measurements, these heights are 541 and 417 meters respectively.

Safety design features include 91-centimeter (3 feet) thick reinforced concrete walls for all stairwells and elevator shafts. Escape strategies include a blast-resistant concrete ‘base’ to the building (effectively pushing the first truly occupied office floor up to the 20th floor),  two wide emergency stairs, an extra dedicated stairwell exclusively for the use of firefighters, and biological / chemical filters throughout its ventilation system. At its closest point, West Street, a main artery to the west of the tower, will be 20 meters (65 feet) away. Additionally, the windows on this side of the building will be equipped with specially tempered blast-resistant plastic.

Part of the concrete core on the lobby level One World Trade Center going up

The upcoming 2011 Issue III of the CTBUH Journal will be a themed issue focused on what has happened in the tall building world in the decade since 9/11, including a case study paper on One World Trade Center. In this issue, we will reflect on the impact that the events of September 11, 2001 have had on the tall building world over the past ten years.

The tour of One World Trade Center was kindly hosted by Nick Houselog of the Port Authority of New York & New Jersey, Nicole Dosso, who is an Associate Director at SOM and the Senior Technical Architect on One WTC, and Julie Hiromoto, Project Manager. 

More information on One World Trade Center can be found in our Tall Buildings Database.

Left to right: Antony Wood, Marshall Gerometta, Dario Trabucco, Sang Dae Kim, Patrick Bayard, Julie Hiromoto, Nick Houselog and Nicole Dosso.
CTBUH Chairman Prof Sang Dae Kim (left) presenting the 2010 Awards Book to our tour guides Nick Houslog and Nicole Dosso.

7 World Trade Center
Unlike the number suggests, the 226-meter (741-feet) tall 7 World Trade Center tower was the first building to be constructed as part of the recent redevelopment of the World Trade Center area. Almost immediately after the site was cleared of debris from the collapsed 7 World Trade Center, Skidmore, Owings & Merrill presented their first proposals for a new design.  Construction of the new 7 World Trade Center started on May 7, 2002.

One and 7 World Trade Center 7 World Trade Center seen from street level
First to be completed

The architects designed in a triangular space of the original site footprint unused to allow for the restoration of Greenwich Street. The space is now an eye-pleasing compact square in front of the main entrance to the building. The new 7 World Trade Center has 52 stories of which 42 contain leasable office spaces. The first ten floors of the tower house an electrical substation, which provides power to much of Lower Manhattan. This section of the building contains a panelized wall system with stainless steel triangular rods that provide ventilation for the machinery. The rest of the tower has been clad in ultra-clear, low-iron glass to provide reflectivity and light and makes the building blend into the sky. Silverstein Properties, the developer of 7 World Trade Center, has its offices in the building.

7 World Trade Center's design places an emphasis on safety. It has 60-centimeter (2-foot) thick reinforced-concrete and fireproofed elevator and stairway access shafts. The curtain wall around the lobby uses heavily laminated, heat-strengthened glass that meets high standards for blast resistance. Additionally, the stairways are wider than the original building to permit faster egress. Between the main entrance and the elevator banks, a 20-meter (65-foot) long 4-meter (14-foot) tall structurally fortified wall exists as a security measure. On the entrance side of the wall, artist Jenny Holzer created a large light installation with glowing text moving across wide panels. The entire wall changes color depending on the time of day.

Sculpture by Jeff Koons on the pocket square in front of 7 World Trade Center Safety enhanced strairwells

7 World Trade Center also incorporates numerous environmentally friendly features.  As we visited the tower during the late afternoon, we were able to see that the building is designed to allow for plenty of natural light. Nearly 30 percent of structural steel used in the building consists of recycled steel. Additionally, rainwater is collected and used for irrigation of the park and to cool the building. Power is metered to tenants to encourage them to conserve energy, a steam microturbine generates electricity from incoming high pressure steam for the heating steam and recycled materials are used for insulation and interior materials.

The tour group was accompanied by Skidmore, Owings & Merrill Managing Director and Project Manager Ken Lewis and Associate Julie Hiromoto.

More information on 7 World Trade Center can be found in our Tall Buildings Database.

The tour of the World Trade Center was one of a number of New York City skyscraper tours organized during the 3rd meeting of the Research, Academic and Postgraduate Working Group in the first week of April 2011.