| March 2, 2002|
Burning Diesel Is Cited in Fall of 3rd Tower
By JAMES GLANZ and ERIC LIPTON
structural beams that functioned as a sort of bridge to hold up the
47-story skyscraper known as 7 World Trade Center were compromised in a
disastrous blaze fed by diesel fuel, leading to the building's collapse
on Sept. 11, investigators have concluded in a preliminary report.
The tower was set on fire by debris from the twin towers and burned for
about seven hours before collapsing in the late afternoon under
previously unexplained circumstances. The analysis of its collapse is
one of the first detailed findings by a team of engineers organized by
the Federal Emergency Management Agency and the American Society of
Civil Engineers to understand the fate of all the buildings around the
As much as 42,000 gallons of diesel fuel was stored near
ground level in the tower and ran in pipes up to smaller tanks and
emergency generators for Mayor Rudolph W. Giuliani's command center,
the Secret Service's office and other tenants.
have determined that the burning fuel apparently undermined what is
known as a transfer truss. The trusses, a series of steel beams that
allowed the skyscraper to be built atop multistory electricity
transformers, were critical to the structural integrity of the building
and ran near the smaller diesel tanks.
A failure of the same
type of structural bridge contributed to the collapse of the Alfred P.
Murrah Federal Building in Oklahoma City when it was bombed in 1995.
Federal guidelines for public buildings, created in 1996, warned of the
dangers of such trusses in terrorist attacks.
right in the vicinity where the columns go into this transfer system,"
said a person knowledgeable about the investigators' draft report on
the World Trade Center. "The rest of the building is built on top of
While 7 World Trade Center, which stood across
Vesey Street just to the north of the twin towers, was not formally a
federal building, it did house crucial government offices that included
the city's nerve center for emergency response.
investigators said that their conclusions, combined with other findings
about the failure and collapse of 5 World Trade Center, could prompt
serious changes in the codes used in building construction.
findings are in a draft report that has already been circulated among
government agencies, and are based on videos made on Sept. 11,
witnesses' reports, interviews with firefighters, evidence from the
debris pile and structural analysis. Team members, who described many
of the findings, cautioned that the conclusions on the collapse of 7
World Trade Center could still be modified as reviews proceed.
But Irwin Cantor, one of the building's original structural engineers,
who is now a consulting engineer and member of the City Planning
Commission, said the diesel-related failure of transfer trusses was a
reasonable explanation for the collapse.
He said he believed
that diesel tanks were not envisioned in the original design of the
building. "It ended up with tenants who had diesels," Mr. Cantor said.
"I know none of that was planned at the beginning."
to floor plans submitted to the Port Authority of New York and New
Jersey, which owns the land on which 7 World Trade sat, the building
complied with city fire codes, said Frank Lombardi, the authority's
chief engineer. Those codes permit no more than one fuel tank with a
capacity of 275 gallons or less on above-ground floors, he said.
Jerome M. Hauer, who was the director of Mayor Giuliani's Office of
Emergency Management at the time the command center was opened at 7
World Trade, said several teams of engineers reviewed plans to open the
office there. But no one ever mentioned any hazard associated with
placing fuel tanks above ground, near a transfer truss, he said.
"There were a host of people who looked at this," said Mr. Hauer, who
is now a managing director of the crisis and consequence group at Kroll Worldwide, a security consulting company based in New York. "We relied on their judgment."
Fire officials did at one point question the storage of large amounts
of fuel well above the ground level, saying that one large tank for the
mayor's command center, if ever compromised, might fuel a fire that
would threaten the building.
The Sept. 11 draft report also has
photographs and a description of debris collected from a previously
undisclosed, multistory collapse within 5 World Trade Center, a
nine-story office building that also burned on Sept. 11 but largely
remained standing. The team has found that one specific type of bolted
connection, called a column tree connection, that joined floor-support
beams, failed in the heat of the fires, causing the four- story
collapse in the part of 5 World Trade at the corner of Vesey and Church
Although no one died as a result of the collapses in 5
and 7 World Trade Centers, since both stood long enough to be
evacuated, the team's findings are likely to lead to recommended
changes in the way public and government buildings are constructed,
much the way similar studies did after the Northridge earthquake near
Los Angeles in 1994 and the Oklahoma City bombing.
The team is
still deliberating on how tightly it can pin down the precise train of
events that led to the collapse of the twin towers themselves. But
until now, the collapse of 7 World Trade has stood as one of the
outstanding mysteries of the Sept. 11 attack, since before then, no
modern, steel-reinforced high-rise in the United States had ever
collapsed in a fire.
High-rise buildings are designed to be
able to survive a fire, even if the fire has to burn itself out. The
strategy is to ensure that the steel support structures are strong
enough or protected well enough from fire that they do not give way in
the time it takes for everything inside an office building, like
furniture, to burn.
In major high-rise fires elsewhere in the
country, such as the 1 Meridian Plaza fire in Philadelphia in 1991 and
the First Interstate Bank fire in Los Angeles in 1988, this approach
has worked. The 1 Meridian fire burned for 19 hours, leaping from floor
to floor and burning out as combustible materials were used up. But the
fires at 7 World Trade Center raged mainly on lower floors and never
burned out, and in the chaos of Sept. 11, the Fire Department
eventually decided to stop fighting the blazes.