The Mysterious Leveling of Building WTC-7

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FEMA on Building 7
Despite the inescapable logic, the official theory for the collapse, as published in Chapter 5 of the FEMA report goes as follows:

* At 9:59 AM (after the South Tower collapse), electrical power to the substations in WTC 7 was shut off.
* Due to a design flaw, generators in WTC 7 started up by themselves.
* Debris from the collapsing North Tower breached a fuel oil pipe in a room in the north side of the building. (This means the debris had to travel across WTC 6 and Vesey Street -- a distance of at least 355 feet -- penetrate the outer wall of WTC 6, and smash through about 50 feet of the building, including a concrete masonry wall.)
* This, and other debris (that also made the journey across Building 6 and Vesey Street), managed to start numerous fires in the building. (Unfortunately, this event did not prompt anyone to turn off the generators.)
* The backup mechanism (that should have shut off the fuel oil pumps when a breach occurred) failed to work, and the fuel oil (diesel) was pumped from the tanks on the ground floor to the fifth floor where it ignited. The pumps emptied the tanks of all 12,000 gallons of fuel.
* The extant fires raised the temperature of the spilled fuel oil to the 140 degrees F required for it to ignite.
* The sprinkler system malfunctioned and failed to extinguish the fire.
* The burning diesel fuel heated trusses to the point where they lost most of their strength, precipitating a total collapse of Building 7.

The last point is the greatest stretch, since it asks us to believe that an event that would be expected only to cause the sagging of a floor instead led not only to total collapse, but to such a tidy collapse that directly adjacent buildings were scarcely even damaged. This is surprising behavior for a steel frame skyscraper designed to survive fires, hurricanes, and earthquakes.
After laying out this highly improbable scenario, the FEMA report authors 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. Further research, investigation, and analyses are needed to resolve this issue.
Unfortunately for investigators hoping to resolve this issue, nearly all of the evidence had already been destroyed by the time the FEMA report was published.

But... we have some near better; Analysis of Energy Requirements for the Expansion of the Dust Cloud Following the Collapse of 1 World Trade Center (the North Tower)


Documents Destroyed
At the time of its destruction, Building 7 housed documents relating to numerous SEC investigations. The files for approximately three to four thousand cases were destroyed, according to the Los Angeles Times. Among the destroyed documents were ones that may have demonstrated the relationship between Citigroup and the WorldCom bankruptcy.