Eric Lipton and James Glanz . NYTimes . 13 October
A dump truck filled with debris from the World Trade Center pulled away from the site on Friday. Workers have removed about a quarter of the estimated 1.2 million tons of rubble.
The images beamed around the world showed two skyscrapers imploding one after the other in a rhythmic tumble seemingly straight down. Inside the veil of smoke, dust and terror, it was not so simple.
The top 30 or 40 floors of the World Trade Center's south tower broke off, pivoted and then plummeted eastward onto a neighboring office building. Other sections tumbled west, crushing the Marriott World Trade Hotel, and still others shot northwest, toward Battery Park City's Winter Garden.
As the north tower crashed, the giant steel columns of its facade split away and fell forward, slamming against the office building next door. Chunks of the north tower also were catapulted farther north, igniting a fire in an office tower up the street that quickly engulfed what was once home to the city's Emergency Command Center.
These patterns of collapse unfolded in a matter of seconds. But the new landscape that was formed, to a large extent, is dictating the course of the recovery and cleanup effort, now a month old.
Those efforts, and the strategy driving them, now must take into account the dangers of demolishing the other smaller buildings in the World Trade Center complex. They must be guided to a great deal by the continuing premium placed on locating and recovering human remains, most of which are believed to be confined to one section of the wide debris field. And they must perpetually calculate the risks any of their work poses for the already damaged or imperiled underground subway tunnels and retaining walls, one of which is keeping the Hudson River from rushing in.
Already, working around the clock, 1,300 construction workers and other personnel — including 160 firefighters and 90 police officers — have removed an extraordinary volume of debris: 290,000 tons of the estimated 1.2 million at the site.
The rubble of the 22-story Marriott on the southwest corner of the complex is almost entirely gone and the land where it once stood has already been covered with a fresh, clean layer of blacktoplike material. Much of what was 4 World Trade Center, the squat, L-shaped office building on the complex's southeast corner, has been demolished, swept up and hauled off; an access road now runs through the site.
But most of the heavy lifting is still ahead, with the cleanup and recovery operation expected to last a year. Mountains of debris from the towers remain, as do the burned- out or smashed-in shells of the United States Customs House at the complex's northwest corner and 5 World Trade Center at the northeast corner. There are also six underground levels in the complex, caverns where most of the super-compressed debris from the towers has settled.
The tactics that construction crews are using to demolish and clear all these structures are tightly determined by each building's position within the pattern of devastation. Explosives or any other technique that could quicken the job by bringing down whole structures all at once have been ruled out as too hazardous, officials said. That means the demolition from start to finish must be a slow, methodical effort.
"How do you eat an elephant?" said Mark Loizeaux, president of Controlled Demolition Inc. of Phoenix, Md., a firm that prepared a preliminary demolition plan for the city's Department of Design and Construction, which is overseeing the job. "Carefully and in small bites. They have an elephant."
The job is perhaps most delicate at the northeast corner, a sector that contains the scattered and heaped remains of the north tower next to the shell of the eight-story, 550,000- square-foot Customs House building, at 6 World Trade Center.
When the 110-story north tower collapsed, the huge beams holding up its north facade, a section of colonnade about 150 feet across, weighing perhaps 1,000 tons or more, fell against the south wall of the Customs House, where the colonnade remains precariously tilted.
Debris from higher up the tower, possibly including the building's antenna, fell like a spear and punched a hole through the center of the Customs House, tearing a broad crater deep into the basement levels below.
To dissect this mass of steel and concrete without causing an avalanche, crews must perform at least four different tasks. From the south, a large crane will latch onto the colonnade and hold it in place from above. Ironworkers then will be lowered by another crane to the top of this still-tilting but secured piece of steel. Using torches, they will gradually cut this piece down from the top. At the same time, moving in from the west, other workers using mobile shears and torches will cut back the structure of the Customs House. Finally, if necessary wrecking balls will smash remaining floors.
Everything about the process is gradual and planned, said Pat Muldoon, senior vice president of Amec Construction, which is handling demolition of the Customs House. He said the building and the facade will gradually be trimmed from above."We'll go in and give the building what everybody is calling a haircut," Mr. Muldoon said.
Over the next several months, the remains of the Customs House building should be leveled, and eventually crews will be lowered below ground and into the crater itself to begin clearing debris there, said Frank Lombardi, chief engineer for the Port Authority of New York and New Jersey, which owned six of the center's seven buildings.
"I wouldn't lower anybody until I get the above-surface building down," said Mr. Lombardi. "I don't want to have any more casualties here."
It is far from an idle concern. In the last two weeks, there have been at least four near accidents at the site, according to officials from the federal Occupational Safety and Health Administration.
On Monday, for example, as more than a dozen firefighters and construction workers were working the debris on the west side of the site, a steel beam, weighing an estimated 16 tons, broke loose from a crane and fell. Three days before, as the sound of jackhammering filled the air, a chunk of concrete about 10 inches in diameter fell off what was left of 5 World Trade Center, landing on a spot where someone had been standing seconds before.
Just south of the Customs House, the work is often driven by a mandate different from mere demolition. It is here that workers are most likely to find human remains.
By examining floor plans, interviewing firefighters and studying the way the two towers fell, the Fire Department has at times devised grim work orders about where the construction crews should dig to find bodies or body parts.
"Who did they see in front of them, who did they see behind them, what hints can we get from the radio traffic, as to where people had reported they were trapped?" said Deputy Fire Commissioner Thomas F. Fitzpatrick.
It is an extraordinarily trying chore, for the remains of the World Trade Center are a chaotic jumble. Differences in the direction of how once-connected sections fell, or a buckling in a steel column as it hit the ground, means debris from a single floor is often spread far apart.
Work crews from Bovis Lend Lease, a contractor excavating a sector that includes the south tower, recently went looking for part of a lower floor, said Peter Marchetto, a Bovis executive. Burrowing in at the spot suggested by the Fire Department, they found, instead, "signs for the 86th floor," Mr. Marchetto said.
"We were digging through debris we thought might be from near the tower's bottom that was in fact from near the top," Mr. Marchetto said. "Unfortunately, the corridors and stairwells we were looking for are far down in the pile and there is so much that must be removed before we could get there. Nothing is where you think it is; everything is shifted, moved, bent, compressed."
But every once in a while, the hunt turns up what searchers are looking for. Firefighters are stationed near the construction crews, ready to move in and collect any human remains. At least for the next few weeks, the search for remains is expected to continue to help determine the course of the demolition work in the southwest section of the site, officials said.
"There are so many families out there that have expectations that remains will be found," Mr. Fitzpatrick said.
At other times, working without orders to look specifically for remains, giant backhoes and other machines roar back and forth atop the center of what was once the north and south towers. They collect debris one load at a time, and dump it into waiting trucks.
As work progresses, fires still burn deep within the debris, and an acrid smell, with a distinctly metallic flavor, rises from the ground. It mixes with the cacophony emanating from the site — the beeping of vehicles backing up, the whining of saws cutting steel, the roar of crane engines, the echoing boom of debris being dumped into trucks. And it continues this way, day and night.