7 World Trade Center (7 WTC, WTC-7, or Tower 7), colloquially known as Building 7 or the Salomon Brothers Building, was an office building constructed as part of the original World Trade Center complex in Lower Manhattan, New York City. The tower was located on a city block bounded by West Broadway, Vesey Street, Washington Street, and Barclay Street on the east, south, west, and north, respectively. It was developed by Larry Silverstein, who held a ground lease for the site from the Port Authority of New York and New Jersey, and designed by Emery Roth & Sons. It was destroyed during the September 11 attacks.

The original Trade Center was tall, clad in red granite masonry, and occupied a trapezoidal footprint. An elevated walkway spanning Vesey Street connected the building to the World Trade Center plaza. The building was situated above a Consolidated Edison power substation, which imposed unique structural design constraints. The building opened in 1987, and Salomon Brothers signed a long-term lease the next year, becoming the anchor tenant of .

On September 11, 2001, the structure was substantially damaged by debris when the nearby North Tower (1 World Trade Center) collapsed. The debris cut a large gash in the south side of the building and ignited fires on multiple lower floors, which continued to burn uncontrolled throughout the afternoon. The building's internal fire suppression system lacked water pressure to fight the fires. 7 WTC began to collapse when a critical internal column buckled and triggered cascading failure of nearby columns throughout. This initiated the progressive collapse of the entire building just after , according to FEMA and NIST. The collapse made 7 WTC the first steel skyscraper known to have collapsed primarily due to uncontrolled fires. A new building on the site opened in 2006.

Architecture

The original 7 World Trade Center was a 47-story building, designed by Emery Roth & Sons, with a red granite facade. The building was tall, with a trapezoidal footprint that was long and wide. Tishman Realty & Construction managed construction of the building.

Features

Mechanical features 7 World Trade Center was constructed above a two-story Con Edison substation that had been located on the site since 1967. The substation had a caisson foundation designed to carry the weight of a future building of 25 stories containing . However, the final design for 7 World Trade Center was for a much larger building than originally planned when the substation was built. The structural design of 7 World Trade Center therefore included a system of gravity column transfer trusses and girders, located between floors 5 and 7, to transfer loads to the smaller foundation. Existing caissons installed in 1967 were used, along with new ones, to accommodate the building. The 5th floor functioned as a structural diaphragm, providing lateral stability and the distribution of loads between the new and old caissons. Above the 7th 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.

A shipping and 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 3rd floor, providing space for truck clearance on the shipping ramp. The spray-on fireproofing for structural steel elements was gypsum-based Monokote, which had a two-hour fire rating for steel beams, girders, and trusses, and a three-hour rating for columns.

Mechanical equipment was installed on floors four through seven, including 12 transformers on the 5th floor. Several emergency generators installed in the building were used by the New York City Office of Emergency Management, Salomon Smith Barney, and other tenants. In order to supply the generators, 24,000 gallons (91,000 L) of diesel fuel were stored below ground level. Diesel fuel distribution components were located at ground level, up to the ninth floor. The roof of the building included a small west penthouse and a larger east mechanical penthouse.

Offices Each floor had of rentable office space, which made the building's floor plans considerably larger than most office buildings in the city. In all, 7 World Trade Center had of office space. Two pedestrian bridges connected the main World Trade Center complex, across Vesey Street, to the third floor of 7 World Trade Center. In addition to several acquired artworks, from artists such as Frank Stella, Roy Lichtenstein, and Ross Bleckner, the lobby of 7 World Trade Center housed a large mural by artist Al Held, titled The Third Circle.See:

History The groundbreaking ceremony was hosted on October 2, 1984. The building opened in May 1987 as part of the World Trade Center.

In June 1986, before construction was completed, developer Larry 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. In December 1986, after the Boesky insider-trading scandal, Drexel Burnham Lambert canceled the lease, leaving Silverstein to find other tenants. 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, he had lowered the rent and made other concessions.

In November 1988, Salomon Brothers withdrew from plans to build a large new complex at Columbus Circle in Midtown, instead agreeing to a 20-year lease for the top 19 floors of 7 World Trade Center. The building was extensively renovated in 1989 to accommodate Salomon Brothers, and 7 World Trade Center alternatively became known as the Salomon Brothers building. Most of the three existing floors were removed as tenants continued to occupy other stories, 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. According to Larry Silverstein, the unusual task was possible because it could allow "entire portions of floors to be removed without affecting the building's structural integrity, on the assumption that someone might need double-height floors."

After the World Trade Center bombing 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 not believed to have contributed to the collapse of the building.See:

Final tenants

At the time of the September 11 attacks, Salomon Smith Barney was by far the largest tenant in 7 World Trade Center, occupying (64 percent of the building) which included floors 28–45. 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). 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). The smallest tenants included the New York City Office of Emergency Management, National Association of Insurance Commissioners, Federal Home Loan Bank of New York, First State Management Group Inc., Provident Financial Management, and the Immigration and Naturalization Service. The Department of Defense (DOD) and Central Intelligence Agency (CIA) shared the 25th floor with the IRS. (The clandestine CIA office was revealed only after the 9/11 attacks.) Floors 46–47 were mechanical floors, as were the bottom six floors and part of the seventh floor.

According to CoStar Group, floors 9 and 10 of 7 WTC were occupied by the Secret Service. The CIA had offices on the 25th floor of 7 WTC, as reported by the Associated Press. The National Institute of Standards and Technology's 2008 Final Report on the Collapse of World Trade Center Building 7 confirmed that floor 14 was vacant, and updated the news reports of CoStar and Associated Press from 2001 to show that Salomon Smith Barney leased floors 15 to 17.

Fl# Companies 28–45 Salomon Smith Barney 26–27 Salomon Smith Barney, Standard Chartered Bank 25 Department of Defense, Central Intelligence Agency, Internal Revenue Service Regional Council 24 Salomon Smith Barney, Internal Revenue Service Regional Council 23 Salomon Smith Barney, NYC Office of Emergency Management 22 Salomon Smith Barney, Federal Home Loan Bank 21 Salomon Smith Barney, First State Management Group, Hartford Financial Services Group 20 Salomon Smith Barney, Hartford Financial Services Group 19 Salomon Smith Barney, Hartford Financial Services Group, National Association of Insurance Commissioners Securities 18 Salomon Smith Barney, U.S. Equal Employment Opportunity Commission 15–17 Salomon Smith Barney 14 Vacant 13 Salomon Smith Barney, Provident Bank, American Express, U.S. Securities and Exchange Commission, Standard Chartered Bank 11–12 U.S. Securities and Exchange Commission 10 U.S. Secret Service, Standard Chartered Bank 9 U.S. Secret Service 8 American Express 7 American Express, Provident Bank G, 1–6 Salomon Smith Barney

The total amount of space occupied by each tenant was: TenantSquare feet leasedFloors occupiedIndustrySalomon Smith Barney1,202,9000–6, 13, 15–24, 26-47Financial InstitutionsInternal Revenue Service Regional Council90,43024, 25GovernmentU.S. Secret Service85,3439,10GovernmentAmerican Express Bank International106,1177, 8, 13Financial InstitutionsStandard Chartered Bank111,39810, 13, 26, 27Financial InstitutionsProvident Financial Management9,0007, 13Financial InstitutionsITT Hartford Insurance Group122,59019–21Financial InstitutionsFirst State Management Group4,00021InsuranceFederal Home Loan Bank47,49022Financial InstitutionsNational Association of Insurance Commissioners Securities22,50019InsuranceSecurities & Exchange Commission106,11711, 12, 13GovernmentNew York City Office of Emergency Management45,81523Government

Collapse

As the North Tower (1 World Trade Center) collapsed on September 11, 2001, heavy debris hit 7 World Trade Center, damaging the south face of the building and starting fires that continued to burn throughout the afternoon. The collapse also caused damage to the southwest corner between floors 7 and 17 and on the south face between floor 44 and the roof; other possible structural damage included a large vertical gash near the center of the south face between floors 24 and 41. 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 instead of being a 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. Additionally, water pressure was low, with little or no water to feed sprinklers.