The World Trade Center in New York City, United States (sometimes informally the WTC or Twin Towers) was a complex of seven buildings in Lower Manhattan that were attacked by Al-Qaeda on September 11, 2001. It was mostly designed by Detroit-based architect Minoru Yamasaki and engineer Leslie Robertson and developed by the Port Authority of New York and New Jersey. It was initiated in 1960 by a Lower Manhattan Association created and chaired by David Rockefeller, who had the original idea of building the center, with strong backing from the then-New York governor, his brother Nelson Rockefeller.[2] The World Trade Center, New York, like most World Trade Centers located around the globe, belonged to the family of World Trade Centers Association. Prior to its destruction, Larry Silverstein held the most recent lease to the complex, the Port Authority having leased it to him in July 2001.[3] The complex, located in the heart of New York City's downtown financial district, contained 13.4 million square feet (1.24 million m²) of office space, almost four percent of Manhattan's entire office inventory at that time.[4]
Best known for its iconic 110-story twin towers (101 usable floors, eight engineering-only "service" floors on top of a lobby which was six stories high and 80') the World Trade Center was beset by a fire on February 13, 1975 and a bombing on February 26, 1993.
All seven original buildings in the complex were destroyed during the September 11 attacks. Three of the buildings collapsed: One World Trade Center (1 WTC, the North Tower), Two World Trade Center (2 WTC, the South Tower), and 7 World Trade Center (7 WTC). The Marriott World Trade Center (3 WTC) was crushed by the collapses of 1 WTC and 2 WTC. 4 World Trade Center (4 WTC), 5 World Trade Center (5 WTC), and 6 World Trade Center (6 WTC) were damaged beyond repair and later demolished. Three buildings not part of the complex were also destroyed: St. Nicholas Greek Orthodox Church was destroyed by the collapse of 2 WTC. The Deutsche Bank Building was damaged beyond repair by the explosions and collapse of 1 and 2 WTC; and Borough of Manhattan Community College's Fiterman Hall was damaged beyond repair by the collapse of 7 WTC; these are currently being deconstructed.
Planning and construction
Main article: Construction of the World Trade Center
The idea of establishing a "world trade center" in New York City was first proposed in 1946, with a bill passed by the New York State Legislature that allowed New York Governor Thomas E. Dewey to begin developing plans for the project.[5] In 1949, plans for a "world trade center" were put on hold.[6] In the late 1940s and 1950s, economic growth in New York City was concentrated in Midtown Manhattan, with Lower Manhattan left out. To help stimulate urban renewal, David Rockefeller suggested that the Port Authority should build a "world trade center" in Lower Manhattan.[7]
Initial plans, made public in 1961, identified a site along the East River for the World Trade Center.[7] The Port Authority, as a bi-state agency, required approval from both the governors of New York and New Jersey in order to undertake new proects. New Jersey Governor Robert B. Meyner objected to the plan, resenting that New York would be getting this $335 million project.[7] Toward the end of 1961, negotiations with outgoing New Jersey Governor Meyner regarding the World Trade Center project reached a stalemate.[8]
Meanwhile, ridership on New Jersey's Hudson and Manhattan Railroad (H&M) had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958, after new automobile tunnels and bridges opened across the Hudson River.[9] In a December 1961 meeting between Tobin and newly elected New Jersey Governor Richard J. Hughes, the Port Authority offered to take over the Hudson & Manhattan Railroad, which was renamed the Port Authority Trans-Hudson (PATH). The Port Authority also decided to move the World Trade Center project to the Hudson Terminal building site, on the west side of Lower Manhattan, which was a more convenient location for New Jersey commuters, who could get to the World Trade Center via PATH.[8] The new location, along with Port Authority acquisition of the H&M Railroad, brought New Jersey to agreement on January 22, 1962, in support of the World Trade Center project.[10]
Approval was also needed from New York City Mayor John Lindsay and the New York City Council, with disagreements centering on tax issues. A final agreement was made on August 3, 1966, that the Port Authority would make annual payments to the City, in lieu of taxes, for the portion of the World Trade Center leased to private tenants.[11] In subsequent years, the payments would rise as the real estate tax rate increased.[12]
Architectural design
On September 20, 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect, and Emery Roth & Sons as associate architects.[13] Yamasaki devised the plan to incorporate twin towers, though Yamasaki's original plan called for the towers to be only 80 stories tall.[14] In order to meet the Port Authority's requirement to build 10 million square feet (930,000 m²) of office space, the buildings would each need to be 110 stories tall.[15]
A typical floor layout and elevator arrangement of the WTC towers
A major limiting factor in building heights is elevators; the taller the building, the more elevators are needed to service the building, requiring more space-consuming elevator banks.[15] Yamasaki and the engineers decided to use a new system with sky lobbies, which are floors where people can switch from a large-capacity express elevator, which goes only to the sky lobbies, to a local elevator that goes to each floor in a section (the local elevators can be stacked within the same elevator shaft). Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently, while also increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of required elevator shafts.[16].[17] Altogether, the World Trade Center had 95 express and local elevators.[18] This system was inspired by the New York City Subway system, whose lines include local stations where local trains stop and express stations where all trains stop.[19]
Yamasaki's design for the World Trade Center, which was unveiled to the public on January 18, 1964, called for a square plan, approximately 207 feet (63 m) in dimension on each side.[14][20] The buildings were designed with narrow office windows, only 18 inches (45 cm) wide, which reflected on Yamasaki's fear of heights and desire to make building occupants feel secure.[21] Yamasaki's design included building facades sheathed in aluminum-alloy.[22] The World Trade Center was one of the most striking American implementations of the architectural ethic of Le Corbusier, as well as the seminal expression of Yamasaki's gothic modernist tendencies. In addition to the twin towers, the plan for the World Trade Center complex included four other low-rise buildings; Altogether, the World Trade Center complex occupied a 16 acres (65,000 m2) superblock.
Structural design
The structural engineering firm Worthington, Skilling, Helle & Jackson worked to implement Yamasaki's design, developing the tube-frame structural system used in the buildings. The Port Authority's Engineering Department served as foundation engineers, Joseph R. Loring & Associates as electrical engineers, and Jaros, Baum & Bolles as mechanical engineers. Tishman Realty & Construction Company was the general contractor on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and the Port Authority's Chief Engineer, Rino M. Monti, oversaw the project.[23] As an interstate agency, the Port Authority was not subject to local laws and regulations of the City of New York, including building codes. Nonetheless, the structural engineers of the World Trade Center ended up following draft versions of the new 1968 building codes.[24]
The tube-frame design of the World Trade Center towers was a new approach, which allowed open floor plans, rather than columns distributed throughout the interior to support building loads as had traditionally been done. The World Trade Center towers utilized high-strength, load-bearing perimeter steel columns called Vierendeel trusses that were spaced closely together to form a strong, rigid wall structure, which supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns. The perimeter structure, which contained 59 perimeter columns, narrowly spaced, on each side of the buildings, was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected by spandrel plates.[25] The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop.[26] Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, transmitting shear stress between columns, allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.[25]
The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m), and contained 47 steel columns running from the bedrock to the top of the tower.[25] The large, column-free space between the perimeter and core was bridged by prefabricated floor trusses. The floors supported their own weight, as well as live loads, provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of 4 inch (10 cm) thick lightweight concrete slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors.[25] The trusses connected to the perimeter at alternate columns, and were on 6 foot 8 inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with viscoelastic dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch (100 mm) thick (10 cm) lightweight concrete floor slab, with shear connections for composite action.[25]
Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communication antenna on top of each building.[25] Only 1 WTC (north tower) actually had an antenna fitted, which was added in 1978.[27] The truss system consisted of six trusses along the long axis of the core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.[25]
The tube frame design using steel core and perimeter columns protected with sprayed-on fire resistant material created a relatively lightweight structure that would sway more in response to the wind, compared to traditional structures such as the Empire State Building that have thick, heavy masonry for fireproofing of steel structural elements.[28] During the design process, wind tunnel tests were done to establish design wind pressures that the World Trade Center towers could be subjected to and structural response to those forces.[29] Experiments also were done to evaluate how much sway occupants could comfortably tolerate, however many subjects experienced dizziness and other ill effects.[30] One of the chief engineers Leslie Robertson worked with Canadian engineer Alan G. Davenport to develop viscoelastic dampers to absorb some of the sway. These viscoelastic dampers, used throughout the structures at the joints between floor trusses and perimeter columns, along with some other structural modifications reduced the building sway to an acceptable level.[31]
Construction
1 World Trade Center and 2 World Trade Center under construction; Empire State Building and PanAm Building seen in Midtown, 1970
In March 1965, the Port Authority began acquiring property at the World Trade Center site.[32] Demolition work began on March 21, 1966 to clear thirteen square blocks of low rise buildings in Radio Row for construction of the World Trade Center.[33] Groundbreaking for the construction of the World Trade Center took place on August 5, 1966.[34]
The site of the World Trade Center was located on landfill, with the bedrock located 65 feet (20 m) below.[35] In order to construct the World Trade Center, it was necessary to build the "bathtub", with a slurry wall along the West Street side of the site, which serves the purpose of keeping water from the Hudson River out.[36] The slurry method, devised by Port Authority’s chief engineer, John M. Kyle, Jr., involved digging a trench, and as excavation proceeded, filling the space with a "slurry" mixture, composed of bentonite, which plugged holes and kept water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out.[37] It took fourteen months for the slurry wall to be completed, which was necessary before excavation of material from the interior of the site could begin.[37] The 1.2 million cubic yards (917,000 m³) of material excavated were used to expand the Manhattan shoreline across West Street, creating Battery Park City.[38][39]
In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers, and Karl Koch was hired to erect the steel.[40] Tishman Realty & Construction was hired in February 1967 to oversee construction of the project.[41] Construction work began on the North Tower in August 1968, while construction South Tower was underway in January 1969.[42] The original Hudson Tubes, which carried PATH trains into Hudson Terminal, remained in service as elevated tunnels during the construction process until 1971, when a new PATH station opened.[43] Nearby New York City Subway tubes also needed protection during construction, so that service was not interrupted.[citation needed]
The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971.[42] The first tenants moved into the North Tower in December 1970, and into the South Tower in January 1972.[44] When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.[45] The ribbon cutting ceremony was on April 4, 1973.[46]
Criticism
The World Trade Center in July 2001
Plans to build the World Trade Center were not without controversy. The site for the World Trade Center was the location of Radio Row, which was home to hundreds of commercial and industrial tenants, property owners, small businesses, and approximately 100 residents, many of whom fiercely resisted forced relocation.[7] A group of small businesses affected filed injunction, challenging the Port Authority's power of eminent domain.[47] The case made its way through the court system, reaching the United States Supreme Court, which refused to accept the case.[48][49]
Private real estate developers and members of the Real Estate Board of New York, led by Empire State Building owner Lawrence A. Wien, also expressed concerns about this much "subsidized" office space going on the open market, competing with the private sector when there was already a glut of vacancies.[7][50] Others questioned whether the Port Authority really ought to take on the project, which was described by some as a "mistaken social priority."[51] Initially conceived (as the name suggests) as a complex dedicated to companies and organizations directly taking part in "world trade," they at first failed to attract the expected clientèle. During the early years, various governmental organizations became key tenants of the World Trade Center, including the State of New York. It was not until the 1980s that the city's perilous financial state eased, after which an increasing number of private companies — mostly financial firms tied to Wall Street — became tenants.
The World Trade Center design brought criticism of its aesthetics from the American Institute of Architects and other groups.[52][22] Lewis Mumford, author of The City in History and other works on urban planning, criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets."[53] The twin towers' narrow office windows, only 18 inches (460 mm) wide, were also disliked by many for impairing the view from the buildings.[21]
The trade center's "superblock", which replaced a more traditional, dense neighborhood, was regarded by some critics as an inhospitable environment that disrupted the complicated traffic network typical of Manhattan. For example, in his book The Pentagon of Power, the technical historian Lewis Mumford denounced the center as an "example of the purposeless giantism and technological exhibitionism that are now eviscerating the living tissue of every great city." On the other hand, Mr. Yamasaki saw the expanse as a focal point of serenity amidst the chaos of the city.
For many years, the immense Austin J. Tobin Plaza was unwelcoming, and often beset by brisk winds at the ground level.[54] In 1999, the outdoor plaza reopened after undergoing $12 million renovations, which involved replacing marble pavers with gray and pink granite stones, adding new benches, planters, new restaurants and food kiosks, and outdoor dining areas.[55] In later years, the plaza became a center for outdoor concerts and other activities.
The complex
The Twin Towers
The WTC site building arrangement
With construction of 7 World Trade Center in the 1980s, the World Trade Center had a total of seven buildings, but the most notable were the main twin towers which were each 110 stories tall. 1 WTC (the North Tower, which featured a 360-foot (110 m) high TV and radio antenna added in 1978, stood 1,368 feet (417 m) high, and 2 WTC (the South Tower, which contained the observation deck, was 1,362 feet (415 m) high.[56] The length and breadth of the towers were 208 feet (63.4 m) x 208 feet (63.4 m). Although only Tower 1 featured an antenna, both buildings were designed to carry a broadcast mast. The basement concourse of the World Trade Center included The Mall at the World Trade Center, along with a PATH station.
When completed in 1972, 1 WTC became the tallest building on Earth, unseating the Empire State Building after a 40-year reign. 2 WTC became the second tallest building in the world when completed in 1973. 2 WTC did not need these facilities, so it remained 1,362 feet (415 m). Regardless, the WTC towers held the height record only briefly. As the building neared completion in 1973, work had already begun on Chicago's Sears Tower, which ultimately reached 1,450 feet (442 m).[57] During a press conference in 1973, Minoru Yamasaki was asked, "Why two 110-story buildings? Why not one 220-story building?" His response was: "I didn't want to lose the human scale".[58] With the World Trade Center's destruction, the Empire State Building again became the tallest building in New York, after spending almost 30 years as the third-tallest in the city.
Of the 110 stories, eight were set aside for technical services (mechanical floors) Level B6/B5, Floors 7/8, 41/42, 75/76 and 108/109, in four two-floor areas evenly spread up the building. All the remaining floors were free for open-plan offices. Each floor of the towers had 40,000 square feet (3,700 m2) of space for occupancy.[18] Each tower had 3.8 million square feet (350,000 m²) of office space. Altogether the entire complex of seven buildings had 11.2 million square feet (1.04 km²) of space.
The lobby of the World Trade Center
During the 1990s, approximately 500 companies had offices in the complex, including many financial companies such as Morgan Stanley, Aon Corporation, Salomon Brothers, as well as the Port Authority itself. Electrical service to the towers was supplied by Consolidated Edison (ConEd) at 13,800 volts. This service passed through the World Trade Center Primary Distribution Center (PDC) and sent up through the core of the building to electrical substations located on the mechanical floors. The substations "stepped" the 13,800 primary voltage down to 480/277 volt secondary power and further to 120/208 volt general power and lighting service. The complex also was served by emergency generators located in the sublevels of the towers and on the roof of 5 WTC.[59][60]
The 110th Floor of 1 WTC (North Tower) housed commercial and public service radio & television transmission equipment. The roof of 1 WTC contained a vast array of transmission antennas, including the 360 ft (approx 110m) center antenna mast, which was rebuilt in 1999 by Dielectric Inc. to accommodate DTV. The center mast contained the television signals for almost all NYC television broadcasters: WCBS-TV 2, WNBC-TV 4, WNYW 5, WABC-TV 7, WWOR-TV 9 Secaucus, WPIX 11, WNET 13 Newark, WPXN-TV 31, and WNJU 47. It also had four NYC FM broadcasters on it as well: WPAT-FM 93.1, WNYC 93.9, WKCR 89.9, and WKTU 103.5.[61] Access to the roof was controlled from the WTC Operations Control Center (OCC) located in the B1 level of 2 WTC.
Observation deck and Windows on the World
Midtown Manhattan from the observation deck of the south tower which received an estimated 80,000 visitors a day, during the late 1990s.
Although most of the space in the WTC complex was off-limits to the public, 2 WTC (South Tower) featured a public observation area named "Top Of The World." When visiting the observation deck, visitors would first pass through security checks added after the 1993 World Trade Center bombing. Next, visitors were whisked to the 107th floor indoor observatory at a height of 1,310 feet (399 m) and greeted with a 360-degree view of the New York City skyline, and exhibitions including a three-dimensional scale model of Manhattan, and a simulated helicopter ride around the city. Weather permitting, visitors could take two short escalator rides up from the 107th floor and visit what was the world's highest outdoor viewing platform. At a height of 1,377 feet (420 m), visitors were able to take in a view of the North Tower and New York City unlike any other. On a clear day, visitors could see up to 49 miles (78 km) in any given direction. An anti-suicide fence was placed on the roof itself, with the viewing platform set back and elevated above it, requiring only an ordinary railing and leaving the view unobstructed, unlike the observation deck of the Empire State Building.
The North Tower (1 WTC) had a restaurant on the 107th floor called Windows on the World, which was an elegant restaurant known as a place for big celebrations, such as weddings. Windows on the World, which was developed by Joe Baum at a cost of more than $17 million, opened in April 1976.[62] Aside from the main restaurant, two offshoots were also originally located at the top of the North Tower: "Hors d'Oeuvrerie" (offered a Danish smorgasbord during the day and sushi in the evening) and "Cellar in the Sky" (a small wine bar).[63] Windows on the World also had a wine school program, run by Kevin Zraly. Windows on the World was closed for a period of time following the 1993 World Trade Center bombing, reopening in 1996.[62] Hors d'Oeuvrerie and Cellar in the Sky were replaced with the "Greatest Bar on Earth" and "Wild Blue".[63] In its last full year of operation, 2000, Windows on the World reported revenues of $37 million, making it the highest-grossing restaurant in the United States.[64]
The other buildings
Twin Towers view from Empire State Building, May 2001.
Five smaller buildings stood around the 16-acre (65,000 m²) block. One was the 22-floor hotel which opened in 1981 as the Vista Hotel and in 1995 became the Marriott World Trade Center (3 WTC) at the southwest corner of the site. Three low-rise buildings (4 WTC, 5 WTC, and 6 WTC) in the same hollow tube design as the towers also stood around the plaza. 6 World Trade Center, at the northwest corner, housed the United States Customs Service and the U.S. Commodities Exchange. 5 World Trade Center was located at the northeast corner, above the PATH station, and 4 World Trade Center was at the southeast corner. In 1987, a 47-floor office building called 7 WTC was built north of the block. Beneath the World Trade Center complex was an underground shopping mall, which in turn had connections to various mass transit facilities, including the New York City Subway system and the Port Authority's own PATH trains connecting Manhattan to Jersey City, Hoboken, and Newark.
One of the world's largest gold depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. Seven weeks after the September 11 attacks, $230 million in precious metals were removed from basement vaults of 4 WTC, which included 3,800 100-Troy-ounce registered gold bars and 30,000 1,000-ounce silver bars.[65]
Life and events
On a typical weekday 50,000 people worked in the towers,[18] with another 200,000 passing through as visitors. The complex was so large that it had its own zip code, 10048. The towers offered spectacular views from the observation deck (located on top of the South Tower) and the Windows on the World restaurant (located on top of the North Tower). The Twin Towers became known worldwide, appearing in movies, TV shows, postcards, merchandise, magazines and much more, and became a New York icon, in the same league as the Empire State Building and Statue of Liberty. French high wire acrobatic performer Philippe Petit walked between the towers on a tightrope in 1974, and Brooklyn toymaker George Willig scaled the south tower in 1977.
The 1995 PCA world chess championship, between Garry Kasparov and Viswanathan Anand, was played on the 107th floor of the South Tower.[66] In January 1998, Ralph Guarino collected three men, Melvin, Richie, and Mike Reed to steal up towards 2.8 Million dollars from One World Brink bank on the eleventh floor of the World Trade Center. The heist was completed, however only 1.6 Million was stolen, mostly in Italian lira, francs, and yen. Subsequently all four were arrested; Ralph became an informant for the FBI against the DeCavalcante crime family which operated out of New Jersey.
February 13, 1975 fire
On February 13, 1975, a three-alarm fire broke out on the 11th floor of the North Tower, with fire spreading through the core from the 9th to 14th floors where electrical wiring was damaged. The fire ignited the insulation of telephone cables in a utility shaft that ran vertically between floors. The fire spread to other floors through openings in the floor slabs that were used to carry phone wires. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. Most of the damage was concentrated on the 11th floor, with the fire fueled by cabinets filled with paper, alcohol-based fluid for office machines, and other office equipment. Fireproofing protected the steel from melting and there was no structural damage to the tower. Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above. At that time, the World Trade Center was not equipped with sprinkler systems.[67][68]
Bombing of February 26, 1993
Main article: World Trade Center bombing
On February 26, 1993 at 12:17 PM, a Ryder truck filled with 1,500 pounds (680 kg) of explosives was planted by Ramzi Yousef and detonated in the underground garage of the North Tower, opening a 100 foot (30 m) hole through 5 sublevels of concrete leaving six people dead and 50,000 other workers and visitors gasping for air in the shafts of the 110 story towers.
Damage underground due to the bombing
Many people inside the North Tower were forced to walk down darkened stairwells that contained no emergency lighting, some taking two hours or more to reach safety. As the Port Authority was a bistate agency, the towers were exempt from New York City building codes. Subsequent to the bombing The Port Authority installed emergency lighting in the stairwells. It is believed that this lighting saved many lives during the events of September 11, 2001.
In 1997 and 1998, six Islamist extremists were convicted and sentenced to life in prison for their roles in the bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to destabilize the north tower and send it crashing into the south tower, toppling both landmarks.
As a memorial to the victims of the bombing of the tower, a reflecting pool was installed with the names of those who had been killed in the blast. Following the September 11, 2001 attacks, relief workers found a single fractured piece of the fountain etched with the word "John"; to date it is the only remaining part of the 1993 memorial that survived the collapse of the towers.
The World Trade Center complex was protected by an extensive fire detection and voice evacuation paging system upgraded after the 1993 bombing. Fire Command Stations, staffed by Fire Safety Directors were located in the lobbies of each building and the Operations Control Center (OCC) monitored these systems. An extensive study of the performance of World Trade Center Fire Protection Systems was conducted by the National Institute of Standards and Technology (NIST) following 2001-09-11.[69]
Lease
In 1998, plans were approved by the Port Authority to privatize the World Trade Center.[70] In 2001, the Port Authority sought to lease the World Trade Center to a private entity. Bids for the lease came from Vornado Realty Trust, a joint bid between Brookfield Properties Corporation and Boston Properties,[71] and a joint bid by Silverstein Properties and The Westfield Group.[72] By privatizing the World Trade Center, it would be added to the city's tax rolls.[72] The lease was also intended to raise funds for other Port Authority projects.[73] On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease.[74] Vornado Realty outbid Silverstein by $600 million, though Silverstein upped his offer to $3.22 billion. However, Vornado insisted on last minute changes to the deal, including a shorter 39-year lease, which the Port Authority considered nonnegotiable.[75] Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on April 26, 2001,[76] and closed on July 24, 2001.[77]
September 11, 2001
Main articles: September 11, 2001 attacks and Collapse of the World Trade Center
The World Trade Center on fire with the Statue of Liberty in the foreground
On September 11, 2001 at 8:46 a.m. Eastern Time, Al Qaeda suicide hijackers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175 into the South Tower, which subsequently collapsed at 9:59 a.m.[78] The damage caused to the North Tower by Flight 11 destroyed any means of escape from above the impact zone, trapping 1,344 people.[79] The North Tower collapsed at 10:28, after burning for approximately 102 minutes.[80]
At 5:20 p.m. on September 11, 2001, 7 World Trade Center collapsed due to uncontrolled fires causing structural failure.[81] 3 World Trade Center, a Mariott hotel, was destroyed during the collapse of the two towers. The three remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished. [82] The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned due to the uninhabitable, toxic conditions inside the office tower, and is undergoing deconstruction.[83][84] The Borough of Manhattan Community College's Fiterman Hall at 30 West Broadway was also condemned due to extensive damage in the attacks, and is slated for deconstruction.[85]
At the time of the incident, media reports suggested that tens of thousands might have been killed in the attacks, as on any given day upwards of 50,000 people could be inside the towers. Ultimately, 2,749 death certificates were filed relating to the 9/11 attacks.[86] Of these, 1,614 (59%) were identified from recovered physical remains. Cantor Fitzgerald L.P., an investment bank on the 101st–105th floors of One World Trade Center, lost 658 employees, considerably more than any other employer.[87] Marsh Inc., located immediately below Cantor Fitzgerald on floors 93–101 (the location of Flight 11's impact), lost 295 employees, and 175 employees of Aon Corporation were killed.[88] As well, 343 deaths were New York City firefighters, 84 were Port Authority employees, of whom 37 were members of the Port Authority Police Department, and another 23 were New York City Police Department officers. Of all the people who were still in the towers when they collapsed only 20 of these people were pulled out alive.
Best known for its iconic 110-story twin towers (101 usable floors, eight engineering-only "service" floors on top of a lobby which was six stories high and 80') the World Trade Center was beset by a fire on February 13, 1975 and a bombing on February 26, 1993.
All seven original buildings in the complex were destroyed during the September 11 attacks. Three of the buildings collapsed: One World Trade Center (1 WTC, the North Tower), Two World Trade Center (2 WTC, the South Tower), and 7 World Trade Center (7 WTC). The Marriott World Trade Center (3 WTC) was crushed by the collapses of 1 WTC and 2 WTC. 4 World Trade Center (4 WTC), 5 World Trade Center (5 WTC), and 6 World Trade Center (6 WTC) were damaged beyond repair and later demolished. Three buildings not part of the complex were also destroyed: St. Nicholas Greek Orthodox Church was destroyed by the collapse of 2 WTC. The Deutsche Bank Building was damaged beyond repair by the explosions and collapse of 1 and 2 WTC; and Borough of Manhattan Community College's Fiterman Hall was damaged beyond repair by the collapse of 7 WTC; these are currently being deconstructed.
Planning and construction
Main article: Construction of the World Trade Center
The idea of establishing a "world trade center" in New York City was first proposed in 1946, with a bill passed by the New York State Legislature that allowed New York Governor Thomas E. Dewey to begin developing plans for the project.[5] In 1949, plans for a "world trade center" were put on hold.[6] In the late 1940s and 1950s, economic growth in New York City was concentrated in Midtown Manhattan, with Lower Manhattan left out. To help stimulate urban renewal, David Rockefeller suggested that the Port Authority should build a "world trade center" in Lower Manhattan.[7]
Initial plans, made public in 1961, identified a site along the East River for the World Trade Center.[7] The Port Authority, as a bi-state agency, required approval from both the governors of New York and New Jersey in order to undertake new proects. New Jersey Governor Robert B. Meyner objected to the plan, resenting that New York would be getting this $335 million project.[7] Toward the end of 1961, negotiations with outgoing New Jersey Governor Meyner regarding the World Trade Center project reached a stalemate.[8]
Meanwhile, ridership on New Jersey's Hudson and Manhattan Railroad (H&M) had declined substantially from a high of 113 million riders in 1927 to 26 million in 1958, after new automobile tunnels and bridges opened across the Hudson River.[9] In a December 1961 meeting between Tobin and newly elected New Jersey Governor Richard J. Hughes, the Port Authority offered to take over the Hudson & Manhattan Railroad, which was renamed the Port Authority Trans-Hudson (PATH). The Port Authority also decided to move the World Trade Center project to the Hudson Terminal building site, on the west side of Lower Manhattan, which was a more convenient location for New Jersey commuters, who could get to the World Trade Center via PATH.[8] The new location, along with Port Authority acquisition of the H&M Railroad, brought New Jersey to agreement on January 22, 1962, in support of the World Trade Center project.[10]
Approval was also needed from New York City Mayor John Lindsay and the New York City Council, with disagreements centering on tax issues. A final agreement was made on August 3, 1966, that the Port Authority would make annual payments to the City, in lieu of taxes, for the portion of the World Trade Center leased to private tenants.[11] In subsequent years, the payments would rise as the real estate tax rate increased.[12]
Architectural design
On September 20, 1962, the Port Authority announced the selection of Minoru Yamasaki as lead architect, and Emery Roth & Sons as associate architects.[13] Yamasaki devised the plan to incorporate twin towers, though Yamasaki's original plan called for the towers to be only 80 stories tall.[14] In order to meet the Port Authority's requirement to build 10 million square feet (930,000 m²) of office space, the buildings would each need to be 110 stories tall.[15]
A typical floor layout and elevator arrangement of the WTC towers
A major limiting factor in building heights is elevators; the taller the building, the more elevators are needed to service the building, requiring more space-consuming elevator banks.[15] Yamasaki and the engineers decided to use a new system with sky lobbies, which are floors where people can switch from a large-capacity express elevator, which goes only to the sky lobbies, to a local elevator that goes to each floor in a section (the local elevators can be stacked within the same elevator shaft). Located on the 44th and 78th floors of each tower, the sky lobbies enabled the elevators to be used efficiently, while also increasing the amount of usable space on each floor from 62 to 75 percent by reducing the number of required elevator shafts.[16].[17] Altogether, the World Trade Center had 95 express and local elevators.[18] This system was inspired by the New York City Subway system, whose lines include local stations where local trains stop and express stations where all trains stop.[19]
Yamasaki's design for the World Trade Center, which was unveiled to the public on January 18, 1964, called for a square plan, approximately 207 feet (63 m) in dimension on each side.[14][20] The buildings were designed with narrow office windows, only 18 inches (45 cm) wide, which reflected on Yamasaki's fear of heights and desire to make building occupants feel secure.[21] Yamasaki's design included building facades sheathed in aluminum-alloy.[22] The World Trade Center was one of the most striking American implementations of the architectural ethic of Le Corbusier, as well as the seminal expression of Yamasaki's gothic modernist tendencies. In addition to the twin towers, the plan for the World Trade Center complex included four other low-rise buildings; Altogether, the World Trade Center complex occupied a 16 acres (65,000 m2) superblock.
Structural design
The structural engineering firm Worthington, Skilling, Helle & Jackson worked to implement Yamasaki's design, developing the tube-frame structural system used in the buildings. The Port Authority's Engineering Department served as foundation engineers, Joseph R. Loring & Associates as electrical engineers, and Jaros, Baum & Bolles as mechanical engineers. Tishman Realty & Construction Company was the general contractor on the World Trade Center project. Guy F. Tozzoli, director of the World Trade Department at the Port Authority, and the Port Authority's Chief Engineer, Rino M. Monti, oversaw the project.[23] As an interstate agency, the Port Authority was not subject to local laws and regulations of the City of New York, including building codes. Nonetheless, the structural engineers of the World Trade Center ended up following draft versions of the new 1968 building codes.[24]
The tube-frame design of the World Trade Center towers was a new approach, which allowed open floor plans, rather than columns distributed throughout the interior to support building loads as had traditionally been done. The World Trade Center towers utilized high-strength, load-bearing perimeter steel columns called Vierendeel trusses that were spaced closely together to form a strong, rigid wall structure, which supported virtually all lateral loads, such as wind loads, and shared the gravity loads with the core columns. The perimeter structure, which contained 59 perimeter columns, narrowly spaced, on each side of the buildings, was constructed with extensive use of prefabricated modular pieces, which consisted of three columns, three stories tall, connected by spandrel plates.[25] The spandrel plates were welded to the columns to create the modular pieces off-site at the fabrication shop.[26] Adjacent modules were bolted together, with the splices occurring at mid-span of the columns and spandrels. The spandrel plates were located at each floor, transmitting shear stress between columns, allowing them to work together in resisting lateral loads. The joints between modules were staggered vertically, so the column splices between adjacent modules were not at the same floor.[25]
The building's core housed the elevator and utility shafts, restrooms, three stairwells, and other support spaces. The core of each tower was a rectangular area 87 by 135 feet (27 by 41 m), and contained 47 steel columns running from the bedrock to the top of the tower.[25] The large, column-free space between the perimeter and core was bridged by prefabricated floor trusses. The floors supported their own weight, as well as live loads, provided lateral stability to the exterior walls, and distributed wind loads among the exterior walls. The floors consisted of 4 inch (10 cm) thick lightweight concrete slabs laid on a fluted steel deck. A grid of lightweight bridging trusses and main trusses supported the floors.[25] The trusses connected to the perimeter at alternate columns, and were on 6 foot 8 inch (2.03 m) centers. The top chords of the trusses were bolted to seats welded to the spandrels on the exterior side and a channel welded to the core columns on the interior side. The floors were connected to the perimeter spandrel plates with viscoelastic dampers, which helped reduce the amount of sway felt by building occupants. The trusses supported a 4-inch (100 mm) thick (10 cm) lightweight concrete floor slab, with shear connections for composite action.[25]
Hat trusses (or "outrigger truss") located from the 107th floor to the top of the buildings were designed to support a tall communication antenna on top of each building.[25] Only 1 WTC (north tower) actually had an antenna fitted, which was added in 1978.[27] The truss system consisted of six trusses along the long axis of the core and four along the short axis. This truss system allowed some load redistribution between the perimeter and core columns and supported the transmission tower.[25]
The tube frame design using steel core and perimeter columns protected with sprayed-on fire resistant material created a relatively lightweight structure that would sway more in response to the wind, compared to traditional structures such as the Empire State Building that have thick, heavy masonry for fireproofing of steel structural elements.[28] During the design process, wind tunnel tests were done to establish design wind pressures that the World Trade Center towers could be subjected to and structural response to those forces.[29] Experiments also were done to evaluate how much sway occupants could comfortably tolerate, however many subjects experienced dizziness and other ill effects.[30] One of the chief engineers Leslie Robertson worked with Canadian engineer Alan G. Davenport to develop viscoelastic dampers to absorb some of the sway. These viscoelastic dampers, used throughout the structures at the joints between floor trusses and perimeter columns, along with some other structural modifications reduced the building sway to an acceptable level.[31]
Construction
1 World Trade Center and 2 World Trade Center under construction; Empire State Building and PanAm Building seen in Midtown, 1970
In March 1965, the Port Authority began acquiring property at the World Trade Center site.[32] Demolition work began on March 21, 1966 to clear thirteen square blocks of low rise buildings in Radio Row for construction of the World Trade Center.[33] Groundbreaking for the construction of the World Trade Center took place on August 5, 1966.[34]
The site of the World Trade Center was located on landfill, with the bedrock located 65 feet (20 m) below.[35] In order to construct the World Trade Center, it was necessary to build the "bathtub", with a slurry wall along the West Street side of the site, which serves the purpose of keeping water from the Hudson River out.[36] The slurry method, devised by Port Authority’s chief engineer, John M. Kyle, Jr., involved digging a trench, and as excavation proceeded, filling the space with a "slurry" mixture, composed of bentonite, which plugged holes and kept water out. When the trench was dug out, a steel cage was inserted, with concrete poured in, forcing the "slurry" out.[37] It took fourteen months for the slurry wall to be completed, which was necessary before excavation of material from the interior of the site could begin.[37] The 1.2 million cubic yards (917,000 m³) of material excavated were used to expand the Manhattan shoreline across West Street, creating Battery Park City.[38][39]
In January 1967, the Port Authority awarded $74 million in contracts to various steel suppliers, and Karl Koch was hired to erect the steel.[40] Tishman Realty & Construction was hired in February 1967 to oversee construction of the project.[41] Construction work began on the North Tower in August 1968, while construction South Tower was underway in January 1969.[42] The original Hudson Tubes, which carried PATH trains into Hudson Terminal, remained in service as elevated tunnels during the construction process until 1971, when a new PATH station opened.[43] Nearby New York City Subway tubes also needed protection during construction, so that service was not interrupted.[citation needed]
The topping out ceremony of 1 WTC (North Tower) took place on December 23, 1970, while 2 WTC's ceremony (South Tower) occurred later on July 19, 1971.[42] The first tenants moved into the North Tower in December 1970, and into the South Tower in January 1972.[44] When the World Trade Center twin towers were completed, the total costs to the Port Authority had reached $900 million.[45] The ribbon cutting ceremony was on April 4, 1973.[46]
Criticism
The World Trade Center in July 2001
Plans to build the World Trade Center were not without controversy. The site for the World Trade Center was the location of Radio Row, which was home to hundreds of commercial and industrial tenants, property owners, small businesses, and approximately 100 residents, many of whom fiercely resisted forced relocation.[7] A group of small businesses affected filed injunction, challenging the Port Authority's power of eminent domain.[47] The case made its way through the court system, reaching the United States Supreme Court, which refused to accept the case.[48][49]
Private real estate developers and members of the Real Estate Board of New York, led by Empire State Building owner Lawrence A. Wien, also expressed concerns about this much "subsidized" office space going on the open market, competing with the private sector when there was already a glut of vacancies.[7][50] Others questioned whether the Port Authority really ought to take on the project, which was described by some as a "mistaken social priority."[51] Initially conceived (as the name suggests) as a complex dedicated to companies and organizations directly taking part in "world trade," they at first failed to attract the expected clientèle. During the early years, various governmental organizations became key tenants of the World Trade Center, including the State of New York. It was not until the 1980s that the city's perilous financial state eased, after which an increasing number of private companies — mostly financial firms tied to Wall Street — became tenants.
The World Trade Center design brought criticism of its aesthetics from the American Institute of Architects and other groups.[52][22] Lewis Mumford, author of The City in History and other works on urban planning, criticized the project and described it and other new skyscrapers as "just glass-and-metal filing cabinets."[53] The twin towers' narrow office windows, only 18 inches (460 mm) wide, were also disliked by many for impairing the view from the buildings.[21]
The trade center's "superblock", which replaced a more traditional, dense neighborhood, was regarded by some critics as an inhospitable environment that disrupted the complicated traffic network typical of Manhattan. For example, in his book The Pentagon of Power, the technical historian Lewis Mumford denounced the center as an "example of the purposeless giantism and technological exhibitionism that are now eviscerating the living tissue of every great city." On the other hand, Mr. Yamasaki saw the expanse as a focal point of serenity amidst the chaos of the city.
For many years, the immense Austin J. Tobin Plaza was unwelcoming, and often beset by brisk winds at the ground level.[54] In 1999, the outdoor plaza reopened after undergoing $12 million renovations, which involved replacing marble pavers with gray and pink granite stones, adding new benches, planters, new restaurants and food kiosks, and outdoor dining areas.[55] In later years, the plaza became a center for outdoor concerts and other activities.
The complex
The Twin Towers
The WTC site building arrangement
With construction of 7 World Trade Center in the 1980s, the World Trade Center had a total of seven buildings, but the most notable were the main twin towers which were each 110 stories tall. 1 WTC (the North Tower, which featured a 360-foot (110 m) high TV and radio antenna added in 1978, stood 1,368 feet (417 m) high, and 2 WTC (the South Tower, which contained the observation deck, was 1,362 feet (415 m) high.[56] The length and breadth of the towers were 208 feet (63.4 m) x 208 feet (63.4 m). Although only Tower 1 featured an antenna, both buildings were designed to carry a broadcast mast. The basement concourse of the World Trade Center included The Mall at the World Trade Center, along with a PATH station.
When completed in 1972, 1 WTC became the tallest building on Earth, unseating the Empire State Building after a 40-year reign. 2 WTC became the second tallest building in the world when completed in 1973. 2 WTC did not need these facilities, so it remained 1,362 feet (415 m). Regardless, the WTC towers held the height record only briefly. As the building neared completion in 1973, work had already begun on Chicago's Sears Tower, which ultimately reached 1,450 feet (442 m).[57] During a press conference in 1973, Minoru Yamasaki was asked, "Why two 110-story buildings? Why not one 220-story building?" His response was: "I didn't want to lose the human scale".[58] With the World Trade Center's destruction, the Empire State Building again became the tallest building in New York, after spending almost 30 years as the third-tallest in the city.
Of the 110 stories, eight were set aside for technical services (mechanical floors) Level B6/B5, Floors 7/8, 41/42, 75/76 and 108/109, in four two-floor areas evenly spread up the building. All the remaining floors were free for open-plan offices. Each floor of the towers had 40,000 square feet (3,700 m2) of space for occupancy.[18] Each tower had 3.8 million square feet (350,000 m²) of office space. Altogether the entire complex of seven buildings had 11.2 million square feet (1.04 km²) of space.
The lobby of the World Trade Center
During the 1990s, approximately 500 companies had offices in the complex, including many financial companies such as Morgan Stanley, Aon Corporation, Salomon Brothers, as well as the Port Authority itself. Electrical service to the towers was supplied by Consolidated Edison (ConEd) at 13,800 volts. This service passed through the World Trade Center Primary Distribution Center (PDC) and sent up through the core of the building to electrical substations located on the mechanical floors. The substations "stepped" the 13,800 primary voltage down to 480/277 volt secondary power and further to 120/208 volt general power and lighting service. The complex also was served by emergency generators located in the sublevels of the towers and on the roof of 5 WTC.[59][60]
The 110th Floor of 1 WTC (North Tower) housed commercial and public service radio & television transmission equipment. The roof of 1 WTC contained a vast array of transmission antennas, including the 360 ft (approx 110m) center antenna mast, which was rebuilt in 1999 by Dielectric Inc. to accommodate DTV. The center mast contained the television signals for almost all NYC television broadcasters: WCBS-TV 2, WNBC-TV 4, WNYW 5, WABC-TV 7, WWOR-TV 9 Secaucus, WPIX 11, WNET 13 Newark, WPXN-TV 31, and WNJU 47. It also had four NYC FM broadcasters on it as well: WPAT-FM 93.1, WNYC 93.9, WKCR 89.9, and WKTU 103.5.[61] Access to the roof was controlled from the WTC Operations Control Center (OCC) located in the B1 level of 2 WTC.
Observation deck and Windows on the World
Midtown Manhattan from the observation deck of the south tower which received an estimated 80,000 visitors a day, during the late 1990s.
Although most of the space in the WTC complex was off-limits to the public, 2 WTC (South Tower) featured a public observation area named "Top Of The World." When visiting the observation deck, visitors would first pass through security checks added after the 1993 World Trade Center bombing. Next, visitors were whisked to the 107th floor indoor observatory at a height of 1,310 feet (399 m) and greeted with a 360-degree view of the New York City skyline, and exhibitions including a three-dimensional scale model of Manhattan, and a simulated helicopter ride around the city. Weather permitting, visitors could take two short escalator rides up from the 107th floor and visit what was the world's highest outdoor viewing platform. At a height of 1,377 feet (420 m), visitors were able to take in a view of the North Tower and New York City unlike any other. On a clear day, visitors could see up to 49 miles (78 km) in any given direction. An anti-suicide fence was placed on the roof itself, with the viewing platform set back and elevated above it, requiring only an ordinary railing and leaving the view unobstructed, unlike the observation deck of the Empire State Building.
The North Tower (1 WTC) had a restaurant on the 107th floor called Windows on the World, which was an elegant restaurant known as a place for big celebrations, such as weddings. Windows on the World, which was developed by Joe Baum at a cost of more than $17 million, opened in April 1976.[62] Aside from the main restaurant, two offshoots were also originally located at the top of the North Tower: "Hors d'Oeuvrerie" (offered a Danish smorgasbord during the day and sushi in the evening) and "Cellar in the Sky" (a small wine bar).[63] Windows on the World also had a wine school program, run by Kevin Zraly. Windows on the World was closed for a period of time following the 1993 World Trade Center bombing, reopening in 1996.[62] Hors d'Oeuvrerie and Cellar in the Sky were replaced with the "Greatest Bar on Earth" and "Wild Blue".[63] In its last full year of operation, 2000, Windows on the World reported revenues of $37 million, making it the highest-grossing restaurant in the United States.[64]
The other buildings
Twin Towers view from Empire State Building, May 2001.
Five smaller buildings stood around the 16-acre (65,000 m²) block. One was the 22-floor hotel which opened in 1981 as the Vista Hotel and in 1995 became the Marriott World Trade Center (3 WTC) at the southwest corner of the site. Three low-rise buildings (4 WTC, 5 WTC, and 6 WTC) in the same hollow tube design as the towers also stood around the plaza. 6 World Trade Center, at the northwest corner, housed the United States Customs Service and the U.S. Commodities Exchange. 5 World Trade Center was located at the northeast corner, above the PATH station, and 4 World Trade Center was at the southeast corner. In 1987, a 47-floor office building called 7 WTC was built north of the block. Beneath the World Trade Center complex was an underground shopping mall, which in turn had connections to various mass transit facilities, including the New York City Subway system and the Port Authority's own PATH trains connecting Manhattan to Jersey City, Hoboken, and Newark.
One of the world's largest gold depositories was stored underneath the World Trade Center, owned by a group of commercial banks. The 1993 bomb detonated close to the vault, but it withstood the explosion, as did the towers. Seven weeks after the September 11 attacks, $230 million in precious metals were removed from basement vaults of 4 WTC, which included 3,800 100-Troy-ounce registered gold bars and 30,000 1,000-ounce silver bars.[65]
Life and events
On a typical weekday 50,000 people worked in the towers,[18] with another 200,000 passing through as visitors. The complex was so large that it had its own zip code, 10048. The towers offered spectacular views from the observation deck (located on top of the South Tower) and the Windows on the World restaurant (located on top of the North Tower). The Twin Towers became known worldwide, appearing in movies, TV shows, postcards, merchandise, magazines and much more, and became a New York icon, in the same league as the Empire State Building and Statue of Liberty. French high wire acrobatic performer Philippe Petit walked between the towers on a tightrope in 1974, and Brooklyn toymaker George Willig scaled the south tower in 1977.
The 1995 PCA world chess championship, between Garry Kasparov and Viswanathan Anand, was played on the 107th floor of the South Tower.[66] In January 1998, Ralph Guarino collected three men, Melvin, Richie, and Mike Reed to steal up towards 2.8 Million dollars from One World Brink bank on the eleventh floor of the World Trade Center. The heist was completed, however only 1.6 Million was stolen, mostly in Italian lira, francs, and yen. Subsequently all four were arrested; Ralph became an informant for the FBI against the DeCavalcante crime family which operated out of New Jersey.
February 13, 1975 fire
On February 13, 1975, a three-alarm fire broke out on the 11th floor of the North Tower, with fire spreading through the core from the 9th to 14th floors where electrical wiring was damaged. The fire ignited the insulation of telephone cables in a utility shaft that ran vertically between floors. The fire spread to other floors through openings in the floor slabs that were used to carry phone wires. The fires on other floors were extinguished almost immediately, and the main fire was put out in a few hours. Most of the damage was concentrated on the 11th floor, with the fire fueled by cabinets filled with paper, alcohol-based fluid for office machines, and other office equipment. Fireproofing protected the steel from melting and there was no structural damage to the tower. Other than the damage caused by the fire, a few floors below suffered water damage from the extinguishing of the fires above. At that time, the World Trade Center was not equipped with sprinkler systems.[67][68]
Bombing of February 26, 1993
Main article: World Trade Center bombing
On February 26, 1993 at 12:17 PM, a Ryder truck filled with 1,500 pounds (680 kg) of explosives was planted by Ramzi Yousef and detonated in the underground garage of the North Tower, opening a 100 foot (30 m) hole through 5 sublevels of concrete leaving six people dead and 50,000 other workers and visitors gasping for air in the shafts of the 110 story towers.
Damage underground due to the bombing
Many people inside the North Tower were forced to walk down darkened stairwells that contained no emergency lighting, some taking two hours or more to reach safety. As the Port Authority was a bistate agency, the towers were exempt from New York City building codes. Subsequent to the bombing The Port Authority installed emergency lighting in the stairwells. It is believed that this lighting saved many lives during the events of September 11, 2001.
In 1997 and 1998, six Islamist extremists were convicted and sentenced to life in prison for their roles in the bombing. According to a presiding judge, the conspirators' chief aim at the time of the attack was to destabilize the north tower and send it crashing into the south tower, toppling both landmarks.
As a memorial to the victims of the bombing of the tower, a reflecting pool was installed with the names of those who had been killed in the blast. Following the September 11, 2001 attacks, relief workers found a single fractured piece of the fountain etched with the word "John"; to date it is the only remaining part of the 1993 memorial that survived the collapse of the towers.
The World Trade Center complex was protected by an extensive fire detection and voice evacuation paging system upgraded after the 1993 bombing. Fire Command Stations, staffed by Fire Safety Directors were located in the lobbies of each building and the Operations Control Center (OCC) monitored these systems. An extensive study of the performance of World Trade Center Fire Protection Systems was conducted by the National Institute of Standards and Technology (NIST) following 2001-09-11.[69]
Lease
In 1998, plans were approved by the Port Authority to privatize the World Trade Center.[70] In 2001, the Port Authority sought to lease the World Trade Center to a private entity. Bids for the lease came from Vornado Realty Trust, a joint bid between Brookfield Properties Corporation and Boston Properties,[71] and a joint bid by Silverstein Properties and The Westfield Group.[72] By privatizing the World Trade Center, it would be added to the city's tax rolls.[72] The lease was also intended to raise funds for other Port Authority projects.[73] On February 15, 2001, the Port Authority announced that Vornado Trust Realty had won the lease for the World Trade Center, paying $3.25 billion for the 99-year lease.[74] Vornado Realty outbid Silverstein by $600 million, though Silverstein upped his offer to $3.22 billion. However, Vornado insisted on last minute changes to the deal, including a shorter 39-year lease, which the Port Authority considered nonnegotiable.[75] Vornado later withdrew and Silverstein's bid for the lease to the World Trade Center was accepted on April 26, 2001,[76] and closed on July 24, 2001.[77]
September 11, 2001
Main articles: September 11, 2001 attacks and Collapse of the World Trade Center
The World Trade Center on fire with the Statue of Liberty in the foreground
On September 11, 2001 at 8:46 a.m. Eastern Time, Al Qaeda suicide hijackers crashed American Airlines Flight 11 into the northern facade of the North Tower. Seventeen minutes later, at 9:03 a.m., a second team of hijackers crashed United Airlines Flight 175 into the South Tower, which subsequently collapsed at 9:59 a.m.[78] The damage caused to the North Tower by Flight 11 destroyed any means of escape from above the impact zone, trapping 1,344 people.[79] The North Tower collapsed at 10:28, after burning for approximately 102 minutes.[80]
At 5:20 p.m. on September 11, 2001, 7 World Trade Center collapsed due to uncontrolled fires causing structural failure.[81] 3 World Trade Center, a Mariott hotel, was destroyed during the collapse of the two towers. The three remaining buildings in the WTC plaza sustained heavy damage from debris, and were ultimately demolished. [82] The Deutsche Bank Building across Liberty Street from the World Trade Center complex was later condemned due to the uninhabitable, toxic conditions inside the office tower, and is undergoing deconstruction.[83][84] The Borough of Manhattan Community College's Fiterman Hall at 30 West Broadway was also condemned due to extensive damage in the attacks, and is slated for deconstruction.[85]
At the time of the incident, media reports suggested that tens of thousands might have been killed in the attacks, as on any given day upwards of 50,000 people could be inside the towers. Ultimately, 2,749 death certificates were filed relating to the 9/11 attacks.[86] Of these, 1,614 (59%) were identified from recovered physical remains. Cantor Fitzgerald L.P., an investment bank on the 101st–105th floors of One World Trade Center, lost 658 employees, considerably more than any other employer.[87] Marsh Inc., located immediately below Cantor Fitzgerald on floors 93–101 (the location of Flight 11's impact), lost 295 employees, and 175 employees of Aon Corporation were killed.[88] As well, 343 deaths were New York City firefighters, 84 were Port Authority employees, of whom 37 were members of the Port Authority Police Department, and another 23 were New York City Police Department officers. Of all the people who were still in the towers when they collapsed only 20 of these people were pulled out alive.
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