World Trade Center 7 (1982-2001)

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World Trade Center 7 was a 47-story building, designed by Emery Roth & Sons, with a red granite façade. The building was 610 feet (186 m) tall, with a trapezoidal footprint that was 330 ft (101 m) long and 140 ft (43 m) wide.[1][2] Tishman Realty & Construction managed construction of the building, which began in 1983.[1] In March 1987, the building opened, becoming the seventh structure of the World Trade Center.

The building was constructed above a Con Edison substation that had been on the site since 1967.[3] The substation had a caisson foundation designed to carry the weight of a future building of 25 stories containing 600,000 sq ft (55,700 m²).[4] The final design for 7 World Trade Center was for a much larger building covering a larger footprint than originally planned when the substation was built.[5]

The structural design of 7 World Trade Center included features to allow a larger building than originally planned to be constructed. A system of gravity column transfer trusses and girders was located between floors 5 and 7 to transfer loads to the smaller foundation.[3] Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The fifth floor functioned as a structural diaphragm, providing lateral stability and distribution of loads between the new and old caissons. Above the seventh floor, the building's structure was a typical tube-frame design, with columns in the core and on the perimeter, and lateral loads resisted by perimeter moment frames.[4]

A shipping/receiving ramp, which served the entire World Trade Center complex, occupied the eastern quarter of the 7 World Trade Center footprint. The building was open below the third floor, providing space for truck clearance on the shipping ramp.[4] The spray-on fireproofing for structural steel elements was gypsum-based Monokote which had a two-hour fire rating for steel beams, girders and truss, and a three-hour rating for columns.[6]

Mechanical equipment was installed on floors four through seven, including 12 transformers on the fifth floor. Several generators in the building were used by the Office of Emergency Management, Salomon Smith Barney and others.[6] Storage tanks contained 24,000 gallons (91,000 L) of diesel fuel to supply the generators.[7] Fuel oil distribution components were located at ground level, up to the ninth floor.[8] After the World Trade Center bombings of February 26, 1993, New York City mayor Rudy Giuliani decided to situate the emergency command center and associated fuel tanks at 7 World Trade Center. Although this decision was criticized in light of the events of 9/11, the fuel in the building is today not believed to have contributed to the collapse of the building.[9][10][11][12][13][14][15] The roof of the building included a small west penthouse and a larger east mechanical penthouse.[3]

Each floor had 47,000 sq ft (4,366 m²) of rentable office space which made the building's floor plans considerably larger than most office buildings in the City.[16] In all, 7 World Trade Center had 1,868,000 sq ft (174,000 m²) of office space.[6] Two pedestrian bridges connected the main World Trade Center complex, across Vesey Street, to the third floor of 7 World Trade Center. The lobby of 7 World Trade Center had three murals by artist Al Held: The Third Circle, Pan North XII, and Vorces VII.[17][18] A sculpture by Alexander Calder, called WTC Stabile (also known by other names, The Cockeyed Propeller and Three Wings) was on a plaza in front of the building.[19]



In June 1986, before construction was completed, Silverstein signed Drexel Burnham Lambert as a tenant to lease the entire 7 World Trade Center building for $3 billion over a term of 30 years.[20] In December 1986, after the Boesky insider-trading scandal, Drexel Burnham Lambert canceled the lease, leaving Silverstein to find other tenants.[21] Spicer & Oppenheim agreed to lease 14 percent of the space, but for more than a year, as Black Monday and other factors adversely affected the Lower Manhattan real estate market, Silverstein was unable to find tenants for the remaining space. By April 1988, Silverstein had lowered the rent and made other concessions.[22]

In November 1988, Salomon Brothers withdrew from plans to build a large new complex at Columbus Circle in Midtown and agreed to a 20-year lease for the top 19 floors of 7 World Trade Center.[23] The building was extensively renovated in 1989 to accommodate the needs of Salomon Brothers.[24] Most of three existing floors were removed as tenants continued to occupy other floors, and more than 350 tons (U.S.) of steel were added to construct three double-height trading floors. Nine diesel generators were installed on the 5th floor as part of a backup power station. "Essentially, Salomon is constructing a building within a building - and it's an occupied building, which complicates the situation," said a district manager of Silverstein Properties. The unusual task was possible, said Larry Silverstein, because it was designed to allow for "entire portions of floors to be removed without affecting the building's structural integrity, on the assumption that someone might need double-height floors."[24]

At the time of the September 11, 2001 attacks, Salomon Smith Barney was by far the largest tenant in 7 World Trade Center, occupying 1,202,900 sq ft (111,750 m²) (64 percent of the building) which included floors 28–45.[25][6] Other major tenants included ITT Hartford Insurance Group (122,590 sq ft/11,400 m²), American Express Bank International (106,117 sq ft/9,900 m²), Standard Chartered Bank (111,398 sq ft/10,350 m²), and the Securities and Exchange Commission (106,117 sq ft/9,850 m²).[25] Smaller tenants included the Internal Revenue Service Regional Council (90,430 sq ft/8,400 m²) and the United States Secret Service (85,343 sq ft/7,900 m²).[25] The smallest tenants included the New York City Office of Emergency Management, National Association of Insurance Commissioners, Federal Home Loan Bank, First State Management Group Inc., Provident Financial Management, and the Immigration and Naturalization Service.[25] The Department of Defense (DOD) and Central Intelligence Agency (CIA) shared the 25th floor with the IRS.[6] Floors 46–47 were mechanical floors, as were the bottom six floors and part of the seventh floor.[6][26]


As the North Tower collapsed on September 11, 2001, debris hit 7 World Trade Center, causing heavy damage to the south face of the building.[3] The bottom portion of the building's south face was heavily damaged from debris, including damage to the southwest corner from the 8th to 18th floors, a large vertical gash on the center-bottom extending at least ten floors, and other damage as high as the 18th floor.[3] The building was equipped with a sprinkler system, but had many single-point vulnerabilities for failure: the sprinkler system required manual initiation of the electrical fire pumps, rather than being fully automatic system; the floor-level controls had a single connection to the sprinkler water riser; and the sprinkler system required some power for the fire pump to deliver water. Also, water pressure was low, with little or no water to feed sprinklers.[27][28]

After the North Tower collapsed, some firefighters entered 7 World Trade Center to search the building. They attempted to extinguish small pockets of fire, but low water pressure hindered their efforts.[29] A massive fire burned into the afternoon on the 11th and 12th floors of 7 World Trade Center, the flames visible on the east side of the building.[30][31] During the afternoon, fire was also seen on floors 6–10, 13–14, 19–22, and 29–30.[3] At approximately 2:00 p.m., firefighters noticed a bulge in the southwest corner of 7 World Trade Center between the 10th and 13th floors, a sign that the building was unstable and might collapse.[32] During the afternoon, firefighters also heard creaking sounds coming from the building.[33] Around 3:30 pm FDNY Chief Daniel Nigro decided to halt rescue operations, surface removal, and searches along the surface of the debris near 7 World Trade Center and evacuate the area due to concerns for the safety of personnel.[34][32] At 5:20 p.m. EDT on September 11, 2001, 7 World Trade Center collapsed. Some have claimed the collapse was the result of a controlled demolition.

In May 2002, the Federal Emergency Management Agency (FEMA) issued a report on the collapse based on a preliminary investigation conducted jointly with the Structural Engineering Institute of the American Society of Civil Engineers under leadership of Dr. W. Gene Corley, P.E. FEMA made preliminary findings that the collapse was not primarily caused by actual impact damage from the collapse of 1 WTC and 2 WTC but by fires on multiple stories ignited by debris from the other two towers that continued unabated due to lack of water for sprinklers or manual firefighting. According to FEMA, structural elements were exposed to high temperatures for a sufficient period of time to reduce their strength to the point of collapse[6]; nevertheless, it has since been determined that the fires burned out in 20 minutes at any given location.[15]

The report did not reach final conclusions about the cause of the collapse and called for further investigation:

Loss of structural integrity was likely a result of weakening caused by fires on the 5th to 7th floors. The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time. Although the total diesel fuel on the premises contained massive potential energy, the best hypothesis has only a low probability of occurrence. Further research, investigation, and analyses are needed to resolve this issue. [Ch. 5, p. 31.]

In response to FEMA's concerns, the Commerce Department’s National Institute of Standards and Technology (NIST) was authorized to lead an investigation into the structural failure and collapse of the World Trade Center twin towers and 7 World Trade Center.[35] The investigation, led by Dr S. Shyam Sunder, drew not only upon in-house technical expertise, but also upon the knowledge of several outside private institutions, including the Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE), the Society of Fire Protection Engineers (SFPE), the National Fire Protection Association (NFPA), the American Institute of Steel Construction (AISC), the Council on Tall Buildings and Urban Habitat (CTBUH), and the Structural Engineers Association of New York (SEAoNY).[36]

NIST has released a video and still-photo analysis of 7 World Trade Center before its collapse that appears to indicate a greater degree of structural damage from falling debris than originally assumed by FEMA. Specifically, NIST's interim report on 7 World Trade Center displays photographs of the southwest façade of the building that show it to have significant damage. The report also highlights a 10-story gash in the center of the south façade, toward the bottom, extending approximately a quarter of the way into the interior.[37][3] A unique aspect of the design of 7 World Trade Center was that each outer structural column was responsible for supporting 2,000 sq ft (186 m²) of floor space, suggesting that the simultaneous removal of a number of columns severely compromised the structure's integrity.[38] Consistent with this theory, news footage shows cracking and bowing of the building's east wall immediately before the collapse, which began at the penthouse floors.[3] In video of the collapse, taken from the north by CBS News and other news media, the first visible sign of collapse is movement in the east penthouse 8.2 seconds before the north wall began to collapse, which took at least another 7 seconds.[3][39]

A progress report was released in June 2004, outlining NIST's working hypothesis.[40][3] The hypothesis, which was reiterated in a June 2007 status update, is that an initial failure in a critical column occurred below the 13th floor, caused by damage from fire and/or debris from the collapse of the two main towers. The collapse progressed vertically up to the east mechanical penthouse. The interior structure was unable to handle the redistributed load, resulting in horizontal progression of the failure across lower floors, particularly the 5th to 7th floors. This resulted in "a disproportionate collapse of the entire structure."[41]

NIST anticipates the release of a draft report of 7 World Trade Center in 2008.[42] NIST is utilizing ANSYS to model events leading up to collapse initiation and LS-DYNA models to simulate the global response to initiating events.[43] According to NIST, the investigation of 7 World Trade Center has been delayed for a number of reasons, including that NIST staff who had been working on 7 World Trade Center were assigned full-time from June 2004 to September 2005 to work on the investigation of the collapse of the twin towers.[44] In June 2007, Shyam Sunder explained, "We are proceeding as quickly as possible while rigorously testing and evaluating a wide range of scenarios to reach the most definitive conclusion possible. The 7 WTC investigation is in some respects just as challenging, if not more so, than the study of the towers. However, the current study does benefit greatly from the significant technological advances achieved and lessons learned from our work on the towers."[41]

Conspiracy theorists believe the building collapses on September 11, including that of building seven, were the result of controlled demolition.[45][46][47][48][49] In spring 2008, a civil engineering journal published a letter written by supporters of the controlled demolition theory.[50] NIST states it has "found no evidence of a blast or controlled demolition event". In its final report on building 7, it would "like to determine the magnitude of hypothetical blast scenarios that could have led to the structural failure of one or more critical elements".[44]

When 7 World Trade Center collapsed, debris caused substantial damage and contamination to the Borough of Manhattan Community College's Fiterman Hall building, located adjacent at 30 West Broadway, to the extent that the building is not salvageable. As of August 2007, Fiterman Hall is undergoing deconstruction.[51] The adjacent Verizon Building, an art deco building constructed in 1926, had extensive damage to its east façade from the collapse of 7 World Trade Center, though was able to be restored at a cost of US$1.4 billion.[52]



  1. 1.0 1.1 Lew, H.S., Richard W. Bukowski, Nicholas J. Carino (September 2005). Design, Construction, and Maintenance of Structural and Life Safety Systems (NCSTAR 1-1). National Institute of Standards and Technology (NIST), p. 13. 
  2. Seven World Trade Center (pre-9/11). Retrieved on 2006-05-07.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Interim Report on WTC 7 (pdf). Appendix L. National Institute of Standards and Technology (2004). Retrieved on 2007-08-20.
  4. 4.0 4.1 4.2 Salvarinas, John J. (1986). "Seven World Trade Center, New York, Fabrication and Construction Aspects". Proceedings of the 1986 Canadian Structural Engineering Conference. Vancouver: Canadian Steel Construction Council. 
  5. Lew, H.S., et al (September 2005). "NIST NCSTAR 1-1: Design, Construction, and Maintenance of Structural and Life Safety Systems", Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster (pdf), NIST, p. xxxvii. Retrieved on 2008-02-17. 
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Gilsanz, Ramon, Edward M. DePaola, Christopher Marrion, and Harold "Bud" Nelson (May 2002). "WTC7 (Chapter 5)", World Trade Center Building Performance Study (pdf), FEMA. Retrieved on 2008-02-17. 
  7. Milke, James (Spring 2003). "Study of Building Performance in the WTC Disaster". Fire Protection Engineering. Retrieved on 2008-02-17.
  8. Grill, Raymond A., Duane A. Johnson (September 2005). "NIST NCSTAR 1-1J: Documentation of the Fuel System for Emergency Power in World Trade Center 7", Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster (pdf), NIST. Retrieved on 2008-02-17. 
  9. Glanz, James and Eric Lipton (2001-12-20). "A Nation Challenged: The Trade Center; City Had Been Warned of Fuel Tank at 7 World Trade Center". New York Times. Retrieved 2007-11-21. 
  10. "Rudy Giuliani's 5 Big Lies About 9/11: On the Stump, Rudy Can't Help Spreading Smoke and Ashes About His Dubious Record," Village Voice August 8–14, 2007, pp. 22–36.
  11. Ruddy, Christopher (2004-05-24). Replying to Giuliani. NewsMax. Retrieved on 2007-06-12.
  12. Transcript: Rudy Giuliani on Fox News Sunday. Fox News (2007-05-14). Retrieved on 2007-09-29. “Then why did he say the building — he said it's not — the place in Brooklyn is not as visible a target as buildings in Lower Manhattan”
  13. Russ Buettner (2007-05-22). "Onetime Giuliani Insider Is Now a Critic". New York Times. Retrieved 2007-06-12. 
  14. Giuliani Blames Aide for Poor Emergency Planning. Daily Intelligencer (2007-05-15). Retrieved on 2007-06-12.
  15. 15.0 15.1 National Construction Safety Team Advisory Committee. Transcript: Meeting of the National Construction Safety Team Advisory Committee, December 18, 2007.
  16. Horsley, Carter B (1981-10-25). "Lower Manhattan Luring Office Developers". The New York Times. Retrieved 2008-02-17. 
  17. Al Held. National Gallery of Australia. Retrieved on 2007-05-29.
  18. Plagens, Peter (1989-04-17). "Is Bigger Necessarily Better?". Newsweek. 
  19. Wenegrat, Saul (2002-02-28). "Public Art at the World Trade Center". International Foundation for Art Research. Retrieved 2007-07-27. 
  20. Scardino, Albert (1986-07-11). "A Realty Gambler's Big Coup". The New York Times. 
  21. Scardino, Albert (1986-12-03). "$3 Billion Office Pact Canceled by Drexel". The New York Times. 
  22. Berg, Eric N (1988-04-07). "Talking Deals; Developer Plays A Waiting Game". The New York Times. Retrieved 2008-02-17. 
  23. Berkowitz, Harry (1988-11-29). "Salomon to Move Downtown". Newsday. 
  24. 24.0 24.1 McCain, Mark (1989-02-19). "The Salomon Solution; A Building Within a Building, at a Cost of $200 Million". The New York Times. Retrieved 2007-02-17. 
  25. 25.0 25.1 25.2 25.3 "Building: 7 World Trade Center". CNN. 2001. Retrieved 2007-09-12. 
  26. CIA Lost Office In WTC: A secret office operated by the CIA was destroyed in the terrorist attacks on the World Trade Center, seriously disrupting intelligence operations'. / AP (2001-11-05). Retrieved on 2008-02-17.
  27. Grosshandler, William. Active Fire Protection Systems Issues (pdf). NIST. Retrieved on 2007-09-11.
  28. Evans, David D (September 2005). Active Fire Protection Systems (pdf). NIST. Retrieved on 2007-09-11.
  29. Oral Histories From Sept. 11 - Interview with Captain Anthony Varriale (pdf). The New York Times (2001-12-12). Retrieved on 2007-08-22.
  30. Spak, Steve. (September 11). WTC 9-11-01 Day of Disaster. [Video]. New York City: Spak, Steve. 
  31. Scheuerman, Arthur (2006-12-08). "The Collapse of Building 7" (pdf). NIST. Retrieved on 2007-06-29.
  32. 32.0 32.1 WTC: This Is Their Story, Interview with Chief Peter Hayden. (2002-09-09). Retrieved on 2007-06-28.
  33. WTC: This Is Their Story, Interview with Captain Chris Boyle. (August 2002). Retrieved on 2007-08-22.
  34. Oral Histories From Sept. 11 - Interview with Chief Daniel Nigro. The New York Times (2001-10-24). Retrieved on 2007-06-28.
  35. NIST’s World Trade Center Investigation. NIST. Retrieved on 2007-08-20.
  36. Final Report on the Collapse of the World Trade Center (pdf). National Institute of Standards and Technology (NIST) (September 2005). Retrieved on 2008-02-17.
  37. "Debunking the 9/11 Myths: Special Report". Popular Mechanics. March 2005. Retrieved 2008-01-17. 
  38. NIST Response to the World Trade Center Disaster (Part IIC - WTC 7 Collapse) (pdf). NIST (2005-04-05). Retrieved on 2007-08-23.
  39. CBS News. (September 11). CBS Sept. 11, 2001 4:51 pm - 5:33 pm (September 11, 2001). [Television]. WUSA, CBS 9, Washington, D.C.  - View footage of the collapse captured by CBS
  40. Key Findings of NIST’s June 2004 Progress Report on the Federal Building and Fire Safety Investigation of the World Trade Center Disaster. Fact sheets from NIST. National Institute of Standards and Technology (2004). Retrieved on 2006-07-28.
  41. 41.0 41.1 National Institute of Standards and Technology (2007-06-29). "NIST Status Update on World Trade Center 7 Investigation". Press release. Retrieved 2008-02-17. 
  42. Sunder, S. Shyam (2007-12-18). "Opening Remarks and Overview of WTC 7 Investigation" (pdf). Proceedings. NCST Advisory Committee Meeting. NIST. Retrieved 2008-02-17. 
  43. McAllister, Therese (2006-12-12). WTC 7 Technical Approach and Status Summary (pdf). NIST. Retrieved on 2008-02-17.
  44. 44.0 44.1 Answers to Frequently Asked Questions. National Institute of Standards and Technology (August 2006). Retrieved on 2008-02-17.
  45. Thomas Hargrove (July 2006). Third of Americans suspect 9-11 government conspiracy. ScrippsNews. Retrieved on 2007-06-26.
  46. Sullivan, Will (2006-09-03). "Viewing 9/11 From a Grassy Knoll". U.S. News & World Report. Retrieved 2008-02-17. 
  47. The AE911Truth Petition: to the members of the house of representatives and of the Senate of the United States of America. Architects and Engineers for 9/11 Truth.
  48. "The evolution of a conspiracy theory". BBC News. 2008-07-04. Retrieved 2008-07-04. 
  49. Asquith, Christina (Sept 2006). "Conspiracies continue to abound surrounding 9/11: on the eve of the fifth anniversary, a group of professors say the attacks were an "inside job.".". Diverse Issues in Higher Education: 12. Retrieved on 2008-07-04.
  50. Steven E. Jones, Frank M. Legge, Kevin R. Ryan, Anthony F. Szamboti, and James R. Gourley (2008). Fourteen Points of Agreement with Official Government Reports on the World Trade Center Destruction". Bentham, The Open Civil Engineering Journal, Volume 2, Issue 1.
  51. Fiterman Hall — Project Updates. Lower Manhattan Construction Command Center/LMDC. Retrieved on 2007-08-23.
  52. Verizon Building Restoration. New York Construction (McGraw Hill). Retrieved on 2007-06-28.

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