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Context of '(10:28 a.m.-5:20 p.m.) September 11, 2001: WTC 7 Suffers Fires ‘on at Least 10 Floors’'

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World Trade Center Building 7 (WTC 7) suffers fires on several floors, some of which last until 5:20 p.m., when the building collapses. [National Institute of Standards and Technology, 8/21/2008] WTC 7 is a 47-story office building located just north of the Twin Towers. It is damaged when the north WTC tower (WTC 1) collapses at 10:28 a.m. (see 10:28 a.m. September 11, 2001). [National Institute of Standards and Technology, 11/2008, pp. 2, 16]
Fires Started by Collapse Debris - Two official reports on the collapse of WTC 7 will tentatively conclude that fires in this building are initiated by debris that is ejected when the North Tower collapses (see 10:28 a.m. September 11, 2001). In a 2002 report (see May 1, 2002), the Federal Emergency Management Agency (FEMA) will state, “It is likely that fires” in WTC 7 “started as a result of debris from the collapse of WTC 1.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-20] In a 2008 report (see November 20, 2008), the National Institute of Standards and Technology (NIST) will state, “Most likely, the WTC 7 fires began as a result of burning debris from the collapse of WTC 1.” However, NIST will add, “visual evidence of fires in the building was not available until around noon.” [National Institute of Standards and Technology, 11/2008, pp. 18]
Fires Spread in WTC 7 - According to NIST, fires are ignited “on at least 10 floors” of WTC 7, but “only the fires on floors 7 through 9 and 11 through 13 grew and lasted until the time of the building collapse.” [National Institute of Standards and Technology, 11/2008, pp. xxxvi] NIST will state, “Early fires were seen on the southwest corner of floors 19, 22, 29, and 30 shortly after noon,” but “These were short-lived.” [National Institute of Standards and Technology, 11/2008, pp. 51] The fires on floors 7 to 9 and 11 to 13, however, “grew and spread, since they were not extinguished either by the automatic sprinkler system or by [the New York City Fire Department], because water was not available in WTC 7.” Fires are “generally concentrated on the east and north sides of the northeast region beginning at about 3 p.m. to 4 p.m.” [National Institute of Standards and Technology, 11/2008, pp. 21] The fires on floors 7 to 9 and 11 to 13 have “characteristics similar to those that have occurred previously in tall buildings,” according to NIST, and “Their growth and spread [are] consistent with ordinary building contents fires.” [National Institute of Standards and Technology, 11/2008, pp. xxxvi] These fires are “fed by combustibles (e.g., desks, chairs, papers, carpet) that were ordinary for commercial occupancies.” However, NIST will point out, there is “no evidence that the fires spread from floor to floor, except, perhaps, just prior to the collapse of the building.” [National Institute of Standards and Technology, 11/2008, pp. 51-52]
Limited Evidence Available - Both FEMA and NIST will admit that their accounts of the fires in WTC 7 are based upon imperfect evidence. In its report on the WTC collapses, published in May 2002, FEMA will note, “Currently, there is limited information about the ignition and development of fires at WTC 7.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-20] In the final report of its investigation of the collapse of WTC 7, NIST will point out that “available images showing fires in WTC 7 did not allow the detailed description of fire spread that was possible for the WTC towers.” The report will add: “It must be kept in mind that [NIST’s] fire observations were based on images of the exterior faces, which provided little indication about the behavior of fires well removed from the exterior walls. It is likely that much of the burning took place beyond the views of the windows.” But, the report will state, “[T]here was sufficient information to derive general descriptions of fire ignition and spread on various floors of the building.” [National Institute of Standards and Technology, 11/2008, pp. 18]
NIST Blames Fires for Collapse - WTC 7 collapses at 5:20 p.m. this afternoon (see (5:20 p.m.) September 11, 2001). In late 2008, at the end of its investigation into WTC 7’s collapse, NIST will blame the fires WTC 7 suffers for causing its collapse (see August 21, 2008 and August 21, 2008). NIST will state: “The heat from the uncontrolled fires caused steel floor beams and girders to thermally expand, leading to a chain of events that caused a key structural column to fail. The failure of this structural column then initiated a fire-induced progressive collapse of the entire building.” [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 11/2008, pp. xxxvi-xxxvii] However, critics will dispute this conclusion, instead blaming explosives for the collapse (see August 21, 2008). [New York Times, 8/21/2008] FEMA will offer no firm conclusions about the possible role fires play in causing WTC 7 to collapse. In its 2002 report it will state, “The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-31]

Entity Tags: World Trade Center, National Institute of Standards and Technology, Federal Emergency Management Agency

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

Jeffrey Scott Shapiro.Jeffrey Scott Shapiro. [Source: University of Florida]Larry Silverstein, who recently took over the lease of the World Trade Center complex (see July 24, 2001), discusses possibly bringing down WTC Building 7 in a controlled demolition in a telephone conversation with his insurance carrier, according to a reporter who is at the WTC site this afternoon. [Fox News, 4/22/2010] WTC 7 is a 47-story office building located just north of the Twin Towers. The National Institute of Standards and Technology (NIST) will say it suffered some structural damage (see 10:28 a.m. September 11, 2001) when the North Tower collapsed (see 10:28 a.m. September 11, 2001) and it has fires on several floors (see (10:28 a.m.-5:20 p.m.) September 11, 2001). It will collapse at 5:20 p.m., apparently becoming the first tall building ever to come down primarily as a result of fire (see (5:20 p.m.) September 11, 2001). [National Institute of Standards and Technology, 11/2008, pp. xxxv-xxxvi]
Silverstein Allegedly Wants WTC 7 Demolished - Investigative reporter Jeffrey Scott Shapiro, who is at the scene of the attacks in New York, will later recall: “Shortly before [WTC 7] collapsed, several NYPD officers and Con Edison workers told me that Larry Silverstein… was on the phone with his insurance carrier to see if they would authorize the controlled demolition of the building, since its foundation was already unstable and expected to fall. A controlled demolition would have minimized the damage caused by the building’s imminent collapse and potentially save lives.” Shapiro will add: “Many law enforcement personnel, firefighters, and other journalists were aware of this possible option. There was no secret.” [Fox News, 4/22/2010] Preparing a large building for demolition usually takes weeks, or even months. This time is spent on operations such as wrapping concrete columns to ensure pieces do not fly off. [Baltimore Sun, 2/26/1995; PBS NOVA, 12/1996; Construction Equipment Guide, 2/24/2005]
Discussion of Demolition Later Denied - Silverstein will later recall discussing WTC 7 over the phone with the commander of the New York Fire Department, and telling him, “We’ve had such terrible loss of life, maybe the smartest thing to do is pull it” (see After 12:00 Noon September 11, 2001), but a spokesman will subsequently claim that Silverstein was referring to withdrawing firefighters from the building, not bringing WTC 7 down with explosives. [US Department of State, 9/16/2005; BBC, 7/4/2008] At the end of a three-year investigation into the building’s collapse, NIST will say WTC 7 “did not collapse from explosives,” but critics will dispute this conclusion (see August 21, 2008). [Associated Press, 8/21/2008; New York Times, 8/21/2008]

Entity Tags: Jeffrey Scott Shapiro, New York City Police Department, Con Edison, World Trade Center, Larry Silverstein

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

A four-image progression of photos showing World Trade Center Building 7 collapsing down into its footprint.A four-image progression of photos showing World Trade Center Building 7 collapsing down into its footprint. [Source: unknown] (click image to enlarge)Building 7 of the World Trade Center complex, a 47-story tower, collapses. No one is killed. [CNN, 9/12/2001; Washington Post, 9/12/2001; MSNBC, 9/22/2001; Associated Press, 8/21/2002] It collapses in 6.6 seconds, which is just 0.6 of a second longer than it would have taken a free-falling object dropped from its roof to hit the ground. [Deseret Morning News, 11/10/2005] Many questions will arise over the cause of its collapse in the coming months and years. Building 7, which was not hit by an airplane, is the first modern, steel-reinforced high-rise to collapse because of fire. [Chicago Tribune, 11/29/2001; Stanford Report, 12/5/2001; New York Times, 3/2/2002] Some will later suggest that the diesel fuel stored in several tanks on the premises may have contributed to the building’s collapse. The building contained a 6,000-gallon tank between its first and second floors and another four tanks, holding as much as 36,000 gallons, below ground level. There were also three smaller tanks on higher floors. [Chicago Tribune, 11/29/2001; New York Times, 3/2/2002; New York Observer, 3/25/2002; Federal Emergency Management Agency, 5/1/2002, pp. 1-17] However, the cause of the collapse is uncertain. A 2002 government report will conclude: “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.” [Federal Emergency Management Agency, 5/1/2002, pp. 1-17] Some reports indicate that the building may have been deliberately destroyed. Shortly after the collapse, CBS News anchor Dan Rather comments that the collapse is “reminiscent of… when a building was deliberately destroyed by well-placed dynamite to knock it down.” [CBS News, 9/11/2001] And moments after the collapse, MSNBC’s Brian Williams joins David Restuccio, an FDNY lieutenant, by phone to ask him about the collapse. “You guys knew this was coming all day?” asks Williams. Restuccio replies: “We had heard reports that the building was unstable, and that it would eventually need to come down on its own, or it would be taken down. I would imagine it came down on its own.” Restuccio does not explain what he means by “it would be taken down.” [MSNBC, 9/11/2001]

Entity Tags: Dan Rather, World Trade Center, David Restuccio

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

FEMA’s World Trade Center Building Performance Study.FEMA’s World Trade Center Building Performance Study. [Source: FEMA]FEMA releases its report of the WTC collapses. It concludes, “[W]ith the information and time available, the sequence of events leading to the collapse of each tower could not be definitively determined.” On Building 7: “The specifics of the fires in WTC 7 and how they caused the building to collapse remain unknown at this time.” [Federal Emergency Management Agency, 5/1/2002]

Entity Tags: World Trade Center, Federal Emergency Management Agency

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

NIST lead investigator Shyam Sunder answering questions about NIST’s three-year study of the collapse of WTC 7.NIST lead investigator Shyam Sunder answering questions about NIST’s three-year study of the collapse of WTC 7. [Source: Don Berkemeyer / National Institute of Standards and Technology]The National Institute of Standards and Technology (NIST) announces the findings of its study of the collapse of World Trade Center Building 7, and says the 47-story tower fell late in the afternoon of 9/11 primarily due to fires. [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 8/21/2008] NIST releases its findings as part of a 915-page report, which is the result of three years’ work by over 50 federal investigators and a dozen contractors (see August 21, 2008). [New York Times, 8/21/2008]
Collapse Is 'No Longer a Mystery' - In a news conference at NIST’s headquarters in Gaithersburg, Maryland, lead investigator Shyam Sunder admits: “[W]e knew from the beginning of our study that understanding what happened to Building 7 on 9/11 would be difficult. It did not fit any textbook description that you could readily point to and say, yes, that’s why the building failed.” But, he says, “[T]he reason for the collapse of World Trade Center 7 is no longer a mystery.” [National Institute of Standards and Technology, 8/21/2008; New York Times, 8/21/2008]
'New Phenomenon' Caused Collapse - Sunder says the “critical factor” that initiated the collapse was “thermal expansion of long-span floor systems located in the east side of the building,” and adds that NIST’s study “has identified thermal expansion as a new phenomenon that can cause structural collapse. For the first time we have shown that fire can induce a progressive collapse.”
Collapse Sequence - Sunder describes the sequence of events NIST believes led to the collapse of WTC 7. He says debris from the collapse of the north WTC tower “started fires on at least 10 floors of the building. The fires burned out of control on six of these 10 floors for about seven hours. The city water main had been cut by the collapse of the two WTC towers, so the sprinklers in Building 7 did not function for much of the bottom half of the building.” He continues: “Fires on floors 7 through 9 and 11 through 13 were particularly severe.… Eventually, a girder on floor 13 lost its connection to a critical interior column.” Floor 13 collapsed, beginning a cascade of floor failures down to the fifth floor. “With the support of these floors gone, column 79 buckled, which initiated the fire-induced progressive collapse of the building.… This in turn caused the failure of nearby columns 80 and 81 and floor failures up to the roof line.… As the roof line begins to fall adjacent columns buckle as well. In quick succession, the remaining interior columns failed from east to west across WTC 7, until the entire core began moving downward. Finally, the remaining outer shell or fa├žade of the building fell.”
NIST Created 'Virtual WTC 7' Model - Sunder says that NIST reached its conclusions about the collapse “by reconstructing the entire building, beam by beam, column by column, connection by connection into a computer model, a virtual WTC 7 building. We then filled that virtual building with as much detail as possible about exactly what types of furnishings were on each floor. Then we set fire to those virtual offices on the floors where video and other visual evidence told us the fires burned.” The investigators “used a well-validated computer program developed at NIST, for studying the growth and spread of fires, to calculate temperatures throughout the building.… And we used well-established data on the properties of structural steel, the sprayed fire resistive material or fireproofing, and other building materials to determine how those temperatures affected the structure.”
Explosives Not Used - Sunder says that the investigators “did not find any evidence that explosives were used to bring the building down” (see August 21, 2008), nor was the collapse “due to fires from the substantial amount of diesel fuel stored in the building” (see August 21, 2008). NIST commenced its investigation of the WTC collapses in 2002 (see August 21, 2002) and issued its findings on the collapses of the Twin Towers in October 2005 (see October 26, 2005). Since then it has been focused on WTC 7. [Government Computer News, 8/21/2008; National Institute of Standards and Technology, 8/21/2008]
Final Report to Be Released - After suggestions are made by members of the public in response to its current report, NIST will release a finished version of the same report in November 2008, thereby completing its WTC investigation (see November 20, 2008). [National Institute of Standards and Technology, 11/20/2008]

Entity Tags: World Trade Center, National Institute of Standards and Technology, Shyam Sunder

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

NIST’s ‘Final Report on the Collapse of World Trade Center Building 7.’NIST’s ‘Final Report on the Collapse of World Trade Center Building 7.’ [Source: National Institute of Standards and Technology.]The National Institute of Standards and Technology (NIST) releases the final report of its three-year investigation of the collapse of World Trade Center Building 7, the 47-story skyscraper which collapsed late in the afternoon of 9/11 (see (5:20 p.m.) September 11, 2001). This is the completed version of the report, and comes three months after a draft version was released for public comment (see August 21, 2008). NIST states that the new report “is strengthened by clarifications and supplemental text suggested by organizations and individuals worldwide in response to the draft WTC 7 report.” NIST conducted an additional computer analysis in response to comments from the building community, and made several minor amendments to the report. But, it says, “the revisions did not alter the investigation team’s major findings and recommendations, which include identification of fire as the primary cause for the building’s failure.” With the release of this report, NIST has completed its six-year investigation of the World Trade Center collapses, which it commenced in August 2002 (see August 21, 2002). The final report of its investigation of the Twin Towers’ collapses was published in October 2005 (see October 26, 2005). [National Institute of Standards and Technology, 11/20/2008; Occupational Health and Safety, 11/25/2008]

Entity Tags: World Trade Center, National Institute of Standards and Technology

Timeline Tags: Complete 911 Timeline, 9/11 Timeline

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